Networking: enabling professional development and institutionalisation of environmental education courses in Southern Africa
- Authors: Lupele, Justin Kalaba
- Date: 2007
- Subjects: SADC Regional Environmental Education Programme Education -- Africa, Southern Environmental education -- Africa, Southern Environmental education -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1678 , http://hdl.handle.net/10962/d1003561
- Description: This study was aimed at understanding how networking can enable or constrain professional development and institutionalisation of environmental education courses in southern Africa in the context of the Course Development Network (CDN), a project of the Southern Africa Development Community Regional Environmental Education Programme (SADC REEP). The study involved 12 institutions (each institution was represented in the CDN by a staff member) in eight SADC member states. It was contextualized through a review of social, political, environmental and educational developments in southern Africa, with specific reference to regionalization processes, as the SADC REEF is constituted under this post-colonial political framework. Relational philosophy informed the research process and methodology. The philosophy underpinned three distinct, yet related theoretical perspectives namely: critical realism, which provided the ontological perspectives of the study; Actor Network Theory; and Community of Practice, which provided the epistemological perspectives. Data was generated during a 33-month period in southern Africa and 12 months in the United Kingdom (and on a one week visit to Italy). During a 12 month Split Site Commonwealth Scholarship award, tenable at Manchester Metropolitan University in the United Kingdom, I studied the Environment and School Initiative (ENSI) and the Sustainability Education for European Primary Schools (SEEPS), to examine whether the same mechanisms that made them successful would apply to the CDN in the context of southern Africa. While these two case studies provided useful insight into the relationship between networking, professional development and institutionalization of environmental education programmes, they were not the main focus of the research. Data analysis was mainly through inductive, abductive and retroductive modes of inference. Inductive data analysis was done by means of Nvivo – a computer software package used for qualitative data analysis. The software aided in revealing features and relationships in the data in more depth as it allowed flexibility in working with data. Abduction is the interpretation of a phenomenon by means of a conceptual framework. In this study, I used Actor Network Theory (ANT) (Latour & Woolgar, 1979; Callon, 1986) and Community of Practice (COP) (Lave, 1988; Lave & Wenger, 1991; Fullan, 2003) as analytical conceptual frameworks to probe networking and professional development respectively. Data on institutionalisation of environmental education courses was analysed by means of retroductive mode of inference, which is a thought operation that enables the understanding of social reality beyond what is empirically observable or experienced. This study reveals that there were a number of necessary (internal) and contingent (external) factors that enabled or constrained networking, professional development and institutionalisation of environmental education courses in the context of the CDN. The key factors included existing cultural capital, donor political economy, power relations, poverty related factors and social transformation trends. The study found that relational approaches and the use of three relational theoretical lenses provided a broader lens which enabled this study to identify different dynamics, greater ontological depth and understanding of the relational dynamics and relations at play in the CDN beyond the participants' experience and observable events. The study also contends that networking can provide a support structure for social transformation and change in environmental education.
- Full Text:
- Date Issued: 2007
- Authors: Lupele, Justin Kalaba
- Date: 2007
- Subjects: SADC Regional Environmental Education Programme Education -- Africa, Southern Environmental education -- Africa, Southern Environmental education -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1678 , http://hdl.handle.net/10962/d1003561
- Description: This study was aimed at understanding how networking can enable or constrain professional development and institutionalisation of environmental education courses in southern Africa in the context of the Course Development Network (CDN), a project of the Southern Africa Development Community Regional Environmental Education Programme (SADC REEP). The study involved 12 institutions (each institution was represented in the CDN by a staff member) in eight SADC member states. It was contextualized through a review of social, political, environmental and educational developments in southern Africa, with specific reference to regionalization processes, as the SADC REEF is constituted under this post-colonial political framework. Relational philosophy informed the research process and methodology. The philosophy underpinned three distinct, yet related theoretical perspectives namely: critical realism, which provided the ontological perspectives of the study; Actor Network Theory; and Community of Practice, which provided the epistemological perspectives. Data was generated during a 33-month period in southern Africa and 12 months in the United Kingdom (and on a one week visit to Italy). During a 12 month Split Site Commonwealth Scholarship award, tenable at Manchester Metropolitan University in the United Kingdom, I studied the Environment and School Initiative (ENSI) and the Sustainability Education for European Primary Schools (SEEPS), to examine whether the same mechanisms that made them successful would apply to the CDN in the context of southern Africa. While these two case studies provided useful insight into the relationship between networking, professional development and institutionalization of environmental education programmes, they were not the main focus of the research. Data analysis was mainly through inductive, abductive and retroductive modes of inference. Inductive data analysis was done by means of Nvivo – a computer software package used for qualitative data analysis. The software aided in revealing features and relationships in the data in more depth as it allowed flexibility in working with data. Abduction is the interpretation of a phenomenon by means of a conceptual framework. In this study, I used Actor Network Theory (ANT) (Latour & Woolgar, 1979; Callon, 1986) and Community of Practice (COP) (Lave, 1988; Lave & Wenger, 1991; Fullan, 2003) as analytical conceptual frameworks to probe networking and professional development respectively. Data on institutionalisation of environmental education courses was analysed by means of retroductive mode of inference, which is a thought operation that enables the understanding of social reality beyond what is empirically observable or experienced. This study reveals that there were a number of necessary (internal) and contingent (external) factors that enabled or constrained networking, professional development and institutionalisation of environmental education courses in the context of the CDN. The key factors included existing cultural capital, donor political economy, power relations, poverty related factors and social transformation trends. The study found that relational approaches and the use of three relational theoretical lenses provided a broader lens which enabled this study to identify different dynamics, greater ontological depth and understanding of the relational dynamics and relations at play in the CDN beyond the participants' experience and observable events. The study also contends that networking can provide a support structure for social transformation and change in environmental education.
- Full Text:
- Date Issued: 2007
On the characterization of photovoltaic devices for concentrator purposes
- Authors: Vorster, Frederick Jacobus
- Date: 2007
- Subjects: Photovoltaic cells , Image processing , Solar cells
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10530 , http://hdl.handle.net/10948/639 , Photovoltaic cells , Image processing , Solar cells
- Description: This study originated from an evaluation of the performance of a commercially available high concentration point focus concentrator PV system. The effect of module design flaws was studied by using current-voltage (I-V) curves obtained from each module in the array. The position of reverse bias steps revealed the severity of mismatch in a string of series-connected cells. By understanding the effects of the various types of mismatch, power losses and damage to the solar cells resulting from hot spot formation can be minimized and several recommendations for improving the basic performance of similar systems were made. Concern over the extent and type of defect failure of the concentrator photovoltaic (CPV) cells prompted an investigation into the use of a light beam induced current (LBIC) technique to investigate the spatial distribution of defects. An overview of current and developing LBIC techniques revealed that the original standard LBIC techniques have found widespread application, and that far-reaching and important developments of the technique have taken place over the years. These developments are driven by natural progression as well as the availability of newly developed advanced measurement equipment. Several techniques such as Lock-in hermography and the use of infrared cameras have developed as complementary techniques to advanced LBIC techniques. As an accurate contactless evaluation tool that is able to image spatially distributed defects in cell material, the basis of this method seemed promising for the evaluation of concentrator cells.
- Full Text:
- Date Issued: 2007
- Authors: Vorster, Frederick Jacobus
- Date: 2007
- Subjects: Photovoltaic cells , Image processing , Solar cells
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10530 , http://hdl.handle.net/10948/639 , Photovoltaic cells , Image processing , Solar cells
- Description: This study originated from an evaluation of the performance of a commercially available high concentration point focus concentrator PV system. The effect of module design flaws was studied by using current-voltage (I-V) curves obtained from each module in the array. The position of reverse bias steps revealed the severity of mismatch in a string of series-connected cells. By understanding the effects of the various types of mismatch, power losses and damage to the solar cells resulting from hot spot formation can be minimized and several recommendations for improving the basic performance of similar systems were made. Concern over the extent and type of defect failure of the concentrator photovoltaic (CPV) cells prompted an investigation into the use of a light beam induced current (LBIC) technique to investigate the spatial distribution of defects. An overview of current and developing LBIC techniques revealed that the original standard LBIC techniques have found widespread application, and that far-reaching and important developments of the technique have taken place over the years. These developments are driven by natural progression as well as the availability of newly developed advanced measurement equipment. Several techniques such as Lock-in hermography and the use of infrared cameras have developed as complementary techniques to advanced LBIC techniques. As an accurate contactless evaluation tool that is able to image spatially distributed defects in cell material, the basis of this method seemed promising for the evaluation of concentrator cells.
- Full Text:
- Date Issued: 2007
On the microstructure and physical properties of hot pressed (Hf, Ti) C
- Authors: Heiligers, Christiané
- Date: 2007
- Subjects: Transition metal carbides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10532 , http://hdl.handle.net/10948/523 , http://hdl.handle.net/10948/d1011722 , Transition metal carbides
- Description: The microstructure and physical properties of hot pressed (Hf, Ti) C have been investigated with the aim of producing a cutting tool material with similar hardness to that of WC-Co and TiC-based cermets. Sintered samples were hot pressed from HfC0.7 and TiC0.9 powders using powder metallurgical techniques and the processing cycle was optimized for this system. Ni was used as a binder in selected samples and C black was added to compensate for sub-stoichiometry and to aid in the reduction of oxides formed during milling. Microstructural analyses were performed by scanning and transmission electron microscopy (SEM and TEM) and the composition was determined from X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDS). The physical properties measured are density and Vickers hardness, and the indentation fracture toughness was determined using the Shetty formula. The fundamental interactions between HfC, TiC and Ni during hot pressing were investigated and the results obtained used to explain the microstructure that develops in samples made from powder mixtures. The interactions studied are the inter-diffusion of HfC and TiC through the solid state, and the dissolution and re-precipitation rate of the carbides in a liquid Ni binder. EDS analysis revealed that the rate at which Ti diffuses into HfC is higher than the rate at which Hf diffuses into TiC. Upper limits to the diffusion coefficients for these processes are determined and show that solid solution carbides will form from HfC + TiC powder mixtures at 2000 ºC in 1 hour if the average powder particle size is less than 5 μm. The diffusion rates decrease with a decrease in hot pressing temperature but mass transport between the phases can be enhanced by addition of a metallic binder. TEM and EDS analysis shows that Ni wets TiC more efficiently than HfC and that the solubility of TiC in Ni is also higher than that of HfC. The grain size of the carbide phases increases with an increase in the rate at which they dissolve into and re-precipitate from the liquid binder. The crystal structure of the binder phase depends on the concentration of Ti and Hf that remain in the binder after cooling and the carbide phase in which the binder is embedded. Analysis of TEM electron diffraction patterns show that the binder phase consists of cubic solid solutions as well as intermetallic and cubic phases in which atomic ordering is observed.
- Full Text:
- Date Issued: 2007
- Authors: Heiligers, Christiané
- Date: 2007
- Subjects: Transition metal carbides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10532 , http://hdl.handle.net/10948/523 , http://hdl.handle.net/10948/d1011722 , Transition metal carbides
- Description: The microstructure and physical properties of hot pressed (Hf, Ti) C have been investigated with the aim of producing a cutting tool material with similar hardness to that of WC-Co and TiC-based cermets. Sintered samples were hot pressed from HfC0.7 and TiC0.9 powders using powder metallurgical techniques and the processing cycle was optimized for this system. Ni was used as a binder in selected samples and C black was added to compensate for sub-stoichiometry and to aid in the reduction of oxides formed during milling. Microstructural analyses were performed by scanning and transmission electron microscopy (SEM and TEM) and the composition was determined from X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDS). The physical properties measured are density and Vickers hardness, and the indentation fracture toughness was determined using the Shetty formula. The fundamental interactions between HfC, TiC and Ni during hot pressing were investigated and the results obtained used to explain the microstructure that develops in samples made from powder mixtures. The interactions studied are the inter-diffusion of HfC and TiC through the solid state, and the dissolution and re-precipitation rate of the carbides in a liquid Ni binder. EDS analysis revealed that the rate at which Ti diffuses into HfC is higher than the rate at which Hf diffuses into TiC. Upper limits to the diffusion coefficients for these processes are determined and show that solid solution carbides will form from HfC + TiC powder mixtures at 2000 ºC in 1 hour if the average powder particle size is less than 5 μm. The diffusion rates decrease with a decrease in hot pressing temperature but mass transport between the phases can be enhanced by addition of a metallic binder. TEM and EDS analysis shows that Ni wets TiC more efficiently than HfC and that the solubility of TiC in Ni is also higher than that of HfC. The grain size of the carbide phases increases with an increase in the rate at which they dissolve into and re-precipitate from the liquid binder. The crystal structure of the binder phase depends on the concentration of Ti and Hf that remain in the binder after cooling and the carbide phase in which the binder is embedded. Analysis of TEM electron diffraction patterns show that the binder phase consists of cubic solid solutions as well as intermetallic and cubic phases in which atomic ordering is observed.
- Full Text:
- Date Issued: 2007
Opportunity and constraint : historicity, hybridity and notions of cultural identity among farm workers in the Sundays River Valley
- Authors: Connor, Teresa Kathleen
- Date: 2007
- Subjects: Agricultural laborers -- South Africa -- Relocation Addo Elephant National Park (South Africa) Xhosa (African people) -- South Africa -- Eastern Cape -- Ethnic identity Forced migration -- South Africa -- Eastern Cape Land settlement -- South Africa -- Government policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2117 , http://hdl.handle.net/10962/d1008367
- Description: This thesis focuses on relationships of opportunity and constraint among farm workers in the Sundays River Valley (SRV), Eastern Cape Province. Relationships of 'constraint' include those experiences of displacement and forced removal and war, including forced removals by the apartheid state in 1960 and 1970. Relationships of 'opportunity' include the ways in which residents in the SRV have contested their experiences of upheaval and domination, and the formation of a regional sense of place and belonging/ investigate how farm workers actually draw elements of locality and identity from their experiences of upheaval, and how displacement bolsters feelings of belonging and place. Instead of viewing displacement as a once-off experience, this thesis investigates displacement in historical terms, as a long-term, 'serial' experience of human movement, which is continued in the present- specifically through the creation of the Greater Addo Elephant National Park. I concentrate on developing a spatialised and cultural notion of movemenUplacement. 'Place' is investigated as a term that refers to rather indeterminate feelings of nostalgia, memory and identity, which depend on a particular connection to territory (ie: 'space'). I emphasise that elements of place in the SRV are drawn from and expressed along dualistic lines, which juxtapose situations of opportunity and constraint. In this way, farm workers' sense of connection to farms and ancestral territory in the SRV depends on their experiences of stable residency and work on farms, as well as their memories of removal from land in the area. I emphasise that those elements of conservatism (expressed as 'tradition' and Redness) among Xhosa-speaking farm workers are indications of a certain hybridity of identity in the region, which depend on differentiation from other groups (such as so-called 'coloured' farm workers and 'white' farmers), as well as associations between these groups. This thesis lays emphasis upon those less visible and definable 'identities' in the Eastern Cape Province, specifically by shifting focus away from the exhomeland states of the Ciskei and Transkei, to more marginal expressions of identity and change (among farm workers) in the Province. I point out that labourers cannot solely be defined by their positions as farm workers, but by their place and sense of cultural belonging in the area. In this sense, I use the idea of work as a loaded concept that can comment on a range of cultural attitudes towards belonging and place, and which is firmly embedded in the private lives of labourers - beyond their simple socio-economic conditions of farm work. I use Bourdieu's conception of habitus and doxa to define work as a set of dispositions that have been historicised and internalised by workers to such an extent, that relationships of domination are sometimes inadvertently obscured through their apparent 'naturalness'. Moreover, I point out that work can be related to ritualised action in the SRV through the use of performance and practice-based anthropological theory. Both work and ritual are symbolic actions, and are sites of struggle within which workers express themselves dualistically. Rituals, specifically, are dramatic events that combine disharmonious and harmonious social processes - juxtaposing the powerlessness of workers (on farms), and the deep sense of belonging and place in the SRV. I argue that the deep historical connections in the SRV have largely been ignored by conservationists in the drive to establish new protected zones (such as the Greater Addo Elephant National Park), and that a new model of shared conservation management is needed for this Park.
- Full Text:
- Date Issued: 2007
- Authors: Connor, Teresa Kathleen
- Date: 2007
- Subjects: Agricultural laborers -- South Africa -- Relocation Addo Elephant National Park (South Africa) Xhosa (African people) -- South Africa -- Eastern Cape -- Ethnic identity Forced migration -- South Africa -- Eastern Cape Land settlement -- South Africa -- Government policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2117 , http://hdl.handle.net/10962/d1008367
- Description: This thesis focuses on relationships of opportunity and constraint among farm workers in the Sundays River Valley (SRV), Eastern Cape Province. Relationships of 'constraint' include those experiences of displacement and forced removal and war, including forced removals by the apartheid state in 1960 and 1970. Relationships of 'opportunity' include the ways in which residents in the SRV have contested their experiences of upheaval and domination, and the formation of a regional sense of place and belonging/ investigate how farm workers actually draw elements of locality and identity from their experiences of upheaval, and how displacement bolsters feelings of belonging and place. Instead of viewing displacement as a once-off experience, this thesis investigates displacement in historical terms, as a long-term, 'serial' experience of human movement, which is continued in the present- specifically through the creation of the Greater Addo Elephant National Park. I concentrate on developing a spatialised and cultural notion of movemenUplacement. 'Place' is investigated as a term that refers to rather indeterminate feelings of nostalgia, memory and identity, which depend on a particular connection to territory (ie: 'space'). I emphasise that elements of place in the SRV are drawn from and expressed along dualistic lines, which juxtapose situations of opportunity and constraint. In this way, farm workers' sense of connection to farms and ancestral territory in the SRV depends on their experiences of stable residency and work on farms, as well as their memories of removal from land in the area. I emphasise that those elements of conservatism (expressed as 'tradition' and Redness) among Xhosa-speaking farm workers are indications of a certain hybridity of identity in the region, which depend on differentiation from other groups (such as so-called 'coloured' farm workers and 'white' farmers), as well as associations between these groups. This thesis lays emphasis upon those less visible and definable 'identities' in the Eastern Cape Province, specifically by shifting focus away from the exhomeland states of the Ciskei and Transkei, to more marginal expressions of identity and change (among farm workers) in the Province. I point out that labourers cannot solely be defined by their positions as farm workers, but by their place and sense of cultural belonging in the area. In this sense, I use the idea of work as a loaded concept that can comment on a range of cultural attitudes towards belonging and place, and which is firmly embedded in the private lives of labourers - beyond their simple socio-economic conditions of farm work. I use Bourdieu's conception of habitus and doxa to define work as a set of dispositions that have been historicised and internalised by workers to such an extent, that relationships of domination are sometimes inadvertently obscured through their apparent 'naturalness'. Moreover, I point out that work can be related to ritualised action in the SRV through the use of performance and practice-based anthropological theory. Both work and ritual are symbolic actions, and are sites of struggle within which workers express themselves dualistically. Rituals, specifically, are dramatic events that combine disharmonious and harmonious social processes - juxtaposing the powerlessness of workers (on farms), and the deep sense of belonging and place in the SRV. I argue that the deep historical connections in the SRV have largely been ignored by conservationists in the drive to establish new protected zones (such as the Greater Addo Elephant National Park), and that a new model of shared conservation management is needed for this Park.
- Full Text:
- Date Issued: 2007
Passing the spear : a grounded theory study of the influence of family business value sets on succession planning in black family-owned businesses
- Authors: Musengi, Sandra
- Date: 2007
- Subjects: Grounded theory Family-owned business enterprises Family-owned business enterprises -- Succession Family-owned business enterprises -- Management Business enterprises, Black Business planning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1192 , http://hdl.handle.net/10962/d1007056
- Description: Literature suggests that a small number of family businesses are able to make the transition from the founder to other family members with a common reason cited being the lack of planning. This study aims to build understanding of leadership succession in family businesses by focusing on the influence of a founder's family business value set on the succession planning process in Black family-owned businesses. Using the Strauss and Corbin (1990) grounded theory method, this study develops a theory of succession planning of Black familyowned businesses labelled Passing the Spear which is comprised of three stages based on an analysis of 21 qualitative interviews. The Spear was an analogy used to represent both the values of the founder and the family business, thus in Passing the Spear, founders where essentially performing a dual transfer of their values and leadership to the successor. The implementation of the process Passing the Spear was influenced by the family business value set of the founder, which in this study, were labelled as Traditional, Progressive, and Transitional. These value sets were distinguished by their behaviour regarding their choice of successor where founders with a traditional value set exhibited gatekeeping behaviour, while the behaviour of founders with a progressive value set was labelled navigating, and finally, founders with a transitional value set demonstrated behaviour labelled exploring. Furthermore, it was found that after the successor had been chosen, founders appeared to follow a generic succession planning process, however, the ease and timing of implementation was influenced by the family business context, evidence of being proactive and the degree of family business resilience. The process of Passing the Spear comprised of three stages of (a) Showing the spear where the founder's focus is on the induction and socialization of the successor using the strategies of bringing the successor into the family business and managing the family-business interface using relationships; (b) Explaining the spear entailed founders using the strategies of sharing knowledge and teaching the successors about the family business; and ( c) Sharing the spear was where founders focused on empowering the successors by implementing strategies of sharing responsibilities and learning from the successor.The process provides insights into the influence of family business values on the succession planning process and can be useful for founders of Black family-owned businesses in planning for succession in their businesses. In addition, the study provides another perspective of succession planning and offers a contribution to the literature for understanding succession in Black family-owned businesses.
- Full Text:
- Date Issued: 2007
- Authors: Musengi, Sandra
- Date: 2007
- Subjects: Grounded theory Family-owned business enterprises Family-owned business enterprises -- Succession Family-owned business enterprises -- Management Business enterprises, Black Business planning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1192 , http://hdl.handle.net/10962/d1007056
- Description: Literature suggests that a small number of family businesses are able to make the transition from the founder to other family members with a common reason cited being the lack of planning. This study aims to build understanding of leadership succession in family businesses by focusing on the influence of a founder's family business value set on the succession planning process in Black family-owned businesses. Using the Strauss and Corbin (1990) grounded theory method, this study develops a theory of succession planning of Black familyowned businesses labelled Passing the Spear which is comprised of three stages based on an analysis of 21 qualitative interviews. The Spear was an analogy used to represent both the values of the founder and the family business, thus in Passing the Spear, founders where essentially performing a dual transfer of their values and leadership to the successor. The implementation of the process Passing the Spear was influenced by the family business value set of the founder, which in this study, were labelled as Traditional, Progressive, and Transitional. These value sets were distinguished by their behaviour regarding their choice of successor where founders with a traditional value set exhibited gatekeeping behaviour, while the behaviour of founders with a progressive value set was labelled navigating, and finally, founders with a transitional value set demonstrated behaviour labelled exploring. Furthermore, it was found that after the successor had been chosen, founders appeared to follow a generic succession planning process, however, the ease and timing of implementation was influenced by the family business context, evidence of being proactive and the degree of family business resilience. The process of Passing the Spear comprised of three stages of (a) Showing the spear where the founder's focus is on the induction and socialization of the successor using the strategies of bringing the successor into the family business and managing the family-business interface using relationships; (b) Explaining the spear entailed founders using the strategies of sharing knowledge and teaching the successors about the family business; and ( c) Sharing the spear was where founders focused on empowering the successors by implementing strategies of sharing responsibilities and learning from the successor.The process provides insights into the influence of family business values on the succession planning process and can be useful for founders of Black family-owned businesses in planning for succession in their businesses. In addition, the study provides another perspective of succession planning and offers a contribution to the literature for understanding succession in Black family-owned businesses.
- Full Text:
- Date Issued: 2007
Pharmaceutical analysis and quality of complementary medicines : sceletium and associated products
- Patnala, Satya Siva Rama Ranganath Srinivas
- Authors: Patnala, Satya Siva Rama Ranganath Srinivas
- Date: 2007
- Subjects: Alternative medicine , Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3872 , http://hdl.handle.net/10962/d1018263
- Description: There has been an upsurge in the use of Complementary and Alternate Medicines (CAMs) in both developed and developing countries. Although herbal medicines have been in use for many centuries, their quality, safety and efficacy are still of major concern. Many countries are in the process of integrating CAMs into conventional health care systems based on the knowledge and use of traditional medicines. The quality control (QC) of herbal products usually presents a formidable analytical challenge in view of the complexity of the constituents in plant material and the commercial non-availability of appropriate qualified reference standards. Sceletium, a genus belonging to the family Aizoaceae, has been reported to contain psychoactive alkaloids, specifically mesembrine, mesembrenone, mesembrenol and some other related alkaloids. Sceletium is marketed as dried plant powder and as phyto-pharmaceutical dosage forms. Sceletium products and plant material marketed through health shops and on the internet are associated with unjustified claims of specific therapeutic efficacy and may be of dubious quality. Validated analytical methods to estimate Sceletium alkaloids have not previously been reported in the scientific literature and the available methods have focused only on qualitative estimation. Furthermore, since appropriate markers were not commercially available for use as reference standards, a primary objective of this study was to isolate relevant compounds, qualify them as reference standards which could be applied to develop appropriate validated qualitative and quantitative analytical methods for fingerprinting and assay of Sceletium plant material and dosage forms. The alkaloidal markers mesembrine, mesembrenone and ∆⁷ mesembrenone were isolated by solvent extraction and chromatography from dried plant material. Mesembranol and epimesembranol were synthesised by hydrogenation of the isolated mesembrine using the catalyst platinum (IV) oxide and then further purified by semi-preparative column chromatography. All compounds were subjected to analysis by ¹H, ¹³C, 2-D nuclear magnetic resonance and liquid chromatography-tandem mass spectroscopy. Mesembrine was converted to hydrochloride crystals and mesembranol was isolated as crystals from the hydrogenation reaction mass. These compounds were analysed and characterised by X-ray crystallography. A relatively simple HPLC method for the separation and quantitative analysis of five relevant alkaloidal components in Sceletium was developed and validated. The method was applied to determine the alkaloids in plant material and dosage forms containing Sceletium. An LCMS method developed during the study provided accurate identification of the five relevant Sceletium alkaloids. The method was applied for the quantitative analysis and QC of Sceletium plant material and its dosage forms. This LCMS method was found to efficiently ionize the relevant alkaloidal markers in order to facilitate their detection, identification and quantification in Sceletium plant material as well as for the assay and QC of dosage forms containing Sceletium. The chemotaxonomy of some Sceletium species and commercially available Sceletium dosage forms were successfully studied by the LCMS method. The HPLC and LCMS methods were also used to monitor the bio-conversion of some of the alkaloids while processing the plant material as per traditional method of fermentation. Additionally a high resolution CZE method was developed for the separation of several Sceletium alkaloids in relatively short analysis times. This analytical method was used successfully to fingerprint the alkaloids and quantify mesembrine in Sceletium and its products. Sceletium species grown under varying conditions at different locations, when analyzed, showed major differences in their composition of alkaloids and an enormous difference was found to exist between the various species with respect to the presence and content of alkaloids. Sceletium and its products marketed through health shops and the internet may thus have problems with respect to the quality and related therapeutic efficacy. The QC of Sceletium presents a formidable challenge as Sceletium plants and products contain a complex mixture of compounds. The work presented herein contributes to a growing body of scientific knowledge to improve the QC standards of herbal medicines and also to provide vital information regarding the selection of plant species and information on the specific alkaloidal constituents to the cultivators of Sceletium and the manufacturers of its products.
- Full Text:
- Date Issued: 2007
- Authors: Patnala, Satya Siva Rama Ranganath Srinivas
- Date: 2007
- Subjects: Alternative medicine , Herbs -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3872 , http://hdl.handle.net/10962/d1018263
- Description: There has been an upsurge in the use of Complementary and Alternate Medicines (CAMs) in both developed and developing countries. Although herbal medicines have been in use for many centuries, their quality, safety and efficacy are still of major concern. Many countries are in the process of integrating CAMs into conventional health care systems based on the knowledge and use of traditional medicines. The quality control (QC) of herbal products usually presents a formidable analytical challenge in view of the complexity of the constituents in plant material and the commercial non-availability of appropriate qualified reference standards. Sceletium, a genus belonging to the family Aizoaceae, has been reported to contain psychoactive alkaloids, specifically mesembrine, mesembrenone, mesembrenol and some other related alkaloids. Sceletium is marketed as dried plant powder and as phyto-pharmaceutical dosage forms. Sceletium products and plant material marketed through health shops and on the internet are associated with unjustified claims of specific therapeutic efficacy and may be of dubious quality. Validated analytical methods to estimate Sceletium alkaloids have not previously been reported in the scientific literature and the available methods have focused only on qualitative estimation. Furthermore, since appropriate markers were not commercially available for use as reference standards, a primary objective of this study was to isolate relevant compounds, qualify them as reference standards which could be applied to develop appropriate validated qualitative and quantitative analytical methods for fingerprinting and assay of Sceletium plant material and dosage forms. The alkaloidal markers mesembrine, mesembrenone and ∆⁷ mesembrenone were isolated by solvent extraction and chromatography from dried plant material. Mesembranol and epimesembranol were synthesised by hydrogenation of the isolated mesembrine using the catalyst platinum (IV) oxide and then further purified by semi-preparative column chromatography. All compounds were subjected to analysis by ¹H, ¹³C, 2-D nuclear magnetic resonance and liquid chromatography-tandem mass spectroscopy. Mesembrine was converted to hydrochloride crystals and mesembranol was isolated as crystals from the hydrogenation reaction mass. These compounds were analysed and characterised by X-ray crystallography. A relatively simple HPLC method for the separation and quantitative analysis of five relevant alkaloidal components in Sceletium was developed and validated. The method was applied to determine the alkaloids in plant material and dosage forms containing Sceletium. An LCMS method developed during the study provided accurate identification of the five relevant Sceletium alkaloids. The method was applied for the quantitative analysis and QC of Sceletium plant material and its dosage forms. This LCMS method was found to efficiently ionize the relevant alkaloidal markers in order to facilitate their detection, identification and quantification in Sceletium plant material as well as for the assay and QC of dosage forms containing Sceletium. The chemotaxonomy of some Sceletium species and commercially available Sceletium dosage forms were successfully studied by the LCMS method. The HPLC and LCMS methods were also used to monitor the bio-conversion of some of the alkaloids while processing the plant material as per traditional method of fermentation. Additionally a high resolution CZE method was developed for the separation of several Sceletium alkaloids in relatively short analysis times. This analytical method was used successfully to fingerprint the alkaloids and quantify mesembrine in Sceletium and its products. Sceletium species grown under varying conditions at different locations, when analyzed, showed major differences in their composition of alkaloids and an enormous difference was found to exist between the various species with respect to the presence and content of alkaloids. Sceletium and its products marketed through health shops and the internet may thus have problems with respect to the quality and related therapeutic efficacy. The QC of Sceletium presents a formidable challenge as Sceletium plants and products contain a complex mixture of compounds. The work presented herein contributes to a growing body of scientific knowledge to improve the QC standards of herbal medicines and also to provide vital information regarding the selection of plant species and information on the specific alkaloidal constituents to the cultivators of Sceletium and the manufacturers of its products.
- Full Text:
- Date Issued: 2007
Phthalocyanines : photochemical, electrochemical and biomimetic catalytic behaviour
- Authors: Sehlotho, Nthapo
- Date: 2007
- Subjects: Phthalocyanines Photochemistry Electrochemistry Biomimetics Oxidation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4336 , http://hdl.handle.net/10962/d1004997
- Description: This thesis explored use of metallophthalocyanines as electrocatalysts towards thiol and thiocyanate oxidation, nitrosothiol decomposition and reduction of oxygen, as well as biomimetic and photo-catalysts of cyclohexene oxidation. 2-mercaptoethanol (2-ME), L-cysteine (CYS) and reduced glutathione (GSH) thiols were oxidized on cobalt tetra ethoxythiophene and cobalt tetra phenoxy pyrrole phthalocyanine modified glassy carbon electrodes, whose catalytic activity was found to depend on pH, film thickness and method of electrode modification. Oxidation of thiocyanate (SCN-), CYS and 2-ME was catalyzed by a selfassembled monolayer of cobalt tetraethoxythiophene Thiocyanate oxidation occurred via two electron transfer, whereas that of CYS and 2-ME required 1 electron. The oxidations of SCN- and 2-ME were catalyzed by ring based processes, while CYS was catalyzed by both Co[superscript III]/Co[superscript II] process and ring-based processes. Oxidation of GSH and 2-ME was conducted on screen printed graphite electrodes modified with cobalt phthalocyanine. Activity depended on method of electrode modification and CoPc % composition. Decomposition of Snitrosoglutathione occurred in the presence of copper ions and NaBH[subscript 4]. Reduced and oxidized glutathione were detected as products using cobalt phthalocyanine adsorbed on an ordinary pyrolytic graphite electrode. Reduction of oxygen was electro-catalyzed by adsorbed manganese phthalocyanine complexes on glassy carbon electrodes. FePc, FePc(Cl)[subscript 16], CoPc and CoPc substituted with phenoxypyrrole and ethoxythiophene ligands were also used as electro-catalysts. Oxygen reduction occurred via two electron transfer in acidic and neutral media forming hydrogen peroxide, while water was formed in basic media via four electron transfer. Cyclohexene oxidation using tert-butylhydroperoxide or chloroperoxy benzoic acid as oxidants in the presence of FePc, FePc(Cl)[subscript 16] and CoPc formed cyclohexene oxide, 2-cyclohexen-1-ol, 2- cyclohexen-1-one and adipic acid. Product selectivity depended on the nature of catalyst and oxidant. The FePc(Cl)[subscript 16] catalyst was transformed into a µ-oxo dimer during the oxidation process while M[superscript III]Pc intermediates were formed with Co[superscript II]Pc and Fe[superscript II]Pc catalysts. Cyclohexene photooxidation catalyzed by zinc phthalocyanine using either red or white light formed 2-cyclohexen-1-one, 2-cyclohexen-1-ol, transcyclohexane diol, cyclohexene oxide and cyclohexene hydroperoxide via singlet oxygen and radical mechanisms. Product yields depended on the light wavelength and intensity, solvent, irradiation time and the rate of photodegradation of the catalyst.
- Full Text:
- Date Issued: 2007
- Authors: Sehlotho, Nthapo
- Date: 2007
- Subjects: Phthalocyanines Photochemistry Electrochemistry Biomimetics Oxidation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4336 , http://hdl.handle.net/10962/d1004997
- Description: This thesis explored use of metallophthalocyanines as electrocatalysts towards thiol and thiocyanate oxidation, nitrosothiol decomposition and reduction of oxygen, as well as biomimetic and photo-catalysts of cyclohexene oxidation. 2-mercaptoethanol (2-ME), L-cysteine (CYS) and reduced glutathione (GSH) thiols were oxidized on cobalt tetra ethoxythiophene and cobalt tetra phenoxy pyrrole phthalocyanine modified glassy carbon electrodes, whose catalytic activity was found to depend on pH, film thickness and method of electrode modification. Oxidation of thiocyanate (SCN-), CYS and 2-ME was catalyzed by a selfassembled monolayer of cobalt tetraethoxythiophene Thiocyanate oxidation occurred via two electron transfer, whereas that of CYS and 2-ME required 1 electron. The oxidations of SCN- and 2-ME were catalyzed by ring based processes, while CYS was catalyzed by both Co[superscript III]/Co[superscript II] process and ring-based processes. Oxidation of GSH and 2-ME was conducted on screen printed graphite electrodes modified with cobalt phthalocyanine. Activity depended on method of electrode modification and CoPc % composition. Decomposition of Snitrosoglutathione occurred in the presence of copper ions and NaBH[subscript 4]. Reduced and oxidized glutathione were detected as products using cobalt phthalocyanine adsorbed on an ordinary pyrolytic graphite electrode. Reduction of oxygen was electro-catalyzed by adsorbed manganese phthalocyanine complexes on glassy carbon electrodes. FePc, FePc(Cl)[subscript 16], CoPc and CoPc substituted with phenoxypyrrole and ethoxythiophene ligands were also used as electro-catalysts. Oxygen reduction occurred via two electron transfer in acidic and neutral media forming hydrogen peroxide, while water was formed in basic media via four electron transfer. Cyclohexene oxidation using tert-butylhydroperoxide or chloroperoxy benzoic acid as oxidants in the presence of FePc, FePc(Cl)[subscript 16] and CoPc formed cyclohexene oxide, 2-cyclohexen-1-ol, 2- cyclohexen-1-one and adipic acid. Product selectivity depended on the nature of catalyst and oxidant. The FePc(Cl)[subscript 16] catalyst was transformed into a µ-oxo dimer during the oxidation process while M[superscript III]Pc intermediates were formed with Co[superscript II]Pc and Fe[superscript II]Pc catalysts. Cyclohexene photooxidation catalyzed by zinc phthalocyanine using either red or white light formed 2-cyclohexen-1-one, 2-cyclohexen-1-ol, transcyclohexane diol, cyclohexene oxide and cyclohexene hydroperoxide via singlet oxygen and radical mechanisms. Product yields depended on the light wavelength and intensity, solvent, irradiation time and the rate of photodegradation of the catalyst.
- Full Text:
- Date Issued: 2007
Prime near-ring modules and their links with the generalised group near-ring
- Authors: Juglal, Shaanraj
- Date: 2007
- Subjects: Near-rings
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10507 , http://hdl.handle.net/10948/714 , Near-rings
- Description: In view of the facts that the definition of a ring led to the definition of a near- ring, the definition of a ring module led to the definition of a near-ring module, prime rings resulted in investigations with respect to primeness in near-rings, one is naturally inclined to attempt to define the notion of a group near-ring seeing that the group ring had already been defined and investigated into by, interalia, Groenewald in [7] . However, in trying to define the group near-ring along the same lines as the group ring was defined, it was found that the resulting multiplication was, in general, not associative in the near-ring case due to the lack of one distributive property. In 1976, Meldrum [19] achieved success in defining the group near-ring. How- ever, in his definition, only distributively generated near-rings were considered and the distributive generators played a vital role in the construction. In 1989, Le Riche, Meldrum and van der Walt [17], adopted a similar approach to that which led to a successful and fruitful definition of matrix near-rings, and defined the group near-ring in a more general sense. In particular, they defined R[G], the group near-ring of a group G over a near-ring R, as a subnear-ring of M(RG), the near-ring of all mappings of the group RG into itself. More recently, Groenewald and Lee [14], further generalised the definition of R[G] to R[S : M], the generalised semigroup near-ring of a semigroup S over any faithful R-module M. Again, the natural thing to do would be to extend the results obtained for R[G] to R[S : M], and this they achieved with much success.
- Full Text:
- Date Issued: 2007
- Authors: Juglal, Shaanraj
- Date: 2007
- Subjects: Near-rings
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10507 , http://hdl.handle.net/10948/714 , Near-rings
- Description: In view of the facts that the definition of a ring led to the definition of a near- ring, the definition of a ring module led to the definition of a near-ring module, prime rings resulted in investigations with respect to primeness in near-rings, one is naturally inclined to attempt to define the notion of a group near-ring seeing that the group ring had already been defined and investigated into by, interalia, Groenewald in [7] . However, in trying to define the group near-ring along the same lines as the group ring was defined, it was found that the resulting multiplication was, in general, not associative in the near-ring case due to the lack of one distributive property. In 1976, Meldrum [19] achieved success in defining the group near-ring. How- ever, in his definition, only distributively generated near-rings were considered and the distributive generators played a vital role in the construction. In 1989, Le Riche, Meldrum and van der Walt [17], adopted a similar approach to that which led to a successful and fruitful definition of matrix near-rings, and defined the group near-ring in a more general sense. In particular, they defined R[G], the group near-ring of a group G over a near-ring R, as a subnear-ring of M(RG), the near-ring of all mappings of the group RG into itself. More recently, Groenewald and Lee [14], further generalised the definition of R[G] to R[S : M], the generalised semigroup near-ring of a semigroup S over any faithful R-module M. Again, the natural thing to do would be to extend the results obtained for R[G] to R[S : M], and this they achieved with much success.
- Full Text:
- Date Issued: 2007
Race against democracy: a case study of the Mail & Guardian during the early years of the Mbeki presidency, 1999-2002
- Authors: Steenveld, Lynette Noreen
- Date: 2007
- Subjects: Mbeki, Thabo -- In mass media , Mail & Guardian , South African newspapers , Press -- South Africa , Press and politics -- South Africa , Journalism -- South Africa , Mass media and race relations -- South Africa , Racism in the press -- South Africa , Mass media -- Political aspects -- South Africa , South Africa -- Politics and government -- 20th century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3537 , http://hdl.handle.net/10962/d1015572
- Description: This thesis examines the 1998 complaint of racism against the Mail & Guardian, a leading exponent of South Africa's alternative press in the 1980s, and important contemporary producer of investigative journalism. The study is framed within a cultural studies approach, analysing the Mail & Guardian as constituted by a 'circuit of production': its social context, production, texts, and audiences. The thesis makes three main arguments. First, that the claim of racism cannot be understood outside of a consideration of both the changing political milieu, and subtle changes within the Mail & Guardian itself. Significant social changes relate to the reconfiguration of racial and class identities wrought by the 'Mbeki state'. Within the Mail & Guardian, the thesis argues for the importance of the power and subjectivity of the editor as a key 'factor' shaping the identity of the paper, evidenced in its production practices and textual outputs. In this regard, the thesis departs from a functionalist analysis of particular 'roles' within the newsroom, drawing instead on a post-structuralist approach to organisational studies. Based on this production and social context, the thesis examines key texts which deal with aspects of South Africa's social transformation, and which exemplify aspects of the Mail & Guardian's reporting which led to the complaint of racism by the Black Lawyers Association (BLA) and the Association of Black Accountants (ABASA). Their complaint was that the Mail & Guardian's reporting impugned the dignity of black people, and in so doing was a violation of their rights to dignity and equality which are constitutionally guaranteed. However, as freedom of the press is also guaranteed by the South African constitution, their complaint to the South African Human Rights Commission (SAHRC) resulted in public debate about these contending rights. My second argument relates to the jurisprudential approach to racism, and the related issue of affirmative action, which informed the complaint against the paper. Contrary to the 'normative', liberal approach to these issues, this thesis highlights Critical Race Theory as the jurisprudential basis for both the claimants' accusation of racism against the Mail & Guardian, and aspects of its implicit use in South African human rights adjudication. The thesis argues that in failing to recognise these different philosophical and political bases of legal reasoning, the media, including the Mail & Guardian, in reporting on these matters failed in their purported role of serving the public interest. The thesis concludes by applying Fraser's critique of Habermas's notion of a single, bourgeois public sphere to journalism, thereby suggesting ways in which the critiques of some of the Mail & Guardian's own journalists could be employed to enlarge its approach to journalism - giving voice to constituencies seldom heard in mainstream media.
- Full Text:
- Date Issued: 2007
- Authors: Steenveld, Lynette Noreen
- Date: 2007
- Subjects: Mbeki, Thabo -- In mass media , Mail & Guardian , South African newspapers , Press -- South Africa , Press and politics -- South Africa , Journalism -- South Africa , Mass media and race relations -- South Africa , Racism in the press -- South Africa , Mass media -- Political aspects -- South Africa , South Africa -- Politics and government -- 20th century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3537 , http://hdl.handle.net/10962/d1015572
- Description: This thesis examines the 1998 complaint of racism against the Mail & Guardian, a leading exponent of South Africa's alternative press in the 1980s, and important contemporary producer of investigative journalism. The study is framed within a cultural studies approach, analysing the Mail & Guardian as constituted by a 'circuit of production': its social context, production, texts, and audiences. The thesis makes three main arguments. First, that the claim of racism cannot be understood outside of a consideration of both the changing political milieu, and subtle changes within the Mail & Guardian itself. Significant social changes relate to the reconfiguration of racial and class identities wrought by the 'Mbeki state'. Within the Mail & Guardian, the thesis argues for the importance of the power and subjectivity of the editor as a key 'factor' shaping the identity of the paper, evidenced in its production practices and textual outputs. In this regard, the thesis departs from a functionalist analysis of particular 'roles' within the newsroom, drawing instead on a post-structuralist approach to organisational studies. Based on this production and social context, the thesis examines key texts which deal with aspects of South Africa's social transformation, and which exemplify aspects of the Mail & Guardian's reporting which led to the complaint of racism by the Black Lawyers Association (BLA) and the Association of Black Accountants (ABASA). Their complaint was that the Mail & Guardian's reporting impugned the dignity of black people, and in so doing was a violation of their rights to dignity and equality which are constitutionally guaranteed. However, as freedom of the press is also guaranteed by the South African constitution, their complaint to the South African Human Rights Commission (SAHRC) resulted in public debate about these contending rights. My second argument relates to the jurisprudential approach to racism, and the related issue of affirmative action, which informed the complaint against the paper. Contrary to the 'normative', liberal approach to these issues, this thesis highlights Critical Race Theory as the jurisprudential basis for both the claimants' accusation of racism against the Mail & Guardian, and aspects of its implicit use in South African human rights adjudication. The thesis argues that in failing to recognise these different philosophical and political bases of legal reasoning, the media, including the Mail & Guardian, in reporting on these matters failed in their purported role of serving the public interest. The thesis concludes by applying Fraser's critique of Habermas's notion of a single, bourgeois public sphere to journalism, thereby suggesting ways in which the critiques of some of the Mail & Guardian's own journalists could be employed to enlarge its approach to journalism - giving voice to constituencies seldom heard in mainstream media.
- Full Text:
- Date Issued: 2007
Regulation of hyu gene expression in Agrobacterium tumefaciens strains RU-AE01 and RU-OR
- Authors: Jiwaji, Meesbah
- Date: 2007
- Subjects: Agrobacterium tumefaciens Amino acids Gene expression Hydrolysis Hydantoin Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3983 , http://hdl.handle.net/10962/d1004042
- Description: Several Agrobacterium tumefaciens strains have been isolated for their ability to produce D-amino acids from D, L-substituted hydantoins. The optically pure D-amino acids are used in the synthesis of pharmaceuticals, as food additives and as insecticides. This hydrolysis of D, L-substituted hydantoins is catalysed by two hydantoin-hydrolyzing enzymes, an hydantoinase and an N-carbamyl amino acid amidohydrolase. While the hydantoin-hydrolyzing enzymes have been studied in detail, the mechanisms that control expression of the hyu genes have not. The research reported in this work elucidates some of the mechanisms involved in the regulation of the hyu genes in A. tumefaciens strains. The hydantoin-hydrolyzing enzyme activity from the environmental isolate A. tumefaciens RU-AE01 was characterized. A broad host range vector for the simultaneous analysis of divergent promoters was constructed. The promoter regions responsible for the activation of transcription of hyuH and hyuC were identified by deletion analysis. It was proposed that transcription of hyuH was activated by a putative σ[superscript 54]-dependent promoter or a putative σ[superscript 70]-dependent promoter identified upstream of the hyuH gene. The hyuC gene was activated by a putative σ[superscript 70]-dependent promoter identified upstream of the hyuC gene. The regulation of hydantoinase and N-carbamyl amino acid amidohydrolase enzyme activity was compared to the regulation of transcription from the RU-AE01 hyuH-hyuC region. Expression of the hydantoin-hydrolyzing enzymes was regulated by induction which correlated with reporter enzyme expression from the hyuH and hyuC promoter regions. However, the expression of the hydantoin-hydrolyzing enzymes was also regulated by nitrogen catabolite repression (NCR). This did not correlate to the reporter gene expression of the hyuH promoter region but did compare to the reporter gene expression of the hyuC promoter region. This suggested that NCR of hyuH was at the post-translational level whereas NCR of the hyuC promoter was at the transcriptional level. Pathways involved in the regulation of the hyu genes were characterized. The production of the hydantoin-hydrolyzing enzymes in both A. tumefaciens strains RU-AE01 and RU-OR were regulated by proteins involved in the global ntr pathway. The levels of the hydantoin-hydrolyzing enzymes in strain RU-AE01 were elevated in the presence of increased levels of NtrB and NtrC illustrating the importance of the ntr pathway in the regulation of the levels of the hydantoin-hydrolyzing enzymes. Similarly, in RU-OR the presence of exogenous NtrB and NtrC elevated levels of N-carbamyl amino acid amidohydrolase activity. However, the levels of hydantoinase enzyme activity in strain RU-OR were elevated in the presence of NtrC alone. In addition, the presence of a His6-tagged NtrC molecule abolished the elevation in the levels of the hydantoinase but not the N-carbamyl amino acid amidohydrolase enzyme activity in strain RU-OR. This suggests that NtrC has a direct role in the regulation of the expression of hyuH in RU-OR. In addition, it indicates that the hyu genes in the two A. tumefaciens strains RU-AE01 and RU-OR are different. The presence of the RU-AE01 hyuH-hyuC fragment caused a dramatic increase in the hydantoin-hydrolyzing enzyme activity in strain RU-OR but not strain RU-AE01. This implied the incidence of a possible repressor protein in RU-OR, which is titrated out by the presence of the RU-AE01 hyuH-hyuC fragment. Protein-DNA binding assays suggest that this putative repressor may be 38 kDa in RU-OR cells.
- Full Text:
- Date Issued: 2007
- Authors: Jiwaji, Meesbah
- Date: 2007
- Subjects: Agrobacterium tumefaciens Amino acids Gene expression Hydrolysis Hydantoin Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3983 , http://hdl.handle.net/10962/d1004042
- Description: Several Agrobacterium tumefaciens strains have been isolated for their ability to produce D-amino acids from D, L-substituted hydantoins. The optically pure D-amino acids are used in the synthesis of pharmaceuticals, as food additives and as insecticides. This hydrolysis of D, L-substituted hydantoins is catalysed by two hydantoin-hydrolyzing enzymes, an hydantoinase and an N-carbamyl amino acid amidohydrolase. While the hydantoin-hydrolyzing enzymes have been studied in detail, the mechanisms that control expression of the hyu genes have not. The research reported in this work elucidates some of the mechanisms involved in the regulation of the hyu genes in A. tumefaciens strains. The hydantoin-hydrolyzing enzyme activity from the environmental isolate A. tumefaciens RU-AE01 was characterized. A broad host range vector for the simultaneous analysis of divergent promoters was constructed. The promoter regions responsible for the activation of transcription of hyuH and hyuC were identified by deletion analysis. It was proposed that transcription of hyuH was activated by a putative σ[superscript 54]-dependent promoter or a putative σ[superscript 70]-dependent promoter identified upstream of the hyuH gene. The hyuC gene was activated by a putative σ[superscript 70]-dependent promoter identified upstream of the hyuC gene. The regulation of hydantoinase and N-carbamyl amino acid amidohydrolase enzyme activity was compared to the regulation of transcription from the RU-AE01 hyuH-hyuC region. Expression of the hydantoin-hydrolyzing enzymes was regulated by induction which correlated with reporter enzyme expression from the hyuH and hyuC promoter regions. However, the expression of the hydantoin-hydrolyzing enzymes was also regulated by nitrogen catabolite repression (NCR). This did not correlate to the reporter gene expression of the hyuH promoter region but did compare to the reporter gene expression of the hyuC promoter region. This suggested that NCR of hyuH was at the post-translational level whereas NCR of the hyuC promoter was at the transcriptional level. Pathways involved in the regulation of the hyu genes were characterized. The production of the hydantoin-hydrolyzing enzymes in both A. tumefaciens strains RU-AE01 and RU-OR were regulated by proteins involved in the global ntr pathway. The levels of the hydantoin-hydrolyzing enzymes in strain RU-AE01 were elevated in the presence of increased levels of NtrB and NtrC illustrating the importance of the ntr pathway in the regulation of the levels of the hydantoin-hydrolyzing enzymes. Similarly, in RU-OR the presence of exogenous NtrB and NtrC elevated levels of N-carbamyl amino acid amidohydrolase activity. However, the levels of hydantoinase enzyme activity in strain RU-OR were elevated in the presence of NtrC alone. In addition, the presence of a His6-tagged NtrC molecule abolished the elevation in the levels of the hydantoinase but not the N-carbamyl amino acid amidohydrolase enzyme activity in strain RU-OR. This suggests that NtrC has a direct role in the regulation of the expression of hyuH in RU-OR. In addition, it indicates that the hyu genes in the two A. tumefaciens strains RU-AE01 and RU-OR are different. The presence of the RU-AE01 hyuH-hyuC fragment caused a dramatic increase in the hydantoin-hydrolyzing enzyme activity in strain RU-OR but not strain RU-AE01. This implied the incidence of a possible repressor protein in RU-OR, which is titrated out by the presence of the RU-AE01 hyuH-hyuC fragment. Protein-DNA binding assays suggest that this putative repressor may be 38 kDa in RU-OR cells.
- Full Text:
- Date Issued: 2007
Severe convective storm risk in the Eastern Cape Province of South Africa
- Authors: Pyle, Desmond Mark
- Date: 2007
- Subjects: Storms -- South Africa -- Eastern Cape Natural disasters -- South Africa -- Eastern Cape Disasters -- South Africa -- Eastern Cape Disaster relief -- South Africa -- Eastern Cape -- Management Meteorology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4853 , http://hdl.handle.net/10962/d1005529
- Description: This study investigates the temporal, spatial and impact characteristics of severe convective storm hazard and risk in the Eastern Cape Province of South Africa. Using historical data on severe convective storms dating from 1897, patterns of the hazard threat and risk to various geographic populations were investigated. A conceptual framework that emphasises the combined role hazard and vulnerability play in defining risk was used for the study. A methodology for ranking the severity of the storms in the historical dataset, based on recorded damage/impact, was specifically developed for the study. It is intended that this methodology will have a potentially wider application and may be adapted to a range of hazard impact and risk studies in South Africa and internationally. The study was undertaken within the context of the South African Disaster Management Act of 2002. Findings of the study show that severe convective storms can occur throughout the province, but there are clearly demarcated areas of higher frequency and concentration. The impact of storms is particularly severe on impoverished and vulnerable rural populations in the eastern parts of the province, where there is an urgent need for building capacity in disaster risk management. A major outcome of the study is the production of a severe convective storm hazard/risk map of the Eastern Cape, which it is hoped will be of benefit to a number of stakeholders in the province, particularly disaster management, but also the South African Weather Service, agricultural organisations, development/planning authorities, educational authorities and risk insurers. It is hoped that this map and the study in general will assist in guiding the operational responses of the various authorities, especially in terms of those interventions aimed at disaster risk reduction in the Eastern Cape.
- Full Text:
- Date Issued: 2007
- Authors: Pyle, Desmond Mark
- Date: 2007
- Subjects: Storms -- South Africa -- Eastern Cape Natural disasters -- South Africa -- Eastern Cape Disasters -- South Africa -- Eastern Cape Disaster relief -- South Africa -- Eastern Cape -- Management Meteorology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4853 , http://hdl.handle.net/10962/d1005529
- Description: This study investigates the temporal, spatial and impact characteristics of severe convective storm hazard and risk in the Eastern Cape Province of South Africa. Using historical data on severe convective storms dating from 1897, patterns of the hazard threat and risk to various geographic populations were investigated. A conceptual framework that emphasises the combined role hazard and vulnerability play in defining risk was used for the study. A methodology for ranking the severity of the storms in the historical dataset, based on recorded damage/impact, was specifically developed for the study. It is intended that this methodology will have a potentially wider application and may be adapted to a range of hazard impact and risk studies in South Africa and internationally. The study was undertaken within the context of the South African Disaster Management Act of 2002. Findings of the study show that severe convective storms can occur throughout the province, but there are clearly demarcated areas of higher frequency and concentration. The impact of storms is particularly severe on impoverished and vulnerable rural populations in the eastern parts of the province, where there is an urgent need for building capacity in disaster risk management. A major outcome of the study is the production of a severe convective storm hazard/risk map of the Eastern Cape, which it is hoped will be of benefit to a number of stakeholders in the province, particularly disaster management, but also the South African Weather Service, agricultural organisations, development/planning authorities, educational authorities and risk insurers. It is hoped that this map and the study in general will assist in guiding the operational responses of the various authorities, especially in terms of those interventions aimed at disaster risk reduction in the Eastern Cape.
- Full Text:
- Date Issued: 2007
Spermiogenesis, sperm ultrastructure and reproductive tract morphology in cicadas implications for systematic relationships
- Chawanji, Abraham Simbarashe
- Authors: Chawanji, Abraham Simbarashe
- Date: 2007
- Subjects: Cicadas Cicadas -- Reproduction Spermiogenesis in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5770 , http://hdl.handle.net/10962/d1005458
- Description: Sperm structure in five species of cicadine cicadas (Albanycada albigera, Azanicada zuluensis, Platypleura capensis, P. hirtipennis and Pycna semiclara) and five species of cicadettine cicadas (Melampsalta leucoptera, Quintilia walkeri, Stagira simplex, Xosopsaltria thunbergi and Monomatapa matoposa) was investigated by light and electron microscopy. In addition, spermiogenesis in cicadas was described; the information was derived from two cicadettines (Diceroprocta biconica and M. matoposa) and three cicadines (Kongota punctigera, P. capensis and P. semiclara). Mature spermatozoa of all species investigated are elongate and filiform, consisting of three distinct regions: the head (acrosome and nucleus), mid-piece and tail. All species produce more than one discrete length of nucleated, motile sperm, a form of sperm polymorphism termed polymegaly. Polymegaly is expressed in three ways; sperm have uni-, bi- or trimodal nucleus and tail lengths. Besides the differences in length, there are also notable differences in the size of nuclei. The anterior parts of sperm heads are embedded in an elongate homogenous matrix forming spermatodesmata. The conical acrosome is deeply invaginated posteriorly, and sits on top of the nucleus. The acrosomal contents are differentiated internally with a tubular substructure and a subacrosomal space. The anterior of the nucleus intrudes into the posterior section of the subacrosomal space. Anteriorly the acrosome is laterally flattened; posteriorly it extends as two tubular processes on either side of the nucleus that gradually decrease in diameter. The homogenously electron-dense nucleus is pointed anteriorly and is generally cylindrical, although posteriorly there is a lateral invagination that extends part-way along the nucleus. This invagination houses fine granular material of the putative centriolar adjunct which does not form in close proximity to the centriole and hence may not be a true centriolar adjunct. The lamellate disposition of the centriolar adjunct material within the sperm-midpiece of cicadettine cicadas is distinct, and separates these cicadas from their cicadine counterparts in which the centriolar adjunct material is non-lamellate. Vesicle-like elements that are associated with both the posterior nucleus and the centriolar adjunct are also found within the invagination. Immediately posterior of and adjoining the centriolar adjunct is a pair of mitochondrial derivatives that are elongated and extend for almost the entire length of the tail. Except for size the architecture of short and long spermatozoa is generally similar in all species. The absence of accessory bodies in cicada sperm suggests that within the Cicadomorpha, the families Cicadidae and Cercopidae are closely related. Only long nuclei were observed in the fertilized eggs of A. zuluensis indicating that sperm with long nuclei might be favoured for fertilization. Spermiogenesis involves: (a) development of the acrosome from a proacrosomal granule; (b) development of the nucleus, characterized by elongation and streamlining with a simultaneous condensation of chromatin; (c) development of the axoneme from the centriole; (d) amalgamation of individual small mitochondria to form elongated mitochondrial derivatives in which cristae are arranged into regularly spaced lamellae; and (f) elimination of cytoplasm. The presence of a manchette, a transient microtubular organelle, which surrounds the acrosome, nucleus and mitochondrial derivatives, is a characteristic feature of spermiogenesis. The gross morphology of the reproductive tract in both male and female cicadas exhibits an organization similar to that in most oviparous insects. The non-functional spermatheca is the only exceptional feature in the female reproductive tract. Its role has been taken over by the common oviduct which, subsequently, has become modified into a swollen, differentiated structure with a dual role of receiving oocytes from the paired ovaries and storage of spermatozoa. Testis mass varies between cicada species; this variation might be linked to the intensity of sperm competition which has been found to be positively correlated with relative investment in spermatogenesis. Based on the preliminary findings of this study, K. punctigera, with its larger testis relative to body size, would be the ideal candidate to show the greatest levels of sperm competition. Accessory glands in both male and female A. zuluensis, D. biconica, P. hirtipennis and O. quadraticollis are very long; this character might be of phylogenetic significance. Despite being notoriously refractory spermiocladistics is potentially valuable in systematic and phylogenic studies of cicadas, especially at the subfamily level.
- Full Text:
- Date Issued: 2007
- Authors: Chawanji, Abraham Simbarashe
- Date: 2007
- Subjects: Cicadas Cicadas -- Reproduction Spermiogenesis in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5770 , http://hdl.handle.net/10962/d1005458
- Description: Sperm structure in five species of cicadine cicadas (Albanycada albigera, Azanicada zuluensis, Platypleura capensis, P. hirtipennis and Pycna semiclara) and five species of cicadettine cicadas (Melampsalta leucoptera, Quintilia walkeri, Stagira simplex, Xosopsaltria thunbergi and Monomatapa matoposa) was investigated by light and electron microscopy. In addition, spermiogenesis in cicadas was described; the information was derived from two cicadettines (Diceroprocta biconica and M. matoposa) and three cicadines (Kongota punctigera, P. capensis and P. semiclara). Mature spermatozoa of all species investigated are elongate and filiform, consisting of three distinct regions: the head (acrosome and nucleus), mid-piece and tail. All species produce more than one discrete length of nucleated, motile sperm, a form of sperm polymorphism termed polymegaly. Polymegaly is expressed in three ways; sperm have uni-, bi- or trimodal nucleus and tail lengths. Besides the differences in length, there are also notable differences in the size of nuclei. The anterior parts of sperm heads are embedded in an elongate homogenous matrix forming spermatodesmata. The conical acrosome is deeply invaginated posteriorly, and sits on top of the nucleus. The acrosomal contents are differentiated internally with a tubular substructure and a subacrosomal space. The anterior of the nucleus intrudes into the posterior section of the subacrosomal space. Anteriorly the acrosome is laterally flattened; posteriorly it extends as two tubular processes on either side of the nucleus that gradually decrease in diameter. The homogenously electron-dense nucleus is pointed anteriorly and is generally cylindrical, although posteriorly there is a lateral invagination that extends part-way along the nucleus. This invagination houses fine granular material of the putative centriolar adjunct which does not form in close proximity to the centriole and hence may not be a true centriolar adjunct. The lamellate disposition of the centriolar adjunct material within the sperm-midpiece of cicadettine cicadas is distinct, and separates these cicadas from their cicadine counterparts in which the centriolar adjunct material is non-lamellate. Vesicle-like elements that are associated with both the posterior nucleus and the centriolar adjunct are also found within the invagination. Immediately posterior of and adjoining the centriolar adjunct is a pair of mitochondrial derivatives that are elongated and extend for almost the entire length of the tail. Except for size the architecture of short and long spermatozoa is generally similar in all species. The absence of accessory bodies in cicada sperm suggests that within the Cicadomorpha, the families Cicadidae and Cercopidae are closely related. Only long nuclei were observed in the fertilized eggs of A. zuluensis indicating that sperm with long nuclei might be favoured for fertilization. Spermiogenesis involves: (a) development of the acrosome from a proacrosomal granule; (b) development of the nucleus, characterized by elongation and streamlining with a simultaneous condensation of chromatin; (c) development of the axoneme from the centriole; (d) amalgamation of individual small mitochondria to form elongated mitochondrial derivatives in which cristae are arranged into regularly spaced lamellae; and (f) elimination of cytoplasm. The presence of a manchette, a transient microtubular organelle, which surrounds the acrosome, nucleus and mitochondrial derivatives, is a characteristic feature of spermiogenesis. The gross morphology of the reproductive tract in both male and female cicadas exhibits an organization similar to that in most oviparous insects. The non-functional spermatheca is the only exceptional feature in the female reproductive tract. Its role has been taken over by the common oviduct which, subsequently, has become modified into a swollen, differentiated structure with a dual role of receiving oocytes from the paired ovaries and storage of spermatozoa. Testis mass varies between cicada species; this variation might be linked to the intensity of sperm competition which has been found to be positively correlated with relative investment in spermatogenesis. Based on the preliminary findings of this study, K. punctigera, with its larger testis relative to body size, would be the ideal candidate to show the greatest levels of sperm competition. Accessory glands in both male and female A. zuluensis, D. biconica, P. hirtipennis and O. quadraticollis are very long; this character might be of phylogenetic significance. Despite being notoriously refractory spermiocladistics is potentially valuable in systematic and phylogenic studies of cicadas, especially at the subfamily level.
- Full Text:
- Date Issued: 2007
Study of titanium, tantalum and chromium catalysts for use in industrial transformations
- Authors: Tau, Prudence Lerato
- Date: 2007
- Subjects: Titanium Tantalum Phthalocyanines Electrochemistry Photochemotherapy Chromium Spectrum analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4363 , http://hdl.handle.net/10962/d1005028
- Description: PART A The syntheses, spectroscopic and electrochemical characterisation of a series of titanium and tantalum phthalocyanine complexes are reported. The complexes are unsubstituted and substituted at either the peripheral or non-peripheral positions with sulphonates, aryloxy, arylthio or amino groups. The complexes mostly exhibit Qbands in the near-infrared region as well as interesting properties in different solvents. The interaction of differently sulphonated titanium and tantalum phthalocyanine complexes with methyl viologen (MV[superscript 2+]), and hence the stoichiometry and association constants are evaluated. Detailed photophysicochemical properties of the complexes were investigated and are for the first time presented with fluorescence lifetimes easily obtained from fluorescence quenching studies. The transformation of 1-hexene photocatalysed by aryloxy- and arylthio-appended complexes is also presented for the first time. The electrochemical properties of the complexes are unknown and are thus presented. Cyclic (CV) and square wave (SWV) voltammetries, chronocoulometry and spectroelectrochemistry are employed in the study of the complexes. Two oneelectron reductions and a simultaneous 4-electron reduction are observed for the unsubstituted Cl[subscript 3]TaPc. Reduction occurs first at the metal followed by ring-based processes. The tetra- and octa-substituted derivatives however exhibit peculiar electrochemical behaviour where a multi-electron transfer process occurs for complexes bearing certain substituents. For all complexes, the first two reductions are metal-based followed by ring-based processes. A comparative study of the electrocatalytic activities of the complexes towards the oxidation of nitrite is also investigated. The complexes are immobilised onto a glassy carbon electrode either by drop-dry or electropolymerisation methods. All the modified electrodes exhibit improved electrocatalytic oxidation of nitrite than the unmodified electrodes by a twoelectron mechanism producing nitrate ions. Catalytic currents are enhanced and nitrite overpotential reduced to ~ 0.60 V. Kinetic parameters are determined for all complexes and a mechanism is proposed. PART B: The syntheses and electrochemical characterisation of chromium and titanium complexes for the selective trimerisation of ethylene to 1-hexene are presented. The synthesis of the chromium complex requires simple steps while tedious steps are used for the air-sensitive titanium complex. The spectroscopic interaction of the chromium complex with the co-catalyst methylaluminoxane is investigated. The complexes are characterised by electrochemical methods such as cyclic voltammetry and spectroelectrochemistry.
- Full Text:
- Date Issued: 2007
- Authors: Tau, Prudence Lerato
- Date: 2007
- Subjects: Titanium Tantalum Phthalocyanines Electrochemistry Photochemotherapy Chromium Spectrum analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4363 , http://hdl.handle.net/10962/d1005028
- Description: PART A The syntheses, spectroscopic and electrochemical characterisation of a series of titanium and tantalum phthalocyanine complexes are reported. The complexes are unsubstituted and substituted at either the peripheral or non-peripheral positions with sulphonates, aryloxy, arylthio or amino groups. The complexes mostly exhibit Qbands in the near-infrared region as well as interesting properties in different solvents. The interaction of differently sulphonated titanium and tantalum phthalocyanine complexes with methyl viologen (MV[superscript 2+]), and hence the stoichiometry and association constants are evaluated. Detailed photophysicochemical properties of the complexes were investigated and are for the first time presented with fluorescence lifetimes easily obtained from fluorescence quenching studies. The transformation of 1-hexene photocatalysed by aryloxy- and arylthio-appended complexes is also presented for the first time. The electrochemical properties of the complexes are unknown and are thus presented. Cyclic (CV) and square wave (SWV) voltammetries, chronocoulometry and spectroelectrochemistry are employed in the study of the complexes. Two oneelectron reductions and a simultaneous 4-electron reduction are observed for the unsubstituted Cl[subscript 3]TaPc. Reduction occurs first at the metal followed by ring-based processes. The tetra- and octa-substituted derivatives however exhibit peculiar electrochemical behaviour where a multi-electron transfer process occurs for complexes bearing certain substituents. For all complexes, the first two reductions are metal-based followed by ring-based processes. A comparative study of the electrocatalytic activities of the complexes towards the oxidation of nitrite is also investigated. The complexes are immobilised onto a glassy carbon electrode either by drop-dry or electropolymerisation methods. All the modified electrodes exhibit improved electrocatalytic oxidation of nitrite than the unmodified electrodes by a twoelectron mechanism producing nitrate ions. Catalytic currents are enhanced and nitrite overpotential reduced to ~ 0.60 V. Kinetic parameters are determined for all complexes and a mechanism is proposed. PART B: The syntheses and electrochemical characterisation of chromium and titanium complexes for the selective trimerisation of ethylene to 1-hexene are presented. The synthesis of the chromium complex requires simple steps while tedious steps are used for the air-sensitive titanium complex. The spectroscopic interaction of the chromium complex with the co-catalyst methylaluminoxane is investigated. The complexes are characterised by electrochemical methods such as cyclic voltammetry and spectroelectrochemistry.
- Full Text:
- Date Issued: 2007
Synthesis, properties and reactions of Novel Quinone Methides
- Authors: Taljaard, Jana Heloïse
- Date: 2007
- Subjects: Quinone , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10408 , http://hdl.handle.net/10948/616 , Quinone , Chemistry, Organic
- Description: Novel p-quinone methides have been synthesized by the dealkylation of 5-(p-alkyloxyaryl)- 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ols and related compounds. Aspects of the dealkylation reaction were investigated using computational methods in order to identify possible intermediates and postulate reasons for the observed reactivity patterns. This included studying the effect of varying the size of the central B-ring, changing the alkyloxy group, and altering the substitution pattern on the parent alcohols. We have assessed the relative energies of reaction intermediates and have also evaluated the influence of factors such as charge delocalisation, LUMO properties of the carbocations and thermodynamic factors on the dealkylation reaction. The use of different dealkylating reagents was also briefly investigated. Demethylation of 1,3- dimethyl-11-(4-methoxyphenyl)-6,11-dihydrodibenzo[b,e]oxepin-11-ol with pyridine hydrochloride led to acid-catalyzed ring-contraction of the parent alcohol to form a novel substituted anthraquinone, 9-(4-hydroxyphenyl)-1,3-dimethyl-anthracen-10-(9H)-one, in good yield. The general reactivity of the p-quinone methides of interest to us was explored by subjecting these compounds to reaction with a range of nucleophiles (bases, Grignard reagents and alcohols). A range of aryl Grignard reagents were reacted with the p-quinone methides, with the main product isolated in almost all cases being the aryl-coupled 1,2-addition product. The nucleophilic addition reactions of alcohols were supported by a computational study and a probable reaction mechanism has been postulated. A base-catalyzed rearrangement is proposed to account for the formation of products in which dehydrogenation of the ethane bridge was observed. These studies showed that in these p-quinone methides, chemical reactivity is strongly influenced by steric crowding, resulting in reversal of the normal 1,2- vs. 1,6- selectivities expected for nucleophilic addition. The ketalization process was explored further using diols and thiols. Products analogous to those obtained with the monohydric alcohols resulted from the diols, along with a series of novel bis-ethers. A range of miscellaneous reactions of 4-(dibenzo[a,d]cycloheptan-5-ylidene)cyclohexa-2,5,- dienone and related systems were investigated. Functionalization by epoxidation, dichlorocarbenation and Diels-Alder reactions, photochemical and [2+2] cycloaddition were attempted and reduction and oxidation reactions were also explored. Photochemical demethylation of an ortho-methoxyl substituent on the p-quinone methide system was observed to occur in good yield. The p-quinone methides underwent reductive coupling in the presence of Zn/AlCl3. The electronic spectra of highly conjugated carbocations were obtained and their potential as novel dyes evaluated. A low-temperature Grignard exchange reaction followed by spontaneous cyclization upon workup, was successful in synthesizing the lactone, spiro[10,11- dihydro-5H-dibenzo[a,d]cyclohepten-(3’,4’H)-phenyl-5,2’(5’H)-furan-5’-one], in one step from the starting ketone. A novel seven-membered Malachite Green dye analogue, 11-(4- dimethylamino-phenyl)-3-morpholin-4-yl-6,11-dihydro-dibenzo[b,e]oxepin-11-ol, was also synthesized and its electronic spectra compared to that of the unannulated Malachite Green dye series. All novel compounds synthesized were characterized using NMR, IR and HRMS-analysis.
- Full Text:
- Date Issued: 2007
- Authors: Taljaard, Jana Heloïse
- Date: 2007
- Subjects: Quinone , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10408 , http://hdl.handle.net/10948/616 , Quinone , Chemistry, Organic
- Description: Novel p-quinone methides have been synthesized by the dealkylation of 5-(p-alkyloxyaryl)- 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ols and related compounds. Aspects of the dealkylation reaction were investigated using computational methods in order to identify possible intermediates and postulate reasons for the observed reactivity patterns. This included studying the effect of varying the size of the central B-ring, changing the alkyloxy group, and altering the substitution pattern on the parent alcohols. We have assessed the relative energies of reaction intermediates and have also evaluated the influence of factors such as charge delocalisation, LUMO properties of the carbocations and thermodynamic factors on the dealkylation reaction. The use of different dealkylating reagents was also briefly investigated. Demethylation of 1,3- dimethyl-11-(4-methoxyphenyl)-6,11-dihydrodibenzo[b,e]oxepin-11-ol with pyridine hydrochloride led to acid-catalyzed ring-contraction of the parent alcohol to form a novel substituted anthraquinone, 9-(4-hydroxyphenyl)-1,3-dimethyl-anthracen-10-(9H)-one, in good yield. The general reactivity of the p-quinone methides of interest to us was explored by subjecting these compounds to reaction with a range of nucleophiles (bases, Grignard reagents and alcohols). A range of aryl Grignard reagents were reacted with the p-quinone methides, with the main product isolated in almost all cases being the aryl-coupled 1,2-addition product. The nucleophilic addition reactions of alcohols were supported by a computational study and a probable reaction mechanism has been postulated. A base-catalyzed rearrangement is proposed to account for the formation of products in which dehydrogenation of the ethane bridge was observed. These studies showed that in these p-quinone methides, chemical reactivity is strongly influenced by steric crowding, resulting in reversal of the normal 1,2- vs. 1,6- selectivities expected for nucleophilic addition. The ketalization process was explored further using diols and thiols. Products analogous to those obtained with the monohydric alcohols resulted from the diols, along with a series of novel bis-ethers. A range of miscellaneous reactions of 4-(dibenzo[a,d]cycloheptan-5-ylidene)cyclohexa-2,5,- dienone and related systems were investigated. Functionalization by epoxidation, dichlorocarbenation and Diels-Alder reactions, photochemical and [2+2] cycloaddition were attempted and reduction and oxidation reactions were also explored. Photochemical demethylation of an ortho-methoxyl substituent on the p-quinone methide system was observed to occur in good yield. The p-quinone methides underwent reductive coupling in the presence of Zn/AlCl3. The electronic spectra of highly conjugated carbocations were obtained and their potential as novel dyes evaluated. A low-temperature Grignard exchange reaction followed by spontaneous cyclization upon workup, was successful in synthesizing the lactone, spiro[10,11- dihydro-5H-dibenzo[a,d]cyclohepten-(3’,4’H)-phenyl-5,2’(5’H)-furan-5’-one], in one step from the starting ketone. A novel seven-membered Malachite Green dye analogue, 11-(4- dimethylamino-phenyl)-3-morpholin-4-yl-6,11-dihydro-dibenzo[b,e]oxepin-11-ol, was also synthesized and its electronic spectra compared to that of the unannulated Malachite Green dye series. All novel compounds synthesized were characterized using NMR, IR and HRMS-analysis.
- Full Text:
- Date Issued: 2007
The biology and systematics of South African pipefishes of the genus Syngnathus
- Authors: Mwale, Monica
- Date: 2007
- Subjects: Pipefishes -- South Africa Syngnathus -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5237 , http://hdl.handle.net/10962/d1005080
- Description: Syngnathus the most speciose genus in the family Syngnathidae is widely in the Atlantic and Eastern Pacific oceans. However, it is poorly represented in the Indian Ocean with the only two species, Syngnathus temminckii and S. watermeyeri occurring in Southern African estuaries and coastal areas. Syngnathus temminckii the most common South African pipefish has been synonymised with S. acus, as the morphological and genetic divergence between these two populations has not been documented. There is also uncertainty in the taxonomic status of S. watermeyeri, an endemic estuarine pipefish that is restricted to two Eastern Cape estuaries. The purpose of this study was therefore to compare biological, morphological and genetic variation of South African Syngnathus species among different populations/locations, and with European populations of S. acus. Sixteen meristic and ten morphometric characteristics were quantified from specimens obtained from field as well as various international natural history museum collections. Univariate (ANOVA) and multivariate (principal component analysis and discriminant analyses) analyses were used to assess morphological differences among the species. Morphometric variables were adjusted as ratios of the standard length and using an allometric procedure. ANCOVA analysis indicated significant differences between S. acus and S. temminckii for the relationships of the standard length (SL) and all morphological characters. There was no significant correlation between SL and snout length, snout depth, inter-orbital width and trunk depth for S. watermeyeri. The analyses provided evidence for distinct populations of S. acus, S. temminckii and S. watermeyeri although morphological character differentiation was greater between S. watermeyeri and the other two larger species. Although, significant differences were observed for meristic characters, pairwise comparisons did not reflect a clear pattern of variability. Most of the measured morphological characters contributed more than 70% to the morphological variation between the populations. Plot of the canonical scores for the variables resulted in the specimens clustering according to species groups and locations of S. temminckii. Sequences of 750 base pairs of the mitochondrial cytochrome gene from 11 localities were compared with published sequences of other species of Syngnathus. Phylogenetic analysis was performed using parsimony, maximum likelihood (ML) and Bayesian inference (BI). The South African species were revealed to be sister-taxa with about 6 % divergence, while S. temminckii and S. acus had about 11% sequence divergence. 20 haplotypes among 46 total specimens from the three species. Gene flow was estimated at approximately 3 migrants per generation between the two South African populations and about 1 per generation between S. temminckii and S. acus. Such strong stock structuring among presumably recently established post-Pliocene (< 2 Million years ago) populations suggests that these species are reproductively isolated. Morphological and genetic variation observed in this study combined with current knowledge of life history attributes of the South African pipefishes indicate that conservative management decisions are necessary until the patterns and extent of differentiation among populations species-wide can be investigated further. It is thus being proposed that the name of the South African population of S. acus be changed to Syngnathus temminckii (Kaup, 1856).
- Full Text:
- Date Issued: 2007
- Authors: Mwale, Monica
- Date: 2007
- Subjects: Pipefishes -- South Africa Syngnathus -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5237 , http://hdl.handle.net/10962/d1005080
- Description: Syngnathus the most speciose genus in the family Syngnathidae is widely in the Atlantic and Eastern Pacific oceans. However, it is poorly represented in the Indian Ocean with the only two species, Syngnathus temminckii and S. watermeyeri occurring in Southern African estuaries and coastal areas. Syngnathus temminckii the most common South African pipefish has been synonymised with S. acus, as the morphological and genetic divergence between these two populations has not been documented. There is also uncertainty in the taxonomic status of S. watermeyeri, an endemic estuarine pipefish that is restricted to two Eastern Cape estuaries. The purpose of this study was therefore to compare biological, morphological and genetic variation of South African Syngnathus species among different populations/locations, and with European populations of S. acus. Sixteen meristic and ten morphometric characteristics were quantified from specimens obtained from field as well as various international natural history museum collections. Univariate (ANOVA) and multivariate (principal component analysis and discriminant analyses) analyses were used to assess morphological differences among the species. Morphometric variables were adjusted as ratios of the standard length and using an allometric procedure. ANCOVA analysis indicated significant differences between S. acus and S. temminckii for the relationships of the standard length (SL) and all morphological characters. There was no significant correlation between SL and snout length, snout depth, inter-orbital width and trunk depth for S. watermeyeri. The analyses provided evidence for distinct populations of S. acus, S. temminckii and S. watermeyeri although morphological character differentiation was greater between S. watermeyeri and the other two larger species. Although, significant differences were observed for meristic characters, pairwise comparisons did not reflect a clear pattern of variability. Most of the measured morphological characters contributed more than 70% to the morphological variation between the populations. Plot of the canonical scores for the variables resulted in the specimens clustering according to species groups and locations of S. temminckii. Sequences of 750 base pairs of the mitochondrial cytochrome gene from 11 localities were compared with published sequences of other species of Syngnathus. Phylogenetic analysis was performed using parsimony, maximum likelihood (ML) and Bayesian inference (BI). The South African species were revealed to be sister-taxa with about 6 % divergence, while S. temminckii and S. acus had about 11% sequence divergence. 20 haplotypes among 46 total specimens from the three species. Gene flow was estimated at approximately 3 migrants per generation between the two South African populations and about 1 per generation between S. temminckii and S. acus. Such strong stock structuring among presumably recently established post-Pliocene (< 2 Million years ago) populations suggests that these species are reproductively isolated. Morphological and genetic variation observed in this study combined with current knowledge of life history attributes of the South African pipefishes indicate that conservative management decisions are necessary until the patterns and extent of differentiation among populations species-wide can be investigated further. It is thus being proposed that the name of the South African population of S. acus be changed to Syngnathus temminckii (Kaup, 1856).
- Full Text:
- Date Issued: 2007
The development and transfer of core competencies in multinational corporations : a study of three South African originated multinational corporations, compared and contrasted with a leading United States multinational
- Authors: Harvey, Neil M
- Date: 2007
- Subjects: Management -- South Africa International business enterprises -- South Afrca International business enterprises -- United States Core competencies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1197 , http://hdl.handle.net/10962/d1008369
- Description: The thesis studies the development and transfer of core competencies in multinational corporations. It aims to advance the general body of knowledge relating to core competencies, to have practical applicability for management practitioners and academics, to explain how three companies from South Africa became global leaders in their fields and to examine the lessons they learned about international business. Three South African originated multinationals and a US multinational company were studied. The basic methodology is a case study. The methods of research were personal interviews, telephone interviews, written questionnaires, documents, archival records and direct observations. Value chains were used to evaluate the effectiveness of methods of development and transfer and the success of transfer of core competencies. It is concluded that different and multiple methods are needed to develop and transfer core competencies. The effectiveness of methods varies by company and value chain location. There is a significant high degree of correlation between the ratings of success in transferring core competencies and the effectiveness of the methods used to transfer them. This gives substantial credibility to the information provided by the companies and highlights the importance of selecting appropriate methods. There are some variances between the research results and established literature on the development and transfer of core competencies. There are notable differences between the companies from South Africa and the US multinational on the effectiveness of methods used to develop and transfer core competencies. There are also areas where all the companies are in accord. "Roadmaps" covering the effectiveness of methods for developing and transferring core competencies in different locations in a value chain are presented. Practical examples of the companies' actions relating to acquisitions and post-acquisition integration, their experiences in different countries, challenges they face, the methods used to assess transfer, avoid pitfalls and improve transfer, and other issues are also provided.The success of the multinationals from South Africa is explained by a combination of history, competitive factor conditions, management practices, attributes and leadership. The conclusions of the thesis are followed by recommendations on how to improve the management, development and transfer of core competencies.
- Full Text:
- Date Issued: 2007
- Authors: Harvey, Neil M
- Date: 2007
- Subjects: Management -- South Africa International business enterprises -- South Afrca International business enterprises -- United States Core competencies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1197 , http://hdl.handle.net/10962/d1008369
- Description: The thesis studies the development and transfer of core competencies in multinational corporations. It aims to advance the general body of knowledge relating to core competencies, to have practical applicability for management practitioners and academics, to explain how three companies from South Africa became global leaders in their fields and to examine the lessons they learned about international business. Three South African originated multinationals and a US multinational company were studied. The basic methodology is a case study. The methods of research were personal interviews, telephone interviews, written questionnaires, documents, archival records and direct observations. Value chains were used to evaluate the effectiveness of methods of development and transfer and the success of transfer of core competencies. It is concluded that different and multiple methods are needed to develop and transfer core competencies. The effectiveness of methods varies by company and value chain location. There is a significant high degree of correlation between the ratings of success in transferring core competencies and the effectiveness of the methods used to transfer them. This gives substantial credibility to the information provided by the companies and highlights the importance of selecting appropriate methods. There are some variances between the research results and established literature on the development and transfer of core competencies. There are notable differences between the companies from South Africa and the US multinational on the effectiveness of methods used to develop and transfer core competencies. There are also areas where all the companies are in accord. "Roadmaps" covering the effectiveness of methods for developing and transferring core competencies in different locations in a value chain are presented. Practical examples of the companies' actions relating to acquisitions and post-acquisition integration, their experiences in different countries, challenges they face, the methods used to assess transfer, avoid pitfalls and improve transfer, and other issues are also provided.The success of the multinationals from South Africa is explained by a combination of history, competitive factor conditions, management practices, attributes and leadership. The conclusions of the thesis are followed by recommendations on how to improve the management, development and transfer of core competencies.
- Full Text:
- Date Issued: 2007
The effect of HIV and AIDS on the viability and management of forestry contracting businesses in South Africa
- Authors: Steenkamp, Jacob Cornelus
- Date: 2007
- Subjects: Forest products Industry -- South Africa -- Employees -- Disease , AIDS (Disease) -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Doctoral , DBA
- Identifier: vital:8768 , http://hdl.handle.net/10948/735 , Forest products Industry -- South Africa -- Employees -- Disease , AIDS (Disease) -- Economic aspects -- South Africa
- Description: The aim of the research is to quantify the HIV prevalence in human resources of forestry contracting businesses and to develop a management framework to promote economic sustainability of forestry contractors. HIV tests were conducted in the forest industry on the employees of contracting concerns from 2002/2003 to 2004/2005 with an accompanying questionnaire to collect demographic data. The HIV test results were analyzed with the demographic data to determine relationships between HIV prevalence and demographic factors. Contractors responded to a questionnaire on the effect of HIV and AIDS prevalence on (their) contracting businesses. The questionnaire also collected information about HIV and AIDS interventions and assistance to HIV and AIDS affected employees. Key stakeholders of other forestry sub-sectors were interviewed to facilitate comparison of the different sub-sectors and to establish if there were major differences between the sub-sectors, however, the focus was on the human resources of the forestry contracting sub-sector. The research results indicated that the HIV prevalence was increasing for the research period and was, in some regions, exceeding 40 per cent. The highest prevalence was recorded in the Highveld and Zululand regions and the lowest prevalence in the North-Eastern Cape. The HIV prevalence for females was constantly higher than the incidence for males and the ratio of males to females (all regions) approximated 68 per cent to 32 per cent. The high prevalence of HIV results in major social and economic impacts. The economic impact is aggravated through regulation (due to perceived market failure) and a bid for more equal distribution of wealth in the economy. The result of the sum of the impacts alludes to a conversion from labour to capital; however, to make well-informed decisions, various scenarios should be simulated to establish the optimum labour to capital ratio. The research further established that appropriate staffing is increasingly difficult and that the development of human capital is under pressure due to the high prevalence of HIV and AIDS. HIV and AIDS mitigation programmes will make a significant contribution to the return on human capital assets, as the economic life and productivity of such assets will be enhanced by such interventions. The management framework developed was assessed to be visually acceptable and useful by domain experts; however, to realise the full potential of the framework it should be used with anticipation of the research results regarding prevalence and future estimated AIDS releases and in conjunction with industry cost simulation models.
- Full Text:
- Date Issued: 2007
- Authors: Steenkamp, Jacob Cornelus
- Date: 2007
- Subjects: Forest products Industry -- South Africa -- Employees -- Disease , AIDS (Disease) -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Doctoral , DBA
- Identifier: vital:8768 , http://hdl.handle.net/10948/735 , Forest products Industry -- South Africa -- Employees -- Disease , AIDS (Disease) -- Economic aspects -- South Africa
- Description: The aim of the research is to quantify the HIV prevalence in human resources of forestry contracting businesses and to develop a management framework to promote economic sustainability of forestry contractors. HIV tests were conducted in the forest industry on the employees of contracting concerns from 2002/2003 to 2004/2005 with an accompanying questionnaire to collect demographic data. The HIV test results were analyzed with the demographic data to determine relationships between HIV prevalence and demographic factors. Contractors responded to a questionnaire on the effect of HIV and AIDS prevalence on (their) contracting businesses. The questionnaire also collected information about HIV and AIDS interventions and assistance to HIV and AIDS affected employees. Key stakeholders of other forestry sub-sectors were interviewed to facilitate comparison of the different sub-sectors and to establish if there were major differences between the sub-sectors, however, the focus was on the human resources of the forestry contracting sub-sector. The research results indicated that the HIV prevalence was increasing for the research period and was, in some regions, exceeding 40 per cent. The highest prevalence was recorded in the Highveld and Zululand regions and the lowest prevalence in the North-Eastern Cape. The HIV prevalence for females was constantly higher than the incidence for males and the ratio of males to females (all regions) approximated 68 per cent to 32 per cent. The high prevalence of HIV results in major social and economic impacts. The economic impact is aggravated through regulation (due to perceived market failure) and a bid for more equal distribution of wealth in the economy. The result of the sum of the impacts alludes to a conversion from labour to capital; however, to make well-informed decisions, various scenarios should be simulated to establish the optimum labour to capital ratio. The research further established that appropriate staffing is increasingly difficult and that the development of human capital is under pressure due to the high prevalence of HIV and AIDS. HIV and AIDS mitigation programmes will make a significant contribution to the return on human capital assets, as the economic life and productivity of such assets will be enhanced by such interventions. The management framework developed was assessed to be visually acceptable and useful by domain experts; however, to realise the full potential of the framework it should be used with anticipation of the research results regarding prevalence and future estimated AIDS releases and in conjunction with industry cost simulation models.
- Full Text:
- Date Issued: 2007
The evaluation of a pedagogical-program development environment for Novice programmers : a comparative study
- Authors: Vogts, Dieter
- Date: 2007
- Subjects: Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10477 , http://hdl.handle.net/10948/638 , Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Description: It is an acknowledged fact that many novice programmers experience difficulty in the process of learning to program. One of the contributing factors to this difficulty is the Program Development Environment (PDE). Professional-PDEs are those developed specifically for professional programmers, but are often used by educational institutions in the instruction of programming. It has long been accepted that such environments are inappropriate in the instruction of programming due to unnecessary complexity and lack of support for novice programmers in the learning process. Numerous pedagogical-PDEs supporting the mechanics of programming have been developed in response to this. A review of literature, however, indicates that very limited empirical studies comparing pedagogical-PDEs and professional-PDEs have been conducted. The current study investigates whether there are measurable benefits to using a pedagogical-PDE supporting the mechanics of programming in the instruction of programming instead of a professional-PDE. A comparative study of this nature requires a representative pedagogical-PDE and representative professional-PDE be compared with one another. The first part of the current study determines a set of requirements that a pedagogical- PDE should adhere to based on literature. A set of representative features for a pedagogical-PDE is derived by examining the features of existing PDEs in conjunction with the set of requirements. Based on these features, a pedagogical-PDE, known as SimplifIDE, is developed that implements the representative set of features and that meets are the requirements for a pedagogical-PDE. The second part of the current study is the specification and administration of an empirical experiment in which SimplifIDE and Borland© DelphiTM are compared with one another. A holistic approach in determining the differences between the PDEs is taken and three main areas are examined, namely academic performance, perceptions and programming behavior.
- Full Text:
- Date Issued: 2007
- Authors: Vogts, Dieter
- Date: 2007
- Subjects: Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10477 , http://hdl.handle.net/10948/638 , Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Description: It is an acknowledged fact that many novice programmers experience difficulty in the process of learning to program. One of the contributing factors to this difficulty is the Program Development Environment (PDE). Professional-PDEs are those developed specifically for professional programmers, but are often used by educational institutions in the instruction of programming. It has long been accepted that such environments are inappropriate in the instruction of programming due to unnecessary complexity and lack of support for novice programmers in the learning process. Numerous pedagogical-PDEs supporting the mechanics of programming have been developed in response to this. A review of literature, however, indicates that very limited empirical studies comparing pedagogical-PDEs and professional-PDEs have been conducted. The current study investigates whether there are measurable benefits to using a pedagogical-PDE supporting the mechanics of programming in the instruction of programming instead of a professional-PDE. A comparative study of this nature requires a representative pedagogical-PDE and representative professional-PDE be compared with one another. The first part of the current study determines a set of requirements that a pedagogical- PDE should adhere to based on literature. A set of representative features for a pedagogical-PDE is derived by examining the features of existing PDEs in conjunction with the set of requirements. Based on these features, a pedagogical-PDE, known as SimplifIDE, is developed that implements the representative set of features and that meets are the requirements for a pedagogical-PDE. The second part of the current study is the specification and administration of an empirical experiment in which SimplifIDE and Borland© DelphiTM are compared with one another. A holistic approach in determining the differences between the PDEs is taken and three main areas are examined, namely academic performance, perceptions and programming behavior.
- Full Text:
- Date Issued: 2007
The idea of regionalism in West and Southern Africa : a critical social enquiry
- Authors: Lindsay, Albert Domson
- Date: 2007
- Subjects: Regionalism -- Africa, West Regionalism -- Africa, Southern Africa, West -- Politics and government Africa, Southern -- Politics and government Africa -- Foreign relations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2848 , http://hdl.handle.net/10962/d1006118
- Description: Traditional views on International Relations dominate regional analyses. These invariably emphasize the dominance of state and market forces in inter-state relations. Experiences and expectations of people are less prominent in these discourses, and the practices they foster. This thesis critically analyses the regional processes in West and southern Africa within the framework of Critical Theory. It argues that these processes are constrained by instability and the increasing legitimacy crises of the State. The thesis demonstrates that the State, through exclusive nationalist practices, hinder the growth of a cosmopolitan order, and it argues that neo-liberal regionalism is a contested phenomenon because of its exclusive nature. Finally, the thesis suggests steps needed to resolve the legitimacy crises and to build an inclusive regional order, based on cosmopolitan values.
- Full Text:
- Date Issued: 2007
- Authors: Lindsay, Albert Domson
- Date: 2007
- Subjects: Regionalism -- Africa, West Regionalism -- Africa, Southern Africa, West -- Politics and government Africa, Southern -- Politics and government Africa -- Foreign relations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2848 , http://hdl.handle.net/10962/d1006118
- Description: Traditional views on International Relations dominate regional analyses. These invariably emphasize the dominance of state and market forces in inter-state relations. Experiences and expectations of people are less prominent in these discourses, and the practices they foster. This thesis critically analyses the regional processes in West and southern Africa within the framework of Critical Theory. It argues that these processes are constrained by instability and the increasing legitimacy crises of the State. The thesis demonstrates that the State, through exclusive nationalist practices, hinder the growth of a cosmopolitan order, and it argues that neo-liberal regionalism is a contested phenomenon because of its exclusive nature. Finally, the thesis suggests steps needed to resolve the legitimacy crises and to build an inclusive regional order, based on cosmopolitan values.
- Full Text:
- Date Issued: 2007
The kinetics and associated equilibria of high oxidation state osmium complexes
- Authors: McFadzean, Belinda Julie
- Date: 2007
- Subjects: Chemical equilibrium , Osmium , Chemical kinetics , Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10371 , http://hdl.handle.net/10948/732 , Chemical equilibrium , Osmium , Chemical kinetics , Chemistry
- Description: The reduction of osmium tetroxide by a series of alcohols was studied spectrophotometrically. The reaction was observed to occur in two steps, unlike previously reported studies on this reaction. The identities of both reactants and products were established via a range of techniques. Equilibrium and kinetic data were gathered and reaction models were evaluated using equilibrium and kinetic modelling software. The following complexation reaction model emerged that simulates both the equilibrium and kinetic data. Os(VIII) + RCH2OHOs(VI) + RCHO2 Os(VIII) + Os(VI)k+2k1Complexk-2 Conditional rate constants and equilibrium constants were generated. Rate constants for the alcohol reactions were correlated with the Taft σ* constant. The ρ* value obtained (-1.4) is consistent with a hydride transfer mechanism coupled with synchronous removal of the hydroxyl proton. The identity of the osmium(VIII)-osmium(VI) complex has been suggested. Thermodynamic parameters were also reported. The rate constants for benzyl alcohol and 2-chloroethanol deviated from those predicted by the Taft plot. An explanation of enhanced resonance effects is offered for benzyl alcohol and an alternative reaction mechanism, involving proton abstraction, is offered for 2-chloroethanol. The reaction of the oxidation products of alcohols, namely ketones, with osmium tetroxide produced rate constants that were, perhaps surprisingly, far larger than those of the alcohols. A reaction mechanism for the oxidation of the ketones is suggested, which involves the enolate ion as the reactive starting reagent.
- Full Text:
- Date Issued: 2007
- Authors: McFadzean, Belinda Julie
- Date: 2007
- Subjects: Chemical equilibrium , Osmium , Chemical kinetics , Chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10371 , http://hdl.handle.net/10948/732 , Chemical equilibrium , Osmium , Chemical kinetics , Chemistry
- Description: The reduction of osmium tetroxide by a series of alcohols was studied spectrophotometrically. The reaction was observed to occur in two steps, unlike previously reported studies on this reaction. The identities of both reactants and products were established via a range of techniques. Equilibrium and kinetic data were gathered and reaction models were evaluated using equilibrium and kinetic modelling software. The following complexation reaction model emerged that simulates both the equilibrium and kinetic data. Os(VIII) + RCH2OHOs(VI) + RCHO2 Os(VIII) + Os(VI)k+2k1Complexk-2 Conditional rate constants and equilibrium constants were generated. Rate constants for the alcohol reactions were correlated with the Taft σ* constant. The ρ* value obtained (-1.4) is consistent with a hydride transfer mechanism coupled with synchronous removal of the hydroxyl proton. The identity of the osmium(VIII)-osmium(VI) complex has been suggested. Thermodynamic parameters were also reported. The rate constants for benzyl alcohol and 2-chloroethanol deviated from those predicted by the Taft plot. An explanation of enhanced resonance effects is offered for benzyl alcohol and an alternative reaction mechanism, involving proton abstraction, is offered for 2-chloroethanol. The reaction of the oxidation products of alcohols, namely ketones, with osmium tetroxide produced rate constants that were, perhaps surprisingly, far larger than those of the alcohols. A reaction mechanism for the oxidation of the ketones is suggested, which involves the enolate ion as the reactive starting reagent.
- Full Text:
- Date Issued: 2007