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
- Full Text:
- Date Issued: 2023-04
- 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
- Full Text:
- Date Issued: 2023-04
Validation and adaptation of statistical models based on the SAPS III score to predict in-hospital mortality in a South African ICU
- Authors: Pazi, Sisa
- Date: 2023-04
- Subjects: Police -- South Africa -- Eastern Cape , Statistics – South Africa , Mortality – South Africa
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/61360 , vital:70602
- Description: In-hospital mortality prediction remains an important task in Intensive Care Units (ICUs). In particular, the estimated in-hospital mortality risk is essential to describe case-mix, for research and clinical auditing purposes. Furthermore, in settings with limited hospital resources (e.g beds) such as the South African public health care system, the estimated in-hospital mortality risk is essential for resource allocation and to inform local patient triage guidelines. Commonly used models for prediction of in-hospital mortality in ICU patients includes, but not limited to, the Simplified Acute Physiology Score III (SAPS III). The SAPS III model was developed in 2005. Notably, the SAPS III model was developed without data collected from African based hospitals. Given the general application of the SAPS III model, including benchmarking and quality control, the development of such a model based on local data is of paramount importance. To this end, this study developed a model for prediction of in-hospital mortality based on data collected in a hospital in South Africa. Logistic regression modelling was used to develop the proposed mortality risk assessment model. The results indicated that the proposed model exhibited superior discrimination and classification abilities compared to the SAPS III model. Future research includes the external validation of the proposed model in different hospitals in South Africa. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Pazi, Sisa
- Date: 2023-04
- Subjects: Police -- South Africa -- Eastern Cape , Statistics – South Africa , Mortality – South Africa
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/61360 , vital:70602
- Description: In-hospital mortality prediction remains an important task in Intensive Care Units (ICUs). In particular, the estimated in-hospital mortality risk is essential to describe case-mix, for research and clinical auditing purposes. Furthermore, in settings with limited hospital resources (e.g beds) such as the South African public health care system, the estimated in-hospital mortality risk is essential for resource allocation and to inform local patient triage guidelines. Commonly used models for prediction of in-hospital mortality in ICU patients includes, but not limited to, the Simplified Acute Physiology Score III (SAPS III). The SAPS III model was developed in 2005. Notably, the SAPS III model was developed without data collected from African based hospitals. Given the general application of the SAPS III model, including benchmarking and quality control, the development of such a model based on local data is of paramount importance. To this end, this study developed a model for prediction of in-hospital mortality based on data collected in a hospital in South Africa. Logistic regression modelling was used to develop the proposed mortality risk assessment model. The results indicated that the proposed model exhibited superior discrimination and classification abilities compared to the SAPS III model. Future research includes the external validation of the proposed model in different hospitals in South Africa. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
A model to predict the development of preeclampsia in South African women
- Authors: Smith, Nathan
- Date: 2022-12
- Subjects: Medical instruments and apparatus -- Design and construction , Hypertension in pregnancy -- measurements-- South Africa , Fetus -- Physiology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59980 , vital:62724
- Description: Preeclampsia is the new onset of hypertension and is one of the leading causes of maternal mortality in South Africa and the world. Preeclampsia is usually diagnosed after 20 weeks’ gestation. Due to South Africa’s poor level of antenatal care, the prediction of pregnant women at risk of developing preeclampsia can be an essential component of improving the level of antenatal. This study used an antenatal care dataset from a South African obstetrician. A review of the literature and existing systems was conducted to identify the eight risk factors. These risk factors are systolic blood pressure, diastolic blood pressure, maternal age, body mass index, diabetes status, hypertension history, nulliparity, and maternal disease. This study used antenatal care datasets from a South African obstetrician. Two models were developed that could accurately predict the development of preeclampsia, one before 16 weeks’ gestation and the other within three check-ups. The model was evaluated using five evaluation metrics: classification accuracy, area under the curve, precision, recall and F-Score. The results of this study show a promising future for the use of machine learning models in health care. To the researcher’s knowledge, this model is the first machine learning model for predicting preeclampsia using a South African dataset. Future work will revolve around validating the model on data collected from field studies in hospitals and clinics around South Africa , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Smith, Nathan
- Date: 2022-12
- Subjects: Medical instruments and apparatus -- Design and construction , Hypertension in pregnancy -- measurements-- South Africa , Fetus -- Physiology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59980 , vital:62724
- Description: Preeclampsia is the new onset of hypertension and is one of the leading causes of maternal mortality in South Africa and the world. Preeclampsia is usually diagnosed after 20 weeks’ gestation. Due to South Africa’s poor level of antenatal care, the prediction of pregnant women at risk of developing preeclampsia can be an essential component of improving the level of antenatal. This study used an antenatal care dataset from a South African obstetrician. A review of the literature and existing systems was conducted to identify the eight risk factors. These risk factors are systolic blood pressure, diastolic blood pressure, maternal age, body mass index, diabetes status, hypertension history, nulliparity, and maternal disease. This study used antenatal care datasets from a South African obstetrician. Two models were developed that could accurately predict the development of preeclampsia, one before 16 weeks’ gestation and the other within three check-ups. The model was evaluated using five evaluation metrics: classification accuracy, area under the curve, precision, recall and F-Score. The results of this study show a promising future for the use of machine learning models in health care. To the researcher’s knowledge, this model is the first machine learning model for predicting preeclampsia using a South African dataset. Future work will revolve around validating the model on data collected from field studies in hospitals and clinics around South Africa , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
A social media analytics framework for decision-making in citizen relationship management
- Authors: Yakobi, Khulekani
- Date: 2022-12
- Subjects: Social Media Analytics -- South Africa , Decision making --Mathematical models , Service delivery
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60048 , vital:62815
- Description: Globally social media has shown unprecedented levels of adoption and Social Media Analytics (SMA) is a rapidly growing topic. For governments, SMA holds the promise of providing tools and frameworks to collect, monitor, analyse and visualise social media data, usually driven by specific requirements from a target application. However, social media data is noisy and unstructured, and organisations struggle to extract knowledge from this data, and convert it into actual intelligence. This study argues that SMA can support intelligent decision-making for Citizen Relationship Management (CzRM). CzRM is a growing effort of governments around the world to strive to respond rapidly to their citizens by fostering a closer relationship thereby creating more effective and efficient service delivery. However, there is a little evidence in literature on empirical studies of any existing decision-making framework for CzRM and SMA adoption. In particular, there is a gap with regards incorporating SMA into decision-making for CzRM of governments, particularly in developing countries like South Africa. The aim of this study was to develop a framework that provides guidelines, including methods and tools, incorporating SMA into decision-making for CzRM in the Gauteng Provincial Government (GPG) and the Free State Provincial Government (FSPG) of South Africa. A Systematic Literature Review (SLR) and conceptual analysis method was conducted to design the Social Media Analytics Framework for Decision-making in the context of CzRM (the SMAF). The findings from the literature review revealed several benefits and challenges with SMA, in particular the shortage of skills, guidelines, methods and tools for SMA. These challenges were used to draft guidelines that were included in the framework, which consists of five components that can be used to derive intelligent information from SMA. The pragmatic philosophy and a case study design was used to generate an in-depth, multifaceted understanding of the underlying problems in the case of the GPG and the FSPG. The German North-West Metropolitan region was used as a third case study to provide a more global perspective and a case of a developed country in terms of Gross Domestic Product. The scope of the study was limited to social media posts by provincial citizens related to CzRM and service delivery. Both formative and summative evaluations of the proposed theoretical framework were conducted. The formative evaluation was conducted v | Page as an Expert Review to receive feedback of the framework from the experts in the field of Computer Science and Information Systems. The findings validated the framework and some minor improvements were made based on the experts’ recommendations. Focus Group Discussions (FGDs) with participants from government managers and decision makers in the three cases were conducted. Case documents for the three cases were collected and reviewed. All collected data was analysed using the Qualitative Content Analysis (QCA) method and common categories and themes were identified. Summative evaluations were conducted in the form of a Field Study, which consisted of an analysis of Twitter data from the three cases, and a closing FGD with Business Intelligence (BI) experts at the primary case of the e-Government department of the GPG. The findings revealed that SMA has been adopted in all three cases; however, while their strategies are comprehensive their implementations are very much in their early stages. The findings also highlighted the status of SMA in government and some potential gaps and areas for implementing the framework. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Yakobi, Khulekani
- Date: 2022-12
- Subjects: Social Media Analytics -- South Africa , Decision making --Mathematical models , Service delivery
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60048 , vital:62815
- Description: Globally social media has shown unprecedented levels of adoption and Social Media Analytics (SMA) is a rapidly growing topic. For governments, SMA holds the promise of providing tools and frameworks to collect, monitor, analyse and visualise social media data, usually driven by specific requirements from a target application. However, social media data is noisy and unstructured, and organisations struggle to extract knowledge from this data, and convert it into actual intelligence. This study argues that SMA can support intelligent decision-making for Citizen Relationship Management (CzRM). CzRM is a growing effort of governments around the world to strive to respond rapidly to their citizens by fostering a closer relationship thereby creating more effective and efficient service delivery. However, there is a little evidence in literature on empirical studies of any existing decision-making framework for CzRM and SMA adoption. In particular, there is a gap with regards incorporating SMA into decision-making for CzRM of governments, particularly in developing countries like South Africa. The aim of this study was to develop a framework that provides guidelines, including methods and tools, incorporating SMA into decision-making for CzRM in the Gauteng Provincial Government (GPG) and the Free State Provincial Government (FSPG) of South Africa. A Systematic Literature Review (SLR) and conceptual analysis method was conducted to design the Social Media Analytics Framework for Decision-making in the context of CzRM (the SMAF). The findings from the literature review revealed several benefits and challenges with SMA, in particular the shortage of skills, guidelines, methods and tools for SMA. These challenges were used to draft guidelines that were included in the framework, which consists of five components that can be used to derive intelligent information from SMA. The pragmatic philosophy and a case study design was used to generate an in-depth, multifaceted understanding of the underlying problems in the case of the GPG and the FSPG. The German North-West Metropolitan region was used as a third case study to provide a more global perspective and a case of a developed country in terms of Gross Domestic Product. The scope of the study was limited to social media posts by provincial citizens related to CzRM and service delivery. Both formative and summative evaluations of the proposed theoretical framework were conducted. The formative evaluation was conducted v | Page as an Expert Review to receive feedback of the framework from the experts in the field of Computer Science and Information Systems. The findings validated the framework and some minor improvements were made based on the experts’ recommendations. Focus Group Discussions (FGDs) with participants from government managers and decision makers in the three cases were conducted. Case documents for the three cases were collected and reviewed. All collected data was analysed using the Qualitative Content Analysis (QCA) method and common categories and themes were identified. Summative evaluations were conducted in the form of a Field Study, which consisted of an analysis of Twitter data from the three cases, and a closing FGD with Business Intelligence (BI) experts at the primary case of the e-Government department of the GPG. The findings revealed that SMA has been adopted in all three cases; however, while their strategies are comprehensive their implementations are very much in their early stages. The findings also highlighted the status of SMA in government and some potential gaps and areas for implementing the framework. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
An evaluation of hibiscus sabdariffa gold nanoparticles for the treatment of triple negative breast cancer
- Authors: Reddy, Nireshini
- Date: 2022-12
- Subjects: Breast--Cancer--Treatment--Technological innovations , Nanomedicine – South Africa , Roselle
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59945 , vital:62697
- Description: Cancer is responsible for the millions of deaths worldwide every year, being ranked as the second leading cause of mortality in the world. Triple negative breast cancer (TNBC) is the most severe type of breast cancer, as it is the most aggressive and difficult to treat. Current treatment methods involve surgery, hormonal-, radiation- and chemotherapy. These are costly and often have severe adverse effects. There has been increasing research in the development of alternative treatment methods to reduce the side effects of cancer therapeutics, as well as the cost. The rapidly growing field of nanotechnology has allowed for the incorporation of several diagnostic, targeting, and therapeutic agents into nanomaterials for cancer treatment. The application of gold nanoparticles (AuNPs) in the diagnosis and treatment of various types of cancers has been widely investigated. AuNPs vary in size, shape, and structure, allowing for the development of diverse formulations for various treatments. The use of green materials, particularly plant material, to synthesise nanomaterials has allowed for the safe, cost-friendly and eco-friendly production of AuNPs that can be used to treat TNBC. The aim of this study was to evaluate the efficiency of green AuNPs synthesised with Hibiscus sabdariffa to treat TNBC in a pilot murine model. Spherical AuNPs were synthesised using an aqueous extract of the calyces of this plant. The AuNPs were characterised using UV-Vis spectrometry, dynamic light scattering, high resolution – transmission electron microscopy, and in vitro stability testing. A cell viability assay showed that these AuNPs exhibited cytotoxicity towards E0771 cells in a dose-dependent manner, where cells treated with the highest concentration of AuNPs (250 µg/mL) exhibited the lowest cell viability (7%). During the in vivo pilot study, C57BL/6 mice were inoculated with TNBC using the E0771 cells. It was found that TNBC had rapidly spread, resulting in metastasis in the liver, as well as omentum and mesentery. This resulted in a number of mice dying; therefore, shortening treatment time of the AuNPs. It is suggested that AuNP treatment may have exacerbated mouse death by promoting ROS production in metastasised tissue, suggesting that AuNP treatment may not be suitable for stage 4 TNBC. Tumor analysis of caspase-3 content showed that the AuNPs exhibited potential pro-apoptotic activity in the tumours, prompting further research into the tumour uptake and apoptotic mechanism of these AuNPs. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Reddy, Nireshini
- Date: 2022-12
- Subjects: Breast--Cancer--Treatment--Technological innovations , Nanomedicine – South Africa , Roselle
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59945 , vital:62697
- Description: Cancer is responsible for the millions of deaths worldwide every year, being ranked as the second leading cause of mortality in the world. Triple negative breast cancer (TNBC) is the most severe type of breast cancer, as it is the most aggressive and difficult to treat. Current treatment methods involve surgery, hormonal-, radiation- and chemotherapy. These are costly and often have severe adverse effects. There has been increasing research in the development of alternative treatment methods to reduce the side effects of cancer therapeutics, as well as the cost. The rapidly growing field of nanotechnology has allowed for the incorporation of several diagnostic, targeting, and therapeutic agents into nanomaterials for cancer treatment. The application of gold nanoparticles (AuNPs) in the diagnosis and treatment of various types of cancers has been widely investigated. AuNPs vary in size, shape, and structure, allowing for the development of diverse formulations for various treatments. The use of green materials, particularly plant material, to synthesise nanomaterials has allowed for the safe, cost-friendly and eco-friendly production of AuNPs that can be used to treat TNBC. The aim of this study was to evaluate the efficiency of green AuNPs synthesised with Hibiscus sabdariffa to treat TNBC in a pilot murine model. Spherical AuNPs were synthesised using an aqueous extract of the calyces of this plant. The AuNPs were characterised using UV-Vis spectrometry, dynamic light scattering, high resolution – transmission electron microscopy, and in vitro stability testing. A cell viability assay showed that these AuNPs exhibited cytotoxicity towards E0771 cells in a dose-dependent manner, where cells treated with the highest concentration of AuNPs (250 µg/mL) exhibited the lowest cell viability (7%). During the in vivo pilot study, C57BL/6 mice were inoculated with TNBC using the E0771 cells. It was found that TNBC had rapidly spread, resulting in metastasis in the liver, as well as omentum and mesentery. This resulted in a number of mice dying; therefore, shortening treatment time of the AuNPs. It is suggested that AuNP treatment may have exacerbated mouse death by promoting ROS production in metastasised tissue, suggesting that AuNP treatment may not be suitable for stage 4 TNBC. Tumor analysis of caspase-3 content showed that the AuNPs exhibited potential pro-apoptotic activity in the tumours, prompting further research into the tumour uptake and apoptotic mechanism of these AuNPs. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Beauty from Ashes:short term postfire regeneration of dune fynbos -thicket vegetation in the South Eastern Cape floristic region
- Authors: Gcina, Sinenjongo
- Date: 2022-12
- Subjects: Fynbos ecology – Nelson Mandela University Campus Nature Reserve , Forest fires -- Prevention and control
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59666 , vital:62319
- Description: Aim This study aims to provide an understanding and a description of the short-term postfire regeneration and ecology of the fynbos-thicket vegetation on a coastal dune system in the southeastern Cape Floristic Region. Another aim is to assess the recovery of the vegetation community by assessing the growth forms and the disturbance response across a range of species from thicket and fynbos communities and to provide a belowground bud bank classification for each of these species in the coastal dune systems. Location The study site was the Mandela University Reserve and the Noordhoek dune fields, situated in Gqeberha, Eastern Cape, which is part of the south-eastern Cape Floristic Region. The study site hosts thicket-fynbos mosaic vegetation type that occurs in a Mediterranean-Climate Ecosystem (MCE). Methods Firstly, field observations and photographs of plant species were taken weekly to assess and identify the species that were emerging and persisting in the dune system in the first 12 months postfire. Phenological events of the species that emerged (e.g., flowering, fruiting, leaf growth, leaf yellowing, and leaf abscission) were also observed and reported on. Secondly, an excavation of 21 species (e.g., Jamesbrittenia microphylla, Euclea racemosa, Olea exasperata, Searsia laevigata) was conducted to classify the species into their belowground bud bank types. Results There was a rapid emergence of resprouters (facultative resprouters and obligate resprouters) in the first 12 months postfire. This was followed by their growth; primarily occurring after the rainfall events. The dominant resprouting species (facultative resprouters and obligate resprouters) entered the system two weeks after the fire. There was a significant difference in the time to the first emergence of the different regeneration groups postfire (P < 0.001): on average, obligate sprouters (OS) appeared 1 month after fire – two months earlier than facultative sprouters (FS) and four months earlier than non-sprouters (NS). There was no statistical evidence to suggest that the FS and non-sprouters NS emerged at different times postfire; however, most NS species were observed in the system 5 months after fire. 4 Exceptions were the NS species Pelargonium grossularoides and Mesembryanthemum aitonis, both annuals that emerged 1 month after fire. A wide range of OS species that appeared earlier in the system (e.g., Euclea racemosa, Olea exasperata, Searsia laevigata, and Lauridia tetragona) exhibit underground lateral growth with belowground bud banks (BBBs) from which they recover after disturbance. In total, six BBB types were recorded in this study, namely: bud-bearing root, rhizome, rhizophore, woody rhizome, stem tuber, and corms. The bud-bearing root from woody species was the dominant BBB in this system. Main conclusion The return of species that occurs in the first year after fire occurs rapidly in the first 2 months as resprouting species (primarily OS) appear in the system. Following this, the rate of return of species decreases as reseeding species (primarily NS) gradually reestablish and occupy the gaps in the dune fynbos-thicket vegetation. This study has shown that plant species in this ecosystem are adapted to fire disturbance as their populations are able to reestablish through various regeneration strategies, including resprouting from different types of BBB. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Gcina, Sinenjongo
- Date: 2022-12
- Subjects: Fynbos ecology – Nelson Mandela University Campus Nature Reserve , Forest fires -- Prevention and control
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59666 , vital:62319
- Description: Aim This study aims to provide an understanding and a description of the short-term postfire regeneration and ecology of the fynbos-thicket vegetation on a coastal dune system in the southeastern Cape Floristic Region. Another aim is to assess the recovery of the vegetation community by assessing the growth forms and the disturbance response across a range of species from thicket and fynbos communities and to provide a belowground bud bank classification for each of these species in the coastal dune systems. Location The study site was the Mandela University Reserve and the Noordhoek dune fields, situated in Gqeberha, Eastern Cape, which is part of the south-eastern Cape Floristic Region. The study site hosts thicket-fynbos mosaic vegetation type that occurs in a Mediterranean-Climate Ecosystem (MCE). Methods Firstly, field observations and photographs of plant species were taken weekly to assess and identify the species that were emerging and persisting in the dune system in the first 12 months postfire. Phenological events of the species that emerged (e.g., flowering, fruiting, leaf growth, leaf yellowing, and leaf abscission) were also observed and reported on. Secondly, an excavation of 21 species (e.g., Jamesbrittenia microphylla, Euclea racemosa, Olea exasperata, Searsia laevigata) was conducted to classify the species into their belowground bud bank types. Results There was a rapid emergence of resprouters (facultative resprouters and obligate resprouters) in the first 12 months postfire. This was followed by their growth; primarily occurring after the rainfall events. The dominant resprouting species (facultative resprouters and obligate resprouters) entered the system two weeks after the fire. There was a significant difference in the time to the first emergence of the different regeneration groups postfire (P < 0.001): on average, obligate sprouters (OS) appeared 1 month after fire – two months earlier than facultative sprouters (FS) and four months earlier than non-sprouters (NS). There was no statistical evidence to suggest that the FS and non-sprouters NS emerged at different times postfire; however, most NS species were observed in the system 5 months after fire. 4 Exceptions were the NS species Pelargonium grossularoides and Mesembryanthemum aitonis, both annuals that emerged 1 month after fire. A wide range of OS species that appeared earlier in the system (e.g., Euclea racemosa, Olea exasperata, Searsia laevigata, and Lauridia tetragona) exhibit underground lateral growth with belowground bud banks (BBBs) from which they recover after disturbance. In total, six BBB types were recorded in this study, namely: bud-bearing root, rhizome, rhizophore, woody rhizome, stem tuber, and corms. The bud-bearing root from woody species was the dominant BBB in this system. Main conclusion The return of species that occurs in the first year after fire occurs rapidly in the first 2 months as resprouting species (primarily OS) appear in the system. Following this, the rate of return of species decreases as reseeding species (primarily NS) gradually reestablish and occupy the gaps in the dune fynbos-thicket vegetation. This study has shown that plant species in this ecosystem are adapted to fire disturbance as their populations are able to reestablish through various regeneration strategies, including resprouting from different types of BBB. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Characterising termite mound spatial patterns in the Eastern Cape Karoo : applying drone remote sensing,GIS and spatial statistics
- Mngcele, Lizalise Sive Nqaba
- Authors: Mngcele, Lizalise Sive Nqaba
- Date: 2022-12
- Subjects: Drone aircraft in remote sensing – Eastern Cape Karoo , Termites , Geographic information Systems – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59555 , vital:62169
- Description: The Eastern Cape Karoo in South Africa has been earmarked for potential Shale Gas development, which has necessitated the understanding of existing ecosystems to be quantiĄed pre-development, in order to have a baseline against which the exploration can be monitored. Termite mounds as baseline mechanisms, are known to be sensitive to ecosystem disturbance and because of their abundance in the exploration zone, have been studied as indicator species. They are both a surface and subsurface phenomena which makes them an ideal baseline monitoring mechanism. Termite mound height, basal circumference and geospatial data was collected against natural and anthropogenic factors: elevation, vegetation, water, soil, geology, human settlements and roads. Mound distributions were observed across four study sites, and seven plots, using a DJI Phantom 4 Pro drone, an aerial and ground survey. Observed mound data on the drone and aerial survey was compared to that of the ground survey. Overall, the drone survey outperformed the aerial survey in recording accurate termite mound data. This was largely attributed to the scale of the study which gave the drone a competitive advantage. It allowed for drone data to be collected at 40 m altitude with an image resolution of 2-6 cm/pixel on each plot. In addition, drone detection accuracy was improved through the ability to generate digital surface models (DSMs) through point clouds and overlaying them with orthomosaics. Considering observed mound spatial point patterns, both the drone and aerial survey were more than 50% percent consistent with the ground survey, although the drone survey detected 28.57% more accurate mound spatial point patterns than the aerial survey. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mngcele, Lizalise Sive Nqaba
- Date: 2022-12
- Subjects: Drone aircraft in remote sensing – Eastern Cape Karoo , Termites , Geographic information Systems – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59555 , vital:62169
- Description: The Eastern Cape Karoo in South Africa has been earmarked for potential Shale Gas development, which has necessitated the understanding of existing ecosystems to be quantiĄed pre-development, in order to have a baseline against which the exploration can be monitored. Termite mounds as baseline mechanisms, are known to be sensitive to ecosystem disturbance and because of their abundance in the exploration zone, have been studied as indicator species. They are both a surface and subsurface phenomena which makes them an ideal baseline monitoring mechanism. Termite mound height, basal circumference and geospatial data was collected against natural and anthropogenic factors: elevation, vegetation, water, soil, geology, human settlements and roads. Mound distributions were observed across four study sites, and seven plots, using a DJI Phantom 4 Pro drone, an aerial and ground survey. Observed mound data on the drone and aerial survey was compared to that of the ground survey. Overall, the drone survey outperformed the aerial survey in recording accurate termite mound data. This was largely attributed to the scale of the study which gave the drone a competitive advantage. It allowed for drone data to be collected at 40 m altitude with an image resolution of 2-6 cm/pixel on each plot. In addition, drone detection accuracy was improved through the ability to generate digital surface models (DSMs) through point clouds and overlaying them with orthomosaics. Considering observed mound spatial point patterns, both the drone and aerial survey were more than 50% percent consistent with the ground survey, although the drone survey detected 28.57% more accurate mound spatial point patterns than the aerial survey. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Comparison of in vitro activities of selected Ganoderma species in relation to skin diseases
- Authors: Van Aardt, Robin Kaylah
- Date: 2022-12
- Subjects: Ganoderma diseases of plants -- South Africa , Macrophages
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61143 , vital:69766
- Description: Ganoderma species of macrofungi have been reported to have a multitude of medicinal properties, however, there is limited information on this genus in South Africa. The goal of this study was to compare biological activities of selected Ganoderma spp. in relation to skin diseases with emphasis on the antibacterial, antioxidant, anti-inflammatory and cytotoxic in vitro activities. Ethanolic and aqueous extracts prepared from six samples of G. lucidum [two commercial products (MG-LZ8 and Medi Mushroom Reishi extract), polar, antler, fruiting body and mycelium] and ten cultivated Ganoderma spp. were screened for bioactivities. Antibacterial activity was assessed using the 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium (INT) assay against skin pathogens (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae). Cytotoxicity was determined using bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst/ PI) staining on the B16F10 melanoma cell line. The 2,2-Diphenyl-1- picrylhydrazyl (DPPH) and Ferric reducing ability of plasma (FRAP) assays were used to investigate antioxidant activity. Immune modulatory effects included detection of phagocytic activity and phenotypic changes of RAW 264.7 murine macrophage cells. The phenotypic macrophage polarisation of the extracts on RAW 264.7 murine macrophage cells was tested by treating the cells with the extracts and measuring the fluorescence of cell surface markers. CD86 was used as indicator for the M1 phenotype and CD206 as a general marker for M2 phenotypes. The commercially available and cultivated G. lucidum extracts did not show antibacterial activity within the 0-2mg/mL concentration range tested. The commercially available MG-LZ8 G. lucidum extract expressed cytotoxic activity with an IC50 value of 21.26 µg/mL while the ethanolic conk fruiting body and mycelial G. lucidum extract showed a significant reduction in live cells, indicating anti-proliferative activity. G. destructans mycelial ethanol extract displayed anti-proliferative activity at a concentration of 200 μg/mL which shows great potential as a mycelial extract. All the G. lucidum extracts exhibited free radical scavenging abilities with the Ganoderma spp. showing little to no measurable activity. G. lucidum and Ganoderma spp extracts had similar responses without inflammatory activity for the concentration ranges tested. The extracts did not increase macrophage phagocytic activity using the pHrodo™ Green E. coli iii BioParticles™ Conjugate. G. lucidum and Ganoderma spp. extracts induced macrophage polarisation toward the M2 phenotype, with the G. lucidum antler and conk fruiting body extracts displaying significant activity. This study illustrates one of the first investigations of the bioactivity of indigenous Ganoderma spp.; G. destructans type and G. eickeri, spp. nov. identified by Coeztee et al (2015). , Thesis (MSc) -- Faculty of Science, School of Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2022-12
- Authors: Van Aardt, Robin Kaylah
- Date: 2022-12
- Subjects: Ganoderma diseases of plants -- South Africa , Macrophages
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61143 , vital:69766
- Description: Ganoderma species of macrofungi have been reported to have a multitude of medicinal properties, however, there is limited information on this genus in South Africa. The goal of this study was to compare biological activities of selected Ganoderma spp. in relation to skin diseases with emphasis on the antibacterial, antioxidant, anti-inflammatory and cytotoxic in vitro activities. Ethanolic and aqueous extracts prepared from six samples of G. lucidum [two commercial products (MG-LZ8 and Medi Mushroom Reishi extract), polar, antler, fruiting body and mycelium] and ten cultivated Ganoderma spp. were screened for bioactivities. Antibacterial activity was assessed using the 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium (INT) assay against skin pathogens (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae). Cytotoxicity was determined using bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst/ PI) staining on the B16F10 melanoma cell line. The 2,2-Diphenyl-1- picrylhydrazyl (DPPH) and Ferric reducing ability of plasma (FRAP) assays were used to investigate antioxidant activity. Immune modulatory effects included detection of phagocytic activity and phenotypic changes of RAW 264.7 murine macrophage cells. The phenotypic macrophage polarisation of the extracts on RAW 264.7 murine macrophage cells was tested by treating the cells with the extracts and measuring the fluorescence of cell surface markers. CD86 was used as indicator for the M1 phenotype and CD206 as a general marker for M2 phenotypes. The commercially available and cultivated G. lucidum extracts did not show antibacterial activity within the 0-2mg/mL concentration range tested. The commercially available MG-LZ8 G. lucidum extract expressed cytotoxic activity with an IC50 value of 21.26 µg/mL while the ethanolic conk fruiting body and mycelial G. lucidum extract showed a significant reduction in live cells, indicating anti-proliferative activity. G. destructans mycelial ethanol extract displayed anti-proliferative activity at a concentration of 200 μg/mL which shows great potential as a mycelial extract. All the G. lucidum extracts exhibited free radical scavenging abilities with the Ganoderma spp. showing little to no measurable activity. G. lucidum and Ganoderma spp extracts had similar responses without inflammatory activity for the concentration ranges tested. The extracts did not increase macrophage phagocytic activity using the pHrodo™ Green E. coli iii BioParticles™ Conjugate. G. lucidum and Ganoderma spp. extracts induced macrophage polarisation toward the M2 phenotype, with the G. lucidum antler and conk fruiting body extracts displaying significant activity. This study illustrates one of the first investigations of the bioactivity of indigenous Ganoderma spp.; G. destructans type and G. eickeri, spp. nov. identified by Coeztee et al (2015). , Thesis (MSc) -- Faculty of Science, School of Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2022-12
Converged data and sensing over optical fiber networks
- Authors: Shumane, Vela
- Date: 2022-12
- Subjects: Optical fiber subscriber loops -- South Africa , Chemical detectors , Internet -- Technological innovations
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59968 , vital:62722
- Description: Internet connectivity, data and sensors have become increasingly important across all spheres of business and industry, especially in the mining sector. Recent years have seen deeper mining explorations as a result of the depletion of natural resources in shallow strata. Due to complex and unexpected geological conditions as well as significant ground stresses, deep stratum mining operations encounter a number of difficulties. It is essential that the mining industry be more innovative with their equipment and monitoring systems given the rise in expenses caused by energy consumption, concessions to surface integrity, worldwide freshwater shortage, as well as health and safety of miners. Any attempt to eliminate these mining consequences must start with early discovery. An effective plan to anticipate, prevent, or manage geohazards events must be in place because to these complex and unpredictably occurring geological circumstances. Due to their capacity to combine gigabits of data from remote locations within the mine to a centralized control centre, optical fiber offers a variety of distinctive advantages within the mining industry. In order to attain maximum productivity, modern and effective mining operations use enhanced control techniques and increasing mechanization. Additionally, optical fibers can be utilized in a mine to safely monitor seismic activity, methane, roof collapses, rock bursts, explosions, and dangerous underground mine settings. Multimode or multi-core fibers represent a particularly intriguing alternative for transmissions over small distances, especially for broad band local area networks like LANs, as they enable the use of affordable components. Due to the current state of these issues, there is a drive to create fiber optic communication links that can also function as distributed optical fiber sensors, where each point along the fiber can function as a continuous array of sensors. In this thesis, we suggested and experimentally demonstrated a converged solution for precise vibration sensing and high-speed data in mining applications. With wireless access for people and equipment inside cavities, the solution uses multimode fiber to link nearby mining cavities. To track vibrations and earth tremors causing rock falls, polarization-based vibration sensors over multimode fiber is used. With a modal dispersion penalty of just 1.6 dB, photonic data transmission across 100 m of multimode fiber is successfully accomplished. Successful 1.7 GHz wireless transmission across a distance of 1 m is demonstrated, and vibrations between 50 Hz and 1 kHz may be reliably detected to within 0.02 percent of the true value. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Shumane, Vela
- Date: 2022-12
- Subjects: Optical fiber subscriber loops -- South Africa , Chemical detectors , Internet -- Technological innovations
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59968 , vital:62722
- Description: Internet connectivity, data and sensors have become increasingly important across all spheres of business and industry, especially in the mining sector. Recent years have seen deeper mining explorations as a result of the depletion of natural resources in shallow strata. Due to complex and unexpected geological conditions as well as significant ground stresses, deep stratum mining operations encounter a number of difficulties. It is essential that the mining industry be more innovative with their equipment and monitoring systems given the rise in expenses caused by energy consumption, concessions to surface integrity, worldwide freshwater shortage, as well as health and safety of miners. Any attempt to eliminate these mining consequences must start with early discovery. An effective plan to anticipate, prevent, or manage geohazards events must be in place because to these complex and unpredictably occurring geological circumstances. Due to their capacity to combine gigabits of data from remote locations within the mine to a centralized control centre, optical fiber offers a variety of distinctive advantages within the mining industry. In order to attain maximum productivity, modern and effective mining operations use enhanced control techniques and increasing mechanization. Additionally, optical fibers can be utilized in a mine to safely monitor seismic activity, methane, roof collapses, rock bursts, explosions, and dangerous underground mine settings. Multimode or multi-core fibers represent a particularly intriguing alternative for transmissions over small distances, especially for broad band local area networks like LANs, as they enable the use of affordable components. Due to the current state of these issues, there is a drive to create fiber optic communication links that can also function as distributed optical fiber sensors, where each point along the fiber can function as a continuous array of sensors. In this thesis, we suggested and experimentally demonstrated a converged solution for precise vibration sensing and high-speed data in mining applications. With wireless access for people and equipment inside cavities, the solution uses multimode fiber to link nearby mining cavities. To track vibrations and earth tremors causing rock falls, polarization-based vibration sensors over multimode fiber is used. With a modal dispersion penalty of just 1.6 dB, photonic data transmission across 100 m of multimode fiber is successfully accomplished. Successful 1.7 GHz wireless transmission across a distance of 1 m is demonstrated, and vibrations between 50 Hz and 1 kHz may be reliably detected to within 0.02 percent of the true value. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
Development of a continuous flow process towards the synthesis of fluvastatin: a lipid lowering drug
- Authors: Singata, Mzuvukile
- Date: 2022-12
- Subjects: Drug development – South Africa , Drugs --Law and legislation , Pharmaceutical technology -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59587 , vital:62175
- Description: Access to pharmaceuticals in low to middle income countries affects not only the health of a nation, but also the economy. Global pandemics such as the SARS COVID-19 pandemic have demonstrated this disparity. A potential solution to this crisis is an efficient and reliable means of local production of active pharmaceutical ingredients. Current manufacturing plants heavily rely on batch processes as their primary form of production. Batch production has been shown to have numerous disadvantages that impede the reliable production of drugs. Flow chemistry presents a possible solution to this impediment. Numerous advantages of flow chemistry make this technology a better and safer option for production; these include improved safety, faster reaction times and improved reaction control. In this research we present the use of flow chemistry towards the synthesis of fluvastatin, a lipid lowering drug for individuals that suffer from hypercholesterolemia, which is characterised by elevated levels of low-density lipoprotein that is sometimes referred to as bad cholesterol. Chapter 1 provides a detailed description of the background to the problem of hypercholesterolemia; in this chapter the role of cholesterol in the body and how it can end up becoming a problem is outlined. An in-depth analysis of flow chemistry is provided and finally the problem statement, aims and objectives are presented. Chapter 2 give a detailed description of the instrumentation and chemicals used in the research. A description of experimental methodology towards the synthesis of all intermediates in batch and flow systems is provided. Chapter 3 provides all the data collected from the research and describes a multivariate optimization of the intermediates towards the synthesis of fluvastatin. The first intermediate was successfully synthesized in batch (60%) and flow systems at an improved conversion of 98% in a residence time of 15 minutes. The second intermediate was also obtained in batch (32%) and using continuous flow systems at a conversion of 75% and a residence time of 25 minutes. The third intermediate was successfully cyclized in batch using ZnCl2 (50%) and via continuous flow using Amberlite IR120 in a packed column reactor at a residence time of 15 minutes at 95°C, to obtain a conversion of 98%. The final intermediate was successfully synthesized in batch (62%) and in flow; it was obtained at 98% at a residence time of 15 minutes using continuous flow. Chapter 4 provides a conclusion of the study; it also provides a description of the future work and recommendations for this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Development of a continuous flow process towards the synthesis of fluvastatin: a lipid lowering drug
- Authors: Singata, Mzuvukile
- Date: 2022-12
- Subjects: Drug development – South Africa , Drugs --Law and legislation , Pharmaceutical technology -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59587 , vital:62175
- Description: Access to pharmaceuticals in low to middle income countries affects not only the health of a nation, but also the economy. Global pandemics such as the SARS COVID-19 pandemic have demonstrated this disparity. A potential solution to this crisis is an efficient and reliable means of local production of active pharmaceutical ingredients. Current manufacturing plants heavily rely on batch processes as their primary form of production. Batch production has been shown to have numerous disadvantages that impede the reliable production of drugs. Flow chemistry presents a possible solution to this impediment. Numerous advantages of flow chemistry make this technology a better and safer option for production; these include improved safety, faster reaction times and improved reaction control. In this research we present the use of flow chemistry towards the synthesis of fluvastatin, a lipid lowering drug for individuals that suffer from hypercholesterolemia, which is characterised by elevated levels of low-density lipoprotein that is sometimes referred to as bad cholesterol. Chapter 1 provides a detailed description of the background to the problem of hypercholesterolemia; in this chapter the role of cholesterol in the body and how it can end up becoming a problem is outlined. An in-depth analysis of flow chemistry is provided and finally the problem statement, aims and objectives are presented. Chapter 2 give a detailed description of the instrumentation and chemicals used in the research. A description of experimental methodology towards the synthesis of all intermediates in batch and flow systems is provided. Chapter 3 provides all the data collected from the research and describes a multivariate optimization of the intermediates towards the synthesis of fluvastatin. The first intermediate was successfully synthesized in batch (60%) and flow systems at an improved conversion of 98% in a residence time of 15 minutes. The second intermediate was also obtained in batch (32%) and using continuous flow systems at a conversion of 75% and a residence time of 25 minutes. The third intermediate was successfully cyclized in batch using ZnCl2 (50%) and via continuous flow using Amberlite IR120 in a packed column reactor at a residence time of 15 minutes at 95°C, to obtain a conversion of 98%. The final intermediate was successfully synthesized in batch (62%) and in flow; it was obtained at 98% at a residence time of 15 minutes using continuous flow. Chapter 4 provides a conclusion of the study; it also provides a description of the future work and recommendations for this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Development of a crumb rubber adsorbent for the sorption of lead and copper from waste water: Optimization of sorption in a binary component system
- Authors: Hlabana,Relebohile Gladys
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59688 , vital:62356
- Description: Waste tyre is becoming a global environmental problem due to challenges in its disposal management and the fact that it poses fire hazards and metal leaching risk. Waste tyre can also breed mosquitos if it traps water thereby becoming an environmental health problem. There is also a portion of unused tyre in a waste tyre that is valuable and should be recycled. In South Africa waste tyre recycling is in three industries, one of which is crumb rubber where waste tyre is applied into various sized particles called crumb rubber. Crumb rubber can be applied in environmental remediation as an organic and inorganic pollutants’ adsorbent. Considering the fact that South Africa’s environment is loaded with heavy metal pollutants due to contributions by mining and agriculture as examples, it is postulated that crumb rubber produced in South Africa could be used to remediate the environment of these toxic metals. In this study adsorption of Pb (II) and Cu (II) from the synthetic waste water using waste tyre crumb rubber produced in South Africa was studied. Crumb rubber was activated using aqueous NaOH (0.02%) to make crumb rubber wettable followed by it being treated with 0.02 % acidified KMnO4 for modification of its ability to sorp positively charged metal species. Trial sorption experiments on 50 mg / L Cu (II) were successful with sorption of over 70% in 250 minutes. Final optimization of the sorption of combined Pb (II) and Cu (II) was studied using a full factorial design and optimum conditions of sorption were found to be pH 5.4; [metal] 0.617 mmol / L for Pb (II); and pH 5.4; the optimization of Cu (II) was found to be pH 5.4; [metal] 0.777 mmol / L. In Pb (II) sorptions the mechanism of adsorption on the activated crumb rubber was found to be following the Freundlich model indicating that the adsorption seemed to occur on a multilayer adsorbent, while the mechanism of copper(II) adsorption on to the activated crumb rubber was found to be following Langmuir model, indicating that the adsorption seemed to occur on a monolayer. With adsorption percentages ranging from 98.2 % to 100.0 %, for Pb (II), the crumb rubber produced under the conditions of this study, can be used in South Africa for selective removal of Pb (II). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Hlabana,Relebohile Gladys
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59688 , vital:62356
- Description: Waste tyre is becoming a global environmental problem due to challenges in its disposal management and the fact that it poses fire hazards and metal leaching risk. Waste tyre can also breed mosquitos if it traps water thereby becoming an environmental health problem. There is also a portion of unused tyre in a waste tyre that is valuable and should be recycled. In South Africa waste tyre recycling is in three industries, one of which is crumb rubber where waste tyre is applied into various sized particles called crumb rubber. Crumb rubber can be applied in environmental remediation as an organic and inorganic pollutants’ adsorbent. Considering the fact that South Africa’s environment is loaded with heavy metal pollutants due to contributions by mining and agriculture as examples, it is postulated that crumb rubber produced in South Africa could be used to remediate the environment of these toxic metals. In this study adsorption of Pb (II) and Cu (II) from the synthetic waste water using waste tyre crumb rubber produced in South Africa was studied. Crumb rubber was activated using aqueous NaOH (0.02%) to make crumb rubber wettable followed by it being treated with 0.02 % acidified KMnO4 for modification of its ability to sorp positively charged metal species. Trial sorption experiments on 50 mg / L Cu (II) were successful with sorption of over 70% in 250 minutes. Final optimization of the sorption of combined Pb (II) and Cu (II) was studied using a full factorial design and optimum conditions of sorption were found to be pH 5.4; [metal] 0.617 mmol / L for Pb (II); and pH 5.4; the optimization of Cu (II) was found to be pH 5.4; [metal] 0.777 mmol / L. In Pb (II) sorptions the mechanism of adsorption on the activated crumb rubber was found to be following the Freundlich model indicating that the adsorption seemed to occur on a multilayer adsorbent, while the mechanism of copper(II) adsorption on to the activated crumb rubber was found to be following Langmuir model, indicating that the adsorption seemed to occur on a monolayer. With adsorption percentages ranging from 98.2 % to 100.0 %, for Pb (II), the crumb rubber produced under the conditions of this study, can be used in South Africa for selective removal of Pb (II). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Effects of Lignin on the properties of reclaimed rubber /natural rubber blends
- Makhelema, Junith Matshidiso
- Authors: Makhelema, Junith Matshidiso
- Date: 2022-12
- Subjects: Lignin – South Africa , Tires – Recycling
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59744 , vital:62409
- Description: The environmental challenge posed by waste tyres is a serious global crisis from which South Africa is not isolated. The concept of tyre rubber reclamation into reusable rubber over the years has been on the increase, however, despite the environmental and economic advantages offered by the reclaiming process the main demerits of the resulting rubber include its relatively poor physical and mechanical properties when compared to newly manufactured rubber. The deterioration of these properties arises from the structural changes which occur during the reclaiming process. To overcome this disadvantage, reclaimed rubber can be blended with other rubbers such as natural rubber to compensate for its weak properties. However, there is stilll a limited industrial application of reclaimed/natural rubber blends due to their brittleness and relatively poor impact strength. By adding reinforcing fillers, the mechanical properties of the blends can be significantly improved. In recent years, there has been a renewed interest in the use of lignocellulosic materials as fillers, modifiers and reinforcements in polymeric materials. They are receiving attention because they are the most abundantly available raw materials on earth, and they offer greater versatility compared to inorganic fillers. Being the most abundant renewable agricultural derived lignocellulosic biomass after cellulose, and as far as polymer composites and blends are concerned, lignin has shown promise as a well-received and sustainable alternative to inorganic fillers due to its low-cost production and ability to improve on the biodegradability of polyolefins and minimise loss of ultimate mechanical properties of polymer matrices. The main aim of the research is to investigate the effect of lignin on the properties of reclaimed/natural rubber (RR/NR) blends for possible low-density and eco-friendly rubber materials. The motivation for the research arises from the global challenges that are connected to the dynamic increase of rubber wastes, especially in the form of used tyres and the potential availability of lignin from its annual production from the sugarcane pulp mills, which is regarded as waste. A mixture design of experiments was used to formulate different blends of lignin with reclaimed and natural rubber. The rubber blends and the lignin-rubber , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Makhelema, Junith Matshidiso
- Date: 2022-12
- Subjects: Lignin – South Africa , Tires – Recycling
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59744 , vital:62409
- Description: The environmental challenge posed by waste tyres is a serious global crisis from which South Africa is not isolated. The concept of tyre rubber reclamation into reusable rubber over the years has been on the increase, however, despite the environmental and economic advantages offered by the reclaiming process the main demerits of the resulting rubber include its relatively poor physical and mechanical properties when compared to newly manufactured rubber. The deterioration of these properties arises from the structural changes which occur during the reclaiming process. To overcome this disadvantage, reclaimed rubber can be blended with other rubbers such as natural rubber to compensate for its weak properties. However, there is stilll a limited industrial application of reclaimed/natural rubber blends due to their brittleness and relatively poor impact strength. By adding reinforcing fillers, the mechanical properties of the blends can be significantly improved. In recent years, there has been a renewed interest in the use of lignocellulosic materials as fillers, modifiers and reinforcements in polymeric materials. They are receiving attention because they are the most abundantly available raw materials on earth, and they offer greater versatility compared to inorganic fillers. Being the most abundant renewable agricultural derived lignocellulosic biomass after cellulose, and as far as polymer composites and blends are concerned, lignin has shown promise as a well-received and sustainable alternative to inorganic fillers due to its low-cost production and ability to improve on the biodegradability of polyolefins and minimise loss of ultimate mechanical properties of polymer matrices. The main aim of the research is to investigate the effect of lignin on the properties of reclaimed/natural rubber (RR/NR) blends for possible low-density and eco-friendly rubber materials. The motivation for the research arises from the global challenges that are connected to the dynamic increase of rubber wastes, especially in the form of used tyres and the potential availability of lignin from its annual production from the sugarcane pulp mills, which is regarded as waste. A mixture design of experiments was used to formulate different blends of lignin with reclaimed and natural rubber. The rubber blends and the lignin-rubber , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Evaluation of the mesozooplankton functional diversity indices in Algoa Bay as proxies to assess the stability of the food chain leading to the African penguin (Spheniscus demersus)
- Authors: Rukuni, Praxedes Vimbai
- Date: 2022-12
- Subjects: Marine zooplankton --South Africa -- Algoa bay , Penguins -- South Africa -- Conservation , Fishes -- Predators of -- South Africa -- Algoa Bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59956 , vital:62698
- Description: Current unprecedented environmental changes threaten food web and ecosystem stability, which is particularly concerning in areas with vulnerable species such as the endangered African penguin Spheniscus demersus. In this study I adopted a holistic approach integrating many ecosystem levels to better understand African penguin behavioural ecology and food web stability. I investigated interplay between physico-chemical parameters and zooplankton functional diversity at various temporal and spatial scales in Algoa Bay. The study further investigated the applicability of zooplankton functional diversity (FD) in inferring African penguin food web stability by comparing the FD of zooplankton found in anchovies regurgitated from African penguins and the ones found in the Bay PELTER Stations. Gut contents of anchovies regurgitated from Bird Island and St Croix penguins were also evaluated using Frequency of Occurrence and Dominance methods and compared between colonies. Zooplankton FD in Algoa Bay varied over time but not at spatial scales with chlorophyll-a, Sea Surface Temperature (SST), turbidity and salinity being potential drivers of zooplankton FD. Chlorophyll-a and salinity were positively correlated with FD, meanwhile FD was inversely correlated to turbidity and SST. The study also observed minor differences in the physico-chemical parameters associated with African penguin foraging grounds, though different dietary preferences were found between the anchovies regurgitated from penguins from the two colonies. Anchovies regurgitated by penguins from Bird Island targeted large sized groups such as Decapods, meanwhile anchovies from the St Croix penguin colony targeted small sized Ostracods and Cirripedia. This study therefore, provides insight on the influence of fluctuations in physico-chemical parameters in shaping zooplankton communities in Algoa Bay. The study also emphasises anchovy dietary plasticity, switching from selective feeding to opportunistic feeding in instances of prey shortages which contributes to a stable African penguin food web in the face of climate change. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Rukuni, Praxedes Vimbai
- Date: 2022-12
- Subjects: Marine zooplankton --South Africa -- Algoa bay , Penguins -- South Africa -- Conservation , Fishes -- Predators of -- South Africa -- Algoa Bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59956 , vital:62698
- Description: Current unprecedented environmental changes threaten food web and ecosystem stability, which is particularly concerning in areas with vulnerable species such as the endangered African penguin Spheniscus demersus. In this study I adopted a holistic approach integrating many ecosystem levels to better understand African penguin behavioural ecology and food web stability. I investigated interplay between physico-chemical parameters and zooplankton functional diversity at various temporal and spatial scales in Algoa Bay. The study further investigated the applicability of zooplankton functional diversity (FD) in inferring African penguin food web stability by comparing the FD of zooplankton found in anchovies regurgitated from African penguins and the ones found in the Bay PELTER Stations. Gut contents of anchovies regurgitated from Bird Island and St Croix penguins were also evaluated using Frequency of Occurrence and Dominance methods and compared between colonies. Zooplankton FD in Algoa Bay varied over time but not at spatial scales with chlorophyll-a, Sea Surface Temperature (SST), turbidity and salinity being potential drivers of zooplankton FD. Chlorophyll-a and salinity were positively correlated with FD, meanwhile FD was inversely correlated to turbidity and SST. The study also observed minor differences in the physico-chemical parameters associated with African penguin foraging grounds, though different dietary preferences were found between the anchovies regurgitated from penguins from the two colonies. Anchovies regurgitated by penguins from Bird Island targeted large sized groups such as Decapods, meanwhile anchovies from the St Croix penguin colony targeted small sized Ostracods and Cirripedia. This study therefore, provides insight on the influence of fluctuations in physico-chemical parameters in shaping zooplankton communities in Algoa Bay. The study also emphasises anchovy dietary plasticity, switching from selective feeding to opportunistic feeding in instances of prey shortages which contributes to a stable African penguin food web in the face of climate change. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Fixed point theory in metric and normed Spaces
- Authors: Naude, Luan
- Date: 2022-12
- Subjects: Metric spaces – South Africa , Banach spaces – South Africa , Mappings (Mathematics)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59898 , vital:62686
- Description: In this dissertation, we present major results in the theory of fixed points in metric and normed spaces. We start with a review of the Banach fixed point theorem and some of its applications (in systems of linear equations, differential equations, integral equations, and dynamical systems), and then discuss many of its extensions and generalizations. We look at the theorem of Edelstein ([8, Remark 3.1]) in compact metric spaces, and a generalizaton of it proved by Suzuki ([19, Theorem 3]) in 2009. We then give a detailed account of the work of Meyers: In [11], Meyers proved generalizations of the Banach fixed point theorem to uniform local contractions, and, in [10], a converse to the Banach fixed point theorem. Finally, we look at some of Browder’s work in fixed point theory. In [6], he showed the existence of fixed points for nonexpansive mappings on bounded, closed, and convex sets in uniformly convex Banach spaces, and, in [5], he proved similar results in Hilbert spaces using a connection between nonexpansive mappings and monotone operators. Keywords: Fixed point, Functional analysis, Metric spaces, Banach spaces, Hilbert spaces, contractions, Banach fixed point theorem, nonexpansive mappings. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Naude, Luan
- Date: 2022-12
- Subjects: Metric spaces – South Africa , Banach spaces – South Africa , Mappings (Mathematics)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59898 , vital:62686
- Description: In this dissertation, we present major results in the theory of fixed points in metric and normed spaces. We start with a review of the Banach fixed point theorem and some of its applications (in systems of linear equations, differential equations, integral equations, and dynamical systems), and then discuss many of its extensions and generalizations. We look at the theorem of Edelstein ([8, Remark 3.1]) in compact metric spaces, and a generalizaton of it proved by Suzuki ([19, Theorem 3]) in 2009. We then give a detailed account of the work of Meyers: In [11], Meyers proved generalizations of the Banach fixed point theorem to uniform local contractions, and, in [10], a converse to the Banach fixed point theorem. Finally, we look at some of Browder’s work in fixed point theory. In [6], he showed the existence of fixed points for nonexpansive mappings on bounded, closed, and convex sets in uniformly convex Banach spaces, and, in [5], he proved similar results in Hilbert spaces using a connection between nonexpansive mappings and monotone operators. Keywords: Fixed point, Functional analysis, Metric spaces, Banach spaces, Hilbert spaces, contractions, Banach fixed point theorem, nonexpansive mappings. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
Growth performance of three F1 Hybrid tomato (Solanum lycopersicum L.) Cultivars grown in Peat moss and Sawdust
- Authors: Mondile, Landile
- Date: 2022-12
- Subjects: Agricultural development projects -- South Africa -- Eastern Cape , Tomatoes – Irrigation – Management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59853 , vital:62450
- Description: The tomato is one of the most important and commonly grown vegetable crops cultivated by subsistence as well as commercial farmers in South Africa. Even though hydroponic tomato production has gained popularity, tomato production in South Africa is mostly practised open field. This is because most South African households in rural communities depend on agriculture for their livelihoods. Tomatoes are one of the “cash crops” − meaning cash in hand for many farmers. As a staple food for many rural communities and households, tomatoes are prepared as relish daily. Including tomatoes in the human diet provides the benefit of various important nutrients, such as Vitamin C, amongst others. The main aim of this study was to evaluate the growth performance − by assessing the number of leaves, stem diameter, plant height and number of flowers per plant − in three Solanum lycopersicum L. cultivars, namely: F1 hybrids Star9006, TF4009 and TF4011, grown in peat moss and sawdust respectively. In addition, the research aimed at investigating how peat moss and sawdust, as growing media, influenced the growth performance of the tomato cultivars under study. The study was conducted at the Döhne Agricultural Development Institute near Stutterheim in the Eastern Cape. The experiment was laid out in a split randomized complete block design (RCBD) in which the growing media, namely: sawdust and peat moss, were assigned as main plots and the tomato cultivars to sub-plots, with three replicates. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mondile, Landile
- Date: 2022-12
- Subjects: Agricultural development projects -- South Africa -- Eastern Cape , Tomatoes – Irrigation – Management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59853 , vital:62450
- Description: The tomato is one of the most important and commonly grown vegetable crops cultivated by subsistence as well as commercial farmers in South Africa. Even though hydroponic tomato production has gained popularity, tomato production in South Africa is mostly practised open field. This is because most South African households in rural communities depend on agriculture for their livelihoods. Tomatoes are one of the “cash crops” − meaning cash in hand for many farmers. As a staple food for many rural communities and households, tomatoes are prepared as relish daily. Including tomatoes in the human diet provides the benefit of various important nutrients, such as Vitamin C, amongst others. The main aim of this study was to evaluate the growth performance − by assessing the number of leaves, stem diameter, plant height and number of flowers per plant − in three Solanum lycopersicum L. cultivars, namely: F1 hybrids Star9006, TF4009 and TF4011, grown in peat moss and sawdust respectively. In addition, the research aimed at investigating how peat moss and sawdust, as growing media, influenced the growth performance of the tomato cultivars under study. The study was conducted at the Döhne Agricultural Development Institute near Stutterheim in the Eastern Cape. The experiment was laid out in a split randomized complete block design (RCBD) in which the growing media, namely: sawdust and peat moss, were assigned as main plots and the tomato cultivars to sub-plots, with three replicates. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Habitat use by Juvenile coastal fish in subtidal vegetated habitats of Algoa Bay;s shallow water seascape
- Authors: Mkhize,Thembani
- Date: 2022-12
- Subjects: Sailing ships -- South Africa -- Algoa Bay --History , Marine fishes -- Algoa Bay -- South Africa , Fish improvement habitat
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59788 , vital:62429
- Description: Structurally complex habitats such as seagrass, mangroves, and seaweed are important as nurseries in estuaries and nearshore marine environments. While numerous studies have focussed on structurally complex vegetated habitats in estuaries, few studies have focussed on vegetated nursery habitats (particularly seaweed) in coastal areas and their importance. The main aim of this project is to examine the nature of shallow water vegetated habitat (Zostera capensis seagrass and Plocamium corallorhiza macroalga) usage by juvenile fish in the Algoa Bay shallow water seascape (Swartkops Estuary and Flat Rocks nearshore subtidal reef). This aim was achieved by quantifying and comparing complexity of these two habitat-forming species, and the fish assemblages (relative abundance, richness, size structure and behaviour) across the two habitats. To measure and compare complexity of Z. capensis and P. corallorhiza, canopy height, density and leaf/blade width were sampled. In addition to these structural complexity indices, Fractal D (dimensionless complexity indices) was also quantified using Image software. Zostera capensis (1553.3 Indiv/m2 ) had a slightly higher mean density compared to P. corallorhiza (1303.7 Indiv/m2 ) but the difference was not significant. When sites (within each habitat) were compared, density did not show any significant differences between sites. Canopy height of Z. capensis (56.9 cm) was significantly higher compared to P. corallorhiza (16.6 cm), with no significant differences between sites. On the other hand, P. corallorhiza (0.9 cm) blades were significantly wider than Z. capensis (0.2 cm) leaves. Fractal D values followed the same trend as leaf/blade width with, with P. corallorhiza (1.8) having significantly higher Fractal D values than Z. capensis (1.5). The last two indices also had a positive relationship as Fractal D increased with increasing leaf/blade width. These results show that overall P. corallorhiza is more structurally complex than Z. capensis. Calibrated mini stereo underwater remote video systems (mini stereo-RUVs) were optimised in these two studied habitats to ensure they were suitable to measure and identify juvenile fishes. A pilot optimization study found that a minimum of five deployments and a minimum of 45 minutes filming duration is required to study fish assemblages in these two habitats. For comparison of fish assemblages and assessment of habitat use by fish, mini stereo-RUVs were deployed in both habitats (three sites per habitat) and were left to record for 60 minutes for a v total of five sampling occasions in seagrass and seven sampling occasions in macroalga between 7 September 2020 and 9 April 2021. Collected videos were analysed, with relative abundance (MaxN), richness and fish length extracted. Fish behaviour was also analysed and compared between habitats. Mean fish MaxN was slightly higher in Z. capensis (3.4) than in P. corallorhiza (2.9), although this result was not significant. Species diversity was significantly higher in P. corallorhiza as shown by both richness (Z. capensis = 11 and P. corallorhiza = 18) and the Shannon diversity index (Z. capensis = 1.3 and P. corallorhiza = 1.7). Both habitats were dominated by species from the family Sparidae, with six estuary-associated marine species common between the two habitats. Both Z. capensis and P. corallorhiza were dominated by juvenile fish, with more than 70 % of measured fish being juveniles. Fish length was not significantly different in the two habitats. Juvenile fish assemblages were significantly distinct between the two habitats (ANOSIM). In terms of habitat use, fish behaviour analysis showed that fish use both habitats as nurseries. There was no significant difference in fish behaviour in the two habitats and fish behaviours associated with higher levels of habitat use (slow meandering and feeding) were the most common behaviours in both habitats. Although not significant, feeding behaviour (also associated with a high degree of habitat use) was observed more in macroalga than in the seagrass habitat. Although none of the studied complexity indices could be related to abundance, both leaf/blade width and Fractal Dimension showed a positive relationship with the number of species recorded, while canopy height showed a strong negative relationship with the number of species. Overall, this study shows that Plocamium corallorhiza red macroalga in the shallow marine environment may be as important in shallow marine environments as Zostera capensis seagrass in estuaries as nursery habitats for marine fi , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mkhize,Thembani
- Date: 2022-12
- Subjects: Sailing ships -- South Africa -- Algoa Bay --History , Marine fishes -- Algoa Bay -- South Africa , Fish improvement habitat
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59788 , vital:62429
- Description: Structurally complex habitats such as seagrass, mangroves, and seaweed are important as nurseries in estuaries and nearshore marine environments. While numerous studies have focussed on structurally complex vegetated habitats in estuaries, few studies have focussed on vegetated nursery habitats (particularly seaweed) in coastal areas and their importance. The main aim of this project is to examine the nature of shallow water vegetated habitat (Zostera capensis seagrass and Plocamium corallorhiza macroalga) usage by juvenile fish in the Algoa Bay shallow water seascape (Swartkops Estuary and Flat Rocks nearshore subtidal reef). This aim was achieved by quantifying and comparing complexity of these two habitat-forming species, and the fish assemblages (relative abundance, richness, size structure and behaviour) across the two habitats. To measure and compare complexity of Z. capensis and P. corallorhiza, canopy height, density and leaf/blade width were sampled. In addition to these structural complexity indices, Fractal D (dimensionless complexity indices) was also quantified using Image software. Zostera capensis (1553.3 Indiv/m2 ) had a slightly higher mean density compared to P. corallorhiza (1303.7 Indiv/m2 ) but the difference was not significant. When sites (within each habitat) were compared, density did not show any significant differences between sites. Canopy height of Z. capensis (56.9 cm) was significantly higher compared to P. corallorhiza (16.6 cm), with no significant differences between sites. On the other hand, P. corallorhiza (0.9 cm) blades were significantly wider than Z. capensis (0.2 cm) leaves. Fractal D values followed the same trend as leaf/blade width with, with P. corallorhiza (1.8) having significantly higher Fractal D values than Z. capensis (1.5). The last two indices also had a positive relationship as Fractal D increased with increasing leaf/blade width. These results show that overall P. corallorhiza is more structurally complex than Z. capensis. Calibrated mini stereo underwater remote video systems (mini stereo-RUVs) were optimised in these two studied habitats to ensure they were suitable to measure and identify juvenile fishes. A pilot optimization study found that a minimum of five deployments and a minimum of 45 minutes filming duration is required to study fish assemblages in these two habitats. For comparison of fish assemblages and assessment of habitat use by fish, mini stereo-RUVs were deployed in both habitats (three sites per habitat) and were left to record for 60 minutes for a v total of five sampling occasions in seagrass and seven sampling occasions in macroalga between 7 September 2020 and 9 April 2021. Collected videos were analysed, with relative abundance (MaxN), richness and fish length extracted. Fish behaviour was also analysed and compared between habitats. Mean fish MaxN was slightly higher in Z. capensis (3.4) than in P. corallorhiza (2.9), although this result was not significant. Species diversity was significantly higher in P. corallorhiza as shown by both richness (Z. capensis = 11 and P. corallorhiza = 18) and the Shannon diversity index (Z. capensis = 1.3 and P. corallorhiza = 1.7). Both habitats were dominated by species from the family Sparidae, with six estuary-associated marine species common between the two habitats. Both Z. capensis and P. corallorhiza were dominated by juvenile fish, with more than 70 % of measured fish being juveniles. Fish length was not significantly different in the two habitats. Juvenile fish assemblages were significantly distinct between the two habitats (ANOSIM). In terms of habitat use, fish behaviour analysis showed that fish use both habitats as nurseries. There was no significant difference in fish behaviour in the two habitats and fish behaviours associated with higher levels of habitat use (slow meandering and feeding) were the most common behaviours in both habitats. Although not significant, feeding behaviour (also associated with a high degree of habitat use) was observed more in macroalga than in the seagrass habitat. Although none of the studied complexity indices could be related to abundance, both leaf/blade width and Fractal Dimension showed a positive relationship with the number of species recorded, while canopy height showed a strong negative relationship with the number of species. Overall, this study shows that Plocamium corallorhiza red macroalga in the shallow marine environment may be as important in shallow marine environments as Zostera capensis seagrass in estuaries as nursery habitats for marine fi , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
In vitro evaluation of vernonia amygdalina gold nanoparticles to stimulate apoptosis in breast cancer lines
- Authors: Pali, Zenande
- Date: 2022-12
- Subjects: Breast--Cancer--Treatment--Technological innovations , Apoptosis -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59933 , vital:62696
- Description: Breast cancer is the most prevalent cancer in women and triple negative breast cancer (TNBC) is one of the most aggressive breast cancer subtypes. Current breast cancer therapies are associated with several side effects and less effective treatment. Therefore, the development of new approaches to improve cancer treatment are needed. The use of gold nanoparticles (AuNPs) for anti-cancer effects is one of the most promising research areas in the field of nanotechnology, because nanoparticles are readily functionalized and can passively accumulate at the tumor site without affecting healthy tissues. The green synthesis of AuNPs is an eco-friendly, costeffective, fast, and non-toxic method that is associated with fewer side effects.The aim of this study was to evaluate the cytotoxicity and apoptotic activity exhibted by Vernonia amygdalina gold nanoparticles (VA-AuNPs) in triple negative breast cancer cell lines. The aqueous extract of Vernonia amygdalina was used to reduce gold salts to form VA-AuNPs. The VA-AuNPs were synthesised at a temperature of 100 °C and pH 7. The synthesised green AuNPs were charactised using ultraviolet-visible spectroscopy, dynamic light scattering, and high resolution transmission electron microscopy. Spherical VA-AuNPs were succesfully synthesized with average size of 17.11 ± 2.82 nm and a zeta potential of -36.55 ± 1.15 mV. The MTT assay revealed that VA-AuNPs significantly reduced (p cell viability for both mouse (E0771) and human (MDA-MB231) TNBC cell lines in a dose-dependent manner. The PrestoBlue assay showed a consistent decrease in cell numbers over time, suggesting either a decrease in proliferation or increase in apoptosis. The apoptotic effects of VAAuNPs were assessed using the CaspGLOW Fluorescein active caspase-8 staining kit. It indicated that caspase 8 was activated when cells were treated with VA-AuNPs. E0771 and MDA-MB231 cells were compared when treated with VA-AuNP and a similar trend was established. The HRTEM image showed VA-AuNPs in an vesiclelike structure inside the cell. It can be concluded that the VA-AuNPs showed anticancer activities against TNBC cells. Caspase 8 is activated by VA-AuNPs, confirming the induction of apoptosis, but does not exclude the activation of the intrinsic apoptotic pathway or inhibition of proliferation activity. E0771 and MDA-MB231 cells showed similar cytotoxic activity and thus expected that the mechanism of action in these cell lines should also be similar. Future in vivo research, using the mouse model inoculated with E0771 TNBC cells, should be justified and comparable with human TNBC cells. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Pali, Zenande
- Date: 2022-12
- Subjects: Breast--Cancer--Treatment--Technological innovations , Apoptosis -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59933 , vital:62696
- Description: Breast cancer is the most prevalent cancer in women and triple negative breast cancer (TNBC) is one of the most aggressive breast cancer subtypes. Current breast cancer therapies are associated with several side effects and less effective treatment. Therefore, the development of new approaches to improve cancer treatment are needed. The use of gold nanoparticles (AuNPs) for anti-cancer effects is one of the most promising research areas in the field of nanotechnology, because nanoparticles are readily functionalized and can passively accumulate at the tumor site without affecting healthy tissues. The green synthesis of AuNPs is an eco-friendly, costeffective, fast, and non-toxic method that is associated with fewer side effects.The aim of this study was to evaluate the cytotoxicity and apoptotic activity exhibted by Vernonia amygdalina gold nanoparticles (VA-AuNPs) in triple negative breast cancer cell lines. The aqueous extract of Vernonia amygdalina was used to reduce gold salts to form VA-AuNPs. The VA-AuNPs were synthesised at a temperature of 100 °C and pH 7. The synthesised green AuNPs were charactised using ultraviolet-visible spectroscopy, dynamic light scattering, and high resolution transmission electron microscopy. Spherical VA-AuNPs were succesfully synthesized with average size of 17.11 ± 2.82 nm and a zeta potential of -36.55 ± 1.15 mV. The MTT assay revealed that VA-AuNPs significantly reduced (p cell viability for both mouse (E0771) and human (MDA-MB231) TNBC cell lines in a dose-dependent manner. The PrestoBlue assay showed a consistent decrease in cell numbers over time, suggesting either a decrease in proliferation or increase in apoptosis. The apoptotic effects of VAAuNPs were assessed using the CaspGLOW Fluorescein active caspase-8 staining kit. It indicated that caspase 8 was activated when cells were treated with VA-AuNPs. E0771 and MDA-MB231 cells were compared when treated with VA-AuNP and a similar trend was established. The HRTEM image showed VA-AuNPs in an vesiclelike structure inside the cell. It can be concluded that the VA-AuNPs showed anticancer activities against TNBC cells. Caspase 8 is activated by VA-AuNPs, confirming the induction of apoptosis, but does not exclude the activation of the intrinsic apoptotic pathway or inhibition of proliferation activity. E0771 and MDA-MB231 cells showed similar cytotoxic activity and thus expected that the mechanism of action in these cell lines should also be similar. Future in vivo research, using the mouse model inoculated with E0771 TNBC cells, should be justified and comparable with human TNBC cells. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Investigation of thermal and electrical characteristics of crystalline silicon photovoltaic modules under varying operational conditions
- Authors: Vumbugwa, Monphias
- Date: 2022-12
- Subjects: Photovoltaic power generation -- South Africa , Silicon crystals -- South Africa , Solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60014 , vital:62733
- Description: Solar energy has become an attractive and environmentally mindful method in electrical power generation as it contributes significantly to meeting the high demand for the power needed for socio and economic developments. The rise in deployment of Photovoltaic (PV) facilities with large capacity creates the need for accurate and reliable PV inspection techniques for optimum performance, the longevity of PV modules and quick return on PV investment. The performance of PV modules in the field is often monitored through several inspection methods that require a rapid throughput such as Thermal Infrared (TIR) imaging and current-voltage (I-V) measurements. Unmanned Aerial Vehicle (UAV) based TIR imaging is widely applied in large PV plants since it is cost-effective and is usually conducted in-situ while the plant is operating at irradiance levels above 600 W.m-2 . One of the outcomes of the interpretations of TIR images is an attempt to quantify the energy loss in PV plants associated with the abnormal thermal signatures identified on TIR images. No standard procedure has yet outlined the quantification of energy loss related to TIR images of underperforming modules since the interpretation of TIR images remains a challenge. PV modules operate under dynamic operating conditions which can influence the results and interpretation of thermal and electrical characterisation measurements. Dynamic operation conditions refer to any disorders in the operation of the modules and cells which cause a change in the current and voltage characteristics of the PV source. These dynamic operation conditions include; changesin load conditions, irradiance, soiling and shading levels. The tests were done under steady state conditions. Although measurements are generally done while the operating conditions are as steady as possible, some changes in conditions have a profound effect on thermal and electrical measurements. In this study, these effects and some of the changes in conditions that cause them were studied. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Vumbugwa, Monphias
- Date: 2022-12
- Subjects: Photovoltaic power generation -- South Africa , Silicon crystals -- South Africa , Solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60014 , vital:62733
- Description: Solar energy has become an attractive and environmentally mindful method in electrical power generation as it contributes significantly to meeting the high demand for the power needed for socio and economic developments. The rise in deployment of Photovoltaic (PV) facilities with large capacity creates the need for accurate and reliable PV inspection techniques for optimum performance, the longevity of PV modules and quick return on PV investment. The performance of PV modules in the field is often monitored through several inspection methods that require a rapid throughput such as Thermal Infrared (TIR) imaging and current-voltage (I-V) measurements. Unmanned Aerial Vehicle (UAV) based TIR imaging is widely applied in large PV plants since it is cost-effective and is usually conducted in-situ while the plant is operating at irradiance levels above 600 W.m-2 . One of the outcomes of the interpretations of TIR images is an attempt to quantify the energy loss in PV plants associated with the abnormal thermal signatures identified on TIR images. No standard procedure has yet outlined the quantification of energy loss related to TIR images of underperforming modules since the interpretation of TIR images remains a challenge. PV modules operate under dynamic operating conditions which can influence the results and interpretation of thermal and electrical characterisation measurements. Dynamic operation conditions refer to any disorders in the operation of the modules and cells which cause a change in the current and voltage characteristics of the PV source. These dynamic operation conditions include; changesin load conditions, irradiance, soiling and shading levels. The tests were done under steady state conditions. Although measurements are generally done while the operating conditions are as steady as possible, some changes in conditions have a profound effect on thermal and electrical measurements. In this study, these effects and some of the changes in conditions that cause them were studied. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-12
Mesozooplankton and particle dynamics in Algoa Bay, South Africa
- Engelbrecht, Melindi Frances
- Authors: Engelbrecht, Melindi Frances
- Date: 2022-12
- Subjects: Marine zooplankton – Algoa bay -- South Africa , Estuarine ecology , Zooplankton –Ecology --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59544 , vital:62157
- Description: Coastal ecosystems provide society with important ecosystem services: climate regulation, biogeochemical nutrient and waste cycling, food security, shoreline protection, tourism, and recreational support. Increased anthropogenic pressure on coastal ecosystems and changing environmental variables ultimately affect the provision of ecosystem services. Mesozooplankton are key trophic species and biological indicators of change within the marine environment and provide sound predictions of ecosystem responses to a changing climate due to their short life cycles and physiology linked to temperature. Algoa Bay has been the subject of extensive research and monitoring and encompasses a marine protected area (Addo Elephant National Park MPA). The Underwater Vision Profiler 5 (UVP5) was utilised with conventional sampling techniques of the PELTER monitoring program (i.e., Bongo nets) to investigate mesozooplankton (200 – 2000 µm) and particle (> 100 µm) dynamics within the dynamic coastal ecosystem of Algoa Bay, located within warmtemperate South Africa, in spring 2020 and summer 2021. This study revealed seasonal shifts in mesozooplankton taxa succession from spring herbivorous/omnivorous, dominated by copepods, to summer omnivorous/carnivorous mesozooplankton, dominated by copepods, Noctiluca sp., Cladocera, doliolids, salps and siphonophores. The mesozooplankton integrated abundance (mean ± standard error) increased from spring to summer, with 101 ± 26 (min. – max.: 18 – 200) x 103 ind m¯ 2 and 422 ± 80 (min. – max.: 37 – 1056) x 103 ind m¯ 2 , respectively. In summer, mesozooplankton composition was affected by the passage of a Natal Pulse, identified from satellite-derived sea level anomaly data. This study also provided the first vertical profiles of copepod distributions and suspended particles in Algoa Bay, with a peak of small particle (< 1 mm ESD) biomass close to the bottom and often, but not systematically, higher copepod abundances above the thermocline. The results presented herein are expected to contribute to the understanding of the coastal pelagic ecosystem in Algoa Bay in response to environmental perturbations , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Engelbrecht, Melindi Frances
- Date: 2022-12
- Subjects: Marine zooplankton – Algoa bay -- South Africa , Estuarine ecology , Zooplankton –Ecology --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59544 , vital:62157
- Description: Coastal ecosystems provide society with important ecosystem services: climate regulation, biogeochemical nutrient and waste cycling, food security, shoreline protection, tourism, and recreational support. Increased anthropogenic pressure on coastal ecosystems and changing environmental variables ultimately affect the provision of ecosystem services. Mesozooplankton are key trophic species and biological indicators of change within the marine environment and provide sound predictions of ecosystem responses to a changing climate due to their short life cycles and physiology linked to temperature. Algoa Bay has been the subject of extensive research and monitoring and encompasses a marine protected area (Addo Elephant National Park MPA). The Underwater Vision Profiler 5 (UVP5) was utilised with conventional sampling techniques of the PELTER monitoring program (i.e., Bongo nets) to investigate mesozooplankton (200 – 2000 µm) and particle (> 100 µm) dynamics within the dynamic coastal ecosystem of Algoa Bay, located within warmtemperate South Africa, in spring 2020 and summer 2021. This study revealed seasonal shifts in mesozooplankton taxa succession from spring herbivorous/omnivorous, dominated by copepods, to summer omnivorous/carnivorous mesozooplankton, dominated by copepods, Noctiluca sp., Cladocera, doliolids, salps and siphonophores. The mesozooplankton integrated abundance (mean ± standard error) increased from spring to summer, with 101 ± 26 (min. – max.: 18 – 200) x 103 ind m¯ 2 and 422 ± 80 (min. – max.: 37 – 1056) x 103 ind m¯ 2 , respectively. In summer, mesozooplankton composition was affected by the passage of a Natal Pulse, identified from satellite-derived sea level anomaly data. This study also provided the first vertical profiles of copepod distributions and suspended particles in Algoa Bay, with a peak of small particle (< 1 mm ESD) biomass close to the bottom and often, but not systematically, higher copepod abundances above the thermocline. The results presented herein are expected to contribute to the understanding of the coastal pelagic ecosystem in Algoa Bay in response to environmental perturbations , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Moult and energetics in three species from the Euplectes genus representing a gradient of elaborate plumage ornamentation
- Authors: Webb, Stacey Leigh
- Date: 2022-12
- Subjects: Sexual selection in animals – South Africa , Bird watching -- Africa, Southern , Plumage
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60026 , vital:62734
- Description: Elaborate plumage ornamentation in birds has fascinated scientists since the 1800s. The evolution and persistence of elaborate and costly ornamentation seemed to be in opposition to the theory of natural selection. However, over the years research has revealed the role and functional significance of elaborate plumage ornamentation in sexual selection. Recent studies have shown that the energetic costs associated with moulting into new plumages are higher than maintenance costs, but these costs have not been quantified for species that exhibit elaborate breeding plumage ornamentation for sexual selection. In addition, for these sexually selected ornamental traits (signals) to have evolved and be maintained, there must be some aspect of individual quality that they convey to the receiver. Despite a large body of literature on sexual selection, honest signalling and ornamental plumage in birds, the physiological correlates of honest signalling during sexual selection and the messages these signals convey to the receivers are poorly understood. In this study, I investigated four aspects related to the honesty of the sexual selection signal. These were (i) seasonal variation in standardised resting metabolic rates of breeding and non-breeding birds, (ii) moult phenology, (iii) physiological parameters linked to honest signalling, and (iv) the energetic costs of production and maintenance of elaborate plumage ornamentation using three species from the Euplectes genus as model species. The three species selected, the red-collared widowbird (Euplectes ardens), fan-tailed widowbird (Euplectes axillaris) and the southern red bishop (Euplectes orix) represent a gradient of plumage elaboration and although the receivers of the sexual selection signals are known for these three species, the energetic cost of the signals and the underlying message the signals convey remain unknown. I measured seasonal variation in resting metabolic rate (RMR), body mass (Mb), thermoneutral zone (TNZ) and body temperature (Tb) over the course of two years in the three selected Euplectes species (E. ardens, E. axillaris and E. orix; chapter 2). My results showed no significant effect of season on RMR (except in E. orix females) suggesting that in these species the metabolic costs in summer (associated with breeding season) are comparable to the metabolic costs associated with thermoregulation during winter. Contrary to my prediction that metabolic costs would increase along a gradient of increasing tail length (due to the energetic costs Webb V associated with elaborate plumage ornamentation), I found no significant effect of species. The lack of a significant result indicates that once the initial investment in plumage is complete, other predictor variables play a role (in this case body mass). , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Webb, Stacey Leigh
- Date: 2022-12
- Subjects: Sexual selection in animals – South Africa , Bird watching -- Africa, Southern , Plumage
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60026 , vital:62734
- Description: Elaborate plumage ornamentation in birds has fascinated scientists since the 1800s. The evolution and persistence of elaborate and costly ornamentation seemed to be in opposition to the theory of natural selection. However, over the years research has revealed the role and functional significance of elaborate plumage ornamentation in sexual selection. Recent studies have shown that the energetic costs associated with moulting into new plumages are higher than maintenance costs, but these costs have not been quantified for species that exhibit elaborate breeding plumage ornamentation for sexual selection. In addition, for these sexually selected ornamental traits (signals) to have evolved and be maintained, there must be some aspect of individual quality that they convey to the receiver. Despite a large body of literature on sexual selection, honest signalling and ornamental plumage in birds, the physiological correlates of honest signalling during sexual selection and the messages these signals convey to the receivers are poorly understood. In this study, I investigated four aspects related to the honesty of the sexual selection signal. These were (i) seasonal variation in standardised resting metabolic rates of breeding and non-breeding birds, (ii) moult phenology, (iii) physiological parameters linked to honest signalling, and (iv) the energetic costs of production and maintenance of elaborate plumage ornamentation using three species from the Euplectes genus as model species. The three species selected, the red-collared widowbird (Euplectes ardens), fan-tailed widowbird (Euplectes axillaris) and the southern red bishop (Euplectes orix) represent a gradient of plumage elaboration and although the receivers of the sexual selection signals are known for these three species, the energetic cost of the signals and the underlying message the signals convey remain unknown. I measured seasonal variation in resting metabolic rate (RMR), body mass (Mb), thermoneutral zone (TNZ) and body temperature (Tb) over the course of two years in the three selected Euplectes species (E. ardens, E. axillaris and E. orix; chapter 2). My results showed no significant effect of season on RMR (except in E. orix females) suggesting that in these species the metabolic costs in summer (associated with breeding season) are comparable to the metabolic costs associated with thermoregulation during winter. Contrary to my prediction that metabolic costs would increase along a gradient of increasing tail length (due to the energetic costs Webb V associated with elaborate plumage ornamentation), I found no significant effect of species. The lack of a significant result indicates that once the initial investment in plumage is complete, other predictor variables play a role (in this case body mass). , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12