Somerset East, South Africa
Somerset East, South Africa

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Lafane S.,Algerian Center de Développement des Techniques Avancées | Kerdja T.,Algerian Center de Développement des Techniques Avancées | Abdelli-Messaci S.,Algerian Center de Développement des Techniques Avancées | Malek S.,Algerian Center de Développement des Techniques Avancées | Maaza M.,IThemba LABS National Research Foundation
Applied Physics A: Materials Science and Processing | Year: 2010

In this paper, the plume expansion dynamics of an ablated Sm 2O3, Nd2O3 and NiO mixture oxides target by KrF laser into background oxygen atmosphere has been investigated using a fast ICCD imaging. The laser fluence was fixed at 2 J cm-2 and the surrounding ambient gas pressure was varied from vacuum to 50 mbar. Some effects as double plume splitting, plume sharpening and plume stopping were observed. The imaging data were used to create position-time plots of the luminous front. The plume behaviour was found to be influenced by the gas pressure above a certain threshold. Exceeding this pressure threshold, in earlier time the expansion was almost linear independently of the background gas pressure used. However, as time evolves, the plume is decelerated and comes to rest. The plasma plume dynamics was analysed in the framework of a shock-wave model and a drag model. It was found that the shock-wave model is valid in distances range which depends on the gas pressure. At later time, it is rather the drag model which is valid since it predicts exactly the stopping distance observed at high pressures. Using the dimensionless variables, a general description of the plasma plume dynamics was given. Finally, the plasma plume width-time evolution was studied. © 2009 Springer-Verlag.


Khamlich S.,IThemba LABS National Research Foundation | Khamlich S.,Tshwane University of Technology | Khamlich S.,South African Council for Scientific and Industrial Research | McCrindle R.,Tshwane University of Technology | And 5 more authors.
Applied Surface Science | Year: 2013

A cost-effective and environmentally friendly green chemical method, the so-called aqueous chemical growth (ACG) method, was used to deposit chromium/alpha-chromium(III) oxide, Cr/α-Cr2O3, monodispersed particles, for solar absorbers applications. The deposited particles were annealed at various temperatures in a hydrogen atmosphere for 2 h to study the annealing temperature dependence of the structural, chemical and optical properties of the particles grown on tantalum substrates. The deposited Cr/α-Cr2O3 was characterized by X-ray diffraction (XRD), attenuated total reflection (ATR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and diffuse reflectance UV-vis-NIR spectroscopy. The XRD and ATR analysis indicated that by increasing annealing temperature, the particles crystallinity was improved and Ta2O 5 was formed around 600°C, due to the fast oxygen diffusion from the deposited α-Cr2O3 toward the tantalum substrate. The optical measurements show that samples annealed at 400 and 500°C exhibit the targeted high absorbing optical characteristics of "Black chrome", while those annealed below 400°C and above 500°C show a significant low absorptivity and high emissivity. Copyright © 2012 Published by Elsevier B.V. All rights reserved.


Nuru Z.Y.,IThemba LABS National Research Foundation | Nuru Z.Y.,University of the Western Cape | Nuru Z.Y.,University of South Africa | Msimanga M.,IThemba LABS Gauteng | And 4 more authors.
Applied Surface Science | Year: 2014

An AlxOy/Pt/AlxOy multilayer solar absorber for use in solar-thermal applications has been deposited onto copper substrate by electron beam (e-beam) vacuum evaporation at room temperature. Different samples were annealed at different temperatures in air and characterized by spectrophotometry, emissometry, heavy ion elastic recoil detection analysis (HI-ERDA), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The AlxOy/Pt/Al xOy multilayer solar absorbers heated up to 500 C were found to exhibit good spectral selectivity (α/É) of 0.951/0.08. However, beyond 500 C the spectral selectivity decreased to 0.846/0.11, possibly due to thermally activated atomic interdiffusion profiles. HI-ERDA has been used to study depth-dependent atomic concentration profiles. These measurements revealed outward diffusion of the copper substrate towards the surface and therefore, the decrease in the constituents of the coating. The decrease in the intensity of Pt grains and formation of CuO and Cu2O phases at 700 C were confirmed by XRD and EDS. © 2014 Elsevier B.V.


Nuru Z.Y.,IThemba LABS National Research Foundation | Nuru Z.Y.,University of the Western Cape | Nuru Z.Y.,University of South Africa | Arendse C.J.,University of the Western Cape | And 6 more authors.
Solar Energy Materials and Solar Cells | Year: 2014

This paper reports the effect of thermal annealing on AlxO y/Pt/AlxOy multilayer solar absorber coatings deposited by an electron beam (e-beam) vacuum evaporator onto copper substrate at room temperature. The samples were annealed at different temperatures for different duration in air. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), Raman spectroscopy, UV-vis spectrophotometer and emissometer. The results showed changes in morphology, structure, composition, and optical properties depend on both temperature and duration of annealing. The XRD pattern showed the intensity of Pt decreased with increasing annealing temperature and therefore, disappeared at high temperature. With increasing annealing temperature, an increase in the size of Pt particles was observed from SEM. The AlxOy/Pt/Al xOy multilayer solar absorber coatings deposited onto Cu substrate were found to be thermally stable up to 500 C in air for 2 h with good spectral selectivity (α/ε) of 0.951/0.09. At 600 C and 700 C, the spectral selectivity decreased to 0.92/0.10 and 0.846/0.11 respectively, which is attributed to the diffusion of Cu and formation of CuO and Cu2O phases. The formation of CuO and Cu2O phases were confirmed by XRD, Raman spectroscopy and optical modelling. Long term thermal stability study showed the coatings were thermally stable in air up to 450 C for 24 h. © 2013 Elsevier B.V.


PubMed | Chris Hani Baragwanath Academic Hospital, iThemba LABS National Research Foundation, Ghent University, Charlotte Maxeke Johannesburg Academic Hospital and Donald Gordon Medical Center and University of Witwatersrand
Type: | Journal: BMC cancer | Year: 2015

Current knowledge of the aetiology of hereditary breast cancer in the four main South African population groups (black, coloured, Indian and white) is limited. Risk assessments in the black, coloured and Indian population groups are challenging because of restricted information regarding the underlying genetic contributions to inherited breast cancer in these populations. We focused this study on premenopausal patients (diagnosed with breast cancer before the age of 50; n=78) and triple negative breast cancer (TNBC) patients (n=30) from the four South African ethnic groups. The aim of this study was to determine the frequency and spectrum of germline mutations in BRCA1, BRCA2 and PALB2 and to evaluate the presence of the CHEK2 c.1100delC allele in these patients.In total, 108 South African breast cancer patients underwent mutation screening using a Next-Generation Sequencing (NGS) approach in combination with Multiplex Ligation-dependent Probe Amplification (MLPA) to detect large rearrangements in BRCA1 and BRCA2.In 13 (12 %) patients a deleterious mutation in BRCA1/2 was detected, three of which were novel mutations in black patients. None of the study participants was found to have an unequivocal pathogenic mutation in PALB2. Two (white) patients tested positive for the CHEK2 c.1100delC mutation, however, one of these also carried a deleterious BRCA2 mutation. Additionally, six variants of unknown clinical significance were identified (4 in BRCA2, 2 in PALB2), all in black patients. Within the group of TNBC patients, a higher mutation frequency was obtained (23.3 %; 7/30) than in the group of patients diagnosed before the age of 50 (7.7 %; 6/78).This study highlights the importance of evaluating germline mutations in major breast cancer genes in all of the South African population groups. This NGS study shows that mutation analysis is warranted in South African patients with triple negative and/or in premenopausal breast cancer.


Abdellaoui I.,Abou Bekr Belkaid University Tlemcen | Merad G.,Abou Bekr Belkaid University Tlemcen | Maaza M.,IThemba LABS National Research Foundation | Abdelkader H.S.,Abou Bekr Belkaid University Tlemcen
Journal of Alloys and Compounds | Year: 2016

The energetic, electronic structures and optical properties of Mg-, F-doped and Mg-,F-codoped M1-VO2 systems have been investigated using first-principles calculations with the HSE06 functional theory. The results show that the energetic stability can be easily prepared the desirables Mg-doped at O-rich conditions, and F- and Mg-,F-codoped VO2 at V-rich conditions. In addition, the incorporation of F and Mg into M1-VO2 serves to reduce the absorption under visible-light irradiation. Consequently, the band-gap is widened between lower d|| and π∗sub-bands; this is due to the internal stress induced by Mg atom along a-axis, and the high electronegativity of F atoms compared to that of O atoms. © 2015 Elsevier B.V.


Nuru Z.Y.,University of South Africa | Nuru Z.Y.,IThemba LABS National Research Foundation | Arendse C.J.,University of the Western Cape | Mongwaketsi N.,IThemba LABS National Research Foundation | And 4 more authors.
Renewable Energy | Year: 2015

We report the effects of substrate temperatures on the thermal stability of AlxOy/Pt/AlxOy multilayered selective solar absorber coating (MSSAC). The samples were deposited at different substrate temperatures (from room temperature up to 250°C), and then annealed at various temperatures (300-600°C) in air for 2h. Characterizations are made via X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Atomic Force Microscopy (AFM), Raman Spectroscopy, UV-Vis and emissometeric measurements. These coatings were found to be thermally stable up to 500°C with good spectral selectivity of 0.930/0.11. Furthermore, the observed decrease in the spectral selectivity 0.883/0.13 at 600°C is attributed to the diffusion of Cu and the formation of CuO phase. Such phase formation was confirmed using XRD and Raman spectral analysis. The insensitiveness of the thermal stability of such coatings on the substrate temperature is demonstrated. © 2014 Elsevier Ltd.


Nuru Z.Y.,University of South Africa | Nuru Z.Y.,IThemba LABS National Research Foundation | Arendse C.J.,University of the Western Cape | Khamlich S.,University of South Africa | And 5 more authors.
Solar Energy | Year: 2014

The effect of a thin Tantalum layer on the thermal stability of Al. xO. y/Pt/Al. xO. y multilayered selective solar absorber coatings has been investigated. The resulting samples were annealed at different temperatures for different durations in air. These were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Atomic force microscopy, Raman spectroscopy, UV-vis-NIR spectrophotometer and emissometer. The Cu/Ta/Al. xO. y/Pt/Al. xO. y multilayer solar absorber coatings were found to be thermally stable up to 700. °C in air for 2. h with good spectral selectivity (α/. ε) of 0.932/0.10. At 800. °C, the spectral selectivity decreased to 0.870/0.12, which is attributed to the diffusion of Cu and formation of CuO phase. The formation of CuO phase was confirmed by X-rays diffraction, energy dispersive spectroscopy and Raman spectroscopy. Long term thermal stability study showed that the coatings were thermally stable in air up to ~550. °C for about 24. h. © 2014 Elsevier Ltd.


Sackey J.,iThemba Labs National Research Foundation | Sackey J.,University of South Africa | Nuru Z.Y.,iThemba Labs National Research Foundation | Nuru Z.Y.,University of South Africa | And 3 more authors.
Materials Today: Proceedings | Year: 2015

This paper investigates the self-assembled chitin based nanostructures of the Caligo Memnon Nymphalidae Felder (1866) butterfly's scales that are responsible for the colour formation on the butterfly's "artificial eyespot". The Fourier transform analysis of the digital scanning electron microscope images and the calculation of the corresponding half-width Airy disc allowed an effective estimation of the temporal resolution of this "artificial eyespot" as well as its optical sensitivity and optical absorption/light trapping. It was observed that Land equation remains an excellent tool for computing optical sensitivity of nanostructure materials. © 2015 Elsevier Ltd.


Maaza M.,University of South Africa | Maaza M.,IThemba LABS National Research Foundation | Ngom B.D.,University of South Africa | Ngom B.D.,IThemba LABS National Research Foundation | And 4 more authors.
Vacuum | Year: 2015

This contribution reports on novel physical properties of specific oxides in their nano scaled configuration. This includes the ultrafast optical limiting of VO2 thin films, the magneto-optical tunability of the ESR response of α-Cr2O3 nano-spheres, and the reversible control of the surface tension of ZnO oriented nano-rods as well as the validation of the synthesis of high crystalline stoichiometric of rare earth nanostructures by the so called local gas feeding beam pulsed laser deposition. © 2015 Elsevier Ltd. All rights reserved.

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