BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:The mean focal length of an aberrated lens DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5034@events.saip.org.za DESCRIPTION:Speakers: Cosmas Mafusire (CSIR National Laser Centre)\nWe out line an approach for the calculation of the mean focal length of an aberra ted lens\, and provide closed form solutions that show that the focal leng th of the lens is dependent on the presence of defocus\, x-astigmatism and spherical aberration. The results are applicable to Gaussian beams in the presence of arbitrary sized apertures. The theoretical results are confir med experimentally\, showing excellent agreement. As the final results are in algebraic form\, the theory may readily be applied in the laboratory i f the aberration coefficients of the lens are known.\n\nhttps://events.sai p.org.za/event/7/contributions/5034/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5034/ END:VEVENT BEGIN:VEVENT SUMMARY:Modification of the bandoffset in boronitrene DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4941@events.saip.org.za DESCRIPTION:Speakers: Kingsley Obodo (University of Pretoria\, South Afric a)\nWe carried out ab initio self-consistent calculations to study the mod ification of the band offsets by polar layers. We considered a double line of C in a monolayer of hexagonal BN\, also known as Boronitrene. This eff ectively introduces a line of dipoles at the interface. We considered BN/C zigzag and armchair configurations. The BN/C zigzag-short is found to be energetically most stable and with the smallest (1.51eV). We show that a t wo dimensional diode can be constructed from this structure\, with changes to the electronic and optical properties of the host system.\n\nhttps://e vents.saip.org.za/event/7/contributions/4941/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4941/ END:VEVENT BEGIN:VEVENT SUMMARY:Open Quantum Random Walks DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4948@events.saip.org.za DESCRIPTION:Speakers: Ilya Sinayskiy (School of Physics and NITheP\, Unive rsity of KwaZulu-Natal)\nQuantum Random Walks have been introduced almost 20 years by Y. Aharonov et al. [Phys. Rev. A\, 48(2):1687–1690\, 1993] a nd have found wide applications in quantum computing. As is often the case in quantum theory\, Quantum Walks differ strongly from classical random w alks. In joint work of S. Attal\, C. Sabot\, F. Petruccione and I. Sinaysk iy the concept of Open Quantum Random Walks was introduced\, by taking int o account dissipation and decoherence that occur in open quantum systems. The connection to classical and unitary random is discussed as well as the potential of Open Quantum Random Walks for quantum computing and efficien t quantum transport.\n\nhttps://events.saip.org.za/event/7/contributions/4 948/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4948/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational modelling study of PtAs2 and PtAsS struct ures DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4849@events.saip.org.za DESCRIPTION:Speakers: Dinah Makgai (university of limpopo)\nWe have invest igated the electronic\, structural and optical properties of the PtAs< sub >< /sub>2 and PtAsS structures using the density functional theory in th e framework of Vienna Ab initio Simulation Package (VASP) code within the generalized gradient approximations of Perdew\, Burke and Erzenhof (GGA-PB E) . The total energy calculation of PtAs < sub >< /sub>2 and PtAsS have b een computed and predict equilibrium lattice parameters that are in good a greement with the experiment. Elastic constants of these structures compar e well with experimental measurements\, both PtAs< sub >< /sub>2 and PtAsS gave positive independent elastic moduli\, condition of mechanical stabil ity. We found good correlation between heats of formation\, elastic consta nts and phonon dispersion curves\, all satisfying stability conditions. In particular the phonon dispersion display real frequencies along high symm etry direction of the Brillion zone.\n\nhttps://events.saip.org.za/event/7 /contributions/4849/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4849/ END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic vector charges in the mystery of a circular current’s p air of distinct Cartesian elemental magnetic dipoles DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4850@events.saip.org.za DESCRIPTION:Speakers: Max Chirwa (Walter Sisulu University)\nA circular el ectric current\, perpendicularly bisected by a field plane\, was modelled as a continuum of pairs of distinct Cartesian component elemental magnetic vector charges normal and parallel to the field plane. The Cartesian elem ental magnetic vector charges normal to the field plane pair up into Carte sian elemental magnetic dipoles with intra-dipolar displacements parallel to the plane. These dipoles generate the overall magnetic vector potential at the field point. The Cartesian elemental magnetic vector charge compon ents parallel to the field plane form Cartesian elemental magnetic dipoles (with intra-dipolar displacements perpendicular to the field plane) which individually and collectively contribute nothing to the overall magnetic vector potential. Each continuum of these two sets of Cartesian elemental magnetic dipoles independently yields the traditionally renowned “magnet ic dipolar moment of a circular current”. However\, together their two d istinct magnetic fields\, as well as their two distinct magnetic torques\, constitute the circular current’s overall magnetic field and the total magnetic torque respectively. These results reconcile only if the magnetic dipolar moments of both sets are endorsed\, that is a circular current of any spatial size is a continuum of pairs of distinct Cartesian elemental magnetic dipoles and that consequently its overall magnetic dipolar moment is numerically twice the traditional value. In addition the customary ad hoc definition of the magnetic dipole moment of a current loop is deceptiv ely erroneous\, thus prompting a review of many relations involving it. Th ese include the magnetic torque and magnetic field generated by it\, and t he classical magneto-mechanical ratio.\n\nhttps://events.saip.org.za/event /7/contributions/4850/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4850/ END:VEVENT BEGIN:VEVENT SUMMARY:Elemental magnetic vector charges linked to zero outward magnetic flux from any surface enclosing non-dipolar magnetic sources DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4851@events.saip.org.za DESCRIPTION:Speakers: Max Chirwa (Walter Sisulu University)\nA harmonious formulation of the inverse–square laws for fields shows that elemental s ources are rightfully represented as scalars for both gravitational and el ectric fields\, but as vectors for magnetic fields. This permits an effect ive simple illustration that\, unlike the gravitational or electric flux\, the magnetic flux out of any closed surface is zero irrespective of wheth er the enclosed magnetic source is dipolar or non-dipolar. Then Gauss’ l aws for gravitational\, electric and magnetic fields can be re-stated as: Out of any enclosing surface\, if the source is a scalar quantity then the net flux is equal to the source itself\; whereas if the enclosed source i s any vector quantity\, the net flux is the scalar zero.\n\nhttps://events .saip.org.za/event/7/contributions/4851/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4851/ END:VEVENT BEGIN:VEVENT SUMMARY:Ultrafast Transient Absorption measurements on Indoline D149 Dye DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4852@events.saip.org.za DESCRIPTION:Speakers: Egmont Rohwer (Stellenbosch University)\nD149 Dye ha s proven to be an effective photo-absorber for use in dye sensitized solar cells. Pump-probe measurements were conducted on D149 dye as well as D149 adsorbed to Zinc Oxide semi-conducting particles. Ultrafast dynamics on a sub-ps time scale\, easily resolved by the current experimental setup at the LRI\, were observed in both samples. Significant quenching of the exci ted state dynamics of the D149 molecule was seen in samples adsorbed to Zi nc oxide\, indicating the occurence of intermolecular charge transfer of p hoto-excited electrons from the singlet excited state of the D149 molecule and subsequent injection into the conduction band of the Zinc Oxide parti cles.\n\nhttps://events.saip.org.za/event/7/contributions/4852/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4852/ END:VEVENT BEGIN:VEVENT SUMMARY:Ab-initio study of the energy of formation and diffusion paths of self-interstitials in silicon DTSTART;VALUE=DATE-TIME:20110714T120000Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4853@events.saip.org.za DESCRIPTION:Speakers: Jacques Pienaar (University of Pretoria)\nThe format ion energy of self-interstitial defects in silicon was studied. The 〈110 〉split site was found to be the lowest energy position for the silicon s elf-interstitial at neutral charge state\, as well as singly and doubly ne gative charged state. The tetrahedral site is found to be the lowest energ y site for the singly and doubly charged positive states. The energy barri ers for diffusion from the 〈110〉split site to the hexagonal and tetrah edral sites were found to be 0.370 and 0.361 eV respectively. Diffusion be tween the tetrahedral and hexagonal sites has an energy barrier of 0.074 e V. These energy barriers are found to be too great to account for athermal diffusion of the silicon self-interstitial\, and diffusion paths involvin g cyclic changes in charge state are most likely to be responsible for the athermal diffusion observed at low temperature.\n\nhttps://events.saip.or g.za/event/7/contributions/4853/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4853/ END:VEVENT BEGIN:VEVENT SUMMARY:The Mechanical and Structural Properties of the Pt-Ti and Ir-Ti Al loy Systems DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4854@events.saip.org.za DESCRIPTION:Speakers: Miguel Cavero (University of KwaZulu-Natal)\nAb init io density functional calculations within the generalised gradient approxi mation (GGA) have been carried out on a wide range of phases and stoichiom etries for the platinum-titanium (Pt-Ti) and iridium-titanium (Ir-Ti) allo y systems\, using the Vienna Ab Initio Simulation Package (VASP). The ela stic constants and elastic moduli are calculated and the electronic struct ure and density of states (DOS) are considered to understand the hardness and stability properties of the alloys.\n\nhttps://events.saip.org.za/even t/7/contributions/4854/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4854/ END:VEVENT BEGIN:VEVENT SUMMARY:Structure-property relationship of sol-gel synthesised zinc-oxide nanoparticles DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4865@events.saip.org.za DESCRIPTION:Speakers: Natasha Venita Peterson (University of the Western C ape)\nZinc-oxide nanoparticles are well known for their novel optical and electronic properties for applications in various fields such as solar cel ls\, ultra violet shielding\, gas sensors\, paint and heat mirrors. We rep ort on the relation between the structure and optical properties of ZnO na noparticles synthesized via the sol-gel technique\, with specific emphasis on the effect of growth and reaction temperatures. High-resolution micros copy techniques\, complemented by Raman spectroscopy and x-ray diffraction \, confirm that the crystallinity and particle size of ZnO nanoparticles i s directly related to the synthesis conditions. Optical absorption and emi ssion spectroscopy show that optical band gap and photoluminescence of the ZnO nanoparticles are intimately related to its structural properties\, a scribed to the quantum confinement effect. Photoluminescence spectroscopy confirm the emission peaks in the ultraviolet (380 nm) and visible (500 nm ) region\; the latter attributed to the presence of the singly ionized oxy gen vacancies in the nanoparticle.\n\nhttps://events.saip.org.za/event/7/c ontributions/4865/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4865/ END:VEVENT BEGIN:VEVENT SUMMARY:Cathodoluminescence and energy transfer between Er3+\, Tm3+and Ho3 + rare earth ions in SiO2 nanoparticles DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4855@events.saip.org.za DESCRIPTION:Speakers: Simon Dhlamini (University of South Africa)\nPrepara tion of Er3+\, Ho3+ and Tm3+ ions co-doped SiO2 nanoparticle phosphor powd ers by sol gel method is reported. The morphology and the particle size of the SiO2 host matrix were confirmed by field emission scanning electron m icroscopy (FESEM). Ultraviolet\, visible (UV/VIS) and cathodoluminescence measurements were carried out in order to investigate the optical properti es of our powder phosphors. Green emissions at 520 nm from Er3+ and 544 nm from Ho3+\, and red emissions at 665 nm from both Er3+ and Ho3+ ions are reported. Another emission peak in the near infra-red (NIR) region at 875 nm from Er3+ was also measured. Blue emission at 460 nm\, red at 705 nm an d a NIR peak in the region of 865 nm from Tm3+ were observed. Red\, green and blue (RGB) colours were measured from both SiO2:Er3+\,Tm3+ and SiO2:Ho 3+\,Tm3+ systems. The change in the intensities of the emission peaks in b oth the SiO2:Ho3+\,Tm3+ and SiO2:Er3+\,Tm3+ systems with the change in acc elerating beam voltage is shown. Energy transfer from Tm3+ ions to Er3+ an d Ho3+ ions was observed. A mechanism explaining the increase and decrease behaviour of the emission with accelerating beam voltage from both system s is reported.\n\nhttps://events.saip.org.za/event/7/contributions/4855/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4855/ END:VEVENT BEGIN:VEVENT SUMMARY:Ab initio thermodynamic and elastic properties of Pt-Cr binary all oys DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4856@events.saip.org.za DESCRIPTION:Speakers: Malebo Tibane (University of South Africa)\nPlanewav e pseudopotential calculations were conducted to predict the phase stabili ty of Pt-Cr binary alloys. The heats of formation are determined for five different phases\, L12\, A15\, DOC\, DO'C and tP16 of Pt3Cr and PtCr3. We observed that the cubic L12 Pt3Cr is the most stable structure in agreemen t with the experiments. The results for PtCr3 indicate the negative heat o f formation for the A15 phase whereas all the remaining studied phases hav e positive heats of formation. In addition the phase stability study was p erformed on two phases\, B2 and L10 of the PtCr alloy. L10 phase was found to be more stable compared with the PtCr B2 phase. Elastic constants and moduli were investigated to determine the strength of the Pt-Cr systems. T he strength of PtCr L10 is greater than that of B2 phase. The ratio of she ar to bulk modulus (G/B) has been used to predict the ductility or the bri ttleness of the material.\n\nhttps://events.saip.org.za/event/7/contributi ons/4856/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4856/ END:VEVENT BEGIN:VEVENT SUMMARY:The pair-model of monopolar and dipolar moments of elemental elect ric scalar and magnetic vector charges DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4857@events.saip.org.za DESCRIPTION:Speakers: Max Chirwa (Walter Sisulu University)\nA sequel to r epresenting elemental sources of magnetic fields as elemental magnetic vec tor charges is realizing that electric and magnetic dipole moments are dif ferent classes of moments. The distinction between monopolar and dipolar m oments becomes clearer when any distribution of electric scalar charge or magnetic vector charge is depicted as one or more pairs of charges with eq ual magnitudes. It is shown here that separation of the charges (electric scalar or magnetic vector) is essential for the very existence and other a ttributes of a dipole\, but not for a monopole. These representations are markedly different from the traditional analogous representations and noti ons of electric and magnetic dipole moments as sources of corresponding fi elds or potentials. It also emphasizes that fields and potentials are gene rated by the sources and not by their moments\; hence the difference betwe en these two entities.\n\nhttps://events.saip.org.za/event/7/contributions /4857/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4857/ END:VEVENT BEGIN:VEVENT SUMMARY:Critical behaviour near magnetic phase transition in CeCuGe DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4858@events.saip.org.za DESCRIPTION:Speakers: Buyi Sondezi-Mhlungu (University of Johannesburg)\nC eCuGe is one of the few compounds to order ferromagnetically at low temper atures. The compound has been observed to exhibit paramagnetic-ferromagnet ic (PM-FM) magnetic transition\, TC = 10 K This magnetic ordering has been observed from specific heat (Cp)\, magnetization\, (M(T\,B)) and resistiv ity data.\nIsothermal magnetization of a hexagonal\, highly ordered CeCuGe were measured in order to study the critical scaling behavior in the vici nity of magnetic ordering in this polycrystalline compound. From the analy ses of the magnetization data\, TC was confirmed using modified Arrott plo t technique. It was also observed from the critical exponents\, beta\, gam ma and sigma corresponding to the spontaneous magnetization\, initial susc eptibility and isothermal magnetization were obtained\, respectively. The resulting critical exponents obtained reveals that the system falls within Heisenberg and 3-D Ising model.\n\nhttps://events.saip.org.za/event/7/con tributions/4858/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4858/ END:VEVENT BEGIN:VEVENT SUMMARY:The impurity levels of lanthanide ions in silica DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4859@events.saip.org.za DESCRIPTION:Speakers: R.E. Kroon (Physics Dept\, University of the Free St ate)\nSilica is a basic material of technological importance for optics\, microelectronics\, photonics and fibre optics. Its high absorption edge e nergy makes its particularly useful for UV applications and it has been us ed as a host material for a variety of luminescent lanthanide ions due to its chemical stability and non-hygroscopic nature. For lanthanide ions the 4f electron energy levels are shielded from the host environment by the f illed outer 5s and 5p orbitals\, so that the transitions between these sta tes and therefore the luminescent wavelengths are relatively insensitive t o the host. For this reason little attention has been paid until recently to the location of the impurity levels of the lanthanide ions within the energy gaps of their hosts. However\, luminescence from some lanthanide i ons\, e.g. cerium\, occurs due to f-d transitions from the unshielded 5d s tate of which the energy relative to the f-states is therefore host depend ent. The absolute positions of the 4f and 5d states relative to the ener gy gap of the host also affect quenching and charge trapping phenomena and so they are required for proper modeling of phosphor performance. Recent ly Dorenbos has suggested that the energy levels of any of the 13 divalent lanthanides relative to the band edges of the host can be found using onl y three parameters. However\, obtaining this data for a particular host is not always straightforward e.g. use can be made of the f-d transition ene rgy of cerium\, but different values for this parameter in silica have bee n reported. In this paper a scheme for the energy levels of both the diva lent and trivalent lanthanide ions in silica is proposed and compared to t he experimental data.\n\nhttps://events.saip.org.za/event/7/contributions/ 4859/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4859/ END:VEVENT BEGIN:VEVENT SUMMARY:Protein localization and folding mechanisms revealed by molecular dynamics simulations DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4866@events.saip.org.za DESCRIPTION:Speakers: James Gumbart (Argonne National Laboratory)\nMany na scent proteins\, including nearly all membrane and secreted\nproteins\, mu st traverse a membrane-bound protein-conducting channel prior to their ful l maturation. This channel\, the Sec translocon\, is found in all domains of life and possesses the novel ability to direct nascent proteins to the membrane or to the extracellular space\, depending on their sequences\, o ften concomitant with their synthesis by the ribosome. By combining atomi c structures with cryo-electron microscopy data using the molecular dynami cs flexible fitting method\, we have developed some of the first views of inactive and active translocons in complex with the ribosome. These views reveal a conserved mode of interaction between translocon and ribosome as well as the roles of specific elements of both in protein localization. W e also carried out two-dimensional potential-of-mean-force calculations to explore the structure of the nascent peptide within the translocon enviro nment. The calculations revealed that the translocon exerts a small bias on the peptide towards a helical state. This bias can serve to\nfacilitat e\, e.g.\, the insertion of nascent membrane proteins into the otherwise\n inhospitable lipid bilayer.\n\nhttps://events.saip.org.za/event/7/contribu tions/4866/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4866/ END:VEVENT BEGIN:VEVENT SUMMARY:Temperature dependent I-V characteristics of Sulphur passivated Au /n-GaSb Schottky barrier diodes DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4860@events.saip.org.za DESCRIPTION:Speakers: Davison Munyaradzi Murape (NMMU)\nThe current-voltag e (I-V) characteristics of sulphur passivated n-GaSb have been studied in the temperature range 80 K - 330 K using Au Schottky barrier diodes (SBDs) . The forward I-V characteristics have been analysed assuming that thermi onic emission is the dominant current transport mechanism and that the bar rier height patchiness takes on a Gaussian distribution. It has been found that sulphur treatment of the GaSb accompanied by prior etching steps lea d to a significant improvement in the quality of the SBDs as is evidenced by the improvement in the ideality factor (n)\, rectification ratio\, seri es resistance (Rs) and the barrier height (Φb) of the device\, These impr ovements were attributed to removal of predominantly Sb-O from the GaSb su rface together with passivation of surface states acting as recombination centres. Typical diode parameters obtained at room temperature (300K) wer e found to be to be 1.12 (n)\, 19.4Ω (Rs) and 0.52eV (Φb)) \nThe idea lity factor was found to diverge from unity whereas the barrier height inc reased with decrease in temperature. The increase in the ideality factor i s attributed to the dominance of field assisted tunnelling over thermionic emission at low temperatures and is particularly severe for high free car rier concentration material. Finally\, the surface state densities for su lphurized material were quantified using I-V measurements and compared to that of untreated material.\n\nhttps://events.saip.org.za/event/7/contribu tions/4860/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4860/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational study of the effect of polydimethylsiloxane (PDMS) s ide chain size and spacing on the mobility of the polyethylene oxide (PEO) . DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4861@events.saip.org.za DESCRIPTION:Speakers: Thomas Kubai (university of Limpopo)\nThe effects of side chain size and spacing on the mobility of the PEO backbone have been studied using molecular dynamics (MD) in Forcite code of Materials studio . The systems investigated contain a PEO chain of 186 ethylene oxide (EO) monomers to which side chains of 5\, 6\, 7\, 8 and 9 PDMS monomers have be en attached. The separations of the side chains used are 5\, 10\, 15\, 20 and 50 EO monomers. The overall mobility of the polymer host system is fou nd to have minima at side chain size of 6 and 7. A maximum is seen at side chain spacing of 8 and 9. No evident was found to suggest that side chain spacing has an effect on the mobility of the PEO polymer backbone. Furthe rmore\, the point of attachment of the side chain has no effect on the pol ymer mobility.\n\nhttps://events.saip.org.za/event/7/contributions/4861/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4861/ END:VEVENT BEGIN:VEVENT SUMMARY:The effect of ventilation on the thermal performance of an energy efficient house DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4862@events.saip.org.za DESCRIPTION:Speakers: Thabiso Vincent Mthimunye (ufh)\nAn energy efficient passive solar house was designed\, constructed and its natural ventilatio n efficiency monitored. Carbon tracer test was used to measure the ventil ation efficiency of each ventilation component. Windows were found to have higher impact on the ventilation rate than doors. The correct operation o f the ventilation components was found to be the main contribution factor in natural ventilation.Tracer gas tests were conducted over a period of ti me to measure actual air change rates. Carbon dioxide was injected into th e house and its concentration monitored over time to determine how quickly the gas dissipates through the house’s envelope. The west side ventilat ion components were used to control the indoor environment by regulating t he amount of air flowing into the house. A carbon dioxide sensor was place d in the centre of the house at a height of about 0.45 m above the floor. A fan was used to pump the indoor air into the sensor at a rate of about 3 00 ml/min. To investigate the effects of each of the ventilation component configurations\, the ventilation rate tests were done in four configurati ons. A carbon dioxide sensor connected to a CR1000 data logger and a compu ter was used to monitor carbon dioxide concentration in the house. \nresul ts:The tracer gas technique was used to measure the air exchange rate. The average indoor and outdoor temperatures during these tests were\, Tin = 2 0 °C and Tout =17 °C\, and an average wind speed of 0.5 m/s blowing from W(600 150)N.when both windows and doors were opens. Results indicate that the concentration decays exponentially to the background concentration wi thin a period of 16 minutes. Assuming that the west window and door are th e only paths through which the westerly winds enter the house\, then the m ass air flow rate through the door and window is approximated.Take the ave rage air density to be 1.2 kg/m3\, an average indoor and outdoor pressure difference to be 4 Pa. For wide-open windows and doors\, the opening area is the sum of the windows and doors areas\, which gives 2.06 m2 and taking the discharge coefficient Cd=0.6 the average mass airflow was found to b e approximately 3.83 kg/s.Natural ventilation varies greatly on local fact ors such as wind speed and temperature which also influence at which occup ants open ventilation components.\n\nhttps://events.saip.org.za/event/7/co ntributions/4862/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4862/ END:VEVENT BEGIN:VEVENT SUMMARY:Comparative Efficiency Study of a Solar Trough Receiver: Hot mirro r and Selective coating DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4863@events.saip.org.za DESCRIPTION:Speakers: Marie Chantal CYULINYANA (University of the Witwater srand)\nWe consider a solar trough system in which cylindrical parabolic m irrors focus the sun’s radiation onto a receiver pipe\, heating it. Conv entionally\, the pipe is enclosed in a glass cover under vacuum and the do minant radiation losses are reduced by the use of a selective coating on t he receiver pipe. We study the suitability of applying a ‘hot mirror’ coating on the glass cover instead\, which transmits in the visible but re flects well in the infra-red. We compare the performance of the ‘selecti ve’ with a ‘hot mirror’ coating using the results from simulations f or a general heat transfer model. It is seen that a hot mirror is a viable alternative\, and certainly allows higher temperatures of the working flu id and therefore higher Carnot efficiency. The optimum is a hybrid system\ , with selective coating applied at the low temperature end of the receive r pipe and the hot mirror being used at higher temperatures.\n\nhttps://ev ents.saip.org.za/event/7/contributions/4863/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4863/ END:VEVENT BEGIN:VEVENT SUMMARY:Status of the Electron Cyclotron Resonance Ion Sources (ECRIS) at iThemba Labs DTSTART;VALUE=DATE-TIME:20110715T094500Z DTEND;VALUE=DATE-TIME:20110715T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4864@events.saip.org.za DESCRIPTION:Speakers: Sifiso Senzo Ntshangase (iThemba LABS)\nHeavy ion be ams at iThemba LABS have been produced in a 10GHz Minimafos electron cyclo tron resonance ion source (ECRIS) for the past two decades. The typical va lues for the injection and extraction coil current are in the range of 100 0A. The operating pressure is about 10-6 mbar depending of the ion produce d. The Minimafios ECRIS allow the use of supporting gas like helium\, oxyg en etc. It accommodate up to from 10KV up to 20KV extraction voltage. For electron enhancement a biased disc at -50V was introduced at the injection side of the plasma chamber. Examples of beams which have been produced us ing the Minimafios are: H\, He\, B\, C\, N\, O\, Ar\, Ne\, Al\, Si\, Cl\, Zn\, Kr\, I\, Xe\, Li.The increase in demand for new ion species and high intensity beams from the nuclear physics community has led to a decision t o procure a new 2nd generation ECRIS. The procured source is a room temper ature ECRIS based on the Grenoble Test Source (GTS) design. It uses two mi crowave frequencies\, 14.5GHz and 18GHz to deliver positive ions. It was m ade to accommodate to oven. The axial field can be varied between 0.5T and 1.2T using three solenoid coils and a radial field of 1.3T achieved by us ing FeNdB permanent magnet. The source has been assembled and is being com missioned at iThemba LABS. \n\n The Hahn-Meitner-Institute (HMI) in Berlin donated their 14.5GHz ECRIS4 to iThemba LABS where it is presently operat ional. This source consist of a water-cooled plasma chamber (length 18cm\, diameter 7cm) surrounded by feNdB permanent magnets which produce a hexap ole field of 1T at the wall of the chamber for plasma confinement. Two sol enoid coils produce an axial field which confines the plasma axially. The field on axis typically varies from 0.4 to 1.1T. The microwave power is co upled into the source via a wave guide. It generator can deliver up to 2KW of microwave power. Furthermore\, iThemba LABS is one of the few laborato ries which produce nuclear polarized proton beams using the so-called pola rized ion source. In this report the status of the four ion sources will b e presented.\n\nhttps://events.saip.org.za/event/7/contributions/4864/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4864/ END:VEVENT BEGIN:VEVENT SUMMARY:Monte Carlo simulation using GEANT 4 of MuSR DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4886@events.saip.org.za DESCRIPTION:Speakers: Jonathan Hartman (University of Johannesburg)\nGEANT 4 is a C++ library developed by CERN to simulate particle physics experim ents. However\, GEANT 4 can be also be used for other applications that ne ed not have anything to do with particle or high-energy physics. Here we d iscuss an application of GEANT 4 that simulates the EMU Spectrometer for M uon Spin Relaxation measurements at the ISIS facility in the Rutherford Ap pleton Laboratory. Both the incident muon and decay positron trajectories are affected. This changes the stopping location of muons for small sample s and also the efficiency of the positron detection\, in a strongly field dependent way. This leads to a systematic field dependent false asymmetry. The simulation has been performed in support of the interpretation of exp eriments todetermine the effect on diamond samples doped with muonium\, wh ich is a known analogue of the hydrogen atom.\n\nhttps://events.saip.org.z a/event/7/contributions/4886/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4886/ END:VEVENT BEGIN:VEVENT SUMMARY:Search for Higgs boson to 4 leptons through new gauge bosons DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4867@events.saip.org.za DESCRIPTION:Speakers: Mathieu Aurousseau (University of Johannesburg)\nThe H -> ZZ(*) -> 4leptons channel is one of the most promising channels for a low-mass Higgs boson\, as it has both a clean signature and a large bran ching fraction for Higgs mass below a few hundred GeV. The ATLAS experimen t has explored this channel using the LHC collisions data at a center-of-m ass energy of 7 TeV\, using data-driven background estimation techniques. Some Abelian Hidden Sector models predict the existence of new Higgs and g auge (Z') bosons\, weakly coupled to the Standard Model (SM) sector. The d ecay of the SM Higgs to a pair of Z' bosons is allowed\, possibly with a l arge branching fraction\, by the mixing of the Higgs sectors. The decay of the Z' bosons to lepton pairs with a large branching fraction can then be explored in the same way as the standard H -> ZZ(*) -> 4l channel\, by re laxing the constraints on the di-lepton invariant mass. Perspectives on th is new approach with the ATLAS experiment are presented.\n\nhttps://events .saip.org.za/event/7/contributions/4867/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4867/ END:VEVENT BEGIN:VEVENT SUMMARY:Constraining Viewing Geometries of Pulsars With Single-Peaked Gamm a-ray Profiles Using A Multiwavelength Approach DTSTART;VALUE=DATE-TIME:20110713T103000Z DTEND;VALUE=DATE-TIME:20110713T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4868@events.saip.org.za DESCRIPTION:Speakers: Albertus Seyffert (North-West University)\nSince the launch of the Large Area Telescope (LAT) on board the Fermi spacecraft in June 2008\, the number of observed gamma-ray pulsars has increased dramat ically. A large number of these are also observed at radio frequencies. We ltevrede et al. (2010) derived constraints on the viewing geometries of 6 gamma-ray pulsars exhibiting single-peaked gamma-ray profiles using high-q uality radio polarization data. We obtain independent constraints on the v iewing geometries by using a geometric emission code to model the Fermi-LA T and radio light curves. We find fits for the magnetic inclination and ob server angles by searching the solution space by eye. Our results are gene rally consistent with those obtained by Weltevrede et al. (2010)\, althoug h we do find differences in some cases. We will indicate how the gamma-ray and radio pulse shapes as well as their relative phase lags lead to const raints in the solution space. A more rigorous approach\, the Monte Carlo M arkov Chain technique\, is able to statistically find best-fit light curve s in addition to constraining several model parameters and estimating erro rs on these.\n\nhttps://events.saip.org.za/event/7/contributions/4868/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4868/ END:VEVENT BEGIN:VEVENT SUMMARY:The Giant Graviton on AdS4xCP3 DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4869@events.saip.org.za DESCRIPTION:Speakers: Andrea Prinsloo (NITheP\, Stellenbosch University)\n A new correspondence between type IIA string theory on AdS4×CP3 and an N= 6 Super Chern-Simons-matter theory was proposed by Aharony\, Bergman\, Jaf feris and Maldacena (ABJM) in 2008. We construct the D4-brane giant gravit on\, extended and moving in the complex projective space\, which is dual t o a subdeterminant operator in ABJM theory. This dynamically stable config uration factorizes at maximum size into two topologically stable D4-branes (each wrapped on a different CP2 cycle) dual to ABJM dibaryons. We also m ention our more recent results obtained from an analysis of small fluctuat ions around this CP3 giant graviton.\n\nhttps://events.saip.org.za/event/7 /contributions/4869/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4869/ END:VEVENT BEGIN:VEVENT SUMMARY:Low temperature synthesis and characterization of ZnO nanoparticle s using Polyvinylpyrrolidone (PVP) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4870@events.saip.org.za DESCRIPTION:Speakers: Modiehi Amelia Tshabalala (University of the Free St ate)\nZnO and PVP capped ZnO nanoparticles were synthesised using the sol- gel method at low temperature with ethanol as a solvent\, zinc acetate as a precursor and methanol as the cleaning agent. The influence of temperatu re on the morphology\, structure and the optical properties of the ZnO nan oparticles were investigated. The effect of addition different molar masse s of the PVP during the synthesis on the ZnO emission peaks was systematic ally monitored. Polyvinyl pyrrolidone (PVP) is utilized to cap ZnO nanorod s from a zinc acetate precursor at low temperature\, since the PVP can be easily removed by burning the solid products. The photoluminescence (PL) c haracterization of the ZnO nanostructures exhibited a broad emission in th e visible range with maximum peaks at 449 and/or 530nm\, this was influenc ed by the addition of different molar masses of the PVP. The scanning elec tron microscopy (SEM) images of ZnO and PVP capped ZnO has showed the pres ence of the agglomerated ZnO particles which could be due to the agglomera tion of the smaller particles. The x-ray diffraction (XRD) spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes o f wurtzite ZnO\, indicating a single phase. The absorption edges of these ZnO nanoparticles are shifted by additions of PVP polymer. The absorption spectra of the ZnO showed slight shifts with reference to the various mola r masses of PVP.\n\nhttps://events.saip.org.za/event/7/contributions/4870/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4870/ END:VEVENT BEGIN:VEVENT SUMMARY:The Surface Orientation Dependence of the Pre-Exponential Factors Extracted from the Segregation Profiles of a Cu(111/110) Bi-crystal DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4871@events.saip.org.za DESCRIPTION:Speakers: Charl Jafta (Energy and Processes Unit\, CSIR)\nPrev ious experimental investigations have only shown\, without explanation\, t hat the pre-exponential factor (D0)\, in the diffusion coefficient of Sb s egregating in Cu\, is dependent on the surface orientation of a crystal. In this study\, the surface concentration of Sb in a Sb doped Cu(111/110) bi-crystal was measured using a method combining AES and linear temperatur e heating. Segregation parameters\, including the D0’s are extracted fr om the experimental data of surface concentration versus temperature using the modified Darken model. The difference in the two pre-exponential fac tors D0 (Sb in Cu(111)) and D0 (Sb in Cu(110)) is explained thermodynamica lly in terms of entropy change ΔS that is calculated\, for the first time \, for a Cu(111/110) bi-crystal.\n\nhttps://events.saip.org.za/event/7/con tributions/4871/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4871/ END:VEVENT BEGIN:VEVENT SUMMARY:Electrical Resistivity and magnetic properties of (Ce1xTbx) Pt2 Si2 (0  x  1) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4872@events.saip.org.za DESCRIPTION:Speakers: zwelithini Mahlubi (University of the western cape)\ nMeasurements of X-rays diffraction (XRD)\, electrical resistivity (T)\ , magnetic susceptibility (T)\, and magnetization (µ0H) are repeate d for the pseudo-ternary alloy (Ce1xTbx) Pt2Si2. XRD results for all th e compositions of (Ce1xTbx) Pt2Si2 system indicate a tetragonal CaBe2Ge 2-type structure. (T) results indicate evolution from coherent Kondo la ttice to incoherent single ion Kondo scattering with increase in Tb conten t up to x=0.8\, and followed by a metallic behavior above x = 0.8. (T) data at high temperatures follow the Currie-Weiss relation for all alloy c ompositions and give effective moment value µeff which increases graduall y from value of 2.54 µB for Ce3+- ion to the expected values of 9.72 µB for Tb3+ -ion. The alloys compositions in the concentration range of 0.7  x 1 exhibit antiferromagnetism and the low temperature (T) data were used to find the Neel temperature TN as a function of x. (µ0H) da ta are presented for all investigated compositions.\n\nhttps://events.saip .org.za/event/7/contributions/4872/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4872/ END:VEVENT BEGIN:VEVENT SUMMARY:How do the features of experiments influence the experience of fir st year physics students? DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5048@events.saip.org.za DESCRIPTION:Speakers: Johan van der Merwe (Military Academy)\nThe Faculty of Military Science of Stellenbosch University presents an Algebra-based P hysics course to first year students. The practical component comprises o f a range of experiments that differ significantly in characteristics. Qu estionnaires are yearly completed by the students to evaluate the theoreti cal and practical components of this course. This paper will explore some of the results of these surveys\, focusing especially on the experience o f the student with regards to the features of experiments that are present ed.\n\nhttps://events.saip.org.za/event/7/contributions/5048/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5048/ END:VEVENT BEGIN:VEVENT SUMMARY:Decomposition of the field within an apertured plano-concave reson ator DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4873@events.saip.org.za DESCRIPTION:Speakers: Darryl Naidoo (Council for Scientific and Industrial Research)\nA method of experimentally decomposing a field within an apert ured plano-concave resonator cavity into a forward propagating field (plan e to concave) and a backward propagating field (concave to plane) is prese nted. The use of an intra-cavity aperture which is a simple method of lase r beam shaping is a means of mode selection as higher-order modes are acti vely discriminated. This apertured cavity is modelled by two fundamental r esonator theories\, namely\, Fox-Li analysis and Laguerre-Gaussian decompo sition where they are used in the determination of the respective beam pro files at a specific plane. These theories traditionally differ from one an other for an apertured cavity where the Gaussian beam within the cavity is truncated. A preliminary set-up is characterized for Gaussian propagation in an attempt to verify that the cavity is viable and accurate. A compari son of experimental data with the theories is presented.\n\nhttps://events .saip.org.za/event/7/contributions/4873/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4873/ END:VEVENT BEGIN:VEVENT SUMMARY:Generation of a Laguerre-Gaussian TEM01 mode in a monolithic micro chip laser DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4874@events.saip.org.za DESCRIPTION:Speakers: Darryl Naidoo (Council for Scientific and Industrial Research)\nWe explore a method in the selection of a specific higher-orde r mode through judicious shaping of the pump light to create a high modal overlap with the desired mode. To demonstrate this principle\, we create a donut-shaped pump profile in the focal plane of a converging lens by use of a beam shaping element. This pump profile is used to longitudinally pum p a monolithic microchip laser and a plano-concave resonator cavity where we achieve a TEM01 output with powers of ~12 mW and ~14 mW at slope effici encies of 17% and 21% respectively. In both cases the modal purity is high with a beam quality factor of ~2. Diffractive pump shaping of this form i s advantageous as it allows for high pump intensity even with low pumping powers\, thus ensuring sufficient gain is achieved for laser oscillation.\ n\nhttps://events.saip.org.za/event/7/contributions/4874/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4874/ END:VEVENT BEGIN:VEVENT SUMMARY:Solar-cycle dependent relationship between cosmic-ray intensity an d the heliospheric current sheet tilt angle DTSTART;VALUE=DATE-TIME:20110715T093000Z DTEND;VALUE=DATE-TIME:20110715T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4875@events.saip.org.za DESCRIPTION:Speakers: KATLEGO MOLOTO (NORTH WEST UNIVERSITY)\nWe investiga te cosmic-ray intensities as measured by neutron monitors as function of t he corresponding heliospheric current sheet tilt angle. Three solar cycles with three changes in solar magnetic polarity are examined. The results a re compared to predictions of cosmic-ray modulation models that include dr ift effects. The intensity-tilt plots produce open loops with clockwise ro tations for solar cycles 21 and 23 and with anticlockwise rotation for sol ar cycle 22\, as predicted by drift models. However\, the observed intensi ty-tilt loops for cycles 21 and 23 are larger than the loop for cycle 22 c ontrary to the drift model predictions. To explain this difference we use the time dependence of the tilt angle and show that the loops then become very similar. We show that from this renormalization\, the approximate tim e it takes for particles to travel from the termination shock to Earth can be estimated\, and that the time is consistent with model predictions.\n\ nhttps://events.saip.org.za/event/7/contributions/4875/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4875/ END:VEVENT BEGIN:VEVENT SUMMARY:Comparison of thermal and structural Properties of HRT nuclear fue l Composite and nuclear graded graphite DTSTART;VALUE=DATE-TIME:20110715T091500Z DTEND;VALUE=DATE-TIME:20110715T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4876@events.saip.org.za DESCRIPTION:Speakers: phathutshedzo murovhi (university of pretoria)\nGrap hite composite comprising of 64 wt% of natural graphite\, 16 wt% of synthe tic graphite and 20 wt% of phenolic resin binder heat treated at 1800 0C h ave been used to encapsulate the TRISO coated fuel particles in the PBMR a nd considered to serve in the initial state of neutron moderation as well as heat conduction. The structural and thermal properties of the pristine and irradiated samples will be compared to IG110 nuclear graphite so as to check its degree of applicability in the nuclear reactor. The structure a nd disorder of both materials is investigated using X-ray diffraction (XRD ) and Raman spectroscopy\, while Low and high temperature thermal and elec trical properties is investigated using physical property measuring system (PPMS) and laser flash analyser (LFA) respectively.\n\nhttps://events.sai p.org.za/event/7/contributions/4876/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4876/ END:VEVENT BEGIN:VEVENT SUMMARY:Phase calibration of the Shack-Hartmann wavefront sensor using a p hase-only spatial light modulator DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4877@events.saip.org.za DESCRIPTION:Speakers: Cosmas Mafusire (CSIR National Laser Centre)\nThe ph ase measurements of a Shack-Hartmann wavefront sensor are calibrated. The process involves creating holograms of known amounts of individual phase a berrations on a spatial light modulator and reflects an aberration free la ser beam off of the modulator’s liquid crystal display thereby giving th e beam that aberration. The beam is then relayed onto the sensor for direc t measurement. The results show that the method is accurate to the extent that the results accurately replicate the response of the wavelength calib ration of the spatial light modulator.\n\nhttps://events.saip.org.za/event /7/contributions/4877/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4877/ END:VEVENT BEGIN:VEVENT SUMMARY:Analysis of aberrations generated in aerodynamic random media usin g computational fluid dynamics DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4878@events.saip.org.za DESCRIPTION:Speakers: Cosmas Mafusire (CSIR National Laser Centre)\nMedia generated by random mixing of hot and cold gases can be of great importanc e for laser beam propagation. However\, it is not always possible to repre sent the media’s behaviour using simple formulation. This opens the door for the use of numerical methods. We show that\, for aerodynamic media\, we can use computational fluid dynamics (CFD) software to acquire density distribution data to characterize both local and overall behaviour of the media. Using the Gladstone-Dale law\, we acquired refractive index distrib ution which we use to calculate Zernike coefficients from the respective l ocal phase values at various sections of the media. We show that once we h ave this data\, we can simulate the propagation of laser beams of various shapes in such media. We apply the method to analyse a spinning pipe gas l ens (SPGL) which is a horizontal pipe whose walls are heated rotated along its axis. We show that the results from the model agree with the SPGL exp erimental results.\n\nhttps://events.saip.org.za/event/7/contributions/487 8/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4878/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and photoluminescence studies of (Ba1-xSrx)Al2O4:Eu2+\;Nd3+ prep ared by combustion method DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4879@events.saip.org.za DESCRIPTION:Speakers: Mantwa Annah Lephoto (University of The Free State)\ nBarium-substituted phosphor powders of (Ba1-xSrx)Al2O4:Eu2+ \;Nd3+ compos ition were prepared by combustion method at an initiating temperature of 5 000C\, using urea as reducer. The powders were then annealed at higher tem peratures of 8000C and 10000C for 3 hours. Their crystallinity and phase w ere characterized by x-ray diffraction (XRD). The x-ray diffraction shows that the crystallinity of (Ba1-xSrx)Al2O4:Eu2+\;Nd3+ at (x=0) greatly impr oved after annealing at the higher temperature of 10000C and shows the hex agonal structure that closely correspond with the JCPDS data (PDF#17-0306) . The morphology of the (Ba1-xSrx)Al2O4:Eu2+\;Nd3+ composition were invest igated using Scanning Electron Microscopy (SEM). The effect of varying th e Ba/Sr concentration on the thermoluminescence (TL) glow curves was inves tigated using the Thermoluminescence Reader (Integral-Pc Based) Nucleonix TL 1009I. Photoluminescence (PL) properties of all phosphor samples were i nvestigated by measuring their emission spectra using a 325nm He-Cd laser. For the as-prepared phosphor samples\, the sample with x=0 (BaAl2O4:Eu2+\ ;Nd3+showed a much higher intensity compared to both the sample with x=1 ( SrAl2O4:Eu2+\;Nd3+and the mixed composition of the two. (BaAl2O4:Eu2+\;Nd3 +(x=0) and SrAl2O4:Eu2+\;Nd3+ (x=1)showed a broad emission at 505nm and 52 2nm respectively while the mixed composition showed two peaks at 447nm and 517nm. The broad emission peaks attributed to 4f65d1-4f 7 transitions of Eu2+ were obtained. Their phosphorescence was investigated by using the fl uorescence Cary eclipse spectrophotometer coupled with a xenon lamp. Phosp horescence show higher luminescence for (Ba1-xSrx)Al2O4:Eu2+\;Nd3+at (x=0) .\n\nhttps://events.saip.org.za/event/7/contributions/4879/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4879/ END:VEVENT BEGIN:VEVENT SUMMARY:Mathematical Modeling of a Concentrator-Diffuser Wind Energy syste m DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4880@events.saip.org.za DESCRIPTION:Speakers: Peace-Maker Masukume (University of Fort Hare\, Depa rtment of Physics)\n\nOptimization of power output from ducted wind turbin es has been the focus of many researchers in recent years. However many ha ve dwelt much on diffusers than concentrators (nozzles) . Diffusers are ch aracterized by flow separation due to deceleration of the fluid and this l eads to energy dissipation. On the other hand a concentrator is accompanie d by a favourable pressure gradient which stabilizes the boundary layer a nd thus minimizes energy dissipation. This study presents a mathematical m odel of a concentrator-Diffuser system which has been developed to optimiz e the power output of a low speed wind turbine. Optimization of the inclin ation angles of both the concentrator and the diffuser\, ducts exit ratios and the reduction in backpressure were found to augment the mass flow a t the rotor due to increased pressure drop and reduction in flow separatio n. It is illustrated that Power coefficients (Cp) of about 0.65 are achiev able.\n\nhttps://events.saip.org.za/event/7/contributions/4880/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4880/ END:VEVENT BEGIN:VEVENT SUMMARY:Using classroom response systems as a tool to enhance interactive engagement and formative assessment in the classroom DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4881@events.saip.org.za DESCRIPTION:Speakers: Mark Herbert (University of the Western Cape)\nEduca tional technology in the form of classroom response systems (clickers)have become a tool in classroom instruction. In the classroom the clickers are used to promote interactive student engagement and immediate assessment o f student understanding. \nThe paper reports on a study using clickers as well as flash cards (a low tech version of the clicker) as a tool to enhan ce interactive engagement and formative assessment in the Extended Curricu lum Programme (ECP) Physics at UWC. The results suggest that clickers may be a useful tool for the instructor to engage students in class discussion s and to monitor their understanding and for students to have immediate fe edback on their own progress. Overall the students’ attitudes towards cl ickers were positive. They enjoyed the interactive nature of the clickers because of their familiarity with mobile phones and digital media. They al so felt the anonymity associated with the assessment results decreased pee r pressure.\n\nhttps://events.saip.org.za/event/7/contributions/4881/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4881/ END:VEVENT BEGIN:VEVENT SUMMARY:Quasifree alpha cluster knockout studies DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4882@events.saip.org.za DESCRIPTION:Speakers: Anthony Cowley (Stellenbosch University)\nCluster-li ke structures in the shell-model description of the ground state of nuclei can be conveniently studied by means of knockout reactions. Of these the (p\, p alpha) reaction is perhaps the simplest\, especially from the viewp oint of the tractability of theoretical calculations used to interpret exp erimental results. The distorted wave impulse approximation (DWIA) is a ve rsatile theory which is applicable to a knockout reaction. Fortunately its results appear to be reasonably insensitive to uncertainties in the exac t ingredients\, such as distorting optical potentials\, which are obtained from unrelated elastic scattering studies. It will be shown that a number of surprisingly simple approximations in the DWIA hold for alpha-cluster knockout from light nuclei. Furthermore\, results for a medium-mass nuclea r target such as 40Ca are also consistent with expectation. Extracted spec troscopic factors are in reasonable agreement with shell-model estimates.\ n\nhttps://events.saip.org.za/event/7/contributions/4882/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4882/ END:VEVENT BEGIN:VEVENT SUMMARY:Batch anaerobic co-digestion of cow dung and donkey manure DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4883@events.saip.org.za DESCRIPTION:Speakers: Patrick Mukumba (University of Fort Hare)\nBiogas fr om anaerobic digestion can be a solution to current and future energy need s in South Africa. One option for improving biogas yield of anaerobic dige stion of organic matter is co-digestion. Cow dung and donkey manure were c o-digested together at different mixing ratios. Total Solids (TS) and vola tile solids (VS)\, ammonia-nitrogen\, pH\, alkalinity\, volatile fatty aci ds (VFA) and chemical oxygen demand (COD) were determined by using the sta ndard methods of the American Public Health Association (ALPHA). The press ure of the biogas was measured daily by means of a pressure gauge fixed on top on the batch biogas digester. Methane and carbon dioxide contents in the biogas were sensed by non-dispersive infra red sensors. Palladium/Nick el sensors were used for sensing hydrogen and hydrogen sulphide in biogas. Highest biogas yield was obtained for a mixing ratio of 50% cow dung to 5 0% donkey manure\, however lowest biogas yield was obtained from cow dung. For all the substrates the gas yield increased with time and then attains a constant value. However the co-digestion of cow dung and donkey manure attained maximum gas yield on 24th day while for cow dung it was on 28th d ay and for donkey manure it was on 26th day. Co-digestion of cow dung and donkey manure increased the gas yield by about 43%. Pure samples produced less biogas than co-digested samples. There was a strong positive relatio nship between gas production and % of co-substrates used (R2 = 0.999). The biogas produced from co-digestion can be a solution to lack of energy in rural areas in Eastern Cape Province of South Africa where plenty of donke ys and cattle are kept.\n\nhttps://events.saip.org.za/event/7/contribution s/4883/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4883/ END:VEVENT BEGIN:VEVENT SUMMARY:Low-temperature Electrical conductivity and Magneto-resistance of Reduced Graphene Oxide Layers DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4884@events.saip.org.za DESCRIPTION:Speakers: Ross McIntosh (WITS)\nWe report on the electrical tr ansport properties of graphene oxide (GO) and GO reduced using an organic acid (RGO). Two terminal GO and RGO devices were assembled via dielectroph oresis. The current-voltage characteristics of these devices were studied at low temperatures (77 K to 300 K) using a micromanipulated probe station . The I-V characteristics for RGO devices were found to be almost linear\, indicating metallic behavior. This is in contrast to reports by other gro ups who have suggested variable range hopping (both Mott and Efros-Shklovs kii) or space charge limited conduction. The density of states at the Ferm i level in RGO was found to be an order of magnitude greater than that of GO. This was confirmed by four probe low temperature RT data (3 K to 300 K) which showed a T^2 dependence. Further support for the metallic nature of RGO was confirmed with magnetoresistance data at low temperatures (from 3 K) and fields up to 12 T. We believe reduction with organic acid does n ot introduce a high defect density\, unlike the conventional reducing agen t hydrazine. The superb electronic properties of RGO synthesized with this new method could find use in high-speed spintronic and magnetic memory de vices.\n\nhttps://events.saip.org.za/event/7/contributions/4884/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4884/ END:VEVENT BEGIN:VEVENT SUMMARY:The neutron superfluid in the interior of neutron stars. DTSTART;VALUE=DATE-TIME:20110714T070000Z DTEND;VALUE=DATE-TIME:20110714T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4885@events.saip.org.za DESCRIPTION:Speakers: Garreth Kemp (University of Johannesburg)\nIn his wo rk on superfluid helium\, Feynman gave both qualitative and quantitative d escriptions of the excitation spectrum of superfluid helium. I briefly rev iew Feynman's approach to superfluid helium and assess the applicability o f this theory to neutron star interiors.\n\nhttps://events.saip.org.za/eve nt/7/contributions/4885/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4885/ END:VEVENT BEGIN:VEVENT SUMMARY:Antimatter production in pp and in heavy-ion collisions at ultrare lativistic energies DTSTART;VALUE=DATE-TIME:20110715T091500Z DTEND;VALUE=DATE-TIME:20110715T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5059@events.saip.org.za DESCRIPTION:Speakers: Jean Cleymans (University of Cape Town)\nOne of the striking features of particle production at high beam energies\nis the nea r equal abundance of matter and antimatter in the central rapidity region. \nIn this paper we would like to study how this symmetry is \nreached as the beam energy is increased. In particular \nwe quantify explicitly the e nergy dependence of the approach to matter/antimatter \nsymmetry. \nExpect ations are presented for the production of more complex forms of\nantimatt er like antihypernuclei.\n\nhttps://events.saip.org.za/event/7/contributio ns/5059/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5059/ END:VEVENT BEGIN:VEVENT SUMMARY:Enhanced green emission from UV down-converting Ce3+-Tb 3+ co -activated ZnAl2O4 phosphor DTSTART;VALUE=DATE-TIME:20110714T070000Z DTEND;VALUE=DATE-TIME:20110714T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4888@events.saip.org.za DESCRIPTION:Speakers: Kamohelo George Tshabalala (University of the Free S tate)\nRare–earths (Tb3+ or Ce3+) doped zinc aluminate (ZnAl2O4) nanocry stals were successfully prepared by a modified combustion method using ure a (CH4N2O\, 99–99.5%) as fuel and characterized to investigate down-conv erted emission by energy transfer from Ce3+ to Tb3+ . The post-preparatio n annealing of the samples was carried out in a reducing atmosphere of 4%H 2/96%N2 mixture at an elevated temperature of 7000C for 4 hours. This was meant to reduce non-emitting Ce4+ to Ce3+ and also to improve crystallini ty. As confirmed by X-ray diffraction (XRD) data\, the materials were hig hly crystalline and the XRD patterns were consistent with the closed-packe d face centered cubic spinel structure of ZnAl2O4. The photoluminescence excitation and photoluminescence data collected when ZnAl2O4:Ce3+\,Tb3+ sa mples\, with different concentrations of Ce3+ and Tb3+ ions\, were excited at different wavelengths (230―325nm) showed that green emission of Tb3 + was sensitized by Ce3+\, i.e. there was energy transfer from Ce3+ to Tb 3+ resulting in improvement of green emission due to the 5D4 → 7F5 trans itions of Tb3+ ions. This study therefore\, sets out to discuss the sensi tizing effect of Ce3+ and the effect of post annealing on the structure of ZnAl2O4:Ce3+\,Tb3+. The results indicate the potential of the phosphor p owders for applications in luminescent display panels and further developm ent as UV down-converters for improved performance of conventional photovo ltaic cells.\n\nhttps://events.saip.org.za/event/7/contributions/4888/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4888/ END:VEVENT BEGIN:VEVENT SUMMARY:High Performance Computing in Solid State Physics DTSTART;VALUE=DATE-TIME:20110712T120000Z DTEND;VALUE=DATE-TIME:20110712T124000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4889@events.saip.org.za DESCRIPTION:Speakers: Enrico Lombardi (UNISA)\nhttps://events.saip.org.za/ event/7/contributions/4889/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4889/ END:VEVENT BEGIN:VEVENT SUMMARY:Using Python in Computational Physics DTSTART;VALUE=DATE-TIME:20110712T100000Z DTEND;VALUE=DATE-TIME:20110712T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4890@events.saip.org.za DESCRIPTION:Speakers: Moritz Braun (University of South Africa)\nhttps://e vents.saip.org.za/event/7/contributions/4890/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4890/ END:VEVENT BEGIN:VEVENT SUMMARY:The structure and flexibility of the photosynthetic machinery in p lants and algal cells DTSTART;VALUE=DATE-TIME:20110714T120000Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4891@events.saip.org.za DESCRIPTION:Speakers: Gyözö Garab (Biological Research Center\, Hung. Ac ad. Sci.)\nIn order to increase the efficiency of light capturing\, all ph otosynthetic organisms capable of oxygen evolution have evolved multilamel lar membrane systems of the thylakoid membranes\, flat closed bilayer lipi d vesicles\, which accommodate the densely packed protein complexes in ord ered\, often semi-crystalline arrays. This highly organized system with su bstantial stability exhibit remarkable structural and functional flexibili ty at different levels of complexity\, which enables these organisms to ca rry out rapid adaptations in response to changes in the environmental cond itions. In this talk\, my attention will be focused on the macro-organizat ion of the protein complexes - and their role in determining the multilame llar membrane ultrastructure\, and will show mechanisms that allow well id entifiable reversible reorganizations in the internal order of the complex es and in the membrane system. \nWe have shown that the main chlorophyll a /b light harvesting complexes of photosystem II (LHCII) form chirally orga nized macrodomains both in vivo and in vitro. These macrodomains\, togethe r with stacking\, play important roles in the lateral segregation (sorting ) of the two photosystems between the granum and stroma membranes\, and th us in the assembly and stabilization of the membrane ultrastructure [Must árdy and Garab\, 2003\, TIPS 8: 117]\, which has been determined by elect ron tomography [Mustárdy et al.\, 2008\, Plant Cell 20: 2552]. The macrod omains also possess a remarkable structural flexibility\, being capable of undergoing light-induced reversible reorganizations\, that are largely in dependent of the photochemical activity of thylakoids\, and are approximat ely linearly proportional to the light intensity above the saturation of p hotosynthesis – an important\, unique feature with respect to protection of plants against excess excitation [Barzda et al.\, 1996\, Biochemistry 35: 8981]. This type of reorganizations include (i) unstacking of membrane s\, (ii) a lateral desorganization of the macrodomains\, and (iii) monomer ization of the LHCII trimers [Dobrikova et al.\, 2003\, Biochemistry 42: 1 12726]. Isolated\, lipid-enriched\, loosely stacked lamellar aggregates of LHCII also possess the ability to undergo similar reorganizations\, accom panied by fluorescence quenching transients. These structural transitions are accounted for by a biological thermo-optic mechanism: fast thermal tra nsients\, arising from dissipated excitation energy\, which can lead to el ementary structural transitions in the close vicinity of the site of dissi pation due to the presence of ‘built-in’ thermal structure-instabiliti es [Cseh et al.\, 2005\, Photosynth Res 86: 263]. They lend local structur al flexibility to molecular (macro)assemblies of high stability\, and appe ar to be involved in important enzymatic reactions\, as revealed in other laboratories [Zer et al.\, 1999\, PNAS 96: 8277\, Yang et al.\, 2000\, FEB S Lett 466: 385]. The lipid content of the membranes is self regulated by non-bilayer lipids\, via their segregation capability. By this means they safe-guard the high protein content of the thylakoid membranes and\, at th e same time\, they contribute to the structural flexibility of the membran e system [Garab et al.\, 2000 Trends Plant Sci. 5:489\; Krumova et al.\, 2 008\, Biochim. Biophys. Acta\, Biomembranes 1778: 997].\nIn order to chara cterize the multilamellar membrane system\, we determined characteristic r epeat distances of the photosynthetic membranes in living cyanobacterial a nd eukaryotic algal cells and in intact thylakoid membranes isolated from higher plants with time-resolved small-angle neutron scattering (SANS). It has been shown how the different organization of multilamellar membrane s ystem can be correlated with different compositions and protein macro-orga nizations in different organisms. SANS also revealed small (~10 Å) but we ll identifiable light-induced reversible changes in these organisms\, obse rved for the first time in living cyanobacteria and diatom cells. These re organizations\, which could be recorded with time resolutions of several s econds and minutes\, appear to be associated with functional changes in vi vo [Nagy et al.\, 2011\, Biochem J. 436: 225].\n\nhttps://events.saip.org. za/event/7/contributions/4891/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4891/ END:VEVENT BEGIN:VEVENT SUMMARY:Top Down Causation and the Emergence of Complexity DTSTART;VALUE=DATE-TIME:20110713T073000Z DTEND;VALUE=DATE-TIME:20110713T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4892@events.saip.org.za DESCRIPTION:Speakers: George Ellis (UCT)\nThe emergence of true complexity (such as life and the human brain) on the basis of the underlying physics is enabled by top-down processes in the hierarchy of complexity. This tal k will propose that there are five different types of top down causation t hat can all be shown by many examples to exist and be causally effective i n the real world. There is room for them at the bottom both because of sta tistical and quantum randomness at lower levels\, and because the nature o f lower level elements is altered by top down effects. While the evidence for top-down effects is very strong in the life sciences\, computers\, and engineering systems\, there may also be cases in physics where their infl uence is significant\; examples are the arrow of time\, the origin of iner tia\, and both state preparation and decoherence in quantum theory.\n\nhtt ps://events.saip.org.za/event/7/contributions/4892/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4892/ END:VEVENT BEGIN:VEVENT SUMMARY:Building a National Digital Library for Computational Physics Educ ation at All Levels DTSTART;VALUE=DATE-TIME:20110713T140000Z DTEND;VALUE=DATE-TIME:20110713T150000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4893@events.saip.org.za DESCRIPTION:Speakers: Wolfgang Christian (Davidson College)\nOver the past dozen years we have produced some of the most widely used interactive com puter-based curricular materials for the teaching of introductory and adva nced physics courses. These materials are now hosted on and distributed fr om the Open Source Physics (OSP) Collection of the ComPADRE National Scien ce Digital Library. This talk outlines the tripartite integration of ComPA DRE with the Easy Java Simulations modeling and authoring tool and the OSP code library. The pedagogical and technical features of this learning pla tform and our current efforts to align this material with United States na tional and state standards for science teaching are described. The Open So urce Physics Collection is available on the: http://www.compadre.org/osp/ Partial funding for this work was obtained through NSF grants DUE-0442581 and DUE-0937731.\n\nhttps://events.saip.org.za/event/7/contributions/4893/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4893/ END:VEVENT BEGIN:VEVENT SUMMARY:The Photochemistry and Photophysics of DNA DTSTART;VALUE=DATE-TIME:20110714T073000Z DTEND;VALUE=DATE-TIME:20110714T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4894@events.saip.org.za DESCRIPTION:Speakers: Anthony Parker (Central Laser Facility\,)\nOur DNA i s constantly being subjected to chemical and physical changes. Understandi ng the molecular dynamics of this biological stress and how it leads to mu tation and the onset of cancer represents a key scientific challenge. Duri ng evolution cells have evolved an enormous array of weaponry to minimise the risks of mutation\, however\, under certain conditions things can go b adly wrong. A primary example is the over exposure of sunlight to skin. Th e initial photophysical processes that take place following from the initi al absorption of a photon to chemical reaction occur in the ultrafast (fem toseconds to picoseconds) time domain. As such studying these reactions fa lls into the world of ultrafast laser spectroscopy and both linear (pump a nd probe) and non-linear (2D-IR\, stimulated fluorescence) methods are uti lised. The major factor of the components that make up DNA\, the four nucl eic acid bases\, that gives them exceptional photo-stability is the fact t hat they posses exceptional short lifetimes (ps). The presentation will in troduce DNA photochemistry and photophysics\, the technology used to inves tigate them and emphasise how time-resolved infrared spectroscopy can be a pplied to gain insights into structural changes occurring in the ultrafast molecular time frame.\n\nhttps://events.saip.org.za/event/7/contributions /4894/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4894/ END:VEVENT BEGIN:VEVENT SUMMARY:Molecular Dynamics Simulations : An experimental laboratory for a computational physicist. DTSTART;VALUE=DATE-TIME:20110712T090000Z DTEND;VALUE=DATE-TIME:20110712T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4895@events.saip.org.za DESCRIPTION:Speakers: Debashish Mukherji (Max-Planck Institute for Polymer Research)\nhttps://events.saip.org.za/event/7/contributions/4895/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4895/ END:VEVENT BEGIN:VEVENT SUMMARY:Easy Java Simulations: A Computational Tool For Science Education and Research DTSTART;VALUE=DATE-TIME:20110712T074500Z DTEND;VALUE=DATE-TIME:20110712T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4896@events.saip.org.za DESCRIPTION:Speakers: FRANCISCO ESQUEMBRE (Universidad de Murcia)\nhttps:/ /events.saip.org.za/event/7/contributions/4896/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4896/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational Physics And The Physics Curriculum DTSTART;VALUE=DATE-TIME:20110712T064500Z DTEND;VALUE=DATE-TIME:20110712T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4897@events.saip.org.za DESCRIPTION:Speakers: Wolfgang Christian (Davidson College)\nhttps://event s.saip.org.za/event/7/contributions/4897/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4897/ END:VEVENT BEGIN:VEVENT SUMMARY:Ion irradiation effects on the formation of metal nanoparticles in crystals DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4898@events.saip.org.za DESCRIPTION:Speakers: Anna Kozakiewicz (Wits)\nMetal nanoparticles (MNP) w ere synthesized by room temperature ion implantation of high fluences (fro m 6x1016 to 5x1017 cm-2) of 150 keV Ag and 15 -22 MeV Au ions into Al2O3 a nd MgO single crystals.\nOptical absorption (OA) spectra show surface plas mon resonance (SPR) bands characteristic of the implanted metal ions. Upon annealing (300°-1200°C) the optical response of the metal nanostructure s changes\, related directly to their morphology\, shape and size. High re solution transmission electron micrographs indicate that the particles are often crystalline. The implanted ions profiles were obtained from 1.6 MeV He+ Rutherford Backscattering (RBS) for the silver implanted substrates a nd High Resolution Transmission Electron Microscopy (HRTEM)\, revealed bur ied layers of implanted ions.\n\nhttps://events.saip.org.za/event/7/contri butions/4898/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4898/ END:VEVENT BEGIN:VEVENT SUMMARY:Laser Irradiation: A Complementary Treatment for Wounds? DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4899@events.saip.org.za DESCRIPTION:Speakers: Nicolette Houreld (Laser Research Centre\, Universit y of Johannesburg)\nSince the invention of the laser\, its application in the health sector has been studied and in an attempt to discover effective alternative treatments\, Low Level Laser Therapy (LLLT)\, commonly known as biostimulation or photo-biostimulation\, has emerged. This therapy has been successfully used both in in vitro and in vivo studies in wound heali ng. Although this therapy is in use worldwide\, the full mechanisms of act ion are not fully understood. Various cell culture models\, such as wounde d\, diabetic wounded and hypoxic\, have been exposed to visible and infra- red laser light and the effect on cell migration\, cell survival\, prolife ration\, cytotoxicity\, mitochondrial responses\, nitric oxide\, secondary messengers\, DNA damage and pro-inflammatory cytokines have been studied. Laser irradiation at the correct wavelength and fluence has shown to have a positive effect on stressed cells in vitro. There is an increase in mig ration\, survival and proliferation\, mitochondrial activity\, nitric oxid e and secondary messengers. A decrease in cytotoxicity\, DNA damage and pr o-inflammatory cytokines is also seen. LLLT offers an alternative wound he aling therapy. At a biochemical level there is a positive effect on cells\ , with stressed cells being pushed into cell survival pathways.\n\nhttps:/ /events.saip.org.za/event/7/contributions/4899/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4899/ END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic behavior of the Cr-Al alloys system round the triple poin t concentration DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4901@events.saip.org.za DESCRIPTION:Speakers: Aletta Prinsloo (Department of Physics\, University of Johannesburg)\nRecent measurements on an antiferromagnetic (AFM) Cr0.97 8Al0.022 alloy single crystal suggest that the triple point (TP) on the ma gnetic phase diagram (MPD) might be a special type of critical point. This suggestion is further investigated here through electrical resistivity an d specific heat measurements on a series of Cr1-xAlx alloy single crystals with x around the triple point concentration (xc). Néel temperatures (TN )\, obtained from the resistivity measurements\, indicate that xc ≈ 0.02 is situated at the position of a rather sharp and deep minimum of the AFM -paramagnetic phase transition line on the T - x MPD. The minimum is deepe r than that generally accepted for this alloy system. The Sommerfeld elect ronic specific heat coefficient\, obtained from the specific heat measurem ents\, shows an interesting aspect. The Sommerfeld electronic specific hea t coefficient as function of Al concentration peaks relatively sharply at xc\, an aspect for which the explanation is two-fold: either the phase bou ndary line separating the incommensurate (I) and commensurate (C) spin-den sity-wave (SDW) phases on the MPD\, starts at the TP and reaches T = 0 K v ertically below this point\, or the TP itself is situated close to T = 0 K . It is reasoned that the latter seems a more likely possibility\, making this system unique in exhibiting a critical point at 0 K where ISDW\, CSDW and paramagnetic (P) phases coexist.\n\nhttps://events.saip.org.za/event/ 7/contributions/4901/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4901/ END:VEVENT BEGIN:VEVENT SUMMARY:Laser-induced breakdown spectroscopy for monitoring heavy metals i n soils DTSTART;VALUE=DATE-TIME:20110715T091500Z DTEND;VALUE=DATE-TIME:20110715T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4902@events.saip.org.za DESCRIPTION:Speakers: Abayneh Ambushe (CSIR and Tshwane University of Tech nology)\nThe growing social concern for environmental protection and human health has driven widespread interest in analysis of heavy metals in the various environmental compartments including soil. Soil is unanimously con sidered as one of the recipients of heavy metals released by several human activities. Rapid analysis of heavy metals in soil is an important factor in modelling the effect of industrial pollution on agricultural soil. Qua ntification of heavy metals in natural and polluted soils is generally con ducted using flame-atomic absorption spectrometry (F-AAS)\, graphite furna ce-atomic absorption spectrometry (GF-AAS)\, inductively coupled plasma-op tical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) after appropriate sample pre-treatment. The use of l aser-induced breakdown spectroscopy (LIBS) has emerged as a good alternati ve technique for quantitative analysis of heavy metals in environmental ma trices. There is no need for pre-treatment of the sample in LIBS. Furtherm ore\, the speed of analysis is far superior to other techniques\, and the technique may be developed for in situ analysis. In this work we demonstra te the feasibility of LIBS for detection and quantification of heavy metal s in soils and sediments and identify best parameters for such analysis.\n \nhttps://events.saip.org.za/event/7/contributions/4902/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4902/ END:VEVENT BEGIN:VEVENT SUMMARY:Theoretical study on possible structures for crystalline silicon d icarbide DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4903@events.saip.org.za DESCRIPTION:Speakers: Richard Andrew (University of Pretoria)\nSi\, C and SiC are very well known technologically important materials. They have be en extensively studied in their multitude of structures and polytypes\, bu t there is a surprising dearth of information for off-50:50 compounds invo lving Si and C. What are the possible stable structures for such compound s? Using ab initio techniques\, we investigate two proposed structures fo r crystalline SiC2: cubic pyrite and a tetragonal glitter structure. We f ind both structures to be metallic and mechanically stable. From their el astic properties\, we make an assessment of the hardness of both structure s. We find the tetragonal glitter phase to be lowest in energy with a pre ssure transition from the glitter to pyrite phase at 24.7 GPa.\n\nhttps:// events.saip.org.za/event/7/contributions/4903/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4903/ END:VEVENT BEGIN:VEVENT SUMMARY:Learners’ Understanding of Ammeter and Voltmeter in a DC Schemat ic Circuit DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4904@events.saip.org.za DESCRIPTION:Speakers: Ramaite Thomas Mautjana (NMISA and University of Lim popo)\nThis study explores learners’ knowledge of measuring instruments (Ammeter and Voltmeter) in a direct current resistive circuit. It investig ates learners’ understanding of how instruments should be connected and why they have to be connected in a particular way. Ammeter and voltmeter a re used to determine the behavior of a circuit by indicating the readings of current and voltage\, respectively. An educator sees an ammeter as an “invisible” component because it does not change the characteristics o f a circuit. However\, a learner views an ammeter differently. A paper-and -pencil questionnaire was administerd to grade 12 learners. Group intervie ws were conducted in order to validate and support the results of the ques tionnaire. The results indicate that learners lacked the basic understand ing of the role played by meters (why we need them in electrical circuits) . It was also evident that due to lack of practical experience with real circuits\, learners did not know how these meters should be connected. Thi s paper will report on some of the results and their implications for teac hing/learning of electricity.\n\nhttps://events.saip.org.za/event/7/contri butions/4904/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4904/ END:VEVENT BEGIN:VEVENT SUMMARY:Determining optical performance and current generation of a CPV d ue to intensity distribution DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4905@events.saip.org.za DESCRIPTION:Speakers: Ross Schultz (Nelson Mandela Metropolitian Universit y)\nHigh concentration photovoltaic (CPV) systems utilize non-imaging opti cs to concentrate and distribute the solar flux uniformly onto a solar rec eiver to achieve maximum performance and power output from a CPV module. H owever\, in many cases due to mechanical misalignment\, tracker error and imperfections in the optical material\, the optimum performance of the mod ule is compromised.\nA LabVIEW programme employing visualization was used to determine the main contributing factor for current generation\, i.e. po sition and intensity of the distribution. The topography was determined by multiple roster scans with a spectroradiometer and optical fiber in the p lane of the reflective secondary’s aperture where the cell would be plac ed. The results showed different currents been generated at different poin ts on the cell surface. These results were put into a CPV cell current-vol tage (I-V) characteristic simulator to extract I-V curve at each point. Th ese were then compared with measured I-V curves obtained from the CPV syst em. The results showed that there was a non-uniform current densities (Jsc ) distribution due to non-uniform spectral and intensity distribution acro ss the cell surface.\n\nhttps://events.saip.org.za/event/7/contributions/4 905/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4905/ END:VEVENT BEGIN:VEVENT SUMMARY:Effect of pH on the morphology and orientation of Fe2O3 nanostruct ures grown using aqueous chemical growth DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4906@events.saip.org.za DESCRIPTION:Speakers: Cebo Ndlangamandla (Student)\nFe2O3 nanostructures w ere synthesized for various pH values on Corning glass substrates by aqueo us chemical growth (ACG) using a solution of ferric chloride (FeCl3). It w as found that increasing the pH from 1.16 to 5.0 of the solution significa ntly leads to a modification of the Fe2O3 morphology or orientation from r andomly parallel needle shaped rod-like to randomly perpendicular rectangu lar structure on to a substrate.\n\nhttps://events.saip.org.za/event/7/con tributions/4906/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4906/ END:VEVENT BEGIN:VEVENT SUMMARY:Effect of growth rate and ZnO buffer layer on the structural and o ptical properties of MOCVD-grown MgxZn1-xO thin films DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4907@events.saip.org.za DESCRIPTION:Speakers: Kharouna Talla (Nelson Mandela Metropolitan Universi ty)\nMgxZn1-xO films were grown on c-plane sapphire substrates by metal or ganic chemical vapour deposition. The effects of growth rate and low tempe rature (280ºC) ZnO buffer layer thickness on the incorporation efficiency of Mg as well as the optical and structural properties of the MgxZn1-xO f ilms were investigated. Low growth rates enhance the segregation of Mg\, l eading to a magnesium rich region near the interface with the sapphire sub strate. Hence\, a shoulder is observed on the higher energy side of the ma in donor bound exciton in the photoluminescence spectrum. The effect of a ZnO buffer layer grown for 5 min and 10 min at 280ºC for MgxZn1-xO films with low Mg content (xv = 0.2) and for MgxZn1-xO with high Mg content (xv = 0.5) was also investigated. The ZnO buffer layer causes an improvement in the Mg incorporation but deteriorates the structural and optical proper ties for all the films. The MgxZn1-xO thin films grown on a thinner ZnO bu ffer layer showed the best optical and structural properties. Furthermore\ , the deposition of thin films on a ZnO buffer layer leads to an increase in lateral growth rate\, which enhances the width of columnar grains. A Zn O buffer layer does not prevent the formation of a Mg rich interfacial lay er.\n\nhttps://events.saip.org.za/event/7/contributions/4907/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4907/ END:VEVENT BEGIN:VEVENT SUMMARY:Campaign for Vicarious Calibration of SumbandilaSat in Argentina DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4908@events.saip.org.za DESCRIPTION:Speakers: Lufuno Vhengani (CSIR)\nThe importance of calibratin g satellite imagers has been explained in literature such as K Arai (2007) and K J Thome (2001). Calibration of satellite sensors (imagers) is cruci al for data consistency\, reliability and comparability. To perform a mean ingful analysis of a satellite image\, the Digital Numbers (DNs) of the im age are first converted to absolute radiance by using the sensor-specific radiometric calibration coefficients. Satellite imagers are calibrated pre -launch and for continuous assessment\, they are also calibrated post-laun ch. Various post-launch techniques exist including cross-sensor\, solar\, lunar and vicarious calibration. Vicarious calibration relies on in-situ m easurements of surface reflectance and atmospheric transmittance to estima te Top-Of-Atmosphere (TOA) spectral radiance. A vicarious calibration fiel d campaign was executed in Argentina to support monitoring of the radiomet ric response of the multispectral imager aboard SumbandilaSat. Results obt ained using two Radiative Transfer Codes (RTCs) MODTRAN and 6S are present ed.\n\nhttps://events.saip.org.za/event/7/contributions/4908/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4908/ END:VEVENT BEGIN:VEVENT SUMMARY:ThunderKAT: The MeerKAT Large Survey Project for Radio Transients DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4909@events.saip.org.za DESCRIPTION:Speakers: Patrick Woudt (Department of Astronomy\, University of Cape Town)\nThunderKAT is one of ten accepted MeerKAT Large Survey Proj ects. \nThunderKAT will study all aspects of transient radio emission asso ciated with accretion and explosive events. Through a comprehensive and co mplementary programme of monitoring Galactic synchrotron transients (acros s a range of compact accretors and a range of other explosive phenomena) a nd exploring distinct populations of extragalactic synchrotron transients (microquasars\, supernovae (SNe) and possibly yet unknown transient phenom ena) we will revolutionise our understanding of the dynamic and explosive transient radio sky. \nWe will give an overview of ThunderKAT and discuss the prospects of studying the transient sky with KAT-7.\n\nhttps://events. saip.org.za/event/7/contributions/4909/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4909/ END:VEVENT BEGIN:VEVENT SUMMARY:Vanadium Dioxide Nanoplatelets Based nanocomposites for IR Solar R adiation Modulation DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4910@events.saip.org.za DESCRIPTION:Speakers: Aline SIMO (PHD Student)\nExamples of novel coating technologies towards Infrared solar radiation regulation/modulation in sma rt glass windows for the satellite sector include electrochromic and therm ochromic based high vacuum manufactured dynamic coatings. The latter two t echnologies are solar radiations control oriented technologies in the visi ble and infrared radiation respectively. The thermochromic smart coated wi ndows are infrared active and self regulating systems. Due to its natural phase transition around 68°C\, vanadium dioxide coated systems exhibit an exceptional reversible and self induced optical modulation in the infrare d solar spectrum. If the temperature of the vanadium dioxide coated on a g lass window is smaller than 68°C\, the smart window is transparent to the solar infrared radiations i.e. heat transmitting while it reflects the in frared radiations if its temperature is higher than 68°C i.e. heat opaque . To apply such a thermochromic smart material on a large scale in automot ive and building sector\, it is required to shift their transition tempera ture to about 25°C as well as innovating a physical-chemical process for production of large surface coatings. While the first requirement can be a chieved by tungsten doping\, the second could be reached by a hybrid polym er- VO2 (M) nanoparticles based coatings. This contribution reports the ph ysical and specifically the optical characteristics of VO2 nanoplatelets/P VP nano-composites.\n\nhttps://events.saip.org.za/event/7/contributions/49 10/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4910/ END:VEVENT BEGIN:VEVENT SUMMARY:Successes and Failures of Numerical Solutions to the 1-Dimentional Marchenko Integral Equation for Quantum Inverse Scattering DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4911@events.saip.org.za DESCRIPTION:Speakers: Serle Shuman (UNISA)\nThe origin of numerical errors \, which in certain cases lead\nto complete failure of the direct method f or solving the 1-dimensional Marchenko\nintegral equation\, are investigat ed. Bargmann and block potentials\, for which exact analytical\nexpression s exist\, are used to compare the accuracy of numerical results. In\nparti cular\, numerical results from the Nystrom method are compared to those of two\nnovel collocation methods. The results indicate that\, for roughly t he same\ncomputational effort\, the three method may be ranked in order of increasing accuracy: \nNystrom method\, equidistant collocation method an d non-equidistant collocation method. \nIn all three cases the origin of t he failure\, which occurs for barrier-like potentials of relatively \nlarg e width and height\, may be attributed to the numerical instability introd uced in both the Fourier \ninversion and the linearization steps. Subseque ntly these errors produce perturbations on \nthe matrix elements of the in version matrix\, a matrix which is found to become increasingly \nill-cond itioned as the height and width of the potential increases. At the current limits of\nsuccessful inversion\, we attribute the "early" onset of inver sion failures\, to the\naforementioned matrix element perturbations. Howev er at still higher potential height\nand width\, the inherent ill-conditio ning of the inversion matrix alone\, accounts for\nthe inversion failures. We therefore conclude that there is an inherent upper-bound on the\nappli cation of the direct inversion method for inverting relatively high and wi de\npotentials.\n\nhttps://events.saip.org.za/event/7/contributions/4911/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4911/ END:VEVENT BEGIN:VEVENT SUMMARY:A Diagnostic 'tool' to prevent the consequences of material failur e DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4912@events.saip.org.za DESCRIPTION:Speakers: Ike Sikakana (Vaal University of Technology)\nIn mat erials’ manufacturing\, evaluation and/or characterization is a key fina l stage in the production process. This quality assurance tests whether t he product meets an industry norm or specified standard required by the cu stomer.\nThe evaluation is also required on machinery / plant parts that a re already in operation. The parts are periodically ‘tested’ to ascer tain as to whether they can still function safely and as originally design ed.\nThe evaluation\, characterization\, testing is conducted using techni ques that do not damage these parts / materials. This novel way of materia ls’ examination\; referred to as Non-Destructive Testing / Evaluation (N DT/E)\; is finding increasing applications is numerous industries.\nThis p aper focuses\, first\, on the use of NDT/E in selected industries and its critical nature in the safe operation of plant machinery and structures.\n Secondly\, an overview of the education and training required in NDT/E is discussed. The qualification offered at the Vaal University of Technology (VUT) and its impact on the NDT/E profession in South Africa is reflected upon.\nThirdly\, the rewards of an NDT/E career are discussed. This is c ontrasted with the perceived low profile of NDT/E amongst practicing engin eers in South Africa.\nLastly\, an argument for the urgent need of a legis lative framework for the regulation and recognition of NDT/E qualification s and certification in South Africa is advanced. It is emphasized that thi s is a necessary measure to have accountability and a code of ethics entre nched in this growing profession.\n\nhttps://events.saip.org.za/event/7/co ntributions/4912/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4912/ END:VEVENT BEGIN:VEVENT SUMMARY:Modeling X-ray Emission and the SED of the Binary Radio Pulsar AE Aquarii DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4914@events.saip.org.za DESCRIPTION:Speakers: Bosco Oruru (University of the Free State)\nThe high ly transient novalike variable AE Aqr is perhaps an ideal laboratory to st udy accretion related astrophysical fluid dynamics. It consists of a fast spinning highly magnetic white dwarf (WD) orbiting\, and accreting mass\, from a low-mass main sequence companion. The system emits\, and has been d etected in almost all wavelengths. AE Aqr is in a propeller state\, and mo st of its emission properties are associated with the turbulent interactio n between the accretion flow and the fast rotating magnetosphere of the WD . We have analysed its X-ray spectra using contemporaneous Chandra and Swi ft X-ray data. The results of this study show that the X-ray emission has both thermal and non-thermal characteristics. The thermal X-ray emission i s modeled to be the result of bremsstrahlung emission of heated mass outfl ow above the polar caps\, whereas the non-thermal X-ray emission is the re sult of synchrotron radiation of accelerated electrons outside the light c ylinder radius of the WD. In this paper\, some of the results\, based on t he constraints of the proposed thermal and non-thermal emission mechanisms \, will be presented.\n\nhttps://events.saip.org.za/event/7/contributions/ 4914/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4914/ END:VEVENT BEGIN:VEVENT SUMMARY:NON-SPECIALIST: Spectroscopy in Chemistry DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4920@events.saip.org.za DESCRIPTION:Speakers: Christian Litwinski (Rhodes University)\nSince the 1 960's\, in many fields of Chemistry\, spectroscopy is an important diagnos tic tool. The key to the widespread use of spectroscopy in chemistry is th at it permits one to probe the microscopic structure of molecules\; the ul timate building blocks of the chemical sciences. Spectroscopy is used for a wide variety of procedures in chemistry. \nThis talk will present an ove rview of the spectroscopic methods used in the Chemistry Department and th e DST/Mintek Nanotechnology Innovation Centre (NIC) at Rhodes University. Examples of simple steady state absorption measurements to check the purit y of synthesized phthalocyanine molecules over time resolved fluorescence spectroscopy to investigate energy transfer between phthalocyanines and na noparticles to surface analysis with x-ray photoelectron spectroscopy will be presented. The applications of phthalocyanines range from sensors for pesticides to drugs for photodynamic therapy of cancer.\n\nhttps://events. saip.org.za/event/7/contributions/4920/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4920/ END:VEVENT BEGIN:VEVENT SUMMARY:Influence of solvent effects on Qy transitions in chlorophyll DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4915@events.saip.org.za DESCRIPTION:Speakers: Jacoba Smit (CSIR Biosciences\, Pretoria\, South Afr ica)\nThe most abundant and efficient light harvesting\, energy transfer a nd transduction systems are found in nature within the process of photosyn thesis. Although the processing sequences of an absorbed solar photon in t he photosynthetic apparatus have been deciphered\, the underlying physical basis of photosynthesis is not well understood yet. Our research aims to contribute to this understanding by characterising the level of organisati on of the Light Harvesting II complexes (LHCII) and energy transfer system s when incorporated into artificial vesicles called PheroidTM. LHCII was e xtracted from spinach leaves in a 20 mM Tricine buffer to stabilise the pr oteins. Raman\, FTIR and absorbance spectra of samples were compared. The Qy transitions of chlorophyll in the red (Qy) region of the absorption spe ctra appears to red-shift by 3.5 – 5.5 nm\; indicating a possible change in organisation of the light harvesting system after incorporation into t he PheroidTM. These shifts however could also be interpreted as bathochrom ic solvent effects due to the Tricine buffer. The objectives of this study were (1) to investigate whether the red-shifts were due to the Tricine bu ffer and (2) if so\, whether the alternative use of a 20 mM K2HPO4 / KH2PO 4 buffer could eliminate the bathochromic solvent effects. The Tricine buf fer was dialysed out of the samples directly into a 20 mM K2HPO4 / KH2PO4 buffer to prevent denaturing of the LHCII proteins. Preliminary results in dicated a lessening of the bathochromic effects with the K2HPO4 / KH2PO4 b uffer.\n\nhttps://events.saip.org.za/event/7/contributions/4915/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4915/ END:VEVENT BEGIN:VEVENT SUMMARY:Optimised Hyperchaotic Modes of a Triple Pendulum DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4917@events.saip.org.za DESCRIPTION:Speakers: André Botha (Unisa)\nAnalytical equations of motion \, in the form dxi ⁄ dt = fi(x\,t)\, are derived for a damped harmonical ly driven triple plane pendulum. This form of the equations clearly displa ys the nature of the non-linear coupling and provides a basis for physical interpretation. The equations also facilitate the derivation of the Jacob ian matrix in analytical form\, a result which is important for the accura te numerical computation of the Lyapunov exponents. It is shown that sets of optimised parameters\, such as the lengths and masses of the pendulum\, may be derived by using the Nelder-Mead simplex optimisation algorithm. T his method gives precise control over the Lyapunov exponents and may be us eful in a wide variety of other non-linear applications\, such as those oc curring in biophysics and information technology (for secure communication ). As an example of the technique it is used to predict periodic and quasi -periodic orbits of the un-damped pendulum\, as well as its chaotic and hy perchaotic modes. The maximum positive Lyapunov exponents for the pendulum are found to vary from zero\, for periodic orbits\, to as high as ten for the optimised hyperchaotic modes. Numerical simulations\, coded in Python \, are used to visualise the results. \n\nhttps://events.saip.org.za/event /7/contributions/4917/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4917/ END:VEVENT BEGIN:VEVENT SUMMARY:A Century of Nuclear Theory: a greatly condensed treatment DTSTART;VALUE=DATE-TIME:20110715T114500Z DTEND;VALUE=DATE-TIME:20110715T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4918@events.saip.org.za DESCRIPTION:Speakers: Ken Amos (School of Physics\, University of Melbourn e)\nOver centuries\, defining the underlying structure of matter has been a holy grail for scientists and the public alike. The discovery of the ‘ ultimate’ nature of matter has often been seen as offering the ability t o explain almost everything else in the universe\, from life to the cosmos . During the twentieth century\, nuclear physics became a science which pr omised to reveal many of these secrets. Through theory and experiment\, nu clear scientists charted the underlying structure of matter and gave new i nsights into the\nfundamental nature of things. Over the last century\, pr ogress in nuclear physics has relied on a symbiotic relationship between t heory and experiment. I will begin this talk with some (highly condensed) history of the first half century of developments in nuclear theory. I wil l then discuss the original shell model and the three stage view which Wei sskopf proposed for nuclear reactions\, as both are watersheds of the 50 ’s. The period between the 1950’s and 1990’s was one of incredible d evelopments in nuclear physics. There were many practitioners\, the comput er revolution made possible more and more complex evaluations\, the number s of models for structure and reactions became legion. Thus I will give on ly abridged catalogues of structure models and reaction types before a spe cific note on Butler’s identification of direct reaction theory of deute ron stripping\; a major process in defining spin-parities of nuclear state s. Next\, as it is one of the central aspects of scattering theories\, I c onsider the optical model for nucleons\, just what it should be\, and its use in direct reaction theory of inelastic scattering. I restrict consider ation to just two methods\, the MCAS and the g-folding methods\, with whic h I am most familiar. They were used to obtain results involving the scatt ering radio-active ions\, that appear subsequently. Finally I look at the nuclear landscape as it is today\, with the exotic nuclear systems\, some of which are termed Borromean. I show how some are needed in the CNO stell ar burning cycle and then give examples of spectra evaluation and scatteri ng analyses made using the specific two methods considered.\n\nhttps://eve nts.saip.org.za/event/7/contributions/4918/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4918/ END:VEVENT BEGIN:VEVENT SUMMARY:Mass Distribution in Galaxies using Multi-Wavelength 3D Spectrosco py DTSTART;VALUE=DATE-TIME:20110714T140000Z DTEND;VALUE=DATE-TIME:20110714T150000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4919@events.saip.org.za DESCRIPTION:Speakers: Claude Carignan (University of Cape Town)\nSpiral an d dwarf galaxies are known to present an important mass discrepancy betwee n their dynamical and visible masses. The commonly accepted hypothesis is to assume a more or less spherical halo of unseen matter in addition to th e stars and gas. To study properly this mass discrepancy\, different obser vational techniques at different wavelengths need to be combined in order to probe as best as possible the gravitational potential at all radii and different theoretical tools are necessary to sort out which distribution l aw represents best the dark matter component.\nThis Multi-wavelength appro ach will be illustrated by discussing the radio HI aperture synthesis obse rvations of our Local Group neighbours\, M31 (Andromeda) and M33 and the o ptical Ha Fabry-Perot interferometric observations of the SINGS sample of galaxies. As an example\, it will be showed how important it is to model p roperly velocity perturbations\, such as those produced by bars\, before u sing the kinematics to derive the gravitational potential as a tracer of b oth the luminous and the dark matter components.\n\nhttps://events.saip.or g.za/event/7/contributions/4919/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4919/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum Physics with Trapped Ions DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4921@events.saip.org.za DESCRIPTION:Speakers: Hermann Uys (National Laser Centre\, CSIR)\nIn this non-specialist lecture I will provide an overview of the field of ion trap ping. Ion traps are used world wide to push the limits of quantum technolo gies. They are a lead contender for building quantum computers\, they are capable of measuring tiny forces at the level of yocto (10-24) Newton and to date they hold the record for the most accurate atomic clock (that cloc k would neither gain nor lose a second in about 4 billion years!). Moreove r\, the technological capability of trapping single ions make these traps ideal for studying quantum optical phenomena.\n\nhttps://events.saip.org.z a/event/7/contributions/4921/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4921/ END:VEVENT BEGIN:VEVENT SUMMARY:Soft Matter Properties: What can we learn from computer simulation s? DTSTART;VALUE=DATE-TIME:20110715T073000Z DTEND;VALUE=DATE-TIME:20110715T083000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4923@events.saip.org.za DESCRIPTION:Speakers: Debashish Mukherji (Max-Planck Institute for Polymer Research)\nI will present three unrelated examples in which efficient com puter simulations have been employed to address soft matter properties. Th e first example will deal with the dynamics of polymers near surfaces. Des pite the significant progress within the last decade\, in particular on th e structure and thermodynamic properties in confinement\, their dynamics r emained an active field of research. Unlike some of the prior studies\, we introduced atomic scale roughness of the confining surface(s) while absta ining from introducing any artificially-imposed divergent obstacles. Becau se of this type of modeling\, we could reproduce the scaling of the single polymer dynamics near attractive surface and relate the dynamics of adsor bed polymer films with the degree with which they interlock with the surfa ce. The second example will explore the mechanical behavior of highly cros s-linked polymer (HCP) glasses\; such as epoxy and vinyl-ester thermosets\ , which are used as both high-strength adhesives and as composite matrices . One particular property of HCPs which limits their usefulness is their l ack of toughness. Fully cured epoxies\, for example\, can have about 2 GPa of tensile strength but are brittle\, failing at about 1% strain. Using c omputer simulations\, we were able to devise ways of toughening the HCP ne tworks by introducing engineered micro-voids. We have also performed exper iments on amine cured epoxy networks by introducing voids using reactive e ncapsulation of nonreactive solvent tetrahydrofuran. The experiments were consistent with our prediction. Lastly\, as the third example\, I will bri efly mention our recent work on the solvation properties of liquid mixture s using an Adaptive Resolution Molecular Dynamics Scheme in which particle s can change their resolution (atomic or coarse-grained) on the fly.\n\nht tps://events.saip.org.za/event/7/contributions/4923/ LOCATION:Universe URL:https://events.saip.org.za/event/7/contributions/4923/ END:VEVENT BEGIN:VEVENT SUMMARY:Astrophysics Poster Blitz DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4924@events.saip.org.za DESCRIPTION:https://events.saip.org.za/event/7/contributions/4924/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4924/ END:VEVENT BEGIN:VEVENT SUMMARY:Space Physics Poster Blitz DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4925@events.saip.org.za DESCRIPTION:https://events.saip.org.za/event/7/contributions/4925/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4925/ END:VEVENT BEGIN:VEVENT SUMMARY:Adding Flavour to Nonplanar Integrability DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4926@events.saip.org.za DESCRIPTION:Speakers: Stephanie Smith (University of the Witwatersrand)\nN =4 SYM theory has been extensively studied in the planar limit. A very\nsi gnificant result of this study is a map from the planar dilatation\noperat or to the Hamiltonian of an integrable spin chain. In this talk\nwe consid er a large N (but not planar) limit of the theory. This is\na considerably more complicated problem since non-planar corrections\nneed to be summed. This summation is accomplished by employing the\nrestricted Schur polynom ials. We give an analytic formula for the\naction of the dilatation operat or on the resticted Schur polynomials\nand then proceed to calculate the o ne loop anomalous dimensions.\nOur result shows that the dilatation operat or reduces to a set of\ndecoupled harmonic oscillators\, generalizing resu lts known from the\nsector of theory constructed using two complex Higgs f ields (two flavors)\nto the sector with three complex Higgs fields (three flavors).\n\nhttps://events.saip.org.za/event/7/contributions/4926/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4926/ END:VEVENT BEGIN:VEVENT SUMMARY:A comparison of analysis methods of gamma-ray spectra obtained wit h a LaBr3 scintillation detector DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4927@events.saip.org.za DESCRIPTION:Speakers: M.W van Rooy (Stellenbosch University\; iThemba LAB S)\nThe goal of any measurement and data-analysis technique should always be to minimize uncertainties\, whether it is statistical or systematic. Al though uncertainties are unavoidable\, one can find ways to reduce them de pending on the circumstances. High-precision measurements play a crucial r ole in constraining various quantities.\n \nRecently a new inorganic scint illation detector has become available in large cylindrical sizes (e.g. 7. 6 cm in diameter and with length over 15 cm). It consists of LaBr3 and has an energy resolution which is not as good as HPGe\, but superior to the e nergy resolution of NaI and CsI\, and does not need to be cooled to LN2 te mperatures. Since La has a naturally radioactive isotope\, 138La\, which e mits γ-rays\, the detector has an internal calibration source for energy and dead-time corrections. Moreover it produces pulses with fast rise time \, which allows setting up the electronics such that measurements can be m ade with a high count rate and a low dead time. Gamma-ray spectra were col lected with a 3"×3" LaBr3 detector for LaBr3 intrinsic background\, 22Na and 137Cs which exhibit some gain drifts. A set of off-line analysis metho ds of these spectra is presented to select the procedure that yields the o ptimal precision and accuracy.\n\nhttps://events.saip.org.za/event/7/contr ibutions/4927/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4927/ END:VEVENT BEGIN:VEVENT SUMMARY:Energetic stability and charge states of 3d transition metals in d iamond: Towards a diamond based diluted magnetic semiconductor DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4928@events.saip.org.za DESCRIPTION:Speakers: Evans Benecha (University of South Africa (UNISA))\n Energetic stability of magnetically ordering dopants in diamond holds the prospect of achieving a diamond based diluted magnetic semiconductor which \, in addition to diamond’s extreme properties may successfully be consi dered for spintronic device applications. However\, one of the problems to be addressed is that of predicting the most energetically stable lattice configurations or charge states in which such dopants can remain electrica lly or optically active\, and at the same time induce magnetic moments whe n incorporated into diamond. We report ab initio DFT calculations on the f ormation energies of isolated 3d transition metal impurities at various la ttice sites and charge states in diamond\, and show that these impurities introduce deep donor and acceptor levels in the band gap of diamond. We fu rther show that the formation energies as well as the magnetic ordering pr operties are critically dependent on the position of the Fermi level in th e diamond band gap\, with formation energies across the 3d series being lo wer in n-type or p-type diamond compared to intrinsic diamond\, suggesting that co-doping with impurities such as boron\, nitrogen or phosphorus wil l considerably enhance their stability in diamond. The majority of the 3d transition metals are found to be energetically most stable at a divacancy site in any charge state\, with the formation energy of transition metals in the middle of the 3d series (Cr\, Mn\, Fe\, Ni\, Co) being lowest at a ny lattice site.\n\nhttps://events.saip.org.za/event/7/contributions/4928/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4928/ END:VEVENT BEGIN:VEVENT SUMMARY:Stable interferometer for orbital angular momentum sorting DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4930@events.saip.org.za DESCRIPTION:Speakers: Angela Dudley (CSIR National Laser Centre)\nOur inte rferometer is based on a previously reported orbital angular momentum (OAM ) sorting device. By introducing a specially designed phase- and intensity -inverting prism into each arm of the interferometer\, decoupling the vert ical and horizontal alignment in each arm\, we are able to reduce the degr ees of freedom within the interferometer from initially being associated w ith very optical component to a mere one degree of freedom\; the optical p ath length. The interferometer induces a phase shift\, which is proportion al to both the OAM of the incoming beam and the relative angle\, θ\, betw een the two phase- and intensity-inverting prisms. When the angle between the two phase- and intensity-inverting prisms is 90 degrees\, and the pat h length is appropriately selected\, constructive interference will occur in one of the two output ports for even l-valued states and in the opposit e port for odd l-valued states. Apart from adjusting the path length of th e interferometer\, two external degrees of freedom\, two mirrors\, are use d to align the incoming beam into the interferometer. \nTo test the effect iveness of the interferometer in separating odd and even l-states\, the in tensity of the interference pattern in one of the output ports was monitor ed\, while the path length of one of the arms of the interferometer oscill ated back and forth between constructive and destructive interference. The Michelson contrast was calculated for various incoming l-states. We obtai n a maximum Michelson contrast measurement of 92% at an OAM value of l=0 a nd 85.3% at l=±10.\n\nhttps://events.saip.org.za/event/7/contributions/49 30/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4930/ END:VEVENT BEGIN:VEVENT SUMMARY:Indoor temperature predictions in an energy efficient solar house DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4931@events.saip.org.za DESCRIPTION:Speakers: Sosten Ziuku (Fort Hare Institute of Technology)\nTh is paper presents results of long term temperature monitoring in an energy efficient solar house at the University of Fort Hare\, South Africa. Meas ured data was stored by a datalogger every 10 minutes. Formulas for predic ting the daily indoor maximum\, average and minimum temperatures were deve loped on the basis of outdoor climatic parameters. Passive solar housing a ims to raise and lower indoor temperatures in winter and summer respective ly. As a result\, analysis of the data and development of predictive formu las of indoor temperature were done separately on part of the winter and s ummer seasons. The models were then validated against measurements taken i n different time periods. Results indicated that indoor maximum\, average and minimum temperatures can be predicted on the basis of outdoor temperat ure. Prediction of maximum indoor temperature was improved by incorporatin g daily solar irradiance in the formula. It was also revealed that indoor temperatures are affected by outdoor temperatures of the previous two day s. The different ways at which the house is cooling and heating were also investigated.\n\nhttps://events.saip.org.za/event/7/contributions/4931/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4931/ END:VEVENT BEGIN:VEVENT SUMMARY:Search for Low Spin Collective Structures in 158Er and 159Er DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4932@events.saip.org.za DESCRIPTION:Speakers: Tshepo Dinoko (University of the Western Cape)\nThe nuclei 158\,15968Er are classic examples of many phenomena in the study of nuclei at high spin. However\, although the multi-quasi particle structur es of 158\,15968Er are well established\, there is not much spectroscopic information on the vibrational structures in 158Er or how these couple to the odd neutron in 159Er. Additionally\, there are several bands where the spins and/or parities are not firmly assigned. The relative lack of infor mation at low spins is probably due to a combination of the low spins of the ground states of the nuclei 158\,15969Tm that β+/ec decay to 158\,159 68Er\, 2- and 5/2+ respectively.\n\nTwo experiments were performed in the AFRODITE spectrometer to populate 158Er and 159Er using 1mg/cm2 150Sm(12C \,4n) and 150Sm(13C\,4n) reactions respectively at 65MeV\, The intention i s to study their yrare states below spin 20ħ. Preliminary results will be presented.\n\nA Coulomb excitation of 155Gd with 86Kr ions experiment is scheduled for early May at iThemba LABS. The Physics interest is in lookin g for collective core excitations of 154Gd that are coupled to the ground state neutron in 155Gd. The outcome of this experiment will be presented a s well.\n\nhttps://events.saip.org.za/event/7/contributions/4932/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4932/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermoluminescent properties of BaAl2O4:Eu2+\,Gd3+phosphors prepar ed by combustion method at different initiating temperatures. DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4933@events.saip.org.za DESCRIPTION:Speakers: Bakang Moses Mothudi (University of South Africa)\nE uropium (Eu2+) and gadolinium (Gd3+) doped BaAl2O4 powder phosphors were p repared by combustion method at different initiating temperatures (400-100 0 oC)\, using urea as a comburent. The powders were annealed at different temperatures in the range of 400-1000 oC for 3 hours. X-ray diffraction da ta show that the crystallinity of the BaAl2O4 structure greatly improved a s the annealing temperature increased. The FT-IR absorption bands observed at 533\, 629 and 798 cm-1 for the samples annealed at higher temperatures (1100-1200 oC) are consistent with the stretching mode frequencies of BaA l2O4. Blue-green photoluminescence\, with persistent / long afterglow\, wa s observed at 503 nm.This emission was attributed to the 4f65d1- 4f7 trans itions of the Eu2+ ions. The phosphorescence decay curves were obtained by irradiating the samples with a monochromatized xenon lamp at an excitatio n wavelength of 393 nm.The glow curves and the decay curves of the samples irradiated by UV source (360 nm) were investigated using investigated usi ng the Thermoluminescence Reader (Integral-Pc Based) Nucleonix TL 1009I.\n \nhttps://events.saip.org.za/event/7/contributions/4933/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4933/ END:VEVENT BEGIN:VEVENT SUMMARY:The soilid-state interaction of palladium on 6H-SiC DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4934@events.saip.org.za DESCRIPTION:Speakers: Jeaneth Thokozile Kabini (Univerity of Pretoria)\nTh e interaction of Pd and SiC samples during thermal annealing were investig ated using x-ray diffraction (XRD)\, Rutherford backscattering spectrometr y (RBS) as well as Scanning Electron Microscopy (SEM). Two sample configur ation were used (1) the palladium (50nm) was deposited onto a degreased 6H -SiC substrate and (2) palladium ions were implanted into the 6H-SiC subs trate at room temperature and at 200°C with a fluency of 1 x 1015cm-2. Bo th sets of the samples were annealed between temperatures of 200°C-800°C for a period of 60 min. The study showed that the thermally annealed Pd o n SiC showed no detectable reaction after annealing at 200°C-400°C. At 500°C the RBS spectra shows that the Pd had reacted with SiC. Using XRD i t was observed that metal rich silicides Pd3Si tend to form first after an nealing at 500°C followed by the formation of Pd2Si after annealing at 60 0°C\, 700°C and 800°C. No Carbon compounds were detected by XRD in thes e annealing temperature ranges. The implanted samples showed no detectable phase formation after annealing at temperature ranges of 200°C-800°C fo r a period of 60 min and at 1000°C for 10 hours. The RBS / Channeling res ults for the implanted samples are also shown.\n\nhttps://events.saip.org. za/event/7/contributions/4934/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4934/ END:VEVENT BEGIN:VEVENT SUMMARY:Lightning – Scientific knowledge versus mythological beliefs DTSTART;VALUE=DATE-TIME:20110714T060000Z DTEND;VALUE=DATE-TIME:20110714T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5060@events.saip.org.za DESCRIPTION:Speakers: Sam Ramaila (University of Johannesburg)\nLightning has in recent times wreaked havoc during the rainy season in several parts of South Africa and this prompted the physics community under the auspice s of the South African Institute of Physics (SAIP) to devise meaningful st rategies for promoting public awareness. In response to this call\, first year physics students at the University of Johannesburg responded to a car efully designed questionnaire that seeks to probe students’ level of und erstanding of lightning. Analysis of responses reveals lack of scientific understanding of lightning as a natural phenomenon. Amongst others\, this can to some degree be attributed to superstitious or cultural beliefs.\n\n https://events.saip.org.za/event/7/contributions/5060/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5060/ END:VEVENT BEGIN:VEVENT SUMMARY:A Quantum Hall Effect without Landau Levels in a Carbon Nanotube. DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4935@events.saip.org.za DESCRIPTION:Speakers: Nanette Brand (Stellenbosch University)\nThe spectru m of a carbon nanotube in a strong enough magnetic field (>50T for a 3nm n anotube) revealed an almost dispersionless band at the Fermi energy. The f ormation of Landau levels has been theoretically and experimentally invest igated. In experimental studies the existence of Landau levels is indirect ly derived from longitudinal conductance measurements. We will show that a more direct indication of Landau Levels in the system exists\, namely a q uantized Hall effect. We present numerical results that show the applicati on of an electric field along the length of the tube lead to a current cir culating the circumference and\, furthermore\, that the conductance is exa ctly e2/h. This is interesting because the magnetic flux averages to zero around the tube’s circumference. This phenomenon could be explained in t erms of the two-dimensional topological theory for the quantum Hall effect even though this system is quasi-one dimensional.\n\nhttps://events.saip. org.za/event/7/contributions/4935/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4935/ END:VEVENT BEGIN:VEVENT SUMMARY:Testing the Cosmic Ray-Lightning Connection Hypothesis DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4936@events.saip.org.za DESCRIPTION:Speakers: Andrew Collier (University of KwaZulu-Natal)\nThe pr oposed dependence of atmospheric electrical properties on the ionizing inf luence of cosmic rays has resulted in numerous attempts to obtain convinci ng correlations. While most of the studies remain largely theoretical\, a few results (e.g. Stozhkov\, 2003) indicate that there is a plausible link between lightning activity and the cosmic ray ionization rate measured at specific locations on Earth. The present work uses data from the World Wi de Lightning Location Network (WWLLN) to investigate the impact of cosmic rays on lightning on a global scale. The availability of global lightning data from WWLLN\, and assimilated cosmic ray data from a global network of neutron monitors provides a good opportunity to study the relationship be tween cosmic ray variations and lightning occurrence on a larger spatial s cale than was previously possible.\n\nhttps://events.saip.org.za/event/7/c ontributions/4936/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4936/ END:VEVENT BEGIN:VEVENT SUMMARY:Intermediate valence and antiferromagnetic Kondo lattice behaviour in Ce(Au1-xNix)2Si2. DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4937@events.saip.org.za DESCRIPTION:Speakers: Moise Bertin Tchoula Tchokonte (University of the We stern Cape)\nThe transition from intermediate valence (IV) behaviour in Ce Ni2Si2 to magnetically ordered Kondo lattice behaviour in CeAu2Si2 is inve stigated through measurements of X-ray diffraction (XRD)\, electrical resi stivity &rho(T)\, magnetization &sigma(µ0H) and magnetic susceptibility & chi(T) on the polycrystalline Ce(Au1-xNix)2Si2 (0 ≤ x ≤ 1) alloy serie s. Lattice parameters as derived from XRD measurements deviate from Vegard ’s rule around x = 0.6 – 0.8. &rho(T) data indicate Kondo lattice beha vior in the presence of a crystal field for x ≤ 0.6\, the occurrence of magnetic ordering for x = 0 and fluctuating valency for x ≥ 0.8. &chi(T) data at high temperatures\, follow the Curie-Weiss relation for alloys in the concentration 0 ≤ x ≤ 0.6 (Kondo lattice region) and give effecti ve magnetic moment values µeff close to that expected for the free Ce3+-i on. The low temperature &chi(T) data indicate the onset of antiferromagnet ic ordering for x ≤ 0.78. For alloys in the concentration range 0.8 ≤ x ≤ 1 (IV region)\, &chi(T) data are described within the framework of t he paramagnon model. &sigma(µ0H) measurements indicate metamagnetic behav ior for alloys in the concentration range 0 ≤ x ≤ 0.1.\n\nhttps://even ts.saip.org.za/event/7/contributions/4937/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4937/ END:VEVENT BEGIN:VEVENT SUMMARY:Atmospheric turbidity over Gauteng DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4938@events.saip.org.za DESCRIPTION:Speakers: Thabang Sethabane (Dept. Physics\, University of Joh annesburg)\nWe have analysed broad-band global solar irradiation measureme nts collected at the Soweto campus of the University of Johannesburg over the two-year period 1998-1999. We estimate the direct and diffuse irradiat ion using radiation models\, and utilise the results to determine the atmo spheric turbidity for all cloud-free days. From this we calculate aerosol densities and the solar radiation potential for the location. We further evaluate the applicability of several irradiation models\, incorporating m olecular absorption\, Rayleigh and Mie scattering\, to this part of Gauten g.\n\nhttps://events.saip.org.za/event/7/contributions/4938/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4938/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards Scientific Establishment and Validation of Quality Standar ds for Digital Thermal Neutron Imaging DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4939@events.saip.org.za DESCRIPTION:Speakers: Mabuti Jacob Radebe Radebe (Necsa)\nDigital thermal neutron imaging (radiography and tomography) is a powerful non-destructive analytical tool and has demonstrated its importance in industrial and res earch application world-wide. However\, standards through test samples\, methods and procedures\, which are essential when the technique is to be a pplied in the national and international industrial and research environme nt\, do not exist yet. Firstly\, characterization of the hardware faciliti es is essential in order to determine their capabilities in terms of beam properties\, detection properties and subsequent combinations of the two s uch as spatial and temporal resolution\, acquisition period\, L/D\, S/N ra tio\, etc. This can be achieved through the implementation of test sample s and test methods which entails the efforts towards achieving the correct test specimens\, procedures and practices. \nSecondly\, obtaining accurat e quantitative information from digital thermal neutron images is an impor tant development of this decade\, and establishment and finalization of st andardization in this regard is essential. A properly validated methodolog y to standardize quantitative digital thermal neutron imaging is of import ance in a number of current research fields of global interest which inclu des in-situ investigations of fuel cell dynamics as well as quantification in porous media. This presentation provides the layout of the proposal fo r the PhD study intended at contributing towards the establishment of nati onal and international standards for digital thermal neutron imaging. This entails a contribution towards the establishment\, evaluation\, validatio n and improvement of special test specimens as well as the creation and re finement of measurements\, procedures and practice utilizing digital neutr on radiographs and tomograms.\n\nhttps://events.saip.org.za/event/7/contri butions/4939/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4939/ END:VEVENT BEGIN:VEVENT SUMMARY:XPS analysis and luminescence properties of commercially Gd2O2S:Tb powder phosphor DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4940@events.saip.org.za DESCRIPTION:Speakers: JAPPIE DOLO (University of the free state)\nWe repor t on the characterization of commercially terbium doped gadolinium oxysulf ide (Gd2O2S:Tb) phosphor and the degradation of the Gd2O2S:Tb green phosph or for its application in CRT screens. As a result\, degradation of the ca thodoluminescence (CL) intensity during irradiation of the powder with 2 k eV electrons in an oxygen pressure of 1 x 10-6 Torr was studied. The ESSCR mechanisms was used to explain the effects of sulphur desorption and the formation of a non-luminescent oxide layer. A dead layer of Gd2O3 and Gd2S 3 are responsible for the degradation of the CL intensity with an increase in electron dose. The XPS results have proved the presence of Gd2O3 and G d2S3 on the degraded powder spots.\n\nhttps://events.saip.org.za/event/7/c ontributions/4940/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4940/ END:VEVENT BEGIN:VEVENT SUMMARY:The Physics of Exceptional Points DTSTART;VALUE=DATE-TIME:20110715T103000Z DTEND;VALUE=DATE-TIME:20110715T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5061@events.saip.org.za DESCRIPTION:Speakers: W. Dieter Heiss (Dpt of Physics\, University Stellen bosch)\nA short resume about the nature of EPs followed by a discussion ab out their ubiquitous occurrence\nin a great variety of physical problems. EPs feature in quantum phase transition\, quantum chaos\,\nthey produce dr amatic effects in multichannel scattering\, specific time dependence and m ore.\nIn nuclear physics they are associated with instabilities and affect approximation schemes.\nEPs could be of interest for weakly bound states such as halos and nuclei along the drip line.\n\nhttps://events.saip.org.z a/event/7/contributions/5061/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5061/ END:VEVENT BEGIN:VEVENT SUMMARY:The extent of the chorus observed at Marion Island DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4942@events.saip.org.za DESCRIPTION:Speakers: Andrew Collier (Hermanus Magnetic Observatory)\nOn t he 4 August 2010\, chorus was observed at Marion Island from 03:00 - 07:00 UT (06:00 - 10:00 LT). Marion Island (46.9°S/37.1°E\, L = 2.62) is with in the plasmasphere during periods of low geomagnetic disturbance\, making the observation of chorus there a rare occurrence. On the 4 August\, a mo derate geomagnetic storm occurred\, with a maximum Kp of 6+\, and a minumu m DST of -70nT. These conditions compressed the plasmasphere to such an ex tent that Marion Island was near to\, or outside\, the plasmaspause at the time of the emission\, making the observation of chorus possible. On the same day\, there chorus was also observed at SANAE IV (L = 4.32). The spec tral properties of these chorus are different\, meaning that the chorus ob served at SANAE IV was generated in a different region to that observed at Marion Island. We present broadband data from both Marion Island and SANA E IV\, and extent of the chorus generating region is inferred from DEMETE R data.\n\nhttps://events.saip.org.za/event/7/contributions/4942/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4942/ END:VEVENT BEGIN:VEVENT SUMMARY:Black Cr/α-Cr2O3 Nanoparticles Based Solar Absorbers: Growth Kine tic DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4943@events.saip.org.za DESCRIPTION:Speakers: Saleh Khamlich (iThemba LABS)\nBlack chromium-chromi um (III) oxide cermet (Ceramic-Metal) nano-composites exhibit attractive s olar absorbance characteristics. They are used widely as selective solar h eat thermal collector nano-coatings. These black chromium-chromium (III) o xide selective solar absorbers are produced by various physical vapor depo sition techniques such as DC and RF reactive sputtering\, pulsed sputterin g method\, and e-beam and thermal evaporation techniques. This contributio n reports on large surface coatings of black chromium-chromium (III) oxide cermet by using a novel cost effective physical-chemical method: the Aque ous Chemical Growth (ACG). More specifically\, the present study addresses the growth mechanism of the uniform fine (in the range of micron to nano) -spherical particles of α-Cr2O3 using the ACG method at low temperature. The growth kinetic of the quasi-mono-dispersed spherical particles of chro mium (III) oxide\, α-Cr2O3\, in aqueous solution was studied as a functio n of ageing time. The small fine spherical particles of α-Cr2O3 revealed by SEM micrographs suggests a growth mechanism based on the diffusion-limi ted Ostwald ripening process on the basis of LSW theory. The experimental data were analyzed in the frame of existing coarsening and particle growth mechanisms\, i.e. Ostwald ripening. A good fits of the growth of α-Cr2O3 particles with d3 model confirms the growth mechanism to be mainly diffus ion-controlled.Two major configurations have been considered initially: Cr black coated α-Cr2O3 nano-particles coatings/Cupper substrate and Cr bla ck coated α-Cr2O3 nano-particles coatings/discontinuous ultra-thin Cr lay er/Cupper substrate. The optimized configurations exhibit a low diffuse re flectance as well as low transmittance in the VIS-NIR spectrum sustaining therefore their high solar absorbance property.\n\nhttps://events.saip.org .za/event/7/contributions/4943/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4943/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational study of some Carbon modification DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4944@events.saip.org.za DESCRIPTION:Speakers: MOSHIBUDI SHAI (UNIVERSITY OF LIMPOPO)\nClassical mo lecular dynamics simulations were used to study the modification of some c arbon forms. The type of carbons that were used is diamond and nanocarbon. Carbon is unique among other elements in its ability to form strong chemi cal bonds with a variety of coordination numbers. The simulations predict that the behaviour of diamond and nanocarbon are similar although the nano tube has low minimum energy compared to the bulk diamond. The radial distr ibution functions of the two forms differ by half a magnitude.\n\nhttps:// events.saip.org.za/event/7/contributions/4944/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4944/ END:VEVENT BEGIN:VEVENT SUMMARY:Assessment of glassy carbon as a high-level nuclear waste containm ent material DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4945@events.saip.org.za DESCRIPTION:Speakers: Johan Malherbe (University of Pretoria)\nThe world i s experiencing an ever-growing demand for energy. This coupled with the d emand to decrease the carbon-footprint have led to a reconsideration of nu clear power as an alternative to fossil fuel power stations. Many countri es have either started again to build nuclear power plants while others\, like South Africa\, are planning to build ones in the near future.\n\nOne of the most negative aspects of nuclear power plants is the long term stor age of radioactive nuclear waste. The type of container material and cont ainment materials and methods are still issues being actively researched. Presently borosilicate and phosphate glasses are the preferred materials for capturing high-level radioactive in a solid matrix. This waste is the n stored in multi-walled stainless steel chambers. A favoured method is t o then store these in containers in geological stable sites like Vaalputs in the Northern Cape. These containers must fulfill a number of criteria\ , such as a high resistance against radiation damage from the radioactive waste\, chemical-resistance against corrosive materials\, thermally conduc tive to dissipate the heat generated by the nuclear decay processing happe ning in the waste\, a diffusion barrier for the radioactive waste in order not to contaminate the environment\, etc.\n\nGlassy carbon\, also known a s vitrious carbon or as polymeric carbon\, is a relatively new form of car bon with many properties completely different to the common graphite form of carbon. This talk will argue the case that glassy should be considered as a container material for the (solid) nuclear waste in stead of the usu al metallic (such as steel) materials. Some of the research being done at the University of Pretoria will also be presented.\n\nhttps://events.saip .org.za/event/7/contributions/4945/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4945/ END:VEVENT BEGIN:VEVENT SUMMARY:B3-B1 phase transition in GaAs: A Quantum Monte Carlo Study DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4946@events.saip.org.za DESCRIPTION:Speakers: Cecil Ouma (Student)\nThe pressure induced B3-B1 pha se transition has been studied using both density functional theory (DFT) and quantum Monte Carlo (QMC) methods. We present results obtained using the local density approximation (LDA)\, PW91-GGA generalized gradient appr oximation\, hybrid density functionals and QMC. The changes in the equatio n of state has also been investigated using the different functionals and form the results obtained\, we find that the choice of functional signific antly effect the to the equation of state. The results of the B3-B1 phase transition pressure for DFT using the different functionals and QMC are re ported and they demonstrate good agreement with experimental data.\n\nhttp s://events.saip.org.za/event/7/contributions/4946/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4946/ END:VEVENT BEGIN:VEVENT SUMMARY:Brillouin scattering study of TiC hard films DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4947@events.saip.org.za DESCRIPTION:Speakers: Clemence Sumanya (DST/NRF Centre of Excellence in St rong Materials)\nThe dispersion relation of surface acoustic waves in TiC thin hard films of various thicknesses on silicon and silicon carbide subs trate is studied using Surface Brillouin scattering. Simulations of surfac e Brillouin scattering (SBS) spectra of TiC thin hard films on silicon and SiC substrates have been carried out over a range of film thickness from 5nm to 1000nm. The simulations are based on the elastodynamic Green's func tion method that predicts the surface displacement amplitudes of acoustic phonons. These simulations provide information essential to understand and analyze experimental data emerging from SBS experiments. There are striki ng differences in both the simulated and experimental SBS spectra dependin g on the respective elastic properties of the film and the substrate. In f ast on slow situations (TiC on Silicon)\, the Rayleigh mode is accompanied by broadened resonances\; in slow on fast situations (TiC on SiC)\, sever al orders of Sezawa modes are observed together with the Rayleigh mode and sharper resonances. The velocity dispersion of the modes as a function of the product of surface wavevector and thickness (k//d) has also been simu lated and obtained experimentally\, allowing the elastic constants of the films to be determined.\n\nhttps://events.saip.org.za/event/7/contribution s/4947/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4947/ END:VEVENT BEGIN:VEVENT SUMMARY:Carbon-Nickel Oxide Nanocomposite coatings: Preparation and charac terization DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4949@events.saip.org.za DESCRIPTION:Speakers: Ngcali Tile (CSIR NLC\, School of Physics University of KwaZulu Natal)\nNanocomposite materials have wide range of application s in solar energy conversion. In this work\, C-NiO nanocomposite coatings are prepared using sol-gel synthesis and deposited on aluminium substrates using a spin coater. The coatings are prepared from alcoholic sols based on Ni-acetate using diethalonamine as a chelating agent and polyethylene g lycol (PEG) as organic template. Sucrose is used as a carbon source. Sols with different PEG and sucrose concentrations are prepared and coated on a luminium substrates. The effect of heat temperature on the properties is a lso investigated. The optical and structural changes of the nanocomposite coatings are characterized by UV-Vis\, FTIR\, thermal emissometer\, Raman\ , and SEM techniques. It has been shown that the solar absorption increase s with increasing the heating temperature in the temperature range 300 – 550 °C due to the increase in carbon content in the composite material. Preliminary durability studies on these samples will also be presented\n\n https://events.saip.org.za/event/7/contributions/4949/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4949/ END:VEVENT BEGIN:VEVENT SUMMARY:Comparison of phase-dependent only and complete Laguerre-Gaussian beams using modal decomposition DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4950@events.saip.org.za DESCRIPTION:Speakers: Melanie McLaren (CSIR)\nLaguerre-Gaussian (LG) beams possess many interesting properties\, one of which is that they carry orb ital angular momentum\, an extrinsic component of angular momentum\, when the electric field or mode has an azimuthal angular dependence of exp(il )\, where l is the azimuthal mode index. These beams are easily generat ed using spatial light modulators (SLMs)\, where a Gaussian beam incident on an SLM is shaped according to a predetermined phase pattern. For LG bea ms\, this phase pattern has typically only included the azimuthally depend ent phase component of the field\, ignoring the amplitude and radial compo nents present in the full LG expression. Although this approximation has yielded azimuthal modes which compare well with theory\, it excites higher order transverse modes. We show both theoretically and experimentally\, u sing a method of modal decomposition\, that higher order transverse modes are excited. The results were compared to the full LG expression\, where n o higher order modes were seen. This is of particular interest regarding t he orbital angular momentum carried by these beams.\n\nhttps://events.saip .org.za/event/7/contributions/4950/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4950/ END:VEVENT BEGIN:VEVENT SUMMARY:Application of Electroluminescence and Thermal Imaging in Defect I dentification in Photovoltaic Modules DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4951@events.saip.org.za DESCRIPTION:Speakers: Jacqui Crozier (NMMU)\nIn order for solar energy to become an alternative to traditional fossil fuel energy it is important th at defects in photovoltaic (PV) modules can be easily identified. Typicall y a module is characterised by measuring the current-voltage (I-V) charact eristics under standard test conditions. In addition to this electrolumine scence (EL) and thermal imaging can be used to identify the location of de fects in the module. A cooled Si CCD camera is used to detect the EL emitt ed from a forward biased PV module. The intensity of this light is related to the minority carrier concentration and the emitted EL thus provides a visual representation of defects in the cell. Infrared imaging can be used to identify irregular heating patterns which are indicative of defective cells or contacts. In this study we used both techniques in conjunction to assess the defects present in a 36 cell custom-made single crystalline si licon module. Defects that were identified in this study showed that areas around the contacts appeared very bright in EL images and this correspon ded with hot areas in the infrared images. These results show that the ele ctrical contacts in these areas are poor.\n\nhttps://events.saip.org.za/ev ent/7/contributions/4951/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4951/ END:VEVENT BEGIN:VEVENT SUMMARY:Low-lying magnetism in heavy-fermion CeRh2Sn2 DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4952@events.saip.org.za DESCRIPTION:Speakers: Andre Strydom (University of Johannesburg)\nThe exis tence of the ternary intermetallic compound CeRh2Sn2 has been known since the crystallographic report of Selsane et al on the CeM2Sn2 family of comp ounds in which M is a d–electron element. The crystal structure is well ordered and the sole magnetic species\, Ce\, occupies a unique symmetry si te in the unit cell. Subsequent studies into these compounds revealed a ge neral trend of magnetic ordering at very low temperatures. CeRh2Sn2 was fo und to order antiferromagnetic through a peculiar smeared out transition a round TN=0.4 K. Most significantly though was the giant electronic specifi c heat witnessed in the Sommerfield coefficient Cp(T)/T which was found to develop in this compound even well above the magnetic ordering temperatur e. The behaviour of this system was explained in the framework of a heavy- electron quasiparticle state forming out of the many-body Kondo interactio n between localized magnetic moments of Ce ions and the conduction electro ns. This results in an exceedingly high electronic density of states at th e Fermi energy EF. In this work we present a detailed study of specific h eat\, magnetic susceptibility\, and electrical resistivity of CeRh2Sn2 in order to map the field stability of salient cooperative effects. The magne tic ordering is found to be instable to fields beyond about 0.5 T. At the same time\, applied magnetic fields displace the huge 4f-electron entropy towards higher temperatures. Further evidence for the importance of the Ko ndo effect in CeRh2Sn2 will be discussed.\n\nhttps://events.saip.org.za/ev ent/7/contributions/4952/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4952/ END:VEVENT BEGIN:VEVENT SUMMARY:The Effects Of High Atomic Material On Photon Beams At The Interfa ce DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4953@events.saip.org.za DESCRIPTION:Speakers: Enoch Sithole (University of Limpopo)\nThe purpose o f this work was to study the dose enhancement factor (DEF) by high-Z mater ial in water phantom\, irradiated by photon beams. Two energies\, 6 and 15 MeV generated by Varian linear accelerator were used. Monte Carlo techniq ue (EGSnrc code) was used in this study. The source model was validated ag ainst measured data. The effect of photon beam quality\, atomic number (Z) and the material thickness in the water phantom were studied. Calculation s for a variety of materials and photon beams showed that dose enhancement factor increase with Z\; decrease with decreasing material thickness\; an d decrease with decreasing incident photon beam energy.\n\nhttps://events. saip.org.za/event/7/contributions/4953/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4953/ END:VEVENT BEGIN:VEVENT SUMMARY:The Pinhole Camera: A fascinating optical device for physics fresh men. DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4954@events.saip.org.za DESCRIPTION:Speakers: John Motsoeneng (University of Pretoria)\nA simple p inhole camera was used to demonstrate to students that light travels in a straight line. The one to one correspondence between a point on the object and a point on the image was used to explain why the image was upside dow n and reversed from left to right.\n\nhttps://events.saip.org.za/event/7/c ontributions/4954/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4954/ END:VEVENT BEGIN:VEVENT SUMMARY:Forces: A difficult area for the students DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4955@events.saip.org.za DESCRIPTION:Speakers: Edwin Mapasha (University of Pretoria)\nThe investig ation reflects on the causes of unsatisfactory students’ performance on the section involving forces during tests. It has been realized that more often than not students tend to be excited after undertaking a test on for ces. However\, subsequent feedback usually paints a different picture and this has become a worrying trend. The results of the investigation in this regard seem to suggest that students have inadequate understanding of siz es\, directions and points of actions on the body. In addition\, students also appear to encounter difficulties in distinguishing between the pushin g and the pulling interactions.\n\nhttps://events.saip.org.za/event/7/cont ributions/4955/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4955/ END:VEVENT BEGIN:VEVENT SUMMARY:Visualizing Physics: Good Vibrations DTSTART;VALUE=DATE-TIME:20110715T061500Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4956@events.saip.org.za DESCRIPTION:Speakers: Derek Fish (University of Zululand)\nThis talk forms part of the author’s Masters investigation into perceptions of Physics in school visitors to Unizul Science Centre. Visitors typically fall into three distinct groups with very different needs and responses. Those comin g from: rural schools\, township schools and urban schools. In this study\ , pupils were exposed to an interactive Science Show: Good Vibrations\, pr esenting the basics of sound and waves through musical instruments. They w ere then asked to respond to questions requiring both written and graphica l answers. From these\, conclusions are drawn as to the ability of these p upils to understand sound both visually and conceptually. These conclusion s will be used to inform best practice when dealing with different groups of visitors with different needs.\n\nhttps://events.saip.org.za/event/7/co ntributions/4956/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4956/ END:VEVENT BEGIN:VEVENT SUMMARY:Blended thin films of tris-(8-hydroxyquinoline) aluminium (Alq3) embedded in polymethyl methacrylate (PMMA) and polystyrene (PS). DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4958@events.saip.org.za DESCRIPTION:Speakers: Mart-Mari Duvenhage (University of the Free State)\n Alq3 is widely used in organic light emitting diodes (OLEDs) as emission a nd electron transport layer. During the fabrication of OLEDs the current t rend is to use solution-processing\; however\, Alq3 must be vacuum deposit ed. One possible way to overcome this problem is to use different polymers containing the Alq3. In this study blended thin films of Alq3 embedded in PMMA and PS matrices at different molar concentration ranging from 0.5% t o 15% was investigated. The photoluminescence (PL) characteristics of the blended films of Alq3:PMMA and Alq3:PS was obtained. This was done by expo sure of the films to 335 nm light. Emission peaks were obtained at 520 nm and 517 nm for the Alq3:PMMA and Alq3:PS films\, respectively. The measure ments were repeated for a period of one month\, with one week intervals be tween measurements\, to confirm the results and also to see if there is an y decrease in luminescence intensity over time. Degradation in emission wa s observed during this period. Absorption measurements were performed on t he blended and unblended films to investigate the effect of the polymer ma trix. The x-ray diffraction (XRD) spectra confirmed the amorphous nature o f the blended films. Atomic force microscopy (AFM) measurements showed tha t smooth uniform films had formed.\n\nhttps://events.saip.org.za/event/7/c ontributions/4958/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4958/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational study of hematite(Fe2O3) and i lmenite(FeTiO3) structures DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4959@events.saip.org.za DESCRIPTION:Speakers: peace prince mkhonto (University of Limpopo)\nWe inv estigate the transformation from hematite to ilmenite structure by solid s olution approach using ab initio quantum-mechanical simulation technique. The method uses the Density functional theory with the plane-wave (PW) pse udopotential method within the CASTEP code. We performed full structural r elaxation allowing lattice parameters and cell violume to change to their mechanical equilibrium. We found that the transformation process does not change the structure (space group) as observed during geometry optimizatio n. Our calculated properties i.e bond length\, cell volume\, lattice param eters\, bulk modulus and density of states shows that hematite and ilmenit e structures have similar property behavior with the lattice parameters co rresponding to the experimental value\, being large by 0.12%. The bond len gth from 20% to 50% shows the dominant of the Ti-O bond\, in agreement wit h the experimental value. This bond length behavior is consistent with the density of state. However\, we observe that the states overlap from VB to CB in VCA which is not expected from the experimental observations of the hematite and ilmenite crystal structures. The transformation from hematit e to ilmenite structure due to doping was observed from 20% atomic titaniu m.\n\nhttps://events.saip.org.za/event/7/contributions/4959/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4959/ END:VEVENT BEGIN:VEVENT SUMMARY:Polarization Encoded QKD in Fibre DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4960@events.saip.org.za DESCRIPTION:Speakers: Sharmini Pillay (University of KwaZulu-Natal)\nQuant um Key Distribution employs the laws of quantum mechanics for the purpose of cryptography. Two parties\, called Alice and Bob\, are able to create a random key which is used to encrypt a message. QKD is a provably secure m ethod for cryptography because any eavesdropper attempting to anonymously retrieve the key must make measurements\, thereby disturbing the system. U sing this principle\, a high error rate between the two authenticated part ies indicates a compromise in the system and the process by which the key is shared is aborted.\nThe quantum channel can be implemented using a free -space link between Alice and Bob\, but in many instances\, this is not pr actical for implementations. Fibre optic cables provide an alternative wit h current technology. In order to implement protocols such as the BB84 pro tocol\, the state of polarization of photons must be maintained between Al ice and Bob. This is because the BB84 protocol utilizes the states of pola rization of photons as qubits (quantum bits). However\, the polarization o f light is altered when passed through a fibre. This is due to impurities in the fibre\, manufacturing errors or environmental stresses such as heat ing or movement. This causes refractive differences between polarized stat es which change the state of polarization. This property is called birefri ngence.\nPolarization mode dispersion allows for the state of polarization to be corrected when a photon is transmitted through fibre. If the fibre is fixed\, the environmental stresses result in a unique and constant chan ge of polarization [4]. This can be compensated for by rotating each photo n appropriately before being measured and each length of fibre will requir e its own unique adjustment. If the fibre is subjected to variable conditi ons\, changes in the state of polarization of photons must be monitored an d adjustments must be made at suitable time intervals. Using this method\, polarization encoded QKD can be implemented in fibre.\n\nhttps://events.s aip.org.za/event/7/contributions/4960/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4960/ END:VEVENT BEGIN:VEVENT SUMMARY:The annealing effects on Pt-Mo coating mophology DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4966@events.saip.org.za DESCRIPTION:Speakers: Zakhelumuzi Khumalo (ithemba LABS)\nThe study of ann ealing effects on platinum binary systems has both the fundamental and app lied aspects. It is due to the fact that the formation of ordered domains increases the strength and surface hardness and could also have an impact on surface activity and chemical properties. The changes of mechanical\, p hysical and chemical properties caused by annealing could be of significan t importance for application of platinum systems as catalysis\, gas sensor s\, fuel cells\, glass industry\, electronics and biomedicine.\nThe Pt-Mo coatings used in this study were deposited by electron beam and sputtering methods. In order to study annealing effects the Pt-Mo coated systems wer e subjected to heat treatment at elevated temperatures for different annea ling periods. Several complimentary techniques such as X-ray Diffraction ( XRD)\, Rutherford Backscattering Spectroscopy (RBS)\, Particle Induced X-r ay Emission (PIXE)\, and Scanning Electron Microscopy (SEM) were used for coatings characterisation.\n\nhttps://events.saip.org.za/event/7/contribut ions/4966/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4966/ END:VEVENT BEGIN:VEVENT SUMMARY:Exploratory investigation of spin density wave behaviour of a (Cr< sub>86 Re14)100-y Vy alloy system DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4961@events.saip.org.za DESCRIPTION:Speakers: Bincy Susan Jacobs (University Of Johannesburg)\nThe Cr-Re alloy system was chosen in order to investigate a previous observat ion of the co-existence of superconductivity and antiferromagnetism\, as w ell as the possibility of a quantum critical point (QCP) in this alloy sys tem. For the initial studies a Cr86Re14 mother alloy was doped with V in o rder to decrease the electron to atom ratio\, resulting in a decrease in t he Néel temperature (TN). The preliminary study focused on first obtainin g a pure body centered cubic (BCC) Cr86Re14 mother alloy\, as in this allo y system\, a secondary A15 phase may co-exist. X-ray diffraction and elect ron microprobe analyses of as-cast and annealed samples revealed only BCC structure with good homogeneity and actual Re concentration of 16 ± 1 ato mic percent. In order to initiate investigations into the magnetic propert ies and possible quantum criticality in this system\, electrical resistivi ty and magnetic susceptibility measurements as a function of temperature are reported for (Cr86Re14)100-yVy alloys with y = 0\, 5\, 7 and 9. Elect rical resistivity as a function of temperature for these samples reveal an anomaly on cooling through TN. The anomaly observed shifts down to lower temperatures as the V concentration is increased. Magnetic susceptibility data supports these observations. These promising results warrant further investigation into this alloy system with the possibility of contributing towards the current interest in quantum criticality in chromium alloy syst ems.\n\nhttps://events.saip.org.za/event/7/contributions/4961/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4961/ END:VEVENT BEGIN:VEVENT SUMMARY:Contrasts between student and examiner perceptions of the nature o f assessment tasks DTSTART;VALUE=DATE-TIME:20110715T090000Z DTEND;VALUE=DATE-TIME:20110715T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4962@events.saip.org.za DESCRIPTION:Speakers: Douglas Clerk (School of Physics\, University of the Witwatersrand)\nFor several years an on-going study has examined student performance in relation to the types of assessment task encountered in fir st year physics examinations. The typology used recognises four basic task types: routine operations\, novel problems\, interpretive questions and b ookwork. Thus far it appears that average student performance is strongest for routine operations\, variable for bookwork\, weak for novel problems and weakest for interpretive questions. The present phase of the study exa mines the question of whether the students experience a given assessment t ask in the way the examiner intended – e.g. if a given question was inte nded by the examiner as a routine operation\, do the students experience i t as a routine operation or as a novel problem? The answer would appear to depend on the nature and degree of the students’ preparation. In additi on it seems that no one assessment task fits neatly into a single task cat egory. A student can experience a given task as a mix of several operation s\, each belonging to one of the four types.\n\nhttps://events.saip.org.za /event/7/contributions/4962/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4962/ END:VEVENT BEGIN:VEVENT SUMMARY:Inflammatory response of injured diabetic fibroblasts after low in tensity laser irradiation at a wavelength of 830 nm DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4964@events.saip.org.za DESCRIPTION:Speakers: Palesa Sekhejane (DTech Student)\nDiabetes mellitus (DM) is a chronic disease characterized by impeded glucose metabolism and preceded by diabetic ulcers which are chronic due to deteriorated healing process. Hypoxia\, decreased fibroblast proliferation and impaired growth factors are amongst root factors that contribute to impaired healing. Phot ostimulation is a non-invasive treatment that utilizes low intensity laser irradiation (LILI) to provide healing or stimulate appropriate cellular f unctions. Human skin fibroblast cells (WS1) were used in this study that c onsisted of four groups viz. normal\, normal wounded\, diabetic wounded an d hypoxic\, each with a non-irradiated control. Wounding was simulated by creating a central scratch using a pipette. A diabetic state was induced b y growing cells in media that contained excess glucose to a final concentr ation of 22.56 mM\, and for hypoxic insult cells were incubated under anae robic conditions (0% O2 and 20% CO2) for 4 h. Cells were then irradiated a t a wavelength of 830 nm with 5 J/cm2 and incubated for 1 or 24 h. Morphol ogical changes were observed by light microscopy\; ELISA and flow cytometr y were used to determine interleukin (IL)-1β\, IL-6 and tumour necrosis f actor (TNF)-α as inflammatory markers\; and caspase 3/7 for apoptosis was determined by luminescence. After a 24 h incubation period the wounded ar ea appeared decreased and hypoxic cells had regained normal morphologic fe atures when irradiated\, TNF-α and IL-1β had decreased in irradiated sam ples\, whereas IL-6 was increased. Caspase 3/7 had decreased in irradiated samples at both 1 and 24 h. This study demonstrated the beneficial effect s of LILI since the results showed significantly reduced inflammatory resp onse in vitro and hastened wound healing particularly under diabetic and h ypoxic conditions.\n\nhttps://events.saip.org.za/event/7/contributions/496 4/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/4964/ END:VEVENT BEGIN:VEVENT SUMMARY:Compression of highly charged electron pulses for single shot femt osecond time-resolved electron diffraction experiments DTSTART;VALUE=DATE-TIME:20110714T121500Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4965@events.saip.org.za DESCRIPTION:Speakers: Nicolas Erasmus (Stellenbosch University)\nObtaining single shot electron diffraction patterns is highly desirable when dealin g with samples that are either destroyed or display irreversible structura l changes upon photo-excitation. Such single shot measurements demand high ly charged pulses that contain in the order of 105 – 106 electrons. Main taining femtosecond pulse duration in the presence of the inevitably large Coulomb forces inside such electron bunches is currently a major challeng e in the field of ultrafast electron diffraction. One of the suggested sol utions is to recompress the pulses. Conventional RF cavity compressors hav e been successfully constructed and implemented\, but factors such as thei r bulkiness\, high cost and difficulty of manufacturing constitute a limit to this approach. Here we present an alternative compressor concept based upon a radio frequency cavity shunted by a pair of gallium arsenide photo conductive semiconductor switches (PCSS). The PCSS’s are triggered by tw o synchronous femtosecond laser pulses\, resulting in a low jitter 5 GHz o scillation of the cavity. We report here results from our prototype device \, which has achieved compression of an electron pulse containing 40 000e- /pulse from a 14ps down to a 500fs duration\, as confirmed by measurements from our in-house developed femtosecond streak camera. We believe that ou r electron bunch compressor device will be easier to implement and much mo re cost effective than traditional RF cavities.\n\nhttps://events.saip.org .za/event/7/contributions/4965/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4965/ END:VEVENT BEGIN:VEVENT SUMMARY:Characterization of Cluster States in 16O with the (p\, t) reaction DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4967@events.saip.org.za DESCRIPTION:Speakers: Justin Mabiala (Stellenbosch University/iThemba LABS )\nMotivated by several theoretical cluster calculations that predict the existence of the 06+ state in 16O located at 15.1 MeV as a very good cand idate for the equivalence of the Hoyle state in 12C\, a high resolution me asurement of 16O spectrum in coincidence with the 16O decay products was p roposed using a (p\,t) reaction at 200 MeV and 0o. The decay products of t he excited 16O recoil nucleus were detected by means of Double Sided Silic on Detectors and the outgoing tritons were identified in the K600 magnetic spectrometer focal plane. Data were collected with targets containing 18O \, 16O\, 12C and 7Li. First results on precise measurement of energy spect ra of the corresponding recoil nuclei using the K600 as the master trigger and extracted cross sections will be discussed.\n\nhttps://events.saip.or g.za/event/7/contributions/4967/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4967/ END:VEVENT BEGIN:VEVENT SUMMARY:Effect of annealing on the Ce3+/Ce4+ ratio measured by XPS in lumi nescent SiO2:Ce DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4968@events.saip.org.za DESCRIPTION:Speakers: Hassan Seed Ahmed (University of the Free State)\nCe doped silica has potential applications for a luminescent material as pho sphors for cathodoluminescence\, scintillators and detectors. Ce ions can occur in a trivalent or a tetravalent state: only the trivalent Ce3+ state with a single 4f electron is optically active\, while the tetravalent Ce4 + ion is non-luminescent. X-ray photoelectron spectroscopy (XPS) is a sui table technique to investigate the oxidation states of Ce in cerium oxides and such studies have been carried out because of the importance of CeO2/ Ce2O3 conversion in automotive exhaust catalysts. However\, the XPS Ce(3d) spectrum of cerium oxide is rather complex as it contains ten closely spa ced and overlapping peaks on a strong background. The main challenge is to obtain accurate fits to experimental data while still maintaining a good physical basis for the fitting parameters. The analysis of Ce in SiO2:Ce i s even more challenging since the Ce concentration for luminescent samples is only in the region of 1%. Although it has been experimentally shown th at to improve the luminescence efficiency of Ce doped silica it can be use ful to anneal the glass in a reducing atmosphere\, with the implication th at this increases the concentration of Ce3+ luminescent ions\, we are not aware of XPS measurements that correlate the relative concentrations of th e Ce3+ and Ce4+ ions to the luminescent properties. In this work\, cerium doped silica was prepared by the sol-gel method. The effect of annealing temperature and atmosphere on the luminescent properties are correlated to XPS measurements of the oxidation state of Ce in the samples.\n\nhttps:// events.saip.org.za/event/7/contributions/4968/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4968/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and Characterization of Structural and Luminescent prope rties of long afterglow CaAl2O4: Eu2+\, N d3+\, Dy3+ nano-scaled phosphors by solution – com bustion technique. DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4969@events.saip.org.za DESCRIPTION:Speakers: Ali Wako (University Of The Free State\, QwaQwa Camp us.)\nLong afterglow calcium aluminate phosphors doped with Eu2+ and co-do ped with Nd3+ /or Dy3+ (CaAl2O4:Eu2+\, Nd3+\, Dy3+) were fabricated by ure a-nitrate solution – combustion method at 500 °C.\nThe effects of varyi ng concentrations of Ca:Al and co-dopants molar ratio (Nd3+:Dy3+) on the s tructural and luminescent properties of the phosphor were investigated. It was observed that Ca:Al molar ratios greatly affect the crystalline struc ture of the material. The results of the X-ray diffraction (XRD) analysis reveal that the formation of several crystalline phases depends on the mol ar ratios of the host material. The peaks show the presence of other phase s such as Ca3Al2O6 and CaAl4O7 but the predominant phase formed was that o f CaAl2O4. As the concentration of Ca ions increase\, the peak intensity i ncrease which led to formation of monoclinic CaAl2O4 as a single phase for the 1.5% Ca. However it was found that the crystalline structure is gener ally not affected by variation of the co-dopants concentration. \nPL studi es revealed a general rise in intensity with increase in the mole ratio of Ca:Al . The highest PL intensity was observed with 1.5% Ca but was weak w ith 0.1% Ca. Also it is evident that as the fraction of Nd3+ increase and that of Dy3+ decrease proportionally good emission intensities are formed in the region 400nm-500nm at the ratio 1:1. The initial luminescent intens ity and rate of decay vary from each other when co-doped with various prop ortions of Nd3+ and Dy3+. Low Nd3+ exhibited high initial luminescent inte nsity but low decay rate because of insufficient trap vacancies in the hos t matrix.\n\nhttps://events.saip.org.za/event/7/contributions/4969/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4969/ END:VEVENT BEGIN:VEVENT SUMMARY:Conductivity crossover in hot filament CVD grown nano-crystalline diamond films doped with nitrogen. DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4970@events.saip.org.za DESCRIPTION:Speakers: George Chimowa (Wits)\nWe report on the synthesis an d electrical characterization of nano-crystalline diamond films grown by h ot filament chemical vapor deposition. Low temperature magnetoresistance m easurements have shown a crossover in conductivity from hopping\, activate d to semi-metallic conduction as the nitrogen level in the CVD chamber is increased from 10% - 15%\, 20% to 22% respectively. Raman spectroscopy stu dies and SEM micrograph indicate a change in morphology with deposition pa rameters such as pressure\, temperature and gas chemistry while AFM microg raph suggests a columnar growth process. In the semi-metallic regime the c onduction is characterized by anisotropic 3D weak localization mechanism w ith a weak temperature dependence of the dephasing time (D) approximate ly (D)  T-0.7. Such behavior has been reported in Superlattice struc tures. Understanding of the transport properties in nano-crystalline diamo nd films is a perquisite for the application of diamond films in nano-elec tronics for fast switching and field emission devices.\n\nhttps://events.s aip.org.za/event/7/contributions/4970/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4970/ END:VEVENT BEGIN:VEVENT SUMMARY:Four–year program students expectations and reactions DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4971@events.saip.org.za DESCRIPTION:Speakers: Denise Dale (University of Pretoria)\nAn Investigati on of students’ expectations when they are accepted to study at the Univ ersity of Pretoria\, how they study for physics and their reactions after the first semester test. We find that most students are shocked after thei r first semester test\, because they expected to obtain high marks and don ’t\, or the other way around.\n\nhttps://events.saip.org.za/event/7/cont ributions/4971/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/4971/ END:VEVENT BEGIN:VEVENT SUMMARY:Determining the impact of anthropogenic activities on the environm ent by using In Situ gamma ray measurements. DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4972@events.saip.org.za DESCRIPTION:Speakers: Jacques Bezuidenhout (Stellenboch University)\nSalda nha Bay on the West Coast of South Africa is surrounded by various nature reserves and protected areas which amongst other includes heritage sites l ike the West Coast Fossil Park. Large parts of these sensitive areas were however exposed to anthropogenic activities\, which includes farming and mining as well as training and preparation for war. This article investig ates the prospect of determining the impact that anthropogenic activities had on areas via mapping of primordial radioactive isotopes. For this pur pose In Situ gamma ray data were obtained from selected locations around S aldanha Bay. The variation in radioactive isotope concentrations is compa red to historical data of anthropogenic activities.\n\nhttps://events.saip .org.za/event/7/contributions/4972/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4972/ END:VEVENT BEGIN:VEVENT SUMMARY:Fine structure of the Isoscalar Giant Quadrupole Resonance and 2+ level densities in spherical to deformed nuclei across the isot ope chain 142\,144\,146\,148\,150Nd using the (p\,p') reaction DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4973@events.saip.org.za DESCRIPTION:Speakers: Chamunorwa Oscar Kureba (University of the Witwaters rand)\nA systematic experimental investigation of the phenomenon of fine s tructure\, with emphasis on the region of the Isoscalar Giant Quadrupole R esonance (ISGQR)\, in nuclei across stable even-even neodymium isotopes ha s been performed. Measurements were made using the K600 Magnetic Spectrome ter of iThemba Laboratory for Accelerator Based Sciences\, a facility whic h is situated at Faure near Cape Town\, South Africa. Unique high energy-r esolution inelastic proton scattering experiments were performed at an inc ident proton energy of Ep = 200 MeV on targets 142\,144\,146\,148\,150Nd. Nuclei with mass number A ≈ 150 and neutron number N ≈ 90 are of speci al interest since they occupy that region of the nuclide chart wherein the onset of permanent prolate deformation occurs. The stable neodymium (Z = 60) isotopes have been chosen in the present study\, in order to investiga te the effects accompanying the onset of deformation\, on the excitation e nergy spectra in the ISGQR region (10 ≤ Ex ≤ 25 MeV)\, since they exte nd from the semi-magic N = 82 nucleus (142Nd) to the permanently deformed N = 90 (150Nd) nucleus. An important further step is to test the effect th at the transition from spherical to deformed nuclei has on level densities . Experimental details\, data extraction and analysis techniques\, togethe r with preliminary results will be presented.\n\nhttps://events.saip.org.z a/event/7/contributions/4973/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4973/ END:VEVENT BEGIN:VEVENT SUMMARY:xygen adsorption on (110) surfaces of Pyrolusite MnO2 a nd Anatase TiO2 DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4974@events.saip.org.za DESCRIPTION:Speakers: khomotso Maenetja (University Of Limpopo)\nRecent st udies have employed manganese dioxide (MnO2) catalysts to improve the effi ciency of Li-air batteries\, while other studies have revealed that the Li /O2 cell can be recharged with high efficiency without a catalyst using an appropriate porous carbon electrode. Interestingly\, charge voltages of t hese cells are similar to those of the MnO2\, while both of these exhibits higher charge voltages than the cobalt-catalyzed cells. However\, it has been observed that in the absence of a catalyst the recharge occurs at abo ut high voltage\, a large hysteresis between charge and discharge voltages . Ab initio planewave pseudopotential method will be used to investigate t he interaction of the oxygen molecule with the (110) surfaces of MnO2\, in particular tendencies of oxygen reduction. Their surface and adsorption e nergies were determined together with the distances between O-O of the oxy gen molecule\, in the vertical and horizontal orientation\, the metal and oxygen molecule before and after relaxation. We found that manganese dioxi de is more effective and gave lowest adsorption energies\, and reduces oxy gen molecule better than titanium dioxide. However the horizontal orientat ion of the oxygen molecule is more favourable in terms of oxygen reduction than the vertical orientation.\n\nhttps://events.saip.org.za/event/7/cont ributions/4974/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4974/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational study of some tin dioxide phases DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4975@events.saip.org.za DESCRIPTION:Speakers: NDUMA NTIMANE (UNIVERSITY OF LIMPOPO)\nRutile and an atase structured tin dioxide ceramics have been intensively studied in rec ent years because of their potential in sensing and fuel cells.The present work uses classical molecular dynamics simulations focused on the structu re and possible transformation from anatase to rutile tin dioxide.The empi rical Buckingham potential has been used to describe the interatomic inter actions in tin dioxide.The total energy of the NVE ensemble of the two str uctures at various temperatures has been calculated in order to determine the transition temperature and pressure.The results obtained showed an ene rgy increase with temperature which was constantly compared with experimen ts.The radial distribution functions for the two structures suggest the tr ansformations at temperature above 900 degrees celcious in agreement with the experiments.\n\nhttps://events.saip.org.za/event/7/contributions/4975/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4975/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and characterization of Water soluble Covellite Copper S ulphide Quantum Dots DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4976@events.saip.org.za DESCRIPTION:Speakers: Swikisani Nelwamondo (University of Johannesburg)\nC ovellite copper monosulphide (CuS) is a representative I–VI chalcogenide semiconductor with the unique photoelectricity transformation characteris tic. Due to quantum confinement effect\, CuS nanoparticles exhibit optical and electrical properties as compared to the bulk materials. CuS is an in direct semiconductor with a bandgap around 1.7 eV. At high temperature CuS exhibits fast ion conduction and shows metal-like electrical conductivity and is an important semiconductor because of its excellent optical and el ectronic functionality. Colloidal method was used to develop CuS nanoparti cles from copper acetate monohydrate and Thioacetamide in water and methan ol using alanine as a stabilizing agent at pH 10 at different low temperat ures. Water soluble CuS quantum dots in the form of rods and spherical sha ped with an average diameter of 3-10 nm has been successfully obtained. Th e as-obtained CuS nanoparticles were characterized by X-ray diffractometry (XRD)\, scanning electron microscope (SEM)\, energy-dispersive X-ray spec troscopy (EDS)\, Infrared spectra (FT-IR)\, UV-visible spectroscopy (UV) a nd Photoluminescence (PL). Effect of temperature was investigated for the stability of nanoparticles\n\nhttps://events.saip.org.za/event/7/contribut ions/4976/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4976/ END:VEVENT BEGIN:VEVENT SUMMARY:Genetic algorithms in astronomy and astrophysics DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4977@events.saip.org.za DESCRIPTION:Speakers: Vinesh Rajpaul (UCT)\nGenetic algorithms form a clas s of search heuristics that incorporate\, in a computational setting\, the biological notion of evolution by means of mutation and natural selection . Compared to more conventional search and optimisation techniques\, genet ic algorithms are very easy to implement and they tend to be extremely rob ust and versatile. Although already ubiquitous in fields such as computer science\, engineering and artificial intelligence\, genetic algorithms hav e not yet been widely adopted in the physical sciences.\n\nI provide a ver y brief introduction to genetic algorithms and outline their relevance to a number of diverse problems in astronomy and astrophysics\, from stellar structure modelling and astroseismological analyses to robotic telescope s cheduling. In particular I discuss a difficult optimisation problem in gra vitational microlensing analysis for which it is hoped that genetic algori thms might facilitate an efficient exploration of an enormous parameter sp ace.\n\nhttps://events.saip.org.za/event/7/contributions/4977/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4977/ END:VEVENT BEGIN:VEVENT SUMMARY:Evaluation of WC-9Co-4Cr laser surface alloyed coatings on stainle ss steel DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4985@events.saip.org.za DESCRIPTION:Speakers: BABATUNDE OBADELE (TSHWANE UNIVERSITY OF TECHNOLOGY) \nIn order to examine the effect of Cr on the microstructure and hardness behaviour of WC cermet\, coatings have been obtained by laser surface allo ying technique. WC-9Co-4Cr particulate was injected into the surface of AI SI 304L stainless steel under different processing variables. The morpholo gies and microstructures of the composite coatings were investigated using optical microscopy and high resolution scanning electron microscopy\, whi le the phase changed were observed using x-ray diffraction. The surface ha rdness was determined using the Vickers microhardness tester. The excessiv e heat from the laser beam partially melt the WC-Co which results in carbo n deficiency and precipitation of carbon as graphite to form CO2 pores wi thin the coatings. 4% Cr has been added to compensate for the precipitatio n of graphite to form Cr3C2. A considerable increase in hardness value fro m 246 to 1331 Hv0.1 was achieved when alloying was carried out at high las er power and speed\, the pores being completely eliminated.\n\nhttps://eve nts.saip.org.za/event/7/contributions/4985/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4985/ END:VEVENT BEGIN:VEVENT SUMMARY:Finite Element Calculations for Molecules with multiple Coulomb Ce nters DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4978@events.saip.org.za DESCRIPTION:Speakers: Moritz Braun (University of South Africa)\nEfficient and reliable methods to solve effective three dimensional Schroedinger e quations are an important ingredient for both density functional as well as Hartree Fock methods used to calculate the properties of molecules and solids. In order to judge the accuracy of popular methods such as using G aussian basis functions or smooth pseudo potentials it is desirable to use a method that promises to be less basis dependent. \nSuch a method is the finite element method\, where the convergence of the wave functions and e igen values can be systemically improved. In combination with using a prod uct ansatz of a function f(r) satisfying the cusp conditions at all nucl ei and a smooth function phi(r) for the wave function this provides a meth od to calculate all electron wave functions. The efficiency of this appro ach in practice depends crucially on finding a finite element grid which p rovides enough points where needed but does not “waste “ points where not required. In this contribution results obtained for simple molecules v ia two and three dimensional calculations are given.In addition the fin ite element calculations are discussed in some detail.\n\nhttps://events.s aip.org.za/event/7/contributions/4978/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4978/ END:VEVENT BEGIN:VEVENT SUMMARY:Mirror symmetry for nuclei near or beyond the proton drip line DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4979@events.saip.org.za DESCRIPTION:Speakers: Steven Karataglidis (University of Johannesburg)\nTh e notion of mirror symmetry is well-established for nuclei on or near the valley of stability\, and this has its roots in the (largely) charge indep endent nature of the nuclear force. We have applied this assumption to nu clei near or beyond the drip lines\, in particular\, the mass-15 system fo r 15F and 15C. Using information on the bound states in 15C we predicted s tates in 15F in 2006 which were subsequently found in 2009. We have extend ed our searches to other mirror pairs of exotic nuclei: in particular mass -17. In the case of mass-17 nuclei\, we obtain interactions by considering the states in 17C\, from which we may obtain information on other exotic mass-17 nuclei.\n\nhttps://events.saip.org.za/event/7/contributions/4979/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4979/ END:VEVENT BEGIN:VEVENT SUMMARY:Clay/sawdust porous pots for water treatment DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4980@events.saip.org.za DESCRIPTION:Speakers: Joseph A Varkey (University of Swaziland)\nThe suppl y of adequate clean water to communities is a problem in many countries\, especially in Africa where the rural population depend on water from river s\, dams and streams for domestic use. Such water contains many chemical s ubstances and microorganisms that affect the health of human beings and an imals. Use of simple water purification systems\, like filters\, by househ olds\, is a possible solution to this problem. In our laboratory\, we hav e developed a porous pot water filter using sawdust and clay. Both materi als are available locally. Sawdust was sieved using 100\, 250 and 600 micr ometer sieve and then mixed with clay in the clay/ sawdust ratio of 1:3 by volume. The mixture was then used to make pots\, which were porous. These pots were tested for their capacity to purify contaminated water collecte d from rivers. The filtration rate\, as a function of the clay/coal ratio\ , was also measured. Subsequently\, quality tests were done on the filtere d water and raw water to determine the potability of the filtered water. T he tests included microbiological\, physical and chemical properties. The results were then compared with standards provided by World Health Organiz ation.\n\nhttps://events.saip.org.za/event/7/contributions/4980/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4980/ END:VEVENT BEGIN:VEVENT SUMMARY:Density-matrix renormalization group study of the electro-absorpti on in conjugated polymers DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4981@events.saip.org.za DESCRIPTION:Speakers: Anas Abdelwahab (Sudan University of Science and Tec hnology)\nA symmetrized and dynamical density matrix renormalization group is used to study 1-dimensional extended Peierls-Hubbard model at half-fil ling. We have investigated the optical conductivity spectrum and electro-a bsorption spectrum for low-lying optical exciton with strong\, intermediat e and weak coupling parameter sets for the on-site and neighbor interactio ns. We were able to capture the Stark effect in the case of strong couplin g under static electric field. The intermediate coupling was found to be c lear for weak electric field and destroyed for strong one. We were not abl e to resolve the splitting in the case of weak coupling due to the small b inding energy so that small value of electric field could distroy the exci ton.\n\nhttps://events.saip.org.za/event/7/contributions/4981/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4981/ END:VEVENT BEGIN:VEVENT SUMMARY:Algebraic density functionals DTSTART;VALUE=DATE-TIME:20110715T094500Z DTEND;VALUE=DATE-TIME:20110715T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4982@events.saip.org.za DESCRIPTION:Speakers: Steven Karataglidis (University of Johannesburg)\nA systematic strategy for the algebraic calculation of density functionals c onsists in coding information about the density and the energy into polyno mials of the degrees of freedom of the wave functions. Density functionals and Kohn-Sham potentials are then obtained by standard elimination proced ures of such degrees of freedom between the polynomials. Numerical example s illustrate the formalism.\n\nhttps://events.saip.org.za/event/7/contribu tions/4982/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/4982/ END:VEVENT BEGIN:VEVENT SUMMARY:Properties of the Interstellar medium in nearby galaxies DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4984@events.saip.org.za DESCRIPTION:Speakers: Roger IANJAMASIMANANA (University of Cape Town)\nWe use the HI velocity profiles of The HI Nearby Galaxy Survey (THINGS) to st udy the phase structure of the ISM and its relation to galaxy properties a nd morphology. To construct high S/N profiles\, we use a method analogous to the stacking method sometimes used in high redshift HI observations. We call these high S/N profiles super profiles. By decomposing the super pro files into Gaussian components\, we found broad and narrow components whic h are evidence of the presence of Cold Neutral Medium (CNM) and Warm Neutr al Medium (WNM). We also derive radial super profiles of the THINGS galaxi es and we found some correspondance between the shapes of the super profil es and their location within the galaxies. We found that the narrrow compo nents dominate inside the optical radius r25. We also analyze the shapes o f the super profiles in low\, moderate and high star formation rate (SFR) regions and we found that the narrow component dominates in high SFR regio ns. The profiles also tend to be more asymmetric and broader in high SFR r egions.\n\nhttps://events.saip.org.za/event/7/contributions/4984/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/4984/ END:VEVENT BEGIN:VEVENT SUMMARY:Deposition\,Optical and Electrical Characterization of Silicon Car bide Thin Films for Solar Cell Applications DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4986@events.saip.org.za DESCRIPTION:Speakers: Sihle Mkhwanazi (University of the Western Cape)\nSi licon carbide (SiC) materials have attracted a lot of attention because of their good optical and electrical properties. In recent years there has b een an intense focus in research on controlling the optical and electrical properties of amorphous SiC thin films deposited at low temperature of th e substrate. SiC has a wide bandgap which can be tuned by varying the carb on content in the thin film. The SiC thin films also have a high electron mobility\, high electron saturation velocity\, optical transparency which make them candidates for use as window layer in solar cells. The low depos ition rate issue in SiC thin films processing has not yet been resolved. T his contribution will focus on optimizing the deposition rate by studying the influence of the deposition parameters on the deposition rate. The thi n films ranging from amorphous to microcrystalline SiC has been deposited by magnetron sputtering and hot wire chemical vapour deposition at low sub strate temperature of the substrate below 300 oC. The optical properties o f the films have been investigated transmission/reflectance spectrum using the OJL model in SCOUT and by computation using the iterative method of S wanepoel. The electrical properties such as conductivity\, bulk concentrat ion and mobility will be investigated by Hall Effect measurements.\n\nhttp s://events.saip.org.za/event/7/contributions/4986/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4986/ END:VEVENT BEGIN:VEVENT SUMMARY:Low level counting using a NaI(Tl) detector DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4987@events.saip.org.za DESCRIPTION:Speakers: Sive Noncolela (UWC)\nIn this work a 7.5 cm x 7.5 cm NaI (Tl) detector was used to study activity concentrations of primordial radionuclides in soil and sand samples. The detector and the sample were placed inside a lead castle to reduce background measurements from the sur roundings such as the wall and the floor. The samples were placed inside a 1L Marinelli beaker which surrounds the detector for better relative. Add itional lead bricks were placed below the detector to further reduce the b ackground by 10%. \nA Full Spectrum Analysis (FSA) method was used to extr act the activity concentrations of 238U\, 232Th and 40K from the measured data. The FSA method uses standard spectra corresponding to the radionucli des being investigated\, which are multiplied by the activity concentratio ns and then added to fit the measured spectrum. Accurate concentrations ar e then extracted using a chi-squared (χ2) minimization procedure.\nEight samples were measured using the NaI detector and analyzed using the FSA me thod. The samples were measured for about 24 hours for good statistics. Th e 238U activity concentration values varied from 10 ± 2 Bq/kg (iThemba s oil\, HS6) to 256 ± 10 Bq/kg (Kloof sample). The 232Th activity concentra tion values varied from 7 ± 1 Bq/kg (Anstip beach sand) to 45 ± 5 Bq/kg (Rawsonille soil #B31). The 40K activity concentration values varied from 45 ± 27 Bq/kg (iThemba soil\, HS6) to 120 ± 9 Bq/kg (Rawsonille soil\, # B28). The χ2 values also varied from sample to sample with the lowest bei ng 0.13 (Anstip beach sand) and the highest being 6820 (iThemba soil\, HS1 ). A high χ2 value usually represents incomplete gain drift corrections\, improper set of fitting functions\, proper inclusion of coincidence summi ng or the presence of anthropogenic radionuclei.\n\nhttps://events.saip.o rg.za/event/7/contributions/4987/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4987/ END:VEVENT BEGIN:VEVENT SUMMARY:ZnO Nanorods/Nanoplates for Gratzel-Type Dye Solar Cells Applicati ons: Growth Mechanism DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4988@events.saip.org.za DESCRIPTION:Speakers: Joseph Sithole (NRF iThemba Labs)\nZinc oxide is a d irect\, wide bandgap semiconductor material with many promising properties for blue/UV optoelectronics\, transparent electronics\, spintronic device s and sensor applications. ZnO has been commonly used in its polycrystalli ne form in a wide range of applications such as sunscreens\, catalysts\, p iezoelectric transducers\, varistors\, and as transparent conducting elect rodes. ZnO has numerous attractive characteristics for electronics and opt oelectronics devices especially in solar cells. It has direct bandgap ener gy of 3.37 eV\, comparable to of TiO2 which makes it transparent in visibl e light. The exciton binding energy is about 60 meV for ZnO. The room temp erature electron Hall mobility in single crystal ZnO is of the order of 2 00 cm2 V-1. Unlike TiO2\, ZnO can be grown easily in anisotropic shape\, s pecifically in form of nanorods or nanotubes. This central geometry of nan o-scaled ZnO\, in addition to the high surface/volume ratio for the adsorp tion of light-harvesting molecules\, would offer a larger free mean path f or electronic charge transfer and minimizes the e-hole recombination in a ZnO nanorods/nanotubes based excitonic Gratzel dye solar photocells. Indee d\, this tubular ZnO geometry would enhance the device efficiency through the direct electrical pathways provided by the nanorods/nanotubes\, ensure s the rapid collection of carriers generated throughout the device\, in a ddition to an effective light trapping. This contribution reports the grow th mechanism of the ZnO nanorods by the so called Vayssieres hydrothermal method. It is demonstrated for the first time that in a large pH range wit hin the hydrothermal process\, the growth mode of the ZnO nanorods is a pu re Frank-van der Merwe driven process. More precisely\, nano-platellets of ZnO are formed at the early growth stage growing towards nano-rods. From crystallographic view point\, both the ZnO nano-plattelets and nanorods ex hibit the standard hexagonal wurtzite crystal structure\, with (002) main orientation and lattice parameters a=~3.25 Å and c=~5.12 Å. The room tem perature luminescence and Raman investigations indicates that the defects are mainly O deficiency driven.\n\nhttps://events.saip.org.za/event/7/cont ributions/4988/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/4988/ END:VEVENT BEGIN:VEVENT SUMMARY:Deposition and structural properties of Silicon Carbide thin films for solar cells applications DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4989@events.saip.org.za DESCRIPTION:Speakers: Joshua Khoele (University of the Western Cape)\nAmor phous and nanocrystalline silicon carbide thin films were deposited on cor ning glass 7059 and c-Si (100) substrates using the Hot Wire Chemical Vapo r Deposition (HWCVD) and Magnetron Sputtering (MS) techniques. Samples wer e prepared at low substrate temperatures below 300 degrees celsius and a g as mixture of SiH4/CH4/H2 was used in case of HWCVD. For MS\, the temperat ure of the substrate was varied between 300-600 degrees celsius and Ar pla sma was used to sputter a SiC target in a H2 plume environment. X-ray diff raction (XRD) and transmission electron microscopy (TEM) were used to inve stigate the phase changes and crystallinity in the films. Plan view and cr oss section specimen were prepared by the TRIPOD polishing technique for t he TEM structural investigation. Fourier Transform Infrared Spectroscopy ( FTIR) was used to investigate the hydrogen content and the SiC vibrational bonds in the samples.\n\nhttps://events.saip.org.za/event/7/contributions /4989/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4989/ END:VEVENT BEGIN:VEVENT SUMMARY:Schottky contact on GaN DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4990@events.saip.org.za DESCRIPTION:Speakers: Mmantsae Diale (University of Pretoria)\nMetal Au\, Ni and Ni/Au contacts on n-GaN were studied for metal contacts for the fab rication of Shottky barrier ultraviolet photodetectors. AES\, RBS and curr ent-voltage measurements were used to study the samples. Figure 2 shows th e current voltage mechanism of Au\, Ni and Ni/Au transparent contacts onto GaN. The Schottky barrier heights of Au contacts were averaged at 0.84 ± 0.02 eV and the ideality factors of 1.7 ± 0.3. Series resistance for the se contacts was about 481 ± 4 Ω. Ni contacts onto GaN are dominated by t unneling currents and the leakage current is higher than that of Au. The S chottky barrier heights of Ni contacts were averaged at 0.82 ± 0.04 eV an d the ideality factors of 1.9 ± 0.2. Series resistance for these contacts was about 38 ± 1 Ω\, far less than that of Au contacts. Ni/Au contacts are annealed at 500 °C for transparency. The leakage current of Ni/Au is two orders of magnitude lower than that of Ni and Au\, and the Schottky ba rrier height was averaged at 2.04 ± 0.01 eV for ideality factors of about 1.6 ± 0.4.\n\nhttps://events.saip.org.za/event/7/contributions/4990/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4990/ END:VEVENT BEGIN:VEVENT SUMMARY:The optical syringe for selective differentiation of pluripotent s tem cells DTSTART;VALUE=DATE-TIME:20110714T070000Z DTEND;VALUE=DATE-TIME:20110714T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4991@events.saip.org.za DESCRIPTION:Speakers: Patience Mthunzi (CSIR - NLC)\nDue to their self-ren ewal and pluripotency characteristics\, stem cells possess the potential t o dramatically advance current therapies in tissue regeneration and engine ering. Nonetheless\, there still remains a pressing necessity to answer th e biological questions concerning how stem cell renewal and differentiatio n programs are operated and regulated at the genetic level. Genetic manipu lation such as delivery of exogenous gene expression or knockout with smal l interfering RNA (siRNA) is relatively rare in mouse embryonic stem (ES) cells. However\, genetic species can be selectively introduced and subsequ ently expressed in live mammalian cells via optical systems\, a technique normally referred to as photo-transfection. During photo-transfection\, lo calized application of femtosecond (fs) laser pulses onto the cell plasma membrane induces transient submicrometer holes\, thereby facilitating cyto solic uptake of extracellular exogenous materials. This novel optical cell transfection technique allows targeted treatment of cells promoting limit ed use of reagents or chemicals that can cause spontaneous differentiation and also interfere with the physiological properties of ES cells. In this work\, we report for the first time that fs laser pulses can be utilized as an optical syringe for successful transient photo-transfection and indu ced differentiation of mouse ES cell colonies. This was achieved by using a tightly focused titanium sapphire laser beam spot (~1.1 µm diameter spo t size\, 790nm\, 80MHz\, 200fs and 50 mW average power output)\, where E14 g2a cells were differentiated into the extraembryonic endoderm via photo-t ransfection with the Gata-6 transcription factor.\n\nhttps://events.saip.o rg.za/event/7/contributions/4991/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4991/ END:VEVENT BEGIN:VEVENT SUMMARY:Equivalent parameters for empirical pseudopotential and k•p mode ls DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4992@events.saip.org.za DESCRIPTION:Speakers: Kagiso Mpshe (Unisa)\nAfter thirty-five years the em pirical pseudopotential electronic band structures that were fitted by Jam es R. Chelikowsky and Marvin L. Cohen (Phys. Rev. B 14\, 556\, 1976) are s till used widely and are regarded by some workers as being among the best. Although the original paper by Chelikowsky and Cohen has received more th an 600 citations\, not all subsequent workers have been able to reproduce the band structures accurately. In a few of the citing papers\, significan t errors were introduced by\, for example\, incorrectly adding the effects of non-locality in the core potentials and spin-orbit coupling. In the or iginal work both of these effects were added as perturbations. In the pres ent work it is shown that the original calculations of Chelikowsky and Coh en can be reproduced accurately\, even without the use of perturbation the ory. This reproduction allows the original band structures to be used with great ease. As an example\, the original band structures are used as inpu t to an optimization calculation which produces equivalent fourteen-band a nd thirty-band (full-zone) k•p parameters for the original eleven diamon d and zinc-blende semiconductors. The original band structures are also co mpared to those obtained through state-of-the-art ab-initio density functi onal calculations.\n\nhttps://events.saip.org.za/event/7/contributions/499 2/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4992/ END:VEVENT BEGIN:VEVENT SUMMARY:Electrical characterization of two metastable defects introduced i n GaN by Eu-ion implantation DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4993@events.saip.org.za DESCRIPTION:Speakers: Walter Meyer (University of Pretoria)\nDefects intro duced by 300 keV Eu ions in HVPE grown Si-doped GaN were investigated by m eans of deep level transient spectroscopy (DLTS). After implantation\, the samples were annealed at 1000 °C and Ti/Al/Ni/Au ohmic and Ni/Au Schottk y contacts were deposited. The Schottky contacts were found to be of high quality\, with leakage current at 1 V reverse bias of below 10 8 A.\n\nTwo peaks in the DLTS spectrum showed metastable behaviour. They were labelle d E1 and E2 and had activation enthalpies of 0.20 eV and 0.28 eV respectiv ely. Laplace analysis showed that the E1 was a due to a single exponential decay\, while the E2 consisted of the sum of three exponential decays. We found that the E1 and E2 defects are metastable\, and that the E2 defect may be reversibly transformed to the E1 defect by a zero bias. We found th at the transition between these defects is not described well by a single exponential decay\, but rather by the integral over a range of exponential decays.\n\nhttps://events.saip.org.za/event/7/contributions/4993/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4993/ END:VEVENT BEGIN:VEVENT SUMMARY:Electrical characterization of irradiated n-GaN DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4994@events.saip.org.za DESCRIPTION:Speakers: Maisela Morongwa (University of Pretoria)\nWe invest igate the electrical parameters of n- GaN irradiated at room temperature w ith 5.4 MeV alpha-particles from an americium-241 (Am-241) radio-nuclide s ource under dark conditions. The radiation damage was studied using curren t–voltage (I–V) and capacitance –voltage (C–V) characteristics for a total irradiation time of 14 hours at a dose rate of and the correspo nding dose range of . Diode parameters such as the Schottky barrier heigh t\, ideality factor\, saturation current\, free carrier concentration and reverse leakage current were monitored from the I–V and C–V measuremen ts that were recorded by a computer programme developed using National Ins trument’s LabView software. The irradiation results reveal an increase i n the ideality factor\, series resistance\, saturation current and reverse leakage current over the dose range investigated. The free carrier densit y and the Schottky barrier height were found to decrease with increasing d ose. Our results suggest that the observed effects are as a result of the radiation damage to our sample.\n\nhttps://events.saip.org.za/event/7/cont ributions/4994/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4994/ END:VEVENT BEGIN:VEVENT SUMMARY:Coulomb excitation of light nuclei. DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4995@events.saip.org.za DESCRIPTION:Speakers: Nico Orce (University of the Western Cape)\nThe Coul omb excitation of light nuclei can provide unique information on the matri x elements for excited states. This contribution will discuss experiments to measure such excitation as well as ab initio large shell model calcula tions calculations that can be tested by these measurements.\n\nhttps://ev ents.saip.org.za/event/7/contributions/4995/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/4995/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and Characterization of Y2O2S:Eu N anophosphors Using Sol-combustion Method DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4996@events.saip.org.za DESCRIPTION:Speakers: Ali Abdub Guyo Ali (University of the free State\, Q waqwa campus.)\nRare earth oxysulfide materials exhibit high luminescence efficiency as well as excellent chemical stability. These materials are wi dely used as luminescent host materials of several commercially available red emitting phosphors. However\, there still remain issues affecting the operational parameters such as luminescence efficiency\, stability against temperature\, high color purity and long afterglow. Y2O2S:Eu nano powders were prepared by low-temperature synthesis method using sulfur-contained organic fuel in an ethanol-aqueous solution. The prepared nano powders wer e characterized by Scanning electron microscope\, X-ray diffraction\, phot oluminescence spectra and X-ray photoelectron spectroscopy. It is shown th at the assistant fuel ethanol has the effect of decreasing the water neede d\, simplifying the experiment procedure by dissolving rare earth nitrate and sulfur-contained organic fuel into an even solution\, and prompting th e formation of rare earth oxysulfide by igniting first during heating that leads to combustion decomposition reaction. Y2O2S:Eu nano crystallines wi th strong photoluminescence and X-ray luminescence are obtained using thio urea as organic fuel. Mixtures of Y2O3:Eu and Y2O2S:Eu are acquired using thiourea as fuel\, and the content of Y2O2S:Eu increases until reaches to about half of the Y2O3:Eu with the increasing amount of thiourea. Y2O2SO4: Eu emerges when S/Y=6 and increases with increasing thiourea content. \n\n https://events.saip.org.za/event/7/contributions/4996/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4996/ END:VEVENT BEGIN:VEVENT SUMMARY:CSIR-NLC mobile LIDAR for atmospheric remote sensing DTSTART;VALUE=DATE-TIME:20110715T100000Z DTEND;VALUE=DATE-TIME:20110715T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4997@events.saip.org.za DESCRIPTION:Speakers: Venkataraman Sivakumar (CSIR-National Laser Centre)\ nLight Detection and Ranging (LIDAR) studies on particulate matter (Aeroso ls) and pollutants\; elucidate their distribution and concentration in the atmosphere. Particulate matter plays a key role in atmospheric physical and chemical processes from local to global scale. The complexity of thes e processes have been largely reviewed in literatures and LIDAR measuremen ts have mostly contributed to a better understanding the role of atmospher e dynamics and particle microphysics. The atmospheric backscatter measurem ents of Aerosols (solid particles floating in the air and formed by combin ation of different pollutants)\, can be used to identify the stratificatio n of pollutants and will enable the classification of the source regions\, such as industrial\, biological and anthropogenic sources. \n\nA mobile L IDAR system is developed at the Council for Scientific and Industrial Rese arch (CSIR) National Laser Centre NLC)\, Pretoria (25º 44' S\; 28º 11' E )\, South Africa. The system currently employed for atmospheric remote sen sing including aerosols\, clouds\, boundary and mixed layers and other met eorological applications. The LIDAR is operated at 532 nm and 355 nm wave length and capable of providing the backscatter information from ground to 40 km with the range resolution of 10 m (see. Fig.1). \n\nIn this present ation\, we shall present the results obtained from LIDAR and further ongoi ng research activities.\n\nhttps://events.saip.org.za/event/7/contribution s/4997/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/4997/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and Characterization of Ba1-xMgxAl2O4:Eu nanophosphors P repared Using Solution – Combustion Method. DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4998@events.saip.org.za DESCRIPTION:Speakers: Francis Dejene (University of the Free State)\nEurop ium-doped barium magnesium aluminate (BaMgAlx0y:Eu) phosphors were obtaine d at low temperatures (500˚C) using the solution - combustion of correspo nding metal nitrate–urea solution mixtures. The particle size and morpho logy and the structural and luminescent properties of the as-synthesized p hosphors were examined by means of scanning electron microscopy (SEM)\, X- ray diffraction (XRD)\, Auger spectroscopy\, transmission electron spectro scopy (TEM) and photoluminescence (PL). It was found that the Ba:Mg molar ratios showed greatly influence not only on the particle size and morpholo gy\, but also on their PL spectra and crystalline structure. The BaMgAl2O4 nanophosphors display a monoclinic structure indicating a small change in peak position at high angles due to differences in size between Ba and Mg ions. The peak of the emission band occurs at longer wavelength (around 6 15nm) with increase in Mg concentration but display a broad band emission at 515 nm for lower Mg concentration. The green emission is probably due t o the influence of 5d electron states of Eu2+ in the crystal field because of atomic size variation causing crystal defects while the red emission i s due to f-f transitions. This finding clearly demonstrate the possibility of fine tuning the color emission and solid solubility limit in Ba1-xMgxA l204:Eu phosphors through the simple and cheap process. A green phosphor w ith almost pure phase with significantly enhanced luminescence and longer after glow can be easily prepared by solution combustion method by doping with slight magnesium concentration (1 mole % Mg).\n\nhttps://events.saip. org.za/event/7/contributions/4998/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/4998/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and photoluminescence properties of CaxSiyOz:Tb3+ nanoph osphors prepared using solution-combustion method. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-4999@events.saip.org.za DESCRIPTION:Speakers: Francis Dejene (University of the Free State)\nTb3+- activated calcium silicate (CaxSyyOz:Tb3+) nanophosphors have been synthes ized by means of simple and low temperatures (500°C) using the solution-c ombustion of corresponding metal nitrate\, TEOS and urea solution mixtures . The structural evolution of the phosphor was studied by X-ray powder dif fraction (XRD)\, scanning electron microscopy (SEM)\, and the luminescence properties of the phosphor powders investigated as a function of terbium concentration. The XRD study indicates that new peaks appear as the terbiu m concentration increase results in phase changes from CaSiO3 to Ca3Si2O7. The later phase may be favored as a result of some Si sites substituted b y the Tb ions as the concentration of Tb was changed from 1 to 4 mol. %. The CaxSiyOz:Tb phosphor powders show the characteristic emission of Tb3+ under UV excitation\, with the emission transitions of (5D4→7F3\,4\,5\,6 ) with excitation 257nm have been measured. Particularly\, the green emiss ion transition at 545nm has been found to be more prominent and intense wh ich is due to an electronic transition of 5D4-7F5. The decay curves implie d that these phosphors contain fast\, medium and slow-decay process. The o xygen vacancies trap levels may be considered to be responsible for the lo ng afterglow phosphorescence at room temperature. Such green strong emissi on displaying powder phosphor will find applications in the development of coated screens in certain electronic systems.\n\nhttps://events.saip.org. za/event/7/contributions/4999/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/4999/ END:VEVENT BEGIN:VEVENT SUMMARY:The Giant Graviton Oscillator DTSTART;VALUE=DATE-TIME:20110714T070000Z DTEND;VALUE=DATE-TIME:20110714T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5000@events.saip.org.za DESCRIPTION:Speakers: Robert de Mello Koch (University of the Witwatersran d)\nN=4 SYM theory has been extensively studied in the planar limit. An im portant result is that the planar dilatation operator can be mapped to the Hamiltonian of an integrable system.\n\nIn this talk we study certain lar ge N (but not planar) limits of the theory. We argue that the dilatation o perator remains\nintegrable: it reduces to a set of decoupled harmonic osc illators. This challenges claims that integrability is spoiled by non-plan ar corrections.\n\nWe argue that the decoupled oscillators that arise desc ribe the vibration modes of a quantum membrane.\n\nhttps://events.saip.org .za/event/7/contributions/5000/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5000/ END:VEVENT BEGIN:VEVENT SUMMARY:Computer simulation of cobalt pentlandite DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5001@events.saip.org.za DESCRIPTION:Speakers: Mofuti Mehlape (University Of Limpopo (Turfloop Camp us))\nCobalt pentlandite (Co9S8)is the major source of cobalt. Of the seve ral cobalt minerals\, cobalt pentlandite is the most abundant and has the widest geographical distribution. This presentation looks at the computer simulation of Co9S8 structure using different computer simulation techniqu es\, i.e. METADISE\, VASP. These techniques have been employed to investig ate the effect of molecular adsorption of water on the low-index surfaces of Co9S8\n\nhttps://events.saip.org.za/event/7/contributions/5001/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5001/ END:VEVENT BEGIN:VEVENT SUMMARY:Construction and thermal analysis of a parabolic collector for sma ll scale concentrating thermal system DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5002@events.saip.org.za DESCRIPTION:Speakers: Tomas Nhabetse (Eduardo Mondlane University\, Maputo \, Mozambique)\n\nFew options are apparent for achieving a benign\, sustai nable energy future except those relying on the utilization of solar energ y in one way or another. Experience with fossil and nuclear sources has re vealed an array of unsolved problems of increasing concern as more evidenc e and understanding emerges. Africa has the world’s best solar resources . Several countries have exploited solar energy for water heating\, crop d rying\, medical applications\, and telecommunications\, among other things . Solar energy can contribute to supply heat energy in households of Sub-S aharan African countries. Having this in mind a small scale dish concentra ting solar energy system is being developed at the Eduardo Mondlane Univer sity in Mozambique. The system comprises of the collector\, the heat stora ge and the oven. The main structure of the system has been constructed\, c onsisting of the dish reflector\, the sun tracker and the piping mechanism . The reflector consists of 6 petals which together resemble nearly a para bolic surface with the following parameters: \nDiameter................ Dp = 2400mm\nFocal length............ f = 915mm\nF/D ratio............ ......... n=0.135\nHalf opening angle..............66.50o \nHalf comp lementary angle........23.49o\nAngle of incidence..............33.26 \ n\nThe process of gluing trapezoidal mirrors was done on individual petals using the laser beam radiation. Using reflection laws on planar surfaces which states that rays of light parallel to the parabola axis are reflecte d to a focal point\, each trapezoidal mirror tile gluing was preceded by s canning its reflection close to the theoretical focal point. An individual petal was covered by 163 mirror tiles. The reflector surface is comprised by 978 mirror tiles.\nAn infrared camera was used to scan the temperature of the concentrated heat. The maximum temperature reached so far is 350oC . The experimental focal area was found by mapping the reflections of the whole reflective surface. The shape of the receiver/absorber obtained by t he scanning process is semi-spherical. \nThe future work is the study of e fficiency of the collector as a whole. This will be done by measuring the ambient air temperature\, the inlet and outlet temperature of the absorber .\n\nhttps://events.saip.org.za/event/7/contributions/5002/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5002/ END:VEVENT BEGIN:VEVENT SUMMARY:Ionospheric response during the geomagnetic storm events on 24-27 July 2004: Long-duration positive storm effect DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5003@events.saip.org.za DESCRIPTION:Speakers: Chigomezyo Ngwira (Rhodes University/SANSA Space Sci ence)\nIonospheric storms represent large global disturbances in the ionos pheric F2 region electron density in response to geomagnetic storms. The m echanisms for generation of negative storms are well understood and accept ed. In contrast\, positive storms show different characteristics and have not been fully understood. In this study\, we investigate the ionospheric response during the geomagnetic storm events on 24-27 July 2004 using a mu lti-instrument approach. The period was characterised by strong geomagneti c activity that produced a positive ionospheric total electron content (TE C) effect over a four day period\, but the most significant enhancements ( with respect to the quiet day reference) were observed on 25 and 27 July a nd are presented here. It is noted that the enhancement on 25 July (40 TEC U) was about twice as high as that observed on 27 July\, even-though the l ater day was more geomagnetically disturbed. The positive storm enhancemen t on 25 July lasted over 9 hours and that on 27 July lasted about 7 hours\ , thus can both be classified as long-duration positive storm effects. Als o\, IMF Bz had a southward orientation for more than 15 hours on 25 July a nd could have been the mean by which energy was continuous fed into the ma gnetosphere. The DMSP F15 satellite which flew over the region of positive storm also observed the enhancement. In addition\, the F-region critical frequency (foF2) values observed at two ionosonde stations showed marked p ositive responses and were associated with increase in ionospheric height. \n\nhttps://events.saip.org.za/event/7/contributions/5003/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5003/ END:VEVENT BEGIN:VEVENT SUMMARY:Performance monitoring of a downdraft System Johansson Biomass Gas ifier™ DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5004@events.saip.org.za DESCRIPTION:Speakers: Sampson Mamphweli (University of Fort Hare)\nBiomass gasification for electricity generation has attracted much attention over the past few years. This is due to the fact that biomass is a renewable r esource\, which is also considered to be carbon neutral. However electrici ty generation using biomass gasifiers can only be technically and economic ally achieved at small scale using downdraft gasifier systems\, which prod uce gas that has very little quantities of tar. This paper presents the te chnical and operational challenges experienced in biomass gasification for electricity generation. The data was collected at the System Johansson Bi omass Gasifier installed by Eskom. NDIR and Pd/Ni gas sensors were used to measure the gas profiles while type K thermocouples were used to measure the temperature in the reactor. This paper presents the performance monito ring results including the gasifier operating conditions\, fuel properties \, gas profiles as well as gas heating value and cold gas efficiency.\n\nh ttps://events.saip.org.za/event/7/contributions/5004/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5004/ END:VEVENT BEGIN:VEVENT SUMMARY:Vibrational properties of Mass produced graphene monolayer by chem ical method DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5005@events.saip.org.za DESCRIPTION:Speakers: MOHAMMED KHENFOUCH (PhD STUDENT)\nGraphene is a two- dimensional crystal of carbon atoms arranged in a honeycomb lattice. It is a zero band gap semimetal with very unique electronic optical and mechani cal properties which make it useful for many applications such as ultra-hi gh-speed field-effect transistors\, p-n junction diodes\, terahertz oscill ators\, and low-noise electronic\, NEMS and optical sensors.\nThe high qua lity mass production of this nanomaterial is a big challenge\, for this wo rk we have used chemical method which helped to get this goal. Raman and F TIR vibrational spectroscopies were investigated to the examination of the production quality.\n\nhttps://events.saip.org.za/event/7/contributions/5 005/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5005/ END:VEVENT BEGIN:VEVENT SUMMARY:An investigation of high velocity flows in HF radar data during no rthward interplanetary magnetic field\, non-substorm intervals DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5006@events.saip.org.za DESCRIPTION:Speakers: Zolile Mtumela (University of KwaZulu-Natal)\nSevera l previous studies\, including one using early Sanae radar data\, have fou nd examples of high speed ionospheric plasma flows on the nightside\, mapp ing to the magnetospheric tail\, during periods which were magnetically qu iet. These high speed flows were interpreted to be associated with the rel ease of energy from a rapid reconfiguration of tail magnetic field lines d ue to reconnection. Such events are now known as ‘TRINNIs’ or ‘tail reconnection during IMF northward\, non-substorm intervals’. The purpose of this study was to identify further TRINNI events\, using SuperDARN dat a from both hemispheres. In situations where the y-component of the Interp lanetary Magnetic Field dominates over the z-component\, the directions of both the high speed flows and the underlying convection pattern depend on the direction of the y-component. Some examples of likely TRINNI events f or cases where the y-component was positive and negative are presented and discussed. The assumption of a non-substorm interval is justified by magn etometer and GOES satellite data\, and the observations are discussed in r elation to magnetic reconnection in the magnetotail.\n\nhttps://events.sai p.org.za/event/7/contributions/5006/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5006/ END:VEVENT BEGIN:VEVENT SUMMARY:Many-boson Quantum Walks on Graphs with Shared Coins DTSTART;VALUE=DATE-TIME:20110713T103000Z DTEND;VALUE=DATE-TIME:20110713T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5024@events.saip.org.za DESCRIPTION:Speakers: Dibwe Pierrot Musumbu (University of KwaZulu-Natal)\ nQuantum walks of particles obeying bose statistics are introduced. In suc h a quantum walks the conditional\nshift operation is performed with the s ingle coin tossing for the whole lattice. An explicit form for the transit ion\nprobabilities in a single step is derived. This allow to describe the evolution of an arbitrary state and an arbitrary\nnumber of steps. This m odel easily embrace the concepts such as the join probability\, the counti ng statistics and\nthe high order correlations. It also presents the compu tational challenges arising from the exponential increase in the\nnumber o f basis states entering into the lattice state as a function of the number quantum walkers and the number of\nsteps. Possible solutions are proposed in some applications of the model to quantum walks on finite graphs.\n\nh ttps://events.saip.org.za/event/7/contributions/5024/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5024/ END:VEVENT BEGIN:VEVENT SUMMARY:Nuclear and related analytical techniques for biotechnology DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5008@events.saip.org.za DESCRIPTION:Speakers: Marina Frontasyeva (Joint Institute for Nuclear Rese arch)\nSome results from applying nuclear and related analytical technique s in medical\, environmental and industrial biotechnologies are presented. In the biomedical experiments biomass from the blue-green alga Spirulina platensis has been used as a matrix for the development of pharmaceutical substances containing such essential trace elements as selenium\, chromium and iodine. The feasibility of target-oriented introduction of these elem ents into Spirulina platensis biocomplexes retaining its protein compositi on and natural beneficial properties was shown. The negative influence of mercury on growth dynamics of Spirulina platensis was observed. Detoxifica tion of Cr and Hg by Arthrobacter globiformis 151B was demonstrated. Micro bial synthesis of technologically important silver nanoparticles by the no vel actinomycete strain Streptomyces glaucus 71 MD was characterized by a combined use of Transmission Electron Microscopy (TEM) and ENAA. It was es tablished that the tested actinomycete Streptomyces glaucus 71 MD produces silver nanoparticles extracellularly when acted upon by the silver nitrat e solution\, which offers a great advantage over an intracellular process of synthesis from the point of view of applications. The synthesis of silv er nanoparticles by Spirulina platensis proceeded differently under the sh ort-term and long-term silver action. Our studies will help to develop a r ational microbial nanoparticle synthesis procedure.\n\nhttps://events.saip .org.za/event/7/contributions/5008/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5008/ END:VEVENT BEGIN:VEVENT SUMMARY:Reactive DC magnetron sputter deposition and characterization of Z rN thin films DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5009@events.saip.org.za DESCRIPTION:Speakers: Thembinkosi Goodman Nyawo (University of Zululand)\n ZrN films were deposited on Si<100> substrates\, Al and brass strips by DC magnetron sputtering under varying conditions of power\, pressure\, argon and nitrogen gas flow rates as well as temperature and characterized by S EM\, AFM\, RBS\, resonant RBS\, and XRD. The films are transparent and se miconducting. They tend to absorb oxygen. The films were found to adhere w ell to the substrates. The colour of the films varied depending on deposit ion conditions and have been expressed in the Lab* colour system. Potent ial uses of such films are as protective hard coatings as well as decorati ve layers.\n\nhttps://events.saip.org.za/event/7/contributions/5009/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5009/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigating the effect of atmospheric dymanics on HF propagation DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5010@events.saip.org.za DESCRIPTION:Speakers: Racheal Athieno (South African National Space Agency (SANSA) Space Science)\nHF propagation involves transmission and receptio n of radio signals within a frequency range of 3 − 30 MHz. It finds appl ications in a number of communication fields such as international short w ave broadcasting\, mobile telephone systems\, radio navigation and operati on of radar systems. However\, it depends on the ionosphere which is cons tantly varying mainly due changes in the neutral atmosphere which are a co nsequence of atmospheric dynamics. In this paper\, we investigate the effe ct of atmospheric dynamics on High Frequency (HF) propagation using the co -located radars at SANSA Space Science (19.2o E\, 34.4o S)\, Hermanus\, So uth Africa. These radars include the HF Doppler radar\, Ionosonde\, Globa l Positioning System (GPS) receiver and GPS Ionospheric Scintillation Tota l Electron Content (TEC) Monitor (GISTM). HF propagation results from the HF Doppler radar are presented. The comparison of results of the HF Dopp ler radar with other radars is also included. Results show that radio comm unication is affected by atmospheric dynamics which results into signal fa ding or at worst signal loss.\n\nhttps://events.saip.org.za/event/7/contri butions/5010/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5010/ END:VEVENT BEGIN:VEVENT SUMMARY:Simulation of a pencil proton beam in a water phantom using variou s monte carlo codes. DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5011@events.saip.org.za DESCRIPTION:Speakers: Carmen Jacobs (University of the Western Cape)\n\nTh is study investigates the Pencil Proton Beam scanning technique to determi ne the dosage obtained during clinical treatments due to secondary radiati on. Simulations in MCNPX and GEANT4/GATE are of particular interest in thi s study. The study is based on a variation of the traditional Hogstrom Pen cil beam model for electron beams to provide a description of clinical pro ton beams. This new Hogstrom model is based on the Fermi-Eyges theory of p article transport.\n \nThe method used in this investigation is to simulat e a proton pencil beam entering a water phantom at various discrete energi es and determining the secondary particles distributed throughout the wate r phantom by studying both Coulombic and Nuclear interactions of the incid ent proton in water. This allows one to determine how much of the total do sage obtained by the patient is from the primary particle and what part of the dosage is due to the secondary particles. In order to accurately comp are the Monte Carlo codes\, a further study was done to understand the und erlying physics principles used by MCNPX and GEANT4. The development of an analytical model for primary proton beams which included depth distributi on\, propagations of protons in matter\, and scattering theory was also in vestigated. \n\nBesides comparing Monte Carlo codes this study also has re al life implications. Pencil beam scanning leads to improving and advancin g treatment planning.\n\nhttps://events.saip.org.za/event/7/contributions/ 5011/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5011/ END:VEVENT BEGIN:VEVENT SUMMARY:Spectroscopy with a mode-locked Femtosecond Laser Frequency Comb DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5012@events.saip.org.za DESCRIPTION:Speakers: Vela Lincoln Mbele (School of Physics\, University o f the Witwatersrand)\nThe Nobel prize winning technology involving a mode- locked femtosecond laser frequency comb (FLFC) has been at the epi-centre of a scientific revolution over the last two or so decades. Even though or iginally designed to count cycles in optical clocks\, it has had a profoun d impact on other research areas\, with a range of applications including spectroscopy\, trace gas detection\, signal processing\, astrophysics and many others. In the near future most of these applications may be taken ov er by the compact monolithic micro-resonator generated frequency combs\, t here is\, however\, no doubt that mode-locked FLFC will continue growing t heir range of applicability over the next few decades.\n\nWe present a bri ef overview of two simple high-resolution high-precision spectroscopy expe riments. One experiment is of caesium-133 atoms contained in a vapour cell \, and the other molecular spectroscopy where multi-channels are simultane ously detected by a charge coupled device (CCD) camera with a specimen imp rinting its unique fingerprint. In both experiments excitation is through radiation from a mode-locked FLFC. \n\nIn the caesium experiment the laser beam is set counter-propagating after the beamsplitting cube\, focussed t o a reasonable waist in the interaction region in the vapour cell\, thereb y exciting a multitude of low lying magnetic dipole and electric quadrupol e transitions allowing the measurement of transition energies and hyperfin e coupling coefficients for the 8S\, 9S and 7D3/2\,5/2 states. \n\nIn the second experiment the comb is filtered by a Fabry-Perot cavity changing th e repetition rate of the laser from 1 GHz to repetition rates in the range 3 - 15 GHz to match the resolution of the spectrometre. The spectrometre comprises of the Virtually Image Phased Array\, the 2400 lines/mm reflecti on grating and the CCD camera.\n\nWe discuss\, the spectrometre\, the resu lts of both experiments\, and briefly some other possible applications of laser comb.\n\nhttps://events.saip.org.za/event/7/contributions/5012/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5012/ END:VEVENT BEGIN:VEVENT SUMMARY:Wave-packet scattering off a soliton DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5025@events.saip.org.za DESCRIPTION:Speakers: Ahmed Abdelhady (Stellenbosch University)\nWe invest igate the scattering of a wave-packet off a soliton in the (1+1) dimension al kink model. We solve the classical\, time-dependent field equation num erically subject to the initial condition that the wave-packet is widely separated from the kink soliton at very early times and propagates towards the soliton. After some time the wave-packet interacts with the static so liton and departs from it at later times. At very late times the wave-pack et is finally again separated from the soliton. We then extract the scatte ring matrix from the distorted wave-packet and compare it to the known res ult from the static scattering calculation. This investigation constitutes a first step towards studying crossing symmetry in soliton models\, i.e. in a framework beyond perturbation theory.\n\nhttps://events.saip.org.za/e vent/7/contributions/5025/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5025/ END:VEVENT BEGIN:VEVENT SUMMARY:The Magnetocaloric Effect in Ferromagnetic PrSi: Evidence of a Nov el Magnetic Gound State and Higher Order Exchange Interactions DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5014@events.saip.org.za DESCRIPTION:Speakers: Jasper Snyman Snyman (University of Johannesburg)\nT he discovery of the giant magnetocaloric effect (MCE) in Gd5Si2Ge2\, a mem ber of the substitution series Gd5Si4-xGex has generated significant inter est into MCE phenomena in rare earth intermetalic compounds. Much recent effort has gone into determining how the MCE in such systems is influenced by the many salient features associated with rare earth magnetism. Here the MCE in polycrystalline ferromagnetic PrSi is determined from specific heat measurements. While the magnitude of the MCE in PrSi is found to be modest when compared to other binary systems\, the power of MCE analyses i n probing electronic and ground-state properties in magnetic systems is em phasized in this work. We forward a description in terms of a novel magnet ic ground state for the 4f -electrons associated with the Pr3+ -ions in th is particular compound. It is found that the MCE in this system can be ac curately reproduced by modeling the system as a modified Ising-type ferrom agnet with the addition of a significant higher order exchange term and as suming that the ground state of the 4f-electrons is the unperturbed 9-fold degenerate free-ion spin-orbit coupled ground state multiplet. Such a gr ound state would imply that the usual splitting of the degenerate energy l evels of the free ion multiplet by the crystalline electric field is absen t in this system\, which in turn implies that significant multipolar inter actions may be responsible for the higher order exchange terms present in the magnetic Hamiltonian.\n\nhttps://events.saip.org.za/event/7/contributi ons/5014/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5014/ END:VEVENT BEGIN:VEVENT SUMMARY:Training Senior student to be "IIL" competent Physics lecturers DTSTART;VALUE=DATE-TIME:20110714T070000Z DTEND;VALUE=DATE-TIME:20110714T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5015@events.saip.org.za DESCRIPTION:Speakers: CABLE MOJI (UNIVERSITY OF PRETORIA)\nTraditional lec turing of Physics in a preaching pattern to a multitude stduent masses in a large lecture theatre\, has not succeeded in attracting more number into Physics further than second year. University of Pretoria Physics Educatio n Research Group (UPPERG) has introduced "Interactive-Inquiry Learning" Te aching where Masters and Doctoral students are guided to lecture groups of 40 BSc4Y program students\, in smaller laboratories: discussing Physics t heories and concepts while supervising practiacls and encouraging these yo uger students into excercises and tutorials of Physics.\n\nRegular observa tion is done where eight senior students of Physics Department of the Univ ersity of Pretoria lecture the twelve groups of students in the BSc4Y prog ram. "Lecturers" use the IIL Teaching method. Some results of this teachin g are shown.\n\nFurther observation show that contact and consultation are more spontaneous to younger senior students lecturers than to older folk lecturers. Bitter interacions in cases of "accommodation in conceptual cha nge" ensue often leading to successful learning\, which otherwise would se ldonm occur when a "matured proffessor" lectures the youngsters.\n\nhttps: //events.saip.org.za/event/7/contributions/5015/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5015/ END:VEVENT BEGIN:VEVENT SUMMARY:Towards the unconditional security proof for the Coherent-One-Way (COW) protocol DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5016@events.saip.org.za DESCRIPTION:Speakers: Mhlambululi Mafu (Centre for Quantum Technology)\nQu antum Cryptography\, one aspect of which is Quantum Key Distri-\nbution (Q KD)\, provides the only physically secure and proven method\nfor the trans mission of a secret key between two distant parties\, Alice and Bob. The g oal of QKD is to guarantee that a possible eavesdropper (Eve)\, with acces s to the communication channel is unable to obtain useful information abou t the message.\n\nThe Coherent-One-Way (COW) protocol is one of the most r ecent practical QKD protocols. However\, its security proof still remains unrealized. We therefore present a necessary condition for the security of the COW protocol. In the proof\, we describe bob's measurements by non-co mmuting POVM elements which satisfies this proof.\n\nhttps://events.saip.o rg.za/event/7/contributions/5016/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5016/ END:VEVENT BEGIN:VEVENT SUMMARY:Heat treatment of glassy carbon implanted with strontium at room a nd high temperatures DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5017@events.saip.org.za DESCRIPTION:Speakers: Dolly Langa (University of Limpopo and University of Pretoria)\nThe effects of annealing temperature and time on glassy carbon implanted with 360 keV strontium ions at room and high temperatures are r eported. The samples were implanted with strontium ions to a fluence of 2 x 1016 ions/cm2 at room temperatures\, 350ºC and 600ºC. The room temper ature implanted samples were isochronally vacuum annealed at temperatures from 200ºC to 700ºC for 1 hour. The depth profiles of the implanted samp les before and after annealing were obtained by ion beam technique\, viz. Rutherford Backscattering Scattering (RBS). Scanning Electron Microscopy ( SEM) was employed to investigate the effect of implanted ions and annealin g temperatures on the microstructure of the substrate.\n\nhttps://events.s aip.org.za/event/7/contributions/5017/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5017/ END:VEVENT BEGIN:VEVENT SUMMARY:Identification of compounds in materials using tomography imaging\ , a possibility at the SANRAD facility DTSTART;VALUE=DATE-TIME:20110715T061500Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5018@events.saip.org.za DESCRIPTION:Speakers: Robert Nshimirimana (NECSA)\nThe South African Neutr on Radiography (SANRAD) facility hosts a neutron/x-ray tomography system w hich is extensively being utilized in non-destructive examination experime nts where it is necessary to characterize and determine the properties (e. g. size\, porosity\, permeability and morphology) of samples. Sometimes\, quantitative information is needed about the type elemental composition of the sample or the constituencies of the sample\, in a non-destructive man ner. Different compounds within the sample interact differently with a neu tron/x-ray source\, hence it is possible not only to reveal the internal s tructure of the material but also to identify the compound within the mate rial. This talk demonstrates first research results obtained at the SANRAD facility for the calibration and quantifying of compounds\, or minerals\, within geological samples by means of transmission radiography and tomogr aphy.\n\nhttps://events.saip.org.za/event/7/contributions/5018/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5018/ END:VEVENT BEGIN:VEVENT SUMMARY:South African e-Infrastructure for physics applications DTSTART;VALUE=DATE-TIME:20110714T121500Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5019@events.saip.org.za DESCRIPTION:Speakers: Sean Murray (iThemba LABS)\nPhysics is one of the mo st digitally-intensive areas of modern research and has traditionally led the development of tools to increase the efficiency and capability of rese arch activities. The integration of the tools necessary for today's compet itive physics research projects\, from HPC centres to data resources\, met adata catalogues\, and services to enable collaboration in virtual organis ations has been done to a great extent in South Africa through the activit ies of the South African National Grid (SAGrid). By forming a collaboratio n to integrate their various computing facilities through the deployment o f a common middleware\, the members of the SAGrid Joint Research Unit prov ide many research communities with an integrated services infrastructure f or collaboration. \nWe will give an overview of the grid in South Africa a nd how it is connected to other regional infrastructure in Europe\, North Africa\, Latin America and the U.S. We will show how it has enabled the So uth African physicsists working on LHC experiments at CERN (ATLAS and ALIC E) to conduct their work irrespective of their location. We will also show some examples of how the grid has enabled collaborative research in areas of physics\, and what application porting and user training services are at the disposal of the general research communities. Advanced aspects of t he grid middleware\, such as data management\, workflow\, and usage of met adata catalogues will also be presented.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5019/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5019/ END:VEVENT BEGIN:VEVENT SUMMARY:Effect of carbon modification on the electrical\, structural and o ptical properties of TiO2 electrodes and their performance in lab-scale dy e sensitized solar cells DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5020@events.saip.org.za DESCRIPTION:Speakers: Raymond Taziwa (University of Fort hare)\nCarbon mod ified titanium dioxide nanoparticles (C:TiO2 NPs) have been synthesized by ultrasonic nebulizer spray pyrolysis (USP) and pneumatic spray pyrolysis (PSP) techniques using titanium tetraethoxide as the precursor solution. H igh resolution transmission electron microscopy on the NPs shows differenc e in lattice spacing in the NP structures prepared by the two methods – 2.02 Å for the USP NPs and an average of 3.74 Å for the PSP NPs. The mos t probable particle sizes are 3.11 nm and 5.5 nm respectively. The carbon doping only changes the lattice spacings of the TiO2 lattice\; the most pr edominant plane is the (101) in TiO2 reciprocal lattice as determined from the fast Fourier transform of most of the particle images. Raman spectros copy supported by FTIR confirms the TiO2 polymorph to be anatase with the intense phonon frequency at 153 cm-1 blue-shifted from 141 cm-1 due to bot h carbon doping and particle size. A modified phonon confinement model fo r nanoparticles has been used to extract phonon dispersion and other param eters for anatase for the first time. Electronic measurements show “nega tive conductance” at some critical bias voltage\, which is characteristi c of n-type conductivity in the carbon doped TiO2 NPs as confirmed by the calculated areas under the I-V curves. This is a necessary material proper ty for the Grätzel type of solar cells application. Practical solar cells built from carbon doped TiO2 electrodes show up to 5 times improvement in efficiency compared to pure TiO2 electrodes of similar construction.\n\nh ttps://events.saip.org.za/event/7/contributions/5020/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5020/ END:VEVENT BEGIN:VEVENT SUMMARY:Trajectories of electrons in a realistic model of the Earth's magn etic field DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5021@events.saip.org.za DESCRIPTION:Speakers: Mahassin Nemair (University of KawZulu-Natal)\nDurin g the onset of a substorm\, a burst of energetic (10-100 keV) electrons is injected into the inner\nmagnetosphere. The subsequent motion of these el ectrons is dictated by their energy\, pitch angle\nand the Earth's magneti c field geometry. More specifically\, if the Earth's magnetic field is not \nvarying rapidly then the three adiabatic invariants associated with each of the electrons' periodic\nmotions (drift\, bounce and gyration) are con served. In this work we study the motion of electrons in\nthe Earth's magn etic field. A realistic magnetic field geometry is employed which depends on\nconditions in the solar wind by applying time varying magnetic filed c alculated from Tsyganenko\nmodel. The initial electron source location is presumed to be at L = 9 at midnight. The trajectories\nof electrons with e nergies of 10-100 KeV are studied using Tsyganenko model of the\nmagnetosp here. Results are compared with other model simulated .\n\nhttps://events. saip.org.za/event/7/contributions/5021/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5021/ END:VEVENT BEGIN:VEVENT SUMMARY:Low-temperature magnetic ordering in Ce6Pd12In5 DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5022@events.saip.org.za DESCRIPTION:Speakers: Andre Strydom (University of Johannesburg)\nThe nove l ternary intermetallic compound Ce6Pd12In5 forms in a well-defined atomic stoichiometry with a hexagonal crystal structure (space group P63/mcm) an d a unique atom in each of the crystallographic sites available in this sp ace group. The bonding lengths are comparatively short and suggest strong interaction especially between Ce and Pd atoms. \nIn this work we report o n our findings of the first studies into the physical properties of Ce6Pd1 2In5. A key finding is the occurrence of long-range ferromagnetic-like ord er below TC =1.6 K\, where the specific turns into a lambda-like anomaly p eaking at CP = 8 J/(mol Ce K). The electrical resistivity hints at a low-l ying Kondo scale in this compound. The magnetic susceptibility shows well- defined Curie-Weiss behaviour over an extended temperature range with an e ffective magnetic moment value that is indicative of conduction-electron h ybridization effects on the Ce localized moment. The 4f–electron derived magnetic contributions to the entropy and to the electrical resistivity i n Ce6Pd12In5 are assessed by means of the nonmagnetic counterpart La6Pd12I n5.\n\nhttps://events.saip.org.za/event/7/contributions/5022/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5022/ END:VEVENT BEGIN:VEVENT SUMMARY:Low Temperature Synthesis of ZnO nanoparticles and Nanorods via We t Chemistry Route DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5023@events.saip.org.za DESCRIPTION:Speakers: Pontsho Sylvia Mbule (University of the Free State)\ nA wet chemistry route is an essential method used today to synthesize hig h quality ZnO nanoparticles and nanorods. It is a novel low cost method to produce nanoparticles and nanorods with relatively high dispersivity. In this study optical properties and morphology of the nanoparticles and nano rods were investigated. The X-ray diffraction (XRD) patterns of both nanop articles and nanorods revealed the hexagonal wurtzite structure\, the diff raction peaks matched well with the JCPDS (card no 80-0075) standard data. The transmission electron microscopy (TEM) revealed the nanoparticles and nanorods with different diameters and lengths. The optical absorption and photoluminescence (PL) were also obtained and it was demonstrated that th e PL exhibited a strong near-band-edge emission (UV) and weak visible emis sion bands. The PL intensity increased with increasing precursor concentra tion (0.1M-1.5M) and was quenched at higher concentrations\, which may be attributed to concentration quenching effects. The fourier transform infra red spectroscopy (FTIR) was used to determine the distinct stretching mode frequencies. The ZnO nanoparticles and nanorods were investigated for pos sible applications in transparent electrodes in solar cells and gas sensor s.\n\nhttps://events.saip.org.za/event/7/contributions/5023/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5023/ END:VEVENT BEGIN:VEVENT SUMMARY:A search for the 5 alpha condensate state in 20Ne DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5026@events.saip.org.za DESCRIPTION:Speakers: Cobus Swartz (Stellenbosch University & iThemba LABS )\nQuantum condensation of alpha particles is believed to occur in cluster states of the self-conjugate alpha nuclei 12C and 16O. This phenomenon is similar to the Bose-Einstein condensation observed through the laser cool ing of atoms such as Rb or Na. A state of this nature\, which must be of 0 + character\, is expected to exist just above the 5 alpha decay threshold in 20Ne. In this region\, only high spin states Jiπ≥4+ are known. This is mainly due to the types of reactions usually used to populate states in this nucleus. Alpha-particle inelastic scattering will be performed close to zero degrees with the K600 magnetic spectrometer at iThemba LABS. This will provide a sensitive probe for states of the 0+ character which may b e associated with the 5 alpha particle condensate state\, while enhancing the L = 0 angular momentum peaks. Additionally\, measurements will be made at two larger angles in order to demonstrate the L = 0 character.\n\nhttp s://events.saip.org.za/event/7/contributions/5026/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5026/ END:VEVENT BEGIN:VEVENT SUMMARY:Pulsed laser deposition of multiwall carbon nanotube/NiO nanocompo site thin films DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5027@events.saip.org.za DESCRIPTION:Speakers: Brian Yalisi (CSIR\, UKZN)\nIn this work\, we report on the fabrication of multiwall carbon nanotubes (MWCNT)/NiO nanocomposit e thin films by the pulsed laser deposition technique on to aluminium subs trates. Samples were prepared with different MWCNT content\, and varying substrate temperatures. Structural and optical properties were investigate d by scanning electron microscopy\, x-ray diffraction\, Raman spectroscopy \, UV-Vis spectroscopy and the thermal emissometer. The morphological and structural changes induced by laser beam will also be presented.\n\nhttps: //events.saip.org.za/event/7/contributions/5027/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5027/ END:VEVENT BEGIN:VEVENT SUMMARY:Designing reservoirs for 1/t decoherence process in Jaynes-Cummin gs model DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5028@events.saip.org.za DESCRIPTION:Speakers: Filippo Giraldi (University of KwaZulu-Natal)\nDecoh erence indicates the process that a quantum system undergoes through th e interaction with an external environment.\nThe central issue and one of the greatest challenges in Nanotechnology and Quantum Information Processi ng is the way to control or delay the destructive effect of the environmen t on qubit coherence. For this reason\, a qubit interacting with a reservo ir of bosons (external environment)\, described by a Jaynes-Cummings model \, is considered. The decoherence process corresponding to Lorentzian type distributions of field modes results in exponential like relaxations. At this stage we adopt the engineering reservoir approach as the way of delay ing the decoherence process. \nA special class of reservoirs of field mode s is designed in order to obtain a decoherence process resulting\, over es timated long time scales\, in inverse power laws with powers decreasing co ntinuously to unity according to the choice of the particular reservoir. \ nThe designed reservoirs exhibit a photonic band gap coinciding with the q ubit transition frequency and are piecewise similar to those usually adopt ed in Quantum Optics\, i.e.\, sub-ohmic at low frequencies and inverse pow er laws at high frequencies. Initially\, the reservoir is assumed to be in the vacuum state and is unentangled from the qubit versing in a generic s tate. The exact dynamics results to be described by series of Fox $H$-func tions. The simple form of the designed reservoir can be accessible experim entally.\n\nhttps://events.saip.org.za/event/7/contributions/5028/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5028/ END:VEVENT BEGIN:VEVENT SUMMARY:Derivation of the master equation for a particle in an external fi eld which is subject to continuous measurement. DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5029@events.saip.org.za DESCRIPTION:Speakers: Kevin Garapo (Centre for Quantum Technology\, Univer sity of Kwazulu-Natal.)\nThe theory of continuous measurement provides a t ool to monitor the evolution of the wave function of a single quantum syst em in real time. We derive the master equation in the non-selective regime for the dynamics of the wave function of a particle in an external potent ial which is subject to continuous measurement of position. In the derivat ion we view continuous measurement as the limit of a sequence of unsharp position measurements. Unsharp position measurements are described by gen eralised measurement observables\, or in mathematical terms\, positive ope rator valued measures (POVM) rather than the standard von Neumann projecti on operators which are a special class of the sub-class of POVM's called p rojection valued measures (PVM). We discuss a method which introduces a co mmutative algebra for non-commuting operators in order to carry out the su mmation of the corresponding measurement operators. In addition we reveal the stochastic Ito equations for the selective regime of measurement.\n\nh ttps://events.saip.org.za/event/7/contributions/5029/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5029/ END:VEVENT BEGIN:VEVENT SUMMARY:Stellar Masses of Star Forming Galaxies in Galaxy Cluster DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5030@events.saip.org.za DESCRIPTION:Speakers: Solohery Randriamampandry (SAAO/UWC)\nWe determine t he stellar mass of star forming galaxies in the X-ray luminous cluster MS 0451.6-0305 at z ∼ 0.54. The stellar masses are estimated from fitting m odel spectral energy distributions (SEDs) to deep\, optical UBRIz observat ions obtained from WIYN 3.5m telescope and public NIR K-band image from Pa lomar Observatory telescope. The model SEDs are based on the stellar popul ation synthesis (SPS) model of Bruzual & Charlot (2003) and Conroy et al. (2009) that span a wide range of age\, star formation history\, initial ma ss function\, metallicity and dust content. We measure stellar masses for galaxies down to M* ∼ 2x108Mʘ. We find a tight correlation between stel lar masses derived from the two SPSs. We compare the derived stellar masse s to the dynamical masses for a set of 25 star-forming galaxies. The dynam ical masses are derived from high resolution\, spectroscopic observations of emission lines from the DEIMOS spectrograph on the Keck telescope. A st rong correlation is seen between the dynamical and stellar mass for the ga laxies\; and the star forming galaxies show fairly constant ratio between stellar and dynamical mass. When comparing to the field sample of Guzmán et al. (2003) of luminous compact blue galaxies\, we see an excess of low mass galaxies in the cluster.\n\nhttps://events.saip.org.za/event/7/contri butions/5030/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5030/ END:VEVENT BEGIN:VEVENT SUMMARY:Omega Meson electroproduction analysis DTSTART;VALUE=DATE-TIME:20110714T060000Z DTEND;VALUE=DATE-TIME:20110714T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5031@events.saip.org.za DESCRIPTION:Speakers: Doomnull Attah Unwuchola (University of Johannnesbur g)\nThis work is part of a program based on the electro-production of bary onic resonances. In part\, the physics goals are to assess the relevant de grees of freedom appropriate to describe high momentum transfer exclusive reactions. In particular\, the interest is in the region where the four – momentum transfer squared\, t ~ Q2 varies beyond the validity of the c onstituent quark model (CQM)\, towards the region where one may search for evidence of pQCD. In this work\, the differential cross section for p(e\ ,e’ω)p has been studied at a Q2 ≈ 5.5 GeV. We present further analys is including comparison with other data. A significant divergence from an extrapolation of previous data is obvious.\n\nhttps://events.saip.org.za/e vent/7/contributions/5031/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5031/ END:VEVENT BEGIN:VEVENT SUMMARY:Overview of the Center for High Performance Computing DTSTART;VALUE=DATE-TIME:20110712T125000Z DTEND;VALUE=DATE-TIME:20110712T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5032@events.saip.org.za DESCRIPTION:Speakers: Daniel Mojalefa Moeketsi (CSIR Meraka Institute (CHP C))\nhttps://events.saip.org.za/event/7/contributions/5032/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5032/ END:VEVENT BEGIN:VEVENT SUMMARY:Practical demonstrations on the use of the CHPC Cluster. DTSTART;VALUE=DATE-TIME:20110712T140000Z DTEND;VALUE=DATE-TIME:20110712T144500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5033@events.saip.org.za DESCRIPTION:Speakers: Daniel Mojalefa Moeketsi (CSIR Meraka Institute (CHP C))\nhttps://events.saip.org.za/event/7/contributions/5033/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5033/ END:VEVENT BEGIN:VEVENT SUMMARY:Ionizing Radiation as Imaging Tool in Coal Characetrization and Ga sification Research DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5035@events.saip.org.za DESCRIPTION:Speakers: Jakobus Hoffman (Necsa)\nAround 70 million tones of coal are burned annually in power stations whilst around 50 million tones of coal are converted to chemicals in the petrochemical sector in the same period of time. Researchers\, nationally and internationally\, aim to op timize the processes to extract the most energy from the limited coal rese rves. One such petrochemical process that is of significance to South Afr ica is gasification\, since many industrially important chemicals and fuel s are produced through the gasification process of coal. \nThe process of gasification is influenced by many factors including temperature\, pressu re\, coal composition\, coal size\, etc. and an understanding of each of t hese factors is crucial to optimize and manage a gasifier. The primary wa ys in which information is obtained on these factors are usually destructi ve experimental methods that are applied to powders and small particles. Powders and very small particles are not representative of the mined coal since it usually represents either average or homogeneous coal structures. \nIt is therefore beneficial to conduct research on coal in order to stu dy the coal structure and processes to beneficiate coal in a non-destructi ve fashion. One such technique is micro-focus X-ray Computed Tomography (C T) which enables the researcher to visualize and quantify the coal composi tion and spatial distribution of constituents and voids (cleats and fractu res). Armed with this knowledge the scientist can investigate and optimiz e conversion processes such as gasification as well as other physical proc ess (methane extraction and carbon dioxide adsorption). \nThis presentati on deals with the characterization of coal and the investigating of the fi rst stages of gasification in a non-destructive manner. Coal particles wi th two distinct coal macerals (organic components) were investigated and t he information obtained was compared to data from a thermo gravimetric ana lyzer (TGA). The main objective of this study was therefore to obtain a b etter understanding of gasification through a non-destructive analytical t echnique.\n\nhttps://events.saip.org.za/event/7/contributions/5035/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5035/ END:VEVENT BEGIN:VEVENT SUMMARY:AES and XRD study of In/Cu thin films deposited onto SiO2 by electron beam evaporation DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5036@events.saip.org.za DESCRIPTION:Speakers: Moshawe Madito (Student)\nIn order to investigate th e diffusion of indium (In) when an In thin film is coated with a copper (C u) thin film\, thin In/Cu films were grown on a silicon dioxide (SiO2) sub strate. Both the In and the Cu layers were grown by electron beam evaporat ion. The temperature during evaporation of the films ranged between 27 an d 38 oC. The In films (500 Å) were coated with Cu films (500 Å and 1000 Å). The films were characterized with X-ray diffraction (XRD) and Auger electron spectroscopy (AES). The In/Cu layers interdiffused during evapo ration and formed intermetallic CuIn2 and Cu11In9 phases. The In layer co mpletely reacted with the Cu layers during the deposition process. The In layer was effectively coated with a Cu layer (1000 Å). The In (500 Å)/C u (1000 Å) films were annealed at temperatures ranging between 150 and 30 0 oC for times varying between 25 and 121 min. For annealed films the dif fraction data demonstrated peaks only for Cu and Cu11In9 and AES depth pro files pointed out the stability of the Cu11In9 and In diffusion to the sur face of the film. The results of this work provide insight towards the In doping of Cu crystals at temperatures higher than the melting point of In (156.6 oC).\n\nhttps://events.saip.org.za/event/7/contributions/5036/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5036/ END:VEVENT BEGIN:VEVENT SUMMARY:Ion sputtering yield coefficients from In thin films bombarded by different energy Ar+ ions DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5037@events.saip.org.za DESCRIPTION:Speakers: Moshawe Madito (Student)\nNoble gas ion sputtering c ombined with Auger analysis has been applied extensively to determine the elemental composition as function of sputtering depth. Data from these de pth profiles have been used to determine the sputter yield coefficients (S ) of elements that are of fundamental interests in many fields\, such as i n: sample preparations particularly were the sputter ion source is applied \, surface cleaning (the surface is usually cleaned by cyclic ion bombard ment and annealing)\, and understanding the theoretical studies of ion sp uttering\, etc.\nMany published data on the Auger-ion (Ar+) sputtering of indium (In) focused on In compounds like indium nitride (InN)\, indium pho sphide (InP) etc. In this study\, the focus is on metal In films that wer e grown by electron beam evaporation on silica substrates. The APPH's (Au ger peak to peak heights) were measured while the In films were subjected to different energy Ar+ ion sputtering. The Ar+ ion energy was varied from 0.5 to 4.0 keV. The normal to the film surfaces was kept at a tilt angle of 30o with respect to the direction of the incident electron beam. The s putter yield coefficients (S) of the In films were determined as 4.5\, 6.4 \, 10.6\, 11.5 and 10.7 atoms/ion for the Ar+ energies 0.5\, 1.0\, 2.0\, 3 .0 and 4.0 keV respectively.\n\nhttps://events.saip.org.za/event/7/contrib utions/5037/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5037/ END:VEVENT BEGIN:VEVENT SUMMARY:Femtosecond amplifier pulse characterization: FROG and shaper-assi sted techniques DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5038@events.saip.org.za DESCRIPTION:Speakers: Attie Hendriks (SAIP member)\nWe present pulse chara cterization of various amplified shaped pulses\, using second harmonic aut ocorrelation\, frequency resolved optical gating (FROG)\, as well as their analogue techniques using only the pulse shaper and no moving parts in th e experimental setup. This involves creating double pulse seperations usin g the pulse shaper only and recording the resulting SHG autocorrelation an d FROG signals. Pulse shaper assisted characterization is presented in det ail for our setup which includes an acousto-optic programmable dispersive filter (Dazzler) coupled with a Matlab program incorporating pulse energy stabilization to compensate for shaper efficiency changes.\n\nhttps://even ts.saip.org.za/event/7/contributions/5038/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5038/ END:VEVENT BEGIN:VEVENT SUMMARY:On the Possibility of Visualizing and Minimizing Student Disappoin tment DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5039@events.saip.org.za DESCRIPTION:Speakers: André Botha (UNISA)\nIn recent years student satisf action surveys have become increasingly popular in universities. Whether t his gain in popularity is because students themselves know best when they are learning\, or whether it is because universities merely wish to ensure that they have satisfied customers\, is still a matter of debate. Neverth eless\, the importance of student satisfaction surveys in universities is undeniable\, and consequently it is of interest to understand the most imp ortant contributing factors to student satisfaction\, or equivalently to s tudent disappointment. \n\nBy induction\, based on our own teaching experi ence\, we have made the following bold postulate: Students will be least d isappointed in courses where they perform equally well in all aspects of t he course that are assessed. Conversely\, students will be most disappoint ed in courses where they perform very differently in two or more assessmen ts of the course. In science courses\, for example\, there are typically f our different assessments: a practical\, three or four assignments\, a mid term exam\, and a final exam. \n \nAlthough the above hypothesis remains u ntested in this preliminary work\, some of its consequences will be explor ed through the visualisation of assessment data gathered at the University of Victoria\, Canada. In this talk a new way of visualizing and understan ding the various components of the assessment data will be presented. The visualisation is constructed to be consistent with the above hypothesis. A concrete example of how the visualization may be used in a modern univers ity setting\, the problem of adjusting marks is considered. Such mark adju stments are apparently necessary to increase throughput rates. In this cas e it is shown that the visualization may be used to achieve an optimized a djustment which both increases the throughput rate and at the same time mi nimizes student disappointment\, assuming the hypothesis is correct.\n\nht tps://events.saip.org.za/event/7/contributions/5039/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5039/ END:VEVENT BEGIN:VEVENT SUMMARY:Recent results from gamma ray studies of rare earth nuclei DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5068@events.saip.org.za DESCRIPTION:Speakers: Maciej Stankiewicz (University of Cape Town)\nRecent theoretical work has suggested that some nuclei in the rare earth region might exhibit tetrahderal deformations. Several nuclei have been studied at iThemba LABS\, resulting in evidence against the possibility of low-lyi ng tetrahedrally deformed bands. In a continued study of the region\, fur ther gamma-ray spectroscopy experiments have been performed at iThemba LAB S\, populating low lying states of nuclei in the (Z\,N)=(70\,90) region. We present some of the results obtained for 156Er\, 160Er and 158Dy\, part icularly referencing the negative parity bands\, and their relative struct ure in relation to the other nuclei in the region. Calculations of the th eoretically predicted observables\, such as the quadrupole deformation and the in-band transition rates and branching ratios will be discussed.\n\nh ttps://events.saip.org.za/event/7/contributions/5068/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5068/ END:VEVENT BEGIN:VEVENT SUMMARY:A comparison of purification schemes for treating the idempotency condition on the density matrix in electronic structure calculations DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5040@events.saip.org.za DESCRIPTION:Speakers: Matthiam Hoffman (UFS)\nDuring the last 15 years the re has been considerable interest in density matrix based methods for elec tronic structure calculations. The “difficult” problem of ensuring ide mpotency conservation of the density matrix through an appropriate purific ation scheme as well as the use of the “nearsightedness” and associate d sparsity of the density matrix to achieve linear scaling with system siz e has been discussed by various authors. \n\nIn this study a density matri x based fictitious electron dynamics method for calculating electronic str ucture is used in a model nanoparticle calculation. This method uses an eq uation of motion that implicitly ensures the idempotency constraint on the density matrix. The effectiveness of this method compared to conventional purification schemes is discussed. \n\nImportant properties of the densit y matrix and its sub matrices\, including its sparsity and conditions for effective linear independence of a column sub matrix of the density matrix are discussed and illustrated within the context of this model system. It is shown how the full density matrix can be reconstructed through a fast QR factorization of a column sub matrix using a Choleski factorization of its principal sub matrix.\n\nhttps://events.saip.org.za/event/7/contributi ons/5040/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5040/ END:VEVENT BEGIN:VEVENT SUMMARY:Higgs Searches with the ATLAS Detector Using Data Collected in 201 0 at the LHC DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5041@events.saip.org.za DESCRIPTION:Speakers: Ketevi Adikle Assamagan (Brookhaven National Laborat ory)\nExperiments at the Large Hadron Collider (LHC) aim to address fundam ental questions in particle physics such as the origin of mass for element ary particles\, the matter/anti-matter asymmetry in the universe\, the na ture of Dark Matter\, the state of matter in the early universe\, etc. The ATLAS detector is one of the four major detectors being exploited at the LHC to shed some light on the questions. The Higgs boson is a hypothesized particle responsible for the elementary particle masses. In this talk\, we will discuss the search strategies of the Higgs boson with the ATLAS d etector at the LHC. In particular\, we will present results based on the A TLAS data collected in 2010.\n\nhttps://events.saip.org.za/event/7/contrib utions/5041/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5041/ END:VEVENT BEGIN:VEVENT SUMMARY:Efficiency Dependence of Tm3+ -Doped Silica Triple-Clad Fiber Lase r DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5042@events.saip.org.za DESCRIPTION:Speakers: Wilfrid Ndebeka (MSc Student)\nWe present measuremen ts of the slope efficiency of a Tm3+ -doped silica triple-clad fiber laser emitting at 2.02 µm using different cooling techniques. The maximum slop e efficiency of 53.6 % was obtained at a temperature of 25o C with a maxim um output power of 5 W for 19 W of absorbed power at the pump wavelength o f 800 nm and 9.9 W threshold. In a slightly different setup\, the output p ower could be increased to 10 W for an absorbed pump power of 32 W.\n\nhtt ps://events.saip.org.za/event/7/contributions/5042/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5042/ END:VEVENT BEGIN:VEVENT SUMMARY:An automated temperature control model for a well-mixed biomass re actor DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5044@events.saip.org.za DESCRIPTION:Speakers: FELIX PAGONA (PHYSICS DEPARTMENT\, UNIVERSITY OF FOR T HARE)\nA mathematical model for temperature control in a continuously st irred tank reactor is developed. The startegy used involves a coil immerse d in a coolant which proves to provide sufficient heat removal by contro lling the coolant flow rate in exponential mode. The approach shows that s pecific ranges of exponents for the coolant flow rate must be used for the reactor to operate optimally.\n\nhttps://events.saip.org.za/event/7/contr ibutions/5044/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5044/ END:VEVENT BEGIN:VEVENT SUMMARY:Crystalline Electric Field Effects in PrNiGe2 DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5045@events.saip.org.za DESCRIPTION:Speakers: Jasper Snyman Snyman (University of Johannesburg)\nW ithin the confines of the standard model of rare earth magnetism\, the hig h temperature magnetic properties of rare earth ions in a crystalline envi ronment are identical to the magnetic behaviour of free tri-positive rare earth ions. At low temperatures deviations from free-ion behaviour occur due to the action of an anisotropic crystalline electric field (CEF). For Pr3+-ions in a low symmetry crystalline environment it is expected that t he 9-fold degeneracy of the spin orbit coupled ground state multiplet asso ciated with the free tri-positive ion should be completely uplifted by the CEF yielding a non-magnetic singlet ground state for the Pr3+ 4f-electron s. PrNiGe2 is known to order ferromagnetically despite the fact that the Pr3+ ions occupy the low-symmetry m2m sites in the CeNiSi2-type structure. This has prompted the current study into the ground state properties of PrNiGe2. The structure of the CEF-split energy levels in this system coul d be determined from specific heat measurements. The analyses point to th e formation of a pseudo-doublet ground state in the system\, and we forwar d a conceptual explanation of the observed magnetic order in PrNiGe2 in te rms a fortuitous merging of electronic singlet levels into a local level d ispensation of higher degeneracy.\n\nhttps://events.saip.org.za/event/7/co ntributions/5045/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5045/ END:VEVENT BEGIN:VEVENT SUMMARY:Tracking a quantum wavefunction in the presence of noise DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5046@events.saip.org.za DESCRIPTION:Speakers: Hermann Uys (National Laser Centre\, CSIR)\nWe simul ate real-time quantum state estimation due to a sequence of so-called "uns harp" measurements applied to a two-level system undergoing Rabi oscillati ons. These measurements allow an experimentalist to extract information a bout the system without destroying the quantum state. They can be realized physically through the use of auxilary quantum states in addition to the quantum state of interest. Here we demonstrate that high fidelity state e stimation is possible even in the presence of significant dephasing and am plitude noise\, thus allowing the quantum state to be monitored long beyon d the coherence time set by the noise in the absence of measurements.\n\nh ttps://events.saip.org.za/event/7/contributions/5046/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5046/ END:VEVENT BEGIN:VEVENT SUMMARY:Defects and Reconstructions in Electron Beam Irradiated Graphene S heets DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5047@events.saip.org.za DESCRIPTION:Speakers: Mopeli Fabiane (University of Pretoria PhD Student)\ nGraphene characterization and device fabrication often require extensive use of the scanning electron microscopy (SEM) and tunneling electron micro scopy (TEM). These techniques involve electron beam irradiation that usual ly causes defects in materials under investigation. The radiation induced defects may lead to significant damage to the material which may alter its properties\, normally an undesirable phenomenon. However\, recent experim ents show that electron radiation can have beneficial effects in materials . Graphenic materials have the ability to reorganize their structures unde r irradiation like no other materials. This property can find application in radiation hard electronics owing to the technological importance of gra phenic materials. Here we report the Raman and scanning tunneling microsco py (STM) results of pristine and heat treated electron -beam irradiated gr aphene sheets (mono-layer and double layers) to demonstrate graphenic reco nstructions. STM creates images of the charge density of electrons at the Fermi level such that all surface atoms can be visible.\n\nhttps://events. saip.org.za/event/7/contributions/5047/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5047/ END:VEVENT BEGIN:VEVENT SUMMARY:The Magnetocaloric Effect in CeAuGe: Scaling Behaviour in the Vici nity of a Ferromagnetic Phase Transition DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5049@events.saip.org.za DESCRIPTION:Speakers: Jasper Snyman Snyman (University of Johannesburg)\nT he magnetocaloric effect (MCE) may become strongly enhanced in systems exh ibiting a second order magnetic phase transition due to critical behaviour of the order parameter in close proximity of the transition region. Rece ntly it has been shown that\, analogous to the order parameter\, the MCE s hows scaling behaviour with the applied magnetic field along the critical isotherm. It has been argued that this behaviour should be indicative of t he universality class of the system. Using ferromagnetic CeAuGe as a model system with high crystallographic and atomic order\, we have determined t he MCE from specific heat measurements in various applied fields. In the low field limit we observe scaling behaviour reminiscent of a mean field f erromagnet. However\, in progressively larger applied fields the MCE in Ce AuGe significantly exceeds that of the mean field reference system\, indic ating that the refrigeration capacity of CeAuGe is significantly larger th an that of a model mean field ferromagnet. Our results are contextualized in terms of a more general amenability of local-moment magnetic compositio ns as model systems for magnetic refrigeration.\n\nhttps://events.saip.org .za/event/7/contributions/5049/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5049/ END:VEVENT BEGIN:VEVENT SUMMARY:Light scattering studies of boron carbide films grown by laser abl ation: thin-film surface quality and elasticity DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5050@events.saip.org.za DESCRIPTION:Speakers: Bhekumusa Mathe (University of the Witwatersrand)\nC ovalently bonded solids based on boron\, carbon\, or nitrogen are the hard est materials\, and B4C is the third hardest after diamond and cubic boron nitride. Thin films of boron carbide were formed by pulsed laser depositi on at room temperature and at higher temperatures up to 800 o C using a si ntered B4C target. Whilst the nature of the particulates embedded in the f ilms and the composition and bonding states of the films is known to vary depending on the laser fluence\, it is of considered interest in this stud y to understand how the surface quality\, microstructure and tensile prope rties of B4C would depend on substrate temperature. The deposition paramet ers such as the laser intensity\, vacuum\, supporting gas conditions\, tar get-substrate distance\, would be controlled such that only substrate temp erature is used to modify the film properties and composition. Raman scatt ering studies and AFM measurements would be used to probe the microstructu re and bonding of the film as the substrate temperature is varied\, whilst Brillouin scattering measurements would be used examine the elasticity ch anges.\n\nhttps://events.saip.org.za/event/7/contributions/5050/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5050/ END:VEVENT BEGIN:VEVENT SUMMARY:Radiometric studies of South African Water bodies DTSTART;VALUE=DATE-TIME:20110715T094500Z DTEND;VALUE=DATE-TIME:20110715T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5051@events.saip.org.za DESCRIPTION:Speakers: Arshath Ramkilowan (CSIR)\nMaintaining\, monitoring and safeguarding South Africa’s oceans and dams is a multifaceted projec t requiring the skills and expertise from several scientific domains-.The radiometric study and spectral characterization through in situ measuremen ts of these water systems is critical to such a project. The objective is to develop and subsequently test 2 prototype radiometers for their reliabi lity and efficacy\, then pending accurate results\, the manufacturing of s everal low cost radiometers. These radiometers will be deployed at strateg ic locations in oceans and dams around South Africa to monitor eutrophicat ion levels. By closely observing the eutrophication stages of these water bodies an early warning system for detecting the initial stages of algal b looms is formed. This is of interest not only to oceanographers and biolog ists but also the military. An additional benefit of the prototype radiome ters is that they provide means of validating ocean colour data obtained f rom satellites. As a result\, the data captured from decades earlier can b e used with true confidence\; such data can be directly linked to climate studies including global warming and global cooling.\n\nhttps://events.sai p.org.za/event/7/contributions/5051/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5051/ END:VEVENT BEGIN:VEVENT SUMMARY:Low voltage electron beam induced degradation and surface chemical changes of Zn3(PO4)2:Tb phosphor DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5052@events.saip.org.za DESCRIPTION:Speakers: I M Nagpure (University of The Free State)\nThe inve stigation of low voltage electron induced cathodoluminescence (CL) degrada tion of Zn3(PO4)2:Tb phosphor has been extended for possible application in low voltage field emission displays (FED). There are two important reas ons for studying phosphate based phosphors. These are their chemical\, the rmal stability and variation in emission colour\, which is influenced by t he site occupied by the light emitting cations. The CL degradation phenome non under low voltage electron beam irradiation of Zn3(PO4)2 has however n ot been reported so far. The primary objective of this study was to invest igate the correlation between the CL emission intensity\, CL degradation b ehaviour and the changes on the surface chemistry from the Zn3(PO4)2:Tb ph osphor after prolonged electron beam exposure. The Zn3(PO4)2:Tb3+ phosphor s was synthesized by a sol-gel combustion method. The surface chemical rea ctions and influence on the CL intensity induced by a prolonged electron b eam bombardment were monitored using in situ Auger electron spectroscopy ( AES) combined with CL spectroscopy. The chemical state of the surface befo re and after prolonged electron exposure of Zn3(PO4)2:Tb3+ phosphor to ele ctron beam was determined using X-ray photoelectron spectroscopy (XPS). Th e bluish green CL emission that were obtained with minor emission peaks a t 380\, 420\, 440 nm were due to the transition from excited level 5D3 → 7F6\, 7F5\, and 7F4 levels of Tb3+ ions\, while the peaks at 490\, 542\, 584 and 620 nm were due to 5D4 → 7F6\,5\,4\,3 transitions when the powde rs were irradiated with a 2 keV and 10 uA electron beam. AES data suggeste d that the Tb3+ CL intensity decreases with an increase in the electron do se rate. The XPS data suggested that a thermodynamically stable ZnO and P2 O5 layer formed on the surface as a result of the electron stimulated surf ace chemical reactions (ESSCRs). The continues growth of this layer is con tributing to the continues CL degradation of the Zn3(PO4)2:Tb phosphor.\n\ nhttps://events.saip.org.za/event/7/contributions/5052/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5052/ END:VEVENT BEGIN:VEVENT SUMMARY:NON-SPECIALIST: Cosmic-ray modulation studies – why Parker neede d Dirac and Kolmogorov DTSTART;VALUE=DATE-TIME:20110715T090000Z DTEND;VALUE=DATE-TIME:20110715T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5053@events.saip.org.za DESCRIPTION:Speakers: Renier Burger (North-West University)\nIn 1958\, Eug ene Parker predicted that the outer parts of the Sun's atmosphere\, the so lar corona\, must be expanding in the form of a supersonic solar wind. Thi s was confirmed by the Mariner 2 spacecraft in 1962. On 16 December 2004\, the Voyager 1 spacecraft crossed the heliospheric termination shock\, whe re the flow becomes subsonic\, and began exploring the heliosheath. In Aug ust 2007\, Voyager 2 also crossed the termination shock. The plasma proper ties of the heliosheath differ greatly from those of the heliosphere insid e of the termination shock and particle transport beyond the termination s hock is not yet fully understood. Different approximations of the cosmic-r ay transport equation\, originally derived by Parker in 1965\, have been u sed for decades to study cosmic-ray modulation in the region inside of the termination shock\, the focus of this presentation. Cosmic rays that reac h Earth are subject to diffusion\, convection\, adiabatic energy changes\, and gradient- and curvature drift due to the non-uniform heliospheric mag netic field. The consequence is that cosmic-ray intensities at Earth are l ower than the interstellar value and is referred to as modulation. The tur bulent heliospheric magnetic field is frozen into the supersonic solar win d. Inside of the termination shock the two hemispheres with oppositely dir ected magnetic field is separated by the so-called wavy neutral sheet\, ac ross which the magnetic field changes direction. We discuss how modulation studies have progressed from using simple spherically symmetric solutions of Parker's transport equation\, to the current situation where in order to properly account for diffusion and drift\, complex turbulence transport models are required as well as detailed knowledge of the form of turbulen ce energy spectra\, the latter which include the so-called inertial range derived by Kolmogorov in 1941. Turning to plasma physics\, we show that wh at appear to be two very different kinds of drift motion\, along and away from the neutral sheet\, actually follow from the standard expression for gradient- and curvature drift\, provided that the particle distribution is nearly isotropic. In the course of this derivation one is confronted by a Dirac delta function that must be replaced by something physically accept able without changing the physics involved. We also discuss why we can stu dy the drift coefficient which determines drift velocity\, while using a u niform background magnetic field that obviously does not cause large-scale drifts.\n\nhttps://events.saip.org.za/event/7/contributions/5053/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5053/ END:VEVENT BEGIN:VEVENT SUMMARY:Lightning induced whistler waves as a cause of electron precipitat ion DTSTART;VALUE=DATE-TIME:20110715T100000Z DTEND;VALUE=DATE-TIME:20110715T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5054@events.saip.org.za DESCRIPTION:Speakers: Marlie van Zyl (University of KwaZulu-Natal)\nLightn ing induced whistler waves are one of the primary causes of energetic elec tron loss from the Earth's radiation belts. This is mainly due to the pitc h angle scattering of the particles by whistler mode waves\, leading to pr ecipitation. The detailed spatial and temporal influence of lightning on p recipitation losses is\, however\, not well known. The World Wide Lightnin g Location Network (WWLLN) gives continuous global lightning coverage with good time resolution. Since the detection efficiency of WWLLN is relative ly low\, it was compared to LIS/OTD data. However\, whereas WWLLN records strokes\, LIS/OTD record flashes. Therefore the flash multiplicity has to be taken into account. By incorporating multiplicity and lightning stroke orientation to the WWLLN global lightning distribution and then transformi ng the resulting data to geomagnetic(MAG)coordinates\, the average VLF pow er that is radiated into the ionosphere can be estimated. This can be used to determine the energy and the spectrum of the waves that go on to enter the magnetosphere. Hence the precipitation losses due to whistler mode wa ves can be studied.\n\nhttps://events.saip.org.za/event/7/contributions/50 54/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5054/ END:VEVENT BEGIN:VEVENT SUMMARY:Studies of thermodynamic\, structural and electronic properties of substitutional defects in models of single-walled carbon and boron nitrid e nanotubes DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5055@events.saip.org.za DESCRIPTION:Speakers: Matete Mashapa (CSIR)\nWe report on studies of therm odynamic\, structural and electronic properties of substitutional defects involving C\, B\, N and vacancies in models of single-walled carbon and bo ron nitride nanotubes. Using the generalized gradient approximation (GGA) for the exchange-correlation functional\, we perform first principles calc ulations within the framework of density functional theory to optimize ful ly the geometries of the systems in their ground states. We give detailed accounts of the relaxed geometries. We compare the heats of formation of t he various point defects\, and we draw conclusions about the relative stab ility of the these defects. We study the changes to the electronic structu re for these defect systems\, and further investigate the detailed nature of the defects. We make a comparative study of the C and BN nanotube syste ms.Where data is available\, comparisons are made.\n\nhttps://events.saip. org.za/event/7/contributions/5055/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5055/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis & Characterization of Porphyrin Nanotubes/Rods for Solar Radiation Harvesting and Solar Cells DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5056@events.saip.org.za DESCRIPTION:Speakers: nametso Mongwaketsi (iThemba LABS)\nPorphyrins are m acro-cycles often organized into nano-scale structures which perform many of the essential light-harvesting-\, electron- and energy-transfer functio ns in various natural and synthetic systems. In addition to the sub-picos econd charge generation and transfer\, they exhibit various shapes and fun ctional properties that make them useful for the construction of ultrafast nanodevices and more specifically solar cells. This latter case would req uire to expand their specific J\, S and Q absorption bands\; a task of thi s research work. They are related to chlorophyll molecules found in natura l systems that carry out light harvesting\, charge separation and energy c onversion.\nUsing the free base and diacid forms of tetrakis (4-sulfonatop henyl) porphyrin and by varying the ionic strength of aqueous solutions us ed\, Schwab et al were able to form single and bundled nanorods\, whereas Wang et al used the mixture of tetrakis (4-sulfonatophenyl) porphyrin and Sn(IV) tetrakis(4-pyridyl) porphyrin to form a mixture of nanotubes and na norods. Once synthesized\, the incorporation of such nanostructures into a functional device presents its own set of unique problems\, but one promi sing approach is to incorporate the nanotubes/rods onto a support to obtai n an array that can be directly used as a device.\nProperties investigated after synthesis included the optical (UV-visible spectroscopy)\, physical (Transmission electron microscopy) and the growth mechanism of the nanotu bes/rods. Understanding the sizes and growth mechanism of nanorods is esse ntial for the successful implementation in PV-like solar cells hybrid syst ems.\n\nhttps://events.saip.org.za/event/7/contributions/5056/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5056/ END:VEVENT BEGIN:VEVENT SUMMARY:The synthesis and characterization of tin oxide SnO2 nanorods DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5057@events.saip.org.za DESCRIPTION:Speakers: Nolwazi Shozi (none)\nIn 2003\, photoluminescence em ission in tin dioxide nanoribbons was reported and it was later demonstrat ed that the absorption of nitrogen dioxide by these structures quenches th e intensity of visible light emission in SnO2 nanobelts which suggested he possibility of developing a new class of contactless devices based on gas sensitive optical devices. The motivation behind this project is to clari fy the fundamental aspects of light emission mechanisms of nanorods instea d of nanoribbons and to characterise their response to gas species in view of their possible applications. The benefits of this project may include enhancing the sensitivity of conductometric gas sensors through the design and synthesis of porous three-dimensional tin oxide nanostructures. Sever al methods have been used to prepare SnO2 nanorods including thermal evapo ration\, thermal decomposition\, solution phase growth and hydrothermal me thods. Amongst these\, the thermal evaporation approach has been used to s ynthesize a wide variety of 1-D materials. This often has involved the use of a catalyst in which nanowire growth proceeds by vapour-liquid-solid (V LS) mechanism. However metal catalysts can serve as impurities and contami nate the nanowires\, possibly forming defect states that limit their appli cations in devices.\n\nThe experiental procedure that will be used to depo sit the tin dioxide (SnO2) nanorods is called pulsed laser deposition (PLD ). These structures were characterized using X-ray powder diffraction\, sc anning electron microscope\, transmission electron microscope and photolum inescence spectroscopy. The XRD patterns of the SnO2 nanorods showed peaks with 2θ values of 26.97 °\, 34.34 °\, 38.26 °\, 52.01 °\, 54.90 °\, 71.28 °\, and 78.40 °\, corresponding to SnO2 tetragonal rutile crystal planes of (110)\, (101)\, (200)\, (211)\, (220)\, (202) and (321) respect ively. Raman spectra taken at room temperature for Sno2 nanorods which sho ws bands at 576 and 359 cm-1 in addition to the Ag1 vibrational mode at 63 5 cm-1. TEM image of the SnO2 nanorods indicates a relatively uniform rod- like morphology. These rods are of 15-20nm in length and 2.5-5nm in diamet er. The room temperature photoluminescence spectra for SnO2 nanorods showe d a red emission at 580nm was observed from the SnO2 nanorods using the He -Cd laser (~325nm) as the excitation source.\n\nhttps://events.saip.org.za /event/7/contributions/5057/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5057/ END:VEVENT BEGIN:VEVENT SUMMARY:Metal-Semiconductor Ohmic Contacts: An ab initio Density Functiona l Theory Study of the Structural and Electronic Properties of Metal-Diamon d (111)-(1x1) Interfaces. DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5058@events.saip.org.za DESCRIPTION:Speakers: Isaac Motochi (PhD student\, University of the Witwa tersrand)\nMetal contacts on clean\, hydrogenated and oxygenated diamond s urfaces have been studied using ab initio Density Functional Theory. Five metals\, i.e.\, gold\, titanium\, tantalum\, vanadium and palladium on the three surfaces were considered. Gold and palladium were found to form wea k bonds on clean\, hydrogenated or oxygenated diamond (111) surfaces compa red to the other three metals. Bulk properties were also studied following the formation of the respective ohmic contacts on the three surfaces. The clean diamond surface was found to have surface states which were modifie d by oxygen but removed by hydrogen. Density of states studies revealed th at all the investigated metals had an effect on the electrical properties of the diamond surface. A peak that is characteristic of diamond was obser ved at ≈ -11.8 eV. For the clean diamond surface terminated with gold an d palladium\, states due to Au-2p orbitals were observed at ≈ -2.5 eV an d ≈ -1.5 eV\, while Pd-5s orbitals were located at ≈ -1.7 eV and ≈ - 0.5 eV on the same surface. Titanium\, tantalum and vanadium showed unique states at high binding energies of ≈ -38 eV for vanadium\, ≈ -34 eV f or tantalum and ≈ -32.5 eV for titanium\, which were thought to be respo nsible for their strong bonding.\nKey words: Metal-diamond interface\, Ads orption\, ohmic contacts\n\nhttps://events.saip.org.za/event/7/contributio ns/5058/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5058/ END:VEVENT BEGIN:VEVENT SUMMARY:Pt –Al203 nanocoatings for high temprature concentrated solar th ermal power applications DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5062@events.saip.org.za DESCRIPTION:Speakers: Zebib Yenus Nuru (iThemba LABS)\nNano-pahsed structu res based on metal-dielectric composites also called cermets (Ceramic-Meta l) are considered among the most effective spectrally selective solar abso rbers. For high temperature applications (stable up to 650°C) noble metal s nanoparticles and refractory oxide host matrices are ideal as per their high temperature chemical inertness and stability: Pt/Al2O3 cermet nano-co mposites are a representative family. This contribution reports on the op tical properties of Pt/Al2O3 cermet nano-composites deposited in a multila yered tandem structure. The radio-frequency sputtering optimized Pt/Al2O3 solar absorbers consist of stainless steel substrate/ Mo coating layer/ Pt-Al2O3/ protective Al2O3 layer and stainless steel substrate/ Mo coating layer /Pt-Al2O3 for different composition and thickness of the Pt-Al2O3 c ermet coatings. The coatings microstructure\, morphology\, composition\, o ptical properties were analyzed by x-ray diffraction\, atomic force micro scopy\, infrared attenuated total reflection and UV-VI-NIR specular reflec tances.\n\nhttps://events.saip.org.za/event/7/contributions/5062/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5062/ END:VEVENT BEGIN:VEVENT SUMMARY:National Curriculum Statement achievement levels – Can they serv e as a measure of science students’ preparedness for university study? DTSTART;VALUE=DATE-TIME:20110713T114500Z DTEND;VALUE=DATE-TIME:20110713T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5063@events.saip.org.za DESCRIPTION:Speakers: Leelakrishna Reddy (University of Johannesburg)\nThe preparedness of matriculants for university studies has been a subject of intense debate and interrogation at various levels of public discourse. I n addition\, the standardization of Grade 12 assessment marks in various s ubjects by the Quality Assurance Body (Umalusi) has of late become a highl y contentious issue. It is in recognition of these considerations that we undertook to investigate the extent to which Grade 12 achievement levels i n Mathematics\, Physical Science and English can serve as a measure of sci ence students’ preparedness for university study. Some of the underlying critical factors that may have a significant bearing on the aforementione d scenario were also investigated.\n\nhttps://events.saip.org.za/event/7/c ontributions/5063/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5063/ END:VEVENT BEGIN:VEVENT SUMMARY:Pulse Repetition Frequency locking by pump modulation in numerical simulations of a diode end pumped passively Q-switched Nd:YAG laser with a Cr4+:YAG saturable absorber DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5064@events.saip.org.za DESCRIPTION:Speakers: oliver collett (National Laser Center)\nPassively Q- switched Nd:YAG lasers with Cr4+:YAG as a saturable absorber that can oper ate with pulse repetition frequencies(PRF) in the hundreds of kilohertz ty pically have problems with pulse to pulse fluctuations of pulse energy and width and the associated timing jitter as well as drift in PRF.\n One tec hnique for stabilizing the PRF and reducing fluctuations is modulation of pump power. This technique has been simulated using a plane wave rate equa tion model with square wave pump modulation at frequency of 100 kHz. Locki ng of the pulse repetition rate is achieved at the modulation frequency ov er a range of pump powers. This locking range is dependent on the modulati on function\, a square wave with a 50% duty cycle and a modulation depth o f 0.5 produced a 13% locking range. Additionally smaller regions of stabil ity also occur at higher pulse repetition frequencies at higher pump power s. The effect on the stability of pulse energy and width\, and the timing rate jitter of this technique have been investigated.\n\nhttps://events.sa ip.org.za/event/7/contributions/5064/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5064/ END:VEVENT BEGIN:VEVENT SUMMARY:Pulsating B stars in the LMC DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5065@events.saip.org.za DESCRIPTION:Speakers: Christian Engelbrecht (University of Johannesburg)\n Pigulski and Kolaczkowski (2002\, A&A 388\, 88) announced the first discov ery of Beta Cephei (BCep) pulsators in the LMC. This was a remarkable disc overy\, since theoretical analyses of pulsational stability had previously predicted that early B main-sequence stars with metallicities lower than Z = 0.01 should not pulsate at all (e.g. Pamyatnykh 1999\, Acta Astron 49\ , 199). Following this announcement\, and announcements of 92 BCep candida tes in the LMC by Kolaczkowski and Pigulski (2006\, MemSAIt. 77\, 336)\, m ore detailed studies adopting a variety of opacity calculations and metal mixtures indicated that BCep pulsations could be explained in low-metallic ity environments after all (Miglio et al. 2007\, MNRAS 375\, L21\; Miglio et al. 2007\, Com.Ast. 151\, 48\; Zdravkov and Pamyatnykh 2008\, J.Phys.Co nf.Ser. 118\, 012079). In order to ascertain the nature of these pulsation s\, multi-colour photometry of sufficient precision is required. \n\nWe ha ve obtained 4 weeks of UBVI photometry on two fields in the LMC that surro und stars which have been identified as strong Beta Cephei candidates from OGLE data. We report on the results of this photometric campaign.\n\nhttp s://events.saip.org.za/event/7/contributions/5065/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5065/ END:VEVENT BEGIN:VEVENT SUMMARY:Searching for signatures of nearby sources of cosmic rays in their local chemical composition DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5066@events.saip.org.za DESCRIPTION:Speakers: Driaan Bisschoff (North-West University)\nThe direct evidence for the acceleration of hadronic cosmic rays at supernova remnan ts underlined the need for a 3D time dependent treatment of the propagatio n of Galactic Cosmic Rays (CRs). Full 3D time dependent calculations of th e propagation of CRs have shown that if CRs indeed originate from supernov a remnants\, transient point-like sources\, the flux of the CR primary com ponent measured at Earth depends strongly on the local source history\, wh ereas the secondary component shows only little or no variations due to ne arby sources. The most widely used steady state\, rotational symmetric mod els (2D) of CR propagation cannot take into account the local source histo ry\, but rather mimic source histories that result in the same local CR fl ux as the smeared-out sources assumed in 2D models and do not necessarily coincide with the real local source history. Using a steady state\, rotati onal symmetric model for a parameter study\, one may expect different best fit values looking at the primary and secondary CR components separately\ , as it is unlikely that the source history mimicked by the 2D models coin cide with the real local source history. \nWe adapted the 2D version of th e GALPROP code to a cluster environment and perform parameter studies comp aring CR spectra with mainly primary and secondary CR data separately. Fir st results of these studies will be presented and recommendations for furt her such studies will be given.\n\nhttps://events.saip.org.za/event/7/cont ributions/5066/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5066/ END:VEVENT BEGIN:VEVENT SUMMARY:Search for Tetrahedral symmetries in 156Dy DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5067@events.saip.org.za DESCRIPTION:Speakers: Siyabonga Majola (UCT/ iThemba Labs)\nNegative-parit y side bands in nuclei localized in the vicinity of N = 90 are known to ha ve strong electric dipole transitions from each level to the ground-state band\, with weak or unseen E2 transitions (E2s) in the medium (~15h) to lo w-spin region. These structures have always been regarded as octupole vibr ational bands. On the other hand\, Dudek et al. recently proposed that the se structures might be associated with tetrahedral symmetries\, as they ha ve very weak inband E2s. \n\nIn this study\, data from the 148Nd (12C\, 4n ) 156Dy reaction\, taken with GAMMASPHERE is analysed. Out of 23 rotationa l bands that have been observed in this present study for 156Dy\, there ar e eleven new bands and more than 266 new transitions. We also report an ob servation of a band with characteristics of that discussed on the paragrap h above i.e. a negative parity band with missing (or weak) inband transiti ons at low spin. Furthermore\, the crossing between this band (tetrahedral candidate) and band 6 around spin 13h has allowed the band mixing calcul ation to be carried out\, so that relative quadrupole moments could be ded uced for these bands. However\, a non-zero quadrupole moment has been dedu ced for our tetrahedral candidate\, and this is incompatible with the tetr ahedral shape. We therefore seek for an alternative description of this ba nd.\n\nhttps://events.saip.org.za/event/7/contributions/5067/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5067/ END:VEVENT BEGIN:VEVENT SUMMARY:Characterization of the Phase Transition of h-BN - c-BN Nanopartic les by Ion Implantation DTSTART;VALUE=DATE-TIME:20110715T101500Z DTEND;VALUE=DATE-TIME:20110715T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5069@events.saip.org.za DESCRIPTION:Speakers: Emily Aradi (University of the Witwatersrand)\nThe s ynthesis of the c-BN (cubic boron nitride) has developed great interest du e to its excellent physico-electrochemical properties. These include\; hi gh hardness values (73 GPa) second after diamond\, wide band gap (6.4 eV)\ , optical transparency in a wide region of the electromagnetic spectrum\, high temperature stability (1200 oC) and chemical inertness. These propert ies enable c-BN to be very useful for various industrial and electrical ap plications such as in cutting and grinding\, fabrication of high temperatu re high frequency devices among many others.\nIn this work\, ion irradiati on effect of the soft graphitic boron nitride (h-BN) is investigated from characterization with Raman Spectroscopy before and after implantation. Th is was to investigate a possible phase transformation of h-BN to c-BN. Bor on\, lithium and helium ions were implanted into the hot pressed h-BN samp les at 150keV\, and with fluences ranging from 1x1014 ions/cm2 to 1x1016 ions/cm2. \nRaman Spectroscopy showed that implantation of all the three ions led to an h-BN to a possible c-BN phase transition\, evident from the longitudinal optical (LO) Raman phonon features occurring at 1303cm-1 in the implanted samples’ spectra. The nature of the phonon peaks and their downshifting is explained using the spatial phonon correlation model. The extent of these peaks was found to depend on the mass of the incident ion and the fluence\, where high ion mass required low fluence compared with the low ion masses.\n\nhttps://events.saip.org.za/event/7/contributions/50 69/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5069/ END:VEVENT BEGIN:VEVENT SUMMARY:A Magnetic Field Study Using Polarized Dust Emission of Nearby Sta rburst Galaxies DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5070@events.saip.org.za DESCRIPTION:Speakers: Lerothodi Leeuw (University of Johannesburg)\nWe wil l present submillimeter (submm) polarized imaging of the nearby star-formi ng galaxies M82 and NGC253. The data\, obtained with the Caltech Submillim eter Observatory in Hawaii\, probe the emission from dust grains aligned b y magnetic fields in these galaxies\, and thus fields in relatively dense regions of the galaxies.\n\nhttps://events.saip.org.za/event/7/contributio ns/5070/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5070/ END:VEVENT BEGIN:VEVENT SUMMARY:The IThemba LABS Radioactive Beam Project DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5071@events.saip.org.za DESCRIPTION:Speakers: Robert Bark (iThemba LABS)\nA feasibility to develop a radioactive beam facility at iThemba LABS has commenced. The proposal e nvisages the addition of a new cyclotron\, a k70 negative-ion accelerator. Such an accelerator can supply two beams simultaneously\, one to be used for isotope production and neutron therapy\, the other to create radioacti ve ions. These can be post accelerated by the existing SSC accelerator to energies of 5~7 MeV/A. It is envisaged that the beamtime available for nu clear physics\, presently restricted to weekends only\, will more than dou ble. The feasibility study aims to minimize costs and maximize performance . However\, many technical challenges remain in producing radioactive beam s so the study also aims at minimizing risks.\n\nhttps://events.saip.org.z a/event/7/contributions/5071/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5071/ END:VEVENT BEGIN:VEVENT SUMMARY:Spectral response as a diagnostic tool for PV and PC solar cells DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5072@events.saip.org.za DESCRIPTION:Speakers: Maibi Malape (Fort Hare Institute of Technology)\nTh e spectral response measurement system is an important tool for optimizati on of solar cells. Its measurement permit an examination of how photons of different wavelength contribute to the cell generated current at zero bia s voltage. In this study photovoltaic (PV) and photochemical (PC) solar ce lls were used and their spectral responses were measured. The aim is to us e the spectral response data in order to investigate the effect of shading on PV and PC solar cells. Preliminary results showed that the shading of cells degrade cells responsivity.\n\nhttps://events.saip.org.za/event/7/co ntributions/5072/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5072/ END:VEVENT BEGIN:VEVENT SUMMARY:The Unique Capabilities of Radiation Beam Lines at Necsa as Probes DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5074@events.saip.org.za DESCRIPTION:Speakers: Frikkie De Beer (Necsa)\nThe concept of radiation\, in the scientific and analytical environment is normally not understood an d has being neglected and not considered as analytical probe due to the la ck of knowledge of the general public and researchers about its potential as analytical probe\, the misunderstanding of the possible “danger’ in the utilization thereof and the “unavailability” of facilities in Sou th Africa for researchers to utilize.\nGamma-rays\, neutrons and X-ray’s have not any significance for a researcher unless they are controlled and directed in beams with considerable intensity. These collimated beams hav e major potential in revealing the “unknown” information normally hidd en within the objects under investigation e.g. nuclear materials\, museum artifacts’\, precious fossils\, concrete\, etc. \nThis paper is an intro duction to the unique properties of neutron- and X-ray radiation beams in general. The capabilities of these beams as analytical probes are discusse d with special attention to the beam line facilities located at Necsa. Th e availability of these beam lines to be utilized by post graduate student s and researchers will be highlighted.\n\nhttps://events.saip.org.za/event /7/contributions/5074/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5074/ END:VEVENT BEGIN:VEVENT SUMMARY:Decoherence-assisted transport in a dimer system DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5075@events.saip.org.za DESCRIPTION:Speakers: Ilya Sinayskiy (UKZN and NiTheP)\nThe transfer of en ergy and information in quantum networks plays an important role in both q uantum communication and quantum computation. The quantum system inevitabl y interacts with the surrounding environment\, and such interaction leads to dissipation and decoherence\, which are processes typically associated with a destruction of quantum coherence in the system. However\, recently evidence of surprisingly long-lived quantum coherence has been identified in conjugate polymers and in photosynthetic light harvesting complexes. \n \nHere\, the dynamics of a dimer under the influence of decoherence are st udied. An exact analytical expression for the transition probability in th e dimer system is obtained for different situations\, i.e.\, for the dimer coupled to two independent environments\, and coupled to two correlated e nvironments\, both in a spin star configuration. In all cases considered\, it is shown that there exist well-defined ranges of parameters for which decoherent interaction with the environment assists energy transfer in the dimer system. In particular\, it is found that correlated environments ca n assist energy transfer more efficiently than separate baths. \n\nThis si mple and analytically solvable model for energy transfer in a dimer system is easily extendible to more complex quantum networks\, and more complex environmental models.\n\nhttps://events.saip.org.za/event/7/contributions/ 5075/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5075/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and Characterization of CaAl204:Tb 3+ Phosphor using Solution – Combustion Method. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5076@events.saip.org.za DESCRIPTION:Speakers: Kewele Emily Foka (University of the Fee Stae)\nPres ently Ca AlxOy:Tb green phosphors are mainly prepared by the solid-state p rocess which is more feasible than others in terms of operation and large- scale production. However\, the raw materials are usually not mixed well a nd very high temperature is needed to synthesize the final powder using th e solid-state process. In order to solve these problems\, Terbium ion dope d calcium aluminate (Ca AlxOy:Tb3+ green phosphors were obtained at low te mperatures (500ºC) by the solution - combustion of corresponding metal ni trate–urea solution mixtures\, over a time of 5 min. The morphology and structural properties were characterized by scanning electron microscopy ( SEM) and X-ray diffraction (XRD)\, SEM shows that the particles are irregu lar shape and are aggregated and the structural analysis revealed the pres ence of monoclinic CaAl4O7 at optimized fuel to nitrate molar ratio. The characteristic luminescence properties were investigated using emission sp ectra. It was found that the oxidizer: fuel molar ratios showed greatly in fluence not only on morphology\, but also on their PL spectra. The photolu minescence (PL) excitation spectrum was characterized by a dominant broad band centered on 239 nm. Intense emission bands were observed at 489 nm\, 544 nm\, 587 nm and 622 nm originating from the 5 D4 to 7 FJ transition and other bands were observed at 379\, 417 and 438nm originating from 5 D3 to 7 FJ transition\, which correspond to the crystal field splitting com ponents of the Tb3+ 4f states in Ca Al4 O7. The effects of doping concentr ation of Tb3+ on luminescence lifetimes and intensities were also investig ated. The samples with Tb concentration of 1.0 mole % exhibited the highes t luminescence enhancement and longer luminescence lifetimes.\n\nhttps://e vents.saip.org.za/event/7/contributions/5076/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5076/ END:VEVENT BEGIN:VEVENT SUMMARY:Capabilities of Accelerator Beam Lines in Research and Development at Necsa DTSTART;VALUE=DATE-TIME:20110715T090000Z DTEND;VALUE=DATE-TIME:20110715T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5077@events.saip.org.za DESCRIPTION:Speakers: Graham Daniels (Necsa)\nP-LABS at Necsa consists of two linear particle accelerator facilities\; a Van de Graaff with terminal potential up to 4 MV and two radio frequency quadrapole (RFQ) accelerator systems that can accelerate D+ ions to 3.7 - 5.1 MeV (or protons to 1.8 – 2.5 MeV). Depending on the beam target used these accelerators can pro duce fast neutrons (and associated gamma rays) at a rate of 10^6 - 10^12 n /cm^2/s. \n\nOne can utilize the high penetrative nature of the fast neutr ons as well its ability to distinguish between different elements\, to con duct radiography and tomography on samples. These fast neutrons can also b e used to conduct time of flight analysis. One can also utilize the associ ated gamma rays together with the fast neutrons for material identificatio n and non destructive testing including identification of threat material within cargo. Utilization of the Monte Carlo Neutral Particle code (MCNP) is also done to simulate the facility and experiments beforehand. Some of the techniques currently being investigated will be presented here.\n\nhtt ps://events.saip.org.za/event/7/contributions/5077/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5077/ END:VEVENT BEGIN:VEVENT SUMMARY:Accurately and precisely determining the strength of an optical tr ap DTSTART;VALUE=DATE-TIME:20110714T071500Z DTEND;VALUE=DATE-TIME:20110714T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5078@events.saip.org.za DESCRIPTION:Speakers: Yaseera Ismail (CSIR-National Laser Centre)\nSince i ts inception\, optical trapping has found its place in the field of physic s\, biology and recently in micro-fluidics. To a physicist\, this techniqu e opens up avenues to carry out force measurement with utmost accuracy and precision on the micro-scale level. This is attained by measuring the mag nitude of the trapping force required to restrain a trapped particle to it s equilibrium position. Here three such methods will be discussed in light of their relevance to the current optical system in the laboratory. The m ost direct method carried out was the drag force method\, by keeping the p article fixed while accurately controlling the movement of the automated s tage we were able to measure the magnitude of the force applied to a parti cle in order to release it from the trap. Alternatively\, since trapped pa rticles are submerged in liquid medium\, any thermal fluctuation within th e medium would lead to the trapped particle displacing from its equilibriu m position. Under this condition\, the particle is said to behave as a sim ple harmonic oscillator. By measuring the variation of the trapped particl e with respect to its equilibrium position we were able determine the trap stiffness using the Equipartition theorem. Lastly\, we discuss the Allan variance method. Since most systems contain some form of noise\, the Allan variance method was used to eliminate any form of white noise that could exist to accurately and precisely determine the trapping force using CMOS technology. Most scientific programs can be used to determine the Allan va riance\; we used Labview as a platform for the analysis. An overview of al l the methods mentioned will be discussed in detail to give an understandi ng of the most accurate and precise method of calibrating an optical trap. \n\nhttps://events.saip.org.za/event/7/contributions/5078/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5078/ END:VEVENT BEGIN:VEVENT SUMMARY:Use of raman spectroscopy to study fatigue type processes in polyc rystalline diamond (PCD) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5079@events.saip.org.za DESCRIPTION:Speakers: Maxwell Vhareta (University of the Witwatersrand)\nP olycrystalline diamond (PCD) cylindrical cutters used in oil well drilling are susceptible to fracture due to the hostile environment of randomly oc curring high impact loads. These cutters commonly consist of a PCD layer s intered onto a cobalt-tungsten carbide (Co-WC) substrate. The fact that th e cutters fail after repeated use gives rise to the possibility of fatigue type processes in diamond. The study of stress fields and their relative geometries thus become crucial in the quest to have extended lives for the se cutters. Since the diamond Raman line reveals both the nature and magni tude of the stress present in the material this technique was employed in this work. Room temperature measurements show a general compressive stress field on the PCD before being fatigued using a ball on three balls test r ig and it then gradually deteriorates to a residual tensile stress field. Whereas a general compressive stress is desirable in the PCD layer as it i nhibits the propagation of cracks\, on the contrary tensile stresses facil itate formation of cracks leading to catastrophic failure of the cutters.\ n\nhttps://events.saip.org.za/event/7/contributions/5079/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5079/ END:VEVENT BEGIN:VEVENT SUMMARY:Application of Dual Energy X-ray Radiography/Tomography on Nuclear and Related Materials DTSTART;VALUE=DATE-TIME:20110715T093000Z DTEND;VALUE=DATE-TIME:20110715T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5080@events.saip.org.za DESCRIPTION:Speakers: Takalani Ndanduleni (University of Johannesburg)\nTh is study investigates the principle and capabilities of Dual Energy X-Ray Radiography/Tomography when applied on nuclear and related materials. The dual-energy X-ray technique is a significant improvement to X-ray imaging systems and gives additional information on the composition of the object being imaged. Within this technique\, two radiographs are obtained at two distinct X-ray energies and are combined (divided\, subtracted) to give de tailed information about the material features with improvement of the ima ge contrast. \nX-rays for this research\, will be generated with a new 225 kV microfocus X-ray system to be commissioned by June 2011 at the Nuclear Energy Cooperation of South Africa (Necsa). This system will be able to g enerate different peak energy X-rays at different anode target materials a t very small focal spot sizes in order to obtain high-resolution images. Different X-ray filters will be utilized to shape the energy of the X-ray beam for high energy X-rays to interact with the material.\nThis presentat ion focuses on the principles of X-ray generation with different anode mat erials and the utilization thereof in radiographs and tomograms.\n\nhttps: //events.saip.org.za/event/7/contributions/5080/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5080/ END:VEVENT BEGIN:VEVENT SUMMARY:Time-domain Terahertz Spectroscopy: Principles and applications DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5081@events.saip.org.za DESCRIPTION:Speakers: Pieter Neethling (Laser Research Institute\, Univers ity of Stellenbosch)\nTime-domain terahertz (TD-THz) spectroscopy has emer ged as a valuable tool for studying material properties in the THz region of the electromagnetic spectrum. Many classes of materials exhibit charac teristic absorption signatures in this previously unstudied portion of the electromagnetic spectrum. This opens up the possibility for non-destruc tive and non-invasive testing and analysis of materials which previously h ave proven difficult. Time domain T Hz spectroscopy entails measuring the electric field of the generated THz pulse in the time domain\, and extrac ting the spectral information from the pulse through a Fourier Transform. Two main mechanisms for generating short\, broadband THz pulses have emer ged namely optical rectification in a nonlinear crystal of a femtosecond l aser pulse and THz generation from a photo-conductive antenna (PCA). Rece ntly\, a photo-conductive antenna TD-THz setup has been established at the Laser Research Institute\, University of Stellenbosch. This presentation will focus on the basic principles of operation and on the layout of the setup as well as the possible applications envisaged using the setup.\n\nh ttps://events.saip.org.za/event/7/contributions/5081/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5081/ END:VEVENT BEGIN:VEVENT SUMMARY:Validation of a numerical simulation to study the decoherence of q uantum orbital angular momentum entanglement due to atmospheric turbulence DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5082@events.saip.org.za DESCRIPTION:Speakers: Alpha Hamadou Ibrahim (CSIR\, National Laser Center) \nThe orbital angular momentum (OAM) state of light has been the object of much interest within the quantum information community lately mainly beca use it can be used to implement higher dimensional entanglement. Unfortuna tely\, the OAM cannot be used for quantum communication through optical fi bers in use today because these fibers support only modes with zero OAM va lues. One can alternatively use free-space communication. However\, one ne eds to understand how atmospheric turbulence affects quantum entanglement. In recent years\, numerical simulation has become a very important and su ccessful approach for solving complex problems and to gain more insight in to scientific phenomena. In this work\, we present a numerical simulation to study the decoherence of quantum entanglement between a pair of qubits due to atmospheric turbulence. The qubits are photons entangled in their O AM mode. The photons propagate in a turbulent atmosphere modeled by a seri es of consecutive phase screens based on the Kolmogorov theory of turbulen ce and the concurrence is used as entanglement measure. We validate our si mulation scheme with the formula derived in "Nature Physics 4 99 - 102 (20 08)" stating that the entanglement reduction under a one-sided noisy chann el is independent of the initial state and completely determined by the ch annels action on a maximally entangled state.\n\nhttps://events.saip.org.z a/event/7/contributions/5082/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5082/ END:VEVENT BEGIN:VEVENT SUMMARY:Monitoring a grid-assist photovoltaic system DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5083@events.saip.org.za DESCRIPTION:Speakers: Warren Alistoun (NMMU)\nRecent developments in elect ricity regulatory environment and the possible inclusion of small\, kW-sca le\, photovoltaic (PV) systems in the feed-in tariff framework has led to an increased interest in these systems. In South Africa\, grid reliabilit y issues are not fully mitigated by employing a straight grid-tie PV syste m\, with users sometimes wanting some battery backup for load-shed periods at night. In this study a system comprising a PV array\, maximum power p oint tracker\, a battery bank and inverter was monitored using a custom-bu ild data acquisition system. The monitored parameters include\; environme ntal conditions\, DC and AC power\, and energy flow within the system. Th is paper will discuss the influence of environmental parameters and load r equirements on the performance of the system. Issues such as soiling and other loss mechanisms are also discussed.\n\nhttps://events.saip.org.za/ev ent/7/contributions/5083/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5083/ END:VEVENT BEGIN:VEVENT SUMMARY:Bilinear expansion of the photon quantum field and the emergence o f classical mechanics from quantum field theory DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5084@events.saip.org.za DESCRIPTION:Speakers: Jan Greben (CSIR)\nThe electro-magnetic field is exp anded in a bilinear series consisting of products of quark creation and an nihilation operators. This bilinear form is suggested by the equations of motion for the electromagnetic field and provides a very powerful quantum representation\, which is devoid of many of the technical problems associa ted with standard quantization. In this approach the energy of the physica l photon can be expressed as an expectation value of the energy-momentum t ensor. The direct term already yields the correct result\, so one has to e liminate the additional cross term to maintain this correct result. In ord er to affect this elimination one needs to introduce a continuous set of “hidden” quantum numbers\, which can be related to the classical posit ional coordinate of the particle. These “big bang variables” are intro duced as state labels\, just like the momentum variable. The quantum ampli tudes are insensitive to the choice of these coordinates\, so that the int roduction of classical coordinates does not conflict with standard quantum field theory calculations or with the Heisenberg uncertainty principle. H owever\, in a many-body system coherence make these coordinates emerge as the relative classical coordinates. Hence\, classical mechanics emerges na turally from many-body quantum field theory. Without violating quantum mec hanics\, particles can thus be specified in terms of momentum and position \, in clear analogy to classical physics and statistical mechanics. Compos ite particle systems are then identified by having identical classical coo rdinate labels\, while independent particles have distinct labels and are not subject to the Pauli principle in the remaining variables.\n\nhttps:// events.saip.org.za/event/7/contributions/5084/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5084/ END:VEVENT BEGIN:VEVENT SUMMARY:Daytime modeling of VLF radio waves over land and sea\, comparison to DEMETER satellite data. DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5085@events.saip.org.za DESCRIPTION:Speakers: Andrew Collier (Hermanus Magnetic Observatory)\nVery Low Frequency (VLF) radio waves travel with little attenuation in the Ear th-ionosphere waveguide. The waveguide propagation conditions are determi ned by a variety of factors including the surface of the Earth and the fre e electron density profile. Perturbations of the lower ionosphere modify the waveguide and the propagation conditions in it. A model based on Wait 's mode theory is developed and used to investigate the propagation of VLF radio waves under different conditions. As the VLF radio waves reflect o ff the lower ionosphere\, a portion of the energy leaks up into space\, le aving a 'fingerprint' of the modal interference pattern of the waveguide m odes. This idea is used to test the validity of the model by comparing si mulation results with satellite data from DEMETER taken over the NWC trans mitter in North-West Australia.\n\nhttps://events.saip.org.za/event/7/cont ributions/5085/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5085/ END:VEVENT BEGIN:VEVENT SUMMARY:Search for the Standard Model Higgs boson to WW with a hadronic ta u channel DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5122@events.saip.org.za DESCRIPTION:Speakers: Simon Connell (University of Johannesburg)\nIn the l arge mass region\, the dominant decay mode of the Higgs boson is to two W bosons\, where the Higgs can be produced via either gluon fusion or vector boson fusion. Of the possible W decay modes\, the current analyses focus on the W(->l nu)W(->l nu) decay channels where the lepton is either an ele ctron or muon. At a center of mass energy of 7 TeV\, the results from the ATLAS detector are combined for each of the three modes ee\, e mu\, or mu mu\, in order to maximise the signal sensitivity. We investigate the possi ble sensitivity gained in including a single hadronic tau channel (W->tau nu->(tau_had nu) nu) in this analysis\, and discuss the method in comparis on to the standard H->WW->l nu l nu search. Our work currently focuses on the hadronic tau identification and understanding the jet -> tau fake rate .\n\nhttps://events.saip.org.za/event/7/contributions/5122/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5122/ END:VEVENT BEGIN:VEVENT SUMMARY:Development of a laser cooling and magneto-optical trapping experi ment for Rubidium 87 atoms DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5086@events.saip.org.za DESCRIPTION:Speakers: Charles Rigby (Laser Research Institute\, Stellenbos ch University)\nA magneto optical trap (MOT) is capable of trapping a vapo r cloud consisting of atoms cooled down to the micro Kelvin range. Three o rthogonal pairs of counter-propagating laser beams of the correct circular polarisation form an optical molasses which facilitates the cooling of ne utral atoms. Additionally a spatially non-uniform\nmagnetic field produced by two current carrying coils in a Maxwell gradient configuration is used to trap the cooled atoms.\n\nIn this poster the effects of the trap param eters\, including the laser beam intensity and frequency detuning\, beam d iameter and magnetic field gradient\, on the number of trapped atoms are d iscussed. The nature of the beam polarisation and its importance in the co ntext of the experiment is measured and discussed.\n\nThe current status o f our development of an experimental setup for laser cooling and trapping of 87Rb atoms in vacuum with the aid of a MOT is presented.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5086/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5086/ END:VEVENT BEGIN:VEVENT SUMMARY:Eclipsing Contact Binary Stars – Period Analysis using SuperWASP data DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5088@events.saip.org.za DESCRIPTION:Speakers: Patricia Skelton (UNISA)\nSome eclipsing contact bin ary stars of the W UMa-type are known to undergo changes in orbital period . These changes can be as a result of the light travel time effect if the contact binary is a member of a multiple stellar system or due to some in trinsic phenomena that are poorly understood at this stage. Analysing sys tems that appear to be undergoing changes in orbital period may shed some light on the important physical processes that occur in close binary syste ms. Pilecki et al. (2007) searched through the All Sky Automated Survey ( ASAS) database for semi-detached and contact binary systems with high peri od change rates. They present 31 interacting binaries whose periods eithe r increased (10) or decreased (21) in a five year interval of observations . Using data from the Wide Angle Search for Planets (SuperWASP) project\, it has been possible to do period analyses using O – C diagrams which p rovide a more reliable measure of period change. The results of the analy ses will be presented.\n\nhttps://events.saip.org.za/event/7/contributions /5088/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5088/ END:VEVENT BEGIN:VEVENT SUMMARY:The unusual Seyfert Markarian 926 - a link to the LINERs? DTSTART;VALUE=DATE-TIME:20110715T103000Z DTEND;VALUE=DATE-TIME:20110715T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5090@events.saip.org.za DESCRIPTION:Speakers: Hartmut Winkler (Dept. Physics\, University of Johan nesburg)\nMarkarian 926 (= MCG-2-58-22) is one of the earliest Seyfert gal axies identified. At discovery it was one of the most luminous nearby acti ve galactic nuclei (AGN)\, with strong\, wide broad lines. In the late 198 0's it started fading\, eventually settling at barely ~10% of its recorded peak luminosity. The luminosity decrease was accompanied by significant s pectral changes\, with the broad-line component now much weaker and highly asymmetrical. Low ionisation narrow lines\, however\, are now unusually s trong\, more typical of the AGN class referred to as LINERs rather than a Seyfert. This peculiar low-luminosity phase spectum has remained relativel y constant over the last decade. The paper will discuss the spectral and o ther characteristics of Markarian 926 and compare these to standard Seyfer t models. It will furthermore investigate Markarian 926's relationship to the LINERs\, and whether SALT observations of this object could shed light on the interrelationship between Seyferts and LINERs.\n\nhttps://events.s aip.org.za/event/7/contributions/5090/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5090/ END:VEVENT BEGIN:VEVENT SUMMARY:Photometric solutions of eclipsing binary stars DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5091@events.saip.org.za DESCRIPTION:Speakers: Derck Smits (University of SA)\nKazarovets et al. (1 999) gave General Catalogue of Variable Star (GCVS) designations to 3157 v ariable stars that had been identified from observations made using the Hi pparcos satellite. The variables were classified into standard GCVS categ ories according to their photometric light curves\, but no other parameter s of the variables were documented. V-band photometric data for many of t he Hipparcos-identified eclipsing binaries can be found in the All Sky Aut omated Survey (ASAS) and Wide Angle Search for Planets (SuperWASP) databas es. In several cases the ASAS classifications\, which were done semi-auto matically and without cross referencing other databases\, differ from thos e presented in IBVS 4659. Using the ASAS and/or SuperWASP data\, the clas sifications are being checked\, orbital periods are being determined and\, where possible\, photometric solutions to the light curves are being obta ined. This talk will present the results of this investigation.\n\nhttps: //events.saip.org.za/event/7/contributions/5091/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5091/ END:VEVENT BEGIN:VEVENT SUMMARY:Ultraluminous X-ray Sources in Nearby Galaxies DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5130@events.saip.org.za DESCRIPTION:Speakers: Deatrick Foster (South African Astronomical Observat ory)\nFor many Galactic black hole binaries\, there exists kinematic data that constrain the black hole masses to be within the stellar-mass regime. However\, due to their extragalactic distances\, ultraluminous X-ray sour ces (ULXs) have no such available dynamical information. Hence\, in order to constrain the system parameters\, we must use indirect methods. We pres ent an analysis of recent observations which suggest that\, rather than be ing powered by intermediate-mass black holes\, ULXs may represent an extre me form of "conventional" stellar-mass black holes.\n\nhttps://events.saip .org.za/event/7/contributions/5130/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5130/ END:VEVENT BEGIN:VEVENT SUMMARY:Numerical modelling of stellar winds for supernova progenitors DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5092@events.saip.org.za DESCRIPTION:Speakers: Stefanus Petrus van den Heever (North West Universit y)\nA two-dimensional hydrodynamic numerical model is extended and applied to simulate the interaction between stellar winds and the interstellar me dium (ISM). In particular\, the stellar wind evolution of O-and B-type sta rs is calculated. First\, the evolution of a stellar wind into the ISM and also a more dense molecular cloud are considered for the case of no relat ive motion between the star and the ISM. This interaction results in a cav ity being blown into the ISM. Of importance is the boundary radius (astrop ause) and the location where the outflow speed decreases from supersonic t o subsonic speeds\, the termination shock. Parameters like ISM density\, o utflow speed and mass-loss rate were varied to study the difference in the computed astropause (AP) and termination shock (TS) radii. The evolution of these structures is presented to a simulation time of 1 My. The evoluti on of stellar winds into the ISM including relative motion is also conside red. It is shown that the positions of the TS and AP are dependent on the mass-loss rate and stellar wind outflow speed of the star and the interste llar medium density and relative speed. When these massive stars reach the end of their life\, they end their life in a supernova explosion. The exp losion results in a blast wave moving outward\, called the forward shock ( FS) and a reverse shock (RS) also forms which moves inward. Ferreira and d e Jager 2008 simulated supernova remnant (SNR) evolution for the case of e volution into the undisturbed ISM (no cavity). The evolution of SNR is sim ulated taking also into account the pre-existing cavity blown out by the s tellar winds of these massive stars. The results of this study showed that the evolution of the SNR is definitely influenced by the presence of a st ellar wind cavity even if the cavity is only a few pc in extent.\n\nhttps: //events.saip.org.za/event/7/contributions/5092/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5092/ END:VEVENT BEGIN:VEVENT SUMMARY:Enhancing the understanding of entropy through computation DTSTART;VALUE=DATE-TIME:20110715T090000Z DTEND;VALUE=DATE-TIME:20110715T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5093@events.saip.org.za DESCRIPTION:Speakers: Trisha Salagaram (University of Pretoria)\nWe devise a hierarchy of computational algorithms to enumerate the microstates of a system comprising N independent\, distinguishable particles. An important challenge is to cope with integers that increase exponentially with syste m size\, and which very quickly become too large to be addressed by the co mputer. A related problem is that the computational time for the most obvi ous brute-force method scales exponentially with the system size which mak es it difficult to study the system in the large N limit. Our methods addr ess these issues in a systematic and hierarchical manner. We apply our met hods to a simple model with single particle energy spectrum given by ε(p \, q) = ε0 (p2 + q 4 )\, where p and q are non-negative integers. However \, our methods are very general and applicable to a wide class of problems . Working within the microcanonical\nensemble\, our methods enable one to directly monitor the approach to the thermodynamic limit (N → ∞)\, and in so doing\, the equivalence with the canonical ensemble is made more ma nifest. Various thermodynamic quantities as a function of N may be compute d using our methods\; in this paper\, we focus on the entropy\, the chemic al potential and the temperature.\n\nhttps://events.saip.org.za/event/7/co ntributions/5093/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5093/ END:VEVENT BEGIN:VEVENT SUMMARY:Electrical and surface morphological studies of palladium and ruth enium Schottky diodes on n-Ge (100) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5094@events.saip.org.za DESCRIPTION:Speakers: Albert Chawanda (University of Pretoria)\nPalladium (Pd) and ruthenium (Ru) Schottky barrier diodes were fabricated on (100) S b-doped n-type germanium using resistive evaporation and electron beam dep osition systems\, respectively. Electrical characterization of these diode s using current-voltage (I-V) measurements was performed under various ann ealing conditions. The morphological evolution of the surface was analysed using the scanning electron microscopy. The variation of the electrical a nd structural properties of these Schottky diodes can be attributed to com bined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of both the Pd/n-Ge (100) and Ru/n-Ge (100) Schottky diodes is maintained up to annealing temperature of 550°C . Results have also indicated that the onset temperature for agglomeration in Pd/n-Ge (100) system occurs between 500 – 600°C\, and in Ru/n-Ge (1 00) system occurs between 600 – 700°C.\n\nhttps://events.saip.org.za/ev ent/7/contributions/5094/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5094/ END:VEVENT BEGIN:VEVENT SUMMARY:Monte Carlo Simulations of Magnetite Nanoparticles Stabilised With Sebaccic Acid and 1\, 10-Decanediol Surfactants DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5095@events.saip.org.za DESCRIPTION:Speakers: Richard Harris (Mintek)\nIron oxide-based nanomagnet s\, such as maghemite (Fe2O3) and magnetite (Fe3O4)\, have attracted a gre at deal of attention in nanomedicine over the past decade. On the nanosc ale\, superparamagnetic iron oxide nanoparticles can only be magnetized in the presence of an external magnetic field. This property makes these na noparticles capable of forming stable colloids in a physio-biological medi um. Their superparamagnetic property\, together with other intrinsic prope rties\, such as low cytotoxicity\, colloidal stability and bioactive-conju gation\, makes such nanomagnets ideal for both in vitro and in vivo biomed ical applications.\nSeveral methods for the synthesis of iron oxide nanopa rticles have been developed. The most common ones for contrast agent synt hesis are based on the precipitation of magnetite nanoparticles from solut ions containing stabilizing agents such as synthetic or natural polymers\; or adsorption of stabilizing agents on the magnetite particle surface aft er synthesis. The first method often leads to the formation of multicore particles\, while the second one demands coating stabilisation by cross-li nking\, that can lead to particle aggregation. For this reason the stabil ising properties of two surfactants\, sebaccic acid (with carboxylic acid groups on the peripheries) and 1\, 10-decanediol (with hydroxyl groups on the peripheries)\, were investigated and compared theoretically. DFT adso rbance simulations were run and the average total energies of the two liga nds adsorbed onto the magnetite nanoparticles were compared. XRD measurem ents also revealed a change in crystal structure for the Fe3O4 nanoparticl es when stabilised with the different ligands.\n\nhttps://events.saip.org. za/event/7/contributions/5095/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5095/ END:VEVENT BEGIN:VEVENT SUMMARY:Reversible Semiconductor – Metal Transition study in nano-FePt s ystem DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5096@events.saip.org.za DESCRIPTION:Speakers: Steven Nkosi (CSIR and University of the Witwatersra nd)\nHighly crystalline nano-spherical Fe-Pt systems were produced by 248 nm laser irradiation of liquid precursor at different laser fluence rangin g from 100 – 375 mJ/cm2. The influence of laser intensity on the particl e size\, iron composition and vibrational properties was systematically in vestigated. The study reveals that the larger particles have higher iron c ontent. The prepared precursor solution through Fe (III) acetyacetonate an d Pt (II) acetyacetonate underwent a deep photolysis to polycrystalline of nano Fe-Pt alloys. Fe (II) and Pt (I) acetyacetone decompose into Fe0 and Pt0 nanoparticles (NPs). The material is shown to contain only iron and p latinum by EDS. We have observed hysteretic loop in structural phase trans ition of Fe60Pt40 NPs. The material shows high resistance (~2\,700 Ohms) a t lower temperatures and low resistance (~2\,200 Ohms) at higher temperatu res. Pan theory was used to exemplify the phase transition.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5096/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5096/ END:VEVENT BEGIN:VEVENT SUMMARY:Active Learning in the Third Year Statistical Physics Course at th e University of the Witwatersrand DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5097@events.saip.org.za DESCRIPTION:Speakers: Jonathan Keartland (University of the Witwatersrand) \nActive learning techniques were used for the first time in the Statistic al Physics module presented to third year students at the University of th e Witwatersrand in the first semester of 2009. The reaction of the studen ts\, recorded in a formal Student Assessment of Lecturer Performance\, adm inistered by the Centre for Teaching and Learning Development at the Unive rsity\, was overwhelmingly positive. In addition\, the final results of t he students were excellent. This paper reports on the methods employed\, the results of the student survey and the course results. These results a re compared with the results of the same group of students in the second y ear Thermal Physics module\, taught by the same lecturer using more tradit ional methods of instruction\, during the second semester of 2008. The em ployment of innovative teaching strategies makes a significant difference to the confidence and attitude of the students\, and an increase in the le vel of performance of the majority of students is apparent. Active learni ng is now the standard method of instruction in both the second and third year Thermal and Statistical Physics courses\, and details of the material s developed over the last three years will be provided.\n\nhttps://events. saip.org.za/event/7/contributions/5097/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5097/ END:VEVENT BEGIN:VEVENT SUMMARY:Characterization of nitrogen-doped carbon nanospheres using electr on magnetic resonance DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5098@events.saip.org.za DESCRIPTION:Speakers: Jonathan Keartland (University of the Witwatersrand) \nCarbon nanospheres were produced using two different sets of apparatus i n the School of Chemistry at the University of the Witwatersrand. Nitroge n was introduced into the samples using a several sources of nitrogen\, in cluding pyridine. Electron magnetic resonance (EMR) was used to character ize a range of samples of varying concentrations of nitrogen at room tempe rature. The spheres doped with nitrogen show a strong paramagnetic peak a t g = 2\, indicating that the nitrogen takes up substitutional sites in th e carbon matrix. Careful analysis enables us to determine the nitrogen co ntent in each of the samples by integration of the resonance peak\, and no rmalising to the mass of the sample. Comparison with a reference sample a llows us the extract the g for each sample. Power saturation experiments show the the relaxation rates of the nitrogen ions are large in all the sa mples studied.\n\nhttps://events.saip.org.za/event/7/contributions/5098/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5098/ END:VEVENT BEGIN:VEVENT SUMMARY:Instructional Design Principles applied to Physics laboratory and tutorial courses DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5099@events.saip.org.za DESCRIPTION:Speakers: Deena Naidoo (School of Physics\, University of the Witwatersrand)\nThis study examines the effect on the learning experiences of students of changes to the running of laboratory and tutorial sessions of the first year auxiliary physics course at the University of the Witwa tersrand\, between 2001 and 2010. This research is underpinned by the prin ciples of indirect interactive instructional skills and experiential learn ing. Two concerns drove this study: the first being a mismatch between the marks awarded to students for their laboratory reports\, and their subseq uent performance in formal practical tests. The second was the students’ poor engagement – and hence performance in problem solving - during tut orial sessions. Several possible contributing factors were identified and changes were implemented in an attempt to improve the learning experience d by the students. Three sources of data suggest that the changes have had a positive effect on the learning of physics by the students in this cour se.\n\nhttps://events.saip.org.za/event/7/contributions/5099/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5099/ END:VEVENT BEGIN:VEVENT SUMMARY:Brightest Cluster Galaxies - Ages and metallicities of stellar pop ulations DTSTART;VALUE=DATE-TIME:20110714T103000Z DTEND;VALUE=DATE-TIME:20110714T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5100@events.saip.org.za DESCRIPTION:Speakers: Viljoen Danièl (North-West University)\nThe aim of this project is to study the stellar populations\, and thereby evolution a nd star formation histories of brightest cluster galaxies (BCGs). In parti cular\, I will determine if a Single Stellar Populations (SSP) or Composit e Stellar Populations (CSP) provides the most significant fit for the BCGs using high signal-to-noise ratio (S/N)\, long-slit spectra\, obtained on the Gemini and WHT telescopes. By using the ULySS software package\, the d ata will be fitted against the Pegase. HR and Vazdekis/Miles stellar popul ation models to simultaneously derive the SSP equivalent ages and metallic ities of the BCGs. Furthermore the stellar populations will be decomposed into two or more components\, and the chi square (χ2) value for each comp onent is used to determine whether a SSP or CSP represents the BCGs most a ccurately. We find that both young and old stars are present in the stella r populations of these BCGs\, and those BCGs\, therefore show surprisingly diverse star formation histories.\n\nhttps://events.saip.org.za/event/7/c ontributions/5100/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5100/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermoluminescence Study of Long Persistent CaAl2O4:Eu2+\, Nd3+ and/or Dy3+. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5101@events.saip.org.za DESCRIPTION:Speakers: Ali Wako (University Of The Free State\, QwaQwa Camp us.)\nIt is evident that the Eu2+ ion acts as a luminescent centre emittin g in the blue (λmax ~ 440 nm) spectral region for CaAl2O4:Eu2+. The R3+ i on is believed to act as a trap or somehow modify the trap properties in t hese phosphors. Despite a large number of research on the phenomenon the m echanism of the persistent luminescence of the CaAl2O4:Eu2+\,R3+ material s has not been well presented. The theories that have so far been put forw ard are generally contradictory therefore much less agreement exists on th e role of the R3+ co-dopant.\n New emerging applications for the long phos phorescent materials such as radiation detection and sensors for structura l damage\, fracture of materials and temperature\, require the exact lumin escence mechanisms and the identification of the trap levels/locations. An alysis of the thermoluminescence (TL) glow curves is one of the most signi ficant ways to measure the number and also the activation energy of the tr apping levels in these materials. \nIn the present study the TL properties of the Eu2+\, R3+ doped CaAl2O4:Eu2+\, Nd3+/Dy3+ were investigated above room temperature. The trap depths were estimated with the aid of the peak shape method. The glow curve of CaAl2O4:Eu2+ with a first peak at 50 °C w as found to correspond to several traps. The Nd3+ and Dy3+ ions were obser ved to greatly enhance the intensity of the high-temperature TL peaks and also form most of the traps suitable for intense and long-lasting persiste nt luminescence. The trap- depths and the R3+ or R2+ level positions did n ot exhibit any well defined relationship. The traps may thus involve more complex mechanisms than the simple charge transfer to (or from) the R3+ io ns.\n\nhttps://events.saip.org.za/event/7/contributions/5101/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5101/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and Labelling of DISIDA (N-2\,6-diisopropyl-phenylcarbam oylmethyliminodicetic) acid DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5108@events.saip.org.za DESCRIPTION:Speakers: KWETANA MUSA LONWABO (UNIVERSITY OF PRETORIA)\nRadio pharmaceuticals is compounds labelled with a radioactive isotope that are used for studying different organs in the human body. Technetium-99m (99mT c) labelled iminodiacetic acid (IDA) derivatives are commonly used as hepa tobiliary imaging agents.\n\nRadiopharmaceuticals used for hepatobiliary i maging are divided into two groups based on the physiologic function of th e liver they are designed to evaluate.The IDA agent of choice for NTP is D ISIDA (N-2\,6-diisopropyl-phenylcarbamoylmethyliminodicetic acid).A cold k it is a pre prepared vial consisting of the compound to be labelled with t he radioactive isotope and a suitable reducing agent. The radioactive isot ope of choice for IDA labelling is 99mTc.\n\nKits for DISIDA is commercial ly available and usually contain the IDA derivative and stannous chloride dihydrate as the reducing agent. Twenty gram DISIDA is needed for each pro duction batch of DISIDA kits \nLabelling is accomplished by adding 99mTcO4 - to the kit and mixing well.\n\nApproximately 3 to 5 mCi (111-185 MBq) 99 mTc-IDA derivative is injected intravenously into patients who have fasted for 4 to 6 hours prior to administration. The biodistribution DISIDA was confirmed by performing a biodistribution study on a Chacma baboon.The yie ld of the DISIDA synthesis was improved from 26 - 34 g to 76 g (53%).The l abelling with technetium give > 95% radiochemical purity.The improved synt hesis resulted in increased cost effectiveness of the commercial DISIDA ki ts.\n\nhttps://events.saip.org.za/event/7/contributions/5108/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5108/ END:VEVENT BEGIN:VEVENT SUMMARY:Red emission of Pr3+ enhancement by addition of Ba2+ and In3+ in C aTiO3:Pr phosphor DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5102@events.saip.org.za DESCRIPTION:Speakers: Luyanda Lunga Noto (University of Free State (Studen t))\nCaTiO3 exhibits a Perovskite structures that has an ABO3 stochiometr y where A and B represent metal cations with a combined charge of 6+ valen cy and O with 6- valency\, and thus bring about charge neutrality to the c ompound. Upon introducing Pr3+ ions in the site of Ca2+ ions\, charge imb alance occurs by introducing a 7+ valency\, and this force the material to compensate for this effect by introducing negative Ca & Ti vacancies\, an d positive O vacancies. These act by hampering the material luminescence. Thus substitution of Ti4+ by co-doping with Ba2+ and In3+ ions result into a 6+ valency and thus an electrically neutral compound. This reinforces t he red emission of Pr3+ ions inside CaTiO3. CaTiO3: Pr3+ exhibiting red em ission is synthesized via solid state reaction\, and its luminescence is e nhanced by co-doping with Ba2+ and In3+ that act as charge compensators. T his optimal emission of CaTiO3:Pr3+\,Ba2+\,In2+ is achieved by solid state reaction at 1300 oC for 4h\, by direct firing\, according to 1:1 molar ra tio of TiO2 Anatase and CaCO3 compounds\, doping with 0.3 mol%Pr3+ (PrCl3) and charge compensating by adding In3+ (In(NO3)3) and Ba2+ (Ba(NO3)2).The observed 613 nm photoluminescence (PL) peak\, when exciting the material with 330 nm ultraviolet light to promote (2p(O) → 3d (Ti)) absorption us ing the PL spectrometer\, is attributed to the 1D2 → 3H4 transition of t he Pr3+ ions. The glow curves were measured using Thermo luminescence (TL) spectroscopy. Addition of Ba2+ and In3+ ions into CaTiO3:Pr3+ phosphor en hances the optical performance of the Pr3+ red-emission. Additionally the phase was identified using the X-ray diffraction (XRD) and the surface mor phology identified using Scanning Electron Microscopy (SEM).\n\nhttps://ev ents.saip.org.za/event/7/contributions/5102/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5102/ END:VEVENT BEGIN:VEVENT SUMMARY:Measuring the effect of surface evaporation on the segregation pro cess DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5103@events.saip.org.za DESCRIPTION:Speakers: S Cronje (UFS)\nMetallurgical products play an impor tant role in everyday life. The search for alloys with better material pro perties such as strength\, wear and corrosion resistance continues to this day. In addition to these desirable properties\, the search for ways to r educe production costs and time has led to a large amount of research bein g conducted on the processes which determines the material properties of m etals and alloys. One of these processes is known as segregation. To impro ve segregation studies the influence of surface evaporation should be cons idered. As experimental segregation studies are performed under high vacuu m conditions\, certain elements are prone to this neglected phenomenon. Al though some attempts have been made to develop segregations models that ta ke surface evaporation into account\, these models can only predict segreg ation in either the kinetic region or when equilibrium has been reached. I n addition the effect of evaporation has received little attention in prev ious experimental studies. In this study surface evaporation during segreg ation of a Sb/Cu system was measured. These results together with the modi fied Darken model will be used to simultaneously predict kinetic and equil ibrium segregation including the effects of surface evaporation. A first a pproximation will be discussed as well as modifications made to an Auger s ystem in order to measure the actual surface evaporation that takes place during segregation.\n\nhttps://events.saip.org.za/event/7/contributions/51 03/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5103/ END:VEVENT BEGIN:VEVENT SUMMARY:Parametric Resonance Features in the Coupled Josephson Junctions DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5104@events.saip.org.za DESCRIPTION:Speakers: Yury Shukrinov (BLTP\, JINR\, Dubna)\nA review of ou r last results on the phase dynamics of a stack of coupled Josephson junct ions in layered superconductors is presented. The current voltage characte ristics (CVC) of intrinsic Josephson junctions (IJJ) are numerically calcu lated in capacitively coupled Josephson junction model (CCJJ model) and C CJJ model with diffusion current (CCJJ+DC model). We discuss the features of the parametric resonance and its manifestation in the breakpoint region of CVC. We demonstrate the fine structure in CVC and investigate it by c harge-charge and current-current correlation functions. The ideas concerni ng the experimental observation of the breakpoint features are considered. Charge creation in superconducting layers and nucleation of longitudinal plasma wave (LPW) for stacks with different number of junctions are predic ted. Time dependence of the charge oscillations in the superconducting lay ers is analyzed at different values of bias current. We demonstrate the di fferent time stages in the development of the LPW and present the results of FFT analysis at different values of bias current. The effects of noise in the bias current and the external microwave radiation on the charge dyn amics of the coupled Josephson junctions are found. These effects introduc e a way to regulate the process of LPW nucleation in the stack of IJJ.\n A role of diffusion current in the hysteretic behavior of coupled Josephson junctions is discussed. The superconducting\, quasiparticle\, diffusion\, and displacement currents have been calculated as functions of the total current through the system. The role of the diffusion current in the forma tion of the CVC curves has been studied and its influence on the CVC curve branching and the magnitude of the return current has been revealed. The calculation results agree qualitatively with the experimental data.\n\nhtt ps://events.saip.org.za/event/7/contributions/5104/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5104/ END:VEVENT BEGIN:VEVENT SUMMARY:International Astronomical Union Global Office of Astronomy for De velopment DTSTART;VALUE=DATE-TIME:20110715T091500Z DTEND;VALUE=DATE-TIME:20110715T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5105@events.saip.org.za DESCRIPTION:Speakers: Kevindran Govender (IAU Office of Astronomy for Deve lopment)\nThe International Astronomical Union (IAU)\, in recognition of t he immense use of astronomy to stimulate development\, has developed a dec adal strategic plan entitled "Astronomy for the Developing World". At the heart of the implementation of this plan is the Global Office of Astronomy for Development. South Africa bid in 2010 to host this office and was sel ected as the host country\, with the South African Astronomical Observator y\, a facility of the National Research Foundation\, being selected as the host organisation. With stong support from the Department of Science and Technology and the IAU\, the Office began its work on 1st March 2011. The history and implications of this Office will be discussed\, as well as its implementation plan moving into the future.\n\nhttps://events.saip.org.za /event/7/contributions/5105/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5105/ END:VEVENT BEGIN:VEVENT SUMMARY:Structured Light DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5106@events.saip.org.za DESCRIPTION:Speakers: Andrew Forbes (CSIR)\nWith modern liquid crystal dev ices it is possible to implement digital holograms for the modulation in a mplitude and phase of light: so called 'structured light'. In this non-sp ecialist talk\, we will introduce the concept of complex amplitude modulat ion\, and show how light can be tailored to have interesting properties: d efying diffraction\, twisted like a spring in intensity and phase\, and ma de to bend around corners! The ability to create arbitrarily complex fiel ds opens up a plethora of applications\, from controlling the micro-world through optical traps\, to probing the quantum world with twisted light.\n \nhttps://events.saip.org.za/event/7/contributions/5106/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5106/ END:VEVENT BEGIN:VEVENT SUMMARY:Direct water cooling effect on a photovoltaic module DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5107@events.saip.org.za DESCRIPTION:Speakers: Busiso Mtunzi (Fort Hare Institute of Technology\, U niversity of Fort Hare\, Physics Department)\nThis paper gives the details of a photovoltaic water heating system and the effects of direct water co oling on the performance of a photovoltaic module. The SW 80 polcrystallin e modules were used in the investigation. They wehre both fixed next toe a ch other on a north facing rack located on roof top. One of the modules h ad a batch water cooling container and the other module had no cooling sys tem attached to it. The water cooled module wer noted to operate at an ave rage temperature of 43°C on a sunny cloudless day\, while the uncooled mo dule's temperature rose to about 70°C impacting negatively on electricity production.Photovoltaic water heating system may improve life span of the module and at the same time alleviate the burden of conventional energy c onsumption in South Africa for heating and lighting purposes.\n\nhttps://e vents.saip.org.za/event/7/contributions/5107/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5107/ END:VEVENT BEGIN:VEVENT SUMMARY:Variability of methanol maser in the massive star formation region s DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5109@events.saip.org.za DESCRIPTION:Speakers: jabulani Paul maswanganye (Wits University/HartRAO)\ nStar formation constitutes one of the basic problems of astrophysics due to the fact that stars are fundamental objects of astronomy. Shu et al. (1 987) reviews the theory of low mass star formation from the molecular clou d via accretion disk-outflow. The formation of high mass stars is still no t well understood. They may also be formed through accretion disk plus out flow (Shu et al. 1987) or by collision-coalescence which was proposed by Wolfire \\& Cassinelli (1987) and Bonnell et al. (1998)\, but most observ ations support the accretion disk-outflow model.\nThe brightest methanol m asers occur at 6668 MHz and 12178 MHz and are found in the star forming r egions containing very young massive protostars even before the formation of an ultracompact HII region (Longmore et al. 2007). These masers serve as useful tools to study these regions.\nThe poster will be on the analys is of the time series of 6668 MHz and 12178 MHz methanol maser emission li nes in some of the sources which were showing periodic variations in monit oring before the 26 meter Hartebeesthoek Radio Astronomy Observatory (Hart RAO) Telescope bearing failure in 2008. After the telescope was repaired i n 2010\, the programme to monitor these sources was restarted. These two m ethanol emission lines are radiatively pumped which implies that their var iability could be due to the decrease or increase in the seed photons at t he radio frequency\, or the infrared radiation field that pumps the masers . Since there has been a two year gap in the monitoring program of these s ources\, we want to establish whether the periodic variations continue. Su ch periodic behaviour has not been seen in other maser species in star f orming regions\, so it can provide new insights into what is happening in these regions.\n\nhttps://events.saip.org.za/event/7/contributions/5109/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5109/ END:VEVENT BEGIN:VEVENT SUMMARY:Observations of the 22GHz Water maser in the source Orion KL DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5110@events.saip.org.za DESCRIPTION:Speakers: Sunelle Otto (HartRAO)\nStars are believed to be for med from massive stable gas clouds\, which under enough perturbation will collapse to form a protostar. The protostar evolves to form a star by accr eting matter until the fusion is initiated in the dense core. Surrounding these protostars are ionized hydrogen (HII) regions and molecule species w here masing occurs. MASER is an acronym for Microwave Amplification by Sti mulated Emission of Radiation. It is here that Water masers are also found . Amongst the sources of water masers\, is the Orion KL source region. Fl ares in this region from the 1.35cm water maser emission line occurred in 1984\, with the second flare in 1998 and again this year (2011) there have been reports of the flare. The flare is very intense\, increasing its fl ux density from around hundreds to millions of janskies. This poster will show the summary of observations made by the Hartebeesthoek Radio Astronom y Observatory (HartRAO) telescope for the water maser in the Orion KL sour ce region as well as the calibration method. Jupiter is used as the calibr ator source\, while the absorption by atmospheric water vapour must also b e allowed for. This uses estimates based on atmospheric temperature and hu mdity or can also be based on the time delay of GPS signals\, corrected fo r barometric pressure.\n\nhttps://events.saip.org.za/event/7/contributions /5110/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5110/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray crystallographic studies and quantum mechanical modeling of the amidase reaction mechanism DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5111@events.saip.org.za DESCRIPTION:Speakers: Bryan Trevor Sewell (University of Cape Town)\nThe a midases catalyse the conversion of amides to the corresponding carboxylic acid and ammonia. We have visualized the structure of the amidase (MW= 30 kDa) from a bacterium\, Nesterenkonia sp. at atomic resolution by X-ray c rystallography. The primary components of the active site are two negative ly charged carboxylates (E1 and E2) arising from two conserved glutamate s ide chains\, a positively charged amino group (K) arising from a conserved lysine\, a sulphydryl arising from a conserved cysteine and a water molec ule. Mutation of the active site residues has enabled us to visualize the unreacted substrate and a number of artificial intermediate states which h ave led to our insights. We propose a reaction mechanism which passes thro ugh a thioester adduct to the cysteine. Although this in itself is not co ntroversial\, our studies demonstrate for the first time how exquisitely a ccurate geometrical placement of the various groups leads to accurate ster eoelectronic alignment which allows the transition states to form. The con figuration of E1\, E2 and K ensures that K remains positively charged thro ughout the reaction thus enabling it to act as an acid catalyst and provid e an oxyanion hole to stabilize the tetrahedral transition states. The con figuration also accurately positions the substrate for nucleophilic attack by the sulphydryl by hydrogen bonding to the amide\, positions E1 as a b ase catalyst and positions the water with the correct stereoelectronic ali gnment for a nucleophilic attack on the thioester. The transition state en ergies\, electron densities and hydrogen placements calculated using Gauss ian09 demonstrate the plausibility of our proposal.\n\nhttps://events.saip .org.za/event/7/contributions/5111/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5111/ END:VEVENT BEGIN:VEVENT SUMMARY:Three-dimensional electron microscopy and molecular modelling stud ies of a spiral-forming biocatalyst DTSTART;VALUE=DATE-TIME:20110714T103000Z DTEND;VALUE=DATE-TIME:20110714T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5112@events.saip.org.za DESCRIPTION:Speakers: Jean Watermeyer (University of Cape Town)\nNitrilase and amidase enzymes catalyse the conversion of nitriles and amides to the ir corresponding acid and ammonia - chemistry which is useful in synthesis of drug compounds and fine chemicals. The conversion of cyanide\, a nitr ile\, to ammonia and formic acid is useful in detoxification of contaminat ed wastewater. The cyanide dihydratase from Bacillus pumilus (CynDpum) ca talyses this reaction and is thus a potentially useful biocatalyst. CynDp um and related nitrilase enzymes become activated by formation of spiral-s haped multimers. Evidence suggests that multimer formation regulates acti vity\, by mechanisms which are still not clear. We have used a combinatio n of transmission electron microscopy (EM) with 3-D image reconstruction\, molecular modelling\, and mutagenesis to investigate the mechanism of hel ix formation in CynDpum. We have implemented a new routine in the molecul ar dynamics package\, NAMD\, that allows helical symmetry to be used as a constraint\, together with the EM volume. This method improves on asymmet rical modelling procedures and has aided in our atomic-level interpretatio n of low-resolution 3-D maps from negative-stain EM. This in turn has all owed us to make testable predictions about the importance of specific amin o acids for the mechanical stability of the spirals. We show that salt br idges in one interface are not required for complex formation\, but that m utations in this area can enhance the mechanical stability of the enzyme.\ n\nhttps://events.saip.org.za/event/7/contributions/5112/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5112/ END:VEVENT BEGIN:VEVENT SUMMARY:Structure of Few-Hyperon Systems Studied with the Integro-Differen tial Equations Approach DTSTART;VALUE=DATE-TIME:20110713T131500Z DTEND;VALUE=DATE-TIME:20110713T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5121@events.saip.org.za DESCRIPTION:Speakers: John S. Nkuna (University of South Africa)\nGround-s tate properties of three-nucleon systems consisting of one \nand two hyper ons are studied with the integro-differential equations approach. The Hami ltonian of the systems is constructed with semi-realistic nucleon-nucleon interactions and phenomenological nucleon-hyperon interactions. The result s obtained for the ground-state energies and root-mean-square radii are co mpared with the findings of other theoretical methods.\n\nhttps://events.s aip.org.za/event/7/contributions/5121/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5121/ END:VEVENT BEGIN:VEVENT SUMMARY:The reduction of melting temperature with size in Gold DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5113@events.saip.org.za DESCRIPTION:Speakers: Mokete Mahladisa (University of Limpopo (Turfloop ca mpus))\n\nThe importance of gold for scientific use is of fundamental impo rtance to research and technology developments. The bulk gold shows reluct ance to participate in chemical reactions\, the effect which has been corr ected by the change in the size towards nanoclusters and\, this makes the study of temperature effects on gold very important. We have performed mol ecular dynamics simulations on bulk and nanomaterials of gold at various t emperatures to study the effect of size on the melting temperature. Meltin g temperature of bulk gold was determined to be 1320 K and this in good ag reement with the experimental value of 1337 K. Different gold nanoclusters and nanotubes melt at temperatures lower than 1200 K which is a significa nt decrease in the melting temperature from the bulk. The face centered cu bic (fcc) bulk gold structure remains intact at high temperatures while sp herical nanoclusters and cylindrical nanotubes respectively transform into tetragonal structures and patches of spherical clusters.\n\nhttps://event s.saip.org.za/event/7/contributions/5113/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5113/ END:VEVENT BEGIN:VEVENT SUMMARY:Space Weather Prediction and Forecast in South Africa DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5114@events.saip.org.za DESCRIPTION:Speakers: Mpho Tshisaphungo (SANSA Space Science)\nSpace weath er describes the conditions in space that affect both Earth- and Space bou nd technological and biological systems. It is a consequence of the behavi or of the Sun\, the nature of the Earth’s magnetic field and atmosphere\ , and our location in the solar system. Space weather is one of the princi pal threats to modern technology. With the increase in technological syste ms the need for accurate space weather predictions and forecasts has incre ased. The paper presents the space weather predictions and forecasts done by African Space Weather Centre at the Hermanus Magnetic Observatory (HMO) . The African Space Weather Centre has been appointed by ISES (Internation al Space Environment Service) as the Regional Warning Center (RWC) for Afr ica.\n\nhttps://events.saip.org.za/event/7/contributions/5114/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5114/ END:VEVENT BEGIN:VEVENT SUMMARY:Electromagnetic Form Factors of Three-Nucleon Systems DTSTART;VALUE=DATE-TIME:20110714T103000Z DTEND;VALUE=DATE-TIME:20110714T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5115@events.saip.org.za DESCRIPTION:Speakers: Gaotsiwe Joel Rampho (University of South Africa)\nT he angular-momentum-projected and parity-projected \nantisymmetrized molec ular dynamics is used to analyse the charge and magnetic form factors of t he three-nucleon systems. Non-relativistic nuclear charge and current oper ators with relativistic corrections are employed. The Hamiltonian of the n uclear systems is described with a semi-realistic nucleon-nucleon potentia l. The results obtained are compared with results obtained using other the oretical methods as well as some experimental data.\n\nhttps://events.saip .org.za/event/7/contributions/5115/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5115/ END:VEVENT BEGIN:VEVENT SUMMARY:Structure of Few-Nucleon Systems Studied with the Extended Antisym metrized Molecular Dynamics DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5116@events.saip.org.za DESCRIPTION:Speakers: Gaotsiwe Joel Rampho (University of South Africa)\nG round-state properties of three-nucleon and four-nucleon systems \nare stu died with the angular-momentum-projected and parity-projected antisymmetri zed molecular dynamics. The Hamiltonian of the systems is constructed with semi-realistic nucleon-nucleon interactions. The results obtained for the ground-state energies\, root-mean-square radii and magnetic dipole moment s are compared with the findings of other theoretical methods.\n\nhttps:// events.saip.org.za/event/7/contributions/5116/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5116/ END:VEVENT BEGIN:VEVENT SUMMARY:Intervalley and Intravalley Scattering in Diamond Structure\, Si a nd Ge DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5117@events.saip.org.za DESCRIPTION:Speakers: Augusto Machatine (University of Pretoria)\nOptical selection rules for the intervalley scattering for direct and indirect tra nsitions are investigated. The non-zero matrix elements of the scattering tensors are derived by the method of vector coupling coefficients. These c oefficients are needed for the understanding of Gunn effect.\n\nhttps://ev ents.saip.org.za/event/7/contributions/5117/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5117/ END:VEVENT BEGIN:VEVENT SUMMARY:Superresolution beams DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5118@events.saip.org.za DESCRIPTION:Speakers: Sandile Ngcobo (CSIR)\nThe transformation of a Gauss ian beam into a symmetrical TEMp0 Laguerre Gaussian beam (LGB) intensity d istribution which has transverse superresolution properties is very useful in improving the spatial resolution of optical imaging microscopes by mak ing the central diffractive spot smaller than the Airy spot. The beam shap ing is achieved by using an annular binary Diffractive Optical Element (DO E) whose geometry is in connection with the location of the Laguerre polyn omial zeros. The DOE imposes positions of p zeros of intensity distributio ns on the Gaussian beam\, resulting to a generation of TEMp0 beams where t here are minimum losses. \n\nThe LGBs are well-known family of exact orth ogonal solutions of free-space paraxial wave equation in cylindrical coord inates. Theoretical and experimental results will be demonstration for hig her order TEMp0 modes of LGBs.\n\nhttps://events.saip.org.za/event/7/contr ibutions/5118/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5118/ END:VEVENT BEGIN:VEVENT SUMMARY:Black-Hole Decay and Detection at LHC DTSTART;VALUE=DATE-TIME:20110714T060000Z DTEND;VALUE=DATE-TIME:20110714T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5120@events.saip.org.za DESCRIPTION:Speakers: Warren Carlson (University of the Witwatersrand)\nMo dels with extra spacial dimensions offer a new way to address outstanding problems in and beyond the standard model. In such models the Planck scal e in the bulk can be of the order of the electro-weak symmetry breaking sc ale. This allows the coupling strength of gravity to increase to a size si milar to the other interactions\, opening the way to the unification of gr avity and the gauge interactions. The increased strength of gravity in the bulk space-time means quantum gravity effects would be observable in the TeV energy range - an energy range now attainable in modern particle colli ders. If the Planck scale is low enough\, black-holes could form during co llisions at particle colliders. These black-holes will emit radiation\, l osing mass\, energy\, momentum\, etc. This radiation should be detectable making it\, possible to "see" black-holes in particle colliders.\n\nhttps ://events.saip.org.za/event/7/contributions/5120/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5120/ END:VEVENT BEGIN:VEVENT SUMMARY:Simulating chorus generation via Particle-in-cell simulations DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5123@events.saip.org.za DESCRIPTION:Speakers: Marlie van Zyl (University of KwaZulu Natal)\nChorus emissions are whistler mode waves propagating through the Earth’s magne tosphere in two distinct frequency bands\, typically in the range of 0.1-0 .8 fce\, where fce is the equatorial electron gyro-frequency. Chorus consi sts of discrete elements\, which are normally rising tones\, each of which lasts for a few tenths of a second. Chorus is predominantly observed duri ng the onset of the substorm expansion phase when energetic electrons are injected into the magnetosphere. As these electrons drift eastward around towards noon\, their distribution becomes unstable to the amplifiation of whistler mode waves. It is thought that the amplification process proceeds via the Doppler-shifted cyclotron resonance interaction. Particle-in-cell (PIC) simulations\, which simulate the motion of groups of similar partic les on a two dimensional grid subject to the self-consistent electric and magnetic fields generated by their spatial distribution and motion\, are u sed to simulate the amplification of whistler-mode waves propagating along the magnetic field. A population of electrons having a velocity distribut ion with a thermal anisotropy is injected into the plasma and the growth o f the resulting waves is investigated.\n\nhttps://events.saip.org.za/event /7/contributions/5123/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5123/ END:VEVENT BEGIN:VEVENT SUMMARY:Digital control of a pulsed Ho:YLF ring laser DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5124@events.saip.org.za DESCRIPTION:Speakers: Cobus Jacobs (CSIR National Laser Centre)\nWe have p reviously demonstrated a novel laser pulse energy control system based on two analog controllers to control a Q-switched Nd:YLF laser. We now presen t the improved technique based on a custom-designed high-speed FPGA (field programmable gate array) digital logic controller\, together with experim ental results from controlling a high-energy Ho:YLF ring laser. \n\nLaser pulses of constant and predictable energies are required in most applicati ons\, especially materials processing\, micro-machining and medical laser surgery. Furthermore\, for these applications the time between individual laser pulses may be purposely varied\, which result in significant pulse-t o-pulse variations in energy. These variations can cause damage and/or non -uniform processing of optics and target materials. \n\nSimultaneous elect ronic control of both an intra-cavity loss modulator (acousto-optic modula tor) and the laser pump source (laser diode) provides the means to accurat ely stabilise and control the output pulse energy. This “dual loop” el ectronic feedback technique has been successfully demonstrated using two a nalog PID (proportional\, integral and derivative) controllers. We have no w implemented the control in a high-speed digital controller\, adding seve ral advantages in terms of computer programmability\, flexibility and accu racy. The digital electronics consist of a FPGA processing unit (which can calculate programmed control algorithms at high-speed in parallel) sandwi ched between high-speed analog-to-digital and digital-to-analog converters . \n\nThe digital dual loop pulse control system was connected to a custom developed 2 micron single-frequency Ho:YLF ring laser. Normally\, injecti on-seeding and resonator-length control (based on the Pound-Drever-Hall te chnique) are used to achieve stable single-frequency pulsed operation. The digital pulse control system provided a less expensive and more compact m ethod for stable operation\, and could selectively produce between 15 – 45mJ pulses set via a computer control interface. The control could also m aintain constant pulse energies (within 4.3% of the set-point) across a ra nge of pulse repetition rates.\n\nhttps://events.saip.org.za/event/7/contr ibutions/5124/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5124/ END:VEVENT BEGIN:VEVENT SUMMARY:Structural features of the Cu-In-Ga-Se precursors for formation of Cu(In\,Ga)Se2 thin films by thermal reaction of InSe/Cu/GaSe alloys to el emental Se vapour. DTSTART;VALUE=DATE-TIME:20110715T061500Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5125@events.saip.org.za DESCRIPTION:Speakers: Francis Dejene (University of the Free State)\nThe q uaternary compound semiconductor Cu(In\,Ga)Se2 is one of the most attracti ve materials for high efficiency solar cells due to its tunable band gap t o match well the solar spectrum. In this study\, semiconducting Cu(In\,Ga) Se2 thin films were prepared by a classical two-step growth process\, whic h involves the selenization and/or sulfurization of In/Cu-Ga precursor. D uring the precursor formation step metallic In/Cu-Ga alloys were deposited onto the Mo coated soda lime glass substrates by DC magnetron sputter pro cess. The respective precursors were subsequently reacted with H2Se and/or H2S gasses\, at elevated temperatures. By optimizing the selenization par ameters\, such as the gas concentrations\, reaction time\, reaction temper ature\, and the flow of H2Se and H2S\, high quality\, single phase quatern ary films were obtained. The gallium and sulfur diffusion behaviors were f ound to depend strongly on the selenization/sulfurization profile. The sur face morphology\, phase structure and composition of the layers were analy zed by scanning electron microscope (SEM)\, atomic force microscopy (AFM)\ , X-ray diffraction (XRD)\, and electron diffraction spectroscopy (EDS). P hotoluminescence (PL) measurements were performed to examine the optical p roperties of the films.\n\nhttps://events.saip.org.za/event/7/contribution s/5125/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5125/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigating the thermal performance of a hybrid PV solar system DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5126@events.saip.org.za DESCRIPTION:Speakers: Michael Simon (FHIT)\nPhotovoltaic thermal heating s ystem have gained momentum in the recent years with many investigations be been done on how to maximize the heat harnessing mechanisms. In some cas e copper tubes fixed on the back part of the module\, are used to circulat e forced water around them by external driving force e.g. pumps and\, in t he process extract heat from the module and provide the cooling effect as well. As more heat is extracted from the these devices\, the final water temperature rises above the ordinary ambient temperature and stays hot for longer hours after the sun has gone down. This effect on the performance of the PV system due to long temperature lag and uneven heat distribution on the back of the module as a result of thermodynamics processes in the water will be presented in the final paper.\n\nhttps://events.saip.org.za/ event/7/contributions/5126/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5126/ END:VEVENT BEGIN:VEVENT SUMMARY:Radon escape from mine tailings dams DTSTART;VALUE=DATE-TIME:20110713T121500Z DTEND;VALUE=DATE-TIME:20110713T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5127@events.saip.org.za DESCRIPTION:Speakers: Joash Ongori (UWC)\nGold mine tailings dams contain considerable amounts of Ra-226 and have therefore been identified as larg e sources of radon. In this contribution we will discuss measurements at a disused Kloof mine dump near Carletonville to investigate the radon exh alation from the dump as well as the gamma radiation from the dump. \n\nWe have also taken soil samples in order to find the activity concentrations as well as to study the diffusion and emanation of radon.\n\nhttps://even ts.saip.org.za/event/7/contributions/5127/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5127/ END:VEVENT BEGIN:VEVENT SUMMARY:From few-body to many-body problems DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5128@events.saip.org.za DESCRIPTION:Speakers: Mantile Lekala (UNISA)\nProblems involving bound sta tes of few particles can be solved exactly since the number of degrees of freedom are small. Several methods in this direction exist. One of these i s the Integro-differential equation approximation method (IDEA). These few -body methods have been succesfully applied to obtained bound and scatteri ng states for three- and four-body problems for nuclear and molecular syst ems. \n\nOn the other hand\, calculating observables for many-body systems \, such as Bose-Einstein condensates\, is quite involved. Approximations a t different levels\, i.e. formalism and numerical\, are necessary. In this work we show that the IDEA method can be extended to many-body systems vi a the transformation of the kernel\, and this transformation accelerate co nvergence quite dramatically. Examples of molecular systems consisting of particles upto 1000 atoms are handled quite easily. Technical aspects of t he method are discussed.\n\nhttps://events.saip.org.za/event/7/contributio ns/5128/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5128/ END:VEVENT BEGIN:VEVENT SUMMARY:One-way Quantum Computing with Photonic Orbital Angular Momentum DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5129@events.saip.org.za DESCRIPTION:Speakers: Humairah Bassa (UKZN)\nOne-Way Quantum computing is based on the preparation of certain entangled states of several particles\ , which are subsequently individually measured. The measurements serve to process information as well as to read out the final result of the computa tion. The implementation with  OAM carrying \nphotons is based on the usa ge of qubits (only two OAM values are relevant) but is a first step toward s the implementation of  a generalized form of One-Way Quantum computing by means of qudits (involving more then two OAM values).\n\nhttps://events .saip.org.za/event/7/contributions/5129/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5129/ END:VEVENT BEGIN:VEVENT SUMMARY:NON-SPECIALIST: Organic solar cells: An overview focusing on metal oxide buffer layer and post-fabrication annealing DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5131@events.saip.org.za DESCRIPTION:Speakers: Odireleng Ntwaeaborwa (University of the Free State) \nPhotovoltaic cell devices constructed from organic materials are becomin g increasingly efficient because of the discovery of the bulk heterojuncti on concept. Today\, organic photovoltaic cell (OPVC) devices fabricated f rom the blends of poly(3-hyxylthiopene) (P3HT) and [6\,6] –phenyl C61-bu tyric acid methyl ester (PCBM) are the most widely studied bulk heterojunc tion systems because of their relatively good photovoltaic (PV) properties . Although the P3HT:PCBM based solar devices exhibit excellent PV properti es compared to other bulk heterojunction polymer solar cells\, their effic iency ( 8%) is still too low compared to that ( 20%) of conventional silicon PV cells. One way of improving the performance of these devices i s by inserting a metal oxide buffer layer between the active layer and the anode. In addition\, the PV properties of OPVC devices can also be impro ved by post-fabrication heat treatment (or annealing). This review provide s an overview of OPVC devices focusing on: a brief history of the OPVC dev ices\, device construction\, and the effects of ZnO nanoparticles buffer l ayer and post-fabrication annealing on the general performance of P3HT:PC BM based solar devices.\n\nhttps://events.saip.org.za/event/7/contribution s/5131/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5131/ END:VEVENT BEGIN:VEVENT SUMMARY:Nanostructured WO3 thin films by Aqueous Chemical Growth: Structur al\, Optical and Gas sensing characteristics DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5132@events.saip.org.za DESCRIPTION:Speakers: Bertrand SONE (Materials Research Department\, iThem ba LABS)\nCrystalline thin solid films of WO3 have been prepared on Cornin g glass\, FTO and Si through the low temperature\, wet chemistry method of Aqueous Chemical Growth. SEM images of the thin films produced show that the surface morphology of the films is influenced by the kind of substrate used for the synthesis. While nanoplatelet-containing flower-like structu res were consistently obtained on the Corning glass substrates\, nanorod-c ontaining urchin-like structures were consistently produced on the F-doped SnO2-glass substrates. A review\, using SEM\, is done here of the differe nt kind of nanostructures that make up the thin films produced on these di fferent substrates. Structural characterization of the different thin film s synthesized on all three substrates was carried out using XRD\, TEM\, HR TEM and SAED. These showed that the films produced were made up of WO3 in the monoclinic\, triclinic\, cubic and hexagonal phase depending on what h eat-treatment procedures the different substrates were subjected to post-s ynthesis. The quantum confinement effect is clearly demonstrated in the th in films as the optical band gap calculated for these films is seen to und ergo a blue shift from the theoretical values of 2\,7eV in the bulk to val ues of 3.18 eV\, 3.93eV and 4.12 eV at the nano/microscale. This can be ex plained as being a consequence of the reduction of the grain size in these films to values in the nano-range\, values as small as 9nm. By varying th e time of synthesis for these films\, a growth mechanism for the nanostruc tures produced is proposed. A comparative study of the hydrogen sensing pr operties of the WO3 thin films produced on all three substrates is carried out. This is compared to hydrogen sensing carried out on WO3 thin films p repared on Corning Glass\, FTO and Si via the method of electrospinning. T he structure-property relationship for gas sensing is thus assessed.\n\nht tps://events.saip.org.za/event/7/contributions/5132/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5132/ END:VEVENT BEGIN:VEVENT SUMMARY:Spectral method for studying nuclear four-body reactions DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5133@events.saip.org.za DESCRIPTION:Speakers: Dithlase Masita (UNISA)\nReactions involving four pa rticles\, either in the entrance or final channel\, are quite involved whe n computing observables in comparison to three-body reactions. Yet these r eactions are of interest in studying reactions of astrophysical interest\, such as hep process\, which is essential for describing the quantitative solar model. \n\nAt lower solar energies\, it is difficult to measure the cross-section for the hep reaction. Moreover\, there are discrepancies in calculations of the S-factor using different models and compared to the va lue predicted by the Standard Solar model. This problem in turn implies pr oblems in estimating the correct value for the reaction cross-section whic h is crucial for the understanding of the Standard Solar model. In order t o address this discrepancy and other observables\, a reliable numerical te chnique is necessary. In this work we propose a new spectral method capabl e of calculating low-energy phase shifts for scattering of the nucleon off a light nucleus. We consider reactions of the type (3+1) --> (3+1)\, with in the Faddeev-Yakubovsky framework. We show that these equations can be t ransformed into spectral-type set of equations that are numerical less exp ensive to solve in comparison to competing methods.\n\nhttps://events.saip .org.za/event/7/contributions/5133/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5133/ END:VEVENT BEGIN:VEVENT SUMMARY:An African VLBI Network of Radio Telescopes DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5134@events.saip.org.za DESCRIPTION:Speakers: Michael Gaylard (HartRAO)\nThe advent of internation al wideband communication by optical fibre has produced a revolution in co mmunications and the use of the internet. Many African countries are now connected to undersea fibre linking them to other African countries and to other continents. Previously international communication was by microwav e links through geostationary satellites. These are becoming redundant in some countries as optical fibre takes over\, as this provides 1000 times the bandwidth of the satellite links.\n\nIn the 1970's and 1980's some two dozen large (30m diameter class) antennas were built in various African c ountries to provide the satellite links. As these antennas become redunda nt\, the possibility exists to convert them for radio astronomy at a cost of roughly one tenth that of a new antenna of similar size. \n\nHartRAO a nd the SA SKA Project have started exploring this possibility with some of the African countries.\n\nhttps://events.saip.org.za/event/7/contribution s/5134/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5134/ END:VEVENT BEGIN:VEVENT SUMMARY:Hydrogenation of Ti6Al4V alloy DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5135@events.saip.org.za DESCRIPTION:Speakers: Zeldah Sentsho (iThemba labs)\nHydrogen is the light est element and it has the highest energy content per unit of weight of an y known element and thus\, it can be used as a source of clean energy. Pre vious research studies on hydrogen storage show that storing hydrogen as a solid hydride is preferred compared to liquid and gas because of the very high pressures and low temperatures needed to maintain the system. Hydrog en storage in solid form offers the safest alternative for transportation and storage of hydrogen. Metal hydrides are known to possess high volumetr ic hydrogen densities (of the order of 3 to 8 wt. %) along with the abilit y to store hydrogen at atmospheric pressure and room temperature. Moreover \, many metals and alloys are capable of reversibly absorbing large amount s of hydrogen. The unique properties of hydrogen storage alloys are used i n numerous applications such as rechargeable batteries\, cooling devices\, hydrogen storage systems for fuel cells and in gas sensors applications. \n\nThe research interest of this project is placed on Ti6Al4V alloy as pr omising candidate for hydrogen storage. The changes in microstructure (vol ume fractions of alpha- and beta-phase) will be studied as a function of h ydrogen concentration and pressure. X Ray Diffraction (XRD) will be used f or phase analysis\, while the hydrogen content and hydrogen depth profile will be determined by Electron Recoil Detection Analysis (ERDA) and Heavy Ions (ERDA) methods.\n\nhttps://events.saip.org.za/event/7/contributions/5 135/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5135/ END:VEVENT BEGIN:VEVENT SUMMARY:Effects of ZnO and Ce3+ incorporation on the photoluminescence and cathodoluminescence intensity of Pr3+ doped SiO2. DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5142@events.saip.org.za DESCRIPTION:Speakers: Gugu Mhlongo (CSIR/UFS)\nThe successful incorporatio n of ZnO nanoparticles and Ce3+ ions in Pr3+ doped SiO2 using a sol-gel pr ocess is reported. SiO2:Pr3+ gels\, with or without ZnO and Ce3+\, were d ried at room temperature and annealed at 600 oC. The Field Emission Scanni ng Electron Microscopy (FESEM) indicated clustered SiO2 nanoparticles with with particle size diameter ranging between 20 to 120 nm while the high r esolution transmission electron microscopy (HRTEM) revealed and energy dis persive x-ray spectroscopy (EDS) the presence of Zn\, Ce\, and Pr nanoclus tures enveloped in SiO2 matrix.. The emission intensity from SiO2:Pr3+-Ce3 + was slightly enhanced compared to single doped SiO2:Ce3+. For ZnO.SiO2:P r3+\, the ZnO green emission was suppressed and enhanced emission from Pr3 + was observed. Energy transfer mechanism between Pr3+and Ce3+ as well as between ZnO and Pr3+ ¬ is discussed in detail.\n\nhttps://events.saip.org .za/event/7/contributions/5142/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5142/ END:VEVENT BEGIN:VEVENT SUMMARY:Radiation Shielding calculations using MCNPX transport code for co st optimization of the shielding material to be used in the new cyclotron vault at iThemba Labs DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5136@events.saip.org.za DESCRIPTION:Speakers: Zipho Ngcobo (iThemba Labs)\nIon Beam Applications ( IBA) commercial cyclotron (IBA Cyclone 70) with capability of accelerating protons up to 70MeV and 350µA of current is to be constructed at iThemba Labs to increase the capacity of the current facility. The two opposite s imultaneous extraction of beams using the Carbon foil stripper\, enable fo r the concurrent production of radioactive ion beam (RIB) for nuclear rese arch and isotope production.\nThis high energy beam is expected to have lo sses of about 10% in total meaning 70µA of the total beam will interact w ith surrounding materials during acceleration. Thus this proton beam is a possible radiation source\, presenting a threat of ionising radiation. The cyclotron is mainly made of magnetic steel which is rather stable provind ing local shielding inside the vault. There are not many significant openi ngs for the radiation to rather escape in the less dense media to the surr ounding other than in the extraction sides. Between the two poles of the c yclotron\, the strip made of steel\, which seals the two poles\, is thick enough to shield radiation. Considering efficiencies at the extraction sid e of the cyclotron\, it is expected that radiation contamination will accu mulate and be transported to the vault and surroundings during cyclotron o perations.\nParticles of concern are neutrons and photons formed during pr oton beam interaction. Bremstrahlung x-rays (photons) could be from proton acceleration and neutrons could be produced by (p\, n) reactions. Photons and neutrons are not easy to shield. There is a need to simulate the radi ation transport using MCNPX transport code so that the levels of doses can be investigated to provide extra safety cautions and adequate selection o f materials and correct dimensions for shielding walls to keep the dose ra tes at acceptable levels. Additionally\, water in the cooling system as i t consists of Hydrogen isotopes that can react with protons to produce neu trons will also be investigated as it will increase the neutron flux into the vault.\n\nhttps://events.saip.org.za/event/7/contributions/5136/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5136/ END:VEVENT BEGIN:VEVENT SUMMARY:Dielectric barrier discharge CO2 TEA laser operated at frequencies up to 400 Hz DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5137@events.saip.org.za DESCRIPTION:Speakers: Peter Baricholo (National University of Science and Technology\, Stellenbosch University)\n\nA dielectric barrier discharge CO 2 TEA laser excited by a thyratron driven power supply has been developed and characterized. Laser output was observed at frequencies up to 25 Hz fo r an electrode separation of 10 mm with 1.8 mm Suprasil glass covering the electrodes. At this gap separation\, pulsed power output of about 9 W was detected for gas pressures between 100 and 400 mbar. Changing the electro de gap separation to 5 mm and using 1.4 mm Suprasil glass dielectric incre ased the output power to 23 W and enabled laser output to be observed at g as pressures up to 700 mbar and maximum pulse excitation frequencies of up to 400 Hz. The developed laser does not require water cooling since the s ystem operates in burst pulse mode.\n\nhttps://events.saip.org.za/event/7/ contributions/5137/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5137/ END:VEVENT BEGIN:VEVENT SUMMARY:Implementation of intra–cavity beam shaping technique to enhance pump efficiency DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5138@events.saip.org.za DESCRIPTION:Speakers: Igor Litvin (CSIR NLC)\nIn this work we propose an i mplementation of a new intra–cavity beam shaping technique to vary the i ntensity distribution of the fundamental mode in a resonator cavity while maintaining a constant intensity distribution at the output. This method c an be useful for fitting a transversal intensity profile of the required m ode with a pump beam profile in the region of the active medium to increas e mode discrimination.\n\nhttps://events.saip.org.za/event/7/contributions /5138/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5138/ END:VEVENT BEGIN:VEVENT SUMMARY:The behavior of an instantaneous Poynting vector in the laser beam s DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5139@events.saip.org.za DESCRIPTION:Speakers: Igor Litvin (CSIR NLC)\nIn this work we investigate the behavior of an instantaneous Poynting vector for different types of cy lindrical symmetric beams such Gaussian beams\, Bessel beams and so on. In most investigations for energy flow in real laser beams\, the oscillation component of the Poynting vector is not considered. However this componen t of the Poynting vector carries useful information regarding beam behavio r such as beam divergence\, self reconstruction and diffraction effects\, which are difficult or nearly impossible to extract from the field of the beam or the time averaged component of the pointing vector. The behavior o f the Poynting vector is different in the near and far fields and understa nding such differences leads to useful interpretation of the different bea m behavior in these regions which is also part of what is investigated in this study.\n\nhttps://events.saip.org.za/event/7/contributions/5139/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5139/ END:VEVENT BEGIN:VEVENT SUMMARY:Behaviour of iodine implanted in HOPG after heat treatment DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5140@events.saip.org.za DESCRIPTION:Speakers: Mxolisi Mukhawana (University of Pretoria)\nThe beha viour of iodine implanted in highly oriented pyrolytic graphite (HOPG) has been investigated using Rutherford backscattering spectrometry (RBS)\, sc anning electron microscopy (SEM) and x-ray diffraction (XRD). Iodine ions were implanted into HOPG using an energy of 360 keV and a dose of 1×1015 atoms cm-2 at room temperature. The implanted samples were annealed in vac uum at 900 0C\, 1000 0C\, 1100 0C and 1200 0C\, all for 9 hours. The resul ts revealed that iodine was released from the HOPG at the above annealing temperatures. RBS evaluation of the full width at half maximum (FWHM) and the number of iodine atoms before and after annealing did not reveal Ficki an diffusion as the mechanism by which the iodine atoms were released from the HOPG. Evaluation of (002) peak intensities using XRD revealed an incr ease in preferred orientation of the graphitic layers after heat treatment of 1200 0C. The high resolution SEM micrographs of the HOPG samples befor e and after heat treatment showed no evidence of alterations on the polish ed surface.\n\nhttps://events.saip.org.za/event/7/contributions/5140/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5140/ END:VEVENT BEGIN:VEVENT SUMMARY:Quantum cryptography for satellite communication DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5141@events.saip.org.za DESCRIPTION:Speakers: Marco Mariola (University of Kwazulu-Natal)\nQuantu m key distribution (QKD) is a secure method of transferring encryption key s between two distant parties. It provides a physical layer of security ra ther than a mathematical algorithm used in conventional encryption systems . As QKD is of paramount importance in the future ICT landscape\, various innovative solutions have been developed and tested to expand the spatial coverage of these networks [R. Alleaume\, 2007\, C. Elliott\, 2004\, F. Xu \,2009]. One such technique to create a global QKD network is to couple qu antum-secured MANs with secured ground-to-satellite links.\nWe present our recent work in ground-to-balloon QKD systems as an intermediary to the sa tellite QKD.\n\nWe have considered a number of parameters in developing ou r solution. Firstly\, the link with the earth station should be guaranteed and robust. Other parameters that we have taken into account include the design of the payload\, tracking systems\, synchronization balloon/satelli te and ground station and choice of the public channel.\n\nThe balloon or satellite will send the QKD signal to the ground station. We use the radio modulation PSK for the transmission of data and synchronize the laser sig nal for QKD. In this way the distance and velocity relative between earth and satellite ( or Balloon ) is not a constraint. The public channel will be used to send a string of bits ( from satellite to earth ) that indicate s the data start and from that moment\, for every bit of the clock\, the s atellite sends the quantum bit. Radio communication will be used also for the public communication during the QKD transmission. Data for correction for the tracking laser will be controlled by a feedback loop on the ground station\, however\, the tracking system of the Balloon or satellite must work separated from the ACS.\n\nhttps://events.saip.org.za/event/7/contrib utions/5141/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5141/ END:VEVENT BEGIN:VEVENT SUMMARY:The influence of Pr3+ co-doping on the photoluminescence and catho doluminescence properties of SiO2:Eu3+ /Tb3+. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5143@events.saip.org.za DESCRIPTION:Speakers: Gugu Mhlongo (CSIR/UFS)\nPr3+-Tb3+\, and Pr3+-Eu3+ i on pairs co-doped in SiO2 matrix were prepared by a sol-gel method. The ph otoluminescence (PL) measurements revealed the red and green emissions cen tred at 614 nm (5D0-7F2) and 541 nm (5D4→7F5) for single doped Eu3+ and Tb3+ ions in SiO2\, respectively. Co-doping of Eu3+ and Tb3+ ions with Pr3 + in SiO2 showed that the energy transfer between Pr3+ and nearest Eu3+ an d Tb3+ ions takes place. At the same time\, however\, there was evidence o f luminescence quenching of Eu3+ and Tb3+ emissions at certain concentrati ons of Pr3+. The quenching was also confirmed by cathodoluminescence (CL) measurements recorded from the same powders. . Possible mechanism of energ y transfer from Pr3+ to Eu3+ and Tb3+ and its quenching effects are discus sed.\n\nhttps://events.saip.org.za/event/7/contributions/5143/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5143/ END:VEVENT BEGIN:VEVENT SUMMARY:Non-resonant microwave absorption in FeSi thin films DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5144@events.saip.org.za DESCRIPTION:Speakers: Happison Gavi (UP)\nNon-resonant microwave absorptio n measurements at 9.4 GHz(X-band)using electron spin resonance spectromete r (ESR)\, were carried out on pulsed laser deposited(PLD)polycrystalline F eSi thin films grown on Si(111)substrate. The low-field microwave absorpti on(LFA)properties of the films were investigated as a function of DC modul ation field\, temperature\, microwave power and angle. The DC field and AC field were orientated parallel to the film surface. The DC field was ori entated normal to the AC field. The anisotropy field was observed to have a central influence on the LFA shape on all the measurements made\, which makes LFA very similar to giant magneto-impedance(GMI). Thin films of FeS i could be potential\ncandidates for magnetic field sensors(based on their GMI). Magnetic anisotropy could be a signature of ferromagnetic state of a material and hence thin films of FeSi are promising candidates for Spint ronics applications.\n\nhttps://events.saip.org.za/event/7/contributions/5 144/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5144/ END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic vector charges in the realization of nonzero magnetic wor k DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5145@events.saip.org.za DESCRIPTION:Speakers: Max Chirwa (Walter Sisulu University)\nTraditionally magnetic forces are supposed to act on moving electric scalar charges and the hitherto undetected Dirac’s magnetic (scalar) charges\, and that wo rk done by such forces is always zero. Any possible evidence to the contra ry is vehemently denied in order to justify this long held myth. Following our recently developed and validated concept of magnetic vector charges a s sources of magnetic fields\, we show that magnetic forces\, like gravita tional and electric forces\, act on objects with corresponding physical at tributes\, and do nonzero work. This is illustrated here by depicting the mechanical generation of electricity and operation of simple electric moto rs in terms of magnetic vector charges. Other supporting examples and tech nological applications that can be cited include the jumping ring experime nt\, Gouy magnetic balance\, Hall magnetic field probe\, vibrating sample magnetometer\, magnetic levitation and magnetic separation of materials. T his simple realization may have far-reaching implications on our overall u nderstanding of magnetism and its ultimate effective utilization.\n\nhttps ://events.saip.org.za/event/7/contributions/5145/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5145/ END:VEVENT BEGIN:VEVENT SUMMARY:On the shape of rotating stars. DTSTART;VALUE=DATE-TIME:20110713T131500Z DTEND;VALUE=DATE-TIME:20110713T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5146@events.saip.org.za DESCRIPTION:Speakers: Peter Nicol (University of Johannesburg)\nI adapt a recent work by Zahn et al. on the shape of rapidly rotating stars to explo re the degree of oblateness for uniform\, differential and shellular rotat ion of the star. I also discuss the relation of these results to the class ical Roche limit.\n\nhttps://events.saip.org.za/event/7/contributions/5146 / LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5146/ END:VEVENT BEGIN:VEVENT SUMMARY:Theoretical derivation of an equation for planetary distances from the sun DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5147@events.saip.org.za DESCRIPTION:Speakers: Pieter Wagener (Dept Physics\, NMMU)\nApplying the q uantisation of action variables to a theory of gravitation one derives dis crete values for planetary distances from the sun. The calculated values a gree with the observed values of all the planets. The derived equation als o applies to the exoplanets. The application is similar to that of the Wil son-Sommerfeld rule for atomic orbits.\n\nhttps://events.saip.org.za/event /7/contributions/5147/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5147/ END:VEVENT BEGIN:VEVENT SUMMARY:Solution-processed CuSe Quantum Dots Photovoltaics DTSTART;VALUE=DATE-TIME:20110715T061500Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5148@events.saip.org.za DESCRIPTION:Speakers: Nosipho Moloto (University of the Witwatersrand)\nTh ere have been tremendous inputs into improving the efficiencies of nanostr ucture solar cells by extending their absorption wavelength to the near-in frared. This can potentially be achieved by using colloidal nanocrystal qu antum dots as the light-harvesting material\, as their optical band gap ca n be tuned to a desired range. Copper selenide is an interesting semicondu ctor with a bulk band gap of 1.39 eV. It has been shown to have good elect rical conductivity properties. It is also used as a precursor for the prep aration of CIDS solar cells. Herein\, colloidal CuSe nanocrystals are synt hesized using a modified solvothermal method and characterized with absorp tion and photoluminescence spectroscopy\, XRD and HRTEM. The resultant nan ocrystals are then used as the active material in a Schottky and hybrid so lar cell.\n\nhttps://events.saip.org.za/event/7/contributions/5148/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5148/ END:VEVENT BEGIN:VEVENT SUMMARY:A synthetic diamond probe for both low-energy mammography X-rays a nd high-energy electron therapy beams DTSTART;VALUE=DATE-TIME:20110715T090000Z DTEND;VALUE=DATE-TIME:20110715T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5149@events.saip.org.za DESCRIPTION:Speakers: Nicholas Ade (None)\nAlthough diamond has been studi ed for dosimetry principally due to its near tissue-equivalence\, its use in both low-energy X-rays and high-energy electron beams has not been repo rted. This report is based on dosimetric studies of a synthetic diamond pr obe when subjected to diagnostic mammography X-ray photons and megavoltage electron therapy beams. The probe\, constructed using entirely tissue-equ ivalent Perspex body was configured for radiation dose measurement in eith er ‘edge-on’ or ‘flat-on’ exposure geometry without having first\, to re-orientate the diamond within the body of the detector\, and it was designed to be compatible with commercial electrometer systems. The radiat ion response of the diamond tested showed negligible energy dependence\; i ts minimal background signal\, high sensitivity (547.52 nC Gy-1mm-3) and s uitability for measurements in small radiation fields of steep dose gradie nts due to its small size make it suitable for clinical dosimetry. The pre sented probe has the potential advantage of replacing conventional radiati on dosimeters.\n\nhttps://events.saip.org.za/event/7/contributions/5149/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5149/ END:VEVENT BEGIN:VEVENT SUMMARY:Photoluminescence Surface Mapping as a Probe for Quantum Well Diso rder DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5150@events.saip.org.za DESCRIPTION:Speakers: Kaumba Godfrey Chinyama (University of Fort Hare)\nS urface mapping of quantum well structures using photoluminescence measurem ents is ideal for determining the overall behaviour of such samples with r egard to their chemical composition and well-width fluctuations. In some a reas where the structural variations are large over a sample\, photolumine scence mapping can yield information which would otherwise require several samples to be grown. Well thickness and strain variations across a sample will show as a small spatially-dependent change in the peak energy and th e full wave half maximum\, so that variations in confinement energies in t he QW due to non-uniformity in the film growth can be observed with this m ethod. In this work\, spatial variations in the exciton band of photolumin escence spectra were measured using surface mapping of the emission by sca nning the sample laterally in the plane of the quantum well across the sam ple area. The luminescence intensity was then mapped as a function of the emission peak energy (and emission linewidth) and the spatial coordinates x and y\, resulting in contour plots.\n\nThe results show that knowledge a bout whether the structures are alloy-disordered or rough (characterised b y thickness fluctuations) can be derived through this simple photoluminesc ence mapping. In rough structures\, there is strong correlation between va riations in peak energy position and linewidth of the main exciton band. O n the other hand\, in alloy-disordered structures\, there is virtually no correlation between the peak energy and linewidth in comparison to the rou gh structures. Surface mapping has also revealed variations in peak energy across the rough samples do not only correspond to monolayer fluctuations in well-width\, but fluctuations in steps of submonolayers are very commo n. This explains why thinner QWs give narrower lines compared to thicker o nes in these CdSe-ZnSe systems studied here. Further\, this analysis shows alloy-disordered structures give good quality samples in terms of optical properties.\n\nhttps://events.saip.org.za/event/7/contributions/5150/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5150/ END:VEVENT BEGIN:VEVENT SUMMARY:Dependence of Aspect Ratio of InSb Self-Assembled Quantum Dots on Thickness and Indium Mole Fractions of Spacer Layers DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5152@events.saip.org.za DESCRIPTION:Speakers: MOHIT GODBOLE (NELSON MANDELA METROPOLITAN UNIVERSIT Y)\nShort range biaxial and hydrostatic strains in quantum dots caused by spacer layers affect the aspect ratio to a great extent\, leading to varia tions in the conduction and valence band energy levels. This paper aims to study the effect of the indium mole fraction and thickness of the spacer layer on the size and shape of multi-stack quantum dots grown by metalorga nic vapour phase epitaxy. Quantum dots of varying aspect ratios (height:wi dth) have been grown. Structures containing two stacks of quantum dots hav e been grown on etched GaSb (001) substrate\, with different thickness and indium content of the GaInSb spacer layers. Experiments are currently und er way to study the effect of the thickness of the spacer and the composit ion on the size distribution\, shape and density of three stacks of InSb q uantum dots. The structures are characterized by X-ray diffraction\, photo luminescence\, scanning and transmission electron microscopy.\n\nhttps://e vents.saip.org.za/event/7/contributions/5152/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5152/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermal transport in the cage-compounds RFe2Al10 (R=Y\, Yb) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5154@events.saip.org.za DESCRIPTION:Speakers: Andre Strydom (University of Johannesburg)\nSince th e first report of the anomalous magnetic and electronic phenomena in CeRu2 Al10 this intermetallic class of compounds\, incorporating also members wi th elements Os and Fe in the place of Ru\, have attracted considerable int erest. N spite of large interatomic distances antiferromagnetic order sets in at TN =27 K in the ru and Os derivatives\, with simultaneous energy ga p formation in the electronic energy levels. In this work we studied the e lectronic and thermal transport in two novel members of the 1:2:10 series\ , YFe2Al10 and YbFe2Al10. These two compounds were synthesized with the pu rpose of studying the effects of a unit cell volume that is compressed wel l beyond that of CeRu2Al10 in order to expose the role of Fe-based magneti sm in the observed electronic correlations. \nHere we discuss our results of thermal and electronic transport in the pair of compounds YFe2Al10 and YbFe2Al10. Both exhibit anomalous thermopower behavior and a peak that dev elops at low temperatures. This is attributed to an enhanced density of st ates that is achieved through hybridization between conduction electrons a nd magnetic moments with a localized nature. The thermal conductivity of b oth compounds shows a weak temperature dependence and especially in the ca se of YFe2Al10 is the observed behavior amenable to a description in terms of glass-like behavior that most likely results from optical phonon modes which effectively scatter heat-carrying quasiparticles. The electrical re sistivity suggests low-lying magnetic cooperative behavior.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5154/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5154/ END:VEVENT BEGIN:VEVENT SUMMARY:Current Status of Ultrafast Electron Diffraction at the Laser Rese arch Institute DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5160@events.saip.org.za DESCRIPTION:Speakers: Ilana Boshoff (University of Stellenbosch (Laser Res earch Institute))\nWe will show the changes and improvements made to the U ltrafast Electron Diffraction setup which led us to doing the first time-r esolved experiments. \nWe have implemented beam tracking and correction s ystems in both the pump and probe beams\, ensuring that we keep spatial ov erlap during a measurement. By using a different cathode and metal coati ng we were able to improve the electron efficiency. These improvements en able us to do measurements of up to 20 hours without losing the electron s ignal.\nPreciously a commercial 8-bit Nikon camera was used to gather data . We have switched to a 16-bit EHD CCD Camera to increase the amount of i nformation we get from one data point.\nPrevious problems concerning the b ackground were solved by reducing the electron energy and applying a small voltage to the sample holder to prevent photo electrons from reaching the detector.\nA big challenge in UED is the preparation of thin (<100nm) sam ples. We will show the techniques we use to overcome this problem.\n\nhtt ps://events.saip.org.za/event/7/contributions/5160/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5160/ END:VEVENT BEGIN:VEVENT SUMMARY:The transition from high school Physics to first-year Physics: How well prepared are our students? DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5155@events.saip.org.za DESCRIPTION:Speakers: Paul Molefe (University of Johannesburg)\nPremature withdrawal from university due to academic failure has the potential to pr esent problems to both students and educators. The demand from industry fo r a larger pool of science and engineering graduates in South Africa is in line with international norms. This state of affairs is compounded by a s hrinking pool of good quality school leavers. For the desired growth in gr aduate numbers to occur\, physics educators are required to respond effect ively through curriculum reform to optimize success and retention of stude nts at first year level. The research project in this regard aims to inves tigate the level of preparedness in relation to Physics I students and to identify key success factors in this course. This course is compulsory for most first year science students and is largely perceived as difficult in comparison with other first year courses. More students are pursuing Phys ical Science at school and consequently study science\, engineering and te chnology at universities (DoE\, 2010) and University of Johannesburg is no exception. For many students\, the first year at university represents a transition during which a variety of academic and social challenges are en countered. To this end\, students’ entry-level preparedness was investig ated through analysis of their high school examination results\, administr ation of a diagnostic test and first year university assessment results. T he results reveal that high school examination results appear not to be th e only independent factor characterising students’ readiness for first y ear physics studies at university.\n\nhttps://events.saip.org.za/event/7/c ontributions/5155/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5155/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and characterization of reproducible stoichiometry of co balt sulfide nanoparticles using sulphur containing single-source precurso rs DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5156@events.saip.org.za DESCRIPTION:Speakers: Simon Bonginkosi Sibokoza (Student at Vaal Universit y of Technology)\nCobalt sulphide nanoparticles are one of the most comple x and challenging particles to synthesize due to strongly reducibility of the cobalt ion and the oxidizable nature of the sulphide ion. Cobalt sulph ide therefore exist in various phases with different compositions includin g Co4S3\, Co9S8\, CoS\, Co1-xS\, Co3S4\, Co2S3 and CoS2. Herein\, we descr ibe the synthesis of CoxSy nanoparticles\; furthermore we interrogate the influence of the reaction conditions on the structure and optical properti es of the nanoparticles. CoxSy nanoparticles were synthesized by thermoly sis of N\, N\, N´\, N´-tetramethylthiuram disulphide cobalt (II) complex in the presence of stabilizing agent Hexadecylamine (HDA). The advantage of this method is that the bond between the cobalt and sulphur atoms alrea dy exist\, therefore decomposition of the complex at write conditions will result in the formation of CoxSy nanoparticles. The cobalt sulfide nanopa rticles were prepared by varying concentration from the range 5.0 mg to 5. 0 g of the CoCl2[(CH3)2NCS2S2CN(CH3)2]2 complex at 130 °C temperature. Th e effect of temperature was also investigated by varying the temperature f rom 80 to 250 °C. The nanoparticles were characterised by a combination o f absorption spectroscopy\, photoluminescence (PL)\, X-ray diffractometry (XRD) and transmission electron microscopy (TEM).\n\nhttps://events.saip.o rg.za/event/7/contributions/5156/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5156/ END:VEVENT BEGIN:VEVENT SUMMARY:Stellar perturbation via Lie derivatives. DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5157@events.saip.org.za DESCRIPTION:Speakers: Fabio Frescura (U Witwatersrand)\nPerturbation theor y uses Lagrangian techniques that require vector fields to be compared at finitely separated points. This method can be generalised to the strong gr avitational field regime in one of two ways\, using either covariant or Li e derivatives. In this paper\, I argue that those methods based on the Lie derivative are more useful. The Lie derivative provides a clear picture o f how the deformation of the fluid flow takes place. It also provides a na tural way to discuss large perturbations. I apply this method to some elem entary stability problems in the study of stellar structure.\n\nhttps://ev ents.saip.org.za/event/7/contributions/5157/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5157/ END:VEVENT BEGIN:VEVENT SUMMARY:Cross phase modulation induced depolarization of a probe signal an d its impact on polarization mode dispersion compensators DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5158@events.saip.org.za DESCRIPTION:Speakers: Timothy Gibbon (Nelson Mandela Metropolitan Universi ty)\nNonlinear effects are easily observed in single mode optical fibres b ecause of the fibre small spot size and extreme low loss. At high optical intensities in fibres the refractive index becomes a function of the inten sity of the optical signal. This refractive index is known as the Kerr non linearity. This leads to the optical Kerr effect where the nonlinear phase shift induced by an intense high power pump changes the characteristics o f the probe beam. Cross phase modulation (XPM) refers to a nonlinear effec t where a pump beam with high intensity changes the phase of a low power p robe beam.\nIn this work\, we consider the composite problem of polarizati on mode dispersion (PMD) and XPM in wavelength division multiplexing (WDM) networks. PMD continues to pose a treat to high speed optical networks he nce the need for PMD compensators (PMDCs). PMDCs monitor the link PMD in a n indirect manner where a popular monitoring technique tracks the degree o f polarization (DOP) of a signal in the link. It can be shown that in a tw o channel WDM system an intensity modulated pump modulates the state of po larization (SOP) of a probe signal at the pump bit rate. In this work we e xperimentally demonstrate the depolarization of a probe signal in the pres ence of an intensity modulated pump signal. The results show that minimum interaction between the pump and probe signal occur when the pump and prob e input Stokes vectors are parallel and anti-parallel. Hence the probe sig nal incurs maximum depolarization when the two signals are arranged in an orthogonal configuration. These results are crucial to PMDC because the so urce of the DOP degradation may mislead the compensator.\n\nhttps://events .saip.org.za/event/7/contributions/5158/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5158/ END:VEVENT BEGIN:VEVENT SUMMARY:Optical design of low concentration photovoltaic modules DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5161@events.saip.org.za DESCRIPTION:Speakers: Mario Benecke (Nelson Mandela Metropolitan Universit y)\nThe benefit of concentrating sunlight onto solar cells is that expensi ve solar cell material can be reduced and replaced with relatively inexpen sive optical elements\, which has the potential to reduce the cost of sola r energy.\nIn low concentration photovoltaics (LCPV)\, solar cells are sub jected to higher irradiance levels. The electrical output\, and hence effi ciency of a LCPV module is dependent on the amount of irradiance\, tempera ture and more importantly the uniformity of illumination across the solar cells. \nThis paper discusses the design and characterization of the optic al subsystem of a LCPV concentrator. By optimizing the aperture area of th e LCPV concentrator while still maintaining a uniform illumination intensi ty across the solar cells\, the module’s electrical performance can be m aximized. In the study a mathematical model was developed to design and ev aluate suitable optical elements for LCPV application. This model was base d on a facetted reflector that was designed to meet a predetermined set of boundary conditions.\nInitial evaluation of an experimental LCPV concentr ator\, based on this type of design\, will be discussed in this paper. Res ults from the model illustrate the angles and positions of receiver and re flectors for maximum geometric concentration ratio as well as the best ill umination profile across the receiver.\n\nhttps://events.saip.org.za/event /7/contributions/5161/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5161/ END:VEVENT BEGIN:VEVENT SUMMARY:On the Thermal and Electrical Properties of Low Concentrator Photo voltaic (LCPV) Modules DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5162@events.saip.org.za DESCRIPTION:Speakers: Jacques Gerber (Nelson Mandela Metropolitan Universi ty)\nEfficient thermal management of low concentrator photovoltaic (LCPV) modules ensures that the maximum power capabilities of the LCPV system are harnessed\, and may substantially prolong the operating lifetime of the p hotovoltaic (PV) cells. A general understanding of the thermal transfer p roperties of PV modules is thus necessary to effectively design\, construc t\, and implement viable LCPV systems. \n\nA basic thermal model based on one-dimensional heat transfer was developed and includes various energy di ssipation mechanisms\, such as convection and radiation. Panel fans were used to simulate air flow across the surface of the PV module and temperat ure measurements of the front and back surface of the PV module were recor ded to analyse energy dissipation in accordance with the basic thermal mod el.\n\nInitial results indicate that 50% of the incoming irradiance is dis sipated through convection and radiation. Optical losses will also be in curred through reflection from the surface of the PV module. The basic th ermal model manages to account for most of the energy incident on a PV mod ule\, and thus effectively illustrates the principle of energy conservatio n within the PV system.\n\nhttps://events.saip.org.za/event/7/contribution s/5162/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5162/ END:VEVENT BEGIN:VEVENT SUMMARY:Miniaturization of electrostatic ion engine through ionization/acc eleration coupling: corona model DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5163@events.saip.org.za DESCRIPTION:Speakers: Marius Tchonang Pokaha (Wits University)\nElectrosta tic ion propulsion systems resist miniaturization due to constraints impos ed by the size of the discharge chamber. We introduce a thruster concept w here the same field is responsible for both ionization of the neutrals and acceleration of the ions\, by letting the neutral propellant gas escape i nto a high field region through a thin\, hollow needle at high electric po tential. The ionization mechanism is thus reminiscent of corona ionization . Although the thruster only ionizes a small fraction of the neutral gas\, the ions nevertheless impart a great deal of momentum to the plume\, crea ting an ion wind. We propose a model to estimate the electric behavior of the system\, and two further models for the obtained thrust. A comparison with experimental data shows that the models capture the dominant physical effects and give a reasonable description of the system. Apart from being about a thousand times less massive than conventional systems\, the thrus ter\, which is at the proof-of-concept stage\, performed quite well yieldi ng around 0.3 mN/Watt during initial tests. The thruster small size and si mplicity are advantageous in many situations\, such as for satellite stati on keeping and deep space probes.\n\nhttps://events.saip.org.za/event/7/co ntributions/5163/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5163/ END:VEVENT BEGIN:VEVENT SUMMARY:Vanadium dioxide based on nano-devices for photonic apllications DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5165@events.saip.org.za DESCRIPTION:Speakers: itani given madiba (university of western cape)\nVan adium dioxide falls into the category of smart thermochromic materials\, o ne where the property of the material changes due to the effect of tempera ture. High quality pure thermochromic thin films of vanadium dioxide were prepared by using two physical methods\, Rf-reactive sputtering and pulsed laser deposition methods. These deposition methods were used to study the effect of deposition temperature on vanadium dioxide thin films microstru cture\, electrical and optical properties. The deposition conditions (oxyg en pressure\, substrate-target distance\, substrate temperature and etc) o n both methods were carefully optimized for the quality of VO2 thin films on a glass substrate\, with a substrate temperature ranging from 350-600 d egrees celcius. All the vo2 thin films prepared by Pulse laser deposition technique and Rf- reactive sputtering were characterized by X-ray diffract ion technique\, observed to be crystallized showing the first peak at 27.8 7 degrees celcius which corresponds to the (011) plane and the monoclinic structure of VO2. This peak indicates the existence of Vanadium dioxide. T hermochromic properties of VO2 thin films were investigated by measuring t he optical and electrical properties below and above the critical temperat ure using the UV/VIS technique. T he atomic force microscopy was also used to investigate the surface roughness of all the VO2 thin films.\nRBS was used for quantitative analysis of composition\, thickness and depth profil es of VO2 thin films and it was conducted using a 2 MeV beam of alpha part icles\, other techniques as well as TEM\, SEM\, FTIR were also employed to investigate the morphology\, composition\, and crystallographic informati on on VO2 thin films.\n\nhttps://events.saip.org.za/event/7/contributions/ 5165/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5165/ END:VEVENT BEGIN:VEVENT SUMMARY:CMB Tensor Anisotropies in f(R) Gravity DTSTART;VALUE=DATE-TIME:20110714T060000Z DTEND;VALUE=DATE-TIME:20110714T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5166@events.saip.org.za DESCRIPTION:Speakers: Hassan Bourhrous (University of Cape Town)\nThe cosm ic microwave background (CMB) carries information from the last scattering surface that puts constraints on the multitude of proposed cosmological m odels and the gravity theories they are based on. Amongst such theories ar e the f(R) theories of gravity which have become an interesting endeavour to correct for the degeneracies of the concordance model.\nWe present a de scription of CMB anisotropies generated by tensor perturbations in f(R) th eories of gravity. The power spectra of the observables TT and EE in the s pecial case of f(R)=Rn are computed using a modified version of CAMB.\n\nh ttps://events.saip.org.za/event/7/contributions/5166/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5166/ END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic properties of carbon nanospheres at low temperatures DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5167@events.saip.org.za DESCRIPTION:Speakers: Makhosonke Dubazane (University of the Witwatersrand )\nThe magnetic and electrical properties of nitrogen doped carbon nanosph eres can be probed using Electron Magnetic Resonance (EMR) techniques. Pre vious Raman spectroscopy studies show that both the pristine and doped sph eres are graphitic in character. However\, XRD measurement showed that the se spheres consist of graphitic crystallites embedded in an amorphous phas e. Previous ESR measurements showed large peak on nitrogen doped spheres\, implying that the nitrogen occupies substitutional sites in graphitic lat tice. The EMR measurements clearly showed large Curie-type paramagnetism a t low temperatures for all the samples investigated. The EMR peak-to-peak linewidth have provided evidence of the phonon bottleneck effect in one of the sample investigated\, meaning to say that there is a strong interacti on between localized and conduction electrons. The broadening of linewidth may be manifested by a Korringa type interaction whereby the spin-lattice relaxation time T1 is inversely proportional to the temperature. The sam ple with the highest concentration of nitrogen behaves very differently fr om the other samples studied in th temperature range 77 K to 300 K\, and t his behaviour is not well understood at present. This may involve contrib utions from electron scattering with stationary nitrogen impurities\, and therefore different spin relaxation mechanisms which are related to the El liot and Yafet mechanisms.\n\nhttps://events.saip.org.za/event/7/contribut ions/5167/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5167/ END:VEVENT BEGIN:VEVENT SUMMARY:Atomic processes in gaseous nebulae DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5168@events.saip.org.za DESCRIPTION:Speakers: Andri Prozesky (Unisa)\nThe atomic physics relevant to gaseous nebulae is critically examined using modeling software with par ticular emphasis on recombination spectral lines that occur in the radio r egime. The spectral line intensities that we observe from nebulae can be d educed if we know the population structure of the bound electrons in the g as under non-thermal equilibrium conditions. The population structure of h ydrogen is solved for various environments using a capture-collision-casca de model.\n \nThe validity of assuming Case B of Baker & Menzel (1938) whe n modeling astronomical nebulae is investigated. It is known that Case B i s appropriate for levels with small principle quantum numbers (n < 40)\, b ut this assumption should be re-examined for high energy levels which are relevant to radio recombination lines.\n \nThe effect of an ambient radiat ion field on the population structure is examined and processes that are s timulated by a radiation field are included in the model. This is done as a preliminary investigation to extend the model to a full photoionization code that will be geometry-dependent and include an external radiation fie ld as well as the diffuse field that is emitted by the nebula itself.\n\nh ttps://events.saip.org.za/event/7/contributions/5168/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5168/ END:VEVENT BEGIN:VEVENT SUMMARY:Minimization of optically active structural defects in MOCVD grown ZnO films using oxygen and NO DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5169@events.saip.org.za DESCRIPTION:Speakers: Kouadio Julien Dangbegnon (Nelson Mandela Metropolit an University)\nThe optical and structural properties of ZnO grown with a mixture of oxygen and nitric oxide as oxidants are investigated. With R de fined as the ratio of oxygen to nitric oxide molar flow rates\, samples gr own with R ≥ 1 (i.e. a higher low rate of oxygen compared to nitric oxid e) reveal a 3D growth mode with columns perpendicular to the substrate\, w hile for R < 1 a preferential 2D growth mode is observed. The low temperat ure photoluminescence studies show that the columnar growth observed for R ≥ 1 coincides with an increase in intensity of the transitions around 3 .31 eV arising from structural defects whereas this emission is quenched f or R < 1. The disappearance of the transition at 3.31 eV is followed by th e emergence of a transition at ~3.356 eV\, which is assigned to an accepto r bound exciton related to nitrogen. Furthermore\, this transition is not visible in the oxygen-rich regime\, due to the high density of structural defects in the samples. This work aims to show the importance in minimizin g structural defects in order to achieve acceptor bound exciton emission i n ZnO doped with nitrogen and possibly stable p-type ZnO.\n\nhttps://event s.saip.org.za/event/7/contributions/5169/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5169/ END:VEVENT BEGIN:VEVENT SUMMARY:On the orbital rehybridization in tetrahedral amorphous carbon DTSTART;VALUE=DATE-TIME:20110714T120000Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5170@events.saip.org.za DESCRIPTION:Speakers: Aniekan Magnus Ukpong (University of the Witwatersra nd)\nThe use of tetrahedral amorphous carbon thin films in bolometers depe nds strongly on the ability to tune its optical properties. This can be ac hieved by controlling the density of dangling bond defects and the disorde r in the material. The pi-orbital axis vector theory is used in this study to investigate the phenomenon of rehybridization of the carbon bonding in tetrahedral amorphous carbon. It is shown that the correlated pi - pi* or bitals is locally entangled due to the competition between the on-site Cou lomb interaction and the hybridization. A microscopic model is proposed fo r the reduction in strain in the material due to hydrogenation\, based on the the sp3 – sp2 conversion reaction. It is demonstrated that the activ ation energy for this conversion is dependent on the Urbach energy\, and t herefore on the disorder. The implication of the results on the manifestat ion of strain in similar\, carbon-based\, materials is discussed.\n\nhttps ://events.saip.org.za/event/7/contributions/5170/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5170/ END:VEVENT BEGIN:VEVENT SUMMARY:“Seeing is believing”: Visual perceptions and the learning of kinematics DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5171@events.saip.org.za DESCRIPTION:Speakers: Miriam Lemmer (North-West University (Potchefstroom) )\nThe proverb “seeing is believing” is generally applied in science e ducation today. Many of the contemporary teaching strategies engage the le arners in activities that guide them in making their own observations. Sti ll\, problems regarding the learning of physics\, especially the prevalenc e of alternative conceptions\, remain a head-ache in physics education res earch. \n\nA variety of causes are ascribed to the occurrence of alternat ive conceptions\, e.g. that textbooks contain them\, teachers themselves h ave them or do not attend to learners’ intuitive ideas or that learners focus to contextual features of an event and do not observe what we intend them to. Even with seemingly sufficient experimental proof\, some alterna tive conceptions remain persistent. The study reported here investigated l earners’ visual perceptions as possible cause for the existence\, persis tence and transfer of the intuitive conception in kinematics that DiSessa called changes-take-time. An example of this conception is the assertion t hat a cannon ball keeps on accelerating after the shell has been launched. A questionnaire\, group discussions and individual questioning contribute d to the investigation. Grade 9 and 10 physical science learners as well a s student teachers participated in the study. \n\nThe results revealed tha t although the learners’ intuitive conceptions are context-dependent\, t he majority of them feel confident about their responses. Limitations and inaccuracies in visual perceptions (such as differences in real and percei ved velocities and changes in velocities) seem to contribute to their intu itive conceptions. A teaching sequence that attends to learners’ visual perceptions is developed. The sequence further intends the conceptual refi nement of learners’ productive experiential knowledge in the learning of kinematics. Consistent application of physics concepts and principles in a variety of everyday and classroom experiences is emphasized for the form ation of a meaningful explanatory model.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5171/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5171/ END:VEVENT BEGIN:VEVENT SUMMARY:Non-locality without inequality and generalized non-local theory DTSTART;VALUE=DATE-TIME:20110714T100000Z DTEND;VALUE=DATE-TIME:20110714T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5194@events.saip.org.za DESCRIPTION:Speakers: Sujit Kumar Choudhary (University of KwaZulu-Natal)\ nWe find non-local but non-signaling probabilities satisfying the 'nonloca lity without inequality’ arguments for multiple two-level systems. Maxim um probability of success of these arguments are obtained in the framework of a generalized nonlocal theory. Interestingly\, for two two-level syste ms\, the probability of success of these arguments converge to a common ma ximum\nin this framework. This is in sharp contrast with the quantum case\ , where for such systems\, Cabello’s argument succeeds more than that of Hardy’s. We also find that the maximum probability of success of Hardy ’s argument is the same for both the two and three two-level systems in the framework of this more generalized theory.\n\nhttps://events.saip.org. za/event/7/contributions/5194/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5194/ END:VEVENT BEGIN:VEVENT SUMMARY:The effective ionization region and its variation with geometrical and electrical properties of the HVDC transmission system DTSTART;VALUE=DATE-TIME:20110713T130000Z DTEND;VALUE=DATE-TIME:20110713T131500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5172@events.saip.org.za DESCRIPTION:Speakers: Richmore Kaseke (Fort Hare Institute of Technology)\ nHigh Voltage Direct Current (HVDC) overhead power transmission trends are currently advancing toward high system voltages over very long distances in a bid to viably tap from remotely located renewable energy sources. Co rona effect plays a very crucial role in the design of overhead power tran smission systems. Through corona\, part of the energy carried on the tran smission line is expended through ionization and movement of charges in th e air dielectric. Corona limitations influence selection of key line para meters such as diameter of phase conductors\, the number of conductors per phase and conductor clearances to the ground. Since overhead transmissio n lines are installed in open air\, the generated electric fields are non- uniform. As a result\, the accompanying ionization in the surrounding air is non-uniform and does not occur throughout the inter-electrode gap. In stead\, the ionization is confined to a very small region around the high voltage fitting referred to as the Effective Ionization Region (EIR). As such\, corona power loss is proportional to the size of the EIR. This pap er discusses the concept of effective ionization region from a theoretical perspective. Computer modeling was used to investigate the effect of geo metrical as well as electrical line parameters on the size of the EIR. A comparison is made between single and bundled conductor configurations. R esults show that the radius of the EIR of a single conductor that is energ ized at 800 kVDC drops by about 45% if the conductor were a sub-conductor in a four-bundle configuration.\n\nhttps://events.saip.org.za/event/7/cont ributions/5172/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5172/ END:VEVENT BEGIN:VEVENT SUMMARY:Quasi-elastic binary breakup in the interaction of 12C with 12C\, 93Nb and 197Au at 400 MeV inci dent energy DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5173@events.saip.org.za DESCRIPTION:Speakers: Joele Mira (University of Stellenbosch/iThemba LABS) \nIn heavy ion reactions the emission of Intermediate Mass Fragments (IMFs ) at forward angles is dominated by the direct break-up process. To improv e our understanding of this process in the reaction mechanisms involving t he interaction of light projectiles with light to heavy target nuclei\, a coincidence measurement was performed at iThemba LABS. Standard ΔE-E dete ctor telescopes were used to identify and measure the energies of the of t he correlated 8Be and alpha particles produced in the binary break-up of 1 2C projectiles at an incident energy of 400 MeV. While the 8Be fragments w ere detected in their ground state at a fixed angle of 9º\, the correlate d alpha particles were measured on the opposite side of the beam\, coverin g an angular range from 16º to 26º. Two dimensional energy spectra were generated for each alpha-particle angle in order to distinguish quasi-elas tic events from inelastic break-up events. These spectra also allowed to i dentify events originating from the interaction of the 12C beam with an H contaminant on the target foils and to subsequently correct for these even ts in the extraction of angular distributions for alpha particles in coinc idence with quasi-elastic 8Be particles. The angular distributions obtaine d from the interaction of 12C with 93Nb and 197Au show a smooth decreasing trend with respect to the alpha-particle angle\, which suggests that the binary break-up of 12C seems to be independent of the target nucleus. A de viation from this trend is however observed for the 12C target. As a first attempt to interpret these results a comparison between the measured angu lar distributions and GEANT4 simulations will be presented.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5173/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5173/ END:VEVENT BEGIN:VEVENT SUMMARY:2 µm pumped HBr Oscillator-amplifier DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5174@events.saip.org.za DESCRIPTION:Speakers: M J Daniel Esser (CSIR National Laser Centre)\nOptic ally pumped molecular lasers are attractive alternatives to generate high energy pulses in the mid-infrared wavelength range\, compared to non-linea r conversion that can suffer from optical damage. One such laser is based on HBr\, for which it has been experimentally demonstrated to emit laser l ight in the 4 µm wavelength range when pumped at 1.3 µm or at 2 µm. Pri or to the work presented here the highest reported output energy from an o ptically pumped HBr oscillator was 2.5 mJ in a 132 ns pulse at 50 Hz repet ition rate when pumped at 2.064 µm. \n\nTo scale the output energy of thi s technology we have designed and implemented an HBr master oscillator pow er amplifier (MOPA) system which was pumped by a Ho:YLF slab amplifier (pu mped by a Tm:YLF slab laser) which amplified the 70 mJ output of our singl e longitudinal mode 2.064 µm Ho:YLF oscillator (pumped by a Tm:fibre lase r) to 330 mJ per pulse at 50 Hz pulse repetition rate. \n\nInitially all t he available pump energy from the Ho:YLF amplifier was coupled into the HB r oscillator which produced up to 5.5 mJ per pulse for 200 mJ incident ene rgy\, at which point optical damage of the HBr oscillator cell window was observed due to the high intensity of the pump light in the double-pass co nfiguration. The oscillator was subsequently operated at a reduced input e nergy of 50 – 60 mJ at the point where the HBr laser was most efficient with respect to incident energy. \n\nThe HBr MOPA system produced 9 mJ per pulse when seeded with 2.3 mJ from the HBr oscillator and pumped with 200 mJ incident energy\, of which approximately 75% was absorbed when the HBr amplifier cell pressure was 60 mBar. The measured output wavelengths of t he HBr MOPA were 4.20 µm and 4.34 µm.\n\nhttps://events.saip.org.za/even t/7/contributions/5174/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5174/ END:VEVENT BEGIN:VEVENT SUMMARY:Industrial application for Global Quantum Communication DTSTART;VALUE=DATE-TIME:20110713T131500Z DTEND;VALUE=DATE-TIME:20110713T133000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5176@events.saip.org.za DESCRIPTION:Speakers: Abdul Mirza (UKZN)\nIn the last decade the quantum c ommunication community has witnessed great advances in photonic quantum cr yptography technology with the research\, development and commercializatio n of automated Quantum Key Distribution (QKD) devices. These first generat ion devices are however bottle necked by the achievable spacial coverage. This is due to the intrinsic absorption of the quantum particle into the c ommunication line. As QKD is of paramount importance in the future ICT lan dscape\, various innovative solutions have been developed and tested to ex pand the spatial coverage of these networks [R. Alleaume\, 2007\, C. Ellio tt\, 2004\, F. Xu\, 2009] as in the QuantumCity initiative. One such techn ique that is being considered for the creation of a global QKD network is to couple quantum-secured Metropolitan Area Networks(MANs) with secured gr ound-to-satellite links as access points to the global network. This techn ique\, however\, is susceptible to atmospheric parameters and provides ver y limited contact times for the quantum key exchange. \nAs parallel step t o the development of satellite-based QKD networks\, we intend to investiga ting the use of commercial aircrafts as secure transport mechanisms for a global QKD network. Commercial airliners create an ideal alternate global network for key distribution in terms of coverage\, reliability and freque ncy. Further the airports at each connected city have the appropriate supp orting infrastructure to serve as an access point to the global network.\n The quantum-secured global network will provide the infrastructure to crea te\, distribute and manage encryption keys for use in secure global commun ication.\nThe objective of this initial concept to create a proof of conce pt test network to investigate the aforementioned global QKD Network with the use of commercial airliners. The initial systems that are to be used w ill require the aircraft to be a trusted zone although certified tamper-pr oofing techniques will be used. The longterm objective is to upgrade the s ystems to contain quantum security through the use of quantum-powered memo ry solutions.\nA secure key management network layer will also be develope d and implemented to control the flow and usage of keys within the global network. The secure key management network layer will further control the distribution of keys and encryption within the MAN.\n\nhttps://events.saip .org.za/event/7/contributions/5176/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5176/ END:VEVENT BEGIN:VEVENT SUMMARY:Depth-resolved studies of plasma sprayed hydroxyapatite coatings b y means of diffraction techniques DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5178@events.saip.org.za DESCRIPTION:Speakers: Tshepo Ntsoane (Necsa)\nHydroxyapatite coating (HAp\ , Ca10(PO4)6OH2)\, produced by air plasma spraying\, was investigated for depth profiling behavior of phase composition\, crystallinity and residual stress using diffractometry techniques. Probing was carried out using con ventional 8 keV laboratory X-rays\, 11 keV and 100 keV radiations from 2nd and 3rd synchrotron facilities\, respectively. The latter employed measur ements in transmission geometry. Results showed HAp together with its ther mal products tetracalcium phosphate (TTCP)\, tricalcium phosphate (TCP) an d calcium oxide to be present throughout the coating thickness. Quantitati ve refinement results employing Rietveld refinement showed HAp and TTCP to be the two main phases\, with the former decreasing with depth whilst the latter increases. The largest changes occurred in the former showed a sig nificant decrease in the first 45 m. Crystallinity investigation indica ted the coating to be more crystalline at the near-surface region decreasi ng with depth below the surface. Both the normal stresses 11 and 33 show a change in stress state i.e. from compressive in first 135m to te nsile towards the coating-substrate interface.\n\nhttps://events.saip.org. za/event/7/contributions/5178/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5178/ END:VEVENT BEGIN:VEVENT SUMMARY:Beyond the Planar Limit in ABJM Theory DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5179@events.saip.org.za DESCRIPTION:Speakers: Badr Mohammed (PhD student at university of the Witw atersrand)\nABJM theory is an N=6 Superconformal Chern-Simons theory with gauge group U(N)XU(N). This gauge theory has been extensively studied in t he planar limit. Motivated by similar results for N=4 SYM\, the planar dil atation operator of ABJM theory has been mapped to the Hamiltonian of an i ntegrable system.\n\nRecently\, it has been argued that there are large N (but not planar) limits of N=4 SYM theory for which the dilatation operato r remains integrable. Indeed\, it reduces to a set of decoupled harmonic o scillators.\n\nMotivated by this result\, in this talk we study large N bu t non-planar limits of the ABJM theory. This is accomplished by constructi ng a complete set of gauge invariant operators for the theory. The free tw o point functions of these operators is computed and the action of the dil atation operator on these gauge invariant operators is constructed.\n\nhtt ps://events.saip.org.za/event/7/contributions/5179/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5179/ END:VEVENT BEGIN:VEVENT SUMMARY:Study of fusion evaporation channels in the 18 O+ 18 O reaction at 65 MeV DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5180@events.saip.org.za DESCRIPTION:Speakers: ESRA Khaleel (Stellenbosch University)\nThe fusion e vaporation reaction is mainly used to populate high spin states in atomic nuclei. Using stable beams\, a large number of β + unstable nuclei were s tudied i.e. those\nnuclei on the neutron deficient side of the valley of s tability. A plethora of experimental data is available in a wide range of mass A ∼ 20 to A ∼ 250 and was used to test the\nstatistical model cod es such as PACE\, CASCADE\, GEMINI.\nWith the advent of radioactive beams\ , a new landscape will be available to provide further tests to the models . However\, a study of fusion evaporation reactions will only be possible\ nwith sufficient beam intensities. In this research β − unstable nuclei were populated with one of the few reactions where nuclei approaching the neutron rich region can be populated with stable beams. Due to the relati vely low Coulomb barrier the evaporation of charged particles is a relativ ely strong channel. The DIAMANT light charged particle detector was set in coincidence with the AFRODITE γ-ray spectrometer to trigger between ligh t charged particles and γ-rays. The coincident data allows the evaporatio n channels involving p\, d\, t and particles to be identified due to excel lent particle identification with the CsI charged particle detectors\nwhil e the A\, Z of the residual nuclei are identified with the gamma transitio ns measured with germanium detectors.\nIn this work\, the cross sections o f the residual nuclei were calculated with the statistical model code CACA RIZO\, a Monte Carlo version of CASCADE based on the Hauser-Feshbach forma lism. Experimental and theoretical results and charged particle energy spe ctra are compared.\n\nhttps://events.saip.org.za/event/7/contributions/518 0/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5180/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermal damage study on diamond tools at varying laser heating pow er and temperature by Raman spectroscopy DTSTART;VALUE=DATE-TIME:20110714T103000Z DTEND;VALUE=DATE-TIME:20110714T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5181@events.saip.org.za DESCRIPTION:Speakers: Bathusile Masina (CSIR-National Laser Centre)\nDiamo nd tools are generally made of sintered polycrystalline diamond (PCD) on a hard metal tungsten carbide (WC-Co) substrate during the High Pressure Hi gh Temperature (HPHT) process. The diamond tools are used widely as cuttin g and drilling tools due to their unique combination of superior propertie s. However\, there are several issues that need to be resolved about the d iamond tools. At present it is known that diamond tools degrade with time as it is normally used at high temperatures\, but what is not known is the damage mechanism and how the degradation varies as a function of temperat ure. In this study\, we have made use of a laser based system to raise the temperature of the diamond tool and measure the diamond tool temperature. A study of the thermal damage on the diamond tool with respect to the las er heating power and temperature has been carried out using Raman spectros copy\; to determine the structure and composition of the resulting diamond tool. We have shown the radical changes on the diamond tool as the laser heating power and temperature increases.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5181/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5181/ END:VEVENT BEGIN:VEVENT SUMMARY:Isochronal annealing of argon ion bombarded GaAs with Raman and su rface Brillouin scattering DTSTART;VALUE=DATE-TIME:20110714T060000Z DTEND;VALUE=DATE-TIME:20110714T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5182@events.saip.org.za DESCRIPTION:Speakers: Kudakwashe Jakata (University of the Witwatersrand)\ nSemiconductors are important because of their numerous technological appl ications. As such\, there have been a number of investigations on the recr ystallization of amorphous GaAs. We present results of the isochronal anne aling of an ̴ 140nm amorphous layer of GaAs on a crystalline substrate p roduced by bombarding with 100 KeV argon ions with a fluence of 5×1015 io ns/cm2. Raman measurements were taken at room temperature which was the ba se temperature. Sharp peaks characteristic of polycrystalline GaAs were ob served at 600o C. Similar experiments have also been carried out with the technique of Brillouin scattering (SBS). SBS is a laser based technique us ed to study the acoustic phonons and elastic properties of materials. SBS spectra were collected using a 514.5 nm laser in a backscattering arrangem ent and analysed using a Fabry-P`erot interferometer supplied by Sandercoc k. Changes in the elastic properties during the isochronal anneal were obs erved at temperatures below 400o C\, in agreement with results previously obtained. The differences in the Raman spectroscopy and SBS results may be explained by the differences in the two techniques.\n\nhttps://events.sai p.org.za/event/7/contributions/5182/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5182/ END:VEVENT BEGIN:VEVENT SUMMARY:Magneto-optical trap - First step towards BEC DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5183@events.saip.org.za DESCRIPTION:Speakers: Malehlohonolo Semonyo (University of KwaZulu-Natal)\ nThe experimental demonstration of Bose-Einstein Condensation (BEC) is one of the most exciting developments of recent years. It has enabled researc hers to study a macroscopic quantum object with well controllable paramete rs. This has sparked a lasting flurry of experiments covering an enormous range of fields\, which have made significant contributions to our underst anding of atomic and molecular physics\, precision metrology and future te chnologies in quantum optics and quantum information science. The success of these experiments has led to the award of several Nobel Prizes in recen t years. \n\nThe first step in the construction of an experiment for reali zing a Bose-Einstein condensation is obtaining an appropriate reservoir of cold atoms with sub-microKelvin temperatures. In our experiment\, we coo led and trapped Rubidium atoms by using a combination of lasers and magnet ic fields known as a magneto-optical trap (MOT) [2]. The MOT will be used as a reliable and robust source of cold atoms that will be cooled further to create a BEC. We report here on the construction of the MOT\, in partic ular we describe the absorption saturation spectroscopy used for locking t he lasers\, the type of lasers used as well as the construction of the mag netic coils needed for generating the field used for spatial trapping of t he atoms. We also describe the design and construction of the glass cell we used as the vacuum chamber and finally report on our main objective of realizing a BEC through evaporative cooling.\n\nhttps://events.saip.org.za /event/7/contributions/5183/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5183/ END:VEVENT BEGIN:VEVENT SUMMARY:Entanglement dynamics in an oscillating bipartite Gaussian state c oupled to reservoirs with different temperatures DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5184@events.saip.org.za DESCRIPTION:Speakers: Anne Ghesquiere (National Institute for Theoretical Physics)\nAn entangled bipartite Gaussian state is coupled to two thermal reservoirs\, one for each particle. A harmonic oscillation is allowed betw een the two particles. The reservoirs are assumed to have different temper atures and to be coupled to the particles with different coupling strength s. This allows for a realistic situation where a bipartite state may be sh ared between two parties who ”keep” their part in different environmen ts. A master equation\, previously derived in the non-rotating wave approx imation\, is solved for the system. The effects of a variation in the bath temperature on the entanglement\, as well as that of the variation in cou pling strengths are shown. For high temperatures\, the entanglement vanish es if the coupling strength is large\, whereas for low temperatures\, the effect is reversed and it survives longest for a stronger coupling strengt h. The stationary dynamics of the system is also examined.\n\nhttps://even ts.saip.org.za/event/7/contributions/5184/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5184/ END:VEVENT BEGIN:VEVENT SUMMARY:Tungsten Oxide Nanostructures synthesized by Laser Pyrolysis DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5185@events.saip.org.za DESCRIPTION:Speakers: Malcolm Govender (CSIR)\nLaser pyrolysis has been us ed to synthesize tungsten oxide (WO3-x) nanostructures\, and here we repor t on the production of six-sided nanostars. The proposed mechanism used to explain the growth of the stars is the concentration difference and gradi ent mechanism which speculates that a high local concentration of one reac tant mixed with a low concentration of another reactant under ambient cond itions\, and the high concentration favoured the thermodynamic conditions for crystal growth and the low concentration resulted in a diffusion-contr olled kinetic environment for growth of hierarchical structures. Apart fro m precursor concentration\, further analysis was carried out to determine the influence of varying laser wavelengths and power densities in such exp eriments. The laser wavelength was varied between 9.22-10.82 m at a fix ed power density of 51.2 W/cm2\, and the laser power density was varied be tween 17-110 W/cm2 at a fixed wavelength of 10.6 m. Annealing the sampl es at 450oC in argon atmosphere for 17 hours appeared to be an essential s tep for further growth of nanostructures. Particle size and morphology wer e determined by scanning and transmission electron microscopy and the chem ical composition was determined by x-ray diffraction studies in conjunctio n with Raman spectroscopy and energy dispersive x-ray spectroscopy to conf irm the tungsten oxide phase as a function of the laser parameters.\n\nhtt ps://events.saip.org.za/event/7/contributions/5185/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5185/ END:VEVENT BEGIN:VEVENT SUMMARY:Optical properties of SrGa2S4:Ce3+ films prepared by pulsed reactive cross laser beam ablation method (PRCL A) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5186@events.saip.org.za DESCRIPTION:Speakers: Pulane Moleme (200922)\nSrGa2S4:Ce3+ thin films are promising for full colour thin-film electroluminescent (EL) and field emis sion displays (FED’s) because of its good optical properties. These film s were previously prepared using several different techniques such as sput tering (RF)\, molecular beam epitaxy (MBE)\, reactive multi-source deposit ion (MSD)\, metal-organic chemical vapour deposition (MOCVD)\, deposition from binary vapours (DBV) and Pulsed Laser Deposition (PLD). \nIn the pres ent study\, Ce doped SrGa2S4 thin films were prepared for the first time u sing pulsed reactive cross laser ablation (PRCLA) technique. Characterizat ion of the films was carried out with scanning electron microscopy (SEM)\, atomic force microscopy (AFM) and x-ray diffraction (XRD). Cathodolumines cence (CL) and photoluminescence (PL) measurements were taken with a S2000 Ocean Optics Spectrometer and a Varian Cary Eclipse Fluorescence Spectrop hotometer respectively. The substrate temperature\, number of pulses and t he working pressure are the parameters that were varied during the prepara tion of the thin films. \nA single-phase SrGa2S4 layer with high crystall inity was obtained at the growth temperature of 400oC. XRD patterns also s howed that the properties of the films are relatively sensitive to substra te temperature. PL showed one broad band that can fit two Gaussian peaks a ccording to the two Ce3+ emission peaks which are known to originate from radiative transitions from 5d (T2g) → 4f (2F5/2) and from 5d (T2g) → 4 f ((2F7/2) respectively. CL showed two broad emission peaks around 441nm a nd 478nm which are due to Ce3+ transitions. The AFM images of the films pr epared had a rough surface\, which became smooth after annealing in vacuum at 700oC temperature. Non-uniformity in particles of the films and rough surface were observed from the SEM images.\n\nhttps://events.saip.org.za/e vent/7/contributions/5186/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5186/ END:VEVENT BEGIN:VEVENT SUMMARY:The radioactive ion beam facility project at iThemba Labs and its potencial uses for materials research DTSTART;VALUE=DATE-TIME:20110714T090000Z DTEND;VALUE=DATE-TIME:20110714T091500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5187@events.saip.org.za DESCRIPTION:Speakers: Carlos Pineda-Vargas (iThemba LABS)\nAn introduction to the new development project on the implementation of a radioactive ion beam (RIB) facility at iThemba LABS will be presented. In particular with relation to the uses of the RIB for the application of research in conden se matter and materials research. Some leading examples by international l aboratories using radioactive nuclei as probes to enhance the understandin g of structural and/or electronic/magnetic lattice environment in material s (metals\, insulators or semiconductors) will be also presented. The main procedures of such investigations are implantation induced lattice damage and its annealing behavior\, the lattice site of the implanted ion after annealing\, the interaction between impurities or impurities and intrinsic defects\, the electronic and optical properties of the implanted species and the identification of defects and impurities. The understanding and th e control of diffusion profiles of intrinsic and extrinsic defects particu larly in semiconductors is significantly enhanced using radioactive tracer diffusion.\n\nhttps://events.saip.org.za/event/7/contributions/5187/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5187/ END:VEVENT BEGIN:VEVENT SUMMARY:Aspects of DC circuits: a fine grained investigation of student co nceptions DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5188@events.saip.org.za DESCRIPTION:Speakers: Ignatius John (CPUT)\nThis is the second part of our study\, where we are analysing the reasons and explanations behind each a nswer of each student. In the first part of our study (2010) using an op en circuit (battery\, single wire\, resistive element) in which the resist ive element (resistor\, heating element\, light bulb) and the words (“cu rrent’\, “charge flow”) are inter-changed in an electrically equival ent circuit and the students answers were found to be influenced by the di fferent elements and words.\n\nhttps://events.saip.org.za/event/7/contribu tions/5188/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5188/ END:VEVENT BEGIN:VEVENT SUMMARY:Graphene Coatings:Snythesi/Physical-Chemical Investigations DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5189@events.saip.org.za DESCRIPTION:Speakers: Nangamso Nathaniel Nyangiwe (iTemba LABS and Univers ity of the Western Cape)\nThe main aim of this project is to synthesize\, isolate\, identify and characterize graphene\, defined as a one-atom layer of hexagonally bonded carbon atoms using mechanical exfoliation method. M oreover\, this technique is based on pulling apart the layers of a piece o f highly oriented pyrolytic graphite(HOPG) and transfer layers from the g raphite onto a SiO2 substrate. Graphene is the first truly 2D dimensional material and has a number of remarkable mechanical and electrical properti es. It is substantially stronger than steel\, and it is very stretchable. The thermal and electrical conductivity is very high and it can be used as a flexible conductor. Graphene is a zero-gap semiconductor and has a nove l electron structure\, with its conduction and valence bands meeting at th e Dirac point. This characteristic enables the electron conduction by shif ting the Fermi level with applied field.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5189/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5189/ END:VEVENT BEGIN:VEVENT SUMMARY:Pc3 pulsations during low density events DTSTART;VALUE=DATE-TIME:20110715T071500Z DTEND;VALUE=DATE-TIME:20110715T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5190@events.saip.org.za DESCRIPTION:Speakers: Stefan Lotz (SANSA: Rhodes University)\nWe study the generation of Pc3 geomagnetic pulsations (22 – 100 mHz) measured at Tih any\, Hungary during intervals of very low solar wind (SW) proton density (low density events - LDE’s) when Np ~ 1/cc. We know the main SW based d rivers of Pc3's are SW velocity and interplanetary magnetic field (IMF) di rection. However\, it is observed that under very low SW density pulsation activity measured on the ground is paused\, regardless of otherwise favou rable conditions. A simple statistical study is performed to show the depe ndence of pulsation activity on Np\, and we estimate a threshold Np\, belo w which pulsations cease. Furthermore we use the growth rate of the ion be am instability\, that generates the ULF waves upstream of the bow shock (w hich drive Pc3's)\, to explain the observed dependence of Pc3 pulsations o n solar wind density.\n\nhttps://events.saip.org.za/event/7/contributions/ 5190/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5190/ END:VEVENT BEGIN:VEVENT SUMMARY:Study of di-photon events in the ATLAS detector at the LHC : cross -section measurement and application to Higgs searches in the di-photon ch annel DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5191@events.saip.org.za DESCRIPTION:Speakers: Mathieu Aurousseau (University of Johannesburg)\nThe measurement of the isolated di-photon cross-section at the LHC is crucial as these events constitute an irreducible background to new physics proce sses\, such as a Higgs boson or graviton decaying to two photons. These ev ents also provide important information for the understanding of QCD proce sses. The di-photon cross-section has been measured in ATLAS using the ful l 2010 data sample\, corresponding to an integrated luminosity of 37 pb-1. Results as a function of the di-photon invariant mass\, transverse moment um and azimuthal separation are presented and compared with NLO theoretica l predictions. Focusing on the invariant mass region between 100 and 150 G eV where a light Higgs boson is searched for in the di-photon channel\, ex clusion limits are set on the Standard Model prediction. The results obtai ned are already at the level of the results from TeVatron experiments in t his channel.\n\nhttps://events.saip.org.za/event/7/contributions/5191/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5191/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational modelling of Zr-Nb alloys by solid solution approach DTSTART;VALUE=DATE-TIME:20110714T114500Z DTEND;VALUE=DATE-TIME:20110714T120000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5192@events.saip.org.za DESCRIPTION:Speakers: Moyahabo Chuma (Materials Modelling Centre)\nWe use density functional theory to investigate the structural\, elastic properti es and energetic stabilities of Zr\, Nb and its alloys in the alpha and be ta phases\, employing pseudopotential plane wave methods within the Pardew -Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA). The structu res were fully optimized in a non-magnetic state\, allowing atomic positio ns\, cell volume and shape to change. Lattice parameters for the pure phas es gave excellent agreement with the available experimental data. We also found that the phonon dispersions curves display soft-modes for the metast able beta-Zr phase which is lacking on the alpha-Zr and beta-Nb\, conditio n of mechanical stability. The solid solution calculations show that an in crease in the Nb contents destabilizes the structures in both the alpha an d beta phases. Interestingly\, the calculated elastic moduli for Zr-2.3%Nb are in good agreement to the experimental results of Zr-2.5%Nb.\n\nhttps: //events.saip.org.za/event/7/contributions/5192/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5192/ END:VEVENT BEGIN:VEVENT SUMMARY:Numerical Field Analysis of the Magnets for a proposed Ionisation Beam Profile Monitor for High Current Synchrotron and Cooler Rings. DTSTART;VALUE=DATE-TIME:20110715T091500Z DTEND;VALUE=DATE-TIME:20110715T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5193@events.saip.org.za DESCRIPTION:Speakers: John Garrett de Villiers (iThemba LABS)\niThemba LAB S was requested by the Institut für Kernphysik at Forschungszentrum Jüli ch\, Germany\, to design and calculate a magnet system for a proposed non- destructive Ionization Beam Profile Monitor (IBPM) that can measure beam p rofiles using the secondary ions produced in the rest gas\, planned to be implemented with the FAIR-GSI project in Darmstadt\n\nApart from the geome trical restrictions by the available space\, the main requirements for the magnet system are to comply with the specified field intensity and homoge neity at the plane of measurement and to deliver the primary beam unchange d and aligned with the original beam direction within the GSI storage ring . \n\nThe calculated magnets for the IBPM consists of four window-frame\, room-temperature\, water-cooled\, laminated\, dipole DC-electromagnets in line with the primary beam. The inner two dipoles of the set are respectiv ely used for horizontal and vertical beam profile analysis and the correct delivery of the beam from the system is facilitated with the aid of two c orrector magnets. The magnets are mounted outside and around the vacuum ch amber that contains other essential components and therefore will have unu sually large pole gaps that are in the order of 0.5 m\, which\, together w ith the relative short drift lengths between the magnets\, cause significa nt interference between the magnetic flux distributions of the magnets. Th is necessitated the use of 3D numerical field analysis that incorporates a l the magnets.\n\nThe field homogeneities in the regions where the beam pr ofiles are to be measured were found to be very sensitive to the magnet ge ometries and layout\, but a workable solution was found and the calculated results of these magnets and multi-pole and ion beam optics analysis of t he system will be presented.\n\nhttps://events.saip.org.za/event/7/contrib utions/5193/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5193/ END:VEVENT BEGIN:VEVENT SUMMARY:Spectroscopic studies of nanofluorides doped with Ln3+ synthesized via thermal decomposition of organic precursors DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5195@events.saip.org.za DESCRIPTION:Speakers: Marek Gusowski (Department of Physics University of the Free State)\nThere has been a growing demand for quantum cutting and u pconverting efficient nano luminescent materials during the last decades. Wide band gap luminescent materials\, specially the fluoride\, are one of the major role players. Due to a number of advantages such as the excelle nt transparency in theinfrared (IR) to far ultraviolet (UV) range and low- energy phonons as well as low toxicity they have recently gathered conside rable attention for their potential applications in bioimaging\, disease d etection and diagnostics. The same group of materials having downconversio n characteristics can be applied for the improvement of solar cell effici ency in the quantum cutting processes. Here\, we report on the synthesis a nd luminescence properties of colloidal double fluorides which belong to the general composition MF-LnF3 co-doped with optically active rare earth ions. During the thermal decomposition of the alkaline metals trifluoroace tate and lanthanide trifluoroacetate precursors NaYF4\, KYF4\, and KY3F10 samples have been obtained. The noncoordinating\, high-boiling solvent oct adecene was selected as the growth medium for the nanoparticles. Oleiamine and oleic acid were employed as the surfactant\, which attached to the p article surface during the crystal growth and kept the nanoparticles well- separated from each other. Nanocrystals of RE3+ doped in the range of 40 n m were obtained. High Resolution Transmission Electron Microscopy (HRTEM) was used to evaluate the morphology and particle size distribution (PSD) o f the prepared nanoparticles. The structural (XRD) and spectroscopic prop erties of optically active lanthanides doped fluorides have been determin ed based on the excitation spectra\, emission spectra and luminescence dec ay curves recorded in the UV-Vis spectral regions.\n\nhttps://events.saip. org.za/event/7/contributions/5195/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5195/ END:VEVENT BEGIN:VEVENT SUMMARY:Transmission electron microscopy investigation of radiation damage caused by keV implantation in single-crystal diamond. DTSTART;VALUE=DATE-TIME:20110715T094500Z DTEND;VALUE=DATE-TIME:20110715T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5196@events.saip.org.za DESCRIPTION:Speakers: Emmanuel Korawinga Nshingabigwi (University of the W itwatersrand)\nAn understanding of the types of defects produced during th e doping/implantation of diamond remains essential for the optimization of high-temperature\, high-power electronic applications.\n\nThus this study focuses on investigating the nature of the radiation damage produced duri ng the multi-implantation of carbon ions in synthetic type Ib and natural diamonds\, according to the CIRA (Cold-Implantation-Rapid-Annealing) routi ne. The implanted and annealed diamond samples were characterized using b right field transmission electron microscopy (BFTEM) in conjunction with s elected area diffraction (SAD).\n\nFor low fluence implantations\, the dam aged diamond retains its crystallinity after annealing at 1600K\, while i mplanting using doses above the amorphisation/graphitization threshold\, f ollowed by rapid thermal annealing (RTA) at 1600K\, results in a multi-lay er of graphite/amorphous carbon close to the surface.\n\nhttps://events.sa ip.org.za/event/7/contributions/5196/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5196/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermal and electronic transport studies of the Kondo energy scale in the heavy-fermion system CeCu5-xAlx DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5197@events.saip.org.za DESCRIPTION:Speakers: Andre Strydom (University of Johannesburg)\nThe bina ry compound CeCu5 is an archetypal heavy-fermion Kondo lattice with an ant iferromagnetic ground state. Strong hybridization effects between the loca lized 4f-electron moment and conduction electrons result in incoherent spi n scattering in the electronic transport at high temperatures\, but with a n effective magnetic moment nearly equal to that of the free-ion Ce3+ stat e. Long-range magnetic ordering at TN = 3.9 K and the Kondo temperature TK =2.2 K are of similar energy scales\, making this system ideally suited to studies of competing magnetic interactions in the strongly correlated ele ctron class of systems. In this work we synthesized a series of pseudo-bin ary compounds CeCu5-xAlx. The dilution of Cu by Al results in augmenting t he electronic density of states close to the Fermi energy\, which is also the location of the magnetic and hybridized 4f electron levels resonance.\ nOur studies of the temperature and magnetic field dependencies of thermoe lectric power and electrical resistivity in the CeCu5-xAlx series of compo unds will be discussed in terms of comparitive calculations of the Kondo e nergy scale from data of magnetoresistivity (the single-ion Bethe Ansatz t heory) and from the thermoelectric power (phenomenological description in presence of intermediate valency) by means of two different theoretical mo dels.\n\nhttps://events.saip.org.za/event/7/contributions/5197/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5197/ END:VEVENT BEGIN:VEVENT SUMMARY:Validating The Auroral Zone Lower Ionosphere Model DTSTART;VALUE=DATE-TIME:20110715T061500Z DTEND;VALUE=DATE-TIME:20110715T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5198@events.saip.org.za DESCRIPTION:Speakers: MICHAEL AFFUL (UNIVERSITY OF CAPE TOWN)\nThe ionosph ere is known to behave predictably as a function of solar zenith angle\, s olar activity and season. In the past\, analytical models have been develo ped to predict the behaviour of the ionosphere according to these paramete rs. This project aims to validate the IMAZ model\, a recently developed em pirical model for the lower ionosphere in the auroral zone to predict elec tron densities in the D-region as well as compare to other existing models designed for the same purpose. Rocket-bourne measurements were used as a database of reliable lower ionosphere data. A response in the lower ionosp here was analysed based on the contribution of some input parameters. The output was the electron density for a given set of inputs at a particular pressure surface as predicted by the IMAZ model. Furthermore\, the ability of the IMAZ model to predict accurately within the auroral zone was estab lished and the need for further improvements was presented.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5198/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5198/ END:VEVENT BEGIN:VEVENT SUMMARY:Stabilities of low and high pressure structures of CoPO4 and MnPO4 DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5199@events.saip.org.za DESCRIPTION:Speakers: NDANDULENI LESLEY LETHOLE (SAIP)\nCrystals of LiFePO 4 and related materials have recently received a lot of attention due to t heir promising use as cathodes in rechargeable lithium ion batteries. Thes e compounds have been known for good stability and low cost. The Co based compound LiCoPO4\, has rapidly become of particular interest as recent mea surements found a potential of 4.8 V\, while the Mn based compound structu re has an equilibrium voltage of 4.1 V\, which is compatible with the elec trolyte presently used in Li-ion batteries. \nBefore the introduction of a morphisation recrystallisation methods to quaternary LiMPO4 (M=Mn and Co)\ , it will be important to commence with ternaries (CoPO4 and MnPO4)\, sinc e ternaries are less complex. Hence we investigate the mechanical\, optica l and structural stabilities of the different polymorphs of CoPO4 and MnPO 4\, before atomistic simulations\, by employing the pseudo-potential plane wave calculations within the Local Density Approximation (LDA) and Pardew- Wang Generalized Gradient Approximation (GGA).\n\nhttps://events.saip.org. za/event/7/contributions/5199/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5199/ END:VEVENT BEGIN:VEVENT SUMMARY:Statistical Analysis of Outer Electron Radiation Belt Dropouts: Ge osynchronous and Low Earth Orbit Responses During Stream Interfaces DTSTART;VALUE=DATE-TIME:20110715T101500Z DTEND;VALUE=DATE-TIME:20110715T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5216@events.saip.org.za DESCRIPTION:Speakers: Olakunle Ogunjobi (University of KwaZulu-Natal)\nThe OMNI-2 data set enables a correlation study of solar wind and geomagnetic parameters\, allowing the stream Interfaces events (SIs) to be examined. A superposed epoch analysis of these events was performed to determine the threshold levels of IMF Bz and other geophysical parameters. Based on ene rgy\, temporal and spatial characteristics\, statistical analysis of elect ron flux data from LANL-SOPA and NOAA-POES satellites were use to study ou ter zone electron dropouts and precipitation. The deepest minimum of elect ron flux was observed after the impact of a SI\, which coincided with the time of slower-decaying peak of electron precipitation. Result suggest tha t the mechanism causing the precipitation could also be responsible for th e observe electron flux dropout during Stream Interference.\n\nhttps://eve nts.saip.org.za/event/7/contributions/5216/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5216/ END:VEVENT BEGIN:VEVENT SUMMARY:Atomistic Simulation Study on Lithiated Manganese Dioxide Nanostru ctures DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5200@events.saip.org.za DESCRIPTION:Speakers: Kenneth Kgatwane (University of Limpopo)\nNanostruct ured materials are used to develop lithium-ion batteries with high energy\ , high-rate capability and excellent cycling stability due to their huge s urface area\, short distance for mass and charge transport and freedom for volume change. They are capable of reversibly accommodating large amount of Li\, on intercalation mesoporous β-MnO2 can accommodate Li/Mn = 0.92:1 with 81% capacity retention. This is contrast to a very limited amount of Li\, that could be intercalated electrochemically into the bulk crystalli ne MnO2. The electrochemical properties of MnO2 are governed by the rich a nd complex microstructure it accommodates and characterisation at the atom istic level is difficult experimentally. \n\nAtomistic computer simulation s offer a unique platform of exploring structural features at the nanoscal e. Simulated amorphisation and recrystallisation technique\, involving ten s of thousands of atoms\, has been successfully used to generate models of various nano-forms of the complex manganese dioxides\, which include micr ostructural details. In the current study\, we apply this method to study lithium insertion into the nanospheres\, nanosheets\, nanorods and nanopor ous structures of the binary manganese dioxides. Different Li concentratio ns (up to Li:Mn = 0.73:1) were inserted into the different nanostructures. Molecular dynamics simulation under the NPT ensemble was performed\, in o rder to allow the system to expand. The variation of mechanical properties and changes of microstructural features with low and high lithium concent ration are investigated. The resulting microstructure provides valuable in sights into the origins of electrochemical activity which could make it a suitable battery electrode.\n\nhttps://events.saip.org.za/event/7/contribu tions/5200/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5200/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigation of S diffusion in bulk Fe – a DFT study DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5201@events.saip.org.za DESCRIPTION:Speakers: Pieter Barnard (UFS)\nThe diffusion of a dilute S so lution in Fe was investigated in order to determine the diffusion path and the energy required\, Q\, for diffusion in a bulk Fe crystal structure. D ifferent pseudototentials were investigated in order to determine the pseu dototential that best describes the ground state of the bulk Fe structure. Pseudototentials that gave a good description of the ground state were su bsequently tested to find the appropriate bulk cell size that will give th e best description of S diffusion in Fe. This was done by calculating the binding energy of pure Fe and that of S in Fe for different cell sizes and to find the cell size were the binding energy converges. Using the approp riate cell size\, an investigation was performed in order to determine the diffusion mechanism of S in Fe. The nudged elastic band method was employ ed to calculate the minimum energy path of S diffusion in Fe\, which gives the energy required for diffusion of S in Fe\, namely the activation ener gy\, Q. Activation energies for both interstitial S and substitutional S i n the Fe crystal was calculated by the nudged elastic band method in order to determine the most energetically favourable diffusion mechanism for S in bulk Fe.\n\nhttps://events.saip.org.za/event/7/contributions/5201/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5201/ END:VEVENT BEGIN:VEVENT SUMMARY:Determining the bulk concentration of S in Fe-S: a Auger electron spectroscopy study DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5202@events.saip.org.za DESCRIPTION:Speakers: Pieter Barnard (UFS)\nAn Auger electron spectroscopy study was performed in order to determine the bulk concentration of S in Fe-S. A number of studies have been performed that employs AES to study di ffusion and segregation in metals. The most common application is the use of the technique to determine the diffusion parameters i.e. activation ene rgy (Q) and the pre-exponential factor (D0). This approach makes use of a known bulk concentration and uses Fick`s semi-infinite solution to extract the diffusion parameters. Our research employs AES to determine the bulk S concentration in Fe-S. With the diffusion parameters obtained from liter ature and the use of the adapted t1/2 equation\, derived from Fick`s semi- infinite solution\, the bulk concentration of S was determined. AES measur ements were performed at various temperatures for a fixed period of time i n order to observe the segregation of S from the bulk of Fe to the surface . These constant temperature measurements were performed at temperatures i n the range 200-800 °C where the temperature was increased in increments of 50 °C. A non-linear least square software program was developed to fi t the adapted t1/2 equation to the data\, in order to extract values for t he bulk concentration of S. An average concentration value was calculated for the range of temperatures investigated and compared to concentration v alues obtain by linear programmed heating performed over the same temperat ure range with a linear increase in temperature.\n\nhttps://events.saip.or g.za/event/7/contributions/5202/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5202/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and photoluminescence properties of Tb3+-cdop ed SrZnAl2O4 nano crystals phosphor prepared via com bustion process DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5203@events.saip.org.za DESCRIPTION:Speakers: Samy Shaat (Department of Physics at University of F ree State)\nTb3+-doped SrZnAl2O4 nanocrystalline phosphor with good crysta llinity were successfully prepared by a combustion method at a relatively low temperature (500o-C)\, using urea as fuel and metal nitrates as precur sors. The effects of Sr and Zn concentrations on the structure and lumines cent properties of the material were investigated. In addition\, different concentrations of Tb3+- were also used to determine the concentration tha t gives maximum intensity. The samples obtained were characterized by X-r ay diffraction\, scanning electron microscopy (SEM) and transmission elect ron micrograph (TEM)\, and photoluminescence (PL) properties of doped samp les were investigated. The green emission obtained is associated with 5-D4 →7F5 transitions of Tb3+- at 543 nm. This emission was shown to increas e with the concentration of Tb3+- and it quenched at high concentrations. This was attributed to concentration quenching effects. The SrZnAl2O4:Tb3 +- phosphor was evaluated for possible application in different types of l ight emitting devices.\n\nhttps://events.saip.org.za/event/7/contributions /5203/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5203/ END:VEVENT BEGIN:VEVENT SUMMARY:Hi-speed Random Number Generator DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5204@events.saip.org.za DESCRIPTION:Speakers: Adedayo Olatinwo (University of Kwazulu Natal)\n Rec ently\, I . Kanter et al\, developed an Ultra fast random bit generator\, based on a semiconductor laser\, having time delayed self-feedback\, which operates reliably at rate up to 300 GB/s. The method uses a high derivati ve of the digitized laser intensity and generates the random sequence by r etaining a number of the least significant bits of the high derivative val ue. The generator is insensitive to laser operational parameters and elimi nate the necessity for all external constraints such as incommensurate sam pling rates and laser external cavity round trip time. The randomness of l ong bit string is verified by standard statistical tests\n\n An improved Random Number generator is proposed by making use of Zener noise. At the s ame time Field programmable Gateway Array for processing the final genera ted random numbers instead of using the Nth and Least Synthetic Bits (LSBS ). All the output from the FPGA will be transferred through USB cable into a connected PC where the random number is interpreted.\n\nhttps://events .saip.org.za/event/7/contributions/5204/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5204/ END:VEVENT BEGIN:VEVENT SUMMARY:On TeV Gamma-rays from Galactic X-ray Binary Systems with H.E.S.S. array DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5205@events.saip.org.za DESCRIPTION:Speakers: Isak Delberth Davids (North-West University\, Potche fstroom Campus)\nWith the birth of the new generation ground-based gamma-r ay imaging atmospheric Cherenkov telescope arrays (such as H.E.S.S.\, MAGI C and VERITAS)\, there is a growing need to probe X-ray binary stars for v ery high energy gamma-ray emissions. Since the discovery of the first extr a-solar X-ray binary (XRB)\, namely the Scorpius X-1 in 1962\, XRBs are no w well-established systems in the realm of X-ray astronomy. Today Scorpius X-1\, with X-ray output energy 100 000 times greater than the total radia tion of the Sun at all wavelengths\, is today known as a microquasar. In o rder to foster the multi-wavelength campaigns of the day\, we selected can didate XRBs from the Galaxy that were observed by H.E.S.S. for purposes of searching for significant TeV gamma-ray emission from these. Paredes (200 8) confirmed four XRBs to be candidates that can be listed on the gamma-ra y sky map. These were PSR B1259-63\, LS I +61 303\, LS 5039 and Cygnus X-1 . From a survey of 125 known XRBs\, Dickinson (2009) reported no conclusiv e detections of TeV emissions. The present study presents the Cherenkov te chnique\, a briefing on X-ray binaries\, known radiation mechanisms\, rele vant analysis techniques\, and report on the preliminary results of Galact ic XRBs that do not add any of the candidate XRBs to the envisaged catalog ue of TeV gamma-ray binaries. It is an astrophysical hope that the envisag ed CTA (Cherenkov Telescope Array)\, which may be hosted by South Africa\, will provide the anticipated discoveries\, providing a deep insight of th e TeV gamma-ray sky.\n\nhttps://events.saip.org.za/event/7/contributions/5 205/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5205/ END:VEVENT BEGIN:VEVENT SUMMARY:First time resolved diffraction experiments with the Stellenbosch Ultrafast Electron Gun DTSTART;VALUE=DATE-TIME:20110714T120000Z DTEND;VALUE=DATE-TIME:20110714T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5206@events.saip.org.za DESCRIPTION:Speakers: Kerstin Haupt (LRI\, Stellenbosch University)\nWe ob serve ultrafast structural dynamics in crystals. For that\, we use the 'Pu mp Probe Technique': The 'Pump' triggers a fast process\, the 'Probe' take s a snapshot of it at a specific time. We are interested in observing proc esses\, which happen on a picosecond timescale. That means\, the duration of our 'Probe' must be in the order of ~ 100 fs. The only source of a 100 fs short signal\, produced and controlled by humans\, is a short pulsed La ser. We therefore convert short laser pulses to electron pulses of about t he same duration (~ 200 fs). The electrons get diffracted on the atomic st ructure of the sample and form a pattern on the detector\, which is record ed by a 16 bit camera. From the diffraction pattern we can work out the st ructure of the sample material at that specific time step. By repeating th e experiment for different time delays between pump and probe\, we gather information about the whole process we want to observe.\nWe will show and discuss our latest measurements on charged density waves in TaSe2.\n\nhttp s://events.saip.org.za/event/7/contributions/5206/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5206/ END:VEVENT BEGIN:VEVENT SUMMARY:Miniaturization of electrostatic space thrusters using ionization/ acceleration coupling in discharge mode DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5207@events.saip.org.za DESCRIPTION:Speakers: phil ferrer (wits)\nMiniaturization of space prolusi on systems has many advantages\, both from an economic and performance per spective. One of the most promising propulsion technologies\, the gridded electrostatic ion engine\, resists miniaturization due to the poor down-sc aling characteristics of the ion producing discharge chamber. We investiga te a system where the ionization and acceleration mechanisms are coupled\, thereby making the same electric field responsible for both. This sideste ps the need of a discharge chamber and allows for design of a much smaller engine. We introduce the concept and present some initial results\, comme nting on the feasibility of such a design.\n\nhttps://events.saip.org.za/e vent/7/contributions/5207/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5207/ END:VEVENT BEGIN:VEVENT SUMMARY:Ab initio studies on stabilities of products related to Li/S and L i/O batteries DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5208@events.saip.org.za DESCRIPTION:Speakers: Cliffton Masedi (University of Limpopo)\nAb-intio De nsity Fuctional Theory has been employed to investigate the stabilities of Li< sub >2< /sub >O\, Li< sub >2< /sub >S\, Li< sub >2< /sub >O< sub >2< /sub > and Li< sub >2< /sub >S< sub >2< /sub > systems. Calculations were carried out utilizing Plane-wave Pseudopotential method within GGA-PBE usi ng VASP CODE.\nWe found good agreement between predicted data and experim ental data of lattice parameters . The elastic constant for Li< sub >2< / sub >O\, Li< sub >2< /sub >S accord well with experimental results and tho se of Li< sub >2< /sub >O< sub >2< /sub > and Li< sub >2< /sub >S< sub >2< /sub > are reasonably predicted\, and satisfied stability conditions. P honon dispersion of Li< sub >2< /sub >O and Li< sub >2< /sub >S compare we ll with those obtained from neutron scattering experiments. We predicted p honon dispersion of Li< sub >2< /sub >O< sub >2< /sub > suggest that the s tructure is stable\, while those of Li< sub >2< /sub >S< sub >2< /sub >< s ub >2< /sub > display soft modes along along Г direction hence suggestin g structural instabilities. Furthermore phonon density of states attribute the instability to the vibrations of the sulphur atoms in the ab plane.\n \nhttps://events.saip.org.za/event/7/contributions/5208/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5208/ END:VEVENT BEGIN:VEVENT SUMMARY:Learners’ and prospective teachers’ productive intuitive conce ptions in magnetism DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5209@events.saip.org.za DESCRIPTION:Speakers: Benita Erasmus (North-West university)\nDuring the p ast decades there has been an increasing interest in alternative conceptio ns in physics. An alternative conception in science refers to a conceptio n which in some aspects is contradictory to or inconsistent with the conce pt as intended by the scientists. Research in this domain tries to answer questions such as which misconceptions occur\, what are their origins\, ho w extensive are they and what can we do about them? Investigations of conc eptual change approaches to remedy learners’ alternative conceptions oft en showed that they are resistant to change. \n\nIn this study we intend t o follow a different approach that focuses more positively on productive i ntuitive concepts of learners and students\, i.e. concepts that may serve as a potential base for further refinement towards the science concept. St udents’ and learners’ initial conceptions are investigated and analyze d for productive resources. A teaching sequence will then be developed bas ed on conceptual refinement of their resources rather than using a cogniti ve conflict strategy that intends to accomplish conceptual change of alter native conceptions.\n\nThe study is still in progress and the presentation will discuss the results of interviews conducted with learners in grades 10\, 11 and 12 and with prospective teachers enrolled in the first year un iversity physical sciences programme. The learners’ and students’ intu itive concepts were probed in the field of magnetism. A clinical interview approach was followed with semi-structured open-ended questions. The data was transcribed and coded according to a conceptual development scheme. \ n\nThe results of the interviews will inform the compilation. The subject s in depth understanding of magnetic phenomena’s and their positive intu itive concepts were probed and documented. The results of completing the i nterviews lead to the compilation of a structured questionnaire to investi gate the consistency of potential positive intuitive concepts in magnetism . The findings lead to the potential refinement of specific magnetic conce pts to the scientifically correct.\n\nThe results showed deficiencies in t he subjects’ knowledge in magnetism as well as productive intuitive conc epts that can be used for further refinement to a more scientifically corr ect understanding of magnetic concepts.\n\nhttps://events.saip.org.za/even t/7/contributions/5209/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5209/ END:VEVENT BEGIN:VEVENT SUMMARY:Constraining the Phase Space for Chameleon Dark Energy DTSTART;VALUE=DATE-TIME:20110714T121500Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5210@events.saip.org.za DESCRIPTION:Speakers: Muzikayise Sikhonde (University of Cape Town)\nA num ber of solutions to the dark energy problem have been proposed in literatu re\, the simplest is the cosmological constant Λ. But the cosmological co nstant lacks theoretical explanation for its extremely small value\, thus dark energy is more generally modeled as quintessence scalar field rolling down a flat potential. For the quintessence scalar field to be evolving o n\ncosmological scales to day its mass must be of order H0 \, which is the present value of the Hubble constant. A scalar field φ whose mass varies with the background energy density was proposed by Khoury and Weltman(200 3). This scalar field can evolve cosmologically while having coupling (β) to different matter fields of order unity. Such a scalar field also coupl es to photons in the presence of an external magnetic field via the φF2 i nteraction\, where F stands for the electromagnetic field strength tensor. The chameleon(φ)-photon coupling of this nature causes a conversion of p hotons to light Chameleon(φ) particles and vice versa. In this work we in vestigate this effect on pulsars\, and we constrain the parameter space of this theory.\n\nhttps://events.saip.org.za/event/7/contributions/5210/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5210/ END:VEVENT BEGIN:VEVENT SUMMARY:Enhancement of hydrogen production using biomass gasification proc ess DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5211@events.saip.org.za DESCRIPTION:Speakers: Sampson Mamphweli (University of Fort Hare\, Institu te of Technology)\nHydrogen production from biomass holds the greatest pro mise\, since biomass is abundantly available everywhere in the world. Howe ver\, hydrogen from biomass has major challenges. The yield of hydrogen is low from biomass since the hydrogen content in biomass is low to begin wi th (approximately 6%) and the energy content is low due to the 40% oxygen content of biomass. A novel gasification method for hydrogen production fr om carbonaceous materials using a CO2 sorbent has been widely used. It mai nly uses steam as gasification agent. For this study the above method has been adopted to test if it will work for air-blown biomass gasifiers. The main purpose of this project is to enhance the yield of hydrogen from air- blown biomass gasification process. The produced hydrogen will be further separated and purified for fuel cell application. Ultimate and proximate a nalyses of the biomass material were conducted and the obtained results we re used for the simulations in order to determine the efficiency of the ga sifier with biomass and biomass/sorbent blends. It was found that the biom ass/sorbent blends increase the yield of not only H2 but also other syngas constituents such as CO leading to enhancement of the gasifier efficiency since it is dependent on the volume of combustible gases.\n\nhttps://even ts.saip.org.za/event/7/contributions/5211/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5211/ END:VEVENT BEGIN:VEVENT SUMMARY:Resin phantoms as skin simulating layers DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5212@events.saip.org.za DESCRIPTION:Speakers: Aletta Karsten (CSIR\, National Laser Centre)\nIn or der to apply light treatment to skin\, the absorption through the outer la yers of the skin needs to be considered. Human skin is a highly scattering medium and the melanin in the epidermal layer of the skin is a major abso rber of light in the visible and near infrared wavelengths. Darker skin ha s a higher concentration of melanin in the epidermis and absorbs more ligh t than fair skin. Ideally the effect of the skin treatment on the outer la yers of the skin should be tested on in vitro multi layer skin models. Thi s is not always feasible. For this work phantoms were used together with s kin cancer cells to test the effect of outer layer absorption on the effic iency of Photo Dynamic Therapy treatment.\nThree solid phantoms were prepa red from clear resin\, TiO particles (scattering particles) and carbon bla ck (absorption particles). Different carbon black concentrations were used to simulate different skin types. Cells were prepared and treated with th e photosensitiser. The phantoms were placed inside the wells containing th e photosensitised cells\, just touching the media in the well. The attenua tion of the different phantoms was calculated and the laser treatment time s were adjusted to keep the light dose delivered to the cells at 4.5 J/cm2 . After laser treatment cell viability was measured\, using the Cell Titer Blue Viability Assay\, for each of the wells. The phantoms attenuated the laser light by between 10 and 30%. Cell viability for the wells with the phantoms was less than without the phantoms and the differences are attrib uted to the reduced oxygen in the presence of the phantom. The initial res ults of the experiment indicate that the phantoms can be used to optically mimic the effect of the outer skin layers. For future work the experiment al set-up will be refined.\n\nhttps://events.saip.org.za/event/7/contribut ions/5212/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5212/ END:VEVENT BEGIN:VEVENT SUMMARY:Optical Coherence Tomography as a diagnostic tool (Biophysics) DTSTART;VALUE=DATE-TIME:20110714T063000Z DTEND;VALUE=DATE-TIME:20110714T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5213@events.saip.org.za DESCRIPTION:Speakers: Ann Singh (CSIR\,National Laser Centre)\nOptical Coh erence tomography (OCT) is a non-invasive imaging technique that is known to be used to monitor changes and differences in different types of materi als. In the field of Biophysics/Biophotonics OCT can be used to non-invasi vely detect changes occurring in tissue. This study will look at using OC T to detect skin cancer. Similar work has been done by other groups\, how ever the influence of skin tone for such detection has not been evaluated to a great extent. The effect of skin tone on detection of skin cancer wi ll form a core part of the investigations as well as determining the effic acy of the system for early cancer detection. Preliminary work will be don e using phantoms that simulate the different skin tones. Melanin is the c omponent found in the skin\, largely responsible for the different skin to nes and will incorporated into our phantoms as carbon black\, black ink or synthetic melanin. The optical properties of such phantoms can be determ ined on the Integrating Sphere (IS) and OCT systems. A correlation will t hen be drawn between the optical properties and the OCT signals obtained. Once the preliminary tests are done to optimise the method for image anal ysis\, further studies will be done on patients and compared against conve ntional histology results. This talk will thus look at some OCT applicati ons\, some of the preliminary work done using our OCT system and the steps to determining the effect of skin tone on cancer detection.\n\nhttps://ev ents.saip.org.za/event/7/contributions/5213/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5213/ END:VEVENT BEGIN:VEVENT SUMMARY:Evaluation of satellites LAGEOS I and II\; general relativistic ac celerations in the Schwarzschild field of Earth DTSTART;VALUE=DATE-TIME:20110715T094500Z DTEND;VALUE=DATE-TIME:20110715T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5214@events.saip.org.za DESCRIPTION:Speakers: Ludwig Combrinck (HartRAO)\nSolutions of General Rel ativity Theory (GRT) pertaining to space geodesy are weak field\, slow mot ion approximations. These approximations are valid as the gravitational f ield in which the solutions are performed has a potential of small magnitu de and the velocities involved for any of the satellites are much smaller than the velocity of light. The basic effects of GRT on space geodetic mea surements are related to how GRT affects the observables and dynamics of s atellite orbits. We evaluate the GRT accelerations ascribed to the Schwarz schild field\, as well as those due to Lense-Thirring precession (frame dr agging) and de Sitter precession. The Shapiro delay for a laser pulse as a pplied to Satellite LAser Ranging (SLR)is calculated and the importance of including this GRT correction in the range corrections for SLR is describ ed in terms of evaluation of the Observed-Computed residuals. Post-post Ne wtonian corrections are calculated and their relevance discussed in terms of accuracy improvements.\n\nhttps://events.saip.org.za/event/7/contributi ons/5214/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5214/ END:VEVENT BEGIN:VEVENT SUMMARY:Study of rare modes of "collinear cluster tri-partition" of 252Cf( sf) DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5215@events.saip.org.za DESCRIPTION:Speakers: Vusi Malaza (Stellenbosch University\, Military Acad emy\, SAIP member)\nIn our experiments devoted to studying of a new ternar y decay of low excited heavy nuclei called “collinear cluster tri-partit ion” (CCT) a specific CCT mode was observed based on double magic 132Sn cluster. Pre-scission configuration which presumably gives rise to the mod e under discussion can be obtained. The Sn cluster can "move" as a whole a long the cylinder-like configuration that consists of residual nucleons. T wo light fragments accompanying this cluster and marked by symbols M1 and M2 were actually detected in previous experiments. The value of M2 lies be tween 0amu and the difference between the initial mass of 252Cf and the de tected fragments. M1 cannot assume any value less than 95amu (deformed mag ic 95Rb). The question that arises is whether 132Sn can also be changed by double magic 208Pb. This would lead to a new type of lead radioactivity. Searching for such a mode is one of the goals of our forthcoming experimen t\, which will require better statistics and more precise time-of-flights measurements. Testing of a specially designed setup aimed at addressing an d solving these problems is one of our current plans.\n\nhttps://events.sa ip.org.za/event/7/contributions/5215/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5215/ END:VEVENT BEGIN:VEVENT SUMMARY:Multi-instrument observations of spread F irregularities over Sout h Africa DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5217@events.saip.org.za DESCRIPTION:Speakers: Emirant Bertillas Amabayo (SANSA Space Science and R hodes University)\nAn ionospheric eight year study (2001-2008) over South Africa (SA) was conducted using ionosonde data observed by DPS-4 digisonde s with a time resolution of 10\, 15 and 30 minutes from Madimbo\, Grahamst own and Louisvale. Spread F (SF) characterized by ionograms is observed wh en the pulses returned from the F region of the ionosphere are of longer d uration than the transmitted signals. Separate occurrence of horizontal an d vertical spreading of the returned echoes from the ionosphere are classi fied as range spread F (RSF) and frequency spread F (FSF) respectively. Th e overlap of echoes of range and frequency spreading can occur simultaneou sly giving rise to mixed SF (MSF). These types of SF show a seasonal\, sol ar cycle and diurnal patterns over this midlatitude region. These variatio nal patterns were obtained by viewing the ionograms from the ionosondes ma nually using the SAO Explorer. The diurnal pattern of SF peaks between 23: 00 UT and 00:00 UT for all seasons and types of SF in 2001 and 2005\, exce pt during autumn and spring (for RSF) in 2001. The \\% occurrence of both MSF and FSF tends to increase with decreasing sunspot number (SSN). The MS F and FSF occurrence maximum are most frequent during the winter months in 2007 and 2006 respectively.\n\nhttps://events.saip.org.za/event/7/contrib utions/5217/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5217/ END:VEVENT BEGIN:VEVENT SUMMARY:Nanoscale manipulataion of lamellar copolymers using electric fiel ds. DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5218@events.saip.org.za DESCRIPTION:Speakers: Simiso Mkhonta (University of Swaziland)\nBlock copo lymers can self-assemble into lamellar and cylindrical phases with a funda mental period of 10-100nm. These nanoscopic phases are a basis for a great range of applications in nanotechnology.\nWe describe how electric fields can be utilized to tune the lamellar period of copolymers that consist of liquid-crystal sub-units. Copolymers that are swollen in liquid-crystals have anisotropic chains and liquid-crystals have a dielectric anisotropy. We evaluate the critical electric field required to tilt the liquid-cryst al director relative to the lamellar normal in terms of the repulsive inte raction between the chemical dissimilar copolymer blocks. We show that the tilting of the liquid-crystal director can lead to an adjustment of the l amellar period with an amplitude that is proportional the chain anisotropy . \nThis reversible tuning of the lamellar period of block copolymers can lead to interesting applications in nanotechnology.\n\nhttps://events.saip .org.za/event/7/contributions/5218/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5218/ END:VEVENT BEGIN:VEVENT SUMMARY:Predicting human epidermal melanin concentrations for different sk in tones DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5219@events.saip.org.za DESCRIPTION:Speakers: Jacoba Smit (CSIR)\nIn the past 50 years lasers has found numerous applications in medicine. One of their advantages is their use for minimalistic or non-invasive diagnosis and treatment. Often that m eans light penetration through skin and the correct dose required relies o n accurate information regarding the skin’s optical properties. Light ab sorption in the epidermal layer is a major factor in determining the laser light fluence that reaches the deeper skin levels. Darker skin has an epi dermal melanin volume fraction about twice that of lighter skin. Due to me lanin absorption\, less laser light reaches the deeper skin layers in dark skin tones. Laser-tissue interaction modelling software can correct for t his by adapting the dose applied to the skin. To correctly apply such soft ware it is important to characterise the skin in terms of skin tone with a n easy and reliable method. Measuring the melanin content of the skin is t he best method\, but it needs to be done non-invasively. However\, access to samples of all skin types is often limited and skin-like phantoms are u sed instead. The objective of this study is to compare experimentally meas ured absorption features of liquid skin-like phantoms representing Skin Ty pes I to VI with computational simulated skin from the Realistic Skin Mode l (RSM) part of the ASAP® software from Breault Research. Skin-like phant oms were prepared by adding Intralipid (20% fat emulsion) to samples of in creasing melanin concentration at pH ~ 7. UV-VIS transmittance spectra of the samples were measured over the wavelength range 370 to 900 nm and comp ared to simulated results from ASAP® using the same optical parameters. E xperimental and computational results indicated that at shorter wavelength s melanin absorption displayed non-monotonic features that may allow for m ore accurate ways of determining melanin concentration and therefore the e xpected absorption through the epidermal layer. This suggests that the pha ntoms may be able to represent optical characteristics of real skin.\n\nht tps://events.saip.org.za/event/7/contributions/5219/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5219/ END:VEVENT BEGIN:VEVENT SUMMARY:The study of the distortion of F- and Ba- sublattices in superioni c BaF2 at elevated temperatures using positron annihilation technique. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5220@events.saip.org.za DESCRIPTION:Speakers: Thulani Jili (University of Zululand)\nThere is a ge neral misunderstanding regarding the creation of Frenkel pairs in the vici nity of the observed critical temperature Tc in superionic materials. The measured conductivity increases sharply at a temperature coinciding with t he deviation of temperature-dependent lattice constant from 6.2086 A. Fren kel pairs responsible for superionic conduction are gradually generated we ll below the critical temperature and this is informed by the calculation of S-parameter through the measurements of Doppler Broadening at various t emperature points. It is interesting to note that the lattice constant pla ys a pivotal role in the superionic conductivity threshold. Positron annih ilation spectroscopy\, through the determination of positron lifetime and Doppler broadening\, reveals that the generation rate of Frenkel pairs bec omes prominent at 100 K below the critical temperature of 693 K. This is a lso a clear indication of continuous disordering of fluorine sublattice no ticeable at a temperature of 593 K. The fact that the defect positron life time is constant in the temperature range (300 – 900) K confirms a non-d istortion of Ba-sublattice.\n\nhttps://events.saip.org.za/event/7/contribu tions/5220/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5220/ END:VEVENT BEGIN:VEVENT SUMMARY:What Can We Learn from Phase Alignment of Gamma-ray and Radio Puls ar Light Curves? DTSTART;VALUE=DATE-TIME:20110713T101500Z DTEND;VALUE=DATE-TIME:20110713T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5221@events.saip.org.za DESCRIPTION:Speakers: Christo Venter (North-west University\, Potchefstroo m Campus)\nThe Fermi Large Area Telescope (LAT) has revolutionized high-en ergy (HE) astronomy\, and is making enormous contributions particularly to gamma-ray pulsar science. As a result of the many new pulsar discoveries\ , the gamma-ray pulsar population is now approaching 100. Some very famous millisecond pulsars (MSPs) have also been detected: J1939+2134 (a.k.a. B1 937+21)\, the first MSP ever discovered\, as well as J1959+2048 (a.k.a. J1 957+20)\, the first black widow pulsar system. These along with other MSPs such as PSR J0034-0534 and J2214+3000 (and also including the Crab pulsar )\, are unique among the pulsar population in that they exhibit nearly pha se-aligned radio and gamma-ray light curves (LCs). Traditionally\, pulsar LCs have been modeled using standard HE models in conjunction with low-alt itude conal beam radio models. However\, a different approach is needed to account for phase-aligned LCs. We explored two scenarios: one where both the radio and gamma-ray emission originate in the outer magnetosphere\, an d one where the emission comes from near the polar caps on the stellar sur face. We find best-fit LCs using a Markov Chain Monte Carlo technique for the first class of models. The first scenario seems to be somewhat preferr ed\, as is also hinted at by the radio polarization data. This implies tha t the phase-aligned LCs are possibly of caustic origin produced in the out er magnetosphere\, in contrast to the usual lower-altitude conal beam radi o models. We lastly constrain the emission altitudes with typical uncertai nties of 10% of the light cylinder radius. The modelled pulsars are member s of a third gamma-ray MSP subclass\, in addition to two others with non-a ligned radio and gamma-ray LCs.\n\nhttps://events.saip.org.za/event/7/cont ributions/5221/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5221/ END:VEVENT BEGIN:VEVENT SUMMARY:The decoration of vicinal copper polycrystalline surfaces by Antim ony DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5222@events.saip.org.za DESCRIPTION:Speakers: Gebhu Ndlovu (Student)\nMost properties of polycryst alline materials are controlled by the structure and interfaces they posse ss – e.g.\, grain boundaries. When a Cu surface is alloyed with antimony \, the Sb atoms appear to diffuse to the growth surface and continuing to act as a surfactant throughout the growth process. Copper alloys are impor tant commercial materials\, which are often used at temperatures where seg regation and diffusion processes has a huge influence on their properties. An important characteristic of these alloys is that segregation of one co mponent to the alloy surface causes the surface composition to differ sign ificantly from the bulk composition. This study utilizes an ultrahigh vacc um Variable temperature Scanning Tunneling Microscopy (UHV-VTSTM) and Low- Energy Electron Diffraction-Auger Electron Spectroscopy (LEED-AES) to dete rmine the segregation and dissolution temperatures of Sb on Cu polycrystal s and the growth mechanism. The VT-STM images of the Cu surfaces showed l ocalization of Sb atoms in the vicinity of the step edges. The STM data sh owed that alloying initially occurred at the monatomic steps and a homogen eously spread Cu-Sb surface alloy was formed by the migration of Sb atoms. \n\nhttps://events.saip.org.za/event/7/contributions/5222/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5222/ END:VEVENT BEGIN:VEVENT SUMMARY:Transitional 150Sm and 152Gd DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5223@events.saip.org.za DESCRIPTION:Speakers: Suzan Phumudzo Bvumbi (University of Johannesburg)\n Nuclei near N=90 are considered transitional\, since they lie between nucl ei that display vibrational spectra and nuclei that display rotational spe ctra. The structure of these transitional nulei\, in particular the nature of the low-lying first excited states |0+2> still pose a great challenge with various theoretical models competing. A new perspective to the unders tanding of the structure of the N=88 and N=90 nuclei is brought by the pro position that the low-lying first excited 0+ states in these nuclei are no t β-vibrations but constitute a second vacuum |0+2> coexisting with the g round state vacuum |0+1>.\n\nAs part of a campaign studying nuclei near N= 90\, the low and high spin states of the N=88 nucleus 150Sm have been popu lated via 148Nd(α\, 2n)150Sm at a beam energy of25MeV and 136Xe(18O\, 4n) 150Sm at 75MeV respectively. These experiments have been conducted on worl d-class multi-detector gamma-ray spectrometer arrays\, namely JUROGAM at J yvakyla in Finland as well as the AFRODITE at iThemba LABS Cape town here in South Africa. The isotone 152Gd has been studied via 152Sm(α\,4n)152Gd at 45MeV fusion evaporation reaction taken with AFRODITE.\n\nPreliminary results focusing on the observed band structres for the two isotones 150Sm and 152Gd will be presented.\n\nhttps://events.saip.org.za/event/7/contri butions/5223/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5223/ END:VEVENT BEGIN:VEVENT SUMMARY:Influence of ruthenium on the oxidation behaviour of Cu-CNT nanoco mposite interconnect DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5224@events.saip.org.za DESCRIPTION:Speakers: RASIDI SULE (MTech Stuent at TUT)\n\nCopper based in terconnect are widely used in the electronic industry. They provide the co nductive path required to achieve connection from one circuit element to a nother. However\, the application of copper based interconnect is often li mited by the oxidation behaviour of copper. At elevated temperature and hu midity\, the bonding strength of copper interconnect deteriorates due to c opper oxide formation on the surface which could result at device failure. Effort is made in this study to investigate the effect of ruthenium incor poration on the oxidation and electronic interconnection characteristic of Cu-CNT nanocomposite synthesized through the powder metallurgical techniq ue. The compacted samples were sintered by conventional sintering method. Oxidation test was performed in tube furnace. The samples were oxidized i sothermally at different temperature. Electronics weighed balance with the precision of 0.01mg was employed to investigate the weight gain of the sa mple due to oxidation. The morphology structure\, oxide layer thickness a nd possible crack on the sintered sample were examined using scanning elec tron microscope with energy dispersive X-ray spectroscopy (SEM/EDS). Phase identification was performed using an X-ray diffraction spectroscopy (XRD ). It could be concluded from the result obtained that minor addition of R u has a positive effect on the oxidation resistance of Cu-CNT nanocomposit e due to formation of a well protected oxide.\n\nhttps://events.saip.org.z a/event/7/contributions/5224/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5224/ END:VEVENT BEGIN:VEVENT SUMMARY:Thermodynamic Properties and Inelastic Neutron Scattering of Ferro magnetic CeCuSi DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5225@events.saip.org.za DESCRIPTION:Speakers: Buyi Sondezi-Mhlungu (University of Johannesburg)\nC erium-based ternary compounds demonstrate different and interesting phenom ena depending on the valence of the Ce ion. The hybridization between Ce-4 f electrons and the neighbouring conduction electrons is responsible for t he anomolous properties observed in different systems. Depending on the st rength of the f-ligand hybridization\, one observes in these compounds phe nomena such as magnetic ordering\, heavy fermion behaviour\, Kondo effect and valence fluctuations. The derived local magnetic moments associated wi th the state of Ce ions order antiferromagnetically in most cases. CeCuGe\ , CeCuSi and CeAuGe belong to a small family of equiatomic Ce based compou nds that order ferromagnetically at low temperatures. The ordering tempera tures are TC = 10 K\, 15.5 K and 10 K for CeCuGe\, CeCuSi and CeAuGe respe ctively. \n\n\nHere we report on the continuation of our studies into the thermodynamic and magnetic-field sensitivity of magnetic ordering\, TC in CeCuSi compound\, which has been identified to exhibit ferromagnetic groun d state below TC = 15 K. CeCuSi crystallizes in an ordered hexagonal ZrBeS i-type structure (space group P63/mmc No. 194). Magnetization and suscepti bility measurements were performed and the fit to the Curie-Weiss law was done\, calculating paramagnetic temperature\, and effective moment. The fe rromagnetic nature of the transition in this compound is indicated by a la mda-type anomaly at low temperatures from specific heat (Cp) data. At high er temperatures\, the magnetic contribution to the specific heat\, C4f (T) (which is accessed by subtracting an isostructural non-magnetic reference data\, LaCuSi) is characterized by a broad Schottky anomaly resulting fro m electronic excitations to crystal electric field (CEF) levels. Least-squ ares Schottky fit for a two-level system yielded energy separation value o f about 110 K. The presence of CEF in this compound was confirmed by inela stic neutron scattering (INS) data.\n\nhttps://events.saip.org.za/event/7/ contributions/5225/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5225/ END:VEVENT BEGIN:VEVENT SUMMARY:Micromachining of optical fibers with a Nd:YAG laser at 532 nm usi ng a spatial filter DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5227@events.saip.org.za DESCRIPTION:Speakers: Diethelm Schmieder (University of Johannesburg)\nMic romachining of single-mode telecommunication fibres (SMF28) was accomplish ed with a Nd:YAG laser at a wavelength of 532 nm. The goal of the micromac hining process is to machine miniature Fabry-Perot interferometers in the fiber to manufacture fast temperature sensors. To produce micro features b y direct machining the laser beam is focused to spot sizes of 30 µm and b elow. The different shapes of the micro features are accomplished with sma ll apertures in close proximity and in line with the machining lens (focal length 24.5 mm). \n\nWe describe the experimental setup and the monitorin g process. Two mirrors BB1-E02 were installed at an angle of 45 degrees to eliminate the infrared radiation at 1.064 µm. The apertures in line with the machining lens are projected onto the fiber\, which was mounted on a three axis translation stage. The apertures could also be projected agains t the wall to assure homogeneous illumination. The fiber can be shifted be tween the machining area and a camera with 400 x magnification. The images are recorded with ProScope software\, stored in a computer and displayed on a screen.\n\nThe focal point is established by generating a white light supercontinuum by air breakdown. The centre position on the fibre is foun d with the help of the diffraction pattern produced by the fibre. The mach ining frequency was 10 Hz and we found the best laser beam powers between 1 – 3 mW or 0.1 – 0.3 mJ/pulse. We managed to machine right through t he fiber. The machining results will be presented.\n\nhttps://events.saip. org.za/event/7/contributions/5227/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5227/ END:VEVENT BEGIN:VEVENT SUMMARY:Ferromagnetism in nuclear matter DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5228@events.saip.org.za DESCRIPTION:Speakers: Jacobus Diener (Stellenbosch University)\nUnderstand ing the magnetic effects of ultra-dense\, cold nuclear matter is of partic ular importance when investigating the magnetic properties of dense matter systems such as neutron stars. One property that we are interested in is the possibility of generating a magnetic field in nuclear matter as the c entral density increases. We investigate this possibility by employing a relativistic\, self-consistent calculation to capture the interaction of t he neutrons\, protons and electrons with the magnetic field. In this talk we present this model for describing ferromagnetism in dense nuclear matt er systems. Our current results will also be presented.\n\nhttps://events. saip.org.za/event/7/contributions/5228/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5228/ END:VEVENT BEGIN:VEVENT SUMMARY:Super star clusters in nearby Luminous Infrared Galaxies DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5229@events.saip.org.za DESCRIPTION:Speakers: Zara Randriamanakoto (University of Cape Town)\nApar t from the presence of an active AGN\, very young and massive super star c lusters (SSCs) are likely \nto be found in local starbursts and interactin g luminous infrared galaxies. SSCs are responsible of a high \nstar format ion rate (SFR) of the host galaxy. From an on-going deep NIR AO imaging s urvey\, we were able to observe some\nSSCs hidden by the dusty central reg ions. To better understand the formation and the evolution of massive star \nclusters we derived the K-band SSC luminosity functions (LFs) of our sam ple.\n\nhttps://events.saip.org.za/event/7/contributions/5229/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5229/ END:VEVENT BEGIN:VEVENT SUMMARY:Frequency spectrum of nonlinear electric field structures in a mag netized dusty plasma DTSTART;VALUE=DATE-TIME:20110715T070000Z DTEND;VALUE=DATE-TIME:20110715T071500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5230@events.saip.org.za DESCRIPTION:Speakers: Shimul Kumar Maharaj (South African National Space A gency (SANSA) Space Science (formally NRF Hermanus Magnetic Observatory))\ nA magnetized dusty plasma composed of an adiabatic negatively charged\ndu st fluid\, Boltzmann ions and Boltzmann electrons is considered for\nwhich coupled nonlinear dust-acoustic and dust-cyclotron waves hav-\ning sinuso idal\, sawtooth or spiky electric field waveforms are found\nto be support ed when charge neutrality is assumed (Maharaj et al\,\n2008). The focus of this investigation is to make use of a suitable Fast\nFourier Transform ( FFT) algorithm to decompose the nonlinear waveforms into Fourier component s in an attempt to identify the dominant\nfrequency components of the nonl inear structures. The possibility of\nobtaining oscilloton solutions will also be investigated.\n\nhttps://events.saip.org.za/event/7/contributions/ 5230/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5230/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigation of First Year University Students’ Interpretation of Graphs in Mathematics and Kinematics DTSTART;VALUE=DATE-TIME:20110713T091500Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5231@events.saip.org.za DESCRIPTION:Speakers: Itumeleng Phage (Honorary)\nMathematics is an essent ial tool in studying physics\, i.e.\, it will be difficult to study Physic s without the sound basics of Mathematics. It is even called the “langua ge of physics” (Redish\, 2005). Physicists blend conceptual physics with mathematical skills and use them to solve and interpret equations and gra phs. For instance\, in kinematics\, different aspects from mathematics suc h as knowledge of functions and the solving of equations are combined with physics concepts. \nMany introductory physics students perform poorly on the use of mathematical skills and interpretations of graphs in physics. T wo possible reasons may be: (1) Students lack the necessary mathematical s kills needed to solve the physics problems and (2) Students do not know ho w to apply and relate their mathematical skills in the context of physics. These possible reasons were investigated in a Masters Research project wh ich is still in progress\, which probed first year university students’ interpretations of graphs in kinematics and in mathematics. This paper wil l use the idea of Beichner’s standardized questionnaire on kinematic gra phs. From this questionnaire\, an equivalent questionnaire was devised in the context of Mathematical equations and graphs. The results of the inves tigation tend to indicate the deficiencies in the students’ mathematical conceptual knowledge as well as in the transfer of mathematical skills th at they possess to solve kinematic equations and graphs.\n\nhttps://events .saip.org.za/event/7/contributions/5231/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5231/ END:VEVENT BEGIN:VEVENT SUMMARY:Electrical characterisation of the interface in a Au \\ Ni \\ n -A l0.18Ga0.82N Scottky contact system DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5232@events.saip.org.za DESCRIPTION:Speakers: W. E. Meyer (University of Pretoria)\nThe AlxGa1-xN materials system is important for realising tuneable LED and laser sources and short wavelength photodetectors. While AlxGa1-xN (x = 0) is fairly kn own\, there is interest in studying the effects of an increasing Al fracti on on properties of devices. In particular\, on the properties of a bi-met al Ni\\ Au Schottky contact.\nWe utilise Current-Voltage (I-V) and the for ward Capacitance-Voltage (C-V) characteristics\; and\, Admittance (Capacit ance-Frequency (C-f) and Conductance-Frequency (G-f) techniques to study t he Ni\\ Au Schottky barrier contact by monitoring the diode ideality (n)\, the Schottky barrier height and the density of interface states (Dit).\nT he as deposited Ni\\ Au Schottky contact is non- ideal with an ideality fa ctor\, n = 1.6 eV. We also observe for low forward voltages\, a Recombinat ion-Generation (R-G) component to current conduction. The forward C-V meas urements reveal an anomalous peak at 0.45 V confirming the observed non-id eality. The as deposited Dit increases exponentially to about 4.5 x 1011 e V-1 cm-2 towards the mid band gap. G-f measurements reveal a broad peak ar ound 300 kHz at room temperature\, which below 240 K evolves into two peak s centred around 40 kHz and 1 MHz.\nPreliminary isochronal annealing in Ox ygen between room temperature and 623 K indicate that the I-V characterist ics improve with idealities around 1 eV and the Dit is reduced from 4.5 x 1011 eV-1 cm-2 to about 3.5 x 1010 eV-1 cm-2 in the annealed samples. Our results are consistent with a metal-oxide-semiconductor model for the anne aled Ni\\ Au Scottky contact.\n\nhttps://events.saip.org.za/event/7/contri butions/5232/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5232/ END:VEVENT BEGIN:VEVENT SUMMARY:Einstein - Eddington generalized gravity DTSTART;VALUE=DATE-TIME:20110715T101500Z DTEND;VALUE=DATE-TIME:20110715T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5233@events.saip.org.za DESCRIPTION:Speakers: Evgeny Davydov (Joint Insitute for Nuclear Research) \nThe present observational data strongly suggest that Einstein's gravity must be modified\, one of the popular modifications being provided by supe rstring ideas. In view of the mathematical problems of the string theory\, other\, much simpler\, modifications of gravity that affect only the grav itational sector (not touching other interactions) are also popular.\n\nOn e of them is based on Einstein's idea to formulate the gravity theory in a non-Riemannian space with a symmetric connection by use of a special vari ational principle that allows one to determine the connection from a “ge ometric” Lagrangian. This Lagrangian is assumed to depend on the general ized Ricci curvature tensor and on other fundamental tensors and is varied in the connection coefficients.\n\nWe discuss new models of this “affin e” theory of gravity in multidimensional space-times with symmetric conn ections. We use and generalize Einstein's proposal to specify the space-ti me geometry by use of the Hamilton principle to determine the connection c oefficients from a geometric Lagrangian that is an arbitrary function of t he generalized Ricci curvature tensor and of other fundamental tensors. Su ch a theory supplements the standard Einstein gravity with dark energy (th e cosmological constant\, in the first approximation)\, a neutral massive (or tachyonic) vector field (vecton)\, and massive (or tachyonic) scalar f ields. These fields couple only to gravity and can generate dark matter an d/or inflation. The concrete choice of the geometric Lagrangian determines further details of the theory. The most natural geometric models look sim ilar to recently proposed brane models of cosmology usually derived from s tring theory.\n\nhttps://events.saip.org.za/event/7/contributions/5233/ LOCATION: Acro5 URL:https://events.saip.org.za/event/7/contributions/5233/ END:VEVENT BEGIN:VEVENT SUMMARY:Intra-cavity beam control: a comparison of spatial light modulator s and adaptive mirrors DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5234@events.saip.org.za DESCRIPTION:Speakers: Liesl Burger (National Laser Centre)\nIt is well und erstood that the fundamental mode of a cavity may be selected by suitable choice of intra-cavity amplitude or phase elements. If one wishes to dyna mically control the mode\, for example\, to manage thermal aberrations\, t hen intra-cavity elements that are controllable are required. Two such el ements are adaptive mirrors and spatial light modulators (SLMs). In this poster we present early results on the intra-cavity use of SLMs\, and high light some expected and unexpected problems. We then compare our results to our first attempts at the use of an intra-cavity adaptive mirror.\n\nht tps://events.saip.org.za/event/7/contributions/5234/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5234/ END:VEVENT BEGIN:VEVENT SUMMARY:Developing a laser ionization test bench for radioactive beams DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5235@events.saip.org.za DESCRIPTION:Speakers: Lucky Makhathini (University of Zululand\, stellenbo sch and iThemba labs)\nNuclear reactions employed in the production of neu tron-rich radioactive beams often produce many species simultaneously. To extract these beams\, they must not only be ionized\, but ionized selecti vely\, so that only the desired species is extracted.\nWe are developing t he laser resonant ionization technique to fulfil these requirements. The m ethod makes use of high power pulsed lasers\, making it possible to assume that the ionization probability of atoms entering the laser beam zone wil l be close to 100%. A test setup-is being developed to ionize stable atoms . In our test bench\, a stream of atoms is produced by evaporation. Atoms in the stream are ionized by lasers and transported to an ion detector wit h the assistance of an electric field. Ionization can be either non-resona nt through a continuum of levels or resonant through excitation of an auto -ionizing state. For efficient atom ionization the transition must be satu rated at all excitation stages. The condition of saturation means 100% pro bability of excitation of all atoms in the laser radiation zone in the tim e shorter than the life time of the level being excited. \nThe lasers that are employed are the excimer laser and dye laser. The excimer laser is us ed to pump the dye laser and the dye laser is used to tune the wavelength. Instruments such as Fabry-Perot interferometers and diffraction gratings are used to select the wavelength required. The laser beam for ionization is directed to the chamber by means of mirrors and lenses.\nSeparation of ion makes it possible to obtain individual spectra of each ion without the use of mass separator.\n\nhttps://events.saip.org.za/event/7/contribution s/5235/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5235/ END:VEVENT BEGIN:VEVENT SUMMARY:The Extended Curriculum Programme (ECP) Physics at University of t he Western Cape (UWC): Giving students’ access to study the physical sciences in higher education\, particularly further studies in physics. DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5236@events.saip.org.za DESCRIPTION:Speakers: Mark Herbert (University of the Western Cape)\nThis paper addresses what has been done in the Science Faculty at the Universit y of the Western Cape (UWC). The Extended Curriculum Programme (ECP) Physi cs at UWC centers its focus on giving students access to the studies of th e Physical Sciences and improving their success. The paper notes that the incoming students enter university with educational disadvantage backgroun ds. For this reason the ECP Physics has undertaken an initiative to addre ss this under-preparedness by aligning with the UWC graduate attributes to produce good quality graduates. \nCentral to addressing the students’ under-preparedness\, the ECP Physics makes an effort to create a learning environment that is conducive to meaningful learning. In this way\, a goo d foundation is laid for further studies in Physical Sciences. Students ar e oriented as soon as they come in to the Physics classes about their role and the lectures role in their learning. In the paper\, discussion on how the curriculum\, learning outcomes\, learning activities\, assessments of the learning activities and the research into teaching and learning are a ligned to the graduate attributes. \nData will be collected through a surv ey questionnaire about how the past and the current students perceive the ECP Physics learning environment and what their experiences are. The chall enges that come across throughout the Physics course will be presented and discussed in depth.\n\nhttps://events.saip.org.za/event/7/contributions/5 236/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5236/ END:VEVENT BEGIN:VEVENT SUMMARY:Identification of ultrafast processes in the spectroscopy of ZnPc DTSTART;VALUE=DATE-TIME:20110713T123000Z DTEND;VALUE=DATE-TIME:20110713T124500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5237@events.saip.org.za DESCRIPTION:Speakers: Saturnin OMBINDA-LEMBOUMBA (CSIR National Laser Cent re)\nThe transient absorption of Zinc phthalocyanine (ZnPc) has been studi ed by femtosecond pump-probe spectroscopy. We present results on the ultra fast spectroscopy of ZnPc\, specifically identifying three ultrafast compo nents observed. These are the inertial solvation dynamics (~1.8 ps)\, the dielectric solvation dynamics (~39 ps) and vibrational relaxation (~2.7 ps ) in the electronic excited state. Results using different pump wavelength s\, different sample concentrations and different solvents help to clarify the mechanisms behind the observed signals. The red shift of the ground s tate (Q band) spectra is also discussed.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5237/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5237/ END:VEVENT BEGIN:VEVENT SUMMARY:Lightning DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5246@events.saip.org.za DESCRIPTION:Speakers: Case Rijsdijk (SAAO (retd)/ASSA)\nEvery year over a hundred people die unnecessarily from lighting in South Africa. Recent rep orting and correspondence in the media clearly indicated a total lack of k nowledge on the part of the public\, from Ministerial level down\, about t he causes and effects of lightning. Much work has been done by organizatio ns such as the CSIR and SA Weather Bureau\, and there are several commerci al concerns addressing this problem in both urban and wealthy rural areas such as game lodges and other tourist resorts. Recently it has been report ed that the Department of Science and Technology\, DST\, has initiated a p rogamme to install lightning conductors in rural areas. The SAIP can\, and should be\, playing a leading role in addressing this problem and this pr esentation will discuss an assortment of possible ways that the SAIP can a ssist in sustaining remedial efforts in rural areas.\n\nhttps://events.sai p.org.za/event/7/contributions/5246/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5246/ END:VEVENT BEGIN:VEVENT SUMMARY:Fabrication of MWCNT/NiO nanocomposite thin films for optically se lective solar absorbers DTSTART;VALUE=DATE-TIME:20110713T103000Z DTEND;VALUE=DATE-TIME:20110713T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5238@events.saip.org.za DESCRIPTION:Speakers: Kittessa Roro (NLC-CSIR)\nCarbon nanoparticles embed ded in thin NiO layers have shown an increasing interest for application i n spectrally selective solar absorbers that can be used for low temperatur e photothermal applications. It is expected that the size and shape of car bon nanoparticles in the NiO matrix is extremely important in tuning the s electivity of the coatings. In this work\, multiwall carbon nanotubes (MWC NT)/NiO composite films of different CNT contents were prepared by sol-gel technique\, and their structural and optical properties were investigated by scanning electron microscopy\, x-ray diffraction\, Raman spectroscopy\ , UV-Vis spectroscopy and emissometer. Preliminary durability study on the se coatings will also be presented. The results demonstrate promising spec trally selective properties indicating that the CNT/NiO composite is an ex cellent choice for solar water heating applications.\n\nhttps://events.sai p.org.za/event/7/contributions/5238/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5238/ END:VEVENT BEGIN:VEVENT SUMMARY:Strong Gravitational Effects on Pulsar Signals Emanating from Clos e Compact Binary Systems DTSTART;VALUE=DATE-TIME:20110714T071500Z DTEND;VALUE=DATE-TIME:20110714T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5240@events.saip.org.za DESCRIPTION:Speakers: Bevan Tucker (University of the Witwatersrand)\nThe advent of the MeerKAT and SKA radio telescope projects will allow for vast ly improved precision in the measurement of pulsar radio frequency emissio ns. Thus\, the propagation of a pulsar’s conical radio beam through the strong gravitational field region in the vicinity of a compact object\, i .e. black-hole or another neutron star\, will probe the metric of spacetim e in the high-field regime. This talk outlines the theoretical and associ ated numerical predictions of General Relativistic effects\, such as the L ense-Thirring effect\, on such a pulsar signal.\n\nhttps://events.saip.org .za/event/7/contributions/5240/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5240/ END:VEVENT BEGIN:VEVENT SUMMARY:Variation of different compositions of Ti-Pt within the B2 region using solid solution method employed in CASTEP DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5241@events.saip.org.za DESCRIPTION:Speakers: Rosinah Mahlangu (University of Limpopo)\nDifferent compositions of Ti-Pt were varied within the B2 region i.e. 45-55 at% Pt u sing solid solution method employed in CASTEP code. The Ti50Pt50 structure was found to be more stable as compared with other different compositions with the heats of formation of -0.8584 eV. We also observed that the more we increase the Ti and decrease the Pt composition\, the change of the he ats of formation becomes minimal and this was observed on the plotted curv es of the heats of formation against the composition range. The elastic pr operties of the compositions were also calculated.\n\nhttps://events.saip. org.za/event/7/contributions/5241/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5241/ END:VEVENT BEGIN:VEVENT SUMMARY:Carbon structures generated by carbon ion implantation into FeCr t hin films DTSTART;VALUE=DATE-TIME:20110715T100000Z DTEND;VALUE=DATE-TIME:20110715T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5242@events.saip.org.za DESCRIPTION:Speakers: Daniel Wamwangi (wits university)\nWe present result s on the synthesis of precise and thickness controlled carbon structures u sing ion implantation into thin films of a typical metal catalyst\, for Sc hottky contacts and spintronic applications. Thin films of FeCr on a sili con substrate was prepared using magnetron sputtering and then implanted w ith carbon ions at controlled thicknesses close to the surface at elevated temperatures (600C) in an attempt to catalyse the formation of carbon nan otubes. The energy and the dose of the carbon ions to be deposited close to the surface was determined from SRIM simulations. The nature and qualit y of the carbon nanotubes was probed using Raman\, electrical and magnetic measurements.\n\nhttps://events.saip.org.za/event/7/contributions/5242/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5242/ END:VEVENT BEGIN:VEVENT SUMMARY:Density Functional Calculation of Metal Dithizonates DTSTART;VALUE=DATE-TIME:20110713T124500Z DTEND;VALUE=DATE-TIME:20110713T130000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5243@events.saip.org.za DESCRIPTION:Speakers: OLUFEMI OPEYEMI OLAOYE (STELLENBOSCH UNIVERSITY)\nUn derstanding molecular dynamics on potential energy surfaces has been at th e heart of ultrafast transient absorption in the recent years [Philipp K\, etal.\, 2005]\,[Karel G\, etal.\, 2008]. Based on the on-going experiment at our ultrafast laboratory\, we ran density functional calculations on m etal dithizonates\, starting with their kernel molecule\, formaldimine\, t o validate what we observe experimentally. This we treated in terms of gro und state energy\, absorption spectrum\, vibrational frequency and potenti al energy surface using two different softwares: Amsterdam Density Functio nal (ADF) and Gausian(09). The overall results show that B3LYP functional combined with CEP-31G basis set gave the closest results to the experiment ally observed data.\n\nhttps://events.saip.org.za/event/7/contributions/52 43/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5243/ END:VEVENT BEGIN:VEVENT SUMMARY:Nitrogen-vacancy in diamond for Solid-state quantum computing DTSTART;VALUE=DATE-TIME:20110714T061500Z DTEND;VALUE=DATE-TIME:20110714T063000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5244@events.saip.org.za DESCRIPTION:Speakers: Bheki Zulu (Student)\nEver since the inception of th e quantum computing idea\, many technologies for its realization have been tried. The fundamental intention is to implement and manipulate a two-dim ensional quantum mechanical unit of information that is termed a quantum b it (qubit). In this context during the past decade\, solid-state fluoresci ng defects have drawn huge interest. The promising candidates for solid-st ate qubits are nitrogen-vacancy (NV) centers in diamonds due to their indi vidual addressability\, optical spin polarization and spin coherence time of milliseconds at room-temperature. \n\nHere\, an on-going study on enhan cing NV centres creation and NV electronic spin coherence times is reporte d. The vacancies in diamond crystal samples are created using Van der Graa f accelerator and then the samples are annealed at elevated temperatures t o form NV centres. Sample measurements in terms of detecting the defects a nd their concentrations and electron spin coherence times are performed us ing techniques such as Raman spectroscopy\, absorption spectrum\, photolum inescence and confocal microscopy equipped with Electronic spin resonance (ESR).\n\nhttps://events.saip.org.za/event/7/contributions/5244/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5244/ END:VEVENT BEGIN:VEVENT SUMMARY:Synthesis and characterization of PbS nanorods using the chemical bath deposition method DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5245@events.saip.org.za DESCRIPTION:Speakers: Lehlohonolo Koao (UFS (Qwa Qwa Campus))\nCrystalline lead sulfide (PbS) nanorods were synthesized by chemical bath deposition (CBD) method using the mixed aqueous solutions of lead acetate\, thiourea and ammonium solution. The lead acetate concentrations were varied in the deposition process to determine the effect thereof. The temperature of the bath was maintained at 80ºC. The final yields were characterized for str uctural\, morphology and optical properties. The X-ray diffraction (XRD) s pectra of the PbS nanorods correspond to the various planes of cubic PbS. A single phase was obtained. The average particle sizes calculated using t he XRD spectra were found to be 14±0.5 nm for particles stirred for 10 mi nutes and 16±0.5 nm for samples stirred for 5 minutes respectively. When the concentration of lead acetate was increased the particle size also inc reased. Scanning electron microscopy (SEM) micrographs depict nanorod stru ctures for a high mol concentration of lead acetate and a spherical shape for a low mol percentage. Energy dispersive X-ray (EDS) analyses confirm t he presence of all the expected elements. The solid powder nanorods show g ood optical properties with high absorptions in the UV and visible regions . The band gap energies were estimated to be 1.69 to 1.84 eV which are hig her than the bulk PbS band gap of 0.37 eV. The absorption edge and the ban d gap energies of these PbS nanorods have shifted depending on the ionic s trength of the precursors.\n\nhttps://events.saip.org.za/event/7/contribut ions/5245/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5245/ END:VEVENT BEGIN:VEVENT SUMMARY:Computational study of some tin dioxide phases. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5247@events.saip.org.za DESCRIPTION:Speakers: James Ntimane (University of Limpopo)\nRutile and an atase structured tin dioxide ceramics have been intensively studied in rec ent years because of their potential in sensing and fuel cells. The presen t work uses classical molecular dynamics simulations focused on the struc ture and possible transformation from anatase to rutile tin dioxide. The e mpirical Buckingham potential has been used to describe the interatomic in teractions in tin dioxide. The total energy of the NVE ensemble of the two structures at various temperatures has been calculated in order to determ ine the transition temperature and pressure. The results obtained showed a n energy increase with temperature which was constantly compared with expe riments. The radial distribution functions for the two structures suggest the transformations at temperature above 900 ºC in agreement with the exp eriments.\n\nhttps://events.saip.org.za/event/7/contributions/5247/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5247/ END:VEVENT BEGIN:VEVENT SUMMARY:Non-linear Fowler-Nordheim plots in thin film polymer-fullerene co mposite devices: Transition from electron-only to hole-only conduction DTSTART;VALUE=DATE-TIME:20110714T091500Z DTEND;VALUE=DATE-TIME:20110714T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5248@events.saip.org.za DESCRIPTION:Speakers: Zivayi Chiguvare (University of the Witwatersrand)\n We studied charge injection and transport mechanisms in blends of poly(3-h exylthiophene) (P3HT) and [6\,6]-phenyl C61-butyric acid methylester (PCBM )\, by analysing dark\, temperature dependent current-voltage characteris tics of the P3HT:PCBM blend thin films sandwiched between aluminium electr odes in a MIM configuration. We present a general method of interpreting F owler - Nordheim plots of metal/semiconductor/metal devices with pronounce d non-linear characteristics by dividing them into several regions based o n physical origins. We show that by applying appropriate electric fields it is possible to switch from electron-only conduction to hole-only conduc tion in a single Al/P3HT:PCBM/Al device. We affirm that electrons can be s electively transported through the lowest unoccupied molecular orbital of PCBM at low applied voltages and low temperatures\; and alternatively hole s can be transported through the highest occupied molecular orbital of P3H T at higher applied voltages and high temperature\, within a single device .\n\nhttps://events.saip.org.za/event/7/contributions/5248/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5248/ END:VEVENT BEGIN:VEVENT SUMMARY:Pre knowledge of physics 1 students on vectors DTSTART;VALUE=DATE-TIME:20110713T094500Z DTEND;VALUE=DATE-TIME:20110713T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5249@events.saip.org.za DESCRIPTION:Speakers: Motlalepula Rebecca Mhlongo (University of Limpopo)\ nThe purpose of this study was to investigate the pre-knowledge of the Phy sics I students on vectors. The study was conducted on 234 Physics I stud ents from the University of Limpopo (Medunsa campus). The sample was divi ded into four groups\, where the first group (n = 119) did their grade 12 in 2010\, the second group (n = 46) did their grade 12 prior 2010\, the th ird group (n = 42) did Foundation Physics in 2010 and the fourth group (n = 27) were those repeating Physics I. An ex post facto research design was chosen for the study whereby all the groups were given a vector test at t he beginning. The test was divided into three questions\, testing definiti ons\, classifications\, drawing and interpretations of graphs. Results sh owed a less difference between average percentage of the groups whereby th e group before 2010 (47.4%)\, foundation group (47.3%)\, the repeaters (44 .3%) and those who did grade 12 in 2010 (44.1%).\n\nhttps://events.saip.or g.za/event/7/contributions/5249/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5249/ END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic and strong correlation effect in CeT2Al8 (T=Fe\,Co) DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5250@events.saip.org.za DESCRIPTION:Speakers: SARIT KUMAR GHOSH (UNIVERSITY OF JOHANNESBURG)\nWe p resent specific heat\, electrical resistivity\, susceptibility\, and therm opower measurements on the two novel intermetallic compounds CeFe2Al8 and CeCo2Al8. They form in an orthorhombic crystal structure of space group Pb am. In the unit cell representation Ce atom occupies only one lattice site \,having Ce-Ce interatomic distance of 4.03Å. Magnetic susceptibility of CeFe2Al8 in the range of 1.9K - 400K yields an effective paramagnetic mome nt value of 3.89μB together with prevailing antiferromagnetic interaction through Weiss temperature Θ=-745.8K. The overall temperature dependence suggests valence instability in this compound and we model the appearance of broad peak around T=230K in the susceptibility to a T2lnT dependence at tributed to an intermediate valent state. On the other hand for CeCo2Al8 t he local moment state is depicted through an effective moment close to the free Ce3+ ion value. No long-range magnetic ordering is found in either o f the two compounds down to 1.9K. The magnetic contribution of electrical resistivity on CeFe2Al8 and CeCo2Al8 compounds follows –lnT behavior at intermediate temperatures which is typical of incoherent Kondo interaction s between conduction electrons and magnetic Ce ions. A Fermi liquid behavi or in resistivity measurement is observed in CeFe2Al8 compound towards the ground state\,whereas clear deviations from standard Fermi liquid behavio r are indicative of strong electronic correlation effects in CeCo2Al8. At 2K the electronic specific heat of this compound reaches γ =0.106J/mol-K2 \,and exhibits a –lnT divergence towards T→0. We explain this behavior in terms of quantum criticality that stems from low-lying magnetic orderi ng effects. In studies of the thermoelectric power\,a maximum is reached a t T=140K(S=24μV/K) and T=30K(S=23μV/K) for CeFe2Al8 and CeCo2Al8 compoun ds respectively. We propose a description for this behavior in terms of fo rmation of fine structure in the electronic density of states near the Fer mi energy(EF).\n\nhttps://events.saip.org.za/event/7/contributions/5250/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5250/ END:VEVENT BEGIN:VEVENT SUMMARY:Tuning Carbon Nanotubes for Application in Photovoltaic Devices DTSTART;VALUE=DATE-TIME:20110713T103000Z DTEND;VALUE=DATE-TIME:20110713T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5251@events.saip.org.za DESCRIPTION:Speakers: George Bepete (University of the Witwatersrand)\nCon trol of diameter\, length and level of nitrogen doping in synthesis of nit rogen doped carbon nanotubes (N-CNTs) can be achieved by careful selection of catalyst\, precursor mixture and chemical vapour deposition (CVD) synt hesis temperature. Solutions of ethanol and acetonitrile (20% acetonitril e) were pyrolysed over a Fe/Al/MgO catalyst in a CVD reactor at temperatur es from 700 OC to 1000 OC. The products were characterised by TGA\, TEM a nd Raman spectroscopy. N-CNTs with well graphitised morphology\, small di ameter\, and narrow diameter distribution were obtained at CVD temperature s from 850 OC to 900 OC. Below 800 OC the N-CNTs with large seized diamete rs were formed and above 900 OC the product yield became very low and the carbon nanotubes were malformed with wide diameter distribution. By pyrol ysing precursor mixtures of acetonitrile and alcohols (methanol\, ethanol\ , propanol\, butanol\, pentanol\, hexanol\, heptanol and octanol) we found out that short\, 500 nm in length N-CNTs were obtained by the pyrolysis o f long chain alcohols\, (heptanol and octanol) and acetonitrile solution w hilst longer N-CNTs were formed from pyrolysis of earlier alcohols (methan ol\, ethanol and propanol). Short and thin carbon nanotubes can be useful in carbon based nanoelectronics and photovoltaic devices since there is l ess entanglement of N-CNTs which will result in good dispersion of carbon nanotubes in solutions and polymer matrix. Preliminary results of the dev ices made from N-CNTs will be presented.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5251/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5251/ END:VEVENT BEGIN:VEVENT SUMMARY:Identification of isotopes using time differential\, event-by-even t gamma spectroscopy DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5252@events.saip.org.za DESCRIPTION:Speakers: Martin Cook (University of Johannesburg)\nIn the con text of activation studies\, in order to uniquely identify an isotope via gamma spectroscopy\, both the lifetime and the energy of the emitted gamma rays are required. Traditional detectors collect only integral data\, los ing information about the timing of individual events. This makes lifetime analysis a manually intensive task\, as data points must be obtained by c ycling the target in front of the detectors for well defined times at well defined intervals. Lifetime accuracy is limited by the manual details of this cycling procedure. \n\nA gamma spectroscopy system based on event-by- event acquisition implemented on the VME standard offers the advantage of recording time-stamped energy data for each event. The system described is capable of both coincident and single photon detection - enabling in addi tion the identification of PET isotopes amongst the other nuclides. The da ta can then be analyzed offline in a time differential manner\, to provide both the gamma-line energy and lifetime. If necessary\, the lifetime anal ysis can accommodate correlated and uncorrelated multiple lifetimes. One d etection run will therefore yield complete information about both the ener gies and lifetimes of all isotopes present\, allowing for unique isotope i dentification.\n\nThis poster outlines this technique\, then goes on to sh ow results from its application to the study of isotopes excited when an e lectron beam is incident on high Z targets. These experiments were conduct ed in the context of obtaining activation data for a diamond sorting techn ique based on positron emission tomography.\n\nhttps://events.saip.org.za/ event/7/contributions/5252/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5252/ END:VEVENT BEGIN:VEVENT SUMMARY:The South African Physics Olympiad\, SAPhO DTSTART;VALUE=DATE-TIME:20110715T060000Z DTEND;VALUE=DATE-TIME:20110715T061500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5253@events.saip.org.za DESCRIPTION:Speakers: Case Rijsdijk (SAAO (retd)/ASSA)\nWith the current s uccess of physics and astronomy and their technological support bases in S outh Africa\, there is a need to identify and nurture talent in physics. I t is clear that the current South African schooling system has little chan ce of doing this\, and thus it becomes imperative that alternative means a re found to grow local talent. This need was identified by the Internation al Physics Review Panel\, recommendation 4.1.4\, but there has been very l ittle progress since the International Year of Physics in 2005\, when the first Physics Olympiad was held. A possible way forward will be outlined\, what is needed and how it will be implemented will be discussed. A brief look will also be taken at the future potential of SAPhO including the for mation of a Pan African Physics Olympiad\, PAPhO\, as a potential precurso r to participation in the IPhO. Some concluding remarks on the challenges facing formation of the SAPhO will also be addressed\, including possible solutions and necessary mechanisms that will need to be in place.\n\nhttps ://events.saip.org.za/event/7/contributions/5253/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5253/ END:VEVENT BEGIN:VEVENT SUMMARY:Ferromagnetic neutron stars DTSTART;VALUE=DATE-TIME:20110714T064500Z DTEND;VALUE=DATE-TIME:20110714T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5254@events.saip.org.za DESCRIPTION:Speakers: Jacobus Diener (Stellenbosch University)\nIt is well known that neutron stars have very strong magnetic fields and that these fields impact the behaviour of the star. The focus of our research is on t he interaction between the magnetic field and the constituent matter in th e neutron star’s interior. In particular we investigate the possibility of a ferromagnetic phase in the neutron star interior being the source of the star’s ultra-strong magnetic field. Considering such a phase provid es us with a feedback mechanism between the constituent matter and the mag netic field and vice versa\, which we believe is a necessary component in understanding the evolution of the neutron star’s magnetic field. In th is talk we will shortly introduce a description of ferromagnetism in the n eutron star interior. We will also discuss the impact of such a phase as well as allude to possible observational consequences.\n\nhttps://events.s aip.org.za/event/7/contributions/5254/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5254/ END:VEVENT BEGIN:VEVENT SUMMARY:Emittance measurements of ion beams extracted from a prototype mic rowave ion source using the Slit-Grid technique DTSTART;VALUE=DATE-TIME:20110715T093000Z DTEND;VALUE=DATE-TIME:20110715T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5255@events.saip.org.za DESCRIPTION:Speakers: Blaine B. D. Lomberg (University of the Western Cape & iThemba LABS)\nIn recent years the need to produce low charge state ion beams\nwith good beam quality and ion sources with good gas efficiency ar e on an increasing demand. The various applications of these specific ion beams are ranging from radioactive ion beam production to high energy ion implanters. The Accelerator Physics Department at iThemba LABS has develo ped a prototype microwave ion source. The source consists of a ceramic pla sma chamber\, a four bar permanent-magnet arrangement and a coaxial microw ave feed. This paper involves measurements that were carried out to charac terize the ion beam quality from the source. A slit-grid emittance device with a computer controlled data acquisition system was used to measure the transverse phase space distribution of ion beams. These measurements incl uded beam RMS-emittance with noise filtering and TWISS parameter determina tions. The beam emittance is fundamentally inferred by taking spatial and angular positions of beam-lets of particles and mapping it into a four-dim ensional phase space.\n\nhttps://events.saip.org.za/event/7/contributions/ 5255/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5255/ END:VEVENT BEGIN:VEVENT SUMMARY:Tailoring of Mechanical\, thermal and electrical properties of pol ymers composite: A micro fuel cell perspective DTSTART;VALUE=DATE-TIME:20110714T121500Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5256@events.saip.org.za DESCRIPTION:Speakers: Hao Chen (CSIR)\nFuel cells have been intensively re searched for the past few decades for macro applications. However\, micro fuel cells have not received so much attention. A micro fuel cell delivers power in the mW-W range\, and would be suitable for mobile purposes\, e.g . as a charger for cell-phone or other small devices. We consider polymers such as polydimethylsiloxane (PDMS) as a prospective structural material candidate for a Micro Fuel Cell. The introduction of such a polymer as str uctural material will reduce the mass and the size of the micro fuel cell and therefore optimize the current micro fuel cell models. In this perspec tive\, our work focuses on the tailorability and optimization of thermal\, mechanical\, and electrical properties of PDMS with different micro/nano fillers such as silver particles\, carbon black\,. The mechanical property is characterized by Dynamic Mechanical Analysis(DMA). The thermal propert ies are measured using Thermal Gravimetric Analysis (TGA) and Cut-Bar ther mal conductivity measurement. Four point probe was used for electrical con ductivity measurement. Scanning Electron Microscopy (SEM) was used for sur face morphology characterization.\n\nhttps://events.saip.org.za/event/7/co ntributions/5256/ LOCATION: Acro1 URL:https://events.saip.org.za/event/7/contributions/5256/ END:VEVENT BEGIN:VEVENT SUMMARY:Effect of Low Intensity Laser Irradiation (LILI) and Epidermal Gro wth Factor (EGF) on Adult Human Adipose Derived Stem Cells (hADSCs) DTSTART;VALUE=DATE-TIME:20110714T093000Z DTEND;VALUE=DATE-TIME:20110714T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5257@events.saip.org.za DESCRIPTION:Speakers: Bernard Mvula (Doctoral Student)\nThe study investig ated the effects of low intensity laser radiation (LILI) and epidermal gro wth factor (EGF) on adult adipose derived stem cells (hADSCs) isolated fro m human adipose tissue. Isolated cells were cultured in complete Dulbeco ’s Modified Eagle Medium (DMEM) containing 10% featal bovine serum (FBS) \, EGF and antibiotics and incubated at 37°C in 85% humidified atmosphere of 5% CO2. Semi-confluent monolayers of ADSCs were exposed to low intens ity laser at 5 J/cm2 using 636 nm diode laser. Cell viability and prolife ration were monitored using adenosine triphosphate (ATP) luminescence and optical density at 0\, 24 and 48 h post irradiation. Application of low in tensity laser irradiation and EGF on human ADSCs at 5 J/cm2 increased the viability and proliferation of these cells. Therefore low intensity laser therapy would probably enhance differentiation and proliferation of stem cells in vitro and these cells could be used in reconstructive surgery and tissue engineering.\n\nhttps://events.saip.org.za/event/7/contributions/5 257/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5257/ END:VEVENT BEGIN:VEVENT SUMMARY:2 µm Ho doped amplifiers DTSTART;VALUE=DATE-TIME:20110713T100000Z DTEND;VALUE=DATE-TIME:20110713T101500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5258@events.saip.org.za DESCRIPTION:Speakers: Hencharl Johan Strauss (CSIR (National Laser Centre) )\nLasers and amplifiers emitting 2µm single-frequency pulses are used fo r spectroscopy\, remote sensing\, and defence applications. The laser sour ces group at the CSIR National Laser Centre has developed a number of 2µm lasers and amplifiers over the course of five years. We report on three o f these\, all of which achieved record breaking output energies. \n\nTo ge nerate the high energy 2µm pulses\, we developed a 70mJ single-frequency\ , Q-switched Ho:YLF ring MOPA. Both the ring laser and pre-amplifier were pumped by a single commercial 80W\, 1940nm\, Tm:fibre laser from IPG. The seed laser system delivered up to 73mJ per pulse at 50Hz\, with a pulse du ration of ~365ns in a diffraction limited beam. This system set two world records: it delivered the highest energy from a Ho doped laser\, pumped wi th one Tm:fibre laser\, and it was also the highest single-frequency singl y-doped Ho:YLF laser. \n\nIn order to scale these pulse energies even furt her\, we developed a Tm:YLF pumped slab amplifier system. Amplified single -frequency pulses of up to 210mJ were generated from a 43mm long Brewster cut Ho:YLF and a 20mm long Ho:LuLF slab crystal. However\, numerical simul ations indicated that longer Ho doped crystals between 80 to 120mm in leng th would perform significantly better. \n\nA new Ho:YLF slab amplifier was therefore built which consisted of two 50mm long crystals placed close to gether in series in a double seed pass configuration. This amplifier deliv ered >330mJ of single-frequency pulses and a small signal gain in excess o f 40. This is the highest reported single-frequency 2µm energy from a Ho: YLF slab MOPA system. \n\nThe high-energy 2µm pulses were then used to pu mp a 4µm molecular HBr MOPA\, which will also be reported at this confere nce.\n\nhttps://events.saip.org.za/event/7/contributions/5258/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5258/ END:VEVENT BEGIN:VEVENT SUMMARY:The electric field gradient in mercuric chloride DTSTART;VALUE=DATE-TIME:20110715T071500Z DTEND;VALUE=DATE-TIME:20110715T073000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5259@events.saip.org.za DESCRIPTION:Speakers: Jonathan Keartland (University of the Witwatersrand) \nThe temperature dependence of the 35Cl quadrupolar resonance frequency h as been measured in a high purity sample of mercuric chloride (HgCl2) over the temperature range 4 K - 460 K. The results allow the temperature dep endence of the electric field gradient (efg) at the two inequivalent sites of the chlorine atoms to be determined. Several models were considered t o describe the experimental observations\, including both librational and vibrational modes. The Bayer model for librational modes provides a satis factory description of the changes in the efg over the entire temperature range\, when the temperature variation of the lattice modes is taken into account\, while the other mechanisms considered provide less convincing de scriptions. A single librational mode with a wavenumber of approximately 26 cm-1 can account for the variation of the electric field gradient over the temperature range investigated. Our conclusions are consistent with t he results of optical spectroscopy investigations.\n\nhttps://events.saip. org.za/event/7/contributions/5259/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5259/ END:VEVENT BEGIN:VEVENT SUMMARY:Fine Structure of the Isovector Giant Dipole Resonance: a survey w ith (p\,p') scattering at zero degrees DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5260@events.saip.org.za DESCRIPTION:Speakers: Maxwell Jingo (University of the Witwatersrand\, Sou th Africa)\nA survey of the fine structure phenomenon of the Isovector Gia nt Dipole Resonance (IVGDR) was investigated\, using the newly commissione d Zero-degree Facility of the K = 600 magnetic spectrometer of iThemba LAB S. Measurements were performed for inelastic proton scattering at an incid ent energy of 200 MeV for targets ranging from 27Al to 208Pb. Targets of a real density of 1 – 2 mg/cm2 gave an energy resolution of 45 keV Full Wi dth at Half Maximum (FWHM) after utilising the faint-beam dispersion-match ing technique. A reasonable background subtraction procedure allowed for t he extraction of excitation energy spectra with low background. The data f rom the survey promise to give a unique insight into the competition of th e various damping mechanisms contributing to the decay of the IVGDR. Furth ermore\, level densities of Jπ = 1– states can be extracted in a model- independent way\, which serves as an important input to models applied in astrophysics. Finally\, this survey will simultaneously provide bench-mark s on the capabilities and limitations of the new Zero-degree Facility impo rtant for planning of the future experimental work. The experimental techn iques\, experimental results and preliminary theoretical calculations for the measurement of 0o proton scattering will be presented.\n\nhttps://even ts.saip.org.za/event/7/contributions/5260/ LOCATION: Acro8 URL:https://events.saip.org.za/event/7/contributions/5260/ END:VEVENT BEGIN:VEVENT SUMMARY:Remote detection of light organic elements using PET DTSTART;VALUE=DATE-TIME:20110715T063000Z DTEND;VALUE=DATE-TIME:20110715T064500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5261@events.saip.org.za DESCRIPTION:Speakers: Martin Cook (University of Johannesburg)\nWe look at the use of Positron Emission Tomography to detect light organic elements in two different contexts\, namely to locate diamonds within partially cru shed kimberlite (Mineral PET)\, and to locate buried land mines.\n\nLight organic elements such as carbon have traditionally proved difficult to loc ate\, and currently mines crush rock down to a fine size\, and then employ manual sorting methods to find diamonds. If diamond bearing rocks could b e identified before the final crush\, up to 98% of the electricity and wat er used for crushing could be saved\, and larger diamonds preserved. The p roposed technique is to use bremsstrahlung from a 40 MeV electron source t o excite the giant dipole resonance in target nuclei\, which have a large branching ratio to decay by emission of a neutron\, forming PET isotopes. Such isotopes release positrons\, which annihilate to create back-to-back 511 keV gamma rays. A 3D density map of possible sources allows the identi fication of hotspots. Complications arise from having to account for the e xcitation of many different nuclei\, and having to distinguish diamond fro m homogeneously distributed carbon. In order to be industrially feasible\, small diamonds need to be located\, requiring significant advances in det ection and image processing. We will look at simulations of the process\, imaging algorithms\, quantifying radiation doses and detector technologies .\n\nLand mines are a huge global problem. 2009 estimates place the number of buried land mines at over 100 million\, covering approximately 3 000 s quare kilometers of land worldwide. Between 1999 and 2008\, these have le ad to 73 576 mine casualties in 119 countries. Overall demining programme costs in third world environments are typically one to two million dollars per square kilometer of cleared land. Advances in land mine technology me an that mines can contain little or no metal\, making demining an expensiv e\, slow and dangerous activity. Most common elements in explosives are PE T emitters\, including Oxygen\, Carbon\, Nitrogen and Flourine\, raising t he possibility that PET could provide an effective method of mine detectio n.\n\nhttps://events.saip.org.za/event/7/contributions/5261/ LOCATION: Acro3 URL:https://events.saip.org.za/event/7/contributions/5261/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray Timing and Spectral Analysis of the Propeller Driven Pulsar- like White Dwarf AE Aquarii DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5262@events.saip.org.za DESCRIPTION:Speakers: Bosco Oruru (University of the Free State)\nThe high ly transient multi-wavelength system AE Aqr consists of a fast rotating hi ghly magnetic WD\, accreting mass from a K3-5 secondary companion. This ma gnetic CV has a characteristic orbital period of 9.88 h\, and is in a prop eller state. The turbulent interaction between the fast spinning WD magnet osphere and the accretion flow is believed to play a crucial role in the m ulti-wavelength emission in the system. We have analysed the system's X-ra y lightcurves and spectra from data observed with Chandra and Swift-XRT\, and the results of this study show that the X-ray characteristics are uniq ue. In this paper\, the results of the analysis will be discussed\, with t he view to propose suitable models for the X-ray emission mechanisms.\n\nh ttps://events.saip.org.za/event/7/contributions/5262/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5262/ END:VEVENT BEGIN:VEVENT SUMMARY:A Comparison of the THINGS HI and HERACLES CO Velocity Dispersion in Nearby Galaxies DTSTART;VALUE=DATE-TIME:20110714T101500Z DTEND;VALUE=DATE-TIME:20110714T103000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5263@events.saip.org.za DESCRIPTION:Speakers: Keoikantse Moses Mogotsi (UCT)\nIn this project data from The HI Nearby Galaxy Survey (THINGS) and from the HERA CO Extragalac tic Line Survey (HERACLES) is being used to compare the HI (neutral hydrog en) and CO dispersions in nearby galaxies in order to see if they are rela ted. This is important in improving star formation laws (as they currentl y only use HI dispersions\, but stars form from molecular gas) and to bett er understand turbulence in galaxies. Preliminary analysis indicates that the HI has higher velocity dispersions than the CO.\n\nhttps://events.saip .org.za/event/7/contributions/5263/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5263/ END:VEVENT BEGIN:VEVENT SUMMARY:Spin-density-wave behaviour of the (Cr100-xAlx)95Mo5 alloy system DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5264@events.saip.org.za DESCRIPTION:Speakers: Blessed Muchono (University of Johannesburg)\nPrevio us studies in our laboratory on the (Cr100-xAlx)95Mo5 alloy system through electrical resistivity and magnetoelastic measurements suggest that spin- density-wave (SDW) antiferromagnetism is fully suppressed down to 4 K in t he concentration range 2.0 ≤ x ≤ 5.0 at.% Al. The current interest in quantum criticality in Cr and Cr alloy systems warrants further detailed i nvestigation into this aspect. In this regard we report results of electri cal resistivity\, Seebeck coefficient and Sommerfeld electronic specific h eat coefficient (obtained from specific heat measurements) for an extended alloy range 0 ≤ x ≤ 8.1 at.% Al. The Seebeck coefficient turns out to be a more sensitive parameter than electrical resistivity in obtaining ma gnetic phase transition temperatures for this alloy system\, particularly for the commensurate (C) SDW phase region x ≥ 5.0 at.% Al. The electrica l resistivity and Seebeck coefficient data depicts total suppression of AF M down to 2 K for 1.5 ≤ x ≤ 5.3 at.% Al. The results of Sommerfeld ele ctronic specific heat coefficient confirms this finding\, showing a sharp increase in the incommensurate (I) SDW phase up to x ≈ 1.5 at.% Al\, rou ghly leveling off in the paramagnetic range 2.0 ≤ x ≤ 4.6 at.% Al\, fo llowed by a slow decreasing trend in the CSDW phase x ≥ 5.0 at.% Al. Fro m the present study it appears that both points (x ≈ 1.5 at.% Al\, T = 0 K) and (x ≈ 5.0 at.% Al\, T = 0 K) are possible quantum critical points on the magnetic phase diagram of the (Cr100-xAlx)95Mo5 alloy system. It i s then rather unique to have both ISDW-P and P-CSDW quantum critical point s existing in the same alloy system.\n\nhttps://events.saip.org.za/event/7 /contributions/5264/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5264/ END:VEVENT BEGIN:VEVENT SUMMARY:Foundation Provision: Any Difference in Students’ Performance? DTSTART;VALUE=DATE-TIME:20110713T120000Z DTEND;VALUE=DATE-TIME:20110713T121500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5265@events.saip.org.za DESCRIPTION:Speakers: Buyi Sondezi-Mhlungu (University of Johannesburg)\nS cience\, Engineering and Technology (SET) have become essential in the dev elopment of the country in all its facets. It has been observed over the p ast few years that students entering university for degree studies in thei r respective fields experience considerable level of difficulty. Inadequat e understanding of basic mathematics and physics concepts has been identif ied as a critical deficiency characterizing the performance of SET first y ear students. As a norm\, the intake is usually based on Grade 12 results. Admission to mainstream (three year) programme or a four year extended pr ogramme is determined on the basis of M-Scores by various respective insti tutions. Analysis of students’ performance in the four year programme a t the University of Johannesburg painted a bleak picture and this led to t he introduction of the Foundation Provision Programme (PFP) as a precursor to the normal first year curriculum. This programme serves to adequately develop the basic or foundational competencies necessary for students to e mbark on successful first year physics studies and beyond. The sample in t his study comprised a group of freshmen from Grade 12 registered for vario us degrees in Science \, Engineering and Optometry. All these groups recei ve physics tuition in one lecture class. The Foundation Provision Programm e was implemented for the first time at the University of Johannesburg in 2010 and the results obtained were compared to the results of students’ performance obtained from previous years.\n\nhttps://events.saip.org.za/ev ent/7/contributions/5265/ LOCATION: Acro7 URL:https://events.saip.org.za/event/7/contributions/5265/ END:VEVENT BEGIN:VEVENT SUMMARY:Demonstration of a wavelength tuneable mid-IR molecular laser DTSTART;VALUE=DATE-TIME:20110713T103000Z DTEND;VALUE=DATE-TIME:20110713T104500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5266@events.saip.org.za DESCRIPTION:Speakers: Wayne Koen (CSIR National Laser Centre)\nTo our know ledge\, we have demonstrated the first optically pumped tunable HBr oscill ator lasing on both the P- and the R-branches. Through the implementation of an intra-cavity diffractive grating\, we could tune the wavelength ove r a range of 538 nm from 3872 nm to 4410 nm. \n\nA single-frequency Ho:YLF ring laser and amplifier system was used as pump source. The oscillator w as pumped in a double pass configuration with 50 mJ\, 2064 nm pulses at a repetition rate of 50 Hz. The HBr was kept at 52 mBar\, 20 degrees Celsius in a 510 mm tube. \n\nThe resonator cavity consisted of a flat output cou pler mirror with a reflectivity of R=80% at 4 μm\, and a high-reflective coating at 2 μm. The input coupler mirror had a concave curvature of 5 m and was coated to be highly reflective at 4 μm and highly transmissive at 2 μm to allow pumping of the HBr. The input coupler mirror was slightly tilted to reflect light unto a flat mirror which in turn reflected unto th e diffractive grating which was blazed at 5 μm. The diffractive holograph ic grating therefore acted as the backreflector mirror\, and the wavelengt h could be selected by rotating the grating.\n\nLasing was demonstrated on eight lines of the P-branch with wavelengths ranging from 4102 nm to 4410 nm\, and five lines of the R-branch ranging from 3872 nm to 3999 nm. The highest output energy for the given pump power was 1.1 mJ at 4131 nm.\n\nh ttps://events.saip.org.za/event/7/contributions/5266/ LOCATION: Acro4 URL:https://events.saip.org.za/event/7/contributions/5266/ END:VEVENT BEGIN:VEVENT SUMMARY:DRS\, XRD and SEM studies of the effects of metal dopants (Pt\, Au and Pd) on the structural and optical properties of TiO2. DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5267@events.saip.org.za DESCRIPTION:Speakers: Jacob Ramodika Moloantoa (University of Limpopo)\nTi tania is a cheap and nontoxic polymorphic material of current interest for a variety of technological applications like in gas sensing and photovolt aic cells. Generally\, TiO2\, with a band gap of 3.2 eV\, can only be exci ted by a small UV fraction of solar light\, which accounts for only 3-5% o f the solar energy. Various strategies have been pursued including doping with metallic elements (e.g. Fe) or nonmetallic elements (e.g. N) with th e aim of shifting the absorption into the visible range. In the present wo rk TiO2 was doped with platinum (Pt)\, palladium (Pd) and gold (Au) at dop ing levels of 5% weight\, following the standard sol-gel methods. Structur al characterization was carried out using scanning electron microscopy (SE M) and X-ray diffraction (XRD). Optical properties were studied using the Diffuse Reflectance Spectroscopy (DRS). The results of the lattice paramet er calculations from the XRD patterns of metal loaded TiO2 are almost the same as for the undoped. Doping with Pt and Pd resulted in a lower anatase to rutile phase transformation temperature while doping with Au did not a ffect the transformation temperature. SEM micrographs show that the surfac e contains irregular shaped particles which are the aggregation of tiny cr ystals for lower temperatures. At higher temperatures (900 °C)\, we obse rve spheroids of metallic nanocrystals on the surface of TiO2.The reflecta nce spectra of the metal loaded TiO2 reveal substantial reduction in refle ction (i.e. they show enhanced absorption)from 400nm to the entire visible region.\n\nhttps://events.saip.org.za/event/7/contributions/5267/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5267/ END:VEVENT BEGIN:VEVENT SUMMARY:Ab-initio study of structural stability and electronic structure o f monoclinic and cubic ZrO2-xSxx for 0 ≤ X < 2 DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5268@events.saip.org.za DESCRIPTION:Speakers: Masilu Godfrey Mulaudzi (University of Limpopo)\nThe system ZrO2-xSxx is limited by the cases ZrO2 and ZrS2 (x = 0\, 2). Physi cal properties of such systems for 0 < x < 2 are of great interest\, but d ifficult to obtain from first principles calculation. A recently suggested approach\, i.e virtual crystal approximation\, allows simulation for chan ges in composition\, while retaining a small unit cell. In this paper we e mploy Density Functional Theory (DFT) within the Generalized Gradient Appr oximation (GGA)to study the zirconium dioxide – sulfide system ZrO2-xSxx \, using the CASTEP code. We investigated geometric cell size effects\, me chanical properties and electronic structure for these systems at various amounts of sulfur concentrations. For the treatment of solid solutions in the recently introduced VCA approach\, CASTEP allows to define partial occ upancies for atomic sites\; in our case\, the anionic lattice sites of ZrO 2-xSxx crystal are defined to be less than fully oxygen occupied: (2-x)\; and consequently similar sites can then be attributed a partial sulfur cha racter: (x). The lattice parameters and cell size increases for zirconia a s the sulfur content is increased. Furthermore\, the trend of Fermi level and the electron distributions differ\, giving rise to reduced band gap as S is increased. The cubic structure ZrO2-xSxx is stable for x<1.2\, howev er\, the structure gives negative tetragonal shear modulus at x≥1.2\, co ndition of mechanical instability.\n\nhttps://events.saip.org.za/event/7/c ontributions/5268/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5268/ END:VEVENT BEGIN:VEVENT SUMMARY:Radon from building materials DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5269@events.saip.org.za DESCRIPTION:Speakers: RABECCA RAMOKONE THELEDI (UWC)\nRadon is a naturally occurring radioactive inert gas in the decay chain of uranium-238. High radon levels in houses have been linked to the occurrence of lung cancer via the deposition of radon progeny in the lungs.\nThe radon activity in h ouses depends on the concentration of radium in the soil below the house a nd the diffusion of radon into the house. Another pathway is the concentra tion of radium in building materials. There has been concerns that indoor radon from granite countertops and zircon tiles might contribute signific antly to the radon concentration in a house. \nThe aim of this work is to look at how much radon is coming out of some South African tiles and gran ite used in houses\, as well as other building materials. Radium content has been measured using a NaI detector and radon with the use of a RAD7 co ntinuous radon monitor as well as electrets ion chambers. Preliminary meas urements will be presented on material that has been used in construction in South Africa.\n\nhttps://events.saip.org.za/event/7/contributions/5269/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5269/ END:VEVENT BEGIN:VEVENT SUMMARY:Orbital Environment Risk Assessment for SumbandilaSAT DTSTART;VALUE=DATE-TIME:20110715T064500Z DTEND;VALUE=DATE-TIME:20110715T070000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5270@events.saip.org.za DESCRIPTION:Speakers: Chijioke Nwosa (NASSP/SAAO)\nSatellites have to oper ate in a hostile space environment that poses numerous threats from radiat ion\, charged particles\, residual atmosphere\, micrometeoritic impacts\, space debris and other operational and defunct satellites.\nThe region of outer space around the Earth is becoming polluted from anthropogenic space system junk and fragments. Currently\, according to US Space Surveillance Network\, 21\,000 objects (roughly 10cm or larger) orbiting Earth are tra cked.\nWith the Knowledge of the state of the Sun’s behavior\, in terms of the 11-year solar cycle and sun-induced space weather phenomena\, the p assage through meteor showers and the population of known man-made space o bjects\, it is possible to model the environmental impositions on Sumbandi la during its operational lifetime.\nThis paper aims to assess the risk po sed by the natural space material and man-made space objects to Sumbandila SAT during its operational lifetime.\n\nhttps://events.saip.org.za/event/7 /contributions/5270/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5270/ END:VEVENT BEGIN:VEVENT SUMMARY:Optical study of the Southern high mass star forming region RCW 34 DTSTART;VALUE=DATE-TIME:20110714T094500Z DTEND;VALUE=DATE-TIME:20110714T100000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5271@events.saip.org.za DESCRIPTION:Speakers: Robert Czanik (North-West University\, Potchefstroom )\nTo understand the formation of stars one must be able to identify young objects. RCW 34 is a star forming region in the constellation of Vela. A study was conducted in the near-infrared where it was found that a large n umber of stars surrounding the nebula shows NIR characteristics of lower m ass pre-main sequence stars. To prove the suspicions a follow-up study was conducted in the optical. The results of a photometric and spectroscopic study on the the nebula and stars within a 7 arcmin x 7 arcmin region arou nd the nebula will be presented.\n\nhttps://events.saip.org.za/event/7/con tributions/5271/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5271/ END:VEVENT BEGIN:VEVENT SUMMARY:KIC Rumple\, the binary system with eclipses and δ Scuti pulsatio ns DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5272@events.saip.org.za DESCRIPTION:Speakers: Christopher Middleton (University of Johannesburg)\n Studying pulsating stars in Eclipsing binaries has the potential to be an exacting test of theoretical stellar models as a result of the large numbe r of constraints physically that can be imposed on individual components i n the binary system. In this particular example\, Kpl Rumple\, the measur ement of the large number of frequencies in the star of precisely known ma ss and radius from binary modelling will enable the identification of puls ation modes. This is vital as a proper physical understanding of δ Scuti pulsations will ensue. It also holds the promise of direct detection of th e spatial distribution of pulsations on stellar surfaces.\n\nAsteroseismol ogy is the ultimate goal: the derivation of internal rotational behaviour in stars\, accurate determination of stellar aging with associated metalli cities and the determination of the amount of convective core overshooting in stellar interiors.\n\nThe research involves the analysis of data obtai ned through membership of the Kepler Asteroseismic Consortium Working Grou p 9\, analysing proprietary data received from the Kepler Space Telescope. \n\nThe data are de-trended\, and subject to refined sophisticated analys is routines using many software platforms based on sound physical principl es in the determination of the binary parameters and pulsating frequencies of the pair. \n\nAnticipated conclusions that might be derived from the c onclusion of this project are discussed.\n\nhttps://events.saip.org.za/eve nt/7/contributions/5272/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5272/ END:VEVENT BEGIN:VEVENT SUMMARY:Investigation of broken symmetry of Sb/Cu(111) surface alloys by V T- STM DTSTART;VALUE=DATE-TIME:20110713T093000Z DTEND;VALUE=DATE-TIME:20110713T094500Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5273@events.saip.org.za DESCRIPTION:Speakers: Gebhu Ndlovu (Student)\nThe adsorption of Sb on the (111) plane of noble metals surfaces such as copper and silver has long be en of practical interest in the fields of surface science and technology. The electronic properties of such surface alloys are important for several surface and interface related applications like metal-metal or semiconduc tor-metal heteroepitaxy\, heterogeneous catalysis\, sensors and spintronic s applications. The structure of these monolayers on metal substrates is a complex interplay of electronic\, stress and geometric effects\, all rela ted to each other. Theoretical calculations have suggested that the energe tics of the Sb/Cu(111) system are such that in the ordered 0.33 ML Cu(111) (√3x√3) R30°-Sb phase the Sb atoms substitute one-third of the outer most Cu atoms to produce an ordered surface alloy after annealing. Due to its ability to act as a surfactant (low surface energy)\, Sb segregates fr om the bulk of the substrate to remain on the surface\, thus forming a sur face alloy. This work present an in situ Variable Temperature Scanning Tun neling Microscopy (VT-STM) study of the segregation and dissolution kineti cs of Sb/Cu(111) studied at various temperatures. The study shows the grow th mechanism of Sb mediated by the kinetics and thermodynamics at the subs trate surface. After deposition of ~0.3 ML Sb on a clean Cu(111) surface\ , STM images exhibit Sb atoms as bright spots surrounded by six copper a toms at the surface with perturbed atomic positions resulting in a broken structural inversion symmetry at the surface.. The atomic arrangements of Sb remain stable during several STM scans.\n\nhttps://events.saip.org.za/e vent/7/contributions/5273/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5273/ END:VEVENT BEGIN:VEVENT SUMMARY:NON-SPECIALIST: The Recommissioning of SALT DTSTART;VALUE=DATE-TIME:20110713T090000Z DTEND;VALUE=DATE-TIME:20110713T093000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5274@events.saip.org.za DESCRIPTION:Speakers: Phil Charles (SAAO)\nFollowing the repair of the SAL T optics in late 2010\, the telescope has reentered the commissioning phas e with its principal scientific instruments\, SALTICAM and RSS. Both thes e instruments have undergone major refurbishments in their own right\, and their current status and that of the telescope will be described\, togeth er with an update on its performance.\n\nhttps://events.saip.org.za/event/ 7/contributions/5274/ LOCATION: Acro2 URL:https://events.saip.org.za/event/7/contributions/5274/ END:VEVENT BEGIN:VEVENT SUMMARY:Germanium-Carbide Formation on Crystal Germanium Substrate DTSTART;VALUE=DATE-TIME:20110714T121500Z DTEND;VALUE=DATE-TIME:20110714T123000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5275@events.saip.org.za DESCRIPTION:Speakers: Genene Tessema Mola (University of Kwazulu-Natal)\nM icrocrystalline germanium-carbide formation was studied in germanium subst rate using perturbed gamma-gamma angular correlation (PAC) method. Informa tion about the lattice location of carbon atoms\, in the host matrix\, can be obtained via the interaction between carbon and unstable probe nucleus (111In). At high dose carbon implantation\, in crystal germanium substrat e\, two defect complexes have been identified by the corresponding unique nuclear quadrupole interaction frequencies. The measured frequencies\,  Q = 207(1) MHz (eta = 0.2) and Q = 500(1) MHz ( eta= 0)\, are associate d with the formation of carbon related microcrystalline system in germaniu m. The frequencies are attributed to two different types of carbon-indium pairs in the substrate lattice. The orientations of the measured electric field gradients and thermal stability of the defect complexes are studied. The results are encouraging towards attaining germanium carbide crystal w hich has interesting potential for applications.\n\nhttps://events.saip.or g.za/event/7/contributions/5275/ LOCATION: Parthenon URL:https://events.saip.org.za/event/7/contributions/5275/ END:VEVENT BEGIN:VEVENT SUMMARY:The Infrared Plasma Resonance of P in SiC DTSTART;VALUE=DATE-TIME:20110713T150000Z DTEND;VALUE=DATE-TIME:20110713T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5276@events.saip.org.za DESCRIPTION:Speakers: JAPIE ENGELBRECHT (NMMU)\nThe concentration of any d opant in a semiconductor can usually easily and readily be established usi ng the plasma resonance minimum. Infrared reflectance spectroscopy was us ed to assess the doping of SiC wafers by phosphor implantation. However\, results obtained did not match the theoretical predictions. The problem was investigated\, including an assessment of the applicable theory. Resu lts will be presented and discussed.\n\nhttps://events.saip.org.za/event/7 /contributions/5276/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5276/ END:VEVENT BEGIN:VEVENT SUMMARY:Simple Pendulum: A first year students' dilemma. DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5279@events.saip.org.za DESCRIPTION:Speakers: Itumeleng Phage (Honorary)\nInvestigation of the Fir st-year students' abilities to use mathematical concepts of straight line equation and graph to analyse Physics properties with particular reference s to a Simple Pendulum motion experiment.\n\nhttps://events.saip.org.za/ev ent/7/contributions/5279/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5279/ END:VEVENT BEGIN:VEVENT SUMMARY:PLASMON: Data Assimilation of the Earth's Plasmasphere DTSTART;VALUE=DATE-TIME:20110714T150000Z DTEND;VALUE=DATE-TIME:20110714T170000Z DTSTAMP;VALUE=DATE-TIME:20260417T052022Z UID:indico-contribution-7-5280@events.saip.org.za DESCRIPTION:Speakers: Andrew Collier (Hermanus Magnetic Observatory)\nThe principal source and loss mechanisms in the Earth's radiation belts are cu rrently not completely understood. Loss rates are important since they det ermine the duration of exposure of satellites to enhanced radiation condit ions during a geomagnetic storm. The dominant loss process is relativistic electron precipitation via resonant interactions with a variety of wave m odes. These interactions are governed by the characteristics of the plasma sphere. Current models provide an inadequate representation of the spatial and temporal evolution of the plasmasphere. In situ measurements of the p lasmasphere provide only local characteristics and are thus unable to yiel d a complete global picture. Ground based measurements\, based on the anal ysis of Very Low Frequency (VLF) whistlers and Field Line Resonances (FLRs )\, are able to describe large sections of the plasmasphere\, extending ov er significant radial distances and many hours of local time. These measur ements provide electron number and plasma mass densities.\n\nPLASMON is a funded FP7 project between 11 international partners. PLASMON intends to a ssimilate near real time measurements of plasmaspheric densities into a dy namic plasmasphere model. The VLF whistler analyses will be conducted by a utomatic retrieval of equatorial electron densities using data from AWDAne t. Equatorial mass densities will be constructed from FLR measurements alo ng meridional magnetometer chains. The resulting model will facilitate the prediction of precipitation rates. The predicted rates will be compared t o observations from the AARDDVARK network.\n\nhttps://events.saip.org.za/e vent/7/contributions/5280/ LOCATION: Asteria URL:https://events.saip.org.za/event/7/contributions/5280/ END:VEVENT END:VCALENDAR