The feeding ecology of extralimital Nyala (Tragelaphus Angasii) in the Arid Mosaic thicket of the Southern Cape
- Authors: Pienaar, Ryno Cuyler
- Date: 2013
- Subjects: Nyala -- Feeding and feeds , Nyala -- Nutrition -- South Africa -- Southern Cape , Nyala -- Ecology -- South Africa -- Southern Cape , Animal-plant relationships -- South Africa -- Southern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10757 , http://hdl.handle.net/10948/d1021012
- Description: The nyala on Buffelsdrift Private Game Reserve were found to be mainly browsers and made little use of grass during the study period. Browse contributed 87.8 percent to the annual diet, while grass contributed 12.2 percent. Only six species formed > 5 percent of the annual diet. Of these six only three species formed > 10 percent. They are the shrubs Acacia karroo, Pappea capensis and Grewia robusta. These were followed by the shrub Portulacaria afra, the dwarf shrub Zygophyllum lichtensteinianum and the grass Cynodon dactylon all contributing between 5 - 10 percent. There were definite seasonal dietary shifts with preference to different plant species. The shift takes place between the wet seasons (winter and spring) and the dry season (summer). Herbaceous species such as Cynodon dactylon and Erharta calycina were favoured in the winter/wet season. Shrubs such as P. capensis, P. afra and dwarf shrubs such as Limeum aethiopicum and Z. lichtensteinianum were favoured during the spring/wet and summer/dry seasons. Nyala habitat use in BPGR differed significantly from expected use when taking the relative area of habitats into consideration. However nyala did not display signififcantly different habitat preferences between seasons. Male and female nyala displayed differences in foraging behaviour at the plant form, plant species and habitat scale. Males preferred a greater proportion of shrubs and females a greater proportion of dwarf shrubs. Males preferred the shrubs Pappea capensis and Portulacaria afra the most and females preferred the dwarf shrubs Limeum aethiopicum and Zygophyllum lichtensteinianum the most. Plant species site availability varied significantly between the sexes, indicating that males and females selected different feeding paths. The difference in their feeding strategy appears to be related to the selection of plants that best satisfy the nutrient requirements of each sex. These findings are in agreement with the results from earlier studies on nyala sexual dimorphism. At the habitat scale females selected more for open dwarf shrubland and males more for densely vegetated habitats. This appears to be as a result of males attempting to maximize their foraging opportunities by selecting areas that offer food in greater quantities. Nyala in BPGR appear to co-exist with kudu and eland through spatial resource partitioning. This is suggested to be due to the influence of body size-gut size relationships on forage selectivity.
- Full Text:
- Date Issued: 2013
- Authors: Pienaar, Ryno Cuyler
- Date: 2013
- Subjects: Nyala -- Feeding and feeds , Nyala -- Nutrition -- South Africa -- Southern Cape , Nyala -- Ecology -- South Africa -- Southern Cape , Animal-plant relationships -- South Africa -- Southern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10757 , http://hdl.handle.net/10948/d1021012
- Description: The nyala on Buffelsdrift Private Game Reserve were found to be mainly browsers and made little use of grass during the study period. Browse contributed 87.8 percent to the annual diet, while grass contributed 12.2 percent. Only six species formed > 5 percent of the annual diet. Of these six only three species formed > 10 percent. They are the shrubs Acacia karroo, Pappea capensis and Grewia robusta. These were followed by the shrub Portulacaria afra, the dwarf shrub Zygophyllum lichtensteinianum and the grass Cynodon dactylon all contributing between 5 - 10 percent. There were definite seasonal dietary shifts with preference to different plant species. The shift takes place between the wet seasons (winter and spring) and the dry season (summer). Herbaceous species such as Cynodon dactylon and Erharta calycina were favoured in the winter/wet season. Shrubs such as P. capensis, P. afra and dwarf shrubs such as Limeum aethiopicum and Z. lichtensteinianum were favoured during the spring/wet and summer/dry seasons. Nyala habitat use in BPGR differed significantly from expected use when taking the relative area of habitats into consideration. However nyala did not display signififcantly different habitat preferences between seasons. Male and female nyala displayed differences in foraging behaviour at the plant form, plant species and habitat scale. Males preferred a greater proportion of shrubs and females a greater proportion of dwarf shrubs. Males preferred the shrubs Pappea capensis and Portulacaria afra the most and females preferred the dwarf shrubs Limeum aethiopicum and Zygophyllum lichtensteinianum the most. Plant species site availability varied significantly between the sexes, indicating that males and females selected different feeding paths. The difference in their feeding strategy appears to be related to the selection of plants that best satisfy the nutrient requirements of each sex. These findings are in agreement with the results from earlier studies on nyala sexual dimorphism. At the habitat scale females selected more for open dwarf shrubland and males more for densely vegetated habitats. This appears to be as a result of males attempting to maximize their foraging opportunities by selecting areas that offer food in greater quantities. Nyala in BPGR appear to co-exist with kudu and eland through spatial resource partitioning. This is suggested to be due to the influence of body size-gut size relationships on forage selectivity.
- Full Text:
- Date Issued: 2013
The fitting of statistical distributions to wind data in coastal areas of South Africa
- Authors: Moodley, Kirshnee
- Date: 2013
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10584
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2013
- Authors: Moodley, Kirshnee
- Date: 2013
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10584
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2013
The fitting of statistical distributions to wind data in coastal areas of South Africa
- Authors: Moodley, Kirshnee
- Date: 2012
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10579
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2012
- Authors: Moodley, Kirshnee
- Date: 2012
- Subjects: Winds -- South Africa -- Port Elizabeth -- Speed -- Measurement , Wind power -- South Africa -- Port Elizabeth , Winds -- South Africa -- Port Elizabeth -- Measurement -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10579
- Description: Coastal South African cities like Port Elizabeth are said to have a strong potential for wind energy. This study aims to model wind data in order to be able assess the power potential belonging to a given site. The main challenge in modelling wind direction data is that it is categorized as circular data and therefore requires special techniques for handling that are different from usual statistical samples. Statistical tools such as descriptive measures and distribution fitting, were re-invented for directional data by researchers in this field. The von Mises distribution is a predominant distribution in circular statistics and is commonly used to describe wind directions. In this study, the circular principles described by previous researchers were developed by using the statistical software, Mathematica. Graphical methods to present the wind data were developed to give an overview of the behaviour of the winds in any given area. Data collected at Coega, an area near Port Elizabeth, South Africa, was used to illustrate the models which were established in this study. Circular distributions were fit to the directional data in order to make appropriate conclusions about the prevailing wind directions in this area.
- Full Text:
- Date Issued: 2012
The foraging ecology of female Cape fur seals (Arctocephalus pusillus pusillus) in South Africa
- Botha, Jonathan Aubrey, Kirkman, Stephen, Lombard, Amanda
- Authors: Botha, Jonathan Aubrey , Kirkman, Stephen , Lombard, Amanda
- Date: 2022-04
- Subjects: Seals (Animals)--Habitat—Conservation , Marine ecology—South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55965 , vital:54559
- Description: The marine environment is spatially and temporally dynamic and many marine ecosystems are experiencing impacts of broad-scale climate change. Within these ecosystems, marine predators play a crucial role in ecosystem function through their top-down influences on prey populations. These predators may also respond to bottom-up influences and changes at lower trophic levels. A thorough understanding of marine predator foraging ecology is thus important to improve our understanding of ecosystem function, inform conservation and management measures, and to predict the response of predators to future environmental change. The Cape fur seal (Arctocephalus pusillus pusillus) comprises a major proportion of the southern African marine predator biomass. However, little is known about the foraging distribution and behaviour of the species, despite its obvious importance within the ecosystem and increasing concerns regarding seal-fisheries conflict. Using a variety of technologies, including, GPS and satellite-linked tags, dive behaviour recorders, accelerometers and stable isotope analysis, this thesis investigated the foraging ecology of female Cape fur seals breeding on the coast of South Africa. First, to identify important foraging areas and assess the influence of geographic, temporal and environmental factors on these areas, lactating females from three breeding colonies were fitted with GPS or Argos-linked tracking devices, while individuals from two of these colonies were also fitted with dive behaviour recorders. Results revealed geographic differences in the foraging distributions and ranges of individuals between breeding colonies, which likely reflects a combined influence of ecological setting and density dependant competition. In addition, dive behaviour recorders revealed the occurrence of benthic foraging at both sites where they were deployed, and the dominance of this strategy in some individuals. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Botha, Jonathan Aubrey , Kirkman, Stephen , Lombard, Amanda
- Date: 2022-04
- Subjects: Seals (Animals)--Habitat—Conservation , Marine ecology—South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55965 , vital:54559
- Description: The marine environment is spatially and temporally dynamic and many marine ecosystems are experiencing impacts of broad-scale climate change. Within these ecosystems, marine predators play a crucial role in ecosystem function through their top-down influences on prey populations. These predators may also respond to bottom-up influences and changes at lower trophic levels. A thorough understanding of marine predator foraging ecology is thus important to improve our understanding of ecosystem function, inform conservation and management measures, and to predict the response of predators to future environmental change. The Cape fur seal (Arctocephalus pusillus pusillus) comprises a major proportion of the southern African marine predator biomass. However, little is known about the foraging distribution and behaviour of the species, despite its obvious importance within the ecosystem and increasing concerns regarding seal-fisheries conflict. Using a variety of technologies, including, GPS and satellite-linked tags, dive behaviour recorders, accelerometers and stable isotope analysis, this thesis investigated the foraging ecology of female Cape fur seals breeding on the coast of South Africa. First, to identify important foraging areas and assess the influence of geographic, temporal and environmental factors on these areas, lactating females from three breeding colonies were fitted with GPS or Argos-linked tracking devices, while individuals from two of these colonies were also fitted with dive behaviour recorders. Results revealed geographic differences in the foraging distributions and ranges of individuals between breeding colonies, which likely reflects a combined influence of ecological setting and density dependant competition. In addition, dive behaviour recorders revealed the occurrence of benthic foraging at both sites where they were deployed, and the dominance of this strategy in some individuals. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
The foraging ecology of Wedge-tailed Shearwaters (Ardenna Pacifica) in the tropical Western Indian Ocean
- Authors: Keys, Danielle Zuanda
- Date: 2018
- Subjects: Birds of prey -- Behavior -- South Africa -- Western Cape , Animal behavior , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31251 , vital:31348
- Description: The distribution and abundance of prey largely influences how marine predators forage. Thus, understanding how marine predators respond to such changes becomes imperative when making decisions in marine spatial planning, especially in light of global climate change. Tropical marine systems are known for their relatively low productivity and high unpredictability of prey resources. Compared to higher latitudes, very few studies on seabirds have been implemented in the tropics. The Wedge-tailed Shearwater Ardenna pacifica is an Indo-Pacific tropical seabird with a wide distributional range. However, like many other seabirds, its population numbers are currently declining. Very little is known about the at-sea distribution of Wedge-tailed Shearwaters in the tropical western Indian Ocean. Therefore, this thesis investigates the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean by tracking the fine scale movements of individuals at sea. This study was conducted in two different oceanic environments, namely D’Arros Island and Fouquet Island, St Joseph Atoll in the Amirantes Group in Seychelles archipelago as well as Réunion Island in the Mascarene archipelago during the Wedge-tailed Shearwaters breeding seasons. Here I aimed to investigate the foraging distribution of Wedge-tailed Shearwaters on Réunion Island in relation to different stages of the breeding period. I also compared the foraging ecology of all three populations, subjected to different abiotic and biotic factors. Furthermore, I investigated foraging site fidelity in individuals and repeatability within individual flight characteristics. To my knowledge, this is the first study to comprehensively investigate the foraging ecology of Wedge-tailed Shearwaters using global positioning system (GPS) loggers. This study demonstrated that the Wedge-tailed Shearwaters implement flexible foraging strategies throughout different stages of their breeding period and between different islands. In Réunion, during the shearwater breeding season, sexual segregation was prominent during early chick rearing and both sexes implemented dual foraging. As suggested by previous studies, it is likely that long trips were implemented for self-maintenance, whereas multiple short trips were implemented to meet the high energetic demands of the chicks. Several important foraging areas were identified for these Wedge-tailed Shearwaters. During incubation, shearwaters from Réunion faithfully foraged towards the south east of Madagascar near the East Madagascar Current and flew over large areas of the Mascarene Basin. During chick rearing, shearwaters significantly constricted their range closer to the colony and exploited deep waters on the south-west of Réunion Island. Shearwaters concentrated near oceanographic features such as the Pérouse Seamount (which is a known area of high productivity) as well as the Bourdonnais Ridge. There was no clear evidence for spatial or sexual segregation between individuals from the two study colonies in Seychelles during incubation and birds utilized a broader foraging range than birds from Réunion. This is likely to be the result of a large annual phytoplankton bloom which coincides with the shearwater breeding season in Seychelles, providing many foraging opportunities within the Seychelles Basin. The shearwaters from Seychelles exploited the Amirante Basin, East Somali Basin, and parts of the Seychelles archipelago. Shearwaters from D’Arros flew further east and foraged in the Mascarene Basin. Shearwaters from all populations foraged over deep, relatively unproductive waters with relatively high sea surface temperatures which are similar oceanographic features favoured by tuna. Foraging plasticity between individuals from different colonies was observed with varying flight bearings, flight durations and the maximum distances travelled from their respective colonies. Shearwaters displayed dissimilar levels of site fidelity, where shearwaters from Réunion faithfully foraged towards south east Madagascar, while shearwaters from Seychelles foraged over a wide range over the Seychelles Basin. Foraging effort for shearwaters from Fouquet was lower than shearwaters from Reunion and they spent less time at sea and foraged closer to their colony. These difference in behaviour responses between colonies may be advantageous to shearwaters, indicating that they may be able to respond to some level of environmental variability resulting from climate change and anthropogenic pressures. Lastly, during chick rearing, though shearwaters showed low levels of repeatability in flight characterising, foraging site fidelity was high amongst some of the individuals. Here we see that shearwaters continuously rely on permanent features, like seamounts and possibly fish aggregating devices, which are known to attract high abundances of tuna. Shearwaters may to some extent be relying on memory to find prey in a seemingly unpredictable environment. This study has helped us gain valuable insight about the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean. Together with similar studies determining the at-sea behaviour of seabirds, better informed recommendations can be made to marine spatial planners as to where much needed pelagic marine protection should be implemented to preserve marine life in this fascinating part of the global ocean.
- Full Text:
- Date Issued: 2018
- Authors: Keys, Danielle Zuanda
- Date: 2018
- Subjects: Birds of prey -- Behavior -- South Africa -- Western Cape , Animal behavior , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31251 , vital:31348
- Description: The distribution and abundance of prey largely influences how marine predators forage. Thus, understanding how marine predators respond to such changes becomes imperative when making decisions in marine spatial planning, especially in light of global climate change. Tropical marine systems are known for their relatively low productivity and high unpredictability of prey resources. Compared to higher latitudes, very few studies on seabirds have been implemented in the tropics. The Wedge-tailed Shearwater Ardenna pacifica is an Indo-Pacific tropical seabird with a wide distributional range. However, like many other seabirds, its population numbers are currently declining. Very little is known about the at-sea distribution of Wedge-tailed Shearwaters in the tropical western Indian Ocean. Therefore, this thesis investigates the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean by tracking the fine scale movements of individuals at sea. This study was conducted in two different oceanic environments, namely D’Arros Island and Fouquet Island, St Joseph Atoll in the Amirantes Group in Seychelles archipelago as well as Réunion Island in the Mascarene archipelago during the Wedge-tailed Shearwaters breeding seasons. Here I aimed to investigate the foraging distribution of Wedge-tailed Shearwaters on Réunion Island in relation to different stages of the breeding period. I also compared the foraging ecology of all three populations, subjected to different abiotic and biotic factors. Furthermore, I investigated foraging site fidelity in individuals and repeatability within individual flight characteristics. To my knowledge, this is the first study to comprehensively investigate the foraging ecology of Wedge-tailed Shearwaters using global positioning system (GPS) loggers. This study demonstrated that the Wedge-tailed Shearwaters implement flexible foraging strategies throughout different stages of their breeding period and between different islands. In Réunion, during the shearwater breeding season, sexual segregation was prominent during early chick rearing and both sexes implemented dual foraging. As suggested by previous studies, it is likely that long trips were implemented for self-maintenance, whereas multiple short trips were implemented to meet the high energetic demands of the chicks. Several important foraging areas were identified for these Wedge-tailed Shearwaters. During incubation, shearwaters from Réunion faithfully foraged towards the south east of Madagascar near the East Madagascar Current and flew over large areas of the Mascarene Basin. During chick rearing, shearwaters significantly constricted their range closer to the colony and exploited deep waters on the south-west of Réunion Island. Shearwaters concentrated near oceanographic features such as the Pérouse Seamount (which is a known area of high productivity) as well as the Bourdonnais Ridge. There was no clear evidence for spatial or sexual segregation between individuals from the two study colonies in Seychelles during incubation and birds utilized a broader foraging range than birds from Réunion. This is likely to be the result of a large annual phytoplankton bloom which coincides with the shearwater breeding season in Seychelles, providing many foraging opportunities within the Seychelles Basin. The shearwaters from Seychelles exploited the Amirante Basin, East Somali Basin, and parts of the Seychelles archipelago. Shearwaters from D’Arros flew further east and foraged in the Mascarene Basin. Shearwaters from all populations foraged over deep, relatively unproductive waters with relatively high sea surface temperatures which are similar oceanographic features favoured by tuna. Foraging plasticity between individuals from different colonies was observed with varying flight bearings, flight durations and the maximum distances travelled from their respective colonies. Shearwaters displayed dissimilar levels of site fidelity, where shearwaters from Réunion faithfully foraged towards south east Madagascar, while shearwaters from Seychelles foraged over a wide range over the Seychelles Basin. Foraging effort for shearwaters from Fouquet was lower than shearwaters from Reunion and they spent less time at sea and foraged closer to their colony. These difference in behaviour responses between colonies may be advantageous to shearwaters, indicating that they may be able to respond to some level of environmental variability resulting from climate change and anthropogenic pressures. Lastly, during chick rearing, though shearwaters showed low levels of repeatability in flight characterising, foraging site fidelity was high amongst some of the individuals. Here we see that shearwaters continuously rely on permanent features, like seamounts and possibly fish aggregating devices, which are known to attract high abundances of tuna. Shearwaters may to some extent be relying on memory to find prey in a seemingly unpredictable environment. This study has helped us gain valuable insight about the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean. Together with similar studies determining the at-sea behaviour of seabirds, better informed recommendations can be made to marine spatial planners as to where much needed pelagic marine protection should be implemented to preserve marine life in this fascinating part of the global ocean.
- Full Text:
- Date Issued: 2018
The further development, optimisation and application of a Yarn Dismantler
- Authors: Fassihi, Ali Akbar
- Date: 2012
- Subjects: Textile industry , Cotton yarn industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10452 , http://hdl.handle.net/10948/d1016066
- Description: The fibre properties of cotton, which vary widely according to genetic and environmental conditions, determine its price and textile processing performance and product quality. It is therefore hardly surprising that cotton fibre properties are routinely measured for trading and quality control purposes, with a great deal of research having been, and still being, devoted towards developing instruments which enable the various fibre properties to be measured rapidly and accurately. In many cases, it is also necessary to be able to measure properties of cotton fibres when they have already been converted into yarn and fabric form. To do so, the yarn has to be dismantled into its component fibres, preferably without significantly changing the fibre properties. This could only be done by manually untwisting the yarn and carefully extracting the fibres from the untwisted yarn, care being taken not to break or lose any fibres in the process. This is a time consuming, laborious and labour intensive process. In view of this, a „yarn dismantler‟ which could automatically, cost effectively and within acceptable time frames, dismantle a cotton yarn into its constituent fibres, without undue damage or changes to the fibres, was developed and patented. This thesis reports the results of research undertaken to further develop, evaluate and optimize the yarn dismantler into the final prototype, as well as those relating to its practical applications, including tracking changes in fibre properties during miniature and pilot scale processing, up to, and including the yarn stage. Initial research undertaken on the original bench and first prototype models indicated that, although they produced very promising results, certain improvements and modifications were necessary, if the dismantler was to perform in an efficient and operator friendly manner at the required speeds. These included changes in the axial position of the untwisting spindle and the perforated screen of the suction drum, increasing the air suction at the perforated drum, installing a new motor for the untwisting spindle drive, separating the drives to the different parts of the unit in order to control them independently, integrating a more effective steaming unit into the unit etc. It was found that the dismantling rate had to be set to equal about 95 percent of the original twist in the yarn, and that steaming of the dismantled (untwisted) yarn on the perforated drum was necessary in order to eliminate any twist liveliness (residual torque) in the dismantled yarn, and enable it to be handled and tested on the AFIS instrument. When the final prototype Yarn Dismantler was produced, incorporating all the above mentioned improvements, it functioned very well at dismantling speeds of at least 2m/min, enabling the length of yarn required for subsequent AFIS testing to be dismantled within an acceptable time of less than 10 minutes, with excellent reproducibility and repeatability of results, also under commercial conditions. It was found that the AFIS measured length characteristics of fibres from the instrument dismantled yarns compared very well with those of fibres from manually dismantled yarns, differences in fibre length generally being less than 1mm, and it was concluded from these and other evaluation tests, that the yarn dismantler produced fibres without any significant fibre breakage. Some limited tests, carried out on commercially produced carded and combed yarns, indicated that short fibre content and dust and trash levels, as measured by the AFIS on fibres from dismantled yarn, together with the corresponding Uster Statistics, could enable a carded cotton yarn to be distinguished from a combed cotton yarn. Statistical analysis of fibre test results obtained at the different stages during miniature and pilot plant scale processing of various cottons, clearly showed that very significant changes in fibre properties could be caused by certain of the processes. For example, significant fibre breakage occurred during the drafting on the spinning frame, prior to twist insertion. The thesis provides detailed results of changes in various fibre properties, including length, short fibre content, maturity, immature fibre content, seed coat neps and fibrous neps, which occurred from the lint to the final yarn, as well as on the relationship between the properties of the fibres from the dismantled yarn and those from the lint. The results obtained have clearly demonstrated the practical value of the yarn dismantler in enabling yarns to be automatically dismantled into their constituent fibres, which can then be tested by an instrument, such as the AFIS, and the test results related to those of the original lint fibres, thereby opening up many fields of research and practical applications, some of which are captured under „Recommended Further Work‟.
- Full Text:
- Date Issued: 2012
- Authors: Fassihi, Ali Akbar
- Date: 2012
- Subjects: Textile industry , Cotton yarn industry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10452 , http://hdl.handle.net/10948/d1016066
- Description: The fibre properties of cotton, which vary widely according to genetic and environmental conditions, determine its price and textile processing performance and product quality. It is therefore hardly surprising that cotton fibre properties are routinely measured for trading and quality control purposes, with a great deal of research having been, and still being, devoted towards developing instruments which enable the various fibre properties to be measured rapidly and accurately. In many cases, it is also necessary to be able to measure properties of cotton fibres when they have already been converted into yarn and fabric form. To do so, the yarn has to be dismantled into its component fibres, preferably without significantly changing the fibre properties. This could only be done by manually untwisting the yarn and carefully extracting the fibres from the untwisted yarn, care being taken not to break or lose any fibres in the process. This is a time consuming, laborious and labour intensive process. In view of this, a „yarn dismantler‟ which could automatically, cost effectively and within acceptable time frames, dismantle a cotton yarn into its constituent fibres, without undue damage or changes to the fibres, was developed and patented. This thesis reports the results of research undertaken to further develop, evaluate and optimize the yarn dismantler into the final prototype, as well as those relating to its practical applications, including tracking changes in fibre properties during miniature and pilot scale processing, up to, and including the yarn stage. Initial research undertaken on the original bench and first prototype models indicated that, although they produced very promising results, certain improvements and modifications were necessary, if the dismantler was to perform in an efficient and operator friendly manner at the required speeds. These included changes in the axial position of the untwisting spindle and the perforated screen of the suction drum, increasing the air suction at the perforated drum, installing a new motor for the untwisting spindle drive, separating the drives to the different parts of the unit in order to control them independently, integrating a more effective steaming unit into the unit etc. It was found that the dismantling rate had to be set to equal about 95 percent of the original twist in the yarn, and that steaming of the dismantled (untwisted) yarn on the perforated drum was necessary in order to eliminate any twist liveliness (residual torque) in the dismantled yarn, and enable it to be handled and tested on the AFIS instrument. When the final prototype Yarn Dismantler was produced, incorporating all the above mentioned improvements, it functioned very well at dismantling speeds of at least 2m/min, enabling the length of yarn required for subsequent AFIS testing to be dismantled within an acceptable time of less than 10 minutes, with excellent reproducibility and repeatability of results, also under commercial conditions. It was found that the AFIS measured length characteristics of fibres from the instrument dismantled yarns compared very well with those of fibres from manually dismantled yarns, differences in fibre length generally being less than 1mm, and it was concluded from these and other evaluation tests, that the yarn dismantler produced fibres without any significant fibre breakage. Some limited tests, carried out on commercially produced carded and combed yarns, indicated that short fibre content and dust and trash levels, as measured by the AFIS on fibres from dismantled yarn, together with the corresponding Uster Statistics, could enable a carded cotton yarn to be distinguished from a combed cotton yarn. Statistical analysis of fibre test results obtained at the different stages during miniature and pilot plant scale processing of various cottons, clearly showed that very significant changes in fibre properties could be caused by certain of the processes. For example, significant fibre breakage occurred during the drafting on the spinning frame, prior to twist insertion. The thesis provides detailed results of changes in various fibre properties, including length, short fibre content, maturity, immature fibre content, seed coat neps and fibrous neps, which occurred from the lint to the final yarn, as well as on the relationship between the properties of the fibres from the dismantled yarn and those from the lint. The results obtained have clearly demonstrated the practical value of the yarn dismantler in enabling yarns to be automatically dismantled into their constituent fibres, which can then be tested by an instrument, such as the AFIS, and the test results related to those of the original lint fibres, thereby opening up many fields of research and practical applications, some of which are captured under „Recommended Further Work‟.
- Full Text:
- Date Issued: 2012
The GARCH-EVT-Copula model and simulation in scenario-based asset allocation
- McEwan, Peter Gareth Fredric
- Authors: McEwan, Peter Gareth Fredric
- Date: 2016
- Subjects: Extreme value theory GARCH model
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11732 , vital:26961
- Description: Financial market integration, in particular, portfolio allocations from advanced economies to South African markets, continues to strengthen volatility linkages and quicken volatility transmissions between participating markets. Largely as a result, South African portfolios are net recipients of returns and volatility shocks emanating from major world markets. In light of these, and other, sources of risk, this dissertation proposes a methodology to improve risk management systems in funds by building a contemporary asset allocation framework that offers practitioners an opportunity to explicitly model combinations of hypothesised global risks and the effects on their investments. The framework models portfolio return variables and their key risk driver variables separately and then joins them to model their combined dependence structure. The separate modelling of univariate and multivariate (MV) components admits the benefit of capturing the data generating processes with improved accuracy. Univariate variables were modelled using ARMA-GARCH-family structures paired with a variety of skewed and leptokurtic conditional distributions. Model residuals were fit using the Peaks-over-Threshold method from Extreme Value Theory for the tails and a non-parametric, kernel density for the interior, forming a completed semi-parametric distribution (SPD) for each variable. Asset and risk factor returns were then combined and their dependence structure jointly modelled with a MV Student t copula. Finally, the SPD margins and Student t copula were used to construct a MV meta t distribution. Monte Carlo simulations were generated from the fitted MV meta t distribution on which an out-of-sample test was conducted. The 2014-to-2015 horizon served to proxy as an out-of-sample, forward-looking scenario for a set of key risk factors against which a hypothetical, diversified portfolio was optimised. Traditional mean-variance and contemporary mean-CVaR optimisation techniques were used and their results compared. As an addendum, performance over the in-sample 2008 financial crisis was reported. The final Objective (7) addressed management and conservation strategies for the NMBM. The NMBM wetland database that was produced during this research is currently being used by the Municipality and will be added to the latest National Wetland Map. From the database, and tools developed in this research, approximately 90 wetlands have been identified as being highly vulnerable due to anthropogenic and environmental factors (Chapter 6) and should be earmarked as key conservation priority areas. Based on field experience and data collected, this study has also made conservation and rehabilitation recommendations for eight locations. Recommendations are also provided for six more wetland systems (or regions) that should be prioritised for further research, as these systems lack fundamental information on where the threat of anthropogenic activities affecting them is greatest. This study has made a significant contribution to understanding the underlying geomorphological processes in depressions, seeps and wetland flats. The desktop mapping component of this study illustrated the dominance of wetlands in the wetter parts of the Municipality. Perched wetland systems were identified in the field, on shallow bedrock, calcrete or clay. The prevalence of these perches in depressions, seeps and wetland flats also highlighted the importance of rainfall in driving wetland formation, by allowing water to pool on these perches, in the NMBM. These perches are likely to be a key factor in the high number of small, ephemeral wetlands that were observed in the study area, compared to other semi-arid regions. Therefore, this research highlights the value of multi-faceted and multi-scalar wetland research and how similar approaches should be used in future research methods has been highlighted. The approach used, along with the tools/methods developed in this study have facilitated the establishment of priority areas for conservation and management within the NMBM. Furthermore, the research approach has revealed emergent wetland properties that are only apparent when looking at different spatial scales. This research has highlighted the complex biological and geomorphological interactions between wetlands that operate over various spatial and temporal scales. As such, wetland management should occur across a wetland complex, rather than individual sites, to account for these multi-scalar influences.
- Full Text:
- Date Issued: 2016
- Authors: McEwan, Peter Gareth Fredric
- Date: 2016
- Subjects: Extreme value theory GARCH model
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11732 , vital:26961
- Description: Financial market integration, in particular, portfolio allocations from advanced economies to South African markets, continues to strengthen volatility linkages and quicken volatility transmissions between participating markets. Largely as a result, South African portfolios are net recipients of returns and volatility shocks emanating from major world markets. In light of these, and other, sources of risk, this dissertation proposes a methodology to improve risk management systems in funds by building a contemporary asset allocation framework that offers practitioners an opportunity to explicitly model combinations of hypothesised global risks and the effects on their investments. The framework models portfolio return variables and their key risk driver variables separately and then joins them to model their combined dependence structure. The separate modelling of univariate and multivariate (MV) components admits the benefit of capturing the data generating processes with improved accuracy. Univariate variables were modelled using ARMA-GARCH-family structures paired with a variety of skewed and leptokurtic conditional distributions. Model residuals were fit using the Peaks-over-Threshold method from Extreme Value Theory for the tails and a non-parametric, kernel density for the interior, forming a completed semi-parametric distribution (SPD) for each variable. Asset and risk factor returns were then combined and their dependence structure jointly modelled with a MV Student t copula. Finally, the SPD margins and Student t copula were used to construct a MV meta t distribution. Monte Carlo simulations were generated from the fitted MV meta t distribution on which an out-of-sample test was conducted. The 2014-to-2015 horizon served to proxy as an out-of-sample, forward-looking scenario for a set of key risk factors against which a hypothetical, diversified portfolio was optimised. Traditional mean-variance and contemporary mean-CVaR optimisation techniques were used and their results compared. As an addendum, performance over the in-sample 2008 financial crisis was reported. The final Objective (7) addressed management and conservation strategies for the NMBM. The NMBM wetland database that was produced during this research is currently being used by the Municipality and will be added to the latest National Wetland Map. From the database, and tools developed in this research, approximately 90 wetlands have been identified as being highly vulnerable due to anthropogenic and environmental factors (Chapter 6) and should be earmarked as key conservation priority areas. Based on field experience and data collected, this study has also made conservation and rehabilitation recommendations for eight locations. Recommendations are also provided for six more wetland systems (or regions) that should be prioritised for further research, as these systems lack fundamental information on where the threat of anthropogenic activities affecting them is greatest. This study has made a significant contribution to understanding the underlying geomorphological processes in depressions, seeps and wetland flats. The desktop mapping component of this study illustrated the dominance of wetlands in the wetter parts of the Municipality. Perched wetland systems were identified in the field, on shallow bedrock, calcrete or clay. The prevalence of these perches in depressions, seeps and wetland flats also highlighted the importance of rainfall in driving wetland formation, by allowing water to pool on these perches, in the NMBM. These perches are likely to be a key factor in the high number of small, ephemeral wetlands that were observed in the study area, compared to other semi-arid regions. Therefore, this research highlights the value of multi-faceted and multi-scalar wetland research and how similar approaches should be used in future research methods has been highlighted. The approach used, along with the tools/methods developed in this study have facilitated the establishment of priority areas for conservation and management within the NMBM. Furthermore, the research approach has revealed emergent wetland properties that are only apparent when looking at different spatial scales. This research has highlighted the complex biological and geomorphological interactions between wetlands that operate over various spatial and temporal scales. As such, wetland management should occur across a wetland complex, rather than individual sites, to account for these multi-scalar influences.
- Full Text:
- Date Issued: 2016
The Geography of Inequality in Port Elizabeth : Post-apartheid Trends
- Authors: Mc Arthur, Brogan Erin
- Date: 2020
- Subjects: Equality -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48478 , vital:40880
- Description: This study aims to identify post-apartheid trends of inequality within Port Elizabeth, by analysing the spatial distribution of social well-being from 1996 to 2011. The spatial distribution of social well-being highlights the geography of inequality within Port Elizabeth, focusing on social indicators as a measure of social well-being. Mapping of these social indicators illustrates various levels of social well-being throughout Port Elizabeth based on the formulation of social indicators, application of these social indicators to census data, data processing and mapping. This results in the mapping of poverty, employment, education and standard of living for the census years of 1996, 2001 and 2011. From the mapping process, trends of social well-being and the associated inequality are illustrated and analysed, while providing insight into the progress of social well-being within a South African city. The findings of this study suggest that social well-being has incurred changes over time which have aided in the improvement of social well-being throughout Port Elizabeth. This improvement is marked by the relative increase and decrease of selected social indicators and their interrelated nature. The various social indicators, although focused on different datasets, highlight similar patterns of progress throughout their spatial distribution over time. As such, similar patterns of inequality can be noted throughout Port Elizabeth for various social indicators. Based on these similarities and the trends identified within the spatial distribution of inequality in Port Elizabeth, a progression towards a more even distribution throughout the study area was noted from 1996 through to 2011.
- Full Text:
- Date Issued: 2020
- Authors: Mc Arthur, Brogan Erin
- Date: 2020
- Subjects: Equality -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48478 , vital:40880
- Description: This study aims to identify post-apartheid trends of inequality within Port Elizabeth, by analysing the spatial distribution of social well-being from 1996 to 2011. The spatial distribution of social well-being highlights the geography of inequality within Port Elizabeth, focusing on social indicators as a measure of social well-being. Mapping of these social indicators illustrates various levels of social well-being throughout Port Elizabeth based on the formulation of social indicators, application of these social indicators to census data, data processing and mapping. This results in the mapping of poverty, employment, education and standard of living for the census years of 1996, 2001 and 2011. From the mapping process, trends of social well-being and the associated inequality are illustrated and analysed, while providing insight into the progress of social well-being within a South African city. The findings of this study suggest that social well-being has incurred changes over time which have aided in the improvement of social well-being throughout Port Elizabeth. This improvement is marked by the relative increase and decrease of selected social indicators and their interrelated nature. The various social indicators, although focused on different datasets, highlight similar patterns of progress throughout their spatial distribution over time. As such, similar patterns of inequality can be noted throughout Port Elizabeth for various social indicators. Based on these similarities and the trends identified within the spatial distribution of inequality in Port Elizabeth, a progression towards a more even distribution throughout the study area was noted from 1996 through to 2011.
- Full Text:
- Date Issued: 2020
The geology of the Witteberg group, Cape supergroup, with specific focus on the Perdepoort member as a potential silica source
- Authors: Olivier, Wernich Corné
- Date: 2010
- Subjects: Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10660 , http://hdl.handle.net/10948/1386 , http://hdl.handle.net/10948/d1012889 , Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Description: Selected outcrops of the Upper Devonian to Lower Carboniferous, Witteberg Group, Cape Supergroup were mineralogically and structurally analyzed. The study area is located approximately 30km northwest of Kirkwood and 10km south of Darlington Dam, Eastern Cape, South Africa. Strata predominantly consist of arenaceous Witpoort Formation, which includes the Perdepoort, and Rooirand Members. The Perdepoort Member is a thinly bedded quartzite also known as the "white streak". The Rooirand Member quartzite is a highly iron stained red-brown quartzite. The dark-grey, pyritic rich shales of the Kweekvlei Formation overlie the Witpoort Formation in the southern half of the study site. These shales are highly deformed and display closely spaced thrust faults and close folds. The study area encapsulates a range of folding from tight to open folds. Faulting consists of low angle north verging thrust fault, south verging back thrusts, south and north dipping normal faults, and strike-slip faults. Closely spaced, fore-land verging thrusts faults predominate over hinterland verging back thrusts. Normal faulting post-dates thrust faulting and utilized weaknesses in axial planar cleavage and in certain instances existing thrust fault planes. Strike-slip faulting post-dates thrusting and has in places reactivated pre-existing thrust fault planes. Macro scale folding includes overturned synclines and large anticlines which have been eroded, exposing older strata. Fold axes plunge at low to moderate angles west-southwest. This correlates with tension gashes which indicate north westward directed forces. Eastward directed forces are confirmed by the presence of tension gashes and strike-slip movement. The local geology displays north westward directed compression followed by strike-slip movement. Normal faulting post-dates all other structures and is associated with the Mesozoic break-up of Gondwana. The Perdepoort Member was sampled along strike, at different outcrop latitudes. Seven samples were selected for scanning electron microscope analysis. Samples are composed almost entirely of quartz; accessories include, biotite, muscovite, sericite, baryte, and apatite. Epigenetic hematite is present along cracks within certain samples Epigenetic hematite occur along cracks with oxides and phosphates in the form of rutile, apatite and monazite present in a number of samples. When compared to other silica extraction operations the Perdepoort Member appears viable for explotation. However, for the solar cell industry the purity of this horizon is clearly far below that required for industy.
- Full Text:
- Date Issued: 2010
- Authors: Olivier, Wernich Corné
- Date: 2010
- Subjects: Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10660 , http://hdl.handle.net/10948/1386 , http://hdl.handle.net/10948/d1012889 , Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Description: Selected outcrops of the Upper Devonian to Lower Carboniferous, Witteberg Group, Cape Supergroup were mineralogically and structurally analyzed. The study area is located approximately 30km northwest of Kirkwood and 10km south of Darlington Dam, Eastern Cape, South Africa. Strata predominantly consist of arenaceous Witpoort Formation, which includes the Perdepoort, and Rooirand Members. The Perdepoort Member is a thinly bedded quartzite also known as the "white streak". The Rooirand Member quartzite is a highly iron stained red-brown quartzite. The dark-grey, pyritic rich shales of the Kweekvlei Formation overlie the Witpoort Formation in the southern half of the study site. These shales are highly deformed and display closely spaced thrust faults and close folds. The study area encapsulates a range of folding from tight to open folds. Faulting consists of low angle north verging thrust fault, south verging back thrusts, south and north dipping normal faults, and strike-slip faults. Closely spaced, fore-land verging thrusts faults predominate over hinterland verging back thrusts. Normal faulting post-dates thrust faulting and utilized weaknesses in axial planar cleavage and in certain instances existing thrust fault planes. Strike-slip faulting post-dates thrusting and has in places reactivated pre-existing thrust fault planes. Macro scale folding includes overturned synclines and large anticlines which have been eroded, exposing older strata. Fold axes plunge at low to moderate angles west-southwest. This correlates with tension gashes which indicate north westward directed forces. Eastward directed forces are confirmed by the presence of tension gashes and strike-slip movement. The local geology displays north westward directed compression followed by strike-slip movement. Normal faulting post-dates all other structures and is associated with the Mesozoic break-up of Gondwana. The Perdepoort Member was sampled along strike, at different outcrop latitudes. Seven samples were selected for scanning electron microscope analysis. Samples are composed almost entirely of quartz; accessories include, biotite, muscovite, sericite, baryte, and apatite. Epigenetic hematite is present along cracks within certain samples Epigenetic hematite occur along cracks with oxides and phosphates in the form of rutile, apatite and monazite present in a number of samples. When compared to other silica extraction operations the Perdepoort Member appears viable for explotation. However, for the solar cell industry the purity of this horizon is clearly far below that required for industy.
- Full Text:
- Date Issued: 2010
The Grootfontein aquifer at Mahikeng, South Africa as hydro-social system
- Authors: Cobbing, Jude Edmund
- Date: 2017
- Subjects: Groundwater -- South Africa -- Mahikeng Hydrogeology -- South Africa -- Mahikeng
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21351 , vital:29484
- Description: The Grootfontein aquifer is located about 20 km south east of Mahikeng, North West Province, South Africa, and currently supplies about 20% of Mahikeng’s water. Formed in weathered Malmani Subgroup dolomites, the aquifer contains good quality groundwater that could potentially supply more of Mahikeng’s water, as well as provide a strategic reserve of water for use during droughts. Over-abstraction of groundwater from the aquifer, mainly by irrigating farmers but also by the boreholes supplying Mahikeng, has caused the natural groundwater level to drop at a rate of about 0.4 m per year since the 1970s, leading to water level declines of as much as 28 m in parts of the aquifer. Although the Grootfontein aquifer is one of the best studied aquifers in South Africa hydrogeologically, efforts to address these declines since the 1970s have largely failed. This research combines hydrogeological evidence with social research (interviews and participant-observation) and the principles of Earth Stewardship Science to argue that the aquifer functions as a hydro-social system, and that institutional characteristics are the root cause of a collective inability to restore the aquifer to its full potential as a water resource. A sub-optimal and undesirable Nash equilibrium prevails, in which major groundwater users are unable or unwilling to reduce abstraction. The situation has significant cost and risk implications for the environmental, economic and social sectors, and contributes to insecurity, pessimism, inequality and mistrust. An effective local forum with appropriate powers, supported and mandated by the Department of Water and Sanitation, is needed to begin the work of dismantling the sub-optimal equilibrium to realise the potential of the Grootfontein aquifer. Such a forum would require a shared understanding of the hydrogeological mechanisms of the aquifer as well as its social and institutional functioning, since these influence each other in complex ways.
- Full Text:
- Date Issued: 2017
- Authors: Cobbing, Jude Edmund
- Date: 2017
- Subjects: Groundwater -- South Africa -- Mahikeng Hydrogeology -- South Africa -- Mahikeng
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21351 , vital:29484
- Description: The Grootfontein aquifer is located about 20 km south east of Mahikeng, North West Province, South Africa, and currently supplies about 20% of Mahikeng’s water. Formed in weathered Malmani Subgroup dolomites, the aquifer contains good quality groundwater that could potentially supply more of Mahikeng’s water, as well as provide a strategic reserve of water for use during droughts. Over-abstraction of groundwater from the aquifer, mainly by irrigating farmers but also by the boreholes supplying Mahikeng, has caused the natural groundwater level to drop at a rate of about 0.4 m per year since the 1970s, leading to water level declines of as much as 28 m in parts of the aquifer. Although the Grootfontein aquifer is one of the best studied aquifers in South Africa hydrogeologically, efforts to address these declines since the 1970s have largely failed. This research combines hydrogeological evidence with social research (interviews and participant-observation) and the principles of Earth Stewardship Science to argue that the aquifer functions as a hydro-social system, and that institutional characteristics are the root cause of a collective inability to restore the aquifer to its full potential as a water resource. A sub-optimal and undesirable Nash equilibrium prevails, in which major groundwater users are unable or unwilling to reduce abstraction. The situation has significant cost and risk implications for the environmental, economic and social sectors, and contributes to insecurity, pessimism, inequality and mistrust. An effective local forum with appropriate powers, supported and mandated by the Department of Water and Sanitation, is needed to begin the work of dismantling the sub-optimal equilibrium to realise the potential of the Grootfontein aquifer. Such a forum would require a shared understanding of the hydrogeological mechanisms of the aquifer as well as its social and institutional functioning, since these influence each other in complex ways.
- Full Text:
- Date Issued: 2017
The growth and recovery of mangroves at three South African study sites
- Authors: Mbense, Sinegugu
- Date: 2017
- Subjects: Mangrove forests -- South Africa Mangrove ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11931 , vital:27008
- Description: Mangroves in South Africa are prone to anthropogenic pressures such as browsing and trampling by livestock and by natural disturbances such as drought and floods. These mangroves exist at one of the most southerly limits in the world providing a unique opportunity to study recovery and resilience to change. This study used long term data at three South African study sites located in the subtropical (St Lucia Estuary) and warm temperate regions (Nxaxo and Kobonqaba estuaries) to compare mangrove growth rate, population structure and responses to disturbance. The first objective was investigated at St Lucia Estuary where site specific or microhabitat differences were measured to assess the influence of these on mangrove growth and population structure. It was suggested that site - specific variability would ensure mangrove survival and analysis showed that seedlings were present at different sites in different years. There was always some recruitment but often little survival to the next size class. Over time seedling numbers were quite variable and self – thinning of adults was evident. The second objective was to identify the environmental factors influencing population density and growth. Results showed that sediment moisture and salinity influenced seedling and adult density due to fluctuations in estuary water level. Mangrove growth rates for Avicennia marina in terms of height was faster (40 – 75 cm yr-1 ) at Site 1 where conditions were waterlogged and moderately saline and slower (5 – 25 cm yr1 ) in dry and hypersaline conditions at Site 4. Overall mangroves at St Lucia have shown persistence through drought and fluctuations in environmental conditions however resilience may be hindered at sites that are subjected to partially flooding and prolonged waterlogging. The second site was Nxaxo Estuary in the Eastern Cape where cattle exclusion plots (nonbrowsed) and control plots (browsed) were used to assess the recovery of A. marina trees from cattle browsing. Trees in the browsed plots showed no vertical growth while trees in the non-browsed plots grew significantly faster (5.4 ± 0.5 cm yr-1). When cattle were prevented from entering the mangrove area, the trees recovered fairly quickly and within 3 years growth was similar in both the non – browsed (17.9 ± 3.2 cm yr -1) and browsed plots (18 ± 1.6 cm yr -1). Lastly, mangrove recovery was investigated at Kobonqaba Estuary where long-term closure of the mouth to the sea resulted in high water levels, inundation of pneumatophores and die-back of the majority of the mangroves. This study measured the recovery of the mangroves by assessing changes in vegetation cover and sediment characteristics along transects. High initial porewater nutrient concentrations promoted salt marsh growth and plants increased average cover from 0% in 2011 to 18.9% (2013) and 50% in 2015. The total number of A. marina individuals increased from only seven to 27 individuals over four years. Salt marsh competition and facilitation will likely influence mangrove recovery in the future. Overall it was concluded that when a short term pressure (cattle browsing) is alleviated, mangrove forests even at warm temperate sites are able to recovery rapidly by increasing growth and seedling establishment. However, mangroves in the subtropical sites show more resilience and recovery potential to long term pressures such as fluctuating environmental conditions because of faster growth rates.
- Full Text:
- Date Issued: 2017
- Authors: Mbense, Sinegugu
- Date: 2017
- Subjects: Mangrove forests -- South Africa Mangrove ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11931 , vital:27008
- Description: Mangroves in South Africa are prone to anthropogenic pressures such as browsing and trampling by livestock and by natural disturbances such as drought and floods. These mangroves exist at one of the most southerly limits in the world providing a unique opportunity to study recovery and resilience to change. This study used long term data at three South African study sites located in the subtropical (St Lucia Estuary) and warm temperate regions (Nxaxo and Kobonqaba estuaries) to compare mangrove growth rate, population structure and responses to disturbance. The first objective was investigated at St Lucia Estuary where site specific or microhabitat differences were measured to assess the influence of these on mangrove growth and population structure. It was suggested that site - specific variability would ensure mangrove survival and analysis showed that seedlings were present at different sites in different years. There was always some recruitment but often little survival to the next size class. Over time seedling numbers were quite variable and self – thinning of adults was evident. The second objective was to identify the environmental factors influencing population density and growth. Results showed that sediment moisture and salinity influenced seedling and adult density due to fluctuations in estuary water level. Mangrove growth rates for Avicennia marina in terms of height was faster (40 – 75 cm yr-1 ) at Site 1 where conditions were waterlogged and moderately saline and slower (5 – 25 cm yr1 ) in dry and hypersaline conditions at Site 4. Overall mangroves at St Lucia have shown persistence through drought and fluctuations in environmental conditions however resilience may be hindered at sites that are subjected to partially flooding and prolonged waterlogging. The second site was Nxaxo Estuary in the Eastern Cape where cattle exclusion plots (nonbrowsed) and control plots (browsed) were used to assess the recovery of A. marina trees from cattle browsing. Trees in the browsed plots showed no vertical growth while trees in the non-browsed plots grew significantly faster (5.4 ± 0.5 cm yr-1). When cattle were prevented from entering the mangrove area, the trees recovered fairly quickly and within 3 years growth was similar in both the non – browsed (17.9 ± 3.2 cm yr -1) and browsed plots (18 ± 1.6 cm yr -1). Lastly, mangrove recovery was investigated at Kobonqaba Estuary where long-term closure of the mouth to the sea resulted in high water levels, inundation of pneumatophores and die-back of the majority of the mangroves. This study measured the recovery of the mangroves by assessing changes in vegetation cover and sediment characteristics along transects. High initial porewater nutrient concentrations promoted salt marsh growth and plants increased average cover from 0% in 2011 to 18.9% (2013) and 50% in 2015. The total number of A. marina individuals increased from only seven to 27 individuals over four years. Salt marsh competition and facilitation will likely influence mangrove recovery in the future. Overall it was concluded that when a short term pressure (cattle browsing) is alleviated, mangrove forests even at warm temperate sites are able to recovery rapidly by increasing growth and seedling establishment. However, mangroves in the subtropical sites show more resilience and recovery potential to long term pressures such as fluctuating environmental conditions because of faster growth rates.
- Full Text:
- Date Issued: 2017
The hepatoprotective capacity of selected natural products from South Africa
- Authors: Reddy, Shanika
- Date: 2019
- Subjects: Hepatology , Liver -- Physiology Liver -- Pathophysiology Liver -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43622 , vital:36948
- Description: Drug-induced liver injury (DILI) is recognized as a significant clinical problem, which may account for up to 50% of all cases of acute liver failure. DILI is initiated by the bioactivation of parent drug molecules to produce chemically reactive metabolites. These reactive intermediates induce mitochondrial dysfunction and oxidative stress leading to glutathione (GSH) depletion and damage to cellular proteins, lipids and nucleic acids, which eventually culminates in necrotic cell death. The principal objective of this study is to establish an in vitro screening platform to identify potential hepatoprotective natural products (plants and mushrooms) from South Africa (SA). Aqueous plant extracts (Cyclopia intermedia, Opuntia ficus indica and Kigelia africana), and aqueous and ethanolic macrofungal extracts (Ganoderma lucidum, Russula capensis, Pleurotus ostreatus and Lenzites elegans) were prepared and screened against HepG2 and VERO cells to assess their safety using Hoechst 33342-PI dual labelling. A drug-induced hepatotoxic model was established, using the dietary supplement menadione (vitamin K3). Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling was used for necrosis, oxidative stress and mitochondrial membrane potential depolarization (ΔΨm) detection, respectively. The accuracy of the hepatoprotection model was confirmed through HepG2 cellbased assays (Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling) that measured the protective effects of natural products against the menadione-induced toxicity, anti-oxidant assays (DPPH, NO, ORAC, CAPe and FRAP) that measured their anti-oxidant potential and enzyme assays (βglucuronidase, carboxylesterase and CYP450 isoform 3A4) that measured their effects on drug metabolism. Silymarin was used as a positive control for each assay. Menadione displayed significant cell death, increased oxidative stress and decreased ΔΨm at an elevated concentration of 100 μM; confirming the hepatotoxicity model, where necroptosis was suspected to be menadione’s cell death mode. Only ethanolic G. lucidum was cytotoxic. All three aqueous plant extracts demonstrated strong anti-oxidant capacities out of all the tested extracts; where C. intermedia displayed the most promising DPPH, NO, ORAC, CAPe and FRAP activity, followed by aqueous G. lucidum. Aqueous plant and ethanolic macrofungal extracts (C. intermedia, O. ficus indica, K. africana, and ethanolic P. ostreatus, R. capensis) displayed decreased menadione-induced ROS production and protected against menadione-induced ΔΨm depolarization, posing them and aqueous G. lucidum potential therapeutic interventions for DILI. Ethanolic L. elegans demonstrated the highest enzyme inhibition for each assay and presented genotoxicity, ruling it out as a therapeutic strategy against DILI. Together these assays addressed several aspects relating to DILI and hepatoprotection, and served as a good starting point in evaluating the therapeutic value of natural products from South Africa.
- Full Text:
- Date Issued: 2019
- Authors: Reddy, Shanika
- Date: 2019
- Subjects: Hepatology , Liver -- Physiology Liver -- Pathophysiology Liver -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43622 , vital:36948
- Description: Drug-induced liver injury (DILI) is recognized as a significant clinical problem, which may account for up to 50% of all cases of acute liver failure. DILI is initiated by the bioactivation of parent drug molecules to produce chemically reactive metabolites. These reactive intermediates induce mitochondrial dysfunction and oxidative stress leading to glutathione (GSH) depletion and damage to cellular proteins, lipids and nucleic acids, which eventually culminates in necrotic cell death. The principal objective of this study is to establish an in vitro screening platform to identify potential hepatoprotective natural products (plants and mushrooms) from South Africa (SA). Aqueous plant extracts (Cyclopia intermedia, Opuntia ficus indica and Kigelia africana), and aqueous and ethanolic macrofungal extracts (Ganoderma lucidum, Russula capensis, Pleurotus ostreatus and Lenzites elegans) were prepared and screened against HepG2 and VERO cells to assess their safety using Hoechst 33342-PI dual labelling. A drug-induced hepatotoxic model was established, using the dietary supplement menadione (vitamin K3). Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling was used for necrosis, oxidative stress and mitochondrial membrane potential depolarization (ΔΨm) detection, respectively. The accuracy of the hepatoprotection model was confirmed through HepG2 cellbased assays (Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling) that measured the protective effects of natural products against the menadione-induced toxicity, anti-oxidant assays (DPPH, NO, ORAC, CAPe and FRAP) that measured their anti-oxidant potential and enzyme assays (βglucuronidase, carboxylesterase and CYP450 isoform 3A4) that measured their effects on drug metabolism. Silymarin was used as a positive control for each assay. Menadione displayed significant cell death, increased oxidative stress and decreased ΔΨm at an elevated concentration of 100 μM; confirming the hepatotoxicity model, where necroptosis was suspected to be menadione’s cell death mode. Only ethanolic G. lucidum was cytotoxic. All three aqueous plant extracts demonstrated strong anti-oxidant capacities out of all the tested extracts; where C. intermedia displayed the most promising DPPH, NO, ORAC, CAPe and FRAP activity, followed by aqueous G. lucidum. Aqueous plant and ethanolic macrofungal extracts (C. intermedia, O. ficus indica, K. africana, and ethanolic P. ostreatus, R. capensis) displayed decreased menadione-induced ROS production and protected against menadione-induced ΔΨm depolarization, posing them and aqueous G. lucidum potential therapeutic interventions for DILI. Ethanolic L. elegans demonstrated the highest enzyme inhibition for each assay and presented genotoxicity, ruling it out as a therapeutic strategy against DILI. Together these assays addressed several aspects relating to DILI and hepatoprotection, and served as a good starting point in evaluating the therapeutic value of natural products from South Africa.
- Full Text:
- Date Issued: 2019
The hepatoprotective capacity of selected natural products from South Africa
- Authors: Reddy, Shanika
- Date: 2019
- Subjects: Liver -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43611 , vital:36929
- Description: Drug-induced liver injury (DILI) is recognized as a significant clinical problem, which may account for up to 50% of all cases of acute liver failure. DILI is initiated by the bioactivation of parent drug molecules to produce chemically reactive metabolites. These reactive intermediates induce mitochondrial dysfunction and oxidative stress leading to glutathione (GSH) depletion and damage to cellular proteins, lipids and nucleic acids, which eventually culminates in necrotic cell death. The principal objective of this study is to establish an in vitro screening platform to identify potential hepatoprotective natural products (plants and mushrooms) from South Africa (SA). Aqueous plant extracts (Cyclopia intermedia, Opuntia ficus indica and Kigelia africana), and aqueous and ethanolic macrofungal extracts (Ganoderma lucidum, Russula capensis, Pleurotus ostreatus and Lenzites elegans) were prepared and screened against HepG2 and VERO cells to assess their safety using Hoechst 33342-PI dual labelling. A drug-induced hepatotoxic model was established, using the dietary supplement menadione (vitamin K3). Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling was used for necrosis, oxidative stress and mitochondrial membrane potential depolarization (ΔΨm) detection, respectively. The accuracy of the hepatoprotection model was confirmed through HepG2 cellbased assays (Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling) that measured the protective effects of natural products against the menadione-induced toxicity, anti-oxidant assays (DPPH, NO, ORAC, CAPe and FRAP) that measured their anti-oxidant potential and enzyme assays (βglucuronidase, carboxylesterase and CYP450 isoform 3A4) that measured their effects on drug metabolism. Silymarin was used as a positive control for each assay. Menadione displayed significant cell death, increased oxidative stress and decreased ΔΨm at an elevated concentration of 100 μM; confirming the hepatotoxicity model, where necroptosis was suspected to be menadione’s cell death mode. Only ethanolic G. lucidum was cytotoxic. All three aqueous plant extracts demonstrated strong anti-oxidant capacities out of all the tested extracts; where C. intermedia displayed the most promising DPPH, NO, ORAC, CAPe and FRAP activity, followed by aqueous G. lucidum. Aqueous plant and ethanolic macrofungal extracts (C. intermedia, O. ficus indica, K. africana, and ethanolic P. ostreatus, R. capensis) displayed decreased menadione-induced ROS production and protected against menadione-induced ΔΨm depolarization, posing them and aqueous G. lucidum potential therapeutic interventions for DILI. Ethanolic L. elegans demonstrated the highest enzyme inhibition for each assay and presented genotoxicity, ruling it out as a therapeutic strategy against DILI. Together these assays addressed several aspects relating to DILI and hepatoprotection, and served as a good starting point in evaluating the therapeutic value of natural products from South Africa.
- Full Text:
- Date Issued: 2019
- Authors: Reddy, Shanika
- Date: 2019
- Subjects: Liver -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43611 , vital:36929
- Description: Drug-induced liver injury (DILI) is recognized as a significant clinical problem, which may account for up to 50% of all cases of acute liver failure. DILI is initiated by the bioactivation of parent drug molecules to produce chemically reactive metabolites. These reactive intermediates induce mitochondrial dysfunction and oxidative stress leading to glutathione (GSH) depletion and damage to cellular proteins, lipids and nucleic acids, which eventually culminates in necrotic cell death. The principal objective of this study is to establish an in vitro screening platform to identify potential hepatoprotective natural products (plants and mushrooms) from South Africa (SA). Aqueous plant extracts (Cyclopia intermedia, Opuntia ficus indica and Kigelia africana), and aqueous and ethanolic macrofungal extracts (Ganoderma lucidum, Russula capensis, Pleurotus ostreatus and Lenzites elegans) were prepared and screened against HepG2 and VERO cells to assess their safety using Hoechst 33342-PI dual labelling. A drug-induced hepatotoxic model was established, using the dietary supplement menadione (vitamin K3). Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling was used for necrosis, oxidative stress and mitochondrial membrane potential depolarization (ΔΨm) detection, respectively. The accuracy of the hepatoprotection model was confirmed through HepG2 cellbased assays (Hoechst 33342- PI, -CellROX® Orange and -TMRE dual labelling) that measured the protective effects of natural products against the menadione-induced toxicity, anti-oxidant assays (DPPH, NO, ORAC, CAPe and FRAP) that measured their anti-oxidant potential and enzyme assays (βglucuronidase, carboxylesterase and CYP450 isoform 3A4) that measured their effects on drug metabolism. Silymarin was used as a positive control for each assay. Menadione displayed significant cell death, increased oxidative stress and decreased ΔΨm at an elevated concentration of 100 μM; confirming the hepatotoxicity model, where necroptosis was suspected to be menadione’s cell death mode. Only ethanolic G. lucidum was cytotoxic. All three aqueous plant extracts demonstrated strong anti-oxidant capacities out of all the tested extracts; where C. intermedia displayed the most promising DPPH, NO, ORAC, CAPe and FRAP activity, followed by aqueous G. lucidum. Aqueous plant and ethanolic macrofungal extracts (C. intermedia, O. ficus indica, K. africana, and ethanolic P. ostreatus, R. capensis) displayed decreased menadione-induced ROS production and protected against menadione-induced ΔΨm depolarization, posing them and aqueous G. lucidum potential therapeutic interventions for DILI. Ethanolic L. elegans demonstrated the highest enzyme inhibition for each assay and presented genotoxicity, ruling it out as a therapeutic strategy against DILI. Together these assays addressed several aspects relating to DILI and hepatoprotection, and served as a good starting point in evaluating the therapeutic value of natural products from South Africa.
- Full Text:
- Date Issued: 2019
The hypolithic invertebrate community in the eastern Karoo: the role of rock size, microclimate and recolonization
- Authors: Van der Westhuizen, Tara
- Date: 2019
- Subjects: Habitat (Ecology) -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo Invertebrates Ecosystem management -- South Africa -- Karoo Soil microbial ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44191 , vital:37128
- Description: Hypolithic habitats are important for the persistence of fauna that utilize these habitats as refuges and resource patches. Little is known, however, about the composition and structure of this community in the semi-arid Karoo. The current study therefore aims to explore the patterns and processes behind hypolithic communities, through determining the effect of rock size and baboon presence on the hypolithic community, the influence of rock size on the microclimate experienced under rocks, as well as determining the short- (over five days) and long- (over 12 months) term colonisation of the hypolithic habitat following a rock rolling disturbance, in a semi-arid Karoo environment. The hypolithic fauna encountered, and the temperature and moisture content experienced under a range of rock sizes were measured. Additionally, hypolithic fauna under rocks that were rolled to mimic rock rolling by baboons were sampled after a set period (i.e. over five days and 12 months). Large rocks were found to provide a more stable microclimate than small rocks. The probability of hypolithic fauna presence was influenced by rock size and season, and hypolithic fauna abundance (except in the dry season), richness, body size and biomass did not correlate with rock size. Additionally, the probability of detecting hypolithic fauna under intermediate sized and larger rocks was greater in the presence of baboons than in the absence of baboons, and in the presence of baboons hypolithic fauna richness increased with rock size. Furthermore, it was shown that hypolithic fauna abundance and biomass did not differ under rolled rocks over a short- (i.e. over five days) or long- (i.e. over 12 months) term period. The short-term colonisation of hypolithic habitats was not influenced by season or rock density. Lastly, most of the change in hypolithic community composition (over 12 months) occurred in the first three months and thereafter the hypolithic community composition approached pre-disturbance levels in month 12. The hypolithic habitat was shown to be influenced by a variety of conditions and processes affecting hypolithic community composition and structure. This study therefore contributes to our understanding of the hypolithic invertebrate community in the eastern Karoo, and the influence of rock size, baboon presence, microclimate and colonisation on hypolithic community composition and structure.
- Full Text:
- Date Issued: 2019
- Authors: Van der Westhuizen, Tara
- Date: 2019
- Subjects: Habitat (Ecology) -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo Invertebrates Ecosystem management -- South Africa -- Karoo Soil microbial ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44191 , vital:37128
- Description: Hypolithic habitats are important for the persistence of fauna that utilize these habitats as refuges and resource patches. Little is known, however, about the composition and structure of this community in the semi-arid Karoo. The current study therefore aims to explore the patterns and processes behind hypolithic communities, through determining the effect of rock size and baboon presence on the hypolithic community, the influence of rock size on the microclimate experienced under rocks, as well as determining the short- (over five days) and long- (over 12 months) term colonisation of the hypolithic habitat following a rock rolling disturbance, in a semi-arid Karoo environment. The hypolithic fauna encountered, and the temperature and moisture content experienced under a range of rock sizes were measured. Additionally, hypolithic fauna under rocks that were rolled to mimic rock rolling by baboons were sampled after a set period (i.e. over five days and 12 months). Large rocks were found to provide a more stable microclimate than small rocks. The probability of hypolithic fauna presence was influenced by rock size and season, and hypolithic fauna abundance (except in the dry season), richness, body size and biomass did not correlate with rock size. Additionally, the probability of detecting hypolithic fauna under intermediate sized and larger rocks was greater in the presence of baboons than in the absence of baboons, and in the presence of baboons hypolithic fauna richness increased with rock size. Furthermore, it was shown that hypolithic fauna abundance and biomass did not differ under rolled rocks over a short- (i.e. over five days) or long- (i.e. over 12 months) term period. The short-term colonisation of hypolithic habitats was not influenced by season or rock density. Lastly, most of the change in hypolithic community composition (over 12 months) occurred in the first three months and thereafter the hypolithic community composition approached pre-disturbance levels in month 12. The hypolithic habitat was shown to be influenced by a variety of conditions and processes affecting hypolithic community composition and structure. This study therefore contributes to our understanding of the hypolithic invertebrate community in the eastern Karoo, and the influence of rock size, baboon presence, microclimate and colonisation on hypolithic community composition and structure.
- Full Text:
- Date Issued: 2019
The identification of criteria to be utilised in mathematical diagnostic tests
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
The immobilization of Microcystis aeruginosa PCC7806 on a membrane nutrient-gradostat bioreacator for the production of the secondary metobolites
- Authors: Strong, Peter James
- Date: 2002
- Subjects: Microcystis aeruginosa , Myrocystins , Bioreactors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11083 , http://hdl.handle.net/10948/283 , Microcystis aeruginosa , Myrocystins , Bioreactors
- Description: A module and an inoculation technique were developed that would allow for the efficient immobilization of Microcystis aeruginosa PCC7806 on a synthetic membrane. A variety of module types, membranes (ceramic, tubular polyethersulfone and externally skinless polyethersulfone capillary membrane), and methods of immobilization (adsorption, pressure filtration and a developed technique that involved drying a cell slurry on a membrane) were assessed. The morphological properties that affected the immobilization of Microcystis aeruginosa PCC7806, as well as the effects of immobilization upon cell morphology were assessed. Cells in the stationary growth phase, which had a well-developed extra-cellular polysaccharide layer and no gas vesicles, were optimal for immobilization. Microcystin production under immobilized conditions was assessed under different nitrate concentrations, light intensities, biofilm thickness and immobilization times. Additional work included assaying for Microcystin production of two airlift-grown cultures under a high light intensity and complete nutrient deprivation and the inoculation of a ceramic membrane. An immunological technique was used to elucidate where toxin production was greatest within a biofilm immobilized upon an externally skinless polyethersulfone capillary membrane. The externally skinless polyethersulfone capillary membrane was evaluated to assess homogeneity and the physical differences between membrane batches that led to the erratic, incomplete biofilm formation, as a biofilm of a constant thickness could not be immobilized. Microcystis aeruginosa PCC7806 was exposed to a variety of solvents in order to permeabilize the cyanobacteria, as that would have enabled a truly continuous extraction process for the metabolite. FDA hydrolysis had to be optimized in order to use it as an indicator of cell viability. In addition a single-step extraction of Microcystin was attempted using live bacteria. A capillary membrane module, containing the externally skinless polyethersulfone capillary membrane, inoculated using pressure filtration, was the most efficient combination to establish a biofilm. Cells that were no longer actively dividing and that lacked buoyancy displayed superior immobilization to cells that were actively dividing and buoyant. The immobilized cells did produce Microcystin but in much lower concentrations to cells grown in an airlift culture. Biofilms grown with a higher nitrate concentration, a lower biofilm thickness and a lower light intensity had a higher specific microcystin content, while biofilms with a higher nitrate concentration a lower light intensity and a longer growth period displayed the a greater toxin production per mm2 of membrane. Microcystin occurred at its highest concentration in cells just above the pore opening. The diffusion of nutrients occurred relatively quickly to the outside layers of the biofilm, with a true gradient being established laterally from these nutrient veins that were above the pores. Permeabilization of the cells proved unsuccessful, as cells that remained viable did not release the intracellular compound into the surrounding medium.
- Full Text:
- Date Issued: 2002
- Authors: Strong, Peter James
- Date: 2002
- Subjects: Microcystis aeruginosa , Myrocystins , Bioreactors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11083 , http://hdl.handle.net/10948/283 , Microcystis aeruginosa , Myrocystins , Bioreactors
- Description: A module and an inoculation technique were developed that would allow for the efficient immobilization of Microcystis aeruginosa PCC7806 on a synthetic membrane. A variety of module types, membranes (ceramic, tubular polyethersulfone and externally skinless polyethersulfone capillary membrane), and methods of immobilization (adsorption, pressure filtration and a developed technique that involved drying a cell slurry on a membrane) were assessed. The morphological properties that affected the immobilization of Microcystis aeruginosa PCC7806, as well as the effects of immobilization upon cell morphology were assessed. Cells in the stationary growth phase, which had a well-developed extra-cellular polysaccharide layer and no gas vesicles, were optimal for immobilization. Microcystin production under immobilized conditions was assessed under different nitrate concentrations, light intensities, biofilm thickness and immobilization times. Additional work included assaying for Microcystin production of two airlift-grown cultures under a high light intensity and complete nutrient deprivation and the inoculation of a ceramic membrane. An immunological technique was used to elucidate where toxin production was greatest within a biofilm immobilized upon an externally skinless polyethersulfone capillary membrane. The externally skinless polyethersulfone capillary membrane was evaluated to assess homogeneity and the physical differences between membrane batches that led to the erratic, incomplete biofilm formation, as a biofilm of a constant thickness could not be immobilized. Microcystis aeruginosa PCC7806 was exposed to a variety of solvents in order to permeabilize the cyanobacteria, as that would have enabled a truly continuous extraction process for the metabolite. FDA hydrolysis had to be optimized in order to use it as an indicator of cell viability. In addition a single-step extraction of Microcystin was attempted using live bacteria. A capillary membrane module, containing the externally skinless polyethersulfone capillary membrane, inoculated using pressure filtration, was the most efficient combination to establish a biofilm. Cells that were no longer actively dividing and that lacked buoyancy displayed superior immobilization to cells that were actively dividing and buoyant. The immobilized cells did produce Microcystin but in much lower concentrations to cells grown in an airlift culture. Biofilms grown with a higher nitrate concentration, a lower biofilm thickness and a lower light intensity had a higher specific microcystin content, while biofilms with a higher nitrate concentration a lower light intensity and a longer growth period displayed the a greater toxin production per mm2 of membrane. Microcystin occurred at its highest concentration in cells just above the pore opening. The diffusion of nutrients occurred relatively quickly to the outside layers of the biofilm, with a true gradient being established laterally from these nutrient veins that were above the pores. Permeabilization of the cells proved unsuccessful, as cells that remained viable did not release the intracellular compound into the surrounding medium.
- Full Text:
- Date Issued: 2002
The impact of an in-depth code comprehension tool in an introductory programming module
- Authors: Leppan, Ronald George
- Date: 2008
- Subjects: Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10471 , http://hdl.handle.net/10948/847 , Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
- Description: Reading and understanding algorithms is not an easy task and often neglected by educators in an introductory programming course. One proposed solution to this problem is the incorporation of a technological support tool to aid program comprehension in introductory programming. Many researchers advocate the identification of beacons and the use of chunking as support for code comprehension. Beacon recognition and chunking can also be used as support in the teaching model of introductory programming. Educators use a variety of different support tools to facilitate program comprehension in introductory programming. Review of a variety of support tools fails to deliver an existing tool to support a teaching model that incorporates chunking and the identification of beacons. The experimental support tool in this dissertation (BeReT) is primarily designed to encourage a student to correctly identify beacons within provided program extracts. BeReT can also be used to allow students to group together related statements and to learn about plans implemented in any semantically and syntactically correct algorithm uploaded by an instructor. While these requirements are evident in the design and implementation of BeReT, data is required to measure the effect BeReT has on the indepth comprehension of introductory programming algorithms. A between-groups experiment is described which compares the program comprehension of students that used BeReT to study various introductory algorithms, with students that relied solely on traditional lecturing materials. The use of an eye tracker was incorporated into the empirical study to visualise the results of controlled experiments. The results indicate that a technological support tool like BeReT can have a significantly positive effect on student comprehension of algorithms traditionally taught in introductory programming. This research provides educators with an alternative way for the incorporation of in-depth code comprehension skills in introductory programming.
- Full Text:
- Date Issued: 2008
- Authors: Leppan, Ronald George
- Date: 2008
- Subjects: Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10471 , http://hdl.handle.net/10948/847 , Algorithms , Computer programming , Algorithms -- Study and teaching -- South Africa , Visual perception
- Description: Reading and understanding algorithms is not an easy task and often neglected by educators in an introductory programming course. One proposed solution to this problem is the incorporation of a technological support tool to aid program comprehension in introductory programming. Many researchers advocate the identification of beacons and the use of chunking as support for code comprehension. Beacon recognition and chunking can also be used as support in the teaching model of introductory programming. Educators use a variety of different support tools to facilitate program comprehension in introductory programming. Review of a variety of support tools fails to deliver an existing tool to support a teaching model that incorporates chunking and the identification of beacons. The experimental support tool in this dissertation (BeReT) is primarily designed to encourage a student to correctly identify beacons within provided program extracts. BeReT can also be used to allow students to group together related statements and to learn about plans implemented in any semantically and syntactically correct algorithm uploaded by an instructor. While these requirements are evident in the design and implementation of BeReT, data is required to measure the effect BeReT has on the indepth comprehension of introductory programming algorithms. A between-groups experiment is described which compares the program comprehension of students that used BeReT to study various introductory algorithms, with students that relied solely on traditional lecturing materials. The use of an eye tracker was incorporated into the empirical study to visualise the results of controlled experiments. The results indicate that a technological support tool like BeReT can have a significantly positive effect on student comprehension of algorithms traditionally taught in introductory programming. This research provides educators with an alternative way for the incorporation of in-depth code comprehension skills in introductory programming.
- Full Text:
- Date Issued: 2008
The impact of re-establishment practices on tree survival, growth and uniformity in South African eucalypt plantations
- Authors: Hechter, Ullrich
- Date: 2019
- Subjects: Forests and forestry -- South Africa -- KwaZulu-Natal , Forest nurseries -- South Africa -- KwaZulu Natal Forest management -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/40338 , vital:36142
- Description: Commercial forestry plantations in South Africa play an important role in the economy of the country, contributing 1.2% towards the gross domestic product, as well as with job creation in rural communities. Currently plantation forests occupy 1.1% (1.2 million hectares) of the South African land surface, of which 75 000 hectares are re-established each year. Eucalypts are the preferred species in the commercial forestry industry as they have the ability to grow fast. In addition, desirable characteristics from different eucalypt species can be combined to develop hybrids that can be used to further improve productivity. In South Africa, eucalypt plantations are mostly found in the warm temperate and sub-tropical zones situated in the KwaZulu-Natal and Mpumalanga Provinces. Various strategies are used to increase productivity and maximise site occupancy, including genetic tree improvement, site-species matching, optimising stand densities, management for risk (abiotic and biotic), as well as improved silviculture. Intensive silviculture is practiced by forest companies to maximise initial tree survival and reduce the time to canopy closure. This includes practices such as site preparation, slash management, tree protection, pruning and thinning, fertilisation and vegetation management treatments. Of the silvicultural aspects that are important during re-establishment, pitting, plant quality (plant size) and watering techniques/regimes have all been shown to influence short-term stand productivity. Despite research carried out on these individual components, recommendations as to best operating practices are varied and have changed over the years, with the application of these practices also varying across companies. Furthermore, there is limited published information related to the interaction between these practices, as well as any longer-term impacts of these factors on stand productivity. The objective of the present study was to gain an understanding of the impacts of pitting, plant quality (plant size), planting depth and watering on tree survival, growth and uniformity in South African Eucalyptus plantations. The study was carried out using three separate field trial series. In a first experiment, two field trials compared post-establishment performance of eucalypts planted using various pitting methods. The two trials were planted using Eucalyptus grandis and E. grandis x E. nitens on two contrasting sites, one at Greenhill in the KwaZulu-Natal Midlands and one at Vroegeveld in Mpumalanga. Four manual (notch, agricultural hoe, mattock, road pick) and three motor-manual heads (inverted A, Archimedes screw and Mondi-designed pitting head) were used to prepare and determine the effect of pit size/quality on tree survival, growth and uniformity. The notch pit implement created the smallest pit (1 L volume) compared to the other pitting implements (4 – 6 L volumes). For both trials, pitting method did not have a significant impact on the success of re-establishment or longer-term tree performance (6 yrs 7 mos at Greenhill and 3 yrs 7 mos at Vroegeveld). This indicates that for the sites and the species tested, all pitting implements could be considered viable alternatives. Other factors, such as operational costs, efficiency and ergonomics should be considered when selecting appropriate pitting methods together with tree performance. In a second experiment, three field trials were implemented to test three main factors: plant size (small and large); planting depth (standard and deep); and watering (dry and water planting). The eight treatments (2 x 2 x 2 factorial) were replicated four times and laid out in a randomised complete blocks design. The trials were established across a range of site types (Mt Home in Kwazulu-Natal, Vroegeveld in Mpumalanga and Trust in Zululand) in the summer rainfall region of South Africa using various eucalypt genera (E. dunnii, E. grandis x E. nitens and E. grandis x E. urophylla). Tree performance was assessed, with results up to four, six and seven years presented for the different sites. Results show that planting larger plants had the highest overall survival (x̄ = 81%) compared to smaller plants (x̄ = 58%), which also resulted in improved basal area and volume across all sites. Larger plants were able to tolerate a wider range of site conditions, thus providing an advantage for re-establishment. The cost-to-benefit of this however needs to be assessed, particularly in the context of current operational nursery standards. The benefits of deeper planting and applying water at planting are less clear, but appear to be beneficial under water stress conditions, such as on sandy sites when the weather is hot and dry. A third experiment tested the interaction between different methods of pit preparation (manual versus motor-manual), dry versus water planting, and re-watering at periodic intervals. The experiment consisted of one field trial established with E. dunnii in Greytown, KwaZulu-Natal. Twelve treatments (2 x 6 factorial) were replicated four times and laid out in a split-plot design, with the main factor of watering regime forming the whole plots, and pitting method the sub-plots. Differences in pit size, pit quality and tree performance were assessed. Pit dimensions and soil friability for the two pitting treatments were different, but pit volumes were similar (manually prepared pits = 4.7 L; motor-manually prepared pits = 4.4 L). Differences in pit soil moisture content were detected between dry planting (4.1%) and all other treatments (9.9%). Rainfall occurred in week 1 - 4 after planting (55.2 mm). Subsequently re-watering, relative to watering only at planting, was not beneficial. No significant growth differences occurred between the two pitting methods, nor was there any interaction between the main factors (pitting methods x watering regimes). Survival for dry planting (75%) was significantly lower than all the other treatments (92%), with a weakly significant difference in Biomass index (corrected) (BIc) at one year. Different pit qualities, determined by pitting method, will not significantly affect early eucalypt performance. However, the addition of water or hydrogel (as opposed to dry planting) will improve early eucalypt survival and growth. Eucalypt survival, growth and uniformity in South Africa continue to be impacted by an increase in mechanisation, changing climate conditions and the use of unskilled labour. It is therefore necessary to implement silvicultural practices which improve survival, growth and uniformity. Planting seedlings into good quality pits (regardless of pitting method) with water has shown to improve survival. It is also beneficial in terms of survival to plant larger (prime) plants at a deeper depth especially on sites with drought conditions. Despite all the establishment trials which have been implemented under controlled conditions, high mortality is still experienced and could be due to the lack of knowledge on the effects of plant quality and handling on post planting performance (particularly survival). In future, plant quality and handling in combination with various planting densities and the application of plant stress relievers should be considered to improve survival..
- Full Text:
- Date Issued: 2019
- Authors: Hechter, Ullrich
- Date: 2019
- Subjects: Forests and forestry -- South Africa -- KwaZulu-Natal , Forest nurseries -- South Africa -- KwaZulu Natal Forest management -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/40338 , vital:36142
- Description: Commercial forestry plantations in South Africa play an important role in the economy of the country, contributing 1.2% towards the gross domestic product, as well as with job creation in rural communities. Currently plantation forests occupy 1.1% (1.2 million hectares) of the South African land surface, of which 75 000 hectares are re-established each year. Eucalypts are the preferred species in the commercial forestry industry as they have the ability to grow fast. In addition, desirable characteristics from different eucalypt species can be combined to develop hybrids that can be used to further improve productivity. In South Africa, eucalypt plantations are mostly found in the warm temperate and sub-tropical zones situated in the KwaZulu-Natal and Mpumalanga Provinces. Various strategies are used to increase productivity and maximise site occupancy, including genetic tree improvement, site-species matching, optimising stand densities, management for risk (abiotic and biotic), as well as improved silviculture. Intensive silviculture is practiced by forest companies to maximise initial tree survival and reduce the time to canopy closure. This includes practices such as site preparation, slash management, tree protection, pruning and thinning, fertilisation and vegetation management treatments. Of the silvicultural aspects that are important during re-establishment, pitting, plant quality (plant size) and watering techniques/regimes have all been shown to influence short-term stand productivity. Despite research carried out on these individual components, recommendations as to best operating practices are varied and have changed over the years, with the application of these practices also varying across companies. Furthermore, there is limited published information related to the interaction between these practices, as well as any longer-term impacts of these factors on stand productivity. The objective of the present study was to gain an understanding of the impacts of pitting, plant quality (plant size), planting depth and watering on tree survival, growth and uniformity in South African Eucalyptus plantations. The study was carried out using three separate field trial series. In a first experiment, two field trials compared post-establishment performance of eucalypts planted using various pitting methods. The two trials were planted using Eucalyptus grandis and E. grandis x E. nitens on two contrasting sites, one at Greenhill in the KwaZulu-Natal Midlands and one at Vroegeveld in Mpumalanga. Four manual (notch, agricultural hoe, mattock, road pick) and three motor-manual heads (inverted A, Archimedes screw and Mondi-designed pitting head) were used to prepare and determine the effect of pit size/quality on tree survival, growth and uniformity. The notch pit implement created the smallest pit (1 L volume) compared to the other pitting implements (4 – 6 L volumes). For both trials, pitting method did not have a significant impact on the success of re-establishment or longer-term tree performance (6 yrs 7 mos at Greenhill and 3 yrs 7 mos at Vroegeveld). This indicates that for the sites and the species tested, all pitting implements could be considered viable alternatives. Other factors, such as operational costs, efficiency and ergonomics should be considered when selecting appropriate pitting methods together with tree performance. In a second experiment, three field trials were implemented to test three main factors: plant size (small and large); planting depth (standard and deep); and watering (dry and water planting). The eight treatments (2 x 2 x 2 factorial) were replicated four times and laid out in a randomised complete blocks design. The trials were established across a range of site types (Mt Home in Kwazulu-Natal, Vroegeveld in Mpumalanga and Trust in Zululand) in the summer rainfall region of South Africa using various eucalypt genera (E. dunnii, E. grandis x E. nitens and E. grandis x E. urophylla). Tree performance was assessed, with results up to four, six and seven years presented for the different sites. Results show that planting larger plants had the highest overall survival (x̄ = 81%) compared to smaller plants (x̄ = 58%), which also resulted in improved basal area and volume across all sites. Larger plants were able to tolerate a wider range of site conditions, thus providing an advantage for re-establishment. The cost-to-benefit of this however needs to be assessed, particularly in the context of current operational nursery standards. The benefits of deeper planting and applying water at planting are less clear, but appear to be beneficial under water stress conditions, such as on sandy sites when the weather is hot and dry. A third experiment tested the interaction between different methods of pit preparation (manual versus motor-manual), dry versus water planting, and re-watering at periodic intervals. The experiment consisted of one field trial established with E. dunnii in Greytown, KwaZulu-Natal. Twelve treatments (2 x 6 factorial) were replicated four times and laid out in a split-plot design, with the main factor of watering regime forming the whole plots, and pitting method the sub-plots. Differences in pit size, pit quality and tree performance were assessed. Pit dimensions and soil friability for the two pitting treatments were different, but pit volumes were similar (manually prepared pits = 4.7 L; motor-manually prepared pits = 4.4 L). Differences in pit soil moisture content were detected between dry planting (4.1%) and all other treatments (9.9%). Rainfall occurred in week 1 - 4 after planting (55.2 mm). Subsequently re-watering, relative to watering only at planting, was not beneficial. No significant growth differences occurred between the two pitting methods, nor was there any interaction between the main factors (pitting methods x watering regimes). Survival for dry planting (75%) was significantly lower than all the other treatments (92%), with a weakly significant difference in Biomass index (corrected) (BIc) at one year. Different pit qualities, determined by pitting method, will not significantly affect early eucalypt performance. However, the addition of water or hydrogel (as opposed to dry planting) will improve early eucalypt survival and growth. Eucalypt survival, growth and uniformity in South Africa continue to be impacted by an increase in mechanisation, changing climate conditions and the use of unskilled labour. It is therefore necessary to implement silvicultural practices which improve survival, growth and uniformity. Planting seedlings into good quality pits (regardless of pitting method) with water has shown to improve survival. It is also beneficial in terms of survival to plant larger (prime) plants at a deeper depth especially on sites with drought conditions. Despite all the establishment trials which have been implemented under controlled conditions, high mortality is still experienced and could be due to the lack of knowledge on the effects of plant quality and handling on post planting performance (particularly survival). In future, plant quality and handling in combination with various planting densities and the application of plant stress relievers should be considered to improve survival..
- Full Text:
- Date Issued: 2019
The Impact of socio-Economic and institutional factors on the Livelihoods of artisanal fisherfolk of Korsten, Gqeberha.
- Authors: Forbes-Liberty,Abigail
- Date: 2022-04
- Subjects: Fishing--Social aspects -- South Africa , Korsten-- Gqeberha
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55584 , vital:53334
- Description: his dissertation focuses on a relatively underrepresented group of the fishing industry: subsistence fisherfolk. By using a Sustainable Livelihoods Approach (SLA) and Community Capitals Framework (CCF) as a theoretical framework and interpretive lens, the purpose of this qualitative study is to explore the impact of socio-economic and institutional factors on the livelihoods of artisanal fisherfolk of Korsten, Gqeberha (formerly known as Port Elizabeth). By highlighting the socio-spatial implications of the forced removals of the past, this dissertation shows that legislative reforms should consider the population that they affect. Food security is a major issue on a global scale and South Africa is not impervious to food security concerns. This dissertation focuses on the negative impact that socio-economic climate and legislation has had on subsistence fisherfolk. Hunger and poverty eradication is one of the key goals of sustainable development. In this case, subsistence fishers faced legislative reforms at two distinct points in its tumultuous past, both of which had a detrimental impact on this sector of society's ability to support a healthy livelihood. This research fills a theoretical and practical gap in research regarding the current livelihoods, policies, and laws, as well as provides a deeper understanding of the socio-economic context of the subsistence fishing community of Korsten, Gqeberha. The SLA and CCF helps readers understand how subsistence fishers contribute to local livelihoods and integrate into the greater processes of the community. Further, exploration of the institutional policies limiting subsistence fishers helps understand decision making processes and laws in artisanal fisheries and the implications thereof. A snowball sampling method was used to recruit and enrol participants for this study. The sample size consisted of fourteen (14) participants consisting of eight (8) subsistence fishers and six (6) relatives of subsistence fisherfolk. Narrative analysis is a qualitative method that was conducted in this study. Participant observation and semi-structured interviews were conducted as the methods of data collection and analysed in ATLAS.ti 9 Qualitative Analysis Software. Most participants indicated that fishing plays an integral part of their lives. It contributes to and still ensures the food security in the families of Korsten. In addition, participants highlighted the constant legislative and socio-economic barriers as well as the social and personal benefits of fishing in the community. A key recommendation is made for policy-makers to be cognizant of subsistence fishers and to include this underrepresented group in decision making processes. , Thesis (MSc) -- Faculty of Science, Geosciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Forbes-Liberty,Abigail
- Date: 2022-04
- Subjects: Fishing--Social aspects -- South Africa , Korsten-- Gqeberha
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55584 , vital:53334
- Description: his dissertation focuses on a relatively underrepresented group of the fishing industry: subsistence fisherfolk. By using a Sustainable Livelihoods Approach (SLA) and Community Capitals Framework (CCF) as a theoretical framework and interpretive lens, the purpose of this qualitative study is to explore the impact of socio-economic and institutional factors on the livelihoods of artisanal fisherfolk of Korsten, Gqeberha (formerly known as Port Elizabeth). By highlighting the socio-spatial implications of the forced removals of the past, this dissertation shows that legislative reforms should consider the population that they affect. Food security is a major issue on a global scale and South Africa is not impervious to food security concerns. This dissertation focuses on the negative impact that socio-economic climate and legislation has had on subsistence fisherfolk. Hunger and poverty eradication is one of the key goals of sustainable development. In this case, subsistence fishers faced legislative reforms at two distinct points in its tumultuous past, both of which had a detrimental impact on this sector of society's ability to support a healthy livelihood. This research fills a theoretical and practical gap in research regarding the current livelihoods, policies, and laws, as well as provides a deeper understanding of the socio-economic context of the subsistence fishing community of Korsten, Gqeberha. The SLA and CCF helps readers understand how subsistence fishers contribute to local livelihoods and integrate into the greater processes of the community. Further, exploration of the institutional policies limiting subsistence fishers helps understand decision making processes and laws in artisanal fisheries and the implications thereof. A snowball sampling method was used to recruit and enrol participants for this study. The sample size consisted of fourteen (14) participants consisting of eight (8) subsistence fishers and six (6) relatives of subsistence fisherfolk. Narrative analysis is a qualitative method that was conducted in this study. Participant observation and semi-structured interviews were conducted as the methods of data collection and analysed in ATLAS.ti 9 Qualitative Analysis Software. Most participants indicated that fishing plays an integral part of their lives. It contributes to and still ensures the food security in the families of Korsten. In addition, participants highlighted the constant legislative and socio-economic barriers as well as the social and personal benefits of fishing in the community. A key recommendation is made for policy-makers to be cognizant of subsistence fishers and to include this underrepresented group in decision making processes. , Thesis (MSc) -- Faculty of Science, Geosciences, 2022
- Full Text:
- Date Issued: 2022-04
The impact of the slum upgrading approach on the livelihoods of scheme participants in Uganda : using the sustainable livelihoods framework
- Authors: Karungi, Doreen
- Date: 2020
- Subjects: Slums -- Public welfare -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48412 , vital:40874
- Description: International and local agencies recommend implementing slum upgrading projects in slum areas for slum improvement. However, with no model or guiding principles provided to slum upgrading project implementers on how to upgrade a slum, slum clearance and redevelopment are implemented rather than slum upgrading consequently projects fail to benefit the target group, slum dwellers. Data collection, took place in five areas in Uganda that implemented slum upgrading. In depth interviews were held with project beneficiaries, local council officials and association executives, and government officials at the Ministry of Lands, Housing and Urban Development. Field observation, and document analysis was carried out. Data analysis involved the use of the sustainable livelihoods framework. This study demonstrates that the slum upgrading approach adopted in Uganda exhibited low sustainability and undercut the sustainability of livelihoods of scheme participants. Slum dwellers faced vulnerabilities from loss of land, characterized by rights based actions resulting in minimal to no compensation or eviction and loss of existing livelihoods. Slum upgrading projects introduced new livelihood opportunities that were too few for slum dwellers, were not sustainable and ended during or with project implementation, leaving beneficiaries without employment or income opportunities. Increased vulnerability was observed as slum dwellers that did not benefit from the project were displaced to worse conditions while slum dwellers that benefitted, project beneficiaries remained poor and in debt, with project loans to repay. Although project beneficiaries were provided with access to assets, they were unable to draw on these to build their livelihoods. Some beneficiaries sold plots and project houses allocated to them and moved to adjacent slums, where they lived in worse conditions. At the time of the current research, good quality houses in the slum upgrading areas did not belong to the original beneficiaries old dilapidated structures were occupied by project beneficiaries. This study shows that income earning activities carried out at the time of the study were similar to those carried out prior to the introduction of slum upgrading in project areas and were destroyed during project implementation or banned by implementers. These activities were however carried out in incomplete houses, vacant plots, temporary structures in project areas and in adjacent swamps and forest. Generally, after completion of slum upgrading projects, project areas, adjacent swamps and forest were characterized by haphazard developments including: rentals, informal businesses, farming, brewing and distilling local alcohol used by beneficiaries to derive livelihoods, in other words, slums were recreated, a problem slum upgrading project implementers set out to solve - except in one study area where the project was implemented differently as a result of persist rights based actions.
- Full Text:
- Date Issued: 2020
- Authors: Karungi, Doreen
- Date: 2020
- Subjects: Slums -- Public welfare -- Uganda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48412 , vital:40874
- Description: International and local agencies recommend implementing slum upgrading projects in slum areas for slum improvement. However, with no model or guiding principles provided to slum upgrading project implementers on how to upgrade a slum, slum clearance and redevelopment are implemented rather than slum upgrading consequently projects fail to benefit the target group, slum dwellers. Data collection, took place in five areas in Uganda that implemented slum upgrading. In depth interviews were held with project beneficiaries, local council officials and association executives, and government officials at the Ministry of Lands, Housing and Urban Development. Field observation, and document analysis was carried out. Data analysis involved the use of the sustainable livelihoods framework. This study demonstrates that the slum upgrading approach adopted in Uganda exhibited low sustainability and undercut the sustainability of livelihoods of scheme participants. Slum dwellers faced vulnerabilities from loss of land, characterized by rights based actions resulting in minimal to no compensation or eviction and loss of existing livelihoods. Slum upgrading projects introduced new livelihood opportunities that were too few for slum dwellers, were not sustainable and ended during or with project implementation, leaving beneficiaries without employment or income opportunities. Increased vulnerability was observed as slum dwellers that did not benefit from the project were displaced to worse conditions while slum dwellers that benefitted, project beneficiaries remained poor and in debt, with project loans to repay. Although project beneficiaries were provided with access to assets, they were unable to draw on these to build their livelihoods. Some beneficiaries sold plots and project houses allocated to them and moved to adjacent slums, where they lived in worse conditions. At the time of the current research, good quality houses in the slum upgrading areas did not belong to the original beneficiaries old dilapidated structures were occupied by project beneficiaries. This study shows that income earning activities carried out at the time of the study were similar to those carried out prior to the introduction of slum upgrading in project areas and were destroyed during project implementation or banned by implementers. These activities were however carried out in incomplete houses, vacant plots, temporary structures in project areas and in adjacent swamps and forest. Generally, after completion of slum upgrading projects, project areas, adjacent swamps and forest were characterized by haphazard developments including: rentals, informal businesses, farming, brewing and distilling local alcohol used by beneficiaries to derive livelihoods, in other words, slums were recreated, a problem slum upgrading project implementers set out to solve - except in one study area where the project was implemented differently as a result of persist rights based actions.
- Full Text:
- Date Issued: 2020