Systematic effects and mitigation strategies in observations of cosmic re-ionisation with the Hydrogen Epoch of Reionization Array
- Authors: Charles, Ntsikelelo
- Date: 2024
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432605 , vital:72886
- Description: The 21 cm transition from neutral Hydrogen promises to be the best observational probe of the Epoch of Reionisation (EoR). It has driven the construction of the new generation of lowfrequency radio interferometric arrays, including the Hydrogen Epoch of Reionization Array (HERA). The main difficulty in measuring the 21 cm signal is the presence of bright foregrounds that require very accurate interferometric calibration. However, the non-smooth instrumental response of the antenna as a result of mutual coupling complicates the calibration process by introducing non-smooth calibration errors. Additionally, incomplete sky models are typically used in calibration due to the limited depth and resolution of current source catalogues. Combined with the instrumental response, the use of incomplete sky models during calibration can result in non-smooth calibration errors. These, overall, impart spectral structure on smooth foregrounds, leading to foreground power leakage into the EoR window. In this thesis we explored the use of fringe rate filters (Parsons et al., 2016) as a mean to mitigate calibration errors resulting from the effects of mutual coupling and the use of an incomplete sky model during calibration. We found that the use of a simple notch filter mitigates calibration errors reducing the foreground power leakage into the EoR window by a factor of ∼ 102. Thyagarajan et al. (2018) proposed the use of closure phase quantities as a means to detect the 21 cm signal, which has the advantage of being independent (to first order) from calibration errors and, therefore, bypasses the need for accurate calibration. In this thesis, we explore the impact of primary beam patterns affected by mutual coupling on the closure phase. We found that primary beams affected by mutual coupling lead to a leakage of foreground power into the EoR window, which can be up to ∼ 104 times and is mainly caused by the unsmooth spectral structure primary of primary beam sidelobes affected by mutual coupling. This power leakage was confined to k < 0.3 pseudo h Mpc−1. Lastly, we also proposed and demonstrated an analysis technique that can be used to derive a flux scale correction in post-calibrated HERA data. We found that after applying flux scale correction to calibrated HERA data, the bandpass error reduces significantly, with an improvement of 6%. The derived flux scale correction was antenna-independent, and it can be applied to fix the overall visibility spectrum scale of H4C data post-calibration in a fashion similar to Jacobs et al. (2013). , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024
- Authors: Charles, Ntsikelelo
- Date: 2024
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432605 , vital:72886
- Description: The 21 cm transition from neutral Hydrogen promises to be the best observational probe of the Epoch of Reionisation (EoR). It has driven the construction of the new generation of lowfrequency radio interferometric arrays, including the Hydrogen Epoch of Reionization Array (HERA). The main difficulty in measuring the 21 cm signal is the presence of bright foregrounds that require very accurate interferometric calibration. However, the non-smooth instrumental response of the antenna as a result of mutual coupling complicates the calibration process by introducing non-smooth calibration errors. Additionally, incomplete sky models are typically used in calibration due to the limited depth and resolution of current source catalogues. Combined with the instrumental response, the use of incomplete sky models during calibration can result in non-smooth calibration errors. These, overall, impart spectral structure on smooth foregrounds, leading to foreground power leakage into the EoR window. In this thesis we explored the use of fringe rate filters (Parsons et al., 2016) as a mean to mitigate calibration errors resulting from the effects of mutual coupling and the use of an incomplete sky model during calibration. We found that the use of a simple notch filter mitigates calibration errors reducing the foreground power leakage into the EoR window by a factor of ∼ 102. Thyagarajan et al. (2018) proposed the use of closure phase quantities as a means to detect the 21 cm signal, which has the advantage of being independent (to first order) from calibration errors and, therefore, bypasses the need for accurate calibration. In this thesis, we explore the impact of primary beam patterns affected by mutual coupling on the closure phase. We found that primary beams affected by mutual coupling lead to a leakage of foreground power into the EoR window, which can be up to ∼ 104 times and is mainly caused by the unsmooth spectral structure primary of primary beam sidelobes affected by mutual coupling. This power leakage was confined to k < 0.3 pseudo h Mpc−1. Lastly, we also proposed and demonstrated an analysis technique that can be used to derive a flux scale correction in post-calibrated HERA data. We found that after applying flux scale correction to calibrated HERA data, the bandpass error reduces significantly, with an improvement of 6%. The derived flux scale correction was antenna-independent, and it can be applied to fix the overall visibility spectrum scale of H4C data post-calibration in a fashion similar to Jacobs et al. (2013). , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2024
- Full Text:
- Date Issued: 2024
Rationalisation of magisterial districts to transform the judiciary and widen access to justice under the RSA constitution of 1996
- Authors: Skosana, Jacob
- Date: 2024-01
- Subjects: Justice, Administration of , Law and socialism , Human rights -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/28162 , vital:72777
- Description: The study examines how pre-1994 magisterial districts jurisdictions denied access to justice to many South Africans, and ongoing efforts to reverse this injustice. Delayed rationalisation of the judiciary and reform of the courts territorial jurisdiction during the apartheid era exacerbated the problem. The courts administered justice along spatial racial divide, and given the location of the courts, many black communities had to commute long distances to access justice and at a great cost and inconvenience. The Constitution of South Africa of 1996 provides not only for the right to equality before the law and equal protection and benefit of the law but also the right to access the courts and seek recourse. In a period spanning eight years from December 2014, new magisterial districts were proclaimed in all the nine provinces of South Africa. Despite this milestone and the imperative of the 1996 Constitution, the rationalisation process is still in its infancy: old legislation and judicial structures remain intact; divisions of the High Court continue to exercise jurisdictions determined for the pre-1994 constitutional dispensation. The status quo continues to perpetuate the denial of access to justice to communities especially those living in areas that hitherto formed part of the former homelands and self-governing ‘states’. The study was conducted through a desktop survey of primary and secondary material relevant to the rationalisation process. It drew lessons from the re-demarcation of municipal boundaries which, like magisterial districts, were based on racial laws and policies of the past. It also contrasted rationalisation principles in comparable jurisdictions. The findings provide a useful contribution to the ongoing effort to effect rationalisation of the court system. They also contribute to knowledge and enriches our understanding of the relationship that underpins the administration of justice in a dispensation driven by democratic, human rights and constitutional ethos. , Thesis (PhD (LLD)) -- Faculty of Law, 2024
- Full Text:
- Date Issued: 2024-01
- Authors: Skosana, Jacob
- Date: 2024-01
- Subjects: Justice, Administration of , Law and socialism , Human rights -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/28162 , vital:72777
- Description: The study examines how pre-1994 magisterial districts jurisdictions denied access to justice to many South Africans, and ongoing efforts to reverse this injustice. Delayed rationalisation of the judiciary and reform of the courts territorial jurisdiction during the apartheid era exacerbated the problem. The courts administered justice along spatial racial divide, and given the location of the courts, many black communities had to commute long distances to access justice and at a great cost and inconvenience. The Constitution of South Africa of 1996 provides not only for the right to equality before the law and equal protection and benefit of the law but also the right to access the courts and seek recourse. In a period spanning eight years from December 2014, new magisterial districts were proclaimed in all the nine provinces of South Africa. Despite this milestone and the imperative of the 1996 Constitution, the rationalisation process is still in its infancy: old legislation and judicial structures remain intact; divisions of the High Court continue to exercise jurisdictions determined for the pre-1994 constitutional dispensation. The status quo continues to perpetuate the denial of access to justice to communities especially those living in areas that hitherto formed part of the former homelands and self-governing ‘states’. The study was conducted through a desktop survey of primary and secondary material relevant to the rationalisation process. It drew lessons from the re-demarcation of municipal boundaries which, like magisterial districts, were based on racial laws and policies of the past. It also contrasted rationalisation principles in comparable jurisdictions. The findings provide a useful contribution to the ongoing effort to effect rationalisation of the court system. They also contribute to knowledge and enriches our understanding of the relationship that underpins the administration of justice in a dispensation driven by democratic, human rights and constitutional ethos. , Thesis (PhD (LLD)) -- Faculty of Law, 2024
- Full Text:
- Date Issued: 2024-01
An exploration of stakeholder perceptions of the quality of teaching and learning in higher education
- Authors: Jackson,Linda Grace
- Date: 2023-12
- Subjects: Quality assurance --Education (Higher)-- South Africa , Teaching and learning – Nelson Mandela University , Quality education—South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62464 , vital:72757
- Description: Quality in higher education is a complex and evolving concept that has been a subject of measurement, assurance and promotion in universities globally for the past three decades. However, its precise definition remains elusive due to its fluid nature, influenced by various contextual factors and stakeholder perspectives. This study explored the concepts of quality teaching and quality learning within the specific context of Nelson Mandela University, focusing on two critical internal stakeholder groups, lecturers and students. By maintaining a constant context, the study sought to gain a deeper understanding of how these stakeholders perceived and contributed to the overall quality of education at the institution. Defining quality in higher education (HE) is important, as it directly impacts on the evaluation processes within educational institutions. Presently, most Higher Education Institutions (HEIs) assess quality using tangible inputs and outputs, resulting in a quantifiable representation of quality. Despite this approach, realistically, the anticipated improvements in the quality of teaching and learning are not apparent, leading to concerns about graduate readiness for the demands of the workforce. This situation raises imperative questions about the quality of teaching and learning within HEIs, necessitating a response to address this issue. This study used the conceptual model Schindler et al. (2015) developed to investigate stakeholder perceptions of quality teaching and quality learning in higher education (HE). The research followed a novel perspective by uncoupling quality in HE from the prevailing neoliberal approach and considering quality in HE within social inclusion interventions (Gidley et al., 2010a) already in place in HE settings. The research methodology expanded on social inclusion theory and employed a qualitative, participative and visual approach adapted from Mmogo-method®, an indigenous method. The research design fostered active participation from the participants, who assumed the role of co-researchers. Participants constructed their answers to the research question using unstructured materials, subsequently sharing, explaining, and interpreting their viewpoints within the group setting. , Thesis (PhD) -- Faculty of Education, School of teaching and learning, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Jackson,Linda Grace
- Date: 2023-12
- Subjects: Quality assurance --Education (Higher)-- South Africa , Teaching and learning – Nelson Mandela University , Quality education—South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62464 , vital:72757
- Description: Quality in higher education is a complex and evolving concept that has been a subject of measurement, assurance and promotion in universities globally for the past three decades. However, its precise definition remains elusive due to its fluid nature, influenced by various contextual factors and stakeholder perspectives. This study explored the concepts of quality teaching and quality learning within the specific context of Nelson Mandela University, focusing on two critical internal stakeholder groups, lecturers and students. By maintaining a constant context, the study sought to gain a deeper understanding of how these stakeholders perceived and contributed to the overall quality of education at the institution. Defining quality in higher education (HE) is important, as it directly impacts on the evaluation processes within educational institutions. Presently, most Higher Education Institutions (HEIs) assess quality using tangible inputs and outputs, resulting in a quantifiable representation of quality. Despite this approach, realistically, the anticipated improvements in the quality of teaching and learning are not apparent, leading to concerns about graduate readiness for the demands of the workforce. This situation raises imperative questions about the quality of teaching and learning within HEIs, necessitating a response to address this issue. This study used the conceptual model Schindler et al. (2015) developed to investigate stakeholder perceptions of quality teaching and quality learning in higher education (HE). The research followed a novel perspective by uncoupling quality in HE from the prevailing neoliberal approach and considering quality in HE within social inclusion interventions (Gidley et al., 2010a) already in place in HE settings. The research methodology expanded on social inclusion theory and employed a qualitative, participative and visual approach adapted from Mmogo-method®, an indigenous method. The research design fostered active participation from the participants, who assumed the role of co-researchers. Participants constructed their answers to the research question using unstructured materials, subsequently sharing, explaining, and interpreting their viewpoints within the group setting. , Thesis (PhD) -- Faculty of Education, School of teaching and learning, 2023
- Full Text:
- Date Issued: 2023-12
Assessing the effects of fish stock management on Cape gannet foraging behaviour in South Africa
- Strydom, Zanri, Grémillet, David, Pichegru, Lorien
- Authors: Strydom, Zanri , Grémillet, David , Pichegru, Lorien
- Date: 2023-12
- Subjects: Gannets -- South Africa , Birds of prey -- Behavior -- South Africa , Fish stock assessment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62622 , vital:72887
- Description: Seabirds are one of the most threatened groups of birds under both marine and terrestrial pressures. Among seabirds, the Cape gannet Morus capensis is a southern African endemic species facing several pressures of anthropogenic origin, including competition with industrial fisheries on small pelagic fish stocks. Cape gannets, being a long-lived species that is sensitive to environmental changes, are sentinels of change in oceanic environments granting it important to understand which factors influence their foraging behaviour and breeding outputs. For example, factors like age can result in a loss of physical capabilities which can lead to behavioral compensation and subsequent changes in chick provisioning rates and amounts. With the current fisheries management the fish stocks are continually decreasing, indicating the importance of an updated fine-scale assessment on the spatiotemporal overlap between foraging gannets and fisheries. The first objective of this thesis was to determine the influence of adult Cape gannets’ age and sex on their foraging characteristics and energy expenditure during foraging. I equipped chick-rearing Cape gannets of known age and sex with a 3D accelerometer and GPS device. Foraging effort (trip duration, foraging path and maximum distance to the nest) did not differ between sexes nor with age in Cape gannets. Both sexes rested less on the water with age. Aging females also spent more time in flight than males. The age- and sexual differences in energy expenditure prevalent in our study might reflect niche and/or risk partitioning strategies to ensure adequate provisioning to the chick. The second objective of this thesis was to determine the influence of fisheries catch rates, sardine and anchovy biomass, and adult foraging effort on chick growth rates in Cape gannets, using a long-term dataset collected between 2005 and 2020 on Malgas Island. I equipped chick-rearing adults with a GPS device and I weighed the chicks for between 3 to 6 increments to calculate the average daily mass increment. Of all the variables, foraging trip duration was the main determinant of daily growth rates, with chicks benefitting from parents’ shorter foraging trip durations. Chicks tended to grow slower when fisheries catch of sardine and anchovy were higher, possibly an effect of competition with fisheries. Chicks also grew faster when fish biomass was higher. This long-term monitoring demonstrated the possible effect of food competition between Cape gannets and fisheries, with negative impacts on gannet fitness as determined via chick growth rates. The third objective of this thesis was to determine the influence of both the biomass and fisheries catch rates of sardine and anchovy on Cape gannet foraging effort at a spatial and temporal scale. This was achieved by equipping a total of 668 chick-rearing Cape gannets with a GPS device. With an increase in fisheries catch there was an increase in the birds’ foraging effort. To reduce competition between the gannets and fisheries, the gannets’ core foraging areas seldomly overlapped with the fisheries catch locations, at the cost of the gannets’ increased foraging effort. One method to halt the Cape gannet population decline would be to conserve the fish resources close to the breeding colonies. This would reduce the birds’ foraging whereby increasing their fitness. Safeguarding small pelagic fish to ensure the perseverance of the remaining Benguela seabird populations, would lead to preserving the Benguela marine ecosystem as a whole. My study provided new insight into effects of fish stock management on Cape gannet foraging behaviour in South Africa, and the need for adequate management to ensure population persistence. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Strydom, Zanri , Grémillet, David , Pichegru, Lorien
- Date: 2023-12
- Subjects: Gannets -- South Africa , Birds of prey -- Behavior -- South Africa , Fish stock assessment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62622 , vital:72887
- Description: Seabirds are one of the most threatened groups of birds under both marine and terrestrial pressures. Among seabirds, the Cape gannet Morus capensis is a southern African endemic species facing several pressures of anthropogenic origin, including competition with industrial fisheries on small pelagic fish stocks. Cape gannets, being a long-lived species that is sensitive to environmental changes, are sentinels of change in oceanic environments granting it important to understand which factors influence their foraging behaviour and breeding outputs. For example, factors like age can result in a loss of physical capabilities which can lead to behavioral compensation and subsequent changes in chick provisioning rates and amounts. With the current fisheries management the fish stocks are continually decreasing, indicating the importance of an updated fine-scale assessment on the spatiotemporal overlap between foraging gannets and fisheries. The first objective of this thesis was to determine the influence of adult Cape gannets’ age and sex on their foraging characteristics and energy expenditure during foraging. I equipped chick-rearing Cape gannets of known age and sex with a 3D accelerometer and GPS device. Foraging effort (trip duration, foraging path and maximum distance to the nest) did not differ between sexes nor with age in Cape gannets. Both sexes rested less on the water with age. Aging females also spent more time in flight than males. The age- and sexual differences in energy expenditure prevalent in our study might reflect niche and/or risk partitioning strategies to ensure adequate provisioning to the chick. The second objective of this thesis was to determine the influence of fisheries catch rates, sardine and anchovy biomass, and adult foraging effort on chick growth rates in Cape gannets, using a long-term dataset collected between 2005 and 2020 on Malgas Island. I equipped chick-rearing adults with a GPS device and I weighed the chicks for between 3 to 6 increments to calculate the average daily mass increment. Of all the variables, foraging trip duration was the main determinant of daily growth rates, with chicks benefitting from parents’ shorter foraging trip durations. Chicks tended to grow slower when fisheries catch of sardine and anchovy were higher, possibly an effect of competition with fisheries. Chicks also grew faster when fish biomass was higher. This long-term monitoring demonstrated the possible effect of food competition between Cape gannets and fisheries, with negative impacts on gannet fitness as determined via chick growth rates. The third objective of this thesis was to determine the influence of both the biomass and fisheries catch rates of sardine and anchovy on Cape gannet foraging effort at a spatial and temporal scale. This was achieved by equipping a total of 668 chick-rearing Cape gannets with a GPS device. With an increase in fisheries catch there was an increase in the birds’ foraging effort. To reduce competition between the gannets and fisheries, the gannets’ core foraging areas seldomly overlapped with the fisheries catch locations, at the cost of the gannets’ increased foraging effort. One method to halt the Cape gannet population decline would be to conserve the fish resources close to the breeding colonies. This would reduce the birds’ foraging whereby increasing their fitness. Safeguarding small pelagic fish to ensure the perseverance of the remaining Benguela seabird populations, would lead to preserving the Benguela marine ecosystem as a whole. My study provided new insight into effects of fish stock management on Cape gannet foraging behaviour in South Africa, and the need for adequate management to ensure population persistence. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Evaluation of the antidiabetic potential, safety and efficacy of selected natural products using zebrafish larvae and in vitro bioassays
- Reddy, Shanika, Dambuza, Ntokozo
- Authors: Reddy, Shanika , Dambuza, Ntokozo
- Date: 2023-12
- Subjects: Traditional medicine -- Research -- South Africa , Medicinal plants -- South Africa -- Research , Insulin resistance
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62575 , vital:72825
- Description: Abstract. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Reddy, Shanika , Dambuza, Ntokozo
- Date: 2023-12
- Subjects: Traditional medicine -- Research -- South Africa , Medicinal plants -- South Africa -- Research , Insulin resistance
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62575 , vital:72825
- Description: Abstract. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Evidence of Late Holocene extreme marine wave event (tsunami) deposits along the South African coast and implications for coastal zone management
- Authors: Mfikili, Athi Nkosibonile
- Date: 2023-12
- Subjects: Tsunamis -- South Africa , Coasts -- Risk assessment , Sediments (Geology)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62517 , vital:72811
- Description: Although extreme marine wave events such as tsunamis and storm surges have always been part of human existence, their impact on ever-growing coastal population of the world’s coast was highlighted by the recent catastrophic events over the past three decades. Although in situ observations and eyewitness accounts have improved our ability to record and interpret wave inundation by modern extreme marine events, records documenting inundation by pre-historic and historical events are relatively sparse to provide reasonable information on their distribution, magnitude and frequency intervals in most parts of the world. Owing to consequences these natural coastal hazards have on coastal population and infrastructure of the world’s coast, onshore sedimentary deposits preserved in the geological records have been extensively utilized by scientists worldwide to reconstruct the record of pre-historic and historical events and establish the recurrence interval of future events. Although studies investigating inundation of past tsunami has increased worldwide over the past two decades, research on extreme marine inundation has received little attention along the South African coast, despite known inundation by recent events and potential source mechanisms. Therefore, the aim of this study is to investigate sedimentary evidence of past tsunamis and related extreme marine wave events (i.e., storm surges) preserved in the recent geological archive of several coastal environments along the South African coast. The Swartkops, Kabeljous, Kromme and Keurbooms estuaries located in log-spiral bays along the south-east coast and sheltered coastal systems of the Berg Estuary and Verlorenvlei as well as coastal lowlands of the Dwarskersbos on the west coast were selected as the study sites. The sediment cores were collected from these coastal environments and identification of extreme marine wave inundation was based on the recognition of distinct anomalous sand layers. To characterise sediment transport and reconstruct provenance source origin of the deposits, a combination of sedimentological (i.e., grain size distribution), exoscopy (i.e., quartz grain surface microtextures) and micropaleontological (i.e., foraminiferal assemblages) proxies were utilized. Furthermore, age estimation of the deposits was determined using a combination of radiocarbon (14C) and radiometric (137Cs and 210Pb) dating methods.Evidence of coastal flooding by high-energy marine wave events is found preserved in the stratigraphic records of Swartkops and Kabeljous estuaries along the south-east coast and lowlands of Dwarskersbos on the west coast in the form of anomalous sand deposits (layers). The anomalous deposits of Swartkops and Kabeljous estuaries generally consist of gravel-sized shell fragments often with a sharp erosive contact suggesting deposition by a highly energetic marine wave event. Although the preservation varies between cores, a maximum of three anomalous sand depositional layers are preserved in the Swartkops whereas only a single layer in the Kabeljous Estuary with a basal layer of calcrete deposits. 210Pb and 14C dating, constrain the ages of the younger deposits (i.e., the uppermost layer) at Swartkops between 1770-1804 AD and 339-3 cal. BP (1611-1947 cal. AD), respectively. Although these ages span over a wide period, they are interpreted to represent evidence of one of the historical tsunamis generated in the subduction zones of the Indian Ocean e.g., 1762 AD and 1797 AD events generated by 8.8 and 8.0 Mw earthquakes in the Arakan and Sunda Subduction Zones, respectively. Furthermore, the deposits could also represent geological evidence of the 1833 Mentawai events whereas evidence of 1883 Krakatau tsunami is not disregarded, since this event reportedly inundated Algoa Bay. On the other hand, the 14C dating constrain the ages of the second anomalous deposits between 1526-1253 cal. BP (424-697 cal. AD), whereas the older anomalous deposits preserved in the deeper sections of the Swartkops cores as well as the backwater channel of the Kabeljous Estuary are constrained to have been deposited around 4000 cal. BP. Although there is no known locally documented extreme marine wave event during this period, these deposits are interpreted to represent late and mid-Holocene tsunamis associated with mega-thrust subduction zones of the Indian Ocean whereas local submarine landslide generated event are also not disregarded entirely. On the west coast, three anomalous deposits representing extreme marine wave inundation are preserved in the coastal lowlands of the Dwarskersbos. Although the general sedimentary features and thickness vary between the deposits, the first anomalous deposits in the uppermost section of the cores consist of medium sand with scattered shell fragments whereas, the third anomalous deposits in the deeper section of the cores are generally coarser with gravel-sized shell fragments and sharp erosive basal contacts. By contrast, the second anomalous deposits consist of three successive sub-layers of yellow sand with variable sedimentary features and these layers represent successive wave inundation events. Although the sedimentary characteristics of these sub-layers varies, it was noted that the lowermost layers consist of coarser and less well sorted sediments often with basal erosive contact, suggesting that the first wave was more energetic than the two-succeeding waves. Furthermore, calibrated 14C dated shell fragments from the first and second anomalous deposits yielded ‘post-bomb’ ages suggesting deposition after 1950 AD. Given their position within the stratigraphic records, the two deposits are interpreted to represent first geological evidence of the 2008 west coast and 1969 Dwarskersbos events, respectively. On the other hand, the 14C dated shell fragments constrain the deposition of the third anomalous deposits between 315-0 cal. BP (1635-11950 cal. AD) and 358-0 cal. BP (1592-1950 cal. AD), respectively. The third anomalous deposits are interpreted to the 07 April 1620 event, which was described as ‘Two startling thunderclaps’ near Robben Island. Although initially associated to earthquakes, there are no records of an earthquake during this period, therefore, we postulate that the 1620 event could have been a similar event to that of 2008 that inundated the west coast region and/or an unknown event. While it is acknowledged that the absence of reliable source mechanisms poses a great challenge in the reconstruction of extreme marine wave events inundation along the south-east coast, the findings of exoscopy and micropaleontological analyses suggest that the deposits were transported to their depositional environments, although resultant microtextural features and occurrence of individual foraminiferal species and their taphonomical conditions is dependent on coastal setting. The south-east coast deposits consist of highly diverse foraminiferal assemblages, which are dominated by marine and marginal-marine taxa with relatively low abundances of estuarine-brackish species and variable taphonomical conditions. Furthermore, the mechanical-induced features such as percussion marks, fresh surfaces with sharp edges were still preserved on quartz grain surface of the Swartkops deposits, despite dominance by chemical-induced features such as dissolution. By contrast, grain surface microtextural signatures of the Dwarskersbos deposits are dominated by mechanical features such as fresh surfaces and v-percussion marks. Furthermore, the foraminiferal assemblages of the Dwarskersbos deposits consist of exclusively marine and marginal-marine species, suggesting that the sediments were sourced from shallow water environments as well as the adjacent beach. It was further noted that the foraminiferal tests of these deposits consist of higher abundance of corroded and fragmented tests indicating deposition by high-energy conditions. , Thesis (D.Phil) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Mfikili, Athi Nkosibonile
- Date: 2023-12
- Subjects: Tsunamis -- South Africa , Coasts -- Risk assessment , Sediments (Geology)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/62517 , vital:72811
- Description: Although extreme marine wave events such as tsunamis and storm surges have always been part of human existence, their impact on ever-growing coastal population of the world’s coast was highlighted by the recent catastrophic events over the past three decades. Although in situ observations and eyewitness accounts have improved our ability to record and interpret wave inundation by modern extreme marine events, records documenting inundation by pre-historic and historical events are relatively sparse to provide reasonable information on their distribution, magnitude and frequency intervals in most parts of the world. Owing to consequences these natural coastal hazards have on coastal population and infrastructure of the world’s coast, onshore sedimentary deposits preserved in the geological records have been extensively utilized by scientists worldwide to reconstruct the record of pre-historic and historical events and establish the recurrence interval of future events. Although studies investigating inundation of past tsunami has increased worldwide over the past two decades, research on extreme marine inundation has received little attention along the South African coast, despite known inundation by recent events and potential source mechanisms. Therefore, the aim of this study is to investigate sedimentary evidence of past tsunamis and related extreme marine wave events (i.e., storm surges) preserved in the recent geological archive of several coastal environments along the South African coast. The Swartkops, Kabeljous, Kromme and Keurbooms estuaries located in log-spiral bays along the south-east coast and sheltered coastal systems of the Berg Estuary and Verlorenvlei as well as coastal lowlands of the Dwarskersbos on the west coast were selected as the study sites. The sediment cores were collected from these coastal environments and identification of extreme marine wave inundation was based on the recognition of distinct anomalous sand layers. To characterise sediment transport and reconstruct provenance source origin of the deposits, a combination of sedimentological (i.e., grain size distribution), exoscopy (i.e., quartz grain surface microtextures) and micropaleontological (i.e., foraminiferal assemblages) proxies were utilized. Furthermore, age estimation of the deposits was determined using a combination of radiocarbon (14C) and radiometric (137Cs and 210Pb) dating methods.Evidence of coastal flooding by high-energy marine wave events is found preserved in the stratigraphic records of Swartkops and Kabeljous estuaries along the south-east coast and lowlands of Dwarskersbos on the west coast in the form of anomalous sand deposits (layers). The anomalous deposits of Swartkops and Kabeljous estuaries generally consist of gravel-sized shell fragments often with a sharp erosive contact suggesting deposition by a highly energetic marine wave event. Although the preservation varies between cores, a maximum of three anomalous sand depositional layers are preserved in the Swartkops whereas only a single layer in the Kabeljous Estuary with a basal layer of calcrete deposits. 210Pb and 14C dating, constrain the ages of the younger deposits (i.e., the uppermost layer) at Swartkops between 1770-1804 AD and 339-3 cal. BP (1611-1947 cal. AD), respectively. Although these ages span over a wide period, they are interpreted to represent evidence of one of the historical tsunamis generated in the subduction zones of the Indian Ocean e.g., 1762 AD and 1797 AD events generated by 8.8 and 8.0 Mw earthquakes in the Arakan and Sunda Subduction Zones, respectively. Furthermore, the deposits could also represent geological evidence of the 1833 Mentawai events whereas evidence of 1883 Krakatau tsunami is not disregarded, since this event reportedly inundated Algoa Bay. On the other hand, the 14C dating constrain the ages of the second anomalous deposits between 1526-1253 cal. BP (424-697 cal. AD), whereas the older anomalous deposits preserved in the deeper sections of the Swartkops cores as well as the backwater channel of the Kabeljous Estuary are constrained to have been deposited around 4000 cal. BP. Although there is no known locally documented extreme marine wave event during this period, these deposits are interpreted to represent late and mid-Holocene tsunamis associated with mega-thrust subduction zones of the Indian Ocean whereas local submarine landslide generated event are also not disregarded entirely. On the west coast, three anomalous deposits representing extreme marine wave inundation are preserved in the coastal lowlands of the Dwarskersbos. Although the general sedimentary features and thickness vary between the deposits, the first anomalous deposits in the uppermost section of the cores consist of medium sand with scattered shell fragments whereas, the third anomalous deposits in the deeper section of the cores are generally coarser with gravel-sized shell fragments and sharp erosive basal contacts. By contrast, the second anomalous deposits consist of three successive sub-layers of yellow sand with variable sedimentary features and these layers represent successive wave inundation events. Although the sedimentary characteristics of these sub-layers varies, it was noted that the lowermost layers consist of coarser and less well sorted sediments often with basal erosive contact, suggesting that the first wave was more energetic than the two-succeeding waves. Furthermore, calibrated 14C dated shell fragments from the first and second anomalous deposits yielded ‘post-bomb’ ages suggesting deposition after 1950 AD. Given their position within the stratigraphic records, the two deposits are interpreted to represent first geological evidence of the 2008 west coast and 1969 Dwarskersbos events, respectively. On the other hand, the 14C dated shell fragments constrain the deposition of the third anomalous deposits between 315-0 cal. BP (1635-11950 cal. AD) and 358-0 cal. BP (1592-1950 cal. AD), respectively. The third anomalous deposits are interpreted to the 07 April 1620 event, which was described as ‘Two startling thunderclaps’ near Robben Island. Although initially associated to earthquakes, there are no records of an earthquake during this period, therefore, we postulate that the 1620 event could have been a similar event to that of 2008 that inundated the west coast region and/or an unknown event. While it is acknowledged that the absence of reliable source mechanisms poses a great challenge in the reconstruction of extreme marine wave events inundation along the south-east coast, the findings of exoscopy and micropaleontological analyses suggest that the deposits were transported to their depositional environments, although resultant microtextural features and occurrence of individual foraminiferal species and their taphonomical conditions is dependent on coastal setting. The south-east coast deposits consist of highly diverse foraminiferal assemblages, which are dominated by marine and marginal-marine taxa with relatively low abundances of estuarine-brackish species and variable taphonomical conditions. Furthermore, the mechanical-induced features such as percussion marks, fresh surfaces with sharp edges were still preserved on quartz grain surface of the Swartkops deposits, despite dominance by chemical-induced features such as dissolution. By contrast, grain surface microtextural signatures of the Dwarskersbos deposits are dominated by mechanical features such as fresh surfaces and v-percussion marks. Furthermore, the foraminiferal assemblages of the Dwarskersbos deposits consist of exclusively marine and marginal-marine species, suggesting that the sediments were sourced from shallow water environments as well as the adjacent beach. It was further noted that the foraminiferal tests of these deposits consist of higher abundance of corroded and fragmented tests indicating deposition by high-energy conditions. , Thesis (D.Phil) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
A comprehensive review of the taxonomic diversity within the freshwater catfish genus Parauchenoglanis (Siluriformes, Auchenoglanididae)
- Authors: Sithole, Yonela
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/402992 , vital:69912
- Description: Thesis embargoed. To be released early 2026. , Thesis (PhD) -- Faculty of Science, Ichthyology & Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Sithole, Yonela
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/402992 , vital:69912
- Description: Thesis embargoed. To be released early 2026. , Thesis (PhD) -- Faculty of Science, Ichthyology & Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-10-13
A formative evaluation and critical analysis of an alcohol and pregnancy intervention in the Eastern Cape of South Africa
- Authors: Graham, Nicola Susan Jearey
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432541 , vital:72879 , DOI 10.21504/10962/432541
- Description: Some communities in South Africa have the highest documented rates of Foetal Alcohol Spectrum Disorders (FASD) in the world. Interventions to reduce alcohol consumption during pregnancy are crucial, but evaluations of such interventions are sparse. Formative evaluations are indicated to assist in the development of interventions. Harmful alcohol consumption during pregnancy is undergirded by a range of social injustices, including those imposed by colonisation and patriarchy; a feminist, decolonial approach to evaluations is, therefore, important. A research project, consisting of three arms, examined alcohol use during pregnancy in an under-resourced urban area of the Eastern Cape, and this research was one of those arms. An intervention was being rolled out in this area and I gathered a range of data from it. I engaged in a formative evaluation of it, and I reflect on the difficulties that I encountered in this endeavour. In the bulk of this thesis, I examine the power apparatuses and technologies that were used during the intervention to discursively position pregnant women. My analysis was guided by Foucauldian and post-Foucauldian theories, using Foucauldian Discourse Analysis and simplified Conversation Analysis (CA). Power apparatuses of coloniality, patriarchy, and pastoral power were used in the intervention to construct positions for pregnant women who drink alcohol as ignorant children, sinners, criminals, or “Mommies”. The foetus was constructed as a precious, vulnerable baby, while the person with FASD was constructed as the defiled Other, responsible for societal dissolution. The intervention used various disciplinary techniques to exhort women to follow their dictates. Women were generally compliant with being positioned as ignorant children, which absolved them from any blame for pre-natal drinking. However, some resistance was evident. I then introduce an ethics of care and justice, and I argue that pregnant/newly parenting women need to be positioned within such an ethics, which acknowledges both the universal resources that they require for reproductive freedoms, as well as their particular care needs. I highlight the few times when women were positioned in this way in the data, and I look at how the common positions could be altered or expanded to promote such an ethics. I conclude by arguing that alcohol use during pregnancy cannot be separated from the larger context of the cultural hegemony of alcohol use in some communities, and the social injustices that potentiate this use. I provide suggestions for country-wide policies and interventions, as well as specific FASD prevention programmes, and I argue that a feminist decolonising approach, within an ethics of care and justice, should guide interventions at all levels. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Graham, Nicola Susan Jearey
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432541 , vital:72879 , DOI 10.21504/10962/432541
- Description: Some communities in South Africa have the highest documented rates of Foetal Alcohol Spectrum Disorders (FASD) in the world. Interventions to reduce alcohol consumption during pregnancy are crucial, but evaluations of such interventions are sparse. Formative evaluations are indicated to assist in the development of interventions. Harmful alcohol consumption during pregnancy is undergirded by a range of social injustices, including those imposed by colonisation and patriarchy; a feminist, decolonial approach to evaluations is, therefore, important. A research project, consisting of three arms, examined alcohol use during pregnancy in an under-resourced urban area of the Eastern Cape, and this research was one of those arms. An intervention was being rolled out in this area and I gathered a range of data from it. I engaged in a formative evaluation of it, and I reflect on the difficulties that I encountered in this endeavour. In the bulk of this thesis, I examine the power apparatuses and technologies that were used during the intervention to discursively position pregnant women. My analysis was guided by Foucauldian and post-Foucauldian theories, using Foucauldian Discourse Analysis and simplified Conversation Analysis (CA). Power apparatuses of coloniality, patriarchy, and pastoral power were used in the intervention to construct positions for pregnant women who drink alcohol as ignorant children, sinners, criminals, or “Mommies”. The foetus was constructed as a precious, vulnerable baby, while the person with FASD was constructed as the defiled Other, responsible for societal dissolution. The intervention used various disciplinary techniques to exhort women to follow their dictates. Women were generally compliant with being positioned as ignorant children, which absolved them from any blame for pre-natal drinking. However, some resistance was evident. I then introduce an ethics of care and justice, and I argue that pregnant/newly parenting women need to be positioned within such an ethics, which acknowledges both the universal resources that they require for reproductive freedoms, as well as their particular care needs. I highlight the few times when women were positioned in this way in the data, and I look at how the common positions could be altered or expanded to promote such an ethics. I conclude by arguing that alcohol use during pregnancy cannot be separated from the larger context of the cultural hegemony of alcohol use in some communities, and the social injustices that potentiate this use. I provide suggestions for country-wide policies and interventions, as well as specific FASD prevention programmes, and I argue that a feminist decolonising approach, within an ethics of care and justice, should guide interventions at all levels. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13
A grounded theory study of the identity and career decisions of artistic creative entrepreneurs
- Gibson-Tessendorf, Jacoba Cornelia
- Authors: Gibson-Tessendorf, Jacoba Cornelia
- Date: 2023-10-13
- Subjects: Entrepreneurship , Creative entrepreneurship , Personality and creative ability , Career choice , Creative industries , Identity (Psychology)
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/419208 , vital:71625 , DOI 10.21504/10962/419208
- Description: This research, in the field of creative careers, identity and entrepreneurship, aims to develop a grounded theory to explain the interaction between the phenomena of identity and career decision-making, focusing on Artistic Creative entrepreneurs in the creative industries. Artistic Creatives have unique characteristics and creative identities, presenting unique career opportunities. This research is interested in the different values of Artistic Creatives compared to those of Artistic Creative Entrepreneurs, who often experience a tension between their creative identity and their entrepreneurial identities The methodology used is the Straussian Grounded Theory. A Qualitative Research Approach used interviews to collect data on the careers and identity of Artistic Creative entrepreneurs in an area in the Eastern Cape Province of South Africa. Creative entrepreneurs work in the fields of fine art, design and crafts. The research procedure was recorded in detail, which enhances dependability. Ethics approval was obtained prior to the data collection. The data was analysed through open coding, axial coding and using a Straussian paradigm model. The findings present the values and identity of the Artistic Creative with Artistic Creative Archetypes and the entrepreneurial identities as Artistic Creative Entrepreneur Profiles. The Thesis by JC Gibson-Tessendorf effects of identity and contextual factors on their career patterns, especially as entrepreneurs, are analysed. The contribution that this study makes towards the creation of new knowledge is through, firstly, presenting aspiring creatives with career opportunities that relate to individual values. Secondly, it provides a model of Career Stage Options and Strategies that Artistic Creative Entrepreneurs may follow to either become part-time creative entrepreneurs or use the model as a guide for career planning. The study also developed a substantial theory proposing that the identities of Artistic Creative Entrepreneurs are 1) firstly multiple, 2) flexible and open to change, 2) driven by their values, 3) enacting across the tripartite identity framework, being personal identity, role identity and social identity. The concept of a tripartite of identities was taken from Brewer and Gardner (1996). , Thesis (PhD) -- Faculty of Commerce, Rhodes Business School, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Gibson-Tessendorf, Jacoba Cornelia
- Date: 2023-10-13
- Subjects: Entrepreneurship , Creative entrepreneurship , Personality and creative ability , Career choice , Creative industries , Identity (Psychology)
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/419208 , vital:71625 , DOI 10.21504/10962/419208
- Description: This research, in the field of creative careers, identity and entrepreneurship, aims to develop a grounded theory to explain the interaction between the phenomena of identity and career decision-making, focusing on Artistic Creative entrepreneurs in the creative industries. Artistic Creatives have unique characteristics and creative identities, presenting unique career opportunities. This research is interested in the different values of Artistic Creatives compared to those of Artistic Creative Entrepreneurs, who often experience a tension between their creative identity and their entrepreneurial identities The methodology used is the Straussian Grounded Theory. A Qualitative Research Approach used interviews to collect data on the careers and identity of Artistic Creative entrepreneurs in an area in the Eastern Cape Province of South Africa. Creative entrepreneurs work in the fields of fine art, design and crafts. The research procedure was recorded in detail, which enhances dependability. Ethics approval was obtained prior to the data collection. The data was analysed through open coding, axial coding and using a Straussian paradigm model. The findings present the values and identity of the Artistic Creative with Artistic Creative Archetypes and the entrepreneurial identities as Artistic Creative Entrepreneur Profiles. The Thesis by JC Gibson-Tessendorf effects of identity and contextual factors on their career patterns, especially as entrepreneurs, are analysed. The contribution that this study makes towards the creation of new knowledge is through, firstly, presenting aspiring creatives with career opportunities that relate to individual values. Secondly, it provides a model of Career Stage Options and Strategies that Artistic Creative Entrepreneurs may follow to either become part-time creative entrepreneurs or use the model as a guide for career planning. The study also developed a substantial theory proposing that the identities of Artistic Creative Entrepreneurs are 1) firstly multiple, 2) flexible and open to change, 2) driven by their values, 3) enacting across the tripartite identity framework, being personal identity, role identity and social identity. The concept of a tripartite of identities was taken from Brewer and Gardner (1996). , Thesis (PhD) -- Faculty of Commerce, Rhodes Business School, 2023
- Full Text:
- Date Issued: 2023-10-13
A molecular investigation of stem-galling Tetramesa Walker (Hymenoptera: Eurytomidae) on African grasses: applications to biological control
- Van Steenderen, Clarke Julian Mignon
- Authors: Van Steenderen, Clarke Julian Mignon
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432565 , vital:72881 , DOI 10.21504/10962/432565
- Description: South Africa is a larger donor than receiver of alien grasses, where approximately 15% (_ 165 spp.) of the country's native grass species have become naturalised elsewhere. Many of these grasses have become serious invaders, causing significant damage to native species, habitat structure, and ecosystem functioning. Biological control is a sustainable and cost-effective method for the control of invasive weeds, but its application to invasive grasses has been approached with trepidation in the past due to the fears of a lack of host-specific herbivores that may cause non-target damage to agriculturally-important crops. The Tetramesa Walker genus (Hymenoptera: Eurytomidae) is one of three genera in the family that feed exclusively on grasses, and have a record of being host-specific to a particular species, or complex of closely-related congeners. There are over 200 described Tetramesa species, but this taxonomic effort has occurred almost exclusively in the Northern Hemisphere. Only about 2% of the described species are from Africa, with none from southern Africa despite the high diversity of grasses in the region. The low morphological variability between many Tetramesa groups has made identification difficult, where there may in fact be multiple undiscovered cryptic species. This thesis generated genetic sequence data (mitochondrial COI and nuclear 28S) that revealed at least eight native southern African Tetramesa taxa that are new to science, focusing particularly on the assemblages associated with Eragrostis curvula Nees (African lovegrass) and Sporobolus pyramidalis Beauv. and S. natalensis Steud. (giant rat's tail grass) which are alien invasive pests in Australia. Approximately 200 eurytomid wasps were collected and sequenced from 19 grass species across six South African provinces. Additionally, 27 grass species were sequenced using four gene regions (rps16-trnK, rps16, rpl32-trnL, and ITS), which were added to existing sequence data to build a dataset comprising over 700 sequences. Field host ranges and the use of host grass genetic proxies were important in making inferences about the host-specificity of eurytomid wasps of interest. Nine Tetramesa groups appeared to be host-specific to a single grass species, while six Tetramesa were associated with multiple species in a single grass genus. Since S. pyramidalis, S. natalensis, S. africanus, Hyparrhenia hirta, E. trichophora, and Andropogon gayanus are weeds elsewhere, there are at least six potential Tetramesa biological control agents that have been identified. A high diversity of Tetramesa on grasses within the Eragrostis genus was reported, with at least four taxa associated with E. curvula. It is currently uncertain whether these taxa represent different cryptic species or intraspecific populations that are the result of geographic sub-structuring. No-choice host-specificity testing using Tetramesa sp. 4 on E. curvula revealed that the wasp could complete its lifecycle on two non-target African grasses; namely E. plana and E. planiculmis. The wasp was also recorded on other Eragrostis species in the field (namely E. biflora and E. capensis). Using grass genetic sequences obtained in this study, it was found that there are four native Australian Eragrostis species that are more closely related to target E. curvula than to the non-target E. plana and E. planiculmis. This suggests that Tetramesa sp. 4 may not be suitably host-specific for use as a biological control agent. Further host-specificity testing on these native Australian species is required, however, before this insect is ruled out completely. The Tetramesa on S. pyramidalis (Tetramesa sp. 1), and the unidentified Sporobolus species presumed to be S. africanus, were suitably host-specific to be used as biological control agents. Since it was unclear whether some phylogenetic clades were true species or intraspecific populations, which is essential to understand when selecting agents for biological control, a new piece of software, SPEDE-sampler", was developed. It offers users of the Generalised Mixed Yule Coalescent (GMYC) species delimitation model a means of assessing the degree to which sampling effects such as data size and parameter choice can influence species diversity estimates. When applied to the Tetramesa data set, the software assisted in identifying which groups may contain cryptic species, uncovering that the COI marker is affected more by singletons than the 28S marker (i.e. species diversity tends to be overestimated), and confirming putative Tetramesa taxa that could be useful for biological control programmes going forward. This thesis has provided evidence that South Africa contains a diverse assemblage of Tetramesa and other eurytomids that are closely associated with their grass hosts, and that many of these taxa hold promise for grass biological control. This work has also highlighted the importance of integrative taxonomy in the discovery of novel taxa, and that biological control practitioners need to be aware of the caveats of each line of evidence used in the delimitation of putative species. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Van Steenderen, Clarke Julian Mignon
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432565 , vital:72881 , DOI 10.21504/10962/432565
- Description: South Africa is a larger donor than receiver of alien grasses, where approximately 15% (_ 165 spp.) of the country's native grass species have become naturalised elsewhere. Many of these grasses have become serious invaders, causing significant damage to native species, habitat structure, and ecosystem functioning. Biological control is a sustainable and cost-effective method for the control of invasive weeds, but its application to invasive grasses has been approached with trepidation in the past due to the fears of a lack of host-specific herbivores that may cause non-target damage to agriculturally-important crops. The Tetramesa Walker genus (Hymenoptera: Eurytomidae) is one of three genera in the family that feed exclusively on grasses, and have a record of being host-specific to a particular species, or complex of closely-related congeners. There are over 200 described Tetramesa species, but this taxonomic effort has occurred almost exclusively in the Northern Hemisphere. Only about 2% of the described species are from Africa, with none from southern Africa despite the high diversity of grasses in the region. The low morphological variability between many Tetramesa groups has made identification difficult, where there may in fact be multiple undiscovered cryptic species. This thesis generated genetic sequence data (mitochondrial COI and nuclear 28S) that revealed at least eight native southern African Tetramesa taxa that are new to science, focusing particularly on the assemblages associated with Eragrostis curvula Nees (African lovegrass) and Sporobolus pyramidalis Beauv. and S. natalensis Steud. (giant rat's tail grass) which are alien invasive pests in Australia. Approximately 200 eurytomid wasps were collected and sequenced from 19 grass species across six South African provinces. Additionally, 27 grass species were sequenced using four gene regions (rps16-trnK, rps16, rpl32-trnL, and ITS), which were added to existing sequence data to build a dataset comprising over 700 sequences. Field host ranges and the use of host grass genetic proxies were important in making inferences about the host-specificity of eurytomid wasps of interest. Nine Tetramesa groups appeared to be host-specific to a single grass species, while six Tetramesa were associated with multiple species in a single grass genus. Since S. pyramidalis, S. natalensis, S. africanus, Hyparrhenia hirta, E. trichophora, and Andropogon gayanus are weeds elsewhere, there are at least six potential Tetramesa biological control agents that have been identified. A high diversity of Tetramesa on grasses within the Eragrostis genus was reported, with at least four taxa associated with E. curvula. It is currently uncertain whether these taxa represent different cryptic species or intraspecific populations that are the result of geographic sub-structuring. No-choice host-specificity testing using Tetramesa sp. 4 on E. curvula revealed that the wasp could complete its lifecycle on two non-target African grasses; namely E. plana and E. planiculmis. The wasp was also recorded on other Eragrostis species in the field (namely E. biflora and E. capensis). Using grass genetic sequences obtained in this study, it was found that there are four native Australian Eragrostis species that are more closely related to target E. curvula than to the non-target E. plana and E. planiculmis. This suggests that Tetramesa sp. 4 may not be suitably host-specific for use as a biological control agent. Further host-specificity testing on these native Australian species is required, however, before this insect is ruled out completely. The Tetramesa on S. pyramidalis (Tetramesa sp. 1), and the unidentified Sporobolus species presumed to be S. africanus, were suitably host-specific to be used as biological control agents. Since it was unclear whether some phylogenetic clades were true species or intraspecific populations, which is essential to understand when selecting agents for biological control, a new piece of software, SPEDE-sampler", was developed. It offers users of the Generalised Mixed Yule Coalescent (GMYC) species delimitation model a means of assessing the degree to which sampling effects such as data size and parameter choice can influence species diversity estimates. When applied to the Tetramesa data set, the software assisted in identifying which groups may contain cryptic species, uncovering that the COI marker is affected more by singletons than the 28S marker (i.e. species diversity tends to be overestimated), and confirming putative Tetramesa taxa that could be useful for biological control programmes going forward. This thesis has provided evidence that South Africa contains a diverse assemblage of Tetramesa and other eurytomids that are closely associated with their grass hosts, and that many of these taxa hold promise for grass biological control. This work has also highlighted the importance of integrative taxonomy in the discovery of novel taxa, and that biological control practitioners need to be aware of the caveats of each line of evidence used in the delimitation of putative species. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
Action Research reflecting the process of a collaborative, multi-theoretical group intervention with foster parents of children affected by childhood trauma
- Authors: Cahill, Susan Mary
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432297 , vital:72859 , DOI 10.21504/10962/432297
- Description: Children are received into the Care of the State in the Republic of Ireland due to chronic or acute maltreatment in their families of origin. Maltreatment may include neglect; physical, sexual, or emotional abuse; exposure to domestic violence; or a combination of these. Resulting emotional and behavioural consequences may be challenging to foster parents who might experience stress, secondary trauma, compassion fatigue or burnout, which along with the child’s emotional and behavioural difficulties can result in placement breakdown. After reviewing the literature on fostering internationally and in Ireland, this study sought to determine the types and level of stress in a sample of foster parents and the types of challenging emotional and behavioural difficulties of their fostered children. Results revealed that foster parents found fostering stressful; factors included biological parents; organisational issues; and the child’s behaviour. According to the foster parents, nearly 60% of the foster children in this sample were showing high levels of emotional and behavioural distress. These difficulties differed according to age and gender. Adolescent Girls and Young Boys (5 – 11 years) were reported as having the most difficulties, including symptoms of behavioural and Conduct Disorder (CD). Symptoms associated with CD were reported in at least 40% of every age and gender category of children over five years. Further, this study outlines the development, facilitation and outcomes of a small group psychoeducational-reflective foster parenting Course, involving six separate groups of parents (n=38) each meeting for eight sessions. In this Course, foster children were conceptualised from a bio-psycho-social-ecological viewpoint, utilising theoretical concepts from Prenatal Development, Attachment and Trauma, pertaining to vulnerable children to illustrate the cumulative effects of adversities. Time for discussion and reflection on the material was structured into the Course. This combination of knowledge, practical skills, reflection and support for parents aimed to promote healing relationship-based practices for the child within their foster home. This multi-faceted study was grounded in Community Psychology, using mixed methods to gather data during action research processes, to reflect the different components of an action cycle. Ideas and modifications to the Course based on feedback from the foster parent participants’ experiences have been included. It is recommended that the Course be provided to other foster parents and audiences such as social workers, teachers and solicitors. Furthermore, suggestions are made regarding assessment, diagnosis and interventions for foster children and parents, based on a multidisciplinary consultancy model. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Cahill, Susan Mary
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432297 , vital:72859 , DOI 10.21504/10962/432297
- Description: Children are received into the Care of the State in the Republic of Ireland due to chronic or acute maltreatment in their families of origin. Maltreatment may include neglect; physical, sexual, or emotional abuse; exposure to domestic violence; or a combination of these. Resulting emotional and behavioural consequences may be challenging to foster parents who might experience stress, secondary trauma, compassion fatigue or burnout, which along with the child’s emotional and behavioural difficulties can result in placement breakdown. After reviewing the literature on fostering internationally and in Ireland, this study sought to determine the types and level of stress in a sample of foster parents and the types of challenging emotional and behavioural difficulties of their fostered children. Results revealed that foster parents found fostering stressful; factors included biological parents; organisational issues; and the child’s behaviour. According to the foster parents, nearly 60% of the foster children in this sample were showing high levels of emotional and behavioural distress. These difficulties differed according to age and gender. Adolescent Girls and Young Boys (5 – 11 years) were reported as having the most difficulties, including symptoms of behavioural and Conduct Disorder (CD). Symptoms associated with CD were reported in at least 40% of every age and gender category of children over five years. Further, this study outlines the development, facilitation and outcomes of a small group psychoeducational-reflective foster parenting Course, involving six separate groups of parents (n=38) each meeting for eight sessions. In this Course, foster children were conceptualised from a bio-psycho-social-ecological viewpoint, utilising theoretical concepts from Prenatal Development, Attachment and Trauma, pertaining to vulnerable children to illustrate the cumulative effects of adversities. Time for discussion and reflection on the material was structured into the Course. This combination of knowledge, practical skills, reflection and support for parents aimed to promote healing relationship-based practices for the child within their foster home. This multi-faceted study was grounded in Community Psychology, using mixed methods to gather data during action research processes, to reflect the different components of an action cycle. Ideas and modifications to the Course based on feedback from the foster parent participants’ experiences have been included. It is recommended that the Course be provided to other foster parents and audiences such as social workers, teachers and solicitors. Furthermore, suggestions are made regarding assessment, diagnosis and interventions for foster children and parents, based on a multidisciplinary consultancy model. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13
African population prevalent genetic variations of dihydropyrimidine dehydrogenase as the 5-flourouracil cancer drug metabolizing enzyme: computational approaches towards pharmacogenomics studies
- Authors: Tendwa, Maureen Bilinga
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432263 , vital:72856 , DOI 10.21504/10962/432270
- Description: In an era of newly emerging cases of non-communicable diseases such as cancer, research is vital for both the medical and economic well-being of humanity. Pharmacogenomics has laidthegroundworkfor the identification of potential genes in cancer progression and treatment outcome investigations. Researchers are increasingly discovering heterogeneity in the efficacy and toxicity responses of drugmetabolizing enzymes (DMEs) in diverse patient populations receiving anti-cancer therapy. DMEs comprise of Phase I (Cytochrome P450s) and Phase II (glutathione-S-transferases (GSTs), UDP-glucuronosyltransferases (UGTs), and dihydropyrimidine dehydrogenases (DPD)enzymes. The main cause of disparity in DME treatment outcomes is genetic variation,which causes missense mutations leading to structural and kinetic properties of the enzyme. These modifications have a deleterious impact on the pharmacodynamics and pharmacokinetics of drugs through multiple mechanisms. Presently, most cancer medicines are manufacturedin developed countries based on the genetic background of non-African subpopulations. Thus, these drugs may not be optimally effective or can cause adverse side effects. Even though heterogeneity in toxicity and efficacy of these drugs has been observed in African descent, the basis of this population variance remains partially understood. For instance,a deficiencyof DPD, the first-rate limiting metabolizing enzyme in the pyrimidinepathway, causes severe toxicity when exposed to 5-fluorouracil (5-FU) chemotherapy. However, minimum studies have been conducted to unravel itsmolecular mechanismwhich may unravel the observed drug treatment outcomes.The aim of this pharmacogenomics study was to determine the underlying mechanism by which DPD missense mutations, which are associated with an African ancestry subpopulation, provoke dysfunctional 5-FU metabolism, resulting in drug toxicity. This knowledge will be critical in designing drug modulators to aid in the restoration of DPD function, a hallmark of precision medicine. Therefore, in the first part of the research we identified and reviewed the general role of Phase I and Phase II cancer drug metabolizing enzymes. We then used World Health Organization (WHO) essential medicine and drug.com to authenticate the usage of 5-FU as an anti-cancer treatment agent. The 3D structure and chemical structure of the agent was then downloaded from the Drug bank. Subsequently, Human Mutation Analysis - Variant Analysis PORtal (HUMA) and Mendelian Inheritance in Man (OMIM) were used to obtain data on DPD non-synonymous genetic variants. Additionally, the aggregate information of DPD missense mutations and their relation to human health were extracted from ClinVar and Pharmacogenomics Knowledge Base (PharmKGB). This information, along with additional data from single nucleotide polymorphisms (dbSNP), 1000 Genomes Project and Exome Sequencing Project (ESP MAF) considering variants classified based on their minor allele frequency (MAF) of 0.001, as well as research articles, consolidated information on missense mutations associated with African subpopulations. Finally, the wild type (WT) and detected mutation sequences were obtained from the Universal Protein Resources database (UniProt). However, because the 3D structure of human DPD was missing, the dimeric wild type (WT) human 3-dimensional (3D) structure was modeled via MODELLER using the pig’s structure as a template. PRIMO, HHpred, and the Protein Data Bank (PDB) were all used to locate the suitable template. As a result, six clinical (C29R, M166V, Y186C, S534N, I543V, and D949V) and thirteen non-clinical (S201R, K259E, D342N, D432N, S492L, R592Q, A664S, G674D, A721T, V732G, T768K, R886C, and L993R) mutations were discovered. Using AMBER tools, we then determined accurate force field parameters for each monomer of DPD protein's Fe2+ centers. Following the creation of each mutation model structure in Discovery Studio, the resulting AMBER force field parameters were inferred. For each model structure, a drug free (inactive/open-conformation) and drug bound (active/closed-conformation) model structure was created (WT and mutations). The model structures were validated using the consensus of three validation programs, namely ERRAT, PROCHECK, and ProSA. Similarly, the impact on structural functionalities was predicted by consensus from Variant Analysis Porta (VAPOR) web server, which include three support vector machines (SVM)-based tools; PhD-SNP, MUpro, and I-Mutation. After protonation in the H++ web server, the six clinical and thirteen non-clinical (six active site and seven non-active site) mutations identified were then exposed to 600 ns molecular dynamic (MD) simulation. The non-clinical data was divided into two categories to better understand the impact of the mutation based on its position in the protein: six catalytic-domain (R592Q, A664S, G674D, A721T, V732G, and T768K) and seven remote (S201R, K259E, D342N, D432N, S492L, R886C, and L993R) missense mutations. The post-MD analysis was done using the typical existing computational global investigations [RMSD, all versus all RMSD, RMSF, RG, hydrogen bonds (H-bonds) and dynamic cross correlation (DCC)]. In addition, we used in silico tools newly developed within the Research Unit in Bioinformatics (RUBI) group, such as comparative essential dynamics (ED)-principal component analysis and dynamic residue network (DRN) multi-metric [betweenness centrality (BC), closeness centrality (CC), degree of centrality (DC), eigen-centrality (EC) and Katz centrality (KC)] analysis algorithms. From the analysis, it was observed that the loop regions of the mutation proteins had increased loop flexibility, particularly around the catalytic loop, which could account for the enhanced asymmetric behavior of the mutation’s monomers compared to the WT. Notably, the A664S mutant showed relatively lower fluctuations, deviating from the observed heightened flexibility in other mutants. A general decrease in hydrogen bonds was observed in the 5-FU binding environment of the mutations compared to the WT. In particular, 5-FU contact analysis of the WT versus the mutation revealed a reduction in contact between core 5-FU binding residues and catalytic residues Cys671 and Ser670, which form hydrogen bonds that initiate DPD catalytic action. Additionally, BC was used to quantify the importance of a protein residue based on how often it acted as a bridge along the shortest paths between other residues. It reflected the potential control or influence a residue may have over communication between different parts of a protein structure. DC assesses the number of connections or interactions a residue had with other residues in the protein, indicating its overall connectivity within the structure. In both drug free and drug bound state, DPD data from the active site hubs' BC and DC revealed a dimeric asymmetric communication pathway per monomer involving a cluster of newly introduced hubs ensemble along the oxidoreduction conduit from NADPH to 5-FU. The two BC communication pathways were located more on the interior of the oxidoreduction conduit, while the two DC communication pathways were located on the exterior. In both cases, one pathway dominated the other. Partially lost function reported in mutation systems could be credited to the compensation communication response to the catalytic site via the least compromised routes. Similar patterns were observed in allosteric communication pathways to the active site induced by remote mutations. Mutations may have destabilized the active-loop and 5-FU binding environment, resulting in a compensatory mechanism seen by the addition of new hubs to the communication network. Surprisingly, EC hubs in the WT were found within the catalytic site domain, indicating that the region is important in 5-FU metabolism. EC measured the importance of a residue by considering both its own degree of connectivity and the degrees of connectivity with its neighboring residues, highlighting its significance in information flow and communication. Herein, EC hubs in mutant systems were found to lose this importance, with active site domain mutations suffering the most. This could explain why non-clinical catalytic domain mutations R592Q, A664S, and G674D, as well as clinical catalytic domain mutations S534N and I543V, experienced drug exit in one of their monomers during simulation. In contrast, there was no 5-FU exit in the non-clinical remote domain. Additionally, aside from the active site, KC hubs were also found around the cofactors, indicating that these components were equally important in DPD overall function. KC combines the concepts of both degree centrality and eigen-centrality, it incorporated both direct and indirect interactions to evaluate the importance of a residue, assigning higher centrality to residues that have connections to other highly central residues. Hence, providing a more comprehensive measure of influence within the protein network. More importantly, CC is known to measure how efficiently a residue can interact with other residues in the protein, considering the shortest path lengths. It indicates the proximity of a residue to others, suggesting its potential for information transfer or functional integration. CC revealed that the majority of persistent hubs were found within the protein-cores known as cold-spots. Overall, this study highlighted the communication pathways triggered by active site domain mutations, as well as the allosteric communication pathways triggered by each remote mutation in both drug free and drug bound states of the DPD enzyme. Both clinical and non-clinical mutations revealed each protein's adaptive compensation mechanism, which results in partial function loss. In each case, the communication network of the different monomers changed from inactive to activated DPD protein. Cold-spot areas were discovered to contain key persistent residues involved in protein function and stability. These areas have been proposed as potential targets for new or repurposed pharmacological modulators that can restore enzyme function. In the pursuit of precision medicine, it also lays the groundwork for detecting and explaining the molecular mechanisms of other drug metabolizing enzymes related to the African-descent subpopulation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Tendwa, Maureen Bilinga
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432263 , vital:72856 , DOI 10.21504/10962/432270
- Description: In an era of newly emerging cases of non-communicable diseases such as cancer, research is vital for both the medical and economic well-being of humanity. Pharmacogenomics has laidthegroundworkfor the identification of potential genes in cancer progression and treatment outcome investigations. Researchers are increasingly discovering heterogeneity in the efficacy and toxicity responses of drugmetabolizing enzymes (DMEs) in diverse patient populations receiving anti-cancer therapy. DMEs comprise of Phase I (Cytochrome P450s) and Phase II (glutathione-S-transferases (GSTs), UDP-glucuronosyltransferases (UGTs), and dihydropyrimidine dehydrogenases (DPD)enzymes. The main cause of disparity in DME treatment outcomes is genetic variation,which causes missense mutations leading to structural and kinetic properties of the enzyme. These modifications have a deleterious impact on the pharmacodynamics and pharmacokinetics of drugs through multiple mechanisms. Presently, most cancer medicines are manufacturedin developed countries based on the genetic background of non-African subpopulations. Thus, these drugs may not be optimally effective or can cause adverse side effects. Even though heterogeneity in toxicity and efficacy of these drugs has been observed in African descent, the basis of this population variance remains partially understood. For instance,a deficiencyof DPD, the first-rate limiting metabolizing enzyme in the pyrimidinepathway, causes severe toxicity when exposed to 5-fluorouracil (5-FU) chemotherapy. However, minimum studies have been conducted to unravel itsmolecular mechanismwhich may unravel the observed drug treatment outcomes.The aim of this pharmacogenomics study was to determine the underlying mechanism by which DPD missense mutations, which are associated with an African ancestry subpopulation, provoke dysfunctional 5-FU metabolism, resulting in drug toxicity. This knowledge will be critical in designing drug modulators to aid in the restoration of DPD function, a hallmark of precision medicine. Therefore, in the first part of the research we identified and reviewed the general role of Phase I and Phase II cancer drug metabolizing enzymes. We then used World Health Organization (WHO) essential medicine and drug.com to authenticate the usage of 5-FU as an anti-cancer treatment agent. The 3D structure and chemical structure of the agent was then downloaded from the Drug bank. Subsequently, Human Mutation Analysis - Variant Analysis PORtal (HUMA) and Mendelian Inheritance in Man (OMIM) were used to obtain data on DPD non-synonymous genetic variants. Additionally, the aggregate information of DPD missense mutations and their relation to human health were extracted from ClinVar and Pharmacogenomics Knowledge Base (PharmKGB). This information, along with additional data from single nucleotide polymorphisms (dbSNP), 1000 Genomes Project and Exome Sequencing Project (ESP MAF) considering variants classified based on their minor allele frequency (MAF) of 0.001, as well as research articles, consolidated information on missense mutations associated with African subpopulations. Finally, the wild type (WT) and detected mutation sequences were obtained from the Universal Protein Resources database (UniProt). However, because the 3D structure of human DPD was missing, the dimeric wild type (WT) human 3-dimensional (3D) structure was modeled via MODELLER using the pig’s structure as a template. PRIMO, HHpred, and the Protein Data Bank (PDB) were all used to locate the suitable template. As a result, six clinical (C29R, M166V, Y186C, S534N, I543V, and D949V) and thirteen non-clinical (S201R, K259E, D342N, D432N, S492L, R592Q, A664S, G674D, A721T, V732G, T768K, R886C, and L993R) mutations were discovered. Using AMBER tools, we then determined accurate force field parameters for each monomer of DPD protein's Fe2+ centers. Following the creation of each mutation model structure in Discovery Studio, the resulting AMBER force field parameters were inferred. For each model structure, a drug free (inactive/open-conformation) and drug bound (active/closed-conformation) model structure was created (WT and mutations). The model structures were validated using the consensus of three validation programs, namely ERRAT, PROCHECK, and ProSA. Similarly, the impact on structural functionalities was predicted by consensus from Variant Analysis Porta (VAPOR) web server, which include three support vector machines (SVM)-based tools; PhD-SNP, MUpro, and I-Mutation. After protonation in the H++ web server, the six clinical and thirteen non-clinical (six active site and seven non-active site) mutations identified were then exposed to 600 ns molecular dynamic (MD) simulation. The non-clinical data was divided into two categories to better understand the impact of the mutation based on its position in the protein: six catalytic-domain (R592Q, A664S, G674D, A721T, V732G, and T768K) and seven remote (S201R, K259E, D342N, D432N, S492L, R886C, and L993R) missense mutations. The post-MD analysis was done using the typical existing computational global investigations [RMSD, all versus all RMSD, RMSF, RG, hydrogen bonds (H-bonds) and dynamic cross correlation (DCC)]. In addition, we used in silico tools newly developed within the Research Unit in Bioinformatics (RUBI) group, such as comparative essential dynamics (ED)-principal component analysis and dynamic residue network (DRN) multi-metric [betweenness centrality (BC), closeness centrality (CC), degree of centrality (DC), eigen-centrality (EC) and Katz centrality (KC)] analysis algorithms. From the analysis, it was observed that the loop regions of the mutation proteins had increased loop flexibility, particularly around the catalytic loop, which could account for the enhanced asymmetric behavior of the mutation’s monomers compared to the WT. Notably, the A664S mutant showed relatively lower fluctuations, deviating from the observed heightened flexibility in other mutants. A general decrease in hydrogen bonds was observed in the 5-FU binding environment of the mutations compared to the WT. In particular, 5-FU contact analysis of the WT versus the mutation revealed a reduction in contact between core 5-FU binding residues and catalytic residues Cys671 and Ser670, which form hydrogen bonds that initiate DPD catalytic action. Additionally, BC was used to quantify the importance of a protein residue based on how often it acted as a bridge along the shortest paths between other residues. It reflected the potential control or influence a residue may have over communication between different parts of a protein structure. DC assesses the number of connections or interactions a residue had with other residues in the protein, indicating its overall connectivity within the structure. In both drug free and drug bound state, DPD data from the active site hubs' BC and DC revealed a dimeric asymmetric communication pathway per monomer involving a cluster of newly introduced hubs ensemble along the oxidoreduction conduit from NADPH to 5-FU. The two BC communication pathways were located more on the interior of the oxidoreduction conduit, while the two DC communication pathways were located on the exterior. In both cases, one pathway dominated the other. Partially lost function reported in mutation systems could be credited to the compensation communication response to the catalytic site via the least compromised routes. Similar patterns were observed in allosteric communication pathways to the active site induced by remote mutations. Mutations may have destabilized the active-loop and 5-FU binding environment, resulting in a compensatory mechanism seen by the addition of new hubs to the communication network. Surprisingly, EC hubs in the WT were found within the catalytic site domain, indicating that the region is important in 5-FU metabolism. EC measured the importance of a residue by considering both its own degree of connectivity and the degrees of connectivity with its neighboring residues, highlighting its significance in information flow and communication. Herein, EC hubs in mutant systems were found to lose this importance, with active site domain mutations suffering the most. This could explain why non-clinical catalytic domain mutations R592Q, A664S, and G674D, as well as clinical catalytic domain mutations S534N and I543V, experienced drug exit in one of their monomers during simulation. In contrast, there was no 5-FU exit in the non-clinical remote domain. Additionally, aside from the active site, KC hubs were also found around the cofactors, indicating that these components were equally important in DPD overall function. KC combines the concepts of both degree centrality and eigen-centrality, it incorporated both direct and indirect interactions to evaluate the importance of a residue, assigning higher centrality to residues that have connections to other highly central residues. Hence, providing a more comprehensive measure of influence within the protein network. More importantly, CC is known to measure how efficiently a residue can interact with other residues in the protein, considering the shortest path lengths. It indicates the proximity of a residue to others, suggesting its potential for information transfer or functional integration. CC revealed that the majority of persistent hubs were found within the protein-cores known as cold-spots. Overall, this study highlighted the communication pathways triggered by active site domain mutations, as well as the allosteric communication pathways triggered by each remote mutation in both drug free and drug bound states of the DPD enzyme. Both clinical and non-clinical mutations revealed each protein's adaptive compensation mechanism, which results in partial function loss. In each case, the communication network of the different monomers changed from inactive to activated DPD protein. Cold-spot areas were discovered to contain key persistent residues involved in protein function and stability. These areas have been proposed as potential targets for new or repurposed pharmacological modulators that can restore enzyme function. In the pursuit of precision medicine, it also lays the groundwork for detecting and explaining the molecular mechanisms of other drug metabolizing enzymes related to the African-descent subpopulation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
An analysis of power relations, affiliation and individuation in selected coup, secession, and inaugural speeches of Nigerian leaders, 1960-2015
- Authors: Unegbu, Osondu Chukwuemeka
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432399 , vital:72867 , DOI 10.21504/10962/432399
- Description: This study examines the positioning of Zimbabwe and the United Kingdom (UK) in the language of news articles about diplomatic relations between the two countries published in two prominent Zimbabwean newspapers, The Herald and The Standard, between 2016 and 2020, using Systemic Functional Linguistics (SFL) and Legitimation Code Theory (LCT). Zimbabwe's present diplomatic discourses are a product of its colonial and post-independence history. This thesis places The Herald and The Standard within the larger context of the Zimbabwean media landscape as a state-owned and a privately owned newspaper, respectively. It contends that the two newspapers influence the positioning of Zimbabwe and the United Kingdom in public spheres where readers engage with the news concerning diplomatic ties. The research begins with a corpus-based examination of 42 news articles published between 2016 and 2020 in The Herald and The Standard. The investigation identified several angles through which Zimbabwe and the UK are positioned in the coverage. Zimbabwe is positioned through reference to its reform agenda, intentions for free and fair elections, and its diplomatic re-engagement drive. The UK is positioned as a source of development funding and new trade agreements, while improved diplomatic relations and the removal of restrictive measures against Zimbabwe are anticipated. Fine-grained analysis was conducted on four articles, two from each newspaper, selected to reflect the trends found in the corpus analysis. The fine-grained analyses showed how linguistic resources contributed to the positioning of the UK and Zimbabwe. Complementary analyses of these articles were conducted using LCT and SFL to describe how readers' knowledge of diplomatic relations is built using language in The Herald and The Standard. The study used the concepts of constellations and cosmologies from LCT to demonstrate how diplomatic knowledge is built in these news articles. In the articles, the constellations are related to policies such as Zimbabwe's reform agenda, people (diplomats and government officials) and moral judgments. Both newspapers contain both positive and negative positioning of Zimbabwe and the UK. However, The Standard is generally critical of removing the UK's sanctions on Zimbabwe and of the Zimbabwean government's reform agenda. Meanwhile, The Herald justifies Zimbabwe's Fast-track Land Reform Programme as resulting from Britain's refusal to fund a land redistribution programme as per the 1979 Lancaster House Agreement. The use of SFL's Appraisal framework helps to examine the linguistic resources used by The Herald and The Standard to describe the positioning of the two countries in relation to each other. Lexical strings help to establish diplomatic positioning in the news articles. These couple with Appraisal to accomplish individuation and affiliation. Affect and Judgement resources revealed the decisions taken by the UK to solve the conflict by encouraging the implementation of a reform agenda by Zimbabwe. Negative evaluation is consistently used to disalign with sanctions. The emerging patterns in the data show that diplomats representing the UK affiliate with Zimbabwe's stated economic and political reforms, and the government of Zimbabwe affiliates with the new trade agreement between Zimbabwe and the UK. At the same time, the UK diplomats individuate away from human rights abuses and the Fast-track Land Reform Programme. Affiliation strengthens confidence in diplomatic ties between Zimbabwe and the UK because the emphasis is placed on restoring them despite the conditions attached. The Herald and The Standard position Zimbabwe as a reformed country ready to implement policies to improve citizens' lives and as a country violating human rights and the rule of law. They position the UK as asserting power over Zimbabwe, willing to resolve the crisis through its foreign policy, and credited for assisting Zimbabwe. This strengthens re-engagement in diplomatic relations and commercial trade between the UK and Zimbabwe. In light of these findings, Zimbabweans are encouraged to cultivate an awareness that enables them to reflect on the challenges associated with diplomatic discourses and the implications for critically analysing the re-engagement initiative. They can promote re-engagement by being cognisant of specific values portrayed in The Herald and The Standard and challenging these values in the light of policy transformation to revive the relations between the two countries. The re-engagement process requires a transformation in Zimbabwe's modus operandi to improve the country's positioning in the diplomatic relations between it and the UK. , Thesis (PhD) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Unegbu, Osondu Chukwuemeka
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432399 , vital:72867 , DOI 10.21504/10962/432399
- Description: This study examines the positioning of Zimbabwe and the United Kingdom (UK) in the language of news articles about diplomatic relations between the two countries published in two prominent Zimbabwean newspapers, The Herald and The Standard, between 2016 and 2020, using Systemic Functional Linguistics (SFL) and Legitimation Code Theory (LCT). Zimbabwe's present diplomatic discourses are a product of its colonial and post-independence history. This thesis places The Herald and The Standard within the larger context of the Zimbabwean media landscape as a state-owned and a privately owned newspaper, respectively. It contends that the two newspapers influence the positioning of Zimbabwe and the United Kingdom in public spheres where readers engage with the news concerning diplomatic ties. The research begins with a corpus-based examination of 42 news articles published between 2016 and 2020 in The Herald and The Standard. The investigation identified several angles through which Zimbabwe and the UK are positioned in the coverage. Zimbabwe is positioned through reference to its reform agenda, intentions for free and fair elections, and its diplomatic re-engagement drive. The UK is positioned as a source of development funding and new trade agreements, while improved diplomatic relations and the removal of restrictive measures against Zimbabwe are anticipated. Fine-grained analysis was conducted on four articles, two from each newspaper, selected to reflect the trends found in the corpus analysis. The fine-grained analyses showed how linguistic resources contributed to the positioning of the UK and Zimbabwe. Complementary analyses of these articles were conducted using LCT and SFL to describe how readers' knowledge of diplomatic relations is built using language in The Herald and The Standard. The study used the concepts of constellations and cosmologies from LCT to demonstrate how diplomatic knowledge is built in these news articles. In the articles, the constellations are related to policies such as Zimbabwe's reform agenda, people (diplomats and government officials) and moral judgments. Both newspapers contain both positive and negative positioning of Zimbabwe and the UK. However, The Standard is generally critical of removing the UK's sanctions on Zimbabwe and of the Zimbabwean government's reform agenda. Meanwhile, The Herald justifies Zimbabwe's Fast-track Land Reform Programme as resulting from Britain's refusal to fund a land redistribution programme as per the 1979 Lancaster House Agreement. The use of SFL's Appraisal framework helps to examine the linguistic resources used by The Herald and The Standard to describe the positioning of the two countries in relation to each other. Lexical strings help to establish diplomatic positioning in the news articles. These couple with Appraisal to accomplish individuation and affiliation. Affect and Judgement resources revealed the decisions taken by the UK to solve the conflict by encouraging the implementation of a reform agenda by Zimbabwe. Negative evaluation is consistently used to disalign with sanctions. The emerging patterns in the data show that diplomats representing the UK affiliate with Zimbabwe's stated economic and political reforms, and the government of Zimbabwe affiliates with the new trade agreement between Zimbabwe and the UK. At the same time, the UK diplomats individuate away from human rights abuses and the Fast-track Land Reform Programme. Affiliation strengthens confidence in diplomatic ties between Zimbabwe and the UK because the emphasis is placed on restoring them despite the conditions attached. The Herald and The Standard position Zimbabwe as a reformed country ready to implement policies to improve citizens' lives and as a country violating human rights and the rule of law. They position the UK as asserting power over Zimbabwe, willing to resolve the crisis through its foreign policy, and credited for assisting Zimbabwe. This strengthens re-engagement in diplomatic relations and commercial trade between the UK and Zimbabwe. In light of these findings, Zimbabweans are encouraged to cultivate an awareness that enables them to reflect on the challenges associated with diplomatic discourses and the implications for critically analysing the re-engagement initiative. They can promote re-engagement by being cognisant of specific values portrayed in The Herald and The Standard and challenging these values in the light of policy transformation to revive the relations between the two countries. The re-engagement process requires a transformation in Zimbabwe's modus operandi to improve the country's positioning in the diplomatic relations between it and the UK. , Thesis (PhD) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
- Full Text:
- Date Issued: 2023-10-13
An examination of the use and value of support systems for people living with HIV/AIDS in Makhanda
- Authors: Gorham, Catherine Margaret
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432411 , vital:72868 , DOI 10.21504/10962/432411
- Description: Through the experiences of five people, this study asks how support systems develop, are used and are valued for those faced with the everyday challenges of living with HIV. Additional evidence is found in accounts from those identified as essential sources of support. These are primarily friends, sometimes family. This perspective is rounded out by insights gathered from those working in local organisations and in the analysis of services offered by the state. The three women and two men at the centre of this study live in Makhanda in the Eastern Cape, South Africa. Makhanda (formerly Grahamstown) is characterised by extremes of poverty and wealth, reflected in low employment, expanding informal and low-income settlement areas but also in a high level of community activism and access to resources. Each of the five tested positive for HIV variously between 1998 and 2008. These years were pivotal in the development of the local and national epidemic. The rapid expansion of infection rates, contestation over forms of and access to treatment, followed by emphasis of a biomedical response, in equal measure bracket and cut across their experiences. To this point, research is less concerned with what individual experiences say about living through the HIV/AIDS epidemic. Preoccupations lie more generally with macro- or micro-level factors, with behaviour change, managing risk and so public health – not the processes linking individual circumstances and choices to opportunities and outcomes described by individual, community and structural, socio-economic contexts. Personal accounts and observations of a developing, community-based, local response to an unfolding epidemic are therefore considered against the analysis of available medical and nonmedical resources. This enables identification and investigation of social processes operating between proximal and distal conditions, determining possibilities for access to support. The focus of this study thus falls to the interrelations of structure, agency and action. It contributes to an empirical and theoretical understanding of what “support” is, what “coping” means and what unfolds where diagnosis with HIV disrupts and challenges existing ways of coping and forms of support. The accounts gathered for this study offer an “insider” perspective, focused on what follows from testing positive to identifying what resources hold significance. Connections between individual, community and society, through psycho-social, local and macro-level processes are explored. Along with the empirical study of individual accounts, the thesis offers a theoretical framework that uses a grounded-theory approach in conjunction with the tools of narrative analysis. These are critically adapted from a sociology of illness studies. Ideas of risk and response, of material and social capital, of the nature of HIV/AIDS as an experience that is inclusive of both chronic, everyday challenge and critical, life-threatening crisis disrupting a sense of time, biography and self, are brought together in the analysis. In this way the understanding of what support means, how it develops and is used (systematically or not), and of the links operating between structural and social conditions, individual agency and action, can be developed. What the thesis finds is that, beyond the medical system of hospitals and clinics, there is surprisingly little use of available resources. There is thus an absence of any systematic support for those faced with the physical, psychological, social and material impacts of HIV/AIDS. Given the nature of personal circumstances, embedded as they are within local conditions that reflect structural constraints of the broader economy and society, this should not be surprising. A system of support exists in only the most limited definition. Against this, what is novel in these findings is the role that psycho-social processes play in negotiating these conditions and how this works, determining what unfolds. A key finding is that it is more through chance than choice that people do find conventional forms of support. The reasons for this have to do not only with limitations to state and institutional capacity, but also with the impact on individuals of perceptions of themselves shaped by the impact of the epidemic and also the past. The result is that under the burden of HIV/AIDS, in the context of extreme inequalities and the absence of an adequate response from the state, already invisible individuals who do not “count” run the risk of becoming doubly invisible. It is through a process of personal adaptation in which shifts in identity and a sense of self are key that they must find their own way. This involves re-conceptualisations of identity, a sense of self and place in the world. The focus on five people and the community in which they live is a limit to the scope of study Yet it is this focus which allows for a new understanding of the social processes involved, and so the links operating between individuals and society. This is of significance beyond the study of HIV/AIDS alone, contributing to the broader sociological project of understanding what it means to “be human”. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Gorham, Catherine Margaret
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432411 , vital:72868 , DOI 10.21504/10962/432411
- Description: Through the experiences of five people, this study asks how support systems develop, are used and are valued for those faced with the everyday challenges of living with HIV. Additional evidence is found in accounts from those identified as essential sources of support. These are primarily friends, sometimes family. This perspective is rounded out by insights gathered from those working in local organisations and in the analysis of services offered by the state. The three women and two men at the centre of this study live in Makhanda in the Eastern Cape, South Africa. Makhanda (formerly Grahamstown) is characterised by extremes of poverty and wealth, reflected in low employment, expanding informal and low-income settlement areas but also in a high level of community activism and access to resources. Each of the five tested positive for HIV variously between 1998 and 2008. These years were pivotal in the development of the local and national epidemic. The rapid expansion of infection rates, contestation over forms of and access to treatment, followed by emphasis of a biomedical response, in equal measure bracket and cut across their experiences. To this point, research is less concerned with what individual experiences say about living through the HIV/AIDS epidemic. Preoccupations lie more generally with macro- or micro-level factors, with behaviour change, managing risk and so public health – not the processes linking individual circumstances and choices to opportunities and outcomes described by individual, community and structural, socio-economic contexts. Personal accounts and observations of a developing, community-based, local response to an unfolding epidemic are therefore considered against the analysis of available medical and nonmedical resources. This enables identification and investigation of social processes operating between proximal and distal conditions, determining possibilities for access to support. The focus of this study thus falls to the interrelations of structure, agency and action. It contributes to an empirical and theoretical understanding of what “support” is, what “coping” means and what unfolds where diagnosis with HIV disrupts and challenges existing ways of coping and forms of support. The accounts gathered for this study offer an “insider” perspective, focused on what follows from testing positive to identifying what resources hold significance. Connections between individual, community and society, through psycho-social, local and macro-level processes are explored. Along with the empirical study of individual accounts, the thesis offers a theoretical framework that uses a grounded-theory approach in conjunction with the tools of narrative analysis. These are critically adapted from a sociology of illness studies. Ideas of risk and response, of material and social capital, of the nature of HIV/AIDS as an experience that is inclusive of both chronic, everyday challenge and critical, life-threatening crisis disrupting a sense of time, biography and self, are brought together in the analysis. In this way the understanding of what support means, how it develops and is used (systematically or not), and of the links operating between structural and social conditions, individual agency and action, can be developed. What the thesis finds is that, beyond the medical system of hospitals and clinics, there is surprisingly little use of available resources. There is thus an absence of any systematic support for those faced with the physical, psychological, social and material impacts of HIV/AIDS. Given the nature of personal circumstances, embedded as they are within local conditions that reflect structural constraints of the broader economy and society, this should not be surprising. A system of support exists in only the most limited definition. Against this, what is novel in these findings is the role that psycho-social processes play in negotiating these conditions and how this works, determining what unfolds. A key finding is that it is more through chance than choice that people do find conventional forms of support. The reasons for this have to do not only with limitations to state and institutional capacity, but also with the impact on individuals of perceptions of themselves shaped by the impact of the epidemic and also the past. The result is that under the burden of HIV/AIDS, in the context of extreme inequalities and the absence of an adequate response from the state, already invisible individuals who do not “count” run the risk of becoming doubly invisible. It is through a process of personal adaptation in which shifts in identity and a sense of self are key that they must find their own way. This involves re-conceptualisations of identity, a sense of self and place in the world. The focus on five people and the community in which they live is a limit to the scope of study Yet it is this focus which allows for a new understanding of the social processes involved, and so the links operating between individuals and society. This is of significance beyond the study of HIV/AIDS alone, contributing to the broader sociological project of understanding what it means to “be human”. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2023
- Full Text:
- Date Issued: 2023-10-13
Analysis of the role and regulation of HOP1a and HOP1b splice variants in cancer biology
- Authors: Schwarz, Kelly
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432240 , vital:72854
- Description: Restricted access. Expected lease date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Schwarz, Kelly
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432240 , vital:72854
- Description: Restricted access. Expected lease date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
Anonymous testimony and epistemic responsibility
- Authors: Ajiboro, Aderonke Adeyinka
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432286 , vital:72858 , DOI 10.21504/10962/432286
- Description: In this thesis, I examine anonymous testimony in both offline (face-to-face) and online (internet and social media) interactions and the epistemic concerns it raises in relation to belief, knowledge, justification, and normative assessments of assertions. I discuss anonymous testimony as involving a relation between the hearer and the content of the testimony in comparison to ordinary cases where the speaker of an assertion is known. In anonymous testimony, the hearer has the burden of epistemic responsibility to arrive at a testimonial belief or arguably acceptance. The hearer is also accountable for the anonymous testimony in the event of re-assertion. I also assess the norms of assertion for anonymous testimony and argue that knowledge, truth, and belief norms that apply in cases where the speaker is known should not be applied to cases of anonymous speakers. Epistemologists have paid little attention to anonymous testimony and its implications on the norms of interaction. This is a study in the epistemology of testimony and it aims at providing further understanding of the epistemic responsibility of hearers of anonymous testimony. In Chapter One, I argue that anonymous testimony can be appropriately described as testimony; where the properties of an assertion to induce belief in the hearer are sufficient to describe the assertion as testimony. I examine the kinds of anonymity and the burden of epistemic responsibility for the hearer. I introduce basically anonymous testimony in offline and online contexts of interaction. A basically anonymous testimony occurs where, at the instance of receiving testimony and making an epistemic decision on it, the speaker is unidentifiable to the hearer. In Chapter Two, I discuss the kinds of epistemic attitudes hearers may have when they receive anonymous testimony. I discuss reductionism, antireductionism, and entitlement theory as accounts of the justification for believing testimony. I argue that acceptance is the appropriate attitude and the entitlement theory provides a basis for accepting anonymous testimony. I also argue that practical reasons are a sufficient to accept anonymous testimony. Also, I discuss the possibility that a hearer of anonymous testimony can make a wrongful presumption by assigning an identity to a person as the speaker of an anonymous testimony. This can cause harm to the ‘person’ of the presumed speaker such as an unwarranted credibility assessment of the person by other people in the community. I also argue that making a credibility assessment of a presumed speaker constitutes harm to a proper epistemic assessment of the content. In Chapter Three, I discuss the possibility of trust relations between an anonymous speaker and a hearer. I argue that the hearer is solely responsible for making an epistemic decision from anonymous testimony. I argue that anonymous testimony can be relevant to a hearer given the value of its content. In Chapter Four, I discuss the applicability of knowledge, truth, belief, reasonable to believe and supportive reasons norms for the re-assertion of anonymous testimony. Hence, I argue that the supportive reasons norm, which acknowledges acceptance of an assertion, the relevance of contexts, and admits both epistemic and practical reasons to make an assertion, should guide the re-assertion of anonymous testimony. I also argue that a hearer should be epistemically conscientiousness for responsible re-assertion of received anonymous testimony. , Thesis (PhD) -- Faculty of Humanities, Philosophy, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ajiboro, Aderonke Adeyinka
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432286 , vital:72858 , DOI 10.21504/10962/432286
- Description: In this thesis, I examine anonymous testimony in both offline (face-to-face) and online (internet and social media) interactions and the epistemic concerns it raises in relation to belief, knowledge, justification, and normative assessments of assertions. I discuss anonymous testimony as involving a relation between the hearer and the content of the testimony in comparison to ordinary cases where the speaker of an assertion is known. In anonymous testimony, the hearer has the burden of epistemic responsibility to arrive at a testimonial belief or arguably acceptance. The hearer is also accountable for the anonymous testimony in the event of re-assertion. I also assess the norms of assertion for anonymous testimony and argue that knowledge, truth, and belief norms that apply in cases where the speaker is known should not be applied to cases of anonymous speakers. Epistemologists have paid little attention to anonymous testimony and its implications on the norms of interaction. This is a study in the epistemology of testimony and it aims at providing further understanding of the epistemic responsibility of hearers of anonymous testimony. In Chapter One, I argue that anonymous testimony can be appropriately described as testimony; where the properties of an assertion to induce belief in the hearer are sufficient to describe the assertion as testimony. I examine the kinds of anonymity and the burden of epistemic responsibility for the hearer. I introduce basically anonymous testimony in offline and online contexts of interaction. A basically anonymous testimony occurs where, at the instance of receiving testimony and making an epistemic decision on it, the speaker is unidentifiable to the hearer. In Chapter Two, I discuss the kinds of epistemic attitudes hearers may have when they receive anonymous testimony. I discuss reductionism, antireductionism, and entitlement theory as accounts of the justification for believing testimony. I argue that acceptance is the appropriate attitude and the entitlement theory provides a basis for accepting anonymous testimony. I also argue that practical reasons are a sufficient to accept anonymous testimony. Also, I discuss the possibility that a hearer of anonymous testimony can make a wrongful presumption by assigning an identity to a person as the speaker of an anonymous testimony. This can cause harm to the ‘person’ of the presumed speaker such as an unwarranted credibility assessment of the person by other people in the community. I also argue that making a credibility assessment of a presumed speaker constitutes harm to a proper epistemic assessment of the content. In Chapter Three, I discuss the possibility of trust relations between an anonymous speaker and a hearer. I argue that the hearer is solely responsible for making an epistemic decision from anonymous testimony. I argue that anonymous testimony can be relevant to a hearer given the value of its content. In Chapter Four, I discuss the applicability of knowledge, truth, belief, reasonable to believe and supportive reasons norms for the re-assertion of anonymous testimony. Hence, I argue that the supportive reasons norm, which acknowledges acceptance of an assertion, the relevance of contexts, and admits both epistemic and practical reasons to make an assertion, should guide the re-assertion of anonymous testimony. I also argue that a hearer should be epistemically conscientiousness for responsible re-assertion of received anonymous testimony. , Thesis (PhD) -- Faculty of Humanities, Philosophy, 2023
- Full Text:
- Date Issued: 2023-10-13
Arbuscular mycorrhizal fungi associated with maize in South Africa, under conventional and conservation agricultural cultivation
- Maússe Sitoe, Sílvia Natal David
- Authors: Maússe Sitoe, Sílvia Natal David
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431846 , vital:72808
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Maússe Sitoe, Sílvia Natal David
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431846 , vital:72808
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-10-13
Arbuscular mycorrhizal fungi associated with wheat under conventional and conservation agricultural cultivation
- Authors: Dube, Makasithembe
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431688 , vital:72796
- Description: Access restricted. Expected release date in 2024. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Dube, Makasithembe
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431688 , vital:72796
- Description: Access restricted. Expected release date in 2024. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Asymmetrical zinc(II) phthalocyanines conjugated to nanomaterials for degradation of organic pollutants and inactivation of Staphylococcus aureus bacteria
- Authors: Mgidlana, Sithi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431859 , vital:72809 , DOI 10.21504/10962/431860
- Description: This thesis reports on the syntheses and characterization of asymmetrical phthalocyanines (Pcs) with different ring substituents (tert-butyl, ester, diimide, trimethoxy, acetophenone, heptanoylphenoxy, perfluorophenoxy, dimethoxy, propanoic acid, acetic acid, carboxylic acid, aminophenoxy, acrylic acid). Several nanoparticles including metal tungstate, capped with glutathione and 1-mercaptohexanol are prepared and characterized using analytical techniques. The synthesized Pcs are covalently linked to various nanoparticles (NPs) through ester and amide bonds to form Pc-NP conjugates, in order to improve their catalytic properties. The Pcs and their conjugates are characterized using different analytical techniques. The photophysics and photochemistry of the MPcs and conjugates are studied. The conjugates T). The complexes and the conjugates with nanomaterials are evaluated for singlet oxygen-generating ability. Conjugates generate higher singlet oxygen in comparison to Pc complexes alone. The photocatalytic activity of the conjugates of ZnPc complexes with NiWO4, Ag2WO4, Bi2WO6, CoWO4, and Ag-Fe3O4-based nanoparticles is evaluated based on photodegradation of methylene blue, tetracycline, and dibenzothiophene. The photocatalytic efficiencies of the synthesized phthalocyanine complexes increased in the presence of nanoparticles. This work also reports on the photodynamic antimicrobial chemotherapy activity of these materials against Staphylococcus aureus (S. aureus) bacteria in DMSO. The results indicated that silver-based nanoconjugates exhibit high antimicrobial activity with high log reductions compared to NiWO4, CoWO4, and Ag-Fe3O4-based materials. The z-scan technique is employed to experimentally test the nonlinear optical response of complexes and nanoconjugates in solution. The nonlinear absorption coefficient, third-order optical susceptibility and optical limiting threshold of the materials are obtained from the Z-scan aperture data. The nonlinear absorption parameters improved in the presence of semiconductor quantum dots, with 1-ethanoic-CdTe/ZnSeS/ZnO giving the best results due to the presence of electron-donating substituents. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mgidlana, Sithi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431859 , vital:72809 , DOI 10.21504/10962/431860
- Description: This thesis reports on the syntheses and characterization of asymmetrical phthalocyanines (Pcs) with different ring substituents (tert-butyl, ester, diimide, trimethoxy, acetophenone, heptanoylphenoxy, perfluorophenoxy, dimethoxy, propanoic acid, acetic acid, carboxylic acid, aminophenoxy, acrylic acid). Several nanoparticles including metal tungstate, capped with glutathione and 1-mercaptohexanol are prepared and characterized using analytical techniques. The synthesized Pcs are covalently linked to various nanoparticles (NPs) through ester and amide bonds to form Pc-NP conjugates, in order to improve their catalytic properties. The Pcs and their conjugates are characterized using different analytical techniques. The photophysics and photochemistry of the MPcs and conjugates are studied. The conjugates T). The complexes and the conjugates with nanomaterials are evaluated for singlet oxygen-generating ability. Conjugates generate higher singlet oxygen in comparison to Pc complexes alone. The photocatalytic activity of the conjugates of ZnPc complexes with NiWO4, Ag2WO4, Bi2WO6, CoWO4, and Ag-Fe3O4-based nanoparticles is evaluated based on photodegradation of methylene blue, tetracycline, and dibenzothiophene. The photocatalytic efficiencies of the synthesized phthalocyanine complexes increased in the presence of nanoparticles. This work also reports on the photodynamic antimicrobial chemotherapy activity of these materials against Staphylococcus aureus (S. aureus) bacteria in DMSO. The results indicated that silver-based nanoconjugates exhibit high antimicrobial activity with high log reductions compared to NiWO4, CoWO4, and Ag-Fe3O4-based materials. The z-scan technique is employed to experimentally test the nonlinear optical response of complexes and nanoconjugates in solution. The nonlinear absorption coefficient, third-order optical susceptibility and optical limiting threshold of the materials are obtained from the Z-scan aperture data. The nonlinear absorption parameters improved in the presence of semiconductor quantum dots, with 1-ethanoic-CdTe/ZnSeS/ZnO giving the best results due to the presence of electron-donating substituents. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Beyond mastery: jazz, gender and power in postapartheid South Africa
- Authors: Williams, Ulagh
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432505 , vital:72876 , DOI 10.21504/10962/432512
- Description: This dissertation studies the musical lives of seven South African women who have built highprofile national and international careers as jazz musicians. Empirically it records self-reported experiences and actions that they have identified as relevant to their success within a notoriously patriarchal field. Drawing on feminist research methods and Interpretative Phenomenological Analysis the dissertation strives to develop an empathic yet critical epistemological framework attuned to the complexities of their lived experiences as women and as jazz musicians. Theoretically it investigates the power relations at play in the myriad ways they negotiate or have been impelled to negotiate gender and patriarchy as musicians. Chapter one draws attention to the ubiquity of patriarchy in South African and international jazz culture, and highlights the research participants’ numerous successes to date as performers, educators, composers, and bandleaders. Chapter two positions this study in relation to cognate work in South African jazz studies, international feminist jazz studies and feminist phenomenology. Chapters three to five successively consider the participants’ early enculturation as musical and gendered subjects, their agentic responses to structures of patriarchy and/or race as emerging and established professionals, and the ways these experiences have found expression in some of their musical utterances as performers and composers. Fusing art and activism, the participants challenge and transcend masculinist discourses of mastery that still dominate South African jazz as a field of production and aesthetic practice. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Williams, Ulagh
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432505 , vital:72876 , DOI 10.21504/10962/432512
- Description: This dissertation studies the musical lives of seven South African women who have built highprofile national and international careers as jazz musicians. Empirically it records self-reported experiences and actions that they have identified as relevant to their success within a notoriously patriarchal field. Drawing on feminist research methods and Interpretative Phenomenological Analysis the dissertation strives to develop an empathic yet critical epistemological framework attuned to the complexities of their lived experiences as women and as jazz musicians. Theoretically it investigates the power relations at play in the myriad ways they negotiate or have been impelled to negotiate gender and patriarchy as musicians. Chapter one draws attention to the ubiquity of patriarchy in South African and international jazz culture, and highlights the research participants’ numerous successes to date as performers, educators, composers, and bandleaders. Chapter two positions this study in relation to cognate work in South African jazz studies, international feminist jazz studies and feminist phenomenology. Chapters three to five successively consider the participants’ early enculturation as musical and gendered subjects, their agentic responses to structures of patriarchy and/or race as emerging and established professionals, and the ways these experiences have found expression in some of their musical utterances as performers and composers. Fusing art and activism, the participants challenge and transcend masculinist discourses of mastery that still dominate South African jazz as a field of production and aesthetic practice. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
- Date Issued: 2023-10-13