OpenUCT is the open access institutional repository of the University of Cape Town (UCT). It preserves and makes UCT scholarly outputs digitally and freely available, including theses and dissertations, journal articles, book chapters, technical and research reports, as well as open educational resources.
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Selected β-lactam resistance in selected species of gram-negative bacteria
(2004) Nelson, Elton; Elisha, B.G
The molecular basis of β-lactam resistance was investigated in this study. Selected gram-negative clinical isolates potentially displaying therapeutic problems were chosen as the subjects. Clinical diagnostic tests are not always very accurate and informative about the molecular nature of β-lactam resistance, thus molecular investigations are carried out to more fully and comprehensibly explain the clinically observed phenomena. In the view of Enterobacteria being some of the most commonly isolated, clinically problematic, bacteria, E. coli and K. pneumoniae isolates with unusual β-lactam resistance profiles were investigated. The first cluster of E. coli isolates were investigated with respect to their resistance to the cephalosporins and the cephamycin, cefoxitin. β-lactamase promoter mutations were identified and expression studies were performed to corroborate overexpression of the AmpC enzyme. The second group of E. coli isolates displayed resistance to the inhibitor combination, amoxicillin-clavulanate. In this group, the resistance genes were identified, with their promoters. Resistance was attributed to TEM overproduction and overproduction of a specially adapted TEM (IRTs) β-lactamase. Primer extension was used to determine the transcriptional start site of the IRT. The K. pneumoniae isolates were investigated for their resistance to the cephalosporins, cefoxitin and amoxicillin clavulanate. The resistance was attributed to an interplay of β-lactamase production and the loss of permeability. Since A. baumannii is becoming an increasingly popular opportunistic pathogen in the clinical setting, strain RAN was also investigated. The presence of β-lactamase resistance genes was investigated. The chromosomal ampC gene was confirmed to be present, cloned and sequenced. The regulation of the ampC gene was examined. The ampC gene was also studied in terms of its genetic context. Sequence analysis suggests that the ampC might be associated with a stabilized transposition event.
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Open Access
The El Nino Southern Oscillation, rainfall and wheat yields in South Africa
(2005) Begley, Paul
This thesis assesses the relationships between the El Nino-Southern Oscillation (ENSO), rainfall and South African commercial winter wheat yields from 1974 - 2000. The analysis is through a combination of the Pearson's product moment correlation coefficient and an assessment of the magnitude and consistency of rainfall and wheat anomalies in the year of, and the year following warm (El Nino) and cold (La Nina) ENSO events. The ENSO - rainfall relationship is analysed on timescales from 1 - 24 months and this study finds that there are more unusually dry and unusually wet months during El Nino events than during La Nina episodes (where dry and wet months are <75% and over 25% more than the 1921 - 2000 mean, respectively) and these conditions are consistently found in some rainfall areas during each El Nino or La Nina event; there is marked inter - El Nino and inter La Nina variation in late summer and annual rainfall; and that there has been a significant shift in the timings of maximum rainfall anomalies during El Nino episodes from an earlier investigation. The effects of rainfall on the wheat yield vary spatially, but are most apparent in the Free State where severe droughts have resulted in reduced yields. In the Northern Cape and Western Cape anomalously wet conditions, especially in late summer, coincide with reduced wheat yields. The ENSO - wheat yield relationship is not a simple linear one, and despite yields in the Northern Cape and Western Cape tracking Pacific sea surface temperatures by nearly a year, El Nino and La Nina years are not synonymous with increased or decreased yields in any province. ln fact, maximum and minimum yields in the Free State and Northern Cape are found in the year of, or year following a La Nina event, and consequently the present predictability of wheat yields by ENSO is limited. The relationships between ENSO, rainfall and wheat yield in South Africa is not readily apparent, which may be due to the short (<30 years) data set or mediating factors outside this study such as farm management strategies or hemispheric variation in the evolution of El Nino and La Nina events.
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Psychological explanation : the influence of the "orthodox" view of science of psychology
(1975) MacKay, Nigel
It is characteristic of science and art and other exercises of the human mind, practical and theoretical, that they may be profoundly influenced by doctrines and ideas that originate at some distance from them. Often the assumptions an determining philosophies that back up the practices of a science remain tacit and unacknowledged, hidden perhaps from even those who operate under their influence. Psychology shares these characteristics. The methods and theories of behavioural science are more than convenient ways of handling and expressing psychological facts. They are the exercise of philosophical preconceptions about humans, and ideas about the kind of knowledge that may be gained of their activities.
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Open Access
Urban resilience through diversity
(2022) Nduku, Ntsindiso Charles; Ewing, Kathryn
The objective of the research is to contribute to the development of the theory and body of knowledge that seeks to address urban sprawl, spatial inequalities, and spatial fragmentation left by the legacy of apartheid planning. I begin my research with the investigation of existing levels of Diversity, and I employ mapping to see the area which reflects more diverse characteristics. Furthermore, I seek to develop a design framework that links the social, economic, and environment. The objective of the framework is to inform the acknowledgement of existing Diversity, the making of sensitive interventions that will improve existing Diversity, and the addition of more diverse elements which will enhance the urban performance of Gugulethu. Kayatekin, 2019 argues that urban Diversity contributes towards resilient and sustainable cities. He argues that for one to understand the importance of Diversi ty in an urban context, there needs to be an understanding of the meaning and definition of Resilience. According to Kayatekin, 2019, Landman 2012, there are different meanings of Resilience in urban terms. Kayatekin, 2019 also simplifies the definition into two parts, with one drawing from Material Science and another from Ecology. The fundamental tenet of this argument is the placing of urban Diversity as the cornerstone for cities' Resilience. I likened this perspective to that of Zuniga-Teran's, 2016, point of view, which describes Diversity as a critical element of urban Resilience.
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Open Access
In-Silico design and verification of an extracorporeal normothermic cardiac perfusion system for use during heart transplantation procedures
(2025) Van Den Berg, Ronald; Sivarasu, Sudesh
Heart transplantation relies on effective donor organ preservation to ensure successful graft viability. Since the first human heart transplant in 1967 by Christiaan Barnard, organ preservation techniques have evolved from static cold storage with cardioplegic arrest to continuous blood perfusion, which enhances metabolic support and extends viable ischemic time. This study explores the development of a system for continuous myocardial perfusion to improve donor heart preservation during transplantation. Using in-silico modelling and simulation, the study defines functional requirements for a proof-of-concept system capable of achieving physiologically relevant pressure and flow waveforms necessary for sustained coronary perfusion. A cardiovascular hemodynamic simulation environment was established by adapting lumped parameter models and integrating computed tomography angiograms, facilitating both in-silico and coupled in-vitro validation analyses. This enabled the development of a bench testing model that replicated physiologically relevant coronary perfusion dynamics. The bench testing model provided critical insights for refining in-silico simulations and optimising design parameters for improved myocardial perfusion. Validation was performed through vessel-specific flow rate comparisons with computational fluid dynamics simulations. Experimental results identified a time delay in relation to the identified set of functional and control parameters when achieving target physiological pressures, informing future system optimisation. Further findings allowed for the identification of relative flow proportion exiting through the Left Circumflex and Right Major Coronary arteries and was shown to behave as a second order time derivative with respect to the inflow waveform applied to a fabricated flow phantom during testing. Similarly, the proportion of flow exiting through the Left Anterior Descending and Ramus Intermedius arteries exhibited first order time derivative behaviour in relation to the inflow signal. The resultant outcomes of testing and analysis allowed for the tuning of an embedded pump control system yielding the optimised parameter control values for proportional, integral and derivative gain of 147.74, 2.57 and -4974.96 respectively. The findings of this study establish a framework for the development of an automated continuous myocardial perfusion system, contributing to enhanced donor heart preservation strategies for clinical transplantation. .