Database and guide for Lesotho wool and mohair production and quality
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020
Decision analysis to inform invasive alien plant management in the Garden Route Biosphere Reserve
- Authors: Masunungure, Current
- Date: 2020
- Subjects: Invasive plants -- South Africa , Alien plants -- South Africa , Biodiversity -- South Africa -- Management , Ecosystem management -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49159 , vital:41606
- Description: Invasive alien plants (IAP) pose significant threats to global economies and biodiversity and are often considered as wicked problems. With an increasing number of IAP and limited resources, their management and decision-making processes are becoming difficult because of uncertainty, multiple and conflicting objectives, and diverse stakeholder views, facts and values. This is particularly challenging given the complex interactions between economic, ecological, and social elements that exist in invaded areas. Consequently, it is important to incorporate new ways of thinking and novel methodologies to improve our understanding of IAP management and the decision-making processes around them, which are currently inadequate. Decision analysis can help with dealing with these challenges and support decision-making under uncertainty. Drawing on the systems thinking approach and the concepts of leverage points, transition management and transformational change, the aim of this thesis was to explore the effectiveness of IAP management and the decision-making process in the Garden Route Biosphere Reserve (GRBR). This was achieved using a mixed methods approach involving: social-ecological inventory (identifying relevant stakeholders); review of literature on the available decision support tools; key informant interviews (stakeholder perspectives on the current decision-making process); and stakeholder workshop and expert consultation (casual loop modelling). The results of this thesis provide evidence that application of the proposed principles of robust decision-making has the potential to overcome the weaknesses of the current decision-making process and as such, enables decision-makers to efficiently allocate resources towards IAS management. A novel causal loop diagram (CLD) was developed to highlight the interconnections between key variables in IAP management and decision-making. This revealed that to transcend ‘policy resistance’ and ‘quickfixes that fail’ archetypes, and improve IAP management, the stakeholders need to consider deep leverage points, for example, fostering trust and shared understanding among different stakeholder groups. These can be realistically maintained over the long-term and can cause a fundamental change in IAP management, rather than focusing on shallow leverage points that are relatively easy to implement but do not result in significant systemic change. The findings of this thesis are flexible and could guide various stakeholder groups at local, national, and international scales in improving the effectiveness of IAP management and decision-making.
- Full Text:
- Date Issued: 2020
- Authors: Masunungure, Current
- Date: 2020
- Subjects: Invasive plants -- South Africa , Alien plants -- South Africa , Biodiversity -- South Africa -- Management , Ecosystem management -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49159 , vital:41606
- Description: Invasive alien plants (IAP) pose significant threats to global economies and biodiversity and are often considered as wicked problems. With an increasing number of IAP and limited resources, their management and decision-making processes are becoming difficult because of uncertainty, multiple and conflicting objectives, and diverse stakeholder views, facts and values. This is particularly challenging given the complex interactions between economic, ecological, and social elements that exist in invaded areas. Consequently, it is important to incorporate new ways of thinking and novel methodologies to improve our understanding of IAP management and the decision-making processes around them, which are currently inadequate. Decision analysis can help with dealing with these challenges and support decision-making under uncertainty. Drawing on the systems thinking approach and the concepts of leverage points, transition management and transformational change, the aim of this thesis was to explore the effectiveness of IAP management and the decision-making process in the Garden Route Biosphere Reserve (GRBR). This was achieved using a mixed methods approach involving: social-ecological inventory (identifying relevant stakeholders); review of literature on the available decision support tools; key informant interviews (stakeholder perspectives on the current decision-making process); and stakeholder workshop and expert consultation (casual loop modelling). The results of this thesis provide evidence that application of the proposed principles of robust decision-making has the potential to overcome the weaknesses of the current decision-making process and as such, enables decision-makers to efficiently allocate resources towards IAS management. A novel causal loop diagram (CLD) was developed to highlight the interconnections between key variables in IAP management and decision-making. This revealed that to transcend ‘policy resistance’ and ‘quickfixes that fail’ archetypes, and improve IAP management, the stakeholders need to consider deep leverage points, for example, fostering trust and shared understanding among different stakeholder groups. These can be realistically maintained over the long-term and can cause a fundamental change in IAP management, rather than focusing on shallow leverage points that are relatively easy to implement but do not result in significant systemic change. The findings of this thesis are flexible and could guide various stakeholder groups at local, national, and international scales in improving the effectiveness of IAP management and decision-making.
- Full Text:
- Date Issued: 2020
Defect Classification in Photovoltaic Modules through Thermal Infrared Imaging using Machine Learning
- Dunderdale, Christopher, Clohessy, C M
- Authors: Dunderdale, Christopher , Clohessy, C M
- Date: 2020
- Subjects: Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48280 , vital:40838
- Description: As the global energy demand continues to soar, solar energy has become an attractive and environmentally conscious method to meet this demand. This study examines the use of machine learning techniques for defect detection and classification in photovoltaic systems using thermal infrared images. A deep learning and feature-based approach is also investigated for the purpose of detecting and classifying defective photovoltaic modules. The VGG-16 and MobileNet deep learning models are shown to provide good performance for the classification of defects. The scale invariant feature transform (SIFT) descriptor, combined with the random forest and support vector machine classifier, is also used to discriminate between defective and non-defective photovoltaic modules in a South African setting. The successful implementation of this approach has significant potential for cost reduction in defect classification over currently available methods.
- Full Text:
- Date Issued: 2020
- Authors: Dunderdale, Christopher , Clohessy, C M
- Date: 2020
- Subjects: Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48280 , vital:40838
- Description: As the global energy demand continues to soar, solar energy has become an attractive and environmentally conscious method to meet this demand. This study examines the use of machine learning techniques for defect detection and classification in photovoltaic systems using thermal infrared images. A deep learning and feature-based approach is also investigated for the purpose of detecting and classifying defective photovoltaic modules. The VGG-16 and MobileNet deep learning models are shown to provide good performance for the classification of defects. The scale invariant feature transform (SIFT) descriptor, combined with the random forest and support vector machine classifier, is also used to discriminate between defective and non-defective photovoltaic modules in a South African setting. The successful implementation of this approach has significant potential for cost reduction in defect classification over currently available methods.
- Full Text:
- Date Issued: 2020
Defining the potential ecological roles of three sea turtle species (Caretta caretta, Chelonia mydas and Eretmochelys imbricata) along the Eastern seaboard of South Africa
- Authors: Ramboran, Ryan
- Date: 2020
- Subjects: Sea turtles -- Conservation -- South Africa , Sea turtles -- Habitat -- Conservation -- South Africa Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49343 , vital:41623
- Description: Sea turtles were once key species, driving the ecosystem process and energy flows, the past loss of their ecological roles, however has resulted in reduced ecosystem functionality through food web shifts and trophic cascades. Therefore understanding the past and present ecological roles of sea turtles is identified as one of the global research priorities for sea turtle management and conservation.
- Full Text: false
- Date Issued: 2020
- Authors: Ramboran, Ryan
- Date: 2020
- Subjects: Sea turtles -- Conservation -- South Africa , Sea turtles -- Habitat -- Conservation -- South Africa Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49343 , vital:41623
- Description: Sea turtles were once key species, driving the ecosystem process and energy flows, the past loss of their ecological roles, however has resulted in reduced ecosystem functionality through food web shifts and trophic cascades. Therefore understanding the past and present ecological roles of sea turtles is identified as one of the global research priorities for sea turtle management and conservation.
- Full Text: false
- Date Issued: 2020
Designing a parental involvement programme to enhance parental engagement in the educational support programme at a disadvantaged primary school in the Nelson Mandela Bay Metropole, South Africa through participatory action research
- WIlliams, Pearl Juanita Cherrol
- Authors: WIlliams, Pearl Juanita Cherrol
- Date: 2020
- Subjects: Education -- Parent participation -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47303 , vital:39841
- Description: Over the past decades parental involvement in education has increased rapidly within disadvantaged schools in South Africa. This transformation is evident in the legislation of the country which celebrates a spirit of Ubuntu in a democratised society, and, education at large. The ideal of effective school-home partnership across racial boundaries are, for example, emphasised and strengthened via parental involvement at all public schools. Parents, according to the Department of Education (DoE, 1996b:11; 2000c:29; 2001b:29; 2008:23; 2009:17; 2014b:27; n.d.:6), are considered key role-players in school governance and encouraged to support equal educational opportunities for all learners. It implies that the praxis of parental involvement – especially at disadvantaged schools – is a huge benefit to learners with existing backlogs in education. In relation to this view, Stofile and Green (2007:63) emphasise the significance of parental involvement in school life as it can assist greatly in addressing the divere needs of disadvantaged learners. The dynamics associated with parental involvement are investigated in this study through two cycles of participatory action research. Initially ten parents from one of the disadvantaged primary schools within the Nelson Mandela Bay Metropole were purposively selected to participate in an in-depth qualitative research study pertaining to the design of a suitable parental involvement programme for disadvantaged learners. All the relevant information was gathered during action learning sets, individual interviews, and observations to triangulate the data and fill in possible gaps. This data was coded and categorised throughout the cyclical process via inductive participatory data analysis, as described by Patton (2015:216 & 551). Three main themes with sub-themes emerged from the study, namely (1) deficits of the academic programme: remedial education, teacher-assistants, homeworksupport, technical abilities; (2) the neglect of social wellness programmes: need for parental guidance, necessary professional assistance, upgrading of safety measures, availability of clothing bank, sustainability of a nutritional programme; and (3) voids in communication and relationships: the home environment, community, school environment. These themes and sub-themes successfully answered all the research questions. An increasing number of learners at disadvataged primary schools are neglected and/or leave school at a very young age. This scenario is often linked to poor communication and/or a lack of adequate educational support programmes to enhance better learning outcomes. The design of a PIP aimed to address the diverse needs of learners at a specific disadvantaged primary school with the full cooperation of their parents. Nested within the Ecological Model of Bronfenbrenner, the participating parents were engaged in comprehensive discussions about educational support programmes that the school could embark on with them. Numerous programmes were identified as fundamental to transforming the quality of education for many disadvantaged learners. This research therefore encouraged greater parental involvement at disadvantaged primary schools in order to sustain better learning outcomes.
- Full Text:
- Date Issued: 2020
- Authors: WIlliams, Pearl Juanita Cherrol
- Date: 2020
- Subjects: Education -- Parent participation -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/47303 , vital:39841
- Description: Over the past decades parental involvement in education has increased rapidly within disadvantaged schools in South Africa. This transformation is evident in the legislation of the country which celebrates a spirit of Ubuntu in a democratised society, and, education at large. The ideal of effective school-home partnership across racial boundaries are, for example, emphasised and strengthened via parental involvement at all public schools. Parents, according to the Department of Education (DoE, 1996b:11; 2000c:29; 2001b:29; 2008:23; 2009:17; 2014b:27; n.d.:6), are considered key role-players in school governance and encouraged to support equal educational opportunities for all learners. It implies that the praxis of parental involvement – especially at disadvantaged schools – is a huge benefit to learners with existing backlogs in education. In relation to this view, Stofile and Green (2007:63) emphasise the significance of parental involvement in school life as it can assist greatly in addressing the divere needs of disadvantaged learners. The dynamics associated with parental involvement are investigated in this study through two cycles of participatory action research. Initially ten parents from one of the disadvantaged primary schools within the Nelson Mandela Bay Metropole were purposively selected to participate in an in-depth qualitative research study pertaining to the design of a suitable parental involvement programme for disadvantaged learners. All the relevant information was gathered during action learning sets, individual interviews, and observations to triangulate the data and fill in possible gaps. This data was coded and categorised throughout the cyclical process via inductive participatory data analysis, as described by Patton (2015:216 & 551). Three main themes with sub-themes emerged from the study, namely (1) deficits of the academic programme: remedial education, teacher-assistants, homeworksupport, technical abilities; (2) the neglect of social wellness programmes: need for parental guidance, necessary professional assistance, upgrading of safety measures, availability of clothing bank, sustainability of a nutritional programme; and (3) voids in communication and relationships: the home environment, community, school environment. These themes and sub-themes successfully answered all the research questions. An increasing number of learners at disadvataged primary schools are neglected and/or leave school at a very young age. This scenario is often linked to poor communication and/or a lack of adequate educational support programmes to enhance better learning outcomes. The design of a PIP aimed to address the diverse needs of learners at a specific disadvantaged primary school with the full cooperation of their parents. Nested within the Ecological Model of Bronfenbrenner, the participating parents were engaged in comprehensive discussions about educational support programmes that the school could embark on with them. Numerous programmes were identified as fundamental to transforming the quality of education for many disadvantaged learners. This research therefore encouraged greater parental involvement at disadvantaged primary schools in order to sustain better learning outcomes.
- Full Text:
- Date Issued: 2020
Development and process verification of a linear friction welding platform for small Ti6AI4V coupons
- Mohlala, Narishe Taetso Arnold
- Authors: Mohlala, Narishe Taetso Arnold
- Date: 2020
- Subjects: Friction welding , Pressure welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46196 , vital:39513
- Description: This thesis reports on a study conducted to establish the feasibility of implementing linear friction welding as a joining technique for small Ti6AI4V coupons. The main of this project is to facilitate the manufacturing of high-integrity near-net-shape components for aerospace, automotive and medical appliances. LFW is a solid-state welding technique that uses frictional heat generated by the rubbing of surfaces under an axially applied load, thereby forming a weld at temperature below beta tranus. This technique is advantageous as it has the potential to reduce defeats normally associated with conventional welding of this material. The first part of the study will describe the development of an experimental platform to facilitate the evaluation of the influence of selected process parameters on joint integrity.
- Full Text:
- Date Issued: 2020
Development and process verification of a linear friction welding platform for small Ti6AI4V coupons
- Authors: Mohlala, Narishe Taetso Arnold
- Date: 2020
- Subjects: Friction welding , Pressure welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46196 , vital:39513
- Description: This thesis reports on a study conducted to establish the feasibility of implementing linear friction welding as a joining technique for small Ti6AI4V coupons. The main of this project is to facilitate the manufacturing of high-integrity near-net-shape components for aerospace, automotive and medical appliances. LFW is a solid-state welding technique that uses frictional heat generated by the rubbing of surfaces under an axially applied load, thereby forming a weld at temperature below beta tranus. This technique is advantageous as it has the potential to reduce defeats normally associated with conventional welding of this material. The first part of the study will describe the development of an experimental platform to facilitate the evaluation of the influence of selected process parameters on joint integrity.
- Full Text:
- Date Issued: 2020
Development framework in the Mdantsane central business district
- Authors: Zenani, Pumzile
- Date: 2020
- Subjects: Central business district -- South Africa -- East London , City planning -- South Africa -- East London Public utilities -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47292 , vital:39840
- Description: The study sought to investigate a development performance and management of Mdantsane CBD. The performance measurement framework may enhance the chances of economic success in the CBD. The study was conducted by means of a review of related literature and by conducting an empirical study. The empirical study was conducted using a quantitative approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study was to develop a framework for perceived enhanced development for the Mdantsane CBD. A descriptive survey was conducted among the population within Mdantsane Township. The framework includes strategic factors of planning during apartheid era, reviewed strategic planning during democratic era and it provides an understanding of the current spatial and physical characteristics of the study area. Key issues such as spatial planning, infrastructure, environment, health, safety, economics and management of the CBD were also identified. Findings were based on the survey’s results from the community members. Findings suggest that the following variables: strategic factors (democratic); spatial development framework and infrastructure implementation; budget alignment; PESTEL factors (Political, Economic, Social, Technological, Ecological and Legal); environmental health and safety, transport and transport engineering, project management (body of knowledge) and the National Development Plan positively influenced the perceived enhanced development of Mdantsane CBD. All these variables were identified in the empirical framework affecting the perceived enhanced development of Mdantsane CBD. This study may contribute to the South African spatial and development planning body of knowledge by addressing factors which are faced by planners in development of the settlements.
- Full Text:
- Date Issued: 2020
- Authors: Zenani, Pumzile
- Date: 2020
- Subjects: Central business district -- South Africa -- East London , City planning -- South Africa -- East London Public utilities -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47292 , vital:39840
- Description: The study sought to investigate a development performance and management of Mdantsane CBD. The performance measurement framework may enhance the chances of economic success in the CBD. The study was conducted by means of a review of related literature and by conducting an empirical study. The empirical study was conducted using a quantitative approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study was to develop a framework for perceived enhanced development for the Mdantsane CBD. A descriptive survey was conducted among the population within Mdantsane Township. The framework includes strategic factors of planning during apartheid era, reviewed strategic planning during democratic era and it provides an understanding of the current spatial and physical characteristics of the study area. Key issues such as spatial planning, infrastructure, environment, health, safety, economics and management of the CBD were also identified. Findings were based on the survey’s results from the community members. Findings suggest that the following variables: strategic factors (democratic); spatial development framework and infrastructure implementation; budget alignment; PESTEL factors (Political, Economic, Social, Technological, Ecological and Legal); environmental health and safety, transport and transport engineering, project management (body of knowledge) and the National Development Plan positively influenced the perceived enhanced development of Mdantsane CBD. All these variables were identified in the empirical framework affecting the perceived enhanced development of Mdantsane CBD. This study may contribute to the South African spatial and development planning body of knowledge by addressing factors which are faced by planners in development of the settlements.
- Full Text:
- Date Issued: 2020
Development of a UV-tolerant strain of the South African isolate of Cryptophlebia leucotreta granulovirus for use as an enhanced biopesticide for Thaumatotibia leucotreta control on citrus
- Authors: Mwanza, Patrick
- Date: 2020
- Subjects: Baculoviruses -- South Africa , Ultraviolet astronomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48533 , vital:40885
- Description: Baculoviruses are pathogenic to insects in the orders Diptera, Hymenoptera, and Lepidoptera. As a result of this natural relationship with insects they provide an environmentally friendly method to combat crop and forest pests. As such, a number of baculoviruses have been formulated into biopesticides. The use of baculovirus biopesticides is gaining popularity as the use of chemical pesticides has come under stringent regulatory conditions imposed by governments and continental blocks such as the European Union. Baculoviruses have a narrow host range and therefore do not harm non-pests or humans who consume the crops. One such baculovirus is Cryptophlebia leucotreta granulovirus (CrleGV), which is pathogenic to the citrus pest Thaumatotibia leucotreta, commonly referred to as the false codling moth (FCM). CrleGV has an occlusion body (OB) that encloses a single virion. Several CrleGV biopesticides have been registered in South Africa for use on citrus, avocadoes, macadamias, grapes and other crops by two commercial producers, River Bioscience (SA) and Andermatt (Switzerland). These biopesticides are used as part of the FCM integrated pest management (IPM) programme, a multifacetted approach to controlling FCM. However, baculoviruses are susceptible to the ultraviolet (UV) radiation component of sunlight and lose their activity within hours to a few days, after exposure to UV. Several substances have been tested as UV protectants to improve the persistence of baculovirus biopesticides in the field. These include optical brighteners, UV absorbers and anti-oxidants. While very promising in the laboratory, UV-protectants have not been as successful in the field. A few published reports have reported, that UV-tolerant baculoviruses could be isolated from a population by repeatedly exposing and re-exposing the virus to UV irradiation with a propagation step in insect host fourth or fifth instars between each exposure cycle. In this study, the South African isolate of Cryptophlebia leucotreta (CrleGV-SA) was exposed to UV irradiation for 5 exposure cycles in a Q-Sun Xe-3 HC test chamber (Qlab, USA) with parameters set to mimic a typical summer day in the Sundays River Valley, Eastern Cape Province, in South Africa. In between exposures the virus survivors were allowed to multiply in FCM fifth instars. Surface dose bioassays were also conducted to determine the LC50 of the virus after each exposure cycle. Samples from exposure cycle 1 and cycle 5 (UV-tolerant) irradiated for 72 h were prepared for Next Generation Sequencing (NGS) of DNA. The resultant sequence data were analysed using the Geneious R11 software (New Zealand) and compared with the unexposed CrleGV-SA sequence. In-silico restriction enzyme analsysis (REN) with several enzymes was also carried on both the cycle 1 and cycle 5 exposed samples and the resulting digestion patterns were compared with the original CrleGV-SA digestion patterns. The same samples were also analysed by transmission electron microscopy (TEM) and Attenuated Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to evaluate the effect of UV irradiation on the structure of the CrleGV-SA OB. In addition, three UV protectants, lignin sulphate (Sappi, SA), BREAK-THRU®OE446 (OE446) (Evonik Industries, Germany) and Uvinul Easy (BASF, Germany) were prepared with CrleGV-SA to give final protectant concentrations of 0.09 %, 0.9 % and 9 %. The protectant-virus suspensions were exposed to UV for 24 h in the Q-Sun test chamber and bioassays conducted to determine the protective effect of each protectant concentration. The most successful protectants were then combined with the UV-tolerant CrleGV-SA and exposed to UV for 24 h in the Q-Sun test chamber and surface dose bioassays conducted afterwards. Samples exposed to UV in cycle 5 had lower LC50 values compared to samples in the early cycles. With each re-exposure cycle the LC50 values moved closer to that of the unexposed control. The LC50 of virus samples decreased from 2.89 x 108 OBs/ml after 24 h UV-exposure in cycle 1 to 2.16 x 105 OBs/ml after the same duration of exposure in cycle 5; and from 2.11 x 109 OBs/ml in cycle 1 after 72 h UV-exposure to 1.73 x 106 OBs/ml after the same duration of exposure. This represented a 1338-fold difference and a 1220-fold difference, respectively. When the UV-tolerant samples were sequenced seven SNPs were identified in cycle 1, which were thought to help establish UV tolerance, while a further seven SNPs were identified in cycle 5 samples; these were thought to further establish and maintain the UV-tolerance. Additionally, REN analysis with EcoR1 for both test samples yielded digestion patterns that were different from those of the original CrleGV-SA. TEM data showed that UV damages the virion as well as the crystalline structure of the OB. This is the first time visual evidence for UV damage to baculoviruses has been published. Comparison of cycle 1 and cycle 5 UV exposed OBs revealed that the cycle 5 OBs were significantly larger than the cycle 1 OBs (P<0.05). In addition, several peaks in the fingerprint region were shown to have either appeared or disapeered from the ATR-FTIR spectra after UV irradiation. However, there was no difference in the spectra of the Cycle 1 and Cycle 5 virus samples. The tests with potential UV-protectants revealed that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy were the most effective in protecting the virus from UV. However, there was no significant difference in their protection of UV tolerant CrleGV-SA and wild type CrleGV-SA. Going forward, it is recommended that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy combinations be explored further in future studies, particulary in the field. This study therefore forms an important foundation for the development of UV-tolerant baculovirus that will last longer in the field.
- Full Text:
- Date Issued: 2020
- Authors: Mwanza, Patrick
- Date: 2020
- Subjects: Baculoviruses -- South Africa , Ultraviolet astronomy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48533 , vital:40885
- Description: Baculoviruses are pathogenic to insects in the orders Diptera, Hymenoptera, and Lepidoptera. As a result of this natural relationship with insects they provide an environmentally friendly method to combat crop and forest pests. As such, a number of baculoviruses have been formulated into biopesticides. The use of baculovirus biopesticides is gaining popularity as the use of chemical pesticides has come under stringent regulatory conditions imposed by governments and continental blocks such as the European Union. Baculoviruses have a narrow host range and therefore do not harm non-pests or humans who consume the crops. One such baculovirus is Cryptophlebia leucotreta granulovirus (CrleGV), which is pathogenic to the citrus pest Thaumatotibia leucotreta, commonly referred to as the false codling moth (FCM). CrleGV has an occlusion body (OB) that encloses a single virion. Several CrleGV biopesticides have been registered in South Africa for use on citrus, avocadoes, macadamias, grapes and other crops by two commercial producers, River Bioscience (SA) and Andermatt (Switzerland). These biopesticides are used as part of the FCM integrated pest management (IPM) programme, a multifacetted approach to controlling FCM. However, baculoviruses are susceptible to the ultraviolet (UV) radiation component of sunlight and lose their activity within hours to a few days, after exposure to UV. Several substances have been tested as UV protectants to improve the persistence of baculovirus biopesticides in the field. These include optical brighteners, UV absorbers and anti-oxidants. While very promising in the laboratory, UV-protectants have not been as successful in the field. A few published reports have reported, that UV-tolerant baculoviruses could be isolated from a population by repeatedly exposing and re-exposing the virus to UV irradiation with a propagation step in insect host fourth or fifth instars between each exposure cycle. In this study, the South African isolate of Cryptophlebia leucotreta (CrleGV-SA) was exposed to UV irradiation for 5 exposure cycles in a Q-Sun Xe-3 HC test chamber (Qlab, USA) with parameters set to mimic a typical summer day in the Sundays River Valley, Eastern Cape Province, in South Africa. In between exposures the virus survivors were allowed to multiply in FCM fifth instars. Surface dose bioassays were also conducted to determine the LC50 of the virus after each exposure cycle. Samples from exposure cycle 1 and cycle 5 (UV-tolerant) irradiated for 72 h were prepared for Next Generation Sequencing (NGS) of DNA. The resultant sequence data were analysed using the Geneious R11 software (New Zealand) and compared with the unexposed CrleGV-SA sequence. In-silico restriction enzyme analsysis (REN) with several enzymes was also carried on both the cycle 1 and cycle 5 exposed samples and the resulting digestion patterns were compared with the original CrleGV-SA digestion patterns. The same samples were also analysed by transmission electron microscopy (TEM) and Attenuated Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to evaluate the effect of UV irradiation on the structure of the CrleGV-SA OB. In addition, three UV protectants, lignin sulphate (Sappi, SA), BREAK-THRU®OE446 (OE446) (Evonik Industries, Germany) and Uvinul Easy (BASF, Germany) were prepared with CrleGV-SA to give final protectant concentrations of 0.09 %, 0.9 % and 9 %. The protectant-virus suspensions were exposed to UV for 24 h in the Q-Sun test chamber and bioassays conducted to determine the protective effect of each protectant concentration. The most successful protectants were then combined with the UV-tolerant CrleGV-SA and exposed to UV for 24 h in the Q-Sun test chamber and surface dose bioassays conducted afterwards. Samples exposed to UV in cycle 5 had lower LC50 values compared to samples in the early cycles. With each re-exposure cycle the LC50 values moved closer to that of the unexposed control. The LC50 of virus samples decreased from 2.89 x 108 OBs/ml after 24 h UV-exposure in cycle 1 to 2.16 x 105 OBs/ml after the same duration of exposure in cycle 5; and from 2.11 x 109 OBs/ml in cycle 1 after 72 h UV-exposure to 1.73 x 106 OBs/ml after the same duration of exposure. This represented a 1338-fold difference and a 1220-fold difference, respectively. When the UV-tolerant samples were sequenced seven SNPs were identified in cycle 1, which were thought to help establish UV tolerance, while a further seven SNPs were identified in cycle 5 samples; these were thought to further establish and maintain the UV-tolerance. Additionally, REN analysis with EcoR1 for both test samples yielded digestion patterns that were different from those of the original CrleGV-SA. TEM data showed that UV damages the virion as well as the crystalline structure of the OB. This is the first time visual evidence for UV damage to baculoviruses has been published. Comparison of cycle 1 and cycle 5 UV exposed OBs revealed that the cycle 5 OBs were significantly larger than the cycle 1 OBs (P<0.05). In addition, several peaks in the fingerprint region were shown to have either appeared or disapeered from the ATR-FTIR spectra after UV irradiation. However, there was no difference in the spectra of the Cycle 1 and Cycle 5 virus samples. The tests with potential UV-protectants revealed that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy were the most effective in protecting the virus from UV. However, there was no significant difference in their protection of UV tolerant CrleGV-SA and wild type CrleGV-SA. Going forward, it is recommended that the 0.9 % lignin, 9 % OE446 and 9 % Uvinul Easy combinations be explored further in future studies, particulary in the field. This study therefore forms an important foundation for the development of UV-tolerant baculovirus that will last longer in the field.
- Full Text:
- Date Issued: 2020
Development of bio-based xylan composites for food packaging applications
- Authors: Naidu, Darrel Sarvesh
- Date: 2020
- Subjects: Xylanases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48544 , vital:40886
- Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
- Full Text:
- Date Issued: 2020
- Authors: Naidu, Darrel Sarvesh
- Date: 2020
- Subjects: Xylanases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48544 , vital:40886
- Description: Currently a large number of chemicals and plastics are produced from petroleum-based resources. However, due to the concerns surrounding the depletion of petroleum resources and growing carbon emissions, there is a desire to produce chemicals and plastics from renewable and carbon natural sources. Lignocellulosic biomass (biomass consisting of cellulose, lignin and hemicellulose) is the most common biomass on earth and is renewable and carbon neutral. Of the three main constituents of lignocellulosic biomass, hemicellulose is composed of a mixture of sugars which can be converted into chemicals and plastics. The most common form of hemicellulose found in nature is xylan. This study is aimed at extracting xylan from maize stalk waste residues and the development of xylan films with properties that are suitable for food packaging applications. Xylan was extracted from maize stalk waste residues using an alkaline pre-treatment method. The effects of bleaching conditions (time, temperature and bleach concentration) prior to alkaline treatment on the yield and purity of xylan extracted was studied using a Box-Behnken experimental design. It was observed that the experimental conditions tested had no effect on the yield of the xylan extracted but the bleach concentration had a significant effect on the purity of the xylan extracted. The samples with the lowest lignin content were found to be the samples treated with 3wt% bleach prior to alkaline pre-treatment. One of the main disadvantages of xylan is that it has poor film forming properties, a method of overcoming this is to combine it with another abundantly available biopolymer that has good film forming properties, such as alginate. The effect of xylan, alginate and glycerol content on the mechanical, thermal, moisture uptake and water barrier properties of the films were investigated. It was observed that with an increase in the alginate content there was an increase in the tensile strength and Young’s modulus of the films, whereas the water vapour permeability (WVP) of the films decreased. This was attributed to the greater cohesion between alginate polymer chains compared to the cohesion between xylan polymer chains. The xylanalginate films exhibited better optical and water sorption properties at higher xylan content. In order to improve the inherently poor mechanical and barrier properties of the xylan-alginate films, bentonite and halloysite were incorporated into the films. It was found that 5wt% incorporation of either bentonite or halloysite resulted in a 49% decrease of the WVP, which was attributed to water vapour impermeable nature of the silicate layers that make up both clays. The incorporation of the clays into the xylan-alginate matrix resulted in a significant
- Full Text:
- Date Issued: 2020
Development of MOVPE-grown InAsSb for barrier diode applications
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
Development of Tio 2 nanostructure arrays for photonic extraction of hydrogen gas
- Authors: Suliali, Nyasha Joseph
- Date: 2020
- Subjects: Nanostructures , Nanostructured materials Hydrogen
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49314 , vital:41620
- Description: Amid the energy crisis of the 21st century, renewable energy is a thriving field of study, light harvesting materials being a central theme due to the abundance of solar energy. Nanostructured TiO2 is the most studied photocatalysis material, since the discovery of its energy harvesting properties by Fujishima and Honda in 1972. Environmentally friendly products such as hydrogen fuel, can be produced using TiO2 due to its non-toxicity, chemical stability and photocatalytic activity. The surprising aspect of this important material is that it can be prepared using cost-effective methods such as hydrothermal synthesis, solution gelation and anodic oxidation. This research focused on the three key elements required to develop TiO2 photoelectrodes i.e. the deposition of Ti films on transparent substrates, a thorough analysis of the chemistry of the anodic oxidation process and the development of the TiO2 thin films. Glass substrates that have Ti films are the base component for TiO2 photoelectrode production. Ti films with thicknesses up to 4 μm, were developed on commercial F-doped SnO2 (FTO) glass substrates using high-power impulse magnetron sputtering (HiPIMS). The sputter deposition experiments were performed in the 1 to 8 kW range at a substrate temperature of 500 °C and Ar pressure of 400 mPa. At higher powers, thicker films were deposited, resulting in increased intensity of Xray-diffraction peaks. However, on comparing the XRD patterns, the (001) peak outgrew the rest regardless of thickness of the film. The deposition process therefore favoured orientation of most of the α-Ti phase crystallites with the [001] axis perpendicular to the substrate surface. Surface roughness results were interesting, showing a non-linear dependence of the surface roughness on HiPIMS pulse energy in the 1 to 8 kW range. The surface roughness is highest at the starting deposition power of 1450 W and reduces to a minimum at 4500 W. From this minimum, it increases to its second highest value at 7900 W. From this data, the parameters required to produce Ti films of lowest surface roughness, for deposition on commercial Technistro® FTO glass, were deduced at the inflection point, where the deposition power was 4500 W. The surface roughness obtained is a critical result for the anodic production of quality TiO2 photoelectrodes, which if high, leads to uneven etching, thus irregular and inefficient photoelectrodes. Direct current magnetron sputtering was also carried out in the 1 to 5 kW range to obtain ratios of power-normalised growth rates of the Ti films. This investigation provided the Ti films on FTO glass, the transparent, conductive substrates which were used to develop TiO2 photoelectrodes. To elucidate the chemistry of anodic oxidation of Ti, a mathematical model of the anodic current density, which had not been reported at the time of its publication, was developed. The technique, a highlight of this research, is a predictive numerical computation of the instantaneous quantities of species that participate in the anodization process. From eleven chemical reactions, 14 first order ordinary differential equations were compiled using the principles of chemical reaction kinetics. The pattern, transient behaviour and response to anodization parameters of the current density signal, were successfully predicted. Strong agreement between the model and measurements was demonstrated in seven experiments. The results confirm that the current density signal is a numerical integral of the kinetics of redox reactions of water. The bulk of this research was on the development of TiO2 nanotubular arrays on Ti foil substrates and Ti films on FTO glass. TiO2 films with well-defined tubular structures were synthesised. The films were developed in anhydrous, polar organic hosts with water and etching agents in the range of 10 V to 70 V. The control of geometrical properties of the tubes such as the length, pore diameter, wall thickness, tube separation and number of nanotubes per unit area was demonstrated. Anatase only and mixed anatase-rutile phase compositions were obtained at different annealing temperatures. Nanotubes with diameters as small as 20 nm and thickness as high as 29 μm were produced. Apart from an increase in nanotube thickness, a decrease in distance between nanotubes grown in diethylene glycol was observed at longer anodization times. Studies of the effects of anodization parameters on the current density measured, morphological and crystallographic properties of the nanotube films were conducted in three main investigations. The first was the study of the effect of anodization parameters on current density. Besides the obvious increase of current density with anodic voltage, the first steady state of the growth process was found to depend on the NH4F concentration. The second investigation focused on the effect of accelerated growth of TiO2 nanotubular films. In the study, 9 μm-thick nanotube films were synthesised at twice the growth rate of a 9 μm-thick control sample. The array obtained by accelerated growth had distinguishable nanotubes, however, the morphological quality was reduced. The third investigation demonstrates the control of the number of nanotubes per unit area. By varying the etchant content, the anodic voltage and the viscosity of the electrolyte host, various distributions were obtained. The research ends with a photoelectrochemical application: measurement on photocurrents generated in a two-electrode setup. The photocurrent densities measured in the off and on conditions were 30 nA/cm2 and 2.57 μA/cm2, respectively, demonstrating photoactivity of the developed films.
- Full Text:
- Date Issued: 2020
- Authors: Suliali, Nyasha Joseph
- Date: 2020
- Subjects: Nanostructures , Nanostructured materials Hydrogen
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49314 , vital:41620
- Description: Amid the energy crisis of the 21st century, renewable energy is a thriving field of study, light harvesting materials being a central theme due to the abundance of solar energy. Nanostructured TiO2 is the most studied photocatalysis material, since the discovery of its energy harvesting properties by Fujishima and Honda in 1972. Environmentally friendly products such as hydrogen fuel, can be produced using TiO2 due to its non-toxicity, chemical stability and photocatalytic activity. The surprising aspect of this important material is that it can be prepared using cost-effective methods such as hydrothermal synthesis, solution gelation and anodic oxidation. This research focused on the three key elements required to develop TiO2 photoelectrodes i.e. the deposition of Ti films on transparent substrates, a thorough analysis of the chemistry of the anodic oxidation process and the development of the TiO2 thin films. Glass substrates that have Ti films are the base component for TiO2 photoelectrode production. Ti films with thicknesses up to 4 μm, were developed on commercial F-doped SnO2 (FTO) glass substrates using high-power impulse magnetron sputtering (HiPIMS). The sputter deposition experiments were performed in the 1 to 8 kW range at a substrate temperature of 500 °C and Ar pressure of 400 mPa. At higher powers, thicker films were deposited, resulting in increased intensity of Xray-diffraction peaks. However, on comparing the XRD patterns, the (001) peak outgrew the rest regardless of thickness of the film. The deposition process therefore favoured orientation of most of the α-Ti phase crystallites with the [001] axis perpendicular to the substrate surface. Surface roughness results were interesting, showing a non-linear dependence of the surface roughness on HiPIMS pulse energy in the 1 to 8 kW range. The surface roughness is highest at the starting deposition power of 1450 W and reduces to a minimum at 4500 W. From this minimum, it increases to its second highest value at 7900 W. From this data, the parameters required to produce Ti films of lowest surface roughness, for deposition on commercial Technistro® FTO glass, were deduced at the inflection point, where the deposition power was 4500 W. The surface roughness obtained is a critical result for the anodic production of quality TiO2 photoelectrodes, which if high, leads to uneven etching, thus irregular and inefficient photoelectrodes. Direct current magnetron sputtering was also carried out in the 1 to 5 kW range to obtain ratios of power-normalised growth rates of the Ti films. This investigation provided the Ti films on FTO glass, the transparent, conductive substrates which were used to develop TiO2 photoelectrodes. To elucidate the chemistry of anodic oxidation of Ti, a mathematical model of the anodic current density, which had not been reported at the time of its publication, was developed. The technique, a highlight of this research, is a predictive numerical computation of the instantaneous quantities of species that participate in the anodization process. From eleven chemical reactions, 14 first order ordinary differential equations were compiled using the principles of chemical reaction kinetics. The pattern, transient behaviour and response to anodization parameters of the current density signal, were successfully predicted. Strong agreement between the model and measurements was demonstrated in seven experiments. The results confirm that the current density signal is a numerical integral of the kinetics of redox reactions of water. The bulk of this research was on the development of TiO2 nanotubular arrays on Ti foil substrates and Ti films on FTO glass. TiO2 films with well-defined tubular structures were synthesised. The films were developed in anhydrous, polar organic hosts with water and etching agents in the range of 10 V to 70 V. The control of geometrical properties of the tubes such as the length, pore diameter, wall thickness, tube separation and number of nanotubes per unit area was demonstrated. Anatase only and mixed anatase-rutile phase compositions were obtained at different annealing temperatures. Nanotubes with diameters as small as 20 nm and thickness as high as 29 μm were produced. Apart from an increase in nanotube thickness, a decrease in distance between nanotubes grown in diethylene glycol was observed at longer anodization times. Studies of the effects of anodization parameters on the current density measured, morphological and crystallographic properties of the nanotube films were conducted in three main investigations. The first was the study of the effect of anodization parameters on current density. Besides the obvious increase of current density with anodic voltage, the first steady state of the growth process was found to depend on the NH4F concentration. The second investigation focused on the effect of accelerated growth of TiO2 nanotubular films. In the study, 9 μm-thick nanotube films were synthesised at twice the growth rate of a 9 μm-thick control sample. The array obtained by accelerated growth had distinguishable nanotubes, however, the morphological quality was reduced. The third investigation demonstrates the control of the number of nanotubes per unit area. By varying the etchant content, the anodic voltage and the viscosity of the electrolyte host, various distributions were obtained. The research ends with a photoelectrochemical application: measurement on photocurrents generated in a two-electrode setup. The photocurrent densities measured in the off and on conditions were 30 nA/cm2 and 2.57 μA/cm2, respectively, demonstrating photoactivity of the developed films.
- Full Text:
- Date Issued: 2020
Differences in swimming stroke mechanics and kinematics derived from tri-axial accelerometers during a 200-IM event in South African national swimmers
- Authors: Musson, Courtney Ruth
- Date: 2020
- Subjects: Swimming
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/46337 , vital:39588
- Description: Context: Swimming is a highly competitive sport, with elite swimmers and coaches constantly looking for ways to improve and challenge themselves to meet new performance goals. The implementation of technology in swimming has proven to be a vital tool in athlete monitoring and in providing coaches with additional information on the swimmer’s performance. Example of this technology is the use of inertial sensory devices such as tri-axial accelerometers. The accelerometers can be used to provide kinematic information with regards to the swimmer’s stroke rate, stroke length and stroke mechanics. In a typical training session, coaches would have to manually time and count their swimmer’s strokes to be able to gain the kinematic information they require. Hence, the use ofinertial sensory technology, such as accelerometers, would provide the necessary information coaches require, allowing them to concentrate on other performance aspects such as theirswimmer’s technique.Aim and objectives: The aim of this study was to determine the kinematic parameters and swimming stroke mechanics that could be derived from tri-axial accelerometers, during a 200-m individual medley (IM) event in South African national level swimmers. Three objectives were set to meet the aim of the study. The first was to identify and differentiate each of the stroking styles using tri-axial accelerometers. The second was to identify and differentiate the kinematic parametersand stroke mechanicsfor all four strokes using tri-axial accelerometers. The third objective was to implement machine learning to automate the identification and interpretation of the accelerometer data. Method:A quantitative, non-experimental descriptive one group post-test only design was used, in which 15 national level swimmers, of which seven male and eight female (mean ±SD: age: 20.9 ± 2.90 years; height: 173.28 ± 10.61 cm; weight: 67.81 ± 8.09 kg; arm span: 178.21 ± 12.15 cm) were tested. Three anthropometric measures were taken (height, weight and arm span) prior to testing, with two tri-axial accelerometers and Polar V800watch and heart rate belt attached to the swimmers left wrist, upper-back and chest, respectively. All swimmerswere required to perform three main swimming sets: 50-m IM, 100-m variation and 200-mIM. Variousdescriptivestatisticsincluding mean, standard deviation and confidence intervals (95%)were used to describe the data. with further inferential statistics including paired t-test, intra-class correlation and Bland Altman analysis wereused to describe the relationship ivbetween the accelerometer and the manually estimated parameters. Additionally, arepeated measures one-way ANOVA (with post-hoc Tukey HSD test) werealso used in an inter-comparison of the stroke parameters between each of the stroking styles. A confusion matrix wasused to measure the classification accuracy of the machine learning model implemented on the accelerometer data.Results:The accelerometers proved successful in identifyingand discerningthe stroke mechanics for each of the four stroking styles, with the use of video footage to validatethe findings. In the stroke kinematic differentiation, theBland Altman analysisresultsshowed an agreement between themanual method and accelerometer-derived estimates, although a discrepancy was evident for several of the kinematic parameters, with a significant difference found with the estimated lap time, average swimming velocity and stroke rate (paired t-test: p <0.001 for all swim sets). The inter-comparison between the stroke parameters per stroking style showed a significant difference with average swimming velocity (repeated one-way ANOVA: F = 1789.37, p <0.001), averages stroke rate (repeated one-way ANOVA: F = 671.70, p <0.001) and average stroke length (repeated one-way ANOVA: F = 346.46, p<0.001) for the population group tested. Furtheranalysis with post-hoc Tukey HSD test showed no significant difference wereevident for the average swimming velocity(Tukey: p > 0.05for all strokes)andbetween freestyle and backstroke for the average stroke rate and stroke length (Tukey:p = 0.0968 andp = 0.997, respectively).Lastly, the machine learning model found a classification accuracy of 96.6% in identifyingand labelling the stroking styles fromthe accelerometer data.Conclusion: It was shown that the tri-axial accelerometers were successful in the identification and differentiation of all the stroking styles, stroke mechanics and kinematics, although a discrepancy was found with the average swimming velocity, stroke rate and lap time estimations. The machine learning model implemented proved the benefits of using artificial intelligence to ease the data process and interpretation by automatically labelling the accelerometer data. Therefore, the use of tri-axial accelerometers as a coaching aid has major potential in the swimming community. However, further research is required to eliminate the time-consuming data processingand to increasetheaccuracy of the accelerometer in the measurement of all the stroke kinematics.
- Full Text:
- Date Issued: 2020
- Authors: Musson, Courtney Ruth
- Date: 2020
- Subjects: Swimming
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/46337 , vital:39588
- Description: Context: Swimming is a highly competitive sport, with elite swimmers and coaches constantly looking for ways to improve and challenge themselves to meet new performance goals. The implementation of technology in swimming has proven to be a vital tool in athlete monitoring and in providing coaches with additional information on the swimmer’s performance. Example of this technology is the use of inertial sensory devices such as tri-axial accelerometers. The accelerometers can be used to provide kinematic information with regards to the swimmer’s stroke rate, stroke length and stroke mechanics. In a typical training session, coaches would have to manually time and count their swimmer’s strokes to be able to gain the kinematic information they require. Hence, the use ofinertial sensory technology, such as accelerometers, would provide the necessary information coaches require, allowing them to concentrate on other performance aspects such as theirswimmer’s technique.Aim and objectives: The aim of this study was to determine the kinematic parameters and swimming stroke mechanics that could be derived from tri-axial accelerometers, during a 200-m individual medley (IM) event in South African national level swimmers. Three objectives were set to meet the aim of the study. The first was to identify and differentiate each of the stroking styles using tri-axial accelerometers. The second was to identify and differentiate the kinematic parametersand stroke mechanicsfor all four strokes using tri-axial accelerometers. The third objective was to implement machine learning to automate the identification and interpretation of the accelerometer data. Method:A quantitative, non-experimental descriptive one group post-test only design was used, in which 15 national level swimmers, of which seven male and eight female (mean ±SD: age: 20.9 ± 2.90 years; height: 173.28 ± 10.61 cm; weight: 67.81 ± 8.09 kg; arm span: 178.21 ± 12.15 cm) were tested. Three anthropometric measures were taken (height, weight and arm span) prior to testing, with two tri-axial accelerometers and Polar V800watch and heart rate belt attached to the swimmers left wrist, upper-back and chest, respectively. All swimmerswere required to perform three main swimming sets: 50-m IM, 100-m variation and 200-mIM. Variousdescriptivestatisticsincluding mean, standard deviation and confidence intervals (95%)were used to describe the data. with further inferential statistics including paired t-test, intra-class correlation and Bland Altman analysis wereused to describe the relationship ivbetween the accelerometer and the manually estimated parameters. Additionally, arepeated measures one-way ANOVA (with post-hoc Tukey HSD test) werealso used in an inter-comparison of the stroke parameters between each of the stroking styles. A confusion matrix wasused to measure the classification accuracy of the machine learning model implemented on the accelerometer data.Results:The accelerometers proved successful in identifyingand discerningthe stroke mechanics for each of the four stroking styles, with the use of video footage to validatethe findings. In the stroke kinematic differentiation, theBland Altman analysisresultsshowed an agreement between themanual method and accelerometer-derived estimates, although a discrepancy was evident for several of the kinematic parameters, with a significant difference found with the estimated lap time, average swimming velocity and stroke rate (paired t-test: p <0.001 for all swim sets). The inter-comparison between the stroke parameters per stroking style showed a significant difference with average swimming velocity (repeated one-way ANOVA: F = 1789.37, p <0.001), averages stroke rate (repeated one-way ANOVA: F = 671.70, p <0.001) and average stroke length (repeated one-way ANOVA: F = 346.46, p<0.001) for the population group tested. Furtheranalysis with post-hoc Tukey HSD test showed no significant difference wereevident for the average swimming velocity(Tukey: p > 0.05for all strokes)andbetween freestyle and backstroke for the average stroke rate and stroke length (Tukey:p = 0.0968 andp = 0.997, respectively).Lastly, the machine learning model found a classification accuracy of 96.6% in identifyingand labelling the stroking styles fromthe accelerometer data.Conclusion: It was shown that the tri-axial accelerometers were successful in the identification and differentiation of all the stroking styles, stroke mechanics and kinematics, although a discrepancy was found with the average swimming velocity, stroke rate and lap time estimations. The machine learning model implemented proved the benefits of using artificial intelligence to ease the data process and interpretation by automatically labelling the accelerometer data. Therefore, the use of tri-axial accelerometers as a coaching aid has major potential in the swimming community. However, further research is required to eliminate the time-consuming data processingand to increasetheaccuracy of the accelerometer in the measurement of all the stroke kinematics.
- Full Text:
- Date Issued: 2020
Dismissal for racist remarks and racism
- Authors: Du Plessis, Armand
- Date: 2020
- Subjects: Employees -- Dismissal of -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/47359 , vital:39850
- Description: Racism has always been a hard and tough battle fought by all South Africans. Since the independence of the Republic of South Africa has racism in the workplace become a very popular tendency. Ever since has there been a number of legislation which has been incorporated to specifically address this behaviour, but remains the question whether this legislation has achieved what its drafters aimed to have achieved. There will also be a comparison to the implemented legislations of Australia and England aimed at addressing and prohibiting racism in the workplace. Throughout this study, attention will be brought to specific words which have been used in the past by particular employees towards their fellow employees and the consequences thereof. Recently, the Supreme Court of Appeal and our Constitutional Court had to relook at the definition of “hate speech” in terms of certain legislation within South African and came to the conclusion that this definition must be amended to include, and also exclude, particular words and phrases in order for the existing definition thereof to be more precise and clear. The main aim of this study is to determine whether the dismissal of an employee, based on racism in the workplace, or for the utter of racism remarks in the workplace, can warrant the dismissal of that specific employee, and should dismissal not be the appropriate sanction, to determine what sanction would be appropriate in such circumstances. The writer hereof, has aspired to achieve his goal throughout this study that racism in the workplace should not be tolerated, and that employees who make themselves guilty thereof, should be punished in a serious manner.
- Full Text:
- Date Issued: 2020
- Authors: Du Plessis, Armand
- Date: 2020
- Subjects: Employees -- Dismissal of -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/47359 , vital:39850
- Description: Racism has always been a hard and tough battle fought by all South Africans. Since the independence of the Republic of South Africa has racism in the workplace become a very popular tendency. Ever since has there been a number of legislation which has been incorporated to specifically address this behaviour, but remains the question whether this legislation has achieved what its drafters aimed to have achieved. There will also be a comparison to the implemented legislations of Australia and England aimed at addressing and prohibiting racism in the workplace. Throughout this study, attention will be brought to specific words which have been used in the past by particular employees towards their fellow employees and the consequences thereof. Recently, the Supreme Court of Appeal and our Constitutional Court had to relook at the definition of “hate speech” in terms of certain legislation within South African and came to the conclusion that this definition must be amended to include, and also exclude, particular words and phrases in order for the existing definition thereof to be more precise and clear. The main aim of this study is to determine whether the dismissal of an employee, based on racism in the workplace, or for the utter of racism remarks in the workplace, can warrant the dismissal of that specific employee, and should dismissal not be the appropriate sanction, to determine what sanction would be appropriate in such circumstances. The writer hereof, has aspired to achieve his goal throughout this study that racism in the workplace should not be tolerated, and that employees who make themselves guilty thereof, should be punished in a serious manner.
- Full Text:
- Date Issued: 2020
Disputes about the interpretation, application and breach of collective agreements
- Roelofse, Cornelius Johannes
- Authors: Roelofse, Cornelius Johannes
- Date: 2020
- Subjects: Collective labor agreements -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/47414 , vital:39988
- Description: Section 24 of the Labour Relations Act 66 of 1995 (the Act) regulates disputes about the interpretation and application of collective agreements. On the face of it, there is nothing particularly complicated about section 24 of the Act. This section provides that, if there is a dispute about the interpretation or application of a collective agreement, any party to the dispute may refer the dispute to the CCMA; firstly, if the agreement itself does not provide for its resolution by conciliation or arbitration by another body; secondly, if the dispute resolution procedure is inoperative and finally, if a party is frustrating the resolution of the dispute under the dispute resolution provisions of the collective agreement. Most bargaining council main agreements provide for the resolution of disputes concerning the interpretation or application of their collective agreements by conciliation or, if that fails, by arbitration. But what exactly is the scope of these provisions, and what are the powers of arbitrators when entertaining such matters? These questions are significant. If the scope of section 24 of the Act is as limitless as it seems, and if arbitrators acting in terms of that section have full powers not only to interpret and apply the provisions of collective agreements, but also to order parties not only to comply with them, and to make restitution to the other party if they haven’t, then statutory arbitrators may make orders equivalent to those that courts may make in actions for breaches of contract and, potentially, arbitrate matters over which they would not otherwise have jurisdiction. This could complicate affairs if the collective agreement being interpreted and applied is incorporated into the employment contracts of the employees concerned. The Act does not expressly set out the powers of arbitrators dealing with disputes under section 24 of the Act. For a long time after the promulgation of the Act, statutory arbitrators were generally of the view that section 24 meant what it apparently says, that it empowers arbitrators both to declare the true meaning of collective agreements to apply and to enforce them, also to order defaulting employers to compensate employees for the financial loss they have suffered in consequence of the breach. However, this understanding of what section 24 of the Act entails was thrown into confusion by two judgments of the Labour Appeal Court (LAC), Johannesburg City Parks v Mphahlani NO1 (Johannesburg City Parks) and Minister of Safety and Security v SSSBC (SSSBC). 2 In this treatise a discussion and analysis will follow of how these two judgments influenced future case law about the meaning and scope of section 24 of the Act and the uncertainties it created.
- Full Text:
- Date Issued: 2020
- Authors: Roelofse, Cornelius Johannes
- Date: 2020
- Subjects: Collective labor agreements -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/47414 , vital:39988
- Description: Section 24 of the Labour Relations Act 66 of 1995 (the Act) regulates disputes about the interpretation and application of collective agreements. On the face of it, there is nothing particularly complicated about section 24 of the Act. This section provides that, if there is a dispute about the interpretation or application of a collective agreement, any party to the dispute may refer the dispute to the CCMA; firstly, if the agreement itself does not provide for its resolution by conciliation or arbitration by another body; secondly, if the dispute resolution procedure is inoperative and finally, if a party is frustrating the resolution of the dispute under the dispute resolution provisions of the collective agreement. Most bargaining council main agreements provide for the resolution of disputes concerning the interpretation or application of their collective agreements by conciliation or, if that fails, by arbitration. But what exactly is the scope of these provisions, and what are the powers of arbitrators when entertaining such matters? These questions are significant. If the scope of section 24 of the Act is as limitless as it seems, and if arbitrators acting in terms of that section have full powers not only to interpret and apply the provisions of collective agreements, but also to order parties not only to comply with them, and to make restitution to the other party if they haven’t, then statutory arbitrators may make orders equivalent to those that courts may make in actions for breaches of contract and, potentially, arbitrate matters over which they would not otherwise have jurisdiction. This could complicate affairs if the collective agreement being interpreted and applied is incorporated into the employment contracts of the employees concerned. The Act does not expressly set out the powers of arbitrators dealing with disputes under section 24 of the Act. For a long time after the promulgation of the Act, statutory arbitrators were generally of the view that section 24 meant what it apparently says, that it empowers arbitrators both to declare the true meaning of collective agreements to apply and to enforce them, also to order defaulting employers to compensate employees for the financial loss they have suffered in consequence of the breach. However, this understanding of what section 24 of the Act entails was thrown into confusion by two judgments of the Labour Appeal Court (LAC), Johannesburg City Parks v Mphahlani NO1 (Johannesburg City Parks) and Minister of Safety and Security v SSSBC (SSSBC). 2 In this treatise a discussion and analysis will follow of how these two judgments influenced future case law about the meaning and scope of section 24 of the Act and the uncertainties it created.
- Full Text:
- Date Issued: 2020
Domestication of the international-law prohibition of child soldiering
- Authors: Govender, Nikita
- Date: 2020
- Subjects: Child soldiers (International law) , International law , Humanitarian law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/48982 , vital:41572
- Description: Children and their participation in armed conflict or the ‘child soldiering phenomenon’ as referred to throughout this dissertation is a global crisis which has been inadequately regulated by international law. Customary international law and the three branches of public international law (international humanitarian law (IHL), international human rights law and international criminal law (ICL)) which purport to regulate this phenomenon are not lacking in their substance but rather in their coherency. Four core aspects of the existing international child soldiering norms are identified by this dissertation as being worthy of concern since they unduly prejudice children. These four core aspects being the definition of a child, the nature of child recruitment or enlistment, the nature of child participation in armed conflict and the nature of the obligation on States to prevent child soldiering. The norms established in terms of the abovementioned branches of law not only span across various international instruments within each branch of public international law, but the standards established conflict with one another to the detriment of the children to which it purports to extend protection. States which ratify these instruments therefore find themselves bound to conflicting international obligations insofar as child soldiering is concerned. The question thus becomes how these States, whether monist or dualist, ought to implement such fragmented and conflicting international obligations at national level. Following consideration of the existing State practice, it is evident that the way in which States choose to establish national law based on international obligations is pivotal. Notwithstanding their binding international obligations, States may adopt national legislation in such a way that the existing lacunae and the legal conundrums caused by those conflicting norms are circumvented. In order to assist States to establish national legislation in this way, the question becomes whether or not a model law on child soldiers could serve this purpose. This study determines that the quandary posed by model laws, specifically in relation to the broad interpretative leeway afforded to States, makes it an unsuitable solution to assist States to implement their international obligations in a less fragmented and less inconsistent way. As a model law proves to be an unfeasible solution, this dissertation seeks an alternative solution in the form of a manual on child soldiers. This study concludes that such a manual of which the substantive norms are based on binding treaty law and non-binding soft law, serves as a more appropriate solution. The manual, which shall be based on the notion of “the best interests of the child”, ought to adopt one uniform and consistent approach regarding the regulation of child soldiering, particularly insofar as it ought to extend an unfettered protection to all children. To ensure that such an unfettered protection is maintained throughout the manual, guidelines on the specific substantive norms of the manual are provided by this dissertation. Each guideline considers each of the four core aspects of the existing international child soldiering norms identified by this dissertation as unduly prejudicing children. Finally, this dissertation concludes that the lacunae in the existing international child soldiering norms contribute to the realities on the ground and the starting point in bridging this gap is at State level. It is therefore the overarching recommendation of this dissertation that a manual on child soldiers be established to assist States to implement and subsequently enforce their international child soldiering obligations in a less fragmented and less inconsistent manner.
- Full Text:
- Date Issued: 2020
- Authors: Govender, Nikita
- Date: 2020
- Subjects: Child soldiers (International law) , International law , Humanitarian law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/48982 , vital:41572
- Description: Children and their participation in armed conflict or the ‘child soldiering phenomenon’ as referred to throughout this dissertation is a global crisis which has been inadequately regulated by international law. Customary international law and the three branches of public international law (international humanitarian law (IHL), international human rights law and international criminal law (ICL)) which purport to regulate this phenomenon are not lacking in their substance but rather in their coherency. Four core aspects of the existing international child soldiering norms are identified by this dissertation as being worthy of concern since they unduly prejudice children. These four core aspects being the definition of a child, the nature of child recruitment or enlistment, the nature of child participation in armed conflict and the nature of the obligation on States to prevent child soldiering. The norms established in terms of the abovementioned branches of law not only span across various international instruments within each branch of public international law, but the standards established conflict with one another to the detriment of the children to which it purports to extend protection. States which ratify these instruments therefore find themselves bound to conflicting international obligations insofar as child soldiering is concerned. The question thus becomes how these States, whether monist or dualist, ought to implement such fragmented and conflicting international obligations at national level. Following consideration of the existing State practice, it is evident that the way in which States choose to establish national law based on international obligations is pivotal. Notwithstanding their binding international obligations, States may adopt national legislation in such a way that the existing lacunae and the legal conundrums caused by those conflicting norms are circumvented. In order to assist States to establish national legislation in this way, the question becomes whether or not a model law on child soldiers could serve this purpose. This study determines that the quandary posed by model laws, specifically in relation to the broad interpretative leeway afforded to States, makes it an unsuitable solution to assist States to implement their international obligations in a less fragmented and less inconsistent way. As a model law proves to be an unfeasible solution, this dissertation seeks an alternative solution in the form of a manual on child soldiers. This study concludes that such a manual of which the substantive norms are based on binding treaty law and non-binding soft law, serves as a more appropriate solution. The manual, which shall be based on the notion of “the best interests of the child”, ought to adopt one uniform and consistent approach regarding the regulation of child soldiering, particularly insofar as it ought to extend an unfettered protection to all children. To ensure that such an unfettered protection is maintained throughout the manual, guidelines on the specific substantive norms of the manual are provided by this dissertation. Each guideline considers each of the four core aspects of the existing international child soldiering norms identified by this dissertation as unduly prejudicing children. Finally, this dissertation concludes that the lacunae in the existing international child soldiering norms contribute to the realities on the ground and the starting point in bridging this gap is at State level. It is therefore the overarching recommendation of this dissertation that a manual on child soldiers be established to assist States to implement and subsequently enforce their international child soldiering obligations in a less fragmented and less inconsistent manner.
- Full Text:
- Date Issued: 2020
Early diagnosis of colorectal cancer using gold nanoparticles : a pilot study
- Authors: Noguda, Njabulo
- Date: 2020
- Subjects: Colon (Anatomy) -- Cancer -- Diagnosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48577 , vital:40892
- Description: Introduction: Colorectal cancer (CRC) is ranked amongst the top three most diagnosed cancers in humans worldwide. Colorectal cancer is the fourth most common cancer in South Africa and the sixth most common cause of death. If diagnosed during the early stages, the 5year relative survival rate can be as high as 90%. However, in most cases, the diagnosis is only made at a later stage when the cancer has metastasised, as the detection depends on the symptoms and non-specific screening. Many attempts have been made to achieve an early detected of CRC. Aim: To induce CRC in rats to investigate the use of targeted gold nanoparticles (AuNPs) as a diagnostic tool for CRC. Methods: Ten Wistar rats were injected with 1,2-dimethylhydrazine (DMH), 25 µg/Kg bodyweight once per week, for 5 consecutive weeks to induce CRC. This was followed by an incubation period of 22 weeks. At the end of the incubation period, AuNPs were synthesized using Turkevich’s citrate reduction method, and conjugated with peptide p.L. The rats were then injected intraperitoneally with p.L-PEG-AuNPs to detect CRC. Six rats were kept as controls and did not receive any treatment. Results: Five injections of DMH did not induce CRC in the rats. Conclusion: Even though CRC could not be induced using DMH in this study, 14 nm p.L-AuNPs were synthesized successfully.
- Full Text:
- Date Issued: 2020
- Authors: Noguda, Njabulo
- Date: 2020
- Subjects: Colon (Anatomy) -- Cancer -- Diagnosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48577 , vital:40892
- Description: Introduction: Colorectal cancer (CRC) is ranked amongst the top three most diagnosed cancers in humans worldwide. Colorectal cancer is the fourth most common cancer in South Africa and the sixth most common cause of death. If diagnosed during the early stages, the 5year relative survival rate can be as high as 90%. However, in most cases, the diagnosis is only made at a later stage when the cancer has metastasised, as the detection depends on the symptoms and non-specific screening. Many attempts have been made to achieve an early detected of CRC. Aim: To induce CRC in rats to investigate the use of targeted gold nanoparticles (AuNPs) as a diagnostic tool for CRC. Methods: Ten Wistar rats were injected with 1,2-dimethylhydrazine (DMH), 25 µg/Kg bodyweight once per week, for 5 consecutive weeks to induce CRC. This was followed by an incubation period of 22 weeks. At the end of the incubation period, AuNPs were synthesized using Turkevich’s citrate reduction method, and conjugated with peptide p.L. The rats were then injected intraperitoneally with p.L-PEG-AuNPs to detect CRC. Six rats were kept as controls and did not receive any treatment. Results: Five injections of DMH did not induce CRC in the rats. Conclusion: Even though CRC could not be induced using DMH in this study, 14 nm p.L-AuNPs were synthesized successfully.
- Full Text:
- Date Issued: 2020
Ecological health assessment and ecosystem service provision of two urban wetlands in Port Elizabeth, Eastern Cape (South Africa)
- Authors: Larsen, Michael
- Date: 2020
- Subjects: Ecological assessment (Biology) -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , Msc
- Identifier: http://hdl.handle.net/10948/48434 , vital:40876
- Description: The exponential increase in population numbers has imposed greater demands on the natural environment to meet energy demands for food, transportation, water treatment and the production of consumable goods (Faulkner, 2004). The majority of the African continent is dominated by arid and semi-arid climates and as a result freshwater is limited with many regions experiencing severe water shortages on a regular basis (Schuyt, 2005). Increased natural resource consumption, technological advancements that increase the rate at which resources are harvested and global population growth have had numerous effects on the natural environment. Wide spread degradation of natural habitats is occurring globally resulting in changes to both fauna and flora and can lead to changes in species distribution and abundance, community composition and ecosystem function (Faulkner, 2004).
- Full Text:
- Date Issued: 2020
- Authors: Larsen, Michael
- Date: 2020
- Subjects: Ecological assessment (Biology) -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , Msc
- Identifier: http://hdl.handle.net/10948/48434 , vital:40876
- Description: The exponential increase in population numbers has imposed greater demands on the natural environment to meet energy demands for food, transportation, water treatment and the production of consumable goods (Faulkner, 2004). The majority of the African continent is dominated by arid and semi-arid climates and as a result freshwater is limited with many regions experiencing severe water shortages on a regular basis (Schuyt, 2005). Increased natural resource consumption, technological advancements that increase the rate at which resources are harvested and global population growth have had numerous effects on the natural environment. Wide spread degradation of natural habitats is occurring globally resulting in changes to both fauna and flora and can lead to changes in species distribution and abundance, community composition and ecosystem function (Faulkner, 2004).
- Full Text:
- Date Issued: 2020
Effects of economic growth on greenhouse emissions
- Mkunyana, Asebenzile Priscilla
- Authors: Mkunyana, Asebenzile Priscilla
- Date: 2020
- Subjects: Greenhouse gases -- Environmental aspects -- Africa , Climate change mitigation
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/50404 , vital:42162
- Description: This study employs the panel cointegration and Pooled Mean Group technique to examine the effects of economic growth on greenhouse emissions using the panel data from the period of 1970 to 2014 for five Southern African Development Community group of countries. The increase in the combustion of burning fossil fuels has become the global threat in environmental quality. The Environmental Kuznets Curve hypothesis postulates that at the primary stages of industrial economies there is more extracting of natural resources and more agricultural activities taking place as a result the waste generation and resource depletion accelerate. However, as the economic development improves more, the curve reaches a threshold where it starts to decline due to the increase in economic growth and the change to information-based industries. Based on the empirical evidence, the variables of this study were found to be stationary at first difference and integrated of I(0) and I(1) using Im, Pesaran & Shin W-stat, Fisher ADF, and Levin, Lin & Chu panel unit root test. The existing long-run relationship between the variables were found in both the Pedroni and Kao cointegration test and were significant at 5% in finding the relationship between the variables. The Pooled Mean Group demonstrated mixed results in the study’s regressions, monotonic relationship was found between carbon dioxide and economic growth. The strong existence relationship between economic growth and energy consumption was found to be significant at the 1% level. These results are in line with the EKC hypothesis, which assumes that as the income level increases the society will start to be environmentally friendly and the technology advancement will decrease the emission of pollutants. In addition, in finding the causal relationship between variables, the researcher used the Granger causality test, with the results from this test revealing a unidirectional and bidirectional relationship between all the chosen variables. These results are important for policy makers.
- Full Text:
- Date Issued: 2020
- Authors: Mkunyana, Asebenzile Priscilla
- Date: 2020
- Subjects: Greenhouse gases -- Environmental aspects -- Africa , Climate change mitigation
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/50404 , vital:42162
- Description: This study employs the panel cointegration and Pooled Mean Group technique to examine the effects of economic growth on greenhouse emissions using the panel data from the period of 1970 to 2014 for five Southern African Development Community group of countries. The increase in the combustion of burning fossil fuels has become the global threat in environmental quality. The Environmental Kuznets Curve hypothesis postulates that at the primary stages of industrial economies there is more extracting of natural resources and more agricultural activities taking place as a result the waste generation and resource depletion accelerate. However, as the economic development improves more, the curve reaches a threshold where it starts to decline due to the increase in economic growth and the change to information-based industries. Based on the empirical evidence, the variables of this study were found to be stationary at first difference and integrated of I(0) and I(1) using Im, Pesaran & Shin W-stat, Fisher ADF, and Levin, Lin & Chu panel unit root test. The existing long-run relationship between the variables were found in both the Pedroni and Kao cointegration test and were significant at 5% in finding the relationship between the variables. The Pooled Mean Group demonstrated mixed results in the study’s regressions, monotonic relationship was found between carbon dioxide and economic growth. The strong existence relationship between economic growth and energy consumption was found to be significant at the 1% level. These results are in line with the EKC hypothesis, which assumes that as the income level increases the society will start to be environmentally friendly and the technology advancement will decrease the emission of pollutants. In addition, in finding the causal relationship between variables, the researcher used the Granger causality test, with the results from this test revealing a unidirectional and bidirectional relationship between all the chosen variables. These results are important for policy makers.
- Full Text:
- Date Issued: 2020
Effects of high-intensity speed training on the speed reserve of university middle-distance and field sport athletes
- Authors: Thomas, Emma Jayne
- Date: 2020
- Subjects: Athletes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/46346 , vital:39599
- Description: Context: Despite the multiple differences between athletic events and sports, they all share the sporadic bouts of moderate to extreme intensities and all require some contribution from an integrated bioenergetic system to allow for optimal performance. Although D’ is often considered as an ‘anaerobic work capacity’, such a definition is over-simplistic and its precise composition is nebulous, especially given the mixed findings of the experimental evidence. Clearly, further research is needed to provide a more complete understanding of the D’ parameter, as well as the speed reserve(range of speeds exceeding critical speed) especially within high-intensity exercise. Purpose (Aim): The aim of this study is to determine whether a short term high-intensity speed training intervention within the severe intensity domain effects speed reserve in athletic and non-athletic individuals considered moderately trained.Methods: A quantitative research design was used. Participantscompletedbaseline testing (pre-test), after which they were assigned into two groups. Both groups received a HIIT training program, with group 1 (G140%) receiving a program based on intensity prescription (work bouts performed at 140% of CS)and group 2 (G90-s) receiving a program based on time intervals (work bouts performed for 90-s). HIIT sessions were performed twice-weekly for a total of 6-weeks. A post-test assessment was then conducted by both groups to determine whether any changes have accrued in any of the physiological variables in question. Participants of the study met a specific criterion(18 –30 years of age, residing in Nelson Mandela Bay, and met the minimum fitness requirements). Results: No significant between-group differences were evident prior to and following cessation of the HIIT intervention. Findings that can be highlighted holistically include improvements in CS(G140%: M = 0.62 m.s-1; G90-s: M = 0.46 m.s-1)and 𝑉̇𝑂2𝑚𝑎𝑥 (G140%: +3.81 ml.kg-1.min-1; G90-s: +5.19 ml.kg-1.min-1)and a decrease in fatigue index (G140%: M = -6.75%; G90-s: M = -4.38%) and D’(G140%: M = -56.34 m; G90-s: M = -18.36 m).Normative data were generated for athletic and non-athletic participants using the standard nine (Stanine) categorization to facilitate interpretation and recommendations of key parameters for coaches and clinicians. Moreover, a deterministic model was also generated which revealed novel interactions and the strength of the relationship between variables-potentially opening new and innovative areas of future research. Conclusions: The interval durations and speeds utilised in the present study were insufficient to stimulate an increase in D’. To elicit an increase of D’, one would have to decrease the duration of the intervals performed(i.e. < 90-sec), while increasing speed at which the intervals performed at some speed greater than 140% of CS, but below MSS. Further research is needed to understand the physiological underpinning of the D’ parameter both in isolation and in conjunction with CS. It is clear that D’ is influenced by parameters such as MSS, 𝜏d and FI%; therefore, these sub-parameters should be explored further as potentiators for moderating the D’ parameter.
- Full Text:
- Date Issued: 2020
- Authors: Thomas, Emma Jayne
- Date: 2020
- Subjects: Athletes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/46346 , vital:39599
- Description: Context: Despite the multiple differences between athletic events and sports, they all share the sporadic bouts of moderate to extreme intensities and all require some contribution from an integrated bioenergetic system to allow for optimal performance. Although D’ is often considered as an ‘anaerobic work capacity’, such a definition is over-simplistic and its precise composition is nebulous, especially given the mixed findings of the experimental evidence. Clearly, further research is needed to provide a more complete understanding of the D’ parameter, as well as the speed reserve(range of speeds exceeding critical speed) especially within high-intensity exercise. Purpose (Aim): The aim of this study is to determine whether a short term high-intensity speed training intervention within the severe intensity domain effects speed reserve in athletic and non-athletic individuals considered moderately trained.Methods: A quantitative research design was used. Participantscompletedbaseline testing (pre-test), after which they were assigned into two groups. Both groups received a HIIT training program, with group 1 (G140%) receiving a program based on intensity prescription (work bouts performed at 140% of CS)and group 2 (G90-s) receiving a program based on time intervals (work bouts performed for 90-s). HIIT sessions were performed twice-weekly for a total of 6-weeks. A post-test assessment was then conducted by both groups to determine whether any changes have accrued in any of the physiological variables in question. Participants of the study met a specific criterion(18 –30 years of age, residing in Nelson Mandela Bay, and met the minimum fitness requirements). Results: No significant between-group differences were evident prior to and following cessation of the HIIT intervention. Findings that can be highlighted holistically include improvements in CS(G140%: M = 0.62 m.s-1; G90-s: M = 0.46 m.s-1)and 𝑉̇𝑂2𝑚𝑎𝑥 (G140%: +3.81 ml.kg-1.min-1; G90-s: +5.19 ml.kg-1.min-1)and a decrease in fatigue index (G140%: M = -6.75%; G90-s: M = -4.38%) and D’(G140%: M = -56.34 m; G90-s: M = -18.36 m).Normative data were generated for athletic and non-athletic participants using the standard nine (Stanine) categorization to facilitate interpretation and recommendations of key parameters for coaches and clinicians. Moreover, a deterministic model was also generated which revealed novel interactions and the strength of the relationship between variables-potentially opening new and innovative areas of future research. Conclusions: The interval durations and speeds utilised in the present study were insufficient to stimulate an increase in D’. To elicit an increase of D’, one would have to decrease the duration of the intervals performed(i.e. < 90-sec), while increasing speed at which the intervals performed at some speed greater than 140% of CS, but below MSS. Further research is needed to understand the physiological underpinning of the D’ parameter both in isolation and in conjunction with CS. It is clear that D’ is influenced by parameters such as MSS, 𝜏d and FI%; therefore, these sub-parameters should be explored further as potentiators for moderating the D’ parameter.
- Full Text:
- Date Issued: 2020
Efficacy of the rind physiological disorder oleocellosis control measures in lemon fruit (Citrus limon) under shade netting
- Authors: Njili, Zamazima
- Date: 2020
- Subjects: Citrus fruits--Storage--Diseases and injuries , Citrus--Diseases and pests Citrus fruit industry Citrus products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49237 , vital:41613
- Description: Lemon growers aim to produce fruit with no blemishes on the rind. Fruit without blemishes is regarded as high value fruit required for the export market. Leakage of phytotoxic oil from the rind tissues damages them and results in the development of oleocellosis symptoms. Four experiments were conducted to investigate methods of avoiding and controlling the development of oleocellosis during harvest and post-harvest handling. The first experiment indicated that the rind oil release pressure (RORP) test is the method most effective at predicting oleocellosis incidents. The experiment also suggested that fruit not exposed to the sun are the most susceptible to oleocellosis due to low temperatures that cause high turgidity. Oleocellosis results when turgid fruit is mishandled. A cultivar experiment was carried out to ascertain the lemon cultivar most susceptible to oleocellosis. The results show that the Limoneira cultivar is the most susceptible to oleocellosis and 2PH seedless is the least susceptible cultivar when compared to other lemon cultivars such as Lisbon, Eureka and Genoa. When the use of shade netting was tested to determine its effect on oleocellosis severity, it was found that using shade netting did not have an effect. Fruit grown under shade netting had the same colour and average diameter as fruit grown in an open orchard. In the same experiment, mature fruit were shown to be more susceptible to oleocellosis than immature fruit. The final part of the project investigated harvesting and post-harvest practices to determine those that cause oleocellosis the most. It was found that fruit after degreening had greater oleocellosis due to exposure to moisture conditions and rough handling. Another practice that results in oleocellosis occurs before waxing when the fruit was roughly transferred from the bins into the packline. The third oleocellosis inducing practice was moving fruit along the conveyor belt while it is turgid. Improvement of handling procedures to reduce oleocellosis can increase export volume and result in higher value of fruit per carton.
- Full Text:
- Date Issued: 2020
- Authors: Njili, Zamazima
- Date: 2020
- Subjects: Citrus fruits--Storage--Diseases and injuries , Citrus--Diseases and pests Citrus fruit industry Citrus products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49237 , vital:41613
- Description: Lemon growers aim to produce fruit with no blemishes on the rind. Fruit without blemishes is regarded as high value fruit required for the export market. Leakage of phytotoxic oil from the rind tissues damages them and results in the development of oleocellosis symptoms. Four experiments were conducted to investigate methods of avoiding and controlling the development of oleocellosis during harvest and post-harvest handling. The first experiment indicated that the rind oil release pressure (RORP) test is the method most effective at predicting oleocellosis incidents. The experiment also suggested that fruit not exposed to the sun are the most susceptible to oleocellosis due to low temperatures that cause high turgidity. Oleocellosis results when turgid fruit is mishandled. A cultivar experiment was carried out to ascertain the lemon cultivar most susceptible to oleocellosis. The results show that the Limoneira cultivar is the most susceptible to oleocellosis and 2PH seedless is the least susceptible cultivar when compared to other lemon cultivars such as Lisbon, Eureka and Genoa. When the use of shade netting was tested to determine its effect on oleocellosis severity, it was found that using shade netting did not have an effect. Fruit grown under shade netting had the same colour and average diameter as fruit grown in an open orchard. In the same experiment, mature fruit were shown to be more susceptible to oleocellosis than immature fruit. The final part of the project investigated harvesting and post-harvest practices to determine those that cause oleocellosis the most. It was found that fruit after degreening had greater oleocellosis due to exposure to moisture conditions and rough handling. Another practice that results in oleocellosis occurs before waxing when the fruit was roughly transferred from the bins into the packline. The third oleocellosis inducing practice was moving fruit along the conveyor belt while it is turgid. Improvement of handling procedures to reduce oleocellosis can increase export volume and result in higher value of fruit per carton.
- Full Text:
- Date Issued: 2020