A study of the airflow on the windward slope of a transverse dune in the Alexandria coastal dunefield
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Habitat suitability and behaviour of springbok (Antidorcas marsupialis) at Augrabies Falls National Park, South Africa
- Authors: Reid, Caroline
- Date: 2005
- Subjects: Springbok -- Habitat suitability index models -- South Africa -- Augrabies Falls National Park , Springbok -- Behavior -- South Africa -- Augrabies Falls National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11079 , http://hdl.handle.net/10948/362 , Springbok -- Habitat suitability index models -- South Africa -- Augrabies Falls National Park , Springbok -- Behavior -- South Africa -- Augrabies Falls National Park
- Description: Habitat selection may be considered a behavioural consequence of an individual actively selecting where it lives or passively persisting in a certain habitat. There are a variety of approaches to assessing habitat selection, including relating densities to predefined habitats and the characteristics of these habitats, measuring the behaviour of animals within predefined habitats in order to assess the relative benefits to the animal and comparing these between habitats, and using optimality theory to allow the animal to provide measures of its preference for particular habitats or patches. Each approach provides different perspectives on an animal’s choice and use of habitat, with some approaches working more effectively with certain species or habitats than others. There have, however, been no attempts to apply all these approaches to a single species at a single site. The objective of this study was therefore to apply the three above-mentioned approaches to assess habitat use and quality to a single species, the springbok (Antidorcas marsupialis) at the Augrabies Falls National Park (AFNP), on the northern bank of the Orange River, in order to provide the basis for further work on comparing and integrating these approaches. The relative abundance of springbok in Augrabies Falls National park was used to develop a habitat suitability model for the park, and thus determine the habitat variables that influenced habitat suitability. Isodar analysis revealed information on the mechanisms underlying habitat preference. Behavioural models were developed to improve our understanding of how springbok behaviour changes in relation to the habitat, and incorporated the variables identified in the habitat suitability model. The different spatial and temporal scales influencing springbok habitat selection were determined using optimal foraging theory and giving-up densities. Springbok preferred open habitats providing high food quality. Springbok behaviour was related to the foraging and predation risk characteristics of the habitat, and springbok varied their temporal and spatial utilisation so as to minimise their risk of predation and maximise their food intake. The habitat suitability model, behaviour models and giving-up densities were compared for ease of use and applicability. Using giving-up densities to reveal habitat suitability had greater applicability and was both efficient and objective.
- Full Text:
- Date Issued: 2005
- Authors: Reid, Caroline
- Date: 2005
- Subjects: Springbok -- Habitat suitability index models -- South Africa -- Augrabies Falls National Park , Springbok -- Behavior -- South Africa -- Augrabies Falls National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11079 , http://hdl.handle.net/10948/362 , Springbok -- Habitat suitability index models -- South Africa -- Augrabies Falls National Park , Springbok -- Behavior -- South Africa -- Augrabies Falls National Park
- Description: Habitat selection may be considered a behavioural consequence of an individual actively selecting where it lives or passively persisting in a certain habitat. There are a variety of approaches to assessing habitat selection, including relating densities to predefined habitats and the characteristics of these habitats, measuring the behaviour of animals within predefined habitats in order to assess the relative benefits to the animal and comparing these between habitats, and using optimality theory to allow the animal to provide measures of its preference for particular habitats or patches. Each approach provides different perspectives on an animal’s choice and use of habitat, with some approaches working more effectively with certain species or habitats than others. There have, however, been no attempts to apply all these approaches to a single species at a single site. The objective of this study was therefore to apply the three above-mentioned approaches to assess habitat use and quality to a single species, the springbok (Antidorcas marsupialis) at the Augrabies Falls National Park (AFNP), on the northern bank of the Orange River, in order to provide the basis for further work on comparing and integrating these approaches. The relative abundance of springbok in Augrabies Falls National park was used to develop a habitat suitability model for the park, and thus determine the habitat variables that influenced habitat suitability. Isodar analysis revealed information on the mechanisms underlying habitat preference. Behavioural models were developed to improve our understanding of how springbok behaviour changes in relation to the habitat, and incorporated the variables identified in the habitat suitability model. The different spatial and temporal scales influencing springbok habitat selection were determined using optimal foraging theory and giving-up densities. Springbok preferred open habitats providing high food quality. Springbok behaviour was related to the foraging and predation risk characteristics of the habitat, and springbok varied their temporal and spatial utilisation so as to minimise their risk of predation and maximise their food intake. The habitat suitability model, behaviour models and giving-up densities were compared for ease of use and applicability. Using giving-up densities to reveal habitat suitability had greater applicability and was both efficient and objective.
- Full Text:
- Date Issued: 2005
A comparison of programming notations for a tertiary level introductory programming course
- Authors: Cilliers, Charmain Barbara
- Date: 2004
- Subjects: Computer programming -- Study and teaching (Higher) -- South Africa , Computer programmers -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11093 , http://hdl.handle.net/10948/d1019679
- Description: Increasing pressure from national government to improve throughput at South African tertiary education institutions presents challenges to educators of introductory programming courses. In response, educators must adopt effective methods and strategies that encourage novice programmers to be successful in such courses. An approach that seeks to increase and maintain satisfactory throughput is the modification of the teaching model in these courses by adjusting presentation techniques. This thesis investigates the effect of integrating an experimental iconic programming notation and associated development environment with existing conventional textual technological support in the teaching model of a tertiary level introductory programming course. The investigation compares the performance achievement of novice programmers using only conventional textual technological support with that of novice programmers using the integrated iconic and conventional textual technological support. In preparation for the investigation, interpretation of existing knowledge on the behaviour of novice programmers while learning to program results in a novel framework of eight novice programmer requirements for technological support in an introductory programming course. This framework is applied in the examination of existing categories of technological support as well as in the design of new technological support for novice programmers learning to program. It thus provides information for the selection of existing and the design of new introductory programming technological support. The findings of the investigation suggest strong evidence that performance achievement of novice programmers in a tertiary level introductory programming course improves significantly with the inclusion of iconic technological support in the teaching model. The benefits are particularly evident in the portion of the novice programmer population who have been identified as being at risk of being successful in the course. Novice programmers identified as being at risk perform substantially better when using iconic technological support concurrently with conventional textual technological support than their equals who use only the latter form. Considerably more at risk novice programmers using the integrated form of technological support are in fact successful in the introductory programming course when compared with their counterparts who use conventional textual technological support only. The contributions of this thesis address deficiencies existing in current documented research. These contributions are primarily apparent in a number of distinct areas, namely: • formalisation of a novel framework of novice programmer requirements for technological support in an introductory programming course; • application of the framework as a formal evaluation technique; • application of the framework in the design of a visual iconic programming notation and development environment; • enhancement of existing empirical evidence and experimental research methodology typically applied to studies in programming; as well as • a proposal for a modified introductory programming course teaching model. The thesis has effectively applied substantial existing research on the cognitive model of the novice programmer as well as that on experimental technological support. The increase of throughput to a recommended rate of 75 percent in the tertiary level introductory programming course at the University of Port Elizabeth is attributed solely to the incorporation of iconic technological support in the teaching model of the course.
- Full Text:
- Date Issued: 2004
- Authors: Cilliers, Charmain Barbara
- Date: 2004
- Subjects: Computer programming -- Study and teaching (Higher) -- South Africa , Computer programmers -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11093 , http://hdl.handle.net/10948/d1019679
- Description: Increasing pressure from national government to improve throughput at South African tertiary education institutions presents challenges to educators of introductory programming courses. In response, educators must adopt effective methods and strategies that encourage novice programmers to be successful in such courses. An approach that seeks to increase and maintain satisfactory throughput is the modification of the teaching model in these courses by adjusting presentation techniques. This thesis investigates the effect of integrating an experimental iconic programming notation and associated development environment with existing conventional textual technological support in the teaching model of a tertiary level introductory programming course. The investigation compares the performance achievement of novice programmers using only conventional textual technological support with that of novice programmers using the integrated iconic and conventional textual technological support. In preparation for the investigation, interpretation of existing knowledge on the behaviour of novice programmers while learning to program results in a novel framework of eight novice programmer requirements for technological support in an introductory programming course. This framework is applied in the examination of existing categories of technological support as well as in the design of new technological support for novice programmers learning to program. It thus provides information for the selection of existing and the design of new introductory programming technological support. The findings of the investigation suggest strong evidence that performance achievement of novice programmers in a tertiary level introductory programming course improves significantly with the inclusion of iconic technological support in the teaching model. The benefits are particularly evident in the portion of the novice programmer population who have been identified as being at risk of being successful in the course. Novice programmers identified as being at risk perform substantially better when using iconic technological support concurrently with conventional textual technological support than their equals who use only the latter form. Considerably more at risk novice programmers using the integrated form of technological support are in fact successful in the introductory programming course when compared with their counterparts who use conventional textual technological support only. The contributions of this thesis address deficiencies existing in current documented research. These contributions are primarily apparent in a number of distinct areas, namely: • formalisation of a novel framework of novice programmer requirements for technological support in an introductory programming course; • application of the framework as a formal evaluation technique; • application of the framework in the design of a visual iconic programming notation and development environment; • enhancement of existing empirical evidence and experimental research methodology typically applied to studies in programming; as well as • a proposal for a modified introductory programming course teaching model. The thesis has effectively applied substantial existing research on the cognitive model of the novice programmer as well as that on experimental technological support. The increase of throughput to a recommended rate of 75 percent in the tertiary level introductory programming course at the University of Port Elizabeth is attributed solely to the incorporation of iconic technological support in the teaching model of the course.
- Full Text:
- Date Issued: 2004
Algorithms for the solution of the quadratic programming problem
- Authors: Vankova, Martina
- Date: 2004
- Subjects: Quadratic programming , Nonlinear programming , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11086 , http://hdl.handle.net/10948/348 , Quadratic programming , Nonlinear programming , Algorithms
- Description: The purpose of this dissertation was to provide a review of the theory of Optimization, in particular quadratic programming, and the algorithms suitable for solving both convex and non-convex quadratic programming problems. Optimization problems arise in a wide variety of fields and many can be effectively modeled with linear equations. However, there are problems for which linear models are not sufficient thus creating a need for non-linear systems. This dissertation includes a literature study of the formal theory necessary for understanding optimization and an investigation of the algorithms available for solving a special class of the non-linear programming problem, namely the quadratic programming problem. It was not the intention of this dissertation to discuss all possible algorithms for solving the quadratic programming problem, therefore certain algorithms for convex and non-convex quadratic programming problems were selected for a detailed discussion in the dissertation. Some of the algorithms were selected arbitrarily, because limited information was available comparing the efficiency of the various algorithms. Algorithms available for solving general non-linear programming problems were also included and briefly discussed as they can be used to solve quadratic programming problems. A number of algorithms were then selected for evaluation, depending on the frequency of use in practice and the availability of software implementing these algorithms. The evaluation included a theoretical and quantitative comparison of the algorithms. The quantitative results were analyzed and discussed and it was shown that the results supported the theoretical comparison. It was also shown that it is difficult to conclude that one algorithm is better than another as the efficiency of an algorithm greatly depends on the size of the problem, the complexity of an algorithm and many other implementation issues. Optimization problems arise continuously in a wide range of fields and thus create the need for effective methods of solving them. This dissertation provides the fundamental theory necessary for the understanding of optimization problems, with particular reference to quadratic programming problems and the algorithms that solve such problems. Keywords: Quadratic Programming, Quadratic Programming Algorithms, Optimization, Non-linear Programming, Convex, Non-convex.
- Full Text:
- Date Issued: 2004
- Authors: Vankova, Martina
- Date: 2004
- Subjects: Quadratic programming , Nonlinear programming , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11086 , http://hdl.handle.net/10948/348 , Quadratic programming , Nonlinear programming , Algorithms
- Description: The purpose of this dissertation was to provide a review of the theory of Optimization, in particular quadratic programming, and the algorithms suitable for solving both convex and non-convex quadratic programming problems. Optimization problems arise in a wide variety of fields and many can be effectively modeled with linear equations. However, there are problems for which linear models are not sufficient thus creating a need for non-linear systems. This dissertation includes a literature study of the formal theory necessary for understanding optimization and an investigation of the algorithms available for solving a special class of the non-linear programming problem, namely the quadratic programming problem. It was not the intention of this dissertation to discuss all possible algorithms for solving the quadratic programming problem, therefore certain algorithms for convex and non-convex quadratic programming problems were selected for a detailed discussion in the dissertation. Some of the algorithms were selected arbitrarily, because limited information was available comparing the efficiency of the various algorithms. Algorithms available for solving general non-linear programming problems were also included and briefly discussed as they can be used to solve quadratic programming problems. A number of algorithms were then selected for evaluation, depending on the frequency of use in practice and the availability of software implementing these algorithms. The evaluation included a theoretical and quantitative comparison of the algorithms. The quantitative results were analyzed and discussed and it was shown that the results supported the theoretical comparison. It was also shown that it is difficult to conclude that one algorithm is better than another as the efficiency of an algorithm greatly depends on the size of the problem, the complexity of an algorithm and many other implementation issues. Optimization problems arise continuously in a wide range of fields and thus create the need for effective methods of solving them. This dissertation provides the fundamental theory necessary for the understanding of optimization problems, with particular reference to quadratic programming problems and the algorithms that solve such problems. Keywords: Quadratic Programming, Quadratic Programming Algorithms, Optimization, Non-linear Programming, Convex, Non-convex.
- Full Text:
- Date Issued: 2004
An evaluation of paired comparison models
- Venter, Daniel Jacobus Lodewyk
- Authors: Venter, Daniel Jacobus Lodewyk
- Date: 2004
- Subjects: Paired comparisons (Statistics) , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11087 , http://hdl.handle.net/10948/364 , Paired comparisons (Statistics) , Mathematical statistics
- Description: Introduction: A typical task in quantitative data analysis is to derive estimates of population parameters based on sample statistics. For manifest variables this is usually a straightforward process utilising suitable measurement instruments and standard statistics such the mean, median and standard deviation. Latent variables on the other hand are typically more elusive, making it difficult to obtain valid and reliable measurements. One of the most widely used methods of estimating the parameter value of a latent variable is to use a summated score derived from a set of individual scores for each of the various attributes of the latent variable. A serious limitation of this method and other similar methods is that the validity and reliability of measurements depend on whether the statements included in the questionnaire cover all characteristics of the variable being measured and also on respondents’ ability to correctly indicate their perceived assessment of the characteristics on the scale provided. Methods without this limitation and that are especially useful where a set of objects/entities must be ranked based on the parameter values of one or more latent variables, are methods of paired comparisons. Although the underlying assumptions and algorithms of these methods often differ dramatically, they all rely on data derived from a series of comparisons, each consisting of a pair of specimens selected from the set of objects/entities being investigated. Typical examples of the comparison process are: subjects (judges) who have to indicate for each pair of objects which of the two they prefer; sport teams that compete against each other in matches that involve two teams at a time. The resultant data of each comparison range from a simple dichotomy to indicate which of the two objects are preferred/better, to an interval or ratio scale score for e d Bradley-Terry models, and were based on statistical theory assuming that the variable(s) being measured is either normally (Thurstone-Mosteller) or exponentially (Bradley-Terry) distributed. For many years researchers had to rely on these PCM’s when analysing paired comparison data without any idea about the implications if the distribution of the data from which their sample were obtained differed from the assumed distribution for the applicable PCM being utilised. To address this problem, PCM’s were subsequently developed to cater for discrete variables and variables with distributions that are neither normal or exponential. A question that remained unanswered is how the performance, as measured by the accuracy of parameter estimates, of PCM's are affected if they are applied to data from a range of discrete and continuous distribution that violates the assumptions on which the applicable paired comparison algorithm is based. This study is an attempt to answer this question by applying the most popular PCM's to a range of randomly derived data sets that spans typical continuous and discrete data distributions. It is hoped that the results of this study will assist researchers when selecting the most appropriate PCM to obtain accurate estimates of the parameters of the variables in their data sets.
- Full Text:
- Date Issued: 2004
- Authors: Venter, Daniel Jacobus Lodewyk
- Date: 2004
- Subjects: Paired comparisons (Statistics) , Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11087 , http://hdl.handle.net/10948/364 , Paired comparisons (Statistics) , Mathematical statistics
- Description: Introduction: A typical task in quantitative data analysis is to derive estimates of population parameters based on sample statistics. For manifest variables this is usually a straightforward process utilising suitable measurement instruments and standard statistics such the mean, median and standard deviation. Latent variables on the other hand are typically more elusive, making it difficult to obtain valid and reliable measurements. One of the most widely used methods of estimating the parameter value of a latent variable is to use a summated score derived from a set of individual scores for each of the various attributes of the latent variable. A serious limitation of this method and other similar methods is that the validity and reliability of measurements depend on whether the statements included in the questionnaire cover all characteristics of the variable being measured and also on respondents’ ability to correctly indicate their perceived assessment of the characteristics on the scale provided. Methods without this limitation and that are especially useful where a set of objects/entities must be ranked based on the parameter values of one or more latent variables, are methods of paired comparisons. Although the underlying assumptions and algorithms of these methods often differ dramatically, they all rely on data derived from a series of comparisons, each consisting of a pair of specimens selected from the set of objects/entities being investigated. Typical examples of the comparison process are: subjects (judges) who have to indicate for each pair of objects which of the two they prefer; sport teams that compete against each other in matches that involve two teams at a time. The resultant data of each comparison range from a simple dichotomy to indicate which of the two objects are preferred/better, to an interval or ratio scale score for e d Bradley-Terry models, and were based on statistical theory assuming that the variable(s) being measured is either normally (Thurstone-Mosteller) or exponentially (Bradley-Terry) distributed. For many years researchers had to rely on these PCM’s when analysing paired comparison data without any idea about the implications if the distribution of the data from which their sample were obtained differed from the assumed distribution for the applicable PCM being utilised. To address this problem, PCM’s were subsequently developed to cater for discrete variables and variables with distributions that are neither normal or exponential. A question that remained unanswered is how the performance, as measured by the accuracy of parameter estimates, of PCM's are affected if they are applied to data from a range of discrete and continuous distribution that violates the assumptions on which the applicable paired comparison algorithm is based. This study is an attempt to answer this question by applying the most popular PCM's to a range of randomly derived data sets that spans typical continuous and discrete data distributions. It is hoped that the results of this study will assist researchers when selecting the most appropriate PCM to obtain accurate estimates of the parameters of the variables in their data sets.
- Full Text:
- Date Issued: 2004
In vitro anti-HIV activities of Sutherlandia frutescens and Lobostemon trigonum extracts
- Authors: Harnett, Siobhán Margaret
- Date: 2004
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11072 , http://hdl.handle.net/10948/347 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Description: Currently, the approved anti-HIV drugs on the market only target the three HIV enzymes: reverse transcriptase, protease and more recently, integrase. Due to the limited nature of the current therapy, it is possible that a multi-drug resistant virus can emerge. The main concerns in developing countries however, are the expense and availability of the drugs and because of this, it is essential to investigate all alternatives. Traditional medicine offers many advantages as compared to allopathic treatment in so far as being relatively cheaper, accessible and it is broadly accepted in the population groups of the developing countries. Little is known though, of the exact efficacy and toxicity of these remedies so it is vital that these possible leads be investigated thoroughly. For the purpose of this study, two plants, Sutherlandia frutescens and Lobostemon trigonum were studied to ascertain their potential anti-HIV activity. Sutherlandia has received international attention as a possible cheap herbal remedy to improve the health of AIDS sufferers. Anecdotal evidence from health workers claim that HIV- infected patients on Sutherlandia treatment have shown improved CD4 counts, decreased viral loads and a general improvement in well-being. Extracts were prepared from dried leaves and flowers in methanol, ethanol, acetone, methylene dichloride or distilled water. Sulphated polysaccharides have been described extensively in literature with regards to their anti-HIV activity, so as a form of dereplication; an ethanol precipitation was performed on the aqueous extracts to remove sulphated polysaccharides. A toxicity study was performed on all crude extracts using uninfected peripheral mononuclear blood cells (PBMCs) isolated from whole blood. To measure anti-HIV activity, HIV-infected PBMCs were cultured with each of the crude extracts and cell viability measured using the tetrazolium salt, XTT. HIV-infected CEM-NKR-CCR5 cells were also used and supernatant from the viral studies was tested for the HIV antigen p24. xii Results varied greatly between assays but with the inclusion of a point-scale system to evaluate the extracts it was clear that overall the organic extracts of the Sutherlandia flowers, especially the acetone extract (SFA), showed great anti-HIV potential. SFA in every case decreased p24 levels and in the toxicity study did not decrease cell proliferation. With the HIV-infected PBMCs SFA actually helped improve cell proliferation despite the infection. To determine the specific anti- HIV activity, all crude extracts were tested for inhibition of HIV-I reverse transcriptase, the glycohydrolase enzymes: a-glucosidase, ß-glucosidase, ßglucuronidase, HIV-I integrase and HIV-II protease. No significant inhibition was seen with these experiments except for the HIV-I RT assay. The aqueous extract of the Lobostemon leaves produced an inhibitor of HIV-RT with a very low IC50 value of 0.049mg/ml. Some inhibitory effect was lost with the removal of the sulphated polysaccharides and the addition of BSA to the assay, but still 64% inhibition of the HIVRT remained, which confirmed that the inhibitor could be something novel, and not of the polysaccharide or tannin compounds.
- Full Text:
- Date Issued: 2004
- Authors: Harnett, Siobhán Margaret
- Date: 2004
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11072 , http://hdl.handle.net/10948/347 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Description: Currently, the approved anti-HIV drugs on the market only target the three HIV enzymes: reverse transcriptase, protease and more recently, integrase. Due to the limited nature of the current therapy, it is possible that a multi-drug resistant virus can emerge. The main concerns in developing countries however, are the expense and availability of the drugs and because of this, it is essential to investigate all alternatives. Traditional medicine offers many advantages as compared to allopathic treatment in so far as being relatively cheaper, accessible and it is broadly accepted in the population groups of the developing countries. Little is known though, of the exact efficacy and toxicity of these remedies so it is vital that these possible leads be investigated thoroughly. For the purpose of this study, two plants, Sutherlandia frutescens and Lobostemon trigonum were studied to ascertain their potential anti-HIV activity. Sutherlandia has received international attention as a possible cheap herbal remedy to improve the health of AIDS sufferers. Anecdotal evidence from health workers claim that HIV- infected patients on Sutherlandia treatment have shown improved CD4 counts, decreased viral loads and a general improvement in well-being. Extracts were prepared from dried leaves and flowers in methanol, ethanol, acetone, methylene dichloride or distilled water. Sulphated polysaccharides have been described extensively in literature with regards to their anti-HIV activity, so as a form of dereplication; an ethanol precipitation was performed on the aqueous extracts to remove sulphated polysaccharides. A toxicity study was performed on all crude extracts using uninfected peripheral mononuclear blood cells (PBMCs) isolated from whole blood. To measure anti-HIV activity, HIV-infected PBMCs were cultured with each of the crude extracts and cell viability measured using the tetrazolium salt, XTT. HIV-infected CEM-NKR-CCR5 cells were also used and supernatant from the viral studies was tested for the HIV antigen p24. xii Results varied greatly between assays but with the inclusion of a point-scale system to evaluate the extracts it was clear that overall the organic extracts of the Sutherlandia flowers, especially the acetone extract (SFA), showed great anti-HIV potential. SFA in every case decreased p24 levels and in the toxicity study did not decrease cell proliferation. With the HIV-infected PBMCs SFA actually helped improve cell proliferation despite the infection. To determine the specific anti- HIV activity, all crude extracts were tested for inhibition of HIV-I reverse transcriptase, the glycohydrolase enzymes: a-glucosidase, ß-glucosidase, ßglucuronidase, HIV-I integrase and HIV-II protease. No significant inhibition was seen with these experiments except for the HIV-I RT assay. The aqueous extract of the Lobostemon leaves produced an inhibitor of HIV-RT with a very low IC50 value of 0.049mg/ml. Some inhibitory effect was lost with the removal of the sulphated polysaccharides and the addition of BSA to the assay, but still 64% inhibition of the HIVRT remained, which confirmed that the inhibitor could be something novel, and not of the polysaccharide or tannin compounds.
- Full Text:
- Date Issued: 2004
On the mocvd growth of ZnO
- Authors: Pagni, Olivier Demeno
- Date: 2004
- Subjects: Zinc oxide thin films , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11075 , http://hdl.handle.net/10948/382 , Zinc oxide thin films , Metal organic chemical vapor deposition
- Description: Zinc oxide (ZnO) is a II-VI semiconductor material that offers tremendous potential as a light emitter in the blue-to-UV range. It has a wurtzite structure, and a direct band gap that can be tuned from 3.0 to 4.0 eV by alloying with Cd or Mg, respectively. In this work, ZnO thin films were grown by metalorganic chemical vapor deposition (MOCVD) on n-Si 2 ° off (100), amorphous glass, n-GaAs (100), and c-plane sapphire substrates. Diethyl zinc (DEZn) and tert-butanol (TBOH) were chosen as precursors. For the first time, Second Harmonic Generation Imaging was applied to the mapping of ZnO epilayers. The images obtained highlighted the polycrystalline character of the thin films, and provided insight as to the growth mode of ZnO on Si. The influence of substrate temperature on the structural properties of the epilayers was investigated by X-ray diffraction and optical microscopy. Grain sizes as high as 54 nm were measured. The optimum temperature range for this system proved to be 450 – 500 °C. The influence of the VI:II ratio during growth on the optical properties of the epilayers was studied by UV-vis-near IR spectroscopy. The lowest Urbach tail E0 parameter was measured for material grown at a VI:II ratio of 18:1. The films’ free electron concentration was shown to decrease by over two orders of magnitude, from 1019 to 1017 cm-3, as the VI:II ratio increased from 10 to 60:1. This decrease in carrier concentration with rising VI:II ratio was paralleled to the surge at 12 K of a photoluminescence (PL) emission band characteristic of p-type ZnO. The band gap energies extracted from room temperature transmission spectra ranged between 3.35 and 3.38 eV, in agreement with the value of 3.35 eV measured by room temperature PL. Moreover, variable temperature PL spectra were recorded between 12 and 298 K on ZnO grown on Si. The 12 K spectrum was dominated by a donor-bound exciton (D°X) at 3.36 eV, while the 298 K scan displayed strong free exciton emission (FX) at 3.29 eV. The width of the D°X band proved to be as narrow as 7 meV. The intensity ratio between the room temperature near-band edge emission and the defect-related green band was as high as 28:1, highlighting the optical quality of the layers deposited in this work. The electrical properties of the thin films were studied by Hall measurements (van der Pauw configuration), and a maximum room temperature mobility of 11 cm2/Vs was recorded. Furthermore, a palladium (Pd) Schottky barrier diode on ZnO was fabricated. The barrier height and ideality factor were calculated from current–voltage measurements to be 0.83 eV and 1.6, respectively. The capacitance–voltage curve of the diode yielded a carrier concentration in the depletion region of 8·1017 cm-3. This study has shown that the optical and electrical properties of ZnO depend strongly on the growth conditions employed. A suitable choice of growth parameters can yield high quality ZnO that may be used for various devices. Keywords: Hall, MOCVD, optical spectroscopy, photoluminescence, Schottky barrier diode, SH Imaging, X-ray diffraction, ZnO.
- Full Text:
- Date Issued: 2004
- Authors: Pagni, Olivier Demeno
- Date: 2004
- Subjects: Zinc oxide thin films , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11075 , http://hdl.handle.net/10948/382 , Zinc oxide thin films , Metal organic chemical vapor deposition
- Description: Zinc oxide (ZnO) is a II-VI semiconductor material that offers tremendous potential as a light emitter in the blue-to-UV range. It has a wurtzite structure, and a direct band gap that can be tuned from 3.0 to 4.0 eV by alloying with Cd or Mg, respectively. In this work, ZnO thin films were grown by metalorganic chemical vapor deposition (MOCVD) on n-Si 2 ° off (100), amorphous glass, n-GaAs (100), and c-plane sapphire substrates. Diethyl zinc (DEZn) and tert-butanol (TBOH) were chosen as precursors. For the first time, Second Harmonic Generation Imaging was applied to the mapping of ZnO epilayers. The images obtained highlighted the polycrystalline character of the thin films, and provided insight as to the growth mode of ZnO on Si. The influence of substrate temperature on the structural properties of the epilayers was investigated by X-ray diffraction and optical microscopy. Grain sizes as high as 54 nm were measured. The optimum temperature range for this system proved to be 450 – 500 °C. The influence of the VI:II ratio during growth on the optical properties of the epilayers was studied by UV-vis-near IR spectroscopy. The lowest Urbach tail E0 parameter was measured for material grown at a VI:II ratio of 18:1. The films’ free electron concentration was shown to decrease by over two orders of magnitude, from 1019 to 1017 cm-3, as the VI:II ratio increased from 10 to 60:1. This decrease in carrier concentration with rising VI:II ratio was paralleled to the surge at 12 K of a photoluminescence (PL) emission band characteristic of p-type ZnO. The band gap energies extracted from room temperature transmission spectra ranged between 3.35 and 3.38 eV, in agreement with the value of 3.35 eV measured by room temperature PL. Moreover, variable temperature PL spectra were recorded between 12 and 298 K on ZnO grown on Si. The 12 K spectrum was dominated by a donor-bound exciton (D°X) at 3.36 eV, while the 298 K scan displayed strong free exciton emission (FX) at 3.29 eV. The width of the D°X band proved to be as narrow as 7 meV. The intensity ratio between the room temperature near-band edge emission and the defect-related green band was as high as 28:1, highlighting the optical quality of the layers deposited in this work. The electrical properties of the thin films were studied by Hall measurements (van der Pauw configuration), and a maximum room temperature mobility of 11 cm2/Vs was recorded. Furthermore, a palladium (Pd) Schottky barrier diode on ZnO was fabricated. The barrier height and ideality factor were calculated from current–voltage measurements to be 0.83 eV and 1.6, respectively. The capacitance–voltage curve of the diode yielded a carrier concentration in the depletion region of 8·1017 cm-3. This study has shown that the optical and electrical properties of ZnO depend strongly on the growth conditions employed. A suitable choice of growth parameters can yield high quality ZnO that may be used for various devices. Keywords: Hall, MOCVD, optical spectroscopy, photoluminescence, Schottky barrier diode, SH Imaging, X-ray diffraction, ZnO.
- Full Text:
- Date Issued: 2004
Purification and characterisation of 20S proteasome from ostrich skeletal muscle and its role in meat tenderisation
- Authors: Thomas, Adele René
- Date: 2004
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:11081 , http://hdl.handle.net/10948/320 , Proteolytic enzymes , Ostrich products industry
- Description: The proteasome is renowned for its high molecular weight, multisubunit and mulicatalytic nature. One of its many suggested roles is the degradation of myofibrillar proteins, and therefore it has been proposed to play a role in the meat tenderisation process. The aim of this study was therefore to isolate, purify and characterise the 20S proteasome from ostrich skeletal muscle, with a view to ultimately investigating its role in the tenderisation process of ostrich meat. The 20S proteasome was successfully isolated and purified from ostrich skeletal muscle using Toyopearl Super Q-650S, Sephacryl S-300, hydroxylapatite and Mono Q chromatographies. The intact molecule showed a molecular weight of 725 K and a pI of 6.67. The subunits showed a molecular weight range of 22.2-33.5 K and a pI range of 3-9. 2D-PAGE revealed at least 14 polypeptides. The amino acid composition of the intact enzyme and of each of the eight subunits separating on SDSPAGE, as well as the N-terminal sequences of five of the eight subunits, were determined. The trypsinlike (Tr-L), chymotrypsin-like (ChT-L), peptidylglutamyl peptide hydrolase (PGPH) and caseinolytic activities showed pH optima of 11, 9, 7-8 and 10.3, and temperature optima of 40, 60, 70 and 60oC, respectively. The pH stability range for all four activities was 5-12. The ChT-L and PGPH activities showed thermostabilities up to 60oC, whereas the Tr-L and caseinolytic activities were stable up to 40o C. The enzyme showed complex kinetics. It was inhibited by the peptide aldehyde Z-LLL-CHO and cysteine protease inhibitors. Cations had negligible effects on the enzyme, excepting for Ca2+ and Mg2+. Of the detergents tested, SDS had the most potent stimulatory effect, particularly on the PGPH and caseinolytic activities. The fatty acid studies showed that unsaturation enhanced the ChT-L and the caseinolytic activities, while it completely suppressed the Tr-L activity. Heating at 60oC for 1-2 min stimulated the caseinolytic and PGPH activities. The studies on the role of ostrich skeletal muscle 20S proteasome in ostrich meat tenderisation suggested a definite but minor role of this enzyme, based on the fact that it remained active throughout the 12 days of storage of ostrich M. iliofibularis meat at 4oC and that it participated in myofibril degradation of post-mortem muscle, but to a small degree. These results support the proposal that the proteasome comes into play after the calpains have initiated degradation. However, there was a lack of improvement in tenderness values and minimal myofibrillar degradation over the 12-day storage period of the ostrich M. iliofibularis meat, leading to the conclusion that the tenderisation of this meat was incomplete after 12 days.
- Full Text:
- Date Issued: 2004
- Authors: Thomas, Adele René
- Date: 2004
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:11081 , http://hdl.handle.net/10948/320 , Proteolytic enzymes , Ostrich products industry
- Description: The proteasome is renowned for its high molecular weight, multisubunit and mulicatalytic nature. One of its many suggested roles is the degradation of myofibrillar proteins, and therefore it has been proposed to play a role in the meat tenderisation process. The aim of this study was therefore to isolate, purify and characterise the 20S proteasome from ostrich skeletal muscle, with a view to ultimately investigating its role in the tenderisation process of ostrich meat. The 20S proteasome was successfully isolated and purified from ostrich skeletal muscle using Toyopearl Super Q-650S, Sephacryl S-300, hydroxylapatite and Mono Q chromatographies. The intact molecule showed a molecular weight of 725 K and a pI of 6.67. The subunits showed a molecular weight range of 22.2-33.5 K and a pI range of 3-9. 2D-PAGE revealed at least 14 polypeptides. The amino acid composition of the intact enzyme and of each of the eight subunits separating on SDSPAGE, as well as the N-terminal sequences of five of the eight subunits, were determined. The trypsinlike (Tr-L), chymotrypsin-like (ChT-L), peptidylglutamyl peptide hydrolase (PGPH) and caseinolytic activities showed pH optima of 11, 9, 7-8 and 10.3, and temperature optima of 40, 60, 70 and 60oC, respectively. The pH stability range for all four activities was 5-12. The ChT-L and PGPH activities showed thermostabilities up to 60oC, whereas the Tr-L and caseinolytic activities were stable up to 40o C. The enzyme showed complex kinetics. It was inhibited by the peptide aldehyde Z-LLL-CHO and cysteine protease inhibitors. Cations had negligible effects on the enzyme, excepting for Ca2+ and Mg2+. Of the detergents tested, SDS had the most potent stimulatory effect, particularly on the PGPH and caseinolytic activities. The fatty acid studies showed that unsaturation enhanced the ChT-L and the caseinolytic activities, while it completely suppressed the Tr-L activity. Heating at 60oC for 1-2 min stimulated the caseinolytic and PGPH activities. The studies on the role of ostrich skeletal muscle 20S proteasome in ostrich meat tenderisation suggested a definite but minor role of this enzyme, based on the fact that it remained active throughout the 12 days of storage of ostrich M. iliofibularis meat at 4oC and that it participated in myofibril degradation of post-mortem muscle, but to a small degree. These results support the proposal that the proteasome comes into play after the calpains have initiated degradation. However, there was a lack of improvement in tenderness values and minimal myofibrillar degradation over the 12-day storage period of the ostrich M. iliofibularis meat, leading to the conclusion that the tenderisation of this meat was incomplete after 12 days.
- Full Text:
- Date Issued: 2004
Search algorithms on structured and unstructured data in a large database
- Du Plessis, Mathys Cornelius
- Authors: Du Plessis, Mathys Cornelius
- Date: 2004
- Subjects: Online algorithms , Database searching -- South Africa -- Port Elizabeth , Information retrieval -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11094 , http://hdl.handle.net/10948/d1019681
- Description: This project is concerned with the development of a search algorithm for a large archival database. The Port Elizabeth Genealogical Information System (PEGIS) contains a database consisting of almost 600000 individuals. The standard search algorithms are no longer sufficient to locate individuals in the database. A new algorithm was required that allows searches on any of the words or dates in the database, as well as a means to specify where in the desired record a word should occur. A ranking function of retrieved records was also required. A literature study on the field of Information Retrieval and on algorithms designed specifically for the PEGIS was done. These algorithms were adapted and hybridized to yield a search algorithm that allows for the boolean formulation of queries and the specification of the structure of search words in the desired records. The algorithm ranks retrieved records in assumed relevance to the user. The new algorithms were evaluated with regards to retrieval speed and accuracy and were found to be very effective.
- Full Text:
- Date Issued: 2004
- Authors: Du Plessis, Mathys Cornelius
- Date: 2004
- Subjects: Online algorithms , Database searching -- South Africa -- Port Elizabeth , Information retrieval -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11094 , http://hdl.handle.net/10948/d1019681
- Description: This project is concerned with the development of a search algorithm for a large archival database. The Port Elizabeth Genealogical Information System (PEGIS) contains a database consisting of almost 600000 individuals. The standard search algorithms are no longer sufficient to locate individuals in the database. A new algorithm was required that allows searches on any of the words or dates in the database, as well as a means to specify where in the desired record a word should occur. A ranking function of retrieved records was also required. A literature study on the field of Information Retrieval and on algorithms designed specifically for the PEGIS was done. These algorithms were adapted and hybridized to yield a search algorithm that allows for the boolean formulation of queries and the specification of the structure of search words in the desired records. The algorithm ranks retrieved records in assumed relevance to the user. The new algorithms were evaluated with regards to retrieval speed and accuracy and were found to be very effective.
- Full Text:
- Date Issued: 2004
The challenge of applying systematic conservation planning to the marine environment using expert knowledge (focus: Sparidae)
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
The concentration of ten metals in the tissues of shark species Squalus megalops and Mustelus mustelus (Chondrichthyes) occuring along the Southeastern coast of South Africa
- Erasmus, Christina Petronella
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on. , Marine pollutio -- South Africa.
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11095 , http://hdl.handle.net/10948/d1019683
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on. , Marine pollutio -- South Africa.
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11095 , http://hdl.handle.net/10948/d1019683
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
The concentration of ten metals in the tissues of shark species Squalus megalops and Mustelus mustelus (chondrichthyes) occuring along the Southeastern coast of South Africa
- Erasmus, Christina Petronella
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11085 , http://hdl.handle.net/10948/328 , Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
- Authors: Erasmus, Christina Petronella
- Date: 2004
- Subjects: Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11085 , http://hdl.handle.net/10948/328 , Sharks -- South Africa -- Effect of metals on , Marine pollution -- South Africa
- Description: The southeastern coast of South Africa is deemed unpolluted and with the exception of a few localized areas, is believed to be pristine. This study aimed to (1) assess the concentration of metals in the water and sharks (Squalus megalops, Mustelus mustelus) from different sites along the southeastern coast, (2) determine the effects that metals have on each other and investigate the accumulation and storage of metals in different shark tissues, (3) determine the effects of length and sex on metal concentration and the presence of metallothioneins in the liver. Metal concentrations in water from seven sites along the southeastern coast revealed concentrations below the detection limit of the extraction method, except for iron at St. Francis Bay which was below the recommended levels as supplied by DWAF. Met al concentrations in S. megalops from the seven sites revealed significantly elevated levels in individuals from Algoa and St. Francis Bay when compared to the other 5 sites. This was observed for all metals except manganese, which had a higher concentration at Cape Agulhas. After comparing the metal levels in muscle tissue (S. megalops) with data from the Department of Health it was concluded that the sharks caught at Algoa and St. Francis Bay were unsuited for human consumption. Liver and vertebral tissues from both S. megalops and M. mustelus were deemed unsuited for human consumption but further research should be conducted especially on vertebral metal concentrations. Comparing the metal concentration in different tissue types of S. megalops and M. mustelus significant difference were observed and attributed to differences in the maturity (thus age) of the two species. Significant differences in the metal concentration of males and females for both the species were observed. A higher number of differences were however observed in M. mustelus than in S. megalops, most probably due to the differences in maturity. Length and weight vs. metal concentration regressions in the males and females of both species revealed more negative than positive trends. This was found to be in accordance with other studies from around the world. Using the life stages of S. megalops, significant differences in the average concentration of metals were observed between the life stages, with embryos usually having the highest concentration. The metal concentration series determined for S. megalops were similar to that which have been reported in the literature in that iron and zinc occupied the highest concentration positions while cadmium, copper and manganese occupied the last three. The spleen usually had the highest metal concentration except for aluminium in skin and arsenic in muscle tissue. Pearson correlation revealed significant negative correlations between cadmium and the mentioned metals suggesting that cadmium replaces essential metals such as manganese, iron and copper as. Negative correlations between essential metals were observed most probably due to the competition for binding positions on ligands. Positive correlations were observed between metals in sp ecific tissue types and may be indicative of synergistic effects, e.g. aluminium may result in the accumulation of other metals such as cadmium. Positive and negative correlations between a specific metal and different tissue types have also been observed and it appears that there are movement of metals between tissue types. Positive correlation for essential metals between yolk and other tissue have been observed, although no correlations for non-essential metals were observed. This could potentially indicate a mechanism that prevents the accumulation of nonessential metals in embryos. Though no metallothioneins were isolated form the liver, the presence of cadmium in other proteins indicate that that cadmium is substituted for essential metals, and as this may result in deleterious physiological effects, further studies should be conducted. In conclusion it can be said that although some of the results were expected there are still quite a few unanswered question and further studies should be conducted.
- Full Text:
- Date Issued: 2004
The effects of selected proline-based cyclic dipeptides on growth and induction of apoptosis in cancer cells
- Authors: Brauns, Seth Clint Aron
- Date: 2004
- Subjects: Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11088 , http://hdl.handle.net/10948/396 , Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Description: An increasing number of cyclic dipeptides (CDPs) have been shown to exhibit important biological activity including antifungal, antibacterial, anticonvulsant and immunomodulatory activity. Furthermore, some CDP derivatives have been shown to exhibit antitumour activity in vitro and in vivo. Several proline-based CDPs that exhibit biological activity have been detected in various processed foods and beverages. In the present study, the potential of seven proline-based CDPs to inhibit cancer cell growth was investigated in HT-29 (colon), HeLa (cervical), MCF-7 (breast) and WHCO3 (oesophageal) cancer cell lines. The CDPs used in this study were cyclo(Phe-Pro), cyclo(Tyr-Pro), cyclo(Gly-Pro), cyclo(Pro- Pro), cyclo(His-Pro), cyclo(Leu-Pro) and cyclo(Thr-Pro). The sulforhodamine B (SRB) cell growth assay was used in an initial screening phase to investigate the effects of the CDPs in HT-29, HeLa and MCF-7 cells. After exposing the cells to 10mM of the respective CDPs for 48 hours, the SRB assay results showed that only cyclo(Phe-Pro) exhibited more than 50% growth inhibition (p<0.01) in the three cell lines. The other CDPs showed comparatively marginal growth-inhibitory effects, except for cyclo(Tyr-Pro), which exhibited a pronounced effect in MCF-7 cells compared to HT-29 and HeLa cells. The MTT assay was used to confirm the SRB assay results for cyclo(Phe-Pro) and cyclo(Tyr-Pro), extending the investigation to the use of the fourth cell line WHCO3 and using a longer exposure time of 72 hours. The MTT assay demonstrated a dosedependent (0.008-10 mM) growth inhibition by cyclo(Phe-Pro) with an IC50 value of 4.04 ± 1.15 mM for HT-29 cells. Cyclo(Phe-Pro) was subsequently used to investigate whether the growth-inhibitory effects of this CDP were related to the induction of apoptosis in HT-29 cells. Hoechst 33342 staining showed that 5mM cyclo(Phe-Pro) induced characteristic chromatin condensation and nuclear fragmentation in 18.3 ± 2.8% (p<0.01) of HT-29 cells after 72 hours. Furthermore, annexin V binding revealed that HT-29 cells treated with 5 mM cyclo(Phe-Pro) displayed phosphatidylserine externalization after 48 hours. In addition, it was shown that 10 mM cyclo(Phe-Pro) induced poly(ADP-ribose)polymerase PARP cleavage, one of the hallmark events of apoptosis. The use of the broad-range caspase inhibitor Z-VAD-FMK, showed that this PARP cleavage was caspase-dependent, which in turn was confirmed by demonstrating an increase in caspase-3 activity (p<0.01) in cyclo(Phe- Pro)-treated HT-29 cells. In conclusion, these findings demonstrate that cyclo(Phe-Pro) inhibited the growth of HT- 29, MCF-7, HeLa and WHCO3 cells, and induced apoptosis in HT-29 colon cancer cells, suggesting the potential antitumour activity of cyclo(Phe-Pro)-related CDPs.
- Full Text:
- Date Issued: 2004
- Authors: Brauns, Seth Clint Aron
- Date: 2004
- Subjects: Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11088 , http://hdl.handle.net/10948/396 , Cyclic peptides , Antineoplastic agents -- Testing , Apoptosis
- Description: An increasing number of cyclic dipeptides (CDPs) have been shown to exhibit important biological activity including antifungal, antibacterial, anticonvulsant and immunomodulatory activity. Furthermore, some CDP derivatives have been shown to exhibit antitumour activity in vitro and in vivo. Several proline-based CDPs that exhibit biological activity have been detected in various processed foods and beverages. In the present study, the potential of seven proline-based CDPs to inhibit cancer cell growth was investigated in HT-29 (colon), HeLa (cervical), MCF-7 (breast) and WHCO3 (oesophageal) cancer cell lines. The CDPs used in this study were cyclo(Phe-Pro), cyclo(Tyr-Pro), cyclo(Gly-Pro), cyclo(Pro- Pro), cyclo(His-Pro), cyclo(Leu-Pro) and cyclo(Thr-Pro). The sulforhodamine B (SRB) cell growth assay was used in an initial screening phase to investigate the effects of the CDPs in HT-29, HeLa and MCF-7 cells. After exposing the cells to 10mM of the respective CDPs for 48 hours, the SRB assay results showed that only cyclo(Phe-Pro) exhibited more than 50% growth inhibition (p<0.01) in the three cell lines. The other CDPs showed comparatively marginal growth-inhibitory effects, except for cyclo(Tyr-Pro), which exhibited a pronounced effect in MCF-7 cells compared to HT-29 and HeLa cells. The MTT assay was used to confirm the SRB assay results for cyclo(Phe-Pro) and cyclo(Tyr-Pro), extending the investigation to the use of the fourth cell line WHCO3 and using a longer exposure time of 72 hours. The MTT assay demonstrated a dosedependent (0.008-10 mM) growth inhibition by cyclo(Phe-Pro) with an IC50 value of 4.04 ± 1.15 mM for HT-29 cells. Cyclo(Phe-Pro) was subsequently used to investigate whether the growth-inhibitory effects of this CDP were related to the induction of apoptosis in HT-29 cells. Hoechst 33342 staining showed that 5mM cyclo(Phe-Pro) induced characteristic chromatin condensation and nuclear fragmentation in 18.3 ± 2.8% (p<0.01) of HT-29 cells after 72 hours. Furthermore, annexin V binding revealed that HT-29 cells treated with 5 mM cyclo(Phe-Pro) displayed phosphatidylserine externalization after 48 hours. In addition, it was shown that 10 mM cyclo(Phe-Pro) induced poly(ADP-ribose)polymerase PARP cleavage, one of the hallmark events of apoptosis. The use of the broad-range caspase inhibitor Z-VAD-FMK, showed that this PARP cleavage was caspase-dependent, which in turn was confirmed by demonstrating an increase in caspase-3 activity (p<0.01) in cyclo(Phe- Pro)-treated HT-29 cells. In conclusion, these findings demonstrate that cyclo(Phe-Pro) inhibited the growth of HT- 29, MCF-7, HeLa and WHCO3 cells, and induced apoptosis in HT-29 colon cancer cells, suggesting the potential antitumour activity of cyclo(Phe-Pro)-related CDPs.
- Full Text:
- Date Issued: 2004
A study of the structural geology of the Witteberg Group and lowermost Karoo Supergroup, Darlington Dam, Jansenville District, Eastern Cape
- Goossens, Angelique Emily Maria
- Authors: Goossens, Angelique Emily Maria
- Date: 2003
- Subjects: Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11071 , http://hdl.handle.net/10948/291 , Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Description: A number of outcrops of the Witteberg Group and lowermost Karoo Supergroup rocks were studied in the area south of the Darlington Dam, Jansenville District, with the aim of documenting structural characteristics of the area. All lithologies are folded with fold styles varying from gentle to near isoclinal (based on interlimb angle). Fold axes are either sub-horizontal or plunging at gentle to moderate angles whereas axial planes dip gently to vertically (predominantly steep to sub-vertical). Folds verge predominantly towards the north but where southward verging they are associated with faulting or strongly folded areas. Folds plunge gently to the east-southeast and west-northwest. The area consists of a large anticlinorium with both first and second order folds occurring. Eastwest striking faults occur in the study area and are classified as normal, reverse and thrust faults. A study of the joint sets shows that there are four dominant joint directions, namely 18o, 33o, 97o and 107o (in order from least to most important). An interpretation of the tectonic history is presented in which the relationships between faults and folds show that faults formed during and after folding. Folding, and reverse and thrust faulting, occurred during the compressional events that formed the Cape Fold Belt, whereas the normal faults formed during the relaxation of these compressional forces or during the break-up of Gondwana.
- Full Text:
- Date Issued: 2003
- Authors: Goossens, Angelique Emily Maria
- Date: 2003
- Subjects: Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11071 , http://hdl.handle.net/10948/291 , Folds (Geology) -- South Africa -- Eastern Cape , Faults (Geology) -- South Africa -- Eastern Cape , Geology, Structural -- South Africa -- Eastern Cape
- Description: A number of outcrops of the Witteberg Group and lowermost Karoo Supergroup rocks were studied in the area south of the Darlington Dam, Jansenville District, with the aim of documenting structural characteristics of the area. All lithologies are folded with fold styles varying from gentle to near isoclinal (based on interlimb angle). Fold axes are either sub-horizontal or plunging at gentle to moderate angles whereas axial planes dip gently to vertically (predominantly steep to sub-vertical). Folds verge predominantly towards the north but where southward verging they are associated with faulting or strongly folded areas. Folds plunge gently to the east-southeast and west-northwest. The area consists of a large anticlinorium with both first and second order folds occurring. Eastwest striking faults occur in the study area and are classified as normal, reverse and thrust faults. A study of the joint sets shows that there are four dominant joint directions, namely 18o, 33o, 97o and 107o (in order from least to most important). An interpretation of the tectonic history is presented in which the relationships between faults and folds show that faults formed during and after folding. Folding, and reverse and thrust faulting, occurred during the compressional events that formed the Cape Fold Belt, whereas the normal faults formed during the relaxation of these compressional forces or during the break-up of Gondwana.
- Full Text:
- Date Issued: 2003
An assessment of bait availability, utilization and management guidelines in Eastern Cape estuaries
- Authors: Jooste, Jakobus Gerrit
- Date: 2003
- Subjects: Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11073 , http://hdl.handle.net/10948/334 , Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Description: Aspects around the management of benthic soft sediment bait organisms, with special focus on the mud prawn (Upogebia africana) of eastern Cape estuaries was investigated. The recreational linefishery of the Gamtoos estuary was described, and compared to previous studies. Target fish species was identified, and a large dependency on bait sourced from estuaries needed for the capture of these species was noted, especially for spotted grunter (Pomadasys commersonnii). A comparison between bait use, success and the natural diet of target fish species was also made. The structure and distribution of sediments in the old channel mud banks was described and compared with historical data. The influence of sediments on mud prawn distribution was investigated, but no significant interactions were found at the study site. The impacts of once-off pumping and digging events, and monthly trampling on the sediments and mud prawn population was studied over a 7-month period. Initial removal rates as well as recovery time varied significantly between the two collection methods, while the largest decline in prawn numbers (to zero) with no recovery visible after seven months was caused by trampling. All disturbances caused some alteration in sediment composition, but not to such an extent that the sediments became unfavorable for mud prawns. Trampling did, however, result in the compaction of sediments to such a degree that prawns could not construct burrows. Issues around current removal quotas of bait species as well as the creation of a small-scale commercial (SSC) bait selling operation at Swartkops estuary were critically evaluated, and suggestions for the future removal rates of mud prawns based on production export calculations were made. The distribution, size, sex ratios and number of gravid females occurring along a tidal gradient as well as along horizontal gradient of the mud bank during growth (January – March) and reproductive (September – October) periods was investigated. Changes in the distribution of females between the two study periods were significant, while the distribution of reproductively active females were closely linked to the low water mark (Lower tidal levels). Females occurring in this zone were also significantly larger than females occurring towards the back of the study site. Some minor changes along the horizontal gradient were also observed. The sediment compos ition of the mud bank was found not to play a role in this distribution, leading to the suggestion that exposure to ebb and flood tide currents could influence female prawn distributions. Management recommendations based on these observations were made.
- Full Text:
- Date Issued: 2003
- Authors: Jooste, Jakobus Gerrit
- Date: 2003
- Subjects: Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11073 , http://hdl.handle.net/10948/334 , Upogebia african -- Effects of sediments on -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishing baits -- Conservation -- South Africa -- Eastern Cape
- Description: Aspects around the management of benthic soft sediment bait organisms, with special focus on the mud prawn (Upogebia africana) of eastern Cape estuaries was investigated. The recreational linefishery of the Gamtoos estuary was described, and compared to previous studies. Target fish species was identified, and a large dependency on bait sourced from estuaries needed for the capture of these species was noted, especially for spotted grunter (Pomadasys commersonnii). A comparison between bait use, success and the natural diet of target fish species was also made. The structure and distribution of sediments in the old channel mud banks was described and compared with historical data. The influence of sediments on mud prawn distribution was investigated, but no significant interactions were found at the study site. The impacts of once-off pumping and digging events, and monthly trampling on the sediments and mud prawn population was studied over a 7-month period. Initial removal rates as well as recovery time varied significantly between the two collection methods, while the largest decline in prawn numbers (to zero) with no recovery visible after seven months was caused by trampling. All disturbances caused some alteration in sediment composition, but not to such an extent that the sediments became unfavorable for mud prawns. Trampling did, however, result in the compaction of sediments to such a degree that prawns could not construct burrows. Issues around current removal quotas of bait species as well as the creation of a small-scale commercial (SSC) bait selling operation at Swartkops estuary were critically evaluated, and suggestions for the future removal rates of mud prawns based on production export calculations were made. The distribution, size, sex ratios and number of gravid females occurring along a tidal gradient as well as along horizontal gradient of the mud bank during growth (January – March) and reproductive (September – October) periods was investigated. Changes in the distribution of females between the two study periods were significant, while the distribution of reproductively active females were closely linked to the low water mark (Lower tidal levels). Females occurring in this zone were also significantly larger than females occurring towards the back of the study site. Some minor changes along the horizontal gradient were also observed. The sediment compos ition of the mud bank was found not to play a role in this distribution, leading to the suggestion that exposure to ebb and flood tide currents could influence female prawn distributions. Management recommendations based on these observations were made.
- Full Text:
- Date Issued: 2003
An evaluation of the Xenopus laevis liver slice model to study the toxic effects of microcystin
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
An investigation into the induction of oxidative stress and apoptosis by microcystin-LR in the CaCo2 cell line and intestinal tract of Balb/c mice
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
Aplousobranch ascidians (Tunicata: Ascidiacea) from Southern Africa
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
- Authors: Parker-Nance, Shirley
- Date: 2003
- Subjects: Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11078 , http://hdl.handle.net/10948/311 , Sea squirts -- South Africa -- Classification , Aplousobranchia -- South Africa -- Classification
- Description: The ascidian (subphylum Tunicata: class Ascidiacea) fauna along the southern African coast constitutes an important component of the sessile benthic reef fauna. Little is known of the species composition, biodiversity and distribution of ascidians on southern African intertidal and subtidal reefs. Past research on the ascidian fauna of South Africa was sporadic and limited, with only about one hundred and seventy species recorded during the last one hundred and twenty years. This is the first taxonomic study undertaken by a South African resident scientist. The study focused on six genera in four families (Euherdmaniidae, Polyclinidae, Pseudodistomidae and Didemnidae) belonging to the class Ascidiacea and suborder Aplousobranchia. Five species new to science, two Polyclinum, two Pseudodistoma and one Polysyncraton species are described. New additional information on the distribution of five species previously known to science, including one recorded for the first time along the South African coast, is presented. A literature review and comparison of the taxonomic important characteristics is made of all species known globally for the six genera. These six genera comprise twelve Euherdmania, fifteen Aplidiopsis, forty Polyclinum thirty-one Pseudodistoma, six Atriolum and sixty-eight Polysyncraton species.
- Full Text:
- Date Issued: 2003
Investigations into the asymmetric reduction of ketones
- Authors: Bena, Luvuyo Clifford
- Date: 2003
- Subjects: Ketones , Asymmetric synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11065 , http://hdl.handle.net/10948/323 , Ketones , Asymmetric synthesis
- Description: A six-step synthesis of salbutamol from methyl salicylate with an overall yield of 17% has been completed, although the yield was not optimised. In the process, Zn(BH4)2 was found to selectively reduce a ketone carbonyl group in the presence of an ester unit. In contrast, borane was found to reduce both the ketone and ester carbonyl groups. Reduction of phenacyl bromide with borane in the presence of chiral catalysts based on (R)-alaninol and (R,S)-ephidrine resulted a measure of enantioselectivity in the product. However, the configuration of the alcohol obtained in the case of (R)-alaninol was contrary to expectations based both on experimental trends observed elsewhere as well as our own theoretical predictions. The asymmetric reduction of methyl 5-bromoacetyl-2-benzyloxybenzoate was accomplished with both borane and Zn(BH4)2 in the presence of a range of chiral catalysts. Optically active products were obtained in all cases, although the optical rotations were significantly smaller in the case of Zn(BH4)2. Unfortunately, we were not successful in determining the enantiomeric excesses of these reactions. The use of a NMR lanthanide shift reagent resulted in a complex spectrum that was impossible to interpret unambiguously. This presumably arises from the presence of several Lewis base sites in the product at which complexation with the shift reagent can take place. It was also not possible to determine the optical rotation of salbutamol itself owing to the relatively small amount of material obtained. A conformational analysis of salbutamol, where NMR data was correlated with molecular modelling results, was successfully carried out and revealed a strong preference for that conformer family characterised by O–C–C–N and Ar–C–C–N torsion angles of ca. 60º and 180º, respectively. Interestingly, these conformers are found to be stabilised by OH…N rather than NH…O hydrogen bonding. This study has also confirmed the effectiveness of the MMFF94 force field for conformational analysis studies in compounds of this kind. Lastly, a relatively simple method for modelling the BH3/oxazaborolidine reduction of ketones at the PM3 semiempirical MO level of approximation was devised. This approach has provided insights into the mechanism of the reaction and has furthermore enabled us to predict the enantioselectivities likely to result from various catalysts and ketones. In comparing our theoretical and experimental findings, an anomalous result was observed in the case of (R)-alaninol; this will have to be investigated further, particularly at the experimental level. However, we believe that our approach provides a sound basis for aiding the design and screening of new, potentially better catalysts.
- Full Text:
- Date Issued: 2003
- Authors: Bena, Luvuyo Clifford
- Date: 2003
- Subjects: Ketones , Asymmetric synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11065 , http://hdl.handle.net/10948/323 , Ketones , Asymmetric synthesis
- Description: A six-step synthesis of salbutamol from methyl salicylate with an overall yield of 17% has been completed, although the yield was not optimised. In the process, Zn(BH4)2 was found to selectively reduce a ketone carbonyl group in the presence of an ester unit. In contrast, borane was found to reduce both the ketone and ester carbonyl groups. Reduction of phenacyl bromide with borane in the presence of chiral catalysts based on (R)-alaninol and (R,S)-ephidrine resulted a measure of enantioselectivity in the product. However, the configuration of the alcohol obtained in the case of (R)-alaninol was contrary to expectations based both on experimental trends observed elsewhere as well as our own theoretical predictions. The asymmetric reduction of methyl 5-bromoacetyl-2-benzyloxybenzoate was accomplished with both borane and Zn(BH4)2 in the presence of a range of chiral catalysts. Optically active products were obtained in all cases, although the optical rotations were significantly smaller in the case of Zn(BH4)2. Unfortunately, we were not successful in determining the enantiomeric excesses of these reactions. The use of a NMR lanthanide shift reagent resulted in a complex spectrum that was impossible to interpret unambiguously. This presumably arises from the presence of several Lewis base sites in the product at which complexation with the shift reagent can take place. It was also not possible to determine the optical rotation of salbutamol itself owing to the relatively small amount of material obtained. A conformational analysis of salbutamol, where NMR data was correlated with molecular modelling results, was successfully carried out and revealed a strong preference for that conformer family characterised by O–C–C–N and Ar–C–C–N torsion angles of ca. 60º and 180º, respectively. Interestingly, these conformers are found to be stabilised by OH…N rather than NH…O hydrogen bonding. This study has also confirmed the effectiveness of the MMFF94 force field for conformational analysis studies in compounds of this kind. Lastly, a relatively simple method for modelling the BH3/oxazaborolidine reduction of ketones at the PM3 semiempirical MO level of approximation was devised. This approach has provided insights into the mechanism of the reaction and has furthermore enabled us to predict the enantioselectivities likely to result from various catalysts and ketones. In comparing our theoretical and experimental findings, an anomalous result was observed in the case of (R)-alaninol; this will have to be investigated further, particularly at the experimental level. However, we believe that our approach provides a sound basis for aiding the design and screening of new, potentially better catalysts.
- Full Text:
- Date Issued: 2003
Observed metabolic changes in male Wistar rats after treatment with an antidepressant implied in undesirable weight gain, or Sutherlandia frutescens for Type II diabetes
- Authors: Chadwick, Wayne
- Date: 2003
- Subjects: Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11068 , http://hdl.handle.net/10948/313 , Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Description: Type II diabetes is fast becoming a growing problem in developed countries worldwide. Traditionally the median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve has shifted to the left. Western countries boast the worst statistics in which type II diabetes is being reported in children under the age of ten. At such a young age the disease often goes undiagnosed for long periods of time allowing considerable damage to occur. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with a characteristically unhealthy western diet. Type II diabetes is an extremely expensive disease to manage, and with the rapid growth of this pandemic our country will soon feel the economic burden of this disease. It is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight or appetite thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of the S. frutescens, metformin (a well known type II diabetes medication) and amitriptyline (a common tricyclic antidepressant) was administered to three groups of ten male Wistar rats. The control group received water without any medication. The rat’s weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after four months of medicinal compliance and glucose uptake, in the presence and absence of insulin, was tested in epididymal fat, liver and muscle. Fasting plasma glucose levels, lipoprotein, cholesterol and triglyceride concentrations were also determined.
- Full Text:
- Date Issued: 2003
- Authors: Chadwick, Wayne
- Date: 2003
- Subjects: Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11068 , http://hdl.handle.net/10948/313 , Rats -- Metabolism , Non-insulin-dependent diabetes -- Research , Rats as laboratory animals
- Description: Type II diabetes is fast becoming a growing problem in developed countries worldwide. Traditionally the median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve has shifted to the left. Western countries boast the worst statistics in which type II diabetes is being reported in children under the age of ten. At such a young age the disease often goes undiagnosed for long periods of time allowing considerable damage to occur. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with a characteristically unhealthy western diet. Type II diabetes is an extremely expensive disease to manage, and with the rapid growth of this pandemic our country will soon feel the economic burden of this disease. It is for this reason that cheaper medication needs to be investigated in the form of traditional plants, such as Sutherlandia frutescens. Prescription medication, such as tricyclic antidepressants, may also increase body weight or appetite thereby playing a role in obesity. The cause of weight gain in such cases may go unrecognized or lead to cessation of the medication with or without the practitioner’s knowledge or approval. It is therefore necessary to investigate the causative agents responsible for the excessive weight gain. Drinking water containing extracts of the S. frutescens, metformin (a well known type II diabetes medication) and amitriptyline (a common tricyclic antidepressant) was administered to three groups of ten male Wistar rats. The control group received water without any medication. The rat’s weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after four months of medicinal compliance and glucose uptake, in the presence and absence of insulin, was tested in epididymal fat, liver and muscle. Fasting plasma glucose levels, lipoprotein, cholesterol and triglyceride concentrations were also determined.
- Full Text:
- Date Issued: 2003