in the council chambers
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229862 , vital:49718 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229862 , vital:49718 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
in a park in Europe
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229851 , vital:49717 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229851 , vital:49717 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
consumed society
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229840 , vital:49716 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
- Authors: Krueger, Anton
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229840 , vital:49716 , xlink:href="https://hdl.handle.net/10520/EJC47802"
- Full Text:
- Date Issued: 2008
Fungal remediation of winery and distillery wastewaters using Trametes pubescens MB 89 and the enhanced production of a high-value enzyme therein
- Authors: Strong, Peter James
- Date: 2008
- Subjects: Fungal remediation Distilleries -- Waste disposal Wine and wine making -- Waste disposal Bioremediation Laccase Enzymes -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3932 , http://hdl.handle.net/10962/d1003991
- Description: In this study white-rot fungi were investigated for their efficiency at distillery wastewater remediation and the production of laccase as a valuable by-product. Distillery wastewaters are high in organic load and low in pH. The presence of phenolic compounds can lead to extremely colour-rich wastewaters and can be toxic to microorganisms. The presence of the inorganic ions may also affect biological treatment. White-rot fungi are unique among eukaryotic or prokaryotic microbes in possessing powerful oxidative enzyme systems that can degrade lignin to carbon dioxide. These ligninolytic enzymes, such as lignin peroxidase, manganese peroxidase and laccase, are capable of degrading a vast range of toxic, recalcitrant environmental pollutants and this makes the white-rot fungi strong candidates for the bioremediation of polluted soils and waters. The laccase enzyme alone has shown remediation potential in wastewaters such as beer production effluent, olive mill wastewater, alcohol distillery wastes, dye-containing wastewaters from the textile industry as well as wastewaters from the paper and pulp industry. It has been shown to be capable of remediating soils and waters polluted with chlorinated phenolic compounds, polyaromatic hydrocarbons, nitrosubstituted compounds and fungicides, herbicides and insecticides.
- Full Text:
- Date Issued: 2008
- Authors: Strong, Peter James
- Date: 2008
- Subjects: Fungal remediation Distilleries -- Waste disposal Wine and wine making -- Waste disposal Bioremediation Laccase Enzymes -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3932 , http://hdl.handle.net/10962/d1003991
- Description: In this study white-rot fungi were investigated for their efficiency at distillery wastewater remediation and the production of laccase as a valuable by-product. Distillery wastewaters are high in organic load and low in pH. The presence of phenolic compounds can lead to extremely colour-rich wastewaters and can be toxic to microorganisms. The presence of the inorganic ions may also affect biological treatment. White-rot fungi are unique among eukaryotic or prokaryotic microbes in possessing powerful oxidative enzyme systems that can degrade lignin to carbon dioxide. These ligninolytic enzymes, such as lignin peroxidase, manganese peroxidase and laccase, are capable of degrading a vast range of toxic, recalcitrant environmental pollutants and this makes the white-rot fungi strong candidates for the bioremediation of polluted soils and waters. The laccase enzyme alone has shown remediation potential in wastewaters such as beer production effluent, olive mill wastewater, alcohol distillery wastes, dye-containing wastewaters from the textile industry as well as wastewaters from the paper and pulp industry. It has been shown to be capable of remediating soils and waters polluted with chlorinated phenolic compounds, polyaromatic hydrocarbons, nitrosubstituted compounds and fungicides, herbicides and insecticides.
- Full Text:
- Date Issued: 2008
ATP mimics as glutamine synthetase inhibitors : an exploratory synthetic study
- Authors: Salisu, Sheriff Tomilola
- Date: 2008
- Subjects: Glutamine synthetase Tuberculosis -- Treatment Tuberculosis -- Chemotherapy Adenosine triphosphate Adenosine triphosphate -- Synthesis Drug development
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4408 , http://hdl.handle.net/10962/d1006715
- Description: Using a mechanism-based approach to drug discovery, efforts have been directed towards developing novel ATP mimics that can act as GS inhibitors. The purine-based systems, adenosine, adenine and allopurinol, were identified as possible scaffolds for potential ATP mimics, while various meta-disubstituted benzenoid compounds, 3-aminobenzonitrile, 3-aminophenol, resorcinol, 3-aminobenzyl alcohol, 3-hydroxybenzoic acid and 3-aminobenzoic acid have been explored as adenine analogues. These compounds were treated with different alkylating and acylating agents. Allylation of all the substrates was achieved using allyl bromide and N-9 alkylation of protected allopurinol was effected using a number of specially prepared Baylis-Hillman adducts. Acylation of the benzenoid precursors with chloroacetyl chloride, acetoxyacetyl chloride, acryloyl chloride and specially prepared 2,3,4,5,6-pentaacetylgluconoyl chloride afforded the corresponding mono- and /or diacylated products in varying yields (4-96%). Elaboration of the alkylated and acylated products has involved the reaction of hydroxy systems with diethyl chloro phosphate and chloro derivatives with triethyl phosphite in Arbuzov-type reactions to afford phosphorylated products. In all cases, products were fully characterized using 1- and 2-D NMR analysis and, where appropriate, high-resolution mass spectrometry. The application of Modgraph and ChemWindow NMR prediction programmes has been explored and the resulting data have been compared with experimental chemical shift assignments to confirm chemical structures and, in some cases, to establish the position of allylation or acylation. Experimental assignments were found to be generally comparable with the Modgraph data, but not always with the ChemWindow values. The docking of selected products in the 'active-site' of GS and their structural homology with ATP, both in their free and bound conformations have been studied using the ACCELERYS Cerius² platform. All the selected ATP mimics exhibit some form of interaction with the 'active-site' residues, and a number of them appear to be promising GS ligands.
- Full Text:
- Date Issued: 2008
- Authors: Salisu, Sheriff Tomilola
- Date: 2008
- Subjects: Glutamine synthetase Tuberculosis -- Treatment Tuberculosis -- Chemotherapy Adenosine triphosphate Adenosine triphosphate -- Synthesis Drug development
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4408 , http://hdl.handle.net/10962/d1006715
- Description: Using a mechanism-based approach to drug discovery, efforts have been directed towards developing novel ATP mimics that can act as GS inhibitors. The purine-based systems, adenosine, adenine and allopurinol, were identified as possible scaffolds for potential ATP mimics, while various meta-disubstituted benzenoid compounds, 3-aminobenzonitrile, 3-aminophenol, resorcinol, 3-aminobenzyl alcohol, 3-hydroxybenzoic acid and 3-aminobenzoic acid have been explored as adenine analogues. These compounds were treated with different alkylating and acylating agents. Allylation of all the substrates was achieved using allyl bromide and N-9 alkylation of protected allopurinol was effected using a number of specially prepared Baylis-Hillman adducts. Acylation of the benzenoid precursors with chloroacetyl chloride, acetoxyacetyl chloride, acryloyl chloride and specially prepared 2,3,4,5,6-pentaacetylgluconoyl chloride afforded the corresponding mono- and /or diacylated products in varying yields (4-96%). Elaboration of the alkylated and acylated products has involved the reaction of hydroxy systems with diethyl chloro phosphate and chloro derivatives with triethyl phosphite in Arbuzov-type reactions to afford phosphorylated products. In all cases, products were fully characterized using 1- and 2-D NMR analysis and, where appropriate, high-resolution mass spectrometry. The application of Modgraph and ChemWindow NMR prediction programmes has been explored and the resulting data have been compared with experimental chemical shift assignments to confirm chemical structures and, in some cases, to establish the position of allylation or acylation. Experimental assignments were found to be generally comparable with the Modgraph data, but not always with the ChemWindow values. The docking of selected products in the 'active-site' of GS and their structural homology with ATP, both in their free and bound conformations have been studied using the ACCELERYS Cerius² platform. All the selected ATP mimics exhibit some form of interaction with the 'active-site' residues, and a number of them appear to be promising GS ligands.
- Full Text:
- Date Issued: 2008
Synthesis, photochemical and photophysical properties of gallium and indium phthalocyanine derivatives
- Authors: Chauke, Vongani Portia
- Date: 2008
- Subjects: Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4375 , http://hdl.handle.net/10962/d1005040 , Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Description: The syntheses of octasubstituted and unsusbstitituted Gallium(III) chloride and indium(III) chloride phthalocyanines (GaPc and InPc), their photophysical, photochemical and nonlinear optical parameters are hereby presented. The photocatalytic oxidation of 1-hexene using the synthesized GaPc and InPc complexes as well as electrochemical characterization is also presented in this thesis. Fluorescence quantum yields do not vary much among the four Ga complexes, except for complex 21c; therefore it was concluded that the effect of substituents is not significant among them. Solvents however, had an effect on the results. Lower Φ[subscript F] values were obtained in low viscosity solvents like toluene, relative to highly viscous solvents, such as DMSO. The triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. Photodegradation and singlet oxygen quantum yields have also been reported. There was no clear correlation between the latter parameters. It was however established that the four gallium MPcs were stable, within the allowed stability range for phthalocyanines. High quantum yields of triplet state (Φ[subscript T] ranging from 0.70 to 0.91 in dimethysulfoxide, DMSO) and singlet oxygen generation (Φ[subscript greek capital letter delta], ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50 to 60 μs were obtained in DMSO). Calculated non-linear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. The optical limiting threshold intensity (I[subscript lim]) values for the InPc and GaPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The octasubstituted were found to be better optical limiters. Photocatalytic oxidation of 1-hexene by GaPc (21a-c) and InPc (22a-c) derivatives is also presented. The photocatalytic oxidation products for 1-hexene were 1,2- epoxyhexane and 1-hexen-3-ol. The % conversion values of 1-hexene and % selectivity of 1,2-epoxyhexane were generally higher for InPc derivatives. Even though InPc derivatives showed better photocatalytic results than GaPc derivatives, the former were less stable relative to the latter. Both type I and type II mechanism were implicated in the photocatalysis mechanism.
- Full Text:
- Date Issued: 2008
- Authors: Chauke, Vongani Portia
- Date: 2008
- Subjects: Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4375 , http://hdl.handle.net/10962/d1005040 , Phthalocyanines , Photochemotherapy , Electrochemistry , Gallium , Indium
- Description: The syntheses of octasubstituted and unsusbstitituted Gallium(III) chloride and indium(III) chloride phthalocyanines (GaPc and InPc), their photophysical, photochemical and nonlinear optical parameters are hereby presented. The photocatalytic oxidation of 1-hexene using the synthesized GaPc and InPc complexes as well as electrochemical characterization is also presented in this thesis. Fluorescence quantum yields do not vary much among the four Ga complexes, except for complex 21c; therefore it was concluded that the effect of substituents is not significant among them. Solvents however, had an effect on the results. Lower Φ[subscript F] values were obtained in low viscosity solvents like toluene, relative to highly viscous solvents, such as DMSO. The triplet quantum yields were found to be lower in DMSO than in DMF and toluene. The rate constants for fluorescence, intersystem crossing and internal conversion as well as fluorescence and triplet lifetimes are reported. Photodegradation and singlet oxygen quantum yields have also been reported. There was no clear correlation between the latter parameters. It was however established that the four gallium MPcs were stable, within the allowed stability range for phthalocyanines. High quantum yields of triplet state (Φ[subscript T] ranging from 0.70 to 0.91 in dimethysulfoxide, DMSO) and singlet oxygen generation (Φ[subscript greek capital letter delta], ranging from 0.61 to 0.79 in DMSO) were obtained. Short triplet lifetimes 50 to 60 μs were obtained in DMSO). Calculated non-linear parameters of these complexes are compared with those of the corresponding GaPc derivatives and tetrasubstituted GaPc and InPc complexes. The optical limiting threshold intensity (I[subscript lim]) values for the InPc and GaPc derivatives were calculated and compared with those of corresponding tetrasubstituted InPc and GaPc complexes. The octasubstituted were found to be better optical limiters. Photocatalytic oxidation of 1-hexene by GaPc (21a-c) and InPc (22a-c) derivatives is also presented. The photocatalytic oxidation products for 1-hexene were 1,2- epoxyhexane and 1-hexen-3-ol. The % conversion values of 1-hexene and % selectivity of 1,2-epoxyhexane were generally higher for InPc derivatives. Even though InPc derivatives showed better photocatalytic results than GaPc derivatives, the former were less stable relative to the latter. Both type I and type II mechanism were implicated in the photocatalysis mechanism.
- Full Text:
- Date Issued: 2008
An evaluation of the questions posed to child witnesses in court to determine whether they are developmentally appropriate
- Authors: Erasmus, Ronell
- Date: 2008
- Subjects: Child witnesses -- South Africa , Law -- Language
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10267 , http://hdl.handle.net/10948/747 , Child witnesses -- South Africa , Law -- Language
- Description: Children are often required to testify viva voce in criminal trials. The question arises whether children understand what is communicated to them during their testimony in court. In the courtroom, the witness serves as a source of information. In child abuse cases in particular, the meaningful participation of the child in court proceedings is crucial due to the fact that the child is often the key witness, or the only witness, for the prosecution. The proper evaluation of the child’s evidence, however, requires that all role-players involved in the judicial process have a sound knowledge of those aspects which deal with child psychology, especially the cognitive and language abilities of children who testify. The procedure that is followed in court is not understood by the ordinary lay person, even less by children, and the language used is formalistic and very specialized. Legal language in general often contains cognitively and linguistically inappropriate questions which prevent children from relating their stories. Furthermore their responses do not sufficiently reflect their knowledge and experience of the incident of alleged sexual assault. Court language creates serious problems for children and accordingly prevents them from being effective witnesses and taking part in the judicial process in a meaningful way. The researcher, in her capacity as a Regional Court Magistrate, realized that children have limited understanding of the criminal trial process and often become secondary victims as a result of a system that does not acknowledge their cognitive and linguistic developmental levels. The purpose of this research was therefore to test the validity of the following hypotheses: • During the examination of children in a criminal trial developmentally and linguistically inappropriate questions are posed to them; and This results in ineffective communication. Eight court transcripts of criminal cases heard in the regional courts of the Eastern Cape and Mpumalanga by different presiding officers were chosen at random. These transcripts were analyzed and evaluated in order to determine whether questions posed to children when they testify are cognitively and linguistically appropriate. Each question in each of the eight transcripts was numbered and analyzed. The findings of the analysis were categorized in terms of whether they were cognitively and linguistically inappropriate questions. It was clear that the majority of questions put to the child witnesses were cognitively and linguistically inappropriate. It is evident from the evaluation that the manner in which the children’s evidence in court was presented and the way in which they were questioned created a communication barrier which placed a distorted version of events before the court. It is therefore recommended that full account be taken of the cognitive and language capabilities of each particular child in order to elicit reliable information during the child’s testimony. It is of the utmost importance that questioning be conducted in such a fashion so as to ensure that the child witness understands not only the content of the questions, but also what answers or responses are expected from them. At present, acknowledgement of linguistic and cognitive developmental appropriateness, concern and comprehension for the psychology of the child witness are ignored at best, and totally exploited at worst. This lack of knowledge about child development impacts adversely upon the child’s credibility in court. To elevate and enhance the credibility of children, it is of the utmost importance for society in general and court role-players in particular to appreciate the various stages and faces of child development. The main recommendation is that court role-players should make a paradigm shift and children, including victims of sexual assault, should be given the opportunity to tell their own stories in their own language supported by other methods of communication. In evaluating any possible changes, it is necessary to adopt and develop a holistic and multi-disciplinary approach based on scientific principles. A specialized system is required to deal with children in the criminal justice system and innovative methods to achieve this are necessary. There is a strong need to change or adjust the present manner in which the criminal justice system accommodates child witnesses. Such a change or adjustment will be in the best interests of children as envisaged in section 28 of the Constitution of the Republic of South Africa Act.
- Full Text:
- Date Issued: 2008
- Authors: Erasmus, Ronell
- Date: 2008
- Subjects: Child witnesses -- South Africa , Law -- Language
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10267 , http://hdl.handle.net/10948/747 , Child witnesses -- South Africa , Law -- Language
- Description: Children are often required to testify viva voce in criminal trials. The question arises whether children understand what is communicated to them during their testimony in court. In the courtroom, the witness serves as a source of information. In child abuse cases in particular, the meaningful participation of the child in court proceedings is crucial due to the fact that the child is often the key witness, or the only witness, for the prosecution. The proper evaluation of the child’s evidence, however, requires that all role-players involved in the judicial process have a sound knowledge of those aspects which deal with child psychology, especially the cognitive and language abilities of children who testify. The procedure that is followed in court is not understood by the ordinary lay person, even less by children, and the language used is formalistic and very specialized. Legal language in general often contains cognitively and linguistically inappropriate questions which prevent children from relating their stories. Furthermore their responses do not sufficiently reflect their knowledge and experience of the incident of alleged sexual assault. Court language creates serious problems for children and accordingly prevents them from being effective witnesses and taking part in the judicial process in a meaningful way. The researcher, in her capacity as a Regional Court Magistrate, realized that children have limited understanding of the criminal trial process and often become secondary victims as a result of a system that does not acknowledge their cognitive and linguistic developmental levels. The purpose of this research was therefore to test the validity of the following hypotheses: • During the examination of children in a criminal trial developmentally and linguistically inappropriate questions are posed to them; and This results in ineffective communication. Eight court transcripts of criminal cases heard in the regional courts of the Eastern Cape and Mpumalanga by different presiding officers were chosen at random. These transcripts were analyzed and evaluated in order to determine whether questions posed to children when they testify are cognitively and linguistically appropriate. Each question in each of the eight transcripts was numbered and analyzed. The findings of the analysis were categorized in terms of whether they were cognitively and linguistically inappropriate questions. It was clear that the majority of questions put to the child witnesses were cognitively and linguistically inappropriate. It is evident from the evaluation that the manner in which the children’s evidence in court was presented and the way in which they were questioned created a communication barrier which placed a distorted version of events before the court. It is therefore recommended that full account be taken of the cognitive and language capabilities of each particular child in order to elicit reliable information during the child’s testimony. It is of the utmost importance that questioning be conducted in such a fashion so as to ensure that the child witness understands not only the content of the questions, but also what answers or responses are expected from them. At present, acknowledgement of linguistic and cognitive developmental appropriateness, concern and comprehension for the psychology of the child witness are ignored at best, and totally exploited at worst. This lack of knowledge about child development impacts adversely upon the child’s credibility in court. To elevate and enhance the credibility of children, it is of the utmost importance for society in general and court role-players in particular to appreciate the various stages and faces of child development. The main recommendation is that court role-players should make a paradigm shift and children, including victims of sexual assault, should be given the opportunity to tell their own stories in their own language supported by other methods of communication. In evaluating any possible changes, it is necessary to adopt and develop a holistic and multi-disciplinary approach based on scientific principles. A specialized system is required to deal with children in the criminal justice system and innovative methods to achieve this are necessary. There is a strong need to change or adjust the present manner in which the criminal justice system accommodates child witnesses. Such a change or adjustment will be in the best interests of children as envisaged in section 28 of the Constitution of the Republic of South Africa Act.
- Full Text:
- Date Issued: 2008
Thermal, spectroscopic and x-ray diffraction studies of copper(II) 1,2,4,5-Benzenetetracarboxylates and copper(II) oxalate a study of metal-organic frameworks
- Authors: Lamprecht, Emmanuel
- Date: 2008
- Subjects: Organometallic compounds Copper Oxalates -- Thermal properties Organic compounds -- Synthesis Spectrum analysis X-rays -- Diffraction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4389 , http://hdl.handle.net/10962/d1005054
- Description: Novel and known metal organic frameworks with copper(II), sodium and 1,2,4,5-benzenetetracarboxylate were prepared by ambient precipitation, solvothermal and gel-synthesis methods, and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetry with FTIR evolved-gas analysis. Some of these complexes were investigated for guest inclusion properties with water (the original guest species), methanol, ethanol and pyridine. The gel-synthesis products were the most interesting. The novel threedimensional metal-organic framework complex Cu₂ Na(OH)L·7H₂O (where L=1,2,4,5-benzenetetracarboxylate) -formed by gel-synthesis- is a covalent three-dimensional metal organic framework polymer with open channels containing both guest water molecules and water molecules coordinated to sodium. The structure collapsed on dehydration, but was essentially restored to the original structure on rehydration in moist air. On exposure of the dehydrated material to methanol and ethanol vapour, significant uptake of these solvents was observed, and the resolvated structures closely resembled that of the parent material. On heating in dry nitrogen, small amounts of methanol and ethanol remained until about 280 °C, when loss of the remaining guest triggered decomposition of the framework. The related complex, Cu₂¼(OH)½ L·7½H₂O (or possibly Cu₂⅓ (OH)⅔L·8H₂O) -formed by gel-synthesis- had a different physical appearance to Cu₂Na(OH)L·7H₂O above, but had nearly identical X-ray diffraction pattern, mid-infrared spectrum and thermal behaviour. The novel complex Cu₄Na₄L₃·14H₂O -formed by gel-synthesis- is a covalent three-dimensional metal-organic framework with small channels containing both guest water molecules and water coordinated to sodium and copper. Upon dehydration the structure collapsed, but on rehydration in moist air the original structure was partly restored. The dehydrated material did not absorb methanol. Known two-dimensional polymeric complexes [Cu₂L·6H₂O]·4H₂O and [Cu₂L·4H₂O]·2H₂O were also obtained by gel-synthesis, and were characterized and investigated for guest inclusion properties. The structures of these complexes collapsed on dehydration, and were only partly restored on rehydration in saturated water vapour. The dehydrated materials did not absorb methanol. The two-dimensional polymeric mixed-ligand complex Cu₂(pyridine)₄·6H₂O -formed very slowly by gel-synthesis- was characterized by TG-FTIR, and was shown to undergo a complicated decomposition involving the loss of water and pyridine, carbon dioxide and carbon monoxide in various stages. Solvothermal synthesis did not yield materials suitable for single-crystal X-ray diffraction studies or inclusion studies, producing only an anhydrous or hemihydrate complex with the formula Cu₂L·0.65H2O. Ambient precipitation syntheses did not yield materials suitable for singlecrystal diffraction studies, forming products approximately equivalent to the complexes [Cu₂L·6H₂O]·4H₂O and Cu₂¼(OH)½L·7 ½H₂O above. During the course of the above study it was discovered that, on changing the DSC purge from nitrogen to argon, the normally exothermic carboxylate decompositions appeared to become endothermic. The effects of the supposedly inert atmospheres of argon and nitrogen on the decomposition-mechanism of copper(II) oxalate -a well-studied copper carboxylate- were therefore studied by DSC, TG, TG-FTIR and XRPD. DSC experiments were performed in nitrogen and argon at different flow-rates, in various mixtures of nitrogen and argon, and at various heating rates. Regardless of the proportions of nitrogen and argon, the DSC residues consisted mainly of copper metal, a small amount of copper(I) oxide (cuprite) and, in some circumstances, traces of copper(II) oxide (tenorite). Also, regardless of whether TG-FTIR experiments were performed under argon or nitrogen, the gaseous decomposition products consisted mainly of carbon dioxide, with traces of carbon monoxide being detected over part of the decomposition period. Various explanations for the thermal behaviour are discussed, and it is possible that small amounts of O2 or monatomic oxygen were given off during the decomposition under argon. The design and implementation of a low-cost prototype X-ray proportional counter detector system, consisting of a hybrid analog-digital computer built using commonly available electronic components, is presented. This system was designed to replace ageing discrete-transistor designs still in use in earlier X-ray diffractometers. The prototype performs the functions of pulse-shaping, pulseheight discrimination, counting and scaling, and provides both digital and scaled analog outputs.
- Full Text:
- Date Issued: 2008
- Authors: Lamprecht, Emmanuel
- Date: 2008
- Subjects: Organometallic compounds Copper Oxalates -- Thermal properties Organic compounds -- Synthesis Spectrum analysis X-rays -- Diffraction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4389 , http://hdl.handle.net/10962/d1005054
- Description: Novel and known metal organic frameworks with copper(II), sodium and 1,2,4,5-benzenetetracarboxylate were prepared by ambient precipitation, solvothermal and gel-synthesis methods, and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetry with FTIR evolved-gas analysis. Some of these complexes were investigated for guest inclusion properties with water (the original guest species), methanol, ethanol and pyridine. The gel-synthesis products were the most interesting. The novel threedimensional metal-organic framework complex Cu₂ Na(OH)L·7H₂O (where L=1,2,4,5-benzenetetracarboxylate) -formed by gel-synthesis- is a covalent three-dimensional metal organic framework polymer with open channels containing both guest water molecules and water molecules coordinated to sodium. The structure collapsed on dehydration, but was essentially restored to the original structure on rehydration in moist air. On exposure of the dehydrated material to methanol and ethanol vapour, significant uptake of these solvents was observed, and the resolvated structures closely resembled that of the parent material. On heating in dry nitrogen, small amounts of methanol and ethanol remained until about 280 °C, when loss of the remaining guest triggered decomposition of the framework. The related complex, Cu₂¼(OH)½ L·7½H₂O (or possibly Cu₂⅓ (OH)⅔L·8H₂O) -formed by gel-synthesis- had a different physical appearance to Cu₂Na(OH)L·7H₂O above, but had nearly identical X-ray diffraction pattern, mid-infrared spectrum and thermal behaviour. The novel complex Cu₄Na₄L₃·14H₂O -formed by gel-synthesis- is a covalent three-dimensional metal-organic framework with small channels containing both guest water molecules and water coordinated to sodium and copper. Upon dehydration the structure collapsed, but on rehydration in moist air the original structure was partly restored. The dehydrated material did not absorb methanol. Known two-dimensional polymeric complexes [Cu₂L·6H₂O]·4H₂O and [Cu₂L·4H₂O]·2H₂O were also obtained by gel-synthesis, and were characterized and investigated for guest inclusion properties. The structures of these complexes collapsed on dehydration, and were only partly restored on rehydration in saturated water vapour. The dehydrated materials did not absorb methanol. The two-dimensional polymeric mixed-ligand complex Cu₂(pyridine)₄·6H₂O -formed very slowly by gel-synthesis- was characterized by TG-FTIR, and was shown to undergo a complicated decomposition involving the loss of water and pyridine, carbon dioxide and carbon monoxide in various stages. Solvothermal synthesis did not yield materials suitable for single-crystal X-ray diffraction studies or inclusion studies, producing only an anhydrous or hemihydrate complex with the formula Cu₂L·0.65H2O. Ambient precipitation syntheses did not yield materials suitable for singlecrystal diffraction studies, forming products approximately equivalent to the complexes [Cu₂L·6H₂O]·4H₂O and Cu₂¼(OH)½L·7 ½H₂O above. During the course of the above study it was discovered that, on changing the DSC purge from nitrogen to argon, the normally exothermic carboxylate decompositions appeared to become endothermic. The effects of the supposedly inert atmospheres of argon and nitrogen on the decomposition-mechanism of copper(II) oxalate -a well-studied copper carboxylate- were therefore studied by DSC, TG, TG-FTIR and XRPD. DSC experiments were performed in nitrogen and argon at different flow-rates, in various mixtures of nitrogen and argon, and at various heating rates. Regardless of the proportions of nitrogen and argon, the DSC residues consisted mainly of copper metal, a small amount of copper(I) oxide (cuprite) and, in some circumstances, traces of copper(II) oxide (tenorite). Also, regardless of whether TG-FTIR experiments were performed under argon or nitrogen, the gaseous decomposition products consisted mainly of carbon dioxide, with traces of carbon monoxide being detected over part of the decomposition period. Various explanations for the thermal behaviour are discussed, and it is possible that small amounts of O2 or monatomic oxygen were given off during the decomposition under argon. The design and implementation of a low-cost prototype X-ray proportional counter detector system, consisting of a hybrid analog-digital computer built using commonly available electronic components, is presented. This system was designed to replace ageing discrete-transistor designs still in use in earlier X-ray diffractometers. The prototype performs the functions of pulse-shaping, pulseheight discrimination, counting and scaling, and provides both digital and scaled analog outputs.
- Full Text:
- Date Issued: 2008
The perceptions and experiences of out-of-school youth regarding youth services in KwaZakhele
- Authors: Mpini, Buyiswa Sylvia
- Date: 2008
- Subjects: Youth -- Services for -- South Africa -- Port Elizabeth , Youth -- South Africa -- Port Elizabeth , Youth -- Employment -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10003 , http://hdl.handle.net/10948/667 , Youth -- Services for -- South Africa -- Port Elizabeth , Youth -- South Africa -- Port Elizabeth , Youth -- Employment -- South Africa -- Port Elizabeth
- Description: This research study has been conducted to explore and describe the perceptions and experiences of out-of-school youth regarding their access to the youth services available to them. A qualitative approach is followed and an exploratory, descriptive and contextual research design is utilized. The sample of the study was procured by means of purposive sampling. Data were collected by means of focus group discussions which were conducted using a questioning guide. Data were analysed according to the steps for qualitative data analysis provided by Tesch in Creswell (1994). To ensure the trustworthiness of the research findings, Guba’s model in Krefting (1991) was employed. The research findings were verified against the existing body of knowledge in order to compare and contrast the themes and sub-themes that emerged from the process of data analysis. The main themes that emerged from the study are lack of knowledge regarding available services, Needs or desires of out-of-school youth, hindrances or obstacles to access available youth services, suggestions for services relevant to needs of out-of-school youth and suggestions to make out-of-school youth aware of available services.
- Full Text:
- Date Issued: 2008
- Authors: Mpini, Buyiswa Sylvia
- Date: 2008
- Subjects: Youth -- Services for -- South Africa -- Port Elizabeth , Youth -- South Africa -- Port Elizabeth , Youth -- Employment -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10003 , http://hdl.handle.net/10948/667 , Youth -- Services for -- South Africa -- Port Elizabeth , Youth -- South Africa -- Port Elizabeth , Youth -- Employment -- South Africa -- Port Elizabeth
- Description: This research study has been conducted to explore and describe the perceptions and experiences of out-of-school youth regarding their access to the youth services available to them. A qualitative approach is followed and an exploratory, descriptive and contextual research design is utilized. The sample of the study was procured by means of purposive sampling. Data were collected by means of focus group discussions which were conducted using a questioning guide. Data were analysed according to the steps for qualitative data analysis provided by Tesch in Creswell (1994). To ensure the trustworthiness of the research findings, Guba’s model in Krefting (1991) was employed. The research findings were verified against the existing body of knowledge in order to compare and contrast the themes and sub-themes that emerged from the process of data analysis. The main themes that emerged from the study are lack of knowledge regarding available services, Needs or desires of out-of-school youth, hindrances or obstacles to access available youth services, suggestions for services relevant to needs of out-of-school youth and suggestions to make out-of-school youth aware of available services.
- Full Text:
- Date Issued: 2008
Novel camphor derivatives as potential asymmetric alkylation auxiliaries
- Authors: Skiti-Mama, Neliswa
- Date: 2008
- Subjects: Alkylation , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10372 , http://hdl.handle.net/10948/1077 , Alkylation , Chemistry, Organic
- Description: The investigation has been focussed on the synthesis and characterisation of camphor-derived chiral auxiliaries that incorporate two camphor skeletons and an evaluation of their stereodirecting potential in ester α-benzylation reactions. Two regioisomeric camphorquinone-derived monoketals were synthesised and identified by 1D- and 2D-NMR, and X-ray crystallography. The stereo-directing potential of the alcohols that resulted from reduction of these ketones as chiral auxiliaries in the alkylation of carboxylate ester derivatives has been studied. The diastereoselectivities shown by NMR spectroscopy range from 14- 30 % d.e. for (1R,2 S, 3R) -2 ,2-[ (1R, 2 S, 3R) -bornane-2,3-dioxy] - bornan-3-ol and 68-74 % d.e. for (1R, 2S ,3R) -3 ,3-[ (1R, 2S ,3R) - bornane-2, 3 -dioxy]bornan-2-ol with selectivities that correlate with the size of the alkyl group in the ester moiety. Trapping of the enolates generated from (1R, 2S ,3R)-2, 2 -[(1R,2 S, 3R) -bornane- 2,3-dioxy]bornan-3-yl propanoate afforded both E- and Z-silyl ketene acetal derivatives in the ratio of 64:36 confirming the formation of both possible enolate structures during enolization. Chiral auxiliaries containing a hemiaminal ether blocking group as well as two chiral alcohols containing monothio-ketal blocking groups have also been synthesised. α-Benzylation of their corresponding propanoate esters afforded the alkylated product with disappointingly low diastereos electivities. Asymmetric reduction of α-keto esters attached to (1R, 2 S, 3R) - 2,2- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-3-ol and (1R, 2S ,3R) - 3,3- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-2-ol with metal hydrides proceeded with selectivities of up to 30 % d.e. Modelling of the keto ester derivatives at DFT levels provided useful insights into possible conformations adopted by the two α-keto esters and hence the preferred face of attack by metal hydride during reduction.
- Full Text:
- Date Issued: 2008
- Authors: Skiti-Mama, Neliswa
- Date: 2008
- Subjects: Alkylation , Chemistry, Organic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10372 , http://hdl.handle.net/10948/1077 , Alkylation , Chemistry, Organic
- Description: The investigation has been focussed on the synthesis and characterisation of camphor-derived chiral auxiliaries that incorporate two camphor skeletons and an evaluation of their stereodirecting potential in ester α-benzylation reactions. Two regioisomeric camphorquinone-derived monoketals were synthesised and identified by 1D- and 2D-NMR, and X-ray crystallography. The stereo-directing potential of the alcohols that resulted from reduction of these ketones as chiral auxiliaries in the alkylation of carboxylate ester derivatives has been studied. The diastereoselectivities shown by NMR spectroscopy range from 14- 30 % d.e. for (1R,2 S, 3R) -2 ,2-[ (1R, 2 S, 3R) -bornane-2,3-dioxy] - bornan-3-ol and 68-74 % d.e. for (1R, 2S ,3R) -3 ,3-[ (1R, 2S ,3R) - bornane-2, 3 -dioxy]bornan-2-ol with selectivities that correlate with the size of the alkyl group in the ester moiety. Trapping of the enolates generated from (1R, 2S ,3R)-2, 2 -[(1R,2 S, 3R) -bornane- 2,3-dioxy]bornan-3-yl propanoate afforded both E- and Z-silyl ketene acetal derivatives in the ratio of 64:36 confirming the formation of both possible enolate structures during enolization. Chiral auxiliaries containing a hemiaminal ether blocking group as well as two chiral alcohols containing monothio-ketal blocking groups have also been synthesised. α-Benzylation of their corresponding propanoate esters afforded the alkylated product with disappointingly low diastereos electivities. Asymmetric reduction of α-keto esters attached to (1R, 2 S, 3R) - 2,2- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-3-ol and (1R, 2S ,3R) - 3,3- [ (1R,2 S, 3R) -bornane-2, 3 -dioxy]bornan-2-ol with metal hydrides proceeded with selectivities of up to 30 % d.e. Modelling of the keto ester derivatives at DFT levels provided useful insights into possible conformations adopted by the two α-keto esters and hence the preferred face of attack by metal hydride during reduction.
- Full Text:
- Date Issued: 2008
Studies in marine diterpene chemistry
- Van Wyk, Albert Wynand Wincke
- Authors: Van Wyk, Albert Wynand Wincke
- Date: 2008
- Subjects: Natural products Diterpenes Mollusks Marine metabolites Chemical oceanography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4354 , http://hdl.handle.net/10962/d1005019
- Description: This thesis comprises both a natural product investigation and a synthetic component. The natural product investigations are presented in Chapters Two and Three. In Chapter Two the isolation and spectroscopic identification of the new isocopalane diterpene 12S,13R,14Sisocopalan- 13-ol-12,14-diacetate (2.1) and two known 3-(14S)-isocopal-12-ene-15-oyl-1- acetyl-sn-glycerol (2.2) and 3-(14S)-isocopal-12-ene-15-oyl-2-acetyl-sn-glycerol (2.3) from a single, large, unidentified sub-Antarctic nudibranch, collected near Marion Island, approximately 2000 km south of Cape Town are described. Chapter Three discusses the isolation, spectroscopic structure elucidation and anti-oesophageal cancer activity (3.1-3.4 only) of two known labdane diterpenes 6β,7α-diacetoxylabda-8,13E-dien-15-ol (3.1) and 2α,6β,7α-triacetoxylabda-8,13E-dien-15-ol (3.2) and one new 6β,7α,15-triacetoxylabda 8,13E-diene (3.3), as well as new 3α,11-dihydroxy-9,11-seco-cholest-4,7-dien-6,9-dione (3.4) and cholest 7-en-3,5,7-triol (3.5) from the endemic pulmonate mollusc, Trimusculus costatus. The absolute configuration of 3.2, and hence 3.1 and 3.3 (from biogenetic arguments) was determined through X-ray diffraction of a single crystal of the camphanate ester of 3.2. The absolute configuration of the secondary hydroxyl at C-3 of 3.4 was established using the Modified Mosher’s method. The synthetic component of the thesis commences in Chapter Four with the semi-synthesis of labdane diterpene nitriles 9α-cyano-15,16-epoxy-7β-hydroxylabda-13(16),14-dien-6-one (4.1), 9α-cyano-15,16-epoxy-7-hydroxylabda-7,13(16),14-trien-6-one (4.2) and 9α-cyano-15,16- epoxy-6β,7β dihydroxylabda-13(16),14-diene (4.3) from the terrestrial labdane diterpene, hispanolone (4.4). This work is an extension of previous synthetic studies directed towards the synthesis of T. costatus metabolites. Diterpenes 4.1-4.3 exhibited in planta activity against the economically important crop pathogens, Magnaporthea grisea and Puccinia recondita. Chapter Five describes the successful semi-synthesis of two isomeric marine molluscan labdane diterpene aldehyde metabolites, labd-13E-ene-8β-ol-15-al (5.1) and labd-13Z-ene- 8β-ol-15-al (5.2) from the commercially available, terrestrial plant derived, labdane diterpene manool (5.3). Diterpenes 5.1 and 5.2, originally isolated from the Mediterranean nudibranch,Pleurobranchaea meckelii and selected diterpenes arising from this synthesis were evaluated for their activity against an oesophageal cancer cell line (WHCO1). Chapter Six further develops the research discussed in Chapter Five, where ethyl 17-norabiet-13(15)-E-en-8β-ol- 16-oate (5.49) and ethyl 17-norabiet-13(15)-Z-en-8β-ol-16-oate (5.50) were first semisynthesized serendipitously. Based on their structural relationship to naturally occurring tricyclic diterpenes with anti-plasmodial activity, tricyclic diterpenes, 17-norpimaran-13α- ethoxy-8,16-olactone (6.6), 17-norisopimar-15-ene-8β,13β-diol (6.7), 17-norisopimarane- 8β,16-diol (6.8) and 17-norabiet-13(15)-ene-8β,16-diol (6.9) were semi-synthesized from the terrestrial labdane diterpene, 5.3, and critically evaluated for their antimalarial potential from parasite inhibition and haemolytic studies.
- Full Text:
- Date Issued: 2008
- Authors: Van Wyk, Albert Wynand Wincke
- Date: 2008
- Subjects: Natural products Diterpenes Mollusks Marine metabolites Chemical oceanography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4354 , http://hdl.handle.net/10962/d1005019
- Description: This thesis comprises both a natural product investigation and a synthetic component. The natural product investigations are presented in Chapters Two and Three. In Chapter Two the isolation and spectroscopic identification of the new isocopalane diterpene 12S,13R,14Sisocopalan- 13-ol-12,14-diacetate (2.1) and two known 3-(14S)-isocopal-12-ene-15-oyl-1- acetyl-sn-glycerol (2.2) and 3-(14S)-isocopal-12-ene-15-oyl-2-acetyl-sn-glycerol (2.3) from a single, large, unidentified sub-Antarctic nudibranch, collected near Marion Island, approximately 2000 km south of Cape Town are described. Chapter Three discusses the isolation, spectroscopic structure elucidation and anti-oesophageal cancer activity (3.1-3.4 only) of two known labdane diterpenes 6β,7α-diacetoxylabda-8,13E-dien-15-ol (3.1) and 2α,6β,7α-triacetoxylabda-8,13E-dien-15-ol (3.2) and one new 6β,7α,15-triacetoxylabda 8,13E-diene (3.3), as well as new 3α,11-dihydroxy-9,11-seco-cholest-4,7-dien-6,9-dione (3.4) and cholest 7-en-3,5,7-triol (3.5) from the endemic pulmonate mollusc, Trimusculus costatus. The absolute configuration of 3.2, and hence 3.1 and 3.3 (from biogenetic arguments) was determined through X-ray diffraction of a single crystal of the camphanate ester of 3.2. The absolute configuration of the secondary hydroxyl at C-3 of 3.4 was established using the Modified Mosher’s method. The synthetic component of the thesis commences in Chapter Four with the semi-synthesis of labdane diterpene nitriles 9α-cyano-15,16-epoxy-7β-hydroxylabda-13(16),14-dien-6-one (4.1), 9α-cyano-15,16-epoxy-7-hydroxylabda-7,13(16),14-trien-6-one (4.2) and 9α-cyano-15,16- epoxy-6β,7β dihydroxylabda-13(16),14-diene (4.3) from the terrestrial labdane diterpene, hispanolone (4.4). This work is an extension of previous synthetic studies directed towards the synthesis of T. costatus metabolites. Diterpenes 4.1-4.3 exhibited in planta activity against the economically important crop pathogens, Magnaporthea grisea and Puccinia recondita. Chapter Five describes the successful semi-synthesis of two isomeric marine molluscan labdane diterpene aldehyde metabolites, labd-13E-ene-8β-ol-15-al (5.1) and labd-13Z-ene- 8β-ol-15-al (5.2) from the commercially available, terrestrial plant derived, labdane diterpene manool (5.3). Diterpenes 5.1 and 5.2, originally isolated from the Mediterranean nudibranch,Pleurobranchaea meckelii and selected diterpenes arising from this synthesis were evaluated for their activity against an oesophageal cancer cell line (WHCO1). Chapter Six further develops the research discussed in Chapter Five, where ethyl 17-norabiet-13(15)-E-en-8β-ol- 16-oate (5.49) and ethyl 17-norabiet-13(15)-Z-en-8β-ol-16-oate (5.50) were first semisynthesized serendipitously. Based on their structural relationship to naturally occurring tricyclic diterpenes with anti-plasmodial activity, tricyclic diterpenes, 17-norpimaran-13α- ethoxy-8,16-olactone (6.6), 17-norisopimar-15-ene-8β,13β-diol (6.7), 17-norisopimarane- 8β,16-diol (6.8) and 17-norabiet-13(15)-ene-8β,16-diol (6.9) were semi-synthesized from the terrestrial labdane diterpene, 5.3, and critically evaluated for their antimalarial potential from parasite inhibition and haemolytic studies.
- Full Text:
- Date Issued: 2008
'The Most Amazing Show': performative interactions with postelection South African society and culture
- Authors: Scholtz, Brink
- Date: 2008
- Subjects: Performing arts , Drama -- Study and teaching , Recreational activities
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/57527 , vital:26963
- Description: This research investigates contemporary South African performance within the context of prominent social and cultural change following the political transition from an apartheid state to democracy. Specifically, it looks at the relationship between a popular comic variety show The Most Amazing Show (TMAS), and aspects of contemporary South African society and culture, particularly relating to prominent efforts to affect post-election transformation of South African society and culture through the construction of a South African 'rainbow nation'. By analysing TMAS in terms of broader historical, performative and discursive contexts, it engages a relational reading of the performance. The study argues that TMAS both challenges and participates in the manner in which rainbow nation discourse constructs South African society and culture. Firstly, it considers the performance's construction of hybrid South African identities, including white Afrikaans, white English and white masculine identities. It argues that these reconstructions undermine the tendency within rainbow nation discourse to construct cultural hybridity in terms of stereotypically distinct identities. Secondly, it considers TMAS' construction of collective experience and social integration, which subverts the often glamorised and superficial representations of social healing and integration that are constructed within rainbow nation discourse. The analysis makes prominent reference to the notion of 'liminality' in order to describe the manner in which TMAS constructs significance within the tension that it establishes between oppositional, and often contradictory, positions. Furthermore, it attempts to establish a link between this notion of liminality and notions of theatrical syncretism that are prominent in contemporary South African theatre scholarship, and emphasise processes of signification that are constantly shifting and unstable.
- Full Text:
- Date Issued: 2008
- Authors: Scholtz, Brink
- Date: 2008
- Subjects: Performing arts , Drama -- Study and teaching , Recreational activities
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/57527 , vital:26963
- Description: This research investigates contemporary South African performance within the context of prominent social and cultural change following the political transition from an apartheid state to democracy. Specifically, it looks at the relationship between a popular comic variety show The Most Amazing Show (TMAS), and aspects of contemporary South African society and culture, particularly relating to prominent efforts to affect post-election transformation of South African society and culture through the construction of a South African 'rainbow nation'. By analysing TMAS in terms of broader historical, performative and discursive contexts, it engages a relational reading of the performance. The study argues that TMAS both challenges and participates in the manner in which rainbow nation discourse constructs South African society and culture. Firstly, it considers the performance's construction of hybrid South African identities, including white Afrikaans, white English and white masculine identities. It argues that these reconstructions undermine the tendency within rainbow nation discourse to construct cultural hybridity in terms of stereotypically distinct identities. Secondly, it considers TMAS' construction of collective experience and social integration, which subverts the often glamorised and superficial representations of social healing and integration that are constructed within rainbow nation discourse. The analysis makes prominent reference to the notion of 'liminality' in order to describe the manner in which TMAS constructs significance within the tension that it establishes between oppositional, and often contradictory, positions. Furthermore, it attempts to establish a link between this notion of liminality and notions of theatrical syncretism that are prominent in contemporary South African theatre scholarship, and emphasise processes of signification that are constantly shifting and unstable.
- Full Text:
- Date Issued: 2008
Rhodes University Research Report 2008
- Authors: Rhodes University
- Date: 2008
- Language: English
- Type: Text
- Identifier: vital:563 , http://hdl.handle.net/10962/d1011963
- Description: [From Preface] This report outlines the extent and quality of our research outputs for 2008. Rhodes possesses an admirable research milieu and culture that provides the space for intellectual development, debate, and the flourishing of ideas. As the smallest university in South Africa, we take special pride in Rhodes University having amongst the highest per capita research outputs. One of the core goals of a university is to produce knowledge, a public responsibility that Rhodes takes very seriously, and we continuously seek new opportunities to do so. Many of Rhodes University’s academics, departments, institutes, centres, and units are at the leading edge of research and are actively advancing knowledge in a range of disciplines and fields. During 2008, Rhodes launched three new centres. The DST/Mintek Nanotechnology Innovation Centre (Sensors) was founded under the directorship of Professor Tebello Nyokong; the Centre for Higher Education Research, Teaching & Learning, was formed out of a much expanded Academic Development Centre, under the leadership of the Dean of Teaching and Learning, Professor Chrissie Boughey; and the Centre for the Study of Democracy was launched under the leadership of Professor Stephen Friedman as a joint venture of Rhodes and the University of Johannesburg. A second DST/NRF South African Research Chair was launched in the field of Marine Biology, with Professor Christopher McQuaid as its incumbent. Rhodes’s first DST/NRF Chair, Professor Tebello Nyokong, in the area of Medicinal Chemistry and Nanotechnology, had an outstanding year, with accolades coming from a range of sources. She was officially recognized by the National Research Foundation as one of the most productive researchers in the country with 35 ISI indexed journal papers published during the year, an extraordinary achievement by anyone’s standard, and with a large number of additional accredited outputs by her and her group during the year. In the area of the creative arts, Mrs Janet Buckland of our Drama Department won special recognition as the recipient of the national Woman of the Year award promoted by Shopright-Checkers and SABC 2, in both the Arts and culture section and as the overall recipient. Professor Fackson Banda of our Journalism Department won the 2008 MISA (Media Institute of Southern Africa) Press Freedom Award. In the Geology Department, Professor Goonie Marsh was awarded the Geological Society of South Africa’s highest scientific award, the Draper Memorial Medal, in recognition of his outstanding contribution to geological sciences in general, and particularly for his research work in the petrology of volcanic rocks and igneous provinces in South Africa. The Vice-Chancellor's Distinguished Senior Research Award for 2008 went to Professor Peter Vale of the Department of Political and International Studies, for the national and international impact of his scholarly activities over a sustained period. The Vice-Chancellor's Book Award for 2008 went to Professor Dan Wylie of the Department of English, for Myth of Iron - Shaka in History (UKZN Press, 2008). Rhodes postgraduates continue to excel in winning prestigious international and local scholarships, including the Rhodes (Oxford), Mandela Rhodes, Flanagan, Commonwealth, and Fulbright. A major challenge facing South African Universities is the development of a new generation of teacher-scholars, one that Rhodes University has been engaging with for a number of years. We acknowledge the strong support of the Mellon Foundation, which has assisted us in creating a focused programme aimed at cultivating a new generation of black and women researchers, and in making a contribution towards transforming our academic body in the process. I am pleased to be able to announce that the Kresge Foundation has agreed to fund this initiative for a further four years. I extend my congratulations and thanks to all of our researchers, collaborators, funders, donors, and partners who contributed to making 2008 a year in which research at Rhodes University flourished. Your expertise, dedication, rigour and generosity make Rhodes University the rich and distinctive intellectual space that it is.
- Full Text:
- Date Issued: 2008
- Authors: Rhodes University
- Date: 2008
- Language: English
- Type: Text
- Identifier: vital:563 , http://hdl.handle.net/10962/d1011963
- Description: [From Preface] This report outlines the extent and quality of our research outputs for 2008. Rhodes possesses an admirable research milieu and culture that provides the space for intellectual development, debate, and the flourishing of ideas. As the smallest university in South Africa, we take special pride in Rhodes University having amongst the highest per capita research outputs. One of the core goals of a university is to produce knowledge, a public responsibility that Rhodes takes very seriously, and we continuously seek new opportunities to do so. Many of Rhodes University’s academics, departments, institutes, centres, and units are at the leading edge of research and are actively advancing knowledge in a range of disciplines and fields. During 2008, Rhodes launched three new centres. The DST/Mintek Nanotechnology Innovation Centre (Sensors) was founded under the directorship of Professor Tebello Nyokong; the Centre for Higher Education Research, Teaching & Learning, was formed out of a much expanded Academic Development Centre, under the leadership of the Dean of Teaching and Learning, Professor Chrissie Boughey; and the Centre for the Study of Democracy was launched under the leadership of Professor Stephen Friedman as a joint venture of Rhodes and the University of Johannesburg. A second DST/NRF South African Research Chair was launched in the field of Marine Biology, with Professor Christopher McQuaid as its incumbent. Rhodes’s first DST/NRF Chair, Professor Tebello Nyokong, in the area of Medicinal Chemistry and Nanotechnology, had an outstanding year, with accolades coming from a range of sources. She was officially recognized by the National Research Foundation as one of the most productive researchers in the country with 35 ISI indexed journal papers published during the year, an extraordinary achievement by anyone’s standard, and with a large number of additional accredited outputs by her and her group during the year. In the area of the creative arts, Mrs Janet Buckland of our Drama Department won special recognition as the recipient of the national Woman of the Year award promoted by Shopright-Checkers and SABC 2, in both the Arts and culture section and as the overall recipient. Professor Fackson Banda of our Journalism Department won the 2008 MISA (Media Institute of Southern Africa) Press Freedom Award. In the Geology Department, Professor Goonie Marsh was awarded the Geological Society of South Africa’s highest scientific award, the Draper Memorial Medal, in recognition of his outstanding contribution to geological sciences in general, and particularly for his research work in the petrology of volcanic rocks and igneous provinces in South Africa. The Vice-Chancellor's Distinguished Senior Research Award for 2008 went to Professor Peter Vale of the Department of Political and International Studies, for the national and international impact of his scholarly activities over a sustained period. The Vice-Chancellor's Book Award for 2008 went to Professor Dan Wylie of the Department of English, for Myth of Iron - Shaka in History (UKZN Press, 2008). Rhodes postgraduates continue to excel in winning prestigious international and local scholarships, including the Rhodes (Oxford), Mandela Rhodes, Flanagan, Commonwealth, and Fulbright. A major challenge facing South African Universities is the development of a new generation of teacher-scholars, one that Rhodes University has been engaging with for a number of years. We acknowledge the strong support of the Mellon Foundation, which has assisted us in creating a focused programme aimed at cultivating a new generation of black and women researchers, and in making a contribution towards transforming our academic body in the process. I am pleased to be able to announce that the Kresge Foundation has agreed to fund this initiative for a further four years. I extend my congratulations and thanks to all of our researchers, collaborators, funders, donors, and partners who contributed to making 2008 a year in which research at Rhodes University flourished. Your expertise, dedication, rigour and generosity make Rhodes University the rich and distinctive intellectual space that it is.
- Full Text:
- Date Issued: 2008
Pilates for postural stability in computer users
- Authors: Strydom, Lana
- Date: 2008
- Subjects: Pilates method , Human beings -- Attitude and movement
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10094 , http://hdl.handle.net/10948/867 , Pilates method , Human beings -- Attitude and movement
- Description: The impact of computer use is evident in every day life (Harrington, Carter, Birrell and Gompertz, 2000:264). Lind (2002:18) explains that global trends continue to show that the most severe work-related health problems that exist amongst computer users are musculoskeletal disorders. As technology has lead to increases in automation, so it has lead to increases in work-related illnesses. Although studies have explored the effects of ergonomics (Thibodeau, 1995:322) in static working positions there has been little evidence supporting a solution in overcoming poor occupational postures. Many health practitioners argue that occupationally caused, or aggravated, musculoskeletal disorders are steadily increasing. Thus, even though computers have improved productivity and made work easier for the population in general, they have adverse effects as well. Designing the proper tools or a setup of the work place is of prime importance for the elimination of chronic diseases attributed to sedentary lifestyles. Regular physical activity had long been regarded as an important component of a healthy lifestyle. This notion has recently been reinforced by scientific evidence linking regular physical activity with a wide array of physical and mental health benefits, synonymous with an improvement in wellness (Pratt, Macera, and Wang, 2000:63). According to Pratt et al. (2000:63) higher direct medical costs associates with physical inactivity. Further cross-sectional epidemiologic studies and controlled experimental investigations conducted by Okura, Nakata and Tanaka (2003:1131) had demonstrated that physically active adults, in contrast to their sedentary counterparts, tend to develop and maintain higher levels of physical fitness. These studies had not only demonstrated the positive results of physical activity, such as an improvement in blood lipid profile, body composition, glucose tolerance and insulin sensitivity, but had also shown that participation in such activity decreased the risk of developing several chronic hypokinetic diseases, including coronary heart disease (CHD), hypertension, non-insulin dependant diabetes mellitus (type II), osteoporosis, colon cancer, anxiety and depression. In addition, low levels of habitual physical activity and the subsequent low levels of physical fitness were associated with a marked increase in all-cause mortality rates. Okura et al. (2003:1131) confirm that effects of exercise intensity on physical fitness and risk factors for coronary Herat disease.
- Full Text:
- Date Issued: 2008
- Authors: Strydom, Lana
- Date: 2008
- Subjects: Pilates method , Human beings -- Attitude and movement
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10094 , http://hdl.handle.net/10948/867 , Pilates method , Human beings -- Attitude and movement
- Description: The impact of computer use is evident in every day life (Harrington, Carter, Birrell and Gompertz, 2000:264). Lind (2002:18) explains that global trends continue to show that the most severe work-related health problems that exist amongst computer users are musculoskeletal disorders. As technology has lead to increases in automation, so it has lead to increases in work-related illnesses. Although studies have explored the effects of ergonomics (Thibodeau, 1995:322) in static working positions there has been little evidence supporting a solution in overcoming poor occupational postures. Many health practitioners argue that occupationally caused, or aggravated, musculoskeletal disorders are steadily increasing. Thus, even though computers have improved productivity and made work easier for the population in general, they have adverse effects as well. Designing the proper tools or a setup of the work place is of prime importance for the elimination of chronic diseases attributed to sedentary lifestyles. Regular physical activity had long been regarded as an important component of a healthy lifestyle. This notion has recently been reinforced by scientific evidence linking regular physical activity with a wide array of physical and mental health benefits, synonymous with an improvement in wellness (Pratt, Macera, and Wang, 2000:63). According to Pratt et al. (2000:63) higher direct medical costs associates with physical inactivity. Further cross-sectional epidemiologic studies and controlled experimental investigations conducted by Okura, Nakata and Tanaka (2003:1131) had demonstrated that physically active adults, in contrast to their sedentary counterparts, tend to develop and maintain higher levels of physical fitness. These studies had not only demonstrated the positive results of physical activity, such as an improvement in blood lipid profile, body composition, glucose tolerance and insulin sensitivity, but had also shown that participation in such activity decreased the risk of developing several chronic hypokinetic diseases, including coronary heart disease (CHD), hypertension, non-insulin dependant diabetes mellitus (type II), osteoporosis, colon cancer, anxiety and depression. In addition, low levels of habitual physical activity and the subsequent low levels of physical fitness were associated with a marked increase in all-cause mortality rates. Okura et al. (2003:1131) confirm that effects of exercise intensity on physical fitness and risk factors for coronary Herat disease.
- Full Text:
- Date Issued: 2008
Synthetic, spectrometric and computer modelling studies of novel ATP analogues
- Gxoyiya, Babalwa Siliziwe Blossom
- Authors: Gxoyiya, Babalwa Siliziwe Blossom
- Date: 2008
- Subjects: Spectrum analysis Tuberculosis -- Treatment Chemotherapy Adenosine triphosphate Adenosine triphosphate -- Synthesis Adenosine triphosphate -- Computer simulation Adenosine triphosphate -- Spectrometric imaging Glutamine synthetase Tuberculosis -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4386 , http://hdl.handle.net/10962/d1005051
- Description: This study has been concerned with the design and synthesis of A TP analogues with the potential to act as inhibitors of glutamine synthetase - a novel target for therapeutic intervention in the treatment of tuberculosis. Using a structural -analogy approach, various 3-indolylalkanoic acid, benzimidazole and pyrazolo[3,4-dJpyrimidine derivatives have been prepared and characterized. Alkylation of the heterocyclic bases using 4-(bromomethyl)-2,2-dimethyl-1 ,3-d ioxolane, 2-(bromomethoxy)ethyl acetate and 2-(chloroethoxy)ethanol in the presence of either NaH or BulOK afforded the corresponding N-alkylated derivatives of benzimidazole and 4-aminopyrazolo[3,4-dJpyrimidine (4-APP). Similar reactions with 3-indo lylalkanoic esters resulted in O-alkyl cleavage with the formation of new esters. Alkylation of benzimidazole with allyl bromide, 4-bromobutene and 2-methylbut-2-ene has also been shown to afford the corresponding l-alkenylbenzimidazoles in moderate to excellent yield (43-96%). Subsequent oxidation of these products using CTAP, gave the dihydroxy derivatives in poor to good yields (26-77%). Phosphorylation of various hydroxy derivatives of benzimidazole and 4-APP has been achieved using diethyl chlorophosphate to afford the corresponding monophosphate and 1,2-diphosphate esters. Glycosylation of each of the heterocyclic bases has been successfully achieved using 1,2,3,4,6-penta-O-acetyl-D-glucopyranose and SnCl4 in acetonitri le, while methanolysis of the resulting tetraacetates, using methanolic NaOMe, afforded the hydroxy derivatives in good yield (50-70%). Various 1- and 2-dimensional NMR spectroscopic methods (e.g., IH, 13C, lip, COSY, HSQC and HMBC) have been used to confirm the structures of the synthesized A IP analogues. The application of NMR prediction programmes has been explored, permitting assessment of their agreement with the experimental data and confirmation of assigned structures. High-resolution electron impact (EI) mass spectrometric data have been used to explore the mass fragmentation pathways exhibited by selected derivatives, and certain common fragmentations have been identified. Molecular modelling of selected products as potential glutamine synthetase ligands has been performed on the Accelrys Cerius2 platform, and interactive receptor-ligand docking studies have been conducted using the Ligand-Fit module. These studies have revealed possible hydrogen-boding interactions between the selected analogues and various amino acid residues in the glutamine synthetase active site.
- Full Text:
- Date Issued: 2008
- Authors: Gxoyiya, Babalwa Siliziwe Blossom
- Date: 2008
- Subjects: Spectrum analysis Tuberculosis -- Treatment Chemotherapy Adenosine triphosphate Adenosine triphosphate -- Synthesis Adenosine triphosphate -- Computer simulation Adenosine triphosphate -- Spectrometric imaging Glutamine synthetase Tuberculosis -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4386 , http://hdl.handle.net/10962/d1005051
- Description: This study has been concerned with the design and synthesis of A TP analogues with the potential to act as inhibitors of glutamine synthetase - a novel target for therapeutic intervention in the treatment of tuberculosis. Using a structural -analogy approach, various 3-indolylalkanoic acid, benzimidazole and pyrazolo[3,4-dJpyrimidine derivatives have been prepared and characterized. Alkylation of the heterocyclic bases using 4-(bromomethyl)-2,2-dimethyl-1 ,3-d ioxolane, 2-(bromomethoxy)ethyl acetate and 2-(chloroethoxy)ethanol in the presence of either NaH or BulOK afforded the corresponding N-alkylated derivatives of benzimidazole and 4-aminopyrazolo[3,4-dJpyrimidine (4-APP). Similar reactions with 3-indo lylalkanoic esters resulted in O-alkyl cleavage with the formation of new esters. Alkylation of benzimidazole with allyl bromide, 4-bromobutene and 2-methylbut-2-ene has also been shown to afford the corresponding l-alkenylbenzimidazoles in moderate to excellent yield (43-96%). Subsequent oxidation of these products using CTAP, gave the dihydroxy derivatives in poor to good yields (26-77%). Phosphorylation of various hydroxy derivatives of benzimidazole and 4-APP has been achieved using diethyl chlorophosphate to afford the corresponding monophosphate and 1,2-diphosphate esters. Glycosylation of each of the heterocyclic bases has been successfully achieved using 1,2,3,4,6-penta-O-acetyl-D-glucopyranose and SnCl4 in acetonitri le, while methanolysis of the resulting tetraacetates, using methanolic NaOMe, afforded the hydroxy derivatives in good yield (50-70%). Various 1- and 2-dimensional NMR spectroscopic methods (e.g., IH, 13C, lip, COSY, HSQC and HMBC) have been used to confirm the structures of the synthesized A IP analogues. The application of NMR prediction programmes has been explored, permitting assessment of their agreement with the experimental data and confirmation of assigned structures. High-resolution electron impact (EI) mass spectrometric data have been used to explore the mass fragmentation pathways exhibited by selected derivatives, and certain common fragmentations have been identified. Molecular modelling of selected products as potential glutamine synthetase ligands has been performed on the Accelrys Cerius2 platform, and interactive receptor-ligand docking studies have been conducted using the Ligand-Fit module. These studies have revealed possible hydrogen-boding interactions between the selected analogues and various amino acid residues in the glutamine synthetase active site.
- Full Text:
- Date Issued: 2008
Integer optimization for the selection of a twenty20 cricket team
- Authors: Lourens, Mark
- Date: 2008
- Subjects: Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10568 , http://hdl.handle.net/10948/1000 , http://hdl.handle.net/10948/d1009631 , Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Description: During the last few years, much effort has been devoted to measuring the ability of sport teams, as well as that of the individual players. Much research has been on the game of cricket, and the comparison, or ranking, of players according to their abilities. This study continues preceding research using an optimization approach, namely, a binary integer programme, to select an SA domestic Pro20 cricket team.
- Full Text:
- Date Issued: 2008
- Authors: Lourens, Mark
- Date: 2008
- Subjects: Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10568 , http://hdl.handle.net/10948/1000 , http://hdl.handle.net/10948/d1009631 , Cricket -- Coaching , Teamwork (Sports) , Cricket players , Sports -- Research -- Methodology
- Description: During the last few years, much effort has been devoted to measuring the ability of sport teams, as well as that of the individual players. Much research has been on the game of cricket, and the comparison, or ranking, of players according to their abilities. This study continues preceding research using an optimization approach, namely, a binary integer programme, to select an SA domestic Pro20 cricket team.
- Full Text:
- Date Issued: 2008
Studies directed towards the synthesis of chromone carbaldehyde-derived HIV-1 protease inhibitors
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
A bioinorganic study of some cobalt(II) Schiff base complexes of variously substituted hydroxybenzaldimines
- Authors: Shaibu, Rafiu Olarewaju
- Date: 2008
- Subjects: Cobalt Schiff bases Artemia Spectrum analysis Ligands -- Analysis Bioinorganic chemistry Antineoplastic agents Cancer -- Chemotherapy Ligands -- Toxicity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4394 , http://hdl.handle.net/10962/d1006009
- Description: Syntheses of Schiff bases were carried out by reacting salicylaldyhde, ortho-vanillin, para-vanillin or vanillin with aniline, 1-aminonaphthalene, 4- and 3-aminopyridine, and also with 2- and 3-aminomethylpyridine. The various Schiff bases obtained from the condensation reaction were reacted with CoCl₂.6H₂0, triethylamine stripped CoCl₂.6H₂0 or Co(CH₃COO)₂ to form cobalt(Il) complexes of ratio 2:1. The complexes obtained from cobalt chloride designated as the "A series" are of the general formulae ML₂X₂.nH₂0 , (L = Schiff base, X = chlorine) while those obtained from cobalt acetate or triethylamine stripped cobalt chloride denoted as "B" and C" are of the general formulae ML₂. nH₂0. The few complexes that do not follow the general formulae highlighted above are: IA [M(HL)₃.Cl₂], (L = N-phenylsalicylaldimine), 4A = (MLCl₂), (L = N-phenylvanaldiminato), 7 A and 21 A (ML₂), (L = N-naphthyl-o-vanaldiminato, and N-methy-2-pyridylsalicylaldiminato respectively), 8A = MLCI, (L = N-naphthylvanaldiminato), 12A = M₂L₃Cl₂, (L = N-4-pyridylvanaldiminato), 15A (MLCI), (L = N-3-pyridyl-o-vanaldiminato). The ligands and their complexes were characterized using elemental analyses and cobalt analysis using ICP, FT-IR spectroscopy (mid and far-IR), NIR-UV/vis (diffuse reflectance), UV/vis in an aprotic and a protic solvents, while mass spectrometry, ¹HNMR and ¹³CNMR, was used to further characterized the ligands. The tautomeric nature of the Schiff bases were determined by examining the behaviour of Schiff bases and their complexes in a protic (e.g. MeOH) and non-protic (e.g. DMF) polar solvents. The effects of solvents on the electronic behaviour of the compounds were also examined. Using CDCl₃, the NMR technique was further used to confirm the structures of the Schiff bases. The tentative geometry of the complexes was determined using the spectra information obtained from the far infrared and the diffuse reflectance spectroscopy. With few exceptions, most of the "A" series are tetrahedral or distorted tetrahedral, while the "B + C" are octahedral or pseudooctahedral. A small number of complexes are assigned square-planar geometry owing to the characteristic spectral behaviour shown. In order to determine their biological activity, two biological assay methods (antimicrobial testing and brine shrimp lethality assay) were used. Using disc method, the bacteriostatic and fungicidal activities of the various Schiff bases and their respective complexes to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa as well as Aspergillus niger, were measured and the average inhibition zones are tabulated and analysed. Both the Schiff bases and their complexes showed varying bacteriostatic and fungicidal activity against the bacteria and fungus tested. The inhibition activity is concentration dependent and potential antibiotic and fungicides are identified. To determine the toxicity of the ligands and their corresponding cobalt(II) complexes, brine shrimp lethality assay was used. The LD₅₀ of the tested compounds were calculated and the results obtained were tabulated for comparison.
- Full Text:
- Date Issued: 2008
- Authors: Shaibu, Rafiu Olarewaju
- Date: 2008
- Subjects: Cobalt Schiff bases Artemia Spectrum analysis Ligands -- Analysis Bioinorganic chemistry Antineoplastic agents Cancer -- Chemotherapy Ligands -- Toxicity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4394 , http://hdl.handle.net/10962/d1006009
- Description: Syntheses of Schiff bases were carried out by reacting salicylaldyhde, ortho-vanillin, para-vanillin or vanillin with aniline, 1-aminonaphthalene, 4- and 3-aminopyridine, and also with 2- and 3-aminomethylpyridine. The various Schiff bases obtained from the condensation reaction were reacted with CoCl₂.6H₂0, triethylamine stripped CoCl₂.6H₂0 or Co(CH₃COO)₂ to form cobalt(Il) complexes of ratio 2:1. The complexes obtained from cobalt chloride designated as the "A series" are of the general formulae ML₂X₂.nH₂0 , (L = Schiff base, X = chlorine) while those obtained from cobalt acetate or triethylamine stripped cobalt chloride denoted as "B" and C" are of the general formulae ML₂. nH₂0. The few complexes that do not follow the general formulae highlighted above are: IA [M(HL)₃.Cl₂], (L = N-phenylsalicylaldimine), 4A = (MLCl₂), (L = N-phenylvanaldiminato), 7 A and 21 A (ML₂), (L = N-naphthyl-o-vanaldiminato, and N-methy-2-pyridylsalicylaldiminato respectively), 8A = MLCI, (L = N-naphthylvanaldiminato), 12A = M₂L₃Cl₂, (L = N-4-pyridylvanaldiminato), 15A (MLCI), (L = N-3-pyridyl-o-vanaldiminato). The ligands and their complexes were characterized using elemental analyses and cobalt analysis using ICP, FT-IR spectroscopy (mid and far-IR), NIR-UV/vis (diffuse reflectance), UV/vis in an aprotic and a protic solvents, while mass spectrometry, ¹HNMR and ¹³CNMR, was used to further characterized the ligands. The tautomeric nature of the Schiff bases were determined by examining the behaviour of Schiff bases and their complexes in a protic (e.g. MeOH) and non-protic (e.g. DMF) polar solvents. The effects of solvents on the electronic behaviour of the compounds were also examined. Using CDCl₃, the NMR technique was further used to confirm the structures of the Schiff bases. The tentative geometry of the complexes was determined using the spectra information obtained from the far infrared and the diffuse reflectance spectroscopy. With few exceptions, most of the "A" series are tetrahedral or distorted tetrahedral, while the "B + C" are octahedral or pseudooctahedral. A small number of complexes are assigned square-planar geometry owing to the characteristic spectral behaviour shown. In order to determine their biological activity, two biological assay methods (antimicrobial testing and brine shrimp lethality assay) were used. Using disc method, the bacteriostatic and fungicidal activities of the various Schiff bases and their respective complexes to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa as well as Aspergillus niger, were measured and the average inhibition zones are tabulated and analysed. Both the Schiff bases and their complexes showed varying bacteriostatic and fungicidal activity against the bacteria and fungus tested. The inhibition activity is concentration dependent and potential antibiotic and fungicides are identified. To determine the toxicity of the ligands and their corresponding cobalt(II) complexes, brine shrimp lethality assay was used. The LD₅₀ of the tested compounds were calculated and the results obtained were tabulated for comparison.
- Full Text:
- Date Issued: 2008
Camphor derivatives in asymmetric synthesis: a synthetic, mechanistic and theoretical study
- Authors: Lobb, Kevin Alan
- Date: 2008
- Subjects: Chemistry, Organic -- Research Esters Organic compounds -- Synthesis Alkylation Chemical reactions -- Computer simulation Chemical kinetics Camphor Cinnamomum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4414 , http://hdl.handle.net/10962/d1006770
- Description: A series of 3,3-ethylenedioxy-exo- and endo- bornyl esters have been prepared and subjected to α-benzylation using lithium diisopropylamide and benzyl bromide. In the exo-series of esters the diastereofacial selectivity of benzylation was found to improve (up to 34% d.e.) as the steric bulk of the O-alkyl group increased, whereas in the endo-series, a surprising decrease in stereoselectivity was observed as the steric bulk increased – an observation attributed to flexibility of the metal-coordinated endo-enolate system, compared to the relative rigidity of the exo analogues. The conformational options for each series was explored at the density functional theory level. Reductive cyclization of a range of specially prepared N-carbobenzyloxy-amino acid esters has been shown to afford the corresponding derivatives, contrary to previous reports that the cyclization is limited to the glycine derivative. The cyclization sequence has been explored in detail, and the yield has been shown to be critically dependent on the stereochemistry of the α-amino acid moiety. Moreover, it seems that reductive cyclization occurs more readily with the endo- rather than the exo-bornyl N-CBZ-amino acid esters. Molecular modelling of relevant transition states at the DFT levels indicates that L-amino acid-derived systems should cyclize preferably in the exo-series and D-amino acid-derived systems should cyclize preferably in the endo series. Studies of alkylation of an iminolactone system have reported an interesting anomaly - exo-methylation is observed while endo-alkylation predominates for larger alkyl groups. This has been studied in detail at the DFT level, and the anomaly is attributed to thermodynamic control in the methyl case, whereas kinetic control is the norm in this system. Preliminary computer modelling of the intramolecular rearrangement of a 3,3-xylylbornyl system at the HF/STO-3G level raised doubts concerning the structure assigned by Evans to one of the rearrangement products, prompting an X-ray crystallographic analysis and leading to the revision of its structure from a pinene to a camphene derivative. The previously elusive spiro[bornane-3,2’-indan]-2-exo-tosylate has been successfully isolated, and the kinetics of its ready decomposition to the two camphene products has been followed by 1H NMR spectroscopy. The endo-tosylate analogue, on the other hand, was found to be remarkably stable. Kinetic data obtained for rearrangement of this exo-bornyl tosylate have indicated the operation of tandem autocatalytic and pseudo-first-order transformations leading sequentially to the two isomeric camphene products. An extensive coset analysis of all possible rearrangement processes of the initially-formed cation formed from decomposition of the exo-tosylate has afforded a graph containing 336 classical cations (modelled at the AM1 and B3LYP levels) and 526 transition-state complexes (modelled at the AM1 level). This analysis afforded a viable 4-step classical mechanism connecting the first camphene product with the second. A more realistic study, involving non-classical carbocations, has afforded a graph of all possible (classical and non-classical) cations that could be formed by rearrangment of the initiallyformed cation. The resulting graph confirms that the only energetically feasible path corresponds to the classical mechanism, but simply involves two steps, including a novel, concerted Wagner-Meerwein – 6,2-hydride shift – Wagner-Meerwein rearrangement.
- Full Text:
- Date Issued: 2008
- Authors: Lobb, Kevin Alan
- Date: 2008
- Subjects: Chemistry, Organic -- Research Esters Organic compounds -- Synthesis Alkylation Chemical reactions -- Computer simulation Chemical kinetics Camphor Cinnamomum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4414 , http://hdl.handle.net/10962/d1006770
- Description: A series of 3,3-ethylenedioxy-exo- and endo- bornyl esters have been prepared and subjected to α-benzylation using lithium diisopropylamide and benzyl bromide. In the exo-series of esters the diastereofacial selectivity of benzylation was found to improve (up to 34% d.e.) as the steric bulk of the O-alkyl group increased, whereas in the endo-series, a surprising decrease in stereoselectivity was observed as the steric bulk increased – an observation attributed to flexibility of the metal-coordinated endo-enolate system, compared to the relative rigidity of the exo analogues. The conformational options for each series was explored at the density functional theory level. Reductive cyclization of a range of specially prepared N-carbobenzyloxy-amino acid esters has been shown to afford the corresponding derivatives, contrary to previous reports that the cyclization is limited to the glycine derivative. The cyclization sequence has been explored in detail, and the yield has been shown to be critically dependent on the stereochemistry of the α-amino acid moiety. Moreover, it seems that reductive cyclization occurs more readily with the endo- rather than the exo-bornyl N-CBZ-amino acid esters. Molecular modelling of relevant transition states at the DFT levels indicates that L-amino acid-derived systems should cyclize preferably in the exo-series and D-amino acid-derived systems should cyclize preferably in the endo series. Studies of alkylation of an iminolactone system have reported an interesting anomaly - exo-methylation is observed while endo-alkylation predominates for larger alkyl groups. This has been studied in detail at the DFT level, and the anomaly is attributed to thermodynamic control in the methyl case, whereas kinetic control is the norm in this system. Preliminary computer modelling of the intramolecular rearrangement of a 3,3-xylylbornyl system at the HF/STO-3G level raised doubts concerning the structure assigned by Evans to one of the rearrangement products, prompting an X-ray crystallographic analysis and leading to the revision of its structure from a pinene to a camphene derivative. The previously elusive spiro[bornane-3,2’-indan]-2-exo-tosylate has been successfully isolated, and the kinetics of its ready decomposition to the two camphene products has been followed by 1H NMR spectroscopy. The endo-tosylate analogue, on the other hand, was found to be remarkably stable. Kinetic data obtained for rearrangement of this exo-bornyl tosylate have indicated the operation of tandem autocatalytic and pseudo-first-order transformations leading sequentially to the two isomeric camphene products. An extensive coset analysis of all possible rearrangement processes of the initially-formed cation formed from decomposition of the exo-tosylate has afforded a graph containing 336 classical cations (modelled at the AM1 and B3LYP levels) and 526 transition-state complexes (modelled at the AM1 level). This analysis afforded a viable 4-step classical mechanism connecting the first camphene product with the second. A more realistic study, involving non-classical carbocations, has afforded a graph of all possible (classical and non-classical) cations that could be formed by rearrangment of the initiallyformed cation. The resulting graph confirms that the only energetically feasible path corresponds to the classical mechanism, but simply involves two steps, including a novel, concerted Wagner-Meerwein – 6,2-hydride shift – Wagner-Meerwein rearrangement.
- Full Text:
- Date Issued: 2008
Nuclear translocation of the phosphoprotein Hop (Hsp70/Hsp90 organizing protein) occurs under heat shock, and its proposed nuclear localization signal is involved in Hsp90 binding
- Daniel, Sheril, Bradley, Graeme, Longshaw, Victoria M, Söti, Csaba, Csermely, Peter, Blatch, Gregory L
- Authors: Daniel, Sheril , Bradley, Graeme , Longshaw, Victoria M , Söti, Csaba , Csermely, Peter , Blatch, Gregory L
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6472 , http://hdl.handle.net/10962/d1005951 , http://dx.doi.org/10.1016/j.bbamcr.2008.01.014
- Description: The Hsp70–Hsp90 complex is implicated in the folding and regulation of numerous signaling proteins, and Hop, the Hsp70–Hsp90 Organizing Protein, facilitates the association of this multichaperone machinery. Phosphatase treatment of mouse cell extracts reduced the number of Hop isoforms compared to untreated extracts, providing the first direct evidence that Hop was phosphorylated in vivo. Furthermore, surface plasmon resonance (SPR) spectroscopy showed that a cdc2 kinase phosphorylation mimic of Hop had reduced affinity for Hsp90 binding. Hop was predominantly cytoplasmic, but translocated to the nucleus in response to heat shock. A putative bipartite nuclear localization signal (NLS) has been identified within the Hsp90-binding domain of Hop. Although substitution of residues within the major arm of this proposed NLS abolished Hop–Hsp90 interaction as determined by SPR, this was not sufficient to prevent the nuclear accumulation of Hop under leptomycin-B treatment and heat shock conditions. These results showed for the first time that the subcellular localization of Hop was stress regulated and that the major arm of the putative NLS was not directly important for nuclear translocation but was critical for Hop–Hsp90 association in vitro. We propose a model in which the association of Hop with Hsp90 and the phosphorylated status of Hop both play a role in the mechanism of nucleo-cytoplasmic shuttling of Hop.
- Full Text:
- Date Issued: 2008
- Authors: Daniel, Sheril , Bradley, Graeme , Longshaw, Victoria M , Söti, Csaba , Csermely, Peter , Blatch, Gregory L
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6472 , http://hdl.handle.net/10962/d1005951 , http://dx.doi.org/10.1016/j.bbamcr.2008.01.014
- Description: The Hsp70–Hsp90 complex is implicated in the folding and regulation of numerous signaling proteins, and Hop, the Hsp70–Hsp90 Organizing Protein, facilitates the association of this multichaperone machinery. Phosphatase treatment of mouse cell extracts reduced the number of Hop isoforms compared to untreated extracts, providing the first direct evidence that Hop was phosphorylated in vivo. Furthermore, surface plasmon resonance (SPR) spectroscopy showed that a cdc2 kinase phosphorylation mimic of Hop had reduced affinity for Hsp90 binding. Hop was predominantly cytoplasmic, but translocated to the nucleus in response to heat shock. A putative bipartite nuclear localization signal (NLS) has been identified within the Hsp90-binding domain of Hop. Although substitution of residues within the major arm of this proposed NLS abolished Hop–Hsp90 interaction as determined by SPR, this was not sufficient to prevent the nuclear accumulation of Hop under leptomycin-B treatment and heat shock conditions. These results showed for the first time that the subcellular localization of Hop was stress regulated and that the major arm of the putative NLS was not directly important for nuclear translocation but was critical for Hop–Hsp90 association in vitro. We propose a model in which the association of Hop with Hsp90 and the phosphorylated status of Hop both play a role in the mechanism of nucleo-cytoplasmic shuttling of Hop.
- Full Text:
- Date Issued: 2008