3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Determination of the calcaemic status of oncology patients at the Charlotte Maxeke Johannesburg academic hospital, using unadjusted serum total calcium(2019) Khan, Shaida BibiBackground: When total serum calcium (TCa) is used to determine the calcaemic status of patients, it has to be adjusted, using one of several formulae to limit the effect of low or raised serum albumin levels. All the existing adjustment formulae, were not validated against ionised calcium, neither have they been adjusted for the presence of paraproteins. They have also not been validated for use in cancer patients complicated with chronic kidney disease and cachexia. This study therefore aimed to determine whether unadjusted serum TCa measurement, could be used successfully to determine the calcaemic status instead of the gold standard, ionised calcium (ICa), in two sub-groups of hospital patients with breast cancer (BCA) and multiple myeloma (MM). Material and methods: 202 paired TCa/ICa data points for MM and 3 467 for BCA were reviewed retrospectively over a 1-year period for diagnostic concordance and discordance using ICa as the gold standard. Results: In the MM sub-group, the diagnostic concordance was 60.1% (18 - 59 years) and 78.8% (60 - 90 years) for hypocalcaemia, and 7.4% (18-59 years) and 42.9% (60 -90 years) for hypercalcaemia. Whilst in the BCA sub-group, the diagnostic concordance was 46.1% (18 - 59 years) and 44.5% (60 - 90 years) for hypocalcaemia, and 14.7% (18-59 years) and 21.5% (60 -90 years) for hypercalcaemia. Conclusion: In all cancer sub-groups, both hypocalcaemia and hypercalcaemia were underestimated to various degrees. This was similar to other studies published in non-cancer- specific patients. The poor performance of unadjusted TCa in the study prompted a recommendation that ICa should be used preferentially in cancer patients.Item The use of time-lapse electrical resistivity tomography to determine the footprint of acid mine drainage on groundwater(2017) Zulu, Sbonelo MfezekoThe costs of acid mine drainage (AMD) monitoring result in the quest for alternative noninvasive method that can provide qualitative data on the progression of the pollution plume and ground geophysics was the ideal solution. However, the monitoring of AMD plume progression by ground geophysics (time-lapse electrical resistance) proves to be noninvasive but also time consuming. This study focuses on the modeling of different geophysical anomalies (mainly geoelectrical resistivity response) of the karstic aquifers. The models are generated from field parameters such as the electrical resistivity of the host rock and the target rock, depth to the target, noise level and electrode configuration in order to ensure that the model outcomes represent the actual field data. This process uses Complex Resistivity Model (CRMod) and Complex Resistivity Tomography (CRTomo) to generate geoelectric subsurface models. Different resistivity values are applied to targets in order to assess the difference against the baseline model for each target scenario. The resistivity difference is reduced to smallest possible value between the reference and new models in order to gauge the lowest percentage change in the model at which the background noises start to have impact on the results. The study shows that the behavior of targets (aquifer) could be clearly detected through resistivity difference tomography rather than inversion tomography. The electrode array plays a significant part in the detection of target areas and their differences in resistance because of its sensitivity. This therefore indicates that the electrode array should be chosen according to study requirements. Furthermore, this study shows that the modelling of different target sizes, alignments and shapes plays huge role in the final results. Future studies that can provide a correlation between the field quantitative data from sampling and the model outcomes have the ability to add to the knowledge of geophysical modeling, thus reducing costs associated with field based plume AMD monitoring. Key words: Acid mine drainage, geophysics, karst aquifer, complex resistance, modelling, tomographyItem Surface wave tomography and shear wave velocity structure of the Southwestern block of the Congo craton(2012-02-27) Mangongolo, AzangiRayleigh wave dispersion curves are used to invert for the group velocity maps of the southwestern block of the Congo craton. The group velocity maps were then inverted to obtain the three dimensional shear-wave velocity of the lithosphere beneath the region. In the process, the adjacent Kalahari craton and Damara mobile belt were also mapped to help constrain the southernmost edge of the Congo craton. To obtain the surface wave group velocity tomography, event-station dispersion curves of Rayleigh waves were measured using the multiple filter analysis method. Then the dispersion curves were inverted using the conjugate gradient least-square (CGLSQR) inversion method. To check the reliability of the result, a checkerboard test was performed. The 2-dimensional group velocities and 3-dimensonal shear-wave velocities were found to be faster beneath the southwestern block of the Congo craton and the Kalahari craton and slower in the Damara mobile belt. The group velocity map at 20s period shows that basins are 0 to 3% slower than PREM model. For longer period (50s to 120s), the Central and East African Rift system are ~ 5 % faster, cratons are 5 to 8% faster, and the adjacent mobile belts are 0 to 4% faster than the PREM model. The Afar depression is the slowest, up to 6% slower than the continental PREM model at all periods. The shear-wave velocity maps reveal that (1) the Afar area is the slowest (up to 8% slower than the IASP91 model), (2) the cratons are faster (up to 6% faster than IASP91) than the surrounding mobile belts (up to 2% faster than IASP91). The East African Rifts system is also slow (up to 5%). The Damara mobile belt constitutes a clear separation terrain between the Congo craton and the Kalahari craton. This result is consistent with previous studies by Pasyanos and Nyblade (2007), and Priestly et al. (2006, 2008), who also found faster shear-wave velocities beneath the Kalahari, Congo and Tanzania cratons. The relatively slow seismic velocities (-1 to 2% compared to IASP91) in the Proterozoic Damara mobile belt between the southwestern block of the Congo craton and the Kalahari craton are explained by the view that the Proterozoic lithosphere has hotter rock materials than the SW block of the Congo craton and the Kalahari craton. Our model of faster lithosphere beneath the SW block of the Congo and the Kalahari craton is also consistent with the model of strongly depleted (in basaltic components) lithosphere beneath these craton; compared to less depleted lithosphere beneath the DMB.