Ground- and marine water inputs into supratidal microbialite systems along the Nelson Mandela Bay coastline
- Authors: O’Connell, Tristin Wade
- Date: 2024-12
- Subjects: Groundwater -- South Africa -- Nelson Mandela Bay , Earth sciences , Geology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69415 , vital:77253
- Description: Extant supratidal microbialite systems are especially numerous and well-developed along the rocky coastline of Nelson Mandela Bay (NMB), South Africa. Precipitating in a hydrological environment formed by the input of constant, fresh groundwater discharge and periodic marine water intrusion these systems form part of the longest uninterrupted geological record of life on Earth (~3.4 billion years ago). Microbialites are layered organosedimentary deposits which potentially provide a window into historical environmental conditions. This study focusses on the fresh groundwater and saline marine water inputs of these microbialite pools, and the corresponding microbialite accretion rates. Severe regional drought in the NMB area resulted in rapid anthropogenic groundwater abstraction of the coastal aquifers on which the microbialite systems rely for groundwater inflow. This study provides insight into the current state of the coastal aquifers of NMB through the quantification of groundwater discharge via microbialite systems in terms of volume and flow rate. This is paired with in situ hourly microbialite pool water temperature and conductivity data to determine the effect of marine intrusion and the role of tidal flushing in these pools. A spatial assessment of groundwater discharge conducted using quantitative and semi-quantitative measurement techniques indicated that the total discharge of the study area is ~45.8 L/s or 3.8 ML/d. Over 1,500 freshwater seeps were identified, of which 78% showed microbialite deposits. Topography of the coast indicated that this might influence the flowrate. Calcareous sediment of sandy beaches within the study area supported lower discharge, while rocky shores with lithified rock had higher discharge. Seasonal differences in the volume discharged were evident, with winter having higher flowrates. Flow paths and discharge rates are affected by inland lithological differences and indicate variability linked to rainfall events that show lag effects depending on aquifer origins. This study is the first spatial analysis of the volume of groundwater discharging through microbialite-fed seeps. Marine intrusion and the corresponding pool flushing dynamics identified three types of microbailite systems: groundwater-dominant, dynamic input, and fast-reacting sites. A novel measurement technique for microbialite accretion determined accretion rates for systems under varying pool conditions. Although the average accretion rates of the Nelson Mandela Bay microbialites were in the order of erosion of 0.35 mm per year, there was significant variability in these measurements likely linked to differential localised vulnerability to storm events or responses to groundwater ix flow variability. It remains to be determined whether these factors are definitive risks to the sensitive supratidal microbialite systems. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: O’Connell, Tristin Wade
- Date: 2024-12
- Subjects: Groundwater -- South Africa -- Nelson Mandela Bay , Earth sciences , Geology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69415 , vital:77253
- Description: Extant supratidal microbialite systems are especially numerous and well-developed along the rocky coastline of Nelson Mandela Bay (NMB), South Africa. Precipitating in a hydrological environment formed by the input of constant, fresh groundwater discharge and periodic marine water intrusion these systems form part of the longest uninterrupted geological record of life on Earth (~3.4 billion years ago). Microbialites are layered organosedimentary deposits which potentially provide a window into historical environmental conditions. This study focusses on the fresh groundwater and saline marine water inputs of these microbialite pools, and the corresponding microbialite accretion rates. Severe regional drought in the NMB area resulted in rapid anthropogenic groundwater abstraction of the coastal aquifers on which the microbialite systems rely for groundwater inflow. This study provides insight into the current state of the coastal aquifers of NMB through the quantification of groundwater discharge via microbialite systems in terms of volume and flow rate. This is paired with in situ hourly microbialite pool water temperature and conductivity data to determine the effect of marine intrusion and the role of tidal flushing in these pools. A spatial assessment of groundwater discharge conducted using quantitative and semi-quantitative measurement techniques indicated that the total discharge of the study area is ~45.8 L/s or 3.8 ML/d. Over 1,500 freshwater seeps were identified, of which 78% showed microbialite deposits. Topography of the coast indicated that this might influence the flowrate. Calcareous sediment of sandy beaches within the study area supported lower discharge, while rocky shores with lithified rock had higher discharge. Seasonal differences in the volume discharged were evident, with winter having higher flowrates. Flow paths and discharge rates are affected by inland lithological differences and indicate variability linked to rainfall events that show lag effects depending on aquifer origins. This study is the first spatial analysis of the volume of groundwater discharging through microbialite-fed seeps. Marine intrusion and the corresponding pool flushing dynamics identified three types of microbailite systems: groundwater-dominant, dynamic input, and fast-reacting sites. A novel measurement technique for microbialite accretion determined accretion rates for systems under varying pool conditions. Although the average accretion rates of the Nelson Mandela Bay microbialites were in the order of erosion of 0.35 mm per year, there was significant variability in these measurements likely linked to differential localised vulnerability to storm events or responses to groundwater ix flow variability. It remains to be determined whether these factors are definitive risks to the sensitive supratidal microbialite systems. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Gymnopilus junonius and Rhodofomitopsis lilacinogilva: In vitro evaluation of antimycobacterial activity, safety assessment and isolation of active compounds
- Authors: Didloff, Jenske
- Date: 2024-12
- Subjects: Antibacterial agents , Plants, Useful -- South Africa , Medicinal plants -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68840 , vital:77122
- Description: Tuberculosis remains a significant public health challenge due to the complexity and compliance issues of its treatment, the prevalence of latent infections, the high rate of HIV co-infection, and the spread of drug-resistant strains. This highlights the need to search for new antimycobacterial drugs. Natural products have historically been used as sources for the discovery of pharmaceuticals. Although medicinal macrofungi have been exploited in traditional folk medicines for the treatment of various diseases, research into their antimycobacterial activity remains limited.The aim of this study was to isolate, identify, and characterise the antimycobacterial compound(s) present in ethanol fruiting body extracts of Gymnopilus junonius (Fr.) P.D. Orton (Hymenogastraceae) and Rhodofomitopsis lilacinogilva (Berk.) B.K. Cui, M.L. Han, & Y.C. Dai (Fomitopsidaceae), as well as to investigate their mechanism of action and potential toxicity using in vitro and in vivo screening methods.Bioassay-guided fractionation was conducted using column chromatography and preparative thin-layer chromatography to isolate the active antimycobacterial fraction/compound from ethanol extracts of G. junonius and R. lilacinogilva. Antimycobacterial activity against M. tuberculosis H37Rv was screened using a resazurin microplate assay (REMA). The chemical structure was elucidated employing 1D-(1H NMR) and 2D NMR spectroscopy (HSQC, HMBC) techniques, along with High- Performance Liquid Chromatography High-Resolution Electron Spray Ionisation Mass Spectrometry (HPLC-HRESI-MS). Transmission electron microscopy (TEM) was utilised to observe the ultrastructural changes in M. tuberculosis induced by the active fraction/compound. Toxicity assessment was performed on African green monkeykidney (Vero) and human hepatoma (C3A) cell lines using various staining techniques to observe the potential risk for hepatotoxicity (CellRox orange, TMRE, and MTG staining) and genotoxicity (NucRed staining). In vivo toxicity of extracts was evaluated using a zebrafish embryo/larvae model to observe developmental and teratogenic effects.The bioassay-guided fractionation of G. junonius and R. lilacinogilva extracts yielded an active compound and a fraction displaying inhibitory activity against M. tuberculosis, with MIC values of 31.25 μg/mL and 250 μg/mL, respectively. Gymnopilene was identified as the main active compound isolated from G. junonius, while fraction 8 from R. lilacinogilva contained a predominant constituent resembling a pachymic acid derivative. Transmission electron microscopy revealed ultrastructural damage to M. tuberculosis cells upon treatment with gymnopilene and fraction 8, which was observed as the disruption and disintegration of the cell wall. In vitro toxicity assessment indicated a reduction in the cell density in both Vero and C3A cell lines following exposure to the fractions/gymnopilene. Although there were no significant alterations in the production of reactive oxygen species, changes in mitochondrial dynamics were observed. Genotoxic assessment showed no significant changes. In vivo toxicity assessment showed no significant effects for G. junonius against the zebrafish embryos/larvae, whereas R. lilacinogilva remained toxic and induced developmental abnormalities over a 72-hour time period.The findings of this study highlight the potential of macrofungi as a valuable source of bioactive compounds, confirming the significance of natural products in drug discovery. Notably, this research represents the first to demonstrate that the predominant compound, gymnopilene, isolated from G. junonius exhibits inhibitory activity against M. tuberculosis, contributing to the novelty of the study. Furthermore, the study expands our understanding of the antimycobacterial properties of the selected macrofungal species, G. junonius and R. lilacinogilva, by demonstrating the ultrastructural damage to M. tuberculosis cell wall induced by treatment. However, it is important to recognise the potential toxicity identified through in vitro and/or in vivo screening assays. The observed toxicity may hamper their suitability formdrug development. Future investigations could explore the inclusion of additional in vitro based models, perhaps more complex and physiologically relevant models alongside the in vivo screening model to assess the therapeutic potential of isolated fractions/compounds. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Didloff, Jenske
- Date: 2024-12
- Subjects: Antibacterial agents , Plants, Useful -- South Africa , Medicinal plants -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68840 , vital:77122
- Description: Tuberculosis remains a significant public health challenge due to the complexity and compliance issues of its treatment, the prevalence of latent infections, the high rate of HIV co-infection, and the spread of drug-resistant strains. This highlights the need to search for new antimycobacterial drugs. Natural products have historically been used as sources for the discovery of pharmaceuticals. Although medicinal macrofungi have been exploited in traditional folk medicines for the treatment of various diseases, research into their antimycobacterial activity remains limited.The aim of this study was to isolate, identify, and characterise the antimycobacterial compound(s) present in ethanol fruiting body extracts of Gymnopilus junonius (Fr.) P.D. Orton (Hymenogastraceae) and Rhodofomitopsis lilacinogilva (Berk.) B.K. Cui, M.L. Han, & Y.C. Dai (Fomitopsidaceae), as well as to investigate their mechanism of action and potential toxicity using in vitro and in vivo screening methods.Bioassay-guided fractionation was conducted using column chromatography and preparative thin-layer chromatography to isolate the active antimycobacterial fraction/compound from ethanol extracts of G. junonius and R. lilacinogilva. Antimycobacterial activity against M. tuberculosis H37Rv was screened using a resazurin microplate assay (REMA). The chemical structure was elucidated employing 1D-(1H NMR) and 2D NMR spectroscopy (HSQC, HMBC) techniques, along with High- Performance Liquid Chromatography High-Resolution Electron Spray Ionisation Mass Spectrometry (HPLC-HRESI-MS). Transmission electron microscopy (TEM) was utilised to observe the ultrastructural changes in M. tuberculosis induced by the active fraction/compound. Toxicity assessment was performed on African green monkeykidney (Vero) and human hepatoma (C3A) cell lines using various staining techniques to observe the potential risk for hepatotoxicity (CellRox orange, TMRE, and MTG staining) and genotoxicity (NucRed staining). In vivo toxicity of extracts was evaluated using a zebrafish embryo/larvae model to observe developmental and teratogenic effects.The bioassay-guided fractionation of G. junonius and R. lilacinogilva extracts yielded an active compound and a fraction displaying inhibitory activity against M. tuberculosis, with MIC values of 31.25 μg/mL and 250 μg/mL, respectively. Gymnopilene was identified as the main active compound isolated from G. junonius, while fraction 8 from R. lilacinogilva contained a predominant constituent resembling a pachymic acid derivative. Transmission electron microscopy revealed ultrastructural damage to M. tuberculosis cells upon treatment with gymnopilene and fraction 8, which was observed as the disruption and disintegration of the cell wall. In vitro toxicity assessment indicated a reduction in the cell density in both Vero and C3A cell lines following exposure to the fractions/gymnopilene. Although there were no significant alterations in the production of reactive oxygen species, changes in mitochondrial dynamics were observed. Genotoxic assessment showed no significant changes. In vivo toxicity assessment showed no significant effects for G. junonius against the zebrafish embryos/larvae, whereas R. lilacinogilva remained toxic and induced developmental abnormalities over a 72-hour time period.The findings of this study highlight the potential of macrofungi as a valuable source of bioactive compounds, confirming the significance of natural products in drug discovery. Notably, this research represents the first to demonstrate that the predominant compound, gymnopilene, isolated from G. junonius exhibits inhibitory activity against M. tuberculosis, contributing to the novelty of the study. Furthermore, the study expands our understanding of the antimycobacterial properties of the selected macrofungal species, G. junonius and R. lilacinogilva, by demonstrating the ultrastructural damage to M. tuberculosis cell wall induced by treatment. However, it is important to recognise the potential toxicity identified through in vitro and/or in vivo screening assays. The observed toxicity may hamper their suitability formdrug development. Future investigations could explore the inclusion of additional in vitro based models, perhaps more complex and physiologically relevant models alongside the in vivo screening model to assess the therapeutic potential of isolated fractions/compounds. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Investigating the implementation of teaching strategies used by foundation phase teachers in multilingual classrooms
- Authors: Green, Marizanne
- Date: 2024-12
- Subjects: Multiculturalism -- Study and teaching , Language and languages -- Study and teaching , Education, Bilingual -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68322 , vital:76974
- Description: In South Africa, there are eleven official languages: English and Afrikaans and nine indigenous languages. However, the dominant language of learning and teaching in multilingual classrooms is English. Teachers are not all equipped to cater for a multilingual classroom that is conducive to learning. Hence, it is important that teaching strategies teachers used need to support learners’ access to knowledge and their language proficiency through the learning process. This qualitative case study aimed at investigating the teaching strategies used by Foundation Phase teachers in multilingual classrooms. The study was guided by an interpretivist paradigm which was helpful in providing in-depth knowledge on multilingual Foundation Phase classrooms and the teaching strategies that teachers implement. The study used a purposive sampling strategy with 4 Foundation phase teachers teaching Grades R-4. Drawing upon classroom observations and semi-structured individual interviews as the primary methods of data collection, the study explored the teaching strategies teachers use in multilingual foundation phase classrooms. A thematic data analysis was employed. Findings revealed a need for inclusive practices in FP multilingual classrooms, need to support learning using various teaching strategies, need to recognize realities in multilingual classrooms and a role that stakeholders can play in learning. Recommendations are provided for SGB’s, Curriculum designers, FP teachers and parents. , Thesis (MEd) -- Faculty of Education, School of Primary School Education, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Green, Marizanne
- Date: 2024-12
- Subjects: Multiculturalism -- Study and teaching , Language and languages -- Study and teaching , Education, Bilingual -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68322 , vital:76974
- Description: In South Africa, there are eleven official languages: English and Afrikaans and nine indigenous languages. However, the dominant language of learning and teaching in multilingual classrooms is English. Teachers are not all equipped to cater for a multilingual classroom that is conducive to learning. Hence, it is important that teaching strategies teachers used need to support learners’ access to knowledge and their language proficiency through the learning process. This qualitative case study aimed at investigating the teaching strategies used by Foundation Phase teachers in multilingual classrooms. The study was guided by an interpretivist paradigm which was helpful in providing in-depth knowledge on multilingual Foundation Phase classrooms and the teaching strategies that teachers implement. The study used a purposive sampling strategy with 4 Foundation phase teachers teaching Grades R-4. Drawing upon classroom observations and semi-structured individual interviews as the primary methods of data collection, the study explored the teaching strategies teachers use in multilingual foundation phase classrooms. A thematic data analysis was employed. Findings revealed a need for inclusive practices in FP multilingual classrooms, need to support learning using various teaching strategies, need to recognize realities in multilingual classrooms and a role that stakeholders can play in learning. Recommendations are provided for SGB’s, Curriculum designers, FP teachers and parents. , Thesis (MEd) -- Faculty of Education, School of Primary School Education, 2024
- Full Text:
- Date Issued: 2024-12
Investigation of potential in-situ polymerization reactions for use in lithium-ion batteries
- Authors: Dube, Tafara
- Date: 2024-12
- Subjects: Lithium ion batteries , Lithium cells , Electrochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68851 , vital:77127
- Description: With the rise in popularity of electric vehicles and portable electronic devices, having a reliable, lightweight, and long-lasting battery is crucial. This has led to the mass commercialisation of lithium-ion batteries (LIB’s) because they offer several advantages over other battery technologies. Over the years, one of the concerns was with the ease with which the batteries can burn or explode when subjected to certain extreme conditions. In order to build trust in these products and to expand the technology into more diverse applications, safety aspects of the batteries has become of widespread concern resulting in a key area of research. One aspect of improving the safety is by reducing the flammability of the battery by the addition of certain chemicals that stop or suppress the thermal runaway effect. However, this in-turn reduces the battery’s capacity and life-cycle performance. Researchers have used the idea of encapsulating these chemicals thereby physically separating them within the lithium-ion battery (LIB) electrolyte system with a minimum effect on performance. This research aims to explore use of R-diols and R-amines as additives that upon a thermal trigger would react with the lithium-ion battery electrolyte to stop the effect of the thermal runaway by forming carbamate derivatives which are gel-like or form solid aggregates. The R-diols or R-amines can react with electrolyte at higher temperatures with the lithium-hexafluorophosphate acting as a catalyst. This change in the physical state of the electrolyte increases the resistance inside the battery which then hinders ion movement and forms a physical barrier to reduce the effect of short circuiting when the separator or other components are damaged due to higher temperatures. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Dube, Tafara
- Date: 2024-12
- Subjects: Lithium ion batteries , Lithium cells , Electrochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68851 , vital:77127
- Description: With the rise in popularity of electric vehicles and portable electronic devices, having a reliable, lightweight, and long-lasting battery is crucial. This has led to the mass commercialisation of lithium-ion batteries (LIB’s) because they offer several advantages over other battery technologies. Over the years, one of the concerns was with the ease with which the batteries can burn or explode when subjected to certain extreme conditions. In order to build trust in these products and to expand the technology into more diverse applications, safety aspects of the batteries has become of widespread concern resulting in a key area of research. One aspect of improving the safety is by reducing the flammability of the battery by the addition of certain chemicals that stop or suppress the thermal runaway effect. However, this in-turn reduces the battery’s capacity and life-cycle performance. Researchers have used the idea of encapsulating these chemicals thereby physically separating them within the lithium-ion battery (LIB) electrolyte system with a minimum effect on performance. This research aims to explore use of R-diols and R-amines as additives that upon a thermal trigger would react with the lithium-ion battery electrolyte to stop the effect of the thermal runaway by forming carbamate derivatives which are gel-like or form solid aggregates. The R-diols or R-amines can react with electrolyte at higher temperatures with the lithium-hexafluorophosphate acting as a catalyst. This change in the physical state of the electrolyte increases the resistance inside the battery which then hinders ion movement and forms a physical barrier to reduce the effect of short circuiting when the separator or other components are damaged due to higher temperatures. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Low-income area electrification systems
- Authors: Tshabeni, Thulisa
- Date: 2024-12
- Subjects: Rural electrification -- Economic aspects -- South Africa , Rural electrification -- South Africa , Remote area power supply systems -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68807 , vital:77115
- Description: This research investigated electrification systems for low-income, informal settlement areas via grid extension, photovoltaic mini-grids and solar home system (SHS). Six electrification systems were analysed; four mini-grid systems, a 100 W solar home system and a grid extension. All have different maximum power capacities and differ in the way they contribute to sustainable development. Affordability for the consumer of the total energy required (electrical and other sources) is a key factor for the sustainability of any electrification system. Two battery technologies, lithium-ion and lead acid batteries were compared for each system based on technical and economic performance. The study determined that despite the intial very high cost, lithium-ion batteries can achieve a lower levelized cost of electricity (LCOE) due to their long life span. It was found that the batteries cost between 58% and 95% of the project’s capital cost. The battery cost occurs not only in the capital cost, but in the replacement cost. This cost is so high, that it makes all the solar systems uneconomic. This research found that extending the national power grid is still much more economically viable than all other PV electrification systems, but it requires land tenure. The issue of land tenure could be solved by making some agreement with the land owner for rental. It was found that the PV systems could only be economic if they increased the income of the communities substantially. , Thesis (MEg) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Tshabeni, Thulisa
- Date: 2024-12
- Subjects: Rural electrification -- Economic aspects -- South Africa , Rural electrification -- South Africa , Remote area power supply systems -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68807 , vital:77115
- Description: This research investigated electrification systems for low-income, informal settlement areas via grid extension, photovoltaic mini-grids and solar home system (SHS). Six electrification systems were analysed; four mini-grid systems, a 100 W solar home system and a grid extension. All have different maximum power capacities and differ in the way they contribute to sustainable development. Affordability for the consumer of the total energy required (electrical and other sources) is a key factor for the sustainability of any electrification system. Two battery technologies, lithium-ion and lead acid batteries were compared for each system based on technical and economic performance. The study determined that despite the intial very high cost, lithium-ion batteries can achieve a lower levelized cost of electricity (LCOE) due to their long life span. It was found that the batteries cost between 58% and 95% of the project’s capital cost. The battery cost occurs not only in the capital cost, but in the replacement cost. This cost is so high, that it makes all the solar systems uneconomic. This research found that extending the national power grid is still much more economically viable than all other PV electrification systems, but it requires land tenure. The issue of land tenure could be solved by making some agreement with the land owner for rental. It was found that the PV systems could only be economic if they increased the income of the communities substantially. , Thesis (MEg) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2024
- Full Text:
- Date Issued: 2024-12
Portfolio effect and bet-hedging adaptations in sea turtles
- Authors: Hoekstra, Shaun
- Date: 2024-12
- Subjects: Wildlife conservation , Sea turtles -- South Africa , Animal behavior
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68873 , vital:77153
- Description: A great proportion of marine species are at risk of going extinct as a result of profound changes in the world’s oceans, primarily driven by human activities. Sea turtles are not exempt from this fate. Despite sea turtles being exposed to a range of environmental conditions and threats that vary in frequency and intensity, these ancient marine reptiles have persisted for millennia. In the past, sea turtles have been able to adapt to natural perturbations while other animal groups have not. The ability of sea turtles to adapt to contemporary changes in conditions, produced by human activities, has become limited. The persistence of sea turtles may be explained by the application of a concept termed “portfolio effect”. An aggregate system is more stable and less prone to fluctuations over time (i.e. portfolio effect) if a diversity of finer components comprises the entire system and displays asynchronous fluctuations over time. Biological entities (e.g. species measured by the abundance trend) may achieve long-term stability even though the individual components (e.g. populations measured in abundance trend) display weak or negative correlations with each other in space and time. Different sea turtle populations may display independent trends in abundances over time, resulting in a portfolio effect at species levels. Trends in sea turtle abundances may be affected by individual behaviour. The adoption of bet-hedging adaptations may enable populations to thrive despite environmental changes or stochasticity, by lowering short-term fitness in exchange for maximising long-term fitness. Individual sea turtles may exhibit bet-hedging adaptations through changes in their temporal nesting behaviour, including the remigration interval. Since remigration interval length regulates the number of nesting females per nesting season, changes in remigration interval will affect abundance trends. The ability of individuals to change their remigration interval allows them to “skip” the breeding migration when environmental conditions seem unfavourable. The overall aim of this thesis was to investigate potential reasons for observed sea turtle abundance trends at species, population, and rookery levels. I tested whether the portfolio effect applies to sea turtles by analysing and interpreting spatiotemporal trends in loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) abundances at the population and species levels using global datasets. The application of bet-hedging strategies was tested at a local level using data from the long-term monitoring program for South African nesting sea turtles. The majority of loggerhead rookeries displayed an increase in abundance over time, while most leatherback rookeries declined (Chapter 2). Population growth rates also differed among rookeries within Regional Management Units (RMUs) (Chapter 2). This diversity in abundance trends among rookeries suggested spatiotemporal variation in environmental conditions, threats and/or level of protection accompanying sea turtles. The species-level growth rate for both species displayed an overall increase in abundance over time. However, larger (more turtles) leatherback rookeries/RMUs experienced more rapid declines in abundance compared to smaller rookeries/RMUs, resulting in a recent species-level decline. Uncorrelated trends in abundances at the RMU-level could have stabilised species-level trends. Differences in the remigration intervals as a possible bet-hedging adaptation could potentially explain differences in population recovery rates between South Africa’s loggerhead and leatherback sea turtles (Chapter 3), but found no evidence that individuals from either species exhibit bet-hedging adaptations. Loggerheads, however, have increased their remigration intervals over time, while leatherbacks have not. These increases were accompanied by declines in adult body size (previously established) which could be an effect of diminishing foraging area quality. The increased remigration interval shown by loggerheads may be a response rather than an adaptation to the prevailing environmental conditions that impact their food supply in their foraging areas. The population growth rate of leatherback sea turtles may surpass that of the loggerheads in the near future, although there is a global decline in abundance (Chapter 2). This dissertation provides information on possible reasons for observed trends in sea turtle abundances at various levels of biological organisation. While a variety of factors have the potential to influence trends in sea turtle abundance, the possible occurrence of portfolio effects and investigating nesting behaviour may resolve any uncertainties regarding the reasons for observed trends in abundance. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Hoekstra, Shaun
- Date: 2024-12
- Subjects: Wildlife conservation , Sea turtles -- South Africa , Animal behavior
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68873 , vital:77153
- Description: A great proportion of marine species are at risk of going extinct as a result of profound changes in the world’s oceans, primarily driven by human activities. Sea turtles are not exempt from this fate. Despite sea turtles being exposed to a range of environmental conditions and threats that vary in frequency and intensity, these ancient marine reptiles have persisted for millennia. In the past, sea turtles have been able to adapt to natural perturbations while other animal groups have not. The ability of sea turtles to adapt to contemporary changes in conditions, produced by human activities, has become limited. The persistence of sea turtles may be explained by the application of a concept termed “portfolio effect”. An aggregate system is more stable and less prone to fluctuations over time (i.e. portfolio effect) if a diversity of finer components comprises the entire system and displays asynchronous fluctuations over time. Biological entities (e.g. species measured by the abundance trend) may achieve long-term stability even though the individual components (e.g. populations measured in abundance trend) display weak or negative correlations with each other in space and time. Different sea turtle populations may display independent trends in abundances over time, resulting in a portfolio effect at species levels. Trends in sea turtle abundances may be affected by individual behaviour. The adoption of bet-hedging adaptations may enable populations to thrive despite environmental changes or stochasticity, by lowering short-term fitness in exchange for maximising long-term fitness. Individual sea turtles may exhibit bet-hedging adaptations through changes in their temporal nesting behaviour, including the remigration interval. Since remigration interval length regulates the number of nesting females per nesting season, changes in remigration interval will affect abundance trends. The ability of individuals to change their remigration interval allows them to “skip” the breeding migration when environmental conditions seem unfavourable. The overall aim of this thesis was to investigate potential reasons for observed sea turtle abundance trends at species, population, and rookery levels. I tested whether the portfolio effect applies to sea turtles by analysing and interpreting spatiotemporal trends in loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) abundances at the population and species levels using global datasets. The application of bet-hedging strategies was tested at a local level using data from the long-term monitoring program for South African nesting sea turtles. The majority of loggerhead rookeries displayed an increase in abundance over time, while most leatherback rookeries declined (Chapter 2). Population growth rates also differed among rookeries within Regional Management Units (RMUs) (Chapter 2). This diversity in abundance trends among rookeries suggested spatiotemporal variation in environmental conditions, threats and/or level of protection accompanying sea turtles. The species-level growth rate for both species displayed an overall increase in abundance over time. However, larger (more turtles) leatherback rookeries/RMUs experienced more rapid declines in abundance compared to smaller rookeries/RMUs, resulting in a recent species-level decline. Uncorrelated trends in abundances at the RMU-level could have stabilised species-level trends. Differences in the remigration intervals as a possible bet-hedging adaptation could potentially explain differences in population recovery rates between South Africa’s loggerhead and leatherback sea turtles (Chapter 3), but found no evidence that individuals from either species exhibit bet-hedging adaptations. Loggerheads, however, have increased their remigration intervals over time, while leatherbacks have not. These increases were accompanied by declines in adult body size (previously established) which could be an effect of diminishing foraging area quality. The increased remigration interval shown by loggerheads may be a response rather than an adaptation to the prevailing environmental conditions that impact their food supply in their foraging areas. The population growth rate of leatherback sea turtles may surpass that of the loggerheads in the near future, although there is a global decline in abundance (Chapter 2). This dissertation provides information on possible reasons for observed trends in sea turtle abundances at various levels of biological organisation. While a variety of factors have the potential to influence trends in sea turtle abundance, the possible occurrence of portfolio effects and investigating nesting behaviour may resolve any uncertainties regarding the reasons for observed trends in abundance. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Prevalence and correlates of sickness presenteeism among secondary school teachers in the Bukedi region of eastern Uganda
- Authors: Majwala,Henry
- Date: 2024-12
- Subjects: Employees -- Mental health , Psychology, Industrial , Industrial psychiatry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68355 , vital:76989
- Description: Education is regarded as one of the main cornerstones for sustainable development, especially if the majority of the global citizenry manage to achieve it at secondary school level. The efficaciousness thereof, however, almost entirely depends on the productivity and performance of teachers meant to instill various skill sets among secondary school learners. Sickness presenteeism among secondary school teachers has previously emerged and gained attention as the single most important antagonist of secondary school productivity. However, it has been reported to be increasing in magnitude as absenteeism has gradually decreased over the years. The aim of the study was to establish the prevalence and correlates of sickness presenteeism among secondary school teachers in the Bukedi region in Eastern Uganda. The study adopted a pragmatic philosophy and a sequential explanatory mixed methods design targeting 433 secondary school teachers in the Bukedi sub region of Eastern Uganda. The schools were stratified by district first and then each district was stratified by ownership. Simple random sampling was used to sample half the number of schools per stratum, simple random sampling was used to sample the teachers. Key informants such as principals and teachers were purposively sampled and engaged in key informant semi-structured interviews. Quantitative data emerging from an analysis of the questionnaires was analyzed in SPSS version 25 using the log-binomial model, while the qualitative data from the semi-structured interviews was analyzed thematically. This study disclosed that the majority (68.3%) of the teachers engaged in sickness presenteeism. Moon lighting, egocentrism and heavy workload were the significant intrapersonal correlates of sickness presenteeism, while under staffing was a prominent institutional correlate. This study confirms findings from global research that staff working in people-based service sectors are most likely to engage in sickness presenteeism. The recommendations include the following: MoES to formulate a comprehensive policy on sickness presenteeism for teachers, DEOs to make follow ups to address the prevalent sickness presenteeism among secondary school teachers, the school administration to set up a special committee dealing with teachers’ welfare regarding ill health and work, and teachers are to be educated, sensitized about the dangers associated with sickness presenteeism and how to handle it with the school administration. , Thesis (DPhil) -- Faculty of Education, School of Post Schooling, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Majwala,Henry
- Date: 2024-12
- Subjects: Employees -- Mental health , Psychology, Industrial , Industrial psychiatry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68355 , vital:76989
- Description: Education is regarded as one of the main cornerstones for sustainable development, especially if the majority of the global citizenry manage to achieve it at secondary school level. The efficaciousness thereof, however, almost entirely depends on the productivity and performance of teachers meant to instill various skill sets among secondary school learners. Sickness presenteeism among secondary school teachers has previously emerged and gained attention as the single most important antagonist of secondary school productivity. However, it has been reported to be increasing in magnitude as absenteeism has gradually decreased over the years. The aim of the study was to establish the prevalence and correlates of sickness presenteeism among secondary school teachers in the Bukedi region in Eastern Uganda. The study adopted a pragmatic philosophy and a sequential explanatory mixed methods design targeting 433 secondary school teachers in the Bukedi sub region of Eastern Uganda. The schools were stratified by district first and then each district was stratified by ownership. Simple random sampling was used to sample half the number of schools per stratum, simple random sampling was used to sample the teachers. Key informants such as principals and teachers were purposively sampled and engaged in key informant semi-structured interviews. Quantitative data emerging from an analysis of the questionnaires was analyzed in SPSS version 25 using the log-binomial model, while the qualitative data from the semi-structured interviews was analyzed thematically. This study disclosed that the majority (68.3%) of the teachers engaged in sickness presenteeism. Moon lighting, egocentrism and heavy workload were the significant intrapersonal correlates of sickness presenteeism, while under staffing was a prominent institutional correlate. This study confirms findings from global research that staff working in people-based service sectors are most likely to engage in sickness presenteeism. The recommendations include the following: MoES to formulate a comprehensive policy on sickness presenteeism for teachers, DEOs to make follow ups to address the prevalent sickness presenteeism among secondary school teachers, the school administration to set up a special committee dealing with teachers’ welfare regarding ill health and work, and teachers are to be educated, sensitized about the dangers associated with sickness presenteeism and how to handle it with the school administration. , Thesis (DPhil) -- Faculty of Education, School of Post Schooling, 2024
- Full Text:
- Date Issued: 2024-12
Screening drug candidates for sars-cov-2 spike protein variants within the SANCDB (South African Natural Compounds Database) and drug bank
- Authors: van der Merwe, Vicky
- Date: 2024-12
- Subjects: COVID-19 (Disease) , Vaccines -- Development , Viral vaccines
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69499 , vital:77263
- Description: The WHO declared the Coronavirus Infectious Disease 2019 (COVID-19) pandemic as over on the 5th of May 2023. However, the Severe Acute Respiratory Syndrome Coronavirus 2 Virus (SARS-CoV-2) is still prevalently spread within populations, causing hospitalization and death in serious infections. Most anti-COVID-19 agents are weakly or conditionally or even strongly recommended against in non-severe cases with low to medium risk of hospitalisation and further highlight the significance of effective treatments for SARS-CoV-2 infected patients. The host’s Angiotensin-Converting Enzyme 2 (ACE2) interaction with the viral spike protein’s Receptor-Binding Domain (RBD) of SARS-CoV-2 leads to the subsequent infection, viral replication, and further propagation of the virus. This establishes the spike protein’s RBD as a vital target for drug design. Through HADDOCK and AlphaFold driven structural refinement, the then novel SARS-CoV-2 delta [3.34 Å (PDB ID: 7WBQ)] and omicron [3.00 Å (PDB ID: 7WBP)] crystalline structures of the variants’ RBD, in complex with its host receptor human ACE2, were modelled to improve the low-resolution starting structures. Models predicted by HADDOCK independently yielded refined structures with improved resolutions of 2.49 Å (delta) and 2.41 Å (omicron). SARS-CoV-2 spike protein RBD of delta and omicron variants were screened for less frequently considered allosteric binding sites that could block ACE2-RBD engagement. Eight potential allosteric binding sites were identified through CavityPlus for both variants, with a single best druggable potential allosteric site identified for each. The search for potential inhibiting hit compounds involved using the SANCDB and DrugBank databanks and screening both the allosteric and orthosteric binding sites through molecular docking. Despite differences in mutated interacting residues and bond interactions, a lead compound for orthosteric binding sites (SANC00290) and potential allosteric modulators of both delta and omicron (SANC00746 and DB01029) were found. These compounds show promise in blocking ACE2-RBD engagement to potentially reduce viral interaction and infection of, and potentially withstanding further mutational residues. This study contributes to further investigation of affordable SA natural compound COVID-19 treatment and a starting point for in vitro analysis studies. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: van der Merwe, Vicky
- Date: 2024-12
- Subjects: COVID-19 (Disease) , Vaccines -- Development , Viral vaccines
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69499 , vital:77263
- Description: The WHO declared the Coronavirus Infectious Disease 2019 (COVID-19) pandemic as over on the 5th of May 2023. However, the Severe Acute Respiratory Syndrome Coronavirus 2 Virus (SARS-CoV-2) is still prevalently spread within populations, causing hospitalization and death in serious infections. Most anti-COVID-19 agents are weakly or conditionally or even strongly recommended against in non-severe cases with low to medium risk of hospitalisation and further highlight the significance of effective treatments for SARS-CoV-2 infected patients. The host’s Angiotensin-Converting Enzyme 2 (ACE2) interaction with the viral spike protein’s Receptor-Binding Domain (RBD) of SARS-CoV-2 leads to the subsequent infection, viral replication, and further propagation of the virus. This establishes the spike protein’s RBD as a vital target for drug design. Through HADDOCK and AlphaFold driven structural refinement, the then novel SARS-CoV-2 delta [3.34 Å (PDB ID: 7WBQ)] and omicron [3.00 Å (PDB ID: 7WBP)] crystalline structures of the variants’ RBD, in complex with its host receptor human ACE2, were modelled to improve the low-resolution starting structures. Models predicted by HADDOCK independently yielded refined structures with improved resolutions of 2.49 Å (delta) and 2.41 Å (omicron). SARS-CoV-2 spike protein RBD of delta and omicron variants were screened for less frequently considered allosteric binding sites that could block ACE2-RBD engagement. Eight potential allosteric binding sites were identified through CavityPlus for both variants, with a single best druggable potential allosteric site identified for each. The search for potential inhibiting hit compounds involved using the SANCDB and DrugBank databanks and screening both the allosteric and orthosteric binding sites through molecular docking. Despite differences in mutated interacting residues and bond interactions, a lead compound for orthosteric binding sites (SANC00290) and potential allosteric modulators of both delta and omicron (SANC00746 and DB01029) were found. These compounds show promise in blocking ACE2-RBD engagement to potentially reduce viral interaction and infection of, and potentially withstanding further mutational residues. This study contributes to further investigation of affordable SA natural compound COVID-19 treatment and a starting point for in vitro analysis studies. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Social dynamics of spotted hyaenas (Crocuta crocuta) in fenced protected areas: Implications for conservation management of a socially intelligent species
- Authors: Honiball, Terry-Lee
- Date: 2024-12
- Subjects: Spotted hyena -- Behavior -- South Africa , Wildlife conservation -- South Africa , Wildlife management -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68884 , vital:77159
- Description: It is important to understand the impact of fenced protected area management on the behaviour and fitness of less popular species, such as the spotted hyeana (Crocuta crocuta), that have been historically overlooked in species management across protected areas. As a result of this oversight, hyaena population densities have reached high levels, making it critical to study the effects of fenced protected area management on these species. There is a lack of understanding of how species adapt to the potentially high-pressure systems (through the restriction of resources spatially) created by fenced protected areas and the intrinsic effects that management regimes may have on wildlife. Due to the spotted hyaena’s high behavioural plasticity, they make excellent candidates to explore the effects of management regimes in fenced protected areas while enhancing our understanding of spotted hyaena ecology. Therefore, the aim of this study was to explore the ecology and social behaviour of high density spotted hyaena populations in fenced protected areas to understand the effects of different management regimes and how spotted hyaenas respond to these differing pressures. This was achieved through four main objectives which consider different aspects of spotted hyaena ecology and the influence of management regimes and environmental variables in two fenced protected areas in South Africa; Madikwe Game Reserve (a socio-economically incentivised reserve) and Addo Elephant National Park (a reserve incentivised by the promotion of biodiversity), between 2021 and 2023. This study explored 1) range residency patterns and third order habitat selection in spotted hyaena movement, 2) interspecific interactions at shared food sources to understand the role of lion, Panthera leo, and spotted hyaenas dynamics in top-down pressure in carnivore structure, 3) territorial interactions when defending resources to understand spotted hyaena social dominance when occurring at high densities, 4) welfare considerations and allostatic load of spotted hyaenas, and additionally we provided insight into the social hierarchy disruptions which occur when removing the matriarch from a clan through an opportunistic record. By assessing the effects of socio-economic or biodiversity driven management regimes, this study provided novel accounts of social behaviour and responses of spotted hyaenas to pressures in fenced protected areas, highlighting the top-down pressure that lions have on multiple aspects of spotted hyaena functioning. Road networks and infrastructure in fenced protected areas were generally utilised by spotted hyaenas and despite high abundance, prey availability remained an important aspect of spotted hyaena ecology regardless of management regimes. Further, we showed that when food is abundant, spotted hyaenas are tolerant of subordinate carnivores, which emphasises their dynamic behavioural plasticity. We showed that spotted hyaenas gauge territorial responses according to the perceived threat and are less tolerant to familiar intruders than to unfamiliar individuals, which is an important inbreeding avoidance tactic that remains in place in fenced protected areas. And lastly, we showed that management regimes influence the adrenal function of spotted hyaenas, where fenced protected areas incentivised by wildlife photographic tourism may negatively affect species fitness through elevated epidandrosterone levels over time. However, spotted hyaenas appear to have adapted to elevated hormone levels, thus not affecting fecundity in fenced protected areas, resulting in high density populations. This study provides a holistic overview of the effects of management regimes on spotted hyaenas in fenced protected areas and provides insights into how spotted hyaenas adapt to pressures when occurring at high densities in these areas. This study contributes to the understanding of spotted hyaena ecology and the intrinsic effects on wildlife of different approaches to management regimes in fenced protected areas. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Honiball, Terry-Lee
- Date: 2024-12
- Subjects: Spotted hyena -- Behavior -- South Africa , Wildlife conservation -- South Africa , Wildlife management -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68884 , vital:77159
- Description: It is important to understand the impact of fenced protected area management on the behaviour and fitness of less popular species, such as the spotted hyeana (Crocuta crocuta), that have been historically overlooked in species management across protected areas. As a result of this oversight, hyaena population densities have reached high levels, making it critical to study the effects of fenced protected area management on these species. There is a lack of understanding of how species adapt to the potentially high-pressure systems (through the restriction of resources spatially) created by fenced protected areas and the intrinsic effects that management regimes may have on wildlife. Due to the spotted hyaena’s high behavioural plasticity, they make excellent candidates to explore the effects of management regimes in fenced protected areas while enhancing our understanding of spotted hyaena ecology. Therefore, the aim of this study was to explore the ecology and social behaviour of high density spotted hyaena populations in fenced protected areas to understand the effects of different management regimes and how spotted hyaenas respond to these differing pressures. This was achieved through four main objectives which consider different aspects of spotted hyaena ecology and the influence of management regimes and environmental variables in two fenced protected areas in South Africa; Madikwe Game Reserve (a socio-economically incentivised reserve) and Addo Elephant National Park (a reserve incentivised by the promotion of biodiversity), between 2021 and 2023. This study explored 1) range residency patterns and third order habitat selection in spotted hyaena movement, 2) interspecific interactions at shared food sources to understand the role of lion, Panthera leo, and spotted hyaenas dynamics in top-down pressure in carnivore structure, 3) territorial interactions when defending resources to understand spotted hyaena social dominance when occurring at high densities, 4) welfare considerations and allostatic load of spotted hyaenas, and additionally we provided insight into the social hierarchy disruptions which occur when removing the matriarch from a clan through an opportunistic record. By assessing the effects of socio-economic or biodiversity driven management regimes, this study provided novel accounts of social behaviour and responses of spotted hyaenas to pressures in fenced protected areas, highlighting the top-down pressure that lions have on multiple aspects of spotted hyaena functioning. Road networks and infrastructure in fenced protected areas were generally utilised by spotted hyaenas and despite high abundance, prey availability remained an important aspect of spotted hyaena ecology regardless of management regimes. Further, we showed that when food is abundant, spotted hyaenas are tolerant of subordinate carnivores, which emphasises their dynamic behavioural plasticity. We showed that spotted hyaenas gauge territorial responses according to the perceived threat and are less tolerant to familiar intruders than to unfamiliar individuals, which is an important inbreeding avoidance tactic that remains in place in fenced protected areas. And lastly, we showed that management regimes influence the adrenal function of spotted hyaenas, where fenced protected areas incentivised by wildlife photographic tourism may negatively affect species fitness through elevated epidandrosterone levels over time. However, spotted hyaenas appear to have adapted to elevated hormone levels, thus not affecting fecundity in fenced protected areas, resulting in high density populations. This study provides a holistic overview of the effects of management regimes on spotted hyaenas in fenced protected areas and provides insights into how spotted hyaenas adapt to pressures when occurring at high densities in these areas. This study contributes to the understanding of spotted hyaena ecology and the intrinsic effects on wildlife of different approaches to management regimes in fenced protected areas. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Solution of some cross-diffusion equations in biosciences using finite difference methods and artificial neural networks
- Authors: de Waal, Gysbert Nicolaas
- Date: 2024-12
- Subjects: Mathematics , Difference equations , Functional equations
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68829 , vital:77121
- Description: In this dissertation, three cross-diffusion models which require positivity-preserving solutions are solved using standard and nonstandard finite difference methods and physics-informed neural networks. The three models are a basic reaction-diffusion-chemotaxis model, a convective predator-prey pursuit and evasion model, and a two-dimensional Keller-Segel chemotaxis model. All three models involve systems of nonlinear coupled partial differential equations subject to some specified initial and boundary conditions for which no exact solution is known. It is not possible to obtain the stability region of the standard finite difference methods for the three models theoretically and therefore a range of values of temporal step size at a given spatial step size for reasonable solutions is obtained by running some numerical experiments. It is observed that the standard finite difference schemes are not always positivity-preserving, and this is why nonstandard finite difference schemes are necessary. Chapter 1 provides some background detail on partial differential equations, cross-diffusion equations, finite difference methods, and artificial neural networks. In Chapter 2, the cross-diffusion models considered in this dissertation are provided, namely a basic reaction-diffusion–chemotaxis model for two cases, a convective predator-prey pursuit and evasion model, and a two-dimensional Keller-Segel chemotaxis model for two cases. In Chapter 3, the basic reaction-diffusion–chemotaxis model is solved for the two cases using some standard and nonstandard finite difference schemes. It is determined that the standard methods give reasonable positivity-preserving numerical solutions if the temporal step size, 𝑘, is chosen such that 𝑘 ≤ 0.25 with the spatial step size, ℎ, fixed at ℎ = 1.0. Two nonstandard finite difference methods abbreviated as NSFD1 and NSFD2 are considered from Chapwanya et al. (2014). It is shown that NSFD1 preserves the positivity of the continuous model if the following criteria are satisfied: 𝜙(𝑘)[𝜓(ℎ)]2=12𝛾≤12𝜎+𝛽 and 𝛽≤𝜎. NSFD1 is modified to obtain NSFD2, which is positivity-preserving if 𝑅=𝜙(𝑘)[𝜓(ℎ)]2=12𝛾 and 2𝜎𝑅≤1, that is, 𝜎≤𝛾. In this work, it is shown that NSFD2 does not always achieve consistency, and it is proven that consistency can be achieved if 𝛽→0 and 𝑘ℎ2→0. Lastly, it is demonstrated that the numerical rate of convergence in time of the finite difference methods is approximately one for case 2 of the chemotaxis model. In Chapter 4, one standard and two nonstandard finite difference methods are constructed to solve the convective predator-prey model. Through some numerical experiments, it is observed that reasonable , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: de Waal, Gysbert Nicolaas
- Date: 2024-12
- Subjects: Mathematics , Difference equations , Functional equations
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68829 , vital:77121
- Description: In this dissertation, three cross-diffusion models which require positivity-preserving solutions are solved using standard and nonstandard finite difference methods and physics-informed neural networks. The three models are a basic reaction-diffusion-chemotaxis model, a convective predator-prey pursuit and evasion model, and a two-dimensional Keller-Segel chemotaxis model. All three models involve systems of nonlinear coupled partial differential equations subject to some specified initial and boundary conditions for which no exact solution is known. It is not possible to obtain the stability region of the standard finite difference methods for the three models theoretically and therefore a range of values of temporal step size at a given spatial step size for reasonable solutions is obtained by running some numerical experiments. It is observed that the standard finite difference schemes are not always positivity-preserving, and this is why nonstandard finite difference schemes are necessary. Chapter 1 provides some background detail on partial differential equations, cross-diffusion equations, finite difference methods, and artificial neural networks. In Chapter 2, the cross-diffusion models considered in this dissertation are provided, namely a basic reaction-diffusion–chemotaxis model for two cases, a convective predator-prey pursuit and evasion model, and a two-dimensional Keller-Segel chemotaxis model for two cases. In Chapter 3, the basic reaction-diffusion–chemotaxis model is solved for the two cases using some standard and nonstandard finite difference schemes. It is determined that the standard methods give reasonable positivity-preserving numerical solutions if the temporal step size, 𝑘, is chosen such that 𝑘 ≤ 0.25 with the spatial step size, ℎ, fixed at ℎ = 1.0. Two nonstandard finite difference methods abbreviated as NSFD1 and NSFD2 are considered from Chapwanya et al. (2014). It is shown that NSFD1 preserves the positivity of the continuous model if the following criteria are satisfied: 𝜙(𝑘)[𝜓(ℎ)]2=12𝛾≤12𝜎+𝛽 and 𝛽≤𝜎. NSFD1 is modified to obtain NSFD2, which is positivity-preserving if 𝑅=𝜙(𝑘)[𝜓(ℎ)]2=12𝛾 and 2𝜎𝑅≤1, that is, 𝜎≤𝛾. In this work, it is shown that NSFD2 does not always achieve consistency, and it is proven that consistency can be achieved if 𝛽→0 and 𝑘ℎ2→0. Lastly, it is demonstrated that the numerical rate of convergence in time of the finite difference methods is approximately one for case 2 of the chemotaxis model. In Chapter 4, one standard and two nonstandard finite difference methods are constructed to solve the convective predator-prey model. Through some numerical experiments, it is observed that reasonable , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-12
Student teacher's experiences of teaching mathematics using isiXhosa in foundation phase classrooms during teaching practice
- Bangiso, Innocentia Queen Zintle
- Authors: Bangiso, Innocentia Queen Zintle
- Date: 2024-12
- Subjects: Mathematics -- Study and teaching , Native language and education -- Africa , African languages -- Study and teaching
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68297 , vital:76972
- Description: In South Africa, learning in the Foundation Phase happens in a child’s home language, thus all eleven official languages, nine of them being African languages, must and are used as languages of teaching and learning in this phase. Teacher training, however, does not happen in all eleven official languages. The dominant language of training teachers across the country is English, even in classroom contexts where the language of learning and teaching may be an African language. This raises concerns about whether student teachers trained in English can translate mathematics content knowledge into an African language. This is particularly concerning given the country’s consistent underperformance in mathematics and literacy. Against this backdrop, this qualitative study aimed to explore Foundation Phase student teachers’ perspectives on their experiences of teaching mathematics using isiXhosa during teaching practice. The question that this study sought to answer was: what are student teachers’ perspectives on their experiences of teaching mathematics in isiXhosa during teaching practice? Drawing upon classroom observations and semi-structured individual interviews as the primary methods of data collection, the study explored the mediation of mathematics learning using isiXhosa, the pedagogical challenges encountered by student teachers, the strategies employed to address these challenges, and the influence of university training on their preparation. Findings reveal a significant discrepancy between the language of instruction used in university training which is English, and the language required for teaching practice which is isiXhosa. Student teachers expressed struggles in translating theoretical knowledge into practical application, leading to diminished confidence and pedagogical inefficacy. However, participants also demonstrated resilience through innovative strategies such as code-switching, visual aids, and collaborative learning approaches. The study highlights the urgent need for comprehensive language support and pedagogical training programmes to bridge the gap between theory and practice in isiXhosa-medium mathematics instruction. Recommendations are provided for educational institutions, especially the case study university, to enhance the preparation of student teachers and promote effective mathematics education in multilingual contexts. , Thesis (MEd) -- Faculty of Education, School of Primary School Education: Foundation Phase, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Bangiso, Innocentia Queen Zintle
- Date: 2024-12
- Subjects: Mathematics -- Study and teaching , Native language and education -- Africa , African languages -- Study and teaching
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68297 , vital:76972
- Description: In South Africa, learning in the Foundation Phase happens in a child’s home language, thus all eleven official languages, nine of them being African languages, must and are used as languages of teaching and learning in this phase. Teacher training, however, does not happen in all eleven official languages. The dominant language of training teachers across the country is English, even in classroom contexts where the language of learning and teaching may be an African language. This raises concerns about whether student teachers trained in English can translate mathematics content knowledge into an African language. This is particularly concerning given the country’s consistent underperformance in mathematics and literacy. Against this backdrop, this qualitative study aimed to explore Foundation Phase student teachers’ perspectives on their experiences of teaching mathematics using isiXhosa during teaching practice. The question that this study sought to answer was: what are student teachers’ perspectives on their experiences of teaching mathematics in isiXhosa during teaching practice? Drawing upon classroom observations and semi-structured individual interviews as the primary methods of data collection, the study explored the mediation of mathematics learning using isiXhosa, the pedagogical challenges encountered by student teachers, the strategies employed to address these challenges, and the influence of university training on their preparation. Findings reveal a significant discrepancy between the language of instruction used in university training which is English, and the language required for teaching practice which is isiXhosa. Student teachers expressed struggles in translating theoretical knowledge into practical application, leading to diminished confidence and pedagogical inefficacy. However, participants also demonstrated resilience through innovative strategies such as code-switching, visual aids, and collaborative learning approaches. The study highlights the urgent need for comprehensive language support and pedagogical training programmes to bridge the gap between theory and practice in isiXhosa-medium mathematics instruction. Recommendations are provided for educational institutions, especially the case study university, to enhance the preparation of student teachers and promote effective mathematics education in multilingual contexts. , Thesis (MEd) -- Faculty of Education, School of Primary School Education: Foundation Phase, 2024
- Full Text:
- Date Issued: 2024-12
Studies on soil acidity management strategies for sustainable agriculture
- Authors: Swart, Nicolas
- Date: 2024-12
- Subjects: Soil acidity , Soil fertility , Sustainable agriculture
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69475 , vital:77260
- Description: Soil acidity is a widespread problem which reduces plant growth and yield. There are calls for alternative crop and soil management strategies that can be used by farmers to deal with soil acidification in a sustainable manner. Current literature suggests that the benefits of sustainable soil management systems on soil acidity are highly variable, and within the context of conservation agriculture (CA), farmers need recommendations for techniques to improve liming efficiency. Such techniques include acid resistant cultivars and soil amendments such as biochar. However, dedicated scientific research is still needed to increase our understanding of the benefits of integrating various sustainable agriculture approaches on reducing the acidity on cropped lands. A series of experiments were thus conducted to test whether the integration of reduced lime dosages with organic amendments such as biochar, along with acid resistant wheat cultivars could improve nutrient availability and reduce the harms of acidity on plant roots. It was hypothesised that if lower than recommended doses of lime are applied in combination with biochar and acid resistant cultivars, there will be significant improvement of nutrient availability, soil acidity amelioration benefits and crop growth. The first experiment was a 60–day incubation trial to examine the interaction effects of reduced lime application rates and black wattle (Acacia mearnsii) biochar on the acidity and plant nutrient availability of a sandy clay loam, acidic podzolic soil. The changes in pH water (pHw) across treatments were monitored at 10-day intervals over the incubation period. Additionally, the initial and final status of each treatment in terms of essential macro-and micronutrients, pH(KCl), extractable aluminium (ext Al), exchangeable acidity (EA) and acid saturation (AS) were also measured. The second experiment examined the genotype × biochar × lime interaction effects on wheat plant root growth in the acid soil. Soil incubation results showed that the interaction effect of lime rate and biochar was not significant (p>0.05) for any of the tested soil nutrient availability and soil acidity parameters, except for pHw. However, lime rate effects were significant (p<0.05) on AS, EA, pH(KCl) and ext Al. As lime rate increased, the acidity decreased. Increasing the lime application rate significantly (p<0.05) enhanced the cation exchange capacity (CEC), calcium (Ca), magnesium (Mg) and phosphorous (P), but decreased potassium (K) and sulphur (S). The availability of micro-nutrients namely copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) also decreased as the lime rate increased. Biochar effects on EA, AS, pH(KCl) and ext Al were not significant (p>0.05). However, the biochar significantly reduced the availability of Ca and Mn but did not have a significant effecton all the other nutrients at the tested application rates. Unenriched biochar at 10 t ha-1 had an acidifying effect on the soil as it increased EA, when compared to enriched biochar. The significant (p <0.05) biochar × lime × time interaction effect on pHw showed that biochar applied without lime increased pHw, and the benefits were greatest at 10 t ha-1 biochar application rate. Similarly, lime applied without biochar also had a significant positive effect on pHw and the benefit increased at higher lime application rates. After 60 days of incubation, the lime applied at the highest rate of 5 t ha-1 without biochar (0 t ha-1 biochar) had the highest final pHw value. The 3-way interaction of lime, biochar and genotype was not significant (p>0.05). Koonap, the acid tolerant wheat variety outperformed the sensitive variety, Gariep under all treatments in the acid soil, as expected. There was, however, a significant (p<0.05) lime rate × biochar interaction. The highest application rates of lime (5 t ha-1) and biochar (10 t ha-1) were the best combination for root length for both the varieties. Overall, these results suggested a possible buffering effect of biochar at low lime application rates, thus limited benefits of combining reduced lime doses with biochar on reducing soil acidity or enhancing nutrient availability. The null hypothesis was thus rejected, and it was concluded that co-application of reduced lime rates and biochar will not significantly enhance benefits of liming. However, a positive interaction from co-application of biochar and lime on both pH and plant growth is possible at high application rates of both biochar and lime. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Swart, Nicolas
- Date: 2024-12
- Subjects: Soil acidity , Soil fertility , Sustainable agriculture
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69475 , vital:77260
- Description: Soil acidity is a widespread problem which reduces plant growth and yield. There are calls for alternative crop and soil management strategies that can be used by farmers to deal with soil acidification in a sustainable manner. Current literature suggests that the benefits of sustainable soil management systems on soil acidity are highly variable, and within the context of conservation agriculture (CA), farmers need recommendations for techniques to improve liming efficiency. Such techniques include acid resistant cultivars and soil amendments such as biochar. However, dedicated scientific research is still needed to increase our understanding of the benefits of integrating various sustainable agriculture approaches on reducing the acidity on cropped lands. A series of experiments were thus conducted to test whether the integration of reduced lime dosages with organic amendments such as biochar, along with acid resistant wheat cultivars could improve nutrient availability and reduce the harms of acidity on plant roots. It was hypothesised that if lower than recommended doses of lime are applied in combination with biochar and acid resistant cultivars, there will be significant improvement of nutrient availability, soil acidity amelioration benefits and crop growth. The first experiment was a 60–day incubation trial to examine the interaction effects of reduced lime application rates and black wattle (Acacia mearnsii) biochar on the acidity and plant nutrient availability of a sandy clay loam, acidic podzolic soil. The changes in pH water (pHw) across treatments were monitored at 10-day intervals over the incubation period. Additionally, the initial and final status of each treatment in terms of essential macro-and micronutrients, pH(KCl), extractable aluminium (ext Al), exchangeable acidity (EA) and acid saturation (AS) were also measured. The second experiment examined the genotype × biochar × lime interaction effects on wheat plant root growth in the acid soil. Soil incubation results showed that the interaction effect of lime rate and biochar was not significant (p>0.05) for any of the tested soil nutrient availability and soil acidity parameters, except for pHw. However, lime rate effects were significant (p<0.05) on AS, EA, pH(KCl) and ext Al. As lime rate increased, the acidity decreased. Increasing the lime application rate significantly (p<0.05) enhanced the cation exchange capacity (CEC), calcium (Ca), magnesium (Mg) and phosphorous (P), but decreased potassium (K) and sulphur (S). The availability of micro-nutrients namely copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) also decreased as the lime rate increased. Biochar effects on EA, AS, pH(KCl) and ext Al were not significant (p>0.05). However, the biochar significantly reduced the availability of Ca and Mn but did not have a significant effecton all the other nutrients at the tested application rates. Unenriched biochar at 10 t ha-1 had an acidifying effect on the soil as it increased EA, when compared to enriched biochar. The significant (p <0.05) biochar × lime × time interaction effect on pHw showed that biochar applied without lime increased pHw, and the benefits were greatest at 10 t ha-1 biochar application rate. Similarly, lime applied without biochar also had a significant positive effect on pHw and the benefit increased at higher lime application rates. After 60 days of incubation, the lime applied at the highest rate of 5 t ha-1 without biochar (0 t ha-1 biochar) had the highest final pHw value. The 3-way interaction of lime, biochar and genotype was not significant (p>0.05). Koonap, the acid tolerant wheat variety outperformed the sensitive variety, Gariep under all treatments in the acid soil, as expected. There was, however, a significant (p<0.05) lime rate × biochar interaction. The highest application rates of lime (5 t ha-1) and biochar (10 t ha-1) were the best combination for root length for both the varieties. Overall, these results suggested a possible buffering effect of biochar at low lime application rates, thus limited benefits of combining reduced lime doses with biochar on reducing soil acidity or enhancing nutrient availability. The null hypothesis was thus rejected, and it was concluded that co-application of reduced lime rates and biochar will not significantly enhance benefits of liming. However, a positive interaction from co-application of biochar and lime on both pH and plant growth is possible at high application rates of both biochar and lime. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2024
- Full Text:
- Date Issued: 2024-12
Supramolecular chemistry considerations of fluorenyl-derived host compounds
- Authors: McFarlane, Duncan William
- Date: 2024-12
- Subjects: Supramolecular chemistry , Organic compounds , Chemistry, Organic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69371 , vital:77227
- Description: This work examined various supramolecular aspects of 9-fluorenone-derived host compounds, namely 4,4’-(9-fluorenylidene)diphenol (H1), 9,9-(1,4-phenylene)bis(fluoren-9-ol) (H2), 9,9- (ethyne-1,2-diyl)bis(fluoren-9-ol) (H3) and 9,9-(biphenyl-4,4-diyl)bis(fluoren-9-ol) (H4). These compounds were successfully synthesized and then screened for their host ability for, and host behaviour in, various organic compounds. At the outset, molecular modelling calculations were carried out on each of the four host compounds. Various structural parameters and the geometries of the low energy conformers that were calculated were then compared with these aspects of the guest-free host molecules obtained from single crystal X-ray diffraction (SCXRD) analysis. The host behaviour of H1 was, furthermore, assessed in the presence of four alkylnitriles, namely acetonitrile (ACE), acrylonitrile (ACRY), propionitrile (PROP) and butyronitrile (BUT). All four guests complexed with H1 with 1:1 host:guest (H:G) ratios. From SCXRD analyses, each of the complexes crystallized in the monoclinic crystal system and the centrosymmetric space group P21/n, and the host packing was isostructural in each instance. The complexes were stabilized by a plethora of short inter- and intramolecular contacts. The thermal stabilities of the four complexes were also examined together with Hirshfeld surface considerations. Finally, lattice energy calculations were carried out and the results of these compared with the relative thermal stabilities of the four complexes. The compounds H2 and H3 were examined for their selectivity behaviour in mixtures of aniline, N-methylaniline and N,N’-dimethylaniline (ANI, NMA and DMA). Both host compounds were able to form complexes with ANI and DMA with various H:G ratios, while only H3 possessed enclathration ability for NMA (H:G 1:1). SCXRD analyses showed that all of the complexes were stabilized by means of classical (host)O‒H···N(guest) hydrogen bonds in addition to other short contacts. Equimolar binary guest competition experiments with H2 revealed an extremely high host selectivity for DMA (ANI/DMA and DMA/NMA experiments furnished crystals with > 91% DMA), while the experiment with all three anilines present also resulted in a complex with an , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: McFarlane, Duncan William
- Date: 2024-12
- Subjects: Supramolecular chemistry , Organic compounds , Chemistry, Organic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69371 , vital:77227
- Description: This work examined various supramolecular aspects of 9-fluorenone-derived host compounds, namely 4,4’-(9-fluorenylidene)diphenol (H1), 9,9-(1,4-phenylene)bis(fluoren-9-ol) (H2), 9,9- (ethyne-1,2-diyl)bis(fluoren-9-ol) (H3) and 9,9-(biphenyl-4,4-diyl)bis(fluoren-9-ol) (H4). These compounds were successfully synthesized and then screened for their host ability for, and host behaviour in, various organic compounds. At the outset, molecular modelling calculations were carried out on each of the four host compounds. Various structural parameters and the geometries of the low energy conformers that were calculated were then compared with these aspects of the guest-free host molecules obtained from single crystal X-ray diffraction (SCXRD) analysis. The host behaviour of H1 was, furthermore, assessed in the presence of four alkylnitriles, namely acetonitrile (ACE), acrylonitrile (ACRY), propionitrile (PROP) and butyronitrile (BUT). All four guests complexed with H1 with 1:1 host:guest (H:G) ratios. From SCXRD analyses, each of the complexes crystallized in the monoclinic crystal system and the centrosymmetric space group P21/n, and the host packing was isostructural in each instance. The complexes were stabilized by a plethora of short inter- and intramolecular contacts. The thermal stabilities of the four complexes were also examined together with Hirshfeld surface considerations. Finally, lattice energy calculations were carried out and the results of these compared with the relative thermal stabilities of the four complexes. The compounds H2 and H3 were examined for their selectivity behaviour in mixtures of aniline, N-methylaniline and N,N’-dimethylaniline (ANI, NMA and DMA). Both host compounds were able to form complexes with ANI and DMA with various H:G ratios, while only H3 possessed enclathration ability for NMA (H:G 1:1). SCXRD analyses showed that all of the complexes were stabilized by means of classical (host)O‒H···N(guest) hydrogen bonds in addition to other short contacts. Equimolar binary guest competition experiments with H2 revealed an extremely high host selectivity for DMA (ANI/DMA and DMA/NMA experiments furnished crystals with > 91% DMA), while the experiment with all three anilines present also resulted in a complex with an , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Synthesis of two tartaric acid-derived host compounds and their behaviour in mixed pyridines and mixed heterocyclic guest compounds
- Authors: Recchia, Daniella Loridana
- Date: 2024-12
- Subjects: Compounds -- guest/host , Chemistry, Organic , Chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69441 , vital:77256
- Description: The host compounds (4R,5R)-bis(diphenylhydroxymethyl)-2-spiro-1’-cyclopentane-1,3-dioxolane (TADDOL5) and (4R,5R)-bis(diphenylhydroxymethyl)-2-spiro-1’-cyclohexane-1,3-dioxolane (TADDOL6) were successfully synthesized after initially reacting diethyl tartrate with either 1,1-dimethoxycyclopentane or 1,1-dimethoxycyclohexane to afford the intermediates diethyl 2-spiro-1’-cyclopentane-1,3-dioxolan-4,5-dicarboxylate or diethyl 2-spiro-1’-cyclohexane-1,3-dioxolan-4,5-dicarboxylate. These were then each subjected to a Grignard addition reaction with PhMgBr to furnish TADDOL5 and TADDOL6 in reasonably high yields (77 and 80%, respectively). Computational calculations were performed on TADDOL5 and TADDOL6 using the software programs Avogadro and ORCA. The optimised geometries of these host molecules were obtained using the MMFF94 force field in Avogadro, while ORCA was used to perform the computational modelling at the BLYP level using the 6-31G*, 6-31G**, 6-311G* and 6-311G** basis sets and, also, the B3LYP functional (with the same basis sets) to obtain the three lowest energy conformers. The final geometries of each conformer for both TADDOL5 and TADDOL6 at the B3LYP 6-311G* level were overlaid with the molecules obtained from their crystal structures. Significantly different geometries were thus noted for the calculated conformers compared with the guest-free TADDOL5 and TADDOL6 structures obtained from the SCXRD experiments. When TADDOL5 was crystallized independently from each of PYR, 2MP, 3MP and 4MP, 1:1 H:G inclusion complexes formed in each instance. This host compound was then investigated for its host separation ability of mixed pyridines through supramolecular chemistry protocols. These mixed guest experiments revealed that TADDOL5 possessed a notable selectivity towards 3MP and PYR (in the absence of 3MP) followed by 4MP and 2MP, and it was shown that TADDOL5 is a suitable host candidate for the separation of many of the mixed pyridines employed here. The results of the SCXRD analyses indicated that the only significant (host)π···π(guest) stacking interaction present was between TADDOL5 and the most favoured guest species PYR and 3MP. Furthermore, significantly shorter (host)O‒H···N(guest) hydrogen bonds were also observed in the complexes formed between this host compound and 3MP and PYR compared with these bonds involving disfavoured 4MP and 2MP. Hirshfeld surface considerations provided an explanation for the affinity of TADDOL5 for PYR (but not 3MP), while thermal analyses successfully explained this affinity: the 3MP-containing complex with the most preferred guest species was the most thermally stable one, followed by TADDOL5·PYR, as obtained through a consideration of the Ton values (the temperature at which the guest release event initiated) of the four complexes. As with TADDOL5, TADDOL6 formed 1:1 H:G inclusion compounds with each of the four pyridines. TADDOL6 was, furthermore, also assessed for its separation ability for mixed pyridines, and these guest competition experiments showed that the selectivity of TADDOL6 was for PYR and 3MP (in the absence of PYR), followed by 4MP and 2MP. (Interestingly, TADDOL5 preferred 3MP and then PYR, while both host compounds disfavoured 4MP and 2MP.) The results obtained in this work indicated that TADDOL6 may also serve as an efficient host candidate for the separation of many of these pyridyl solutions. SCXRD experiments demonstrated that the only significant (host)π···π(guest) stacking interactions were those between TADDOL6 and preferred PYR and 3MP, as was the case for TADDOL5. These experiments also revealed that the strongest (host)O‒H···N(guest) hydrogen bonds were between TADDOL6 and these favoured guest species. A consideration of Hirshfeld surfaces and quantification of the (guest)N···H(host) intermolecular interactions correlated with the host selectivity order, as did thermal analyses, where the Ton values confirmed that the thermal stabilities of these complexes decreased in the guest order PYR > 3MP > 4MP > 2MP. The behaviour of TADDOL5 was further investigated in guest compounds DIO, PYR, PIP and MOR. Each guest solvent formed 1:1 H:G inclusion complexes with the host species, with the exception of DIO, which formed a 2:1 H:G complex. Mixed guest experiments revealed a clear preference for PIP and MOR, while PYR and DIO were less favoured. The host selectivity was demonstrated to be in the order PIP > MOR > PYR > DIO. SCXRD experiments showed that TADDOL5 formed a much shorter (and more linear) (host)O‒H···N(guest) hydrogen bond with the most favoured guest, PIP, compared to those involving MOR and PYR. A (host)O‒H···O(guest) hydrogen bond was also observed in the DIO-containing inclusion complex. A consideration of the Hirshfeld surface interactions was not useful in explaining the host selectivity order for these heterocyclic guests, but thermal analyses confirmed that the most stable complex was the one with favoured PIP, followed by those with PYR, MOR and DIO. TADDOL6, on the other hand, formed 1:1 H:G inclusion compounds with all four of the heterocyclic guest solvents. Experiments in mixed guests showed that the selectivity of this host compound for these guests was in the order PYR > PIP > MOR > DIO, which differed from the TADDOL5 (which favoured PIP and then MOR). Interestingly, the strongest classical hydrogen bond was not formed with the most favoured guest PYR, but with PIP instead (this bond with TADDOL5 was also strongest with PIP, but PIP was favoured in that work). Hirshfeld surface investigations again were not useful in understanding the host selectivity behaviour. However, thermal analyses agreed with the observations made in the mixed guest experiments: the most stable complex was with PYR (favoured) and the least stable one was with DIO (least preferred). , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Recchia, Daniella Loridana
- Date: 2024-12
- Subjects: Compounds -- guest/host , Chemistry, Organic , Chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69441 , vital:77256
- Description: The host compounds (4R,5R)-bis(diphenylhydroxymethyl)-2-spiro-1’-cyclopentane-1,3-dioxolane (TADDOL5) and (4R,5R)-bis(diphenylhydroxymethyl)-2-spiro-1’-cyclohexane-1,3-dioxolane (TADDOL6) were successfully synthesized after initially reacting diethyl tartrate with either 1,1-dimethoxycyclopentane or 1,1-dimethoxycyclohexane to afford the intermediates diethyl 2-spiro-1’-cyclopentane-1,3-dioxolan-4,5-dicarboxylate or diethyl 2-spiro-1’-cyclohexane-1,3-dioxolan-4,5-dicarboxylate. These were then each subjected to a Grignard addition reaction with PhMgBr to furnish TADDOL5 and TADDOL6 in reasonably high yields (77 and 80%, respectively). Computational calculations were performed on TADDOL5 and TADDOL6 using the software programs Avogadro and ORCA. The optimised geometries of these host molecules were obtained using the MMFF94 force field in Avogadro, while ORCA was used to perform the computational modelling at the BLYP level using the 6-31G*, 6-31G**, 6-311G* and 6-311G** basis sets and, also, the B3LYP functional (with the same basis sets) to obtain the three lowest energy conformers. The final geometries of each conformer for both TADDOL5 and TADDOL6 at the B3LYP 6-311G* level were overlaid with the molecules obtained from their crystal structures. Significantly different geometries were thus noted for the calculated conformers compared with the guest-free TADDOL5 and TADDOL6 structures obtained from the SCXRD experiments. When TADDOL5 was crystallized independently from each of PYR, 2MP, 3MP and 4MP, 1:1 H:G inclusion complexes formed in each instance. This host compound was then investigated for its host separation ability of mixed pyridines through supramolecular chemistry protocols. These mixed guest experiments revealed that TADDOL5 possessed a notable selectivity towards 3MP and PYR (in the absence of 3MP) followed by 4MP and 2MP, and it was shown that TADDOL5 is a suitable host candidate for the separation of many of the mixed pyridines employed here. The results of the SCXRD analyses indicated that the only significant (host)π···π(guest) stacking interaction present was between TADDOL5 and the most favoured guest species PYR and 3MP. Furthermore, significantly shorter (host)O‒H···N(guest) hydrogen bonds were also observed in the complexes formed between this host compound and 3MP and PYR compared with these bonds involving disfavoured 4MP and 2MP. Hirshfeld surface considerations provided an explanation for the affinity of TADDOL5 for PYR (but not 3MP), while thermal analyses successfully explained this affinity: the 3MP-containing complex with the most preferred guest species was the most thermally stable one, followed by TADDOL5·PYR, as obtained through a consideration of the Ton values (the temperature at which the guest release event initiated) of the four complexes. As with TADDOL5, TADDOL6 formed 1:1 H:G inclusion compounds with each of the four pyridines. TADDOL6 was, furthermore, also assessed for its separation ability for mixed pyridines, and these guest competition experiments showed that the selectivity of TADDOL6 was for PYR and 3MP (in the absence of PYR), followed by 4MP and 2MP. (Interestingly, TADDOL5 preferred 3MP and then PYR, while both host compounds disfavoured 4MP and 2MP.) The results obtained in this work indicated that TADDOL6 may also serve as an efficient host candidate for the separation of many of these pyridyl solutions. SCXRD experiments demonstrated that the only significant (host)π···π(guest) stacking interactions were those between TADDOL6 and preferred PYR and 3MP, as was the case for TADDOL5. These experiments also revealed that the strongest (host)O‒H···N(guest) hydrogen bonds were between TADDOL6 and these favoured guest species. A consideration of Hirshfeld surfaces and quantification of the (guest)N···H(host) intermolecular interactions correlated with the host selectivity order, as did thermal analyses, where the Ton values confirmed that the thermal stabilities of these complexes decreased in the guest order PYR > 3MP > 4MP > 2MP. The behaviour of TADDOL5 was further investigated in guest compounds DIO, PYR, PIP and MOR. Each guest solvent formed 1:1 H:G inclusion complexes with the host species, with the exception of DIO, which formed a 2:1 H:G complex. Mixed guest experiments revealed a clear preference for PIP and MOR, while PYR and DIO were less favoured. The host selectivity was demonstrated to be in the order PIP > MOR > PYR > DIO. SCXRD experiments showed that TADDOL5 formed a much shorter (and more linear) (host)O‒H···N(guest) hydrogen bond with the most favoured guest, PIP, compared to those involving MOR and PYR. A (host)O‒H···O(guest) hydrogen bond was also observed in the DIO-containing inclusion complex. A consideration of the Hirshfeld surface interactions was not useful in explaining the host selectivity order for these heterocyclic guests, but thermal analyses confirmed that the most stable complex was the one with favoured PIP, followed by those with PYR, MOR and DIO. TADDOL6, on the other hand, formed 1:1 H:G inclusion compounds with all four of the heterocyclic guest solvents. Experiments in mixed guests showed that the selectivity of this host compound for these guests was in the order PYR > PIP > MOR > DIO, which differed from the TADDOL5 (which favoured PIP and then MOR). Interestingly, the strongest classical hydrogen bond was not formed with the most favoured guest PYR, but with PIP instead (this bond with TADDOL5 was also strongest with PIP, but PIP was favoured in that work). Hirshfeld surface investigations again were not useful in understanding the host selectivity behaviour. However, thermal analyses agreed with the observations made in the mixed guest experiments: the most stable complex was with PYR (favoured) and the least stable one was with DIO (least preferred). , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
Synthesis, X-Ray characterization, spectroscopic and Hirshfeld surface analysis of dimeric metal centers featuring phenacyl-esters
- Authors: Qomfo, Vuyiseka
- Date: 2024-12
- Subjects: Spectrum analysis , Spectroscopic imaging , Diagnostic imaging -- Digital techniques
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69426 , vital:77254
- Description: In this study, the synthesis and characterization of carboxylate paddlewheel copper complexes were investigated and reported. The complexes consist of O-, and N- donor ligands which coordinated in the apical positions of the copper (II) paddlewheel complexes. The primary focus was the investigation of the influence of the incoming substituents on the structure; more especially with regards to the spectral properties and thermal properties of the synthesized compounds. Synthesized complexes ranged from simple mononuclear complexes and dinuclear dimers to supramolecular 1D networks and a tetranuclear copper (II) compound. Characterization of complexes was done using analytical, and spectroscopic techniques such as single crystal diffraction studies, FT-IR spectroscopy, thermal analysis and Hirshfeld surface analysis. Structural analysis of the mononuclear complex obtained in the reaction of the Cu2(o-CH3-PhCO2)4(THF)2 with the ligand ,2-oxo-phenylethylnicotinate, revealed a square-planar geometry. The series of dinuclear paddlewheel complexes obtained with ligands (L = THF (1), C4H8O (2), C14H11NO3 (3)) revealed a square pyramidal geometry with the methyl-substituted phenyl carboxylate groups bridging the two copper atoms in the syn-syn coordination mode. Extended supramolecular complexes were synthesized via the reaction of three synthesized structurally bifunctional organic ligands and the tetrakis(μ-carboxylato-O,O)dicopper(II) core. Two of the six reactions synthesized successfully to form paddlewheel cage type structures; resulting in dinuclear paddlewheel complexes with four carboxylate ligands occupying the equatorial positions and the bifunctional ligands coordinating in the apical positions. Four of the nine reactions produced mononuclear copper complexes. Due to the inconsistent power supply because of load-shedding, the other three crystals synthesized could not be confirmed by single-crystal diffraction before the submission of this thesis. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Qomfo, Vuyiseka
- Date: 2024-12
- Subjects: Spectrum analysis , Spectroscopic imaging , Diagnostic imaging -- Digital techniques
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69426 , vital:77254
- Description: In this study, the synthesis and characterization of carboxylate paddlewheel copper complexes were investigated and reported. The complexes consist of O-, and N- donor ligands which coordinated in the apical positions of the copper (II) paddlewheel complexes. The primary focus was the investigation of the influence of the incoming substituents on the structure; more especially with regards to the spectral properties and thermal properties of the synthesized compounds. Synthesized complexes ranged from simple mononuclear complexes and dinuclear dimers to supramolecular 1D networks and a tetranuclear copper (II) compound. Characterization of complexes was done using analytical, and spectroscopic techniques such as single crystal diffraction studies, FT-IR spectroscopy, thermal analysis and Hirshfeld surface analysis. Structural analysis of the mononuclear complex obtained in the reaction of the Cu2(o-CH3-PhCO2)4(THF)2 with the ligand ,2-oxo-phenylethylnicotinate, revealed a square-planar geometry. The series of dinuclear paddlewheel complexes obtained with ligands (L = THF (1), C4H8O (2), C14H11NO3 (3)) revealed a square pyramidal geometry with the methyl-substituted phenyl carboxylate groups bridging the two copper atoms in the syn-syn coordination mode. Extended supramolecular complexes were synthesized via the reaction of three synthesized structurally bifunctional organic ligands and the tetrakis(μ-carboxylato-O,O)dicopper(II) core. Two of the six reactions synthesized successfully to form paddlewheel cage type structures; resulting in dinuclear paddlewheel complexes with four carboxylate ligands occupying the equatorial positions and the bifunctional ligands coordinating in the apical positions. Four of the nine reactions produced mononuclear copper complexes. Due to the inconsistent power supply because of load-shedding, the other three crystals synthesized could not be confirmed by single-crystal diffraction before the submission of this thesis. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
The effect of the 2020 to 2021 alcohol ban on alcohol consumption and consumer preferences
- Authors: Dullabh, Curtis
- Date: 2024-12
- Subjects: Drinking customs , Alcoholic beverages , Consumer behavior -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69565 , vital:77714
- Description: This study examines the effect of the alcohol ban from 2020 to 2021 on consumer preferences and consumption habits. The COVID-19 virus was first detected in China, in 2019. The virus spread rapidly, crippling health care systems across the world. As the disease spread, countries began looking at ways to reduce the strain on the health care system caused by other factors (Gu, 2020). The first case in South Africa was recorded on 5 March 2020. South Africa reacted quickly and decided to implement a hard lockdown on alcohol, 22 days after the first case was recorded (Murhula & Nunlall, 2021). Due to the high number of trauma-related cases, which affected the healthcare system and South Africa’s reputation for being a country that consumes high volumes of alcohol, the government needed swift action. This alcohol ban sent shock waves across the country and alcohol consumers began to panic (BBC, 2020). In addition, the alcohol ban caused people to alter their consumption behaviours and some even resorted to homebrewing alcohol during the lockdown. Alcohol was available through the illicit market, which came at a premium price with limited options. This study originated from the alcohol ban, as consumers were exposed to brands, they otherwise would not have considered if all alcohol beverages were available. The scarcity of alcohol products, the excessive prices of alcohol and the effort it took to obtain alcohol, played a major role in altering drinking behaviours and brand preferences post the alcohol ban. Results from the study indicated that age and gender played no significant role in alcohol consumption, brand preference across categories were affected with two of nine alcohol categories experiencing a decline in consumption, from before to after the ban. During the ban, the majority of respondents consumed alcohol with some resorting to homebrewed alcohol, which showed a significant increase in consumption during the ban. The opportunity to further this study would be to investigate the increase in low alcoholic beverages and non-alcohol beverages as key avenues for organisations within the alcohol industry. , Thesis (MBA) -- Faculty of Business and Economic Sciences, Business School, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Dullabh, Curtis
- Date: 2024-12
- Subjects: Drinking customs , Alcoholic beverages , Consumer behavior -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69565 , vital:77714
- Description: This study examines the effect of the alcohol ban from 2020 to 2021 on consumer preferences and consumption habits. The COVID-19 virus was first detected in China, in 2019. The virus spread rapidly, crippling health care systems across the world. As the disease spread, countries began looking at ways to reduce the strain on the health care system caused by other factors (Gu, 2020). The first case in South Africa was recorded on 5 March 2020. South Africa reacted quickly and decided to implement a hard lockdown on alcohol, 22 days after the first case was recorded (Murhula & Nunlall, 2021). Due to the high number of trauma-related cases, which affected the healthcare system and South Africa’s reputation for being a country that consumes high volumes of alcohol, the government needed swift action. This alcohol ban sent shock waves across the country and alcohol consumers began to panic (BBC, 2020). In addition, the alcohol ban caused people to alter their consumption behaviours and some even resorted to homebrewing alcohol during the lockdown. Alcohol was available through the illicit market, which came at a premium price with limited options. This study originated from the alcohol ban, as consumers were exposed to brands, they otherwise would not have considered if all alcohol beverages were available. The scarcity of alcohol products, the excessive prices of alcohol and the effort it took to obtain alcohol, played a major role in altering drinking behaviours and brand preferences post the alcohol ban. Results from the study indicated that age and gender played no significant role in alcohol consumption, brand preference across categories were affected with two of nine alcohol categories experiencing a decline in consumption, from before to after the ban. During the ban, the majority of respondents consumed alcohol with some resorting to homebrewed alcohol, which showed a significant increase in consumption during the ban. The opportunity to further this study would be to investigate the increase in low alcoholic beverages and non-alcohol beverages as key avenues for organisations within the alcohol industry. , Thesis (MBA) -- Faculty of Business and Economic Sciences, Business School, 2024
- Full Text:
- Date Issued: 2024-12
The inhibitory effects of cannabinoids from cannabis sativa on the enzymes dipeptidyl peptidase-IV, sucrase and maltase as a new therapeutic treatment for type 2 diabetes
- Authors: Viljoen, Zenobia
- Date: 2024-12
- Subjects: Diabetes -- Treatment , Cannabinoids -- Therapeutic use , Medical Marijuana -- therapeutic use
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69516 , vital:77264
- Description: Type 2 diabetes is one of the most prevalent diseases worldwide. The treatments used to manage diabetes often have severe side effects and patients develop resistance to traditional treatment. The project aimed to test if phytocannabinoids from Cannabis sativa inhibited key enzymes involved in glycaemic homeostatic regulation, namely dipeptidyl peptidase 4 (DPP-4), sucrase, and maltase. This study investigated the inhibitory effects of 3 M-128 M cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), and Δ9- tetrahydrocannabinol (THC). CD spectroscopy was used to investigate the changes in the secondary structure of DPP-4 with interacting inhibitors. The effect of 1.25, 2.5, and 5 mg/kg rat THC cannabis extract on the activity of DPP-4 in blood plasma and rat pancreatic tissue of the diabetic rat model and obese rat model. The effect of 1.25, 2.5, and 5 mg/kg rat THC cannabis extract on glucagon concentration in the blood plasma of the diabetic rat model and obese rat model was investigated. The carbohydrate digestive enzymes namely -amylase, -glucosidase and maltase are not inhibited by any of the cannabinoids. CBN had inhibitory effects on sucrase. CBN, CBG, and CBD are mixed inhibitors of DPP-4, thus they can inhibit DPP-4 competitively and uncompetitively depending on the concentration of the cannabinoid. THC was shown in kinetic and rat model studies to be a very weak inhibitor of DPP-4. CD spectroscopy showed that sitagliptin (FDA-approved drug and competitive inhibitor) and CBG mimic the denatured structure of DPP-4. CBD, CBN and THC mimic the free (active) form of DPP-4. A reduction in pancreatic DPP-4 activity was observed with 2.5 and 5 mg/kg rat THC (diabetic model). This study showed that diet plays a role in glycaemic dysregulation (obese rat model) and that insulin-resistant rats had four times higher glucagon levels compared to the lean control (diabetic model). 1.25 mg/kg rat THC reduced blood plasma DPP-4 activity and blood plasma glucagon. Cannabis sativa can be a feasible treatment to help manage type 2 diabetes by inhibiting DPP-4, especially medical strains of Cannabis sativa with high concentrations of CBD and CBG. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Viljoen, Zenobia
- Date: 2024-12
- Subjects: Diabetes -- Treatment , Cannabinoids -- Therapeutic use , Medical Marijuana -- therapeutic use
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/69516 , vital:77264
- Description: Type 2 diabetes is one of the most prevalent diseases worldwide. The treatments used to manage diabetes often have severe side effects and patients develop resistance to traditional treatment. The project aimed to test if phytocannabinoids from Cannabis sativa inhibited key enzymes involved in glycaemic homeostatic regulation, namely dipeptidyl peptidase 4 (DPP-4), sucrase, and maltase. This study investigated the inhibitory effects of 3 M-128 M cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), and Δ9- tetrahydrocannabinol (THC). CD spectroscopy was used to investigate the changes in the secondary structure of DPP-4 with interacting inhibitors. The effect of 1.25, 2.5, and 5 mg/kg rat THC cannabis extract on the activity of DPP-4 in blood plasma and rat pancreatic tissue of the diabetic rat model and obese rat model. The effect of 1.25, 2.5, and 5 mg/kg rat THC cannabis extract on glucagon concentration in the blood plasma of the diabetic rat model and obese rat model was investigated. The carbohydrate digestive enzymes namely -amylase, -glucosidase and maltase are not inhibited by any of the cannabinoids. CBN had inhibitory effects on sucrase. CBN, CBG, and CBD are mixed inhibitors of DPP-4, thus they can inhibit DPP-4 competitively and uncompetitively depending on the concentration of the cannabinoid. THC was shown in kinetic and rat model studies to be a very weak inhibitor of DPP-4. CD spectroscopy showed that sitagliptin (FDA-approved drug and competitive inhibitor) and CBG mimic the denatured structure of DPP-4. CBD, CBN and THC mimic the free (active) form of DPP-4. A reduction in pancreatic DPP-4 activity was observed with 2.5 and 5 mg/kg rat THC (diabetic model). This study showed that diet plays a role in glycaemic dysregulation (obese rat model) and that insulin-resistant rats had four times higher glucagon levels compared to the lean control (diabetic model). 1.25 mg/kg rat THC reduced blood plasma DPP-4 activity and blood plasma glucagon. Cannabis sativa can be a feasible treatment to help manage type 2 diabetes by inhibiting DPP-4, especially medical strains of Cannabis sativa with high concentrations of CBD and CBG. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-12
The legality of euthanasia conducted by medical practitioners
- Authors: Davids, Sesam Isipho
- Date: 2024-12
- Subjects: Euthanasia -- Law and legislation , Assisted suicide -- Law and legislation , Euthanasia -- Moral and ethical aspects
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68681 , vital:77081
- Description: Euthanasia remains a contentious subject of debate in countries around the world and in South Africa. The South African court system has been faced with requests for the decriminalisation of euthanasia. However, it remains illegal to practice euthanasia in South Africa. This is set by common law as there is no legislation formally regulating euthanasia. Euthanasia provides relief from suffering for patients with terminal illnesses that cause severe suffering and a decrease in their quality of life. Individual autonomy is recognised as patients are given the ability to choose how to end their lives once they make the decision to terminate their lives. In this study, an examination on physician-assisted euthanasia and its current legal position in South Africa will be conducted. Key terms are defined, such as euthanasia - distinguishing active and passive euthanasia as well as physician-assisted suicide. South African law permits the withdrawal of life-sustaining treatments which may be viewed as passive euthanasia. This is done with the consent of the patient and the medical practitioners involved are not held criminally liable should the withholding of treatment cause the death of the patient. Relevant constitutional rights will be examined to make a case for the legalisation of physician-assisted euthanasia. These rights include the right to dignity, the right to life, the right to equality, the right to freedom of religion, belief and opinion, and the limitation clause. Common law, case law and statutory law will also be considered. The recommendations of the South African Law Commission in its report (project 86) will be examined as well. An analysis will be conducted on how foreign jurisdictions have accepted physician-assisted euthanasia and implemented legislative measures to safeguard and regulate how medical practitioners practice it. Canada is an example of such a jurisdiction and an analysis has been conducted on how courts in Canada have made a case for the decriminalisation of physician-assisted euthanasia. Canadian courts relied on rights such as the right to life and freedom of opinion. viii When arguing for or against the legalisation of euthanasia, the ethical perspectives of both arguments must be considered. The ‘slippery slope’ will be discussed to demonstrate an ethical argument against euthanasia. The ethical framework of utilitarianism will be discussed as an argument for euthanasia. In line with the title of this research, the physician’s role in the process of euthanasia will also be discussed. After weighing the key arguments, this research concludes that physician-assisted euthanasia ought to be legalised in South Africa. Recommendations are further suggested on how euthanasia ought to be regulated should it be legalised. The recommendations serve as a means of addressing the possibility of abuse and illegal conduct from medical practitioners and the public. Through this study, the aim is to contribute to the debate on physician-assisted euthanasia and to advance the development of a euthanasia-related legislation in South Africa. , Thesis (LLM) -- Faculty of Law, School of Criminal and Procedural Law, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Davids, Sesam Isipho
- Date: 2024-12
- Subjects: Euthanasia -- Law and legislation , Assisted suicide -- Law and legislation , Euthanasia -- Moral and ethical aspects
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/68681 , vital:77081
- Description: Euthanasia remains a contentious subject of debate in countries around the world and in South Africa. The South African court system has been faced with requests for the decriminalisation of euthanasia. However, it remains illegal to practice euthanasia in South Africa. This is set by common law as there is no legislation formally regulating euthanasia. Euthanasia provides relief from suffering for patients with terminal illnesses that cause severe suffering and a decrease in their quality of life. Individual autonomy is recognised as patients are given the ability to choose how to end their lives once they make the decision to terminate their lives. In this study, an examination on physician-assisted euthanasia and its current legal position in South Africa will be conducted. Key terms are defined, such as euthanasia - distinguishing active and passive euthanasia as well as physician-assisted suicide. South African law permits the withdrawal of life-sustaining treatments which may be viewed as passive euthanasia. This is done with the consent of the patient and the medical practitioners involved are not held criminally liable should the withholding of treatment cause the death of the patient. Relevant constitutional rights will be examined to make a case for the legalisation of physician-assisted euthanasia. These rights include the right to dignity, the right to life, the right to equality, the right to freedom of religion, belief and opinion, and the limitation clause. Common law, case law and statutory law will also be considered. The recommendations of the South African Law Commission in its report (project 86) will be examined as well. An analysis will be conducted on how foreign jurisdictions have accepted physician-assisted euthanasia and implemented legislative measures to safeguard and regulate how medical practitioners practice it. Canada is an example of such a jurisdiction and an analysis has been conducted on how courts in Canada have made a case for the decriminalisation of physician-assisted euthanasia. Canadian courts relied on rights such as the right to life and freedom of opinion. viii When arguing for or against the legalisation of euthanasia, the ethical perspectives of both arguments must be considered. The ‘slippery slope’ will be discussed to demonstrate an ethical argument against euthanasia. The ethical framework of utilitarianism will be discussed as an argument for euthanasia. In line with the title of this research, the physician’s role in the process of euthanasia will also be discussed. After weighing the key arguments, this research concludes that physician-assisted euthanasia ought to be legalised in South Africa. Recommendations are further suggested on how euthanasia ought to be regulated should it be legalised. The recommendations serve as a means of addressing the possibility of abuse and illegal conduct from medical practitioners and the public. Through this study, the aim is to contribute to the debate on physician-assisted euthanasia and to advance the development of a euthanasia-related legislation in South Africa. , Thesis (LLM) -- Faculty of Law, School of Criminal and Procedural Law, 2024
- Full Text:
- Date Issued: 2024-12
The lived experiences of final-year undergraduate diagnostic radiography students applying radiation protection measures during clinical practice
- Authors: Campbell, Sydney Samuel
- Date: 2024-12
- Subjects: Radiographers , College students -- South Africa , Experiential learning
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68311 , vital:76973
- Description: Radiographers use ionising radiation to produce radiographic images and the use of ionising radiation in healthcare has both benefits and risks for patients and healthcare professionals. It is therefore important that radiographers mitigate the risks associated with ionising radiation. It is for this reason that radiation protection measures are applied to ensure the safety of patients, staff, and the public. Furthermore, radiographers are also responsible for mentoring radiography students and inculcate the use of radiation protection measures when students undergo their workplace learning. This mentoring takes place in the clinical setting with its characteristics that may or may not advance the application of radiation protection measures. The aim of this study was to investigate the lived experiences of final-year undergraduate radiography students applying radiation protection measures in the clinical setting and to propose strategies to foster the integration of radiation protection theory into clinical practice. This study was located in the interpretivist paradigm using phenomenology as a research method and theoretical framework to achieve the stated aim. The target population for this qualitative study included all registered final-year undergraduate radiography students at the local university who perform their WPL at the accredited training hospitals in the Eastern Cape Province as this cohort of students have more clinical experience than the first-, second- and third-year students. The target population comprised 28 students. Purposive sampling was employed to select the group of radiography students to interview. The study used phenomenological interviews as a data collection tool and the collected data was explicated using a self-developed method. The trustworthiness of the study was ensured by applying Guba’s model of trustworthiness that includes credibility, transferability, confirmability, dependability and authenticity and was further enhanced by reflecting on the balanced integration, openness, concreteness, and resonance of the study. This study employed an ethical framework referred to as principlism that includes the notions of autonomy, beneficence, non-maleficence and justice.Data explication was conducted using three cycles of explication. Cycle one produced interpretive profiles for each participant. The interpretive profiles revealed the life histories of each participant as well as the utterances of participants related to the three sub-questions. Cycle two produced four themes. Theme one described participants’ being with others such as radiographers, clinical supervisors, medical doctors, and patients and revealed the tension between participants’ belonging and being unwanted. Theme two characterised the clinical setting as a place where several factors flow together to provide participants with their individualised experiences. Theme two revealed the emotional distress; the learning through trial-and-error; the independent learning; learning that is coupled with humiliation as experienced by participants. The clinical space was also characterised as a place to be survived, a place where students have to be inconspicuous and understand the acceptable levels of engagement with others. It is also a place where theory and practice at times is in alignment at other times not in alignment. The clinical setting could also be a place of self-doubt and insecurity, a place of personal growth, and a place where historical events are significant. Theme three disclosed the unspoken lessons that were conveyed through the actions and behaviours of individuals in the clinical environment. Unintended lesson one is that radiation protection measures are not important. Lesson two suggest that classroom teaching about radiation protection is not valid in the clinical setting, and finally that incivility towards radiography students is acceptable. Theme four revealed the difficulties experienced by radiography students when navigating ethical dilemmas. The theme revealed radiographers’ and radiologists’ indifference towards radiation protection, the non-application of radiation protection measures, and the inconsistency and apathy towards radiation protection measures. Cycle three viewed the experiences of participants through the lens of Dasein’s disclosedness. This revealed the exclusive language used by participants, the largely negative mood and participants’ disconnection from the imaging department.Finally, the study presented new and important insights by probing the topic of radiation protection in a novel way by using phenomenology to focus on the lived experiences of final-year undergraduate students applying radiation protection measures in the clinical setting. The findings of the study also allowed for the development of Enhancement strategies that could be used by institutions of higher education to promote the integration of the theory and practice of radiation protection measures in the clinical setting. It is recommended, though, that a study that includes all South African institutions of higher learning offering radiography be conducted using phenomenology. Furthermore, the views of South African radiographers and clinical supervisors should also be elicited to corroborate the views of participants in this study. , Thesis (PhD) -- Faculty of Education, School of Secondary Education, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Campbell, Sydney Samuel
- Date: 2024-12
- Subjects: Radiographers , College students -- South Africa , Experiential learning
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68311 , vital:76973
- Description: Radiographers use ionising radiation to produce radiographic images and the use of ionising radiation in healthcare has both benefits and risks for patients and healthcare professionals. It is therefore important that radiographers mitigate the risks associated with ionising radiation. It is for this reason that radiation protection measures are applied to ensure the safety of patients, staff, and the public. Furthermore, radiographers are also responsible for mentoring radiography students and inculcate the use of radiation protection measures when students undergo their workplace learning. This mentoring takes place in the clinical setting with its characteristics that may or may not advance the application of radiation protection measures. The aim of this study was to investigate the lived experiences of final-year undergraduate radiography students applying radiation protection measures in the clinical setting and to propose strategies to foster the integration of radiation protection theory into clinical practice. This study was located in the interpretivist paradigm using phenomenology as a research method and theoretical framework to achieve the stated aim. The target population for this qualitative study included all registered final-year undergraduate radiography students at the local university who perform their WPL at the accredited training hospitals in the Eastern Cape Province as this cohort of students have more clinical experience than the first-, second- and third-year students. The target population comprised 28 students. Purposive sampling was employed to select the group of radiography students to interview. The study used phenomenological interviews as a data collection tool and the collected data was explicated using a self-developed method. The trustworthiness of the study was ensured by applying Guba’s model of trustworthiness that includes credibility, transferability, confirmability, dependability and authenticity and was further enhanced by reflecting on the balanced integration, openness, concreteness, and resonance of the study. This study employed an ethical framework referred to as principlism that includes the notions of autonomy, beneficence, non-maleficence and justice.Data explication was conducted using three cycles of explication. Cycle one produced interpretive profiles for each participant. The interpretive profiles revealed the life histories of each participant as well as the utterances of participants related to the three sub-questions. Cycle two produced four themes. Theme one described participants’ being with others such as radiographers, clinical supervisors, medical doctors, and patients and revealed the tension between participants’ belonging and being unwanted. Theme two characterised the clinical setting as a place where several factors flow together to provide participants with their individualised experiences. Theme two revealed the emotional distress; the learning through trial-and-error; the independent learning; learning that is coupled with humiliation as experienced by participants. The clinical space was also characterised as a place to be survived, a place where students have to be inconspicuous and understand the acceptable levels of engagement with others. It is also a place where theory and practice at times is in alignment at other times not in alignment. The clinical setting could also be a place of self-doubt and insecurity, a place of personal growth, and a place where historical events are significant. Theme three disclosed the unspoken lessons that were conveyed through the actions and behaviours of individuals in the clinical environment. Unintended lesson one is that radiation protection measures are not important. Lesson two suggest that classroom teaching about radiation protection is not valid in the clinical setting, and finally that incivility towards radiography students is acceptable. Theme four revealed the difficulties experienced by radiography students when navigating ethical dilemmas. The theme revealed radiographers’ and radiologists’ indifference towards radiation protection, the non-application of radiation protection measures, and the inconsistency and apathy towards radiation protection measures. Cycle three viewed the experiences of participants through the lens of Dasein’s disclosedness. This revealed the exclusive language used by participants, the largely negative mood and participants’ disconnection from the imaging department.Finally, the study presented new and important insights by probing the topic of radiation protection in a novel way by using phenomenology to focus on the lived experiences of final-year undergraduate students applying radiation protection measures in the clinical setting. The findings of the study also allowed for the development of Enhancement strategies that could be used by institutions of higher education to promote the integration of the theory and practice of radiation protection measures in the clinical setting. It is recommended, though, that a study that includes all South African institutions of higher learning offering radiography be conducted using phenomenology. Furthermore, the views of South African radiographers and clinical supervisors should also be elicited to corroborate the views of participants in this study. , Thesis (PhD) -- Faculty of Education, School of Secondary Education, 2024
- Full Text:
- Date Issued: 2024-12
The optimisation of Eucalyptus regeneration practices for improved survival, growth and uniformity in South African pulpwood plantations
- Authors: Hechter, Ullrich
- Date: 2024-12
- Subjects: Eucalyptus -- Regeneration -- South Africa , Forests and forestry -- Economic aspects , Forests and forestry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68862 , vital:77135
- Description: Commercial forestry plantations in South Africa play an important role in the economy of the country, contributing 1.2% towards the gross domestic product. Currently plantation forests occupy 1.1% (1.2 million hectares) of the South African land surface, of which 75 000 hectares are re-established each year. Eucalypts constitute 43% of planted area, of which 88% is grown for pulpwood. Achieving high tree survival (>90%) is important in terms of optimising rotation-end yield. The industry origin of a 90% survival benchmark is unclear, although company procedures incorporate this as the minimum threshold in terms of re-establishment success. Past research indicates that most mortality occurs within a narrow period post-establishment and is often associated with substandard re-establishment practices and/or a stressed micro-environment. An improved understanding is needed about the various mitigation measures needed to minimize mortality during eucalypt re-establishment. Before making decisions related to mortality mitigation measures, comprehensive data are required as to their commercial applicability as well as outcomes from multiple trials that accurately quantify any impacts on tree survival and financial return. The overall purpose of this dissertation was the optimisation of Eucalyptus re-establishment practices for improved survival, growth and uniformity in South African pulpwood plantations. To achieve this, five inter-linked objectives were determined. The first objective was to highlight the most important factors contributing to increased mortality in eucalypt plantations during re-establishment. This was achieved through conducting a literature review. Citations were ranked in terms of credibility, with the importance ratings (derived from the literature sources) applied to the different factors affecting survival and growth during eucalypt re-establishment. Of the various factors impacting early eucalypt mortality, water stress and planting stock quality were considered highly important. The manner and quality of site preparation (soil and slash), planting practices (planting depth included), timing of planting (during dry, hot periods), various post-planting operations (incorrect fertiliser placement or herbicide drift) and insect pests and diseases also contribute to mortality, but to a lesser extent. These factors cannot be considered in isolation due to the complex interactions that exist between them and determining the primary causes of mortality can be elusive, especially as their impacts tend to be additive by nature. The second objective was to link survival to silvicultural treatments, site-related physiographic factors and climatic variables in South Africa. This was achieved by conducting an integrated analysis of 43 Eucalyptus trials. Of the seven re-establishment practices considered, watering, planting depth and fertiliser application were significant, with plant size, pitting method, residue management and insecticide application were not significant. However, when environmental variables were included within the analyses, there were significant site x treatment interactions for planting depth, plant size, residue management and fertiliser application. This highlights the importance of taking site related factors into consideration when interpreting the causes of mortality. The third objective was to determine the interaction between planting density and mortality on Eucalyptus growth, uniformity and financial yield at rotation end in South Africa. This was carried out to verify whether planting at different densities may be used as a preventative (before planting) mitigation measure. One trial was used to answer four keys sub-objectives: 1) The impact of three planting densities (1 102, 1 500, 1 959 SPH) with no mortality on yield at rotation-end; 2) The impact of mortality (0%, 10%, 20%, 30%, 40%) on rotation-end yield; 3) The quantification of tree performance when planting at a higher density and accepting a certain degree of mortality; and 4) The financial impact of different planting densities and mortality on rotation-end profit. Higher planting densities resulted in smaller individual trees, but with an increase in stand level performance. At rotation-end, lower mortality (0% and 10%) had significantly higher volumes ha-1 than the higher mortality (30% and 40%). Planting at higher densities (1 722 and 1 959 SPH) and accepting a certain degree of mortality resulted in non-significant differences for volume at rotation-end compared to the fully stocked 1 500 SPH treatment. A higher SPH resulted in a higher yield, but with an increase in estimated establishment/tending and harvesting costs. In contrast, an increase in mortality and/or lower SPH (in the absence of mortality) resulted in more variable stand growth, together with an increase in estimated machine harvesting productivity and reduced costs. Irrespective of SPH, the higher the mortality the greater the loss of income, with the best profit within each treatment related to full stocking (0% mortality). Within the higher panting densities, the profit gained following low mortality (10 and 20%) was similar to that of no mortality (0%), indicating that higher mortality may be tolerated when planting at higher densities, confirming the 90% survival threshold the industry aims to achieve post-establishment. The fourth objective was to determine if silviculture intervention (blanking at 1, 2 and 3 months or coppicing and interplanting at 6 months) will result in acceptable eucalypt stocking, if mortality is higher than 10% (remedial mitigation measure). Data from a re-establishment trial were analysed to determine which of the mitigation measures performed best in terms of stocking and growth. Coppicing and interplanting with larger plants was not a viable option as a mitigation measure for mortality as most of the coppice shoots have died. This may have been a result of frost. Although high re-establishment costs may be incurred, disaster clearing to waste followed by replanting is an option if mortality is unacceptably high (as opposed to leaving the stand as is). The results of this objective confirm that blanking as the current Best Operating Practice is still appropriate in South African forestry (i.e., try to have survival >90% and blank as soon as possible to retain >90% of stems). Blanked plants do contribute to volume, but for this to occur, blanking should be carried out within 4 weeks after planting to gain maximum benefit. In addition, it highlights the importance of implementing remedial mitigation measures to achieve >90% survival so as to gain maximum benefit. Using the outcomes from objectives 1-4, the fifth objective focussed on the development of a decision support system (DSS) for implementation of mitigation measures to improve survival within commercial eucalypt pulpwood plantations in South Africa. Improved survival starts with the implementation of good re-establishment practices and good quality planting stock. Mitigation measures for poor survival can be implemented either prior to re-establishment (before mortality occurs) or post re-establishment (after mortality has occurred). If poor survival still occurs after the implementation of good silviculture practices and pre-re-establishment mitigation practices (planting at higher densities), one should consider the various options available in terms of post re-establishment mitigation practices (remedial practices) such as blanking or replanting if mortality is high. Overall, the outcomes from this dissertation provide benchmark data and derived information as to the necessity for various mortality mitigation options within the commercial forestry sector in South Africa. In addition, the DSS will assist with decision making in terms of implementing the best silviculture practices and mitigation measures for improved survival during eucalypt re-establishment in South African pulpwood plantations. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Science & Management, 2024
- Full Text:
- Date Issued: 2024-12
- Authors: Hechter, Ullrich
- Date: 2024-12
- Subjects: Eucalyptus -- Regeneration -- South Africa , Forests and forestry -- Economic aspects , Forests and forestry
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/68862 , vital:77135
- Description: Commercial forestry plantations in South Africa play an important role in the economy of the country, contributing 1.2% towards the gross domestic product. Currently plantation forests occupy 1.1% (1.2 million hectares) of the South African land surface, of which 75 000 hectares are re-established each year. Eucalypts constitute 43% of planted area, of which 88% is grown for pulpwood. Achieving high tree survival (>90%) is important in terms of optimising rotation-end yield. The industry origin of a 90% survival benchmark is unclear, although company procedures incorporate this as the minimum threshold in terms of re-establishment success. Past research indicates that most mortality occurs within a narrow period post-establishment and is often associated with substandard re-establishment practices and/or a stressed micro-environment. An improved understanding is needed about the various mitigation measures needed to minimize mortality during eucalypt re-establishment. Before making decisions related to mortality mitigation measures, comprehensive data are required as to their commercial applicability as well as outcomes from multiple trials that accurately quantify any impacts on tree survival and financial return. The overall purpose of this dissertation was the optimisation of Eucalyptus re-establishment practices for improved survival, growth and uniformity in South African pulpwood plantations. To achieve this, five inter-linked objectives were determined. The first objective was to highlight the most important factors contributing to increased mortality in eucalypt plantations during re-establishment. This was achieved through conducting a literature review. Citations were ranked in terms of credibility, with the importance ratings (derived from the literature sources) applied to the different factors affecting survival and growth during eucalypt re-establishment. Of the various factors impacting early eucalypt mortality, water stress and planting stock quality were considered highly important. The manner and quality of site preparation (soil and slash), planting practices (planting depth included), timing of planting (during dry, hot periods), various post-planting operations (incorrect fertiliser placement or herbicide drift) and insect pests and diseases also contribute to mortality, but to a lesser extent. These factors cannot be considered in isolation due to the complex interactions that exist between them and determining the primary causes of mortality can be elusive, especially as their impacts tend to be additive by nature. The second objective was to link survival to silvicultural treatments, site-related physiographic factors and climatic variables in South Africa. This was achieved by conducting an integrated analysis of 43 Eucalyptus trials. Of the seven re-establishment practices considered, watering, planting depth and fertiliser application were significant, with plant size, pitting method, residue management and insecticide application were not significant. However, when environmental variables were included within the analyses, there were significant site x treatment interactions for planting depth, plant size, residue management and fertiliser application. This highlights the importance of taking site related factors into consideration when interpreting the causes of mortality. The third objective was to determine the interaction between planting density and mortality on Eucalyptus growth, uniformity and financial yield at rotation end in South Africa. This was carried out to verify whether planting at different densities may be used as a preventative (before planting) mitigation measure. One trial was used to answer four keys sub-objectives: 1) The impact of three planting densities (1 102, 1 500, 1 959 SPH) with no mortality on yield at rotation-end; 2) The impact of mortality (0%, 10%, 20%, 30%, 40%) on rotation-end yield; 3) The quantification of tree performance when planting at a higher density and accepting a certain degree of mortality; and 4) The financial impact of different planting densities and mortality on rotation-end profit. Higher planting densities resulted in smaller individual trees, but with an increase in stand level performance. At rotation-end, lower mortality (0% and 10%) had significantly higher volumes ha-1 than the higher mortality (30% and 40%). Planting at higher densities (1 722 and 1 959 SPH) and accepting a certain degree of mortality resulted in non-significant differences for volume at rotation-end compared to the fully stocked 1 500 SPH treatment. A higher SPH resulted in a higher yield, but with an increase in estimated establishment/tending and harvesting costs. In contrast, an increase in mortality and/or lower SPH (in the absence of mortality) resulted in more variable stand growth, together with an increase in estimated machine harvesting productivity and reduced costs. Irrespective of SPH, the higher the mortality the greater the loss of income, with the best profit within each treatment related to full stocking (0% mortality). Within the higher panting densities, the profit gained following low mortality (10 and 20%) was similar to that of no mortality (0%), indicating that higher mortality may be tolerated when planting at higher densities, confirming the 90% survival threshold the industry aims to achieve post-establishment. The fourth objective was to determine if silviculture intervention (blanking at 1, 2 and 3 months or coppicing and interplanting at 6 months) will result in acceptable eucalypt stocking, if mortality is higher than 10% (remedial mitigation measure). Data from a re-establishment trial were analysed to determine which of the mitigation measures performed best in terms of stocking and growth. Coppicing and interplanting with larger plants was not a viable option as a mitigation measure for mortality as most of the coppice shoots have died. This may have been a result of frost. Although high re-establishment costs may be incurred, disaster clearing to waste followed by replanting is an option if mortality is unacceptably high (as opposed to leaving the stand as is). The results of this objective confirm that blanking as the current Best Operating Practice is still appropriate in South African forestry (i.e., try to have survival >90% and blank as soon as possible to retain >90% of stems). Blanked plants do contribute to volume, but for this to occur, blanking should be carried out within 4 weeks after planting to gain maximum benefit. In addition, it highlights the importance of implementing remedial mitigation measures to achieve >90% survival so as to gain maximum benefit. Using the outcomes from objectives 1-4, the fifth objective focussed on the development of a decision support system (DSS) for implementation of mitigation measures to improve survival within commercial eucalypt pulpwood plantations in South Africa. Improved survival starts with the implementation of good re-establishment practices and good quality planting stock. Mitigation measures for poor survival can be implemented either prior to re-establishment (before mortality occurs) or post re-establishment (after mortality has occurred). If poor survival still occurs after the implementation of good silviculture practices and pre-re-establishment mitigation practices (planting at higher densities), one should consider the various options available in terms of post re-establishment mitigation practices (remedial practices) such as blanking or replanting if mortality is high. Overall, the outcomes from this dissertation provide benchmark data and derived information as to the necessity for various mortality mitigation options within the commercial forestry sector in South Africa. In addition, the DSS will assist with decision making in terms of implementing the best silviculture practices and mitigation measures for improved survival during eucalypt re-establishment in South African pulpwood plantations. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Science & Management, 2024
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- Date Issued: 2024-12