Towards measuring corporate sustainability in the Nelson Mandela Bay automotive manufacturing sector
- Authors: Adams, Abulele
- Date: 2015
- Subjects: Sustainability -- South Africa -- Port Elizabeth Sustainable development -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18465 , vital:28648
- Description: This study explored the methods available for measuring corporate sustainability and created an instrument to measure corporate sustainability in the Nelson Mandela Bay (NMB) automotive manufacturing sector. The instrument was created based on three components of sustainability which are environment, society and economy. The study went a step further and added a fourth dimension, current trends to design a measuring instrument. The instrument was then applied on participating companies and further refined to improve it. A total of 16 multi-dimensional indicators to measure corporate sustainability were created and applied to 12 companies in the automotive manufacturing sector. The indicators were used to create a composite corporate sustainability index which can be used to compare the corporate sustainability performance of companies. These indicators were created based on theoretical research and fist hand experience observing the automotive manufacturing sector in the NMB. The indicators were applied to companies as a pilot to test whether they are feasible. Following this, the indicators were refined, improved and applied to more companies to measure corporate sustainability performance. The results of the study were the measuring instrument created, the creation of a composite index as well as the application of the instrument on 12 companies to determine whether the instrument was refined enough to detect differences in the corporate sustainability performance of companies. The results are discussed and further recommendations are made for improvements in the creation and application of the instrument to measure corporate sustainability in the NMB automotive manufacturing sector.
- Full Text:
- Date Issued: 2015
Towards measuring corporate sustainability in the Nelson Mandela Bay automotive manufacturing sector
- Authors: Adams, Abulele
- Date: 2015
- Subjects: Sustainability -- South Africa -- Port Elizabeth Sustainable development -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18465 , vital:28648
- Description: This study explored the methods available for measuring corporate sustainability and created an instrument to measure corporate sustainability in the Nelson Mandela Bay (NMB) automotive manufacturing sector. The instrument was created based on three components of sustainability which are environment, society and economy. The study went a step further and added a fourth dimension, current trends to design a measuring instrument. The instrument was then applied on participating companies and further refined to improve it. A total of 16 multi-dimensional indicators to measure corporate sustainability were created and applied to 12 companies in the automotive manufacturing sector. The indicators were used to create a composite corporate sustainability index which can be used to compare the corporate sustainability performance of companies. These indicators were created based on theoretical research and fist hand experience observing the automotive manufacturing sector in the NMB. The indicators were applied to companies as a pilot to test whether they are feasible. Following this, the indicators were refined, improved and applied to more companies to measure corporate sustainability performance. The results of the study were the measuring instrument created, the creation of a composite index as well as the application of the instrument on 12 companies to determine whether the instrument was refined enough to detect differences in the corporate sustainability performance of companies. The results are discussed and further recommendations are made for improvements in the creation and application of the instrument to measure corporate sustainability in the NMB automotive manufacturing sector.
- Full Text:
- Date Issued: 2015
A natural user interface architecture using gestures to facilitate the detection of fundamental movement skills
- Authors: Amanzi, Richard
- Date: 2015
- Subjects: Human activity recognition , Human-computer interaction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6204 , vital:21055
- Description: Fundamental movement skills (FMSs) are considered to be one of the essential phases of motor skill development. The proper development of FMSs allows children to participate in more advanced forms of movements and sports. To be able to perform an FMS correctly, children need to learn the right way of performing it. By making use of technology, a system can be developed that can help facilitate the learning of FMSs. The objective of the research was to propose an effective natural user interface (NUI) architecture for detecting FMSs using the Kinect. In order to achieve the stated objective, an investigation into FMSs and the challenges faced when teaching them was presented. An investigation into NUIs was also presented including the merits of the Kinect as the most appropriate device to be used to facilitate the detection of an FMS. An NUI architecture was proposed that uses the Kinect to facilitate the detection of an FMS. A framework was implemented from the design of the architecture. The successful implementation of the framework provides evidence that the design of the proposed architecture is feasible. An instance of the framework incorporating the jump FMS was used as a case study in the development of a prototype that detects the correct and incorrect performance of a jump. The evaluation of the prototype proved the following: - The developed prototype was effective in detecting the correct and incorrect performance of the jump FMS; and - The implemented framework was robust for the incorporation of an FMS. The successful implementation of the prototype shows that an effective NUI architecture using the Kinect can be used to facilitate the detection of FMSs. The proposed architecture provides a structured way of developing a system using the Kinect to facilitate the detection of FMSs. This allows developers to add future FMSs to the system. This dissertation therefore makes the following contributions: - An experimental design to evaluate the effectiveness of a prototype that detects FMSs - A robust framework that incorporates FMSs; and - An effective NUI architecture to facilitate the detection of fundamental movement skills using the Kinect.
- Full Text:
- Date Issued: 2015
- Authors: Amanzi, Richard
- Date: 2015
- Subjects: Human activity recognition , Human-computer interaction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6204 , vital:21055
- Description: Fundamental movement skills (FMSs) are considered to be one of the essential phases of motor skill development. The proper development of FMSs allows children to participate in more advanced forms of movements and sports. To be able to perform an FMS correctly, children need to learn the right way of performing it. By making use of technology, a system can be developed that can help facilitate the learning of FMSs. The objective of the research was to propose an effective natural user interface (NUI) architecture for detecting FMSs using the Kinect. In order to achieve the stated objective, an investigation into FMSs and the challenges faced when teaching them was presented. An investigation into NUIs was also presented including the merits of the Kinect as the most appropriate device to be used to facilitate the detection of an FMS. An NUI architecture was proposed that uses the Kinect to facilitate the detection of an FMS. A framework was implemented from the design of the architecture. The successful implementation of the framework provides evidence that the design of the proposed architecture is feasible. An instance of the framework incorporating the jump FMS was used as a case study in the development of a prototype that detects the correct and incorrect performance of a jump. The evaluation of the prototype proved the following: - The developed prototype was effective in detecting the correct and incorrect performance of the jump FMS; and - The implemented framework was robust for the incorporation of an FMS. The successful implementation of the prototype shows that an effective NUI architecture using the Kinect can be used to facilitate the detection of FMSs. The proposed architecture provides a structured way of developing a system using the Kinect to facilitate the detection of FMSs. This allows developers to add future FMSs to the system. This dissertation therefore makes the following contributions: - An experimental design to evaluate the effectiveness of a prototype that detects FMSs - A robust framework that incorporates FMSs; and - An effective NUI architecture to facilitate the detection of fundamental movement skills using the Kinect.
- Full Text:
- Date Issued: 2015
On the characterisation of photovoltaic device parameters using light beam induced current measurements
- Bezuidenhout, Lucian John-Ross
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2015
- Subjects: Solar cells--Materials , Semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10551 , http://hdl.handle.net/10948/d1020282
- Description: Light Beam Induced Current (LBIC) measurement is a non-destructive technique used to perform localized characterization of solar cells using a light beam as a probe. The technique allows the determination of local photo response of a cell, the electrical parameters and defects that occur in the individual solar cell. The semiconductor materials used to create solar cells are not always defect free and these defects reduce the electrical performance of the device. It is therefore important to use a system that will allow the characterization and extract the solar cell parameters as can be done using the LBIC system. By analysing these parameters and cell defects, further studies can be done to enhance the cell’s lifetime and hence its efficiency. Light beam induced current (LBIC) is a technique that focuses light onto a solar cell device and thus creating a photo-generated current that can be measured in the external circuit for analyses. By scanning this beam probe across a solar cell while measuring the current-voltage characteristics, a map of various parameters can be obtained. This thesis presents the design of the LBIC system, the software interfacing of the data acquisition system and local photo-response within different solar cell technologies. In addition, this thesis represent two curve fitting algorithms namely: the Gradient Descent Optimisation and the Differential Evolution used for the extraction of solar cell device parameters. The algorithms are based on the one-diode solar cell model and make use of the light generated current-voltage (I-V) data obtained from the LBIC system. Different solar cell technologies namely; single crystalline (c-Si) and multicrystalline silicon (mc-Si) was used for analysis. LBIC maps and I-V characteristics of both technologies was obtained. The LBIC maps shows performance degrading defects present in the bulk and the surface of the solar cells as a function of spatial distribution. These localised defects acts as trapping mechanism for the charge carriers and therefore limits recombination within the solar cell and thus decreasing the performance of the solar cell device. The resulting I-V characteristics obtained from the LBIC system were used to determine the performance parameters using the two algorithms. The resultant effect of these parameters on the performance of the solar cells was observed. The overall results showed that LBIC is a useful tool for identifying and characterising defects in solar cells.
- Full Text:
- Date Issued: 2015
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2015
- Subjects: Solar cells--Materials , Semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10551 , http://hdl.handle.net/10948/d1020282
- Description: Light Beam Induced Current (LBIC) measurement is a non-destructive technique used to perform localized characterization of solar cells using a light beam as a probe. The technique allows the determination of local photo response of a cell, the electrical parameters and defects that occur in the individual solar cell. The semiconductor materials used to create solar cells are not always defect free and these defects reduce the electrical performance of the device. It is therefore important to use a system that will allow the characterization and extract the solar cell parameters as can be done using the LBIC system. By analysing these parameters and cell defects, further studies can be done to enhance the cell’s lifetime and hence its efficiency. Light beam induced current (LBIC) is a technique that focuses light onto a solar cell device and thus creating a photo-generated current that can be measured in the external circuit for analyses. By scanning this beam probe across a solar cell while measuring the current-voltage characteristics, a map of various parameters can be obtained. This thesis presents the design of the LBIC system, the software interfacing of the data acquisition system and local photo-response within different solar cell technologies. In addition, this thesis represent two curve fitting algorithms namely: the Gradient Descent Optimisation and the Differential Evolution used for the extraction of solar cell device parameters. The algorithms are based on the one-diode solar cell model and make use of the light generated current-voltage (I-V) data obtained from the LBIC system. Different solar cell technologies namely; single crystalline (c-Si) and multicrystalline silicon (mc-Si) was used for analysis. LBIC maps and I-V characteristics of both technologies was obtained. The LBIC maps shows performance degrading defects present in the bulk and the surface of the solar cells as a function of spatial distribution. These localised defects acts as trapping mechanism for the charge carriers and therefore limits recombination within the solar cell and thus decreasing the performance of the solar cell device. The resulting I-V characteristics obtained from the LBIC system were used to determine the performance parameters using the two algorithms. The resultant effect of these parameters on the performance of the solar cells was observed. The overall results showed that LBIC is a useful tool for identifying and characterising defects in solar cells.
- Full Text:
- Date Issued: 2015
Studies on flax/polypropylene-reinforced composites for automotive applications
- Authors: Biyana, Nobuhle Yvonne
- Date: 2015
- Subjects: Polypropylene fibers , Fibrous composites , Reinforced plastics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10456 , http://hdl.handle.net/10948/d1021150
- Description: The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.
- Full Text:
- Date Issued: 2015
- Authors: Biyana, Nobuhle Yvonne
- Date: 2015
- Subjects: Polypropylene fibers , Fibrous composites , Reinforced plastics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10456 , http://hdl.handle.net/10948/d1021150
- Description: The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.
- Full Text:
- Date Issued: 2015
Stratigraphic characterisation of the Collingham formation in the context of shale gas from a borehole (SFT 2) near Jansenville, Eastern Cape, South Africa
- Authors: Black, Dawn Ebony
- Date: 2015
- Subjects: Geology, Stratigraphic , Formations (Geology) -- South Africa , Collingham formation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10676 , http://hdl.handle.net/10948/d1021148
- Description: This study is an extensive lithological, petrographical, mineralogical and geochemical description of fresh Collingham Formation core samples collected from borehole SFT 2, located on the farm Slangfontein, south of Jansenville in the Eastern Cape, South Africa. The borehole, drilled to 295 m on the northerly limb of a shallow westerly plunging syncline, intersected the lower Ecca Group rocks of the Ripon, Collingham, Whitehill and Prince Albert Formations and terminated in the upper Dwyka Group. A comprehensive log and stratigraphic column were compiled for the Collingham Formation and fresh core samples were analysed using X-Ray Diffraction (“XRD”), X-Ray Fluorescence (“XRF”), mercury porosimetry, and Total Organic Carbon (“TOC”). Thin section microscopy and Scanning Electron Microscopy (“SEM”) analyses were carried out on selected samples of core from borehole SFT 2. The matrix supported, massive to laminated lithological units of the Collingham Formation are interpreted as detrital, terrigenous sediments. These sediments are composed of intercalated fine-grained, poorly sorted, non-fissile mudstone; fine- to very fine-grained, predominantly pyroclastic airfall tephra; and less common fine-grained sandstones. Sediments of the Collingham Formation are considered to be immature, composed primarily of clay and aluminosilicates. The predominance of a clay fraction and aluminosilicates in mudstone samples is indicated by elevated K2O/Al2O3 ratio values, and the relationship of Zr, Al2O3 and TiO2. The presence of glauconite within the Collingham Formation indicates deposition in a mildly alkaline, slightly reducing marine environment. Rb/K ratio values (1.9 – 2.3 x 10-3) indicate brackish to slightly marine conditions, while low Zr/Rb ratio values indicate a low hydro-energy environment, with stable bottom water conditions. Hf and Nb concentrations indicate that detrital input was greatest during the deposition of tuffaceous units; while stable mineral assemblages and a low Fe2O3/K2O ratio values indicate deposition close to the source. A variation in Si/Ca values indicate times when sediments were affected by turbidity, interspersed with times of relative quiescence. The predominance of K2O over Na2O indicates that the Collingham Formation is alkali-rich, while SiO2/Al2O3 ratio values and the relationship of Zr, Al2O3 and TiO2 indicate that sediments are immature. In the lower portion of the formation, non-sulphidic, anoxic conditions are indicated by Mn/Al, V/(V+Ni), V/Cr ratio values, the Fe-Mn- V content, and the correlation between V and TOC. The upper portion of the formation is considered dysoxic, due to the presence and distribution of pyrite framboids, which indicate a fluctuating O2 level, likely indicating deposition at the interface between anoxic and slightly more oxic conditions. V/Cr ratio values indicate that the O2 regime was lowest during the deposition of the mudstones. The Chemical Index of Alteration (“CIA”) indicates a consistent weathering regime throughout the deposition of the Collingham Formation, associated with a temperate climate on the interface between glacial and tropical conditions. Although an anoxic and low hydro-energy environment is generally favourable for hydrocarbon accumulation, the Collingham Formation contains low levels of Total Organic Carbon (well below 0.9 per cent) and low porosities (ranging from 0.35 per cent to a maximum of 2.22 per cent), both of which are characteristic of a poor source for gas accumulation. Due to the laminate nature, permeability and fracturability of the Collingham Formation, there is the potential that the formation may form a good sealing sequence to the potentially gas-rich Whitehill Formation below. The metamorphic impact related to the Cape Orogeny (± 250 Ma), and reflected in the textures of the minerals making up the sediments of the Collingham Formation, suggests the enhancement in the sealing efficiency of this formation.
- Full Text:
- Date Issued: 2015
- Authors: Black, Dawn Ebony
- Date: 2015
- Subjects: Geology, Stratigraphic , Formations (Geology) -- South Africa , Collingham formation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10676 , http://hdl.handle.net/10948/d1021148
- Description: This study is an extensive lithological, petrographical, mineralogical and geochemical description of fresh Collingham Formation core samples collected from borehole SFT 2, located on the farm Slangfontein, south of Jansenville in the Eastern Cape, South Africa. The borehole, drilled to 295 m on the northerly limb of a shallow westerly plunging syncline, intersected the lower Ecca Group rocks of the Ripon, Collingham, Whitehill and Prince Albert Formations and terminated in the upper Dwyka Group. A comprehensive log and stratigraphic column were compiled for the Collingham Formation and fresh core samples were analysed using X-Ray Diffraction (“XRD”), X-Ray Fluorescence (“XRF”), mercury porosimetry, and Total Organic Carbon (“TOC”). Thin section microscopy and Scanning Electron Microscopy (“SEM”) analyses were carried out on selected samples of core from borehole SFT 2. The matrix supported, massive to laminated lithological units of the Collingham Formation are interpreted as detrital, terrigenous sediments. These sediments are composed of intercalated fine-grained, poorly sorted, non-fissile mudstone; fine- to very fine-grained, predominantly pyroclastic airfall tephra; and less common fine-grained sandstones. Sediments of the Collingham Formation are considered to be immature, composed primarily of clay and aluminosilicates. The predominance of a clay fraction and aluminosilicates in mudstone samples is indicated by elevated K2O/Al2O3 ratio values, and the relationship of Zr, Al2O3 and TiO2. The presence of glauconite within the Collingham Formation indicates deposition in a mildly alkaline, slightly reducing marine environment. Rb/K ratio values (1.9 – 2.3 x 10-3) indicate brackish to slightly marine conditions, while low Zr/Rb ratio values indicate a low hydro-energy environment, with stable bottom water conditions. Hf and Nb concentrations indicate that detrital input was greatest during the deposition of tuffaceous units; while stable mineral assemblages and a low Fe2O3/K2O ratio values indicate deposition close to the source. A variation in Si/Ca values indicate times when sediments were affected by turbidity, interspersed with times of relative quiescence. The predominance of K2O over Na2O indicates that the Collingham Formation is alkali-rich, while SiO2/Al2O3 ratio values and the relationship of Zr, Al2O3 and TiO2 indicate that sediments are immature. In the lower portion of the formation, non-sulphidic, anoxic conditions are indicated by Mn/Al, V/(V+Ni), V/Cr ratio values, the Fe-Mn- V content, and the correlation between V and TOC. The upper portion of the formation is considered dysoxic, due to the presence and distribution of pyrite framboids, which indicate a fluctuating O2 level, likely indicating deposition at the interface between anoxic and slightly more oxic conditions. V/Cr ratio values indicate that the O2 regime was lowest during the deposition of the mudstones. The Chemical Index of Alteration (“CIA”) indicates a consistent weathering regime throughout the deposition of the Collingham Formation, associated with a temperate climate on the interface between glacial and tropical conditions. Although an anoxic and low hydro-energy environment is generally favourable for hydrocarbon accumulation, the Collingham Formation contains low levels of Total Organic Carbon (well below 0.9 per cent) and low porosities (ranging from 0.35 per cent to a maximum of 2.22 per cent), both of which are characteristic of a poor source for gas accumulation. Due to the laminate nature, permeability and fracturability of the Collingham Formation, there is the potential that the formation may form a good sealing sequence to the potentially gas-rich Whitehill Formation below. The metamorphic impact related to the Cape Orogeny (± 250 Ma), and reflected in the textures of the minerals making up the sediments of the Collingham Formation, suggests the enhancement in the sealing efficiency of this formation.
- Full Text:
- Date Issued: 2015
Sedimentological and geochemical investigations on borehole cores of the Lower Ecca Group black shales, for their gas potential : Karoo basin, South Africa
- Authors: Chere, Naledi
- Date: 2015
- Subjects: Sediments (Geology) -- South Africa , Gas reservoirs -- South Africa , Natural gas reserves -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10679 , http://hdl.handle.net/10948/d1021201
- Description: In the recent years, the shale gas discourse has become central to discussions about future energy supply in South Africa. In particular, the Permian black shales of the Lower Ecca Group formations in the Karoo Basin are considered potential source rocks for shale gas. The research presented in this thesis advances the understanding of the shale gas potential of mainly the Prince Albert, Whitehill and Tierberg/Collingham Formations. These shale sequences were sampled from eight deep boreholes spread across the main Karoo Basin and geochemically analysed at the GFZ - Helmholtz Centre Potsdam, Germany. Three key questions guided the study, these are: (i) what is the lithology of the sequence; (ii) where in the basin do the shale sequences attain maximum thickness at optimum depth i.e. beneath 1000-1500m; and (iii) and their shale characteristics. To evaluate these, borehole core logging, petrology and organic geochemistry were used extensively. Petrology involved the use of thin section, scanned electron and transmission electron microscopy for mineralogy as well as the identification of sedimentary features, organic matter and nano-scale porosity. These were coupled with standard organic geochemistry techniques such as Rock Eval. analysis, open pyrolysis gas chromatography and thermovaporisation to quantify the free gas, total organic carbon (TOC), present-day gas generative potential and kerogen type. The results show that the Whitehill Formation, away from the CFB and not intruded by dolerite, has the most potential for shale gas. Microscopic studies of this pyritic black shale reveal the occurrence of porous amorphous matter, indicating thermal maturity within the gas generation zone (i.e. > 1.1 percent Ro, 120ºC). The TOC content is consistently high within the Whitehill (exceeding industry requirement of 2 percent), attaining maximum of 7.3 percent. The highest yields of free and desorbed gas, especially methane, were emitted within this formation (S1 and nC1 peaks); mostly within its dolomitic units. In addition, dissolution porosity within dolomite units of the Whitehill Formation was identified as the predominant type of porosity. Thus, it is deduced that the dolomitic units of Whitehill Formation potentially contain the greatest volumes of free gas. HI values attain maximum of 25 mg HC/g TOC, whereas the OI values 26 mg CO2/g TOC. Such low HI and OI values are typically attributed to the dominance of Type IV kerogen, and consistent with overmaturity. Open pyrolysis (GC) show the main the chemical compound of the organic matter to be m-p-xylene, consistent with a mix of Type III, Type I/II and Type IV kerogen. Lithologically, the Whitehill Formation is composed of ~ 35 quartz, 13 percent feldspar, 26 percent illite and ~ 23 percent dolomite with variable amounts of pyrite. The dominance of quartz is directly proportional to the brittleness of the rock. Thus it can be deduced that the Whitehill Formation is relatively brittle and therefore fraccable. Burial trends indicate increasing depth (from ground level) to the top of the Whitehill Formation towards the south and south-eastern portion of the basin. It is in the southern region where thicknesses of this black shale exceeding 50m occur at depths more than 1500m; 1000m beneath fresh water aquifers. It therefore concluded that Whitehill Formation in the southern portion of Karoo Basin, but away from the thermo-tectonic overprint of the Cape Orogeny, is the most probable shale gas reservoir in South Africa.
- Full Text:
- Date Issued: 2015
- Authors: Chere, Naledi
- Date: 2015
- Subjects: Sediments (Geology) -- South Africa , Gas reservoirs -- South Africa , Natural gas reserves -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10679 , http://hdl.handle.net/10948/d1021201
- Description: In the recent years, the shale gas discourse has become central to discussions about future energy supply in South Africa. In particular, the Permian black shales of the Lower Ecca Group formations in the Karoo Basin are considered potential source rocks for shale gas. The research presented in this thesis advances the understanding of the shale gas potential of mainly the Prince Albert, Whitehill and Tierberg/Collingham Formations. These shale sequences were sampled from eight deep boreholes spread across the main Karoo Basin and geochemically analysed at the GFZ - Helmholtz Centre Potsdam, Germany. Three key questions guided the study, these are: (i) what is the lithology of the sequence; (ii) where in the basin do the shale sequences attain maximum thickness at optimum depth i.e. beneath 1000-1500m; and (iii) and their shale characteristics. To evaluate these, borehole core logging, petrology and organic geochemistry were used extensively. Petrology involved the use of thin section, scanned electron and transmission electron microscopy for mineralogy as well as the identification of sedimentary features, organic matter and nano-scale porosity. These were coupled with standard organic geochemistry techniques such as Rock Eval. analysis, open pyrolysis gas chromatography and thermovaporisation to quantify the free gas, total organic carbon (TOC), present-day gas generative potential and kerogen type. The results show that the Whitehill Formation, away from the CFB and not intruded by dolerite, has the most potential for shale gas. Microscopic studies of this pyritic black shale reveal the occurrence of porous amorphous matter, indicating thermal maturity within the gas generation zone (i.e. > 1.1 percent Ro, 120ºC). The TOC content is consistently high within the Whitehill (exceeding industry requirement of 2 percent), attaining maximum of 7.3 percent. The highest yields of free and desorbed gas, especially methane, were emitted within this formation (S1 and nC1 peaks); mostly within its dolomitic units. In addition, dissolution porosity within dolomite units of the Whitehill Formation was identified as the predominant type of porosity. Thus, it is deduced that the dolomitic units of Whitehill Formation potentially contain the greatest volumes of free gas. HI values attain maximum of 25 mg HC/g TOC, whereas the OI values 26 mg CO2/g TOC. Such low HI and OI values are typically attributed to the dominance of Type IV kerogen, and consistent with overmaturity. Open pyrolysis (GC) show the main the chemical compound of the organic matter to be m-p-xylene, consistent with a mix of Type III, Type I/II and Type IV kerogen. Lithologically, the Whitehill Formation is composed of ~ 35 quartz, 13 percent feldspar, 26 percent illite and ~ 23 percent dolomite with variable amounts of pyrite. The dominance of quartz is directly proportional to the brittleness of the rock. Thus it can be deduced that the Whitehill Formation is relatively brittle and therefore fraccable. Burial trends indicate increasing depth (from ground level) to the top of the Whitehill Formation towards the south and south-eastern portion of the basin. It is in the southern region where thicknesses of this black shale exceeding 50m occur at depths more than 1500m; 1000m beneath fresh water aquifers. It therefore concluded that Whitehill Formation in the southern portion of Karoo Basin, but away from the thermo-tectonic overprint of the Cape Orogeny, is the most probable shale gas reservoir in South Africa.
- Full Text:
- Date Issued: 2015
Efficiency evaluation of South Africa tertiary education institutions using data envelopment analysis
- Authors: Chitekedza, Ignatious
- Date: 2015
- Subjects: Data envelopment analysis -- South Africa , Principal components analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4764 , vital:20674
- Description: With an increasing number of students enrolling at higher education institutions in South Africa, it has become important to investigate whether these institutions are using their resources adequately. This study uses data envelopment analysis (DEA) to estimate the efficiency of 23 South African tertiary education institutions based on both teaching and research outputs. Using DEA we are able to rank South African universities according to their use of resources in these two areas. These rankings can identify institutions which are performing well and also those which require improvement. The effect that merging institutions has on this efficiency is also determined. Owing to the limited sample size, variable reduction techniques, including the efficiency contribution measure (ECM) and principal components analysis (PCA-DEA), were used to improve the discrimination of the analysis.
- Full Text:
- Date Issued: 2015
- Authors: Chitekedza, Ignatious
- Date: 2015
- Subjects: Data envelopment analysis -- South Africa , Principal components analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4764 , vital:20674
- Description: With an increasing number of students enrolling at higher education institutions in South Africa, it has become important to investigate whether these institutions are using their resources adequately. This study uses data envelopment analysis (DEA) to estimate the efficiency of 23 South African tertiary education institutions based on both teaching and research outputs. Using DEA we are able to rank South African universities according to their use of resources in these two areas. These rankings can identify institutions which are performing well and also those which require improvement. The effect that merging institutions has on this efficiency is also determined. Owing to the limited sample size, variable reduction techniques, including the efficiency contribution measure (ECM) and principal components analysis (PCA-DEA), were used to improve the discrimination of the analysis.
- Full Text:
- Date Issued: 2015
A geoscientific framework for the proposed site of South Africa's second nuclear power plant: Thyspunt, Eastern Cape
- Authors: Claassen, Debbie
- Date: 2015
- Subjects: Geology, Structural -- South Africa -- Eastern Cape , Geology, Stratigraphic , Geochemistry , Rock mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10678 , http://hdl.handle.net/10948/d1021182
- Description: This study describes the bedrock lithologies and structure of the Ordovician to early Devonian (485-419 Ma) Table Mountain Group (TMG), the Devonian (419-358 Ma) lower Bokkeveld Group, and the Miocene to Holocene (<23 Ma) overburden sediments of the Algoa Group within an area identified by Eskom for the potential construction of South Africa’s second proposed nuclear power plant (NPP), ‘Nuclear-1’. The study area is located along the southern coastal margin of the Eastern Cape Province, South Africa, between Oyster Bay and St. Francis (approximately 88 km west of Port Elizabeth), and encompasses the Thyspunt site where the proposed NPP will be built. The study aims to supplement existing information about the Thyspunt area, related to the geoscientific topic ‘Geological Setting’, as outlined in section 2.5.1.1 of the US Nuclear Regulatory Commission (USNRC) Standard Review Plan NUREG-800, which details the geological information required for review of a proposed NPP. The results obtained from geoscientific studies are used to determine geological factors that may potentially affect site specific design. Factors considered include: bedrock lithology, stratigraphic bedrock contacts, bedrock palaeotopography, thickness of overburden sediments and structural geology. Work by previous authors is combined with new data to create a GIS based 2½D model of the study area’s geology (geomodel) and on which future research or interpretations can be based. Field mapping and petrographic analyses of the TMG, comprising the Peninsula, Cedarberg, Goudini, Skurweberg and Baviaanskloof Formations as well as the lower undifferentiated Bokkeveld Group were undertaken to define the study area’s lithologies and structure. Interpretation of geophysical results and the integration of existing borehole data aided in defining the variability in overburden sediments, the identification of contacts between TMG formations beneath overburden, and the palaeotopography of bedrock. Borehole data indicates a clear N-S trend in the thickness distribution of Algoa Group aeolian and marine related sediments. Four coast-parallel trending thickness zones (zones A – D) are recognized within the study area. At Thyspunt overburden thickness reaches a maximum of 61 m, approximately 1200 m from the coastline, in areas underlain by the argillaceous Goudini and Cedarberg Formations. Overburden thickness is influenced by a combination of dune relief, bedrock lithology, palaeotopography and the area’s sediment supply. Interpolation of bedrock elevation points and detailed cross sections across bedrock reveals four NW-SE trending palaeovalleys at Thyspunt, Tony’s Bay, Cape St. Francis and St. Francis, where bedrock relief (beneath overburden) is formed to be below present day sea-level. Approximately 450 m NW of Thys Bay, a 1050 m2 (area below sea-level) palaeovalley, gently sloping SE to a depth of -15.5 m asl, is cut into strata of the Goudini Formation resulting in thicker overburden fill in that area. Structural analysis of the TMG confirms that NE-SW striking strata form part of the regional SE plunging, north verging Cape St. Francis anticline. Bedding inclination is controlled by the distance away from the fold axis, varying from a 5° SE dip along the broad fold hinge to 65° along its moderately steeper SE limb. Folds within the study area plunge gently southeastward at shallow angles, with axial planes dipping steeply SW or NE. Fold axes orientated perpendicular to the fold axis of the Cape St. Francis anticline indicate a secondary stress orientation oblique to the main palaeostress direction. The previously identified 40 km long, NW-SE trending Cape St. Francis fault occurring offshore within 17.5 km of Thyspunt show no onshore continuation within the bounds of the study area. Late jointing is pervasive within the study area and four joint systems are identified. The dominant joint set J1, trends N-S to NNE - SSW; perpendicular to bedding and has a subvertical dip. Normal right-lateral and left-lateral micro-faults dip subvertically, with a displacement that ranges from a few centimetres to <3 m. Micro-faults trend parallel to joints sets J1 and J4 (ESE-WSW). Inferred faults, identified by the Atomic Energy Co-operation (AEC), are interpreted as zones of closely spaced jointing (shatter zones), and show little to no recognizable displacement. Faults and joints do not extend into the younger cover deposits of the Algoa Group and are therefore older than 23 Ma years.
- Full Text:
- Date Issued: 2015
- Authors: Claassen, Debbie
- Date: 2015
- Subjects: Geology, Structural -- South Africa -- Eastern Cape , Geology, Stratigraphic , Geochemistry , Rock mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10678 , http://hdl.handle.net/10948/d1021182
- Description: This study describes the bedrock lithologies and structure of the Ordovician to early Devonian (485-419 Ma) Table Mountain Group (TMG), the Devonian (419-358 Ma) lower Bokkeveld Group, and the Miocene to Holocene (<23 Ma) overburden sediments of the Algoa Group within an area identified by Eskom for the potential construction of South Africa’s second proposed nuclear power plant (NPP), ‘Nuclear-1’. The study area is located along the southern coastal margin of the Eastern Cape Province, South Africa, between Oyster Bay and St. Francis (approximately 88 km west of Port Elizabeth), and encompasses the Thyspunt site where the proposed NPP will be built. The study aims to supplement existing information about the Thyspunt area, related to the geoscientific topic ‘Geological Setting’, as outlined in section 2.5.1.1 of the US Nuclear Regulatory Commission (USNRC) Standard Review Plan NUREG-800, which details the geological information required for review of a proposed NPP. The results obtained from geoscientific studies are used to determine geological factors that may potentially affect site specific design. Factors considered include: bedrock lithology, stratigraphic bedrock contacts, bedrock palaeotopography, thickness of overburden sediments and structural geology. Work by previous authors is combined with new data to create a GIS based 2½D model of the study area’s geology (geomodel) and on which future research or interpretations can be based. Field mapping and petrographic analyses of the TMG, comprising the Peninsula, Cedarberg, Goudini, Skurweberg and Baviaanskloof Formations as well as the lower undifferentiated Bokkeveld Group were undertaken to define the study area’s lithologies and structure. Interpretation of geophysical results and the integration of existing borehole data aided in defining the variability in overburden sediments, the identification of contacts between TMG formations beneath overburden, and the palaeotopography of bedrock. Borehole data indicates a clear N-S trend in the thickness distribution of Algoa Group aeolian and marine related sediments. Four coast-parallel trending thickness zones (zones A – D) are recognized within the study area. At Thyspunt overburden thickness reaches a maximum of 61 m, approximately 1200 m from the coastline, in areas underlain by the argillaceous Goudini and Cedarberg Formations. Overburden thickness is influenced by a combination of dune relief, bedrock lithology, palaeotopography and the area’s sediment supply. Interpolation of bedrock elevation points and detailed cross sections across bedrock reveals four NW-SE trending palaeovalleys at Thyspunt, Tony’s Bay, Cape St. Francis and St. Francis, where bedrock relief (beneath overburden) is formed to be below present day sea-level. Approximately 450 m NW of Thys Bay, a 1050 m2 (area below sea-level) palaeovalley, gently sloping SE to a depth of -15.5 m asl, is cut into strata of the Goudini Formation resulting in thicker overburden fill in that area. Structural analysis of the TMG confirms that NE-SW striking strata form part of the regional SE plunging, north verging Cape St. Francis anticline. Bedding inclination is controlled by the distance away from the fold axis, varying from a 5° SE dip along the broad fold hinge to 65° along its moderately steeper SE limb. Folds within the study area plunge gently southeastward at shallow angles, with axial planes dipping steeply SW or NE. Fold axes orientated perpendicular to the fold axis of the Cape St. Francis anticline indicate a secondary stress orientation oblique to the main palaeostress direction. The previously identified 40 km long, NW-SE trending Cape St. Francis fault occurring offshore within 17.5 km of Thyspunt show no onshore continuation within the bounds of the study area. Late jointing is pervasive within the study area and four joint systems are identified. The dominant joint set J1, trends N-S to NNE - SSW; perpendicular to bedding and has a subvertical dip. Normal right-lateral and left-lateral micro-faults dip subvertically, with a displacement that ranges from a few centimetres to <3 m. Micro-faults trend parallel to joints sets J1 and J4 (ESE-WSW). Inferred faults, identified by the Atomic Energy Co-operation (AEC), are interpreted as zones of closely spaced jointing (shatter zones), and show little to no recognizable displacement. Faults and joints do not extend into the younger cover deposits of the Algoa Group and are therefore older than 23 Ma years.
- Full Text:
- Date Issued: 2015
Environmental flows, health and importance of macrophytes in the estuaries of water management area 11
- Authors: Cowie, Meredith
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7930 , vital:24324
- Description: Estuaries require sufficient quantity, quality and appropriate timing of freshwater inflow, referred to as environmental flow requirements, to ensure adequate health and functioning. In South Africa the environmental flow requirements of estuaries is determined using Resource Directed Measures (RDM). The present health and importance of an estuary must be considered when determining the ecological flow required to maintain an estuary in its desired state. An Estuarine Health Index that quantifies changes in abiotic and biotic components from natural conditions to present day is used. Health of biotic components is assessed according to changes in species richness, abundance and community composition. There has, however, been debate regarding the calculation of these attributes. In particular, for macrophytes, the inclusion of all habitat within the Estuarine Functional Zone (i.e. 5 m topographical contour) would affect the health and changes over time determined in past assessments. This is due to different areas being included as different areas would be included The aim of this study was to test the validity and suggest improvements to South Africa’s RDM macrophyte health score determination. The health of macrophytes were assessed at varying levels of intensity from desktop studies to thorough field studies. Rapid field studies provided a visual estimate of macrophyte health; while the intermediate and comprehensive assessments quantified change by mapping the distribution of macrophyte habitats from aerial photographs. These approaches were applied to the 64 estuaries within the Mvoti-Mzimkulu Water Management Area (WMA 11), situated in KwaZulu-Natal (KZN) on the subtropical east coast. Historically, these estuaries have supported restricted macrophyte habitats. Consequently, estuaries that presently or historically supported range limited habitats such as mangroves and swamp forest are considered important. Submerged macrophytes are scarce in KZN estuaries due to siltation and low turbidity and thus estuaries supporting this macrophyte habitat are also important. Based on available literature important estuaries were highlighted and selected for field studies. Transects spanning from the estuary water channel to the boundary of the EFZ provided a generalised distribution of KZN vegetation along an elevation gradient. The transition from estuarine to terrestrial vegetation can be used to improve the current EFZ boundaries, as estuarine area has been found to occur outside of the 5 m contour in some estuaries. Results from the desktop assessment indicated that most of the estuaries are moderately modified. There was a 50 % similarity in the macrophyte health scores determined by the desktop assessment to the 2011 National Biodiversity Assessment (NBA). Field studies mostly confirmed the desktop assessment aside from seven estuaries that had different scores. There has been a significant loss of macrophyte habitat with 100% loss of certain habitats from 9 of the 22 estuaries for which there were field assessments. Submerged macrophytes were not found at any of the estuaries that were assessed in the field. Black mangroves, Bruguiera gymnorrhiza (L.) Lam., were rediscovered at Ngane Estuary, however the few individuals could not be considered a ‘mappable’ community (i.e. <0.5 ha). Mtamvuna and Mkomazi estuaries both supported small stands of mangroves that, compared to data from 2006, appeared healthy. Macrophyte habitats and surrounding coastal forest matched the species composition described in the Vegetation Map of South Africa. The freshwater mangrove or Powder puff tree, Barringtonia racemosa (L.) Roxb, was not abundant in the estuaries. It was only found at four (Damba, Fafa, Little Amanzimtoti and Mvoti) of the estuaries that were assessed in the field. Important estuaries, from a botanical perspective, included some of the larger estuaries such as Mgeni, Durban Bay and Sipingo. Smaller, healthier estuaries that presently support mangrove and swamp forest habitat were also identified as important from a botanical perspective. Macrophyte habitats have mainly been lost due to non-flow related pressures. Sugarcane cultivation occurred within the floodplain of 25% of the estuaries. Nutrient enrichment was evident for 12.5% of the estuaries and reed encroachment was evident for 27% of estuaries for which there were field assessments. Development, aside from the N2 road bridges, was evident for 40% of the estuaries assessed in the field. Invasive plant species, including aquatic invasive plants, were present in all estuaries assessed in the field. The extent of invasive plant species was related to the degree of disturbance and surrounding land use pressures. The Mkomazi and Mvoti estuaries that were assessed at a comprehensive level, as they have earmarked for further water abstraction, had the poorest macrophyte health scores. The macrophyte health of these estuaries was much lower than previously determined by the NBA. The decline in health was attributed to the removal of macrophyte habitat for sugarcane cultivation and development as well as displacement by invasive plant species. The areas covered by the macrophyte habitats also differed from the NBA highlighting the importance of updated mapping and ground truthing. Largely differing macrophyte health scores were produced when attributes were calculated using different combinations of macrophyte habitats. Results indicate that only macrophyte habitats and no other floodplain vegetation should be included when calculating abundance. All macrophyte habitats, physical habitats and floodplain should be incorporated when calculating community composition. The minimum of these attributes is used as the overall macrophyte health score as a precautionary approach is followed. Scoring of health is subjective and the only benchmark for determining the most appropriate method is comparion with previous RDM studies. This study illustrates the need for a standardised RDM scoring method that is presented in a manner that ensures the same results irregardless of the speciliast conducting the study. The updated estuary health and importance scores for WMA 11 are necessary to inform management, particularly as few of the estuaries receive formal protection. In conclusion, this study contributed to the limited knowledge of the estuaries of WMA 11 and assisted in determining appropriate methods for assessing the health and importance of estuary macrophytes.
- Full Text:
- Date Issued: 2015
- Authors: Cowie, Meredith
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7930 , vital:24324
- Description: Estuaries require sufficient quantity, quality and appropriate timing of freshwater inflow, referred to as environmental flow requirements, to ensure adequate health and functioning. In South Africa the environmental flow requirements of estuaries is determined using Resource Directed Measures (RDM). The present health and importance of an estuary must be considered when determining the ecological flow required to maintain an estuary in its desired state. An Estuarine Health Index that quantifies changes in abiotic and biotic components from natural conditions to present day is used. Health of biotic components is assessed according to changes in species richness, abundance and community composition. There has, however, been debate regarding the calculation of these attributes. In particular, for macrophytes, the inclusion of all habitat within the Estuarine Functional Zone (i.e. 5 m topographical contour) would affect the health and changes over time determined in past assessments. This is due to different areas being included as different areas would be included The aim of this study was to test the validity and suggest improvements to South Africa’s RDM macrophyte health score determination. The health of macrophytes were assessed at varying levels of intensity from desktop studies to thorough field studies. Rapid field studies provided a visual estimate of macrophyte health; while the intermediate and comprehensive assessments quantified change by mapping the distribution of macrophyte habitats from aerial photographs. These approaches were applied to the 64 estuaries within the Mvoti-Mzimkulu Water Management Area (WMA 11), situated in KwaZulu-Natal (KZN) on the subtropical east coast. Historically, these estuaries have supported restricted macrophyte habitats. Consequently, estuaries that presently or historically supported range limited habitats such as mangroves and swamp forest are considered important. Submerged macrophytes are scarce in KZN estuaries due to siltation and low turbidity and thus estuaries supporting this macrophyte habitat are also important. Based on available literature important estuaries were highlighted and selected for field studies. Transects spanning from the estuary water channel to the boundary of the EFZ provided a generalised distribution of KZN vegetation along an elevation gradient. The transition from estuarine to terrestrial vegetation can be used to improve the current EFZ boundaries, as estuarine area has been found to occur outside of the 5 m contour in some estuaries. Results from the desktop assessment indicated that most of the estuaries are moderately modified. There was a 50 % similarity in the macrophyte health scores determined by the desktop assessment to the 2011 National Biodiversity Assessment (NBA). Field studies mostly confirmed the desktop assessment aside from seven estuaries that had different scores. There has been a significant loss of macrophyte habitat with 100% loss of certain habitats from 9 of the 22 estuaries for which there were field assessments. Submerged macrophytes were not found at any of the estuaries that were assessed in the field. Black mangroves, Bruguiera gymnorrhiza (L.) Lam., were rediscovered at Ngane Estuary, however the few individuals could not be considered a ‘mappable’ community (i.e. <0.5 ha). Mtamvuna and Mkomazi estuaries both supported small stands of mangroves that, compared to data from 2006, appeared healthy. Macrophyte habitats and surrounding coastal forest matched the species composition described in the Vegetation Map of South Africa. The freshwater mangrove or Powder puff tree, Barringtonia racemosa (L.) Roxb, was not abundant in the estuaries. It was only found at four (Damba, Fafa, Little Amanzimtoti and Mvoti) of the estuaries that were assessed in the field. Important estuaries, from a botanical perspective, included some of the larger estuaries such as Mgeni, Durban Bay and Sipingo. Smaller, healthier estuaries that presently support mangrove and swamp forest habitat were also identified as important from a botanical perspective. Macrophyte habitats have mainly been lost due to non-flow related pressures. Sugarcane cultivation occurred within the floodplain of 25% of the estuaries. Nutrient enrichment was evident for 12.5% of the estuaries and reed encroachment was evident for 27% of estuaries for which there were field assessments. Development, aside from the N2 road bridges, was evident for 40% of the estuaries assessed in the field. Invasive plant species, including aquatic invasive plants, were present in all estuaries assessed in the field. The extent of invasive plant species was related to the degree of disturbance and surrounding land use pressures. The Mkomazi and Mvoti estuaries that were assessed at a comprehensive level, as they have earmarked for further water abstraction, had the poorest macrophyte health scores. The macrophyte health of these estuaries was much lower than previously determined by the NBA. The decline in health was attributed to the removal of macrophyte habitat for sugarcane cultivation and development as well as displacement by invasive plant species. The areas covered by the macrophyte habitats also differed from the NBA highlighting the importance of updated mapping and ground truthing. Largely differing macrophyte health scores were produced when attributes were calculated using different combinations of macrophyte habitats. Results indicate that only macrophyte habitats and no other floodplain vegetation should be included when calculating abundance. All macrophyte habitats, physical habitats and floodplain should be incorporated when calculating community composition. The minimum of these attributes is used as the overall macrophyte health score as a precautionary approach is followed. Scoring of health is subjective and the only benchmark for determining the most appropriate method is comparion with previous RDM studies. This study illustrates the need for a standardised RDM scoring method that is presented in a manner that ensures the same results irregardless of the speciliast conducting the study. The updated estuary health and importance scores for WMA 11 are necessary to inform management, particularly as few of the estuaries receive formal protection. In conclusion, this study contributed to the limited knowledge of the estuaries of WMA 11 and assisted in determining appropriate methods for assessing the health and importance of estuary macrophytes.
- Full Text:
- Date Issued: 2015
Transformation adaptation: developing a framework for donor organisation support of climate change adaptation in resource poor communities
- Authors: Dada, Rehana
- Date: 2015
- Subjects: Climatic changes , Human beings -- Effect of climate on , Acclimatization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4158 , vital:20560
- Description: Poor communities already face severe challenges in meeting their basic needs, whether because of poor income opportunities, inadequate service delivery, or degraded ecosystems that can no longer support the needs of people. Non profit organisations who provide support for development are also challenged by financial restrictions and social and political structures that prevent or limit project development. Climate change is understood to have the most severe impact on the most vulnerable communities and sectors of communities by reducing the availability and accessibility of basic resources such as water, food and energy, impacting severely on human health and wellbeing, and further reducing the capacity of ecosystems to support livelihoods. This will add a layer of significant new complications to the ability of poor communities to maintain or improve standards of living, and further challenge non profit organisations that support such communitiesAnticipatory adaptation to climate change can reduce some of the impacts of climate change, and also address some key development stresses. This thesis aims to provide a framework that is relevant for supporting adaptation to climate change within the context of resource poor communities in a developing country. Non profit organisations and donor agencies could support success and autonomy in adaptation processes by making provision for locally defined understanding of adaptation, and locally determined processes and programmes. This can be taken further into implementation of programming that addresses local short term development priorities alongside, or as part of long term adaptation work. The research followed a number of steps involving a multitude of techniques including literature review, interviews, a survey, consultation with an expert group, further consultation with stakeholders, and a final electronic review. Its outcome is a strategy that can be used to support climate change adaptation in resource poor communities. A definition for adaptation is proposed as an interpretation of adaptation that is relevant in this context. The intended end goal of adaptation as defined in this research is a better form of development that : supports a harmonious and respectful relationship between humans and their natural resource base; averts further destructive global change or at the very least prevents it from becoming unmanageable; and manages the impacts of past and ongoing destructive change so that there is lowest possible loss of natural, human, or cultural resources. The term transformative adaptation emerged from the research processes to describe adaptation to climate change that concurrently addresses development challenges, is grounded in community development aspirations, integrates programming work across multiple thematic areas and approaches, and addresses the causes of climate change within adaptation interventions. The following broad guidelines are used to inform programming within the framework of transformative adaptation : Human communities are faced with an enormous challenge resulting from global change and sociopolitical injustices; Well planned anticipatory adaptation can limit exposure and vulnerability to at least some of the projected impacts of climate change; Adaptation to climate change incorporates a reduction of vulnerability to underlying development stresses, alongside a reduction of vulnerability to specific climate change stresses; Existing development work forms the foundation for adaptation interventions, acknowledging the interdependence of social, natural and economic systems and the need to maintain their health; Adaptation decision making is community based, and acknowledges that resource poor communities are best placed to establish their own development needs, drive implementation of interventions in own spaces, and identify own limits to adaptation; Adaptation work incorporates mitigation objectives so that the causes of climate change are addressed as part of the strategy for coping with climate change; Adaptation programming acknowledges the strong interlinkages between, and integrates work across, the thematic areas of water security, food sovereignty, energy security, land security, human wellbeing and livelihood diversity; Adaptation uses a broad set of approaches that spans research, knowledge sharing, advocacy, and investment in technology and infrastructure; There is flexibility in project design and implementation to allow room for experimentation with new concepts, and also to change design as knowledge, understanding, and geophysical, biophysical and sociopolitical conditions change.
- Full Text:
- Date Issued: 2015
- Authors: Dada, Rehana
- Date: 2015
- Subjects: Climatic changes , Human beings -- Effect of climate on , Acclimatization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4158 , vital:20560
- Description: Poor communities already face severe challenges in meeting their basic needs, whether because of poor income opportunities, inadequate service delivery, or degraded ecosystems that can no longer support the needs of people. Non profit organisations who provide support for development are also challenged by financial restrictions and social and political structures that prevent or limit project development. Climate change is understood to have the most severe impact on the most vulnerable communities and sectors of communities by reducing the availability and accessibility of basic resources such as water, food and energy, impacting severely on human health and wellbeing, and further reducing the capacity of ecosystems to support livelihoods. This will add a layer of significant new complications to the ability of poor communities to maintain or improve standards of living, and further challenge non profit organisations that support such communitiesAnticipatory adaptation to climate change can reduce some of the impacts of climate change, and also address some key development stresses. This thesis aims to provide a framework that is relevant for supporting adaptation to climate change within the context of resource poor communities in a developing country. Non profit organisations and donor agencies could support success and autonomy in adaptation processes by making provision for locally defined understanding of adaptation, and locally determined processes and programmes. This can be taken further into implementation of programming that addresses local short term development priorities alongside, or as part of long term adaptation work. The research followed a number of steps involving a multitude of techniques including literature review, interviews, a survey, consultation with an expert group, further consultation with stakeholders, and a final electronic review. Its outcome is a strategy that can be used to support climate change adaptation in resource poor communities. A definition for adaptation is proposed as an interpretation of adaptation that is relevant in this context. The intended end goal of adaptation as defined in this research is a better form of development that : supports a harmonious and respectful relationship between humans and their natural resource base; averts further destructive global change or at the very least prevents it from becoming unmanageable; and manages the impacts of past and ongoing destructive change so that there is lowest possible loss of natural, human, or cultural resources. The term transformative adaptation emerged from the research processes to describe adaptation to climate change that concurrently addresses development challenges, is grounded in community development aspirations, integrates programming work across multiple thematic areas and approaches, and addresses the causes of climate change within adaptation interventions. The following broad guidelines are used to inform programming within the framework of transformative adaptation : Human communities are faced with an enormous challenge resulting from global change and sociopolitical injustices; Well planned anticipatory adaptation can limit exposure and vulnerability to at least some of the projected impacts of climate change; Adaptation to climate change incorporates a reduction of vulnerability to underlying development stresses, alongside a reduction of vulnerability to specific climate change stresses; Existing development work forms the foundation for adaptation interventions, acknowledging the interdependence of social, natural and economic systems and the need to maintain their health; Adaptation decision making is community based, and acknowledges that resource poor communities are best placed to establish their own development needs, drive implementation of interventions in own spaces, and identify own limits to adaptation; Adaptation work incorporates mitigation objectives so that the causes of climate change are addressed as part of the strategy for coping with climate change; Adaptation programming acknowledges the strong interlinkages between, and integrates work across, the thematic areas of water security, food sovereignty, energy security, land security, human wellbeing and livelihood diversity; Adaptation uses a broad set of approaches that spans research, knowledge sharing, advocacy, and investment in technology and infrastructure; There is flexibility in project design and implementation to allow room for experimentation with new concepts, and also to change design as knowledge, understanding, and geophysical, biophysical and sociopolitical conditions change.
- Full Text:
- Date Issued: 2015
An analysis of soil properties associated with badland and gully erosion in rural catchments of the Ngqushwa District, Eastern Cape Province
- Authors: De Jager, Megan Joan
- Date: 2015
- Subjects: Soil mechanics -- South Africa -- Eastern Cape , Soils -- South Africa -- Eastern Cape -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3519 , vital:20438
- Description: Accelerated soil erosion holds strong links to excessive land degradation, socioeconomic problems and accelerated climate change, particularly in developing countries such as South Africa. An analysis of the properties of severely eroded soils is undertaken to determine which characteristic properties influence the erodibility of the soils at several gully and badland sites in three catchments of the Ngqushwa rural municipality, which is tagged as one of the area’s most severely affected by soil erosion and degradation in the Eastern Cape. Physical, biological and chemical properties of the soils were analysed, including aggregate stability, soil texture, organic matter- and carbon content, clay mineralogy, sesquioxide content as Fe2O3 and cation composition. The distribution of a number of these properties was also determined, particularly between erosion sites, along hillslope profiles and with depth. The study area comprises three catchments, namely Mgwalana, Bira and Gqora which share common soil parent materials, land use history, exhibit similar topography and advanced degree of erosion. A total of 63 soil samples were strategically collected from identified erosion zones and site controls devoid of active erosion; where stability was evident by means of vegetation cover and soil surface condition. Surface samples were collected above 30cm depth and subsurface samples at depths greater than 30cm. To determine the fate of carbon additional samples were collected from runon and sink zones at the Mgwalana catchment along a transect from top to bottom slope. Laboratory analyses was performed to determine the soil properties, whereby C content was measured by the dry combustion method, Fe2O3- and cation content by Atomic Absorption (AA) Spectrometer, texture by the separation method described by Schlichting, Blume & Stahr (1995), clay mineralogy by X-Ray Diffraction and organic matter content by conversion of total C. In addition to these properties being used to infer aggregate stability, the wet sieving method was also used for this purpose and for validation of the other soil properties. The results revealed that no one soil property has a greater influence on aggregate stability than the others, but rather that the stability of the soil is dependent on the combinations of these properties in the soil and the interactions that occur between them. Based on this, the results indicated greater stability for runon, sink and control samples, mainly in the topsoil, which were characterised by a relatively higher C- and organic matter content, loam texture and higher concentrations of Ca2+. Furthermore, the less stable eroded samples were characterised by a more clay rich texture particularly in the subsoil, relatively lower C- and organic matter contents and a greater sodicity due to higher concentrations of Na+. The least stable soils belonged to the Gqora catchment, which were found to consist of higher silt content in the topsoil and a higher Fe2O3 content in the subsoil. The clay mineralogy was relatively uniform across all catchments, comprising of primarily illite and secondly kaolinite. The sample with the highest sodicity in terms of ESP contained smectite clay in addition to illite and kaolinite which is assumed to contribute to this increased Na+ concentration. These findings aid in the conclusion that the chemical characteristics of the soils, in association with biological and, to a less extent, physical properties of the soil exacerbate the erosion problem initiated by the extrinsic contributors, such as climate and topography. Investigation into the fate of carbon on eroded lands revealed a topographically driven dynamic whereby the total carbon content was found to be greater at the top and middle slope positions as well as in the sink zone. These hillslope sections were found to have a lower slope gradient and slightly more pronounced concave shape to those sections with lower C values. These topographic variables influence the degree of gully erosion taking place at different hillslope sections, which tends to be greater where slope angle is increased and convexity exists, resulting in the removal of soil C at these positions and its deposition in areas of accumulation, namely the runon and sink zones of low angle concave slope sections. The findings of this research may be used to develop restoration and management strategies with the ultimate goal to reduce the soils vulnerability to erosion by enhancing those soil properties conducive to greater aggregate stability as determined in the present study.
- Full Text:
- Date Issued: 2015
- Authors: De Jager, Megan Joan
- Date: 2015
- Subjects: Soil mechanics -- South Africa -- Eastern Cape , Soils -- South Africa -- Eastern Cape -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3519 , vital:20438
- Description: Accelerated soil erosion holds strong links to excessive land degradation, socioeconomic problems and accelerated climate change, particularly in developing countries such as South Africa. An analysis of the properties of severely eroded soils is undertaken to determine which characteristic properties influence the erodibility of the soils at several gully and badland sites in three catchments of the Ngqushwa rural municipality, which is tagged as one of the area’s most severely affected by soil erosion and degradation in the Eastern Cape. Physical, biological and chemical properties of the soils were analysed, including aggregate stability, soil texture, organic matter- and carbon content, clay mineralogy, sesquioxide content as Fe2O3 and cation composition. The distribution of a number of these properties was also determined, particularly between erosion sites, along hillslope profiles and with depth. The study area comprises three catchments, namely Mgwalana, Bira and Gqora which share common soil parent materials, land use history, exhibit similar topography and advanced degree of erosion. A total of 63 soil samples were strategically collected from identified erosion zones and site controls devoid of active erosion; where stability was evident by means of vegetation cover and soil surface condition. Surface samples were collected above 30cm depth and subsurface samples at depths greater than 30cm. To determine the fate of carbon additional samples were collected from runon and sink zones at the Mgwalana catchment along a transect from top to bottom slope. Laboratory analyses was performed to determine the soil properties, whereby C content was measured by the dry combustion method, Fe2O3- and cation content by Atomic Absorption (AA) Spectrometer, texture by the separation method described by Schlichting, Blume & Stahr (1995), clay mineralogy by X-Ray Diffraction and organic matter content by conversion of total C. In addition to these properties being used to infer aggregate stability, the wet sieving method was also used for this purpose and for validation of the other soil properties. The results revealed that no one soil property has a greater influence on aggregate stability than the others, but rather that the stability of the soil is dependent on the combinations of these properties in the soil and the interactions that occur between them. Based on this, the results indicated greater stability for runon, sink and control samples, mainly in the topsoil, which were characterised by a relatively higher C- and organic matter content, loam texture and higher concentrations of Ca2+. Furthermore, the less stable eroded samples were characterised by a more clay rich texture particularly in the subsoil, relatively lower C- and organic matter contents and a greater sodicity due to higher concentrations of Na+. The least stable soils belonged to the Gqora catchment, which were found to consist of higher silt content in the topsoil and a higher Fe2O3 content in the subsoil. The clay mineralogy was relatively uniform across all catchments, comprising of primarily illite and secondly kaolinite. The sample with the highest sodicity in terms of ESP contained smectite clay in addition to illite and kaolinite which is assumed to contribute to this increased Na+ concentration. These findings aid in the conclusion that the chemical characteristics of the soils, in association with biological and, to a less extent, physical properties of the soil exacerbate the erosion problem initiated by the extrinsic contributors, such as climate and topography. Investigation into the fate of carbon on eroded lands revealed a topographically driven dynamic whereby the total carbon content was found to be greater at the top and middle slope positions as well as in the sink zone. These hillslope sections were found to have a lower slope gradient and slightly more pronounced concave shape to those sections with lower C values. These topographic variables influence the degree of gully erosion taking place at different hillslope sections, which tends to be greater where slope angle is increased and convexity exists, resulting in the removal of soil C at these positions and its deposition in areas of accumulation, namely the runon and sink zones of low angle concave slope sections. The findings of this research may be used to develop restoration and management strategies with the ultimate goal to reduce the soils vulnerability to erosion by enhancing those soil properties conducive to greater aggregate stability as determined in the present study.
- Full Text:
- Date Issued: 2015
An assessment of vegetation condition of small, ephemeral wetlands ecosystem in a conserved and non-conserved area of the Nelson Mandela Bay Metropole
- Authors: Dlamini, Mandla E
- Date: 2015
- Subjects: Wetland conservation -- South Africa -- Nelson Mandela Bay Municipality , Wetland ecology -- South Africa -- Nelson Mandela Bay Municipality , Remote sensing -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4653 , vital:20626
- Description: Wetlands in South Africa are increasingly coming under threat from agriculture and urban development and rapidly disappearing, especially small, ephemeral wetlands. In response to the many threats to wetlands, South Africa has seen an increased interest in wetland research, which has introduced many methods to help standardize the approach to research, management and conservation of wetlands. Remote sensing can be a powerful tool to monitor changes in wetland vegetation and degradation leading to losses in wetlands. However, research into wetland ecosystems has focused on large systems (> 8 ha). Small wetlands (< 2 ha), by contrast, are often overlooked and unprotected due to the lack of detailed inventories at a scale that is appropriate for their inclusion. The main aim of this study was to determine if remote sensing (RS) and Geographical Information System (GIS) techniques could detect changes in small, ephemeral wetlands within areas under different management regimes in the Nelson Mandela Bay Metropole (NMBM) at different time intervals. Further, to explore the potential of hyperspectral remote sensing for the discrimination between plant species and to see if differences could be detected in the same species within two areas different management regimes. Four SPOT satellite images taken within a 6-year period (2006-2012) were analysed to detect land cover land changes. Supervised classification to classify land cover classes and post-classification change detection was used. Proportions of dense vegetation were higher in the conservation area and bare surface was higher outside that conservation area in the metropolitan open space area. Statistical tests were performed to compare the spectral responses of the four individual wetland sites using Normalized Difference Vegetation Index (NDVI) and red edge position (REP) .REP results for conserved sites showed significant differences (P < 0.05), as opposed to non-conserved ones. By implication, wetland vegetation that is in less degraded condition can be spectrally discriminated, than the one that is most degraded. Field spectroscopy and multi-temporal imagery can be useful in studying small wetlands.
- Full Text:
- Date Issued: 2015
- Authors: Dlamini, Mandla E
- Date: 2015
- Subjects: Wetland conservation -- South Africa -- Nelson Mandela Bay Municipality , Wetland ecology -- South Africa -- Nelson Mandela Bay Municipality , Remote sensing -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4653 , vital:20626
- Description: Wetlands in South Africa are increasingly coming under threat from agriculture and urban development and rapidly disappearing, especially small, ephemeral wetlands. In response to the many threats to wetlands, South Africa has seen an increased interest in wetland research, which has introduced many methods to help standardize the approach to research, management and conservation of wetlands. Remote sensing can be a powerful tool to monitor changes in wetland vegetation and degradation leading to losses in wetlands. However, research into wetland ecosystems has focused on large systems (> 8 ha). Small wetlands (< 2 ha), by contrast, are often overlooked and unprotected due to the lack of detailed inventories at a scale that is appropriate for their inclusion. The main aim of this study was to determine if remote sensing (RS) and Geographical Information System (GIS) techniques could detect changes in small, ephemeral wetlands within areas under different management regimes in the Nelson Mandela Bay Metropole (NMBM) at different time intervals. Further, to explore the potential of hyperspectral remote sensing for the discrimination between plant species and to see if differences could be detected in the same species within two areas different management regimes. Four SPOT satellite images taken within a 6-year period (2006-2012) were analysed to detect land cover land changes. Supervised classification to classify land cover classes and post-classification change detection was used. Proportions of dense vegetation were higher in the conservation area and bare surface was higher outside that conservation area in the metropolitan open space area. Statistical tests were performed to compare the spectral responses of the four individual wetland sites using Normalized Difference Vegetation Index (NDVI) and red edge position (REP) .REP results for conserved sites showed significant differences (P < 0.05), as opposed to non-conserved ones. By implication, wetland vegetation that is in less degraded condition can be spectrally discriminated, than the one that is most degraded. Field spectroscopy and multi-temporal imagery can be useful in studying small wetlands.
- Full Text:
- Date Issued: 2015
Enantioselective transformations using tetrol as a chiral mediator
- Authors: Dorfling, Sasha-Lee
- Date: 2015
- Subjects: Enantioselective catalysis , Trichothecenes , Catalysts , Titanium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10445 , http://hdl.handle.net/10948/d1021195
- Description: (+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives were reacted with varying molar ratios of titanium isopropoxide (2:1, 1:1 and 1:2 tetraol:titanium isopropoxide) in an attempt to prepare potential titanium-based tetraol catalysts for enantioselective transformations. In each case, infrared and HNMR spectra suggested that the product was formed. We tentatively proposed that the structure of the catalyst was a spiro-type, but we could not determine conclusively what its exact structure was, despite using numerous techniques at our disposal (molecular modelling calculations, H NMR and IR spectroscopy, thermal analyses, powder diffraction, and single crystal X-ray diffraction). The catalyst and derivatives thereof were able to act catalytically for the enantioselective additions of diethylzinc compounds to aldehydes. The effects of temperature and solvent were investigated, and toluene and -78 °C were selected as optimal from the results obtained. (The reaction could, however, not be maintained at this low temperature for extended periods due to the fact that we did not have, at our disposal, the correct equipment. Each 16 h reaction was thus allowed to reach room temperature in each case.) The selectivity for the product 1-phenylpropan-1-ol (when benzaldehyde was the starting aldehyde) varied depending on the nature of the aryl substituents of the titanium-based catalyst. Using 0.2 molar equivalents of the chiral titanates, the highest selectivity was 42 percent (e.e.), but only when excess Ti(O-i-Pr)4 had been added to the reaction mixture. This was achieved with the tetra(ortho-methoxyphenyl)-TETROLate derivative. TETROL and its derivatives were also successful in metal-free catalysis where higher conversions and selectivities were observed, compared to when these were complexed to titanium. The highest selectivity was 70 percent (e.e.), achieved with the tetra(ortho-methylphenyl)TETROL derivative.
- Full Text:
- Date Issued: 2015
- Authors: Dorfling, Sasha-Lee
- Date: 2015
- Subjects: Enantioselective catalysis , Trichothecenes , Catalysts , Titanium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10445 , http://hdl.handle.net/10948/d1021195
- Description: (+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives were reacted with varying molar ratios of titanium isopropoxide (2:1, 1:1 and 1:2 tetraol:titanium isopropoxide) in an attempt to prepare potential titanium-based tetraol catalysts for enantioselective transformations. In each case, infrared and HNMR spectra suggested that the product was formed. We tentatively proposed that the structure of the catalyst was a spiro-type, but we could not determine conclusively what its exact structure was, despite using numerous techniques at our disposal (molecular modelling calculations, H NMR and IR spectroscopy, thermal analyses, powder diffraction, and single crystal X-ray diffraction). The catalyst and derivatives thereof were able to act catalytically for the enantioselective additions of diethylzinc compounds to aldehydes. The effects of temperature and solvent were investigated, and toluene and -78 °C were selected as optimal from the results obtained. (The reaction could, however, not be maintained at this low temperature for extended periods due to the fact that we did not have, at our disposal, the correct equipment. Each 16 h reaction was thus allowed to reach room temperature in each case.) The selectivity for the product 1-phenylpropan-1-ol (when benzaldehyde was the starting aldehyde) varied depending on the nature of the aryl substituents of the titanium-based catalyst. Using 0.2 molar equivalents of the chiral titanates, the highest selectivity was 42 percent (e.e.), but only when excess Ti(O-i-Pr)4 had been added to the reaction mixture. This was achieved with the tetra(ortho-methoxyphenyl)-TETROLate derivative. TETROL and its derivatives were also successful in metal-free catalysis where higher conversions and selectivities were observed, compared to when these were complexed to titanium. The highest selectivity was 70 percent (e.e.), achieved with the tetra(ortho-methylphenyl)TETROL derivative.
- Full Text:
- Date Issued: 2015
Changes in diet resource use by elephants, Loxodonta Africana, due to changes in resource availability in the Addo National Park
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
An assessment of the in vitro neuroprotective potential of selected Algerian and South African medicinal plant extracts
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
The anti-ageing potential of rooibos: preserving preadipocyte funtion
- Authors: Hattingh, Anna C
- Date: 2015
- Subjects: Natural products , Aging -- Prevention , Cosmetics industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7804 , vital:24288
- Description: Treatments with natural products rich in anti-oxidants have attracted remarkable interest in the cosmetic and pharmaceutical industry to combat oxidative stress and reverse the effects of ageing. Rooibos (Aspalathus linearis) is a South African fynbos plant, well-known for its strong anti-oxidant capacity and use in many cosmetic products. However, little published research exists on its potential as an anti-ageing treatment. The anti-ageing properties of fermented and green rooibos were investigated using an in vitro cell culture model designed to evaluate the involvement of mitochondrial dysfunction in the age related decline in preadipocyte function. Mitochondrial DNA (mtDNA) deficient preadipocytes, ρ0 3T3-L1preadipocytes, were generated following continuous long-term exposure to sub lethal concentrations of ethidium bromide (EtBr). Depletion of the mtDNA resulted in a significantly reduced mitochondrial membrane potential, rate of proliferation in culture, as well as an increased glucose utilization and lactate production. Treatment with the green rooibos (100 μg/mL) stimulated cell growth rates for both the wildtype and mutant cell lines. MtDNA depleted cells showed arrest in the G1 phase (48.8 ± 3.34%) compared to wildtype cells (44.6 ± 1.38%), which was significantly attenuated after treatment with green rooibos for mutant (42.0 ± 0.83%) and wildtype (36.5 ± 5.80%) treated cells. The results obtained for glucose utilization and lactate production, indicated a significant increase in glucose utilization along with a concomitant increase in lactate production after treatment with both green and fermented rooibos for wildtype and mutant cell lines. A significant improvement in mitochondrial membrane potential was also later observed after treatment with green and fermented rooibos on both the wildtype and mutant cell lines. The results obtained indicate that rooibos extracts, particularly the green rooibos, exhibit effects which preserve the functional capacity of preadipocytes exposed to ageing related insults, and indicate that rooibos could cause a metabolic shift in cells redirecting carbon flow away from mitochondrial metabolism, and towards lactate production and consequently, cells become resistant to mitochondrial dysfunction.
- Full Text:
- Date Issued: 2015
- Authors: Hattingh, Anna C
- Date: 2015
- Subjects: Natural products , Aging -- Prevention , Cosmetics industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7804 , vital:24288
- Description: Treatments with natural products rich in anti-oxidants have attracted remarkable interest in the cosmetic and pharmaceutical industry to combat oxidative stress and reverse the effects of ageing. Rooibos (Aspalathus linearis) is a South African fynbos plant, well-known for its strong anti-oxidant capacity and use in many cosmetic products. However, little published research exists on its potential as an anti-ageing treatment. The anti-ageing properties of fermented and green rooibos were investigated using an in vitro cell culture model designed to evaluate the involvement of mitochondrial dysfunction in the age related decline in preadipocyte function. Mitochondrial DNA (mtDNA) deficient preadipocytes, ρ0 3T3-L1preadipocytes, were generated following continuous long-term exposure to sub lethal concentrations of ethidium bromide (EtBr). Depletion of the mtDNA resulted in a significantly reduced mitochondrial membrane potential, rate of proliferation in culture, as well as an increased glucose utilization and lactate production. Treatment with the green rooibos (100 μg/mL) stimulated cell growth rates for both the wildtype and mutant cell lines. MtDNA depleted cells showed arrest in the G1 phase (48.8 ± 3.34%) compared to wildtype cells (44.6 ± 1.38%), which was significantly attenuated after treatment with green rooibos for mutant (42.0 ± 0.83%) and wildtype (36.5 ± 5.80%) treated cells. The results obtained for glucose utilization and lactate production, indicated a significant increase in glucose utilization along with a concomitant increase in lactate production after treatment with both green and fermented rooibos for wildtype and mutant cell lines. A significant improvement in mitochondrial membrane potential was also later observed after treatment with green and fermented rooibos on both the wildtype and mutant cell lines. The results obtained indicate that rooibos extracts, particularly the green rooibos, exhibit effects which preserve the functional capacity of preadipocytes exposed to ageing related insults, and indicate that rooibos could cause a metabolic shift in cells redirecting carbon flow away from mitochondrial metabolism, and towards lactate production and consequently, cells become resistant to mitochondrial dysfunction.
- Full Text:
- Date Issued: 2015
Visualising M-learning system usage data
- Authors: Kamuhanda, Dany
- Date: 2015
- Subjects: Database management Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11015 , vital:26876
- Description: Data storage is an important practice for organisations that want to track their progress. The evolution of data storage technologies from manual methods of storing data on paper or in spreadsheets, to the automated methods of using computers to automatically log data into databases or text files has brought an amount of data that is beyond the level of human interpretation and comprehension. One way of addressing this issue of interpreting large amounts of data is data visualisation, which aims to convert abstract data into images that are easy to interpret. However, people often have difficulty in selecting an appropriate visualisation tool and visualisation techniques that can effectively visualise their data. This research proposes the processes that can be followed to effectively visualise data. Data logged from a mobile learning system is visualised as a proof of concept to show how the proposed processes can be followed during data visualisation. These processes are summarised into a model that consists of three main components: the data, the visualisation techniques and the visualisation tool. There are two main contributions in this research: the model to visualise mobile learning usage data and the visualisation of the usage data logged from a mobile learning system. The mobile learning system usage data was visualised to demonstrate how students used the mobile learning system. Visualisation of the usage data helped to convert the data into images (charts and graphs) that were easy to interpret. The evaluation results indicated that the proposed process and resulting visualisation techniques and tool assisted users in effectively and efficiently interpreting large volumes of mobile learning system usage data.
- Full Text:
- Date Issued: 2015
- Authors: Kamuhanda, Dany
- Date: 2015
- Subjects: Database management Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11015 , vital:26876
- Description: Data storage is an important practice for organisations that want to track their progress. The evolution of data storage technologies from manual methods of storing data on paper or in spreadsheets, to the automated methods of using computers to automatically log data into databases or text files has brought an amount of data that is beyond the level of human interpretation and comprehension. One way of addressing this issue of interpreting large amounts of data is data visualisation, which aims to convert abstract data into images that are easy to interpret. However, people often have difficulty in selecting an appropriate visualisation tool and visualisation techniques that can effectively visualise their data. This research proposes the processes that can be followed to effectively visualise data. Data logged from a mobile learning system is visualised as a proof of concept to show how the proposed processes can be followed during data visualisation. These processes are summarised into a model that consists of three main components: the data, the visualisation techniques and the visualisation tool. There are two main contributions in this research: the model to visualise mobile learning usage data and the visualisation of the usage data logged from a mobile learning system. The mobile learning system usage data was visualised to demonstrate how students used the mobile learning system. Visualisation of the usage data helped to convert the data into images (charts and graphs) that were easy to interpret. The evaluation results indicated that the proposed process and resulting visualisation techniques and tool assisted users in effectively and efficiently interpreting large volumes of mobile learning system usage data.
- Full Text:
- Date Issued: 2015
Assessing symptoms of eutrophication in estuaries
- Authors: Lemley, Daniel Alan
- Date: 2015
- Subjects: Estuarine eutrophication -- South Africa , Water quality -- South Africa , Ecological integrity -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3427 , vital:20429
- Description: Water quality and ecological integrity of estuaries reflect activities within the entire upstream catchment. Much emphasis has been placed on the response of estuaries to anthropogenic stressors through the use of monitoring programmes. Key to the success of these programmes is the use of indicators as they transform data into useful information. The ultimate aim of this study was to identify eutrophic symptoms in selected estuaries in the Gouritz Water Management Area (WMA) using a multi-metric classification method. The study sites included the permanently open Duiwenhoks, Goukou, Gouritz, and Kaaimans estuaries, as well as the temporarily open/closed Hartenbos, Klein Brak, Great Brak, Gwaing, and Goukamma estuaries. Initially, the “pressure” associated with all the estuaries in the Gouritz WMA was determined (e.g. total daily nutrient loads and changes in river inflow affecting flushing time) using long-term flow and water quality monitoring data provided by the Department of Water Affairs (DWA). Subsequently, the “state” of the selected estuaries was assessed using a variety of indicators, including: inorganic nutrients (~ N and P), phytoplankton, epiphytes and microphytobenthos. Estuaries with longer flushing time suggested greater vulnerability to eutrophication. For example, the Gwaing (281.11 kg DIN d-1; 78.85 kg DIP d-1) and Hartenbos (38.33 kg DIN d-1; 21.51 kg DIP d-1) estuaries generally received the highest daily inorganic nutrient loads. However, at the time of sampling, the Hartenbos Estuary had a longer flushing time (i.e. weeks) compared to the Gwaing Estuary (i.e. couple of days). Field data confirmed the greater vulnerability to eutrophication associated with longer flushing times, as the indicators measured in the Hartenbos Estuary exceeded all the proposed ‘thresholds’ of a eutrophic system (~ overall ‘Poor’ condition). The Great Brak Estuary (~ overall ‘Fair’ condition) provided an interesting example where eutrophic symptoms were only detected when assessing the microalgal primary producers (i.e. high biomass and low diversity). Furthermore, the need to distinguish between naturally and anthropogenically induced symptoms was highlighted. One such scenario was noted in the Kaaimans Estuary, where its natural hydro-morphological characteristics (i.e. steep banks, low river inflow, and deep/narrow channel) led to the possible exaggeration of its overall eutrophic condition, i.e. received a ‘Fair’ rather than ‘Good’ rating, arising from ‘Poor’ ratings for dissolved oxygen and benthic diatom diversity. Overall, this study demonstrated the importance of adopting a holistic approach when assessing the condition and trophic status of estuaries. Studies such as these allow for the detection of vulnerable and degraded systems, which can provide important information with regards to the identification of management priorities.
- Full Text:
- Date Issued: 2015
- Authors: Lemley, Daniel Alan
- Date: 2015
- Subjects: Estuarine eutrophication -- South Africa , Water quality -- South Africa , Ecological integrity -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3427 , vital:20429
- Description: Water quality and ecological integrity of estuaries reflect activities within the entire upstream catchment. Much emphasis has been placed on the response of estuaries to anthropogenic stressors through the use of monitoring programmes. Key to the success of these programmes is the use of indicators as they transform data into useful information. The ultimate aim of this study was to identify eutrophic symptoms in selected estuaries in the Gouritz Water Management Area (WMA) using a multi-metric classification method. The study sites included the permanently open Duiwenhoks, Goukou, Gouritz, and Kaaimans estuaries, as well as the temporarily open/closed Hartenbos, Klein Brak, Great Brak, Gwaing, and Goukamma estuaries. Initially, the “pressure” associated with all the estuaries in the Gouritz WMA was determined (e.g. total daily nutrient loads and changes in river inflow affecting flushing time) using long-term flow and water quality monitoring data provided by the Department of Water Affairs (DWA). Subsequently, the “state” of the selected estuaries was assessed using a variety of indicators, including: inorganic nutrients (~ N and P), phytoplankton, epiphytes and microphytobenthos. Estuaries with longer flushing time suggested greater vulnerability to eutrophication. For example, the Gwaing (281.11 kg DIN d-1; 78.85 kg DIP d-1) and Hartenbos (38.33 kg DIN d-1; 21.51 kg DIP d-1) estuaries generally received the highest daily inorganic nutrient loads. However, at the time of sampling, the Hartenbos Estuary had a longer flushing time (i.e. weeks) compared to the Gwaing Estuary (i.e. couple of days). Field data confirmed the greater vulnerability to eutrophication associated with longer flushing times, as the indicators measured in the Hartenbos Estuary exceeded all the proposed ‘thresholds’ of a eutrophic system (~ overall ‘Poor’ condition). The Great Brak Estuary (~ overall ‘Fair’ condition) provided an interesting example where eutrophic symptoms were only detected when assessing the microalgal primary producers (i.e. high biomass and low diversity). Furthermore, the need to distinguish between naturally and anthropogenically induced symptoms was highlighted. One such scenario was noted in the Kaaimans Estuary, where its natural hydro-morphological characteristics (i.e. steep banks, low river inflow, and deep/narrow channel) led to the possible exaggeration of its overall eutrophic condition, i.e. received a ‘Fair’ rather than ‘Good’ rating, arising from ‘Poor’ ratings for dissolved oxygen and benthic diatom diversity. Overall, this study demonstrated the importance of adopting a holistic approach when assessing the condition and trophic status of estuaries. Studies such as these allow for the detection of vulnerable and degraded systems, which can provide important information with regards to the identification of management priorities.
- Full Text:
- Date Issued: 2015
Factors affecting the success of reseeding rehabilitation in the semi-arid Karoo, South Africa
- Authors: Matthee, Willem
- Date: 2015
- Subjects: Ecological disturbances -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Environmental degradation -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2889 , vital:20360
- Description: Due to overgrazing, mining and other anthropogenic disturbances, large sections of the Karoo region have been degraded, resulting in areas with low vegetation cover, where erosion rates are high and vegetation is dominated by unpalatable species. These areas have low and unpredictable rainfall, with slow to non-existent autogenic recovery, and this often forces landowners to implement reseeding rehabilitation in an attempt to increase both overall vegetation cover and the relative abundance of palatable plants. Landowners use soil preparation treatments, which include creating micro-catchments, ripping, mulching and brush packing, to supplement land rehabilitation. This study investigated the significance of initial rainfall, mean monthly rainfall, soil preparation techniques, slope, existing vegetation cover, litter, mulch and stone cover in determining the success of reseeding rehabilitation. Rainfall had the most significant influence, where long-lived shrubs established best under low initial rainfall and high mean monthly rainfall, and grasses established best after receiving high initial rainfall. Micro-catchments proved the most successful soil preparation technique for the establishment of long-lived shrubs, while ripping and mulching impacted negatively on grass establishment. A combination of mulch and micro-catchments aided Osteospermum sinuatum establishment in soils where soil shrinkage cracks occurred. Temperature influenced seed germination and drought tolerance of Lessertia annularis, Fingerhuthia africana and O. sinuatum, with higher germination success of O. sinuatum under temperatures simulating summer, and of F. africana under temperatures simulating winter. L. annularis germination had a faster growth rate and higher survival when germinated under autumn/spring temperatures. Landowners are advised to sow seeds of more than one species during rehabilitation, to include micro-catchments as soil preparation treatment, and to sow seeds during a time when rainfall is predicted to be high.
- Full Text:
- Date Issued: 2015
- Authors: Matthee, Willem
- Date: 2015
- Subjects: Ecological disturbances -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Environmental degradation -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2889 , vital:20360
- Description: Due to overgrazing, mining and other anthropogenic disturbances, large sections of the Karoo region have been degraded, resulting in areas with low vegetation cover, where erosion rates are high and vegetation is dominated by unpalatable species. These areas have low and unpredictable rainfall, with slow to non-existent autogenic recovery, and this often forces landowners to implement reseeding rehabilitation in an attempt to increase both overall vegetation cover and the relative abundance of palatable plants. Landowners use soil preparation treatments, which include creating micro-catchments, ripping, mulching and brush packing, to supplement land rehabilitation. This study investigated the significance of initial rainfall, mean monthly rainfall, soil preparation techniques, slope, existing vegetation cover, litter, mulch and stone cover in determining the success of reseeding rehabilitation. Rainfall had the most significant influence, where long-lived shrubs established best under low initial rainfall and high mean monthly rainfall, and grasses established best after receiving high initial rainfall. Micro-catchments proved the most successful soil preparation technique for the establishment of long-lived shrubs, while ripping and mulching impacted negatively on grass establishment. A combination of mulch and micro-catchments aided Osteospermum sinuatum establishment in soils where soil shrinkage cracks occurred. Temperature influenced seed germination and drought tolerance of Lessertia annularis, Fingerhuthia africana and O. sinuatum, with higher germination success of O. sinuatum under temperatures simulating summer, and of F. africana under temperatures simulating winter. L. annularis germination had a faster growth rate and higher survival when germinated under autumn/spring temperatures. Landowners are advised to sow seeds of more than one species during rehabilitation, to include micro-catchments as soil preparation treatment, and to sow seeds during a time when rainfall is predicted to be high.
- Full Text:
- Date Issued: 2015
Defect-related photoluminescence of zinc oxide nanorods
- Authors: Mbulanga, Crispin Munyelele
- Date: 2015
- Subjects: Photoluminescence Zinc oxide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/10318 , vital:26652
- Description: In this dissertation, Zinc oxide (ZnO) nanorods grown by a two-step chemical bath deposition method on Si substrate is characterized. Research was conducted on ZnO nanorods for the understanding of their optical properties at room temperature (RT), with the emphasis on the visible luminescence. To this end, controlled thermal treatments of as-grown ZnO nanorods were conducted under different conditions, such as annealing time and environment, at atmospheric pressure. Results related to the following studies are reported: an investigation of the structure of ZnO nanorods, an analysis of the chemical composition of the surface, an investigation of the surface stoichiometry of the rods, and a study of defect-related photoluminescence of ZnO nanorods upon thermal treatment in different ambients.To achieve this, the samples were investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and room temperature (RT) photoluminescence Spectroscopy (PL). As-grown ZnO nanorods exhibit a hexagonal shape and have the wurtzite structure; they have, respectively, an average length and diameter of ~900 nm and ~50 nm, and most of the rods are perpendicular to the substrate. The main extrinsic species found in as-grown nanostructures are C, H, F, S, and Cl. ToF-SIMS and XPS confirmed the presence of H related-defects, and the oxygen 1 S XPS peak at 531.5 eV is therefore assigned to oxygen bound to H-related defects. Based on stoichiometry studies, it is found that the near surface regions of as-grown ZnO nanorods (2 to 10 monolayers) are rich in Zn. The RT luminescence of as-grown ZnO nanorods exhibits a near band edge emission centered at ~379.5 nm and deep level emission extending from ~450 nm to ~850 nm. When these nanorods are thermally treated at high temperatures (>850 oC), it is found that even though their crystalline quality is preserved, their morphology is significantly affected, regardless of annealing ambient. Furthermore, in the near surface regions of annealed ZnO nanorods it is found that the Zn/O stoichiometric ratios deviate from unity. Specifically, oxygen vacancies form within the first 100 nm from the sample surface. Further from the surface, the material is deficient in Zn. It is deduced from XPS and AES that the ambient affects the activation rate of intrinsic defects. Furthermore, the only extrinsic defects that are affected by thermal treatment are found to be H-related defects. At high annealing temperatures (300 oC to ~700 oC), H-related defects are removed, and this removal process is found to affect significantly the RT luminescence properties of ZnO nanorods. Specifically, hydrogen passivates vacancy-related defects, depending on the thermal treatment. PL spectroscopy is used to follow this passivation effect as a function of annealing temperature, which causes an initial quenching followed by an enhancement of the green and the red luminescence, regardless of the ambient. Finally, the green luminescence that arises following annealing above ~800 oC is assigned to Zn vacancy-related defects, while the red luminescence that dominates the visible band of ZnO nanorods upon annealing between 400 oC and 600 oC is suggested to be due to oxygen vacancy-related defects.
- Full Text:
- Date Issued: 2015
- Authors: Mbulanga, Crispin Munyelele
- Date: 2015
- Subjects: Photoluminescence Zinc oxide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/10318 , vital:26652
- Description: In this dissertation, Zinc oxide (ZnO) nanorods grown by a two-step chemical bath deposition method on Si substrate is characterized. Research was conducted on ZnO nanorods for the understanding of their optical properties at room temperature (RT), with the emphasis on the visible luminescence. To this end, controlled thermal treatments of as-grown ZnO nanorods were conducted under different conditions, such as annealing time and environment, at atmospheric pressure. Results related to the following studies are reported: an investigation of the structure of ZnO nanorods, an analysis of the chemical composition of the surface, an investigation of the surface stoichiometry of the rods, and a study of defect-related photoluminescence of ZnO nanorods upon thermal treatment in different ambients.To achieve this, the samples were investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and room temperature (RT) photoluminescence Spectroscopy (PL). As-grown ZnO nanorods exhibit a hexagonal shape and have the wurtzite structure; they have, respectively, an average length and diameter of ~900 nm and ~50 nm, and most of the rods are perpendicular to the substrate. The main extrinsic species found in as-grown nanostructures are C, H, F, S, and Cl. ToF-SIMS and XPS confirmed the presence of H related-defects, and the oxygen 1 S XPS peak at 531.5 eV is therefore assigned to oxygen bound to H-related defects. Based on stoichiometry studies, it is found that the near surface regions of as-grown ZnO nanorods (2 to 10 monolayers) are rich in Zn. The RT luminescence of as-grown ZnO nanorods exhibits a near band edge emission centered at ~379.5 nm and deep level emission extending from ~450 nm to ~850 nm. When these nanorods are thermally treated at high temperatures (>850 oC), it is found that even though their crystalline quality is preserved, their morphology is significantly affected, regardless of annealing ambient. Furthermore, in the near surface regions of annealed ZnO nanorods it is found that the Zn/O stoichiometric ratios deviate from unity. Specifically, oxygen vacancies form within the first 100 nm from the sample surface. Further from the surface, the material is deficient in Zn. It is deduced from XPS and AES that the ambient affects the activation rate of intrinsic defects. Furthermore, the only extrinsic defects that are affected by thermal treatment are found to be H-related defects. At high annealing temperatures (300 oC to ~700 oC), H-related defects are removed, and this removal process is found to affect significantly the RT luminescence properties of ZnO nanorods. Specifically, hydrogen passivates vacancy-related defects, depending on the thermal treatment. PL spectroscopy is used to follow this passivation effect as a function of annealing temperature, which causes an initial quenching followed by an enhancement of the green and the red luminescence, regardless of the ambient. Finally, the green luminescence that arises following annealing above ~800 oC is assigned to Zn vacancy-related defects, while the red luminescence that dominates the visible band of ZnO nanorods upon annealing between 400 oC and 600 oC is suggested to be due to oxygen vacancy-related defects.
- Full Text:
- Date Issued: 2015