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
Spatial and temporal analysis of the critical zone in the Western rift valley corridor: towards earth stewardship science in East Africa
- Authors: Miller, Warren David
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/59771 , vital:62423
- Description: Over the coming decades, Africa is expected to experience disturbing effects due to climate change and increased land cover change due to human influences presenting a significant concern for the future well-being of human and biological systems, the latter being the foundation of ecosystem services supplied to humanity. Therefore, unprecedented transdisciplinary cooperation, coordination, and integration amongst researchers, government, and civil society are necessary to increase the resiliency of these systems. This study aims to provide an outline of the Africa Alive Corridors (AAC) as an essential model for the encouragement of sustainable development through Earth Stewardship science. These aims are accompanied by the quantification and forward modelling for land cover change of the Critical Zone over 10 Great Lake Basins across one of the AAC, the Western Rift Valley Corridor (WRVC), in East Africa between the years 2018 and 2060. This approach provides the foundation for implementing improved regional governance, better encouragement of sustainable development beyond the 2030 United Nations Sustainable Development Goals, and education programs, such as the AAC, that promote socio-ecological resilience through Earth Stewardship Science. The AAC archives a portion of East Africa as the WRVC, a corridor along the western branch of the East African Rift System that highlights twenty heritage nodes, primarily great lakes, mountain ranges, national parks, and biological hotspots. These heritage entities are associated with ca. 12-million-years of evolution and transformation of the East African topography and related African Great Lake (AGL) systems. The thesis defines the study area by delineating AGL basins intersected by the WRVC. Across these basins, land cover change analysis provides a platform for an integrated assessment of the projected health of the corridor region. Existing land cover datasets provide the initial conditions of the study area for 2008 and 2013. Land cover between 2008 and 2013 is cross-tabulated using the Land Cover Module in the Terrset software, followed by the iii delineation of sub-models and driver variable identification. The Multi-Layer Perceptron algorithm provides the transition potentials between tree cover, urban area, cropland, wetland, and open area classes. Change quantification and prediction using Markov Chain analysis are then established for 2018, 2030, and 2060. The model successfully simulated future land cover change and concluded that: (1) proximity to existing human activity, proximity to existing tree cover, and population are the primary drivers of change; (2) the dominant land cover of the ten lake basins for 2018 was cropland at ca. 48%, followed by tree cover at ca. 33%; (3) total anthropogenic change over the coming four decades equates to over ca. 52 000 km2 (5 200 000 ha), and particularly (4) an urban area is expected to increase by >130%. This assessment ultimately provides a platform for regional governance development at the basin scale and Earth Stewardship science in East Africa. These changes require transdisciplinary action from researchers to civil society. The AAC provides the foundation for understanding the dynamics of the systems that support life across broader spatial and temporal resolutions in Africa, highlighting the need for future generations to build socio-ecological resilience to anticipate challenges such as biodiversity loss posed by climate change and excessive land cover change. , Thesis (DSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Miller, Warren David
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/59771 , vital:62423
- Description: Over the coming decades, Africa is expected to experience disturbing effects due to climate change and increased land cover change due to human influences presenting a significant concern for the future well-being of human and biological systems, the latter being the foundation of ecosystem services supplied to humanity. Therefore, unprecedented transdisciplinary cooperation, coordination, and integration amongst researchers, government, and civil society are necessary to increase the resiliency of these systems. This study aims to provide an outline of the Africa Alive Corridors (AAC) as an essential model for the encouragement of sustainable development through Earth Stewardship science. These aims are accompanied by the quantification and forward modelling for land cover change of the Critical Zone over 10 Great Lake Basins across one of the AAC, the Western Rift Valley Corridor (WRVC), in East Africa between the years 2018 and 2060. This approach provides the foundation for implementing improved regional governance, better encouragement of sustainable development beyond the 2030 United Nations Sustainable Development Goals, and education programs, such as the AAC, that promote socio-ecological resilience through Earth Stewardship Science. The AAC archives a portion of East Africa as the WRVC, a corridor along the western branch of the East African Rift System that highlights twenty heritage nodes, primarily great lakes, mountain ranges, national parks, and biological hotspots. These heritage entities are associated with ca. 12-million-years of evolution and transformation of the East African topography and related African Great Lake (AGL) systems. The thesis defines the study area by delineating AGL basins intersected by the WRVC. Across these basins, land cover change analysis provides a platform for an integrated assessment of the projected health of the corridor region. Existing land cover datasets provide the initial conditions of the study area for 2008 and 2013. Land cover between 2008 and 2013 is cross-tabulated using the Land Cover Module in the Terrset software, followed by the iii delineation of sub-models and driver variable identification. The Multi-Layer Perceptron algorithm provides the transition potentials between tree cover, urban area, cropland, wetland, and open area classes. Change quantification and prediction using Markov Chain analysis are then established for 2018, 2030, and 2060. The model successfully simulated future land cover change and concluded that: (1) proximity to existing human activity, proximity to existing tree cover, and population are the primary drivers of change; (2) the dominant land cover of the ten lake basins for 2018 was cropland at ca. 48%, followed by tree cover at ca. 33%; (3) total anthropogenic change over the coming four decades equates to over ca. 52 000 km2 (5 200 000 ha), and particularly (4) an urban area is expected to increase by >130%. This assessment ultimately provides a platform for regional governance development at the basin scale and Earth Stewardship science in East Africa. These changes require transdisciplinary action from researchers to civil society. The AAC provides the foundation for understanding the dynamics of the systems that support life across broader spatial and temporal resolutions in Africa, highlighting the need for future generations to build socio-ecological resilience to anticipate challenges such as biodiversity loss posed by climate change and excessive land cover change. , Thesis (DSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
The co-evolution of Africa’s eastern margin and its primate fauna: implications for hominin evolution
- Authors: Mambalu, Philasande
- 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/10948/59755 , vital:62418
- Description: I investigated potential links between the diversification of African primate lineages and the physical evolution of the continent. I compared published phylogenetic trees based on mitochondrial and nuclear DNA for five clades: (a) Lorisoidea (galagos and pottos); (b) arboreal guenon monkeys (Cercopithecus and its allies); (c) living apes (including humans); (d) Papionini (baboons); and (e) savanna or “vervet” monkeys (Chlorocebus). I compared primate divergence dates with the ages of tectonic events, patterns of climatic change, and their palaeo-vegetational consequences. Based on present primate distributions, I estimated likely geographic locations of the divergence events. Finally, I compared the phylogenetic patterns of the primate clades with hominin evolutionary scenarios. Phylogenetic comparisons indicated three time periods when rates of speciation increased across the five primate clades: the Eocene – Oligocene transition (34 – 32 Ma); the mid-late Miocene (10 – 5 Ma); and the Pliocene – Pleistocene transition (2.7 – 2.3 Ma). Concentrated bursts of lineage splitting indicate a broadscale causal relationship between environmental change and lineage divergence. Human evolution followed similar biogeographic patterns to those of other primate clades. Tectonic events, climatic changes and palaeo-vegetational shifts are intimately connected, and have synergistic effects on biotic diversity. Tectonic events influence climatic change through their effects on oceanic circulation, planetary temperatures and rainfall patterns. Additionally, tectonic uplift and erosion may create geographic barriers to organismal dispersal across the continent, increasing the likelihood of geographic separation of populations and speciation. Recently evolved primate species show high levels of hybridisation for several generations after their initial divergence. Genus Homo generated ~10 species over 2.5 Ma. The emergence of these taxa likely involved substantial hybridisation, as demonstrated by the presence of Neanderthal genes within the H. sapiens genome. I suggest that this hybridisation contributed to the difficulties palaeoanthropologists often experience in distinguishing fossil hominin taxa. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mambalu, Philasande
- 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/10948/59755 , vital:62418
- Description: I investigated potential links between the diversification of African primate lineages and the physical evolution of the continent. I compared published phylogenetic trees based on mitochondrial and nuclear DNA for five clades: (a) Lorisoidea (galagos and pottos); (b) arboreal guenon monkeys (Cercopithecus and its allies); (c) living apes (including humans); (d) Papionini (baboons); and (e) savanna or “vervet” monkeys (Chlorocebus). I compared primate divergence dates with the ages of tectonic events, patterns of climatic change, and their palaeo-vegetational consequences. Based on present primate distributions, I estimated likely geographic locations of the divergence events. Finally, I compared the phylogenetic patterns of the primate clades with hominin evolutionary scenarios. Phylogenetic comparisons indicated three time periods when rates of speciation increased across the five primate clades: the Eocene – Oligocene transition (34 – 32 Ma); the mid-late Miocene (10 – 5 Ma); and the Pliocene – Pleistocene transition (2.7 – 2.3 Ma). Concentrated bursts of lineage splitting indicate a broadscale causal relationship between environmental change and lineage divergence. Human evolution followed similar biogeographic patterns to those of other primate clades. Tectonic events, climatic changes and palaeo-vegetational shifts are intimately connected, and have synergistic effects on biotic diversity. Tectonic events influence climatic change through their effects on oceanic circulation, planetary temperatures and rainfall patterns. Additionally, tectonic uplift and erosion may create geographic barriers to organismal dispersal across the continent, increasing the likelihood of geographic separation of populations and speciation. Recently evolved primate species show high levels of hybridisation for several generations after their initial divergence. Genus Homo generated ~10 species over 2.5 Ma. The emergence of these taxa likely involved substantial hybridisation, as demonstrated by the presence of Neanderthal genes within the H. sapiens genome. I suggest that this hybridisation contributed to the difficulties palaeoanthropologists often experience in distinguishing fossil hominin taxa. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
The development of a flow route to synthesize 3- benzyl-6-bromo-2-methoxyquinoline, an intermediate of an anti-TB drug, bedaquilin
- Authors: Mpalala, Anele
- Date: 2022-12
- Subjects: Multidrug-resistant tuberculosis -- South Africa , Tuberculosis --Chemotherapy -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59864 , vital:62455
- Description: SA has a high number of reported cases of multidrug-resistant tuberculosis (MDR-TB). Bedaquiline is a newly approved active ingredient of an anti-tuberculosis drug with high potency against MDR-TB. The limited access to this life-saving medicine to many people in the world has driven a great deal of research effort by the scientific community to find new, better and more practical approaches to this drug. However, many of the reported synthetic procedures suffer from long reaction times, which in turn require many hours of effort by the chemists conducting the reactions. This has prompted us to investigate an efficient process towards the synthesis to produce the key intermediates of bedaquiline using continuous flow technology. Additionally, since there is not much literature on continuous flow synthesis of bedaquiline, this research revealed interesting continuous flow processes towards the drug. Chapter 1: In order to provide insight, the first chapter of this dissertation presents a comprehensive background and literature review on tuberculosis; its pathogenesis, impact, medicines available for the treatment as well as the drug classes with novel mode of action and new chemical entities. Furthermore, bedaquiline is discussed in detail with the various synthetic protocols of the drug. An introduction to continuous flow chemistry is discussed, along with an outline of its advantages and disadvantages. Chapter 2: The second chapter encompasses the experimental procedures utilized for both batch and continuous flow syntheses. The three key intermediates of bedaquiline were synthesized in batch synthesis and these compounds were characterized using 1H-NMR, 13C-NMR and FT-IR spectroscopy. Subsequently, the continuous flow synthesis protocols for the preparations of these intermediates and their optimization are outlined. Chapter 3: The results are explained in this chapter with detailed discussions of the batch synthesis and the continuous flow optimization of each step within the scope of this research. The investigation started with the batch preparation of the primary intermediate, N-(4-bromophenyl)-3-phenylpropanamide via an amidation reaction between 3-phenylpropanoyl chloride and p-bromoaniline. The primary intermediate then undergoes a subsequent formylation and cyclization via a Vilsmeier–Haack reaction to yield 3-benzyl-6-bromo-2-chloroquinoline. The chloroquinoline ii intermediate undergoes a methoxylation reaction to form 3-benzyl-6-bromo-2- methoxyquinoline. Subsequently, the batch protocol was transferred into continuous flow systems, optimized by varying reaction parameters within the synthesis route to achieve the as much yield as possible. The optimization studies showed an improvement in conversions in the various steps with shorter reaction times. The first step was optimized in a 0.2ml microreactor and because of the enhanced safety of flow chemistry, this exothermic amidation reaction was optimised at elevated temperatures to afford the primary intermediate at a 100% conversion within a residence time of 5 seconds using DMF as a solvent with DIPEA as a base. Next, the Vilsmier-Haack cyclization and chlorination was optimised in flow to afford the 2-chloroquinoline intermediate. The ability to use a back pressure regulator allowed for investigation of the effect of high temperature on the reaction and the 2- chloroquinoline intermediate was obtained at 78% conversion in a residence time of 30 min at 150 ⁰C using acetonitrile as a solvent. Subsequently, the optimization of the third step in flow to afford the central core intermediate of bedaquiline, 3-benzyl-6-bromo-2-methoxyquinoline, achieved 100% conversion in DMSO/MeOH solvent system at a residence time of 5 min. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The results obtained from this study clearly demonstrated the successful establishment of an efficient flow chemistry protocol that can be used to successfully synthesize all intermediates within the scope of this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mpalala, Anele
- Date: 2022-12
- Subjects: Multidrug-resistant tuberculosis -- South Africa , Tuberculosis --Chemotherapy -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59864 , vital:62455
- Description: SA has a high number of reported cases of multidrug-resistant tuberculosis (MDR-TB). Bedaquiline is a newly approved active ingredient of an anti-tuberculosis drug with high potency against MDR-TB. The limited access to this life-saving medicine to many people in the world has driven a great deal of research effort by the scientific community to find new, better and more practical approaches to this drug. However, many of the reported synthetic procedures suffer from long reaction times, which in turn require many hours of effort by the chemists conducting the reactions. This has prompted us to investigate an efficient process towards the synthesis to produce the key intermediates of bedaquiline using continuous flow technology. Additionally, since there is not much literature on continuous flow synthesis of bedaquiline, this research revealed interesting continuous flow processes towards the drug. Chapter 1: In order to provide insight, the first chapter of this dissertation presents a comprehensive background and literature review on tuberculosis; its pathogenesis, impact, medicines available for the treatment as well as the drug classes with novel mode of action and new chemical entities. Furthermore, bedaquiline is discussed in detail with the various synthetic protocols of the drug. An introduction to continuous flow chemistry is discussed, along with an outline of its advantages and disadvantages. Chapter 2: The second chapter encompasses the experimental procedures utilized for both batch and continuous flow syntheses. The three key intermediates of bedaquiline were synthesized in batch synthesis and these compounds were characterized using 1H-NMR, 13C-NMR and FT-IR spectroscopy. Subsequently, the continuous flow synthesis protocols for the preparations of these intermediates and their optimization are outlined. Chapter 3: The results are explained in this chapter with detailed discussions of the batch synthesis and the continuous flow optimization of each step within the scope of this research. The investigation started with the batch preparation of the primary intermediate, N-(4-bromophenyl)-3-phenylpropanamide via an amidation reaction between 3-phenylpropanoyl chloride and p-bromoaniline. The primary intermediate then undergoes a subsequent formylation and cyclization via a Vilsmeier–Haack reaction to yield 3-benzyl-6-bromo-2-chloroquinoline. The chloroquinoline ii intermediate undergoes a methoxylation reaction to form 3-benzyl-6-bromo-2- methoxyquinoline. Subsequently, the batch protocol was transferred into continuous flow systems, optimized by varying reaction parameters within the synthesis route to achieve the as much yield as possible. The optimization studies showed an improvement in conversions in the various steps with shorter reaction times. The first step was optimized in a 0.2ml microreactor and because of the enhanced safety of flow chemistry, this exothermic amidation reaction was optimised at elevated temperatures to afford the primary intermediate at a 100% conversion within a residence time of 5 seconds using DMF as a solvent with DIPEA as a base. Next, the Vilsmier-Haack cyclization and chlorination was optimised in flow to afford the 2-chloroquinoline intermediate. The ability to use a back pressure regulator allowed for investigation of the effect of high temperature on the reaction and the 2- chloroquinoline intermediate was obtained at 78% conversion in a residence time of 30 min at 150 ⁰C using acetonitrile as a solvent. Subsequently, the optimization of the third step in flow to afford the central core intermediate of bedaquiline, 3-benzyl-6-bromo-2-methoxyquinoline, achieved 100% conversion in DMSO/MeOH solvent system at a residence time of 5 min. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The results obtained from this study clearly demonstrated the successful establishment of an efficient flow chemistry protocol that can be used to successfully synthesize all intermediates within the scope of this research. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-12
The effect of limestone ammonium nitrate and chicken manure fertilizers on growth, yield and quality of two cabbage cultivators
- Authors: Nongogo Chumani
- Date: 2022-12
- Subjects: Cabbage -- South Africa , Field crops -- Nutrition -- South Africa , fertilizers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59922 , vital:62695
- Description: Cabbage is a well-known and popular crop in South Africa. As a highly nutritious leafy green vegetable, it is produced and sold to a variety of markets, from formal markets to hawkers, for human consumption and as animal feed. The cabbage crop contributes positively to food security, health, and households’ financial wellbeing. As a crop, cabbage is known to be a heavy feeder due to its high nutritional requirements (in terms of fertiliser) particularly nitrogen. This high requirement can be supplied by either synthetic or by organic fertilisers in the form of animal manures. However, fertiliser has proven to be a challenge due to its high costs, as its prices increase rapidly each year. The current study aimed to determine the most effective fertilisation method for the growth, quality, and yield of cabbage (Brassica oleracea var. capitata). Two fertiliser types (chicken manure and limestone ammonium nitrate) were applied, and the treatments were repeated five times over two planting sessions on two cultivars, Grandslam and Empowa, at concentrations of 0%, 100% and 150%. A control for each treatment / cultivar was also grown. The parameters plant height, head diameter, pests and disease development, quality and dry mass were measured to determine the effect on growth, yield, and quality of the cabbage crop. From each planting, a total of 60 cabbages served as specimens for data collection purposes. The research trial was conducted in open field and laid out in a split-plot block method. The cultivar was allocated to the main plot, while the fertiliser treatments served as the sub-plots. The study was carried out for a period of six months, which allowed for data collection to be done in two different growing conditions. Planting was done manually by hand in planting bags, and washed river sand was used as a substrate (growing medium). The data collected during the experiment was analysed by means of statistical data analysis software STATISTICA and the methods applied were a three-way analysis of variance (ANOVA). The analysis of variance was performed at a significance level of p as a means to determine a correlation of relationships for all set parameters (variables) for both cultivars, treatments and plantings. The results of the study showed that the two fertiliser types, namely limestone ammonium nitrate (LAN) and chicken manure, both had a significant effect (p on plant height, head diameter, dry mass. Also, the pest and disease development and quality of cabbage were significantly influenced by the fertiliser types and season (climate). The interactive effect of cultivar and fertiliser was statistically significant. Empowa showed better results on chicken manure compared to LAN. In the case of Grandslam, however, no significant fertiliser effect was observed. The study also showed that fertilisation with a fertiliser that contains high nitrogen (N) content promotes pest and disease incidence. Increasing N application rate resulted into an increase of pest and disease incidence. The change of season, which promotes different growth conditions (in terms of temperature, water requirements, pests, and diseases) for the plants was found to have had an influence on the study results. Lasty, it was observed that chicken manure fertiliser yields a cabbage with a good internal and external quality compared to limestone ammonium nitrate fertiliser. Lastly, when considering all treatment rates applied, the recommended quantity of 100% (in both chicken manure and LAN) yielded favorable results. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Nongogo Chumani
- Date: 2022-12
- Subjects: Cabbage -- South Africa , Field crops -- Nutrition -- South Africa , fertilizers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59922 , vital:62695
- Description: Cabbage is a well-known and popular crop in South Africa. As a highly nutritious leafy green vegetable, it is produced and sold to a variety of markets, from formal markets to hawkers, for human consumption and as animal feed. The cabbage crop contributes positively to food security, health, and households’ financial wellbeing. As a crop, cabbage is known to be a heavy feeder due to its high nutritional requirements (in terms of fertiliser) particularly nitrogen. This high requirement can be supplied by either synthetic or by organic fertilisers in the form of animal manures. However, fertiliser has proven to be a challenge due to its high costs, as its prices increase rapidly each year. The current study aimed to determine the most effective fertilisation method for the growth, quality, and yield of cabbage (Brassica oleracea var. capitata). Two fertiliser types (chicken manure and limestone ammonium nitrate) were applied, and the treatments were repeated five times over two planting sessions on two cultivars, Grandslam and Empowa, at concentrations of 0%, 100% and 150%. A control for each treatment / cultivar was also grown. The parameters plant height, head diameter, pests and disease development, quality and dry mass were measured to determine the effect on growth, yield, and quality of the cabbage crop. From each planting, a total of 60 cabbages served as specimens for data collection purposes. The research trial was conducted in open field and laid out in a split-plot block method. The cultivar was allocated to the main plot, while the fertiliser treatments served as the sub-plots. The study was carried out for a period of six months, which allowed for data collection to be done in two different growing conditions. Planting was done manually by hand in planting bags, and washed river sand was used as a substrate (growing medium). The data collected during the experiment was analysed by means of statistical data analysis software STATISTICA and the methods applied were a three-way analysis of variance (ANOVA). The analysis of variance was performed at a significance level of p as a means to determine a correlation of relationships for all set parameters (variables) for both cultivars, treatments and plantings. The results of the study showed that the two fertiliser types, namely limestone ammonium nitrate (LAN) and chicken manure, both had a significant effect (p on plant height, head diameter, dry mass. Also, the pest and disease development and quality of cabbage were significantly influenced by the fertiliser types and season (climate). The interactive effect of cultivar and fertiliser was statistically significant. Empowa showed better results on chicken manure compared to LAN. In the case of Grandslam, however, no significant fertiliser effect was observed. The study also showed that fertilisation with a fertiliser that contains high nitrogen (N) content promotes pest and disease incidence. Increasing N application rate resulted into an increase of pest and disease incidence. The change of season, which promotes different growth conditions (in terms of temperature, water requirements, pests, and diseases) for the plants was found to have had an influence on the study results. Lasty, it was observed that chicken manure fertiliser yields a cabbage with a good internal and external quality compared to limestone ammonium nitrate fertiliser. Lastly, when considering all treatment rates applied, the recommended quantity of 100% (in both chicken manure and LAN) yielded favorable results. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Uptake and storage of nutrients by primary producers in the Swartkops Estuary
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Using spatial explicit capture-recapture model to investigate the demography and spatial dynamics of lion prides in Pilanesberg National Park
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
A 5G Communication system based on flexible spectrum technology for the SKA
- Authors: Karembera, Reinhard Siwombe
- Date: 2022-04
- Subjects: Mobile communication systems--Technological innovations , Wireless communication systems -- Standards --South Africa
- Language: English
- Type: Doctoral theses
- Identifier: http://hdl.handle.net/10948/56177 , vital:56013
- Description: Faculty of Science Radio astronomy research is rapidly expanding across the African continent. At the same time, the fifth generation (5G) of mobile communication systems are also being researched and developed. Throughout history, mobile communication networks are known to affect the activities of radio astronomy. If not carefully managed, radio frequencies from mobile communication devices can severely affect radio astronomy observations. To that end, many techniques have been proposed to protect the radio astronomer from RFIs coming from radio communication networks. Some of the proposed techniques such as RFI quite zones and spectrum assignment by regulatory authorities will not be convenient during the implementation of 5G mobile networks. This is because 5G radio communication systems are expected to support spectrum-hungry application such as video-on-demand, augmented realities, high-definition television and so on. To realize this, the 5G networks will be forced to have access to protected radio spectrum, including those at which radio astronomy activities are being researched. To facilitate this, the 5G radio communication networks should have the intelligence to coexist within such protected spectrums without the consequences of radio frequency interferences (RFI) to the primary user. In this thesis, we present novel 5G networks with the intelligence that allow them to coexist within radio astronomy areas without introducing RFIs to the primary user. We proposed a photonic solution, keeping in mind the characteristic requirements for future 5G radio communication networks. The thesis begins by reviewing the current trend of radio astronomy research in Africa. It was found that radio astronomy research in Africa is growing rapidly. Many African countries such as South Africa and Ghana are at advanced stages when it comes to radio astronomy research. Therefore, the finding and proposal of this thesis will be valuable to such countries. In order to develop a radio access network (RAN) that can coexist within radio astronomy areas, the thesis reviewed past and present state-of-the-art RANs. Each access network was analyses for its feasibility to be implemented within radio astronomy areas to realize mobile communication without the consequences of RFIs to the astronomer. It was motivated that the current centralized radio access network (C-RAN) the best solution to be developed for radio communication within radio astronomy areas. This is because the C-RAN architecture is centralized by pooling network resources to a common point. From such pool, network resources can be controlled and shared among 5G network user, including radio astronomers and the surrounding communities. The next chapters reviewed photonic RF transmitters and their associated lasers currently being proposed to be used within C-RANs. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Karembera, Reinhard Siwombe
- Date: 2022-04
- Subjects: Mobile communication systems--Technological innovations , Wireless communication systems -- Standards --South Africa
- Language: English
- Type: Doctoral theses
- Identifier: http://hdl.handle.net/10948/56177 , vital:56013
- Description: Faculty of Science Radio astronomy research is rapidly expanding across the African continent. At the same time, the fifth generation (5G) of mobile communication systems are also being researched and developed. Throughout history, mobile communication networks are known to affect the activities of radio astronomy. If not carefully managed, radio frequencies from mobile communication devices can severely affect radio astronomy observations. To that end, many techniques have been proposed to protect the radio astronomer from RFIs coming from radio communication networks. Some of the proposed techniques such as RFI quite zones and spectrum assignment by regulatory authorities will not be convenient during the implementation of 5G mobile networks. This is because 5G radio communication systems are expected to support spectrum-hungry application such as video-on-demand, augmented realities, high-definition television and so on. To realize this, the 5G networks will be forced to have access to protected radio spectrum, including those at which radio astronomy activities are being researched. To facilitate this, the 5G radio communication networks should have the intelligence to coexist within such protected spectrums without the consequences of radio frequency interferences (RFI) to the primary user. In this thesis, we present novel 5G networks with the intelligence that allow them to coexist within radio astronomy areas without introducing RFIs to the primary user. We proposed a photonic solution, keeping in mind the characteristic requirements for future 5G radio communication networks. The thesis begins by reviewing the current trend of radio astronomy research in Africa. It was found that radio astronomy research in Africa is growing rapidly. Many African countries such as South Africa and Ghana are at advanced stages when it comes to radio astronomy research. Therefore, the finding and proposal of this thesis will be valuable to such countries. In order to develop a radio access network (RAN) that can coexist within radio astronomy areas, the thesis reviewed past and present state-of-the-art RANs. Each access network was analyses for its feasibility to be implemented within radio astronomy areas to realize mobile communication without the consequences of RFIs to the astronomer. It was motivated that the current centralized radio access network (C-RAN) the best solution to be developed for radio communication within radio astronomy areas. This is because the C-RAN architecture is centralized by pooling network resources to a common point. From such pool, network resources can be controlled and shared among 5G network user, including radio astronomers and the surrounding communities. The next chapters reviewed photonic RF transmitters and their associated lasers currently being proposed to be used within C-RANs. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
- Full Text:
- Date Issued: 2022-04