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Magister Scientiae - MSc / In this study we report on the effect of the deposition parameters on the morphology and structural properties of CNTs, synthesized by means of the hot-wire chemical vapour deposition technique. SEM, Raman and XRD results show that the optimum deposition conditions for the HWCVD synthesis of aligned MWCNTs, with diameters between 50 and 150 nm and lengths in the micrometer range are: Furnace temperature of 500 ºC, deposition pressure between 150 and 200 Torr, methane/hydrogen dilution of 0.67 and a substrateto- filament distance of 10 cm. / South Africa

Analysis and results are presented from EXOSAT observations of Seyfert type active galactic nuclei (AGN). The sample chosen for study axe 48 hard X-ray selected Seyfert type AGN including all 29 of the emission line AGN in the Piccinotti sample making this the largest such survey to date. EXOSAT, its detectors and methods of data analysis axe detailed, with emphasis on background subtraction techniques. One of the most important new results from EXOSAT data is the discovery that rapid variability (factor 2 over a few thousand seconds) is common in AGN. No evidence is found in the sample sources for any characteristic timescales of variability. Combining EXOSAT LE and ME data allowed us to obtain broad band X-ray spectra over the range 0.1-10 keV. Spectra in the ∼ 2-10 keV range are found to be well described by a simple power-law. The distribution of spectral indices across the sample can be approximated by a Gaussian distribution of mean a = 0.70 and a = 0.17. The spectra are not all consistent with this mean at the 90% confidence level and there must some intrinsic spread in AGN slopes. This spread can be constrained to 0.14. EXOSAT has also revealed a significant number of sources with complex soft X-ray spectra. These include spectra with a second spectral component at soft X-ray energies and sources with ''leaky" absorbing columns. Evidence that soft excess components occur in at least 50% of Seyfert type AGN, together with detection of rapid variability in the soft component provides the strongest support to date for an accretion disc model for AGN.

M.Sc. / Aerosol samples were collected at stations using simple filter unit, loaded with a 4 7 mm diameter pore size Nuclepore membrane filter. The sampling duration was 24 hours for each sample, with the total of 11 samples: seven for Thohoyandou and four for Bethlehem. The samples were analyzed with energy dispersive X-ray fluorescence spectrometry for up to 20 elements. Comparison for elemental concentrations of the data showed that the samples fall into three clusters on average (major: Ca, Cl, Si. S, Fe and AI; intermediate: K, Ti, Pb, Brand Zn; minor: Mn, Cr, As, Sr, Ni and Cu), with the samples collected from Bethlehem having high concentrations in all clusters. High concentrations in the samples collected on Bethlehem were attributed to entrainement of dust particles during the dry winter period. The results also show that the elements are associated with anthropogenic emissions. Therefore, the sampling station at Thohoyandou is considered as a background station due to the low aerosol concentration. The aerosol concentration levels at Thohoyandou can be attributed to biogenic sources because of the large presence of large forest areas in the region and in the vicinity of the sampling location. The samples collected in both regions reveal highly enriched sulphur, chlorine, zinc and lead. It is clearly proved that these elements come from local soil. Chromium and copper were both slightly enriched in Thohoyandou, but the concentration data for these two elements are not available. However it is supposed that these elements come from local soil as well. In another aerosol analysis, passive (diffusive) samplers were used to measure concentration levels for sulphur dioxide and nitrogen dioxide. The measurement campaign was carried out from Soweto in Johannesburg and Bohlokong in Bethlehem with the campaign lasting for two months during the w~nter season. A very clear result derived for sulphur dioxide was the dominating source contribution from use of coal for heating and cooking in both areas. For nitrogen dioxide, it was found that contribution from traffic in highly populated areas and from industrial activities in the neighbourhood of the two areas was the source. The role played by wood burning, is also another additional source used for domestic heating and even cooking.

M.Sc. (Geology) / Refer to full text for abstract

Magister Scientiae - MSc / In this study, the capabilities of Neutron Radiography (NRad) and -Tomography (NTomo), as well as X-ray Radiography (XRad) to investigate chlorides and chlorides corrosion effects within steel reinforced laboratory concrete samples are practically explored. Capabilities of Scanning Electron Microscopy (SEM), Prompt Gamma Neutron Activation Analysis (PGNAA), Particle Induced X-ray Emission (PIXE), Small-Angle Neutron Scattering (SANS), Neutron Diffraction (NDIFF) and X-ray Diffraction (XDIFF) analytical techniques are also explored through review of literature.

Magister Pharmaceuticae - MPharm / In this study, new solid supramolecular derivatised forms of bis(adamantine-1-aminium) carbonate (ADTCO3) were prepared. ADTCO3 is a derivative of amantadine used for Parkinson’s disease and has antiviral properties against influenza-A, dengue fever and pharmacological activity towards Parkinson’s disease. The new forms prepared were polymorphic and co-crystal forms of ADTCO3. Polymorphism is a phenomenon where the ability of a substance to exist in two or more crystalline forms occurs when crystallised under different conditions and co-crystallization is the process of formation of multicomponent crystals of a drug substance. New solid forms often display different mechanical, physicochemical and thermal properties that can remarkably influence the bioavailability, hygroscopicity and stability of active pharmaceutical ingredients (APIs). For the formation of polymorphs of ADTCO3, techniques such as dry grinding, solvent-drop grinding, co-precipitation, sublimation and vapour diffusion were applied. For the development of co-crystals and/or complex formation, ADTCO3 was treated in combination with ten selected co-formers viz; benzoic acid, 4-hydroxybenzoic acid, cinnamic acid, 4-hydroxycinnamic acid, succinic acid, tartaric acid, salicylic acid, L-glutamic acid, citric acid monohydrate and L-glutaric acid using similar techniques as applied in the polymorphism study. The first four co-formers were selected for their potential biological activity and the latter six were selected for their generally regarded as safe (GRAS) status. All products were isolated and characterized using different analytical techniques to assess the thermal behaviour of the products by hot stage microscopy (HSM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). FTIR spectroscopy and proton-nuclear magnetic resonance (1HNMR) were used to identify and determine the purity of the parent compounds and the modified forms. X-ray powder diffraction was used to determine the formation of a new phase and single crystal X-ray diffraction was applied at the initial stages to identify ADTCO3 by its unit cell parameters. Furthermore, the Cambridge Structural Database (CSD) and other resources were used to generate information on the molecular structures of all elucidated parent compounds, their polymorphs and reported co-crystals. Four different polymorphic forms of ADTCO3 were identified (viz. ADTCO3 Forms I to IV) and sixteen co-crystals (viz. ADTCO3BA1 to ADTCO3BA5, ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SUC, ADTCO3LTTA, ADTCO3SA, ADTCO3CA, ADTCO3GLA, ADTCO3GA) were synthesised. Of the sixteen co-crystals 5 were identified as ADTCO3BA “salt” co-crystal polymorphic forms and 2 as ADTCO3SUC co-crystal polymorphic forms. Two solvated “salt” co-crystal forms were also identified, namely; ADTCO3GLA and ADTCO3LTTA. ADTCO3GLA had a mass loss of 10.3% (n = 2.4) and ADTCO3LTTA had a mass loss of 5.25% (n = 0.86). Finally, the rest of the co-crystals ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SA, ADTCO3CA and ADTCO3GA all crystallised as “salt” co-crystals.