Modelling parallel and distributed virtual reality systems for performance analysis and comparison
- Authors: Bangay, Shaun Douglas
- Date: 1997
- Subjects: Virtual reality Computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4657 , http://hdl.handle.net/10962/d1006656
- Description: Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems.
- Full Text:
- Date Issued: 1997
- Authors: Bangay, Shaun Douglas
- Date: 1997
- Subjects: Virtual reality Computer simulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4657 , http://hdl.handle.net/10962/d1006656
- Description: Most Virtual Reality systems employ some form of parallel processing, making use of multiple processors which are often distributed over large areas geographically, and which communicate via various forms of message passing. The approaches to parallel decomposition differ for each system, as do the performance implications of each approach. Previous comparisons have only identified and categorized the different approaches. None have examined the performance issues involved in the different parallel decompositions. Performance measurement for a Virtual Reality system differs from that of other parallel systems in that some measure of the delays involved with the interaction of the separate components is required, in addition to the measure of the throughput of the system. Existing performance analysis approaches are typically not well suited to providing both these measures. This thesis describes the development of a performance analysis technique that is able to provide measures of both interaction latency and cycle time for a model of a Virtual Reality system. This technique allows performance measures to be generated as symbolic expressions describing the relationships between the delays in the model. It automatically generates constraint regions, specifying the values of the system parameters for which performance characteristics change. The performance analysis technique shows strong agreement with values measured from implementation of three common decomposition strategies on two message passing architectures. The technique is successfully applied to a range of parallel decomposition strategies found in Parallel and Distributed Virtual Reality systems. For each system, the primary decomposition techniques are isolated and analysed to determine their performance characteristics. This analysis allows a comparison of the various decomposition techniques, and in many cases reveals trends in their behaviour that would have gone unnoticed with alternative analysis techniques. The work described in this thesis supports the Performance Analysis and Comparison of Parallel and Distributed Virtual Reality systems. In addition it acts as a reference, describing the performance characteristics of decomposition strategies used in Virtual Reality systems.
- Full Text:
- Date Issued: 1997
Eco-ethology of shell-dwelling cichlids in Lake Tanganyika
- Authors: Bills, Ian Roger
- Date: 1997
- Subjects: Cichlids -- Africa, East , Cichlids -- Tanganyika, Lake , Fishes -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5265 , http://hdl.handle.net/10962/d1005109 , Cichlids -- Africa, East , Cichlids -- Tanganyika, Lake , Fishes -- Behavior
- Description: Observations of habitats are reported. A series of underwater experiments were conducted in natural habitats to answer questions concerning a) why Lamprologus ocellatus and Lamprologus ornatipinnis bury gastropod shells refuges into the substrate, and b) to examine interspecies differences in shell-using behaviours. Some behaviour patterns were analysed using phylogenetic methods. Lamprologus ocellatus and L. ornatipinnis responded to new shells in a variety of ways, shells were moved, buried (and used) or hidden (buried and not used). How shells are utilised seems to be dependant on a complex of factors such as the size and quality of new the shell and the number already in the territory. Shell use may also be affected by neighbour species, sex, size and predation levels. There are interspecific differences in the size of shells used and the methods of shell use. The latter results in species-characteristic shell orientations, vertical burial in L. ocellatus and horizontal burial in L. ornatipinnis. Shell orientation does affect other species/use of shells. Shell movement and vertical orientation appear to be apomorphic while shell hiding and burial are pleisiomorphic within the genus Lamprologus. Numerous cues are involved in stimulating shell burial. Most of these cues are actively sought by the fish by external and internal inspections. Shell burial therefore appears to be a method of reducing the information gathering ability of potential shell-dwelling competitors. Shell burial can therefore be regarded as an investment process which enhances the residents ability to defend its territory. Males can also control the distribution of open shells within teritories and thus control mate access to shells. This behaviour could be a significant factor in the evolution of marked sexual dichromatism exhibited within the genus.
- Full Text:
- Date Issued: 1997
- Authors: Bills, Ian Roger
- Date: 1997
- Subjects: Cichlids -- Africa, East , Cichlids -- Tanganyika, Lake , Fishes -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5265 , http://hdl.handle.net/10962/d1005109 , Cichlids -- Africa, East , Cichlids -- Tanganyika, Lake , Fishes -- Behavior
- Description: Observations of habitats are reported. A series of underwater experiments were conducted in natural habitats to answer questions concerning a) why Lamprologus ocellatus and Lamprologus ornatipinnis bury gastropod shells refuges into the substrate, and b) to examine interspecies differences in shell-using behaviours. Some behaviour patterns were analysed using phylogenetic methods. Lamprologus ocellatus and L. ornatipinnis responded to new shells in a variety of ways, shells were moved, buried (and used) or hidden (buried and not used). How shells are utilised seems to be dependant on a complex of factors such as the size and quality of new the shell and the number already in the territory. Shell use may also be affected by neighbour species, sex, size and predation levels. There are interspecific differences in the size of shells used and the methods of shell use. The latter results in species-characteristic shell orientations, vertical burial in L. ocellatus and horizontal burial in L. ornatipinnis. Shell orientation does affect other species/use of shells. Shell movement and vertical orientation appear to be apomorphic while shell hiding and burial are pleisiomorphic within the genus Lamprologus. Numerous cues are involved in stimulating shell burial. Most of these cues are actively sought by the fish by external and internal inspections. Shell burial therefore appears to be a method of reducing the information gathering ability of potential shell-dwelling competitors. Shell burial can therefore be regarded as an investment process which enhances the residents ability to defend its territory. Males can also control the distribution of open shells within teritories and thus control mate access to shells. This behaviour could be a significant factor in the evolution of marked sexual dichromatism exhibited within the genus.
- Full Text:
- Date Issued: 1997
Towards a developed regional order: which way forward southern Africa?
- Authors: Blaauw, Abraham Lesley
- Date: 1997
- Subjects: Common Market for Eastern and Southern Africa , Regional planning -- Africa, Southern , Regional planning -- South Africa , Southern African Customs Union , Southern African Development Community , Africa, Southern -- Economic conditions , Africa, Southern -- Politics and government -- 1975-1994
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2760 , http://hdl.handle.net/10962/d1002970 , Common Market for Eastern and Southern Africa , Regional planning -- Africa, Southern , Regional planning -- South Africa , Southern African Customs Union , Southern African Development Community , Africa, Southern -- Economic conditions , Africa, Southern -- Politics and government -- 1975-1994
- Description: The regionalisation of politics on a global scale, Call be seen as one of the defining features of contemporary international relations. Given this phenomenon, the tasks which confronted this thesis, was to consider the conditions and requirements necessary within the Southern African region to build an all-embracing developed regional order. The urgency with which the latter task should be undertaken, is premised on an increased realisation that the region, and indeed the continent as a whole, are becoming of lesser significance in international affairs. However, a number of impediments will have to be overcome, before the goal of a developed regional order can be achieved, which will contribute to lasting security in the region. Foremost amongst many issues, is how to employ the approaches to integration, in attempting to explain how the goal of a developed order should be achieved. A second problem which this thesis was confronted with, relates to which organisation shoulO be' considered the best vehicle, to drive the integration process forward- COMESA, SACU or SADC. The decision take SADC as the organisation to drive the integration process forward, is premised on a number of factors. Amongst many, it qualifies in geographical terms as a region, the historical linkages of the countries of the region (based on their fight against apartheid, division of labour, etc.), serves as a basis for building a sense of community. Thirdly its institutions can be developed to achieve the goal of an all-embracing regional order. Lastly and most importantly, SADC realises that regional integration will remain unattainable without the involvement of the peoples of Southern Africa. The identification of the organisation to drive the integration process forward, serves to bolster moves towards a maximalist order. However, significant changes in the structure and institutions of SADC is necessary, before it can be considered an all-embracing and developed regional order. Not suprisingly, therefore, we have witness a number of institutional changes to the SADC structures. Amongst many, the establishment of the Organ on Politics, Defence and Security , the signing of the SADC Trade Facilitation Protocol, and the commitment to democracy and a human rights culture, are most significant and will, it is hoped, provide the building-blocks for deeper integration in Southern Africa. Apart from the above, which occur between and among the states of the region, steps are underway between and among the agents of civil society to work closely with each other, to establish a regional civil society. Most notably, the establishment of a media society for Southern Africa, the calls by COSATU for a Social Charter with a regional flavour, the establishment of environmental and human rights networks, and the support for the Gay and Lesbian Movement of Zimbabwe (GALZ), represent landmarks, in the search for a developed regional order. However, the reluctance of the governments of the Southern African countries, to consult with the NGOs, before the adoption of the Organ Politics, clearly bears testimony to their present inability to take the necessary steps needed to move from a minimalist to a maximalist conception of regional organisation. The suggestion of this thesis is that the move-away from minimalism to maximalism can be facilitated by the development of a political centre-around which both governments and NGO activities can be articulated, since both are primarily concerned with the security and welfare of the Southern African region.
- Full Text:
- Date Issued: 1997
- Authors: Blaauw, Abraham Lesley
- Date: 1997
- Subjects: Common Market for Eastern and Southern Africa , Regional planning -- Africa, Southern , Regional planning -- South Africa , Southern African Customs Union , Southern African Development Community , Africa, Southern -- Economic conditions , Africa, Southern -- Politics and government -- 1975-1994
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2760 , http://hdl.handle.net/10962/d1002970 , Common Market for Eastern and Southern Africa , Regional planning -- Africa, Southern , Regional planning -- South Africa , Southern African Customs Union , Southern African Development Community , Africa, Southern -- Economic conditions , Africa, Southern -- Politics and government -- 1975-1994
- Description: The regionalisation of politics on a global scale, Call be seen as one of the defining features of contemporary international relations. Given this phenomenon, the tasks which confronted this thesis, was to consider the conditions and requirements necessary within the Southern African region to build an all-embracing developed regional order. The urgency with which the latter task should be undertaken, is premised on an increased realisation that the region, and indeed the continent as a whole, are becoming of lesser significance in international affairs. However, a number of impediments will have to be overcome, before the goal of a developed regional order can be achieved, which will contribute to lasting security in the region. Foremost amongst many issues, is how to employ the approaches to integration, in attempting to explain how the goal of a developed order should be achieved. A second problem which this thesis was confronted with, relates to which organisation shoulO be' considered the best vehicle, to drive the integration process forward- COMESA, SACU or SADC. The decision take SADC as the organisation to drive the integration process forward, is premised on a number of factors. Amongst many, it qualifies in geographical terms as a region, the historical linkages of the countries of the region (based on their fight against apartheid, division of labour, etc.), serves as a basis for building a sense of community. Thirdly its institutions can be developed to achieve the goal of an all-embracing regional order. Lastly and most importantly, SADC realises that regional integration will remain unattainable without the involvement of the peoples of Southern Africa. The identification of the organisation to drive the integration process forward, serves to bolster moves towards a maximalist order. However, significant changes in the structure and institutions of SADC is necessary, before it can be considered an all-embracing and developed regional order. Not suprisingly, therefore, we have witness a number of institutional changes to the SADC structures. Amongst many, the establishment of the Organ on Politics, Defence and Security , the signing of the SADC Trade Facilitation Protocol, and the commitment to democracy and a human rights culture, are most significant and will, it is hoped, provide the building-blocks for deeper integration in Southern Africa. Apart from the above, which occur between and among the states of the region, steps are underway between and among the agents of civil society to work closely with each other, to establish a regional civil society. Most notably, the establishment of a media society for Southern Africa, the calls by COSATU for a Social Charter with a regional flavour, the establishment of environmental and human rights networks, and the support for the Gay and Lesbian Movement of Zimbabwe (GALZ), represent landmarks, in the search for a developed regional order. However, the reluctance of the governments of the Southern African countries, to consult with the NGOs, before the adoption of the Organ Politics, clearly bears testimony to their present inability to take the necessary steps needed to move from a minimalist to a maximalist conception of regional organisation. The suggestion of this thesis is that the move-away from minimalism to maximalism can be facilitated by the development of a political centre-around which both governments and NGO activities can be articulated, since both are primarily concerned with the security and welfare of the Southern African region.
- Full Text:
- Date Issued: 1997
Teaching disciplinary discourse and implementing language-across-the-curriculum at tertiary level problems and prospects
- Authors: Caldwell, Candice Anne
- Date: 1997
- Subjects: Rhodes University. Dept. of Psychology , Compensatory education -- South Africa , College students -- Study and teaching , College teachers -- Training of -- South Africa , Curriculum evaluation -- South Africa , Discourse analysis , Language arts -- Correlation with content subjects , Learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2340 , http://hdl.handle.net/10962/d1002622
- Description: The premise of this thesis is that "learning", particularly in terms of students and universities, is capable of being seen as a specific and developed culture. This study is a contribution to the ethnography of that learning, the ultimate aim being to produce a descriptive theory of learning as a cultural system. This research was conducted within the context of the recent proposals made by the South African Commission on Higher Education. The proposals relevant to this study were, broadly, increased access to higher education and national funding for academic staff development programmes. There are, however, serious obstacles in the way of realising the aims of the higher education system outlined by the NCHE. Given the limited time and resources available for higher education development, it is imperative that the major flaws and obstacles in the system be identified and addressed as soon as possible. In view of this need, it was the concern of this study to conduct research which would assist in the designing of staff development programmes for academics teaching in English-medium tertiary institutions, like Rhodes University, where more than half the intake of first-year students already speaks English as a second, or other, language. Founded on the social constructionist view of knowledge, the aim of the study was to identify the needs of academic staff as well as the possible obstacles to the implementation of a "Language Across the Curriculum" policy. A genre-centred, ethnographic approach was used to access a disciplinary discourse community (the Psychology Department) in order to describe the practices of the community as well as to analyse the community's orders of discourse, particularly those which occurred at points of contact between lecturers and first-year students. It is argued that staff development programmes should promote the use of collaborative learning, which implies a reframing of the roles of both academic staff and students.
- Full Text:
- Date Issued: 1997
- Authors: Caldwell, Candice Anne
- Date: 1997
- Subjects: Rhodes University. Dept. of Psychology , Compensatory education -- South Africa , College students -- Study and teaching , College teachers -- Training of -- South Africa , Curriculum evaluation -- South Africa , Discourse analysis , Language arts -- Correlation with content subjects , Learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2340 , http://hdl.handle.net/10962/d1002622
- Description: The premise of this thesis is that "learning", particularly in terms of students and universities, is capable of being seen as a specific and developed culture. This study is a contribution to the ethnography of that learning, the ultimate aim being to produce a descriptive theory of learning as a cultural system. This research was conducted within the context of the recent proposals made by the South African Commission on Higher Education. The proposals relevant to this study were, broadly, increased access to higher education and national funding for academic staff development programmes. There are, however, serious obstacles in the way of realising the aims of the higher education system outlined by the NCHE. Given the limited time and resources available for higher education development, it is imperative that the major flaws and obstacles in the system be identified and addressed as soon as possible. In view of this need, it was the concern of this study to conduct research which would assist in the designing of staff development programmes for academics teaching in English-medium tertiary institutions, like Rhodes University, where more than half the intake of first-year students already speaks English as a second, or other, language. Founded on the social constructionist view of knowledge, the aim of the study was to identify the needs of academic staff as well as the possible obstacles to the implementation of a "Language Across the Curriculum" policy. A genre-centred, ethnographic approach was used to access a disciplinary discourse community (the Psychology Department) in order to describe the practices of the community as well as to analyse the community's orders of discourse, particularly those which occurred at points of contact between lecturers and first-year students. It is argued that staff development programmes should promote the use of collaborative learning, which implies a reframing of the roles of both academic staff and students.
- Full Text:
- Date Issued: 1997
Struggle in discourse the International's discourse against racism in the labour-movement in South Africa (1915-1919)
- Authors: Caldwell, Marc Anthony
- Date: 1997
- Subjects: International (Johannesburg, South Africa) -- History , International Socialist League (S.A.) -- History , South African newspapers -- Language , Mass media and race relations -- South Africa , Mass media and language -- South Africa , Labor unions and mass media -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3419 , http://hdl.handle.net/10962/d1002872 , International (Johannesburg, South Africa) -- History , International Socialist League (S.A.) -- History , South African newspapers -- Language , Mass media and race relations -- South Africa , Mass media and language -- South Africa , Labor unions and mass media -- South Africa
- Description: The International, as the weekly newspaper of the International Socialist League, articulated from 1915 to 1919 an ideology which stood opposed both to organised labour and nationalist movements in South Africa. This situation reflected significant historical struggles during this period, which constitutes essential background to the discourse of the International. The International's writers opposed the institution of trade unionism in the labour movement because it was fragmented on the lines of skill and race. They opposed both the National Party and the South African Native National Congress because they advocated racial (and national) rather than working class interests. Instead, these writers, according to their international socialist paradigm, advocated a working class united irrespective of race and skill at the level of industry. To analyse these ideological positions, discourse analysis provides a fruitful method for locating its dynamics in relation to other positions and extra-ideological (contextual) practices: The International's writers g~nerated a socialist position against racism by engaging in an ideological struggle in discourse. They articulated their anti-racist position from international socialism's critique of the 'languages' of both militarism and trade unionism in the discourse of labour. Within the discourse of militarism, the working class was signified as divided between hostile nations. These writers applied this as a metaphor to the division of the local labour movement and criticised the latter accordingly. In their view, just as workers were divided between the nations (nationalism), so they were divided within the nation (racism) in South Africa. One context cohered with the other, and both agreed with imperatives of international capitalism. This was fundamentally opposed to the principles of international socialism which characterised the International's discourse. Within the dominant discourse oflabour, workers were signified as divided between different trade unions on the basis of skills. Furthermore, in the South African context, trade unions organised only white workers, and ignored the far larger proportion of black labour. In this context, the International advocated industrial unionism, and criticised the narrow base of the white trade unions for fragmenting and weakening the working class in South African. The International's writers were thus led by the discourse of international socialism to a new discourse, whereby not white workers alone, but a racially-united working class movement would be the key to a socialist future in South Africa. Their struggle entailed a bid in and over discourse to rearticulate the sign of the 'native worker' within their own discourse as the dominant discourse type. Underpinning their struggle was a fundamental opposition to capitalist class relations.
- Full Text:
- Date Issued: 1997
- Authors: Caldwell, Marc Anthony
- Date: 1997
- Subjects: International (Johannesburg, South Africa) -- History , International Socialist League (S.A.) -- History , South African newspapers -- Language , Mass media and race relations -- South Africa , Mass media and language -- South Africa , Labor unions and mass media -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3419 , http://hdl.handle.net/10962/d1002872 , International (Johannesburg, South Africa) -- History , International Socialist League (S.A.) -- History , South African newspapers -- Language , Mass media and race relations -- South Africa , Mass media and language -- South Africa , Labor unions and mass media -- South Africa
- Description: The International, as the weekly newspaper of the International Socialist League, articulated from 1915 to 1919 an ideology which stood opposed both to organised labour and nationalist movements in South Africa. This situation reflected significant historical struggles during this period, which constitutes essential background to the discourse of the International. The International's writers opposed the institution of trade unionism in the labour movement because it was fragmented on the lines of skill and race. They opposed both the National Party and the South African Native National Congress because they advocated racial (and national) rather than working class interests. Instead, these writers, according to their international socialist paradigm, advocated a working class united irrespective of race and skill at the level of industry. To analyse these ideological positions, discourse analysis provides a fruitful method for locating its dynamics in relation to other positions and extra-ideological (contextual) practices: The International's writers g~nerated a socialist position against racism by engaging in an ideological struggle in discourse. They articulated their anti-racist position from international socialism's critique of the 'languages' of both militarism and trade unionism in the discourse of labour. Within the discourse of militarism, the working class was signified as divided between hostile nations. These writers applied this as a metaphor to the division of the local labour movement and criticised the latter accordingly. In their view, just as workers were divided between the nations (nationalism), so they were divided within the nation (racism) in South Africa. One context cohered with the other, and both agreed with imperatives of international capitalism. This was fundamentally opposed to the principles of international socialism which characterised the International's discourse. Within the dominant discourse oflabour, workers were signified as divided between different trade unions on the basis of skills. Furthermore, in the South African context, trade unions organised only white workers, and ignored the far larger proportion of black labour. In this context, the International advocated industrial unionism, and criticised the narrow base of the white trade unions for fragmenting and weakening the working class in South African. The International's writers were thus led by the discourse of international socialism to a new discourse, whereby not white workers alone, but a racially-united working class movement would be the key to a socialist future in South Africa. Their struggle entailed a bid in and over discourse to rearticulate the sign of the 'native worker' within their own discourse as the dominant discourse type. Underpinning their struggle was a fundamental opposition to capitalist class relations.
- Full Text:
- Date Issued: 1997
Parasitism and invasive species : an ecological study of mussel populations
- Calvo Ugarteburu, Miren Gurutze
- Authors: Calvo Ugarteburu, Miren Gurutze
- Date: 1997
- Subjects: Perna -- Parasites Mytilidae -- Parasites Perna -- Ecology Mytilidae -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5736 , http://hdl.handle.net/10962/d1005422
- Description: The Mediterranean mussel Mytilus galloprovincialis, was introduced accidentally to South Africa and has since become invasive. One possible explanation for the success of this species is that it has been released from the effects of parasites which affect the indigenous species of mussels. The aim of this work was to examine the parasitic load of different mussel populations along the southern African coast and to assess the effects of parasites on their hosts. A survey was done to quantify the levels of parasitism in indigenous populations of Perna perna from Southern Africa and of Mytilus galloprovincialis from South Africa (where it is exotic) and Spain (where it is indigenous). This survey was carried out at three different geographic scales: small scale (metres), studying the incidence of parasites within a mussel bed; medium scale (kilometres to tens of kilometres), comparing prevalences of infection among different localities; and large scale (hundreds to thousands of kilometres), examining infection rates along the Southern African coast, as well as the coast of the Basque Country (North Spain). During this survey metazoan parasites other than trematodes were rare. Four species of trematodes were commonly found infecting the indigenous mussel Perna perna. These were metacercariae of the genus Proctoeces, bucephalid sporocysts, encysted metacercariae on the labial palps and gelatinous cysts with metacercariae inside. A detailed description of Proctoeces is given; the other parasites are described elsewhere. No parasites were found in M. galloprovincialis either in South Africa or in Spain. This thesis concentrates on the study of prevalences of Proctoeces and bucephalid sporocysts and their effects on Perna perna. Infection rates with Proctoeces are highly dependent on the sex of the host, with more females than males being infected, and are also size dependent, though only for females. Identification of the sex of mussels infected with bucephalid sporocysts is often not possible since the sporocysts spread over the gonad and replace it. Prevalence of infection with this parasite also increases with the size of the host. To study the influence of Proctoeces and bucephalid sporocysts on the ecological fitness of Perna perna, their effects on survival and competitive ability were tested. The results showed significant negative effects. Both parasites significantly depressed condition but only after spawning, when the mussels were already stressed. In order to check for effects on host survival, the effects of both parasites on mortality rates, gaping behaviour and water loss of mussels exposed to air were also examined. Neither parasite affected mortality rate or gaping behaviour of Perna perna. Proctoeces did not affect the amount of water lost by mussels, but the bucephalid sporocysts did. Mussels infected with sporocysts lost significantly more water than non-infected individuals. This increase in water loss was not related to the gaping behaviour, but a test of the strength of the adductor muscles showed that less force was needed to open mussels with bucephalid sporocysts than non-infected mussels. This was not the case for mussels infected by Proctoeces. Weaker mussels will fail to seal the valves properly, resulting in an increase of water loss on exposure to air by evaporation. Another factor that will have an obvious effect on a population is the reproductive output of the animals. Histological sections of the gonad of infected and non-infected females were cut to study the effects of both parasites on reproduction. Statistical tests comparing the numbers and sizes of oocytes in females infected with Proctoeces and non-infected females showed no significant differences. However, bucephalid sporocysts have a dramatic effect on reproduction by castrating the host, leaving no trace of sex products. One of the major factors shaping the composition of a mussel bed is competition for space and food, with smaller mussels being at a competitive disadvantage. Thus, in order to examine effects of both parasites on the competitive ability of Perna perna, summer and winter growth rates were compared for infected and non-infected mussels. Proctoeces reduced growth both in summer and in winter whilst bucephalid sporocysts had no significant effect. Both growth and reproduction are important components of the energy budget of an animal, and each is affected by either Proctoeces or the bucephalid sporocysts. In an attempt to test if Perna perna compensates energetically for these negative effects, filtration rates and oxygen consumption of mussels with and without parasites were measured. Neither parasite had a significant effect on filtration rates or oxygen consumption of the host. All these results indicate that both Proctoeces and the bucephalid sporocysts have a detrimental effect on their host, and that the mussels do not compensate for these negative effects. There is neither an increase in filtration, nor a decrease in respiration to balance the energy lost to the parasite. The two parasites studied affect the host in different but complementary ways. The effects of both parasites are concentrated on those size classes of mussel which channel most energy into the portion of the energy budget affected by the parasite. Proctoeces affects growth only in the smaller individuals, which under normal conditions would put most energy into growth; and the bucephalid sporocysts castrate the bigger mussels, which would expend most energy on reproduction. By reducing growth rates of small mussels or castrating large mussels, these parasites effectively remove them from the breeding population and reduce their competitive abilities. These negative effects, together with the high prevalence of both parasites in Perna perna along the South African coast and their absence in Mytilus galloprovincialis, suggest that parasites may be an important reason for the success of Mytilus.
- Full Text:
- Date Issued: 1997
- Authors: Calvo Ugarteburu, Miren Gurutze
- Date: 1997
- Subjects: Perna -- Parasites Mytilidae -- Parasites Perna -- Ecology Mytilidae -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5736 , http://hdl.handle.net/10962/d1005422
- Description: The Mediterranean mussel Mytilus galloprovincialis, was introduced accidentally to South Africa and has since become invasive. One possible explanation for the success of this species is that it has been released from the effects of parasites which affect the indigenous species of mussels. The aim of this work was to examine the parasitic load of different mussel populations along the southern African coast and to assess the effects of parasites on their hosts. A survey was done to quantify the levels of parasitism in indigenous populations of Perna perna from Southern Africa and of Mytilus galloprovincialis from South Africa (where it is exotic) and Spain (where it is indigenous). This survey was carried out at three different geographic scales: small scale (metres), studying the incidence of parasites within a mussel bed; medium scale (kilometres to tens of kilometres), comparing prevalences of infection among different localities; and large scale (hundreds to thousands of kilometres), examining infection rates along the Southern African coast, as well as the coast of the Basque Country (North Spain). During this survey metazoan parasites other than trematodes were rare. Four species of trematodes were commonly found infecting the indigenous mussel Perna perna. These were metacercariae of the genus Proctoeces, bucephalid sporocysts, encysted metacercariae on the labial palps and gelatinous cysts with metacercariae inside. A detailed description of Proctoeces is given; the other parasites are described elsewhere. No parasites were found in M. galloprovincialis either in South Africa or in Spain. This thesis concentrates on the study of prevalences of Proctoeces and bucephalid sporocysts and their effects on Perna perna. Infection rates with Proctoeces are highly dependent on the sex of the host, with more females than males being infected, and are also size dependent, though only for females. Identification of the sex of mussels infected with bucephalid sporocysts is often not possible since the sporocysts spread over the gonad and replace it. Prevalence of infection with this parasite also increases with the size of the host. To study the influence of Proctoeces and bucephalid sporocysts on the ecological fitness of Perna perna, their effects on survival and competitive ability were tested. The results showed significant negative effects. Both parasites significantly depressed condition but only after spawning, when the mussels were already stressed. In order to check for effects on host survival, the effects of both parasites on mortality rates, gaping behaviour and water loss of mussels exposed to air were also examined. Neither parasite affected mortality rate or gaping behaviour of Perna perna. Proctoeces did not affect the amount of water lost by mussels, but the bucephalid sporocysts did. Mussels infected with sporocysts lost significantly more water than non-infected individuals. This increase in water loss was not related to the gaping behaviour, but a test of the strength of the adductor muscles showed that less force was needed to open mussels with bucephalid sporocysts than non-infected mussels. This was not the case for mussels infected by Proctoeces. Weaker mussels will fail to seal the valves properly, resulting in an increase of water loss on exposure to air by evaporation. Another factor that will have an obvious effect on a population is the reproductive output of the animals. Histological sections of the gonad of infected and non-infected females were cut to study the effects of both parasites on reproduction. Statistical tests comparing the numbers and sizes of oocytes in females infected with Proctoeces and non-infected females showed no significant differences. However, bucephalid sporocysts have a dramatic effect on reproduction by castrating the host, leaving no trace of sex products. One of the major factors shaping the composition of a mussel bed is competition for space and food, with smaller mussels being at a competitive disadvantage. Thus, in order to examine effects of both parasites on the competitive ability of Perna perna, summer and winter growth rates were compared for infected and non-infected mussels. Proctoeces reduced growth both in summer and in winter whilst bucephalid sporocysts had no significant effect. Both growth and reproduction are important components of the energy budget of an animal, and each is affected by either Proctoeces or the bucephalid sporocysts. In an attempt to test if Perna perna compensates energetically for these negative effects, filtration rates and oxygen consumption of mussels with and without parasites were measured. Neither parasite had a significant effect on filtration rates or oxygen consumption of the host. All these results indicate that both Proctoeces and the bucephalid sporocysts have a detrimental effect on their host, and that the mussels do not compensate for these negative effects. There is neither an increase in filtration, nor a decrease in respiration to balance the energy lost to the parasite. The two parasites studied affect the host in different but complementary ways. The effects of both parasites are concentrated on those size classes of mussel which channel most energy into the portion of the energy budget affected by the parasite. Proctoeces affects growth only in the smaller individuals, which under normal conditions would put most energy into growth; and the bucephalid sporocysts castrate the bigger mussels, which would expend most energy on reproduction. By reducing growth rates of small mussels or castrating large mussels, these parasites effectively remove them from the breeding population and reduce their competitive abilities. These negative effects, together with the high prevalence of both parasites in Perna perna along the South African coast and their absence in Mytilus galloprovincialis, suggest that parasites may be an important reason for the success of Mytilus.
- Full Text:
- Date Issued: 1997
Towards an understanding of Amayeza esiXhosa stores (African chemists): how they operate, and the services they offer in the Eastern Cape
- Authors: Cocks, Michelle L
- Date: 1997
- Subjects: Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2096 , http://hdl.handle.net/10962/d1002659 , Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: In medical anthropology there has been a tendency to dichotomize western biomedical . healtb services, on the one hand, and traditional health care practices on the other. Much attention has been focused on the comparison between these two approaches in the hope that they might be reconciled. The problem with this approach is twofold. In the first place, it has not always acknowledged the local, historic~1, political and economic contexts in which different approaches to health care have evolved and in the second place, health care services which belong to neither the western nor traditional healing spheres and which are driven by commercial interests have been almost completely neglected because they fall outside of the basic dichotomy. Amayeza stores have been a feature of South African towns and cities for many years. They mayor may not be run by Africans, but their clientele is almost exclusively African in this region. They deal in a bewildering variety of products and remedies, from untreated herbal and animal products to pharmaceuticals specially prepared for the African market, to Dutch and Indian Remedies. These stores both reflect transfonnations in indigenous perceptions of health care and, by virtue of the choices they offer, generate change. In this empirical study three stores in the Eastern Cape are selected for detailed study - two in King William's Town, the regional capital, and one in the small town of Peddie. The approach is holistic, emphasizing the social, political and economic context, the business histories and running of each shop, and, in particular, the perceptions and choices of a sample of the customers in each case. The success of the amayeza phenomenon derives from its eclecticism and syncretism. These stores impose neither a western nor a traditional model of health care on their clients, but offer them a range of choices that reflects the complex multicultural history of their own South African society.
- Full Text:
- Date Issued: 1997
- Authors: Cocks, Michelle L
- Date: 1997
- Subjects: Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2096 , http://hdl.handle.net/10962/d1002659 , Medical anthropology -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: In medical anthropology there has been a tendency to dichotomize western biomedical . healtb services, on the one hand, and traditional health care practices on the other. Much attention has been focused on the comparison between these two approaches in the hope that they might be reconciled. The problem with this approach is twofold. In the first place, it has not always acknowledged the local, historic~1, political and economic contexts in which different approaches to health care have evolved and in the second place, health care services which belong to neither the western nor traditional healing spheres and which are driven by commercial interests have been almost completely neglected because they fall outside of the basic dichotomy. Amayeza stores have been a feature of South African towns and cities for many years. They mayor may not be run by Africans, but their clientele is almost exclusively African in this region. They deal in a bewildering variety of products and remedies, from untreated herbal and animal products to pharmaceuticals specially prepared for the African market, to Dutch and Indian Remedies. These stores both reflect transfonnations in indigenous perceptions of health care and, by virtue of the choices they offer, generate change. In this empirical study three stores in the Eastern Cape are selected for detailed study - two in King William's Town, the regional capital, and one in the small town of Peddie. The approach is holistic, emphasizing the social, political and economic context, the business histories and running of each shop, and, in particular, the perceptions and choices of a sample of the customers in each case. The success of the amayeza phenomenon derives from its eclecticism and syncretism. These stores impose neither a western nor a traditional model of health care on their clients, but offer them a range of choices that reflects the complex multicultural history of their own South African society.
- Full Text:
- Date Issued: 1997
Structural and stereochemical investigations of terrestrial and marine pyrone metabolites
- Authors: Collett, Lynne Alison
- Date: 1997
- Subjects: Metabolites , Stereochemistry , Siphonaria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4348 , http://hdl.handle.net/10962/d1005013 , Metabolites , Stereochemistry , Siphonaria
- Description: This thesis presents an investigation into the chemistry of 6 substituted 5, 6-dihydro-a-pyrone compounds. A comprehensive review of these compounds was published in 1989 and the subsequent literature is covered in an updated review presented below. Eight 6-substituted 5,6-dihydro-a-pyrone metabolites from three different South African plant species Cryptocarya latijolia, Syncolostemon densiflorus, and Syncolostemon argenteus have been the subject of structural and stereochemical investigations. The absolute stereochemistry of the known compound "triacetate" from C. latijolia has been established as 6R-[2R,4S,6S-(triacetyloxy)heptylJ-5,6-dihydro-2H-pyran-2-one (74) using CD and acetonide formation with subsequent application of the modified Moshers method. The absolute stereochemistry of the related metabolite "diacetate", also from C. latijolia, has been assigned as 6R-[2S,4S-diacetyloxypentylJ-5,6-dihydro-2H-pyran-2-one (76). In addition, the outstanding stereochemistry at C-5' in syndenolide, from S. densiflorus, followed from conversion to its diacetonide and subsequent NMR analysis. Syndenolide is therefore 6R-[5S-(acetoxy)-IR,2R,3S-(trihydroxy)-heptylJ-5,6- dihydro-2H -pyran-2-one. The genus Syncolostemon has proved to be a rich source of a-pyrone compounds and the chemistry of S. argenteus, not investigated previously, was examined as part of an ongoing search for new 5,6-dihydro-a-pyrones. The study yielded five new a-pyrone natural products, synargentolide A-E. The structure of synargentolide A (82) has been assigned as 6R[4R,5R,6S-triacetyloxy-lE-heptenylJ-5,6-dihydro-2H-pyran-2-one using CD and NMR techniques. The structures of synargentolide B (87), C (92) and E (94) also followed from a detailed NMR analysis and the stereochemistry tentatively assigned based on CD and NMR data. Synargentolide D (93) was thermally unstable, and a paucity of material prevented stereochemical investigations, however the structure was determined from initial NMR analysis. The marine molluscs of the genus Siphonaria have only become the subject of chemical studies in the last fifteen years. These molluscs characteristically produce polypropionate type natural products. A review of Siphonarian polypropionate metabolites containing a pyrone functionality is presented. Examination of an endemic South African species Siphonaria serrata yielded one novel polypropionate metabolite containing a ),-pyrone functionality, siserrone A (131). The structure of this compound was unambiguously established using standard NMR experiments. The relative stereochemisty of the hemi-ketal moiety was assigned from a careful analysis of the ROESY NMR spectrum and the stereochemisty of the acyclic portion determined from a comparison of the 13C and 'H NMR data of a degradation product with the corresponding data of a synthetic compound. It was also established that the modified Moshers method could not be used to determine the absolute stereochemistry of the secondary hydroxy I substituent at C-11. The absolute stereochemistry of 131 was thus assigned in accordance with the proven stereochemistry of Siphonarian metabolites.
- Full Text:
- Date Issued: 1997
- Authors: Collett, Lynne Alison
- Date: 1997
- Subjects: Metabolites , Stereochemistry , Siphonaria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4348 , http://hdl.handle.net/10962/d1005013 , Metabolites , Stereochemistry , Siphonaria
- Description: This thesis presents an investigation into the chemistry of 6 substituted 5, 6-dihydro-a-pyrone compounds. A comprehensive review of these compounds was published in 1989 and the subsequent literature is covered in an updated review presented below. Eight 6-substituted 5,6-dihydro-a-pyrone metabolites from three different South African plant species Cryptocarya latijolia, Syncolostemon densiflorus, and Syncolostemon argenteus have been the subject of structural and stereochemical investigations. The absolute stereochemistry of the known compound "triacetate" from C. latijolia has been established as 6R-[2R,4S,6S-(triacetyloxy)heptylJ-5,6-dihydro-2H-pyran-2-one (74) using CD and acetonide formation with subsequent application of the modified Moshers method. The absolute stereochemistry of the related metabolite "diacetate", also from C. latijolia, has been assigned as 6R-[2S,4S-diacetyloxypentylJ-5,6-dihydro-2H-pyran-2-one (76). In addition, the outstanding stereochemistry at C-5' in syndenolide, from S. densiflorus, followed from conversion to its diacetonide and subsequent NMR analysis. Syndenolide is therefore 6R-[5S-(acetoxy)-IR,2R,3S-(trihydroxy)-heptylJ-5,6- dihydro-2H -pyran-2-one. The genus Syncolostemon has proved to be a rich source of a-pyrone compounds and the chemistry of S. argenteus, not investigated previously, was examined as part of an ongoing search for new 5,6-dihydro-a-pyrones. The study yielded five new a-pyrone natural products, synargentolide A-E. The structure of synargentolide A (82) has been assigned as 6R[4R,5R,6S-triacetyloxy-lE-heptenylJ-5,6-dihydro-2H-pyran-2-one using CD and NMR techniques. The structures of synargentolide B (87), C (92) and E (94) also followed from a detailed NMR analysis and the stereochemistry tentatively assigned based on CD and NMR data. Synargentolide D (93) was thermally unstable, and a paucity of material prevented stereochemical investigations, however the structure was determined from initial NMR analysis. The marine molluscs of the genus Siphonaria have only become the subject of chemical studies in the last fifteen years. These molluscs characteristically produce polypropionate type natural products. A review of Siphonarian polypropionate metabolites containing a pyrone functionality is presented. Examination of an endemic South African species Siphonaria serrata yielded one novel polypropionate metabolite containing a ),-pyrone functionality, siserrone A (131). The structure of this compound was unambiguously established using standard NMR experiments. The relative stereochemisty of the hemi-ketal moiety was assigned from a careful analysis of the ROESY NMR spectrum and the stereochemisty of the acyclic portion determined from a comparison of the 13C and 'H NMR data of a degradation product with the corresponding data of a synthetic compound. It was also established that the modified Moshers method could not be used to determine the absolute stereochemistry of the secondary hydroxy I substituent at C-11. The absolute stereochemistry of 131 was thus assigned in accordance with the proven stereochemistry of Siphonarian metabolites.
- Full Text:
- Date Issued: 1997
Exploitation of the bait organism Upogebia africana (Crustacea: Anomura) in the Knysna estuary
- Authors: Cretchley, Robyn
- Date: 1997
- Subjects: Upogebia africana -- South Africa -- Knysna , Mud shrimps -- South Africa -- Knysna , Fishing baits -- South Africa -- Knysna
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5691 , http://hdl.handle.net/10962/d1005377 , Upogebia africana -- South Africa -- Knysna , Mud shrimps -- South Africa -- Knysna , Fishing baits -- South Africa -- Knysna
- Description: In South African estuaries the anomuran mud prawn, Upogebia africana (Ortmann), is the main organism exploited as bait by recreational and subsistence anglers. In the Knysna estuary, three groups of bait collectors were identified on the basis of their source of income: subsistence fishermen who rely on bait-collecting and fishing for their income, supplementary anglers who catch fish to supplement their income and leisure anglers who draw no income from fishing. Two groups were identified based on the methods used: lelsure anglers who collect bait using a prawn pusher or pump and fish using a fishing rod and tackle, and non-leisure anglers who collect mud prawns using tin cans and fish with handlines. The hypothesis was erected that bait-collecting does not affect the U africana populations in the Knysna estuary. The approach adopted was to assess the distribution, density, population structure and reproductive patterns of the bait stock and to estimate the intensity of bait collection, to test the validity of the hypothesis. U africana has an extensive distribution, occupying 62 % of the available intertidal area of the Knysna estuary. Mud prawns have a broad intertidal distribution from the high water level (Spartina zone) to the shallow subtidal. The density, biomass and population structure of the mud prawns vary significantly with distance up the estuary and with tidal height on each shore. The Invertebrate Reserve supports very low densities of U africana (x = 11.7 m⁻²), whereas a relatively inaccessible centre bank in the middle reaches of the estuary appears to be a very effective natural mud prawn reserve as it supports the highest densities (x = 176.5m⁻²). The mud prawn stock of the estuary is estimated to be 2.19 x 108 prawns (82.7 tonnes dry mass). The numbers of bait collectors present per mudbank is highest on public holidays (x = 34) and higher during the summer holidays (x = 16) than during the winter (x = 4). A total of 1.858 x 106 U africana or 700.53 kg (dry mass) are removed by bait collectors annually from the 6 popular bait-collecting sites studied. This represents 8.49 % of the mud prawn stocks at these sites and 0.85 % of the entire estuary stock. 85 % of the U africana taken as bait annually, is removed by the 77.12 % of bait collectors who are non-leisure anglers. Recreational or leisure anglers are responsible for removing 14.2 %. The reproduction of female U africana in the Knysna estuary is seasonal and occurs from late July to April. There is evidence that this breeding season consists of two merging breeding cycles. The largest percentage (63 %) of ovigerous females is found in the middle reaches of the Knysna estuary at the Oyster Bank where the highest numbers of stage 1 larvae (165 m⁻³) are released. Larvae were exported from the estuary on the crepuscular ebb tide with peaks in abundance of nearly 1500 m⁻³ in November 1995 and January 1996. Although numbers caught are not significantly higher, larvae are nearly twice as abundant on crepuscular neap tides following a new moon (waxing quarter) than on those following a full moon (waning quarter). Recruitment of juvenile U africana to populations in the estuary was highest in December (45 m⁻²) and decreased over the summer. The highest numbers of recruits (31 m⁻²) were found at those sites closest to the mouth or on the main channel. Recruitment to the Leisure Isle and Thesens sites which are intensively exploited by bait collectors is high (20 - 32 m⁻²). The number of juveniles recruiting to U africana populations is estimated to be four times as high as the numbers of mud prawns taken by bait collectors. Legal methods of bait collection used in the Knysna estuary by the majority of anglers appear to cause minimal sediment disturbance and are not likely to affect the associated infauna. Illegal bait-collecting methods are however highly destructive and must be prohibited. It is concluded that the null hypothesis is acceptable, as mud prawn stocks of the Knysna estuary are not over-exploited and appear to be naturally regulated. The recruitment rate of juvenile U africana is estimated to be sufficiently high to sustain the present levels of exploitation.
- Full Text:
- Date Issued: 1997
- Authors: Cretchley, Robyn
- Date: 1997
- Subjects: Upogebia africana -- South Africa -- Knysna , Mud shrimps -- South Africa -- Knysna , Fishing baits -- South Africa -- Knysna
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5691 , http://hdl.handle.net/10962/d1005377 , Upogebia africana -- South Africa -- Knysna , Mud shrimps -- South Africa -- Knysna , Fishing baits -- South Africa -- Knysna
- Description: In South African estuaries the anomuran mud prawn, Upogebia africana (Ortmann), is the main organism exploited as bait by recreational and subsistence anglers. In the Knysna estuary, three groups of bait collectors were identified on the basis of their source of income: subsistence fishermen who rely on bait-collecting and fishing for their income, supplementary anglers who catch fish to supplement their income and leisure anglers who draw no income from fishing. Two groups were identified based on the methods used: lelsure anglers who collect bait using a prawn pusher or pump and fish using a fishing rod and tackle, and non-leisure anglers who collect mud prawns using tin cans and fish with handlines. The hypothesis was erected that bait-collecting does not affect the U africana populations in the Knysna estuary. The approach adopted was to assess the distribution, density, population structure and reproductive patterns of the bait stock and to estimate the intensity of bait collection, to test the validity of the hypothesis. U africana has an extensive distribution, occupying 62 % of the available intertidal area of the Knysna estuary. Mud prawns have a broad intertidal distribution from the high water level (Spartina zone) to the shallow subtidal. The density, biomass and population structure of the mud prawns vary significantly with distance up the estuary and with tidal height on each shore. The Invertebrate Reserve supports very low densities of U africana (x = 11.7 m⁻²), whereas a relatively inaccessible centre bank in the middle reaches of the estuary appears to be a very effective natural mud prawn reserve as it supports the highest densities (x = 176.5m⁻²). The mud prawn stock of the estuary is estimated to be 2.19 x 108 prawns (82.7 tonnes dry mass). The numbers of bait collectors present per mudbank is highest on public holidays (x = 34) and higher during the summer holidays (x = 16) than during the winter (x = 4). A total of 1.858 x 106 U africana or 700.53 kg (dry mass) are removed by bait collectors annually from the 6 popular bait-collecting sites studied. This represents 8.49 % of the mud prawn stocks at these sites and 0.85 % of the entire estuary stock. 85 % of the U africana taken as bait annually, is removed by the 77.12 % of bait collectors who are non-leisure anglers. Recreational or leisure anglers are responsible for removing 14.2 %. The reproduction of female U africana in the Knysna estuary is seasonal and occurs from late July to April. There is evidence that this breeding season consists of two merging breeding cycles. The largest percentage (63 %) of ovigerous females is found in the middle reaches of the Knysna estuary at the Oyster Bank where the highest numbers of stage 1 larvae (165 m⁻³) are released. Larvae were exported from the estuary on the crepuscular ebb tide with peaks in abundance of nearly 1500 m⁻³ in November 1995 and January 1996. Although numbers caught are not significantly higher, larvae are nearly twice as abundant on crepuscular neap tides following a new moon (waxing quarter) than on those following a full moon (waning quarter). Recruitment of juvenile U africana to populations in the estuary was highest in December (45 m⁻²) and decreased over the summer. The highest numbers of recruits (31 m⁻²) were found at those sites closest to the mouth or on the main channel. Recruitment to the Leisure Isle and Thesens sites which are intensively exploited by bait collectors is high (20 - 32 m⁻²). The number of juveniles recruiting to U africana populations is estimated to be four times as high as the numbers of mud prawns taken by bait collectors. Legal methods of bait collection used in the Knysna estuary by the majority of anglers appear to cause minimal sediment disturbance and are not likely to affect the associated infauna. Illegal bait-collecting methods are however highly destructive and must be prohibited. It is concluded that the null hypothesis is acceptable, as mud prawn stocks of the Knysna estuary are not over-exploited and appear to be naturally regulated. The recruitment rate of juvenile U africana is estimated to be sufficiently high to sustain the present levels of exploitation.
- Full Text:
- Date Issued: 1997
Negotiating a comprehensive long-term relationship between South Africa and the European Union: from free trade to trade and development
- Authors: Cross, Peter John
- Date: 1997
- Subjects: Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2768 , http://hdl.handle.net/10962/d1002978 , Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Description: On 10 May 1994 the European Union offeredSouth Africa a package of measures to ... send a strong political signal to the incoming govemment and to the South African population, thus proving its firm determination to support the transition towards democracy and its willingness to contribute to the reconstruction and economic development of South Africa after the elections. This package consisted of two parts: 1. A series of short term implementations to take place with immediate effect to help South Africa's development and transition, and 2. An offer to negotiate a comprehensive long-term relationship with South Africa should the new government so request. South Africa accepted the European Union's offer to negotiate a long-term relationship, and in response requested membership of the structure governing the Union's relations with the rest of the countries in Sub-Saharan Africa and some countries in the Caribbean and Pacific, namely the Lomé Convention. Due to various incompatibilities South Africa was not allowed to join this organisation. In its place the European Union offered to negotiate an agreement with South Africa that would lead to a Free Trade Area. This agreement was in keeping with the rules as laid down by the World Trade Organisation. It envisaged the lowering of tariffs and trade barriers between the Union and South Africa over a period not exceeding 12 years, allowing for asymmetry in terms of time constraints in implementation only. South Africa saw this type of agreement as inconsistent with the desire expressed by the European Union to support the countries development and the integration of the Southern African region. In its place South Africa proposed a new concept in trade agreement, this concept, known as the Trade and Development Agreement, embodied both trade liberalisation and support for development. This agreement would introduce a new paradigm of thought to govern trade between developed countries and developing countries within the World Trade Organisation's rules. This paper explores the events that unfolded in these negotiations. It attempts to discover whether, in the current global environment, it is possible, or beneficial, for the developed world to act in an altruistic manner towards another state in order to assist its development.
- Full Text:
- Date Issued: 1997
- Authors: Cross, Peter John
- Date: 1997
- Subjects: Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2768 , http://hdl.handle.net/10962/d1002978 , Economic development -- South Africa -- 1994- , European Economic Community , European Economic Community countries -- Foreign economic relations -- South Africa , South Africa -- Foreign relations -- European Economic Community countries
- Description: On 10 May 1994 the European Union offeredSouth Africa a package of measures to ... send a strong political signal to the incoming govemment and to the South African population, thus proving its firm determination to support the transition towards democracy and its willingness to contribute to the reconstruction and economic development of South Africa after the elections. This package consisted of two parts: 1. A series of short term implementations to take place with immediate effect to help South Africa's development and transition, and 2. An offer to negotiate a comprehensive long-term relationship with South Africa should the new government so request. South Africa accepted the European Union's offer to negotiate a long-term relationship, and in response requested membership of the structure governing the Union's relations with the rest of the countries in Sub-Saharan Africa and some countries in the Caribbean and Pacific, namely the Lomé Convention. Due to various incompatibilities South Africa was not allowed to join this organisation. In its place the European Union offered to negotiate an agreement with South Africa that would lead to a Free Trade Area. This agreement was in keeping with the rules as laid down by the World Trade Organisation. It envisaged the lowering of tariffs and trade barriers between the Union and South Africa over a period not exceeding 12 years, allowing for asymmetry in terms of time constraints in implementation only. South Africa saw this type of agreement as inconsistent with the desire expressed by the European Union to support the countries development and the integration of the Southern African region. In its place South Africa proposed a new concept in trade agreement, this concept, known as the Trade and Development Agreement, embodied both trade liberalisation and support for development. This agreement would introduce a new paradigm of thought to govern trade between developed countries and developing countries within the World Trade Organisation's rules. This paper explores the events that unfolded in these negotiations. It attempts to discover whether, in the current global environment, it is possible, or beneficial, for the developed world to act in an altruistic manner towards another state in order to assist its development.
- Full Text:
- Date Issued: 1997
Fungal and substrate-associated factors affecting lignocellulolytic mushroom cultivation on wood sources available in South African [i.e. Africa]
- Authors: Da Serra, Maria Fatima
- Date: 1997
- Subjects: Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4020 , http://hdl.handle.net/10962/d1004080 , Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Description: Vast- quantities of lignocellulosic materials, representing potential substrates for the cultivation of speciality mushrooms, are produced annually in South Africa. A number of these materials are derived as waste products of the timber and agricultural industries, e.g. Maranti (Shorea spp.) and Port Jackson Willow (Acacia longifolia) respectively. The screening of various wood-degrading fungi, which are cultivated worldwide for their production of speciality mushrooms, indicated that under the environmental conditions considered, certain species were adapted to cultivation on these lignocellulosic wastes (Pleurotus species) whereas others were not (Lentinus edodes and Flammulina velutipes). Furthermore, intra- and interspecies specific differences in the growth and production potential of the various lignocellulolytic fungi investigated on synthetic and natural medium were discovered. Biochemical and genetical investigations of these strains indicated differences between and within species which were often significant. Species varied qualitatively and quantitatively in the lignocellulolytic enzymes produced, which was loosely correlated with productivity on the different media investigated. Genetical studies, using RAPD fingerprinting, indicated that the Pleurotus genus is highly variable which supports the observed differences in growth, yield and enzymatic activity between different strains and species.
- Full Text:
- Date Issued: 1997
- Authors: Da Serra, Maria Fatima
- Date: 1997
- Subjects: Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4020 , http://hdl.handle.net/10962/d1004080 , Lignocellulose , Mushroom culture , Cultivated mushroom , Fungi -- Cultures and culture media , Fungi -- Biotechnology , Mushroom culture -- South Africa
- Description: Vast- quantities of lignocellulosic materials, representing potential substrates for the cultivation of speciality mushrooms, are produced annually in South Africa. A number of these materials are derived as waste products of the timber and agricultural industries, e.g. Maranti (Shorea spp.) and Port Jackson Willow (Acacia longifolia) respectively. The screening of various wood-degrading fungi, which are cultivated worldwide for their production of speciality mushrooms, indicated that under the environmental conditions considered, certain species were adapted to cultivation on these lignocellulosic wastes (Pleurotus species) whereas others were not (Lentinus edodes and Flammulina velutipes). Furthermore, intra- and interspecies specific differences in the growth and production potential of the various lignocellulolytic fungi investigated on synthetic and natural medium were discovered. Biochemical and genetical investigations of these strains indicated differences between and within species which were often significant. Species varied qualitatively and quantitatively in the lignocellulolytic enzymes produced, which was loosely correlated with productivity on the different media investigated. Genetical studies, using RAPD fingerprinting, indicated that the Pleurotus genus is highly variable which supports the observed differences in growth, yield and enzymatic activity between different strains and species.
- Full Text:
- Date Issued: 1997
Investigations into the larval rearing of two South African sparid species
- Authors: Davis, Jerome Adam
- Date: 1997
- Subjects: Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5293 , http://hdl.handle.net/10962/d1005138 , Sparidae
- Description: The most significant bottleneck to the development of marine finfish culture is a reliable production of juveniles for growout. This is due to the small size at hatch and delicate nature of the pelagic larvae produced by most commercially desirable species. However, over the last 30 years, improved larviculture techniques have been developed to the extent that many species are being successfully cultured worldwide. These techniques were applied to two endemic species as a preliminary step towards establishing marine finfish aquaculture in South Africa. Adult roman Chtysoblephus laticeps and carpenter Argyrozona argyrozona (Pisces: Sparidae) were caught in the Tsitsikamma National Park. Both species responded to injection with pituitary extract, HCG and LHRHa, and were succesfully stripped up to 48 hours after injection. Fish were stripped twice, the second stripping producing better quality eggs. Chyrysoblephus laticeps also spawned naturally after injection with LHRHa. The fertilised eggs were incubated and the larvae reared in a fully recirculating seawater system. One batch of A. argyrozona and three batches of C. laticeps were reared through metamorphosis on a diet of enriched rotifers and Anemia, and inert foods, following commonly used rearing procedures. Both species followed developmental patterns of other cultured larvae, displaying typical critical stages; high mortalities at first-feeding and cannibalism from 26-30 days after hatch resulted in survival rates ranging from 0.1-0.5%. Growth, survival, size of gape at first-feeding, and ease of weaning onto an inert diet of C. laticeps was comparable to other species being reared for the first time, indicating some potential as a candidate species. The numbers of A. argyrozona larvae reared were insufficient to make comparisons with other studies. The adults also proved to be susceptible to physical damage while in captivity and were, therefore, considered unsuitable for aquaculture. The thesis describes the spawning procedure, the systems developed and the larval rearing process. The critical stages of first-feeding, swim bladder inflation, settlement and cannibalism are discussed and the development of the larvae described. The ontogeny of both species is described in detail. Both species displayed typical sparid developmental patterns, but differed with respect to pigmentation, head spination and morphometrics.
- Full Text:
- Date Issued: 1997
- Authors: Davis, Jerome Adam
- Date: 1997
- Subjects: Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5293 , http://hdl.handle.net/10962/d1005138 , Sparidae
- Description: The most significant bottleneck to the development of marine finfish culture is a reliable production of juveniles for growout. This is due to the small size at hatch and delicate nature of the pelagic larvae produced by most commercially desirable species. However, over the last 30 years, improved larviculture techniques have been developed to the extent that many species are being successfully cultured worldwide. These techniques were applied to two endemic species as a preliminary step towards establishing marine finfish aquaculture in South Africa. Adult roman Chtysoblephus laticeps and carpenter Argyrozona argyrozona (Pisces: Sparidae) were caught in the Tsitsikamma National Park. Both species responded to injection with pituitary extract, HCG and LHRHa, and were succesfully stripped up to 48 hours after injection. Fish were stripped twice, the second stripping producing better quality eggs. Chyrysoblephus laticeps also spawned naturally after injection with LHRHa. The fertilised eggs were incubated and the larvae reared in a fully recirculating seawater system. One batch of A. argyrozona and three batches of C. laticeps were reared through metamorphosis on a diet of enriched rotifers and Anemia, and inert foods, following commonly used rearing procedures. Both species followed developmental patterns of other cultured larvae, displaying typical critical stages; high mortalities at first-feeding and cannibalism from 26-30 days after hatch resulted in survival rates ranging from 0.1-0.5%. Growth, survival, size of gape at first-feeding, and ease of weaning onto an inert diet of C. laticeps was comparable to other species being reared for the first time, indicating some potential as a candidate species. The numbers of A. argyrozona larvae reared were insufficient to make comparisons with other studies. The adults also proved to be susceptible to physical damage while in captivity and were, therefore, considered unsuitable for aquaculture. The thesis describes the spawning procedure, the systems developed and the larval rearing process. The critical stages of first-feeding, swim bladder inflation, settlement and cannibalism are discussed and the development of the larvae described. The ontogeny of both species is described in detail. Both species displayed typical sparid developmental patterns, but differed with respect to pigmentation, head spination and morphometrics.
- Full Text:
- Date Issued: 1997
An overview of the early-proterozoic, auriferous Black Reef placer in the Transvaal Basin
- Authors: De Bever, Johannes Nicolaas
- Date: 1997
- Subjects: Geology, Economic -- South Africa , Placer deposits -- South Africa , Prospecting -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4984 , http://hdl.handle.net/10962/d1005596 , Geology, Economic -- South Africa , Placer deposits -- South Africa , Prospecting -- Research -- South Africa
- Full Text:
- Date Issued: 1997
- Authors: De Bever, Johannes Nicolaas
- Date: 1997
- Subjects: Geology, Economic -- South Africa , Placer deposits -- South Africa , Prospecting -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4984 , http://hdl.handle.net/10962/d1005596 , Geology, Economic -- South Africa , Placer deposits -- South Africa , Prospecting -- Research -- South Africa
- Full Text:
- Date Issued: 1997
Determination of the optimum environmental requirements of juvenile marine fish : the development of a protocol
- Authors: Deacon, Neil
- Date: 1997
- Subjects: Mariculture Fishes -- Ecology Grunts (Fishes) -- Ecology Pomadasys -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5254 , http://hdl.handle.net/10962/d1005097
- Description: The spotted grunter, Pomodasys commersonnii, has been identified as a candidate species for mariculture in South Africa due to its high market demand and apparent biological suitability for culture. In common with most other potential mariculture species the spotted grunter has an estuarine juvenile phase. In this respect, the difficulties encountered in determining the optimum environmental requirements of spotted grunter are applicable to the majority of other potential mariculture species. Due the variability of estuarine habitats determination of the optimum environmental requirements of estuarine species under laboratory conditions are a prerequisite to subsequent evaluation of aquaculture potential. Therefore, using the spotted grunter as a representative of a typical potent ial mariculture species, the aim of this study was to contribute to the protocol for evaluating the environmental requirements of potential aquaculture species. The growth of fish is dependent on the relationship between food intake, metabolism and environmental factors. In this relationship, environmental factors do not act on growth per se, but rather act through metabolism on growth. Consequently, the environmental factors affecting the growth of a fish species can be classified into functional categories according to their respective influence on metabolic processes. Five functional categories are recognised, namely: controlling, limiting, masking, directive and lethal factors. In this study, the functional categories were sequenced to develop a theoretical protocol for determining the optimum environmental requirements of potential mariculture species under artificial conditions. It was hypothesised that the correct sequence for experimentally determining the optimum environmental requirements of a species should correspond to theoretical protocol. The hypothesis was tested from the experimental investigation into the individual effects of temperature, salinity, light intensity, photoperiod and food intake on growth performance of juvenile spotted grunter. The investigations quantified the relative effects of controlling, masking, directive and limiting factors on growth performance. The results of the studies were statistically compared to obtain a ranking of the effects of the environmental factors (e.g. temperature, salinity, etc.) on growth performance of juvenile spotted grunter. The statistical ranking facilitated the formulation of a second protocol for sequentially determining the optimum environmental requirements of a species. The second protocol was derived purely from the experimental data. Based on the corroboration between the theoretical protocol and that formulated from the experimental investigations, the hypothesis was accepted. Confirmation of the protocol for examining the effects of controlling, limiting, masking and directive factors provided a basis for the development of a preliminary experimental sequence for determining the optimum environmental requirements of juvenile marine fish. In the development of the experimental sequence, the protocol was interpreted in conjunction with the experimental methods used to determine the effects of environmental factors on the growth of juvenile spotted grunter. The experimental sequence provides a logical frame work within which the optimum environmental requirements of other marine fish species can be determined. In addition, evaluation of growth performance by this method provides a basis for comparison of the mariculture potential between species.
- Full Text:
- Date Issued: 1997
- Authors: Deacon, Neil
- Date: 1997
- Subjects: Mariculture Fishes -- Ecology Grunts (Fishes) -- Ecology Pomadasys -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5254 , http://hdl.handle.net/10962/d1005097
- Description: The spotted grunter, Pomodasys commersonnii, has been identified as a candidate species for mariculture in South Africa due to its high market demand and apparent biological suitability for culture. In common with most other potential mariculture species the spotted grunter has an estuarine juvenile phase. In this respect, the difficulties encountered in determining the optimum environmental requirements of spotted grunter are applicable to the majority of other potential mariculture species. Due the variability of estuarine habitats determination of the optimum environmental requirements of estuarine species under laboratory conditions are a prerequisite to subsequent evaluation of aquaculture potential. Therefore, using the spotted grunter as a representative of a typical potent ial mariculture species, the aim of this study was to contribute to the protocol for evaluating the environmental requirements of potential aquaculture species. The growth of fish is dependent on the relationship between food intake, metabolism and environmental factors. In this relationship, environmental factors do not act on growth per se, but rather act through metabolism on growth. Consequently, the environmental factors affecting the growth of a fish species can be classified into functional categories according to their respective influence on metabolic processes. Five functional categories are recognised, namely: controlling, limiting, masking, directive and lethal factors. In this study, the functional categories were sequenced to develop a theoretical protocol for determining the optimum environmental requirements of potential mariculture species under artificial conditions. It was hypothesised that the correct sequence for experimentally determining the optimum environmental requirements of a species should correspond to theoretical protocol. The hypothesis was tested from the experimental investigation into the individual effects of temperature, salinity, light intensity, photoperiod and food intake on growth performance of juvenile spotted grunter. The investigations quantified the relative effects of controlling, masking, directive and limiting factors on growth performance. The results of the studies were statistically compared to obtain a ranking of the effects of the environmental factors (e.g. temperature, salinity, etc.) on growth performance of juvenile spotted grunter. The statistical ranking facilitated the formulation of a second protocol for sequentially determining the optimum environmental requirements of a species. The second protocol was derived purely from the experimental data. Based on the corroboration between the theoretical protocol and that formulated from the experimental investigations, the hypothesis was accepted. Confirmation of the protocol for examining the effects of controlling, limiting, masking and directive factors provided a basis for the development of a preliminary experimental sequence for determining the optimum environmental requirements of juvenile marine fish. In the development of the experimental sequence, the protocol was interpreted in conjunction with the experimental methods used to determine the effects of environmental factors on the growth of juvenile spotted grunter. The experimental sequence provides a logical frame work within which the optimum environmental requirements of other marine fish species can be determined. In addition, evaluation of growth performance by this method provides a basis for comparison of the mariculture potential between species.
- Full Text:
- Date Issued: 1997
A case-study of principal succession : the experience of a high school principal and staff
- Authors: Dowding, Susan Patricia
- Date: 1997
- Subjects: Educational leadership School principals -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1440 , http://hdl.handle.net/10962/d1003321
- Description: This is a study of a principal succession In a non-racial, multicultural High-School in the North West Province of South Africa, formerly the independent homeland known as "Bophuthatswana". I was employed at the school at the time and am, therefore, a complete member-researcher. I use a qualitative research approach which relies mostly on in-depth interviews, individually and in groups. I chose my sample by administering a short biographical questionnaire. I have sought to establish "what is happening?" in the succession process by reporting the insights and experiences of a staff and its new principal. While I use the stage frameworks of more traditional researchers in succession to provide a coherent structure for my analysis, I use the organisational socialisation perspective extensively to analyse the insights provided by the staff and principal. Unlike other principal succession studies, I include the insights of both the principal and the staff. The organisational socialisation approach emphasises that succession is an interactive, multidirectional process. My study reinforces many of the observations of other researchers in leadership succession, whether in business or Education. However, two elements of succession emerge which appear to be unique in terms of other succession literature. These elements include the impact of socio-political events and what I call "ethno-cultural" aspects on the succession socialisation process. I provide examples of the influence these factors exert in this principal succession. This study is therefore of potential significance to administrators in both Education and business in the South African context where there are significant changes taking place in the power structures and ethnic makeup of relevant organisations. I also identify a number of areas for further research.
- Full Text:
- Date Issued: 1997
- Authors: Dowding, Susan Patricia
- Date: 1997
- Subjects: Educational leadership School principals -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1440 , http://hdl.handle.net/10962/d1003321
- Description: This is a study of a principal succession In a non-racial, multicultural High-School in the North West Province of South Africa, formerly the independent homeland known as "Bophuthatswana". I was employed at the school at the time and am, therefore, a complete member-researcher. I use a qualitative research approach which relies mostly on in-depth interviews, individually and in groups. I chose my sample by administering a short biographical questionnaire. I have sought to establish "what is happening?" in the succession process by reporting the insights and experiences of a staff and its new principal. While I use the stage frameworks of more traditional researchers in succession to provide a coherent structure for my analysis, I use the organisational socialisation perspective extensively to analyse the insights provided by the staff and principal. Unlike other principal succession studies, I include the insights of both the principal and the staff. The organisational socialisation approach emphasises that succession is an interactive, multidirectional process. My study reinforces many of the observations of other researchers in leadership succession, whether in business or Education. However, two elements of succession emerge which appear to be unique in terms of other succession literature. These elements include the impact of socio-political events and what I call "ethno-cultural" aspects on the succession socialisation process. I provide examples of the influence these factors exert in this principal succession. This study is therefore of potential significance to administrators in both Education and business in the South African context where there are significant changes taking place in the power structures and ethnic makeup of relevant organisations. I also identify a number of areas for further research.
- Full Text:
- Date Issued: 1997
A comparative photostability study of four propyl piperzine-substituted phenothiazines
- Authors: Drummond, Patricia Mary
- Date: 1997
- Subjects: Phenothiazine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3756 , http://hdl.handle.net/10962/d1003234 , Phenothiazine
- Description: Four structurally related phenothiazines available in South Africa in a variety of dosage forms and as fine chemicals were investigated to ascertain whether their structural differences in terms of the 2-chloro-/ trifluoromethyl-substituents on the phenothiazine nucleus and the methyl-/ ß-hydroxethyl groups on the piperazine ring accouning for the differences in pharmacological activity can be correlated with their photostability².The four propyl piperazine-substituted derivatives are ranked in the following decreasing order of neuroleptic activity: fluphenazine> trifluoperazine> perphenazine > rochlorperazine. In order to assess their photostability an HPLC method was developed and validated for linearity, accuracy and precision, selectivity, limit of detection and quantitation and ruggedness. Preliminary solution photostudies under controlled light conditions (UV, sunlight, fluorescent light) indicated that the rate of degradation followed first-order kinetics with perphenazine the most susceptible to.photodegradation under all light conditions studied. In vitro and in vivo metabolism yielding the 5-sulphoxide and its reported presence on decomposition of the phenothiazines25 led to the development of a synthetic procedure suitable for the sutphoxides of all four derivatives based on the method proposed by Owens et al. in order to provide standards for comparison in the photostudies⁷. Since ICH regulations require that impurities> 0.1 % are examined and identified⁷⁴ and semi-preparative isolation of photoproducts proved unsuccessful, LC-MS having been well documented for structural.elucidation⁷⁵ ⁷⁵ ⁷⁶ ⁷⁷ was used to characterize solution (UV, sunlight, fluorescent light) and preliminary solid (UV) photostudies. The chloroderivatives underwent dechlorination and sulphoxidation with subsequent photosubstitution in the case of prochlorperazine to yield the 2-hydroxy derivative and sulphoxidation of the dechloro-derivative of perphenazine. The sulphoxides of both trifluoperazine and fluphenazine were formed with further oxidation to the respective sulphones occurring. Preliminary solid state (UV) photostudies showed fluphenazine to be the least stable with 30.71 % degradation as opposed to 7.57% for prochlorperazine, 4.28% for perphenazine and 7.10% for trifluoperazine witn sulphoxidation observed to be. the major degradation pathway. Since in vitro metabolism of perazine derivatives is reported to occur via N-oxidation, N-demethylation, sulphoxidation and aromatic hydroxylation¹⁸ it does appear that there is some correlation between metabolic and photoproducts. However the fact that solution (UV) photostudies indicates trifluoperazine to be the most and perphenazine the least stable does not concur with the proposed order of pharmacological activity.
- Full Text:
- Date Issued: 1997
- Authors: Drummond, Patricia Mary
- Date: 1997
- Subjects: Phenothiazine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3756 , http://hdl.handle.net/10962/d1003234 , Phenothiazine
- Description: Four structurally related phenothiazines available in South Africa in a variety of dosage forms and as fine chemicals were investigated to ascertain whether their structural differences in terms of the 2-chloro-/ trifluoromethyl-substituents on the phenothiazine nucleus and the methyl-/ ß-hydroxethyl groups on the piperazine ring accouning for the differences in pharmacological activity can be correlated with their photostability².The four propyl piperazine-substituted derivatives are ranked in the following decreasing order of neuroleptic activity: fluphenazine> trifluoperazine> perphenazine > rochlorperazine. In order to assess their photostability an HPLC method was developed and validated for linearity, accuracy and precision, selectivity, limit of detection and quantitation and ruggedness. Preliminary solution photostudies under controlled light conditions (UV, sunlight, fluorescent light) indicated that the rate of degradation followed first-order kinetics with perphenazine the most susceptible to.photodegradation under all light conditions studied. In vitro and in vivo metabolism yielding the 5-sulphoxide and its reported presence on decomposition of the phenothiazines25 led to the development of a synthetic procedure suitable for the sutphoxides of all four derivatives based on the method proposed by Owens et al. in order to provide standards for comparison in the photostudies⁷. Since ICH regulations require that impurities> 0.1 % are examined and identified⁷⁴ and semi-preparative isolation of photoproducts proved unsuccessful, LC-MS having been well documented for structural.elucidation⁷⁵ ⁷⁵ ⁷⁶ ⁷⁷ was used to characterize solution (UV, sunlight, fluorescent light) and preliminary solid (UV) photostudies. The chloroderivatives underwent dechlorination and sulphoxidation with subsequent photosubstitution in the case of prochlorperazine to yield the 2-hydroxy derivative and sulphoxidation of the dechloro-derivative of perphenazine. The sulphoxides of both trifluoperazine and fluphenazine were formed with further oxidation to the respective sulphones occurring. Preliminary solid state (UV) photostudies showed fluphenazine to be the least stable with 30.71 % degradation as opposed to 7.57% for prochlorperazine, 4.28% for perphenazine and 7.10% for trifluoperazine witn sulphoxidation observed to be. the major degradation pathway. Since in vitro metabolism of perazine derivatives is reported to occur via N-oxidation, N-demethylation, sulphoxidation and aromatic hydroxylation¹⁸ it does appear that there is some correlation between metabolic and photoproducts. However the fact that solution (UV) photostudies indicates trifluoperazine to be the most and perphenazine the least stable does not concur with the proposed order of pharmacological activity.
- Full Text:
- Date Issued: 1997
Die ontwikkeling van 'n plattelandse tak van die ACVV 1900-1996
- Authors: du Plessis, Alette Marjorie
- Date: 1997
- Subjects: Afrikaanse Christelike Vrouevereniging -- History , Charities -- South Africa -- Eastern Cape -- Cradock -- History , Afrikaners -- South Africa -- Eastern Cape -- Cradock -- Charities -- History
- Language: Afrikaans
- Type: Thesis , Masters , MSocSc
- Identifier: vital:694 , http://hdl.handle.net/10962/d1006387 , Afrikaanse Christelike Vrouevereniging -- History , Charities -- South Africa -- Eastern Cape -- Cradock -- History , Afrikaners -- South Africa -- Eastern Cape -- Cradock -- Charities -- History
- Description: Die ACVV is een van die oudste gesinsorgorganisasies in Suid-Afrika en die oudste vrou-welsynsvereniging. Die organisasie is in 1904 gestig, maar dit word bewys dat dit in werklikheid ouer is. Die ontstaan is die gevolg van noodlenigingswerk wat in sovele Kaaplandse dorpe en stede aangepak is deur die Afrikaanse vroue om sover moontlik die smarte van die Anglo-Boere-oorlog te verlig. Dit was veral in die jare 1900 en 1902 toe plaaslike komitees in verskeie dorpe gestig is om eetware, klere en leesstof aan die krygsgevangenes in die kamp te stuur en later aan die vroue in konsentrasiekampe. Hieruit kan afgelei word dat die organisasie ontstaan het met oorlewing as oogmerk. Toe die oorlog verby is, het die begeerte posgevat om van hierdie komitees iets blywends te maak. Lambrechts en Theron (1959:31) bepaal dat daar drie tydperke onderskei word by die nagaan van die werksaamhede van die ACVV. In die bestudering van die plaaslike omstandighede word die stelling as waar bewys, maar word die tydperke aangepas om die situasie in 'n wyer spektrum waar te neem. Die eerste tydperk word hoofsaaklik gekenmerk deur die groei van die vereniging en die reelings wat getref is vir die doeltreffende organisasie van die werk wat verrig is deur vrywillige werkers. Die tweede tydperk val saam met 'n algehele nuwe benadering teenoor welsynswerk wat gevloei het uit die vermeerderde kennis en studie van Sosiale Wetenskappe en die vraagstuk van verarming in Suid-Afrika na die jare van droogte en depressie. 'n Derde tydperk is geëidentifiseer waarin die land tred gehou het met die wereldtendens waarin die staat 'n groter aandeel in welsynsdienste begin neem het. 'n Toenemende toepassing van die beleid van staatshulp aan partikuliere organisasies is 'n erkenning van staatsweë dat daar bepaalde take is wat beter deur hierdie organisasies vervul kan word. Dit het ACW-takke in staat gestel om maatskaplike werkers aan te stel in gesubsidieerde poste. Die ACVV se dienste het gedurig ontwikkeling getoon en het noodleniging, gesinsorgdienste, groepdienste en residensiële sorg ingesluit. Dienste het sekondêr ontwikkel en baie klem is op bejaardesorg geplaas wat onder andere die oprigting en bestuur van tehuise en dienssentrums tot gevolg gehad het. Gesinsorgwerk vorm die eintlike kern van die werksaamhede van die ACVV, want al sy ondernemings het ten doel die bevordering van 'n gesonde gesinslewe. Dienste van die vereniging aan die individuele gesinslid het steeds ten doel om beter by sy gesin, en gevolglik ook beter by die samelewing aan te pas. 'n Duidelike ontwikkeling word beskryf wat vanaf 1990 tot 'n punt van verdere veranderinge gedryf word deur omstandighede buite die ACVV. Die belangrikste hiervan is 'n dramatiese verandering in regeringsbeleid waarby die ACVV moes aansluit. Dit het wesentlike aanpassings meegebring op die gebied van werksarea en die kliêntesisteem, aangesien die ACVV in die verlede hoofsaaklik in die behoeftes van die blanke kultuurgroep voorsien het. Later het subsidievereistes die vereniging verhoed om buite hierdie beperkings te werk. Die aanpassings het egter nie tot gevolg gehad dat die vereniging doelstellings, waardes en norme moes laat vaar nie. Verskeie rolspelers is betrokke by praktiese en basiese dienslewering tot besluitneming op die hoogste vlak. Die ACVV se struktuur het grootliks dieselfde gebly met die Kongres as hoogste gesag. Die dienste van die Hoofbestuur het sodanig uitgebrei dat dit leiding kon bied aan takke op grondvlak. Dit is deurgaans duidelik dat die vrywillige werker binne die organisasie die kern en basis vorm waarop die vereniging voortbestaan. Die ACVV sal in die toekoms steeds In rol het om te vervul in 'n veranderde omgewing wat uitdagings bied vir dienslewering en waar uitgebreide behoeftes ten opsigte van maatskaplike ontwikkeling bestaan
- Full Text:
- Date Issued: 1997
- Authors: du Plessis, Alette Marjorie
- Date: 1997
- Subjects: Afrikaanse Christelike Vrouevereniging -- History , Charities -- South Africa -- Eastern Cape -- Cradock -- History , Afrikaners -- South Africa -- Eastern Cape -- Cradock -- Charities -- History
- Language: Afrikaans
- Type: Thesis , Masters , MSocSc
- Identifier: vital:694 , http://hdl.handle.net/10962/d1006387 , Afrikaanse Christelike Vrouevereniging -- History , Charities -- South Africa -- Eastern Cape -- Cradock -- History , Afrikaners -- South Africa -- Eastern Cape -- Cradock -- Charities -- History
- Description: Die ACVV is een van die oudste gesinsorgorganisasies in Suid-Afrika en die oudste vrou-welsynsvereniging. Die organisasie is in 1904 gestig, maar dit word bewys dat dit in werklikheid ouer is. Die ontstaan is die gevolg van noodlenigingswerk wat in sovele Kaaplandse dorpe en stede aangepak is deur die Afrikaanse vroue om sover moontlik die smarte van die Anglo-Boere-oorlog te verlig. Dit was veral in die jare 1900 en 1902 toe plaaslike komitees in verskeie dorpe gestig is om eetware, klere en leesstof aan die krygsgevangenes in die kamp te stuur en later aan die vroue in konsentrasiekampe. Hieruit kan afgelei word dat die organisasie ontstaan het met oorlewing as oogmerk. Toe die oorlog verby is, het die begeerte posgevat om van hierdie komitees iets blywends te maak. Lambrechts en Theron (1959:31) bepaal dat daar drie tydperke onderskei word by die nagaan van die werksaamhede van die ACVV. In die bestudering van die plaaslike omstandighede word die stelling as waar bewys, maar word die tydperke aangepas om die situasie in 'n wyer spektrum waar te neem. Die eerste tydperk word hoofsaaklik gekenmerk deur die groei van die vereniging en die reelings wat getref is vir die doeltreffende organisasie van die werk wat verrig is deur vrywillige werkers. Die tweede tydperk val saam met 'n algehele nuwe benadering teenoor welsynswerk wat gevloei het uit die vermeerderde kennis en studie van Sosiale Wetenskappe en die vraagstuk van verarming in Suid-Afrika na die jare van droogte en depressie. 'n Derde tydperk is geëidentifiseer waarin die land tred gehou het met die wereldtendens waarin die staat 'n groter aandeel in welsynsdienste begin neem het. 'n Toenemende toepassing van die beleid van staatshulp aan partikuliere organisasies is 'n erkenning van staatsweë dat daar bepaalde take is wat beter deur hierdie organisasies vervul kan word. Dit het ACW-takke in staat gestel om maatskaplike werkers aan te stel in gesubsidieerde poste. Die ACVV se dienste het gedurig ontwikkeling getoon en het noodleniging, gesinsorgdienste, groepdienste en residensiële sorg ingesluit. Dienste het sekondêr ontwikkel en baie klem is op bejaardesorg geplaas wat onder andere die oprigting en bestuur van tehuise en dienssentrums tot gevolg gehad het. Gesinsorgwerk vorm die eintlike kern van die werksaamhede van die ACVV, want al sy ondernemings het ten doel die bevordering van 'n gesonde gesinslewe. Dienste van die vereniging aan die individuele gesinslid het steeds ten doel om beter by sy gesin, en gevolglik ook beter by die samelewing aan te pas. 'n Duidelike ontwikkeling word beskryf wat vanaf 1990 tot 'n punt van verdere veranderinge gedryf word deur omstandighede buite die ACVV. Die belangrikste hiervan is 'n dramatiese verandering in regeringsbeleid waarby die ACVV moes aansluit. Dit het wesentlike aanpassings meegebring op die gebied van werksarea en die kliêntesisteem, aangesien die ACVV in die verlede hoofsaaklik in die behoeftes van die blanke kultuurgroep voorsien het. Later het subsidievereistes die vereniging verhoed om buite hierdie beperkings te werk. Die aanpassings het egter nie tot gevolg gehad dat die vereniging doelstellings, waardes en norme moes laat vaar nie. Verskeie rolspelers is betrokke by praktiese en basiese dienslewering tot besluitneming op die hoogste vlak. Die ACVV se struktuur het grootliks dieselfde gebly met die Kongres as hoogste gesag. Die dienste van die Hoofbestuur het sodanig uitgebrei dat dit leiding kon bied aan takke op grondvlak. Dit is deurgaans duidelik dat die vrywillige werker binne die organisasie die kern en basis vorm waarop die vereniging voortbestaan. Die ACVV sal in die toekoms steeds In rol het om te vervul in 'n veranderde omgewing wat uitdagings bied vir dienslewering en waar uitgebreide behoeftes ten opsigte van maatskaplike ontwikkeling bestaan
- Full Text:
- Date Issued: 1997
The use of remote sensing and Geographic Information System (GIS) techniques, to interpret savanna ecosystem patterns in the Sabi Sand Game Reserve, Mpumalanga province
- Fortescue, Alexander Kenneth John
- Authors: Fortescue, Alexander Kenneth John
- Date: 1997
- Subjects: Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4857 , http://hdl.handle.net/10962/d1005533 , Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Description: This thesis explores techniques which ultimately strive to optimize production systems in rangeland areas of southern Africa. By linking spatially significant, satellite derived data to practical measurements of vegetation structure, valuable insight has been derived on processes of ecosystem function, in the Sabi Sand Game Reserve. A broad ecosystem response mechanism has been established from a conventional Normalized Differentiation Vegetation Index (NDVI). By responding to increases in production, which are driven by disturbance, this index has allowed quantitative systems theory in savanna to be tested and refined. Methods of biomass and production estimation which are specifically designed to reduce the cost and time involved with the more conventional method of destructive harvesting have been tested in the savanna at the Sabi Sand Game Reserve. Results from these estimates relate well with data derived through destructive harvesting in structurally similar savanna. Moreover, by relating the above-ground woody production estimates to remere sensing indices, it was possible to demonstrate that the problem of extrapolation, universal to most biomass and production studies can be overcome. Since remote sensing encompasses an array of tools fundamental to rangeland inventory, monitoring and management, valuable spatially significant information pertaining to ecosystem structure and function has been provided for managers in the Sabi Sand Game Reserve.
- Full Text:
- Date Issued: 1997
- Authors: Fortescue, Alexander Kenneth John
- Date: 1997
- Subjects: Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4857 , http://hdl.handle.net/10962/d1005533 , Sabi-Sand Game Reserve (South Africa) , Savanna ecology -- South Africa -- Mpumalanga , Geographic information systems , Savanna ecology -- Remote sensing
- Description: This thesis explores techniques which ultimately strive to optimize production systems in rangeland areas of southern Africa. By linking spatially significant, satellite derived data to practical measurements of vegetation structure, valuable insight has been derived on processes of ecosystem function, in the Sabi Sand Game Reserve. A broad ecosystem response mechanism has been established from a conventional Normalized Differentiation Vegetation Index (NDVI). By responding to increases in production, which are driven by disturbance, this index has allowed quantitative systems theory in savanna to be tested and refined. Methods of biomass and production estimation which are specifically designed to reduce the cost and time involved with the more conventional method of destructive harvesting have been tested in the savanna at the Sabi Sand Game Reserve. Results from these estimates relate well with data derived through destructive harvesting in structurally similar savanna. Moreover, by relating the above-ground woody production estimates to remere sensing indices, it was possible to demonstrate that the problem of extrapolation, universal to most biomass and production studies can be overcome. Since remote sensing encompasses an array of tools fundamental to rangeland inventory, monitoring and management, valuable spatially significant information pertaining to ecosystem structure and function has been provided for managers in the Sabi Sand Game Reserve.
- Full Text:
- Date Issued: 1997
Responding to literature: empowering girls to speak with their own voices in a multicultural context
- Authors: Foster, Lesley
- Date: 1997
- Subjects: Reader-response criticism--South Africa Multicultural education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1742 , http://hdl.handle.net/10962/d1003626
- Description: The purpose of this study was to investigate whether the space provided by a readerresponse transaction between girls and the text, Roll of Thunder, Hear My Cry (Taylor 1977) .. empowered pupils to tell their own stories. It also sought to identify ways in which the problems and possibilities perceived by these pupils might guide curriculum decisions in a transforming education system. In addition to engaging in reader-response activities around the text, drama and videos providing social context were integral to the programme. Related work in the subject areas of history and lifeskills was also undertaken. Data was drawn from pupils' reading journals, responses to specific passages, transcripts of small group discussions, and interviews. The study is ethnographic in nature and all the data qualitative. Theoretical insights were drawn from the felds of cultural studies, postmodern criticism, and postructural modes of cultural and social analysis inasfar as they illuminate and inform the relationship between language, knowledge and power. The research was conducted in an historically white, girls' school which adopted a nonracial admissions policy in January 1991. Despite the fact that existing traditions and values of the the school to a very large extent influence what is taught, the data suggests that pupils were becoming agents in their own learning and were taking up multiple identities both within and without the world of the school.
- Full Text:
- Date Issued: 1997
Responding to literature: empowering girls to speak with their own voices in a multicultural context
- Authors: Foster, Lesley
- Date: 1997
- Subjects: Reader-response criticism--South Africa Multicultural education
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1742 , http://hdl.handle.net/10962/d1003626
- Description: The purpose of this study was to investigate whether the space provided by a readerresponse transaction between girls and the text, Roll of Thunder, Hear My Cry (Taylor 1977) .. empowered pupils to tell their own stories. It also sought to identify ways in which the problems and possibilities perceived by these pupils might guide curriculum decisions in a transforming education system. In addition to engaging in reader-response activities around the text, drama and videos providing social context were integral to the programme. Related work in the subject areas of history and lifeskills was also undertaken. Data was drawn from pupils' reading journals, responses to specific passages, transcripts of small group discussions, and interviews. The study is ethnographic in nature and all the data qualitative. Theoretical insights were drawn from the felds of cultural studies, postmodern criticism, and postructural modes of cultural and social analysis inasfar as they illuminate and inform the relationship between language, knowledge and power. The research was conducted in an historically white, girls' school which adopted a nonracial admissions policy in January 1991. Despite the fact that existing traditions and values of the the school to a very large extent influence what is taught, the data suggests that pupils were becoming agents in their own learning and were taking up multiple identities both within and without the world of the school.
- Full Text:
- Date Issued: 1997
An investigation of nondeterminism in functional programming languages
- Authors: Graham, Gwyneth Clare
- Date: 1997
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4658 , http://hdl.handle.net/10962/d1006658 , Functional programming languages
- Description: This thesis investigates nondeterminism in functional programming languages. To establish a precise understanding of nondeterministic language properties, Sondergaard and Sestoft's analysis and definitions of functional language properties are adopted as are the characterizations of weak and strong nondeterminism. This groundwork is followed by a denotational semantic description of a nondeterministic language (suggested by Sondergaard and Sestoft). In this manner, a precise characterization of the effects of strong nondeterminism is developed. Methods used to hide nondeterminism to in order to overcome or sidestep the problem of strong nondeterminism in pure functional languages are defined. These different techniques ensure that functional languages remain pure but also include some of the advantages of nondeterminism. Lastly, this discussion of nondeterminism is applied to the area of functional parallel language implementation to indicate that the related problem and the possible solutions are not purely academic. This application gives rise to an interesting discussion on optimization of list parallelism. This technique relies on the ability to decide when a bag may be used instead of a list.
- Full Text:
- Date Issued: 1997
- Authors: Graham, Gwyneth Clare
- Date: 1997
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4658 , http://hdl.handle.net/10962/d1006658 , Functional programming languages
- Description: This thesis investigates nondeterminism in functional programming languages. To establish a precise understanding of nondeterministic language properties, Sondergaard and Sestoft's analysis and definitions of functional language properties are adopted as are the characterizations of weak and strong nondeterminism. This groundwork is followed by a denotational semantic description of a nondeterministic language (suggested by Sondergaard and Sestoft). In this manner, a precise characterization of the effects of strong nondeterminism is developed. Methods used to hide nondeterminism to in order to overcome or sidestep the problem of strong nondeterminism in pure functional languages are defined. These different techniques ensure that functional languages remain pure but also include some of the advantages of nondeterminism. Lastly, this discussion of nondeterminism is applied to the area of functional parallel language implementation to indicate that the related problem and the possible solutions are not purely academic. This application gives rise to an interesting discussion on optimization of list parallelism. This technique relies on the ability to decide when a bag may be used instead of a list.
- Full Text:
- Date Issued: 1997