The diversity of root fungi associated with Erica species occurring in the Albany Centre of Endemism
- Authors: Bizabani, Christine
- Date: 2015
- Subjects: Ericaceae , Ericas , Roots (Botany) -- Diseases and pests , Mycorrhizal fungi , Polymerase chain reaction , Fungi -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4160 , http://hdl.handle.net/10962/d1018575
- Description: South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.
- Full Text:
- Date Issued: 2015
The diversity of root fungi associated with Erica species occurring in the Albany Centre of Endemism
- Authors: Bizabani, Christine
- Date: 2015
- Subjects: Ericaceae , Ericas , Roots (Botany) -- Diseases and pests , Mycorrhizal fungi , Polymerase chain reaction , Fungi -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4160 , http://hdl.handle.net/10962/d1018575
- Description: South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.
- Full Text:
- Date Issued: 2015
Transcending state-centrism: new regionalism and the future of Southern African regional integration
- Authors: Blaauw, Lesley
- Date: 2007
- Subjects: Southern African Development Community Southern African Customs Union Southern African Development Coordination Conference Regionalism -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2761 , http://hdl.handle.net/10962/d1002971
- Description: This dissertation argues that in the 1990s and beyond, the character and functions of regions and regionalism have experienced a major transformation. This requires a reconceptualisation of regions and regionalism that transcends state-centrism. The argument here is that the definition of regions and regionalism needs to recognise that other actors also participate in the construction of regions and the practise of regionalism. Up to now, however, theories of integration incompletely deal with outcomes appropriate to developing countries, states and regions. In the context where people remain vulnerable to top-down forms of regionalism driven by the forces of globalisation, this calls for a new approach in the analytical study of regionalism in a transnational context. The contention is that new regionalism, and its variant, developmental regionalism pay attention to the role those organised civil society actors and those marginalised by both globalisation and regionalisation play in promoting regionalism in a transnational context. Historically, state-centric regionalism in southern Africa was not aimed at achieving developmental objectives. In the case of SACU, the argument is that South Africa used its economic strength in a hegemonial way. To counter-act apartheid South Africa’s economic hegemony, SADCC was formed. SADCC achieved limited success in the fields of infrastructural development and in attracting donor aid. The end of the Cold War and the downfall of apartheid compelled these organisations to recast their objectives and purpose. For SACU this meant changing from an organisation dominated by South Africa to a fully-fledged inter-state one. Disconcertedly, however, about the reforms undertook by SACU, is that the disposition of member states remain important in determining the content and scope of regionalism. SADC, on the other hand, has also not sufficiently reform itself to achieve the ambitious goals it set-out for itself. Moreover, while SADC has since its inception in 1992 set-out to involve non-state actors in its regional integration efforts, limited institutional reform in 2000 and beyond, and elites at the forefront of institutional restructuring make it difficult for non-state actors to contribute to sustainable regional integration. In conclusion, this dissertation maintains that sustainable regionalist orders are best built by recognising that beyond the geometry of state-sovereignty, civil society organisations with a regional focus and the ordinary people of the region also contribute to regioness and as such to the re-conceptualisation of regional community in southern Africa.
- Full Text:
- Date Issued: 2007
Transcending state-centrism: new regionalism and the future of Southern African regional integration
- Authors: Blaauw, Lesley
- Date: 2007
- Subjects: Southern African Development Community Southern African Customs Union Southern African Development Coordination Conference Regionalism -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2761 , http://hdl.handle.net/10962/d1002971
- Description: This dissertation argues that in the 1990s and beyond, the character and functions of regions and regionalism have experienced a major transformation. This requires a reconceptualisation of regions and regionalism that transcends state-centrism. The argument here is that the definition of regions and regionalism needs to recognise that other actors also participate in the construction of regions and the practise of regionalism. Up to now, however, theories of integration incompletely deal with outcomes appropriate to developing countries, states and regions. In the context where people remain vulnerable to top-down forms of regionalism driven by the forces of globalisation, this calls for a new approach in the analytical study of regionalism in a transnational context. The contention is that new regionalism, and its variant, developmental regionalism pay attention to the role those organised civil society actors and those marginalised by both globalisation and regionalisation play in promoting regionalism in a transnational context. Historically, state-centric regionalism in southern Africa was not aimed at achieving developmental objectives. In the case of SACU, the argument is that South Africa used its economic strength in a hegemonial way. To counter-act apartheid South Africa’s economic hegemony, SADCC was formed. SADCC achieved limited success in the fields of infrastructural development and in attracting donor aid. The end of the Cold War and the downfall of apartheid compelled these organisations to recast their objectives and purpose. For SACU this meant changing from an organisation dominated by South Africa to a fully-fledged inter-state one. Disconcertedly, however, about the reforms undertook by SACU, is that the disposition of member states remain important in determining the content and scope of regionalism. SADC, on the other hand, has also not sufficiently reform itself to achieve the ambitious goals it set-out for itself. Moreover, while SADC has since its inception in 1992 set-out to involve non-state actors in its regional integration efforts, limited institutional reform in 2000 and beyond, and elites at the forefront of institutional restructuring make it difficult for non-state actors to contribute to sustainable regional integration. In conclusion, this dissertation maintains that sustainable regionalist orders are best built by recognising that beyond the geometry of state-sovereignty, civil society organisations with a regional focus and the ordinary people of the region also contribute to regioness and as such to the re-conceptualisation of regional community in southern Africa.
- Full Text:
- Date Issued: 2007
The ecology of juvenile Rhabdosargus holubi (Steinachner) (Teleostei : Sparidae)
- Authors: Blaber, Stephen J M
- Date: 1974
- Subjects: Osteichthyes Fishes -- Breeding Fish populations Fish culture -- South Africa Estuaries -- South Africa -- Eastern Cape Aquatic ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5672 , http://hdl.handle.net/10962/d1005357
- Description: INTRODUCTION: Estuaries have received considerable attention from biologists in southern Africa in the past thirty years. Professor J.H. Day and the Zoology Department of the University of Cape Town have undertaken ecological surveys of a large number of estuaries of a variety of types, laying the important groundwork for more detailed studies of single species or problems. Their studies showed that the fish populations of southern African estuaries consist mainly of marine species. Why and when these species enter or leave the estuaries and whether they grow or breed in them were not established. The only relatively detailed study of a fish in southern African estuaries was that of Talbot (1955) who investigated aspects of the growth, feeding and reproduction of Rhabdosargus globiceps (Cuvier). No quantitative information has been published on any of the fish species, perhaps due to the difficulty of obtaining such data; results such as population estimates, mortality rates and growth rates are particularly unreliable when the area being investigated is in direct contact with the sea. Studies relating to even a single species of fish are hampered by immigration and emigration between estuary and sea, which make the population continuously variable. The larger estuaries are also difficult to sample adequately, especially with regard to netting, except perhaps on a very large scale using expensive commercial equipment. Along the southern African coast many of the smaller estuaries with a limited catchment area are cut off from the sea for most of the year due to erratic rainfall and longshore drift of sand. These closed or 'blind' estuaries of south eastern Africa, of which there are at least thirty in the eastern Cape Province, provide excellent areas for studying estuarine fish populations which enter when the estuary is open to the sea, but become isolated once it closes. These fish which become cut off in closed estuaries are subject to a new series of conditions. They are exposed to the wider temperature and salinity fluctuations of an estuary and they are forced to utilise the food resources of the estuary. Additionally they may be subjected to predation from piscivorous birds, and those predatory fish which are also cut off in the estuary. These factors will affect the size, mortality, and growth rates of a fish population. Since the fish are isolated no recruitment from the sea can take place, and any increase in numbers would have to come from breeding within the estuary. It is inevitable that the most numerous species should receive attention first. Rhabdosargus holubi (Steindachner) (Synonomy : Sargus holubi Stndr, Austrosparus tricuspidens Smith, Rhabdosargus tricuspidens (Smith))(Plate 1) is one of the most abundant fish in the estuaries of the eastern Cape Province. According to Smith (1965) it is endemic to southern Africa, occurring from the Cape to Zululand, being most common between Mossel Bay and East London. It is largely replaced by Rhabdosargus sarba (Forskal) in the north of its range and by Rhabdosargus globiceps (Cuvier) in the south. Commonly called the 'flatty' or silver bream it is considered only as being of nuisance value by fishermen, seldom exceeding 30 cm in length. In this study the ecology of R.holubi was examined in relation to the closed West Kleinemond estuary which is a small 'blind' estuary typical of those found along the eastern Cape coast. The growth, mortality and population size of R.holubi in this estuary were investigated and linked where possible with predation and detailed studies into the tolerances, food, and feeding of the species. It was not known at the commencement of the study whether breeding could occur in estuaries, although Smith (1965) stated that R.holubi does breed in estuaries. During the course of the sampling programme in the West Kleinemond estuary, measurements of the growth and population structure of two other species of fish were recorded for comparison with R.holubi: the sparid Lithognathus lithognathus (Cuvier) (White Steenbras) and the piscivorous carangid Hypacanthas amia (L.) (Leervis or garrick). Laboratory studies on R.holubi were possible due to the fact that large numbers of this species could be caught in eastern Cape estuaries and transported to Grahamstown, where they could be maintained in captivity for up to four months in recirculating seawater aquaria. During the course of the study over 2000 fish were kept in captivity at different times for a variety of experiments. Another 2500 were preserved for gut analyses and lipid determinations, while over 5000 were captured, examined and released in the field.
- Full Text:
- Date Issued: 1974
- Authors: Blaber, Stephen J M
- Date: 1974
- Subjects: Osteichthyes Fishes -- Breeding Fish populations Fish culture -- South Africa Estuaries -- South Africa -- Eastern Cape Aquatic ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5672 , http://hdl.handle.net/10962/d1005357
- Description: INTRODUCTION: Estuaries have received considerable attention from biologists in southern Africa in the past thirty years. Professor J.H. Day and the Zoology Department of the University of Cape Town have undertaken ecological surveys of a large number of estuaries of a variety of types, laying the important groundwork for more detailed studies of single species or problems. Their studies showed that the fish populations of southern African estuaries consist mainly of marine species. Why and when these species enter or leave the estuaries and whether they grow or breed in them were not established. The only relatively detailed study of a fish in southern African estuaries was that of Talbot (1955) who investigated aspects of the growth, feeding and reproduction of Rhabdosargus globiceps (Cuvier). No quantitative information has been published on any of the fish species, perhaps due to the difficulty of obtaining such data; results such as population estimates, mortality rates and growth rates are particularly unreliable when the area being investigated is in direct contact with the sea. Studies relating to even a single species of fish are hampered by immigration and emigration between estuary and sea, which make the population continuously variable. The larger estuaries are also difficult to sample adequately, especially with regard to netting, except perhaps on a very large scale using expensive commercial equipment. Along the southern African coast many of the smaller estuaries with a limited catchment area are cut off from the sea for most of the year due to erratic rainfall and longshore drift of sand. These closed or 'blind' estuaries of south eastern Africa, of which there are at least thirty in the eastern Cape Province, provide excellent areas for studying estuarine fish populations which enter when the estuary is open to the sea, but become isolated once it closes. These fish which become cut off in closed estuaries are subject to a new series of conditions. They are exposed to the wider temperature and salinity fluctuations of an estuary and they are forced to utilise the food resources of the estuary. Additionally they may be subjected to predation from piscivorous birds, and those predatory fish which are also cut off in the estuary. These factors will affect the size, mortality, and growth rates of a fish population. Since the fish are isolated no recruitment from the sea can take place, and any increase in numbers would have to come from breeding within the estuary. It is inevitable that the most numerous species should receive attention first. Rhabdosargus holubi (Steindachner) (Synonomy : Sargus holubi Stndr, Austrosparus tricuspidens Smith, Rhabdosargus tricuspidens (Smith))(Plate 1) is one of the most abundant fish in the estuaries of the eastern Cape Province. According to Smith (1965) it is endemic to southern Africa, occurring from the Cape to Zululand, being most common between Mossel Bay and East London. It is largely replaced by Rhabdosargus sarba (Forskal) in the north of its range and by Rhabdosargus globiceps (Cuvier) in the south. Commonly called the 'flatty' or silver bream it is considered only as being of nuisance value by fishermen, seldom exceeding 30 cm in length. In this study the ecology of R.holubi was examined in relation to the closed West Kleinemond estuary which is a small 'blind' estuary typical of those found along the eastern Cape coast. The growth, mortality and population size of R.holubi in this estuary were investigated and linked where possible with predation and detailed studies into the tolerances, food, and feeding of the species. It was not known at the commencement of the study whether breeding could occur in estuaries, although Smith (1965) stated that R.holubi does breed in estuaries. During the course of the sampling programme in the West Kleinemond estuary, measurements of the growth and population structure of two other species of fish were recorded for comparison with R.holubi: the sparid Lithognathus lithognathus (Cuvier) (White Steenbras) and the piscivorous carangid Hypacanthas amia (L.) (Leervis or garrick). Laboratory studies on R.holubi were possible due to the fact that large numbers of this species could be caught in eastern Cape estuaries and transported to Grahamstown, where they could be maintained in captivity for up to four months in recirculating seawater aquaria. During the course of the study over 2000 fish were kept in captivity at different times for a variety of experiments. Another 2500 were preserved for gut analyses and lipid determinations, while over 5000 were captured, examined and released in the field.
- Full Text:
- Date Issued: 1974
Theories of economic underdevelopment: a general equilibrium analysis
- Authors: Black, Philip Andrew
- Date: 1982
- Subjects: Equilibrium (Economics) -- Mathematical models Economic development -- Mathematical models Developing countries -- Economic conditions -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1049 , http://hdl.handle.net/10962/d1006235
- Description: This thesis is mainly concerned with the question whether 'conventional' economic theory - especially the neoclassical theory of general equilibrium - is sufficiently flexible to accommodate the particular conditions prevailing in the developing countries. It is argued that most existing theories of economic underdevelopment adopt an interpretative approach which essentially amounts to relaxing some of the chief assumptions of the neoclassical theory. When applied to the two-sector model of general equilibrium, these theories generally yield predictions which are vastly different from those associated with the neoclassical assumptions of perfect competition, unlimited factor substitutability and unrestricted resource mobility. Several theories seek to explain the development problem in terms of the specific production processes used in poor countries. Myrdal's (1957) theory of cumulative causation, for example, effectively introduces increasing returns to scale in at least one sector or region of the economy; in contrast to the neoclassical theory, he thus nvisages a cumulative process of regional divergence in the output level per worker. Similarly, Richard Eckaus's (1955) explanation of the "factor-proportions problem" is based on the assumption of limited factor substitutability. This enables him to establish the existence of a so-called "unemployment equiIibrium", thus implying that developing countries may be faced with a conflict between the objective of maximizing social -welfare on the one hand, and that of full employment on the other. More recently, Leibenstein (1960) has shown that this trade-off may be complicated by the introduction of capital-biased technological inventions and innovations. The solution to the factor-proportions problem consists in the adoption of more appropriate, usually labour-biased technologies, increased capital formation and a reduction in the rate of population growth. Much of the postwar literature on economic development has focused on the imperfectly competitive structure of the product and the factor markets in developing countries. Myint (1954) has highlighted the role played by monopolies and ligopolies during the "opening-up" process of economic development. Likewise, both Lewis's (1954) dualist theory and Todaro's (1969; 1971) model of rural-urban migration attempt to explain the unemployment problem in terms of various factor price distortions. In an international context, Prebisch (1950; 1959) and Singer (1950) have again shown how prevailing differences in the structure of markets between developed and developing countries may turn the terms of trade against the latter; using a two-sector model, Bhagwati (1958) has demonstrated that such a deterioration in the terms of trade could bring about a net decrease in the welfare level of the countries concerned. Generally, the policy measures relevant to the "market imperfections" problem include the creation of job opportunities in the rural (rather than urban) sector, the encouragement of informal-sector enterprises,and the imposition of factor taxes and subsidies as a means of counteracting the adverse effect of factor price distortions on employment. A more recent approach to the unemployment problem is the plea by the International Labor Office (1970; 1972) for a redistribution of income within the developing countries. In terms of the two-sector model, such a policy may well succeed in eliminating labour unemployment caused by fixed factor proportions and/or factor price distortions. It should be realized, though, that a redistribution of income may lower the aggregate savings level, and hence also the growth rates of capital and labour employment in the economy. On the whole, it would seem that these theories do indeed adopt a modified version of the neoclassical theory in providing a fairly comprehensive explanation of the economic problems of labour unemployment, low incomes and inequality.
- Full Text:
- Date Issued: 1982
- Authors: Black, Philip Andrew
- Date: 1982
- Subjects: Equilibrium (Economics) -- Mathematical models Economic development -- Mathematical models Developing countries -- Economic conditions -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1049 , http://hdl.handle.net/10962/d1006235
- Description: This thesis is mainly concerned with the question whether 'conventional' economic theory - especially the neoclassical theory of general equilibrium - is sufficiently flexible to accommodate the particular conditions prevailing in the developing countries. It is argued that most existing theories of economic underdevelopment adopt an interpretative approach which essentially amounts to relaxing some of the chief assumptions of the neoclassical theory. When applied to the two-sector model of general equilibrium, these theories generally yield predictions which are vastly different from those associated with the neoclassical assumptions of perfect competition, unlimited factor substitutability and unrestricted resource mobility. Several theories seek to explain the development problem in terms of the specific production processes used in poor countries. Myrdal's (1957) theory of cumulative causation, for example, effectively introduces increasing returns to scale in at least one sector or region of the economy; in contrast to the neoclassical theory, he thus nvisages a cumulative process of regional divergence in the output level per worker. Similarly, Richard Eckaus's (1955) explanation of the "factor-proportions problem" is based on the assumption of limited factor substitutability. This enables him to establish the existence of a so-called "unemployment equiIibrium", thus implying that developing countries may be faced with a conflict between the objective of maximizing social -welfare on the one hand, and that of full employment on the other. More recently, Leibenstein (1960) has shown that this trade-off may be complicated by the introduction of capital-biased technological inventions and innovations. The solution to the factor-proportions problem consists in the adoption of more appropriate, usually labour-biased technologies, increased capital formation and a reduction in the rate of population growth. Much of the postwar literature on economic development has focused on the imperfectly competitive structure of the product and the factor markets in developing countries. Myint (1954) has highlighted the role played by monopolies and ligopolies during the "opening-up" process of economic development. Likewise, both Lewis's (1954) dualist theory and Todaro's (1969; 1971) model of rural-urban migration attempt to explain the unemployment problem in terms of various factor price distortions. In an international context, Prebisch (1950; 1959) and Singer (1950) have again shown how prevailing differences in the structure of markets between developed and developing countries may turn the terms of trade against the latter; using a two-sector model, Bhagwati (1958) has demonstrated that such a deterioration in the terms of trade could bring about a net decrease in the welfare level of the countries concerned. Generally, the policy measures relevant to the "market imperfections" problem include the creation of job opportunities in the rural (rather than urban) sector, the encouragement of informal-sector enterprises,and the imposition of factor taxes and subsidies as a means of counteracting the adverse effect of factor price distortions on employment. A more recent approach to the unemployment problem is the plea by the International Labor Office (1970; 1972) for a redistribution of income within the developing countries. In terms of the two-sector model, such a policy may well succeed in eliminating labour unemployment caused by fixed factor proportions and/or factor price distortions. It should be realized, though, that a redistribution of income may lower the aggregate savings level, and hence also the growth rates of capital and labour employment in the economy. On the whole, it would seem that these theories do indeed adopt a modified version of the neoclassical theory in providing a fairly comprehensive explanation of the economic problems of labour unemployment, low incomes and inequality.
- Full Text:
- Date Issued: 1982
A multiscale remote sensing assessment of subtropical indigenous forests along the wild coast, South Africa
- Authors: Blessing, Sithole Vhusomuzi
- Date: 2015
- Subjects: Forests and forestry -- South Africa -- Remote sensing , Forest conservation , Remote sensing , Geographic information systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10677 , http://hdl.handle.net/10948/d1021169
- Description: The subtropical forests located along South Africa’s Wild Coast region, declared as one of the biodiversity hotspots, provide benefits to the local and national economy. However, there is evidence of increased pressure exerted on the forests by growing population and reduced income from activities not related to forest products. The ability of remote sensing to quantify subtropical forest changes over time, perform species discrimination (using field spectroscopy) and integrating field spectral and multispectral data were all assessed in this study. Investigations were conducted at pixel, leaf and sub-pixel levels. Both per-pixel and sub-pixel classification methods were used for improved forest characterisation. Using SPOT 6 imagery for 2013, the study determined the best classification algorithm for mapping sub-tropical forest and other land cover types to be the maximum likelihood classifier. Maximum likelihood outperformed minimum distance, spectral angle mapper and spectral information divergence algorithms, based on overall accuracy and Kappa coefficient values. Forest change analysis was made based on spectral measurements made at top of the atmosphere (TOC) level. When applied to the 2005 and 2009 SPOT 5 images, subtropical forest changes between 2005-2009 and 2009-2013 were quantified. A temporal analysis of forest cover trends in the periods 2005-2009 and 2009-2013 identified a decreasing trend of -3648.42 and -946.98 ha respectively, which translated to 7.81 percent and 2.20 percent decrease. Although there is evidence of a trend towards decreased rates of forest loss, more conservation efforts are required to protect the Wild Coast ecosystem. Using field spectral measurements data, the hierarchical method (comprising One-way ANOVA with Bonferroni correction, Classification and Regression Trees (CART) and Jeffries Matusita method) successfully selected optimal wavelengths for species discrimination at leaf level. Only 17 out of 2150 wavelengths were identified, thereby reducing the complexities related to data dimensionality. The optimal 17 wavelength bands were noted in the visible (438, 442, 512 and 695 nm), near infrared (724, 729, 750, 758, 856, 936, 1179, 1507 and 1673 nm) and mid-infrared (2220, 2465, 2469 and 2482 nm) portions of the electromagnetic spectrum. The Jeffries-Matusita (JM) distance method confirmed the separability of the selected wavelength bands. Using these 17 wavelengths, linear discriminant analysis (LDA) classified subtropical species at leaf level more accurately than partial least squares discriminant analysis (PLSDA) and random forest (RF). In addition, the study integrated field-collected canopy spectral and multispectral data to discriminate proportions of semi-deciduous and evergreen subtropical forests at sub-pixel level. By using the 2013 land cover (using MLC) to mask non-forested portions before sub-pixel classification (using MTMF), the proportional maps were a product of two classifiers. The proportional maps show higher proportions of evergreen forests along the coast while semi-deciduous subtropical forest species were mainly on inland parts of the Wild Coast. These maps had high accuracy, thereby proving the ability of an integration of field spectral and multispectral data in mapping semi-deciduous and evergreen forest species. Overall, the study has demonstrated the importance of the MLC and LDA and served to integrate field spectral and multispectral data in subtropical forest characterisation at both leaf and top-of-atmosphere levels. The success of both the MLC and LDA further highlighted how essential parametric classifiers are in remote sensing forestry applications. Main subtropical characteristics highlighted in this study were species discrimination at leaf level, quantifying forest change at pixel level and discriminating semi-deciduous and evergreen forests at sub-pixel level.
- Full Text:
- Date Issued: 2015
- Authors: Blessing, Sithole Vhusomuzi
- Date: 2015
- Subjects: Forests and forestry -- South Africa -- Remote sensing , Forest conservation , Remote sensing , Geographic information systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10677 , http://hdl.handle.net/10948/d1021169
- Description: The subtropical forests located along South Africa’s Wild Coast region, declared as one of the biodiversity hotspots, provide benefits to the local and national economy. However, there is evidence of increased pressure exerted on the forests by growing population and reduced income from activities not related to forest products. The ability of remote sensing to quantify subtropical forest changes over time, perform species discrimination (using field spectroscopy) and integrating field spectral and multispectral data were all assessed in this study. Investigations were conducted at pixel, leaf and sub-pixel levels. Both per-pixel and sub-pixel classification methods were used for improved forest characterisation. Using SPOT 6 imagery for 2013, the study determined the best classification algorithm for mapping sub-tropical forest and other land cover types to be the maximum likelihood classifier. Maximum likelihood outperformed minimum distance, spectral angle mapper and spectral information divergence algorithms, based on overall accuracy and Kappa coefficient values. Forest change analysis was made based on spectral measurements made at top of the atmosphere (TOC) level. When applied to the 2005 and 2009 SPOT 5 images, subtropical forest changes between 2005-2009 and 2009-2013 were quantified. A temporal analysis of forest cover trends in the periods 2005-2009 and 2009-2013 identified a decreasing trend of -3648.42 and -946.98 ha respectively, which translated to 7.81 percent and 2.20 percent decrease. Although there is evidence of a trend towards decreased rates of forest loss, more conservation efforts are required to protect the Wild Coast ecosystem. Using field spectral measurements data, the hierarchical method (comprising One-way ANOVA with Bonferroni correction, Classification and Regression Trees (CART) and Jeffries Matusita method) successfully selected optimal wavelengths for species discrimination at leaf level. Only 17 out of 2150 wavelengths were identified, thereby reducing the complexities related to data dimensionality. The optimal 17 wavelength bands were noted in the visible (438, 442, 512 and 695 nm), near infrared (724, 729, 750, 758, 856, 936, 1179, 1507 and 1673 nm) and mid-infrared (2220, 2465, 2469 and 2482 nm) portions of the electromagnetic spectrum. The Jeffries-Matusita (JM) distance method confirmed the separability of the selected wavelength bands. Using these 17 wavelengths, linear discriminant analysis (LDA) classified subtropical species at leaf level more accurately than partial least squares discriminant analysis (PLSDA) and random forest (RF). In addition, the study integrated field-collected canopy spectral and multispectral data to discriminate proportions of semi-deciduous and evergreen subtropical forests at sub-pixel level. By using the 2013 land cover (using MLC) to mask non-forested portions before sub-pixel classification (using MTMF), the proportional maps were a product of two classifiers. The proportional maps show higher proportions of evergreen forests along the coast while semi-deciduous subtropical forest species were mainly on inland parts of the Wild Coast. These maps had high accuracy, thereby proving the ability of an integration of field spectral and multispectral data in mapping semi-deciduous and evergreen forest species. Overall, the study has demonstrated the importance of the MLC and LDA and served to integrate field spectral and multispectral data in subtropical forest characterisation at both leaf and top-of-atmosphere levels. The success of both the MLC and LDA further highlighted how essential parametric classifiers are in remote sensing forestry applications. Main subtropical characteristics highlighted in this study were species discrimination at leaf level, quantifying forest change at pixel level and discriminating semi-deciduous and evergreen forests at sub-pixel level.
- Full Text:
- Date Issued: 2015
Audit of community pharmacy activities
- Authors: Blignault, Suzette Martha
- Date: 2010
- Subjects: Pharmacy , Community health services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10130 , http://hdl.handle.net/10948/1533 , Pharmacy , Community health services
- Description: In South Africa the pharmacy profession has experienced a number of changes around the turn of the century such as the introduction of the National Drug Policy (NDP), pharmacy ownership and price regulation. With this the role and earnings of the pharmacy profession, as well as to what extent the pharmacist adds value to the profession and society, are being questioned. Community pharmacists are thus faced with the challenge to prove that the value that they add to society is meaningful. Therefore, the aim of the study was to document community pharmacy availability and activities in South Africa and based on this to quantify the perceived value that the community pharmacist adds to society through the delivery of pharmaceutical services and pharmaceutical care. In order to determine the pharmacist’s true value added two surveys were conducted in 2006; an original pharmacist survey and a general public survey. The results obtained were verified by a follow–up pharmacist survey in 2009 to confirm or reject the results obtained in the original survey. The study was representative of both the community pharmacies and the general public in South Africa and was primarily quantitative in design and analysis. More than half of the responding pharmacies (63.16%) were open seven days a week. The average hours of service per day ranged from 10 hours (Monday to Friday) through to 6.45 hours on Saturdays and 3 hours on Sundays. Pharmacists continuously upgraded their professional knowledge. More than three quarters of pharmacies had the necessary equipment available to perform the services investigated in the study. The general public was not aware of all the services provided by pharmacists and as a result, depending on the service, many people did not make use of these services. The general public that made use of services delivered by community pharmacies mainly perceived the services delivered to be of good quality. The main barrier to practicing pharmaceutical care was indicated by pharmacists as not receiving payment for the advice given followed by pharmaceutical care being time consuming, and that there was not enough time to talk to patients. The general public indicated that they found it difficult to ask questions in pharmacies because other patients could hear what was discussed, or other patients had to wait longer if they asked something, and pharmacy staff being too busy. The results of the original pharmacist and the general public survey were confirmed by the results of the follow-up survey with the exception of dispensing prescription medicine (8 minutes 28 seconds), OTC medicine (7 minutes 23 seconds), counselling of prescription medicine (8 minutes 51 seconds) and OTC medicine (8 minutes) which on average took longer to conduct than in the previous analysis. The study highlighted the value added to the wellness and quality of life of the community of South Africa through the delivery of pharmaceutical care and pharmaceutical services by community pharmacy staff, and proved that pharmacists are committed to the provision of pharmaceutical care and pharmaceutical services.
- Full Text:
- Date Issued: 2010
- Authors: Blignault, Suzette Martha
- Date: 2010
- Subjects: Pharmacy , Community health services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10130 , http://hdl.handle.net/10948/1533 , Pharmacy , Community health services
- Description: In South Africa the pharmacy profession has experienced a number of changes around the turn of the century such as the introduction of the National Drug Policy (NDP), pharmacy ownership and price regulation. With this the role and earnings of the pharmacy profession, as well as to what extent the pharmacist adds value to the profession and society, are being questioned. Community pharmacists are thus faced with the challenge to prove that the value that they add to society is meaningful. Therefore, the aim of the study was to document community pharmacy availability and activities in South Africa and based on this to quantify the perceived value that the community pharmacist adds to society through the delivery of pharmaceutical services and pharmaceutical care. In order to determine the pharmacist’s true value added two surveys were conducted in 2006; an original pharmacist survey and a general public survey. The results obtained were verified by a follow–up pharmacist survey in 2009 to confirm or reject the results obtained in the original survey. The study was representative of both the community pharmacies and the general public in South Africa and was primarily quantitative in design and analysis. More than half of the responding pharmacies (63.16%) were open seven days a week. The average hours of service per day ranged from 10 hours (Monday to Friday) through to 6.45 hours on Saturdays and 3 hours on Sundays. Pharmacists continuously upgraded their professional knowledge. More than three quarters of pharmacies had the necessary equipment available to perform the services investigated in the study. The general public was not aware of all the services provided by pharmacists and as a result, depending on the service, many people did not make use of these services. The general public that made use of services delivered by community pharmacies mainly perceived the services delivered to be of good quality. The main barrier to practicing pharmaceutical care was indicated by pharmacists as not receiving payment for the advice given followed by pharmaceutical care being time consuming, and that there was not enough time to talk to patients. The general public indicated that they found it difficult to ask questions in pharmacies because other patients could hear what was discussed, or other patients had to wait longer if they asked something, and pharmacy staff being too busy. The results of the original pharmacist and the general public survey were confirmed by the results of the follow-up survey with the exception of dispensing prescription medicine (8 minutes 28 seconds), OTC medicine (7 minutes 23 seconds), counselling of prescription medicine (8 minutes 51 seconds) and OTC medicine (8 minutes) which on average took longer to conduct than in the previous analysis. The study highlighted the value added to the wellness and quality of life of the community of South Africa through the delivery of pharmaceutical care and pharmaceutical services by community pharmacy staff, and proved that pharmacists are committed to the provision of pharmaceutical care and pharmaceutical services.
- Full Text:
- Date Issued: 2010
Effect of cultivar on the quality of flax and hemp grown in South Africa
- Authors: Blouw, Langa Sunshine
- Date: 2012
- Subjects: Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9387 , http://hdl.handle.net/10948/d1010997 , Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Description: Bast fibrous renewable materials, as commercial crops for the manufacture of textile based and other products, have been used for thousands of years to satisfy certain human needs, such as for shelter, clothing, source of energy and tools, and to sustain the livelihood of many communities in countries, such as in Asia, Europe and Africa. Concern for the environment has led to a number of global initiatives that favour the use of natural fibres. It is forecast that the global fibre demand by 2050 will be 130 million tonnes, which the cotton and synthetic fibre production will not be able to meet. Other than the environmental concerns, the renewed global interest in natural fibres, such as flax and hemp, forms part of a strategy to satisfy the fibre demand. South Africa, notwithstanding the fact that the flax and hemp industries have long been established for thousands of years in Europe, Asia and Egypt (Africa), has no history of the breeding, growing, processing and production of these cash crops. The renewed global interest in these crops has also stimulated interest from South Africa with respect to the development of a flax and hemp fibre industry so as to address some of the socio-economic challenges confronting the country today in its attempts to bring about real development in the rural areas through the cultivation and complete beneficiation of these fibre crops. In this regard, the relevant stakeholders, namely government, research councils, tertiary education institutions, farmers and communities worked together to investigate whether South Africa has the agronomic and climatic conditions, technical expertise as well as the necessary processing and production infrastructure to support the development of a local flax and hemp agro-industry. The purpose of this study was firstly to evaluate the performance of EU flax and hemp cultivars grown under different agronomic conditions in South Africa, and their effect on straw biomass yield, fibre yield and total fibre yield per hectare as well as associated fibre properties, and secondly to undertake mechanical fibre modification trials aimed at producing flax and hemp fibres with fibre diameters close to those of cotton. The minimum fibre diameter targeted being 20μm. In accordance with the project objectives and work plan, selected dew retted flax and hemp straw samples from the various planting sites selected by the Agriculture Research Council – Institute for Industrial Crops, representing all the agronomic conditions under investigation, were taken to the CSIR for fibre extraction and testing. A relatively inexpensive and easy to operate Russian designed and manufactured machine, the CMT-200M breaker-cum-scutcher, was used for fibre extraction and the resultant extracted fibre bundles were further refined, using a steel comb, to obtain optimal fibre separation before their physical and chemical properties were evaluated. Results obtained in this research study proved that the climatic and agronomic conditions in South Africa were suitable for the cultivation of flax and hemp, notwithstanding the fact that the fibre yields achieved for hemp were lower than the minimum criteria of 23 percent, and that for flax only just exceeded the 25 percent minimum. The lack of local technical expertise on the growing and retting of flax and hemp, contributed to the low fibre yields. The planting parameters which were found to produce good results for the cultivation of hemp were the October planting date, using a row spacing of between 12.5 to 25 cm, with a seeding density of between 80 – 100kg, and the application of 50 – 100kg nitrogen fertiliser. The use of extra artificial lighting and herbicide treatment did not appear to beneficially improve the hemp fibre yields. Similar considerations for flax cultivation in the Southern Cape region, particularly Oudtshoorn and Outeniqua, indicated that May to July planting dates, using inter-row spacing of 25cm and sowing density of 63kg seed.haˉ¹, produced a fibre yield and total fibre yield per hectare above the minimum values of 25 percent and 0,8 tonnes per hectare, respectively, quoted in the literature.
- Full Text:
- Date Issued: 2012
- Authors: Blouw, Langa Sunshine
- Date: 2012
- Subjects: Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9387 , http://hdl.handle.net/10948/d1010997 , Hemp -- South Africa , Flaxseed -- South Africa , Plant varieties , Textile industry
- Description: Bast fibrous renewable materials, as commercial crops for the manufacture of textile based and other products, have been used for thousands of years to satisfy certain human needs, such as for shelter, clothing, source of energy and tools, and to sustain the livelihood of many communities in countries, such as in Asia, Europe and Africa. Concern for the environment has led to a number of global initiatives that favour the use of natural fibres. It is forecast that the global fibre demand by 2050 will be 130 million tonnes, which the cotton and synthetic fibre production will not be able to meet. Other than the environmental concerns, the renewed global interest in natural fibres, such as flax and hemp, forms part of a strategy to satisfy the fibre demand. South Africa, notwithstanding the fact that the flax and hemp industries have long been established for thousands of years in Europe, Asia and Egypt (Africa), has no history of the breeding, growing, processing and production of these cash crops. The renewed global interest in these crops has also stimulated interest from South Africa with respect to the development of a flax and hemp fibre industry so as to address some of the socio-economic challenges confronting the country today in its attempts to bring about real development in the rural areas through the cultivation and complete beneficiation of these fibre crops. In this regard, the relevant stakeholders, namely government, research councils, tertiary education institutions, farmers and communities worked together to investigate whether South Africa has the agronomic and climatic conditions, technical expertise as well as the necessary processing and production infrastructure to support the development of a local flax and hemp agro-industry. The purpose of this study was firstly to evaluate the performance of EU flax and hemp cultivars grown under different agronomic conditions in South Africa, and their effect on straw biomass yield, fibre yield and total fibre yield per hectare as well as associated fibre properties, and secondly to undertake mechanical fibre modification trials aimed at producing flax and hemp fibres with fibre diameters close to those of cotton. The minimum fibre diameter targeted being 20μm. In accordance with the project objectives and work plan, selected dew retted flax and hemp straw samples from the various planting sites selected by the Agriculture Research Council – Institute for Industrial Crops, representing all the agronomic conditions under investigation, were taken to the CSIR for fibre extraction and testing. A relatively inexpensive and easy to operate Russian designed and manufactured machine, the CMT-200M breaker-cum-scutcher, was used for fibre extraction and the resultant extracted fibre bundles were further refined, using a steel comb, to obtain optimal fibre separation before their physical and chemical properties were evaluated. Results obtained in this research study proved that the climatic and agronomic conditions in South Africa were suitable for the cultivation of flax and hemp, notwithstanding the fact that the fibre yields achieved for hemp were lower than the minimum criteria of 23 percent, and that for flax only just exceeded the 25 percent minimum. The lack of local technical expertise on the growing and retting of flax and hemp, contributed to the low fibre yields. The planting parameters which were found to produce good results for the cultivation of hemp were the October planting date, using a row spacing of between 12.5 to 25 cm, with a seeding density of between 80 – 100kg, and the application of 50 – 100kg nitrogen fertiliser. The use of extra artificial lighting and herbicide treatment did not appear to beneficially improve the hemp fibre yields. Similar considerations for flax cultivation in the Southern Cape region, particularly Oudtshoorn and Outeniqua, indicated that May to July planting dates, using inter-row spacing of 25cm and sowing density of 63kg seed.haˉ¹, produced a fibre yield and total fibre yield per hectare above the minimum values of 25 percent and 0,8 tonnes per hectare, respectively, quoted in the literature.
- Full Text:
- Date Issued: 2012
An analysis of how the Senior Certificate examination constructs the language needs of English second language learners
- Authors: Blunt, Sandra Viki
- Date: 2006 , 2013-06-11
- Subjects: Habermas, Jürgen Education, Secondary -- South Africa Examinations -- South Africa -- Evaluation English language -- Examinations -- South Africa English language -- Study and teaching -- South Africa -- Foreign speakers Language and education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1902 , http://hdl.handle.net/10962/d1006243
- Description: The Senior Certificate (SC) examination, a focus of the research described in this thesis, has an important function in terms of the quality of the education system overall and also in terms of the contribution of education to the achievement of national goals. The SC examination functions i) as a measure of achievement at school ii) as an indicator of work readiness and iii) as an indicator of the potential to succeed in higher education. This thesis offers a critique of the SC examination in respect of its functions. The way in which learners' language related needs are constructed is crucial in discussing the SC examination's legitimacy since perceptions about the needs of learners are reflected in what is taught and assessed. Since the majority of candidates writing the SC exarnination do so using a language which is not their mother tongue, the research described in the thesis attempted to identify the way in which the English second language (ESL) SC examination papers construct learners' needs. Examination papers represent a particular domain of social practice and are constructed through discourse. In the context of the research described in this thesis, discourses are understood as sets of ideas which are shared by communities of people and which give rise to practices which then define and sustain those communities and, thus, the discourses themselves. Discourse is language insofar as it converges with power and positions people in the interests of power. The ideological nature of discourse necessitates a critical orientation to research which interrogates, challenges and critiques the status quo. To identify the discourses constructing ESL learners' needs I conducted a critical discourse analysis on a representative sarnple of ESL SC exarnination papers and also interviewed six ESL examiners to corroborate the findings of the analysis. This then allowed me to identify several dominant discourses constructing ESL learners' needs: meaning-related, literature-related and process-related. The first meaning-related discourse, 'Received Tradition' discourse, focuses on the rules of grammar and spelling. Rather than approaching language as a resource to enable learners to understand the ideas to which they are exposed, learners are being taught discrete 'skills' to equip them for higher education study and the workplace. It is argued that school-based language literacy practices are not generalizable to the workplace and to higher education. Another aspect of 'Received Tradition' discourse holds that the study of English literature is a medium for understanding life and that there is moral value in teaching English literature. Learners are therefore constructed as lacking these values and their needs as having to acquire them. 'Received Tradition' discourse also overlaps with a second meaning-related discourse, 'Autonomous Text' discourse, which holds that the text's meaning is explicit and that if the learners can manipulate the rules of English grammar, 'have' vocabulary and can spell, they can retrieve meanings from texts they encounter in a wide range of contexts and construct texts for themselves. It is argued that a lack of awareness that meaning is constructed through recourse to other contexts, texts and the learner's experience is disadvantaging ESL candidates. 'Language as an Instrument of Communication' discourse, the last meaning-related discourse identified, sees language as the vehicle used to convey ideas, thoughts, information and beliefs, which are viewed as having been constructed independently of language. It is assumed that the answers, which, according to 'Autonomous Text' discourse, are in the text, can be conveyed if the tools of language are used correctly. The first literature-related discourse identified is 'Literature Study Develops Language Proficiency'. It is argued this is a misperception since language is learned as part of situated practice and instruction must thus be embedded in meaningful communicative contexts involving situated practice. The second literature-related discourse identified, 'Literature Study is a Medium for Understanding Life', is connected to the 'Received Tradition' discourse referred to above which holds that there is moral value in teaching English literature. This research identifies the ideological implications of these discourses, arguing that values are culture-specific and learners from diverse socio-cultural backgrounds experience life differently from the way it is depicted in English literature. Process-related discourses, which are part of the processes of teaching and assessment, concern the inadequacy of the ESL learner and of the markers and therefore dictate what can and cannot be expected of ESL learners in the SC examination. The research showed how all of the above discourses work through the SC curriculum to impose the values and beliefs of particular dominant groups on the ESL learner. Because of the robust and invidious nature of discourses this is a cause for concern. Although it is difficult to set a school leaving examination which serves both workplace and academic functions, there is a need to move beyond traditional, hegemonic approaches to understanding language learning. This thesis offers an analysis which can be used to inform practice.
- Full Text:
- Date Issued: 2006
- Authors: Blunt, Sandra Viki
- Date: 2006 , 2013-06-11
- Subjects: Habermas, Jürgen Education, Secondary -- South Africa Examinations -- South Africa -- Evaluation English language -- Examinations -- South Africa English language -- Study and teaching -- South Africa -- Foreign speakers Language and education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1902 , http://hdl.handle.net/10962/d1006243
- Description: The Senior Certificate (SC) examination, a focus of the research described in this thesis, has an important function in terms of the quality of the education system overall and also in terms of the contribution of education to the achievement of national goals. The SC examination functions i) as a measure of achievement at school ii) as an indicator of work readiness and iii) as an indicator of the potential to succeed in higher education. This thesis offers a critique of the SC examination in respect of its functions. The way in which learners' language related needs are constructed is crucial in discussing the SC examination's legitimacy since perceptions about the needs of learners are reflected in what is taught and assessed. Since the majority of candidates writing the SC exarnination do so using a language which is not their mother tongue, the research described in the thesis attempted to identify the way in which the English second language (ESL) SC examination papers construct learners' needs. Examination papers represent a particular domain of social practice and are constructed through discourse. In the context of the research described in this thesis, discourses are understood as sets of ideas which are shared by communities of people and which give rise to practices which then define and sustain those communities and, thus, the discourses themselves. Discourse is language insofar as it converges with power and positions people in the interests of power. The ideological nature of discourse necessitates a critical orientation to research which interrogates, challenges and critiques the status quo. To identify the discourses constructing ESL learners' needs I conducted a critical discourse analysis on a representative sarnple of ESL SC exarnination papers and also interviewed six ESL examiners to corroborate the findings of the analysis. This then allowed me to identify several dominant discourses constructing ESL learners' needs: meaning-related, literature-related and process-related. The first meaning-related discourse, 'Received Tradition' discourse, focuses on the rules of grammar and spelling. Rather than approaching language as a resource to enable learners to understand the ideas to which they are exposed, learners are being taught discrete 'skills' to equip them for higher education study and the workplace. It is argued that school-based language literacy practices are not generalizable to the workplace and to higher education. Another aspect of 'Received Tradition' discourse holds that the study of English literature is a medium for understanding life and that there is moral value in teaching English literature. Learners are therefore constructed as lacking these values and their needs as having to acquire them. 'Received Tradition' discourse also overlaps with a second meaning-related discourse, 'Autonomous Text' discourse, which holds that the text's meaning is explicit and that if the learners can manipulate the rules of English grammar, 'have' vocabulary and can spell, they can retrieve meanings from texts they encounter in a wide range of contexts and construct texts for themselves. It is argued that a lack of awareness that meaning is constructed through recourse to other contexts, texts and the learner's experience is disadvantaging ESL candidates. 'Language as an Instrument of Communication' discourse, the last meaning-related discourse identified, sees language as the vehicle used to convey ideas, thoughts, information and beliefs, which are viewed as having been constructed independently of language. It is assumed that the answers, which, according to 'Autonomous Text' discourse, are in the text, can be conveyed if the tools of language are used correctly. The first literature-related discourse identified is 'Literature Study Develops Language Proficiency'. It is argued this is a misperception since language is learned as part of situated practice and instruction must thus be embedded in meaningful communicative contexts involving situated practice. The second literature-related discourse identified, 'Literature Study is a Medium for Understanding Life', is connected to the 'Received Tradition' discourse referred to above which holds that there is moral value in teaching English literature. This research identifies the ideological implications of these discourses, arguing that values are culture-specific and learners from diverse socio-cultural backgrounds experience life differently from the way it is depicted in English literature. Process-related discourses, which are part of the processes of teaching and assessment, concern the inadequacy of the ESL learner and of the markers and therefore dictate what can and cannot be expected of ESL learners in the SC examination. The research showed how all of the above discourses work through the SC curriculum to impose the values and beliefs of particular dominant groups on the ESL learner. Because of the robust and invidious nature of discourses this is a cause for concern. Although it is difficult to set a school leaving examination which serves both workplace and academic functions, there is a need to move beyond traditional, hegemonic approaches to understanding language learning. This thesis offers an analysis which can be used to inform practice.
- Full Text:
- Date Issued: 2006
The border region : a geographical study of land utilization
- Authors: Board, Christopher
- Date: 1961
- Subjects: Land use -- South Africa -- Cape of Good Hope , Vegetation and climate -- South Africa -- Cape of Good Hope , Geology -- South Africa -- Cape of Good Hope , Cape of Good Hope (South Africa) -- Environmental conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4884 , http://hdl.handle.net/10962/d1013512
- Description: From Summary: This is a geographical study of land use in the Eastern Cape Province. The land use pattern, although related closely to the features of the natural environment, is perhaps even more closely related to the spatial variations of the man-made environment, particularly to the disposition of the different racial groups with their different cultures and economies, and to the kaleidoscopic character of the settlement pattern.
- Full Text:
- Date Issued: 1961
- Authors: Board, Christopher
- Date: 1961
- Subjects: Land use -- South Africa -- Cape of Good Hope , Vegetation and climate -- South Africa -- Cape of Good Hope , Geology -- South Africa -- Cape of Good Hope , Cape of Good Hope (South Africa) -- Environmental conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4884 , http://hdl.handle.net/10962/d1013512
- Description: From Summary: This is a geographical study of land use in the Eastern Cape Province. The land use pattern, although related closely to the features of the natural environment, is perhaps even more closely related to the spatial variations of the man-made environment, particularly to the disposition of the different racial groups with their different cultures and economies, and to the kaleidoscopic character of the settlement pattern.
- Full Text:
- Date Issued: 1961
Synthetic and spectroscopic studies of indolizine derivatives
- Authors: Bode, Moira Leanne
- Date: 1994
- Subjects: Indole alkaloids -- Derivatives Spectrum analysis Chemistry, Organic DNA -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4385 , http://hdl.handle.net/10962/d1005050
- Description: The crystalline compound resulting from thermal cyclization of the Baylis-Hillman product, methyl 3-hydroxy-2-methylene-3-(2-pyridyl)propanoate, has been identified as the indolizine derivative, methyl indolizine-2-carboxylate, and this approach involving the reaction of pyridine-2-carboxaldehydes and acrylate analogues has been established as a general route to 2-substituted indolizines. The ease of cyclization the Baylis-Hillman products to indolizines has been shown to increase by converting the hydroxy group to an acetoxy group, and a range of acetylated Baylis-Hillman products were prepared and cyc1ized to the corresponding 2-substituted indolizines, generally in good overall yield. In the reaction of pyridine-2-carboxaldehyde and methyl vinyl ketone, the intermediate cyclized readily and directly to the corresponding indolizine. One- and two-dimensional ¹H and ¹³C NMR analysis of the 2-substituted indolizine products has permitted complete assignment of all ¹H and ¹³C NMR signals, as well as the measurement of all coupling constants for these compounds. A kinetic and mechanistic study has been conducted on the Baylis-Hillman reaction using ¹H NMR spectroscopy. A range of substrates has been examined and the reaction has been found to be third-order overall. A mechanism involving an addition - elimination sequence is proposed, which fits the kinetic data and accounts for observed substituent effects. Reaction of N,N-dimethylacrylamide with pyridine-2-carboxaldehyde in the presence of the tertiary amine catalyst, DABCO, in chloroform, yielded an unexpected product which has been identified by single crystal X-ray diffraction analysis as 1-(2,2,2-trichloro-1-hydroxyethyl)pyridine. Attempted extension of the general indolizine route to the preparation of chromene systems by reacting salicylaldehyde with methyl acrylate in the presence of DABCO, also led to an unexpected, crystalline material, identified by single crystal X-ray diffraction analysis as the coumarin derivative, 3-[(2-formylphenoxy)methyl]coumarin.A series of chloroquine analogues have been prepared from indolizine-2-carboxylic acid, pyrrolo[I,2-a]quinoline-2-carboxylic acid and imidazo[I,2-a]pyridine-2-carboxylic acid by reaction with suitable amines in the presence of the coupling reagent 1, I' -carbonyldiimidazole. This route has been shown to be a vast improvement on earlier procedures and has provided access to both secondary and tertiary indolizine-2-carboxamides. A range of N,N-dialkylindolizine-2-carboxamides have been prepared by this route, and the influence of substituents on their N-CO rotational energy barriers has been determined using variable temperature ¹H and ¹³C NMR techniques. Intercalation with natural DNA by both chloroquine and the synthesized chloroquine analogues has been examined using UV spectrophotometry, and ¹H and ³¹P NMR spectroscopy. The pyrrolo[I,2-a]quinolines have been shown to be DNA intercalators with binding affinities similar to that of the known antimalarial intercalator, chloroquine. In a preliminary study the synthesis of a short oligonucleotide has been undertaken and changes have been observed in the ¹H and ³¹P NMR spectra of the oligonucleotide on addition of the intercalator, chloroquine.
- Full Text:
- Date Issued: 1994
- Authors: Bode, Moira Leanne
- Date: 1994
- Subjects: Indole alkaloids -- Derivatives Spectrum analysis Chemistry, Organic DNA -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4385 , http://hdl.handle.net/10962/d1005050
- Description: The crystalline compound resulting from thermal cyclization of the Baylis-Hillman product, methyl 3-hydroxy-2-methylene-3-(2-pyridyl)propanoate, has been identified as the indolizine derivative, methyl indolizine-2-carboxylate, and this approach involving the reaction of pyridine-2-carboxaldehydes and acrylate analogues has been established as a general route to 2-substituted indolizines. The ease of cyclization the Baylis-Hillman products to indolizines has been shown to increase by converting the hydroxy group to an acetoxy group, and a range of acetylated Baylis-Hillman products were prepared and cyc1ized to the corresponding 2-substituted indolizines, generally in good overall yield. In the reaction of pyridine-2-carboxaldehyde and methyl vinyl ketone, the intermediate cyclized readily and directly to the corresponding indolizine. One- and two-dimensional ¹H and ¹³C NMR analysis of the 2-substituted indolizine products has permitted complete assignment of all ¹H and ¹³C NMR signals, as well as the measurement of all coupling constants for these compounds. A kinetic and mechanistic study has been conducted on the Baylis-Hillman reaction using ¹H NMR spectroscopy. A range of substrates has been examined and the reaction has been found to be third-order overall. A mechanism involving an addition - elimination sequence is proposed, which fits the kinetic data and accounts for observed substituent effects. Reaction of N,N-dimethylacrylamide with pyridine-2-carboxaldehyde in the presence of the tertiary amine catalyst, DABCO, in chloroform, yielded an unexpected product which has been identified by single crystal X-ray diffraction analysis as 1-(2,2,2-trichloro-1-hydroxyethyl)pyridine. Attempted extension of the general indolizine route to the preparation of chromene systems by reacting salicylaldehyde with methyl acrylate in the presence of DABCO, also led to an unexpected, crystalline material, identified by single crystal X-ray diffraction analysis as the coumarin derivative, 3-[(2-formylphenoxy)methyl]coumarin.A series of chloroquine analogues have been prepared from indolizine-2-carboxylic acid, pyrrolo[I,2-a]quinoline-2-carboxylic acid and imidazo[I,2-a]pyridine-2-carboxylic acid by reaction with suitable amines in the presence of the coupling reagent 1, I' -carbonyldiimidazole. This route has been shown to be a vast improvement on earlier procedures and has provided access to both secondary and tertiary indolizine-2-carboxamides. A range of N,N-dialkylindolizine-2-carboxamides have been prepared by this route, and the influence of substituents on their N-CO rotational energy barriers has been determined using variable temperature ¹H and ¹³C NMR techniques. Intercalation with natural DNA by both chloroquine and the synthesized chloroquine analogues has been examined using UV spectrophotometry, and ¹H and ³¹P NMR spectroscopy. The pyrrolo[I,2-a]quinolines have been shown to be DNA intercalators with binding affinities similar to that of the known antimalarial intercalator, chloroquine. In a preliminary study the synthesis of a short oligonucleotide has been undertaken and changes have been observed in the ¹H and ³¹P NMR spectra of the oligonucleotide on addition of the intercalator, chloroquine.
- Full Text:
- Date Issued: 1994
Rural enterprise development as a means to poverty alleviation
- Authors: Bodley, David Cyril
- Date: 2020
- Subjects: Rural development -- South Africa , Economic development projects -- South Africa Poverty alleviation -- methods -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/50361 , vital:42118
- Description: South Africa’s disappointing economic performance over the last decade has resulted in a socio-economic crisis, with unemployment and inequality rates being of the highest rates anywhere in the world. Furthermore, unemployment is concentrated among the young, unskilled, and previously disadvantaged population posing a considerable threat to South Africa’s new democracy. Internationally, a method to absorb job seekers into the economy is to make small business the engine-room of economic growth and development. Consequently, the South African Government has identified in its National Development Plan the establishment of small businesses as a priority, including the development of small businesses in rural and marginalised communities. As rural communities in South Africa experience systemic problems such as the lack of infrastructure, financial capital, skills and potential markets, establishing enterprises in rural settings is often more complex than those more advanced parts of the economy elsewhere where fewer constraints exist. This makes the task of establishing and growing rural entities particularly challenging, suggesting bespoke policy and support is required. This study analyses the literature to gain an understanding of economic development theory and how this intersects with and informs small enterprise development policy. It then looks at South Africa’s strategy and policy framework pertaining to enterprise development. Specifically, the literature examines the role of rural enterprise development to establish whether this enables people to move out of poverty or further entraps people in poverty. The study collates data from a rural and marginalised community through observation and interview techniques. Firstly, multiple in-depth interviews were conducted with nineteen entrepreneurs in a rural community to collect data on business opportunities and explore the type of support entrepreneurs would require from government. Secondly, a focus group interview was conducted with entrepreneurs that had experienced institutional support to understand how well current policy and programmes support rural enterprise development. The primary data was analysed in conjunction with the literature on economic theory and enterprise development using the technique of triangulation to avoid logic leaps and formation of false assumptions. The insights and findings from the analysis reinforced certain facts within the body of knowledge pertaining to enterprise development, but there were also some interesting new insights that emanate from the data. South Africa has been able to introduce a wide range of policy initiatives and has multiple programmes and strategies to support small enterprise development. It has achieved firm success and impetus as well as experiencing certain failures. The study clearly highlights both and makes recommendations to improve policy promoting rural enterprise development as a means to alleviate poverty.
- Full Text:
- Date Issued: 2020
- Authors: Bodley, David Cyril
- Date: 2020
- Subjects: Rural development -- South Africa , Economic development projects -- South Africa Poverty alleviation -- methods -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/50361 , vital:42118
- Description: South Africa’s disappointing economic performance over the last decade has resulted in a socio-economic crisis, with unemployment and inequality rates being of the highest rates anywhere in the world. Furthermore, unemployment is concentrated among the young, unskilled, and previously disadvantaged population posing a considerable threat to South Africa’s new democracy. Internationally, a method to absorb job seekers into the economy is to make small business the engine-room of economic growth and development. Consequently, the South African Government has identified in its National Development Plan the establishment of small businesses as a priority, including the development of small businesses in rural and marginalised communities. As rural communities in South Africa experience systemic problems such as the lack of infrastructure, financial capital, skills and potential markets, establishing enterprises in rural settings is often more complex than those more advanced parts of the economy elsewhere where fewer constraints exist. This makes the task of establishing and growing rural entities particularly challenging, suggesting bespoke policy and support is required. This study analyses the literature to gain an understanding of economic development theory and how this intersects with and informs small enterprise development policy. It then looks at South Africa’s strategy and policy framework pertaining to enterprise development. Specifically, the literature examines the role of rural enterprise development to establish whether this enables people to move out of poverty or further entraps people in poverty. The study collates data from a rural and marginalised community through observation and interview techniques. Firstly, multiple in-depth interviews were conducted with nineteen entrepreneurs in a rural community to collect data on business opportunities and explore the type of support entrepreneurs would require from government. Secondly, a focus group interview was conducted with entrepreneurs that had experienced institutional support to understand how well current policy and programmes support rural enterprise development. The primary data was analysed in conjunction with the literature on economic theory and enterprise development using the technique of triangulation to avoid logic leaps and formation of false assumptions. The insights and findings from the analysis reinforced certain facts within the body of knowledge pertaining to enterprise development, but there were also some interesting new insights that emanate from the data. South Africa has been able to introduce a wide range of policy initiatives and has multiple programmes and strategies to support small enterprise development. It has achieved firm success and impetus as well as experiencing certain failures. The study clearly highlights both and makes recommendations to improve policy promoting rural enterprise development as a means to alleviate poverty.
- Full Text:
- Date Issued: 2020
Application of bacteriocins in the preservation of fruit juice
- Authors: Bodley, Mark David
- Date: 2015
- Subjects: Bacteriocins , Fruit juices -- Preservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10345 , http://hdl.handle.net/10948/d1020188
- Description: Bacteriocins (BCNs) are ribosomally synthesized polypeptides or proteins with antimicrobial activity, produced by different groups of bacteria. Many lactic acid bacteria (LAB) produce BCNs with broad spectra of inhibition. The antimicrobial activity of BCNs against spoilage organisms (SPOs) has raised considerable interest in their application in juice preservation. The objectives of the study were to: (i) isolate, identify and screen BCN producing bacteria for antimicrobial activity against spoilage bacteria and fungi, (ii) optimize production of BCN from selected producers and (iii) investigate the industrial application of the BCN as a preservative in fruit juice. Eleven LAB strains of BCN producers were screened for antimicrobial activity. BCNs from Lactobacillus plantarum and Pediococcus pentosaceus 34 were the most effective against juice spoilage bacteria and fungi. The effect of medium components on bacteriocin production in L. plantarum and P. pentosaceus 34 was also determined. Clementine:Valencia (1:1) juice was used for the first time as the growth medium for L. plantarum and P. pentosaceus 34. The BCN from L. plantarum showed the highest activity and was, therefore, chosen for juice fermentation studies. The identification of L. plantarum was confirmed by biochemical tests, polymerase chain reaction (PCR) and sequencing of the recA gene. The highest BCN activity was observed for L. plantarum grown in De Man-Rogosa-Sharpe (MRS) and a combination of all supplements (i.e. peptone, MnSO4.H2O, Tween 80, glucose and whey), followed by MRS and Tween 80, peptone, MnSO4.H2O and MRS alone. MRS was a better medium for BCN production than juice [Clementine:Valencia (1:1)]. Size exclusion chromatography (SEC) was used to isolate the active L. plantarum BCN fraction which corresponded to an approximate molecular weight of 3.2 kDa and was proteinaceous in nature. Plantaricin structural genes (plnEF, plnJ, plnK, plnN) were detected in the L. plantarum strain by PCR and sequenced, and were chromosomally encoded as no plasmids could be detected. This implies that the BCN from L. plantarum is most likely a type of class IIa plantaricin which is responsible for the broad inhibitory activity observed. For the industrial application studies, L. plantarum BCN-containing cell free supernatant (BCNsup) added to “Ready to Drink” (RTD) Clementine:Valencia (1:1) juice at concentrations of 3 600 - 500 000 ppm decreased growth of SPOs, Lactobacillus acidophilus and Streptococcus thermophilus. At 250 000 ppm, the L. plantarum BCNsup achieved 5.3 and 6.8 log reductions of the L. acidophilus, after 24 and 48 h, respectively, which is larger than the USFDA (2001) requirement of a 5 log reduction in SPO activity, for preservation of fruit juices. However, there was a decrease in the activity when the BCNsup was applied to industrial (Valor) RTD juice (mango-orange) at decreasing concentrations of 100 000, 50 000 and 25 000 ppm. Organoleptic tests showed that the BCN did not alter flavor or taste of the juice and did not cause toxicity or allergic reactions. A food safety risk assessment was conducted in order to determine the Critical Control Point(s) [CCP(s)] at which the BCN could be applied to control identified microbiological hazards, and a Hazard Analysis and Critical Control Point (HACCP) plan was developed. This is the first report on the optimisation of L. plantarum BCN production in juice [Clementine:Valencia (1:1)], followed by inoculation into RTD juice (mango-orange), including a HACCP plan for the application of the BCN as a preservative in juice.
- Full Text:
- Date Issued: 2015
- Authors: Bodley, Mark David
- Date: 2015
- Subjects: Bacteriocins , Fruit juices -- Preservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10345 , http://hdl.handle.net/10948/d1020188
- Description: Bacteriocins (BCNs) are ribosomally synthesized polypeptides or proteins with antimicrobial activity, produced by different groups of bacteria. Many lactic acid bacteria (LAB) produce BCNs with broad spectra of inhibition. The antimicrobial activity of BCNs against spoilage organisms (SPOs) has raised considerable interest in their application in juice preservation. The objectives of the study were to: (i) isolate, identify and screen BCN producing bacteria for antimicrobial activity against spoilage bacteria and fungi, (ii) optimize production of BCN from selected producers and (iii) investigate the industrial application of the BCN as a preservative in fruit juice. Eleven LAB strains of BCN producers were screened for antimicrobial activity. BCNs from Lactobacillus plantarum and Pediococcus pentosaceus 34 were the most effective against juice spoilage bacteria and fungi. The effect of medium components on bacteriocin production in L. plantarum and P. pentosaceus 34 was also determined. Clementine:Valencia (1:1) juice was used for the first time as the growth medium for L. plantarum and P. pentosaceus 34. The BCN from L. plantarum showed the highest activity and was, therefore, chosen for juice fermentation studies. The identification of L. plantarum was confirmed by biochemical tests, polymerase chain reaction (PCR) and sequencing of the recA gene. The highest BCN activity was observed for L. plantarum grown in De Man-Rogosa-Sharpe (MRS) and a combination of all supplements (i.e. peptone, MnSO4.H2O, Tween 80, glucose and whey), followed by MRS and Tween 80, peptone, MnSO4.H2O and MRS alone. MRS was a better medium for BCN production than juice [Clementine:Valencia (1:1)]. Size exclusion chromatography (SEC) was used to isolate the active L. plantarum BCN fraction which corresponded to an approximate molecular weight of 3.2 kDa and was proteinaceous in nature. Plantaricin structural genes (plnEF, plnJ, plnK, plnN) were detected in the L. plantarum strain by PCR and sequenced, and were chromosomally encoded as no plasmids could be detected. This implies that the BCN from L. plantarum is most likely a type of class IIa plantaricin which is responsible for the broad inhibitory activity observed. For the industrial application studies, L. plantarum BCN-containing cell free supernatant (BCNsup) added to “Ready to Drink” (RTD) Clementine:Valencia (1:1) juice at concentrations of 3 600 - 500 000 ppm decreased growth of SPOs, Lactobacillus acidophilus and Streptococcus thermophilus. At 250 000 ppm, the L. plantarum BCNsup achieved 5.3 and 6.8 log reductions of the L. acidophilus, after 24 and 48 h, respectively, which is larger than the USFDA (2001) requirement of a 5 log reduction in SPO activity, for preservation of fruit juices. However, there was a decrease in the activity when the BCNsup was applied to industrial (Valor) RTD juice (mango-orange) at decreasing concentrations of 100 000, 50 000 and 25 000 ppm. Organoleptic tests showed that the BCN did not alter flavor or taste of the juice and did not cause toxicity or allergic reactions. A food safety risk assessment was conducted in order to determine the Critical Control Point(s) [CCP(s)] at which the BCN could be applied to control identified microbiological hazards, and a Hazard Analysis and Critical Control Point (HACCP) plan was developed. This is the first report on the optimisation of L. plantarum BCN production in juice [Clementine:Valencia (1:1)], followed by inoculation into RTD juice (mango-orange), including a HACCP plan for the application of the BCN as a preservative in juice.
- Full Text:
- Date Issued: 2015
Optimization of flexible spectrum in optical transport networks
- Boiyo, Duncan Kiboi, Gamatham, Romeo
- Authors: Boiyo, Duncan Kiboi , Gamatham, Romeo
- Date: 2017
- Subjects: Digital communications Optical fiber communication , Optical communications Fiber optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14609 , vital:27803
- Description: The ever-increasing demand for broadband services by end-user devices utilising 3G/4G/LTE and the projected 5G in the last mile will require sustaining broadband supply from fibre-linked terminals. The eventual outcome of the high demand for broadband is strained optical and electronic devices. The backbone optical fibre transport systems and techniques such as dense wavelength division multiplexing (DWDM), higher modulation formats, coherent detection and signal amplification have increased both fibre capacity and spectrum efficiency. A major challenge to fibre capacity and spectrum efficiency is fibre-faults and optical impairments, network management, routing and wavelength assignment (RWA). In this study, DWDM and flexible spectrum techniques such as wavelength assignment and adjustment, wavelength conversion and switching, optical add and drop multiplexing (OADM) and bitrate variable transmission have been experimentally optimized in a laboratory testbed for short- and long-haul optical fibre networks. This work starts by experimentally optimising different transmitters, fibre-types and receivers suitable for implementing cost effective and energy efficient flexible spectrum networks. Vertical cavity surface-emitting lasers (VCSELs) and distributed feedback (DFB) lasers have been studied to provide up to 10 Gb/s per channel in 1310 nm and 1550 nm transmission windows. VCSELs provide wavelength assignment and adjustment. This work utilises the non-return-to-zero (NRZ) on-off keying (OOK) modulation technique and direct detection due to their cost and simplicity. By using positive intrinsic negative (PIN) photo-receivers with error-free BER sensitivity of -18±1 dBm at the acceptable 10-9-bit error rate (BER) threshold level, unamplified transmission distances between 6 km and 76 km have been demonstrated using G.652 and G.655 single mode fibres (SMFs). For the first time, an all optical VCSEL to VCSEL wavelength conversion, switching, transmission at the 1550 nm window and BER evaluation of a NRZ data signal is experimentally demonstrated. With VCSEL wavelength conversion and switching, wavelength adjustments to a spectrum width of 4.8 nm (600 GHz) can be achieved to provide alternative routes to signals when fibre-cuts and wavelength collision occurs therefore enhancing signal continuity. This work also demonstrates a technique of removing and adding a wavelength in a bundle of DWDM and flexible channels using an OADM. This has been implemented using a VCSEL and a fibre Bragg grating (FBG) providing a wavelength isolation ratio of 31.4 dB and ~0.3 𝑑𝐵 add/drop penalty of 8.5 Gb/s signal. As a result, an OADM improves spectrum efficiency by offering wavelength re-use. Optical impairments such as crosstalk, chromatic dispersion (CD) and effects of polarization mode dispersion (PMD) have been experimentally investigated and mitigated. This work showed that crosstalk penalty increased with fibre-length, bitrate, interfering signal power and reduced channel spacing and as a result, a crosstalk-penalty trade-off is required. Effects of CD on a transmitted 10 Gb/s signal were also investigated and its mitigation techniques used to increase the fibre-reach. This work uses the negative dispersion fibres to mitigate the accumulated dispersion over the distance of transmission. A 5 dB sensitivity improvement is reported for an unamplified 76 km using DFB transmitters and combination of NZDSF true-wave reduced slope (TW-RS) and submarine reduced slope (TW-SRS) with + and – dispersion coefficients respectively. We have also demonstrated up to 52 km 10 Gb/s per channel VCSEL-based transmission and reduced net dispersion. Experimental demonstration of forward Raman amplification has achieved a 4.7 dB on-off gain distributed over a 4.8 nm spectral width and a 1.7 dB improvement of receiver sensitivity in Raman-aided 10 Gb/s per wavelength VCSEL transmission. Finally, 4.25-10 Gb/s PON-based point to point (P2P) and point to multipoint (P2MP) broadcast transmission have been experimentally demonstrated. A 10 Gb/s with a 1:8 passive splitter incurred a 3.7 dB penalty for a 24.7 km fibre-link. In summary, this work has demonstrated cost effective and energy efficient potential flexible spectrum techniques for high speed signal transmission. With the optimized network parameters, flexible spectrum is therefore relevant in short-reach, metro-access and long-haul applications for national broadband networks and the Square Kilometre Array (SKA) fibre-based signal and data transmission.
- Full Text:
- Date Issued: 2017
- Authors: Boiyo, Duncan Kiboi , Gamatham, Romeo
- Date: 2017
- Subjects: Digital communications Optical fiber communication , Optical communications Fiber optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14609 , vital:27803
- Description: The ever-increasing demand for broadband services by end-user devices utilising 3G/4G/LTE and the projected 5G in the last mile will require sustaining broadband supply from fibre-linked terminals. The eventual outcome of the high demand for broadband is strained optical and electronic devices. The backbone optical fibre transport systems and techniques such as dense wavelength division multiplexing (DWDM), higher modulation formats, coherent detection and signal amplification have increased both fibre capacity and spectrum efficiency. A major challenge to fibre capacity and spectrum efficiency is fibre-faults and optical impairments, network management, routing and wavelength assignment (RWA). In this study, DWDM and flexible spectrum techniques such as wavelength assignment and adjustment, wavelength conversion and switching, optical add and drop multiplexing (OADM) and bitrate variable transmission have been experimentally optimized in a laboratory testbed for short- and long-haul optical fibre networks. This work starts by experimentally optimising different transmitters, fibre-types and receivers suitable for implementing cost effective and energy efficient flexible spectrum networks. Vertical cavity surface-emitting lasers (VCSELs) and distributed feedback (DFB) lasers have been studied to provide up to 10 Gb/s per channel in 1310 nm and 1550 nm transmission windows. VCSELs provide wavelength assignment and adjustment. This work utilises the non-return-to-zero (NRZ) on-off keying (OOK) modulation technique and direct detection due to their cost and simplicity. By using positive intrinsic negative (PIN) photo-receivers with error-free BER sensitivity of -18±1 dBm at the acceptable 10-9-bit error rate (BER) threshold level, unamplified transmission distances between 6 km and 76 km have been demonstrated using G.652 and G.655 single mode fibres (SMFs). For the first time, an all optical VCSEL to VCSEL wavelength conversion, switching, transmission at the 1550 nm window and BER evaluation of a NRZ data signal is experimentally demonstrated. With VCSEL wavelength conversion and switching, wavelength adjustments to a spectrum width of 4.8 nm (600 GHz) can be achieved to provide alternative routes to signals when fibre-cuts and wavelength collision occurs therefore enhancing signal continuity. This work also demonstrates a technique of removing and adding a wavelength in a bundle of DWDM and flexible channels using an OADM. This has been implemented using a VCSEL and a fibre Bragg grating (FBG) providing a wavelength isolation ratio of 31.4 dB and ~0.3 𝑑𝐵 add/drop penalty of 8.5 Gb/s signal. As a result, an OADM improves spectrum efficiency by offering wavelength re-use. Optical impairments such as crosstalk, chromatic dispersion (CD) and effects of polarization mode dispersion (PMD) have been experimentally investigated and mitigated. This work showed that crosstalk penalty increased with fibre-length, bitrate, interfering signal power and reduced channel spacing and as a result, a crosstalk-penalty trade-off is required. Effects of CD on a transmitted 10 Gb/s signal were also investigated and its mitigation techniques used to increase the fibre-reach. This work uses the negative dispersion fibres to mitigate the accumulated dispersion over the distance of transmission. A 5 dB sensitivity improvement is reported for an unamplified 76 km using DFB transmitters and combination of NZDSF true-wave reduced slope (TW-RS) and submarine reduced slope (TW-SRS) with + and – dispersion coefficients respectively. We have also demonstrated up to 52 km 10 Gb/s per channel VCSEL-based transmission and reduced net dispersion. Experimental demonstration of forward Raman amplification has achieved a 4.7 dB on-off gain distributed over a 4.8 nm spectral width and a 1.7 dB improvement of receiver sensitivity in Raman-aided 10 Gb/s per wavelength VCSEL transmission. Finally, 4.25-10 Gb/s PON-based point to point (P2P) and point to multipoint (P2MP) broadcast transmission have been experimentally demonstrated. A 10 Gb/s with a 1:8 passive splitter incurred a 3.7 dB penalty for a 24.7 km fibre-link. In summary, this work has demonstrated cost effective and energy efficient potential flexible spectrum techniques for high speed signal transmission. With the optimized network parameters, flexible spectrum is therefore relevant in short-reach, metro-access and long-haul applications for national broadband networks and the Square Kilometre Array (SKA) fibre-based signal and data transmission.
- Full Text:
- Date Issued: 2017
Seasonal changes in pituitary and plasma prolactin concentrations, and the role of Prolactin in the control of delayed implantation in female Miniopterus schreibersii
- Authors: Bojarski, Christina
- Date: 1993
- Subjects: Bats -- Reproduction Prolactin -- Research Pituitary hormones Zoology, Experimental
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5764 , http://hdl.handle.net/10962/d1005452
- Description: Mammotropes were successfully identified in the anterior pituitary gland of Miniopterus schreibersii using immunocytochemical (ICC) staining at the light and electron microscopy level. Mammotropes were distributed throughout the gland, were polygonal in shape and during secretory activity contained numerous large secretory granules (350 - 800nm). Using double ICC labelling, prolactin and growth hormone were never co-localiszed and found in individual cells only. Plasma prolactin levels were successfully measured on a monthly basis using radioimmunoassay and monthly pituitary prolactin levels were quantified using morphometric analysis of immunogold ICC staining and densitometry with polyacrylamide gels. Seasonal changes in the ultrastructure of mammotropes, and pituitary and plasma prolactin concentrations in female Miniopterus schreibersii indicated that there was an increase in prolactin secretion during the second half of the period of delayed implantation and that prolactin secretion remained elevated during normal embryonic development and lactation. This suggests that prolactin may be part of the luteotropic and lactogenic complex, and that the hormone might be responsible for terminating the period of delayed implantation. The latter is supported by experiments, where exogenous prolactin initiated precocious implantation during early delayed implantation, and treatment with bromocryptine (which inhibits prolactin synthesis) retarded implantation. Activation of mammotropes to synthesise prolactin and an increase of plasma prolactin levels occurred shortly after the winter solstice (21 June), suggesting that increasing daylength may be the environmental cue, which terminates the period of delayed implantation in Miniopterus schreibersii.
- Full Text:
- Date Issued: 1993
- Authors: Bojarski, Christina
- Date: 1993
- Subjects: Bats -- Reproduction Prolactin -- Research Pituitary hormones Zoology, Experimental
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5764 , http://hdl.handle.net/10962/d1005452
- Description: Mammotropes were successfully identified in the anterior pituitary gland of Miniopterus schreibersii using immunocytochemical (ICC) staining at the light and electron microscopy level. Mammotropes were distributed throughout the gland, were polygonal in shape and during secretory activity contained numerous large secretory granules (350 - 800nm). Using double ICC labelling, prolactin and growth hormone were never co-localiszed and found in individual cells only. Plasma prolactin levels were successfully measured on a monthly basis using radioimmunoassay and monthly pituitary prolactin levels were quantified using morphometric analysis of immunogold ICC staining and densitometry with polyacrylamide gels. Seasonal changes in the ultrastructure of mammotropes, and pituitary and plasma prolactin concentrations in female Miniopterus schreibersii indicated that there was an increase in prolactin secretion during the second half of the period of delayed implantation and that prolactin secretion remained elevated during normal embryonic development and lactation. This suggests that prolactin may be part of the luteotropic and lactogenic complex, and that the hormone might be responsible for terminating the period of delayed implantation. The latter is supported by experiments, where exogenous prolactin initiated precocious implantation during early delayed implantation, and treatment with bromocryptine (which inhibits prolactin synthesis) retarded implantation. Activation of mammotropes to synthesise prolactin and an increase of plasma prolactin levels occurred shortly after the winter solstice (21 June), suggesting that increasing daylength may be the environmental cue, which terminates the period of delayed implantation in Miniopterus schreibersii.
- Full Text:
- Date Issued: 1993
The demography, breeding biology and management of two mullet species (Pisces : Mugilidae) in the Eastern Cape, South Africa
- Authors: Bok, Anton
- Date: 1984
- Subjects: Fishes -- South Africa -- Eastern Cape Mullidae -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5213 , http://hdl.handle.net/10962/d1004931
- Description: Aspects of the life history of Myxus capensis which were likely to be most affected by man-induced habitat changes, were studied in the eastern Cape. Myxus capensis was found to be specialized for a catadromous life history. The fry migrate into freshwater reaches of rivers within a few months of being spawned at sea and return to an estuarine or marine environment when maximum size has been attained and large energy reserves necessary for spawning have been accumulated. Myxus capensis penetrates considerable distances up eastern Cape rivers and although present in the upper reaches of some estuaries, is only common in freshwater-dominated systems. Myxus capensis has adapted its life history style in a number of ways to overcome the constraints associated with the spatial separation of the freshwater feeding areas and the marine spawning grounds in a region prone to droughts and erratic river flow. Research on the more estuarine-dependent Mugil cephalus, which is also found in the freshwater reaches of eastern Cape rivers, enabled useful comparisons to be drawn. As the latter species is not dependent on a freshwater phase in its life cycle, it is subject to different selection pressures. This comparative approach gave insights into the adaptive significance of the life history tactics of Myxus capensis. Myxus capensis displays a number of life history tactics characteristic of migratory fish species which are thought to increase population fecundity by increasing the number of large females and hence maximizing egg production. These include a sex ratio in favour of females, faster female growth, females remaining longer in the freshwater feeding areas and reaching a larger ultimate size. Possible adaptations to the periodic isolation of the feeding and spawning areas include: (i) the development of ripe gonads only in estuarine or marine areas when access to the spawning grounds is ensured; (ii) year-round spawning and hence recruitment which enables the erratic floods to be used at any time for downriver spawning migrations and reduces the chances of total recruitment failure due to short-term adverse environmental conditions and (iii) a relatively wide range of size and age at first (and final) sexual maturity (2+ to 5+ years); this tends to ensure successful reproduction and recruitment in spite of a series of poor years, as well as dampen population fluctuations after long periods of isolation in fresh water. The dependence of Myxus capensis on the freshwater reaches of eastern Cape rivers makes this species vulnerable to man-induced habitat changes. The erection of barriers to migration has cut off large stretches of suitable habitat and almost completely eliminated Myxus capensis from certain rivers. This detrimental effect has been largely responsible for the recent inclusion of this species on the Red Data list of endangered fish species in South Africa. This study demonstrated the considerable fisheries potential of both mullet species and this should ensure that their conservation and wise utilization be given high priority. Management proposals include: (i) the netting and lifting of Myxus capensis over barriers to migration; (ii) the construction of fish ladders when feasible and (iii) the artificial propagation of this species to enable large-scale stockings of existing man-made impoundments as well as natural habitats to be carried out. It is predicted that the life history characteristics of Myxus capensis, which evolved in response to an erratic freshwater environment, should ensure that when man-induced habitat changes are rectified, this species will again flourish in eastern Cape rivers.
- Full Text:
- Date Issued: 1984
- Authors: Bok, Anton
- Date: 1984
- Subjects: Fishes -- South Africa -- Eastern Cape Mullidae -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5213 , http://hdl.handle.net/10962/d1004931
- Description: Aspects of the life history of Myxus capensis which were likely to be most affected by man-induced habitat changes, were studied in the eastern Cape. Myxus capensis was found to be specialized for a catadromous life history. The fry migrate into freshwater reaches of rivers within a few months of being spawned at sea and return to an estuarine or marine environment when maximum size has been attained and large energy reserves necessary for spawning have been accumulated. Myxus capensis penetrates considerable distances up eastern Cape rivers and although present in the upper reaches of some estuaries, is only common in freshwater-dominated systems. Myxus capensis has adapted its life history style in a number of ways to overcome the constraints associated with the spatial separation of the freshwater feeding areas and the marine spawning grounds in a region prone to droughts and erratic river flow. Research on the more estuarine-dependent Mugil cephalus, which is also found in the freshwater reaches of eastern Cape rivers, enabled useful comparisons to be drawn. As the latter species is not dependent on a freshwater phase in its life cycle, it is subject to different selection pressures. This comparative approach gave insights into the adaptive significance of the life history tactics of Myxus capensis. Myxus capensis displays a number of life history tactics characteristic of migratory fish species which are thought to increase population fecundity by increasing the number of large females and hence maximizing egg production. These include a sex ratio in favour of females, faster female growth, females remaining longer in the freshwater feeding areas and reaching a larger ultimate size. Possible adaptations to the periodic isolation of the feeding and spawning areas include: (i) the development of ripe gonads only in estuarine or marine areas when access to the spawning grounds is ensured; (ii) year-round spawning and hence recruitment which enables the erratic floods to be used at any time for downriver spawning migrations and reduces the chances of total recruitment failure due to short-term adverse environmental conditions and (iii) a relatively wide range of size and age at first (and final) sexual maturity (2+ to 5+ years); this tends to ensure successful reproduction and recruitment in spite of a series of poor years, as well as dampen population fluctuations after long periods of isolation in fresh water. The dependence of Myxus capensis on the freshwater reaches of eastern Cape rivers makes this species vulnerable to man-induced habitat changes. The erection of barriers to migration has cut off large stretches of suitable habitat and almost completely eliminated Myxus capensis from certain rivers. This detrimental effect has been largely responsible for the recent inclusion of this species on the Red Data list of endangered fish species in South Africa. This study demonstrated the considerable fisheries potential of both mullet species and this should ensure that their conservation and wise utilization be given high priority. Management proposals include: (i) the netting and lifting of Myxus capensis over barriers to migration; (ii) the construction of fish ladders when feasible and (iii) the artificial propagation of this species to enable large-scale stockings of existing man-made impoundments as well as natural habitats to be carried out. It is predicted that the life history characteristics of Myxus capensis, which evolved in response to an erratic freshwater environment, should ensure that when man-induced habitat changes are rectified, this species will again flourish in eastern Cape rivers.
- Full Text:
- Date Issued: 1984
A contribution to the benthic biology of some southern African lakes
- Authors: Boltt, R E
- Date: 1969
- Subjects: Aquatic biology -- Africa, Southern Benthos -- Africa, Southern Lake animals -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5836 , http://hdl.handle.net/10962/d1009521
- Description: The benthos of Lake Sibayi, Lake Nhlange, Lake Shengesa and Lake Sifungwe has been sampled by means of a van Veen grab of bite area 0.225m². Except for Lake Shengesa, the substrates of the lakes have been investigated visually by SCUBA divers. Some quantitative sampling, using underwater techniques, has been carried out in Lake Sibayi. In general, the substrate of the lakes consisted of two types, either fine sand with an average particle size of 3.2 phi, or mud with a median phi value of less than 6. The sandy substrata was usually rich in fauna, and the mud usually poor. Lake Sibayi , which is freshwater (135 ppm Cl¯) has estuarine and freshwater species in the benthos. Some of the species, notably Grandidierella lignorum and Apseudes digitalis, show an uneven pattern of distribution with respect to depth. Lake Nhlange is a brackwater lake (3.4‰ salinity) and has mainly an estuarine fauna. Many of the species are different from those found in Lake Sibayi. There is some evidence that the benthic fauna of the lake has increased its range in depth in the years following a flood in January 1966. Only chironomid larvae were found in the benthos of Lake Shengesa. The greater part of the substrate of this lake consisted of a highly organic mud mainly derived from burnt grassland around the periphery of the lake. Lake Sifungwe, which is connected to Lake Nhlange, has a halocline at about 9 metres. The fauna of the benthos has more species than lake Nhlange. There is some evidence to suggest that LGC fauna invades deeper water in summer, and is driven into shallower water in winter because of the fluctuating level of anaerobic conditions below the discontinuity layer. The benthic fauna of the lakes has been compared with that of the estuaries reported on by the Cape Town Ecological Survey. experimental studies on G. lignorum, a species present in Lake Sibayi, suggested that the physiological responses of material from an estuary normally at 35‰ salinity (Kowie River estuary) and from lakes which are normally of low salinity (Groenvlei 2.5‰ salinity, Lake Sibayi) were not different. Studies on substrate choice, and pressure, indicated that these factors do not affect the distribution pattern of G. lignorum in the substrate. Studies on light orientation responses and the effects of rates of carbon dioxide increase of about 20 mm HgC0₂/hr or more, suggest that these may be the principle factors affecting the distribution of G. lignorum in the benthos of Lake Sibayi. Some supporting evidence for the presence of changing pC0₂ has been found. A discussion of the importance of dynamic events at the substrate/water interface is given.
- Full Text:
- Date Issued: 1969
- Authors: Boltt, R E
- Date: 1969
- Subjects: Aquatic biology -- Africa, Southern Benthos -- Africa, Southern Lake animals -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5836 , http://hdl.handle.net/10962/d1009521
- Description: The benthos of Lake Sibayi, Lake Nhlange, Lake Shengesa and Lake Sifungwe has been sampled by means of a van Veen grab of bite area 0.225m². Except for Lake Shengesa, the substrates of the lakes have been investigated visually by SCUBA divers. Some quantitative sampling, using underwater techniques, has been carried out in Lake Sibayi. In general, the substrate of the lakes consisted of two types, either fine sand with an average particle size of 3.2 phi, or mud with a median phi value of less than 6. The sandy substrata was usually rich in fauna, and the mud usually poor. Lake Sibayi , which is freshwater (135 ppm Cl¯) has estuarine and freshwater species in the benthos. Some of the species, notably Grandidierella lignorum and Apseudes digitalis, show an uneven pattern of distribution with respect to depth. Lake Nhlange is a brackwater lake (3.4‰ salinity) and has mainly an estuarine fauna. Many of the species are different from those found in Lake Sibayi. There is some evidence that the benthic fauna of the lake has increased its range in depth in the years following a flood in January 1966. Only chironomid larvae were found in the benthos of Lake Shengesa. The greater part of the substrate of this lake consisted of a highly organic mud mainly derived from burnt grassland around the periphery of the lake. Lake Sifungwe, which is connected to Lake Nhlange, has a halocline at about 9 metres. The fauna of the benthos has more species than lake Nhlange. There is some evidence to suggest that LGC fauna invades deeper water in summer, and is driven into shallower water in winter because of the fluctuating level of anaerobic conditions below the discontinuity layer. The benthic fauna of the lakes has been compared with that of the estuaries reported on by the Cape Town Ecological Survey. experimental studies on G. lignorum, a species present in Lake Sibayi, suggested that the physiological responses of material from an estuary normally at 35‰ salinity (Kowie River estuary) and from lakes which are normally of low salinity (Groenvlei 2.5‰ salinity, Lake Sibayi) were not different. Studies on substrate choice, and pressure, indicated that these factors do not affect the distribution pattern of G. lignorum in the substrate. Studies on light orientation responses and the effects of rates of carbon dioxide increase of about 20 mm HgC0₂/hr or more, suggest that these may be the principle factors affecting the distribution of G. lignorum in the benthos of Lake Sibayi. Some supporting evidence for the presence of changing pC0₂ has been found. A discussion of the importance of dynamic events at the substrate/water interface is given.
- Full Text:
- Date Issued: 1969
Statistical Analysis of the Radio-Interferometric Measurement Equation, a derived adaptive weighting scheme, and applications to LOFAR-VLBI observation of the Extended Groth Strip
- Authors: Bonnassieux, Etienne
- Date: 2019
- Subjects: Radio astronomy , Astrophysics , Astrophysics -- Instruments -- Calibration , Imaging systems in astronomy , Radio interferometers , Radio telescopes , Astronomy -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93789 , vital:30942
- Description: J.R.R Tolkien wrote, in his Mythopoeia, that “He sees no stars who does not see them first, of living silver made that sudden burst, to flame like flowers beneath the ancient song”. In his defense of myth-making, he formulates the argument that the attribution of meaning is an act of creation - that “trees are not ‘trees’ until so named and seen” - and that this capacity for creation defines the human creature. The scientific endeavour, in this context, can be understood as a social expression of a fundamental feature of humanity, and from this endeavour flows much understanding. This thesis, one thread among many, focuses on the study of astronomical objects as seen by the radio waves they emit. What are radio waves? Electromagnetic waves were theorised by James Clerk Maxwell (Maxwell 1864) in his great theoretical contribution to modern physics, their speed matching the speed of light as measured by Ole Christensen R0mer and, later, James Bradley. It was not until Heinrich Rudolf Hertz’s 1887 experiment that these waves were measured in a laboratory, leading to the dawn of radio communications - and, later, radio astronomy. The link between radio waves and light was one of association: light is known to behave as a wave (Young double-slit experiment), with the same propagation speed as electromagnetic radiation. Light “proper” is also known to exist beyond the optical regime: Herschel’s experiment shows that when diffracted through a prism, sunlight warms even those parts of a desk which are not observed to be lit (first evidence of infrared light). The link between optical light and unseen electromagnetic radiation is then an easy step to make, and one confirmed through countless technological applications (e.g. optical fiber to name but one). And as soon as this link is established, a question immediately comes to the mind of the astronomer: what does the sky, our Universe, look like to the radio “eye”? Radio astronomy has a short but storied history: from Karl Jansky’s serendipitous observation of the centre of the Milky Way, which outshines our Sun in the radio regime, in 1933, to Grote Reber’s hand-built back-yard radio antenna in 1937, which successfully detected radio emission from the Milky Way itself, to such monumental projects as the Square Kilometer Array and its multiple pathfinders, it has led to countless discoveries and the opening of a truly new window on the Universe. The work presented in this thesis is a contribution to this discipline - the culmination of three years of study, which is a rather short time to get a firm grasp of radio interferometry both in theory and in practice. The need for robust, automated methods - which are improving daily, thanks to the tireless labour of the scientists in the field - is becoming ever stronger as the SKA approaches, looming large on the horizon; but even today, in the precursor era of LOFAR, MeerKAT and other pathfinders, it is keenly felt. When I started my doctorate, the sheer scale of the task at hand felt overwhelming - to actually be able to contribute to its resolution seemed daunting indeed! Thankfully, as the saying goes, no society sets for itself material goals which it cannot achieve. This thesis took place at an exciting time for radio interferometry: at the start of my doctorate, the LOFAR international stations were - to my knowledge - only beginning to be used, and even then, only tentatively; MeerKAT had not yet shown its first light; the techniques used throughout my work were still being developed. At the time of writing, great strides have been made. One of the greatest technical challenges of LOFAR - imaging using the international stations - is starting to become reality. This technical challenge is the key problem that this thesis set out to address. While we only achieved partial success so far, it is a testament to the difficulty of the task that it is not yet truly resolved. One of the major results of this thesis is a model of a bright resolved source near a famous extragalactic field: properly modeling this source not only allows the use of international LOFAR stations, but also grants deeper access to the extragalactic field itself, which is otherwise polluted by the 3C source’s sidelobes. This result was only achieved thanks to the other major result of this thesis: the development of a theoretical framework with which to better understand the effect of calibration errors on images made from interferometric data, and an algorithm to strongly mitigate them. The structure of this manuscript is as follows: we begin with an introduction to radio interferometry, LOFAR, and the emission mechanisms which dominate for our field of interest. These introductions are primarily intended to give a brief overview of the technical aspects of the data reduced in this thesis. We follow with an overview of the Measurement Equation formalism, which underpins our theoretical work. This is the keystone of this thesis. We then show the theoretical work that was developed as part of the research work done during the doctorate - which was published in Astronomy & Astrophysics. Its practical application - a quality-based weighting scheme - is used throughout our data reduction. This data reduction is the next topic of this thesis: we contextualise the scientific interest of the data we reduce, and explain both the methods and the results we achieve.
- Full Text:
- Date Issued: 2019
- Authors: Bonnassieux, Etienne
- Date: 2019
- Subjects: Radio astronomy , Astrophysics , Astrophysics -- Instruments -- Calibration , Imaging systems in astronomy , Radio interferometers , Radio telescopes , Astronomy -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/93789 , vital:30942
- Description: J.R.R Tolkien wrote, in his Mythopoeia, that “He sees no stars who does not see them first, of living silver made that sudden burst, to flame like flowers beneath the ancient song”. In his defense of myth-making, he formulates the argument that the attribution of meaning is an act of creation - that “trees are not ‘trees’ until so named and seen” - and that this capacity for creation defines the human creature. The scientific endeavour, in this context, can be understood as a social expression of a fundamental feature of humanity, and from this endeavour flows much understanding. This thesis, one thread among many, focuses on the study of astronomical objects as seen by the radio waves they emit. What are radio waves? Electromagnetic waves were theorised by James Clerk Maxwell (Maxwell 1864) in his great theoretical contribution to modern physics, their speed matching the speed of light as measured by Ole Christensen R0mer and, later, James Bradley. It was not until Heinrich Rudolf Hertz’s 1887 experiment that these waves were measured in a laboratory, leading to the dawn of radio communications - and, later, radio astronomy. The link between radio waves and light was one of association: light is known to behave as a wave (Young double-slit experiment), with the same propagation speed as electromagnetic radiation. Light “proper” is also known to exist beyond the optical regime: Herschel’s experiment shows that when diffracted through a prism, sunlight warms even those parts of a desk which are not observed to be lit (first evidence of infrared light). The link between optical light and unseen electromagnetic radiation is then an easy step to make, and one confirmed through countless technological applications (e.g. optical fiber to name but one). And as soon as this link is established, a question immediately comes to the mind of the astronomer: what does the sky, our Universe, look like to the radio “eye”? Radio astronomy has a short but storied history: from Karl Jansky’s serendipitous observation of the centre of the Milky Way, which outshines our Sun in the radio regime, in 1933, to Grote Reber’s hand-built back-yard radio antenna in 1937, which successfully detected radio emission from the Milky Way itself, to such monumental projects as the Square Kilometer Array and its multiple pathfinders, it has led to countless discoveries and the opening of a truly new window on the Universe. The work presented in this thesis is a contribution to this discipline - the culmination of three years of study, which is a rather short time to get a firm grasp of radio interferometry both in theory and in practice. The need for robust, automated methods - which are improving daily, thanks to the tireless labour of the scientists in the field - is becoming ever stronger as the SKA approaches, looming large on the horizon; but even today, in the precursor era of LOFAR, MeerKAT and other pathfinders, it is keenly felt. When I started my doctorate, the sheer scale of the task at hand felt overwhelming - to actually be able to contribute to its resolution seemed daunting indeed! Thankfully, as the saying goes, no society sets for itself material goals which it cannot achieve. This thesis took place at an exciting time for radio interferometry: at the start of my doctorate, the LOFAR international stations were - to my knowledge - only beginning to be used, and even then, only tentatively; MeerKAT had not yet shown its first light; the techniques used throughout my work were still being developed. At the time of writing, great strides have been made. One of the greatest technical challenges of LOFAR - imaging using the international stations - is starting to become reality. This technical challenge is the key problem that this thesis set out to address. While we only achieved partial success so far, it is a testament to the difficulty of the task that it is not yet truly resolved. One of the major results of this thesis is a model of a bright resolved source near a famous extragalactic field: properly modeling this source not only allows the use of international LOFAR stations, but also grants deeper access to the extragalactic field itself, which is otherwise polluted by the 3C source’s sidelobes. This result was only achieved thanks to the other major result of this thesis: the development of a theoretical framework with which to better understand the effect of calibration errors on images made from interferometric data, and an algorithm to strongly mitigate them. The structure of this manuscript is as follows: we begin with an introduction to radio interferometry, LOFAR, and the emission mechanisms which dominate for our field of interest. These introductions are primarily intended to give a brief overview of the technical aspects of the data reduced in this thesis. We follow with an overview of the Measurement Equation formalism, which underpins our theoretical work. This is the keystone of this thesis. We then show the theoretical work that was developed as part of the research work done during the doctorate - which was published in Astronomy & Astrophysics. Its practical application - a quality-based weighting scheme - is used throughout our data reduction. This data reduction is the next topic of this thesis: we contextualise the scientific interest of the data we reduce, and explain both the methods and the results we achieve.
- Full Text:
- Date Issued: 2019
Biology, stock assessment and management of the panga Pterogymnus laniarius on the Agulhas Bank, South Africa
- Authors: Booth, Anthony John
- Date: 1998
- Subjects: Fish stock assessment -- South Africa Bycatches (Fisheries) -- South Africa Pterogymnus laniarius Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5242 , http://hdl.handle.net/10962/d1005085
- Description: The panga, Pterogymnus laniarius (Cuvier, 1830), is a South African endemic sparid fish species. On the Agulhas Bank, South Africa it is a commercially important species, caught as bycatch in the hake directed trawlfisheries and targeted by offshore hook-and-linefishers. Recently there has been considerable interest shown in directing further fishing effort on this species. The lack of a suitable management procedure for teleost bycatch in South Africa was the principal reason for undertaking this study. This thesis investigates aspects the panga's life history, particularly those aspects that have management implications. A full knowledge of this species' distribution and abundance was necessary as this could highlight the existence of any nursery areas, ontogenetic migratory patterns and areas of high spawner biomass. The derived parameter estimates were then included as inputs into stock assessment models to determine the status and productivity of the resource. Growth studies based on sectioned sagittal otoliths revealed that the panga was a relatively slow growing fish with ages of 16 years being recorded. Growth was best described by the von Bertalanffy growth model as Lt=379.4(1-e⁻°·¹³⁽t ⁺ ¹·⁷⁸⁾). Total, natural and fishing mortalities were estimated at 0.36 year⁻¹, 0.28 year⁻¹ and 0.08 year ⁻¹, respectively. Detailed histological examination of the gonads revealed that panga is a late gonochorist, males and females maturing after a non-functional intersexual stage. Females mature at approximately 200 mm fork length or 4 years of age. Reproduction occurs throughout the year although there is a slight peak in winter. Gametogenesis was found to be similar to that of other sparid fishes and marine teleosts in general. The panga feeds predominantly on crustaceans with a distinct ontogenetic shift in feeding habits. Juvenile fish feed predominantly in the water column on mysids after which they move to the benthos. Subadult fish feed principally on ophiuroids and amphipods. Adult fish remain on or near the benthos, feeding predominantly on crabs, and on polychaetes, ophiuroids and fishes to a lesser extent. Several aspects of the panga's biology contribute to its ability to sustain a higher fishing pressure than other sympatric sparid species. These include its late gonochoristic reproductive style, protracted spawning season, maturation before recruitment and preference for soft substratum prey that enables it to utilise large areas of the Agulhas Bank. The panga's longevity, slow growth and low natural mortality rate, however, mitigated against these factors and were considered in the stock assessments. A heterogeneous Geographical Information System (GIS) was developed to analyse the distribution and abundance patterns of the panga. The GIS developed in this thesis makes a significant contribution towards the development of a South African Fisheries Information System to analyse and manage fish resources in general and bycatch resources in particular. The GIS developed in this study combines statistical Generalized Additive Modelling and standard GIS methods. Analysis of fourteen biannual fishery independent biomass surveys, disaggregated by life history stage, revealed that a nursery area for immature fish (<23 cm TL or < 4 years of age) exists on the Central Agulhas Bank. After sexual maturation, approximately 40% of the biomass migrated eastwards, colonising large areas of the Eastern Agulhas Bank.ilie location of the nursery area appears to be a result of the pelagic eggs and larvae being advected towards the coast in an anti-cyclonic gyre, stemming off the Agulhas current and later deposited over the Central Agulhas Bank. The weak bottom currents on the Central Agulhas Bank prevented juvenile loss to the Benguela system. The eurytopy of adult fish to various physical variables such as temperature, dissolved oxygen and stronger currents enabled it to reduce conspecific competition and migrate eastwards with distribution primarily determined by depth. Relative biomass estimates revealed a gradual increase in biomass of 5.5% per annum between 1988 and 1995. Predictions from yield-per-recruit, biomass-per-recruit and spawner biomass-per-recruit analyses showed that there was scope for further exploitation. A FSB₅₀ fishing strategy was considered to be the most appropriate fishing strategy as it did not reduce the spawner biomass-per-recruit to less than 50% of unexploited levels. Effort control was considered the most effective management tool as the age-at-50%-selectivity occurred after age-at-sexual maturity and releasing undersized fish was undesirable due to heavy mortalities resulting from severe barotrauma. The panga resource was also assessed using an age-structured production model. The values for the free parameters of the model were estimated using biomass indices derived from fishery-independent trawl surveys. Although the data were fairly uninformative about the productivity of the resource, the results indicated robustly, that the population has recovered from low levels in the mid-1970's and could sustain higher levels of fishing intensity. Risk analysis calculations were used to assess the sustainability of different catch scenarios. The level of sustainable catch was found to be sensitive to the selectivity pattern of the gear utilised. Both stock assessment methods used in this study to investigate the status of the panga resource showed that the resource could theoretically sustain higher catches. It was found that although the stock could be harvested using available fishing methods, the sympatry of this species with other commercial species was of concern as the latter would form a significant bycatch in a panga directed fishery. The failure of current harvesting methods to address the bycatch problem highlights the management problem in South Africa and stresses the need for creativity by both scientists and fishers in designing new and improved methods for selectively harvesting bycatch fish resources. Considering that no suitable method is currently available to fish the panga stock in a directed fishery the fishery should be managed as status quo until some suitable and efficient gear is developed.
- Full Text:
- Date Issued: 1998
- Authors: Booth, Anthony John
- Date: 1998
- Subjects: Fish stock assessment -- South Africa Bycatches (Fisheries) -- South Africa Pterogymnus laniarius Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5242 , http://hdl.handle.net/10962/d1005085
- Description: The panga, Pterogymnus laniarius (Cuvier, 1830), is a South African endemic sparid fish species. On the Agulhas Bank, South Africa it is a commercially important species, caught as bycatch in the hake directed trawlfisheries and targeted by offshore hook-and-linefishers. Recently there has been considerable interest shown in directing further fishing effort on this species. The lack of a suitable management procedure for teleost bycatch in South Africa was the principal reason for undertaking this study. This thesis investigates aspects the panga's life history, particularly those aspects that have management implications. A full knowledge of this species' distribution and abundance was necessary as this could highlight the existence of any nursery areas, ontogenetic migratory patterns and areas of high spawner biomass. The derived parameter estimates were then included as inputs into stock assessment models to determine the status and productivity of the resource. Growth studies based on sectioned sagittal otoliths revealed that the panga was a relatively slow growing fish with ages of 16 years being recorded. Growth was best described by the von Bertalanffy growth model as Lt=379.4(1-e⁻°·¹³⁽t ⁺ ¹·⁷⁸⁾). Total, natural and fishing mortalities were estimated at 0.36 year⁻¹, 0.28 year⁻¹ and 0.08 year ⁻¹, respectively. Detailed histological examination of the gonads revealed that panga is a late gonochorist, males and females maturing after a non-functional intersexual stage. Females mature at approximately 200 mm fork length or 4 years of age. Reproduction occurs throughout the year although there is a slight peak in winter. Gametogenesis was found to be similar to that of other sparid fishes and marine teleosts in general. The panga feeds predominantly on crustaceans with a distinct ontogenetic shift in feeding habits. Juvenile fish feed predominantly in the water column on mysids after which they move to the benthos. Subadult fish feed principally on ophiuroids and amphipods. Adult fish remain on or near the benthos, feeding predominantly on crabs, and on polychaetes, ophiuroids and fishes to a lesser extent. Several aspects of the panga's biology contribute to its ability to sustain a higher fishing pressure than other sympatric sparid species. These include its late gonochoristic reproductive style, protracted spawning season, maturation before recruitment and preference for soft substratum prey that enables it to utilise large areas of the Agulhas Bank. The panga's longevity, slow growth and low natural mortality rate, however, mitigated against these factors and were considered in the stock assessments. A heterogeneous Geographical Information System (GIS) was developed to analyse the distribution and abundance patterns of the panga. The GIS developed in this thesis makes a significant contribution towards the development of a South African Fisheries Information System to analyse and manage fish resources in general and bycatch resources in particular. The GIS developed in this study combines statistical Generalized Additive Modelling and standard GIS methods. Analysis of fourteen biannual fishery independent biomass surveys, disaggregated by life history stage, revealed that a nursery area for immature fish (<23 cm TL or < 4 years of age) exists on the Central Agulhas Bank. After sexual maturation, approximately 40% of the biomass migrated eastwards, colonising large areas of the Eastern Agulhas Bank.ilie location of the nursery area appears to be a result of the pelagic eggs and larvae being advected towards the coast in an anti-cyclonic gyre, stemming off the Agulhas current and later deposited over the Central Agulhas Bank. The weak bottom currents on the Central Agulhas Bank prevented juvenile loss to the Benguela system. The eurytopy of adult fish to various physical variables such as temperature, dissolved oxygen and stronger currents enabled it to reduce conspecific competition and migrate eastwards with distribution primarily determined by depth. Relative biomass estimates revealed a gradual increase in biomass of 5.5% per annum between 1988 and 1995. Predictions from yield-per-recruit, biomass-per-recruit and spawner biomass-per-recruit analyses showed that there was scope for further exploitation. A FSB₅₀ fishing strategy was considered to be the most appropriate fishing strategy as it did not reduce the spawner biomass-per-recruit to less than 50% of unexploited levels. Effort control was considered the most effective management tool as the age-at-50%-selectivity occurred after age-at-sexual maturity and releasing undersized fish was undesirable due to heavy mortalities resulting from severe barotrauma. The panga resource was also assessed using an age-structured production model. The values for the free parameters of the model were estimated using biomass indices derived from fishery-independent trawl surveys. Although the data were fairly uninformative about the productivity of the resource, the results indicated robustly, that the population has recovered from low levels in the mid-1970's and could sustain higher levels of fishing intensity. Risk analysis calculations were used to assess the sustainability of different catch scenarios. The level of sustainable catch was found to be sensitive to the selectivity pattern of the gear utilised. Both stock assessment methods used in this study to investigate the status of the panga resource showed that the resource could theoretically sustain higher catches. It was found that although the stock could be harvested using available fishing methods, the sympatry of this species with other commercial species was of concern as the latter would form a significant bycatch in a panga directed fishery. The failure of current harvesting methods to address the bycatch problem highlights the management problem in South Africa and stresses the need for creativity by both scientists and fishers in designing new and improved methods for selectively harvesting bycatch fish resources. Considering that no suitable method is currently available to fish the panga stock in a directed fishery the fishery should be managed as status quo until some suitable and efficient gear is developed.
- Full Text:
- Date Issued: 1998
Rhenium (I) and (V) complexes with potentially mulidentate ligands containing the Amino group
- Authors: Booysen, Irvin Noel
- Date: 2009
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10386 , http://hdl.handle.net/10948/1270 , Rhenium , Ligands
- Description: The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab = 1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only in a distorted octahedral coordination geometry around the metal ion. The complex trans- [Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The ‘2 + 1’ complex fac- [Re(CO)3(Hamp)(amp)] (Hamp = 2-aminophenol) was isolated from the reaction of a two molar ratio of Hamp with [Re(CO)5Br] in toluene. The reaction of a 1:1 molar ratio of [Re(CO)5Br] and H2ada led to the isolation of the Re(I) complex, fac- [Re(CO)3Br(H2ada)]. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of trans-[ReOCl3(PPh3)2] with N-(2-aminobenzylidene)-5-amino-1,3-dimethyl uracil (H3dua) in ethanol gave a mixed crystal which contains both the neutral oxorhenium(V) complex [ReOCl(Hdua)] and the imido rhenium(V) [Re(dua)Cl2(PPh3)] in an equimolar ratio in the asymmetric unit. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux led to the isolation of [C12H12N6O4] as only product. The [ReO4]- anion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination Abstract I.N. Booysen Nelson Mandela Metropolitan University vii of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of 2-(2-aminophenyl)benzothiazole (Habt) with [Re(CO)5Br] led to the isolation of the rhenium(I) complex fac-[Re(Habt)(CO)3Br]. With trans-[ReOCl3(PPh3)2], the ligand Habt decomposed to form the oxofree rhenium(V) complex [Re(itp)2Cl(PPh3)] (itp = 2-amidophenylthiolate). From the reaction of trans-[ReOBr3(PPh3)2] with 2-(2- hydroxyphenyl)benzothiazole (Hhpd) the complex [ReVOBr2(hpd)(PPh3)] was obtained. The reaction of a twofold molar excess of H2apb (2-(2-aminophenyl)-1-benzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonalbipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. A new nitrosylrhenium(II) complex salt, [Re(NO)BrL2(PPh3)2](ReO4) (H2L2 = 2-amino-5- (triphenylphosphino)phenol), is the first example of a complex containing the triphenylphosphonium-amidophenolate ligand L2, formed by the nucleophilic attack of a PPh3 on a coordinated amidophenolate ring. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps = N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The X-ray crystal structure show that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry, around the rhenium(V) centre, with the two chlorides in cis positions. A new oxofree rhenium(V) complex salt, [Re(bbd)2](ReO4) ( H2bbd = N-(2- Abstract I.N. Booysen Nelson Mandela Metropolitan University viii aminobenzylidene)benzene-1,2-diamine), has been synthesized and the chelates bbd are coordinated as dianionic tridentate N,N,N-donor diamidoimines. The rhenium(V) ion is centered in a distorted trigonal prism. The rhenium(I) compound fac-[Re(CO)3(daa)].Hpab.H2O (Hpab = N1,N2-(1,2- phenylene)bis(2-aminobenzamide); Hdaa = 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO)5Br] with a two equivalents of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. Daa is coordinated as a diaminoamide via three nitrogen-donor atoms. The reaction of a twofold molar excess of H2amben (H2amben = N1,N2-bis(2-aminobenzylidene)ethane-1,2-diamine) with trans- [ReOBr3(PPh3)2] gave the oxorhenium(V) cationic complex [ReO(amben)]X (X = Br-, PF6 -). The Re(V) oxo-bridged compound, {μ-O}[ReO(omben)]2.H2O (H2omben = N1,N2- bis(2-hydroxybenzylidene)ethane-1,2-diamine) was isolated from the reaction of a 2:1 molar ratio of H2omben and trans-[ReO2(py)4]Cl in methanol. The seven-coordinate rhenium(III) complex cation [ReIII(dhp)(PPh3)2]+ was isolated as the [ReO4]- salt from the reaction of cis-[ReVO2I(PPh3)2] with 2,6-bis(2- hydroxyphenyliminomethyl)pyridine (H2dhp) in ethanol. In the complex fac- [Re(CO)3(H2dhp)Br], prepared from [Re(CO)5Br] and H2dhp in toluene, the H2dhp ligand acts as a neutral bidentate N,N-donor chelate. An equimolar ratio reaction of 2-aminobenzaldehyde and 2-(2-aminophenyl)-1- benzimidazole in methanol led to 2-(5,6-dihydrobenzimidazolo[1,2-c]-quinazolin-6- yl)aniline. In an attempt to explore the template formation of this class of ligand with rhenium, the reaction of salicylaldehyde and 2-(2-aminophenyl)-1-benzimidazole in ethanol which was followed by the addition of trans-[ReOBr3(PPh3)2] led to the formation of the salt, 6-(2-hydroxyphenyl)-5,6-dihydrobenzimidazolo[1,2-c]quinazolin- 12-ium bromide. The compound 6-(2-methylthiophenyl)-5,6-dihydrobenzimidazolo[1,2- c]quinazolin-12-ium was synthesized via the reaction of 2-aminobenzaldehyde and 2- methylthiobenzaldehyde in methanol.
- Full Text:
- Date Issued: 2009
- Authors: Booysen, Irvin Noel
- Date: 2009
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10386 , http://hdl.handle.net/10948/1270 , Rhenium , Ligands
- Description: The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab = 1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only in a distorted octahedral coordination geometry around the metal ion. The complex trans- [Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The ‘2 + 1’ complex fac- [Re(CO)3(Hamp)(amp)] (Hamp = 2-aminophenol) was isolated from the reaction of a two molar ratio of Hamp with [Re(CO)5Br] in toluene. The reaction of a 1:1 molar ratio of [Re(CO)5Br] and H2ada led to the isolation of the Re(I) complex, fac- [Re(CO)3Br(H2ada)]. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of trans-[ReOCl3(PPh3)2] with N-(2-aminobenzylidene)-5-amino-1,3-dimethyl uracil (H3dua) in ethanol gave a mixed crystal which contains both the neutral oxorhenium(V) complex [ReOCl(Hdua)] and the imido rhenium(V) [Re(dua)Cl2(PPh3)] in an equimolar ratio in the asymmetric unit. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux led to the isolation of [C12H12N6O4] as only product. The [ReO4]- anion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination Abstract I.N. Booysen Nelson Mandela Metropolitan University vii of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of 2-(2-aminophenyl)benzothiazole (Habt) with [Re(CO)5Br] led to the isolation of the rhenium(I) complex fac-[Re(Habt)(CO)3Br]. With trans-[ReOCl3(PPh3)2], the ligand Habt decomposed to form the oxofree rhenium(V) complex [Re(itp)2Cl(PPh3)] (itp = 2-amidophenylthiolate). From the reaction of trans-[ReOBr3(PPh3)2] with 2-(2- hydroxyphenyl)benzothiazole (Hhpd) the complex [ReVOBr2(hpd)(PPh3)] was obtained. The reaction of a twofold molar excess of H2apb (2-(2-aminophenyl)-1-benzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonalbipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. A new nitrosylrhenium(II) complex salt, [Re(NO)BrL2(PPh3)2](ReO4) (H2L2 = 2-amino-5- (triphenylphosphino)phenol), is the first example of a complex containing the triphenylphosphonium-amidophenolate ligand L2, formed by the nucleophilic attack of a PPh3 on a coordinated amidophenolate ring. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps = N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The X-ray crystal structure show that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry, around the rhenium(V) centre, with the two chlorides in cis positions. A new oxofree rhenium(V) complex salt, [Re(bbd)2](ReO4) ( H2bbd = N-(2- Abstract I.N. Booysen Nelson Mandela Metropolitan University viii aminobenzylidene)benzene-1,2-diamine), has been synthesized and the chelates bbd are coordinated as dianionic tridentate N,N,N-donor diamidoimines. The rhenium(V) ion is centered in a distorted trigonal prism. The rhenium(I) compound fac-[Re(CO)3(daa)].Hpab.H2O (Hpab = N1,N2-(1,2- phenylene)bis(2-aminobenzamide); Hdaa = 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO)5Br] with a two equivalents of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. Daa is coordinated as a diaminoamide via three nitrogen-donor atoms. The reaction of a twofold molar excess of H2amben (H2amben = N1,N2-bis(2-aminobenzylidene)ethane-1,2-diamine) with trans- [ReOBr3(PPh3)2] gave the oxorhenium(V) cationic complex [ReO(amben)]X (X = Br-, PF6 -). The Re(V) oxo-bridged compound, {μ-O}[ReO(omben)]2.H2O (H2omben = N1,N2- bis(2-hydroxybenzylidene)ethane-1,2-diamine) was isolated from the reaction of a 2:1 molar ratio of H2omben and trans-[ReO2(py)4]Cl in methanol. The seven-coordinate rhenium(III) complex cation [ReIII(dhp)(PPh3)2]+ was isolated as the [ReO4]- salt from the reaction of cis-[ReVO2I(PPh3)2] with 2,6-bis(2- hydroxyphenyliminomethyl)pyridine (H2dhp) in ethanol. In the complex fac- [Re(CO)3(H2dhp)Br], prepared from [Re(CO)5Br] and H2dhp in toluene, the H2dhp ligand acts as a neutral bidentate N,N-donor chelate. An equimolar ratio reaction of 2-aminobenzaldehyde and 2-(2-aminophenyl)-1- benzimidazole in methanol led to 2-(5,6-dihydrobenzimidazolo[1,2-c]-quinazolin-6- yl)aniline. In an attempt to explore the template formation of this class of ligand with rhenium, the reaction of salicylaldehyde and 2-(2-aminophenyl)-1-benzimidazole in ethanol which was followed by the addition of trans-[ReOBr3(PPh3)2] led to the formation of the salt, 6-(2-hydroxyphenyl)-5,6-dihydrobenzimidazolo[1,2-c]quinazolin- 12-ium bromide. The compound 6-(2-methylthiophenyl)-5,6-dihydrobenzimidazolo[1,2- c]quinazolin-12-ium was synthesized via the reaction of 2-aminobenzaldehyde and 2- methylthiobenzaldehyde in methanol.
- Full Text:
- Date Issued: 2009
Sedimentology of the Karoo Supergroup in the Tuli Basin (Limpompo River area, South Africa)
- Authors: Bordy, Emese M
- Date: 2001
- Subjects: River sediments -- South Africa Sedimentology Limpopo river Sedimentology -- Limpopo river Limpopo river (South africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4999 , http://hdl.handle.net/10962/d1005612
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) consist of various terrigenous clastic and chemical deposits (parabreccias, conglo-breccias, conglomerates, sandstones, fine-grained sediments, calcretes and silc~etes). Four stratigraphic units were identified: the Basal, Middle and· Upper Units, and the CI~rens Formation. The palaeo-environmental reconstructions of the four stratigraphic units are based on evidence provided by primary sedimentary structures, palaeo-flow measurements, clast size/shape analysis, petrographic studies, palaeontological findings, borehole data and stratigraphic relations. The facies associations of the Basal Unit are interpreted as colluvial fan and low sinuosity, braid~d river channel with coal-bearing overbank and thaw-lake deposits. The interpreted depositional environment implies a cold climate, non-glacial subarctic fluvio-Iacustrine system. The current indicators of the palaeo-river system suggest flow direction from ENE to WSW. The lithologies of the Basal Unit are very similar to the deposits of the fluvial interval in the Vryheid Formation (Ecca Group) of the main Karoo Basin. There is no indubitable evidence for glacial activity (e.g. striated pavements or clasts, varvites, etc.), therefore the presence of unequivocal Dwyka Group correlatives in the Tuli Basin remains uncertain. The sedimentary structures and palaeo-current analysis indicate that the beds of the Middle Unit were deposited by an ancient river system flowing in a north-northwesterly direction. A lack of good quality exposures did not allow the reconstruction of the fluvial style, but the available data indicate a high-energy, perhaps braided fluvial system. The lack of bio- and chronostr~~igraphic control hampers precise correlation and enables only the lithocorrelation of the Middle Unit with other braided river systems either in the Beaufort Group or in the Molteno Formation of the main Karoo Basin. The depositional environment of the Upper Unit is interpreted as a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the unit, the climate was semi-arid with sparse precipitation resulting -iFlhighmagnitude, low-frequency devastating flash floods. The sediments were built out from a distant northwesterly source to the southeast. The unambiguous correspondence between the Upper Unit and the Elliot Formation (main Karoo Basin) is provided by lithological similarities and prosauropod dinosaurs remains. The palaeo-geographic picture of the Clarens Fonnation indicates a westerly windsdominated erg environment with migrating transverse dune types. The ephemeral stream deposits, fossil wood and trace fossils are only present in the lower part of the Formation, indicating that the wet-desert conditions were progressively replaced by dry-desert conditions. Based on lithological and palaeontological evidence, the Formation correlates with the Clarens Formation in the main Karoo Basin. At this stage, it remains difficult to establish the exact cause of the regional palaeo-slope changes during the deposition of the Karoo Supergroup in the Tuli Basin. It is probable that foreland system tectonics, which affected the lower part of the Supergroup (Basal Unit and Middle Unit?), were replaced by incipient continental extension and rift related tectonic movements in the Middle and Upper Units, and Clarens Formation.
- Full Text:
- Date Issued: 2001
- Authors: Bordy, Emese M
- Date: 2001
- Subjects: River sediments -- South Africa Sedimentology Limpopo river Sedimentology -- Limpopo river Limpopo river (South africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4999 , http://hdl.handle.net/10962/d1005612
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) consist of various terrigenous clastic and chemical deposits (parabreccias, conglo-breccias, conglomerates, sandstones, fine-grained sediments, calcretes and silc~etes). Four stratigraphic units were identified: the Basal, Middle and· Upper Units, and the CI~rens Formation. The palaeo-environmental reconstructions of the four stratigraphic units are based on evidence provided by primary sedimentary structures, palaeo-flow measurements, clast size/shape analysis, petrographic studies, palaeontological findings, borehole data and stratigraphic relations. The facies associations of the Basal Unit are interpreted as colluvial fan and low sinuosity, braid~d river channel with coal-bearing overbank and thaw-lake deposits. The interpreted depositional environment implies a cold climate, non-glacial subarctic fluvio-Iacustrine system. The current indicators of the palaeo-river system suggest flow direction from ENE to WSW. The lithologies of the Basal Unit are very similar to the deposits of the fluvial interval in the Vryheid Formation (Ecca Group) of the main Karoo Basin. There is no indubitable evidence for glacial activity (e.g. striated pavements or clasts, varvites, etc.), therefore the presence of unequivocal Dwyka Group correlatives in the Tuli Basin remains uncertain. The sedimentary structures and palaeo-current analysis indicate that the beds of the Middle Unit were deposited by an ancient river system flowing in a north-northwesterly direction. A lack of good quality exposures did not allow the reconstruction of the fluvial style, but the available data indicate a high-energy, perhaps braided fluvial system. The lack of bio- and chronostr~~igraphic control hampers precise correlation and enables only the lithocorrelation of the Middle Unit with other braided river systems either in the Beaufort Group or in the Molteno Formation of the main Karoo Basin. The depositional environment of the Upper Unit is interpreted as a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the unit, the climate was semi-arid with sparse precipitation resulting -iFlhighmagnitude, low-frequency devastating flash floods. The sediments were built out from a distant northwesterly source to the southeast. The unambiguous correspondence between the Upper Unit and the Elliot Formation (main Karoo Basin) is provided by lithological similarities and prosauropod dinosaurs remains. The palaeo-geographic picture of the Clarens Fonnation indicates a westerly windsdominated erg environment with migrating transverse dune types. The ephemeral stream deposits, fossil wood and trace fossils are only present in the lower part of the Formation, indicating that the wet-desert conditions were progressively replaced by dry-desert conditions. Based on lithological and palaeontological evidence, the Formation correlates with the Clarens Formation in the main Karoo Basin. At this stage, it remains difficult to establish the exact cause of the regional palaeo-slope changes during the deposition of the Karoo Supergroup in the Tuli Basin. It is probable that foreland system tectonics, which affected the lower part of the Supergroup (Basal Unit and Middle Unit?), were replaced by incipient continental extension and rift related tectonic movements in the Middle and Upper Units, and Clarens Formation.
- Full Text:
- Date Issued: 2001