Reproductive biology of the Egyptian free-tailed bat, Tadarida Aegyptiaca
- Authors: Tsita, Johannes Ngoako
- Date: 1994
- Subjects: Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5754 , http://hdl.handle.net/10962/d1005442 , Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Description: The reproductive biology of Tadarida aegyptiaca was studied using specimens collected in the Cape Province of South Africa. The morphology of the reproductive tract of the species was generally similar to that of other molossids, however, the absence of Cowpers glands was unusual. Spermatogenesis began in February and spermatozoa were released to the cauda epididymis during August and September. Follicular development started in March and culminated with the appearance of Graafian follicles in July. Ovulation probably occurred in August and specimens were pregnant by September. Gestation length was estimated to be four to five months and a single young was born in December. The data suggest that T. aegyptiaca is monotocous and monoestrous.
- Full Text:
- Date Issued: 1994
- Authors: Tsita, Johannes Ngoako
- Date: 1994
- Subjects: Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5754 , http://hdl.handle.net/10962/d1005442 , Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Description: The reproductive biology of Tadarida aegyptiaca was studied using specimens collected in the Cape Province of South Africa. The morphology of the reproductive tract of the species was generally similar to that of other molossids, however, the absence of Cowpers glands was unusual. Spermatogenesis began in February and spermatozoa were released to the cauda epididymis during August and September. Follicular development started in March and culminated with the appearance of Graafian follicles in July. Ovulation probably occurred in August and specimens were pregnant by September. Gestation length was estimated to be four to five months and a single young was born in December. The data suggest that T. aegyptiaca is monotocous and monoestrous.
- Full Text:
- Date Issued: 1994
Research priorities for environmental education in southern Africa: Preliminary report
- Authors: Janse van Rensburg, Eureta
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/438781 , vital:73499 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137480"
- Description: In this preliminary research report I introduce initial interpretations of the results of a recently completed study on research priorities in southern Africa. The study has been sponsored by Murray and Roberts, Rhodes University and the HNRE (Human and Natural Resources in the Environment) Programme of the Human Sciences Research Council.
- Full Text:
- Date Issued: 1994
- Authors: Janse van Rensburg, Eureta
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/438781 , vital:73499 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/137480"
- Description: In this preliminary research report I introduce initial interpretations of the results of a recently completed study on research priorities in southern Africa. The study has been sponsored by Murray and Roberts, Rhodes University and the HNRE (Human and Natural Resources in the Environment) Programme of the Human Sciences Research Council.
- Full Text:
- Date Issued: 1994
Resolution on fisheries
- FAWU
- Authors: FAWU
- Date: 1994
- Subjects: FAWU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/173961 , vital:42426
- Description: Historically, access to marine resources was unrestricted. In order to facilitate the monopolisation of the fishing resource by a few white companies, a system of quotas was introduced. In this way many black fisher folk lost the access rights they had had for generations. At the present time, the fishing industry is completely biased in favour of a few large and medium sized white companies. This is illustrated by the fact that just three (3) companies hold : • 72% of the hake quota; • 75% of the abalone quota, and • 71 % of the sole quota Overall, across all species, approximately nine tenths (9/10) of the resource is controlled by a hand-full of companies. Since 1994, some of these companies have attempted to blacken their faces. They have also sold minority shares to some black business consortia. Further, a few members of the black elite have been given quotas. None of the above amounts to any kind of restructuring. None of the historic imbalances have been addressed. The above have merely been attempts to confuse the issue and to frustrate any process that attempts to restructure the industry.
- Full Text:
- Date Issued: 1994
- Authors: FAWU
- Date: 1994
- Subjects: FAWU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/173961 , vital:42426
- Description: Historically, access to marine resources was unrestricted. In order to facilitate the monopolisation of the fishing resource by a few white companies, a system of quotas was introduced. In this way many black fisher folk lost the access rights they had had for generations. At the present time, the fishing industry is completely biased in favour of a few large and medium sized white companies. This is illustrated by the fact that just three (3) companies hold : • 72% of the hake quota; • 75% of the abalone quota, and • 71 % of the sole quota Overall, across all species, approximately nine tenths (9/10) of the resource is controlled by a hand-full of companies. Since 1994, some of these companies have attempted to blacken their faces. They have also sold minority shares to some black business consortia. Further, a few members of the black elite have been given quotas. None of the above amounts to any kind of restructuring. None of the historic imbalances have been addressed. The above have merely been attempts to confuse the issue and to frustrate any process that attempts to restructure the industry.
- Full Text:
- Date Issued: 1994
Resolving ambiguous results of host-specificity tests the case of two Leptinotarsa species (Coleoptera: Chrysomelidae) for biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa
- Olckers, T, Hulley, Patrick E
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452358 , vital:75122 , https://hdl.handle.net/10520/AJA10213589_421
- Description: Two leaf-feeding chrysomelids from North America, Leptinotarsa texana (Schaeffer) and Leptinotarsa defecta (Stal), are promising candidates for the biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa. Permission for release was delayed because the beetles fed on cultivated eggplant (Solanum melongena Linnaeus) under cage conditions. After considerable deliberation and further investigation, it was concluded that the results of the cage tests had been overemphasized. The beetles were cleared for release in South Africa on the following grounds: (i) neither Leptinotarsa species attacks eggplant in their native North American habitats; (ii) in South Africa, many insect herbivores of Solanaceae feed on eggplant in cultivation but cause minor damage relative to cosmopolitan polyphagous pests; (iii) as with L. texana and L. defecta, Conchyloctenia tigrina Olivier, a South African chrysomelid that also occurs on eggplant in cultivation, fed on eggplant in indoor cages, but preferred its natural Solanum hosts in large outdoor cages; (iv) eggplant cultivation methods include crop rotation and severe pesticide regimes, which should exclude Leptinotarsa along with the other insects.
- Full Text:
- Date Issued: 1994
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452358 , vital:75122 , https://hdl.handle.net/10520/AJA10213589_421
- Description: Two leaf-feeding chrysomelids from North America, Leptinotarsa texana (Schaeffer) and Leptinotarsa defecta (Stal), are promising candidates for the biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa. Permission for release was delayed because the beetles fed on cultivated eggplant (Solanum melongena Linnaeus) under cage conditions. After considerable deliberation and further investigation, it was concluded that the results of the cage tests had been overemphasized. The beetles were cleared for release in South Africa on the following grounds: (i) neither Leptinotarsa species attacks eggplant in their native North American habitats; (ii) in South Africa, many insect herbivores of Solanaceae feed on eggplant in cultivation but cause minor damage relative to cosmopolitan polyphagous pests; (iii) as with L. texana and L. defecta, Conchyloctenia tigrina Olivier, a South African chrysomelid that also occurs on eggplant in cultivation, fed on eggplant in indoor cages, but preferred its natural Solanum hosts in large outdoor cages; (iv) eggplant cultivation methods include crop rotation and severe pesticide regimes, which should exclude Leptinotarsa along with the other insects.
- Full Text:
- Date Issued: 1994
Review of the grenadiers (Teleostei: Gadiformes) of Southern Africa, with descriptions of four new species
- Iwamoto, Tomio, Anderson, M Eric
- Authors: Iwamoto, Tomio , Anderson, M Eric
- Date: 1994
- Language: English
- Type: Text
- Identifier: vital:15023 , http://hdl.handle.net/10962/d1019883 , ISBN 0-86810-276-8 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 61
- Description: Grenadier fishes of the families Bathygadidae and Macrouridae from southern Africa are reviewed since publication of the book Smiths’ Sea Fishes (1986). The bathygadid and macrourid fauna is increased to 46 species in 20 genera with the addition of the following new species and new records for southern Africa: Bathygadus cottoides, Caelorinchus kaiyomaru, Caelorinchus karrerrae, Caelorinchus simorhynchus sp.n, (misidentified in southern Africa as Caelorinchus fasciatus), Caelorinchus trunovi sp.n, (misidentified in southern Africa as Caelorinchus flabellispinis), Cetonurus globiceps, Co- ryphaenoides carapinus, Coryphaenoides grahami, Coryphaenoides mcmillani, Haplomacrurus nudirostris, Hymenocephalus heterolepis (uncertain identification), Malacocephalus occidentalis, Nezumia spinosa, Nezumia umbracincta sp.n., Odon- tomacrurus murrayi, Sphagemacrurus richardi, Ventrifossa mystax sp.n, (previously identified as V. sp. aff. divergens), and an indeterminate species of Ventrifossa. Name changes include: formerly Nezumia hebetata in southern Africa changed to Kumba sp.; formerly Nezumia bubonis and N. leonis now included in Kuronezumia; formerly Ventrifossa ori now Lucigadus ori; Paracetonurus sp. now Pseudonezumia sp. The species of Macrourus from southern Africa is identified as M. carinatus (Gunther, 1878). Range extensions of previously known grenadiers include Caelorinchus acanthiger far into the western Indian Ocean and Australia, C. denticulatus to Kenya, Nezumia milleri to southern Namibia, N. propinqua to Natal, Trachonurus villosus to off False Bay, western Cape Province, Ventrifossa mystax, sp. n. to the Cape west coast and V. nasuta to off Port Elizabeth. , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1994
- Authors: Iwamoto, Tomio , Anderson, M Eric
- Date: 1994
- Language: English
- Type: Text
- Identifier: vital:15023 , http://hdl.handle.net/10962/d1019883 , ISBN 0-86810-276-8 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 61
- Description: Grenadier fishes of the families Bathygadidae and Macrouridae from southern Africa are reviewed since publication of the book Smiths’ Sea Fishes (1986). The bathygadid and macrourid fauna is increased to 46 species in 20 genera with the addition of the following new species and new records for southern Africa: Bathygadus cottoides, Caelorinchus kaiyomaru, Caelorinchus karrerrae, Caelorinchus simorhynchus sp.n, (misidentified in southern Africa as Caelorinchus fasciatus), Caelorinchus trunovi sp.n, (misidentified in southern Africa as Caelorinchus flabellispinis), Cetonurus globiceps, Co- ryphaenoides carapinus, Coryphaenoides grahami, Coryphaenoides mcmillani, Haplomacrurus nudirostris, Hymenocephalus heterolepis (uncertain identification), Malacocephalus occidentalis, Nezumia spinosa, Nezumia umbracincta sp.n., Odon- tomacrurus murrayi, Sphagemacrurus richardi, Ventrifossa mystax sp.n, (previously identified as V. sp. aff. divergens), and an indeterminate species of Ventrifossa. Name changes include: formerly Nezumia hebetata in southern Africa changed to Kumba sp.; formerly Nezumia bubonis and N. leonis now included in Kuronezumia; formerly Ventrifossa ori now Lucigadus ori; Paracetonurus sp. now Pseudonezumia sp. The species of Macrourus from southern Africa is identified as M. carinatus (Gunther, 1878). Range extensions of previously known grenadiers include Caelorinchus acanthiger far into the western Indian Ocean and Australia, C. denticulatus to Kenya, Nezumia milleri to southern Namibia, N. propinqua to Natal, Trachonurus villosus to off False Bay, western Cape Province, Ventrifossa mystax, sp. n. to the Cape west coast and V. nasuta to off Port Elizabeth. , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1994
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
SA National Police Cricket XI, 1994
- Date: 1994
- Subjects: Cricket -- South Africa -- Photographs , SOuth African Police Service -- Sports -- Photographs
- Type: still image
- Identifier: http://hdl.handle.net/10962/49345 , vital:25886 , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017. , PIC/M 6752
- Description: SA National Police Cricket X1 1994, Tour to the Netherlands – 1994, Team photograph with cricket players in tracksuits, Group photographs, Colour photographs, Outdoor photographs, Two crossed cricket bats in front, Back Row (left to right): E. Lambrechts, B. van der Linde, J. Riley, A. Hansen, Z. Bosch, G. Dugmore, P. Bruce, T. Weyers, G. Riley, Seated (left to right): C. Fleischmann (Selector), P. Swart (Selector), J. Britz (Coach), J. Groenewald (Captain), Brigadier K. Kukard (Manager), L. Koen (Vice-Captain), D. Lichtenstein, Front Row (left to right): R. Botha, E. Moeti (Development Player – UCB of SA), J. Oosthuizen.
- Full Text: false
- Date Issued: 1994
- Date: 1994
- Subjects: Cricket -- South Africa -- Photographs , SOuth African Police Service -- Sports -- Photographs
- Type: still image
- Identifier: http://hdl.handle.net/10962/49345 , vital:25886 , This image is held at the Cory Library for Humanities Research at Rhodes University. For further information contact cory@ru.ac.za. The digitisation of this image was made possible through a generous grant received from the Andrew W. Mellon Foundation 2014-2017. , PIC/M 6752
- Description: SA National Police Cricket X1 1994, Tour to the Netherlands – 1994, Team photograph with cricket players in tracksuits, Group photographs, Colour photographs, Outdoor photographs, Two crossed cricket bats in front, Back Row (left to right): E. Lambrechts, B. van der Linde, J. Riley, A. Hansen, Z. Bosch, G. Dugmore, P. Bruce, T. Weyers, G. Riley, Seated (left to right): C. Fleischmann (Selector), P. Swart (Selector), J. Britz (Coach), J. Groenewald (Captain), Brigadier K. Kukard (Manager), L. Koen (Vice-Captain), D. Lichtenstein, Front Row (left to right): R. Botha, E. Moeti (Development Player – UCB of SA), J. Oosthuizen.
- Full Text: false
- Date Issued: 1994
Saly
- Tidiane Gaye (lead vocal), Assane Diop (solo guitar), Niankou Sembene (keyboards), Ousseynou Diop (drums), Moussa Sene, Mor Sourang, Thio Mbaye (percussion), Mada Ba (chorus), Galissa (kora), Mamane Thiam (tama), Studio 2000, Samassa Records
- Authors: Tidiane Gaye (lead vocal) , Assane Diop (solo guitar) , Niankou Sembene (keyboards) , Ousseynou Diop (drums) , Moussa Sene, Mor Sourang, Thio Mbaye (percussion) , Mada Ba (chorus) , Galissa (kora) , Mamane Thiam (tama) , Studio 2000 , Samassa Records
- Date: 1994
- Subjects: Popular music--Africa, West , Africa Senegal Dakar f-sg
- Language: Wolof
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/130087 , vital:36374 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC37-05
- Description: Popular Senegalese music incorporating pop, funk, Congolese ndombolo, cut-shifted Ivorian or Afro-dance
- Full Text: false
- Date Issued: 1994
- Authors: Tidiane Gaye (lead vocal) , Assane Diop (solo guitar) , Niankou Sembene (keyboards) , Ousseynou Diop (drums) , Moussa Sene, Mor Sourang, Thio Mbaye (percussion) , Mada Ba (chorus) , Galissa (kora) , Mamane Thiam (tama) , Studio 2000 , Samassa Records
- Date: 1994
- Subjects: Popular music--Africa, West , Africa Senegal Dakar f-sg
- Language: Wolof
- Type: sound recordings , field recordings , sound recording-musical
- Identifier: http://hdl.handle.net/10962/130087 , vital:36374 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC37-05
- Description: Popular Senegalese music incorporating pop, funk, Congolese ndombolo, cut-shifted Ivorian or Afro-dance
- Full Text: false
- 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 transformation in response to the environment crisis: The role of education and research
- Authors: van Rensburg, Eureta J
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450146 , vital:74886 , https://www.cambridge.org/core/journals/australian-journal-of-environmental-education/article/abs/social-transformation-in-response-to-the-environment-crisis-the-role-of-education-and-research/F8B2980AEC1FC8F763E68981373AFB1C
- Description: In this paper I examine two activities which are often attributed with a role to play in social transformation, namely environmental education and research, for their potential to contribute to collective change. I do so by drawing on the results of a recent empirical study in southern Africa, in which I distinguished four orientations to research in/and environmental education. In exploring the transformatory roles of research and environmental education, as conceptualised in these four orientations, I conclude that the most prevalent orientations reveal modernistic assumptions which limit their potential to contribute to social transformation.The decision to interpret the results by focusing on social transformation grew out of what I regarded as the most significant dimensions of the context of the study. These are the global and regional calls for social transformation in response to the environment crisis, the dramatic political changes in parts of southern Africa, the need to improve education in the region, and finally, less obvious global epistemological shifts in the conceptualisation of science, education and social research.
- Full Text:
- Date Issued: 1994
- Authors: van Rensburg, Eureta J
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/450146 , vital:74886 , https://www.cambridge.org/core/journals/australian-journal-of-environmental-education/article/abs/social-transformation-in-response-to-the-environment-crisis-the-role-of-education-and-research/F8B2980AEC1FC8F763E68981373AFB1C
- Description: In this paper I examine two activities which are often attributed with a role to play in social transformation, namely environmental education and research, for their potential to contribute to collective change. I do so by drawing on the results of a recent empirical study in southern Africa, in which I distinguished four orientations to research in/and environmental education. In exploring the transformatory roles of research and environmental education, as conceptualised in these four orientations, I conclude that the most prevalent orientations reveal modernistic assumptions which limit their potential to contribute to social transformation.The decision to interpret the results by focusing on social transformation grew out of what I regarded as the most significant dimensions of the context of the study. These are the global and regional calls for social transformation in response to the environment crisis, the dramatic political changes in parts of southern Africa, the need to improve education in the region, and finally, less obvious global epistemological shifts in the conceptualisation of science, education and social research.
- Full Text:
- Date Issued: 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