The development of sustainability criteria to facilitate the selection of sanitation technologies within the Buffalo City Municipality (Eastern Cape Province, South Africa)
- Authors: Hoossein, Shafick
- Date: 2009
- Subjects: Sanitation -- South Africa -- Buffalo City Sustainable development -- South Africa -- Buffalo City Water -- Purification -- South Africa -- Buffalo City Sewage disposal -- South Africa -- Buffalo City Water quality -- South Africa -- Buffalo City Environmental health -- South Africa -- Buffalo City Environmental management -- South Africa -- Buffalo City
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:32275 , http://hdl.handle.net/10962/d1004595
- Description: Two and a half billion people mostly in sub-Saharan Africa and southern Asia remain without improved sanitation facilities despite the Millennium Development Goal 7's target to halve this number by 2015. While it might be tempting for developing countries such as South Africa to implement the cheapest and most rapidly constructed sanitation services simply to meet the desired target, this could have significant negative implications on human health and the environment over the long-term. As a result, there is a need to ensure that the most appropriate sustainable sanitation technologies are selected during the planning stage. The purpose of this research was therefore to document the development and pilot application of a flexible context-specific decision-support tool for sustainable sanitation technology selection within Buffalo City Municipality (BCM) in the Eastern Cape Province of South Africa. The first step in the development process was to ascertain the current status of sanitation within the municipality, with a specific focus on the main challenges related to the provision, maintenance and performance of these technologies. Thereafter, a participatory approach was employed involving BCM stakeholders to develop a series of sustainability criteria and indicators that took into consideration economic, social, environmental and technical concerns as well as legal requirements. The development process resulted in a list of 38 BCM sustainable sanitation selection criteria that were applied in a pilot study involving rural, urban and peri-urban communities within BCM. Certain criteria related to topographical features and the availability of piped water and land were considered useful for 'coarse screening' while others were applied during 'fine screening'. In order to enhance the context specificity of criteria, each was weighted, through consultation with key BCM stakeholders. This research confirmed that the sanitation situation in BCM was poor and preliminary evidence indicated that sanitation systems were negatively impacting on the quality of water resources within BCM justifying the need for a sustainable sanitation decision support tool. Based on the pilot application of the BCM Sustainability Selection Criteria List, the urine diversion technology was considered the most sustainable technology option in each study site. There were however, certain social criteria that received relatively low sustainability scores and these would need to be addressed prior to the approval of this technology for implementation. The approach adopted in this thesis was considered highly context-specific yet flexible and appropriate for adoption not only by BCM but other municipalities on a range of spatial scales.
- Full Text:
- Date Issued: 2009
- Authors: Hoossein, Shafick
- Date: 2009
- Subjects: Sanitation -- South Africa -- Buffalo City Sustainable development -- South Africa -- Buffalo City Water -- Purification -- South Africa -- Buffalo City Sewage disposal -- South Africa -- Buffalo City Water quality -- South Africa -- Buffalo City Environmental health -- South Africa -- Buffalo City Environmental management -- South Africa -- Buffalo City
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:32275 , http://hdl.handle.net/10962/d1004595
- Description: Two and a half billion people mostly in sub-Saharan Africa and southern Asia remain without improved sanitation facilities despite the Millennium Development Goal 7's target to halve this number by 2015. While it might be tempting for developing countries such as South Africa to implement the cheapest and most rapidly constructed sanitation services simply to meet the desired target, this could have significant negative implications on human health and the environment over the long-term. As a result, there is a need to ensure that the most appropriate sustainable sanitation technologies are selected during the planning stage. The purpose of this research was therefore to document the development and pilot application of a flexible context-specific decision-support tool for sustainable sanitation technology selection within Buffalo City Municipality (BCM) in the Eastern Cape Province of South Africa. The first step in the development process was to ascertain the current status of sanitation within the municipality, with a specific focus on the main challenges related to the provision, maintenance and performance of these technologies. Thereafter, a participatory approach was employed involving BCM stakeholders to develop a series of sustainability criteria and indicators that took into consideration economic, social, environmental and technical concerns as well as legal requirements. The development process resulted in a list of 38 BCM sustainable sanitation selection criteria that were applied in a pilot study involving rural, urban and peri-urban communities within BCM. Certain criteria related to topographical features and the availability of piped water and land were considered useful for 'coarse screening' while others were applied during 'fine screening'. In order to enhance the context specificity of criteria, each was weighted, through consultation with key BCM stakeholders. This research confirmed that the sanitation situation in BCM was poor and preliminary evidence indicated that sanitation systems were negatively impacting on the quality of water resources within BCM justifying the need for a sustainable sanitation decision support tool. Based on the pilot application of the BCM Sustainability Selection Criteria List, the urine diversion technology was considered the most sustainable technology option in each study site. There were however, certain social criteria that received relatively low sustainability scores and these would need to be addressed prior to the approval of this technology for implementation. The approach adopted in this thesis was considered highly context-specific yet flexible and appropriate for adoption not only by BCM but other municipalities on a range of spatial scales.
- Full Text:
- Date Issued: 2009
Synthesis and characterization of novel platinum complexes : their anticancer behaviour
- Authors: Myburgh, Jolanda
- Date: 2009
- Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
- Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
- Full Text:
- Date Issued: 2009
- Authors: Myburgh, Jolanda
- Date: 2009
- Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
- Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
- Full Text:
- Date Issued: 2009
A Speciation study of the chloro-hydroxo complexes of Pt(II)
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
Molecular and biochemical analysis of the diet of the black rhinoceros
- Authors: Kgopa, Ananias Hodi
- Date: 2009 , 2013-07-15
- Subjects: Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- South Africa -- Eastern Cape -- Analysis , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants , Plant ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4064 , http://hdl.handle.net/10962/d1004721 , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- South Africa -- Eastern Cape -- Analysis , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants , Plant ecology -- South Africa -- Eastern Cape
- Description: The black rhinoceros, Diceros bicornis, is listed as critically endangered. The black rhinoceros population in the Great Fish River Reserve (GFRR) has increased steadily to a current estimate of one hundred animals since the re-introduction of four animals in 1986. In an effort to contribute to the effective conservation and management of this species, dietary composition was studied in the medium Portulcaria thicket vegetation of the GFRR. This study used a molecular approach to determine the diet of the black rhinoceros of the GFRR by sequencing the ribulose bisphosphate carboxylase large subunit (rbcL) gene in plants and dung. Twenty-three plant species were collected from the reserve, and 802 bp of the rbcL gene were sequenced. These plant sequences were used as a reference database for the identification of plant sequences generated from black rhinoceros dung. Initial studies investigated the amplification, cloning and sequencing of DNA extracted from the dung samples which indicated the viability of the molecular approach. Thereafter, dung generated rbcL DNA was analyzed by GS FLX sequencing. Of the plant sequences identified by comparison to the GenBank database, Carissa bispinosa was the most prevalent. The study further characterized the antioxidant activities and phenolic content of plants eaten by the black rhinoceros using four different assays. Phyllanthus verrucosus, Putterlickia pyracantha, Maytenus capitata, Euclea undulata and Ozoroa mucrunata consistently had high antioxidant activities when assayed against 2,2-azinobis (3-ethyl benzothiazolium-6-sulfonic acid) (ABTSʹ⁺), 2,2-diphenyl-1-picrylhydrazyl (DPPHʹ), and ferric reducing antioxidant potentials (FRAP) and phenolic content when evaluated using the Folin-Ciocalteu assay. The majority of plants investigated showed low antioxidant potentials and low phenolic content. The extent to which antioxidants influenced the browse selection by the black rhinoceros remains inconclusive.
- Full Text:
- Date Issued: 2009
- Authors: Kgopa, Ananias Hodi
- Date: 2009 , 2013-07-15
- Subjects: Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- South Africa -- Eastern Cape -- Analysis , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants , Plant ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4064 , http://hdl.handle.net/10962/d1004721 , Black rhinoceros -- South Africa -- Eastern Cape , Browse (Animal food) -- South Africa -- Eastern Cape -- Analysis , Black rhinoceros -- Manure -- Analysis , Phenols , Antioxidants , Plant ecology -- South Africa -- Eastern Cape
- Description: The black rhinoceros, Diceros bicornis, is listed as critically endangered. The black rhinoceros population in the Great Fish River Reserve (GFRR) has increased steadily to a current estimate of one hundred animals since the re-introduction of four animals in 1986. In an effort to contribute to the effective conservation and management of this species, dietary composition was studied in the medium Portulcaria thicket vegetation of the GFRR. This study used a molecular approach to determine the diet of the black rhinoceros of the GFRR by sequencing the ribulose bisphosphate carboxylase large subunit (rbcL) gene in plants and dung. Twenty-three plant species were collected from the reserve, and 802 bp of the rbcL gene were sequenced. These plant sequences were used as a reference database for the identification of plant sequences generated from black rhinoceros dung. Initial studies investigated the amplification, cloning and sequencing of DNA extracted from the dung samples which indicated the viability of the molecular approach. Thereafter, dung generated rbcL DNA was analyzed by GS FLX sequencing. Of the plant sequences identified by comparison to the GenBank database, Carissa bispinosa was the most prevalent. The study further characterized the antioxidant activities and phenolic content of plants eaten by the black rhinoceros using four different assays. Phyllanthus verrucosus, Putterlickia pyracantha, Maytenus capitata, Euclea undulata and Ozoroa mucrunata consistently had high antioxidant activities when assayed against 2,2-azinobis (3-ethyl benzothiazolium-6-sulfonic acid) (ABTSʹ⁺), 2,2-diphenyl-1-picrylhydrazyl (DPPHʹ), and ferric reducing antioxidant potentials (FRAP) and phenolic content when evaluated using the Folin-Ciocalteu assay. The majority of plants investigated showed low antioxidant potentials and low phenolic content. The extent to which antioxidants influenced the browse selection by the black rhinoceros remains inconclusive.
- Full Text:
- Date Issued: 2009
Corruption and its effects on the development of the construction industry in Malawi
- Chiocha, Charles Injess Martin
- Authors: Chiocha, Charles Injess Martin
- Date: 2009
- Subjects: Contruction industry -- Corrupt practices -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9692 , http://hdl.handle.net/10948/933 , Contruction industry -- Corrupt practices -- Malawi
- Description: The purpose of this study was to investigate corruption and its effects on the development of the construction industry in Malawi. The major causes were identified and probable solutions as well as preventive measures suggested for all stakeholders in the construction industry in Malawi and neighbouring countries to follow in order to combat bribery and corruption. This treatise consisted of a literature review for the causes of bribery, fraud and corruption, effects of corruption on the construction industry, preventive measures, probable solutions to corruption and a descriptive survey involving responses from building and civil engineering contractors, the built environment professionals, home owners, developers, public works officers amongst others from the construction industry in Malawi. According to the literature study, the construction industry is one of the most corrupt industries in the world, which is a huge concern and threat both to governments, investors and humanity at large. This must be addressed by all the official players in the construction industry, from the innovator of a project to the tradesmen employed on that site. The research showed that all players in the construction industry are aware of the impact of corruption on the development of the construction industry in Malawi. Furthermore, there is room for improvement as far as prevention, reduction and elimination of corruption is concerned.
- Full Text:
- Date Issued: 2009
- Authors: Chiocha, Charles Injess Martin
- Date: 2009
- Subjects: Contruction industry -- Corrupt practices -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9692 , http://hdl.handle.net/10948/933 , Contruction industry -- Corrupt practices -- Malawi
- Description: The purpose of this study was to investigate corruption and its effects on the development of the construction industry in Malawi. The major causes were identified and probable solutions as well as preventive measures suggested for all stakeholders in the construction industry in Malawi and neighbouring countries to follow in order to combat bribery and corruption. This treatise consisted of a literature review for the causes of bribery, fraud and corruption, effects of corruption on the construction industry, preventive measures, probable solutions to corruption and a descriptive survey involving responses from building and civil engineering contractors, the built environment professionals, home owners, developers, public works officers amongst others from the construction industry in Malawi. According to the literature study, the construction industry is one of the most corrupt industries in the world, which is a huge concern and threat both to governments, investors and humanity at large. This must be addressed by all the official players in the construction industry, from the innovator of a project to the tradesmen employed on that site. The research showed that all players in the construction industry are aware of the impact of corruption on the development of the construction industry in Malawi. Furthermore, there is room for improvement as far as prevention, reduction and elimination of corruption is concerned.
- Full Text:
- Date Issued: 2009
Restoration of degraded subtropical thickets in the Baviaanskloof Megareserve, South Africa: the role of carbon stocks and Portulacaria afra survivorship
- Authors: Powell, Michael John
- Date: 2009
- Subjects: Portulacaria afra -- South Africa -- Eastern Cape , Portulacaceae -- South Africa -- Eastern Cape , Biodiversity conservation -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Shrubs -- South Africa -- Eastern Cape , Succulent plants -- South Africa -- Eastern Cape , Baviaanskloof (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4764 , http://hdl.handle.net/10962/d1007164 , Portulacaria afra -- South Africa -- Eastern Cape , Portulacaceae -- South Africa -- Eastern Cape , Biodiversity conservation -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Shrubs -- South Africa -- Eastern Cape , Succulent plants -- South Africa -- Eastern Cape , Baviaanskloof (South Africa)
- Description: The semi-arid forms of subtropical thicket in the Eastern and Western Cape have been heavily degraded through unsustainable pastoralism over the last century or more. The degraded areas exhibit a significant loss of above-ground and belowground carbon stocks, and consequently provide an opportunity for restoration through the formal and informal carbon markets. A prerequisite for the attainment of carbon credits is to ensure sound carbon stock baselines prior to effecting restoration. I report on the carbon stocks (including sub-pools) for a number of intact subtropical thicket types, as well as the differentials between the intact and degraded states (including the sub-pools). Total carbon stocks (TCS in t C ha⁻¹) for intact vegetation (to a soil depth 0–25 cm), ranged from 87.73±6.51 to 70.64±17.24. For degraded vegetation (including old lands), TCS (t C ha⁻¹) ranged from 34.05±3.61 to 21.03±2.70. For all vegetation types, the differentials in TCS along the degradation gradient (0–25 cm) are highly significant and strengthen the possibility for carbon credit financing to catalyse the restoration of the degraded semi-arid subtropical thickets. This study has shown a mean loss of 57.23 t C ha⁻¹ in Baviaanskloof spekboom thickets, when measured to a soil depth of 25 cm. Portulacaria afra is a key species within the semi-arid subtropical thickets, being a canopy dominant and a driver of soil nutrient status, but has been largely lost from the degraded landscapes. Degraded semi-arid subtropical thicket vegetation lacks regeneration via seedling recruitment; restoration therefore requires the manual replanting of P. afra using cut truncheons. Survivorship trials were undertaken infield in 2005 to establish restoration protocols for P. afra, with survivorship being recorded in 2006 and 2008. Overall survivorship for all treatments was found to be 43.2±2.8% in 2006, dropping to 35.8±2.7% in 2008. Planting posture (flat or upright) showed the most significant results of all the factors tested in 2006 and 2008. Micro-damming also influenced survivorship in that micro-damming was associated with marginally higher survivorship (47.4 ±2.0% with damming vs. 39.1±1.5% without damming in 2006, and 39.3±1.9% vs. 32.3±1.5% in 2008). Higher planting density only showed a significant positive impact on survivorship in 2008. Neither stem diameter nor clumping significantly affected degree of survival. A key finding in the study has been the non-static nature of P. afra truncheon survivorship, even after being well established (three years since planting). The results from the study will guide the restoration protocols for the restoration of degraded subtropical thickets, where P. afra requires replanting.
- Full Text:
- Date Issued: 2009
- Authors: Powell, Michael John
- Date: 2009
- Subjects: Portulacaria afra -- South Africa -- Eastern Cape , Portulacaceae -- South Africa -- Eastern Cape , Biodiversity conservation -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Shrubs -- South Africa -- Eastern Cape , Succulent plants -- South Africa -- Eastern Cape , Baviaanskloof (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4764 , http://hdl.handle.net/10962/d1007164 , Portulacaria afra -- South Africa -- Eastern Cape , Portulacaceae -- South Africa -- Eastern Cape , Biodiversity conservation -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Shrubs -- South Africa -- Eastern Cape , Succulent plants -- South Africa -- Eastern Cape , Baviaanskloof (South Africa)
- Description: The semi-arid forms of subtropical thicket in the Eastern and Western Cape have been heavily degraded through unsustainable pastoralism over the last century or more. The degraded areas exhibit a significant loss of above-ground and belowground carbon stocks, and consequently provide an opportunity for restoration through the formal and informal carbon markets. A prerequisite for the attainment of carbon credits is to ensure sound carbon stock baselines prior to effecting restoration. I report on the carbon stocks (including sub-pools) for a number of intact subtropical thicket types, as well as the differentials between the intact and degraded states (including the sub-pools). Total carbon stocks (TCS in t C ha⁻¹) for intact vegetation (to a soil depth 0–25 cm), ranged from 87.73±6.51 to 70.64±17.24. For degraded vegetation (including old lands), TCS (t C ha⁻¹) ranged from 34.05±3.61 to 21.03±2.70. For all vegetation types, the differentials in TCS along the degradation gradient (0–25 cm) are highly significant and strengthen the possibility for carbon credit financing to catalyse the restoration of the degraded semi-arid subtropical thickets. This study has shown a mean loss of 57.23 t C ha⁻¹ in Baviaanskloof spekboom thickets, when measured to a soil depth of 25 cm. Portulacaria afra is a key species within the semi-arid subtropical thickets, being a canopy dominant and a driver of soil nutrient status, but has been largely lost from the degraded landscapes. Degraded semi-arid subtropical thicket vegetation lacks regeneration via seedling recruitment; restoration therefore requires the manual replanting of P. afra using cut truncheons. Survivorship trials were undertaken infield in 2005 to establish restoration protocols for P. afra, with survivorship being recorded in 2006 and 2008. Overall survivorship for all treatments was found to be 43.2±2.8% in 2006, dropping to 35.8±2.7% in 2008. Planting posture (flat or upright) showed the most significant results of all the factors tested in 2006 and 2008. Micro-damming also influenced survivorship in that micro-damming was associated with marginally higher survivorship (47.4 ±2.0% with damming vs. 39.1±1.5% without damming in 2006, and 39.3±1.9% vs. 32.3±1.5% in 2008). Higher planting density only showed a significant positive impact on survivorship in 2008. Neither stem diameter nor clumping significantly affected degree of survival. A key finding in the study has been the non-static nature of P. afra truncheon survivorship, even after being well established (three years since planting). The results from the study will guide the restoration protocols for the restoration of degraded subtropical thickets, where P. afra requires replanting.
- Full Text:
- Date Issued: 2009
Solvent-free synthesis of bisferrocenylimines and their coordination to rhodium (I)
- Authors: Kleyi, Phumelele Eldridge
- Date: 2009
- Subjects: Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10393 , http://hdl.handle.net/10948/1053 , Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Description: Solvent-free reactions possess advantages compared to the solvent route, such as shorter reaction times, less use of energy, better yields, etc. Herein, the synthesis and characterization of bisferrocenylimines and arylbisamines are described. Reduction of the above compounds with LAH resulted in the formation of bisferrocenylamines and arylbisamines, respectively. The coordination chemistry of all the above compounds to rhodium(I) is also discussed in the prepared complexes [Rh(COD)(NN)]ClO4, where NN = bisferrocenylimines, and [Rh(COD)(NN)]BF4, where NN = bisferrocenylamines and arylbisamines. X-ray crystal structures of the complexes [Rh(COD)(NN)]ClO4 ([3.2] and [3.3]) have been obtained. Complexes of the type [Rh(COD)(NN)]BF4 were characterized with IR and UV-vis spectroscopy, cyclic voltammetry and conductometry. The catalytic activity of the complexes was also investigated: [Rh(COD)(NN)]ClO4 for the polymerization of phenylacetylene and [Rh(COD)(NN)]BF4 for the hydroformylation of styrene.
- Full Text:
- Date Issued: 2009
- Authors: Kleyi, Phumelele Eldridge
- Date: 2009
- Subjects: Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10393 , http://hdl.handle.net/10948/1053 , Organic compounds -- Synthesis , Organic solvents , Solution (Chemistry) , Chemistry, Organic , Coordination compounds
- Description: Solvent-free reactions possess advantages compared to the solvent route, such as shorter reaction times, less use of energy, better yields, etc. Herein, the synthesis and characterization of bisferrocenylimines and arylbisamines are described. Reduction of the above compounds with LAH resulted in the formation of bisferrocenylamines and arylbisamines, respectively. The coordination chemistry of all the above compounds to rhodium(I) is also discussed in the prepared complexes [Rh(COD)(NN)]ClO4, where NN = bisferrocenylimines, and [Rh(COD)(NN)]BF4, where NN = bisferrocenylamines and arylbisamines. X-ray crystal structures of the complexes [Rh(COD)(NN)]ClO4 ([3.2] and [3.3]) have been obtained. Complexes of the type [Rh(COD)(NN)]BF4 were characterized with IR and UV-vis spectroscopy, cyclic voltammetry and conductometry. The catalytic activity of the complexes was also investigated: [Rh(COD)(NN)]ClO4 for the polymerization of phenylacetylene and [Rh(COD)(NN)]BF4 for the hydroformylation of styrene.
- Full Text:
- Date Issued: 2009
Efficacy of selected Kenyan medicinal plants used in the treatment and management of Type II Diabetes
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
Detecting changes in elephant body condition in relation to resource quality
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
The impact of angling on smallmouth and largemouth yellowfish, labeobarbus aeneus and labeobarbus kimberleyensis, in Lake Gariep, South Africa
- Authors: Ellender, Bruce Robert
- Date: 2009
- Subjects: Barbus aeneus , Largemouth bass , Labeobarbus , Fishing -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5289 , http://hdl.handle.net/10962/d1005133 , Barbus aeneus , Largemouth bass , Labeobarbus , Fishing -- South Africa -- Gariep Dam
- Description: A large sportfishery that targets both smallmouth (Labeobarbus aeneus) and largemouth (Labeobarbus kimberleyensis) yellowfish exists in South Africa. Both species have high conservation priority, and no assessments documenting the effect of angling on L. aeneus and L. kimberleyensis have been undertaken. The overall aim of this study was to provide an assessment of the impact of angling on L. aeneus and L. kimberleyensis. The specific objectives of this study were to characterise the sectors utilising Lake Gariep, document catch, effort and total catch for the fishery as well as the locality specific biology of L. aeneus and L. kimberleyensis. The study was undertaken on Lake Gariep, South Africa's largest impoundment, situated on the Orange River system in central South Africa. Subsistence fishers were the dominant user group, constituting 60 % of the fishery, the remainder constituted recreational anglers. Angler catches were dominated by carp (Cyprinus carpio; 74 %), followed by mudfish (Labeo capensis; 13 %) and smallmouth yellowfish (8 %). Catches of largemouth yellowfish contributed < 0.5 % to the total catch. The relative abundance of species by weight differed by area (χ² test of independence: χ² = 182, df = 4, p ≤ 0.05). On any sampling day time fished was the best predictor for differences in probability of capture (PC) (Wald X²(1) = 7.169, p = 0.007). The probability of capturing L. aeneus differed significantly between month (Wald X²(5) = 20.690, p = 0.000) and region (Wald X²(3) = 46.755, p = 0.000). The single best predictor of differences in log abundance and non-zero CPUE was region (Factorial ANOVA p ≤ 0.05). Mean CPUE ranged from 0.21 ± 0.06 kg. man⁻¹.hr⁻¹ to 0.82 ± 0.11 kg. man⁻¹.hr⁻¹ in the OV region and 0.42 ± 0.10 kg. man⁻¹.hr⁻¹ to 1.17 ± 0.24 kg. man⁻¹.hr⁻¹ in the GD region. Angler effort was higher in OV than in GD and ranged from 17 ± 3 anglers/day to 45 ± 9 anglers/day and 6 ± 1 anglers/day to 41 ± 8 anglers/day, respectively. Total catch was higher in the GD 46.0 [95 % CI = 15:102.6] t. period⁻¹ than the OV region 40.0 [95 % CI = 13.9:89.6] t. period⁻¹. The total catch from the Lake Gariep fishery between March and December 2007 was estimated to be 86.0 [95 % CI = 40.4:154.8] t. period⁻¹. Age and growth was determined using whole otoliths. The growth of L. aeneus was best described by the von Bertalanffy growth model as Lt = 481.80 (1- e⁻°·²²⁽t⁺°·⁶¹⁾). Gonadal development for L. aeneus was seasonal, with the gonadosomatic index peaking in January, revealing a distinct spawning season. The length at 50 % maturity for female L. aeneus was attained at a fork length of 354.7 mm. Natural mortality (M) was estimated at 0.55 year⁻¹. The growth of L. kimberleyensis was described by the von Bertalanffy growth model as Lt = 763.22 (1- e⁻°·¹¹⁽t⁺°·⁶³⁾). Only 6 mature female and 15 mature male L. kimberleyensis were recorded during the study period. The smallest mature female was a 390 mm FL stage four female and the earliest recorded mature male was a 337 mm FL, ripe running male. Natural mortality (M) was estimated at 0.08 year⁻¹ for L. kimberleyensis. Per recruit analysis indicated that current fishing mortality reduces the L. aeneus spawner biomass by 7 %, which is considered negligible. Labeobarbus kimberleyensis forms an insignificant proportion of anglers catches and stock status is currently considered pristine.
- Full Text:
- Date Issued: 2009
- Authors: Ellender, Bruce Robert
- Date: 2009
- Subjects: Barbus aeneus , Largemouth bass , Labeobarbus , Fishing -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5289 , http://hdl.handle.net/10962/d1005133 , Barbus aeneus , Largemouth bass , Labeobarbus , Fishing -- South Africa -- Gariep Dam
- Description: A large sportfishery that targets both smallmouth (Labeobarbus aeneus) and largemouth (Labeobarbus kimberleyensis) yellowfish exists in South Africa. Both species have high conservation priority, and no assessments documenting the effect of angling on L. aeneus and L. kimberleyensis have been undertaken. The overall aim of this study was to provide an assessment of the impact of angling on L. aeneus and L. kimberleyensis. The specific objectives of this study were to characterise the sectors utilising Lake Gariep, document catch, effort and total catch for the fishery as well as the locality specific biology of L. aeneus and L. kimberleyensis. The study was undertaken on Lake Gariep, South Africa's largest impoundment, situated on the Orange River system in central South Africa. Subsistence fishers were the dominant user group, constituting 60 % of the fishery, the remainder constituted recreational anglers. Angler catches were dominated by carp (Cyprinus carpio; 74 %), followed by mudfish (Labeo capensis; 13 %) and smallmouth yellowfish (8 %). Catches of largemouth yellowfish contributed < 0.5 % to the total catch. The relative abundance of species by weight differed by area (χ² test of independence: χ² = 182, df = 4, p ≤ 0.05). On any sampling day time fished was the best predictor for differences in probability of capture (PC) (Wald X²(1) = 7.169, p = 0.007). The probability of capturing L. aeneus differed significantly between month (Wald X²(5) = 20.690, p = 0.000) and region (Wald X²(3) = 46.755, p = 0.000). The single best predictor of differences in log abundance and non-zero CPUE was region (Factorial ANOVA p ≤ 0.05). Mean CPUE ranged from 0.21 ± 0.06 kg. man⁻¹.hr⁻¹ to 0.82 ± 0.11 kg. man⁻¹.hr⁻¹ in the OV region and 0.42 ± 0.10 kg. man⁻¹.hr⁻¹ to 1.17 ± 0.24 kg. man⁻¹.hr⁻¹ in the GD region. Angler effort was higher in OV than in GD and ranged from 17 ± 3 anglers/day to 45 ± 9 anglers/day and 6 ± 1 anglers/day to 41 ± 8 anglers/day, respectively. Total catch was higher in the GD 46.0 [95 % CI = 15:102.6] t. period⁻¹ than the OV region 40.0 [95 % CI = 13.9:89.6] t. period⁻¹. The total catch from the Lake Gariep fishery between March and December 2007 was estimated to be 86.0 [95 % CI = 40.4:154.8] t. period⁻¹. Age and growth was determined using whole otoliths. The growth of L. aeneus was best described by the von Bertalanffy growth model as Lt = 481.80 (1- e⁻°·²²⁽t⁺°·⁶¹⁾). Gonadal development for L. aeneus was seasonal, with the gonadosomatic index peaking in January, revealing a distinct spawning season. The length at 50 % maturity for female L. aeneus was attained at a fork length of 354.7 mm. Natural mortality (M) was estimated at 0.55 year⁻¹. The growth of L. kimberleyensis was described by the von Bertalanffy growth model as Lt = 763.22 (1- e⁻°·¹¹⁽t⁺°·⁶³⁾). Only 6 mature female and 15 mature male L. kimberleyensis were recorded during the study period. The smallest mature female was a 390 mm FL stage four female and the earliest recorded mature male was a 337 mm FL, ripe running male. Natural mortality (M) was estimated at 0.08 year⁻¹ for L. kimberleyensis. Per recruit analysis indicated that current fishing mortality reduces the L. aeneus spawner biomass by 7 %, which is considered negligible. Labeobarbus kimberleyensis forms an insignificant proportion of anglers catches and stock status is currently considered pristine.
- Full Text:
- Date Issued: 2009
The geological framework and depositional environments of the coal-bearing Karoo strata in the Central Kalahari Karoo Basin, Botswana
- Authors: Segwabe, Tebogo
- Date: 2009
- Subjects: Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4955 , http://hdl.handle.net/10962/d1005567 , Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Description: The investigation of the geological history (i.e., stratigraphy and sedimentology) and the dynamics of coal depositional environments, in particular, the forces responsible for changes in the accommodation space (e.g., subsidence vs. sedimentation rates) in the Permian coal-bearing Karoo strata in the Central Kalahari Karoo Basin (Botswana) revealed new details about the depositional processes and environments. Detailed review of the temporal and spatial stratigraphic variation of the coal-bearing Ecca Group successions via the analysis of facies changes based on core descriptions, gamma logs, field observations and palaeo-current measurements, lead to the identification of two main informal stratigraphic units, namely the Basal and Upper Units. The Basal Unit is characterised by an upward-coarsening succession, and it is interpreted as a product of a progradational deltaic setting (i.e., regressive deltaic cycle). This is followed by five sequences of fining-upward successions of sandstones and siltstones in the Upper Unit, interpreted as deposits of distributary channels (the basal arenaceous member) capped by finer argillaceous sequences of the deltaic floodplains (the upper coal-bearing member). The Upper Unit thus is interpreted as a delta plain facies association which was formed during transgressive phases when conditions for coal-quality peat accumulation (e.g., high water table) were present and the available accommodation space was partly controlled by tectonic uplift (repeated?) at basin margins. Limited palaeo-current analysis indicates deposition by channels flowing from the east, south-east and north-east. The lack of good quality exposures hampers the reconstruction of the plan form of the channel patterns. However, the little available evidence indicates a high-energy fluvio-deltaic system with irregular discharge and a high proportion of bedload sediments. Coal-seam thickness in the upper coal-bearing member reflect the complex control of the geological processes associated with and following peat formation, such as differential compaction of the underlying lithology, and the erosive or protective nature of the immediately overlying lithology.
- Full Text:
- Date Issued: 2009
- Authors: Segwabe, Tebogo
- Date: 2009
- Subjects: Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4955 , http://hdl.handle.net/10962/d1005567 , Coal -- Geology -- Botswana , Sedimentation and deposition -- Botswana
- Description: The investigation of the geological history (i.e., stratigraphy and sedimentology) and the dynamics of coal depositional environments, in particular, the forces responsible for changes in the accommodation space (e.g., subsidence vs. sedimentation rates) in the Permian coal-bearing Karoo strata in the Central Kalahari Karoo Basin (Botswana) revealed new details about the depositional processes and environments. Detailed review of the temporal and spatial stratigraphic variation of the coal-bearing Ecca Group successions via the analysis of facies changes based on core descriptions, gamma logs, field observations and palaeo-current measurements, lead to the identification of two main informal stratigraphic units, namely the Basal and Upper Units. The Basal Unit is characterised by an upward-coarsening succession, and it is interpreted as a product of a progradational deltaic setting (i.e., regressive deltaic cycle). This is followed by five sequences of fining-upward successions of sandstones and siltstones in the Upper Unit, interpreted as deposits of distributary channels (the basal arenaceous member) capped by finer argillaceous sequences of the deltaic floodplains (the upper coal-bearing member). The Upper Unit thus is interpreted as a delta plain facies association which was formed during transgressive phases when conditions for coal-quality peat accumulation (e.g., high water table) were present and the available accommodation space was partly controlled by tectonic uplift (repeated?) at basin margins. Limited palaeo-current analysis indicates deposition by channels flowing from the east, south-east and north-east. The lack of good quality exposures hampers the reconstruction of the plan form of the channel patterns. However, the little available evidence indicates a high-energy fluvio-deltaic system with irregular discharge and a high proportion of bedload sediments. Coal-seam thickness in the upper coal-bearing member reflect the complex control of the geological processes associated with and following peat formation, such as differential compaction of the underlying lithology, and the erosive or protective nature of the immediately overlying lithology.
- Full Text:
- Date Issued: 2009
The response of the red mangrove rhizophora mucronata lam, to changes in salinity, inundation and light : predictions for future climate change
- Hoppe-Speer, Sabine Clara Lisa
- Authors: Hoppe-Speer, Sabine Clara Lisa
- Date: 2009
- Subjects: Mangrove plants , Climatic changes , Red mangrove
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10616 , http://hdl.handle.net/10948/1249 , Mangrove plants , Climatic changes , Red mangrove
- Description: Mangrove forests are subjected to many environmental factors which influence species distribution, zonation patterns as well as succession. Important driving factors in these forests are salinity, water level fluctuations and available light. This study investigated the response of red mangrove (Rhizophora mucronata Lam.) seedlings to these factors in controlled laboratory experiments. Increase in salinity and prolonged inundation within estuaries are predicted impacts resulting from sea level rise due to climate change. The study investigated the effect of five salinity treatments (0, 8, 18, 35 and 45 ppt) with a semi-diurnal tidal cycle on seedling growth. In a separate experiment the effect of different inundation treatments: no inundation, 3, 6, 9 hour tidal cycles and continuous inundation (24 h) were investigated. Both morphological and physiological responses of R. mucronata seedlings were measured. There was a decrease in growth (plant height, biomass and leaf production) with increasing salinity. Seedlings in the seawater, hypersaline and no inundation treatments showed symptoms of stress, having increased leaf necrosis ("burn marks"). The highest growth occurred in the low salinity (8 ppt) treatment, but the highest photosynthetic performance and stomatal conductance occurred in the freshwater treatment (0 ppt). The typical response of stem elongation with increasing inundation was observed in the 24 hr inundation treatment. In the light and salinity combination study there were ten different treatments of five different light treatments (unshaded, 20 percent, 50 percent, 80 percent and 90 percent shade) combined with two salinity concentrations (18 and 35 ppt). In this study the seedling growth: plant height, biomass, leaf surface area and leaf production were higher in the moderate salinity (18 ppt) treatments compared to the seawater (35 ppt) treatments. Biomass in the 35 ppt experiment decreased with increasing shade as well as in the unshaded treatments. Photosynthetic performance and stomatal conductance were lower for the unshaded treatment in both 18 and 35 ppt salinity compared to all other treatments with the same salinity. This suggests that R. mucronata more shade than sun tolerant, but overall it can be concluded that the species has a broad tolerance range. The results may be relevant in mangrove rehabilitation and predicting responses to climate change. This is important as mangrove ecosystems may adapt to changing sea levels and in order to restore areas it will be necessary to choose the mangrove species which will grow best. The results may also help to increase the protection of existing mangrove habitats.
- Full Text:
- Date Issued: 2009
- Authors: Hoppe-Speer, Sabine Clara Lisa
- Date: 2009
- Subjects: Mangrove plants , Climatic changes , Red mangrove
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10616 , http://hdl.handle.net/10948/1249 , Mangrove plants , Climatic changes , Red mangrove
- Description: Mangrove forests are subjected to many environmental factors which influence species distribution, zonation patterns as well as succession. Important driving factors in these forests are salinity, water level fluctuations and available light. This study investigated the response of red mangrove (Rhizophora mucronata Lam.) seedlings to these factors in controlled laboratory experiments. Increase in salinity and prolonged inundation within estuaries are predicted impacts resulting from sea level rise due to climate change. The study investigated the effect of five salinity treatments (0, 8, 18, 35 and 45 ppt) with a semi-diurnal tidal cycle on seedling growth. In a separate experiment the effect of different inundation treatments: no inundation, 3, 6, 9 hour tidal cycles and continuous inundation (24 h) were investigated. Both morphological and physiological responses of R. mucronata seedlings were measured. There was a decrease in growth (plant height, biomass and leaf production) with increasing salinity. Seedlings in the seawater, hypersaline and no inundation treatments showed symptoms of stress, having increased leaf necrosis ("burn marks"). The highest growth occurred in the low salinity (8 ppt) treatment, but the highest photosynthetic performance and stomatal conductance occurred in the freshwater treatment (0 ppt). The typical response of stem elongation with increasing inundation was observed in the 24 hr inundation treatment. In the light and salinity combination study there were ten different treatments of five different light treatments (unshaded, 20 percent, 50 percent, 80 percent and 90 percent shade) combined with two salinity concentrations (18 and 35 ppt). In this study the seedling growth: plant height, biomass, leaf surface area and leaf production were higher in the moderate salinity (18 ppt) treatments compared to the seawater (35 ppt) treatments. Biomass in the 35 ppt experiment decreased with increasing shade as well as in the unshaded treatments. Photosynthetic performance and stomatal conductance were lower for the unshaded treatment in both 18 and 35 ppt salinity compared to all other treatments with the same salinity. This suggests that R. mucronata more shade than sun tolerant, but overall it can be concluded that the species has a broad tolerance range. The results may be relevant in mangrove rehabilitation and predicting responses to climate change. This is important as mangrove ecosystems may adapt to changing sea levels and in order to restore areas it will be necessary to choose the mangrove species which will grow best. The results may also help to increase the protection of existing mangrove habitats.
- Full Text:
- Date Issued: 2009
A feasibility study into the possibility of ionospheric propagation of low VHF (30-35 MHZ) signals between South Africa and Central Africa
- Authors: Coetzee, Petrus Johannes
- Date: 2009
- Subjects: Communications, Military -- South Africa , Communications, Military -- Africa, Central , Digital communications -- South Africa , Digital communications -- Africa, Central , Signals and signaling -- South Africa , Signals and signaling -- Africa, Central , Artificial satellites in telecommunication -- South Africa , Artificial satellites in telecommunication -- Africa, Central , Shortwave radio
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5465 , http://hdl.handle.net/10962/d1005250 , Communications, Military -- South Africa , Communications, Military -- Africa, Central , Digital communications -- South Africa , Digital communications -- Africa, Central , Signals and signaling -- South Africa , Signals and signaling -- Africa, Central , Artificial satellites in telecommunication -- South Africa , Artificial satellites in telecommunication -- Africa, Central , Shortwave radio
- Description: The role of the South African National Defence Force (SANDF) has changed considerably in the last decade. The emphasis has moved from protecting the country's borders to peacekeeping duties in Central Africa and even further North. Communications between the peacekeeping missions and the military bases back in South Africa is vital to ensure the success of these missions. Currently use is made of satellite as well as High Frequency (HF) communications. There are drawbacks associated with these technologies (high cost and low data rates/interference respectively). Successful long distance ionospheric propagation in the low Very High Frequency (VHF) range will complement the existing infrastructure and enhance the success rate of these missions. This thesis presents a feasibility study to determine under what ionospheric conditions such low VHF communications will be possible. The International Reference Ionosphere (IRI) was used to generate ionospheric data for the reflection point(s) of the signal. The peak height of the ionospheric F2 layer (hmF2) was used to calculate the required antenna elevation angle. Once the elevation angle is known it is possible to calculate the required F2 layer critical frequency (foF2). The required foF2 value was calculated by assuming a Maximum Useable Frequency (MUF) of 20% higher than the planned operational frequency. It was determined that single hop propagation is possible during the daytime if the smoothed sunspot number (SSN) exceeds 15. The most challenging requirement for successful single hop propagation is the need of an antenna height of 23 m. For rapid deployment and semi-mobile operations within a jungle environment it may prove to be a formidable obstacle.
- Full Text:
- Date Issued: 2009
- Authors: Coetzee, Petrus Johannes
- Date: 2009
- Subjects: Communications, Military -- South Africa , Communications, Military -- Africa, Central , Digital communications -- South Africa , Digital communications -- Africa, Central , Signals and signaling -- South Africa , Signals and signaling -- Africa, Central , Artificial satellites in telecommunication -- South Africa , Artificial satellites in telecommunication -- Africa, Central , Shortwave radio
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5465 , http://hdl.handle.net/10962/d1005250 , Communications, Military -- South Africa , Communications, Military -- Africa, Central , Digital communications -- South Africa , Digital communications -- Africa, Central , Signals and signaling -- South Africa , Signals and signaling -- Africa, Central , Artificial satellites in telecommunication -- South Africa , Artificial satellites in telecommunication -- Africa, Central , Shortwave radio
- Description: The role of the South African National Defence Force (SANDF) has changed considerably in the last decade. The emphasis has moved from protecting the country's borders to peacekeeping duties in Central Africa and even further North. Communications between the peacekeeping missions and the military bases back in South Africa is vital to ensure the success of these missions. Currently use is made of satellite as well as High Frequency (HF) communications. There are drawbacks associated with these technologies (high cost and low data rates/interference respectively). Successful long distance ionospheric propagation in the low Very High Frequency (VHF) range will complement the existing infrastructure and enhance the success rate of these missions. This thesis presents a feasibility study to determine under what ionospheric conditions such low VHF communications will be possible. The International Reference Ionosphere (IRI) was used to generate ionospheric data for the reflection point(s) of the signal. The peak height of the ionospheric F2 layer (hmF2) was used to calculate the required antenna elevation angle. Once the elevation angle is known it is possible to calculate the required F2 layer critical frequency (foF2). The required foF2 value was calculated by assuming a Maximum Useable Frequency (MUF) of 20% higher than the planned operational frequency. It was determined that single hop propagation is possible during the daytime if the smoothed sunspot number (SSN) exceeds 15. The most challenging requirement for successful single hop propagation is the need of an antenna height of 23 m. For rapid deployment and semi-mobile operations within a jungle environment it may prove to be a formidable obstacle.
- Full Text:
- Date Issued: 2009
Movement bahaviour of three South African inshore sparid species in rocky intertidal and shallow subtidal habitats
- Authors: Watt-Pringle, Peter Andrew
- Date: 2009
- Subjects: Sparidae -- South Africa , Diplodus , Sparodon Durbanensis , Fisheries -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5302 , http://hdl.handle.net/10962/d1005147 , Sparidae -- South Africa , Diplodus , Sparodon Durbanensis , Fisheries -- South Africa
- Description: This study investigated the movement behaviour of three inshore South African sparids – blacktail (Diplodus sargus capensis), zebra (Diplodus cervinus hottentotus) and white musselcracker (Sparodon durbanensis), popular inshore fishery species caught in appreciable numbers along much of the South African coast. The first study component examined movements of juveniles in a rocky intertidal nursery area at Schoenmakerskop near Port Elizabeth. Juveniles in a single gully were tagged with Visible Implant Elastomer (VIE) and resighted at the study site on snorkelling gear over a seven-month period. Tagged zebra and musselcracker displayed limited movement between potential low tide refuges, being observed repeatedly in the same gully over the full duration of the study. However, blacktail displayed greater movements and were seen infrequently in the later period of the study, probably having undergone an ontogenetic habitat shift to subtidal areas. There was evidence that blacktail maintain use of their intertidal nursery over high tide, during which the other two species moved into shallower areas adjacent to their low tide refuge. The results of three national tagging programs were analysed to determine the movement patterns of adolescent and adult fishes. The coast-wide ORI-WWF National Voluntary Tagging Program and two dedicated research programs in marine protected areas (MPAs) at De Hoop MPA and Tsitsikamma National Park (TNP) recorded few large-scale movements of tagged adult blacktail, zebra and juvenile musselcracker. High spatial-resolution data from the TNP suggested movements were usually on scales far smaller than one km. Together with long periods at liberty for many recaptured individuals, this suggests these fishes are longterm residents of small home range areas. However, tagged musselcracker over 600 mm forklength (adults) were observed to make large-scale movements, including some in excess of 800 km from Eastern Cape to KwaZulu-Natal waters. Predominantly eastward movements of adults recaptured during the spawning season indicate seasonal spawning migrations that occur in different regions of the coast. These enable the use of prevailing oceanographic currents to disperse eggs and larvae to suitable rocky nursery habitat. The third component of this study made use of high-resolution data on the temporal and spatial distribution of catches by scientific angling in the TNP to examine the daily activity patterns of the study species in relation to diel and tidal cycles, and habitat use. Blacktail capture probability was correlated with the diurnal light cycle, with peaks close to twilight suggesting elevated crepuscular foraging activity. Catches of blacktail, zebra and small musselcracker were correlated with the tidal cycle, foraging peaking over high tide periods. All three species used shallow inshore habitats extensively for foraging, blacktail showing a preference for sandy areas, while zebra and small musselcracker preferred shallow reef. Capture probability of larger musselcracker, however, was unrelated to habitat, possibly evidence of increasing area and habitat use with an ontogenetic change in diet. The lifetime movement patterns of these three species are discussed in relation to conservation measures and their management in South African fisheries. Restricted movement throughout post-settlement life for blacktail and zebra, and during the juvenile phase for musselcracker, makes local populations vulnerable to overexploitation. At present, MPAs probably play an important role in protecting local blacktail and zebra populations from overexploitation, and limited post-settlement movements mean the degree of larval dispersal between protected and adjacent areas will likely determine the effectiveness of MPAs in enhancing fisheries for these species. By contrast, MPAs likely provide recruits to fisheries for musselcracker during ontogenetic movements and dispersal from MPAs during spawning migrations. MPAs only offer partial protection to adult musselcracker populations in the spawning season, but this could nevertheless be significant under high levels of exploitation.
- Full Text:
- Date Issued: 2009
- Authors: Watt-Pringle, Peter Andrew
- Date: 2009
- Subjects: Sparidae -- South Africa , Diplodus , Sparodon Durbanensis , Fisheries -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5302 , http://hdl.handle.net/10962/d1005147 , Sparidae -- South Africa , Diplodus , Sparodon Durbanensis , Fisheries -- South Africa
- Description: This study investigated the movement behaviour of three inshore South African sparids – blacktail (Diplodus sargus capensis), zebra (Diplodus cervinus hottentotus) and white musselcracker (Sparodon durbanensis), popular inshore fishery species caught in appreciable numbers along much of the South African coast. The first study component examined movements of juveniles in a rocky intertidal nursery area at Schoenmakerskop near Port Elizabeth. Juveniles in a single gully were tagged with Visible Implant Elastomer (VIE) and resighted at the study site on snorkelling gear over a seven-month period. Tagged zebra and musselcracker displayed limited movement between potential low tide refuges, being observed repeatedly in the same gully over the full duration of the study. However, blacktail displayed greater movements and were seen infrequently in the later period of the study, probably having undergone an ontogenetic habitat shift to subtidal areas. There was evidence that blacktail maintain use of their intertidal nursery over high tide, during which the other two species moved into shallower areas adjacent to their low tide refuge. The results of three national tagging programs were analysed to determine the movement patterns of adolescent and adult fishes. The coast-wide ORI-WWF National Voluntary Tagging Program and two dedicated research programs in marine protected areas (MPAs) at De Hoop MPA and Tsitsikamma National Park (TNP) recorded few large-scale movements of tagged adult blacktail, zebra and juvenile musselcracker. High spatial-resolution data from the TNP suggested movements were usually on scales far smaller than one km. Together with long periods at liberty for many recaptured individuals, this suggests these fishes are longterm residents of small home range areas. However, tagged musselcracker over 600 mm forklength (adults) were observed to make large-scale movements, including some in excess of 800 km from Eastern Cape to KwaZulu-Natal waters. Predominantly eastward movements of adults recaptured during the spawning season indicate seasonal spawning migrations that occur in different regions of the coast. These enable the use of prevailing oceanographic currents to disperse eggs and larvae to suitable rocky nursery habitat. The third component of this study made use of high-resolution data on the temporal and spatial distribution of catches by scientific angling in the TNP to examine the daily activity patterns of the study species in relation to diel and tidal cycles, and habitat use. Blacktail capture probability was correlated with the diurnal light cycle, with peaks close to twilight suggesting elevated crepuscular foraging activity. Catches of blacktail, zebra and small musselcracker were correlated with the tidal cycle, foraging peaking over high tide periods. All three species used shallow inshore habitats extensively for foraging, blacktail showing a preference for sandy areas, while zebra and small musselcracker preferred shallow reef. Capture probability of larger musselcracker, however, was unrelated to habitat, possibly evidence of increasing area and habitat use with an ontogenetic change in diet. The lifetime movement patterns of these three species are discussed in relation to conservation measures and their management in South African fisheries. Restricted movement throughout post-settlement life for blacktail and zebra, and during the juvenile phase for musselcracker, makes local populations vulnerable to overexploitation. At present, MPAs probably play an important role in protecting local blacktail and zebra populations from overexploitation, and limited post-settlement movements mean the degree of larval dispersal between protected and adjacent areas will likely determine the effectiveness of MPAs in enhancing fisheries for these species. By contrast, MPAs likely provide recruits to fisheries for musselcracker during ontogenetic movements and dispersal from MPAs during spawning migrations. MPAs only offer partial protection to adult musselcracker populations in the spawning season, but this could nevertheless be significant under high levels of exploitation.
- Full Text:
- Date Issued: 2009
A grid based approach for the control and recall of the properties of IEEE 1394 audio devices
- Authors: Foulkes, Philip James
- Date: 2009
- Subjects: IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4594 , http://hdl.handle.net/10962/d1004836 , IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Description: The control of modern audio studios is complex. Audio mixing desks have grown to the point where they contain thousands of parameters. The control surfaces of these devices do not reflect the routing and signal processing capabilities that the devices are capable of. Software audio mixing desk editors have been developed that allow for the remote control of these devices, but their graphical user interfaces retain the complexities of the audio mixing desk that they represent. In this thesis, we propose a grid approach to audio mixing. The developed grid audio mixing desk editor represents an audio mixing desk as a series of graphical routing matrices. These routing matrices expose the various signal processing points and signal flows that exist within an audio mixing desk. The routing matrices allow for audio signals to be routed within the device, and allow for the device’s parameters to be adjusted by selecting the appropriate signal processing points. With the use of the programming interfaces that are defined as part of the Studio Connections – Total Recall SDK, the audio mixing desk editor was integrated with compatible DAW applications to provide persistence of audio mixing desk parameter states. Many audio studios currently use digital networks to connect audio devices together. Audio and control signals are patched between devices through the use of software patchbays that run on computers. We propose a double grid-based FireWire patchbay aimed to simplify the patching of signals between audio devices on a FireWire network. The FireWire patchbay was implemented in such a way such that it can host software device editors that are Studio Connections compatible. This has allowed software device editors to be associated with the devices that are represented on the FireWire patchbay, thus allowing for studio wide control from a single application. The double grid-based patchbay was implemented such that it can be hosted by compatible DAW applications. Through this, the double grid-based patchbay application is able to provide the DAW application with the state of the parameters of the devices in a studio, as well as the connections between them. The DAW application may save this state data to its native song files. This state data may be passed back to the double grid-based patchbay when the song file is reloaded at a later stage. This state data may then be used by the patchbay to restore the parameters of the patchbay and its device editors to a previous state. This restored state may then be transferred to the hardware devices being represented by the patchbay.
- Full Text:
- Date Issued: 2009
- Authors: Foulkes, Philip James
- Date: 2009
- Subjects: IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4594 , http://hdl.handle.net/10962/d1004836 , IEEE 1394 (Standard) , Computer sound processing , Digital communications , Local area networks (Computer networks) , Sound -- Recording and reproducing -- Digital techniques , Computational grids (Computer systems)
- Description: The control of modern audio studios is complex. Audio mixing desks have grown to the point where they contain thousands of parameters. The control surfaces of these devices do not reflect the routing and signal processing capabilities that the devices are capable of. Software audio mixing desk editors have been developed that allow for the remote control of these devices, but their graphical user interfaces retain the complexities of the audio mixing desk that they represent. In this thesis, we propose a grid approach to audio mixing. The developed grid audio mixing desk editor represents an audio mixing desk as a series of graphical routing matrices. These routing matrices expose the various signal processing points and signal flows that exist within an audio mixing desk. The routing matrices allow for audio signals to be routed within the device, and allow for the device’s parameters to be adjusted by selecting the appropriate signal processing points. With the use of the programming interfaces that are defined as part of the Studio Connections – Total Recall SDK, the audio mixing desk editor was integrated with compatible DAW applications to provide persistence of audio mixing desk parameter states. Many audio studios currently use digital networks to connect audio devices together. Audio and control signals are patched between devices through the use of software patchbays that run on computers. We propose a double grid-based FireWire patchbay aimed to simplify the patching of signals between audio devices on a FireWire network. The FireWire patchbay was implemented in such a way such that it can host software device editors that are Studio Connections compatible. This has allowed software device editors to be associated with the devices that are represented on the FireWire patchbay, thus allowing for studio wide control from a single application. The double grid-based patchbay was implemented such that it can be hosted by compatible DAW applications. Through this, the double grid-based patchbay application is able to provide the DAW application with the state of the parameters of the devices in a studio, as well as the connections between them. The DAW application may save this state data to its native song files. This state data may be passed back to the double grid-based patchbay when the song file is reloaded at a later stage. This state data may then be used by the patchbay to restore the parameters of the patchbay and its device editors to a previous state. This restored state may then be transferred to the hardware devices being represented by the patchbay.
- Full Text:
- Date Issued: 2009
Statistical models for pricing weather derivatives for Port Elizabeth
- Authors: Nasila, Mark Wopicho
- Date: 2009
- Subjects: Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10567 , http://hdl.handle.net/10948/1018 , Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Description: Weather has a significant impact on business activities of many kinds. The list of economic activities subjected to the risk of the weather include: the energy producers and consumers, the industry of leisure, the insurance industry, the food industry and the agricultural industries but the primary industry, namely the energy industry, has given rise to the demand for weather derivatives and has caused the weather risk management industry to evolve actively. A derivative is a contract or security, whose payoffs depend upon the price of an underlying asset price, and is used to control the risks of naturally-arising exposures to such an asset price. Therefore weather derivatives are financial contracts with payouts that depend on weather in some form. It is a contract that provides a payoff in response to an index level based on weather phenomena (West, 2002).The underlying variable can be for example humidity, rain, snowfall, temperature, or even sunshine. The main players who take part in the weather derivatives markets industry can be grouped in to five main categories, namely: 1) End users who are also referred to as hedgers 2) Speculators 3) Market makers 4) Brokers 5) Insurance and re-insurance companies. Since the late 90’s when the first weather derivatives transactions were recorded, the underlying market has witnessed the development of a new derivative market in the United States, which is gradually expanding across Europe. However, the newly developed market for weather derivatives is not liquid in Africa and specifically South Africa mainly due to the following factors: 1) Many companies and business organisations have not yet established a hedging policy or even figured out how their businesses or industries are exposed to weather risks. 2 2) “Since many companies and industries depend on insurance companies to cover their risks, it is possible that the solutions suggested by these companies or industries looking for protection from weather risks differ according to the cover provided by these insurance organisations “(Micali, 2008). The main aim of this study is to review available statistical models for pricing derivatives, with temperature as the underlying which could enable industries, businesses and other organisations in South Africa to protect themselves against losses due to fluctuations in the weather and therefore hedge their risks.
- Full Text:
- Date Issued: 2009
- Authors: Nasila, Mark Wopicho
- Date: 2009
- Subjects: Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10567 , http://hdl.handle.net/10948/1018 , Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Description: Weather has a significant impact on business activities of many kinds. The list of economic activities subjected to the risk of the weather include: the energy producers and consumers, the industry of leisure, the insurance industry, the food industry and the agricultural industries but the primary industry, namely the energy industry, has given rise to the demand for weather derivatives and has caused the weather risk management industry to evolve actively. A derivative is a contract or security, whose payoffs depend upon the price of an underlying asset price, and is used to control the risks of naturally-arising exposures to such an asset price. Therefore weather derivatives are financial contracts with payouts that depend on weather in some form. It is a contract that provides a payoff in response to an index level based on weather phenomena (West, 2002).The underlying variable can be for example humidity, rain, snowfall, temperature, or even sunshine. The main players who take part in the weather derivatives markets industry can be grouped in to five main categories, namely: 1) End users who are also referred to as hedgers 2) Speculators 3) Market makers 4) Brokers 5) Insurance and re-insurance companies. Since the late 90’s when the first weather derivatives transactions were recorded, the underlying market has witnessed the development of a new derivative market in the United States, which is gradually expanding across Europe. However, the newly developed market for weather derivatives is not liquid in Africa and specifically South Africa mainly due to the following factors: 1) Many companies and business organisations have not yet established a hedging policy or even figured out how their businesses or industries are exposed to weather risks. 2 2) “Since many companies and industries depend on insurance companies to cover their risks, it is possible that the solutions suggested by these companies or industries looking for protection from weather risks differ according to the cover provided by these insurance organisations “(Micali, 2008). The main aim of this study is to review available statistical models for pricing derivatives, with temperature as the underlying which could enable industries, businesses and other organisations in South Africa to protect themselves against losses due to fluctuations in the weather and therefore hedge their risks.
- Full Text:
- Date Issued: 2009
Polymers, catalysts and nanostructures a hybrid approach to biomolecule detection
- Authors: Frith, Kelly-Anne
- Date: 2009
- Subjects: Polymers , Nanostructured materials , Biomolecules , Tryptophan , Melatonin , Electrodes , Electrochemistry , Tryptophan oxygenase
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3980 , http://hdl.handle.net/10962/d1004039 , Polymers , Nanostructured materials , Biomolecules , Tryptophan , Melatonin , Electrodes , Electrochemistry , Tryptophan oxygenase
- Description: The main goals in electroanalytical sensing are towards improved sensitivity and selectivity, or specificity, of an analyte. There are several approaches to achieving these goals with the main approach being modification of an electrode surface with synthetic or natural catalysts (enzymes), polymers and also utilisation of nanostructured materials. At present, there is a strong movement towards hybrid sensing which couple different properties of two or more surface modification approaches. In this thesis, a range of these surface modifications were explored for analysis and detection of two main analytes: the amino acid, tryptophan (Trp); and, the neurotransmitter, dopamine (DA). Specifically, this thesis aimed to utilise these methods to enhance the sensitivity and selectivity for Trp over an interferent, the indoleamine, melatonin (Mel); and, DA over the vitamin, ascorbic acid (AA). For Trp detection, immobilisation of an enzyme, Tryptophanase (Trpase) resulted in poor selectivity for the analyte. However, enhanced sensitivity and selectivity was achieved through pH manipulation of the electrolyte medium at a Nafion®-modified electrode surface for both Trp and Mel. At pH 3.0, the Mel and Trp anodic peak potentials were sufficiently resolved allowing for an LOD of 1.60 and 1.62 nM,respectively, and permitting the accurate analysis of Trp in a dietary supplement containing Mel. Multi-walled carbon nanotubes (MWCNTs) suspended in Nafion® exhibited further increases in the signal responses of these analytes at pH 3.0 and 7.4 with minimal change in the resolution of the anodic peaks. A lower sensitivity was, therefore, observed at the Nafion® and MWCNT modified electrode compared to the Nafion®-modified electrode at pH 3.0 with LODs of 0.59 and 0.80 nM exhibited for Trp and Mel, respectively. Enhanced selectivity for Trp in the presence of Mel can be achieved with MWCNTs in the presence of metallotetrasulphonated phthalocyanines (MTSPcs) particularly at pH 3.0, owing to cation exchange effects. However, the lack of sensitivity towards Trp, and even Mel, at this CoTSPc and MWCNT modified electrode remains a drawback. For DA, detection at the MWCNT and Nafion® surface resulted in improved sensitivity over that of both the bare electrode (613.0 nM) and the Nafion® modified electrode (1045.1 nM) with a calculated LOD of 133.9 nM at this layer. Furthermore, improvements in the selectivity of DA were achieved at the Nafion® and MWCNT modified electrode as exclusion of AA (150 μM) was achieved. At the MWCNT and CoTSPc surface, AA was excluded up to 130 μM with sensitivity for DA extending as low as 14.3 nM, far greater than observed for Trp and Mel. These concentrations are well within physiological concentration ranges and represent the most significant solution yet in terms of AA exclusion and enhanced sensitivity for DA. An examination of the surface layering by impedance spectroscopy and atomic force microscopy indicates that the success of the hybrid sensor utilising CoTSPc and MWCNTs lay in improved dispersion of MWCNTs and improved electron transfer kinetics, facilitated by the net charge of the materials present. This thesis, thus, showed the utility of a judicious selection of synthetic and biological catalysts, polymers and carbon nanomaterials towards a hybrid approach to the electrochemical sensing of Trp, Mel, DA and AA with focus on sensitivity and selectivity of these analytes.
- Full Text:
- Date Issued: 2009
- Authors: Frith, Kelly-Anne
- Date: 2009
- Subjects: Polymers , Nanostructured materials , Biomolecules , Tryptophan , Melatonin , Electrodes , Electrochemistry , Tryptophan oxygenase
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3980 , http://hdl.handle.net/10962/d1004039 , Polymers , Nanostructured materials , Biomolecules , Tryptophan , Melatonin , Electrodes , Electrochemistry , Tryptophan oxygenase
- Description: The main goals in electroanalytical sensing are towards improved sensitivity and selectivity, or specificity, of an analyte. There are several approaches to achieving these goals with the main approach being modification of an electrode surface with synthetic or natural catalysts (enzymes), polymers and also utilisation of nanostructured materials. At present, there is a strong movement towards hybrid sensing which couple different properties of two or more surface modification approaches. In this thesis, a range of these surface modifications were explored for analysis and detection of two main analytes: the amino acid, tryptophan (Trp); and, the neurotransmitter, dopamine (DA). Specifically, this thesis aimed to utilise these methods to enhance the sensitivity and selectivity for Trp over an interferent, the indoleamine, melatonin (Mel); and, DA over the vitamin, ascorbic acid (AA). For Trp detection, immobilisation of an enzyme, Tryptophanase (Trpase) resulted in poor selectivity for the analyte. However, enhanced sensitivity and selectivity was achieved through pH manipulation of the electrolyte medium at a Nafion®-modified electrode surface for both Trp and Mel. At pH 3.0, the Mel and Trp anodic peak potentials were sufficiently resolved allowing for an LOD of 1.60 and 1.62 nM,respectively, and permitting the accurate analysis of Trp in a dietary supplement containing Mel. Multi-walled carbon nanotubes (MWCNTs) suspended in Nafion® exhibited further increases in the signal responses of these analytes at pH 3.0 and 7.4 with minimal change in the resolution of the anodic peaks. A lower sensitivity was, therefore, observed at the Nafion® and MWCNT modified electrode compared to the Nafion®-modified electrode at pH 3.0 with LODs of 0.59 and 0.80 nM exhibited for Trp and Mel, respectively. Enhanced selectivity for Trp in the presence of Mel can be achieved with MWCNTs in the presence of metallotetrasulphonated phthalocyanines (MTSPcs) particularly at pH 3.0, owing to cation exchange effects. However, the lack of sensitivity towards Trp, and even Mel, at this CoTSPc and MWCNT modified electrode remains a drawback. For DA, detection at the MWCNT and Nafion® surface resulted in improved sensitivity over that of both the bare electrode (613.0 nM) and the Nafion® modified electrode (1045.1 nM) with a calculated LOD of 133.9 nM at this layer. Furthermore, improvements in the selectivity of DA were achieved at the Nafion® and MWCNT modified electrode as exclusion of AA (150 μM) was achieved. At the MWCNT and CoTSPc surface, AA was excluded up to 130 μM with sensitivity for DA extending as low as 14.3 nM, far greater than observed for Trp and Mel. These concentrations are well within physiological concentration ranges and represent the most significant solution yet in terms of AA exclusion and enhanced sensitivity for DA. An examination of the surface layering by impedance spectroscopy and atomic force microscopy indicates that the success of the hybrid sensor utilising CoTSPc and MWCNTs lay in improved dispersion of MWCNTs and improved electron transfer kinetics, facilitated by the net charge of the materials present. This thesis, thus, showed the utility of a judicious selection of synthetic and biological catalysts, polymers and carbon nanomaterials towards a hybrid approach to the electrochemical sensing of Trp, Mel, DA and AA with focus on sensitivity and selectivity of these analytes.
- Full Text:
- Date Issued: 2009
The effects of a Kenyan antidiabetic plant on insulin homeostasis
- Authors: Suleiman, Khairunisa Yahya
- Date: 2009
- Subjects: Medicinal plants -- Kenya , Insulin resistance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10326 , http://hdl.handle.net/10948/1055 , Medicinal plants -- Kenya , Insulin resistance
- Description: The metabolic disorder diabetes; is a global epidemic affecting people in developed countries and increasingly in developing countries. In two decades time, 350 million people will be diabetic at the current rate of prevalence. In a preliminary study, insulin resistant rats were treated with Prunus Africana (plant A) for 28 days. Plasma samples obtained from P. africana treated rats had increased insulin levels compared to normal and untreated insulin resistant rats (Karachi, 2009). The treatment of insulin resistant rats with P. africana also showed increased glucose uptake in rat adipose tissue (Karachi, 2009), suggesting that P. africana had anti-diabetic properties. The aim of the study was to investigate the mechanism of the anti-diabetic properties of P africana extract. Increased insulin secretion was confirmed by the increased Cpeptide concentration in plasma samples of rats treated with P. africana. In order to explain the high insulin levels, several hypothesis’ were investigated: (1) P. africana may increase insulin secretion in β cells, hence the effect of P. africana on insulin secretion by INS-1 cells was investigated; (2) P. africana may increase insulin secretion by prolonging the half-life of glucagon like peptide-1 (GLP-1) by decreasing dipeptidyl peptidase IV (DPP IV) activity; the effect of P. africana on DPP IV activity was determined spectrophotometrically, (3) P. africana may increase the half-life of insulin in the plasma by decreasing the activity of insulin degrading enzyme (IDE); the effect of P. africana on IDE in rat muscle and spleen samples was investigated. To explain the increased glucose uptake in adipose tissue observed in the previous study two parameters were investigated: (1) increased GLUT4 expression in P. africana treated rats; the effect of P. africana treatment on the expression of glucose transporter 4 (GLUT4) was determined using real-time polymerase chain reaction (RT-PCR), (2) P. africana may increase glucose utilization; the effect of P. africana on glucose utilization was determined in 3T3-L1 cells. The plant extract did not significantly increase insulin secretion by INS-1 cells in the absence of glucose. P. africana decreased DPP IV activity in rat plasma when compared to the untreated insulin resistant rats and this could be a mechanism by which insulin secretion is increased during plant treatment. P. africana decreased IDE activity (however not significantly) when compared to the untreated insulin resistant The effects of a Kenyan antidiabetic plant on insulin homeostasis KY Suleiman VII rats. P. africana appeared to have no effect on GLUT4 expression. The plant appeared to increase glucose utilization in 3T3-L1 cells in the absence of insulin suggesting that P. africana may have insulin like activity. In summary, this study indicates that P. africana is indirectly involved in inhibiting DDPIV. This in turn can increase the half life of GLP-1, which in turn can enhance the secretion of insulin. P. africana increases glucose utilization although there was no evidence that the GLUT 4 transporter has a higher expression in the plant treated rats. Further studies should be conducted to investigate the expression of GLUT1 under the same conditons.
- Full Text:
- Date Issued: 2009
- Authors: Suleiman, Khairunisa Yahya
- Date: 2009
- Subjects: Medicinal plants -- Kenya , Insulin resistance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10326 , http://hdl.handle.net/10948/1055 , Medicinal plants -- Kenya , Insulin resistance
- Description: The metabolic disorder diabetes; is a global epidemic affecting people in developed countries and increasingly in developing countries. In two decades time, 350 million people will be diabetic at the current rate of prevalence. In a preliminary study, insulin resistant rats were treated with Prunus Africana (plant A) for 28 days. Plasma samples obtained from P. africana treated rats had increased insulin levels compared to normal and untreated insulin resistant rats (Karachi, 2009). The treatment of insulin resistant rats with P. africana also showed increased glucose uptake in rat adipose tissue (Karachi, 2009), suggesting that P. africana had anti-diabetic properties. The aim of the study was to investigate the mechanism of the anti-diabetic properties of P africana extract. Increased insulin secretion was confirmed by the increased Cpeptide concentration in plasma samples of rats treated with P. africana. In order to explain the high insulin levels, several hypothesis’ were investigated: (1) P. africana may increase insulin secretion in β cells, hence the effect of P. africana on insulin secretion by INS-1 cells was investigated; (2) P. africana may increase insulin secretion by prolonging the half-life of glucagon like peptide-1 (GLP-1) by decreasing dipeptidyl peptidase IV (DPP IV) activity; the effect of P. africana on DPP IV activity was determined spectrophotometrically, (3) P. africana may increase the half-life of insulin in the plasma by decreasing the activity of insulin degrading enzyme (IDE); the effect of P. africana on IDE in rat muscle and spleen samples was investigated. To explain the increased glucose uptake in adipose tissue observed in the previous study two parameters were investigated: (1) increased GLUT4 expression in P. africana treated rats; the effect of P. africana treatment on the expression of glucose transporter 4 (GLUT4) was determined using real-time polymerase chain reaction (RT-PCR), (2) P. africana may increase glucose utilization; the effect of P. africana on glucose utilization was determined in 3T3-L1 cells. The plant extract did not significantly increase insulin secretion by INS-1 cells in the absence of glucose. P. africana decreased DPP IV activity in rat plasma when compared to the untreated insulin resistant rats and this could be a mechanism by which insulin secretion is increased during plant treatment. P. africana decreased IDE activity (however not significantly) when compared to the untreated insulin resistant The effects of a Kenyan antidiabetic plant on insulin homeostasis KY Suleiman VII rats. P. africana appeared to have no effect on GLUT4 expression. The plant appeared to increase glucose utilization in 3T3-L1 cells in the absence of insulin suggesting that P. africana may have insulin like activity. In summary, this study indicates that P. africana is indirectly involved in inhibiting DDPIV. This in turn can increase the half life of GLP-1, which in turn can enhance the secretion of insulin. P. africana increases glucose utilization although there was no evidence that the GLUT 4 transporter has a higher expression in the plant treated rats. Further studies should be conducted to investigate the expression of GLUT1 under the same conditons.
- Full Text:
- Date Issued: 2009
Electrochemical studies of titanium, manganese and cobalt phthalocyanines
- Authors: Nombona, Nolwazi
- Date: 2009
- Subjects: Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4312 , http://hdl.handle.net/10962/d1004970 , Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being.
- Full Text:
- Date Issued: 2009
- Authors: Nombona, Nolwazi
- Date: 2009
- Subjects: Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4312 , http://hdl.handle.net/10962/d1004970 , Titanium , Manganese , Cobalt , Phthalocyanines , Electrochemistry , Electrodes , Self-assembly (Chemistry)
- Description: Syntheses, spectral, electrochemical and spectroelectrochemical studies of phenylthio and amino derivatised metallophthalocyanines complexes are reported. The complexes are immobilized onto a gold macro disk, gold ultramicroelectrode and gold coated fiber electrodes via self assembly with phenylthio MPc derivatives or onto a glassy carbon electrode via electropolymerisation with amino MPc derivatives. For the first time MPc SAMs were formed on gold coated fiber. The electrocatalytic behavior of the modified electrodes was studied for the detection of nitrite and L-cysteine, all modified electrodes showed improved electrocatalytic oxidation compared to the unmodified electrode. The MPc complexes catalyzed nitrite oxidation via a two-electron mechanism producing nitrate. Cobalt tetraaminophthalocyanine showed the best catalytic activity for nitrite oxidation in terms of overpotential lowering compared to other complexes and thus was used for nitrite detection in a food sample, the nitrite concentration was determined to be 59.13 ppm, well within the limit for cured meat products. Electrocatalytic oxidation of L-cysteine on SAM modified gold coated fiber was reported for the first time. The gold coated fiber and ultamicro cylinder electrode were less stable towards the electro-oxidation of cysteine compared to its oxidation on the gold disk. The gold disk electrode gave better catalytic performance in terms of stability and reduction of overpotential. The phenylthio cobalt phthalocyanine derivative gave the best catalytic activity for L-cysteine oxidation in terms of overpotential lowering compared to other phenylthio derivatized MPc complexes. The amount of L-cysteine in human urine was 2.4 mM, well within the urinary L-cysteine excretion range for a healthy human being.
- Full Text:
- Date Issued: 2009