Case study : profitability drivers in the South African airline industry : a comparative analysis of SAA and Comair
- Authors: Batidzirai, Davison Herbert
- Date: 2015
- Subjects: South African Airways , Comair Limited , Airlines -- South Africa , Corporate profits -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:846 , http://hdl.handle.net/10962/d1017191
- Full Text:
- Date Issued: 2015
- Authors: Batidzirai, Davison Herbert
- Date: 2015
- Subjects: South African Airways , Comair Limited , Airlines -- South Africa , Corporate profits -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:846 , http://hdl.handle.net/10962/d1017191
- Full Text:
- Date Issued: 2015
Celebrating libraries in 20 years of democracy : an overview of library and information services in South Africa
- Authors: Satgoor, Ujala
- Date: 2015
- Subjects: Libraries , Library administration -- South Africa , Information services -- South Africa , Public libraries -- South Africa , Library science -- South Africa
- Language: English
- Type: Article
- Identifier: vital:6997 , http://hdl.handle.net/10962/d1019841 , ISSN ISSN: 0340-0352 , http://journals.sagepub.com/doi/10.1177/0340035215585100
- Description: Since the establishment of the first public library in 1818, the South African library and information services landscape has also been a reflection of the socio-political order and developments in the country. This article presents an historical perspective as well as an overview of libraries in South Africa since 1994, the context within which libraries function, library governance and legislative framework, government funding for redress, library technologies, library and information services education and the professional association. The article further highlights the importance of libraries in meeting the goals of the national development agenda towards entrenching a strong democracy and an educated and informed nation , Original publication is available at: http://dx.doi.org/10.1177/0340035215585100
- Full Text:
- Date Issued: 2015
- Authors: Satgoor, Ujala
- Date: 2015
- Subjects: Libraries , Library administration -- South Africa , Information services -- South Africa , Public libraries -- South Africa , Library science -- South Africa
- Language: English
- Type: Article
- Identifier: vital:6997 , http://hdl.handle.net/10962/d1019841 , ISSN ISSN: 0340-0352 , http://journals.sagepub.com/doi/10.1177/0340035215585100
- Description: Since the establishment of the first public library in 1818, the South African library and information services landscape has also been a reflection of the socio-political order and developments in the country. This article presents an historical perspective as well as an overview of libraries in South Africa since 1994, the context within which libraries function, library governance and legislative framework, government funding for redress, library technologies, library and information services education and the professional association. The article further highlights the importance of libraries in meeting the goals of the national development agenda towards entrenching a strong democracy and an educated and informed nation , Original publication is available at: http://dx.doi.org/10.1177/0340035215585100
- Full Text:
- Date Issued: 2015
Challenges faced by Teachers in applying reading strategies when teaching English reading in the foundation phase in the Mthatha District
- Authors: Cweba, Vuyokazi
- Date: 2015
- Subjects: Reading(Foundation phase) English language -- Study and teaching -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , D Ed
- Identifier: http://hdl.handle.net/11260/856 , vital:29938
- Description: This study sought to investigate challenges faced by teachers in applying reading strategies when teaching reading in the Foundation Phase in the Mthatha District in South Africa. The study was conducted at Four Junior Secondary Schools. It was prompted by a deep concern about challenges faced by teachers in applying reading strategies required in the Foundation Phase. While studies have been carried out on applying reading strategies in the Foundation Phase, few studies have looked at the factors impacting on reading in South African schools, especially in the Mthatha District where isiXhosa is the mother tongue. The method used in this study involved a qualitative approach. The study addressed the following research questions: What strategies are used in the Foundation Phase? What type of challenges are faced by teachers? To what extent are educators trained to teach reading in the Foundation Phase? Does the lack of resources affect the performance of learners? To what extent does the use of a second language affect the performance of Foundation Phase learners? Do teachers receive enough support from the Department of Education to teach reading? The study is a multiple-case study and data were collected through individual interviews and focus group interviews (sixteen teachers were interviewed). Content analysis guided the data analysis through themes derived from the subsidiary questions. Data reporting took the form of thick description and verbatim quotations in line with the qualitative approach of the study. A pilot study was conducted in two Junior Secondary Schools for the purpose of validity and reliability. ii The study`s findings revealed that: Different reading strategies were used by teachers in the Foundation Phase, teachers faced many challenges in applying reading strategies such as teacher training in the teaching of reading. This suggests that intervention is needed by the Department of Education such as providing relevant resources which are essential in order to address the problem of reading. Improvisation by teachers to improve reading material, insufficient allocation of time, multilingualism, teacher competence, lack of motivation and parental involvement in relation to learner performance in reading all need attention in order to solve problems. Furthermore, lack of resources hinders the reading ability of learners. The use of home language as a medium of instruction in teaching reading is highlighted. There is insufficient support by the Department of Education for Foundation Phase teachers to teach reading. Based on the study findings, the researcher has recommended that teachers should be urged to use reading strategies in a way that benefits learners. The use of reading strategies, therefore, needs more attention. Libraries should be built in these schools to enable learners to develop a culture of reading. Education development officers, subject advisors, lead teachers and parents should work together to improve the reading ability of Foundation Phase learners.
- Full Text:
- Date Issued: 2015
- Authors: Cweba, Vuyokazi
- Date: 2015
- Subjects: Reading(Foundation phase) English language -- Study and teaching -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , D Ed
- Identifier: http://hdl.handle.net/11260/856 , vital:29938
- Description: This study sought to investigate challenges faced by teachers in applying reading strategies when teaching reading in the Foundation Phase in the Mthatha District in South Africa. The study was conducted at Four Junior Secondary Schools. It was prompted by a deep concern about challenges faced by teachers in applying reading strategies required in the Foundation Phase. While studies have been carried out on applying reading strategies in the Foundation Phase, few studies have looked at the factors impacting on reading in South African schools, especially in the Mthatha District where isiXhosa is the mother tongue. The method used in this study involved a qualitative approach. The study addressed the following research questions: What strategies are used in the Foundation Phase? What type of challenges are faced by teachers? To what extent are educators trained to teach reading in the Foundation Phase? Does the lack of resources affect the performance of learners? To what extent does the use of a second language affect the performance of Foundation Phase learners? Do teachers receive enough support from the Department of Education to teach reading? The study is a multiple-case study and data were collected through individual interviews and focus group interviews (sixteen teachers were interviewed). Content analysis guided the data analysis through themes derived from the subsidiary questions. Data reporting took the form of thick description and verbatim quotations in line with the qualitative approach of the study. A pilot study was conducted in two Junior Secondary Schools for the purpose of validity and reliability. ii The study`s findings revealed that: Different reading strategies were used by teachers in the Foundation Phase, teachers faced many challenges in applying reading strategies such as teacher training in the teaching of reading. This suggests that intervention is needed by the Department of Education such as providing relevant resources which are essential in order to address the problem of reading. Improvisation by teachers to improve reading material, insufficient allocation of time, multilingualism, teacher competence, lack of motivation and parental involvement in relation to learner performance in reading all need attention in order to solve problems. Furthermore, lack of resources hinders the reading ability of learners. The use of home language as a medium of instruction in teaching reading is highlighted. There is insufficient support by the Department of Education for Foundation Phase teachers to teach reading. Based on the study findings, the researcher has recommended that teachers should be urged to use reading strategies in a way that benefits learners. The use of reading strategies, therefore, needs more attention. Libraries should be built in these schools to enable learners to develop a culture of reading. Education development officers, subject advisors, lead teachers and parents should work together to improve the reading ability of Foundation Phase learners.
- Full Text:
- Date Issued: 2015
Challenges of post-apartheid state-owned company pension fund reform: a case study of the controversy around the Transnet-Transport Pension Fund
- Authors: Goqoza, Noluyolo Juliet
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/54766 , vital:26610
- Description: This thesis examines the restructuring of the pension funds of Transnet, a South African state-owned company involved in transportation, from the 1990s. Two of its main pension funds, the Transport-Transnet Pension sub-Fund (TTPF) and the Transnet Second Defined Benefit Fund (TSDBF), have been surrounded by controversy, with major court actions brought by aggrieved pensioners in 2006-2012 and again from 2013, and smaller cases in 1997-1999 and 2004. (There were also a number of smaller cases, mostly unsuccessful, but the thesis will not examine them). The case that started in 2013 is the biggest class action in the country‟s history, and makes claims of serious mismanagement and bad faith against the Transnet management. But the fundamental grievance is that (according to the 2013 legal case) “more than 80% of pensioners earn less than R4 000.00 a month… 62 % earn less than R2 500.00… 45% of the pensioners earn less than the state‟s ordinary old-age pension” grant for the poor. Although that case is ongoing, this thesis examines the background and controversies that frame the case. It provides an overview of the history and development of the South African pensions system and South African state-owned companies; it examines how these have been shaped by the apartheid and post-apartheid periods, and by the rise of neo-liberalism; it examines the evolution of Transnet and its pensions systems, from the early days of the South African Railways and Harbours Administration (SAR&H, formed 1910), to its restructuring into the South African Transport Services (SATS) in 1982, and then into Transnet in 1990. The thesis shows that the operations of the TTPF and TSDBF, which are closed to new members, have had serious effects on pensioners that rely upon them. Pensions are very low (the main reason for the various court cases), and this is for a range of reasons. Annual increases in pensions are formally set at below-inflation levels, leading to falling real incomes. More pressure on pensioners‟ livelihoods has arisen from Transnet‟s cuts to other benefits, like the medical aid Transmed, provided to pensioners. While the schemes are solvent, the pensions generally started at a low base, partly because most pensioners were relatively poorly paid workers before retirement (and the pensions were linked to former salaries). There is also a racial dimension: while most white workers at SAR&H/ SATS and Transnet were poorly paid, black, Coloured and Indian workers were paid even worse, and, further, were only brought into the pension schemes late. Both TTPF and TSDBF are defined benefit funds, which means members are guaranteed specific benefits at retirement, with the employer obligated to inject funds to meet shortfalls where needed. Yet neither the state nor Transnet has been willing to take actions to lift the basic pensions, such as investments into the funds, or to make systematic ex gratia payments to bring the pensions to a reasonable level, to remove historic racial inequalities between pensioners, to increase medical aid co-payments or coverage or to otherwise address the pensioners‟ situation. It does not seem that the reason for the problems is that the two funds have been severely mismanaged or asset-stripped, as alleged in the 2013 class action: it must be noted that both funds report surpluses. But the surpluses are possible because the pensions are low and falling in real terms, and the numbers of pensioners declining due to deaths. It seems clear that Transnet is unable or unwilling to act to decisively improve the situation of the pensioners: ensuring a surplus on existing pension funds is a major goal. This is partly because Transnet itself has ongoing financial problems, and partly because it operates in the context of neo-liberal restructuring, like corporatisation, commercialisation and privatisation, which places limits on the additional funding of the funds. At the same time, the pensioners have very little real, as opposed to a nominal, say in the administration of the pension schemes, limiting their ability to affect the rules and administration or raise issues. The thesis seeks to use historical institutionalism, which sees policies and major institutions, including state-owned companies, as shaped by power and conflict, especially between classes. This is used to try and explain changing state policies and the changing role and actions of state-owned companies, as a way of understanding Transnet‟s actions, as well as its treatment of its pensioners.
- Full Text:
- Date Issued: 2015
- Authors: Goqoza, Noluyolo Juliet
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/54766 , vital:26610
- Description: This thesis examines the restructuring of the pension funds of Transnet, a South African state-owned company involved in transportation, from the 1990s. Two of its main pension funds, the Transport-Transnet Pension sub-Fund (TTPF) and the Transnet Second Defined Benefit Fund (TSDBF), have been surrounded by controversy, with major court actions brought by aggrieved pensioners in 2006-2012 and again from 2013, and smaller cases in 1997-1999 and 2004. (There were also a number of smaller cases, mostly unsuccessful, but the thesis will not examine them). The case that started in 2013 is the biggest class action in the country‟s history, and makes claims of serious mismanagement and bad faith against the Transnet management. But the fundamental grievance is that (according to the 2013 legal case) “more than 80% of pensioners earn less than R4 000.00 a month… 62 % earn less than R2 500.00… 45% of the pensioners earn less than the state‟s ordinary old-age pension” grant for the poor. Although that case is ongoing, this thesis examines the background and controversies that frame the case. It provides an overview of the history and development of the South African pensions system and South African state-owned companies; it examines how these have been shaped by the apartheid and post-apartheid periods, and by the rise of neo-liberalism; it examines the evolution of Transnet and its pensions systems, from the early days of the South African Railways and Harbours Administration (SAR&H, formed 1910), to its restructuring into the South African Transport Services (SATS) in 1982, and then into Transnet in 1990. The thesis shows that the operations of the TTPF and TSDBF, which are closed to new members, have had serious effects on pensioners that rely upon them. Pensions are very low (the main reason for the various court cases), and this is for a range of reasons. Annual increases in pensions are formally set at below-inflation levels, leading to falling real incomes. More pressure on pensioners‟ livelihoods has arisen from Transnet‟s cuts to other benefits, like the medical aid Transmed, provided to pensioners. While the schemes are solvent, the pensions generally started at a low base, partly because most pensioners were relatively poorly paid workers before retirement (and the pensions were linked to former salaries). There is also a racial dimension: while most white workers at SAR&H/ SATS and Transnet were poorly paid, black, Coloured and Indian workers were paid even worse, and, further, were only brought into the pension schemes late. Both TTPF and TSDBF are defined benefit funds, which means members are guaranteed specific benefits at retirement, with the employer obligated to inject funds to meet shortfalls where needed. Yet neither the state nor Transnet has been willing to take actions to lift the basic pensions, such as investments into the funds, or to make systematic ex gratia payments to bring the pensions to a reasonable level, to remove historic racial inequalities between pensioners, to increase medical aid co-payments or coverage or to otherwise address the pensioners‟ situation. It does not seem that the reason for the problems is that the two funds have been severely mismanaged or asset-stripped, as alleged in the 2013 class action: it must be noted that both funds report surpluses. But the surpluses are possible because the pensions are low and falling in real terms, and the numbers of pensioners declining due to deaths. It seems clear that Transnet is unable or unwilling to act to decisively improve the situation of the pensioners: ensuring a surplus on existing pension funds is a major goal. This is partly because Transnet itself has ongoing financial problems, and partly because it operates in the context of neo-liberal restructuring, like corporatisation, commercialisation and privatisation, which places limits on the additional funding of the funds. At the same time, the pensioners have very little real, as opposed to a nominal, say in the administration of the pension schemes, limiting their ability to affect the rules and administration or raise issues. The thesis seeks to use historical institutionalism, which sees policies and major institutions, including state-owned companies, as shaped by power and conflict, especially between classes. This is used to try and explain changing state policies and the changing role and actions of state-owned companies, as a way of understanding Transnet‟s actions, as well as its treatment of its pensioners.
- Full Text:
- Date Issued: 2015
Challenges to service delivery in the Department of Home Affairs
- Authors: Mahlungulu, Zimkitha
- Date: 2015
- Subjects: Public administration -- South Africa -- Eastern Cape , Customer services -- South Africa -- Eastern Cape , South Africa. Department of Home Affairs
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/6573 , vital:21114
- Description: The South African public sector is important for the sustainable growth and development of the country. One of its major responsibilities is to ensure that all citizens have access to and receive services. Achieving a high degree of productivity is an important objective of public service organisations across the world, given the pressure to deliver quality public goods and services within the limits of ever-increasing resource constraints. The South African public service is no exception to this global phenomenon. The challenge of the public service is therefore to continuously improve performance in order to meet citizens’ needs. The focus of this study is the challenges facing service delivery in the Department of Home Affairs. The aim of this study is to explore and describe the challenges that hinder full transformation and maximum customer/client satisfaction in regards to service delivery offered by the Department of Home Affairs. The objectives are: to identify the challenges experienced by staff offering services to clients at the Department of Home Affairs and to identify the problems experienced by clients who receive services at Home Affairs. The study employs a qualitative research methodology and uses observation and individual interviews as data collections tools. The findings from both sources indicate that the clients were not happy with the quality of service they receive at the ID section. Amongst other things, they complained about lack of information, lack of guidance, unprofessional staff, and technical problems that they had experienced. However, the staff also encountered a number of challenges, including being short staffed, lack of resources, and system problems as the system is new to them and they have not received enough training before it was implemented.
- Full Text:
- Date Issued: 2015
- Authors: Mahlungulu, Zimkitha
- Date: 2015
- Subjects: Public administration -- South Africa -- Eastern Cape , Customer services -- South Africa -- Eastern Cape , South Africa. Department of Home Affairs
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/6573 , vital:21114
- Description: The South African public sector is important for the sustainable growth and development of the country. One of its major responsibilities is to ensure that all citizens have access to and receive services. Achieving a high degree of productivity is an important objective of public service organisations across the world, given the pressure to deliver quality public goods and services within the limits of ever-increasing resource constraints. The South African public service is no exception to this global phenomenon. The challenge of the public service is therefore to continuously improve performance in order to meet citizens’ needs. The focus of this study is the challenges facing service delivery in the Department of Home Affairs. The aim of this study is to explore and describe the challenges that hinder full transformation and maximum customer/client satisfaction in regards to service delivery offered by the Department of Home Affairs. The objectives are: to identify the challenges experienced by staff offering services to clients at the Department of Home Affairs and to identify the problems experienced by clients who receive services at Home Affairs. The study employs a qualitative research methodology and uses observation and individual interviews as data collections tools. The findings from both sources indicate that the clients were not happy with the quality of service they receive at the ID section. Amongst other things, they complained about lack of information, lack of guidance, unprofessional staff, and technical problems that they had experienced. However, the staff also encountered a number of challenges, including being short staffed, lack of resources, and system problems as the system is new to them and they have not received enough training before it was implemented.
- Full Text:
- Date Issued: 2015
Change in Roviana Lagoon Coral Reef ethnobiology:
- Aswani, Shankar, Albert, Simon
- Authors: Aswani, Shankar , Albert, Simon
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/145460 , vital:38440 , ISBN 9783319237633 , DOI: 10.1007/978-3-319-23763-3_10
- Description: Coral reefs are iconic for their beauty and biodiversity, and are of great socioeconomic and cultural importance for many coastal communities across the tropics. However, little is known about people’s local classification and their social and ecological relationship with these habitats. This chapter describes Roviana people’s changing ecological and social relationship with their coral reefs, which are increasingly being damaged by humans. First, we combined ecological and social data to describe people’s classification of local coral reefs in tandem with the productive practices conducted in these habitats. Second, we examined local perceptions and recognized effects of environmental and climatic changes on reefs over the last two decades. Finally, we measured changes in fishing activities and in the taxonomic systems (between 1995 and 2011) to evaluate if recent social and economic change has led to the erosion of marine indigenous ecological knowledge and associated practices. Studying people’s changing perceptions of their coral reefs is crucial to understand their ability to identify and adapt to environmental transformations. Simply, the way local people perceive the state of the environment is not only important in terms of changes in local epistemology but also has important implications for how resources are used and managed, and this information can be coupled with scientific one for a broader management strategy.
- Full Text:
- Date Issued: 2015
- Authors: Aswani, Shankar , Albert, Simon
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/145460 , vital:38440 , ISBN 9783319237633 , DOI: 10.1007/978-3-319-23763-3_10
- Description: Coral reefs are iconic for their beauty and biodiversity, and are of great socioeconomic and cultural importance for many coastal communities across the tropics. However, little is known about people’s local classification and their social and ecological relationship with these habitats. This chapter describes Roviana people’s changing ecological and social relationship with their coral reefs, which are increasingly being damaged by humans. First, we combined ecological and social data to describe people’s classification of local coral reefs in tandem with the productive practices conducted in these habitats. Second, we examined local perceptions and recognized effects of environmental and climatic changes on reefs over the last two decades. Finally, we measured changes in fishing activities and in the taxonomic systems (between 1995 and 2011) to evaluate if recent social and economic change has led to the erosion of marine indigenous ecological knowledge and associated practices. Studying people’s changing perceptions of their coral reefs is crucial to understand their ability to identify and adapt to environmental transformations. Simply, the way local people perceive the state of the environment is not only important in terms of changes in local epistemology but also has important implications for how resources are used and managed, and this information can be coupled with scientific one for a broader management strategy.
- Full Text:
- Date Issued: 2015
Change management: transformational issues in South-African rugby
- Authors: Erasmus, Innis
- Date: 2015
- Subjects: Organizational change -- Management , Rugby football -- South Africa , Sports administration
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/48819 , vital:41143
- Description: The history of the sport rugby evolved from a football game more than a century ago, in England, in a town called Rugby when a young boy by the name of William Webb Ellis picked up the ball and ran to score a try. In the last two decades in South Africa the transformation process in getting more players of colour in the national team has become a real big issue. The fast changing society since 1995, the year in which the Springboks won their first Rugby World Cup, is according to government and critics not represented in the senior national side. Change management is a business management approach to implement procedures to deal with changes and to be able to reach the desired future state by profiting from the changing opportunities. SARU wants to address these issues and changes with their Strategic Transformational Plan. The purpose of this treatise was to study the perception of the junior players on the changes in rugby and the STP. The key drivers which will have influences on change management within the sport organisation were examined by the research. With the research objectives in mind a literature review was performed to create and develop a hypothesized model, which could be tested by the design of a measuring instrument which collected quantitative data for statistical results and analysis. The interpretation of the results of the research showed that Engagement, Coaching and Mentoring, Medical and Healthcare, Education/Schooling and Culture have positive associations and influences on change management. Transformational plans, Conditioning and nutrition’s relationship with change management and influences were accepted for the null hypotheses. Finally, change management and the various issues of transformation in SA Rugby showed to be valuable, measurable to a certain extent, and its recommendations actionable. The practical significant differences between the perceptions of the race groups (White, Coloured and African) illustrated valuable information for future communications and possible studies. This study and its proposed model on change management was a benefit to all the stakeholders and sport organisation going through changes and transformation in South Africa.
- Full Text:
- Date Issued: 2015
- Authors: Erasmus, Innis
- Date: 2015
- Subjects: Organizational change -- Management , Rugby football -- South Africa , Sports administration
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/48819 , vital:41143
- Description: The history of the sport rugby evolved from a football game more than a century ago, in England, in a town called Rugby when a young boy by the name of William Webb Ellis picked up the ball and ran to score a try. In the last two decades in South Africa the transformation process in getting more players of colour in the national team has become a real big issue. The fast changing society since 1995, the year in which the Springboks won their first Rugby World Cup, is according to government and critics not represented in the senior national side. Change management is a business management approach to implement procedures to deal with changes and to be able to reach the desired future state by profiting from the changing opportunities. SARU wants to address these issues and changes with their Strategic Transformational Plan. The purpose of this treatise was to study the perception of the junior players on the changes in rugby and the STP. The key drivers which will have influences on change management within the sport organisation were examined by the research. With the research objectives in mind a literature review was performed to create and develop a hypothesized model, which could be tested by the design of a measuring instrument which collected quantitative data for statistical results and analysis. The interpretation of the results of the research showed that Engagement, Coaching and Mentoring, Medical and Healthcare, Education/Schooling and Culture have positive associations and influences on change management. Transformational plans, Conditioning and nutrition’s relationship with change management and influences were accepted for the null hypotheses. Finally, change management and the various issues of transformation in SA Rugby showed to be valuable, measurable to a certain extent, and its recommendations actionable. The practical significant differences between the perceptions of the race groups (White, Coloured and African) illustrated valuable information for future communications and possible studies. This study and its proposed model on change management was a benefit to all the stakeholders and sport organisation going through changes and transformation in South Africa.
- Full Text:
- Date Issued: 2015
Changes in diet resource use by elephants, Loxodonta Africana, due to changes in resource availability in the Addo National Park
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
Characterisation of performance limiting defects in photovoltaic devices using electroluminescence and related techniques
- Authors: Crozier, Jacqueline Louise
- Date: 2015
- Subjects: Photovoltaic cells Solar cells Photovoltaic power systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11004 , vital:26866
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy an environmentally friendly, sustainable alternative to fossil fuel energy sources. Solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of PV modules can limited by the degradation and defects. PV modules can be characterised using various opto-electronic techniques, each providing information about the performance of the module. The current-voltage (I-V) characteristic curve of a module being the most commonly used characterisation technique. The I-V curve is typically measured in outdoor, fully illuminated, conditions. This allows performance parameters such as short circuit current (ISC), open circuit voltage (VOC) and maximum power (PMAX) to be determined. However, it can be difficult to determine the root cause of the performance drop from the I-V curve alone. Electroluminescence (EL) is a module characterisation technique that allows defects and failures in PV modules to be successfully identified. This study investigates the characterisation of solar cells and photovoltaic modules using EL. EL occurs when a solar cell or module is forward biased and the injected electron-hole pairs recombine radiatively. The intensity of the emitted EL is related the applied voltage and the material properties. EL imaging is a useful characterisation technique in identifying module defects and failures. Defects such as micro-cracks, broken contact fingers and fractures are detected in EL images as well as material features such as grain boundaries. The common defects in crystalline silicon are catalogued and the possible causes are discussed. An experimental setup was developed in order to systematically take a high resolution EL image of every cell in the module and record the applied voltage and current. This produces a very detailed, clear, image of each cell with a pixel size in the micrometre range. This process is time consuming to acquire an EL image of an entire module so alternatively a different setup can be used and an EL image of a whole module can be captured in a single frame with an increased pixel size in the millimetre range. For EL imaging a silicon charge-coupled device (CCD) camera was used because it has very good spatial resolution however this sensor is only sensitive to wavelength in the range of 300-1200 nm. There is an overlap in wavelengths from about 900 to 1100 nm allowing the EL emitted from silicon solar cells to be detected. In conjunction with the high-resolution EL system an image processing program was developed to crop, adjust and align the images so only the relevant cell was included. This program also automatically detects certain defects that have a regular shape. Micro-cracks, broken fingers and striation rings are automatically identified. The program has an adjustable sensitivity to identify small or large defects. Defective cells are distinguished from undamaged cells by comparing the binary images to the ideal, undamaged cell. The current-voltage curves and the performance parameters of modules were compared with the EL images in order to discuss and identify power limiting defects. Features that remove significant portions of the cell from electrical contact such as micro-cracks are shown to have a larger effect of the performance of the module. Other features such as broken contact fingers, contact forming failures and striation rings do not significantly lower the performance of the module. Thus an understanding of how different features affect the module performance is important in order to correctly interpret the EL results. The intensity of the luminescence emitted is related to the applied voltage and the quantum efficiency of the cell material. The spectrum of the emitted luminescence was modelled and related to the recombination properties of the cell such as surface recombination velocity and minority carrier diffusion length/lifetime. In this study the emitted spectrum was modelled and the effects of recombination properties of the cell on the emitted spectrum were examined. The spectrum of the detected EL was modelled, dependent on the sensitivity of the camera, the transmission of the filters and the emitted photon flux. The integration of short-pass filters into the experimental setup in order to isolate short-wavelength luminescence was discussed. There is a proportional relationship between the intensity of the emitted EL and the local junction voltage. Resistive losses like series and shunt resistances lower the applied voltage and thus affect the EL image. The voltage dependence was assessed by comparing EL images taken at different applied biases. Analysis of the variation in EL intensity with voltage was successful in determining the origin of certain features in an EL image. Certain defects, those that are related to series resistance or shunting are highly voltage dependent. When a feature has little or no dependence on voltage then the defect could be in the laminate layers and not in the cell material. The results of this study allow for in-depth analysis of the defects found in PV modules using the high resolution EL imaging system and the image processing routine. The development of an image processing routine allows the interpretation of the EL image to be done automatically, resulting in a faster and more efficient process. By understanding the defects visible in the EL image, the test is more meaningful and allows the results to be used to predict module performance and potential failures.
- Full Text:
- Date Issued: 2015
- Authors: Crozier, Jacqueline Louise
- Date: 2015
- Subjects: Photovoltaic cells Solar cells Photovoltaic power systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11004 , vital:26866
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy an environmentally friendly, sustainable alternative to fossil fuel energy sources. Solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of PV modules can limited by the degradation and defects. PV modules can be characterised using various opto-electronic techniques, each providing information about the performance of the module. The current-voltage (I-V) characteristic curve of a module being the most commonly used characterisation technique. The I-V curve is typically measured in outdoor, fully illuminated, conditions. This allows performance parameters such as short circuit current (ISC), open circuit voltage (VOC) and maximum power (PMAX) to be determined. However, it can be difficult to determine the root cause of the performance drop from the I-V curve alone. Electroluminescence (EL) is a module characterisation technique that allows defects and failures in PV modules to be successfully identified. This study investigates the characterisation of solar cells and photovoltaic modules using EL. EL occurs when a solar cell or module is forward biased and the injected electron-hole pairs recombine radiatively. The intensity of the emitted EL is related the applied voltage and the material properties. EL imaging is a useful characterisation technique in identifying module defects and failures. Defects such as micro-cracks, broken contact fingers and fractures are detected in EL images as well as material features such as grain boundaries. The common defects in crystalline silicon are catalogued and the possible causes are discussed. An experimental setup was developed in order to systematically take a high resolution EL image of every cell in the module and record the applied voltage and current. This produces a very detailed, clear, image of each cell with a pixel size in the micrometre range. This process is time consuming to acquire an EL image of an entire module so alternatively a different setup can be used and an EL image of a whole module can be captured in a single frame with an increased pixel size in the millimetre range. For EL imaging a silicon charge-coupled device (CCD) camera was used because it has very good spatial resolution however this sensor is only sensitive to wavelength in the range of 300-1200 nm. There is an overlap in wavelengths from about 900 to 1100 nm allowing the EL emitted from silicon solar cells to be detected. In conjunction with the high-resolution EL system an image processing program was developed to crop, adjust and align the images so only the relevant cell was included. This program also automatically detects certain defects that have a regular shape. Micro-cracks, broken fingers and striation rings are automatically identified. The program has an adjustable sensitivity to identify small or large defects. Defective cells are distinguished from undamaged cells by comparing the binary images to the ideal, undamaged cell. The current-voltage curves and the performance parameters of modules were compared with the EL images in order to discuss and identify power limiting defects. Features that remove significant portions of the cell from electrical contact such as micro-cracks are shown to have a larger effect of the performance of the module. Other features such as broken contact fingers, contact forming failures and striation rings do not significantly lower the performance of the module. Thus an understanding of how different features affect the module performance is important in order to correctly interpret the EL results. The intensity of the luminescence emitted is related to the applied voltage and the quantum efficiency of the cell material. The spectrum of the emitted luminescence was modelled and related to the recombination properties of the cell such as surface recombination velocity and minority carrier diffusion length/lifetime. In this study the emitted spectrum was modelled and the effects of recombination properties of the cell on the emitted spectrum were examined. The spectrum of the detected EL was modelled, dependent on the sensitivity of the camera, the transmission of the filters and the emitted photon flux. The integration of short-pass filters into the experimental setup in order to isolate short-wavelength luminescence was discussed. There is a proportional relationship between the intensity of the emitted EL and the local junction voltage. Resistive losses like series and shunt resistances lower the applied voltage and thus affect the EL image. The voltage dependence was assessed by comparing EL images taken at different applied biases. Analysis of the variation in EL intensity with voltage was successful in determining the origin of certain features in an EL image. Certain defects, those that are related to series resistance or shunting are highly voltage dependent. When a feature has little or no dependence on voltage then the defect could be in the laminate layers and not in the cell material. The results of this study allow for in-depth analysis of the defects found in PV modules using the high resolution EL imaging system and the image processing routine. The development of an image processing routine allows the interpretation of the EL image to be done automatically, resulting in a faster and more efficient process. By understanding the defects visible in the EL image, the test is more meaningful and allows the results to be used to predict module performance and potential failures.
- Full Text:
- Date Issued: 2015
Characterisation of the HSP70-HSP90 organising protein gene and its link to cancer
- Authors: Weeks, Stacey
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/56006 , vital:26764
- Description: HOP (Heat shock protein 70/ Heat shock protein 90 organising protein) is a co-chaperone essential for client protein transfer from HSP70 to HSP90 within the HSP90 chaperone machine and has been found to be up-regulated in various cancers. However, minimal in vitro information can be found on the regulation of HOP expression. The aim of this study was to analyse the HOP gene structure across known orthologues, identify and characterise the HOP promoter, and identify the regulatory mechanisms influencing the expression of HOP in cancer. We hypothesized that the expression of HOP in cancer cells is likely regulated by oncogenic signalling pathways linked to cis-elements within the HOP promoter. An initial study of the evolution of the HOP gene speciation was performed across identified orthologues using Mega5.2. The evolutionary pathway of the HOP gene was traced from the unicellular organisms to fish, to amphibian and then to land mammal. The synteny across the orthologues was identified and the co-expression profile of HOP analysed. We identified the putative promoter region for HOP in silico and in vitro. Luciferase reporter assays were utilized to demonstrate promoter activity of the upstream region in vitro. Bioinformatic analysis of the active promoter region identified a large CpG island and a range of putative cis-elements. Many of the cis-elements interact with transcription factors which are activated by oncogenic pathways. We therefore tested the regulation of HOP levels by rat sarcoma viral oncogene homologue (RAS). Cancer cell lines were transfected with mutated RAS to observe the effect of constitutively active RAS expression on the production of HOP using qRT-PCR and Western Blot analyses. Additionally, inhibitors of the RAS signalling pathway were utilised to confirm the regulatory effect of mutated RAS on HOP expression. In cancer cell lines containing mutated RAS (Hs578T), HOP was up-regulated via a mechanism involving the MAPK signalling pathway and the ETS-1 and C/EBPβ cis-elements within the HOP promoter. These findings suggest for the first time that Hop expression in cancer may be regulated by RAS activation of the HOP promoter. Additionally, this study allowed us to determine the murine system to be the most suited genetic model organism with which to study the function of human HOP.
- Full Text:
- Date Issued: 2015
- Authors: Weeks, Stacey
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/56006 , vital:26764
- Description: HOP (Heat shock protein 70/ Heat shock protein 90 organising protein) is a co-chaperone essential for client protein transfer from HSP70 to HSP90 within the HSP90 chaperone machine and has been found to be up-regulated in various cancers. However, minimal in vitro information can be found on the regulation of HOP expression. The aim of this study was to analyse the HOP gene structure across known orthologues, identify and characterise the HOP promoter, and identify the regulatory mechanisms influencing the expression of HOP in cancer. We hypothesized that the expression of HOP in cancer cells is likely regulated by oncogenic signalling pathways linked to cis-elements within the HOP promoter. An initial study of the evolution of the HOP gene speciation was performed across identified orthologues using Mega5.2. The evolutionary pathway of the HOP gene was traced from the unicellular organisms to fish, to amphibian and then to land mammal. The synteny across the orthologues was identified and the co-expression profile of HOP analysed. We identified the putative promoter region for HOP in silico and in vitro. Luciferase reporter assays were utilized to demonstrate promoter activity of the upstream region in vitro. Bioinformatic analysis of the active promoter region identified a large CpG island and a range of putative cis-elements. Many of the cis-elements interact with transcription factors which are activated by oncogenic pathways. We therefore tested the regulation of HOP levels by rat sarcoma viral oncogene homologue (RAS). Cancer cell lines were transfected with mutated RAS to observe the effect of constitutively active RAS expression on the production of HOP using qRT-PCR and Western Blot analyses. Additionally, inhibitors of the RAS signalling pathway were utilised to confirm the regulatory effect of mutated RAS on HOP expression. In cancer cell lines containing mutated RAS (Hs578T), HOP was up-regulated via a mechanism involving the MAPK signalling pathway and the ETS-1 and C/EBPβ cis-elements within the HOP promoter. These findings suggest for the first time that Hop expression in cancer may be regulated by RAS activation of the HOP promoter. Additionally, this study allowed us to determine the murine system to be the most suited genetic model organism with which to study the function of human HOP.
- Full Text:
- Date Issued: 2015
Characterization and analysis of NTP amplification based DDoS attacks
- Rudman, Lauren, Irwin, Barry V W
- Authors: Rudman, Lauren , Irwin, Barry V W
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429285 , vital:72573 , 10.1109/ISSA.2015.7335069
- Description: Network Time Protocol based DDoS attacks saw a lot of popularity throughout 2014. This paper shows the characterization and analysis of two large datasets containing packets from NTP based DDoS attacks captured in South Africa. Using a series of Python based tools, the dataset is analysed according to specific parts of the packet headers. These include the source IP address and Time-to-live (TTL) values. The analysis found the top source addresses and looked at the TTL values observed for each address. These TTL values can be used to calculate the probable operating system or DDoS attack tool used by an attacker. We found that each TTL value seen for an address can indicate the number of hosts attacking the address or indicate minor routing changes. The Time-to-Live values, as a whole, are then analysed to find the total number used throughout each attack. The most frequent TTL values are then found and show that the migratory of them indicate the attackers are using an initial TTL of 255. This value can indicate the use of a certain DDoS tool that creates packets with that exact initial TTL. The TTL values are then put into groups that can show the number of IP addresses a group of hosts are targeting.
- Full Text:
- Date Issued: 2015
- Authors: Rudman, Lauren , Irwin, Barry V W
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429285 , vital:72573 , 10.1109/ISSA.2015.7335069
- Description: Network Time Protocol based DDoS attacks saw a lot of popularity throughout 2014. This paper shows the characterization and analysis of two large datasets containing packets from NTP based DDoS attacks captured in South Africa. Using a series of Python based tools, the dataset is analysed according to specific parts of the packet headers. These include the source IP address and Time-to-live (TTL) values. The analysis found the top source addresses and looked at the TTL values observed for each address. These TTL values can be used to calculate the probable operating system or DDoS attack tool used by an attacker. We found that each TTL value seen for an address can indicate the number of hosts attacking the address or indicate minor routing changes. The Time-to-Live values, as a whole, are then analysed to find the total number used throughout each attack. The most frequent TTL values are then found and show that the migratory of them indicate the attackers are using an initial TTL of 255. This value can indicate the use of a certain DDoS tool that creates packets with that exact initial TTL. The TTL values are then put into groups that can show the number of IP addresses a group of hosts are targeting.
- Full Text:
- Date Issued: 2015
Characterization of polychlorinated biphenyl residues in the North End lake and Port Elizabeth harbour, South Africa
- Authors: Kampire, Edwige
- Date: 2015
- Subjects: Marine pollution -- South Africa -- Port Elizabeth , Estuarine pollution -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7903 , vital:24320
- Description: Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) are widespread in aquatic systems, they can bioaccumulate in the tissues of aquatic organisms, especially fish as they occupy a position near the top of the aquatic food web. PCBs are among the most toxic substances and have been shown to cause many adverse effects to humans and wildlife. High health risks are associated with populations that follow a diet high in fat content such as fish and shellfish in which PCBs bioaccumulate. Given the importance of industries and the potential health concerns of exposure to PCBs, the lack of information on environmental levels of PCBs in South Africa (SA) is significant and concerning. Less attention has been directed to analysis of PCBs in the South African environments due to high cost and lack of appropriate equipment. This study was the first conducted in order to assess the levels of PCBs in the environment of Nelson Mandela Bay Municipality (Port Elizabeth). The research was directed at determining the PCB levels in water, sediments, fish and mussels collected in the Nelson Mandela Bay Municipality. The sampling sites, North End Lake (NEL) and Port Elizabeth Harbour (PEH) were selected based on their location and the importance of activities taking place in these areas. In total 456 samples of water (dissolved and particulate phases), sediments, mussels and tissues of fish were analysed. Suitable analytical methods were based on the equipment and materials available at the Nelson Mandela Metropolitan University. Gas chromatography-mass spectrometry (GC/MS) was used to quantify PCBs in the samples using the internal standard method. Six indicator congeners (PCB nos. 28, 52, 101, 138, 153, 180) were chosen because they are mainly present in most PCB mixtures in environmental samples and they are recommended for regular monitoring. These congeners represent about 50% of the total non-dioxin like (NDL) PCBs in food. All these congeners were detected in the samples analysed. The total PCB concentrations in the sediments from the NEL and PEH ranged from 1.60 to 3.06 and from 0.56 to 2.35 ng g-1 dry weight, respectively. The concentrations of total PCBs in Mytilus galloprovincialis ranged from 14.48 to 21.37 ng g-1 wet weight and from 20.84 to 31.34 ng g-1 wet weight in Perna perna. Total PCBs in water ranged from 0.18 to 0.355 ng L-1. The concentrations of total PCBs in the liver, gonads, gills and muscle were 95.69, 57.49, 44.63, 34.14 ng g-1 lipid weight in Cyprinus carpio and 119.73, 59.21, 49.78, 34.63 ng g-1 in Oreochromis mossambicus, respectively. Fish liver was the most contaminated organ due to its high lipid content compared to other parts of fish analysed. The NEL was found to be more contaminated than the PEH. The main potential sources of PCB pollutants in both areas of this study are industrial and municipal discharges. The NEL is surrounded by many industries and serves as a potential pollutant sink due to wastewater and inflow entering into this lake. Four 0.227 kg meals of the edible part of fish (muscle) per month were recommended based on the non-cancer health endpoint and one 0.227 kg meal per month was recommended based on the cancer health endpoint. This research contributed to notify the public and relevant governmental departments on the PCB pollution status of sediments, water and aquatic life in the PEH and NEL.
- Full Text:
- Date Issued: 2015
- Authors: Kampire, Edwige
- Date: 2015
- Subjects: Marine pollution -- South Africa -- Port Elizabeth , Estuarine pollution -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/7903 , vital:24320
- Description: Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) are widespread in aquatic systems, they can bioaccumulate in the tissues of aquatic organisms, especially fish as they occupy a position near the top of the aquatic food web. PCBs are among the most toxic substances and have been shown to cause many adverse effects to humans and wildlife. High health risks are associated with populations that follow a diet high in fat content such as fish and shellfish in which PCBs bioaccumulate. Given the importance of industries and the potential health concerns of exposure to PCBs, the lack of information on environmental levels of PCBs in South Africa (SA) is significant and concerning. Less attention has been directed to analysis of PCBs in the South African environments due to high cost and lack of appropriate equipment. This study was the first conducted in order to assess the levels of PCBs in the environment of Nelson Mandela Bay Municipality (Port Elizabeth). The research was directed at determining the PCB levels in water, sediments, fish and mussels collected in the Nelson Mandela Bay Municipality. The sampling sites, North End Lake (NEL) and Port Elizabeth Harbour (PEH) were selected based on their location and the importance of activities taking place in these areas. In total 456 samples of water (dissolved and particulate phases), sediments, mussels and tissues of fish were analysed. Suitable analytical methods were based on the equipment and materials available at the Nelson Mandela Metropolitan University. Gas chromatography-mass spectrometry (GC/MS) was used to quantify PCBs in the samples using the internal standard method. Six indicator congeners (PCB nos. 28, 52, 101, 138, 153, 180) were chosen because they are mainly present in most PCB mixtures in environmental samples and they are recommended for regular monitoring. These congeners represent about 50% of the total non-dioxin like (NDL) PCBs in food. All these congeners were detected in the samples analysed. The total PCB concentrations in the sediments from the NEL and PEH ranged from 1.60 to 3.06 and from 0.56 to 2.35 ng g-1 dry weight, respectively. The concentrations of total PCBs in Mytilus galloprovincialis ranged from 14.48 to 21.37 ng g-1 wet weight and from 20.84 to 31.34 ng g-1 wet weight in Perna perna. Total PCBs in water ranged from 0.18 to 0.355 ng L-1. The concentrations of total PCBs in the liver, gonads, gills and muscle were 95.69, 57.49, 44.63, 34.14 ng g-1 lipid weight in Cyprinus carpio and 119.73, 59.21, 49.78, 34.63 ng g-1 in Oreochromis mossambicus, respectively. Fish liver was the most contaminated organ due to its high lipid content compared to other parts of fish analysed. The NEL was found to be more contaminated than the PEH. The main potential sources of PCB pollutants in both areas of this study are industrial and municipal discharges. The NEL is surrounded by many industries and serves as a potential pollutant sink due to wastewater and inflow entering into this lake. Four 0.227 kg meals of the edible part of fish (muscle) per month were recommended based on the non-cancer health endpoint and one 0.227 kg meal per month was recommended based on the cancer health endpoint. This research contributed to notify the public and relevant governmental departments on the PCB pollution status of sediments, water and aquatic life in the PEH and NEL.
- Full Text:
- Date Issued: 2015
Characterization of porphyrin nanorods on fluorine doped tin oxide glass sheet
- George, Reama C, Falgenhauer, Jane, Geis, Clemens, Nyokong, Tebello, Schlettwein, Derck
- Authors: George, Reama C , Falgenhauer, Jane , Geis, Clemens , Nyokong, Tebello , Schlettwein, Derck
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193542 , vital:45344 , xlink:href="https://doi.org/10.1142/S1088424615500923"
- Description: Porphyrin nanorods (PNR) have been fabricated by electrostatic self-assembly of two oppositely charged porphyrin molecules. The free base meso-tetra-(4-phenylsulphonate) porphyrin (TPPS4)4) served as negatively charged counterpart for the positively charged metallo meso-tetra(4-NN-methylpyridyl) porphyrins (MTM’PyP) with either Sn, Co, Mn or In as central metal M. Films of PNR were prepared on fluorine doped tin oxide glass sheets (FTO) by using a drop-dry method. The electronic spectra revealed J-aggregation of the charged molecules for the colloid PNR as well as for the films. Transmission electron microscopy confirmed the formation of porphyrin nanorods. The laser microscope and scanning electron microscope (SEM) images of the PNR/FTO films showed the formation of three kinds of structures in the films which consist of differently branched or linear needles with their main axis grown in the direction of the solvent flow during preparation. During cyclic voltammetry either applying negative potentials from 0.0 V to -1.0 V or positive potentials from 0.0 V to ++2.2 V irreversible reduction or oxidation reactions were detected for the films. Consistently, SEM images taken following cyclic voltammetry showed the disintegration of the PNR on the films into smaller subunits. Spectroelectrochemical measurements showed the formation of porphyrin anionic radicals during oxidation by a decrease in the absorption intensities and broadening of spectra with an additional band appearing around 900 nm. A similar trend was observed when negative potentials were applied but in this case the cationic radical was produced. In both cases the decrease of the intensity of the J-aggregate confirms a loss of intermolecular coupling, again consistent with the smaller subunits observed in SEM analysis.
- Full Text:
- Date Issued: 2015
- Authors: George, Reama C , Falgenhauer, Jane , Geis, Clemens , Nyokong, Tebello , Schlettwein, Derck
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193542 , vital:45344 , xlink:href="https://doi.org/10.1142/S1088424615500923"
- Description: Porphyrin nanorods (PNR) have been fabricated by electrostatic self-assembly of two oppositely charged porphyrin molecules. The free base meso-tetra-(4-phenylsulphonate) porphyrin (TPPS4)4) served as negatively charged counterpart for the positively charged metallo meso-tetra(4-NN-methylpyridyl) porphyrins (MTM’PyP) with either Sn, Co, Mn or In as central metal M. Films of PNR were prepared on fluorine doped tin oxide glass sheets (FTO) by using a drop-dry method. The electronic spectra revealed J-aggregation of the charged molecules for the colloid PNR as well as for the films. Transmission electron microscopy confirmed the formation of porphyrin nanorods. The laser microscope and scanning electron microscope (SEM) images of the PNR/FTO films showed the formation of three kinds of structures in the films which consist of differently branched or linear needles with their main axis grown in the direction of the solvent flow during preparation. During cyclic voltammetry either applying negative potentials from 0.0 V to -1.0 V or positive potentials from 0.0 V to ++2.2 V irreversible reduction or oxidation reactions were detected for the films. Consistently, SEM images taken following cyclic voltammetry showed the disintegration of the PNR on the films into smaller subunits. Spectroelectrochemical measurements showed the formation of porphyrin anionic radicals during oxidation by a decrease in the absorption intensities and broadening of spectra with an additional band appearing around 900 nm. A similar trend was observed when negative potentials were applied but in this case the cationic radical was produced. In both cases the decrease of the intensity of the J-aggregate confirms a loss of intermolecular coupling, again consistent with the smaller subunits observed in SEM analysis.
- Full Text:
- Date Issued: 2015
Characterization of some amino acid derivatives of benzoyl isothiocyanate: Crystal structures and theoretical prediction of their reactivity
- Odame, Felix, Hosten, Eric C, Betz, Richard, Lobb, Kevin A, Tshentu, Zenixole R
- Authors: Odame, Felix , Hosten, Eric C , Betz, Richard , Lobb, Kevin A , Tshentu, Zenixole R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447952 , vital:74686 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.05.053"
- Description: The reaction of benzoyl isothiocyanate with L-serine, L-proline, D-methionine and L-alanine gave 2-[(benzoylcarbamothioyl)amino]-3-hydroxypropanoic acid (I), 1-(benzoylcarbamothioyl)pyrrolidine-2-carboxylic acid (II), 2-[(benzoylcarbamothioyl)amino]-4-(methylsulfanyl)butanoic acid (III) and 2-[(benzoylcarbamothioyl)amino]propanoic acid (IV), respectively. The compounds have been characterized by IR, NMR, microanalyses and mass spectrometry. The crystal structures of all the compounds have also been discussed. Compound II showed rotamers in solution. DFT calculations of the frontier orbitals of the compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity of these compounds. The calculations indicated that the carboxylic acid group in these compounds is unreactive hence making the conversion to benzimidazoles via cyclization on the carboxylic acids impractical. This has been further confirmed by the reaction of compounds I–IV, respectively, with o-phenylene diamine which was unsuccessful but gave compound V.
- Full Text:
- Date Issued: 2015
- Authors: Odame, Felix , Hosten, Eric C , Betz, Richard , Lobb, Kevin A , Tshentu, Zenixole R
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447952 , vital:74686 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.05.053"
- Description: The reaction of benzoyl isothiocyanate with L-serine, L-proline, D-methionine and L-alanine gave 2-[(benzoylcarbamothioyl)amino]-3-hydroxypropanoic acid (I), 1-(benzoylcarbamothioyl)pyrrolidine-2-carboxylic acid (II), 2-[(benzoylcarbamothioyl)amino]-4-(methylsulfanyl)butanoic acid (III) and 2-[(benzoylcarbamothioyl)amino]propanoic acid (IV), respectively. The compounds have been characterized by IR, NMR, microanalyses and mass spectrometry. The crystal structures of all the compounds have also been discussed. Compound II showed rotamers in solution. DFT calculations of the frontier orbitals of the compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity of these compounds. The calculations indicated that the carboxylic acid group in these compounds is unreactive hence making the conversion to benzimidazoles via cyclization on the carboxylic acids impractical. This has been further confirmed by the reaction of compounds I–IV, respectively, with o-phenylene diamine which was unsuccessful but gave compound V.
- Full Text:
- Date Issued: 2015
Characterization of some virulence and antibiotic resistance genes of Staphylococcus aureus isolated from cases of Bovine Mastitis in Nkonkobe Municipality, Eastern Cape Province, RSA
- Authors: Pekana, Abongile
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11293 , http://hdl.handle.net/10353/d1021133
- Description: Staphylococcus aureus is one of the predominant causative agents of mastitis disease in dairy herds. Mastitis disease has a negative impact in the economic losses in the dairy sector across the globe. The aim of this study is to detect some of the virulence genes in the S. aureus isolated from 400 milk samples of subclinical and clinical mastitis dairy cows in Fort Hare dairy farm and Middle Drift dairy farm in Alice in the Eastern Cape province of South Africa. In addition antibiotic resistance pattern and antibiotic resistance genes were investigated. Gram-staining, oxidase test, catalase test and API Staph kit were preliminary biochemical tests used for the identification of S. aureus isolates. The MALDI-TOF-MS was also used for further identification. Polymerase chain reaction was performed of genes encoding antibiotic resistance as well as clumping (clfA), coagulase (coa) gene, toxic shock syndrome (tsst), exfoliative toxin A and B (eta and etb), and the gene segment encoding the immunoglobulin G binding region and X region of protein gene spa. A total of 20 (5%) S. aureus strains obtained from 400 milk samples from the two farms were subjected to 16 antibiotics for antibiotic susceptibility testing. In Middle Drift dairy farm 11 (5.5%) isolates were obtained from 200 samples and 9 (4.5%) isolates were obtained in Fort Hare dairy farm from 200 samples. A large percent of the isolates were resistant to penicillin G (60%), followed by trimethoprim (60%) and tetracycline (60%), trimethoprim-sulfamethaxazole (55%), telithroprim (55%) and doxycycline (45%). Most of the isolates were sensitive to several (50-85%) antibiotics. Of the twenty isolates tested 12 samples contained the penicillin antibiotic resistance gene (blaZ gene), 8 samples contained at least one aminoglycoside-modifying enzyme gene (AME gene); the (aac(6’)/aph(2’’) gene and no amplification occurred for aph(3’)-IIIa and ant(4’)-Ia) genes. In the case of the tetracycline antibiotic resistance gene (tetK and tetM), 2 samples contained tetM and a single sample contained tetK gene. No amplification was observed for the erythromycin antibiotic resistance genes (ermA, ermB, ermC, Mef and msrA). All the samples tested were negative for the expression of toxic syndrome gene (tsst), etb, and Immunoglobulin G binding region. However, amplification of the clumping factor was observed in 7 (35%) isolates of S. aureus, exfoliative toxin (eta) expressed 4(20%) isolates; coagulase gene (coa) yielded six DNA bands of six differences sizes from 16 (80%) isolates. A total of four different bands size were expressed for the spa X region from 12 (60%) isolates. The data obtained in this study suggests that poor hygienic practices and inadequate management practices are responsible for the increase in Staphylococcus aureus isolation. The high resistance of S. aureus to antibiotics and the distribution of virulence genes contribute in bovine mastitis in these farms may cause health problems in the community consuming raw milk purchased from these farms.
- Full Text:
- Date Issued: 2015
- Authors: Pekana, Abongile
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Microbiology)
- Identifier: vital:11293 , http://hdl.handle.net/10353/d1021133
- Description: Staphylococcus aureus is one of the predominant causative agents of mastitis disease in dairy herds. Mastitis disease has a negative impact in the economic losses in the dairy sector across the globe. The aim of this study is to detect some of the virulence genes in the S. aureus isolated from 400 milk samples of subclinical and clinical mastitis dairy cows in Fort Hare dairy farm and Middle Drift dairy farm in Alice in the Eastern Cape province of South Africa. In addition antibiotic resistance pattern and antibiotic resistance genes were investigated. Gram-staining, oxidase test, catalase test and API Staph kit were preliminary biochemical tests used for the identification of S. aureus isolates. The MALDI-TOF-MS was also used for further identification. Polymerase chain reaction was performed of genes encoding antibiotic resistance as well as clumping (clfA), coagulase (coa) gene, toxic shock syndrome (tsst), exfoliative toxin A and B (eta and etb), and the gene segment encoding the immunoglobulin G binding region and X region of protein gene spa. A total of 20 (5%) S. aureus strains obtained from 400 milk samples from the two farms were subjected to 16 antibiotics for antibiotic susceptibility testing. In Middle Drift dairy farm 11 (5.5%) isolates were obtained from 200 samples and 9 (4.5%) isolates were obtained in Fort Hare dairy farm from 200 samples. A large percent of the isolates were resistant to penicillin G (60%), followed by trimethoprim (60%) and tetracycline (60%), trimethoprim-sulfamethaxazole (55%), telithroprim (55%) and doxycycline (45%). Most of the isolates were sensitive to several (50-85%) antibiotics. Of the twenty isolates tested 12 samples contained the penicillin antibiotic resistance gene (blaZ gene), 8 samples contained at least one aminoglycoside-modifying enzyme gene (AME gene); the (aac(6’)/aph(2’’) gene and no amplification occurred for aph(3’)-IIIa and ant(4’)-Ia) genes. In the case of the tetracycline antibiotic resistance gene (tetK and tetM), 2 samples contained tetM and a single sample contained tetK gene. No amplification was observed for the erythromycin antibiotic resistance genes (ermA, ermB, ermC, Mef and msrA). All the samples tested were negative for the expression of toxic syndrome gene (tsst), etb, and Immunoglobulin G binding region. However, amplification of the clumping factor was observed in 7 (35%) isolates of S. aureus, exfoliative toxin (eta) expressed 4(20%) isolates; coagulase gene (coa) yielded six DNA bands of six differences sizes from 16 (80%) isolates. A total of four different bands size were expressed for the spa X region from 12 (60%) isolates. The data obtained in this study suggests that poor hygienic practices and inadequate management practices are responsible for the increase in Staphylococcus aureus isolation. The high resistance of S. aureus to antibiotics and the distribution of virulence genes contribute in bovine mastitis in these farms may cause health problems in the community consuming raw milk purchased from these farms.
- Full Text:
- Date Issued: 2015
Characterization of the co-chaperones of Hsp70 and Hsp90 in Trypanosoma brucei and their potential partnerships
- Authors: Mokoena, Fortunate
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54543 , vital:26583
- Description: African Trypanosomiasis, which is caused by Trypanosoma brucei, is one of the crippling agents of social and economic development in Africa. T. brucei cycles between the cold-blooded insect vector, the tsetse fly (Glossina spp), and warm-blooded mammalian hosts. T. brucei, T. cruzi and L. major are mammal infecting kinetoplastid parasites that are collectively referred to as TriTryps. These parasites experience extreme environments as they move between their warm-blooded mammalian hosts and cold-blooded insect vectors which trigger extensive morphological transformations during the life-cycle of the parasite. Molecular chaperones have been implicated in parasite differentiation. TriTryps display significant expansions and diversity in the gene complements encoding molecular chaperones, especially J-proteins. Generally, J-proteins function as co-chaperones of Hsp70s, forming part of vital protein homeostasis processes. Hsp70s show a high degree of conservation, while J-proteins appear to be an extreme case of taxonomic radiation. Although several studies have focused on the molecular and cell biology of Hsp70s in some kinetoplastid parasites, knowledge is still lacking pertaining to J-proteins and their partnerships with Hsp70s. This thesis focused on the classification of kinetoplastid Jproteins into the four types by examining the domain organizations using T. brucei as a guide. The potential partnership of J-proteins and Hsp70s were postulated based on predicted subcellular localization. Kinetoplastid parasites, particularly T. brucei, have evolved an expanded and specialized J-protein machinery, likely to be a consequence of an evolutionary fitness/trait to adapt to diverse environment present in hosts and vectors. These analyses will yield insight into the process of parasite differentiation as well as provide new leads for chemotherapeutic treatments. The presence of the STI1 mediated Hsp90 hetero-complex formation has not been confirmed in T. brucei. To this end, in silico and biochemical techniques were used to characterize the role of TbSTI1, as an adaptor protein of Hsp70 and Hsp90. Through domain architecture analysis, sequence alignments, phylogenetic analysis and three-dimensional structure prediction, TbSTI1 was demonstrated to be the most conserved TPR containing co-chaperone of Hsp70 and Hsp83 in T. brucei and also shown to be highly similar to its eukaryotic homologues. Recombinant TbSTI1 was overproduced and purified in E.coli cells and subsequently shown to associate with TcHsp70 in a concentration dependent manner and associate weakly with TbHsp70.4. TbSTI1 and TbHsp83 were also demonstrated to be expressed and upregulated upon exposure to heat shock at the bloodstream stage of parasite development. In conclusion, this study is the first to report the interaction of TbSTI1 with a chaperone. Interactions between TbSTI1 and Hsp70s were demonstrated and therefore, the formation of the hetero-complex is predicted based the similarity of TbSTI1 to other STI1 proteins.
- Full Text:
- Date Issued: 2015
- Authors: Mokoena, Fortunate
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54543 , vital:26583
- Description: African Trypanosomiasis, which is caused by Trypanosoma brucei, is one of the crippling agents of social and economic development in Africa. T. brucei cycles between the cold-blooded insect vector, the tsetse fly (Glossina spp), and warm-blooded mammalian hosts. T. brucei, T. cruzi and L. major are mammal infecting kinetoplastid parasites that are collectively referred to as TriTryps. These parasites experience extreme environments as they move between their warm-blooded mammalian hosts and cold-blooded insect vectors which trigger extensive morphological transformations during the life-cycle of the parasite. Molecular chaperones have been implicated in parasite differentiation. TriTryps display significant expansions and diversity in the gene complements encoding molecular chaperones, especially J-proteins. Generally, J-proteins function as co-chaperones of Hsp70s, forming part of vital protein homeostasis processes. Hsp70s show a high degree of conservation, while J-proteins appear to be an extreme case of taxonomic radiation. Although several studies have focused on the molecular and cell biology of Hsp70s in some kinetoplastid parasites, knowledge is still lacking pertaining to J-proteins and their partnerships with Hsp70s. This thesis focused on the classification of kinetoplastid Jproteins into the four types by examining the domain organizations using T. brucei as a guide. The potential partnership of J-proteins and Hsp70s were postulated based on predicted subcellular localization. Kinetoplastid parasites, particularly T. brucei, have evolved an expanded and specialized J-protein machinery, likely to be a consequence of an evolutionary fitness/trait to adapt to diverse environment present in hosts and vectors. These analyses will yield insight into the process of parasite differentiation as well as provide new leads for chemotherapeutic treatments. The presence of the STI1 mediated Hsp90 hetero-complex formation has not been confirmed in T. brucei. To this end, in silico and biochemical techniques were used to characterize the role of TbSTI1, as an adaptor protein of Hsp70 and Hsp90. Through domain architecture analysis, sequence alignments, phylogenetic analysis and three-dimensional structure prediction, TbSTI1 was demonstrated to be the most conserved TPR containing co-chaperone of Hsp70 and Hsp83 in T. brucei and also shown to be highly similar to its eukaryotic homologues. Recombinant TbSTI1 was overproduced and purified in E.coli cells and subsequently shown to associate with TcHsp70 in a concentration dependent manner and associate weakly with TbHsp70.4. TbSTI1 and TbHsp83 were also demonstrated to be expressed and upregulated upon exposure to heat shock at the bloodstream stage of parasite development. In conclusion, this study is the first to report the interaction of TbSTI1 with a chaperone. Interactions between TbSTI1 and Hsp70s were demonstrated and therefore, the formation of the hetero-complex is predicted based the similarity of TbSTI1 to other STI1 proteins.
- Full Text:
- Date Issued: 2015
Chemical constituents and biological studies of Tagetes minuta L. and Rauvolfia caffra Sond
- Authors: Mlala, Sithenkosi
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Organic Chemistry)
- Identifier: vital:11358 , http://hdl.handle.net/10353/d1021325
- Description: Consequently, specific parts or the whole plant can be used for various treatments. The aim of this study was to extract, isolate and characterize the biologically active volatile and non-volatile compounds from Tagetes minuta and Rauvolfia caffra respectively. Tagetes minuta plant was considered for extraction of essential oils using hydrodistillation method. Cis-β-ocimene (38.03%), caryophyllene oxide (18.04%), alloocimene (25.35 %), isopropyl tetradecanoate (17.02 %), cis-ocimene (38.14%) and trans-β-ocimene (37.03%) were the major components of essential oil analyzed from fresh stem, dried stem, fresh leaf, dried leaf, fresh flower and dried flower respectively. The volatile compounds were identified by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography (GC). Essential oil of dried stem leaf and flower parts of T. minuta exhibit antioxidant activity as demonstrated by the DPPH and FRAP bioassays. Crude extracts were extracted from R. caffra stem bark using sequence of solvents namely n-hexane, dichloromethane, ethyl acetate, methanol and ethanol. A white powder, a β-sitosterol (non-volatile compound) was isolated by column chromatography from ethyl acetate fractions of R. caffra stem bark and identified on various spectroscopic techniques such as FTIR and (1D and 2D) NMR. Melting point was also determined to be a sharp 129-130 ºC. DCM, EA, MetOH and EtOH fractions as well as β-Sitosterol (compound SM/01), showed antioxidant activity when tested on DPPH, FRAP, total phenolic and flavonoid bioassays. This antioxidant activity might be due to the presence of hydroxyl groups in the compound and crude fractions. On the other hand, T. minuta’s essential oil showed high antioxidant activity when evaluated on the DPPH and FRAP bioassays, which can be attributed to the presence of oxygenated monoterpenes and sesquiterpenes known to act as free radical scavenging and reducing agents. The use of R. caffra stem bark extracts against hypertension and other diseases by traditional healers could be attributed to the presence of phytochemicals (polyphenols and flavonoids) with known health benefits. Thus, it is recommended that the plant should be exploited further using modern techniques involving separation and purification of compounds that can be used for drug formulation. This study supports the use of T. minuta and R. caffra as the potential natural antioxidant source to manage various diseases including hypertension.
- Full Text:
- Date Issued: 2015
- Authors: Mlala, Sithenkosi
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Organic Chemistry)
- Identifier: vital:11358 , http://hdl.handle.net/10353/d1021325
- Description: Consequently, specific parts or the whole plant can be used for various treatments. The aim of this study was to extract, isolate and characterize the biologically active volatile and non-volatile compounds from Tagetes minuta and Rauvolfia caffra respectively. Tagetes minuta plant was considered for extraction of essential oils using hydrodistillation method. Cis-β-ocimene (38.03%), caryophyllene oxide (18.04%), alloocimene (25.35 %), isopropyl tetradecanoate (17.02 %), cis-ocimene (38.14%) and trans-β-ocimene (37.03%) were the major components of essential oil analyzed from fresh stem, dried stem, fresh leaf, dried leaf, fresh flower and dried flower respectively. The volatile compounds were identified by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography (GC). Essential oil of dried stem leaf and flower parts of T. minuta exhibit antioxidant activity as demonstrated by the DPPH and FRAP bioassays. Crude extracts were extracted from R. caffra stem bark using sequence of solvents namely n-hexane, dichloromethane, ethyl acetate, methanol and ethanol. A white powder, a β-sitosterol (non-volatile compound) was isolated by column chromatography from ethyl acetate fractions of R. caffra stem bark and identified on various spectroscopic techniques such as FTIR and (1D and 2D) NMR. Melting point was also determined to be a sharp 129-130 ºC. DCM, EA, MetOH and EtOH fractions as well as β-Sitosterol (compound SM/01), showed antioxidant activity when tested on DPPH, FRAP, total phenolic and flavonoid bioassays. This antioxidant activity might be due to the presence of hydroxyl groups in the compound and crude fractions. On the other hand, T. minuta’s essential oil showed high antioxidant activity when evaluated on the DPPH and FRAP bioassays, which can be attributed to the presence of oxygenated monoterpenes and sesquiterpenes known to act as free radical scavenging and reducing agents. The use of R. caffra stem bark extracts against hypertension and other diseases by traditional healers could be attributed to the presence of phytochemicals (polyphenols and flavonoids) with known health benefits. Thus, it is recommended that the plant should be exploited further using modern techniques involving separation and purification of compounds that can be used for drug formulation. This study supports the use of T. minuta and R. caffra as the potential natural antioxidant source to manage various diseases including hypertension.
- Full Text:
- Date Issued: 2015
CHIP: a co-chaperone for degradation by the proteasome
- Authors: Edkins, Adrienne L
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/164863 , vital:41179 , ISBN 978-3-319-11730-0 , DOI: 10.1007/978-3-319-11731-7_11
- Description: Protein homeostasis relies on a balance between protein folding and protein degradation. Molecular chaperones like Hsp70 and Hsp90 fulfil well-defined roles in protein folding and conformational stability via ATP dependent reaction cycles. These folding cycles are controlled by associations with a cohort of non-client protein co-chaperones, such as Hop, p23 and Aha1. Pro-folding co-chaperones facilitate the transit of the client protein through the chaperone mediated folding process. However, chaperones are also involved in ubiquitin-mediated proteasomal degradation of client proteins. Similar to folding complexes, the ability of chaperones to mediate protein degradation is regulated by co-chaperones, such as the C terminal Hsp70 binding protein (CHIP).
- Full Text:
- Date Issued: 2015
- Authors: Edkins, Adrienne L
- Date: 2015
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/164863 , vital:41179 , ISBN 978-3-319-11730-0 , DOI: 10.1007/978-3-319-11731-7_11
- Description: Protein homeostasis relies on a balance between protein folding and protein degradation. Molecular chaperones like Hsp70 and Hsp90 fulfil well-defined roles in protein folding and conformational stability via ATP dependent reaction cycles. These folding cycles are controlled by associations with a cohort of non-client protein co-chaperones, such as Hop, p23 and Aha1. Pro-folding co-chaperones facilitate the transit of the client protein through the chaperone mediated folding process. However, chaperones are also involved in ubiquitin-mediated proteasomal degradation of client proteins. Similar to folding complexes, the ability of chaperones to mediate protein degradation is regulated by co-chaperones, such as the C terminal Hsp70 binding protein (CHIP).
- Full Text:
- Date Issued: 2015
Classification System for Wetlands and Other Aquatic Ecosystems in South Africa:
- Authors: Ellery, William F N
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144454 , vital:38347 , https://doi.org/10.2989/10220119.2015.1025843
- Description: There have been several attempts to develop a wetland classification for South Africa, with merit in each, but a system that satisfies the needs of a wide range of professionals has been elusive. This is partly to be expected since classification systems are often user-specific. Nevertheless, and at last, the authors of Classification System for Wetlands and Other Aquatic Ecosystems in South Africa. User Manual: Inland Systems (SANBI Biodiversity Series 22) have developed a robust and comprehensive wetland classification system for South Africa that likely will have broad appeal and be widely used. Working for Wetlands, the Water Research Commission (WRC) and SANBI provided considerable support for the development of this system and there was expert input from a wide range of stakeholders.
- Full Text:
- Date Issued: 2015
- Authors: Ellery, William F N
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144454 , vital:38347 , https://doi.org/10.2989/10220119.2015.1025843
- Description: There have been several attempts to develop a wetland classification for South Africa, with merit in each, but a system that satisfies the needs of a wide range of professionals has been elusive. This is partly to be expected since classification systems are often user-specific. Nevertheless, and at last, the authors of Classification System for Wetlands and Other Aquatic Ecosystems in South Africa. User Manual: Inland Systems (SANBI Biodiversity Series 22) have developed a robust and comprehensive wetland classification system for South Africa that likely will have broad appeal and be widely used. Working for Wetlands, the Water Research Commission (WRC) and SANBI provided considerable support for the development of this system and there was expert input from a wide range of stakeholders.
- Full Text:
- Date Issued: 2015
Closed-loop temperature control of friction stir welding
- Authors: Pothier, Raymond Peter
- Date: 2015
- Subjects: Friction welding
- Language: English
- Type: Thesis , Masters , MEngineering
- Identifier: http://hdl.handle.net/10948/10362 , vital:26656
- Description: This study develops and presents a friction stir weld (FSW) quality assurance tool based on control of weld zone temperature. Apart from correct tool geometry, tool tilt angle, traverse speed and forge force during welding, one important requirement is that the weld material be sufficiently plasticised (softened). The level of plasticisation is related to weld zone temperature which is primarily dependent on spindle speed, traverse speed and forge force. When all other conditions are correct, sufficiently plasticised material flows around and consolidates behind the tool without the production of voids in the weld. Typically, weld temperature varies along the weld length which may result in variations in weld quality. Weld zone temperature control makes constant weld zone temperature possible. In this study, thermocouple sensors were embedded in the FSW tool and a weld zone temperature control algorithm was developed. Spindle speed was the actuating mechanism for controlling weld temperature. The system was modelled and controllers were designed using Matlab tools. The system was simulated and the performance was compared to the system performance during welding. The control system ensures that the weld zone temperature can be maintained irrespective of the presence of thermal disturbances. Tensile testing was conducted which confirmed a range of temperature in which the welds resulted in consistent strength.
- Full Text:
- Date Issued: 2015
- Authors: Pothier, Raymond Peter
- Date: 2015
- Subjects: Friction welding
- Language: English
- Type: Thesis , Masters , MEngineering
- Identifier: http://hdl.handle.net/10948/10362 , vital:26656
- Description: This study develops and presents a friction stir weld (FSW) quality assurance tool based on control of weld zone temperature. Apart from correct tool geometry, tool tilt angle, traverse speed and forge force during welding, one important requirement is that the weld material be sufficiently plasticised (softened). The level of plasticisation is related to weld zone temperature which is primarily dependent on spindle speed, traverse speed and forge force. When all other conditions are correct, sufficiently plasticised material flows around and consolidates behind the tool without the production of voids in the weld. Typically, weld temperature varies along the weld length which may result in variations in weld quality. Weld zone temperature control makes constant weld zone temperature possible. In this study, thermocouple sensors were embedded in the FSW tool and a weld zone temperature control algorithm was developed. Spindle speed was the actuating mechanism for controlling weld temperature. The system was modelled and controllers were designed using Matlab tools. The system was simulated and the performance was compared to the system performance during welding. The control system ensures that the weld zone temperature can be maintained irrespective of the presence of thermal disturbances. Tensile testing was conducted which confirmed a range of temperature in which the welds resulted in consistent strength.
- Full Text:
- Date Issued: 2015