Reproductive conflicts in honeybee colonies
- Pirk, Christian Walter Werner
- Authors: Pirk, Christian Walter Werner
- Date: 2002
- Subjects: Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5755 , http://hdl.handle.net/10962/d1005443
- Description: In advanced eusocial hymenopteran societies workers have ovaries and can lay eggs, but are unable to mate. Workers are more related to their own offspring than to every other member of the colony. So worker reproduction contains both worker-worker and worker-queen conflict. The queen- worker conflict is discussed elsewhere, but if the queen mates with more than two males, worker policing should be selected to lower potential conflicts. However in the Cape honeybee it was predicted that worker policing is absent or less expressed than in other honeybee subspecies, because workers produce female offspring thelytokously. So laying workers and their offspring are nearly genetically identical, which results in the fact that other workers are as related to workers derived from eggs laid by the queen as laid by a worker. However, worker reproduction may be costly and therefore worker policing could be an evolutionary adaptation in the Cape honeybee to lower the costs derived from laying worker activity. Indeed, Cape honeybee colonies show efficient egg removal behaviour, suggesting that other factors like colony efficiency could favour egg removal behaviour. Since egg removal behaviour is a colony phenomenon, factors that affect colony performance could also affect egg removal behaviour. Egg removal behaviour was considerably affected by environmental changes, indicating that other tasks have a higher priority than egg removal behaviour. Thousands of queenright colonies of the neighbouring subspecies (A. m. scutellata) were taken over by laying A. m. capensis workers, showing that A. m. capensis workers are facultative social parasites. These observations strongly indicate that laying workers of A. m. capensis are able to evade worker policing and the inhibitory effects of the queen pheromones, but what potential strategies could these laying workers use to increase the survival of their eggs and evade the queen? On the one hand, egg removal behaviour is variable. One behavioural strategy of laying workers to achieve successful reproduction could be that they lay during periods with low egg removal behaviour. On the other hand, the inhibitory effect of the queen’s pheromones diminishes with distance. Maybe the level of egg removal also depends, like the inhibitory effect of the queen pheromones, on the distance from the queen. Indeed, further away from the queen the effect of the queen pheromone and the level of egg removal is reduced, making successful worker reproduction possible. In both subspecies, A. m. capensis and A. m. scutellata, egg removal behaviour is reduced further away from the queen. In the case of A. m. scutellata egg removal is lacking further away from the queen. This explains why colonies of scutellata are so prone to takeovers by laying Cape honeybee workers. One question in the context of parasitic Cape honeybees is how they manage to get into the host colony. One way could be that they get into the colonies during a natural colony merger which is common in African bees. Two unrelated colonies merged and it took them only 24 hours to show effective integration. Because both colonies are unrelated, the potential reproductive conflict among workers should be more strongly expressed than in a normal colony, which is not the result of a merger. Therefore, the effect of nestmate recognition for eggs on the egg removal behaviour was investigated. The results suggest that workers recognise the origin of an egg and that the standard policing experiments overestimate the level of egg removal and only represent relative values. Moreover, the results show that colony specific components on the eggs are more important than a postulated queen egg marking pheromone. Finally, for the first time empirical evidence from a population of the parasitic laying Cape honeybee workers, invading thousands of colonies of A. m. scutellata in northern South Africa, for a short-sighted selection theory is presented.
- Full Text:
- Date Issued: 2002
- Authors: Pirk, Christian Walter Werner
- Date: 2002
- Subjects: Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5755 , http://hdl.handle.net/10962/d1005443
- Description: In advanced eusocial hymenopteran societies workers have ovaries and can lay eggs, but are unable to mate. Workers are more related to their own offspring than to every other member of the colony. So worker reproduction contains both worker-worker and worker-queen conflict. The queen- worker conflict is discussed elsewhere, but if the queen mates with more than two males, worker policing should be selected to lower potential conflicts. However in the Cape honeybee it was predicted that worker policing is absent or less expressed than in other honeybee subspecies, because workers produce female offspring thelytokously. So laying workers and their offspring are nearly genetically identical, which results in the fact that other workers are as related to workers derived from eggs laid by the queen as laid by a worker. However, worker reproduction may be costly and therefore worker policing could be an evolutionary adaptation in the Cape honeybee to lower the costs derived from laying worker activity. Indeed, Cape honeybee colonies show efficient egg removal behaviour, suggesting that other factors like colony efficiency could favour egg removal behaviour. Since egg removal behaviour is a colony phenomenon, factors that affect colony performance could also affect egg removal behaviour. Egg removal behaviour was considerably affected by environmental changes, indicating that other tasks have a higher priority than egg removal behaviour. Thousands of queenright colonies of the neighbouring subspecies (A. m. scutellata) were taken over by laying A. m. capensis workers, showing that A. m. capensis workers are facultative social parasites. These observations strongly indicate that laying workers of A. m. capensis are able to evade worker policing and the inhibitory effects of the queen pheromones, but what potential strategies could these laying workers use to increase the survival of their eggs and evade the queen? On the one hand, egg removal behaviour is variable. One behavioural strategy of laying workers to achieve successful reproduction could be that they lay during periods with low egg removal behaviour. On the other hand, the inhibitory effect of the queen’s pheromones diminishes with distance. Maybe the level of egg removal also depends, like the inhibitory effect of the queen pheromones, on the distance from the queen. Indeed, further away from the queen the effect of the queen pheromone and the level of egg removal is reduced, making successful worker reproduction possible. In both subspecies, A. m. capensis and A. m. scutellata, egg removal behaviour is reduced further away from the queen. In the case of A. m. scutellata egg removal is lacking further away from the queen. This explains why colonies of scutellata are so prone to takeovers by laying Cape honeybee workers. One question in the context of parasitic Cape honeybees is how they manage to get into the host colony. One way could be that they get into the colonies during a natural colony merger which is common in African bees. Two unrelated colonies merged and it took them only 24 hours to show effective integration. Because both colonies are unrelated, the potential reproductive conflict among workers should be more strongly expressed than in a normal colony, which is not the result of a merger. Therefore, the effect of nestmate recognition for eggs on the egg removal behaviour was investigated. The results suggest that workers recognise the origin of an egg and that the standard policing experiments overestimate the level of egg removal and only represent relative values. Moreover, the results show that colony specific components on the eggs are more important than a postulated queen egg marking pheromone. Finally, for the first time empirical evidence from a population of the parasitic laying Cape honeybee workers, invading thousands of colonies of A. m. scutellata in northern South Africa, for a short-sighted selection theory is presented.
- Full Text:
- Date Issued: 2002
Research projects
- Authors: Thomas, Chacko
- Date: 2002
- Subjects: Mathematics -- Study and teaching -- South Africa Competency-based education -- South Africa Mathematics teachers -- Training of -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1856 , http://hdl.handle.net/10962/d1004531
- Description: The South African education is undergoing transformation. The introduction of Curriculum 2005 and Outcome Based Education (OBE) are important aspects of this transformation process. The implementation of the new curriculum however, has not been smooth. A lack of adequately qualified and trained teachers and effective learning support materials have been identified as some of the major problems facing the implementation of OBE at school level. Even though the colleges of education in the country were not brought on board in the planning and implementation levels of the new curriculum, they could have played an important role in training of educators and developing learning materials for the successful take off of the new curriculum. In the first research project I look into the preparedness of the Mathematics Department of a college of education in the Eastern Cape towards the implementation of Outcome Based Education. The first part of the research project consists of a literature review on Curriculum 2005, Outcome Based Education and the expectations of teachers in the new curriculum and the research methodologies used. The findings revealed that the department, as a whole, was not adequately prepared for the implementation of outcome-based education even though there were some indications that the department effected some modifications in its curriculum and practice teaching. As an OBE facilitator and a college lecturer, I developed some learning materials in Linear Programming. These activity-oriented materials were based on constructivist principles and were used by my first year Secondary Teachers Diploma students. In the second research project, I reflect on the results of using these learning materials by my students. In the first chapter of the project, the context and background of the research and the reasons for selecting Linear Programming as the topic for preparing the learning material are described. This is followed by a brief overview of constructivism together with a brief explanation of the reasons for considering the material to be constructivist. The research paradigm followed in the project, the research techniques employed in evaluating the learning material and the strengths and weaknesses of the evaluation techniques are given in the next chapter. In the following chapter, the findings from the various data gathering methods and the results of the implementation of the material are described. The concluding chapter presents a critical reflection on the whole process involved in the material development. The post 1994 government in South Africa seems to attach much importance to mathematics, science and technology education. The majority of the population who were previously denied access to these subjects is given more opportunities to learn them. The international Mathematics Union declared 2000 as the World Mathematical Year. One of the aims of the activities organized as part of the celebrations was improving the public image of mathematics to realize the vision of "Mathematics For All". The South African government shows keen interest to improve mathematics education in the country in an attempt to realize the vision of Mathematics For All. Even though the accessibility rate to mathematics has increased, the success rate has not yet increased as anticipated. In this context I, as a post-graduate student in Mathematics Education, thought of /reviewing the concept of Mathematics For All in the South African context. In the third research project, which is a literature review, initially an attempt is made to unpack the concept of Mathematics for ALL. In analyzing the concept, answers are sought for questions like: What is mathematics and why should it be taught? It is followed by a brief review of some goals of mathematics education. Then the current situation of mathematics education in South Africa and the efforts to improve it are also looked at. This is followed by an analysis pf the reasons for the general unpopularity of mathematics. In the concluding part some suggestions for improving mathematics education in the country are given.
- Full Text:
- Date Issued: 2002
- Authors: Thomas, Chacko
- Date: 2002
- Subjects: Mathematics -- Study and teaching -- South Africa Competency-based education -- South Africa Mathematics teachers -- Training of -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1856 , http://hdl.handle.net/10962/d1004531
- Description: The South African education is undergoing transformation. The introduction of Curriculum 2005 and Outcome Based Education (OBE) are important aspects of this transformation process. The implementation of the new curriculum however, has not been smooth. A lack of adequately qualified and trained teachers and effective learning support materials have been identified as some of the major problems facing the implementation of OBE at school level. Even though the colleges of education in the country were not brought on board in the planning and implementation levels of the new curriculum, they could have played an important role in training of educators and developing learning materials for the successful take off of the new curriculum. In the first research project I look into the preparedness of the Mathematics Department of a college of education in the Eastern Cape towards the implementation of Outcome Based Education. The first part of the research project consists of a literature review on Curriculum 2005, Outcome Based Education and the expectations of teachers in the new curriculum and the research methodologies used. The findings revealed that the department, as a whole, was not adequately prepared for the implementation of outcome-based education even though there were some indications that the department effected some modifications in its curriculum and practice teaching. As an OBE facilitator and a college lecturer, I developed some learning materials in Linear Programming. These activity-oriented materials were based on constructivist principles and were used by my first year Secondary Teachers Diploma students. In the second research project, I reflect on the results of using these learning materials by my students. In the first chapter of the project, the context and background of the research and the reasons for selecting Linear Programming as the topic for preparing the learning material are described. This is followed by a brief overview of constructivism together with a brief explanation of the reasons for considering the material to be constructivist. The research paradigm followed in the project, the research techniques employed in evaluating the learning material and the strengths and weaknesses of the evaluation techniques are given in the next chapter. In the following chapter, the findings from the various data gathering methods and the results of the implementation of the material are described. The concluding chapter presents a critical reflection on the whole process involved in the material development. The post 1994 government in South Africa seems to attach much importance to mathematics, science and technology education. The majority of the population who were previously denied access to these subjects is given more opportunities to learn them. The international Mathematics Union declared 2000 as the World Mathematical Year. One of the aims of the activities organized as part of the celebrations was improving the public image of mathematics to realize the vision of "Mathematics For All". The South African government shows keen interest to improve mathematics education in the country in an attempt to realize the vision of Mathematics For All. Even though the accessibility rate to mathematics has increased, the success rate has not yet increased as anticipated. In this context I, as a post-graduate student in Mathematics Education, thought of /reviewing the concept of Mathematics For All in the South African context. In the third research project, which is a literature review, initially an attempt is made to unpack the concept of Mathematics for ALL. In analyzing the concept, answers are sought for questions like: What is mathematics and why should it be taught? It is followed by a brief review of some goals of mathematics education. Then the current situation of mathematics education in South Africa and the efforts to improve it are also looked at. This is followed by an analysis pf the reasons for the general unpopularity of mathematics. In the concluding part some suggestions for improving mathematics education in the country are given.
- Full Text:
- Date Issued: 2002
Restoring democratic governance in Zimbabwe: a critical investigation of the internet as a possible means of creating new sites of struggle for positive democratic change by Zimbabwean media and activists in Zimbabwe
- Authors: Vennard, Francisca Caroline
- Date: 2002
- Subjects: Zimbabwe -- Politics and government -- 1980- , Internet in publicity , Press and politics -- Zimbabwe , Freedom of the press -- Zimbabwe , Digital media
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2837 , http://hdl.handle.net/10962/d1003047 , Zimbabwe -- Politics and government -- 1980- , Internet in publicity , Press and politics -- Zimbabwe , Freedom of the press -- Zimbabwe , Digital media
- Description: This thesis is a reaction to the state of utter lawlessness and the abuse of human rights by those in power in Zimbabwe over the past two years and it investigates the possibility of restoring democratic governance in that country by increasing the freedom of expression and media freedom, which is considered to be one of the most valuable elements in advancing democratization. Its aim is to establish the Internet as the best means possible to increasing media freedom and creating new ‘sites of struggle’ for activists in a context where the substantive freedom of expression does not exist. This in turn is shown to advance levels of democracy. To this end, the value of the freedom of expression to media freedom and the value of the latter to increasing levels of democracy is developed and the lack of democracy in Zimbabwe at all levels of society is considered. The Internet is seen to increase the freedoms of speech and association in new and interesting ways and it is discussed in various examples in which it has already been instrumental in evading the censorship of the media and increasing the ability of activists to express themselves freely and to organize more efficiently. Finally, the resources that Internet technology makes available to African journalists and activists are considered along with lessons gleaned from international examples of successful Internet use and it is shown to already be of use to Zimbabwean journalists and activists as they create to new cyberspaces in which they can struggle for positive democratic change in Zimbabwe. The Internet is also shown to have tremendous potential for future use in that country.
- Full Text:
- Date Issued: 2002
- Authors: Vennard, Francisca Caroline
- Date: 2002
- Subjects: Zimbabwe -- Politics and government -- 1980- , Internet in publicity , Press and politics -- Zimbabwe , Freedom of the press -- Zimbabwe , Digital media
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2837 , http://hdl.handle.net/10962/d1003047 , Zimbabwe -- Politics and government -- 1980- , Internet in publicity , Press and politics -- Zimbabwe , Freedom of the press -- Zimbabwe , Digital media
- Description: This thesis is a reaction to the state of utter lawlessness and the abuse of human rights by those in power in Zimbabwe over the past two years and it investigates the possibility of restoring democratic governance in that country by increasing the freedom of expression and media freedom, which is considered to be one of the most valuable elements in advancing democratization. Its aim is to establish the Internet as the best means possible to increasing media freedom and creating new ‘sites of struggle’ for activists in a context where the substantive freedom of expression does not exist. This in turn is shown to advance levels of democracy. To this end, the value of the freedom of expression to media freedom and the value of the latter to increasing levels of democracy is developed and the lack of democracy in Zimbabwe at all levels of society is considered. The Internet is seen to increase the freedoms of speech and association in new and interesting ways and it is discussed in various examples in which it has already been instrumental in evading the censorship of the media and increasing the ability of activists to express themselves freely and to organize more efficiently. Finally, the resources that Internet technology makes available to African journalists and activists are considered along with lessons gleaned from international examples of successful Internet use and it is shown to already be of use to Zimbabwean journalists and activists as they create to new cyberspaces in which they can struggle for positive democratic change in Zimbabwe. The Internet is also shown to have tremendous potential for future use in that country.
- Full Text:
- Date Issued: 2002
Rumours of war : de-constructing media discourses of HIV/AIDS in South Africa
- Authors: Connelly, Mark
- Date: 2002
- Subjects: AIDS (Disease) -- South Africa AIDS (Disease) in mass media
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3177 , http://hdl.handle.net/10962/d1007844
- Description: This paper explores discourses of HIV/AIDS evident in a South African daily newspaper from 1985 to 2000, and discusses the implications of these in terms of the way in which HIV/AIDS is constructed in society. In this paper I utilize a Foucauldian analysis of the relationship between power and knowledge. The discursive framework of the war against HIV/AIDS is used to show how different groups of subjects are positioned in relations of power. Within this the power of western science and medicine is influential and supports and informs other discourses of HIV/AIDS. I argue that the discursive framework constructing HIV/AIDS as a war does far more than provide a useful vehicle within which HIV/AIDS can be understood as it supports certain institutions and groups of people above others. The paper concludes by identifying the silenced voices of women and dissidents, and calling for greater reflection concerning the critical analysis of current issues surrounding HIV/AIDS.
- Full Text:
- Date Issued: 2002
- Authors: Connelly, Mark
- Date: 2002
- Subjects: AIDS (Disease) -- South Africa AIDS (Disease) in mass media
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3177 , http://hdl.handle.net/10962/d1007844
- Description: This paper explores discourses of HIV/AIDS evident in a South African daily newspaper from 1985 to 2000, and discusses the implications of these in terms of the way in which HIV/AIDS is constructed in society. In this paper I utilize a Foucauldian analysis of the relationship between power and knowledge. The discursive framework of the war against HIV/AIDS is used to show how different groups of subjects are positioned in relations of power. Within this the power of western science and medicine is influential and supports and informs other discourses of HIV/AIDS. I argue that the discursive framework constructing HIV/AIDS as a war does far more than provide a useful vehicle within which HIV/AIDS can be understood as it supports certain institutions and groups of people above others. The paper concludes by identifying the silenced voices of women and dissidents, and calling for greater reflection concerning the critical analysis of current issues surrounding HIV/AIDS.
- Full Text:
- Date Issued: 2002
Science for all - myth or reality?: a research project
- Authors: Valiathazhel, James Daniel
- Date: 2002
- Subjects: Science -- Study and teaching -- South Africa Motion -- Study and teaching -- South Africa Physics -- Study and teaching -- South Africa Competency-based education -- South Africa Educational change -- South Africa Technical institutes -- South Africa Technical education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1847 , http://hdl.handle.net/10962/d1004391
- Description: Abstract: Transformation at a historically disadvantaged technikon in South Africa : a research project: South Africa is in the seventh year of democracy. During the first term of office, the ANC government proposed radical shift from the system(s) of education that was/were in existence in this country. A change in the education system in South Africa was inevitable. The ANC government have realised the need and proposed plans for a change in the education system in this country. We might be able to overcome the inequalities of the past and have an education system relevant for all South Africans that promote an equal opportunity for success as envisaged by Outcomes Based Education (OBE). This research project, using a qualitative case study methodology, reports on the readiness of Border Technikon in implementing Outcomes Based Education (OBE) as a teaching/lecturing strategy. Since 1998 Border Technikon organised a series of staff training workshops to empower the academic staff in Outcomes Based Education. A preliminary study on the topic was conducted during 1999, in which questionnaires (to 16 academic staff) and semi-structured interviews (with three academic staff) were used to collect data. During 2000, when the second and final round of this study was conducted semistructured interviews were employed with 4 staff members to gather data. Literature review and document analysis was also part of the research. The analysis of data indicated that the very nature of most of the Technikon Programmes demands an OBE approach in teaching/lecturing and hence OBE based teaching/lecturing is largely practised at Border Technikon. However a few areas of concerns were identified. Some of these concerns were: (i) Technikon employed academic staff (from industry, etc...) with no professional qualification in teaching and it was difficult to provide OBE training to such people and (ii) lack of sufficient support from the Technikon Management might be a cause for the poor attendance of academic staff during the training programme. Another aspect emerged from the data analysis was that all academic staff participated in this study expressed the need for further training in OBE and related topics. Abstract: Science for all - myth or reality?: Different educational projects around the world have made Scientific Literacy a world-wide concern. This study through a literature review shows that Scientific Literacy is a term that has many definitions and interpretations. This literature review reveals that, in the present system Science for All is a myth for various reasons. Governments around the world in general, and South Africa in particular, are in the process of introducing different projects such as the Year of Science and Technology (YEAST), science week and science exhibitions for the purpose of popularising science and technology. The Department of Education in Thailand has modified its education system to accommodate Science for All. In this literature review among other issues the status quo in South African science education and the Thailand model were examined. A few recommendations to achieve Science for All are also included in this project. Abstract: Developing and evaluating the use of learning material in science - a constructivist approach towards learning Newton's laws : a research project: The Government of National Unity in 1994 introduced a new educational policy for South Africa. This represented a shift in paradigm from a transmission mode of teaching and learning to a learner-centred education. The shift marks a transformation from a content-based curriculum to an Outcomes Based Education (OBE). Various authors found that different sections in the Physical Science syllabus in South Africa are often misunderstood by students for different reasons. One of the reasons was that students had their own ideas about laws of nature and these (mis)conceptions were resistant to change. From the literature and from the author's personal experience it was found that Bodies in Motion is a topic that is difficult to conceptualise by students of different age groups. The challenge facing educators is how to tackle this issue. In this research project a diagnostic test is developed and used to identify the topics where students have conceptual problems. To address these problem areas further, concept sheets/work sheets where developed and implemented. The different challenges and tasks given in the work sheets/learning material are organised in such a way as to make the students aware of their own ideas about Bodies in Motion in general and the key-concepts in particular and also to make them aware of the ideas of their peers (group members). It was also aimed at offering the learners the scientific alternative to their own beliefs. At the end, it was discovered that, even though the general understanding of the learners has improved in this topic (namely, Bodies in Motion), their original beliefs were largely unaffected. It is the hope of the researcher that the project would be the basis for further research on the development of learning material in science.
- Full Text:
- Date Issued: 2002
- Authors: Valiathazhel, James Daniel
- Date: 2002
- Subjects: Science -- Study and teaching -- South Africa Motion -- Study and teaching -- South Africa Physics -- Study and teaching -- South Africa Competency-based education -- South Africa Educational change -- South Africa Technical institutes -- South Africa Technical education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1847 , http://hdl.handle.net/10962/d1004391
- Description: Abstract: Transformation at a historically disadvantaged technikon in South Africa : a research project: South Africa is in the seventh year of democracy. During the first term of office, the ANC government proposed radical shift from the system(s) of education that was/were in existence in this country. A change in the education system in South Africa was inevitable. The ANC government have realised the need and proposed plans for a change in the education system in this country. We might be able to overcome the inequalities of the past and have an education system relevant for all South Africans that promote an equal opportunity for success as envisaged by Outcomes Based Education (OBE). This research project, using a qualitative case study methodology, reports on the readiness of Border Technikon in implementing Outcomes Based Education (OBE) as a teaching/lecturing strategy. Since 1998 Border Technikon organised a series of staff training workshops to empower the academic staff in Outcomes Based Education. A preliminary study on the topic was conducted during 1999, in which questionnaires (to 16 academic staff) and semi-structured interviews (with three academic staff) were used to collect data. During 2000, when the second and final round of this study was conducted semistructured interviews were employed with 4 staff members to gather data. Literature review and document analysis was also part of the research. The analysis of data indicated that the very nature of most of the Technikon Programmes demands an OBE approach in teaching/lecturing and hence OBE based teaching/lecturing is largely practised at Border Technikon. However a few areas of concerns were identified. Some of these concerns were: (i) Technikon employed academic staff (from industry, etc...) with no professional qualification in teaching and it was difficult to provide OBE training to such people and (ii) lack of sufficient support from the Technikon Management might be a cause for the poor attendance of academic staff during the training programme. Another aspect emerged from the data analysis was that all academic staff participated in this study expressed the need for further training in OBE and related topics. Abstract: Science for all - myth or reality?: Different educational projects around the world have made Scientific Literacy a world-wide concern. This study through a literature review shows that Scientific Literacy is a term that has many definitions and interpretations. This literature review reveals that, in the present system Science for All is a myth for various reasons. Governments around the world in general, and South Africa in particular, are in the process of introducing different projects such as the Year of Science and Technology (YEAST), science week and science exhibitions for the purpose of popularising science and technology. The Department of Education in Thailand has modified its education system to accommodate Science for All. In this literature review among other issues the status quo in South African science education and the Thailand model were examined. A few recommendations to achieve Science for All are also included in this project. Abstract: Developing and evaluating the use of learning material in science - a constructivist approach towards learning Newton's laws : a research project: The Government of National Unity in 1994 introduced a new educational policy for South Africa. This represented a shift in paradigm from a transmission mode of teaching and learning to a learner-centred education. The shift marks a transformation from a content-based curriculum to an Outcomes Based Education (OBE). Various authors found that different sections in the Physical Science syllabus in South Africa are often misunderstood by students for different reasons. One of the reasons was that students had their own ideas about laws of nature and these (mis)conceptions were resistant to change. From the literature and from the author's personal experience it was found that Bodies in Motion is a topic that is difficult to conceptualise by students of different age groups. The challenge facing educators is how to tackle this issue. In this research project a diagnostic test is developed and used to identify the topics where students have conceptual problems. To address these problem areas further, concept sheets/work sheets where developed and implemented. The different challenges and tasks given in the work sheets/learning material are organised in such a way as to make the students aware of their own ideas about Bodies in Motion in general and the key-concepts in particular and also to make them aware of the ideas of their peers (group members). It was also aimed at offering the learners the scientific alternative to their own beliefs. At the end, it was discovered that, even though the general understanding of the learners has improved in this topic (namely, Bodies in Motion), their original beliefs were largely unaffected. It is the hope of the researcher that the project would be the basis for further research on the development of learning material in science.
- Full Text:
- Date Issued: 2002
Self-respecting practical reason: an analysis of self-respect and its implications for practical reason
- Authors: Roberts, Deborah Joan
- Date: 2002
- Subjects: Williams, Bernard Arthur Owen -- Ethics , Ethics, Modern -- 20th century , Self-esteem
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2719 , http://hdl.handle.net/10962/d1002849 , Williams, Bernard Arthur Owen -- Ethics , Ethics, Modern -- 20th century , Self-esteem
- Description: What should I do? As long as I am aware of the relevant facts of the situation and deliberating soundly, Bernard Williams argues that I should do what I want to do. It makes no sense to say that there are reasons that are fixed objects of concern, or values, that exist for an agent regardless of what she is in fact motivated to do. Reasons, for Williams, are hypothetical. I argue that he takes this view of practical reason because of a prior answer to the question “How should I live?”. A universal account of the good life would mean an account of values, or interests, that all human beings should have. Williams thinks it is not possible to give a universal account of the good life for human beings; any such account must be constructed out of the particular reasons of a community. But, he takes a constructivist view of the good life because he thinks that to be universal an account of the good life would have to be objective. Since objectivity cannot be achieved, he argues, neither can universality. Williams is only half right. That objectivity is not possible is inconsequential. A foundation for ethics has to be internal, but this does not preclude it being universal. I develop such a foundation based on the Aristotelian conception of human nature. A life cannot be wholly good if it is not self-respecting. Moreover, self-respect fits the framework for the specification of the good life that this foundation provides: I argue that self-respect can be shown to have a structure which provides an account of real interests - reasons that are objects of fixed concern. As such, reasons recognise rather than construct the good, making categorical reasons possible. A person can have a reason to change or act, even if reason itself cannot effect that change or action. Thus, I can be wrong about what I should do not only by being wrong about what would count as a satisfaction of my interests, but also by being wrong about what my interests are.
- Full Text:
- Date Issued: 2002
- Authors: Roberts, Deborah Joan
- Date: 2002
- Subjects: Williams, Bernard Arthur Owen -- Ethics , Ethics, Modern -- 20th century , Self-esteem
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2719 , http://hdl.handle.net/10962/d1002849 , Williams, Bernard Arthur Owen -- Ethics , Ethics, Modern -- 20th century , Self-esteem
- Description: What should I do? As long as I am aware of the relevant facts of the situation and deliberating soundly, Bernard Williams argues that I should do what I want to do. It makes no sense to say that there are reasons that are fixed objects of concern, or values, that exist for an agent regardless of what she is in fact motivated to do. Reasons, for Williams, are hypothetical. I argue that he takes this view of practical reason because of a prior answer to the question “How should I live?”. A universal account of the good life would mean an account of values, or interests, that all human beings should have. Williams thinks it is not possible to give a universal account of the good life for human beings; any such account must be constructed out of the particular reasons of a community. But, he takes a constructivist view of the good life because he thinks that to be universal an account of the good life would have to be objective. Since objectivity cannot be achieved, he argues, neither can universality. Williams is only half right. That objectivity is not possible is inconsequential. A foundation for ethics has to be internal, but this does not preclude it being universal. I develop such a foundation based on the Aristotelian conception of human nature. A life cannot be wholly good if it is not self-respecting. Moreover, self-respect fits the framework for the specification of the good life that this foundation provides: I argue that self-respect can be shown to have a structure which provides an account of real interests - reasons that are objects of fixed concern. As such, reasons recognise rather than construct the good, making categorical reasons possible. A person can have a reason to change or act, even if reason itself cannot effect that change or action. Thus, I can be wrong about what I should do not only by being wrong about what would count as a satisfaction of my interests, but also by being wrong about what my interests are.
- Full Text:
- Date Issued: 2002
South African memoirs in a decade of transition: Athol Fugard's Cousins (1994), J.M. Coetzee's Boyhood (1997), and Breyten Breytenbach's Dog Heart (1999)
- Authors: Roux, Christine Ann
- Date: 2002
- Subjects: Autobiography , Fugard, Athol , Coetzee, J. M., 1940 , Breytenbach, Breyten
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2191 , http://hdl.handle.net/10962/d1002233 , Autobiography , Fugard, Athol , Coetzee, J. M., 1940 , Breytenbach, Breyten
- Description: This thesis examines three South African memoirs using M. M. Bakhtin’s theories of the dialogical relationship in language and literature. By offering an alternative to a postmodern or multicultural interpretation of autobiographies, Bakhtin’s precepts, that define a dialogic, help to reframe a way of discussing memoirs and avoiding dead-ends previously arrived at by essayists in James Olney’s 1980 collection. Bakhtin’s ideas discussed here, which include the “once-occurrent moment”, “architectonic contraposition”, ”emotional-volitional tone”, “alibi”, “non-alibi”, and “centripetal” and “centrifugal” force, help to rebuild a discussion based on temporary and evolving self truth rather than fiction, the postmodern interpretation, or confession, the new-age secular spiritualism based on multicultural and politically correct standards. For this, each author’s memoir had to be examined separately and a conclusion was arrived at through inductive analysis. Rather than try to find similar characteristics, I focused on what made each memoir different and unique. Janet Varner Gunn’s Autobiography: Toward A Poetics of Experience (1982) refocused the debate over autobiography on process. The question, what steps did each author take toward writing about himself, led the discussion to an examination of the priorities each author exemplified. Beginning with Fugard who emphasized spatial, concrete, and sensory detail to help him contain his emotional life, the thesis moves on to an examination of Coetzee’s sense of justice. From the physical and intellectual world follows Breytenbach’s spiritual space-making. In each memoir, control of space is evident on different levels of experience. Articulating space inevitably leads to a discussion of boundaries. Here, Charles Taylor’s emphasis on the modern self’s need to articulate a horizon or a framework is helpful in generalizing the effect of the autobiographical process. The conclusion reached is that autobiography is inherently centrifugal: it moves away from the center of cultural thinking because its “truth” bolsters itself on dialogical process which does not depend on a fixed authority but rather on communicative exchange. As an example of exchange, autobiography’s central truth is that it returns to a “unique point of origin”, namely the self, only to reconnect to the other in a potentially eternal exchange of responsiveness moving away from the center.
- Full Text:
- Date Issued: 2002
- Authors: Roux, Christine Ann
- Date: 2002
- Subjects: Autobiography , Fugard, Athol , Coetzee, J. M., 1940 , Breytenbach, Breyten
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2191 , http://hdl.handle.net/10962/d1002233 , Autobiography , Fugard, Athol , Coetzee, J. M., 1940 , Breytenbach, Breyten
- Description: This thesis examines three South African memoirs using M. M. Bakhtin’s theories of the dialogical relationship in language and literature. By offering an alternative to a postmodern or multicultural interpretation of autobiographies, Bakhtin’s precepts, that define a dialogic, help to reframe a way of discussing memoirs and avoiding dead-ends previously arrived at by essayists in James Olney’s 1980 collection. Bakhtin’s ideas discussed here, which include the “once-occurrent moment”, “architectonic contraposition”, ”emotional-volitional tone”, “alibi”, “non-alibi”, and “centripetal” and “centrifugal” force, help to rebuild a discussion based on temporary and evolving self truth rather than fiction, the postmodern interpretation, or confession, the new-age secular spiritualism based on multicultural and politically correct standards. For this, each author’s memoir had to be examined separately and a conclusion was arrived at through inductive analysis. Rather than try to find similar characteristics, I focused on what made each memoir different and unique. Janet Varner Gunn’s Autobiography: Toward A Poetics of Experience (1982) refocused the debate over autobiography on process. The question, what steps did each author take toward writing about himself, led the discussion to an examination of the priorities each author exemplified. Beginning with Fugard who emphasized spatial, concrete, and sensory detail to help him contain his emotional life, the thesis moves on to an examination of Coetzee’s sense of justice. From the physical and intellectual world follows Breytenbach’s spiritual space-making. In each memoir, control of space is evident on different levels of experience. Articulating space inevitably leads to a discussion of boundaries. Here, Charles Taylor’s emphasis on the modern self’s need to articulate a horizon or a framework is helpful in generalizing the effect of the autobiographical process. The conclusion reached is that autobiography is inherently centrifugal: it moves away from the center of cultural thinking because its “truth” bolsters itself on dialogical process which does not depend on a fixed authority but rather on communicative exchange. As an example of exchange, autobiography’s central truth is that it returns to a “unique point of origin”, namely the self, only to reconnect to the other in a potentially eternal exchange of responsiveness moving away from the center.
- Full Text:
- Date Issued: 2002
Speed-related isokinetic and psychophysical responses of female military personnel
- Authors: Kennedy, Dale Charles
- Date: 2002
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21028 , http://hdl.handle.net/10962/6063
- Description: The present study aims to contribute in an area that has long been neglected, the indigenous female population, about whose physical strength and work-capacity very little is known. Speed-related isokinetic and psychophysical responses of female military personnel were assessed (N=32). Furthermore benchmark data was established for Work-Simulation isokinetic responses where there appears to be limited publication. Analysis of the data showed significant differences in torque, work and power outputs as velocity increased. Only wrench-turning left and right rotation for peak torque and total work did not show significant reductions. Consistency of effort level recorded an average of 72% across the selected isokinetic tests. No discernible morphological and strength expression differences were observed between military office workers and infantry personnel, and no significant correlations were recorded between heart rate and RPE values.
- Full Text:
- Date Issued: 2002
- Authors: Kennedy, Dale Charles
- Date: 2002
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21028 , http://hdl.handle.net/10962/6063
- Description: The present study aims to contribute in an area that has long been neglected, the indigenous female population, about whose physical strength and work-capacity very little is known. Speed-related isokinetic and psychophysical responses of female military personnel were assessed (N=32). Furthermore benchmark data was established for Work-Simulation isokinetic responses where there appears to be limited publication. Analysis of the data showed significant differences in torque, work and power outputs as velocity increased. Only wrench-turning left and right rotation for peak torque and total work did not show significant reductions. Consistency of effort level recorded an average of 72% across the selected isokinetic tests. No discernible morphological and strength expression differences were observed between military office workers and infantry personnel, and no significant correlations were recorded between heart rate and RPE values.
- Full Text:
- Date Issued: 2002
State or public service broadcasting?: an analysis of the coverage of political issues and debates during an election campaign on television news
- Authors: Macha, Herbert
- Date: 2002
- Subjects: Public service television programs -- Zambia , Television in politics , Television broadcasting of news -- Zambia , Elections -- Zambia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3502 , http://hdl.handle.net/10962/d1006234 , Public service television programs -- Zambia , Television in politics , Television broadcasting of news -- Zambia , Elections -- Zambia
- Description: Public Service Television remains a key institution of democratisation in the context of emerging democracies in Africa, especially with the advent of liberalisation and commercialisation of the media. The democratic changes taking place in Zambia require a genuine public service broadcasting television that will promote pluralism in the public sphere. Among the many available strategies and mechanisms for fostering a sustainable democratic and cultural environment, public service broadcasting is still the best. This study set out to examine representation of political issues and debates during election campaign on ZNBC television news to assess the extent to which it plays a role as a public broadcaster in the mediation of pluralistic politics. Election news on television, in line with the public sphere argument was found to be essential for investigating the nature of public service television from the point of view of impartiality, universality and diversity. Using both qualitative and quantitative methods the study has confirmed the hypothesis that the role of a public service television in the mediation of pluralistic politics is compromised by ZNBC's partial and unbalanced coverage of elections. As a result ZNBC, as a public service broadcaster is undermining the very democracy it is expected to promote. Public service television should take new forms if it is to be recognised and appreciated by the public as a genuine, open and democratic public sphere. I therefore recommend that a system of license fee for viewers be introduced. Secondly, government should increase funding into public service television to supplement revenue from license fee and advertising. Thirdly, I recommend the appointment of an independent board whose members will be appointed for a fixed term, by public nomination and a process of public hearing, according to publicly available criteria, which guarantees diversity of political, ethnic, social and professional background. Fourthly I suggest the formation of an Election News Coverage Committee comprising of journalists, academicians, the church and civic organisation that will formulate and implement editorial policy on election coverage and above all monitor and the coverage of elections on ZNBC television news.
- Full Text:
- Date Issued: 2002
- Authors: Macha, Herbert
- Date: 2002
- Subjects: Public service television programs -- Zambia , Television in politics , Television broadcasting of news -- Zambia , Elections -- Zambia
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3502 , http://hdl.handle.net/10962/d1006234 , Public service television programs -- Zambia , Television in politics , Television broadcasting of news -- Zambia , Elections -- Zambia
- Description: Public Service Television remains a key institution of democratisation in the context of emerging democracies in Africa, especially with the advent of liberalisation and commercialisation of the media. The democratic changes taking place in Zambia require a genuine public service broadcasting television that will promote pluralism in the public sphere. Among the many available strategies and mechanisms for fostering a sustainable democratic and cultural environment, public service broadcasting is still the best. This study set out to examine representation of political issues and debates during election campaign on ZNBC television news to assess the extent to which it plays a role as a public broadcaster in the mediation of pluralistic politics. Election news on television, in line with the public sphere argument was found to be essential for investigating the nature of public service television from the point of view of impartiality, universality and diversity. Using both qualitative and quantitative methods the study has confirmed the hypothesis that the role of a public service television in the mediation of pluralistic politics is compromised by ZNBC's partial and unbalanced coverage of elections. As a result ZNBC, as a public service broadcaster is undermining the very democracy it is expected to promote. Public service television should take new forms if it is to be recognised and appreciated by the public as a genuine, open and democratic public sphere. I therefore recommend that a system of license fee for viewers be introduced. Secondly, government should increase funding into public service television to supplement revenue from license fee and advertising. Thirdly, I recommend the appointment of an independent board whose members will be appointed for a fixed term, by public nomination and a process of public hearing, according to publicly available criteria, which guarantees diversity of political, ethnic, social and professional background. Fourthly I suggest the formation of an Election News Coverage Committee comprising of journalists, academicians, the church and civic organisation that will formulate and implement editorial policy on election coverage and above all monitor and the coverage of elections on ZNBC television news.
- Full Text:
- Date Issued: 2002
Synthetic approaches to marine labdane diterpenes
- Authors: Wisch, Gregory Albert
- Date: 2002 , 2013-05-10
- Subjects: Diterpenes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4289 , http://hdl.handle.net/10962/d1003131 , Diterpenes
- Description: The work presented in this thesis describes the synthesis of labd-13-en-8ß, 15-diol (46) a stable reduced derivative of an unstable marine natural product aldehyde [8ß-hydroxylabd-13E-en-15-al (6)] isolated by Cimino, et al. from the skin of a Notaspidean mollusc Pleurobranchaea meckelii. The rationale for the synthesis was to provide sufficient 46 for eventual mild oxidation to 6 and investigation of the biological activity of this latter compound. (-)-Sclareol (32), a common diterpene synthetic precursor, was the starting point for the ten step synthesis of 46 described in this thesis. A search of the literature revealed that only one non stereospecific synthesis of 46 had been previously reported. To provide the necessary background to the synthetic component of this thesis, both the occurrence of labdane and ent-labdane in the marine environment and the use of sclareol in the synthesis of marine natural products, was reviewed. The initial step in the synthesis of 46 was the potassium permanganate oxidation of sclareol to give a bisnorlabdane ketone. Reduction of this ketone with lithium aluminium hydride produced a mixture of diols which, through t-butyldimethysilyl triflate protection, afforded a quantitative route to protecting the C-13 ketone in an effort to prevent unwanted intramolecular cyclization reactions. Dehydration of the tertiary alcohol moiety at C-8 with phosphorous oxychloride yielded the Δ⁸·¹⁵ exocyclic alkene required for the next oxidation step. Ozonolysis succeeded in producing the desired C-8 ketone after much deliberation and research into alternative oxidation strategies. Methyl lithium methylation quantitatively afforded the desired a-methyl substitution at C-8, identified at the onset as the key step in the synthesis. Tetra-butylarnmonium fluoride deprotection yielded the 8ß,13-dihydoxylated product, which was in turn subjected to a Swern oxidition to give the desired 8ß-hydroxy-bisnorlabda-13-one. A modified Horner-Wadsworth-Emmons reaction allowed for elaboration at C-13 to yield a to Δ¹³ olefin with a terminal C-15 ethyl ester. Diisobutylaluminium hydride reduction of the ester produced the desired labd-13-en-8ß, 15-diol (46) in a low overall yield of 3.4%. Although opportunities for optimization of at least three steps in the synthesis exist, time constraints prevented both optimization of these steps and an investigation of the oxidation of 46 to 6. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002
- Authors: Wisch, Gregory Albert
- Date: 2002 , 2013-05-10
- Subjects: Diterpenes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4289 , http://hdl.handle.net/10962/d1003131 , Diterpenes
- Description: The work presented in this thesis describes the synthesis of labd-13-en-8ß, 15-diol (46) a stable reduced derivative of an unstable marine natural product aldehyde [8ß-hydroxylabd-13E-en-15-al (6)] isolated by Cimino, et al. from the skin of a Notaspidean mollusc Pleurobranchaea meckelii. The rationale for the synthesis was to provide sufficient 46 for eventual mild oxidation to 6 and investigation of the biological activity of this latter compound. (-)-Sclareol (32), a common diterpene synthetic precursor, was the starting point for the ten step synthesis of 46 described in this thesis. A search of the literature revealed that only one non stereospecific synthesis of 46 had been previously reported. To provide the necessary background to the synthetic component of this thesis, both the occurrence of labdane and ent-labdane in the marine environment and the use of sclareol in the synthesis of marine natural products, was reviewed. The initial step in the synthesis of 46 was the potassium permanganate oxidation of sclareol to give a bisnorlabdane ketone. Reduction of this ketone with lithium aluminium hydride produced a mixture of diols which, through t-butyldimethysilyl triflate protection, afforded a quantitative route to protecting the C-13 ketone in an effort to prevent unwanted intramolecular cyclization reactions. Dehydration of the tertiary alcohol moiety at C-8 with phosphorous oxychloride yielded the Δ⁸·¹⁵ exocyclic alkene required for the next oxidation step. Ozonolysis succeeded in producing the desired C-8 ketone after much deliberation and research into alternative oxidation strategies. Methyl lithium methylation quantitatively afforded the desired a-methyl substitution at C-8, identified at the onset as the key step in the synthesis. Tetra-butylarnmonium fluoride deprotection yielded the 8ß,13-dihydoxylated product, which was in turn subjected to a Swern oxidition to give the desired 8ß-hydroxy-bisnorlabda-13-one. A modified Horner-Wadsworth-Emmons reaction allowed for elaboration at C-13 to yield a to Δ¹³ olefin with a terminal C-15 ethyl ester. Diisobutylaluminium hydride reduction of the ester produced the desired labd-13-en-8ß, 15-diol (46) in a low overall yield of 3.4%. Although opportunities for optimization of at least three steps in the synthesis exist, time constraints prevented both optimization of these steps and an investigation of the oxidation of 46 to 6. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002
Teacher responses to the Namibian education reform : a case study of two Caprivi schools
- Authors: Kamwi, Kamwi Kenneth
- Date: 2002
- Subjects: Education -- Namibia Education and state -- Namibia Educational change -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1791 , http://hdl.handle.net/10962/d1003676
- Description: Effective implementation of education reforms consists of alterations in curriculum materials, instructional practices and behaviour, beliefs and understandings on the part of the teachers involved in the reform (Fullan and Hargreaves, 1993: 5). A process of implementation is therefore, a learning process, learning how to do something new (ibid.). This study was done to establish how Biology teachers in Caprivi have responded to the reform process ten years down the line. I used a qualitative case study of two secondary schools. Four Biology teachers, two school principals and two groups of learners participated in the study. Data was collected by means of interviews, lesson observations, a workshop, and school inventories. The data was analysed within an interpretive framework. The results of the study show a move into 'activity-based teaching'. It shows a shift from the traditional transmission teaching approach. In general teachers seem to equate 'activity-based teaching' with the learner-centred approach.
- Full Text:
- Date Issued: 2002
- Authors: Kamwi, Kamwi Kenneth
- Date: 2002
- Subjects: Education -- Namibia Education and state -- Namibia Educational change -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1791 , http://hdl.handle.net/10962/d1003676
- Description: Effective implementation of education reforms consists of alterations in curriculum materials, instructional practices and behaviour, beliefs and understandings on the part of the teachers involved in the reform (Fullan and Hargreaves, 1993: 5). A process of implementation is therefore, a learning process, learning how to do something new (ibid.). This study was done to establish how Biology teachers in Caprivi have responded to the reform process ten years down the line. I used a qualitative case study of two secondary schools. Four Biology teachers, two school principals and two groups of learners participated in the study. Data was collected by means of interviews, lesson observations, a workshop, and school inventories. The data was analysed within an interpretive framework. The results of the study show a move into 'activity-based teaching'. It shows a shift from the traditional transmission teaching approach. In general teachers seem to equate 'activity-based teaching' with the learner-centred approach.
- Full Text:
- Date Issued: 2002
The adaptation of the Clark (1997) treatment for social phobia into a group therapy format, and a preliminary evaluation
- Authors: Kannan, Swetha
- Date: 2002
- Subjects: Social phobia -- Treatment , Group psychotherapy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3109 , http://hdl.handle.net/10962/d1004547 , Social phobia -- Treatment , Group psychotherapy
- Description: Clark and Wells (1995) constructed a comprehensive cognitive model of social phobic behaviour, in terms of which social phobic behaviour is activated and maintained by a system consisting of negative thoughts and beliefs, anxiety s)mptoms, avoidance and safety behaviours, and processing of self as a social object. The interaction of these elements creates a series of vicious circles which escalate and which keep the phobic individual in a state of chronic -disability, either because they chronically avoid significant social situations or because they find themselves incapacitated by anxiety when they enter them. The Clark and Wells (1995) treatment programme is designed to alleviate the social phobia by targeting the components that form the vicious maintenance cycle and replacing these by new patterns of cognition and behaviour. This treatment programme was designed for individual treatment, and the present study adapted it to a group format. Seven social phobic university students participated in the adapted group treatment format over the course of 13, 2-hour group sessions. Regular assessment of participants' response to the programme was carried out weekly and at two follow-up assessments, with the use of a series of questionnaires. In addition, sessions were audio taped and videotaped, facilitators took notes during sessions and keep records made by participants of their homework exercises. Individual case studies were written for all participants (including two non-completers) in which case narratives were juxtaposed against their responses to each of the self-report questionnaires. These we used as a basis for evaluating the validity of the Clark and Wells theoretical model and in examining the effectiveness of the treatment programme in bringing to awareness and interrupting the cycles that maintained the phobic behaviour. It is concluded that the group programme showed evidence of being very effective and, a group treatment manual was constructed so that it can be employed clinically and in future research.
- Full Text:
- Date Issued: 2002
- Authors: Kannan, Swetha
- Date: 2002
- Subjects: Social phobia -- Treatment , Group psychotherapy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3109 , http://hdl.handle.net/10962/d1004547 , Social phobia -- Treatment , Group psychotherapy
- Description: Clark and Wells (1995) constructed a comprehensive cognitive model of social phobic behaviour, in terms of which social phobic behaviour is activated and maintained by a system consisting of negative thoughts and beliefs, anxiety s)mptoms, avoidance and safety behaviours, and processing of self as a social object. The interaction of these elements creates a series of vicious circles which escalate and which keep the phobic individual in a state of chronic -disability, either because they chronically avoid significant social situations or because they find themselves incapacitated by anxiety when they enter them. The Clark and Wells (1995) treatment programme is designed to alleviate the social phobia by targeting the components that form the vicious maintenance cycle and replacing these by new patterns of cognition and behaviour. This treatment programme was designed for individual treatment, and the present study adapted it to a group format. Seven social phobic university students participated in the adapted group treatment format over the course of 13, 2-hour group sessions. Regular assessment of participants' response to the programme was carried out weekly and at two follow-up assessments, with the use of a series of questionnaires. In addition, sessions were audio taped and videotaped, facilitators took notes during sessions and keep records made by participants of their homework exercises. Individual case studies were written for all participants (including two non-completers) in which case narratives were juxtaposed against their responses to each of the self-report questionnaires. These we used as a basis for evaluating the validity of the Clark and Wells theoretical model and in examining the effectiveness of the treatment programme in bringing to awareness and interrupting the cycles that maintained the phobic behaviour. It is concluded that the group programme showed evidence of being very effective and, a group treatment manual was constructed so that it can be employed clinically and in future research.
- Full Text:
- Date Issued: 2002
The biology and molecular ecology of floating sulphur biofilms
- Authors: Bowker, Michelle Louise
- Date: 2002
- Subjects: Biofilms , Microbial ecology , Sulfur
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4056 , http://hdl.handle.net/10962/d1004117 , Biofilms , Microbial ecology , Sulfur
- Description: Floating sulphur biofilms have been observed to occur on sulphate-containing natural systems and waste stabilization ponds. It has been postulated that these biofilms form on the surface of the water because sulphate reducing bacteria present in the bottom layers of the water body reduce sulphate to sulphide which then diffuses upwards and is oxidized under the correct redox conditions to sulphur by sulphide oxidizing bacteria. Very little information exists on these complex floating systems and in order to study them further, model systems were designed. The Baffle Reactor was successfully used to cultivate floating sulphur biofilms. Conditions within the reactor could be closely scrutinized in the laboratory and it was found that sulphate levels decreased, sulphide levels increased and that sulphur was produced over a period of 2 weeks. The success of this system led to it being scaled-up and currently a method to harvest sulphur from the biofilm is under development. It is thought that biofilms are highly complex, heterogeneous structures with different bacteria distributed in different layers. Preliminary work suggested that bacteria were differentially distributed along nutrient and oxygen gradients within the biofilm. Biofilms are very thin structures and therefore difficult to study and Gradient systems were developed in an attempt to spatially separate the biofilm species into functional layers. Gradient Tubes were designed; these provided a gradient of high-sulphide, low oxygen conditions to high-oxygen, low-sulphide conditions. Bacteria were observed to grow in different layers of these systems. The Gradient Tubes could be sectioned and the chemical characteristics of each section as well as the species present could be determined. Silicon Tubular Bioreactors were also developed and these were very efficient at producing large amounts of sulphur under strictly controlled redox conditions. Microscopy and molecular methods including the amplification of a section of Ribosomal Ribonucleic acid by Polymerase Chain Reaction were used in an attempt to characterize the populations present in these biofilm systems. Denaturing Gradient Gel Electrophoresis was used to create band profiles of the populations; individual bands were excised from the gels and sequenced. Identified species included Ectothiorhodospira sp., Dethiosulfovibrio russensis, Pseudomonas geniculata, Thiobacillus baregensis and Halothiobacillus kellyi.
- Full Text:
- Date Issued: 2002
- Authors: Bowker, Michelle Louise
- Date: 2002
- Subjects: Biofilms , Microbial ecology , Sulfur
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4056 , http://hdl.handle.net/10962/d1004117 , Biofilms , Microbial ecology , Sulfur
- Description: Floating sulphur biofilms have been observed to occur on sulphate-containing natural systems and waste stabilization ponds. It has been postulated that these biofilms form on the surface of the water because sulphate reducing bacteria present in the bottom layers of the water body reduce sulphate to sulphide which then diffuses upwards and is oxidized under the correct redox conditions to sulphur by sulphide oxidizing bacteria. Very little information exists on these complex floating systems and in order to study them further, model systems were designed. The Baffle Reactor was successfully used to cultivate floating sulphur biofilms. Conditions within the reactor could be closely scrutinized in the laboratory and it was found that sulphate levels decreased, sulphide levels increased and that sulphur was produced over a period of 2 weeks. The success of this system led to it being scaled-up and currently a method to harvest sulphur from the biofilm is under development. It is thought that biofilms are highly complex, heterogeneous structures with different bacteria distributed in different layers. Preliminary work suggested that bacteria were differentially distributed along nutrient and oxygen gradients within the biofilm. Biofilms are very thin structures and therefore difficult to study and Gradient systems were developed in an attempt to spatially separate the biofilm species into functional layers. Gradient Tubes were designed; these provided a gradient of high-sulphide, low oxygen conditions to high-oxygen, low-sulphide conditions. Bacteria were observed to grow in different layers of these systems. The Gradient Tubes could be sectioned and the chemical characteristics of each section as well as the species present could be determined. Silicon Tubular Bioreactors were also developed and these were very efficient at producing large amounts of sulphur under strictly controlled redox conditions. Microscopy and molecular methods including the amplification of a section of Ribosomal Ribonucleic acid by Polymerase Chain Reaction were used in an attempt to characterize the populations present in these biofilm systems. Denaturing Gradient Gel Electrophoresis was used to create band profiles of the populations; individual bands were excised from the gels and sequenced. Identified species included Ectothiorhodospira sp., Dethiosulfovibrio russensis, Pseudomonas geniculata, Thiobacillus baregensis and Halothiobacillus kellyi.
- Full Text:
- Date Issued: 2002
The biotransformation of phenolic pollutants using polyphenol oxidase
- Authors: Boshoff, Aileen
- Date: 2002
- Subjects: Polyphenol oxidase Sewage -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3976 , http://hdl.handle.net/10962/d1004035
- Description: The potential of using mushroom polyphenol oxidase (EC 1.14.18.1) as a biocatalyst for the biotransformation of phenols to produce catechols in an aqueous medium was investigated. Polyphenol oxidase is characterised by two distinct reactions i.e., the ortho-hydroxylation of phenols to catechols (cresolase activity) and the subsequent oxidation of catechols to orthoquinones (catecholase activity). In order to facilitate the development of a process to produce catechols, the accumulation of catechol as a true intermediate product released in the reaction system needed to be investigated, as its release had been disputed due to the oxidation of catechols to o-quinones. Using LC-MS, catechol products were successfully identified as true intermediate products formed during biocatalytic reactions in water.
- Full Text:
- Date Issued: 2002
- Authors: Boshoff, Aileen
- Date: 2002
- Subjects: Polyphenol oxidase Sewage -- Purification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3976 , http://hdl.handle.net/10962/d1004035
- Description: The potential of using mushroom polyphenol oxidase (EC 1.14.18.1) as a biocatalyst for the biotransformation of phenols to produce catechols in an aqueous medium was investigated. Polyphenol oxidase is characterised by two distinct reactions i.e., the ortho-hydroxylation of phenols to catechols (cresolase activity) and the subsequent oxidation of catechols to orthoquinones (catecholase activity). In order to facilitate the development of a process to produce catechols, the accumulation of catechol as a true intermediate product released in the reaction system needed to be investigated, as its release had been disputed due to the oxidation of catechols to o-quinones. Using LC-MS, catechol products were successfully identified as true intermediate products formed during biocatalytic reactions in water.
- Full Text:
- Date Issued: 2002
The characterisation of a South African isolate of Cryptophlebia leucotreta Granulovirus (CIGV)
- Authors: Singh, Shalene
- Date: 2002
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control -- Africa , DNA viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4067 , http://hdl.handle.net/10962/d1004929 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control -- Africa , DNA viruses
- Description: The false codling moth (FCM), Cryptophlehia Leucatreta, causes widespread damage to economically important fruit crops throughout sub-Saharan Africa. Fruit are rendered unfit for consumption once they have been stung by FCM larvae. Larval infestation of fruit can lead to significant pre-harvest losses or post-harvest waste, posing a major problem to the citrus industry. Current control of the pest includes the use of chemical pesticides. The larval form of FCM is known to be infected by a granulovirus called Cryptophlebia leucotreta granulovirus (CIGV). Granuloviruses are highly specific against their hosts and are harmless to vertebrates, plants and the environment. The development of CIGV into a biological control agent would offer an attractive and safer alternative for the control of this pest. A full characterisation of CIGV is required prior to the virus being disseminated into the environment. In this project, the characteristics of CIGV will be examined. Viral DNA was extracted from infected larvae and the DNA analysed by restriction fragment length polymorphism (RFLP). Fragmentation profiles of the South African and Cape Verde (CV3) isolates of the virus were compared, revealing distinct differences between them. The size of the CIGV-SA genome was calculated to be 112 kbp, identical to the size of the CV3 isolate. Physical maps for five restriction enzymes were constructed for the CIGV-SA genome. The alignment of these maps with maps the CV3 isolate (for the same enzymes) further highlighted the differences between the isolates. The genetic engineering of granuloviruses could significantly improve the speed of kill of these viruses. Therefore essential genes like egt and granulin were isolated (by PCR) and their position located in the genome. Both genes were sequenced and their phylogeny with other granulin and egt genes investigated. Finally, tbe incidence of CIGV in natural populations of FCM larvae was investigated, by screening field-collected larvae for the presence of the virus. CIGV was successfully detected from dot blots of larval DNA using both radiolabelled and non-radiolabelled probes and by PCR. Trends regarding the incidence of CIGV in natural populations of larvae were also determined.
- Full Text:
- Date Issued: 2002
- Authors: Singh, Shalene
- Date: 2002
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control -- Africa , DNA viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4067 , http://hdl.handle.net/10962/d1004929 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control -- Africa , DNA viruses
- Description: The false codling moth (FCM), Cryptophlehia Leucatreta, causes widespread damage to economically important fruit crops throughout sub-Saharan Africa. Fruit are rendered unfit for consumption once they have been stung by FCM larvae. Larval infestation of fruit can lead to significant pre-harvest losses or post-harvest waste, posing a major problem to the citrus industry. Current control of the pest includes the use of chemical pesticides. The larval form of FCM is known to be infected by a granulovirus called Cryptophlebia leucotreta granulovirus (CIGV). Granuloviruses are highly specific against their hosts and are harmless to vertebrates, plants and the environment. The development of CIGV into a biological control agent would offer an attractive and safer alternative for the control of this pest. A full characterisation of CIGV is required prior to the virus being disseminated into the environment. In this project, the characteristics of CIGV will be examined. Viral DNA was extracted from infected larvae and the DNA analysed by restriction fragment length polymorphism (RFLP). Fragmentation profiles of the South African and Cape Verde (CV3) isolates of the virus were compared, revealing distinct differences between them. The size of the CIGV-SA genome was calculated to be 112 kbp, identical to the size of the CV3 isolate. Physical maps for five restriction enzymes were constructed for the CIGV-SA genome. The alignment of these maps with maps the CV3 isolate (for the same enzymes) further highlighted the differences between the isolates. The genetic engineering of granuloviruses could significantly improve the speed of kill of these viruses. Therefore essential genes like egt and granulin were isolated (by PCR) and their position located in the genome. Both genes were sequenced and their phylogeny with other granulin and egt genes investigated. Finally, tbe incidence of CIGV in natural populations of FCM larvae was investigated, by screening field-collected larvae for the presence of the virus. CIGV was successfully detected from dot blots of larval DNA using both radiolabelled and non-radiolabelled probes and by PCR. Trends regarding the incidence of CIGV in natural populations of larvae were also determined.
- Full Text:
- Date Issued: 2002
The development assumptions of Botswana television : an assessment
- Authors: Mmusi, Bishy
- Date: 2002
- Subjects: Television -- Social aspects -- Botswana , Botswana -- Social conditions , AIDS (Disease) -- Botswana
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3511 , http://hdl.handle.net/10962/d1007668 , Television -- Social aspects -- Botswana , Botswana -- Social conditions , AIDS (Disease) -- Botswana
- Description: This study researched a project to set up a national television service for Botswana to find out whether the service could be used for rural development generally, and in particular to assist the Ministry of Health to implement its health projects in the rural areas and including the fight against the AIDS disease. It reviews conceptions of development and also analyses various communication models that usefully inform the conceptualisation of a TV service that can contribute to development. The study was done by going through reports of feasibility studies on the project and through letters of official correspondence among officials of the Government of Botswana who debated the subject of whether or not the country should have a national TV service. The reports and correspondence were supplemented with interviews of key people involved in the implementation of the project, as well as interviews of officials of the Ministry of Health. The findings of the study are that the Botswana television service project started and ended on a footing that forgot about television, a medium that is dependent on professional and organisational capacity and purpose, and as a result the project did not take-off. A qualitative method was used as the study required in-depth interviews during which new issues kept on emerging and nothing could be pre-determined because the study took place as the project was being implemented. The study was completed in June 2000, at a point where the project should have been completed but it was discovered that the station could not go on air as a television service had not been conceptualised and there was no management structure in place and the Government of Botswana appealed to the British Government for the staff of the British Broadcasting Corporation to come quickly to Botswana to rescue the project and put it on track, supposedly. The study has concluded that the Botswana television service project became stillborn because there was a lack of professional and intellectual capacity to conceptualise the service, and instead there had been too much concentration on the construction of the TV building and acquisition of equipment.
- Full Text:
- Date Issued: 2002
- Authors: Mmusi, Bishy
- Date: 2002
- Subjects: Television -- Social aspects -- Botswana , Botswana -- Social conditions , AIDS (Disease) -- Botswana
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3511 , http://hdl.handle.net/10962/d1007668 , Television -- Social aspects -- Botswana , Botswana -- Social conditions , AIDS (Disease) -- Botswana
- Description: This study researched a project to set up a national television service for Botswana to find out whether the service could be used for rural development generally, and in particular to assist the Ministry of Health to implement its health projects in the rural areas and including the fight against the AIDS disease. It reviews conceptions of development and also analyses various communication models that usefully inform the conceptualisation of a TV service that can contribute to development. The study was done by going through reports of feasibility studies on the project and through letters of official correspondence among officials of the Government of Botswana who debated the subject of whether or not the country should have a national TV service. The reports and correspondence were supplemented with interviews of key people involved in the implementation of the project, as well as interviews of officials of the Ministry of Health. The findings of the study are that the Botswana television service project started and ended on a footing that forgot about television, a medium that is dependent on professional and organisational capacity and purpose, and as a result the project did not take-off. A qualitative method was used as the study required in-depth interviews during which new issues kept on emerging and nothing could be pre-determined because the study took place as the project was being implemented. The study was completed in June 2000, at a point where the project should have been completed but it was discovered that the station could not go on air as a television service had not been conceptualised and there was no management structure in place and the Government of Botswana appealed to the British Government for the staff of the British Broadcasting Corporation to come quickly to Botswana to rescue the project and put it on track, supposedly. The study has concluded that the Botswana television service project became stillborn because there was a lack of professional and intellectual capacity to conceptualise the service, and instead there had been too much concentration on the construction of the TV building and acquisition of equipment.
- Full Text:
- Date Issued: 2002
The ecology of the red-billed quelea Quelea Quelea (Linnaeus) and other granivorous birds at Eastern Cape feedlots
- Whittington-Jones, Craig Alun
- Authors: Whittington-Jones, Craig Alun
- Date: 2002
- Subjects: Quelea quelea -- South Africa -- Eastern Cape Granivores -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5618 , http://hdl.handle.net/10962/d1003286
- Description: Red-billed Quelea Quelea quelea have expanded their range in the Eastern Cape and now occur throughout the year in new areas. Recent changes in agricultural practice have probably been a contributing factor as flocks are larger than previously recorded and were more often associated with artificial food sources than natural grasses. Ringing and census data indicate that quelea have reduced movements during the non-breeding season and may display strong fidelity (over successive years) to dry season quarters with reliable food supplies. Although the recapture/recovery rate for quelea in the Eastern Cape (1.0-2.5%) was higher than the national average, it was still lower than expected and there may be considerable movement between nearby feeding sites. Some quelea breed locally, but most disperse during summer and their numbers at the feedlots were generally highest in winter and spring. The breeding season of quelea is later than other ploceids in the region and post-nuptial moult overlaps with winter. Replacement of primary wing feathers is relatively slow (124 days), and this is considered an adaptation to minimise disruption of flight capabilities and insulation. Significantly more quelea in the Eastern Cape have breeding plumage suffused with pink than in other southern African populations. However, during the non-breeding season there is apparently considerable intermixing between local populations and those from further north and the existence of a local sub-species is not supported. Seeds of two grass species, Echinochloa sp. and Urochloa panicoides, and two weed species, Amaranthus sp. and Chenopodium sp., were important in the diet of both quelea and Laughing Doves Streptopelia senegalensis. Maize comprised a large proportion of the diet of these species and losses at one ostrich feedlot were estimated at over R 17 000 in two years. Dependence on artificial food sources was generally greatest in winter and spring, but economically significant damage was not confined to this period. Alpha-chloralose showed good potential for reducing numbers of problem birds at livestock feedlots. However, the dynamic nature of problem bird populations favours a non-lethal management approach. Reduction of feed loss through manipulation of the ostrich ration could provide a relatively cheap and effective alternative to lethal control if applied appropriately.
- Full Text:
- Date Issued: 2002
- Authors: Whittington-Jones, Craig Alun
- Date: 2002
- Subjects: Quelea quelea -- South Africa -- Eastern Cape Granivores -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5618 , http://hdl.handle.net/10962/d1003286
- Description: Red-billed Quelea Quelea quelea have expanded their range in the Eastern Cape and now occur throughout the year in new areas. Recent changes in agricultural practice have probably been a contributing factor as flocks are larger than previously recorded and were more often associated with artificial food sources than natural grasses. Ringing and census data indicate that quelea have reduced movements during the non-breeding season and may display strong fidelity (over successive years) to dry season quarters with reliable food supplies. Although the recapture/recovery rate for quelea in the Eastern Cape (1.0-2.5%) was higher than the national average, it was still lower than expected and there may be considerable movement between nearby feeding sites. Some quelea breed locally, but most disperse during summer and their numbers at the feedlots were generally highest in winter and spring. The breeding season of quelea is later than other ploceids in the region and post-nuptial moult overlaps with winter. Replacement of primary wing feathers is relatively slow (124 days), and this is considered an adaptation to minimise disruption of flight capabilities and insulation. Significantly more quelea in the Eastern Cape have breeding plumage suffused with pink than in other southern African populations. However, during the non-breeding season there is apparently considerable intermixing between local populations and those from further north and the existence of a local sub-species is not supported. Seeds of two grass species, Echinochloa sp. and Urochloa panicoides, and two weed species, Amaranthus sp. and Chenopodium sp., were important in the diet of both quelea and Laughing Doves Streptopelia senegalensis. Maize comprised a large proportion of the diet of these species and losses at one ostrich feedlot were estimated at over R 17 000 in two years. Dependence on artificial food sources was generally greatest in winter and spring, but economically significant damage was not confined to this period. Alpha-chloralose showed good potential for reducing numbers of problem birds at livestock feedlots. However, the dynamic nature of problem bird populations favours a non-lethal management approach. Reduction of feed loss through manipulation of the ostrich ration could provide a relatively cheap and effective alternative to lethal control if applied appropriately.
- Full Text:
- Date Issued: 2002
The ecophysiology of selected coastal dune pioneer plants of the Eastern Cape
- Authors: Ripley, B S
- Date: 2002
- Subjects: Sand dune plants -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Sand dune plants -- Ecophysiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4222 , http://hdl.handle.net/10962/d1003791
- Description: Understanding the mechanisms and adaptations that allow only certain species to thrive in the potentially stressful foredune environment requires a knowledge of the basic ecophysiology of foredune species. Ecophysiological measurements were conducted on the foredune pioneer species Arctotheca populifolia (Berg.) Norl., Ipomoea pes-caprae(L.) R. Br. and Scaevola plumieri (L.) Vahl. and showed significant differences among species with respect to the physiology associated with biomass production, water and nutrient relations. Differences related to CO₂ assimilation included differences in photosynthetic and respiratory rates, susceptibility to light stress and leaf and stem non-structural carbohydrate concentrations. These resulted in differences in primary production rates of shoots. Mechanisms leading to the differences in CO₂ assimilation among species included differences in stomatal behaviour, carboxylation efficiencies, efficiencies of utilisation of incident photosynthetic photon flux density (PPFD) and rates of ribulose-1,6-bisphosphate (RuBP) regeneration. Correlated with differences in photosynthetic capacity were differences in chlorophyll contents but not differences in leaf nitrogen content. Differences in interspecific stomatal behaviour resulted in significantly different transpiration rates which in combination with differences in assimilation rates resulted in differences in water-use efficiency. The absolute amounts of water transpired, although significantly different among species, were moderate to high in comparison with species from other ecosystems and were typical of mesophytes. Transpiration rates in combination with plant hydraulic conductances and soil water availability resulted in leaf water potentials that were not very negative and none of the investigated species showed evidence of osmotic adjustment. The volume of water transpired by each of the species per unit land surface area was estimated from the relationship between abiotic factors and plant water loss. These relationships varied among species and had varying degrees of predictability as a result of differences in stomatal behaviour between the three species. The water requirements of A. populifolia and S. plumieri were adequately met by the water supplied by rainfall and the water stored in the dune sands. It was therefore not necessary to invoke the utilisation of ground water or the process of internal dew formation to supply sufficient water to meet the requirements. However, I. pes-caprae despite its lower transpiration rates and due to its higher biomass, lost greater volumes of water per unit dune surface area than either A. populifolia or S. plumieri. This resulted in periods of potential water limitation for I. pes-caprae. Incident light was the most important determinant of leaf photosynthetic CO₂ assimilation and transpiration, particularly as a linear relationship between incident PPFD and atmospheric vapour pressure deficit (VPD) could be demonstrated. Whole plant photosynthetic production by S. plumieri was shown to be light limited as a result of mutual shading despite high incident and reflected PPFD occurring in the foredune environment. The leaf hair-layer of A. populifolia was shown to be important in reducing transmitted UV and hence reducing photoinhibition but it also caused reduced transpiration rates because of the thicker boundary layer and thus increased leaf temperatures. The nutrient content of above-ground plant parts of the investigated species were typical of higher plants despite the low nutrient content measured for the dune soils. With the possible exception of nitrogen the nutrient demand created by above-ground production was adequately met by the supply of nutrients either from sand-water or from aquifer-water transpired by the plants. Differences in the volumes of water transpired, and hence the quantity of nutrients potentially taken up via the transpiration stream, resulted in interspecific differences in above-ground plant macronutrient content. The reallocation patterns of nutrients differed both between the various nutrients measured and interspecifically. Standing biomass and the density of plants per unit land area was low in comparison to that of other ecosystems and was different among investigated species. This may be important in maintaining the adequate supply of resources (water, nutrients and light). As a result of the interspecific differences in biomass when production was expressed per unit land surface area the resultant productivity was not dissimilar among species. Productivity was high when comparisons were made with species from other ecosystems. No single resource (water, nutrients or light) could be identified as the controlling factor in the foredune environment and a combination of both resource stress and environmental disturbance are likely to be involved. Physiology, production, growth and growth characteristics conveyed certain adaptive advantages to these species in respect to both resource stress and environmental disturbance. Interspecific differences in these adaptations can be used to offer explanations for the observed microhabitat preferences of the three investigated species. Furthermore features common to all three species offer some explanations as to why these species and not others are able to inhabit the foredunes.
- Full Text:
- Date Issued: 2002
- Authors: Ripley, B S
- Date: 2002
- Subjects: Sand dune plants -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Sand dune plants -- Ecophysiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4222 , http://hdl.handle.net/10962/d1003791
- Description: Understanding the mechanisms and adaptations that allow only certain species to thrive in the potentially stressful foredune environment requires a knowledge of the basic ecophysiology of foredune species. Ecophysiological measurements were conducted on the foredune pioneer species Arctotheca populifolia (Berg.) Norl., Ipomoea pes-caprae(L.) R. Br. and Scaevola plumieri (L.) Vahl. and showed significant differences among species with respect to the physiology associated with biomass production, water and nutrient relations. Differences related to CO₂ assimilation included differences in photosynthetic and respiratory rates, susceptibility to light stress and leaf and stem non-structural carbohydrate concentrations. These resulted in differences in primary production rates of shoots. Mechanisms leading to the differences in CO₂ assimilation among species included differences in stomatal behaviour, carboxylation efficiencies, efficiencies of utilisation of incident photosynthetic photon flux density (PPFD) and rates of ribulose-1,6-bisphosphate (RuBP) regeneration. Correlated with differences in photosynthetic capacity were differences in chlorophyll contents but not differences in leaf nitrogen content. Differences in interspecific stomatal behaviour resulted in significantly different transpiration rates which in combination with differences in assimilation rates resulted in differences in water-use efficiency. The absolute amounts of water transpired, although significantly different among species, were moderate to high in comparison with species from other ecosystems and were typical of mesophytes. Transpiration rates in combination with plant hydraulic conductances and soil water availability resulted in leaf water potentials that were not very negative and none of the investigated species showed evidence of osmotic adjustment. The volume of water transpired by each of the species per unit land surface area was estimated from the relationship between abiotic factors and plant water loss. These relationships varied among species and had varying degrees of predictability as a result of differences in stomatal behaviour between the three species. The water requirements of A. populifolia and S. plumieri were adequately met by the water supplied by rainfall and the water stored in the dune sands. It was therefore not necessary to invoke the utilisation of ground water or the process of internal dew formation to supply sufficient water to meet the requirements. However, I. pes-caprae despite its lower transpiration rates and due to its higher biomass, lost greater volumes of water per unit dune surface area than either A. populifolia or S. plumieri. This resulted in periods of potential water limitation for I. pes-caprae. Incident light was the most important determinant of leaf photosynthetic CO₂ assimilation and transpiration, particularly as a linear relationship between incident PPFD and atmospheric vapour pressure deficit (VPD) could be demonstrated. Whole plant photosynthetic production by S. plumieri was shown to be light limited as a result of mutual shading despite high incident and reflected PPFD occurring in the foredune environment. The leaf hair-layer of A. populifolia was shown to be important in reducing transmitted UV and hence reducing photoinhibition but it also caused reduced transpiration rates because of the thicker boundary layer and thus increased leaf temperatures. The nutrient content of above-ground plant parts of the investigated species were typical of higher plants despite the low nutrient content measured for the dune soils. With the possible exception of nitrogen the nutrient demand created by above-ground production was adequately met by the supply of nutrients either from sand-water or from aquifer-water transpired by the plants. Differences in the volumes of water transpired, and hence the quantity of nutrients potentially taken up via the transpiration stream, resulted in interspecific differences in above-ground plant macronutrient content. The reallocation patterns of nutrients differed both between the various nutrients measured and interspecifically. Standing biomass and the density of plants per unit land area was low in comparison to that of other ecosystems and was different among investigated species. This may be important in maintaining the adequate supply of resources (water, nutrients and light). As a result of the interspecific differences in biomass when production was expressed per unit land surface area the resultant productivity was not dissimilar among species. Productivity was high when comparisons were made with species from other ecosystems. No single resource (water, nutrients or light) could be identified as the controlling factor in the foredune environment and a combination of both resource stress and environmental disturbance are likely to be involved. Physiology, production, growth and growth characteristics conveyed certain adaptive advantages to these species in respect to both resource stress and environmental disturbance. Interspecific differences in these adaptations can be used to offer explanations for the observed microhabitat preferences of the three investigated species. Furthermore features common to all three species offer some explanations as to why these species and not others are able to inhabit the foredunes.
- Full Text:
- Date Issued: 2002
The effect of energy and protein nutritional levels on production of breeding ostriches
- Authors: Brand, Zanell
- Date: 2002
- Subjects: Ostriches -- Nutrition , Ostriches -- Breeding--South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5805 , http://hdl.handle.net/10962/d1006312 , Ostriches -- Nutrition , Ostriches -- Breeding--South Africa
- Description: Adequate and appropriate nutrition is essential for the production of high quality commercially farmed animal species. Although South Africa has had a well-established ostrich industry for over a century, little information on ostrich nutrition, in particular the specific nutritional requirements at different stages of production, is available. The industry has consequently relied heavily on data derived from poultry and pigs, but this has often proved to be unsatisfactory for ostriches and has resulted in serious nutritional-related problems. Recent studies on the metabolisable energy of specific components of diet formulations and balanced diets have indicated that ostriches have enhanced digestibility compared with poultry and pigs. At the same time, in the present economic climate, it is necessary to find cost-effective diets for breeding birds without compromising egg and chick production. This study primarily assessed the effect of different dietary protein and energy levels on production parameters and body condition of breeding female and male ostriches. The energy content of the diet appears to be the main constraint to egg production and breeders on low energy diets laid fewer eggs and lost more body condition compared with breeders fed higher energy diets. A diet with 8.5 MJ/kg DM and 10% protein with well balanced amino acids appears to be sufficient for female breeders without compromising production and a diet with 7.5 MJ/kg DM and 10% protein appears suitable for breeding male ostriches. Different dietary energy and protein levels similarly had little or no effect on egg quality and composition. This study also assessed the carry-over effect of the nutritional regime in one year on the production in the following breeding season. Females fed diets as low as 7.5 MJ/kg ME in the previous breeding season produced significantly fewer eggs in the next breeding season, which resulted in lower chick production. Energy had no effect on the percentage infertile eggs or on the initial egg weight. Different levels of dietary protein had no effect on egg production, egg weight, fertility, hatchability and initial chick weight.
- Full Text:
- Date Issued: 2002
- Authors: Brand, Zanell
- Date: 2002
- Subjects: Ostriches -- Nutrition , Ostriches -- Breeding--South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5805 , http://hdl.handle.net/10962/d1006312 , Ostriches -- Nutrition , Ostriches -- Breeding--South Africa
- Description: Adequate and appropriate nutrition is essential for the production of high quality commercially farmed animal species. Although South Africa has had a well-established ostrich industry for over a century, little information on ostrich nutrition, in particular the specific nutritional requirements at different stages of production, is available. The industry has consequently relied heavily on data derived from poultry and pigs, but this has often proved to be unsatisfactory for ostriches and has resulted in serious nutritional-related problems. Recent studies on the metabolisable energy of specific components of diet formulations and balanced diets have indicated that ostriches have enhanced digestibility compared with poultry and pigs. At the same time, in the present economic climate, it is necessary to find cost-effective diets for breeding birds without compromising egg and chick production. This study primarily assessed the effect of different dietary protein and energy levels on production parameters and body condition of breeding female and male ostriches. The energy content of the diet appears to be the main constraint to egg production and breeders on low energy diets laid fewer eggs and lost more body condition compared with breeders fed higher energy diets. A diet with 8.5 MJ/kg DM and 10% protein with well balanced amino acids appears to be sufficient for female breeders without compromising production and a diet with 7.5 MJ/kg DM and 10% protein appears suitable for breeding male ostriches. Different dietary energy and protein levels similarly had little or no effect on egg quality and composition. This study also assessed the carry-over effect of the nutritional regime in one year on the production in the following breeding season. Females fed diets as low as 7.5 MJ/kg ME in the previous breeding season produced significantly fewer eggs in the next breeding season, which resulted in lower chick production. Energy had no effect on the percentage infertile eggs or on the initial egg weight. Different levels of dietary protein had no effect on egg production, egg weight, fertility, hatchability and initial chick weight.
- Full Text:
- Date Issued: 2002
The effects of control design and working posture on strength and work output: an isokinetic investigation
- Dirkse Van Schalkwyk, Charles Joseph
- Authors: Dirkse Van Schalkwyk, Charles Joseph
- Date: 2002
- Subjects: Posture , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5118 , http://hdl.handle.net/10962/d1005196 , Posture , Human engineering
- Description: he objective of the present study was to assess the isokinetic, cardiovascular and psychophysical responses of young adult males (N=30) during valve turning exercises. It aimed to evaluate the variables in relation to changes in control design and working posture. Isokinetic testing and ergonomics have not been widely linked and it was an aim of this study to show the advantages to the field of ergonomics. Furthermore, the “work-simulation” package used in the present study has not been widely exploited and it was believed that this study could thus contribute significantly to the literature. Testing was carried out using a CYBEX ® 6000 isokinetic dynamometer, a polar heart watch, an Omron M1 semi-automatic blood pressure monitor and various perceptual rating scales. Testing involved the subjects having to perform 4 maximal turning efforts in 18 different conditions. These conditions were made up by using 6 different control designs in 3 varying positions. Subjects were required to attend two sessions, each approximately one hour long, in which nine randomised conditions were tested in each session. During these sessions, isokinetic responses: peak torque (Nm), total work (J) and average power (W); cardiovascular responses: heart rate (bt.min[superscript -1]) and blood pressure (mmHg); and psychophysical responses: RPE and discomfort, were observed. The results of the tests showed that in general significant differences were encountered for isokinetic, cardiovascular and psychophysical responses in relation to changes in the control design. However, significant differences were far less evident, and in most cases non existent, in relation to changes in the spatial orientation of the control types. The essence being that operator position with respect to the control is not as crucial as the control design.
- Full Text:
- Date Issued: 2002
- Authors: Dirkse Van Schalkwyk, Charles Joseph
- Date: 2002
- Subjects: Posture , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5118 , http://hdl.handle.net/10962/d1005196 , Posture , Human engineering
- Description: he objective of the present study was to assess the isokinetic, cardiovascular and psychophysical responses of young adult males (N=30) during valve turning exercises. It aimed to evaluate the variables in relation to changes in control design and working posture. Isokinetic testing and ergonomics have not been widely linked and it was an aim of this study to show the advantages to the field of ergonomics. Furthermore, the “work-simulation” package used in the present study has not been widely exploited and it was believed that this study could thus contribute significantly to the literature. Testing was carried out using a CYBEX ® 6000 isokinetic dynamometer, a polar heart watch, an Omron M1 semi-automatic blood pressure monitor and various perceptual rating scales. Testing involved the subjects having to perform 4 maximal turning efforts in 18 different conditions. These conditions were made up by using 6 different control designs in 3 varying positions. Subjects were required to attend two sessions, each approximately one hour long, in which nine randomised conditions were tested in each session. During these sessions, isokinetic responses: peak torque (Nm), total work (J) and average power (W); cardiovascular responses: heart rate (bt.min[superscript -1]) and blood pressure (mmHg); and psychophysical responses: RPE and discomfort, were observed. The results of the tests showed that in general significant differences were encountered for isokinetic, cardiovascular and psychophysical responses in relation to changes in the control design. However, significant differences were far less evident, and in most cases non existent, in relation to changes in the spatial orientation of the control types. The essence being that operator position with respect to the control is not as crucial as the control design.
- Full Text:
- Date Issued: 2002