Movement ecology of a West African sciaenid fish, Argyrosomus coronus, in southern Angola
- Authors: Parkinson, Matthew Cameron
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432203 , vital:72851 , DOI 10.21504/10962/432203
- Description: Argyrosomus coronus is a large sciaenid species with a primary distribution between Cape Frio, in Namibia, and Luanda, in Angola, where it exists as a panmictic stock. Early juveniles (< 300 mm TL) occur on muddy offshore substrata (50–80 m deep) and at one year of age they recruit into the inshore zone. Adults are thought to predominantly occur inshore. Spawning occurs in the species during late spring. The species is heavily targeted by the recreational, subsistence, artisanal and commercial fisheries as juveniles through to adults and there are signs of population decline with declines in catch per unit effort (CPUE) and maximum size. A basic understanding of their movement ecology has emerged from previous studies, based on conventional tagging (mark-recapture) and CPUE monitoring from a shore-based recreational fishery. Juveniles were thought to be resident, with larger fish undertaking long distance migration southward in the austral summer and returning during the austral winter. In addition to the fishery-related threats faced by the species, the southern Angolan region has been identified to be an ocean warming hotspot, and this has been linked to a southward distribution shift and the recent hybridisation of A. coronus with its congener A. inodorus, in Namibia. This study aims to expand the knowledge of the movement ecology of A. coronus and to interrogate our current understanding of the movement patterns of the species using passive acoustic telemetry. Passive acoustic receivers were deployed at three study sites, Flamingo, where all tagging occurred, which lies ~ 200 km north of the Angolan border with Namibia, is a relatively exposed stretch of coastline; Tombua Bay, which lies 30 km south of Flamingo, is a small, sheltered natural embayment; and Baia dos Tigres, which lies 100 km south of Tombua Bay, is a sheltered lagoon in the lee of an island ~ 10 km from the mainland. Tagging occurred in two batches, one year apart. In the first batch, sub-adults (n = 3) and adults (n = 17) were tagged and monitored for two years. In the second batch, juveniles (n = 7) and sub-adults (n = 3) were tagged and monitored for one year. The first objective of this thesis (Chapter 3) was to examine the spatio-temporal dynamics of A. coronus at a regional-level (across study sites, to investigate the prevalence of the longshore migration), and at a local-level (within a study site), and to categorise the movement behaviour of juveniles, sub-adults and adults. Traditional seasons were not used in this thesis, as the study region alternates between ‘warm’ periods (up to ~ 26 °C mean daily water temperature), when Angola Current water covers the area, and ‘cold’ periods (down to ~ 15 °C mean daily water temperature), when Benguela Current water covers the area. A high degree of residency of tagged fish to the Flamingo study site, where tagging was conducted, was found, with juveniles and sub-adults never being detected outside of the Flamingo study site. Five adults (29 %) were detected haphazardly for between one and 36 days at Tombua Bay, following which they were typically detected again at the Flamingo study site. No fish were ever detected at the southernmost site, Baia dos Tigres, suggesting that none migrated to Namibia. Within the Flamingo study site, adults were found to group at the inshore mid-region of the study site during ‘cold’ periods, dispersing again during ‘warm’ periods, when there was a concomitant offshore shift in their area use. This explained the absence of the species from catches in the shore-based recreational fishery during ‘warm’ periods. These results challenge previous migration hypotheses for the species. Therefore, longshore return migrations which were evident from previously conducted conventional tagging, are probably not the norm for the species, but likely occur at a low frequency. The species exhibited a high degree of residency to their tagging site, despite the drastic seasonal changes in water temperatures and station-keeping was the dominant behaviour across all life stages. The constrained area-use noted in this study, relative to the known distribution of the species, suggests that A. coronus exists as a metapopulation, consisting of a network of subpopulations interconnected by gene flow that is most likely facilitated during their pelagic egg and larval phase. The second objective of this thesis was to examine the group formation observed at the Flamingo study site during ‘cold’ periods (Chapter 4). While this grouping of individuals was found to be correlated with water temperature, it was unlikely to be a causal relationship, as the water temperature was not dissimilar to adjacent areas. The area where individuals were concentrated is known to frequently attract large shoals of their dominant prey, Sardinella aurita. While the timing of this group formation aligns with a pre-spawning period, no studies have assessed the existence of local spawning. A. coronus were, however, likely utilising an abundant prey source, during the important pre-spawning period, in order to build up energy reserves. Group formation is a common feature of sciaenids, but literature on the subject is restricted to spawning congregations. Fish are not only more vulnerable to capture during these periods but may also be disturbed during these potentially important social periods. The third objective of this thesis was to investigate the presence of sociality in the species (Chapter 5). Evidence for sociality during and outside the seasonal group formation was explored using network analyses. There was evidence for sociality, with several groups, characterized by co-locations among individuals, identified. While these groups were fluid through time, there was evidence of persistent sociality, with two individuals in particular being consistently co-located over the entire study period. Due to the persistent nature of sociality, group foraging is suggested as an explanation for this, with anecdotal evidence of coordinated hunting supporting this. Acoustic telemetry vastly improved the knowledge of the movement ecology of A. coronus. Despite their panmictic population genetic structure, they were found to be largely resident, likely occurring as a metapopulation across their distribution, with egg and larval dispersal likely the primary mechanism for maintaining panmixia. Evidence for sociality was also found, which was previously unexplored in the species. The persistent nature of social groupings throughout the year, suggests that it may be linked with group foraging and is supported by anecdotal evidence of coordinated hunting by the species. While this study highlights the value of acoustic telemetry in studying movement ecology, it also shows the importance of drawing on multiple methods to fully understand a species’ spatial ecology, including mark-recapture, population genetics, and fishery catch and effort data. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Parkinson, Matthew Cameron
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432203 , vital:72851 , DOI 10.21504/10962/432203
- Description: Argyrosomus coronus is a large sciaenid species with a primary distribution between Cape Frio, in Namibia, and Luanda, in Angola, where it exists as a panmictic stock. Early juveniles (< 300 mm TL) occur on muddy offshore substrata (50–80 m deep) and at one year of age they recruit into the inshore zone. Adults are thought to predominantly occur inshore. Spawning occurs in the species during late spring. The species is heavily targeted by the recreational, subsistence, artisanal and commercial fisheries as juveniles through to adults and there are signs of population decline with declines in catch per unit effort (CPUE) and maximum size. A basic understanding of their movement ecology has emerged from previous studies, based on conventional tagging (mark-recapture) and CPUE monitoring from a shore-based recreational fishery. Juveniles were thought to be resident, with larger fish undertaking long distance migration southward in the austral summer and returning during the austral winter. In addition to the fishery-related threats faced by the species, the southern Angolan region has been identified to be an ocean warming hotspot, and this has been linked to a southward distribution shift and the recent hybridisation of A. coronus with its congener A. inodorus, in Namibia. This study aims to expand the knowledge of the movement ecology of A. coronus and to interrogate our current understanding of the movement patterns of the species using passive acoustic telemetry. Passive acoustic receivers were deployed at three study sites, Flamingo, where all tagging occurred, which lies ~ 200 km north of the Angolan border with Namibia, is a relatively exposed stretch of coastline; Tombua Bay, which lies 30 km south of Flamingo, is a small, sheltered natural embayment; and Baia dos Tigres, which lies 100 km south of Tombua Bay, is a sheltered lagoon in the lee of an island ~ 10 km from the mainland. Tagging occurred in two batches, one year apart. In the first batch, sub-adults (n = 3) and adults (n = 17) were tagged and monitored for two years. In the second batch, juveniles (n = 7) and sub-adults (n = 3) were tagged and monitored for one year. The first objective of this thesis (Chapter 3) was to examine the spatio-temporal dynamics of A. coronus at a regional-level (across study sites, to investigate the prevalence of the longshore migration), and at a local-level (within a study site), and to categorise the movement behaviour of juveniles, sub-adults and adults. Traditional seasons were not used in this thesis, as the study region alternates between ‘warm’ periods (up to ~ 26 °C mean daily water temperature), when Angola Current water covers the area, and ‘cold’ periods (down to ~ 15 °C mean daily water temperature), when Benguela Current water covers the area. A high degree of residency of tagged fish to the Flamingo study site, where tagging was conducted, was found, with juveniles and sub-adults never being detected outside of the Flamingo study site. Five adults (29 %) were detected haphazardly for between one and 36 days at Tombua Bay, following which they were typically detected again at the Flamingo study site. No fish were ever detected at the southernmost site, Baia dos Tigres, suggesting that none migrated to Namibia. Within the Flamingo study site, adults were found to group at the inshore mid-region of the study site during ‘cold’ periods, dispersing again during ‘warm’ periods, when there was a concomitant offshore shift in their area use. This explained the absence of the species from catches in the shore-based recreational fishery during ‘warm’ periods. These results challenge previous migration hypotheses for the species. Therefore, longshore return migrations which were evident from previously conducted conventional tagging, are probably not the norm for the species, but likely occur at a low frequency. The species exhibited a high degree of residency to their tagging site, despite the drastic seasonal changes in water temperatures and station-keeping was the dominant behaviour across all life stages. The constrained area-use noted in this study, relative to the known distribution of the species, suggests that A. coronus exists as a metapopulation, consisting of a network of subpopulations interconnected by gene flow that is most likely facilitated during their pelagic egg and larval phase. The second objective of this thesis was to examine the group formation observed at the Flamingo study site during ‘cold’ periods (Chapter 4). While this grouping of individuals was found to be correlated with water temperature, it was unlikely to be a causal relationship, as the water temperature was not dissimilar to adjacent areas. The area where individuals were concentrated is known to frequently attract large shoals of their dominant prey, Sardinella aurita. While the timing of this group formation aligns with a pre-spawning period, no studies have assessed the existence of local spawning. A. coronus were, however, likely utilising an abundant prey source, during the important pre-spawning period, in order to build up energy reserves. Group formation is a common feature of sciaenids, but literature on the subject is restricted to spawning congregations. Fish are not only more vulnerable to capture during these periods but may also be disturbed during these potentially important social periods. The third objective of this thesis was to investigate the presence of sociality in the species (Chapter 5). Evidence for sociality during and outside the seasonal group formation was explored using network analyses. There was evidence for sociality, with several groups, characterized by co-locations among individuals, identified. While these groups were fluid through time, there was evidence of persistent sociality, with two individuals in particular being consistently co-located over the entire study period. Due to the persistent nature of sociality, group foraging is suggested as an explanation for this, with anecdotal evidence of coordinated hunting supporting this. Acoustic telemetry vastly improved the knowledge of the movement ecology of A. coronus. Despite their panmictic population genetic structure, they were found to be largely resident, likely occurring as a metapopulation across their distribution, with egg and larval dispersal likely the primary mechanism for maintaining panmixia. Evidence for sociality was also found, which was previously unexplored in the species. The persistent nature of social groupings throughout the year, suggests that it may be linked with group foraging and is supported by anecdotal evidence of coordinated hunting by the species. While this study highlights the value of acoustic telemetry in studying movement ecology, it also shows the importance of drawing on multiple methods to fully understand a species’ spatial ecology, including mark-recapture, population genetics, and fishery catch and effort data. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-10-13
Native-range studies on insect herbivores associated with African Lovegrass (Eragrostis curvula) in South Africa: prospects for biological control in Australia
- Authors: Yell, Liam Dougal
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424446 , vital:72154
- Description: Eragrostis curvula (Schrad.) Nees. (African Lovegrass) is an African native species of grass that was intentionally introduced for pasture in Australia. It has since escaped cultivation and has become widespread and highly invasive. Eragrostis curvula has been recorded in every state and territory in Australia where it has altered fire regimes, disrupted nutrient cycles and can reduce livestock carrying capacity by up to 50%. The Centre for Biological Control at Rhodes University and the New South Wales Department of Primary Industries have been working in collaboration to identify and screen herbivorous insects as biological control agents for E. curvula in Australia. Native-range surveys were conducted between 2021 and 2022 on E. curvula at twenty-two sites across South Africa to identify herbivorous natural enemies associated with it. Species accumulation curves were generated to ensure adequate sampling was performed to identify all the insects associated with E. curvula. Twenty-nine non-target grass species were surveyed simultaneously to determine the field-host range of the natural enemies associated with the target weed. Herbivorous natural enemies were prioritised as possible biological control agents against E. curvula in Australia based on field-host range, predicted efficacy and climatic suitability. Four insect species were consistently found on E. curvula, two of which were herbivorous, as well as a parasitoid and a detritivore. Species accumulation curves show that the insect community was adequately sampled in South Africa. The two herbivorous insects were identified to the lowest taxonomic level using COI barcoding. Both species are undescribed phytophagous wasps in the genus Tetramesa (Hymenoptera: Eurytomidae). Because Tetramesa species have been shown to be host specific and highly damaging in previous biological control programs for other invasive grass weeds, we assessed their suitability as candidate biological control agents for use on E. curvula in Australia. Both Tetramesa species (“sp. 4” and “sp. 5”) were found on several native congeners under field conditions in South Africa. Congeneric South African-native non-target grass species were used as phylogenetic proxies to assess the risk posed to Australian native Eragrostis species. This highlighted three non-target Australian native Eragrostis species, namely: E. parviflora (R. Br.) Trin., E. leptocarpa Benth. fl., and E. trachycarpa Benth., that are at risk of being attacked by the two candidate agents based on their phylogenetic proximity to E. curvula. Predicted efficacy trials were conducted at five long-term repeat survey sites and revealed that Tetramesa sp. 4 does not reduce the probability of E. curvula tiller survival or reproduction, while Tetramesa sp. 5 does not reduce the probability of tiller reproduction but does increase the probability of tiller survival. This result was unexpected and may be a plant compensatory response to herbivory. The sites where both Tetramesa species were collected in South Africa are climatically similar to the invaded range of E. curvula in Australia, and as such, the Tetramesa spp. are likely to be suitably adapted to the climate where they would be released in Australia. These results suggest that both Tetramesa species associated with E. curvula may have too broad a host range to be used as biological control agents in Australia. However, further quarantine-based host-range assessments on Australian native Eragrostis species are recommended to confirm this. The field-based methods used in this study have reduced the number of insect and plant species that host-range assessments will be required to be performed on, thus preventing wasted resources. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Yell, Liam Dougal
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424446 , vital:72154
- Description: Eragrostis curvula (Schrad.) Nees. (African Lovegrass) is an African native species of grass that was intentionally introduced for pasture in Australia. It has since escaped cultivation and has become widespread and highly invasive. Eragrostis curvula has been recorded in every state and territory in Australia where it has altered fire regimes, disrupted nutrient cycles and can reduce livestock carrying capacity by up to 50%. The Centre for Biological Control at Rhodes University and the New South Wales Department of Primary Industries have been working in collaboration to identify and screen herbivorous insects as biological control agents for E. curvula in Australia. Native-range surveys were conducted between 2021 and 2022 on E. curvula at twenty-two sites across South Africa to identify herbivorous natural enemies associated with it. Species accumulation curves were generated to ensure adequate sampling was performed to identify all the insects associated with E. curvula. Twenty-nine non-target grass species were surveyed simultaneously to determine the field-host range of the natural enemies associated with the target weed. Herbivorous natural enemies were prioritised as possible biological control agents against E. curvula in Australia based on field-host range, predicted efficacy and climatic suitability. Four insect species were consistently found on E. curvula, two of which were herbivorous, as well as a parasitoid and a detritivore. Species accumulation curves show that the insect community was adequately sampled in South Africa. The two herbivorous insects were identified to the lowest taxonomic level using COI barcoding. Both species are undescribed phytophagous wasps in the genus Tetramesa (Hymenoptera: Eurytomidae). Because Tetramesa species have been shown to be host specific and highly damaging in previous biological control programs for other invasive grass weeds, we assessed their suitability as candidate biological control agents for use on E. curvula in Australia. Both Tetramesa species (“sp. 4” and “sp. 5”) were found on several native congeners under field conditions in South Africa. Congeneric South African-native non-target grass species were used as phylogenetic proxies to assess the risk posed to Australian native Eragrostis species. This highlighted three non-target Australian native Eragrostis species, namely: E. parviflora (R. Br.) Trin., E. leptocarpa Benth. fl., and E. trachycarpa Benth., that are at risk of being attacked by the two candidate agents based on their phylogenetic proximity to E. curvula. Predicted efficacy trials were conducted at five long-term repeat survey sites and revealed that Tetramesa sp. 4 does not reduce the probability of E. curvula tiller survival or reproduction, while Tetramesa sp. 5 does not reduce the probability of tiller reproduction but does increase the probability of tiller survival. This result was unexpected and may be a plant compensatory response to herbivory. The sites where both Tetramesa species were collected in South Africa are climatically similar to the invaded range of E. curvula in Australia, and as such, the Tetramesa spp. are likely to be suitably adapted to the climate where they would be released in Australia. These results suggest that both Tetramesa species associated with E. curvula may have too broad a host range to be used as biological control agents in Australia. However, further quarantine-based host-range assessments on Australian native Eragrostis species are recommended to confirm this. The field-based methods used in this study have reduced the number of insect and plant species that host-range assessments will be required to be performed on, thus preventing wasted resources. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
Natural Language Processing with machine learning for anomaly detection on system call logs
- Authors: Goosen, Christo
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424699 , vital:72176
- Description: Host intrusion detection systems and machine learning have been studied for many years especially on datasets like KDD99. Current research and systems are focused on low training and processing complex problems such as system call returns, which lack the system call arguments and potential traces of exploits run against a system. With respect to malware and vulnerabilities, signatures are relied upon, and the potential for natural language processing of the resulting logs and system call traces needs further experimentation. This research looks at unstructured raw system call traces from x86_64 bit GNU Linux operating systems with natural language processing and supervised and unsupervised machine learning techniques to identify current and unseen threats. The research explores whether these tools are within the skill set of information security professionals, or require data science professionals. The research makes use of an academic and modern system call dataset from Leipzig University and applies two machine learning models based on decision trees. Random Forest as the supervised algorithm is compared to the unsupervised Isolation Forest algorithm for this research, with each experiment repeated after hyper-parameter tuning. The research finds conclusive evidence that the Isolation Forest Tree algorithm is effective, when paired with a Principal Component Analysis, in identifying anomalies in the modern Leipzig Intrusion Detection Data Set (LID-DS) dataset combined with samples of executed malware from the Virus Total Academic dataset. The base or default model parameters produce sub-optimal results, whereas using a hyper-parameter tuning technique increases the accuracy to within promising levels for anomaly and potential zero day detection. , Thesis (MSc) -- Faculty of Science, Computer Science, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Goosen, Christo
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424699 , vital:72176
- Description: Host intrusion detection systems and machine learning have been studied for many years especially on datasets like KDD99. Current research and systems are focused on low training and processing complex problems such as system call returns, which lack the system call arguments and potential traces of exploits run against a system. With respect to malware and vulnerabilities, signatures are relied upon, and the potential for natural language processing of the resulting logs and system call traces needs further experimentation. This research looks at unstructured raw system call traces from x86_64 bit GNU Linux operating systems with natural language processing and supervised and unsupervised machine learning techniques to identify current and unseen threats. The research explores whether these tools are within the skill set of information security professionals, or require data science professionals. The research makes use of an academic and modern system call dataset from Leipzig University and applies two machine learning models based on decision trees. Random Forest as the supervised algorithm is compared to the unsupervised Isolation Forest algorithm for this research, with each experiment repeated after hyper-parameter tuning. The research finds conclusive evidence that the Isolation Forest Tree algorithm is effective, when paired with a Principal Component Analysis, in identifying anomalies in the modern Leipzig Intrusion Detection Data Set (LID-DS) dataset combined with samples of executed malware from the Virus Total Academic dataset. The base or default model parameters produce sub-optimal results, whereas using a hyper-parameter tuning technique increases the accuracy to within promising levels for anomaly and potential zero day detection. , Thesis (MSc) -- Faculty of Science, Computer Science, 2023
- Full Text:
- Date Issued: 2023-10-13
Octa carboxy metal (II) phthalocyanine covalent films as pH sensitive electrochemical sensor for neurotransmitters
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Moyo, Iphithuli
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424525 , vital:72161
- Description: Octa acyl chloride metallophthalocyanines of cobalt (CoOAClPc) and iron (FeOAClPc) were synthesized and characterized using spectroscopic and electrochemical techniques. The metallophthalocyanines were fabricated as thin films onto phenylethylamine (PEA) pre-grafted Au electrode following a covalent amide reaction. The spectroscopic and electrochemical characterization confirmed the modification of the bare Au with PEA monolayer thin film (Au-PEA) and the covalent immobilization of MOAClPc to yield Au-PEA-MOAClPc (where M is Co and Fe). The acyl chloride functional groups were hydrolyzed forming pH sensitive thin films of terminal carboxylic acid (-COOH) functional groups (Au-PEA-MOCAPc). The Au-PEA-MOCAPc electrode exhibited pH selectivity and sensitivity properties towards the negatively charged [Fe(CN)6]3-/4- and positively charged [Ru(NH3)6]2+/3+ redox probes. The Au-PEA-MOCAPc electrodes were studied for their electrocatalytic and electroanalytical properties towards the detection of catecholamine neurotransmitters; dopamine (DA), epinephrine (EP) and norepinephrine (NOR). The electrodes were further investigated in the screening of ascorbic and uric acids by means of pH sensitive functional groups. The modification process exhibited good reproducibility. Excellent electrocatalytic and electroanalytical properties were observed. The limits of detection (LOD) determined using 3σ/m was found to be 64 nM, 0.22 μM and 0.17 μM for DA, EP and NOR respectively using Au-PEA-CoOCAPc. For Au-PEA-FeOCAPc, the LOD was found to 0.24 μM, 0.45 μM and 0.34 μM for DA, EP and NOR respectively. The Au-PEA-MOCAPc electrodes screened off the strong interferents, ascorbic and uric acid. The Au-PEA-FeOCAPc electrode was evaluated for its potential application in real sample analysis using new born calf serum, and it showed excellent percentage recoveries. , Thesis (MSc) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Origin and metallogenic significance of alkali metasomatism in the Paleoproterozoic Mapedi Formation, Kalahari Manganese Field, South Africa
- Authors: Ikwen, Emmanuella Biye
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424632 , vital:72170
- Description: The occurrence of alkali-rich metasomatic assemblages has been widely reported in various regions of the Kalahari Manganese Field (KMF). This alkali metasomatism has been characterized by the secondary introduction of elements such as K, Na, Li, Ba, P, V, Zn, As, amongst others. This study further explores the possibility of widespread alkali metasomatism in the KMF by reporting on and examining the occurrence of sugilite and other alkali-rich minerals at the contact between the Transvaal and Olifantshoek Supergroups in the Hotazel Mine area of the north-eastern KMF. The lithologies observed at the contact show macroscopic (such as cross cutting veins) and microscopic evidence of hydrothermal alteration. Using analytical methods such as X-ray diffraction, X-ray fluorescence, and scanning electron microscopy, results showed that in the north-eastern region of the KMF, the metasomatism observed at the Transvaal-Olifantshoek contact is mainly characterized by enrichment in sodium, and the occurrence of sodium minerals, predominantly in the form of aegirine. The aegirine forms exclusively in the quartzites of the Mapedi Formation along with minerals such as sugilite, baryte, banalsite, amongst others. Albite also occurs within the quartzites, but also within the Mapedi red shales. The secondary nature of these minerals is established by geochemical comparisons with pristine, as well as alkali-metasomatized samples of the same formation which were obtained from other parts of the KMF and Postmasburg. These comparisons showed that the Mapedi quartzites in the north-eastern KMF have undergone extensive oxidation compared to samples of the same formation which were obtained from Postmasburg. The north-eastern quartzites have an average hematite abundance of 17 wt.% compared to Postmasburg quartzite which have an average of 7 wt.% hematite. Furthermore, some quartzite samples contained up to 40 wt.% in hematite content. The comparisons also showed that Mapedi quartzites from the north-eastern KMF are substantially more sodium enriched compared to Mapedi quartzites from the Postmasburg region, which on average have sodium oxide content below detection limits. Geochemical comparisons were made between pristine Hotazel Formation samples from north-western KMF (Gloria Mine) and samples obtained from the north-eastern KMF (Hotazel Mine). Results showed that the samples obtained from the top of the Hotazel Formation (in the Hotazel mine area) are likely altered hematite lutite and not Banded Iron Formation, evident by their substantially high manganese oxide content (over 30 wt.% in some cases). When compared to pristine samples, the lutite also showed evidence of hydrothermal alteration, predominantly in the form of phosphate and barium enrichment, evident by the occurrence of baryte and apatite. The alkali metasomatism occurring at the contact between the Transvaal and Olifantshoek Supergroups was shown to be predominantly characterized by enrichment in Na, K, Li, Al, Ba, Sr, and P. The metasomatism characterized in this study was also proposed to possibly post-date an earlier metasomatic event which was characterized by leaching of silica and extensive oxidation of the rocks observed at the Transvaal-Olifantshoek contact in the north-eastern KMF. The occurrence of the alkali-rich minerals outlined above geochemically parallels other alkali-rich metasomatic assemblages reported in other parts of the KMF, as well as in the Postmasburg Manganese Field. Thus, based on the consistent occurrence of secondary, alkali-rich mineral assemblages across the KMF, characterized by the common occurrence of aegirine along with minerals such as sugilite and albite, there is evidence of a large-scale alkali metasomatism in the KMF. This study also explores the possible role that the Transvaal-Olifantshoek unconformity might have played in acting as a major conduit for fluid propagation because the observed mineral assemblages occur right at the contact between the Hotazel and Mapedi Formations. The occurrence of the alkali-rich minerals predominantly around the unconformity, as well as the relative depletion of phosphates in stratigraphically deeper parts of the Hotazel suggest that the fluid metasomatism was aided by the Olifantshoek-Transvaal unconformity surface. This study concludes that there is evidence for a strong link between the metasomatism occurring at the contact between the Hotazel and Mapedi formations (in the north-eastern KMF) and what is observed in the broader KMF region. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ikwen, Emmanuella Biye
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424632 , vital:72170
- Description: The occurrence of alkali-rich metasomatic assemblages has been widely reported in various regions of the Kalahari Manganese Field (KMF). This alkali metasomatism has been characterized by the secondary introduction of elements such as K, Na, Li, Ba, P, V, Zn, As, amongst others. This study further explores the possibility of widespread alkali metasomatism in the KMF by reporting on and examining the occurrence of sugilite and other alkali-rich minerals at the contact between the Transvaal and Olifantshoek Supergroups in the Hotazel Mine area of the north-eastern KMF. The lithologies observed at the contact show macroscopic (such as cross cutting veins) and microscopic evidence of hydrothermal alteration. Using analytical methods such as X-ray diffraction, X-ray fluorescence, and scanning electron microscopy, results showed that in the north-eastern region of the KMF, the metasomatism observed at the Transvaal-Olifantshoek contact is mainly characterized by enrichment in sodium, and the occurrence of sodium minerals, predominantly in the form of aegirine. The aegirine forms exclusively in the quartzites of the Mapedi Formation along with minerals such as sugilite, baryte, banalsite, amongst others. Albite also occurs within the quartzites, but also within the Mapedi red shales. The secondary nature of these minerals is established by geochemical comparisons with pristine, as well as alkali-metasomatized samples of the same formation which were obtained from other parts of the KMF and Postmasburg. These comparisons showed that the Mapedi quartzites in the north-eastern KMF have undergone extensive oxidation compared to samples of the same formation which were obtained from Postmasburg. The north-eastern quartzites have an average hematite abundance of 17 wt.% compared to Postmasburg quartzite which have an average of 7 wt.% hematite. Furthermore, some quartzite samples contained up to 40 wt.% in hematite content. The comparisons also showed that Mapedi quartzites from the north-eastern KMF are substantially more sodium enriched compared to Mapedi quartzites from the Postmasburg region, which on average have sodium oxide content below detection limits. Geochemical comparisons were made between pristine Hotazel Formation samples from north-western KMF (Gloria Mine) and samples obtained from the north-eastern KMF (Hotazel Mine). Results showed that the samples obtained from the top of the Hotazel Formation (in the Hotazel mine area) are likely altered hematite lutite and not Banded Iron Formation, evident by their substantially high manganese oxide content (over 30 wt.% in some cases). When compared to pristine samples, the lutite also showed evidence of hydrothermal alteration, predominantly in the form of phosphate and barium enrichment, evident by the occurrence of baryte and apatite. The alkali metasomatism occurring at the contact between the Transvaal and Olifantshoek Supergroups was shown to be predominantly characterized by enrichment in Na, K, Li, Al, Ba, Sr, and P. The metasomatism characterized in this study was also proposed to possibly post-date an earlier metasomatic event which was characterized by leaching of silica and extensive oxidation of the rocks observed at the Transvaal-Olifantshoek contact in the north-eastern KMF. The occurrence of the alkali-rich minerals outlined above geochemically parallels other alkali-rich metasomatic assemblages reported in other parts of the KMF, as well as in the Postmasburg Manganese Field. Thus, based on the consistent occurrence of secondary, alkali-rich mineral assemblages across the KMF, characterized by the common occurrence of aegirine along with minerals such as sugilite and albite, there is evidence of a large-scale alkali metasomatism in the KMF. This study also explores the possible role that the Transvaal-Olifantshoek unconformity might have played in acting as a major conduit for fluid propagation because the observed mineral assemblages occur right at the contact between the Hotazel and Mapedi Formations. The occurrence of the alkali-rich minerals predominantly around the unconformity, as well as the relative depletion of phosphates in stratigraphically deeper parts of the Hotazel suggest that the fluid metasomatism was aided by the Olifantshoek-Transvaal unconformity surface. This study concludes that there is evidence for a strong link between the metasomatism occurring at the contact between the Hotazel and Mapedi formations (in the north-eastern KMF) and what is observed in the broader KMF region. , Thesis (MSc) -- Faculty of Science, Geology, 2023
- Full Text:
- Date Issued: 2023-10-13
Phylogeography of two small owl species in South Africa: population genetics and phenotypic variation in the African Barred Owlet (Glaucidium capense) and the African Scops Owl (Otus senegalensis)
- Authors: Balmer, Jonathan Peter
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424369 , vital:72147
- Description: Embargoed. Expected release date in 2025. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Balmer, Jonathan Peter
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424369 , vital:72147
- Description: Embargoed. Expected release date in 2025. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
Phytoplankton and aquatic macroinvertebrate assemblages from coastal and inland lakes of South Africa
- Authors: Nkibi, Esethu
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424435 , vital:72153
- Description: Freshwater lakes are generally defined as permanent natural standing water bodies, with some of them having a direct and indirect connection with groundwater, rivers, and the ocean. Freshwater lakes provide essential socio-economic and ecological goods and services including recreation, aesthetic, support aquatic biodiversity, food in a form of fisheries and water for domestic use. Given their critical role in sustainability in providing socio-economic services, freshwater lakes are among the most threatened ecosystems globally due to intense human impacts over the last decades. South Africa has limited freshwater lakes, which according to the National Biodiversity Assessment (NBA 2018), we know little about their current biology except historic aquatic biodiversity studies conducted in the early 1940s. There are no management strategies in place to protect and conserve freshwater lake biodiversity and important ecosystem services. This thesis aims to: (1) produce a biodiversity inventory of phytoplankton and aquatic macroinvertebrate species and, (2) investigate important environmental drivers responsible for phytoplankton and aquatic macroinvertebrate species composition from six South African freshwater lakes. It was hypothesized that the three lake types will show different phytoplankton and aquatic macroinvertebrates species composition attributed by the geographical region (coastal and inland lake) and related physico-chemical parameters. Study sites consisted of two Northern KwaZulu-Natal coastal lakes (hereafter Coastal Lakes, CL) i.e., Lake Sibaya, Lake Mzingazi; two fresh inland lakes (hereafter Fresh Inland Lakes, FIL) i.e., Lake Banagher fresh and Lake Tevrede Se Pan; and two inland salt lakes (hereafter Salt Inland Lakes, SIL) i.e., Lake Banagher salt and Lake Chrissiesmeer, all inland lakes are situated in Mpumalanga province, together with other Pans making up the Mpumalanga Lake District of South Africa. The study sites were categorized based on their geographical position i.e., coastal vs inland and physico-chemical characteristics i.e., the presence and absence of aquatic vegetation, dominate substrate, salinity and different physico-chemical concentration i.e., Temperature, Dissolved Oxygen. Aquatic macroinvertebrates were collected from four littoral zone sites (< 1-meter depth) around each lake, whereas phytoplankton samples were collected from four water column sites (> 5-meters depth) and (0.5-meter depth) from the water surface at each lake during summer and winter season. The results were consistent with our hypothesis that both phytoplankton and aquatic macroinvertebrate species composition were influenced by physico-chemical parameters and that the differences in salinity concentration and aquatic vegetation between CL, FIL, and SIL were the driving factors for phytoplankton and aquatic macroinvertebrate species composition. In summary, one hundred and twenty-two phytoplankton taxa were collected and identified during this study, belonging to seven Phyla which included Chlorophyta, Bacillariophyta, Cyanophyta, Chrysophyta, Dinophyta, Euglenophyta, and Cryptophyta. The most abundant phytoplankton groups were Bacillariophyta and Chlorophyta. Phytoplankton relative taxa abundance, Pielou’s evenness, taxa richness, and Shannon diversity were significantly different between lake types. Aquatic macroinvertebrates, on the other hand, summed up to 10 orders, 67 families, and 80 taxa. The most abundant group were the order Coleoptera, Hemiptera, Odonata, and Gastropoda. Aquatic macroinvertebrate relative taxa abundance, taxa richness, and Shannon diversity were also significantly different between lake types. Aquatic macroinvertebrate relative taxa abundance, Pielous evenness, and Shannon diversity index were not significant between seasons, and only taxa richness was significant. Canonical analysis of principal coordinates (CAP) results further showed unique and distinct phytoplankton and aquatic macroinvertebrates community composition between lake types. The present study provides baseline biodiversity inventory (or species list) for important lake ecosystems biological indicators i.e., phytoplankton and aquatic macroinvertebrates and species composition in relation to lake type for six freshwater lakes in South Africa. Furthermore, the study provides empirical evidence that will inform policy and the development of management strategies for freshwater lakes in South Africa which is currently missing. The current study will also contribute to the next National Biodiversity Assessment Report (2024), concerning the freshwater lakes biological data deficiency noted in the previous NBA (2018) report. The study will also fill up the gaps to better understand species composition in lake systems and how they function which is currently limited. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Nkibi, Esethu
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424435 , vital:72153
- Description: Freshwater lakes are generally defined as permanent natural standing water bodies, with some of them having a direct and indirect connection with groundwater, rivers, and the ocean. Freshwater lakes provide essential socio-economic and ecological goods and services including recreation, aesthetic, support aquatic biodiversity, food in a form of fisheries and water for domestic use. Given their critical role in sustainability in providing socio-economic services, freshwater lakes are among the most threatened ecosystems globally due to intense human impacts over the last decades. South Africa has limited freshwater lakes, which according to the National Biodiversity Assessment (NBA 2018), we know little about their current biology except historic aquatic biodiversity studies conducted in the early 1940s. There are no management strategies in place to protect and conserve freshwater lake biodiversity and important ecosystem services. This thesis aims to: (1) produce a biodiversity inventory of phytoplankton and aquatic macroinvertebrate species and, (2) investigate important environmental drivers responsible for phytoplankton and aquatic macroinvertebrate species composition from six South African freshwater lakes. It was hypothesized that the three lake types will show different phytoplankton and aquatic macroinvertebrates species composition attributed by the geographical region (coastal and inland lake) and related physico-chemical parameters. Study sites consisted of two Northern KwaZulu-Natal coastal lakes (hereafter Coastal Lakes, CL) i.e., Lake Sibaya, Lake Mzingazi; two fresh inland lakes (hereafter Fresh Inland Lakes, FIL) i.e., Lake Banagher fresh and Lake Tevrede Se Pan; and two inland salt lakes (hereafter Salt Inland Lakes, SIL) i.e., Lake Banagher salt and Lake Chrissiesmeer, all inland lakes are situated in Mpumalanga province, together with other Pans making up the Mpumalanga Lake District of South Africa. The study sites were categorized based on their geographical position i.e., coastal vs inland and physico-chemical characteristics i.e., the presence and absence of aquatic vegetation, dominate substrate, salinity and different physico-chemical concentration i.e., Temperature, Dissolved Oxygen. Aquatic macroinvertebrates were collected from four littoral zone sites (< 1-meter depth) around each lake, whereas phytoplankton samples were collected from four water column sites (> 5-meters depth) and (0.5-meter depth) from the water surface at each lake during summer and winter season. The results were consistent with our hypothesis that both phytoplankton and aquatic macroinvertebrate species composition were influenced by physico-chemical parameters and that the differences in salinity concentration and aquatic vegetation between CL, FIL, and SIL were the driving factors for phytoplankton and aquatic macroinvertebrate species composition. In summary, one hundred and twenty-two phytoplankton taxa were collected and identified during this study, belonging to seven Phyla which included Chlorophyta, Bacillariophyta, Cyanophyta, Chrysophyta, Dinophyta, Euglenophyta, and Cryptophyta. The most abundant phytoplankton groups were Bacillariophyta and Chlorophyta. Phytoplankton relative taxa abundance, Pielou’s evenness, taxa richness, and Shannon diversity were significantly different between lake types. Aquatic macroinvertebrates, on the other hand, summed up to 10 orders, 67 families, and 80 taxa. The most abundant group were the order Coleoptera, Hemiptera, Odonata, and Gastropoda. Aquatic macroinvertebrate relative taxa abundance, taxa richness, and Shannon diversity were also significantly different between lake types. Aquatic macroinvertebrate relative taxa abundance, Pielous evenness, and Shannon diversity index were not significant between seasons, and only taxa richness was significant. Canonical analysis of principal coordinates (CAP) results further showed unique and distinct phytoplankton and aquatic macroinvertebrates community composition between lake types. The present study provides baseline biodiversity inventory (or species list) for important lake ecosystems biological indicators i.e., phytoplankton and aquatic macroinvertebrates and species composition in relation to lake type for six freshwater lakes in South Africa. Furthermore, the study provides empirical evidence that will inform policy and the development of management strategies for freshwater lakes in South Africa which is currently missing. The current study will also contribute to the next National Biodiversity Assessment Report (2024), concerning the freshwater lakes biological data deficiency noted in the previous NBA (2018) report. The study will also fill up the gaps to better understand species composition in lake systems and how they function which is currently limited. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
Playing it back: audible traces in contemporary African art
- Authors: Panchia, Bhavisha Laximi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432455 , vital:72872
- Description: Access restricted. Exptected release date 2025. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Panchia, Bhavisha Laximi
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432455 , vital:72872
- Description: Access restricted. Exptected release date 2025. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
- Date Issued: 2023-10-13
Porphyrinoid dyes for photodynamic anticancer and antimicrobial therapy treatments
- Authors: Soy, Rodah Cheruto
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432252 , vital:72855 , DOI 10.21504/10962/432252
- Description: The search for alternative therapies and non-toxic photosensitizer drugs that can efficiently generate cytotoxic reactive oxygen species for biomedical applications, such as in alternative photodynamic therapy (PDT) for cancer treatment and photodynamic antimicrobial chemotherapy (PACT) for drug-resistant bacteria treatment is on the rise. Nevertheless, the lack of photosensitizer dyes that absorb light strongly within the therapeutic window (620−850 nm) that can locally target the tumor and bacterial cells and generate singlet oxygen efficiently are some of the main challenges in PDT and PACT treatment. This study sought to address the challenges that impede PDT and PACT from realizing their full potential by synthesizing a series of meso-aryltetrapyrrolic photosensitizer dyes that absorb light within the therapeutic window. These include meso-tetraarylporphyrin (Por), A3-type meso-triarylcorrole (Cor), meso-tetraarylchlorin (Chl), and N-confused meso-tetraarylporphyrin (NCP) dyes with 4-thiomethylphenyl (1), thien-3-yl (2), thien-2-yl (3), 5-bromo-thien-2-yl (4), 4-methoxyphenyl (5), 3-methoxyphenyl (6), 4-hydroxyphenyl (7) and 4-hydroxy-3-methoxyphenyl (8) meso-aryl rings. Por, Cor, Chl and NCP dyes and and their Ga(III), P(V), In(III) and/or Sn(IV) complexes with 1-8, 1-4, 5-8 and 5 meso-aryl rings were studied, along with two A2B-type Ga(III) meso-triarylcorroles with pentafluorophenyl rings at the A2 positions and 3,6-di-t-butyl-9H-carbazole (9) or N-butyl-4-carbazole (10) rings at the B position that were prepared in the laboratory of Prof. Xu Liang of Jiangsu University in the People’s Republic of China. The carbazole nitrogen of 10-GaCor was quaternized at Rhodes University with ethyl iodide to form a cationic species (10-GaCor-Q) for PDT and PACT activity studies. The structures of the synthesized dyes were confirmed using UV-visible absorption and 1H NMR spectroscopy, and MALDI-TOF-mass spectrometry. 1-4-InPor In(III) porphyrins, 1-4-PVCor, 1-4-GaCor A3 PV and GaIII corrole dyes were also conjugated to gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) via sulfur-gold and sulfur-silver affinities. The successful conjugation of the dyes onto the nanoparticles to form dye-AuNP or dye-AgNP nanoassemblies was confirmed using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray powered diffraction (XRD), and (X-ray photon spectroscopy) XPS. The photophysicochemical, photostability, and lipophilicity properties of the dyes and their PDT and PACT activities were investigated, and the structure-property relationships were analyzed. This was accomplished by analyzing the changes in the properties of the dyes due to the meso-aryl substituents, central ions, molecular symmetry, and heavy atom effects. Time-dependent-density functional theory (TD-DFT) calculations were also used to further probe the electronic and optical spectroscopic properties of the dyes. The analysis of the photophysicochemical, photostability, and lipophilicity data for the synthesized dyes demonstrated that there are inherent structure-property relationships for the dyes studied. The TD-DFT calculations also assisted in rationalizing the observed optical spectroscopic data for the dyes. The introduction of different meso-aryl substituents resulted in minor absorption spectral changes on the parent structures of the dyes due to their inductive and mesomeric effects, while the insertion of Ga(III), In(III), and Sn(IV) electropositive metal centers resulted in marked red shifts of the B bands due to favorable interactions with the porphyrin or porphyrinoid ligand core. The lower symmetries of the corrole, chlorin, and N-confused porphyrin dyes resulted in enhanced absorption properties within the therapeutic window relative to porphyrins. The heavy atom effect from the Ga(III), In(III), and Sn(IV) central ions, the meso-aryl groups, and the external heavy atom effect from the AuNPs and AgNPs significantly reduced the fluorescence quantum yield values of the dyes resulting in high singlet oxygen quantum yields. The dye complexes also exhibited properly balanced lipophilic properties and high photostabilities. The P(V) ion of the A3 PV corrole dyes reduced the aggregation effects, enhanced cellular uptake, and lowered the lipophilicity values relative to the A3 GaIII corrole dyes. The porphyrin and porphyrinoid complexes studied exhibited relatively low in vitro dark cytotoxicity toward MCF-7 cancer cells, which is enhanced for AuNP nanoconjugates of 1-InPor, 1-3-PVCor, and 1-3-GaCor. The dyes also have low in vitro dark cytotoxicity toward planktonic and biofilm cells of S. aureus and E. coli. The complexes also exhibited favorable PDT and PACT activities toward MCF-7 cancer cells, and planktonic and biofilm S. aureus and E. coli bacteria due to their high singlet oxygen quantum yields. AuNP and AgNP nanoconjugates of 1-4-InPor, 1-4-PVCor, and 1-4-GaCor exhibited enhanced PDT and PACT activities due to the favorable synergistic effects of nanoparticles. The PDT and PACT activities of A3 PV corrole dyes and the nanoconjugates of 1-4-PVCor are slightly higher than those of A3-type GaIII corroles and their nanoconjugates due to decreased aggregation effects and enhanced PS drug uptake. The cationic 10-GaCor-Q species also exhibit favorable PDT and PACT activities in contrast to the neutral 9-10-GaCor dyes due to enhanced PS drug penetration into the tumor or bacteria cells. The complexes also exhibited high Log10 reduction values for planktonic S. aureus suggesting that the dyes are highly efficient PS dyes. The activities of the complexes toward planktonic E. coli bacteria are moderate except for 10-GaCor-Q, 2-4-PVCor-AgNPs, and 5-8-SnChl chlorins exhibiting relatively favorable activity with > 3 Log10 CFU.mL−1 values. The dyes also exhibit moderate activities toward the S. aureus and E. coli biofilm cells, which are lower than for the planktonic cells, as shown by their lower Log10 reduction values. The data demonstrate that the low symmetry corrole, chlorin, and N-confused porphyrin complexes that absorb light strongly within the therapeutic window have significantly enhanced PDT and PACT activities relative to their porphyrin analogs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Soy, Rodah Cheruto
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432252 , vital:72855 , DOI 10.21504/10962/432252
- Description: The search for alternative therapies and non-toxic photosensitizer drugs that can efficiently generate cytotoxic reactive oxygen species for biomedical applications, such as in alternative photodynamic therapy (PDT) for cancer treatment and photodynamic antimicrobial chemotherapy (PACT) for drug-resistant bacteria treatment is on the rise. Nevertheless, the lack of photosensitizer dyes that absorb light strongly within the therapeutic window (620−850 nm) that can locally target the tumor and bacterial cells and generate singlet oxygen efficiently are some of the main challenges in PDT and PACT treatment. This study sought to address the challenges that impede PDT and PACT from realizing their full potential by synthesizing a series of meso-aryltetrapyrrolic photosensitizer dyes that absorb light within the therapeutic window. These include meso-tetraarylporphyrin (Por), A3-type meso-triarylcorrole (Cor), meso-tetraarylchlorin (Chl), and N-confused meso-tetraarylporphyrin (NCP) dyes with 4-thiomethylphenyl (1), thien-3-yl (2), thien-2-yl (3), 5-bromo-thien-2-yl (4), 4-methoxyphenyl (5), 3-methoxyphenyl (6), 4-hydroxyphenyl (7) and 4-hydroxy-3-methoxyphenyl (8) meso-aryl rings. Por, Cor, Chl and NCP dyes and and their Ga(III), P(V), In(III) and/or Sn(IV) complexes with 1-8, 1-4, 5-8 and 5 meso-aryl rings were studied, along with two A2B-type Ga(III) meso-triarylcorroles with pentafluorophenyl rings at the A2 positions and 3,6-di-t-butyl-9H-carbazole (9) or N-butyl-4-carbazole (10) rings at the B position that were prepared in the laboratory of Prof. Xu Liang of Jiangsu University in the People’s Republic of China. The carbazole nitrogen of 10-GaCor was quaternized at Rhodes University with ethyl iodide to form a cationic species (10-GaCor-Q) for PDT and PACT activity studies. The structures of the synthesized dyes were confirmed using UV-visible absorption and 1H NMR spectroscopy, and MALDI-TOF-mass spectrometry. 1-4-InPor In(III) porphyrins, 1-4-PVCor, 1-4-GaCor A3 PV and GaIII corrole dyes were also conjugated to gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) via sulfur-gold and sulfur-silver affinities. The successful conjugation of the dyes onto the nanoparticles to form dye-AuNP or dye-AgNP nanoassemblies was confirmed using transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray powered diffraction (XRD), and (X-ray photon spectroscopy) XPS. The photophysicochemical, photostability, and lipophilicity properties of the dyes and their PDT and PACT activities were investigated, and the structure-property relationships were analyzed. This was accomplished by analyzing the changes in the properties of the dyes due to the meso-aryl substituents, central ions, molecular symmetry, and heavy atom effects. Time-dependent-density functional theory (TD-DFT) calculations were also used to further probe the electronic and optical spectroscopic properties of the dyes. The analysis of the photophysicochemical, photostability, and lipophilicity data for the synthesized dyes demonstrated that there are inherent structure-property relationships for the dyes studied. The TD-DFT calculations also assisted in rationalizing the observed optical spectroscopic data for the dyes. The introduction of different meso-aryl substituents resulted in minor absorption spectral changes on the parent structures of the dyes due to their inductive and mesomeric effects, while the insertion of Ga(III), In(III), and Sn(IV) electropositive metal centers resulted in marked red shifts of the B bands due to favorable interactions with the porphyrin or porphyrinoid ligand core. The lower symmetries of the corrole, chlorin, and N-confused porphyrin dyes resulted in enhanced absorption properties within the therapeutic window relative to porphyrins. The heavy atom effect from the Ga(III), In(III), and Sn(IV) central ions, the meso-aryl groups, and the external heavy atom effect from the AuNPs and AgNPs significantly reduced the fluorescence quantum yield values of the dyes resulting in high singlet oxygen quantum yields. The dye complexes also exhibited properly balanced lipophilic properties and high photostabilities. The P(V) ion of the A3 PV corrole dyes reduced the aggregation effects, enhanced cellular uptake, and lowered the lipophilicity values relative to the A3 GaIII corrole dyes. The porphyrin and porphyrinoid complexes studied exhibited relatively low in vitro dark cytotoxicity toward MCF-7 cancer cells, which is enhanced for AuNP nanoconjugates of 1-InPor, 1-3-PVCor, and 1-3-GaCor. The dyes also have low in vitro dark cytotoxicity toward planktonic and biofilm cells of S. aureus and E. coli. The complexes also exhibited favorable PDT and PACT activities toward MCF-7 cancer cells, and planktonic and biofilm S. aureus and E. coli bacteria due to their high singlet oxygen quantum yields. AuNP and AgNP nanoconjugates of 1-4-InPor, 1-4-PVCor, and 1-4-GaCor exhibited enhanced PDT and PACT activities due to the favorable synergistic effects of nanoparticles. The PDT and PACT activities of A3 PV corrole dyes and the nanoconjugates of 1-4-PVCor are slightly higher than those of A3-type GaIII corroles and their nanoconjugates due to decreased aggregation effects and enhanced PS drug uptake. The cationic 10-GaCor-Q species also exhibit favorable PDT and PACT activities in contrast to the neutral 9-10-GaCor dyes due to enhanced PS drug penetration into the tumor or bacteria cells. The complexes also exhibited high Log10 reduction values for planktonic S. aureus suggesting that the dyes are highly efficient PS dyes. The activities of the complexes toward planktonic E. coli bacteria are moderate except for 10-GaCor-Q, 2-4-PVCor-AgNPs, and 5-8-SnChl chlorins exhibiting relatively favorable activity with > 3 Log10 CFU.mL−1 values. The dyes also exhibit moderate activities toward the S. aureus and E. coli biofilm cells, which are lower than for the planktonic cells, as shown by their lower Log10 reduction values. The data demonstrate that the low symmetry corrole, chlorin, and N-confused porphyrin complexes that absorb light strongly within the therapeutic window have significantly enhanced PDT and PACT activities relative to their porphyrin analogs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Prediction of mass spectra using an ab initio approach
- Authors: Novokoza, Yolanda
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:72818
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Novokoza, Yolanda
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:72818
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Quantifying the training demands of an amateur women’s Rugby union team using Global Positioning System
- Authors: Mbane, Nomabhelu
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424289 , vital:72140
- Description: Rugby union is a dynamic sport that has grown to not only be played by men but by women too. The professionalisation of the sport that happened in 1995 developed the game immeasurably including the focus given to its scientific research. This is important as literature on the demands of the game has become vital in improving the performance of Rugby union players (Deutch et al., 1998; Kay and Gill, 2004; Kruger, 2012). Scientific evidence-based data on the physical and physiological demands is imperative in the planning and setting up of training regimes (Deutch et al., 1998; Kay and Gill, 2004; Kruger, 2012). Unfortunately, the growth in the participation of women’s Rugby union has not been matched with scientific evidence-based literature that seeks to improve the performance of this population of players. Therefore, due to the unavailability of match-play during the COVID-19 outbreak, this study aimed to quantify the physical and physiological demands of training sessions of amateur women’s Rugby union players from the Sarah Baartman District, South Africa using Global Positioning System (GPS). The training’ data collected was compared to previous literature, including studies that also focused on match-play. Furthermore, players were categorized into forwards and backs, allowing for the comparison between the two playing categories. An exploratory, descriptive, observational, and comparative research design was used for the current study. The physical and physiological demands of eighteen women Rugby union players (eight forwards and ten backs) aged between 18 – 36 years old were assessed during training (for a total of nine sessions). To inform the participants’ characteristics, the players’ demographic, and anthropometric characteristics (age, stature, and body mass) were obtained. Using GPS and Zephyr technology the players’ training physical (time spent in speed zones, maximum speed, total distance travelled, number of impacts in the various impact zones) and physiological (heart rate) demands were explored. Statistical analysis methods including descriptive, independent t-test, one-way and two-way ANOVA tests were employed to analyse the data and evaluate the differences between forwards and backs. The mean age and stature for all players was 25,44±5,6 years and 1,60±0,06 m respectively, with no significant differences found between backs and forwards. With regards to body mass, forwards weighed 82,0±9,4 kg while backs weighed significantly lighter at 58,0±5,8 kg. Significant differences (p < 0,05) were found for all players in the time spent in speed zones and the number of impacts in impact zones. When all forwards’ and backs’ physical and physiological demands were compared the results showed no significant differences. The average time spent in all six speed zones combined was 11,41 and 11,62 mins for forwards and backs, respectively. The maximum speeds reached by forwards (21,35±5,72 km/h) and backs (22,85±3,88 km/h) were similar. All players combined travelled an average total distance of 2,14±0,76 km. The total number of impacts in all six impact zones, totalled 116 impacts for forwards and 97 for backs. Heart rate responses recorded for forwards and backs were 139±15 bpm and 134±13 bpm. Based on the findings of this study, the training intensity of amateur women’s Rugby union was lower than the demands experienced in the training and match-play of previous research. It was also observed that there was no specificity with regards to the training programs allocated between forwards and backs of this study. Further research on amateur women’s Rugby union is required to characterise training and match-play demands of these players. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mbane, Nomabhelu
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424289 , vital:72140
- Description: Rugby union is a dynamic sport that has grown to not only be played by men but by women too. The professionalisation of the sport that happened in 1995 developed the game immeasurably including the focus given to its scientific research. This is important as literature on the demands of the game has become vital in improving the performance of Rugby union players (Deutch et al., 1998; Kay and Gill, 2004; Kruger, 2012). Scientific evidence-based data on the physical and physiological demands is imperative in the planning and setting up of training regimes (Deutch et al., 1998; Kay and Gill, 2004; Kruger, 2012). Unfortunately, the growth in the participation of women’s Rugby union has not been matched with scientific evidence-based literature that seeks to improve the performance of this population of players. Therefore, due to the unavailability of match-play during the COVID-19 outbreak, this study aimed to quantify the physical and physiological demands of training sessions of amateur women’s Rugby union players from the Sarah Baartman District, South Africa using Global Positioning System (GPS). The training’ data collected was compared to previous literature, including studies that also focused on match-play. Furthermore, players were categorized into forwards and backs, allowing for the comparison between the two playing categories. An exploratory, descriptive, observational, and comparative research design was used for the current study. The physical and physiological demands of eighteen women Rugby union players (eight forwards and ten backs) aged between 18 – 36 years old were assessed during training (for a total of nine sessions). To inform the participants’ characteristics, the players’ demographic, and anthropometric characteristics (age, stature, and body mass) were obtained. Using GPS and Zephyr technology the players’ training physical (time spent in speed zones, maximum speed, total distance travelled, number of impacts in the various impact zones) and physiological (heart rate) demands were explored. Statistical analysis methods including descriptive, independent t-test, one-way and two-way ANOVA tests were employed to analyse the data and evaluate the differences between forwards and backs. The mean age and stature for all players was 25,44±5,6 years and 1,60±0,06 m respectively, with no significant differences found between backs and forwards. With regards to body mass, forwards weighed 82,0±9,4 kg while backs weighed significantly lighter at 58,0±5,8 kg. Significant differences (p < 0,05) were found for all players in the time spent in speed zones and the number of impacts in impact zones. When all forwards’ and backs’ physical and physiological demands were compared the results showed no significant differences. The average time spent in all six speed zones combined was 11,41 and 11,62 mins for forwards and backs, respectively. The maximum speeds reached by forwards (21,35±5,72 km/h) and backs (22,85±3,88 km/h) were similar. All players combined travelled an average total distance of 2,14±0,76 km. The total number of impacts in all six impact zones, totalled 116 impacts for forwards and 97 for backs. Heart rate responses recorded for forwards and backs were 139±15 bpm and 134±13 bpm. Based on the findings of this study, the training intensity of amateur women’s Rugby union was lower than the demands experienced in the training and match-play of previous research. It was also observed that there was no specificity with regards to the training programs allocated between forwards and backs of this study. Further research on amateur women’s Rugby union is required to characterise training and match-play demands of these players. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
Quantifying the work demands of municipal waste workers to determine physical workload and perception
- Authors: Mamabolo, Lerato
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424267 , vital:72138
- Description: Objective: This study aimed to quantify physical and perceptual workloads through the nature of the work demands of municipal waste workers. Waste workers investigated were waste collectors, street sweepers [or public cleansers], drivers and mechanics. Methods: 154 City of Tshwane municipal waste workers volunteered to participate in the study. Observation-based tools were used to measure physical workload namely, the RAMP 1 and 2, REBA and RULA, and the hand-held dynamometer was used for pushing and pulling tasks. Subjective perceptual questionnaires were used to measure Perceptual load namely the NASA TLX and the QWIQ. Results: Differences in physical workload were evident between the occupation groups. Round bin collection was the waste collection type pertaining to the highest work-related risk of musculoskeletal development. Public cleansers and flatbed truck collectors' results displayed lower task-related risks associated in relation to the other occupations. Significant differences were found between the groups, particularly between waste collectors and drivers [had high workload outputs] in relation to public cleansers [low workload] for both perceptual workload tools. A significant difference was found in the mental and physical demands, as well as the organisational constraints and quantitative workloads. Mechanics showed no significant differences between groups but had high levels of frustration. Conclusion: A relationship between physical and perceived workload intensity is evident. development of musculoskeletal diseases and injury shall incur if measures are not reinstated. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mamabolo, Lerato
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424267 , vital:72138
- Description: Objective: This study aimed to quantify physical and perceptual workloads through the nature of the work demands of municipal waste workers. Waste workers investigated were waste collectors, street sweepers [or public cleansers], drivers and mechanics. Methods: 154 City of Tshwane municipal waste workers volunteered to participate in the study. Observation-based tools were used to measure physical workload namely, the RAMP 1 and 2, REBA and RULA, and the hand-held dynamometer was used for pushing and pulling tasks. Subjective perceptual questionnaires were used to measure Perceptual load namely the NASA TLX and the QWIQ. Results: Differences in physical workload were evident between the occupation groups. Round bin collection was the waste collection type pertaining to the highest work-related risk of musculoskeletal development. Public cleansers and flatbed truck collectors' results displayed lower task-related risks associated in relation to the other occupations. Significant differences were found between the groups, particularly between waste collectors and drivers [had high workload outputs] in relation to public cleansers [low workload] for both perceptual workload tools. A significant difference was found in the mental and physical demands, as well as the organisational constraints and quantitative workloads. Mechanics showed no significant differences between groups but had high levels of frustration. Conclusion: A relationship between physical and perceived workload intensity is evident. development of musculoskeletal diseases and injury shall incur if measures are not reinstated. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
Relating vegetation distribution to cycles of erosion and deposition in the Kromme River wetlands
- Authors: Jarvis, Samuel Cameron
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424582 , vital:72166
- Description: The role of geomorphic disturbance has been increasingly recognized as fundamental in the creation and functioning of wetlands. This is true of the Kromme River wetland which has been formed through repeated cycles of erosion and deposition. However, the response – and influence – of wetland plants to these sorts of disturbance has not been investigated. This study sought to fill this knowledge gap by classifying vegetation communities over a range of hydrological and geomorphic disturbance regimes that have happened over the last few decades, and relating those vegetation communities to environmental factors. The study identified seven vegetation communities based on their species composition and abundance, which were related to geomorphic disturbance events. A conceptual model that accounts for vegetation distribution in the Kromme wetland was developed. Soil saturation was the most important factor explaining vegetation community distribution, which, in turn, is influenced by cycles of erosion and deposition. Following an erosional event on the valley floor, Prionium serratum dominated wetland is converted to a number of other vegetation communities. On the floodplain surface adjacent to the eroded gully, the Prionium serratum dominated wetland is transformed over time to Cynodon dactylon and Sporobolus fimbriatus communities. Prionium serratum clumps immediately adjacent to the recently incised gullies are able to persist, having sufficient access to water. Within the newly formed gullies, Juncus lomatophyllus colonizes the gully beds flooded to a shallow depth, Miscanthus capensis colonizes the gully bars and Setaria incrassata colonizes the exposed gully banks. Localised depositional features close to the thalweg in the gully are colonized by Prionium serratum seedlings and vegetative propagules. These plants represent the regenerating phase of Prionium serratum wetland, which also colonizes depositional floodouts downstream of the newly-formed gully. The Stenotaphrum secundatum community dominates drier, more elevated areas of the floodout. Over time, as the gully fills, Prionium serratum expands beyond the gully onto the valley floor, to replace the floodplain communities Cynodon dactylon and Sporobolus fimbriatus. Over time, Prionium serratum is thought to colonize the valley floor as the gully fills, stabilising it and promoting diffuse flow. Many restoration efforts in damaged palmiet wetlands have been focused on the preservation of intact palmiet communities upstream of erosional headcuts, with limited understanding of vegetation dynamics associated with the cut-and-fill cycles that naturally occur in these wetlands. Understanding the regeneration of Prionium serratum following erosional events is thus important for wetland restoration, as it should focus more attention on promoting palmiet restoration on depositional floodouts downstream of eroded gullies. A secondary aim of this study was to explore the possibility of mapping palmiet communities in Kromme River wetland using remote sensing techniques. Using a combination of ground-truthed data from this and previous studies in the Kromme River wetland, together with raster layers derived from a LiDAR survey, an overlay analysis was developed to effectively map the distribution of the Prionium serratum dominated community. The overlay was created using a machine learning library in RStudios known as Rpart. The results found that the model were 91% effective in classifying the distribution of the Prionium serratum community. A secondary finding was that the inclusion of a Relative Elevation Model in the overlay analysis allowed for the identification of Prionium serratum communities vulnerable to degradation following previous geomorphic disturbance events and those Prionium serratum communities that are likely to persist following a geomorphic disturbance event. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Jarvis, Samuel Cameron
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424582 , vital:72166
- Description: The role of geomorphic disturbance has been increasingly recognized as fundamental in the creation and functioning of wetlands. This is true of the Kromme River wetland which has been formed through repeated cycles of erosion and deposition. However, the response – and influence – of wetland plants to these sorts of disturbance has not been investigated. This study sought to fill this knowledge gap by classifying vegetation communities over a range of hydrological and geomorphic disturbance regimes that have happened over the last few decades, and relating those vegetation communities to environmental factors. The study identified seven vegetation communities based on their species composition and abundance, which were related to geomorphic disturbance events. A conceptual model that accounts for vegetation distribution in the Kromme wetland was developed. Soil saturation was the most important factor explaining vegetation community distribution, which, in turn, is influenced by cycles of erosion and deposition. Following an erosional event on the valley floor, Prionium serratum dominated wetland is converted to a number of other vegetation communities. On the floodplain surface adjacent to the eroded gully, the Prionium serratum dominated wetland is transformed over time to Cynodon dactylon and Sporobolus fimbriatus communities. Prionium serratum clumps immediately adjacent to the recently incised gullies are able to persist, having sufficient access to water. Within the newly formed gullies, Juncus lomatophyllus colonizes the gully beds flooded to a shallow depth, Miscanthus capensis colonizes the gully bars and Setaria incrassata colonizes the exposed gully banks. Localised depositional features close to the thalweg in the gully are colonized by Prionium serratum seedlings and vegetative propagules. These plants represent the regenerating phase of Prionium serratum wetland, which also colonizes depositional floodouts downstream of the newly-formed gully. The Stenotaphrum secundatum community dominates drier, more elevated areas of the floodout. Over time, as the gully fills, Prionium serratum expands beyond the gully onto the valley floor, to replace the floodplain communities Cynodon dactylon and Sporobolus fimbriatus. Over time, Prionium serratum is thought to colonize the valley floor as the gully fills, stabilising it and promoting diffuse flow. Many restoration efforts in damaged palmiet wetlands have been focused on the preservation of intact palmiet communities upstream of erosional headcuts, with limited understanding of vegetation dynamics associated with the cut-and-fill cycles that naturally occur in these wetlands. Understanding the regeneration of Prionium serratum following erosional events is thus important for wetland restoration, as it should focus more attention on promoting palmiet restoration on depositional floodouts downstream of eroded gullies. A secondary aim of this study was to explore the possibility of mapping palmiet communities in Kromme River wetland using remote sensing techniques. Using a combination of ground-truthed data from this and previous studies in the Kromme River wetland, together with raster layers derived from a LiDAR survey, an overlay analysis was developed to effectively map the distribution of the Prionium serratum dominated community. The overlay was created using a machine learning library in RStudios known as Rpart. The results found that the model were 91% effective in classifying the distribution of the Prionium serratum community. A secondary finding was that the inclusion of a Relative Elevation Model in the overlay analysis allowed for the identification of Prionium serratum communities vulnerable to degradation following previous geomorphic disturbance events and those Prionium serratum communities that are likely to persist following a geomorphic disturbance event. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
Remote sensing as a monitoring solution for water hyacinth (Pontederia crassipes) in the context of the biological control programme at Hartbeespoort Dam
- Authors: Kinsler, David Louis
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424599 , vital:72167
- Description: Water hyacinth (Pontederia crassipes (C.Mart.) Solms (Pontederiaceae)) is a significant aquatic weed both globally and in South Africa. Despite notable success with biological control of other invasive macrophytes, the plant remains as a problematic weed in many aquatic systems in South Africa, particularly due to the eutrophic status of many of its water systems, as well as the plant’s tolerance to cooler climatic conditions than most of its existing biological control agents. Hartbeespoort Dam, located about 30 kilometres west of Pretoria, South Africa, has been infamously infested with water hyacinth for decades, which impacts the important socioeconomic utility of the dam and functioning of natural ecological processes in the system. The dam has a long history of efforts to control water hyacinth, which include widespread herbicidal spray, mechanical removal and classical biological control programmes since the early 1990s - mostly with limited or short-lived success. However, after the introduction of a new, cold-tolerant biological control agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae) in 2018 with an inundative release strategy, the water hyacinth dropped significantly from a maximum cover of about 45 percent (819 hectares) down to less than two percent (40 hectares) over a three-month period (November 2019 – January 2020). This was significant, as it marked the first successful biological control of water hyacinth in a eutrophic, temperate system in South Africa. However, due to the scale of Hartbeespoort Dam (1820 hectares) and the high spatiotemporal variation of the floating mats across time and space, quantifying and monitoring these rapid changes has proved difficult. In response to this problem, this thesis proposed a remote sensing solution to address the need for accurate, timely and readily accessible monitoring data of the water hyacinth population on the dam. Leveraging the temporally frequent (< 5 days revisit time) Sentinel-2 multispectral satellite data, as well as the powerful cloud-computing resources of Google Earth Engine, this thesis developed and deployed a relatively simple and robust index-based decision tree classification method to demonstrate the value of these technologies as an effective monitoring and analysis tool for monitoring large macrophyte infestations. To this end, several challenges had to be overcome in order to produce easily accessible data that was accurate and reliable. For example, due to the size of the Sentinel-2 Level-1C image dataset from August 2015 to March 2021 (n = 654), an automated process of filtering out clouded images was required. Additionally, the co-presence of algal and cyanobacterial blooms necessitated the development of a novel index, coined the Algae Resistant Macrophyte Index (ARMI), to deal with the challenges of accurate macrophyte detection. The high spatiotemporal variability of the floating mats meant that a typical, location-based confusion matrix as a means of assessing the accuracy of the decision tree classifier required a different approach which compared the total classified areas with higher resolution images. This thesis aims to demonstrate the utility of remote sensing tools to provide effective monitoring information to managers, researchers and other stakeholders. There is scope to expand to more areas in South Africa and beyond and may prove an invaluable tool to augment and support on-going and future macrophyte monitoring programmes. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Kinsler, David Louis
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424599 , vital:72167
- Description: Water hyacinth (Pontederia crassipes (C.Mart.) Solms (Pontederiaceae)) is a significant aquatic weed both globally and in South Africa. Despite notable success with biological control of other invasive macrophytes, the plant remains as a problematic weed in many aquatic systems in South Africa, particularly due to the eutrophic status of many of its water systems, as well as the plant’s tolerance to cooler climatic conditions than most of its existing biological control agents. Hartbeespoort Dam, located about 30 kilometres west of Pretoria, South Africa, has been infamously infested with water hyacinth for decades, which impacts the important socioeconomic utility of the dam and functioning of natural ecological processes in the system. The dam has a long history of efforts to control water hyacinth, which include widespread herbicidal spray, mechanical removal and classical biological control programmes since the early 1990s - mostly with limited or short-lived success. However, after the introduction of a new, cold-tolerant biological control agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae) in 2018 with an inundative release strategy, the water hyacinth dropped significantly from a maximum cover of about 45 percent (819 hectares) down to less than two percent (40 hectares) over a three-month period (November 2019 – January 2020). This was significant, as it marked the first successful biological control of water hyacinth in a eutrophic, temperate system in South Africa. However, due to the scale of Hartbeespoort Dam (1820 hectares) and the high spatiotemporal variation of the floating mats across time and space, quantifying and monitoring these rapid changes has proved difficult. In response to this problem, this thesis proposed a remote sensing solution to address the need for accurate, timely and readily accessible monitoring data of the water hyacinth population on the dam. Leveraging the temporally frequent (< 5 days revisit time) Sentinel-2 multispectral satellite data, as well as the powerful cloud-computing resources of Google Earth Engine, this thesis developed and deployed a relatively simple and robust index-based decision tree classification method to demonstrate the value of these technologies as an effective monitoring and analysis tool for monitoring large macrophyte infestations. To this end, several challenges had to be overcome in order to produce easily accessible data that was accurate and reliable. For example, due to the size of the Sentinel-2 Level-1C image dataset from August 2015 to March 2021 (n = 654), an automated process of filtering out clouded images was required. Additionally, the co-presence of algal and cyanobacterial blooms necessitated the development of a novel index, coined the Algae Resistant Macrophyte Index (ARMI), to deal with the challenges of accurate macrophyte detection. The high spatiotemporal variability of the floating mats meant that a typical, location-based confusion matrix as a means of assessing the accuracy of the decision tree classifier required a different approach which compared the total classified areas with higher resolution images. This thesis aims to demonstrate the utility of remote sensing tools to provide effective monitoring information to managers, researchers and other stakeholders. There is scope to expand to more areas in South Africa and beyond and may prove an invaluable tool to augment and support on-going and future macrophyte monitoring programmes. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
Revisionist narratives: locating six Black artist-teachers onto the map of twentieth-century modern art in Zimbabwe
- Authors: Muvhuti, Tichapera Barnabas
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432444 , vital:72871 , DOI 10.21504/10962/432444
- Description: Job Kekana (1916-1995) was a South African sculptor and teacher who moved to Zimbabwe in 1944, where he founded the Kekana School of Art and Craft in the early 1960s. There were also a few Black Zimbabwean artist-teachers, namely, Sam Songo (1929-1977), Cornelius Manguma (b. 1935), Lazarus Khumalo (1930-2015), Joram Mariga (1927-2000) John Hlatywayo (b. 1928), who were either working with missionaries Canon Edward Paterson (1895-1974) and Father John Groeber (1903-1973) at the Cyrene and Serima workshops respectively and later on at the Mzilikazi Arts and Crafts Centre, or with Frank McEwen (1907- 1994) at the National Gallery school. This thesis examines the relative invisibility of Kekana and the selected Black artist-teachers in the dominant discourse of the history and development of modern art in Zimbabwe. Employing the biographical approach as a methodology, and modernism as an analytical tool and foregrounding African thinkers like Chika Okeke-Agulu Elizabeth Georgis, Emma Wolukau- Wanambwa and Salah Hassan, this research exposes the possible reasons for their exclusion from the canon, which are rooted in a gatekeeping culture shown by actors in the local art scene, including art historians and scholars, as well as cultural workers in institutions like the National Gallery of Zimbabwe who have not sufficiently questioned and possibly shaken the enshrined legacies of Paterson, Groeber and McEwen. Canons mostly tend to tell a story that privileges and excludes others from the art narrative of a nation. With the arrival of Frank McEwen on the scene in the late 1950s the stone sculpture tradition rose to prominence in such a way that it overshadowed other forms of art produced in the two mission schools or workshops at Serima and Cyrene. In the process, Kekana and his students at the Kekana School of Art and Craft were relegated to the peripheries of the canon as they carved in wood and tended to work in a more representational style. While there is literature acknowledging the role of the missionaries in laying the foundation of modern art in Zimbabwe, local artists-cum-teachers working with them are only recognised as a footnote on the nation’s map of modern art. Recognising that canons are always evolving and shifting, and without discrediting the work of the three mentioned expatriates – and to an extent that of Tom Blomefield of the Tengenenge Workshop – this thesis attempts to expand the canon by arguing for the inclusion of the critiqued overlooked six. Citing the efforts of researchers, scholars and curators in multicultural South Africa to bring the previously marginalised generation of Black modernists into the mainstream, this thesis demonstrates that it is possible to spotlight the narratives of the Black artists and teachers who continue to occupy peripheral space in the history of Zimbabwe. This comparative analysis is done bearing in mind the temptation of falling into the trap of glorifying ‘South African exceptionalism’. In analysing the Black artist-teachers’ contributions as a counter-narrative, this research proposes a more heterogeneous modernism and revisionist art history. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Muvhuti, Tichapera Barnabas
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432444 , vital:72871 , DOI 10.21504/10962/432444
- Description: Job Kekana (1916-1995) was a South African sculptor and teacher who moved to Zimbabwe in 1944, where he founded the Kekana School of Art and Craft in the early 1960s. There were also a few Black Zimbabwean artist-teachers, namely, Sam Songo (1929-1977), Cornelius Manguma (b. 1935), Lazarus Khumalo (1930-2015), Joram Mariga (1927-2000) John Hlatywayo (b. 1928), who were either working with missionaries Canon Edward Paterson (1895-1974) and Father John Groeber (1903-1973) at the Cyrene and Serima workshops respectively and later on at the Mzilikazi Arts and Crafts Centre, or with Frank McEwen (1907- 1994) at the National Gallery school. This thesis examines the relative invisibility of Kekana and the selected Black artist-teachers in the dominant discourse of the history and development of modern art in Zimbabwe. Employing the biographical approach as a methodology, and modernism as an analytical tool and foregrounding African thinkers like Chika Okeke-Agulu Elizabeth Georgis, Emma Wolukau- Wanambwa and Salah Hassan, this research exposes the possible reasons for their exclusion from the canon, which are rooted in a gatekeeping culture shown by actors in the local art scene, including art historians and scholars, as well as cultural workers in institutions like the National Gallery of Zimbabwe who have not sufficiently questioned and possibly shaken the enshrined legacies of Paterson, Groeber and McEwen. Canons mostly tend to tell a story that privileges and excludes others from the art narrative of a nation. With the arrival of Frank McEwen on the scene in the late 1950s the stone sculpture tradition rose to prominence in such a way that it overshadowed other forms of art produced in the two mission schools or workshops at Serima and Cyrene. In the process, Kekana and his students at the Kekana School of Art and Craft were relegated to the peripheries of the canon as they carved in wood and tended to work in a more representational style. While there is literature acknowledging the role of the missionaries in laying the foundation of modern art in Zimbabwe, local artists-cum-teachers working with them are only recognised as a footnote on the nation’s map of modern art. Recognising that canons are always evolving and shifting, and without discrediting the work of the three mentioned expatriates – and to an extent that of Tom Blomefield of the Tengenenge Workshop – this thesis attempts to expand the canon by arguing for the inclusion of the critiqued overlooked six. Citing the efforts of researchers, scholars and curators in multicultural South Africa to bring the previously marginalised generation of Black modernists into the mainstream, this thesis demonstrates that it is possible to spotlight the narratives of the Black artists and teachers who continue to occupy peripheral space in the history of Zimbabwe. This comparative analysis is done bearing in mind the temptation of falling into the trap of glorifying ‘South African exceptionalism’. In analysing the Black artist-teachers’ contributions as a counter-narrative, this research proposes a more heterogeneous modernism and revisionist art history. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2023
- Full Text:
- Date Issued: 2023-10-13
Screening isolation and biological characterization of antibacterial secondary metabolites from macrofauna endemic to the southern African coast
- Authors: Njanje, Idris
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431944 , vital:72817
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Njanje, Idris
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431944 , vital:72817
- Description: Access restricted. Expected release date in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
Seeing diplomatic constellations through diplomatic relations: an analysis of the positioning of Zimbabwe and the UK in Zimbabwean news articles
- Mvundura, Emaculate Musimeki
- Authors: Mvundura, Emaculate Musimeki
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432388 , vital:72866 , DOI 10.21504/10962/432389
- Description: This study examines the positioning of Zimbabwe and the United Kingdom (UK) in the language of news articles about diplomatic relations between the two countries published in two prominent Zimbabwean newspapers, The Herald and The Standard, between 2016 and 2020, using Systemic Functional Linguistics (SFL) and Legitimation Code Theory (LCT). Zimbabwe's present diplomatic discourses are a product of its colonial and post-independence history. This thesis places The Herald and The Standard within the larger context of the Zimbabwean media landscape as a state-owned and a privately owned newspaper, respectively. It contends that the two newspapers influence the positioning of Zimbabwe and the United Kingdom in public spheres where readers engage with the news concerning diplomatic ties. The research begins with a corpus-based examination of 42 news articles published between 2016 and 2020 in The Herald and The Standard. The investigation identified several angles through which Zimbabwe and the UK are positioned in the coverage. Zimbabwe is positioned through reference to its reform agenda, intentions for free and fair elections, and its diplomatic re-engagement drive. The UK is positioned as a source of development funding and new trade agreements, while improved diplomatic relations and the removal of restrictive measures against Zimbabwe are anticipated. Fine-grained analysis was conducted on four articles, two from each newspaper, selected to reflect the trends found in the corpus analysis. The fine-grained analyses showed how linguistic resources contributed to the positioning of the UK and Zimbabwe. Complementary analyses of these articles were conducted using LCT and SFL to describe how readers' knowledge of diplomatic relations is built using language in The Herald and The Standard. The study used the concepts of constellations and cosmologies from LCT to demonstrate how diplomatic knowledge is built in these news articles. In the articles, the constellations are related to policies such as Zimbabwe's reform agenda, people (diplomats and government officials) and moral judgments. Both newspapers contain both positive and negative positioning of Zimbabwe and the UK. However, The Standard is generally critical of removing the UK's sanctions on Zimbabwe and of the Zimbabwean government's reform agenda. Meanwhile, The Herald justifies Zimbabwe's Fast-track Land Reform Programme as resulting from Britain's refusal to fund a land redistribution programme as per the 1979 Lancaster House Agreement. The use of SFL's Appraisal framework helps to examine the linguistic resources used by The Herald and The Standard to describe the positioning of the two countries in relation to each other. Lexical strings help to establish diplomatic positioning in the news articles. These couple with Appraisal to accomplish individuation and affiliation. Affect and Judgement resources revealed the decisions taken by the UK to solve the conflict by encouraging the implementation of a reform agenda by Zimbabwe. Negative evaluation is consistently used to disalign with sanctions. The emerging patterns in the data show that diplomats representing the UK affiliate with Zimbabwe's stated economic and political reforms, and the government of Zimbabwe affiliates with the new trade agreement between Zimbabwe and the UK. At the same time, the UK diplomats individuate away from human rights abuses and the Fast-track Land Reform Programme. Affiliation strengthens confidence in diplomatic ties between Zimbabwe and the UK because the emphasis is placed on restoring them despite the conditions attached. The Herald and The Standard position Zimbabwe as a reformed country ready to implement policies to improve citizens' lives and as a country violating human rights and the rule of law. They position the UK as asserting power over Zimbabwe, willing to resolve the crisis through its foreign policy, and credited for assisting Zimbabwe. This strengthens re-engagement in diplomatic relations and commercial trade between the UK and Zimbabwe. In light of these findings, Zimbabweans are encouraged to cultivate an awareness that enables them to reflect on the challenges associated with diplomatic discourses and the implications for critically analysing the re-engagement initiative. They can promote re-engagement by being cognisant of specific values portrayed in The Herald and The Standard and challenging these values in the light of policy transformation to revive the relations between the two countries. The re-engagement process requires a transformation in Zimbabwe's modus operandi to improve the country's positioning in the diplomatic relations between it and the UK. , Thesis (PhD) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mvundura, Emaculate Musimeki
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432388 , vital:72866 , DOI 10.21504/10962/432389
- Description: This study examines the positioning of Zimbabwe and the United Kingdom (UK) in the language of news articles about diplomatic relations between the two countries published in two prominent Zimbabwean newspapers, The Herald and The Standard, between 2016 and 2020, using Systemic Functional Linguistics (SFL) and Legitimation Code Theory (LCT). Zimbabwe's present diplomatic discourses are a product of its colonial and post-independence history. This thesis places The Herald and The Standard within the larger context of the Zimbabwean media landscape as a state-owned and a privately owned newspaper, respectively. It contends that the two newspapers influence the positioning of Zimbabwe and the United Kingdom in public spheres where readers engage with the news concerning diplomatic ties. The research begins with a corpus-based examination of 42 news articles published between 2016 and 2020 in The Herald and The Standard. The investigation identified several angles through which Zimbabwe and the UK are positioned in the coverage. Zimbabwe is positioned through reference to its reform agenda, intentions for free and fair elections, and its diplomatic re-engagement drive. The UK is positioned as a source of development funding and new trade agreements, while improved diplomatic relations and the removal of restrictive measures against Zimbabwe are anticipated. Fine-grained analysis was conducted on four articles, two from each newspaper, selected to reflect the trends found in the corpus analysis. The fine-grained analyses showed how linguistic resources contributed to the positioning of the UK and Zimbabwe. Complementary analyses of these articles were conducted using LCT and SFL to describe how readers' knowledge of diplomatic relations is built using language in The Herald and The Standard. The study used the concepts of constellations and cosmologies from LCT to demonstrate how diplomatic knowledge is built in these news articles. In the articles, the constellations are related to policies such as Zimbabwe's reform agenda, people (diplomats and government officials) and moral judgments. Both newspapers contain both positive and negative positioning of Zimbabwe and the UK. However, The Standard is generally critical of removing the UK's sanctions on Zimbabwe and of the Zimbabwean government's reform agenda. Meanwhile, The Herald justifies Zimbabwe's Fast-track Land Reform Programme as resulting from Britain's refusal to fund a land redistribution programme as per the 1979 Lancaster House Agreement. The use of SFL's Appraisal framework helps to examine the linguistic resources used by The Herald and The Standard to describe the positioning of the two countries in relation to each other. Lexical strings help to establish diplomatic positioning in the news articles. These couple with Appraisal to accomplish individuation and affiliation. Affect and Judgement resources revealed the decisions taken by the UK to solve the conflict by encouraging the implementation of a reform agenda by Zimbabwe. Negative evaluation is consistently used to disalign with sanctions. The emerging patterns in the data show that diplomats representing the UK affiliate with Zimbabwe's stated economic and political reforms, and the government of Zimbabwe affiliates with the new trade agreement between Zimbabwe and the UK. At the same time, the UK diplomats individuate away from human rights abuses and the Fast-track Land Reform Programme. Affiliation strengthens confidence in diplomatic ties between Zimbabwe and the UK because the emphasis is placed on restoring them despite the conditions attached. The Herald and The Standard position Zimbabwe as a reformed country ready to implement policies to improve citizens' lives and as a country violating human rights and the rule of law. They position the UK as asserting power over Zimbabwe, willing to resolve the crisis through its foreign policy, and credited for assisting Zimbabwe. This strengthens re-engagement in diplomatic relations and commercial trade between the UK and Zimbabwe. In light of these findings, Zimbabweans are encouraged to cultivate an awareness that enables them to reflect on the challenges associated with diplomatic discourses and the implications for critically analysing the re-engagement initiative. They can promote re-engagement by being cognisant of specific values portrayed in The Herald and The Standard and challenging these values in the light of policy transformation to revive the relations between the two countries. The re-engagement process requires a transformation in Zimbabwe's modus operandi to improve the country's positioning in the diplomatic relations between it and the UK. , Thesis (PhD) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2023
- Full Text:
- Date Issued: 2023-10-13
Selected medicinal plants leaves identification: a computer vision approach
- Authors: Deyi, Avuya
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424552 , vital:72163
- Description: Identifying and classifying medicinal plants are valuable and essential skills during drug manufacturing because several active pharmaceutical ingredients (API) are sourced from medicinal plants. For many years, identifying and classifying medicinal plants have been exclusively done by experts in the domain, such as botanists, and herbarium curators. Recently, powerful computer vision technologies, using machine learning and deep convolutional neural networks, have been developed for classifying or identifying objects on images. A convolutional neural network is a deep learning architecture that outperforms previous advanced approaches in image classification and object detection based on its efficient features extraction on images. In this thesis, we investigate different convolutional neural networks and machine learning algorithms for identifying and classifying leaves of three species of the genus Brachylaena. The three species considered are Brachylaena discolor, Brachylaena ilicifolia and Brachylaena elliptica. All three species are used medicinally by people in South Africa to treat diseases like diabetes. From 1259 labelled images of those plants species (at least 400 for each species) split into training, evaluation and test sets, we trained and evaluated different deep convolutional neural networks and machine learning models. The VGG model achieved the best results with 98.26% accuracy from cross-validation. , Thesis (MSc) -- Faculty of Science, Mathematics, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Deyi, Avuya
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424552 , vital:72163
- Description: Identifying and classifying medicinal plants are valuable and essential skills during drug manufacturing because several active pharmaceutical ingredients (API) are sourced from medicinal plants. For many years, identifying and classifying medicinal plants have been exclusively done by experts in the domain, such as botanists, and herbarium curators. Recently, powerful computer vision technologies, using machine learning and deep convolutional neural networks, have been developed for classifying or identifying objects on images. A convolutional neural network is a deep learning architecture that outperforms previous advanced approaches in image classification and object detection based on its efficient features extraction on images. In this thesis, we investigate different convolutional neural networks and machine learning algorithms for identifying and classifying leaves of three species of the genus Brachylaena. The three species considered are Brachylaena discolor, Brachylaena ilicifolia and Brachylaena elliptica. All three species are used medicinally by people in South Africa to treat diseases like diabetes. From 1259 labelled images of those plants species (at least 400 for each species) split into training, evaluation and test sets, we trained and evaluated different deep convolutional neural networks and machine learning models. The VGG model achieved the best results with 98.26% accuracy from cross-validation. , Thesis (MSc) -- Faculty of Science, Mathematics, 2023
- Full Text:
- Date Issued: 2023-10-13
Silica supported sulfuric acid-catalysed one-pot processes for the synthesis of n-heterocycles
- Authors: Ndagano, Urbain Nshokano
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431921 , vital:72815
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Ndagano, Urbain Nshokano
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/431921 , vital:72815
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Chemistry, 2023
- Full Text:
- Date Issued: 2023-10-13
South African women’s experience of the decision, procedure and recovery from “feticide” and late termination of pregnancy due to the presence of severe fetal abnormality: women’s and health service providers’ perspectives
- Authors: Vorster, Angela Carol
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432359 , vital:72864 , DOI 10.21504/10962/432359
- Description: Routine antenatal care, including sonography and genetic testing, assist healthcare providers in identifying the presence of severe fetal abnormality. In countries where it is legal, the option to abort such a pregnancy may be presented to the pregnant person. When abortion takes place after the thirteenth week of gestation, it is generally referred to as a late termination of pregnancy and may entail the induction of labour or caesarean section. In cases where termination of the pregnancy is decided upon, and the gestation is further than 21 weeks and six days, the feticide procedure is recommended in order to ensure stillbirth. The feticide procedure entails the injection of potassium chloride directly into the fetal heart in order to ensure fetal demise. Existing literature on “feticide” and late termination of pregnancy (LTOP) owing to fetal abnormalities mostly takes a medical or psychological perspective in researching these procedures. Within the South African context, there are very few studies on feticide and LTOP, with none of these studies (to date – 8 January 2023) taking a feminist approach. This paucity of research that takes into account power relations, structural inequality and factors that affect decision-making and choice is one of the reasons that this study was undertaken. The main research question focused on in this study is: What are South African women’s experiences of feticide and late termination of pregnancy due to the presence of severe fetal abnormality, as related by the women themselves and the health service providers who perform the procedure or provide care? The sub-questions that initially drove the study were: How do the women relate their experience of the process of coming to the decision, undergoing and recovering from the procedure, and how do health service providers relate the experiences of these women? The methodological and theoretical framework employed in this research was a Feminist Social Constructionist approach to Grounded Theory. This reflexive, subjectivist, feminist lens encouraged awareness of the influence of gender, race, class and other structural and systemic factors on women’s experiences within the two healthcare systems. Data collection entailed semi-structured interviews conducted with 12 women, who had undergone feticide and LTOP procedures between one and five years prior to the interviews, in either the public or private healthcare system in South Africa. Semi-structured interviews were also conducted with 13 healthcare providers. The providers included medical specialists and participants from the fields of clinical psychology, genetic counselling and nursing and were employed in public or private healthcare in South Africa. Data relevant to public healthcare users and providers were collected from one tertiary (academic) public healthcare hospital and data regarding private healthcare users and providers were collected from across South Africa. Women’s constructions of their experiences of feticide and LTOP included stark contrasts between public and private healthcare users in South Africa, as well as women experiencing “no choice” and their voices being ignored or silenced. Healthcare providers’ constructions were frequently contradictory, referring to women as having freedom of choice and their needs largely prioritised within the healthcare system, while the providers within the public healthcare system relayed their own frustrations and emotional burden due to systemic failures. Findings from women and providers’ constructions were synthesised into a theoretical understanding of women’s experiences of feticide and LTOP in South Africa, which is grounded in, and emergent from, the data. Women’s experiences of feticide and LTOP in South Africa were conceptualised by framing the three phases of these experiences, namely the decision-making phase (I), undergoing the procedures and in-hospital recovery (phase II) and the recovery phase (III). The most prominent themes emerging in these phases included the schism between the public and private healthcare systems in South Africa, the lack of real choice women experience, as well as the silencing of women and providers with regard to feticide and LTOP. Underlying the three phases, and directly influencing the three prominent themes affecting women’s experiences, were the underlying and insidious structural inequality that undermined reproductive justice with regard to women’s decision-making, experiences of and recovery from feticide and LTOP. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Vorster, Angela Carol
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432359 , vital:72864 , DOI 10.21504/10962/432359
- Description: Routine antenatal care, including sonography and genetic testing, assist healthcare providers in identifying the presence of severe fetal abnormality. In countries where it is legal, the option to abort such a pregnancy may be presented to the pregnant person. When abortion takes place after the thirteenth week of gestation, it is generally referred to as a late termination of pregnancy and may entail the induction of labour or caesarean section. In cases where termination of the pregnancy is decided upon, and the gestation is further than 21 weeks and six days, the feticide procedure is recommended in order to ensure stillbirth. The feticide procedure entails the injection of potassium chloride directly into the fetal heart in order to ensure fetal demise. Existing literature on “feticide” and late termination of pregnancy (LTOP) owing to fetal abnormalities mostly takes a medical or psychological perspective in researching these procedures. Within the South African context, there are very few studies on feticide and LTOP, with none of these studies (to date – 8 January 2023) taking a feminist approach. This paucity of research that takes into account power relations, structural inequality and factors that affect decision-making and choice is one of the reasons that this study was undertaken. The main research question focused on in this study is: What are South African women’s experiences of feticide and late termination of pregnancy due to the presence of severe fetal abnormality, as related by the women themselves and the health service providers who perform the procedure or provide care? The sub-questions that initially drove the study were: How do the women relate their experience of the process of coming to the decision, undergoing and recovering from the procedure, and how do health service providers relate the experiences of these women? The methodological and theoretical framework employed in this research was a Feminist Social Constructionist approach to Grounded Theory. This reflexive, subjectivist, feminist lens encouraged awareness of the influence of gender, race, class and other structural and systemic factors on women’s experiences within the two healthcare systems. Data collection entailed semi-structured interviews conducted with 12 women, who had undergone feticide and LTOP procedures between one and five years prior to the interviews, in either the public or private healthcare system in South Africa. Semi-structured interviews were also conducted with 13 healthcare providers. The providers included medical specialists and participants from the fields of clinical psychology, genetic counselling and nursing and were employed in public or private healthcare in South Africa. Data relevant to public healthcare users and providers were collected from one tertiary (academic) public healthcare hospital and data regarding private healthcare users and providers were collected from across South Africa. Women’s constructions of their experiences of feticide and LTOP included stark contrasts between public and private healthcare users in South Africa, as well as women experiencing “no choice” and their voices being ignored or silenced. Healthcare providers’ constructions were frequently contradictory, referring to women as having freedom of choice and their needs largely prioritised within the healthcare system, while the providers within the public healthcare system relayed their own frustrations and emotional burden due to systemic failures. Findings from women and providers’ constructions were synthesised into a theoretical understanding of women’s experiences of feticide and LTOP in South Africa, which is grounded in, and emergent from, the data. Women’s experiences of feticide and LTOP in South Africa were conceptualised by framing the three phases of these experiences, namely the decision-making phase (I), undergoing the procedures and in-hospital recovery (phase II) and the recovery phase (III). The most prominent themes emerging in these phases included the schism between the public and private healthcare systems in South Africa, the lack of real choice women experience, as well as the silencing of women and providers with regard to feticide and LTOP. Underlying the three phases, and directly influencing the three prominent themes affecting women’s experiences, were the underlying and insidious structural inequality that undermined reproductive justice with regard to women’s decision-making, experiences of and recovery from feticide and LTOP. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2023
- Full Text:
- Date Issued: 2023-10-13