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An exploration of the Participatory Guarantee System (PGS) facilitating the growth and certification of small-scale organic farmers: Giyani, Garden Route and Overberg case studies

  • Authors: Mashele,N’wa-Jama
  • Date: 2023-04
  • Subjects: Organic farming – Case studies --South Africa , Organic farming research
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/60741 , vital:66574
  • Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
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  • Date Issued: 2023-04

Billing system, communication strategies, and organisation change in Zimbabwe: the case of telone customers’ postpaid to prepaid migration

  • Authors: Dube, Sizalobuhle
  • Date: 2023-04
  • Subjects: Communication , Organizational change , Organizational change -- Management
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10353/27336 , vital:66942
  • Description: This study investigated the effectiveness of the communication strategies used to implement the migration of telephone services from post-paid to prepaid billing at TelOne Zimbabwe. This study adopted the Freeman‟s stakeholder theory and the Lewin‟s change model to analyse the factors that influenced the effectiveness of the communication strategies used by TelOne before, during and after the change implementation as a way to communicate the initiative with its stakeholders. A qualitative approach was utilised and the key research methods used included document analysis, participant observation, as well as 21 face-to-face and 79 telephonic semi-structured interviews conducted with respondents from among TelOne managers, employees and the customers. The documents and respondents were purposively sampled based on the researcher‟s knowledge of their relevance in the study. The findings revealed several factors that mired effective change communication strategies such as company image, stakeholder recognition and communication centralisation. To curb these communication challenges, the study proposes Thrive organisational communication change model TOCC that encourages organisations to communicate the initiative to its relevant internal and external stakeholders considering their views and addressing factors that might hinder effective communication as a strategy to enhance successful change management. , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2023
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  • Date Issued: 2023-04

Evaluation of the toxicity of secondary metabolites in Solanum incanum L. to advance community knowledge

  • Authors: Zivanayi, William
  • Date: 2023-04
  • Subjects: Solanum -- Zimbabwe , Pesticides -- Toxicology , Medicinal plants
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/61018 , vital:69686
  • Description: The effects of pests and the need to produce adequate food have influenced small-scale farmers in disadvantaged communities to adopt and utilise natural plant pesticides to improve harvests in many Southern African Development Communities. However, the phytochemistry associated with these indigenous plants’ pesticide activity still needs to be explored. The lack of evidence of scientific knowledge of the plant species has caused a lot of health issues among the users of indigenous plant pesticides. Solanum incanum is among the plants utilised to control cabbage aphids in Mkoba village, Zimbabwe. Solanum species are known for their steroidal compounds which comprise glycoalkaloids and saponins. This study evaluated the knowledge, opinions, and attitudes of the vegetable peasant farming community in Gweru regarding their use of the indigenous plant (S. incanum) as a pesticide. The study also reported the phytochemical profiling, structural characterisation of the isolated compounds, and biological and pesticidal activity evaluation of phytochemicals isolated from S. incanum. A descriptive survey was carried out to assess the knowledge, attitude, and practices of a conveniently sampled group of vegetable farmers in Mkoba village who use S. incanum as a pesticide. Forty-nine respondents comprised of 19 males and 30 females of ages ranging from 15 to above 60 years took part in the study by answering an open and closed-ended questionnaire. The survey revealed that parents and neighbours were instrumental in disseminating pesticidal information in the community. Brassica napus were the most grown.vegetable and vulnerable to cabbage aphids. Mixed opinions amongst the respondents varied regarding the health and environmental impact of S. incanum as a pesticide. Seventy-five percent (75%) of the respondents supported the use of S. incanum as a pesticide whilst 25% claimed that the use of S. incanum was the source of the health problems experienced in the community. The survey demonstrated that (45)91% of the farmers displayed poor practices regarding the disposal of empty pesticide containers and the use of personal protective clothing. The most prevalent symptoms in the community were skin rash, nausea, headache, and poor vision and these symptoms were common in the age group 30 to 60 years. , Thesis (PhD) -- Faculty of Science, School of biomolecular and Chemical Sciences, 2023
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  • Date Issued: 2023-04

Experiences of youths participating in combination social protection and HIV prevention programme in resource constrained settings of Gauteng Province in South Africa: a collective case study design

  • Authors: Zibengwa, Enock
  • Date: 2023-04
  • Subjects: HIV infections -- Prevention , HIV (Viruses) , HIV infections -- Africa
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10353/27347 , vital:66944
  • Description: South Africa continues to experience unacceptably high Human Immunodeficiency Virus HIV incidence rates among youths aged 15 to 24 years. Remarkably, this is despite the numerous youth HIV prevention programmes that have been implemented in the country. Unfortunately, the programmes have not significantly curbed the spread of HIV due to the partial and fragmented nature of their implementation. The programmes are also observed to be weak in addressing complex economic factors recognised as important structural drivers for vulnerabilities that put youths at risk of HIV infection. To address this challenge, there is increased adoption and implementation of the Combination Social Protection introduced in this research as the CSP by Non-Governmental Organisations NGOs. The CSP is a youth empowerment programming strategy whose critical foundations are entrenched in combining economic strengthening interventions and HIV prevention education. CSP could provide youths with a set of indispensable life skills that enhance their competencies and agency to make informed and effective decisions regarding their health and economic lives. Despite its growing traction, little is known regarding links between the CSP and its abilities to improve HIV prevention outcomes for youths. Given the paucity of research, this study aimed to explore the experiences of youths participating in the CSP and HIV prevention programme, with a particular focus on the resource-constrained settings of Gauteng Province in South Africa. This study employed a collective case study design, within the qualitative approach, and was exploratory. In-depth individual interviews were conducted with 30 youths from six established NGOs in the City of Johannesburg (CoJ). Qualitative thematic analysis was employed as a data analysis strategy. Focus groups were separately with six practitioners from the same six NGOs, and five officials from the Department of Social Development (DSD). Both phases of data collection were guided by interview themes, which were aligned with the objectives of the study. The findings of the study point to the fact that the CSP’s innovative and holistic approach offered numerous transformative and empowering benefits to youths. It equipped them with basic informational resources, capabilities, and social assets to safeguard their health and aid their economic advancement. The programme’s mixedgender sessions provided space, freedom, and support for youths to engage on issues of gender, differential access to health and socio-economic opportunities. Another major finding of the study was that improvement of economic aptitude (brought about by financial literacy education), employability, and entrepreneurship training stirred a sense of agency and purposefulness among youths, which in turn, prompted them to be more focused on achieving long-term objectives instead of indulging in risky sexual practices. Conversely, findings revealed that the programme had limited opportunities and did not create an adequate supportive environment for youths to develop successful entrepreneurial or income-generating projects. There was also no structure to assist youths to access apprenticeship and employment markets. The study specifically recognised that the programme’s efforts to develop youths’ entrepreneurship and employability capabilities were curtailed by a lack of mentorshipnand access to financial capital for start-up costs. With these findings in mind, recommendations are made for the creation of an enabling environment by purposefully engaging youths, establishing collaborative relations with communities, and building networks with businesses and financial institutions that can help youths with capital, mentorship, and linkages to internship and wage employment. Such collaborations could be fundamental in unravelling the impact of the programme on building livelihoods and reducing HIV among youths. Hence, this study proposes a model with strategies to support the successful implementation of economic strengthening interventions for youths. , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2023
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  • Date Issued: 2023-04

Integration of digital media and pedagogy in the twenty first century classroom: a survey of selected high schools in Eastern Cape, South Africa

  • Authors: Mhlomi, Yolisa
  • Date: 2023-04
  • Subjects: Teaching , Digital media , Classroom learning centers
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10353/27369 , vital:66952
  • Description: The essence of this thesis was to study the effectiveness of integrating digital media technologies within the pedagogical approaches adopted and implemented in private and public high schools in a comparative manner. The study looked closely at private and public high schools of the Eastern Cape Province, to study the gaps of accessibility to technology by schools. The study identified the Eastern Cape Province as having a problem of poor performance in matric results at the end of each year as compared to other South African provinces. In order to select the relevant sample for the study, the researcher has utilized two secondary schools private and public in Makhanda Grahamstown and one public secondary school in Alice. The pragmatic paradigm was used to inform the study and used the mixed methods approach to data collection. The researcher distributed closed ended questionnaires to the learners in the three selected secondary schools and semi-structured interviews for the principals of the schools. The key findings reveal that the digital media tools are used for the teaching and learning purposes as well as communication to the schools’ stakeholders. The findings also revealed that various online platforms are utilized for teaching and sharing of information. For example, D6 and Ibambisa School Communicator app, WhatsApp groups for learners, Facebook, Instagram and School website for potential stakeholders. Hence, the results of this study should contribute to the field of ICTs and education in the country to solve the problems facing the teaching and learning systems of private and public schools of the Eastern Cape. Most schools (especially the public) do not have access to digital media tools in their classrooms. Thus, they still depend heavily on the textbooks, which may be outdated or not enough for all learners. In response to the issues faced by the Eastern Cape secondary schools and the findings, the researcher has suggested a model named the Digital Media and Pedagogy Integration DMPI Model of Communication. This model will contribute to the body of knowledge by providing advice to the Department of Basic Education on how teachers and learners can utilize digital media tools effectively. Also, the study has recommended that there is a need for provision of computer literacy training for teachers in secondary schools in this digital age. , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2023
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  • Date Issued: 2023-04

Microstructural based creep life assessment of 1CrMov Turbine rotor steels after long-term service

  • Authors: Nyembe, Hlanganani Siphelele
  • Date: 2023-04
  • Subjects: Materials – Creep –South Africa , Steel -- Creep
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/61380 , vital:70622
  • Description: Creep-resistant 1CrMoV steels are used for high-pressure turbine rotors in fossil fuel power stations operating at steam temperatures up to 565 °C in the creep regime. The upper bainitic microstructure of 1CrMoV rotors changes when exposed to high temperature service over long periods. The aim of this study was to relate these microstructural changes for service exposed 1CrMoV rotor steels to the remaining creep life as determined using existing methods. Analytical electron microscopy was used to quantitatively study the microstructural evolution of service-exposed 1CrMoV steel rotors. 1CrMoV rotor steel samples were characterised in the initial state, and three long-term (272 h to 300 kh) service exposed states. Detailed microstructural investigations were conducted to analyse the cavities; bainitic laths and packets; dislocations; carbide phases and their size, population, composition. The creep life fractions were estimated using conventional life assessment methods based on creep cavitation and hardness. The creep life fraction consumed of the rotors, estimated based on the creep cavities and hardness data, ranged from ~0.5 to 1. Electron backscattered diffraction (EBSD) was used to analyse the bainitic packets, laths, misorientations, and dislocations, which showed that the bainitic lath surface area to volume (SV) correlated with service time. The precipitates were extracted from the Fe-matrix using extraction replication and were further investigated using transmission Kikuchi diffraction (TKD), scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDS). STEM-EDS and TKD identified M3C, MC, M2C, M7C3, and M23C6 (M = Fe, Cr, Mo, V, Mn) in the 1CrMoV steels. STEM-EDS measurements revealed that Fe/Cr ratios in M3C decreased from 4.5 (initial state) to 2.5 (>272 kh). The Fe/Cr and Fe/Mo ratios in overall carbides decreased from 5 and 10 (initial state) to 1 and 2 (>272 kh), respectively. The TKD analysis indicated that the relative phase proportion of M2C and M7C3 carbides, relative to the total extracted carbides, is positively correlated with service exposure. These microstructural features correlate with the creep life fraction consumed and could potentially be used as another indicator of the remnant creep life. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics. 2023
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  • Date Issued: 2023-04

The effect of Cannabis extract on the morphological and metabolic characteristics of various fat depots in diet-induced Obese and STZ-induced male wistar rats

  • Authors: Ramlugon, Sonaal
  • Date: 2023-04
  • Subjects: Rats as laboratory animals , Diabetes in practice , Cannabis -- South Africa
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/61282 , vital:70044
  • Description: To investigate the potential anti-diabetic/obesity properties of oral cannabis administration in an obese and streptozotocin (STZ)-induced diabetic rat model, as well as an obese rat model, and to determine the mechanism of action, with a focus on the peritoneal and intramuscular fat depots. Experimental Design: Obese and STZ-induced diabetic rats were allocated a high fat diet (HFD) and intraperitoneally injected with STZ to mimic an obese and diabetic state. The rats were then orally administered cannabis extract (CE) of 1.25, 2.5 and 5.0 mg/kg body weight (relative to tetrahydrocannabinol (THC) content) or metformin as a positive control. For the obese rat model, the rats were allocated either a high carbohydrate diet (HCD) or high fat diet (HFD) and orally administered with cannabis extract of 1.25 mg/kg body weight (relative to THC content). Weight, blood and insulin-resistant parameters of the rats were monitored. The mitochondrial to genomic DNA ratio (MT:18S DNA), average adipocyte area of the various adipose tissues, citrate synthase and carnitine palmitoyltransferase 1 (CPT1) enzyme activities of the peritoneal and intramuscular fat were measured. Gene expression levels of uncoupling protein 1 (UCP1), cell-death inducing DNA fragmentation factor alpha like effector-a (Cidea), perilipin, hormone-sensitive lipase (HSL) and mitochondrial transcription factor A (TFAM) were measured in peritoneal fat, intramuscular fat and brown adipose tissue (BAT). Main Findings: Obese and STZ-induced diabetic rat model: Due to the biphasic nature of cannabinoids, cannabis dosage plays an important role in the observed effects. CE1.25 was the only cannabis treatment effective in improving the insulinresistant parameters of the rats unlike the other higher cannabis concentrations (CE2.5 and CE5.0). In the peritoneal fat, CE1.25 increased MT:18S DNA, increased citrate synthase activity, and decreased the average adipocyte area when compared to the STZ group. CE1.25 also induced fat beigeing by upregulating gene expression levels of UCP1 and Cidea. XIX Furthermore, an increase in gene expression levels of perilipin, HSL, and TFAM showed increased fat mobilization and metabolic activity. In the intramuscular fat, CE1.25 also reduced the average adipocytes area. However, a different mechanism of action was observed where CE1.25 did not induce fat beigeing, but instead increased both citrate synthase and CPT1 enzyme activities and gene expression levels of HSL, thereby indicating increased fat oxidation and mitochondrial activity. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
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  • Date Issued: 2023-04

Unleashing the nexus between climate change and food security in rural South Africa: role of three community radio stations in the Eastern Cape Province

  • Authors: Bamigboye, Foluke Bosede
  • Date: 2023-04
  • Subjects: Climatic changes , Food security , South Africa -- Rural conditions
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10353/27325 , vital:66939
  • Description: This study investigates the role of Forte FM, Mdantsane FM and Rhodes Music Community Radios in disseminating the different kinds of messages on the nexus between the impacts of climate change and food security in the Eastern Cape Province, South Africa. Therefore, the study aims to investigate how these community radio stations play their informative, educative and entertainment roles regarding climate change and food security awareness programmes to their listeners. The study employed the qualitative research approach and convenience, and non-probability samplings techniques were subsequently used to select samples for this study. In-depth interviews were conducted individually for Forte FM, Mdantsane FM and Rhodes Music community radio programme managers respectively, who serve as the key informants. One focus group discussion each was held with residents of Golf Course, Mdantsane and Grahamstown areas where these radio stations broadcast from, with eight participants in each focus group. The total number of participants for the focus group discussions was 24 participants. The collected data were coded into themes using NVivo 12 software to generate the theme nodes and case nodes as key findings, analysis and then interpreted. The findings of this study confirmed that these three community radio stations do contribute to climate change communication through their programmes that focus on climate change and food security related issues. Another vital finding from the study showed that listeners do benefit immensely from these climate change and food security related programmes of the under-study community radio stations. Hence, listeners physical, social, and cognitive well-being of their climatic environment have been greatly impacted. In the same vein, the findings of this study further revealed that the rural communities who are mostly affected by the impacts of climate change on food security have been well informed and enlightened on the suitable ways to enhance a sustainable food security and climate adaptation system through Forte FM, Mdantsane FM, and Rhodes Music community radio stations. Significantly, this study has been able to come up with two suggested models and the conceptual frameworks, which are the Local Action Adaptive Communication (LAAC) Model and the Indigenous Behavioral Change Conceptual (IBCC) Model. These models are focused on increasing listeners interests, adaptation, and behavioral change on climate change issues. The models are also aimed at ensuring better climate change and food security communication Author. , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2023
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  • Date Issued: 2023-04

Use of flow reactors for an improved synthesis of Tenofovir derivatives

  • Authors: Sonti, Thembela
  • Date: 2023-04
  • Subjects: Antiviral agents -- South Africa , HIV infections –Treatment
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/61190 , vital:69792
  • Description: Tenofovir disoproxil fumarate (TDF) is a prescription drug used to treat and prevent human immunodeficiency virus (HIV) infections. It aids in the reduction of HIV in the body, allowing the immune system to function more effectively. This reduces the risk of HIV complications, such as infections, whilst improving the quality of life. TDF belongs to the nucleotide reverse transcriptase inhibitors category of drugs. These drugs limit the ability of the reverse transcriptase, an enzyme essential for each virus to replicate itself. A reduction in the cost of HIV treatment could improve supply security and make it more accessible to patients in need. Thus, this project aims to use flow technology to achieve a guaranteed supply chain and access. In this thesis, a method for the synthesis of TDF was developed using microreactors starting from the readily available adenine. The method was adapted from the traditional batch synthesis as currently there is no literature on the synthesis of TDF in flow chemistry. The batch methods used for the synthesis of the working standards were successfully translated to flow systems. For the best results to be obtained, optimisation of the reaction temperature, reagent molar equivalents and concentration was critical. From the optimisation studies, an improvement in conversion is evident throughout all stages. The flow synthesis of the first intermediate resulted in a conversion of 100 % in N,N-dimethylformamide in 6 min residence time. This study was conducted at 200 °C, which is higher than the boiling point of the solvent with the aid of a back pressure regulator. A key reagent in the synthesis of tenofovir, namely ((tosyloxy)methyl)phosphonic acid, had to be synthesised and it was successfully produced in 96 % yield. The second intermediate was synthesised through a successful coupling reaction between (R)-9-(2-hydroxypropyl)adenine and ((tosyloxy)methyl)- phosphonic acid, which afforded a 100 % conversion of tenofovir in 20 min total residence time. The multistep synthesis of tenofovir was a success as it afforded a 65 % overall conversion. The prodrug TDF was successfully synthesised at 120 °C with a 30 min residence time, yielding a conversion of 100 %. ii | P a g e This thesis consists of four chapters. Chapter one describes the background on HIV and a literature review on HIV drugs. This chapter also demonstrates flow chemistry and microreactors in detail and different routes for the synthesis of TDF in traditional batch methods. Chapter two provides a detailed methodology for batch synthesis and flow synthesis with analytical data. 1H-NMR, 13C-NMR and FTIR spectroscopy was used to evaluate all the compounds synthesised in this chapter. Chapter three thoroughly discusses the results that were obtained graphically, showing that the flow synthesis gives better yields than batch synthesis. In chapter 4, the conclusion of the whole investigation is stated along with the future work for the preparation of TDF. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
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  • Date Issued: 2023-04

Viability of government funded broiler production : lessons from Northern KwaZulu Natal, South Africa

  • Authors: Mdletshe, Sifiso Themba Clement https://orcid.org/0000-0002-2668-0193
  • Date: 2023-04
  • Subjects: Broilers (Chickens) -- Economic aspects , Broilers (Poultry) , Broilers (Chickens) -- Breeding
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10353/27843 , vital:69947
  • Description: Generally, rural areas continue to experience high poverty levels and low incomes, which seem to be occasioned by high unemployment rates, limited educational attainments, and devastating floods and droughts. This situation is further exacerbated by increase in crime rates, making livelihoods even more difficult. To mitigate such adverse situations, rural households employ diverse strategies, including maintaining community gardens, one-home-one-garden schemes, as well as livestock and poultry production. The most prevalent livelihood strategy in South Africa or KwaZulu-Natal is broiler production, since it needs less space and a short production cycle compared to other livestock or crop enterprises. At the same time, income is generated over a short period. Besides, the government of KwaZulu Natal has actively intervened in the sector as part of its broader poverty reduction strategy and farmer support programmes. In KwaZulu-Natal Province, the provincial government has been supporting broiler producers for many years. While substantial research work has been done in the province on livelihood strategies, including livestock production on a province-wide basis, there is no information about how successful the broiler production funded by the government has being. Broader concerns about production problems have not been assuaged based on systematic studies and evidence. It is this wise that this study was initiated. The objective is to assess the economic viability of government-funded small-scale broiler projects in the KwaZulu-Natal Province of South Africa and determine the implications for poverty reduction and food security. Data were collected from the government-funded small-scale broiler producers that are residing in Northern KwaZulu-Natal districts uThungulu, Zululand and uMkhanyakude. A total of 75 small-scale broiler projects 25 broiler projects in each district were selected by probability sampling procedure for the interviews. Questionnaires that combined both close-ended and open-ended questions were used to collect primary data, which include production and marketing, as well as the factors that influence the profitability of the small-scale broiler projects. After collection, data were captured and encoded on spreadsheets in Microsoft Excel and exported to Statistical Package for the Social Science (SPSS) software version 26 and STATA for analyses. Descriptive statistics applied include frequencies and means. In addition, a gross margin (GM) and gross profit margin (GPM) analysis were employed to assess the profitability of government-funded small-scale broiler projects. Both profitability and gross margin analyses were used as proxies for farmers’ motivation and incentives to participate in broiler production. Further analyses were conducted to determine the model that best explains the underlying relationships. Initially, the Multiple Linear Regression Model was applied to determine the factors influencing the profitability of government-funded small-scale broiler projects. The indication was that while positive profits were revealed, the system seemed to fall short of its potential. In light of that, it was decided to fit another model to estimate the technical efficiency of the system and gain an understanding of the causes of any inefficiency that might exist in the production system. In that regard, the one-step Stochastic Frontier Model was employed to show that the technical efficiency of broiler production systems in the project area was positively and significantly influenced by flock size, the quantity of feeds and labour costs, while medication played no role possibly because of weak extension coverage. An inefficiency model fitted as part of the one-step model suggested that age, gender and educational level were significant influencers of technical inefficiency, with the possibility that the older the farmers, the more technically inefficient the system possibly because of the strenuousness of commercial poultry production. In addition, it was found that the more educated the farmer, the less inefficient the farm, which conversely means that the system becomes more efficient as the farmer receives more education. The negative coefficient of the gender variable also implies that for farms managed by female farmers, the system was less inefficient, which is more technically efficient, and this can be explained by women’s propensity to be more gentle, caring and sensitive in managing the chickens than their male counterparts. Heteroskedasticity tests and corrections were conducted in the one-step estimation technique to show that variations in the inefficiency term (μ) and the stochastic error term were explained by age and educational level for the most part. Clearly, improvements in the broiler industry in KwaZulu-Natal will depend to a large extent on the knowledge and experience of the farmers and substantial enlargement of the flock size of adequately fed birds. Attention to these elements is expected to have important practical implications for sustainable broiler poultry development and food security in the project area, as well as locations possessing identical features and characteristics. , Thesis (MSci) -- Faculty of Science and Agriculture, 2023
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  • Date Issued: 2023-04

A compliance framework for IT governance adoption and use by state-owned entities in South Africa

  • Authors: Nxozi, Monelo
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/419244 , vital:71628
  • Description: Embargoed. Possible release date in early 2025. , Thesis (PhD) -- Faculty of Commerce, Information Systems, 2023
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  • Date Issued: 2023-03-31

A native weevil and an exotic planthopper: investigating potential biological control agents for nymphaea mexicana zuccarini (nymphaeaceae) and its hybrids in South Africa

  • Authors: Reid, Megan Kim
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422554 , vital:71957 , DOI 10.21504/10962/422554
  • Description: Nymphaea mexicana Zuccarini (Nymphaeaceae) is an invasive plant originating from southern USA and Mexico that has become problematic in South Africa, invading several water bodies around the country. Manual removal of this plant is very labour intensive and is not cost efficient or effective for long term control, while the use of herbicides is damaging to the environment and expensive. Consequently, this plant is a desirable candidate for biological control, which takes advantage of enemy release of the target weed and aims to re-establish population suppression induced by host specific natural enemies. Initiating biological control requires that several steps are followed to maximise the success of the programme, and the first few of these, including overseas surveys in the native range of the plant, have already been completed. This thesis aimed to continue biological control research for this species to take further steps at effectively managing the plant. Firstly, pre-release surveys in the invaded range are necessary to: determine what factors (including enemy release) contribute to the invasiveness of the target weed; establish a baseline of information to allow for comparison after biological control agents have been released; and identify any insect herbivores that may already be present in the country. The pre-release surveys conducted in this study revealed useful information about N. mexicana invasions in South Africa and provided evidence that enemy release is applicable to this case. However, these studies determined that a native weevil, Bagous longulus Gyllenhal (Coleoptera: Curculionidae), has expanded its host range to include the exotic N. mexicana at three sites, and may thus have potential for management of the species through augmentative releases. The invasion of N. mexicana in South Africa is further complicated by the presence of several Nymphaea hybrids originating from a complex history of horticultural trade. Although previous research has shown that several hybrid groups are present in South Africa, their parentage is not known. As biological control requires the use of host specific insects adapted to overcome the unique chemical and morphological defences utilised by plant species, hybrids are notoriously difficult to manage because they possess intermediate characters inherited from parent species to which natural enemies may not have adapted. Although biological control of hybrids is challenging, other case studies have demonstrated that it is possible to find suitable agents, but the chances of success are increased if putative parents of the hybrids are known so that they can be surveyed for natural enemies. Further molecular studies including possible parents of the Nymphaea hybrids in South Africa were thus carried out in this thesis to focus future surveying efforts. Two main hybrid groups were identified with genetic similarity to two tested putative Nymphaea parents, and this will allow further investigations of these species to improve the chances of successfully managing these hybrid groups. Some of the tested hybrids showed genetic contributions from multiple groups, some of which were unidentified, so it is necessary to prioritise the most problematic hybrids for biological control. With more insight into the genetic makeup of the Nymphaea hybrids in South Africa, investigations into the host specificity of potential biological control agents can be conducted. The ideal biological control agent should have a broad enough host range to impact and survive on both N. mexicana and its hybrids, but without a host range so broad that it would pose risk to native South African species. Host specificity trials are thus necessary to determine the suitability of potential agents. The identification of B. longulus feeding on N. mexicana during pre-release surveys motivated further investigations to determine the natural distribution, field host range, and host specificity of B. longulus in experimentally controlled conditions. Further surveys were therefore conducted at native Nymphaea sites around South Africa in addition to host specificity trials using the native Nymphaea nouchali Burm. f. (Nymphaeaceae), two populations of N. mexicana, and a cultivated hybrid. Results from the surveys and host specificity tests suggest that B. longulus is widely distributed across South Africa, is specific to Nymphaea with no observed preference between N. mexicana and the native N. nouchali, and does not perform well on Nymphaea hybrids. Hence, B. longulus is promising for use in new association biological control through augmentative releases but is not suitable for management of hybrids. In addition to the potential use of the South African B. longulus, it is necessary to conduct host specificity trials for natural enemies from the native range of N. mexicana that were prioritised in previous studies. Megamelus toddi Beamer (Hemiptera: Delphacidae) is one such species that was imported into quarantined laboratory conditions from Florida, USA. Host specificity trials were conducted using the same test plants as described for the studies on B. longulus, in addition to multigeneration trials to determine how long M. toddi could survive on non-target host plants. As with the B. longulus studies, no statistically significant differences in preference were observed between N. mexicana and N. nouchali, but M. toddi could not complete development on the test hybrid, indicating that this species is also unsuitable for the management of Nymphaea hybrids. Despite suboptimal plant health, M. toddi completed development for three generations on the native N. nouchali. This lack of host specificity deems M. toddi unsafe for release in South Africa but highlights the importance of following predefined steps to develop a biological control programme. The concluding chapter of this thesis discusses the aforementioned findings in a broader context by considering the driving forces of plant invasions in general and specifically for N. mexicana in South Africa. Case studies are also consulted to provide insight into how to proceed with managing Nymphaea hybrids in South Africa, while the factors governing host specificity and host range expansion are also discussed and considered in the context of B. longulus and M. toddi. Finally, after a consideration of the limitations of these studies, recommendations are made to continue the development of biological control for N. mexicana in South Africa. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2023
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  • Date Issued: 2023-03-31

A statistical study of travelling ionospheric disturbances over the African-European and American sectors

  • Authors: Thaganyana, Golekamang Piet
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422541 , vital:71956 , DOI 10.21504/10962/422543
  • Description: This research presents a long-term statistical study of travelling ionospheric disturbances (TIDs) of low- and high-latitude origin over the American and African-European sectors between 2010 and 2018. The TIDs of low latitude origin (hereafter known as poleward TIDs) were studied in both quiet and disturbed conditions, whereas the equatorward TIDs were only studied during quiet conditions. The Kp > 4 and Dst_ -50 nT was used as a criterion for geomagnetic disturbed conditions, while the four geomagnetically quiet days were selected each month based on Kp < 3. Observations of TIDs are made using Global Navigational Satellite Systems (GNSS) total electron content derived data. During quiet conditions, seven and two transhemispheric TIDs were identified over the African-European and American sectors, respectively. The observed TIDs originated from the wintertime hemisphere and propagated into the summertime hemisphere. The horizontal velocity, periods, and horizontal wavelengths of TIDs are in range of cH = 120-274 m/s, 48-80 min and _H = 379-1104 km, respectively. These quiet-time equatorward TIDs have been associated with tertiary gravity waves (GWs) from the dissipation of secondary GWs which are in turn generated from the dissipation of mountain waves (MWs) as a result of excited orographic forcing. The poleward TIDs during geomagnetically quiet conditions over the African and American sectors occur mainly during local daytime. Poleward TIDs were observed mostly in the African-European sector than the American sector. Their horizontal propagation velocities and periods range between 129-280 m/s and 39-70 min over African-European and American sectors. Although the mechanisms responsible for launching quiet-time poleward TIDs have not been established in this study, lower atmospheric processes such as convection systems, sudden stratospheric warming and cold weather fronts may have a role in their generation. During geomagnetic storms in the African sector, almost all poleward TIDs (with the exception of two cases) during the main phase were large-scale with horizontal velocities and periods ranging from 250-503 m/s and 30 min to 2 hours. During recovery phase, poleward TIDs fall under the category of medium scale. In the American sector, the majority of poleward TIDs occurred during the storm's main phase, as opposed to the African-European sector, which experienced a significant number of poleward TIDs during the recovery phase. The periods and horizontal velocities of TIDs range from 45 min-1.5 h and 180-296 m/s during main phase. During the recovery phase, the horizontal velocity and period range from 177-271 m/s and 40-1.5 h, respectively. Overall, it has been shown that statistically, changes in equatorial electrodynamics related to enhanced eastward electric _eld and hence increased equatorial electrojet (vertical E_B drift) correlates highly with the reported poleward TIDs. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2023
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  • Date Issued: 2023-03-31

Characterization of Trypanosoma brucei Sti1 and its interactions with Trypanosoma brucei Hsp83 and human Hsp90

  • Authors: Jamabo, Miebaka
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422629 , vital:71963 , DOI 10.21504/10962/422629
  • Description: Neglected tropical diseases continue to pose global concern due to their impact on health and socio-economic status of developing countries in sub-Saharan Africa. African trypanosomiasis is one of the neglected tropical diseases caused by the kinetoplastid flagellate parasite Trypanosoma brucei (T. brucei). The disease is fatal if untreated and the toolbox to combat the disease has been plagued with many difficulties such as drug resistance, toxic chemotherapeutics, and cumbersome drug delivery processes. In recent years, the disease has received attention from organizations such as the Drugs for Neglected Diseases initiative (DNDi) in partnership with WHO as well as academia and industry to provide alternatives to the existing drugs as part of a targeted approach to eliminate human African trypanosomiasis by 2030. The life cycle of the T. brucei parasite requires that it transitions between a cold-blooded vector (the tsetse fly) and a human host. To survive this extreme environmental change and maintain its infectious cycle, the parasite has evolved an arsenal of tools which include a strong immune evasion technique and a robust molecular chaperone system. Heat shock protein 90 (Hsp90) is one of the most abundant eukaryotic molecular chaperones that has been extensively studied in many organisms. It is indispensable for maintaining proteostasis in some organisms and its inhibition is currently being explored as a drug target for cancer and other parasitic diseases. In T. brucei, cytosolic Hsp90 is specifically referred to as Hsp83 due to variations in the sizes amongst different orthologues. Hsp90 is present in high levels in all stages of the T. brucei cell cycle both constitutively and on exposure to stress. To function in the cell, Hsp90 is dependent on co-chaperones, one of which can be found in most organisms, namely, the stress-inducible protein 1 (Sti1). The Hsp90-Sti1 interaction was shown to be crucial for growth in the intracellular kinetoplastid parasite, Leishmania donovani. However, this partnership has not been explored in the extracellular parasite T. brucei. To analyse the interaction of Hsp90 with Sti1 in T. brucei, this study combined in silico, in vitro and in vivo tools. In silico analyses of the Hsp90 complement in T. brucei revealed the presence of twelve putative Hsp90 genes, ten of which code for the cytosolic protein and are arranged in tandem in a head to tail fashion on the same chromosome. One gene each was found for the mitochondrial and ER paralogues of Hsp90, similar to all other species analysed. Eight putative co-chaperones specific to T. brucei were also discovered: six tetratricopeptide repeat domain (TPR) containing co-chaperones and two non-TPR containing co-chaperones. Structural and evolutionary analysis also confirmed that the domains were conserved across the species analysed. T. brucei Sti1 (TbSti1), T. brucei cytosolic Hsp90 (TbHsp83) and human cytosolic Hsp90 (hHsp90) were heterologously overproduced in E. coli and purified using nickel affinity chromatography. With specific antibodies, the expression and localization of the proteins were confirmed. TbSti1 showed strong affinity to the Hsp90s in the nanomolar range, with higher affinity for hHsp90 compared to TbHsp83. TbHsp83 and hHsp90 showed typical chaperone properties by suppressing the aggregation of thermolabile substrate MDH at equimolar concentrations and both chaperones had potent ATP hydrolysis activity. TbSti1, on the other hand, showed no MDH suppression activity and did not affect the ATP hydrolysis activity of TbHsp83 or hHsp90. Ex-vivo experiments using HeLa CRISPR Hop knockout (KO) human cell lines transfected with pcDNA3.1(+)HA-TbSti1 revealed TbSti1 also localized to the cytoplasm. The transfected cells showed a distinct fibroblast-like morphology which was different from the circular morphology seen in the Hop KO untransfected and wild type untransfected cells. Finally, co-immunoprecipitation studies revealed that TbSti1 co-immunoprecipitated with hHsp90. These results show the first characterization of the TbHsp83-TbSti1 partnership in T. brucei. The strong association between both proteins suggests a functional role for this partnership in T. brucei and could provide an updated context for understanding Trypanosome brucei biology. , Thesis (PhD) -- Faculty of Science, Biotechnology and Innovation Centre, 2023
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  • Date Issued: 2023-03-31

Economically important cephalopods of southern Angola, with a focus on the artisanal jig fishery

  • Authors: Vázquez Morán, Chénelle Lesley
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422529 , vital:71955 , DOI 10.21504/10962/422529
  • Description: The global decline in marine finfish stocks has been met with a concomitant expansion of fisheries for cephalopods. Despite the increase in the exploitation and commercialization of cephalopods, there is a dearth of scientific information for over 90% of the extant species and this is even more marked in the developing world. Angolan capture fisheries production noted a tenfold increase in cephalopod landings between 1994 and 2003. One of the important fisheries is a cephalopod directed jig fishery that targets the squid Loligo reynaudii and the cuttlefish Sepia vermiculata in southern Angola, however, there is a complete lack of socio-ecological information available for this fishery. Hence the aim of this thesis was to provide basic biological and demographic information on L. reynaudii and S. vermiculata distributed off the coast of southern Angola, assess the importance and dependence of local artisanal fishers on these two species and examine the current management strategies and policies in the region This study found that the artisanal cephalopod jig fishery is critical for the livelihoods of the coastal communities of southern Angola, particularly due to the limited alternative income generating opportunities available. The cephalopod jig fishery is highly labour intensive, with fishers spending a considerable amount of time per day, drifting over known fishing grounds. Catch composition of the artisanal jig fishery indicated that squid is the dominant species within the fishery, in terms of numerical abundance and weight. The productivity and progression of the fishery is hampered by a number of ecological, socio-economic and governance constraints, as highlighted by socio-economic surveys conducted with local squid fishers. Such constraints include, but are not limited to declining catches, increased negative interactions with seals, increased inter-sector competition, lack of infrastructure, poor quality fishing equipment as well as a lack of communication and support from government officials. To examine aspects of the biology and demography of L. reynaudii, whole specimens were collected monthly, from the two primary fishing areas in southern Angola; Namibe and Tombua, during two main sampling periods, June 2008 – May 2009 (Period 1) and June 2014 – May 2015 (Period 2). Male L. reynaudii were found to be significantly larger in size and weight than females, however both the average and maximum dorsal mantle length (DML) decreased between sampling periods. Length-at-50% maturity was larger for male L. reynaudii (170.47 mm DML – 1st period, 165.44 mm DML – 2nd period) than female L. reynaudii (114.71 mm DML – 1st period, 109.43 mm DML – 2nd period). Gonadosomatic indices (GSI) varied significantly during month and season for both sexes. Peak GSI coincided with a low catches in the artisanal jig fishery suggesting that the population may undergo a spawning migration away from fishing grounds, during late spring and summer. The theory of a seasonal spawning migration is further supported in this study by the low abundance of juvenile and sub-adult L, reynaudii collected during the study, along with the inability to detect egg beds in known fishing grounds. Stomach content analysis indicated that teleosts were the most important dietary item (66.3% F of the stomach contents). Trachurus capensis and Engraulis encrasicolus are both highly abundant small pelagic fishes in the cold nutrient rich waters of the Benguela Current and dominated the diet of sampled squid during autumn and winter months. It is likely that the prevalence of large, adult squid off the coast of Angola, as observed within the current study, may be ascribed to the suitable environmental conditions and the abundance of suitable prey. The results from the current study indicate that the southern Angolan subpopulation reveals similarities to that of the West Coast subpopulation of squid in South Africa, with regards to demographics and reproductive characteristics. It is likely that the population in southern Angola is an extension of the South African subpopulation of L. reynaudii on the western extremities. To examine the basic population biology and ecology of S. vermiculata off southern Angola whole specimens were collected from the fishery between December 2014 and April 2015. Morphological results indicate clear sexual dimorphism in soft part characteristics, cuttlebone and beak morphometry. Length-at-50% maturity was smaller in male S. vermiculata (217.53 mm DML) than female S. vermiculata (231.13 mm DML), although these differences were not significant. Stomach content analysis indicated that S. vermiculata predominantly fed on teleost species which were found within 64.5% of stomachs. Teleosts were more dominant in the diet of male S. vermiculata (78.6% F) than female S. vermiculata (53.0% F), which ate a more varied diet including crustaceans (41.2% F) and cephalopods (17.7% F). Availability and abundance of cuttlefish in Namibe indicates that the species may undergo a spatio-temporal shift in distribution, with majority of the artisanal catches of S. vermiculata occurring during summer months. The results from the current study highlights the fisheries potential of L. reynaudii and S. vermiculata and the dependence of artisanal fishers in southern Angola on cephalopods, and more specifically squid. The development of sustainable fisheries management strategies for the artisanal cephalopod jig fishery is critical, particularly as the global exploitation of cephalopods continues to increase with declining finfish populations. Failure to implement management strategies may remove this critical economic safety net for vulnerable coastal communities which have little alternative livelihood opportunities. Ongoing ecological research, a co-management approach and an increased consideration of local ecological knowledge will assist in designing appropriate management plans for the southern Angolan cephalopod jig fishery. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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  • Date Issued: 2023-03-31

Evaluation of the effectiveness of small aperture network telescopes as IBR data sources

  • Authors: Chindipha, Stones Dalitso
  • Date: 2023-03-31
  • Subjects: Computer networks Monitoring , Computer networks Security measures , Computer bootstrapping , Time-series analysis , Regression analysis , Mathematical models
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/366264 , vital:65849 , DOI https://doi.org/10.21504/10962/366264
  • Description: The use of network telescopes to collect unsolicited network traffic by monitoring unallocated address space has been in existence for over two decades. Past research has shown that there is a lot of activity happening in this unallocated space that needs monitoring as it carries threat intelligence data that has proven to be very useful in the security field. Prior to the emergence of the Internet of Things (IoT), commercialisation of IP addresses and widespread of mobile devices, there was a large pool of IPv4 addresses and thus reserving IPv4 addresses to be used for monitoring unsolicited activities going in the unallocated space was not a problem. Now, preservation of such IPv4 addresses just for monitoring is increasingly difficult as there is not enough free addresses in the IPv4 address space to be used for just monitoring. This is the case because such monitoring is seen as a ’non-productive’ use of the IP addresses. This research addresses the problem brought forth by this IPv4 address space exhaustion in relation to Internet Background Radiation (IBR) monitoring. In order to address the research questions, this research developed four mathematical models: Absolute Mean Accuracy Percentage Score (AMAPS), Symmetric Absolute Mean Accuracy Percentage Score (SAMAPS), Standardised Mean Absolute Error (SMAE), and Standardised Mean Absolute Scaled Error (SMASE). These models are used to evaluate the research objectives and quantify the variations that exist between different samples. The sample sizes represent different lens sizes of the telescopes. The study has brought to light a time series plot that shows the expected proportion of unique source IP addresses collected over time. The study also imputed data using the smaller /24 IPv4 net-block subnets to regenerate the missing data points using bootstrapping to create confidence intervals (CI). The findings from the simulated data supports the findings computed from the models. The CI offers a boost to decision making. Through a series of experiments with monthly and quarterly datasets, the study proposed a 95% - 99% confidence level to be used. It was known that large network telescopes collect more threat intelligence data than small-sized network telescopes, however, no study, to the best of our knowledge, has ever quantified such a knowledge gap. With the findings from the study, small-sized network telescope users can now use their network telescopes with full knowledge of gap that exists in the data collected between different network telescopes. , Thesis (PhD) -- Faculty of Science, Computer Science, 2023
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  • Date Issued: 2023-03-31

Phytoplankton communities provide insight into ecosystem functioning of the Agulhas Current system

  • Authors: Gibb, Ross-Lynne Alida
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422646 , vital:71965
  • Description: Access restricted. Embargoed until 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
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  • Date Issued: 2023-03-31

Rapid Synthesis of Thiol-Co-Capped CdTe/CdSe/ZnSe Multi-Core-Shell QDs and Their Encapsulation in Liposomes and Chitosan Nanoparticles; Comparative Bio-compatibility Studies Using Hela and Vero Cells

  • Authors: Daramola, Olamide Abiodun
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422617 , vital:71962 , DOI 10.21504/10962/422617
  • Description: The common method that has been used to reduce the toxicity posed to living cells by CdTe Quantum Dots (QDs) is through the synthesis of CdTe multi-core-shells nanoparticles. In this process, the surface of CdTe QDs is usually coated by less toxic ZnS or ZnSe shells. This heterostructure compound does not only reduce the toxicity of CdTe QDs but can also be used in applications such as deep tissue imaging. The heterostructures can be in numerous forms such as CdTe/CdSe/ZnSe or CdTe/CdSe/ZnS or CdTe/CdS/ZnS multi-core-shell QDs. However, the drawbacks attributed to the fabrication of these compounds is long synthesis times (6- 24 h) in achieving the highest wavelength emission maxima. Others are the use of toxic reagents and poor reproducibility of synthesized materials. An additional problem is that the ZnSe or ZnS coating is insufficient to completely protect the highly toxic Cd metal from escaping into immediate solution. This limits their use in biochemistry and with living systems. Liposomes and biopolymers such as chitosan are known to be environmentally friendly compounds that have been used in various studies as delivery systems for QDs and model drugs for drug delivery applications. They are generally non-toxic and highly bio-compatible. In this study, the rapid synthesis of thiol-co-capped CdTe/CdSe/ZnSe multi-core-shell QDs with a maximum reaction time of 35 mins, gave reliable QDs with emission maxima at 625 nm. The multi-core-shell QDs were encapsulated in two different bio-compatible environments, namely liposome and chitosan nanoparticles (CNP) at 14 different formulations (F) for liposome and 12 different formulations for CNP. Cytotoxicity and florescence imaging studies using HeLa and Vero cells, were used to investigate the improved bio-compatibility. Various characterization techniques were used to elucidate the optical properties, morphology and physico-chemical properties of the QDs and nanocomposites. Two of the best formulations, QD-liposome vesicles (LVs)-F12 and QD-CNP-F9 (with chitosan), demonstrated high loading efficiencies of 42 ± 6 % and 59 ± 5 %, respectively. While the plain CdTe QDs showed high toxicity, some of the encapsulated materials, QD-LVs-F1 and F12, depicted no-toxicity against the cells (IC50 > 0.5 mg/ml). The QDs also retained most of their fluorescence and properties and could easily be tracked in cells and visualized around the nucleus, indicating the successful internalization of the QDs in the cytosol. These results shows that encapsulation of CdTe multi-core-shell QDs in liposomes produce better bio-compatibility compared to multi-core-shell QDs and better than CNP coating. These particles therefore show good promise in cell-labelling, drug delivery studies. Their core-shell nanoparticles have also shown good behavior in enhancing the memory of a device which is based on some recent collaborated works. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-03-31

South African supratidal microbialites: prokaryote communities, metabolic capabilities, and biogeochemical processes

  • Authors: Isemonger, Eric William
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422641 , vital:71964
  • Description: Access restricted. Embargoed until 2025. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2023
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  • Date Issued: 2023-03-31

The development of ionic zinc(II) phthalocyanines for sono-photodynamic combination therapy of cervical and breast cancer

  • Authors: Nene, Lindokuhle Cindy
  • Date: 2023-03-31
  • Subjects: Uncatalogued
  • Language: English
  • Type: Academic theses , Doctoral theses , text
  • Identifier: http://hdl.handle.net/10962/422565 , vital:71958 , DOI 10.21504/10962/422565
  • Description: This study focuses on the development of the sono-photodynamic combination therapy (SPDT) activity of phthalocyanines (Pcs) on the cervical and breast cancer cell lines in vitro. The SPDT technique utilizes ultrasound in combination with light to elicit cytotoxic effects for cancer eradication. In this work, a selection of tetra-peripherally substituted Zn(II) cationic and zwitterionic Pcs were prepared. The photophysical parameters of the Pcs were determined including their fluorescence behaviours and efficiency of the triplet excited state population. The effects of the ultrasonic parameters (frequencies (MHz) and power (W.cm-2)) on the stability of the Pcs were evaluated. Four parameters were evaluated: Par I (1 MHz: 1 W.cm-2), Par II (1 MHz: 2 W.cm-2), Par III (3 MHz: 1 W.cm-2) and Par IV (3 MHz: 2 W.cm-2). The stability of the Pcs reduced with the increase in the ultrasonic power (for Par II and Par IV). The Par I showed the least degradation compared to the other parameters and was therefore used for the SPDT treatments. The sonodynamic (SDT), photodynamic (PDT) therapy activities of the Pcs were studied and compared to their SPDT efficacies. The Pcs showed reactive oxygen species generation during the SDT, PDT and SPDT treatments. For the SDT and SPDT, singlet oxygen (1O2) and hydroxyl radicals (•OH) were detected. For PDT, only the 1O2 were detected. The cell cytotoxicity studies for the Pcs showed relatively higher therapeutic efficacies for the SDT treatments compared to the PDT treatments, where the SPDT showed higher therapeutic efficacies compared to both the SDT and PDT monotreatments on both the cell lines in vitro. Overall, the combination treatments were better compared to the monotreatments. The activities of the Pcs were compared by their differences in structures, including the type of R-group, type of quaternizing agent and type of nanoparticle conjugates. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
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  • Date Issued: 2023-03-31
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