The survival of Heliothis Armiger (Hübner) (Lepidoptera: Noctuidae) eggs on cotton plants in relation to simulated rain and overhead irrigation
- Basson, Nicolaas Cornelius Johannes
- Authors: Basson, Nicolaas Cornelius Johannes
- Date: 1987
- Subjects: Helicoverpa armigera Lepidoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5598 , http://hdl.handle.net/10962/d1002048
- Description: Crop pests are known to be adversely affected by rain. Because limited information on this aspect was available for Heliothis spp. occurring on cotton, this study was undertaken to examine the effect of water droplets from overhead irrigation and simulated rain on the survival of H. armiger eggs on cotton. Three aspects were examined: the effects of submersion, the physical impact of droplets on the eggs and the washing off of the eggs from cotton plants in the field. The first two aspects were examined in terms of the structure and respiratory system of the eggs, confirming that H. armiger eggs are able to survive initial wetting in the field. The wash-off of H. armiger eggs from cotton plants is explained in the light of the selection of oviposition sites by the moths, adhesion of the eggs to the plant parts and the dislodging and wash-off by water from simulated rain and overhead irrigation. The data are discussed in terms of the other mortality factors which occur in commercial cotton fields. All in all, it was found that while overhead irrigation should be taken into account in surveys of H. armiger for pest management purposes, it does not offer a viable control strategy and should not be investigated further
- Full Text:
- Date Issued: 1987
- Authors: Basson, Nicolaas Cornelius Johannes
- Date: 1987
- Subjects: Helicoverpa armigera Lepidoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5598 , http://hdl.handle.net/10962/d1002048
- Description: Crop pests are known to be adversely affected by rain. Because limited information on this aspect was available for Heliothis spp. occurring on cotton, this study was undertaken to examine the effect of water droplets from overhead irrigation and simulated rain on the survival of H. armiger eggs on cotton. Three aspects were examined: the effects of submersion, the physical impact of droplets on the eggs and the washing off of the eggs from cotton plants in the field. The first two aspects were examined in terms of the structure and respiratory system of the eggs, confirming that H. armiger eggs are able to survive initial wetting in the field. The wash-off of H. armiger eggs from cotton plants is explained in the light of the selection of oviposition sites by the moths, adhesion of the eggs to the plant parts and the dislodging and wash-off by water from simulated rain and overhead irrigation. The data are discussed in terms of the other mortality factors which occur in commercial cotton fields. All in all, it was found that while overhead irrigation should be taken into account in surveys of H. armiger for pest management purposes, it does not offer a viable control strategy and should not be investigated further
- Full Text:
- Date Issued: 1987
Localizing selected endocytosis protein candidates in Plasmodium falciparum using GFP-tagged fusion constructs
- Authors: Basson, Travis
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2680 , vital:20316
- Description: Malaria is a mosquito-borne infectious disease caused by several obligate intracellular protozoan parasites in the Plasmodium genus, with Plasmodium falciparum causing the most widespread cases and malaria deaths. In 2013 there were approximately 190 million cases of the disease and between 584,000 and 855,000 deaths. It is essential to identify novel drug targets and develop novel drug candidates due to the increase in resistance of P. falciparum parasites to the current arsenal of antimalarial drugs. Endocytosis is an essential process in eukaryotic cells in which the external environment is internalized by the cell in order to obtain various particles from the extracellular space. This extracellular cytoplasm is internalized in membrane-bound invaginations at the plasma membrane. During the blood stage of malaria infection, the parasite requires nutrients from the host red blood cell. To obtain these nutrients, the parasite internalizes haemoglobin in large amounts and degrades it in an acidic, lysosome-like organelle, known as the digestive vacuole. Whilst the exact molecular mechanism of malaria parasite endocytosis is not yet fully understood, a number of proteins have been suggested to be involved. The most expedient approach in identifying candidate endocytosis proteins is to investigate parasite homologues of proteins known to be involved in endocytosis in mammalian cells. The three proteins selected for investigation in this study were the P. falciparum homologues of coronin, dynamin 2, and μ4. The coding sequences for the candidate endocytosis proteins were amplified by PCR and cloned into the pARL2-GFP expression vector. P. falciparum 3D7 parasites were transfected with these vectors and the episomal expression of full-length GFP-tagged fusion protein was confirmed by Western blot analysis using commercially available anti-GFP antibodies. Microscopic analysis of live parasites using fluorescence and confocal microscopy was used to determine the localization of the candidate endocytosis proteins. Coronin appeared to display diffuse cytoplasmic GFP localization during the trophozoite stage, arguing against a role in endocytosis. However, distinct localization during the schizont stage at what appears to be the inner membrane complex was observed. Coronin is thus likely required to coordinate the formation of the actin network between the merozoite IMC and the plasma membrane on which the glideosome is dependant for generating the motile forces required for the merozoite motility and invasion of RBCs. Dynamin 2 displayed localization at three potential locii: the parasite periphery (plasma membrane), punctuate regions within the cytoplasm (potentially at membrane bound organelles) and at the parasite food vacuole. The data suggested that dynamin 2 is involved in endocytosis and membrane trafficking in a similar manner to classical dynamins, potentially as a vesicle scission molecule at the plasma membrane, mediating vesicle formation at the food vacuole to recycle membrane to the plasma membrane, and possibly mitochondria organelle division. μ4 displayed transient localization, cycling between cytosolic localization, and localization to distinct regions at the plasma membrane and the food vacuole. Localization of Pfμ4 to the plasma membrane is indicative of a role for μ4 as a part of an adaptor protein (AP) complex which may be responsible for recruitment of clathrin to initiate endocytosis in a manner similar to mammalian AP-2. As was observed with PfDYN2, Pfμ4 localizes to the FV, which suggests that Pfμ4 forms part of a coat complex that mediates the formation of vesicles that recycle membrane from the FV to the parasite plasma membrane. This study showed that expressing proteins as full-length GFP-tagged fusion constructs is an effective approach in the early stages of determining the localization and function of P. falciparum proteins in vitro, and distinguishing between candidates that have a potential role in endocytosis and those that are unlikely to do so.
- Full Text:
- Date Issued: 2016
- Authors: Basson, Travis
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2680 , vital:20316
- Description: Malaria is a mosquito-borne infectious disease caused by several obligate intracellular protozoan parasites in the Plasmodium genus, with Plasmodium falciparum causing the most widespread cases and malaria deaths. In 2013 there were approximately 190 million cases of the disease and between 584,000 and 855,000 deaths. It is essential to identify novel drug targets and develop novel drug candidates due to the increase in resistance of P. falciparum parasites to the current arsenal of antimalarial drugs. Endocytosis is an essential process in eukaryotic cells in which the external environment is internalized by the cell in order to obtain various particles from the extracellular space. This extracellular cytoplasm is internalized in membrane-bound invaginations at the plasma membrane. During the blood stage of malaria infection, the parasite requires nutrients from the host red blood cell. To obtain these nutrients, the parasite internalizes haemoglobin in large amounts and degrades it in an acidic, lysosome-like organelle, known as the digestive vacuole. Whilst the exact molecular mechanism of malaria parasite endocytosis is not yet fully understood, a number of proteins have been suggested to be involved. The most expedient approach in identifying candidate endocytosis proteins is to investigate parasite homologues of proteins known to be involved in endocytosis in mammalian cells. The three proteins selected for investigation in this study were the P. falciparum homologues of coronin, dynamin 2, and μ4. The coding sequences for the candidate endocytosis proteins were amplified by PCR and cloned into the pARL2-GFP expression vector. P. falciparum 3D7 parasites were transfected with these vectors and the episomal expression of full-length GFP-tagged fusion protein was confirmed by Western blot analysis using commercially available anti-GFP antibodies. Microscopic analysis of live parasites using fluorescence and confocal microscopy was used to determine the localization of the candidate endocytosis proteins. Coronin appeared to display diffuse cytoplasmic GFP localization during the trophozoite stage, arguing against a role in endocytosis. However, distinct localization during the schizont stage at what appears to be the inner membrane complex was observed. Coronin is thus likely required to coordinate the formation of the actin network between the merozoite IMC and the plasma membrane on which the glideosome is dependant for generating the motile forces required for the merozoite motility and invasion of RBCs. Dynamin 2 displayed localization at three potential locii: the parasite periphery (plasma membrane), punctuate regions within the cytoplasm (potentially at membrane bound organelles) and at the parasite food vacuole. The data suggested that dynamin 2 is involved in endocytosis and membrane trafficking in a similar manner to classical dynamins, potentially as a vesicle scission molecule at the plasma membrane, mediating vesicle formation at the food vacuole to recycle membrane to the plasma membrane, and possibly mitochondria organelle division. μ4 displayed transient localization, cycling between cytosolic localization, and localization to distinct regions at the plasma membrane and the food vacuole. Localization of Pfμ4 to the plasma membrane is indicative of a role for μ4 as a part of an adaptor protein (AP) complex which may be responsible for recruitment of clathrin to initiate endocytosis in a manner similar to mammalian AP-2. As was observed with PfDYN2, Pfμ4 localizes to the FV, which suggests that Pfμ4 forms part of a coat complex that mediates the formation of vesicles that recycle membrane from the FV to the parasite plasma membrane. This study showed that expressing proteins as full-length GFP-tagged fusion constructs is an effective approach in the early stages of determining the localization and function of P. falciparum proteins in vitro, and distinguishing between candidates that have a potential role in endocytosis and those that are unlikely to do so.
- Full Text:
- Date Issued: 2016
An ion imprinted polymer for the selective extraction of mercury (II) ions in aqueous media
- Authors: Batlokwa, Bareki Shima
- Date: 2010 , 2013-07-18
- Subjects: Mercury , Metal ions , Imprinted polymers , Polymerization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4294 , http://hdl.handle.net/10962/d1004541 , Mercury , Metal ions , Imprinted polymers , Polymerization
- Description: This thesis presents the application of an imprinted mercury(lI) polymer that we synthesized by copolymerizing the functional and cross-linking monomers, N'-[3-(Trimethoxysilyl)propyl] diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS) in the presence of mercury (II) ions as template. A bulk polymerization method following a double-imprinting procedure and employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer was employed in the synthesis. The imprinted polymer particles were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and their average size determined by screen analysis using standard test sieves. The relative selective coefficients (k') of the imprinted polymer evaluated from selective binding studies between Hg ²⁺and Cu²⁺ or Hg²⁺ and Cd²⁺, were 10588 and 3147, respectively. These values indicated highly favored Hg²⁺ extractions over the two competing ions. Application of the polymer to various real water samples (tap, sea, river, pulverized coal solution, treated and untreated sewerage from the vicinity of Grahamstown in South Africa) showed high extraction efficiencies (EEs) of Hg²⁺ ions; (over 84% in all cases) as evaluated from the detected unextracted Hg²⁺ ions by inductively coupled plasma optical emission spectroscopy (ICP-OES). The limit of detection (LOD, 3ơ) of the method was evaluated to be 0.036 ng ml⁻¹ and generally the data (n=10) had percentage relative standard deviation (%RSD) of less than 4%. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre-concentration of mercury(lI) ions in aqueous environments. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2010
- Authors: Batlokwa, Bareki Shima
- Date: 2010 , 2013-07-18
- Subjects: Mercury , Metal ions , Imprinted polymers , Polymerization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4294 , http://hdl.handle.net/10962/d1004541 , Mercury , Metal ions , Imprinted polymers , Polymerization
- Description: This thesis presents the application of an imprinted mercury(lI) polymer that we synthesized by copolymerizing the functional and cross-linking monomers, N'-[3-(Trimethoxysilyl)propyl] diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS) in the presence of mercury (II) ions as template. A bulk polymerization method following a double-imprinting procedure and employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer was employed in the synthesis. The imprinted polymer particles were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and their average size determined by screen analysis using standard test sieves. The relative selective coefficients (k') of the imprinted polymer evaluated from selective binding studies between Hg ²⁺and Cu²⁺ or Hg²⁺ and Cd²⁺, were 10588 and 3147, respectively. These values indicated highly favored Hg²⁺ extractions over the two competing ions. Application of the polymer to various real water samples (tap, sea, river, pulverized coal solution, treated and untreated sewerage from the vicinity of Grahamstown in South Africa) showed high extraction efficiencies (EEs) of Hg²⁺ ions; (over 84% in all cases) as evaluated from the detected unextracted Hg²⁺ ions by inductively coupled plasma optical emission spectroscopy (ICP-OES). The limit of detection (LOD, 3ơ) of the method was evaluated to be 0.036 ng ml⁻¹ and generally the data (n=10) had percentage relative standard deviation (%RSD) of less than 4%. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre-concentration of mercury(lI) ions in aqueous environments. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2010
Synthesis and application of novel coumarin-triazole-based polymeric sensors towards metal ion sensing
- Authors: Battison, Aidan Leigh
- Date: 2018
- Subjects: Polymers -- Optical properties , Polymers -- Electric properties Biosensors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23636 , vital:30591
- Description: One of the greatest challenges in the South African society is the pollutants which we are exposed to within our environment. The mismanagement and release of toxic analytes via different chemical, agricultural and industrial processes has led to a critical need for advanced monitoring systems for environmental protection, remediation and restoration. Industrial processes release a plethora of different pollutants into the earth, atmosphere, and aquatic ecosystems. Most pollutant causing activities are due to mining, agriculture, industry and chemical storage. Most contaminants released by these processes are not biodegradable and may be able to exude into water systems where they present an immense threat to environmental and human health. The number of different analytes released into the environment is greater than the number of sensors able to detect these species. Clearly, there is a need for a rapid and low-cost means of detection, recognition, and monitoring of these analytes. Fluorescent coumarin-triazole-based polymeric materials were designed and investigated as potential sensors for these metal ionic species. The Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes was the focus method of polymerization to form the fluorescence enhancing triazole moiety. The coumarin-triazole units formed the backbone of these polymeric material. The photophysical properties of the starting monomers and polymers were investigated in THF solvent. The polymers showed to have higher absorption and emission intensities than their respective starting monomers. The chemosensing capabilities of the polymers for metal ions were investigated through their emission properties. The polymers showed to have the greatest response towards Hg2+ and Ag+. Furthermore, the polymers displayed a reversible response towards Hg2+ in the presence of EDTA. The most responsive and reversible polymer system was applied for metal sensing capabilities towards Hg2+ from a known water source. This polymer proved to be a sensitive and reversible chemosensor for Hg2+ ions. The site of metal complexation on the polymer systems was verified by 1H NMR and FT-IR spectroscopy and was found to be mainly the triazole moieties from the polymer backbone. Finally, the possible mechanism for the fluorescent response of Hg2+ and Ag+ was also investigated.
- Full Text:
- Date Issued: 2018
- Authors: Battison, Aidan Leigh
- Date: 2018
- Subjects: Polymers -- Optical properties , Polymers -- Electric properties Biosensors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23636 , vital:30591
- Description: One of the greatest challenges in the South African society is the pollutants which we are exposed to within our environment. The mismanagement and release of toxic analytes via different chemical, agricultural and industrial processes has led to a critical need for advanced monitoring systems for environmental protection, remediation and restoration. Industrial processes release a plethora of different pollutants into the earth, atmosphere, and aquatic ecosystems. Most pollutant causing activities are due to mining, agriculture, industry and chemical storage. Most contaminants released by these processes are not biodegradable and may be able to exude into water systems where they present an immense threat to environmental and human health. The number of different analytes released into the environment is greater than the number of sensors able to detect these species. Clearly, there is a need for a rapid and low-cost means of detection, recognition, and monitoring of these analytes. Fluorescent coumarin-triazole-based polymeric materials were designed and investigated as potential sensors for these metal ionic species. The Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes was the focus method of polymerization to form the fluorescence enhancing triazole moiety. The coumarin-triazole units formed the backbone of these polymeric material. The photophysical properties of the starting monomers and polymers were investigated in THF solvent. The polymers showed to have higher absorption and emission intensities than their respective starting monomers. The chemosensing capabilities of the polymers for metal ions were investigated through their emission properties. The polymers showed to have the greatest response towards Hg2+ and Ag+. Furthermore, the polymers displayed a reversible response towards Hg2+ in the presence of EDTA. The most responsive and reversible polymer system was applied for metal sensing capabilities towards Hg2+ from a known water source. This polymer proved to be a sensitive and reversible chemosensor for Hg2+ ions. The site of metal complexation on the polymer systems was verified by 1H NMR and FT-IR spectroscopy and was found to be mainly the triazole moieties from the polymer backbone. Finally, the possible mechanism for the fluorescent response of Hg2+ and Ag+ was also investigated.
- Full Text:
- Date Issued: 2018
A reconciliation study of different resource estimation methods and drill hole spacing as applied to the Langer Heinrich calcrete-hosted uranium deposit, Namibia
- Authors: Baufeldt, Sven
- Date: 2018
- Subjects: Uranium -- Namibia , Calcretes -- Namibia , Carnotite -- Namibia , Uranium mines and mining -- Namibia , Uranium ores -- Geology -- Namibia , Langer-Heinrich Uranium mine
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62527 , vital:28203
- Description: The Langer Heinrich calcrete hosted uranium deposit is situated approximately 90 km to east of the coastal town of Swakopmund in Namibia. It is run by an Australian owned company, Paladin Energy Limited, along with China National Nuclear Corporation (CNNC) who maintain 25% of the shares. Production commenced in 2007 and has been ongoing. Carnotite is the primary and only ore mineral, and the nature of mineralisation within the Langer Heinrich palaeo channel dictates westward-directed continuous open pit mining. Smaller-scale 1micro pits target near-surface, high-grade, lenses toward the east. The high variability in uranium grade over relatively short distances complicates the grade estimation process. This combined with a low uranium price, and a study aimed at optimising of mine production is one of the key drivers for the research presented in this thesis. The efficacy of four resource estimation techniques, commonly used in the mining industry, are investigated by application to variable exploration, infill drilling and grade-control drill pattern spacing. The drill spacing includes regular grids of 50 m x 50 m, 25 m x 25 m and 12,5 m x 12,5 m exploration data. Also included is grade control drill data, drilled on a 4 m x 4 m spacing. The current selective mining unit (SMU) is 4mE x 4mN x 3mRl which is an indication of the minimum dimension whereby the loading equipment can separate ore from waste. The two datasets are processed by four estimation techniques: Inverse Distance Weighting (IDW, squared and cubed), Ordinary Kriging (OK), Multiple Indicator Kriging (MIK) and Conditional Simulation (CS). The two datasets consisted of real-time mining data from pit G1 (micro-pit) in the eastern parts of the mining licence, and pit H1 (continuous larger open pit) in the western area of the palaeo channel. The reconciliation project aims to provide results suitable for devising optimised mining strategies, particularly in future targets where drill spacing can perhaps be improved to provide suitable data with a greater cost saving strategy. Along with the optimal drill spacing or combination thereof, a preferred estimation technique can be suggested and recommended for future operations that involve mining of surficial calcrete-hosted uranium deposits. Results of this study show that 12,5 m x 12,5 m drill spacing provided estimation accuracies similar to that of the narrow 4 m x 4 m grade control spacing (blast hole drilling spacing). The 12,5 m x 12,5m spacing has potential for accurate grade estimations during mining, and could be supplemented by infill downhole radiometric logging on a 4 m x 4 m spacing when 1 Micro pit: Small pits within palaeo channel usually targeted for their near surface high-grade ore necessary. In general, Multiple Indicator Kriging (MIK) provided the most accurate and robust estimations on the wider spaced exploration data and conditional simulation (CS) proved more efficient on the narrow grade control data. These results correspond with current exploration practices for surficial uranium deposits world-wide. Deposit type, therefore complexity and hence SMU sizes play a pivotal role in drill hole planning and estimation accuracies.
- Full Text:
- Date Issued: 2018
- Authors: Baufeldt, Sven
- Date: 2018
- Subjects: Uranium -- Namibia , Calcretes -- Namibia , Carnotite -- Namibia , Uranium mines and mining -- Namibia , Uranium ores -- Geology -- Namibia , Langer-Heinrich Uranium mine
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62527 , vital:28203
- Description: The Langer Heinrich calcrete hosted uranium deposit is situated approximately 90 km to east of the coastal town of Swakopmund in Namibia. It is run by an Australian owned company, Paladin Energy Limited, along with China National Nuclear Corporation (CNNC) who maintain 25% of the shares. Production commenced in 2007 and has been ongoing. Carnotite is the primary and only ore mineral, and the nature of mineralisation within the Langer Heinrich palaeo channel dictates westward-directed continuous open pit mining. Smaller-scale 1micro pits target near-surface, high-grade, lenses toward the east. The high variability in uranium grade over relatively short distances complicates the grade estimation process. This combined with a low uranium price, and a study aimed at optimising of mine production is one of the key drivers for the research presented in this thesis. The efficacy of four resource estimation techniques, commonly used in the mining industry, are investigated by application to variable exploration, infill drilling and grade-control drill pattern spacing. The drill spacing includes regular grids of 50 m x 50 m, 25 m x 25 m and 12,5 m x 12,5 m exploration data. Also included is grade control drill data, drilled on a 4 m x 4 m spacing. The current selective mining unit (SMU) is 4mE x 4mN x 3mRl which is an indication of the minimum dimension whereby the loading equipment can separate ore from waste. The two datasets are processed by four estimation techniques: Inverse Distance Weighting (IDW, squared and cubed), Ordinary Kriging (OK), Multiple Indicator Kriging (MIK) and Conditional Simulation (CS). The two datasets consisted of real-time mining data from pit G1 (micro-pit) in the eastern parts of the mining licence, and pit H1 (continuous larger open pit) in the western area of the palaeo channel. The reconciliation project aims to provide results suitable for devising optimised mining strategies, particularly in future targets where drill spacing can perhaps be improved to provide suitable data with a greater cost saving strategy. Along with the optimal drill spacing or combination thereof, a preferred estimation technique can be suggested and recommended for future operations that involve mining of surficial calcrete-hosted uranium deposits. Results of this study show that 12,5 m x 12,5 m drill spacing provided estimation accuracies similar to that of the narrow 4 m x 4 m grade control spacing (blast hole drilling spacing). The 12,5 m x 12,5m spacing has potential for accurate grade estimations during mining, and could be supplemented by infill downhole radiometric logging on a 4 m x 4 m spacing when 1 Micro pit: Small pits within palaeo channel usually targeted for their near surface high-grade ore necessary. In general, Multiple Indicator Kriging (MIK) provided the most accurate and robust estimations on the wider spaced exploration data and conditional simulation (CS) proved more efficient on the narrow grade control data. These results correspond with current exploration practices for surficial uranium deposits world-wide. Deposit type, therefore complexity and hence SMU sizes play a pivotal role in drill hole planning and estimation accuracies.
- Full Text:
- Date Issued: 2018
The challenge of applying systematic conservation planning to the marine environment using expert knowledge (focus: Sparidae)
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
Property development in Mthatha: an interactive framework
- Authors: Bavu, Sonwabile
- Date: 2017
- Subjects: Real estate development -- South Africa -- Eastern Cape Land use -- South Africa -- Eastern Cape , Sustainable development -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14553 , vital:27761
- Description: Property development (PD) is basically driven by the need or demand from the people. Sustainable property development has emerged in response to a global problem – and the need to maintain environmental integrity, according to Gurry (2011) cited by Botha (2013: 7). Keeping and Shiers (2004) state that property development, as a whole, has to balance social, economic and environmental needs. Emanating from the above, any successful development project must offer investors security, infrastructure and efficiency and should also put the needs of citizens at the forefront of all its planning activities. Availability of land, existing infrastructure, availability of finance, economic conditions, political influence and corruption always influence growth of property development in any area. This study aims to identify factors that contribute to lack of property development in Mthatha. Data collected shows that the challenges sometimes lead to failure and delays of the development. The purpose of this study is to identify these challenges, investigate the available literature, consider what has been done so far to address these challenges and make recommendations. It is essential to understand the state of the town and perceptions of the people in the area dealing with Property Development. Mthatha is the main focus of the study because of the perceived number of failed and delayed property development initiatives. The primary and secondary data collected provide the basis for understanding challenges that lead to such failures and delays. This research was conducted by means of a review of the related literature and an empirical study. The empirical study was conducted using a quantitative statistical approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study is to develop a framework for successful implementation of property developments in Mthatha. The study’s findings reveal shortcomings which contribute to the study’s identified problems relating to property development in Mthatha, namely: decaying infrastructure, shortage of land, implementation of the IDP, availability of finance to promote real estate developments, political influence and corruption. Wikipedia defines Property Development as a “multifaceted business encompassing activities that range from the renovations and release of existing buildings to the purchase of land and the sale of improved land or parcels to others”. Harvey and Jowsey (2004), as cited by Botha (2013: 5), define Property Development as a process that involves changing or intensifying the use of land to produce buildings for occupation.
- Full Text:
- Date Issued: 2017
- Authors: Bavu, Sonwabile
- Date: 2017
- Subjects: Real estate development -- South Africa -- Eastern Cape Land use -- South Africa -- Eastern Cape , Sustainable development -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/14553 , vital:27761
- Description: Property development (PD) is basically driven by the need or demand from the people. Sustainable property development has emerged in response to a global problem – and the need to maintain environmental integrity, according to Gurry (2011) cited by Botha (2013: 7). Keeping and Shiers (2004) state that property development, as a whole, has to balance social, economic and environmental needs. Emanating from the above, any successful development project must offer investors security, infrastructure and efficiency and should also put the needs of citizens at the forefront of all its planning activities. Availability of land, existing infrastructure, availability of finance, economic conditions, political influence and corruption always influence growth of property development in any area. This study aims to identify factors that contribute to lack of property development in Mthatha. Data collected shows that the challenges sometimes lead to failure and delays of the development. The purpose of this study is to identify these challenges, investigate the available literature, consider what has been done so far to address these challenges and make recommendations. It is essential to understand the state of the town and perceptions of the people in the area dealing with Property Development. Mthatha is the main focus of the study because of the perceived number of failed and delayed property development initiatives. The primary and secondary data collected provide the basis for understanding challenges that lead to such failures and delays. This research was conducted by means of a review of the related literature and an empirical study. The empirical study was conducted using a quantitative statistical approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study is to develop a framework for successful implementation of property developments in Mthatha. The study’s findings reveal shortcomings which contribute to the study’s identified problems relating to property development in Mthatha, namely: decaying infrastructure, shortage of land, implementation of the IDP, availability of finance to promote real estate developments, political influence and corruption. Wikipedia defines Property Development as a “multifaceted business encompassing activities that range from the renovations and release of existing buildings to the purchase of land and the sale of improved land or parcels to others”. Harvey and Jowsey (2004), as cited by Botha (2013: 5), define Property Development as a process that involves changing or intensifying the use of land to produce buildings for occupation.
- Full Text:
- Date Issued: 2017
Epidemiological and aetiological aspects of diarrhoeal disease in the Eastern Cape
- Authors: Baxter, Esther
- Date: 1993
- Subjects: Diarrhea -- South Africa , Intestines -- Diseases , Pathogenic microorganisms -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4045 , http://hdl.handle.net/10962/d1004106 , Diarrhea -- South Africa , Intestines -- Diseases , Pathogenic microorganisms -- South Africa
- Description: Diarrhoeal disease is a major cause of mortality in children in developing countries. It also remains a serious problem among all age groups throughout the world. Whereas studies to determine the epidemiological and aetiological factors of diarrhoeal disease have been reported for other parts of South Africa and the world, as yet no information is available for the Eastern Cape. Therefore this study was undertaken to determine the factors for this area. Enteropathogens were compared for the different ages in the various population groups and, where possible, seasonal and geographical differences were emphasised. A total of 7 278 faecal samples were examined by six laboratories in the Eastern Cape during the period November 1988 to October 1990. Data was recorded noting the age, sex and population group of the patients. The towns selected were Port Elizabeth, Uitenhage, Cradock, Grahamstown and their surrounding areas. The isolation rates for the pathogens studied in the various population groups were compared to those reported in similar studies in other countries. The seasonal incidences of the various selected pathogens were compared with those reported from elsewhere in South Africa. It was thought that the higher temperature of summer may influence the finding in the White population group, while rainfall would play a greater role for the Coloured and Black populations. The geographical distribution of the pathogens emphasised the difference in living conditions between the different population groups. For example a generally higher infestation rate of Helminths occurred in rural areas and in the groups living under poorer conditions. The low isolation rates for certain bacteria and the large percentage of samples from which no pathogens were isolated indicate the need for further research. However, the finding should be valuable for determining Public Health priorities and in the management of outbreaks of diarrhoeal disease.
- Full Text:
- Date Issued: 1993
- Authors: Baxter, Esther
- Date: 1993
- Subjects: Diarrhea -- South Africa , Intestines -- Diseases , Pathogenic microorganisms -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4045 , http://hdl.handle.net/10962/d1004106 , Diarrhea -- South Africa , Intestines -- Diseases , Pathogenic microorganisms -- South Africa
- Description: Diarrhoeal disease is a major cause of mortality in children in developing countries. It also remains a serious problem among all age groups throughout the world. Whereas studies to determine the epidemiological and aetiological factors of diarrhoeal disease have been reported for other parts of South Africa and the world, as yet no information is available for the Eastern Cape. Therefore this study was undertaken to determine the factors for this area. Enteropathogens were compared for the different ages in the various population groups and, where possible, seasonal and geographical differences were emphasised. A total of 7 278 faecal samples were examined by six laboratories in the Eastern Cape during the period November 1988 to October 1990. Data was recorded noting the age, sex and population group of the patients. The towns selected were Port Elizabeth, Uitenhage, Cradock, Grahamstown and their surrounding areas. The isolation rates for the pathogens studied in the various population groups were compared to those reported in similar studies in other countries. The seasonal incidences of the various selected pathogens were compared with those reported from elsewhere in South Africa. It was thought that the higher temperature of summer may influence the finding in the White population group, while rainfall would play a greater role for the Coloured and Black populations. The geographical distribution of the pathogens emphasised the difference in living conditions between the different population groups. For example a generally higher infestation rate of Helminths occurred in rural areas and in the groups living under poorer conditions. The low isolation rates for certain bacteria and the large percentage of samples from which no pathogens were isolated indicate the need for further research. However, the finding should be valuable for determining Public Health priorities and in the management of outbreaks of diarrhoeal disease.
- Full Text:
- Date Issued: 1993
Identification of SANCDB compounds against G2019S and I2020T variants of leucine-rich repeat Kinase 2 (LRRK2) for the development of drugs against Parkinson’s Disease
- Authors: Baye, Bertha Cinthia
- Date: 2020
- Subjects: Antiparkinsonian agents , Parkinson's disease -- Treatment , Protein kinases , Parkinson's disease -- Chemotherapy , Molecules -- Models
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138764 , vital:37671
- Description: Parkinson’s disease is a type of movement disorder that occurs when nerve cells in the brain stop producing dopamine. It is the second neurodegenerative disease affecting 1-2% of people above the ages of 65 years old. There is a worldwide prevalence of 7 to 10 million affected people of all cultures and race. Studies have shown that mutation that causes Parkinson’s disease result in increased kinase activity. The c.6055 G > A in exon 41 is the most prevalent LRRK2 variation which causes a substitution of glycine to serine in G2019S in the highly activated loop of its MAP kinase domain. The LRRK2 G2019S variant is the most common genetic determinant of Parkinson’s disease identified to date. This work focused on building accurate 3D models of the LRRK2 kinase domain, that were used for large-scale in silico docking against South African natural compounds from the South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/). Molecular docking was performed to identify compounds that formed interactions with the active site of the protein and had the lowest binding energy scores. Molecular dynamics simulations showed different movements of the protein-ligand complexes and behavioural difference of the wildtype and the variants, all three structures proved to be compact. Network analysis was done to study residue interactions, contact maps, dynamic cross correlations, average BC and average L were used to study the residue interactions and general residue contribution to the functioning of the protein..
- Full Text:
- Date Issued: 2020
- Authors: Baye, Bertha Cinthia
- Date: 2020
- Subjects: Antiparkinsonian agents , Parkinson's disease -- Treatment , Protein kinases , Parkinson's disease -- Chemotherapy , Molecules -- Models
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138764 , vital:37671
- Description: Parkinson’s disease is a type of movement disorder that occurs when nerve cells in the brain stop producing dopamine. It is the second neurodegenerative disease affecting 1-2% of people above the ages of 65 years old. There is a worldwide prevalence of 7 to 10 million affected people of all cultures and race. Studies have shown that mutation that causes Parkinson’s disease result in increased kinase activity. The c.6055 G > A in exon 41 is the most prevalent LRRK2 variation which causes a substitution of glycine to serine in G2019S in the highly activated loop of its MAP kinase domain. The LRRK2 G2019S variant is the most common genetic determinant of Parkinson’s disease identified to date. This work focused on building accurate 3D models of the LRRK2 kinase domain, that were used for large-scale in silico docking against South African natural compounds from the South African Natural Compounds Database (SANCDB; https://sancdb.rubi.ru.ac.za/). Molecular docking was performed to identify compounds that formed interactions with the active site of the protein and had the lowest binding energy scores. Molecular dynamics simulations showed different movements of the protein-ligand complexes and behavioural difference of the wildtype and the variants, all three structures proved to be compact. Network analysis was done to study residue interactions, contact maps, dynamic cross correlations, average BC and average L were used to study the residue interactions and general residue contribution to the functioning of the protein..
- Full Text:
- Date Issued: 2020
Short-term changes to the life history of shad, Pomatomus saltatrix (Perciformes: Pomatomidae), in Southern Angola
- Authors: Bealey, Roy Steven John
- Date: 2015
- Subjects: Shad -- Angola , Bluefish -- Angola , Bluefish -- Climatic factors -- Angola , Bluefish -- Effect of temperature on -- Angola , Bluefish -- Effect of global warming on -- Angola , Bluefish -- Effect of fishing on -- Angola , Bluefish -- Life cycles , Pomatomidae -- Angola , Fishery management -- Angola , Climatic changes -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5379 , http://hdl.handle.net/10962/d1017211
- Description: A general lack of biological information is hampering the effective management of Angola’s fisheries. While this lack of information is largely a result of the country’s extended civil war that ended in 2002, the subsequent rapid expansion of fisheries is most likely impacting fish abundance and influencing the biology of this regions fishes. Besides the influence of fisheries, the southern Angolan coastal region is considered to be a climate change “hotspot” due to rapidly (>0.8°C/decade) increasing water temperatures. These changes are thought to drive further changes to the biology of fishes. It is therefore critical to provide baseline biological information and to identify the impacts of exploitation and warming on the biology of southern Angolan fishes. Pomatomus saltatrix is a warm-temperate marine fish species that forms an important component of fisheries throughout its broad distribution. P. saltatrix is a migratory predator that displays variable growth and maturity schedules. Typically it is heavily targeted in a range of coastal fisheries of Angola and is therefore an ideal candidate to study the biological impacts of exploitation and climate change. The aim of this study was to provide the first description of P. saltatrix biology in Angola and examine recent changes of the species biological parameters in an attempt to uncouple fishery driven from climate driven changes. Samples of P. saltatrix were collected monthly using standardised biological methods from June 2005 to December 2006 (period 1) and from June 2012 to February 2013 (period 2). The average (508mm – 1st period, 462mm – 2nd period) and maximum (760mm – 1st period, 746mm – 2nd period) size of P. saltatrix was smaller during the second period to suggest selective overharvesting of large individuals by developing fisheries. Angolan P. saltatrix grew very rapidly in their first year and thereafter, relatively slowly when compared to other populations globally. However, fish grew faster (ω = 103 – 1st period, ω = 124 – 2nd period), matured at a larger size (303mm - 1st period, 336mm - 2nd period) and younger age (0.83 years - 1st period, 0.67 years – 2nd period) during the second period. Peaks in reproductive activity remained similar (November) during both periods but a temperature anomaly appears to have influenced spawning during period 2. Sardinella aurita was the dominant prey during both periods but a greater dependence upon mugilids was observed during the second period. Although the changes in life history were not statistically significant, the faster growth observed during period two could be attributed to both increasing temperature and/or exploitation. Fishes generally grow faster, mature smaller and attain a smaller maximum size in warmer temperatures. Fisheries targeting small and large specimens of a species (as observed in this study) largely have the same impacts as ocean warming. With rapidly increasing water temperatures and exploitation rates, faster growth and earlier maturation of P. saltatrix populations will mitigate the impacts of exploitation in the short-term. However, the sustainability of Angola’s P. saltatrix stock is questionable as phenotypic adaptation will have a limited thermal scope and overexploitation will, like in all fisheries, negatively influence recruitment. Ultimately, strict monitoring, regulation and control will be necessary to ensure the sustainability of the P. saltatrix resource in Angola as it continues to face increasing anthropogenic and environmental pressures. Management guidelines and future research suggestions are therefore outlined with reference to the results of analyses conducted during this study.
- Full Text:
- Date Issued: 2015
- Authors: Bealey, Roy Steven John
- Date: 2015
- Subjects: Shad -- Angola , Bluefish -- Angola , Bluefish -- Climatic factors -- Angola , Bluefish -- Effect of temperature on -- Angola , Bluefish -- Effect of global warming on -- Angola , Bluefish -- Effect of fishing on -- Angola , Bluefish -- Life cycles , Pomatomidae -- Angola , Fishery management -- Angola , Climatic changes -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5379 , http://hdl.handle.net/10962/d1017211
- Description: A general lack of biological information is hampering the effective management of Angola’s fisheries. While this lack of information is largely a result of the country’s extended civil war that ended in 2002, the subsequent rapid expansion of fisheries is most likely impacting fish abundance and influencing the biology of this regions fishes. Besides the influence of fisheries, the southern Angolan coastal region is considered to be a climate change “hotspot” due to rapidly (>0.8°C/decade) increasing water temperatures. These changes are thought to drive further changes to the biology of fishes. It is therefore critical to provide baseline biological information and to identify the impacts of exploitation and warming on the biology of southern Angolan fishes. Pomatomus saltatrix is a warm-temperate marine fish species that forms an important component of fisheries throughout its broad distribution. P. saltatrix is a migratory predator that displays variable growth and maturity schedules. Typically it is heavily targeted in a range of coastal fisheries of Angola and is therefore an ideal candidate to study the biological impacts of exploitation and climate change. The aim of this study was to provide the first description of P. saltatrix biology in Angola and examine recent changes of the species biological parameters in an attempt to uncouple fishery driven from climate driven changes. Samples of P. saltatrix were collected monthly using standardised biological methods from June 2005 to December 2006 (period 1) and from June 2012 to February 2013 (period 2). The average (508mm – 1st period, 462mm – 2nd period) and maximum (760mm – 1st period, 746mm – 2nd period) size of P. saltatrix was smaller during the second period to suggest selective overharvesting of large individuals by developing fisheries. Angolan P. saltatrix grew very rapidly in their first year and thereafter, relatively slowly when compared to other populations globally. However, fish grew faster (ω = 103 – 1st period, ω = 124 – 2nd period), matured at a larger size (303mm - 1st period, 336mm - 2nd period) and younger age (0.83 years - 1st period, 0.67 years – 2nd period) during the second period. Peaks in reproductive activity remained similar (November) during both periods but a temperature anomaly appears to have influenced spawning during period 2. Sardinella aurita was the dominant prey during both periods but a greater dependence upon mugilids was observed during the second period. Although the changes in life history were not statistically significant, the faster growth observed during period two could be attributed to both increasing temperature and/or exploitation. Fishes generally grow faster, mature smaller and attain a smaller maximum size in warmer temperatures. Fisheries targeting small and large specimens of a species (as observed in this study) largely have the same impacts as ocean warming. With rapidly increasing water temperatures and exploitation rates, faster growth and earlier maturation of P. saltatrix populations will mitigate the impacts of exploitation in the short-term. However, the sustainability of Angola’s P. saltatrix stock is questionable as phenotypic adaptation will have a limited thermal scope and overexploitation will, like in all fisheries, negatively influence recruitment. Ultimately, strict monitoring, regulation and control will be necessary to ensure the sustainability of the P. saltatrix resource in Angola as it continues to face increasing anthropogenic and environmental pressures. Management guidelines and future research suggestions are therefore outlined with reference to the results of analyses conducted during this study.
- Full Text:
- Date Issued: 2015
The applicability of two simple single event rainfall-runoff models to catchments with different climate and physiography
- Authors: Beater, Anne Brenda
- Date: 1990
- Subjects: Hydrogeology Runoff -- South Africa Runoff -- United States Rain and rainfall -- South Africa Rain and rainfall -- United States
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4796 , http://hdl.handle.net/10962/d1001896
- Description: The study presents the results of applying two isolated event, constant runoff proportion, conceptual models to a range of catchments drawn from various climatic and physiographic regions of South Africa and the USA. The models can be operated in either lumped or semi-distributed modes. The research progressed through the following stages. The initial stage involved the calibration of both models on two sets of catchments so that an initial evaluation of the performance of the models could be carried out and any deficiencies in the model structure identified, and where practical, corrected. The models were then calibrated on a further 8 catchments. An important result of the calibration is that for both models to produce reasonably acceptable simulations, at least one parameter has to vary between storms on the same catchment to account for variations in storm or antecedent moisture characteristics. The next stage consisted of compiling quantitative descriptions of the physical characteristics of the catchments and rainfall events and an attempt to relate the calibrated parameter values to relevant physical characteristics for the purpose of estimating parameter values when calibration is not possible. Despite the difficulties encountered in quantifying some of the hydrological characteristics the general trends exhibited by many of the relationships are encouraging and the format of the combinations of physical variables used, do make sense with respect to the original parameter conceptualisations. The relationships between storm characteristics and parameters of both models are less satisfactory. There is a high degree of scatter and the between-catchment variation in the form of the relationships, indicates that the derived relationships are likely to be of little use for parameter estimation purposes. The final stage involved a validation exercise in which new parameters were estimated from the physical variable-parameter relationships for all the catchments previously used, as well as a further four. The new parameters were used to re-simulate all the storms and comparison of these results were made with the original calibration results. Both models produced poor results and are unlikely to give reliable results where calibration is not possible. The parameter relationships for the parameters related to storm characteristics are so catchment specific that transfer to other areas will produce unpredictable results. Foot note:- For compatability with computer printouts decimal full stops are used in the format of real numbers in tables etc
- Full Text:
- Date Issued: 1990
- Authors: Beater, Anne Brenda
- Date: 1990
- Subjects: Hydrogeology Runoff -- South Africa Runoff -- United States Rain and rainfall -- South Africa Rain and rainfall -- United States
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4796 , http://hdl.handle.net/10962/d1001896
- Description: The study presents the results of applying two isolated event, constant runoff proportion, conceptual models to a range of catchments drawn from various climatic and physiographic regions of South Africa and the USA. The models can be operated in either lumped or semi-distributed modes. The research progressed through the following stages. The initial stage involved the calibration of both models on two sets of catchments so that an initial evaluation of the performance of the models could be carried out and any deficiencies in the model structure identified, and where practical, corrected. The models were then calibrated on a further 8 catchments. An important result of the calibration is that for both models to produce reasonably acceptable simulations, at least one parameter has to vary between storms on the same catchment to account for variations in storm or antecedent moisture characteristics. The next stage consisted of compiling quantitative descriptions of the physical characteristics of the catchments and rainfall events and an attempt to relate the calibrated parameter values to relevant physical characteristics for the purpose of estimating parameter values when calibration is not possible. Despite the difficulties encountered in quantifying some of the hydrological characteristics the general trends exhibited by many of the relationships are encouraging and the format of the combinations of physical variables used, do make sense with respect to the original parameter conceptualisations. The relationships between storm characteristics and parameters of both models are less satisfactory. There is a high degree of scatter and the between-catchment variation in the form of the relationships, indicates that the derived relationships are likely to be of little use for parameter estimation purposes. The final stage involved a validation exercise in which new parameters were estimated from the physical variable-parameter relationships for all the catchments previously used, as well as a further four. The new parameters were used to re-simulate all the storms and comparison of these results were made with the original calibration results. Both models produced poor results and are unlikely to give reliable results where calibration is not possible. The parameter relationships for the parameters related to storm characteristics are so catchment specific that transfer to other areas will produce unpredictable results. Foot note:- For compatability with computer printouts decimal full stops are used in the format of real numbers in tables etc
- Full Text:
- Date Issued: 1990
The significance of unconformities in the development of Witwatersrand gold and uranium placers
- Authors: Beater, Christian Douglas
- Date: 1983 , 2013-04-03
- Subjects: Placer deposits , Gold ores -- Geology -- South Africa -- Witwatersrand , Uranium ores -- Geology -- South Africa -- Witwatersrand
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4925 , http://hdl.handle.net/10962/d1004535 , Placer deposits , Gold ores -- Geology -- South Africa -- Witwatersrand , Uranium ores -- Geology -- South Africa -- Witwatersrand
- Description: Most of the economic gold and uranium placers are developed on low angle disconformities in the Central Rand Group and concentrations of gold and uranium are usually at their optimum on unconformity surfaces. Examples include the Kimberley Reef and South Reef of the East Rand, the Main Reef Leader of the Central Rand, the Carbon Leader of the Carletonville goldfield, the Vaal Reef of the Klerksdorp goldfield and the Basal/Steyn placers of the Welkom goldfield. The individual goldfields represent fluvial fans which are composed of a large number of tectonogenetic sedimentary packages separated by unconformities. The tectonic responses between cycles of sedimentation produced unconformities and tectonically controlled cyclic sedimentation is one of the key factors culminating in the preparation and deposition of auriferous placers within the Witwatersrand succession. Unconformities, which represent breaks in sedimentation, result in the preconditioning of palaeosurfaces and redistribution of sediments and heavy minerals on them. Winnowing of sands produced heavy mineral residual accumulations on erosion surfaces which were generally preserved by small-pebble lags or algal mats. Reworking of units truncated by the unconformities provided additional gold, uranium and heavy minerals to unconformity surfaces.
- Full Text:
- Date Issued: 1983
- Authors: Beater, Christian Douglas
- Date: 1983 , 2013-04-03
- Subjects: Placer deposits , Gold ores -- Geology -- South Africa -- Witwatersrand , Uranium ores -- Geology -- South Africa -- Witwatersrand
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4925 , http://hdl.handle.net/10962/d1004535 , Placer deposits , Gold ores -- Geology -- South Africa -- Witwatersrand , Uranium ores -- Geology -- South Africa -- Witwatersrand
- Description: Most of the economic gold and uranium placers are developed on low angle disconformities in the Central Rand Group and concentrations of gold and uranium are usually at their optimum on unconformity surfaces. Examples include the Kimberley Reef and South Reef of the East Rand, the Main Reef Leader of the Central Rand, the Carbon Leader of the Carletonville goldfield, the Vaal Reef of the Klerksdorp goldfield and the Basal/Steyn placers of the Welkom goldfield. The individual goldfields represent fluvial fans which are composed of a large number of tectonogenetic sedimentary packages separated by unconformities. The tectonic responses between cycles of sedimentation produced unconformities and tectonically controlled cyclic sedimentation is one of the key factors culminating in the preparation and deposition of auriferous placers within the Witwatersrand succession. Unconformities, which represent breaks in sedimentation, result in the preconditioning of palaeosurfaces and redistribution of sediments and heavy minerals on them. Winnowing of sands produced heavy mineral residual accumulations on erosion surfaces which were generally preserved by small-pebble lags or algal mats. Reworking of units truncated by the unconformities provided additional gold, uranium and heavy minerals to unconformity surfaces.
- Full Text:
- Date Issued: 1983
An investigation of a framework to evaluate computer supported collaborative work
- Beauvais, Erik Alexander Maoui
- Authors: Beauvais, Erik Alexander Maoui
- Date: 1999
- Subjects: Computer networks , Teams in the workplace -- Data processing , Technology -- Data processing , Information technology -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1135 , http://hdl.handle.net/10962/d1002763 , Computer networks , Teams in the workplace -- Data processing , Technology -- Data processing , Information technology -- Economic aspects
- Description: Rapidly changing technology constantly modifies the way in which tasks are conceived and executed. Furthermore, leading organisations also encourage the use of new technology to support and establish innovative ways of doing business. For example, technology has helped to drive the globalization and tighter integration of world markets. This has facilitated, and even necessitated, business organisations to compete for work across national borders. For geographically dispersed organisations, collaboration has become critical. But this has presented time and space work complexities. Communication and collaboration technologies, for example, are needed to support such emerging co-operative business practices. The short development cycle of technology, communication and collaborative technologies included, leaves little time for testing and less for understanding the impact of new technology. To compound the problem, no established formulae exist for matching technology with work: over-investment is a waste of resources, while under-investment could lead to work failure. This research proposes a framework to assist organisations in selecting the appropriate level of technology with the work required. In this study, the methodology developed by the Evaluation Working Group, the DARPA Intelligent Collaboration and Visualization program is extended, and a matrix framework is constructed which compares the success of generic work tasks against a range of technology resources. The framework is tested using a low resource configuration, with selected work task types generally found in software development. (The Joint Application Development (JAD) methodology for software development is used as the contextual basis of the experiment.) All activities are evaluated according to selected measure components of success. A collection of research methods known as ethnography is used to examine and test the framework. Methods employed include questionnaires, interviews, interaction analysis and ethnomethodology. The results indicate that even at a low resource level, given selected criteria, collaborative technology successfully supports certain collaborative work activities. Findings also indicate that softer people issues require much more attention in order for technology to support natural collaborative work. Finally, user defined parameter testing has indicated that the framework functions as expected and designed.
- Full Text:
- Date Issued: 1999
- Authors: Beauvais, Erik Alexander Maoui
- Date: 1999
- Subjects: Computer networks , Teams in the workplace -- Data processing , Technology -- Data processing , Information technology -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1135 , http://hdl.handle.net/10962/d1002763 , Computer networks , Teams in the workplace -- Data processing , Technology -- Data processing , Information technology -- Economic aspects
- Description: Rapidly changing technology constantly modifies the way in which tasks are conceived and executed. Furthermore, leading organisations also encourage the use of new technology to support and establish innovative ways of doing business. For example, technology has helped to drive the globalization and tighter integration of world markets. This has facilitated, and even necessitated, business organisations to compete for work across national borders. For geographically dispersed organisations, collaboration has become critical. But this has presented time and space work complexities. Communication and collaboration technologies, for example, are needed to support such emerging co-operative business practices. The short development cycle of technology, communication and collaborative technologies included, leaves little time for testing and less for understanding the impact of new technology. To compound the problem, no established formulae exist for matching technology with work: over-investment is a waste of resources, while under-investment could lead to work failure. This research proposes a framework to assist organisations in selecting the appropriate level of technology with the work required. In this study, the methodology developed by the Evaluation Working Group, the DARPA Intelligent Collaboration and Visualization program is extended, and a matrix framework is constructed which compares the success of generic work tasks against a range of technology resources. The framework is tested using a low resource configuration, with selected work task types generally found in software development. (The Joint Application Development (JAD) methodology for software development is used as the contextual basis of the experiment.) All activities are evaluated according to selected measure components of success. A collection of research methods known as ethnography is used to examine and test the framework. Methods employed include questionnaires, interviews, interaction analysis and ethnomethodology. The results indicate that even at a low resource level, given selected criteria, collaborative technology successfully supports certain collaborative work activities. Findings also indicate that softer people issues require much more attention in order for technology to support natural collaborative work. Finally, user defined parameter testing has indicated that the framework functions as expected and designed.
- Full Text:
- Date Issued: 1999
Structural controls of gold mineralisation in Seguelen pit of Siguiri gold mine, Guinea
- Authors: Beavogui, Massa
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Geology, Structural -- Guinea -- Siguiri (Region) , Faults (Geology) -- Guinea -- Siguiri (Region) , Folds (Geology) -- Guinea -- Siguiri (Region) , Turbidites -- Guinea -- Siguiri (Region) , Metamorphism (Geology) -- Guinea -- Siguiri (Region) , Hydrothermal alteration -- Guinea -- Siguiri (Region)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5091 , http://hdl.handle.net/10962/d1019879
- Description: The present study provides the results of detailed mapping and analysis of structures encountered in Seguelen pit of Siguiri gold mine, Guinea, where the Siguiri mine is geo-tectonically located in the Baoulé-Mossi domain of Man Shield in West African craton. The gold deposit is hosted in low-grade metamorphic sediments of turbidites sequences which form part of the Lower Proterozoic of Birimian Super group. Three rock formations of Balato, Fatoya and Kintinian underlay the overall pits. The Siguiri gold mine is characterized by the deep weathering profile, developed over the rocks reaching 200 m below the surface in some areas and often capped by the lateritic gravel or duricrust. The rock formations at Seguelen area are characterised by strong bedding monotonously dipping towards SW and trending NW-SE. The lithology of the host rocks has strong control on the disseminated mineralisation throughout the deposit. Two domains of rock formations are clearly distinguished at Seguelen: Fatoya Formation(Ffm) domain ; and Kintinian Formation (Kfm) domain. The two domains are separated by a contact zone of 1.7 m wide parallel to bedding and characterised by the presence of quartz fragments as well as thinly sheeted shale and black shale. This contact zone is identified as disconformity. The major tectonic deformation which has affected the region is known as D2 corresponding to the Eburnean orogeny. The major D2 related structures is the regional thrust striking N-S over an area of 12 km long and 3 km wide and within which corridors all Siguiri gold Mine open pits are located. In the N-S trending structures, there is east-northeast shortening and north-northwest extension. There is pervasive hydrothermal alteration (carbonatization and sideritization) and supergene alteration in the all pits. The hydrothermal alteration attests the intensity of hydrothermal fluid-flow over the host rocks. The hydrothermal fluids flowed along the fractures and within the wall rocks through bedding plans to form numerous auriferous quartz veins bearing disseminated sulphides through chemical reaction between fluids and wall rocks, which are remarkable at Seguelen pit. Three quartz vein sets are distinguished at Seguelen: NNE-SSW quartz vein set NE-SW quartz vein set NW-SE quartz vein set The NE-SW and NNE-SSW quartz veins are often lenticular and associated with the bulk mineralisation.
- Full Text:
- Date Issued: 2015
- Authors: Beavogui, Massa
- Date: 2015
- Subjects: AngloGold Ashanti Ltd. , Gold mines and mining -- Guinea -- Siguiri (Region) , Geochemical surveys -- Guinea -- Siguiri (Region) , Geology, Structural -- Guinea -- Siguiri (Region) , Faults (Geology) -- Guinea -- Siguiri (Region) , Folds (Geology) -- Guinea -- Siguiri (Region) , Turbidites -- Guinea -- Siguiri (Region) , Metamorphism (Geology) -- Guinea -- Siguiri (Region) , Hydrothermal alteration -- Guinea -- Siguiri (Region)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5091 , http://hdl.handle.net/10962/d1019879
- Description: The present study provides the results of detailed mapping and analysis of structures encountered in Seguelen pit of Siguiri gold mine, Guinea, where the Siguiri mine is geo-tectonically located in the Baoulé-Mossi domain of Man Shield in West African craton. The gold deposit is hosted in low-grade metamorphic sediments of turbidites sequences which form part of the Lower Proterozoic of Birimian Super group. Three rock formations of Balato, Fatoya and Kintinian underlay the overall pits. The Siguiri gold mine is characterized by the deep weathering profile, developed over the rocks reaching 200 m below the surface in some areas and often capped by the lateritic gravel or duricrust. The rock formations at Seguelen area are characterised by strong bedding monotonously dipping towards SW and trending NW-SE. The lithology of the host rocks has strong control on the disseminated mineralisation throughout the deposit. Two domains of rock formations are clearly distinguished at Seguelen: Fatoya Formation(Ffm) domain ; and Kintinian Formation (Kfm) domain. The two domains are separated by a contact zone of 1.7 m wide parallel to bedding and characterised by the presence of quartz fragments as well as thinly sheeted shale and black shale. This contact zone is identified as disconformity. The major tectonic deformation which has affected the region is known as D2 corresponding to the Eburnean orogeny. The major D2 related structures is the regional thrust striking N-S over an area of 12 km long and 3 km wide and within which corridors all Siguiri gold Mine open pits are located. In the N-S trending structures, there is east-northeast shortening and north-northwest extension. There is pervasive hydrothermal alteration (carbonatization and sideritization) and supergene alteration in the all pits. The hydrothermal alteration attests the intensity of hydrothermal fluid-flow over the host rocks. The hydrothermal fluids flowed along the fractures and within the wall rocks through bedding plans to form numerous auriferous quartz veins bearing disseminated sulphides through chemical reaction between fluids and wall rocks, which are remarkable at Seguelen pit. Three quartz vein sets are distinguished at Seguelen: NNE-SSW quartz vein set NE-SW quartz vein set NW-SE quartz vein set The NE-SW and NNE-SSW quartz veins are often lenticular and associated with the bulk mineralisation.
- Full Text:
- Date Issued: 2015
The influence of soil properties on the growth and distribution of Portulacaria Afra in subtropical thicket, South Africa
- Authors: Becker, Carina Helene
- Date: 2013
- Subjects: Portulacaria afra -- South Africa , Plant conservation -- South Africa , Shrubs -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10753 , http://hdl.handle.net/10948/d1013046
- Description: Subtropical Thicket is the dominant vegetation biome in the Eastern Cape, and extends through to parts of the Western Cape. It is dominated by Portulacaria afra (spekboom), a woody succulent plant recognised for its importance as an ecosystem engineer and its carbon sequestration potential. Due to excessive grazing from domestic stock, spekboom has been completely removed from some areas. The Subtropical Thicket Restoration Programme (STRP) initiated a large scale restoration programme of planting spekboom cuttings in these degraded areas. Their efforts have been met with varying levels of success and improvement of the programme relies on continuous monitoring and scientific evaluation. I investigated the influence of selected soil properties on spekboom growth, mortality and landscape distribution, at both restoration sites and natural intact areas, and through experiments. Site or location was the most important factor influencing spekboom success at restoration plots, whereby sites in the eastern end of spekboom distribution perform better. Moving westwards slope orientation emerged as an important factor, whereby north facing slopes are preferred by spekboom. Although high levels of soil salinity (NaCl) restricted spekboom growth and affected its health, it could tolerate the levels it was exposed too. Soil pH, above 7, and phosphorous concentration, above 70 mg.kg-1, were the only limiting factors to spekboom survival found in the restoration sites. This preference for acidic soils was mirrored in intact Thicket. However in general, soil is not a major factor influencing spekboom growth and distribution, and spekboom is tolerant of a wide range of soil conditions. Spekbooms constraint is most likely a function of climate, which varies greatly across the biome. This study answered some vital questions regarding the possible influence of soil in spekboom growth and distribution. It disapproved the theory that a catena effect may be responsible for the lack of spekboom growing in bottomland areas. The study also indicates and supports the versatility of spekboom as a plant for restoring degraded lands across a range of different geologies and soil types. To maximise spekboom survival rates, restoration efforts should be focussed towards the eastern end of its distribution and to avoid planting in soils with pH levels higher than 7.
- Full Text:
- Date Issued: 2013
- Authors: Becker, Carina Helene
- Date: 2013
- Subjects: Portulacaria afra -- South Africa , Plant conservation -- South Africa , Shrubs -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10753 , http://hdl.handle.net/10948/d1013046
- Description: Subtropical Thicket is the dominant vegetation biome in the Eastern Cape, and extends through to parts of the Western Cape. It is dominated by Portulacaria afra (spekboom), a woody succulent plant recognised for its importance as an ecosystem engineer and its carbon sequestration potential. Due to excessive grazing from domestic stock, spekboom has been completely removed from some areas. The Subtropical Thicket Restoration Programme (STRP) initiated a large scale restoration programme of planting spekboom cuttings in these degraded areas. Their efforts have been met with varying levels of success and improvement of the programme relies on continuous monitoring and scientific evaluation. I investigated the influence of selected soil properties on spekboom growth, mortality and landscape distribution, at both restoration sites and natural intact areas, and through experiments. Site or location was the most important factor influencing spekboom success at restoration plots, whereby sites in the eastern end of spekboom distribution perform better. Moving westwards slope orientation emerged as an important factor, whereby north facing slopes are preferred by spekboom. Although high levels of soil salinity (NaCl) restricted spekboom growth and affected its health, it could tolerate the levels it was exposed too. Soil pH, above 7, and phosphorous concentration, above 70 mg.kg-1, were the only limiting factors to spekboom survival found in the restoration sites. This preference for acidic soils was mirrored in intact Thicket. However in general, soil is not a major factor influencing spekboom growth and distribution, and spekboom is tolerant of a wide range of soil conditions. Spekbooms constraint is most likely a function of climate, which varies greatly across the biome. This study answered some vital questions regarding the possible influence of soil in spekboom growth and distribution. It disapproved the theory that a catena effect may be responsible for the lack of spekboom growing in bottomland areas. The study also indicates and supports the versatility of spekboom as a plant for restoring degraded lands across a range of different geologies and soil types. To maximise spekboom survival rates, restoration efforts should be focussed towards the eastern end of its distribution and to avoid planting in soils with pH levels higher than 7.
- Full Text:
- Date Issued: 2013
Synthesis and characterization of MXS (M = Mo & V) and carbon supported MXS nanocomposites as Pt-free counter electrodes for electrode for DSSC application
- Authors: Bede, Asanda
- Date: 2020
- Subjects: Voltammetry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18599 , vital:42612
- Description: It has been reported that the morphology, crystalline phase composition and electrochemical properties of counter electrode materials such MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials was of considerable importance because it governs the efficiency of many photon assisted chemical and physical reactions in dye sensitized solar cells (DSSCs). The efficiency of DSSCs with composite counter electrode materials is reliant on the stability of the photochemistry reactions which can be optimized by appropriate doping levels of the composite materials. Moreover, the microstructure such as surface area, distribution of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials, and the stability of the electrostatic bonds between the MxS (Mo, V) with the carbon support also play a significant role in the performance of the DSSCs. This work evaluates the effect of different mole ratios of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials on the morphological, structural and electrochemical properties of the composite materials. MoS2 nanoflakes nanostructures have been synthesized by hydrothermal technique using sodium orthovanadate (Na2MoO4) as precursor. In this work Carbon supported MoS2 NFs have been prepared by physically/chemically mixing different mole ratios of MoS2 NFs with multi-walled carbon nanotubes (MWCNTs) and polyvinylidene in N-methyl-2-pyrrolidinone. The morphological, structural and electrochemical properties of the composite counter electrode materials have been investigated using SEM, XRD FTIR, TEM, RS and CV. SEM analysis has revealed the presence of large MoS2 nanoflakes (NFs) as synthesized. SEM analysis has also revealed significant change in the surface morphology of carbon supported MoS2 composite nanostructures with the change in the mole ratio of the MoS2 NFs and carbon support multi-walled carbon nanotubes. Structural analysis through HRTEM analysis revealed a d-spacing of 0.65 nm with a corresponding (002) lattice plane belonging to a trigonal crystalline phase of MoS2. Also, HRTEM analysis has revealed d-spacing of 0.291 nm corresponding to 002 plane of MWCNTs. Raman spectroscopy has revealed Characteristic Raman vibration frequencies and symmetries at 264.6 cm-1(Eg), 354.2 cm-1 (Ag ) belonging trigonal phase of MoS2 (1T-MoS2). FTIR analysis has revealed a narrow peak at 457.6 cm-1 due Mo-S vibration bond. This observation confirms the success of synthesis of MoS2 nanostructures. Cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS) measurements have revealed that the ratio 6:3:1 have shown to be optimum ratio due to its large reduction rate compared to pristine MoS2 NFs and other carbon supported MoS2 NFs. Calculated Rreduction for the carbon supported MoS2 NFs is the order 3:6:1>1:8:1>6:3:1>8:1:1 indicating the trend of ratio 3:6:1 appeared to have higher reduction rate than the rest of the material and it had far less ΔEpp than the rest of other ratios. All CV curves for both pristine MoS2 NFs and carbon supported MoS2 NFs confirmed a distinct Faradic characteristic. The VS2 nanosheets (NSs) and carbon supported VS2 NSs were also effectively synthesized via hydrothermal method. The SEM micrographs for VS2 NSs and carbon supported VS2 NSs samples reveals level increased. Furthermore, SEM-EDX analysis have confirmed the presence of V and S as well as C and O on carbon supported VS2 nanocomposites, and it clearly shown a gradually blending as the ratios increases. The structural studies through XRD analysis have revealed peaks at 2θ angles of 15.4◦, 28.2◦, 34.2◦, 36.2◦, 43.3◦,48.3◦, 54.4◦, 57.7◦ and 66.2◦ which correspond to the lattice planes (001), (002), (100), (011), (102), (003), (110), (103) and (201) belonging to hexagonal VS2 (H-VS2) crystalline phase as per JCPDS card 36-1139. The HRTEM have revealed that the VS2 NSs have an edge to edge length of ~ 0.294 – 1.248 µm. Also, HRTEM micrographs of VS2 NSs have revealed interplanar d spacing of 0.571 nm belonging to the (001) lattice plane of hexagonal VS2 (H-VS2) structure. FTIR analysis have shown a peak at 558 cm-1 attributed to V-S which is evident that sulfur has bonded with the metal (V) and is in agreement with EDS. CV, CD and EIS measurements have shown that the ratio 1:8:1 is more superior to VS2 NSs and other carbon supported VS2 NSs. Based on Rreduction for the carbon supported nanosheets VS2 nanosheets are ordered as 1:8:1>3:6:1>6:3:1>8:1:1. Carbon supported VS2 NSs of the mole ratio 1:8:1 showed a small resistance of 0.32 Ω. This is further evidence that the carbon supported VS2 NSs of the mole ratio 1:8:1 in addition to revealing excellent catalytic behaviour is also more chemically stable and has good conductivity properties._________
- Full Text:
- Date Issued: 2020
- Authors: Bede, Asanda
- Date: 2020
- Subjects: Voltammetry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18599 , vital:42612
- Description: It has been reported that the morphology, crystalline phase composition and electrochemical properties of counter electrode materials such MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials was of considerable importance because it governs the efficiency of many photon assisted chemical and physical reactions in dye sensitized solar cells (DSSCs). The efficiency of DSSCs with composite counter electrode materials is reliant on the stability of the photochemistry reactions which can be optimized by appropriate doping levels of the composite materials. Moreover, the microstructure such as surface area, distribution of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials, and the stability of the electrostatic bonds between the MxS (Mo, V) with the carbon support also play a significant role in the performance of the DSSCs. This work evaluates the effect of different mole ratios of the MxS (Mo, V) and carbon supported MxS (Mo, V) composite nanomaterials on the morphological, structural and electrochemical properties of the composite materials. MoS2 nanoflakes nanostructures have been synthesized by hydrothermal technique using sodium orthovanadate (Na2MoO4) as precursor. In this work Carbon supported MoS2 NFs have been prepared by physically/chemically mixing different mole ratios of MoS2 NFs with multi-walled carbon nanotubes (MWCNTs) and polyvinylidene in N-methyl-2-pyrrolidinone. The morphological, structural and electrochemical properties of the composite counter electrode materials have been investigated using SEM, XRD FTIR, TEM, RS and CV. SEM analysis has revealed the presence of large MoS2 nanoflakes (NFs) as synthesized. SEM analysis has also revealed significant change in the surface morphology of carbon supported MoS2 composite nanostructures with the change in the mole ratio of the MoS2 NFs and carbon support multi-walled carbon nanotubes. Structural analysis through HRTEM analysis revealed a d-spacing of 0.65 nm with a corresponding (002) lattice plane belonging to a trigonal crystalline phase of MoS2. Also, HRTEM analysis has revealed d-spacing of 0.291 nm corresponding to 002 plane of MWCNTs. Raman spectroscopy has revealed Characteristic Raman vibration frequencies and symmetries at 264.6 cm-1(Eg), 354.2 cm-1 (Ag ) belonging trigonal phase of MoS2 (1T-MoS2). FTIR analysis has revealed a narrow peak at 457.6 cm-1 due Mo-S vibration bond. This observation confirms the success of synthesis of MoS2 nanostructures. Cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS) measurements have revealed that the ratio 6:3:1 have shown to be optimum ratio due to its large reduction rate compared to pristine MoS2 NFs and other carbon supported MoS2 NFs. Calculated Rreduction for the carbon supported MoS2 NFs is the order 3:6:1>1:8:1>6:3:1>8:1:1 indicating the trend of ratio 3:6:1 appeared to have higher reduction rate than the rest of the material and it had far less ΔEpp than the rest of other ratios. All CV curves for both pristine MoS2 NFs and carbon supported MoS2 NFs confirmed a distinct Faradic characteristic. The VS2 nanosheets (NSs) and carbon supported VS2 NSs were also effectively synthesized via hydrothermal method. The SEM micrographs for VS2 NSs and carbon supported VS2 NSs samples reveals level increased. Furthermore, SEM-EDX analysis have confirmed the presence of V and S as well as C and O on carbon supported VS2 nanocomposites, and it clearly shown a gradually blending as the ratios increases. The structural studies through XRD analysis have revealed peaks at 2θ angles of 15.4◦, 28.2◦, 34.2◦, 36.2◦, 43.3◦,48.3◦, 54.4◦, 57.7◦ and 66.2◦ which correspond to the lattice planes (001), (002), (100), (011), (102), (003), (110), (103) and (201) belonging to hexagonal VS2 (H-VS2) crystalline phase as per JCPDS card 36-1139. The HRTEM have revealed that the VS2 NSs have an edge to edge length of ~ 0.294 – 1.248 µm. Also, HRTEM micrographs of VS2 NSs have revealed interplanar d spacing of 0.571 nm belonging to the (001) lattice plane of hexagonal VS2 (H-VS2) structure. FTIR analysis have shown a peak at 558 cm-1 attributed to V-S which is evident that sulfur has bonded with the metal (V) and is in agreement with EDS. CV, CD and EIS measurements have shown that the ratio 1:8:1 is more superior to VS2 NSs and other carbon supported VS2 NSs. Based on Rreduction for the carbon supported nanosheets VS2 nanosheets are ordered as 1:8:1>3:6:1>6:3:1>8:1:1. Carbon supported VS2 NSs of the mole ratio 1:8:1 showed a small resistance of 0.32 Ω. This is further evidence that the carbon supported VS2 NSs of the mole ratio 1:8:1 in addition to revealing excellent catalytic behaviour is also more chemically stable and has good conductivity properties._________
- Full Text:
- Date Issued: 2020
Using information visualization techniques to support web service discovery
- Authors: Beets, Simone
- Date: 2011
- Subjects: Information visualization , Web services , Information visualization -- Computer programs
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10457 , http://hdl.handle.net/10948/1659 , Information visualization , Web services , Information visualization -- Computer programs
- Description: The increasing number of web services published over the Web highlights the need for an effective method for users to find appropriate web services. Existing web service discovery methods do not effectively aid a user in finding suitable web services. The current methods provide textual lists of web services that the user is required to explore and manually evaluate. Thus, these methods lead to time-consuming and ineffective web service discovery. The aim of this research was to investigate using information visualization (IV) techniques to effectively support web service discovery. The node-and-link network IV technique was selected as the most appropriate IV technique to visualize web service collections. A prototype, called SerViz, was developed as a tool for interactive visualization of web service collections incorporating the node-and-link IV technique and an alphabetical list-based technique. SerViz used the Programmable Web web service collection as the sample web service collection. A usability evaluation was conducted to compare these techniques. Ninety percent of participants preferred the network IV technique for visualizing web service collections. The network IV technique was also faster for browsing. Several usability problems were identified with the network IV technique. This motivated a need for implementing an alternative IV technique in SerViz. The node-and-link tree IV technique was selected as it was more structured than the network IV technique. A usability evaluation was conducted to compare the network and tree IV techniques. Participants slightly preferred the tree IV technique as the technique to visualize web service collections. The tree IV technique was faster for browsing the web service collection while the network IV technique was faster for searching and filtering. This research has determined that IV techniques can be used to effectively support web service discovery. Future work will involve using IV techniques to support collaborative web service discovery. Keywords: Web Service Discovery, Information Visualization, Web Service Collections, Information Visualization Techniques.
- Full Text:
- Date Issued: 2011
- Authors: Beets, Simone
- Date: 2011
- Subjects: Information visualization , Web services , Information visualization -- Computer programs
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10457 , http://hdl.handle.net/10948/1659 , Information visualization , Web services , Information visualization -- Computer programs
- Description: The increasing number of web services published over the Web highlights the need for an effective method for users to find appropriate web services. Existing web service discovery methods do not effectively aid a user in finding suitable web services. The current methods provide textual lists of web services that the user is required to explore and manually evaluate. Thus, these methods lead to time-consuming and ineffective web service discovery. The aim of this research was to investigate using information visualization (IV) techniques to effectively support web service discovery. The node-and-link network IV technique was selected as the most appropriate IV technique to visualize web service collections. A prototype, called SerViz, was developed as a tool for interactive visualization of web service collections incorporating the node-and-link IV technique and an alphabetical list-based technique. SerViz used the Programmable Web web service collection as the sample web service collection. A usability evaluation was conducted to compare these techniques. Ninety percent of participants preferred the network IV technique for visualizing web service collections. The network IV technique was also faster for browsing. Several usability problems were identified with the network IV technique. This motivated a need for implementing an alternative IV technique in SerViz. The node-and-link tree IV technique was selected as it was more structured than the network IV technique. A usability evaluation was conducted to compare the network and tree IV techniques. Participants slightly preferred the tree IV technique as the technique to visualize web service collections. The tree IV technique was faster for browsing the web service collection while the network IV technique was faster for searching and filtering. This research has determined that IV techniques can be used to effectively support web service discovery. Future work will involve using IV techniques to support collaborative web service discovery. Keywords: Web Service Discovery, Information Visualization, Web Service Collections, Information Visualization Techniques.
- Full Text:
- Date Issued: 2011
An investigation into the origin and evolution of the Tierkloof Wetland, a peatland dominated by Prionium serratum, in the Western Cape
- Authors: Bekker, Debra Jane
- Date: 2017
- Subjects: Prionium serratum , Tierkloof Wetland (Western Cape, South Africa) , Wetlands -- South Africa -- Western Cape , Aquatic plants -- South Africa -- Western Cape Cape , Peatland ecology -- South Africa -- Western Cape , Kromme River (Eastern Cape, South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53689 , vital:26311
- Description: The Tierkloof Wetland in the Western Cape has been damaged through erosion down to bedrock with gullies that are up to 50 m wide and 7 m deep. The purpose of this study was to investigate the origin and evolution of the Tierkloof Wetland and consider the role both natural and human-induced processes have played in its degradation. The main methods used were digital mapping using GIS software, satellite and aerial photographic interpretation of past and current land use, detailed topographic surveying, coring to bedrock, stratigraphic analysis of valley-fill sediments, and radio carbon dating of peat samples. Nine GIS-produced topographic profiles across the valley were plotted to analyse downstream changes in valley width and morphology along the length of the Tierkloof valley. Detailed cross sections of the stream channel were produced using topographic survey data. Depth to bedrock analysis indicated that there is evidence of a degree of planing of bedrock over geological time periods. Survey data indicates that the longitudinal slope of the former wetland surface is remarkably uniform over most of its length and there is an overall thinning of the valley fill from the head to the toe of the wetland. The stratigraphy and associated organic matter content of the wetland soils showed that the sedimentary fill varies considerably. There are appreciable accumulations of organic sediment, including sandy peat and peat layers with organic content of up to 50 %. The two radio carbon dates obtained from the gully wall midway down the Tierkloof Wetland suggest that peat accumulation started following the last glacial maximum. The peat has accumulated consistently and is mostly associated with the growth of the palmiet, Prionium serratum. Evidence from past and current land-use activities from aerial photographic interpretation show that natural vegetation in the Tierkloof Wetland has been severely degraded, alien plants are extremely common, and road-building and artificial drainage in the wetland have influenced fluvial processes. It is likely that these activities, exacerbated by the high rainfall events in the early 2000s, have triggered the erosional phase that was initiated a few decades ago. However, longer term processes (thousands to tens-of-thousands of years), such as the planing of the bedrock, also indicate that erosional processes have been a natural part of the Tierkloof Wetland development. A conceptual model of wetland development is thus proposed, based on long-term erosional and depositional processes that are linked with climate change and the current aggradation phase of peat formation that is being driven by the ecosystem engineering processes of palmiet plant growth. It is further suggested that relatively recent land-use activities have resulted in an already vulnerable wetland, in geomorphological terms, to cross a threshold to become a severely degraded, gulley- dominated wetland.
- Full Text:
- Date Issued: 2017
- Authors: Bekker, Debra Jane
- Date: 2017
- Subjects: Prionium serratum , Tierkloof Wetland (Western Cape, South Africa) , Wetlands -- South Africa -- Western Cape , Aquatic plants -- South Africa -- Western Cape Cape , Peatland ecology -- South Africa -- Western Cape , Kromme River (Eastern Cape, South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53689 , vital:26311
- Description: The Tierkloof Wetland in the Western Cape has been damaged through erosion down to bedrock with gullies that are up to 50 m wide and 7 m deep. The purpose of this study was to investigate the origin and evolution of the Tierkloof Wetland and consider the role both natural and human-induced processes have played in its degradation. The main methods used were digital mapping using GIS software, satellite and aerial photographic interpretation of past and current land use, detailed topographic surveying, coring to bedrock, stratigraphic analysis of valley-fill sediments, and radio carbon dating of peat samples. Nine GIS-produced topographic profiles across the valley were plotted to analyse downstream changes in valley width and morphology along the length of the Tierkloof valley. Detailed cross sections of the stream channel were produced using topographic survey data. Depth to bedrock analysis indicated that there is evidence of a degree of planing of bedrock over geological time periods. Survey data indicates that the longitudinal slope of the former wetland surface is remarkably uniform over most of its length and there is an overall thinning of the valley fill from the head to the toe of the wetland. The stratigraphy and associated organic matter content of the wetland soils showed that the sedimentary fill varies considerably. There are appreciable accumulations of organic sediment, including sandy peat and peat layers with organic content of up to 50 %. The two radio carbon dates obtained from the gully wall midway down the Tierkloof Wetland suggest that peat accumulation started following the last glacial maximum. The peat has accumulated consistently and is mostly associated with the growth of the palmiet, Prionium serratum. Evidence from past and current land-use activities from aerial photographic interpretation show that natural vegetation in the Tierkloof Wetland has been severely degraded, alien plants are extremely common, and road-building and artificial drainage in the wetland have influenced fluvial processes. It is likely that these activities, exacerbated by the high rainfall events in the early 2000s, have triggered the erosional phase that was initiated a few decades ago. However, longer term processes (thousands to tens-of-thousands of years), such as the planing of the bedrock, also indicate that erosional processes have been a natural part of the Tierkloof Wetland development. A conceptual model of wetland development is thus proposed, based on long-term erosional and depositional processes that are linked with climate change and the current aggradation phase of peat formation that is being driven by the ecosystem engineering processes of palmiet plant growth. It is further suggested that relatively recent land-use activities have resulted in an already vulnerable wetland, in geomorphological terms, to cross a threshold to become a severely degraded, gulley- dominated wetland.
- Full Text:
- Date Issued: 2017
The execution of the financial management function in small to medium-sized building contractors as a means of promoting business sustainability
- Authors: Bekker, Jakobus Petrus
- Date: 2004
- Subjects: Contractors' operation -- Finance , Construction industry -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11004 , http://hdl.handle.net/10948/336 , Contractors' operation -- Finance , Construction industry -- Finance
- Description: The objective of this study was to investigate the extent to which small to medium-sized building contractors beneficially utilise the financial management function in their enterprises to improve and ensure business sustainability. Financial management focuses on the principles of decision-making, which requires action, without perfect knowledge of the outcome. To effectively execute the financial function, using the primary inputs in decision-making, financial management requires the ability to: understand and interpret financial statements and reports; make reasoned and objective decisions in controlling the operations of the enterprise; have a thorough knowledge of the internal functioning of the enterprise; and have a thorough knowledge of current and expected future economic conditions in the external environment. To do this, requires an effectively applied financial management function in the enterprises, which includes the utilisation of the financial management criteria to ensure business sustainability. However, without an appreciation of what financial management is, how important financial management is, and how financial management must be applied in the enterprise, small to medium-sized building contractors will find it difficult to effectively perform the financial management function and its different activities. It was therefore important to determine how well owners and construction managers of the average small to medium-sized building contractor deal with and utilise the financial management function in their enterprises. Consequently, a survey was carried out amongst small to medium-sized building contractors in the Nelson Mandela Metropolitan Municipal (NMMM) area, which revealed information that was used to come to certain conclusions: Firstly, it can be concluded that the financial management function is generally exercised superficially. This is supported by the responses of small to medium-sized building contractors, which implied that more than half the contractors do not fully perform financial management tasks. Secondly, it was concluded that the financial management criteria generally do not play a role in the business sustainability considerations of small to medium-sized building contractors. This is supported by the results, which imply that more than half the contractors do not fully utilise the financial management criteria.
- Full Text:
- Date Issued: 2004
- Authors: Bekker, Jakobus Petrus
- Date: 2004
- Subjects: Contractors' operation -- Finance , Construction industry -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11004 , http://hdl.handle.net/10948/336 , Contractors' operation -- Finance , Construction industry -- Finance
- Description: The objective of this study was to investigate the extent to which small to medium-sized building contractors beneficially utilise the financial management function in their enterprises to improve and ensure business sustainability. Financial management focuses on the principles of decision-making, which requires action, without perfect knowledge of the outcome. To effectively execute the financial function, using the primary inputs in decision-making, financial management requires the ability to: understand and interpret financial statements and reports; make reasoned and objective decisions in controlling the operations of the enterprise; have a thorough knowledge of the internal functioning of the enterprise; and have a thorough knowledge of current and expected future economic conditions in the external environment. To do this, requires an effectively applied financial management function in the enterprises, which includes the utilisation of the financial management criteria to ensure business sustainability. However, without an appreciation of what financial management is, how important financial management is, and how financial management must be applied in the enterprise, small to medium-sized building contractors will find it difficult to effectively perform the financial management function and its different activities. It was therefore important to determine how well owners and construction managers of the average small to medium-sized building contractor deal with and utilise the financial management function in their enterprises. Consequently, a survey was carried out amongst small to medium-sized building contractors in the Nelson Mandela Metropolitan Municipal (NMMM) area, which revealed information that was used to come to certain conclusions: Firstly, it can be concluded that the financial management function is generally exercised superficially. This is supported by the responses of small to medium-sized building contractors, which implied that more than half the contractors do not fully perform financial management tasks. Secondly, it was concluded that the financial management criteria generally do not play a role in the business sustainability considerations of small to medium-sized building contractors. This is supported by the results, which imply that more than half the contractors do not fully utilise the financial management criteria.
- Full Text:
- Date Issued: 2004
The effect of tulbaghia violacea plant extract on the growth of aspergillus species
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2009
- Subjects: Plant products , Plant extracts , Traditional medicine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10315 , http://hdl.handle.net/10948/d1008186 , Plant products , Plant extracts , Traditional medicine
- Description: Traditional medicine has become an important part of healthcare worldwide. It is estimated that about 25 percent of prescribed medicines contain plant products or active compounds derived from plants. In South Africa, traditional medicine forms part of the culture and tradition of most communities. Garlic compounds have been shown to have a variety of antimicrobial properties. Amongst these are antifungal, antibacterial, antiviral and anti protozoal activities. Allicin and its breakdown products have been shown to be the main active compounds which possess these properties. Tulbaghia violacea has been used for the treatment of a variety of illnesses including asthma, fever, oesophageal cancer, constipation and hypertension. This study investigated the antifungal nature of T.violacea on the morphology, spore germination and lipid synthesis of Aspergillus flavus and Aspergillus parasiticus. The results of this study showed that the plant extract inhibited A. flavus growth at a minimal inhibitory concentration of 15mg/ml and was fungicidal at 20mg/ml and above. A. parasiticus was not inhibited at 25mg/ml indicating resistance to the inhibitory component of the plant extract. A measure of metabolic activity using the XTT assay showed reduced metabolic activity in the presence of increasing concentrations of the plant extract. Higher extract concentrations resulted in higher percentage inhibition of fungal growth for both fungal species with up to 98 percent inhibition being observed for the highest extract concentrations for both fungi. Germination was also delayed in the presence of 15mg/ml plant extract concentration by up to 60hr for A. flavus and 48hr for A. parasititcus. The TEM results showed increased thickening of the cell wall with higher extract concentrations. The thickening was greater for A. flavus than for A. parasiticus. Cell wall thickening may be the reason for the delay in germination in both species. Lipid production was reduced in the presence of plant extracts when compared to the control. The plant extracts inhibited triglyceride production at 15mg/ml for both A. flavus and A. parasiticus. The results therefore indicate that T. violacea extracts are antifungal and probably affect germination through interactions with the cell wall. It is possible that the extract affects lipid production in Aspergillus species.
- Full Text:
- Date Issued: 2009
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2009
- Subjects: Plant products , Plant extracts , Traditional medicine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10315 , http://hdl.handle.net/10948/d1008186 , Plant products , Plant extracts , Traditional medicine
- Description: Traditional medicine has become an important part of healthcare worldwide. It is estimated that about 25 percent of prescribed medicines contain plant products or active compounds derived from plants. In South Africa, traditional medicine forms part of the culture and tradition of most communities. Garlic compounds have been shown to have a variety of antimicrobial properties. Amongst these are antifungal, antibacterial, antiviral and anti protozoal activities. Allicin and its breakdown products have been shown to be the main active compounds which possess these properties. Tulbaghia violacea has been used for the treatment of a variety of illnesses including asthma, fever, oesophageal cancer, constipation and hypertension. This study investigated the antifungal nature of T.violacea on the morphology, spore germination and lipid synthesis of Aspergillus flavus and Aspergillus parasiticus. The results of this study showed that the plant extract inhibited A. flavus growth at a minimal inhibitory concentration of 15mg/ml and was fungicidal at 20mg/ml and above. A. parasiticus was not inhibited at 25mg/ml indicating resistance to the inhibitory component of the plant extract. A measure of metabolic activity using the XTT assay showed reduced metabolic activity in the presence of increasing concentrations of the plant extract. Higher extract concentrations resulted in higher percentage inhibition of fungal growth for both fungal species with up to 98 percent inhibition being observed for the highest extract concentrations for both fungi. Germination was also delayed in the presence of 15mg/ml plant extract concentration by up to 60hr for A. flavus and 48hr for A. parasititcus. The TEM results showed increased thickening of the cell wall with higher extract concentrations. The thickening was greater for A. flavus than for A. parasiticus. Cell wall thickening may be the reason for the delay in germination in both species. Lipid production was reduced in the presence of plant extracts when compared to the control. The plant extracts inhibited triglyceride production at 15mg/ml for both A. flavus and A. parasiticus. The results therefore indicate that T. violacea extracts are antifungal and probably affect germination through interactions with the cell wall. It is possible that the extract affects lipid production in Aspergillus species.
- Full Text:
- Date Issued: 2009