An understanting of mirrors and mirroring in a schizophrenic patient obsessed with his appearance
- Authors: Zworestine, Barry John
- Date: 1993-04
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191702 , vital:45149
- Description: This work addresses the role of mirroring and mirrors encountered while working with a patient obsessed with his appearance. At the same time, however, it also attempts to provide an understanding of the process of mirroring from the developing unborn child to the adult. It examines the womb as a reflective space, the mirroring role of the mother, psychological work as mirror work, the psychopathologies of disruptive mirroring and the nature of reflection as a story, confusion and a ghostly other, and finally, the relationship between mirror reflection and psychological life. What is examined and described in this process applies not only to the specific case in study but is relevant at a universal level to all of mankind regardless of race or religion. The case-study method was used to examine the process of therapy that took place over three months. The patient’s identifying data, reasons for referral, presenting problem, family background, basic personality, interpersonal relationships, mental state, diagnosis, dynamic formulation and rationale for psychotherapy were covered in detail. The process of psychotherapy over 27 sessions was recounted and discussed in detail. Theoretical understandings drawn on to facilitate an understanding of the case were from Davis and Walbridge on Winnicolt, Winnicot, Liedloff, Kay, Romanyshyn, Bettelheim, Schwartz and others. , Thesis (MA) -- Faculty of Humanities, Psychology, 1993
- Full Text:
- Date Issued: 1993-04
- Authors: Zworestine, Barry John
- Date: 1993-04
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191702 , vital:45149
- Description: This work addresses the role of mirroring and mirrors encountered while working with a patient obsessed with his appearance. At the same time, however, it also attempts to provide an understanding of the process of mirroring from the developing unborn child to the adult. It examines the womb as a reflective space, the mirroring role of the mother, psychological work as mirror work, the psychopathologies of disruptive mirroring and the nature of reflection as a story, confusion and a ghostly other, and finally, the relationship between mirror reflection and psychological life. What is examined and described in this process applies not only to the specific case in study but is relevant at a universal level to all of mankind regardless of race or religion. The case-study method was used to examine the process of therapy that took place over three months. The patient’s identifying data, reasons for referral, presenting problem, family background, basic personality, interpersonal relationships, mental state, diagnosis, dynamic formulation and rationale for psychotherapy were covered in detail. The process of psychotherapy over 27 sessions was recounted and discussed in detail. Theoretical understandings drawn on to facilitate an understanding of the case were from Davis and Walbridge on Winnicolt, Winnicot, Liedloff, Kay, Romanyshyn, Bettelheim, Schwartz and others. , Thesis (MA) -- Faculty of Humanities, Psychology, 1993
- Full Text:
- Date Issued: 1993-04
Synthesis, characterization and antiparasitic evaluation of chalcone hybrids
- Authors: Zulu, Ayanda Ignatia
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192853 , vital:45271
- Description: Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Zulu, Ayanda Ignatia
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192853 , vital:45271
- Description: Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
Marine plastic pollution impacts on ecosystem services and livelihoods in South Africa: a review and stakeholder perceptions
- Authors: Yose, Papama
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424743 , vital:72180
- Description: Marine plastic pollution is one of the major environmental problems globally, with adverse impacts on marine ecosystem services, functions and benefits and people. Yet, compared to plastic pollution impacts on terrestrial ecosystems, the impacts of plastic waste on marine ecosystems are little studied and poorly understood in South Africa. In response, research interest on the ecological and economic impacts of marine plastic pollution has grown rapidly but socio-cultural impacts remain poorly conceptualized and little understudied. This trend is arguably driven by the dominance of a quantitative paradigm which is arguably inadequate to respond to dynamic socio-cultural issues and contexts. Further, in South Africa, marine ecosystems are used by diverse groups of people ranging from subsistence users, tourism operators, commercial fishers and recreational users, meaning that addressing marine plastic pollution requires a multi-stakeholder approach. However, few studies explore the perceptions of diverse stakeholders regarding marine plastic pollution, its impacts and potential interventions. Against this background, the objective of the thesis are twofold: (a) to argue for a more nuanced understanding of marine plastic pollution impacts on human well-being in order to strengthen conceptualization of impacts that goes beyond direct and quantitatively measured impacts (ecological, health and economic) but considers the socio-cultural dimensions of impacts (lifestyle disruptions, mental health costs and cultural and heritage impacts), and (b) examine stakeholders’ perceptions of marine plastic pollution, its impacts and potential interventions in South Africa. Drawing on case studies, this study provides a working definition of the socio-cultural impacts of marine plastic pollution and a conceptual framework for categorizing the impacts. It highlights three dimensions of the socio-cultural impacts of marine plastic pollution (lifestyle, mental health, and cultural and heritage impacts). It also illustrates connections between marine ecosystems and marine-based livelihood activities with the social and cultural dimensions of human wellbeing to show the links between marine environments and socio-cultural contexts. Concerning stakeholder perceptions, the study showed a tendency to associate marine plastic pollution with immediate, noticeable and easily quantifiable ecological impacts such as entanglement and ingestion of marine organisms, economic impacts and social impacts (e.g., loss of aesthetic appeal). However, secondary impacts such as loss of marine biodiversity and social impacts such as human health, were largely unknown. Moreover, there was heterogeneity in perceptions of marine plastic pollution impacts among the stakeholder groups. Prospective studies researching marine plastic pollution impacts should consider divergent and diverse perceptions of different stakeholders to capture the real costs of marine plastic pollution. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Yose, Papama
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424743 , vital:72180
- Description: Marine plastic pollution is one of the major environmental problems globally, with adverse impacts on marine ecosystem services, functions and benefits and people. Yet, compared to plastic pollution impacts on terrestrial ecosystems, the impacts of plastic waste on marine ecosystems are little studied and poorly understood in South Africa. In response, research interest on the ecological and economic impacts of marine plastic pollution has grown rapidly but socio-cultural impacts remain poorly conceptualized and little understudied. This trend is arguably driven by the dominance of a quantitative paradigm which is arguably inadequate to respond to dynamic socio-cultural issues and contexts. Further, in South Africa, marine ecosystems are used by diverse groups of people ranging from subsistence users, tourism operators, commercial fishers and recreational users, meaning that addressing marine plastic pollution requires a multi-stakeholder approach. However, few studies explore the perceptions of diverse stakeholders regarding marine plastic pollution, its impacts and potential interventions. Against this background, the objective of the thesis are twofold: (a) to argue for a more nuanced understanding of marine plastic pollution impacts on human well-being in order to strengthen conceptualization of impacts that goes beyond direct and quantitatively measured impacts (ecological, health and economic) but considers the socio-cultural dimensions of impacts (lifestyle disruptions, mental health costs and cultural and heritage impacts), and (b) examine stakeholders’ perceptions of marine plastic pollution, its impacts and potential interventions in South Africa. Drawing on case studies, this study provides a working definition of the socio-cultural impacts of marine plastic pollution and a conceptual framework for categorizing the impacts. It highlights three dimensions of the socio-cultural impacts of marine plastic pollution (lifestyle, mental health, and cultural and heritage impacts). It also illustrates connections between marine ecosystems and marine-based livelihood activities with the social and cultural dimensions of human wellbeing to show the links between marine environments and socio-cultural contexts. Concerning stakeholder perceptions, the study showed a tendency to associate marine plastic pollution with immediate, noticeable and easily quantifiable ecological impacts such as entanglement and ingestion of marine organisms, economic impacts and social impacts (e.g., loss of aesthetic appeal). However, secondary impacts such as loss of marine biodiversity and social impacts such as human health, were largely unknown. Moreover, there was heterogeneity in perceptions of marine plastic pollution impacts among the stakeholder groups. Prospective studies researching marine plastic pollution impacts should consider divergent and diverse perceptions of different stakeholders to capture the real costs of marine plastic pollution. , Thesis (MSc) -- Faculty of Science, Environmental Science, 2023
- Full Text:
- Date Issued: 2023-10-13
Evaluation of traditional and residual momentum strategies during the Covid period on the Johannesburg Stock Exchange
- Authors: Yengwa, Mphathi Lubabalo
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462834 , vital:76339
- Description: Traditional momentum is a concept which was first discovered by Jegadeesh and Titman (1993), defined as a tendency of stocks to experience a continuation in their relative performance. A stock that performed relatively well will continue to perform relatively well, and vice versa. It has been observed by other researchers that during market crises, traditional momentum tends to produce large negative returns for investors, defined as a momentum crash. To mitigate momentum crashes, many researchers have developed new momentum strategies which have better performance than traditional momentum during market crises; such strategies include residual momentum. While both residual and traditional momentum have been studied in international markets and locally, the performance of both the residual and traditional momentum strategies have not been examined in the most recent Covid-fuelled financial crisis on the Johannesburg Stock Exchange. The study compares the performance of hypothetical long-only winner traditional and residual momentum portfolios (from 2018–2022) using various risk metrics, which include the tracking error, Sharpe ratio, Jensen’s alpha and information ratio. To compare the statistical significance of the difference in mean returns of residual and traditional momentum strategies to the benchmark (FTSE/Johannesburg Stock Exchange (JSE) Top 40) the study uses Welch’s t-test. The study uses an Auto regressive distributed lag (ARDL) regression to examine the effect that various market conditions (bull market, bear market and extreme volatility) have on the returns of residual and traditional momentum strategies. Given the limited period examined in this study, the Monte Carlo simulation was used to extrapolate potential outcomes of how the momentum strategies might perform under different market conditions (as mentioned) in 1 000 iterations of each condition. The simple return analysis undertaken in this research revealed that traditional momentum outperformed residual momentum both before and throughout the COVID period. In the risk-adjusted performance measures, traditional momentum outperformed at all four risk indicators during the 2020 COVID year. The statistical significance tests, which compared the strategies' mean returns to the benchmark, demonstrated no statistically significant difference in returns over the COVID year. Furthermore, when evaluating the strategies over a five-year period (2018-2022), the difference in mean returns was shown to be statistically insignificant. However, statistical significance in returns was shown in some individual years. The ARDL regression findings show that bull, bear, and volatility factors explain relatively little of the returns for both momentum strategies, which is consistent with previous research. The Monte Carlo simulation, using the bear variable, forecasted that traditional momentum would result in negative returns during market declines, but residual momentum would provide positive returns and surpass traditional momentum with a probability of 26%. When using the bull variable, the simulation discovered that both traditional and residual momentum strategies resulted in positive returns. However, the residual momentum strategy outperformed in terms of returns and had an 84% likelihood of outperforming the traditional momentum strategy across 1,000 iterations. Nevertheless, when the simulation included the volatility variable, it projected negative returns for residual momentum and positive returns for traditional momentum. Additionally, it estimated a 14% probability of residual momentum surpassing traditional momentum under volatile market circumstances. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Yengwa, Mphathi Lubabalo
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462834 , vital:76339
- Description: Traditional momentum is a concept which was first discovered by Jegadeesh and Titman (1993), defined as a tendency of stocks to experience a continuation in their relative performance. A stock that performed relatively well will continue to perform relatively well, and vice versa. It has been observed by other researchers that during market crises, traditional momentum tends to produce large negative returns for investors, defined as a momentum crash. To mitigate momentum crashes, many researchers have developed new momentum strategies which have better performance than traditional momentum during market crises; such strategies include residual momentum. While both residual and traditional momentum have been studied in international markets and locally, the performance of both the residual and traditional momentum strategies have not been examined in the most recent Covid-fuelled financial crisis on the Johannesburg Stock Exchange. The study compares the performance of hypothetical long-only winner traditional and residual momentum portfolios (from 2018–2022) using various risk metrics, which include the tracking error, Sharpe ratio, Jensen’s alpha and information ratio. To compare the statistical significance of the difference in mean returns of residual and traditional momentum strategies to the benchmark (FTSE/Johannesburg Stock Exchange (JSE) Top 40) the study uses Welch’s t-test. The study uses an Auto regressive distributed lag (ARDL) regression to examine the effect that various market conditions (bull market, bear market and extreme volatility) have on the returns of residual and traditional momentum strategies. Given the limited period examined in this study, the Monte Carlo simulation was used to extrapolate potential outcomes of how the momentum strategies might perform under different market conditions (as mentioned) in 1 000 iterations of each condition. The simple return analysis undertaken in this research revealed that traditional momentum outperformed residual momentum both before and throughout the COVID period. In the risk-adjusted performance measures, traditional momentum outperformed at all four risk indicators during the 2020 COVID year. The statistical significance tests, which compared the strategies' mean returns to the benchmark, demonstrated no statistically significant difference in returns over the COVID year. Furthermore, when evaluating the strategies over a five-year period (2018-2022), the difference in mean returns was shown to be statistically insignificant. However, statistical significance in returns was shown in some individual years. The ARDL regression findings show that bull, bear, and volatility factors explain relatively little of the returns for both momentum strategies, which is consistent with previous research. The Monte Carlo simulation, using the bear variable, forecasted that traditional momentum would result in negative returns during market declines, but residual momentum would provide positive returns and surpass traditional momentum with a probability of 26%. When using the bull variable, the simulation discovered that both traditional and residual momentum strategies resulted in positive returns. However, the residual momentum strategy outperformed in terms of returns and had an 84% likelihood of outperforming the traditional momentum strategy across 1,000 iterations. Nevertheless, when the simulation included the volatility variable, it projected negative returns for residual momentum and positive returns for traditional momentum. Additionally, it estimated a 14% probability of residual momentum surpassing traditional momentum under volatile market circumstances. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
Native-range studies on insect herbivores associated with African Lovegrass (Eragrostis curvula) in South Africa: prospects for biological control in Australia
- Authors: Yell, Liam Dougal
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424446 , vital:72154
- Description: Eragrostis curvula (Schrad.) Nees. (African Lovegrass) is an African native species of grass that was intentionally introduced for pasture in Australia. It has since escaped cultivation and has become widespread and highly invasive. Eragrostis curvula has been recorded in every state and territory in Australia where it has altered fire regimes, disrupted nutrient cycles and can reduce livestock carrying capacity by up to 50%. The Centre for Biological Control at Rhodes University and the New South Wales Department of Primary Industries have been working in collaboration to identify and screen herbivorous insects as biological control agents for E. curvula in Australia. Native-range surveys were conducted between 2021 and 2022 on E. curvula at twenty-two sites across South Africa to identify herbivorous natural enemies associated with it. Species accumulation curves were generated to ensure adequate sampling was performed to identify all the insects associated with E. curvula. Twenty-nine non-target grass species were surveyed simultaneously to determine the field-host range of the natural enemies associated with the target weed. Herbivorous natural enemies were prioritised as possible biological control agents against E. curvula in Australia based on field-host range, predicted efficacy and climatic suitability. Four insect species were consistently found on E. curvula, two of which were herbivorous, as well as a parasitoid and a detritivore. Species accumulation curves show that the insect community was adequately sampled in South Africa. The two herbivorous insects were identified to the lowest taxonomic level using COI barcoding. Both species are undescribed phytophagous wasps in the genus Tetramesa (Hymenoptera: Eurytomidae). Because Tetramesa species have been shown to be host specific and highly damaging in previous biological control programs for other invasive grass weeds, we assessed their suitability as candidate biological control agents for use on E. curvula in Australia. Both Tetramesa species (“sp. 4” and “sp. 5”) were found on several native congeners under field conditions in South Africa. Congeneric South African-native non-target grass species were used as phylogenetic proxies to assess the risk posed to Australian native Eragrostis species. This highlighted three non-target Australian native Eragrostis species, namely: E. parviflora (R. Br.) Trin., E. leptocarpa Benth. fl., and E. trachycarpa Benth., that are at risk of being attacked by the two candidate agents based on their phylogenetic proximity to E. curvula. Predicted efficacy trials were conducted at five long-term repeat survey sites and revealed that Tetramesa sp. 4 does not reduce the probability of E. curvula tiller survival or reproduction, while Tetramesa sp. 5 does not reduce the probability of tiller reproduction but does increase the probability of tiller survival. This result was unexpected and may be a plant compensatory response to herbivory. The sites where both Tetramesa species were collected in South Africa are climatically similar to the invaded range of E. curvula in Australia, and as such, the Tetramesa spp. are likely to be suitably adapted to the climate where they would be released in Australia. These results suggest that both Tetramesa species associated with E. curvula may have too broad a host range to be used as biological control agents in Australia. However, further quarantine-based host-range assessments on Australian native Eragrostis species are recommended to confirm this. The field-based methods used in this study have reduced the number of insect and plant species that host-range assessments will be required to be performed on, thus preventing wasted resources. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Yell, Liam Dougal
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424446 , vital:72154
- Description: Eragrostis curvula (Schrad.) Nees. (African Lovegrass) is an African native species of grass that was intentionally introduced for pasture in Australia. It has since escaped cultivation and has become widespread and highly invasive. Eragrostis curvula has been recorded in every state and territory in Australia where it has altered fire regimes, disrupted nutrient cycles and can reduce livestock carrying capacity by up to 50%. The Centre for Biological Control at Rhodes University and the New South Wales Department of Primary Industries have been working in collaboration to identify and screen herbivorous insects as biological control agents for E. curvula in Australia. Native-range surveys were conducted between 2021 and 2022 on E. curvula at twenty-two sites across South Africa to identify herbivorous natural enemies associated with it. Species accumulation curves were generated to ensure adequate sampling was performed to identify all the insects associated with E. curvula. Twenty-nine non-target grass species were surveyed simultaneously to determine the field-host range of the natural enemies associated with the target weed. Herbivorous natural enemies were prioritised as possible biological control agents against E. curvula in Australia based on field-host range, predicted efficacy and climatic suitability. Four insect species were consistently found on E. curvula, two of which were herbivorous, as well as a parasitoid and a detritivore. Species accumulation curves show that the insect community was adequately sampled in South Africa. The two herbivorous insects were identified to the lowest taxonomic level using COI barcoding. Both species are undescribed phytophagous wasps in the genus Tetramesa (Hymenoptera: Eurytomidae). Because Tetramesa species have been shown to be host specific and highly damaging in previous biological control programs for other invasive grass weeds, we assessed their suitability as candidate biological control agents for use on E. curvula in Australia. Both Tetramesa species (“sp. 4” and “sp. 5”) were found on several native congeners under field conditions in South Africa. Congeneric South African-native non-target grass species were used as phylogenetic proxies to assess the risk posed to Australian native Eragrostis species. This highlighted three non-target Australian native Eragrostis species, namely: E. parviflora (R. Br.) Trin., E. leptocarpa Benth. fl., and E. trachycarpa Benth., that are at risk of being attacked by the two candidate agents based on their phylogenetic proximity to E. curvula. Predicted efficacy trials were conducted at five long-term repeat survey sites and revealed that Tetramesa sp. 4 does not reduce the probability of E. curvula tiller survival or reproduction, while Tetramesa sp. 5 does not reduce the probability of tiller reproduction but does increase the probability of tiller survival. This result was unexpected and may be a plant compensatory response to herbivory. The sites where both Tetramesa species were collected in South Africa are climatically similar to the invaded range of E. curvula in Australia, and as such, the Tetramesa spp. are likely to be suitably adapted to the climate where they would be released in Australia. These results suggest that both Tetramesa species associated with E. curvula may have too broad a host range to be used as biological control agents in Australia. However, further quarantine-based host-range assessments on Australian native Eragrostis species are recommended to confirm this. The field-based methods used in this study have reduced the number of insect and plant species that host-range assessments will be required to be performed on, thus preventing wasted resources. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
- Full Text:
- Date Issued: 2023-10-13
An exploratory study of leadership and organisational change through the lens of organisational behaviour: a secondary school in Makhanda
- Authors: Yedwa, Sesonasipho
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434595 , vital:73088
- Description: Access restricted. Expected release in 2025. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
- Full Text:
- Date Issued: 2024-04-03
- Authors: Yedwa, Sesonasipho
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434595 , vital:73088
- Description: Access restricted. Expected release in 2025. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
- Full Text:
- Date Issued: 2024-04-03
Quantifying feed intake and feeding intensity using two experimental conditions and the effect of different feeding strategies on the production parameters of farmed South African abalone, haliotis midae
- Authors: Wortley, Ross Michael
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:71932
- Description: As abalone are slow-growing animals there is a high investment of capital, running costs and labour in commercial abalone farming. Revenue needs to be maximised by achieving fast growth rates. A foremost driver of abalone growth is feed intake and feeding intensity of the abalone as well as the feeding regimen a farm utilises. While feed intake is well-documented in H. midae, there is a paucity of information regarding this aspect in abalone above 70 g and the relationship between feeding intensity, feed conversion rate (FCR) and daily growth rate needs to be documented. Similarly, there are a limited number of studies dealing with the effects of different pellet types of the same formulation, that differ only in shape and size, on feed intake and production in H. midae. This study made use of both a controlled laboratory experiment and commercial-scale farm experiment with the aim of testing whether feed intake information produced under laboratory conditions can provide good estimates of feed intake under farming conditions, which can further be implemented into feeding strategies on abalone farms. This study quantified daily feed intake (F) in 10 – 20 g, 100 – 110 g and 150 – 160 g abalone weight classes using two different pellet types and determined the relationship between the duration of feed availability and feed intake under laboratory conditions. The effect of three different pellet type strategies (fed daily: a leaf-only strategy = L d-1, a short-pellet only strategy = SP d-1, and a strategy that used both = B d-1) on abalone production parameters under farming conditions such as growth rate, feed conversion ratio (FCR), feeding intensity (FI) and weight variation of 30 – 40 g H. midae was also investigated. A commercial-scale farm study was designed to test the effect of four commercially relevant feeding regimens (three size-specific regimens and one commercially practiced feeding method) on the growth, FCR, feeding intensity and weight variation of these three abalone weight classes while taking into account an economic model to assess the profitability of each feeding regimen. Daily feed intake as a percentage of body mass (% BM d-1) was a function of abalone weight class between the 10 – 20 g and two larger weight classes 100 – 110 g and 150 – 160 g p < 0.0001), however feed intake was not different between the 100 – 110 g and 150 – 160 g weight classes. Pellet type did not affect feed intake in all abalone weight classes (p = 0.15). Feed intake (F) was positively linearly correlated with duration of feed availability (h) in the 10 – 20 g weight class (r2 = 0.76, p <0.00001) and logarithmically correlated in the 100 – 110 g (r2 = 0.25, p < 0.02) and 150 – 160 g (r2 = 0.52, p < 0.0001) weight classes (10 – 20 g abalone-1: 3 F (% BM) = 0.02(h) + 0.1976, 100 – 110 g abalone-1: F (% BM) = log10(h)*0.17 + 0.17, 150 – 160 g abalone-1: F (% BM) = log10(h)*0.36 + 0.07). There was no significant difference in monthly average abalone weight, daily growth rate (G), FCR and feeding intensity between each pellet type strategy (G: p = 0.60, FCR: p = 0.62, FI: p = 0.54 ). However, abalone grew well over the 112-day growth period with average abalone weight increasing significantly between each monthly sample time (pooled pellet type strategy: Huynh-Feldt correction; p < 0.00001). Furthermore, abalone fed the leaf-only pellet type strategy (L d-1) fell into higher weight classes after a 112-day growth period (Z test: 50 – 70 g: 72%) which was 16.1 % higher compared to the SP d-1 and B d-1 strategies. Daily growth rate (r2 = 0.34, p < 0.01) and FCR (r2 = 0.42, p < 0.004) was negatively correlated and FCR was positively correlated with daily feeding intensity, respectively (G = - 2.59 (FI) + 1.526, FCR = 8.8082 (FI) – 2.7108). Feeding regimen affected the production parameters of three abalone weight classes. The method practiced on the farm resulted in the best growth in the 10 – 20 g abalone weight class. The farm feeding method resulted in slower yet more efficient growth rates (lowest FCR values) in the abalone weight classes, 100 – 110 g and 150 – 160 g abalone- 1. However, size-specific feeding regimens resulted in the fastest growth rates but resulted in higher FCR values (less efficient). The relationship between feeding intensity, daily growth rate and FCR all showed that an increase in feeding intensity results in increased daily growth rates and FCR values. The economic model suggests that the higher FCR values associated with size-specific regimens, which have higher associated costs to producing abalone, were greatly outweighed by the growth attained by the abalone in the 100 – 110 g and 150 – 160 g weight classes. The size-specific regimens generated a higher potential monetary value of abalone after a 112-day period, which would consequently result in higher income for abalone farms. For abalone ranging from 100 – 110 and 150 – 160 grams, the economic model suggested that in a quarterly grading schedule (112 days) that abalone be fed the size specific daily rations, which is a function of body mass, at 0.35 % BM d-1 and 0.352 % BM d-1, respectively. The two experimental conditions used in this study produced feed intake and production parameter information that is beneficial to South African abalone farmers. The small-scale laboratory study produced information on feed intake that can be used as reference values as to what abalone in these weight classes can consume on a daily basis. The laboratory study can provide estimates of feed intake under farming conditions but should only be used as minimum 4 values when determining size-specific feeding regimens. To maximise abalone growth, farmers should utilise size-specific feeding regimens for abalone above 30 g. Daily growth rate and FCR can be predicted as a function of the abalone’s feeding intensity. Further studies are needed to determine the effects of abalone weight class on production parameters when testing different pellet types as well as an exploration into behavioural studies focusing on diet preferences. Additionally, future studies need to take into consideration abalone above the weight of 100 g with additional focus of research on behavioural, genetic and environmental aspects on abalone feed intake. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Wortley, Ross Michael
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/${Handle} , vital:71932
- Description: As abalone are slow-growing animals there is a high investment of capital, running costs and labour in commercial abalone farming. Revenue needs to be maximised by achieving fast growth rates. A foremost driver of abalone growth is feed intake and feeding intensity of the abalone as well as the feeding regimen a farm utilises. While feed intake is well-documented in H. midae, there is a paucity of information regarding this aspect in abalone above 70 g and the relationship between feeding intensity, feed conversion rate (FCR) and daily growth rate needs to be documented. Similarly, there are a limited number of studies dealing with the effects of different pellet types of the same formulation, that differ only in shape and size, on feed intake and production in H. midae. This study made use of both a controlled laboratory experiment and commercial-scale farm experiment with the aim of testing whether feed intake information produced under laboratory conditions can provide good estimates of feed intake under farming conditions, which can further be implemented into feeding strategies on abalone farms. This study quantified daily feed intake (F) in 10 – 20 g, 100 – 110 g and 150 – 160 g abalone weight classes using two different pellet types and determined the relationship between the duration of feed availability and feed intake under laboratory conditions. The effect of three different pellet type strategies (fed daily: a leaf-only strategy = L d-1, a short-pellet only strategy = SP d-1, and a strategy that used both = B d-1) on abalone production parameters under farming conditions such as growth rate, feed conversion ratio (FCR), feeding intensity (FI) and weight variation of 30 – 40 g H. midae was also investigated. A commercial-scale farm study was designed to test the effect of four commercially relevant feeding regimens (three size-specific regimens and one commercially practiced feeding method) on the growth, FCR, feeding intensity and weight variation of these three abalone weight classes while taking into account an economic model to assess the profitability of each feeding regimen. Daily feed intake as a percentage of body mass (% BM d-1) was a function of abalone weight class between the 10 – 20 g and two larger weight classes 100 – 110 g and 150 – 160 g p < 0.0001), however feed intake was not different between the 100 – 110 g and 150 – 160 g weight classes. Pellet type did not affect feed intake in all abalone weight classes (p = 0.15). Feed intake (F) was positively linearly correlated with duration of feed availability (h) in the 10 – 20 g weight class (r2 = 0.76, p <0.00001) and logarithmically correlated in the 100 – 110 g (r2 = 0.25, p < 0.02) and 150 – 160 g (r2 = 0.52, p < 0.0001) weight classes (10 – 20 g abalone-1: 3 F (% BM) = 0.02(h) + 0.1976, 100 – 110 g abalone-1: F (% BM) = log10(h)*0.17 + 0.17, 150 – 160 g abalone-1: F (% BM) = log10(h)*0.36 + 0.07). There was no significant difference in monthly average abalone weight, daily growth rate (G), FCR and feeding intensity between each pellet type strategy (G: p = 0.60, FCR: p = 0.62, FI: p = 0.54 ). However, abalone grew well over the 112-day growth period with average abalone weight increasing significantly between each monthly sample time (pooled pellet type strategy: Huynh-Feldt correction; p < 0.00001). Furthermore, abalone fed the leaf-only pellet type strategy (L d-1) fell into higher weight classes after a 112-day growth period (Z test: 50 – 70 g: 72%) which was 16.1 % higher compared to the SP d-1 and B d-1 strategies. Daily growth rate (r2 = 0.34, p < 0.01) and FCR (r2 = 0.42, p < 0.004) was negatively correlated and FCR was positively correlated with daily feeding intensity, respectively (G = - 2.59 (FI) + 1.526, FCR = 8.8082 (FI) – 2.7108). Feeding regimen affected the production parameters of three abalone weight classes. The method practiced on the farm resulted in the best growth in the 10 – 20 g abalone weight class. The farm feeding method resulted in slower yet more efficient growth rates (lowest FCR values) in the abalone weight classes, 100 – 110 g and 150 – 160 g abalone- 1. However, size-specific feeding regimens resulted in the fastest growth rates but resulted in higher FCR values (less efficient). The relationship between feeding intensity, daily growth rate and FCR all showed that an increase in feeding intensity results in increased daily growth rates and FCR values. The economic model suggests that the higher FCR values associated with size-specific regimens, which have higher associated costs to producing abalone, were greatly outweighed by the growth attained by the abalone in the 100 – 110 g and 150 – 160 g weight classes. The size-specific regimens generated a higher potential monetary value of abalone after a 112-day period, which would consequently result in higher income for abalone farms. For abalone ranging from 100 – 110 and 150 – 160 grams, the economic model suggested that in a quarterly grading schedule (112 days) that abalone be fed the size specific daily rations, which is a function of body mass, at 0.35 % BM d-1 and 0.352 % BM d-1, respectively. The two experimental conditions used in this study produced feed intake and production parameter information that is beneficial to South African abalone farmers. The small-scale laboratory study produced information on feed intake that can be used as reference values as to what abalone in these weight classes can consume on a daily basis. The laboratory study can provide estimates of feed intake under farming conditions but should only be used as minimum 4 values when determining size-specific feeding regimens. To maximise abalone growth, farmers should utilise size-specific feeding regimens for abalone above 30 g. Daily growth rate and FCR can be predicted as a function of the abalone’s feeding intensity. Further studies are needed to determine the effects of abalone weight class on production parameters when testing different pellet types as well as an exploration into behavioural studies focusing on diet preferences. Additionally, future studies need to take into consideration abalone above the weight of 100 g with additional focus of research on behavioural, genetic and environmental aspects on abalone feed intake. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
- Full Text:
- Date Issued: 2023-03-29
Exploring the use of in vitro colorimetric and bioluminescence assays to distinguish between Arf GTPase isoforms and detect Arf GTPase activity
- Authors: Woolf, Alexander Robert
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192582 , vital:45240
- Description: Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Woolf, Alexander Robert
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192582 , vital:45240
- Description: Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
- Full Text:
- Date Issued: 2021-10-29
Developing biological control agents for the management of the invasive tree Robinia pseudoacacia
- Authors: Wolmarans, Abigail
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435717 , vital:73181 , DOI 10.21504/10962/435717
- Description: Robinia pseudoacacia (Fabaceae) is a deciduous tree native to the Appalachian Mountains of North America but has become naturalised and invasive in other countries such as temperate North America, Europe, Australia, and Southern Africa. In South Africa the tree is classified as a category 1B invasive alien under the National Environmental Management Act (NEMBA), which stipulates the species requires some form of control as it has already caused extensive negative ecological and economic impacts. In the invaded range the tree creates monocultures that displace native species and spreads rapidly from suckering roots, making it a proficient invader. The South Africa plant prioritisation system suggests R. pseudoacacia is in the top three species which should be considered for classical weed biological control in South Africa. This thesis investigates which insects known to be associated with tree should be prioritised as candidate agents, as well as offering interesting insights into prioritising insects for weed biological control and using plant phylogenies and available literature to predict insect specificity. To ensure that no candidate biological control agents were already present in South Africa as well as to prioritise which guilds of the tree to prioritise for potential biological control, pre-release surveys were conducted across nine sites where the tree has invaded South Africa. It was found that no insects from the native range of R. pseudoacacia were present in South Africa. Seed surveys revealed that generalist insects attack a sizable proportion (68 %) of the seeds on the trees. In combination with a low seed soil bank (15.8 %) this suggests that seed- feeding agents may be helpful, however, candidate agents which damage leaves should be prioritised due to R. pseudoacacia relying heavily upon vegetative reproduction and much less on sexual reproduction. Leaves may therefor reduce the spread of these invasive trees. The insect assemblages in the native range of R. pseudoacacia are well understood. In addition, several associated insects have unintentionally followed the tree on its global spread, where they are often regarded as pests. The third chapter is therefore aimed at prioritising the known insects associated with the tree in both the native and invaded range. Literature surveys and Harris (1973) prioritisation systems were used to prioritise close to 64 candidate biological control agents down to three foliage- feeding agents, namely Odontota dorsalis (Coleoptera, Chrysomelidae), Macrosaccus robiniella (Lepidoptera, Gracillariidae) and Obolodiplosis robiniae (Diptera, Cecidomyiidae). To further prioritise the six selected agents in Chapter 4, species distribution were modelled with known climatic variables. This was done by using the species known occurrence localities, from both the native and where applicable invaded ranges, to identify which species that would best match with South Africa’s climate. The study showed that O. dorsalis is best suited to survive in South Africa, followed by O. robiniae and then M. robiniella. Collected data aided in the introduction of the prioritised O. robiniae into South African quarantine facilities. Unfortunately, despite several attempts, cultures could not be established, making conventional host specificity testing impossible. Thus, in Chapter 5 we aimed to determine the potential host range of the midge using information from experts in the field of galling insects, literature surveys, agricultural pest lists, and social science platforms coupled with native and invaded range surveys. The list of non-target species to consider as potential hosts was refined by developing phylogenetic trees of closely related Fabaceae that share the same distribution (native and invaded) as R. pseudoacacia. Through the available information gathered, and field surveys of these species, O. robiniae has not been shown to utilise any species, other than those from the Robinoid clade. In addition, the midge has also never been recorded on a number of closely related leguminous fodder and horticultural species growing in close proximity at high densities to R. pseudoacacia - suggesting negligible risk to South African growers of the same species. Host-specificity assessments through field surveys can be regarded as one of the best indicators of the ecological host range, however, this information is difficult to quantify and infrequently available, thus seldom used when determining the safety of a candidate biocontrol agent. In this unique study, using the extensive data collected we are able to show that O. robiniae would be potentially safe for release in South Africa. However, open field tests exposing closely related non-target plant species under natural and semi-natural conditions are planned in Switzerland over the next two years aiming to confirm these conclusions. By identifying and prioritizing potential biological control agents, this research contributes to the development of a targeted and sustainable solution for managing R. pseudoacacia in South Africa. The economic implications of successful biological control include reduced costs associated with invasive species management and ecosystem restoration. Additionally, by mitigating the negative ecological impacts, the agricultural systems in affected regions stand to benefit from enhanced resilience and productivity. Furthermore, the study's approach of using plant phylogenies and available literature to predict insect specificity offers a valuable methodological contribution to the broader field of weed biological control. This methodology can be adapted and applied to other invasive species, providing a framework for efficient and informed decision-making in weed management strategies. In essence, this research not only addresses the specific challenges posed by R. pseudoacacia in South Africa but also provides a template for tackling similar issues in different geographical contexts, thereby contributing to global efforts in sustainable agriculture and environmental conservation. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Wolmarans, Abigail
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435717 , vital:73181 , DOI 10.21504/10962/435717
- Description: Robinia pseudoacacia (Fabaceae) is a deciduous tree native to the Appalachian Mountains of North America but has become naturalised and invasive in other countries such as temperate North America, Europe, Australia, and Southern Africa. In South Africa the tree is classified as a category 1B invasive alien under the National Environmental Management Act (NEMBA), which stipulates the species requires some form of control as it has already caused extensive negative ecological and economic impacts. In the invaded range the tree creates monocultures that displace native species and spreads rapidly from suckering roots, making it a proficient invader. The South Africa plant prioritisation system suggests R. pseudoacacia is in the top three species which should be considered for classical weed biological control in South Africa. This thesis investigates which insects known to be associated with tree should be prioritised as candidate agents, as well as offering interesting insights into prioritising insects for weed biological control and using plant phylogenies and available literature to predict insect specificity. To ensure that no candidate biological control agents were already present in South Africa as well as to prioritise which guilds of the tree to prioritise for potential biological control, pre-release surveys were conducted across nine sites where the tree has invaded South Africa. It was found that no insects from the native range of R. pseudoacacia were present in South Africa. Seed surveys revealed that generalist insects attack a sizable proportion (68 %) of the seeds on the trees. In combination with a low seed soil bank (15.8 %) this suggests that seed- feeding agents may be helpful, however, candidate agents which damage leaves should be prioritised due to R. pseudoacacia relying heavily upon vegetative reproduction and much less on sexual reproduction. Leaves may therefor reduce the spread of these invasive trees. The insect assemblages in the native range of R. pseudoacacia are well understood. In addition, several associated insects have unintentionally followed the tree on its global spread, where they are often regarded as pests. The third chapter is therefore aimed at prioritising the known insects associated with the tree in both the native and invaded range. Literature surveys and Harris (1973) prioritisation systems were used to prioritise close to 64 candidate biological control agents down to three foliage- feeding agents, namely Odontota dorsalis (Coleoptera, Chrysomelidae), Macrosaccus robiniella (Lepidoptera, Gracillariidae) and Obolodiplosis robiniae (Diptera, Cecidomyiidae). To further prioritise the six selected agents in Chapter 4, species distribution were modelled with known climatic variables. This was done by using the species known occurrence localities, from both the native and where applicable invaded ranges, to identify which species that would best match with South Africa’s climate. The study showed that O. dorsalis is best suited to survive in South Africa, followed by O. robiniae and then M. robiniella. Collected data aided in the introduction of the prioritised O. robiniae into South African quarantine facilities. Unfortunately, despite several attempts, cultures could not be established, making conventional host specificity testing impossible. Thus, in Chapter 5 we aimed to determine the potential host range of the midge using information from experts in the field of galling insects, literature surveys, agricultural pest lists, and social science platforms coupled with native and invaded range surveys. The list of non-target species to consider as potential hosts was refined by developing phylogenetic trees of closely related Fabaceae that share the same distribution (native and invaded) as R. pseudoacacia. Through the available information gathered, and field surveys of these species, O. robiniae has not been shown to utilise any species, other than those from the Robinoid clade. In addition, the midge has also never been recorded on a number of closely related leguminous fodder and horticultural species growing in close proximity at high densities to R. pseudoacacia - suggesting negligible risk to South African growers of the same species. Host-specificity assessments through field surveys can be regarded as one of the best indicators of the ecological host range, however, this information is difficult to quantify and infrequently available, thus seldom used when determining the safety of a candidate biocontrol agent. In this unique study, using the extensive data collected we are able to show that O. robiniae would be potentially safe for release in South Africa. However, open field tests exposing closely related non-target plant species under natural and semi-natural conditions are planned in Switzerland over the next two years aiming to confirm these conclusions. By identifying and prioritizing potential biological control agents, this research contributes to the development of a targeted and sustainable solution for managing R. pseudoacacia in South Africa. The economic implications of successful biological control include reduced costs associated with invasive species management and ecosystem restoration. Additionally, by mitigating the negative ecological impacts, the agricultural systems in affected regions stand to benefit from enhanced resilience and productivity. Furthermore, the study's approach of using plant phylogenies and available literature to predict insect specificity offers a valuable methodological contribution to the broader field of weed biological control. This methodology can be adapted and applied to other invasive species, providing a framework for efficient and informed decision-making in weed management strategies. In essence, this research not only addresses the specific challenges posed by R. pseudoacacia in South Africa but also provides a template for tackling similar issues in different geographical contexts, thereby contributing to global efforts in sustainable agriculture and environmental conservation. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
An ethnographic exploration of black lesbians rape survivors’ access to support services in Cape Town South Africa
- Wilson, Kaythrine Esther Jacqueline
- Authors: Wilson, Kaythrine Esther Jacqueline
- Date: 2022-04
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/232646 , vital:50010
- Description: Thesis (PhD) -- Faculty of Humanities, Sociology, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Wilson, Kaythrine Esther Jacqueline
- Date: 2022-04
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/232646 , vital:50010
- Description: Thesis (PhD) -- Faculty of Humanities, Sociology, 2022
- Full Text:
- Date Issued: 2022-04
A study on white leather tannage
- Authors: Williams-Wynn, D A
- Date: 1950
- Subjects: Uncatalogued
- Language: English
- Type: Diploma theses , text
- Identifier: http://hdl.handle.net/10962/193713 , vital:45389
- Description: As has been noted in the previous section little or no complex formation occurs with either formate or acetate except possibly above pH 9*0 or so. These anions do not stabilise the aluminium solutions to precipitation - they may* however, be of value in controlling pH, as solutions of these salts buffer strongly in the region pH 4 to 5. The other salts, lactate, tartrate and citrate all show tendencies to complex formation though the degree to which this occurs varies with the anion. The complexes formed by lactate at high pH must be very unstable because on the addition of acid the pH corresponds to the calculated blank. Below pH 9.0 however, the curves deviate quite considerably showing that more acid must be added to reach a certain pH value than is required by the blank. This means complex formation has occurred with loss of -COGH groups. In this system too, buffering is apparent. The same is true of tartrate but this salt is not as efficient a buffering agent. This is probably due to the fact that the excess tartrate is not available as a buffer as it is precipitated as the acid salt which is only sparingly soluble. Citrate on the other hand must form very stable complexes, the effect of which is apparent at even very high pH values. In other words, addition of strong acid liberates free -GOGH groups which are immediately incorporated in the complex. This evidently does not occur with lactate or tartrate until lower pH values are reached. The ratio of lactate and citrate to aluminium appears to have some influence on the degree of masking as greater complex formation is found to occur at the higher ratio levels. Tartrate on the other hand apparently has a fixed complex forming capacity between 1 and 4 mols/mol aluminium, since the same deviation from the blank was observed irrespective of which ratio of the masking agent to aluminium, was employed. However, at ratios of less than 1 mol tartrate/mol aluminium, deviations from the blank were reduced and less stabilisation occurs as evidenced by the formation of precipitates containing aluminium under these conditions. In view of these facts it may be suggested that 1 mol tartrate combines with 1 mol aluminium to form a complex containing equimolar proportions of aluminium and tartrate. The effect of boiling apart from one or two exceptions always has the same effect, i.e. a shift to the acid side of the curve. Free acid must have been liberated which is an indication that olation might have occurred. In the lactate and citrate series dilution appears to reduce the complex forming capacity of these ions but tartrate is unaffected. Thus it would appear that the tartrate complex is more stable than those formed by lactate. Citrate stabilises aluminium solutions with fewer equivalents than tartrate, but the complex does not contain a constant ratio of masking agent to aluminium further quantities of tartrate cannot enter the complex even in the presence of large excess of the anion probably due to the effect of steric hindrance. , Thesis (Dip) -- Leather Industries Research Institute, 1950
- Full Text:
- Date Issued: 1950
- Authors: Williams-Wynn, D A
- Date: 1950
- Subjects: Uncatalogued
- Language: English
- Type: Diploma theses , text
- Identifier: http://hdl.handle.net/10962/193713 , vital:45389
- Description: As has been noted in the previous section little or no complex formation occurs with either formate or acetate except possibly above pH 9*0 or so. These anions do not stabilise the aluminium solutions to precipitation - they may* however, be of value in controlling pH, as solutions of these salts buffer strongly in the region pH 4 to 5. The other salts, lactate, tartrate and citrate all show tendencies to complex formation though the degree to which this occurs varies with the anion. The complexes formed by lactate at high pH must be very unstable because on the addition of acid the pH corresponds to the calculated blank. Below pH 9.0 however, the curves deviate quite considerably showing that more acid must be added to reach a certain pH value than is required by the blank. This means complex formation has occurred with loss of -COGH groups. In this system too, buffering is apparent. The same is true of tartrate but this salt is not as efficient a buffering agent. This is probably due to the fact that the excess tartrate is not available as a buffer as it is precipitated as the acid salt which is only sparingly soluble. Citrate on the other hand must form very stable complexes, the effect of which is apparent at even very high pH values. In other words, addition of strong acid liberates free -GOGH groups which are immediately incorporated in the complex. This evidently does not occur with lactate or tartrate until lower pH values are reached. The ratio of lactate and citrate to aluminium appears to have some influence on the degree of masking as greater complex formation is found to occur at the higher ratio levels. Tartrate on the other hand apparently has a fixed complex forming capacity between 1 and 4 mols/mol aluminium, since the same deviation from the blank was observed irrespective of which ratio of the masking agent to aluminium, was employed. However, at ratios of less than 1 mol tartrate/mol aluminium, deviations from the blank were reduced and less stabilisation occurs as evidenced by the formation of precipitates containing aluminium under these conditions. In view of these facts it may be suggested that 1 mol tartrate combines with 1 mol aluminium to form a complex containing equimolar proportions of aluminium and tartrate. The effect of boiling apart from one or two exceptions always has the same effect, i.e. a shift to the acid side of the curve. Free acid must have been liberated which is an indication that olation might have occurred. In the lactate and citrate series dilution appears to reduce the complex forming capacity of these ions but tartrate is unaffected. Thus it would appear that the tartrate complex is more stable than those formed by lactate. Citrate stabilises aluminium solutions with fewer equivalents than tartrate, but the complex does not contain a constant ratio of masking agent to aluminium further quantities of tartrate cannot enter the complex even in the presence of large excess of the anion probably due to the effect of steric hindrance. , Thesis (Dip) -- Leather Industries Research Institute, 1950
- Full Text:
- Date Issued: 1950
Beyond mastery: jazz, gender and power in postapartheid South Africa
- Authors: Williams, Ulagh
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432505 , vital:72876 , DOI 10.21504/10962/432512
- Description: This dissertation studies the musical lives of seven South African women who have built highprofile national and international careers as jazz musicians. Empirically it records self-reported experiences and actions that they have identified as relevant to their success within a notoriously patriarchal field. Drawing on feminist research methods and Interpretative Phenomenological Analysis the dissertation strives to develop an empathic yet critical epistemological framework attuned to the complexities of their lived experiences as women and as jazz musicians. Theoretically it investigates the power relations at play in the myriad ways they negotiate or have been impelled to negotiate gender and patriarchy as musicians. Chapter one draws attention to the ubiquity of patriarchy in South African and international jazz culture, and highlights the research participants’ numerous successes to date as performers, educators, composers, and bandleaders. Chapter two positions this study in relation to cognate work in South African jazz studies, international feminist jazz studies and feminist phenomenology. Chapters three to five successively consider the participants’ early enculturation as musical and gendered subjects, their agentic responses to structures of patriarchy and/or race as emerging and established professionals, and the ways these experiences have found expression in some of their musical utterances as performers and composers. Fusing art and activism, the participants challenge and transcend masculinist discourses of mastery that still dominate South African jazz as a field of production and aesthetic practice. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Williams, Ulagh
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/432505 , vital:72876 , DOI 10.21504/10962/432512
- Description: This dissertation studies the musical lives of seven South African women who have built highprofile national and international careers as jazz musicians. Empirically it records self-reported experiences and actions that they have identified as relevant to their success within a notoriously patriarchal field. Drawing on feminist research methods and Interpretative Phenomenological Analysis the dissertation strives to develop an empathic yet critical epistemological framework attuned to the complexities of their lived experiences as women and as jazz musicians. Theoretically it investigates the power relations at play in the myriad ways they negotiate or have been impelled to negotiate gender and patriarchy as musicians. Chapter one draws attention to the ubiquity of patriarchy in South African and international jazz culture, and highlights the research participants’ numerous successes to date as performers, educators, composers, and bandleaders. Chapter two positions this study in relation to cognate work in South African jazz studies, international feminist jazz studies and feminist phenomenology. Chapters three to five successively consider the participants’ early enculturation as musical and gendered subjects, their agentic responses to structures of patriarchy and/or race as emerging and established professionals, and the ways these experiences have found expression in some of their musical utterances as performers and composers. Fusing art and activism, the participants challenge and transcend masculinist discourses of mastery that still dominate South African jazz as a field of production and aesthetic practice. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2023
- Full Text:
- Date Issued: 2023-10-13
The influence of electronic-consumer experience (e-CX) on consumer post-purchase outcomes of South African e-commerce retail organisations
- Authors: Williams, Alyssa Shawntay
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434828 , vital:73108
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Commerce, Management, 2024
- Full Text:
- Date Issued: 2024-04-03
- Authors: Williams, Alyssa Shawntay
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/434828 , vital:73108
- Description: Access restricted. Expected release in 2026. , Thesis (PhD) -- Faculty of Commerce, Management, 2024
- Full Text:
- Date Issued: 2024-04-03
Application of in vitro release testing (IVRT) to assess “sameness”/differences of topical clotrimazole formulations
- Wellington, Hannah Margaret Mary
- Authors: Wellington, Hannah Margaret Mary
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/419599 , vital:71658
- Description: Embargoed. Possible release date early 2025 pending publications. , Thesis (MSC Pharm) -- Faculty of Pharmacy, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Wellington, Hannah Margaret Mary
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/419599 , vital:71658
- Description: Embargoed. Possible release date early 2025 pending publications. , Thesis (MSC Pharm) -- Faculty of Pharmacy, 2023
- Full Text:
- Date Issued: 2023-10-13
Development of a protocol for extracting and quantifying the concentration of thiafentanil in blesbok (Damaliscus pygargus phillipsi) matrices 72-74 hours post administration
- Authors: Webber, Judith Tracy
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164738 , vital:41159
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2020
- Authors: Webber, Judith Tracy
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164738 , vital:41159
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2020
Co-occurrence of Sympatric Poroderma Species
- Authors: Watson, Ralph Gareth Andrew
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/436649 , vital:73289 , DOI 10.21504/10962/436649
- Description: Species exploiting similar ecological niches are expected to adapt their behaviour, which can either promote or hinder coexistence. This study examined the ecological (dis)similarity between the endemic Poroderma africanum (pyjama catshark) and Poroderma pantherinum (leopard catshark) in Mossel Bay, South Africa. The co-occurrence of these species was examined along the ecological axes of time, trophic position and space, between October 2015 and April 2018, through the use of Baited Remote Underwater Videos (BRUV), gastric lavage, and acoustic telemetry. Through the deployment of 197 BRUVs, P. africanum showed a seasonal, higher Relative Abundance (RA = 0.52), occurring more frequently during winter months, while showing an overall decline in RA over the course of the study period. Poroderma pantherinum on the other hand, showed a lower, unseasonal RA (0.20), remaining relatively stable throughout the study period. The BRUV deployments indicated that the two species showed a positive co-occurrence with one other, being sighted in BRUV deployments more frequently together as opposed to in isolation/at random. Acoustic telemetry indicated that the two species were active during different diel periods, influenced by a complex combination of tidal and diel rhythms, while P. pantherinum showed a higher residency compared to P. africanum (P. pantherinum: Continuous Residency Time (CRT)24 = 3.32 days (mean), 95% CI: 2.53–4.11 days; P. africanum: CRT24 = 2.01 days, 95% CI: 1.66–2.36 days). While the two species are sympatric in nature, and have an overlapping, endemic, distribution, acoustic telemetry indicated that 1 ABSTRACT P. africanum showed higher degrees of movement throughout the acoustic receiver array (P. africanum: edge density (ED) = 0.25; P. pantherinum: ED = 0.12); however, certain areas of the bay showed to be of high importance for both species. Both species revealed high levels of intra- and inter-specific variation in both residency and movement behaviour. Gastric lavage indicated partially overlapping trophic niches, between the two Poroderma spp. Poroderma africanum had a generalist diet, dominated by teleosts (Index of Relative Importance (IRI)% = 22.69), octopus (IRI% = 11.48) and discarded bait (IRI% = 64.54), while P. pantherinum showed indications of being a specialist predator, with a diet dominated by cephalopods (IRI% = 83.68). The two Poroderma spp. showed a partially overlapping, but separate trophic niches, while displaying spatial dissimilarity in diet. The study suggests that the two species are able to coexist within the same geographical area through niche differentiation across trophic and temporal ecological axes, with varying spatial use. The intra- and inter-specific differences between the two species may complicate elasmobranch management efforts for these co-occurring endemic catsharks, and as such, efforts should follow either an individual species approach, which is often not feasible, or an ecosystem-based approach, as opposed to considering the genus as a whole. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Watson, Ralph Gareth Andrew
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/436649 , vital:73289 , DOI 10.21504/10962/436649
- Description: Species exploiting similar ecological niches are expected to adapt their behaviour, which can either promote or hinder coexistence. This study examined the ecological (dis)similarity between the endemic Poroderma africanum (pyjama catshark) and Poroderma pantherinum (leopard catshark) in Mossel Bay, South Africa. The co-occurrence of these species was examined along the ecological axes of time, trophic position and space, between October 2015 and April 2018, through the use of Baited Remote Underwater Videos (BRUV), gastric lavage, and acoustic telemetry. Through the deployment of 197 BRUVs, P. africanum showed a seasonal, higher Relative Abundance (RA = 0.52), occurring more frequently during winter months, while showing an overall decline in RA over the course of the study period. Poroderma pantherinum on the other hand, showed a lower, unseasonal RA (0.20), remaining relatively stable throughout the study period. The BRUV deployments indicated that the two species showed a positive co-occurrence with one other, being sighted in BRUV deployments more frequently together as opposed to in isolation/at random. Acoustic telemetry indicated that the two species were active during different diel periods, influenced by a complex combination of tidal and diel rhythms, while P. pantherinum showed a higher residency compared to P. africanum (P. pantherinum: Continuous Residency Time (CRT)24 = 3.32 days (mean), 95% CI: 2.53–4.11 days; P. africanum: CRT24 = 2.01 days, 95% CI: 1.66–2.36 days). While the two species are sympatric in nature, and have an overlapping, endemic, distribution, acoustic telemetry indicated that 1 ABSTRACT P. africanum showed higher degrees of movement throughout the acoustic receiver array (P. africanum: edge density (ED) = 0.25; P. pantherinum: ED = 0.12); however, certain areas of the bay showed to be of high importance for both species. Both species revealed high levels of intra- and inter-specific variation in both residency and movement behaviour. Gastric lavage indicated partially overlapping trophic niches, between the two Poroderma spp. Poroderma africanum had a generalist diet, dominated by teleosts (Index of Relative Importance (IRI)% = 22.69), octopus (IRI% = 11.48) and discarded bait (IRI% = 64.54), while P. pantherinum showed indications of being a specialist predator, with a diet dominated by cephalopods (IRI% = 83.68). The two Poroderma spp. showed a partially overlapping, but separate trophic niches, while displaying spatial dissimilarity in diet. The study suggests that the two species are able to coexist within the same geographical area through niche differentiation across trophic and temporal ecological axes, with varying spatial use. The intra- and inter-specific differences between the two species may complicate elasmobranch management efforts for these co-occurring endemic catsharks, and as such, efforts should follow either an individual species approach, which is often not feasible, or an ecosystem-based approach, as opposed to considering the genus as a whole. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-04-05
Biochemical and genetic analysis of the Mycobacterium smegmatis CnoX Chaperedoxin
- Authors: Watkins, Ariana Heloise Jo
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422403 , vital:71939
- Description: Mycobacterium (M.) tuberculosis (Mtb) encounters numerous physical and chemical stresses associated with host immunity during infection. These include exposure to reactive oxygen, chlorine and nitrogen species, low pH, hypoxia, nutrient starvation, and metal toxicity. Cellular proteins are particularly susceptible to damage by these stresses, and the ability to prevent their irreversible damage is consequently crucial for bacterial growth and survival. Mtb employs a network of proteins that includes chaperones, disaggregases, and proteases to maintain the integrity of its proteome. The chaperedoxin, CnoX, is a recently identified stress-inducible chaperone that combines redox and holdase activities to prevent the over-oxidation and aggregation of proteins in E. coli and other proteobacterial species. In this study, we identified orthologs of the E. coli CnoX (EcCnoX) in Mtb and M. smegmatis (Msm). Bioinformatics analysis of the Mtb and Msm CnoX orthologs (MtCnoX and MsCnoX, respectively) revealed that they possess similar domains, domain architectures and predicted tertiary structures as previously characterised CnoX enzymes, i.e. an N-terminal thioredoxin (Trx) domain fused to a C-terminal TPR-motif containing domain. The EcCnoX, MsCnoX, and MtCnoX enzymes were expressed as recombinant, His-tagged proteins in E. coli and purified to near homogeneity. Biochemical analysis of the recombinant CnoX enzymes revealed that the MsCnoX and MtCnoX both lack thiol-disulphide oxidoreductase (thioredoxin) activity, as evidenced by their inability to catalyse the reduction of the disulphide bonds of insulin in vitro. Both mycobacterial CnoX enzymes displayed activity as chaperones (holdases) during thermal aggregation assays of the model substrate, malate dehydrogenase (MDH). In contrast to previously reported findings for EcCnoX, the holdase activity of the mycobacterial CnoX enzymes was constitutive and did not require exposure to hypochlorous acid (HOCl) for activation. To establish the physiological role of CnoX in Msm, cnoX knockdown (KD) and knockout (KO) mutants were generated using CRISPRi-mediated gene silencing or homologous recombination, respectively. Consistent with previous findings, CnoX activity was not essential for the growth of Msm under conventional growth conditions. Reducing or eliminating CnoX activity in the Msm KD or KO mutants, respectively, did not confer increased sensitivity to HOCl as has been observed for an E. coli cnoX mutant. Reduced CnoX activity in Msm did, however, confer sensitivity to the superoxide generator, plumbagin, and front-line antitubercular drugs rifampicin and isoniazid. The combination of biochemical and physiological data presented suggests that MsCnoX may function as a holdase for substrates following proteotoxic damage induced by certain types of oxidants, a line of investigation that will be pursued in future studies. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Watkins, Ariana Heloise Jo
- Date: 2023-03-29
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/422403 , vital:71939
- Description: Mycobacterium (M.) tuberculosis (Mtb) encounters numerous physical and chemical stresses associated with host immunity during infection. These include exposure to reactive oxygen, chlorine and nitrogen species, low pH, hypoxia, nutrient starvation, and metal toxicity. Cellular proteins are particularly susceptible to damage by these stresses, and the ability to prevent their irreversible damage is consequently crucial for bacterial growth and survival. Mtb employs a network of proteins that includes chaperones, disaggregases, and proteases to maintain the integrity of its proteome. The chaperedoxin, CnoX, is a recently identified stress-inducible chaperone that combines redox and holdase activities to prevent the over-oxidation and aggregation of proteins in E. coli and other proteobacterial species. In this study, we identified orthologs of the E. coli CnoX (EcCnoX) in Mtb and M. smegmatis (Msm). Bioinformatics analysis of the Mtb and Msm CnoX orthologs (MtCnoX and MsCnoX, respectively) revealed that they possess similar domains, domain architectures and predicted tertiary structures as previously characterised CnoX enzymes, i.e. an N-terminal thioredoxin (Trx) domain fused to a C-terminal TPR-motif containing domain. The EcCnoX, MsCnoX, and MtCnoX enzymes were expressed as recombinant, His-tagged proteins in E. coli and purified to near homogeneity. Biochemical analysis of the recombinant CnoX enzymes revealed that the MsCnoX and MtCnoX both lack thiol-disulphide oxidoreductase (thioredoxin) activity, as evidenced by their inability to catalyse the reduction of the disulphide bonds of insulin in vitro. Both mycobacterial CnoX enzymes displayed activity as chaperones (holdases) during thermal aggregation assays of the model substrate, malate dehydrogenase (MDH). In contrast to previously reported findings for EcCnoX, the holdase activity of the mycobacterial CnoX enzymes was constitutive and did not require exposure to hypochlorous acid (HOCl) for activation. To establish the physiological role of CnoX in Msm, cnoX knockdown (KD) and knockout (KO) mutants were generated using CRISPRi-mediated gene silencing or homologous recombination, respectively. Consistent with previous findings, CnoX activity was not essential for the growth of Msm under conventional growth conditions. Reducing or eliminating CnoX activity in the Msm KD or KO mutants, respectively, did not confer increased sensitivity to HOCl as has been observed for an E. coli cnoX mutant. Reduced CnoX activity in Msm did, however, confer sensitivity to the superoxide generator, plumbagin, and front-line antitubercular drugs rifampicin and isoniazid. The combination of biochemical and physiological data presented suggests that MsCnoX may function as a holdase for substrates following proteotoxic damage induced by certain types of oxidants, a line of investigation that will be pursued in future studies. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2023-03-29
Application of the modified pitman and swat models for groundwater recharge estimation in the upstream area of the Uitenhage artesian basin, South Africa
- Authors: Wasswa, Peter
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435400 , vital:73154
- Description: The world's most plentiful source of freshwater is thought to be groundwater. During extended dry times, it serves as an essential storage component and guards against environmental catastrophes. Despite its critical functions in the aforementioned scenarios, it is often insufficiently understood and inadequately managed. As a result, it calls for the adoption of integrated methods to comprehend the dynamics of groundwater recharge. Thus, the current study evaluated the applicability and suitability of the Modified Pitman and SWAT models for groundwater recharge estimation in the upstream area of UAB for the period that spanned from 1993 to 2021. It was achieved by using a qualitative conceptual-perceptual model to inform the two hydrological models, Modified Pitman, and SWAT. The developed qualitative conceptual-perceptual model depicted the dominancy of irregularly folded and fractured TMG rock outcrops coupled with fault systems in the upstream area. In the downward section, TMG is overlaid by the aquiclude from the Uitenhage Group which is responsible for the artesian conditions. Groundwater potential zones were classified as Poor, Fair, Good, and Excellent, with 65.4% and 8.7% of the upstream area attributed to Good and Excellent zones respectively. Both Modified Pitman and SWAT predicted decreasing rates of groundwater recharge in the upstream area over time, though Mann-Kendal trend tests done at 5% signifance level depicted significant decreasing rates in SWAT predicted recharge compared to Modified Pitman predicted recharge. The two models did also predict recharge and other water balance components with differing peaks, lows and timings. Modified Pitman predicted mean annual recharge of 63.3-92.8 mm where as SWAT predicted mean annual recharge of 14.4-182.8 mm. In reference to earlier findings within TMG areas, estimated percentages of groundwater recharge were close to those simulated by both Pitman and SWAT models. Modified Pitman and SWAT models appear to both be reasonable tools to estimate recharge in TMG setting, producing relatively similar results to one another and to other regional estimates. Since the current study estimated low recharge rates (Modified Pitman; ~9.3-13.6% MAP), (SWAT; ~2.1-26.7% MAP) which are close to those predicted in other TMG areas, the study recommends exercising caution when developing a water supply strategy in the current study area. The recharge rates within the pertinent recharging areas should be considered when designing and sitting abstraction points such as boreholes and a sustainable abstraction rate in any one borehole for improved sustainable management of groundwater resources. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-04-04
- Authors: Wasswa, Peter
- Date: 2024-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435400 , vital:73154
- Description: The world's most plentiful source of freshwater is thought to be groundwater. During extended dry times, it serves as an essential storage component and guards against environmental catastrophes. Despite its critical functions in the aforementioned scenarios, it is often insufficiently understood and inadequately managed. As a result, it calls for the adoption of integrated methods to comprehend the dynamics of groundwater recharge. Thus, the current study evaluated the applicability and suitability of the Modified Pitman and SWAT models for groundwater recharge estimation in the upstream area of UAB for the period that spanned from 1993 to 2021. It was achieved by using a qualitative conceptual-perceptual model to inform the two hydrological models, Modified Pitman, and SWAT. The developed qualitative conceptual-perceptual model depicted the dominancy of irregularly folded and fractured TMG rock outcrops coupled with fault systems in the upstream area. In the downward section, TMG is overlaid by the aquiclude from the Uitenhage Group which is responsible for the artesian conditions. Groundwater potential zones were classified as Poor, Fair, Good, and Excellent, with 65.4% and 8.7% of the upstream area attributed to Good and Excellent zones respectively. Both Modified Pitman and SWAT predicted decreasing rates of groundwater recharge in the upstream area over time, though Mann-Kendal trend tests done at 5% signifance level depicted significant decreasing rates in SWAT predicted recharge compared to Modified Pitman predicted recharge. The two models did also predict recharge and other water balance components with differing peaks, lows and timings. Modified Pitman predicted mean annual recharge of 63.3-92.8 mm where as SWAT predicted mean annual recharge of 14.4-182.8 mm. In reference to earlier findings within TMG areas, estimated percentages of groundwater recharge were close to those simulated by both Pitman and SWAT models. Modified Pitman and SWAT models appear to both be reasonable tools to estimate recharge in TMG setting, producing relatively similar results to one another and to other regional estimates. Since the current study estimated low recharge rates (Modified Pitman; ~9.3-13.6% MAP), (SWAT; ~2.1-26.7% MAP) which are close to those predicted in other TMG areas, the study recommends exercising caution when developing a water supply strategy in the current study area. The recharge rates within the pertinent recharging areas should be considered when designing and sitting abstraction points such as boreholes and a sustainable abstraction rate in any one borehole for improved sustainable management of groundwater resources. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-04-04
Two dermestid pests of hide and skins in South Africa
- Authors: Walker, J D
- Date: 1941
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193702 , vital:45387
- Description: In a paper entitled "Bacteria of the Soil", Dr. Russell of Rothamsted is quoted as saying, ”The top six lashes might almost be called a separate world? 80 great is the number and variety of its inhabitants”• It is with a few forms belonging to this enormous biological complex that the author intends to deal, viz*, representatives of the Orders Pauropoda, Symphyla, Protura, Coleoptera and Hemiptera. Time does not permit the inclusion of a study of the multitude of Arthropod, species that occur in the soil, but a more complete work on these soil groups is intended in the future. McCullogh and Hayes (1922,p.288) state that the soil is an integral factor In the study of biological problems. Hence an understanding of the organic life of the soil, which is of great importance in relation to the other aspects of pedology, is a necessary adjunct to the study of the soil ae a whole. , Thesis (MSc) -- Faculty of Science, 1941
- Full Text:
- Date Issued: 1941
- Authors: Walker, J D
- Date: 1941
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193702 , vital:45387
- Description: In a paper entitled "Bacteria of the Soil", Dr. Russell of Rothamsted is quoted as saying, ”The top six lashes might almost be called a separate world? 80 great is the number and variety of its inhabitants”• It is with a few forms belonging to this enormous biological complex that the author intends to deal, viz*, representatives of the Orders Pauropoda, Symphyla, Protura, Coleoptera and Hemiptera. Time does not permit the inclusion of a study of the multitude of Arthropod, species that occur in the soil, but a more complete work on these soil groups is intended in the future. McCullogh and Hayes (1922,p.288) state that the soil is an integral factor In the study of biological problems. Hence an understanding of the organic life of the soil, which is of great importance in relation to the other aspects of pedology, is a necessary adjunct to the study of the soil ae a whole. , Thesis (MSc) -- Faculty of Science, 1941
- Full Text:
- Date Issued: 1941
The impacts of bottom-up and top-down drivers in shaping the herbivore community in Pafuri, Kruger National Park, South Africa
- Authors: Walker, Gareth Alexander
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435703 , vital:73180 , DOI 10.21504/10962/435703
- Description: Globally, terrestrial mammal populations are facing critical population declines and range contractions owing to habitat fragmentation and destruction, wildlife overexploitation, and climate change driven by expansion of the human population. Mammalian herbivores are integral for maintaining ecosystem structure and functionality. They do this this through herbivory, by acting as prey and cycling soil nutrients. The impacts of herbivores on ecosystems, however, vary with their spatial occupancy which is influenced by interacting bottom-up and top-down factors. Modelling the drivers of herbivore communities is no trivial task given the myriad of potential bottom-up and top-down factors, and the interactions between the two, as well as the species-specific variations in intrinsic functional traits (e.g., foraging strategy, body size, metabolic rate, etc.) influencing herbivore responses (e.g., social structure, space-use, activity patterns, etc.) to these drivers. Consequently, few studies have attempted to model both bottom-up and top-down drivers in structuring herbivore communities, particularly in an African context where predator-prey guilds include multiple species, exposed to high levels of human activity. Therefore, the overarching aim of my research was to quantify the relative effects of both bottom-up and top-down factors driving the herbivore community in the northern Pafuri region of Kruger National Park, South Africa. I utilized a combination of field (i.e., camera trap and vegetation surveys) and analytical (i.e., stable carbon isotopes from faeces and plants) techniques in conjunction with geospatial data to evaluate the impacts of bottom-up (i.e., forage quantity, quality, and water availability) and top-down (i.e., predation and anthropogenic risks) factors on herbivore spatial occupancy and activity patterns. Herbivore responses to bottom-up and top-down factors were species-specific, even among members of the same feeding guild. Specifically, I found that herbivores (varying in body size and foraging strategy) displayed temporal, spatial and in some instances, dietary shifts that reflect species-specific, ecological trade-offs between resource acquisition, and predator and human avoidance. For example, kudu (Tragelaphus strepsiceros) displayed temporal and spatial avoidance of predators and humans, and exhibited previously undocumented levels of seasonal dietary shifts which suggests that the species traded forage acquisition for reduced predation and anthropogenic risks. Further, high levels of human activity appeared to eclipse the risks associated with natural predators resulting in human induced landscapes of fear. For example, warthogs (Phacochoerus africanus) and zebra (Equus quagga) occupied habitats with higher predation risks, but displayed spatial avoidance of nature reserve boundaries which were synonymous with high levels of bushmeat poaching. Most studies focussing on the impacts of bottom-up and top-down drivers neglect to consider the roles that humans play in structuring ecological communities. The results of my thesis, however, emphasize the importance of including anthropogenic drivers when investigating the roles that various bottom-up and top-down factors play in shaping ecological communities. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Walker, Gareth Alexander
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435703 , vital:73180 , DOI 10.21504/10962/435703
- Description: Globally, terrestrial mammal populations are facing critical population declines and range contractions owing to habitat fragmentation and destruction, wildlife overexploitation, and climate change driven by expansion of the human population. Mammalian herbivores are integral for maintaining ecosystem structure and functionality. They do this this through herbivory, by acting as prey and cycling soil nutrients. The impacts of herbivores on ecosystems, however, vary with their spatial occupancy which is influenced by interacting bottom-up and top-down factors. Modelling the drivers of herbivore communities is no trivial task given the myriad of potential bottom-up and top-down factors, and the interactions between the two, as well as the species-specific variations in intrinsic functional traits (e.g., foraging strategy, body size, metabolic rate, etc.) influencing herbivore responses (e.g., social structure, space-use, activity patterns, etc.) to these drivers. Consequently, few studies have attempted to model both bottom-up and top-down drivers in structuring herbivore communities, particularly in an African context where predator-prey guilds include multiple species, exposed to high levels of human activity. Therefore, the overarching aim of my research was to quantify the relative effects of both bottom-up and top-down factors driving the herbivore community in the northern Pafuri region of Kruger National Park, South Africa. I utilized a combination of field (i.e., camera trap and vegetation surveys) and analytical (i.e., stable carbon isotopes from faeces and plants) techniques in conjunction with geospatial data to evaluate the impacts of bottom-up (i.e., forage quantity, quality, and water availability) and top-down (i.e., predation and anthropogenic risks) factors on herbivore spatial occupancy and activity patterns. Herbivore responses to bottom-up and top-down factors were species-specific, even among members of the same feeding guild. Specifically, I found that herbivores (varying in body size and foraging strategy) displayed temporal, spatial and in some instances, dietary shifts that reflect species-specific, ecological trade-offs between resource acquisition, and predator and human avoidance. For example, kudu (Tragelaphus strepsiceros) displayed temporal and spatial avoidance of predators and humans, and exhibited previously undocumented levels of seasonal dietary shifts which suggests that the species traded forage acquisition for reduced predation and anthropogenic risks. Further, high levels of human activity appeared to eclipse the risks associated with natural predators resulting in human induced landscapes of fear. For example, warthogs (Phacochoerus africanus) and zebra (Equus quagga) occupied habitats with higher predation risks, but displayed spatial avoidance of nature reserve boundaries which were synonymous with high levels of bushmeat poaching. Most studies focussing on the impacts of bottom-up and top-down drivers neglect to consider the roles that humans play in structuring ecological communities. The results of my thesis, however, emphasize the importance of including anthropogenic drivers when investigating the roles that various bottom-up and top-down factors play in shaping ecological communities. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05