Surface properties and electrocatalytic applications of metallophthalocyanines confined on electrode surfaces
- Authors: Akinbulu, Isaac Adebayo
- Date: 2011
- Subjects: Phthalocyanines Electrochemistry Electrocatalysis Pesticides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4365 , http://hdl.handle.net/10962/d1005030
- Description: New cobalt (13, 16 19 and 22), manganese (14, 17, 20 and 23) and iron (15, 18, 21 and 24)phthalocyanine complexes were synthesized and characterized. The UV-Vis spectral properties of the complexes were typical of the nature of central metal and position of substituent on the Pc ligand. Their electrochemical behaviors were signatures of the central metals, with varying influences of the nature and position of substituents. Nanocomposite of complex 18 and single walled carbon nanotubes (SWCNTs) (SWCNT-18)was fabricated. Formation of this nano-composite was confirmed by infrared (IR)spectroscopy, X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Self-assembled monolayers (SAMs) of SWCNT-18, complexes 13-15, and 20 were electropolymerized on glassy carbon electrodes (GCE). Complex 14 was also electrodeposited on GCE. Surface properties of the SAMs were consistent with the molecular feature of the substituent and the nature of central metal in the adsorbed species, while those of the MnPc modified GCEs were dependent on point of substitution and number of substituent. The SAM-modified gold electrodes were used for the electrocatalytic oxidation of the carbamate insecticide, carbofuran. Amplification of the current signal of the insecticide, at more energetically feasible oxidation potentials, on the SAM-modified gold electrodes, relative to bare gold electrode,justified electrocatalysis. There was enhanced sensitivity (attributed to the presence of SWCNT) of the SWCNT-18-SAM-modified gold electrode towards carbofuran, relative to the signals observed on the other SAMs. Current response of the insecticide,bendiocarb, was also intensified, at more favorable oxidation potentials, on the MnPc (14 and 17) modified GCEs, relative to the response on bare GCE, substantiating electrocatalysis. Also, catalysis of the oxidation of the herbicide, bentazon, was observed on polymeric film of complex 20. The current response of the herbicide on this film was better than that observed on bare GCE. Electrocatalysis of the analytes, on the respective modified electrodes, occurred via closely related mechanisms.
- Full Text:
- Date Issued: 2011
- Authors: Akinbulu, Isaac Adebayo
- Date: 2011
- Subjects: Phthalocyanines Electrochemistry Electrocatalysis Pesticides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4365 , http://hdl.handle.net/10962/d1005030
- Description: New cobalt (13, 16 19 and 22), manganese (14, 17, 20 and 23) and iron (15, 18, 21 and 24)phthalocyanine complexes were synthesized and characterized. The UV-Vis spectral properties of the complexes were typical of the nature of central metal and position of substituent on the Pc ligand. Their electrochemical behaviors were signatures of the central metals, with varying influences of the nature and position of substituents. Nanocomposite of complex 18 and single walled carbon nanotubes (SWCNTs) (SWCNT-18)was fabricated. Formation of this nano-composite was confirmed by infrared (IR)spectroscopy, X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Self-assembled monolayers (SAMs) of SWCNT-18, complexes 13-15, and 20 were electropolymerized on glassy carbon electrodes (GCE). Complex 14 was also electrodeposited on GCE. Surface properties of the SAMs were consistent with the molecular feature of the substituent and the nature of central metal in the adsorbed species, while those of the MnPc modified GCEs were dependent on point of substitution and number of substituent. The SAM-modified gold electrodes were used for the electrocatalytic oxidation of the carbamate insecticide, carbofuran. Amplification of the current signal of the insecticide, at more energetically feasible oxidation potentials, on the SAM-modified gold electrodes, relative to bare gold electrode,justified electrocatalysis. There was enhanced sensitivity (attributed to the presence of SWCNT) of the SWCNT-18-SAM-modified gold electrode towards carbofuran, relative to the signals observed on the other SAMs. Current response of the insecticide,bendiocarb, was also intensified, at more favorable oxidation potentials, on the MnPc (14 and 17) modified GCEs, relative to the response on bare GCE, substantiating electrocatalysis. Also, catalysis of the oxidation of the herbicide, bentazon, was observed on polymeric film of complex 20. The current response of the herbicide on this film was better than that observed on bare GCE. Electrocatalysis of the analytes, on the respective modified electrodes, occurred via closely related mechanisms.
- Full Text:
- Date Issued: 2011
Synthesis and evaluation of novel HIV-1 enzyme inhibitors
- Olomola, Temitope Oloruntoba
- Authors: Olomola, Temitope Oloruntoba
- Date: 2011
- Subjects: HIV infections -- Treatment HIV infections -- Chemotherapy HIV (Viruses) Enzyme inhibitors AZT (Drug) Reverse transcriptase Proteolytic enzymes Ligands Psoralens Resorcinol
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4369 , http://hdl.handle.net/10962/d1005034
- Description: This study has involved the design, synthesis and evaluation of novel HIV-1 enzyme inhibitors accessed by synthetic elaboration of Baylis-Hillman adducts. Several series of complex coumarin-AZT and cinnamate ester-AZT conjugates have been prepared, in high yields, by exploiting the click reaction between appropriate Baylis-Hillman derived precursors and azidothymidine (AZT), all of which have been fully characterised using spectroscopic techniques. These conjugates, designed as potential dual-action HIV-1 inhibitors, were tested against the appropriate HIV-1 enzymes, i.e. HIV-1 reverse transcriptase and protease or HIV-1 reverse transcriptase and integrase. A number of the ligands have exhibited % inhibition levels and IC50 values comparable to drugs in clinical use, permitting their identification as lead compounds for the development of novel dual-action inhibitors. In silico docking of selected ligands into the active sites of the respective enzymes has provided useful insight into binding conformations and potential hydrogen-bonding interactions with active-site amino acid residues. A series of furocoumarin carboxamide derivatives have been synthesised in four steps starting from resorcinol and these compounds have also been tested for HIV-1 integrase inhibition activity. The structures of unexpected products isolated from Aza-Baylis-Hillman reactions of N-tosylaldimines have been elucidated by spectroscopic analysis, and confirmed by single crystal X-ray analysis. A mechanism for what appears to be an unprecedented transformation has been proposed. Microwave-assisted SeO₂ oxidation of Baylis-Hillman-derived 3-methylcoumarins has provided convenient and efficient access to coumarin-3-carbaldehydes, and a pilot study has revealed the potential of these coumarin-3-carbaldehydes as scaffolds for the construction of tricyclic compounds. The HCl-catalysed reaction of tert-butyl acrylate derived Baylis-Hillman adducts has been shown to afford 3-(chloromethyl)coumarins and α-(chloromethyl)cinnamic acids, the Zstereochemistry of the latter being established by X-ray crystallography. ¹H NMR-based experimental kinetic and DFT-level theoretical studies have been undertaken to establish the reaction sequence and other mechanistic details. Base-catalysed cyclisation on the other hand, has been shown to afford 2H-chromene rather than coumarin derivatives.
- Full Text:
- Date Issued: 2011
- Authors: Olomola, Temitope Oloruntoba
- Date: 2011
- Subjects: HIV infections -- Treatment HIV infections -- Chemotherapy HIV (Viruses) Enzyme inhibitors AZT (Drug) Reverse transcriptase Proteolytic enzymes Ligands Psoralens Resorcinol
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4369 , http://hdl.handle.net/10962/d1005034
- Description: This study has involved the design, synthesis and evaluation of novel HIV-1 enzyme inhibitors accessed by synthetic elaboration of Baylis-Hillman adducts. Several series of complex coumarin-AZT and cinnamate ester-AZT conjugates have been prepared, in high yields, by exploiting the click reaction between appropriate Baylis-Hillman derived precursors and azidothymidine (AZT), all of which have been fully characterised using spectroscopic techniques. These conjugates, designed as potential dual-action HIV-1 inhibitors, were tested against the appropriate HIV-1 enzymes, i.e. HIV-1 reverse transcriptase and protease or HIV-1 reverse transcriptase and integrase. A number of the ligands have exhibited % inhibition levels and IC50 values comparable to drugs in clinical use, permitting their identification as lead compounds for the development of novel dual-action inhibitors. In silico docking of selected ligands into the active sites of the respective enzymes has provided useful insight into binding conformations and potential hydrogen-bonding interactions with active-site amino acid residues. A series of furocoumarin carboxamide derivatives have been synthesised in four steps starting from resorcinol and these compounds have also been tested for HIV-1 integrase inhibition activity. The structures of unexpected products isolated from Aza-Baylis-Hillman reactions of N-tosylaldimines have been elucidated by spectroscopic analysis, and confirmed by single crystal X-ray analysis. A mechanism for what appears to be an unprecedented transformation has been proposed. Microwave-assisted SeO₂ oxidation of Baylis-Hillman-derived 3-methylcoumarins has provided convenient and efficient access to coumarin-3-carbaldehydes, and a pilot study has revealed the potential of these coumarin-3-carbaldehydes as scaffolds for the construction of tricyclic compounds. The HCl-catalysed reaction of tert-butyl acrylate derived Baylis-Hillman adducts has been shown to afford 3-(chloromethyl)coumarins and α-(chloromethyl)cinnamic acids, the Zstereochemistry of the latter being established by X-ray crystallography. ¹H NMR-based experimental kinetic and DFT-level theoretical studies have been undertaken to establish the reaction sequence and other mechanistic details. Base-catalysed cyclisation on the other hand, has been shown to afford 2H-chromene rather than coumarin derivatives.
- Full Text:
- Date Issued: 2011
Synthesis of novel inhibitors of 1-Deoxy-D-xylulose-5-phosphate reductoisomerase as potential anti-malarial lead compounds
- Authors: Mutorwa, Marius Kudumo
- Date: 2011
- Subjects: Antimalarials -- Development Plasmodium falciparum Malaria -- Chemotherapy Drug development Lead compounds Phosphonates Phosphonic acids Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4372 , http://hdl.handle.net/10962/d1005037
- Description: This research has focused on the development of novel substrate mimics as potential DXR inhibitors of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate-independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate (DOXP) into 2C-methyl-D-erithrytol 4-phosphate (MEP) and has been validated as an attractive target for the development of novel anti-malarial chemotherapeutic agents. Reaction of various amines with specially prepared 4-phosphonated crotonic acid in the presence of the peptide coupling reagent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), has afforded a series of amido-phosphonate esters in moderate to good yields (48% - 73%) which, using a RuCl₃/CeCl₃/NaIO₄ catalyst system, have been dihydroxylated to furnish the dihydroxy-amido phosphonate ester pro-drugs; subsequent hydrolysis under microwave irradiation has afforded the corresponding phosphonic acids. A second series of potential inhibitors viz., 3-substituted aniline-derived phosphonate esters, their corresponding phosphonic acids and mono-sodium salts, have also been successfully synthesised. In these compounds, the essential functional groups are separated by one, two, three or four methylene groups, Deprotonation of the 3-substituted aniline substrates, followed by reaction with the appropriate ω-chloroalkanoyl chloride produced the ω-chloroamide intermediates, which were subjected to the Michaelis-Arbuzov reaction to afford the diethyl phosphonate esters in moderate to good yields (48% - 74%). Microwave-assisted TMSBrmediated cleavage of the phosphonate esters furnished the phosphonic acids, neutralisation of which afforded the mono-sodium salts. Furan-derived phosphate esters and phosphonic acids have been prepared as conformationally-restricted DOXP analogues. Functionalization at C-5 of the trityl-protected furan was achieved using the Vilsmeier-Haack formylation and Friedel-Crafts acylation reactions and, following de-tritylation, phosphorylation and oximation, using hydroxylamine hydrochloride, the novel oxime derivatives have been isolated as a third series of potential DXR inhibitors in very good yields (87% - 96%). Finally, in order to exploit an additional binding pocket in the PƒDXR active site, a series of N-benzylated phosphoramidic derivatives were obtained in seven steps from the starting material, diethyl phosphoramidate. The known inhibitors, fosmidomycin and its acetyl derivative FR900098, were also successfully synthesised as standards for STD-NMR binding and inhibition assays. In all, over 200 compounds (136 novel) have been prepared and appropriately characterised using 1-and 2-D NMR and IR spectroscopic analysis and, where necessary, HRMS or combustion analysis. Saturation Transfer Difference (STD) protein-NMR experiments, undertaken using selected compounds, have revealed binding of most of the ligands examined to EcDXR. Computersimulated docking studies have also been used to explore the preferred ligand-binding conformations and interactions between the ligands and essential DXR active-site residues, while DXR-enzyme inhibition assays of selected synthesised ligands have revealed certain patterns of inhibitory activity.
- Full Text:
- Date Issued: 2011
- Authors: Mutorwa, Marius Kudumo
- Date: 2011
- Subjects: Antimalarials -- Development Plasmodium falciparum Malaria -- Chemotherapy Drug development Lead compounds Phosphonates Phosphonic acids Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4372 , http://hdl.handle.net/10962/d1005037
- Description: This research has focused on the development of novel substrate mimics as potential DXR inhibitors of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate-independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate (DOXP) into 2C-methyl-D-erithrytol 4-phosphate (MEP) and has been validated as an attractive target for the development of novel anti-malarial chemotherapeutic agents. Reaction of various amines with specially prepared 4-phosphonated crotonic acid in the presence of the peptide coupling reagent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), has afforded a series of amido-phosphonate esters in moderate to good yields (48% - 73%) which, using a RuCl₃/CeCl₃/NaIO₄ catalyst system, have been dihydroxylated to furnish the dihydroxy-amido phosphonate ester pro-drugs; subsequent hydrolysis under microwave irradiation has afforded the corresponding phosphonic acids. A second series of potential inhibitors viz., 3-substituted aniline-derived phosphonate esters, their corresponding phosphonic acids and mono-sodium salts, have also been successfully synthesised. In these compounds, the essential functional groups are separated by one, two, three or four methylene groups, Deprotonation of the 3-substituted aniline substrates, followed by reaction with the appropriate ω-chloroalkanoyl chloride produced the ω-chloroamide intermediates, which were subjected to the Michaelis-Arbuzov reaction to afford the diethyl phosphonate esters in moderate to good yields (48% - 74%). Microwave-assisted TMSBrmediated cleavage of the phosphonate esters furnished the phosphonic acids, neutralisation of which afforded the mono-sodium salts. Furan-derived phosphate esters and phosphonic acids have been prepared as conformationally-restricted DOXP analogues. Functionalization at C-5 of the trityl-protected furan was achieved using the Vilsmeier-Haack formylation and Friedel-Crafts acylation reactions and, following de-tritylation, phosphorylation and oximation, using hydroxylamine hydrochloride, the novel oxime derivatives have been isolated as a third series of potential DXR inhibitors in very good yields (87% - 96%). Finally, in order to exploit an additional binding pocket in the PƒDXR active site, a series of N-benzylated phosphoramidic derivatives were obtained in seven steps from the starting material, diethyl phosphoramidate. The known inhibitors, fosmidomycin and its acetyl derivative FR900098, were also successfully synthesised as standards for STD-NMR binding and inhibition assays. In all, over 200 compounds (136 novel) have been prepared and appropriately characterised using 1-and 2-D NMR and IR spectroscopic analysis and, where necessary, HRMS or combustion analysis. Saturation Transfer Difference (STD) protein-NMR experiments, undertaken using selected compounds, have revealed binding of most of the ligands examined to EcDXR. Computersimulated docking studies have also been used to explore the preferred ligand-binding conformations and interactions between the ligands and essential DXR active-site residues, while DXR-enzyme inhibition assays of selected synthesised ligands have revealed certain patterns of inhibitory activity.
- Full Text:
- Date Issued: 2011
Systematics, morphology, phylogeny and historical biogeography of the Mayfly family Prosopistomatidae (Ephemeroptera: Insecta) of the world
- Barber-James, Helen Margaret
- Authors: Barber-James, Helen Margaret
- Date: 2011
- Subjects: Mayflies Mayflies -- Classification Mayflies -- Morphology Mayflies -- Phylogeny Mayflies -- Geographical distribution Ephemeridae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5785 , http://hdl.handle.net/10962/d1005473
- Description: The diversity, classification and historical biogeography of the mayfly family Prosopistomatidae are explored. First, the higher classification of the Ephemeroptera is reviewed, focussing on the phylogenetic placement of the Prosopistomatidae relative to other mayfly families. All relevant literature from 1762 to 2010 is synthesized. Baetiscidae are established as the probable sister lineage of Prosopistomatidae, the two constituting the superfamily Baetiscoidea. Next, qualitative morphological variation within the Prosopistomatidae is reviewed and revised, emphasizing nymphs because imaginal specimens are few. The labium and associated structures and the hypopharynx of nymphs, and the highly-derived wing venation of the imaginal stages, are re-interpreted. The structure of the male tarsal claws changes considerably between subimago and imago, which, together with deeply scalloped ridges on male imaginal forelegs and unusual pits on the female thorax, are interpreted as providing an unusual mating mechanism. These structures provide morphological characters for species definition and phylogenetic analyses. Two approaches to species delimitation are explored. First, morphometric variation is analysed using Principal Component Analysis, revealing groupings that can be interpreted as species, although there is some overlap between them. Discriminant Function Analysis shows that head width and carapace shape have the most value in identifying nymphs of different species. The carapace of Prosopistoma nymphs is shown to grow allometrically and gradually, in contrast with that of Baetisca, indicating a difference in early ontogeny. Second, an Artificial Neural Network algorithm applied to nymphal morphological characters accurately identified species. This computer-driven artificial intelligence method has power to provide future easy-to-use electronic identification aids. Phylogenetic analysis of nymphal morphology using the parsimony method shows two clades of Prosopistomatidae, one sharing characters with the type species, Prosopistoma variegatum and the other predominating in Africa, although also occurring in Asia; these clades are named the “P. variegatum” and “African” clades, respectively. Parsimony analysis of adult morphology supports these two clades, but supertree analysis obscures the relationships, nesting the “P. variegatum” lineage within the other clade. Preliminary molecular phylogenetic analysis of the 16S rRNA, (mitochondrial) 18S rRNA and Histone-3 genes using Bayesian Inference methods does not support the two clades shown by morphology. Instead, there is a strong relationship between the European species and one African species, with the single Asian representative being most distantly related. These results are limited by lack of fresh material, patchy taxon sampling, and problems with finding suitable primers. A molecular clock program, BEAST, calibrated using fossils, suggests divergence times for the oldest crown-group Prosopistoma clade, represented by the Asian P. wouterae, of about 131 Ma, with the youngest species, the African P. crassi, of 1.21 Ma. Stem-group relationships are analysed using parsimony analysis, focussing on wing characters of the Baetiscoidea, other extant mayfly lineages, and extinct stem-group lineages. This suggests that the Baetiscoidea diverged from main-line Ephemeroptera earlier than any other extant mayfly lineage. This approach expands upon ideas hinted at by earlier scientists. Finally, historical biogeographical analysis of the distribution of known Baetiscoidea s.s. stem-group fossils implies a once Pangean distribution of the lineage. Changing palaeo-climate, catastrophic extinction events and plate tectonic movements in relation to the distribution of crown-group species are reviewed. Other approaches to historical biogeography that build on both morphological and molecular phylogenies are used to interpret disperalist and vacarianist arguments. Distribution patterns of eight unrelated freshwater organisms which share a similar distribution pattern are compared, assuming that shared patterns indicate similar historic biogeographic processes. The distribution of recent Prosopistoma species is seen to be the product of evolution resulting from both vicariance and dispersal. In conclusion, this thesis encompasses a variety of disciplines. It successfully recognises new characters and distinguishes previously unknown species. It uses new approaches to delimiting species and known methods to determine phylogeny from several angles. The analysis of stem-group relationships offers an insight into possible early lineage splitting within Ephemeroptera. Interpretation of historical biogeography allows for both a Gondwanan origin of Prosopistomatidae, with rafting of species on the Deccan plate to Asia, and for subsequent dispersal from Asia down to Australia and across to Europe, and possibly back to Africa.
- Full Text:
- Date Issued: 2011
- Authors: Barber-James, Helen Margaret
- Date: 2011
- Subjects: Mayflies Mayflies -- Classification Mayflies -- Morphology Mayflies -- Phylogeny Mayflies -- Geographical distribution Ephemeridae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5785 , http://hdl.handle.net/10962/d1005473
- Description: The diversity, classification and historical biogeography of the mayfly family Prosopistomatidae are explored. First, the higher classification of the Ephemeroptera is reviewed, focussing on the phylogenetic placement of the Prosopistomatidae relative to other mayfly families. All relevant literature from 1762 to 2010 is synthesized. Baetiscidae are established as the probable sister lineage of Prosopistomatidae, the two constituting the superfamily Baetiscoidea. Next, qualitative morphological variation within the Prosopistomatidae is reviewed and revised, emphasizing nymphs because imaginal specimens are few. The labium and associated structures and the hypopharynx of nymphs, and the highly-derived wing venation of the imaginal stages, are re-interpreted. The structure of the male tarsal claws changes considerably between subimago and imago, which, together with deeply scalloped ridges on male imaginal forelegs and unusual pits on the female thorax, are interpreted as providing an unusual mating mechanism. These structures provide morphological characters for species definition and phylogenetic analyses. Two approaches to species delimitation are explored. First, morphometric variation is analysed using Principal Component Analysis, revealing groupings that can be interpreted as species, although there is some overlap between them. Discriminant Function Analysis shows that head width and carapace shape have the most value in identifying nymphs of different species. The carapace of Prosopistoma nymphs is shown to grow allometrically and gradually, in contrast with that of Baetisca, indicating a difference in early ontogeny. Second, an Artificial Neural Network algorithm applied to nymphal morphological characters accurately identified species. This computer-driven artificial intelligence method has power to provide future easy-to-use electronic identification aids. Phylogenetic analysis of nymphal morphology using the parsimony method shows two clades of Prosopistomatidae, one sharing characters with the type species, Prosopistoma variegatum and the other predominating in Africa, although also occurring in Asia; these clades are named the “P. variegatum” and “African” clades, respectively. Parsimony analysis of adult morphology supports these two clades, but supertree analysis obscures the relationships, nesting the “P. variegatum” lineage within the other clade. Preliminary molecular phylogenetic analysis of the 16S rRNA, (mitochondrial) 18S rRNA and Histone-3 genes using Bayesian Inference methods does not support the two clades shown by morphology. Instead, there is a strong relationship between the European species and one African species, with the single Asian representative being most distantly related. These results are limited by lack of fresh material, patchy taxon sampling, and problems with finding suitable primers. A molecular clock program, BEAST, calibrated using fossils, suggests divergence times for the oldest crown-group Prosopistoma clade, represented by the Asian P. wouterae, of about 131 Ma, with the youngest species, the African P. crassi, of 1.21 Ma. Stem-group relationships are analysed using parsimony analysis, focussing on wing characters of the Baetiscoidea, other extant mayfly lineages, and extinct stem-group lineages. This suggests that the Baetiscoidea diverged from main-line Ephemeroptera earlier than any other extant mayfly lineage. This approach expands upon ideas hinted at by earlier scientists. Finally, historical biogeographical analysis of the distribution of known Baetiscoidea s.s. stem-group fossils implies a once Pangean distribution of the lineage. Changing palaeo-climate, catastrophic extinction events and plate tectonic movements in relation to the distribution of crown-group species are reviewed. Other approaches to historical biogeography that build on both morphological and molecular phylogenies are used to interpret disperalist and vacarianist arguments. Distribution patterns of eight unrelated freshwater organisms which share a similar distribution pattern are compared, assuming that shared patterns indicate similar historic biogeographic processes. The distribution of recent Prosopistoma species is seen to be the product of evolution resulting from both vicariance and dispersal. In conclusion, this thesis encompasses a variety of disciplines. It successfully recognises new characters and distinguishes previously unknown species. It uses new approaches to delimiting species and known methods to determine phylogeny from several angles. The analysis of stem-group relationships offers an insight into possible early lineage splitting within Ephemeroptera. Interpretation of historical biogeography allows for both a Gondwanan origin of Prosopistomatidae, with rafting of species on the Deccan plate to Asia, and for subsequent dispersal from Asia down to Australia and across to Europe, and possibly back to Africa.
- Full Text:
- Date Issued: 2011
Tailoring a lean product development framework for the South African automotive industry
- Authors: Mund, Klaudia
- Date: 2011
- Subjects: Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8792 , http://hdl.handle.net/10948/d1015737
- Description: Globalization in the automotive industry exerts enormous pressure on automotive manufacturers and forces many global companies to expand into emerging markets, which results in adopting new ways to manage product design and development. Excellence in product design and development offers an opportunity to gain competitive advantage and can be achieved by implementing Toyota´s Lean Product Development System (LPDS). Although in the last three years Toyota has been severely challenged by the global economic crisis, by a series of recalls resulting in reputation damage and also by natural disasters such as the recent tsunamis - the world can still learn from Toyota´s successes embodied in the lean concept and practices, which are integral to Toyota´s ‘way of life’. The LPDS model (Morgan & Liker 2006) has captured the attention of academics worldwide (including this researcher) thanks to the following key characteristics: shorter development times, less engineering hours involved in development, lower manufacturing costs, higher customer satisfaction and fewer defects reported. In the academic world, lean product development (LPD) is a new field of exploration and thus relevant literature and numbers of studies available are limited. However, scientists are asking questions about successful adaptation and adoption of this model to other environments beyond Toyota. Similarly, the researcher aimed in this thesis to find answers to its main research question, namely: ‘What would be a suitable LPD model for the South African automotive industry?’ South Africa (SA) is a country with a strong manufacturing tradition and although the automotive sector is the third-largest segment in the South African economy and its vehicle market is the largest on the African continent in a global perspective SA´s contribution is relatively small as it produces only 0.61percent of the global motor vehicle volume (OICA 2011). While the country strives to secure sustainable development for the automotive industry and seeks to improve its global competitiveness, companies operating in SA are currently faced with several unique challenges and problems. Lean has been expanding slowly in SA and some companies in the local automotive industry have implemented the lean concept into production areas to improve their operational excellence and performance. However, it is a search for excellence in product development (PD) that could best contribute to improved sustainability for the automotive industry and also provide an important strategic spur towards global competitiveness. The primary intention of this research was to develop an integrated LPD framework tailored for SA´s automotive industry. Considering this, it was necessary to determine current PD capabilities at domestic and international companies operating in SA´s automotive industry so as to examine levels of adaptation of LPD practices. A questionnaire survey and personal interviews involving all seven locally operating Original Equipment Manufacturers (OEMs), including Toyota, as well as 36 local automotive suppliers provided an empirical base for this investigation. This study indicates that SA plays an important supportive role in the global PD context. In spite of a strong manufacturing focus and very limited PD capabilities, SA´s automotive companies have already achieved a high level of ‘leanness’ in product engineering processes. However, on the downside, it appears that industry leaders and senior managers are sceptical about current and future capabilities and opportunities for SA in the designing and developing of global products.
- Full Text:
- Date Issued: 2011
- Authors: Mund, Klaudia
- Date: 2011
- Subjects: Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8792 , http://hdl.handle.net/10948/d1015737
- Description: Globalization in the automotive industry exerts enormous pressure on automotive manufacturers and forces many global companies to expand into emerging markets, which results in adopting new ways to manage product design and development. Excellence in product design and development offers an opportunity to gain competitive advantage and can be achieved by implementing Toyota´s Lean Product Development System (LPDS). Although in the last three years Toyota has been severely challenged by the global economic crisis, by a series of recalls resulting in reputation damage and also by natural disasters such as the recent tsunamis - the world can still learn from Toyota´s successes embodied in the lean concept and practices, which are integral to Toyota´s ‘way of life’. The LPDS model (Morgan & Liker 2006) has captured the attention of academics worldwide (including this researcher) thanks to the following key characteristics: shorter development times, less engineering hours involved in development, lower manufacturing costs, higher customer satisfaction and fewer defects reported. In the academic world, lean product development (LPD) is a new field of exploration and thus relevant literature and numbers of studies available are limited. However, scientists are asking questions about successful adaptation and adoption of this model to other environments beyond Toyota. Similarly, the researcher aimed in this thesis to find answers to its main research question, namely: ‘What would be a suitable LPD model for the South African automotive industry?’ South Africa (SA) is a country with a strong manufacturing tradition and although the automotive sector is the third-largest segment in the South African economy and its vehicle market is the largest on the African continent in a global perspective SA´s contribution is relatively small as it produces only 0.61percent of the global motor vehicle volume (OICA 2011). While the country strives to secure sustainable development for the automotive industry and seeks to improve its global competitiveness, companies operating in SA are currently faced with several unique challenges and problems. Lean has been expanding slowly in SA and some companies in the local automotive industry have implemented the lean concept into production areas to improve their operational excellence and performance. However, it is a search for excellence in product development (PD) that could best contribute to improved sustainability for the automotive industry and also provide an important strategic spur towards global competitiveness. The primary intention of this research was to develop an integrated LPD framework tailored for SA´s automotive industry. Considering this, it was necessary to determine current PD capabilities at domestic and international companies operating in SA´s automotive industry so as to examine levels of adaptation of LPD practices. A questionnaire survey and personal interviews involving all seven locally operating Original Equipment Manufacturers (OEMs), including Toyota, as well as 36 local automotive suppliers provided an empirical base for this investigation. This study indicates that SA plays an important supportive role in the global PD context. In spite of a strong manufacturing focus and very limited PD capabilities, SA´s automotive companies have already achieved a high level of ‘leanness’ in product engineering processes. However, on the downside, it appears that industry leaders and senior managers are sceptical about current and future capabilities and opportunities for SA in the designing and developing of global products.
- Full Text:
- Date Issued: 2011
Tailoring a lean product development framework for the South African automotive industry
- Authors: Mund, Klaudia
- Date: 2011
- Subjects: Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Language: English
- Type: Thesis , Doctoral , DTech (Operations Management)
- Identifier: vital:9605 , http://hdl.handle.net/10948/1660 , Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Description: Globalization in the automotive industry exerts enormous pressure on automotive manufacturers and forces many global companies to expand into emerging markets, which results in adopting new ways to manage product design and development. Excellence in product design and development offers an opportunity to gain competitive advantage and can be achieved by implementing Toyota´s Lean Product Development System (LPDS). Although in the last three years Toyota has been severely challenged by the global economic crisis, by a series of recalls resulting in reputation damage and also by natural disasters such as the recent tsunamis - the world can still learn from Toyota´s successes embodied in the lean concept and practices, which are integral to Toyota´s ‘way of life’. The LPDS model (Morgan & Liker 2006) has captured the attention of academics worldwide (including this researcher) thanks to the following key characteristics: shorter development times, less engineering hours involved in development, lower manufacturing costs, higher customer satisfaction and fewer defects reported. In the academic world, lean product development (LPD) is a new field of exploration and thus relevant literature and numbers of studies available are limited. However, scientists are asking questions about successful adaptation and adoption of this model to other environments beyond Toyota. Similarly, the researcher aimed in this thesis to find answers to its main research question, namely: ‘What would be a suitable LPD model for the South African automotive industry?’ South Africa (SA) is a country with a strong manufacturing tradition and although the automotive sector is the third-largest segment in the South African economy and its vehicle market is the largest on the African continent in a global perspective SA´s contribution is relatively small as it produces only 0.61% of the global motor vehicle volume (OICA 2011). While the country strives to secure sustainable development for the automotive industry and seeks to improve its global competitiveness, companies operating in SA are currently faced with several unique challenges and problems. Lean has been expanding slowly in SA and some companies in the local automotive industry have implemented the lean concept into production areas to improve their operational excellence and performance. However, it is a search for excellence in product development (PD) that could best contribute to improved sustainability for the iv automotive industry and also provide an important strategic spur towards global competitiveness. The primary intention of this research was to develop an integrated LPD framework tailored for SA´s automotive industry. Considering this, it was necessary to determine current PD capabilities at domestic and international companies operating in SA´s automotive industry so as to examine levels of adaptation of LPD practices. A questionnaire survey and personal interviews involving all seven locally operating Original Equipment Manufacturers (OEMs), including Toyota, as well as 36 local automotive suppliers provided an empirical base for this investigation. This study indicates that SA plays an important supportive role in the global PD context. In spite of a strong manufacturing focus and very limited PD capabilities, SA´s automotive companies have already achieved a high level of ‘leanness’ in product engineering processes. However, on the downside, it appears that industry leaders and senior managers are sceptical about current and future capabilities and opportunities for SA in the designing and developing of global products.
- Full Text:
- Date Issued: 2011
- Authors: Mund, Klaudia
- Date: 2011
- Subjects: Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Language: English
- Type: Thesis , Doctoral , DTech (Operations Management)
- Identifier: vital:9605 , http://hdl.handle.net/10948/1660 , Lean manufacturing , Automobile industry and trade -- South Africa , Production management -- South Africa , Globalization
- Description: Globalization in the automotive industry exerts enormous pressure on automotive manufacturers and forces many global companies to expand into emerging markets, which results in adopting new ways to manage product design and development. Excellence in product design and development offers an opportunity to gain competitive advantage and can be achieved by implementing Toyota´s Lean Product Development System (LPDS). Although in the last three years Toyota has been severely challenged by the global economic crisis, by a series of recalls resulting in reputation damage and also by natural disasters such as the recent tsunamis - the world can still learn from Toyota´s successes embodied in the lean concept and practices, which are integral to Toyota´s ‘way of life’. The LPDS model (Morgan & Liker 2006) has captured the attention of academics worldwide (including this researcher) thanks to the following key characteristics: shorter development times, less engineering hours involved in development, lower manufacturing costs, higher customer satisfaction and fewer defects reported. In the academic world, lean product development (LPD) is a new field of exploration and thus relevant literature and numbers of studies available are limited. However, scientists are asking questions about successful adaptation and adoption of this model to other environments beyond Toyota. Similarly, the researcher aimed in this thesis to find answers to its main research question, namely: ‘What would be a suitable LPD model for the South African automotive industry?’ South Africa (SA) is a country with a strong manufacturing tradition and although the automotive sector is the third-largest segment in the South African economy and its vehicle market is the largest on the African continent in a global perspective SA´s contribution is relatively small as it produces only 0.61% of the global motor vehicle volume (OICA 2011). While the country strives to secure sustainable development for the automotive industry and seeks to improve its global competitiveness, companies operating in SA are currently faced with several unique challenges and problems. Lean has been expanding slowly in SA and some companies in the local automotive industry have implemented the lean concept into production areas to improve their operational excellence and performance. However, it is a search for excellence in product development (PD) that could best contribute to improved sustainability for the iv automotive industry and also provide an important strategic spur towards global competitiveness. The primary intention of this research was to develop an integrated LPD framework tailored for SA´s automotive industry. Considering this, it was necessary to determine current PD capabilities at domestic and international companies operating in SA´s automotive industry so as to examine levels of adaptation of LPD practices. A questionnaire survey and personal interviews involving all seven locally operating Original Equipment Manufacturers (OEMs), including Toyota, as well as 36 local automotive suppliers provided an empirical base for this investigation. This study indicates that SA plays an important supportive role in the global PD context. In spite of a strong manufacturing focus and very limited PD capabilities, SA´s automotive companies have already achieved a high level of ‘leanness’ in product engineering processes. However, on the downside, it appears that industry leaders and senior managers are sceptical about current and future capabilities and opportunities for SA in the designing and developing of global products.
- Full Text:
- Date Issued: 2011
The business sustainability of an automotive refinish paint distributor
- Authors: Msuthwana, Vusumzi M
- Date: 2011
- Subjects: Business enterprises -- Development , Business enterprises -- Marketing , Business -- Sustainability
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9371 , http://hdl.handle.net/10948/d1012376 , Business enterprises -- Development , Business enterprises -- Marketing , Business -- Sustainability
- Description: From a broad overview of business management literature, the proposition emerged that strategic conditions within an organisation can translate into sustainable business development outcomes. However, in the rapidly evolving business environment, the quest to grow or sustain competitive advantage demands that business practices become more proactive, creative and innovative. Globalisation and technological advances drive the need for innovation within a business context and the resultant rapid pace of change demands that businesses adopt a customer-focused entrepreneurial orientation to accommodate this need for innovation. This study investigated whether the principles of marketing, business management tools and management of the customer-base could be incorporated as key drivers to develop innovative and creative tactics that could serve as viable solutions to sustain business development strategies of automotive refinish paint distributors. An initial step in this research comprised a theoretical overview of the internal business environment as a system of the enterprise that aims to provide an in-depth understanding of the organisation, which could be applied to support strategic business goals and objectives. The literature review further entailed an investigation and explorations regarding best practices that automotive refinish paint distributors could follow in order to identify, focus on and develop their source of competitive advantage, sustainability and profitability. From the literature review, a methodological framework was developed that could be applied to specific success indicators, moulded to produce distinctive competencies in the automotive refinish paint industry; defining a significant foundation from which the objectives of this study could be researched. The study adopted the qualitative research approach and focused on a single case of a refinish paint distributor. The reason for selecting the case study method is that an entire organisation could be investigated in depth with particular attention to detail. A detailed questionnaire was drawn up in order to conduct face-to-face interviews with selected respondents, based on the profound expertise of the selected personnel. This was done to enable the researcher to assess the prevalent elements of business sustainability applied by the automotive refinish distributor to enhance their competitive advantage. The design of the empirical element of this study, aimed at providing a blueprint that would enable the researcher to structure the research problem in such a way that the outcome of the study would be valid, objective and reliable. Due to the qualitative nature of this study, the results are interpreted through inductive reasoning, observations, projective and participatory approaches all of which are integrated into a comprehensive model indicating key drivers to promote, improve and facilitate the business sustainability of the automotive refinish paint distributor. A range of recommendations and managerial implications extracted from the results of the empirical study are presented in the final chapter.
- Full Text:
- Date Issued: 2011
- Authors: Msuthwana, Vusumzi M
- Date: 2011
- Subjects: Business enterprises -- Development , Business enterprises -- Marketing , Business -- Sustainability
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9371 , http://hdl.handle.net/10948/d1012376 , Business enterprises -- Development , Business enterprises -- Marketing , Business -- Sustainability
- Description: From a broad overview of business management literature, the proposition emerged that strategic conditions within an organisation can translate into sustainable business development outcomes. However, in the rapidly evolving business environment, the quest to grow or sustain competitive advantage demands that business practices become more proactive, creative and innovative. Globalisation and technological advances drive the need for innovation within a business context and the resultant rapid pace of change demands that businesses adopt a customer-focused entrepreneurial orientation to accommodate this need for innovation. This study investigated whether the principles of marketing, business management tools and management of the customer-base could be incorporated as key drivers to develop innovative and creative tactics that could serve as viable solutions to sustain business development strategies of automotive refinish paint distributors. An initial step in this research comprised a theoretical overview of the internal business environment as a system of the enterprise that aims to provide an in-depth understanding of the organisation, which could be applied to support strategic business goals and objectives. The literature review further entailed an investigation and explorations regarding best practices that automotive refinish paint distributors could follow in order to identify, focus on and develop their source of competitive advantage, sustainability and profitability. From the literature review, a methodological framework was developed that could be applied to specific success indicators, moulded to produce distinctive competencies in the automotive refinish paint industry; defining a significant foundation from which the objectives of this study could be researched. The study adopted the qualitative research approach and focused on a single case of a refinish paint distributor. The reason for selecting the case study method is that an entire organisation could be investigated in depth with particular attention to detail. A detailed questionnaire was drawn up in order to conduct face-to-face interviews with selected respondents, based on the profound expertise of the selected personnel. This was done to enable the researcher to assess the prevalent elements of business sustainability applied by the automotive refinish distributor to enhance their competitive advantage. The design of the empirical element of this study, aimed at providing a blueprint that would enable the researcher to structure the research problem in such a way that the outcome of the study would be valid, objective and reliable. Due to the qualitative nature of this study, the results are interpreted through inductive reasoning, observations, projective and participatory approaches all of which are integrated into a comprehensive model indicating key drivers to promote, improve and facilitate the business sustainability of the automotive refinish paint distributor. A range of recommendations and managerial implications extracted from the results of the empirical study are presented in the final chapter.
- Full Text:
- Date Issued: 2011
The development of novel cancer targeting agents
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
The discoursal construction of female physical identity in selected works in children's literature
- Authors: Hunt, Sally Ann
- Date: 2011 , 2013-09-20
- Subjects: Rowling, J K -- Criticism and interpretation Lewis, C S (Clive Staples), 1898-1963 -- Criticism and interpretation Girls in literature Girls -- Identity Human body in literature Gender identity in literature Sex role in literature Children's stories, English -- History and criticism Young women in literature Women in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2377 , http://hdl.handle.net/10962/d1005965
- Description: This thesis reports on an analysis of the discursive construction of female and male physical identity in children’s literature and explicitly combines corpus linguistic methods with a critical discourse approach. Based on three novels from each of the Chronicles of Narnia and the Harry Potter series, it shows clear gendering of body parts, not only in terms of the purely quantitative preferences for certain body parts to be associated with one or other gender, but in terms of discourse prosody, or the uses to which the body parts are put. Human body parts in these series are mostly used in the following four ways, all of which show differences in realisation in terms of gender: · to describe individuals, physically, in order to distinguish one from the other; · to convey emotion, unintentionally as well as consciously; · for physical interaction between people and · for interaction with the world more broadly: responses to danger and agency, i.e. the ability to act on the world and the nature of what is achieved. The use of body parts by characters to express emotion and act agentively on the world is revealed to be strongly gendered in the two series. I characterise the most prominent patterns in terms of the bodily products blood, sweat and tears, of which the last is strongly connected to female characters, who are generally associated with emotion. The other two, referring to active participation in fighting and injury, as well as agency, are almost exclusively reserved for males, with female characters rendered unable to act on the physical world as a result of overwhelming feelings. The females’ response to danger suggests stereotyped discourses of inequality which see women and girls as requiring protection and being physically incapable. Thus gender is still a particularly salient aspect in these widely-read examples of children’s literature, despite plots which appear to be fairly positive towards women. The strength of the inclusion of a corpus approach in this study lies in its capacity to reveal objective, and often fairly covert, trends in language use. These in turn enrich the critical analysis of discourses in these influential texts, which facilitates social change through linguistic analysis.
- Full Text:
- Date Issued: 2011
- Authors: Hunt, Sally Ann
- Date: 2011 , 2013-09-20
- Subjects: Rowling, J K -- Criticism and interpretation Lewis, C S (Clive Staples), 1898-1963 -- Criticism and interpretation Girls in literature Girls -- Identity Human body in literature Gender identity in literature Sex role in literature Children's stories, English -- History and criticism Young women in literature Women in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2377 , http://hdl.handle.net/10962/d1005965
- Description: This thesis reports on an analysis of the discursive construction of female and male physical identity in children’s literature and explicitly combines corpus linguistic methods with a critical discourse approach. Based on three novels from each of the Chronicles of Narnia and the Harry Potter series, it shows clear gendering of body parts, not only in terms of the purely quantitative preferences for certain body parts to be associated with one or other gender, but in terms of discourse prosody, or the uses to which the body parts are put. Human body parts in these series are mostly used in the following four ways, all of which show differences in realisation in terms of gender: · to describe individuals, physically, in order to distinguish one from the other; · to convey emotion, unintentionally as well as consciously; · for physical interaction between people and · for interaction with the world more broadly: responses to danger and agency, i.e. the ability to act on the world and the nature of what is achieved. The use of body parts by characters to express emotion and act agentively on the world is revealed to be strongly gendered in the two series. I characterise the most prominent patterns in terms of the bodily products blood, sweat and tears, of which the last is strongly connected to female characters, who are generally associated with emotion. The other two, referring to active participation in fighting and injury, as well as agency, are almost exclusively reserved for males, with female characters rendered unable to act on the physical world as a result of overwhelming feelings. The females’ response to danger suggests stereotyped discourses of inequality which see women and girls as requiring protection and being physically incapable. Thus gender is still a particularly salient aspect in these widely-read examples of children’s literature, despite plots which appear to be fairly positive towards women. The strength of the inclusion of a corpus approach in this study lies in its capacity to reveal objective, and often fairly covert, trends in language use. These in turn enrich the critical analysis of discourses in these influential texts, which facilitates social change through linguistic analysis.
- Full Text:
- Date Issued: 2011
The druggable antimalarial target 1-deoxy-D-xylulose-5-phosphate reductoisomerase: purfication, kinetic characterization and inhibition studies
- Authors: Goble, Jessica Leigh
- Date: 2011
- Subjects: Antimalarials -- Development Plasmodium falciparum Drug development Plasmodium falciparum -- Purification Plasmodium falciparum -- Inhibitors Enzyme kinetics Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3949 , http://hdl.handle.net/10962/d1004008
- Description: Plasmodium falciparum 1–deoxy–D–xylulose–5 phosphatereductoisomerase (PfDXR) plays a role in isoprenoid biosynthesis in the malaria parasite and is absent in the human host, making this parasite enzyme an attractive target for antimalarial drug design. To characterize PfDXR, it is necessary to produce large quantities of the enzyme in a soluble and functional form. However, the over–production of malarial proteins in prokaryotic host systems often results in the formation of truncated proteins or insoluble protein aggregates. A heterologous expression system was developed for the production of active PfDXR using codon harmonization and tight control of expression in the presence of lac repressor. Yields of up to 2 mg/l of enzyme were reported using the optimised expression system, which is 8 to 10– fold greater than previously reported yields. The kinetic parameters Km, Vmax and kcat were determined for PfDXR; values reported in this study were consistent with those reported in the literature for other DXR enzymes. A three–dimensional model of the malarial drug target protein PfDXR was generated, and validated using structure–checking programs and protein docking studies. Structural and functional features unique to PfDXR were identified using the model and comparative sequence analyses with apicomplexan and non–apicomplexan DXR proteins. Residues Val44 and Asn45, essential for NADPH binding; and catalytic hatch residues Lys224 and Lys226, which are unique to the species of Plasmodium, were mutated to resemble those of E. coli DXR. Interestingly,these mutations resulted in significant reductions in substrate affinity, when compared to the unmutated PfDXR. Mutant enzymes PfDXR(VN43,44AG) and PfDXR(KK224,226NS) also demonstrated a decreased ability to turnover substrate by 4–fold and 2–fold respectively. This study indicates a difference in the role of the catalytic hatch of PfDXR with regards to the way in which it captures substrates. The study also highlights subtle differences in cofactor binding to PfDXR, compared with the well characterized EcDXR enzyme. The validated PfDXR model was also used to develop a novel efficient in silico screening method for potential tool compounds for use in the rational design of novel DXR inhibitors. Following in silico screening of 46 potential DXR inhibitors, a two–tiered in vitro screening approach was undertaken. DXR inhibition was assessed for the 46 novel compounds using an NADPH– ependant DXP enzyme inhibition assay and antimalarial potential was assessed using P.falciparum–infected erythrocyte growth assays. Select compounds were tested in human cells in order to determine whether they were toxic to the host. From the parallel in silico and in vitro drug screening, it was evident that only a single compound demonstrated reasonable potential binding to DXR (determined using in silico docking), inhibited DXR in vitro and inhibited P. falciparum growth, without being toxic to human cells. Its potential as a lead compound in antimalarial drug development is therefore feasible. Two outcomes were evident from this work. Firstly, analogues of known antimalarial natural products can be screened against malaria, which may then lead towards the rational design of novel compounds that are effective against a specific antimalarial drug target enzyme, such as PfDXR. Secondly, the rational design of novel compounds against a specific antimalarial drug target enzyme can be untaken by adopting a coupled in silico and in vitro approach to drug discovery.
- Full Text:
- Date Issued: 2011
- Authors: Goble, Jessica Leigh
- Date: 2011
- Subjects: Antimalarials -- Development Plasmodium falciparum Drug development Plasmodium falciparum -- Purification Plasmodium falciparum -- Inhibitors Enzyme kinetics Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3949 , http://hdl.handle.net/10962/d1004008
- Description: Plasmodium falciparum 1–deoxy–D–xylulose–5 phosphatereductoisomerase (PfDXR) plays a role in isoprenoid biosynthesis in the malaria parasite and is absent in the human host, making this parasite enzyme an attractive target for antimalarial drug design. To characterize PfDXR, it is necessary to produce large quantities of the enzyme in a soluble and functional form. However, the over–production of malarial proteins in prokaryotic host systems often results in the formation of truncated proteins or insoluble protein aggregates. A heterologous expression system was developed for the production of active PfDXR using codon harmonization and tight control of expression in the presence of lac repressor. Yields of up to 2 mg/l of enzyme were reported using the optimised expression system, which is 8 to 10– fold greater than previously reported yields. The kinetic parameters Km, Vmax and kcat were determined for PfDXR; values reported in this study were consistent with those reported in the literature for other DXR enzymes. A three–dimensional model of the malarial drug target protein PfDXR was generated, and validated using structure–checking programs and protein docking studies. Structural and functional features unique to PfDXR were identified using the model and comparative sequence analyses with apicomplexan and non–apicomplexan DXR proteins. Residues Val44 and Asn45, essential for NADPH binding; and catalytic hatch residues Lys224 and Lys226, which are unique to the species of Plasmodium, were mutated to resemble those of E. coli DXR. Interestingly,these mutations resulted in significant reductions in substrate affinity, when compared to the unmutated PfDXR. Mutant enzymes PfDXR(VN43,44AG) and PfDXR(KK224,226NS) also demonstrated a decreased ability to turnover substrate by 4–fold and 2–fold respectively. This study indicates a difference in the role of the catalytic hatch of PfDXR with regards to the way in which it captures substrates. The study also highlights subtle differences in cofactor binding to PfDXR, compared with the well characterized EcDXR enzyme. The validated PfDXR model was also used to develop a novel efficient in silico screening method for potential tool compounds for use in the rational design of novel DXR inhibitors. Following in silico screening of 46 potential DXR inhibitors, a two–tiered in vitro screening approach was undertaken. DXR inhibition was assessed for the 46 novel compounds using an NADPH– ependant DXP enzyme inhibition assay and antimalarial potential was assessed using P.falciparum–infected erythrocyte growth assays. Select compounds were tested in human cells in order to determine whether they were toxic to the host. From the parallel in silico and in vitro drug screening, it was evident that only a single compound demonstrated reasonable potential binding to DXR (determined using in silico docking), inhibited DXR in vitro and inhibited P. falciparum growth, without being toxic to human cells. Its potential as a lead compound in antimalarial drug development is therefore feasible. Two outcomes were evident from this work. Firstly, analogues of known antimalarial natural products can be screened against malaria, which may then lead towards the rational design of novel compounds that are effective against a specific antimalarial drug target enzyme, such as PfDXR. Secondly, the rational design of novel compounds against a specific antimalarial drug target enzyme can be untaken by adopting a coupled in silico and in vitro approach to drug discovery.
- Full Text:
- Date Issued: 2011
The effects of the transformation process on the health service in Limpopo provincial government of South Africa
- Madzivhandila, Mushavhani Wilson
- Authors: Madzivhandila, Mushavhani Wilson
- Date: 2011
- Subjects: Provincial government -- South Africa -- Limpopo , Human services -- South Africa -- Limpopo , Medical care -- South Africa -- Limpopo , Public health -- South Africa -- Limpopo , Apartheid -- South Africa -- Limpopo , Limpopo (South Africa) -- Economic conditions , Limpopo (South Africa) -- Social conditions , Limpopo (South Africa) -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11662 , http://hdl.handle.net/10353/d1007095 , Provincial government -- South Africa -- Limpopo , Human services -- South Africa -- Limpopo , Medical care -- South Africa -- Limpopo , Public health -- South Africa -- Limpopo , Apartheid -- South Africa -- Limpopo , Limpopo (South Africa) -- Economic conditions , Limpopo (South Africa) -- Social conditions , Limpopo (South Africa) -- Politics and government
- Description: The Republic of South Africa emerged as 'a product of a historical moment' and also as a reaction against imperialism, colonialism, racial discrimination and domination over the majority of black South Africans by the white minority. The democratic dispensation came into being also for the first time in its life in memorial for a long turbulent history followed by the general democratic elections held on 27th April 1994. The 1994 first general election liberated South Africa from the apartheid system and its subsequent primary objective was “… to transform South Africa into a non-racial and democratic society”. The new democratic government now looks politically different from the racist regime because the current government since 1994 has been, and to date still is, a truly and broadly representative of the South African citizens and also a transparent one, whereas the defunct apartheid government was characterized primarily by, among other things, the violation of human rights, denying black South Africans of any rights of basic services, no rights of owning property or land, no freedom of association and speeches and firmly practised discrimination which was detrimental to the majority of the black population groups in this country. According to the then President Nelson Mandela whilst addressing the ANC masses that were commemorating the eighty-third (83rd) anniversary of the African National Congress on the 8th January 1995, democracy entails “… a thorough-going process of transformation, of overcoming the political, social and economic legacy of apartheid colonialism, of racism, sexism and class oppression.” The government is still grappling with the challenge of ensuringa better life for all the citizens of this country (http://www.anc.org.za/show.php?doc=ancdocs/history/jan8-95html:1).
- Full Text:
- Date Issued: 2011
- Authors: Madzivhandila, Mushavhani Wilson
- Date: 2011
- Subjects: Provincial government -- South Africa -- Limpopo , Human services -- South Africa -- Limpopo , Medical care -- South Africa -- Limpopo , Public health -- South Africa -- Limpopo , Apartheid -- South Africa -- Limpopo , Limpopo (South Africa) -- Economic conditions , Limpopo (South Africa) -- Social conditions , Limpopo (South Africa) -- Politics and government
- Language: English
- Type: Thesis , Doctoral , PhD (in Public Administration)
- Identifier: vital:11662 , http://hdl.handle.net/10353/d1007095 , Provincial government -- South Africa -- Limpopo , Human services -- South Africa -- Limpopo , Medical care -- South Africa -- Limpopo , Public health -- South Africa -- Limpopo , Apartheid -- South Africa -- Limpopo , Limpopo (South Africa) -- Economic conditions , Limpopo (South Africa) -- Social conditions , Limpopo (South Africa) -- Politics and government
- Description: The Republic of South Africa emerged as 'a product of a historical moment' and also as a reaction against imperialism, colonialism, racial discrimination and domination over the majority of black South Africans by the white minority. The democratic dispensation came into being also for the first time in its life in memorial for a long turbulent history followed by the general democratic elections held on 27th April 1994. The 1994 first general election liberated South Africa from the apartheid system and its subsequent primary objective was “… to transform South Africa into a non-racial and democratic society”. The new democratic government now looks politically different from the racist regime because the current government since 1994 has been, and to date still is, a truly and broadly representative of the South African citizens and also a transparent one, whereas the defunct apartheid government was characterized primarily by, among other things, the violation of human rights, denying black South Africans of any rights of basic services, no rights of owning property or land, no freedom of association and speeches and firmly practised discrimination which was detrimental to the majority of the black population groups in this country. According to the then President Nelson Mandela whilst addressing the ANC masses that were commemorating the eighty-third (83rd) anniversary of the African National Congress on the 8th January 1995, democracy entails “… a thorough-going process of transformation, of overcoming the political, social and economic legacy of apartheid colonialism, of racism, sexism and class oppression.” The government is still grappling with the challenge of ensuringa better life for all the citizens of this country (http://www.anc.org.za/show.php?doc=ancdocs/history/jan8-95html:1).
- Full Text:
- Date Issued: 2011
The efficacy and toxicological effects of aloe ferox mill. used in the management of constipation in Nkonkobe municipality of the Eastern Cape province, South Africa
- Authors: Wintola, Olubunmi Abosede A
- Date: 2011
- Subjects: Asphodelaceae -- South Africa -- Eastern Cape , Aloe -- South Africa -- Eastern Cape , Herbs -- Therapeutic use -- South Africa -- Eastern Cape , Medicinal plants -- South Africa -- Eastern Cape , Constipation -- South Africa -- Eastern Cape , Poisonous plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Ethnobotany)
- Identifier: vital:11882 , http://hdl.handle.net/10353/485 , Asphodelaceae -- South Africa -- Eastern Cape , Aloe -- South Africa -- Eastern Cape , Herbs -- Therapeutic use -- South Africa -- Eastern Cape , Medicinal plants -- South Africa -- Eastern Cape , Constipation -- South Africa -- Eastern Cape , Poisonous plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: Herbal remedies are commonly used in developing countries for the treatment of various diseases, including constipation. The rationale for utilizing medicinal plants for the treatment of diseases rested largely on the belief that they are safe and free of side effects. However, there is limited scientific evidence on the safety and efficacy of these herbal medicines to back up their continued therapeutic application. Aloe ferox Mill. (Aspodelaceae), known as Cape aloe, locally called ikhala is a medicinal plant used by the people of the Eastern Cape Province for the treatment of gastrointestinal problems and constipation. The plant is a perennial shrub with thick succulent leaves bearing brown thorns on the margin and bright orange flowers arranged in oval lanceolate. It occurs in all weather in bush veld, road side, gardens and undisturbed places. According to the ethnomedicinal information, A. ferox is used as purgative. This research project was therefore designed to evaluate its ability in the treatment of constipation and to investigate its possible toxicological property. At the beginning of this programme, a survey of plants used for the treatment of constipation in Nkonkobe Municipality of the Eastern Cape Province was carried out using a questionnaire, which was administered to herbalists, traditional healers and rural dwellers. The study revealed 10 plant species from 8 families that are used for the treatment of constipation in the province. Four plants, Aloe ferox Mill, Boophone distischa L.f Herb, Alepidea amatybica Eckl and Artemisia afra Jacq, were repeatedly mentioned. Based on the frequency of usage, perceived efficacy and availability to the rural dwellers and the traditional healers, Aloe ferox was the most commonly used of the plants for the treatment of constipation. The plant was thus, chosen for the study. The invivo laxative effect of the aqueous extract of Aloe ferox in the treatment of loperamide-induced constipation in Wistar rats was investigated at varying concentrations. The leaf extract at all the dosages investigated (50, 100 and 200 mg/kg body weight) improved intestinal motility, increased fecal volume and normalized body weight in the constipated rats. This was an indication of its laxative properties. However, the laxative property of the herb at 200 mg/kg body weight of the extract showed best efficacy and compares favourably well with senokot, a standard laxative drug. These findings have therefore, lent scientific credence to the folkloric use of the herb by the people of the Eastern Cape of South Africa as a laxative agent. Toxicological evaluation of aqueous leaf extract of Aloe ferox in loperamide-induced constipation was studied at 50, 100, and 200 mg/kg body weight. The oral administration of the extracts did not show any significant effect on the liver and kidney body weight ratios as well as the kidney and liver function indices. The extracts, at all the dosages investigated, did not alter the levels of creatinine, uric acid, urea, calcium and potassium ions. Similarly, the levels of total protein, albumin, bilirubin and gamma glutamyl transferase (GGT) were not significantly different from the control. The plant extract appreciably normalized the elevated activities of alkaline phosphatase (ALP), alanine transaminase (ALT) and aspartate transaminase (AST) in the untreated constipated rats following treatment with the extract. The extract did not show a significant effect on the hematological parameters except for the increase in the lymphocyte count in the untreated constipated rats, which was attenuated after administering the herb. ThThe available evidence in this study suggests that A. ferox may be safe as an oral remedy for constipation. Generally, the effect of the extract compared favourably well with senokot, a recommended drug for the treatment of constipation. The antioxidant activities against 1, 1 diphenyl- 2 picrylhydrazl (DPPH), 2,2’ – azinobis [3- ethylbenzothiazoline -6- sulfonic acid] diammonium salt (ABTS), hydrogen peroxide (H2O2), Nitric oxide (NO), lipid peroxidation and the ferric reducing agents were investigated spectrophotometrically. Alkaloids, saponins, tannins, total phenols, flavonoids, flavonols and proanthocyanidin were also determined to assess their effects on the antioxidants activity of this plant. The phytochemical content of the ethanol and acetone extracts were consistently high compared to other solvents extracts. The level of tannins was not significant (P > 0.05) as compared with other solvent extracts. The free radical scavenging activity of the extracts was high even at lower concentrations (0.025 mg/ml) except in DPPH and lipid peroxidation. The ferric reducing potential of the extracts was concentration dependent and significantly different from Vitamin C and butylated hydroxytoluene (BHT) that were used as standard drugs. The present study showed a high level of scavenging activity of the leaf extracts of Aloe ferox in all the solvent extracts. Both ethanol and methanolic extract showed potent antioxidant activities than acetone and aqueous extracts. The study indicated that the leaf extracts of Aloe ferox might be a valuable source of natural antioxidant for both medicine and food industries. A. ferox leaf consists of the gel, latex and mesophyll layer; however, the main active constituents of the latex and the leaf exudate of Aloe ferox are anthraquinones which are believed to be responsible for the laxative property. The laxative compound in Aloe ferox leaf extract was isolated and characterized by extracting the plant material in methanol and extract suspended in distilled water. Partitioning was done with n-hexane, ethyl acetate and butanol respectively and was co-spotted with the over-the-counter (OTC) laxative drugs. This led to the successive column chromatography and thin layer chromatography (TLC) of the most active ethyl acetate fraction on silica gel with benzene/ethanol/ammonia hydroxide (BEA: 90:10:1), ethyl acetate/methanol/water (EMW: 40:5.4:5) and chloroform/ethyl acetate/formic acid (CEF: 50:40:10) as the mobile phase. The successive chromatograph and TLC afforded two compounds of Rf 0.420 (blue) and 0.831 (yellow) with the over-the-counter (OTC) drugs. These compounds were not totally elucidated due to their small quantity and instability. However, hydroxyl (OH) and carboxyl groups (COOH) was established as common to the extracted compounds, which might be responsible for the biological activity recorded for the plant extract.
- Full Text:
- Date Issued: 2011
- Authors: Wintola, Olubunmi Abosede A
- Date: 2011
- Subjects: Asphodelaceae -- South Africa -- Eastern Cape , Aloe -- South Africa -- Eastern Cape , Herbs -- Therapeutic use -- South Africa -- Eastern Cape , Medicinal plants -- South Africa -- Eastern Cape , Constipation -- South Africa -- Eastern Cape , Poisonous plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD (Ethnobotany)
- Identifier: vital:11882 , http://hdl.handle.net/10353/485 , Asphodelaceae -- South Africa -- Eastern Cape , Aloe -- South Africa -- Eastern Cape , Herbs -- Therapeutic use -- South Africa -- Eastern Cape , Medicinal plants -- South Africa -- Eastern Cape , Constipation -- South Africa -- Eastern Cape , Poisonous plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
- Description: Herbal remedies are commonly used in developing countries for the treatment of various diseases, including constipation. The rationale for utilizing medicinal plants for the treatment of diseases rested largely on the belief that they are safe and free of side effects. However, there is limited scientific evidence on the safety and efficacy of these herbal medicines to back up their continued therapeutic application. Aloe ferox Mill. (Aspodelaceae), known as Cape aloe, locally called ikhala is a medicinal plant used by the people of the Eastern Cape Province for the treatment of gastrointestinal problems and constipation. The plant is a perennial shrub with thick succulent leaves bearing brown thorns on the margin and bright orange flowers arranged in oval lanceolate. It occurs in all weather in bush veld, road side, gardens and undisturbed places. According to the ethnomedicinal information, A. ferox is used as purgative. This research project was therefore designed to evaluate its ability in the treatment of constipation and to investigate its possible toxicological property. At the beginning of this programme, a survey of plants used for the treatment of constipation in Nkonkobe Municipality of the Eastern Cape Province was carried out using a questionnaire, which was administered to herbalists, traditional healers and rural dwellers. The study revealed 10 plant species from 8 families that are used for the treatment of constipation in the province. Four plants, Aloe ferox Mill, Boophone distischa L.f Herb, Alepidea amatybica Eckl and Artemisia afra Jacq, were repeatedly mentioned. Based on the frequency of usage, perceived efficacy and availability to the rural dwellers and the traditional healers, Aloe ferox was the most commonly used of the plants for the treatment of constipation. The plant was thus, chosen for the study. The invivo laxative effect of the aqueous extract of Aloe ferox in the treatment of loperamide-induced constipation in Wistar rats was investigated at varying concentrations. The leaf extract at all the dosages investigated (50, 100 and 200 mg/kg body weight) improved intestinal motility, increased fecal volume and normalized body weight in the constipated rats. This was an indication of its laxative properties. However, the laxative property of the herb at 200 mg/kg body weight of the extract showed best efficacy and compares favourably well with senokot, a standard laxative drug. These findings have therefore, lent scientific credence to the folkloric use of the herb by the people of the Eastern Cape of South Africa as a laxative agent. Toxicological evaluation of aqueous leaf extract of Aloe ferox in loperamide-induced constipation was studied at 50, 100, and 200 mg/kg body weight. The oral administration of the extracts did not show any significant effect on the liver and kidney body weight ratios as well as the kidney and liver function indices. The extracts, at all the dosages investigated, did not alter the levels of creatinine, uric acid, urea, calcium and potassium ions. Similarly, the levels of total protein, albumin, bilirubin and gamma glutamyl transferase (GGT) were not significantly different from the control. The plant extract appreciably normalized the elevated activities of alkaline phosphatase (ALP), alanine transaminase (ALT) and aspartate transaminase (AST) in the untreated constipated rats following treatment with the extract. The extract did not show a significant effect on the hematological parameters except for the increase in the lymphocyte count in the untreated constipated rats, which was attenuated after administering the herb. ThThe available evidence in this study suggests that A. ferox may be safe as an oral remedy for constipation. Generally, the effect of the extract compared favourably well with senokot, a recommended drug for the treatment of constipation. The antioxidant activities against 1, 1 diphenyl- 2 picrylhydrazl (DPPH), 2,2’ – azinobis [3- ethylbenzothiazoline -6- sulfonic acid] diammonium salt (ABTS), hydrogen peroxide (H2O2), Nitric oxide (NO), lipid peroxidation and the ferric reducing agents were investigated spectrophotometrically. Alkaloids, saponins, tannins, total phenols, flavonoids, flavonols and proanthocyanidin were also determined to assess their effects on the antioxidants activity of this plant. The phytochemical content of the ethanol and acetone extracts were consistently high compared to other solvents extracts. The level of tannins was not significant (P > 0.05) as compared with other solvent extracts. The free radical scavenging activity of the extracts was high even at lower concentrations (0.025 mg/ml) except in DPPH and lipid peroxidation. The ferric reducing potential of the extracts was concentration dependent and significantly different from Vitamin C and butylated hydroxytoluene (BHT) that were used as standard drugs. The present study showed a high level of scavenging activity of the leaf extracts of Aloe ferox in all the solvent extracts. Both ethanol and methanolic extract showed potent antioxidant activities than acetone and aqueous extracts. The study indicated that the leaf extracts of Aloe ferox might be a valuable source of natural antioxidant for both medicine and food industries. A. ferox leaf consists of the gel, latex and mesophyll layer; however, the main active constituents of the latex and the leaf exudate of Aloe ferox are anthraquinones which are believed to be responsible for the laxative property. The laxative compound in Aloe ferox leaf extract was isolated and characterized by extracting the plant material in methanol and extract suspended in distilled water. Partitioning was done with n-hexane, ethyl acetate and butanol respectively and was co-spotted with the over-the-counter (OTC) laxative drugs. This led to the successive column chromatography and thin layer chromatography (TLC) of the most active ethyl acetate fraction on silica gel with benzene/ethanol/ammonia hydroxide (BEA: 90:10:1), ethyl acetate/methanol/water (EMW: 40:5.4:5) and chloroform/ethyl acetate/formic acid (CEF: 50:40:10) as the mobile phase. The successive chromatograph and TLC afforded two compounds of Rf 0.420 (blue) and 0.831 (yellow) with the over-the-counter (OTC) drugs. These compounds were not totally elucidated due to their small quantity and instability. However, hydroxyl (OH) and carboxyl groups (COOH) was established as common to the extracted compounds, which might be responsible for the biological activity recorded for the plant extract.
- Full Text:
- Date Issued: 2011
The existence of the value premium on the Johannesburg Stock Exchange from 1972 to 2001 and extrapolation as explanation
- Authors: Beukes, Anna
- Date: 2011
- Subjects: Johannesburg Stock Exchange Stocks -- Prices -- South Africa Rational expectations (Economic theory) Investments -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:977 , http://hdl.handle.net/10962/d1002711
- Description: This study investigates the existence of the value premium in South Africa’s equity market, and tests extrapolation as a possible explanation for it. The value premium refers to the widely reported superior performance of share price returns of value companies compared to growth companies. The value premium represents an anomaly in mainstream rational finance theory, because it should not persist, unless it could be explained as the result of some composite form of risk. What is highly vexing is the fact that the value premium not only persists in most financial markets over a long period, but that the risk explanation cannot be upheld convincingly. This contributed to the rise of behavioral finance, an approach which introduces psychological factors to provide new explanations for financial phenomena. The behavioral finance explanation for the value premium observation is extrapolation (the tendency to project recent experience too far into the future). This study applies propositions and methods from behavioral finance to investigate the South African equity market. The existence of a value premium in South Africa was investigated by using twenty-nine years’ worth of accounting and share price data. The study employed one- and two-dimensional tests for portfolio formation, and tracked share price returns for up to five years after portfolio formation. The results indicated that a statistically and economically significant value premium existed in South Africa for the period between 1972 and 2001. Extrapolation as a potential explanation for the value premium observation was investigated by applying internationally used methods. Extrapolation was found to provide a robust explanation for the South African value premium.
- Full Text:
- Date Issued: 2011
- Authors: Beukes, Anna
- Date: 2011
- Subjects: Johannesburg Stock Exchange Stocks -- Prices -- South Africa Rational expectations (Economic theory) Investments -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:977 , http://hdl.handle.net/10962/d1002711
- Description: This study investigates the existence of the value premium in South Africa’s equity market, and tests extrapolation as a possible explanation for it. The value premium refers to the widely reported superior performance of share price returns of value companies compared to growth companies. The value premium represents an anomaly in mainstream rational finance theory, because it should not persist, unless it could be explained as the result of some composite form of risk. What is highly vexing is the fact that the value premium not only persists in most financial markets over a long period, but that the risk explanation cannot be upheld convincingly. This contributed to the rise of behavioral finance, an approach which introduces psychological factors to provide new explanations for financial phenomena. The behavioral finance explanation for the value premium observation is extrapolation (the tendency to project recent experience too far into the future). This study applies propositions and methods from behavioral finance to investigate the South African equity market. The existence of a value premium in South Africa was investigated by using twenty-nine years’ worth of accounting and share price data. The study employed one- and two-dimensional tests for portfolio formation, and tracked share price returns for up to five years after portfolio formation. The results indicated that a statistically and economically significant value premium existed in South Africa for the period between 1972 and 2001. Extrapolation as a potential explanation for the value premium observation was investigated by applying internationally used methods. Extrapolation was found to provide a robust explanation for the South African value premium.
- Full Text:
- Date Issued: 2011
The impact of toys as educative curriculum material on pre-service primary school Natural Sciences teachers' understanding of energy
- Authors: Meiring, Leslie Frank
- Date: 2011
- Subjects: Educational toys , Science -- Study and teaching (Primary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9477 , http://hdl.handle.net/10948/1332 , Educational toys , Science -- Study and teaching (Primary) -- South Africa
- Description: In this study toys were used as educative curriculum material in an intervention on the topic of energy aimed at Intermediate Phase pre-service science teachers (n= 87) registered for a BEd degree at the Nelson Mandela Metropolitan University, South Africa. The intervention consisted of, amongst other elements, lectures, assignments and toy workshops, with the latter being a key driver in the process. The choice of toys as the educative curriculum material was informed by the fact that there is a huge variety of simple, reasonably priced and easily procured toys that are suitable to demonstrate the concept of energy from both theoretical and practical perspectives. The conclusions that can be drawn from the study are that the use of toys in the preparation of pre-service primary school teachers has the potential to substantially improve their subject content knowledge (SCK), pedagogical content knowledge (PCK), and their confidence related to these two constructs with respect to their understandings of energy. The data generated also suggest that when appropriate educative curriculum materials are integrated into a topic in science-teacher education, there may be a substantial positive impact on pre-service teachers‘ confidence in both their understanding of the science content and their perceptions of their ability to teach this content. An additional finding of the study was that, despite its popularity, status and usefulness over many years, the Science Teacher Efficacy Belief Instrument (STEBI-B) shows low sensitivity to measuring changes in efficacy as a consequence of the so-called ‗ceiling effect‘. The ceiling effect is a result of initial high scores which provide little opportunity to show iii substantial positive change as a result of an appropriate intervention that is designed to improve efficacy. While this study did not directly address this lacuna in STEBI-B, it made use of an innovative descriptive statistic, ‗percentage gain of potential‘, in an attempt to describe and interpret even small changes in efficacy as measured by STEBI-B.
- Full Text:
- Date Issued: 2011
- Authors: Meiring, Leslie Frank
- Date: 2011
- Subjects: Educational toys , Science -- Study and teaching (Primary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9477 , http://hdl.handle.net/10948/1332 , Educational toys , Science -- Study and teaching (Primary) -- South Africa
- Description: In this study toys were used as educative curriculum material in an intervention on the topic of energy aimed at Intermediate Phase pre-service science teachers (n= 87) registered for a BEd degree at the Nelson Mandela Metropolitan University, South Africa. The intervention consisted of, amongst other elements, lectures, assignments and toy workshops, with the latter being a key driver in the process. The choice of toys as the educative curriculum material was informed by the fact that there is a huge variety of simple, reasonably priced and easily procured toys that are suitable to demonstrate the concept of energy from both theoretical and practical perspectives. The conclusions that can be drawn from the study are that the use of toys in the preparation of pre-service primary school teachers has the potential to substantially improve their subject content knowledge (SCK), pedagogical content knowledge (PCK), and their confidence related to these two constructs with respect to their understandings of energy. The data generated also suggest that when appropriate educative curriculum materials are integrated into a topic in science-teacher education, there may be a substantial positive impact on pre-service teachers‘ confidence in both their understanding of the science content and their perceptions of their ability to teach this content. An additional finding of the study was that, despite its popularity, status and usefulness over many years, the Science Teacher Efficacy Belief Instrument (STEBI-B) shows low sensitivity to measuring changes in efficacy as a consequence of the so-called ‗ceiling effect‘. The ceiling effect is a result of initial high scores which provide little opportunity to show iii substantial positive change as a result of an appropriate intervention that is designed to improve efficacy. While this study did not directly address this lacuna in STEBI-B, it made use of an innovative descriptive statistic, ‗percentage gain of potential‘, in an attempt to describe and interpret even small changes in efficacy as measured by STEBI-B.
- Full Text:
- Date Issued: 2011
The implementation of the right to education in South Africa and Nigeria
- Authors: Taiwo, Elijah Adewale
- Date: 2011
- Subjects: Right to education -- South Africa , Right to education -- Nigeria , Human rights -- Study and teaching , Comparative education , Education -- South Africa , Education -- Nigeria , Right to education -- Law and legislation -- South Africa , Right to education -- Law and legislation -- Nigeria
- Language: English
- Type: Thesis , Doctoral , LLD
- Identifier: vital:10279 , http://hdl.handle.net/10948/1392 , Right to education -- South Africa , Right to education -- Nigeria , Human rights -- Study and teaching , Comparative education , Education -- South Africa , Education -- Nigeria , Right to education -- Law and legislation -- South Africa , Right to education -- Law and legislation -- Nigeria
- Description: The thesis examines the right to education in South Africa and Nigeria. It presents the right to education as an empowerment right which is given a wide recognition in a number of important international and regional human rights instruments as well as in national constitutions. It asserts that the right to education is a right with a multiplying effect in the sense that where it is effectively guaranteed, it enhances the enjoyment of all other rights and freedoms, and when it is denied, it precludes the enjoyment of many other human rights. The thesis examines the provisions of relevant international and regional human rights instruments to assess the adequacy of a framework that applies to South Africa and Nigeria's obligations regarding the right to education. It argues that those instruments impose obligations on all the States to make primary, secondary and higher levels of education available, accessible, acceptable and adaptable to all in their territories. It argues that by having ratified those international agreements in which the right to education is protected, both South Africa and Nigeria assume obligations under international law, enjoining them to realise the right to education and to respect freedoms in education. The study adopts a comparative approach and relies on primary and secondary sources of data; the data is subjected to an in-depth content analysis. The focus of the comparison is on whether the South African's position regarding the right to education can inform Nigeria's interpretation of the right to education. The reason being that the Nigerian Constitution does not provide for the right to education as a basic right as exists in South Africa. The Nigerian Constitution categorised the right to education under “fundamental objectives and directive principles” which are non-justiciable. In this sense, the thesis argues that the legal classification of the right to education, to a large extent, affects its realisation in Nigeria. It suggests that an important area where Nigeria could learn from South Africa is the issue of justiciability and constitutionalising the right to education as well as other socio-economic rights. In terms of implementation, the thesis submits that despite the international obligations and commitments to provide education for all, there is a significant gap between what is stipulated and the practical realities in the two countries. It argues that the right to education is more than a mere school attendance, how well a learner progresses in school is equally important. It posits that the high failure rates and the progressive slide in students' performances in schools xx examinations as shown in the study illustrate the poor quality and falling standard of education in the two countries. South Africa enjoys one of the highest rates of formal school enrolment of any developing country, yet the link between access and success is also weak in the South African schools just as in Nigerian schools. Inadequate planning, poor implementation of policies, lack of adequate resources and commitments are identified as the prime factors hampering the implementation of the right to education in both countries. Solving these problems and making the right to education realisable call for a renewed government commitments and investment of appropriate human and financial resources on education. This also requires a strong political will as well as concerted efforts of all the various actors in the educational sector in the two countries.
- Full Text:
- Date Issued: 2011
- Authors: Taiwo, Elijah Adewale
- Date: 2011
- Subjects: Right to education -- South Africa , Right to education -- Nigeria , Human rights -- Study and teaching , Comparative education , Education -- South Africa , Education -- Nigeria , Right to education -- Law and legislation -- South Africa , Right to education -- Law and legislation -- Nigeria
- Language: English
- Type: Thesis , Doctoral , LLD
- Identifier: vital:10279 , http://hdl.handle.net/10948/1392 , Right to education -- South Africa , Right to education -- Nigeria , Human rights -- Study and teaching , Comparative education , Education -- South Africa , Education -- Nigeria , Right to education -- Law and legislation -- South Africa , Right to education -- Law and legislation -- Nigeria
- Description: The thesis examines the right to education in South Africa and Nigeria. It presents the right to education as an empowerment right which is given a wide recognition in a number of important international and regional human rights instruments as well as in national constitutions. It asserts that the right to education is a right with a multiplying effect in the sense that where it is effectively guaranteed, it enhances the enjoyment of all other rights and freedoms, and when it is denied, it precludes the enjoyment of many other human rights. The thesis examines the provisions of relevant international and regional human rights instruments to assess the adequacy of a framework that applies to South Africa and Nigeria's obligations regarding the right to education. It argues that those instruments impose obligations on all the States to make primary, secondary and higher levels of education available, accessible, acceptable and adaptable to all in their territories. It argues that by having ratified those international agreements in which the right to education is protected, both South Africa and Nigeria assume obligations under international law, enjoining them to realise the right to education and to respect freedoms in education. The study adopts a comparative approach and relies on primary and secondary sources of data; the data is subjected to an in-depth content analysis. The focus of the comparison is on whether the South African's position regarding the right to education can inform Nigeria's interpretation of the right to education. The reason being that the Nigerian Constitution does not provide for the right to education as a basic right as exists in South Africa. The Nigerian Constitution categorised the right to education under “fundamental objectives and directive principles” which are non-justiciable. In this sense, the thesis argues that the legal classification of the right to education, to a large extent, affects its realisation in Nigeria. It suggests that an important area where Nigeria could learn from South Africa is the issue of justiciability and constitutionalising the right to education as well as other socio-economic rights. In terms of implementation, the thesis submits that despite the international obligations and commitments to provide education for all, there is a significant gap between what is stipulated and the practical realities in the two countries. It argues that the right to education is more than a mere school attendance, how well a learner progresses in school is equally important. It posits that the high failure rates and the progressive slide in students' performances in schools xx examinations as shown in the study illustrate the poor quality and falling standard of education in the two countries. South Africa enjoys one of the highest rates of formal school enrolment of any developing country, yet the link between access and success is also weak in the South African schools just as in Nigerian schools. Inadequate planning, poor implementation of policies, lack of adequate resources and commitments are identified as the prime factors hampering the implementation of the right to education in both countries. Solving these problems and making the right to education realisable call for a renewed government commitments and investment of appropriate human and financial resources on education. This also requires a strong political will as well as concerted efforts of all the various actors in the educational sector in the two countries.
- Full Text:
- Date Issued: 2011
The influence of genetic relatedness on sociality and demography of female African elephants
- Authors: Munishi, Linus Kasian
- Date: 2011
- Subjects: African elephant , Wildlife conservation , Elephants -- Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10711 , http://hdl.handle.net/10948/d1011612 , African elephant , Wildlife conservation , Elephants -- Africa
- Description: Many elephant populations across Africa were or are being devastated by poaching and habitat loss, making population and range size for the species important issues of conservation concern in elephant ranging areas, including Tarangire National Park (TNP). Poaching and/or overhunting are known to have direct effects on the demography of elephant populations. The current understanding of the indirect effects of poaching on the sociality and demography of elephant populations is relatively poor, both at the group and an individual level. In this thesis the importance of genetic relatedness (as influenced by poaching) on sociality and demography of the female elephants was studied, using a combination of genetic, observation of behaviour and two decades of demography data collected from the northern subpopulation of TNP. I investigated and characterized the relatedness categories within elephant groups. Using a conceptual model for group size analysis in aggregation economies, I hypothesized that elephant populations subject to social disruptions due to poaching would exhibit characteristics of the free entry model, whereas more stable, closed populations would better fit the group-controlled model. I present a rare quantitative analysis of genetic relatedness and group size patterns among groups of adult female elephants in two wild populations: one in Tarangire National Park (TNP), Tanzania, and another in Addo Elephant National Park (AENP), South Africa. I demonstrate that the group size in African elephant populations is governed by genetic relatedness, and that poaching/overhunting has a significant influence upon the apparent group formation and size in elephants. I then focused on the effect of relatedness on agonistic interactions between adult females. I hypothesized that individual-based aggressive interactions among adult female African elephants would vary according to degree of kinship, with closely related dyads showing less aggression towards each other in resource-limited environments, thereby leading to indirect fitness benefits for individuals. As predicted, females did not show agonistic interactions to their close kin most often, and the frequency and intensity of aggressive interactions was inversely related to the degree of relatedness of the interactants. The effect of group relatedness and structure on reproductive success of individual female African elephant in TNP was also investigated. Adult female reproductive success was significantly influenced by within- group relatedness and structure. Higher reproductive success (with higher frequency of calf production and survival and more female calves produced) were more evident in the closely related groups than groups with low relatedness, suggesting that females from genetically disrupted groups are less likely to be reproductive than those in closely related groups. The possibility of negative effects of poaching on the subsequent generation of poached adult females and the alternative of a positive demographic response through reduced density was assessed by analysing the demographic patterns of the first generation (F1) females of prime-aged adult female African elephants in TNP using within- group relatedness and size. I also compared vital rate (age of first birth and interbirth interval) responses of first generation (F1) cows from Tarangire (poached) elephants with other females from poached (Northern Luangwa National Park, Zambia) and unpoached (Amboseli National Park, Kenya and Addo Elephant National Park, South Africa) populations. Group relatedness had no significant effect on sex ratio of the F1 cows‟ calves. There was a significant difference between the mean age of first birth and interbirth interval of F1 cows from the two (poached, Tarangire and unpoached, Amboseli National Park) elephant populations, suggesting that elephant populations reduced by poaching to low levels show an increase vigour through release from density constraints. Based on these results, the broader implications of secondary effects of poaching on elephant populations are critically evaluated. Also the importance of understanding the consequences of these effects is highlighted in light of other elephant conservation and management approaches. This understanding is useful in making conservation and management decisions for elephants and other biodiversity.
- Full Text:
- Date Issued: 2011
- Authors: Munishi, Linus Kasian
- Date: 2011
- Subjects: African elephant , Wildlife conservation , Elephants -- Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10711 , http://hdl.handle.net/10948/d1011612 , African elephant , Wildlife conservation , Elephants -- Africa
- Description: Many elephant populations across Africa were or are being devastated by poaching and habitat loss, making population and range size for the species important issues of conservation concern in elephant ranging areas, including Tarangire National Park (TNP). Poaching and/or overhunting are known to have direct effects on the demography of elephant populations. The current understanding of the indirect effects of poaching on the sociality and demography of elephant populations is relatively poor, both at the group and an individual level. In this thesis the importance of genetic relatedness (as influenced by poaching) on sociality and demography of the female elephants was studied, using a combination of genetic, observation of behaviour and two decades of demography data collected from the northern subpopulation of TNP. I investigated and characterized the relatedness categories within elephant groups. Using a conceptual model for group size analysis in aggregation economies, I hypothesized that elephant populations subject to social disruptions due to poaching would exhibit characteristics of the free entry model, whereas more stable, closed populations would better fit the group-controlled model. I present a rare quantitative analysis of genetic relatedness and group size patterns among groups of adult female elephants in two wild populations: one in Tarangire National Park (TNP), Tanzania, and another in Addo Elephant National Park (AENP), South Africa. I demonstrate that the group size in African elephant populations is governed by genetic relatedness, and that poaching/overhunting has a significant influence upon the apparent group formation and size in elephants. I then focused on the effect of relatedness on agonistic interactions between adult females. I hypothesized that individual-based aggressive interactions among adult female African elephants would vary according to degree of kinship, with closely related dyads showing less aggression towards each other in resource-limited environments, thereby leading to indirect fitness benefits for individuals. As predicted, females did not show agonistic interactions to their close kin most often, and the frequency and intensity of aggressive interactions was inversely related to the degree of relatedness of the interactants. The effect of group relatedness and structure on reproductive success of individual female African elephant in TNP was also investigated. Adult female reproductive success was significantly influenced by within- group relatedness and structure. Higher reproductive success (with higher frequency of calf production and survival and more female calves produced) were more evident in the closely related groups than groups with low relatedness, suggesting that females from genetically disrupted groups are less likely to be reproductive than those in closely related groups. The possibility of negative effects of poaching on the subsequent generation of poached adult females and the alternative of a positive demographic response through reduced density was assessed by analysing the demographic patterns of the first generation (F1) females of prime-aged adult female African elephants in TNP using within- group relatedness and size. I also compared vital rate (age of first birth and interbirth interval) responses of first generation (F1) cows from Tarangire (poached) elephants with other females from poached (Northern Luangwa National Park, Zambia) and unpoached (Amboseli National Park, Kenya and Addo Elephant National Park, South Africa) populations. Group relatedness had no significant effect on sex ratio of the F1 cows‟ calves. There was a significant difference between the mean age of first birth and interbirth interval of F1 cows from the two (poached, Tarangire and unpoached, Amboseli National Park) elephant populations, suggesting that elephant populations reduced by poaching to low levels show an increase vigour through release from density constraints. Based on these results, the broader implications of secondary effects of poaching on elephant populations are critically evaluated. Also the importance of understanding the consequences of these effects is highlighted in light of other elephant conservation and management approaches. This understanding is useful in making conservation and management decisions for elephants and other biodiversity.
- Full Text:
- Date Issued: 2011
The role of small antelope in ecosystem functioning in the Matobo Hills, Zimbabwe
- Authors: Lunt, Nicola
- Date: 2011
- Subjects: Antelopes -- Zimbabwe -- Rhodes Matopos National Park Ecosystem health -- Zimbabwe -- Rhodes Matopos National Park Forest ecology -- Zimbabwe -- Rhodes Matopos National Park Savanna ecology -- Zimbabwe -- Rhodes Matopos National Park Woody plants -- Effect of fires on -- Zimbabwe -- Rhodes Matopos National Park Duikers -- Zimbabwe -- Rhodes Matopos National Park Bushbuck -- Zimbabwe -- Rhodes Matopos National Park Greater kudu -- Zimbabwe -- Rhodes Matopos National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5760 , http://hdl.handle.net/10962/d1005448
- Description: The 28-month study assessed the impacts of five syntopic medium-sized mammalian browsers and one fire event in a woodland savanna in the Matobo Hills, Zimbabwe. Aspects of herbivory, mechanical pressures, seed dispersal and nutrient cycling were investigated for three species of small antelope (common duiker [Sylvicapra grimmia]1, klipspringer [Oreotragus oreotragus] and steenbok [Raphicerus campestris]) and two medium-sized species (bushbuck [Tragelaphus scriptus] and greater kudu [T. strepsiceros]). Focusing on Burkea africana2 woodland, in a system that does not include elephant (Loxodonta africana), effects of browsing antelope on woody and herbaceous vegetation development were investigated using exclusion plots. Browsers regulated woody plant cover (measured as basal stem area), with smaller antelope having a greater impact than larger species. This was linked to feeding height, feeding selectivity and mechanical pressures (e.g. twig breakage and trampling). Fire caused an initial reduction in above-ground standing biomass, but in the presence of fauna, pre-fire equilibria were attained within 15 months. In antelope exclosures, herbaceous biomass increased and woody biomass decreased following fire. Responses by woody vegetation to browsing varied among species, with highly palatable species typically exhibiting compensatory regrowth. Woody species richness and abundance (especially of palatable species) increased in the absence of browsers, but species richness of the herbaceous layer was promoted by moderate disturbance (trampling or fire). Faecal deposition behaviour, primarily the use of latrines by small antelope, resulted in localised soil enrichment within defended territories. Decomposition rates (and therefore return of nutrients to the soil) varied among species and seasons, due to defecation site selection, accessibility to decomposers and desiccation rates of faecal pellets. Controlled seed germination experiments indicated that ingestion by small antelope enhances germination rates of large, hard-seeded fruits such as Sclerocarya birrea. However, germination of savanna seeds may require multiple cues. This study demonstrated the critical roles of small antelope in ecosystem functioning, and highlights the importance of the less visible impacts of frequently overlooked smaller mammalian herbivores. Perturbations to the faunal community, especially small antelope, are predicted to have substantial impacts on woody plant cover.
- Full Text:
- Date Issued: 2011
- Authors: Lunt, Nicola
- Date: 2011
- Subjects: Antelopes -- Zimbabwe -- Rhodes Matopos National Park Ecosystem health -- Zimbabwe -- Rhodes Matopos National Park Forest ecology -- Zimbabwe -- Rhodes Matopos National Park Savanna ecology -- Zimbabwe -- Rhodes Matopos National Park Woody plants -- Effect of fires on -- Zimbabwe -- Rhodes Matopos National Park Duikers -- Zimbabwe -- Rhodes Matopos National Park Bushbuck -- Zimbabwe -- Rhodes Matopos National Park Greater kudu -- Zimbabwe -- Rhodes Matopos National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5760 , http://hdl.handle.net/10962/d1005448
- Description: The 28-month study assessed the impacts of five syntopic medium-sized mammalian browsers and one fire event in a woodland savanna in the Matobo Hills, Zimbabwe. Aspects of herbivory, mechanical pressures, seed dispersal and nutrient cycling were investigated for three species of small antelope (common duiker [Sylvicapra grimmia]1, klipspringer [Oreotragus oreotragus] and steenbok [Raphicerus campestris]) and two medium-sized species (bushbuck [Tragelaphus scriptus] and greater kudu [T. strepsiceros]). Focusing on Burkea africana2 woodland, in a system that does not include elephant (Loxodonta africana), effects of browsing antelope on woody and herbaceous vegetation development were investigated using exclusion plots. Browsers regulated woody plant cover (measured as basal stem area), with smaller antelope having a greater impact than larger species. This was linked to feeding height, feeding selectivity and mechanical pressures (e.g. twig breakage and trampling). Fire caused an initial reduction in above-ground standing biomass, but in the presence of fauna, pre-fire equilibria were attained within 15 months. In antelope exclosures, herbaceous biomass increased and woody biomass decreased following fire. Responses by woody vegetation to browsing varied among species, with highly palatable species typically exhibiting compensatory regrowth. Woody species richness and abundance (especially of palatable species) increased in the absence of browsers, but species richness of the herbaceous layer was promoted by moderate disturbance (trampling or fire). Faecal deposition behaviour, primarily the use of latrines by small antelope, resulted in localised soil enrichment within defended territories. Decomposition rates (and therefore return of nutrients to the soil) varied among species and seasons, due to defecation site selection, accessibility to decomposers and desiccation rates of faecal pellets. Controlled seed germination experiments indicated that ingestion by small antelope enhances germination rates of large, hard-seeded fruits such as Sclerocarya birrea. However, germination of savanna seeds may require multiple cues. This study demonstrated the critical roles of small antelope in ecosystem functioning, and highlights the importance of the less visible impacts of frequently overlooked smaller mammalian herbivores. Perturbations to the faunal community, especially small antelope, are predicted to have substantial impacts on woody plant cover.
- Full Text:
- Date Issued: 2011
The role of the mite Orthogalumna terebrantis in the biological control programme for water hyacinth, Eichhornia crassipes, in South Africa
- Authors: Marlin, Danica
- Date: 2011
- Subjects: Water hyacinth -- Biological control -- South Africa Aquatic weeds -- South Africa Invasive plants -- South Africa Mites -- South Africa Mites as biological pest control agents -- South Africa Biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5762 , http://hdl.handle.net/10962/d1005450
- Description: Water hyacinth (Eichhornia crassipes) is an aquatic macrophyte originating from the Amazon basin. Due to its beautiful appearance it has been introduced into numerous countries across the world as an ornamental pond plant. It was introduced into South Africa in the early 1900s and has since reached pest proportions in many of the country’s fresh water bodies, causing significant economic and ecological losses. It is now considered to be the worst aquatic weed in South Africa. Efforts to control the spread of the weed began in the early 1970s and there have been some successes. Biological control has been used widely as an alternative to mechanical and chemical controls because it is cost-effective, self-sustaining and environmentally friendly. To date, six biological control agents have been introduced onto water hyacinth in South Africa. However, due to factors such as cold winter temperatures and interference from chemical control, the agent populations are occasionally knocked-down and thus the impact of biological control on the weed population is variable. In addition, many South African water systems are highly eutrophic, and in these systems the plant growth may be accelerated to such an extent that the negative impact of the agents’ herbivory is mitigated. One of the agents established on the weed is the galumnid mite Orthogalumna terebrantis, which originates from Uruguay. In South Africa, the mite was initially discovered on two water hyacinth infestations in the Mpumalanga Province in 1989 and it is now established at 17 sites across the country. Many biological control researchers believe that the mite is a good biological control agent but, prior to this thesis, little quantitative data existed to confirm the belief. Thus, this thesis is a post-release evaluation of O. terebrantis in which various aspects of the mite-plant relationship were investigated to determine the efficacy of the mite and thus better understand the role of the mite in the biological control programme of water hyacinth in South Africa. From laboratory experiments, in which mite densities were lower than densities occurring in the field, it was found that water hyacinth growth is largely unaffected by mite herbivory, except possibly at very high mite densities. When grown in high nutrient conditions the growth of the plant is so great that any affect the mite has is nullified. Plant growth is thus more affected by nutrients than by mite herbivory. However, mite feeding was also influenced by water nutrient levels and mite herbivory was greatest on plants grown in high nutrient conditions. The presence of the mite had a positive effect on the performance of the mirid Eccritotarsus catarinensis, such that the interactions of the two agents together had a greater negative impact on the plant’s growth than the individual agents had alone. Furthermore, water hyacinth physiological parameters, such as the plant’s photosynthetic ability, were negatively impacted by the mite, even at the very low mite densities used in the study. Plant growth rate is dependent on photosynthetic ability i.e. the rate of photosynthesis, and thus a decrease in the plant’s photosynthetic ability will eventually be translated into decreased plant growth rates which would ultimately result in the overall reduction of water hyacinth populations. In addition, temperature tolerance studies showed that the mite was tolerant of low temperatures. The mite already occurs at some of the coldest sites in South Africa. Therefore, the mite should be able to establish at all of the water hyacinth infestations in the country, but because it is a poor disperser it is unlikely to establish at new sites without human intervention. It is suggested that the mite be used as an additional biological control agent at sites where it does not yet occur, specifically at cold sites where some of the other, less cold-tolerant, agents have failed to establish. Finally, conditions of where, how many and how often the mite should be distributed to water hyacinth infestation in South Africa are discussed.
- Full Text:
- Date Issued: 2011
- Authors: Marlin, Danica
- Date: 2011
- Subjects: Water hyacinth -- Biological control -- South Africa Aquatic weeds -- South Africa Invasive plants -- South Africa Mites -- South Africa Mites as biological pest control agents -- South Africa Biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5762 , http://hdl.handle.net/10962/d1005450
- Description: Water hyacinth (Eichhornia crassipes) is an aquatic macrophyte originating from the Amazon basin. Due to its beautiful appearance it has been introduced into numerous countries across the world as an ornamental pond plant. It was introduced into South Africa in the early 1900s and has since reached pest proportions in many of the country’s fresh water bodies, causing significant economic and ecological losses. It is now considered to be the worst aquatic weed in South Africa. Efforts to control the spread of the weed began in the early 1970s and there have been some successes. Biological control has been used widely as an alternative to mechanical and chemical controls because it is cost-effective, self-sustaining and environmentally friendly. To date, six biological control agents have been introduced onto water hyacinth in South Africa. However, due to factors such as cold winter temperatures and interference from chemical control, the agent populations are occasionally knocked-down and thus the impact of biological control on the weed population is variable. In addition, many South African water systems are highly eutrophic, and in these systems the plant growth may be accelerated to such an extent that the negative impact of the agents’ herbivory is mitigated. One of the agents established on the weed is the galumnid mite Orthogalumna terebrantis, which originates from Uruguay. In South Africa, the mite was initially discovered on two water hyacinth infestations in the Mpumalanga Province in 1989 and it is now established at 17 sites across the country. Many biological control researchers believe that the mite is a good biological control agent but, prior to this thesis, little quantitative data existed to confirm the belief. Thus, this thesis is a post-release evaluation of O. terebrantis in which various aspects of the mite-plant relationship were investigated to determine the efficacy of the mite and thus better understand the role of the mite in the biological control programme of water hyacinth in South Africa. From laboratory experiments, in which mite densities were lower than densities occurring in the field, it was found that water hyacinth growth is largely unaffected by mite herbivory, except possibly at very high mite densities. When grown in high nutrient conditions the growth of the plant is so great that any affect the mite has is nullified. Plant growth is thus more affected by nutrients than by mite herbivory. However, mite feeding was also influenced by water nutrient levels and mite herbivory was greatest on plants grown in high nutrient conditions. The presence of the mite had a positive effect on the performance of the mirid Eccritotarsus catarinensis, such that the interactions of the two agents together had a greater negative impact on the plant’s growth than the individual agents had alone. Furthermore, water hyacinth physiological parameters, such as the plant’s photosynthetic ability, were negatively impacted by the mite, even at the very low mite densities used in the study. Plant growth rate is dependent on photosynthetic ability i.e. the rate of photosynthesis, and thus a decrease in the plant’s photosynthetic ability will eventually be translated into decreased plant growth rates which would ultimately result in the overall reduction of water hyacinth populations. In addition, temperature tolerance studies showed that the mite was tolerant of low temperatures. The mite already occurs at some of the coldest sites in South Africa. Therefore, the mite should be able to establish at all of the water hyacinth infestations in the country, but because it is a poor disperser it is unlikely to establish at new sites without human intervention. It is suggested that the mite be used as an additional biological control agent at sites where it does not yet occur, specifically at cold sites where some of the other, less cold-tolerant, agents have failed to establish. Finally, conditions of where, how many and how often the mite should be distributed to water hyacinth infestation in South Africa are discussed.
- Full Text:
- Date Issued: 2011
The role of the press in political conflicts in Kenya : a case study of the performance of the nation and the East African Standard Newspapers
- Authors: Nyambuga, Charles Ongadi
- Date: 2011
- Subjects: Press and politics -- Kenya , Government and the press -- Kenya , Mass media -- Political aspects , Kenya -- Politics and government
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:16135 , http://hdl.handle.net/10948/1449 , Press and politics -- Kenya , Government and the press -- Kenya , Mass media -- Political aspects , Kenya -- Politics and government
- Description: This study focuses on the role of the press in violent political conflicts in Kenya in the period that preceded the 2005 referendum on the draft constitution. Based on media reports, six major thematic areas of concern emerged during constitution making. These were: land tenure, devolution of power, the executive, the legislature, the Bill of Rights, and the provincial administration. These sections of the draft constitution caused a remarkable divergence of opinion. The citizens either supported or opposed the draft constitution on the basis of how the draft had treated those sections in the draft constitution. Besides the major thematic areas, newspapers regularly focused and reported on ethnicity, violence, political leaders‟ utterances, the process of constitution making, and political conflicts. Three main objectives guided the study. The first objective focused on the relationship between media content and different levels of political conflict. The influence of media content and how these may have led to high political conflict, medium political conflict, low political conflict and no political conflict, are tested in this study. The second objective highlighted the kind of coverage that the draft constitution got during the period that preceded the referendum in November, 2005. This objective facilitated interrogation of media content and whether media content focused on aspects of the draft constitution such as land ownership, the executive, devolution, the legislature and religion, as highlighted in the draft constitution of Kenya 2005. The third objective examined the thematic emphasis that the media undertook in the period that preceded the referendum. The themes that were dominant in the period before the referendum could have impacted on readers' perceptions of the critical issues that could have informed the voters' decisions. Three primary questions were addressed in the study: Firstly, was there a link between media content and different levels of political conflict in weak democracies such as Kenya? Secondly, did media content influence ethnicity and did it encourage ethnic conflict in diverse societies? Finally, what were the key thematic areas of coverage by the press, and how were they used during the referendum? In order to study these research objectives, I used a combination of theories to enhance understanding of the interplay between media content and audience in the society. The theories are: agenda setting, two-step flow, priming, framing, and the public sphere. The study adopts a triangulation convergence design in mixed- methods research that involves both qualitative and quantitative methods. A structured questionnaire and content analysis were used to seek responses to the research questions of the study and to meet the stated objectives. The research revealed that the two newspapers under investigation, namely the East African Standard and the Nation, provided more coverage to issues that were not central to the content of the draft constitution, such as political leaders' utterances, violence, ethnicity, and the process of constitution making. This showed that the newspapers tended to sensationalise issues instead of providing objective coverage of political matters. These newspapers used their opinion pages to educate their readers on how the referendum was turning violent. The theme of political leaders' utterances is closely linked to that of violence. This suggests that the violence was influenced by some of the leaders' statements. These utterances, and more so those that touched on ethnicity, could therefore have been a potential cause of the ensuing political conflicts during the 2005 referendum on the draft constitution. The findings reveal that newspaper editors tended to focus on political conflict at the expense of the actual content of the draft constitution. This would have provided insight and knowledge on the document and avoided sensational reporting, which could have contributed to violent political conflicts during the period that preceded the referendum on the draft constitution of Kenya.
- Full Text:
- Date Issued: 2011
- Authors: Nyambuga, Charles Ongadi
- Date: 2011
- Subjects: Press and politics -- Kenya , Government and the press -- Kenya , Mass media -- Political aspects , Kenya -- Politics and government
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:16135 , http://hdl.handle.net/10948/1449 , Press and politics -- Kenya , Government and the press -- Kenya , Mass media -- Political aspects , Kenya -- Politics and government
- Description: This study focuses on the role of the press in violent political conflicts in Kenya in the period that preceded the 2005 referendum on the draft constitution. Based on media reports, six major thematic areas of concern emerged during constitution making. These were: land tenure, devolution of power, the executive, the legislature, the Bill of Rights, and the provincial administration. These sections of the draft constitution caused a remarkable divergence of opinion. The citizens either supported or opposed the draft constitution on the basis of how the draft had treated those sections in the draft constitution. Besides the major thematic areas, newspapers regularly focused and reported on ethnicity, violence, political leaders‟ utterances, the process of constitution making, and political conflicts. Three main objectives guided the study. The first objective focused on the relationship between media content and different levels of political conflict. The influence of media content and how these may have led to high political conflict, medium political conflict, low political conflict and no political conflict, are tested in this study. The second objective highlighted the kind of coverage that the draft constitution got during the period that preceded the referendum in November, 2005. This objective facilitated interrogation of media content and whether media content focused on aspects of the draft constitution such as land ownership, the executive, devolution, the legislature and religion, as highlighted in the draft constitution of Kenya 2005. The third objective examined the thematic emphasis that the media undertook in the period that preceded the referendum. The themes that were dominant in the period before the referendum could have impacted on readers' perceptions of the critical issues that could have informed the voters' decisions. Three primary questions were addressed in the study: Firstly, was there a link between media content and different levels of political conflict in weak democracies such as Kenya? Secondly, did media content influence ethnicity and did it encourage ethnic conflict in diverse societies? Finally, what were the key thematic areas of coverage by the press, and how were they used during the referendum? In order to study these research objectives, I used a combination of theories to enhance understanding of the interplay between media content and audience in the society. The theories are: agenda setting, two-step flow, priming, framing, and the public sphere. The study adopts a triangulation convergence design in mixed- methods research that involves both qualitative and quantitative methods. A structured questionnaire and content analysis were used to seek responses to the research questions of the study and to meet the stated objectives. The research revealed that the two newspapers under investigation, namely the East African Standard and the Nation, provided more coverage to issues that were not central to the content of the draft constitution, such as political leaders' utterances, violence, ethnicity, and the process of constitution making. This showed that the newspapers tended to sensationalise issues instead of providing objective coverage of political matters. These newspapers used their opinion pages to educate their readers on how the referendum was turning violent. The theme of political leaders' utterances is closely linked to that of violence. This suggests that the violence was influenced by some of the leaders' statements. These utterances, and more so those that touched on ethnicity, could therefore have been a potential cause of the ensuing political conflicts during the 2005 referendum on the draft constitution. The findings reveal that newspaper editors tended to focus on political conflict at the expense of the actual content of the draft constitution. This would have provided insight and knowledge on the document and avoided sensational reporting, which could have contributed to violent political conflicts during the period that preceded the referendum on the draft constitution of Kenya.
- Full Text:
- Date Issued: 2011
The survival strategies of unemployed rural women : a case study of Wooldridge
- Authors: Dyubhele, Noluntu Stella
- Date: 2011
- Subjects: Women in rural development -- South Africa -- Eastern Cape , Rural women -- South Africa -- Eastern Cape , Unemployment -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape , Rural poor -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:8982 , http://hdl.handle.net/10948/1651 , Women in rural development -- South Africa -- Eastern Cape , Rural women -- South Africa -- Eastern Cape , Unemployment -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape , Rural poor -- South Africa -- Eastern Cape
- Description: Despite decades of gender research and public action by civil society, policy makers continue to neglect the role of women as breadwinners who work at improving the socio-economic conditions in rural areas such as Wooldridge, a traditional rural village in the Amathole district of the Eastern Cape Province. The apartheid system created an environment that continues to perpetuate both poverty and gender inequality in rural areas. Hence, rural women in Wooldridge still experience poverty, despite welfare benefits. They are located in a poverty-stricken area without basic infrastructure and with little or no access to economic assets. They use primitive methods and indigenous knowledge to develop survival strategies. This study argues that unemployed rural women in Wooldridge cannot survive without assistance from government. Indigenous knowledge and agricultural as well as non-agricultural activities are critical to household livelihoods in Wooldridge. These activities are an important route through which these rural women can escape poverty. The primary objective of this research was to obtain a better understanding of how unemployed rural women survive in Wooldridge. Furthermore, the necessary conditions required to sustain livelihood in the rural areas were identified. This was mainly done to help alleviate the plight of rural women in Wooldridge and to improve the quality of life of the rural population. The aim is to generate a policy response to rural women that is economically development-oriented. The study was based on five research objectives. The first objective was to identify the survival strategies of unemployed rural women in Wooldridge; the second to ascertain what can be done to alleviate the plight of rural women in Wooldridge. The third objective was to ascertain what has been v done to address the needs of rural women in the Wooldridge area by actors of development, such as government and non-governmental organisations. The fourth objective was to identify the constraints faced by unemployed rural women in Wooldridge in achieving food security and generating income, with the last objective to make recommendations regarding policies that can enhance rural economic development and assist unemployed rural women to reduce poverty. The main finding in terms of the first research objective is that the survival strategies of unemployed rural women are welfare benefits, the selling of assets, remittances, handicraft production and vegetable gardens. In terms of the second research objective, the main finding is that investment in human capital through the empowerment of women will assist them in improving the quality of life of the Wooldridge community. Empowerment involves skills and training, education and access to basic services, expertise regarding credit, land, the growing of vegetables and income-generating projects. The main finding in terms of the third research objective is that the Peddie Women Support Centre that is located in the city centre of Ngqushwa does not have the capacity to reach out to rural areas. Rural women in Wooldridge have not received responses to their plights from government or from development practitioners. These actors of development play an important role in empowerment. In terms of the fourth research objective, the main finding is that structural constraints hinder the economic activity of rural women in Wooldridge. Government policy that encourages investment in infrastructure using labour-intensive methods will eliminate service backlogs in underserviced areas such as Wooldridge. The main finding in terms of the fifth research objective is to ascertain the impact that new legislation can have to ensure that rural women have the same access and entitlement to land and resources as women from urban areas. Furthermore, service-improvement programmes should be developed and micro-enterprises and agricultural and non-agricultural activities that will generate income and employment should be encouraged in order to reduce poverty in Wooldridge.
- Full Text:
- Date Issued: 2011
- Authors: Dyubhele, Noluntu Stella
- Date: 2011
- Subjects: Women in rural development -- South Africa -- Eastern Cape , Rural women -- South Africa -- Eastern Cape , Unemployment -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape , Rural poor -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:8982 , http://hdl.handle.net/10948/1651 , Women in rural development -- South Africa -- Eastern Cape , Rural women -- South Africa -- Eastern Cape , Unemployment -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape , Rural poor -- South Africa -- Eastern Cape
- Description: Despite decades of gender research and public action by civil society, policy makers continue to neglect the role of women as breadwinners who work at improving the socio-economic conditions in rural areas such as Wooldridge, a traditional rural village in the Amathole district of the Eastern Cape Province. The apartheid system created an environment that continues to perpetuate both poverty and gender inequality in rural areas. Hence, rural women in Wooldridge still experience poverty, despite welfare benefits. They are located in a poverty-stricken area without basic infrastructure and with little or no access to economic assets. They use primitive methods and indigenous knowledge to develop survival strategies. This study argues that unemployed rural women in Wooldridge cannot survive without assistance from government. Indigenous knowledge and agricultural as well as non-agricultural activities are critical to household livelihoods in Wooldridge. These activities are an important route through which these rural women can escape poverty. The primary objective of this research was to obtain a better understanding of how unemployed rural women survive in Wooldridge. Furthermore, the necessary conditions required to sustain livelihood in the rural areas were identified. This was mainly done to help alleviate the plight of rural women in Wooldridge and to improve the quality of life of the rural population. The aim is to generate a policy response to rural women that is economically development-oriented. The study was based on five research objectives. The first objective was to identify the survival strategies of unemployed rural women in Wooldridge; the second to ascertain what can be done to alleviate the plight of rural women in Wooldridge. The third objective was to ascertain what has been v done to address the needs of rural women in the Wooldridge area by actors of development, such as government and non-governmental organisations. The fourth objective was to identify the constraints faced by unemployed rural women in Wooldridge in achieving food security and generating income, with the last objective to make recommendations regarding policies that can enhance rural economic development and assist unemployed rural women to reduce poverty. The main finding in terms of the first research objective is that the survival strategies of unemployed rural women are welfare benefits, the selling of assets, remittances, handicraft production and vegetable gardens. In terms of the second research objective, the main finding is that investment in human capital through the empowerment of women will assist them in improving the quality of life of the Wooldridge community. Empowerment involves skills and training, education and access to basic services, expertise regarding credit, land, the growing of vegetables and income-generating projects. The main finding in terms of the third research objective is that the Peddie Women Support Centre that is located in the city centre of Ngqushwa does not have the capacity to reach out to rural areas. Rural women in Wooldridge have not received responses to their plights from government or from development practitioners. These actors of development play an important role in empowerment. In terms of the fourth research objective, the main finding is that structural constraints hinder the economic activity of rural women in Wooldridge. Government policy that encourages investment in infrastructure using labour-intensive methods will eliminate service backlogs in underserviced areas such as Wooldridge. The main finding in terms of the fifth research objective is to ascertain the impact that new legislation can have to ensure that rural women have the same access and entitlement to land and resources as women from urban areas. Furthermore, service-improvement programmes should be developed and micro-enterprises and agricultural and non-agricultural activities that will generate income and employment should be encouraged in order to reduce poverty in Wooldridge.
- Full Text:
- Date Issued: 2011