A field investigation of physical workloads imposed on harvesters in South African forestry
- Authors: Christie, Candice Jo-Anne
- Date: 2006
- Subjects: Forests and forestry -- South Africa Employees -- Workload Forest products industry -- South Africa Work -- Physiological aspects Heart rate monitoring Foresters -- South Africa -- Workload Oxygen -- Physiological transport
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5122 , http://hdl.handle.net/10962/d1005200
- Description: The focus of this field investigation was an analysis of the work demands being placed on South African forestry workers, in particular Chainsaw Operators and Stackers. Working postures, physiological and perceptual responses were assessed on a sample of 58 workers (29 Chainsaw Operators and 29 Stackers) during a ‘normal’ working shift. Body mass was measured before and after work in order to determine dehydration levels. Polar heart rate monitors were fitted to six workers each day over a period of two weeks in order to record ‘working’ heart rates. Fluid and food intake was monitored and recorded during this initial data collection phase. The Rating of Perceived Exertion and Body Discomfort Scales were explained in Zulu, their native language, and workers were asked to rate their perceptions of effort at regular intervals during work, while areas and intensity of body discomfort was obtained on completion of work. After completing a work shift, a 30 minute ‘recovery’ period was given, thereafter a portable ergospirometer, the k4b², was attached to the worker who then participated in a progressive, submaximal step test for the purpose of establishing individual, and group, heart rate-oxygen uptake (HR/VO[subscript 2]) regressions for predicting oxygen uptake from ‘working’ heart rate responses. These procedures were repeated four weeks later following the introduction of a fluid and nutritional supplement during work which was delivered to the workers while they were executing their tasks. The results revealed awkward working postures with a predominance of trunk flexion during all the harvesting tasks; these postures, adopted for long periods during work, are very likely to lead to the development of musculoskeletal injuries. The mean working heart rates were 123.3 bt.min[superscript (-1)] and 117.6 bt.min[superscript (-1)] during chainsaw operations and stacking respectively. During the step test, the mean heart rate and oxygen uptake responses were 127.9 bt.min[superscript (-1)] and 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Chainsaw Operators) and 116.9 bt.min[superscript (-1)] and 24.0 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Stackers), revealing no significant difference between the ‘working’ heart rates and the heart rates recorded during the step test. Physiological responses were analyzed over the full work shift which was divided into four quarters. Heart rate and oxygen uptake were significantly higher during the last half of the Chainsaw Operators’ work shift compared to the first half. Heart rate increased from 120.7 bt.min[superscript (-1)] during the first quarter to 127.4 bt.min[superscript (-1)] during the last quarter of chainsaw operations. Likewise, oxygen uptake increased from 19.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] to 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] from the first to the last quarter of work. During stacking the heart rate (mean of 117.6 bt.min[superscript (-1)]) and oxygen uptake (mean of 24.6 ml.kg[superscript (-1)].min[superscript (-1)]) responses remained stable over the duration of the working shift. Workers lost, on average, 2.8% body mass during work while felling and cross-cutting and 3.6% during stacking. This reduced significantly to a loss of 0.4% body mass when re-tested following the introduction of water and food during the work period. Likewise, the energy deficit was significantly improved due to the introduction of a nutritional supplement. Pre-intervention the deficit was 8861.8 kJ (Chainsaw Operators) and 8804.2 kJ (Stackers) while in the post-intervention phase this deficit was reduced by approximately 50% for both groups of workers.
- Full Text:
- Date Issued: 2006
- Authors: Christie, Candice Jo-Anne
- Date: 2006
- Subjects: Forests and forestry -- South Africa Employees -- Workload Forest products industry -- South Africa Work -- Physiological aspects Heart rate monitoring Foresters -- South Africa -- Workload Oxygen -- Physiological transport
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5122 , http://hdl.handle.net/10962/d1005200
- Description: The focus of this field investigation was an analysis of the work demands being placed on South African forestry workers, in particular Chainsaw Operators and Stackers. Working postures, physiological and perceptual responses were assessed on a sample of 58 workers (29 Chainsaw Operators and 29 Stackers) during a ‘normal’ working shift. Body mass was measured before and after work in order to determine dehydration levels. Polar heart rate monitors were fitted to six workers each day over a period of two weeks in order to record ‘working’ heart rates. Fluid and food intake was monitored and recorded during this initial data collection phase. The Rating of Perceived Exertion and Body Discomfort Scales were explained in Zulu, their native language, and workers were asked to rate their perceptions of effort at regular intervals during work, while areas and intensity of body discomfort was obtained on completion of work. After completing a work shift, a 30 minute ‘recovery’ period was given, thereafter a portable ergospirometer, the k4b², was attached to the worker who then participated in a progressive, submaximal step test for the purpose of establishing individual, and group, heart rate-oxygen uptake (HR/VO[subscript 2]) regressions for predicting oxygen uptake from ‘working’ heart rate responses. These procedures were repeated four weeks later following the introduction of a fluid and nutritional supplement during work which was delivered to the workers while they were executing their tasks. The results revealed awkward working postures with a predominance of trunk flexion during all the harvesting tasks; these postures, adopted for long periods during work, are very likely to lead to the development of musculoskeletal injuries. The mean working heart rates were 123.3 bt.min[superscript (-1)] and 117.6 bt.min[superscript (-1)] during chainsaw operations and stacking respectively. During the step test, the mean heart rate and oxygen uptake responses were 127.9 bt.min[superscript (-1)] and 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Chainsaw Operators) and 116.9 bt.min[superscript (-1)] and 24.0 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Stackers), revealing no significant difference between the ‘working’ heart rates and the heart rates recorded during the step test. Physiological responses were analyzed over the full work shift which was divided into four quarters. Heart rate and oxygen uptake were significantly higher during the last half of the Chainsaw Operators’ work shift compared to the first half. Heart rate increased from 120.7 bt.min[superscript (-1)] during the first quarter to 127.4 bt.min[superscript (-1)] during the last quarter of chainsaw operations. Likewise, oxygen uptake increased from 19.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] to 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] from the first to the last quarter of work. During stacking the heart rate (mean of 117.6 bt.min[superscript (-1)]) and oxygen uptake (mean of 24.6 ml.kg[superscript (-1)].min[superscript (-1)]) responses remained stable over the duration of the working shift. Workers lost, on average, 2.8% body mass during work while felling and cross-cutting and 3.6% during stacking. This reduced significantly to a loss of 0.4% body mass when re-tested following the introduction of water and food during the work period. Likewise, the energy deficit was significantly improved due to the introduction of a nutritional supplement. Pre-intervention the deficit was 8861.8 kJ (Chainsaw Operators) and 8804.2 kJ (Stackers) while in the post-intervention phase this deficit was reduced by approximately 50% for both groups of workers.
- Full Text:
- Date Issued: 2006
A genetic and ecophysiological comparison of co-occuring indigenous (Perna perna) and invasive (Mytilus galloprovincialis) intertidal mussels
- Authors: Zardi, Gerardo Ivan
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
- Authors: Zardi, Gerardo Ivan
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
A global ionospheric F2 region peak electron density model using neural networks and extended geophysically relevant inputs
- Authors: Oyeyemi, Elijah Oyedola
- Date: 2006
- Subjects: Neural networks (Computer science) Ionospheric electron density Ionosphere Ionosphere -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5470 , http://hdl.handle.net/10962/d1005255
- Description: This thesis presents my research on the development of a neural network (NN) based global empirical model of the ionospheric F2 region peak electron density using extended geophysically relevant inputs. The main principle behind this approach has been to utilize parameters other than simple geographic co-ordinates, on which the F2 peak electron density is known to depend, and to exploit the technique of NNs, thereby establishing and modeling the non-linear dynamic processes (both in space and time)associated with the F2 region electron density on a global scale. Four different models have been developed in this work. These are the foF2 NN model, M(3000)F2 NN model, short-term forecasting foF2 NN, and a near-real time foF2 NN model. Data used in the training of the NNs were obtained from the worldwide ionosonde stations spanning the period 1964 to 1986 based on availability, which included all periods of calm and disturbed magnetic activity. Common input parameters used in the training of all 4 models are day number (day of the year, DN), Universal Time (UT), a 2 month running mean of the sunspot number (R2), a 2 day running mean of the 3-hour planetary magnetic index ap (A16), solar zenith angle (CHI), geographic latitude (q), magnetic dip angle (I), angle of magnetic declination (D), angle of meridian relative to subsolar point (M). For the short-term and near-real time foF2 models, additional input parameters related to recent past observations of foF2 itself were included in the training of the NNs. The results of the foF2 NN model and M(3000)F2 NN model presented in this work, which compare favourably with the IRI (International Reference Ionosphere) model successfully demonstrate the potential of NNs for spatial and temporal modeling of the ionospheric parameters foF2 and M(3000)F2 globally. The results obtained from the short-term foF2 NN model and nearreal time foF2 NN model reveal that, in addition to the temporal and spatial input variables, short-term forecasting of foF2 is much improved by including past observations of foF2 itself. Results obtained from the near-real time foF2 NN model also reveal that there exists a correlation between measured foF2 values at different locations across the globe. Again, comparisons of the foF2 NN model and M(3000)F2 NN model predictions with that of the IRI model predictions and observed values at some selected high latitude stations, suggest that the NN technique can successfully be employed to model the complex irregularities associated with the high latitude regions. Based on the results obtained in this research and the comparison made with the IRI model (URSI and CCIR coefficients), these results justify consideration of the NN technique for the prediction of global ionospheric parameters. I believe that, after consideration by the IRI community, these models will prove to be valuable to both the high frequency (HF) communication and worldwide ionospheric communities.
- Full Text:
- Date Issued: 2006
- Authors: Oyeyemi, Elijah Oyedola
- Date: 2006
- Subjects: Neural networks (Computer science) Ionospheric electron density Ionosphere Ionosphere -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5470 , http://hdl.handle.net/10962/d1005255
- Description: This thesis presents my research on the development of a neural network (NN) based global empirical model of the ionospheric F2 region peak electron density using extended geophysically relevant inputs. The main principle behind this approach has been to utilize parameters other than simple geographic co-ordinates, on which the F2 peak electron density is known to depend, and to exploit the technique of NNs, thereby establishing and modeling the non-linear dynamic processes (both in space and time)associated with the F2 region electron density on a global scale. Four different models have been developed in this work. These are the foF2 NN model, M(3000)F2 NN model, short-term forecasting foF2 NN, and a near-real time foF2 NN model. Data used in the training of the NNs were obtained from the worldwide ionosonde stations spanning the period 1964 to 1986 based on availability, which included all periods of calm and disturbed magnetic activity. Common input parameters used in the training of all 4 models are day number (day of the year, DN), Universal Time (UT), a 2 month running mean of the sunspot number (R2), a 2 day running mean of the 3-hour planetary magnetic index ap (A16), solar zenith angle (CHI), geographic latitude (q), magnetic dip angle (I), angle of magnetic declination (D), angle of meridian relative to subsolar point (M). For the short-term and near-real time foF2 models, additional input parameters related to recent past observations of foF2 itself were included in the training of the NNs. The results of the foF2 NN model and M(3000)F2 NN model presented in this work, which compare favourably with the IRI (International Reference Ionosphere) model successfully demonstrate the potential of NNs for spatial and temporal modeling of the ionospheric parameters foF2 and M(3000)F2 globally. The results obtained from the short-term foF2 NN model and nearreal time foF2 NN model reveal that, in addition to the temporal and spatial input variables, short-term forecasting of foF2 is much improved by including past observations of foF2 itself. Results obtained from the near-real time foF2 NN model also reveal that there exists a correlation between measured foF2 values at different locations across the globe. Again, comparisons of the foF2 NN model and M(3000)F2 NN model predictions with that of the IRI model predictions and observed values at some selected high latitude stations, suggest that the NN technique can successfully be employed to model the complex irregularities associated with the high latitude regions. Based on the results obtained in this research and the comparison made with the IRI model (URSI and CCIR coefficients), these results justify consideration of the NN technique for the prediction of global ionospheric parameters. I believe that, after consideration by the IRI community, these models will prove to be valuable to both the high frequency (HF) communication and worldwide ionospheric communities.
- Full Text:
- Date Issued: 2006
An analysis of how the Senior Certificate examination constructs the language needs of English second language learners
- Authors: Blunt, Sandra Viki
- Date: 2006 , 2013-06-11
- Subjects: Habermas, Jürgen Education, Secondary -- South Africa Examinations -- South Africa -- Evaluation English language -- Examinations -- South Africa English language -- Study and teaching -- South Africa -- Foreign speakers Language and education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1902 , http://hdl.handle.net/10962/d1006243
- Description: The Senior Certificate (SC) examination, a focus of the research described in this thesis, has an important function in terms of the quality of the education system overall and also in terms of the contribution of education to the achievement of national goals. The SC examination functions i) as a measure of achievement at school ii) as an indicator of work readiness and iii) as an indicator of the potential to succeed in higher education. This thesis offers a critique of the SC examination in respect of its functions. The way in which learners' language related needs are constructed is crucial in discussing the SC examination's legitimacy since perceptions about the needs of learners are reflected in what is taught and assessed. Since the majority of candidates writing the SC exarnination do so using a language which is not their mother tongue, the research described in the thesis attempted to identify the way in which the English second language (ESL) SC examination papers construct learners' needs. Examination papers represent a particular domain of social practice and are constructed through discourse. In the context of the research described in this thesis, discourses are understood as sets of ideas which are shared by communities of people and which give rise to practices which then define and sustain those communities and, thus, the discourses themselves. Discourse is language insofar as it converges with power and positions people in the interests of power. The ideological nature of discourse necessitates a critical orientation to research which interrogates, challenges and critiques the status quo. To identify the discourses constructing ESL learners' needs I conducted a critical discourse analysis on a representative sarnple of ESL SC exarnination papers and also interviewed six ESL examiners to corroborate the findings of the analysis. This then allowed me to identify several dominant discourses constructing ESL learners' needs: meaning-related, literature-related and process-related. The first meaning-related discourse, 'Received Tradition' discourse, focuses on the rules of grammar and spelling. Rather than approaching language as a resource to enable learners to understand the ideas to which they are exposed, learners are being taught discrete 'skills' to equip them for higher education study and the workplace. It is argued that school-based language literacy practices are not generalizable to the workplace and to higher education. Another aspect of 'Received Tradition' discourse holds that the study of English literature is a medium for understanding life and that there is moral value in teaching English literature. Learners are therefore constructed as lacking these values and their needs as having to acquire them. 'Received Tradition' discourse also overlaps with a second meaning-related discourse, 'Autonomous Text' discourse, which holds that the text's meaning is explicit and that if the learners can manipulate the rules of English grammar, 'have' vocabulary and can spell, they can retrieve meanings from texts they encounter in a wide range of contexts and construct texts for themselves. It is argued that a lack of awareness that meaning is constructed through recourse to other contexts, texts and the learner's experience is disadvantaging ESL candidates. 'Language as an Instrument of Communication' discourse, the last meaning-related discourse identified, sees language as the vehicle used to convey ideas, thoughts, information and beliefs, which are viewed as having been constructed independently of language. It is assumed that the answers, which, according to 'Autonomous Text' discourse, are in the text, can be conveyed if the tools of language are used correctly. The first literature-related discourse identified is 'Literature Study Develops Language Proficiency'. It is argued this is a misperception since language is learned as part of situated practice and instruction must thus be embedded in meaningful communicative contexts involving situated practice. The second literature-related discourse identified, 'Literature Study is a Medium for Understanding Life', is connected to the 'Received Tradition' discourse referred to above which holds that there is moral value in teaching English literature. This research identifies the ideological implications of these discourses, arguing that values are culture-specific and learners from diverse socio-cultural backgrounds experience life differently from the way it is depicted in English literature. Process-related discourses, which are part of the processes of teaching and assessment, concern the inadequacy of the ESL learner and of the markers and therefore dictate what can and cannot be expected of ESL learners in the SC examination. The research showed how all of the above discourses work through the SC curriculum to impose the values and beliefs of particular dominant groups on the ESL learner. Because of the robust and invidious nature of discourses this is a cause for concern. Although it is difficult to set a school leaving examination which serves both workplace and academic functions, there is a need to move beyond traditional, hegemonic approaches to understanding language learning. This thesis offers an analysis which can be used to inform practice.
- Full Text:
- Date Issued: 2006
- Authors: Blunt, Sandra Viki
- Date: 2006 , 2013-06-11
- Subjects: Habermas, Jürgen Education, Secondary -- South Africa Examinations -- South Africa -- Evaluation English language -- Examinations -- South Africa English language -- Study and teaching -- South Africa -- Foreign speakers Language and education -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1902 , http://hdl.handle.net/10962/d1006243
- Description: The Senior Certificate (SC) examination, a focus of the research described in this thesis, has an important function in terms of the quality of the education system overall and also in terms of the contribution of education to the achievement of national goals. The SC examination functions i) as a measure of achievement at school ii) as an indicator of work readiness and iii) as an indicator of the potential to succeed in higher education. This thesis offers a critique of the SC examination in respect of its functions. The way in which learners' language related needs are constructed is crucial in discussing the SC examination's legitimacy since perceptions about the needs of learners are reflected in what is taught and assessed. Since the majority of candidates writing the SC exarnination do so using a language which is not their mother tongue, the research described in the thesis attempted to identify the way in which the English second language (ESL) SC examination papers construct learners' needs. Examination papers represent a particular domain of social practice and are constructed through discourse. In the context of the research described in this thesis, discourses are understood as sets of ideas which are shared by communities of people and which give rise to practices which then define and sustain those communities and, thus, the discourses themselves. Discourse is language insofar as it converges with power and positions people in the interests of power. The ideological nature of discourse necessitates a critical orientation to research which interrogates, challenges and critiques the status quo. To identify the discourses constructing ESL learners' needs I conducted a critical discourse analysis on a representative sarnple of ESL SC exarnination papers and also interviewed six ESL examiners to corroborate the findings of the analysis. This then allowed me to identify several dominant discourses constructing ESL learners' needs: meaning-related, literature-related and process-related. The first meaning-related discourse, 'Received Tradition' discourse, focuses on the rules of grammar and spelling. Rather than approaching language as a resource to enable learners to understand the ideas to which they are exposed, learners are being taught discrete 'skills' to equip them for higher education study and the workplace. It is argued that school-based language literacy practices are not generalizable to the workplace and to higher education. Another aspect of 'Received Tradition' discourse holds that the study of English literature is a medium for understanding life and that there is moral value in teaching English literature. Learners are therefore constructed as lacking these values and their needs as having to acquire them. 'Received Tradition' discourse also overlaps with a second meaning-related discourse, 'Autonomous Text' discourse, which holds that the text's meaning is explicit and that if the learners can manipulate the rules of English grammar, 'have' vocabulary and can spell, they can retrieve meanings from texts they encounter in a wide range of contexts and construct texts for themselves. It is argued that a lack of awareness that meaning is constructed through recourse to other contexts, texts and the learner's experience is disadvantaging ESL candidates. 'Language as an Instrument of Communication' discourse, the last meaning-related discourse identified, sees language as the vehicle used to convey ideas, thoughts, information and beliefs, which are viewed as having been constructed independently of language. It is assumed that the answers, which, according to 'Autonomous Text' discourse, are in the text, can be conveyed if the tools of language are used correctly. The first literature-related discourse identified is 'Literature Study Develops Language Proficiency'. It is argued this is a misperception since language is learned as part of situated practice and instruction must thus be embedded in meaningful communicative contexts involving situated practice. The second literature-related discourse identified, 'Literature Study is a Medium for Understanding Life', is connected to the 'Received Tradition' discourse referred to above which holds that there is moral value in teaching English literature. This research identifies the ideological implications of these discourses, arguing that values are culture-specific and learners from diverse socio-cultural backgrounds experience life differently from the way it is depicted in English literature. Process-related discourses, which are part of the processes of teaching and assessment, concern the inadequacy of the ESL learner and of the markers and therefore dictate what can and cannot be expected of ESL learners in the SC examination. The research showed how all of the above discourses work through the SC curriculum to impose the values and beliefs of particular dominant groups on the ESL learner. Because of the robust and invidious nature of discourses this is a cause for concern. Although it is difficult to set a school leaving examination which serves both workplace and academic functions, there is a need to move beyond traditional, hegemonic approaches to understanding language learning. This thesis offers an analysis which can be used to inform practice.
- Full Text:
- Date Issued: 2006
An investigation into the neuroprotective properties of the non-steroidal anti-inflammatory agents tolmetin, sulindac and turmeric
- Authors: Dairam, Amichand
- Date: 2006
- Subjects: Nonsteroidal anti-inflammatory agents Antioxidants Tolmetin -- Therapeutic use Sulindac -- Therapeutic use Turmeric -- Therapeutic use Nervous system -- Degeneration -- Prevention Alzheimer's disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3752 , http://hdl.handle.net/10962/d1003230
- Description: Accumulating evidence suggests that anti-inflammatory agents and antioxidants have neuroprotective properties and may be beneficial in the treatment of neurodegenerative disorders. In the present study, the possible neuroprotective properties of tolmetin, sulindac and turmeric were investigated. The antioxidant effects of tolmetin and sulindac were determined by inducing free radical generation with quinolinic acid (QA), cyanide or iron (II) in rat brain homogenates or primary hippocampal neurons. Tolmetin and sulindac significantly reduce lipid peroxidation and scavenge the superoxide anion. Metal binding studies were conducted to determine whether metal chelation is a possible mechanism through which these agents reduce QA and iron (II)-induced lipid peroxidation. UV/VIS, infrared spectroscopy as well as electrochemical studies show that both agents bind to iron (II) and/or iron (III). Histological examination of the hippocampus showed that pre-treatment of animals with tolmetin or sulindac offers protection against intrahippocampal injections of QA. These agents also attenuate QA-induced apoptosis and reduce the loss of neurons in the hippocampus. The co-incubation of primary hippocampal neurons with the NSAIDS also enhanced cell viability which is significantly reduced by QA. Behavioural studies using a water maze showed that the treatment of animals after QA-induced neurotoxicity reduces QA-induced spatial memory loss. Tolmetin and sulindac also reduced glutathione depletion and protein oxidation in rat hippocampus. Both NSAIDS inhibit liver tryptophan 2,3-dioxygenase activity in vitro and in vivo and subsequently increased hippocampal serotonin levels. However, both NSAIDS also reduce dopamine levels in rat striatum. Tolmetin but not sulindac increased the synthesis of melatonin by the pineal gland. The active components of turmeric known as the curcuminoids were separated using preparative thin layer chromatography (TLC). The purity was confirmed by TLC, NMR and mass spectrometry. The environmental toxin lead, induces lipid peroxidation and reduces primary hippocampal neuronal viability. The co-incubation of the neurons with the curcuminoids significantly reduces lead-induced lipid peroxidation and enhances neuronal cell viability in the presence of lead. Lead-induced spatial memory deficit is also attenuated with curcumin, demethoxycurcumin but not bisdemethoxycurcumin. The curcuminoids also reduce lead-induced hippocampal glutathione depletion and protein oxidation. Metal binding studies show that the curcuminoids bind to lead and is another possible mechanism through which the curcuminoids reduce lead-induced neurotoxicity. The findings of this study indicate a possible role of tolmetin, sulindac and turmeric in neurodegenerative disorders such as Alzheimer’s disease. However, tolmetin and sulindac reduce dopamine levels.
- Full Text:
- Date Issued: 2006
- Authors: Dairam, Amichand
- Date: 2006
- Subjects: Nonsteroidal anti-inflammatory agents Antioxidants Tolmetin -- Therapeutic use Sulindac -- Therapeutic use Turmeric -- Therapeutic use Nervous system -- Degeneration -- Prevention Alzheimer's disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3752 , http://hdl.handle.net/10962/d1003230
- Description: Accumulating evidence suggests that anti-inflammatory agents and antioxidants have neuroprotective properties and may be beneficial in the treatment of neurodegenerative disorders. In the present study, the possible neuroprotective properties of tolmetin, sulindac and turmeric were investigated. The antioxidant effects of tolmetin and sulindac were determined by inducing free radical generation with quinolinic acid (QA), cyanide or iron (II) in rat brain homogenates or primary hippocampal neurons. Tolmetin and sulindac significantly reduce lipid peroxidation and scavenge the superoxide anion. Metal binding studies were conducted to determine whether metal chelation is a possible mechanism through which these agents reduce QA and iron (II)-induced lipid peroxidation. UV/VIS, infrared spectroscopy as well as electrochemical studies show that both agents bind to iron (II) and/or iron (III). Histological examination of the hippocampus showed that pre-treatment of animals with tolmetin or sulindac offers protection against intrahippocampal injections of QA. These agents also attenuate QA-induced apoptosis and reduce the loss of neurons in the hippocampus. The co-incubation of primary hippocampal neurons with the NSAIDS also enhanced cell viability which is significantly reduced by QA. Behavioural studies using a water maze showed that the treatment of animals after QA-induced neurotoxicity reduces QA-induced spatial memory loss. Tolmetin and sulindac also reduced glutathione depletion and protein oxidation in rat hippocampus. Both NSAIDS inhibit liver tryptophan 2,3-dioxygenase activity in vitro and in vivo and subsequently increased hippocampal serotonin levels. However, both NSAIDS also reduce dopamine levels in rat striatum. Tolmetin but not sulindac increased the synthesis of melatonin by the pineal gland. The active components of turmeric known as the curcuminoids were separated using preparative thin layer chromatography (TLC). The purity was confirmed by TLC, NMR and mass spectrometry. The environmental toxin lead, induces lipid peroxidation and reduces primary hippocampal neuronal viability. The co-incubation of the neurons with the curcuminoids significantly reduces lead-induced lipid peroxidation and enhances neuronal cell viability in the presence of lead. Lead-induced spatial memory deficit is also attenuated with curcumin, demethoxycurcumin but not bisdemethoxycurcumin. The curcuminoids also reduce lead-induced hippocampal glutathione depletion and protein oxidation. Metal binding studies show that the curcuminoids bind to lead and is another possible mechanism through which the curcuminoids reduce lead-induced neurotoxicity. The findings of this study indicate a possible role of tolmetin, sulindac and turmeric in neurodegenerative disorders such as Alzheimer’s disease. However, tolmetin and sulindac reduce dopamine levels.
- Full Text:
- Date Issued: 2006
An investigation of the binding capacities of recombinant domain mutants of the human Polymeric Immunoglobulin Receptor (pIgR)
- Authors: Prinsloo, Earl Adin Gerard
- Date: 2006
- Subjects: Immunoglobulins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10307 , http://hdl.handle.net/10948/403 , Immunoglobulins
- Description: The membrane bound glycoprotein, polymeric immunoglobulin receptor (pIgR) is the primary transport molecule of the polymeric immunoglobulins, dimeric IgA and pentameric IgM, across epithelial cells. This process, known as transcytosis, is essential in order to establish immunity at mucosal surfaces. Typically, pIgR binds to the polymeric immunoglobulin at the basolateral surface of the epithelial cell, via five homologous immunoglobulin-like domains of the ectodomain. Binding is covalent to IgA and non-covalent to IgM; the IgM binding varying among species. The pIgR-bound complex is released at the apical surface of the cell after cleavage of pIgR at Arg585, thereafter referred to as secretory component (SC). SC confers protective and immunologic functions to the polymeric immunoglobulin. Free SC, i.e. not complexed with polymeric immunoglobulins, is also known to be released into mucosal secretions; and binds to pathogenic bacteria and bacterial products. It is known that domain I of the ectodomain is the primary domain in the interaction with polymeric immunoglobulins, while domain V is involved in a covalent linkage with IgA. However, little is known of domains II-IV and their role in immunoglobulin binding, particularly to IgM. This study aimed to characterize the binding of recombinant human pIgR domain mutants to polymeric IgM using immunological, biophysical and cell based techniques; thereby allowing greater insight into the contribution of each of the five domains. The unique domain structure allowed for selective amplification of single and multiple domain mutants from cloned human PIGR ectodomain cDNA. Mutants were cloned and expressed in Esherichia coli BL21 (DE3) as inclusion bodies. Recombinant mutant proteins were refolded in vitro by equilibrium gradient dialysis and purified to homogeneity. Equilibrium binding data show significant contributions to specific binding as a factor of domain presence. Binding kinetics determined by biophysical surface plasmon resonance measurements show the interplay between association and dissociation rates as defined by individual domains. In vitro competitive binding studies using the human intestinal carcinoma, HT29, known to constitutively express pIgR, show that the constructed recombinant domain mutants outcompete native pIgR. The level of competition is shown to be dependant on the domains downstream of domain I. The data also confirm the biological activity of the first in vitro refolded recombinant human SC.
- Full Text:
- Date Issued: 2006
- Authors: Prinsloo, Earl Adin Gerard
- Date: 2006
- Subjects: Immunoglobulins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10307 , http://hdl.handle.net/10948/403 , Immunoglobulins
- Description: The membrane bound glycoprotein, polymeric immunoglobulin receptor (pIgR) is the primary transport molecule of the polymeric immunoglobulins, dimeric IgA and pentameric IgM, across epithelial cells. This process, known as transcytosis, is essential in order to establish immunity at mucosal surfaces. Typically, pIgR binds to the polymeric immunoglobulin at the basolateral surface of the epithelial cell, via five homologous immunoglobulin-like domains of the ectodomain. Binding is covalent to IgA and non-covalent to IgM; the IgM binding varying among species. The pIgR-bound complex is released at the apical surface of the cell after cleavage of pIgR at Arg585, thereafter referred to as secretory component (SC). SC confers protective and immunologic functions to the polymeric immunoglobulin. Free SC, i.e. not complexed with polymeric immunoglobulins, is also known to be released into mucosal secretions; and binds to pathogenic bacteria and bacterial products. It is known that domain I of the ectodomain is the primary domain in the interaction with polymeric immunoglobulins, while domain V is involved in a covalent linkage with IgA. However, little is known of domains II-IV and their role in immunoglobulin binding, particularly to IgM. This study aimed to characterize the binding of recombinant human pIgR domain mutants to polymeric IgM using immunological, biophysical and cell based techniques; thereby allowing greater insight into the contribution of each of the five domains. The unique domain structure allowed for selective amplification of single and multiple domain mutants from cloned human PIGR ectodomain cDNA. Mutants were cloned and expressed in Esherichia coli BL21 (DE3) as inclusion bodies. Recombinant mutant proteins were refolded in vitro by equilibrium gradient dialysis and purified to homogeneity. Equilibrium binding data show significant contributions to specific binding as a factor of domain presence. Binding kinetics determined by biophysical surface plasmon resonance measurements show the interplay between association and dissociation rates as defined by individual domains. In vitro competitive binding studies using the human intestinal carcinoma, HT29, known to constitutively express pIgR, show that the constructed recombinant domain mutants outcompete native pIgR. The level of competition is shown to be dependant on the domains downstream of domain I. The data also confirm the biological activity of the first in vitro refolded recombinant human SC.
- Full Text:
- Date Issued: 2006
Application of CE, HPLC and LC-MS-MS for the analysis and quality control of Ginkgo biloba dosage forms
- Authors: Dubber, Mary-Jean
- Date: 2006
- Subjects: Pharmaceutical chemistry -- Quality control Ginkgo Micelles Capillary electrophoresis High performance liquid chromatography Drugs -- Dosage forms Flavonoids Terpenes Herbals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3757 , http://hdl.handle.net/10962/d1003235
- Description: Natural products are complex mixtures of compounds with therapeutic effects which are often reported to be due to the synergistic action of multiple and sometimes unknown components. Consequently, standardization of these products is complex and a lack of effective quality control (QC) criteria in most countries has led to marketing of commercial products with questionable quality, safety and efficacy (QSE). The aim of this study was therefore to develop qualitative and quantitative analytical methods for use in the QC of Ginkgo biloba solid oral dosage forms. Initially, a micellar electrokinetic chromatography (MEKC) method was developed for the identification of the flavonol glycosides, rutin and quercitrin as well as 3 flavonol aglycones, quercetin, kaempferol and isorhamnetin in crude extracts of 4 Ginkgo biloba solid oral dosage forms using ultraviolet (UV) detection. A reversed-flow cyclodextrin-modified MEKC method was subsequently developed for the simultaneous determination of the aforementioned flavonols as well as ginkgolide A, B, C, J and bilobalide (all positive markers) in Ginkgo commercial products. A non-aqueous capillary electrophoresis (CE) method was also developed for fingerprinting the presence of ginkgolic acids (negative markers) in Ginkgo biloba leaf extracts, which are purported to be associated with toxic properties. This method was also applied to 2 Ginkgo biloba commercial products. Since the flavonols have strong UV absorbing chromophores, a reversed phase high-performance liquid chromatographic (RP-HPLC) method was developed and validated using photo-diode-array (PDA) detection which was then successfully applied to fingerprint commercially available Ginkgo biloba solid oral dosage forms as well as quantify the relevant flavonol markers present in these extracts. Sample preparation was simple, rapid and cost efficient with minimal clean-up and the employment of a minibore column which requires low mobile phase flow rates contributed to the economy of the method. Unlike the conventional QC approach, samples were not hydrolyzed and direct determination of 2 intact flavonol glycosides, together with the usual aglycone markers was facilitated which provided maximal content information for fingerprint comparisons. On the other hand, terpene trilactones possess poor chromophores and an alternative detection method to UV was required in order to obtain suitable sensitivity. RP-HPLC with evaporative light scattering detection (ELSD) was selected for quantification of these non-volatile constituents in Ginkgo dosage forms and this method was deemed suitable for the routine QC analysis of these positive markers in commercial products. Since approximately 33 flavonoids have been identified in Ginkgo biloba leaf extracts, baseline separation using UV/PDA detection normally requires complex gradient programs and long analysis times. In addition, unequivocal identification of the flavonoids with similar UV spectra and elution times cannot be guaranteed. A liquid chromatographic tandem mass spectrometric (LC-MS-MS) method was therefore developed and validated in order to ensure accurate quantification of the selected flavonol marker compounds in Ginkgo commercial products. LC-MS-MS analysis of Ginkgo extracts revealed, in addition to rutin, the possible presence of other quercetin analogues, quercetin-3-Orhamnoside-7-O-glucoside or quercetin-3-O-glucoside-7-O-rhamnoside, previously unreported in Ginkgo biloba leaf extracts or dosage forms. In terms of evaluating the most suitable analytical method for QC, CE shows exceptional potential in the future analysis of Ginkgo biloba dosage forms while HPLC-PDA and HPLC-ELSD are currently the most affordable and practical instruments for the routine analysis of the flavonols and terpenoids, respectively. LC-MS-MS proved to be pivotal for the accurate identification and quantification of the flavonols due to interference by other flavonoid compounds with similar retention times and UV spectra to the peaks of interest. All quantitative and qualitative results revealed large discrepancies in the marker content between the products regardless of which batch was analysed and product labels disclosed little relevant information. Although currently not required by most regulatory agencies, some of the usual quality criteria applied to orthodox medicines was evaluated. In particular, dissolution analysis, disintegration, tablet hardness and weight uniformity were assessed and revealed similar inconsistencies. This thesis emphasises that implementation of effective QC criteria is long overdue and is essential to ensure consistent product QSE of commercially available Ginkgo biloba solid oral dosage forms.
- Full Text:
- Date Issued: 2006
- Authors: Dubber, Mary-Jean
- Date: 2006
- Subjects: Pharmaceutical chemistry -- Quality control Ginkgo Micelles Capillary electrophoresis High performance liquid chromatography Drugs -- Dosage forms Flavonoids Terpenes Herbals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3757 , http://hdl.handle.net/10962/d1003235
- Description: Natural products are complex mixtures of compounds with therapeutic effects which are often reported to be due to the synergistic action of multiple and sometimes unknown components. Consequently, standardization of these products is complex and a lack of effective quality control (QC) criteria in most countries has led to marketing of commercial products with questionable quality, safety and efficacy (QSE). The aim of this study was therefore to develop qualitative and quantitative analytical methods for use in the QC of Ginkgo biloba solid oral dosage forms. Initially, a micellar electrokinetic chromatography (MEKC) method was developed for the identification of the flavonol glycosides, rutin and quercitrin as well as 3 flavonol aglycones, quercetin, kaempferol and isorhamnetin in crude extracts of 4 Ginkgo biloba solid oral dosage forms using ultraviolet (UV) detection. A reversed-flow cyclodextrin-modified MEKC method was subsequently developed for the simultaneous determination of the aforementioned flavonols as well as ginkgolide A, B, C, J and bilobalide (all positive markers) in Ginkgo commercial products. A non-aqueous capillary electrophoresis (CE) method was also developed for fingerprinting the presence of ginkgolic acids (negative markers) in Ginkgo biloba leaf extracts, which are purported to be associated with toxic properties. This method was also applied to 2 Ginkgo biloba commercial products. Since the flavonols have strong UV absorbing chromophores, a reversed phase high-performance liquid chromatographic (RP-HPLC) method was developed and validated using photo-diode-array (PDA) detection which was then successfully applied to fingerprint commercially available Ginkgo biloba solid oral dosage forms as well as quantify the relevant flavonol markers present in these extracts. Sample preparation was simple, rapid and cost efficient with minimal clean-up and the employment of a minibore column which requires low mobile phase flow rates contributed to the economy of the method. Unlike the conventional QC approach, samples were not hydrolyzed and direct determination of 2 intact flavonol glycosides, together with the usual aglycone markers was facilitated which provided maximal content information for fingerprint comparisons. On the other hand, terpene trilactones possess poor chromophores and an alternative detection method to UV was required in order to obtain suitable sensitivity. RP-HPLC with evaporative light scattering detection (ELSD) was selected for quantification of these non-volatile constituents in Ginkgo dosage forms and this method was deemed suitable for the routine QC analysis of these positive markers in commercial products. Since approximately 33 flavonoids have been identified in Ginkgo biloba leaf extracts, baseline separation using UV/PDA detection normally requires complex gradient programs and long analysis times. In addition, unequivocal identification of the flavonoids with similar UV spectra and elution times cannot be guaranteed. A liquid chromatographic tandem mass spectrometric (LC-MS-MS) method was therefore developed and validated in order to ensure accurate quantification of the selected flavonol marker compounds in Ginkgo commercial products. LC-MS-MS analysis of Ginkgo extracts revealed, in addition to rutin, the possible presence of other quercetin analogues, quercetin-3-Orhamnoside-7-O-glucoside or quercetin-3-O-glucoside-7-O-rhamnoside, previously unreported in Ginkgo biloba leaf extracts or dosage forms. In terms of evaluating the most suitable analytical method for QC, CE shows exceptional potential in the future analysis of Ginkgo biloba dosage forms while HPLC-PDA and HPLC-ELSD are currently the most affordable and practical instruments for the routine analysis of the flavonols and terpenoids, respectively. LC-MS-MS proved to be pivotal for the accurate identification and quantification of the flavonols due to interference by other flavonoid compounds with similar retention times and UV spectra to the peaks of interest. All quantitative and qualitative results revealed large discrepancies in the marker content between the products regardless of which batch was analysed and product labels disclosed little relevant information. Although currently not required by most regulatory agencies, some of the usual quality criteria applied to orthodox medicines was evaluated. In particular, dissolution analysis, disintegration, tablet hardness and weight uniformity were assessed and revealed similar inconsistencies. This thesis emphasises that implementation of effective QC criteria is long overdue and is essential to ensure consistent product QSE of commercially available Ginkgo biloba solid oral dosage forms.
- Full Text:
- Date Issued: 2006
Aspects of the sentencing process in child sexual abuse cases
- Authors: Van der Merwe, Annette
- Date: 2006
- Subjects: Child sexual abuse -- South Africa , Sexually abused children -- Legal status, laws, etc -- South Africa , Child abuse -- Law and legislation -- South Africa , Sex crimes -- South Africa , Sentences(Criminal procedure) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3696 , http://hdl.handle.net/10962/d1003211 , Child sexual abuse -- South Africa , Sexually abused children -- Legal status, laws, etc -- South Africa , Child abuse -- Law and legislation -- South Africa , Sex crimes -- South Africa , Sentences(Criminal procedure) -- South Africa
- Description: This thesis investigates current sentencing practices relating to the diverse, complex and emotionally laden phenomenon of child sexual abuse. It focuses on relevant legislative provisions, on case law and on an empirical study conducted amongst regional court magistrates. Trends, developments and problems are analysed and possible solutions to the main problems identified are investigated. The thesis concludes with proposed guidelines regarding the sentencing process in child sexual abuse cases. Such guidelines address general and specific principles, the use of victim impact statements, the increased recognition and use of behavioural science in the sentencing phase with regard to both the victim and the offender, and relevant aggravating and mitigating factors. The guidelines are an attempt to give some structure to the current haphazard approach adopted by the courts with regard to harm experienced by the victim. They are also aimed at assisting experts to provide more effective and reliable pre-sentence reports. Further, the thesis attempts to provide clarity concerning the factors that are considered to be aggravating or mitigating in the offence category, child sexual abuse, as well as with regard to the weight that should be attached to them. In addition, recommendations are made for the purpose of possible law reform and further research in relation to the regulation of judicial discretion through the introduction of formal sentencing guidelines, victim impact statements and the accommodation of behavioural science in the sentencing process pertaining to sexual offenders. This proposal is based on current South African sentencing practices as reflected in the consolidation of local judgments scattered over many years in different law reports and, to some extent, on English, Canadian, Australian and American sentencing practices as researched in this study.
- Full Text:
- Date Issued: 2006
- Authors: Van der Merwe, Annette
- Date: 2006
- Subjects: Child sexual abuse -- South Africa , Sexually abused children -- Legal status, laws, etc -- South Africa , Child abuse -- Law and legislation -- South Africa , Sex crimes -- South Africa , Sentences(Criminal procedure) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3696 , http://hdl.handle.net/10962/d1003211 , Child sexual abuse -- South Africa , Sexually abused children -- Legal status, laws, etc -- South Africa , Child abuse -- Law and legislation -- South Africa , Sex crimes -- South Africa , Sentences(Criminal procedure) -- South Africa
- Description: This thesis investigates current sentencing practices relating to the diverse, complex and emotionally laden phenomenon of child sexual abuse. It focuses on relevant legislative provisions, on case law and on an empirical study conducted amongst regional court magistrates. Trends, developments and problems are analysed and possible solutions to the main problems identified are investigated. The thesis concludes with proposed guidelines regarding the sentencing process in child sexual abuse cases. Such guidelines address general and specific principles, the use of victim impact statements, the increased recognition and use of behavioural science in the sentencing phase with regard to both the victim and the offender, and relevant aggravating and mitigating factors. The guidelines are an attempt to give some structure to the current haphazard approach adopted by the courts with regard to harm experienced by the victim. They are also aimed at assisting experts to provide more effective and reliable pre-sentence reports. Further, the thesis attempts to provide clarity concerning the factors that are considered to be aggravating or mitigating in the offence category, child sexual abuse, as well as with regard to the weight that should be attached to them. In addition, recommendations are made for the purpose of possible law reform and further research in relation to the regulation of judicial discretion through the introduction of formal sentencing guidelines, victim impact statements and the accommodation of behavioural science in the sentencing process pertaining to sexual offenders. This proposal is based on current South African sentencing practices as reflected in the consolidation of local judgments scattered over many years in different law reports and, to some extent, on English, Canadian, Australian and American sentencing practices as researched in this study.
- Full Text:
- Date Issued: 2006
Assessment of the effect of Goukamma Marine Protected Area on community structure and fishery dynamics
- Authors: Götz, Albrecht
- Date: 2006
- Subjects: Goukamma Marine Protected Area Reef fishes -- South Africa Marine fishes -- South Africa Fishery management -- South Africa Marine resources conservation -- South Africa Marine parks and reserves -- South Africa Chrysoblephus laticeps Merluccius Argyrosomus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5230 , http://hdl.handle.net/10962/d1005073
- Description: This study presents a detailed investigation into size, density and community structure of temperate marine reef fish in the medium-sized Goukamma Marine Protected Area (Goukamma MPA) and adjacent fishing grounds on the south coast of South Africa. The oceanographic conditions, the spatial distribution of the benthic community and the prevailing fishing effort are also described. Life history traits and per-recruit (PR) models for the principle target species, roman (Crysoblephus laticeps) are compared between the protected and exploited area. From the study results, various strategies are proposed for the use of MPAs in the conservation and management of linefish species along South Africa’s south coast. The distribution and topography of reefs in the protected and exploited sections of the study area were found to be comparable. Atmospheric pressure ranged from 992 to 1,032 mb, being significantly lower in summer. Wind speeds ranged from 0.7 to 71.3 km/h. Water temperatures ranged between 9.0 and 22.2 ºC and turbidity between 0.3 and 45.8 NTU. Water temperature and clarity were uniformly low in winter. In summer the water was generally warm, clear and stratified, with a thermocline at around 20 m, although intermittent upwelling events caused water temperature to decrease and clarity to deteriorate. Current speeds ranged between 0.11 and 2.59 km/h and were significantly higher in spring and autumn. Easterly currents prevailed in spring, summer and autumn and westerly and southerly currents in winter. Hake (Merluccius capensis), various resident reef fish and kob (Argyrosomus japonicus) were most frequently targeted by the local linefishery. A significant amount of illegal fishing was found to occur in the protected area. Fishing effort was found to be highest around the border of the MPA (2.7 boats/km²) and lowest in the core of the MPA (0.2 boats/km²). If law enforcement remains poor it may be necessary to adapt the management strategy to extend the reserve, thereby mitigating against illegal fishing and ensuring a core area of no exploitation. Various other alternatives were investigated and it was demonstrated that the amount of fish caught of legal size could be increased by about 23% and post-release mortality of undersized fish reduced by 50% through the introduction of a suit of restrictive measures. Randomly stratified underwater visual census (UVC) and controlled fishing were used to investigate the ichthyofauna and benthic community at protected and exploited sites in the study area. Resulting density and size data from 273 fishing sites and 177 point counts were analyzed using generalized linear models (GLMs). Fish communities were found to vary significantly, depending on the level of exploitation. Roman, the principle reef fish species targeted by the fishery had significantly higher densities within the protected parts of the study area (CPUE: 4.3 fish/anglerhour; UVC: 2.2 fish/point-count) as compared to the exploited part (CPUE: 3.4 fish/anglerhour; UVC: 1.8 fish/point-count), correlating strongly with the observed fishing effort. Also mean sizes were significantly higher in the protected area (299 mm from fishing survey and 233 mm from diving estimates) as compared to the exploited section (283 mm from fishing survey and 198 mm from diving estimates). Although other fish species also had significantly higher mean sizes at protected sites in most cases their densities were significantly lower. This suggests a top-down control of the fish community by the dominant predator (roman). The results of the UVC showed the diversity of the ichthyofauna to be significantly higher inside the protected area. Interestingly this did not apply to the results of the controlled fishing experiment where the diversity of fish in the catch was lower in the protected area - a result that may be explained by the selectivity of fishing for the most aggressive species – and a reminder of the limitations of controlled fishing experiments. Possibly the most important finding of the study revolved around the benthic community. These were significantly different at exploited and protected sites, with algae and crinoids more abundant at exploited sites. Crinoids are the principle food of roman and were low in abundance where roman abundances were high, suggesting that the dominant top predator reduced crinoids. Furthermore, it substantiates the correlation of roman abundance with fishing effort, since habitat preferences can be ruled out by the observed causal predator-prey distribution pattern. Low algae abundances at protected sites correlated with high strepie (Sarpa salpa) frequencies within the fish communities encountered there. Strepie, a shoaling and abundant benthic grazer, does not compete for food with roman, suggesting a high potential for coexistence of the two species. As expected, and found by other studies, life history traits of roman differed between protected and exploited sample-sites. With a significantly lower age-at-maturity and age-atsex- change, the exploited population showed a typical response to fishing effort. The sex ratio of this protogynous hermaphrodite was found to be sustained at healthy levels by phenotypic plasticity. However, one important additional factor was highlighted by the study; the average condition factor of the protected population was significantly lower (0.0283 g/cm³) compared to the exploited population (0.0295 g/cm³). This was probably due to the higher intra-specific competition for lower food abundance in the protected area. Interestingly the diving and fishing survey methods yielded similar mortality results for roman. Total mortality rate estimates derived from length frequency analysis from the diving and fishing survey were not different (0.32 and 0.29 y⁻¹, respectively) as were natural mortality rate estimates (0.24 and 0.19 y⁻¹, respectively). Natural mortality rate (M) estimates indicated by Pauly’s and Hoenig’s relationship were similar (0.25 and 0.23 y⁻¹, respectively). Detailed yield-per-recruit (Y/R) and spawner biomass-per-recruit (SB/R) analyses were presented for different levels of M, varying age-at-recruitment (tR) and fishing mortality (F). Current tR (7.60 y) and F (0.16 and 0.25 y⁻¹, from the diving and fishing dataset, respectively) suggests an optimal exploitation of the population in the exploited part of the study area. However, a separate SB/R analysis of the male part of the population showed their vulnerability to over-exploitation, even at reduced age-at-sex-change from fishing. There therefore remains a high risk of recruitment failure for the roman population. Of course MPAs can be used to measure stock status directly if the influence of factors such as cachability, habitat and sampling method on CPUE assessments can be limited or reduced. The experimental design in this study allowed for contemporary CPUE comparisons across the border of the Goukamma MPA. Results were similar to those obtained by the SB/R analyses. CPUE extrapolations therefore, using small MPAs, can provide reliable and consistent estimates, and offer a practical alternative to conventional assessment strategies. This study has highlighted the importance of ensuring a well structured and comprehensive survey design when undertaking a comparison of protected and exploited marine areas. The results provide a comprehensive framework for future management of the Goukamma MPA and other protected areas along the temperate coastline of South Africa.
- Full Text:
- Date Issued: 2006
- Authors: Götz, Albrecht
- Date: 2006
- Subjects: Goukamma Marine Protected Area Reef fishes -- South Africa Marine fishes -- South Africa Fishery management -- South Africa Marine resources conservation -- South Africa Marine parks and reserves -- South Africa Chrysoblephus laticeps Merluccius Argyrosomus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5230 , http://hdl.handle.net/10962/d1005073
- Description: This study presents a detailed investigation into size, density and community structure of temperate marine reef fish in the medium-sized Goukamma Marine Protected Area (Goukamma MPA) and adjacent fishing grounds on the south coast of South Africa. The oceanographic conditions, the spatial distribution of the benthic community and the prevailing fishing effort are also described. Life history traits and per-recruit (PR) models for the principle target species, roman (Crysoblephus laticeps) are compared between the protected and exploited area. From the study results, various strategies are proposed for the use of MPAs in the conservation and management of linefish species along South Africa’s south coast. The distribution and topography of reefs in the protected and exploited sections of the study area were found to be comparable. Atmospheric pressure ranged from 992 to 1,032 mb, being significantly lower in summer. Wind speeds ranged from 0.7 to 71.3 km/h. Water temperatures ranged between 9.0 and 22.2 ºC and turbidity between 0.3 and 45.8 NTU. Water temperature and clarity were uniformly low in winter. In summer the water was generally warm, clear and stratified, with a thermocline at around 20 m, although intermittent upwelling events caused water temperature to decrease and clarity to deteriorate. Current speeds ranged between 0.11 and 2.59 km/h and were significantly higher in spring and autumn. Easterly currents prevailed in spring, summer and autumn and westerly and southerly currents in winter. Hake (Merluccius capensis), various resident reef fish and kob (Argyrosomus japonicus) were most frequently targeted by the local linefishery. A significant amount of illegal fishing was found to occur in the protected area. Fishing effort was found to be highest around the border of the MPA (2.7 boats/km²) and lowest in the core of the MPA (0.2 boats/km²). If law enforcement remains poor it may be necessary to adapt the management strategy to extend the reserve, thereby mitigating against illegal fishing and ensuring a core area of no exploitation. Various other alternatives were investigated and it was demonstrated that the amount of fish caught of legal size could be increased by about 23% and post-release mortality of undersized fish reduced by 50% through the introduction of a suit of restrictive measures. Randomly stratified underwater visual census (UVC) and controlled fishing were used to investigate the ichthyofauna and benthic community at protected and exploited sites in the study area. Resulting density and size data from 273 fishing sites and 177 point counts were analyzed using generalized linear models (GLMs). Fish communities were found to vary significantly, depending on the level of exploitation. Roman, the principle reef fish species targeted by the fishery had significantly higher densities within the protected parts of the study area (CPUE: 4.3 fish/anglerhour; UVC: 2.2 fish/point-count) as compared to the exploited part (CPUE: 3.4 fish/anglerhour; UVC: 1.8 fish/point-count), correlating strongly with the observed fishing effort. Also mean sizes were significantly higher in the protected area (299 mm from fishing survey and 233 mm from diving estimates) as compared to the exploited section (283 mm from fishing survey and 198 mm from diving estimates). Although other fish species also had significantly higher mean sizes at protected sites in most cases their densities were significantly lower. This suggests a top-down control of the fish community by the dominant predator (roman). The results of the UVC showed the diversity of the ichthyofauna to be significantly higher inside the protected area. Interestingly this did not apply to the results of the controlled fishing experiment where the diversity of fish in the catch was lower in the protected area - a result that may be explained by the selectivity of fishing for the most aggressive species – and a reminder of the limitations of controlled fishing experiments. Possibly the most important finding of the study revolved around the benthic community. These were significantly different at exploited and protected sites, with algae and crinoids more abundant at exploited sites. Crinoids are the principle food of roman and were low in abundance where roman abundances were high, suggesting that the dominant top predator reduced crinoids. Furthermore, it substantiates the correlation of roman abundance with fishing effort, since habitat preferences can be ruled out by the observed causal predator-prey distribution pattern. Low algae abundances at protected sites correlated with high strepie (Sarpa salpa) frequencies within the fish communities encountered there. Strepie, a shoaling and abundant benthic grazer, does not compete for food with roman, suggesting a high potential for coexistence of the two species. As expected, and found by other studies, life history traits of roman differed between protected and exploited sample-sites. With a significantly lower age-at-maturity and age-atsex- change, the exploited population showed a typical response to fishing effort. The sex ratio of this protogynous hermaphrodite was found to be sustained at healthy levels by phenotypic plasticity. However, one important additional factor was highlighted by the study; the average condition factor of the protected population was significantly lower (0.0283 g/cm³) compared to the exploited population (0.0295 g/cm³). This was probably due to the higher intra-specific competition for lower food abundance in the protected area. Interestingly the diving and fishing survey methods yielded similar mortality results for roman. Total mortality rate estimates derived from length frequency analysis from the diving and fishing survey were not different (0.32 and 0.29 y⁻¹, respectively) as were natural mortality rate estimates (0.24 and 0.19 y⁻¹, respectively). Natural mortality rate (M) estimates indicated by Pauly’s and Hoenig’s relationship were similar (0.25 and 0.23 y⁻¹, respectively). Detailed yield-per-recruit (Y/R) and spawner biomass-per-recruit (SB/R) analyses were presented for different levels of M, varying age-at-recruitment (tR) and fishing mortality (F). Current tR (7.60 y) and F (0.16 and 0.25 y⁻¹, from the diving and fishing dataset, respectively) suggests an optimal exploitation of the population in the exploited part of the study area. However, a separate SB/R analysis of the male part of the population showed their vulnerability to over-exploitation, even at reduced age-at-sex-change from fishing. There therefore remains a high risk of recruitment failure for the roman population. Of course MPAs can be used to measure stock status directly if the influence of factors such as cachability, habitat and sampling method on CPUE assessments can be limited or reduced. The experimental design in this study allowed for contemporary CPUE comparisons across the border of the Goukamma MPA. Results were similar to those obtained by the SB/R analyses. CPUE extrapolations therefore, using small MPAs, can provide reliable and consistent estimates, and offer a practical alternative to conventional assessment strategies. This study has highlighted the importance of ensuring a well structured and comprehensive survey design when undertaking a comparison of protected and exploited marine areas. The results provide a comprehensive framework for future management of the Goukamma MPA and other protected areas along the temperate coastline of South Africa.
- Full Text:
- Date Issued: 2006
Balancing leadership patterns to promote sense of community during cell-church transitioning: a grounded theory of strategic leadership and change
- Authors: Pearse, Noel J
- Date: 2006
- Subjects: Leadership -- South Africa Christian leadership Church management Strategic planning -- South Africa Grounded theory Organizational change -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1426 , http://hdl.handle.net/10962/d1003307
- Description: The aim of this research was to develop a substantive grounded theory describing the process of change and the management of organizational inertia, or resistance to change, by strategic leaders transitioning churches from a programme-based to a cell-based model. The grounded theory was developed using the conventions of the Straussian version of the grounded theory method, and relying largely upon the collection of incidents through interviews with leaders of churches that embarked upon the cell-church transition. In all, 38 interviews were conducted with leaders of churches representing a range of denominations located in a number of provinces in South Africa. Based on the premise that substantive theories are contextually bound rather than context free, the contextual characteristics of this study are highlighted. Drawing from organizational theory, it is recognised that churches can be conceptualised as solidary organizations, normative organizations, congregations and voluntary organizations or associations. Viewing churches as solidary organizations highlights the role of solidary rewards in the change process, while viewing them as congregations, emphasises their religious character. Furthermore, the context of the study is embedded in the nature of the specific type of change being embarked upon, as represented by the cell-church transition. Drawing on concepts derived from the change management literature, the type of change I investigated, I classified as intangible, episodic, teleological, second-order change, highlighting the importance of social interaction. The grounded theory that was constructed describes the phases of the change process, and how the actions of leaders interact with the sense of community of the church. Three effective patterns of leadership were identified (i.e. the freewheeler, the focused-pioneer and the reflexive-accommodator) along with their ineffective counterparts (i.e. the static non-leader, the rigid combatant and the popular people pleaser). It was argued that effective leadership involves balancing the three effective patterns over time, and that a failure to achieve this balance produced an ineffective pattern. Furthermore, ineffective leadership damaged the credibility of leaders, as their actions harmed the sense of community. A loss of credibility compromised the leader’s ability to lead change. A number of approaches to understanding organizational inertia or resistance to change were examined in an attempt to locate the grounded theory in the literature and to use the literature to shed light on the findings of this study. While this literature did provide some useful insights and confirmations, no single theoretical perspective seemed to supply a comprehensive explanation. Instead, social capital theory offered a more encompassing explanation, and as such, showed much promise as a body of literature that can be used to develop an understanding of organizational change. Finally, recommendations are made for future research and the value of this research is discussed.
- Full Text:
- Date Issued: 2006
- Authors: Pearse, Noel J
- Date: 2006
- Subjects: Leadership -- South Africa Christian leadership Church management Strategic planning -- South Africa Grounded theory Organizational change -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1426 , http://hdl.handle.net/10962/d1003307
- Description: The aim of this research was to develop a substantive grounded theory describing the process of change and the management of organizational inertia, or resistance to change, by strategic leaders transitioning churches from a programme-based to a cell-based model. The grounded theory was developed using the conventions of the Straussian version of the grounded theory method, and relying largely upon the collection of incidents through interviews with leaders of churches that embarked upon the cell-church transition. In all, 38 interviews were conducted with leaders of churches representing a range of denominations located in a number of provinces in South Africa. Based on the premise that substantive theories are contextually bound rather than context free, the contextual characteristics of this study are highlighted. Drawing from organizational theory, it is recognised that churches can be conceptualised as solidary organizations, normative organizations, congregations and voluntary organizations or associations. Viewing churches as solidary organizations highlights the role of solidary rewards in the change process, while viewing them as congregations, emphasises their religious character. Furthermore, the context of the study is embedded in the nature of the specific type of change being embarked upon, as represented by the cell-church transition. Drawing on concepts derived from the change management literature, the type of change I investigated, I classified as intangible, episodic, teleological, second-order change, highlighting the importance of social interaction. The grounded theory that was constructed describes the phases of the change process, and how the actions of leaders interact with the sense of community of the church. Three effective patterns of leadership were identified (i.e. the freewheeler, the focused-pioneer and the reflexive-accommodator) along with their ineffective counterparts (i.e. the static non-leader, the rigid combatant and the popular people pleaser). It was argued that effective leadership involves balancing the three effective patterns over time, and that a failure to achieve this balance produced an ineffective pattern. Furthermore, ineffective leadership damaged the credibility of leaders, as their actions harmed the sense of community. A loss of credibility compromised the leader’s ability to lead change. A number of approaches to understanding organizational inertia or resistance to change were examined in an attempt to locate the grounded theory in the literature and to use the literature to shed light on the findings of this study. While this literature did provide some useful insights and confirmations, no single theoretical perspective seemed to supply a comprehensive explanation. Instead, social capital theory offered a more encompassing explanation, and as such, showed much promise as a body of literature that can be used to develop an understanding of organizational change. Finally, recommendations are made for future research and the value of this research is discussed.
- Full Text:
- Date Issued: 2006
Between the 'sectional' and the 'national' : oil, grassroots discontent and civic discourse in Nigeria
- Authors: Akpan, Wilson Ndarake
- Date: 2006
- Subjects: Petroleum industry and trade -- Nigeria Revenue -- Nigeria Nigeria -- Social conditions Nigeria -- Economic conditions Niger River Delta (Nigeria) -- Environmental conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3294 , http://hdl.handle.net/10962/d1003082
- Description: This thesis examines the social character of petroleum-related grassroots struggles in Nigeria’s oil-producing region. It does this against the background of the dominant scholarly narratives that portray the struggles as: a) a disguised pursuit of an ethnic/sectional agenda, b) a 'minority rights' project, and c) a minority province’s protest against 'selective' environmental 'victimisation' by the majority ethnic nationalities. While the dominant scholarly analyses of the struggles are based on the activities of the better known activist organisations operating in the oil region, this thesis focuses primarily on the everyday 'grammar' of discontent and lived worlds of ordinary people vis-à-vis upstream petroleum operations and petroleum resource utilisation. The aim has been to gain an understanding of the forces driving community struggles in the oil region and their wider societal significance. Examined alongside the narratives of ordinary people are the legal/institutional framework for upstream petroleum operations and the operational practices of the oil-producing companies. Using primary data obtained through ethnography, focus group discussions, in-depth interviews and visual sociology, as well as relevant secondary data, the researcher constructs a discourse matrix, showing how grassroots narratives in selected oilproducing communities intersect with contemporary civic discourses in the wider Nigerian context. The thesis highlights the theoretical and policy difficulties that arise when the social basis of petroleum-related grassroots struggles and ordinary people’s narratives are explained using an essentialist idiom. It reveals, above all, the conditions under which so-called 'locale-specific' struggles in a multi-ethnic, oil-rich African country can become a campaign for the emancipation of ordinary people in the wider society. This research extends the existing knowledge on citizen mobilisation, extractive capitalism, transnational corporate behaviour, and Nigeria’s contemporary development predicament. It sheds light on some of the processes through which ordinary people are forcing upon the state a change agenda that could drive the country along a more socially sensitive development and democratisation trajectory.
- Full Text:
- Date Issued: 2006
- Authors: Akpan, Wilson Ndarake
- Date: 2006
- Subjects: Petroleum industry and trade -- Nigeria Revenue -- Nigeria Nigeria -- Social conditions Nigeria -- Economic conditions Niger River Delta (Nigeria) -- Environmental conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3294 , http://hdl.handle.net/10962/d1003082
- Description: This thesis examines the social character of petroleum-related grassroots struggles in Nigeria’s oil-producing region. It does this against the background of the dominant scholarly narratives that portray the struggles as: a) a disguised pursuit of an ethnic/sectional agenda, b) a 'minority rights' project, and c) a minority province’s protest against 'selective' environmental 'victimisation' by the majority ethnic nationalities. While the dominant scholarly analyses of the struggles are based on the activities of the better known activist organisations operating in the oil region, this thesis focuses primarily on the everyday 'grammar' of discontent and lived worlds of ordinary people vis-à-vis upstream petroleum operations and petroleum resource utilisation. The aim has been to gain an understanding of the forces driving community struggles in the oil region and their wider societal significance. Examined alongside the narratives of ordinary people are the legal/institutional framework for upstream petroleum operations and the operational practices of the oil-producing companies. Using primary data obtained through ethnography, focus group discussions, in-depth interviews and visual sociology, as well as relevant secondary data, the researcher constructs a discourse matrix, showing how grassroots narratives in selected oilproducing communities intersect with contemporary civic discourses in the wider Nigerian context. The thesis highlights the theoretical and policy difficulties that arise when the social basis of petroleum-related grassroots struggles and ordinary people’s narratives are explained using an essentialist idiom. It reveals, above all, the conditions under which so-called 'locale-specific' struggles in a multi-ethnic, oil-rich African country can become a campaign for the emancipation of ordinary people in the wider society. This research extends the existing knowledge on citizen mobilisation, extractive capitalism, transnational corporate behaviour, and Nigeria’s contemporary development predicament. It sheds light on some of the processes through which ordinary people are forcing upon the state a change agenda that could drive the country along a more socially sensitive development and democratisation trajectory.
- Full Text:
- Date Issued: 2006
Developing self-regulated learning through the use of meta-cognitive strategies in adventure-based activities
- Authors: Galbraith, Ian William
- Date: 2006
- Subjects: Lilyfontein School Adventure education Education -- South Africa -- Curricula Competency-based education -- South Africa Educational psychology Cognitive learning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1495 , http://hdl.handle.net/10962/d1003376
- Description: This research investigates the benefits of adventure-based activities used as a learning experience at school level. In order to scientifically investigate these benefits the study is located at a school where an adventure-based programme is being developed as part of the school's curriculum. This programme consists of a range of adventure type experiences including, rock climbing, abseiling, canoeing, mountain biking, group dynamic activities, survival camps, ropes courses and adventure racing. At Lilyfontein School these activities form part of the Life Orientation and life Skill programmes from grade 1 to grade 11. Specialized and qualified staff are used to conduct some of these programmes. Adventure-based activities are rigorous and contain elements of risk which require problem solving, good decision making and sound emotional management. These aspects present both physical and mental challenges to any participant. This study postulates that learners engaged in these adventure type activities are faced with using meta-cognitive strategies to help them through these mental and physical challenges. In doing these activities regularly learners will develop meta-cognitive strategies that will enable them to become better self-regulated learners. A self-regulated learner is able to use meta-cognitive strategies like problem solving, decision making, selfevaluation, self-monitoring, self-reflective thinking or emotional control in life generally. The aim of this research is to conduct an on-going action research study of the adventure-based programmes to determine their worth for the learners at Lilyfontein School and consequently the future of such experiences in a school's curriculum. This forms the primary goal of this research. The secondary goal is to gather valid and reliable evidence required to make an argument for the School's Governing Body (SGB) and Curriculum Development Committee (CDC) to be able to substantiate decisions relating to any such future programmes. This research regards the school context as the activity system which forms a primary case study. In order to extract maximum information from this educational system, embedded case studies will be conducted and monitored. These embedded case studies will be made up of the following groups of people: firstly the learners engaged in a variety of adventure-based experiences, secondly the educators as they observe and perceive the consequences of these experiences, and thirdly the parents as they identifY possible influences of adventure-based experiences on the behaviours, beliefs or habits of their children. In this research study data collecting techniques are used to extract infonnation from the embedded cases. Infonnation is elicited from parents and educators through the use of questionnaires and interviews. For learners, narratives and interviews are used to get a more qualitative sense of their beliefs and feelings on adventure-based experiences. However, in order to capture and document the learners' use of metacognitive strategies as they engage in the rigours of an adventure-based activity a more empirical approach is used. This approach uses in-depth observation, recording and measuring of the learners in action. Video footage is used to record the learners' reactions as they battle with fear, mental-strength, fatigue and decision making to accomplish their goal during an adventure activity. This study claims that an adventure-based experience helps to mediate the learning that will develop selfregulatory strategies in a learner. The limited research in the adventure-based learning field and more significantly the lack of empirical evidence of how meta-cognitive strategies fonn a crucial component of adventure-based activities has meant that the researcher has developed his own recording, measuring and analytical tools to serve this end. He has chosen to use Engestrom's third generation Activity Theory model which provides a useful underlying theory as well as an analytical and interpretive framework for this study. The research was conducted over a period of three years. Findings are considered in relation to the National Curriculum Statement for the GET and FET bands to ensure its relevance in the school context to the National Department of Education's expectations for the Life Orientation curriculum. The empirical findings of this study at Lilyfontein School and their relevance to the curriculum content of the National Curriculum Statement ought to provide convincing data for very important curriculum policy decisions at Lilyfontein School and in the broader educational context.
- Full Text:
- Date Issued: 2006
- Authors: Galbraith, Ian William
- Date: 2006
- Subjects: Lilyfontein School Adventure education Education -- South Africa -- Curricula Competency-based education -- South Africa Educational psychology Cognitive learning
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1495 , http://hdl.handle.net/10962/d1003376
- Description: This research investigates the benefits of adventure-based activities used as a learning experience at school level. In order to scientifically investigate these benefits the study is located at a school where an adventure-based programme is being developed as part of the school's curriculum. This programme consists of a range of adventure type experiences including, rock climbing, abseiling, canoeing, mountain biking, group dynamic activities, survival camps, ropes courses and adventure racing. At Lilyfontein School these activities form part of the Life Orientation and life Skill programmes from grade 1 to grade 11. Specialized and qualified staff are used to conduct some of these programmes. Adventure-based activities are rigorous and contain elements of risk which require problem solving, good decision making and sound emotional management. These aspects present both physical and mental challenges to any participant. This study postulates that learners engaged in these adventure type activities are faced with using meta-cognitive strategies to help them through these mental and physical challenges. In doing these activities regularly learners will develop meta-cognitive strategies that will enable them to become better self-regulated learners. A self-regulated learner is able to use meta-cognitive strategies like problem solving, decision making, selfevaluation, self-monitoring, self-reflective thinking or emotional control in life generally. The aim of this research is to conduct an on-going action research study of the adventure-based programmes to determine their worth for the learners at Lilyfontein School and consequently the future of such experiences in a school's curriculum. This forms the primary goal of this research. The secondary goal is to gather valid and reliable evidence required to make an argument for the School's Governing Body (SGB) and Curriculum Development Committee (CDC) to be able to substantiate decisions relating to any such future programmes. This research regards the school context as the activity system which forms a primary case study. In order to extract maximum information from this educational system, embedded case studies will be conducted and monitored. These embedded case studies will be made up of the following groups of people: firstly the learners engaged in a variety of adventure-based experiences, secondly the educators as they observe and perceive the consequences of these experiences, and thirdly the parents as they identifY possible influences of adventure-based experiences on the behaviours, beliefs or habits of their children. In this research study data collecting techniques are used to extract infonnation from the embedded cases. Infonnation is elicited from parents and educators through the use of questionnaires and interviews. For learners, narratives and interviews are used to get a more qualitative sense of their beliefs and feelings on adventure-based experiences. However, in order to capture and document the learners' use of metacognitive strategies as they engage in the rigours of an adventure-based activity a more empirical approach is used. This approach uses in-depth observation, recording and measuring of the learners in action. Video footage is used to record the learners' reactions as they battle with fear, mental-strength, fatigue and decision making to accomplish their goal during an adventure activity. This study claims that an adventure-based experience helps to mediate the learning that will develop selfregulatory strategies in a learner. The limited research in the adventure-based learning field and more significantly the lack of empirical evidence of how meta-cognitive strategies fonn a crucial component of adventure-based activities has meant that the researcher has developed his own recording, measuring and analytical tools to serve this end. He has chosen to use Engestrom's third generation Activity Theory model which provides a useful underlying theory as well as an analytical and interpretive framework for this study. The research was conducted over a period of three years. Findings are considered in relation to the National Curriculum Statement for the GET and FET bands to ensure its relevance in the school context to the National Department of Education's expectations for the Life Orientation curriculum. The empirical findings of this study at Lilyfontein School and their relevance to the curriculum content of the National Curriculum Statement ought to provide convincing data for very important curriculum policy decisions at Lilyfontein School and in the broader educational context.
- Full Text:
- Date Issued: 2006
Ectomycorrhizal characterisation, species diversity and community dynamics in Pinus patula Schelcht. et Cham. plantations
- Authors: Hawley, Greer Leigh
- Date: 2006
- Subjects: Mycorrhizas Ectomycorrhizal fungi Pinus patula -- Irrigation -- South Africa Forests and forestry -- South Africa Forest ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3951 , http://hdl.handle.net/10962/d1004010
- Description: Ectomycorrhizal (ECM) associations are important elements of forest biomes, connecting and transferring nutrients through an intricate and complex system of hyphal networks, ensuring plants of the nutrients they require, in nutrient poor soil. ECM research and particularly investigations into the diversity of the fungal partners has not received much attention in South Africa, hindering the advance of research in this field. This has been attributed to the difficulty of identifying the mycobionts involved in the symbiosis. The objectives of this study were to examine the ECM fungal diversity associating with Pinus patula, in selected forest plantations in Mpumalanga, South Africa. Both morphological and molecular techniques were used to identify specimens of both sporocarp collections and ECM root tip morphotypes. Morphological analysis of the ECM root tips involved characterisation of root morphology such as colour, branching and texture, and anatomical analysis examined hyphal arrangement in the root mantle and rhizomorphs. Molecular analysis involved sequencing of the Internal Transcribed Spacer (ITS) region and comparative BLAST analysis. Twenty-four sporocarp species were identified from 13 genera, namely: Amanita, Boletus, Clavulina, Inocybe, Lactarius, Rhizopogon, Russula, Scleroderma, Suillus, Tricholoma, Thelephora, Tomentella and Xerocomus. ECM root tip analysis led to the characterisation of 7 wild-type morphotypes identified as an Albatrellus sp., 2 Amanita species, a Rhizopogon sp., Thelephora terrestris, a Tomentella sp. and Scleroderma citrinum. A secondary objective was to determine whether fertilisation treatments within the study sites were responsible for differences in fungal species community structure. No evidence of a change in species diversity or shift in species composition was encountered. It is envisaged that these comprehensive ECM descriptions will be used as reference material to stimulate continued research in this field in South Africa.
- Full Text:
- Date Issued: 2006
- Authors: Hawley, Greer Leigh
- Date: 2006
- Subjects: Mycorrhizas Ectomycorrhizal fungi Pinus patula -- Irrigation -- South Africa Forests and forestry -- South Africa Forest ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3951 , http://hdl.handle.net/10962/d1004010
- Description: Ectomycorrhizal (ECM) associations are important elements of forest biomes, connecting and transferring nutrients through an intricate and complex system of hyphal networks, ensuring plants of the nutrients they require, in nutrient poor soil. ECM research and particularly investigations into the diversity of the fungal partners has not received much attention in South Africa, hindering the advance of research in this field. This has been attributed to the difficulty of identifying the mycobionts involved in the symbiosis. The objectives of this study were to examine the ECM fungal diversity associating with Pinus patula, in selected forest plantations in Mpumalanga, South Africa. Both morphological and molecular techniques were used to identify specimens of both sporocarp collections and ECM root tip morphotypes. Morphological analysis of the ECM root tips involved characterisation of root morphology such as colour, branching and texture, and anatomical analysis examined hyphal arrangement in the root mantle and rhizomorphs. Molecular analysis involved sequencing of the Internal Transcribed Spacer (ITS) region and comparative BLAST analysis. Twenty-four sporocarp species were identified from 13 genera, namely: Amanita, Boletus, Clavulina, Inocybe, Lactarius, Rhizopogon, Russula, Scleroderma, Suillus, Tricholoma, Thelephora, Tomentella and Xerocomus. ECM root tip analysis led to the characterisation of 7 wild-type morphotypes identified as an Albatrellus sp., 2 Amanita species, a Rhizopogon sp., Thelephora terrestris, a Tomentella sp. and Scleroderma citrinum. A secondary objective was to determine whether fertilisation treatments within the study sites were responsible for differences in fungal species community structure. No evidence of a change in species diversity or shift in species composition was encountered. It is envisaged that these comprehensive ECM descriptions will be used as reference material to stimulate continued research in this field in South Africa.
- Full Text:
- Date Issued: 2006
Empirical studies of fish movement behaviour and their application in spatially explicit models for marine conservation
- Authors: Kerwath, Sven Ebo
- Date: 2006
- Subjects: Fishing -- South Africa Fishes -- Behavior -- South Africa Fish tagging Marine parks and reserves -- South Africa Marine resources conservation Pomadasys -- South Africa Reef fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5277 , http://hdl.handle.net/10962/d1005121
- Description: This thesis investigates the movement behaviour of South African two coastal fish species and evaluates the effectiveness of marine protected areas (MPAs) in their protection and management. Its primary focus is on resolving the movement patterns of roman Chrysoblephus laticeps (Sparidae) in and around the Goukamma and Castle Rock MPAs in the Western Cape province of South Africa. A pilot study of the methodology investigated the movement behaviour of spotted grunter Pomadasys commersonnii (Haemulidae) in the sheltered East Kleinmonde Estuary in the Eastern Cape province. The application of different tagging methods was tested in a controlled tank experiment. Tagged roman were monitored over a 198-day period. Barbed dart, t-bar anchor and Visible Implanted Fluorescent Elastomer (VIFE) tags were compared. Application techniques and underwater visibility of VIFE tags were tested on roman and on fransmadam Boobsoidia inornata in a pilot study. Needles of gauge 25 were found to be optimal for VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on roman. VIFE tagged fish could be identified by divers from a distance of three metres under ambient light in an observation tank in five metres water depth. There was no significant difference in growth rate between groups of roman with different tags and controls after 198 days. High tag loss rates were experienced for barbed dart and t-bar anchor tags, although barbed dart tags performed better than t-bar anchor tags. Although some of the VIFE marks had deteriorated, all VIFE tagged fish were individually recognised at the end of the study. Conventional dart and VIFE tags are feasible methods to tag roman. However, the high tag loss rate of conventional tags must be taken into account in the design of a tagging study. Previous mark and recapture studies on roman are beset with a number of problems. Poor experimental design and low precision of capture positions resulted in equivocal results of limited value. A tagging experiment was designed to eliminate ambiguity in data interpretation and to produce a dataset that could be used to model roman residency and dispersal. A combination of conventional barbed dart tags and Visible Implanted Fluorescent Elastomer tags was used to tag roman in the Goukamma Marine Protected Area (GMPA) on the temperate South African south coast. Sixty one percent of roman were recaptured within 50 m of the tagging position. A small proportion moved considerable distances of up to four kilometres. The extent of these movements was not dependent on fish size or sex. Data from this experiment and from a previous tagging study in the Tsitsikamma National Park (TNP) were used to model the resident behaviour of roman. The model suggests a probability of 91% (GMPA) and 94% (TNP) of residency within a 10000 m² cell. This result suggests that individual roman will benefit from protection in small MPAs. A different experimental approach was required to investigate the exact home range of this species. Firstly the feasibility of using acoustic telemetry to study the movement of coastal fish in South Africa was investigated. The telemetry equipment comprised two VEMCO V8 transmitters and a VEMCO VR60 receiver linked to a directional hydrophone. A tank experiment was conducted to examine the effects of the transmitter implantation. A tracking experiment was conducted on spotted grunter Pomadasys commersonnii in the East Kleinmonde Estuary. Operated fish recovered quickly and, with respect to swimming behaviour and growth rates, no differences were found between fish with implants and controls. The maximum detection range in the estuary was 400 m. Interference between different transmitter frequencies was negligible. Transmitter location recordings were found to be accurate within five metres. Two fish were tracked over a seven-day period. The fish preferred the lower reaches of the estuary where they made repeated and prolonged use of specific areas. The success of the initial experiments allowed this method to be used to investigate the spatial utilisation and activity patterns of roman Chrysoblephus laticeps. Surgically implanted VEMCO V8, V13 and V16 transmitters were used to track 13 roman inside the Castle Rock MPA in False Bay. Transmitters implanted into C. laticeps in tanks had no apparent effects on growth and physiology. Manual boatand diver-based tracking experiments covered a 17-month period. A VEMCO VRAP radio acoustic positioning system was used over two one-month periods during and after the spawning season of roman. Analysis of data using a 95% fixed kernel algorithm suggests that roman are resident throughout their adult life, occupying home ranges between 1000 and 3000 m². Activity was lower at night. During periods of cold-water upwelling, fish retreated into caves. During the spawning season, females extended their home ranges, possibly to mate with different males. These results confirm that this species is well suited for protection and management with small MPAs. The effect of two MPAs on the South African south coast on the population of C. laticeps was simulated with a spatially explicit individual based model (IBM). Life history parameters determined in recent studies and the effect of fishing on the size of sex change was taken into account. Fish densities and size frequencies were based on recent underwater visual census. The distribution of suitable habitat in the study areas was also incorporated. The results show a rapid recovery of the fish size frequency spectrum and sex ratio to pre-exploitation levels inside both MPAs. Little 'spillover' of fish into the fished areas occurred resulting in negligible improvement of catches. The results suggest that for resident species like roman, even small MPAs offer sufficient protection.
- Full Text:
- Date Issued: 2006
- Authors: Kerwath, Sven Ebo
- Date: 2006
- Subjects: Fishing -- South Africa Fishes -- Behavior -- South Africa Fish tagging Marine parks and reserves -- South Africa Marine resources conservation Pomadasys -- South Africa Reef fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5277 , http://hdl.handle.net/10962/d1005121
- Description: This thesis investigates the movement behaviour of South African two coastal fish species and evaluates the effectiveness of marine protected areas (MPAs) in their protection and management. Its primary focus is on resolving the movement patterns of roman Chrysoblephus laticeps (Sparidae) in and around the Goukamma and Castle Rock MPAs in the Western Cape province of South Africa. A pilot study of the methodology investigated the movement behaviour of spotted grunter Pomadasys commersonnii (Haemulidae) in the sheltered East Kleinmonde Estuary in the Eastern Cape province. The application of different tagging methods was tested in a controlled tank experiment. Tagged roman were monitored over a 198-day period. Barbed dart, t-bar anchor and Visible Implanted Fluorescent Elastomer (VIFE) tags were compared. Application techniques and underwater visibility of VIFE tags were tested on roman and on fransmadam Boobsoidia inornata in a pilot study. Needles of gauge 25 were found to be optimal for VIFE tag application. Whereas VIFE tagging caused fin rot in fransmadam, it had no negative effect on roman. VIFE tagged fish could be identified by divers from a distance of three metres under ambient light in an observation tank in five metres water depth. There was no significant difference in growth rate between groups of roman with different tags and controls after 198 days. High tag loss rates were experienced for barbed dart and t-bar anchor tags, although barbed dart tags performed better than t-bar anchor tags. Although some of the VIFE marks had deteriorated, all VIFE tagged fish were individually recognised at the end of the study. Conventional dart and VIFE tags are feasible methods to tag roman. However, the high tag loss rate of conventional tags must be taken into account in the design of a tagging study. Previous mark and recapture studies on roman are beset with a number of problems. Poor experimental design and low precision of capture positions resulted in equivocal results of limited value. A tagging experiment was designed to eliminate ambiguity in data interpretation and to produce a dataset that could be used to model roman residency and dispersal. A combination of conventional barbed dart tags and Visible Implanted Fluorescent Elastomer tags was used to tag roman in the Goukamma Marine Protected Area (GMPA) on the temperate South African south coast. Sixty one percent of roman were recaptured within 50 m of the tagging position. A small proportion moved considerable distances of up to four kilometres. The extent of these movements was not dependent on fish size or sex. Data from this experiment and from a previous tagging study in the Tsitsikamma National Park (TNP) were used to model the resident behaviour of roman. The model suggests a probability of 91% (GMPA) and 94% (TNP) of residency within a 10000 m² cell. This result suggests that individual roman will benefit from protection in small MPAs. A different experimental approach was required to investigate the exact home range of this species. Firstly the feasibility of using acoustic telemetry to study the movement of coastal fish in South Africa was investigated. The telemetry equipment comprised two VEMCO V8 transmitters and a VEMCO VR60 receiver linked to a directional hydrophone. A tank experiment was conducted to examine the effects of the transmitter implantation. A tracking experiment was conducted on spotted grunter Pomadasys commersonnii in the East Kleinmonde Estuary. Operated fish recovered quickly and, with respect to swimming behaviour and growth rates, no differences were found between fish with implants and controls. The maximum detection range in the estuary was 400 m. Interference between different transmitter frequencies was negligible. Transmitter location recordings were found to be accurate within five metres. Two fish were tracked over a seven-day period. The fish preferred the lower reaches of the estuary where they made repeated and prolonged use of specific areas. The success of the initial experiments allowed this method to be used to investigate the spatial utilisation and activity patterns of roman Chrysoblephus laticeps. Surgically implanted VEMCO V8, V13 and V16 transmitters were used to track 13 roman inside the Castle Rock MPA in False Bay. Transmitters implanted into C. laticeps in tanks had no apparent effects on growth and physiology. Manual boatand diver-based tracking experiments covered a 17-month period. A VEMCO VRAP radio acoustic positioning system was used over two one-month periods during and after the spawning season of roman. Analysis of data using a 95% fixed kernel algorithm suggests that roman are resident throughout their adult life, occupying home ranges between 1000 and 3000 m². Activity was lower at night. During periods of cold-water upwelling, fish retreated into caves. During the spawning season, females extended their home ranges, possibly to mate with different males. These results confirm that this species is well suited for protection and management with small MPAs. The effect of two MPAs on the South African south coast on the population of C. laticeps was simulated with a spatially explicit individual based model (IBM). Life history parameters determined in recent studies and the effect of fishing on the size of sex change was taken into account. Fish densities and size frequencies were based on recent underwater visual census. The distribution of suitable habitat in the study areas was also incorporated. The results show a rapid recovery of the fish size frequency spectrum and sex ratio to pre-exploitation levels inside both MPAs. Little 'spillover' of fish into the fished areas occurred resulting in negligible improvement of catches. The results suggest that for resident species like roman, even small MPAs offer sufficient protection.
- Full Text:
- Date Issued: 2006
Epitaxial growth and characterisation of CuGaS2
- Authors: Branch, Matthew Stewart
- Date: 2006
- Subjects: Epitaxy , Chalcopyrite , Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10541 , http://hdl.handle.net/10948/438 , http://hdl.handle.net/10948/d1012893 , Epitaxy , Chalcopyrite , Semiconductors
- Description: In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.
- Full Text:
- Date Issued: 2006
- Authors: Branch, Matthew Stewart
- Date: 2006
- Subjects: Epitaxy , Chalcopyrite , Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10541 , http://hdl.handle.net/10948/438 , http://hdl.handle.net/10948/d1012893 , Epitaxy , Chalcopyrite , Semiconductors
- Description: In this work, the growth and characterisation of the chalcopyrite semiconductor CuGaS2 is presented. The purpose of this study is to gain a better understanding of the defect chemistry of this class of materials through a systematic study relating the structural and optical properties to the composition of thin films grown by metalorganic vapour phase epitaxy. Details associated with the optimisation of the growth process are presented in a format relating the changes in the composition and morphology to variations in the growth process. The structural properties of thin films grown on GaAs(001) substrates are described. A dominance of polycrystalline growth is found to occur for Cu-rich material, whereas near-stoichiometric to Ga-rich material is typified by epitaxial growth. Secondary phases are identified by X-ray diffractometry and Raman spectroscopy for severely non-stoichiometric material. In some cases, the formation of the cubic zincblende and CuPt polytype of CuGaS2 are identified by transmission electron microscopy. It will be shown that changes in the Cu/Ga ratio of the solid strongly influence the photoluminescence response of the layers. Weak excitonic luminescence is observed for both slightly Ga-rich and Cu-rich material. Near stoichiometric layers exhibit luminescence centered at ~2.4 eV. Cu-rich layers are dominated by a line occurring at ~2.1 eV, whereas a different line at ~2.25 eV dominates for Ga-rich layers. A clear picture emerges of the radiative mechanisms dominating for Cu-rich and Ga-rich layers.
- Full Text:
- Date Issued: 2006
Habitat segregation in competing species of intertidal mussels in South Africa
- Authors: Bownes, Sarah
- Date: 2006
- Subjects: Mussels -- South Africa Mussels -- Growth Mussels -- Habitat -- South Africa Mussels -- Larvae Perna -- South Africa Mytilus galloprovincialis -- South Africa Choromytilus meridionalis -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5706 , http://hdl.handle.net/10962/d1005392
- Description: Mytilus galloprovincialis is invasive on rocky shores on the west coast of South Africa where it has become the dominant intertidal mussel. The success of this species on the west coast and its superior competitive abilities, have led to concern that it may become invasive on the south coast at the expense of the indigenous mussel Perna perna. On shores where these species co-occur, there appears to be habitat segregation among zones occupied by mussels. M.galloprovincialis dominates the high-shore and P.perna the low-shore, with a mixed zone at mid-shore level. This study examined the factors responsible for these differences in distribution and abundance. The study was conducted in Plettenberg Bay and Tsitsikamma (70km apart) on the south coast of South Africa. Each site included two randomly selected locations (300-400m apart). A third mussel species, Choromytilus meridionalis, is found in large numbers at the sand/rock interface at one location in Plettenberg Bay. Aspects of settlement, recruitment, growth and mortality of juvenile and adult mussels were examined at different tidal heights at each site. Quantitative analysis of mussel population structure at these sites supported the initial observation of vertical habitat segregation. Post-larvae were identified to species and this was confirmed using hinge morphology and mitochondrial DNA analysis. Size at settlement was determined for each species to differentiate between primary and secondary settlement. Adult distribution of C.meridionalis was primarily determined by settlement, which was highly selective in this species. Settlement, recruitment and growth of P.perna decreased with increasing tidal height, while post-settlement mortality and adult mortality increased higher upshore. Thus all aspects of P.perna’s life history contribute to the adult distribution of this species. Presumably, the abundance of P.perna on the high-shore is initially limited by recruitment while those that survive remain prone to elimination throughout adulthood. M.galloprovincialis displayed the same patterns of settlement and recruitment as P.perna. However, post-settlement mortality in this species was consistently low in the low and high zones. Juvenile growth also decreased upshore, suggesting that M.galloprovincialis may be able to maintain high densities on the high-shore through the persistence of successive settlements of slow-growing individuals. The low cover of M.galloprovincialis on the lowshore appeared to be determined by adult interactions. M.galloprovincialis experienced significantly higher adult mortality rates than P.perna in this zone. There were seasonal variations in the competitive advantages enjoyed by each species through growth, recruitment or mortality on the low-shore. In summer, P.perna had higher recruitment rates, faster growth and lower mortality rates, while M.galloprovincialis had slightly higher recruitment rates and faster growth rates in winter. P.perna is a warm water species while M.galloprovincialis thrives on the cold-temperate west coast of South Africa. Therefore both species appear to be at the edge of their optimal temperature regimes on the south coast, which may explain the seasonal advantages of each. Nevertheless, P.perna has maintained spatial dominance on the low-shore suggesting that it may ultimately be the winner in competition between these species. M.galloprovincialis appears to have a refuge from competition with P.perna on the high-shore due to its greater tolerance of desiccation stress, while being competitively excluded from the low-shore. Warm water temperatures coupled with poor recruitment rates at most sites may limit the success of M.galloprovincialis on this coast.
- Full Text:
- Date Issued: 2006
- Authors: Bownes, Sarah
- Date: 2006
- Subjects: Mussels -- South Africa Mussels -- Growth Mussels -- Habitat -- South Africa Mussels -- Larvae Perna -- South Africa Mytilus galloprovincialis -- South Africa Choromytilus meridionalis -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5706 , http://hdl.handle.net/10962/d1005392
- Description: Mytilus galloprovincialis is invasive on rocky shores on the west coast of South Africa where it has become the dominant intertidal mussel. The success of this species on the west coast and its superior competitive abilities, have led to concern that it may become invasive on the south coast at the expense of the indigenous mussel Perna perna. On shores where these species co-occur, there appears to be habitat segregation among zones occupied by mussels. M.galloprovincialis dominates the high-shore and P.perna the low-shore, with a mixed zone at mid-shore level. This study examined the factors responsible for these differences in distribution and abundance. The study was conducted in Plettenberg Bay and Tsitsikamma (70km apart) on the south coast of South Africa. Each site included two randomly selected locations (300-400m apart). A third mussel species, Choromytilus meridionalis, is found in large numbers at the sand/rock interface at one location in Plettenberg Bay. Aspects of settlement, recruitment, growth and mortality of juvenile and adult mussels were examined at different tidal heights at each site. Quantitative analysis of mussel population structure at these sites supported the initial observation of vertical habitat segregation. Post-larvae were identified to species and this was confirmed using hinge morphology and mitochondrial DNA analysis. Size at settlement was determined for each species to differentiate between primary and secondary settlement. Adult distribution of C.meridionalis was primarily determined by settlement, which was highly selective in this species. Settlement, recruitment and growth of P.perna decreased with increasing tidal height, while post-settlement mortality and adult mortality increased higher upshore. Thus all aspects of P.perna’s life history contribute to the adult distribution of this species. Presumably, the abundance of P.perna on the high-shore is initially limited by recruitment while those that survive remain prone to elimination throughout adulthood. M.galloprovincialis displayed the same patterns of settlement and recruitment as P.perna. However, post-settlement mortality in this species was consistently low in the low and high zones. Juvenile growth also decreased upshore, suggesting that M.galloprovincialis may be able to maintain high densities on the high-shore through the persistence of successive settlements of slow-growing individuals. The low cover of M.galloprovincialis on the lowshore appeared to be determined by adult interactions. M.galloprovincialis experienced significantly higher adult mortality rates than P.perna in this zone. There were seasonal variations in the competitive advantages enjoyed by each species through growth, recruitment or mortality on the low-shore. In summer, P.perna had higher recruitment rates, faster growth and lower mortality rates, while M.galloprovincialis had slightly higher recruitment rates and faster growth rates in winter. P.perna is a warm water species while M.galloprovincialis thrives on the cold-temperate west coast of South Africa. Therefore both species appear to be at the edge of their optimal temperature regimes on the south coast, which may explain the seasonal advantages of each. Nevertheless, P.perna has maintained spatial dominance on the low-shore suggesting that it may ultimately be the winner in competition between these species. M.galloprovincialis appears to have a refuge from competition with P.perna on the high-shore due to its greater tolerance of desiccation stress, while being competitively excluded from the low-shore. Warm water temperatures coupled with poor recruitment rates at most sites may limit the success of M.galloprovincialis on this coast.
- Full Text:
- Date Issued: 2006
High speed end-to-end connection management in a bridged IEEE 1394 network of professional audio devices
- Authors: Okai-Tettey, Harold A
- Date: 2006
- Subjects: IEEE 1394 (Standard) Digital communications Computer networks Sound -- Recording and reproducing -- Digital techniques Computer sound processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4653 , http://hdl.handle.net/10962/d1006638
- Description: A number of companies have developed a variety of network approaches to the transfer of audio and MIDI data. By doing this, they have addressed the configuration complications that were present when using direct patching for analogue audio, digital audio, word clock, and control connections. Along with their approaches, controlling software, usually running on a PC, is used to set up and manage audio routings from the outputs to the inputs of devices. However one of the advantages of direct patching is the conceptual simplicity it provides for a user in connecting plugs of devices, the ability to connect from the host plug of one device to the host plug of another. The connection management or routing applications of the current audio networks do not allow for such a capability, and instead employ what is referred to as a two-step approach to connection management. This two-step approach requires that devices be first configured at the transport layer of the network for input and output routings, after which the transmit and receive plugs of devices are manually configured to transmit or receive data. From a user’s point of view, it is desirable for the connection management or audio routing applications of the current audio networks to be able to establish routings directly between the host plugs of devices, and not the audio channels exposed by a network’s transport, as is currently the case. The main goal of this work has been to retain the conceptual simplicity of point-to-point connection management within digital audio networks, while gaining all the benefits that digital audio networking can offer.
- Full Text:
- Date Issued: 2006
- Authors: Okai-Tettey, Harold A
- Date: 2006
- Subjects: IEEE 1394 (Standard) Digital communications Computer networks Sound -- Recording and reproducing -- Digital techniques Computer sound processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4653 , http://hdl.handle.net/10962/d1006638
- Description: A number of companies have developed a variety of network approaches to the transfer of audio and MIDI data. By doing this, they have addressed the configuration complications that were present when using direct patching for analogue audio, digital audio, word clock, and control connections. Along with their approaches, controlling software, usually running on a PC, is used to set up and manage audio routings from the outputs to the inputs of devices. However one of the advantages of direct patching is the conceptual simplicity it provides for a user in connecting plugs of devices, the ability to connect from the host plug of one device to the host plug of another. The connection management or routing applications of the current audio networks do not allow for such a capability, and instead employ what is referred to as a two-step approach to connection management. This two-step approach requires that devices be first configured at the transport layer of the network for input and output routings, after which the transmit and receive plugs of devices are manually configured to transmit or receive data. From a user’s point of view, it is desirable for the connection management or audio routing applications of the current audio networks to be able to establish routings directly between the host plugs of devices, and not the audio channels exposed by a network’s transport, as is currently the case. The main goal of this work has been to retain the conceptual simplicity of point-to-point connection management within digital audio networks, while gaining all the benefits that digital audio networking can offer.
- Full Text:
- Date Issued: 2006
Metabolic effects brought about by tricyclic antidepressants and the contribution of a medicinal plant in alleviating high fat diet induced insulin resistance in male wistar rats
- Authors: Chadwick, Wayne
- Date: 2006
- Subjects: Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10329 , http://hdl.handle.net/10948/461 , Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Description: Type II diabetes is becoming a growing problem in developed countries worldwide. The median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve shifting left. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with an unhealthy western diet. Type II diabetes is an expensive disease to manage, 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 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 S. frutescens or metformin was administered to two groups of eleven insulin resistant male Wistar rats. The insulin resistant control group received water without any medication. Rats were sacrificed after 8 weeks allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. The effect of the medication and the diet on muscle post receptor insulin signaling proteins was determined through Western blots. Liver proteomics was also performed using 2-D electrophoresis. In a separate experiment 26 male Wistar rats were exposed to strepotozotocin toxin, 7 of these rats received intravenous insulin treatment, 7 rats received S. frutescens extract and 7 rats received a combination of both medications, the remaining 5 received no treatment and served as the control. Rats were sacrificed after 6 days allowing for fasting blood glucose, insulin and tissue glycogen content determination. Two groups of 14 male Wistar rats received amitriptyline or trimipramine (common tricyclic antidepressants) in their drinking water, the control group (30 rats) received water without any medication. The rats’ weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after 6 weeks or 14 weeks of medicinal compliance allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. S. frutescens treatment normalized circulating serum insulin levels and significantly increased the rate of glucose clearance. Certain post receptor insulin signaling proteins were also significantly increased relative to the insulin resistant control group. 2-D electrophoresis identified the normalization of protein levels associated with the urea cycle. S. frutescens was also able to, independently; maintain normoglycaemic levels in the strepotozotocin treated group. The tricyclic antidepressants significantly increased blood glucose levels while significantly reducing tissue glycogen levels for both sacrifice periods. Serum insulin remained unchanged while a significant increase in insulin degradation and insulin degrading enzyme levels were found for both antidepressants. S. frutescens shows promise as a low cost antidiabetic medication for future use. Although the antidepressants did not promote weight gain, the increase in blood glucose levels may be cause for concern in patients with a pre-disposition toward developing diabetes.
- Full Text:
- Date Issued: 2006
- Authors: Chadwick, Wayne
- Date: 2006
- Subjects: Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10329 , http://hdl.handle.net/10948/461 , Rats -- Metabolism , Diabetes -- Research , Medicinal plants -- South Africa
- Description: Type II diabetes is becoming a growing problem in developed countries worldwide. The median age for diagnosis was around sixty, but recent surveys have shown that the entire age distribution curve shifting left. The incidence of type II diabetes is thought to be parallel with the growing rate of obesity associated with an unhealthy western diet. Type II diabetes is an expensive disease to manage, 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 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 S. frutescens or metformin was administered to two groups of eleven insulin resistant male Wistar rats. The insulin resistant control group received water without any medication. Rats were sacrificed after 8 weeks allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. The effect of the medication and the diet on muscle post receptor insulin signaling proteins was determined through Western blots. Liver proteomics was also performed using 2-D electrophoresis. In a separate experiment 26 male Wistar rats were exposed to strepotozotocin toxin, 7 of these rats received intravenous insulin treatment, 7 rats received S. frutescens extract and 7 rats received a combination of both medications, the remaining 5 received no treatment and served as the control. Rats were sacrificed after 6 days allowing for fasting blood glucose, insulin and tissue glycogen content determination. Two groups of 14 male Wistar rats received amitriptyline or trimipramine (common tricyclic antidepressants) in their drinking water, the control group (30 rats) received water without any medication. The rats’ weight and food consumption was monitored throughout the trial and their oxygen consumption was also determined. Rats were sacrificed after 6 weeks or 14 weeks of medicinal compliance allowing for fasting blood glucose, insulin and tissue glycogen content determination. Glucose uptake was also determined using [3H] deoxyglucose. S. frutescens treatment normalized circulating serum insulin levels and significantly increased the rate of glucose clearance. Certain post receptor insulin signaling proteins were also significantly increased relative to the insulin resistant control group. 2-D electrophoresis identified the normalization of protein levels associated with the urea cycle. S. frutescens was also able to, independently; maintain normoglycaemic levels in the strepotozotocin treated group. The tricyclic antidepressants significantly increased blood glucose levels while significantly reducing tissue glycogen levels for both sacrifice periods. Serum insulin remained unchanged while a significant increase in insulin degradation and insulin degrading enzyme levels were found for both antidepressants. S. frutescens shows promise as a low cost antidiabetic medication for future use. Although the antidepressants did not promote weight gain, the increase in blood glucose levels may be cause for concern in patients with a pre-disposition toward developing diabetes.
- Full Text:
- Date Issued: 2006
Metathesis catalysts : an integrated computational, mechanistic and synthetic study
- Authors: Sabbagh, Ingrid Theresa
- Date: 2006
- Subjects: Metathesis (Chemistry) Catalysis Metal catalysts Chemical kinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4397 , http://hdl.handle.net/10962/d1006208
- Description: An integrated approach to the design of potential rutheniun-based metathesis catalysts is described, in which closely defined synthetic forays provide the focus and rationale for detailed computational and mechanistic studies. The ground-state geometry of a 1st-generation Grubbs catalyst has been explored at the molecular mechanics, semi-empirical and DFT levels, and the resulting structures have been shown to compare favourably with literature data and with the structure of a known crystalline analogue. The DMol³ DFT code has also been shown to represent accurately both the geometry of the corresponding co-ordinatively unsaturated monophosphine derivative, and the ligand dissociation energy associated with its formation. A DFT free-energy profile of the degenerate metathesis of ethylene has been generated, using a truncated model of the 1st-generation Grubbs catalyst, permitting location, for the first time, of the three expected transition states and providing new information regarding the rate-determining step. DFT methods have been used to facilitate the design of a tridentate camphor-derived ligand for use in the construction of a novel Grubbs-type catalyst. The phosphine ligand dissociation energy of the putative catalyst and the ethylene metathesis energy profile of a truncated model have also been studies at the DFT level. The attempted synthesis of the proposed ligand proceeded via a novel 8-bromocamphoric anhydride intermediate and afforded several unexpected and novel products, including a cisfused γ-Iactone, and a bromo camphoric acid derivative. Single crystal X-ray analysis of the latter reveals a chiral, polymeric H-bonded packing arrangement, rendering it suitable for chiral inclusion studies. Computational methods, including the GAUSSIAN-based GIAO NMR prediction technique, were used to support the structural characterisation of the novel camphor derivatives. DFT-Ievel computational analysis of the C-8- and C-9 bromination of camphor has afforded theoretical insights which permit the reconciliation of two earlier empirical explanations regarding the regioselectivity of these transformations; moreover, the theoretical results suggest that a third, previously disregarded factor, plays a significant role. A coset analysis, in conjunction with DFT-Ievel energy profiling, has also been used to resolve conflicting opinions regarding the origin of the major byproduct. Computed electronic parameters (CEP's) have been calculated for the anionic ligands involved in a series of 2nd-generation Grubbs-Hoveyda-type catalysts, and used to explain some apparently anomalous trends in catalyst activity. A linear relationship between ligand CEP's and selected ¹H NMR chemical shifts has also been demonstrated and used to identify a transient ruthenium complex in solution. The ability of the malonate di-anion to bind to ruthenium in a bidentate manner has been explored and demonstrated, under suitable conditions. DFT methods have been used to design and assess the ruthenium-chelating potential of a novel tridentate malonate derivative. A synthetic pathway to this ligand has been designed and several novel heterocyclic intermediates have been isolated and characterised. An NMR-based kinetic study of the Grubbs-catalysed self-metathesis of l-octene has been completed, and the effects of temperature, concentration and solvent variations on the kinetic parameters have been studied. Application of the Guggenheim method and a simplified mechanistic model has permitted the accurate calculation of pseudorate constants for the initiation and, for the first time, the propagation phase of the reaction. Theoretical studies of this reaction at the DFT and molecular mechanics levels have been shown to support previous assumptions regarding the selectivity and temperature-dependence of metallacycle formation.
- Full Text:
- Date Issued: 2006
- Authors: Sabbagh, Ingrid Theresa
- Date: 2006
- Subjects: Metathesis (Chemistry) Catalysis Metal catalysts Chemical kinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4397 , http://hdl.handle.net/10962/d1006208
- Description: An integrated approach to the design of potential rutheniun-based metathesis catalysts is described, in which closely defined synthetic forays provide the focus and rationale for detailed computational and mechanistic studies. The ground-state geometry of a 1st-generation Grubbs catalyst has been explored at the molecular mechanics, semi-empirical and DFT levels, and the resulting structures have been shown to compare favourably with literature data and with the structure of a known crystalline analogue. The DMol³ DFT code has also been shown to represent accurately both the geometry of the corresponding co-ordinatively unsaturated monophosphine derivative, and the ligand dissociation energy associated with its formation. A DFT free-energy profile of the degenerate metathesis of ethylene has been generated, using a truncated model of the 1st-generation Grubbs catalyst, permitting location, for the first time, of the three expected transition states and providing new information regarding the rate-determining step. DFT methods have been used to facilitate the design of a tridentate camphor-derived ligand for use in the construction of a novel Grubbs-type catalyst. The phosphine ligand dissociation energy of the putative catalyst and the ethylene metathesis energy profile of a truncated model have also been studies at the DFT level. The attempted synthesis of the proposed ligand proceeded via a novel 8-bromocamphoric anhydride intermediate and afforded several unexpected and novel products, including a cisfused γ-Iactone, and a bromo camphoric acid derivative. Single crystal X-ray analysis of the latter reveals a chiral, polymeric H-bonded packing arrangement, rendering it suitable for chiral inclusion studies. Computational methods, including the GAUSSIAN-based GIAO NMR prediction technique, were used to support the structural characterisation of the novel camphor derivatives. DFT-Ievel computational analysis of the C-8- and C-9 bromination of camphor has afforded theoretical insights which permit the reconciliation of two earlier empirical explanations regarding the regioselectivity of these transformations; moreover, the theoretical results suggest that a third, previously disregarded factor, plays a significant role. A coset analysis, in conjunction with DFT-Ievel energy profiling, has also been used to resolve conflicting opinions regarding the origin of the major byproduct. Computed electronic parameters (CEP's) have been calculated for the anionic ligands involved in a series of 2nd-generation Grubbs-Hoveyda-type catalysts, and used to explain some apparently anomalous trends in catalyst activity. A linear relationship between ligand CEP's and selected ¹H NMR chemical shifts has also been demonstrated and used to identify a transient ruthenium complex in solution. The ability of the malonate di-anion to bind to ruthenium in a bidentate manner has been explored and demonstrated, under suitable conditions. DFT methods have been used to design and assess the ruthenium-chelating potential of a novel tridentate malonate derivative. A synthetic pathway to this ligand has been designed and several novel heterocyclic intermediates have been isolated and characterised. An NMR-based kinetic study of the Grubbs-catalysed self-metathesis of l-octene has been completed, and the effects of temperature, concentration and solvent variations on the kinetic parameters have been studied. Application of the Guggenheim method and a simplified mechanistic model has permitted the accurate calculation of pseudorate constants for the initiation and, for the first time, the propagation phase of the reaction. Theoretical studies of this reaction at the DFT and molecular mechanics levels have been shown to support previous assumptions regarding the selectivity and temperature-dependence of metallacycle formation.
- Full Text:
- Date Issued: 2006
Pharmaceutical analysis and drug interaction studies : African potato (Hypoxis hemerocallidea)
- Purushothaman Nair, Vipin Devi Prasad
- Authors: Purushothaman Nair, Vipin Devi Prasad
- Date: 2006
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3865 , http://hdl.handle.net/10962/d1015802
- Description: In order for a medicinal product to produce a consistent and reliable therapeutic response, it is essential that the final composition of the product is invariable and that the active ingredient/s is/are present in appropriate, non-toxic amounts. However, due to the complexity involved in the standardization of natural products, quality control (QC) criteria and procedures for the registration and market approval of such products are conspicuously absent in most countries around the world. African Potato (AP) is of great medical interest and this particular plant has gained tremendous popularity following the endorsement by the South African Minister of Health as a remedy for HIV/ AIDS patients. Very little information has appeared in the literature to describe methods for the quantitative analysis of hypoxoside, an important component in AP. It has also been claimed that sterols and sterolins present in AP are responsible for its medicinal property but is yet to be proven scientifically. To-date, no QC methods have been reported for the simultaneous quantitative analysis of the combination, β- sitosterol (BSS)/ stigmasterol (STG)/ stigmastanol (STN), purported to be present in preparations containing AP. The effect of concomitant administration of AP and other herbal medicines on the safety and efficacy of conventional medicines has not yet been fully determined. Amongst the objectives of this study was to develop and validate quantitative analytical methods that are suitable for the assay and quality control of plant material, extracts and commercial formulations containing AP. Hypoxoside was isolated from AP and characterized for use as a reference standard for the quality control of AP products and a stability-indicating HPLC/ UV assay method for the quantitative determination of hypoxoside was developed. In addition, a quantitative capillary zone electrophoretic (CZE) method was developed to determine hypoxoside, specifically for its advantages over HPLC. A HPLC method was also developed and validated for the quantitative analysis of BSS, STG and STN in commercially available oral dosage forms containing AP material or extracts thereof. The antioxidant activity of an aqueous extract of lyophilized corms of AP along with hypoxoside and rooperol were investigated. In comparison with the AP extracts and also with hypoxoside, rooperol showed significant antioxidant activity. The capacity of AP, (extracts, formulations, hypoxoside and rooperol as well as sterols to inhibit in vitro metabolism of drug substrates by human cytochrome P450 (CYP) enzymes such as CYP 3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). Various extracts of AP, AP formulations, stigmasterol and the norlignans, in particular the aglycone rooperol, exhibited inhibitory effects on CYP 3A4, 3A5 and CYP19 mediated metabolism.These results suggest that concurrent therapy with AP and other medicines, in particular antiretroviral drugs, can have important implications for safety and efficacy. Large discrepancies in marker content between AP products were found. Dissolution testing of AP products was investigated as a QC tool and the results also revealed inconsistencies between different AP products.
- Full Text:
- Date Issued: 2006
- Authors: Purushothaman Nair, Vipin Devi Prasad
- Date: 2006
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , AIDS (Disease) -- Treatment , HIV infections -- Drug therapy , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3865 , http://hdl.handle.net/10962/d1015802
- Description: In order for a medicinal product to produce a consistent and reliable therapeutic response, it is essential that the final composition of the product is invariable and that the active ingredient/s is/are present in appropriate, non-toxic amounts. However, due to the complexity involved in the standardization of natural products, quality control (QC) criteria and procedures for the registration and market approval of such products are conspicuously absent in most countries around the world. African Potato (AP) is of great medical interest and this particular plant has gained tremendous popularity following the endorsement by the South African Minister of Health as a remedy for HIV/ AIDS patients. Very little information has appeared in the literature to describe methods for the quantitative analysis of hypoxoside, an important component in AP. It has also been claimed that sterols and sterolins present in AP are responsible for its medicinal property but is yet to be proven scientifically. To-date, no QC methods have been reported for the simultaneous quantitative analysis of the combination, β- sitosterol (BSS)/ stigmasterol (STG)/ stigmastanol (STN), purported to be present in preparations containing AP. The effect of concomitant administration of AP and other herbal medicines on the safety and efficacy of conventional medicines has not yet been fully determined. Amongst the objectives of this study was to develop and validate quantitative analytical methods that are suitable for the assay and quality control of plant material, extracts and commercial formulations containing AP. Hypoxoside was isolated from AP and characterized for use as a reference standard for the quality control of AP products and a stability-indicating HPLC/ UV assay method for the quantitative determination of hypoxoside was developed. In addition, a quantitative capillary zone electrophoretic (CZE) method was developed to determine hypoxoside, specifically for its advantages over HPLC. A HPLC method was also developed and validated for the quantitative analysis of BSS, STG and STN in commercially available oral dosage forms containing AP material or extracts thereof. The antioxidant activity of an aqueous extract of lyophilized corms of AP along with hypoxoside and rooperol were investigated. In comparison with the AP extracts and also with hypoxoside, rooperol showed significant antioxidant activity. The capacity of AP, (extracts, formulations, hypoxoside and rooperol as well as sterols to inhibit in vitro metabolism of drug substrates by human cytochrome P450 (CYP) enzymes such as CYP 3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). Various extracts of AP, AP formulations, stigmasterol and the norlignans, in particular the aglycone rooperol, exhibited inhibitory effects on CYP 3A4, 3A5 and CYP19 mediated metabolism.These results suggest that concurrent therapy with AP and other medicines, in particular antiretroviral drugs, can have important implications for safety and efficacy. Large discrepancies in marker content between AP products were found. Dissolution testing of AP products was investigated as a QC tool and the results also revealed inconsistencies between different AP products.
- Full Text:
- Date Issued: 2006