Rhodes Newsletter
- Date: 1994-Dec
- Subjects: Grahamstown -- Newspapers , Journalism -- South Africa , Rhodes University -- Newspapers , Rhodes University -- Rhodes Newsletter
- Language: English
- Type: Text
- Identifier: vital:14314 , http://hdl.handle.net/10962/d1019019
- Description: The Old Rhodian Union Newsletter keeping in contact with Alumni and informing them of the latest news from Rhodes University. The publication ran from 1951 to 2001, and was subsequenlty replaced with an electronic newsletter distributed via electronic mail.
- Full Text:
- Date Issued: 1994-Dec
- Date: 1994-Dec
- Subjects: Grahamstown -- Newspapers , Journalism -- South Africa , Rhodes University -- Newspapers , Rhodes University -- Rhodes Newsletter
- Language: English
- Type: Text
- Identifier: vital:14314 , http://hdl.handle.net/10962/d1019019
- Description: The Old Rhodian Union Newsletter keeping in contact with Alumni and informing them of the latest news from Rhodes University. The publication ran from 1951 to 2001, and was subsequenlty replaced with an electronic newsletter distributed via electronic mail.
- Full Text:
- Date Issued: 1994-Dec
Rhodes University Annual Report 1994
- Authors: Rhodes University
- Date: 1994
- Subjects: Rhodes University -- history Rhodes University -- employees Rhodes University -- students
- Language: English
- Identifier: vital:20049 , 0035-4678
- Full Text:
- Date Issued: 1994
- Authors: Rhodes University
- Date: 1994
- Subjects: Rhodes University -- history Rhodes University -- employees Rhodes University -- students
- Language: English
- Identifier: vital:20049 , 0035-4678
- Full Text:
- Date Issued: 1994
Rhodes University Graduation Ceremony 1994
- Authors: Rhodes University
- Date: 1994
- Language: English
- Type: text
- Identifier: vital:8128 , http://hdl.handle.net/10962/d1006753
- Description: Rhodes University Graduation Ceremonies Friday, 8 April 1994 at 10:30 a.m. [and] 08:15 p.m. [and] Saturday, 9 April 1994 at 10:30 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday, 14 May 1994 at 11.00 a.m. in the Guild Theatre.
- Full Text:
- Date Issued: 1994
- Authors: Rhodes University
- Date: 1994
- Language: English
- Type: text
- Identifier: vital:8128 , http://hdl.handle.net/10962/d1006753
- Description: Rhodes University Graduation Ceremonies Friday, 8 April 1994 at 10:30 a.m. [and] 08:15 p.m. [and] Saturday, 9 April 1994 at 10:30 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday, 14 May 1994 at 11.00 a.m. in the Guild Theatre.
- Full Text:
- Date Issued: 1994
Ringing the changes
- Authors: Lewis, Colin A
- Date: 1994
- Language: English
- Type: Article
- Identifier: vital:6185 , http://hdl.handle.net/10962/d1012383
- Description: The restoration of the bells of the Grahamstown Cathedral heralds a new interest in bell-ringing in South Africa. Although the music of ringing bells is part of our heritage, few people know much about the development, or even the rules of change ringing. This is the form of ringing typical of Britain and, increasingly, of Australia, New Zealand, U.S.A., Canada, and southern Africa. , Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa.
- Full Text:
- Date Issued: 1994
- Authors: Lewis, Colin A
- Date: 1994
- Language: English
- Type: Article
- Identifier: vital:6185 , http://hdl.handle.net/10962/d1012383
- Description: The restoration of the bells of the Grahamstown Cathedral heralds a new interest in bell-ringing in South Africa. Although the music of ringing bells is part of our heritage, few people know much about the development, or even the rules of change ringing. This is the form of ringing typical of Britain and, increasingly, of Australia, New Zealand, U.S.A., Canada, and southern Africa. , Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa.
- Full Text:
- Date Issued: 1994
Site Tax Campaign Manual
- COSATU
- Authors: COSATU
- Date: 1994
- Subjects: COSATU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/137159 , vital:37493
- Description: Since 1989 most workers in South Africa have had their wages taxed under the Site Tax system. SITE stands for Standard Income Tax on Employees. Under the Site Tax system, the employer is responsible for making sure that workers pay the correct, amount of tax. This is different from the old Pay As You Earn (PAYE) system where the Receiver of Revenue had to make sure that the amount of tax paid was correct. Now the employer works out how much tax has to be paid from the personal information, such as number of children, given to them by each worker. But COSATU has seen that many workers have been taxed too much by their employers. This is mostly because no-one has explained to workers how the Site Tax system works and what tax reductions they are entitled to.
- Full Text:
- Date Issued: 1994
- Authors: COSATU
- Date: 1994
- Subjects: COSATU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/137159 , vital:37493
- Description: Since 1989 most workers in South Africa have had their wages taxed under the Site Tax system. SITE stands for Standard Income Tax on Employees. Under the Site Tax system, the employer is responsible for making sure that workers pay the correct, amount of tax. This is different from the old Pay As You Earn (PAYE) system where the Receiver of Revenue had to make sure that the amount of tax paid was correct. Now the employer works out how much tax has to be paid from the personal information, such as number of children, given to them by each worker. But COSATU has seen that many workers have been taxed too much by their employers. This is mostly because no-one has explained to workers how the Site Tax system works and what tax reductions they are entitled to.
- Full Text:
- Date Issued: 1994
Social constructivist mathematics education in a Ciskeian secondary school classroom
- Authors: Raghavan, Prasannakumary
- Date: 1994
- Subjects: Mathematics -- Curricula -- South Africa -- Ciskei -- Case studies Mathematics -- Study and teaching (Secondary) -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1767 , http://hdl.handle.net/10962/d1003652
- Description: The researcher's experience as a high school mathematics teacher in several African countries convinced her that a good number of mathematics learners exhibit serious difficulties in conceptualising mathematics properly. Her experience in teaching the subject in the Ciskei since 1990 reinforced this conviction. The researcher's natural curiosity to probe into the causes of the poor state of mathematics education in the region served as the springboard into her investigation. Her thoughts developed in line with the emerging educational theories of social constructivism. This provided a conceptual framework for the solution of the problem, the feasibility of which was put to test practically in a Ciskeian classroom. She explicates that the difficulties experienced by the pupils in conceptualising mathematics are philosophically deep rooted and latent in the present system of mathematics education itself, which, in Ciskei, impedes the learners' conceptualisation owing to numerous problems related to their linguistic and cultural situatedness. In the analysis of the present system of mathematics education in the Ciskei she reviews a few recently published mathematics text books in the context of the topics chosen for her research study. The results of her classroom investigation establish that a possible solution to the problem lies in the social constructivist teaching approaches.
- Full Text:
- Date Issued: 1994
- Authors: Raghavan, Prasannakumary
- Date: 1994
- Subjects: Mathematics -- Curricula -- South Africa -- Ciskei -- Case studies Mathematics -- Study and teaching (Secondary) -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1767 , http://hdl.handle.net/10962/d1003652
- Description: The researcher's experience as a high school mathematics teacher in several African countries convinced her that a good number of mathematics learners exhibit serious difficulties in conceptualising mathematics properly. Her experience in teaching the subject in the Ciskei since 1990 reinforced this conviction. The researcher's natural curiosity to probe into the causes of the poor state of mathematics education in the region served as the springboard into her investigation. Her thoughts developed in line with the emerging educational theories of social constructivism. This provided a conceptual framework for the solution of the problem, the feasibility of which was put to test practically in a Ciskeian classroom. She explicates that the difficulties experienced by the pupils in conceptualising mathematics are philosophically deep rooted and latent in the present system of mathematics education itself, which, in Ciskei, impedes the learners' conceptualisation owing to numerous problems related to their linguistic and cultural situatedness. In the analysis of the present system of mathematics education in the Ciskei she reviews a few recently published mathematics text books in the context of the topics chosen for her research study. The results of her classroom investigation establish that a possible solution to the problem lies in the social constructivist teaching approaches.
- Full Text:
- Date Issued: 1994
Social equity and job creation - The key to a stable future
- South African Labour Movement (SALM)
- Authors: South African Labour Movement (SALM)
- Date: Oct 1994
- Subjects: South African Labour Movement (SALM)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/116819 , vital:34448
- Description: Two years after the 1994 elections, South Africa remains a society characterised by vast inequalities, in wealth, economic power and incomes. Much progress has been made to build a common nationhood, to normalise political processes and to create a culture of freedom. We now face the challenge of addressing the glaring inequities in our country. In the process, some hard choices need to be made. As the white population had to give up its monopoly of political power in order to usher in the new democracy, so the economic elite should now be challenged to share the wealth and resources of our country to the benefit of all. This critical requirement for the new democracy — the active promotion of social equity — is the key objective organised labour sets for itself during 1996. We do this because too many South Africans are poor, underpaid or unemployed, homeless and with their basic needs and requirements not satisfied by the economy. Social equity in South Africa, and particularly the reduction of the vast inequalities in the society, must entail substantial redistribution of wealth, the eradication of poverty, the promotion of worker rights, increased employment the development of the full human potential of our people, and the provision of basic infrastructure and services to all citizens. The RDP calls for a programme to satisfy the basic needs of all South Africans. It calls for the development of our people. It calls for workers rights, and the building of the economy. These central pillars of reconstruction in the RDP should now be given concrete expression. Labour puts forward this framework as a first contribution to the current debate, and in order to clarify to the society what our analysis of the current situation is, and what our vision for the future entails.
- Full Text:
- Date Issued: Oct 1994
- Authors: South African Labour Movement (SALM)
- Date: Oct 1994
- Subjects: South African Labour Movement (SALM)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/116819 , vital:34448
- Description: Two years after the 1994 elections, South Africa remains a society characterised by vast inequalities, in wealth, economic power and incomes. Much progress has been made to build a common nationhood, to normalise political processes and to create a culture of freedom. We now face the challenge of addressing the glaring inequities in our country. In the process, some hard choices need to be made. As the white population had to give up its monopoly of political power in order to usher in the new democracy, so the economic elite should now be challenged to share the wealth and resources of our country to the benefit of all. This critical requirement for the new democracy — the active promotion of social equity — is the key objective organised labour sets for itself during 1996. We do this because too many South Africans are poor, underpaid or unemployed, homeless and with their basic needs and requirements not satisfied by the economy. Social equity in South Africa, and particularly the reduction of the vast inequalities in the society, must entail substantial redistribution of wealth, the eradication of poverty, the promotion of worker rights, increased employment the development of the full human potential of our people, and the provision of basic infrastructure and services to all citizens. The RDP calls for a programme to satisfy the basic needs of all South Africans. It calls for the development of our people. It calls for workers rights, and the building of the economy. These central pillars of reconstruction in the RDP should now be given concrete expression. Labour puts forward this framework as a first contribution to the current debate, and in order to clarify to the society what our analysis of the current situation is, and what our vision for the future entails.
- Full Text:
- Date Issued: Oct 1994
South Africa's post-apartheid foreign policy : towards a diplomacy of trade
- Authors: Dullabh, Nitesh Amratlal
- Date: 1994
- Subjects: Foreign trade regulation -- South Africa , South Africa -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2774 , http://hdl.handle.net/10962/d1002984 , Foreign trade regulation -- South Africa , South Africa -- Foreign relations
- Description: This thesis attempts to argue that a post-apartheid foreign policy will no longer be based on seeking legitimacy for the South African Government. Instead, it argues that if South Africa wants to grow, both domestically and nternationally, it will be imperative for it (South Africa) to move from an import substitution trade policy to an export-oriented trade policy. It is further suggested that the export-led strategy will be an important component for the promotion of South African international trade in the post-Cold War era. South Africa cannot improve the status of its trade regime by its own doing. It will require the support and assistance of international organizations and hence, the international community. Following the principles, rules and procedures of the General Agreement on Tariffs and Trade (GATT); it is argued, will help South Africa reconstruct its trade policies on the basis that they are free, fair and above all competitive. Furthermore, maintaining a constantly favourable relationship with the international community will allow easy access to international markets for South African goods and services, and eventually the smooth integration of the South African economy in the international political economy. This study, noting the importance of trade with a dedicated commitment to exports, concludes that although exports would flourish, there will be an immediate need for diplomats to be conversant with contemporary international trade developments. This would require diplomats to be innovative, steadfast and disciplined in their day-to-day negotiations. In the final instance, the role of trade in South Africa's future will ultimately be determined by its trade postures and the type of diplomacy to be used by its diplomats.
- Full Text:
- Date Issued: 1994
- Authors: Dullabh, Nitesh Amratlal
- Date: 1994
- Subjects: Foreign trade regulation -- South Africa , South Africa -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2774 , http://hdl.handle.net/10962/d1002984 , Foreign trade regulation -- South Africa , South Africa -- Foreign relations
- Description: This thesis attempts to argue that a post-apartheid foreign policy will no longer be based on seeking legitimacy for the South African Government. Instead, it argues that if South Africa wants to grow, both domestically and nternationally, it will be imperative for it (South Africa) to move from an import substitution trade policy to an export-oriented trade policy. It is further suggested that the export-led strategy will be an important component for the promotion of South African international trade in the post-Cold War era. South Africa cannot improve the status of its trade regime by its own doing. It will require the support and assistance of international organizations and hence, the international community. Following the principles, rules and procedures of the General Agreement on Tariffs and Trade (GATT); it is argued, will help South Africa reconstruct its trade policies on the basis that they are free, fair and above all competitive. Furthermore, maintaining a constantly favourable relationship with the international community will allow easy access to international markets for South African goods and services, and eventually the smooth integration of the South African economy in the international political economy. This study, noting the importance of trade with a dedicated commitment to exports, concludes that although exports would flourish, there will be an immediate need for diplomats to be conversant with contemporary international trade developments. This would require diplomats to be innovative, steadfast and disciplined in their day-to-day negotiations. In the final instance, the role of trade in South Africa's future will ultimately be determined by its trade postures and the type of diplomacy to be used by its diplomats.
- Full Text:
- Date Issued: 1994
Southern African Journal of Gerontology, volume 3, number 1, April 1994
- Ferreira, Monica (editor), Møller, Valerie (editor), HSRC/UCT Centre for Gerontology
- Authors: Ferreira, Monica (editor) , Møller, Valerie (editor) , HSRC/UCT Centre for Gerontology
- Date: 1994
- Subjects: Gerontology -- South Africa , Older people -- Care -- South Africa
- Language: English
- Type: Text
- Identifier: vital:8068 , http://hdl.handle.net/10962/d1012860
- Description: A typical case, culled from the author's own experience in the Third World, points towards a major crisis in ageing in the near future for many developing countries. Whilst the increase in numbers of elderly, both gross and proportionate, is well-known, it is not so widely realised that the increase in developing countries will far outstrip that in industrialized nations. Although the elderly were historically cared for within the traditional extended family structure, that system is now breaking down before the advance of migration and easy divorce. Many elderly persons are left alone in depopulated communities. Others fail to adapt in the rural-to-urban transition. Most developing countries have no firmly established services for the elderly. However, as awareness of the impending crisis increases, community groups assist the elderly in developing their own initiatives to avoid the local effects of the crisis.
- Full Text:
- Date Issued: 1994
- Authors: Ferreira, Monica (editor) , Møller, Valerie (editor) , HSRC/UCT Centre for Gerontology
- Date: 1994
- Subjects: Gerontology -- South Africa , Older people -- Care -- South Africa
- Language: English
- Type: Text
- Identifier: vital:8068 , http://hdl.handle.net/10962/d1012860
- Description: A typical case, culled from the author's own experience in the Third World, points towards a major crisis in ageing in the near future for many developing countries. Whilst the increase in numbers of elderly, both gross and proportionate, is well-known, it is not so widely realised that the increase in developing countries will far outstrip that in industrialized nations. Although the elderly were historically cared for within the traditional extended family structure, that system is now breaking down before the advance of migration and easy divorce. Many elderly persons are left alone in depopulated communities. Others fail to adapt in the rural-to-urban transition. Most developing countries have no firmly established services for the elderly. However, as awareness of the impending crisis increases, community groups assist the elderly in developing their own initiatives to avoid the local effects of the crisis.
- Full Text:
- Date Issued: 1994
Southern African Journal of Gerontology, volume 3, number 2, October 1994
- Ferreira, Monica (editor), Møller, Valerie (editor), HSRC/UCT Centre for Gerontology
- Authors: Ferreira, Monica (editor) , Møller, Valerie (editor) , HSRC/UCT Centre for Gerontology
- Date: 1994
- Subjects: Gerontology -- South Africa , Older people -- Care -- South Africa
- Language: English
- Type: Text
- Identifier: vital:8069 , http://hdl.handle.net/10962/d1012861
- Description: Intergenerational relations is not a new focus area of study in Southern Africa. Trends in changing relationships between age cohorts have been traced in family, migration and urbanization studies. This special issue of the Southern African Journal of Gerontology presents a case for studying intergenerational relations from a gerontological perspective. The issue includes work from leading international gerontologists and experts in the field of intergenerational relations writing on the United States. Two further contributions come from other parts of Africa - Ghana and Kenya. The articles on intergenerational relations in South Africa, tellingly, come from outside the field of gerontology, a point to be picked up below.
- Full Text:
- Date Issued: 1994
- Authors: Ferreira, Monica (editor) , Møller, Valerie (editor) , HSRC/UCT Centre for Gerontology
- Date: 1994
- Subjects: Gerontology -- South Africa , Older people -- Care -- South Africa
- Language: English
- Type: Text
- Identifier: vital:8069 , http://hdl.handle.net/10962/d1012861
- Description: Intergenerational relations is not a new focus area of study in Southern Africa. Trends in changing relationships between age cohorts have been traced in family, migration and urbanization studies. This special issue of the Southern African Journal of Gerontology presents a case for studying intergenerational relations from a gerontological perspective. The issue includes work from leading international gerontologists and experts in the field of intergenerational relations writing on the United States. Two further contributions come from other parts of Africa - Ghana and Kenya. The articles on intergenerational relations in South Africa, tellingly, come from outside the field of gerontology, a point to be picked up below.
- Full Text:
- Date Issued: 1994
Static analysis of functional languages
- Authors: Mountjoy, Jon-Dean
- Date: 1994 , 2012-10-10
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4669 , http://hdl.handle.net/10962/d1006690 , Functional programming languages
- Description: Static analysis is the name given to a number of compile time analysis techniques used to automatically generate information which can lead to improvements in the execution performance of function languages. This thesis provides an introduction to these techniques and their implementation. The abstract interpretation framework is an example of a technique used to extract information from a program by providing the program with an alternate semantics and evaluating this program over a non-standard domain. The elements of this domain represent certain properties of interest. This framework is examined in detail, as well as various extensions and variants of it. The use of binary logical relations and program logics as alternative formulations of the framework , and partial equivalence relations as an extension to it, are also looked at. The projection analysis framework determines how much of a sub-expression can be evaluated by examining the context in which the expression is to be evaluated, and provides an elegant method for finding particular types of information from data structures. This is also examined. The most costly operation in implementing an analysis is the computation of fixed points. Methods developed to make this process more efficient are looked at. This leads to the final chapter which highlights the dependencies and relationships between the different frameworks and their mathematical disciplines. , KMBT_223
- Full Text:
- Date Issued: 1994
- Authors: Mountjoy, Jon-Dean
- Date: 1994 , 2012-10-10
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4669 , http://hdl.handle.net/10962/d1006690 , Functional programming languages
- Description: Static analysis is the name given to a number of compile time analysis techniques used to automatically generate information which can lead to improvements in the execution performance of function languages. This thesis provides an introduction to these techniques and their implementation. The abstract interpretation framework is an example of a technique used to extract information from a program by providing the program with an alternate semantics and evaluating this program over a non-standard domain. The elements of this domain represent certain properties of interest. This framework is examined in detail, as well as various extensions and variants of it. The use of binary logical relations and program logics as alternative formulations of the framework , and partial equivalence relations as an extension to it, are also looked at. The projection analysis framework determines how much of a sub-expression can be evaluated by examining the context in which the expression is to be evaluated, and provides an elegant method for finding particular types of information from data structures. This is also examined. The most costly operation in implementing an analysis is the computation of fixed points. Methods developed to make this process more efficient are looked at. This leads to the final chapter which highlights the dependencies and relationships between the different frameworks and their mathematical disciplines. , KMBT_223
- Full Text:
- Date Issued: 1994
Stress manipulation in Dunaliella salina and dual-stage [beta]-carotene production
- Authors: Phillips, Trevor David
- Date: 1994
- Subjects: Dunaliella Carotenes Plants -- Effect of stress on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4037 , http://hdl.handle.net/10962/d1004097
- Description: The alga Dunaliella salina accumulates large quantities of β-carotene in response to certain environmental and physiological stresses. This hyper-accumulation process has been commercially exploited. However, the currently employed averaging or single-stage process produces β-carotene yields well below the genetic potential of the organism due to the inverse relationship between growth and secondary metabolite production. A dual-stage process, which separates the distinctive growth and secondary metabolite production stages of the alga, has been proposed. The broad aim of the research programme was to evaluate the practicality, scale-up and economic viability of a dual-stage β-carotene production process from D. salina. Preliminary laboratory studies showed that although stress factors such as high salinity and a range of nutrient limitations enhance β-carotene accumulation in D. salina, high light intensity is the single most important factor inducing β-carotene hyper-accumulation in the alga. Furthermore, the preliminary studies indicated that 6-carotene production could be successfully manipulated by the imposition of stress. The stress response of D. salina to high light stress was examined at a fundamental level. The relative partitioning of β-carotene between thylakoid membrane and interthylakoid globular β-carotene has revealed two responses to high light stress. The first is a response in which the alga adapts to the photoinhibitory effects of high light stress by the rapid accumulation and the peripheral localisation of Jl-carotene to the outer extremities of the chloroplast. This is followed by a maintenance response which is characterised by the recovery of the photosynthetic rate and cell growth. A possible interrelationship between the extent of the photo inhibitory response and the amount of β-carotene hyper-accumulation has been noted. An outdoor evaluation of the growth stage of the dual-stage system has demonstrated that D. salina can be grown in a relatively low salinity, nutrient sufficient medium for extended periods without overgrowth by small non-carotenogenic Dunaliella species. In addition, biomass productivities of three times greater than those obtained in the currently employed averaging system were achieved. The role of high light intensity in β-carotene hyper-accumulation was confirmed in outdoor scale-up stress pond studies. The studies demonstrated the feasibility of stress induced ll-carotene production in outdoor cultures of D. salina and β-carotene yields three times greater than those obtained in the currently employed averaging process were achieved. The dual-stage process imposes the specific requirement of viable cell separation on the harvesting system employed. A flocculation-flotation process and an air-displacement crossflow ultrafiltration system were developed and successfully evaluated for the separation of D. salina from the brine solution in a viable form. The extraction of β-carotene from D. salina was evaluated. Supercritical fluid extraction studies showed that the use of a co-solvent mixture of carbon dioxide and propane could effectively reduce the high extraction pressures associated with supercritical carbon dioxide extraction. In addition, a novel hydrophobic membrane assisted hot oil extraction process was developed which separates the complex oil-water emulsions produced during hot oil extraction of 6-carotene from wet D. salina biomass. Process design and economic evaluation studies were undertaken and showed that the economics of the dual-stage process offer significant advantages over the currently employed averaging process.
- Full Text:
- Date Issued: 1994
- Authors: Phillips, Trevor David
- Date: 1994
- Subjects: Dunaliella Carotenes Plants -- Effect of stress on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4037 , http://hdl.handle.net/10962/d1004097
- Description: The alga Dunaliella salina accumulates large quantities of β-carotene in response to certain environmental and physiological stresses. This hyper-accumulation process has been commercially exploited. However, the currently employed averaging or single-stage process produces β-carotene yields well below the genetic potential of the organism due to the inverse relationship between growth and secondary metabolite production. A dual-stage process, which separates the distinctive growth and secondary metabolite production stages of the alga, has been proposed. The broad aim of the research programme was to evaluate the practicality, scale-up and economic viability of a dual-stage β-carotene production process from D. salina. Preliminary laboratory studies showed that although stress factors such as high salinity and a range of nutrient limitations enhance β-carotene accumulation in D. salina, high light intensity is the single most important factor inducing β-carotene hyper-accumulation in the alga. Furthermore, the preliminary studies indicated that 6-carotene production could be successfully manipulated by the imposition of stress. The stress response of D. salina to high light stress was examined at a fundamental level. The relative partitioning of β-carotene between thylakoid membrane and interthylakoid globular β-carotene has revealed two responses to high light stress. The first is a response in which the alga adapts to the photoinhibitory effects of high light stress by the rapid accumulation and the peripheral localisation of Jl-carotene to the outer extremities of the chloroplast. This is followed by a maintenance response which is characterised by the recovery of the photosynthetic rate and cell growth. A possible interrelationship between the extent of the photo inhibitory response and the amount of β-carotene hyper-accumulation has been noted. An outdoor evaluation of the growth stage of the dual-stage system has demonstrated that D. salina can be grown in a relatively low salinity, nutrient sufficient medium for extended periods without overgrowth by small non-carotenogenic Dunaliella species. In addition, biomass productivities of three times greater than those obtained in the currently employed averaging system were achieved. The role of high light intensity in β-carotene hyper-accumulation was confirmed in outdoor scale-up stress pond studies. The studies demonstrated the feasibility of stress induced ll-carotene production in outdoor cultures of D. salina and β-carotene yields three times greater than those obtained in the currently employed averaging process were achieved. The dual-stage process imposes the specific requirement of viable cell separation on the harvesting system employed. A flocculation-flotation process and an air-displacement crossflow ultrafiltration system were developed and successfully evaluated for the separation of D. salina from the brine solution in a viable form. The extraction of β-carotene from D. salina was evaluated. Supercritical fluid extraction studies showed that the use of a co-solvent mixture of carbon dioxide and propane could effectively reduce the high extraction pressures associated with supercritical carbon dioxide extraction. In addition, a novel hydrophobic membrane assisted hot oil extraction process was developed which separates the complex oil-water emulsions produced during hot oil extraction of 6-carotene from wet D. salina biomass. Process design and economic evaluation studies were undertaken and showed that the economics of the dual-stage process offer significant advantages over the currently employed averaging process.
- Full Text:
- Date Issued: 1994
Structural studies on some enterobacterial capsular antigens
- Authors: Whittaker, Darryl Vanstone
- Date: 1994
- Subjects: Bacterial antigens -- Analysis Antigens Enterobacteriaceae Escherichia coli Klebsiella
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3803 , http://hdl.handle.net/10962/d1003281
- Description: The investigations presented in this thesis form part of a systematic international effort to establish the structures of the capsules produced by the bacterial genera, Escherichia coli and Klebsiella (family enterobacteriaceae). These bacteria are of medical interest as they are opportunistic pathogens and are frequently responsible for serious infections in animals and man. Invasive strains are invariably surrounded by a structurally complex polysaccharide capsule which contributes to the organism's ability to attenuate non-specific host defence mechanisms or, in some instances, to completely prevent an immune response. A knowledge of the chemical composition and structure of the capsule is, therefore, of great value as it provides insight into the mechanisms involved in this process. The E. coli, in particular, have generated considerable interest as their capsules are more structurally diverse and cross-reactivity with other, more pathogenic bacteria has also been demonstrated. Accordingly, the structures of three previously unstudied E. coli K-antigens viz. those produced by serotypes 020:K83:H26, 020:K84:H26, and 09:K48:H9 have been established by chemical and spectroscopic means and are presented in this thesis. In addition, a reinvestigation of the structure of the capsule produced by Klebsiella K15 using a novel enzymatic approach was also undertaken and a revised structure is proposed . The E. coli K48 polysaccharide is of special interest as it was found to contain a new diacetamido trideoxy hexose hitherto unrecorded. A synthesis for this saccharide is also presented. Finally, the application of lithium dissolved in ethylenediamine for the degradation of amino sugar-containing polysaccharides was also investigated using the capsular polysaccharides produced by E. coli serotypes K38 and K84 as model compounds.
- Full Text:
- Date Issued: 1994
- Authors: Whittaker, Darryl Vanstone
- Date: 1994
- Subjects: Bacterial antigens -- Analysis Antigens Enterobacteriaceae Escherichia coli Klebsiella
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3803 , http://hdl.handle.net/10962/d1003281
- Description: The investigations presented in this thesis form part of a systematic international effort to establish the structures of the capsules produced by the bacterial genera, Escherichia coli and Klebsiella (family enterobacteriaceae). These bacteria are of medical interest as they are opportunistic pathogens and are frequently responsible for serious infections in animals and man. Invasive strains are invariably surrounded by a structurally complex polysaccharide capsule which contributes to the organism's ability to attenuate non-specific host defence mechanisms or, in some instances, to completely prevent an immune response. A knowledge of the chemical composition and structure of the capsule is, therefore, of great value as it provides insight into the mechanisms involved in this process. The E. coli, in particular, have generated considerable interest as their capsules are more structurally diverse and cross-reactivity with other, more pathogenic bacteria has also been demonstrated. Accordingly, the structures of three previously unstudied E. coli K-antigens viz. those produced by serotypes 020:K83:H26, 020:K84:H26, and 09:K48:H9 have been established by chemical and spectroscopic means and are presented in this thesis. In addition, a reinvestigation of the structure of the capsule produced by Klebsiella K15 using a novel enzymatic approach was also undertaken and a revised structure is proposed . The E. coli K48 polysaccharide is of special interest as it was found to contain a new diacetamido trideoxy hexose hitherto unrecorded. A synthesis for this saccharide is also presented. Finally, the application of lithium dissolved in ethylenediamine for the degradation of amino sugar-containing polysaccharides was also investigated using the capsular polysaccharides produced by E. coli serotypes K38 and K84 as model compounds.
- Full Text:
- Date Issued: 1994
Studies in asymmetric synthesis
- Authors: Ravindran, Swarnam Shanthi
- Date: 1994
- Subjects: Asymmetric synthesis Chirality Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4352 , http://hdl.handle.net/10962/d1005017
- Description: The stereoselectivity of TiCI₄-catalysed Mukaiyama reactions of a camphor acetal-derived chiral silyl enol ether with a range of substituted aromatic aldehydes has been examined. The enantiomeric excess in each of the resulting ß-hydroxy ketones, determined by ¹H NMR spectroscopy using the lanthanide chiral shift reagent Pr(Etcf₃), ranged between 9 and 13%. The stereo-directing potential of the camphor acetal as a chiral auxiliary in the α-benzylation of carboxylate esters has been studied; the acids were chosen to illustrate substituent effects on asymmetric induction. The observed diastereoselectivity increased with increasing steric bulk of the ester group and α-benzylation of the tert-butylacetate derivative proceeded with 48% diastereoselectivity. It is proposed that the enolate adopts an endo-s-trans conformation in the transition state and preferential attack by the electrophile at the somewhat less hindered Si-face is supported by both the optical rotation data and computer modelling studies. Reductive cleavage and hydrolysis of one of the benzylated esters furnished known products from whose optical rotation the configuration of the major diastereomer was established. In order to improve the steric advantage of Si-facial attack, methods of increasing the steric bulk of the blocking group were explored. A novel 2,2-propylenedioxy hydroxycamphor acetal and its 3,3-propylenedioxy analogue were prepared. Selected carboxylate esters of these propylenedioxy acetals were subjected to α-benzylation and the 2,2-(propylenedioxy)-3-exo-tert-butylacetate derivative showed a diastereoselectivity of 57% during a-benzylation. Hydrolysis of the abenzylated phenylacetate analogue offered the known 2,3-diphenylpropanoic acid whose optical rotation indicated the preferred configuration at the new chiral centre to be (R), a result which is consistent with the proposed approach of the electrophile to the less hindered Re-face of theendo-s-trans enolate moiety and reflects an inversion of the configurational bias observed with 2-v exo-carboxylate analogues. Attempts to prepare the monocatechol acetal of the hydroxy camphor derivative although unsuccessful, led to the isolation of two novel dibornyl ethers whose structures were established by 1- and 2-D NMR spectroscopy. A study of novel applications of camphor-derived auxiliaries in the asymmetric synthesis of α-amino acids has been initiated. The several approaches tried led to the preparation of three novel dural glycine derivatives in good yield
- Full Text:
- Date Issued: 1994
- Authors: Ravindran, Swarnam Shanthi
- Date: 1994
- Subjects: Asymmetric synthesis Chirality Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4352 , http://hdl.handle.net/10962/d1005017
- Description: The stereoselectivity of TiCI₄-catalysed Mukaiyama reactions of a camphor acetal-derived chiral silyl enol ether with a range of substituted aromatic aldehydes has been examined. The enantiomeric excess in each of the resulting ß-hydroxy ketones, determined by ¹H NMR spectroscopy using the lanthanide chiral shift reagent Pr(Etcf₃), ranged between 9 and 13%. The stereo-directing potential of the camphor acetal as a chiral auxiliary in the α-benzylation of carboxylate esters has been studied; the acids were chosen to illustrate substituent effects on asymmetric induction. The observed diastereoselectivity increased with increasing steric bulk of the ester group and α-benzylation of the tert-butylacetate derivative proceeded with 48% diastereoselectivity. It is proposed that the enolate adopts an endo-s-trans conformation in the transition state and preferential attack by the electrophile at the somewhat less hindered Si-face is supported by both the optical rotation data and computer modelling studies. Reductive cleavage and hydrolysis of one of the benzylated esters furnished known products from whose optical rotation the configuration of the major diastereomer was established. In order to improve the steric advantage of Si-facial attack, methods of increasing the steric bulk of the blocking group were explored. A novel 2,2-propylenedioxy hydroxycamphor acetal and its 3,3-propylenedioxy analogue were prepared. Selected carboxylate esters of these propylenedioxy acetals were subjected to α-benzylation and the 2,2-(propylenedioxy)-3-exo-tert-butylacetate derivative showed a diastereoselectivity of 57% during a-benzylation. Hydrolysis of the abenzylated phenylacetate analogue offered the known 2,3-diphenylpropanoic acid whose optical rotation indicated the preferred configuration at the new chiral centre to be (R), a result which is consistent with the proposed approach of the electrophile to the less hindered Re-face of theendo-s-trans enolate moiety and reflects an inversion of the configurational bias observed with 2-v exo-carboxylate analogues. Attempts to prepare the monocatechol acetal of the hydroxy camphor derivative although unsuccessful, led to the isolation of two novel dibornyl ethers whose structures were established by 1- and 2-D NMR spectroscopy. A study of novel applications of camphor-derived auxiliaries in the asymmetric synthesis of α-amino acids has been initiated. The several approaches tried led to the preparation of three novel dural glycine derivatives in good yield
- Full Text:
- Date Issued: 1994
Studies on the bioactivities of selected Eastern Cape seaweeds
- Authors: Carter, Anne Margaret
- Date: 1994
- Subjects: Marine algae -- South Africa -- Eastern Cape , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4033 , http://hdl.handle.net/10962/d1004093 , Marine algae -- South Africa -- Eastern Cape , Marine algae
- Description: In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.
- Full Text:
- Date Issued: 1994
- Authors: Carter, Anne Margaret
- Date: 1994
- Subjects: Marine algae -- South Africa -- Eastern Cape , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4033 , http://hdl.handle.net/10962/d1004093 , Marine algae -- South Africa -- Eastern Cape , Marine algae
- Description: In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.
- Full Text:
- Date Issued: 1994
Studies related to the process of program development
- Authors: Williams, Morgan Howard
- Date: 1994
- Subjects: Computer programming
- Language: English
- Type: Thesis , Doctoral , DSc
- Identifier: vital:4680 , http://hdl.handle.net/10962/d1007235
- Description: The submitted work consists of a collection of publications arising from research carried out at Rhodes University (1970-1980) and at Heriot-Watt University (1980-1992). The theme of this research is the process of program development, i.e. the process of creating a computer program to solve some particular problem. The papers presented cover a number of different topics which relate to this process, viz. (a) Programming methodology programming. (b) Properties of programming languages. aspects of structured. (c) Formal specification of programming languages. (d) Compiler techniques. (e) Declarative programming languages. (f) Program development aids. (g) Automatic program generation. (h) Databases. (i) Algorithms and applications.
- Full Text:
- Date Issued: 1994
- Authors: Williams, Morgan Howard
- Date: 1994
- Subjects: Computer programming
- Language: English
- Type: Thesis , Doctoral , DSc
- Identifier: vital:4680 , http://hdl.handle.net/10962/d1007235
- Description: The submitted work consists of a collection of publications arising from research carried out at Rhodes University (1970-1980) and at Heriot-Watt University (1980-1992). The theme of this research is the process of program development, i.e. the process of creating a computer program to solve some particular problem. The papers presented cover a number of different topics which relate to this process, viz. (a) Programming methodology programming. (b) Properties of programming languages. aspects of structured. (c) Formal specification of programming languages. (d) Compiler techniques. (e) Declarative programming languages. (f) Program development aids. (g) Automatic program generation. (h) Databases. (i) Algorithms and applications.
- Full Text:
- Date Issued: 1994
Surficial placer gold deposits
- Authors: Mann, P L
- Date: 1994
- Subjects: Gold mines and mining , Gold ores -- Geology , Placer deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5088 , http://hdl.handle.net/10962/d1018245
- Description: This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
- Full Text:
- Date Issued: 1994
- Authors: Mann, P L
- Date: 1994
- Subjects: Gold mines and mining , Gold ores -- Geology , Placer deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5088 , http://hdl.handle.net/10962/d1018245
- Description: This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
- Full Text:
- Date Issued: 1994
Synthesis and conformational studies of indolizines
- Authors: George, Rosemary
- Date: 1994
- Subjects: Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4367 , http://hdl.handle.net/10962/d1005032 , Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Description: The present investigation has involved a kinetic and mechanistic study of the thermal cyclization of 3-acetoxy-3-(2-pyridyl)-2-methylenepropanoate esters and related compounds to 2-substituted indolizines. Substrates for the kinetic study were prepared via the Baylis-Hillmann reaction of pyridine-2-carboxaldehydes with acrylate esters, acrylonitrile and methyl vinyl ketone. The resulting hydroxy compounds were then acetylated to afford the acetoxy derivatives, thermal cyclization of which gave the corresponding 2-substituted indolizines. The cyclization reactions was followed using 'H NMR spectroscopy and were shown to follow firstorder kinetics. The influence of the various substituents on the observed first-order rate constants has been examined and variable temperature studies have permitted evaluation of activation parameters for the formation of methyl indolizine-2-carboxylate and ethyl indolizine-2-carboxylate. An alternative route to 2-substituted indolizines via halogenated derivatives was explored and several halogenated 2-pyridyl derivatives were synthesised and their thermal cyclization to indolizines was attempted. Novel 5-methylindolizine-2-carboxamides were prepared as part of this investigation and dynamic NMR spectroscopy was used to study internal rotation about the amide N-CO bond in these compounds.
- Full Text:
- Date Issued: 1994
- Authors: George, Rosemary
- Date: 1994
- Subjects: Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4367 , http://hdl.handle.net/10962/d1005032 , Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Description: The present investigation has involved a kinetic and mechanistic study of the thermal cyclization of 3-acetoxy-3-(2-pyridyl)-2-methylenepropanoate esters and related compounds to 2-substituted indolizines. Substrates for the kinetic study were prepared via the Baylis-Hillmann reaction of pyridine-2-carboxaldehydes with acrylate esters, acrylonitrile and methyl vinyl ketone. The resulting hydroxy compounds were then acetylated to afford the acetoxy derivatives, thermal cyclization of which gave the corresponding 2-substituted indolizines. The cyclization reactions was followed using 'H NMR spectroscopy and were shown to follow firstorder kinetics. The influence of the various substituents on the observed first-order rate constants has been examined and variable temperature studies have permitted evaluation of activation parameters for the formation of methyl indolizine-2-carboxylate and ethyl indolizine-2-carboxylate. An alternative route to 2-substituted indolizines via halogenated derivatives was explored and several halogenated 2-pyridyl derivatives were synthesised and their thermal cyclization to indolizines was attempted. Novel 5-methylindolizine-2-carboxamides were prepared as part of this investigation and dynamic NMR spectroscopy was used to study internal rotation about the amide N-CO bond in these compounds.
- Full Text:
- Date Issued: 1994
Synthetic and spectroscopic studies of 1,4-benzodiazepine analogues
- Authors: Mphahlele, Malose Jack
- Date: 1994
- Subjects: Benzodiazepines Tranquilizing drugs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4384 , http://hdl.handle.net/10962/d1005049
- Description: In this project, an extensive range of benzodiazepine analogues have been synthesised via Schmidt reaction of specially prepared flavanone, 4-quinolone and l-thioflavanone precursors; nitrogen insertion being effected by use of trimethylsilyl azide in trifluoroacetic acid. In some cases, several of the benzodiazepine analogues have also been prepared by alternative cyclisation routes. A detailed kinetic-mechanistic study of the Schmidt reaction of flavanones has been carried out using 'H NMR spectroscopy to explain the observed regiochemistry of nitrogen insertion. The reaction rates, for the formation of both amide and tetrazolo derivatives have been found to be influenced by the electronic effects of the A- and B-ring substituents. A series of benzodiazepine analogues have been shown to undergo regioselective A-ring chlorination with t-butylhypochlorite; the products being characterised by 'H NMR, IR and mass spectroscopy. The mass spectrometric fragmentation patterns of series of 2-aryl-4-quinolones, and 2-aryl-l ,4-benzodiazepinones and their tetrazolo[l ,5-dl analogues have been elucidated using a combination of low-resolution, high-resolution and metastable-peak analyses. The binding affinities of various benzodiazepine analogues for rat brain benzodiazepine receptors have been evaluated using a radioreceptor assay technique. Structure-activity relationships were investigated to establish the effects of various A-, B- and Coring substituents on binding affinity. The conformational preferences of selected systems have been studied using a combination of multi-pulse 'H NMR spectroscopy, X-ray crystallography and computer modelling techniques with a view to establishing the influence of conformation on binding affinity.
- Full Text:
- Date Issued: 1994
- Authors: Mphahlele, Malose Jack
- Date: 1994
- Subjects: Benzodiazepines Tranquilizing drugs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4384 , http://hdl.handle.net/10962/d1005049
- Description: In this project, an extensive range of benzodiazepine analogues have been synthesised via Schmidt reaction of specially prepared flavanone, 4-quinolone and l-thioflavanone precursors; nitrogen insertion being effected by use of trimethylsilyl azide in trifluoroacetic acid. In some cases, several of the benzodiazepine analogues have also been prepared by alternative cyclisation routes. A detailed kinetic-mechanistic study of the Schmidt reaction of flavanones has been carried out using 'H NMR spectroscopy to explain the observed regiochemistry of nitrogen insertion. The reaction rates, for the formation of both amide and tetrazolo derivatives have been found to be influenced by the electronic effects of the A- and B-ring substituents. A series of benzodiazepine analogues have been shown to undergo regioselective A-ring chlorination with t-butylhypochlorite; the products being characterised by 'H NMR, IR and mass spectroscopy. The mass spectrometric fragmentation patterns of series of 2-aryl-4-quinolones, and 2-aryl-l ,4-benzodiazepinones and their tetrazolo[l ,5-dl analogues have been elucidated using a combination of low-resolution, high-resolution and metastable-peak analyses. The binding affinities of various benzodiazepine analogues for rat brain benzodiazepine receptors have been evaluated using a radioreceptor assay technique. Structure-activity relationships were investigated to establish the effects of various A-, B- and Coring substituents on binding affinity. The conformational preferences of selected systems have been studied using a combination of multi-pulse 'H NMR spectroscopy, X-ray crystallography and computer modelling techniques with a view to establishing the influence of conformation on binding affinity.
- Full Text:
- Date Issued: 1994
Synthetic and spectroscopic studies of indolizine derivatives
- Authors: Bode, Moira Leanne
- Date: 1994
- Subjects: Indole alkaloids -- Derivatives Spectrum analysis Chemistry, Organic DNA -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4385 , http://hdl.handle.net/10962/d1005050
- Description: The crystalline compound resulting from thermal cyclization of the Baylis-Hillman product, methyl 3-hydroxy-2-methylene-3-(2-pyridyl)propanoate, has been identified as the indolizine derivative, methyl indolizine-2-carboxylate, and this approach involving the reaction of pyridine-2-carboxaldehydes and acrylate analogues has been established as a general route to 2-substituted indolizines. The ease of cyclization the Baylis-Hillman products to indolizines has been shown to increase by converting the hydroxy group to an acetoxy group, and a range of acetylated Baylis-Hillman products were prepared and cyc1ized to the corresponding 2-substituted indolizines, generally in good overall yield. In the reaction of pyridine-2-carboxaldehyde and methyl vinyl ketone, the intermediate cyclized readily and directly to the corresponding indolizine. One- and two-dimensional ¹H and ¹³C NMR analysis of the 2-substituted indolizine products has permitted complete assignment of all ¹H and ¹³C NMR signals, as well as the measurement of all coupling constants for these compounds. A kinetic and mechanistic study has been conducted on the Baylis-Hillman reaction using ¹H NMR spectroscopy. A range of substrates has been examined and the reaction has been found to be third-order overall. A mechanism involving an addition - elimination sequence is proposed, which fits the kinetic data and accounts for observed substituent effects. Reaction of N,N-dimethylacrylamide with pyridine-2-carboxaldehyde in the presence of the tertiary amine catalyst, DABCO, in chloroform, yielded an unexpected product which has been identified by single crystal X-ray diffraction analysis as 1-(2,2,2-trichloro-1-hydroxyethyl)pyridine. Attempted extension of the general indolizine route to the preparation of chromene systems by reacting salicylaldehyde with methyl acrylate in the presence of DABCO, also led to an unexpected, crystalline material, identified by single crystal X-ray diffraction analysis as the coumarin derivative, 3-[(2-formylphenoxy)methyl]coumarin.A series of chloroquine analogues have been prepared from indolizine-2-carboxylic acid, pyrrolo[I,2-a]quinoline-2-carboxylic acid and imidazo[I,2-a]pyridine-2-carboxylic acid by reaction with suitable amines in the presence of the coupling reagent 1, I' -carbonyldiimidazole. This route has been shown to be a vast improvement on earlier procedures and has provided access to both secondary and tertiary indolizine-2-carboxamides. A range of N,N-dialkylindolizine-2-carboxamides have been prepared by this route, and the influence of substituents on their N-CO rotational energy barriers has been determined using variable temperature ¹H and ¹³C NMR techniques. Intercalation with natural DNA by both chloroquine and the synthesized chloroquine analogues has been examined using UV spectrophotometry, and ¹H and ³¹P NMR spectroscopy. The pyrrolo[I,2-a]quinolines have been shown to be DNA intercalators with binding affinities similar to that of the known antimalarial intercalator, chloroquine. In a preliminary study the synthesis of a short oligonucleotide has been undertaken and changes have been observed in the ¹H and ³¹P NMR spectra of the oligonucleotide on addition of the intercalator, chloroquine.
- Full Text:
- Date Issued: 1994
- Authors: Bode, Moira Leanne
- Date: 1994
- Subjects: Indole alkaloids -- Derivatives Spectrum analysis Chemistry, Organic DNA -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4385 , http://hdl.handle.net/10962/d1005050
- Description: The crystalline compound resulting from thermal cyclization of the Baylis-Hillman product, methyl 3-hydroxy-2-methylene-3-(2-pyridyl)propanoate, has been identified as the indolizine derivative, methyl indolizine-2-carboxylate, and this approach involving the reaction of pyridine-2-carboxaldehydes and acrylate analogues has been established as a general route to 2-substituted indolizines. The ease of cyclization the Baylis-Hillman products to indolizines has been shown to increase by converting the hydroxy group to an acetoxy group, and a range of acetylated Baylis-Hillman products were prepared and cyc1ized to the corresponding 2-substituted indolizines, generally in good overall yield. In the reaction of pyridine-2-carboxaldehyde and methyl vinyl ketone, the intermediate cyclized readily and directly to the corresponding indolizine. One- and two-dimensional ¹H and ¹³C NMR analysis of the 2-substituted indolizine products has permitted complete assignment of all ¹H and ¹³C NMR signals, as well as the measurement of all coupling constants for these compounds. A kinetic and mechanistic study has been conducted on the Baylis-Hillman reaction using ¹H NMR spectroscopy. A range of substrates has been examined and the reaction has been found to be third-order overall. A mechanism involving an addition - elimination sequence is proposed, which fits the kinetic data and accounts for observed substituent effects. Reaction of N,N-dimethylacrylamide with pyridine-2-carboxaldehyde in the presence of the tertiary amine catalyst, DABCO, in chloroform, yielded an unexpected product which has been identified by single crystal X-ray diffraction analysis as 1-(2,2,2-trichloro-1-hydroxyethyl)pyridine. Attempted extension of the general indolizine route to the preparation of chromene systems by reacting salicylaldehyde with methyl acrylate in the presence of DABCO, also led to an unexpected, crystalline material, identified by single crystal X-ray diffraction analysis as the coumarin derivative, 3-[(2-formylphenoxy)methyl]coumarin.A series of chloroquine analogues have been prepared from indolizine-2-carboxylic acid, pyrrolo[I,2-a]quinoline-2-carboxylic acid and imidazo[I,2-a]pyridine-2-carboxylic acid by reaction with suitable amines in the presence of the coupling reagent 1, I' -carbonyldiimidazole. This route has been shown to be a vast improvement on earlier procedures and has provided access to both secondary and tertiary indolizine-2-carboxamides. A range of N,N-dialkylindolizine-2-carboxamides have been prepared by this route, and the influence of substituents on their N-CO rotational energy barriers has been determined using variable temperature ¹H and ¹³C NMR techniques. Intercalation with natural DNA by both chloroquine and the synthesized chloroquine analogues has been examined using UV spectrophotometry, and ¹H and ³¹P NMR spectroscopy. The pyrrolo[I,2-a]quinolines have been shown to be DNA intercalators with binding affinities similar to that of the known antimalarial intercalator, chloroquine. In a preliminary study the synthesis of a short oligonucleotide has been undertaken and changes have been observed in the ¹H and ³¹P NMR spectra of the oligonucleotide on addition of the intercalator, chloroquine.
- Full Text:
- Date Issued: 1994