A 5G Communication system based on flexible spectrum technology for the SKA
- Authors: Karembera, Reinhard Siwombe
- Date: 2022-04
- Subjects: Mobile communication systems--Technological innovations , Wireless communication systems -- Standards --South Africa
- Language: English
- Type: Doctoral theses
- Identifier: http://hdl.handle.net/10948/56177 , vital:56013
- Description: Faculty of Science Radio astronomy research is rapidly expanding across the African continent. At the same time, the fifth generation (5G) of mobile communication systems are also being researched and developed. Throughout history, mobile communication networks are known to affect the activities of radio astronomy. If not carefully managed, radio frequencies from mobile communication devices can severely affect radio astronomy observations. To that end, many techniques have been proposed to protect the radio astronomer from RFIs coming from radio communication networks. Some of the proposed techniques such as RFI quite zones and spectrum assignment by regulatory authorities will not be convenient during the implementation of 5G mobile networks. This is because 5G radio communication systems are expected to support spectrum-hungry application such as video-on-demand, augmented realities, high-definition television and so on. To realize this, the 5G networks will be forced to have access to protected radio spectrum, including those at which radio astronomy activities are being researched. To facilitate this, the 5G radio communication networks should have the intelligence to coexist within such protected spectrums without the consequences of radio frequency interferences (RFI) to the primary user. In this thesis, we present novel 5G networks with the intelligence that allow them to coexist within radio astronomy areas without introducing RFIs to the primary user. We proposed a photonic solution, keeping in mind the characteristic requirements for future 5G radio communication networks. The thesis begins by reviewing the current trend of radio astronomy research in Africa. It was found that radio astronomy research in Africa is growing rapidly. Many African countries such as South Africa and Ghana are at advanced stages when it comes to radio astronomy research. Therefore, the finding and proposal of this thesis will be valuable to such countries. In order to develop a radio access network (RAN) that can coexist within radio astronomy areas, the thesis reviewed past and present state-of-the-art RANs. Each access network was analyses for its feasibility to be implemented within radio astronomy areas to realize mobile communication without the consequences of RFIs to the astronomer. It was motivated that the current centralized radio access network (C-RAN) the best solution to be developed for radio communication within radio astronomy areas. This is because the C-RAN architecture is centralized by pooling network resources to a common point. From such pool, network resources can be controlled and shared among 5G network user, including radio astronomers and the surrounding communities. The next chapters reviewed photonic RF transmitters and their associated lasers currently being proposed to be used within C-RANs. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Karembera, Reinhard Siwombe
- Date: 2022-04
- Subjects: Mobile communication systems--Technological innovations , Wireless communication systems -- Standards --South Africa
- Language: English
- Type: Doctoral theses
- Identifier: http://hdl.handle.net/10948/56177 , vital:56013
- Description: Faculty of Science Radio astronomy research is rapidly expanding across the African continent. At the same time, the fifth generation (5G) of mobile communication systems are also being researched and developed. Throughout history, mobile communication networks are known to affect the activities of radio astronomy. If not carefully managed, radio frequencies from mobile communication devices can severely affect radio astronomy observations. To that end, many techniques have been proposed to protect the radio astronomer from RFIs coming from radio communication networks. Some of the proposed techniques such as RFI quite zones and spectrum assignment by regulatory authorities will not be convenient during the implementation of 5G mobile networks. This is because 5G radio communication systems are expected to support spectrum-hungry application such as video-on-demand, augmented realities, high-definition television and so on. To realize this, the 5G networks will be forced to have access to protected radio spectrum, including those at which radio astronomy activities are being researched. To facilitate this, the 5G radio communication networks should have the intelligence to coexist within such protected spectrums without the consequences of radio frequency interferences (RFI) to the primary user. In this thesis, we present novel 5G networks with the intelligence that allow them to coexist within radio astronomy areas without introducing RFIs to the primary user. We proposed a photonic solution, keeping in mind the characteristic requirements for future 5G radio communication networks. The thesis begins by reviewing the current trend of radio astronomy research in Africa. It was found that radio astronomy research in Africa is growing rapidly. Many African countries such as South Africa and Ghana are at advanced stages when it comes to radio astronomy research. Therefore, the finding and proposal of this thesis will be valuable to such countries. In order to develop a radio access network (RAN) that can coexist within radio astronomy areas, the thesis reviewed past and present state-of-the-art RANs. Each access network was analyses for its feasibility to be implemented within radio astronomy areas to realize mobile communication without the consequences of RFIs to the astronomer. It was motivated that the current centralized radio access network (C-RAN) the best solution to be developed for radio communication within radio astronomy areas. This is because the C-RAN architecture is centralized by pooling network resources to a common point. From such pool, network resources can be controlled and shared among 5G network user, including radio astronomers and the surrounding communities. The next chapters reviewed photonic RF transmitters and their associated lasers currently being proposed to be used within C-RANs. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
A case study assessment of the ecological and social status of the South African boat-based whale watching industry
- Authors: Tolsma, Minke
- Date: 2022-04
- Subjects: Whale watching --South Africa , Dolphin watching
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55887 , vital:54397
- Description: Boat-based whale-watching (BBWW) is a rapidly growing marine tourism industry globally and in South Africa (SA). BBWW in SA was established in 1998, and since then the number of permits available has doubled from 20 to 40. However, the establishment and past growth of the industry was undertaken without ecological research or impact assessments. Global research has shown that BBWW has the potential to cause short-term changes in cetacean behaviour and movement, which in turn can have long-term population-level consequences. National policies to grow ocean economies in SA may encourage excessive growth in the BBWW industry, impacting the ecological sustainability. In the absence of long-term impact data, the BBWW industry should be managed to minimise short-term changes. This study aimed to determine the social and ecological status of the SA BBWW industry, using Plettenberg Bay as a case study, to inform its long term sustainability. To achieve this aim: 1) the short-term behavioural and movement responses of six cetacean species to encounters with commercial BBWW vessels were measured; 2) the efficacy of three permit regulations (approach speed, approach angle, and encounter duration) to prevent short-term behavioural changes in three cetacean species was measured; 3) rates of compliance of BBWWoperators with current regulations were recorded; 4) BBWW tourists’ expectations of and satisfaction with the industry were investigated; as well as 5) operators’ views on the current permit regulations of the industry All research was conducted between September 2018 and November 2020 in Plettenberg Bay (SA) where two BBWW companies operating two vessels each are active. Three dolphin (bottlenose, common and humpback dolphins) and three whale (Bryde’s, humpback and southern right whales) species are targeted by the industry, and were encountered during this study. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Tolsma, Minke
- Date: 2022-04
- Subjects: Whale watching --South Africa , Dolphin watching
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55887 , vital:54397
- Description: Boat-based whale-watching (BBWW) is a rapidly growing marine tourism industry globally and in South Africa (SA). BBWW in SA was established in 1998, and since then the number of permits available has doubled from 20 to 40. However, the establishment and past growth of the industry was undertaken without ecological research or impact assessments. Global research has shown that BBWW has the potential to cause short-term changes in cetacean behaviour and movement, which in turn can have long-term population-level consequences. National policies to grow ocean economies in SA may encourage excessive growth in the BBWW industry, impacting the ecological sustainability. In the absence of long-term impact data, the BBWW industry should be managed to minimise short-term changes. This study aimed to determine the social and ecological status of the SA BBWW industry, using Plettenberg Bay as a case study, to inform its long term sustainability. To achieve this aim: 1) the short-term behavioural and movement responses of six cetacean species to encounters with commercial BBWW vessels were measured; 2) the efficacy of three permit regulations (approach speed, approach angle, and encounter duration) to prevent short-term behavioural changes in three cetacean species was measured; 3) rates of compliance of BBWWoperators with current regulations were recorded; 4) BBWW tourists’ expectations of and satisfaction with the industry were investigated; as well as 5) operators’ views on the current permit regulations of the industry All research was conducted between September 2018 and November 2020 in Plettenberg Bay (SA) where two BBWW companies operating two vessels each are active. Three dolphin (bottlenose, common and humpback dolphins) and three whale (Bryde’s, humpback and southern right whales) species are targeted by the industry, and were encountered during this study. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
A Functional Data Analysis approach to understand patterns imbedded within various data types
- Authors: Mangisa, Siphumlile
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Data mining
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52091 , vital:43426
- Description: The thesis investigates the use of the novel Functional Data Analysis (FDA) methods in tackling various data types. Strong motivation is provided for the use of interesting opportunities offered by FDA to analyse not only economic data, but generally, data from any domain. The use of these methods is illustrated using three unique self-contained case-studies from econometrics. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Mangisa, Siphumlile
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Data mining
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52091 , vital:43426
- Description: The thesis investigates the use of the novel Functional Data Analysis (FDA) methods in tackling various data types. Strong motivation is provided for the use of interesting opportunities offered by FDA to analyse not only economic data, but generally, data from any domain. The use of these methods is illustrated using three unique self-contained case-studies from econometrics. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
A social media analytics framework for decision-making in citizen relationship management
- Authors: Yakobi, Khulekani
- Date: 2022-12
- Subjects: Social Media Analytics -- South Africa , Decision making --Mathematical models , Service delivery
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60048 , vital:62815
- Description: Globally social media has shown unprecedented levels of adoption and Social Media Analytics (SMA) is a rapidly growing topic. For governments, SMA holds the promise of providing tools and frameworks to collect, monitor, analyse and visualise social media data, usually driven by specific requirements from a target application. However, social media data is noisy and unstructured, and organisations struggle to extract knowledge from this data, and convert it into actual intelligence. This study argues that SMA can support intelligent decision-making for Citizen Relationship Management (CzRM). CzRM is a growing effort of governments around the world to strive to respond rapidly to their citizens by fostering a closer relationship thereby creating more effective and efficient service delivery. However, there is a little evidence in literature on empirical studies of any existing decision-making framework for CzRM and SMA adoption. In particular, there is a gap with regards incorporating SMA into decision-making for CzRM of governments, particularly in developing countries like South Africa. The aim of this study was to develop a framework that provides guidelines, including methods and tools, incorporating SMA into decision-making for CzRM in the Gauteng Provincial Government (GPG) and the Free State Provincial Government (FSPG) of South Africa. A Systematic Literature Review (SLR) and conceptual analysis method was conducted to design the Social Media Analytics Framework for Decision-making in the context of CzRM (the SMAF). The findings from the literature review revealed several benefits and challenges with SMA, in particular the shortage of skills, guidelines, methods and tools for SMA. These challenges were used to draft guidelines that were included in the framework, which consists of five components that can be used to derive intelligent information from SMA. The pragmatic philosophy and a case study design was used to generate an in-depth, multifaceted understanding of the underlying problems in the case of the GPG and the FSPG. The German North-West Metropolitan region was used as a third case study to provide a more global perspective and a case of a developed country in terms of Gross Domestic Product. The scope of the study was limited to social media posts by provincial citizens related to CzRM and service delivery. Both formative and summative evaluations of the proposed theoretical framework were conducted. The formative evaluation was conducted v | Page as an Expert Review to receive feedback of the framework from the experts in the field of Computer Science and Information Systems. The findings validated the framework and some minor improvements were made based on the experts’ recommendations. Focus Group Discussions (FGDs) with participants from government managers and decision makers in the three cases were conducted. Case documents for the three cases were collected and reviewed. All collected data was analysed using the Qualitative Content Analysis (QCA) method and common categories and themes were identified. Summative evaluations were conducted in the form of a Field Study, which consisted of an analysis of Twitter data from the three cases, and a closing FGD with Business Intelligence (BI) experts at the primary case of the e-Government department of the GPG. The findings revealed that SMA has been adopted in all three cases; however, while their strategies are comprehensive their implementations are very much in their early stages. The findings also highlighted the status of SMA in government and some potential gaps and areas for implementing the framework. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Yakobi, Khulekani
- Date: 2022-12
- Subjects: Social Media Analytics -- South Africa , Decision making --Mathematical models , Service delivery
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60048 , vital:62815
- Description: Globally social media has shown unprecedented levels of adoption and Social Media Analytics (SMA) is a rapidly growing topic. For governments, SMA holds the promise of providing tools and frameworks to collect, monitor, analyse and visualise social media data, usually driven by specific requirements from a target application. However, social media data is noisy and unstructured, and organisations struggle to extract knowledge from this data, and convert it into actual intelligence. This study argues that SMA can support intelligent decision-making for Citizen Relationship Management (CzRM). CzRM is a growing effort of governments around the world to strive to respond rapidly to their citizens by fostering a closer relationship thereby creating more effective and efficient service delivery. However, there is a little evidence in literature on empirical studies of any existing decision-making framework for CzRM and SMA adoption. In particular, there is a gap with regards incorporating SMA into decision-making for CzRM of governments, particularly in developing countries like South Africa. The aim of this study was to develop a framework that provides guidelines, including methods and tools, incorporating SMA into decision-making for CzRM in the Gauteng Provincial Government (GPG) and the Free State Provincial Government (FSPG) of South Africa. A Systematic Literature Review (SLR) and conceptual analysis method was conducted to design the Social Media Analytics Framework for Decision-making in the context of CzRM (the SMAF). The findings from the literature review revealed several benefits and challenges with SMA, in particular the shortage of skills, guidelines, methods and tools for SMA. These challenges were used to draft guidelines that were included in the framework, which consists of five components that can be used to derive intelligent information from SMA. The pragmatic philosophy and a case study design was used to generate an in-depth, multifaceted understanding of the underlying problems in the case of the GPG and the FSPG. The German North-West Metropolitan region was used as a third case study to provide a more global perspective and a case of a developed country in terms of Gross Domestic Product. The scope of the study was limited to social media posts by provincial citizens related to CzRM and service delivery. Both formative and summative evaluations of the proposed theoretical framework were conducted. The formative evaluation was conducted v | Page as an Expert Review to receive feedback of the framework from the experts in the field of Computer Science and Information Systems. The findings validated the framework and some minor improvements were made based on the experts’ recommendations. Focus Group Discussions (FGDs) with participants from government managers and decision makers in the three cases were conducted. Case documents for the three cases were collected and reviewed. All collected data was analysed using the Qualitative Content Analysis (QCA) method and common categories and themes were identified. Summative evaluations were conducted in the form of a Field Study, which consisted of an analysis of Twitter data from the three cases, and a closing FGD with Business Intelligence (BI) experts at the primary case of the e-Government department of the GPG. The findings revealed that SMA has been adopted in all three cases; however, while their strategies are comprehensive their implementations are very much in their early stages. The findings also highlighted the status of SMA in government and some potential gaps and areas for implementing the framework. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
A theoretical study of alkoxyl radical and radical cation mediated cyclisation reactions in unsaturated alkanols
- Authors: Lee, Peter Mattison Clarke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Density functionals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52130 , vital:43430
- Description: A large part of this computational study focussed on selectivity patterns for 4-penten- 1-oxyl radical 1,5- and 1,6-cyclisations and for those of analogous 5-hexenyl, 4- penten-1-aminyl, 4-penten-1-iminyl and 3-phenylpropan-1-oxyl radicals. The study furthermore included cyclisation reactions of the radical cations of 4-penten-1-ol and 3-phenylpropan-1-ol. Calculations were performed for all applicable species involved in the two cyclisation modes studied, i.e. 1,5- and 1,6-cyclisation. These species included radical and radical cation precursors, as well as relevant radical transition state structures and radical adducts. All cyclisation systems investigated used the Density Functional Theory (DFT) functional B3LYP with a combination of eight basis sets. Each basis set used was a progressively higher level of theory than B3LYP/6-31G* which was used as a starting point. Cyclisations for unsubstituted species, e.g. the 4-penten-1-oxyl radical 1,5- and 1,6-cyclisations, were also simulated using the ωB97X-D and ωB97X-V functionals which account for dispersive effects. The same set of eight basis sets were used with these two functionals. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Lee, Peter Mattison Clarke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Density functionals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52130 , vital:43430
- Description: A large part of this computational study focussed on selectivity patterns for 4-penten- 1-oxyl radical 1,5- and 1,6-cyclisations and for those of analogous 5-hexenyl, 4- penten-1-aminyl, 4-penten-1-iminyl and 3-phenylpropan-1-oxyl radicals. The study furthermore included cyclisation reactions of the radical cations of 4-penten-1-ol and 3-phenylpropan-1-ol. Calculations were performed for all applicable species involved in the two cyclisation modes studied, i.e. 1,5- and 1,6-cyclisation. These species included radical and radical cation precursors, as well as relevant radical transition state structures and radical adducts. All cyclisation systems investigated used the Density Functional Theory (DFT) functional B3LYP with a combination of eight basis sets. Each basis set used was a progressively higher level of theory than B3LYP/6-31G* which was used as a starting point. Cyclisations for unsubstituted species, e.g. the 4-penten-1-oxyl radical 1,5- and 1,6-cyclisations, were also simulated using the ωB97X-D and ωB97X-V functionals which account for dispersive effects. The same set of eight basis sets were used with these two functionals. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
An efficient approach for the synthesis of dolutegravir and its analogue exploiting flow chemistry
- Authors: Nqeketo, Sinazo
- Date: 2023-04
- Subjects: HIV (Viruses) – Enzymes –Inhibitors , Antiviral agents -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:70635
- Description: Africa has the highest Human Immunodeficiency Virus (HIV) prevalence in the world and has invested heavily in running its HIV programmes and conducting research of medical significance. Despite efforts in combating this disease the production, distribution, cost, and availability of antiretroviral (ARV) generics remains a major problem as they are imported from China and India. Exploring the recently emerged “enabling technique”, namely flow chemistry in the production of APIs has gained a lot of attention. This study was devoted on exploring the application of flow chemistry on the synthesis of a newly approved anti-HIV drug dolutegravir (DTG); an integrase inhibitor with a high genetic barrier to resistance with a daily dosing scheduled compared to other ARVs and its third-generation inhibitor analogue, cabotegravir. Chapter one covers a comprehensive background and literature review of the HIV epidemic, an introduction of antiretroviral therapy as well as detailed dolutegravir and cabotegravir synthesis. A brief introduction of continuous flow technology with its advantages and disadvantages is discussed in this chapter. The efficient seven-step continuous flow procedure afforded dolutegravir and cabotegravir in improved reaction times and yields compared to the traditional batch procedure was demonstrated. The significant advantage of this flow process includes the reduction of the overall reaction time from step one to step seven, from prolonged 68 hours in batch to 34 minutes. The overall yield of each reaction step improved dramatically upon flow optimization. The yields of the second step (selective ester hydrolysis), fourth step (cyclization) and fifth step (amidation) increased from 64 %, 40 % and 33 % in batch to 98 %, 71 % and 100 % yield by HPLC respectively. Other than improved yields and residence times which was aided advantages of microreactor technology including intensive mixing, the flow process is also much better because it is cost effective. Most importantly, a novel process on the formation of pyridinone intermediate using ion-exchange resin catalysts towards the synthesis of dolutegravir and cabotegravir was described in this study , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Science, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Nqeketo, Sinazo
- Date: 2023-04
- Subjects: HIV (Viruses) – Enzymes –Inhibitors , Antiviral agents -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:70635
- Description: Africa has the highest Human Immunodeficiency Virus (HIV) prevalence in the world and has invested heavily in running its HIV programmes and conducting research of medical significance. Despite efforts in combating this disease the production, distribution, cost, and availability of antiretroviral (ARV) generics remains a major problem as they are imported from China and India. Exploring the recently emerged “enabling technique”, namely flow chemistry in the production of APIs has gained a lot of attention. This study was devoted on exploring the application of flow chemistry on the synthesis of a newly approved anti-HIV drug dolutegravir (DTG); an integrase inhibitor with a high genetic barrier to resistance with a daily dosing scheduled compared to other ARVs and its third-generation inhibitor analogue, cabotegravir. Chapter one covers a comprehensive background and literature review of the HIV epidemic, an introduction of antiretroviral therapy as well as detailed dolutegravir and cabotegravir synthesis. A brief introduction of continuous flow technology with its advantages and disadvantages is discussed in this chapter. The efficient seven-step continuous flow procedure afforded dolutegravir and cabotegravir in improved reaction times and yields compared to the traditional batch procedure was demonstrated. The significant advantage of this flow process includes the reduction of the overall reaction time from step one to step seven, from prolonged 68 hours in batch to 34 minutes. The overall yield of each reaction step improved dramatically upon flow optimization. The yields of the second step (selective ester hydrolysis), fourth step (cyclization) and fifth step (amidation) increased from 64 %, 40 % and 33 % in batch to 98 %, 71 % and 100 % yield by HPLC respectively. Other than improved yields and residence times which was aided advantages of microreactor technology including intensive mixing, the flow process is also much better because it is cost effective. Most importantly, a novel process on the formation of pyridinone intermediate using ion-exchange resin catalysts towards the synthesis of dolutegravir and cabotegravir was described in this study , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Science, 2023
- Full Text:
- Date Issued: 2023-04
An evaluation of the effectiveness of area-based conservation interventions in avoiding biodiversity loss in South Africa
- Authors: Von Staden, Lize
- Date: 2023-04
- Subjects: Environmental policy , Conservation of natural resources -- Government policy -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61115 , vital:69762
- Description: Counterfactual impact evaluation studies form an important evidence base for the effectiveness of conservation projects, programs, and policies (collectively referred to as conservation interventions). In South Africa, counterfactual impact evaluation methods have rarely been applied to local conservation interventions, and therefore evidence for the effectiveness of key strategic national conservation approaches is lacking. This study evaluated three area-based interventions that together aim to avoid the loss of areas most important for the persistence of biodiversity in the terrestrial realm as evidence towards the effectiveness of South Africa’s landscape approach to biodiversity conservation. The first intervention, South Africa’s National Protected Area Expansion Strategy (NPAES), set ambitious targets to double the extent of South Africa’s protected area network while ensuring that the expansion preferentially occurs in areas of under-represented biodiversity. The strategy was evaluated in terms of its effectiveness in guiding protected area expansion towards more equitable representation of South Africa’s biodiversity through an assessment of changes in indicators of protected area expansion decision-making before and after the implementation of the strategy. The second intervention is the use of maps of biodiversity priorities to guide land use change decisions outside protected areas. Impact was evaluated as avoided loss of Critical Biodiversity Areas (CBAs), which need to remain in a natural condition to meet in situ conservation targets for species, ecosystems, and ecological processes. Avoided loss in CBAs was benchmarked against avoided loss in protected areas, to contextualize the effectiveness of land use planning as a conservation intervention. Lastly, the effectiveness of stricter land use regulations for threatened ecosystems to reduce land conversion pressure on these ecosystems was evaluated. Key findings were that protected areas are highly effective conservation interventions where they can be implemented, but their capacity for conservation impact is limited by severe constraints on strategic expansion. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Von Staden, Lize
- Date: 2023-04
- Subjects: Environmental policy , Conservation of natural resources -- Government policy -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61115 , vital:69762
- Description: Counterfactual impact evaluation studies form an important evidence base for the effectiveness of conservation projects, programs, and policies (collectively referred to as conservation interventions). In South Africa, counterfactual impact evaluation methods have rarely been applied to local conservation interventions, and therefore evidence for the effectiveness of key strategic national conservation approaches is lacking. This study evaluated three area-based interventions that together aim to avoid the loss of areas most important for the persistence of biodiversity in the terrestrial realm as evidence towards the effectiveness of South Africa’s landscape approach to biodiversity conservation. The first intervention, South Africa’s National Protected Area Expansion Strategy (NPAES), set ambitious targets to double the extent of South Africa’s protected area network while ensuring that the expansion preferentially occurs in areas of under-represented biodiversity. The strategy was evaluated in terms of its effectiveness in guiding protected area expansion towards more equitable representation of South Africa’s biodiversity through an assessment of changes in indicators of protected area expansion decision-making before and after the implementation of the strategy. The second intervention is the use of maps of biodiversity priorities to guide land use change decisions outside protected areas. Impact was evaluated as avoided loss of Critical Biodiversity Areas (CBAs), which need to remain in a natural condition to meet in situ conservation targets for species, ecosystems, and ecological processes. Avoided loss in CBAs was benchmarked against avoided loss in protected areas, to contextualize the effectiveness of land use planning as a conservation intervention. Lastly, the effectiveness of stricter land use regulations for threatened ecosystems to reduce land conversion pressure on these ecosystems was evaluated. Key findings were that protected areas are highly effective conservation interventions where they can be implemented, but their capacity for conservation impact is limited by severe constraints on strategic expansion. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
An exploration of the Participatory Guarantee System (PGS) facilitating the growth and certification of small-scale organic farmers: Giyani, Garden Route and Overberg case studies
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
Applying a systems analysis approach to support marine spatial planning in Algoa Bay, South Africa
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
Cape Vultures (Gyps coprotheres) and the threat of wind farms: a race to extinction?
- Authors: Brooke, Francis Rae
- Date: 2022-04
- Subjects: Wind Turbines --Blades --Materials , Gyps --South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55910 , vital:54399
- Description: The development of wind energy is increasing globally and is often considered more environmentally friendly when compared to fossil fuel technologies. However, one of the ecological drawbacks of wind energy are the collisions of wildlife with turbine blades. In addition, the resulting anthropogenic landscape transformation can negatively impact populations. The Cape Vulture (Gyps coprotheres), a large endangered southern African endemic species, thus may be at risk from turbine development. The species has decreased dramatically in the past 50 years and understanding how additional mortalities from wind turbine impacts affect the population is needed to ensure effective conservation efforts. This study aimed to determine the population response to this emerging threat. This study first reviewed the species-, site- and wind farm- specific traits that make Gyps species vulnerable to collision with wind energy infrastructure. It examined the monitoring practices employed during the pre- and post-construction phase and mitigation measures in South Africa and compared it with international standards. Furthermore, wind energy development may disrupt landscape connectivity and understanding which, and how habitat patches are used is needed. Using network theory combined with telemetry data from tagged individuals across three age classes, habitat patch use was identified. Further, environmental variables associated with identified habitat patches were identified. Additionally, considering the wind energy industry is expanding in South Africa, exploring how the Cape Vulture population will respond to this novel and emerging threat may aid future conservation management plans. Therefore, using a population viability analysis approach, the study explored how present and future wind turbine mortality scenarios impact the Cape Vulture population and how the population will respond to increased wind turbine development. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Brooke, Francis Rae
- Date: 2022-04
- Subjects: Wind Turbines --Blades --Materials , Gyps --South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55910 , vital:54399
- Description: The development of wind energy is increasing globally and is often considered more environmentally friendly when compared to fossil fuel technologies. However, one of the ecological drawbacks of wind energy are the collisions of wildlife with turbine blades. In addition, the resulting anthropogenic landscape transformation can negatively impact populations. The Cape Vulture (Gyps coprotheres), a large endangered southern African endemic species, thus may be at risk from turbine development. The species has decreased dramatically in the past 50 years and understanding how additional mortalities from wind turbine impacts affect the population is needed to ensure effective conservation efforts. This study aimed to determine the population response to this emerging threat. This study first reviewed the species-, site- and wind farm- specific traits that make Gyps species vulnerable to collision with wind energy infrastructure. It examined the monitoring practices employed during the pre- and post-construction phase and mitigation measures in South Africa and compared it with international standards. Furthermore, wind energy development may disrupt landscape connectivity and understanding which, and how habitat patches are used is needed. Using network theory combined with telemetry data from tagged individuals across three age classes, habitat patch use was identified. Further, environmental variables associated with identified habitat patches were identified. Additionally, considering the wind energy industry is expanding in South Africa, exploring how the Cape Vulture population will respond to this novel and emerging threat may aid future conservation management plans. Therefore, using a population viability analysis approach, the study explored how present and future wind turbine mortality scenarios impact the Cape Vulture population and how the population will respond to increased wind turbine development. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Chemical analysis of selected Eastern Cape medicinal plants
- Authors: Mahanjana, Lungelwa
- Date: 2022-04
- Subjects: Medicinal plants -- South Africa --Eastern Cape , Traditional medicine --South Africa -- Eastern Cape Maps
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55976 , vital:54560
- Description: In the rural parts of the Eastern Cape Province of South Africa, the use of medicinal plants to treat or manage diseases, including those associated with diabetes and HIV, is a common practice. However, the phytochemistry, safety and efficacy of these medicinal plants remain less investigated. Based on available traditional medicinal knowledge (through traditional healers, university library resources, ethnobotanical and science journals and other internet resources), traditional uses and availability, three plant species, namely Bulbine latifolia L. Wild, Dicerothamnus rhinocerotis Koek. and Olea europaea subsp. africana (Mill.) P.S. Green were selected and investigated for their hytoconstituents and biological effects. Phytochemical screening of the three medicinal plants was carried out quantitatively and qualitatively using spectrophotometric methods. Chemical profiling of the crude methanol extracts of all the plant species was successfully done by high-performance thin layer chromatography (HPTLC) and tentative identification of the secondary metabolites was achieved by liquid chromatography–mass spectrometry (LCMS). Cytotoxicity effect investigations on the crude extracts of the three species was done using the 3-[4,5- dimethylthiazole-2-yl]-2,5- hiphenyltetrazolium bromide (MTT) assay against HeLa cervical cancer cells. Isolation and purification of single compounds was done using chromatographic techniques (column chromatography (CC), and preparative thin-layer chromatography (PTLC)). Characterisation of single compounds was achieved using spectroscopic techniques such as Nuclear Magnetic Resonance (NMR), High Resolution Mass Spectrometry (HRMS), Ultra Violet Spectroscopy (UV-vis), Fourier-Transformed Infra-Red Spectroscopy (FTIR) and Single-Crystal X-ray Diffraction (XRD). For the first time from the methanol crude extract of the tubers of B. latifolia, the crystal structure of the phenylanthraquinone, knipholone (3.12) (1-(3-acetyl-2,6- dihydroxy-4- methoxyphenyl)-4,5-dihydroxy-2-methylanthraquinone), was isolated and elucidated along with its derivatives, isoknipholone (3.14), knipholone-6’-methyl (3.27). Moreover, two new compounds, (M)-8-O-β-D-glucopyranosyl-10’-α-L-rhamnopyranosyl-1,1',8',10'-tetrahydroxy 3,3'-dimethyl-[10,7'-bianthracene]-4,9,9'(10'H)-trione (3.23a) and (P)- 8-O-β-D glucopyranosyl-10’-α-L-rhamnopyranosyl-1,1',8',10'-tetrahydroxy-3,3'-dimethyl-[10,7'- bianthracene]-4,9,9'(10'H)-trione (3.23b) were isolated. , Thesis (PhD) -- Faculty of Science, School of Biomecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Mahanjana, Lungelwa
- Date: 2022-04
- Subjects: Medicinal plants -- South Africa --Eastern Cape , Traditional medicine --South Africa -- Eastern Cape Maps
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55976 , vital:54560
- Description: In the rural parts of the Eastern Cape Province of South Africa, the use of medicinal plants to treat or manage diseases, including those associated with diabetes and HIV, is a common practice. However, the phytochemistry, safety and efficacy of these medicinal plants remain less investigated. Based on available traditional medicinal knowledge (through traditional healers, university library resources, ethnobotanical and science journals and other internet resources), traditional uses and availability, three plant species, namely Bulbine latifolia L. Wild, Dicerothamnus rhinocerotis Koek. and Olea europaea subsp. africana (Mill.) P.S. Green were selected and investigated for their hytoconstituents and biological effects. Phytochemical screening of the three medicinal plants was carried out quantitatively and qualitatively using spectrophotometric methods. Chemical profiling of the crude methanol extracts of all the plant species was successfully done by high-performance thin layer chromatography (HPTLC) and tentative identification of the secondary metabolites was achieved by liquid chromatography–mass spectrometry (LCMS). Cytotoxicity effect investigations on the crude extracts of the three species was done using the 3-[4,5- dimethylthiazole-2-yl]-2,5- hiphenyltetrazolium bromide (MTT) assay against HeLa cervical cancer cells. Isolation and purification of single compounds was done using chromatographic techniques (column chromatography (CC), and preparative thin-layer chromatography (PTLC)). Characterisation of single compounds was achieved using spectroscopic techniques such as Nuclear Magnetic Resonance (NMR), High Resolution Mass Spectrometry (HRMS), Ultra Violet Spectroscopy (UV-vis), Fourier-Transformed Infra-Red Spectroscopy (FTIR) and Single-Crystal X-ray Diffraction (XRD). For the first time from the methanol crude extract of the tubers of B. latifolia, the crystal structure of the phenylanthraquinone, knipholone (3.12) (1-(3-acetyl-2,6- dihydroxy-4- methoxyphenyl)-4,5-dihydroxy-2-methylanthraquinone), was isolated and elucidated along with its derivatives, isoknipholone (3.14), knipholone-6’-methyl (3.27). Moreover, two new compounds, (M)-8-O-β-D-glucopyranosyl-10’-α-L-rhamnopyranosyl-1,1',8',10'-tetrahydroxy 3,3'-dimethyl-[10,7'-bianthracene]-4,9,9'(10'H)-trione (3.23a) and (P)- 8-O-β-D glucopyranosyl-10’-α-L-rhamnopyranosyl-1,1',8',10'-tetrahydroxy-3,3'-dimethyl-[10,7'- bianthracene]-4,9,9'(10'H)-trione (3.23b) were isolated. , Thesis (PhD) -- Faculty of Science, School of Biomecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Coordination polymers for denitrogenation of fuel oils
- Authors: Dembaremba, Tendai O
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53630 , vital:45682
- Description: In this thesis, we present adsorptive removal of nitrogen-containing compounds from fuel oil as an alternative to complement conventional hydrotreatment to obtain ultra-low sulfur and nitrogen levels. This is in cognizance of the challenges nitrogen-containing compounds pose to the hydrotreatment process, particularly their inhibition and/or poisoning of the catalysts used in the process, of which basic nitrogen-containing compounds are the major culprits. Selectivity is the biggest challenge for adsorptive removal of nitrogen-containing compounds. We explore reticular synthesis of metal organic frameworks and the use of coordinatively unsaturated metal sites in 1-dimensional coordination polymers to achieve good selectivity for nitrogen-containing compounds. In the first part of the thesis, reticular synthesis of metal organic frameworks to control the size of the cavity, and strategically use the linkers and metal centres was envisaged. In this work we explored variation of the metal centres in the secondary building units (SBUs of the MOFs as the first step to the testing and implementation of the design strategies. Carbazole, representing carbazoles which the major compounds that remain in hydrotreated fuel, was the target compound. Four MOFs of zinc (Zn-CDC-bpe), copper (Cu-CDC-bpe), nickel (Ni-CDC-bpe) and cobalt (Co-CDC-bpe) based on the formation of a dinuclear metal paddlewheel SBUs with the ligand 9H-Carbazole-3,6-dicarboxylic acid (H2CDC) and occupation of the axial positions of the paddlewheel by 1,2-Bis(4-pyridyl)ethane (bpe) to form porous networks were synthesized. A fifth MOF containing only CDC which forms a [Zn4O(O2C-R)5(O2HC-R)] SBU was also synthesized (Zn-CDC). The ligand H2CDC was inspired by the possibility of improving selectivity for carbazole via π–π interactions through the more preferred parallel-offset stacking as well as the possibility for further substitution of the carbazole N-H to add groups that improve selectivity. The sizes of the MOF cavities can then be controlled by choosing different lengths of ligands analogous to 1,2-Bis(4-pyridyl)ethane (bpe), e.g. 4,4’-bipyridine and pyrazine. All the MOFs showed good selectivity of carbazole. The Zn-CDC MOF also had good selectivity for the basic nitrogen-containing compounds tested: quinoline, isoquinoline, quinaldine and 1-naphthylamine. Its uptake of carbazole was also slightly higher. This was attributed to the presence of an unsaturated Zn site in the SBU. Adsorption in all the MOFs was primarily due to physisorption. It was concluded that the role of the metal centre does not play a significant role in the adsorption of carbazole besides providing a template for reticular synthesis. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Dembaremba, Tendai O
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53630 , vital:45682
- Description: In this thesis, we present adsorptive removal of nitrogen-containing compounds from fuel oil as an alternative to complement conventional hydrotreatment to obtain ultra-low sulfur and nitrogen levels. This is in cognizance of the challenges nitrogen-containing compounds pose to the hydrotreatment process, particularly their inhibition and/or poisoning of the catalysts used in the process, of which basic nitrogen-containing compounds are the major culprits. Selectivity is the biggest challenge for adsorptive removal of nitrogen-containing compounds. We explore reticular synthesis of metal organic frameworks and the use of coordinatively unsaturated metal sites in 1-dimensional coordination polymers to achieve good selectivity for nitrogen-containing compounds. In the first part of the thesis, reticular synthesis of metal organic frameworks to control the size of the cavity, and strategically use the linkers and metal centres was envisaged. In this work we explored variation of the metal centres in the secondary building units (SBUs of the MOFs as the first step to the testing and implementation of the design strategies. Carbazole, representing carbazoles which the major compounds that remain in hydrotreated fuel, was the target compound. Four MOFs of zinc (Zn-CDC-bpe), copper (Cu-CDC-bpe), nickel (Ni-CDC-bpe) and cobalt (Co-CDC-bpe) based on the formation of a dinuclear metal paddlewheel SBUs with the ligand 9H-Carbazole-3,6-dicarboxylic acid (H2CDC) and occupation of the axial positions of the paddlewheel by 1,2-Bis(4-pyridyl)ethane (bpe) to form porous networks were synthesized. A fifth MOF containing only CDC which forms a [Zn4O(O2C-R)5(O2HC-R)] SBU was also synthesized (Zn-CDC). The ligand H2CDC was inspired by the possibility of improving selectivity for carbazole via π–π interactions through the more preferred parallel-offset stacking as well as the possibility for further substitution of the carbazole N-H to add groups that improve selectivity. The sizes of the MOF cavities can then be controlled by choosing different lengths of ligands analogous to 1,2-Bis(4-pyridyl)ethane (bpe), e.g. 4,4’-bipyridine and pyrazine. All the MOFs showed good selectivity of carbazole. The Zn-CDC MOF also had good selectivity for the basic nitrogen-containing compounds tested: quinoline, isoquinoline, quinaldine and 1-naphthylamine. Its uptake of carbazole was also slightly higher. This was attributed to the presence of an unsaturated Zn site in the SBU. Adsorption in all the MOFs was primarily due to physisorption. It was concluded that the role of the metal centre does not play a significant role in the adsorption of carbazole besides providing a template for reticular synthesis. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-12
Corrosion and hydrogen resistant modified zirlo surfaces for nuclear fuel cladding
- Authors: Ngongo, Sinoyolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54077 , vital:46252
- Description: Zirconium (Zr) alloys are used as fuel cladding material in all modern water cooled commercial nuclear reactors. Zr alloys have many desirable properties for the nuclear reactor core environment, however, it also has a weakness in that overheated zirconium alloy fuel rods react with hot steam resulting in the release of hydrogen. High temperatures increase the oxidation rate and hence the hydrogen production rate which in turn increase the risk of a hydrogen gas explosion such as what is surmised to have happened in the 2011 Fukushima Daiichi nuclear plant incident. The some of the hydrogen produced will also diffuse into the zirconium alloy and form zirconium hydrides which will weaken the original zirconium alloy material. The development of accident tolerant fuel became a major focus area after the Fukushima event in March 2011 with the U.S. congress directing the U.S. Department of Energy to develop fuel with enhanced accident tolerance at high temperatures. The main objective in the case of zirconium alloy cladding has been the modification of cladding surface layers by coating or doping in order to reduce the oxidation rate and hydrogen generation rate by the reaction of steam with zirconium alloy cladding at high temperatures. This thesis focuses on two surface modifications to decrease the surface corrosion rate of ZIRLOTM (the Zr alloy used in this study) and reduce hydrogen uptake by ZIRLO. The first modification involves an oxidation-resistant nano-crystalline diamond (NCD) film deposited on ZIRLO. The NCD layer was deposited in a microwave plasma-enhanced linear antenna chemical vapor deposition (MW-LA-PECVD) system after immersion of the ZIRLO tubes in a water-based solution containing nanodiamonds. ZIRLO tube samples were coated with 200 nm and 500 nm thick NCD layers. The 200 nm thick NCD coated ZIRLO was kept as control sample whereas the 500 nm thick NCD coated ZIRLO was exposed to steam oxidation at 360 °C for 90 days. The results revealed that the NCD exfoliated in some areas leaving the ZIRLO exposed to the steam. In the areas where the diamond did not exfoliate, the diamond was still attached to the ZIRLO with an amorphous carbon layer present between the NCD and the zirconium oxide layer.The transmission electron microscopy (TEM) results of this study indicate the presence a sp3 – hybridised diamond phase for the NCD layer as well as an intermediate amorphous carbon layer between the NCD and ZrO2 layers. Analyses of the area where the NCD layer had exfoliated showed no evidence of an NCD layer. It is possible that the amorphous carbon layer between the diamond and the zirconium oxide is responsible for weak interfacial bonding leading to partial exfoliation during oxidation in steam 360 °C for 90 days. In the second modification, the effectiveness of a Cr doped ZrO2 layer to reduce the migration rate of hydrogen in ZrO2 was investigated. The ZIRLO tube used for this part of the study did not have a thin oxide passivation surface layer. Two different procedures were used to create chromium doped zirconium oxide surface layers on ZIRLO. The ZIRLO surface was coated with chromium using cathodic arc deposition followed compression plasma flow (CPF) treatment to facilitate intermixing of the Cr and the ZIRLO. In procedure 1, the surface modification was achieved through the incorporation of chromium into the zirconium surface layer using a compression plasma flow (CPF) technique, followed by the oxidation of the chromium doped zirconium. The oxidation process was conducted at 500 °C for 6 hours. In procedure 2, the chromium was incorporated into the zirconium oxide layer again using the CPF technique. Hydrogen desorption was measured from pure ZIRLO and CPF modified samples using a special gas reaction controller system. The key finding of the results is that the chromium doped (incorporated) zirconium oxide layer on ZIRLO sample exhibited the lowest hydrogen desorption rate of all the samples analysed. This indicates that H in the Cr doped zirconium oxide layer had the lowest mobility of all the samples investigated. This is consistent with the theoretical predictions that the doping of ZrO2 by Cr reduces the solubility of hydrogen in ZrO2. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Ngongo, Sinoyolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54077 , vital:46252
- Description: Zirconium (Zr) alloys are used as fuel cladding material in all modern water cooled commercial nuclear reactors. Zr alloys have many desirable properties for the nuclear reactor core environment, however, it also has a weakness in that overheated zirconium alloy fuel rods react with hot steam resulting in the release of hydrogen. High temperatures increase the oxidation rate and hence the hydrogen production rate which in turn increase the risk of a hydrogen gas explosion such as what is surmised to have happened in the 2011 Fukushima Daiichi nuclear plant incident. The some of the hydrogen produced will also diffuse into the zirconium alloy and form zirconium hydrides which will weaken the original zirconium alloy material. The development of accident tolerant fuel became a major focus area after the Fukushima event in March 2011 with the U.S. congress directing the U.S. Department of Energy to develop fuel with enhanced accident tolerance at high temperatures. The main objective in the case of zirconium alloy cladding has been the modification of cladding surface layers by coating or doping in order to reduce the oxidation rate and hydrogen generation rate by the reaction of steam with zirconium alloy cladding at high temperatures. This thesis focuses on two surface modifications to decrease the surface corrosion rate of ZIRLOTM (the Zr alloy used in this study) and reduce hydrogen uptake by ZIRLO. The first modification involves an oxidation-resistant nano-crystalline diamond (NCD) film deposited on ZIRLO. The NCD layer was deposited in a microwave plasma-enhanced linear antenna chemical vapor deposition (MW-LA-PECVD) system after immersion of the ZIRLO tubes in a water-based solution containing nanodiamonds. ZIRLO tube samples were coated with 200 nm and 500 nm thick NCD layers. The 200 nm thick NCD coated ZIRLO was kept as control sample whereas the 500 nm thick NCD coated ZIRLO was exposed to steam oxidation at 360 °C for 90 days. The results revealed that the NCD exfoliated in some areas leaving the ZIRLO exposed to the steam. In the areas where the diamond did not exfoliate, the diamond was still attached to the ZIRLO with an amorphous carbon layer present between the NCD and the zirconium oxide layer.The transmission electron microscopy (TEM) results of this study indicate the presence a sp3 – hybridised diamond phase for the NCD layer as well as an intermediate amorphous carbon layer between the NCD and ZrO2 layers. Analyses of the area where the NCD layer had exfoliated showed no evidence of an NCD layer. It is possible that the amorphous carbon layer between the diamond and the zirconium oxide is responsible for weak interfacial bonding leading to partial exfoliation during oxidation in steam 360 °C for 90 days. In the second modification, the effectiveness of a Cr doped ZrO2 layer to reduce the migration rate of hydrogen in ZrO2 was investigated. The ZIRLO tube used for this part of the study did not have a thin oxide passivation surface layer. Two different procedures were used to create chromium doped zirconium oxide surface layers on ZIRLO. The ZIRLO surface was coated with chromium using cathodic arc deposition followed compression plasma flow (CPF) treatment to facilitate intermixing of the Cr and the ZIRLO. In procedure 1, the surface modification was achieved through the incorporation of chromium into the zirconium surface layer using a compression plasma flow (CPF) technique, followed by the oxidation of the chromium doped zirconium. The oxidation process was conducted at 500 °C for 6 hours. In procedure 2, the chromium was incorporated into the zirconium oxide layer again using the CPF technique. Hydrogen desorption was measured from pure ZIRLO and CPF modified samples using a special gas reaction controller system. The key finding of the results is that the chromium doped (incorporated) zirconium oxide layer on ZIRLO sample exhibited the lowest hydrogen desorption rate of all the samples analysed. This indicates that H in the Cr doped zirconium oxide layer had the lowest mobility of all the samples investigated. This is consistent with the theoretical predictions that the doping of ZrO2 by Cr reduces the solubility of hydrogen in ZrO2. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
Descriptive analysis of organic farming systems and factors affecting adoption and disadoption in Zambia : a case study
- Authors: Munthali, Robert
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic farming -- Zambia
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52111 , vital:43434
- Description: The last 30 years since the early 1990s has seen the heightened promotion of organic farming as a sustainable farming option in Zambia. The main objectives of this research study were to carry out an analysis of organic farming systems in order to understand factors affecting adoption, as well as reasons why some organic farmers discontinue using the approach. The study involved four districts in Zambia: Mazabuka, Chikankata, Lusaka and Chongwe. Specifically, the research investigated challenges and limitations of organic agronomic practices, and analysed factors that influence adopters and disadopters of organic agriculture. Primary data were collected through interviews and by administering semi-structured questionnaires. The research population comprised approximately 250 farmers adopters and disadopters, with the sample size being 50 farmers chosen across four districts using systematic random sampling methods. Additionally, five observation research field trials were conducted in order to gather practical data on individual farmer’s crop management practices. Farmers adopting and maintaining organic methods reported several reasons for embracing the system, some of which are: organic farming is regenerative; it is environmentally responsible; it uses manure, believed to help build healthy soils rich in organic matter with better nutrient and moisture holding capacity; pesticides and synthetic fertilizers are not used, reducing the levels of toxic residues in organic products which ultimately promotes health. Labour constraints, pest and disease challenges and weed problems were some of the reasons for disadoption. Data showed that disadopters had lower education (48% had primary education), were older and with slightly more children. Although there were more women adopting organic agriculture compared to men, the difference was small 56% and 44% women and men respectively. Among disadopters there were more women (67%) compared to men (33%). Overall, the study results suggest that promotion of organic agriculture should be encouraged through liaison with government departments such as the Zambian Department of Agriculture to include organic agriculture when developing policies. In general, organic farmers have positive opinions concerning the benefits resulting from organic agriculture. Organic farmers should enjoy equal opportunities to conventional agriculture in the provision of extension services, input support, infrastructural development, access to financial resources to procure farm machinery, and equipment and most important of all, they should get fair prices for their organic produce and products. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Munthali, Robert
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic farming -- Zambia
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52111 , vital:43434
- Description: The last 30 years since the early 1990s has seen the heightened promotion of organic farming as a sustainable farming option in Zambia. The main objectives of this research study were to carry out an analysis of organic farming systems in order to understand factors affecting adoption, as well as reasons why some organic farmers discontinue using the approach. The study involved four districts in Zambia: Mazabuka, Chikankata, Lusaka and Chongwe. Specifically, the research investigated challenges and limitations of organic agronomic practices, and analysed factors that influence adopters and disadopters of organic agriculture. Primary data were collected through interviews and by administering semi-structured questionnaires. The research population comprised approximately 250 farmers adopters and disadopters, with the sample size being 50 farmers chosen across four districts using systematic random sampling methods. Additionally, five observation research field trials were conducted in order to gather practical data on individual farmer’s crop management practices. Farmers adopting and maintaining organic methods reported several reasons for embracing the system, some of which are: organic farming is regenerative; it is environmentally responsible; it uses manure, believed to help build healthy soils rich in organic matter with better nutrient and moisture holding capacity; pesticides and synthetic fertilizers are not used, reducing the levels of toxic residues in organic products which ultimately promotes health. Labour constraints, pest and disease challenges and weed problems were some of the reasons for disadoption. Data showed that disadopters had lower education (48% had primary education), were older and with slightly more children. Although there were more women adopting organic agriculture compared to men, the difference was small 56% and 44% women and men respectively. Among disadopters there were more women (67%) compared to men (33%). Overall, the study results suggest that promotion of organic agriculture should be encouraged through liaison with government departments such as the Zambian Department of Agriculture to include organic agriculture when developing policies. In general, organic farmers have positive opinions concerning the benefits resulting from organic agriculture. Organic farmers should enjoy equal opportunities to conventional agriculture in the provision of extension services, input support, infrastructural development, access to financial resources to procure farm machinery, and equipment and most important of all, they should get fair prices for their organic produce and products. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Evaluation of the toxicity of secondary metabolites in Solanum incanum L. to advance community knowledge
- Authors: Zivanayi, William
- Date: 2023-04
- Subjects: Solanum -- Zimbabwe , Pesticides -- Toxicology , Medicinal plants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61018 , vital:69686
- Description: The effects of pests and the need to produce adequate food have influenced small-scale farmers in disadvantaged communities to adopt and utilise natural plant pesticides to improve harvests in many Southern African Development Communities. However, the phytochemistry associated with these indigenous plants’ pesticide activity still needs to be explored. The lack of evidence of scientific knowledge of the plant species has caused a lot of health issues among the users of indigenous plant pesticides. Solanum incanum is among the plants utilised to control cabbage aphids in Mkoba village, Zimbabwe. Solanum species are known for their steroidal compounds which comprise glycoalkaloids and saponins. This study evaluated the knowledge, opinions, and attitudes of the vegetable peasant farming community in Gweru regarding their use of the indigenous plant (S. incanum) as a pesticide. The study also reported the phytochemical profiling, structural characterisation of the isolated compounds, and biological and pesticidal activity evaluation of phytochemicals isolated from S. incanum. A descriptive survey was carried out to assess the knowledge, attitude, and practices of a conveniently sampled group of vegetable farmers in Mkoba village who use S. incanum as a pesticide. Forty-nine respondents comprised of 19 males and 30 females of ages ranging from 15 to above 60 years took part in the study by answering an open and closed-ended questionnaire. The survey revealed that parents and neighbours were instrumental in disseminating pesticidal information in the community. Brassica napus were the most grown.vegetable and vulnerable to cabbage aphids. Mixed opinions amongst the respondents varied regarding the health and environmental impact of S. incanum as a pesticide. Seventy-five percent (75%) of the respondents supported the use of S. incanum as a pesticide whilst 25% claimed that the use of S. incanum was the source of the health problems experienced in the community. The survey demonstrated that (45)91% of the farmers displayed poor practices regarding the disposal of empty pesticide containers and the use of personal protective clothing. The most prevalent symptoms in the community were skin rash, nausea, headache, and poor vision and these symptoms were common in the age group 30 to 60 years. , Thesis (PhD) -- Faculty of Science, School of biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Zivanayi, William
- Date: 2023-04
- Subjects: Solanum -- Zimbabwe , Pesticides -- Toxicology , Medicinal plants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61018 , vital:69686
- Description: The effects of pests and the need to produce adequate food have influenced small-scale farmers in disadvantaged communities to adopt and utilise natural plant pesticides to improve harvests in many Southern African Development Communities. However, the phytochemistry associated with these indigenous plants’ pesticide activity still needs to be explored. The lack of evidence of scientific knowledge of the plant species has caused a lot of health issues among the users of indigenous plant pesticides. Solanum incanum is among the plants utilised to control cabbage aphids in Mkoba village, Zimbabwe. Solanum species are known for their steroidal compounds which comprise glycoalkaloids and saponins. This study evaluated the knowledge, opinions, and attitudes of the vegetable peasant farming community in Gweru regarding their use of the indigenous plant (S. incanum) as a pesticide. The study also reported the phytochemical profiling, structural characterisation of the isolated compounds, and biological and pesticidal activity evaluation of phytochemicals isolated from S. incanum. A descriptive survey was carried out to assess the knowledge, attitude, and practices of a conveniently sampled group of vegetable farmers in Mkoba village who use S. incanum as a pesticide. Forty-nine respondents comprised of 19 males and 30 females of ages ranging from 15 to above 60 years took part in the study by answering an open and closed-ended questionnaire. The survey revealed that parents and neighbours were instrumental in disseminating pesticidal information in the community. Brassica napus were the most grown.vegetable and vulnerable to cabbage aphids. Mixed opinions amongst the respondents varied regarding the health and environmental impact of S. incanum as a pesticide. Seventy-five percent (75%) of the respondents supported the use of S. incanum as a pesticide whilst 25% claimed that the use of S. incanum was the source of the health problems experienced in the community. The survey demonstrated that (45)91% of the farmers displayed poor practices regarding the disposal of empty pesticide containers and the use of personal protective clothing. The most prevalent symptoms in the community were skin rash, nausea, headache, and poor vision and these symptoms were common in the age group 30 to 60 years. , Thesis (PhD) -- Faculty of Science, School of biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Flash floods prediction in South African urban areas: Jukskei river catchment as case study
- Authors: Mawasha, Tshepo Sylvester
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Geographic information systems
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52059 , vital:43429
- Description: This study explored the change relation of multi-temporal land-use/land-cover (LULC) conditions in order to determine how they contribute to change in surface runoff volumes and peak discharge, in an effort to predict flash flooding within the Jukskei River catchment. The research is divided into three main parts: (1) LULC change modeling, (2) rainfall-runoff modeling, and (3) flash floods prediction. Three multi-temporal satellite images of Landsat-5 MMS (1987), Landsat-5 TM (2001) and Landsat-8 OLI (2015) were used for LULC modeling. The analysis of the LULC model revealed that there is a continuous increment in built-up area, from 37.7% to 56.2%, in the expense of other LULC classes for the 28-years preceding this study (i.e., 1987 to 2015). Rainfall-runoff model output results revealed that, for these 28 years, there has been an increase in surface runoff due to change in LULC by 21.5%, 32.9% and 45.5% for 1987, 2001 and 2015, respectively. Due to an increase in surface runoff volume and impervious surface over time, the analysis of HEC-RAS/GeoRAS showed that floodplain extent, flood depth, flood velocity, depth-velocity and the level of damage increases especially in low elevation areas and areas at closed proximity to the Jukskei River. Thus, the building structures and infrastructures are at risk of being affected by flash floods during the rainy season. The findings of this study are expected to be used as basic data for the identification of causative factors of flash floods, areas that generate high surface runoff volume, and the prediction of flash floods within the catchment in future. The flood damage maps developed in this study will be useful to policy-makers and the relevant authorities, as well as to local residents, in finding suitable measures for residential development along the floodplain while reducing flood risk in the study area. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Mawasha, Tshepo Sylvester
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Geographic information systems
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52059 , vital:43429
- Description: This study explored the change relation of multi-temporal land-use/land-cover (LULC) conditions in order to determine how they contribute to change in surface runoff volumes and peak discharge, in an effort to predict flash flooding within the Jukskei River catchment. The research is divided into three main parts: (1) LULC change modeling, (2) rainfall-runoff modeling, and (3) flash floods prediction. Three multi-temporal satellite images of Landsat-5 MMS (1987), Landsat-5 TM (2001) and Landsat-8 OLI (2015) were used for LULC modeling. The analysis of the LULC model revealed that there is a continuous increment in built-up area, from 37.7% to 56.2%, in the expense of other LULC classes for the 28-years preceding this study (i.e., 1987 to 2015). Rainfall-runoff model output results revealed that, for these 28 years, there has been an increase in surface runoff due to change in LULC by 21.5%, 32.9% and 45.5% for 1987, 2001 and 2015, respectively. Due to an increase in surface runoff volume and impervious surface over time, the analysis of HEC-RAS/GeoRAS showed that floodplain extent, flood depth, flood velocity, depth-velocity and the level of damage increases especially in low elevation areas and areas at closed proximity to the Jukskei River. Thus, the building structures and infrastructures are at risk of being affected by flash floods during the rainy season. The findings of this study are expected to be used as basic data for the identification of causative factors of flash floods, areas that generate high surface runoff volume, and the prediction of flash floods within the catchment in future. The flood damage maps developed in this study will be useful to policy-makers and the relevant authorities, as well as to local residents, in finding suitable measures for residential development along the floodplain while reducing flood risk in the study area. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Fragmentation of the Albany Thicket Biome: consequences for the biodiversity and health of thicket vegetation
- Authors: Carvalho, Shandon Luke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fragmented landscapes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52344 , vital:43599
- Description: The dense impenetrable vegetation of the Albany Thicket Biome is highly resistant to a wide variety of disturbances but, once disturbed, lacks the regenerative qualities that allow it to return to a stable state. Agricultural development is the main cause of degradation in this biome, creating a landscape consisting of patches of thicket vegetation scattered throughout land cleared for crops or transformed through grazing by domestic livestock. The main objective of this study is to determine the health, status and biodiversity of thicket fragments as it relates to elephant impacts. The level of fragmentation and the remaining extent of intact thicket were investigated as its current status is unknown. The findings suggest that the Thicket Biome is highly fragmented as almost 50% of solid thicket has been cleared, transformed or degraded by agricultural or urban development. For Arid Thicket, the level of fragmentation and the remaining extent of intact thicket could not be determined and both could potentially be greater. For the intact thicket of Dune, Mesic and Valley Thicket types, patch sizes ranged between almost 6 and 876 km2 while the weighted mean was between 2 and 251 km2 . Remote sensing methods (NDVI) were used to determine whether the health of thicket could be remotely assessed. The thicket within and beyond the extent of piospheres around watering holes is subjected to different levels of herbivory. These different levels were compared to corresponding NDVI values with the latter accurately measuring the impact of herbivores along a gradient and providing a method to assess the health of thicket vegetation. Ground surveys of the edge effect, along thicket fragments adjacent to open pastures and separated by cut lines, were conducted. Based on these surveys, the extent of the edge effect was established at a distance of 7 m into thicket fragments separated by cut lines but could not be determined for thicket fragments adjacent to open pastures. Ground surveys were also conducted to assess the health of thicket vegetation exposed to different levels of herbivory, including the impact of elephants (Loxodonta africana). Results showed that different elephant densities produced different levels of impact that could be described in terms of changes in species richness, species diversity, plant height and cover, and growth form composition. Lastly, the findings of the health-based assessments were combined with elephant densities to develop a model that could assess the health of thicket vegetation using a range of ecological variables and relate it to an ideal range of elephant densities. This assessment method was tested at the Addo Elephant National Park and results showed that an elephant density of 1 elephant/km2 would maintain the appropriate diversity, structure and composition of thicket. , Thesis (MSc) -- Faculty of Science, Department of Botany, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Carvalho, Shandon Luke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fragmented landscapes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52344 , vital:43599
- Description: The dense impenetrable vegetation of the Albany Thicket Biome is highly resistant to a wide variety of disturbances but, once disturbed, lacks the regenerative qualities that allow it to return to a stable state. Agricultural development is the main cause of degradation in this biome, creating a landscape consisting of patches of thicket vegetation scattered throughout land cleared for crops or transformed through grazing by domestic livestock. The main objective of this study is to determine the health, status and biodiversity of thicket fragments as it relates to elephant impacts. The level of fragmentation and the remaining extent of intact thicket were investigated as its current status is unknown. The findings suggest that the Thicket Biome is highly fragmented as almost 50% of solid thicket has been cleared, transformed or degraded by agricultural or urban development. For Arid Thicket, the level of fragmentation and the remaining extent of intact thicket could not be determined and both could potentially be greater. For the intact thicket of Dune, Mesic and Valley Thicket types, patch sizes ranged between almost 6 and 876 km2 while the weighted mean was between 2 and 251 km2 . Remote sensing methods (NDVI) were used to determine whether the health of thicket could be remotely assessed. The thicket within and beyond the extent of piospheres around watering holes is subjected to different levels of herbivory. These different levels were compared to corresponding NDVI values with the latter accurately measuring the impact of herbivores along a gradient and providing a method to assess the health of thicket vegetation. Ground surveys of the edge effect, along thicket fragments adjacent to open pastures and separated by cut lines, were conducted. Based on these surveys, the extent of the edge effect was established at a distance of 7 m into thicket fragments separated by cut lines but could not be determined for thicket fragments adjacent to open pastures. Ground surveys were also conducted to assess the health of thicket vegetation exposed to different levels of herbivory, including the impact of elephants (Loxodonta africana). Results showed that different elephant densities produced different levels of impact that could be described in terms of changes in species richness, species diversity, plant height and cover, and growth form composition. Lastly, the findings of the health-based assessments were combined with elephant densities to develop a model that could assess the health of thicket vegetation using a range of ecological variables and relate it to an ideal range of elephant densities. This assessment method was tested at the Addo Elephant National Park and results showed that an elephant density of 1 elephant/km2 would maintain the appropriate diversity, structure and composition of thicket. , Thesis (MSc) -- Faculty of Science, Department of Botany, 2021
- Full Text: false
- Date Issued: 2021-04
Impacts of algal blooms in a temperate Estuarine fish nursery area, South Africa
- Authors: Bornman, Eugin
- Date: 2022-04
- Subjects: Cyanobacterial toxins --Environmental aspects , Estuarine eutrophication --South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55899 , vital:54398
- Description: Anthropogenically-derived eutrophication and Harmful Algal Blooms (HABs) are an increasing threat to estuarine ecosystems globally. The rapid population growth in coastal areas and the mismanagement of water resources have led to the rapid increase in eutrophication in estuaries. Consequently, HABs have become frequent phenomena with severe impacts on the ecological functioning of these systems. A paucity exists in understanding the specific mechanisms of how HABs impact estuarine communities globally. This has not been studied in South Africa, despite the observed increase in the occurrence of HABs in the past few decades. Therefore, this study investigated the impact of HABs on the ecological functioning of the anthropogenically altered Sundays Estuary, South Africa, which is affected by predictable and recurrent HABs of the raphidophyte, Heterosigma akashiwo. This study found that a high density (> 1000 cell m L-1 ) of H. akashiwo was present during all but the winter months in the poly- to mesohaline zone, yet it peaked in warmer spring/summer months with a density of ca. 70 000 cell m L-1 corresponding to 800 µg Chl-a L -1 . This species significantly altered the estuary's water quality, causing supersaturated surface- and hypoxic bottom-water during severe HABs or referred to as hypereutrophic bloom phases (> 60 µg Chl-a L -1 ). Despite these changes, the common copepod, Pseudodiaptomus hessei, occurred at similar densities among HAB phases and responded to similar triggers to the HAB. However, a shift in predator-prey interactions within the zooplankton community was evident, with scavenger or opportunist species such as the isopod, Cirolana fluviatilis, and the polychaete, Perinereis falsovariegata, occurring at higher densities during hypereutrophic bloom phases. The overall abundance of juvenile and small adult fishes were high during HABs, but the diversity decreased during HABs. Some species, notably the Mugilidae occurred at lower densities during HABs. Mugilidae also had pronounced histological gill alterations and a lowered proportion of secondary lamellae available for gas exchange during an in situ cage experiment where fishes were isolated inside and outside the HAB. Deformities such as tumorous growths were also found for the first time in a South African Estuary. This indicated a stressed population of Mugilidae in the Sundays Estuary. The ubiquitous mugilid, Mugil cephalus, actively avoided HABs during an acoustic telemetry study, despite having a home range that overlapped the HAB area. Tagged individuals mostly occupied areas directly above the HAB in the upper mesohaline to lower oligohaline zones and only iv briefly transitioned through the HAB area to utilise the lower reaches of the estuary. Since the formation of HABs is reliant on various factors, including specific species responses, environmental variables, nutrient enrichment, and flow characteristics, the impacts of HABs on estuarine communities may vary between estuarine systems or affected species. Therefore, more research that focuses on the impacts of HABs on estuaries is needed to limit the potential loss of ecosystem services. Particularly in light of further unsustainable development, upstream freshwater abstraction and climate change, will cause more frequent and severe HABs, that may result in fish population declines in the long-term. Better management and mitigation strategies are needed to reduce HAB formation such as reducing nutrient enrichment and restoring natural freshwater flow and flooding events to the Sundays Estuary. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Bornman, Eugin
- Date: 2022-04
- Subjects: Cyanobacterial toxins --Environmental aspects , Estuarine eutrophication --South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55899 , vital:54398
- Description: Anthropogenically-derived eutrophication and Harmful Algal Blooms (HABs) are an increasing threat to estuarine ecosystems globally. The rapid population growth in coastal areas and the mismanagement of water resources have led to the rapid increase in eutrophication in estuaries. Consequently, HABs have become frequent phenomena with severe impacts on the ecological functioning of these systems. A paucity exists in understanding the specific mechanisms of how HABs impact estuarine communities globally. This has not been studied in South Africa, despite the observed increase in the occurrence of HABs in the past few decades. Therefore, this study investigated the impact of HABs on the ecological functioning of the anthropogenically altered Sundays Estuary, South Africa, which is affected by predictable and recurrent HABs of the raphidophyte, Heterosigma akashiwo. This study found that a high density (> 1000 cell m L-1 ) of H. akashiwo was present during all but the winter months in the poly- to mesohaline zone, yet it peaked in warmer spring/summer months with a density of ca. 70 000 cell m L-1 corresponding to 800 µg Chl-a L -1 . This species significantly altered the estuary's water quality, causing supersaturated surface- and hypoxic bottom-water during severe HABs or referred to as hypereutrophic bloom phases (> 60 µg Chl-a L -1 ). Despite these changes, the common copepod, Pseudodiaptomus hessei, occurred at similar densities among HAB phases and responded to similar triggers to the HAB. However, a shift in predator-prey interactions within the zooplankton community was evident, with scavenger or opportunist species such as the isopod, Cirolana fluviatilis, and the polychaete, Perinereis falsovariegata, occurring at higher densities during hypereutrophic bloom phases. The overall abundance of juvenile and small adult fishes were high during HABs, but the diversity decreased during HABs. Some species, notably the Mugilidae occurred at lower densities during HABs. Mugilidae also had pronounced histological gill alterations and a lowered proportion of secondary lamellae available for gas exchange during an in situ cage experiment where fishes were isolated inside and outside the HAB. Deformities such as tumorous growths were also found for the first time in a South African Estuary. This indicated a stressed population of Mugilidae in the Sundays Estuary. The ubiquitous mugilid, Mugil cephalus, actively avoided HABs during an acoustic telemetry study, despite having a home range that overlapped the HAB area. Tagged individuals mostly occupied areas directly above the HAB in the upper mesohaline to lower oligohaline zones and only iv briefly transitioned through the HAB area to utilise the lower reaches of the estuary. Since the formation of HABs is reliant on various factors, including specific species responses, environmental variables, nutrient enrichment, and flow characteristics, the impacts of HABs on estuarine communities may vary between estuarine systems or affected species. Therefore, more research that focuses on the impacts of HABs on estuaries is needed to limit the potential loss of ecosystem services. Particularly in light of further unsustainable development, upstream freshwater abstraction and climate change, will cause more frequent and severe HABs, that may result in fish population declines in the long-term. Better management and mitigation strategies are needed to reduce HAB formation such as reducing nutrient enrichment and restoring natural freshwater flow and flooding events to the Sundays Estuary. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Investigation of thermal and electrical characteristics of crystalline silicon photovoltaic modules under varying operational conditions
- Authors: Vumbugwa, Monphias
- Date: 2022-12
- Subjects: Photovoltaic power generation -- South Africa , Silicon crystals -- South Africa , Solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60014 , vital:62733
- Description: Solar energy has become an attractive and environmentally mindful method in electrical power generation as it contributes significantly to meeting the high demand for the power needed for socio and economic developments. The rise in deployment of Photovoltaic (PV) facilities with large capacity creates the need for accurate and reliable PV inspection techniques for optimum performance, the longevity of PV modules and quick return on PV investment. The performance of PV modules in the field is often monitored through several inspection methods that require a rapid throughput such as Thermal Infrared (TIR) imaging and current-voltage (I-V) measurements. Unmanned Aerial Vehicle (UAV) based TIR imaging is widely applied in large PV plants since it is cost-effective and is usually conducted in-situ while the plant is operating at irradiance levels above 600 W.m-2 . One of the outcomes of the interpretations of TIR images is an attempt to quantify the energy loss in PV plants associated with the abnormal thermal signatures identified on TIR images. No standard procedure has yet outlined the quantification of energy loss related to TIR images of underperforming modules since the interpretation of TIR images remains a challenge. PV modules operate under dynamic operating conditions which can influence the results and interpretation of thermal and electrical characterisation measurements. Dynamic operation conditions refer to any disorders in the operation of the modules and cells which cause a change in the current and voltage characteristics of the PV source. These dynamic operation conditions include; changesin load conditions, irradiance, soiling and shading levels. The tests were done under steady state conditions. Although measurements are generally done while the operating conditions are as steady as possible, some changes in conditions have a profound effect on thermal and electrical measurements. In this study, these effects and some of the changes in conditions that cause them were studied. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Vumbugwa, Monphias
- Date: 2022-12
- Subjects: Photovoltaic power generation -- South Africa , Silicon crystals -- South Africa , Solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60014 , vital:62733
- Description: Solar energy has become an attractive and environmentally mindful method in electrical power generation as it contributes significantly to meeting the high demand for the power needed for socio and economic developments. The rise in deployment of Photovoltaic (PV) facilities with large capacity creates the need for accurate and reliable PV inspection techniques for optimum performance, the longevity of PV modules and quick return on PV investment. The performance of PV modules in the field is often monitored through several inspection methods that require a rapid throughput such as Thermal Infrared (TIR) imaging and current-voltage (I-V) measurements. Unmanned Aerial Vehicle (UAV) based TIR imaging is widely applied in large PV plants since it is cost-effective and is usually conducted in-situ while the plant is operating at irradiance levels above 600 W.m-2 . One of the outcomes of the interpretations of TIR images is an attempt to quantify the energy loss in PV plants associated with the abnormal thermal signatures identified on TIR images. No standard procedure has yet outlined the quantification of energy loss related to TIR images of underperforming modules since the interpretation of TIR images remains a challenge. PV modules operate under dynamic operating conditions which can influence the results and interpretation of thermal and electrical characterisation measurements. Dynamic operation conditions refer to any disorders in the operation of the modules and cells which cause a change in the current and voltage characteristics of the PV source. These dynamic operation conditions include; changesin load conditions, irradiance, soiling and shading levels. The tests were done under steady state conditions. Although measurements are generally done while the operating conditions are as steady as possible, some changes in conditions have a profound effect on thermal and electrical measurements. In this study, these effects and some of the changes in conditions that cause them were studied. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
Large mammalian fauna of the Palaeo-Agulhas Plain: predicting habitat use and range distribution
- Authors: Brooke, Christopher F
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Herbivores
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52332 , vital:43590
- Description: Understanding the variations in structure and abundance of animals and what leads to their distribution within the landscape has captured the attention of ecologists for centuries. Importantly, knowledge of current behaviour of large mammals can be used to inform historic population dynamics and is essential to understanding how early humans used large mammals as a foraging resource. Central to this thesis and improving our understanding of large herbivores is the Palaeo-Agulhas Plain (PAP) where large mammalian herbivores formed a key food resource for early humans. The PAP, now submerged off the southern Cape of South Africa, formed a novel ecosystem during lower sea levels. Characterised by large expanses of nutrient rich grasslands and large grazing herbivores, the PAP stands in stark contrast to the nutrient poor fynbos ecosystems that is in the southern Cape today. In this thesis I focus on the Last Glacial Maximum (LGM; ~20 ka) when the PAP was last fully exposed to answer questions relating to the habitat use and range distribution of large herbivores. Importantly, through the Paleoscape Project, modelled climate, soil and vegetation have made these recreations of large mammals possible. Using modelled climate and vegetation this thesis aims to model the large herbivore communities and understand the influence of early humans on the PAP during the LGM for successful integration into the PaleoscapeABM (the PAP agent-based model). To improve our understanding of large mammals on the PAP I identified five large herbivores that became extinct on the PAP since the LGM and modelled their behavioural and physical traits using k-Nearest Neighbour imputation. I predicted the biomass of large herbivores across the PAP using actual biomass of large herbivores from 39 protected areas across South Africa (spanning five functional groups to include the extinct species) across a rainfall gradient and different biomes. The distribution of large herbivores would likely have been driven by similar top-down and bottom-up drivers we see in large herbivore ecology today. Knowing this, I created a predictive model for large mammals by predicting the probability of occurrence of functional groups of large herbivores in relation to environmental drivers and humans. Results showed that all species (except Antidorcas australis) were adapted to the grassy environment of the PAP and these specialisations likely contributed to their extinction along with changing climates and intensified hunting from humans. When predicting herbivore viii biomass, biome was the most important factor influencing the relationship between herbivores and rainfall. In general, large herbivore biomass increased with rainfall across biomes, except for grassland. Finally, I showed the probability of occurrence of large herbivores was influenced by early humans, water availability and a landscape of fear on the PAP. Through this thesis I have successfully provided detailed accounts of the biomass and probability of occurrence of large herbivores on the PAP. Importantly, this information can be seamlessly integrated into the PaleoscapeABM. Finally, I highlight the importance of this knowledge in understanding early humans, the potential shortcomings of this study and resulting areas where research needs to be focused. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Brooke, Christopher F
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Herbivores
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52332 , vital:43590
- Description: Understanding the variations in structure and abundance of animals and what leads to their distribution within the landscape has captured the attention of ecologists for centuries. Importantly, knowledge of current behaviour of large mammals can be used to inform historic population dynamics and is essential to understanding how early humans used large mammals as a foraging resource. Central to this thesis and improving our understanding of large herbivores is the Palaeo-Agulhas Plain (PAP) where large mammalian herbivores formed a key food resource for early humans. The PAP, now submerged off the southern Cape of South Africa, formed a novel ecosystem during lower sea levels. Characterised by large expanses of nutrient rich grasslands and large grazing herbivores, the PAP stands in stark contrast to the nutrient poor fynbos ecosystems that is in the southern Cape today. In this thesis I focus on the Last Glacial Maximum (LGM; ~20 ka) when the PAP was last fully exposed to answer questions relating to the habitat use and range distribution of large herbivores. Importantly, through the Paleoscape Project, modelled climate, soil and vegetation have made these recreations of large mammals possible. Using modelled climate and vegetation this thesis aims to model the large herbivore communities and understand the influence of early humans on the PAP during the LGM for successful integration into the PaleoscapeABM (the PAP agent-based model). To improve our understanding of large mammals on the PAP I identified five large herbivores that became extinct on the PAP since the LGM and modelled their behavioural and physical traits using k-Nearest Neighbour imputation. I predicted the biomass of large herbivores across the PAP using actual biomass of large herbivores from 39 protected areas across South Africa (spanning five functional groups to include the extinct species) across a rainfall gradient and different biomes. The distribution of large herbivores would likely have been driven by similar top-down and bottom-up drivers we see in large herbivore ecology today. Knowing this, I created a predictive model for large mammals by predicting the probability of occurrence of functional groups of large herbivores in relation to environmental drivers and humans. Results showed that all species (except Antidorcas australis) were adapted to the grassy environment of the PAP and these specialisations likely contributed to their extinction along with changing climates and intensified hunting from humans. When predicting herbivore viii biomass, biome was the most important factor influencing the relationship between herbivores and rainfall. In general, large herbivore biomass increased with rainfall across biomes, except for grassland. Finally, I showed the probability of occurrence of large herbivores was influenced by early humans, water availability and a landscape of fear on the PAP. Through this thesis I have successfully provided detailed accounts of the biomass and probability of occurrence of large herbivores on the PAP. Importantly, this information can be seamlessly integrated into the PaleoscapeABM. Finally, I highlight the importance of this knowledge in understanding early humans, the potential shortcomings of this study and resulting areas where research needs to be focused. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04