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Comparison of the metabolic physiology of exploited and unexploited populations of red roman (Chrysoblephus laticeps) along the south coast of South Africa

  • Authors: Nabani, Xolani Prince
  • Date: 2023-10-13
  • Subjects: Chrysoblephus laticeps , Marine fishes Climatic factors South Africa , Marine fishes Physiology South Africa , Marine fishes Metabolism , Respirometry , Marine protected area , Evolutionary impact of fishing
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424358 , vital:72146
  • Description: Anthropogenic-induced climate change and exploitation pose threat to many marine fishes on which a vast majority of people around the world depend. Rapid changes in sea surface temperature have a direct impact on the physiology of ectothermic organisms such as fish, potentially resulting in changes to population distribution, abundance, and demographics. In the face of climate change, the impacts of increasing temperature variability on fish populations may be exacerbated by exploitation. Understanding how the resilience of exploited populations is affected by climate change is critical to predict how fishes will respond in the future. This study aimed to augment our knowledge on the impact of exploitation and thermal variability on fishes by comparing the thermal physiology of an exploited and unexploited population of the resident, reef-dwelling, Chrysoblephus laticeps. Twenty live fish were collected from the exploited, Cape St Francis and 18 fish from the unexploited, Goukamma Marine Protected Area and transported to the laboratory. The metabolic performance, in terms of standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope (AS) of individual C. laticeps were estimated repeatedly at 10 ℃, 16 °C and 21 °C. Linear mixed effects models were used to examine the relationship between temperature, population, and metabolic rate and a ‘cvequality’ test analysis was used to compare the variance structure of the metabolic rate regression model for each population. Overall, the findings of this study show that Chrysoblephus laticeps from the unexploited population maintains a significantly higher aerobic scope (AS) across all temperature treatments (10, 16 and 21 ℃) when compared with those from the exploited population. In addition, the maximum metabolic rate (MMR) of individuals from the unexploited population was significantly higher than that of individuals from the exploited population, but there was no evidence to suggest that variability was significantly different between the populations. On the other hand, the individuals from an exploited population had a significantly higher standard metabolic rate (SMR) at high temperatures of 21 ℃, while the unexploited population had a low SMR at these high temperatures, but a high SMR at 10 ℃. Despite these differences there was no significant variation in the SMR between the two populations. The findings of this study confirm previous work on different exploited and unexploited populations of C. laticeps and together these findings suggest that hook and line exploitation lead to reduced physiological phenotypic diversity and reduced physiological performance in exploited fish populations. These findings emphasise the importance of incorporating the iii physiological information to develop viable fisheries management tools in the context of climate change. This study also highlights the effectiveness of MPAs in conserving highperformance physiological phenotypes to maintain phenotypic diversity in fish populations. Future research should aim to evaluate the efficacy of existing MPAs in preserving the physiological diversity of important hook and line fisheries species, while fisheries managers should consider augmenting their approaches through the incorporation of well-designed MPA’s to promote physiological diversity. This will be critical to advance the development of sustainable management practices, not only in a South African context but globally, where oceanic and coastal environmental conditions are expected to rapidly change in the future. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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  • Date Issued: 2023-10-13

Composition and physiological roles of gut microbiota in the False Coding Moth (Thaumatotibia leucotreta)

  • Authors: Richardson, Perryn Heather
  • Date: 2023-10-13
  • Subjects: False codling moth , Microbiomes , Insect physiology , Citrus Diseases and pests South Africa , Biological pest control , Cryptophlebia leucotreta
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424457 , vital:72155
  • Description: Gut microbiota can have a profound influence on host performance, behaviour and fitness. For False Codling Moth (FCM), Thaumatotibia leucotreta (Lepidoptera: Tortricidae), a major pest of citrus in South Africa, little work has been undertaken to date on gut microbe diversity or its influence on the host. This thesis aimed to i) characterise the gut microbiome of FCM under laboratory conditions and in FCM from the field, ii) and produce moths with reduced gut microbiota through egg dechorionation, which was followed by iii) the measurement of a suite of physiological traits, namely mass, survival and thermal stress in FCM from normal laboratory, dechorionated laboratory and field collected larvae that may be indicative of overall field performance. We aimed to directly test the hypothesis that gut microbial diversity partly determines insect performance and fitness by measuring its effects on growth, development, and tolerance to cold temperatures in FCM. FCM eggs that underwent dechorionation with sodium hypochlorite had an overall effect on larval survival, egg morphology and both larval and adult moth physiological measures. Increasing concentrations of sodium hypochlorite significantly decreased insect survival, (𝜒2(1, n = 10 850) = 21.724, p-value < 0.0001), with a concentration of ≈3.69% as the concentration limit (p-value < 0.001). Successful dechorionation of FCM was achieved with a wash of sodium hypochlorite at around 3.69% concentration and was visually confirmed by reduction of FCM egg surface area, (𝜒2(25, n = 260) p-value < 0.0001) and Scanning Electron Micrographs of the egg morphology. The gut microbiome of FCM from the different focus treatments was successfully characterized. Identification of the dominant bacterial families in these microbiomes revealed Xanthobacteraceae, Beijerinckiaceae and Burkholderiaceae in both the laboratory reared and field collected larvae, which suggests their systematic association with T. leucotreta. The most abundant genera were revealed as Bradyrhizobium, Methylobacterium and Burkholderia-Caballeronia-Paraburkholderia. Comparison of larval mass showed that treatment (dechorionated or not) had a significant effect on larval mass (𝜒2(2, n = 230) = 22.703, p-value < 0.001), field larvae were heavier than both control larvae and larvae with a disrupted gut microbiome. However, adult insects with a disrupted gut microbiome had more mass than individuals from the control and field-collected larvae with intact gut microbiomes (𝜒2(2, n = 230) = 39.074, p-value < 0.001). Despite the difference in mass between larval treatments, there was no significant difference in relative protein (𝜒2(2, n = 24) = 5.680, p-value = 0.06), carbohydrate (𝜒2(2, n = 24) = 3.940, p-value = 0.14) or lipid (𝜒2(2, n = 24) = 6.032, p-value = 0.05) content between individuals from the control and dechorionated treatments and field-collected individuals. Turning to thermal physiology, insects collected from the field took significantly longer to recover from chill coma than both laboratory treatments with intact and disrupted gut microbiomes (𝜒2(2, n = 129 = 39.659, p-value < 0.001). In addition, exposure to cold stress showed that treatment had a significant effect on insect mortality (𝜒2(2, n = 272) = 9.176, p-value = 0.01), with individuals from the control and dechorionated treatment being less likely to die after experiencing cold stress compared to field-collected individuals. Differences in the mass and thermal tolerance of insects with intact and disrupted gut microbiota suggest that gut microbiota may play an important role in the cold performance of T. leucotreta, and these findings constitute the basis for future molecular work on the functions of these bacterial taxa. This research highlights the need for consideration of the effects of T. leucotreta microbiome in current pest control programs. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
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  • Date Issued: 2023-10-13

Computational studies in human African trypanosomiasis

  • Authors: Muronzi, Tendai
  • Date: 2023-10-13
  • Subjects: African trypanosomiasis , Apolipoprotein L1 , Docking , Protein-protein interactions , Homology modeling , Tetrahydrofolate dehydrogenase , Pteridine reductase
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/431883 , vital:72812 , DOI 10.21504/10962/431885
  • Description: Human African trypanosomiasis (HAT) is a neglected tropical disease (NTD) caused by two subspecies of the parasite, namely Trypanosoma brucei (Tb) gambiense (g-HAT) and rhodesiense (r-HAT). HAT is endemic in sub-Saharan countries, where the parasite transmission vectors, tsetse flies, breed. An estimated 70 million people remain at risk of contracting the disease, where the infection is classified as acute or chronic for g-HAT and r-HAT, respectively, with both forms ending in fatal meningoencephalitis when left untreated. Both g-HAT and r-HAT are responsible for widespread fatal epidemics throughout sub-Saharan African history, resulting from the complex molecular interplay between trypanosomes and humans through unique, innate immunity evasion mechanisms. Of interest, the Tbr subspecies expresses a serum resistance-associated protein (SRA), which binds to human serum lytic factor, apolipoprotein L1 (ApoL1), nullifying any trypanocidal activity. In response, ApoL1 (G1 and G2) variants found in humans of sub-Saharan African lineage have been cited for conferring resistance to the r-HAT infection in an interaction that is not fully elucidated In the event of successful infection, current HAT chemotherapeutics are plagued with complexity of administration, poor efficacy, toxicity, and potential drug resistance, highlighting a need for improved approaches. The parasite folate pathway provides a strategic target for alternative anti-trypanosomal drug development as trypanosomatids are folate auxotrophs, requiring host folate for growth and survival. Validated drug targets pteridine reductase (TbPTR1) and dihydrofolate reductase (TbDHFR) are essential for salvaging cofactors folate and folate biopterin crucial to parasite survival, making them viable targets for anti-folate investigation. The overall aims of this thesis were to a) provide insights into the molecular and dynamic basis of the SRA and ApoL1 interplay in HAT infection and b) identify safer and more efficient anti-folate anti-trypanosomal drug alternatives through in silico approaches. To achieve our first aim, in silico structure prediction was applied to generate 3D models of ApoL1 C-terminal variants G0, G1, G1G/M, G2 and G1G2, and four SRA variants retrieved from the NCBI database. The SRA and ApoL1 structures were inspected dynamically to identify the effect of the variants through molecular dynamics (MD) simulations. Dynamic residue network (DRN) analysis of MD trajectories was fundamental in identifying residues playing a vital role in the intramolecular communication of both proteins in the presence of mutations. Protein-protein docking was then applied to calculate plausible SRA-ApoL1 C-terminal wild-type complex structures to further elucidate the nature of SRA-mediated infection. Through MD simulations, twelve SRA-ApoL1 dimeric structures were narrowed down from five to two energetically sound complexes. The two feasible SRA-ApoL1 complexes (1 and 2) exhibited favourable communication observed through DRN analysis, including the retaining key communication residues identified in prior monomer DRN calculations. ApoL1 C-terminal variants were additionally incorporated into SRA-ApoL1 complexes 1 and 2 for further complex dynamics analysis This investigation into the nature of SRA-ApoL1 binding resulted in five primary outcomes: 1) highlighting the intramolecular effects ApoL1 variants have on the stability of the protein, 2) the identification of crucial SRA and ApoL1 communication residues in both monomeric or dimeric form, 3) the isolation of feasible SRA-ApoL1 complexes determined through global and local structural analyses 4) identification of residues crucial to the complex formation and maintenance of SRA-ApoL1, overlapping with those identified in (1), and 5) the minimal dissociative role of the G1 mutations in the complex, but compounding effect of the G2 deletion mutation. Computational modelling and drug repurposing were employed to achieve the thesis's second aim as they drastically cut down the costs involved in drug discovery and provide a more time-efficient screening method through numerous drug candidates. Using high throughput virtual screening, a subset of 2089 approved DrugBank compounds were screened against TbPTR1. The outputs were filtered to 24 viable compounds in 54 binding poses using binding energy and molecular interactions. Through subsequent MD simulations of 200ns, thirteen potential hit compounds were identified. The resultant hit compounds were subjected to further blind docking against TbDHFR and molecular dynamics to identify compounds with the potential for dual inhibition. The filtered subset was also tested in in vitro single concentration and dose-response bioassays to assess inhibitory properties against Trypanosoma brucei, complementing in silico findings. Post-molecular dynamics, four compounds exhibited high stabilities and molecular interactions with both TbPTR1 and TbDHFR, with two presenting favourable results in the in vitro assays. Three compounds additionally shared common structural moieties. In all, the in silico repurposing highlighted drugs characterised by favourable interactions and stabilities in TbPTR1, thus providing (1) a framework for further studies investigating anti-folate HAT compounds and (2) modulatory scaffolds based on identified moieties that can be used for the design of safe anti-folate trypanosomal drugs. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
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  • Date Issued: 2023-10-13

Controls of lateral and vertical variations in the geochemistry of the Hotazel Fe-Mn Formation at Nchwaning and Gloria mines, Kalahari Manganese Field, South Africa

  • Authors: Dorbor Jr., Stephen Baysah
  • Date: 2023-10-13
  • Subjects: Manganese ores Geology South Africa , Iron ores Geology South Africa , Geochemistry Geology South Africa , Kalahari manganese field , Banded iron formation , Hotazel mine
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424621 , vital:72169
  • Description: The Paleoproterozoic Kalahari manganese field (KMF) in the Northern Cape Province, South Africa, hosts a large resource of manganese ores that has been of great interest over many decades. The Kalahari Manganese deposit (KMD), which is the largest of five erosional relics of the Hotazel Formation in the KMF, hosts three beds of Mn ores with alternating layers of banded iron formation (BIF) and hematite lutite. These three rock types are all evaluated for their mineralogy and geochemistry in this study, with emphasis on lateral and vertical distributions across the Gloria and Nchwaning Mines in the northernmost KMF, an area of high-grade, hydrothermally altered Mn mineralisation. The Mn ores of the Hotazel formation are traditionally categorised into two types. The carbonate-rich low Mn grade (Mn≤40 wt. %) ores (Mamatwan-type) domninates the largest part of the KMD, while carbonate-free, high Mn grade (Mn≥ 45 wt.%) ore (Wessels-type) occurs in the northernmost KMD. The Wessels-type ores are considered as the hydrothermally altered product of Mamatwan-type ores, and as indicated above, are the focus of this study. Five drill cores containing Wessels-type ores from the Nchwaning and Gloria area of the northern KMD were analysed to help understand the petrographic and particularly the geochemical variations in the Hotazel Fe-Mn Formation, both laterally for a given Mn layer of the three, and vertically across Mn layers as captured in specific drillcores. Petrographic and whole-rock geochemical results obtained from the three rock types of the Hotazel Formation show variations in their mineralogical and geochemical compositions, especially in the high-grade Mn ores themselves. Most of the samples of the BIFs layers are dominated by hematite and chert occurring in banded fashion, which is typical of a normal carbonate-free altered BIF discussed in this thesis. The BIFs can also be locally enriched in hematite (ferruginised), occurring as massive hematite ores usually at the top of the stratigraphic profiles. The presence of aegirine-rich assemblages is also noted occurring in some of the BIF and hematite lutite sections immediately above and below the Mn ore beds. The high-grade Mn ore beds vary greatly in mineralogy and texture of the ores laterally and even within a single drill core. In an extreme case, a single drillcore sampled from the Gloria mine (GL57) contains high-grade Wessels-type ore in the upper Mn bed and low-grade, Mamatwan-type ore in the lower Mn layer. Geochemically, the Mn ore bodies also show substantial geochemical variability, although a net increase in the Mn grade downward is usually characterised by a corresponding depletion in mainly bulk Ca, Si and carbonate. However, the Fe content appears to be consistently higher in the upper ore bodies of the drillcores than the lower ones, and the increase in the concentration of the Fe-oxide expectedly causes a relative decrease in the bulk Mn-oxide concentration, usually expressed as an antithetic relationship between the two elements. In terms of trace element distributions, this appears to be more significant in the Mn ores than the other two rock types affected by the same alteration process, probably due to the presence of Mn phases such as hausmannite and braunite serving as good hosts to several trace elements. Cu, Zn, Pb and to a lesser extent Mo are trace metals that appear to show elevated concentration levels (net enrichments) in high-grade Mn ore by comparison to the presumed Mamatwan-type protolith. Ba is an additional element of clear enrichment, manifested mainly as the mineral barite. The Northern KMD has a complex post-depositional history, which includes the intrusion of NE-SW-trending dykes, formation of the Mapedi/Gamagara erosional unconformity, normal faulting associated with the Wessels event and major thrust faults in the western part of the northern KMD. These structural events all have the potential to have contributed to the alteration and subsequent enrichment of the Mn ores in the Nchwaning and Gloria area. As such, the mineralogical, textural, and geochemical variations observed here can tentatively be attributed to the different structural features in the northern KMD. Classic interpretations suggest that normal N-S-trending fault structures have acted as fluid conduits for hydrothermal fluids, which led to the metasomatic alteration of the Mn ore body laterally. Drill cores proximal to and evidently affected by fault-controlled alteration in the SE and SW-portions of the Nchwaning area, have comparable mineralogical and geochemical characteristics for both ore bodies (upper and lower) with subdued alteration effects from the unconformed contact above. Fluids associated with the Mapedi/Gamagara unconformity, would have percolated down-stratigraphy causing oxidative ferruginisation, which led to the formation of massive hematite ores in the top BIF layers and ferruginised Mn ores in the Mn ore beds. This alteration effect appears more prominent in a drill core from the northern part of the study area where the unconformity contact appears more proximal to the upper Mn bed. Drill cores located in the western part of the Nchwaning area seem to also capture evidence of fluid alteration with enrichment in Na recorded in the local abundance of the mineral aegirine. Finally, the dyke structures appear to have acted as impermeable fluid barriers to both lateral and possibly down-dip fluid-flow. , Thesis (MSc) -- Faculty of Science, Geology, 2023
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  • Date Issued: 2023-10-13

Corporate failure and ethical resources: a case study of Steinhoff and Carillion

  • Authors: Mthombeni, Seyijeni Koos
  • Date: 2023-10-13
  • Subjects: Corporate governance , Business ethics , Steinhoff International (Firm) Corrupt practices , Carillion (Firm) Corrupt practices , Business failures , Accounting fraud
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/419165 , vital:71621
  • Description: This study aimed to investigate the impact of disregarding ethical resources on company performance, with a particular focus on Carillion and Steinhoff as case studies. A pragmatist research philosophy was employed using a mixed methods approach, utilizing deductive inferencing to produce archival research. Data was collected from annual financial statements and existing literature on Steinhoff and Carillion's corporate failures. Both content analysis and statistical analysis were employed to analyse the data. The study found that both Carillion and Steinhoff were at the top of their respective industries when they began to underperform due to poor governance. On the part of Carillion, much of its failure can be attributed to aggressive bidding, while for Steinhoff, its failure was due to unscrupulous accounting practices. Corruption and fraud at the top echelon of each of these respective companies began to trickle down to the bottom of the hierarchy. Additionally, Steinhoff used a two-tier board system that promotes information asymmetry between a management board and a supervisory board. This gave Steinhoff’s management board leverage to manipulate company reports and hide information from the supervisory board. Steinhoff equally violated the board’s independence by making former management executives part of the supervisory board, who could potentially be lenient to the management board due to past relationships. This was further exacerbated by the CEO duality, which contributed to Steinhoff’s lack of board independence. Furthermore, Steinhoff’s board was reported to have served as board members for a long time, eventually leading them to create a group culture that negatively affected its board’s independence. Different from Steinhoff, which lacked board independence and board diversity, at face value, Carillion appeared to have a predominantly independent board with diverse experience and external commitments. However, Carillion also lacked board independence in a different way, as some of its board members were previously employed by KPMG. KPMG was also the external auditor of Carillion. This created a scenario where Carillion and KPMG were conniving, which may have affected the objectivity of the external audits on financial performance. Further to this, the CEO held outsized power over the board, which could have also resulted in a lack of independence. This, in turn, facilitated corrupt behaviour within the organisation, which may have contributed to its corporate failure. iv The findings of the study highlight the following three conclusions: i) profits that are premised on reckless, irregular, and fraudulent business and accounting practices are not sustainable; ii) governance structures that do not adhere to sound corporate governance principles result in impaired board independence and negatively affect firm performance; and iii) companies that reach the pinnacle of their success through unethical conduct are ultimately short-lived. , Thesis (MBA) -- Faculty of Commerce, Rhodes Business School, 2023
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  • Date Issued: 2023-10-13

COVID19 and accountability in South Africa: legislation, ethics and disaster risk management

  • Authors: Chapman, Emma Deidre
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/419565 , vital:71655
  • Description: Embargoed. Possible release in 2026 pending publication. , Thesis (MSC Pharm) -- Faculty of Pharmacy, 2023
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  • Date Issued: 2023-10-13

Current psychological distress and coping strategies reported by university staff in reaction to the COVID-19 pandemic

  • Authors: Sekese, Deneo Nande
  • Date: 2023-10-13
  • Subjects: Clinical health psychology , Salutogenesis , Distress (Psychology) , Adjustment (Psychology) , COVID-19 Pandemic, 2020- Influence , College teachers , Sense of coherence
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/425045 , vital:72204
  • Description: The COVID-19 pandemic and the subsequent disruptions brought about by the implementation of non-pharmaceutical interventions, provide an unfortunate but useful opportunity to explore employee wellness in response to a crisis, within the Higher Education context. COVID-19 lockdowns meant that university students could no longer access conventional learning through physical attendance at lectures. In response, university staff had to contend with a number of changes to their work environment. These included adapting teaching, learning, and assessment methods to an online platform, which led to changes in job roles, expectations, and increased workload for both academic and support staff. The focus of this research was to explore correlations between the current psychological distress that university employees are experiencing and their recalled coping strategies and sense of coherence in response to the COVID-19 pandemic. A mixed-method approach using a survey design was used. Surveys were completed by 171 university academic and support staff using the SA CORE-10 and BRIEF Cope, as well as qualitative questions. Results demonstrated that higher levels of current psychological distress correlated positively with avoidant coping strategies, particularly in academic staff as opposed to support staff, while more adaptive coping strategies tracked with a sense of coherence. , Thesis (MA) -- Faculty of Humanities, Psychology, 2023
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  • Date Issued: 2023-10-13

Design of an LMS-mediated tutorial to support deep and effective engagement in the process of learning mathematics

  • Authors: Kigundu, Stephen
  • Date: 2023-10-13
  • Subjects: Learning Management Systems (LMS) , e-learning , Educational technology , Mathematics Study and teaching (Secondary) , Constructivism (Education) , Mixed methods research
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/431565 , vital:72786 , DOI 10.21504/10962/431565
  • Description: Many institutions of Higher Learning have adopted a variety of Learning Management Systems (LMS) as platforms for e-learning implementation. However, the design and nature of LMS technologies present challenges to the design of LMS-based activities that engage students in learning to do mathematics. There are no clear guidelines or strategies for designing LMS-based activities that engage students in complex mathematical processes. Hence, using technologies in mathematics education often replicates instructivist positions and practices. Conversely, using constructivist principles, modes of mathematical engagement, and e-learning tools to mediate learning provides an integrated framework to transform the use of an LMS as a platform for e-learning implementation and promote deep engagement in mathematical learning. The objective of this study was to explore mechanisms that could be useful for conceiving activities to support the learning of Mathematics using an LMS-mediated tutorial. The design, redesign and evaluation of the e-tutorial are reported upon. In preparation for the study, an LMS-based tutorial was designed and developed to be used as a test-bed to investigate how these e-learning tools could support learning to do mathematics. A Trigonometry module, consisting of course content in the form of resources and tasks to help the students to explore, practice and apply right triangle concepts, was used to investigate and derive design strategies. A mixed method research approach with a reflexive self-study research design was used. A group of first-year university student volunteers studying mathematics in the mechanical engineering department were used to test the tutorial. The students were asked to do a series of tasks using the e-learning environment during the Mathematics tutorial period. Data was collected using in-class observations, interviews, screen capture videos, student-written responses, and system-generated data. All students were encouraged to complete a learning journal detailing their experiences during the tutorial using an LMS-based tool. The students were given no training, but a tutor (researcher) was available to answer any questions they may have had. Contradiction analysis was used to evaluate the data, compare purpose and practice and judge whether the activity or tool was fitted for the intended purpose. Findings were in the form of transformations of the e-tutorial system as it was developed. Among the most noteworthy contributory modifications were changing from 1) “read first, then do” to “do first, read when necessary”, 2) “work on the computer” to “work on paper then capture on the computer”, 3) “physically separated work with computer-enabled social contact”, to "individual computer work in face-to-face social settings.” 4) “single-level of resource provision” to “multi-level, demand-driven resource provision” and 5) “self-regulated” learning process regulation to “computer-assisted” learning process regulation. The discussion of these findings indicated that to enable students’ deep and effective engagement in the process of learning fundamental trigonometry within an LMS-mediated tutorial, one needs to design the system with some activities that can create a demand for knowledge, encourage rough work and face-to-face social interaction, supported by multi-level, demand-driven resources, and computer-assisted learning-process regulation. Contributions to research by this study were in the form of 1) Design Principles for LMS-mediated tutorials, 2) Principles for an e-tutorial development methodology, and 3) The LMS-mediated tutorial system. , Thesis (PhD) -- Faculty of Education, Primary and Early Childhood Education, 2023
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  • Date Issued: 2023-10-13

Devastation and restoration: the use of Namibian dense salt blocks and the Cape Cross Salt Pans as visual metaphors

  • Authors: Greyling, Wil-Merie
  • Date: 2023-10-13
  • Subjects: Sculpture , Destruction , Restoration and conservation , Salt pans in art , Grief in art , Loss (Psychology) in art , Visual metaphor , Salt mines and mining Namibia
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/437203 , vital:73352
  • Description: This mini-thesis explores personal experiences during seasons of loss and grief using physical landscapes, specifically Namibian dense salt mining activities at the Cape Cross Salt Pans, as metaphors for devastation and restoration. Furthermore, the thesis investigates the connection between spiritual and physical landscapes through song and dreams to interpret personal experiences of loss and grief. The thesis explores how believers may find physical places of value outside the constraints of formal religious activities and how these experiences could evoke spiritual landscapes. The qualitative auto-ethnographical approach followed in this study proved an appropriate research methodology, explicitly involving observation and documentation of the physical landscape and reflection on personal experiences, such as dreams. In coming to terms with personal experiences of grief and loss, the individual results of the process were generated using methods such as retrospective reflection and observation. In my findings, I unpack how I found personal meaning from my creative and academic explorations. The metaphoric characteristics of dense salt blocks figuratively express ‘metamorphosis’, ‘weeping’, and ‘growth’. My findings include that one can represent healing and restorative elements with artistic value. The Namibian salt mining industry is typically removed from artistic activities and expression, but I succeeded in forging an atypical relationship with the industry players in an area of the salt block mining industry. In my practice, I explored the character of mined resources, in this case, dense salt blocks, by changing their inherent properties from low-value commercial minerals into unique art objects. In the process, I examined the metaphoric associations that organically mined material, in this case, salt blocks, may hold. Therefore, I link personal creative storytelling to a site with spiritual and sacred values and thus become a place to come to terms with loss and grief. , Thesis (MA) -- Faculty of Humanities, Fine Art, 2023
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  • Date Issued: 2023-10-13

Developing a socio-economic framework for assessing the effectiveness of Expanded Public Works Programmes (EPWP): The case of the Prosopis mesquite Working for Water clearing project in the Northern Cape Province, South Africa

  • Authors: Ntsonge, Sinazo
  • Date: 2023-10-13
  • Subjects: Public works South Africa Northern Cape Evaluation , Mesquite , South Africa. Expanded Public Works Programme , Working for Water Programme , Project management Case studies , Livelihood
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/419219 , vital:71626 , DOI 10.21504/10962/419219
  • Description: The EPWP functions as a bridge between unemployment and entry into the labour market by providing work readiness skills training to its beneficiaries who receive below-market rate stipends for the short- term duration of their participation. The EPWP combines service delivery issues with social development objectives by promoting intensive manual labour in its projects. As a social protection strategy, public works programmes cater to those who do not meet the criteria to receive government social grants. As one of the programmes under the EPWP dealing with the control and eradication of invasive alien plants, the Working for Water (WfW) programme also uses intensive manual labour methods for clearing alien plant species. Although the clearing successes of WfW are well documented, the programme has focused little attention to the longer-term livelihood impacts of the temporary work and skills training provided to beneficiaries. This study suggests this could be due to a lack of the appropriate indicators to measure these outcomes. Therefore, an evaluation framework for environmental public works projects is proposed, which consists of outcome indicators to track the livelihood impact of the work experience and skills training on the beneficiaries post-participation, since the aim of these EPWP interventions is to improve beneficiaries’ labour market outcomes. The Northern Cape province’s Prosopis mesquite clearing project was used as the case study to develop and test the evaluation framework. The outcome indicators were informed by the key stakeholders’ interviews and the beneficiaries’ survey, specifically since the beneficiaries were well placed to give feedback on the benefits of the work experience and training post-participation. The combined strengths of the Sustainable Livelihoods Approach and the Capability Approach were useful for formulating the outcomes indicators, while the indicators for the inputs, activities and outputs were formulated from the key stakeholder interviews and online EPWP reports. A mixed methods approach was used and primary data were collected through key stakeholder interviews with the Prosopis mesquite clearing project managers and an online survey with some of the beneficiaries. Online EPWP reports and records obtained from WfW were used as secondary data. Data analysis used RStudio, Microsoft Excel and GraphPad Prism. The data analysis and evaluation framework indicators constituted the results section and aimed to highlight the factors that managers should focus on to achieve the desired livelihood outcomes. The proposed outcome indicators can be used to gauge the effectiveness of environmental public works’ social development interventions. The results revealed that the project budget fluctuations resulted in the Working for Water managers adopting a myopic view in administering the workdays and skills training, which diminished the livelihood impact of the Prosopis mesquite clearing project to merely a ‘make work’ project with no observable longer-term livelihood benefits. The selection input indicators and their utilisation during project activities needs to be better aligned with the desired longer-term livelihood outcomes that these environmental public works projects seek to achieve, mainly that of preparing beneficiaries for jobs in the labour market. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2023
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  • Date Issued: 2023-10-13

Developing and exploring a career education programme for disadvantaged FET-phase learners in the northern areas of Gqeberha: a developmental-contextual approach

  • Authors: Human, Antoinette Charlotte Lucy
  • Date: 2023-10-13
  • Subjects: Vocational education South Africa Gqeberha , Disadvantaged students , Life skills Study and teaching (Secondary) South Africa , Curriculum change South Africa , Context effects (Psychology)
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/432333 , vital:72862 , DOI 10.21504/10962/432333
  • Description: Career development theory and assessments in South Africa have often been unscientifically applied to traditionally disadvantaged individuals, with little consideration of the diverse contexts of indigenous groups in the country. Assessment measures were not suited to the needs of learners from resource-constrained environments, nor could learners from these communities access these due to the associated financial costs. Recent research developments (using more holistic approaches) suggest that career counselling in South Africa should move towards better contextualized approaches to understanding and informing career development. Follow-up research projects show the value of such approaches with youth. Postmodern career development theories and models recognise that career counselling and development should focus on supporting individuals in constructing their careers from their own experiences within their environments, particularly for learners from disadvantaged communities whose career decisions and career development are inextricably influenced by their environments. The present study therefore employed the Developmental-Contextual Framework (DCF) to explore the perspectives of FET-phase Life Orientation (LO) educators on the LO curriculum (LO CAPS) for careers and career choices; as well as contextual factors influencing the career development of disadvantaged learners in public schools. The overall aim of the study was to co-construct and explore a customised career education programme, alongside LO educators, and determine whether FET-phase learners from disadvantaged public schools could benefit from such a programme. The DCF emphasises the dynamic relationship between an individual and the environment and the influences thereof on career development. The study draws from previous South African studies with disadvantaged learners and students that acknowledged the applicability of the DCF in the design of career programmes. This framework acknowledges the embeddedness of the individual in their proximal and distal environments and the role of these environments in the career decisionmaking of learners. The study was conducted in disadvantaged secondary schools in the Northern Areas of Gqeberha in the Eastern Cape, with LO educators in the FET-phase and the LO subject advisor at District level. At the initial interview stage the sample consisted of 9 participants and reduced to 6 participants in the focus group stage. The study underlined the impact of various contextual factors on career decision-making and the inclusion of these in career education programmes, particularly when working with learners from disadvantaged environments. Furthermore, the study illustrated that the career education of FET-phase learners in public high schools is lacking in many ways and that LO educators are not adequately trained to teach careers topics and therefore lack skills to support learners with their career development needs. The lack of, as well as poor and outdated career resources, impact negatively on the career education of learners in many public schools. Underpinned by Action Research, over a series of seven focus group meetings, an applicable and relevant programme of career-related activities based on the DCF was planned and evaluated by educators. The cumulative data were thematically analysed and the study revealed that the customised programme could potentially address the career development needs of learners from disadvantaged public schools, if educators are adequately trained to apply it. Recommendations are made for further piloting and implementation. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
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  • Date Issued: 2023-10-13

Development of an evidence-based framework for the prevention and management of musculoskeletal disorders in South Africa

  • Authors: De Bruyn, Elrico
  • Date: 2023-10-13
  • Subjects: Musculoskeletal system Wounds and injuries South Africa , Musculoskeletal system Wounds and injuries Treatment , Human engineering Handbooks, manuals, etc. , Musculoskeletal system Wounds and injuries Prevention , Industrial engineering South Africa , Work environment South Africa
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424232 , vital:72135
  • Description: Background: Musculoskeletal Disorders (MSDs) are multi-causal soft tissue disorders that result in disability, discomfort, and pain. MSDs are prevalent in 21.5% of the world’s population and carry a great financial and personal burden to individuals, businesses and countries alike. The multi-casual nature of MSDs has resulted in a vast amount of literature being published on how to prevent and manage the disorders, to the extent that navigating through the literature to find effective and context-specific interventions has become time-consuming and difficult. This is the case in South Africa, where ergonomists have no guide or framework to navigate MSD literature, and context-specific literature is limited. Aims: This study aimed to assist ergonomists in South Africa navigate the MSD literature to identify and select appropriate MSD prevention and management interventions. To do so, three objectives of the study were identified: 1. Review MSD literature to identify effective MSD prevention and management interventions. 2. Create a framework to act as a guide for ergonomists to navigate MSD prevention and management studies. 3. To verify the suitability of the framework in the South African context. To achieve these objectives, the study took a two-phased approach. Phase 1: A scoping review of MSD literature was conducted to identify effective MSD prevention and management approaches. Sixteen (n=16) prevention strategies and fourteen (n=14) management strategies were identified. The information from the review was analysed and grouped into five hierarchical levels of interventions (“Law”, “Organisational Policies”, “Management Systems”, Workplace Interventions”, and “Individual”). This information, along with a conceptual model created for the navigation of the literature, was used to create a draft framework for musculoskeletal disorder prevention and management. It was concluded that although there were many effective MSD interventions, there was a lack of South African-specific literature. Phase 2: Interviews with five certified ergonomists working in the South African context were conducted to verify the framework’s suitability for a South African working environment. The interviews identified two MSD prevention and three MSD management themes as effective in South Africa. Both prevention themes (“training and education” and “workplace interventions”) were also mentioned to be part of the stakeholders’ ideal MSD prevention programme, further reinforcing their usefulness. The use of “workplace interventions” was also identified to be effective in MSD management, alongside interventions at the management level and the use of alternative tools and equipment. However, the lack of managerial buy-in was identified as a barrier to MSD prevention. Stakeholders also highlighted that job specification and work hardening was an MSD strategy missing from the framework that was effective in South Africa's MSD management. The use of surveillance practices was found to be ineffective in South Africa, with lots of resistance towards it from workers. Conclusion: The framework presented in Phase 1 identified many effective MSD interventions; however, only a few were found to be applicable to the South African working context during Phase 2. Future research should focus on identifying the success of different MSD interventions in South Africa with participation from the ergonomists involved in the implementation to create an even more suitable guide that matches the South African ergonomist’s needs. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
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  • Date Issued: 2023-10-13

Disaster risk management issues in WASH in South Africa: an examination of selected challenges and development of possible solutions

  • Authors: Madikizela, Phindile
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/431520 , vital:72782
  • Description: Access restricted. Expected release date 2025. , Thesis (PhD) -- Faculty of Pharmacy, Pharmacy, 2023
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  • Date Issued: 2023-10-13

Discovery and classification of compact radio sources in the MeerKAT Galactic Centre data

  • Authors: Rammala, Isabella Dineo
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/432218 , vital:72852
  • Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2023
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  • Date Issued: 2023-10-13

Distribution and habitat preferences of marine megafauna in Nosy Be, Madagascar

  • Authors: Lubbé, Alicea
  • Date: 2023-10-13
  • Subjects: Marine animals Habitat Madagascar Nosy Be , Marine animals Geographical distribution Madagascar Nosy Be , Species distribution modelling , Maximum entropy method , Citizen science , Habitat preference
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424710 , vital:72177
  • Description: Marine megafauna have important ecological roles including the top-down regulation of lower trophic levels and the transport of nutrients. They are also charismatic species of socioeconomic importance, due to their public appeal and focus for ecotourism. However, these taxa face numerous anthropogenic threats including bycatch, habitat-loss, noise disturbance, prey reductions, pollution, and vessel traffic. Northwest Madagascar has been identified as an important marine mammal area and whale shark aggregation site, yet limited information on megafauna within Madagascar exists. In this thesis, I investigated the community structure, distribution trends, related environmental factors (Chapter 2) and predicted habitat suitability (Chapter 3) using a species distribution modelling approach for marine megafauna around Nosy Be, North-west Madagascar. Data collection consisted of opportunistic boatbased surveys conducted while looking for whale sharks, mobulid rays and cetaceans. These activities were performed by dedicated ‘swim with whale shark’ tourism operators, Les Baleines Rand'eau and Safari Baleine during tourism activities directed by the Madagascar Whale Shark Project over four years (2016-2019). A total of 1792 sightings were reported with 13 identified species, including elasmobranchs: whale shark, Rhincodon typus; spinetail mobula ray, Mobula japonica; giant oceanic manta ray, Manta birostris; shortfin devil ray, Mobula kuhlii; balaenids: humpback whale, Megaptera novaeangliae; Omura's whale, Balaenoptera omurai, delphinids: Indo-Pacific bottlenose dolphin, Tursiops aduncus; spinner dolphin, Stenella longirostris; pantropical spotted dolphin, Stenella attenuata; Indian ocean humpback dolphin, Sousa plumbea; false killer whale, Pseudorca crassidens; melonheaded whale, Peponocephala electra and one cheloniid species: leatherback sea turtle, Dermochelys coriacea. Sightings were spatially analysed at a community level according to feeding guilds (i.e., filter feeders vs. predators), and distribution of the megafauna groups v were compared to selected remotely sensed physico-chemical data (sea surface temperature and chlorophyll-a concentration) and bathymetry charts (depth and slope) using generalized linear models (Chapter 2). All four variables had a significant effect on filter feeder distribution. Spatial distribution of filter feeder sightings peaked at an area of steep underwater topography (18-50m; x slope=0.5%) located on the west coast of Nosy Be, where foraging aggregations of large filter feeders (primarily R. typus and B. omurai) were frequently observed. Only SST had a significant effect on the relative abundance of animals in the predator feeding guild, which demonstrated a more longitudinal distribution along the continental shelf. The maximum entropy model (Maxent) was used for predicting habitat preference for the most frequently sighted species (Chapter 3). The distribution of whale sharks, mobulid rays and Omura’s whales were significantly overlapped as they were abundant in two main hotspots, Grand banc de l’entrée (~10 km of the west coast) and near Nosy Mitsio island, (~50 km northeast of Nosy Be). Suitable habitat for the dolphins was in relatively shallow waters in temperatures <28ºC near areas of steep changes in bathymetry. Bottlenose and spinner dolphins had a more widespread distribution across the continental shelf and humpback dolphin was closely associated with inshore reefs and occur in waters <10m. The coastal and inshore region of Nosy Be is an important habitat for a variety of megafaunal species, and the continental shelf provided essential areas for feeding and breeding. The results were similar to those presented for these species in other regions of the Indian Ocean (i.e., Eastern and Southern Africa; Western Australia; Seychelles) as well as outside of the Indian Ocean (i.e., Indonesia; Caribbean; North Atlantic). Thus the results from this thesis could be considered for management recommendations for marine conservation in the region. The value and limitations of data collected by citizen science were outlined (Chapter 4). , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
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  • Date Issued: 2023-10-13

Drought impacts on livestock and crop production along an urban-rural gradient: perceptions and response strategies in the Eastern Cape province, South Africa

  • Authors: Pamla, Avela
  • Date: 2023-10-13
  • Subjects: Livestock Effect of drought on South Africa Eastern Cape , Farms, Small South Africa Eastern Cape , Crops and climate South Africa Eastern Cape , Drought management South Africa Eastern Cape
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424732 , vital:72179
  • Description: Drought is a major challenge threatening agricultural productivity in urban and rural areas across southern Africa. Drought events are expected to be more frequent, severe, last longer, and, impact land-based livelihoods in the coming decades. Despite the growing literature on the impacts of drought on livelihoods, there is limited focus on the impacts of droughts across rural-urban gradients. The study examined small-scale farmers’ perceptions of drought impacts and response strategies in the contexts of persistent droughts in the Eastern Cape province of South Africa. A total of 163 respondents, practicing livestock and/or crop farming across six towns, in urban and rural contexts were purposively identified. The study used snowball sampling approach to identify the relevant respondents. Data were collected through a semi-structured questionnaire survey, exploring the respondents' socio-demographic profiles, agricultural activities, perceptions of drought impacts, and drought response strategies. Qualitative data were coded and analyzed using descriptive statistics, thematic analysis, t-tests, and chi-square tests to identify patterns, themes, and relationships within the data. Nearly all (>95%) respondents owned livestock while substantially more rural farmers (81%) than urban farmers (35%) engaged in crop production. Drought was perceived by a sizeable proportion (>70%) of small-scale farmers as a very serious environmental challenge with adverse socio-economic repercussions on land-based activities. Livestock losses and crop failure were the key impacts reported by small-scale farmers in both rural and urban settings. About 86% of respondents across the sample reported declines in crop yields, with significantly more farmers in rural sites (45%) than urban sites (31%) reporting so. A substantial proportion of farmers across the sample (93%) reported drought response strategies relating to livestock and crop production, such as changing of farming practices, use of drought-resistant crops and government support, with slight differences in the proportion of farmers reporting so between urban (89 %) and rural (95 %) sites. Concerning government support, most respondents (>70%) stated that they were dissatisfied, with slightly more respondents in urban areas (77%) than in rural (70%) areas reporting so. Overall, the results of this study suggest a minimal response capacity of small-scale farmers to droughts in both rural and urban settings due to socio-economic and administrative factors, which calls for the need for drought-response strategies to build adaptive capacity for small-scale farmers. Turning to close cooperation between different stakeholders, such as local farmers, government officials, practitioners, and scientists might allow co-production of knowledge needed to inform drought response strategies. In some instances, attention needs to be given to farmers who are more vulnerable than others. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2023
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  • Date Issued: 2023-10-13

Empty adjectives and excessive intensifiers, or savvy discourse moves? A feminist critical discourse study of gender-based differences in the discourse of businesspeople on LinkedIn

  • Authors: Schmauss, Lindsay Susannah
  • Date: 2023-10-13
  • Subjects: Corpora (Linguistics) , Critical discourse analysis , Intensification (Linguistics) , Women's language , Adjective , Politeness (Linguistics)
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/425111 , vital:72211
  • Description: This Feminist Critical Discourse Analysis (FCDA) examines the use of ‘empty’ adjectives and the equative intensifier so in discourse on LinkedIn, a social network service (SNS) for businesspeople and professionals. These linguistic features soften the impact of what is said in ways that can conform with politeness norms that one should not impose a point of view but can also be negatively construed as weak, uncertain and unclear. The North American sociolinguist, Robin Tolmach Lakoff (1973, 1975, 2004), first associated these linguistic markers with a feminine register in her seminal work, Language and Women’s Place, arguing that there is a social expectation that women talk like a lady and follow politeness conventions, while the speech of men is not similarly constrained. That women are socially conditioned to speak in ways that can undermine their clarity and assertiveness would present a particular dilemma in the business context, where clear, direct and confident communication is valued. This corpus-based study explores the dilemma in the context of LinkedIn where the linguistic behaviour of cisgender women indeed showed evidence of their struggle between conflicting impulses to talk like a lady and a desire to be taken seriously as businesspeople. While the examined features mainly appeared in the discourse of women, it was interesting to note men making use of ‘empty’ adjectives and so in communication contexts where the goal appeared to be relationship-building. As notions of business leadership are evolving to value organisational leadership more, this suggests that linguistic devices that have traditionally been associated more with the communal conversation of the stereotypical ‘woman’ appear to be gaining wider acceptance and relevance, although in domains orientated towards the “soft skill” of building relationships, rather than the “hard work” of business. While the value talking like a lady may be shifting, language that is the opposite of talking like a lady seems to remain the language of serious talk, and the kind of gender-based linguistic discrimination first theorised by Lakoff seems thus to persist, also in the sphere of business discourse. , Thesis (MA) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
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  • Date Issued: 2023-10-13

Enhancement of the electrocatalytic activity of phthalocyanines through the reduction in symmetry and conjugation to detonation nanodiamonds

  • Authors: Ncwane, Lunathi
  • Date: 2023-10-13
  • Subjects: Phthalocyanines , Electrocatalysis , Nanodiamonds , Hydrazine
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424541 , vital:72162
  • Description: This thesis reports on the synthesis of novel phthalocynines tetrakis[(benzo[d]thiazol-2ylthio)phthalocyaninato]cobalt(II)chloride (complex 1) and tris(2-(ethylthio)benzo[d]thiazole)2-(phthalocyanine-9-ylthio)propionate cobalt(II) chloride (complex 2). The complexes are combined with DNDs via different techniques such as π-π stacking, covalent linkage and sequential modification on glassy carbon electrode. The synthesized MPcs and conjugates were characterized using UV-visible, mass, Fourier transform infrared, and Raman spectroscopies as well as transmission electron microscopy and dynamic light scattering. Combining MPcs with DNDs sought to improve electrooxidation of hydrazine. The electrochemical studies were conducted using cyclic voltammetry, chronocoloumetry, electrochemical impedance spectroscopy and chronoamperometry. Hydrazine was utilized as an analyte of interest, due to its mutagenic and carcinogenic effects. Glassy carbon electrodes (GCE) were modified using drop and dry method. The conjugation via covalent linkage proved to be the best way of enhancing electrocatalytic properties. Since it performed better in terms of limit of detection (0.33 μM), even though catalytic rate and sensitivity are not the highest. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-10-13

Enhancing the electrocatalytic activity of phthalocyanines through finding the ideal combination of substituents in push-pull phthalocyanine-based systems

  • Authors: Nkhahle, Reitumetse Precious
  • Date: 2023-10-13
  • Subjects: Phthalocyanines , Electrocatalysis , Hydrazine , Nitrites , Activating group , Deactivating group
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/432578 , vital:72882 , DOI 10.21504/10962/432578
  • Description: Phthalocyanines (Pcs) are a class of synthetic pigments with a similar structure to porphyrins. The work presented in this thesis is centred around these electron-rich macrocycles and their use in electrocatalysis. This body of work provides a more rigorous analysis on asymmetric Pcs, focusing on finding the “ideal” combination of substituents in the synthesis of A3B-type Pcs and how these asymmetric structures compare with their symmetric counterparts (A4) in the electrocatalysis of hydrazine and nitrite. The choice in substituents in the syntheses of the Pcs was such that there is both electron-donating and electron-withdrawing groups to induce a push-pull effect. In the studies involving the electrocatalysis of hydrazine, asymmetric cobalt Pcs (CoPcs) possessing alkyl groups as the primary substituents, with variations in the acid-containing group, along with their symmetric counterparts, probes with potential for further improvement were identified. Using voltammetric and amperometric techniques, the analyte-electrode kinetics, mechanism in which the electrochemical reaction proceeds along with the limits of detection (LoD) were determined. In the general sense, the pentadecylphenoxy-derived CoPcs performed better than those containing the tert-butyl substituent as the dominant substituent with the asymmetric CoPcs producing more favourable results than their symmetric analogues. With respect to the probes designed for nitrite, a multi-dimensional approach was undertaken in that acetaminophen was chosen as the primary substituent whilst multiple changes in the asymmetric component were made. In addition to varying the carboxylic acid-containing substituent, alkyne- and amine-based substituents were also explored in which the alkyne-containing Pc was anchored onto the electrode surface through click chemistry while the amine-bearing Pc was covalently linked (and π-stacked) to nitrogen-doped graphene quantum dots (NGQDs). Another component that was altered was the central metal where CoPcs were compared to manganese Pcs (MnPcs). The most desirable peak oxidation potential for nitrite was observed in the MnPcs as it was the lowest with adsorption sometimes being a better suited method of electrode modification relative to clicking. The inclusion of NGQDs was found to be beneficial when combined with the symmetric CoPc whilst in the presence of an asymmetric Pc complex, less desirable results were observed. Overall, there were variations in the results with the symmetric CoPc sometimes being better than some of the asymmetric CoPcs demonstrating that a blanket-approach in terms of synthesizing and applying asymmetric Pcs is not always viable. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-10-13

Enteric microbial responses to host hyperthermia in southern African insectivorous bats: a test of thermal co-adaptation

  • Authors: Hunter, Amy Alison
  • Date: 2023-10-13
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424391 , vital:72149
  • Description: Embargoed. Expected release date 2025. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
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  • Date Issued: 2023-10-13
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