A phenomenological investigation into undergraduate students' experience of acquiring the discourse of engineering
- Authors: Van Heerden, Karen Ilse
- Date: 2001
- Subjects: Education, Higher -- South Africa Students -- Attitudes Academic writing -- Study and teaching -- South Africa English language -- Rhetoric -- Study and teaching -- South Africa Technical writing -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1698 , http://hdl.handle.net/10962/d1003581
- Description: The area of discourse acquisition and writing in higher education has become a much researched field. In South Africa the interest in discourse acquisition and writing has been partly in response to the change in student profile, particularly over the past ten years. While South African researchers and academics are increasingly focusing their interest in discourse acquisition and writing on the unique circumstances here, they rely on theories based on research done in very different social contexts. These theories are not necessarily universally appropriate. South Africa is currently undergoing a period of transformation in higher education aimed at greater access and equity for black students and academics. The accompanying sense of frustration and disillusionment among students and academics underlines the need to reappraise all aspects of higher education. Much of the research on discourse acquisition and writing is undertaken in arts programmes: vocational fields - such as engineering education - tend to be neglected. If the envisaged growth in science and engineering education is to be realised, it is essential that research in discourse and writing be undertaken in engineering programmes. This study investigates discourse acquisition as experienced by students in a South African engineering faculty. The experiences of six final year technikon students are investigated to gain a better understanding of what it means to acquire the discourse of engineering. The phenomenological method used requires that the researcher suspends or brackets a priori theoretical notions or pre-conceptions so that that which the students experience, rather than what the researcher expects in terms of theory, can emerge. What emerges from the students' experiences is partially congruent with established discourse and writing theories. However, some of the student experiences of discourse acquisition differ in significant ways from what is described in mainstream writing and discourse acquisition theory. The differences in the manner in which these students experience their acquisition of engineering discourse leads to a new understanding of the phenomenon. The students do not experience the alienation or struggle described in mainstream theoretic accounts of discourse acquisition. Students' approaches to writing are affected by their awareness of their multiple identities and the different locations in which they learn. Their approaches to writing are significantly different in some respects from descriptions in mainstream theories in some respects. The description of their experiences gives a different understanding of what it means to acquire the discourse of engineering, and may contribute to the reappraisal of engineering education in a contemporary South African context.
- Full Text:
- Date Issued: 2001
- Authors: Van Heerden, Karen Ilse
- Date: 2001
- Subjects: Education, Higher -- South Africa Students -- Attitudes Academic writing -- Study and teaching -- South Africa English language -- Rhetoric -- Study and teaching -- South Africa Technical writing -- Study and teaching
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1698 , http://hdl.handle.net/10962/d1003581
- Description: The area of discourse acquisition and writing in higher education has become a much researched field. In South Africa the interest in discourse acquisition and writing has been partly in response to the change in student profile, particularly over the past ten years. While South African researchers and academics are increasingly focusing their interest in discourse acquisition and writing on the unique circumstances here, they rely on theories based on research done in very different social contexts. These theories are not necessarily universally appropriate. South Africa is currently undergoing a period of transformation in higher education aimed at greater access and equity for black students and academics. The accompanying sense of frustration and disillusionment among students and academics underlines the need to reappraise all aspects of higher education. Much of the research on discourse acquisition and writing is undertaken in arts programmes: vocational fields - such as engineering education - tend to be neglected. If the envisaged growth in science and engineering education is to be realised, it is essential that research in discourse and writing be undertaken in engineering programmes. This study investigates discourse acquisition as experienced by students in a South African engineering faculty. The experiences of six final year technikon students are investigated to gain a better understanding of what it means to acquire the discourse of engineering. The phenomenological method used requires that the researcher suspends or brackets a priori theoretical notions or pre-conceptions so that that which the students experience, rather than what the researcher expects in terms of theory, can emerge. What emerges from the students' experiences is partially congruent with established discourse and writing theories. However, some of the student experiences of discourse acquisition differ in significant ways from what is described in mainstream writing and discourse acquisition theory. The differences in the manner in which these students experience their acquisition of engineering discourse leads to a new understanding of the phenomenon. The students do not experience the alienation or struggle described in mainstream theoretic accounts of discourse acquisition. Students' approaches to writing are affected by their awareness of their multiple identities and the different locations in which they learn. Their approaches to writing are significantly different in some respects from descriptions in mainstream theories in some respects. The description of their experiences gives a different understanding of what it means to acquire the discourse of engineering, and may contribute to the reappraisal of engineering education in a contemporary South African context.
- Full Text:
- Date Issued: 2001
A taxonomic revision of the shallow-water species of the genera Lethrinops, Tramitichromis and Taeniolethrinops (Teleostei, Cichlidae) from Lake Malawi/Nyasa/Niassa (East Africa)
- Authors: Ngatunga, Benjamin Peter
- Date: 2001
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5347 , http://hdl.handle.net/10962/d1007443
- Description: In order for the SADC/GEF Lake Malawi/Nyasa Biodiversity Conservation Project to draw out sound strategic management and conservation recommendations to the riparian countries of Malawi, Mozambique and Tanzania, the need and urgency for revising the taxonomy of some of the scientifically and economically important fish groups was accorded high priority. This study is a contribution towards achieving those goals. It is a taxonomic revision of the shallow-water species of the genera Taenioiethrinops, Tramitichromis and Lethrinops. These three genera are grouped as Lethrinops 'sensu lato' in this thesis, corresponding to the definition of Lethrinops prior to the revision by Eccles & Trewavas (1989). All members have a characteristic dentition: the outer teeth in the lower jaw curve inwards posteriorly ending just behind the inner row(s), rather than continuing backwards as a single series, as in most other Malawian haplochromines. The decision to consider shallow-water Lethrinops 'sensu lato' separately from the deepwater ones was not arbitrary, but rather based on available ecological and morphological evidence. Unanticipatedly, on the course of this study, evidence from molecular genetics has helped to strengthen the distinction. Economically, Lethrinops is important for human food and for the aquarium trade. Lethrinops are precocial fish producing very few young at a time and are consequently unlikely to recover quickly from heavy fishing pressure. To evolutionary biologists, Lethrinops 'sensu lato' is challenging because until now most theories about the evolution of Lake Malawi cichlids have not taken the sand-dwelling fishes fully into consideration. A better knowledge of the distribution patterns of these cichlids, of which Lethrinops are the major representatives, can help in explaining the underlying mechanisms of speciation in sand-dwelling cichlids. Lethrinops 'sensu lato' is taxonomically one of the most complex groups of Lake MalawilNyasa haplochromines. The species are closely related and very difficult to differentiate, and the taxonomy is confused and in urgent need of revision. This is more important since taxonomy plays an important role in most of the key criteria of conservation.The principal objective of this study was to carry out a taxonomic revision of this group and to provide a key to the identification of the species. Further objectives include the mapping of their distribution and analysing their phylogenetic relationships. Large samples were collected (by trawling, gill netting, beach seining and purchased from local fishermen) from depths less than 20m and from numerous well-defined localities all around the lake. Seventeen type specimens of the 21 described species of the shallow-water Lethrinops 'sensu lato' were examined and compared with this recently collected material. The data of about 500 fish specimens were subjected to principal component analyses (PCA). To further evaluate morphological differences between taxa of comparable size, non- parametric, distribution-free Mann-Whitney U-tests were used. Within the shallow-water Lethrinops 'sensu lato' three genera are recognized which can be separated by characters such as head shape, pharyngeal morphology and dentition, number and shape of gill-rakers, number of the pectoral fin rays and melanin pattern. So far in this study, 28 taxa have been recognized. The overlapping measurements and meristics compound the difficulty inherent in the identification and classification of members of the three genera. The genera Tramitichromis and Taeniolethrinops are typically shallow- water taxa. Within the genus Taeniolethrinops four described species, (T. cyrtonotus, T.forcicauda, T. laticeps and T. praeorbitalis) were distinguished. Within the genus Tramitichromis nine species were distinguished, five of which are described (T. brevis, T. intermedius, T. lituris, T. trilineata and T. variabilis); four represent undescribed species and are given a working name (T. sp. 'brevis 2', T. sp. 'maculae', T. sp. 'pharyngeals' and T. sp. 'variabilis deep'). For convenience, the shallow water Lethrinops 'sensu stricto' were divided into three natural groups, according to shared morphological features. • The first group is the lethrinus group, including three species (L. lunaris, L. leptodon and L. lethrinus) with relatively lolong snouts and remnants of the horizontal stripes. • Another group included eight taxa (L. microstoma, L. macrophthalmus, L. macrochir, L. auritus, L. parvidens, L. sp. 'parvidens deep', L. 'black dorsal auritus', L. sp. 'domira blotch' and L. sp. 'turneri') with a relatively short snout and a small mouth set low on the profile. Within this group, special attention has been paid to the confusion involving L. auritus and a new species to be described soon, L. sp. 'turneri' . • The last group of Lethrinops 'sensu stricto' is ill defmed and has an intermediate snout and with a lesser round head. Within this group L. oculatus, which was described on the basis of a single specimen, is synonymised with L. marginatus. The other valid species of this group are Lethrinops albus and L.furcifer. Nearly all species seem to have a lake-wide distribution. All are associated with sandy substrata where they feed mainly on insect larvae and ostracods. Mitochondrial DNA sequence data indicate that Lethrinops 'sensu lato' as currently defmed is not monophyletic but is paraphyletic or more probably polyphyletic. It is further suggested that the typical Lethrinops dentition provides no particular strong evidence for affimity among shallow-water Lethrinops s.s., Tramitichromis and Taeniolethrinops. The need for management and conservation of this scientifically exciting group of fishes has been pointed out.
- Full Text:
- Date Issued: 2001
- Authors: Ngatunga, Benjamin Peter
- Date: 2001
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5347 , http://hdl.handle.net/10962/d1007443
- Description: In order for the SADC/GEF Lake Malawi/Nyasa Biodiversity Conservation Project to draw out sound strategic management and conservation recommendations to the riparian countries of Malawi, Mozambique and Tanzania, the need and urgency for revising the taxonomy of some of the scientifically and economically important fish groups was accorded high priority. This study is a contribution towards achieving those goals. It is a taxonomic revision of the shallow-water species of the genera Taenioiethrinops, Tramitichromis and Lethrinops. These three genera are grouped as Lethrinops 'sensu lato' in this thesis, corresponding to the definition of Lethrinops prior to the revision by Eccles & Trewavas (1989). All members have a characteristic dentition: the outer teeth in the lower jaw curve inwards posteriorly ending just behind the inner row(s), rather than continuing backwards as a single series, as in most other Malawian haplochromines. The decision to consider shallow-water Lethrinops 'sensu lato' separately from the deepwater ones was not arbitrary, but rather based on available ecological and morphological evidence. Unanticipatedly, on the course of this study, evidence from molecular genetics has helped to strengthen the distinction. Economically, Lethrinops is important for human food and for the aquarium trade. Lethrinops are precocial fish producing very few young at a time and are consequently unlikely to recover quickly from heavy fishing pressure. To evolutionary biologists, Lethrinops 'sensu lato' is challenging because until now most theories about the evolution of Lake Malawi cichlids have not taken the sand-dwelling fishes fully into consideration. A better knowledge of the distribution patterns of these cichlids, of which Lethrinops are the major representatives, can help in explaining the underlying mechanisms of speciation in sand-dwelling cichlids. Lethrinops 'sensu lato' is taxonomically one of the most complex groups of Lake MalawilNyasa haplochromines. The species are closely related and very difficult to differentiate, and the taxonomy is confused and in urgent need of revision. This is more important since taxonomy plays an important role in most of the key criteria of conservation.The principal objective of this study was to carry out a taxonomic revision of this group and to provide a key to the identification of the species. Further objectives include the mapping of their distribution and analysing their phylogenetic relationships. Large samples were collected (by trawling, gill netting, beach seining and purchased from local fishermen) from depths less than 20m and from numerous well-defined localities all around the lake. Seventeen type specimens of the 21 described species of the shallow-water Lethrinops 'sensu lato' were examined and compared with this recently collected material. The data of about 500 fish specimens were subjected to principal component analyses (PCA). To further evaluate morphological differences between taxa of comparable size, non- parametric, distribution-free Mann-Whitney U-tests were used. Within the shallow-water Lethrinops 'sensu lato' three genera are recognized which can be separated by characters such as head shape, pharyngeal morphology and dentition, number and shape of gill-rakers, number of the pectoral fin rays and melanin pattern. So far in this study, 28 taxa have been recognized. The overlapping measurements and meristics compound the difficulty inherent in the identification and classification of members of the three genera. The genera Tramitichromis and Taeniolethrinops are typically shallow- water taxa. Within the genus Taeniolethrinops four described species, (T. cyrtonotus, T.forcicauda, T. laticeps and T. praeorbitalis) were distinguished. Within the genus Tramitichromis nine species were distinguished, five of which are described (T. brevis, T. intermedius, T. lituris, T. trilineata and T. variabilis); four represent undescribed species and are given a working name (T. sp. 'brevis 2', T. sp. 'maculae', T. sp. 'pharyngeals' and T. sp. 'variabilis deep'). For convenience, the shallow water Lethrinops 'sensu stricto' were divided into three natural groups, according to shared morphological features. • The first group is the lethrinus group, including three species (L. lunaris, L. leptodon and L. lethrinus) with relatively lolong snouts and remnants of the horizontal stripes. • Another group included eight taxa (L. microstoma, L. macrophthalmus, L. macrochir, L. auritus, L. parvidens, L. sp. 'parvidens deep', L. 'black dorsal auritus', L. sp. 'domira blotch' and L. sp. 'turneri') with a relatively short snout and a small mouth set low on the profile. Within this group, special attention has been paid to the confusion involving L. auritus and a new species to be described soon, L. sp. 'turneri' . • The last group of Lethrinops 'sensu stricto' is ill defmed and has an intermediate snout and with a lesser round head. Within this group L. oculatus, which was described on the basis of a single specimen, is synonymised with L. marginatus. The other valid species of this group are Lethrinops albus and L.furcifer. Nearly all species seem to have a lake-wide distribution. All are associated with sandy substrata where they feed mainly on insect larvae and ostracods. Mitochondrial DNA sequence data indicate that Lethrinops 'sensu lato' as currently defmed is not monophyletic but is paraphyletic or more probably polyphyletic. It is further suggested that the typical Lethrinops dentition provides no particular strong evidence for affimity among shallow-water Lethrinops s.s., Tramitichromis and Taeniolethrinops. The need for management and conservation of this scientifically exciting group of fishes has been pointed out.
- Full Text:
- Date Issued: 2001
An examination of the development of Christian worship in the Southern Congo United Methodist Church with a view to promoting a relevant and indigenous form of worship
- Authors: Nkonge, Jean-Marie
- Date: 2001
- Subjects: Christianity Christianity -- Congo United Methodist Church -- Congo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1233 , http://hdl.handle.net/10962/d1007445
- Description: The scope of this thesis is the investigation of the nature and purpose of Christian worship with specific reference to its development in the Southern Congo United Methodist Church. The study combines three main sources of information - namely, the study of key theological concepts (chapter 3), the Holy Bible (chapter 4), and the investigation by questionnaires (chapter 6) - in order to address the issue of improving the worship and Christian life style for the contemporary Christian church within the Congolese context. Christian worship has been defined as a twofold event involving God's initiative in and through Jesus Christ, and men and women's response towards God's saving acts through the same Mediator, Jesus Christ. Seeing that the unchangeable Gospel relates to each culture, it is argued in this thesis that Congolese cultural values (local clergy, local languages, art forms, and other cultural elements) could be an integral part of worship. This long and slow process of incarnating the Christian message into the Congolese context could result in finding original and meaningful expressions of the Christian faith in the African context. Insights are drawn from the research to offer theological and pragmatic guidelines. In fact, it is suggested that the integration of Congolese cultural elements should be monitored by a Theological Commission at the congregational level, the district level, and the Annual Conference level. Furthermore, the last section of the last chapter provides helpful suggestions in dealing with practical issues with regard to the overall management of the Southern Congo United Methodist Church.
- Full Text:
- Date Issued: 2001
- Authors: Nkonge, Jean-Marie
- Date: 2001
- Subjects: Christianity Christianity -- Congo United Methodist Church -- Congo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1233 , http://hdl.handle.net/10962/d1007445
- Description: The scope of this thesis is the investigation of the nature and purpose of Christian worship with specific reference to its development in the Southern Congo United Methodist Church. The study combines three main sources of information - namely, the study of key theological concepts (chapter 3), the Holy Bible (chapter 4), and the investigation by questionnaires (chapter 6) - in order to address the issue of improving the worship and Christian life style for the contemporary Christian church within the Congolese context. Christian worship has been defined as a twofold event involving God's initiative in and through Jesus Christ, and men and women's response towards God's saving acts through the same Mediator, Jesus Christ. Seeing that the unchangeable Gospel relates to each culture, it is argued in this thesis that Congolese cultural values (local clergy, local languages, art forms, and other cultural elements) could be an integral part of worship. This long and slow process of incarnating the Christian message into the Congolese context could result in finding original and meaningful expressions of the Christian faith in the African context. Insights are drawn from the research to offer theological and pragmatic guidelines. In fact, it is suggested that the integration of Congolese cultural elements should be monitored by a Theological Commission at the congregational level, the district level, and the Annual Conference level. Furthermore, the last section of the last chapter provides helpful suggestions in dealing with practical issues with regard to the overall management of the Southern Congo United Methodist Church.
- Full Text:
- Date Issued: 2001
An inquiry into the incorporation of a multicultural approach in contemporary textbooks in South Africa
- Authors: Sharma, Anjali
- Date: 2001
- Subjects: Multicultural education -- South Africa Multicultural education -- Curricula Textbooks -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1579 , http://hdl.handle.net/10962/d1003461
- Description: During the past few decades a substantial body of research has emerged in western as well as the developing nations studying the racial bias in children's texts. However, it is only recently in South Africa, with the ascendance of the ANC government, that interest has been focused on eliminating apartheid values and on promoting multicultural tenets in the school curriculum. It is undeniable that the concept of multiculturalism has been severely stigmatised in the South African educational context. Anxieties have been expressed about embracing the discourse of multicultural education within the educational system based on fears that, like the previous educational system, it too will perpetuate group differences. Nevertheless, in recent years, a clear consensus view has emerged that the implementation of multicultural education is imperative if the goal of a rainbow South Africa is to be realised. Against this background, the present study attempts to study the incorporation of a multicultural approach into contemporary textbooks. To realise this aim I selected a sample of four textbooks, one from each of the major disciplines (science, English, geography and history), and SUbjected the texts and pictures from each to content analysis. The findings of this study suggest that a multicultural approach shall at least for the foreseeable future remain a central feature of learning materials produced for the new South African curricula. The findings indicate that multicultural aspects predominate in the texts as compared to other ideologies. This applies to both text content and illustrations. Contrary to the researcher's initial expectation, however, the texts also reveal a strong tendency towards Eurocentric and patriarchal approaches. This research does not conform to traditional, 'scientific' criteria of validity and reliability; it seeks only to investigate textbook material in more depth and thereby contribute to a more comprehensive understanding of the extent to which the texts subscribe to a multicultural approach. Such understanding may help both educationalists and authors in their evaluation of existing textbook material, and in the production of new texts which reflect the reality of South Africa as a multicultural society.
- Full Text:
- Date Issued: 2001
- Authors: Sharma, Anjali
- Date: 2001
- Subjects: Multicultural education -- South Africa Multicultural education -- Curricula Textbooks -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1579 , http://hdl.handle.net/10962/d1003461
- Description: During the past few decades a substantial body of research has emerged in western as well as the developing nations studying the racial bias in children's texts. However, it is only recently in South Africa, with the ascendance of the ANC government, that interest has been focused on eliminating apartheid values and on promoting multicultural tenets in the school curriculum. It is undeniable that the concept of multiculturalism has been severely stigmatised in the South African educational context. Anxieties have been expressed about embracing the discourse of multicultural education within the educational system based on fears that, like the previous educational system, it too will perpetuate group differences. Nevertheless, in recent years, a clear consensus view has emerged that the implementation of multicultural education is imperative if the goal of a rainbow South Africa is to be realised. Against this background, the present study attempts to study the incorporation of a multicultural approach into contemporary textbooks. To realise this aim I selected a sample of four textbooks, one from each of the major disciplines (science, English, geography and history), and SUbjected the texts and pictures from each to content analysis. The findings of this study suggest that a multicultural approach shall at least for the foreseeable future remain a central feature of learning materials produced for the new South African curricula. The findings indicate that multicultural aspects predominate in the texts as compared to other ideologies. This applies to both text content and illustrations. Contrary to the researcher's initial expectation, however, the texts also reveal a strong tendency towards Eurocentric and patriarchal approaches. This research does not conform to traditional, 'scientific' criteria of validity and reliability; it seeks only to investigate textbook material in more depth and thereby contribute to a more comprehensive understanding of the extent to which the texts subscribe to a multicultural approach. Such understanding may help both educationalists and authors in their evaluation of existing textbook material, and in the production of new texts which reflect the reality of South Africa as a multicultural society.
- Full Text:
- Date Issued: 2001
Applications of Baylis-Idllman methodology in the synthesis of chromene derivatives
- Authors: Nocanda, Xolani Wittleton
- Date: 2001
- Subjects: Heterocyclic chemistry , Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4556 , http://hdl.handle.net/10962/d1018257
- Description: The reaction of salicylaldehyde with various activated alkenes, viz., methyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl sulfone, phenyl vinylsulfonate, acrolein and acrylonitrile, under Baylis-Hillman conditions, has been found to proceed with the chemoselective formation of chromene derivatives. The reaction conditions have been optimised and chromene derivatives have been obtained in isolated yields up to 87 %. The generality of the reaction, using 1,4-diazabicyclo[2.2.2]octane (DABCO), as the catalyst, and a heterogeneous (chloroform-water) solvent system, has been established using a range of salicylaldehyde derivatives,. including 2-hydroxynaphthaldehyde. The formation of chromene derivatives, under these conditions, has been assumed to proceed via an initial, Baylis-Hillman reaction, followed by cyclisation involving intramolecular conjugate addition, and subsequent dehydration. Evidence supporting this sequence has been obtained from the isolation ofBaylis-Hillman products from reactions involving the use of tertbutylclimethylsilyl-protected salicylaldehyde, 4-hydroxybenzaldehyde and tert-butyl acrylate as substrates. The potential of the ''Baylis-Hillman zwitterion" to participate as a donor species in Michael-type addition reactions has been explored and a series of climeric products has been isolated. The Baylis-Hillman methodology has also been successfully extended to the synthesis of sulfurcontaining heterocyclic systems, and a range of 3-substituted thiochromenes has been obtained in moderate yields, using 2,2'-dithiobenzaldehyde and various activated alkenes in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst. The electron-impact mass spectra of selected chromene and thiocbromene derivatives have been investigated permitting comparison of the fragmentation of the oxygen- and sulfur-containing analogues. In a study directed at the synthesis of potential HIV -1 protease inhibitors, chromene- and thiocbromene-containing analogues of the clinically useful drug, ritonavir, have been prepared. Thiochromene and chromene derivatives were converted to the corresponding 3 -carboxylic acids and coupled with a specially prepared, hydroxyethylene dipeptide isostere to afford ritonavir analogues containing cbromene and thiochromene termini in ca. 60% yield.
- Full Text:
- Date Issued: 2001
- Authors: Nocanda, Xolani Wittleton
- Date: 2001
- Subjects: Heterocyclic chemistry , Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4556 , http://hdl.handle.net/10962/d1018257
- Description: The reaction of salicylaldehyde with various activated alkenes, viz., methyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl sulfone, phenyl vinylsulfonate, acrolein and acrylonitrile, under Baylis-Hillman conditions, has been found to proceed with the chemoselective formation of chromene derivatives. The reaction conditions have been optimised and chromene derivatives have been obtained in isolated yields up to 87 %. The generality of the reaction, using 1,4-diazabicyclo[2.2.2]octane (DABCO), as the catalyst, and a heterogeneous (chloroform-water) solvent system, has been established using a range of salicylaldehyde derivatives,. including 2-hydroxynaphthaldehyde. The formation of chromene derivatives, under these conditions, has been assumed to proceed via an initial, Baylis-Hillman reaction, followed by cyclisation involving intramolecular conjugate addition, and subsequent dehydration. Evidence supporting this sequence has been obtained from the isolation ofBaylis-Hillman products from reactions involving the use of tertbutylclimethylsilyl-protected salicylaldehyde, 4-hydroxybenzaldehyde and tert-butyl acrylate as substrates. The potential of the ''Baylis-Hillman zwitterion" to participate as a donor species in Michael-type addition reactions has been explored and a series of climeric products has been isolated. The Baylis-Hillman methodology has also been successfully extended to the synthesis of sulfurcontaining heterocyclic systems, and a range of 3-substituted thiochromenes has been obtained in moderate yields, using 2,2'-dithiobenzaldehyde and various activated alkenes in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst. The electron-impact mass spectra of selected chromene and thiocbromene derivatives have been investigated permitting comparison of the fragmentation of the oxygen- and sulfur-containing analogues. In a study directed at the synthesis of potential HIV -1 protease inhibitors, chromene- and thiocbromene-containing analogues of the clinically useful drug, ritonavir, have been prepared. Thiochromene and chromene derivatives were converted to the corresponding 3 -carboxylic acids and coupled with a specially prepared, hydroxyethylene dipeptide isostere to afford ritonavir analogues containing cbromene and thiochromene termini in ca. 60% yield.
- Full Text:
- Date Issued: 2001
Chemical studies of chromone derivatives
- Authors: Sabbagh, Liezel Veronica
- Date: 2001
- Subjects: Benzopyrans Heterocyclic compounds -- Derivatives Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4424 , http://hdl.handle.net/10962/d1006899
- Description:
This study has focussed on several aspects of chromone chemistry, viz., (i) the influence of remote substituents on the basicity of 2-(N,N-dimethylamino)chromones, (ii) MoritaBaylis-Hillman reactions of substituted chromone-3-carbaldehydes and (iii) an investigation into the application of chromone chemistry in the total synthesis of the marine natural product, Rietone A. Selected 2-(N,N-dimethylamino )chromones were prepared using two different methods; firstly, via cyclisation of salicylate-derived N,N-dimethyl-3;.(2-hydroxyphenyl)-3- oxopropanamide precursors and, secondly, via 2-hydroxyacetophenone boron difluoride complexes. ¹³C NMR analysis of the 6- and 7-methoxy-2-(N,N-dimethylamino)chromones confirmed that protonation occurs at the chromone carbonyl oxygen rather than the amino nitrogen - a conclusion supported by mol~cular orbital calculations. Potentiometric analysis of 2-(N,N-dimethylamino )chromones in ethanol-water afforded pKa (pK [subscript a]) values in the range 2.22 - 2.52. The observed trend has been rationalised in terms of substituent effects with the aid of molecular orbital calculations at the semi-empirical and ab initio levels, while hydrogen-bonding effects have been used to account for the apparently anomalous result obtained for the 6-nitro derivative. A series of seven substituted chromone-3-carbaldehydes, prepared by the application of Vilsmeier-Haack methodology to the corresponding 2-hydroxyacetophenones, have been examined as substrates for Morita-Baylis-Hillman reactions, using DABCO as the catalyst and three different activated alkenes, viz., methyl acrylate, methyl vinyl ketone and acrylonitrile. In all cases, with the exception of 6-nitrochromone-3-carbaldehyde, the reactions have been shown to afford the expected Morita-Baylis-Hillman products. Use of methyl acrylate and methyl vinyl ketone as the activated alkene has been observed to afford additional, unprecedented dimeric products, which have been unambiguously characterised using a combination of single crystal X-ray analysis and spectroscopic (high resolution MS and NMR) techniques. Different dimer-like adducts have been isolated from reactions in which acrylonitrile was used as the activated alkene, and the structures of these novel products have-been determined
- Full Text:
- Date Issued: 2001
- Authors: Sabbagh, Liezel Veronica
- Date: 2001
- Subjects: Benzopyrans Heterocyclic compounds -- Derivatives Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4424 , http://hdl.handle.net/10962/d1006899
- Description:
This study has focussed on several aspects of chromone chemistry, viz., (i) the influence of remote substituents on the basicity of 2-(N,N-dimethylamino)chromones, (ii) MoritaBaylis-Hillman reactions of substituted chromone-3-carbaldehydes and (iii) an investigation into the application of chromone chemistry in the total synthesis of the marine natural product, Rietone A. Selected 2-(N,N-dimethylamino )chromones were prepared using two different methods; firstly, via cyclisation of salicylate-derived N,N-dimethyl-3;.(2-hydroxyphenyl)-3- oxopropanamide precursors and, secondly, via 2-hydroxyacetophenone boron difluoride complexes. ¹³C NMR analysis of the 6- and 7-methoxy-2-(N,N-dimethylamino)chromones confirmed that protonation occurs at the chromone carbonyl oxygen rather than the amino nitrogen - a conclusion supported by mol~cular orbital calculations. Potentiometric analysis of 2-(N,N-dimethylamino )chromones in ethanol-water afforded pKa (pK [subscript a]) values in the range 2.22 - 2.52. The observed trend has been rationalised in terms of substituent effects with the aid of molecular orbital calculations at the semi-empirical and ab initio levels, while hydrogen-bonding effects have been used to account for the apparently anomalous result obtained for the 6-nitro derivative. A series of seven substituted chromone-3-carbaldehydes, prepared by the application of Vilsmeier-Haack methodology to the corresponding 2-hydroxyacetophenones, have been examined as substrates for Morita-Baylis-Hillman reactions, using DABCO as the catalyst and three different activated alkenes, viz., methyl acrylate, methyl vinyl ketone and acrylonitrile. In all cases, with the exception of 6-nitrochromone-3-carbaldehyde, the reactions have been shown to afford the expected Morita-Baylis-Hillman products. Use of methyl acrylate and methyl vinyl ketone as the activated alkene has been observed to afford additional, unprecedented dimeric products, which have been unambiguously characterised using a combination of single crystal X-ray analysis and spectroscopic (high resolution MS and NMR) techniques. Different dimer-like adducts have been isolated from reactions in which acrylonitrile was used as the activated alkene, and the structures of these novel products have-been determined
- Full Text:
- Date Issued: 2001
Continuity and change in Xhosa historiography during the nineteenth century : an exploration through textual analysis
- Tisani, Nomathamsanqa Cynthia
- Authors: Tisani, Nomathamsanqa Cynthia
- Date: 2001
- Subjects: Xhosa (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2563 , http://hdl.handle.net/10962/d1002416
- Description: This study is an exploration of the making of Xhosa historiography from the end of the eighteenth century to the close of the nineteenth century. Continuity and change are key features that are identifiable in the writing of Xhosa history over the period. Selected documents provide evidence on how different writers built on the works of their predecessors. At the same time, over a period of hundred years, due to changing socio-political contexts, new ideas and perceptions crept into Xhosa history. European writers, who dominated the writing of Xhosa history, were made up of colonial officials, missionaries, and travellers. Sharing a common European Christian background these writers brought along their particular understanding of history, and held assumptions about the indigenous people and their past. However such assumptions were always in a state of flux. South-east Africans were also major contributors to the making of Xhosa history. Their oral traditions were important sources from which Xhosa history was produced. The African and European encounter in the making of Xhosa history meanHhat historioracy and historiography came together in the production of Xhosa history. At the end of the eighteenth century there were a handful of European travellers who explored the interior of southern Africa and recorded their observations of indigenous communities. These observations of south-east Africans, whom they divided into three racial groups, formed the basis of later writings about the indigenous communiti~s. The beginning of the nineteenth century brought the establishment of British rule at the C,ppe. This introduced new players into the African-European drama that was being acted out on the frontier. Colonial officials set out to inform themselves about the indigenous people, and this meant writing up their history. From the 1820s missionaries were a main source of information on amaXhosa. Xhosa history produced under the missionary influence included works by African converts, among whom Noyi was the most noteworthy. As British imperialism gained ground from the middle of the nineteenth century, history was increasingly used by British officials as a tool to justify their colonial expansion. Under Governor Grey there was a deliberate production of a Xhosa history that depicted amaXhosa as having a barbaric past and in need of civilisation. Theal who consulted Dutch and British archives as well as oral tradition made a major contribution to the writing of Xhosa history. But Theal later began to select evidence to show that amaXhosa were recent immigrants into southeast Africa. During the last quarter ofthe nineteenth century a band of literate Africans, using newspapers like Isigidimi and later Imvo Zabantsundu, embarked on writing African history. This study highlights the development of certain themes in Xhosa history, themes which remained central in later years. The royal theme became pivotal and in the process displaced other histories in African communities, like clan histories. This study has also traced the roots of some historical myths. For example claims by early travellers about an empty land fed into the migration theme which sought to explain amaXhosa as recent immigrants into south-east Africa. Xhosa historiography, just like its European counterpart, marginalised ordinary people, especially women, and became primarily an account of the lives and activities of ruling men.
- Full Text:
- Date Issued: 2001
- Authors: Tisani, Nomathamsanqa Cynthia
- Date: 2001
- Subjects: Xhosa (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2563 , http://hdl.handle.net/10962/d1002416
- Description: This study is an exploration of the making of Xhosa historiography from the end of the eighteenth century to the close of the nineteenth century. Continuity and change are key features that are identifiable in the writing of Xhosa history over the period. Selected documents provide evidence on how different writers built on the works of their predecessors. At the same time, over a period of hundred years, due to changing socio-political contexts, new ideas and perceptions crept into Xhosa history. European writers, who dominated the writing of Xhosa history, were made up of colonial officials, missionaries, and travellers. Sharing a common European Christian background these writers brought along their particular understanding of history, and held assumptions about the indigenous people and their past. However such assumptions were always in a state of flux. South-east Africans were also major contributors to the making of Xhosa history. Their oral traditions were important sources from which Xhosa history was produced. The African and European encounter in the making of Xhosa history meanHhat historioracy and historiography came together in the production of Xhosa history. At the end of the eighteenth century there were a handful of European travellers who explored the interior of southern Africa and recorded their observations of indigenous communities. These observations of south-east Africans, whom they divided into three racial groups, formed the basis of later writings about the indigenous communiti~s. The beginning of the nineteenth century brought the establishment of British rule at the C,ppe. This introduced new players into the African-European drama that was being acted out on the frontier. Colonial officials set out to inform themselves about the indigenous people, and this meant writing up their history. From the 1820s missionaries were a main source of information on amaXhosa. Xhosa history produced under the missionary influence included works by African converts, among whom Noyi was the most noteworthy. As British imperialism gained ground from the middle of the nineteenth century, history was increasingly used by British officials as a tool to justify their colonial expansion. Under Governor Grey there was a deliberate production of a Xhosa history that depicted amaXhosa as having a barbaric past and in need of civilisation. Theal who consulted Dutch and British archives as well as oral tradition made a major contribution to the writing of Xhosa history. But Theal later began to select evidence to show that amaXhosa were recent immigrants into southeast Africa. During the last quarter ofthe nineteenth century a band of literate Africans, using newspapers like Isigidimi and later Imvo Zabantsundu, embarked on writing African history. This study highlights the development of certain themes in Xhosa history, themes which remained central in later years. The royal theme became pivotal and in the process displaced other histories in African communities, like clan histories. This study has also traced the roots of some historical myths. For example claims by early travellers about an empty land fed into the migration theme which sought to explain amaXhosa as recent immigrants into south-east Africa. Xhosa historiography, just like its European counterpart, marginalised ordinary people, especially women, and became primarily an account of the lives and activities of ruling men.
- Full Text:
- Date Issued: 2001
Design, synthesis and evaluation of silver-specific ligands
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
- Authors: Daubinet, André
- Date: 2001
- Subjects: Ligands Ligands -- Design Ligands -- Analysis Ligands -- Evaluation Silver -- Metallurgy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4308 , http://hdl.handle.net/10962/d1004966
- Description: Several series of ligands, designed to chelate silver(I) specifically in the presence of base metals, have been synthesised. The ligands include: - dithiodiamide compounds, prepared by the condensation of acetanilide derivatives with 1,2-dibromoethane; propanenitrile and propanoic ester derivatives prepared from pyridine-2-carbaldehyde via the Morita-Baylis-Hillman reaction; and novel malonamide ligands from the reaction of diethyl malonate with a range of primary amines. The malonamide derivatives were prepared under both conventional thermal and microwave-assisted conditions, the latter proving to be highly efficient. The ligands were all characterised using a combination of spectroscopic and, where appropriate, elemental analysis; in one case, the structural assignment was confirmed by single-crystal X-ray analysis. The fragmentation patterns in the electron-impact mass spectra of the malonamide derivatives have been explored using high-resolution and meta-stable peak scanning techniques. Complexes of the malonamide ligands with copper(II) and silver(I) have been synthesised, and examination of these complexes has revealed distinct differences in their co-ordination preferences towards silver(I) and copper(II). Tentative, computer-modelled structures for the complexes have been proposed using the available spectroscopic and elemental analysis data. Computer modelling, at the Molecular Mechanics level, has also been used to assess the capacity of the ligand systems to adopt conformations suitable for the chelation of tetrahedral silver(I). Solvent extraction studies have been undertaken using aqueous metal ion solutions and various organic solvents. The dithiodiamide derivatives typically presented solubility problems, but one of the ligands, N,N´-bis(3-chlorophenyl)-3,6-dithiaoctanediamide, exhibited significant but slow extraction of silver(I) into toluene. The malonamide derivatives, however, proved to be readily soluble in ethyl acetate and, in some cases, exhibited good to excellent selectivity for silver(I) in the presence of the base metals copper and lead. Atomic absorption analysis revealed rapid equilibration times (<15 min) and high extraction efficiencies over a wide pH range (2.78 - 9.0). Metal selectivity has been determined by ICP-MS analysis of the residual silver, copper and lead present in the aqueous phase after 15 min, and one of the ligands, N,N´-bis(2-benzylsulfanylethyl)malonamide, exhibits excellent (≥ 96 %) silver(I) specificity.
- Full Text:
- Date Issued: 2001
Elements of dream interpretation: laying the foundation of a basic model for clinical practice
- Authors: Schön, Joan
- Date: 2001
- Subjects: Dream interpretation Dreams
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3050 , http://hdl.handle.net/10962/d1002559
- Description: The study addresses certain paradoxes evident in the theory and practice of dream interpretation. These relate to the considerable value afforded to dreams in psychoanalytic thinking, compared with (1) the surprising dearth of literature, research, and training on dream interpretation in clinical practice, (2) the difficulties voiced by clinicians regarding dream interpretation, and (3) the diversity of keys employed by different schools to unlock the ‘truth’ of dreams. The intention of the study is to examine these paradoxes in order to develop a model fordream interpretation which falls within the ambit of psychodynamic psychotherapy. It is argued that there have been few insights over the century to match the seminal work of Freud (1900/1976), except perhaps the work of Carl Jung. As a result of the 1914 rift between these two, Jung’s insights have been largely ignored in mainstream psychoanalytic thinking and the focus on dreams has given way to other areas of development, such as, unconscious thinking, symbol formation, and interpretation in a general sense. These, it is argued, have contributed to a more comprehensive understanding of dreams and their interpretation. Thus a model would need to consider both Freud and Jung’s work, and later salient developments. It would also need to be informed by local, contemporary practice. The method used in this thesis is one of breaking down the process of dream interpretation into component parts, in order to examine useful contributions from different sources and to compare work with dreams to work with other material. The literature review examines the major theoretical contributions in relation to four elements of dreams interpretation: the nature and function of dreams, methods of dream interpretation, the meaning of dreams, and the goals of dream interpretation. A model which accommodates diverse theories without resorting to eclecticism is then proposed. Dream interpretation is further examined in the light of a multiphase clinical study, designed to provide different perspectives on the topic. The study yielded findingscompatible with the literature reviewed, as well as certain problems in relation to the proposed model. These included shortcomings of the elements used in the literature review, particularly the sequence of these elements, and caveats about affording dreams a special focus in the consulting room. Thus a second configuration was posited, namely the idea of viewing dream-work as a triangular situation, comprising the dream, the dreamer, and the dream interpreter. The final model which is the outcome of the study provides two interrelated methods of addressing dream interpretation which accommodate the theory/practice dichotomy. In the first, the elements of dreams and their interpretation are considered sequentially. This method provides a framework for considering theoretical contributions on dreams, as well as issues of technique, without recourse to the introduction of theory in the consulting room. In the second, dream interpretation is regarded as a triangular situation, comprising the interchange between therapist and patient in relation to the patient’s dream-life. This structure accommodates the alliance which is discernible in practice and draws on Segal’s (1957/1986) notion that the process of symbol formation is a triangular situation. The value of regarding ‘dream-work’ in the consulting room as a triangular situation is threefold: (1) it is akin to symbol formation in terms of the meaning reached; (2) dreams cannot be accurately interpreted in isolation from the contributions of both therapist and patient; and (3) it provides ‘dream-work’ in practice with its own structure, highlighting a perspective that dreams are an element of clinical practice, rather than a focus, a subtext within the broader framework of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2001
- Authors: Schön, Joan
- Date: 2001
- Subjects: Dream interpretation Dreams
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3050 , http://hdl.handle.net/10962/d1002559
- Description: The study addresses certain paradoxes evident in the theory and practice of dream interpretation. These relate to the considerable value afforded to dreams in psychoanalytic thinking, compared with (1) the surprising dearth of literature, research, and training on dream interpretation in clinical practice, (2) the difficulties voiced by clinicians regarding dream interpretation, and (3) the diversity of keys employed by different schools to unlock the ‘truth’ of dreams. The intention of the study is to examine these paradoxes in order to develop a model fordream interpretation which falls within the ambit of psychodynamic psychotherapy. It is argued that there have been few insights over the century to match the seminal work of Freud (1900/1976), except perhaps the work of Carl Jung. As a result of the 1914 rift between these two, Jung’s insights have been largely ignored in mainstream psychoanalytic thinking and the focus on dreams has given way to other areas of development, such as, unconscious thinking, symbol formation, and interpretation in a general sense. These, it is argued, have contributed to a more comprehensive understanding of dreams and their interpretation. Thus a model would need to consider both Freud and Jung’s work, and later salient developments. It would also need to be informed by local, contemporary practice. The method used in this thesis is one of breaking down the process of dream interpretation into component parts, in order to examine useful contributions from different sources and to compare work with dreams to work with other material. The literature review examines the major theoretical contributions in relation to four elements of dreams interpretation: the nature and function of dreams, methods of dream interpretation, the meaning of dreams, and the goals of dream interpretation. A model which accommodates diverse theories without resorting to eclecticism is then proposed. Dream interpretation is further examined in the light of a multiphase clinical study, designed to provide different perspectives on the topic. The study yielded findingscompatible with the literature reviewed, as well as certain problems in relation to the proposed model. These included shortcomings of the elements used in the literature review, particularly the sequence of these elements, and caveats about affording dreams a special focus in the consulting room. Thus a second configuration was posited, namely the idea of viewing dream-work as a triangular situation, comprising the dream, the dreamer, and the dream interpreter. The final model which is the outcome of the study provides two interrelated methods of addressing dream interpretation which accommodate the theory/practice dichotomy. In the first, the elements of dreams and their interpretation are considered sequentially. This method provides a framework for considering theoretical contributions on dreams, as well as issues of technique, without recourse to the introduction of theory in the consulting room. In the second, dream interpretation is regarded as a triangular situation, comprising the interchange between therapist and patient in relation to the patient’s dream-life. This structure accommodates the alliance which is discernible in practice and draws on Segal’s (1957/1986) notion that the process of symbol formation is a triangular situation. The value of regarding ‘dream-work’ in the consulting room as a triangular situation is threefold: (1) it is akin to symbol formation in terms of the meaning reached; (2) dreams cannot be accurately interpreted in isolation from the contributions of both therapist and patient; and (3) it provides ‘dream-work’ in practice with its own structure, highlighting a perspective that dreams are an element of clinical practice, rather than a focus, a subtext within the broader framework of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2001
Extractives from six species of South African Marine Opisthobranch Molluscs
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
Feeding ecology of Bathyclarias nyasensis (Siluroidei: Claridae) from Lake Malawi
- Kaunda, Emmanuel Kamlipe Watson Hawkins
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
- Full Text:
- Date Issued: 2001
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
- Full Text:
- Date Issued: 2001
How can cooperative learning be developed to enhance the teaching of biology at secondary school level?
- Authors: Pillay, Paramasivan
- Date: 2001
- Subjects: Biology -- Study and teaching (Secondary) Group work in education Group work in education -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1557 , http://hdl.handle.net/10962/d1003439
- Description: This research was undertaken by a group of practising teachers as a collaborative effort to develop a cooperative approach to the teaching of Biology at Secondary School level. The research focussed on Grade 10 learners at three different schools over a period of one full academic school-year. During this time, four complete cycles within an action research framework were completed and reflected upon. Learners were then surveyed by means of a questionnaire and follow-up interviews. The reflective sessions, together with the responses from the questionnaire and interviews, provided a wealth of information with regard to the development of a cooperative approach to teaching. The cooperative classroom is vastly different from the traditional one. Here, new roles are assumed by both teacher and learner. Learners are largely expected to take charge of their learning experience in the classroom. The teacher, while still responsible for facilitating this learning experience, delegates authority to the learners. It was the experience of the group that the relationship between teacher and learner, as well as between learner and learner, vastly improved in the cooperative class where the participants were more relaxed. Over time, learners became more accountable in terms of their work and learning. Learners’ self-esteem and self-confidence grew, and the majority of learners indicated that their understanding of the work improved. Furthermore, the cooperative structure encouraged and developed self-discipline in the learners. In the early stages of this research, the group did find certain behaviour to be inhibiting: excessive noise, laziness, too much tomfoolery, and absenteeism. These problems were easily addressed within the action research framework, and were nearly non-existent by the end of the research. The group also found that: (i) cooperative lessons required more time than traditional lessons, often at the expense (justifiably) of the syllabus, and that: (ii) cooperative lessons played a major role in reactivating learner interest towards the learning process both in and outside the classroom.
- Full Text:
- Date Issued: 2001
- Authors: Pillay, Paramasivan
- Date: 2001
- Subjects: Biology -- Study and teaching (Secondary) Group work in education Group work in education -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1557 , http://hdl.handle.net/10962/d1003439
- Description: This research was undertaken by a group of practising teachers as a collaborative effort to develop a cooperative approach to the teaching of Biology at Secondary School level. The research focussed on Grade 10 learners at three different schools over a period of one full academic school-year. During this time, four complete cycles within an action research framework were completed and reflected upon. Learners were then surveyed by means of a questionnaire and follow-up interviews. The reflective sessions, together with the responses from the questionnaire and interviews, provided a wealth of information with regard to the development of a cooperative approach to teaching. The cooperative classroom is vastly different from the traditional one. Here, new roles are assumed by both teacher and learner. Learners are largely expected to take charge of their learning experience in the classroom. The teacher, while still responsible for facilitating this learning experience, delegates authority to the learners. It was the experience of the group that the relationship between teacher and learner, as well as between learner and learner, vastly improved in the cooperative class where the participants were more relaxed. Over time, learners became more accountable in terms of their work and learning. Learners’ self-esteem and self-confidence grew, and the majority of learners indicated that their understanding of the work improved. Furthermore, the cooperative structure encouraged and developed self-discipline in the learners. In the early stages of this research, the group did find certain behaviour to be inhibiting: excessive noise, laziness, too much tomfoolery, and absenteeism. These problems were easily addressed within the action research framework, and were nearly non-existent by the end of the research. The group also found that: (i) cooperative lessons required more time than traditional lessons, often at the expense (justifiably) of the syllabus, and that: (ii) cooperative lessons played a major role in reactivating learner interest towards the learning process both in and outside the classroom.
- Full Text:
- Date Issued: 2001
KwaZakele: the politics of transition in South Africa: an Eastern Cape case study
- Authors: Cherry, Janet Mary
- Date: 2001
- Subjects: South Africa -- Transition to democracy Democracy -- South Africa -- Eastern Cape Eastern Cape (South Africa) -- Politics and government Port Elizabeth region (South Africa) -- Political aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2766 , http://hdl.handle.net/10962/d1002976
- Description: This thesis examines the transition to democracy in South Africa through the use of case study methodology. The nature of political participation and the form of democracy to emerge at the end of the transition process are the central subjects of inquiry. They are examined through an in-depth study of the African community of Kwazakele, a township in the Nelson Mandela metropolitan area in the Eastern Cape province of South Africa. The study covers the period from 1993 to 2000, and uses as a primary data source five surveys conducted among residents of Kwazakele during that period. The emphasis of the study lies on the experience of political participation of ‘ordinary people’ – in particular, the African urban working-class in South Africa who make up the core support base for the governing African National Congress. The primary findings of the thesis are as follows: * Representative democracy has been successfully consolidated in the community under study. * Levels of political participation by urban Africans in the Eastern Cape are consistently high, both in formal political institutions (primarily elections) and in institutions of civil society. * As politics has normalised at the end of the transition period, forms of direct democratic participation have declined. * Despite the structural constraints on development, there is still potential for a high level of participation by citizens in effecting change at local level. * Drawing on the experience of ordinary people in structures of direct democracy, this level of participation can result in a deeper and stronger form of democracy than exists in many established representative democracies.
- Full Text:
- Date Issued: 2001
- Authors: Cherry, Janet Mary
- Date: 2001
- Subjects: South Africa -- Transition to democracy Democracy -- South Africa -- Eastern Cape Eastern Cape (South Africa) -- Politics and government Port Elizabeth region (South Africa) -- Political aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2766 , http://hdl.handle.net/10962/d1002976
- Description: This thesis examines the transition to democracy in South Africa through the use of case study methodology. The nature of political participation and the form of democracy to emerge at the end of the transition process are the central subjects of inquiry. They are examined through an in-depth study of the African community of Kwazakele, a township in the Nelson Mandela metropolitan area in the Eastern Cape province of South Africa. The study covers the period from 1993 to 2000, and uses as a primary data source five surveys conducted among residents of Kwazakele during that period. The emphasis of the study lies on the experience of political participation of ‘ordinary people’ – in particular, the African urban working-class in South Africa who make up the core support base for the governing African National Congress. The primary findings of the thesis are as follows: * Representative democracy has been successfully consolidated in the community under study. * Levels of political participation by urban Africans in the Eastern Cape are consistently high, both in formal political institutions (primarily elections) and in institutions of civil society. * As politics has normalised at the end of the transition period, forms of direct democratic participation have declined. * Despite the structural constraints on development, there is still potential for a high level of participation by citizens in effecting change at local level. * Drawing on the experience of ordinary people in structures of direct democracy, this level of participation can result in a deeper and stronger form of democracy than exists in many established representative democracies.
- Full Text:
- Date Issued: 2001
Plaatje's African romance: the translation of tragedy in Mhudi and other writings
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001
Sapphic experience: lesbian gender identity development and diversity
- Authors: Crowley, Michelle Laureen
- Date: 2001
- Subjects: Lesbian couples Gender identity Sexual orientation Heterosexual women Lesbian feminists
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2956 , http://hdl.handle.net/10962/d1002465
- Description: This dissertation explores lesbian experience, or the psychological meaning of being lesbian from the point of view of women who call themselves lesbian. The researcher suspended the binary paradigm of sex and gender, and argued that lesbians' identity development must be understood against the background of how patriarchy understands the category 'woman' through history. Towards this purpose the pOSition of women in the West, as well as contemporary images and literature about lesbians, was reviewed. On the basis of this review questions about lesbian gender construction, lesbian identity development and lesbian individuation were identified. In order to access the psychological meaning of being lesbian, or lesbian experience from the inside out, the dream-series of three lesbians constituted an empirical basis for further exploration. These dream-series were amplified with intensive face-to-face interviews, transcribed, and subjected to a hermeneutic-phenomenological inductive method. Common inter-case concerns were identified and synthesized. In dialogue with the literature reviewed, twenty-two statements of meaning about being lesbian were distilled. These revealed two possible constructions of gender for primary lesbians. In addition, primary lesbians involved in the research demonstrated remarkable flexibility with respect to their gender orientations and gender identifications, were in the process of integrating with and differentiating from different aspects of their masculine and feminine potentials, and developed and negotiated their gender identities in relationship to both their lovers and friends. The explication also revealed that participants identified with archetypal aspects of the father that their fathers' did not express, and desired archetypal aspects of the mother that their mother's did not express. Finally, in so much as the method distinguished ~ sex, sexual identity and sexual orientation from gender, gender identity, gender identification and gender orientation, it may prove useful for exploring gender in heterosexual relating.
- Full Text:
- Date Issued: 2001
- Authors: Crowley, Michelle Laureen
- Date: 2001
- Subjects: Lesbian couples Gender identity Sexual orientation Heterosexual women Lesbian feminists
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2956 , http://hdl.handle.net/10962/d1002465
- Description: This dissertation explores lesbian experience, or the psychological meaning of being lesbian from the point of view of women who call themselves lesbian. The researcher suspended the binary paradigm of sex and gender, and argued that lesbians' identity development must be understood against the background of how patriarchy understands the category 'woman' through history. Towards this purpose the pOSition of women in the West, as well as contemporary images and literature about lesbians, was reviewed. On the basis of this review questions about lesbian gender construction, lesbian identity development and lesbian individuation were identified. In order to access the psychological meaning of being lesbian, or lesbian experience from the inside out, the dream-series of three lesbians constituted an empirical basis for further exploration. These dream-series were amplified with intensive face-to-face interviews, transcribed, and subjected to a hermeneutic-phenomenological inductive method. Common inter-case concerns were identified and synthesized. In dialogue with the literature reviewed, twenty-two statements of meaning about being lesbian were distilled. These revealed two possible constructions of gender for primary lesbians. In addition, primary lesbians involved in the research demonstrated remarkable flexibility with respect to their gender orientations and gender identifications, were in the process of integrating with and differentiating from different aspects of their masculine and feminine potentials, and developed and negotiated their gender identities in relationship to both their lovers and friends. The explication also revealed that participants identified with archetypal aspects of the father that their fathers' did not express, and desired archetypal aspects of the mother that their mother's did not express. Finally, in so much as the method distinguished ~ sex, sexual identity and sexual orientation from gender, gender identity, gender identification and gender orientation, it may prove useful for exploring gender in heterosexual relating.
- Full Text:
- Date Issued: 2001
Sedimentology of the Karoo Supergroup in the Tuli Basin (Limpompo River area, South Africa)
- Authors: Bordy, Emese M
- Date: 2001
- Subjects: River sediments -- South Africa Sedimentology Limpopo river Sedimentology -- Limpopo river Limpopo river (South africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4999 , http://hdl.handle.net/10962/d1005612
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) consist of various terrigenous clastic and chemical deposits (parabreccias, conglo-breccias, conglomerates, sandstones, fine-grained sediments, calcretes and silc~etes). Four stratigraphic units were identified: the Basal, Middle and· Upper Units, and the CI~rens Formation. The palaeo-environmental reconstructions of the four stratigraphic units are based on evidence provided by primary sedimentary structures, palaeo-flow measurements, clast size/shape analysis, petrographic studies, palaeontological findings, borehole data and stratigraphic relations. The facies associations of the Basal Unit are interpreted as colluvial fan and low sinuosity, braid~d river channel with coal-bearing overbank and thaw-lake deposits. The interpreted depositional environment implies a cold climate, non-glacial subarctic fluvio-Iacustrine system. The current indicators of the palaeo-river system suggest flow direction from ENE to WSW. The lithologies of the Basal Unit are very similar to the deposits of the fluvial interval in the Vryheid Formation (Ecca Group) of the main Karoo Basin. There is no indubitable evidence for glacial activity (e.g. striated pavements or clasts, varvites, etc.), therefore the presence of unequivocal Dwyka Group correlatives in the Tuli Basin remains uncertain. The sedimentary structures and palaeo-current analysis indicate that the beds of the Middle Unit were deposited by an ancient river system flowing in a north-northwesterly direction. A lack of good quality exposures did not allow the reconstruction of the fluvial style, but the available data indicate a high-energy, perhaps braided fluvial system. The lack of bio- and chronostr~~igraphic control hampers precise correlation and enables only the lithocorrelation of the Middle Unit with other braided river systems either in the Beaufort Group or in the Molteno Formation of the main Karoo Basin. The depositional environment of the Upper Unit is interpreted as a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the unit, the climate was semi-arid with sparse precipitation resulting -iFlhighmagnitude, low-frequency devastating flash floods. The sediments were built out from a distant northwesterly source to the southeast. The unambiguous correspondence between the Upper Unit and the Elliot Formation (main Karoo Basin) is provided by lithological similarities and prosauropod dinosaurs remains. The palaeo-geographic picture of the Clarens Fonnation indicates a westerly windsdominated erg environment with migrating transverse dune types. The ephemeral stream deposits, fossil wood and trace fossils are only present in the lower part of the Formation, indicating that the wet-desert conditions were progressively replaced by dry-desert conditions. Based on lithological and palaeontological evidence, the Formation correlates with the Clarens Formation in the main Karoo Basin. At this stage, it remains difficult to establish the exact cause of the regional palaeo-slope changes during the deposition of the Karoo Supergroup in the Tuli Basin. It is probable that foreland system tectonics, which affected the lower part of the Supergroup (Basal Unit and Middle Unit?), were replaced by incipient continental extension and rift related tectonic movements in the Middle and Upper Units, and Clarens Formation.
- Full Text:
- Date Issued: 2001
- Authors: Bordy, Emese M
- Date: 2001
- Subjects: River sediments -- South Africa Sedimentology Limpopo river Sedimentology -- Limpopo river Limpopo river (South africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4999 , http://hdl.handle.net/10962/d1005612
- Description: The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) consist of various terrigenous clastic and chemical deposits (parabreccias, conglo-breccias, conglomerates, sandstones, fine-grained sediments, calcretes and silc~etes). Four stratigraphic units were identified: the Basal, Middle and· Upper Units, and the CI~rens Formation. The palaeo-environmental reconstructions of the four stratigraphic units are based on evidence provided by primary sedimentary structures, palaeo-flow measurements, clast size/shape analysis, petrographic studies, palaeontological findings, borehole data and stratigraphic relations. The facies associations of the Basal Unit are interpreted as colluvial fan and low sinuosity, braid~d river channel with coal-bearing overbank and thaw-lake deposits. The interpreted depositional environment implies a cold climate, non-glacial subarctic fluvio-Iacustrine system. The current indicators of the palaeo-river system suggest flow direction from ENE to WSW. The lithologies of the Basal Unit are very similar to the deposits of the fluvial interval in the Vryheid Formation (Ecca Group) of the main Karoo Basin. There is no indubitable evidence for glacial activity (e.g. striated pavements or clasts, varvites, etc.), therefore the presence of unequivocal Dwyka Group correlatives in the Tuli Basin remains uncertain. The sedimentary structures and palaeo-current analysis indicate that the beds of the Middle Unit were deposited by an ancient river system flowing in a north-northwesterly direction. A lack of good quality exposures did not allow the reconstruction of the fluvial style, but the available data indicate a high-energy, perhaps braided fluvial system. The lack of bio- and chronostr~~igraphic control hampers precise correlation and enables only the lithocorrelation of the Middle Unit with other braided river systems either in the Beaufort Group or in the Molteno Formation of the main Karoo Basin. The depositional environment of the Upper Unit is interpreted as a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the unit, the climate was semi-arid with sparse precipitation resulting -iFlhighmagnitude, low-frequency devastating flash floods. The sediments were built out from a distant northwesterly source to the southeast. The unambiguous correspondence between the Upper Unit and the Elliot Formation (main Karoo Basin) is provided by lithological similarities and prosauropod dinosaurs remains. The palaeo-geographic picture of the Clarens Fonnation indicates a westerly windsdominated erg environment with migrating transverse dune types. The ephemeral stream deposits, fossil wood and trace fossils are only present in the lower part of the Formation, indicating that the wet-desert conditions were progressively replaced by dry-desert conditions. Based on lithological and palaeontological evidence, the Formation correlates with the Clarens Formation in the main Karoo Basin. At this stage, it remains difficult to establish the exact cause of the regional palaeo-slope changes during the deposition of the Karoo Supergroup in the Tuli Basin. It is probable that foreland system tectonics, which affected the lower part of the Supergroup (Basal Unit and Middle Unit?), were replaced by incipient continental extension and rift related tectonic movements in the Middle and Upper Units, and Clarens Formation.
- Full Text:
- Date Issued: 2001
Superstition, atheism and reasonable faith in Acts 26: a Graeco-Roman perspective on Paul’s defence before Festus and Agrippa
- Authors: Germiquet, Edouard Ariste
- Date: 2001
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21065 , http://hdl.handle.net/10962/6224
- Description: This thesis investigates Luke‟s presentation of Paul‟s final and climactic defence of the gospel which takes place before Festus and King Agrippa II (Ac.26). It indicates how Luke has made use of the philosophical doctrine of the mean in order to present Christianity as a reasonable and rational faith. This investigation explores how Luke creates a literary framework within which to promote Paul as reasonable and rational through the application of the topos that true piety is the mean between the two extremes of superstition and atheism. The thesis is therefore structured around three dominant sections in which the major themes of superstition, atheism and rational faith are treated independently. Each section consists of an analysis of Luke‟s choice of words and his description of the behavioural patterns of each representative group so that a consistent picture progressively emerges in support of the basic framework. At all stages of the investigation, reference is made to contemporary moral philosophers, Hellenistic Judaism and the early Christian apologists so that the language, literary settings and stereotypes used by Luke can be clearly defined. This not only clarifies the text of Acts 26 but contributes to an overall appreciation of Luke‟s literary technique. At all points in the development of the thesis, the relevance and centrality which the resurrection has for Luke is kept in mind. This not only acts as a backdrop in understanding Luke‟s depiction of the superstitious and the atheist but is crucial in grasping Luke‟s presentation of Christianity as a rational faith. The thesis is brought to a close by a discussion on Luke's intended audience and the significance of his dedication to Theophilus.
- Full Text:
- Date Issued: 2001
- Authors: Germiquet, Edouard Ariste
- Date: 2001
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21065 , http://hdl.handle.net/10962/6224
- Description: This thesis investigates Luke‟s presentation of Paul‟s final and climactic defence of the gospel which takes place before Festus and King Agrippa II (Ac.26). It indicates how Luke has made use of the philosophical doctrine of the mean in order to present Christianity as a reasonable and rational faith. This investigation explores how Luke creates a literary framework within which to promote Paul as reasonable and rational through the application of the topos that true piety is the mean between the two extremes of superstition and atheism. The thesis is therefore structured around three dominant sections in which the major themes of superstition, atheism and rational faith are treated independently. Each section consists of an analysis of Luke‟s choice of words and his description of the behavioural patterns of each representative group so that a consistent picture progressively emerges in support of the basic framework. At all stages of the investigation, reference is made to contemporary moral philosophers, Hellenistic Judaism and the early Christian apologists so that the language, literary settings and stereotypes used by Luke can be clearly defined. This not only clarifies the text of Acts 26 but contributes to an overall appreciation of Luke‟s literary technique. At all points in the development of the thesis, the relevance and centrality which the resurrection has for Luke is kept in mind. This not only acts as a backdrop in understanding Luke‟s depiction of the superstitious and the atheist but is crucial in grasping Luke‟s presentation of Christianity as a rational faith. The thesis is brought to a close by a discussion on Luke's intended audience and the significance of his dedication to Theophilus.
- Full Text:
- Date Issued: 2001
Synthesis and characterisation of novel platinum (II) complexes potential chemotherapeutic drugs
- Authors: Datt, Michael Steven
- Date: 2001
- Subjects: Chemotherapy Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4366 , http://hdl.handle.net/10962/d1005031
- Description: The present study involves the preparation of novel mixed-ligand platinum(II) complexes in the hope of expanding the range of platinum(II) complexes that exhibit anticancer activity and which are less toxic and have a broader spectrum of activity than cisplatin and its analogues. To this end, N-(3-R-benzoyl)-N’,N’-diethylthiourea, N-(3-R-benzoyl)-N’-morpholinothiourea, N-(3-Rbenzoyl)-N’,N’-di(2-hydroxyethyl)thiourea (R = NO2, Cl, H, CH3, OCH3), N,N-diethyl-N’-menthyloxycarbonylthiourea and N-menthyloxycarbonyl-N’-morpholinothiourea ligands, and their corresponding mixed-ligand platinum(II) complexes of the type [PtCl(L)(RR’SO)], were synthesised and characterised by elemental analyses, IR, 1H and 195Pt NMR spectroscopy and, in some cases, X-ray crystallography. Dimethylsulfoxide complexes were prepared using all the ligands, while complexes containing unsymmetrically substituted sulfoxides were prepared using the N-benzoyl-N’,N’-diethylthiourea and ,N-diethyl-’-(-)-(3R)-menthyloxycarbonylthiourea ligands only. The molecular structures of cis-(S,S)-[PtCl(DMSO)(L)] (where L = N-benzoyl-N’,N’-diethylthioureato, N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato), cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(MPSO)] and cis-[Pt(N-benzoyl-N’,N’-diethylthioureato)2] were determined by X-ray crystallography. The X-ray crystal structure of N,N-diethyl-N’- (-)-(3R)-menthyloxycarbonylthiourea was also determined. The spectroscopic and crystallographic data are consistent with complexes containing a (S,O)-chelated ligand and a sulfur-bonded sulfoxide ligand. However, the 1H and 195Pt NMR studies showed that the alkoxycarbonylthioureato complexes exist as geometric isomers with the sulfoxide coordinated either in a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand, whereas the acylthioureato complexes yielded only cis-(S,S)-[PtCl(L)(RR’SO)] complexes. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands was examined further by treatment of the [PtCl(DMSO)(L)] complexes, where L = Nbenzoyl-N’,N’-diethylthioureato, N-benzoyl-N’-morpholinothioureato, N,N-diethyl-N’-(-)-(3R)- menthyloxycarbonylthioureato and N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato, with PPh3 to give the corresponding [PtCl(L)(PPh3)] and [Pt(L)(PPh3)2]+ complexes. 31P NMR studies of these complexes reveal that the alkoxycarbonylthioureato ligands bind less strongly than the acylthioureato ligands, which is consistent with the crystallographic studies. The morpholine derivatives of the acylthioureato and alkoxycarbonylthioureato ligand systems also appear to bind less tightly than the diethyl derivatives. The weaker binding properties of the alkoxycarbonylthioureato ligands might be a possible explanation for the observed geometric isomerisation of these complexes, with the mechanism of isomerisation involving a chelate ringiv opening step. Furthermore, crystallographic and 31P NMR studies suggest that the acylthioureato carbonyl oxygen donor atom is relatively softer and therefore has a greater trans-influence than the carbonyl oxygen donor atom of the alkoxycarbonylthioureato ligand. The substitution kinetics of the chloride and sulfoxide leaving groups by azide, iodide, thiocyanate, triphenylphosphine, 2-mercaptobenzimidazole, 4-(dimethylamino)pyridine and thiourea, from selected cis-(S,S)-[PtCl(N,N-dialkyl-N’-(3-R-benzoyl)thioureato)(RR’SO)] complexes, in methanol, were evaluated to determine if variation of the electronic properties of the chelated ligand and variation of the sulfoxide have a significant influence on the reactivity of these complexes. Two consecutive reactions were observed. It was found that neutral nucleophiles initially substitute the dimethylsulfoxide, while anionic nucleophiles substituted the chloride ligand. For all the nucleophiles studied, the first substitution step was evaluated, except for triphenylphosphine and 4-(dimethylamino)pyridine, where the second step was also evaluated. The overall order of reactivity for the first substitution step was; N3 - < DMAP < I- < SCN- < MBI < thiourea < PPh3, with the rate varying three orders of magnitude. The substitution of the dimethylsulfoxide ligand by PPh3 from cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl-(DMSO)] to form cis-(S,P)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(PPh3)] was confirmed by X-ray crystallography. In general, manipulation of the chelating moiety, as well as interchanging the sulfoxide did not alter the reactivity of these complexes to a great extent. The anticancer activity of all the platinum(II) sulfoxide complexes were evaluated against a HeLa cell line, of which three complexes, cis-(S,S)-[PtCl(DMSO)(N,N-diethyl-N’-(3-nitrobenzoyl)- thioureato)], cis-(S,S)-[PtCl(DMSO)(N-morpholino-N’-(3-nitrorobenzoyl)thioureato)] and cis-(S,S)-[PtCl(DMSO)(N-(3-methoxybenzoyl)-N’-morpholinothioureato)] exhibited a concentration dependent anti-proliferative effect, but were less potent than cisplatin. These three complexes displayed a similar dose response in a MCF-7 cell line. Preliminary morphology studies with the three biologically active complexes in a HeLa cell line suggest that they induce cell death by apoptosis. Preliminary pBR322 plasmid DNA binding studies of selected [Pt(acylthioureato)Cl(RR’SO)]complexes clearly indicate that these complexes have a different mode of binding to DNA than cisplatin.
- Full Text:
- Date Issued: 2001
- Authors: Datt, Michael Steven
- Date: 2001
- Subjects: Chemotherapy Platinum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4366 , http://hdl.handle.net/10962/d1005031
- Description: The present study involves the preparation of novel mixed-ligand platinum(II) complexes in the hope of expanding the range of platinum(II) complexes that exhibit anticancer activity and which are less toxic and have a broader spectrum of activity than cisplatin and its analogues. To this end, N-(3-R-benzoyl)-N’,N’-diethylthiourea, N-(3-R-benzoyl)-N’-morpholinothiourea, N-(3-Rbenzoyl)-N’,N’-di(2-hydroxyethyl)thiourea (R = NO2, Cl, H, CH3, OCH3), N,N-diethyl-N’-menthyloxycarbonylthiourea and N-menthyloxycarbonyl-N’-morpholinothiourea ligands, and their corresponding mixed-ligand platinum(II) complexes of the type [PtCl(L)(RR’SO)], were synthesised and characterised by elemental analyses, IR, 1H and 195Pt NMR spectroscopy and, in some cases, X-ray crystallography. Dimethylsulfoxide complexes were prepared using all the ligands, while complexes containing unsymmetrically substituted sulfoxides were prepared using the N-benzoyl-N’,N’-diethylthiourea and ,N-diethyl-’-(-)-(3R)-menthyloxycarbonylthiourea ligands only. The molecular structures of cis-(S,S)-[PtCl(DMSO)(L)] (where L = N-benzoyl-N’,N’-diethylthioureato, N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato), cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(MPSO)] and cis-[Pt(N-benzoyl-N’,N’-diethylthioureato)2] were determined by X-ray crystallography. The X-ray crystal structure of N,N-diethyl-N’- (-)-(3R)-menthyloxycarbonylthiourea was also determined. The spectroscopic and crystallographic data are consistent with complexes containing a (S,O)-chelated ligand and a sulfur-bonded sulfoxide ligand. However, the 1H and 195Pt NMR studies showed that the alkoxycarbonylthioureato complexes exist as geometric isomers with the sulfoxide coordinated either in a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand, whereas the acylthioureato complexes yielded only cis-(S,S)-[PtCl(L)(RR’SO)] complexes. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands was examined further by treatment of the [PtCl(DMSO)(L)] complexes, where L = Nbenzoyl-N’,N’-diethylthioureato, N-benzoyl-N’-morpholinothioureato, N,N-diethyl-N’-(-)-(3R)- menthyloxycarbonylthioureato and N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato, with PPh3 to give the corresponding [PtCl(L)(PPh3)] and [Pt(L)(PPh3)2]+ complexes. 31P NMR studies of these complexes reveal that the alkoxycarbonylthioureato ligands bind less strongly than the acylthioureato ligands, which is consistent with the crystallographic studies. The morpholine derivatives of the acylthioureato and alkoxycarbonylthioureato ligand systems also appear to bind less tightly than the diethyl derivatives. The weaker binding properties of the alkoxycarbonylthioureato ligands might be a possible explanation for the observed geometric isomerisation of these complexes, with the mechanism of isomerisation involving a chelate ringiv opening step. Furthermore, crystallographic and 31P NMR studies suggest that the acylthioureato carbonyl oxygen donor atom is relatively softer and therefore has a greater trans-influence than the carbonyl oxygen donor atom of the alkoxycarbonylthioureato ligand. The substitution kinetics of the chloride and sulfoxide leaving groups by azide, iodide, thiocyanate, triphenylphosphine, 2-mercaptobenzimidazole, 4-(dimethylamino)pyridine and thiourea, from selected cis-(S,S)-[PtCl(N,N-dialkyl-N’-(3-R-benzoyl)thioureato)(RR’SO)] complexes, in methanol, were evaluated to determine if variation of the electronic properties of the chelated ligand and variation of the sulfoxide have a significant influence on the reactivity of these complexes. Two consecutive reactions were observed. It was found that neutral nucleophiles initially substitute the dimethylsulfoxide, while anionic nucleophiles substituted the chloride ligand. For all the nucleophiles studied, the first substitution step was evaluated, except for triphenylphosphine and 4-(dimethylamino)pyridine, where the second step was also evaluated. The overall order of reactivity for the first substitution step was; N3 - < DMAP < I- < SCN- < MBI < thiourea < PPh3, with the rate varying three orders of magnitude. The substitution of the dimethylsulfoxide ligand by PPh3 from cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl-(DMSO)] to form cis-(S,P)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(PPh3)] was confirmed by X-ray crystallography. In general, manipulation of the chelating moiety, as well as interchanging the sulfoxide did not alter the reactivity of these complexes to a great extent. The anticancer activity of all the platinum(II) sulfoxide complexes were evaluated against a HeLa cell line, of which three complexes, cis-(S,S)-[PtCl(DMSO)(N,N-diethyl-N’-(3-nitrobenzoyl)- thioureato)], cis-(S,S)-[PtCl(DMSO)(N-morpholino-N’-(3-nitrorobenzoyl)thioureato)] and cis-(S,S)-[PtCl(DMSO)(N-(3-methoxybenzoyl)-N’-morpholinothioureato)] exhibited a concentration dependent anti-proliferative effect, but were less potent than cisplatin. These three complexes displayed a similar dose response in a MCF-7 cell line. Preliminary morphology studies with the three biologically active complexes in a HeLa cell line suggest that they induce cell death by apoptosis. Preliminary pBR322 plasmid DNA binding studies of selected [Pt(acylthioureato)Cl(RR’SO)]complexes clearly indicate that these complexes have a different mode of binding to DNA than cisplatin.
- Full Text:
- Date Issued: 2001
The determination of geomorphologically effective flows for selected eastern sea-Board Rivers in South Africa
- Authors: Dollar, Evan S J
- Date: 2001
- Subjects: Rivers--South Africa River channels Geomorphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4824 , http://hdl.handle.net/10962/d1005499
- Description: In South Africa the need to protect and manage the national water resource has led to the development of the Reserve as a basic right under the National Water Act (1998). The Ecological Reserve relates to the quality and quantity of water necessary to protect the sustainable functioning of aquatic ecosystems. The geomorphological contribution to setting the Reserve has focussed on three groups of information requirements: the spatial and temporal availability of habitat, the maintenance of substratum characteristics, and the maintenance of channel form. This thesis focusses on the second and third information requirements. The thesis has attempted to achieve this by adding value to the theoretical and applied understanding of the magnitude and frequency of channel forming discharge for selected southern African rivers. Many of the eastern sea-board rivers are strongly influenced by bed rock in the channel perimeter, and by a highly variable hydrological regime. This has resulted in characteristic channel forms, with an active channel incised into a larger macro-channel being a common feature of eastern seaboard rivers. Within the active channel inset channel benches commonly occur. This alluvial architecture is used to provide clues as to the types of flows necessary to meet the Reserve. Three river basins are considered : the Mkomazi, Mhlathuze and Olifants. The Mkomazi is a relatively un-impacted perennial eastern-sea board river and forms the research component of the study. The Mhlathuze and Olifants rivers are highly regulated systems and form the application component of the study. Utilising synthesised daily hydrological data, bed material data, cross-sectional surveys, hydraulic data and relevant bed material transport equations, channel form was related to dominant discharge and effective discharge in an attempt to identify the magnitude and frequency offlows that can be considered to be ' effective'. Results from the Mkomazi River indicate that no single effective discharge exists, but rather that there is a range of effective discharges in the 5-0.1% range on the 1-day daily flow duration curves that are responsible for the bulk (>80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems
- Full Text:
- Date Issued: 2001
- Authors: Dollar, Evan S J
- Date: 2001
- Subjects: Rivers--South Africa River channels Geomorphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4824 , http://hdl.handle.net/10962/d1005499
- Description: In South Africa the need to protect and manage the national water resource has led to the development of the Reserve as a basic right under the National Water Act (1998). The Ecological Reserve relates to the quality and quantity of water necessary to protect the sustainable functioning of aquatic ecosystems. The geomorphological contribution to setting the Reserve has focussed on three groups of information requirements: the spatial and temporal availability of habitat, the maintenance of substratum characteristics, and the maintenance of channel form. This thesis focusses on the second and third information requirements. The thesis has attempted to achieve this by adding value to the theoretical and applied understanding of the magnitude and frequency of channel forming discharge for selected southern African rivers. Many of the eastern sea-board rivers are strongly influenced by bed rock in the channel perimeter, and by a highly variable hydrological regime. This has resulted in characteristic channel forms, with an active channel incised into a larger macro-channel being a common feature of eastern seaboard rivers. Within the active channel inset channel benches commonly occur. This alluvial architecture is used to provide clues as to the types of flows necessary to meet the Reserve. Three river basins are considered : the Mkomazi, Mhlathuze and Olifants. The Mkomazi is a relatively un-impacted perennial eastern-sea board river and forms the research component of the study. The Mhlathuze and Olifants rivers are highly regulated systems and form the application component of the study. Utilising synthesised daily hydrological data, bed material data, cross-sectional surveys, hydraulic data and relevant bed material transport equations, channel form was related to dominant discharge and effective discharge in an attempt to identify the magnitude and frequency offlows that can be considered to be ' effective'. Results from the Mkomazi River indicate that no single effective discharge exists, but rather that there is a range of effective discharges in the 5-0.1% range on the 1-day daily flow duration curves that are responsible for the bulk (>80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems
- Full Text:
- Date Issued: 2001
The ecology and physiology of the springhare (Pedetes capensis) in the Eastern Cape Province of South Africa
- Authors: Peinke, Dean Michael
- Date: 2001
- Subjects: Hares -- South Africa -- Eastern Cape Hares -- Breeding -- South Africa -- Eastern Cape Hares -- Ecology -- South Africa -- Eastern Cape Hares -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5670 , http://hdl.handle.net/10962/d1005355
- Description: Springhare are large, bipedal, nocturnal, herbivorous, burrowing rodents that are found in arid and semi-arid parts of southern and eastern Africa. In this thesis I examine the general ecology, biology and physiology of these animals in the Eastern Cape Province of South Africa. An investigation of their distribution and activity in the study site showed that springhare exhibit a preference for flat, open, recently disturbed habitat that is dominated by the grass Cynodon dactylon and the sedge Cyperus esculentus. These two species constitute a major proportion of their diet. The impact of spring hare on chicory and grazing is also discussed. Nightly activity generally peaks soon after dark and decreases in the 2-4 hour period before sunrise. This pattern is, however, modified by moonlight. Springhare typically respond to moonlight by reducing aboveground activity, shifting their activity to dark moonless periods of the night, and by reducing their use of open space. Contrary to earlier reports, springhare utilise several different burrow systems spread over large areas. They regularly change burrow systems and seldom spend more than a few consecutive days in each. Springhare do not appear to defend territories but recently used burrows appear to be avoided by conspecifics. Males and females on average use a similar number of burrows, scattered over similar sized areas. Burrows are shown to provide a stable microclimate of moderate temperature and high humidity throughout the year. Reproduction is continuous and there is no synchronised breeding season. The ability to reproduce throughout the year is attributed primarily to their ability to utilise subterranean food stores. The overall reproductive strategy of springhare (a single young with long gestation and weaning) is unusual for a mammal of this size but may be linked to low levels of adult and juvenile mortality. Physiologically, springhare are reasonably well adapted to life in hot, arid environments. They produce a concentrated urine, exhibit a high tolerance to dehydration, are good osmoregulators capable of maintaining plasma volume, osmolality and ion balance over long periods of water deprivation, and are able to produce dry faeces. They are also good thermoregulators at low ambient temperatures, which are usually encountered at night, but are poor thermoregulators at high ambient temperatures, which they avoid behaviourally.
- Full Text:
- Date Issued: 2001
- Authors: Peinke, Dean Michael
- Date: 2001
- Subjects: Hares -- South Africa -- Eastern Cape Hares -- Breeding -- South Africa -- Eastern Cape Hares -- Ecology -- South Africa -- Eastern Cape Hares -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5670 , http://hdl.handle.net/10962/d1005355
- Description: Springhare are large, bipedal, nocturnal, herbivorous, burrowing rodents that are found in arid and semi-arid parts of southern and eastern Africa. In this thesis I examine the general ecology, biology and physiology of these animals in the Eastern Cape Province of South Africa. An investigation of their distribution and activity in the study site showed that springhare exhibit a preference for flat, open, recently disturbed habitat that is dominated by the grass Cynodon dactylon and the sedge Cyperus esculentus. These two species constitute a major proportion of their diet. The impact of spring hare on chicory and grazing is also discussed. Nightly activity generally peaks soon after dark and decreases in the 2-4 hour period before sunrise. This pattern is, however, modified by moonlight. Springhare typically respond to moonlight by reducing aboveground activity, shifting their activity to dark moonless periods of the night, and by reducing their use of open space. Contrary to earlier reports, springhare utilise several different burrow systems spread over large areas. They regularly change burrow systems and seldom spend more than a few consecutive days in each. Springhare do not appear to defend territories but recently used burrows appear to be avoided by conspecifics. Males and females on average use a similar number of burrows, scattered over similar sized areas. Burrows are shown to provide a stable microclimate of moderate temperature and high humidity throughout the year. Reproduction is continuous and there is no synchronised breeding season. The ability to reproduce throughout the year is attributed primarily to their ability to utilise subterranean food stores. The overall reproductive strategy of springhare (a single young with long gestation and weaning) is unusual for a mammal of this size but may be linked to low levels of adult and juvenile mortality. Physiologically, springhare are reasonably well adapted to life in hot, arid environments. They produce a concentrated urine, exhibit a high tolerance to dehydration, are good osmoregulators capable of maintaining plasma volume, osmolality and ion balance over long periods of water deprivation, and are able to produce dry faeces. They are also good thermoregulators at low ambient temperatures, which are usually encountered at night, but are poor thermoregulators at high ambient temperatures, which they avoid behaviourally.
- Full Text:
- Date Issued: 2001