Photoluminescence and electroluminescence imaging of PV devices
- Authors: Roodt, Roelof Petrus
- Date: 2024-04
- Subjects: Photoluminescence , Biosensors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64333 , vital:73676
- Description: Luminescence imaging has become a particularly useful and valuable tool for the characterisation of photovoltaic devices. This study entailed the design, construction, and optimisation of a system for the electroluminescence (EL) and photoluminescence (PL) imaging of various solar cell devices. The system can perform EL and PL imaging of solar cells of different cell technologies and materials systems, including Si, perovskite, and triple-junction concentrator solar cells. This required appropriate electrical power supplies for carrier injection for EL imaging and optical excitation for PL imaging. The different materials systems also required wavelength appropriate filters for PL imaging. In addition, the system utilized a temperature-controlled sample stage and was placed in a chamber for environmental control and isolation of UV radiation from laboratory. In addition to optimization of imaging conditions, luminescence images need to be optimized to facilitate detailed analysis and the application of appropriate algorithms to extract device parameters and hence generate device parameter images of the devices under investigation. For EL imaging, two power supplies were used to inject current into the solar cells. The reason for the two power supplies is that the first power supply had a current range of ± 1 A and an applied voltage capability of ± 21 V. This was used for the smaller solar cells. It was also convenient to use as the power supply could also measure the injected current and applied voltage and digitally store it with the images. For the larger solar cells, a second power supply was utilized, which could inject current into the samples in the range of ± 12 A at an applied voltage of ± 40 V. To measure the current and voltage of the power supply provided, two digital multimeters were utilized. For acquiring images, the same camera was used for EL and PL imaging. The sensor used in the camera is a silicon CMOS sensor. For PL imaging, four light emitting diode (LED) boards, consisting out of sixty-four LED’s, per board, of four different wavelengths, were used to optically excite the solar cells. The four wavelengths emitted by the LED’s were chosen to match the bandgaps of the different solar cell devices investigated. The LEDs were powered with a multi-channel constant voltage power supply, where the current could be varied. The Si solar cell is a 156 x 156 mm commercial solar cell. The perovskite solar module is a 40 x 40 mm module, which consists out of six cells connected in series. The triple-junction concentrator solar cell has a dimension of 10 x 10 mm which consists of three junctions staked on top of one another. These three layers consist of indium gallium phosphate (InGaP), indium gallium arsenide (InGaAs) and germanium (Ge). To capture EL and PL images of these various solar cell devices, filters of specific wavelengths were placed in front of the camera to isolate the light generated by the different devices. In addition to isolating the luminescence observed from the solar cells, an image correction procedure was adapted from literature, to be applicable to acquiring luminescence images of these various solar cells. As there are a range of factors which influence the quality and clarity of the luminescence images, i.e., chromatic aberration, diffraction, and absorption depth, to name a few, the wavelength dependency of these factors was investigated. This was done by acquiring a point spread function (PSF) for each of these devices and then using these PSF's together with a deconvolution algorithm to correct the luminescence images. The PSF was acquired by fitting a point source emission image to a function that includes exponential and Gaussian terms. The point source image was obtained by placing a black piece of vinyl with a pinhole in it over the solar cell. To communicate with all the various devices and to acquire images at various intensities a LABVIEW program was written. This was used then used to control the power supplies, digital multimeters, camera, and the LED's. This allowed for the user to specify at what points along the current-voltage (I-V) curve data points needed to be measured together with the luminescence images captured. For PL imaging the intensity of the LED's was then also adjusted according to user specified values. The system was utilised to acquire EL images of the Si solar cell, EL and PL images of the perovskite solar cell and EL images of the InGaP and InGaAs layers in the triple-junction concentrator solar cell. With the correction procedure utilised in this study, it was seen that the image quality and clarity improved, compared to the conventional way of capturing luminescence images. These statements are supported by the results obtained for the series resistance maps of the Si solar cell and the perovskite solar module, as the series resistance maps obtained from the corrected luminescence images have less noise and more detail compared to the results from the raw luminescence images. From the EL images captured for the two layers of the triple junction concentrator, it was clear that the intensity profile of the two layers is different, as the intensity for the InGaP layers was that the device had bright edges and darker intensity on the interior where exactly the opposite was observed for the InGaAs layer, having a bright interior and darker edges. This is most likely due to the opto-electric coupling of these layers withing the triple junction solar cell. For the series resistance images obtained for the Si solar cell, it is observed that at lower carrier injection, the series resistance is lower compared to higher carrier injection levels. This result can also be influenced by the increase in cell temperature with the increase in injected carriers. The series resistance maps obtained from the perovskite EL images shows an interesting result. As the perovskite solar cell has degraded, three of the six cells have optically inactive regions, showing lower luminescence intensities. The series resistance of the other three cells are much lower compared to these cells that have inactive regions under low injection conditions. As the injection level increases, it is seen that the series resistance values of five of the six cells become comparable to one another. With regards to the PSF, it was found that using a bandpass filter in front of the lens reduced to amount of spreading observed from a single point source across the detector. Furthermore, there is a strong wavelength dependency in the PSF as the severity increased with increase in the emission wavelength of the solar cells under investigation.In this study an opto-electrical characterisation system was constructed to acquire PL and EL images of various solar cell technologies. In addition to this, a range of factors that influence the quality of these images were investigated and used in the image correction procedure to correct the images for all these cell technologies. It was shown that the correction procedure works for all three of the technologies investigated in this study, and all these factors showed a strong wavelength dependency. These corrected luminescence images together with current-voltage (I-V) data was then used to determine characteristic parameters of a one-diode model of the various PV devices. This was not only achieved, but it also clearly indicated that all the correction procedures need to be considered to obtain a clear and accurate representation of the actual PV device. This has a major influence on the understanding and improvement of these PV devices. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Roodt, Roelof Petrus
- Date: 2024-04
- Subjects: Photoluminescence , Biosensors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64333 , vital:73676
- Description: Luminescence imaging has become a particularly useful and valuable tool for the characterisation of photovoltaic devices. This study entailed the design, construction, and optimisation of a system for the electroluminescence (EL) and photoluminescence (PL) imaging of various solar cell devices. The system can perform EL and PL imaging of solar cells of different cell technologies and materials systems, including Si, perovskite, and triple-junction concentrator solar cells. This required appropriate electrical power supplies for carrier injection for EL imaging and optical excitation for PL imaging. The different materials systems also required wavelength appropriate filters for PL imaging. In addition, the system utilized a temperature-controlled sample stage and was placed in a chamber for environmental control and isolation of UV radiation from laboratory. In addition to optimization of imaging conditions, luminescence images need to be optimized to facilitate detailed analysis and the application of appropriate algorithms to extract device parameters and hence generate device parameter images of the devices under investigation. For EL imaging, two power supplies were used to inject current into the solar cells. The reason for the two power supplies is that the first power supply had a current range of ± 1 A and an applied voltage capability of ± 21 V. This was used for the smaller solar cells. It was also convenient to use as the power supply could also measure the injected current and applied voltage and digitally store it with the images. For the larger solar cells, a second power supply was utilized, which could inject current into the samples in the range of ± 12 A at an applied voltage of ± 40 V. To measure the current and voltage of the power supply provided, two digital multimeters were utilized. For acquiring images, the same camera was used for EL and PL imaging. The sensor used in the camera is a silicon CMOS sensor. For PL imaging, four light emitting diode (LED) boards, consisting out of sixty-four LED’s, per board, of four different wavelengths, were used to optically excite the solar cells. The four wavelengths emitted by the LED’s were chosen to match the bandgaps of the different solar cell devices investigated. The LEDs were powered with a multi-channel constant voltage power supply, where the current could be varied. The Si solar cell is a 156 x 156 mm commercial solar cell. The perovskite solar module is a 40 x 40 mm module, which consists out of six cells connected in series. The triple-junction concentrator solar cell has a dimension of 10 x 10 mm which consists of three junctions staked on top of one another. These three layers consist of indium gallium phosphate (InGaP), indium gallium arsenide (InGaAs) and germanium (Ge). To capture EL and PL images of these various solar cell devices, filters of specific wavelengths were placed in front of the camera to isolate the light generated by the different devices. In addition to isolating the luminescence observed from the solar cells, an image correction procedure was adapted from literature, to be applicable to acquiring luminescence images of these various solar cells. As there are a range of factors which influence the quality and clarity of the luminescence images, i.e., chromatic aberration, diffraction, and absorption depth, to name a few, the wavelength dependency of these factors was investigated. This was done by acquiring a point spread function (PSF) for each of these devices and then using these PSF's together with a deconvolution algorithm to correct the luminescence images. The PSF was acquired by fitting a point source emission image to a function that includes exponential and Gaussian terms. The point source image was obtained by placing a black piece of vinyl with a pinhole in it over the solar cell. To communicate with all the various devices and to acquire images at various intensities a LABVIEW program was written. This was used then used to control the power supplies, digital multimeters, camera, and the LED's. This allowed for the user to specify at what points along the current-voltage (I-V) curve data points needed to be measured together with the luminescence images captured. For PL imaging the intensity of the LED's was then also adjusted according to user specified values. The system was utilised to acquire EL images of the Si solar cell, EL and PL images of the perovskite solar cell and EL images of the InGaP and InGaAs layers in the triple-junction concentrator solar cell. With the correction procedure utilised in this study, it was seen that the image quality and clarity improved, compared to the conventional way of capturing luminescence images. These statements are supported by the results obtained for the series resistance maps of the Si solar cell and the perovskite solar module, as the series resistance maps obtained from the corrected luminescence images have less noise and more detail compared to the results from the raw luminescence images. From the EL images captured for the two layers of the triple junction concentrator, it was clear that the intensity profile of the two layers is different, as the intensity for the InGaP layers was that the device had bright edges and darker intensity on the interior where exactly the opposite was observed for the InGaAs layer, having a bright interior and darker edges. This is most likely due to the opto-electric coupling of these layers withing the triple junction solar cell. For the series resistance images obtained for the Si solar cell, it is observed that at lower carrier injection, the series resistance is lower compared to higher carrier injection levels. This result can also be influenced by the increase in cell temperature with the increase in injected carriers. The series resistance maps obtained from the perovskite EL images shows an interesting result. As the perovskite solar cell has degraded, three of the six cells have optically inactive regions, showing lower luminescence intensities. The series resistance of the other three cells are much lower compared to these cells that have inactive regions under low injection conditions. As the injection level increases, it is seen that the series resistance values of five of the six cells become comparable to one another. With regards to the PSF, it was found that using a bandpass filter in front of the lens reduced to amount of spreading observed from a single point source across the detector. Furthermore, there is a strong wavelength dependency in the PSF as the severity increased with increase in the emission wavelength of the solar cells under investigation.In this study an opto-electrical characterisation system was constructed to acquire PL and EL images of various solar cell technologies. In addition to this, a range of factors that influence the quality of these images were investigated and used in the image correction procedure to correct the images for all these cell technologies. It was shown that the correction procedure works for all three of the technologies investigated in this study, and all these factors showed a strong wavelength dependency. These corrected luminescence images together with current-voltage (I-V) data was then used to determine characteristic parameters of a one-diode model of the various PV devices. This was not only achieved, but it also clearly indicated that all the correction procedures need to be considered to obtain a clear and accurate representation of the actual PV device. This has a major influence on the understanding and improvement of these PV devices. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
Preparation and Investigation of coumarin-based chemosensors towards sensing of ions using UV studies in aqueous systems
- Authors: Kotze, Tyla
- Date: 2024-04
- Subjects: Chemistry, Analytic , Water chemistry , Ionic solutions , Aquatic ecology , Geochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64116 , vital:73654
- Description: Humanity's unrelenting expansion has shown little regard for the environment, and this has resulted in tons of toxic heavy metal cations and anions being released into the environment through industrial, agricultural, electronic, and mining dumping. The release of these toxic heavy metals can cause diseases and sometimes lead to death, especially in third-world countries with low-income that reside in informal settlements, who suffer the most. Furthermore, the release of these toxins eventually finds their way back into the environment through bioaccumulation in fish, plants and animals. Although there is an ever need for the growth of these industries; low-cost, sensitive, selective, and organic-based sensors is a positive step forward in highlighting the need for environmental restoration and remediation, whilst striving to avoid unnecessary disease and death through this development. In this project, coumarin-based chemosensors for the detection of cationic and anionic species in aqueous and organic media are described. This project involves the synthesis of six different coumarin-based ether derivatives (E2-E5) and coumarin-based ester derivatives (H1-H2). FT-IR, 1H NMR and 13C NMR were used to confirm the structures of all sensors. The abilities of these novel compounds as chemosensors for detection of cations and anions were investigated using UV-vis analysis. These compounds displayed a favourable interaction with Fe2+ and Fe3+ ions with an increase in absorbance. Ether derivatives E2-E5 did not display any degree of selectivity or sensitivity towards the chosen anions. It was found that in the presence of FeCl2, sensors H1 and H2 displayed a degree of selectivities and further investigations were therefore carried out. From the titration experiments, the limit of detection, limit of quantification and association constants were determined. Job’s plot analyses were performed to determine the binding ratios, which was supported by Benesi-Hildebrand studies. The binding ratio between the sensors and metal cations during complexation was found to be 1:1. Reversibility studies were carried out using EDTA to determine whether the sensors could be reused. Molecular Modelling studies were used to determine the most preferred binding sites. Lastly, real-life application screenings were also run to determine if the sensors will be able to be used in real-life scenarios. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Kotze, Tyla
- Date: 2024-04
- Subjects: Chemistry, Analytic , Water chemistry , Ionic solutions , Aquatic ecology , Geochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64116 , vital:73654
- Description: Humanity's unrelenting expansion has shown little regard for the environment, and this has resulted in tons of toxic heavy metal cations and anions being released into the environment through industrial, agricultural, electronic, and mining dumping. The release of these toxic heavy metals can cause diseases and sometimes lead to death, especially in third-world countries with low-income that reside in informal settlements, who suffer the most. Furthermore, the release of these toxins eventually finds their way back into the environment through bioaccumulation in fish, plants and animals. Although there is an ever need for the growth of these industries; low-cost, sensitive, selective, and organic-based sensors is a positive step forward in highlighting the need for environmental restoration and remediation, whilst striving to avoid unnecessary disease and death through this development. In this project, coumarin-based chemosensors for the detection of cationic and anionic species in aqueous and organic media are described. This project involves the synthesis of six different coumarin-based ether derivatives (E2-E5) and coumarin-based ester derivatives (H1-H2). FT-IR, 1H NMR and 13C NMR were used to confirm the structures of all sensors. The abilities of these novel compounds as chemosensors for detection of cations and anions were investigated using UV-vis analysis. These compounds displayed a favourable interaction with Fe2+ and Fe3+ ions with an increase in absorbance. Ether derivatives E2-E5 did not display any degree of selectivity or sensitivity towards the chosen anions. It was found that in the presence of FeCl2, sensors H1 and H2 displayed a degree of selectivities and further investigations were therefore carried out. From the titration experiments, the limit of detection, limit of quantification and association constants were determined. Job’s plot analyses were performed to determine the binding ratios, which was supported by Benesi-Hildebrand studies. The binding ratio between the sensors and metal cations during complexation was found to be 1:1. Reversibility studies were carried out using EDTA to determine whether the sensors could be reused. Molecular Modelling studies were used to determine the most preferred binding sites. Lastly, real-life application screenings were also run to determine if the sensors will be able to be used in real-life scenarios. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Prevalence of red blood cell alloantibodies in healthy blood donors: A retrospective study
- Authors: Bada, Thandolwethu Sarafina
- Date: 2024-04
- Subjects: Blood--Transfusion , Blood donors , Red blood cell alloantibodies
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63688 , vital:73586
- Description: Background: Blood transfusion is one of the essential supporting therapies in the management of patients and all efforts must be geared towards ensuring greater blood safety. There are studies on the prevalence of red blood cell alloantibodies in numerous transfused patients. However, no research has been done on the population of healthy first-time donors in South Africa who donates blood for transfusion. Red blood cell alloantibodies may be present in the donated units and potentially lead to transfusion reactions or to decreased survival of transfused RBCs. Therefore, it is necessary to know the prevalence of alloantibodies in donors and the clinical significance. Aims and objectives: The aim of this study is to determine the prevalence and identity of red blood cell alloantibodies in healthy first-time blood donors in the South African population, as well as to identify them, with the goal of improving blood safety and transfusion support for patients. Materials and methods: This retrospective and observational study investigates healthy first-time blood donors in the South African population over a five-year period, from January 2015 to December 2019. ABO typing and Rh typing were performed using the fully automated immunohaematology analyser BECKMAN COULTER PK7300 (Danaher Corporation, Brea, California). Erytra Eflexis automated system (8-column DG Gel cards) (Diagnostic Grifols, Barcelona, Spain) was used for antibody screening and antibody identification was performed using the RBC 11 Identisera Diana panel sheet. Approval was obtained from the Ethics Committees of Nelson Mandela University, South African National Blood Services and Western Province Blood Services prior to commencement of the study. Results: A total of 497 711 healthy first-time donors, consisting of 209 604 (42%) males and 288 107 (58%) females, were evaluated for irregular antibodies. The maximum number of donors belonged to the age group 18 to 29. Antibody screening results were positive in 849 donors from the entire population investigated, and 603 were RBC alloantibodies with an overall prevalence of 0.12%. The most frequent RBC alloantibody identified was anti-M from the MNS blood group systems, being present in 129 blood donors. Conclusion: The prevalence of RBC alloantibodies in the donor population in the study was 0.12% (603/497 711). As the inclusion criteria was limited, larger studies examining at all donors (first-time and repeated donations) are needed to determine the actual prevalence of alloantibodies in the population of South African donors. , Thesis (MHSc) -- Faculty of Health Sciences, School of Clinical Care & Medicinal Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Bada, Thandolwethu Sarafina
- Date: 2024-04
- Subjects: Blood--Transfusion , Blood donors , Red blood cell alloantibodies
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63688 , vital:73586
- Description: Background: Blood transfusion is one of the essential supporting therapies in the management of patients and all efforts must be geared towards ensuring greater blood safety. There are studies on the prevalence of red blood cell alloantibodies in numerous transfused patients. However, no research has been done on the population of healthy first-time donors in South Africa who donates blood for transfusion. Red blood cell alloantibodies may be present in the donated units and potentially lead to transfusion reactions or to decreased survival of transfused RBCs. Therefore, it is necessary to know the prevalence of alloantibodies in donors and the clinical significance. Aims and objectives: The aim of this study is to determine the prevalence and identity of red blood cell alloantibodies in healthy first-time blood donors in the South African population, as well as to identify them, with the goal of improving blood safety and transfusion support for patients. Materials and methods: This retrospective and observational study investigates healthy first-time blood donors in the South African population over a five-year period, from January 2015 to December 2019. ABO typing and Rh typing were performed using the fully automated immunohaematology analyser BECKMAN COULTER PK7300 (Danaher Corporation, Brea, California). Erytra Eflexis automated system (8-column DG Gel cards) (Diagnostic Grifols, Barcelona, Spain) was used for antibody screening and antibody identification was performed using the RBC 11 Identisera Diana panel sheet. Approval was obtained from the Ethics Committees of Nelson Mandela University, South African National Blood Services and Western Province Blood Services prior to commencement of the study. Results: A total of 497 711 healthy first-time donors, consisting of 209 604 (42%) males and 288 107 (58%) females, were evaluated for irregular antibodies. The maximum number of donors belonged to the age group 18 to 29. Antibody screening results were positive in 849 donors from the entire population investigated, and 603 were RBC alloantibodies with an overall prevalence of 0.12%. The most frequent RBC alloantibody identified was anti-M from the MNS blood group systems, being present in 129 blood donors. Conclusion: The prevalence of RBC alloantibodies in the donor population in the study was 0.12% (603/497 711). As the inclusion criteria was limited, larger studies examining at all donors (first-time and repeated donations) are needed to determine the actual prevalence of alloantibodies in the population of South African donors. , Thesis (MHSc) -- Faculty of Health Sciences, School of Clinical Care & Medicinal Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Quantifying the impact of the spatio-temporal variability of land use/land cover on surface run-off generation and groundwater recharge in the luvuvhu river catchment area as a study area
- Ramuhovhi, Dakalo Ndivhuwo Stella
- Authors: Ramuhovhi, Dakalo Ndivhuwo Stella
- Date: 2024-04
- Subjects: Remote sensing , Geographic information systems , Groundwater flow
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64322 , vital:73675
- Description: Assessing the spatio-temporal dynamics of land use land cover (LULC) change on hydrological response is vital for catchment sustainability and developing proper management strategies. The study aimed to assess the spatiotemporal effects and implications of LULC dynamics on surface runoff in the Luvuvhu River Catchment, Limpopo Province, using the Soil and Water Assessment Tool (SWAT) model. Satellite images of Landsat 5-thematic mapper and Landsat 8 operational land imager for the years 1990 and 2021 were used to explore the characteristics of LULC for this study by adopting the maximum likelihood (ML) supervised classification method. Five LULC classes were classified in this study; namely, water, built-up area, bare surface, dense vegetation, and sparse vegetation. The classification results show good accuracy values in the range of 76% (1990) and 84% (2021) with overall kappa of 63.8% and 72.8% for 1990 and 2021, respectively. For the purpose of this study, integration of geospatial technique and SWAT model were configured to operate at a monthly time interval over a span of 34 years, specifically from 1979 to 2013 to simulate surface runoff. The SWAT simulation process was executed using a digital elevation model, soil, LULC, and weather data. The analysis of LULC for 1990 and 2021 runoff modelling, it was found that, the runoff depth increased gradually from 3249 mm to 5162.5 mm during 1990 and 2021 LULC change, respectively. The R2, ENS, PBIAS, and RSR values for the calibration and the validation were 0.81 and 0.76, and 0.72 and 0.68, 0.64 and 0.58, 0.54 and 0.63 respectively. These values indicate good correlation between the observed and simulated stream flow data Therefore, suitable and timely management measures must be taken by policy decision-makers to enable sustainable development and to protect the catchment’s natural resources in order to reduce the severity of the changes. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Ramuhovhi, Dakalo Ndivhuwo Stella
- Date: 2024-04
- Subjects: Remote sensing , Geographic information systems , Groundwater flow
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64322 , vital:73675
- Description: Assessing the spatio-temporal dynamics of land use land cover (LULC) change on hydrological response is vital for catchment sustainability and developing proper management strategies. The study aimed to assess the spatiotemporal effects and implications of LULC dynamics on surface runoff in the Luvuvhu River Catchment, Limpopo Province, using the Soil and Water Assessment Tool (SWAT) model. Satellite images of Landsat 5-thematic mapper and Landsat 8 operational land imager for the years 1990 and 2021 were used to explore the characteristics of LULC for this study by adopting the maximum likelihood (ML) supervised classification method. Five LULC classes were classified in this study; namely, water, built-up area, bare surface, dense vegetation, and sparse vegetation. The classification results show good accuracy values in the range of 76% (1990) and 84% (2021) with overall kappa of 63.8% and 72.8% for 1990 and 2021, respectively. For the purpose of this study, integration of geospatial technique and SWAT model were configured to operate at a monthly time interval over a span of 34 years, specifically from 1979 to 2013 to simulate surface runoff. The SWAT simulation process was executed using a digital elevation model, soil, LULC, and weather data. The analysis of LULC for 1990 and 2021 runoff modelling, it was found that, the runoff depth increased gradually from 3249 mm to 5162.5 mm during 1990 and 2021 LULC change, respectively. The R2, ENS, PBIAS, and RSR values for the calibration and the validation were 0.81 and 0.76, and 0.72 and 0.68, 0.64 and 0.58, 0.54 and 0.63 respectively. These values indicate good correlation between the observed and simulated stream flow data Therefore, suitable and timely management measures must be taken by policy decision-makers to enable sustainable development and to protect the catchment’s natural resources in order to reduce the severity of the changes. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Reconstructing the fire history and palaeoenvironment at Thyspunt, Southern Cape Coast, Eastern Cape
- Authors: Ntsondwa, Asithandile
- Date: 2024-04
- Subjects: Paleoecology -- South Africa -- Eastern Cape , Paleoclimatology -- South Africa -- Eastern Cape , Sedimentation analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64277 , vital:73671
- Description: This study aims to comprehensively understand the palaeoenvironments at Thyspunt in the Eastern Cape, a subregion of the Cape Floristic Region, through fire reconstruction and sediment analyses. Given the fire-dependent nature of the dominant vegetation (fynbos) in the area, there is a need for fire reconstructions and an understanding of the broader ecological dynamics within the southern Cape coastal region (SCCR). This research focused on reconstructing the fire regimes using sedimentary micro- and macrocharcoal from a sediment core (TP-1) extracted from the Langefonteinvlei wetland at Thyspunt, covering the last 5000 years. The charcoal fragments were separated into three size classes, with two falling under microcharcoal (size class 1: 10 – 100 μm and size class 2: 100 – 150 μm) and fragments greater than 150 μm representing macrocharcoal. The sedimentary profile of the TP-1 sequence was characterised based on loss on ignition and x-ray fluorescence analyses to provide better insight into the area's geological and geomorphic setting, climate history, and sediment properties. The results from the geochemical data revealed consistently high calcium carbonate composition throughout the sequence with a decrease in concentration at ~2000 cal. yr BP, 1300 cal. yr BP, and from 500 cal. yr BP to recent years. The sediments had relatively high organic content during the last 500 years. The geochemical data also indicate that the sediments are associated with shallow marine and near-shore depositional environments with a sharp increase in fine material at about 4500 cal. yr BP representing a low-energy environment. High fire activities occur around 4000 cal. yr. BP and from 1500 cal. yr BP till present, with former fire activities more likely associated with increased wildfires (driven by climate change) and the latter possibly reflecting human influence at that time. Microcharcoal fragments (size class 1: 10 – 100 μm) had higher concentrations than the other size fragments. This study underpins the importance of a multiproxy study to enrich our understanding of fire histories in Thyspunt and contributes to broader regional insights. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Reconstructing the fire history and palaeoenvironment at Thyspunt, Southern Cape Coast, Eastern Cape
- Authors: Ntsondwa, Asithandile
- Date: 2024-04
- Subjects: Paleoecology -- South Africa -- Eastern Cape , Paleoclimatology -- South Africa -- Eastern Cape , Sedimentation analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64277 , vital:73671
- Description: This study aims to comprehensively understand the palaeoenvironments at Thyspunt in the Eastern Cape, a subregion of the Cape Floristic Region, through fire reconstruction and sediment analyses. Given the fire-dependent nature of the dominant vegetation (fynbos) in the area, there is a need for fire reconstructions and an understanding of the broader ecological dynamics within the southern Cape coastal region (SCCR). This research focused on reconstructing the fire regimes using sedimentary micro- and macrocharcoal from a sediment core (TP-1) extracted from the Langefonteinvlei wetland at Thyspunt, covering the last 5000 years. The charcoal fragments were separated into three size classes, with two falling under microcharcoal (size class 1: 10 – 100 μm and size class 2: 100 – 150 μm) and fragments greater than 150 μm representing macrocharcoal. The sedimentary profile of the TP-1 sequence was characterised based on loss on ignition and x-ray fluorescence analyses to provide better insight into the area's geological and geomorphic setting, climate history, and sediment properties. The results from the geochemical data revealed consistently high calcium carbonate composition throughout the sequence with a decrease in concentration at ~2000 cal. yr BP, 1300 cal. yr BP, and from 500 cal. yr BP to recent years. The sediments had relatively high organic content during the last 500 years. The geochemical data also indicate that the sediments are associated with shallow marine and near-shore depositional environments with a sharp increase in fine material at about 4500 cal. yr BP representing a low-energy environment. High fire activities occur around 4000 cal. yr. BP and from 1500 cal. yr BP till present, with former fire activities more likely associated with increased wildfires (driven by climate change) and the latter possibly reflecting human influence at that time. Microcharcoal fragments (size class 1: 10 – 100 μm) had higher concentrations than the other size fragments. This study underpins the importance of a multiproxy study to enrich our understanding of fire histories in Thyspunt and contributes to broader regional insights. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Relationship Management in All-Boys’ Fee-paying Public Schools in the Eastern Cape, South Africa : Experiences and Perspectives of LGBTQ Alumni
- Authors: Mahlangu, Nhlakanipho
- Date: 2024-04
- Subjects: Gay men , Teenage boys , Public schools -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62237 , vital:72364
- Description: This study explores the perspectives and experiences of LGBTQ alumni of all-boys’ schools in the Eastern Cape. The context of increased competition between schools in the education sector and the importance of inclusion within the sector necessitated a study to investigate the extent to which relationship management is conducted with an orientation towards LGBTQ inclusion in all-boys’ schools in the Eastern Cape. Student protests in South Africa over the past 10 years have expanded concerns about student belonging beyond the widely studied lenses of race and class. A growing body of literature and wider discourse emphasises student belonging as a challenge in the South African education sector. Marginalised students continue to experience educational spaces negatively. LGBTQ student experiences in the South Africa are characterised by violence and ostracisation, thus warranting further investigation and inquiry. The study locates itself in the intersections between gender and sexual diversity and economic citizenship in the broader discourse of school inclusivity. A qualitative research approach was employed, making use of semi-structured, in-depth individual interviews. The sample was derived from alumni of all-boys’ schools in the Eastern Cape through snowball sampling. Ten LGBTQ-identifying alumni of boys’ schools in the Eastern Cape were interviewed. The findings reveal the need to question the extent to which LGBTQ alumni can enjoy the fullness of the value proposition of all-boys’ schools, and what can be done to ensure LGBTQ belonging. The findings of this study concur with existing literature about LGBTQ experiences. Participants defined their school experiences as exclusionary and characterised by fear of failing to assert themselves in a hypermasculine school environment. LGBTQ alumni of all-boys’ schools in the Eastern Cape view relationship management as under-utilised as a tool to facilitate LGBTQ belonging. Instead, relationship management is used to affirm those who fit the mould of the quintessential ‘old boy’ network, by defining the masculine behaviours that learners in all-boys’ schools are compelled to aspire towards. v ABSTRACT The findings illustrate that the culture of silence around non-confirming sexuality is sustained in the post-schooling relationship management life-cycle and results in the absence of the LGBTQ customer voice in the drafting of school strategy and policy. LGBTQ alumni who speak out about controversial issues often face admonition from their former teachers and peers. LGBTQ alumni criticise the relationship management of their former schools for the over-emphasis on fundraising and the complete absence of discussions on diversity. LGBTQ alumni are therefore marginalised in the process of value co-creation, as LGBTQ alumni feel they will never be viewed as legitimate collaborators by their former schools. The suggested recommendations emerging from this study include the need to codify school policies that speak specifically to LGBTQ marginalisation. Furthermore, schools must endeavour to make specific enquiries into LGBTQ student experiences and include LGBTQ concerns in wider school discourse. , Thesis (Ma) -- Faculty of Business and Economic Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Mahlangu, Nhlakanipho
- Date: 2024-04
- Subjects: Gay men , Teenage boys , Public schools -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62237 , vital:72364
- Description: This study explores the perspectives and experiences of LGBTQ alumni of all-boys’ schools in the Eastern Cape. The context of increased competition between schools in the education sector and the importance of inclusion within the sector necessitated a study to investigate the extent to which relationship management is conducted with an orientation towards LGBTQ inclusion in all-boys’ schools in the Eastern Cape. Student protests in South Africa over the past 10 years have expanded concerns about student belonging beyond the widely studied lenses of race and class. A growing body of literature and wider discourse emphasises student belonging as a challenge in the South African education sector. Marginalised students continue to experience educational spaces negatively. LGBTQ student experiences in the South Africa are characterised by violence and ostracisation, thus warranting further investigation and inquiry. The study locates itself in the intersections between gender and sexual diversity and economic citizenship in the broader discourse of school inclusivity. A qualitative research approach was employed, making use of semi-structured, in-depth individual interviews. The sample was derived from alumni of all-boys’ schools in the Eastern Cape through snowball sampling. Ten LGBTQ-identifying alumni of boys’ schools in the Eastern Cape were interviewed. The findings reveal the need to question the extent to which LGBTQ alumni can enjoy the fullness of the value proposition of all-boys’ schools, and what can be done to ensure LGBTQ belonging. The findings of this study concur with existing literature about LGBTQ experiences. Participants defined their school experiences as exclusionary and characterised by fear of failing to assert themselves in a hypermasculine school environment. LGBTQ alumni of all-boys’ schools in the Eastern Cape view relationship management as under-utilised as a tool to facilitate LGBTQ belonging. Instead, relationship management is used to affirm those who fit the mould of the quintessential ‘old boy’ network, by defining the masculine behaviours that learners in all-boys’ schools are compelled to aspire towards. v ABSTRACT The findings illustrate that the culture of silence around non-confirming sexuality is sustained in the post-schooling relationship management life-cycle and results in the absence of the LGBTQ customer voice in the drafting of school strategy and policy. LGBTQ alumni who speak out about controversial issues often face admonition from their former teachers and peers. LGBTQ alumni criticise the relationship management of their former schools for the over-emphasis on fundraising and the complete absence of discussions on diversity. LGBTQ alumni are therefore marginalised in the process of value co-creation, as LGBTQ alumni feel they will never be viewed as legitimate collaborators by their former schools. The suggested recommendations emerging from this study include the need to codify school policies that speak specifically to LGBTQ marginalisation. Furthermore, schools must endeavour to make specific enquiries into LGBTQ student experiences and include LGBTQ concerns in wider school discourse. , Thesis (Ma) -- Faculty of Business and Economic Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Risk Management as a nexus to Ameliorate Citizen Centricity in the Western Cape Provincial Government
- Authors: Micketts, David
- Date: 2024-04
- Subjects: Risk management , Corporate governance -- South Africa -- Case studies , Public administration
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63345 , vital:73259
- Description: This study aims to explore how risk management can be applied by the Western Cape Provincial Government to enhance citizen centricity in the Province. The Provincial Departments and Public Entities in this province are applauded for achieving satisfactory audit results in recent financial years from the Auditor-General South Africa. Despite the aforementioned, service delivery protests remain ongoing, which is indicative of citizen dissatisfaction and distress. Ensuring an effective, efficient, and transparent risk management system is mandatory, as prescribed by relevant legislation in South Africa and citizens are entitled to specific rights articulated in the Bill of Rights chapter of the Constitution. Therefore, it is essential that risk management – which forms part of good governance – be embedded by leadership and in processes to ultimately constrain risks which may hinder citizen centricity. Six chapters are included in this research paper. A qualitative approach was adopted, which considered a comprehensive review of literature, and a desktop analysis was performed. Secondary data and information sources were consulted and applied, without the participation of human subjects, for the purposes of primary data collection. Research findings were presented utilising thematic content analysis. It was found during the study that the Western Cape Government risk management framework is flexible to constrain various categories of risk and embraces local and global best practices in the risk management and citizen-focused governments arenas. Furthermore, the framework advocates and drives collaboration between a myriad of role-players, both internal and external to the organisation, to collectively manage risks posed to the achievement of the defined goals, objectives and priorities. To this end, the study was pursued through the lenses of a New Public Management (NPM) paradigm as well as deliberative democracy theory and public governance theories and administrative practices. , Thesis (MPA) -- Faculty of Humanities, School of Governmental and Social Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Micketts, David
- Date: 2024-04
- Subjects: Risk management , Corporate governance -- South Africa -- Case studies , Public administration
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63345 , vital:73259
- Description: This study aims to explore how risk management can be applied by the Western Cape Provincial Government to enhance citizen centricity in the Province. The Provincial Departments and Public Entities in this province are applauded for achieving satisfactory audit results in recent financial years from the Auditor-General South Africa. Despite the aforementioned, service delivery protests remain ongoing, which is indicative of citizen dissatisfaction and distress. Ensuring an effective, efficient, and transparent risk management system is mandatory, as prescribed by relevant legislation in South Africa and citizens are entitled to specific rights articulated in the Bill of Rights chapter of the Constitution. Therefore, it is essential that risk management – which forms part of good governance – be embedded by leadership and in processes to ultimately constrain risks which may hinder citizen centricity. Six chapters are included in this research paper. A qualitative approach was adopted, which considered a comprehensive review of literature, and a desktop analysis was performed. Secondary data and information sources were consulted and applied, without the participation of human subjects, for the purposes of primary data collection. Research findings were presented utilising thematic content analysis. It was found during the study that the Western Cape Government risk management framework is flexible to constrain various categories of risk and embraces local and global best practices in the risk management and citizen-focused governments arenas. Furthermore, the framework advocates and drives collaboration between a myriad of role-players, both internal and external to the organisation, to collectively manage risks posed to the achievement of the defined goals, objectives and priorities. To this end, the study was pursued through the lenses of a New Public Management (NPM) paradigm as well as deliberative democracy theory and public governance theories and administrative practices. , Thesis (MPA) -- Faculty of Humanities, School of Governmental and Social Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Role of community pharmacies in the management of diabetic foot ulcers in South Africa
- Authors: Greyling, Cosette
- Date: 2024-04
- Subjects: Foot -- Ulcers -- Treatment , Wounds and injuries -- Treatment , Diabetes -- Complications
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63846 , vital:73619
- Description: Appropriate wound care and management are essential to prevent complications in patients with diabetic foot ulcers (DFUs). It is important to evaluate if patients are getting the necessary therapeutic treatment and counselling at community pharmacies. The primary aim was to determine the role of community pharmacies in South Africa in the management of DFUs. This study used a mixed-method research design combining both quantitative and qualitative research methodologies. In 2023 a questionnaire was distributed to a sample of 823 community pharmacists in South Africa with questions regarding DFUs. Data from the questionnaire were analysed and used in the next phase of the study, which was focus group discussions (FGDs). The FGDs were conducted with a group of pharmacy stakeholders. The response rate for the questionnaire was 18.95% (n=156). Only 105 respondents completed the questionnaire. Majority of the respondents (n=45) were located in Gauteng province, practising in corporate pharmacies (n=88) in urban areas (n=104). Majority of respondents (n=73) indicated that they did not have a clinic inside their pharmacies and 46 respondents indicated that they had a nurse employed in the pharmacy. Most frequently seen chronic wounds in community pharmacies were diabetic wounds and surgical wounds. Majority (n=71) of respondents indicated that they have not attended additional training on DFUs. Respondents indicated that they most often used the internet and other healthcare providers as information resources regarding DFUs. The results also indicated that community pharmacists would like to have more training regarding advanced wound care and that pharmacists do have a role to play when managing DFUs. During two FGDs, two main themes emerged namely “Community pharmacists encounter various challenges when treating patients with DFUs” and “There is a gap in training for community pharmacists in treating DFUs”. The focus group discussion (FGD) results complemented the questionnaire survey results. Since there is limited research published in South Africa on the role of community pharmacies managing DFUs, this study indicated that there is a need for additional training on DFUs for pharmacists working in community pharmacies in South Africa. , Thesis (M.Pharm) -- Faculty of Health Science, School of Clinical Care & Medicinal Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Greyling, Cosette
- Date: 2024-04
- Subjects: Foot -- Ulcers -- Treatment , Wounds and injuries -- Treatment , Diabetes -- Complications
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63846 , vital:73619
- Description: Appropriate wound care and management are essential to prevent complications in patients with diabetic foot ulcers (DFUs). It is important to evaluate if patients are getting the necessary therapeutic treatment and counselling at community pharmacies. The primary aim was to determine the role of community pharmacies in South Africa in the management of DFUs. This study used a mixed-method research design combining both quantitative and qualitative research methodologies. In 2023 a questionnaire was distributed to a sample of 823 community pharmacists in South Africa with questions regarding DFUs. Data from the questionnaire were analysed and used in the next phase of the study, which was focus group discussions (FGDs). The FGDs were conducted with a group of pharmacy stakeholders. The response rate for the questionnaire was 18.95% (n=156). Only 105 respondents completed the questionnaire. Majority of the respondents (n=45) were located in Gauteng province, practising in corporate pharmacies (n=88) in urban areas (n=104). Majority of respondents (n=73) indicated that they did not have a clinic inside their pharmacies and 46 respondents indicated that they had a nurse employed in the pharmacy. Most frequently seen chronic wounds in community pharmacies were diabetic wounds and surgical wounds. Majority (n=71) of respondents indicated that they have not attended additional training on DFUs. Respondents indicated that they most often used the internet and other healthcare providers as information resources regarding DFUs. The results also indicated that community pharmacists would like to have more training regarding advanced wound care and that pharmacists do have a role to play when managing DFUs. During two FGDs, two main themes emerged namely “Community pharmacists encounter various challenges when treating patients with DFUs” and “There is a gap in training for community pharmacists in treating DFUs”. The focus group discussion (FGD) results complemented the questionnaire survey results. Since there is limited research published in South Africa on the role of community pharmacies managing DFUs, this study indicated that there is a need for additional training on DFUs for pharmacists working in community pharmacies in South Africa. , Thesis (M.Pharm) -- Faculty of Health Science, School of Clinical Care & Medicinal Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Rural teachers’ experiences during covid-19 pandemic: lessons learnt to cope with future emergencies
- Authors: Dlambewu, Amanda
- Date: 2024-04
- Subjects: COVID-19 (Disease) -- Social aspects -- South Africa , Rural schools -- South Africa , Teachers -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63945 , vital:73629
- Description: This study focused on challenges faced by rural teachers during the COVID-19 pandemic, with the intention of using the outcomes to develop a framework that could assist with coping with similar challenges in future emergencies. The study was situated in the interpretivist paradigm. A qualitative approach was employed using interviews and a focus group discussion. Bronfenbrenner’s ecological theory and the theory of rurality were used as lenses to explore and interpret the challenges that rural teachers experienced during the COVID-19 pandemic. The study's findings reveal that teachers faced the following challenges: mental health, adaptability, impact on personal life, safety, and work environment challenges. Furthermore, the study also found that teachers used the following coping mechanisms to deal with the challenges during the pandemic: adherence to rules and regulations, pastoral services, support from friends and family, collaboration, and physical activity. Finally, after applying both the theory of rurality and Bronfenbrenner's ecological theory to the findings, a framework was developed to assist in coping with future emergencies. , Thesis (MEd) -- Faculty of Education, Post Graduate Education, 2024
- Full Text:
- Date Issued: 2024-04
Rural teachers’ experiences during covid-19 pandemic: lessons learnt to cope with future emergencies
- Authors: Dlambewu, Amanda
- Date: 2024-04
- Subjects: COVID-19 (Disease) -- Social aspects -- South Africa , Rural schools -- South Africa , Teachers -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63945 , vital:73629
- Description: This study focused on challenges faced by rural teachers during the COVID-19 pandemic, with the intention of using the outcomes to develop a framework that could assist with coping with similar challenges in future emergencies. The study was situated in the interpretivist paradigm. A qualitative approach was employed using interviews and a focus group discussion. Bronfenbrenner’s ecological theory and the theory of rurality were used as lenses to explore and interpret the challenges that rural teachers experienced during the COVID-19 pandemic. The study's findings reveal that teachers faced the following challenges: mental health, adaptability, impact on personal life, safety, and work environment challenges. Furthermore, the study also found that teachers used the following coping mechanisms to deal with the challenges during the pandemic: adherence to rules and regulations, pastoral services, support from friends and family, collaboration, and physical activity. Finally, after applying both the theory of rurality and Bronfenbrenner's ecological theory to the findings, a framework was developed to assist in coping with future emergencies. , Thesis (MEd) -- Faculty of Education, Post Graduate Education, 2024
- Full Text:
- Date Issued: 2024-04
Seagrasses in Mozambique: distribution, people’s perceptions and restoration best practice
- Mabuto, Manuela Elisa Manuel Amone, Hollander, Johan
- Authors: Mabuto, Manuela Elisa Manuel Amone , Hollander, Johan
- Date: 2024-04
- Subjects: Seagrasses -- Mozambique , Seagrasses -- Southern Hemisphere , Coastal zone management -- Mozambique , Restoration ecology -- Mozambique
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64126 , vital:73655
- Description: This thesis investigated the restoration of seagrass meadows and their associated biodiversity thus contributing to their conservation and to people's well-being. A mixed methods approach was used, and results presented in five chapters. Chapter I is a general introduction to the study outlining relevant information, research objectives and hypotheses. Chapter II investigates coastal community’s perceptions on the role of seagrass ecosystems, local impacts of coastal erosion and the need for seagrass restoration in Mozambique. It showed that there is a high awareness of the studied communities to seagrass importance for their livelihoods. Communities supported restoration and identified community engagement as a fundamental component for a successful implementation of restoration projects in their area. Chapter III conducted a mapping inventory for seagrass using open access data sources and investigated change detection in seagrass extent in southern Mozambique using Satellite imagery. In addition, Unmanned Aerial Vehicles (drones) were used to map seagrass to the species level at Inhaca Island. The results showed that seagrass habitats have been losing extent in recent years mainly in Bairro dos Pescadores at northwest Maputo Bay, due to sedimentation from flooding and inappropriate gleaning / clam collection practices. Around Inhaca Island seagrass extent has changed in response to natural causes and from anthropogenic disturbance near the main village and port area. For the first time for this area drones were used to rapidly and effectively acquire high- resolution data for detailed seagrass mapping and monitoring. The different mapping approaches were critically analyzed, and a way forward discussed. In Chapter IV, two different field experiments were conducted simultaneously. One, mimicked disturbance of meadows in terms of digging to collect clams, a common practice in northeastern Maputo Bay to assess the time of natural recovery and another replanted Zostera capensis using different plug sizes. The results indicated that once anthropogenic impacts are ceased, Z. capensis meadows are restored 12 months after impact exclusion. There was a 75% survival rate for the mechanical plug restoration approach; positive implications for seagrass transplantation projects that are both time consuming and financially costly. It was clear from the study that a combination of both impact exclusion and active restoration is needed for seagrass survival. Chapter V investigated the influence of seagrass restoration on the abundance and diversity of macroinvertebrates. After two years of observations, replanted seagrass areas had not recovered compared to natural established seagrass beds. However, a strong linear relationship existed between the abundance of seagrasses and the quantity of associated macrofauna species. Chapter VI provided recommendations on better ways to perform seagrass restoration and management. The main findings of this thesis provide new knowledge on the mapping of seagrass on a local to a regional scale as well as on better restoration practice of the seagrass Zostera capensis, an IUCN Red List vulnerable species. Communities’ perceptions on seagrass were investigated contributing to an understanding of the socio-ecological conservation and management of these critical and yet threatened ecosystems. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Mabuto, Manuela Elisa Manuel Amone , Hollander, Johan
- Date: 2024-04
- Subjects: Seagrasses -- Mozambique , Seagrasses -- Southern Hemisphere , Coastal zone management -- Mozambique , Restoration ecology -- Mozambique
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64126 , vital:73655
- Description: This thesis investigated the restoration of seagrass meadows and their associated biodiversity thus contributing to their conservation and to people's well-being. A mixed methods approach was used, and results presented in five chapters. Chapter I is a general introduction to the study outlining relevant information, research objectives and hypotheses. Chapter II investigates coastal community’s perceptions on the role of seagrass ecosystems, local impacts of coastal erosion and the need for seagrass restoration in Mozambique. It showed that there is a high awareness of the studied communities to seagrass importance for their livelihoods. Communities supported restoration and identified community engagement as a fundamental component for a successful implementation of restoration projects in their area. Chapter III conducted a mapping inventory for seagrass using open access data sources and investigated change detection in seagrass extent in southern Mozambique using Satellite imagery. In addition, Unmanned Aerial Vehicles (drones) were used to map seagrass to the species level at Inhaca Island. The results showed that seagrass habitats have been losing extent in recent years mainly in Bairro dos Pescadores at northwest Maputo Bay, due to sedimentation from flooding and inappropriate gleaning / clam collection practices. Around Inhaca Island seagrass extent has changed in response to natural causes and from anthropogenic disturbance near the main village and port area. For the first time for this area drones were used to rapidly and effectively acquire high- resolution data for detailed seagrass mapping and monitoring. The different mapping approaches were critically analyzed, and a way forward discussed. In Chapter IV, two different field experiments were conducted simultaneously. One, mimicked disturbance of meadows in terms of digging to collect clams, a common practice in northeastern Maputo Bay to assess the time of natural recovery and another replanted Zostera capensis using different plug sizes. The results indicated that once anthropogenic impacts are ceased, Z. capensis meadows are restored 12 months after impact exclusion. There was a 75% survival rate for the mechanical plug restoration approach; positive implications for seagrass transplantation projects that are both time consuming and financially costly. It was clear from the study that a combination of both impact exclusion and active restoration is needed for seagrass survival. Chapter V investigated the influence of seagrass restoration on the abundance and diversity of macroinvertebrates. After two years of observations, replanted seagrass areas had not recovered compared to natural established seagrass beds. However, a strong linear relationship existed between the abundance of seagrasses and the quantity of associated macrofauna species. Chapter VI provided recommendations on better ways to perform seagrass restoration and management. The main findings of this thesis provide new knowledge on the mapping of seagrass on a local to a regional scale as well as on better restoration practice of the seagrass Zostera capensis, an IUCN Red List vulnerable species. Communities’ perceptions on seagrass were investigated contributing to an understanding of the socio-ecological conservation and management of these critical and yet threatened ecosystems. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Self-attentive vision in evolutionary robotics
- Authors: Botha, Bouwer
- Date: 2024-04
- Subjects: Evolutionary robotics , Robotics , Neural networks (Computer science)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63628 , vital:73566
- Description: The autonomy of a robot refers to its ability to achieve a task in an environment with minimal human supervision. This may require autonomous solutions to be able to perceive their environment to inform their decisions. An inexpensive and highly informative way that robots can perceive the environment is through vision. The autonomy of a robot is reliant on the quality of the robotic controller. These controllers are the software interface between the robot and environment that determine the actions of the robot based on the perceived environment. Controllers are typically created using manual programming techniques, which become progressively more challenging with increasing complexity of both the robot and task. An alternative to manual programming is the use of machine learning techniques such as those used by Evolutionary Robotics (ER). ER is an area of research that investigates the automatic creation of controllers. Instead of manually programming a controller, an Evolutionary Algorithms can be used to evolve the controller through repeated interactions with the task environment. Employing the ER approach on camera-based controllers, however, has presented problems for conventional ER methods. Firstly, existing architectures that are capable of automatically processing images, have a large number of trained parameters. These architectures over-encumber the evolutionary process due to the large search space of possible configurations. Secondly, the evolution of complex controllers needs to be done in simulation, which requires either: (a) the construction of a photo-realistic virtual environment with accurate lighting, texturing and models or (b) potential reduction of the controller capability by simplifying the problem via image preprocessing. Any controller trained in simulation also raises the inherent concern of not being able to transfer to the real world. This study proposes a new technique for the evolution of camera-based controllers in ER, that aims to address the highlighted problems. The use of self-attention is proposed to facilitate the evolution of compact controllers that are able to evolve specialized sets of task-relevant features in unprocessed images by focussing on important image regions. Furthermore, a new neural network-based simulation approach, Generative Neuro-Augmented Vision (GNAV), is proposed to simplify simulation construction. GNAV makes use of random data collected in a simple virtual environment and the real world. A neural network is trained to overcome the visual discrepancies between these two environments. GNAV enables a controller to be trained in a simple simulated environment that appears similar to the real environment, while requiring minimal human supervision. The capabilities of the new technique were demonstrated using a series of real-world navigation tasks based on camera vision. Controllers utilizing the proposed self-attention mechanism were trained using GNAV and transferred to a real camera-equipped robot. The controllers were shown to be able to perform the same tasks in the real world. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Botha, Bouwer
- Date: 2024-04
- Subjects: Evolutionary robotics , Robotics , Neural networks (Computer science)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63628 , vital:73566
- Description: The autonomy of a robot refers to its ability to achieve a task in an environment with minimal human supervision. This may require autonomous solutions to be able to perceive their environment to inform their decisions. An inexpensive and highly informative way that robots can perceive the environment is through vision. The autonomy of a robot is reliant on the quality of the robotic controller. These controllers are the software interface between the robot and environment that determine the actions of the robot based on the perceived environment. Controllers are typically created using manual programming techniques, which become progressively more challenging with increasing complexity of both the robot and task. An alternative to manual programming is the use of machine learning techniques such as those used by Evolutionary Robotics (ER). ER is an area of research that investigates the automatic creation of controllers. Instead of manually programming a controller, an Evolutionary Algorithms can be used to evolve the controller through repeated interactions with the task environment. Employing the ER approach on camera-based controllers, however, has presented problems for conventional ER methods. Firstly, existing architectures that are capable of automatically processing images, have a large number of trained parameters. These architectures over-encumber the evolutionary process due to the large search space of possible configurations. Secondly, the evolution of complex controllers needs to be done in simulation, which requires either: (a) the construction of a photo-realistic virtual environment with accurate lighting, texturing and models or (b) potential reduction of the controller capability by simplifying the problem via image preprocessing. Any controller trained in simulation also raises the inherent concern of not being able to transfer to the real world. This study proposes a new technique for the evolution of camera-based controllers in ER, that aims to address the highlighted problems. The use of self-attention is proposed to facilitate the evolution of compact controllers that are able to evolve specialized sets of task-relevant features in unprocessed images by focussing on important image regions. Furthermore, a new neural network-based simulation approach, Generative Neuro-Augmented Vision (GNAV), is proposed to simplify simulation construction. GNAV makes use of random data collected in a simple virtual environment and the real world. A neural network is trained to overcome the visual discrepancies between these two environments. GNAV enables a controller to be trained in a simple simulated environment that appears similar to the real environment, while requiring minimal human supervision. The capabilities of the new technique were demonstrated using a series of real-world navigation tasks based on camera vision. Controllers utilizing the proposed self-attention mechanism were trained using GNAV and transferred to a real camera-equipped robot. The controllers were shown to be able to perform the same tasks in the real world. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
South Africa’s regulation of mineral mining activities in the area: lessons from the United Kingdom
- Authors: Karomo, Adelaide Aquiline
- Date: 2024-04
- Subjects: Mineral mining activities , Mining law , Deep Sea mining Act
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64411 , vital:73700
- Description: As they anticipate the benefits associated with mining polymetallic nodules, polymetallic sulphides and ferromanganese crusts, several States are currently exploring or sponsoring State-owned enterprises and private persons to explore for these mineral resources in the seabed, ocean floor and subsoil beyond national jurisdiction (the Area). However, Africa remains the only region that is not actively participating. To guide South Africa in developing a deep seabed mining regime the thesis begins by identifying the international law regulating the Area and the activities therein. Since the mineral resources in the Area have been declared the common heritage of mankind, this principle as regulated by Part XI of the United Nations Convention on the Law of the Sea (UNCLOS), and modified by the Agreement relating to the implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 forms an essential component of this study. As such, the thesis determines, amongst others, the requirements for participating in mining activities in the Area (as set out in Part XI of UNCLOS) and establishes that developing a legislative framework is crucial to exempt UNCLOS States parties from liability associated with the damage caused by sponsored activities. Based on the obligations in international law, the thesis zooms in on three aspects concerning the regulation of the activities in the Area: (i) mining concessions, (ii) the relevant payment system, and (iii) environmental protection measures. In terms of these aspects, how the United Kingdom’s deep seabed mining regime regulates activities in the Area is examined. For this assessment, the thesis pays particular attention to the Deep Sea Mining Act and the domestic licences granted to UK Seabed Resources Ltd (UKSRL). In identifying lessons for South Africa, the thesis assesses the extent to which the United Kingdom’s regime complies with the international law framework and highlights the inconsistencies and legislative gaps. Thereafter, the thesis examines the South African legislative instruments regulating mining activities at sea, such as the Mineral and Petroleum Resources Development Act and the National Environmental Management Act, to determine whether their scope should be amended to regulate mining activities in the Area. As per the observations from international law and the lessons learnt from the United Kingdom's regulatory framework, the thesis argues that South Africa’s current mining framework should not be amended; separate deep seabed mining-specific legislation must be adopted. The thesis concludes by setting out the recommendations for developing such legislation. , Thesis (LLD) -- Faculty of Law, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Karomo, Adelaide Aquiline
- Date: 2024-04
- Subjects: Mineral mining activities , Mining law , Deep Sea mining Act
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64411 , vital:73700
- Description: As they anticipate the benefits associated with mining polymetallic nodules, polymetallic sulphides and ferromanganese crusts, several States are currently exploring or sponsoring State-owned enterprises and private persons to explore for these mineral resources in the seabed, ocean floor and subsoil beyond national jurisdiction (the Area). However, Africa remains the only region that is not actively participating. To guide South Africa in developing a deep seabed mining regime the thesis begins by identifying the international law regulating the Area and the activities therein. Since the mineral resources in the Area have been declared the common heritage of mankind, this principle as regulated by Part XI of the United Nations Convention on the Law of the Sea (UNCLOS), and modified by the Agreement relating to the implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 forms an essential component of this study. As such, the thesis determines, amongst others, the requirements for participating in mining activities in the Area (as set out in Part XI of UNCLOS) and establishes that developing a legislative framework is crucial to exempt UNCLOS States parties from liability associated with the damage caused by sponsored activities. Based on the obligations in international law, the thesis zooms in on three aspects concerning the regulation of the activities in the Area: (i) mining concessions, (ii) the relevant payment system, and (iii) environmental protection measures. In terms of these aspects, how the United Kingdom’s deep seabed mining regime regulates activities in the Area is examined. For this assessment, the thesis pays particular attention to the Deep Sea Mining Act and the domestic licences granted to UK Seabed Resources Ltd (UKSRL). In identifying lessons for South Africa, the thesis assesses the extent to which the United Kingdom’s regime complies with the international law framework and highlights the inconsistencies and legislative gaps. Thereafter, the thesis examines the South African legislative instruments regulating mining activities at sea, such as the Mineral and Petroleum Resources Development Act and the National Environmental Management Act, to determine whether their scope should be amended to regulate mining activities in the Area. As per the observations from international law and the lessons learnt from the United Kingdom's regulatory framework, the thesis argues that South Africa’s current mining framework should not be amended; separate deep seabed mining-specific legislation must be adopted. The thesis concludes by setting out the recommendations for developing such legislation. , Thesis (LLD) -- Faculty of Law, 2024
- Full Text:
- Date Issued: 2024-04
Statistical learning methods for photovoltaic energy output prediction
- Authors: Magaya, Aphiwe
- Date: 2024-04
- Subjects: Photovoltaic power generation , Mathematical statistics , Statistics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64138 , vital:73656
- Description: Predicting solar energy accurately is important for the integration of more renewable energy into the grid, which can help to alleviate the energy demand on traditional coal-powered sources in South Africa. This study aims to assess several statistical learning models to predict the energy output of a 1MW photovoltaic system installed on the Nelson Mandela University South Campus in Gqeberha. Weather data (including temperature, wind speed, wind direction, precipitation, air pressure, and humidity) and solar irradiance data (including global horizontal radiation, diffuse radiation, and direct radiation) are used to predict the energy output of this system using Artificial Neural Networks (ANN), Support Vector Machines (SVM), Multiple Linear Regression (MLR), and Regression Trees (RT). The performance of each of the models was compared and the results indicated that the ANN model performed best. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Magaya, Aphiwe
- Date: 2024-04
- Subjects: Photovoltaic power generation , Mathematical statistics , Statistics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64138 , vital:73656
- Description: Predicting solar energy accurately is important for the integration of more renewable energy into the grid, which can help to alleviate the energy demand on traditional coal-powered sources in South Africa. This study aims to assess several statistical learning models to predict the energy output of a 1MW photovoltaic system installed on the Nelson Mandela University South Campus in Gqeberha. Weather data (including temperature, wind speed, wind direction, precipitation, air pressure, and humidity) and solar irradiance data (including global horizontal radiation, diffuse radiation, and direct radiation) are used to predict the energy output of this system using Artificial Neural Networks (ANN), Support Vector Machines (SVM), Multiple Linear Regression (MLR), and Regression Trees (RT). The performance of each of the models was compared and the results indicated that the ANN model performed best. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
- Full Text:
- Date Issued: 2024-04
Synthesis and applications of hydroxyl-functionalized chemosensors for selective detection of ions in aqueous systems
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2024-04
- Subjects: Molecular recognition , Solution (Chemistry) , Water chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63787 , vital:73613
- Description: Fluorescent molecular chemosensors are crucial tools for monitoring toxic metal ions and environmental compounds that pose risks to both humans and wildlife. Continuous sensing is essential for early detection, and chemosensors offer a sensitive and straightforward approach by detecting challenging analyte’s through optical absorption and fluorescence. Current detection methods, such as flame photometry and mass spectrometry, can be expensive, destructive, and impractical for continuous monitoring. Consequently, fluorescent-based methods present a promising, simple, and highly sensitive alternative for chemical recognition and monitoring. In this project, we successfully synthesized ten highly selective small hydroxyl containing molecule fluorescent and colorimetric sensors; Oxime Dye (OD), Small Sensor 1 (SS1), Small Sensor 2 (SS2), Quinoline Dye 1 (QD1), Quinoline Dye 2 (QD2), Quinoline Dye 3 (QD3), Coumarin Dye 1 (CD1), Coumarin Dye 2 (CD2), Naphthalene Dye 1 (ND1), Naphthalene Dye 2 (ND2). These chemosensors contained benzothiazole, naphthalene, quinoline, and coumarin fluorophores. These sensors facilitate both quantitative and qualitative assessment of cationic and anionic species in aqueous organic media. The chemosensors were synthesized using modified Schiff base, azo dye, and oxime-based reactions, enhancing binding and selectivity with analyte’s. They exhibited selectivity towards various metal ions (Cu2+, Fe2+, Ni2+, and Hg2+) and anions (hydroxyl and cyanate), characterized by distinct absorption bands and significant fluorescent quenching and enhancement. While some sensors were selective towards both cations and anions, others exclusively targeted cations, showing lower selectivity or sensitivity towards anions upon further testing. Conversely, certain sensors were selective towards anions, demonstrating reduced sensitivity or selectivity towards the tested cations. The oxime-based chemosensor, OD, was obtained through an oxime-based reaction. The sensor demonstrates remarkable selectivity for Cu2+ and cyanate ions. During titration experiments, the interaction of Cu2+ with OD resulted in a noticeable fluorescence quenching effect, while the presence of OCN ions led to fluorescence enhancement. These distinct behaviors strongly suggest the formation of specific 1:1 complexes between OD and Cu2+ or OCN ions, a conclusion supported by detailed analysis using the Jobs plot technique. In addition to the fluorescence studies, investigations into the influence of pH on the sensor OD, as well as its complexes with Cu2+ and OCN, were conducted to determine the optimum pH conditions for their operation. Moreover, reversible behavior of the complexes was explored in the presence of EDTA, revealing that only the OD-OCN complex displayed reversibility. Furthermore, molecular modeling studies were performed to validate the binding units and calculate the energy differences between the sensor and its respective complexes. Additionally, four chemosensors (SS1, SS2, CD2, and QD2) were synthesized and characterized using Schiff-based reactions, showcasing their unique absorption behaviors. SS1 and SS2, characterized by benzothiazole fluorophores, demonstrated high sensitivity to hydroxyl anions. Jobs plot studies revealed a stable 1:1 binding stoichiometry. Chemosensor CD2, incorporating a coumarin fluorophore, was structurally confirmed but showed no significant spectral changes when screened with various ions. Chemosensor QD2 exhibited remarkable selectivity for Fe2+ ions, and stable 1:1 complexes were confirmed. Further molecular modeling studies were conducted to identify potential binding sites. Furthermore, five chemosensors (CD1, CD3, QD1, ND1, and ND2) were synthesized and characterized using azo dye reactions, revealing their unique absorption behaviors. Chemosensor CD1 showed high selectivity towards Hg2+ under both absorption and emission spectroscopy. Job's plot studies confirmed a stable 1:1 complex formation. The presence of competing cations did not affect complex formation, emphasizing its stability and selectivity. Another coumarin-containing dye chemosensor, CD3, was synthesized as a novel chemosensor. In the presence of TBA anionic solutions, CD3 exhibited strong absorption bands and selectivity for OH- ions, forming a stable complex with them. Quantitative studies, including the determination of LOD and LOQ, were also conducted. The binding stoichiometry of 1:1 between CD3 and OH- was established through Job's plot analysis. Lastly, two naphthalene dyes were synthesized. However, they did not exhibit selectivity towards cations or anions. Interestingly, their absorption spectra were affected by the change in solvent system, a concept worth exploring in future work. Chemosensor ND1 and ND2 did not show any cation or anion selectivity. However, they demonstrated different spectra and colour responses to cations and anions in different water-DMSO solvent systems. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2024-04
- Subjects: Molecular recognition , Solution (Chemistry) , Water chemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63787 , vital:73613
- Description: Fluorescent molecular chemosensors are crucial tools for monitoring toxic metal ions and environmental compounds that pose risks to both humans and wildlife. Continuous sensing is essential for early detection, and chemosensors offer a sensitive and straightforward approach by detecting challenging analyte’s through optical absorption and fluorescence. Current detection methods, such as flame photometry and mass spectrometry, can be expensive, destructive, and impractical for continuous monitoring. Consequently, fluorescent-based methods present a promising, simple, and highly sensitive alternative for chemical recognition and monitoring. In this project, we successfully synthesized ten highly selective small hydroxyl containing molecule fluorescent and colorimetric sensors; Oxime Dye (OD), Small Sensor 1 (SS1), Small Sensor 2 (SS2), Quinoline Dye 1 (QD1), Quinoline Dye 2 (QD2), Quinoline Dye 3 (QD3), Coumarin Dye 1 (CD1), Coumarin Dye 2 (CD2), Naphthalene Dye 1 (ND1), Naphthalene Dye 2 (ND2). These chemosensors contained benzothiazole, naphthalene, quinoline, and coumarin fluorophores. These sensors facilitate both quantitative and qualitative assessment of cationic and anionic species in aqueous organic media. The chemosensors were synthesized using modified Schiff base, azo dye, and oxime-based reactions, enhancing binding and selectivity with analyte’s. They exhibited selectivity towards various metal ions (Cu2+, Fe2+, Ni2+, and Hg2+) and anions (hydroxyl and cyanate), characterized by distinct absorption bands and significant fluorescent quenching and enhancement. While some sensors were selective towards both cations and anions, others exclusively targeted cations, showing lower selectivity or sensitivity towards anions upon further testing. Conversely, certain sensors were selective towards anions, demonstrating reduced sensitivity or selectivity towards the tested cations. The oxime-based chemosensor, OD, was obtained through an oxime-based reaction. The sensor demonstrates remarkable selectivity for Cu2+ and cyanate ions. During titration experiments, the interaction of Cu2+ with OD resulted in a noticeable fluorescence quenching effect, while the presence of OCN ions led to fluorescence enhancement. These distinct behaviors strongly suggest the formation of specific 1:1 complexes between OD and Cu2+ or OCN ions, a conclusion supported by detailed analysis using the Jobs plot technique. In addition to the fluorescence studies, investigations into the influence of pH on the sensor OD, as well as its complexes with Cu2+ and OCN, were conducted to determine the optimum pH conditions for their operation. Moreover, reversible behavior of the complexes was explored in the presence of EDTA, revealing that only the OD-OCN complex displayed reversibility. Furthermore, molecular modeling studies were performed to validate the binding units and calculate the energy differences between the sensor and its respective complexes. Additionally, four chemosensors (SS1, SS2, CD2, and QD2) were synthesized and characterized using Schiff-based reactions, showcasing their unique absorption behaviors. SS1 and SS2, characterized by benzothiazole fluorophores, demonstrated high sensitivity to hydroxyl anions. Jobs plot studies revealed a stable 1:1 binding stoichiometry. Chemosensor CD2, incorporating a coumarin fluorophore, was structurally confirmed but showed no significant spectral changes when screened with various ions. Chemosensor QD2 exhibited remarkable selectivity for Fe2+ ions, and stable 1:1 complexes were confirmed. Further molecular modeling studies were conducted to identify potential binding sites. Furthermore, five chemosensors (CD1, CD3, QD1, ND1, and ND2) were synthesized and characterized using azo dye reactions, revealing their unique absorption behaviors. Chemosensor CD1 showed high selectivity towards Hg2+ under both absorption and emission spectroscopy. Job's plot studies confirmed a stable 1:1 complex formation. The presence of competing cations did not affect complex formation, emphasizing its stability and selectivity. Another coumarin-containing dye chemosensor, CD3, was synthesized as a novel chemosensor. In the presence of TBA anionic solutions, CD3 exhibited strong absorption bands and selectivity for OH- ions, forming a stable complex with them. Quantitative studies, including the determination of LOD and LOQ, were also conducted. The binding stoichiometry of 1:1 between CD3 and OH- was established through Job's plot analysis. Lastly, two naphthalene dyes were synthesized. However, they did not exhibit selectivity towards cations or anions. Interestingly, their absorption spectra were affected by the change in solvent system, a concept worth exploring in future work. Chemosensor ND1 and ND2 did not show any cation or anion selectivity. However, they demonstrated different spectra and colour responses to cations and anions in different water-DMSO solvent systems. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Synthesis and applications of novel coumarin-based chemosensors for the detection of metal ions using UV-visible spectroscopy
- Authors: Myburgh, Lisa
- Date: 2024-04
- Subjects: Chemical detectors , Molecular recognition , Biosensors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64241 , vital:73667
- Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Myburgh, Lisa
- Date: 2024-04
- Subjects: Chemical detectors , Molecular recognition , Biosensors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64241 , vital:73667
- Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Synthesis and applications of novel coumarin-based chemosensors for the detection of metal ions using UV-visible spectroscopy
- Authors: Myburgh, Lisa
- Date: 2024-04
- Subjects: Biosensors , Molecular recognition , Chemical detectors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64239 , vital:73668
- Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Myburgh, Lisa
- Date: 2024-04
- Subjects: Biosensors , Molecular recognition , Chemical detectors
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64239 , vital:73668
- Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Synthesis of gatifloxacin, an important fluoroquinolone antibiotic using continuous flow technology
- Authors: Moyo, McQuillan
- Date: 2024-04
- Subjects: Antibiotics , Drug resistance in microorganisms , Chemical processes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64204 , vital:73664
- Description: Gatifloxacin belongs to an important class of antibiotics known as fluoroquinolones (the fourth generation). Bristol-Myers Squibb (BMS) introduced gatifloxacin to the market in 1999 under the brand name Tequin® for treating respiratory tract infections. It has recently been widely employed as an ophthalmic solution for treating bacterial conjunctivitis. There is limited literature describing the complete synthesis of gatifloxacin; however, ciprofloxacin, a similar fluoroquinolone, has received much attention recently and is a good guide in the synthesis. Even though there are several similarities between ciprofloxacin and gatifloxacin, key reactions towards the synthesis of gatifloxacin have not been reported, which forms a knowledge gap, for instance, the three steps leading to the synthesis of the benzoyl chloride intermediate. It is estimated that 70-90 % of the active pharmaceutical ingredients (APIs) in drugs consumed in sub-Saharan Africa are imported, mainly from India, China and Europe. To reduce dependence and improve access to life-saving drugs, Africa needs to develop cutting-edge technology that is more advanced than traditional means. We envisage that employing continuous flow technology in synthesising gatifloxacin, previously developed in a batch setup, will offer an improved, future-proof process. Thus, this research aimed to create a more efficient multi-step continuous flow process for synthesising gatifloxacin compared to the current batch methods. The first chapter of this thesis provides an extensive literature review on the synthesis of gatifloxacin and its sister drug, ciprofloxacin. The foreground is based on the manufacture and consumption of APIs, particularly antibiotics. Continuous flow technology is also introduced and discussed as the solution to bridging the gap in Africa’s demand for API manufacturing, which significantly lags. Chapter two describes the results and discusses findings on the continuous flow synthesis of gatifloxacin. A seven-step process is described with reaction optimisation studies for each step, starting from 2,4,5-trifluoro-3-hydroxybenzoic acid. An alternative shorter route (with six steps) is also offered, incorporating microwave-assisted technology instead of the traditional batch process. We also describe several elegant multistep processes for synthesising gatifloxacin and its intermediates, achieved by combining several compatible, optimised steps. Subsequently, Chapter 3 describes all the experimental details of our research. In this study, efficient continuous flow procedures were developed to synthesise gatifloxacin. The seven-step continuous flow procedure we developed afforded gatifloxacin (54 % overall isolated yield) in a total residence time of 15.6 mins, a significant improvement from the reported batch process (52 % overall yield and over 103 hours reaction time). , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Moyo, McQuillan
- Date: 2024-04
- Subjects: Antibiotics , Drug resistance in microorganisms , Chemical processes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/64204 , vital:73664
- Description: Gatifloxacin belongs to an important class of antibiotics known as fluoroquinolones (the fourth generation). Bristol-Myers Squibb (BMS) introduced gatifloxacin to the market in 1999 under the brand name Tequin® for treating respiratory tract infections. It has recently been widely employed as an ophthalmic solution for treating bacterial conjunctivitis. There is limited literature describing the complete synthesis of gatifloxacin; however, ciprofloxacin, a similar fluoroquinolone, has received much attention recently and is a good guide in the synthesis. Even though there are several similarities between ciprofloxacin and gatifloxacin, key reactions towards the synthesis of gatifloxacin have not been reported, which forms a knowledge gap, for instance, the three steps leading to the synthesis of the benzoyl chloride intermediate. It is estimated that 70-90 % of the active pharmaceutical ingredients (APIs) in drugs consumed in sub-Saharan Africa are imported, mainly from India, China and Europe. To reduce dependence and improve access to life-saving drugs, Africa needs to develop cutting-edge technology that is more advanced than traditional means. We envisage that employing continuous flow technology in synthesising gatifloxacin, previously developed in a batch setup, will offer an improved, future-proof process. Thus, this research aimed to create a more efficient multi-step continuous flow process for synthesising gatifloxacin compared to the current batch methods. The first chapter of this thesis provides an extensive literature review on the synthesis of gatifloxacin and its sister drug, ciprofloxacin. The foreground is based on the manufacture and consumption of APIs, particularly antibiotics. Continuous flow technology is also introduced and discussed as the solution to bridging the gap in Africa’s demand for API manufacturing, which significantly lags. Chapter two describes the results and discusses findings on the continuous flow synthesis of gatifloxacin. A seven-step process is described with reaction optimisation studies for each step, starting from 2,4,5-trifluoro-3-hydroxybenzoic acid. An alternative shorter route (with six steps) is also offered, incorporating microwave-assisted technology instead of the traditional batch process. We also describe several elegant multistep processes for synthesising gatifloxacin and its intermediates, achieved by combining several compatible, optimised steps. Subsequently, Chapter 3 describes all the experimental details of our research. In this study, efficient continuous flow procedures were developed to synthesise gatifloxacin. The seven-step continuous flow procedure we developed afforded gatifloxacin (54 % overall isolated yield) in a total residence time of 15.6 mins, a significant improvement from the reported batch process (52 % overall yield and over 103 hours reaction time). , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
- Full Text:
- Date Issued: 2024-04
Technological Pedagogical Content Knowledge (TPACK): investigating senior primary mathematics teachers’ integration of technology in the classroom in Okahao educational circuit
- Shikesho, Hilya Ndahambelela
- Authors: Shikesho, Hilya Ndahambelela
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423913 , vital:72104
- Description: The overwhelming advancement of ICT devices in the contemporary Namibian education system has led to their praise for supporting differentiated instruction, fostering collaboration, and engaging multiple intelligences in teaching and learning. Consequently, the compulsory incorporation of ICTs into the teaching and learning process becomes imperative across various fields of study, including Mathematics. However, the integration of technology-based teaching proves to be a complex and challenging issue, often considered a wicked problem. To explore this matter, a qualitative case study was conducted to investigate how Senior Primary Mathematics Teachers integrated technology to develop their TPACK. The study was conducted among the twenty-seven senior primary mathematics teachers in the Okahao educational circuit in the Omuasti region. The study utilized Vygotsky‘s (1978); Socio-cultural Theory, together with Mishra and Koehler (2006), and; the Technological Pedagogical Content Knowledge (TPACK) framework was used as a lens to analyse the data. The data were gathered through semi-structured questionnaires, semi-structured interviews, focus group interviews, and lesson observations. The study findings indicate that senior primary mathematics teachers utilize the available resources at their respective schools during their classroom instruction. The study further reveals that mathematics teachers exhibit a positive attitude toward the integration of technology. The study uncovers the intricate interplay between technological knowledge, pedagogical expertise, and content knowledge within the context of mathematics education. The findings reveal that while participants demonstrate a high level of proficiency in certain TPACK components such as CK, TK, PK, TPK, and PCK, they expressed a moderate level of expertise in TCK and TPCK. The study also identified challenges in TPACK development, particularly the need for subject specific technology training, lack of technological infrastructure, particularly advanced technology, as well as a deficiency in ICT knowledge. The importance of access to various technologies was emphasized, enabling teachers to seamlessly integrate technology into their practices and address diverse learning styles. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Shikesho, Hilya Ndahambelela
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423913 , vital:72104
- Description: The overwhelming advancement of ICT devices in the contemporary Namibian education system has led to their praise for supporting differentiated instruction, fostering collaboration, and engaging multiple intelligences in teaching and learning. Consequently, the compulsory incorporation of ICTs into the teaching and learning process becomes imperative across various fields of study, including Mathematics. However, the integration of technology-based teaching proves to be a complex and challenging issue, often considered a wicked problem. To explore this matter, a qualitative case study was conducted to investigate how Senior Primary Mathematics Teachers integrated technology to develop their TPACK. The study was conducted among the twenty-seven senior primary mathematics teachers in the Okahao educational circuit in the Omuasti region. The study utilized Vygotsky‘s (1978); Socio-cultural Theory, together with Mishra and Koehler (2006), and; the Technological Pedagogical Content Knowledge (TPACK) framework was used as a lens to analyse the data. The data were gathered through semi-structured questionnaires, semi-structured interviews, focus group interviews, and lesson observations. The study findings indicate that senior primary mathematics teachers utilize the available resources at their respective schools during their classroom instruction. The study further reveals that mathematics teachers exhibit a positive attitude toward the integration of technology. The study uncovers the intricate interplay between technological knowledge, pedagogical expertise, and content knowledge within the context of mathematics education. The findings reveal that while participants demonstrate a high level of proficiency in certain TPACK components such as CK, TK, PK, TPK, and PCK, they expressed a moderate level of expertise in TCK and TPCK. The study also identified challenges in TPACK development, particularly the need for subject specific technology training, lack of technological infrastructure, particularly advanced technology, as well as a deficiency in ICT knowledge. The importance of access to various technologies was emphasized, enabling teachers to seamlessly integrate technology into their practices and address diverse learning styles. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
The Algoa Bay region groundwater cycle – linking source to coast
- Authors: Dodd, Carla
- Date: 2024-04
- Subjects: Ecohydrology , Hydrology , Groundwater -- Management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63722 , vital:73592
- Description: Groundwater is a crucial component of freshwater supply globally, especially in water-scarce regions such as semi-arid climatic areas where surface water resources are climatically limited and further constrained during droughts. Groundwater resources are also important from an ecological perspective as they support numerous surface ecosystems including wetlands and rivers. Coastal groundwater discharge along the South African coast sustains supratidal spring-fed living microbialite ecosystems (SSLiME). These systems act as potential analogues for Earth’s earliest ecosystems and are therefore useful from a palaeoscientific and evolutionary perspective. The Southern Cape coast of South Africa is characterised by both fractured and intergranular aquifers and hosts the most extensive network of SSLiME reported globally. However, the region is frequently affected by water scarcity crises and consequently groundwater development and usage has increased. Yet, it is unclear to what extent coastal discharge is linked to inland aquifers and whether anthropogenic activities influence the quantity and quality of groundwater that flows into SSLiME. This thesis aims to assess the groundwater cycle of the Algoa Bay region along the Southern Cape coast by means of a multi-tracer study. Specifically, it endeavours to develop a better understanding of the hydrogeochemical connectivity between inland groundwater resources and coastal microbialite ecosystems. To achieve this, four groups of hydrochemical tracers were used: H- and O-isotope ratios, major cations and anions, organic micropollutants and macronutrients. Sampling strategies included monthly precipitation collection over twelve months (stable water isotopes), once-off groundwater collection from boreholes, inland springs and coastal discharge (all tracers). In addition, coastal groundwater discharge was sampled during a once-off repeat campaign (all tracers) and seasonally at selected sites (macronutrients). A local meteoric water line (LMWL) for the region was established and compared to the isotopic signature of groundwater. The results indicate that groundwater is likely recharged directly and with little evaporation. Furthermore, similarities in isotopic signatures between inland and coastal aquifer systems suggest some level of hydrogeological connectivity or similar environmental drivers of recharge, such as precipitation amount and moisture source. This is also supported by the physico-chemistry and major ionic composition of the groundwater samples. However, the major ion composition of groundwater is variable and, although it predominantly reflects the sodium-chloride nature of precipitation, lithological and spatial trends are apparent. For example, coastward trends such as increasing conductivity, calcium, total alkalinity, and nitrogen is evident. While isotopes and major ions inform on the environmental drivers and geogenic influence on groundwater recharge, the organic micropollutants and macronutrients provide insight into the nature of anthropogenic impacts on groundwater quality. Micropollutants quantified in the groundwater samples included artificial sweeteners, pharmaceuticals, a biocide, and an illicit drug. These compounds are mostly classed as wastewater indicators and indicate aquifer contamination from leaking reticulation systems and septic tanks. The highest concentrations are associated with the urban and coastal peri-urban areas, while groundwater from rural areas is often devoid of any micropollutants except sulfamic acid, which may be introduced during recharge from precipitation. Furthermore, the presence of selected compounds in groundwater discharge signifies that at least a component of the groundwater is derived from recent infiltration. Similarly, the macronutrient content of groundwater reflects the proximal land use. As such, coastal groundwater discharge sites adjacent to coastal villages reflect higher concentrations compared to rural sites. In addition, the nutrient load supplied to and discharged from SSLiME systems is quantified and the nutrient attenuation is estimated. This thesis contributes recent hydrogeochemical information for a structurally complex semi-arid area under both natural (drought conditions) and human (increased water use, degradation of aquifers) pressures. Collectively, the results indicate that coastal groundwater discharge is likely a mixture of both the intergranular and fractured aquifers and that anthropogenic activities in the hinterland is contaminating the groundwater. This study is an important addition to the baseline hydrological information available for the region and may be useful in terms of sustainable groundwater management strategies and development toward a socio-ecological optimum, especially as related to coastal microbialite system. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Dodd, Carla
- Date: 2024-04
- Subjects: Ecohydrology , Hydrology , Groundwater -- Management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63722 , vital:73592
- Description: Groundwater is a crucial component of freshwater supply globally, especially in water-scarce regions such as semi-arid climatic areas where surface water resources are climatically limited and further constrained during droughts. Groundwater resources are also important from an ecological perspective as they support numerous surface ecosystems including wetlands and rivers. Coastal groundwater discharge along the South African coast sustains supratidal spring-fed living microbialite ecosystems (SSLiME). These systems act as potential analogues for Earth’s earliest ecosystems and are therefore useful from a palaeoscientific and evolutionary perspective. The Southern Cape coast of South Africa is characterised by both fractured and intergranular aquifers and hosts the most extensive network of SSLiME reported globally. However, the region is frequently affected by water scarcity crises and consequently groundwater development and usage has increased. Yet, it is unclear to what extent coastal discharge is linked to inland aquifers and whether anthropogenic activities influence the quantity and quality of groundwater that flows into SSLiME. This thesis aims to assess the groundwater cycle of the Algoa Bay region along the Southern Cape coast by means of a multi-tracer study. Specifically, it endeavours to develop a better understanding of the hydrogeochemical connectivity between inland groundwater resources and coastal microbialite ecosystems. To achieve this, four groups of hydrochemical tracers were used: H- and O-isotope ratios, major cations and anions, organic micropollutants and macronutrients. Sampling strategies included monthly precipitation collection over twelve months (stable water isotopes), once-off groundwater collection from boreholes, inland springs and coastal discharge (all tracers). In addition, coastal groundwater discharge was sampled during a once-off repeat campaign (all tracers) and seasonally at selected sites (macronutrients). A local meteoric water line (LMWL) for the region was established and compared to the isotopic signature of groundwater. The results indicate that groundwater is likely recharged directly and with little evaporation. Furthermore, similarities in isotopic signatures between inland and coastal aquifer systems suggest some level of hydrogeological connectivity or similar environmental drivers of recharge, such as precipitation amount and moisture source. This is also supported by the physico-chemistry and major ionic composition of the groundwater samples. However, the major ion composition of groundwater is variable and, although it predominantly reflects the sodium-chloride nature of precipitation, lithological and spatial trends are apparent. For example, coastward trends such as increasing conductivity, calcium, total alkalinity, and nitrogen is evident. While isotopes and major ions inform on the environmental drivers and geogenic influence on groundwater recharge, the organic micropollutants and macronutrients provide insight into the nature of anthropogenic impacts on groundwater quality. Micropollutants quantified in the groundwater samples included artificial sweeteners, pharmaceuticals, a biocide, and an illicit drug. These compounds are mostly classed as wastewater indicators and indicate aquifer contamination from leaking reticulation systems and septic tanks. The highest concentrations are associated with the urban and coastal peri-urban areas, while groundwater from rural areas is often devoid of any micropollutants except sulfamic acid, which may be introduced during recharge from precipitation. Furthermore, the presence of selected compounds in groundwater discharge signifies that at least a component of the groundwater is derived from recent infiltration. Similarly, the macronutrient content of groundwater reflects the proximal land use. As such, coastal groundwater discharge sites adjacent to coastal villages reflect higher concentrations compared to rural sites. In addition, the nutrient load supplied to and discharged from SSLiME systems is quantified and the nutrient attenuation is estimated. This thesis contributes recent hydrogeochemical information for a structurally complex semi-arid area under both natural (drought conditions) and human (increased water use, degradation of aquifers) pressures. Collectively, the results indicate that coastal groundwater discharge is likely a mixture of both the intergranular and fractured aquifers and that anthropogenic activities in the hinterland is contaminating the groundwater. This study is an important addition to the baseline hydrological information available for the region and may be useful in terms of sustainable groundwater management strategies and development toward a socio-ecological optimum, especially as related to coastal microbialite system. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
The Camdeboo-Mountain Zebra mega-reserve as an opportunity to protect viable populations of medium- to large-sized mammals
- Authors: Davis, Kristen
- Date: 2024-04
- Subjects: Mammals -- Ecology -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63711 , vital:73590
- Description: Conservation planning has focused extensively on representation of species in protected areas (PAs), rather than achieving the persistence of these species in PAs. Consequently, most PAs do not support viable populations of many species represented within them, particularly large mammals, resulting in extinction debt risks. The challenge is therefore to identify opportunities to achieve viable populations and to develop and implement conservation plans to achieve this, e.g., expand and connect existing PAs. A recent meta-analysis provides a minimum viable population (MVP) estimate of 5 000 individuals for mammals. This value was used as the target for modelling conservation opportunities for the South African endemic Cape mountain zebra (Equus zebra zebra), blesbok (Damaliscus pygargus phillipsi), black wildebeest (Connochaetes gnou) and co-existing medium- and large-sized mammal species. This study focused on the region between the Camdeboo and Mountain Zebra national parks (ca. 736 000 ha). Within the envisaged Camdeboo-Mountain Zebra (C-MZ) mega-reserve, a spreadsheet model was used to estimate potential herbivore population sizes, spatial requirement data were used to estimate potential omnivore and insectivore population sizes, and herbivore densities were used to estimate potential large carnivore population sizes. I show that 12 (the three endemic grazers and nine co-existing species) of the 28 modelled medium- and large-sized mammal species will potentially exceed 5 000 individuals, the MVP target, within the envisaged mega-reserve. The remaining 16 species show potential to reach substantial population sizes, however, will likely require ongoing metapopulation management. Using a conservation planning approach, I identify priority areas for the conservation of suitable habitat for Cape mountain zebra, blesbok, and black wildebeest within the envisaged mega-reserve, thus indirectly identifying priority areas for the conservation of these endemic species. I show that the potential incorporation of these priority areas within the envisaged mega-reserve will contribute considerably to the conservation of all focal species. In addition, the potential incorporation of these priority areas will contribute to PA expansion and significantly improve connectivity between existing PAs within the envisaged C-MZ mega-reserve. The importance of adequately-sized PAs to support viable populations of focal species is thus evident, and will ensure their long-term survival and ability to persist by allowing population and evolutionary scale processes. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Davis, Kristen
- Date: 2024-04
- Subjects: Mammals -- Ecology -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/63711 , vital:73590
- Description: Conservation planning has focused extensively on representation of species in protected areas (PAs), rather than achieving the persistence of these species in PAs. Consequently, most PAs do not support viable populations of many species represented within them, particularly large mammals, resulting in extinction debt risks. The challenge is therefore to identify opportunities to achieve viable populations and to develop and implement conservation plans to achieve this, e.g., expand and connect existing PAs. A recent meta-analysis provides a minimum viable population (MVP) estimate of 5 000 individuals for mammals. This value was used as the target for modelling conservation opportunities for the South African endemic Cape mountain zebra (Equus zebra zebra), blesbok (Damaliscus pygargus phillipsi), black wildebeest (Connochaetes gnou) and co-existing medium- and large-sized mammal species. This study focused on the region between the Camdeboo and Mountain Zebra national parks (ca. 736 000 ha). Within the envisaged Camdeboo-Mountain Zebra (C-MZ) mega-reserve, a spreadsheet model was used to estimate potential herbivore population sizes, spatial requirement data were used to estimate potential omnivore and insectivore population sizes, and herbivore densities were used to estimate potential large carnivore population sizes. I show that 12 (the three endemic grazers and nine co-existing species) of the 28 modelled medium- and large-sized mammal species will potentially exceed 5 000 individuals, the MVP target, within the envisaged mega-reserve. The remaining 16 species show potential to reach substantial population sizes, however, will likely require ongoing metapopulation management. Using a conservation planning approach, I identify priority areas for the conservation of suitable habitat for Cape mountain zebra, blesbok, and black wildebeest within the envisaged mega-reserve, thus indirectly identifying priority areas for the conservation of these endemic species. I show that the potential incorporation of these priority areas within the envisaged mega-reserve will contribute considerably to the conservation of all focal species. In addition, the potential incorporation of these priority areas will contribute to PA expansion and significantly improve connectivity between existing PAs within the envisaged C-MZ mega-reserve. The importance of adequately-sized PAs to support viable populations of focal species is thus evident, and will ensure their long-term survival and ability to persist by allowing population and evolutionary scale processes. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
- Full Text:
- Date Issued: 2024-04