Making visible constructions of dis/advantage through genealogical investigation: South African schooled literacies
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147869 , vital:38680 , DOI: 10.1080/02560040701398889
- Description: In this paper I assume the relevance of Foucauldian insights for conducting socio-cultural critique and I argue the significance of genealogical work in relation to understanding the present. Thus, I seek both to establish what could constitute a genealogical investigation and to illustrate this by describing and discussing a study, undertaken within a genealogical frame, into literacy practices within a specifically South African context. I investigated the differing schooled literacies in KwaZulu-Natal province in South Africa over three decades along the language lines of Afrikaans, English and Zulu. The findings propose that the differing sets of literacy practices validate different subjects – and that they are implicated in constructing dis/advantage.
- Full Text:
- Date Issued: 2007
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/147869 , vital:38680 , DOI: 10.1080/02560040701398889
- Description: In this paper I assume the relevance of Foucauldian insights for conducting socio-cultural critique and I argue the significance of genealogical work in relation to understanding the present. Thus, I seek both to establish what could constitute a genealogical investigation and to illustrate this by describing and discussing a study, undertaken within a genealogical frame, into literacy practices within a specifically South African context. I investigated the differing schooled literacies in KwaZulu-Natal province in South Africa over three decades along the language lines of Afrikaans, English and Zulu. The findings propose that the differing sets of literacy practices validate different subjects – and that they are implicated in constructing dis/advantage.
- Full Text:
- Date Issued: 2007
Rhodes University Research Report 2007
- Authors: Rhodes University
- Date: 2007
- Language: English
- Type: Text
- Identifier: vital:562 , http://hdl.handle.net/10962/d1011958
- Description: [From Introduction] For the past 8 years Rhodes University has maintained a research output record (based on publications and Masters and PhD graduates) which has placed it consistently amongst the top three universities in the country on the basis of outputs per capita academic staff member. The past year was no exception. Journal publications were the highest to date (261.9 units) and Masters and PhD graduates (274 units) are amongst the highest achieved, largely due to the record number of PhD graduates (33) in the Science Faculty. In recent years this per capita output has consistently been over 60% higher than the national average. An encouraging aspect of the journal publications in 2007 is the increase in the percentage of articles in subsidy earning journals. While it is appreciated that the most appropriate journals in certain fields of research are not always those that are on the Department of Education’s approved lists, it is financially critical to the University’s research effort and the University as a whole that subsidy earning outputs are maximised. Another positive outcome of the most recent audit of Rhodes’s research outputs (2006; 2007 data will only be available at the end of 2008) is that 89% of the publications in the form of books, chapters and conference proceedings submitted to the Department of Education were approved for subsidy. This is a significantly higher percentage approval than in the past. The award of two highly prestigious NRF/DST Research Chairs to Profs Tebello Nyokong and Christopher McQuaid as part of the first round of the SA Research Chairs Initiative was another major achievement. These Chairs will significantly enhance the research profile and productivity of the University as will the recent award of the highly prestigious Centre of Excellence in Nanotechnology to be headed by Prof Nyokong. Only three such centres of excellence have been established and were officially launched by the Minister of Science and Technology in November 2007. The Centre will be host to researchers from throughout South Africa and will focus on novel technologies for cancer treatment and the development of new biosensors for disease treatment and water contamination. An encouraging statistic recently released by the National Research Foundation indicates that Rhodes has the fourth highest percentage (15.4%) of rated researchers in the country which is an excellent achievement. NRF ratings are awarded to researchers in all disciplines who are regarded as national and international leaders in their fields. Amongst these researchers, three were also recognised by the University and were awarded the Vice-Chancellor’s Research Awards (see highlights section). Postgraduate students have once again been the cornerstone of much of the research activities in all Faculties and have contributed significantly to the research outputs of the University both as co-authors on publications and through the good graduation rates of Masters and PhD candidates. This is particularly evident for example in the Science Faculty, in which Masters and Doctoral students contributed to over 90% of the Faculty and 60% of the University’s outputs. A key factor in the high profile and success of postgraduates at Rhodes is the excellent supervision they receive and all supervisors are to be congratulated for their dedicated approach to what has become an increasingly onerous academic responsibility. They and the Research Office have benefited enormously from the very able support of the Postgraduate Liaison Committee chaired for a second year by Dan Parker. The work of this committee is highly valued. Finally, this will be my last contribution to the annual Rhodes Research Reports as I will be retiring at the end of 2008. I would like to wish my successor with responsibility for Research at Rhodes, the new DVC: R&D Dr Peter Clayton, every success in the future which I am confident will see research at the University going from strength to strength. I would also like to take the opportunity to express my sincere and grateful thanks to all those who have supported me and contributed to the success of Rhodes research in my past 10 years as Dean of Research. This includes two Vice-Chancellors, members of Senior Management, Deans, Heads of Department and staff and postgraduate students in both academic departments and administrative divisions. In particular, a very big thank you to all the staff who have worked in the Research Office and have made such a significant contribution over this past decade. Special mention must be made of my first Assistant, Moira Pogrund, who was instrumental in the establishment and success of the Research Office from its inception in 1998. She gave true meaning to the word efficiency and her outstanding contribution is being continued by the excellent work of her successor, Dr Heather Davies-Coleman. John Gillam has been a tower of strength in the management and administration of postgraduate financial aid and has been an invaluable advisor and confidant to countless postgraduate students over this period.
- Full Text:
- Date Issued: 2007
- Authors: Rhodes University
- Date: 2007
- Language: English
- Type: Text
- Identifier: vital:562 , http://hdl.handle.net/10962/d1011958
- Description: [From Introduction] For the past 8 years Rhodes University has maintained a research output record (based on publications and Masters and PhD graduates) which has placed it consistently amongst the top three universities in the country on the basis of outputs per capita academic staff member. The past year was no exception. Journal publications were the highest to date (261.9 units) and Masters and PhD graduates (274 units) are amongst the highest achieved, largely due to the record number of PhD graduates (33) in the Science Faculty. In recent years this per capita output has consistently been over 60% higher than the national average. An encouraging aspect of the journal publications in 2007 is the increase in the percentage of articles in subsidy earning journals. While it is appreciated that the most appropriate journals in certain fields of research are not always those that are on the Department of Education’s approved lists, it is financially critical to the University’s research effort and the University as a whole that subsidy earning outputs are maximised. Another positive outcome of the most recent audit of Rhodes’s research outputs (2006; 2007 data will only be available at the end of 2008) is that 89% of the publications in the form of books, chapters and conference proceedings submitted to the Department of Education were approved for subsidy. This is a significantly higher percentage approval than in the past. The award of two highly prestigious NRF/DST Research Chairs to Profs Tebello Nyokong and Christopher McQuaid as part of the first round of the SA Research Chairs Initiative was another major achievement. These Chairs will significantly enhance the research profile and productivity of the University as will the recent award of the highly prestigious Centre of Excellence in Nanotechnology to be headed by Prof Nyokong. Only three such centres of excellence have been established and were officially launched by the Minister of Science and Technology in November 2007. The Centre will be host to researchers from throughout South Africa and will focus on novel technologies for cancer treatment and the development of new biosensors for disease treatment and water contamination. An encouraging statistic recently released by the National Research Foundation indicates that Rhodes has the fourth highest percentage (15.4%) of rated researchers in the country which is an excellent achievement. NRF ratings are awarded to researchers in all disciplines who are regarded as national and international leaders in their fields. Amongst these researchers, three were also recognised by the University and were awarded the Vice-Chancellor’s Research Awards (see highlights section). Postgraduate students have once again been the cornerstone of much of the research activities in all Faculties and have contributed significantly to the research outputs of the University both as co-authors on publications and through the good graduation rates of Masters and PhD candidates. This is particularly evident for example in the Science Faculty, in which Masters and Doctoral students contributed to over 90% of the Faculty and 60% of the University’s outputs. A key factor in the high profile and success of postgraduates at Rhodes is the excellent supervision they receive and all supervisors are to be congratulated for their dedicated approach to what has become an increasingly onerous academic responsibility. They and the Research Office have benefited enormously from the very able support of the Postgraduate Liaison Committee chaired for a second year by Dan Parker. The work of this committee is highly valued. Finally, this will be my last contribution to the annual Rhodes Research Reports as I will be retiring at the end of 2008. I would like to wish my successor with responsibility for Research at Rhodes, the new DVC: R&D Dr Peter Clayton, every success in the future which I am confident will see research at the University going from strength to strength. I would also like to take the opportunity to express my sincere and grateful thanks to all those who have supported me and contributed to the success of Rhodes research in my past 10 years as Dean of Research. This includes two Vice-Chancellors, members of Senior Management, Deans, Heads of Department and staff and postgraduate students in both academic departments and administrative divisions. In particular, a very big thank you to all the staff who have worked in the Research Office and have made such a significant contribution over this past decade. Special mention must be made of my first Assistant, Moira Pogrund, who was instrumental in the establishment and success of the Research Office from its inception in 1998. She gave true meaning to the word efficiency and her outstanding contribution is being continued by the excellent work of her successor, Dr Heather Davies-Coleman. John Gillam has been a tower of strength in the management and administration of postgraduate financial aid and has been an invaluable advisor and confidant to countless postgraduate students over this period.
- Full Text:
- Date Issued: 2007
The use of Landsat ETM imagery as a suitable data capture source for alien acacia species for the WFW programme
- Authors: Cobbing, Benedict Louis
- Date: 2007
- Subjects: Geographic information systems , Global Positioning System , Landsat satellites , Agriculture -- Remote sensing , Geography -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4856 , http://hdl.handle.net/10962/d1005532 , Geographic information systems , Global Positioning System , Landsat satellites , Agriculture -- Remote sensing , Geography -- Remote sensing
- Description: Geographic Information System technology today allows for the rapid analysis of vast amounts of spatial and non-spatial data. The power of a GIS can only be effected with the rapid collection of accurate input data. This is particularly true in the case of the South African National Working for Water (WFW) Programme where large volumes of spatial data on alien vegetation infestations are captured throughout the country. Alien vegetation clearing contracts cannot be generated, for WFW, without this data, so that the accurate capture of such data is crucial to the success of the programme. Mapping Invasive Alien Plant (IAP) data within WFW is a perennial problem (Coetzee, pers com, 2002), because not enough mapping is being done to meet the annual requirements of the programme in the various provinces. This is re-iterated by Richardson, 2004, who states that there is a shortage of accurate data on IAP abundance in South Africa. Therefore there is a need to investigate alternate methods of data capture; such as remote sensing, whilst working within the existing WFW data capture standards. The aim of this research was to investigate the use of Landsat ETM imagery as a data capture source for mapping alien vegetation for the WFW Programme in terms of their approved mapping methods, for both automated and manual classification techniques. The automated and manual classification results were compared to control data captured by differential Global Positioning Systems (DGPS). The research tested the various methods of data capture using Landsat ETM images over a range of study sites of varying complexity: a simple grassland area, a medium complexity grassy fynbos site and a complicated indigenous forest site. An important component of the research was to develop a mapping (classification) Ranking System based upon variables identified by WFW as fundamental in data capture decision making: spatial and positional accuracy, time constraints and cost constraints for three typical alien invaded areas. The mapping Ranking System compared the results of the various mapping methods for each factor for the study sites against each other. This provided an indication of which mapping method is the most efficient or suitable for a particular area.
- Full Text:
- Date Issued: 2007
- Authors: Cobbing, Benedict Louis
- Date: 2007
- Subjects: Geographic information systems , Global Positioning System , Landsat satellites , Agriculture -- Remote sensing , Geography -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4856 , http://hdl.handle.net/10962/d1005532 , Geographic information systems , Global Positioning System , Landsat satellites , Agriculture -- Remote sensing , Geography -- Remote sensing
- Description: Geographic Information System technology today allows for the rapid analysis of vast amounts of spatial and non-spatial data. The power of a GIS can only be effected with the rapid collection of accurate input data. This is particularly true in the case of the South African National Working for Water (WFW) Programme where large volumes of spatial data on alien vegetation infestations are captured throughout the country. Alien vegetation clearing contracts cannot be generated, for WFW, without this data, so that the accurate capture of such data is crucial to the success of the programme. Mapping Invasive Alien Plant (IAP) data within WFW is a perennial problem (Coetzee, pers com, 2002), because not enough mapping is being done to meet the annual requirements of the programme in the various provinces. This is re-iterated by Richardson, 2004, who states that there is a shortage of accurate data on IAP abundance in South Africa. Therefore there is a need to investigate alternate methods of data capture; such as remote sensing, whilst working within the existing WFW data capture standards. The aim of this research was to investigate the use of Landsat ETM imagery as a data capture source for mapping alien vegetation for the WFW Programme in terms of their approved mapping methods, for both automated and manual classification techniques. The automated and manual classification results were compared to control data captured by differential Global Positioning Systems (DGPS). The research tested the various methods of data capture using Landsat ETM images over a range of study sites of varying complexity: a simple grassland area, a medium complexity grassy fynbos site and a complicated indigenous forest site. An important component of the research was to develop a mapping (classification) Ranking System based upon variables identified by WFW as fundamental in data capture decision making: spatial and positional accuracy, time constraints and cost constraints for three typical alien invaded areas. The mapping Ranking System compared the results of the various mapping methods for each factor for the study sites against each other. This provided an indication of which mapping method is the most efficient or suitable for a particular area.
- Full Text:
- Date Issued: 2007
Rhenium(V)-Imido complexes with potentially multidentate ligands containing the amino group
- Authors: Booysen, Irvin Noel
- Date: 2007
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10385 , http://hdl.handle.net/10948/479 , Rhenium , Ligands
- Description: The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab=1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The complex trans-[Re(ada)Cl3(PPh3)2] (H2ada=2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re-Cl bond length trans to the Re=N bond is shorter than the two equatorial Re-Cl bond lengths. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux conditions led to the isolation of [C12H12N6O4] as only product. The [ReO4]- ion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of a twofold molar excess of H2apb (H2apb=2-(2-aminophenyl)-1Hbenzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of the formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonal-bipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. The complex has C2-symmetry. The two amino groups are singly deprotonated and provide a negative charge each, so that they are coordinated as amides. The oxo group provides two negative charges. In order to obtain electroneutrality for the rhenium(V) complex, the two coordinated imidazole nitrogens provide one negative charge. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps=N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans- [ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in trans- [Re(mps)Cl(PPh3)2](ReO4) as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The [ReO4]- anion has approximately regular tetrahedral geometry. Two significant hydrogen bonds are formed between two of the perrhenyl oxygens and the water of crystallization. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The Xray crystal structure shows that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.
- Full Text:
- Date Issued: 2007
- Authors: Booysen, Irvin Noel
- Date: 2007
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10385 , http://hdl.handle.net/10948/479 , Rhenium , Ligands
- Description: The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab=1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The complex trans-[Re(ada)Cl3(PPh3)2] (H2ada=2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re-Cl bond length trans to the Re=N bond is shorter than the two equatorial Re-Cl bond lengths. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux conditions led to the isolation of [C12H12N6O4] as only product. The [ReO4]- ion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of a twofold molar excess of H2apb (H2apb=2-(2-aminophenyl)-1Hbenzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of the formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonal-bipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. The complex has C2-symmetry. The two amino groups are singly deprotonated and provide a negative charge each, so that they are coordinated as amides. The oxo group provides two negative charges. In order to obtain electroneutrality for the rhenium(V) complex, the two coordinated imidazole nitrogens provide one negative charge. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps=N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans- [ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in trans- [Re(mps)Cl(PPh3)2](ReO4) as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The [ReO4]- anion has approximately regular tetrahedral geometry. Two significant hydrogen bonds are formed between two of the perrhenyl oxygens and the water of crystallization. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The Xray crystal structure shows that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.
- Full Text:
- Date Issued: 2007
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
Giving children a voice:
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159277 , vital:40283 , https://hdl.handle.net/10520/EJC144676
- Description: It was in Johannesburg, South Africa, that the fifth World Summit on Media and Children took place from 24 to 27 March - a great jamboree where a thousand or so delegates from around 86 countries congregated together with 300 young people between the ages of 13 and 16.
- Full Text:
- Date Issued: 2007
- Authors: Prinsloo, Jeanne
- Date: 2007
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159277 , vital:40283 , https://hdl.handle.net/10520/EJC144676
- Description: It was in Johannesburg, South Africa, that the fifth World Summit on Media and Children took place from 24 to 27 March - a great jamboree where a thousand or so delegates from around 86 countries congregated together with 300 young people between the ages of 13 and 16.
- Full Text:
- Date Issued: 2007
Studies towards the development of novel multidentate ligands
- Authors: Magqi, Nceba
- Date: 2007
- Subjects: Density functionals , Ligands , Ligands -- Design , Ligands -- Analysis , Camphor
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4358 , http://hdl.handle.net/10962/d1005023 , Density functionals , Ligands , Ligands -- Design , Ligands -- Analysis , Camphor
- Description: In this study, attention has been given to the design and synthesis of novel multidentate ligands for use in the construction of ruthenium-based metathesis catalysts, and their chelating potential has been explored by computer modelling at the Density Functional Theory (DFT) level. Both Kemp’s triacid (1,3,5-trimethyl-1,3,5-cyclohexanetricarboxylic acid) and D-(+)-camphor have been investigated as molecular scaffolds for the development of such ligands. However selective elaboration of the functional groups in Kemp’s triacid proved difficult to achieve, and the research has focused on the development of camphor derivatives. The synthesis of the camphor-based ligands has involved C-8 functionalisation and ring-opening of the bicyclic system to afford tridentate products. The formation of 9-iodocamphorquinone bis(ethylene ketal) together with the desired product, the 8-iodo isomer, has been confirmed by single crystal X-ray analysis of both compounds. Formation of the 9-iodo analogue has provided new insights into the intramolecular rearrangement of camphor skeleton, and the mechanistic implications have been assessed by coset analysis. Attempts to effect nucleophilic displacement of the 8-halogeno groups by nucleophilic donor moieties proved unexpectedly difficult and, coupled with the susceptibility of the carbonyl groups to nucleophilic attack, has led to the formation of novel tricyclic products, viz., 1,6-dimethyl-3-(2-pyridylamino)-4-oxatricyclo[4.3.0.0[superscript 3,7]]-2-nonanone and 6,7-dimethyl-3-(2-pyridylamino)-4-oxatricyclo -[4.3.0.0[superscript 3,7]]-2-nonanone. However the diphenylphosphine group was successfully introduced at C-8 and oxidative ring-opening of the camphor skeleton has afforded the tridentate ligands, 2-(diphenylphosphinoylmethyl)-1,2-dimethyl-1,3-cyclopentanedicarboxylic acid and 2-(diphenylphosphinoylmethyl)-1,3-bis(hydroxymethyl)1,2-dimethylcyclopentane. One- and two-dimensional NMR and, where appropriate, high-resolution MS methods have been used to characterise the products. Three [superscript 13]C NMR chemical shift prediction programmes, viz., ChemWindow and the MODGRAPH neural network and HOSE (Hierachially Ordered Spherical description of Environment), have been applied to representative compounds to assess their efficacy. While the predicted shifts correlated reasonably well with the experimental data, they proved to be insufficiently accurate to differentiate the isomeric systems examined.
- Full Text:
- Date Issued: 2007
- Authors: Magqi, Nceba
- Date: 2007
- Subjects: Density functionals , Ligands , Ligands -- Design , Ligands -- Analysis , Camphor
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4358 , http://hdl.handle.net/10962/d1005023 , Density functionals , Ligands , Ligands -- Design , Ligands -- Analysis , Camphor
- Description: In this study, attention has been given to the design and synthesis of novel multidentate ligands for use in the construction of ruthenium-based metathesis catalysts, and their chelating potential has been explored by computer modelling at the Density Functional Theory (DFT) level. Both Kemp’s triacid (1,3,5-trimethyl-1,3,5-cyclohexanetricarboxylic acid) and D-(+)-camphor have been investigated as molecular scaffolds for the development of such ligands. However selective elaboration of the functional groups in Kemp’s triacid proved difficult to achieve, and the research has focused on the development of camphor derivatives. The synthesis of the camphor-based ligands has involved C-8 functionalisation and ring-opening of the bicyclic system to afford tridentate products. The formation of 9-iodocamphorquinone bis(ethylene ketal) together with the desired product, the 8-iodo isomer, has been confirmed by single crystal X-ray analysis of both compounds. Formation of the 9-iodo analogue has provided new insights into the intramolecular rearrangement of camphor skeleton, and the mechanistic implications have been assessed by coset analysis. Attempts to effect nucleophilic displacement of the 8-halogeno groups by nucleophilic donor moieties proved unexpectedly difficult and, coupled with the susceptibility of the carbonyl groups to nucleophilic attack, has led to the formation of novel tricyclic products, viz., 1,6-dimethyl-3-(2-pyridylamino)-4-oxatricyclo[4.3.0.0[superscript 3,7]]-2-nonanone and 6,7-dimethyl-3-(2-pyridylamino)-4-oxatricyclo -[4.3.0.0[superscript 3,7]]-2-nonanone. However the diphenylphosphine group was successfully introduced at C-8 and oxidative ring-opening of the camphor skeleton has afforded the tridentate ligands, 2-(diphenylphosphinoylmethyl)-1,2-dimethyl-1,3-cyclopentanedicarboxylic acid and 2-(diphenylphosphinoylmethyl)-1,3-bis(hydroxymethyl)1,2-dimethylcyclopentane. One- and two-dimensional NMR and, where appropriate, high-resolution MS methods have been used to characterise the products. Three [superscript 13]C NMR chemical shift prediction programmes, viz., ChemWindow and the MODGRAPH neural network and HOSE (Hierachially Ordered Spherical description of Environment), have been applied to representative compounds to assess their efficacy. While the predicted shifts correlated reasonably well with the experimental data, they proved to be insufficiently accurate to differentiate the isomeric systems examined.
- Full Text:
- Date Issued: 2007
Karyology of three evolutionarily hexaploid southern African species of yellowfish, Labeobarbus Rüppel, 1836 (Cyprinidae)
- Naran, D, Skelton, Paul H, Villet, Martin H
- Authors: Naran, D , Skelton, Paul H , Villet, Martin H
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6855 , http://hdl.handle.net/10962/d1011138 , http://dx.doi.org/10.3377/1562-7020(2007)42[254:KOTEHS]2.0.CO;2
- Description: The karyotypes of three species of yellowfish, namely Labeobarbus marequensis (A. Smith, 1841), L. capensis (A. Smith, 1841) and L. polylepis (Boulenger, 1907), were examined by Giemsa staining using an approach improved for the description of high chromosome numbers. In each case, 2n = 150; no heteromorphic chromosomes were detected; chromosomes in all morphological categories ranged smoothly from large to small, with no distinctly large submetacentric pairs; and metacentric chromosomes showed little variation in size. Labeobarbus marequensis had 26 metacentric (m), 44 submetacentric (sm), 42 subtelocentric (st) and 38 acrocentric (a) chromosomes and a fundamental number (FN) of 262; L. capensis had 16 m, 58 sm, 42 st and 34 a chromosomes and FN = 266; and L. polylepis had 18 m, 60 sm, 42 st and 30 a chromosomes and FN = 270. These results, combined with published literature, imply that Labeobarbus Rüppel, 1836 is an evolutionarily hexaploid African lineage and support its removal from synonymy with the evolutionarily tetraploid Asian genus Tor Gray, 1834. A review of fundamental numbers for conspecific Labeobarbus species examined in different studies implicated karyological technique as a confounding factor in assessing details of karyotypes, leading to recommendations for future karyological studies of barbine fishes. Potential synapomorphies are pointed out in karyological characters of species within Labeobarbus.
- Full Text:
- Date Issued: 2007
- Authors: Naran, D , Skelton, Paul H , Villet, Martin H
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6855 , http://hdl.handle.net/10962/d1011138 , http://dx.doi.org/10.3377/1562-7020(2007)42[254:KOTEHS]2.0.CO;2
- Description: The karyotypes of three species of yellowfish, namely Labeobarbus marequensis (A. Smith, 1841), L. capensis (A. Smith, 1841) and L. polylepis (Boulenger, 1907), were examined by Giemsa staining using an approach improved for the description of high chromosome numbers. In each case, 2n = 150; no heteromorphic chromosomes were detected; chromosomes in all morphological categories ranged smoothly from large to small, with no distinctly large submetacentric pairs; and metacentric chromosomes showed little variation in size. Labeobarbus marequensis had 26 metacentric (m), 44 submetacentric (sm), 42 subtelocentric (st) and 38 acrocentric (a) chromosomes and a fundamental number (FN) of 262; L. capensis had 16 m, 58 sm, 42 st and 34 a chromosomes and FN = 266; and L. polylepis had 18 m, 60 sm, 42 st and 30 a chromosomes and FN = 270. These results, combined with published literature, imply that Labeobarbus Rüppel, 1836 is an evolutionarily hexaploid African lineage and support its removal from synonymy with the evolutionarily tetraploid Asian genus Tor Gray, 1834. A review of fundamental numbers for conspecific Labeobarbus species examined in different studies implicated karyological technique as a confounding factor in assessing details of karyotypes, leading to recommendations for future karyological studies of barbine fishes. Potential synapomorphies are pointed out in karyological characters of species within Labeobarbus.
- 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
Enlarged arguments in Bantu : evidence from Chichewa
- Authors: Simango, Silvester Ron
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6140 , http://hdl.handle.net/10962/d1011592
- Description: This paper re-examines two types of constructions that have featured in the discussion of possessor ascension in Bantu: one type – an applicative construction – is associated with alienable possession, and the other – non-applicative – is associated with inalienable possession. The study shows that the former expresses affectedness, and that the possessor reading arises only by construal; whereas the latter expresses a part–whole relationship. The paper argues that the two constructions differ in more significant ways than has previously been acknowledged; and that their distinct derivations cannot be captured by traditional possessor ascension (PA) analyses. The putative “alienable” possessor constructions belong to the class of (benefactive) applicative constructions and should be analyzed as such. The paper proposes that the so-called “inalienable” possessor constructions can best be accounted for by positing the existence of “enlarged arguments” wherein the possessum functions as a nominal predicate which more narrowly pinpoints the locus of the action described by the verb.
- Full Text:
- Date Issued: 2007
- Authors: Simango, Silvester Ron
- Date: 2007
- Language: English
- Type: Article
- Identifier: vital:6140 , http://hdl.handle.net/10962/d1011592
- Description: This paper re-examines two types of constructions that have featured in the discussion of possessor ascension in Bantu: one type – an applicative construction – is associated with alienable possession, and the other – non-applicative – is associated with inalienable possession. The study shows that the former expresses affectedness, and that the possessor reading arises only by construal; whereas the latter expresses a part–whole relationship. The paper argues that the two constructions differ in more significant ways than has previously been acknowledged; and that their distinct derivations cannot be captured by traditional possessor ascension (PA) analyses. The putative “alienable” possessor constructions belong to the class of (benefactive) applicative constructions and should be analyzed as such. The paper proposes that the so-called “inalienable” possessor constructions can best be accounted for by positing the existence of “enlarged arguments” wherein the possessum functions as a nominal predicate which more narrowly pinpoints the locus of the action described by the verb.
- Full Text:
- Date Issued: 2007
Synthesis of novel coumarin derivatives as potential inhibitors of HIV-1 protease
- Authors: Rose, Nathan Rolf
- Date: 2007 , 2013-07-01
- Subjects: Coumarins , Protease Inhibitors , Heterocyclic compounds -- Derivatives , HIV infections -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4430 , http://hdl.handle.net/10962/d1007220 , Coumarins , Protease Inhibitors , Heterocyclic compounds -- Derivatives , HIV infections -- Treatment
- Description: This research has focused on the development of novel coumann derivatives containing peptide-like side chains as potential HIV-1 protease inhibitors. The reaction of various salicylaldehyde derivatives with tert-butyl acrylate In the presence of 1,4- diazabicyclo[2.2.2]octane (DABCO) has afforded a series of Baylis-Hillman adducts in moderate yield. Cyclisation of the adducts in the presence of HCI afforded the corresponding 3-(chloromethyl)coumarin derivatives, which have been reacted with various amine hydrochlorides in the presence of Proton Sponge® to afford a series of novel 3- (aminomethyl)coumarin derivatives, which were fully characterised by NMR and HRMS methods. Various approaches to the introduction of hydroxyl or amino groups at the C-4 position of coumarin and the 3-(chloromethyl)coumarin derivatives have been explored; these have included dihydroxylation of the coumarin double bond, and the synthesis of 4- benzylaminocoumarin derivatives as potential intermediates. The Vilsmeier-Haack and Mannich reactions have also been investigated as possible methods of introducing the desired peptide-like functionality. Computer modelling of selected structures has indicated that some of the novel 3- (aminomethyl)coumarin derivatives may exhibit activity as inhibitors of HIV-1 protease. The planned enzyme inhibition assays were unfortunately precluded by the aqueous insolubility of the selected compounds. Three ¹³C NMR chemical shift algorithms, viz., Modgraph Neural Network, Modgraph HOSE and Chern Window, have been applied to selected compounds prepared in this study. The Modgraph Neural Network algorithm was found, in all cases, to provide the most accurate correlations with the experimentally-determined chemical shifts. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2007
- Authors: Rose, Nathan Rolf
- Date: 2007 , 2013-07-01
- Subjects: Coumarins , Protease Inhibitors , Heterocyclic compounds -- Derivatives , HIV infections -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4430 , http://hdl.handle.net/10962/d1007220 , Coumarins , Protease Inhibitors , Heterocyclic compounds -- Derivatives , HIV infections -- Treatment
- Description: This research has focused on the development of novel coumann derivatives containing peptide-like side chains as potential HIV-1 protease inhibitors. The reaction of various salicylaldehyde derivatives with tert-butyl acrylate In the presence of 1,4- diazabicyclo[2.2.2]octane (DABCO) has afforded a series of Baylis-Hillman adducts in moderate yield. Cyclisation of the adducts in the presence of HCI afforded the corresponding 3-(chloromethyl)coumarin derivatives, which have been reacted with various amine hydrochlorides in the presence of Proton Sponge® to afford a series of novel 3- (aminomethyl)coumarin derivatives, which were fully characterised by NMR and HRMS methods. Various approaches to the introduction of hydroxyl or amino groups at the C-4 position of coumarin and the 3-(chloromethyl)coumarin derivatives have been explored; these have included dihydroxylation of the coumarin double bond, and the synthesis of 4- benzylaminocoumarin derivatives as potential intermediates. The Vilsmeier-Haack and Mannich reactions have also been investigated as possible methods of introducing the desired peptide-like functionality. Computer modelling of selected structures has indicated that some of the novel 3- (aminomethyl)coumarin derivatives may exhibit activity as inhibitors of HIV-1 protease. The planned enzyme inhibition assays were unfortunately precluded by the aqueous insolubility of the selected compounds. Three ¹³C NMR chemical shift algorithms, viz., Modgraph Neural Network, Modgraph HOSE and Chern Window, have been applied to selected compounds prepared in this study. The Modgraph Neural Network algorithm was found, in all cases, to provide the most accurate correlations with the experimentally-determined chemical shifts. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2007
Characterisation of Human Hsj1a : an HSP40 molecular chaperone similar to Malarial Pfj4
- Authors: McNamara, Caryn
- Date: 2007
- Subjects: Heat shock proteins , Protein folding , Proteins -- Analysis , Proteins -- Structure , Plasmodium , Malaria , Molecular chaperones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4083 , http://hdl.handle.net/10962/d1007603
- Description: Protein folding, translocation, oligomeric rearrangement and degradation are vital functions to obtain correctly folded proteins in any cell. The constitutive or stress-induced members of each of the heat shock protein (Hsp) families, namely Hsp70 and Hsp40, make up the Hsp70/Hsp40 chaperone system. The Hsp40 J-domain is important for the Hsp70-Hsp40 interaction and hence function. The type-II Hsp40 proteins, Homo sapiens DnaJ 1a (Hsj1a) and Plasmodium falciparum DnaJ 4 (Pfj4), are structurally similar suggesting possible similar roles during malarial infection. This thesis has focussed on identifying whether Hsj1a and Pfj4 are functionally similar in their interaction with potential partner Hsp70 chaperones. Analysis in silico also showed Pfj4 to have a potential chaperone domain, a region resembling a ubiquitin-interacting motif (UIM) corresponding to UIM1 of HsjIa, and another highly conserved region was noted between residues 232-241. The highly conserved regions within the Hsp40 J-domains, and those amino acids therein, are suggested to be responsible for mediating this Hsp70-Hsp40 partner interaction. The thermosensitive dnaJ cbpA Escherichia coli OD259 mutant strain producing type-I Agrobacterium tumefaciens DnaJ (AgtDnaJ) was used as a model heterologous expression system in this study. AgtDnaJ was able to replace the lack of two E coli Hsp40s in vivo, DnaJ and CbpA, whereas AgtDnaJ(H33Q) was unable to. AgtDnaJ-based chimeras containing the swapped J-domains of similar type-II Hsp40 proteins, namely Hsj1Agt and Pfj4Agt, were also able to replace these in E. coli OD259. Conserved J-domain amino acids were identified and were substituted in these chimeras. Of these mutant proteins, Hsj IAgt(L8A), Hsj1Agt(R24A), Hsj1Agt(H31Q), Pfj4Agt(L 11A) and Pfj4Agt(H34Q) were not able to replace the E. coli Hsp40s, whilst Pfj4Agt(Y8A) and Pfj4Agt(R27A) were only able to partially replace them. This shows the leucine of helix I and the histidine of the loop region are key in the in vivo function of both proteins and that the arginine of helix II is key for Hsj1a. The histidine-tagged Hsj1a protein was also successfully purified from the heterologous system. The in vitro stimulated ATPase activity of human Hsp70 by Hsj1a was found to be approximately 14 nmol Pí[subscript]/min/mg, and yet not stimulated by Pfj4, suggesting a possible species-specific interaction is occurring.
- Full Text:
- Date Issued: 2007
- Authors: McNamara, Caryn
- Date: 2007
- Subjects: Heat shock proteins , Protein folding , Proteins -- Analysis , Proteins -- Structure , Plasmodium , Malaria , Molecular chaperones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4083 , http://hdl.handle.net/10962/d1007603
- Description: Protein folding, translocation, oligomeric rearrangement and degradation are vital functions to obtain correctly folded proteins in any cell. The constitutive or stress-induced members of each of the heat shock protein (Hsp) families, namely Hsp70 and Hsp40, make up the Hsp70/Hsp40 chaperone system. The Hsp40 J-domain is important for the Hsp70-Hsp40 interaction and hence function. The type-II Hsp40 proteins, Homo sapiens DnaJ 1a (Hsj1a) and Plasmodium falciparum DnaJ 4 (Pfj4), are structurally similar suggesting possible similar roles during malarial infection. This thesis has focussed on identifying whether Hsj1a and Pfj4 are functionally similar in their interaction with potential partner Hsp70 chaperones. Analysis in silico also showed Pfj4 to have a potential chaperone domain, a region resembling a ubiquitin-interacting motif (UIM) corresponding to UIM1 of HsjIa, and another highly conserved region was noted between residues 232-241. The highly conserved regions within the Hsp40 J-domains, and those amino acids therein, are suggested to be responsible for mediating this Hsp70-Hsp40 partner interaction. The thermosensitive dnaJ cbpA Escherichia coli OD259 mutant strain producing type-I Agrobacterium tumefaciens DnaJ (AgtDnaJ) was used as a model heterologous expression system in this study. AgtDnaJ was able to replace the lack of two E coli Hsp40s in vivo, DnaJ and CbpA, whereas AgtDnaJ(H33Q) was unable to. AgtDnaJ-based chimeras containing the swapped J-domains of similar type-II Hsp40 proteins, namely Hsj1Agt and Pfj4Agt, were also able to replace these in E. coli OD259. Conserved J-domain amino acids were identified and were substituted in these chimeras. Of these mutant proteins, Hsj IAgt(L8A), Hsj1Agt(R24A), Hsj1Agt(H31Q), Pfj4Agt(L 11A) and Pfj4Agt(H34Q) were not able to replace the E. coli Hsp40s, whilst Pfj4Agt(Y8A) and Pfj4Agt(R27A) were only able to partially replace them. This shows the leucine of helix I and the histidine of the loop region are key in the in vivo function of both proteins and that the arginine of helix II is key for Hsj1a. The histidine-tagged Hsj1a protein was also successfully purified from the heterologous system. The in vitro stimulated ATPase activity of human Hsp70 by Hsj1a was found to be approximately 14 nmol Pí[subscript]/min/mg, and yet not stimulated by Pfj4, suggesting a possible species-specific interaction is occurring.
- Full Text:
- Date Issued: 2007
Camphor-derived chiral auxiliaries: a synthetic, mechanistic and computational study
- Authors: Duggan, Andrew Robert
- Date: 2007
- Subjects: Camphor Chirality Asymmetric synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4415 , http://hdl.handle.net/10962/d1006772
- Description: A broadly based approach has been undertaken to the development and use of camphor derivatives as chiral auxiliaries in asymmetric synthesis – an approach which has embraced synthetic, mechanistic and computational studies. The unambiguous characterization of mono- and dihydroxy-derivatives, obtained by reduction of chiral camphor ether dimers, has been achieved through detailed one- and two-dimensional NMR spectroscopic analysis. The resulting data has been used to establish both the regio- and stereochemistry of the hydroxyl groups. A camphor-derived cyclic iminolactone has been shown to provide a convenient platform for the synthesis of chiral α-amino acids, stereoselective monoalkylation of the iminolactone affording a range of products in yields of 52 - 65 % with up to 85 % d.e. The attempted development of chiral bifunctional Morita-Baylis-Hillman substrates has revealed an unexpected equilibration between isomeric bornane 2,3-diol monoacrylates via acid-catalysed intramolecular transesterification. A detailed [superscript 1]H NMR-based kinetic study of the rearrangement in various media and at various temperatures has permitted the determination of the kinetic and thermodynamic parameters. A computational study at the DFT level has been used to explore the potential energy surfaces of the acid-catalysed and uncatalysed transesterification of the monoacrylate esters. The theoretical data supports the involvement of cyclic intermediates and has provided a rational basis for predicting the favoured reaction pathways. Novel camphor-derived phenyl sulfonate esters and N-adamantylsulfonamides have been synthesised for use as chiral auxiliaries in the Morita-Baylis-Hillman reaction. Modeling at the Molecular Mechanics level has provided useful insights into possible conformational constraints and an adamantyl sulfonate auxiliary has been successfully used in the stereoselective synthesis of a range of products, generally in excellent yield and with up to 95 % d.e.
- Full Text:
- Date Issued: 2007
- Authors: Duggan, Andrew Robert
- Date: 2007
- Subjects: Camphor Chirality Asymmetric synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4415 , http://hdl.handle.net/10962/d1006772
- Description: A broadly based approach has been undertaken to the development and use of camphor derivatives as chiral auxiliaries in asymmetric synthesis – an approach which has embraced synthetic, mechanistic and computational studies. The unambiguous characterization of mono- and dihydroxy-derivatives, obtained by reduction of chiral camphor ether dimers, has been achieved through detailed one- and two-dimensional NMR spectroscopic analysis. The resulting data has been used to establish both the regio- and stereochemistry of the hydroxyl groups. A camphor-derived cyclic iminolactone has been shown to provide a convenient platform for the synthesis of chiral α-amino acids, stereoselective monoalkylation of the iminolactone affording a range of products in yields of 52 - 65 % with up to 85 % d.e. The attempted development of chiral bifunctional Morita-Baylis-Hillman substrates has revealed an unexpected equilibration between isomeric bornane 2,3-diol monoacrylates via acid-catalysed intramolecular transesterification. A detailed [superscript 1]H NMR-based kinetic study of the rearrangement in various media and at various temperatures has permitted the determination of the kinetic and thermodynamic parameters. A computational study at the DFT level has been used to explore the potential energy surfaces of the acid-catalysed and uncatalysed transesterification of the monoacrylate esters. The theoretical data supports the involvement of cyclic intermediates and has provided a rational basis for predicting the favoured reaction pathways. Novel camphor-derived phenyl sulfonate esters and N-adamantylsulfonamides have been synthesised for use as chiral auxiliaries in the Morita-Baylis-Hillman reaction. Modeling at the Molecular Mechanics level has provided useful insights into possible conformational constraints and an adamantyl sulfonate auxiliary has been successfully used in the stereoselective synthesis of a range of products, generally in excellent yield and with up to 95 % d.e.
- 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
The role of pacC in Aspergillus flavus
- Authors: Suleman, Essa
- Date: 2007
- Subjects: Fungi -- Biotechnology , Pathogenic microorganisms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10332 , http://hdl.handle.net/10948/612 , Fungi -- Biotechnology , Pathogenic microorganisms
- Description: Many microorganisms, and in particular fungi, are able to grow over a wide pH range. Thus, these microorganisms must possess some regulatory mechanism or system that senses the environmental pH signal and ensures that gene expression of certain molecules is tailored to the pH of the environment (Penalva and Arst, 2002). In Aspergillus species and several other fungi, pH regulation is mediated by seven genes viz. palA, palB, palC, palF, palH, palI and the global pH regulatory gene, pacC (MacAbe et al, 1996; Negrete-Urtasun, 1999; Denison, 2000). The activated form of the PacC protein activates genes that are required at alkaline pH, e.g. genes coding for alkaline phosphatases, and represses certain genes that are functional at acidic pH, e.g. genes encoding acid phosphatases (Negrete-Urtasun, 1999). PacC (and its homologues) also positively regulates genes involved in penicillin biosynthesis, e.g. the isopenicillin N synthase gene, ipnA, in A. nidulans (Penalva and Arst, 2002). It has also been hypothesised that pacC may negatively regulate aflatoxin biosynthesis, a carcinogenic secondary metabolite in several species of Aspergillus (Keller et al, 1997). To elucidate the role of pacC a novel method of post-transcriptional gene silencing known as RNA interference was utilized. This method involved the cloning of a partial pacC gene fragment first in the forward and then the reverse orientations in a fungal expression cassette to create an RNA interference (RNAi) vector. The unique structure of this vector would allow the cloned fragments to be expressed and the resulting RNA to immediately form a double stranded stem-loop structure or short hairpin RNA (shRNA; McDonald et al, 2005). The formation of this shRNA, in turn, would be responsible for activating the endogenous RNA degradation complexes that would lead to mRNA degradation and subsequent gene silencing (Liu et al, 2003; Kadotoni et al, 2003; McDonald et al, 2005). The results presented here have shown that confirmed pacC RNAi mutants produced aflatoxins irrespective of environmental pH (i.e. the mutants produce aflatoxins under acidic and alkaline conditions). Thus, pacC is essential for pH regulation of aflatoxin production in A. flavus. There are numerous other biological (e.g. presence of oxylipins, lipooxygenases) and non-biological factors (pH, carbon source etc.) which affect maize colonisation and aflatoxin production by A. flavus (Burrow et al, 1996; Wilson et al, 2001; Calvo et al; 2002; Tsitsigiannis et al, 2006). However, all the genetic mechanisms involved have as yet not been identified. It has been shown by Caracuel et al (2003) that pacC acts as a negative virulence regulator in plants and these workers have hypothesised that PacC prevents expression of genes that are important for infection and virulence of the pathogen. Therefore the physiological effects that pacC silencing had on the growth, conidiation and pathogenicity of A. flavus mutants were also investigated. The results of this study showed that pacC does not play a significant role in primary growth and development but does affect conidial production. SEM results showed that mutants have many “open ended” phialides and poorly developed conidiophores. This would suggest that pacC activation of conidial production genes is also required. Furthermore, pacC RNAi silencing severely impaired the ability of the A. flavus mutants to infect and cause damage on maize. The results obtained here are similar to that of pacC null mutants in A. nidulans, C. albicans and F. oxysporum which also exhibited low pathogenicity (Davis et al, 2000; Fonzi, W.A, 2002; Caracuel et al, 2003; Bignell et al, 2005 and Cornet et al, 2005). This study indicates that pathogenicity of A. flavus on maize is directly related to the structural integrity of conidia, which in turn is greatly influenced by PacC. This gene is a global transcriptional regulator and may either repress or activate one or many genes in each of the above pathways (Penalva and Arst, 2002). Studies on the genetic mechanisms of pacC regulation on these pathways are needed to elucidate the mechanisms of activation or repression of these genes.
- Full Text:
- Date Issued: 2007
- Authors: Suleman, Essa
- Date: 2007
- Subjects: Fungi -- Biotechnology , Pathogenic microorganisms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10332 , http://hdl.handle.net/10948/612 , Fungi -- Biotechnology , Pathogenic microorganisms
- Description: Many microorganisms, and in particular fungi, are able to grow over a wide pH range. Thus, these microorganisms must possess some regulatory mechanism or system that senses the environmental pH signal and ensures that gene expression of certain molecules is tailored to the pH of the environment (Penalva and Arst, 2002). In Aspergillus species and several other fungi, pH regulation is mediated by seven genes viz. palA, palB, palC, palF, palH, palI and the global pH regulatory gene, pacC (MacAbe et al, 1996; Negrete-Urtasun, 1999; Denison, 2000). The activated form of the PacC protein activates genes that are required at alkaline pH, e.g. genes coding for alkaline phosphatases, and represses certain genes that are functional at acidic pH, e.g. genes encoding acid phosphatases (Negrete-Urtasun, 1999). PacC (and its homologues) also positively regulates genes involved in penicillin biosynthesis, e.g. the isopenicillin N synthase gene, ipnA, in A. nidulans (Penalva and Arst, 2002). It has also been hypothesised that pacC may negatively regulate aflatoxin biosynthesis, a carcinogenic secondary metabolite in several species of Aspergillus (Keller et al, 1997). To elucidate the role of pacC a novel method of post-transcriptional gene silencing known as RNA interference was utilized. This method involved the cloning of a partial pacC gene fragment first in the forward and then the reverse orientations in a fungal expression cassette to create an RNA interference (RNAi) vector. The unique structure of this vector would allow the cloned fragments to be expressed and the resulting RNA to immediately form a double stranded stem-loop structure or short hairpin RNA (shRNA; McDonald et al, 2005). The formation of this shRNA, in turn, would be responsible for activating the endogenous RNA degradation complexes that would lead to mRNA degradation and subsequent gene silencing (Liu et al, 2003; Kadotoni et al, 2003; McDonald et al, 2005). The results presented here have shown that confirmed pacC RNAi mutants produced aflatoxins irrespective of environmental pH (i.e. the mutants produce aflatoxins under acidic and alkaline conditions). Thus, pacC is essential for pH regulation of aflatoxin production in A. flavus. There are numerous other biological (e.g. presence of oxylipins, lipooxygenases) and non-biological factors (pH, carbon source etc.) which affect maize colonisation and aflatoxin production by A. flavus (Burrow et al, 1996; Wilson et al, 2001; Calvo et al; 2002; Tsitsigiannis et al, 2006). However, all the genetic mechanisms involved have as yet not been identified. It has been shown by Caracuel et al (2003) that pacC acts as a negative virulence regulator in plants and these workers have hypothesised that PacC prevents expression of genes that are important for infection and virulence of the pathogen. Therefore the physiological effects that pacC silencing had on the growth, conidiation and pathogenicity of A. flavus mutants were also investigated. The results of this study showed that pacC does not play a significant role in primary growth and development but does affect conidial production. SEM results showed that mutants have many “open ended” phialides and poorly developed conidiophores. This would suggest that pacC activation of conidial production genes is also required. Furthermore, pacC RNAi silencing severely impaired the ability of the A. flavus mutants to infect and cause damage on maize. The results obtained here are similar to that of pacC null mutants in A. nidulans, C. albicans and F. oxysporum which also exhibited low pathogenicity (Davis et al, 2000; Fonzi, W.A, 2002; Caracuel et al, 2003; Bignell et al, 2005 and Cornet et al, 2005). This study indicates that pathogenicity of A. flavus on maize is directly related to the structural integrity of conidia, which in turn is greatly influenced by PacC. This gene is a global transcriptional regulator and may either repress or activate one or many genes in each of the above pathways (Penalva and Arst, 2002). Studies on the genetic mechanisms of pacC regulation on these pathways are needed to elucidate the mechanisms of activation or repression of these genes.
- Full Text:
- Date Issued: 2007
A model for a context aware machine-based personal memory manager and its implementation using a visual programming environment
- Authors: Tsegaye, Melekam Asrat
- Date: 2007
- Subjects: Visual programming (Computer science) Memory management (Computer science) Memory -- Data processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4640 , http://hdl.handle.net/10962/d1006563
- Description: Memory is a part of cognition. It is essential for an individual to function normally in society. It encompasses an individual's lifetime experience, thus defining his identity. This thesis develops the concept of a machine-based personal memory manager which captures and manages an individual's day-to-day external memories. Rather than accumulating large amounts of data which has to be mined for useful memories, the machine-based memory manager automatically organizes memories as they are captured to enable their quick retrieval and use. The main functions of the machine-based memory manager envisioned in this thesis are the support and the augmentation of an individual's biological memory system. In the thesis, a model for a machine-based memory manager is developed. A visual programming environment, which can be used to build context aware applications as well as a proof-of-concept machine-based memory manager, is conceptualized and implemented. An experimental machine-based memory manager is implemented and evaluated. The model describes a machine-based memory manager which manages an individual's external memories by context. It addresses the management of external memories which accumulate over long periods of time by proposing a context aware file system which automatically organizes external memories by context. It describes how personal memory management can be facilitated by machine using six entities (life streams, memory producers, memory consumers, a memory manager, memory fragments and context descriptors) and the processes in which these entities participate (memory capture, memory encoding and decoding, memory decoding and retrieval). The visual programming environment represents a development tool which contains facilities that support context aware application programming. For example, it provides facilities which enable the definition and use of virtual sensors. It enables rapid programming with a focus on component re-use and dynamic composition of applications through a visual interface. The experimental machine-based memory manager serves as an example implementation of the machine-based memory manager which is described by the model developed in this thesis. The hardware used in its implementation consists of widely available components such as a camera, microphone and sub-notebook computer which are assembled in the form of a wearable computer. The software is constructed using the visual programming environment developed in this thesis. It contains multiple sensor drivers, context interpreters, a context aware file system as well as memory retrieval and presentation interfaces. The evaluation of the machine-based memory manager shows that it is possible to create a machine which monitors the states of an individual and his environment, and manages his external memories, thus supporting and augmenting his biological memory.
- Full Text:
- Date Issued: 2007
- Authors: Tsegaye, Melekam Asrat
- Date: 2007
- Subjects: Visual programming (Computer science) Memory management (Computer science) Memory -- Data processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4640 , http://hdl.handle.net/10962/d1006563
- Description: Memory is a part of cognition. It is essential for an individual to function normally in society. It encompasses an individual's lifetime experience, thus defining his identity. This thesis develops the concept of a machine-based personal memory manager which captures and manages an individual's day-to-day external memories. Rather than accumulating large amounts of data which has to be mined for useful memories, the machine-based memory manager automatically organizes memories as they are captured to enable their quick retrieval and use. The main functions of the machine-based memory manager envisioned in this thesis are the support and the augmentation of an individual's biological memory system. In the thesis, a model for a machine-based memory manager is developed. A visual programming environment, which can be used to build context aware applications as well as a proof-of-concept machine-based memory manager, is conceptualized and implemented. An experimental machine-based memory manager is implemented and evaluated. The model describes a machine-based memory manager which manages an individual's external memories by context. It addresses the management of external memories which accumulate over long periods of time by proposing a context aware file system which automatically organizes external memories by context. It describes how personal memory management can be facilitated by machine using six entities (life streams, memory producers, memory consumers, a memory manager, memory fragments and context descriptors) and the processes in which these entities participate (memory capture, memory encoding and decoding, memory decoding and retrieval). The visual programming environment represents a development tool which contains facilities that support context aware application programming. For example, it provides facilities which enable the definition and use of virtual sensors. It enables rapid programming with a focus on component re-use and dynamic composition of applications through a visual interface. The experimental machine-based memory manager serves as an example implementation of the machine-based memory manager which is described by the model developed in this thesis. The hardware used in its implementation consists of widely available components such as a camera, microphone and sub-notebook computer which are assembled in the form of a wearable computer. The software is constructed using the visual programming environment developed in this thesis. It contains multiple sensor drivers, context interpreters, a context aware file system as well as memory retrieval and presentation interfaces. The evaluation of the machine-based memory manager shows that it is possible to create a machine which monitors the states of an individual and his environment, and manages his external memories, thus supporting and augmenting his biological memory.
- Full Text:
- Date Issued: 2007
Psychosocial barriers to learning in a deprived environment
- Authors: Mack, Esmé Judy
- Date: 2007
- Subjects: Students -- South Africa -- Port Alizabeth -- Social conditions , Children with social disabilities -- Education -- South Africa -- Port Elizabeth , Learning disabilities -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9481 , http://hdl.handle.net/10948/551 , Students -- South Africa -- Port Alizabeth -- Social conditions , Children with social disabilities -- Education -- South Africa -- Port Elizabeth , Learning disabilities -- South Africa
- Description: Many secondary schools in deprived environments are characterized by teenage pregnancies, drug and alcohol abuse, crime, high dropout rates, gangsterism and low pass rates. Teachers are confronted on a daily basis with learners who are exposed to barriers to learning. The purpose of this study is in line with the formulated problem, namely to: investigate the various dimensions of the relationship that exists between psychosocial barriers to learning and environmental deprivation; provide guidelines based on the findings of the research and present them as recommendations for teachers to support learners from a deprived environment who experience barriers to learning. A qualitative, exploratory, descriptive and interpretative research design was utilized to provide acceptable answers to the research problem. A literature study regarding psychosocial barriers to learning was done to explain the concept along with concepts related to environmental deprivation. This study was conducted in two phases: Phase 1 presented an exploration of the problem in the form of a single openended question: What hindrances to learning are you experiencing in your specific physical and social environment? Eight focus group interviews with learners were undertaken at a secondary school in the Nelson Mandela Metropolitan Municipality. A purposive sampling method was used. Data collection took place through open-ended interviews and Tesch’s model was used to analyse the data. After the research investigation was completed the researcher and an independent coder analyzed iv the results from the transcriptions of a voice-recorder. Guba’s model of data verification was used to ensure the trustworthiness of the data. Ethical measures were adhered to during the study. The research findings were evaluated for educational purposes. Consensus was reached between the researcher and the independent coder with regard to the identification of themes, categories and sub-categories. Phase 2 generated recommendations from the findings of Phase 1 to assist the teachers in dealing competently with learners from deprived environments. The following four themes emerged from the results which led to various conclusions: 1. A deprived home situation (relationships, abuse, no privacy, and poverty) generates barriers to learning. Neglect: no interest and a don’t care attitude of parents, no parents at home, rejection and no communication have a negative effect on the learners. Physical, sexual, alcohol and drug abuse in the home situation influence the learners negatively. No privacy: sexual behaviour of parents and overcrowding have a decisive effect on the learners. Poverty: factors such as unemployment, cannot afford school fees, no electricity and no breadwinner make the learner feel desperate and despondent. 2. A deprived school situation (social relationships, physical factors, no resources, racism and distances to school) creates barriers to learning. The following features of social relationships were identified as contributing factors to poor social relationships at school, namely: peer pressure: drugs, dropping out of school, unsafe school environment; relationships with teachers: no respect for teachers and teachers who degrade learners. The following physical factors have a detrimental effect on a learner’s progress: broken windows and roofs, lack of water, electricity and lights, the state of the school grounds, ablutions and big classes. Schools with no resources such as libraries and counselling centres contribute to the poor performance of the learners. Racism, language issues and no mixing of races are contributing factors to barriers to learning. The long distances to school, the cost of transport and the fact that they do not have time for homework affect the learners as hindrances to learning. 3. A deprived environment (with factors such as HIV/AIDS and TB, a community not conducive to learning, unsafe communities and overpopulation) causes barriers to learning. HIV/AIDS and TB, taking care of parents, tiredness, illnesses and discrimination are seen as factors that hamper learning. A community that is not conducive to learning, with a don’t care attitude and that is not very helpful, causes barriers to learning. Unsafe communities, where crime is rampant, with ineffective police services and overpopulation, where noise and loud music are the order of the day, have a negative effect on learning. 4. Learner-related factors (early pregnancies and the susceptibility of youth) create barriers to learning. Teenage pregnancies are detrimental to education where the mother must baby-sit, and is not studying, as well as sexual abuse and rape, are factors that contribute to school dropouts. Cigarettes, drugs, alcohol, taverns, discos, taxis and gangs were identified as factors contributing to learner delinquency. The conclusion was reached that learners in deprived environments are exposed to psychosocial barriers to learning. Recommendations in this regard were proposed to assist the teacher in understanding these learners and the barriers that they are exposed to on a daily basis.
- Full Text:
- Date Issued: 2007
- Authors: Mack, Esmé Judy
- Date: 2007
- Subjects: Students -- South Africa -- Port Alizabeth -- Social conditions , Children with social disabilities -- Education -- South Africa -- Port Elizabeth , Learning disabilities -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:9481 , http://hdl.handle.net/10948/551 , Students -- South Africa -- Port Alizabeth -- Social conditions , Children with social disabilities -- Education -- South Africa -- Port Elizabeth , Learning disabilities -- South Africa
- Description: Many secondary schools in deprived environments are characterized by teenage pregnancies, drug and alcohol abuse, crime, high dropout rates, gangsterism and low pass rates. Teachers are confronted on a daily basis with learners who are exposed to barriers to learning. The purpose of this study is in line with the formulated problem, namely to: investigate the various dimensions of the relationship that exists between psychosocial barriers to learning and environmental deprivation; provide guidelines based on the findings of the research and present them as recommendations for teachers to support learners from a deprived environment who experience barriers to learning. A qualitative, exploratory, descriptive and interpretative research design was utilized to provide acceptable answers to the research problem. A literature study regarding psychosocial barriers to learning was done to explain the concept along with concepts related to environmental deprivation. This study was conducted in two phases: Phase 1 presented an exploration of the problem in the form of a single openended question: What hindrances to learning are you experiencing in your specific physical and social environment? Eight focus group interviews with learners were undertaken at a secondary school in the Nelson Mandela Metropolitan Municipality. A purposive sampling method was used. Data collection took place through open-ended interviews and Tesch’s model was used to analyse the data. After the research investigation was completed the researcher and an independent coder analyzed iv the results from the transcriptions of a voice-recorder. Guba’s model of data verification was used to ensure the trustworthiness of the data. Ethical measures were adhered to during the study. The research findings were evaluated for educational purposes. Consensus was reached between the researcher and the independent coder with regard to the identification of themes, categories and sub-categories. Phase 2 generated recommendations from the findings of Phase 1 to assist the teachers in dealing competently with learners from deprived environments. The following four themes emerged from the results which led to various conclusions: 1. A deprived home situation (relationships, abuse, no privacy, and poverty) generates barriers to learning. Neglect: no interest and a don’t care attitude of parents, no parents at home, rejection and no communication have a negative effect on the learners. Physical, sexual, alcohol and drug abuse in the home situation influence the learners negatively. No privacy: sexual behaviour of parents and overcrowding have a decisive effect on the learners. Poverty: factors such as unemployment, cannot afford school fees, no electricity and no breadwinner make the learner feel desperate and despondent. 2. A deprived school situation (social relationships, physical factors, no resources, racism and distances to school) creates barriers to learning. The following features of social relationships were identified as contributing factors to poor social relationships at school, namely: peer pressure: drugs, dropping out of school, unsafe school environment; relationships with teachers: no respect for teachers and teachers who degrade learners. The following physical factors have a detrimental effect on a learner’s progress: broken windows and roofs, lack of water, electricity and lights, the state of the school grounds, ablutions and big classes. Schools with no resources such as libraries and counselling centres contribute to the poor performance of the learners. Racism, language issues and no mixing of races are contributing factors to barriers to learning. The long distances to school, the cost of transport and the fact that they do not have time for homework affect the learners as hindrances to learning. 3. A deprived environment (with factors such as HIV/AIDS and TB, a community not conducive to learning, unsafe communities and overpopulation) causes barriers to learning. HIV/AIDS and TB, taking care of parents, tiredness, illnesses and discrimination are seen as factors that hamper learning. A community that is not conducive to learning, with a don’t care attitude and that is not very helpful, causes barriers to learning. Unsafe communities, where crime is rampant, with ineffective police services and overpopulation, where noise and loud music are the order of the day, have a negative effect on learning. 4. Learner-related factors (early pregnancies and the susceptibility of youth) create barriers to learning. Teenage pregnancies are detrimental to education where the mother must baby-sit, and is not studying, as well as sexual abuse and rape, are factors that contribute to school dropouts. Cigarettes, drugs, alcohol, taverns, discos, taxis and gangs were identified as factors contributing to learner delinquency. The conclusion was reached that learners in deprived environments are exposed to psychosocial barriers to learning. Recommendations in this regard were proposed to assist the teacher in understanding these learners and the barriers that they are exposed to on a daily basis.
- Full Text:
- Date Issued: 2007
An investigation into the impact of the gender policy on journalistic practices at the Times of Zambia newspaper
- Authors: Mwale, Edna
- Date: 2013-07-24
- Subjects: The Times of Zambia (Zambia) Newspapers -- Zambia Journalism -- Zambia Mass media -- Social aspects -- Zambia Women and journalism -- Zambia Mass media and women Mass media -- Political aspects -- Zambia Zambia -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3521 , http://hdl.handle.net/10962/d1008303
- Description: This study investigates the impact of the Times of Zambia gender policy on journalistic practices. The policy was formulated to address issues of representation of women both in news coverage and at an institutional level. In spite of the implementation of the editorial gender policy, no change in gendered representation is evident. As a media practitioner and a Zambian woman concerned with social justice, I set out to investigate the impact of this policy on journalistic practices. The study is informed by a Cultural Studies approach to media studies, specifically drawing on the 'circuit of culture' (du Guy et ai, 1997) and focused on two specific 'moments', namely representation and production. Data was collected using two qualitative methods, namely document analysis and semi-structured in-depth interviews. The document analysis established that this policy is informed by a liberal feminist approach to media and identified the weaknesses in its formulation. The subsequent semi-structured in-depth interviews probed the practices and perceptions of male and female journalists and editors in relation to the degree of change in gendered representation in the news. This study finds that the editorial gender policy at the Times of Zambia has not had any significant impact on the journalistic practices and it probed the reason for this lack of effectiveness. It argues that this can be partially attributed to the orientation of the policy within a liberal feminist paradigm which neglects the internal and external factors that influence the representation of women and men in news production. Further, this position ignores the societal structures and power relations which impact, albeit unintentional, on the treatment of news. Inter-organisational factors such as profit maximisation, political interference, the use of news values and news beats are identified as leading to the exclusion of representations of women in hard news. At an intra-organisational level, lack of importance attached to the policy by senior staff and their attitudes to news production in general have meant that the policy was not enacted or ensured in any meaningful way. The study also established that the patriarchal values that characterise Zambian society influence journalists ' and editors' treatment of news, thus making the implementation of the policy ineffective. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Mwale, Edna
- Date: 2013-07-24
- Subjects: The Times of Zambia (Zambia) Newspapers -- Zambia Journalism -- Zambia Mass media -- Social aspects -- Zambia Women and journalism -- Zambia Mass media and women Mass media -- Political aspects -- Zambia Zambia -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3521 , http://hdl.handle.net/10962/d1008303
- Description: This study investigates the impact of the Times of Zambia gender policy on journalistic practices. The policy was formulated to address issues of representation of women both in news coverage and at an institutional level. In spite of the implementation of the editorial gender policy, no change in gendered representation is evident. As a media practitioner and a Zambian woman concerned with social justice, I set out to investigate the impact of this policy on journalistic practices. The study is informed by a Cultural Studies approach to media studies, specifically drawing on the 'circuit of culture' (du Guy et ai, 1997) and focused on two specific 'moments', namely representation and production. Data was collected using two qualitative methods, namely document analysis and semi-structured in-depth interviews. The document analysis established that this policy is informed by a liberal feminist approach to media and identified the weaknesses in its formulation. The subsequent semi-structured in-depth interviews probed the practices and perceptions of male and female journalists and editors in relation to the degree of change in gendered representation in the news. This study finds that the editorial gender policy at the Times of Zambia has not had any significant impact on the journalistic practices and it probed the reason for this lack of effectiveness. It argues that this can be partially attributed to the orientation of the policy within a liberal feminist paradigm which neglects the internal and external factors that influence the representation of women and men in news production. Further, this position ignores the societal structures and power relations which impact, albeit unintentional, on the treatment of news. Inter-organisational factors such as profit maximisation, political interference, the use of news values and news beats are identified as leading to the exclusion of representations of women in hard news. At an intra-organisational level, lack of importance attached to the policy by senior staff and their attitudes to news production in general have meant that the policy was not enacted or ensured in any meaningful way. The study also established that the patriarchal values that characterise Zambian society influence journalists ' and editors' treatment of news, thus making the implementation of the policy ineffective. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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African customary law and gender justice in a progressive democracy
- Authors: Ozoemena, Rita Nkiruka
- Date: 2007
- Subjects: Customary law -- Africa , Women's rights -- Africa , Human rights -- Africa , Sex discrimination against women -- Africa , Women and democracy -- Africa , Culture and law -- Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3692 , http://hdl.handle.net/10962/d1003207 , Customary law -- Africa , Women's rights -- Africa , Human rights -- Africa , Sex discrimination against women -- Africa , Women and democracy -- Africa , Culture and law -- Africa
- Description: The constant clash of African culture and traditions with human rights continue to militate against the adequate protection of women’s rights. Thus, African women constantly face challenges resulting from restrictions under customary laws of succession and inheritance, witchcraft violence, degrading treatment to widows, domestic violence; women killed by their partners, rape of women and children under all kinds of circumstances. This thesis was prompted by the issues raised in the Bhe case of the Constitutional Court of South Africa. In this landmark judgment, Ngcobo J dealt with the development of customary law, and how it must be approached by the courts in a manner that would have due regard to the rights of women on one hand and, on the other, would also accord customary law of its proper place, purpose and values within the African context. Against this background, the thesis focused on South Africa, Nigeria and Lesotho as excellent models of the broader challenges for women as well as governments; despite certain legislative measures put in place by the latter, the battle continues unabated for the balance of traditions and culture with women’s rights issues. Although South Africa is more progressive in terms of Constitution and practice than Nigeria and Lesotho, a lot still needs to be done particularly in the area of harmonization of laws. Regrettably, in Nigeria and Lesotho respect for the Constitution is superficial and lacks substantive policies that would promote women’s rights. To this extent, the balance of democratic values and promotion of women’s rights issues within the continent lie in women being partners in development rather than unduly suffering under intense burden of culture, tradition and societal stereotypes.
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- Date Issued: 2007
- Authors: Ozoemena, Rita Nkiruka
- Date: 2007
- Subjects: Customary law -- Africa , Women's rights -- Africa , Human rights -- Africa , Sex discrimination against women -- Africa , Women and democracy -- Africa , Culture and law -- Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3692 , http://hdl.handle.net/10962/d1003207 , Customary law -- Africa , Women's rights -- Africa , Human rights -- Africa , Sex discrimination against women -- Africa , Women and democracy -- Africa , Culture and law -- Africa
- Description: The constant clash of African culture and traditions with human rights continue to militate against the adequate protection of women’s rights. Thus, African women constantly face challenges resulting from restrictions under customary laws of succession and inheritance, witchcraft violence, degrading treatment to widows, domestic violence; women killed by their partners, rape of women and children under all kinds of circumstances. This thesis was prompted by the issues raised in the Bhe case of the Constitutional Court of South Africa. In this landmark judgment, Ngcobo J dealt with the development of customary law, and how it must be approached by the courts in a manner that would have due regard to the rights of women on one hand and, on the other, would also accord customary law of its proper place, purpose and values within the African context. Against this background, the thesis focused on South Africa, Nigeria and Lesotho as excellent models of the broader challenges for women as well as governments; despite certain legislative measures put in place by the latter, the battle continues unabated for the balance of traditions and culture with women’s rights issues. Although South Africa is more progressive in terms of Constitution and practice than Nigeria and Lesotho, a lot still needs to be done particularly in the area of harmonization of laws. Regrettably, in Nigeria and Lesotho respect for the Constitution is superficial and lacks substantive policies that would promote women’s rights. To this extent, the balance of democratic values and promotion of women’s rights issues within the continent lie in women being partners in development rather than unduly suffering under intense burden of culture, tradition and societal stereotypes.
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- 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.
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- 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.
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- Date Issued: 2007