An analysis of the impact of financialisation on commodity futures and spot prices
- Authors: Calitz, Geoffrey George
- Date: 2025-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/479528 , vital:78321
- Description: The debate on the commodity financialisation phenomenon was triggered in response to the steep rise in commodity futures and spot prices during the 2000-2011 super cycle. The two schools of thought regarding the underlying causes of such dramatic price increases are divided between those attributing the super cycle to fundamental drivers, and those who suggest that fundamental drivers alone are an insufficient explanation, and that other non-fundamental drivers are important. Fundamental drivers commonly cited in the literature include the sustained growth in demand for commodities throughout the early 2000s from emerging economies, such as China and India, and shocks to supply chains such as crop failures, export bans, and other factors such as macroeconomic dynamics. However, an alternative school of thought found empirical evidence which suggested that in addition to fundamental drivers, non-fundamental drivers such as key regulatory changes in commodity and financial markets in 1999/2000, and the subsequent changes to the trading activities in commodity derivative markets and the resultant historic growth in the participation of purely financial investors, significantly impacted the structure and price dynamics in commodity markets, in a phenomenon known as the financialisation of commodity markets. This study contributes to the empirical literature by expanding compared with previous studies the time period under investigation, as well as expanding the range of commodities examined. The most recent 2020-2024 period of rising prices is included, and the behavior of both cross-sector and same-sector pairwise return correlations of futures and spot prices in this period is compared to the pre-financialisation period. The study contributes to the literature by examining how the cross market and cross asset return correlation structure has behaved throughout the entire post-financialisation era. The study makes a further contribution by establishing the statistical significance of futures market returns as a predictor of spot market returns. It is found that the financialisation phenomenon impacted both commodity futures and spot markets. Pairwise return correlation is substantially greater throughout Period 2 (post-financialisation) compared to Period 1 (pre-financialisation) for same-sector and cross-sector pairs of futures and spot prices. The structural change in return correlation between these two periods was found to be especially pronounced for cross-sector pairs of futures and spot prices. The financialisation hypothesis is further supported by the findings of persistent structural changes in cross market and cross asset return correlation, which has become even more pronounced in the later stages of financialisation. The most recent period of rising commodity prices, Period 2(c) (2020-2024), is found to show elevated pairwise return correlation for futures and spot prices levels when compared to Period 1 (pre-financialisation), but the increase in correlations is less than in earlier financialisation periods such as Period 2(a) (2000-2011) and Period 2(b) (2012-2019). These findings suggest that index buying may be less important in the later stages of commodity financialisation. It was found that futures market returns are statistically significant predictors of spot market returns. Furthermore, the causal effect of futures market returns on spot market returns under the effect of financialisation (2000-2024) is found to be statistically significant in all five examples (WTI crude oil, gold, silver, LME copper and aluminium) examined in the study. The study finds that a clear structural change occurred in commodity spot and futures markets in the post-financialisation period. The consistency of this structural change is evident when analysing both cross sector and same sector pairwise return correlation behavior of commodity spot and futures prices, and when analysing cross market and cross asset return correlation between commodity markets and financial market benchmarks. The implication for investors is that commodity markets no longer offer certain portfolio diversification benefits and downside protection to drops in equity markets previously found in the empirical literature, and investors need to recalibrate strategies to account for these structural changes. The study concludes that the commodity market financialisation hypothesis is sound, and this implies that further research is required to better understand the impact of such structural changes on commodity futures and spot markets. In addition, because futures market returns are found to be a statistically significant predictor of spot market returns, it is imperative that further research be undertaken which investigates the explicit relationship between futures and spot markets so that policy makers and market regulators better understand the links between these two markets so that policy decisions are better informed. Furthermore, it is necessary that future research investigates how the transmission of information occurs between futures and spot markets, and how this matters for consumers, and addresses what welfare implications may be associated with this. Lastly, the author has advocated for increased transparency and restrictions in commodity markets, suggesting that all trading occurs on open regulated exchanges and that position limits are implemented, so as to prevent any market distortion which may come from institutional speculators taking excessively powerful and large positions. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2025
- Full Text:
- Authors: Calitz, Geoffrey George
- Date: 2025-04-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/479528 , vital:78321
- Description: The debate on the commodity financialisation phenomenon was triggered in response to the steep rise in commodity futures and spot prices during the 2000-2011 super cycle. The two schools of thought regarding the underlying causes of such dramatic price increases are divided between those attributing the super cycle to fundamental drivers, and those who suggest that fundamental drivers alone are an insufficient explanation, and that other non-fundamental drivers are important. Fundamental drivers commonly cited in the literature include the sustained growth in demand for commodities throughout the early 2000s from emerging economies, such as China and India, and shocks to supply chains such as crop failures, export bans, and other factors such as macroeconomic dynamics. However, an alternative school of thought found empirical evidence which suggested that in addition to fundamental drivers, non-fundamental drivers such as key regulatory changes in commodity and financial markets in 1999/2000, and the subsequent changes to the trading activities in commodity derivative markets and the resultant historic growth in the participation of purely financial investors, significantly impacted the structure and price dynamics in commodity markets, in a phenomenon known as the financialisation of commodity markets. This study contributes to the empirical literature by expanding compared with previous studies the time period under investigation, as well as expanding the range of commodities examined. The most recent 2020-2024 period of rising prices is included, and the behavior of both cross-sector and same-sector pairwise return correlations of futures and spot prices in this period is compared to the pre-financialisation period. The study contributes to the literature by examining how the cross market and cross asset return correlation structure has behaved throughout the entire post-financialisation era. The study makes a further contribution by establishing the statistical significance of futures market returns as a predictor of spot market returns. It is found that the financialisation phenomenon impacted both commodity futures and spot markets. Pairwise return correlation is substantially greater throughout Period 2 (post-financialisation) compared to Period 1 (pre-financialisation) for same-sector and cross-sector pairs of futures and spot prices. The structural change in return correlation between these two periods was found to be especially pronounced for cross-sector pairs of futures and spot prices. The financialisation hypothesis is further supported by the findings of persistent structural changes in cross market and cross asset return correlation, which has become even more pronounced in the later stages of financialisation. The most recent period of rising commodity prices, Period 2(c) (2020-2024), is found to show elevated pairwise return correlation for futures and spot prices levels when compared to Period 1 (pre-financialisation), but the increase in correlations is less than in earlier financialisation periods such as Period 2(a) (2000-2011) and Period 2(b) (2012-2019). These findings suggest that index buying may be less important in the later stages of commodity financialisation. It was found that futures market returns are statistically significant predictors of spot market returns. Furthermore, the causal effect of futures market returns on spot market returns under the effect of financialisation (2000-2024) is found to be statistically significant in all five examples (WTI crude oil, gold, silver, LME copper and aluminium) examined in the study. The study finds that a clear structural change occurred in commodity spot and futures markets in the post-financialisation period. The consistency of this structural change is evident when analysing both cross sector and same sector pairwise return correlation behavior of commodity spot and futures prices, and when analysing cross market and cross asset return correlation between commodity markets and financial market benchmarks. The implication for investors is that commodity markets no longer offer certain portfolio diversification benefits and downside protection to drops in equity markets previously found in the empirical literature, and investors need to recalibrate strategies to account for these structural changes. The study concludes that the commodity market financialisation hypothesis is sound, and this implies that further research is required to better understand the impact of such structural changes on commodity futures and spot markets. In addition, because futures market returns are found to be a statistically significant predictor of spot market returns, it is imperative that further research be undertaken which investigates the explicit relationship between futures and spot markets so that policy makers and market regulators better understand the links between these two markets so that policy decisions are better informed. Furthermore, it is necessary that future research investigates how the transmission of information occurs between futures and spot markets, and how this matters for consumers, and addresses what welfare implications may be associated with this. Lastly, the author has advocated for increased transparency and restrictions in commodity markets, suggesting that all trading occurs on open regulated exchanges and that position limits are implemented, so as to prevent any market distortion which may come from institutional speculators taking excessively powerful and large positions. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2025
- Full Text:
An investigation of geospatial technologies in precision agriculture: a case study on a citrus orchard in the Eastern Cape
- Authors: Nish, Declan Mark
- Date: 2024-10-11
- Subjects: Geospatial technology , Agricultural innovations , Precision farming South Africa Eastern Cape , Citrus orchard , Citrus fruit industry , Drone aircraft , Remote sensing
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465080 , vital:76571
- Description: Citrus production is an input-intensive farming practice that carries a high cost of production. A multitude of both local and global factors continue to put pressure on farmers to produce enough food for local consumption as well as international exports. Despite these challenges production and exports continue to increase, fighting to meet the growing rise in global demand for citrus (Genis, 2018). Growers are continuously in search of anything that may provide them with the ‘edge’ or an advantage to overcoming some of these challenges (Jupp, 2018). One way in which these issues could be addressed is the use of precision agriculture (PA). Precision agriculture, particularly that of commercial, Unmanned Aerial Vehicle (UAV) based PA, provides growers with solutions to these issues in the form of high quality, near real-time data, and provides access and benefits from technology driven agriculture to growers at all levels (Sishodia et al. 2020). The aim of this research therefore was to investigate the potential of high resolution, multi-spectral UAV, and satellite imagery to help citrus farmers manage their inputs better, save costs and increase their yields in a sustainable manner. Supervised image classification using a support vector machine (SVM) was applied to map and classify a citrus farm in the Eastern Cape. The approach aided the identification of Phytophthora spp in the section of interest and implies that remotely sensed data can be used to detect changes in citrus health. Guidelines for applying geospatial technologies at farm level were developed to provide a framework for enabling growers to enhance data driven farm management strategies. , Thesis (MSc) -- Faculty of Science, Geography, 2024
- Full Text:
- Authors: Nish, Declan Mark
- Date: 2024-10-11
- Subjects: Geospatial technology , Agricultural innovations , Precision farming South Africa Eastern Cape , Citrus orchard , Citrus fruit industry , Drone aircraft , Remote sensing
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465080 , vital:76571
- Description: Citrus production is an input-intensive farming practice that carries a high cost of production. A multitude of both local and global factors continue to put pressure on farmers to produce enough food for local consumption as well as international exports. Despite these challenges production and exports continue to increase, fighting to meet the growing rise in global demand for citrus (Genis, 2018). Growers are continuously in search of anything that may provide them with the ‘edge’ or an advantage to overcoming some of these challenges (Jupp, 2018). One way in which these issues could be addressed is the use of precision agriculture (PA). Precision agriculture, particularly that of commercial, Unmanned Aerial Vehicle (UAV) based PA, provides growers with solutions to these issues in the form of high quality, near real-time data, and provides access and benefits from technology driven agriculture to growers at all levels (Sishodia et al. 2020). The aim of this research therefore was to investigate the potential of high resolution, multi-spectral UAV, and satellite imagery to help citrus farmers manage their inputs better, save costs and increase their yields in a sustainable manner. Supervised image classification using a support vector machine (SVM) was applied to map and classify a citrus farm in the Eastern Cape. The approach aided the identification of Phytophthora spp in the section of interest and implies that remotely sensed data can be used to detect changes in citrus health. Guidelines for applying geospatial technologies at farm level were developed to provide a framework for enabling growers to enhance data driven farm management strategies. , Thesis (MSc) -- Faculty of Science, Geography, 2024
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Developing transformative community-university partnerships: a participatory assessment of Rhodes University community engagement monitoring and evaluation system
- Authors: Nkwinti, Nosipho
- Date: 2024-10-11
- Subjects: Community engagement , Community and college South Africa Eastern Cape , Rhodes University , Collaboration , Social change
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463592 , vital:76423
- Description: This thesis comprehensively explores transformative community engagement (CE) in higher education, focusing on the context of collaborative community-university partnerships (CUPs) in Makhanda, South Africa. The study aimed to assess and revise the monitoring and evaluation (M&E) system of the Rhodes University Community Engagement division to foster a transformation in CUPs. The research employs an exploratory design to understand the complexities of CUPs and improve the M&E systems by generating new concepts and ideas. A variety of qualitative methods, including focus groups, interviews, and document analysis, were utilized to engage community partners, student leaders, and Rhodes University Community Engagement staff. The participatory approach to research was critical, involving stakeholders in finalizing the M&E framework to ensure it met the shared objective. Data analysis was conducted inductively, with themes emerging from the data to facilitate a bottom-up understanding of the research questions. The study found that diverse community engagement projects at Rhodes University enhanced partnerships between the university and the local community in Makhanda. Participants shared varied understandings and experiences of Community Engagement. They saw CE as crucial for bridging the university-community divide and aiding local development. Furthermore, the research identified the need for a Monitoring and Evaluation system that supports collaborative Community-University Partnerships. Participants collaboratively developed and refined this M&E system, ensuring it aligns with community needs and promotes sustained development in Makhanda. Challenges such as diverse perspectives, logistical issues in focus groups, and power dynamics were also highlighted and addressed through an inclusive and participatory approach. This research highlights the elaborate distinctions of community engagement and the importance of such partnerships in fostering sustainable societal development. The framework developed has practical implications for shaping policies, fostering inclusivity, and promoting responsive university-community engagement that is aligned with community needs. The research concludes by suggesting the value of inclusivity, communication, and a flexible adaptation of practices to maximize the benefits of such partnerships. Future research could explore the longitudinal impacts of university-community partnerships, examine the scalability of the current framework to other universities, and evaluate the long-term socio-economic outcomes of the engaged citizen program on the community. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Authors: Nkwinti, Nosipho
- Date: 2024-10-11
- Subjects: Community engagement , Community and college South Africa Eastern Cape , Rhodes University , Collaboration , Social change
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463592 , vital:76423
- Description: This thesis comprehensively explores transformative community engagement (CE) in higher education, focusing on the context of collaborative community-university partnerships (CUPs) in Makhanda, South Africa. The study aimed to assess and revise the monitoring and evaluation (M&E) system of the Rhodes University Community Engagement division to foster a transformation in CUPs. The research employs an exploratory design to understand the complexities of CUPs and improve the M&E systems by generating new concepts and ideas. A variety of qualitative methods, including focus groups, interviews, and document analysis, were utilized to engage community partners, student leaders, and Rhodes University Community Engagement staff. The participatory approach to research was critical, involving stakeholders in finalizing the M&E framework to ensure it met the shared objective. Data analysis was conducted inductively, with themes emerging from the data to facilitate a bottom-up understanding of the research questions. The study found that diverse community engagement projects at Rhodes University enhanced partnerships between the university and the local community in Makhanda. Participants shared varied understandings and experiences of Community Engagement. They saw CE as crucial for bridging the university-community divide and aiding local development. Furthermore, the research identified the need for a Monitoring and Evaluation system that supports collaborative Community-University Partnerships. Participants collaboratively developed and refined this M&E system, ensuring it aligns with community needs and promotes sustained development in Makhanda. Challenges such as diverse perspectives, logistical issues in focus groups, and power dynamics were also highlighted and addressed through an inclusive and participatory approach. This research highlights the elaborate distinctions of community engagement and the importance of such partnerships in fostering sustainable societal development. The framework developed has practical implications for shaping policies, fostering inclusivity, and promoting responsive university-community engagement that is aligned with community needs. The research concludes by suggesting the value of inclusivity, communication, and a flexible adaptation of practices to maximize the benefits of such partnerships. Future research could explore the longitudinal impacts of university-community partnerships, examine the scalability of the current framework to other universities, and evaluate the long-term socio-economic outcomes of the engaged citizen program on the community. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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Statistical classification, an application to credit default
- Authors: Sikhakhane, Anele Gcina
- Date: 2024-10-11
- Subjects: Binary classification , Default (Finance) , Credit cards , Credit risk , Machine learning , Variables (Mathematics)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465069 , vital:76570
- Description: Statistical learning has been used in both industry and academia to create credit scoring models. These models are used to predict who might default on their loan repayments, thus minimizing the risk financial institutions face. In this study six traditional and one more recent classifier, namely kNN, LDA, CART, RF, AdaBoost, XGBoost and SynBoost were used to predict who might default on their loans. The data set used in this study was imbalanced thus sampling and performance evaluation techniques were investigated and used to balance the class distribution and assess the classifiers performance. In addition to the standard variables and data set, new variables called synthetic variables and synthetic data sets were produced, investigated and used to predict who might default on their loans. This study found that the synthetic data set had strong predictive power and sampling methods negatively affected the classifiers performance. The best-performing classifier was XGBoost, with an AUC score of 0.7732. , Thesis (MSc) -- Faculty of Science, Statistics, 2024
- Full Text:
- Authors: Sikhakhane, Anele Gcina
- Date: 2024-10-11
- Subjects: Binary classification , Default (Finance) , Credit cards , Credit risk , Machine learning , Variables (Mathematics)
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465069 , vital:76570
- Description: Statistical learning has been used in both industry and academia to create credit scoring models. These models are used to predict who might default on their loan repayments, thus minimizing the risk financial institutions face. In this study six traditional and one more recent classifier, namely kNN, LDA, CART, RF, AdaBoost, XGBoost and SynBoost were used to predict who might default on their loans. The data set used in this study was imbalanced thus sampling and performance evaluation techniques were investigated and used to balance the class distribution and assess the classifiers performance. In addition to the standard variables and data set, new variables called synthetic variables and synthetic data sets were produced, investigated and used to predict who might default on their loans. This study found that the synthetic data set had strong predictive power and sampling methods negatively affected the classifiers performance. The best-performing classifier was XGBoost, with an AUC score of 0.7732. , Thesis (MSc) -- Faculty of Science, Statistics, 2024
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Review of the systematics and regional diversity of the diploid barbs (Enteromius Cope, 1867) of southern Africa
- Scheepers, Martinus Johannes
- Authors: Scheepers, Martinus Johannes
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435966 , vital:73216
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Authors: Scheepers, Martinus Johannes
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435966 , vital:73216
- Description: Access restricted. Expected release in 2025. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
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Investigating changes in pineapple (Ananas comosus) cultivation in the Eastern Cape, South Africa, from 1984 to 2020
- Authors: Marriner, Paul Joseph
- Date: 2024-04-04
- Subjects: Pineapple South Africa Eastern Cape , Land use and land cover , Land cover , Remote sensing , Image classification
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435354 , vital:73150
- Description: Land use and land cover change (LULCC) resulting from agricultural activities have significantly impacted landscape transformation and fragmentation. The Albany Thicket Biome in the Eastern Cape Province stands out for its exceptional vegetation diversity and remarkable rates of species endemism. However, the relationship between agricultural activities and the Albany Thicket Biome has not received sufficient attention in the literature, creating a significant gap in understanding the extent of landscape transformation and the vegetation's recovery rate. This study aims to address this gap by utilising remote sensing technologies to investigate the LULCC specifically caused by pineapple cultivation in the Lower Albany area between 1984 and 2020. Analysis, using remotely sensed imagery and spatial analytical tools, provide accurate identification of pineapple fields and enable monitoring of their effects on LULCC dynamics across a wide spatial and temporal scale. Complementary field assessments examined the impacts of pineapple cultivation on land use and cover. Twelve image classifiers were tested to identify the most appropriate technique for mapping pineapple fields, and the Supervised Pixel-based Support Vector Machine (SVM) image classifier was found to be the most suitable. Utilising Landsat 4, 5, 7, and 8 satellite imagery, 27 land cover maps were created, spanning the period from 1984 to 2020. Additionally, field verification was conducted at 59 randomly generated sites to validate the findings. Spatial analysis of the data revealed that the pineapple industry in the study area has expanded by 733 hectares since 1984. Significant land use changes were observed, including converting land to wildlife ranches, grazing areas, and alternative agricultural practices. The land cover analysis identified the emergence of pioneer species in former pineapple fields, suggesting the potential for Albany Thicket regrowth if appropriately managed. This research contributes to a better understanding of the impacts of pineapple cultivation on the Albany Thicket Biome and provides valuable insights for land use planning and monitoring efforts. A comprehensive assessment of LULCC dynamics can be achieved by utilising remote sensing techniques, informing sustainable land management practices in the study area and beyond. , Thesis (MSc) -- Faculty of Science, Geography, 2024
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- Authors: Marriner, Paul Joseph
- Date: 2024-04-04
- Subjects: Pineapple South Africa Eastern Cape , Land use and land cover , Land cover , Remote sensing , Image classification
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/435354 , vital:73150
- Description: Land use and land cover change (LULCC) resulting from agricultural activities have significantly impacted landscape transformation and fragmentation. The Albany Thicket Biome in the Eastern Cape Province stands out for its exceptional vegetation diversity and remarkable rates of species endemism. However, the relationship between agricultural activities and the Albany Thicket Biome has not received sufficient attention in the literature, creating a significant gap in understanding the extent of landscape transformation and the vegetation's recovery rate. This study aims to address this gap by utilising remote sensing technologies to investigate the LULCC specifically caused by pineapple cultivation in the Lower Albany area between 1984 and 2020. Analysis, using remotely sensed imagery and spatial analytical tools, provide accurate identification of pineapple fields and enable monitoring of their effects on LULCC dynamics across a wide spatial and temporal scale. Complementary field assessments examined the impacts of pineapple cultivation on land use and cover. Twelve image classifiers were tested to identify the most appropriate technique for mapping pineapple fields, and the Supervised Pixel-based Support Vector Machine (SVM) image classifier was found to be the most suitable. Utilising Landsat 4, 5, 7, and 8 satellite imagery, 27 land cover maps were created, spanning the period from 1984 to 2020. Additionally, field verification was conducted at 59 randomly generated sites to validate the findings. Spatial analysis of the data revealed that the pineapple industry in the study area has expanded by 733 hectares since 1984. Significant land use changes were observed, including converting land to wildlife ranches, grazing areas, and alternative agricultural practices. The land cover analysis identified the emergence of pioneer species in former pineapple fields, suggesting the potential for Albany Thicket regrowth if appropriately managed. This research contributes to a better understanding of the impacts of pineapple cultivation on the Albany Thicket Biome and provides valuable insights for land use planning and monitoring efforts. A comprehensive assessment of LULCC dynamics can be achieved by utilising remote sensing techniques, informing sustainable land management practices in the study area and beyond. , Thesis (MSc) -- Faculty of Science, Geography, 2024
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Tradition and change in the Imfene dance of the amaMpondo in the Ntabankulu district of the Eastern Cape province
- Authors: Mtsini, Nontuthuzelo
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434791 , vital:73105
- Description: Access restricted. Expected release 2025. , Thesis (MMus) -- Faculty of Humanities, Music and Musicology, 2024
- Full Text:
- Authors: Mtsini, Nontuthuzelo
- Date: 2024-04-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434791 , vital:73105
- Description: Access restricted. Expected release 2025. , Thesis (MMus) -- Faculty of Humanities, Music and Musicology, 2024
- Full Text:
Exploring grade 8 teachers’ code-switching in teaching orthographic drawing in the Khomas Educational Region, Namibia
- Authors: Iita, Gabriel
- Date: 2023-10-13
- Subjects: Code switching (Linguistics) , Orthographic projection Study and teaching (Secondary) Namibia , English-medium instruction Namibia , Language and education , Social justice and education
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424041 , vital:72118
- Description: Studies in learner English proficiency in Namibia have shown that a considerable number of learners in primary and high schools have low proficiency. Naturally, this will be problematic for both learners and teachers who operate under a policy that dictates that from Grade 4 upwards, English is the medium of instruction in government schools. Literature has shown a general bias towards English as a medium of instruction from both the Namibian government and Namibian parents, despite the broader level of low English proficiency among learners. Research reviewed within this study has outlined the multiple benefits of code-switching for both learners and teachers. In fact, a recent study on the perceptions of code-switching in classrooms among Namibian learners indicated a positive attitude towards code-switching as a learning tool. Grade 8 Technical Drawing classes tend to be challenging due to the complexity and novelty of some of the concepts and terminologies used when teaching the subject. This makes it particularly difficult for learners whose first language is not English. Learners struggle to understand and make meaning of the concepts and objects used in Orthographic Drawing. Code-switching has been seen as a beneficial pedagogical tool. The study was therefore conducted to explore the Grade 8 teachers’ code-switching when teaching Orthographic Drawing in the Khomas educational region, Namibia. The study used the Matrix Language Frame Model by Myers-Scotton as the theoretical framework which focuses on two crucial language aspects of participating in code-switching and the matrix and embedded language, which guided this study. The qualitative approach employed a case study design which was used to gain first-hand experience in the Technical Drawing classrooms. Semi-structured interviews and an observation checklist were the research instruments that were used to generate data on the use of code-switching in Orthographic Drawing. Two schools, two Technical Drawing classes with 40 learners and two teachers in the Khomas region, Namibia were conveniently and purposively sampled. The data were analysed using coding, descriptive statistics and thematic data analysis. The primary and secondary results indicate that code-switching occurrence has constructive effects. Consequently, recommendations have been made on the effective use of code-switching along with other pedagogical tools based on the research insights into code-switching when teaching and learning Orthographic Drawing. , Thesis (MEd) -- Faculty of Humanities, Study of Englishes of Africa, 2023
- Full Text:
- Authors: Iita, Gabriel
- Date: 2023-10-13
- Subjects: Code switching (Linguistics) , Orthographic projection Study and teaching (Secondary) Namibia , English-medium instruction Namibia , Language and education , Social justice and education
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424041 , vital:72118
- Description: Studies in learner English proficiency in Namibia have shown that a considerable number of learners in primary and high schools have low proficiency. Naturally, this will be problematic for both learners and teachers who operate under a policy that dictates that from Grade 4 upwards, English is the medium of instruction in government schools. Literature has shown a general bias towards English as a medium of instruction from both the Namibian government and Namibian parents, despite the broader level of low English proficiency among learners. Research reviewed within this study has outlined the multiple benefits of code-switching for both learners and teachers. In fact, a recent study on the perceptions of code-switching in classrooms among Namibian learners indicated a positive attitude towards code-switching as a learning tool. Grade 8 Technical Drawing classes tend to be challenging due to the complexity and novelty of some of the concepts and terminologies used when teaching the subject. This makes it particularly difficult for learners whose first language is not English. Learners struggle to understand and make meaning of the concepts and objects used in Orthographic Drawing. Code-switching has been seen as a beneficial pedagogical tool. The study was therefore conducted to explore the Grade 8 teachers’ code-switching when teaching Orthographic Drawing in the Khomas educational region, Namibia. The study used the Matrix Language Frame Model by Myers-Scotton as the theoretical framework which focuses on two crucial language aspects of participating in code-switching and the matrix and embedded language, which guided this study. The qualitative approach employed a case study design which was used to gain first-hand experience in the Technical Drawing classrooms. Semi-structured interviews and an observation checklist were the research instruments that were used to generate data on the use of code-switching in Orthographic Drawing. Two schools, two Technical Drawing classes with 40 learners and two teachers in the Khomas region, Namibia were conveniently and purposively sampled. The data were analysed using coding, descriptive statistics and thematic data analysis. The primary and secondary results indicate that code-switching occurrence has constructive effects. Consequently, recommendations have been made on the effective use of code-switching along with other pedagogical tools based on the research insights into code-switching when teaching and learning Orthographic Drawing. , Thesis (MEd) -- Faculty of Humanities, Study of Englishes of Africa, 2023
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An ethnomedical study of the role and impact of cannabidiol (CBD) treatment of women living with endometriosis and Polycystic Ovarian Syndrome (PCOS)
- Authors: Norman, Paige Sarah
- Date: 2022-10-14
- Subjects: Polycystic ovary syndrome Alternative treatment , Endometriosis Alternative treatment , Cannabidiol , Cannabis , Pain management , Traditional medicine , Feminist anthropology , Women's health services
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/408652 , vital:70513
- Description: Over the last few years, there has been a notable increase in popularity in the use of cannabidiol (CBD) as a form of alternative medicinal treatment for various illnesses. CBD, a by-product of the cannabis plant, is an isolate and does not contain the psychoactive agent, tetrahydrocannabinol (THC). Endometriosis and Polycystic Ovarian Syndrome (PCOS) are chronic reproductive health sicknesses that are increasingly experienced by women. In the absence of cures, biomedical treatment for these diseases aim to manage symptoms, for example; heavy bleeding, heightened levels of pain, and insomnia. CBD offers an alternative to women who feel that biomedical interventions are no longer able to maintain their health and well-being. CBD positions itself as a natural remedy claiming to be safe and effective. This research study, mainly through qualitative data collection, focused on experiences of Zimbabwean and South African women living with endometriosis and/ or PCOS, who have turned to CBD to manage their symptoms. The importance of this study was to position itself within patients’ lived experiences. The research study found that CBD indeed has numerous benefits, including pain management, alleviating stress, and anxiety. Through the emergent themes from the data, it became clear that women are marginalised and treated unequally in the biomedical healthcare sphere. Feminist Anthropology and Structural Violence was applied to analyse the data collected to explore the patriarchal nature of the biomedical healthcare system and the experiences that women have, which has led them to turn to alternative treatments. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2022
- Full Text:
- Authors: Norman, Paige Sarah
- Date: 2022-10-14
- Subjects: Polycystic ovary syndrome Alternative treatment , Endometriosis Alternative treatment , Cannabidiol , Cannabis , Pain management , Traditional medicine , Feminist anthropology , Women's health services
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/408652 , vital:70513
- Description: Over the last few years, there has been a notable increase in popularity in the use of cannabidiol (CBD) as a form of alternative medicinal treatment for various illnesses. CBD, a by-product of the cannabis plant, is an isolate and does not contain the psychoactive agent, tetrahydrocannabinol (THC). Endometriosis and Polycystic Ovarian Syndrome (PCOS) are chronic reproductive health sicknesses that are increasingly experienced by women. In the absence of cures, biomedical treatment for these diseases aim to manage symptoms, for example; heavy bleeding, heightened levels of pain, and insomnia. CBD offers an alternative to women who feel that biomedical interventions are no longer able to maintain their health and well-being. CBD positions itself as a natural remedy claiming to be safe and effective. This research study, mainly through qualitative data collection, focused on experiences of Zimbabwean and South African women living with endometriosis and/ or PCOS, who have turned to CBD to manage their symptoms. The importance of this study was to position itself within patients’ lived experiences. The research study found that CBD indeed has numerous benefits, including pain management, alleviating stress, and anxiety. Through the emergent themes from the data, it became clear that women are marginalised and treated unequally in the biomedical healthcare sphere. Feminist Anthropology and Structural Violence was applied to analyse the data collected to explore the patriarchal nature of the biomedical healthcare system and the experiences that women have, which has led them to turn to alternative treatments. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2022
- Full Text:
Orthographic knowledge in isiXhosa and its relation to phonological processing, letter-sound knowledge, reading and spelling
- Authors: Daries, Mikaela Ann
- Date: 2022-10-14
- Subjects: Xhosa language Orthography and spelling , Phonological awareness , Psycholinguistics , Oral reading Usage , Literacy South Africa , Reading Phonetic method
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/406703 , vital:70300
- Description: Despite international research confirming its importance, writing and related metalinguistic skills have often been neglected in comparison to reading in literacy research (Cunningham et al., 2001; Castles & Coltheart, 2004; Nag, 2007; Roman et al., 2009; Zhao et al., 2017). On a national level there are very few studies that have explored the writing aspect of literacy in South Africa, and none that has investigated orthographic knowledge in a Southern Bantu language, such as isiXhosa. In an attempt to address this gap, this thesis explores orthographic knowledge and its components in isiXhosa. In particular, it seeks to investigate the unique predictors of word specific and general orthographic knowledge as well as their role for reading and spelling in isiXhosa while controlling for phonological awareness (PA), rapid automatized naming (RAN), and letter-sound knowledge. Furthermore, the thesis attempts to situate its findings within the main premises of the self-teaching hypothesis and dual route approach to orthographic processing in order to contribute to linguistic theories of reading with cross-linguistic evidence (Jorm & Share, 1983; Share & Jorm, 1987; Share, 1995; Grainger & Ziegler, 2011). A quantitative cross-sectional study was conducted with 140 isiXhosa home language third grade learners in which word specific and general orthographic knowledge tasks were specifically designed. These tasks were administered along with oral reading fluency (ORF), spelling, PA, RAN, and letter-sound knowledge. The findings revealed that letter-sound knowledge and PA contributed the largest variance towards both word specific and general orthographic knowledge. Further, word specific orthographic knowledge and letter-sound knowledge were the only significant predictors of spelling. Similarly, both word specific and letter-sound knowledge were significant predictors of reading, along with RAN and general orthographic knowledge. Quantile linear regression analyses revealed that word specific orthographic knowledge was a robust predictor of spelling and letter-sound knowledge was a robust predictor of reading across ability levels confirming the importance for word specific orthographic knowledge for spelling and letter-sound knowledge for reading in isiXhosa. In relation to the two reading theories considered in this thesis, the findings reflect similarities between the assertions of the self-teaching hypothesis and current thesis with suggestions made for further inquiry. The dual route approach to orthographic processing provides insights into the potential processing of orthographic information while reading in isiXhosa. The findings of this study confirm the importance of orthographic knowledge for reading and spelling for languages with transparent orthographies such as isiXhosa. , Thesis (MA) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2022
- Full Text:
- Authors: Daries, Mikaela Ann
- Date: 2022-10-14
- Subjects: Xhosa language Orthography and spelling , Phonological awareness , Psycholinguistics , Oral reading Usage , Literacy South Africa , Reading Phonetic method
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/406703 , vital:70300
- Description: Despite international research confirming its importance, writing and related metalinguistic skills have often been neglected in comparison to reading in literacy research (Cunningham et al., 2001; Castles & Coltheart, 2004; Nag, 2007; Roman et al., 2009; Zhao et al., 2017). On a national level there are very few studies that have explored the writing aspect of literacy in South Africa, and none that has investigated orthographic knowledge in a Southern Bantu language, such as isiXhosa. In an attempt to address this gap, this thesis explores orthographic knowledge and its components in isiXhosa. In particular, it seeks to investigate the unique predictors of word specific and general orthographic knowledge as well as their role for reading and spelling in isiXhosa while controlling for phonological awareness (PA), rapid automatized naming (RAN), and letter-sound knowledge. Furthermore, the thesis attempts to situate its findings within the main premises of the self-teaching hypothesis and dual route approach to orthographic processing in order to contribute to linguistic theories of reading with cross-linguistic evidence (Jorm & Share, 1983; Share & Jorm, 1987; Share, 1995; Grainger & Ziegler, 2011). A quantitative cross-sectional study was conducted with 140 isiXhosa home language third grade learners in which word specific and general orthographic knowledge tasks were specifically designed. These tasks were administered along with oral reading fluency (ORF), spelling, PA, RAN, and letter-sound knowledge. The findings revealed that letter-sound knowledge and PA contributed the largest variance towards both word specific and general orthographic knowledge. Further, word specific orthographic knowledge and letter-sound knowledge were the only significant predictors of spelling. Similarly, both word specific and letter-sound knowledge were significant predictors of reading, along with RAN and general orthographic knowledge. Quantile linear regression analyses revealed that word specific orthographic knowledge was a robust predictor of spelling and letter-sound knowledge was a robust predictor of reading across ability levels confirming the importance for word specific orthographic knowledge for spelling and letter-sound knowledge for reading in isiXhosa. In relation to the two reading theories considered in this thesis, the findings reflect similarities between the assertions of the self-teaching hypothesis and current thesis with suggestions made for further inquiry. The dual route approach to orthographic processing provides insights into the potential processing of orthographic information while reading in isiXhosa. The findings of this study confirm the importance of orthographic knowledge for reading and spelling for languages with transparent orthographies such as isiXhosa. , Thesis (MA) -- Faculty of Humanities, Linguistics and Applied Language Studies, 2022
- Full Text:
Large and multi scale mechanistic modeling of Diels-Alder reactions
- Authors: Isamura, Bienfait Kabuyaya
- Date: 2022-04-06
- Subjects: Computational chemistry , Diels-Alder reaction , Python (Computer program language) , Reaction force theory , Fullerenes , Diolefins , AMADAR (Automated workflow for Mechanistic Analysis of Diels-Alder Reactions , ONIOM
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232317 , vital:49981
- Description: The [4+2] cycloaddition reaction between conjugated dienes and substituted alkenes is known as the Diels-Alder (DA) reaction, in honor of two German chemists, Otto Diels and Kurt Alder, who first reported this marvelous chemical transformation. The DA reaction is one of the most popular reactions in organic chemistry, allowing for the regio- and stereospecific establishment of six-membered rings with up to four stereogenic centers. This pericyclic reaction has found many applications in areas as diverse as natural products chemistry, polymer chemistry, and agrochemistry. Over the past decades, the mechanism of the Diels-Alder (DA) reaction has been the subject of numerous studies, dealing with questions as diverse as the mechanistic pathway, the synchronicity, the use of catalysts, the effect of solvents and salts, etc. On the other hand, as an example, fullerenes (and particularly [60] fullerene) have been found to act as good dienophiles in DA reactions to the extent that many functionalized fullerenes with interesting applications are still synthesized by reacting C60 with dienes. However, despite the very abundant literature about the mechanism of the DA reaction, some pertinent questions have been still pending, including, without being restricted to, the prediction of transition state (TS) geometries and the modeling of DA reactions involving large systems, such as those of C60 fullerene. It must be emphasized that TSs are not easy to predict and the main reason is that many existing algorithms require that the search is initiated from a good starting point (guess TS), which must be very similar to the actual TS. This problem is even more difficult when many TSs are to be located as may be the case in large-scale studies. Moreover, due to the large size of the C60 molecule, the usage of accurate high-level computational methods in the investigation of its reactivity towards dienes is computationally costly, implying the need to find the best threshold between accuracy and computational cost. Therefore, the present study was carried out to contribute to solving the problems of large-scale prediction of DA transition state geometries and the multi-scale modeling of C60 fullerene DA reactions. To address the first problem (large-scale prediction of TSs), we have developed a python program named “AMADAR”, which predicts an unlimited number of DA transition states, using only the SMILES strings of the cycloadducts. AMADAR is customizable and allows for the description of intramolecular DA reactions as well as systems resulting in competing paths. In addition, The AMADAR tool contains two separate modules that perform reaction force analyses and atomic decomposition of energy derivatives from the predicted Intrinsic Reaction Coordinates (IRC) paths. The performance of AMADAR was assessed using 2000 DA cycloadducts and showed a success rate of ~ 95%. Most of the errors were due to basis set inconsistencies or convergence issues that we are still working on. Furthermore, a set of 150 IRC paths generated by the AMADAR program were analyzed to get insight into the (a)synchronicity of DA reactions. This investigation confirmed that the reaction force constant 𝜅 (second derivatives of the system energy with respect to the reaction coordinate) was a good indicator of synchronicity in DA reactions. A close inspection of the profile of 𝜅 has enabled us to propose an alternative classification of DA reactions based on their synchronicity degree, in terms of (quasi)-synchronous, moderate asynchronous, asynchronous, and likely two-steps DA reactions. Natural population analyses seemed to indicate that the global maximum of the reaction force constant could be identified with the formation of all the bonds in the reaction site. Finally, the atomic resolution of energy derivatives suggested that the mechanism of the DA reaction involves two inner elementary processes associated with the formation of each C-C bond. A striking mechanistic difference between synchronous and asynchronous DA reactions emerging from this study is that, in asynchronous reactions, the driving and retarding forces are mainly caused by the fast and slow-forming bonds (elementary process) respectively, while in the case of synchronous ones both elementary processes retard and drive the process concomitantly and equivalently. Regarding the DA reaction of C60 fullerene that was considered to illustrate the problem of multiscale modeling, we have constructed 12 ONIOM2 and 10 ONIOM3 models combining five semi-empirical methods (AM1, PM3, PM3MM, PDDG, PM6) and the LDA(SVWN) functional in conjunction with the B3LYP/6-31G(d) level. Then, their accuracy and efficiency were assessed in comparison with the pure B3LYP/6-31G(d) level considering first the DA reaction between C60 and cyclopentadiene whose experimental data are available. Further, different DFT functionals were employed in place of the B3LYP functional to describe the higher-layer of the best ONIOM partition, and the results obtained were compared to experimental data. At this step, the ONIOM2(M06-2X/6-31 G(d): SVWN/STO-3G) model, where the higher layer encompasses the diene and pyracyclene portion of C60, was found to provide the best tradeoff between accuracy and cost, with respect to experimental data. This model showed errors lower than 2.6 and 2.0 kcal/mol for the estimation of the activation and reaction enthalpies respectively. We have also demonstrated, by comparing several ONIOM2(DFT/6-31G(d): SVWN/STO-3G) models, the importance of dispersion corrections in the accurate estimation of reaction and activation energies. Finally, we have considered a set of 21 dienes, including anthracene, 1,3-butadiene, 1,3-cyclopentadiene, furan, thiophene, selenothiophene, pyrrole and their mono-cyano and hydroxyl derivatives to get insight into the DA reaction of C60 using the best ONIOM2(M06-2X/6-31 G(d): SVWN/STO-3G) model. For a given diene and its derivatives, the analysis of frontier molecular orbitals provides a consistent explanation for the substituent effect on the activation barrier. It revealed that electron-donating (withdrawing) groups such as -OH (–CN) cut down on the activation barrier of the reaction by lowering (extending) of the HOMOdiene – LUMOC60 gap and consequently enhancing (weakening) the interaction between the two reactants. Further, the decomposition of the activation energy into the strain and interaction components suggested that, for a given diene, electron-donating groups (here –OH) diminish the height of the activation barrier not only by favoring the attractive interaction between the diene and C60, but also by reducing the strain energy of the system; the opposite effect is observed for electron-withdrawing groups (here –CN). In contrast with some previous findings on typical DA reactions, we could not infer any general rule applicable to the entire dataset for the prediction of activation energies because the latter does not correlate well with either of the TS polarity, electrophilicity of the diene, or the reaction energy. , Thesis (MSc) -- Faculty of Science, Chemistry, 2022
- Full Text:
- Authors: Isamura, Bienfait Kabuyaya
- Date: 2022-04-06
- Subjects: Computational chemistry , Diels-Alder reaction , Python (Computer program language) , Reaction force theory , Fullerenes , Diolefins , AMADAR (Automated workflow for Mechanistic Analysis of Diels-Alder Reactions , ONIOM
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232317 , vital:49981
- Description: The [4+2] cycloaddition reaction between conjugated dienes and substituted alkenes is known as the Diels-Alder (DA) reaction, in honor of two German chemists, Otto Diels and Kurt Alder, who first reported this marvelous chemical transformation. The DA reaction is one of the most popular reactions in organic chemistry, allowing for the regio- and stereospecific establishment of six-membered rings with up to four stereogenic centers. This pericyclic reaction has found many applications in areas as diverse as natural products chemistry, polymer chemistry, and agrochemistry. Over the past decades, the mechanism of the Diels-Alder (DA) reaction has been the subject of numerous studies, dealing with questions as diverse as the mechanistic pathway, the synchronicity, the use of catalysts, the effect of solvents and salts, etc. On the other hand, as an example, fullerenes (and particularly [60] fullerene) have been found to act as good dienophiles in DA reactions to the extent that many functionalized fullerenes with interesting applications are still synthesized by reacting C60 with dienes. However, despite the very abundant literature about the mechanism of the DA reaction, some pertinent questions have been still pending, including, without being restricted to, the prediction of transition state (TS) geometries and the modeling of DA reactions involving large systems, such as those of C60 fullerene. It must be emphasized that TSs are not easy to predict and the main reason is that many existing algorithms require that the search is initiated from a good starting point (guess TS), which must be very similar to the actual TS. This problem is even more difficult when many TSs are to be located as may be the case in large-scale studies. Moreover, due to the large size of the C60 molecule, the usage of accurate high-level computational methods in the investigation of its reactivity towards dienes is computationally costly, implying the need to find the best threshold between accuracy and computational cost. Therefore, the present study was carried out to contribute to solving the problems of large-scale prediction of DA transition state geometries and the multi-scale modeling of C60 fullerene DA reactions. To address the first problem (large-scale prediction of TSs), we have developed a python program named “AMADAR”, which predicts an unlimited number of DA transition states, using only the SMILES strings of the cycloadducts. AMADAR is customizable and allows for the description of intramolecular DA reactions as well as systems resulting in competing paths. In addition, The AMADAR tool contains two separate modules that perform reaction force analyses and atomic decomposition of energy derivatives from the predicted Intrinsic Reaction Coordinates (IRC) paths. The performance of AMADAR was assessed using 2000 DA cycloadducts and showed a success rate of ~ 95%. Most of the errors were due to basis set inconsistencies or convergence issues that we are still working on. Furthermore, a set of 150 IRC paths generated by the AMADAR program were analyzed to get insight into the (a)synchronicity of DA reactions. This investigation confirmed that the reaction force constant 𝜅 (second derivatives of the system energy with respect to the reaction coordinate) was a good indicator of synchronicity in DA reactions. A close inspection of the profile of 𝜅 has enabled us to propose an alternative classification of DA reactions based on their synchronicity degree, in terms of (quasi)-synchronous, moderate asynchronous, asynchronous, and likely two-steps DA reactions. Natural population analyses seemed to indicate that the global maximum of the reaction force constant could be identified with the formation of all the bonds in the reaction site. Finally, the atomic resolution of energy derivatives suggested that the mechanism of the DA reaction involves two inner elementary processes associated with the formation of each C-C bond. A striking mechanistic difference between synchronous and asynchronous DA reactions emerging from this study is that, in asynchronous reactions, the driving and retarding forces are mainly caused by the fast and slow-forming bonds (elementary process) respectively, while in the case of synchronous ones both elementary processes retard and drive the process concomitantly and equivalently. Regarding the DA reaction of C60 fullerene that was considered to illustrate the problem of multiscale modeling, we have constructed 12 ONIOM2 and 10 ONIOM3 models combining five semi-empirical methods (AM1, PM3, PM3MM, PDDG, PM6) and the LDA(SVWN) functional in conjunction with the B3LYP/6-31G(d) level. Then, their accuracy and efficiency were assessed in comparison with the pure B3LYP/6-31G(d) level considering first the DA reaction between C60 and cyclopentadiene whose experimental data are available. Further, different DFT functionals were employed in place of the B3LYP functional to describe the higher-layer of the best ONIOM partition, and the results obtained were compared to experimental data. At this step, the ONIOM2(M06-2X/6-31 G(d): SVWN/STO-3G) model, where the higher layer encompasses the diene and pyracyclene portion of C60, was found to provide the best tradeoff between accuracy and cost, with respect to experimental data. This model showed errors lower than 2.6 and 2.0 kcal/mol for the estimation of the activation and reaction enthalpies respectively. We have also demonstrated, by comparing several ONIOM2(DFT/6-31G(d): SVWN/STO-3G) models, the importance of dispersion corrections in the accurate estimation of reaction and activation energies. Finally, we have considered a set of 21 dienes, including anthracene, 1,3-butadiene, 1,3-cyclopentadiene, furan, thiophene, selenothiophene, pyrrole and their mono-cyano and hydroxyl derivatives to get insight into the DA reaction of C60 using the best ONIOM2(M06-2X/6-31 G(d): SVWN/STO-3G) model. For a given diene and its derivatives, the analysis of frontier molecular orbitals provides a consistent explanation for the substituent effect on the activation barrier. It revealed that electron-donating (withdrawing) groups such as -OH (–CN) cut down on the activation barrier of the reaction by lowering (extending) of the HOMOdiene – LUMOC60 gap and consequently enhancing (weakening) the interaction between the two reactants. Further, the decomposition of the activation energy into the strain and interaction components suggested that, for a given diene, electron-donating groups (here –OH) diminish the height of the activation barrier not only by favoring the attractive interaction between the diene and C60, but also by reducing the strain energy of the system; the opposite effect is observed for electron-withdrawing groups (here –CN). In contrast with some previous findings on typical DA reactions, we could not infer any general rule applicable to the entire dataset for the prediction of activation energies because the latter does not correlate well with either of the TS polarity, electrophilicity of the diene, or the reaction energy. , Thesis (MSc) -- Faculty of Science, Chemistry, 2022
- Full Text:
Characterization of termite Trinervitermes trinervoides metagenome-derived glycoside hydrolases, the formulation of synergistic core enzyme sets for effective sweet sorghum and corncob saccharification, and their potential industrial applications
- Authors: Mafa, Mpho Stephen
- Date: 2019
- Subjects: Termites , Metagenomics , Glucosides , Hydrolases , Enzymes , Feedstock
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/72414 , vital:30044 , DOI https://doi.org/10.21504/10962/72414
- Description: The current study investigated the biochemical properties of endo-glucanase (GH5E), exo-glucanase (GH5D), xylanase (GH5H) and endo-glucanase/xylanase (GH45), derived from the hindgut bacterial symbionts of a termite (Trinervitermes trinervoides) for their potential role in the biotechnology industry. All these enzymes, except GH5D, exhibited activities on cellulosic and xylan-rich polymeric substrates, which only displayed activity on p-nitrophenyl cellobioside. GH5D, GH5E, GH5H and GH45 enzymes retained more than 80% of their activities at pH 5.5 and also retained more than 80% of their activities at 40ºC. Furthermore, these enzymes were thermostable at 37ºC for 72 hours. GH5E, GH5H and GH45 were generally stable over a range of metal-ion. The kinetic parameters for GH5E were 5.68 mg/ml (KM) and 34.36 U/mg protein (Vmax). GH5D activity did not follow classical Michaelis-Menten kinetics, suggesting product inhibition. GH5H displayed KM values of 5.53, 95.03 and 2.10 mg/ml and Vmax values of 112.36, 144.45 and 180.32 U/mg protein on beechwood xylan, CMC, and xyloglucan, respectively. GH45 displayed a KM of 6.94 mg/ml and a Vmax of 12.30 U/mg protein on CMC. GH5D [cellobiohydrolase (CBH)] and a commercial CBHII (GH6) enzyme outperformed a commercial CBHI (GH7) enzyme when these enzymes hydrolysed β-glucan. GH5D and CBHII also displayed a higher degree of synergy on β-glucan but failed to show synergy on Avicel. We therefore concluded that GH5D and CBHII are β-glucan-specific cellobiohydrolases. The corncob (CC) and sweet sorghum bagasse (SSB) substrates were pretreated with lime, NaOH and NaClO2. Subsequent to pretreatment, these substrates were used to investigate if GH5D, GH5E, GH5H and GH45 could operate in synergy. Results revealed that out of 12 possible core enzyme sets constructed, only two (referred to as CES-E and CES-H) displayed higher activities on pretreated CC or SSB. Simultaneous synergy was generally the most effective mode of synergy during hydrolysis of alkaline pretreated SSB and CC samples by both CES-E and CES-H. Both core enzyme sets did not display synergy on oxidative pretreated substrates. These findings suggest that lime and NaOH are more effective pretreatments for CC and SSB substrates. We used PRotein Interactive MOdeling (PRIMO) software to demonstrate that GH5D protein structure is an (α/β)8 barrel with a tunnel-like active site. Enzymes with this type of protein structure are able to perform transglycosylation, a process in which GH5D produced methyl, ethyl and propyl cellobiosides. We concluded that the GH5D, GH5E, GH5H and GH45 enzymes possess novel biochemical properties and that they form synergy during the hydrolysis of complex substrates (SSB and CC). GH5D transglycosylation could be used to produce novel biodegradable chemicals with special properties (e.g. anti-microbial properties). In conclusion, our findings suggest that GH5D, GH5E, GH5H and GH45 can potentially be used to improve biorefinery processes. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Authors: Mafa, Mpho Stephen
- Date: 2019
- Subjects: Termites , Metagenomics , Glucosides , Hydrolases , Enzymes , Feedstock
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/72414 , vital:30044 , DOI https://doi.org/10.21504/10962/72414
- Description: The current study investigated the biochemical properties of endo-glucanase (GH5E), exo-glucanase (GH5D), xylanase (GH5H) and endo-glucanase/xylanase (GH45), derived from the hindgut bacterial symbionts of a termite (Trinervitermes trinervoides) for their potential role in the biotechnology industry. All these enzymes, except GH5D, exhibited activities on cellulosic and xylan-rich polymeric substrates, which only displayed activity on p-nitrophenyl cellobioside. GH5D, GH5E, GH5H and GH45 enzymes retained more than 80% of their activities at pH 5.5 and also retained more than 80% of their activities at 40ºC. Furthermore, these enzymes were thermostable at 37ºC for 72 hours. GH5E, GH5H and GH45 were generally stable over a range of metal-ion. The kinetic parameters for GH5E were 5.68 mg/ml (KM) and 34.36 U/mg protein (Vmax). GH5D activity did not follow classical Michaelis-Menten kinetics, suggesting product inhibition. GH5H displayed KM values of 5.53, 95.03 and 2.10 mg/ml and Vmax values of 112.36, 144.45 and 180.32 U/mg protein on beechwood xylan, CMC, and xyloglucan, respectively. GH45 displayed a KM of 6.94 mg/ml and a Vmax of 12.30 U/mg protein on CMC. GH5D [cellobiohydrolase (CBH)] and a commercial CBHII (GH6) enzyme outperformed a commercial CBHI (GH7) enzyme when these enzymes hydrolysed β-glucan. GH5D and CBHII also displayed a higher degree of synergy on β-glucan but failed to show synergy on Avicel. We therefore concluded that GH5D and CBHII are β-glucan-specific cellobiohydrolases. The corncob (CC) and sweet sorghum bagasse (SSB) substrates were pretreated with lime, NaOH and NaClO2. Subsequent to pretreatment, these substrates were used to investigate if GH5D, GH5E, GH5H and GH45 could operate in synergy. Results revealed that out of 12 possible core enzyme sets constructed, only two (referred to as CES-E and CES-H) displayed higher activities on pretreated CC or SSB. Simultaneous synergy was generally the most effective mode of synergy during hydrolysis of alkaline pretreated SSB and CC samples by both CES-E and CES-H. Both core enzyme sets did not display synergy on oxidative pretreated substrates. These findings suggest that lime and NaOH are more effective pretreatments for CC and SSB substrates. We used PRotein Interactive MOdeling (PRIMO) software to demonstrate that GH5D protein structure is an (α/β)8 barrel with a tunnel-like active site. Enzymes with this type of protein structure are able to perform transglycosylation, a process in which GH5D produced methyl, ethyl and propyl cellobiosides. We concluded that the GH5D, GH5E, GH5H and GH45 enzymes possess novel biochemical properties and that they form synergy during the hydrolysis of complex substrates (SSB and CC). GH5D transglycosylation could be used to produce novel biodegradable chemicals with special properties (e.g. anti-microbial properties). In conclusion, our findings suggest that GH5D, GH5E, GH5H and GH45 can potentially be used to improve biorefinery processes. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
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