Development of insulin resistance in a rat model and the effects of sutherlandia frutescens as treatment and prevention
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
- Authors: Mackenzie, Janine
- Date: 2010
- Subjects: Metabolic syndrome , Insulin resistance -- Animal models , Obesity -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10340 , http://hdl.handle.net/10948/d1016216
- Description: The global number of obese people has reached pandemic proportions. High caloric diets and reduced physical exercise are to blame for this growing epidemic. Obesity has a very complex association with several other metabolic disorders, such as insulin resistance (IR), diabetes mellitus type 2 (DMT2) and cardiovascular disease. This puts a huge burden on health care systems world wide and claims many lives. Sutherlandia frutescens is a traditionally used herb, which is known to have anti-diabetic properties. However, the direct mode of action of S. frutescens still remains to be elucidated. The aim of this study was to investigate the developmental stages of high fat diet (HFD)-induced IR, to illuminate the pathogenesis of IR with a focal point on modifications in the lipid metabolism. Furthermore, the effects of S. frutescens as a treatment or prevention drug for IR and associated metabolic changes were examined. Two sets of experiments were conducted on male Wistar rats. In the first experiment rats, one week post weaning received a low fat diet (LFD), high fat diet (HFD) or HFD supplemented with S. frutescens (50mg/kg BW/d). Rats were sacrificed at week 0, 1, 2, 4, 8 and 12 in the feeding regime. In a second experiment rats were fed with a LFD or a HFD for 12 weeks and treated thereafter with S. frutescens (50mg/kg BW/d), metformin (13mg/kg BW/d) or water (control) for 28 days. Rats in the second experiment were sacrificed at week 12 to confirm IR while concurrently run rats were sacrificed after 28 days of treatment. For all the experiments rats were anaesthetized, blood was removed and rats were dissected. Plasma samples were analyzed for insulin, glucose, blood lipid parameters and cytokines. Liver, muscle and adipose tissue were analyzed for glucose uptake, total lipid content, lipid profile and fatty acid profile. It was shown that the intake of HFD caused IR and hyperinsulinaemia. The developmental stages in experiment one confirmed that an increase in plasma free fatty acids preceeded the onset of IR. Plasma and tissue lipid parameters (free fatty acid-, triglyceride- and cholesterol concentrations) showed pathological modifications in the HFD group. An ectopic accumulation of fat was observed in muscle and liver, as well as a change in membrane fatty acid profile. The results for circulating cytokines were somewhat inconclusive. Rats supplemented with S. frutescens did not develop HFD-induced IR (study one) or IR was reversed (study two). S. frutescens treatment also resulted in positive changes in plasma and tissue lipid parameters. In summary, an animal model for HFD-induced IR was established and the detrimental effect of elevated plasma FFA on glucose and lipid metabolism was observed. A novel discovery suggests that the anti-diabetic mode of action of S. frutescens is through modulation of lipid metabolism. It was also established that S. frutescens has the potential to prevent IR in vivo.
- Full Text:
- Date Issued: 2010
Evaluating the impact of energy policies on sustainable development in South Africa
- Authors: Julius, Ibitoye Oyebanji
- Date: 2018
- Subjects: Energy policy -- South Africa , Sustainable development -- South Africa Renewable energy sources -- South Africa Sustainable living -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30440 , vital:30944
- Description: The unachieved targets of the Millennium Development Goals (MDGs) at the end of 2015 by some developing countries including South Africa, lead to the evolution of the Sustainable Development Goals (SDGs). Ensuring access to sustainable, affordable, and modern energy is one of the 17 SDGs that the countries are expected to achieve before the end of 2030. Green growth is an important strategy for attaining this goal and a pathway to achieving the other goals. Therefore, an empirical study of the impact of energy policies on sustainable development is pertinent. Despite the importance of such research, there exists a gap in the literature relating to green growth and sustainable development from the SDGs point of view. This study fills the existing lacuna by developing an intertemporal holistic model which allows a study of the impact of energy policies on sustainable development in relation to the SDGs. Specifically, this thesis employs the Autoregressive Distributed Lag (ARDL) and Toda-Yamamoto approaches to analyse the long-run relationship and direction of causality respectively between green growth policies and sustainable development in South Africa from 1984 to 2016. This research provides insights into the importance of green growth for factors such as deforestation, fuel exports, energy imports and agricultural development, thus adding to the existing literature on the impact of renewable energy on a country’s social, environmental and economic conditions. Results from the analysis of the long-run relationship between green growth and macroeconomic variables, indicate a positive unidirectional relationship between changes in green growth policies and gross capital formation. This finding suggests that adopting green growth policies leads to increased investments. In contrast, green growth was found to have a negative effect on national income (gross domestic product). However, the Granger causality tests do not establish causality between these variables. Although green growth policies stimulate investments, high start-up costs associated with the implementation of these policies may mean that the resultant higher investments are yet to be translated to higher income levels in the South African economy. The findings indicate a boost in the South African balance of payment within the study period iv iv as evidenced by the positive long-run relationship between green growth policies and fuel exports. Additionally, the results indicate that green growth energy policies have assisted in improving the resilience to international oil price shocks as shown in the negative and significant long-run relationship between green growth and energy imports. With regard to environmental variables, results suggest a substitutability effect between green growth policies and the consumption of non-renewable energy. However, no evidence is found on the impact of green growth policies on the levels of deforestation and carbon dioxide(CO2) emissions, as well as natural resource depletion. In relation to the social variables, adoption of green growth policies was found to lead to improved educational quality, with causality running in both directions. This finding supports the feedback hypothesis. Similarly, green growth policies had a positive impact on agricultural development, again with causality established in both directions. The outcome of the long-run relationship between green energy consumption and unemployment shows that the green growth policies is yet to have a significant impact on unemployment reduction in South Africa. Green growth also has an insignificant and indirect relationship with GDP per capita; this result was affirmed by the absence of causality between GDP per capita and green energy consumption. This research not only makes contributions to the literature on the relevance of green growth policies for achieving economic, social and environmental sustainability, it also suggests possible policy implications which highlight the need for adoption and continued implementation of green growth policies in developing countries such as South Africa.
- Full Text:
- Date Issued: 2018
- Authors: Julius, Ibitoye Oyebanji
- Date: 2018
- Subjects: Energy policy -- South Africa , Sustainable development -- South Africa Renewable energy sources -- South Africa Sustainable living -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30440 , vital:30944
- Description: The unachieved targets of the Millennium Development Goals (MDGs) at the end of 2015 by some developing countries including South Africa, lead to the evolution of the Sustainable Development Goals (SDGs). Ensuring access to sustainable, affordable, and modern energy is one of the 17 SDGs that the countries are expected to achieve before the end of 2030. Green growth is an important strategy for attaining this goal and a pathway to achieving the other goals. Therefore, an empirical study of the impact of energy policies on sustainable development is pertinent. Despite the importance of such research, there exists a gap in the literature relating to green growth and sustainable development from the SDGs point of view. This study fills the existing lacuna by developing an intertemporal holistic model which allows a study of the impact of energy policies on sustainable development in relation to the SDGs. Specifically, this thesis employs the Autoregressive Distributed Lag (ARDL) and Toda-Yamamoto approaches to analyse the long-run relationship and direction of causality respectively between green growth policies and sustainable development in South Africa from 1984 to 2016. This research provides insights into the importance of green growth for factors such as deforestation, fuel exports, energy imports and agricultural development, thus adding to the existing literature on the impact of renewable energy on a country’s social, environmental and economic conditions. Results from the analysis of the long-run relationship between green growth and macroeconomic variables, indicate a positive unidirectional relationship between changes in green growth policies and gross capital formation. This finding suggests that adopting green growth policies leads to increased investments. In contrast, green growth was found to have a negative effect on national income (gross domestic product). However, the Granger causality tests do not establish causality between these variables. Although green growth policies stimulate investments, high start-up costs associated with the implementation of these policies may mean that the resultant higher investments are yet to be translated to higher income levels in the South African economy. The findings indicate a boost in the South African balance of payment within the study period iv iv as evidenced by the positive long-run relationship between green growth policies and fuel exports. Additionally, the results indicate that green growth energy policies have assisted in improving the resilience to international oil price shocks as shown in the negative and significant long-run relationship between green growth and energy imports. With regard to environmental variables, results suggest a substitutability effect between green growth policies and the consumption of non-renewable energy. However, no evidence is found on the impact of green growth policies on the levels of deforestation and carbon dioxide(CO2) emissions, as well as natural resource depletion. In relation to the social variables, adoption of green growth policies was found to lead to improved educational quality, with causality running in both directions. This finding supports the feedback hypothesis. Similarly, green growth policies had a positive impact on agricultural development, again with causality established in both directions. The outcome of the long-run relationship between green energy consumption and unemployment shows that the green growth policies is yet to have a significant impact on unemployment reduction in South Africa. Green growth also has an insignificant and indirect relationship with GDP per capita; this result was affirmed by the absence of causality between GDP per capita and green energy consumption. This research not only makes contributions to the literature on the relevance of green growth policies for achieving economic, social and environmental sustainability, it also suggests possible policy implications which highlight the need for adoption and continued implementation of green growth policies in developing countries such as South Africa.
- Full Text:
- Date Issued: 2018
Sustainable rural development through community participation: modeling community-based tourism in Nqileni village, Eastern Cape, South Africa
- Authors: Setokoe, Tshepiso Jonathan
- Date: 2019
- Subjects: Rural development -- South Africa -- Eastern Cape , Tourism -- South Africa Tourism -- South Africa -- Eastern Cape Ecotourism
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43379 , vital:36863
- Description: The development of tourism has been heralded to be a mechanism for sustainable rural development. Sustainable development of any nature requires that any efforts aimed at developing rural areas must involve the community in which the development is undertaken. This has given rise to concerted efforts by governments and development practitioners to involve local communities in development initiatives undertaken within their locale. The study analysed the importance of community participation in tourism development, with the aim to ensure the sustainable rural development of areas such as Nqileni village. This was undertaken using a qualitative research approach using semi-structured interviews to solicit data from twenty members of the Nqileni village community. The data was analysed with the assistance of a specialist qualitative data analyst, using the NVivo sytem, version 11, and was objectively interpreted and analysed by the researcher. The results revealed that the community viewed their participation to be paramount in development initiatives undertaken within the area, which also allows for the building of capacity, and ultimately empowers the community to meaningfully participate in the sustainable development of the area. Finally, the study proposed a community-based tourism model for sustainable rural development, which placed community participations at the root of sustainable development. This has been presented in a form that proposes that a leadership that works together in harmony, coupled with a flow of tourists and investment in the area, which can encourage the community to participate in tourism, resulting in a tourism economy that will allow for positive impacts (such as employment, conservation of resources and preservation of culture).This will enable the reduction of poverty, revival of other economic sectors within the area and foster social cohesion, and ultimately developing the area and its people.
- Full Text:
- Date Issued: 2019
- Authors: Setokoe, Tshepiso Jonathan
- Date: 2019
- Subjects: Rural development -- South Africa -- Eastern Cape , Tourism -- South Africa Tourism -- South Africa -- Eastern Cape Ecotourism
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43379 , vital:36863
- Description: The development of tourism has been heralded to be a mechanism for sustainable rural development. Sustainable development of any nature requires that any efforts aimed at developing rural areas must involve the community in which the development is undertaken. This has given rise to concerted efforts by governments and development practitioners to involve local communities in development initiatives undertaken within their locale. The study analysed the importance of community participation in tourism development, with the aim to ensure the sustainable rural development of areas such as Nqileni village. This was undertaken using a qualitative research approach using semi-structured interviews to solicit data from twenty members of the Nqileni village community. The data was analysed with the assistance of a specialist qualitative data analyst, using the NVivo sytem, version 11, and was objectively interpreted and analysed by the researcher. The results revealed that the community viewed their participation to be paramount in development initiatives undertaken within the area, which also allows for the building of capacity, and ultimately empowers the community to meaningfully participate in the sustainable development of the area. Finally, the study proposed a community-based tourism model for sustainable rural development, which placed community participations at the root of sustainable development. This has been presented in a form that proposes that a leadership that works together in harmony, coupled with a flow of tourists and investment in the area, which can encourage the community to participate in tourism, resulting in a tourism economy that will allow for positive impacts (such as employment, conservation of resources and preservation of culture).This will enable the reduction of poverty, revival of other economic sectors within the area and foster social cohesion, and ultimately developing the area and its people.
- Full Text:
- Date Issued: 2019
Enhancing parental involvement in primary schools in disadvantaged communities
- Hendricks, Charlotte Augusta
- Authors: Hendricks, Charlotte Augusta
- Date: 2014
- Subjects: Education, Primary -- Parent participation -- South Africa -- Port Elizabeth , Parent-teacher relationships -- South Africa -- Port Elizabeth , Ecological Systems Theory
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9461 , http://hdl.handle.net/10948/d1020169
- Description: The main research question guiding this study is: “What strategies can be established to enhance parental involvement in primary schools in disadvantaged communities in the Northern Areas of Port Elizabeth”? To answer this question, this study examines parents’ and teachers’ practices concerning parental involvement in the Northern Areas of Nelson Mandela Metropolitan. Parents and teachers were purposely selected from participating schools. In this qualitative study, the researcher proposed strategies to enhance parental involvement at primary schools. Qualitative research methods, associated with phenomenological inquiry were employed to explore the life-world of the participants who have had personal experience with the phenomenon of parental involvement. Data was collected through semi-structured interviews with parents and teachers. This allowed the researcher to gather in-depth information about opinions, beliefs, practices and attitudes concerning the involvement of parents in their children’s education. Bronfenbrenner’s ecosystemic theory served as the theorectical framework of this investigation. Since this study is about parental involvement in primary schools educational policies like inclusive education as well as different models of parental involvement were investigated in the literature study. The results of the study indicated several barriers to the enhancement of parental involvement for instance communication barriers between parents and teachers. The researcher established four strategies for the enhancement of parental involvement and recommended that these strategies should be employed by schools and other stakeholders. She also made further recommendations for parents, teachers, school principals, Department of Basic Education and professionals in the community.
- Full Text:
- Date Issued: 2014
- Authors: Hendricks, Charlotte Augusta
- Date: 2014
- Subjects: Education, Primary -- Parent participation -- South Africa -- Port Elizabeth , Parent-teacher relationships -- South Africa -- Port Elizabeth , Ecological Systems Theory
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9461 , http://hdl.handle.net/10948/d1020169
- Description: The main research question guiding this study is: “What strategies can be established to enhance parental involvement in primary schools in disadvantaged communities in the Northern Areas of Port Elizabeth”? To answer this question, this study examines parents’ and teachers’ practices concerning parental involvement in the Northern Areas of Nelson Mandela Metropolitan. Parents and teachers were purposely selected from participating schools. In this qualitative study, the researcher proposed strategies to enhance parental involvement at primary schools. Qualitative research methods, associated with phenomenological inquiry were employed to explore the life-world of the participants who have had personal experience with the phenomenon of parental involvement. Data was collected through semi-structured interviews with parents and teachers. This allowed the researcher to gather in-depth information about opinions, beliefs, practices and attitudes concerning the involvement of parents in their children’s education. Bronfenbrenner’s ecosystemic theory served as the theorectical framework of this investigation. Since this study is about parental involvement in primary schools educational policies like inclusive education as well as different models of parental involvement were investigated in the literature study. The results of the study indicated several barriers to the enhancement of parental involvement for instance communication barriers between parents and teachers. The researcher established four strategies for the enhancement of parental involvement and recommended that these strategies should be employed by schools and other stakeholders. She also made further recommendations for parents, teachers, school principals, Department of Basic Education and professionals in the community.
- Full Text:
- Date Issued: 2014
Integration of indigenous knowledge in the intermediate phase school curriculum in a selected education district in the Eastern Cape, South Africa
- Mkosi, Nkosinathi Ndumiso Lizo
- Authors: Mkosi, Nkosinathi Ndumiso Lizo
- Date: 2019
- Subjects: Education -- Curricula -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/16136 , vital:40671
- Description: The aims and principles of the post-apartheid South African school curricula, ranging from the Revised National Curriculum Statement Grades R-9 and the National Curriculum Statement Grades 10-12, to include the Curriculum and Assessment Policy Statements (Grades 1-12), have been aligned with the aims and principles of the South African Constitution. The aims and principles, among others, speak to the establishment of human rights, inclusivity, environmental and social justice, and valuing of indigenous knowledge systems. These are the bedrock of all the subjects and do not necessarily confine themselves to the science subjects only; even though the call of inclusion of indigenous knowledge in the sciences is oversubscribed. There has been concerns raised variously that the integration of indigenous knowledge systems in the curriculum, generally, and in the teaching of the respective subjects, particularly, does not necessarily happen as it should be. Thus, the purpose of this mixed methods approach study that adopted a concurrent triangulation mixed methods design and premised on the postpositivist paradigm investigated the integration of indigenous knowledge in the Intermediate Phase school curriculum in a selected Education District in the Eastern Cape Province, South Africa. The guiding lenses adopted for this study were two-fold. The main primary theoretical framework drew from three integration theories: (a) Huang and Newell’s (2003) Knowledge Integration Processes and Dynamics notions; (b) Beane’s (1995) Curriculum Integration and the Disciplines of Knowledge and (c) Harden’s (2000) Integration ladder: A Tool for Curriculum Planning and Evaluation. The ‘secondary’ lens of analysis, which the researcher named, the ‘supplemental framework’, was constituted by notions and constructs derived from the indigenous knowledge systems discourses and postcolonial notions and constructs. The study revealed, among other findings, that (i) whilst a majority of teachers claimed to integrate IK in their classrooms, a significant number did not, and those who claimed to be integrating were unsure about how to integrate (ii) the majority of teachers, HoDs and Subject Advisors were either poorly trained or did not receive any training in the integration of IK (iii) the support and monitoring of IK integration was poor to non-existent. Thus, the study proposes a model, the Integrative Indigenous Knowledge Integration Support and Monitoring Model (IIKISMM), which may act as a framework for the coordination of the support and monitoring of IK integration in the school curriculum. There are significant recommendations offered by the study to teachers and policy makers with regards the integration of indigenous knowledge systems in the school curriculum. Also offered by the study are possibilities for further research in the integration of indigenous knowledge system in the curriculum.
- Full Text:
- Date Issued: 2019
- Authors: Mkosi, Nkosinathi Ndumiso Lizo
- Date: 2019
- Subjects: Education -- Curricula -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/16136 , vital:40671
- Description: The aims and principles of the post-apartheid South African school curricula, ranging from the Revised National Curriculum Statement Grades R-9 and the National Curriculum Statement Grades 10-12, to include the Curriculum and Assessment Policy Statements (Grades 1-12), have been aligned with the aims and principles of the South African Constitution. The aims and principles, among others, speak to the establishment of human rights, inclusivity, environmental and social justice, and valuing of indigenous knowledge systems. These are the bedrock of all the subjects and do not necessarily confine themselves to the science subjects only; even though the call of inclusion of indigenous knowledge in the sciences is oversubscribed. There has been concerns raised variously that the integration of indigenous knowledge systems in the curriculum, generally, and in the teaching of the respective subjects, particularly, does not necessarily happen as it should be. Thus, the purpose of this mixed methods approach study that adopted a concurrent triangulation mixed methods design and premised on the postpositivist paradigm investigated the integration of indigenous knowledge in the Intermediate Phase school curriculum in a selected Education District in the Eastern Cape Province, South Africa. The guiding lenses adopted for this study were two-fold. The main primary theoretical framework drew from three integration theories: (a) Huang and Newell’s (2003) Knowledge Integration Processes and Dynamics notions; (b) Beane’s (1995) Curriculum Integration and the Disciplines of Knowledge and (c) Harden’s (2000) Integration ladder: A Tool for Curriculum Planning and Evaluation. The ‘secondary’ lens of analysis, which the researcher named, the ‘supplemental framework’, was constituted by notions and constructs derived from the indigenous knowledge systems discourses and postcolonial notions and constructs. The study revealed, among other findings, that (i) whilst a majority of teachers claimed to integrate IK in their classrooms, a significant number did not, and those who claimed to be integrating were unsure about how to integrate (ii) the majority of teachers, HoDs and Subject Advisors were either poorly trained or did not receive any training in the integration of IK (iii) the support and monitoring of IK integration was poor to non-existent. Thus, the study proposes a model, the Integrative Indigenous Knowledge Integration Support and Monitoring Model (IIKISMM), which may act as a framework for the coordination of the support and monitoring of IK integration in the school curriculum. There are significant recommendations offered by the study to teachers and policy makers with regards the integration of indigenous knowledge systems in the school curriculum. Also offered by the study are possibilities for further research in the integration of indigenous knowledge system in the curriculum.
- Full Text:
- Date Issued: 2019
Oral narratives as intertexts in selected Nigerian films
- Authors: Usman, Joshua
- Date: 2019
- Subjects: Folk literature -- Nigeria , Oral tradition -- Nigeria Motion pictures -- Nigeria
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43721 , vital:37038
- Description: This research into the interface between orality and Nigerian film builds on previous scholarly works in the field (Ladebo (1992), Onabajo and M’Bayo (2009), Omolola (2013), Ezeigbo (2013), Mgbemere (2015) and Onzuike (2016)). Evident from these studies is the prevalence of recurring patterns of oral narratives in Nigerian film. The aim of this study is to consider the following research questions: Do film producers/directors adopt the use of oral narratives in Nigerian film texts? How do oral narratives translate into films? What is the rate of recurrence of oral narratives in Nigerian films? Do oral narratives aesthetically influence the quality of Nigerian films? For the purpose of this study a selection of nine Nigerian films (three each from the Yoruba, Hausa and Igbo groups). These films are analysed as primary texts to show the occurrence of elements of orature and oral narratives. Underpinning such analysis is the theory of intertextuality as coined by the French linguist Julia Kristeva. Kristeva sees the text as “intertextuality […] within the text of society and history” (Kristeva, 1980: 37). This approach is augmented by the views of Greenblatt on New Historicism, which implies literature should be studied and interpreted within the context of the history of the author and cultural/social context. The nine films under discussion are considered within their cultural/social context.
- Full Text:
- Date Issued: 2019
- Authors: Usman, Joshua
- Date: 2019
- Subjects: Folk literature -- Nigeria , Oral tradition -- Nigeria Motion pictures -- Nigeria
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43721 , vital:37038
- Description: This research into the interface between orality and Nigerian film builds on previous scholarly works in the field (Ladebo (1992), Onabajo and M’Bayo (2009), Omolola (2013), Ezeigbo (2013), Mgbemere (2015) and Onzuike (2016)). Evident from these studies is the prevalence of recurring patterns of oral narratives in Nigerian film. The aim of this study is to consider the following research questions: Do film producers/directors adopt the use of oral narratives in Nigerian film texts? How do oral narratives translate into films? What is the rate of recurrence of oral narratives in Nigerian films? Do oral narratives aesthetically influence the quality of Nigerian films? For the purpose of this study a selection of nine Nigerian films (three each from the Yoruba, Hausa and Igbo groups). These films are analysed as primary texts to show the occurrence of elements of orature and oral narratives. Underpinning such analysis is the theory of intertextuality as coined by the French linguist Julia Kristeva. Kristeva sees the text as “intertextuality […] within the text of society and history” (Kristeva, 1980: 37). This approach is augmented by the views of Greenblatt on New Historicism, which implies literature should be studied and interpreted within the context of the history of the author and cultural/social context. The nine films under discussion are considered within their cultural/social context.
- Full Text:
- Date Issued: 2019
An investigation of the attitudes of South African Police Service management with respect to the viability of computer-assisted training in the Eastern Cape Province
- Authors: Adams, Leinadu
- Date: 2011
- Subjects: Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8190 , http://hdl.handle.net/10948/1410 , Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Description: The South African Police Service (SAPS) as a constituent part of the public service was established to deliver a specific category of services to the public. These services have to conform to requirements that are prescribed by various legislative provisions to promote effective and efficient delivery of public services. The implications of these provisions that are pursued by the study firstly, refer to the emphasis of government on the enhancement of public service delivery, with due consideration given to cost effectiveness and efficiency. Secondly, it refers to government's realisation of the important impact of education, development and training (EDT) on the competency of public service officials with an emphasis on the utilisation of information technology to enhance the effectiveness of EDT. Consequently, the study explores the viability of the utilisation of information technology as a measure to assist EDT interventions within the SAPS of the Eastern Cape Province to equip members of the institution to better fulfil their functions and duties. In this respect the study commenced to ascertain the levels of computer literacy of role-players, access to the appropriate facilities and what the general attitude in the organisation would be towards the utilisation of such an intervention. It was found that the computer literacy levels of role-players may be perceived as a problematic issue in this regard. However, access to suitable facilities was found to be more than sufficient for this intention. Furthermore, role-players agreed that information technology could be optimally applied in the EC SAPS for the mentioned use, thereby portraying an optimistic attitude towards the use thereof to harmonise EDT in the SAPS. The aim of the study has been to develop a model that will incorporate the use of information technology, given the strengths and weaknesses of the SAPS to enhance EDT and learning in the organization.
- Full Text:
- Date Issued: 2011
- Authors: Adams, Leinadu
- Date: 2011
- Subjects: Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:8190 , http://hdl.handle.net/10948/1410 , Education -- South Africa -- Data processing , Education -- Computer-assisted instruction , Information technology -- Study and teaching -- South Africa , Police training -- South Africa , Police -- South Africa -- Attitudes
- Description: The South African Police Service (SAPS) as a constituent part of the public service was established to deliver a specific category of services to the public. These services have to conform to requirements that are prescribed by various legislative provisions to promote effective and efficient delivery of public services. The implications of these provisions that are pursued by the study firstly, refer to the emphasis of government on the enhancement of public service delivery, with due consideration given to cost effectiveness and efficiency. Secondly, it refers to government's realisation of the important impact of education, development and training (EDT) on the competency of public service officials with an emphasis on the utilisation of information technology to enhance the effectiveness of EDT. Consequently, the study explores the viability of the utilisation of information technology as a measure to assist EDT interventions within the SAPS of the Eastern Cape Province to equip members of the institution to better fulfil their functions and duties. In this respect the study commenced to ascertain the levels of computer literacy of role-players, access to the appropriate facilities and what the general attitude in the organisation would be towards the utilisation of such an intervention. It was found that the computer literacy levels of role-players may be perceived as a problematic issue in this regard. However, access to suitable facilities was found to be more than sufficient for this intention. Furthermore, role-players agreed that information technology could be optimally applied in the EC SAPS for the mentioned use, thereby portraying an optimistic attitude towards the use thereof to harmonise EDT in the SAPS. The aim of the study has been to develop a model that will incorporate the use of information technology, given the strengths and weaknesses of the SAPS to enhance EDT and learning in the organization.
- Full Text:
- Date Issued: 2011
Market participation and value chain integration among smallholder homestead and irrigated crop farmers in the Eastern Cape province of South Africa
- Authors: Mdoda, Lelethu
- Date: 2017
- Subjects: Farms, Small -- South Africa -- Eastern Cape Irrigation farming -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/15023 , vital:40152
- Description: The irrigation schemes had been established over the years and now are operational but there is no marked improvement in the living conditions of the rural farmers and households. Smallholder farmers still face numerous constraints in market participation that hinder smallholder farmers, irrigators and homestead growth which have been attributed to lack of access to markets and technical expertise. Despite the government efforts, smallholder farmers effectively functioning in the agro-food chains, high-valued markets and commercial agricultural markets are rare; this indicates that the objective to allow smallholder farmers to advance their livelihood through participating in commercial agro-food chains has not yet been met. Farmers in the Eastern Cape produce many crops which they mainly sell in informal local markets; there is minimal number of smallholder farmers supplying their produce to the formal markets. Irrigation development is very crucial to the development of the agricultural sector as it ensures improvement in yields and reduces rural poverty through creating rural employment, enhance smallholder farmers’ market participation and enhance market access policies by smallholder farmers as means to achieve the Sustainable Development Goals The study was conducted in the Eastern Cape Province and employed survey data obtained from 200 smallholder irrigated crop farmers and homestead gardeners. A multistage stratified sampling procedure was used in which the first stage involved selecting the study areas. This was followed by the selection of the district and then the respondents. The farmers were selected from three District Municipalities which have operational irrigation schemes, namely OR Tambo, Amathole and Chris Hani District Municipalities in the province. STATA and SPSS were used to analyze the data. The Heckman model was applied to examine factors influencing farmers’ decision to participate in market among crop producing farmers in the province. In the first stage Heckman analysis, the decision as to whether or not to participate (which is a binary choice situation) is used to undertake the maximum likelihood estimation (MLE). In the second stage, the conditional quantity sold (continuous variable) is assumed to follow a truncated normal regression model, whereby the MLE is estimated by fitting a truncated normal regression of quantity sold. Gross Margin and Net Farm Income were used to measure farm profit as well as multiple regression analysis to estimate determinants of profitability in the study area. Profit efficiency was measured using the normalized transcendent logarithmic profit frontier approach (translog). he descriptive statistics employed include means, percentages and frequencies mostly of the socio-economic characteristics of farmers in the study area. The results show that males were dominant with the representation of 61.7percent. The majority of farmers were aged and the mean age was 60 years, indicating that farmers in the province are old which has implication for productivity and market participation. High level of illiteracy is shown in the data and mean household size of 5 persons with the household head having at least obtained some primary school education.The irrigated crop farmers and homesteads were found to have farm size under 4 ha. About 86.5percent were full time farmers and Farming is their major source of livelihood. Smallholder irrigators and homestead gardeners derive their income from social grants and remittances. This thesis found out that majority of the farmers do not participate in markets. In this instance, farming becomes a scapegoat for failure to enter alternative labour markets. The average annual on-farm production income from smallholder irrigators was R7 860.27 and homestead gardeners was R5 915.50. The empirical results from probit model suggest that age of the farmer, level of education of the farmer, household size, farm organization, access to extension, distance to markets, occupation and farm experience were some of the key determinants that had significant and positive effects on farmers’ decision to participate in markets while access to credit, transport to the markets and farm size were some of the key determinants that had significant and negative effect on farmers’ decision to participate in markets. The volume of crops sold to the market is determined by gender, age, years spent in school, distance to the market, farm experience, household size, access to extension, membership in farm organization and non-farm income.
- Full Text:
- Date Issued: 2017
- Authors: Mdoda, Lelethu
- Date: 2017
- Subjects: Farms, Small -- South Africa -- Eastern Cape Irrigation farming -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/15023 , vital:40152
- Description: The irrigation schemes had been established over the years and now are operational but there is no marked improvement in the living conditions of the rural farmers and households. Smallholder farmers still face numerous constraints in market participation that hinder smallholder farmers, irrigators and homestead growth which have been attributed to lack of access to markets and technical expertise. Despite the government efforts, smallholder farmers effectively functioning in the agro-food chains, high-valued markets and commercial agricultural markets are rare; this indicates that the objective to allow smallholder farmers to advance their livelihood through participating in commercial agro-food chains has not yet been met. Farmers in the Eastern Cape produce many crops which they mainly sell in informal local markets; there is minimal number of smallholder farmers supplying their produce to the formal markets. Irrigation development is very crucial to the development of the agricultural sector as it ensures improvement in yields and reduces rural poverty through creating rural employment, enhance smallholder farmers’ market participation and enhance market access policies by smallholder farmers as means to achieve the Sustainable Development Goals The study was conducted in the Eastern Cape Province and employed survey data obtained from 200 smallholder irrigated crop farmers and homestead gardeners. A multistage stratified sampling procedure was used in which the first stage involved selecting the study areas. This was followed by the selection of the district and then the respondents. The farmers were selected from three District Municipalities which have operational irrigation schemes, namely OR Tambo, Amathole and Chris Hani District Municipalities in the province. STATA and SPSS were used to analyze the data. The Heckman model was applied to examine factors influencing farmers’ decision to participate in market among crop producing farmers in the province. In the first stage Heckman analysis, the decision as to whether or not to participate (which is a binary choice situation) is used to undertake the maximum likelihood estimation (MLE). In the second stage, the conditional quantity sold (continuous variable) is assumed to follow a truncated normal regression model, whereby the MLE is estimated by fitting a truncated normal regression of quantity sold. Gross Margin and Net Farm Income were used to measure farm profit as well as multiple regression analysis to estimate determinants of profitability in the study area. Profit efficiency was measured using the normalized transcendent logarithmic profit frontier approach (translog). he descriptive statistics employed include means, percentages and frequencies mostly of the socio-economic characteristics of farmers in the study area. The results show that males were dominant with the representation of 61.7percent. The majority of farmers were aged and the mean age was 60 years, indicating that farmers in the province are old which has implication for productivity and market participation. High level of illiteracy is shown in the data and mean household size of 5 persons with the household head having at least obtained some primary school education.The irrigated crop farmers and homesteads were found to have farm size under 4 ha. About 86.5percent were full time farmers and Farming is their major source of livelihood. Smallholder irrigators and homestead gardeners derive their income from social grants and remittances. This thesis found out that majority of the farmers do not participate in markets. In this instance, farming becomes a scapegoat for failure to enter alternative labour markets. The average annual on-farm production income from smallholder irrigators was R7 860.27 and homestead gardeners was R5 915.50. The empirical results from probit model suggest that age of the farmer, level of education of the farmer, household size, farm organization, access to extension, distance to markets, occupation and farm experience were some of the key determinants that had significant and positive effects on farmers’ decision to participate in markets while access to credit, transport to the markets and farm size were some of the key determinants that had significant and negative effect on farmers’ decision to participate in markets. The volume of crops sold to the market is determined by gender, age, years spent in school, distance to the market, farm experience, household size, access to extension, membership in farm organization and non-farm income.
- Full Text:
- Date Issued: 2017
Construction material logistics management: the case of north-central Nigeria
- Authors: Alumbugu, Polycarp Olaku
- Date: 2019
- Subjects: Construction projects-- Nigeria --Management Construction projects --Management Logistics-- Nigeria -- Management , Construction industry -- Nigeria
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/44879 , vital:38179
- Description: The Management of Construction Material Logistics Systems plays a significant role in meeting the goals of cost, quality and time to completion of a construction project. Studies have revealed that the cost of construction materials is usually about 50%-60% of the total cost of the project and that the logistic cost accounts for between 17%-35% of the cost material. Fundamentally, it is accepted that any inefficiency in the delivery of construction material could lead to a time overrun and thus, a rise in construction costs addressing the operational performance of logistics would have a positive impact on the goals of a construction project. The aim of this study was to investigate and evaluate the operational performance of material logistics in North-Central Nigeria as there is little specific research conducted on its effectiveness and efficiency. The methodology used included an extensive literature review and a field study conducted on ten quantitative approach that is rooted in the positivist paradigm, and purposive sampling techniques, was adopted. The descriptive method of data analysis was employed, and the findings and interpretations presented through graphs and images. Analysis of the findings led to the conclusion that material logistics did not operate as a system. There was almost no collaboration and integration of the logistics systems to create a synergistic interrelationship between functions in pursuit of higher overall effectiveness and efficiency. Improvement was needed in warehouse and transport operations and processes; technology and automation of logistics operations were absent, and delivery of material to customers was not effective. The implication was that the current materials logistics system did not meet the delivery goals of cost, quality and time of a construction project. The recommendations suggested included the adoption of the framework developed in this study. This would serve as a guide towards effective and efficient logistics management for material manufacturing firms, and for construction professionals.
- Full Text:
- Date Issued: 2019
- Authors: Alumbugu, Polycarp Olaku
- Date: 2019
- Subjects: Construction projects-- Nigeria --Management Construction projects --Management Logistics-- Nigeria -- Management , Construction industry -- Nigeria
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/44879 , vital:38179
- Description: The Management of Construction Material Logistics Systems plays a significant role in meeting the goals of cost, quality and time to completion of a construction project. Studies have revealed that the cost of construction materials is usually about 50%-60% of the total cost of the project and that the logistic cost accounts for between 17%-35% of the cost material. Fundamentally, it is accepted that any inefficiency in the delivery of construction material could lead to a time overrun and thus, a rise in construction costs addressing the operational performance of logistics would have a positive impact on the goals of a construction project. The aim of this study was to investigate and evaluate the operational performance of material logistics in North-Central Nigeria as there is little specific research conducted on its effectiveness and efficiency. The methodology used included an extensive literature review and a field study conducted on ten quantitative approach that is rooted in the positivist paradigm, and purposive sampling techniques, was adopted. The descriptive method of data analysis was employed, and the findings and interpretations presented through graphs and images. Analysis of the findings led to the conclusion that material logistics did not operate as a system. There was almost no collaboration and integration of the logistics systems to create a synergistic interrelationship between functions in pursuit of higher overall effectiveness and efficiency. Improvement was needed in warehouse and transport operations and processes; technology and automation of logistics operations were absent, and delivery of material to customers was not effective. The implication was that the current materials logistics system did not meet the delivery goals of cost, quality and time of a construction project. The recommendations suggested included the adoption of the framework developed in this study. This would serve as a guide towards effective and efficient logistics management for material manufacturing firms, and for construction professionals.
- Full Text:
- Date Issued: 2019
Gender equality in the provision and utilisation of women administrative personnel : a comparative study of the Camdeboo Local Municipality and Inxuba Yethemba Local Municipality
- Authors: Dywili, Mhlobo Douglas
- Date: 2016
- Subjects: Women -- Government policy -- South Africa -- Eastern Cape Sex discrimination against women -- South Africa -- Eastern Cape Women's rights -- South Africa -- Eastern Cape , Equality -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2414 , vital:27817
- Description: In 2000, cabinet adopted the South African Policy framework for women’s empowerment and gender equality, 2000 (Policy framework) which provided for the establishment of the National Gender Machinery (NGM). The NGM is a network of coordinated structures within and outside government which operate cooperatively in facilitating political, social, economic and other forms of transformation to dismantle systemic gender inequality and promote equality between women and men. The implementation of gender equality policy as a function area has constitutionally been given to the national and provincial legislatures in South Africa. The constitution allocated this function to the local sphere of government. Camdeboo and Inxuba Yethemba local municipal authorities are the facilitators of sustainable gender equality policies to citizens on behalf of the national and provincial spheres of government. The study was thus conducted within the Camdeboo local municipality and Inxuba Yethemba local municipality. Camdeboo locoal municipality is one of nine local municipalities in Sarah Baartman district municipality. Inxuba Yethemba local municipality is in Chris Hani district municipality. The purpose of the study was to evaluate the implementation of gender equality in the Provision and Utilisation of Women administration Personnel a comparative study of the Camdeboo local municipality and the Inxuba Yethemba local municipality and to determine the impact of the existing policy on the gender equality policy on the needs of women of both municipalities. For this purpose the fundamental and overall study problem was found to be that the gender equality at the Camdeboo and Inxuba Yethemba is hampered by the implementation of an inadequate municipality gender equality policy and by incompetent municipal personnel in particular and in general by the municipality itself. These action do not satisfy the main purpose of the Employment Equity Act no 55 of 1998 to achieve in the workplace by promoting equal opportunity and fair treatment in all forms of employment through elimination of unfair discrimination as well as the implementation of affirmative action measures. The hypothesis was furthermore based on the fact that the existing gender policy of Camdeboo local municipality and Inxuba Yethemba local municipality gender equality policy are inadequate to satisfy women and impacts negatively if not harmfully on human being of women. The study revealed that besides the implementation of gender equality policy by these incompetent municipal personnel, there are economic, social, political and physical effects on women. In case of applications for senior management position, preference is always given to their male counterparts at the expense of equally qualified female applications. Secondly, Gender equality in human resource determination forms part of the processing phase in the system theory. These two municipalities should be made to commit themselves by appending their signatures to all control measures put in place to evaluate the level and the extent of gender equality across all the departments/ sections in the municipality. Any section/ department that implements gender equality more effectively should be identified applauded and given recognition. This would motivate and eliminate gender inequality. Personnel provision and utilization is of paramount importance to every organization. It then becomes extremely necessary to examine the gender equality on human resource determination.
- Full Text:
- Date Issued: 2016
- Authors: Dywili, Mhlobo Douglas
- Date: 2016
- Subjects: Women -- Government policy -- South Africa -- Eastern Cape Sex discrimination against women -- South Africa -- Eastern Cape Women's rights -- South Africa -- Eastern Cape , Equality -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2414 , vital:27817
- Description: In 2000, cabinet adopted the South African Policy framework for women’s empowerment and gender equality, 2000 (Policy framework) which provided for the establishment of the National Gender Machinery (NGM). The NGM is a network of coordinated structures within and outside government which operate cooperatively in facilitating political, social, economic and other forms of transformation to dismantle systemic gender inequality and promote equality between women and men. The implementation of gender equality policy as a function area has constitutionally been given to the national and provincial legislatures in South Africa. The constitution allocated this function to the local sphere of government. Camdeboo and Inxuba Yethemba local municipal authorities are the facilitators of sustainable gender equality policies to citizens on behalf of the national and provincial spheres of government. The study was thus conducted within the Camdeboo local municipality and Inxuba Yethemba local municipality. Camdeboo locoal municipality is one of nine local municipalities in Sarah Baartman district municipality. Inxuba Yethemba local municipality is in Chris Hani district municipality. The purpose of the study was to evaluate the implementation of gender equality in the Provision and Utilisation of Women administration Personnel a comparative study of the Camdeboo local municipality and the Inxuba Yethemba local municipality and to determine the impact of the existing policy on the gender equality policy on the needs of women of both municipalities. For this purpose the fundamental and overall study problem was found to be that the gender equality at the Camdeboo and Inxuba Yethemba is hampered by the implementation of an inadequate municipality gender equality policy and by incompetent municipal personnel in particular and in general by the municipality itself. These action do not satisfy the main purpose of the Employment Equity Act no 55 of 1998 to achieve in the workplace by promoting equal opportunity and fair treatment in all forms of employment through elimination of unfair discrimination as well as the implementation of affirmative action measures. The hypothesis was furthermore based on the fact that the existing gender policy of Camdeboo local municipality and Inxuba Yethemba local municipality gender equality policy are inadequate to satisfy women and impacts negatively if not harmfully on human being of women. The study revealed that besides the implementation of gender equality policy by these incompetent municipal personnel, there are economic, social, political and physical effects on women. In case of applications for senior management position, preference is always given to their male counterparts at the expense of equally qualified female applications. Secondly, Gender equality in human resource determination forms part of the processing phase in the system theory. These two municipalities should be made to commit themselves by appending their signatures to all control measures put in place to evaluate the level and the extent of gender equality across all the departments/ sections in the municipality. Any section/ department that implements gender equality more effectively should be identified applauded and given recognition. This would motivate and eliminate gender inequality. Personnel provision and utilization is of paramount importance to every organization. It then becomes extremely necessary to examine the gender equality on human resource determination.
- Full Text:
- Date Issued: 2016
Immobilization of catalyst in a wall-coated micro-structured reactor for gas/liquid oxidation of p-cymene
- Authors: Makgwane, Peter Ramashadi
- Date: 2009
- Subjects: Oxidation , Cymene
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10389 , http://hdl.handle.net/10948/1182 , Oxidation , Cymene
- Description: The selective, liquid phase oxidation of p-cymene is an important synthetic route for the production of p-cresol via the tertiary cymene hydroperoxide (TCHP). The industrial-scale oxidation process is characterised by slow oxidation rates due to limitations in the mass transfer of oxidant (gaseous oxygen) into the liquid phase. However, like all other autoxidation reactions, the oxidation reaction is exothermic, following the typical free radical autoxidation reaction mechanism, which implies that careful temperature control is critical in order to prevent the further reaction of the initially formed hydroperoxide species. In the presence of metal catalysts, the limiting oxidation rate is the transfer of oxygen from the gas to liquid boundary interface. As a result, low product yields and poor productivity space-time yield are typically experienced. At high substrate conversions, by-products resulting from the decomposition of the formed hydroperoxides predominate. For this reason, the conversion of substrate is restricted to preserve the TCHP selectivity. The slow rates in industrial-scale p-cymene oxidations results in long oxidation times, typically 8-12 h. Substrate conversions are typically between 15-20 percent, and the TCHP selectivity ranges between 65-70 percent. The work described in this thesis concerns the oxidation of p-cymene in a microstructured falling film reactor (FFMSR). These reactor systems facilitate chemical reactors to have high mass and heat transfer rates because of high surface area-to-volume ratios. Due to their small internal volumes, these reactors are inherently safe to operate. These properties were exploited to improve the p-cymene oxidation rate and, consequently, the space-time yield. In order to evaluate the suitability of vanadium phosphate oxide (VPO) catalysts for use as supported catalyst in the FFMSR, different catalysts prepared from VOHPO4∙0.5H2O and VO(H2PO4)2 precursors was first evaluated for the oxidation of p-cymene in a well-stirred batch reactor. The results of the two activated catalysts, (VO)2P2O7 and VO(PO3)2 when used as powders in their pure form, showed a significant improvement in p-cymene oxidation rates with conversions up to 40 percent in 3-4 h reaction time with a TCHP selectivity of 75-80 percent. The (VO)2P2O7 catalyst showed better oxidation rates and selectivity when compared to the VO(PO3)2 catalyst obtained from the VO(H2PO4)2 precursor. The (VO)2P2O7 catalyst was supported on a stainless steel plate and the coated plate used to study the long-term stability and catalytic perfornance of the catalyst during p-cymene oxidations in a batch reactor. Comparable oxidation rates and TCHP selectivity were obtained with the stainless steel coated VPO catalyst when compared to the “free powder” (VO)2P2O7 catalyst. The results also showed that the stainless steel coated catalyst displays a slow, yet significant deactivation over extended reaction periods (250 h onstream). Characterization of the exposed (VO)2P2O7 catalyst to p-cymene oxidation conditions by powder XRD, SEM and TGA-MS showed that (VO)2P2O7 phase undergoes structural transformation back to VOHPO4∙0.5H2O phase over time. The (VO)2P2O7/-Al2O3 catalyst was used to coat the micro-channel reaction plates of the FFMSR. Both uncoated and coated micro-channel reaction plates were evaluated in the FFMSR for the oxidation of p-cymene. The FFMSR showed effective improvement of oxidation rates in terms of productivity space-time-yield at comparable batch p-cymene conversions. A Typical 10 percent conversion in catalysed batch oxidations at 1-2 h reaction time was achieved in few seconds (19 s) reaction time in FFMSR. The comparison of uncoated (i.e. uncatalysed) and coated (i.e. catalysed) FFMSR oxidations showed slight differences in oxidation rates. No clear explanation could be established with the present results for the observed same behaviour. However, the insufficient contact time between the gas and liquid reactants with the wall-coated solid catalyst is one of the possible causes for the observed behaviour of the coated and uncoated micro-channel plates. A simple developed kinetic model was used to confirm the obtained batch oxidation results using cumene as probe compound due to its similarity to p-cumene oxidation and extensive studied kinetics. With the estimated K values and available rate constants from literature, it was possible to predict the conversions in a batch reactor at the same typical micro-structured reactor residence time (i.e. of 19 s). The predicted conversions in the batch reactor were less than 0.1 percent even at harsh conditions such as 170 oC when compared to about 10 percent achieved in the micro-structured reactor at the same reaction temperature, reactants concentration and reaction time of 19 s. This difference in the reactor systems performance indicates the unique advantages offered by micro-structured reactors (e.g. improved mass transfer, temperature management and high surface-to-volume ratios) to perform typical gas/liquid mass transfer limited reactions such as cumene and p-cymene autoxidations.
- Full Text:
- Date Issued: 2009
- Authors: Makgwane, Peter Ramashadi
- Date: 2009
- Subjects: Oxidation , Cymene
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10389 , http://hdl.handle.net/10948/1182 , Oxidation , Cymene
- Description: The selective, liquid phase oxidation of p-cymene is an important synthetic route for the production of p-cresol via the tertiary cymene hydroperoxide (TCHP). The industrial-scale oxidation process is characterised by slow oxidation rates due to limitations in the mass transfer of oxidant (gaseous oxygen) into the liquid phase. However, like all other autoxidation reactions, the oxidation reaction is exothermic, following the typical free radical autoxidation reaction mechanism, which implies that careful temperature control is critical in order to prevent the further reaction of the initially formed hydroperoxide species. In the presence of metal catalysts, the limiting oxidation rate is the transfer of oxygen from the gas to liquid boundary interface. As a result, low product yields and poor productivity space-time yield are typically experienced. At high substrate conversions, by-products resulting from the decomposition of the formed hydroperoxides predominate. For this reason, the conversion of substrate is restricted to preserve the TCHP selectivity. The slow rates in industrial-scale p-cymene oxidations results in long oxidation times, typically 8-12 h. Substrate conversions are typically between 15-20 percent, and the TCHP selectivity ranges between 65-70 percent. The work described in this thesis concerns the oxidation of p-cymene in a microstructured falling film reactor (FFMSR). These reactor systems facilitate chemical reactors to have high mass and heat transfer rates because of high surface area-to-volume ratios. Due to their small internal volumes, these reactors are inherently safe to operate. These properties were exploited to improve the p-cymene oxidation rate and, consequently, the space-time yield. In order to evaluate the suitability of vanadium phosphate oxide (VPO) catalysts for use as supported catalyst in the FFMSR, different catalysts prepared from VOHPO4∙0.5H2O and VO(H2PO4)2 precursors was first evaluated for the oxidation of p-cymene in a well-stirred batch reactor. The results of the two activated catalysts, (VO)2P2O7 and VO(PO3)2 when used as powders in their pure form, showed a significant improvement in p-cymene oxidation rates with conversions up to 40 percent in 3-4 h reaction time with a TCHP selectivity of 75-80 percent. The (VO)2P2O7 catalyst showed better oxidation rates and selectivity when compared to the VO(PO3)2 catalyst obtained from the VO(H2PO4)2 precursor. The (VO)2P2O7 catalyst was supported on a stainless steel plate and the coated plate used to study the long-term stability and catalytic perfornance of the catalyst during p-cymene oxidations in a batch reactor. Comparable oxidation rates and TCHP selectivity were obtained with the stainless steel coated VPO catalyst when compared to the “free powder” (VO)2P2O7 catalyst. The results also showed that the stainless steel coated catalyst displays a slow, yet significant deactivation over extended reaction periods (250 h onstream). Characterization of the exposed (VO)2P2O7 catalyst to p-cymene oxidation conditions by powder XRD, SEM and TGA-MS showed that (VO)2P2O7 phase undergoes structural transformation back to VOHPO4∙0.5H2O phase over time. The (VO)2P2O7/-Al2O3 catalyst was used to coat the micro-channel reaction plates of the FFMSR. Both uncoated and coated micro-channel reaction plates were evaluated in the FFMSR for the oxidation of p-cymene. The FFMSR showed effective improvement of oxidation rates in terms of productivity space-time-yield at comparable batch p-cymene conversions. A Typical 10 percent conversion in catalysed batch oxidations at 1-2 h reaction time was achieved in few seconds (19 s) reaction time in FFMSR. The comparison of uncoated (i.e. uncatalysed) and coated (i.e. catalysed) FFMSR oxidations showed slight differences in oxidation rates. No clear explanation could be established with the present results for the observed same behaviour. However, the insufficient contact time between the gas and liquid reactants with the wall-coated solid catalyst is one of the possible causes for the observed behaviour of the coated and uncoated micro-channel plates. A simple developed kinetic model was used to confirm the obtained batch oxidation results using cumene as probe compound due to its similarity to p-cumene oxidation and extensive studied kinetics. With the estimated K values and available rate constants from literature, it was possible to predict the conversions in a batch reactor at the same typical micro-structured reactor residence time (i.e. of 19 s). The predicted conversions in the batch reactor were less than 0.1 percent even at harsh conditions such as 170 oC when compared to about 10 percent achieved in the micro-structured reactor at the same reaction temperature, reactants concentration and reaction time of 19 s. This difference in the reactor systems performance indicates the unique advantages offered by micro-structured reactors (e.g. improved mass transfer, temperature management and high surface-to-volume ratios) to perform typical gas/liquid mass transfer limited reactions such as cumene and p-cymene autoxidations.
- Full Text:
- Date Issued: 2009
Process heat flow model for temperature and hardness prediction during friction taper stud welding of AISI 4140
- Van Zyl, Carlo Angelo Antonio
- Authors: Van Zyl, Carlo Angelo Antonio
- Date: 2013
- Subjects: Friction welding Pressure welding
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/47780 , vital:40373
- Description: Friction Taper Stud Welding (FTSW) is a relatively new solid state welding process, developed from the concepts of friction welding, which theoretically operates below the melting temperatures of the material being welded. During friction welding, heat is generated by conversion of mechanical energy into thermal energy at the interface of the work pieces, during rotation under pressure. Quality welds are dependant on the correct selection of welding process parameters, which are currently chosen empirically, and the FTSW evaluated by mechanical testing. This method is time consuming, uneconomical and could cause that optimised conditions are overlooked. A proposed solution would be to numerically model the process, but reference to successful computational modelling of the FTSW process is currently not available and data regarding the responses during the process are limited. The ultimate aim of the present study is to develop a finite element model to simulate the FTSW process using AISI 4140 medium carbon low alloy steel, delivering temperature profiles and hardness predictions through the Heat Affected Zone (HAZ) – using a combined experimental and numerical study. To achieve the objectives of this study a systematic approach was adopted and conducted in several phases. A weld matrix was configured with ranging weld input parameters to determine the affect of weld input parameters on real-time responses. To provide a relationship between these factors, welding was conducted using a portable friction taper stud welding platform linked to a control and data logging system for measuring the real time axial forces, spindle speed, material displacement, torque and temperature responses as a function of time. The input process parameters applied being motor speed, axial forces, displacement and forging time. The temperature distribution through the weld, by direct measurement, as a function of weld time and position is investigated. During the experimental welds temperature responses, as influenced by welding parameters, were recorded using embedded N-Type thermocouples at various locations in the near vicinity of the weld interface. The main hot spots during welding were identified to be close to the top surface just before weld completion and at the bottom centre surface of the plug weld at the interface line. All the welds showed similar trends and a maximum temperature of 1078°C at the bottom of the weld was reached for a rotational tool speed of 5160rpm, axial friction force of 15kN and displacement of 6.5mm, due to the heat generated by friction between the tool and weld coupon. The weld torque increase rapidly at the start of the weld and reached a peak value shortly after the start of the weld, while a peak temperature of 1366°C, for a rotational tool speed of 5160rpm, axial friction force of 10kN and displacement of 8mm was reached at the top edge of the plug weld. This position of anticipated peak temperature value is due to the heat transferred during the FTSW process together with the accumulation of expelled material forming on the surface of the weld coupon. Statistical methods were applied to obtain knowledge of the trends and relationship between weld input parameters for various weld responses, including energy input, temperature, friction time, torque and displacement rate. Although it was shown that no single parameter solely controls the temperature gradients in the weld, the dominant influence of the rotational speed at the bottom of the weld and that of the displacement, at the top of the weld, were evident. The peak temperatures during the weld are of interest as these temperatures, together with the subsequent cooling rates, determine the Vickers hardness, of the material, through the weld. Spindle speed was found to have the dominant effect on temperature in the bottom half of the weld with displacement having a contributive effect closer to the top of the weld. Friction force dominate the effect on friction time, displacement rate and total energy input with friction force and spindle speed having an equal effect on torque. The multiple regression analysis resulted in valid models with varied, but acceptable accuracy with the equation for friction time resulting in an R predict value of 93.34%. These models provided a clear insight to the influence of weld input parameters on the weld responses and the model for friction time was used as an input parameter to the FTS welding simulation. The accurate prediction of the interface temperature is fundamental for process optimisation which will allow for producing consistent, reliable plug welds. A fully coupled transient two-dimensional axi-symmetrical analysis of heat flow during the FTSW process of AISI 4140 steel and subsequent Vickers hardness profiles through the HAZ, making use of numeric simulation applied in the commercially available FEA software, COMSOL Multiphysics®, is developed and reported on. Process optimisation hinges on a better understanding of the heat distribution during welding, making a major contribution to the resultant hardness. The thermal-plastic flow coupling of the model is such that temperature values are resolved together with that of the velocity field. The simulation utilises a Computational Fluid Dynamics (CFD) two phase laminar flow and Heat Transfer physics, applied in an Eulerian mesh-based scheme. The viscosity of the fluid is based on a constitutive law of the flow stress using the Zener-Hollomon parameter with a flow model based on the Navier-Stokes’ equations to simulate the plastic deformation. Temperature dependant thermo-physical material properties and coefficient of friction are applied, and the application of viscous heating is controlled by a material state variable. The heat source model, required for material softening, is applied as two components, frictional and shear, with the heat source moving along the z-axis delivering sufficient energy to soften the metal, causing flow. The Navier-Stokes approach is applied with solid-state material transport during the weld based on laminar, viscous flow of a non-Newtonian fluid, dependant on temperature and strain rate. Numerically calculated values for temperature profiles and peak temperatures through to the weld as well as subsequent Vickers hardness profiles at points through the HAZ, obtained from the Finite Element model, were found to be in close agreement with values from trial welds. The largest variance was 19% for the peak temperature of weld E4W2, applying an axial friction force of 7.5kN, 6.5mm displacement and a tool rotational speed of 4080rpm – resulting in a friction time of 330 seconds. Predictions of hardness are found to be between 0% and 19% (mean 3%) of experimentally determined values with the biggest variance at the positions of peak temperatures due to the friction interfaces. The heat applied as a result of plastic deformation was found to be 5.4% of the total heat. The FTSW model predicts the temperatures at the friction interface, during the welding process, to be within the range, and frequently exceeding the solidus temperature of AISI 4140 steel. Results show that the models applied in the FTSW simulation show good agreement when compared to experimental values. The main contribution of this thesis, towards knowledge of the FTSW process, is: The relationships between weld input parameters and responses; Temperature dependant models of thermo-physical properties for AISI 4140 in the high temperature region (ranging from ambient to the solidus temperature); Successful application of the Navier-Stokes approach to simulate the plastic flow during FTSW and A numerical finite element model for the prediction of temperature gradients and hardness profiles through a FTSW.
- Full Text:
- Date Issued: 2013
- Authors: Van Zyl, Carlo Angelo Antonio
- Date: 2013
- Subjects: Friction welding Pressure welding
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/47780 , vital:40373
- Description: Friction Taper Stud Welding (FTSW) is a relatively new solid state welding process, developed from the concepts of friction welding, which theoretically operates below the melting temperatures of the material being welded. During friction welding, heat is generated by conversion of mechanical energy into thermal energy at the interface of the work pieces, during rotation under pressure. Quality welds are dependant on the correct selection of welding process parameters, which are currently chosen empirically, and the FTSW evaluated by mechanical testing. This method is time consuming, uneconomical and could cause that optimised conditions are overlooked. A proposed solution would be to numerically model the process, but reference to successful computational modelling of the FTSW process is currently not available and data regarding the responses during the process are limited. The ultimate aim of the present study is to develop a finite element model to simulate the FTSW process using AISI 4140 medium carbon low alloy steel, delivering temperature profiles and hardness predictions through the Heat Affected Zone (HAZ) – using a combined experimental and numerical study. To achieve the objectives of this study a systematic approach was adopted and conducted in several phases. A weld matrix was configured with ranging weld input parameters to determine the affect of weld input parameters on real-time responses. To provide a relationship between these factors, welding was conducted using a portable friction taper stud welding platform linked to a control and data logging system for measuring the real time axial forces, spindle speed, material displacement, torque and temperature responses as a function of time. The input process parameters applied being motor speed, axial forces, displacement and forging time. The temperature distribution through the weld, by direct measurement, as a function of weld time and position is investigated. During the experimental welds temperature responses, as influenced by welding parameters, were recorded using embedded N-Type thermocouples at various locations in the near vicinity of the weld interface. The main hot spots during welding were identified to be close to the top surface just before weld completion and at the bottom centre surface of the plug weld at the interface line. All the welds showed similar trends and a maximum temperature of 1078°C at the bottom of the weld was reached for a rotational tool speed of 5160rpm, axial friction force of 15kN and displacement of 6.5mm, due to the heat generated by friction between the tool and weld coupon. The weld torque increase rapidly at the start of the weld and reached a peak value shortly after the start of the weld, while a peak temperature of 1366°C, for a rotational tool speed of 5160rpm, axial friction force of 10kN and displacement of 8mm was reached at the top edge of the plug weld. This position of anticipated peak temperature value is due to the heat transferred during the FTSW process together with the accumulation of expelled material forming on the surface of the weld coupon. Statistical methods were applied to obtain knowledge of the trends and relationship between weld input parameters for various weld responses, including energy input, temperature, friction time, torque and displacement rate. Although it was shown that no single parameter solely controls the temperature gradients in the weld, the dominant influence of the rotational speed at the bottom of the weld and that of the displacement, at the top of the weld, were evident. The peak temperatures during the weld are of interest as these temperatures, together with the subsequent cooling rates, determine the Vickers hardness, of the material, through the weld. Spindle speed was found to have the dominant effect on temperature in the bottom half of the weld with displacement having a contributive effect closer to the top of the weld. Friction force dominate the effect on friction time, displacement rate and total energy input with friction force and spindle speed having an equal effect on torque. The multiple regression analysis resulted in valid models with varied, but acceptable accuracy with the equation for friction time resulting in an R predict value of 93.34%. These models provided a clear insight to the influence of weld input parameters on the weld responses and the model for friction time was used as an input parameter to the FTS welding simulation. The accurate prediction of the interface temperature is fundamental for process optimisation which will allow for producing consistent, reliable plug welds. A fully coupled transient two-dimensional axi-symmetrical analysis of heat flow during the FTSW process of AISI 4140 steel and subsequent Vickers hardness profiles through the HAZ, making use of numeric simulation applied in the commercially available FEA software, COMSOL Multiphysics®, is developed and reported on. Process optimisation hinges on a better understanding of the heat distribution during welding, making a major contribution to the resultant hardness. The thermal-plastic flow coupling of the model is such that temperature values are resolved together with that of the velocity field. The simulation utilises a Computational Fluid Dynamics (CFD) two phase laminar flow and Heat Transfer physics, applied in an Eulerian mesh-based scheme. The viscosity of the fluid is based on a constitutive law of the flow stress using the Zener-Hollomon parameter with a flow model based on the Navier-Stokes’ equations to simulate the plastic deformation. Temperature dependant thermo-physical material properties and coefficient of friction are applied, and the application of viscous heating is controlled by a material state variable. The heat source model, required for material softening, is applied as two components, frictional and shear, with the heat source moving along the z-axis delivering sufficient energy to soften the metal, causing flow. The Navier-Stokes approach is applied with solid-state material transport during the weld based on laminar, viscous flow of a non-Newtonian fluid, dependant on temperature and strain rate. Numerically calculated values for temperature profiles and peak temperatures through to the weld as well as subsequent Vickers hardness profiles at points through the HAZ, obtained from the Finite Element model, were found to be in close agreement with values from trial welds. The largest variance was 19% for the peak temperature of weld E4W2, applying an axial friction force of 7.5kN, 6.5mm displacement and a tool rotational speed of 4080rpm – resulting in a friction time of 330 seconds. Predictions of hardness are found to be between 0% and 19% (mean 3%) of experimentally determined values with the biggest variance at the positions of peak temperatures due to the friction interfaces. The heat applied as a result of plastic deformation was found to be 5.4% of the total heat. The FTSW model predicts the temperatures at the friction interface, during the welding process, to be within the range, and frequently exceeding the solidus temperature of AISI 4140 steel. Results show that the models applied in the FTSW simulation show good agreement when compared to experimental values. The main contribution of this thesis, towards knowledge of the FTSW process, is: The relationships between weld input parameters and responses; Temperature dependant models of thermo-physical properties for AISI 4140 in the high temperature region (ranging from ambient to the solidus temperature); Successful application of the Navier-Stokes approach to simulate the plastic flow during FTSW and A numerical finite element model for the prediction of temperature gradients and hardness profiles through a FTSW.
- Full Text:
- Date Issued: 2013
Purification and characterisation of 20S proteasome from ostrich skeletal muscle and its role in meat tenderisation
- Authors: Thomas, Adele René
- Date: 2004
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:11081 , http://hdl.handle.net/10948/320 , Proteolytic enzymes , Ostrich products industry
- Description: The proteasome is renowned for its high molecular weight, multisubunit and mulicatalytic nature. One of its many suggested roles is the degradation of myofibrillar proteins, and therefore it has been proposed to play a role in the meat tenderisation process. The aim of this study was therefore to isolate, purify and characterise the 20S proteasome from ostrich skeletal muscle, with a view to ultimately investigating its role in the tenderisation process of ostrich meat. The 20S proteasome was successfully isolated and purified from ostrich skeletal muscle using Toyopearl Super Q-650S, Sephacryl S-300, hydroxylapatite and Mono Q chromatographies. The intact molecule showed a molecular weight of 725 K and a pI of 6.67. The subunits showed a molecular weight range of 22.2-33.5 K and a pI range of 3-9. 2D-PAGE revealed at least 14 polypeptides. The amino acid composition of the intact enzyme and of each of the eight subunits separating on SDSPAGE, as well as the N-terminal sequences of five of the eight subunits, were determined. The trypsinlike (Tr-L), chymotrypsin-like (ChT-L), peptidylglutamyl peptide hydrolase (PGPH) and caseinolytic activities showed pH optima of 11, 9, 7-8 and 10.3, and temperature optima of 40, 60, 70 and 60oC, respectively. The pH stability range for all four activities was 5-12. The ChT-L and PGPH activities showed thermostabilities up to 60oC, whereas the Tr-L and caseinolytic activities were stable up to 40o C. The enzyme showed complex kinetics. It was inhibited by the peptide aldehyde Z-LLL-CHO and cysteine protease inhibitors. Cations had negligible effects on the enzyme, excepting for Ca2+ and Mg2+. Of the detergents tested, SDS had the most potent stimulatory effect, particularly on the PGPH and caseinolytic activities. The fatty acid studies showed that unsaturation enhanced the ChT-L and the caseinolytic activities, while it completely suppressed the Tr-L activity. Heating at 60oC for 1-2 min stimulated the caseinolytic and PGPH activities. The studies on the role of ostrich skeletal muscle 20S proteasome in ostrich meat tenderisation suggested a definite but minor role of this enzyme, based on the fact that it remained active throughout the 12 days of storage of ostrich M. iliofibularis meat at 4oC and that it participated in myofibril degradation of post-mortem muscle, but to a small degree. These results support the proposal that the proteasome comes into play after the calpains have initiated degradation. However, there was a lack of improvement in tenderness values and minimal myofibrillar degradation over the 12-day storage period of the ostrich M. iliofibularis meat, leading to the conclusion that the tenderisation of this meat was incomplete after 12 days.
- Full Text:
- Date Issued: 2004
- Authors: Thomas, Adele René
- Date: 2004
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:11081 , http://hdl.handle.net/10948/320 , Proteolytic enzymes , Ostrich products industry
- Description: The proteasome is renowned for its high molecular weight, multisubunit and mulicatalytic nature. One of its many suggested roles is the degradation of myofibrillar proteins, and therefore it has been proposed to play a role in the meat tenderisation process. The aim of this study was therefore to isolate, purify and characterise the 20S proteasome from ostrich skeletal muscle, with a view to ultimately investigating its role in the tenderisation process of ostrich meat. The 20S proteasome was successfully isolated and purified from ostrich skeletal muscle using Toyopearl Super Q-650S, Sephacryl S-300, hydroxylapatite and Mono Q chromatographies. The intact molecule showed a molecular weight of 725 K and a pI of 6.67. The subunits showed a molecular weight range of 22.2-33.5 K and a pI range of 3-9. 2D-PAGE revealed at least 14 polypeptides. The amino acid composition of the intact enzyme and of each of the eight subunits separating on SDSPAGE, as well as the N-terminal sequences of five of the eight subunits, were determined. The trypsinlike (Tr-L), chymotrypsin-like (ChT-L), peptidylglutamyl peptide hydrolase (PGPH) and caseinolytic activities showed pH optima of 11, 9, 7-8 and 10.3, and temperature optima of 40, 60, 70 and 60oC, respectively. The pH stability range for all four activities was 5-12. The ChT-L and PGPH activities showed thermostabilities up to 60oC, whereas the Tr-L and caseinolytic activities were stable up to 40o C. The enzyme showed complex kinetics. It was inhibited by the peptide aldehyde Z-LLL-CHO and cysteine protease inhibitors. Cations had negligible effects on the enzyme, excepting for Ca2+ and Mg2+. Of the detergents tested, SDS had the most potent stimulatory effect, particularly on the PGPH and caseinolytic activities. The fatty acid studies showed that unsaturation enhanced the ChT-L and the caseinolytic activities, while it completely suppressed the Tr-L activity. Heating at 60oC for 1-2 min stimulated the caseinolytic and PGPH activities. The studies on the role of ostrich skeletal muscle 20S proteasome in ostrich meat tenderisation suggested a definite but minor role of this enzyme, based on the fact that it remained active throughout the 12 days of storage of ostrich M. iliofibularis meat at 4oC and that it participated in myofibril degradation of post-mortem muscle, but to a small degree. These results support the proposal that the proteasome comes into play after the calpains have initiated degradation. However, there was a lack of improvement in tenderness values and minimal myofibrillar degradation over the 12-day storage period of the ostrich M. iliofibularis meat, leading to the conclusion that the tenderisation of this meat was incomplete after 12 days.
- Full Text:
- Date Issued: 2004
Development of MOVPE-grown InAsSb for barrier diode applications
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
Self-determined development practices for a marginalised San community of Tsumkwe East in Otjozondjupa Region, Namibia
- Authors: Chingwe, Shuvai
- Date: 2017
- Subjects: San (African people) -- Namibia San (African people) -- Namibia -- Social conditions , San (African people) -- Namibia -- Politics and government Indigenous peoples -- Namibia
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/33239 , vital:32597
- Description: This study was an exploration of self-determined development practices as a panacea for poverty reduction in the San communities. The main aim of this study was to propose possible strategies for eliminating the marginalisation of San in order to reduce poverty. This study was guided by an Indigenous research paradigm. This study used an Indigenous research methodology because it ensures that research on Indigenous issues is carried out in a more respectful, ethical, correct, sympathetic, useful and beneficial fashion seen from the point of Indigenous people. Nine out of thirty-six villages in Tsumkwe East participated in this study. Data collection was done through key informant interviews and conversational methods namely talking circles and storying. The findings of this study reveal that the marginalisation of the Ju/’hoansi San of Nyae Nyae and other San communities is closely related to their loss of ancestral land during the colonial and post-colonial era. Although the Ju/’hoansi San have fought to maintain their ancestral lands, hunting which is their main livelihood has been restricted by government regulation. The restriction on their hunting and gathering culture has been the major contribution to their marginalisation as they can no longer fend for themselves as their forefathers used to do. Despite a multitude of factors militating against the self-determination of San communities, the Ju/’hoansi San have managed to express their voice through a remnant of their hunting and gathering culture. This study also reveals that there are two important actors in Nyae Nyae namely the government of the Republic of Namibia and the Nyae Nyae Conservancy. Nyae Nyae Conservancy is a community based natural resource management organisation which has taken a participatory developmental approach to the development of Tsumkwe East. The government has taken more of a welfare approach. Although the mainstream has labelled San people lazy, uneducated, backward and uncivilised, the success of the Nyae Nyae Conservancy which is managed by the Ju/’hoansi San is a testimony to the contrary. This study reveals that the government has failed to deliver on its policy of meeting all the welfare needs of the Ju/’hoansi San but the conservancy has risen to be a relevant organisation meeting the needs of the community whilst respecting their culture and identity as a hunting and gathering community. This study concludes that self-determined development practices maybe a panacea for the development of San communities. This can be made possible by supporting the San’s hunting and gathering livelihoods, respecting their culture, securing their land and resource rights, through long-term and consistent capacity building and supporting a culturally relevant education system.
- Full Text:
- Date Issued: 2017
- Authors: Chingwe, Shuvai
- Date: 2017
- Subjects: San (African people) -- Namibia San (African people) -- Namibia -- Social conditions , San (African people) -- Namibia -- Politics and government Indigenous peoples -- Namibia
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/33239 , vital:32597
- Description: This study was an exploration of self-determined development practices as a panacea for poverty reduction in the San communities. The main aim of this study was to propose possible strategies for eliminating the marginalisation of San in order to reduce poverty. This study was guided by an Indigenous research paradigm. This study used an Indigenous research methodology because it ensures that research on Indigenous issues is carried out in a more respectful, ethical, correct, sympathetic, useful and beneficial fashion seen from the point of Indigenous people. Nine out of thirty-six villages in Tsumkwe East participated in this study. Data collection was done through key informant interviews and conversational methods namely talking circles and storying. The findings of this study reveal that the marginalisation of the Ju/’hoansi San of Nyae Nyae and other San communities is closely related to their loss of ancestral land during the colonial and post-colonial era. Although the Ju/’hoansi San have fought to maintain their ancestral lands, hunting which is their main livelihood has been restricted by government regulation. The restriction on their hunting and gathering culture has been the major contribution to their marginalisation as they can no longer fend for themselves as their forefathers used to do. Despite a multitude of factors militating against the self-determination of San communities, the Ju/’hoansi San have managed to express their voice through a remnant of their hunting and gathering culture. This study also reveals that there are two important actors in Nyae Nyae namely the government of the Republic of Namibia and the Nyae Nyae Conservancy. Nyae Nyae Conservancy is a community based natural resource management organisation which has taken a participatory developmental approach to the development of Tsumkwe East. The government has taken more of a welfare approach. Although the mainstream has labelled San people lazy, uneducated, backward and uncivilised, the success of the Nyae Nyae Conservancy which is managed by the Ju/’hoansi San is a testimony to the contrary. This study reveals that the government has failed to deliver on its policy of meeting all the welfare needs of the Ju/’hoansi San but the conservancy has risen to be a relevant organisation meeting the needs of the community whilst respecting their culture and identity as a hunting and gathering community. This study concludes that self-determined development practices maybe a panacea for the development of San communities. This can be made possible by supporting the San’s hunting and gathering livelihoods, respecting their culture, securing their land and resource rights, through long-term and consistent capacity building and supporting a culturally relevant education system.
- Full Text:
- Date Issued: 2017
Productivity and resilience of intertidal resources available to extant human foragers on South Africa’s cape south coast: behavioural implications for early Homo sapiens
- Authors: De Vynck, Jan Carlo
- Date: 2018
- Subjects: Marine invertebrates -- South Africa -- Prehistory , Shellfish -- South Africa -- Prehistory Fishes -- Behavior
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30172 , vital:30854
- Description: Studies of pre-historic lifestyles can be limited by a lack of preserved material and sites and resource misinterpretation is augmented by the vagueness of pre-historic subsistence lifestyles. The present can inform the past and this study‟s ethnoarchaeological approach, through modern analogues, examines productivity, resilience and temporal and spatial size variation of intertidal invertebrates on the Cape‟s south coast. O‟Connell (1995) defined the mutualistic relationship between ethnography and archaeology thus: “Archaeology‟s ultimate aim is understanding past human behaviour by patterns in the form and distribution of objects made or modified by humans in the past and knowledge of human behaviour and its material consequences in the present. The first provides direct evidence of past behaviour; the second, a basis for interpreting that evidence”. Coastal archaeology, specifically the contribution of coastal resources to pre-historic subsistence, has gained increased global interest (Erlandson, 2001; Erlandson and Rick, 2008; Codding et al., 2014). Apart from the high representation of preserved shell in coastal archaeological sites, interest in intertidal resources has also been sparked by their economic value compared to terrestrial resource options. Intertidal resources offer low-risk protein acquisition whereas terrestrial protein can be dangerous to procure. However, in the past intertidal subsistence was thought to offer low caloric yields or unfavourable cost-to-benefit relationships until Meehan (1982) convincingly demonstrated the potential caloric „profit‟ possible from coastal foraging; the Anbarra women of northern Australia were contributing significantly to the overall caloric requirements of those people. In South Africa, two possible evolutionary behavioural hypotheses arose from the addition of intertidal resources to pre-historic diets. As background, it is important to note that the oldest global evidence for shellfish procurement [164 000 years ago (ka)] is found on the Cape‟s south coast (Jerardino and Marean, 2010) and the evidence is enriched by other sites from around 110 ka (Voight, 1973; Thackeray, 1988; Henshilwood et al., 2001; Langejans et al., 2012). Furthermore, this period coincides with the emergence of cognitively modern Homo sapiens as evidenced in xx the palaeoarchives from many sites in the region (d‟Errico et al., 2005; Marean et al., 2007; Wurz, 2008; Henshilwood et al., 2009; Watts, 2010; d‟Errico et al., 2012). These features have greatly enhanced the significance and importance of this area to understanding human evolution. The two hypotheses are centred around the effect that intertidal resources could have had on the emergence of our unique species. The addition of a nutritionally beneficial resource to cognitive development is seen by some (Broadhurst et al., 2002; Parkington, 2010) to have driven this cognitive evolution, where others suggest that resources which are both productive and dependable create pro-social proclivities that drive cognitive development (Whitaker and Byrd, 2014; Marean, 2014) and facilitate the migration of humans (Fa, 2008; Codding et al., 2014). Both hypotheses argue that resources on the Cape‟s coast must have been productive and had to be a frequent addition to diet to underpin brain development. The increased frequency of coastal resource procurement or coastal adaptation is therefore seen as an attribute of, or requisite for our species. This thesis attempts to shed light on the contribution of intertidal resources to prehistoric ‒ especially Middle Stone Age (MSA) – subsistence economy on the Cape‟s south coast and the possible effect thereof on human behavioural evolution. The first aim was to investigate the spatial productivity (once-off patch caloric profitability in numerous patches) of intertidal resources and the environmental and behavioural variables affecting it. The second aim was to investigate the resilience of caloric profitability (numerous harvests in the same patch) of these resources to sustained human predation. Productivity itself cannot affect human temporal social dynamics if the resource is swiftly depleted within a specific patch after one or a few harvests. Archaeological records that show the body size of shellfish decreasing over time are usually interpreted to indicate intensive exploitation and the depletion of these resources, but there may be other explanations for such patterns. Therefore, the third aim was to compare temporal and spatial variations in the body size of Turbo sarmaticus in the MSA, Later Stone Age (LSA) and the present day, in order to investigate whether such variations result from human exploitation or environmental changes.
- Full Text:
- Date Issued: 2018
- Authors: De Vynck, Jan Carlo
- Date: 2018
- Subjects: Marine invertebrates -- South Africa -- Prehistory , Shellfish -- South Africa -- Prehistory Fishes -- Behavior
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30172 , vital:30854
- Description: Studies of pre-historic lifestyles can be limited by a lack of preserved material and sites and resource misinterpretation is augmented by the vagueness of pre-historic subsistence lifestyles. The present can inform the past and this study‟s ethnoarchaeological approach, through modern analogues, examines productivity, resilience and temporal and spatial size variation of intertidal invertebrates on the Cape‟s south coast. O‟Connell (1995) defined the mutualistic relationship between ethnography and archaeology thus: “Archaeology‟s ultimate aim is understanding past human behaviour by patterns in the form and distribution of objects made or modified by humans in the past and knowledge of human behaviour and its material consequences in the present. The first provides direct evidence of past behaviour; the second, a basis for interpreting that evidence”. Coastal archaeology, specifically the contribution of coastal resources to pre-historic subsistence, has gained increased global interest (Erlandson, 2001; Erlandson and Rick, 2008; Codding et al., 2014). Apart from the high representation of preserved shell in coastal archaeological sites, interest in intertidal resources has also been sparked by their economic value compared to terrestrial resource options. Intertidal resources offer low-risk protein acquisition whereas terrestrial protein can be dangerous to procure. However, in the past intertidal subsistence was thought to offer low caloric yields or unfavourable cost-to-benefit relationships until Meehan (1982) convincingly demonstrated the potential caloric „profit‟ possible from coastal foraging; the Anbarra women of northern Australia were contributing significantly to the overall caloric requirements of those people. In South Africa, two possible evolutionary behavioural hypotheses arose from the addition of intertidal resources to pre-historic diets. As background, it is important to note that the oldest global evidence for shellfish procurement [164 000 years ago (ka)] is found on the Cape‟s south coast (Jerardino and Marean, 2010) and the evidence is enriched by other sites from around 110 ka (Voight, 1973; Thackeray, 1988; Henshilwood et al., 2001; Langejans et al., 2012). Furthermore, this period coincides with the emergence of cognitively modern Homo sapiens as evidenced in xx the palaeoarchives from many sites in the region (d‟Errico et al., 2005; Marean et al., 2007; Wurz, 2008; Henshilwood et al., 2009; Watts, 2010; d‟Errico et al., 2012). These features have greatly enhanced the significance and importance of this area to understanding human evolution. The two hypotheses are centred around the effect that intertidal resources could have had on the emergence of our unique species. The addition of a nutritionally beneficial resource to cognitive development is seen by some (Broadhurst et al., 2002; Parkington, 2010) to have driven this cognitive evolution, where others suggest that resources which are both productive and dependable create pro-social proclivities that drive cognitive development (Whitaker and Byrd, 2014; Marean, 2014) and facilitate the migration of humans (Fa, 2008; Codding et al., 2014). Both hypotheses argue that resources on the Cape‟s coast must have been productive and had to be a frequent addition to diet to underpin brain development. The increased frequency of coastal resource procurement or coastal adaptation is therefore seen as an attribute of, or requisite for our species. This thesis attempts to shed light on the contribution of intertidal resources to prehistoric ‒ especially Middle Stone Age (MSA) – subsistence economy on the Cape‟s south coast and the possible effect thereof on human behavioural evolution. The first aim was to investigate the spatial productivity (once-off patch caloric profitability in numerous patches) of intertidal resources and the environmental and behavioural variables affecting it. The second aim was to investigate the resilience of caloric profitability (numerous harvests in the same patch) of these resources to sustained human predation. Productivity itself cannot affect human temporal social dynamics if the resource is swiftly depleted within a specific patch after one or a few harvests. Archaeological records that show the body size of shellfish decreasing over time are usually interpreted to indicate intensive exploitation and the depletion of these resources, but there may be other explanations for such patterns. Therefore, the third aim was to compare temporal and spatial variations in the body size of Turbo sarmaticus in the MSA, Later Stone Age (LSA) and the present day, in order to investigate whether such variations result from human exploitation or environmental changes.
- Full Text:
- Date Issued: 2018
Exploration of Nahoon beach milieu for lignocellulose degrading bacteria and optimizing fermentation conditions for holocellulase production by selected strains
- Authors: Fatokun, Evelyn
- Date: 2016
- Subjects: Lignocellulose Lignocellulose -- Biodegradation Water -- Purification -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/1529 , vital:27413
- Description: A significant trend in the modern day industrial biotechnology is the utilization and application of renewable resources, and ecofriendly approach to industrial processes and waste management. As a consequence thereof, the biotechnology of holocellulases: cellulase and xylanase and, enzymatic hydrolysis of renewable and abundant lignocellulosic biomass to energy and value added products are rapidly increasing; hence, cost effective enzyme system is imperative. In that context, exploration of microbiota for strains and enzymes with novel industrial properties is vital for efficient and commercially viable enzyme biotechnology. Consequent on the complex characteristics of high salinity, variable pressure, temperature and nutritional conditions, bacterial strains from the marine environment are equipped with enzyme machinery of industrial importance for adaptation and survival. In this study, bacterial strains were isolated form Nahoon beach and optimized for holocellulase production. Three isolates selected for lignocellulolytic potential were identified by 16S ribosomal deoxyribonucleic acid (rDNA) sequence analysis. Isolate FS1k had 98 percent similarity with Streptomyces albidoflavus strain AIH12, was designated as Streptomyces albidoflavus strain SAMRC-UFH5 and deposited in the GenBank with accession number KU171373. Similarly, isolates CS14b and CS22d with respective percentage similarity of 98 and 99 (percent) with Bacillus cereus strains and Streptomyces sp. strain WMMB251 were named Bacillus cereus strain SAMRC-UFH9 and Streptomyces sp. strain SAMRC-UFH6; and were deposited in the GenBank with accession number KX524510 and KU171374 respectively. Optimal pH, temperature and agitation speed for cellulase production by S. albidoflavus strain SAMRC-UFH5, and B. cereus strain SAMRC-UFH9 were 6 and 7; 40 and 30 (°C); and 100 and 150 (rpm) respectively; while xylanase production was optimal at pH, temperature and agitation speed of 8 and 7; 40 and 30 (°C); and 150 and 50 (rpm) respectively. Maximum cellulase activity of 0.26 and 0.061(U/mL) by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 were attained at 60 h respectively, while maximal xylanase activity of 18.54 and 16.6 (U/mL) was produced by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 at 48 h and 60 h respectively. Furthermore, xylanase production by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 was maximally induced by wheat straw and xylan respectively, while cellulase production was best induced by mannose and carboxymethyl cellulose respectively. On the other hand, cellulase and xylanase production by Streptomyces sp. strain SAMRC-UFH6 was optimal at pH, temperature and agitation speed of 7 and 8, 40 °C and 100 rpm, respectively. Highest production of cellulase and xylanase was attained at 84 and 60 h with respective activity of 0.065 and 6.34 (U/mL). In addition, cellulase and xylanase production by the strain was best induced by beechwood xylan. Moreover, xylanase produced by Streptomyces sp. strain SAMRC-UFH6 at optimal conditions was characterized by optimal pH and temperature of 8 and 80-90 °C respectively; retaining over 70 percent activity at pH 5-10 after 1 h and 60 percent of initial activity at 90 °C after 90 min of incubation. In all, optimization improved cellulase and xylanase production yields, being 40 and 95.5, 10.89 and 72.17, and 10 and 115- fold increase by S. albidoflavus strain SAMRC-UFH5, B. cereus strain SAMRC-UFH9 and Streptomyces sp. SAMRC-UFH6 respectively. The results of this study suggest that the marine bacterial strains are resource for holocellulase with industrial applications.
- Full Text:
- Date Issued: 2016
- Authors: Fatokun, Evelyn
- Date: 2016
- Subjects: Lignocellulose Lignocellulose -- Biodegradation Water -- Purification -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/1529 , vital:27413
- Description: A significant trend in the modern day industrial biotechnology is the utilization and application of renewable resources, and ecofriendly approach to industrial processes and waste management. As a consequence thereof, the biotechnology of holocellulases: cellulase and xylanase and, enzymatic hydrolysis of renewable and abundant lignocellulosic biomass to energy and value added products are rapidly increasing; hence, cost effective enzyme system is imperative. In that context, exploration of microbiota for strains and enzymes with novel industrial properties is vital for efficient and commercially viable enzyme biotechnology. Consequent on the complex characteristics of high salinity, variable pressure, temperature and nutritional conditions, bacterial strains from the marine environment are equipped with enzyme machinery of industrial importance for adaptation and survival. In this study, bacterial strains were isolated form Nahoon beach and optimized for holocellulase production. Three isolates selected for lignocellulolytic potential were identified by 16S ribosomal deoxyribonucleic acid (rDNA) sequence analysis. Isolate FS1k had 98 percent similarity with Streptomyces albidoflavus strain AIH12, was designated as Streptomyces albidoflavus strain SAMRC-UFH5 and deposited in the GenBank with accession number KU171373. Similarly, isolates CS14b and CS22d with respective percentage similarity of 98 and 99 (percent) with Bacillus cereus strains and Streptomyces sp. strain WMMB251 were named Bacillus cereus strain SAMRC-UFH9 and Streptomyces sp. strain SAMRC-UFH6; and were deposited in the GenBank with accession number KX524510 and KU171374 respectively. Optimal pH, temperature and agitation speed for cellulase production by S. albidoflavus strain SAMRC-UFH5, and B. cereus strain SAMRC-UFH9 were 6 and 7; 40 and 30 (°C); and 100 and 150 (rpm) respectively; while xylanase production was optimal at pH, temperature and agitation speed of 8 and 7; 40 and 30 (°C); and 150 and 50 (rpm) respectively. Maximum cellulase activity of 0.26 and 0.061(U/mL) by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 were attained at 60 h respectively, while maximal xylanase activity of 18.54 and 16.6 (U/mL) was produced by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 at 48 h and 60 h respectively. Furthermore, xylanase production by S. albidoflavus strain SAMRC-UFH5 and B. cereus strain SAMRC-UFH9 was maximally induced by wheat straw and xylan respectively, while cellulase production was best induced by mannose and carboxymethyl cellulose respectively. On the other hand, cellulase and xylanase production by Streptomyces sp. strain SAMRC-UFH6 was optimal at pH, temperature and agitation speed of 7 and 8, 40 °C and 100 rpm, respectively. Highest production of cellulase and xylanase was attained at 84 and 60 h with respective activity of 0.065 and 6.34 (U/mL). In addition, cellulase and xylanase production by the strain was best induced by beechwood xylan. Moreover, xylanase produced by Streptomyces sp. strain SAMRC-UFH6 at optimal conditions was characterized by optimal pH and temperature of 8 and 80-90 °C respectively; retaining over 70 percent activity at pH 5-10 after 1 h and 60 percent of initial activity at 90 °C after 90 min of incubation. In all, optimization improved cellulase and xylanase production yields, being 40 and 95.5, 10.89 and 72.17, and 10 and 115- fold increase by S. albidoflavus strain SAMRC-UFH5, B. cereus strain SAMRC-UFH9 and Streptomyces sp. SAMRC-UFH6 respectively. The results of this study suggest that the marine bacterial strains are resource for holocellulase with industrial applications.
- Full Text:
- Date Issued: 2016
The voice of the child in parental divorce: a narrative inquiry
- Authors: Brand, Carrie
- Date: 2016
- Subjects: Conversation analysis , Children of divorced parents , Divorced parents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/8923 , vital:26443
- Description: Parental divorce is considered one of the most stressful events in the lives of children. The adult perspective has dominated the discourse on divorce, and only recently has research started to consider the viewpoint of children. Research indicates that the nature of the divorce process as experienced by the child is the most important factor in post-divorce adjustment. It also remains a relatively unexplored area, with research on the manner in which children experience the divorce process being limited. The current study aimed to conduct a narrative inquiry into the experiences and perceptions of parental divorce, of a purposive sample of 9 to 10 year old children. The primary aim of the study was to highlight and honour the voice of the child in a parental divorce process. The current research was qualitative in nature and adopted a narrative paradigm. Five children were interviewed qualitatively using an unstructured interview. Data were analysed using thematic analysis. Seven themes were identified. The first theme explored children’s endeavours to describe and explain parental divorce. An additional six themes were developed around the types of stories children told of the divorce process. Themes included, What is a Divorcement, Stories of Loss, Stories of Gain, Stories of Change, Stories of Stability, Healing Stories, and Complicating Stories. This study endeavoured to provide divorced parents and those working with children a greater understanding of the way in which children perceive parental divorce, and insight into the factors that facilitate children’s positive adjustment to parental divorce.
- Full Text:
- Date Issued: 2016
- Authors: Brand, Carrie
- Date: 2016
- Subjects: Conversation analysis , Children of divorced parents , Divorced parents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/8923 , vital:26443
- Description: Parental divorce is considered one of the most stressful events in the lives of children. The adult perspective has dominated the discourse on divorce, and only recently has research started to consider the viewpoint of children. Research indicates that the nature of the divorce process as experienced by the child is the most important factor in post-divorce adjustment. It also remains a relatively unexplored area, with research on the manner in which children experience the divorce process being limited. The current study aimed to conduct a narrative inquiry into the experiences and perceptions of parental divorce, of a purposive sample of 9 to 10 year old children. The primary aim of the study was to highlight and honour the voice of the child in a parental divorce process. The current research was qualitative in nature and adopted a narrative paradigm. Five children were interviewed qualitatively using an unstructured interview. Data were analysed using thematic analysis. Seven themes were identified. The first theme explored children’s endeavours to describe and explain parental divorce. An additional six themes were developed around the types of stories children told of the divorce process. Themes included, What is a Divorcement, Stories of Loss, Stories of Gain, Stories of Change, Stories of Stability, Healing Stories, and Complicating Stories. This study endeavoured to provide divorced parents and those working with children a greater understanding of the way in which children perceive parental divorce, and insight into the factors that facilitate children’s positive adjustment to parental divorce.
- Full Text:
- Date Issued: 2016
The state of constitutionalism in Uganda: 1962-2018
- Authors: Bashasha, Turyatemba Alex
- Date: 2018
- Subjects: Constitutional history -- Uganda , Constitutional history Constitutional law -- Uganda
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23669 , vital:30596
- Description: This Thesis examines the state of constitutionalism in Uganda between 1962 and 2018. The central question which it seeks to answer is: ‘why did Ugandan governments persistently fail to adhere to the basic requirements of the doctrine of constitutionalism between 1962 and 2018?’ In answering this question, which has challenged and continues to challenge many academicians, politicians, government officials, researchers and the international community alike, the Thesis adopts the Theory of Neo-patrimonialism as a theoretical lens through which the behaviours of the post-independence presidents of Uganda are examined. The Thesis discovers that, indeed, Neo-patrimonialism is a fundamental framework for analysing and explaining constitutionalism in post-independence Uganda. Against this backdrop, the Thesis concludes that, the collective behaviours of Uganda’s post-independence presidents viewed through the lens of neo-patrimonialism are more fundamental in understanding the failure of democracy and good governance in Uganda than the country’s structural problems of constitutionalism. The originality of the Thesis is in: (a) its being the first comprehensive investigation into why Ugandan governments have persistently failed to adhere to the basic requirements of the doctrine of constitutionalism for the entire period of 56 years (1962-2018) of post-independence Uganda; and (b) its being the first study to apply the Theory of Neo-patrimonialism in explaining the volatile nature and state of constitutionalism in Uganda. The contribution of the Thesis to the existing knowledge lies in its; (a) generation of detailed and well-researched information about the volatility of constitutionalism in Uganda between 1962 and 2018, (b) recommendation of strategies that should be adopted to effectively enhance consititutionalism in Uganda, and (c) authentication of the validity of the claims that despite its shortcomings, Neo-patrimonialism is a Theory which not only continues to define and drive African politics but its application can suitably be used to explain the volatile nature of constitutionalism in post-independence Uganda and the rest of Africa.
- Full Text:
- Date Issued: 2018
- Authors: Bashasha, Turyatemba Alex
- Date: 2018
- Subjects: Constitutional history -- Uganda , Constitutional history Constitutional law -- Uganda
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23669 , vital:30596
- Description: This Thesis examines the state of constitutionalism in Uganda between 1962 and 2018. The central question which it seeks to answer is: ‘why did Ugandan governments persistently fail to adhere to the basic requirements of the doctrine of constitutionalism between 1962 and 2018?’ In answering this question, which has challenged and continues to challenge many academicians, politicians, government officials, researchers and the international community alike, the Thesis adopts the Theory of Neo-patrimonialism as a theoretical lens through which the behaviours of the post-independence presidents of Uganda are examined. The Thesis discovers that, indeed, Neo-patrimonialism is a fundamental framework for analysing and explaining constitutionalism in post-independence Uganda. Against this backdrop, the Thesis concludes that, the collective behaviours of Uganda’s post-independence presidents viewed through the lens of neo-patrimonialism are more fundamental in understanding the failure of democracy and good governance in Uganda than the country’s structural problems of constitutionalism. The originality of the Thesis is in: (a) its being the first comprehensive investigation into why Ugandan governments have persistently failed to adhere to the basic requirements of the doctrine of constitutionalism for the entire period of 56 years (1962-2018) of post-independence Uganda; and (b) its being the first study to apply the Theory of Neo-patrimonialism in explaining the volatile nature and state of constitutionalism in Uganda. The contribution of the Thesis to the existing knowledge lies in its; (a) generation of detailed and well-researched information about the volatility of constitutionalism in Uganda between 1962 and 2018, (b) recommendation of strategies that should be adopted to effectively enhance consititutionalism in Uganda, and (c) authentication of the validity of the claims that despite its shortcomings, Neo-patrimonialism is a Theory which not only continues to define and drive African politics but its application can suitably be used to explain the volatile nature of constitutionalism in post-independence Uganda and the rest of Africa.
- Full Text:
- Date Issued: 2018
On the development of ZnO nanorods on silicon substrate for light-emitting diode applications
- Djiokap, Stive Roussel Tankio
- Authors: Djiokap, Stive Roussel Tankio
- Date: 2018
- Subjects: Zinc oxide , Chemical reactions , Compound semiconductors
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29973 , vital:30802
- Description: The interest in zinc oxide (ZnO), a promising material for blue/ultraviolet light emitting devices, arises from its large exciton binding energy (60 meV). The main challenge associated with this promising compound semiconductor, however, arises from the difficulty to achieve stable and/or reproducible p-type doping. Since silicon (Si) technology still dominates the semiconductor industry, the objective of this thesis is to probe into the possibility of using ZnO nanorods (NRs) on p-type silicon for opto-electronic devices. ZnO NRs have been grown on seeded Si, as well as on nickel oxide (NiO) and aluminum nitride (AlN) coated Si, using a two-step chemical bath deposition (CBD) process. Various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM), have been used to characterize the samples. The electrical characteristics of the heterojunction between the substrate and the ZnO nanostructures were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. SEM and XRD studies have confirmed that, irrespective of the orientation of the Si substrate (Si (100) and Si (111)), the two-step CBD process yielded NRs that crystallised in the wurtzite structure and exhibited a hexagonal shape. Most of the rods developed perpendicularly to the surface of the substrate, with the orientation and distribution of the rods dictated by the seed layer density. Similarly, irrespective of the substrate, the luminescence of the ZnO nanostructures is dominated by near band edge (NBE) emission in the UV region (~ 3.29 eV) and deep level emission (DLE) in the visible region (2 eV to 2.6 eV). Annealing at moderate temperatures (~ 300 °C) increased the NBE emission and decreased the DLE. The removal of surface adsorbed impurities and enhanced defect passivation by hydrogen are responsible for these changes. The diode characteristics of the ZnO/Si heterojunction was studied by I-V and C-V measurements. Rectification was observed when the Si substrate had a relatively low acceptor density of ~1016 cm-3, while diodes produced on substrate with p ~1018 cm-3 were ohmic. From the C-V analysis the donor density in the ZnO was deduced to be ~1018 cm-3. In the case of rectifying junctions, thermionic emission did not dominate the charge transport. The carrier transport mechanism was therefore probed by the temperature dependent I-V xiii measurements (100 K to 295 K). Defect-assisted multistep tunneling was deduced to dominate in the n-ZnO/p-Si diodes at low forward bias. The band alignment between n-ZnO and p-Si predicts a much smaller barrier for electrons than for holes at the interface, which results in recombination on the Si side of the junction for a forward-biased diode. NiO intermediate layers (formed on Si by the thermal oxidation of Ni) were used to reduce electron injection from ZnO into Si. Scanning probe microscopy (SPM) and XRD analysis showed that while the grain size of the poly-crystalline NiO increased with NiO film thickness, the orientation and distribution of the subsequently grown ZnO nanorods were unaffected by the underlying NiO layer. Also, the photoluminescence response of the ZnO rods remained unchanged. I-V measurements did illustrate rectifying behaviour, with both the forward and reverse currents strongly decreased due to the resistive nature of the NiO. In another attempt at confining electrons to the ZnO side of the junction, AlN-coated Si (111) was used as a substrate for ZnO nanorods. CBD parameters that normally yield nanorods resulted in a plate-like architecture of the ZnO. By modifying the ZnO seed density on the AlN/Si substrate, the rod-like morphology could be recovered. Both the forward and reverse current decreased in these diodes. From studies aimed at identifying the transport mechanism it was concluded that trap-assisted tunnelling, resulting from a high density of defects in the seed layer, dominates in these devices. In conclusion, while no ZnO electroluminescence could be achieved from any of the devices, this study provides insight into the transport mechanisms in n-ZnO/barrier/p-Si heterostructures and highlights the importance of the heterointerface quality for light emitting devices.
- Full Text:
- Date Issued: 2018
- Authors: Djiokap, Stive Roussel Tankio
- Date: 2018
- Subjects: Zinc oxide , Chemical reactions , Compound semiconductors
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29973 , vital:30802
- Description: The interest in zinc oxide (ZnO), a promising material for blue/ultraviolet light emitting devices, arises from its large exciton binding energy (60 meV). The main challenge associated with this promising compound semiconductor, however, arises from the difficulty to achieve stable and/or reproducible p-type doping. Since silicon (Si) technology still dominates the semiconductor industry, the objective of this thesis is to probe into the possibility of using ZnO nanorods (NRs) on p-type silicon for opto-electronic devices. ZnO NRs have been grown on seeded Si, as well as on nickel oxide (NiO) and aluminum nitride (AlN) coated Si, using a two-step chemical bath deposition (CBD) process. Various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM), have been used to characterize the samples. The electrical characteristics of the heterojunction between the substrate and the ZnO nanostructures were evaluated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. SEM and XRD studies have confirmed that, irrespective of the orientation of the Si substrate (Si (100) and Si (111)), the two-step CBD process yielded NRs that crystallised in the wurtzite structure and exhibited a hexagonal shape. Most of the rods developed perpendicularly to the surface of the substrate, with the orientation and distribution of the rods dictated by the seed layer density. Similarly, irrespective of the substrate, the luminescence of the ZnO nanostructures is dominated by near band edge (NBE) emission in the UV region (~ 3.29 eV) and deep level emission (DLE) in the visible region (2 eV to 2.6 eV). Annealing at moderate temperatures (~ 300 °C) increased the NBE emission and decreased the DLE. The removal of surface adsorbed impurities and enhanced defect passivation by hydrogen are responsible for these changes. The diode characteristics of the ZnO/Si heterojunction was studied by I-V and C-V measurements. Rectification was observed when the Si substrate had a relatively low acceptor density of ~1016 cm-3, while diodes produced on substrate with p ~1018 cm-3 were ohmic. From the C-V analysis the donor density in the ZnO was deduced to be ~1018 cm-3. In the case of rectifying junctions, thermionic emission did not dominate the charge transport. The carrier transport mechanism was therefore probed by the temperature dependent I-V xiii measurements (100 K to 295 K). Defect-assisted multistep tunneling was deduced to dominate in the n-ZnO/p-Si diodes at low forward bias. The band alignment between n-ZnO and p-Si predicts a much smaller barrier for electrons than for holes at the interface, which results in recombination on the Si side of the junction for a forward-biased diode. NiO intermediate layers (formed on Si by the thermal oxidation of Ni) were used to reduce electron injection from ZnO into Si. Scanning probe microscopy (SPM) and XRD analysis showed that while the grain size of the poly-crystalline NiO increased with NiO film thickness, the orientation and distribution of the subsequently grown ZnO nanorods were unaffected by the underlying NiO layer. Also, the photoluminescence response of the ZnO rods remained unchanged. I-V measurements did illustrate rectifying behaviour, with both the forward and reverse currents strongly decreased due to the resistive nature of the NiO. In another attempt at confining electrons to the ZnO side of the junction, AlN-coated Si (111) was used as a substrate for ZnO nanorods. CBD parameters that normally yield nanorods resulted in a plate-like architecture of the ZnO. By modifying the ZnO seed density on the AlN/Si substrate, the rod-like morphology could be recovered. Both the forward and reverse current decreased in these diodes. From studies aimed at identifying the transport mechanism it was concluded that trap-assisted tunnelling, resulting from a high density of defects in the seed layer, dominates in these devices. In conclusion, while no ZnO electroluminescence could be achieved from any of the devices, this study provides insight into the transport mechanisms in n-ZnO/barrier/p-Si heterostructures and highlights the importance of the heterointerface quality for light emitting devices.
- Full Text:
- Date Issued: 2018