Ectomycorrhizal fungal assessment of South African Pinus patula seedlings and their biological control potential to enhance seedling growth
- FitzGerald, Véronique Chartier
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- Description: The South Africa forestry industry, covering 1.3 million hectares, is dependent on exotic pine and eucalyptus species. Nursery seedlings are not inoculated with ectomycorrhizal (ECM) fungi or other beneficial microbes. Fusarium circinatum is an economically important pathogen affecting seedling survival. The purpose of this investigation was to assess levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- Description: The South Africa forestry industry, covering 1.3 million hectares, is dependent on exotic pine and eucalyptus species. Nursery seedlings are not inoculated with ectomycorrhizal (ECM) fungi or other beneficial microbes. Fusarium circinatum is an economically important pathogen affecting seedling survival. The purpose of this investigation was to assess levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
Effect of Helicosporidium sp. (Chlorophyta; Trebouxiophyceae) infection on Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae), a biological control agent for the invasive Salvinia molesta D.S. Mitchell (Salviniaceae) in South
- Authors: Mphephu, Tshililo Emmanuel
- Date: 2022-10-14
- Subjects: Salvinia molesta South Africa , Weeds Biological control , Cyrtobagous salviniae , Ketoconazole
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365815 , vital:65792 , DOI https://doi.org/10.21504/10962/365815
- Description: The effectiveness of established biological control agents depends on biotic and abiotic interactions in the introduced range. The weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae), was released as a biological control against Salvinia molesta D.S. Mitchell (Salviniaceae) in South Africa in 1985. This agent has been highly successful against S. molesta and has significantly reduced the weed’s populations around the country. However, in 2007, the parasitic alga, Helicosporidium sp. (an undescribed species), was detected in field-collected C. salviniae adults in South Africa. The distribution and impacts of this disease on the weevil and its efficacy as a control agent were not known. In this thesis, the prevalence, infection load, and impact of Helicosporidium sp. on C. salviniae was determined. In 2019, adult weevils were collected from 10 sites across the Eastern Cape, KwaZulu-Natal, Limpopo, and Western Cape provinces and screened to determine the occurrence, infection load, and geographic distribution of Helicosporidium sp. Transmission mechanisms of this disease in C. salviniae were then evaluated. The possible impact of Helicosporidium sp. was assessed by comparing the feeding rates and the reproductive output of the diseased and healthy adults of C. salviniae. An attempt was then made to eliminate the disease in C. salviniae through the application of the antibiotic, ketoconazole. Further, the role of temperature on infection load in C. salviniae was also assessed. Finally, recommendations for the long-term biological control programme against S. molesta in South Africa were made. The disease covers the entire distribution range of C. salviniae in South Africa, with the disease occurrence rate ranging from 92.15% to 100% insects infected per site. Helicosporidium sp. was found to transmit vertically within the populations of C. salviniae. Infection by the Helicosporidium sp. disease reduced the reproductive output of C. salviniae as well its impact on biomass reduction of S. molesta when a diseased culture was compared to a healthy culture from the USA. 98.44 to 98.55% of Helicosporidium sp. loads were reduced through multiple applications of ketoconazole concentrations under in vitro trials. In vivo treatments resulted in 70% control of Helicosporidium sp. in the adults of C. salviniae that were fed ketoconazole three times over a 21 day period. Adult C. salviniae feeding and survival performances were similar when fed fronds of S. molesta inoculated with ketoconazole and water. The lowest and highest disease loads of Helicosporidium sp. were recorded when the weevils were reared at 30°C and 14°C, respectively. As expected, the highest impact and reproductive output of C. salviniae were at 30°C. The evaluations discussed in this thesis highlight the role of diseases in biological control agents, and gaps in both the pre-release and post-release monitoring that should integrate screening of diseases in these studies. Although the combined application of the antibiotic and temperature will reduce Helicosporidium sp. loads and impact, this technology is most likely only applicable where the weevils are reared in small numbers in a rearing facility and not really applicable to the field situation. It is important to release healthy agents that will cause efficient control of the target weed plant species, therefore, when introducing new biological control agents, the health status of such agents needs to be understood. Therefore, long-term field monitoring and assessment of the impact of C. salviniae on S. molesta should be conducted to track all the changes that may result due to the presence of Helicosporidium sp. This long-term monitoring and assessment will give a more informative role of Helicosporidium sp. in field populations of C. salviniae. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Mphephu, Tshililo Emmanuel
- Date: 2022-10-14
- Subjects: Salvinia molesta South Africa , Weeds Biological control , Cyrtobagous salviniae , Ketoconazole
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365815 , vital:65792 , DOI https://doi.org/10.21504/10962/365815
- Description: The effectiveness of established biological control agents depends on biotic and abiotic interactions in the introduced range. The weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae), was released as a biological control against Salvinia molesta D.S. Mitchell (Salviniaceae) in South Africa in 1985. This agent has been highly successful against S. molesta and has significantly reduced the weed’s populations around the country. However, in 2007, the parasitic alga, Helicosporidium sp. (an undescribed species), was detected in field-collected C. salviniae adults in South Africa. The distribution and impacts of this disease on the weevil and its efficacy as a control agent were not known. In this thesis, the prevalence, infection load, and impact of Helicosporidium sp. on C. salviniae was determined. In 2019, adult weevils were collected from 10 sites across the Eastern Cape, KwaZulu-Natal, Limpopo, and Western Cape provinces and screened to determine the occurrence, infection load, and geographic distribution of Helicosporidium sp. Transmission mechanisms of this disease in C. salviniae were then evaluated. The possible impact of Helicosporidium sp. was assessed by comparing the feeding rates and the reproductive output of the diseased and healthy adults of C. salviniae. An attempt was then made to eliminate the disease in C. salviniae through the application of the antibiotic, ketoconazole. Further, the role of temperature on infection load in C. salviniae was also assessed. Finally, recommendations for the long-term biological control programme against S. molesta in South Africa were made. The disease covers the entire distribution range of C. salviniae in South Africa, with the disease occurrence rate ranging from 92.15% to 100% insects infected per site. Helicosporidium sp. was found to transmit vertically within the populations of C. salviniae. Infection by the Helicosporidium sp. disease reduced the reproductive output of C. salviniae as well its impact on biomass reduction of S. molesta when a diseased culture was compared to a healthy culture from the USA. 98.44 to 98.55% of Helicosporidium sp. loads were reduced through multiple applications of ketoconazole concentrations under in vitro trials. In vivo treatments resulted in 70% control of Helicosporidium sp. in the adults of C. salviniae that were fed ketoconazole three times over a 21 day period. Adult C. salviniae feeding and survival performances were similar when fed fronds of S. molesta inoculated with ketoconazole and water. The lowest and highest disease loads of Helicosporidium sp. were recorded when the weevils were reared at 30°C and 14°C, respectively. As expected, the highest impact and reproductive output of C. salviniae were at 30°C. The evaluations discussed in this thesis highlight the role of diseases in biological control agents, and gaps in both the pre-release and post-release monitoring that should integrate screening of diseases in these studies. Although the combined application of the antibiotic and temperature will reduce Helicosporidium sp. loads and impact, this technology is most likely only applicable where the weevils are reared in small numbers in a rearing facility and not really applicable to the field situation. It is important to release healthy agents that will cause efficient control of the target weed plant species, therefore, when introducing new biological control agents, the health status of such agents needs to be understood. Therefore, long-term field monitoring and assessment of the impact of C. salviniae on S. molesta should be conducted to track all the changes that may result due to the presence of Helicosporidium sp. This long-term monitoring and assessment will give a more informative role of Helicosporidium sp. in field populations of C. salviniae. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Date Issued: 2022-10-14
Embodied difference in manhood: A sociological analysis of the intersection of visible physical impairments and manhood among Xhosa men in the Eastern Cape
- Authors: Sipungu, Thoko Andy
- Date: 2021-10-29
- Subjects: Masculinity South Africa Eastern Cape , Sex role South Africa Eastern Cape , Sex role Psychological aspects , Men with disabilities South Africa Eastern Cape , People with disabilities Social conditions , Xhosa (African people) South Africa Eastern Cape Social life and customs , Male domination (Social structure) South Africa Eastern Cape , Circumcision Social aspects South Africa Eastern Cape
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191658 , vital:45145 , 10.21504/10962/191658
- Description: In this thesis, I outline possible answers to the question of what it means to be a Xhosa man living with a visible physical impairment. Drawing on 17 one-on-one in-depth interviews and through an interpretive phenomenological thematic analysis, this thesis explores the intersection of physical disabilities and manhood masculinity in Xhosa men in selected rural areas in the Eastern Cape, South Africa. The intention for this study is to better our understanding concerning the creation, negotiation, maintenance, and recreation of manhood identities by traditionally circumcised Xhosa men in the Eastern Cape who by birth, accident, or illness find themselves at the intersections of masculinity and physical disability. Research notes that the bodies of men with disabilities serve as a continual reminder that they are at odds with the expectations of the dominant manhood cultures. The main argument from this area of research is that men with disabilities are outside the hegemony because they undermine the normative role and shape of the body in Western cultures. However, this line of argumentation stands in sharp contrast to arguments that the hegemony in Xhosa manhood masculinity is primarily and conclusively achieved by having a traditionally circumcised penis without any consideration of the full embodiments of men. Therefore, this study, in the first instance, seeks to bring embodiment into the analyses of manhood by focusing on physical disability amongst traditionally circumcised Xhosa men. Through an embodied theoretical approach to their disabilities that accounts for the corporeal experience of impairment, and theories of masculinity that centre the context, this thesis establishes, in the first instance, the significance of embodiment in doing Xhosa manhood. Concerning the research aims and objectives, this study sheds light on what it means to be a Xhosa man living with visible physical impairment. In this regard, the original findings are classified according to each research aims and objective, as outlined below. Concerning the first research aim, I found that the participants struggle to speak about their bodies outside of physical labour/work despite their impairments. I explain their inability to talk about their disabled bodies by looking at traditional Xhosa initiation as a grantor of equality and sameness. Secondly, I argue that there is a higher premium on social bodies rather than physical bodies in this context, thus their inability to speak about their conditions. Lastly, I make connections between the participants’ inabilities to talk about their bodies and the lasting impact of colonial and apartheid histories. Concerning the second research aim, I explore ways and strategies they employ to respond to and negotiate Xhosa manhood masculinity's dominant cultural demands. In this regard, I note that the participants who acquired their impairments after initiation consider their disability as a second initiation because they see it as having set them back to square one regarding their manhood responsibilities. In contrast, the participants who acquired their disabilities post-initiation saw initiation as a gateway to a more respectable personhood status. I also note that there is an emergence of alternative Xhosa manhood masculinities. Lastly, I also found that contrary to western scholarship on disability and manhood, the participants distinguish between threatened manhood identity versus threatened status as a man. I outline how they arrive at this distinction. In terms of researching the last research aim, this thesis explores how the participants negotiate their ‘embodied difference’ in mundane everyday living. I explore their taken-for-granted routines in doing and being disabled Xhosa men every day. In this regard, this study presents original and interesting findings regarding sex and intimacy, social interactions and sociability, and everyday home living. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Sipungu, Thoko Andy
- Date: 2021-10-29
- Subjects: Masculinity South Africa Eastern Cape , Sex role South Africa Eastern Cape , Sex role Psychological aspects , Men with disabilities South Africa Eastern Cape , People with disabilities Social conditions , Xhosa (African people) South Africa Eastern Cape Social life and customs , Male domination (Social structure) South Africa Eastern Cape , Circumcision Social aspects South Africa Eastern Cape
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191658 , vital:45145 , 10.21504/10962/191658
- Description: In this thesis, I outline possible answers to the question of what it means to be a Xhosa man living with a visible physical impairment. Drawing on 17 one-on-one in-depth interviews and through an interpretive phenomenological thematic analysis, this thesis explores the intersection of physical disabilities and manhood masculinity in Xhosa men in selected rural areas in the Eastern Cape, South Africa. The intention for this study is to better our understanding concerning the creation, negotiation, maintenance, and recreation of manhood identities by traditionally circumcised Xhosa men in the Eastern Cape who by birth, accident, or illness find themselves at the intersections of masculinity and physical disability. Research notes that the bodies of men with disabilities serve as a continual reminder that they are at odds with the expectations of the dominant manhood cultures. The main argument from this area of research is that men with disabilities are outside the hegemony because they undermine the normative role and shape of the body in Western cultures. However, this line of argumentation stands in sharp contrast to arguments that the hegemony in Xhosa manhood masculinity is primarily and conclusively achieved by having a traditionally circumcised penis without any consideration of the full embodiments of men. Therefore, this study, in the first instance, seeks to bring embodiment into the analyses of manhood by focusing on physical disability amongst traditionally circumcised Xhosa men. Through an embodied theoretical approach to their disabilities that accounts for the corporeal experience of impairment, and theories of masculinity that centre the context, this thesis establishes, in the first instance, the significance of embodiment in doing Xhosa manhood. Concerning the research aims and objectives, this study sheds light on what it means to be a Xhosa man living with visible physical impairment. In this regard, the original findings are classified according to each research aims and objective, as outlined below. Concerning the first research aim, I found that the participants struggle to speak about their bodies outside of physical labour/work despite their impairments. I explain their inability to talk about their disabled bodies by looking at traditional Xhosa initiation as a grantor of equality and sameness. Secondly, I argue that there is a higher premium on social bodies rather than physical bodies in this context, thus their inability to speak about their conditions. Lastly, I make connections between the participants’ inabilities to talk about their bodies and the lasting impact of colonial and apartheid histories. Concerning the second research aim, I explore ways and strategies they employ to respond to and negotiate Xhosa manhood masculinity's dominant cultural demands. In this regard, I note that the participants who acquired their impairments after initiation consider their disability as a second initiation because they see it as having set them back to square one regarding their manhood responsibilities. In contrast, the participants who acquired their disabilities post-initiation saw initiation as a gateway to a more respectable personhood status. I also note that there is an emergence of alternative Xhosa manhood masculinities. Lastly, I also found that contrary to western scholarship on disability and manhood, the participants distinguish between threatened manhood identity versus threatened status as a man. I outline how they arrive at this distinction. In terms of researching the last research aim, this thesis explores how the participants negotiate their ‘embodied difference’ in mundane everyday living. I explore their taken-for-granted routines in doing and being disabled Xhosa men every day. In this regard, this study presents original and interesting findings regarding sex and intimacy, social interactions and sociability, and everyday home living. , Thesis (PhD) -- Faculty of Humanities, Sociology, 2021
- Full Text:
- Date Issued: 2021-10-29
Establishing a water resources assessment system for Eswatini (Swaziland) incorporating data and modelling uncertainty
- Authors: Ndzabandzaba, Coli
- Date: 2021-10-29
- Subjects: Water resources development Eswatini , Water-supply Eswatini Management , Hydrologic models Eswatini , Runoff Mathematical models , Rain and rainfall Mathematical models , Pitman model
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/189009 , vital:44806 , 10.21504/10962/189009
- Description: The uneven distribution of water resources availability globally puts pressure on environmental and human or socio-economic systems and has complex implications for the interactions within these systems. The natural environment and water resources are increasingly threatened by development, and water management crises are still occurring. This is exacerbated by the lack of accurate and adequate information on these systems. In Eswatini, for example, the pressure on the available water resources is mounting due to increasing water demand for irrigation while information about natural hydrological conditions and levels of water resources developments are uncertain. In addition, the practical application of hydrological models for water resources assessments that incorporate uncertainty in Eswatini has yet to be realised. The aim of the study, therefore, was to develop a water resource assessment system that is based on both observed and simulated information and that includes uncertainty. This study focusses on a regional water resource assessment using an uncertainty version of the Pitman monthly rainfall-runoff model whose outputs are constrained by six indices of natural hydrological response (i.e., mean monthly runoff, mean monthly groundwater recharge, Q10, Q50 and Q90 percentage points of the flow duration curve and % time of zero flows) for each of the 122 sub-basins of the transboundary catchments of Eswatini. A 2-step uncertainty modelling approach was tested, validated and then applied to all the sub-basins of Eswatini. The first step of the model run establishes behavioural, but uncertain model parameter ranges for natural incremental sub-basin hydrological responses and the model is typically run 100 000 times for each sub-basin. The parameter space that defines the uncertainty in parameter estimation is sampled based on simple Monte Carlo approach. The second step links all the sub-basin outputs and allows for water use parameters to be incorporated, where necessary, in order to generate cumulative sub-basin outflows. The results from the constraint index analysis have proved to be useful in constraining the model outputs. Generally, the behavioural model outputs produced realistic uncertainty estimates as well as acceptable simulations based on the assessment of the flow duration curves. The modelling results indicated that there is some degree of uncertainty that cannot be easily accounted for due to some identified data issues. The results also showed that there is still a possibility to improve the simulations provided such issues are resolved. The issues about the simulation of stream flow that were detected are mainly related to availability of data to estimate water use parameters. Another challenge in setting up the model was associated with establishing constraints that match the parameters for natural hydrological conditions for specific sub-basins and maintaining consistency in the adjustment of the model output constraints for other sub-basins. In an attempt to overcome this problem, the study recommends additional hydrological response constraints to be used with the Pitman model. Another main recommendation relates to the strong cooperation of relevant catchment management authorities and stakeholders including scientists in order to make information more available to users. The new hydrological insight is derived from the analysis of hydrological indices which highlighted the regional variations in hydrological processes and sub-basin response across the transboundary basins of Eswatini. The adopted modelling approach provides further insight into all the uncertainties associated with quantifying the available water resources of the country. The study has provided further understanding of the spatial variability of the hydrological response and existing development impacts than was previously available. It is envisaged that these new insights will provide an improved basis for future water management in Eswatini. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Ndzabandzaba, Coli
- Date: 2021-10-29
- Subjects: Water resources development Eswatini , Water-supply Eswatini Management , Hydrologic models Eswatini , Runoff Mathematical models , Rain and rainfall Mathematical models , Pitman model
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/189009 , vital:44806 , 10.21504/10962/189009
- Description: The uneven distribution of water resources availability globally puts pressure on environmental and human or socio-economic systems and has complex implications for the interactions within these systems. The natural environment and water resources are increasingly threatened by development, and water management crises are still occurring. This is exacerbated by the lack of accurate and adequate information on these systems. In Eswatini, for example, the pressure on the available water resources is mounting due to increasing water demand for irrigation while information about natural hydrological conditions and levels of water resources developments are uncertain. In addition, the practical application of hydrological models for water resources assessments that incorporate uncertainty in Eswatini has yet to be realised. The aim of the study, therefore, was to develop a water resource assessment system that is based on both observed and simulated information and that includes uncertainty. This study focusses on a regional water resource assessment using an uncertainty version of the Pitman monthly rainfall-runoff model whose outputs are constrained by six indices of natural hydrological response (i.e., mean monthly runoff, mean monthly groundwater recharge, Q10, Q50 and Q90 percentage points of the flow duration curve and % time of zero flows) for each of the 122 sub-basins of the transboundary catchments of Eswatini. A 2-step uncertainty modelling approach was tested, validated and then applied to all the sub-basins of Eswatini. The first step of the model run establishes behavioural, but uncertain model parameter ranges for natural incremental sub-basin hydrological responses and the model is typically run 100 000 times for each sub-basin. The parameter space that defines the uncertainty in parameter estimation is sampled based on simple Monte Carlo approach. The second step links all the sub-basin outputs and allows for water use parameters to be incorporated, where necessary, in order to generate cumulative sub-basin outflows. The results from the constraint index analysis have proved to be useful in constraining the model outputs. Generally, the behavioural model outputs produced realistic uncertainty estimates as well as acceptable simulations based on the assessment of the flow duration curves. The modelling results indicated that there is some degree of uncertainty that cannot be easily accounted for due to some identified data issues. The results also showed that there is still a possibility to improve the simulations provided such issues are resolved. The issues about the simulation of stream flow that were detected are mainly related to availability of data to estimate water use parameters. Another challenge in setting up the model was associated with establishing constraints that match the parameters for natural hydrological conditions for specific sub-basins and maintaining consistency in the adjustment of the model output constraints for other sub-basins. In an attempt to overcome this problem, the study recommends additional hydrological response constraints to be used with the Pitman model. Another main recommendation relates to the strong cooperation of relevant catchment management authorities and stakeholders including scientists in order to make information more available to users. The new hydrological insight is derived from the analysis of hydrological indices which highlighted the regional variations in hydrological processes and sub-basin response across the transboundary basins of Eswatini. The adopted modelling approach provides further insight into all the uncertainties associated with quantifying the available water resources of the country. The study has provided further understanding of the spatial variability of the hydrological response and existing development impacts than was previously available. It is envisaged that these new insights will provide an improved basis for future water management in Eswatini. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-10-29
Establishment of human OCT4 as a putative HSP90 client protein: a case for HSP90 chaperoning pluripotency
- Authors: Sterrenberg, Jason Neville
- Date: 2015
- Subjects: Induced pluripotent stem cells , Heat shock proteins , Stem cells , Transcription factors , Molecular chaperones
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/194010 , vital:45415 , 10.21504/10962/194010
- Description: The therapeutic potential of stem cells is already being harnessed in clinical trails. Of even greater therapeutic potential has been the discovery of mechanisms to reprogram differentiated cells into a pluripotent stem cell-like state known as induced pluripotent stem cells (iPSCs). Stem cell nature is governed and maintained by a hierarchy of transcription factors, the apex of which is OCT4. Although much research has elucidated the transcriptional regulation of OCT4, OCT4 regulated gene expression profiles and OCT4 transcriptional activation mechanisms in both stem cell biology and cellular reprogramming to iPSCs, the fundamental biochemistry surrounding the OCT4 transcription factor remains largely unknown. In order to analyze the biochemical relationship between HSP90 and human OCT4 we developed an exogenous active human OCT4 expression model with human OCT4 under transcriptional control of a constitutive promoter. We identified the direct interaction between HSP90 and human OCT4 despite the fact that the proteins predominantly display differential subcellular localizations. We show that HSP90 inhibition resulted in degradation of human OCT4 via the ubiquitin proteasome degradation pathway. As human OCT4 and HSP90 did not interact in the nucleus, we suggest that HSP90 functions in the cytoplasmic stabilization of human OCT4. Our analysis suggests HSP90 inhibition inhibits the transcriptional activity of human OCT4 dimers without affecting monomeric OCT4 activity. Additionally our data suggests that the HSP90 and human OCT4 complex is modulated by phosphorylation events either promoting or abrogating the interaction between HSP90 and human OCT4. Our data suggest that human OCT4 displays the characteristics describing HSP90 client proteins, therefore we identify human OCT4 as a putative HSP90 client protein. The regulation of the transcription factor OCT4 by HSP90 provides fundamental insights into the complex biochemistry of stem cell biology. This may also be suggestive that HSP90 not only regulates stem cell biology by maintaining routine cellular homeostasis but additionally through the direct regulation of pluripotency factors. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2015
- Full Text:
- Date Issued: 2015
- Authors: Sterrenberg, Jason Neville
- Date: 2015
- Subjects: Induced pluripotent stem cells , Heat shock proteins , Stem cells , Transcription factors , Molecular chaperones
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/194010 , vital:45415 , 10.21504/10962/194010
- Description: The therapeutic potential of stem cells is already being harnessed in clinical trails. Of even greater therapeutic potential has been the discovery of mechanisms to reprogram differentiated cells into a pluripotent stem cell-like state known as induced pluripotent stem cells (iPSCs). Stem cell nature is governed and maintained by a hierarchy of transcription factors, the apex of which is OCT4. Although much research has elucidated the transcriptional regulation of OCT4, OCT4 regulated gene expression profiles and OCT4 transcriptional activation mechanisms in both stem cell biology and cellular reprogramming to iPSCs, the fundamental biochemistry surrounding the OCT4 transcription factor remains largely unknown. In order to analyze the biochemical relationship between HSP90 and human OCT4 we developed an exogenous active human OCT4 expression model with human OCT4 under transcriptional control of a constitutive promoter. We identified the direct interaction between HSP90 and human OCT4 despite the fact that the proteins predominantly display differential subcellular localizations. We show that HSP90 inhibition resulted in degradation of human OCT4 via the ubiquitin proteasome degradation pathway. As human OCT4 and HSP90 did not interact in the nucleus, we suggest that HSP90 functions in the cytoplasmic stabilization of human OCT4. Our analysis suggests HSP90 inhibition inhibits the transcriptional activity of human OCT4 dimers without affecting monomeric OCT4 activity. Additionally our data suggests that the HSP90 and human OCT4 complex is modulated by phosphorylation events either promoting or abrogating the interaction between HSP90 and human OCT4. Our data suggest that human OCT4 displays the characteristics describing HSP90 client proteins, therefore we identify human OCT4 as a putative HSP90 client protein. The regulation of the transcription factor OCT4 by HSP90 provides fundamental insights into the complex biochemistry of stem cell biology. This may also be suggestive that HSP90 not only regulates stem cell biology by maintaining routine cellular homeostasis but additionally through the direct regulation of pluripotency factors. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2015
- Full Text:
- Date Issued: 2015
Ethics of climate change: a normative account
- Authors: Afolabi, Abiodun Paul
- Date: 2021-10-29
- Subjects: Climatic changes Senegal Saint-Louis , Climatic changes Moral and ethical aspects , Cultural property Senegal Saint-Louis , Ethics Senegal Saint-Louis , Applied ethics , Environmental justice Senegal Saint-Louis , Philosophy, African , Normativity (Ethics)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192864 , vital:45272 , 10.21504/10962/192864
- Description: Consider, for instance, you and your family have lived around a place where you enjoyed the flora and fauna of the land as well as the natural environment. Fishing and farming were pleasant activities for your family, and anyone in the community not only to survive but thrive. Your neighbours and the people in the community pride themselves so much in their farming abilities and fishing techniques. Suddenly things start taking a different turn because of rising sea level and changing weather pattern. First, your land began to give way because of sweeping erosion, and later the riverbank serving the community starts drying up. Your neighbour could not hold their own in this grim condition as they started relocating. You even witnessed some of your family and friends leaving the community and you later heard that they have become climate refugees. To put it all together, you were told that what you are experiencing is one of climate change effects. You were told that the loss of the place that you once cherished is not an act of God but the result of the reckless flaring of greenhouse gasses harmful to the environment by some powerful but polluting nations. What will you do? This might sound like a fairy tale. In reality, this is the story of the people of Saint Louis Atlantic Coasts in Senegal, captured by the Global Climate Change Alliance Plus Initiative.1 Their situation has been described as ‘living on the edge’ because for centuries, Saint Louis Atlantic Coasts, home to around 230,000 inhabitants, also known as the ‘Venice of Africa’ has been protected from the pounding Atlantic waves by the ‘Langue de Barbarie,’ a narrow, 30 km peninsula at the mouth of the Senegal river. However, the low-lying sandy spit of land along this World Heritage site is itself rapidly disappearing in the present. This is the consequence of a changing climate and other man-made problems such as illegal sand-mining and over-development. Today, the southern part of the Langue de Barbarie is an island, and the village of Doune Baba Dieye is under more than a metre of water. The villagers have become climate refugees, forced to live in temporary camps on the mainland. Not only have they lost their homes, but they have also lost significant cultural heritage like the farming and fishing culture tied to this place. The ethical considerations that emerge from climate change impacts on the world’s cultural heritage are varied. However, it seems not as self-evident in the way that research on climate change ethics has been framed around economic interest and direct threats to human life and other species. Even when they mention climate impacts on heritage sites around the world, those of Africans have been side-lined. For instance, the impact of climate change on small island nations like Tuvalu, Kiribati2 have gained much traction in climate change discourse, but we do not get to see stories of Africans whose cherished cultural heritage are affected by climate despoliation. How do we respond to this intractable challenge? This is a question of justice and, to be more precise, climate justice. Many principles and proposals for climate justice have been put forward, but the insufficient attention to the vulnerabilities or loss of cultural heritage values of Africans, which is a critical aspect of their social realities, make these theories less persuasive on a global level. This thesis, then, fills this gap in the literature by suggesting that the failure to take cognizance of the injustice in neglecting cultural heritage values when dealing with the burden of climate change is the effect of three problems. One, the value of culture is less understood in this environmental age. Hence, cultural values are excluded or made to be secondary in consideration of principles of climate justice. Second, the idea of Personhood has been neglected in climate ethics and climate justice discourse. Yet, this idea of Personhood can be an enabler of climate justice in that a realization of the significance of cultural heritage to the wellness of the human persons in Africa, makes it loss morally reprehensible. Third, those whose cultural heritage is significantly affected do not get represented in the debate about sharing the burden of climate change. This dissertation thereby builds upon the general findings of the past about anthropogenic climate change, its causes and consequences. Adopting a discursive normative framework, I also address the significance of cultural heritage in this contemporary environmental age and discuss the global justice implications of cultural heritage loss to climate change. This dissertation further provides a critique of mainstream climate justice theories, especially their marginalization of the cultural dimension of climate change. In this regard, the metaphor - ‘cultural storm’ was deployed to argue that climate justice discourses have neither factored the deep socio-cultural impact of climate change nor do they draw on the cultural understanding of justice in putting forward their theories. Given the nature of the indirect, cumulative, and interconnected invisible losses to cultural heritage from climate change, it seems unlikely that they can be addressed by simple tweaks of the climate justice status quo. This dissertation proposes that the idea of personhood in African philosophy, can be conceived to ensure climate justice live up to its expectations in a world of diverse persons dealing with a complex phenomenon like climate change. It argues that a cultural dimension of climate ethics has implications for how mitigation, adaptation and compensation plans should be furthered for global climate justice. At the foundation of my argument, I suggest that what is needed in climate justice discourse is a commitment to explore new and innovative alternatives that will produce an inclusive global climate treaty that is sensitive to the cultural heritage assets that is destroyed by climate change in Africa. This will require a multi-dimensional framework that allows fundamentally different kinds of values and benefits to be given equal visibility and standing in global climate negotiations. The dissertation proceeds in six chapters. In the first chapter, I discuss how climate change denies, damage and destroys cultural heritage values in Africa and argue that it is unjust to ignore this dimension of climate change impact, particularly on the African continent. In the second chapter, I critically discuss the normative value of cultural heritage in an environmentally sustainable and morally appropriate way for this global age. I argue that what is lost when climate change affects cultural heritage is a significant cultural asset that ought to be seriously considered in climate ethics. The third chapter addresses the global justice implications of the destruction of Africa's cultural heritage by climate change that must be paid attention to. In chapter four, I evaluate the plausibility of some of the mainstream climate justice proposals. I offered a different possible critique of current approaches to climate justice to show how they have furthered cultural injustice. The critique of current climate justice theories that I offer, stems from an uninspiring approach that belies logic permitting the sacrificing of that which is connected to others wellbeing as well as the implicit assumptions and the limitation of the idea of justice that undergird these climate justice theories. I offer, in chapter five, a plausible climate ethics theory that recognizes culturally embedded ideas of justice and empower all stakeholders to build by themselves, lives that are, in the light of these ideas, deemed to be adversely impacted by climate change. This theory advances a socio-cultural perspective to climate change which could provide a nuanced basis for understanding and addressing global climate duties that will be sensitive to the loss of cultural heritage. Specifically, I apply the African conception of personhood, to provide a normative basis for a different but intuitive understanding of the cultural dimension of climate ethics. In the final chapter, I discuss how this theory can be applied to rethink current global responses in the form of mitigation, adaptation and compensation in such a way that it takes seriously the impacts of climate change on Africa’s cultural heritage and values. , Thesis (PhD) -- Faculty of Humanities, Philosophy, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Afolabi, Abiodun Paul
- Date: 2021-10-29
- Subjects: Climatic changes Senegal Saint-Louis , Climatic changes Moral and ethical aspects , Cultural property Senegal Saint-Louis , Ethics Senegal Saint-Louis , Applied ethics , Environmental justice Senegal Saint-Louis , Philosophy, African , Normativity (Ethics)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192864 , vital:45272 , 10.21504/10962/192864
- Description: Consider, for instance, you and your family have lived around a place where you enjoyed the flora and fauna of the land as well as the natural environment. Fishing and farming were pleasant activities for your family, and anyone in the community not only to survive but thrive. Your neighbours and the people in the community pride themselves so much in their farming abilities and fishing techniques. Suddenly things start taking a different turn because of rising sea level and changing weather pattern. First, your land began to give way because of sweeping erosion, and later the riverbank serving the community starts drying up. Your neighbour could not hold their own in this grim condition as they started relocating. You even witnessed some of your family and friends leaving the community and you later heard that they have become climate refugees. To put it all together, you were told that what you are experiencing is one of climate change effects. You were told that the loss of the place that you once cherished is not an act of God but the result of the reckless flaring of greenhouse gasses harmful to the environment by some powerful but polluting nations. What will you do? This might sound like a fairy tale. In reality, this is the story of the people of Saint Louis Atlantic Coasts in Senegal, captured by the Global Climate Change Alliance Plus Initiative.1 Their situation has been described as ‘living on the edge’ because for centuries, Saint Louis Atlantic Coasts, home to around 230,000 inhabitants, also known as the ‘Venice of Africa’ has been protected from the pounding Atlantic waves by the ‘Langue de Barbarie,’ a narrow, 30 km peninsula at the mouth of the Senegal river. However, the low-lying sandy spit of land along this World Heritage site is itself rapidly disappearing in the present. This is the consequence of a changing climate and other man-made problems such as illegal sand-mining and over-development. Today, the southern part of the Langue de Barbarie is an island, and the village of Doune Baba Dieye is under more than a metre of water. The villagers have become climate refugees, forced to live in temporary camps on the mainland. Not only have they lost their homes, but they have also lost significant cultural heritage like the farming and fishing culture tied to this place. The ethical considerations that emerge from climate change impacts on the world’s cultural heritage are varied. However, it seems not as self-evident in the way that research on climate change ethics has been framed around economic interest and direct threats to human life and other species. Even when they mention climate impacts on heritage sites around the world, those of Africans have been side-lined. For instance, the impact of climate change on small island nations like Tuvalu, Kiribati2 have gained much traction in climate change discourse, but we do not get to see stories of Africans whose cherished cultural heritage are affected by climate despoliation. How do we respond to this intractable challenge? This is a question of justice and, to be more precise, climate justice. Many principles and proposals for climate justice have been put forward, but the insufficient attention to the vulnerabilities or loss of cultural heritage values of Africans, which is a critical aspect of their social realities, make these theories less persuasive on a global level. This thesis, then, fills this gap in the literature by suggesting that the failure to take cognizance of the injustice in neglecting cultural heritage values when dealing with the burden of climate change is the effect of three problems. One, the value of culture is less understood in this environmental age. Hence, cultural values are excluded or made to be secondary in consideration of principles of climate justice. Second, the idea of Personhood has been neglected in climate ethics and climate justice discourse. Yet, this idea of Personhood can be an enabler of climate justice in that a realization of the significance of cultural heritage to the wellness of the human persons in Africa, makes it loss morally reprehensible. Third, those whose cultural heritage is significantly affected do not get represented in the debate about sharing the burden of climate change. This dissertation thereby builds upon the general findings of the past about anthropogenic climate change, its causes and consequences. Adopting a discursive normative framework, I also address the significance of cultural heritage in this contemporary environmental age and discuss the global justice implications of cultural heritage loss to climate change. This dissertation further provides a critique of mainstream climate justice theories, especially their marginalization of the cultural dimension of climate change. In this regard, the metaphor - ‘cultural storm’ was deployed to argue that climate justice discourses have neither factored the deep socio-cultural impact of climate change nor do they draw on the cultural understanding of justice in putting forward their theories. Given the nature of the indirect, cumulative, and interconnected invisible losses to cultural heritage from climate change, it seems unlikely that they can be addressed by simple tweaks of the climate justice status quo. This dissertation proposes that the idea of personhood in African philosophy, can be conceived to ensure climate justice live up to its expectations in a world of diverse persons dealing with a complex phenomenon like climate change. It argues that a cultural dimension of climate ethics has implications for how mitigation, adaptation and compensation plans should be furthered for global climate justice. At the foundation of my argument, I suggest that what is needed in climate justice discourse is a commitment to explore new and innovative alternatives that will produce an inclusive global climate treaty that is sensitive to the cultural heritage assets that is destroyed by climate change in Africa. This will require a multi-dimensional framework that allows fundamentally different kinds of values and benefits to be given equal visibility and standing in global climate negotiations. The dissertation proceeds in six chapters. In the first chapter, I discuss how climate change denies, damage and destroys cultural heritage values in Africa and argue that it is unjust to ignore this dimension of climate change impact, particularly on the African continent. In the second chapter, I critically discuss the normative value of cultural heritage in an environmentally sustainable and morally appropriate way for this global age. I argue that what is lost when climate change affects cultural heritage is a significant cultural asset that ought to be seriously considered in climate ethics. The third chapter addresses the global justice implications of the destruction of Africa's cultural heritage by climate change that must be paid attention to. In chapter four, I evaluate the plausibility of some of the mainstream climate justice proposals. I offered a different possible critique of current approaches to climate justice to show how they have furthered cultural injustice. The critique of current climate justice theories that I offer, stems from an uninspiring approach that belies logic permitting the sacrificing of that which is connected to others wellbeing as well as the implicit assumptions and the limitation of the idea of justice that undergird these climate justice theories. I offer, in chapter five, a plausible climate ethics theory that recognizes culturally embedded ideas of justice and empower all stakeholders to build by themselves, lives that are, in the light of these ideas, deemed to be adversely impacted by climate change. This theory advances a socio-cultural perspective to climate change which could provide a nuanced basis for understanding and addressing global climate duties that will be sensitive to the loss of cultural heritage. Specifically, I apply the African conception of personhood, to provide a normative basis for a different but intuitive understanding of the cultural dimension of climate ethics. In the final chapter, I discuss how this theory can be applied to rethink current global responses in the form of mitigation, adaptation and compensation in such a way that it takes seriously the impacts of climate change on Africa’s cultural heritage and values. , Thesis (PhD) -- Faculty of Humanities, Philosophy, 2021
- Full Text:
- Date Issued: 2021-10-29
Evaluating and predicting impacts of Australian redclaw crayfish Cherax quadricarinatus and Louisiana red swamp crayfish Procambarus clarkii invasions
- Madzivanzira, Takudzwa Comfort
- Authors: Madzivanzira, Takudzwa Comfort
- Date: 2021-10-29
- Subjects: Cherax Africa , Procambarus clarkii Africa , Freshwater crabs Africa , Crayfish Zambezi River , Crayfish Food Zambezi River , Aquatic biodiversity Africa , Conservation biology Zambezi River , Fishing Catch effort Africa , Introduced freshwater organisms Africa , Fish populations Africa , Functional response (FR)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191137 , vital:45064 , 10.21504/10962/191137
- Description: Freshwater crayfish have become one of the most widely introduced freshwater taxa globally. Crayfish introductions have not spared the African continent, which, apart from Madagascar, is naturally devoid of native freshwater crayfish. These introductions are of concern because invasive crayfish have generally been shown to cause strong impacts on recipient ecosystems outside Africa. This study therefore set out to compile up-to-date information regarding crayfish introductions in Africa, their pathways and distributions and to improve our understanding of the nature and magnitude of their environmental impacts. A systematic review revealed that nine crayfish species have been introduced into the continent with five of those, Astacus astacus, Cherax quadricarinatus, Faxonius limosus, Procambarus clarkii and Procambarus virginalis, having established naturalised populations in fourteen African countries (Chapter 2). The main driver of these crayfish introductions was to provide socio-economic benefits but there is limited evidence of success. The thesis further documents attempts made to address crayfish knowledge gaps in Africa, including standardisation of C. quadricarinatus sampling gear (Chapter 3), determination of the distribution of C. quadricarinatus in the recently invaded Upper Zambezi Basin (Chapter 4), and predicting ecological and socioeconomic impacts of two crayfish species that are spreading rapidly in Southern Africa, namely, C. quadricarinatus and P. clarkii (Chapters 5 – 8). To standardise C. quadricarinatus sampling methods in Africa, two methods used in Southern Africa were compared and the Promar® collapsible trap baited with dry pellets was recommended as the best approach for C. quadricarinatus abundance studies due to the high catch per unit effort (CPUE), probability of capture and the suitability of dry dog food as a standard bait. This standard approach was used for crayfish surveys in the Zambezi Basin to comprehensively determine the spread and establishment of C. quadricarinatus across the basin. The establishment of C. quadricarinatus in the Barotse Floodplain, Upper Zambezi Floodplains freshwater ecoregion was confirmed. Although the probability of capture and catch per unit effort (CPUE) of C. quadricarinatus in the Barotse floodplain were similar to that of older invasions in the basin (Lake Kariba and Kafue River), morphometric differences among C. quadricarinatus populations sampled from these invaded regions were detected. Although crayfish were not detected in other regions, for example, the Okavango Floodplains ecoregions, C. quadricarinatus have the potential to spread at a downstream and upstream rate of 49 and 12 km·year-1, impacting native biota therein. To evaluate the potential for ecological impacts, the consumer-resource dynamics of C. quadricarinatus and P. clarkii were described in comparison to a native trophic analogue, the freshwater crab of the Potamonautes genus, preying on various native taxa ubiquitous to African aquatic and terrestrial ecosystems. The use of functional response (FR) and consumption experiments in this study showed the potential impacts of the two crayfish species on native resources and on resources that support livelihoods in invaded ecosystems. This in most cases was a result of their high attack parameter, which also resulted in high functional responses ratios (FRRs) compared to native crabs. The crayfish FR, FRRs and consumption rates were mostly enhanced under the high temperature treatments. The FRs and consumption results were then combined with the field biomasses of crayfish and crabs to calculate the relative impact potential (RIP) to successfully predict the degree of impact caused by crayfish species relative to crabs. Crayfish species consistently displayed RIP scores > 1 relative to the native crab irrespective of region, which were higher for the summer than the winter season, suggesting greater impact of the invaders compared to the native species. This study further estimated the socioeconomic losses due to catch spoilage by C. quadricarinatus which are up to 1500 t per year in the invaded Kafue River Basin, which translates to an annual income loss of US$ 2 million. Information provided in this study is vital for conservation management and to compel policymakers to develop appropriate conservation management tools within regulatory frameworks, which could stop or minimise the spread of crayfish species and protect Africa from further losing aquatic biodiversity. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Madzivanzira, Takudzwa Comfort
- Date: 2021-10-29
- Subjects: Cherax Africa , Procambarus clarkii Africa , Freshwater crabs Africa , Crayfish Zambezi River , Crayfish Food Zambezi River , Aquatic biodiversity Africa , Conservation biology Zambezi River , Fishing Catch effort Africa , Introduced freshwater organisms Africa , Fish populations Africa , Functional response (FR)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191137 , vital:45064 , 10.21504/10962/191137
- Description: Freshwater crayfish have become one of the most widely introduced freshwater taxa globally. Crayfish introductions have not spared the African continent, which, apart from Madagascar, is naturally devoid of native freshwater crayfish. These introductions are of concern because invasive crayfish have generally been shown to cause strong impacts on recipient ecosystems outside Africa. This study therefore set out to compile up-to-date information regarding crayfish introductions in Africa, their pathways and distributions and to improve our understanding of the nature and magnitude of their environmental impacts. A systematic review revealed that nine crayfish species have been introduced into the continent with five of those, Astacus astacus, Cherax quadricarinatus, Faxonius limosus, Procambarus clarkii and Procambarus virginalis, having established naturalised populations in fourteen African countries (Chapter 2). The main driver of these crayfish introductions was to provide socio-economic benefits but there is limited evidence of success. The thesis further documents attempts made to address crayfish knowledge gaps in Africa, including standardisation of C. quadricarinatus sampling gear (Chapter 3), determination of the distribution of C. quadricarinatus in the recently invaded Upper Zambezi Basin (Chapter 4), and predicting ecological and socioeconomic impacts of two crayfish species that are spreading rapidly in Southern Africa, namely, C. quadricarinatus and P. clarkii (Chapters 5 – 8). To standardise C. quadricarinatus sampling methods in Africa, two methods used in Southern Africa were compared and the Promar® collapsible trap baited with dry pellets was recommended as the best approach for C. quadricarinatus abundance studies due to the high catch per unit effort (CPUE), probability of capture and the suitability of dry dog food as a standard bait. This standard approach was used for crayfish surveys in the Zambezi Basin to comprehensively determine the spread and establishment of C. quadricarinatus across the basin. The establishment of C. quadricarinatus in the Barotse Floodplain, Upper Zambezi Floodplains freshwater ecoregion was confirmed. Although the probability of capture and catch per unit effort (CPUE) of C. quadricarinatus in the Barotse floodplain were similar to that of older invasions in the basin (Lake Kariba and Kafue River), morphometric differences among C. quadricarinatus populations sampled from these invaded regions were detected. Although crayfish were not detected in other regions, for example, the Okavango Floodplains ecoregions, C. quadricarinatus have the potential to spread at a downstream and upstream rate of 49 and 12 km·year-1, impacting native biota therein. To evaluate the potential for ecological impacts, the consumer-resource dynamics of C. quadricarinatus and P. clarkii were described in comparison to a native trophic analogue, the freshwater crab of the Potamonautes genus, preying on various native taxa ubiquitous to African aquatic and terrestrial ecosystems. The use of functional response (FR) and consumption experiments in this study showed the potential impacts of the two crayfish species on native resources and on resources that support livelihoods in invaded ecosystems. This in most cases was a result of their high attack parameter, which also resulted in high functional responses ratios (FRRs) compared to native crabs. The crayfish FR, FRRs and consumption rates were mostly enhanced under the high temperature treatments. The FRs and consumption results were then combined with the field biomasses of crayfish and crabs to calculate the relative impact potential (RIP) to successfully predict the degree of impact caused by crayfish species relative to crabs. Crayfish species consistently displayed RIP scores > 1 relative to the native crab irrespective of region, which were higher for the summer than the winter season, suggesting greater impact of the invaders compared to the native species. This study further estimated the socioeconomic losses due to catch spoilage by C. quadricarinatus which are up to 1500 t per year in the invaded Kafue River Basin, which translates to an annual income loss of US$ 2 million. Information provided in this study is vital for conservation management and to compel policymakers to develop appropriate conservation management tools within regulatory frameworks, which could stop or minimise the spread of crayfish species and protect Africa from further losing aquatic biodiversity. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Evaluation of the effectiveness of small aperture network telescopes as IBR data sources
- Authors: Chindipha, Stones Dalitso
- Date: 2023-03-31
- Subjects: Computer networks Monitoring , Computer networks Security measures , Computer bootstrapping , Time-series analysis , Regression analysis , Mathematical models
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/366264 , vital:65849 , DOI https://doi.org/10.21504/10962/366264
- Description: The use of network telescopes to collect unsolicited network traffic by monitoring unallocated address space has been in existence for over two decades. Past research has shown that there is a lot of activity happening in this unallocated space that needs monitoring as it carries threat intelligence data that has proven to be very useful in the security field. Prior to the emergence of the Internet of Things (IoT), commercialisation of IP addresses and widespread of mobile devices, there was a large pool of IPv4 addresses and thus reserving IPv4 addresses to be used for monitoring unsolicited activities going in the unallocated space was not a problem. Now, preservation of such IPv4 addresses just for monitoring is increasingly difficult as there is not enough free addresses in the IPv4 address space to be used for just monitoring. This is the case because such monitoring is seen as a ’non-productive’ use of the IP addresses. This research addresses the problem brought forth by this IPv4 address space exhaustion in relation to Internet Background Radiation (IBR) monitoring. In order to address the research questions, this research developed four mathematical models: Absolute Mean Accuracy Percentage Score (AMAPS), Symmetric Absolute Mean Accuracy Percentage Score (SAMAPS), Standardised Mean Absolute Error (SMAE), and Standardised Mean Absolute Scaled Error (SMASE). These models are used to evaluate the research objectives and quantify the variations that exist between different samples. The sample sizes represent different lens sizes of the telescopes. The study has brought to light a time series plot that shows the expected proportion of unique source IP addresses collected over time. The study also imputed data using the smaller /24 IPv4 net-block subnets to regenerate the missing data points using bootstrapping to create confidence intervals (CI). The findings from the simulated data supports the findings computed from the models. The CI offers a boost to decision making. Through a series of experiments with monthly and quarterly datasets, the study proposed a 95% - 99% confidence level to be used. It was known that large network telescopes collect more threat intelligence data than small-sized network telescopes, however, no study, to the best of our knowledge, has ever quantified such a knowledge gap. With the findings from the study, small-sized network telescope users can now use their network telescopes with full knowledge of gap that exists in the data collected between different network telescopes. , Thesis (PhD) -- Faculty of Science, Computer Science, 2023
- Full Text:
- Date Issued: 2023-03-31
- Authors: Chindipha, Stones Dalitso
- Date: 2023-03-31
- Subjects: Computer networks Monitoring , Computer networks Security measures , Computer bootstrapping , Time-series analysis , Regression analysis , Mathematical models
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/366264 , vital:65849 , DOI https://doi.org/10.21504/10962/366264
- Description: The use of network telescopes to collect unsolicited network traffic by monitoring unallocated address space has been in existence for over two decades. Past research has shown that there is a lot of activity happening in this unallocated space that needs monitoring as it carries threat intelligence data that has proven to be very useful in the security field. Prior to the emergence of the Internet of Things (IoT), commercialisation of IP addresses and widespread of mobile devices, there was a large pool of IPv4 addresses and thus reserving IPv4 addresses to be used for monitoring unsolicited activities going in the unallocated space was not a problem. Now, preservation of such IPv4 addresses just for monitoring is increasingly difficult as there is not enough free addresses in the IPv4 address space to be used for just monitoring. This is the case because such monitoring is seen as a ’non-productive’ use of the IP addresses. This research addresses the problem brought forth by this IPv4 address space exhaustion in relation to Internet Background Radiation (IBR) monitoring. In order to address the research questions, this research developed four mathematical models: Absolute Mean Accuracy Percentage Score (AMAPS), Symmetric Absolute Mean Accuracy Percentage Score (SAMAPS), Standardised Mean Absolute Error (SMAE), and Standardised Mean Absolute Scaled Error (SMASE). These models are used to evaluate the research objectives and quantify the variations that exist between different samples. The sample sizes represent different lens sizes of the telescopes. The study has brought to light a time series plot that shows the expected proportion of unique source IP addresses collected over time. The study also imputed data using the smaller /24 IPv4 net-block subnets to regenerate the missing data points using bootstrapping to create confidence intervals (CI). The findings from the simulated data supports the findings computed from the models. The CI offers a boost to decision making. Through a series of experiments with monthly and quarterly datasets, the study proposed a 95% - 99% confidence level to be used. It was known that large network telescopes collect more threat intelligence data than small-sized network telescopes, however, no study, to the best of our knowledge, has ever quantified such a knowledge gap. With the findings from the study, small-sized network telescope users can now use their network telescopes with full knowledge of gap that exists in the data collected between different network telescopes. , Thesis (PhD) -- Faculty of Science, Computer Science, 2023
- Full Text:
- Date Issued: 2023-03-31
Exploring aspects of Community of Inquiry (CoI) in Afrophilia learning processes for transformative education using an Afrophilic ‘Philosophy for Children’ approach: a case of Sebakwe resettlement primary schools in the Midlands Province of Zimbabwe
- Authors: Bhurekeni, John
- Date: 2023-03-29
- Subjects: Culturally relevant pedagogy Zimbabwe , Curriculum change Zimbabwe , Philosophy Study and teaching (Elementary) Zimbabwe , Critical thinking , Decolonization Zimbabwe , Technology Political aspects , Representation (Philosophy)
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/366178 , vital:65840 , DOI https://doi.org/10.21504/10962/366178
- Description: This study focused on investigating and developing an Afrophilic orientation to a sociocultural approach to philosophy for children. The main aim was to foster a critical and generative approach to considering the heritage-based curriculum foundations of Zimbabwean primary schools, focusing on Sebakwe resettlement primary schools (the case study area). Afrophilia foundations in the study are regarded as “the discourses that are the medium of philosophical reflexion” (Rettova, 2004, p. 4) in each African society. As articulated in the study, such discourses include African proverbs, poems, stories, music, and folktales which are useful in the initiation of philosophical engagements with children in a community of inquiry approach. A community of inquiry is a framework that reflects a collaborative-dialogical approach to teaching and learning. Curriculum reviews in postcolonial Zimbabwe have revealed an unconscious misalignment of the Zimbabwean education system's philosophical underpinnings because it has continued to align itself with imperial British colonial philosophy, which contradicts the country's developmental needs (Presidential Commission of Inquiry into Education and Training [CIET], 1999, Zimbabwe Ministry of Primary and Secondary Education [MoPSE], 2014). The philosophical misalignment is an extension of the colonial history of Zimbabwe showing that vestiges of colonial rule still shape the education sector. This leaves the education system focusing mainly on abstracted concepts with continued marginalisation of local cultures, discourses, and knowledge. Consequently, it leaves Zimbabwe together with other postcolonial education systems with the task of dealing with the phenomenon of colonial continuity. One implication of these colonial continuities, is learner disinterest in learning, which affects the educational process negatively, affecting the learning of critical reflexive thinking, an issue which I have observed in the Sebakwe resettlement schools involved in this study where I have been teaching for 15 years. To address, this, the study sought to answer the following questions: What historical and contemporary barriers are affecting the promotion of a culture of learning in Zimbabwean resettlement primary schools, particularly as they relate to learners' underdevelopment of critical reflexive thinking skills? In addition, How can the Philosophy for Children Afrophilia curriculum intervention promote a culture of learning in Sebakwe resettlement primary schools that is oriented toward the development of critical reflexive thinking skills in children? In approaching the research questions, I applied postcolonial and decolonisation theory, sociocultural learning theory and curriculum theory aimed at transformative change, that is oriented towards achieving a more contextually oriented approach to teaching and learning, and a paradigm of ‘learning as connection’ (Lotz-Sisitka & Lupele, 2017; Shumba, 2017). This has been identified as a ‘missing’ discourse in mainstream educational quality discourses in southern Africa (Lotz-Sisitka & Lupele, 2017). Furthermore, to create space for curriculum development using multi-actor groups in a community of inquiry, I used decolonial research methodologies in the data generation process. The study is constituted as an interventionist case study, and I applied a four-stage process comprising document analysis, workshops, participant observations involving children between 8-11 years, and reflective interviews with parents, educators and children as instruments for data gathering. I also used process-based analytical tools developed in Philosophy of Children research to analyse the processes of critical reflexive thinking development that emerged from the Philosophy for Children pedagogy involving ten lessons which I facilitated, and videorecorded. Moreover, I used postcolonial and decolonial discourse analysis to provide the broader analytical insights that informed the interpretations of the lesson analysis data from the perspective of the research problem that I address across the research project. This PhD is produced as a PhD by publication, which involves publishing of papers, and orientation to, and interpretation of the papers. The main findings of this study are reported in articles that I prepared for publication, three of which have already been published (see Appendices A1, A4 and A5), and four which have been submitted for publication (A2, A3, A6, A7) with some already at an advanced stage of finalisation via review. The conceptual paper (A1) that served as the foundation for the publication journey revealed that, in addition to the weight of cultural technologies of domination, the curriculum is shaped by the paradox of a superficial interpretation of unhu/ubuntu educational philosophy. As a result, the curriculum becomes disconnected from the learners' real-world experiences. The second paper (A2), which focuses on why Zimbabwe needs the Philosophy for Children approach with a sociocultural medley, unveils Zimbabwe's complex decolonial curriculum reforms and their many contradictions and paradoxes. However, it also emerged that the approach used in this study empowers teachers, is relevant to the emerging constellation of practices in the Sebakwe resettlement, and influences power sharing beyond teacher-child relationships. The third paper (A3), based on children’s philosophy for children practice, defends the study’s decision to bring children’s heritage and cultural lens to bear on curriculum and pedagogical praxis. In essence, the article explores a synergy between philosophy for children and the Zimbabwean heritage-based educational curriculum, serving to enrich both. The fourth paper (A4) makes the case that philosophy for children could be a viable pedagogy for transformative education, and it provides evidence-based implementation of a context-based philosophy for children. According to this paper, the approach is effective in strengthening strong community relationships, instilling pride in local heritage, and advancing curriculum transformation. The fifth paper (A5) focusses on the approach's implications for teachers' roles, practices, and competencies. Six dimensions of teacher roles, practices, and competences surfaced, including the role of the teacher as a decoloniser and pedagogical innovator, among others. The sixth paper (A6), influenced by the previous papers' findings, focused on decolonisation and improving learning opportunities for children in the Sebakwe area using the philosophy for children approach. This paper's data depicts a ‘third space’ in which learners consolidate their cultural capital and curriculum content into their own meaning construction. The implication is that schools become neutral sites that improve learners' interdependence and inclusivity while also taking contextual realities into account. The findings of the seventh and final paper (A7) presented in this write-up advance the idea that a Philosophy for Children approach with a sociocultural medley influences an ethics of care by demonstrating how Afrophilia experiences influence a new path to wildlife conservation and sustainability. The study highlights that integrating Philosophy for Children and Afrophilia foundations of knowledge into the school curriculum promotes critical reflexive thinking skills, helps to address real-life problems and adds relevance to the curriculum. The study further shows that the integration of philosophy for children in the advancement of curriculum transformation in Zimbabwe is a successful formative interventionist approach in the resettlement schools that are characterised by a critical shortage of teaching and learning resources. In essence, the research opens an understanding that curriculum transformation and decolonisation are context-based and multi-actor processes, as showcased in the experiences of parents, teachers, education inspectors, and children in this study. Furthermore, this study posits that situating curriculum decolonization and transformation within unhu/ubuntu dialectical rationality and advancing diversity in reasoning necessitates deeper engagement with heritage-based curriculum and provides teachers with appropriate agency to modify and adapt their pedagogies in alignment with the learners' life world. According to the study, this emerged as a rational possible solution to the problem of curriculum decontextualisation. Curriculum decontextualisation as highlighted in the study via the problem of colonial continuity mentioned above, appears to be further influenced by the emphasis on examination assessment scores which seem to widen the gap between the adult and child worlds, as well as the gap between contextual realities and [curriculum] examination content. Overall, the study offers an approach that can deepen an unhu/ubuntu foundation for the heritage-based curriculum reform in Zimbabwe, and strengthen the learning of children in the resettlement schools, where the case was explored. Implications for further research are elaborated, as are possible implications for policy and practice. , Thesis (PhD) -- Faculty of Education, Education, 2023
- Full Text:
- Date Issued: 2023-03-29
- Authors: Bhurekeni, John
- Date: 2023-03-29
- Subjects: Culturally relevant pedagogy Zimbabwe , Curriculum change Zimbabwe , Philosophy Study and teaching (Elementary) Zimbabwe , Critical thinking , Decolonization Zimbabwe , Technology Political aspects , Representation (Philosophy)
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/366178 , vital:65840 , DOI https://doi.org/10.21504/10962/366178
- Description: This study focused on investigating and developing an Afrophilic orientation to a sociocultural approach to philosophy for children. The main aim was to foster a critical and generative approach to considering the heritage-based curriculum foundations of Zimbabwean primary schools, focusing on Sebakwe resettlement primary schools (the case study area). Afrophilia foundations in the study are regarded as “the discourses that are the medium of philosophical reflexion” (Rettova, 2004, p. 4) in each African society. As articulated in the study, such discourses include African proverbs, poems, stories, music, and folktales which are useful in the initiation of philosophical engagements with children in a community of inquiry approach. A community of inquiry is a framework that reflects a collaborative-dialogical approach to teaching and learning. Curriculum reviews in postcolonial Zimbabwe have revealed an unconscious misalignment of the Zimbabwean education system's philosophical underpinnings because it has continued to align itself with imperial British colonial philosophy, which contradicts the country's developmental needs (Presidential Commission of Inquiry into Education and Training [CIET], 1999, Zimbabwe Ministry of Primary and Secondary Education [MoPSE], 2014). The philosophical misalignment is an extension of the colonial history of Zimbabwe showing that vestiges of colonial rule still shape the education sector. This leaves the education system focusing mainly on abstracted concepts with continued marginalisation of local cultures, discourses, and knowledge. Consequently, it leaves Zimbabwe together with other postcolonial education systems with the task of dealing with the phenomenon of colonial continuity. One implication of these colonial continuities, is learner disinterest in learning, which affects the educational process negatively, affecting the learning of critical reflexive thinking, an issue which I have observed in the Sebakwe resettlement schools involved in this study where I have been teaching for 15 years. To address, this, the study sought to answer the following questions: What historical and contemporary barriers are affecting the promotion of a culture of learning in Zimbabwean resettlement primary schools, particularly as they relate to learners' underdevelopment of critical reflexive thinking skills? In addition, How can the Philosophy for Children Afrophilia curriculum intervention promote a culture of learning in Sebakwe resettlement primary schools that is oriented toward the development of critical reflexive thinking skills in children? In approaching the research questions, I applied postcolonial and decolonisation theory, sociocultural learning theory and curriculum theory aimed at transformative change, that is oriented towards achieving a more contextually oriented approach to teaching and learning, and a paradigm of ‘learning as connection’ (Lotz-Sisitka & Lupele, 2017; Shumba, 2017). This has been identified as a ‘missing’ discourse in mainstream educational quality discourses in southern Africa (Lotz-Sisitka & Lupele, 2017). Furthermore, to create space for curriculum development using multi-actor groups in a community of inquiry, I used decolonial research methodologies in the data generation process. The study is constituted as an interventionist case study, and I applied a four-stage process comprising document analysis, workshops, participant observations involving children between 8-11 years, and reflective interviews with parents, educators and children as instruments for data gathering. I also used process-based analytical tools developed in Philosophy of Children research to analyse the processes of critical reflexive thinking development that emerged from the Philosophy for Children pedagogy involving ten lessons which I facilitated, and videorecorded. Moreover, I used postcolonial and decolonial discourse analysis to provide the broader analytical insights that informed the interpretations of the lesson analysis data from the perspective of the research problem that I address across the research project. This PhD is produced as a PhD by publication, which involves publishing of papers, and orientation to, and interpretation of the papers. The main findings of this study are reported in articles that I prepared for publication, three of which have already been published (see Appendices A1, A4 and A5), and four which have been submitted for publication (A2, A3, A6, A7) with some already at an advanced stage of finalisation via review. The conceptual paper (A1) that served as the foundation for the publication journey revealed that, in addition to the weight of cultural technologies of domination, the curriculum is shaped by the paradox of a superficial interpretation of unhu/ubuntu educational philosophy. As a result, the curriculum becomes disconnected from the learners' real-world experiences. The second paper (A2), which focuses on why Zimbabwe needs the Philosophy for Children approach with a sociocultural medley, unveils Zimbabwe's complex decolonial curriculum reforms and their many contradictions and paradoxes. However, it also emerged that the approach used in this study empowers teachers, is relevant to the emerging constellation of practices in the Sebakwe resettlement, and influences power sharing beyond teacher-child relationships. The third paper (A3), based on children’s philosophy for children practice, defends the study’s decision to bring children’s heritage and cultural lens to bear on curriculum and pedagogical praxis. In essence, the article explores a synergy between philosophy for children and the Zimbabwean heritage-based educational curriculum, serving to enrich both. The fourth paper (A4) makes the case that philosophy for children could be a viable pedagogy for transformative education, and it provides evidence-based implementation of a context-based philosophy for children. According to this paper, the approach is effective in strengthening strong community relationships, instilling pride in local heritage, and advancing curriculum transformation. The fifth paper (A5) focusses on the approach's implications for teachers' roles, practices, and competencies. Six dimensions of teacher roles, practices, and competences surfaced, including the role of the teacher as a decoloniser and pedagogical innovator, among others. The sixth paper (A6), influenced by the previous papers' findings, focused on decolonisation and improving learning opportunities for children in the Sebakwe area using the philosophy for children approach. This paper's data depicts a ‘third space’ in which learners consolidate their cultural capital and curriculum content into their own meaning construction. The implication is that schools become neutral sites that improve learners' interdependence and inclusivity while also taking contextual realities into account. The findings of the seventh and final paper (A7) presented in this write-up advance the idea that a Philosophy for Children approach with a sociocultural medley influences an ethics of care by demonstrating how Afrophilia experiences influence a new path to wildlife conservation and sustainability. The study highlights that integrating Philosophy for Children and Afrophilia foundations of knowledge into the school curriculum promotes critical reflexive thinking skills, helps to address real-life problems and adds relevance to the curriculum. The study further shows that the integration of philosophy for children in the advancement of curriculum transformation in Zimbabwe is a successful formative interventionist approach in the resettlement schools that are characterised by a critical shortage of teaching and learning resources. In essence, the research opens an understanding that curriculum transformation and decolonisation are context-based and multi-actor processes, as showcased in the experiences of parents, teachers, education inspectors, and children in this study. Furthermore, this study posits that situating curriculum decolonization and transformation within unhu/ubuntu dialectical rationality and advancing diversity in reasoning necessitates deeper engagement with heritage-based curriculum and provides teachers with appropriate agency to modify and adapt their pedagogies in alignment with the learners' life world. According to the study, this emerged as a rational possible solution to the problem of curriculum decontextualisation. Curriculum decontextualisation as highlighted in the study via the problem of colonial continuity mentioned above, appears to be further influenced by the emphasis on examination assessment scores which seem to widen the gap between the adult and child worlds, as well as the gap between contextual realities and [curriculum] examination content. Overall, the study offers an approach that can deepen an unhu/ubuntu foundation for the heritage-based curriculum reform in Zimbabwe, and strengthen the learning of children in the resettlement schools, where the case was explored. Implications for further research are elaborated, as are possible implications for policy and practice. , Thesis (PhD) -- Faculty of Education, Education, 2023
- Full Text:
- Date Issued: 2023-03-29
Exploring indiginising the university’s science curriculum through bottom-up decolonisation: Affordances and hindrances
- Authors: Mutanho, Chrispen
- Date: 2021-10-29
- Subjects: Decolonization South Africa , Ethnoscience South Africa , Ubuntu (Philosophy) , Pedagogical content knowledge , Culturally relevant pedagogy , Science Study and teaching South Africa , Science teachers In-service training South Africa , Transformative learning South Africa , Cultural-historical activity theory (CHAT)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191668 , vital:45146 , 10.21504/10962/191668
- Description: The integration of indigenous knowledge (IK) in the science curriculum is a spreading phenomenon driven by the need to bring about relevancy and equality in science education. In South Africa, for instance, the need to integrate IK in science education is part of the global effort to build a democratic state from the debris of apartheid. Henceforth, the integration of IK is backed up by both the National Constitution of the Republic of South Africa (Act 108 of 1996) and the South African Department of Basic Education’s (2011) National Curriculum Assessment Policy Statement. However, the success of this policy seems to be hindered in part by the fact that the teachers who are the implementers of the curriculum changes seem to lack the relevant pedagogical content knowledge (PCK) to integrate IK in their science teaching repertoires. Such a trend is often blamed on their Eurocentric educational background. Interestingly, very little research has been done to explore ways of supporting teachers to develop the relevant conceptual tools and teaching strategies that will enable them to integrate IK in science teaching. It is against this background that an interventionist case study on how to support the Bachelor of Education Natural Sciences in-service teachers in particular to develop exemplar science lessons that integrate IK as easily accessible resources was conducted. The study is underpinned by three complementary paradigms, namely, the interpretive, the critical, and indigenous research paradigms. While the interpretive paradigm enabled me to understand and interpret descriptive data, the critical paradigm enabled me to take an emancipatory stance and challenge the micro-aggressive elements embedded in conventional research practices; within the indigenous research paradigm, Ubuntu was the relational perspective that informed the researcher-participant relationships in this study. Vygotsky’s sociocultural theory was used as an overarching theoretical framework, in conjunction with the cultural historical activity theory. Additionally, the topic-specific pedagogical content knowledge provided the methodological and analytical tools. Data were gathered through questionnaires, individual face-to-face interviews, focus group interview, participatory observation, and the teachers’ reflections. This study established that if teachers are given back the agency to collaboratively resolve the contradictions that confront them in their workplaces, they can generate their own ideas on how to integrate IK in science vii teaching. The teachers in this study experienced a shift in their agency from a paralysed state of resisting the integration of IK at the beginning of the intervention to an ‘I can do it’ attitude at the end of the intervention. Thus, it could be argued that this study’s major contribution to new knowledge lies in demonstrating possible ways of supporting teachers to integrate IK as easily accessible resources in their science teaching. Additionally, the study also challenged the Eurocentric approach to ethics and offered Ubuntu as a relational perspective that can be used to complement the shortcomings of Eurocentric research paradigms. The study thus recommends that continuing professional development or professional learning communities should afford teachers the opportunity to collaboratively engage with the challenges that they face in their workplaces in order to resolve the contradictions that confront them. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mutanho, Chrispen
- Date: 2021-10-29
- Subjects: Decolonization South Africa , Ethnoscience South Africa , Ubuntu (Philosophy) , Pedagogical content knowledge , Culturally relevant pedagogy , Science Study and teaching South Africa , Science teachers In-service training South Africa , Transformative learning South Africa , Cultural-historical activity theory (CHAT)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191668 , vital:45146 , 10.21504/10962/191668
- Description: The integration of indigenous knowledge (IK) in the science curriculum is a spreading phenomenon driven by the need to bring about relevancy and equality in science education. In South Africa, for instance, the need to integrate IK in science education is part of the global effort to build a democratic state from the debris of apartheid. Henceforth, the integration of IK is backed up by both the National Constitution of the Republic of South Africa (Act 108 of 1996) and the South African Department of Basic Education’s (2011) National Curriculum Assessment Policy Statement. However, the success of this policy seems to be hindered in part by the fact that the teachers who are the implementers of the curriculum changes seem to lack the relevant pedagogical content knowledge (PCK) to integrate IK in their science teaching repertoires. Such a trend is often blamed on their Eurocentric educational background. Interestingly, very little research has been done to explore ways of supporting teachers to develop the relevant conceptual tools and teaching strategies that will enable them to integrate IK in science teaching. It is against this background that an interventionist case study on how to support the Bachelor of Education Natural Sciences in-service teachers in particular to develop exemplar science lessons that integrate IK as easily accessible resources was conducted. The study is underpinned by three complementary paradigms, namely, the interpretive, the critical, and indigenous research paradigms. While the interpretive paradigm enabled me to understand and interpret descriptive data, the critical paradigm enabled me to take an emancipatory stance and challenge the micro-aggressive elements embedded in conventional research practices; within the indigenous research paradigm, Ubuntu was the relational perspective that informed the researcher-participant relationships in this study. Vygotsky’s sociocultural theory was used as an overarching theoretical framework, in conjunction with the cultural historical activity theory. Additionally, the topic-specific pedagogical content knowledge provided the methodological and analytical tools. Data were gathered through questionnaires, individual face-to-face interviews, focus group interview, participatory observation, and the teachers’ reflections. This study established that if teachers are given back the agency to collaboratively resolve the contradictions that confront them in their workplaces, they can generate their own ideas on how to integrate IK in science vii teaching. The teachers in this study experienced a shift in their agency from a paralysed state of resisting the integration of IK at the beginning of the intervention to an ‘I can do it’ attitude at the end of the intervention. Thus, it could be argued that this study’s major contribution to new knowledge lies in demonstrating possible ways of supporting teachers to integrate IK as easily accessible resources in their science teaching. Additionally, the study also challenged the Eurocentric approach to ethics and offered Ubuntu as a relational perspective that can be used to complement the shortcomings of Eurocentric research paradigms. The study thus recommends that continuing professional development or professional learning communities should afford teachers the opportunity to collaboratively engage with the challenges that they face in their workplaces in order to resolve the contradictions that confront them. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Exploring pre-service teachers’ reflective practice in the context of video-based lesson analysis
- Authors: Chikiwa, Samukeliso
- Date: 2020-04-30
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/355357 , vital:64492
- Description: This study explored the development of reflective practice in foundation phase pre-service teachers in the context of video-based lesson analysis at a university in South Africa. The study was conducted in the field of mathematics education, responding to the urgent need to equip pre-service South African teachers with the knowledge and skills for effective mathematics teaching. The research is foregrounded by the continuing poor performance of South African learners in mathematics at all levels of education in the country, which has been linked to the inadequate knowledge and skills of mathematics teachers. Pre-service teacher education is putting considerable effort into improving the preparation of mathematics teachers and developing their ability to reflect on their teaching practice is one of the strategies being employed for this purpose. Research has demonstrated the importance of reflective practice (RP) in both developing and extending teachers’ mathematical knowledge for teaching. This study therefore contributes to current research that supports the development of RP as a professional skill for promoting the acquisition of knowledge for teaching in pre-service teacher education. The study adopted a qualitative case study approach with two phases of data collection. In Phase 1 I collected and analysed three sets of 19 pre-service teachers’ written reflections to establish the nature of the reflections that they developed when analysing video-recorded mathematics lessons of experienced teachers’ practice. Phase 2 was conducted with four PSTs who reflected on video-recorded mathematics lessons of their own practice, and similarly sought to investigate the nature of the reflections they developed when reflecting on practice. The four PSTs wrote one set of reflections on their own lessons, went through three sessions of facilitator-guided reflections, then wrote another set of reflections to establish if the support provided in small group facilitator-guided sessions improved their reflections. Iterative content analysis was employed to analyse the PSTs’ written reflections, using an analytic tool that I developed for this purpose through merging Lee’s (2007) and Muir and Beswick’s (2007) levels of reflection frameworks. My model had four levels of reflection: description, explanation, suggestion and reflectivity. The names of each of the levels connect to the key indicator for that level. PSTs’ written reflections were coded and analysed according to these levels. The study found that PSTs’ initial reflections were mostly description of general classroom events with little reflection at the levels of explanation and suggestion, and an absence of reflectivity. Most reflections focused on general events in the lesson rather than mathematical events, even though the six lens framework they were given to guide their reflections prompted them to steer their attention towards mathematical events. The second and third sets of reflections, although mostly still at level 1, showed some shifts towards explanation and suggestion, although an increased focus on mathematical events though reflectivity was still largely absent. No PST reached the fourth level of reflectivity in Phase 1. However, in Phase 2, the PSTs’ reflections after the three small group facilitator-guided sessions included some evidence of reflectivity. The findings suggest the need for pre-service teacher educators to make a concerted effort to teach PSTs what reflection is and how to reflect on their practice. The findings also showed the need for small group facilitator-guided support in the development of PSTs’ reflective practice. , Thesis (PhD) -- Faculty of Education, Education, 2020
- Full Text:
- Date Issued: 2020-04-30
- Authors: Chikiwa, Samukeliso
- Date: 2020-04-30
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/355357 , vital:64492
- Description: This study explored the development of reflective practice in foundation phase pre-service teachers in the context of video-based lesson analysis at a university in South Africa. The study was conducted in the field of mathematics education, responding to the urgent need to equip pre-service South African teachers with the knowledge and skills for effective mathematics teaching. The research is foregrounded by the continuing poor performance of South African learners in mathematics at all levels of education in the country, which has been linked to the inadequate knowledge and skills of mathematics teachers. Pre-service teacher education is putting considerable effort into improving the preparation of mathematics teachers and developing their ability to reflect on their teaching practice is one of the strategies being employed for this purpose. Research has demonstrated the importance of reflective practice (RP) in both developing and extending teachers’ mathematical knowledge for teaching. This study therefore contributes to current research that supports the development of RP as a professional skill for promoting the acquisition of knowledge for teaching in pre-service teacher education. The study adopted a qualitative case study approach with two phases of data collection. In Phase 1 I collected and analysed three sets of 19 pre-service teachers’ written reflections to establish the nature of the reflections that they developed when analysing video-recorded mathematics lessons of experienced teachers’ practice. Phase 2 was conducted with four PSTs who reflected on video-recorded mathematics lessons of their own practice, and similarly sought to investigate the nature of the reflections they developed when reflecting on practice. The four PSTs wrote one set of reflections on their own lessons, went through three sessions of facilitator-guided reflections, then wrote another set of reflections to establish if the support provided in small group facilitator-guided sessions improved their reflections. Iterative content analysis was employed to analyse the PSTs’ written reflections, using an analytic tool that I developed for this purpose through merging Lee’s (2007) and Muir and Beswick’s (2007) levels of reflection frameworks. My model had four levels of reflection: description, explanation, suggestion and reflectivity. The names of each of the levels connect to the key indicator for that level. PSTs’ written reflections were coded and analysed according to these levels. The study found that PSTs’ initial reflections were mostly description of general classroom events with little reflection at the levels of explanation and suggestion, and an absence of reflectivity. Most reflections focused on general events in the lesson rather than mathematical events, even though the six lens framework they were given to guide their reflections prompted them to steer their attention towards mathematical events. The second and third sets of reflections, although mostly still at level 1, showed some shifts towards explanation and suggestion, although an increased focus on mathematical events though reflectivity was still largely absent. No PST reached the fourth level of reflectivity in Phase 1. However, in Phase 2, the PSTs’ reflections after the three small group facilitator-guided sessions included some evidence of reflectivity. The findings suggest the need for pre-service teacher educators to make a concerted effort to teach PSTs what reflection is and how to reflect on their practice. The findings also showed the need for small group facilitator-guided support in the development of PSTs’ reflective practice. , Thesis (PhD) -- Faculty of Education, Education, 2020
- Full Text:
- Date Issued: 2020-04-30
Exploring the potential of imines as antiprotozoan agents with focus on t. Brucei and p. Falciparum
- Authors: Oluwafemi, Kola Augustus
- Date: 2018
- Subjects: Protozoa , Parasites , Imines , Nuclear magnetic resonance , HeLa cells , Plasmodium falciparum , Trypanosoma brucei , Isomerism
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/62235 , vital:28145 , DOI 10.21504/10962/62235
- Description: This work focuses on the design, synthesis and evaluation of imine-containing heterocyclic and acyclic compounds with special focus on their bioactivity against parasitic protozoans (P. falciparum and T. brucei) - given the context of drug resistance in the treatment of malaria and Human African sleeping sickness and the fact that several bioactive organic compounds have been reported to possess the imino group. Starting from 2-aminopyridine, novel #-alkylated-5-bromo-7-azabenzimidazoles and substituted 5-bromo-1-(carbamoylmethy)-7-azabenzimidazole derivatives were prepared, and their bioactivity against parasitic protozoans was assessed. NMR spectra of the substituted 5- bromo-1-(carbamoylmethy)-7-azabenzimidazole derivatives exhibited rotational isomerism, and a dynamic NMR study was used in the estimation of the rate constants and the free- energies of activation for rotation. The free-energy differences between the two rotamers were determined and the more stable conformations were predicted. Novel 2-phenyl-7-azabenzimidazoles were also synthesised from 2-aminopyridine. A convenient method for the regioselective formylation of 2,3-diaminopyridines into 2-amino- 7-(benzylimino)pyridine analogues of 2-phenyl-7-azabenzimidazole was developed, and some of the resulting imino derivatives were hydrogenated to verify the importance of the imino moiety for bioactivity. The 2-phenyl-7-azabenzimidazoles and the 2-amino-7- (benzylimino)pyridine analogues were screened for their anti-protozoal activity and their cytotoxicity level was determined against the HeLa cell line. In order to validate the importance of the pyridine moiety, novel #-(phenyl)-2- hydroxybenzylimines, #-(benzyl)-2-hydroxybenzylimines and (±)-trans-1,2-bis[2- hydroxybenzylimino]cyclohexanes were also synthesized and screened for activity against the parasitic protozoans and for cytotoxicity against the HeLa cell line. The biological assay results indicated that these compounds are not significantly cytotoxic and a good number of them show potential as lead compounds for the development of new malaria and trypanosomiasis drugs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2018
- Full Text:
- Date Issued: 2018
- Authors: Oluwafemi, Kola Augustus
- Date: 2018
- Subjects: Protozoa , Parasites , Imines , Nuclear magnetic resonance , HeLa cells , Plasmodium falciparum , Trypanosoma brucei , Isomerism
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/62235 , vital:28145 , DOI 10.21504/10962/62235
- Description: This work focuses on the design, synthesis and evaluation of imine-containing heterocyclic and acyclic compounds with special focus on their bioactivity against parasitic protozoans (P. falciparum and T. brucei) - given the context of drug resistance in the treatment of malaria and Human African sleeping sickness and the fact that several bioactive organic compounds have been reported to possess the imino group. Starting from 2-aminopyridine, novel #-alkylated-5-bromo-7-azabenzimidazoles and substituted 5-bromo-1-(carbamoylmethy)-7-azabenzimidazole derivatives were prepared, and their bioactivity against parasitic protozoans was assessed. NMR spectra of the substituted 5- bromo-1-(carbamoylmethy)-7-azabenzimidazole derivatives exhibited rotational isomerism, and a dynamic NMR study was used in the estimation of the rate constants and the free- energies of activation for rotation. The free-energy differences between the two rotamers were determined and the more stable conformations were predicted. Novel 2-phenyl-7-azabenzimidazoles were also synthesised from 2-aminopyridine. A convenient method for the regioselective formylation of 2,3-diaminopyridines into 2-amino- 7-(benzylimino)pyridine analogues of 2-phenyl-7-azabenzimidazole was developed, and some of the resulting imino derivatives were hydrogenated to verify the importance of the imino moiety for bioactivity. The 2-phenyl-7-azabenzimidazoles and the 2-amino-7- (benzylimino)pyridine analogues were screened for their anti-protozoal activity and their cytotoxicity level was determined against the HeLa cell line. In order to validate the importance of the pyridine moiety, novel #-(phenyl)-2- hydroxybenzylimines, #-(benzyl)-2-hydroxybenzylimines and (±)-trans-1,2-bis[2- hydroxybenzylimino]cyclohexanes were also synthesized and screened for activity against the parasitic protozoans and for cytotoxicity against the HeLa cell line. The biological assay results indicated that these compounds are not significantly cytotoxic and a good number of them show potential as lead compounds for the development of new malaria and trypanosomiasis drugs. , Thesis (PhD) -- Faculty of Science, Chemistry, 2018
- Full Text:
- Date Issued: 2018
Exploring the structural integrity of a picornavirus capsid
- Authors: Upfold, Nicole Sarah
- Date: 2020
- Subjects: Picornaviruses , Immunoglobulins , Capsids (Virology) , Viruses Morphology , RNA viruses
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/131837 , vital:36758 , DOI https://doi.org/10.21504/10962/131837
- Description: Picornaviruses are a diverse family of small RNA viruses that cause a broad range of human and veterinary diseases. Despite decades of research into the molecular biology of these pathogens, no antivirals and few vaccines are commercially available for the treatment and prevention of picornavirus infections. The capsids of these non-enveloped viruses are involved in many important aspects of the picornavirus lifecycle, such as cell attachment and entry, uncoating, and protection of the viral RNA. Although the structures of many picornavirus capsids have been solved, a broader understanding of the molecular determinants that are required for structural integrity and stability is imperative for an improved understanding of the basic biology of these viruses, and for designing effective control strategies. Collectively, this thesis aims to elucidate the molecular determinants of structural stability and integrity in the Theiler’s murine encephalomyelitis virus capsid (TMEV). To study the TMEV GDVII capsid using biochemical techniques, neutralising polyclonal antibodies were generated against GDVII particles. The antibodies recognised linear epitopes in the C-terminus of the VP1 protein, but not those present in VP2 or VP3. The VP1 C-terminal residues were mapped to a loop above the putative receptor binding pit on the capsid surface, which prompted an investigation into the potential binding site of the TMEV co-receptor, heparan sulphate. Molecular docking revealed that heparan interacts with residues of the receptor binding pocket, as well as residues of the adjoining VP1 C-terminal loop. These findings suggest that the antibodies neutralise virus infection by preventing attachment of the virus to the co-receptor and possibly the unknown primary receptor. Few studies have identified the specific residues and interactions at subunit interfaces that significantly contribute to picornavirus capsid stability, assembly, and function. A novel in-silico screen was developed for the prediction of hotspot residues at protein-protein interfaces of a virus capsid. This screen can be applied to elucidate the residues that contribute significantly to the intraprotomer, interprotomer and interpentamer interfaces of any picornavirus capsid, on condition that the structure of the virus is available. The screen was applied to TMEV GDVII resulting in the identification of hotspots, several of which correspond to residues that are known to be important for aspects of the virus lifecycle, such as those that contribute to pH stability or form part of receptor binding sites. This observation suggests that residues involved in specific capsid functions may also play a role in capsid stability. Many of the residues identified as hotspots in TMEV corresponded to those required for assembly, uncoating, and virus growth in representative picornaviruses from various genera, suggesting that the residues that regulate capsid stability may be somewhat conserved across the family. Hotspots identified at the interpentamer interfaces of TMEV were individually substituted to alanine to further explore their importance to the TMEV lifecycle. All the amino acid substitutions prevented completion of the virus lifecycle as no CPE was observed following transfection of susceptible cells. Immunofluorescence experiments demonstrated that virus protein synthesis and RNA replication were not inhibited by substitution of the hotspot residues, but that infectivity was severely impeded. This confirmed that the residues were required for some aspect of the virus lifecycle, such as capsid assembly, or were critical for maintaining the conformational stability of the TMEV particles. Virus capsids become unstable and are prone to dissociation under certain conditions such as extreme pH and non-physiological temperatures. The thermostability of TMEV was explored by selecting GDVII virions with improved thermal tolerance through serial passage and heat exposure. Thermostable virions that could tolerate temperatures above 57 °C had reduced infective titres compared to the wild type TMEV suggesting that the virus adapted to thermal stress at the expense of viral fitness. Sequencing the capsid encoding regions of the mutant virions revealed a pair of amino acid substitutions that were present in all mutants. Additional substitutions that were unique to viruses selected at different temperatures were also identified. Most of the substitutions were located within the intraprotomer interfaces of the virus, unlike previous studies on enteroviruses where mutations were mostly localised to the receptor binding pocket. This thesis provides the first analysis of the structural determinants of TMEV capsid stability. The generation of tools to further explore the capsid structures of TMEV and other picornaviruses provides an opportunity for future studies which may contribute to the development of novel control strategies against this important family of viruses. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2020
- Full Text: false
- Date Issued: 2020
- Authors: Upfold, Nicole Sarah
- Date: 2020
- Subjects: Picornaviruses , Immunoglobulins , Capsids (Virology) , Viruses Morphology , RNA viruses
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/131837 , vital:36758 , DOI https://doi.org/10.21504/10962/131837
- Description: Picornaviruses are a diverse family of small RNA viruses that cause a broad range of human and veterinary diseases. Despite decades of research into the molecular biology of these pathogens, no antivirals and few vaccines are commercially available for the treatment and prevention of picornavirus infections. The capsids of these non-enveloped viruses are involved in many important aspects of the picornavirus lifecycle, such as cell attachment and entry, uncoating, and protection of the viral RNA. Although the structures of many picornavirus capsids have been solved, a broader understanding of the molecular determinants that are required for structural integrity and stability is imperative for an improved understanding of the basic biology of these viruses, and for designing effective control strategies. Collectively, this thesis aims to elucidate the molecular determinants of structural stability and integrity in the Theiler’s murine encephalomyelitis virus capsid (TMEV). To study the TMEV GDVII capsid using biochemical techniques, neutralising polyclonal antibodies were generated against GDVII particles. The antibodies recognised linear epitopes in the C-terminus of the VP1 protein, but not those present in VP2 or VP3. The VP1 C-terminal residues were mapped to a loop above the putative receptor binding pit on the capsid surface, which prompted an investigation into the potential binding site of the TMEV co-receptor, heparan sulphate. Molecular docking revealed that heparan interacts with residues of the receptor binding pocket, as well as residues of the adjoining VP1 C-terminal loop. These findings suggest that the antibodies neutralise virus infection by preventing attachment of the virus to the co-receptor and possibly the unknown primary receptor. Few studies have identified the specific residues and interactions at subunit interfaces that significantly contribute to picornavirus capsid stability, assembly, and function. A novel in-silico screen was developed for the prediction of hotspot residues at protein-protein interfaces of a virus capsid. This screen can be applied to elucidate the residues that contribute significantly to the intraprotomer, interprotomer and interpentamer interfaces of any picornavirus capsid, on condition that the structure of the virus is available. The screen was applied to TMEV GDVII resulting in the identification of hotspots, several of which correspond to residues that are known to be important for aspects of the virus lifecycle, such as those that contribute to pH stability or form part of receptor binding sites. This observation suggests that residues involved in specific capsid functions may also play a role in capsid stability. Many of the residues identified as hotspots in TMEV corresponded to those required for assembly, uncoating, and virus growth in representative picornaviruses from various genera, suggesting that the residues that regulate capsid stability may be somewhat conserved across the family. Hotspots identified at the interpentamer interfaces of TMEV were individually substituted to alanine to further explore their importance to the TMEV lifecycle. All the amino acid substitutions prevented completion of the virus lifecycle as no CPE was observed following transfection of susceptible cells. Immunofluorescence experiments demonstrated that virus protein synthesis and RNA replication were not inhibited by substitution of the hotspot residues, but that infectivity was severely impeded. This confirmed that the residues were required for some aspect of the virus lifecycle, such as capsid assembly, or were critical for maintaining the conformational stability of the TMEV particles. Virus capsids become unstable and are prone to dissociation under certain conditions such as extreme pH and non-physiological temperatures. The thermostability of TMEV was explored by selecting GDVII virions with improved thermal tolerance through serial passage and heat exposure. Thermostable virions that could tolerate temperatures above 57 °C had reduced infective titres compared to the wild type TMEV suggesting that the virus adapted to thermal stress at the expense of viral fitness. Sequencing the capsid encoding regions of the mutant virions revealed a pair of amino acid substitutions that were present in all mutants. Additional substitutions that were unique to viruses selected at different temperatures were also identified. Most of the substitutions were located within the intraprotomer interfaces of the virus, unlike previous studies on enteroviruses where mutations were mostly localised to the receptor binding pocket. This thesis provides the first analysis of the structural determinants of TMEV capsid stability. The generation of tools to further explore the capsid structures of TMEV and other picornaviruses provides an opportunity for future studies which may contribute to the development of novel control strategies against this important family of viruses. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2020
- Full Text: false
- Date Issued: 2020
Exploring the value of an educational partnership within a multilingual pre-school setting
- Authors: Maritz, Anneliese
- Date: 2022-10-04
- Subjects: Early childhood education Parent participation South Africa Eastern Cape , Early childhood teachers Training of , Home and school South Africa Eastern Cape , Parent-teacher relationships South Africa Eastern Cape , Communication and education South Africa Eastern Cape
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327111 , vital:61082 , DOI 10.21504/10962/327111
- Description: This modest research project was situated in a multilingual Early Childhood Development (ECD) setting in the Eastern Cape (EC) province of South Africa. In the context of high levels of poverty and unemployment in the EC, issues such as under-funding, the nature of the training of practitioners, translating the importance of learning through play into practice, difficulties dealing with diverse cultural practices and the use of multiple languages, all impact ECD provision. Research has shown that parental involvement and creating parent-school partnerships can assist children to progress at school. The overall objectives of this project were to explore how a team in an ECD centre might communicate more effectively with parents and how early stimulation practices in home and school might benefit the child’s development. The theoretical framework draws upon Vygotsky’s (1978) socio-cultural historical theory, Bernstein’s (1971) elaborated and restricted language codes and Bourdieu’s (1977) concepts of social reproduction. A research project in the Netherlands Thuis in School, used an education partnership approach (Iliás et al., 2019). They developed a manual that was adapted for our local context by drawing from the theories mentioned, and to counter the dominant approaches where parenting programs have often been offered from a deficit, narrow perspective. Action Research guided the interventionist approach to workshop sessions, to enable mutual capacity-building of parents and practitioners. To ensure informed consent, participants’ first languages were used. High risk factors related to photographs and videos of participating parents and minor children were successfully addressed. Pre- and post-interviews and workshop data were analysed using template analysis, within a constructivist paradigm. Findings include vignettes to introduce the contexts and parents' ideas prior to the sessions. Then, sessions are summarised as action cycles, with key participants' responses. Finally, post-session evaluations highlight the topics the parents found most meaningful; and parents’ and practitioner accounts of changes in practices. This research illustrates ways that educational partnership elements can influence practice and policy, to improve home and school environments for the benefit of children. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-10-04
- Authors: Maritz, Anneliese
- Date: 2022-10-04
- Subjects: Early childhood education Parent participation South Africa Eastern Cape , Early childhood teachers Training of , Home and school South Africa Eastern Cape , Parent-teacher relationships South Africa Eastern Cape , Communication and education South Africa Eastern Cape
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/327111 , vital:61082 , DOI 10.21504/10962/327111
- Description: This modest research project was situated in a multilingual Early Childhood Development (ECD) setting in the Eastern Cape (EC) province of South Africa. In the context of high levels of poverty and unemployment in the EC, issues such as under-funding, the nature of the training of practitioners, translating the importance of learning through play into practice, difficulties dealing with diverse cultural practices and the use of multiple languages, all impact ECD provision. Research has shown that parental involvement and creating parent-school partnerships can assist children to progress at school. The overall objectives of this project were to explore how a team in an ECD centre might communicate more effectively with parents and how early stimulation practices in home and school might benefit the child’s development. The theoretical framework draws upon Vygotsky’s (1978) socio-cultural historical theory, Bernstein’s (1971) elaborated and restricted language codes and Bourdieu’s (1977) concepts of social reproduction. A research project in the Netherlands Thuis in School, used an education partnership approach (Iliás et al., 2019). They developed a manual that was adapted for our local context by drawing from the theories mentioned, and to counter the dominant approaches where parenting programs have often been offered from a deficit, narrow perspective. Action Research guided the interventionist approach to workshop sessions, to enable mutual capacity-building of parents and practitioners. To ensure informed consent, participants’ first languages were used. High risk factors related to photographs and videos of participating parents and minor children were successfully addressed. Pre- and post-interviews and workshop data were analysed using template analysis, within a constructivist paradigm. Findings include vignettes to introduce the contexts and parents' ideas prior to the sessions. Then, sessions are summarised as action cycles, with key participants' responses. Finally, post-session evaluations highlight the topics the parents found most meaningful; and parents’ and practitioner accounts of changes in practices. This research illustrates ways that educational partnership elements can influence practice and policy, to improve home and school environments for the benefit of children. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-10-04
Formulation of an enzyme cocktail, HoloMix, using cellulolytic and xylanolytic enzyme core-sets for effective degradation of various pre-treated hardwoods
- Authors: Malgas, Samkelo
- Date: 2018
- Subjects: Biomass , Cellulase , Hardwoods , Xylanases
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/62827 , vital:28297 , DOI https://doi.org/10.21504/10962/62827
- Description: Currently, there is a growing interest in utilising hardwoods as feedstocks for bioethanol production due to the vast advantages they have over other feedstocks for fermentable sugar production. In this study, two selected hardwoods, Acacia and Populus spp., were subjected to two pre-treatment processes (Sodium chlorite delignification and Steam explosion) and compared with respect to how these pre-treatments affect their enzymatic saccharification. Hardwoods were selected for this study, because hardwoods are easier to delignify when compared to softwoods, and therefore their polysaccharides are more easily accessible by enzymes for the purpose of producing fermentable sugars. Currently available commercial enzyme mixtures have been developed for optimal hydrolysis of acid-pre-treated corn stover and are therefore not optimal for saccharification of pre-treated hardwoods. In this work, we attempted the empirical design of a hardwood specific enzyme cocktail, HoloMix. Firstly, a cellulolytic core-set, CelMix (in a ratio of Egl 68%: Cel7A 17%: Cel6A 6%: Bgl1 9%), for the optimal release of glucose, and a xylanolytic core-set, XynMix (in a ratio of Xyn2A 60%: XT6 20%: AguA 11%: SXA 9%), for the optimal release of xylose, were formulated using an empirical enzyme ratio approach after biochemically characterising these enzymes. As it is well ̶ known that biomass pre-treatment may result in the generation of compounds that hamper enzymatic hydrolysis and microbial fermentation, the effects of these compounds on CelMix and XynMix were evaluated. Using the optimised CelMix and XynMix cocktails, a HoloMix cocktail was established for optimal reducing sugar, glucose and xylose release from the various pre-treated hardwoods. For delignified biomass, the optimized HoloMix consisted of CelMix to XynMix at 75% to 25% protein loading, while for the untreated and steam exploded biomass the HoloMix consisted of CelMix to XynMix at 93.75% to 6.25% protein loading. Sugar release by the HoloMix at a loading of 27.5 mg protein/g of biomass (or 55 mg protein/g of glucan) after 24 h gave 70-100% sugar yield. Treatment of the hardwoods with a laccase from Agaricus bisporus, especially wood biomass with a higher proportion of lignin, significantly improved saccharification by the formulated HoloMix enzyme cocktails. This study provided insights into the enzymatic hydrolysis of various pre-treated hardwood substrates and assessed whether the same lignocellulolytic cocktail can be used to efficiently hydrolyse different hardwood species. The present study also demonstrated that the hydrolysis efficiency of the optimised HoloMix was comparable to (if not better) than commercial enzyme preparations during hardwood biomass saccharification. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2018
- Full Text:
- Date Issued: 2018
- Authors: Malgas, Samkelo
- Date: 2018
- Subjects: Biomass , Cellulase , Hardwoods , Xylanases
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/62827 , vital:28297 , DOI https://doi.org/10.21504/10962/62827
- Description: Currently, there is a growing interest in utilising hardwoods as feedstocks for bioethanol production due to the vast advantages they have over other feedstocks for fermentable sugar production. In this study, two selected hardwoods, Acacia and Populus spp., were subjected to two pre-treatment processes (Sodium chlorite delignification and Steam explosion) and compared with respect to how these pre-treatments affect their enzymatic saccharification. Hardwoods were selected for this study, because hardwoods are easier to delignify when compared to softwoods, and therefore their polysaccharides are more easily accessible by enzymes for the purpose of producing fermentable sugars. Currently available commercial enzyme mixtures have been developed for optimal hydrolysis of acid-pre-treated corn stover and are therefore not optimal for saccharification of pre-treated hardwoods. In this work, we attempted the empirical design of a hardwood specific enzyme cocktail, HoloMix. Firstly, a cellulolytic core-set, CelMix (in a ratio of Egl 68%: Cel7A 17%: Cel6A 6%: Bgl1 9%), for the optimal release of glucose, and a xylanolytic core-set, XynMix (in a ratio of Xyn2A 60%: XT6 20%: AguA 11%: SXA 9%), for the optimal release of xylose, were formulated using an empirical enzyme ratio approach after biochemically characterising these enzymes. As it is well ̶ known that biomass pre-treatment may result in the generation of compounds that hamper enzymatic hydrolysis and microbial fermentation, the effects of these compounds on CelMix and XynMix were evaluated. Using the optimised CelMix and XynMix cocktails, a HoloMix cocktail was established for optimal reducing sugar, glucose and xylose release from the various pre-treated hardwoods. For delignified biomass, the optimized HoloMix consisted of CelMix to XynMix at 75% to 25% protein loading, while for the untreated and steam exploded biomass the HoloMix consisted of CelMix to XynMix at 93.75% to 6.25% protein loading. Sugar release by the HoloMix at a loading of 27.5 mg protein/g of biomass (or 55 mg protein/g of glucan) after 24 h gave 70-100% sugar yield. Treatment of the hardwoods with a laccase from Agaricus bisporus, especially wood biomass with a higher proportion of lignin, significantly improved saccharification by the formulated HoloMix enzyme cocktails. This study provided insights into the enzymatic hydrolysis of various pre-treated hardwood substrates and assessed whether the same lignocellulolytic cocktail can be used to efficiently hydrolyse different hardwood species. The present study also demonstrated that the hydrolysis efficiency of the optimised HoloMix was comparable to (if not better) than commercial enzyme preparations during hardwood biomass saccharification. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2018
- Full Text:
- Date Issued: 2018
Fucoidans from South African brown seaweeds: establishing the link between their structure and biological properties (anti-diabetic and anti-cancer activities)
- Authors: Mabate, Blessing
- Date: 2022-10-14
- Subjects: Fucoidan , Diabetes Treatment , Cancer Treatment , Brown algae
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365677 , vital:65775 , DOI https://doi.org/10.21504/10962/365677
- Description: Type 2 diabetes mellitus (T2DM) and cancer are major non-communicable diseases causing a heavy morbidity-mortality and economic burden globally. The therapeutic efforts in managing these diseases are primarily chemotherapeutic and are associated with demerits, including side effects and toxicity, limiting the prescribed amounts. These dosage limits may cause drug resistance, another major challenge in maintaining quality global health. The pursuit of novel natural bioproducts is a reasonable strategy to add to the arsenal against T2DM and cancer. Fucoidans, sulphated fucose polysaccharides abundant in brown seaweeds, have recently become popular for their biological activities, including anti-diabetic and anti-cancer properties. However, endemic South African brown seaweeds have not been adequately explored. Therefore, this study sought to characterise fucoidans extracted from South African brown seaweeds and elucidate their structure to their biological activities. Also, this study highlighted carbohydrate and glucose metabolism as major target processes in the control efforts of T2DM and cancer using fucoidans. Harvested brown seaweeds were identified as Ecklonia radiata and Sargassum elegans. E. maxima was kindly donated by KelpX. The fucoidans were then extracted using hot water, EDTA assisted, and acid extraction protocols. The integrity of the extracted fucoidan was confirmed through structural analysis using FTIR, NMR and TGA. The fucoidan extracts were then chemically characterised to determine their carbohydrate and monosaccharide composition and sulphate content. The characterised fucoidans were profiled for inhibiting the major amylolytic enzymes, namely α-amylase and α-glucosidase. The mode of inhibition by fucoidans and synergy experiments with the commercial anti-diabetic drug acarbose were also investigated. Furthermore, the fucoidans were screened for potential anti-cancer activities on the human colorectal HCT116 cancer cell line. The cytotoxicity of fucoidans was quantified using the resazurin assay. The effect of fucoidan on HCT116 cell adhesion on the tissue culture plastic was also investigated using the crystal violet-based cell adhesion assay. In addition, cancer antimigration properties of fucoidans were also investigated using 2D wound healing and 3D spheroid-based assays. Furthermore, the long-term survival of HCT116 cells was investigated through the clonogenic assay after treatment with fucoidans. Lastly, glucose uptake and lactate export assays revealed the influence of fucoidan on glucose uptake and the glycolytic flux of HCT116 cells. Fucoidans were successfully extracted with a yield between 2.2% and 14.2% on a dry weight basis. EDTA extracts produced the highest yields than the water and the acid extracts. Ecklonia spp. fucoidans displayed the highest total carbohydrate content, with glucose and galactose being the major monosaccharides. S. elegans and commercial Fucus vesiculosus had lower carbohydrate contents but contained more sulphates than the Ecklonia spp. fucoidans. Furthermore, the extracted fucoidan contained little to no contaminants, including proteins, phenolics and uronic acids. In addition, the extracted fucoidans were determined to be >100 kDa through ultracentrifugation. Mass spectrometry also detected the most abundant peak for all fucoidans to be around 700 Da (m/z). Extracted fucoidans inhibited the activity of α-glucosidase more strongly than the commercial anti-diabetic agent acarbose but were inactive on α-amylase. Fucoidans were also shown to be mixed inhibitors of α-glucosidase. Compellingly, fucoidans synergistically inhibited α-glucosidase in combination with the anti-diabetic agent acarbose, highlighting prospects for combination therapy. Finally, fucoidans demonstrated some anti-proliferative characteristics on HCT116 cancer cells by inhibiting their ability to adhere to the tissue culture plate matrix. Furthermore, some fucoidan extracts inhibited the migration of HCT116 cancer cells from 3D spheroids. Some of our fucoidan extracts also inhibited HCT116 colony formation, demonstrating inhibition of long-term cell survival. The E. maxima water extract also inhibited glucose uptake by HCT116 cells, thereby influencing the glycolytic flux. In conclusion, biologically active fucoidans were successfully extracted from South African brown seaweeds. These fucoidans demonstrated anti-diabetic and anti-cancer properties, revealing their relevance as potential drugs for these diseases. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Mabate, Blessing
- Date: 2022-10-14
- Subjects: Fucoidan , Diabetes Treatment , Cancer Treatment , Brown algae
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365677 , vital:65775 , DOI https://doi.org/10.21504/10962/365677
- Description: Type 2 diabetes mellitus (T2DM) and cancer are major non-communicable diseases causing a heavy morbidity-mortality and economic burden globally. The therapeutic efforts in managing these diseases are primarily chemotherapeutic and are associated with demerits, including side effects and toxicity, limiting the prescribed amounts. These dosage limits may cause drug resistance, another major challenge in maintaining quality global health. The pursuit of novel natural bioproducts is a reasonable strategy to add to the arsenal against T2DM and cancer. Fucoidans, sulphated fucose polysaccharides abundant in brown seaweeds, have recently become popular for their biological activities, including anti-diabetic and anti-cancer properties. However, endemic South African brown seaweeds have not been adequately explored. Therefore, this study sought to characterise fucoidans extracted from South African brown seaweeds and elucidate their structure to their biological activities. Also, this study highlighted carbohydrate and glucose metabolism as major target processes in the control efforts of T2DM and cancer using fucoidans. Harvested brown seaweeds were identified as Ecklonia radiata and Sargassum elegans. E. maxima was kindly donated by KelpX. The fucoidans were then extracted using hot water, EDTA assisted, and acid extraction protocols. The integrity of the extracted fucoidan was confirmed through structural analysis using FTIR, NMR and TGA. The fucoidan extracts were then chemically characterised to determine their carbohydrate and monosaccharide composition and sulphate content. The characterised fucoidans were profiled for inhibiting the major amylolytic enzymes, namely α-amylase and α-glucosidase. The mode of inhibition by fucoidans and synergy experiments with the commercial anti-diabetic drug acarbose were also investigated. Furthermore, the fucoidans were screened for potential anti-cancer activities on the human colorectal HCT116 cancer cell line. The cytotoxicity of fucoidans was quantified using the resazurin assay. The effect of fucoidan on HCT116 cell adhesion on the tissue culture plastic was also investigated using the crystal violet-based cell adhesion assay. In addition, cancer antimigration properties of fucoidans were also investigated using 2D wound healing and 3D spheroid-based assays. Furthermore, the long-term survival of HCT116 cells was investigated through the clonogenic assay after treatment with fucoidans. Lastly, glucose uptake and lactate export assays revealed the influence of fucoidan on glucose uptake and the glycolytic flux of HCT116 cells. Fucoidans were successfully extracted with a yield between 2.2% and 14.2% on a dry weight basis. EDTA extracts produced the highest yields than the water and the acid extracts. Ecklonia spp. fucoidans displayed the highest total carbohydrate content, with glucose and galactose being the major monosaccharides. S. elegans and commercial Fucus vesiculosus had lower carbohydrate contents but contained more sulphates than the Ecklonia spp. fucoidans. Furthermore, the extracted fucoidan contained little to no contaminants, including proteins, phenolics and uronic acids. In addition, the extracted fucoidans were determined to be >100 kDa through ultracentrifugation. Mass spectrometry also detected the most abundant peak for all fucoidans to be around 700 Da (m/z). Extracted fucoidans inhibited the activity of α-glucosidase more strongly than the commercial anti-diabetic agent acarbose but were inactive on α-amylase. Fucoidans were also shown to be mixed inhibitors of α-glucosidase. Compellingly, fucoidans synergistically inhibited α-glucosidase in combination with the anti-diabetic agent acarbose, highlighting prospects for combination therapy. Finally, fucoidans demonstrated some anti-proliferative characteristics on HCT116 cancer cells by inhibiting their ability to adhere to the tissue culture plate matrix. Furthermore, some fucoidan extracts inhibited the migration of HCT116 cancer cells from 3D spheroids. Some of our fucoidan extracts also inhibited HCT116 colony formation, demonstrating inhibition of long-term cell survival. The E. maxima water extract also inhibited glucose uptake by HCT116 cells, thereby influencing the glycolytic flux. In conclusion, biologically active fucoidans were successfully extracted from South African brown seaweeds. These fucoidans demonstrated anti-diabetic and anti-cancer properties, revealing their relevance as potential drugs for these diseases. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
Functional biogeography: evaluating community assemblage patterns and ecosystem functioning in intertidal systems using trait-based approaches
- Authors: Gusha, Molline Natanah C
- Date: 2022-10-14
- Subjects: Biogeography , Marine algae , Benthic ecology , Invertebrates , Functional redundancy , Ocean temperature , Biology Classification
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365792 , vital:65790 , DOI https://doi.org/10.21504/10962/365792
- Description: Analyses of taxonomic diversity patterns within coastal systems has been critical in the development of the theory of biogeography. Increasing evidence, however, shows that the variety of functions that species perform in ecosystems (rather than their taxonomic identity) is a better predictor of the influence of the environment on the species. This information has been useful in predictive ecology leading to the development of trait-based approaches (TBA). Until the late 1970s, however, limited effort (particularly in marine systems) was channeled towards patterns in functional species traits and how they may be affected by changes in environmental gradients. Here, I mapped the functional biogeography of the South African coastline based on a suite of species' reproduction and development traits. Because species composition is one of the key tools used by zoogeographers to map species distribution patterns, I expected lower variability in trait composition within main biogeographic regions than in intervening transition zones based on the habitat templet theory and following the biomass ratio and limiting similarity hypotheses. In brief, the habitat templet theory proposes that “the habitat provides a templet upon which evolution forges species characteristics”, while the biomass ratio hypothesis assumes that the most abundant species traits determine ecosystem functioning. The limiting similarity hypothesis also sometimes referred to as the niche complementarity hypothesis, however, predicts that species can coexist if their niches complement one another. In light of the habitat being an evolutionary templet, abiotic and biotic habitat patterns were measured as nearshore SST and chlorophyll-a gradients, respectively. I expected the SST gradient to act as the stronger key filter of trait diversification because temperature is often considered the most influential environmental factor affecting species survival with seasonality of SST affecting the timing of spawning and along with food availability, possibly influencing fecundity. Functional trait data were thus compiled for macroinvertebrate species collected from fifty-two rocky shore sites from three main bioregions (east, south, and west) and two transition zones (south-west and south-east). Biological trait analysis and functional diversity indices were used to evaluate how traits related to species development and reproduction respond to temperature and chlorophyll -a (used as a proxy for food availability) gradients along the coastline. GLMM and hierarchical cluster analyses showed distinct patterns/shifts in SST and chlorophyll-a gradients across bioregions, with two main breaks in SST separating the east and south-east overlap (SEO) bioregions from the south, south-west overlap (SWO) and west bioregions. In contrast, chlorophyll-a exhibited three major breaks with the east, SEO–south–SWO, and west clustering independently of each other. The RLQ analysis (a type of co-inertia analysis) which simultaneously ordinates 3-matrix datasets [i.e., (environment × site[R]), (species × site[L]) and (species × traits [Q])] showed that the higher SST gradient on the east and SEO promoted higher abundance and biomass of simultaneous hermaphrodites while higher chlorophyll-a gradients on the SWO and west coasts strongly promoted reproductive maturity at larger-sizes. The combined fourth-corner analyses showed that the modalities within the development trait domain responding to chlorophyll-a gradients primarily included filter feeders, sessile and swimming species and also species living on the infratidal zone. In addition, the reproduction trait domain showed higher sensitivity and association to differences in chlorophyll-a and SST gradients than development traits. Overall, SST and chlorophyll-a gradients influenced the distribution of the most dominant traits as indicated by shifts in community-weighted mean trait values across bioregions. This suggests the importance of habitat filtering on coastal species reproduction. A separate study evaluating the influence of large-scale biogeographic effects vs the micro-scale biogenic habitat structure offered by coralline seaweeds across 24 sites revealed some notable effects of both factors on the diversity and abundance of macroalgal epifauna. There was a notable biogeographic influence on epifauna, with the SEO recording the highest epifaunal species richness and abundance, followed by the south coast, then the SWO and lastly the west coast. In addition, the total biomass gradient of the corallines followed a similar trend. The epifauna however, showed no host-specificity, illustrating that epifauna may not be species–centric as commonly assumed, and the higher diversity of epifaunal diversity may well be simply because those corallines are the available habitat within the sampled part of the coastline. Lastly, macroinvertebrate trait distribution on the South African coastline confirms that the habitat, particularly the biotic filter (in this case chl-a) provides a templet upon which evolution forges species traits. However, since temperature is a proxy for nutrient availability (cold upwelling brings nutrients), then temperature drives chlorophyll-a. Subsequently this means the abiotic component indirectly drives trait distribution by influencing the biotic environment (chl-a). For epifauna species, also, the coralline diversity and composition can also be regarded as a biotic filter influencing the epifaunal abundances and composition across different bioregions. Moreover, since temperature is regarded as a conservative trait in seaweeds, temperature tolerance defines the biogeographical boundaries of seaweeds, therefore temperature may be indirectly affecting epifauna abundances through coralline species diversity and biomass. In summary, considering the deterministic processes governing ecosystem functioning and community assemblage, the mass ratio and limiting similarity hypotheses showed complementary effects. Different bioregions provided variable support for these two hypotheses, but overall, the mass ratio hypothesis (weighted by species biomass) received stronger support and may be more meaningful to the interpretation of ecosystem functioning and persistence within rocky shore systems. Lastly, although, the SWO showed some of the characteristics of a subtraction zone based on the relatively low abundance, diversity, and biomass measures. Nonetheless, there was evidence of high functional redundancy across all other four bioregions. This suggests that in the context of development and reproduction traits, the rocky shore ecosystem along the SA coastline may be functionally stable at this stage. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Gusha, Molline Natanah C
- Date: 2022-10-14
- Subjects: Biogeography , Marine algae , Benthic ecology , Invertebrates , Functional redundancy , Ocean temperature , Biology Classification
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/365792 , vital:65790 , DOI https://doi.org/10.21504/10962/365792
- Description: Analyses of taxonomic diversity patterns within coastal systems has been critical in the development of the theory of biogeography. Increasing evidence, however, shows that the variety of functions that species perform in ecosystems (rather than their taxonomic identity) is a better predictor of the influence of the environment on the species. This information has been useful in predictive ecology leading to the development of trait-based approaches (TBA). Until the late 1970s, however, limited effort (particularly in marine systems) was channeled towards patterns in functional species traits and how they may be affected by changes in environmental gradients. Here, I mapped the functional biogeography of the South African coastline based on a suite of species' reproduction and development traits. Because species composition is one of the key tools used by zoogeographers to map species distribution patterns, I expected lower variability in trait composition within main biogeographic regions than in intervening transition zones based on the habitat templet theory and following the biomass ratio and limiting similarity hypotheses. In brief, the habitat templet theory proposes that “the habitat provides a templet upon which evolution forges species characteristics”, while the biomass ratio hypothesis assumes that the most abundant species traits determine ecosystem functioning. The limiting similarity hypothesis also sometimes referred to as the niche complementarity hypothesis, however, predicts that species can coexist if their niches complement one another. In light of the habitat being an evolutionary templet, abiotic and biotic habitat patterns were measured as nearshore SST and chlorophyll-a gradients, respectively. I expected the SST gradient to act as the stronger key filter of trait diversification because temperature is often considered the most influential environmental factor affecting species survival with seasonality of SST affecting the timing of spawning and along with food availability, possibly influencing fecundity. Functional trait data were thus compiled for macroinvertebrate species collected from fifty-two rocky shore sites from three main bioregions (east, south, and west) and two transition zones (south-west and south-east). Biological trait analysis and functional diversity indices were used to evaluate how traits related to species development and reproduction respond to temperature and chlorophyll -a (used as a proxy for food availability) gradients along the coastline. GLMM and hierarchical cluster analyses showed distinct patterns/shifts in SST and chlorophyll-a gradients across bioregions, with two main breaks in SST separating the east and south-east overlap (SEO) bioregions from the south, south-west overlap (SWO) and west bioregions. In contrast, chlorophyll-a exhibited three major breaks with the east, SEO–south–SWO, and west clustering independently of each other. The RLQ analysis (a type of co-inertia analysis) which simultaneously ordinates 3-matrix datasets [i.e., (environment × site[R]), (species × site[L]) and (species × traits [Q])] showed that the higher SST gradient on the east and SEO promoted higher abundance and biomass of simultaneous hermaphrodites while higher chlorophyll-a gradients on the SWO and west coasts strongly promoted reproductive maturity at larger-sizes. The combined fourth-corner analyses showed that the modalities within the development trait domain responding to chlorophyll-a gradients primarily included filter feeders, sessile and swimming species and also species living on the infratidal zone. In addition, the reproduction trait domain showed higher sensitivity and association to differences in chlorophyll-a and SST gradients than development traits. Overall, SST and chlorophyll-a gradients influenced the distribution of the most dominant traits as indicated by shifts in community-weighted mean trait values across bioregions. This suggests the importance of habitat filtering on coastal species reproduction. A separate study evaluating the influence of large-scale biogeographic effects vs the micro-scale biogenic habitat structure offered by coralline seaweeds across 24 sites revealed some notable effects of both factors on the diversity and abundance of macroalgal epifauna. There was a notable biogeographic influence on epifauna, with the SEO recording the highest epifaunal species richness and abundance, followed by the south coast, then the SWO and lastly the west coast. In addition, the total biomass gradient of the corallines followed a similar trend. The epifauna however, showed no host-specificity, illustrating that epifauna may not be species–centric as commonly assumed, and the higher diversity of epifaunal diversity may well be simply because those corallines are the available habitat within the sampled part of the coastline. Lastly, macroinvertebrate trait distribution on the South African coastline confirms that the habitat, particularly the biotic filter (in this case chl-a) provides a templet upon which evolution forges species traits. However, since temperature is a proxy for nutrient availability (cold upwelling brings nutrients), then temperature drives chlorophyll-a. Subsequently this means the abiotic component indirectly drives trait distribution by influencing the biotic environment (chl-a). For epifauna species, also, the coralline diversity and composition can also be regarded as a biotic filter influencing the epifaunal abundances and composition across different bioregions. Moreover, since temperature is regarded as a conservative trait in seaweeds, temperature tolerance defines the biogeographical boundaries of seaweeds, therefore temperature may be indirectly affecting epifauna abundances through coralline species diversity and biomass. In summary, considering the deterministic processes governing ecosystem functioning and community assemblage, the mass ratio and limiting similarity hypotheses showed complementary effects. Different bioregions provided variable support for these two hypotheses, but overall, the mass ratio hypothesis (weighted by species biomass) received stronger support and may be more meaningful to the interpretation of ecosystem functioning and persistence within rocky shore systems. Lastly, although, the SWO showed some of the characteristics of a subtraction zone based on the relatively low abundance, diversity, and biomass measures. Nonetheless, there was evidence of high functional redundancy across all other four bioregions. This suggests that in the context of development and reproduction traits, the rocky shore ecosystem along the SA coastline may be functionally stable at this stage. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2022
- Full Text:
- Date Issued: 2022-10-14
Gaze patterns of expert and amateur sight-readers with particular focus on the cognitive underpinnings of reading key and time signatures
- Authors: Viljoen, Jacobus Frederick
- Date: 2021-10-29
- Subjects: Sight-reading (Music) , Eye tracking , Cognition , Musical notation , Tonality , Musical meter and rhythm
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190908 , vital:45040 , 10.21504/10962/190908
- Description: Over the last decade, eye-tracking technology has provided researchers with specific tools to study the process of reading (language and music) empirically. Most of these studies have focused on the “Eye-Hand Span” phenomenon (the ability to read ahead of the point of playing). However, little research investigates the cognitive implications of specific aspects of musical notation when performed in real time. This research aimed to observe the fixations patterns of sight-readers in order to investigate the cognitive underpinnings of key and time signatures in music scores. This research project is a quantitative study using a quasi-experimental research design. Tobii eye-tracking equipment and software were used to record the eye movements of 11 expert and 7 amateur keyboard sight-readers. Two key aspects of music notation, key and time signatures, were selected as the main focus of the study. To investigate these aspects, eighteen research participants were provided with seventeen sight-reading examples for one hand (low complexity) and two hands (high complexity) composed specifically by the researcher. Several examples contained one or more unexpected aspects (accidentals or changes of time signature) to test their effect on fixation count and duration. Two variables (fixation count and fixation duration) were utilised to analyze fixation patterns on the selected aspects of the scores. Three main results emerged from the data analysis: 1) Expert sight-readers performed with much greater accuracy than experts in both tests; 2) Expert sight-readers exhibited a higher fixation count on entire scores in complex examples; 3) Both expert and amateur sight-readers fixate more and for longer on certain notational aspects such as key and time signatures than other notational aspects such as deviations or individual notes. This selection of focused attention suggests that both expert and amateur sight-readers cognitively process music scores in a hierarchical order. In conclusion, key and time signatures appear to require more and longer fixations by both groups of readers than other aspects of the score. This supports previous research which suggests that sound musical knowledge may play a positive role in performers’ sight-reading skills, thereby contributing to more successful sight-reading performances. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Viljoen, Jacobus Frederick
- Date: 2021-10-29
- Subjects: Sight-reading (Music) , Eye tracking , Cognition , Musical notation , Tonality , Musical meter and rhythm
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190908 , vital:45040 , 10.21504/10962/190908
- Description: Over the last decade, eye-tracking technology has provided researchers with specific tools to study the process of reading (language and music) empirically. Most of these studies have focused on the “Eye-Hand Span” phenomenon (the ability to read ahead of the point of playing). However, little research investigates the cognitive implications of specific aspects of musical notation when performed in real time. This research aimed to observe the fixations patterns of sight-readers in order to investigate the cognitive underpinnings of key and time signatures in music scores. This research project is a quantitative study using a quasi-experimental research design. Tobii eye-tracking equipment and software were used to record the eye movements of 11 expert and 7 amateur keyboard sight-readers. Two key aspects of music notation, key and time signatures, were selected as the main focus of the study. To investigate these aspects, eighteen research participants were provided with seventeen sight-reading examples for one hand (low complexity) and two hands (high complexity) composed specifically by the researcher. Several examples contained one or more unexpected aspects (accidentals or changes of time signature) to test their effect on fixation count and duration. Two variables (fixation count and fixation duration) were utilised to analyze fixation patterns on the selected aspects of the scores. Three main results emerged from the data analysis: 1) Expert sight-readers performed with much greater accuracy than experts in both tests; 2) Expert sight-readers exhibited a higher fixation count on entire scores in complex examples; 3) Both expert and amateur sight-readers fixate more and for longer on certain notational aspects such as key and time signatures than other notational aspects such as deviations or individual notes. This selection of focused attention suggests that both expert and amateur sight-readers cognitively process music scores in a hierarchical order. In conclusion, key and time signatures appear to require more and longer fixations by both groups of readers than other aspects of the score. This supports previous research which suggests that sound musical knowledge may play a positive role in performers’ sight-reading skills, thereby contributing to more successful sight-reading performances. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2021
- Full Text:
- Date Issued: 2021-10-29
Gem-bearing granitic pegmatites in Malawi: their mineralogy, geochemistry, age, and fluid compositional variations
- Kankuzi, Charles Frienderson
- Authors: Kankuzi, Charles Frienderson
- Date: 2019
- Subjects: Granite , Pegmatites , Geochemistry , Fluid inclusions , Nonferrous metals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/97905 , vital:31505 , DOI https://doi.org/10.21504/10962/97905
- Description: The gem bearing granitic pegmatites from different pegmatite fields across Malawi intrude all important geological entities from the Palaeoproterozoic in the north, the Mesoproterozoic in central Malawi and the Pan-African basement in the south. U/Pb zircon and Rb/Sr mineral isochron ages indicate pegmatite emplacement from the Palaeoproterozoic to Pan-African and Mesozoic time. Most pegmatites are related to the Pan-African cycle; no Mesoproterozoic pegmatites were observed in this study. Within the Pan-African pegmatite groups there are two important subgroups. Some pegmatites show Sr isotopic compositions that indicate mantle components contributing to the parental granites from which the pegmatites evolved. Others show higher Sr initials, indicating crustal granites as primary pegmatite sources or significant crustal contamination. Only for few pegmatites, such as the Palaeoproterozoic and Ordovician gem tourmaline pegmatites in the Chitipa and Dowa Districts, the granitic source is evident from their field context. For all others the granitic origin is interpreted by mineralogical and geochemical evidence. All analysed pegmatites belong to either the Rare Element Class or the Miarolitic Class, but they vary in their degree of fractionation. The more evolved pegmatites are more enriched in incompatible elements such as Be, Li, B, and Ta, which resulted in the formation of gem minerals such as beryl, aquamarine, tourmaline and topaz, which may or may not be associated with tantalite. The Rare Element pegmatites can be further subdivided into the REL-Li subclass, beryl type, beryl-columbite subtype, and in the complex type and elbaite subtype. The Miarolitic pegmatites include Mi-Li subclass and beryl-topaz type. Fluid inclusion studies (heating-cooling stage, Raman spectroscopy) identified a variety of fluid compositions that were present at different times and different places, indicating a variety of fluid sources. They range from aqueous-saline to CO2–rich carbonic fluids (CO2 +C3H8+ N2), or aqueous-carbonic fluids (H2O-CO2-CH4 and H2O-CO2-H2-H2S-CH4). The dominant solutes and species for the pegmatites show genetic variations over time and orogen (Paleo-/Meso-/Neoproterozoic). Uniform homogenisation temperatures and salinities in individual samples indicate that the gem-bearing pegmatites contained homogeneous fluids at the time of their capturing in quartz. Based on fluid inclusion data, the estimated trapping conditions of inclusions in quartz for all studied pegmatites except for one pegmatite suggest low pressures between 0.9 to 2.6 kb at temperatures of 400-600 C. The other pegmatite formed at slightly higher pressures of 2.2 to 3.6 kb. However, the pressure range for all the pegmatites is in agreement with the known liquidus conditions of Rare-Element pegmatite crystallisation. The shallow crustal emplacement level (3.4-9.8 km) and the greater depth (8.3 to 13.6 km) favoured the formation of gemstones. , Thesis (PhD) -- Faculty of Science, Geology, 2019
- Full Text: false
- Date Issued: 2019
- Authors: Kankuzi, Charles Frienderson
- Date: 2019
- Subjects: Granite , Pegmatites , Geochemistry , Fluid inclusions , Nonferrous metals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/97905 , vital:31505 , DOI https://doi.org/10.21504/10962/97905
- Description: The gem bearing granitic pegmatites from different pegmatite fields across Malawi intrude all important geological entities from the Palaeoproterozoic in the north, the Mesoproterozoic in central Malawi and the Pan-African basement in the south. U/Pb zircon and Rb/Sr mineral isochron ages indicate pegmatite emplacement from the Palaeoproterozoic to Pan-African and Mesozoic time. Most pegmatites are related to the Pan-African cycle; no Mesoproterozoic pegmatites were observed in this study. Within the Pan-African pegmatite groups there are two important subgroups. Some pegmatites show Sr isotopic compositions that indicate mantle components contributing to the parental granites from which the pegmatites evolved. Others show higher Sr initials, indicating crustal granites as primary pegmatite sources or significant crustal contamination. Only for few pegmatites, such as the Palaeoproterozoic and Ordovician gem tourmaline pegmatites in the Chitipa and Dowa Districts, the granitic source is evident from their field context. For all others the granitic origin is interpreted by mineralogical and geochemical evidence. All analysed pegmatites belong to either the Rare Element Class or the Miarolitic Class, but they vary in their degree of fractionation. The more evolved pegmatites are more enriched in incompatible elements such as Be, Li, B, and Ta, which resulted in the formation of gem minerals such as beryl, aquamarine, tourmaline and topaz, which may or may not be associated with tantalite. The Rare Element pegmatites can be further subdivided into the REL-Li subclass, beryl type, beryl-columbite subtype, and in the complex type and elbaite subtype. The Miarolitic pegmatites include Mi-Li subclass and beryl-topaz type. Fluid inclusion studies (heating-cooling stage, Raman spectroscopy) identified a variety of fluid compositions that were present at different times and different places, indicating a variety of fluid sources. They range from aqueous-saline to CO2–rich carbonic fluids (CO2 +C3H8+ N2), or aqueous-carbonic fluids (H2O-CO2-CH4 and H2O-CO2-H2-H2S-CH4). The dominant solutes and species for the pegmatites show genetic variations over time and orogen (Paleo-/Meso-/Neoproterozoic). Uniform homogenisation temperatures and salinities in individual samples indicate that the gem-bearing pegmatites contained homogeneous fluids at the time of their capturing in quartz. Based on fluid inclusion data, the estimated trapping conditions of inclusions in quartz for all studied pegmatites except for one pegmatite suggest low pressures between 0.9 to 2.6 kb at temperatures of 400-600 C. The other pegmatite formed at slightly higher pressures of 2.2 to 3.6 kb. However, the pressure range for all the pegmatites is in agreement with the known liquidus conditions of Rare-Element pegmatite crystallisation. The shallow crustal emplacement level (3.4-9.8 km) and the greater depth (8.3 to 13.6 km) favoured the formation of gemstones. , Thesis (PhD) -- Faculty of Science, Geology, 2019
- Full Text: false
- Date Issued: 2019
Human capital in the context of high levels of inequality in South Africa
- Authors: Friderichs, Tamaryn Jean
- Date: 2021-10-29
- Subjects: Human capital South Africa , Income distribution South Africa , Labor market South Africa , Latent variables , Confirmatory factor analysis , Education Economic aspects South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192672 , vital:45248 , 10.21504/10962/192672
- Description: Piketty’s (2014) book titled “Capital in the Twenty-First Century” sparked widespread interest in global inequality, the distinction between wealth and income inequality and the economic, social and political processes accounting for changes in economic inequality over time. Piketty’s (2014) study controversially stated that widening economic inequality is the normal state of affairs in capitalist societies. The return from capital/wealth (terms used interchangeably) will almost always outpace the returns from labour. In contrast with Piketty’s (2014) thesis that the returns on non-human capital drive growing income inequality, economists such as Leibbrandt et al. (2012), Van der Berg (2014) and Hundenborn et al. (2016) have found that the labour market and human capital (HC) are the primary sources of income inequality. The research problem for this study stems from these contrasting views. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Friderichs, Tamaryn Jean
- Date: 2021-10-29
- Subjects: Human capital South Africa , Income distribution South Africa , Labor market South Africa , Latent variables , Confirmatory factor analysis , Education Economic aspects South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192672 , vital:45248 , 10.21504/10962/192672
- Description: Piketty’s (2014) book titled “Capital in the Twenty-First Century” sparked widespread interest in global inequality, the distinction between wealth and income inequality and the economic, social and political processes accounting for changes in economic inequality over time. Piketty’s (2014) study controversially stated that widening economic inequality is the normal state of affairs in capitalist societies. The return from capital/wealth (terms used interchangeably) will almost always outpace the returns from labour. In contrast with Piketty’s (2014) thesis that the returns on non-human capital drive growing income inequality, economists such as Leibbrandt et al. (2012), Van der Berg (2014) and Hundenborn et al. (2016) have found that the labour market and human capital (HC) are the primary sources of income inequality. The research problem for this study stems from these contrasting views. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29