A framework to evaluate usable security in online social networking
- Authors: Yeratziotis, Alexandros
- Date: 2011
- Subjects: Online social networks -- Security measures , Computer security , Data protection
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9807 , http://hdl.handle.net/10948/d1012933
- Description: It is commonly held in the literature that users find security and privacy difficult to comprehend. It is also acknowledged that most end-user applications and websites have built-in security and privacy features. Users are expected to interact with these in order to protect their personal information. However, security is generally a secondary goal for users. Considering the complexity associated with security in combination with the notion that it is not users’ primary task, it makes sense that users tend to ignore their security responsibilities. As a result, they make poor security-related decisions and, consequently, their personal information is at risk. Usable Security is the field that investigates these types of issue, focusing on the design of security and privacy features that are usable. In order to understand and appreciate the complexities that exist in the field of Usable Security, the research fields of Human-Computer Interaction and Information Security should be examined. Accordingly, the Information Security field is concerned with all aspects pertaining to the security and privacy of information, while the field of Human-Computer Interaction is concerned with the design, evaluation and implementation of interactive computing systems for human use. This research delivers a framework to evaluate Usable Security in online social networks. In this study, online social networks that are particular to the health domain were used as a case study and contributed to the development of a framework consisting of three components: a process, a validation tool and a Usable Security heuristic evaluation. There is no existing qualitative process that describes how one would develop and validate a heuristic evaluation. In this regard a heuristic evaluation is a usability inspection method that is used to evaluate the design of an interface for any usability violations in the field of Human-Computer Interaction. Therefore, firstly, a new process and a validation tool were required to be developed. Once this had been achieved, the process could then be followed to develop a new heuristic evaluation that is specific to Usable Security. In order to assess the validity of a new heuristic evaluation a validation tool is used. The development of tools that can improve the design of security and privacy features on end-user applications and websites in terms of their usability is critical, as this will ensure that the intended users experience them as usable and can utilise them effectively. The framework for evaluating Usable Security contributes to this objective in the context of online social networks.
- Full Text:
- Date Issued: 2011
- Authors: Yeratziotis, Alexandros
- Date: 2011
- Subjects: Online social networks -- Security measures , Computer security , Data protection
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9807 , http://hdl.handle.net/10948/d1012933
- Description: It is commonly held in the literature that users find security and privacy difficult to comprehend. It is also acknowledged that most end-user applications and websites have built-in security and privacy features. Users are expected to interact with these in order to protect their personal information. However, security is generally a secondary goal for users. Considering the complexity associated with security in combination with the notion that it is not users’ primary task, it makes sense that users tend to ignore their security responsibilities. As a result, they make poor security-related decisions and, consequently, their personal information is at risk. Usable Security is the field that investigates these types of issue, focusing on the design of security and privacy features that are usable. In order to understand and appreciate the complexities that exist in the field of Usable Security, the research fields of Human-Computer Interaction and Information Security should be examined. Accordingly, the Information Security field is concerned with all aspects pertaining to the security and privacy of information, while the field of Human-Computer Interaction is concerned with the design, evaluation and implementation of interactive computing systems for human use. This research delivers a framework to evaluate Usable Security in online social networks. In this study, online social networks that are particular to the health domain were used as a case study and contributed to the development of a framework consisting of three components: a process, a validation tool and a Usable Security heuristic evaluation. There is no existing qualitative process that describes how one would develop and validate a heuristic evaluation. In this regard a heuristic evaluation is a usability inspection method that is used to evaluate the design of an interface for any usability violations in the field of Human-Computer Interaction. Therefore, firstly, a new process and a validation tool were required to be developed. Once this had been achieved, the process could then be followed to develop a new heuristic evaluation that is specific to Usable Security. In order to assess the validity of a new heuristic evaluation a validation tool is used. The development of tools that can improve the design of security and privacy features on end-user applications and websites in terms of their usability is critical, as this will ensure that the intended users experience them as usable and can utilise them effectively. The framework for evaluating Usable Security contributes to this objective in the context of online social networks.
- Full Text:
- Date Issued: 2011
Post-impoundment population dynamics of non-native common carp Cyprinus Carpio in relation to two large native cyprinids in Lake Gariep, South Africa
- Authors: Winker, Henning
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Gariep Dam Carp -- South Africa -- Gariep Dam Fish populations -- South Africa -- Gariep Dam Fishes -- Physiology -- South Africa -- Gariep Dam Barbus aeneus -- South Africa -- Gariep Dam Mudfishes -- South Africa -- Gariep Dam Freshwater fishes -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5311 , http://hdl.handle.net/10962/d1005156
- Description: To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.
- Full Text:
- Date Issued: 2011
- Authors: Winker, Henning
- Date: 2011
- Subjects: Cyprinidae -- South Africa -- Gariep Dam Carp -- South Africa -- Gariep Dam Fish populations -- South Africa -- Gariep Dam Fishes -- Physiology -- South Africa -- Gariep Dam Barbus aeneus -- South Africa -- Gariep Dam Mudfishes -- South Africa -- Gariep Dam Freshwater fishes -- South Africa -- Gariep Dam
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5311 , http://hdl.handle.net/10962/d1005156
- Description: To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.
- Full Text:
- Date Issued: 2011
Using social marketing to bridge the gap between systematic conservation planning and implementation at the local government level
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
Thermal degradation of diamond compacts: a TEM investigation
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
An analysis of sources and predictability of geomagnetic storms
- Authors: Uwamahoro, Jean
- Date: 2011
- Subjects: Ionospheric storms Solar flares Interplanetary magnetic fields Magnetospheric substorms Coronal mass ejections Space environment Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5451 , http://hdl.handle.net/10962/d1005236
- Description: Solar transient eruptions are the main cause of interplanetary-magnetospheric disturbances leading to the phenomena known as geomagnetic storms. Eruptive solar events such as coronal mass ejections (CMEs) are currently considered the main cause of geomagnetic storms (GMS). GMS are strong perturbations of the Earth’s magnetic field that can affect space-borne and ground-based technological systems. The solar-terrestrial impact on modern technological systems is commonly known as Space Weather. Part of the research study described in this thesis was to investigate and establish a relationship between GMS (periods with Dst ≤ −50 nT) and their associated solar and interplanetary (IP) properties during solar cycle (SC) 23. Solar and IP geoeffective properties associated with or without CMEs were investigated and used to qualitatively characterise both intense and moderate storms. The results of this analysis specifically provide an estimate of the main sources of GMS during an average 11-year solar activity period. This study indicates that during SC 23, the majority of intense GMS (83%) were associated with CMEs, while the non-associated CME storms were dominant among moderate storms. GMS phenomena are the result of a complex and non-linear chaotic system involving the Sun, the IP medium, the magnetosphere and ionosphere, which make the prediction of these phenomena challenging. This thesis also explored the predictability of both the occurrence and strength of GMS. Due to their nonlinear driving mechanisms, the prediction of GMS was attempted by the use of neural network (NN) techniques, known for their non-linear modelling capabilities. To predict the occurrence of storms, a combination of solar and IP parameters were used as inputs in the NN model that proved to predict the occurrence of GMS with a probability of 87%. Using the solar wind (SW) and IP magnetic field (IMF) parameters, a separate NN-based model was developed to predict the storm-time strength as measured by the global Dst and ap geomagnetic indices, as well as by the locally measured K-index. The performance of the models was tested on data sets which were not part of the NN training process. The results obtained indicate that NN models provide a reliable alternative method for empirically predicting the occurrence and strength of GMS on the basis of solar and IP parameters. The demonstrated ability to predict the geoeffectiveness of solar and IP transient events is a key step in the goal towards improving space weather modelling and prediction.
- Full Text:
- Date Issued: 2011
- Authors: Uwamahoro, Jean
- Date: 2011
- Subjects: Ionospheric storms Solar flares Interplanetary magnetic fields Magnetospheric substorms Coronal mass ejections Space environment Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5451 , http://hdl.handle.net/10962/d1005236
- Description: Solar transient eruptions are the main cause of interplanetary-magnetospheric disturbances leading to the phenomena known as geomagnetic storms. Eruptive solar events such as coronal mass ejections (CMEs) are currently considered the main cause of geomagnetic storms (GMS). GMS are strong perturbations of the Earth’s magnetic field that can affect space-borne and ground-based technological systems. The solar-terrestrial impact on modern technological systems is commonly known as Space Weather. Part of the research study described in this thesis was to investigate and establish a relationship between GMS (periods with Dst ≤ −50 nT) and their associated solar and interplanetary (IP) properties during solar cycle (SC) 23. Solar and IP geoeffective properties associated with or without CMEs were investigated and used to qualitatively characterise both intense and moderate storms. The results of this analysis specifically provide an estimate of the main sources of GMS during an average 11-year solar activity period. This study indicates that during SC 23, the majority of intense GMS (83%) were associated with CMEs, while the non-associated CME storms were dominant among moderate storms. GMS phenomena are the result of a complex and non-linear chaotic system involving the Sun, the IP medium, the magnetosphere and ionosphere, which make the prediction of these phenomena challenging. This thesis also explored the predictability of both the occurrence and strength of GMS. Due to their nonlinear driving mechanisms, the prediction of GMS was attempted by the use of neural network (NN) techniques, known for their non-linear modelling capabilities. To predict the occurrence of storms, a combination of solar and IP parameters were used as inputs in the NN model that proved to predict the occurrence of GMS with a probability of 87%. Using the solar wind (SW) and IP magnetic field (IMF) parameters, a separate NN-based model was developed to predict the storm-time strength as measured by the global Dst and ap geomagnetic indices, as well as by the locally measured K-index. The performance of the models was tested on data sets which were not part of the NN training process. The results obtained indicate that NN models provide a reliable alternative method for empirically predicting the occurrence and strength of GMS on the basis of solar and IP parameters. The demonstrated ability to predict the geoeffectiveness of solar and IP transient events is a key step in the goal towards improving space weather modelling and prediction.
- Full Text:
- Date Issued: 2011
Dryland conservation areas, indigenous people, livelihoods and natural resource values in South Africa: the case of Kgalagadi Transfrontier Park
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
- Authors: Thondhlana, Gladman
- Date: 2011
- Subjects: Human ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions biodiversity conservation -- Kgalagadi Transfrontier Park (Botswana and South Africa) Arid regions agriculture -- Kgalagadi Transfrontier Park (Botswana and South Africa) Indigenous peoples -- Ecology -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources conservation areas -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Government policy -- Kgalagadi Transfrontier Park (Botswana and South Africa) Natural resources -- Kgalagadi Transfrontier Park (Botswana and South Africa) -- Management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4777 , http://hdl.handle.net/10962/d1011732
- Description: Contemporary conservation and development understanding in both policy and academic circles espouses that natural resources have a significant contribution to the livelihoods of local people and that knowledge of this can better foster conservation policies that are consistent with livelihood and ecological needs. This thesis is based on research conducted in the southern Kalahari region, South Africa among the San and Mier communities bordering Kgalagadi Transfrontier Park. It looks at the importance of natural resources to the San and Mier community groups and ascertains the extent of resource use and its value within broader livelihood portfolios. It also focuses on the cultural values of natural resources and interactions among institutions and actors and how these shape natural resource governance and livelihood outcomes. Overall, natural resources represent an important livelihood source contributing up to 32 % and 9 % of the total income of the San and Mier respectively or up to 46 % and 23 % if livestock incomes are included. However, the dependence on, diversification patterns and distribution of natural resource income vary substantially between and within the two communities. With regards to the cultural values attached to natural resources by the San and Mier, the findings show that these arise from an incredibly diverse and sometimes conflicting array of values that punctuate the two communities’ way of life and they are inextricably linked to resource use. Lastly, governance of natural resources in the co-managed Park and communitymanaged resettlement farms is characterised by complex institutional arrangements, compounded by the existence of multiple actors that have multiple and sometimes conflicting objectives – as shaped by different meanings and interpretations of natural resources. Heightened inter- and intra-community conflicts are common, notably resource use conflicts between the San and Mier and between the San ‘modernist’ and ‘traditionalist’ groups. This demonstrates that the communities’ livelihood dynamics in general and the dependence on natural resources in particular, are closely linked with ecological, economic and social factors including history, culture and present livelihood needs. By exploring the social-environment interactions, the study highlights the complexities and diversity of resource use for livelihoods that should be taken into consideration for both conservation and development policy interventions and research. The main argument of the study is that the contribution of natural resources to local livelihood portfolios in co- and community-managed areas, can be better understood through a consideration of cultural dynamics and institutional arrangements since these condition natural resource access, value and use.
- Full Text:
- Date Issued: 2011
Development of MgZnO-grown MOCVD for UV Photonic applications
- Authors: Talla, Kharouna
- Date: 2011
- Subjects: Photoluminescence , Photonics , Zinc oxide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10537 , http://hdl.handle.net/10948/d1012585 , Photoluminescence , Photonics , Zinc oxide
- Description: MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.
- Full Text:
- Date Issued: 2011
- Authors: Talla, Kharouna
- Date: 2011
- Subjects: Photoluminescence , Photonics , Zinc oxide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10537 , http://hdl.handle.net/10948/d1012585 , Photoluminescence , Photonics , Zinc oxide
- Description: MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.
- Full Text:
- Date Issued: 2011
Studies in marine quinone chemistry
- Authors: Sunassee, Suthananda Naidu
- Date: 2011
- Subjects: Quinone Marine natural products Marine invertebrates Marine pharmacology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4355 , http://hdl.handle.net/10962/d1005020
- Description: This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer
- Full Text:
- Date Issued: 2011
- Authors: Sunassee, Suthananda Naidu
- Date: 2011
- Subjects: Quinone Marine natural products Marine invertebrates Marine pharmacology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4355 , http://hdl.handle.net/10962/d1005020
- Description: This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer
- Full Text:
- Date Issued: 2011
Mutational analysis of the PacC binding sites within the aflR promoter in Aspergillus flavus
- Authors: Suleman, Essa
- Date: 2011
- Subjects: Mutation (Biology) , Genetic regulation , Proteins -- Synthesis , Microbiological synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10336 , http://hdl.handle.net/10948/d1012683 , Mutation (Biology) , Genetic regulation , Proteins -- Synthesis , Microbiological synthesis
- Description: It is generally known that media containing simple sugars (sucrose, glucose) and organic nitrogen sources (ammonium) when buffered to acidic pH stimulates aflatoxin production in Aspergillus flavus & A. parasiticus while lactose, nitrate and an alkaline pH inhibit aflatoxin biosynthesis. It has been shown that pH of the growth medium is the most important regulatory factor for aflatoxin biosynthesis since media containing stimulatory carbon and/or nitrogen sources (sucrose and ammonia) do not enhance aflatoxin (or sterigmatocystin) production at alkaline pH. RNA interference (in A. flavus) of the pH regulatory transcription factor, PacC, resulted in aflatoxin production under acidic and alkaline pH conditions whilst wildtype Aspergillus flavus produced aflatoxins only under acidic conditions. This conclusively proved that PacC negatively regulates aflatoxin production at alkaline pH in A. flavus. However the exact mechanism involved in PacC repression of aflatoxin biosynthesis at alkaline pH still remains unknown. The AflR protein is essential for expression of several genes in the aflatoxin biosynthetic cluster. In the current study, sequence analysis of the aflR promoter indicated the presence of two putative PacC binding sites within the aflR promoter of A. flavus 3357WT located at positions -162 and -487 bp from the start codon. The presence of the PacC binding sites in the aflR promoter indicated a possible link between aflR expression and PacC regulation under alkaline conditions. Thus, in this study, it was hypothesized that at alkaline pH, PacC inhibits aflR expression by binding to one or both of the PacC binding sites within the aflR promoter. This in turn, would result in inhibition of aflatoxin biosynthesis since expression of several aflatoxin biosynthetic pathway genes is dependent on activation by AflR. The aim and objective of this study was to test the validity of this hypothesis i.e. that at alkaline pH PacC binds to one or both of its recognition sites within the aflR promoter thereby inhibiting aflR expression which subsequently would result in inhibition of aflatoxin biosynthesis. This was done by first mutating each individual and then both PacC binding sites in the A. flavus 3357 aflR promoter via Single-Joint PCR (SJ-PCR) and fusing the wildtype and each mutated aflR promoter to the Green Fluorescent Protein (gfp) gene and the trpC terminator to yield a functional expression vector. These constructs were then transformed into A. flavus 3357.5. Positive transformants were confirmed to express GFP by fluorescence microscopy and spectrofluorometry. Quantification of GFP protein levels of the various transformants in this study indicated that PacC negatively regulated aflR promoter activity at alkaline pH. RT-qPCR was performed on positive transformants after growth on SLS medium at acidic and alkaline pH to determine if PacC negatively regulated aflR promoter activity at alkaline pH and to determine whether PacC binds preferentially to one or both recognition sites within the aflR promoter. RT-qPCR analysis suggest that PacC binds non-preferentially to both recognition sites within the aflR promoter on sucrose and lactose media at alkaline pH, although mutation of PacC binding site 2 results in a slightly higher expression compared to mutation of PacC binding site 1. Increasing the concentration of an aflatoxin conducive nitrogen source stimulated aflR promoter activity but this was not sufficient to overcome negative regulation by PacC. It is generally known that repression of aflR expression results in repression of aflatoxin biosynthesis irrespective of pH. The results of this study strongly suggest that PacC negatively regulates aflR promoter activity at alkaline pH by binding to one or both PacC recognition sites within the aflR promoter. Since aflR promoter activity is repressed by PacC at alkaline pH, this substantiates the hypothesis that PacC represses aflatoxin biosynthesis by inhibiting expression of aflR. Furthermore, the results of this study indicated that there may be some PacC protein present in the active form at acidic pH irrespective of the carbon source and nitrogen source used in the growth medium. RT-qPCR analysis indicated that any active PacC present at acidic pH may cause repression of the aflR promoter based on the position of the PacC binding site relative to the aflR start codon, although it appears that PacC may have a higher affinity for PacC binding site 2 (which is closer to the aflR start codon).
- Full Text:
- Date Issued: 2011
- Authors: Suleman, Essa
- Date: 2011
- Subjects: Mutation (Biology) , Genetic regulation , Proteins -- Synthesis , Microbiological synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10336 , http://hdl.handle.net/10948/d1012683 , Mutation (Biology) , Genetic regulation , Proteins -- Synthesis , Microbiological synthesis
- Description: It is generally known that media containing simple sugars (sucrose, glucose) and organic nitrogen sources (ammonium) when buffered to acidic pH stimulates aflatoxin production in Aspergillus flavus & A. parasiticus while lactose, nitrate and an alkaline pH inhibit aflatoxin biosynthesis. It has been shown that pH of the growth medium is the most important regulatory factor for aflatoxin biosynthesis since media containing stimulatory carbon and/or nitrogen sources (sucrose and ammonia) do not enhance aflatoxin (or sterigmatocystin) production at alkaline pH. RNA interference (in A. flavus) of the pH regulatory transcription factor, PacC, resulted in aflatoxin production under acidic and alkaline pH conditions whilst wildtype Aspergillus flavus produced aflatoxins only under acidic conditions. This conclusively proved that PacC negatively regulates aflatoxin production at alkaline pH in A. flavus. However the exact mechanism involved in PacC repression of aflatoxin biosynthesis at alkaline pH still remains unknown. The AflR protein is essential for expression of several genes in the aflatoxin biosynthetic cluster. In the current study, sequence analysis of the aflR promoter indicated the presence of two putative PacC binding sites within the aflR promoter of A. flavus 3357WT located at positions -162 and -487 bp from the start codon. The presence of the PacC binding sites in the aflR promoter indicated a possible link between aflR expression and PacC regulation under alkaline conditions. Thus, in this study, it was hypothesized that at alkaline pH, PacC inhibits aflR expression by binding to one or both of the PacC binding sites within the aflR promoter. This in turn, would result in inhibition of aflatoxin biosynthesis since expression of several aflatoxin biosynthetic pathway genes is dependent on activation by AflR. The aim and objective of this study was to test the validity of this hypothesis i.e. that at alkaline pH PacC binds to one or both of its recognition sites within the aflR promoter thereby inhibiting aflR expression which subsequently would result in inhibition of aflatoxin biosynthesis. This was done by first mutating each individual and then both PacC binding sites in the A. flavus 3357 aflR promoter via Single-Joint PCR (SJ-PCR) and fusing the wildtype and each mutated aflR promoter to the Green Fluorescent Protein (gfp) gene and the trpC terminator to yield a functional expression vector. These constructs were then transformed into A. flavus 3357.5. Positive transformants were confirmed to express GFP by fluorescence microscopy and spectrofluorometry. Quantification of GFP protein levels of the various transformants in this study indicated that PacC negatively regulated aflR promoter activity at alkaline pH. RT-qPCR was performed on positive transformants after growth on SLS medium at acidic and alkaline pH to determine if PacC negatively regulated aflR promoter activity at alkaline pH and to determine whether PacC binds preferentially to one or both recognition sites within the aflR promoter. RT-qPCR analysis suggest that PacC binds non-preferentially to both recognition sites within the aflR promoter on sucrose and lactose media at alkaline pH, although mutation of PacC binding site 2 results in a slightly higher expression compared to mutation of PacC binding site 1. Increasing the concentration of an aflatoxin conducive nitrogen source stimulated aflR promoter activity but this was not sufficient to overcome negative regulation by PacC. It is generally known that repression of aflR expression results in repression of aflatoxin biosynthesis irrespective of pH. The results of this study strongly suggest that PacC negatively regulates aflR promoter activity at alkaline pH by binding to one or both PacC recognition sites within the aflR promoter. Since aflR promoter activity is repressed by PacC at alkaline pH, this substantiates the hypothesis that PacC represses aflatoxin biosynthesis by inhibiting expression of aflR. Furthermore, the results of this study indicated that there may be some PacC protein present in the active form at acidic pH irrespective of the carbon source and nitrogen source used in the growth medium. RT-qPCR analysis indicated that any active PacC present at acidic pH may cause repression of the aflR promoter based on the position of the PacC binding site relative to the aflR start codon, although it appears that PacC may have a higher affinity for PacC binding site 2 (which is closer to the aflR start codon).
- Full Text:
- Date Issued: 2011
Identity, belonging and ecological crisis in South African speculative fiction
- Authors: Steenkamp, Elzette Lorna
- Date: 2011
- Subjects: South African fiction -- History and criticism Identity (Philosophical concept) in literature Group identity in literature Ecology in literature Science fiction, South African -- History and criticism Fantasy fiction, South African -- History and criticism Ecofiction -- History and criticism Ecocriticism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2219 , http://hdl.handle.net/10962/d1002262
- Description: This study examines a range of South African speculative novels which situate their narratives in futuristic or ‘alternative’ milieus, exploring how these narratives not only address identity formation in a deeply divided and rapidly changing society, but also the ways in which human beings place themselves in relation to Nature and form notions of ‘ecological’ belonging. It offers close readings of these speculative narratives in order to investigate the ways in which they evince concerns which are rooted in the natural, social and political landscapes which inform them. Specific attention is paid to the texts’ treatment of the intertwined issues of identity, belonging and ecological crisis. This dissertation draws on the fields of Ecocriticism, Postcolonial Studies and Science Fiction Studies, and assumes a culturally specific approach to primary texts while investigating possible cross-cultural commonalities between Afrikaans and English speculative narratives, as well as the cross-fertilisation of global SF/speculative features. It is suggested that South African speculative fiction presents a socio-historically situated, rhizomatic approach to ecology – one that is attuned to the tension between humanistic- and ecological concerns.
- Full Text:
- Date Issued: 2011
- Authors: Steenkamp, Elzette Lorna
- Date: 2011
- Subjects: South African fiction -- History and criticism Identity (Philosophical concept) in literature Group identity in literature Ecology in literature Science fiction, South African -- History and criticism Fantasy fiction, South African -- History and criticism Ecofiction -- History and criticism Ecocriticism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2219 , http://hdl.handle.net/10962/d1002262
- Description: This study examines a range of South African speculative novels which situate their narratives in futuristic or ‘alternative’ milieus, exploring how these narratives not only address identity formation in a deeply divided and rapidly changing society, but also the ways in which human beings place themselves in relation to Nature and form notions of ‘ecological’ belonging. It offers close readings of these speculative narratives in order to investigate the ways in which they evince concerns which are rooted in the natural, social and political landscapes which inform them. Specific attention is paid to the texts’ treatment of the intertwined issues of identity, belonging and ecological crisis. This dissertation draws on the fields of Ecocriticism, Postcolonial Studies and Science Fiction Studies, and assumes a culturally specific approach to primary texts while investigating possible cross-cultural commonalities between Afrikaans and English speculative narratives, as well as the cross-fertilisation of global SF/speculative features. It is suggested that South African speculative fiction presents a socio-historically situated, rhizomatic approach to ecology – one that is attuned to the tension between humanistic- and ecological concerns.
- Full Text:
- Date Issued: 2011
Sedimentology of plio-pleistocene gravel barrier deposits in the palaeo-Orange River mouth, Namibia : depositional history and diamond mineralisation
- Authors: Spaggiari, Renato Igino
- Date: 2011 , 2013-08-19
- Subjects: Diamond mines and mining -- Namibia Sediments (Geology) -- South Africa and Namibia -- Orange River Estuary Diamond deposits -- Namibia Orange River Estuary (Namibia and South Africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4927 , http://hdl.handle.net/10962/d1004636
- Description: The largest known marine diamond placer, the Namibian mega-placer, lies along the Atlantic coast of south-western Africa from the Orange River mouth 1,000 km northwards to the Namibian-Angolan border. The most economically viable portion of the Namibian mega-placer (>75 million carats recovered at >95% gem quality) comprises onshore and offshore marine deposits that are developed within ∼100km of the Orange River outfall. For much of the Cainozoic, this long-lived fluvial system has been the main conduit transporting diamonds from kimberlitic and secondary sources in the cratonic hinterland of southern Africa to the Atlantic shelf that has been neutrally buoyant over this period. Highly energetic marine processes, driven in part, by southerly winds with an attendant northward-directed longshore drift, have generated terminal placers that are preserved both onshore and offshore. This study, through detailed field sedimentological and diamond analyses, investigates the development and mineralisation of gravel barrier deposits within the ancestral Orange River mouth area during a major ∼30 m regional transgression ('30 m Package') in the Late Pliocene. At that time, diamond supply from this fluvial conduit was minimal, yet the corresponding onshore marine deposits to the north of the Orange River mouth were significantly diamond enriched, enabling large-scale alluvial diamond mining to take place for over 75 years. Of the entire coastline of south-western Africa, the most complete accumulation of the '30 m Package' is preserved within the palaeo-Orange River mouth as barrier spit and barrier beach deposits. Arranged vertically and laterally in a 16m thick succession, these are deposits of: (1) intertidal beach, (2) lagoon and washover, (3) tidal inlet and spit recurve and (4) storm-dominated subtidal settings. These were parts of larger barrier features, the bulk of which are preserved as highstand deposits that are diamond-bearing with varying, but generally low grades (<13 stones (diamonds) per hundred tons, spht). Intertidal beach and spit recurve deposits have higher economic grades (12-13 spht) due to the energetic sieving and mobile trapping mechanisms associated with their emplacement. In contrast, the less reworked and more sandy subtidal, tidal inlet and washover deposits have un-economic grades (<2 spht). Despite these low grades, the barrier deposits have the largest average stone (diamond) size (1-2 carats/stone, cts/stn) of the entire Namibian mega-placer, given their proximity to the ancestral Orange River outfall. This study demonstrates that barrier shoreline evolution at the fluvial/marine interface was controlled by: (1) a strong and coarse fluvial sediment supply that sustained shoreline growth on a highly energetic coast, (2) accommodation space facilitating sediment preservation and (3) short-duration, high-frequency sea-level cycles superimposed on the∼30 m regional transgression, promoting hierarchal stacking of progradational deposits. During these sea-level fluctuations, diamonds were 'farmed' from older, shelf sequences in the offshore and driven landward to accumulate in '30 m Package' highstand barrier deposits. In spite of the large supply of diamonds, their retention in these deposits was poor due to an incompetent footwall of ancestral Orange River mouth sediment and the inherent cobble-boulder size of the barrier gravels. Thus the principal process controlling diamond entrapment in these barrier deposits was kinetic sieving in a coarse-grained framework. Consequently, at the marine/fluvial interface and down-drift for ∼5 km, larger diamonds (1-2 cts/stn) were retained in low-grade (<2 spht), coarse-gravel barrier shorelines. Smaller diamonds (mostly < I cts/stn) were rejected into the northward-driven littoral sediments and further size-sorted along ∼95 km of Namibian coast to accumulate in finer, high-grade beach placers (> 100 spht) where bedrock footwall promoted such high concentrations. The gravel-dominated palaeo-Orange River mouth is considered to be the ' heart' of the Namibian mega-placer, controlling sediment and diamond supply to the littoral zone further north. Although coarse gravel is retained at the river mouth, the incompetence of this highly energetic setting to trap diamonds renders it sub-economic. This ineffectiveness at the fluvial/marine interface is thus fundamental in enriching the coastal tract farther down-drift and developing highly economic coastal placers along the Atlantic coast of south-western Africa. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2011
- Authors: Spaggiari, Renato Igino
- Date: 2011 , 2013-08-19
- Subjects: Diamond mines and mining -- Namibia Sediments (Geology) -- South Africa and Namibia -- Orange River Estuary Diamond deposits -- Namibia Orange River Estuary (Namibia and South Africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4927 , http://hdl.handle.net/10962/d1004636
- Description: The largest known marine diamond placer, the Namibian mega-placer, lies along the Atlantic coast of south-western Africa from the Orange River mouth 1,000 km northwards to the Namibian-Angolan border. The most economically viable portion of the Namibian mega-placer (>75 million carats recovered at >95% gem quality) comprises onshore and offshore marine deposits that are developed within ∼100km of the Orange River outfall. For much of the Cainozoic, this long-lived fluvial system has been the main conduit transporting diamonds from kimberlitic and secondary sources in the cratonic hinterland of southern Africa to the Atlantic shelf that has been neutrally buoyant over this period. Highly energetic marine processes, driven in part, by southerly winds with an attendant northward-directed longshore drift, have generated terminal placers that are preserved both onshore and offshore. This study, through detailed field sedimentological and diamond analyses, investigates the development and mineralisation of gravel barrier deposits within the ancestral Orange River mouth area during a major ∼30 m regional transgression ('30 m Package') in the Late Pliocene. At that time, diamond supply from this fluvial conduit was minimal, yet the corresponding onshore marine deposits to the north of the Orange River mouth were significantly diamond enriched, enabling large-scale alluvial diamond mining to take place for over 75 years. Of the entire coastline of south-western Africa, the most complete accumulation of the '30 m Package' is preserved within the palaeo-Orange River mouth as barrier spit and barrier beach deposits. Arranged vertically and laterally in a 16m thick succession, these are deposits of: (1) intertidal beach, (2) lagoon and washover, (3) tidal inlet and spit recurve and (4) storm-dominated subtidal settings. These were parts of larger barrier features, the bulk of which are preserved as highstand deposits that are diamond-bearing with varying, but generally low grades (<13 stones (diamonds) per hundred tons, spht). Intertidal beach and spit recurve deposits have higher economic grades (12-13 spht) due to the energetic sieving and mobile trapping mechanisms associated with their emplacement. In contrast, the less reworked and more sandy subtidal, tidal inlet and washover deposits have un-economic grades (<2 spht). Despite these low grades, the barrier deposits have the largest average stone (diamond) size (1-2 carats/stone, cts/stn) of the entire Namibian mega-placer, given their proximity to the ancestral Orange River outfall. This study demonstrates that barrier shoreline evolution at the fluvial/marine interface was controlled by: (1) a strong and coarse fluvial sediment supply that sustained shoreline growth on a highly energetic coast, (2) accommodation space facilitating sediment preservation and (3) short-duration, high-frequency sea-level cycles superimposed on the∼30 m regional transgression, promoting hierarchal stacking of progradational deposits. During these sea-level fluctuations, diamonds were 'farmed' from older, shelf sequences in the offshore and driven landward to accumulate in '30 m Package' highstand barrier deposits. In spite of the large supply of diamonds, their retention in these deposits was poor due to an incompetent footwall of ancestral Orange River mouth sediment and the inherent cobble-boulder size of the barrier gravels. Thus the principal process controlling diamond entrapment in these barrier deposits was kinetic sieving in a coarse-grained framework. Consequently, at the marine/fluvial interface and down-drift for ∼5 km, larger diamonds (1-2 cts/stn) were retained in low-grade (<2 spht), coarse-gravel barrier shorelines. Smaller diamonds (mostly < I cts/stn) were rejected into the northward-driven littoral sediments and further size-sorted along ∼95 km of Namibian coast to accumulate in finer, high-grade beach placers (> 100 spht) where bedrock footwall promoted such high concentrations. The gravel-dominated palaeo-Orange River mouth is considered to be the ' heart' of the Namibian mega-placer, controlling sediment and diamond supply to the littoral zone further north. Although coarse gravel is retained at the river mouth, the incompetence of this highly energetic setting to trap diamonds renders it sub-economic. This ineffectiveness at the fluvial/marine interface is thus fundamental in enriching the coastal tract farther down-drift and developing highly economic coastal placers along the Atlantic coast of south-western Africa. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2011
Modelling the relationship between flow and water quality in South African rivers
- Authors: Slaughter, Andrew Robert
- Date: 2011
- Subjects: Water quality -- Measurement -- South Africa Water quality -- Mathematical models -- South Africa Streamflow -- South Africa Stream measurements -- Mathematical models -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6039 , http://hdl.handle.net/10962/d1006196
- Description: The National Water Act (Act 36 of 1998) provides for an ecological Reserve as the quantity (flow) and quality of water needed to protect aquatic ecosystems. While there are methods available to quantify the ecological Reserve in terms of flow, methods of linking flow to water quality are lacking. Therefore, the research presented in this thesis investigated various modelling techniques to estimate the effect of flow on water quality. The aims of the research presented in this thesis were: Aim 1: Can the relationship between flow and water quality be accurately represented by simple statistical models? Aim 2: Can relatively simple models accurately represent the relationship between flow and water quality? Aim 3: Can the effect of diffuse sources be omitted from a water quality model and still obtain realistic simulations, and if so under what conditions? Aim 4: Can models that solely use historical monitoring data, accurately represent the relationships between flow and water quality? In Chapter 3, simple Q-C regressions of flow and water quality were investigated using Department of Water Affairs (DWA) historical monitoring data. It was found that while flow versus salinity regressions gave good regression fits in many cases, the Q-C regression approach is limited. A mechanistic/statistical model that attempted to estimate the point and diffuse signatures of nutrients in response to flow was developed in Chapter 4 using DWA historical monitoring data. The model was verified as accurate in certain case studies using observed point loading information. In Chapter 5, statistical models that link land cover information to diffuse nutrient signatures in response to flow using DWA historical data were developed. While the model estimations are uncertain due to a lack of data, they do provide an estimation of the diffuse signature within catchments where there is flow and land cover information available. Chapter 6 investigates the extension of an existing mass-balance salinity model to estimate the effect of saline irrigation return flow on in-stream salinity. The model gave accurate salinity estimates for a low order stream with little or no irrigation within its catchment, and for a permanently flowing river within a catchment used extensively for irrigation. Chapter 7 investigated a modelling method to estimate the reaction coefficients involved in nitrification using only DWA historical monitoring data. Here, the model used flow information to estimate the residence time of nutrients within the studied river reaches. While the model obtained good estimations of nitrification for the data it was applied to, very few DWA data sets were suitable for the model. Chapter 8 investigated the ability of the in-stream model QUAL2K to estimate nutrient concentrations downstream of point and diffuse inputs of nutrients. It was found that the QUAL2K model can give accurate results in cases where point sources dominate the total nutrient inputs into a river. However, the QUAL2K simulations are too uncertain in cases where there are large diffuse source inputs of nutrients as the load of the diffuse inputs is difficult to measure in the field. This research highlights the problem of data scarcity in terms of temporal resolution as well as the range of constituents measured within DWA historical monitoring data for water quality. This thesis in addition argues that the approach of applying a number of models is preferable to applying one model to investigate the research aims, as particular models would be suited to particular circumstances, and the development of new models allowed the research aims of this thesis to be explored more thoroughly. It is also argued that simpler models that simulate a few key processes that explain the variation in observed data, are more suitable for implementing Integrated Water Resource Management (IWRM) than large comprehensive water quality models. From this research, it is clear that simple statistical models are not adequate for modelling the relationship between flow and water quality, however, relatively simple mechanistic models that simulate a limited number of processes and water quality variables, can provide accurate representations of this relationship. Under conditions where diffuse sources are not a major factor within a catchment, models that omit diffuse sources can obtain realistic simulations of the relationship between flow and water quality. Most of the models investigated in this thesis demonstrate that accurate simulations of the relationships between flow and water quality can be obtained using solely historical monitoring data.
- Full Text:
- Date Issued: 2011
- Authors: Slaughter, Andrew Robert
- Date: 2011
- Subjects: Water quality -- Measurement -- South Africa Water quality -- Mathematical models -- South Africa Streamflow -- South Africa Stream measurements -- Mathematical models -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6039 , http://hdl.handle.net/10962/d1006196
- Description: The National Water Act (Act 36 of 1998) provides for an ecological Reserve as the quantity (flow) and quality of water needed to protect aquatic ecosystems. While there are methods available to quantify the ecological Reserve in terms of flow, methods of linking flow to water quality are lacking. Therefore, the research presented in this thesis investigated various modelling techniques to estimate the effect of flow on water quality. The aims of the research presented in this thesis were: Aim 1: Can the relationship between flow and water quality be accurately represented by simple statistical models? Aim 2: Can relatively simple models accurately represent the relationship between flow and water quality? Aim 3: Can the effect of diffuse sources be omitted from a water quality model and still obtain realistic simulations, and if so under what conditions? Aim 4: Can models that solely use historical monitoring data, accurately represent the relationships between flow and water quality? In Chapter 3, simple Q-C regressions of flow and water quality were investigated using Department of Water Affairs (DWA) historical monitoring data. It was found that while flow versus salinity regressions gave good regression fits in many cases, the Q-C regression approach is limited. A mechanistic/statistical model that attempted to estimate the point and diffuse signatures of nutrients in response to flow was developed in Chapter 4 using DWA historical monitoring data. The model was verified as accurate in certain case studies using observed point loading information. In Chapter 5, statistical models that link land cover information to diffuse nutrient signatures in response to flow using DWA historical data were developed. While the model estimations are uncertain due to a lack of data, they do provide an estimation of the diffuse signature within catchments where there is flow and land cover information available. Chapter 6 investigates the extension of an existing mass-balance salinity model to estimate the effect of saline irrigation return flow on in-stream salinity. The model gave accurate salinity estimates for a low order stream with little or no irrigation within its catchment, and for a permanently flowing river within a catchment used extensively for irrigation. Chapter 7 investigated a modelling method to estimate the reaction coefficients involved in nitrification using only DWA historical monitoring data. Here, the model used flow information to estimate the residence time of nutrients within the studied river reaches. While the model obtained good estimations of nitrification for the data it was applied to, very few DWA data sets were suitable for the model. Chapter 8 investigated the ability of the in-stream model QUAL2K to estimate nutrient concentrations downstream of point and diffuse inputs of nutrients. It was found that the QUAL2K model can give accurate results in cases where point sources dominate the total nutrient inputs into a river. However, the QUAL2K simulations are too uncertain in cases where there are large diffuse source inputs of nutrients as the load of the diffuse inputs is difficult to measure in the field. This research highlights the problem of data scarcity in terms of temporal resolution as well as the range of constituents measured within DWA historical monitoring data for water quality. This thesis in addition argues that the approach of applying a number of models is preferable to applying one model to investigate the research aims, as particular models would be suited to particular circumstances, and the development of new models allowed the research aims of this thesis to be explored more thoroughly. It is also argued that simpler models that simulate a few key processes that explain the variation in observed data, are more suitable for implementing Integrated Water Resource Management (IWRM) than large comprehensive water quality models. From this research, it is clear that simple statistical models are not adequate for modelling the relationship between flow and water quality, however, relatively simple mechanistic models that simulate a limited number of processes and water quality variables, can provide accurate representations of this relationship. Under conditions where diffuse sources are not a major factor within a catchment, models that omit diffuse sources can obtain realistic simulations of the relationship between flow and water quality. Most of the models investigated in this thesis demonstrate that accurate simulations of the relationships between flow and water quality can be obtained using solely historical monitoring data.
- Full Text:
- Date Issued: 2011
Time series models for paired comparisons
- Authors: Sjolander, Morne Rowan
- Date: 2011
- Subjects: Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10577 , http://hdl.handle.net/10948/d1012858
- Description: The method of paired comparisons is seen as a technique used to rank a set of objects with respect to an abstract or immeasurable property. To do this, the objects get to be compared two at a time. The results are input into a model, resulting in numbers known as weights being assigned to the objects. The weights are then used to rank the objects. The method of paired comparisons was first used for psychometric investigations. Various other applications of the method are also present, for example economic applications, and applications in sports statistics. This study involves taking paired comparison models and making them time-dependent. Not much research has been done in this area. Three new time series models for paired comparisons are created. Simulations are done to support the evidence obtained, and theoretical as well as practical examples are given to illustrate the results and to verify the efficiency of the new models. A literature study is given on the method of paired comparisons, as well as on the areas in which we apply our models. Our first two time series models for paired comparisons are the Linear-Trend Bradley- Terry Model and the Sinusoidal Bradley-Terry Model. We use the maximum likelihood approach to solve these models. We test our models using exact and randomly simulated data for various time periods and various numbers of objects. We adapt the Linear-Trend Bradley-Terry Model and received our third time series model for paired comparisons, the Log Linear-Trend Bradley-Terry Model. The daily maximum and minimum temperatures were received for Port Elizabeth, Uitenhage and Coega for 2005 until 2009. To evaluate the performance of the Linear-Trend Bradley-Terry Model and the Sinusoidal Bradley-Terry Model on estimating missing temperature data, we artificially remove observations of temperature from Coega’s temperature dataset for 2006 until 2008, and use various forms of these models to estimate the missing data points. The exchange rates for 2005 until 2008 between the following currencies: the Rand, Dollar, Euro, Pound and Yen, were obtained and various forms of our Log Linear-Trend Bradley-Terry Model are used to forecast the exchange rate for one day ahead for each month in 2006 until 2008. One of the features of this study is that we apply our time series models for paired comparisons to areas which comprise non-standard paired comparisons; and we want to encourage the use of the method of paired comparisons in a broader sense than what it is traditionally used for. The results of this study can be used in various other areas, like for example, in sports statistics, to rank the strength of sports players and predict their future scores; in Physics, to calculate weather risks of electricity generation, particularly risks related to nuclear power plants, and so forth, as well as in many other areas. It is hoped that this research will open the door to much more research in combining time series analysis with the method of paired comparisons.
- Full Text:
- Date Issued: 2011
- Authors: Sjolander, Morne Rowan
- Date: 2011
- Subjects: Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10577 , http://hdl.handle.net/10948/d1012858
- Description: The method of paired comparisons is seen as a technique used to rank a set of objects with respect to an abstract or immeasurable property. To do this, the objects get to be compared two at a time. The results are input into a model, resulting in numbers known as weights being assigned to the objects. The weights are then used to rank the objects. The method of paired comparisons was first used for psychometric investigations. Various other applications of the method are also present, for example economic applications, and applications in sports statistics. This study involves taking paired comparison models and making them time-dependent. Not much research has been done in this area. Three new time series models for paired comparisons are created. Simulations are done to support the evidence obtained, and theoretical as well as practical examples are given to illustrate the results and to verify the efficiency of the new models. A literature study is given on the method of paired comparisons, as well as on the areas in which we apply our models. Our first two time series models for paired comparisons are the Linear-Trend Bradley- Terry Model and the Sinusoidal Bradley-Terry Model. We use the maximum likelihood approach to solve these models. We test our models using exact and randomly simulated data for various time periods and various numbers of objects. We adapt the Linear-Trend Bradley-Terry Model and received our third time series model for paired comparisons, the Log Linear-Trend Bradley-Terry Model. The daily maximum and minimum temperatures were received for Port Elizabeth, Uitenhage and Coega for 2005 until 2009. To evaluate the performance of the Linear-Trend Bradley-Terry Model and the Sinusoidal Bradley-Terry Model on estimating missing temperature data, we artificially remove observations of temperature from Coega’s temperature dataset for 2006 until 2008, and use various forms of these models to estimate the missing data points. The exchange rates for 2005 until 2008 between the following currencies: the Rand, Dollar, Euro, Pound and Yen, were obtained and various forms of our Log Linear-Trend Bradley-Terry Model are used to forecast the exchange rate for one day ahead for each month in 2006 until 2008. One of the features of this study is that we apply our time series models for paired comparisons to areas which comprise non-standard paired comparisons; and we want to encourage the use of the method of paired comparisons in a broader sense than what it is traditionally used for. The results of this study can be used in various other areas, like for example, in sports statistics, to rank the strength of sports players and predict their future scores; in Physics, to calculate weather risks of electricity generation, particularly risks related to nuclear power plants, and so forth, as well as in many other areas. It is hoped that this research will open the door to much more research in combining time series analysis with the method of paired comparisons.
- Full Text:
- Date Issued: 2011
Exploring opportunities for action competence development through learners' participation in waste management activities in selected primary schools in Botswana
- Authors: Silo, Nthalivi
- Date: 2011
- Subjects: Environmental education -- Botswana -- Case studies Environmental education -- Study and teaching (Primary) -- Botswana -- Case studies Environmental education -- Activity programs -- Botswana -- Case studies Student-centered learning -- Botswana -- Case studies Refuse and refuse disposal -- Environmental aspects -- Botswana -- Case studies Active learning -- Botswana -- Case studies Competency-based education -- Botswana -- Case studies Teacher-student relationships -- Botswana -- Case studies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1541 , http://hdl.handle.net/10962/d1003423
- Description: The broader aim of this study is to probe participation of learners in waste management activities in selected primary schools in Botswana and through these activities, explore opportunities for action competence development. The study starts by tracing and outlining the socio-ecological challenges that confront children and the historical background of learner-centred education which gave rise to an emphasis on learner participation in Botswana education policy. It then maps out the development of children's participation in the global, regional and Botswana contexts by tracing the development of environmental education from early ecological and issue resolution goals of environmental education to sustainable development discourses. The focus is on policy issues and how learner participation has been represented and implemented in environmental education. The study then probes the rhetorical and normalised emphases on participation, and seeks further insight into how learners can be engaged in participatory learning processes that are meaningful, purposeful and that broaden their action competence and civic agency. The study uses the Cultural Historical Activity Theory (CHAT) methodology to build a picture of waste management activity systems in primary schools and to bring to the surface contradictions and tensions in learner participation in these activity systems. These contradictions are used to open up expansive learning participatory processes with learners using the Danish action competence framework. The expansive learning process uses action competence models that provide potential for transformative participation with learners, and new and different opportunities for learner participation. Case study research was used and conducted in the south eastern region of Botswana in three primary schools in three contexts, namely urban, peri-urban and rural. The data was largely generated through focus group interviews during workshops with children and observations of waste management activities. These two methods formed the main data generation methods. They were complemented by semi-structured interviews with teachers, and other actors in the waste management activities, learners' activities and work, learners' notes, photographs and children's drawings as well as show-and-tell explanations by learners. Content analysis and the abductive mode of inference were used to analyse data in all three case studies. Findings from the first phase of the study reveal that participation of learners in waste management activities was largely teacher-directed. This resulted in a mis-match between teachers views of what practices are necessary and important, and children's views of what practices are necessary and important in and for environmental education. Due to culturally and historically formed views of environmental education, the study reveals that teachers wanted children to pick up litter, and this was their primary environmental education concern. Learners on the other hand, identified sanitation management in the school toilets as their primary waste management concern. Teachers had not considered this an environmental education concern. Using the action competence expansive learning approach, the second phase of the study addressed this tension by opening up dialogue between teachers and learners and amongst the learners themselves through an expansive learning process supporting children's participation and action competence development. Through this teacher-learner dialogical engagement, a broader range of possibilities became available and ideas around participation were radically changed. The study further reveals that the achievement of this open dialogue provided for a better relationship within the school community. And with improved communication came better ideas to solve waste management issues that the community still face on a daily basis, such as too much litter. Newly devised solutions were practical and had a broader impact than the initial ones that teachers had always focussed on. They included mobilising the maintenance of toilets, landscaping the school premises and even re-contextualising the litter management that had always caused tensions between learners and teachers. Children seemed to be developing not only a better understanding of the environment, but also developing the ability to resolve conflict amongst themselves and with their elders. By engaging in dialogue with children, they became co-catalysts for change in the school community. This study shows that if children's participation is taken seriously, and if opportunities for dialogue exist between teachers and children, positive changes for a healthier environment can be created in schools. It reveals that children also appeared to be feeling more confident and more equipped to consider changes in their environment outside of the school community. The study further shows that participation in environmental education involves more than cognitive changes as proposed in earlier constructivist literature; it includes in-depth engagement with socio-cultural dynamics and histories in the school context, such as the cultural histories of teachers, schooling and authority structures in the cultural community of the school. The study recommends that there is need to strengthen Teacher Education programmes to develop teaching practices and support for teachers to identify ways of engaging learners' views on issues in the school in open, dialogical ways. Such Teacher Education programmes should deepen teachers' understandings of learners' zone of proximal development (ZPD), demonstrating how dialogue and scaffolding are part of a teacher's role in supporting learning. This is shown in the three case studies that form part of this study. Finally, the study also deepens insights of using the Cultural Historical Activity theory (CHAT) to shed light on issues surrounding learner participation within the socio-cultural and historical environmental education contexts of the schools. The action competence models used in the study provide a tool for revealing forms of learner participation. This tool can be used for critical reflections and monitoring of teaching practices in schools.
- Full Text:
- Date Issued: 2011
- Authors: Silo, Nthalivi
- Date: 2011
- Subjects: Environmental education -- Botswana -- Case studies Environmental education -- Study and teaching (Primary) -- Botswana -- Case studies Environmental education -- Activity programs -- Botswana -- Case studies Student-centered learning -- Botswana -- Case studies Refuse and refuse disposal -- Environmental aspects -- Botswana -- Case studies Active learning -- Botswana -- Case studies Competency-based education -- Botswana -- Case studies Teacher-student relationships -- Botswana -- Case studies
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1541 , http://hdl.handle.net/10962/d1003423
- Description: The broader aim of this study is to probe participation of learners in waste management activities in selected primary schools in Botswana and through these activities, explore opportunities for action competence development. The study starts by tracing and outlining the socio-ecological challenges that confront children and the historical background of learner-centred education which gave rise to an emphasis on learner participation in Botswana education policy. It then maps out the development of children's participation in the global, regional and Botswana contexts by tracing the development of environmental education from early ecological and issue resolution goals of environmental education to sustainable development discourses. The focus is on policy issues and how learner participation has been represented and implemented in environmental education. The study then probes the rhetorical and normalised emphases on participation, and seeks further insight into how learners can be engaged in participatory learning processes that are meaningful, purposeful and that broaden their action competence and civic agency. The study uses the Cultural Historical Activity Theory (CHAT) methodology to build a picture of waste management activity systems in primary schools and to bring to the surface contradictions and tensions in learner participation in these activity systems. These contradictions are used to open up expansive learning participatory processes with learners using the Danish action competence framework. The expansive learning process uses action competence models that provide potential for transformative participation with learners, and new and different opportunities for learner participation. Case study research was used and conducted in the south eastern region of Botswana in three primary schools in three contexts, namely urban, peri-urban and rural. The data was largely generated through focus group interviews during workshops with children and observations of waste management activities. These two methods formed the main data generation methods. They were complemented by semi-structured interviews with teachers, and other actors in the waste management activities, learners' activities and work, learners' notes, photographs and children's drawings as well as show-and-tell explanations by learners. Content analysis and the abductive mode of inference were used to analyse data in all three case studies. Findings from the first phase of the study reveal that participation of learners in waste management activities was largely teacher-directed. This resulted in a mis-match between teachers views of what practices are necessary and important, and children's views of what practices are necessary and important in and for environmental education. Due to culturally and historically formed views of environmental education, the study reveals that teachers wanted children to pick up litter, and this was their primary environmental education concern. Learners on the other hand, identified sanitation management in the school toilets as their primary waste management concern. Teachers had not considered this an environmental education concern. Using the action competence expansive learning approach, the second phase of the study addressed this tension by opening up dialogue between teachers and learners and amongst the learners themselves through an expansive learning process supporting children's participation and action competence development. Through this teacher-learner dialogical engagement, a broader range of possibilities became available and ideas around participation were radically changed. The study further reveals that the achievement of this open dialogue provided for a better relationship within the school community. And with improved communication came better ideas to solve waste management issues that the community still face on a daily basis, such as too much litter. Newly devised solutions were practical and had a broader impact than the initial ones that teachers had always focussed on. They included mobilising the maintenance of toilets, landscaping the school premises and even re-contextualising the litter management that had always caused tensions between learners and teachers. Children seemed to be developing not only a better understanding of the environment, but also developing the ability to resolve conflict amongst themselves and with their elders. By engaging in dialogue with children, they became co-catalysts for change in the school community. This study shows that if children's participation is taken seriously, and if opportunities for dialogue exist between teachers and children, positive changes for a healthier environment can be created in schools. It reveals that children also appeared to be feeling more confident and more equipped to consider changes in their environment outside of the school community. The study further shows that participation in environmental education involves more than cognitive changes as proposed in earlier constructivist literature; it includes in-depth engagement with socio-cultural dynamics and histories in the school context, such as the cultural histories of teachers, schooling and authority structures in the cultural community of the school. The study recommends that there is need to strengthen Teacher Education programmes to develop teaching practices and support for teachers to identify ways of engaging learners' views on issues in the school in open, dialogical ways. Such Teacher Education programmes should deepen teachers' understandings of learners' zone of proximal development (ZPD), demonstrating how dialogue and scaffolding are part of a teacher's role in supporting learning. This is shown in the three case studies that form part of this study. Finally, the study also deepens insights of using the Cultural Historical Activity theory (CHAT) to shed light on issues surrounding learner participation within the socio-cultural and historical environmental education contexts of the schools. The action competence models used in the study provide a tool for revealing forms of learner participation. This tool can be used for critical reflections and monitoring of teaching practices in schools.
- Full Text:
- Date Issued: 2011
An investigation into the replication biology of Helicoverpa armigera stunt virus
- Authors: Short, James Roswell
- Date: 2011
- Subjects: Helicoverpa armigera RNA viruses Viruses -- Reproduction Lepidoptera -- Viruses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3967 , http://hdl.handle.net/10962/d1004026
- Description: Tetraviruses are a family of small non-enveloped positive sense RNA viruses that exclusively infect members of the order Lepidoptera. Their replication biology is poorly studied because, with the exception of Providence virus (PrV), tetraviruses are unable to replicate in tissue culture cells. The overall aim of the research described in this thesis was to develop a fundamental understanding of the replication of tetraviruses, focussing on the site of replication within host cells and in particular, the subcellular localisation of the viral replicase. Helicoverpa armigera stunt virus (HaSV, Genus: Omegatetravirus) was chosen for this study because it is the only tetravirus for which the cDNAs have been shown to be infectious. In the absence of tissue culture cell lines susceptible to HaSV infection, the approach was to use confocal fluorescence microscopy to examine the subcellular localisation of the HaSV replicase fused to enhanced green fluorescent protein (EGFP) in mammalian and insect tissue culture cells. The replicase (with EGFP fused at its C-terminus) localised to punctate structures throughout the cytoplasm of transfected HeLa and Sf9 cells. These structures were then shown – using live cell imaging and time lapse photography – to behave similarly to cellular endocytic organelles and fluorescence partially overlapped with membranes containing the late endosomal marker protein CD63. Biochemical fractionation of Sf9 cells expressing the replicase via a recombinant baculovirus (as well as transfected HeLa and Sf9 cells expressing EGFP-replicase fusion proteins) demonstrated that the replicase was strongly associated with detergentresistant membranes (DRMs) in these cells. Deletion analysis of the replicase coding sequence revealed two regions involved in the generation of the punctuate structures. Firstly, the C-terminal half of the replicase RNAdependant RNA polymerase domain was found to be essential for targeting and the tight association with DRMs while the second region, within the Nterminal 44 amino acids, enhanced localisation through a combination of secondary structural elements and sequence-specific functions. A comparative immunofluorescence study on PrV, which replicates as a persistent infection in an insect midgut cell line, showed that the PrV replicase also localised to punctate structures in the cytoplasm. Biochemical fractionation showed that the replicase was also strongly associated with DRMs. This thesis describes the development of new experimental systems for the study of tetravirus replication biology and the data lead to the conclusion that the HaSV replicase associates with DRMs derived from alternate endocytic pathway organelles.
- Full Text:
- Date Issued: 2011
- Authors: Short, James Roswell
- Date: 2011
- Subjects: Helicoverpa armigera RNA viruses Viruses -- Reproduction Lepidoptera -- Viruses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3967 , http://hdl.handle.net/10962/d1004026
- Description: Tetraviruses are a family of small non-enveloped positive sense RNA viruses that exclusively infect members of the order Lepidoptera. Their replication biology is poorly studied because, with the exception of Providence virus (PrV), tetraviruses are unable to replicate in tissue culture cells. The overall aim of the research described in this thesis was to develop a fundamental understanding of the replication of tetraviruses, focussing on the site of replication within host cells and in particular, the subcellular localisation of the viral replicase. Helicoverpa armigera stunt virus (HaSV, Genus: Omegatetravirus) was chosen for this study because it is the only tetravirus for which the cDNAs have been shown to be infectious. In the absence of tissue culture cell lines susceptible to HaSV infection, the approach was to use confocal fluorescence microscopy to examine the subcellular localisation of the HaSV replicase fused to enhanced green fluorescent protein (EGFP) in mammalian and insect tissue culture cells. The replicase (with EGFP fused at its C-terminus) localised to punctate structures throughout the cytoplasm of transfected HeLa and Sf9 cells. These structures were then shown – using live cell imaging and time lapse photography – to behave similarly to cellular endocytic organelles and fluorescence partially overlapped with membranes containing the late endosomal marker protein CD63. Biochemical fractionation of Sf9 cells expressing the replicase via a recombinant baculovirus (as well as transfected HeLa and Sf9 cells expressing EGFP-replicase fusion proteins) demonstrated that the replicase was strongly associated with detergentresistant membranes (DRMs) in these cells. Deletion analysis of the replicase coding sequence revealed two regions involved in the generation of the punctuate structures. Firstly, the C-terminal half of the replicase RNAdependant RNA polymerase domain was found to be essential for targeting and the tight association with DRMs while the second region, within the Nterminal 44 amino acids, enhanced localisation through a combination of secondary structural elements and sequence-specific functions. A comparative immunofluorescence study on PrV, which replicates as a persistent infection in an insect midgut cell line, showed that the PrV replicase also localised to punctate structures in the cytoplasm. Biochemical fractionation showed that the replicase was also strongly associated with DRMs. This thesis describes the development of new experimental systems for the study of tetravirus replication biology and the data lead to the conclusion that the HaSV replicase associates with DRMs derived from alternate endocytic pathway organelles.
- Full Text:
- Date Issued: 2011
Trials and triumphs in public office: the life and work of E J N Mabuza
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
An international comparative study on the relationship marketing and customer retention of retail banks : lessons for South Africa
- Authors: Rootman, Chantal
- Date: 2011
- Subjects: Banks and banking -- Customer services , Relationship marketing , Customer relations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9358 , http://hdl.handle.net/10948/1376 , Banks and banking -- Customer services , Relationship marketing , Customer relations
- Description: Despite the extensive research undertaken in the subject area of services marketing, much is still unknown to service providers of specific services in terms of firm-client relationships and how customer retention rates can be increased. This study attempts to address this limitation. The study revolves around the relationship marketing and customer retention of banks in South Africa, Canada and the United Kingdom (UK). Service firms, including banks, are vitally important to the economy of any country as they contribute to its Gross Domestic Product (GDP) (for example a 74 percent contribution in South Africa) and its employment rate. However, to survive in a complex, competitive business environment, service firms are required to focus on their clients’ needs. Banks can focus on their relationships with clients and measure their institutions’ success by considering their customer retention rates. When considering firm-client relationships and customer retention rates, it is important to gather and link the viewpoints of both clients and managers in order to ensure that firms perform according to clients’ needs. In order to establish the influence of selected variables on the relationship marketing and customer retention of banks, from the perspectives of both banking clients and managers, an empirical investigation was conducted. The primary aim of this study was to quantify significant relationships among selected variables; therefore the positivistic research paradigm was used. In addition, in designing the measuring instruments for the empirical investigation, the phenomenological paradigm was used. Thus, in order to use multiple sources of data, the strategy of methodological triangulation was adopted for this study. The samples consisted of banking clients and bank managers in South Africa, Canada and the UK. The empirical investigation conducted among banking clients revealed that significant positive relationships exist between six of the seven identified independent variables, namely communication, personalisation, empowerment, ethics, fees and technology, and banks’ relationship marketing. These relationships imply that, according to banking clients, if each of these aspects in banks improves, bank-client relationships would improve. The empirical investigation conducted among bank managers showed that managers only regard communication and fees as influencers of relationship marketing in banks. This result clearly indicated a difference in the viewpoints of banking clients and bank managers. In addition, the empirical investigation revealed that relationship marketing positively influences the customer retention of banks. This relationship implies that if a bank successfully maintains relationships with its clients, the bank’s customer retention rates will increase. Additionally, the empirical investigation revealed that the population group, education level and country of residence of banking client respondents exerted an influence on the perceptions clients have regarding banks’ relationship marketing and customer retention levels. If banking clients are African or are not educated with a qualification beyond secondary school level or are from Canada, they consider the relationship marketing of a bank to be more important and are more likely to be retained by banks. Generally, the study indicated that Canadian banking clients are more positive regarding the empowerment strategies and personalisation efforts of Canadian banks than South Africans are about those of South African banks. In addition, banking clients in the UK are more satisfied with the communication, fees and use of technology of UK banks than South Africans are about these aspects in South African banks. The study indicated that strategies to improve banks’ communication, personalisation, empowerment, ethics, fees and technology should be implemented by banks in ways to positively influence their relationship marketing and ultimately their customer retention. Strategies relating to each of these areas, successfully implemented by banks in Canada and the UK, are recommended to South African banks. In effect, these strategies will contribute to retail banks’ success, the competiveness in the banking industry, banking client benefits as well as the economic stability and prosperity of South Africa.
- Full Text:
- Date Issued: 2011
- Authors: Rootman, Chantal
- Date: 2011
- Subjects: Banks and banking -- Customer services , Relationship marketing , Customer relations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9358 , http://hdl.handle.net/10948/1376 , Banks and banking -- Customer services , Relationship marketing , Customer relations
- Description: Despite the extensive research undertaken in the subject area of services marketing, much is still unknown to service providers of specific services in terms of firm-client relationships and how customer retention rates can be increased. This study attempts to address this limitation. The study revolves around the relationship marketing and customer retention of banks in South Africa, Canada and the United Kingdom (UK). Service firms, including banks, are vitally important to the economy of any country as they contribute to its Gross Domestic Product (GDP) (for example a 74 percent contribution in South Africa) and its employment rate. However, to survive in a complex, competitive business environment, service firms are required to focus on their clients’ needs. Banks can focus on their relationships with clients and measure their institutions’ success by considering their customer retention rates. When considering firm-client relationships and customer retention rates, it is important to gather and link the viewpoints of both clients and managers in order to ensure that firms perform according to clients’ needs. In order to establish the influence of selected variables on the relationship marketing and customer retention of banks, from the perspectives of both banking clients and managers, an empirical investigation was conducted. The primary aim of this study was to quantify significant relationships among selected variables; therefore the positivistic research paradigm was used. In addition, in designing the measuring instruments for the empirical investigation, the phenomenological paradigm was used. Thus, in order to use multiple sources of data, the strategy of methodological triangulation was adopted for this study. The samples consisted of banking clients and bank managers in South Africa, Canada and the UK. The empirical investigation conducted among banking clients revealed that significant positive relationships exist between six of the seven identified independent variables, namely communication, personalisation, empowerment, ethics, fees and technology, and banks’ relationship marketing. These relationships imply that, according to banking clients, if each of these aspects in banks improves, bank-client relationships would improve. The empirical investigation conducted among bank managers showed that managers only regard communication and fees as influencers of relationship marketing in banks. This result clearly indicated a difference in the viewpoints of banking clients and bank managers. In addition, the empirical investigation revealed that relationship marketing positively influences the customer retention of banks. This relationship implies that if a bank successfully maintains relationships with its clients, the bank’s customer retention rates will increase. Additionally, the empirical investigation revealed that the population group, education level and country of residence of banking client respondents exerted an influence on the perceptions clients have regarding banks’ relationship marketing and customer retention levels. If banking clients are African or are not educated with a qualification beyond secondary school level or are from Canada, they consider the relationship marketing of a bank to be more important and are more likely to be retained by banks. Generally, the study indicated that Canadian banking clients are more positive regarding the empowerment strategies and personalisation efforts of Canadian banks than South Africans are about those of South African banks. In addition, banking clients in the UK are more satisfied with the communication, fees and use of technology of UK banks than South Africans are about these aspects in South African banks. The study indicated that strategies to improve banks’ communication, personalisation, empowerment, ethics, fees and technology should be implemented by banks in ways to positively influence their relationship marketing and ultimately their customer retention. Strategies relating to each of these areas, successfully implemented by banks in Canada and the UK, are recommended to South African banks. In effect, these strategies will contribute to retail banks’ success, the competiveness in the banking industry, banking client benefits as well as the economic stability and prosperity of South Africa.
- Full Text:
- Date Issued: 2011
Information security service management : a service management approach to information security management
- Authors: Rastogi, Rahul
- Date: 2011
- Subjects: Information technology -- Security measures
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9755 , http://hdl.handle.net/10948/1389 , Information technology -- Security measures
- Description: In today’s world, information and the associated Information Technology are critical assets for many organizations. Any information security breach, or compromise of these assets, can lead to serious implications for organizations that are heavily dependent on these assets. For such organizations, information security becomes vital. Organizations deploy an information security infrastructure for protecting their information assets. This infrastructure consists of policies and controls. Organizations also create an information security management system for managing information security in the organization. While some of the policies and controls are of a purely technical nature, many depend upon the actions of end-users. However, end-users are known to exhibit both compliant and noncompliant behaviours in respect of these information security policies and controls in the organization. Non-compliant information security behaviours of end-users have the potential to lead to information security breaches. Non-compliance thus needs to be controlled. The discipline of information security and its management have evolved over the years. However, the discipline has retained the technology-driven nature of its origin. In this context, the discipline has failed to adequately appreciate the role played by the end-users and the complexities of their behaviour, as it relates to information security policies and controls. The pervasive information security management philosophy is that of treating end-users as the enemy. Compliance is sought to be achieved through awareness programs, rewards, punishments and evermore strict policies and controls. This has led to a bureaucratic information security management approach. The philosophy of treating end-users as the enemy has had an adverse impact on information security in the organization. It can be said that rather than curbing non-compliance by end-users, the present-day bureaucratic approach to information security management has contributed to non-compliance. This thesis calls this the end-user crisis. This research aims at resolving this crisis by identifying an improved approach to information security management in the organization. This research has applied the service management approach to information security management. The resultant Information Security Service Management (ISSM) views end-users as assets and resources, and not as enemies. The central idea of ISSM is that the end-user is to be treated as a customer, whose needs are to be satisfied. This research presents ISSM. This research also presents the various components of ISSM to aid in its implementation in an organization.
- Full Text:
- Date Issued: 2011
- Authors: Rastogi, Rahul
- Date: 2011
- Subjects: Information technology -- Security measures
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9755 , http://hdl.handle.net/10948/1389 , Information technology -- Security measures
- Description: In today’s world, information and the associated Information Technology are critical assets for many organizations. Any information security breach, or compromise of these assets, can lead to serious implications for organizations that are heavily dependent on these assets. For such organizations, information security becomes vital. Organizations deploy an information security infrastructure for protecting their information assets. This infrastructure consists of policies and controls. Organizations also create an information security management system for managing information security in the organization. While some of the policies and controls are of a purely technical nature, many depend upon the actions of end-users. However, end-users are known to exhibit both compliant and noncompliant behaviours in respect of these information security policies and controls in the organization. Non-compliant information security behaviours of end-users have the potential to lead to information security breaches. Non-compliance thus needs to be controlled. The discipline of information security and its management have evolved over the years. However, the discipline has retained the technology-driven nature of its origin. In this context, the discipline has failed to adequately appreciate the role played by the end-users and the complexities of their behaviour, as it relates to information security policies and controls. The pervasive information security management philosophy is that of treating end-users as the enemy. Compliance is sought to be achieved through awareness programs, rewards, punishments and evermore strict policies and controls. This has led to a bureaucratic information security management approach. The philosophy of treating end-users as the enemy has had an adverse impact on information security in the organization. It can be said that rather than curbing non-compliance by end-users, the present-day bureaucratic approach to information security management has contributed to non-compliance. This thesis calls this the end-user crisis. This research aims at resolving this crisis by identifying an improved approach to information security management in the organization. This research has applied the service management approach to information security management. The resultant Information Security Service Management (ISSM) views end-users as assets and resources, and not as enemies. The central idea of ISSM is that the end-user is to be treated as a customer, whose needs are to be satisfied. This research presents ISSM. This research also presents the various components of ISSM to aid in its implementation in an organization.
- Full Text:
- Date Issued: 2011
Strategies to create a post-merged organisational culture conducive to effective performance management
- Authors: Paul, Gary William
- Date: 2011
- Subjects: Corporate culture , Organizational change , Organizational effectiveness
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9385 , http://hdl.handle.net/10948/d1010857 , Corporate culture , Organizational change , Organizational effectiveness
- Description: Mergers have been described as the most complex business process that an organisation can be faced with, requiring executives and other stakeholders to discharge the promise of a more successful merged organisation. However, several studies have highlighted the factors that led to the demise of the merged organisations. One of the often quoted and frequently blamed aspects related to merger failure has been the lack of effective post-merged organisational culture integration and alignment. Where mergers have been successful, it was attributed to a structured approach to integrating and aligning all aspects related to organisational culture thus ensuring the creation of a high performing organisation, conducive to effective performance management. The main research problem in this study centred around the identification of strategies that could be used to design an integrated model for creating a post-merged organisational culture which is conducive to effectively managing performance. To achieve this objective, the following approaches were adopted: A literature study was conducted with the view to identifying the challenges facing merged organisations in general and post-merged South African Higher Education institutions in particular. The researcher also conducted interviews with senior HR practitioner at the institutions participating in this study to gain insights into their experiences of performance within their merged institutions. The institutions involved in this study were Nelson Mandela Metropolitan University (NMMU), Cape Peninsula University of Technology (CPUT and Durban University of Technology (DUT). The insights gleaned from these interviews were incorporated into the survey questionnaire. The literature study also concerned itself with the identification of strategies that merged organisations could use in its pursuit of organisational culture alignment and integration. These strategies included conducting critical pre-merger assessments or due-diligence studies, adopting structured approaches to dealing with resistance to change, employee engagement, the design, implementation and communication of monitoring and evaluation of merger success measures as well as several other moderating variables referred to in figure 1.2. In terms of sub-problem six of the study, the findings of sub-problems one, two and five were used to develop an eight-step integrated theoretical model to create an organisational culture conducive to effective performance management in a post-merged environment. The model served as a basis for the design of a survey questionnaire. The questionnaire was used to ascertain the extent to which respondents from the three participating institutions (NMMU, CPUT and DUT), perceived the various strategies as being important in establishing a post-merged organisational culture conducive to effective performance management. The results that emerged from the empirical study showed a strong concurrence with the strategies identified in the literature study and included in the integrated theoretical model. The quantitative and qualitative results from the empirical study where incorporated into the integrated theoretical model, which lead to a refined Eight-Step Integrated Post-merged Organisational Culture Creation Model as depicted in Figure 7.1 with associated details in Figure 7.2.
- Full Text:
- Date Issued: 2011
- Authors: Paul, Gary William
- Date: 2011
- Subjects: Corporate culture , Organizational change , Organizational effectiveness
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9385 , http://hdl.handle.net/10948/d1010857 , Corporate culture , Organizational change , Organizational effectiveness
- Description: Mergers have been described as the most complex business process that an organisation can be faced with, requiring executives and other stakeholders to discharge the promise of a more successful merged organisation. However, several studies have highlighted the factors that led to the demise of the merged organisations. One of the often quoted and frequently blamed aspects related to merger failure has been the lack of effective post-merged organisational culture integration and alignment. Where mergers have been successful, it was attributed to a structured approach to integrating and aligning all aspects related to organisational culture thus ensuring the creation of a high performing organisation, conducive to effective performance management. The main research problem in this study centred around the identification of strategies that could be used to design an integrated model for creating a post-merged organisational culture which is conducive to effectively managing performance. To achieve this objective, the following approaches were adopted: A literature study was conducted with the view to identifying the challenges facing merged organisations in general and post-merged South African Higher Education institutions in particular. The researcher also conducted interviews with senior HR practitioner at the institutions participating in this study to gain insights into their experiences of performance within their merged institutions. The institutions involved in this study were Nelson Mandela Metropolitan University (NMMU), Cape Peninsula University of Technology (CPUT and Durban University of Technology (DUT). The insights gleaned from these interviews were incorporated into the survey questionnaire. The literature study also concerned itself with the identification of strategies that merged organisations could use in its pursuit of organisational culture alignment and integration. These strategies included conducting critical pre-merger assessments or due-diligence studies, adopting structured approaches to dealing with resistance to change, employee engagement, the design, implementation and communication of monitoring and evaluation of merger success measures as well as several other moderating variables referred to in figure 1.2. In terms of sub-problem six of the study, the findings of sub-problems one, two and five were used to develop an eight-step integrated theoretical model to create an organisational culture conducive to effective performance management in a post-merged environment. The model served as a basis for the design of a survey questionnaire. The questionnaire was used to ascertain the extent to which respondents from the three participating institutions (NMMU, CPUT and DUT), perceived the various strategies as being important in establishing a post-merged organisational culture conducive to effective performance management. The results that emerged from the empirical study showed a strong concurrence with the strategies identified in the literature study and included in the integrated theoretical model. The quantitative and qualitative results from the empirical study where incorporated into the integrated theoretical model, which lead to a refined Eight-Step Integrated Post-merged Organisational Culture Creation Model as depicted in Figure 7.1 with associated details in Figure 7.2.
- Full Text:
- Date Issued: 2011
Biological control of Pereskia aculeata Miller (Cactaceae)
- Authors: Paterson, Iain Douglas
- Date: 2011
- Subjects: Pereskia -- Biological control -- South Africa Cactus -- Biological control -- South Africa Invasive plants -- Biological control -- South Africa Curculionidae -- South Africa Pyralidae -- South Africa Insects as biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5825 , http://hdl.handle.net/10962/d1007653
- Description: Pereskia aculeata Miller (Cactaceae) is an environmental weed that is damaging to natural ecosystems in South Africa. The plant is native to Central and South America and was first recorded in South Africa in a botanical garden in 1858. In this thesis, research into the biological control of P. aculeata was conducted with the intention of improving the control of the weed. A pre-release study of the relationship between P. aculeata density and native plant biodiversity indicated that P. aculeata has a negative impact on native biodiversity. The native plant biodiversity associated with different P. aculeata densities was used to determine threshold values and goals for the control of the weed. A threshold value of 50% P. aculeata density was calculated, indicating that P. aculeata density must be maintained below 50% in order to conserve native plant biodiversity. The ultimate goal of the control programme should be to maintain P. aculeata densities below 30%. At these densities there was no significant difference in native plant biodiversity from if the weed were absent from the ecosystem. The biological control agent, Phenrica guérini Bechyne (Chrysomelidae), has been released in South Africa but the potential of the agent to impact P. aculeata is not known and no post release evaluation has been conducted. Impact assessment studies indicate that P. guérini does not impact P. aculeata, even at high densities, but the results of greenhouse experiments should be interpreted with caution because of problems with extrapolation into the field. Although observations in the field suggest that P. guérini has reduced P. aculeata densities at one site, it is clear that new biological control agents are needed to reduce the weed to acceptable levels. Identifying the origin of the South African P. aculeata population was believed to be important to the biological control programme due to the disjunct native distribution and intraspecific variation of the species. Natural enemies associated with plant genotypes in different parts of the native distribution may have developed specialised relationships with certain intraspecific variants of the plant, resulting in differences in agent efficacy on certain host plant genotypes. A molecular study indicated that the closest relatives to the South African weed population found in the native distribution were in Rio de Janeiro Province, Brazil. A bioassay experiment in which fitness related traits of the biological control agent, P. guérini, were measured on various P. aculeata genotypes was conducted to determine the importance of host plant intraspecific variation. There was little variation in fitness traits between genotypes and no evidence of intraspecific host plant specialization. Although intraspecific variation had no effect on agent efficacy in the case of P. guérini, it is possible that other natural enemies may be more specialized. Genotype matching is expected to be more important when natural enemies likely to be specialised to individual genotypes are considered for biological control. Potential biological control agents were prioritized from data collected on surveys in the native distribution. The most promising of these, based on the presence of feeding, incidence, predicted host range, climatic matching, genotype matching and mode of damage, are two species of Curculionidae, the current biological control agent P. guérini and the stem boring moth, Maracayia chiorisalis Walker (Crambidae). The two curculionid species and M. chlorisalis should be considered priorities for host specificity studies. Releases of P. guérini and any new biological control agents should be made at sites where the pre-release study was conducted so that post-release evaluation data can be compared with the pre-release data and the impact of biological control can be evaluated. Retrospective analyses of biological control programmes provide important ways of improving aspects of biological control programmes, such as methods of agent selection. The evaluation of success in biological control programmes is essential for retrospective analyses because factors that have lead to successes or failures can be analysed. Retrospective analyses of biological control programmes, such as this thesis, may improve weed management, thereby contributing to the conservation of natural resources.
- Full Text:
- Date Issued: 2011
- Authors: Paterson, Iain Douglas
- Date: 2011
- Subjects: Pereskia -- Biological control -- South Africa Cactus -- Biological control -- South Africa Invasive plants -- Biological control -- South Africa Curculionidae -- South Africa Pyralidae -- South Africa Insects as biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5825 , http://hdl.handle.net/10962/d1007653
- Description: Pereskia aculeata Miller (Cactaceae) is an environmental weed that is damaging to natural ecosystems in South Africa. The plant is native to Central and South America and was first recorded in South Africa in a botanical garden in 1858. In this thesis, research into the biological control of P. aculeata was conducted with the intention of improving the control of the weed. A pre-release study of the relationship between P. aculeata density and native plant biodiversity indicated that P. aculeata has a negative impact on native biodiversity. The native plant biodiversity associated with different P. aculeata densities was used to determine threshold values and goals for the control of the weed. A threshold value of 50% P. aculeata density was calculated, indicating that P. aculeata density must be maintained below 50% in order to conserve native plant biodiversity. The ultimate goal of the control programme should be to maintain P. aculeata densities below 30%. At these densities there was no significant difference in native plant biodiversity from if the weed were absent from the ecosystem. The biological control agent, Phenrica guérini Bechyne (Chrysomelidae), has been released in South Africa but the potential of the agent to impact P. aculeata is not known and no post release evaluation has been conducted. Impact assessment studies indicate that P. guérini does not impact P. aculeata, even at high densities, but the results of greenhouse experiments should be interpreted with caution because of problems with extrapolation into the field. Although observations in the field suggest that P. guérini has reduced P. aculeata densities at one site, it is clear that new biological control agents are needed to reduce the weed to acceptable levels. Identifying the origin of the South African P. aculeata population was believed to be important to the biological control programme due to the disjunct native distribution and intraspecific variation of the species. Natural enemies associated with plant genotypes in different parts of the native distribution may have developed specialised relationships with certain intraspecific variants of the plant, resulting in differences in agent efficacy on certain host plant genotypes. A molecular study indicated that the closest relatives to the South African weed population found in the native distribution were in Rio de Janeiro Province, Brazil. A bioassay experiment in which fitness related traits of the biological control agent, P. guérini, were measured on various P. aculeata genotypes was conducted to determine the importance of host plant intraspecific variation. There was little variation in fitness traits between genotypes and no evidence of intraspecific host plant specialization. Although intraspecific variation had no effect on agent efficacy in the case of P. guérini, it is possible that other natural enemies may be more specialized. Genotype matching is expected to be more important when natural enemies likely to be specialised to individual genotypes are considered for biological control. Potential biological control agents were prioritized from data collected on surveys in the native distribution. The most promising of these, based on the presence of feeding, incidence, predicted host range, climatic matching, genotype matching and mode of damage, are two species of Curculionidae, the current biological control agent P. guérini and the stem boring moth, Maracayia chiorisalis Walker (Crambidae). The two curculionid species and M. chlorisalis should be considered priorities for host specificity studies. Releases of P. guérini and any new biological control agents should be made at sites where the pre-release study was conducted so that post-release evaluation data can be compared with the pre-release data and the impact of biological control can be evaluated. Retrospective analyses of biological control programmes provide important ways of improving aspects of biological control programmes, such as methods of agent selection. The evaluation of success in biological control programmes is essential for retrospective analyses because factors that have lead to successes or failures can be analysed. Retrospective analyses of biological control programmes, such as this thesis, may improve weed management, thereby contributing to the conservation of natural resources.
- Full Text:
- Date Issued: 2011