Constraints in attainment of sustainable human settlements at Kwamaphumulo Local Municipality
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- Kwamaphumulo Local Municipality , Land settlement -- South Africa -- Kwamaphumulo Local Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48808 , vital:41141
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
- Authors: Sikhosana, Phindokuhle
- Date: 2020
- Subjects: Human settlements -- South Africa -- Kwamaphumulo Local Municipality , Land settlement -- South Africa -- Kwamaphumulo Local Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48808 , vital:41141
- Description: This study sought to investigate the constraints in the attainment of sustainable human settlement in KwaMaphumulo Local Municipality at iLembe District in KwaZulu-Natal, South Africa. The aim of this study was to investigate the constraints that limit the achievement of the ideal of sustainable human settlement development in the KwaMaphumulo Local Municipality. Furthermore, the study sought to determine the impact of these constraints on sustainable development and to proffer measures that can be taken to combat stagnant or underdevelopment in the area. A mixed-method approach is followed in this study, which considers a triangulation of quantitative and qualitative data collection, analysis and interpretation techniques. It is important to note that in the past years since South Africa became a democratic country, there have been countless efforts with regard to overcoming the problems created during the apartheid era. These problems stemmed from a distorted spatial, social, economic and political background that was advocated by both segregationist public policies and the planning systems of the Apartheid Regime. In recent years, South African cities have also been faced with environmental issues, which are imperative to the future development of the country. With all these issues in mind, we see that the many efforts that are put in place by government always fall short of solving the problems. This research report looked at the constraints that affect the KwaMaphumulo Local Municipality in attaining sustainable human settlements and whether the efforts of redistribution and equality have been enough to overcome the problems. The key findings of the study were that constraints in attaining sustainable human settlements in the KwaMaphumulo Local Municipality negatively impacts on the development in the area. The level of services being provided is poor. There is an apparent disconnect between traditional leaders and the municipality councillor as development management and vision are concerned. Furthermore, the development programmes and projects do not seem to address the critical needs of the community. Housing development is narrow minded with a focus on the top structure and a failure to include basic services and infrastructure. Houses built that are 6 financed by subsidies are of poor quality. The latter situation results in more able‐ bodied, skilled and capable people emigrating to developed areas.
- Full Text:
- Date Issued: 2020
Continuous flow synthesis of imatinib intermediates
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
The influence of anthropogenic and environmental covariates on the habitat use and density of sympatric carnivores, Limpopo Province, South Africa
- Authors: Faure, J Philip B
- Date: 2020
- Subjects: Carnivorous animals -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48302 , vital:40840
- Description: Carnivores are declining and undergoing substantial range contractions which have largely been attributed to anthropogenic related. Globally, there has been an increase in establishing protected areas for species conservation. However, protected areas may not always effectively conserve all biodiversity, where some areas are too small for viable populations of wide-ranging species, such as leopards Panthera pardus, spotted hyaenas Crocuta crocuta, and brown hyaenas Parahyaena brunnea. The importance of privately-owned areas are gaining increasing recognition for their role in conserving species, and ecosystems. Though such areas may provide key opportunities for the conservation and persistence of biodiversity, little attention (with regards to species conservation planning) is given to these areas. Furthermore, large carnivore populations increasingly have to share the landscapes with humans as the global human population increase. Though anthropogenic impacts can be limited within protected areas, human activities on privately-owned farmlands are mostly dictated by economic activity to sustain human presence (often leading to humancarnivore conflicts). Platjan (South Africa) is one such area. It comprise a matrix of agricultural practices and land-use types, dominated by humans. Consequently, it presented an ideal landscape to investigate how humans and carnivores coexist. Spatial capture-recapture modelling suggest stable populations manifested through low densities for leopards, spotted hyaenas, brown hyaenas, and Africa civet Civettictis civetta within the study area. Densities of the focal species were more similar to what has been found in more arid environments. Though it should be noted, that population fluctuations are common in nature, and this study only provide a brief snapshot of the population. Nonetheless, it provides baseline carnivore density estimates for the area. Single-season, single-species occupancy modelling was used to determine the influence of anthropogenic variables on species probability of site use. Results suggested that leopards and spotted hyaenas avoided crop fields (possibly due to higher human activity in these areas). Whereas black-backed jackal Canis mesomelas were positively influenced by the proportion of survey sites containing human infrastructure (possibly due to additional food sources provided by human presence). The covariates did not suggest any effect on brown hyaena and African civet probability of site use, which may be explained by temporal niche partitioning between the species and humans. Kernel density estimation and selectivity ratios revealed that all carnivores were predominantly crepuscular-nocturnal, with the exception of brown hyaenas which were strictly nocturnal. Among the focal species, brown hyaenas and African civets had the lowest temporal overlap with humans, which may explain why they weren’t affected by any of the anthropogenic variables. Whereas, jackal had the highest overlap, supporting a notion that they may be more tolerant of human presence than the other study animals. Overall, it seems that carnivores are able to coexist with humans on privately-owned farmlands through temporal niche partitioning, but manifest at rather low densities. Nonetheless, this study adds to the current understanding of human-carnivore coadaptation, and provides the first carnivore density estimates for the Platjan region.
- Full Text:
- Date Issued: 2020
- Authors: Faure, J Philip B
- Date: 2020
- Subjects: Carnivorous animals -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48302 , vital:40840
- Description: Carnivores are declining and undergoing substantial range contractions which have largely been attributed to anthropogenic related. Globally, there has been an increase in establishing protected areas for species conservation. However, protected areas may not always effectively conserve all biodiversity, where some areas are too small for viable populations of wide-ranging species, such as leopards Panthera pardus, spotted hyaenas Crocuta crocuta, and brown hyaenas Parahyaena brunnea. The importance of privately-owned areas are gaining increasing recognition for their role in conserving species, and ecosystems. Though such areas may provide key opportunities for the conservation and persistence of biodiversity, little attention (with regards to species conservation planning) is given to these areas. Furthermore, large carnivore populations increasingly have to share the landscapes with humans as the global human population increase. Though anthropogenic impacts can be limited within protected areas, human activities on privately-owned farmlands are mostly dictated by economic activity to sustain human presence (often leading to humancarnivore conflicts). Platjan (South Africa) is one such area. It comprise a matrix of agricultural practices and land-use types, dominated by humans. Consequently, it presented an ideal landscape to investigate how humans and carnivores coexist. Spatial capture-recapture modelling suggest stable populations manifested through low densities for leopards, spotted hyaenas, brown hyaenas, and Africa civet Civettictis civetta within the study area. Densities of the focal species were more similar to what has been found in more arid environments. Though it should be noted, that population fluctuations are common in nature, and this study only provide a brief snapshot of the population. Nonetheless, it provides baseline carnivore density estimates for the area. Single-season, single-species occupancy modelling was used to determine the influence of anthropogenic variables on species probability of site use. Results suggested that leopards and spotted hyaenas avoided crop fields (possibly due to higher human activity in these areas). Whereas black-backed jackal Canis mesomelas were positively influenced by the proportion of survey sites containing human infrastructure (possibly due to additional food sources provided by human presence). The covariates did not suggest any effect on brown hyaena and African civet probability of site use, which may be explained by temporal niche partitioning between the species and humans. Kernel density estimation and selectivity ratios revealed that all carnivores were predominantly crepuscular-nocturnal, with the exception of brown hyaenas which were strictly nocturnal. Among the focal species, brown hyaenas and African civets had the lowest temporal overlap with humans, which may explain why they weren’t affected by any of the anthropogenic variables. Whereas, jackal had the highest overlap, supporting a notion that they may be more tolerant of human presence than the other study animals. Overall, it seems that carnivores are able to coexist with humans on privately-owned farmlands through temporal niche partitioning, but manifest at rather low densities. Nonetheless, this study adds to the current understanding of human-carnivore coadaptation, and provides the first carnivore density estimates for the Platjan region.
- Full Text:
- Date Issued: 2020
Get sleep or get stumped: sleep behaviour in elite South African cricket players during competition
- Authors: McEwan, Kayla
- Date: 2020
- Subjects: Sleep -- Physiological aspects , Cricket players -- Health and hygiene , Cricket players -- South Africa -- Health and hygiene , Cricket -- Health aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147950 , vital:38696
- Description: Introduction: Good sleep behaviour is associated with achieving optimal athletic performance and reducing the risk of injury. Elite cricket players have unique physical and cognitive demands, and must accommodate for congested competition and travel schedules (all of which increase the risk of disruptive sleep). Further, the political pressures and socioeconomic barriers in South African cricket could affect the sleep of the country’s elite players. Previous research in cricket has focussed on the impact that nutrition, equipment specifications, movement physiology and psychology could elicit on performance (where many professional teams hire support staff to supervise these disciplines); however, there is limited empirical application of sleep research in elite cricket players. Therefore, this study aimed to characterise the sleep behaviours of elite South African cricket players during periods of competition and investigate the relationship between pre-match sleep and cricket performance. Methods: A longitudinal field-based investigation was implemented to monitor the sleep behaviour of 26 elite South African cricket players (age: 28.6 ± 4.0 years; height: 1.8 ± 0.1 m; weight: 85.7 ± 10.8 kg; elite experience: 3.7 ± 4.0 years) during home and away competitive tours. The Morningness-Eveningness Questionnaire and Athlete Sleep Behaviour Questionnaire were administered to identify chronotype and poor sleep behaviours. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post-match. Linear mixed model regression was used to compare differences in sleep variables between time-periods, match venues, player roles, match formats, sleep medication and racial groups. Spearman’s correlation (rs) was used to assess the relationship of substance use (alcohol and caffeine), age, elite experience and match performance with selected sleep indices. Statistical significance for all measures was accepted at p < 0.05. Hedge’s (g) were used as the measure of effect size. Results: Light-emitting technology use, effects of travel, late evening alcohol consumption and muscle soreness were the main factors that impacted sleep. Post-match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post-travel (07:53 ± 01:07; g = 1.19 [0.81;1.57]) and pre-match (08:43 ± 01:03; g = 1.97 [1.55;2.39]) total sleep time. Post-travel sleep onset latency and sleep efficiency were significantly (p < 0.05) shorter (g = 0.74 [0.29;1.29]) and higher (g = 1.35 [0.76;1.94]) at home than away. Although not significant (p > 0.05), allrounders took longer to fall asleep (g = 0.90 [0.23;1.57]), obtained less total sleep (0.76 [0.29;1.42]) and had lower morning freshness scores (g = 1.10 [0.42;1.78]) the night before a match compared to batsmen. Wake after sleep onset and get up time were moderately longer (g = 0.61 [0.22;1.26]) and later (g = 0.62 [0.27;1.17]) before. Twenty20 matches compared to One-Day International matches respectively. Further, sleep duration significantly declined from pre-match to post-match during the multi-day Test format (p = 0.04, g= 0.75 [0.40;1.12]). Late alcohol consumption was significantly (p < 0.05) correlated with a decrease in total sleep time, regardless of match venue (home: rs (49) = -0.69; away: rs (27) = -0.57). During the away condition, an increase in age was significantly associated with longer wake after sleep onset durations (rs (13) = 0.52, p = 0.0003), while greater elite experience was significantly associated with longer total sleep time (rs (72) = 0.36, p = 0.02). The non-sleep medication group took significantly longer to fall asleep compared to the sleep medication group during the first week of the away condition (p = 0.02, g = 0.75 [0.25;1.26]) particularly on nights following transmeridian travel. Although not significant ( p > 0.05), Asian/Indian players had moderately longer sleep onset latencies (g = 1.07 [0.66;1.47]), wake after sleep onset durations (g = 0.86 [0.42;1.29]), and lower subjective sleep quality (g = 0.86 [0.46;1.26]) and morning freshness scores (g = 0.89 [0.47;1.27]) compared to Whites. Similarly, Black Africans had moderately lower subjective sleep quality scores compared to Whites (g = 0.71 [0.43;0.97]). Longer sleep onset latencies and shorter total sleep times were significantly (p < 0.05) associated with poorer One-Day International (rs (28) = -0.57) and Test (rs (12) = 0.59) batting performances respectively. Higher subjective sleep quality scores were significantly associated with better Twenty20 bowling economies (rs (8) = -0.52). Discussion: There was no evidence of poor pre-match sleep behaviour, irrespective of venue; however, the most apparent disruption to sleep occurred post-match (similar to that found in other team-sports). Most disparities in sleep between match venues existed post-travel, with better sleep behaviour observed during the home condition. The differences in sleep patterns found in all three match formats were expected given the variations in format scheduling and duration. Although sleep medication was shown to promote better sleep, its long-term effectiveness was limited. The results promote the implementation of practical strategies aimed to reduce bedtime light-emitting technology use, late evening alcohol consumption and muscle pain. Inter-individual sleep behaviour was found between player roles, age, experience level and race. Moderate associations existed between sleep and markers of batting performance, specifically for the longer, strategic formats of the game. Conclusion: The current study provided new insight of the sleep behaviour in elite South African cricket players during competition. Individualized sleep monitoring practices are encouraged, with specific supervision over older, less experienced players as well as the racial minorities and allrounders of the team. The poor post-match sleep behaviour, together with the sleep and performance correlations, provide ideal opportunities for future interventions to focus on match recovery and the use sleep monitoring as a competitive advantage.
- Full Text:
- Date Issued: 2020
- Authors: McEwan, Kayla
- Date: 2020
- Subjects: Sleep -- Physiological aspects , Cricket players -- Health and hygiene , Cricket players -- South Africa -- Health and hygiene , Cricket -- Health aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147950 , vital:38696
- Description: Introduction: Good sleep behaviour is associated with achieving optimal athletic performance and reducing the risk of injury. Elite cricket players have unique physical and cognitive demands, and must accommodate for congested competition and travel schedules (all of which increase the risk of disruptive sleep). Further, the political pressures and socioeconomic barriers in South African cricket could affect the sleep of the country’s elite players. Previous research in cricket has focussed on the impact that nutrition, equipment specifications, movement physiology and psychology could elicit on performance (where many professional teams hire support staff to supervise these disciplines); however, there is limited empirical application of sleep research in elite cricket players. Therefore, this study aimed to characterise the sleep behaviours of elite South African cricket players during periods of competition and investigate the relationship between pre-match sleep and cricket performance. Methods: A longitudinal field-based investigation was implemented to monitor the sleep behaviour of 26 elite South African cricket players (age: 28.6 ± 4.0 years; height: 1.8 ± 0.1 m; weight: 85.7 ± 10.8 kg; elite experience: 3.7 ± 4.0 years) during home and away competitive tours. The Morningness-Eveningness Questionnaire and Athlete Sleep Behaviour Questionnaire were administered to identify chronotype and poor sleep behaviours. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post-match. Linear mixed model regression was used to compare differences in sleep variables between time-periods, match venues, player roles, match formats, sleep medication and racial groups. Spearman’s correlation (rs) was used to assess the relationship of substance use (alcohol and caffeine), age, elite experience and match performance with selected sleep indices. Statistical significance for all measures was accepted at p < 0.05. Hedge’s (g) were used as the measure of effect size. Results: Light-emitting technology use, effects of travel, late evening alcohol consumption and muscle soreness were the main factors that impacted sleep. Post-match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post-travel (07:53 ± 01:07; g = 1.19 [0.81;1.57]) and pre-match (08:43 ± 01:03; g = 1.97 [1.55;2.39]) total sleep time. Post-travel sleep onset latency and sleep efficiency were significantly (p < 0.05) shorter (g = 0.74 [0.29;1.29]) and higher (g = 1.35 [0.76;1.94]) at home than away. Although not significant (p > 0.05), allrounders took longer to fall asleep (g = 0.90 [0.23;1.57]), obtained less total sleep (0.76 [0.29;1.42]) and had lower morning freshness scores (g = 1.10 [0.42;1.78]) the night before a match compared to batsmen. Wake after sleep onset and get up time were moderately longer (g = 0.61 [0.22;1.26]) and later (g = 0.62 [0.27;1.17]) before. Twenty20 matches compared to One-Day International matches respectively. Further, sleep duration significantly declined from pre-match to post-match during the multi-day Test format (p = 0.04, g= 0.75 [0.40;1.12]). Late alcohol consumption was significantly (p < 0.05) correlated with a decrease in total sleep time, regardless of match venue (home: rs (49) = -0.69; away: rs (27) = -0.57). During the away condition, an increase in age was significantly associated with longer wake after sleep onset durations (rs (13) = 0.52, p = 0.0003), while greater elite experience was significantly associated with longer total sleep time (rs (72) = 0.36, p = 0.02). The non-sleep medication group took significantly longer to fall asleep compared to the sleep medication group during the first week of the away condition (p = 0.02, g = 0.75 [0.25;1.26]) particularly on nights following transmeridian travel. Although not significant ( p > 0.05), Asian/Indian players had moderately longer sleep onset latencies (g = 1.07 [0.66;1.47]), wake after sleep onset durations (g = 0.86 [0.42;1.29]), and lower subjective sleep quality (g = 0.86 [0.46;1.26]) and morning freshness scores (g = 0.89 [0.47;1.27]) compared to Whites. Similarly, Black Africans had moderately lower subjective sleep quality scores compared to Whites (g = 0.71 [0.43;0.97]). Longer sleep onset latencies and shorter total sleep times were significantly (p < 0.05) associated with poorer One-Day International (rs (28) = -0.57) and Test (rs (12) = 0.59) batting performances respectively. Higher subjective sleep quality scores were significantly associated with better Twenty20 bowling economies (rs (8) = -0.52). Discussion: There was no evidence of poor pre-match sleep behaviour, irrespective of venue; however, the most apparent disruption to sleep occurred post-match (similar to that found in other team-sports). Most disparities in sleep between match venues existed post-travel, with better sleep behaviour observed during the home condition. The differences in sleep patterns found in all three match formats were expected given the variations in format scheduling and duration. Although sleep medication was shown to promote better sleep, its long-term effectiveness was limited. The results promote the implementation of practical strategies aimed to reduce bedtime light-emitting technology use, late evening alcohol consumption and muscle pain. Inter-individual sleep behaviour was found between player roles, age, experience level and race. Moderate associations existed between sleep and markers of batting performance, specifically for the longer, strategic formats of the game. Conclusion: The current study provided new insight of the sleep behaviour in elite South African cricket players during competition. Individualized sleep monitoring practices are encouraged, with specific supervision over older, less experienced players as well as the racial minorities and allrounders of the team. The poor post-match sleep behaviour, together with the sleep and performance correlations, provide ideal opportunities for future interventions to focus on match recovery and the use sleep monitoring as a competitive advantage.
- Full Text:
- Date Issued: 2020
Default in payment, an application of statistical learning techniques
- Authors: Gcakasi, Lulama
- Date: 2020
- Subjects: Credit -- South Africa -- Risk assessment , Risk management -- Statistical methods -- South Africa , Credit -- Management -- Statistical methods , Commercial statistics
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/141547 , vital:37984
- Description: The ability of financial institutions to detect whether a customer will default on their credit card payment is essential for its profitability. To that effect, financial institutions have credit scoring systems in place to be able to estimate the credit risk associated with a customer. Various classification models are used to develop credit scoring systems such as k-nearest neighbours, logistic regression and classification trees. This study aims to assess the performance of different classification models on the prediction of credit card payment default. Credit data is usually of high dimension and as a result dimension reduction techniques, namely principal component analysis and linear discriminant analysis, are used in this study as a means to improve model performance. Two classification models are used, namely neural networks and support vector machines. Model performance is evaluated using accuracy and area under the curve (AUC). The neuarl network classifier performed better than the support vector machine classifier as it produced higher accuracy rates and AUC values. Dimension reduction techniques were not effective in improving model performance but did result in less computationally expensive models.
- Full Text:
- Date Issued: 2020
- Authors: Gcakasi, Lulama
- Date: 2020
- Subjects: Credit -- South Africa -- Risk assessment , Risk management -- Statistical methods -- South Africa , Credit -- Management -- Statistical methods , Commercial statistics
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/141547 , vital:37984
- Description: The ability of financial institutions to detect whether a customer will default on their credit card payment is essential for its profitability. To that effect, financial institutions have credit scoring systems in place to be able to estimate the credit risk associated with a customer. Various classification models are used to develop credit scoring systems such as k-nearest neighbours, logistic regression and classification trees. This study aims to assess the performance of different classification models on the prediction of credit card payment default. Credit data is usually of high dimension and as a result dimension reduction techniques, namely principal component analysis and linear discriminant analysis, are used in this study as a means to improve model performance. Two classification models are used, namely neural networks and support vector machines. Model performance is evaluated using accuracy and area under the curve (AUC). The neuarl network classifier performed better than the support vector machine classifier as it produced higher accuracy rates and AUC values. Dimension reduction techniques were not effective in improving model performance but did result in less computationally expensive models.
- Full Text:
- Date Issued: 2020
Molecular simulations of potential agents and targets of Alzheimer’s disease
- Authors: Carlisle, Tanya
- Date: 2020
- Subjects: Alzheimer's disease -- Treatment , Alzheimer's disease -- Molecular aspects , Amyloid beta-protein precurs , Amyloid beta-protein
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/140025 , vital:37825
- Description: The World Alzheimer Report statedin 2016 that approximately 46.8 million people were living with dementia and this figure is expected to triple by 2050. Alzheimer’s Disease was discovered to be a precursor to dementia in 1976 and since then efforts to understand Alzheimer’s have been prioritized. To date, there are very few effective forms of treatment for Alzheimer’s, many are known to offer only mild calming of the symptoms and have side effects such as diarrhea, nausea, loss of appetite and sleep disturbances. This has been due to lack of understanding on how Alzheimer’s is caused. With the two main hallmarks of the disease now being more understood it has opened the doorway into the discovery of new treatments for this disease. This study focuses on the hallmark involving the aggregation of the β-amyloid protein to form plaques surrounding the neurons of the brain. Copper, Zinc and Iron have also been found in high concentrations in and surrounding these plaques. This study focused on the screening of the South African Natural Compound database (SANCDB) to discover hits that have potential destabilizing action against the Beta-amyloid aggregate. If one of these compounds could prove to have destabilizing action on the aggregate it could open the doorway to new potential forms of treatment. Over 700 SANCDB compounds were docked, and the top hits were taken to molecular dynamics to further study the interactions of the compounds and the aggregate. However, the hits identified had strong binding to the aggregate causing it to become stable instead of the desired effect of destabilizing the structure. This information, however, does not rule out the possibility of these compounds preventing the formation of the aggregates. Further, interactions of copper with β-amyloid and copper were determined by solubilizing the aggregate and introducing copper ions in a dynamics simulation. Possible interactions between copper and the methionine residues were visualised.
- Full Text:
- Date Issued: 2020
- Authors: Carlisle, Tanya
- Date: 2020
- Subjects: Alzheimer's disease -- Treatment , Alzheimer's disease -- Molecular aspects , Amyloid beta-protein precurs , Amyloid beta-protein
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/140025 , vital:37825
- Description: The World Alzheimer Report statedin 2016 that approximately 46.8 million people were living with dementia and this figure is expected to triple by 2050. Alzheimer’s Disease was discovered to be a precursor to dementia in 1976 and since then efforts to understand Alzheimer’s have been prioritized. To date, there are very few effective forms of treatment for Alzheimer’s, many are known to offer only mild calming of the symptoms and have side effects such as diarrhea, nausea, loss of appetite and sleep disturbances. This has been due to lack of understanding on how Alzheimer’s is caused. With the two main hallmarks of the disease now being more understood it has opened the doorway into the discovery of new treatments for this disease. This study focuses on the hallmark involving the aggregation of the β-amyloid protein to form plaques surrounding the neurons of the brain. Copper, Zinc and Iron have also been found in high concentrations in and surrounding these plaques. This study focused on the screening of the South African Natural Compound database (SANCDB) to discover hits that have potential destabilizing action against the Beta-amyloid aggregate. If one of these compounds could prove to have destabilizing action on the aggregate it could open the doorway to new potential forms of treatment. Over 700 SANCDB compounds were docked, and the top hits were taken to molecular dynamics to further study the interactions of the compounds and the aggregate. However, the hits identified had strong binding to the aggregate causing it to become stable instead of the desired effect of destabilizing the structure. This information, however, does not rule out the possibility of these compounds preventing the formation of the aggregates. Further, interactions of copper with β-amyloid and copper were determined by solubilizing the aggregate and introducing copper ions in a dynamics simulation. Possible interactions between copper and the methionine residues were visualised.
- Full Text:
- Date Issued: 2020
In vitro susceptibility of Staphylococcus aureus to porphyrin-silver mediated photodynamic antimicrobial chemotherapy
- Authors: Shabangu, Samuel Malewa
- Date: 2020
- Subjects: Porphyrins , Nanoparticles , Photochemotherapy , Drug resistance in microorganisms , Staphylococcus aureus
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167476 , vital:41484
- Description: This work reports on the syntheses and characterization of symmetrical and unsymmetrical porphyrin complexes namely, 5,10,15,20-tetra(4-pyridyl)-porphyrinato zinc(II) (1), 5,10,15,20-tetrathienyl porphyrinato zinc(II) (2), 5-(4-hydroxyphenyl)-10, 15, 20-tris(2-thienyl) porphyrinato zinc(II) (3), 5-(4-carboxyphenyl)-10,15,20-tris(pentafluorophenyl)- porphyrinato zinc(II) (4), 5-(4-carboxyphenyl)-10,15,20-triphenyl-porphyrinato zinc(II) (5) and 5-(4-carboxyphenyl)-10, 15, 20-tris(2-thienyl)-porphyrinato zinc(II) (6). The synthesis of silver nanoparticles (AgNPs) was also undertaken in this research work. Complexes 1, 2, 3 and 6 were linked to oleic acid/oleylamine functionalized nanoparticles via self-assembly and 4-6 were linked via covalent interaction through an amide bond to glutathione capped AgNPs. The effect of nature of bond along with symmetry were investigated, of interest were the five membered thienyl substituents. The photophysical and photochemical behaviour of the complexes and their conjugates with AgNPs were investigated in dimethylformamide. The porphyrin and AgNPs conjugates afforded an increase in singlet oxygen quantum yield. Complexes 1-6 and their conjugates were used for photodynamic antimicrobial chemotherapy of Staphylococcus aureus. The antimicrobial studies were done in two different concentrations of 0.36 and 2.0 μg/mL. The thienyl substituted porphyrin complexes and their conjugates gave better photodynamic activity as compared to phenyl analogues
- Full Text:
- Date Issued: 2020
- Authors: Shabangu, Samuel Malewa
- Date: 2020
- Subjects: Porphyrins , Nanoparticles , Photochemotherapy , Drug resistance in microorganisms , Staphylococcus aureus
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167476 , vital:41484
- Description: This work reports on the syntheses and characterization of symmetrical and unsymmetrical porphyrin complexes namely, 5,10,15,20-tetra(4-pyridyl)-porphyrinato zinc(II) (1), 5,10,15,20-tetrathienyl porphyrinato zinc(II) (2), 5-(4-hydroxyphenyl)-10, 15, 20-tris(2-thienyl) porphyrinato zinc(II) (3), 5-(4-carboxyphenyl)-10,15,20-tris(pentafluorophenyl)- porphyrinato zinc(II) (4), 5-(4-carboxyphenyl)-10,15,20-triphenyl-porphyrinato zinc(II) (5) and 5-(4-carboxyphenyl)-10, 15, 20-tris(2-thienyl)-porphyrinato zinc(II) (6). The synthesis of silver nanoparticles (AgNPs) was also undertaken in this research work. Complexes 1, 2, 3 and 6 were linked to oleic acid/oleylamine functionalized nanoparticles via self-assembly and 4-6 were linked via covalent interaction through an amide bond to glutathione capped AgNPs. The effect of nature of bond along with symmetry were investigated, of interest were the five membered thienyl substituents. The photophysical and photochemical behaviour of the complexes and their conjugates with AgNPs were investigated in dimethylformamide. The porphyrin and AgNPs conjugates afforded an increase in singlet oxygen quantum yield. Complexes 1-6 and their conjugates were used for photodynamic antimicrobial chemotherapy of Staphylococcus aureus. The antimicrobial studies were done in two different concentrations of 0.36 and 2.0 μg/mL. The thienyl substituted porphyrin complexes and their conjugates gave better photodynamic activity as compared to phenyl analogues
- Full Text:
- Date Issued: 2020
An ergonomics approach to understanding perceived barriers to the provision of high-quality healthcare: a Sarah Baartman District clinics case study
- Authors: Card, Jason
- Date: 2020
- Subjects: Medical care -- South Africa -- Eastern Cape , Public health -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/170536 , vital:41933
- Description: Background:The complex nature of healthcare systemsoftenresultsinthe emergence of context-specific barriers that limit the ability for healthcare stakeholders to ensure safe and effective care delivery. In low-to middle-income (LMIC) countries, such as South Africa (SA), limited financial, material and human resources coupled withpoor infrastructure and poor public health determinants, includingpoverty andpoor education, affectthe ability to maintain andimprove on quality care outcomes.Understanding what different stakeholders perceive as barriers, and if these barriers are understood at different levels, is therefore important when attempting to mitigate the risk for unsafe or inefficient care delivery. Human Factors and Ergonomics (HFE) adoptssystems and participatory approaches for the exploration, analysis, and design of socio-technical systems to optimize both human wellbeing and system performance.The barriers to safe and effective healthcare delivery, from an HFE perspective, are not known in the South African context, particularly in parts of the Eastern Cape Province. Elucidatingthesebarriers, even if self-reported,may guidefuture efforts aimed at mitigating risks.The purpose of this study, therefore,wasto explore and highlight the perceived systemic barriers to local and national healthcare delivery, within the Sarah Baartman District in the Eastern Cape Province of South Africa.Methods: Ashort discussion aimed at introducing HFE and components of the Work Systems Model, followed by a survey that captured participant demographics, job characteristics, the perceived national and local systemic barriers, and proposed solutions, was administered withhealthcare stakeholders from 14 primary healthcare facilities and 1 department office within the Sarah Baartman District.Participants (n=120) included management, pharmacy, administration, maintenance, community-and home-based care and nursing staff.Data from the surveys were thematically analysed and categorised according to components of the work system model (Carayon, 2009) and respective workgroup.Results: The findings revealed many overlapping,systemic barriersthat includedshortages of staff, poor management and leadership, a lack of equipmentand basic necessities, poor infrastructure, patient complexity,and high workloads. The results further indicate that the way in which the reported barriers affect worksystem interactionsand performance are unique to different workgroups. Stakeholders iiproposedthat,among others, the absorption of contract workers, the provision of training and adequate human and medical resources and the maintenance of facilities may mitigate the barriers and improve healthcare delivery.Conclusion: The findings highlight a myriad of perceived systemic barriers perceived in the Sarah Baartman district, some of which were fundamental for the effective function of any healthcare system. These barriers may have wide-spread implications for stakeholders at all levels, ultimately affecting the performance, satisfaction and safety and the quality of care. It is especially important to consider these barriers in light of the COVID-19 epidemic, which emerged throughout this study and the major threat it presents to South African healthcare systems. Future research should aim to explore how these barriers interact to contribute to processes and outcomes, as well as explore the perceptions at provincial and national levels in order to better identify areas and strategies for improvement.
- Full Text:
- Date Issued: 2020
- Authors: Card, Jason
- Date: 2020
- Subjects: Medical care -- South Africa -- Eastern Cape , Public health -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/170536 , vital:41933
- Description: Background:The complex nature of healthcare systemsoftenresultsinthe emergence of context-specific barriers that limit the ability for healthcare stakeholders to ensure safe and effective care delivery. In low-to middle-income (LMIC) countries, such as South Africa (SA), limited financial, material and human resources coupled withpoor infrastructure and poor public health determinants, includingpoverty andpoor education, affectthe ability to maintain andimprove on quality care outcomes.Understanding what different stakeholders perceive as barriers, and if these barriers are understood at different levels, is therefore important when attempting to mitigate the risk for unsafe or inefficient care delivery. Human Factors and Ergonomics (HFE) adoptssystems and participatory approaches for the exploration, analysis, and design of socio-technical systems to optimize both human wellbeing and system performance.The barriers to safe and effective healthcare delivery, from an HFE perspective, are not known in the South African context, particularly in parts of the Eastern Cape Province. Elucidatingthesebarriers, even if self-reported,may guidefuture efforts aimed at mitigating risks.The purpose of this study, therefore,wasto explore and highlight the perceived systemic barriers to local and national healthcare delivery, within the Sarah Baartman District in the Eastern Cape Province of South Africa.Methods: Ashort discussion aimed at introducing HFE and components of the Work Systems Model, followed by a survey that captured participant demographics, job characteristics, the perceived national and local systemic barriers, and proposed solutions, was administered withhealthcare stakeholders from 14 primary healthcare facilities and 1 department office within the Sarah Baartman District.Participants (n=120) included management, pharmacy, administration, maintenance, community-and home-based care and nursing staff.Data from the surveys were thematically analysed and categorised according to components of the work system model (Carayon, 2009) and respective workgroup.Results: The findings revealed many overlapping,systemic barriersthat includedshortages of staff, poor management and leadership, a lack of equipmentand basic necessities, poor infrastructure, patient complexity,and high workloads. The results further indicate that the way in which the reported barriers affect worksystem interactionsand performance are unique to different workgroups. Stakeholders iiproposedthat,among others, the absorption of contract workers, the provision of training and adequate human and medical resources and the maintenance of facilities may mitigate the barriers and improve healthcare delivery.Conclusion: The findings highlight a myriad of perceived systemic barriers perceived in the Sarah Baartman district, some of which were fundamental for the effective function of any healthcare system. These barriers may have wide-spread implications for stakeholders at all levels, ultimately affecting the performance, satisfaction and safety and the quality of care. It is especially important to consider these barriers in light of the COVID-19 epidemic, which emerged throughout this study and the major threat it presents to South African healthcare systems. Future research should aim to explore how these barriers interact to contribute to processes and outcomes, as well as explore the perceptions at provincial and national levels in order to better identify areas and strategies for improvement.
- Full Text:
- Date Issued: 2020
Mineralogy, geochemistry and origin of the Neoproterozoic Xaudum iron-formation in Botswana
- Authors: Ntantiso, Mawande
- Date: 2020
- Subjects: Xaudum iron-formation , Iron ores -- Botswana , Formations (Geology) -- Botswana , Mineralogy -- Botswana , Paleoclimatology -- Proterozoic
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167211 , vital:41447
- Description: Banded iron-formations (BIF) formed in three different geological periods in the Earth’s history, namely the Archean, Paleoproterozoic and Neoproterozoic. Each of these periods has a corresponding index BIF type attributed to them. The oldest is the Archean Algoma-type BIF which is typically dominated by smaller-volume BIF deposits associated with volcanic rocks and greenstone belts. The next is the volumetrically far more abundant Superior-type BIF of the Paleoproterozoic lacking any obvious volcanic relation. The youngest BIFs were deposited after a hiatus of a billion years in the Neoproterozoic and are believed to be genetically linked to Marinoan ice-age. The global re-introduction and distribution of BIF in the Neoproterozoic highlights a shift in the Earth’s tectonics, climate, biosphere and ocean chemistry from the older Archean and Paleoproterozoic counterparts. Various models have been postulated by researchers in attempts to explain how Neoproterozoic iron-formations formed. In all the available models, the Snowball Earth Hypothesis initially proposed by Kirshvink (1992) is an overarching concept. In this study, four cores from the Neoproterozoic Xaudum iron-formation (XIF) in Ngamiland, northwest of Botswana, were sampled and analysed following a partnership between Postgraduate Research in Iron and Manganese Ore Resources (PRIMOR) and Tsodilo Resources Ltd. The study sets out to explore the mineralogy and chemistry of XIF in order to determine its origin, constrain the redox conditions in the paleo-basin, assess it in the context of other Neoproterozoic iron-formations and older Archean and Paleoproterozoic iron-formations, and inform metallurgical processing. The mineralogy of XIF consists of magnetite, quartz, amphibole, garnet, biotite and chlorite in decreasing abundance. This mineral assemblage is characteristic of medium grade metamorphosed iron-formations. Algoma and Superior-type BIFs which experienced late-diagenetic and very low-grade metamorphism have a complex mineral assemblage consisting of hematite, magnetite, quartz, and several carbonate (dolomite-ankerite series and siderite) and silicate phases (greenalite, riebeckite and stilpnomelane). The geochemical results show that XIF has higher Mn3O4 and Al2O3 average contents when compared to Algoma and Superior type BIF. The detrital components in XIF correlate with High Field Strength Elements (HFSE) suggesting increased delivery of siliciclastic material during deposition. This trend is comparable to other NIF deposits suggesting a global high input of siliciclastic material into Neoproterozoic paleodepositional environments. This trend is different from Archean and Paleoproterozoic BIF deposits which are close to pure chemical sediments lacking measurable detrital contributions. In the XIF, bulk-rock Mn3O4 and Al2O3 in drillcore SW have higher averages of 2.4 and 2.6 wt. % respectively, compared to the other three cores. The Mn3O4 shows a positive statistical relationship with Co, suggesting that Neoproterozoic oceans and atmosphere were possibly more oxic than in the Archean and Paleoproterozoic. The Mn3O4 shows an antithetic relationship with Fe2O3 suggesting that the paleobasin was chemically heterogeneous in terms of redox conditions, with Fe2O3 depositing presumably in deeper parts removed from a detrital source, and Mn3O4 depositing possibly more proximal to a paleo-shoreline in a shallower setting where there was higher delivery of siliciclastic material from the continent due to correspondingly higher Al2O3 and TiO2 contents. The REE patterns of XIF show positive-sloping trends of depletion in LREE and enrichment in HREE which resemble those of seawater. However, the REE slope becomes a lot flatter and resembles closer the signature of PAAS and adjacent diamictite facies, which agrees with the idea of high siliciclastic input in the paleobasin comparable to other NIF. XIF also appears to lack clear Ce or Eu anomalies. The lack of the former points to the oceans possibly not being oxic enough to drive the fractionation of Ce into Mn oxides like in the modern oceans, or that the Ce behaviour is obscured by the high siliciclastic input in XIF. Similarly, the lack of positive Eu anomaly shows a weak to absent hydrothermal signal into to modern shallow seawater where Fe and Si were sourced, or detritally derived REE contamination. Extensive weathering under hot and humid climate during glacial retreat is shown by the low K2O/Al2O3 ratios and high CIA values ranging from 80-99. Re-glaciation signifies the return of cold and arid and it is represented by high K2O/Al2O3 ratios and low CIA values ranging from 64-78. The previous genetic models of NIF by Klein (1993), Baldwin et al. (2012) and Lechte and Wallace (2015) provide an essential foundation for the development of a XIF genetic model. The genetic model of XIF proposes deposition on an open continental shelf characterized by a steady influx of detrital material. The seawater has been anoxic since the Paleoproterozoic and further induced by basin stagnation due to the ice covering the basin. Two overlapping oxidative stages are assumed for the precipitation of Fe and Mn across lateral redox gradients in the paleobasin. The exact oxidative pathways and mechanisms for the above processes remains unconstrained.
- Full Text:
- Date Issued: 2020
- Authors: Ntantiso, Mawande
- Date: 2020
- Subjects: Xaudum iron-formation , Iron ores -- Botswana , Formations (Geology) -- Botswana , Mineralogy -- Botswana , Paleoclimatology -- Proterozoic
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167211 , vital:41447
- Description: Banded iron-formations (BIF) formed in three different geological periods in the Earth’s history, namely the Archean, Paleoproterozoic and Neoproterozoic. Each of these periods has a corresponding index BIF type attributed to them. The oldest is the Archean Algoma-type BIF which is typically dominated by smaller-volume BIF deposits associated with volcanic rocks and greenstone belts. The next is the volumetrically far more abundant Superior-type BIF of the Paleoproterozoic lacking any obvious volcanic relation. The youngest BIFs were deposited after a hiatus of a billion years in the Neoproterozoic and are believed to be genetically linked to Marinoan ice-age. The global re-introduction and distribution of BIF in the Neoproterozoic highlights a shift in the Earth’s tectonics, climate, biosphere and ocean chemistry from the older Archean and Paleoproterozoic counterparts. Various models have been postulated by researchers in attempts to explain how Neoproterozoic iron-formations formed. In all the available models, the Snowball Earth Hypothesis initially proposed by Kirshvink (1992) is an overarching concept. In this study, four cores from the Neoproterozoic Xaudum iron-formation (XIF) in Ngamiland, northwest of Botswana, were sampled and analysed following a partnership between Postgraduate Research in Iron and Manganese Ore Resources (PRIMOR) and Tsodilo Resources Ltd. The study sets out to explore the mineralogy and chemistry of XIF in order to determine its origin, constrain the redox conditions in the paleo-basin, assess it in the context of other Neoproterozoic iron-formations and older Archean and Paleoproterozoic iron-formations, and inform metallurgical processing. The mineralogy of XIF consists of magnetite, quartz, amphibole, garnet, biotite and chlorite in decreasing abundance. This mineral assemblage is characteristic of medium grade metamorphosed iron-formations. Algoma and Superior-type BIFs which experienced late-diagenetic and very low-grade metamorphism have a complex mineral assemblage consisting of hematite, magnetite, quartz, and several carbonate (dolomite-ankerite series and siderite) and silicate phases (greenalite, riebeckite and stilpnomelane). The geochemical results show that XIF has higher Mn3O4 and Al2O3 average contents when compared to Algoma and Superior type BIF. The detrital components in XIF correlate with High Field Strength Elements (HFSE) suggesting increased delivery of siliciclastic material during deposition. This trend is comparable to other NIF deposits suggesting a global high input of siliciclastic material into Neoproterozoic paleodepositional environments. This trend is different from Archean and Paleoproterozoic BIF deposits which are close to pure chemical sediments lacking measurable detrital contributions. In the XIF, bulk-rock Mn3O4 and Al2O3 in drillcore SW have higher averages of 2.4 and 2.6 wt. % respectively, compared to the other three cores. The Mn3O4 shows a positive statistical relationship with Co, suggesting that Neoproterozoic oceans and atmosphere were possibly more oxic than in the Archean and Paleoproterozoic. The Mn3O4 shows an antithetic relationship with Fe2O3 suggesting that the paleobasin was chemically heterogeneous in terms of redox conditions, with Fe2O3 depositing presumably in deeper parts removed from a detrital source, and Mn3O4 depositing possibly more proximal to a paleo-shoreline in a shallower setting where there was higher delivery of siliciclastic material from the continent due to correspondingly higher Al2O3 and TiO2 contents. The REE patterns of XIF show positive-sloping trends of depletion in LREE and enrichment in HREE which resemble those of seawater. However, the REE slope becomes a lot flatter and resembles closer the signature of PAAS and adjacent diamictite facies, which agrees with the idea of high siliciclastic input in the paleobasin comparable to other NIF. XIF also appears to lack clear Ce or Eu anomalies. The lack of the former points to the oceans possibly not being oxic enough to drive the fractionation of Ce into Mn oxides like in the modern oceans, or that the Ce behaviour is obscured by the high siliciclastic input in XIF. Similarly, the lack of positive Eu anomaly shows a weak to absent hydrothermal signal into to modern shallow seawater where Fe and Si were sourced, or detritally derived REE contamination. Extensive weathering under hot and humid climate during glacial retreat is shown by the low K2O/Al2O3 ratios and high CIA values ranging from 80-99. Re-glaciation signifies the return of cold and arid and it is represented by high K2O/Al2O3 ratios and low CIA values ranging from 64-78. The previous genetic models of NIF by Klein (1993), Baldwin et al. (2012) and Lechte and Wallace (2015) provide an essential foundation for the development of a XIF genetic model. The genetic model of XIF proposes deposition on an open continental shelf characterized by a steady influx of detrital material. The seawater has been anoxic since the Paleoproterozoic and further induced by basin stagnation due to the ice covering the basin. Two overlapping oxidative stages are assumed for the precipitation of Fe and Mn across lateral redox gradients in the paleobasin. The exact oxidative pathways and mechanisms for the above processes remains unconstrained.
- Full Text:
- Date Issued: 2020
The effect of waste tyre pyrolysis-derived carbon black on the various properties of natural rubber/styrene-butadiene rubber blends
- Authors: Ketelo, Sisonke
- Date: 2020
- Subjects: Rubber chemistry , Rubber Polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49115 , vital:41602
- Description: Disposal of waste tyres into landfills is common in developing countries, including South Africa. This behaviour is detrimental to human health as well as other living organisms and the environment itself. There are several recycling methods and processes that have been adopted in various countries to mitigate the situation. These include the recovery of materials such as rubber for re-use; shredding of tyres into small crumb particles for secondary applications in various industries such as civil engineering and the automotive sector; and commonly through heating tyres under a controlled environment to produce oil in a process called pyrolysis. The latter is of interest to the study, with a specific interest in valorization of the process’ resultant char/pyrolysis carbon black. In principle, this study considers the advancement of waste tyre material recovery by finding applications for pyrolysis-derived carbon black (pCB) recovered from waste tyres as it is one of the significant products of pyrolysis. The study involved investigating the effectiveness of pyrolysis-derived carbon black in its ability to improve the properties of natural rubber/styrene-butadiene rubber blends for the conveyor belting industry and other related industries. The pyrolysis-derived carbon black was characterized and compared to commercial grades of carbon blacks on properties such as surface area, thermal stability, heat absorption, structure and morphology using various laboratory techniques such as XRD, XRF, TGA, BET, DSC and SEM. It was found that the properties of the unmodified pCB closely matched those of commercial carbon black grade N660. Through internal mixing, rubber compounds were prepared using 40 phr of pCB and of the selected carbon black grades. Improvements were observed in the mechanical properties of the polymer for application specifications, especially tensile properties and abrasion resistance. Pyrolysis-derived carbon black improved tensile properties to a similar magnitude as a reinforcing carbon black grade and produced similar cure times. Partial replacement of a commercial carbon black grade with pCB of 5 to 20 phr in NR/SBR yielded intermediate results. The unmodified pCB can be used to improve the physical properties of natural rubber/styrene-butadiene rubber blends because it exhibits filler behaviour.
- Full Text:
- Date Issued: 2020
- Authors: Ketelo, Sisonke
- Date: 2020
- Subjects: Rubber chemistry , Rubber Polymers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49115 , vital:41602
- Description: Disposal of waste tyres into landfills is common in developing countries, including South Africa. This behaviour is detrimental to human health as well as other living organisms and the environment itself. There are several recycling methods and processes that have been adopted in various countries to mitigate the situation. These include the recovery of materials such as rubber for re-use; shredding of tyres into small crumb particles for secondary applications in various industries such as civil engineering and the automotive sector; and commonly through heating tyres under a controlled environment to produce oil in a process called pyrolysis. The latter is of interest to the study, with a specific interest in valorization of the process’ resultant char/pyrolysis carbon black. In principle, this study considers the advancement of waste tyre material recovery by finding applications for pyrolysis-derived carbon black (pCB) recovered from waste tyres as it is one of the significant products of pyrolysis. The study involved investigating the effectiveness of pyrolysis-derived carbon black in its ability to improve the properties of natural rubber/styrene-butadiene rubber blends for the conveyor belting industry and other related industries. The pyrolysis-derived carbon black was characterized and compared to commercial grades of carbon blacks on properties such as surface area, thermal stability, heat absorption, structure and morphology using various laboratory techniques such as XRD, XRF, TGA, BET, DSC and SEM. It was found that the properties of the unmodified pCB closely matched those of commercial carbon black grade N660. Through internal mixing, rubber compounds were prepared using 40 phr of pCB and of the selected carbon black grades. Improvements were observed in the mechanical properties of the polymer for application specifications, especially tensile properties and abrasion resistance. Pyrolysis-derived carbon black improved tensile properties to a similar magnitude as a reinforcing carbon black grade and produced similar cure times. Partial replacement of a commercial carbon black grade with pCB of 5 to 20 phr in NR/SBR yielded intermediate results. The unmodified pCB can be used to improve the physical properties of natural rubber/styrene-butadiene rubber blends because it exhibits filler behaviour.
- Full Text:
- Date Issued: 2020
Synthesis, crystal structures and characterization of metal–organic framework architectures involving dinuclear copper(ii) benzoic acid derivative complexes
- Authors: Ndima, Lubabalo
- Date: 2020
- Subjects: Supramolecular chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46783 , vital:39657
- Description: Structural copper(II) complexes with aromatic carboxylic acids show a wide spectrum of coordination schemes. Studies of dicopper(II) carboxylates have been associated with a variety of interests for their catalytic, biological and magnetic applications [1]. Various novel dinuclear copper(II) complexes [Cu2(X-benzoate)4L2] with varying substituents (X = CH3, F, Cl, Br, I, NO2 & OCH3) with a desired octahedral geometry have been synthesized. The various complexes were characterized by single crystal X-ray diffraction studies, spectroscopic and thermal methods (UV/Vis, FTIR and TGA, DSC). In most cases, the structures consists of centrosymmetric dimers in which the Cu atoms show a square pyramidal CuO5 coordination. In all cases, dimeric paddle wheel complexes where two copper(II) ions are held together by four benzoates (forming syn– syn bridges between the copper atoms) and the apical coordination site occupied by a solvent ligand (L) or supramolecular linker were obtained. The dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol (solvent ligand) on one Cu(II) and the carboxylate group on an adjacent Cu(II) dimer, including interactions arising from various substituents. π–π Stacking interactions are found to be present in the various crystal structures forming 3D supramolecular array. FTIR and UV/Vis spectra of each complex have shown how the resonance and inductive effect of each substituent affects spectral data of each complex.
- Full Text:
- Date Issued: 2020
- Authors: Ndima, Lubabalo
- Date: 2020
- Subjects: Supramolecular chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46783 , vital:39657
- Description: Structural copper(II) complexes with aromatic carboxylic acids show a wide spectrum of coordination schemes. Studies of dicopper(II) carboxylates have been associated with a variety of interests for their catalytic, biological and magnetic applications [1]. Various novel dinuclear copper(II) complexes [Cu2(X-benzoate)4L2] with varying substituents (X = CH3, F, Cl, Br, I, NO2 & OCH3) with a desired octahedral geometry have been synthesized. The various complexes were characterized by single crystal X-ray diffraction studies, spectroscopic and thermal methods (UV/Vis, FTIR and TGA, DSC). In most cases, the structures consists of centrosymmetric dimers in which the Cu atoms show a square pyramidal CuO5 coordination. In all cases, dimeric paddle wheel complexes where two copper(II) ions are held together by four benzoates (forming syn– syn bridges between the copper atoms) and the apical coordination site occupied by a solvent ligand (L) or supramolecular linker were obtained. The dimers are extended into 1D chains that result from hydrogen bonding between the coordinated methanol (solvent ligand) on one Cu(II) and the carboxylate group on an adjacent Cu(II) dimer, including interactions arising from various substituents. π–π Stacking interactions are found to be present in the various crystal structures forming 3D supramolecular array. FTIR and UV/Vis spectra of each complex have shown how the resonance and inductive effect of each substituent affects spectral data of each complex.
- Full Text:
- Date Issued: 2020
Linking onshore and offshore crustal features, integrating seismic and borehole data in the Gamtoos basin
- Authors: Makuzeni, Manyano
- Date: 2020
- Subjects: Submarine geology , Geology Geophysics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49137 , vital:41604
- Description: The margin of the Southern Africa continent harbours the history about the fragmentation and separation of Gondwana in its basins. The integration of onshore and offshore geology is of primordial importance to understand the complete geological history and evolution of the southern African border. The study focuses on the Gamtoos Basin, where the sediment deposits on the onshore portion are generally unfossiliferous and therefore difficult to correlate with the offshore portion of the basin. In an attempt to do this, several datasets were integrated such as old 2-D seismic reflection data and borehole wells. This data, acquired by SOEKER in the 1970s was purchased from the Petroleum Agency of South Africa (PASA). Some data reprocessing involved digitization and conversion of the old seismic data from TIF format to SEG-Y format. Conventional seismic stratigraphic method (Mitchum, JR, et al., 1977) was used to identify seismic discontinuities and remarkable stratigraphic surfaces and units based on reflection configurations and facies characteristics, and ages of these surfaces were provided by well data. Seismic interpretation was first done on printed seismogram papers, and then integrated into the ‘Kingdom Suite’ software to ensure coherency at all crossing lines. Isochron and Isopach maps (using QGIS, Mirone and tools such as GMT) were created. The first results, allow us to estimate for the first time a precise age calibration of onshore deposit. Furthermore, the delimitation in 5 second-order seismic sequences along the Gamtoos Basin suggest a link between different basin filling dynamics and kinematic phases related to the opening of the Indian and Atlantic Oceans along the southern Africa margins. The study shows that the Gamtoos Basin is an essential area linking the geological histories of both East and Western parts of the Southern Africa continent.
- Full Text:
- Date Issued: 2020
- Authors: Makuzeni, Manyano
- Date: 2020
- Subjects: Submarine geology , Geology Geophysics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49137 , vital:41604
- Description: The margin of the Southern Africa continent harbours the history about the fragmentation and separation of Gondwana in its basins. The integration of onshore and offshore geology is of primordial importance to understand the complete geological history and evolution of the southern African border. The study focuses on the Gamtoos Basin, where the sediment deposits on the onshore portion are generally unfossiliferous and therefore difficult to correlate with the offshore portion of the basin. In an attempt to do this, several datasets were integrated such as old 2-D seismic reflection data and borehole wells. This data, acquired by SOEKER in the 1970s was purchased from the Petroleum Agency of South Africa (PASA). Some data reprocessing involved digitization and conversion of the old seismic data from TIF format to SEG-Y format. Conventional seismic stratigraphic method (Mitchum, JR, et al., 1977) was used to identify seismic discontinuities and remarkable stratigraphic surfaces and units based on reflection configurations and facies characteristics, and ages of these surfaces were provided by well data. Seismic interpretation was first done on printed seismogram papers, and then integrated into the ‘Kingdom Suite’ software to ensure coherency at all crossing lines. Isochron and Isopach maps (using QGIS, Mirone and tools such as GMT) were created. The first results, allow us to estimate for the first time a precise age calibration of onshore deposit. Furthermore, the delimitation in 5 second-order seismic sequences along the Gamtoos Basin suggest a link between different basin filling dynamics and kinematic phases related to the opening of the Indian and Atlantic Oceans along the southern Africa margins. The study shows that the Gamtoos Basin is an essential area linking the geological histories of both East and Western parts of the Southern Africa continent.
- Full Text:
- Date Issued: 2020
Analysis of bacterial Mur amide ligase enzymes for the identification of inhibitory compounds by in silico methods
- Chamboko, Chiratidzo Respina
- Authors: Chamboko, Chiratidzo Respina
- Date: 2020
- Subjects: Pathogenic microorganisms -- Analysis , Drug resistance in microorganisms , Microorganisms -- Effect of drugs on , Antibiotics -- Effectiveness , Pathogenic bacteria , Drug tolerance , Enzymes -- Analysis , Peptide antibiotics
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/161911 , vital:40690
- Description: An increased emergence of resistant pathogenic bacterial strains over the years has resulted in many people dying of untreatable infections. This has become one of the most critical global public health problems, as resistant strains are complicating treatment of infectious diseases, increasing human morbidity, mortality, and health care costs. A very limited amount of effective antibiotics is currently available, but the development of novel classes of antibacterial agents is becoming a priority. Mur amide ligases are enzymes that have been identified as potentially good targets for antibiotics, as they are uniquely found in bacteria. They are responsible for the formation of peptide bonds in a growing peptidoglycan structure for bacterial cell walls. The current work presented here focused on characterizing these Mur amide ligase enzymes and obtaining inhibitory compounds that could potentially be of use in drug discovery of antibacterial agents. To do this, multiple sequence alignment, motif analysis and phylogenetic tree constructions were carried out, followed by docking studies and molecular dynamic simulations. Prior to docking, homology modelling of missing residues in the MurF structure (PDB 1GG4) was performed. Characterization results revealed the Mur amide ligase enzymes contained defined conservation in limited regions, that ultimately mapped towards the central domain responsible for ATP binding (presence of a conserved GKT motif). Further analysis of results further unraveled the unique patterns observed within each group of the family of enzymes. As a result of these findings, docking studies were carried out on each Mur amide ligase structure. At most, two ligands were identified to be sufficiently inhibiting each Mur amide ligase. The ligands obtained were SANC00574 and SANC00575 for MurC, SANC00290 and SANC00438 for MurD, SANC00290 and SANC00525 for MurE and SANC00290 and SANC00434 for MurF. The two best ligands identified for each enzyme had docked in the active site of their respective proteins, passed Lipinski’s rule of five and had substantially low binding energies. Molecular dynamic simulations were then performed to analyze the behavior of the proteins and protein-ligand complexes, to confirm the lead compounds as good inhibitors of the Mur amide ligases. In the case of MurC, MurD and MurE complexes, the identified ligands clearly impacted the behavior of the protein, as the ligand bound proteins became more compact and stable, while flexibility decreased. There was however an opposite effect on MurF complexes, that resulted in identified inhibitors being discarded. As a potential next step, in vivo and in vitro experiments can be performed with identified ligands from this research, to further support the information presented.
- Full Text:
- Date Issued: 2020
- Authors: Chamboko, Chiratidzo Respina
- Date: 2020
- Subjects: Pathogenic microorganisms -- Analysis , Drug resistance in microorganisms , Microorganisms -- Effect of drugs on , Antibiotics -- Effectiveness , Pathogenic bacteria , Drug tolerance , Enzymes -- Analysis , Peptide antibiotics
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/161911 , vital:40690
- Description: An increased emergence of resistant pathogenic bacterial strains over the years has resulted in many people dying of untreatable infections. This has become one of the most critical global public health problems, as resistant strains are complicating treatment of infectious diseases, increasing human morbidity, mortality, and health care costs. A very limited amount of effective antibiotics is currently available, but the development of novel classes of antibacterial agents is becoming a priority. Mur amide ligases are enzymes that have been identified as potentially good targets for antibiotics, as they are uniquely found in bacteria. They are responsible for the formation of peptide bonds in a growing peptidoglycan structure for bacterial cell walls. The current work presented here focused on characterizing these Mur amide ligase enzymes and obtaining inhibitory compounds that could potentially be of use in drug discovery of antibacterial agents. To do this, multiple sequence alignment, motif analysis and phylogenetic tree constructions were carried out, followed by docking studies and molecular dynamic simulations. Prior to docking, homology modelling of missing residues in the MurF structure (PDB 1GG4) was performed. Characterization results revealed the Mur amide ligase enzymes contained defined conservation in limited regions, that ultimately mapped towards the central domain responsible for ATP binding (presence of a conserved GKT motif). Further analysis of results further unraveled the unique patterns observed within each group of the family of enzymes. As a result of these findings, docking studies were carried out on each Mur amide ligase structure. At most, two ligands were identified to be sufficiently inhibiting each Mur amide ligase. The ligands obtained were SANC00574 and SANC00575 for MurC, SANC00290 and SANC00438 for MurD, SANC00290 and SANC00525 for MurE and SANC00290 and SANC00434 for MurF. The two best ligands identified for each enzyme had docked in the active site of their respective proteins, passed Lipinski’s rule of five and had substantially low binding energies. Molecular dynamic simulations were then performed to analyze the behavior of the proteins and protein-ligand complexes, to confirm the lead compounds as good inhibitors of the Mur amide ligases. In the case of MurC, MurD and MurE complexes, the identified ligands clearly impacted the behavior of the protein, as the ligand bound proteins became more compact and stable, while flexibility decreased. There was however an opposite effect on MurF complexes, that resulted in identified inhibitors being discarded. As a potential next step, in vivo and in vitro experiments can be performed with identified ligands from this research, to further support the information presented.
- Full Text:
- Date Issued: 2020
Synthesis of 2,4-Xylidine in continuous flow systems
- Authors: Sagandira, Mellisa Brenda
- Date: 2020
- Subjects: Chemistry, Physical and theoretical -- Research , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49270 , vital:41616
- Description: The continuous flow synthesis of 2,4-xylidine, an important compound in the fine chemical, pharmaceutical as well as the dyes and pigments industries was investigated in this study utilizing 1,3-dimethylbenzene as starting material. The first step involves the highly exothermic nitration of 1,3-dimethylbenzene with mixed acid to afford two nitro isomers, namely 1,3-dimethyl-2-nitrobenzene and 2,4-dimethyl-1-nitrobenzene. Since 2,4-xylidine is the targeted isomer, it is important to get a higher proportion of its nitration precursor 2,4-dimethyl-1-nitrobenzene. A safe and efficient synthesis of 2,4-dimethyl-1-nitrobenzene was therefore developed in continuous flow. This was aided by the micro reactor’s large surface area-to-volume ratio, one of the many features of continuous flow synthesis that enable rapid dissipation of heat allowing exothermic reactions to be conducted safely at ambient or higher temperatures. Two nitration protocols were developed using different micro reactors, a sonicated 1 ml PTFE tube reactor and 2 ml Uniqsis chip reactor. Using a sonicated PTFE tube reactor at room temperature and 15 min residence time, 2,4-dimethyl-1-nitrobenzene was afforded in 100 % conversion and 80 % selectivity. An increase in selectivity to 95 % and 90 % conversion towards 2,4-dimethyl-1-nitrobenzene was achieved using a 2 ml Uniqsis chip reactor at room temperature in 6 min residence time. This was accounted for due to efficient mixing of the two phases brought about by the reactor’s mixing structures, which are designed to create turbulent mixing. Scale-up synthesis of 2,4-dimethyl-1-nitrobenzene was conducted in a 4.5 ml LTF-XXL-ST-04 reactor at room temperature and 6 min residence time affording 90 % conversion and 95 % selectivity with a throughput of 16.6 g/h. Subsequently, reduction of 2,4-dimethyl-1-nitrobenzene to afford 2,4-xylidine was investigated in a 1 ml PTFE tube reactor (0.8 mm ID) using hydrazine in the presence of iron (III) 2,4-pentanedionate catalyst. Maximum conversion of 75 % was achieved at 170 °C in 15 min residence time. A more efficient reduction protocol was developed in a 2.7 ml packed column reactor (10 mm ID) using hydrazine in the presence of Pd/C at 50 °C and 2.5 min residence time affording 94 % conversion towards 2,4-xylidine. Lastly, multistep synthesis of 2,4-xylidine was performed using optimum conditions found using the 2 ml Uniqsis chip reactor and 2.7 ml packed column reactor with the incorporation of a phase separator. Joining the two reactors into a single continuous step afforded 100 % conversion and 95 % selectivity towards 2,4-xylidine with 8 min total residence time. Nitration of other organic compounds followed by reduction of the resultant nitro products was also investigated under respective optimum conditions determined for nitration of 1,3-dimethylbenzene and reduction of 2,4-dimethyl-1-nitrobenzene.
- Full Text:
- Date Issued: 2020
- Authors: Sagandira, Mellisa Brenda
- Date: 2020
- Subjects: Chemistry, Physical and theoretical -- Research , Chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49270 , vital:41616
- Description: The continuous flow synthesis of 2,4-xylidine, an important compound in the fine chemical, pharmaceutical as well as the dyes and pigments industries was investigated in this study utilizing 1,3-dimethylbenzene as starting material. The first step involves the highly exothermic nitration of 1,3-dimethylbenzene with mixed acid to afford two nitro isomers, namely 1,3-dimethyl-2-nitrobenzene and 2,4-dimethyl-1-nitrobenzene. Since 2,4-xylidine is the targeted isomer, it is important to get a higher proportion of its nitration precursor 2,4-dimethyl-1-nitrobenzene. A safe and efficient synthesis of 2,4-dimethyl-1-nitrobenzene was therefore developed in continuous flow. This was aided by the micro reactor’s large surface area-to-volume ratio, one of the many features of continuous flow synthesis that enable rapid dissipation of heat allowing exothermic reactions to be conducted safely at ambient or higher temperatures. Two nitration protocols were developed using different micro reactors, a sonicated 1 ml PTFE tube reactor and 2 ml Uniqsis chip reactor. Using a sonicated PTFE tube reactor at room temperature and 15 min residence time, 2,4-dimethyl-1-nitrobenzene was afforded in 100 % conversion and 80 % selectivity. An increase in selectivity to 95 % and 90 % conversion towards 2,4-dimethyl-1-nitrobenzene was achieved using a 2 ml Uniqsis chip reactor at room temperature in 6 min residence time. This was accounted for due to efficient mixing of the two phases brought about by the reactor’s mixing structures, which are designed to create turbulent mixing. Scale-up synthesis of 2,4-dimethyl-1-nitrobenzene was conducted in a 4.5 ml LTF-XXL-ST-04 reactor at room temperature and 6 min residence time affording 90 % conversion and 95 % selectivity with a throughput of 16.6 g/h. Subsequently, reduction of 2,4-dimethyl-1-nitrobenzene to afford 2,4-xylidine was investigated in a 1 ml PTFE tube reactor (0.8 mm ID) using hydrazine in the presence of iron (III) 2,4-pentanedionate catalyst. Maximum conversion of 75 % was achieved at 170 °C in 15 min residence time. A more efficient reduction protocol was developed in a 2.7 ml packed column reactor (10 mm ID) using hydrazine in the presence of Pd/C at 50 °C and 2.5 min residence time affording 94 % conversion towards 2,4-xylidine. Lastly, multistep synthesis of 2,4-xylidine was performed using optimum conditions found using the 2 ml Uniqsis chip reactor and 2.7 ml packed column reactor with the incorporation of a phase separator. Joining the two reactors into a single continuous step afforded 100 % conversion and 95 % selectivity towards 2,4-xylidine with 8 min total residence time. Nitration of other organic compounds followed by reduction of the resultant nitro products was also investigated under respective optimum conditions determined for nitration of 1,3-dimethylbenzene and reduction of 2,4-dimethyl-1-nitrobenzene.
- Full Text:
- Date Issued: 2020
A genetic analysis of the species and intraspecific lineages of Dactylopius Costa (Hemiptera: Dactylopiidae)
- Authors: Van Steenderen, Clarke
- Date: 2020
- Subjects: Dactylopius
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/151491 , vital:39135
- Description: The Cactaceae family comprises 15 genera and nearly 2000 species. With one exception, these are all native to the Americas. Numerous cactaceous species are invasive in other parts of the world, resulting in considerable damage to ecosystem functioning and agricultural practices. The most successful biological control agents used to combat invasive Cactaceae belong to the Dactylopius genus (Hemiptera: Dactylopiidae), comprising eleven species. The Dactylopiidae are exclusively cactophagous and are usually host-specific. Some intraspecific lineages of dactylopiids, often referred to as `biotypes', also display host-specificity, and are used to control particular species of invasive Cactaceae. To date, two lineages within Dactylopius opuntiae (`ficus' and `stricta'), and two within D. tomentosus (`cholla' and `imbricata') have been released in South Africa to control Opuntia ficus-indica and O. stricta, and Cylindropuntia fulgida and C. imbricata, respectively. The `californica var. parkeri' lineage is currently under consideration for release in South Africa for the control of C. pallida. Australia has already released these five lineages, and approved the release of an additional three in 2017; namely D. tomentosus `bigelovii', `cylindropuntia sp.', and `acanthocarpa x echinocarpa'. Many of the Dactylopius species are so morphologically similar, and in the case of lineages, identical, that numerous misidentifications have been made in the past. These errors have had serious implications, such as failed attempts at the biological control of cactus weeds. This thesis aimed to generate a multi-locus genetic database to enable the identification of the species and lineages in the Dactylopiidae family, and to test its accuracy. Seven species were included in the analysis, including two lineages within D. opuntiae and six within D. tomentosus. Genetic characterisation was achieved through the DNA sequencing of three gene regions; namely mitochondrial 12S rRNA and cytochrome c oxidase I (COI), nuclear 18S rRNA, and fragment analysis using two inter-simple sequence repeats (ISSRs). Nucleotide sequences were very effective for species-level identification, where the 12S, 18S, and COI regions showed 100%, 94.59%, and 100% identification accuracy rates, respectively. Additionally, the 12S and COI markers distinguished between half of the D. tomentosus lineages (`californica', `cholla', and `imbricata'), with identification accuracies of 100%. The `echinocarpa x acanthocarpa', `bigelovii', and `cylindropuntia sp.' lineages formed one clade. None of the DNA genetic markers showed a separation between the `ficus' and `stricta' lineages within D. opuntiae. Fragment analysis through the use of ISSRs provided higher-resolution results, and addressed this gap by showing a well-supported separation between the two lineages, and between wild populations collected in the Eastern Cape Province in South Africa. The identification accuracy of the `ficus' and `stricta' lineages was 81.82%. This is the first time that a method has been developed that can distinguish between these lineages. An additional component of this thesis was the creation of three user-friendly R-based programs to assist with: 1. ISSR data processing. 2. The identification of query Dactylopius nucleotide sequences relative to the gene databases created here. 3. A graphical user interface (GUI) version of the R package `SPIDER', which is useful for the assessment of the accuracy of genetic barcode data. A successful biological control programme relies on the correct identification of the agent in question, and so it is imperative that cactus biological control practitioners are able to distinguish between Dactylopius species and lineages in order to release the most effective ones onto target Cactaceae. The laboratory protocols reported, and data processing tools created here, have largely addressed this need and offer valuable practical applications. These include: 1. The flagging of potential new species, cryptic species, and lineages of dactylopiid species released as new biocontrol agents. 2. Validating the identifications made by taxonomists based on morphology. 3. Confirming to which species, and, where applicable, to which lineage, a field-collected sample belongs. 4. Identifying hybrids resulting from lineage crosses. Ensuring that the correct Dactylopius species are utilised for biological control will improve the control of invasive Cactaceae and protect biodiversity and agricultural productivity.
- Full Text:
- Date Issued: 2020
- Authors: Van Steenderen, Clarke
- Date: 2020
- Subjects: Dactylopius
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/151491 , vital:39135
- Description: The Cactaceae family comprises 15 genera and nearly 2000 species. With one exception, these are all native to the Americas. Numerous cactaceous species are invasive in other parts of the world, resulting in considerable damage to ecosystem functioning and agricultural practices. The most successful biological control agents used to combat invasive Cactaceae belong to the Dactylopius genus (Hemiptera: Dactylopiidae), comprising eleven species. The Dactylopiidae are exclusively cactophagous and are usually host-specific. Some intraspecific lineages of dactylopiids, often referred to as `biotypes', also display host-specificity, and are used to control particular species of invasive Cactaceae. To date, two lineages within Dactylopius opuntiae (`ficus' and `stricta'), and two within D. tomentosus (`cholla' and `imbricata') have been released in South Africa to control Opuntia ficus-indica and O. stricta, and Cylindropuntia fulgida and C. imbricata, respectively. The `californica var. parkeri' lineage is currently under consideration for release in South Africa for the control of C. pallida. Australia has already released these five lineages, and approved the release of an additional three in 2017; namely D. tomentosus `bigelovii', `cylindropuntia sp.', and `acanthocarpa x echinocarpa'. Many of the Dactylopius species are so morphologically similar, and in the case of lineages, identical, that numerous misidentifications have been made in the past. These errors have had serious implications, such as failed attempts at the biological control of cactus weeds. This thesis aimed to generate a multi-locus genetic database to enable the identification of the species and lineages in the Dactylopiidae family, and to test its accuracy. Seven species were included in the analysis, including two lineages within D. opuntiae and six within D. tomentosus. Genetic characterisation was achieved through the DNA sequencing of three gene regions; namely mitochondrial 12S rRNA and cytochrome c oxidase I (COI), nuclear 18S rRNA, and fragment analysis using two inter-simple sequence repeats (ISSRs). Nucleotide sequences were very effective for species-level identification, where the 12S, 18S, and COI regions showed 100%, 94.59%, and 100% identification accuracy rates, respectively. Additionally, the 12S and COI markers distinguished between half of the D. tomentosus lineages (`californica', `cholla', and `imbricata'), with identification accuracies of 100%. The `echinocarpa x acanthocarpa', `bigelovii', and `cylindropuntia sp.' lineages formed one clade. None of the DNA genetic markers showed a separation between the `ficus' and `stricta' lineages within D. opuntiae. Fragment analysis through the use of ISSRs provided higher-resolution results, and addressed this gap by showing a well-supported separation between the two lineages, and between wild populations collected in the Eastern Cape Province in South Africa. The identification accuracy of the `ficus' and `stricta' lineages was 81.82%. This is the first time that a method has been developed that can distinguish between these lineages. An additional component of this thesis was the creation of three user-friendly R-based programs to assist with: 1. ISSR data processing. 2. The identification of query Dactylopius nucleotide sequences relative to the gene databases created here. 3. A graphical user interface (GUI) version of the R package `SPIDER', which is useful for the assessment of the accuracy of genetic barcode data. A successful biological control programme relies on the correct identification of the agent in question, and so it is imperative that cactus biological control practitioners are able to distinguish between Dactylopius species and lineages in order to release the most effective ones onto target Cactaceae. The laboratory protocols reported, and data processing tools created here, have largely addressed this need and offer valuable practical applications. These include: 1. The flagging of potential new species, cryptic species, and lineages of dactylopiid species released as new biocontrol agents. 2. Validating the identifications made by taxonomists based on morphology. 3. Confirming to which species, and, where applicable, to which lineage, a field-collected sample belongs. 4. Identifying hybrids resulting from lineage crosses. Ensuring that the correct Dactylopius species are utilised for biological control will improve the control of invasive Cactaceae and protect biodiversity and agricultural productivity.
- Full Text:
- Date Issued: 2020
Shrub and bird community response to fire in dune thicket of the southeastern Cape, South Africa
- Authors: Strydom, Tiaan
- Date: 2020
- Subjects: Fire prevention -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47635 , vital:40260
- Description: Fire studies within the Cape Floristic Region (CFR) are restricted to the impacts of fire on plants and birds in fire-prone fynbos while little is known about post-fire responses of shrubs and birds in fire-avoiding subtropical dune thicket, which coexists with fynbos but burns on much longer cycles. Fire is deemed important for maintaining the boundaries between fynbos and thicket. It has been hypothesised that high-intensity fires prevent fire-dependent fynbos from being replaced by fireavoiding subtropical thicket (hereafter thicket) on dune landscapes of the CFR. I posit that (1) fire-related thicket shrub mortality would be size dependent, with smaller individuals suffering higher mortality than larger ones; and (2) that survival and resprouting vigour of thicket shrubs would be negatively correlated with fire intensity. In relation to the response of birds to fire I posit that (1) fire reduces bird species richness and bird abundance in thicket during the first two years post-fire; and (2) fire changes feeding guild composition and results in the loss of frugivorous birds. Extensive fires in dune thicket along the southeastern Cape coast presented the opportunity to assess the responses of thicket shrubs and birds to fire. For the thicket shrubs I assessed survival and resprouting vigour of thicket shrubs post-fire in relation to fire intensity and pre-fire shrub size at two dune landscapes (Cape St Francis and Knysna) in the CFR. I furthermore compared bird species richness, bird abundance and feeding guild composition between burnt and unburnt thicket (only at Knysna). A total of 29 species and 1112 individuals of thicket shrub were surveyed, with post-fire survival being high (83-85%). Smaller shrubs had a lower probability of post-fire survival than larger individuals but there was no consistent relationship between shrub mortality and fire intensity. Fire intensity had a positive effect on resprouting shoot count but a variable effect on resprouting volume. In the bird study a total of 66 bird species and 2404 individuals were recorded of which 52 species and 1176 individuals were in burnt thicket and 60 species and 1228 individuals were in unburnt thicket. Ten species occurred only in burnt thicket and 13 species only in unburnt thicket. Insectivores and generalists were the most common feeding guilds in terms of richness and abundance in both burnt and unburnt thicket. Frugivores were more abundant in unburnt thicket than burnt thicket, whereas granivores were more abundant in burnt thicket than unburnt thicket. I conclude that thicket shrubs and bird communities are resilient to fire. Prescribed high-intensity fires in dune landscapes are unlikely to reduce the extent of thicket in fynbos or radically change the bird communities. The effects of fire on thicket shrubs and birds are likely to be short-lived as thicket shrubs resprout vigorously after fire resulting in rapid recovery of vegetation and thus bird habitat structure. However, frequent fires may prevent the encroachment of thicket shrub juveniles into fynbos, owing to the greater vulnerability of small shrubs to fire. Most recruitment of thicket shrub individuals into fynbos is via ramets that likely originate from well-established plants in mature thicket stands. These mature unburnt thicket stands provide habitat for various forest bird species and can function as refuge areas for birds and other wildlife in fire-prone landscapes. However, there is no need for managers to take any precautions when implementing controlled burns or controlling wildfires because not all thicket patches in the landscape are likely to burn.
- Full Text:
- Date Issued: 2020
- Authors: Strydom, Tiaan
- Date: 2020
- Subjects: Fire prevention -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47635 , vital:40260
- Description: Fire studies within the Cape Floristic Region (CFR) are restricted to the impacts of fire on plants and birds in fire-prone fynbos while little is known about post-fire responses of shrubs and birds in fire-avoiding subtropical dune thicket, which coexists with fynbos but burns on much longer cycles. Fire is deemed important for maintaining the boundaries between fynbos and thicket. It has been hypothesised that high-intensity fires prevent fire-dependent fynbos from being replaced by fireavoiding subtropical thicket (hereafter thicket) on dune landscapes of the CFR. I posit that (1) fire-related thicket shrub mortality would be size dependent, with smaller individuals suffering higher mortality than larger ones; and (2) that survival and resprouting vigour of thicket shrubs would be negatively correlated with fire intensity. In relation to the response of birds to fire I posit that (1) fire reduces bird species richness and bird abundance in thicket during the first two years post-fire; and (2) fire changes feeding guild composition and results in the loss of frugivorous birds. Extensive fires in dune thicket along the southeastern Cape coast presented the opportunity to assess the responses of thicket shrubs and birds to fire. For the thicket shrubs I assessed survival and resprouting vigour of thicket shrubs post-fire in relation to fire intensity and pre-fire shrub size at two dune landscapes (Cape St Francis and Knysna) in the CFR. I furthermore compared bird species richness, bird abundance and feeding guild composition between burnt and unburnt thicket (only at Knysna). A total of 29 species and 1112 individuals of thicket shrub were surveyed, with post-fire survival being high (83-85%). Smaller shrubs had a lower probability of post-fire survival than larger individuals but there was no consistent relationship between shrub mortality and fire intensity. Fire intensity had a positive effect on resprouting shoot count but a variable effect on resprouting volume. In the bird study a total of 66 bird species and 2404 individuals were recorded of which 52 species and 1176 individuals were in burnt thicket and 60 species and 1228 individuals were in unburnt thicket. Ten species occurred only in burnt thicket and 13 species only in unburnt thicket. Insectivores and generalists were the most common feeding guilds in terms of richness and abundance in both burnt and unburnt thicket. Frugivores were more abundant in unburnt thicket than burnt thicket, whereas granivores were more abundant in burnt thicket than unburnt thicket. I conclude that thicket shrubs and bird communities are resilient to fire. Prescribed high-intensity fires in dune landscapes are unlikely to reduce the extent of thicket in fynbos or radically change the bird communities. The effects of fire on thicket shrubs and birds are likely to be short-lived as thicket shrubs resprout vigorously after fire resulting in rapid recovery of vegetation and thus bird habitat structure. However, frequent fires may prevent the encroachment of thicket shrub juveniles into fynbos, owing to the greater vulnerability of small shrubs to fire. Most recruitment of thicket shrub individuals into fynbos is via ramets that likely originate from well-established plants in mature thicket stands. These mature unburnt thicket stands provide habitat for various forest bird species and can function as refuge areas for birds and other wildlife in fire-prone landscapes. However, there is no need for managers to take any precautions when implementing controlled burns or controlling wildfires because not all thicket patches in the landscape are likely to burn.
- Full Text:
- Date Issued: 2020
Assessing community structure and trophic interrelationships in three differently impacted headwater streams in the AmatholeWinterberg freshwater ecoregion, South Africa
- Authors: Matomela, Nonjabulo Happy
- Date: 2020
- Subjects: Stream ecology -- South Africa -- Eastern Cape , Freshwater animals -- Ecology -- South Africa -- Eastern Cape , Kat River (South Africa) -- , Lushington River (South Africa) , Elands River (South Africa) , Eyre River (South Africa) , Food chains (Ecology) -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147653 , vital:38658
- Description: Afromontane regions represent some of the highly threatened ecosystems on the planet as they harbour endemic and often relic freshwater fauna. These ecologically sensitive ecosystems have been altered by multiple impacts, including invasion by non-native fishes, replacement of diverse indigenous vegetation with monoculture plantations, agricultural and mining activities, hydrological modifications, and degradation of instream habitats, with potential detrimental effects on aquatic community structures and food web dynamics. The aim of the present study was to compare spatio-temporal patterns of macroinvertebrate and fish communities as well as food web dynamics in three differently impacted headwater tributaries of the Kat River in the Amathole-Winterberg freshwater ecoregion in the Eastern Cape Province of South Africa. The upper Kat River catchment was the ideal model for purposes of the present study as it contains streams with varying degrees of human impact. The streams considered in the present study were (i) the Eyre River which was considered to closely represent near-natural conditions as it is the least impacted stream in this catchment, with the riparian zone dominated by relatively intact and diverse native woody vegetation, (ii) the Elands River whose catchment has been altered by agricultural activities, and (iii) the Lushington River, whose riparian zone has been heavily invaded by black wattle. The three headwater streams were generally distinguished based on the physical-chemical variables. The Elands River was characterised by high conductivity and total dissolved solids (TDS). In addition, the Elands River was more alkaline and relatively warmer than the other two rivers. This suggested the negative influence of agriculture activities on the water quality in the Elands River. In general, the Lushington and Eyre rivers had comparable physical and chemical variables. However, the Lushington River was generally characterised by low streamflow, likely as a consequent of black wattle which is known for altering hydrological regimes of streams .The Eyre River and Lushington River were comparable in terms of macroinvertebrate richness and diversity, whereas the Elands River was characterised by low macroinvertebrate diversity and richness. Redundancy analysis indicated that the macroinvertebrate communities were mostly influenced by seasonality, with land-use accounting for a small but significant difference in community composition. In comparison, the generalised linear mixed-effects models (GLMMs) showed that chubbyhead barb abundance was significantly influenced by land-use patterns. Evaluation of food web dynamics using stable isotope analysis revealed that the food web structure in the three rivers differed substantially as a result of land-use. Specifically, the Eyre River was characterised by less variation in stable isotope values of basal food sources and consequently, the consumer groups had a narrow isotopic breadth. In contrast, the Elands River was characterised by a wide variation in basal food sources and therefore, a wider isotopic breadth for consumers. The Lushington River was spatially variable in terms of basal sources and isotopic breadth for consumers. The study concluded that food webs and trophic interrelationships were a more informative indicator of land-use than community structure was in evaluating the impact of land-use patterns on aquatic communities. In addition, future studies should seek to investigate food webs interrelationships in addition to community structure to infer a more conclusive river assessment.
- Full Text:
- Date Issued: 2020
- Authors: Matomela, Nonjabulo Happy
- Date: 2020
- Subjects: Stream ecology -- South Africa -- Eastern Cape , Freshwater animals -- Ecology -- South Africa -- Eastern Cape , Kat River (South Africa) -- , Lushington River (South Africa) , Elands River (South Africa) , Eyre River (South Africa) , Food chains (Ecology) -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147653 , vital:38658
- Description: Afromontane regions represent some of the highly threatened ecosystems on the planet as they harbour endemic and often relic freshwater fauna. These ecologically sensitive ecosystems have been altered by multiple impacts, including invasion by non-native fishes, replacement of diverse indigenous vegetation with monoculture plantations, agricultural and mining activities, hydrological modifications, and degradation of instream habitats, with potential detrimental effects on aquatic community structures and food web dynamics. The aim of the present study was to compare spatio-temporal patterns of macroinvertebrate and fish communities as well as food web dynamics in three differently impacted headwater tributaries of the Kat River in the Amathole-Winterberg freshwater ecoregion in the Eastern Cape Province of South Africa. The upper Kat River catchment was the ideal model for purposes of the present study as it contains streams with varying degrees of human impact. The streams considered in the present study were (i) the Eyre River which was considered to closely represent near-natural conditions as it is the least impacted stream in this catchment, with the riparian zone dominated by relatively intact and diverse native woody vegetation, (ii) the Elands River whose catchment has been altered by agricultural activities, and (iii) the Lushington River, whose riparian zone has been heavily invaded by black wattle. The three headwater streams were generally distinguished based on the physical-chemical variables. The Elands River was characterised by high conductivity and total dissolved solids (TDS). In addition, the Elands River was more alkaline and relatively warmer than the other two rivers. This suggested the negative influence of agriculture activities on the water quality in the Elands River. In general, the Lushington and Eyre rivers had comparable physical and chemical variables. However, the Lushington River was generally characterised by low streamflow, likely as a consequent of black wattle which is known for altering hydrological regimes of streams .The Eyre River and Lushington River were comparable in terms of macroinvertebrate richness and diversity, whereas the Elands River was characterised by low macroinvertebrate diversity and richness. Redundancy analysis indicated that the macroinvertebrate communities were mostly influenced by seasonality, with land-use accounting for a small but significant difference in community composition. In comparison, the generalised linear mixed-effects models (GLMMs) showed that chubbyhead barb abundance was significantly influenced by land-use patterns. Evaluation of food web dynamics using stable isotope analysis revealed that the food web structure in the three rivers differed substantially as a result of land-use. Specifically, the Eyre River was characterised by less variation in stable isotope values of basal food sources and consequently, the consumer groups had a narrow isotopic breadth. In contrast, the Elands River was characterised by a wide variation in basal food sources and therefore, a wider isotopic breadth for consumers. The Lushington River was spatially variable in terms of basal sources and isotopic breadth for consumers. The study concluded that food webs and trophic interrelationships were a more informative indicator of land-use than community structure was in evaluating the impact of land-use patterns on aquatic communities. In addition, future studies should seek to investigate food webs interrelationships in addition to community structure to infer a more conclusive river assessment.
- Full Text:
- Date Issued: 2020
The taxonomy of the topminnows (Teleostei: Cyprinodontiformes) (Procatopodidae: Procatopodinae) of southern Africa
- Authors: Van Zeeventer, Ryan Matthew
- Date: 2020
- Subjects: Cyprinodontiformes -- Africa, Southern , Killifishes -- Africa, Southern
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145559 , vital:38449
- Description: Taxonomy is a tool that plays a crucial role in the implementation of effective management assessments, the ability to identify different fish species and their life stages, and create effective conservation strategies. Recent years have seen an increase in the discovery of cryptic species which could have an effect on how we implement conservation strategies, increasing the importance of accurate taxonomic assessments. The southern African topminnows of the genera Micropanchax and Lacustricola (Family Procatopodidae) include several species of egg-laying fishes that live in the marginal areas of rivers and lakes throughout the river systems of southern Africa in separated and connected populations. It was recently discovered that these populations showed subtle differences in their morphology and colouration, which led to the belief that new and cryptic species may be present. Previous studies of the Procatopodidae relied heavily on phylogenetic analyses that drew on morphological traits without reliance on molecular methods of analysis. A few of the taxonomic issues were resolved through these limited studies but ultimately the taxonomic status of the Procatopodidae remained poorly understood. Furthermore, these studies had not been updated in recent years and hence the benefits of new technology had not been brought to bear on the issues. A multi-gene analysis using standard phylogenetic methods and five molecular markers (mitochondrial cytochrome C oxidase (COI), mitochondrial cytochrome b (cytb), mitochondrial 16S ribosomal RNA (16S rRNA), nuclear 28S ribosomal RNA (28S rRNA) and mitochondrial Tyrosine Kinase (X-src) (TyrK)) allowed phylogenetic trees to be made which demonstrated clear relationships within Micropanchax and Lacustricola of southern Africa and the out-groups used in the analysis. The inference trees showed that Micropanchax johnstoni was represented by three clades and was shown to be polyphyletic while Micropanchax hutereaui, which was represented by two clades, and Micropanchax katangae, which was represented by one clade, were monophyletic. The two species of Lacustricola, L. myaposae and L. macrurus showed very close relationships to Micropanchax and it is suggested that these two species be transferred to Micropanchax, leaving Lacustricola to only be found in central Africa.
- Full Text:
- Date Issued: 2020
- Authors: Van Zeeventer, Ryan Matthew
- Date: 2020
- Subjects: Cyprinodontiformes -- Africa, Southern , Killifishes -- Africa, Southern
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145559 , vital:38449
- Description: Taxonomy is a tool that plays a crucial role in the implementation of effective management assessments, the ability to identify different fish species and their life stages, and create effective conservation strategies. Recent years have seen an increase in the discovery of cryptic species which could have an effect on how we implement conservation strategies, increasing the importance of accurate taxonomic assessments. The southern African topminnows of the genera Micropanchax and Lacustricola (Family Procatopodidae) include several species of egg-laying fishes that live in the marginal areas of rivers and lakes throughout the river systems of southern Africa in separated and connected populations. It was recently discovered that these populations showed subtle differences in their morphology and colouration, which led to the belief that new and cryptic species may be present. Previous studies of the Procatopodidae relied heavily on phylogenetic analyses that drew on morphological traits without reliance on molecular methods of analysis. A few of the taxonomic issues were resolved through these limited studies but ultimately the taxonomic status of the Procatopodidae remained poorly understood. Furthermore, these studies had not been updated in recent years and hence the benefits of new technology had not been brought to bear on the issues. A multi-gene analysis using standard phylogenetic methods and five molecular markers (mitochondrial cytochrome C oxidase (COI), mitochondrial cytochrome b (cytb), mitochondrial 16S ribosomal RNA (16S rRNA), nuclear 28S ribosomal RNA (28S rRNA) and mitochondrial Tyrosine Kinase (X-src) (TyrK)) allowed phylogenetic trees to be made which demonstrated clear relationships within Micropanchax and Lacustricola of southern Africa and the out-groups used in the analysis. The inference trees showed that Micropanchax johnstoni was represented by three clades and was shown to be polyphyletic while Micropanchax hutereaui, which was represented by two clades, and Micropanchax katangae, which was represented by one clade, were monophyletic. The two species of Lacustricola, L. myaposae and L. macrurus showed very close relationships to Micropanchax and it is suggested that these two species be transferred to Micropanchax, leaving Lacustricola to only be found in central Africa.
- Full Text:
- Date Issued: 2020
The application value and most appropriate mapping scales for site classification and evaluation in the South African forest industry
- Authors: Sibhakabhaka, Thembisa
- Date: 2020
- Subjects: Forests and forestry -- South Africa , Forest products industry -- South Africa Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49281 , vital:41617
- Description: The South African forest industry is challenged with aspects related to socio-political developments, conflicts with biodiversity values, uncertainties related to climate change, several biotic and abiotic risks, and a limited potential for expansion. For this reason, efficient and optimal land-use is essential, which requires sustainable forest management practices and accurate information and decision support systems. Tree growth patterns, productivity and risks vary according to changes in geology, topography, climate and soil conditions. It is therefore required that forest managers, planners and researchers have a conceptual understanding of the concept of forest site classification and evaluation. This is essential not only for improved levels resilience, but also to maintain a competitive industry in terms of socio-economic and environmental performance. The first chapter of the study aimed to investigate the perceptions and interpretations of a range of representative stakeholders from the forestry industry regarding the value, shortcomings, requirements and design of forest site classification and evaluation systems in use in the local industry. A questionnaire with 16 questions was used for this purpose, and data was analysed using quantitative and qualitative techniques. Results indicated variable levels of understanding amongst respondents of terminology and the nature of systems used in industry. Trends in responses were influenced by the background of stakeholders, the role of individuals in the value chain of forestry as well as past experiences. The perceived importance and value of potential site evaluation applications varied substantially amongst different stakeholders. Results point towards a narrow-focus application for site classification and evaluation systems for site-specific forestry, with a lesser regard with aspects of risk management and environmental performance. Several technical aspects related to site variables, data resolution and scale of presentation were also questioned by participants. Listed priorities for research and development include the integration of site classification and evaluation systems into corporate information systems, modernizing technology, more appropriate site evaluation models, advanced climatic modelling and the development of indices of water and nutrient availability related to forest productivity. There is general agreement for the development of a national forest site classification system. The value of this part of the study lies in the contribution it makes towards our knowledge of stakeholder perceptions regarding site classification and evaluation, as well as the valuable comments made by participants for the refinement of such systems that can serve as indicators for entities involved in education, governance and strategic forest management. The second data chapter of the study involved the development of high-resolution site classification systems in the form of Site Types for two selected study areas in South Africa, one located in Mpumalanga, and the other in the southern Cape. This enabled a comparative analysis with existing low-resolution Land Type classifications that were developed by different authors for the same two study areas, in terms of its reliability, accuracy and general usefulness for applications in the plantation forestry value chain. The comparison of the two types of classification systems revealed that the climate data forming part of the database were of equal accuracy and resolution. However, an obvious difference was detected in the information pertaining to soil in terms of descriptive and spatial data. In the case of both study areas, the Site Type classification systems revealed many soil and geological features that were not indicated by the lower-resolution Land Type systems. Variation in characteristics related to parent material, soil classification, soil depth, intensity of subsoil wetness and soil organic matter were not adequately reflected in these systems. This can potentially have important implications for applications such as species choice, predictions of yield, nutrient optimization, ratings of soil resilience, biodiversity management and evaluations for carbon sequestration potential. The data forming part of this study indicate that although Land Type classification systems can provide valuable support at strategic levels of planning and management, there are several limitations for use at finer scales of resolution. The final chapter of the study includes an investigation and qualitative comparison of the usefulness of Site Type vs. Land Type classification systems, based on existing knowledge in the industry. The two systems are compared in terms of its input towards the following applications: site-species matching, timber yield prediction, site amelioration / site preparation requirements, nutrient management requirements, vegetation management / weed control, management of pests and diseases, determination of risk for soil compaction, soil erosion and nutrient loss, decision making regarding forest engineering operations, prediction of wood / fibre properties, biodiversity management and lastly planning of research activities / priorities. This analysis indicated that applications that require data on only climate and general soil patterns can be supported with equal success by both types of site classification systems. On the other hand, in cases where high-resolution data on site factors are required, Land Type classification systems had numerous shortcomings and received a much lower rating of suitability. The outcome of the study can provide guidance on the development and design of future site classification and evaluation systems for the South African forest industry. High-resolution databases of key site factors should receive priority, together with the development of decision support systems based on causal relationships. This will contribute to the resilience and sustainability of an industry that is increasingly confronted with questions related to the placement, design and management of forest plantations.
- Full Text:
- Date Issued: 2020
- Authors: Sibhakabhaka, Thembisa
- Date: 2020
- Subjects: Forests and forestry -- South Africa , Forest products industry -- South Africa Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49281 , vital:41617
- Description: The South African forest industry is challenged with aspects related to socio-political developments, conflicts with biodiversity values, uncertainties related to climate change, several biotic and abiotic risks, and a limited potential for expansion. For this reason, efficient and optimal land-use is essential, which requires sustainable forest management practices and accurate information and decision support systems. Tree growth patterns, productivity and risks vary according to changes in geology, topography, climate and soil conditions. It is therefore required that forest managers, planners and researchers have a conceptual understanding of the concept of forest site classification and evaluation. This is essential not only for improved levels resilience, but also to maintain a competitive industry in terms of socio-economic and environmental performance. The first chapter of the study aimed to investigate the perceptions and interpretations of a range of representative stakeholders from the forestry industry regarding the value, shortcomings, requirements and design of forest site classification and evaluation systems in use in the local industry. A questionnaire with 16 questions was used for this purpose, and data was analysed using quantitative and qualitative techniques. Results indicated variable levels of understanding amongst respondents of terminology and the nature of systems used in industry. Trends in responses were influenced by the background of stakeholders, the role of individuals in the value chain of forestry as well as past experiences. The perceived importance and value of potential site evaluation applications varied substantially amongst different stakeholders. Results point towards a narrow-focus application for site classification and evaluation systems for site-specific forestry, with a lesser regard with aspects of risk management and environmental performance. Several technical aspects related to site variables, data resolution and scale of presentation were also questioned by participants. Listed priorities for research and development include the integration of site classification and evaluation systems into corporate information systems, modernizing technology, more appropriate site evaluation models, advanced climatic modelling and the development of indices of water and nutrient availability related to forest productivity. There is general agreement for the development of a national forest site classification system. The value of this part of the study lies in the contribution it makes towards our knowledge of stakeholder perceptions regarding site classification and evaluation, as well as the valuable comments made by participants for the refinement of such systems that can serve as indicators for entities involved in education, governance and strategic forest management. The second data chapter of the study involved the development of high-resolution site classification systems in the form of Site Types for two selected study areas in South Africa, one located in Mpumalanga, and the other in the southern Cape. This enabled a comparative analysis with existing low-resolution Land Type classifications that were developed by different authors for the same two study areas, in terms of its reliability, accuracy and general usefulness for applications in the plantation forestry value chain. The comparison of the two types of classification systems revealed that the climate data forming part of the database were of equal accuracy and resolution. However, an obvious difference was detected in the information pertaining to soil in terms of descriptive and spatial data. In the case of both study areas, the Site Type classification systems revealed many soil and geological features that were not indicated by the lower-resolution Land Type systems. Variation in characteristics related to parent material, soil classification, soil depth, intensity of subsoil wetness and soil organic matter were not adequately reflected in these systems. This can potentially have important implications for applications such as species choice, predictions of yield, nutrient optimization, ratings of soil resilience, biodiversity management and evaluations for carbon sequestration potential. The data forming part of this study indicate that although Land Type classification systems can provide valuable support at strategic levels of planning and management, there are several limitations for use at finer scales of resolution. The final chapter of the study includes an investigation and qualitative comparison of the usefulness of Site Type vs. Land Type classification systems, based on existing knowledge in the industry. The two systems are compared in terms of its input towards the following applications: site-species matching, timber yield prediction, site amelioration / site preparation requirements, nutrient management requirements, vegetation management / weed control, management of pests and diseases, determination of risk for soil compaction, soil erosion and nutrient loss, decision making regarding forest engineering operations, prediction of wood / fibre properties, biodiversity management and lastly planning of research activities / priorities. This analysis indicated that applications that require data on only climate and general soil patterns can be supported with equal success by both types of site classification systems. On the other hand, in cases where high-resolution data on site factors are required, Land Type classification systems had numerous shortcomings and received a much lower rating of suitability. The outcome of the study can provide guidance on the development and design of future site classification and evaluation systems for the South African forest industry. High-resolution databases of key site factors should receive priority, together with the development of decision support systems based on causal relationships. This will contribute to the resilience and sustainability of an industry that is increasingly confronted with questions related to the placement, design and management of forest plantations.
- Full Text:
- Date Issued: 2020
A social-ecological investigation into urban domestic gardens and avifauna in medium-sized towns of the Eastern Cape, South Africa
- Authors: Tricam, Shayla
- Date: 2020
- Subjects: Urban ecology (Biology) -- South Africa , Biotic communites -- South Africa , Gardens -- South Africa -- Managemenet , Birds – Ecology – South Africa , Gardening to attract birds -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145314 , vital:38427
- Description: Urban domestic gardens are an often overlooked component of urban green infrastructure, despite their potential to contribute to the preservation of urban biodiversity. As opposed to public greenspaces, private gardens are individually owned and managed, thus act as social-ecological systems, where the cumulative actions of urban residents can scale up to influence ecological patterns and processes on a larger scale. The diversity of fauna and flora within urban gardens provide a range of ecosystem goods and services, as well as less tangible benefits in the form of recreation, education and culture. However, little is known about the contribution of urban domestic gardens to urban biodiversity and its potential conservation value in South Africa. This study investigated urban domestic gardens along a socio-economic gradient in two medium-sized towns, Grahamstown and Port Alfred in the Eastern Cape, South Africa. This study found distinct differences among urban resident garden management practices as well as the avifauna which were seen within the gardens across the socio-economic gradient. The Garden Management Intensity index was higher within affluent households compared to other socio-economic levels, with subsequent management scores not differing statistically along the gradient. While there was variation within garden management practices, as well as the number of residents who participated in supplementary bird feeding, little variation was seen in the activities which were enjoyed by the residents, indicating numerous benefits the garden environment provides for all urban residents. The bird community composition along the socio-economic gradient displayed patterns directly reflecting the “luxury effect”, where households with a higher socio-economic status had harbour gardens with greater levels of biodiversity. This study showed that affluent gardens displayed far greater diversity, richness and abundance of urban birds. Multivariate analyses confirmed the patterns by highlighting a distinct bird community in the affluent zone, compared to other two socio-economic zones, which housed a second bird community. Furthermore, the main driver of the bird community composition was dominated by vegetation complexity, most notably tree cover within the gardens. Therefore, this study highlighted that patterns of ecological inequality are highly evident in medium-sized towns in South Africa, where older, affluent suburbs households display greater diversity and abundance of birdlife, compared to subsequent socio-economic zones within the study. Prioritisation with regards to the benefits a garden environment brings to urban residents in terms of a connection to nature, access to urban greenery, and relationship to urban wildlife is vital and should be promoted and planned for across all socio-economic zones.
- Full Text:
- Date Issued: 2020
- Authors: Tricam, Shayla
- Date: 2020
- Subjects: Urban ecology (Biology) -- South Africa , Biotic communites -- South Africa , Gardens -- South Africa -- Managemenet , Birds – Ecology – South Africa , Gardening to attract birds -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145314 , vital:38427
- Description: Urban domestic gardens are an often overlooked component of urban green infrastructure, despite their potential to contribute to the preservation of urban biodiversity. As opposed to public greenspaces, private gardens are individually owned and managed, thus act as social-ecological systems, where the cumulative actions of urban residents can scale up to influence ecological patterns and processes on a larger scale. The diversity of fauna and flora within urban gardens provide a range of ecosystem goods and services, as well as less tangible benefits in the form of recreation, education and culture. However, little is known about the contribution of urban domestic gardens to urban biodiversity and its potential conservation value in South Africa. This study investigated urban domestic gardens along a socio-economic gradient in two medium-sized towns, Grahamstown and Port Alfred in the Eastern Cape, South Africa. This study found distinct differences among urban resident garden management practices as well as the avifauna which were seen within the gardens across the socio-economic gradient. The Garden Management Intensity index was higher within affluent households compared to other socio-economic levels, with subsequent management scores not differing statistically along the gradient. While there was variation within garden management practices, as well as the number of residents who participated in supplementary bird feeding, little variation was seen in the activities which were enjoyed by the residents, indicating numerous benefits the garden environment provides for all urban residents. The bird community composition along the socio-economic gradient displayed patterns directly reflecting the “luxury effect”, where households with a higher socio-economic status had harbour gardens with greater levels of biodiversity. This study showed that affluent gardens displayed far greater diversity, richness and abundance of urban birds. Multivariate analyses confirmed the patterns by highlighting a distinct bird community in the affluent zone, compared to other two socio-economic zones, which housed a second bird community. Furthermore, the main driver of the bird community composition was dominated by vegetation complexity, most notably tree cover within the gardens. Therefore, this study highlighted that patterns of ecological inequality are highly evident in medium-sized towns in South Africa, where older, affluent suburbs households display greater diversity and abundance of birdlife, compared to subsequent socio-economic zones within the study. Prioritisation with regards to the benefits a garden environment brings to urban residents in terms of a connection to nature, access to urban greenery, and relationship to urban wildlife is vital and should be promoted and planned for across all socio-economic zones.
- Full Text:
- Date Issued: 2020