A comparative polarimetric study of the 43 GHz and 86 GHz SiO masers toward the supergiant star VY CMa
- Authors: Richter, Laura
- Date: 2012
- Subjects: Masers Supergiant stars Polarization (Light) Very long baseline interferometry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5454 , http://hdl.handle.net/10962/d1005239
- Description: The aim of this thesis is to perform observational tests of SiO maser polarisation and excitation models, using component-level comparisons of multiple SiO maser transitions in the 43 GHz and 86 GHz bands at milliarcsecond resolution. These observations reqwre very long baseline interferometric imaging with very accurate polarimetric calibration. The supergiant star VY CMa was chosen as the object of this study due to its high SiO maser luminosity, many detected SiO maser lines, and intrinsic scientific interest. Two epochs of full-polarisation VLBA observations of VY CMa were performed. The Epoch 2 observations were reduced using several new data reduction methods developed as part of this work, and designed specifically to improve the accuracy of circular polarisation calibration of spectral-line VLBI observations at millimetre wavelengths. The accuracy is estimated to be better than 1% using these methods. The Epoch 2 images show a concentration of v= l and v=2 J= 1-0 SiO masers to the east and northeast of the assumed stellar position. The v=l J=2-1 masers were more evenly distributed around the star, with a notable lack of emission in the northeast. There is appreciable spatial overlap between these three lines. The nature of the overlap is generally consistent with the predictions of hydrodynamical circumstellar SiO maser simulations. Where the v=l J = 1-0 and J =2-1 features overlap, the v=l J = 2-1 emission is usually considerably weaker. This is not predicted by current hydrodynamical models, but can be explained in the context of collisional pumping in a low density environment. Six observational tests of weak-splitting maser polarisation models were performed, including intercomparisons of linear polarisation in the v=l J=1-0 and J=2-1lines, linear polarisation versus saturation level, linear polarisation versus distance from the star, circular polarisation in the v= l J = 1-0 and J=2-1 lines, circular versus linear polarisation and modeling of ~ 900 electric-vector position angle rotations. The polarisation model tests generally do not support non-Zeeman circular polarisation mechanisms. For the linear polarisation tests, the results are more consistent with models that predict similar linear polarisation across transitions. The scientific importance of these tests is described in detail and avenues for future work are described.
- Full Text:
- Date Issued: 2012
- Authors: Richter, Laura
- Date: 2012
- Subjects: Masers Supergiant stars Polarization (Light) Very long baseline interferometry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5454 , http://hdl.handle.net/10962/d1005239
- Description: The aim of this thesis is to perform observational tests of SiO maser polarisation and excitation models, using component-level comparisons of multiple SiO maser transitions in the 43 GHz and 86 GHz bands at milliarcsecond resolution. These observations reqwre very long baseline interferometric imaging with very accurate polarimetric calibration. The supergiant star VY CMa was chosen as the object of this study due to its high SiO maser luminosity, many detected SiO maser lines, and intrinsic scientific interest. Two epochs of full-polarisation VLBA observations of VY CMa were performed. The Epoch 2 observations were reduced using several new data reduction methods developed as part of this work, and designed specifically to improve the accuracy of circular polarisation calibration of spectral-line VLBI observations at millimetre wavelengths. The accuracy is estimated to be better than 1% using these methods. The Epoch 2 images show a concentration of v= l and v=2 J= 1-0 SiO masers to the east and northeast of the assumed stellar position. The v=l J=2-1 masers were more evenly distributed around the star, with a notable lack of emission in the northeast. There is appreciable spatial overlap between these three lines. The nature of the overlap is generally consistent with the predictions of hydrodynamical circumstellar SiO maser simulations. Where the v=l J = 1-0 and J =2-1 features overlap, the v=l J = 2-1 emission is usually considerably weaker. This is not predicted by current hydrodynamical models, but can be explained in the context of collisional pumping in a low density environment. Six observational tests of weak-splitting maser polarisation models were performed, including intercomparisons of linear polarisation in the v=l J=1-0 and J=2-1lines, linear polarisation versus saturation level, linear polarisation versus distance from the star, circular polarisation in the v= l J = 1-0 and J=2-1 lines, circular versus linear polarisation and modeling of ~ 900 electric-vector position angle rotations. The polarisation model tests generally do not support non-Zeeman circular polarisation mechanisms. For the linear polarisation tests, the results are more consistent with models that predict similar linear polarisation across transitions. The scientific importance of these tests is described in detail and avenues for future work are described.
- Full Text:
- Date Issued: 2012
A critical analysis of the role of public participation in governance and service delivery with specific reference to the Buffalo City Municipality
- Authors: Maphazi, Nondumiso
- Date: 2012
- Subjects: Local government -- South Africa -- Buffalo City -- Citizen participation , Municipal services -- South Africa -- Buffalo City -- Citizen participation , Sustainable development -- South Africa -- Eastern Cape -- Citizen participation , Municipal services -- Management -- South Africa -- Eastern Cape -- Buffalo City Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:8257 , http://hdl.handle.net/10948/d1012147 , Local government -- South Africa -- Buffalo City -- Citizen participation , Municipal services -- South Africa -- Buffalo City -- Citizen participation , Sustainable development -- South Africa -- Eastern Cape -- Citizen participation , Municipal services -- Management -- South Africa -- Eastern Cape -- Buffalo City Municipality
- Description: This study undertook a critical analysis of the role of public participation in local governance and service delivery, with specific reference to the Buffalo City Municipality. The main aims of the study were to identify possible deficiencies in public participation processes, the development of strategies to enhance public participation, the development of mechanisms to ensure coordinated, integrated and focused public participation initiatives and the development of a normative model for improved public participation. The triangulation research methodology was employed with emphasis on the quantitative and qualitative methodologies. The sample comprised of councillors, officials and ward committee members. Questionnaires, with open and closed questions, were employed for the councillors and focus group interviews were conducted with ward committee members. Statistical procedures were utilised to interpret and analyse the quantitative data to determine the results using the Statistica package for data analysis. The qualitative data analysis involved thematic content analysis. Findings suggest that the current public participation strategies are inadequate. The correlation of results further reveals that a significant negative relationship exists between the councillors, officials and ward committee members. Despite various legislative prescriptions pertaining to public participation requirements in local government, the results imply that the Buffalo City Municipality has not fully complied with such prescriptions and national policy directives. The thesis proposes specific recommendations on how the Buffalo City Municipality can address the current short comings in terms of its public participation programmes and strategies. Recommendations include the establishment of a centralised Public Participation Unit, the empowerment of ward committee members and ward councillors, adequate resource allocation for ward committees, enhanced coordination between the various community structures, improved interaction with local communities, enhanced public participation initiatives and the need for additional anti-fraud and anti-corruption strategies within the municipality. A normative model, for enhanced public participation in local government, is also proposed in the thesis.
- Full Text:
- Date Issued: 2012
- Authors: Maphazi, Nondumiso
- Date: 2012
- Subjects: Local government -- South Africa -- Buffalo City -- Citizen participation , Municipal services -- South Africa -- Buffalo City -- Citizen participation , Sustainable development -- South Africa -- Eastern Cape -- Citizen participation , Municipal services -- Management -- South Africa -- Eastern Cape -- Buffalo City Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:8257 , http://hdl.handle.net/10948/d1012147 , Local government -- South Africa -- Buffalo City -- Citizen participation , Municipal services -- South Africa -- Buffalo City -- Citizen participation , Sustainable development -- South Africa -- Eastern Cape -- Citizen participation , Municipal services -- Management -- South Africa -- Eastern Cape -- Buffalo City Municipality
- Description: This study undertook a critical analysis of the role of public participation in local governance and service delivery, with specific reference to the Buffalo City Municipality. The main aims of the study were to identify possible deficiencies in public participation processes, the development of strategies to enhance public participation, the development of mechanisms to ensure coordinated, integrated and focused public participation initiatives and the development of a normative model for improved public participation. The triangulation research methodology was employed with emphasis on the quantitative and qualitative methodologies. The sample comprised of councillors, officials and ward committee members. Questionnaires, with open and closed questions, were employed for the councillors and focus group interviews were conducted with ward committee members. Statistical procedures were utilised to interpret and analyse the quantitative data to determine the results using the Statistica package for data analysis. The qualitative data analysis involved thematic content analysis. Findings suggest that the current public participation strategies are inadequate. The correlation of results further reveals that a significant negative relationship exists between the councillors, officials and ward committee members. Despite various legislative prescriptions pertaining to public participation requirements in local government, the results imply that the Buffalo City Municipality has not fully complied with such prescriptions and national policy directives. The thesis proposes specific recommendations on how the Buffalo City Municipality can address the current short comings in terms of its public participation programmes and strategies. Recommendations include the establishment of a centralised Public Participation Unit, the empowerment of ward committee members and ward councillors, adequate resource allocation for ward committees, enhanced coordination between the various community structures, improved interaction with local communities, enhanced public participation initiatives and the need for additional anti-fraud and anti-corruption strategies within the municipality. A normative model, for enhanced public participation in local government, is also proposed in the thesis.
- Full Text:
- Date Issued: 2012
A critical realist exploration of the implementation of a new curriculum in Swaziland
- Authors: Pereira, Liphie
- Date: 2012
- Subjects: Critical realism Education -- Philosophy Critical pedagogy -- Swaziland Curriculum change -- Swaziland Education -- Swaziland Education and state -- Swaziland Education -- Aims and objectives -- Swaziland Critical discourse analysis International General Certificate of Secondary Education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1484 , http://hdl.handle.net/10962/d1003365
- Description: This study offers an in-depth exploration of the conditions from which the implementation of a curriculum called the International General Certificate of Secondary Education (IGCSE), later localised into Swaziland General Certificate of Secondary Education (SGCSE), emerged and the constraining and enabling conditions for the implementation of the new I/SGCSE curriculum. It derives its theoretical foundation from Roy Bhaskar’s critical realism and Margaret Archer’s concept of analytical separability. The study therefore offers explanations about the curriculum change and its implementation that are based on how structural, cultural, and agential mechanisms operating at a deeper level of reality (the intransitive layer of reality or the domain of the real) and existing independently of what we see, know or believe of them (the transitive layer of reality or domains of the actual and empirical) interacted to condition the emergence of I/SGCSE and the way it is implemented. I conduct a critical discourse analysis of relevant literature, I/SGCSE documents and interview data in order to identify those mechanisms that were cultural and also those that were structural and agential. Bernstein’s concepts of classification and framing are used to analyse observation data in order to explore the influence of these mechanisms on the teaching practices of the teachers who took part in the study. Analysis of the data suggests that the change from General Certificate of Education Ordinary Level (GCE O-level) to I/SGCSE was conditioned by inconsistencies between the cultural and structural mechanisms of the Swazi context. Many of the cultural elements of the Swazi context such as the discourses of good citizens, of competitive advantage, and of quality education draw from global discourses which view relations between people from a postmodernist position and therefore support weakly classified and framed pedagogic practices. In contrast, the discourse of morality and many of the structural elements of the Swazi context, such as the pre2006 education system and the Tinkhundla government system, all view reality from a modernist position, therefore supporting strong relations of power and control. The cultural system therefore exerted more influence in conditioning the change from the strongly classified and framed GCE O-level curriculum to the weakly classified and framed I/SGCSE curriculum. Furthermore, the analysis of interview and observation data suggests that inconsistencies between the global discourses and the discourses and structures that teachers confront in their day-to-day lives, together with the decisions teachers made in response to structural constraints, created constraining conditions for the change from GCE O-level to I/SGCSE. The study adds to knowledge on curriculum change and implementation through insights into the enabling and constraining effects of mechanisms operating at a deeper level of reality on curriculum-change decisions and on the ability of teachers to implement curriculum changes. The focus on the deeper level of reality may therefore contribute towards emancipatory knowledge which could be used not only by the Ministry of Education and Training and teachers in Swaziland but also elsewhere to inform future planning, decision making, and practice in relation to curriculum change and implementation.
- Full Text:
- Date Issued: 2012
- Authors: Pereira, Liphie
- Date: 2012
- Subjects: Critical realism Education -- Philosophy Critical pedagogy -- Swaziland Curriculum change -- Swaziland Education -- Swaziland Education and state -- Swaziland Education -- Aims and objectives -- Swaziland Critical discourse analysis International General Certificate of Secondary Education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1484 , http://hdl.handle.net/10962/d1003365
- Description: This study offers an in-depth exploration of the conditions from which the implementation of a curriculum called the International General Certificate of Secondary Education (IGCSE), later localised into Swaziland General Certificate of Secondary Education (SGCSE), emerged and the constraining and enabling conditions for the implementation of the new I/SGCSE curriculum. It derives its theoretical foundation from Roy Bhaskar’s critical realism and Margaret Archer’s concept of analytical separability. The study therefore offers explanations about the curriculum change and its implementation that are based on how structural, cultural, and agential mechanisms operating at a deeper level of reality (the intransitive layer of reality or the domain of the real) and existing independently of what we see, know or believe of them (the transitive layer of reality or domains of the actual and empirical) interacted to condition the emergence of I/SGCSE and the way it is implemented. I conduct a critical discourse analysis of relevant literature, I/SGCSE documents and interview data in order to identify those mechanisms that were cultural and also those that were structural and agential. Bernstein’s concepts of classification and framing are used to analyse observation data in order to explore the influence of these mechanisms on the teaching practices of the teachers who took part in the study. Analysis of the data suggests that the change from General Certificate of Education Ordinary Level (GCE O-level) to I/SGCSE was conditioned by inconsistencies between the cultural and structural mechanisms of the Swazi context. Many of the cultural elements of the Swazi context such as the discourses of good citizens, of competitive advantage, and of quality education draw from global discourses which view relations between people from a postmodernist position and therefore support weakly classified and framed pedagogic practices. In contrast, the discourse of morality and many of the structural elements of the Swazi context, such as the pre2006 education system and the Tinkhundla government system, all view reality from a modernist position, therefore supporting strong relations of power and control. The cultural system therefore exerted more influence in conditioning the change from the strongly classified and framed GCE O-level curriculum to the weakly classified and framed I/SGCSE curriculum. Furthermore, the analysis of interview and observation data suggests that inconsistencies between the global discourses and the discourses and structures that teachers confront in their day-to-day lives, together with the decisions teachers made in response to structural constraints, created constraining conditions for the change from GCE O-level to I/SGCSE. The study adds to knowledge on curriculum change and implementation through insights into the enabling and constraining effects of mechanisms operating at a deeper level of reality on curriculum-change decisions and on the ability of teachers to implement curriculum changes. The focus on the deeper level of reality may therefore contribute towards emancipatory knowledge which could be used not only by the Ministry of Education and Training and teachers in Swaziland but also elsewhere to inform future planning, decision making, and practice in relation to curriculum change and implementation.
- Full Text:
- Date Issued: 2012
A methodology to institutionalise user experience in a South African provincial government
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
A model for automated topic spotting in a mobile chat based mathematics tutoring environment
- Authors: Butgereit, Laura Lee
- Date: 2012
- Subjects: Mobile communication systems in education , Mathematics -- Study and teaching , Tutors and tutoring -- Mathematics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9809 , http://hdl.handle.net/10948/d1013741
- Description: Systems of writing have existed for thousands of years. The history of civilisation and the history of writing are so intertwined that it is hard to separate the one from the other. These systems of writing, however, are not static. They change. One of the latest developments in systems of writing is short electronic messages such as seen on Twitter and in MXit. One novel application which uses these short electronic messages is the Dr Math® project. Dr Math is a mobile online tutoring system where pupils can use MXit on their cell phones and receive help with their mathematics homework from volunteer tutors around the world. These conversations between pupils and tutors are held in MXit lingo or MXit language – this cryptic, abbreviated system 0f ryting w1ch l0ks lyk dis. Project μ (pronounced mu and indicating MXit Understander) investigated how topics could be determined in MXit lingo and Project μ's research outputs spot mathematics topics in conversations between Dr Math tutors and pupils. Once the topics are determined, supporting documentation can be presented to the tutors to assist them in helping pupils with their mathematics homework. Project μ made the following contributions to new knowledge: a statistical and linguistic analysis of MXit lingo provides letter frequencies, word frequencies, message length statistics as well as linguistic bases for new spelling conventions seen in MXit based conversations; a post-stemmer for use with MXit lingo removes suffixes from the ends of words taking into account MXit spelling conventions allowing words such as equashun and equation to be reduced to the same root stem; a list of over ten thousand stop words for MXit lingo appropriate for the domain of mathematics; a misspelling corrector for MXit lingo which corrects words such as acount and equates it to account; and a model for spotting mathematical topics in MXit lingo. The model was instantiated and integrated into the Dr Math tutoring platform. Empirical evidence as to the effectiveness of the μ Topic Spotter and the other contributions is also presented. The empirical evidence includes specific statistical tests with MXit lingo, specific tests of the misspelling corrector, stemmer, and feedback mechanism, and an extensive exercise of content analysis with respect to mathematics topics.
- Full Text:
- Date Issued: 2012
- Authors: Butgereit, Laura Lee
- Date: 2012
- Subjects: Mobile communication systems in education , Mathematics -- Study and teaching , Tutors and tutoring -- Mathematics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9809 , http://hdl.handle.net/10948/d1013741
- Description: Systems of writing have existed for thousands of years. The history of civilisation and the history of writing are so intertwined that it is hard to separate the one from the other. These systems of writing, however, are not static. They change. One of the latest developments in systems of writing is short electronic messages such as seen on Twitter and in MXit. One novel application which uses these short electronic messages is the Dr Math® project. Dr Math is a mobile online tutoring system where pupils can use MXit on their cell phones and receive help with their mathematics homework from volunteer tutors around the world. These conversations between pupils and tutors are held in MXit lingo or MXit language – this cryptic, abbreviated system 0f ryting w1ch l0ks lyk dis. Project μ (pronounced mu and indicating MXit Understander) investigated how topics could be determined in MXit lingo and Project μ's research outputs spot mathematics topics in conversations between Dr Math tutors and pupils. Once the topics are determined, supporting documentation can be presented to the tutors to assist them in helping pupils with their mathematics homework. Project μ made the following contributions to new knowledge: a statistical and linguistic analysis of MXit lingo provides letter frequencies, word frequencies, message length statistics as well as linguistic bases for new spelling conventions seen in MXit based conversations; a post-stemmer for use with MXit lingo removes suffixes from the ends of words taking into account MXit spelling conventions allowing words such as equashun and equation to be reduced to the same root stem; a list of over ten thousand stop words for MXit lingo appropriate for the domain of mathematics; a misspelling corrector for MXit lingo which corrects words such as acount and equates it to account; and a model for spotting mathematical topics in MXit lingo. The model was instantiated and integrated into the Dr Math tutoring platform. Empirical evidence as to the effectiveness of the μ Topic Spotter and the other contributions is also presented. The empirical evidence includes specific statistical tests with MXit lingo, specific tests of the misspelling corrector, stemmer, and feedback mechanism, and an extensive exercise of content analysis with respect to mathematics topics.
- Full Text:
- Date Issued: 2012
A psycho-educational programme to facilitate the mental health of adolescent girls who are victims of verbal bullying
- Authors: Jacobs, Ruwayda
- Date: 2012
- Subjects: Teenage girls -- Mental health -- South Africa , Psychoanalysis , Bullying
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9946 , http://hdl.handle.net/10948/d1014579
- Description: Bullying appears to be a worldwide phenomenon. It occurs within schools, homes, and in the community too. Bullying is a form of aggressive behaviour. Female bullying is not so easily noticed, as girls hardly ever use physical forms of aggression. Bullying can have a detrimental effect on the mental health of the victim. The victims of bullying experience symptoms of mental discomfort, which include low self esteem, feelings of helplessness, feelings of worthlessness and inferiority, lack of confidence, isolation, self-conscientiousness; and lastly, this can lead to suicide. Some form of intervention is necessary to provide adolescents with skills to combat bullying and help them to become mentally healthy again. The overall goal of the study was to develop, implement and evaluate a psycho-educational programme for female adolescents in a secondary school setting, in order to assist them in coping with bullying. The objectives of the research study were to: Conduct asituational analysis to identify the mental health needs of adolescent girls, as victimsof bullying. Develop a psycho-educational programme to facilitate the promotion of mental health of those adolescent girls who are victims of bullying. Implement the psycho-educational programme to facilitate coping by adolescent girls who are victims of bullying. Assess whether the adolescent girls have benefitted from attending the psycho-educational programme. The researcher used a qualitative, explorative, descriptive and contextual design. The research methodology consisted of four phases. In phase one of the research, a situational analysis was done; and the characteristics of mental discomfort exhibited by the victim were identified. The needs of the adolescent girl who has been bullied have already been described. Phase two involved the development of a psycho-educational programme. The information from the situational analysis was used to develop the conceptual framework. The six concepts in the survey list of Dickoff et al. (1968:422) were described as follows: the recipient is the adolescent girl who has been bullied, the agent is an advanced psychiatric nurse, the context is the community and the secondary school where bullying takes place, the dynamics of the intervention constitute the mental discomfort experienced by the adolescent girl. This is what motivates her to participate in the programme. The procedure was identified as the psycho-educational programme, while the terminus or outcome of the intervention for the adolescent girl would be for her to experience mental health after being exposed to the psycho-educational programme. The relationship between the concepts was used to form the mind map of the conceptual framework. This guided the development of the psycho-educational programme. The content of the programme has already been described. In phase three the psycho-educational programme is implemented and in phase four the programme is evaluated. The psycho-educational programme taught the teenage girls skills and it provided them with knowledge to cope better with the bullying. Attending the programme made the teenagers aware that they needed to change to experience mental health and happiness. The empirical study took place in phase four. The data-gathering method in phase four included the conducting of semi-structured interviews with the adolescent girls who participated in the programme, as well as the teachers of these adolescent girls and their parents. Naïve sketches, reflective journals, observations made and field notes formed part of this database. The data was analyzed by means of Tesch‟s descriptive analysis (in Creswell, 2003:192). The participants had to comment on how they were coping after the implementation of the psycho-educational programme. In conclusion, an intervention in the form of the psycho-educational programme was shown to be beneficial to adolescent girls who were victims of bullying, to assist them in coping with the aftermath of being bullied. Recommendations were made to enhance nursing practice, as well as nursing education and nursing research. Keywords: Adolescent girls, bullying, secondary schools, advanced psychiatric nurse, psycho-educational programme, mental health.
- Full Text:
- Date Issued: 2012
- Authors: Jacobs, Ruwayda
- Date: 2012
- Subjects: Teenage girls -- Mental health -- South Africa , Psychoanalysis , Bullying
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9946 , http://hdl.handle.net/10948/d1014579
- Description: Bullying appears to be a worldwide phenomenon. It occurs within schools, homes, and in the community too. Bullying is a form of aggressive behaviour. Female bullying is not so easily noticed, as girls hardly ever use physical forms of aggression. Bullying can have a detrimental effect on the mental health of the victim. The victims of bullying experience symptoms of mental discomfort, which include low self esteem, feelings of helplessness, feelings of worthlessness and inferiority, lack of confidence, isolation, self-conscientiousness; and lastly, this can lead to suicide. Some form of intervention is necessary to provide adolescents with skills to combat bullying and help them to become mentally healthy again. The overall goal of the study was to develop, implement and evaluate a psycho-educational programme for female adolescents in a secondary school setting, in order to assist them in coping with bullying. The objectives of the research study were to: Conduct asituational analysis to identify the mental health needs of adolescent girls, as victimsof bullying. Develop a psycho-educational programme to facilitate the promotion of mental health of those adolescent girls who are victims of bullying. Implement the psycho-educational programme to facilitate coping by adolescent girls who are victims of bullying. Assess whether the adolescent girls have benefitted from attending the psycho-educational programme. The researcher used a qualitative, explorative, descriptive and contextual design. The research methodology consisted of four phases. In phase one of the research, a situational analysis was done; and the characteristics of mental discomfort exhibited by the victim were identified. The needs of the adolescent girl who has been bullied have already been described. Phase two involved the development of a psycho-educational programme. The information from the situational analysis was used to develop the conceptual framework. The six concepts in the survey list of Dickoff et al. (1968:422) were described as follows: the recipient is the adolescent girl who has been bullied, the agent is an advanced psychiatric nurse, the context is the community and the secondary school where bullying takes place, the dynamics of the intervention constitute the mental discomfort experienced by the adolescent girl. This is what motivates her to participate in the programme. The procedure was identified as the psycho-educational programme, while the terminus or outcome of the intervention for the adolescent girl would be for her to experience mental health after being exposed to the psycho-educational programme. The relationship between the concepts was used to form the mind map of the conceptual framework. This guided the development of the psycho-educational programme. The content of the programme has already been described. In phase three the psycho-educational programme is implemented and in phase four the programme is evaluated. The psycho-educational programme taught the teenage girls skills and it provided them with knowledge to cope better with the bullying. Attending the programme made the teenagers aware that they needed to change to experience mental health and happiness. The empirical study took place in phase four. The data-gathering method in phase four included the conducting of semi-structured interviews with the adolescent girls who participated in the programme, as well as the teachers of these adolescent girls and their parents. Naïve sketches, reflective journals, observations made and field notes formed part of this database. The data was analyzed by means of Tesch‟s descriptive analysis (in Creswell, 2003:192). The participants had to comment on how they were coping after the implementation of the psycho-educational programme. In conclusion, an intervention in the form of the psycho-educational programme was shown to be beneficial to adolescent girls who were victims of bullying, to assist them in coping with the aftermath of being bullied. Recommendations were made to enhance nursing practice, as well as nursing education and nursing research. Keywords: Adolescent girls, bullying, secondary schools, advanced psychiatric nurse, psycho-educational programme, mental health.
- Full Text:
- Date Issued: 2012
A structural and functional specification of a SCIM for service interaction management and personalisation in the IMS
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2012
- Subjects: Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4606 , http://hdl.handle.net/10962/d1004864 , Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Description: The Internet Protocol Multimedia Subsystem (IMS) is a component of the 3G mobile network that has been specified by standards development organisations such as the 3GPP (3rd Generation Partnership Project) and ETSI (European Telecommunication Standards Institute). IMS seeks to guarantee that the telecommunication network of the future provides subscribers with seamless access to services across disparate networks. In order to achieve this, it defines a service architecture that hosts application servers that provide subscribers with value added services. Typically, an application server bundles all the functionality it needs to execute the services it delivers, however this view is currently being challenged. It is now thought that services should be synthesised from simple building blocks called service capabilities. This decomposition would facilitate the re-use of service capabilities across multiple services and would support the creation of new services that could not have originally been conceived. The shift from monolithic services to those built from service capabilities poses a challenge to the current service model in IMS. To accommodate this, the 3GPP has defined an entity known as a service capability interaction manager (SCIM) that would be responsible for managing the interactions between service capabilities in order to realise complex services. Some of these interactions could potentially lead to undesirable results, which the SCIM must work to avoid. As an added requirement, it is believed that the network should allow policies to be applied to network services which the SCIM should be responsible for enforcing. At the time of writing, the functional and structural architecture of the SCIM has not yet been standardised. This thesis explores the current serv ice architecture of the IMS in detail. Proposals that address the structure and functions of the SCIM are carefully compared and contrasted. This investigation leads to the presentation of key aspects of the SCIM, and provides solutions that explain how it should interact with service capabilities, manage undesirable interactions and factor user and network operator policies into its execution model. A modified design of the IMS service layer that embeds the SCIM is subsequently presented and described. The design uses existing IMS protocols and requires no change in the behaviour of the standard IMS entities. In order to develop a testbed for experimental verification of the design, the identification of suitable software platforms was required. This thesis presents some of the most popular platforms currently used by developers such as the Open IMS Core and OpenSER, as well as an open source, Java-based, multimedia communication platform called Mobicents. As a precursor to the development of the SCIM, a converged multimedia service is presented that describes how a video streaming application that is leveraged by a web portal was implemented for an IMS testbed using Mobicents components. The Mobicents SIP Servlets container was subsequently used to model an initial prototype of the SCIM, using a mUlti-component telephony service to illustrate the proposed service execution model. The design focuses on SIP-based services only, but should also work for other types of IMS application servers as well.
- Full Text:
- Date Issued: 2012
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2012
- Subjects: Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4606 , http://hdl.handle.net/10962/d1004864 , Internet Protocol multimedia subsystem , Internet Protocol multimedia subsystem -- Specifications , Long-Term Evolution (Telecommunications) , European Telecommunications Standards Institute , Wireless communication systems , Multimedia communications
- Description: The Internet Protocol Multimedia Subsystem (IMS) is a component of the 3G mobile network that has been specified by standards development organisations such as the 3GPP (3rd Generation Partnership Project) and ETSI (European Telecommunication Standards Institute). IMS seeks to guarantee that the telecommunication network of the future provides subscribers with seamless access to services across disparate networks. In order to achieve this, it defines a service architecture that hosts application servers that provide subscribers with value added services. Typically, an application server bundles all the functionality it needs to execute the services it delivers, however this view is currently being challenged. It is now thought that services should be synthesised from simple building blocks called service capabilities. This decomposition would facilitate the re-use of service capabilities across multiple services and would support the creation of new services that could not have originally been conceived. The shift from monolithic services to those built from service capabilities poses a challenge to the current service model in IMS. To accommodate this, the 3GPP has defined an entity known as a service capability interaction manager (SCIM) that would be responsible for managing the interactions between service capabilities in order to realise complex services. Some of these interactions could potentially lead to undesirable results, which the SCIM must work to avoid. As an added requirement, it is believed that the network should allow policies to be applied to network services which the SCIM should be responsible for enforcing. At the time of writing, the functional and structural architecture of the SCIM has not yet been standardised. This thesis explores the current serv ice architecture of the IMS in detail. Proposals that address the structure and functions of the SCIM are carefully compared and contrasted. This investigation leads to the presentation of key aspects of the SCIM, and provides solutions that explain how it should interact with service capabilities, manage undesirable interactions and factor user and network operator policies into its execution model. A modified design of the IMS service layer that embeds the SCIM is subsequently presented and described. The design uses existing IMS protocols and requires no change in the behaviour of the standard IMS entities. In order to develop a testbed for experimental verification of the design, the identification of suitable software platforms was required. This thesis presents some of the most popular platforms currently used by developers such as the Open IMS Core and OpenSER, as well as an open source, Java-based, multimedia communication platform called Mobicents. As a precursor to the development of the SCIM, a converged multimedia service is presented that describes how a video streaming application that is leveraged by a web portal was implemented for an IMS testbed using Mobicents components. The Mobicents SIP Servlets container was subsequently used to model an initial prototype of the SCIM, using a mUlti-component telephony service to illustrate the proposed service execution model. The design focuses on SIP-based services only, but should also work for other types of IMS application servers as well.
- Full Text:
- Date Issued: 2012
A systematic revision of selected genera of afrotropical curtonotidae (Diptera: schizophora: ephydroidea) : a phylogenetic approach
- Authors: Kirk-Spriggs, Ashley H
- Date: 2012
- Subjects: Curtonotidae -- Research Diptera -- Research Flies -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5627 , http://hdl.handle.net/10962/d1004747
- Description: The first comprehensive phylogeny of the family Curtonotidae is presented based on molecular markers and morphology. This enabled assessment of evolutionary relatedness, species radiation and zoogeography. A revised classification of the world fauna of the family, based on the results of this study is outlined. Nomenclatural acts flowing from these analyses include: the recognition three new Afrotropical species of Axinota van der Wulp; four new species of a new genus, Tigrisomyia Kirk-Spriggs; and nineteen new species of Curtonotum (six Madagascan and thirteen African). Ten informal species-groups of Curtonotum are recognised. Identification keys are provided for the Afrotropical species of these genera and errors in previous interpretations and designation of type specimens are resolved. Species distributions are mapped and interpreted and discussion is made of the historical biogeographical significance of these distributions.
- Full Text:
- Date Issued: 2012
- Authors: Kirk-Spriggs, Ashley H
- Date: 2012
- Subjects: Curtonotidae -- Research Diptera -- Research Flies -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5627 , http://hdl.handle.net/10962/d1004747
- Description: The first comprehensive phylogeny of the family Curtonotidae is presented based on molecular markers and morphology. This enabled assessment of evolutionary relatedness, species radiation and zoogeography. A revised classification of the world fauna of the family, based on the results of this study is outlined. Nomenclatural acts flowing from these analyses include: the recognition three new Afrotropical species of Axinota van der Wulp; four new species of a new genus, Tigrisomyia Kirk-Spriggs; and nineteen new species of Curtonotum (six Madagascan and thirteen African). Ten informal species-groups of Curtonotum are recognised. Identification keys are provided for the Afrotropical species of these genera and errors in previous interpretations and designation of type specimens are resolved. Species distributions are mapped and interpreted and discussion is made of the historical biogeographical significance of these distributions.
- Full Text:
- Date Issued: 2012
A systems approach to project implementation within the public sector towards formulating a framework for project evaluation
- Authors: Greyling, Een Lange
- Date: 2012
- Subjects: Project management -- South Africa , Corporations, Government -- South Africa , Construction industry -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9721 , http://hdl.handle.net/10948/d1021223
- Description: The procurement process, from the demand formulation to the final delivery of a public building to the end-user, is defined by the government in terms of procedures and policies to be followed, which is based to be ineffective and inefficient where the process as a whole from a client-value perpective, is flawed. Presently, the National Department of Public Works(NDPW) as a governmental administration is deemed to be a controlling institution and cost centre rather than a service provider. This mind-set is reflected by the inability of government project implementing agencies such as the NDPW to deliver projects successfully in terms of cost, time, and quality whilst failing to meet the government's socio economic objectives to create employment opportunities, stimulate economic growth, and transfer skills to the previously disadvantaged through black economic empowerment (BEE) initiatives. Client satisfaction has widely been recognised by researchers as one of the key challenges for quality improvement in the construction industry. It is a vital factor in the development and management of the construction process, as well in the creation of efficient organisation-client relationship. In addition, client satisfaction is deemed to be a catalyst for client retention which is a success strategy for any organisation. This thesis is primarily concerned with project performance and service delivery by the NDPW as a government project implementing agency that involves an integrated approach that considers the entire supply chain of a construction project. The success or failure of a project is is not the effect of a single variable, or factor, but a set of variables interacting with each other to produce the final result. An extensive review of related literature that entails the analysis of publications related to the projectimplementation and construction project management realm was deemed necessary to formulate a clear understanding of the complexities of implementing projjects within the public sector. The use of systems thinking as the nucleus of the multi-methodological approach to this research was to assist in ascertaining the primary causes of the problem situation and to clarify the process of project implementation as a sub-system within the greater system of the construction industry. The success of projects depends as much on the client as it does on the implementing agencies, project managers (PMs), consultants, contractors and the suppliers of materials.
- Full Text:
- Date Issued: 2012
- Authors: Greyling, Een Lange
- Date: 2012
- Subjects: Project management -- South Africa , Corporations, Government -- South Africa , Construction industry -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9721 , http://hdl.handle.net/10948/d1021223
- Description: The procurement process, from the demand formulation to the final delivery of a public building to the end-user, is defined by the government in terms of procedures and policies to be followed, which is based to be ineffective and inefficient where the process as a whole from a client-value perpective, is flawed. Presently, the National Department of Public Works(NDPW) as a governmental administration is deemed to be a controlling institution and cost centre rather than a service provider. This mind-set is reflected by the inability of government project implementing agencies such as the NDPW to deliver projects successfully in terms of cost, time, and quality whilst failing to meet the government's socio economic objectives to create employment opportunities, stimulate economic growth, and transfer skills to the previously disadvantaged through black economic empowerment (BEE) initiatives. Client satisfaction has widely been recognised by researchers as one of the key challenges for quality improvement in the construction industry. It is a vital factor in the development and management of the construction process, as well in the creation of efficient organisation-client relationship. In addition, client satisfaction is deemed to be a catalyst for client retention which is a success strategy for any organisation. This thesis is primarily concerned with project performance and service delivery by the NDPW as a government project implementing agency that involves an integrated approach that considers the entire supply chain of a construction project. The success or failure of a project is is not the effect of a single variable, or factor, but a set of variables interacting with each other to produce the final result. An extensive review of related literature that entails the analysis of publications related to the projectimplementation and construction project management realm was deemed necessary to formulate a clear understanding of the complexities of implementing projjects within the public sector. The use of systems thinking as the nucleus of the multi-methodological approach to this research was to assist in ascertaining the primary causes of the problem situation and to clarify the process of project implementation as a sub-system within the greater system of the construction industry. The success of projects depends as much on the client as it does on the implementing agencies, project managers (PMs), consultants, contractors and the suppliers of materials.
- Full Text:
- Date Issued: 2012
An analysis of ionospheric response to geomagnetic disturbances over South Africa and Antarctica
- Authors: Ngwira, Chigomezyo Mudala
- Date: 2012
- Subjects: Geomagnetism -- South Africa , Geomagnetism -- Antarctica , Ionospheric storms -- South Africa , Ionospheric storms -- Antarctica
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5534 , http://hdl.handle.net/10962/d1012957
- Description: The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.
- Full Text:
- Date Issued: 2012
- Authors: Ngwira, Chigomezyo Mudala
- Date: 2012
- Subjects: Geomagnetism -- South Africa , Geomagnetism -- Antarctica , Ionospheric storms -- South Africa , Ionospheric storms -- Antarctica
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5534 , http://hdl.handle.net/10962/d1012957
- Description: The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.
- Full Text:
- Date Issued: 2012
An ecosystem-based spatial conservation plan for the South African sandy beaches
- Authors: Harris, Linda Rozanne
- Date: 2012
- Subjects: Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology , PhD Thesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10688 , http://hdl.handle.net/10948/d1007920 , Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology
- Description: An ecosytem-based spatial conservation plan for the South African sandy beaches. Sandy beaches are valuable ecosystems. They support a collection of species that is unique, comprising many endemic species, and provide a number of key ecosystem goods and services, including scenic vistas for human recreation, nesting sites for turtles and birds, and important areas for biogeochemical recycling, water filtration and purification. However, sandy beaches have not been well understood or appreciated as ecosystems, and consequently have a legacy of poor coastal management. In many instances this has lead to a "tyranny of small decisions", where multiple, seemingly insignificant management decisions and actions have resulted in complete transformation and degradation of the shoreline in several places. In addition to inappropriate management strategies, beaches are also poorly represented in conservation areas. Further, where they are recognised as being "conserved" in marine protected areas, this often is a false sense of protection because the far more sensitive dune portion of the littoral active zone is invariably not included in the reserve. In short, there is a need for a new way to approach sandy beach conservation and management that includes the system (dunes, intertidal beaches and surf zones) as a whole. On one hand, the approach should make provision for use of the abundant natural resources and opportunities associated with sandy shores in ways that are sustainable and contribute to biodiversity stewardship - through ecosystem-based management and marine spatial planning. But, on the other hand, it must simultaneously contribute to securing a sufficient amount of the key ecological attributes of beaches (habitats, biodiversity and processes) in a network of reserves, to ensure that the ecosystem, natural resources, and services all persist in perpetuity - through systematic conservation planning. The aim of this Thesis is to integrate these into a single approach, which I call ecosystem-based spatial conservation planning for sandy beaches, using the South African sandy shores as a case study. To achieve this broad aim, the Thesis is divided into three parts. Part 1 deals with establishing baseline information by quantifying spatial patterns in sandy beach habitats (Chapter 1), biodiversity, key assemblages and processes, and outstanding physical features (Chapter 2). First, mapping sandy beach habitats is a challenge given the vast, linear extent of shorelines and significant resources required to complete the project. Therefore, a novel approach was derived using statistical techniques (conditional inference trees) to identify physical features of beaches that can be observed on Google Earth (or similar) imagery, and that can provide good predictions of beach morphodynamic (habitat) types. Based on the results of this analysis, sandy beaches (and all other coastal habitat types) were mapped digitally in ArcGIS. Second, spatial patterns in sandy beach biodiversity (vertebrates, macrofauna, microflora and foredune plants) were mapped by compiling existing data on the distributions of key species that have been well studied or mapped previously (vertebrates and foredune plants), and by niche modelling (macrofauna and microflora). For the latter, data from all previous sandy-beach sampling events in South Africa were compiled from published and unpublished sources, and supplemented with additional sampling of 23 beaches along the national shoreline, targeting macrofauna and phytoplankton. Altogether, the macrofauna database comprised data from 135 sites and 186 sampling events, and the microflora (phytoplankton and microphytobenthos) database comprised data from 73 sites and 510 samples. The probabilistic distribution of each "resident" species (present at 10 or more sites) was modelled in MaxEnt version 3.3.3k, probability thresholds were determined statistically (to convert the data into predicted presence-absence), and displayed as a digital map. A composite biodiversity map was compiled, and key trends in species richness and endemism along the national shoreline were quantified. To supplement biodiversity proper, additional valued-features of sandy beaches were mapped, including: important assemblages; unique habitat features; and sites associated with key ecological processes. Part 2 considers threats to sandy beaches in the context of deriving an appropriate management strategy that seeks to provide for use of the coast, but in a way that has least overall impact to the ecosystem. A method for assessing cumulative threats to sandy beaches is adapted from an existing framework (Chapter 4). This entailed compiling a list of threats to beaches, and scoring these (out of 10) in terms of the severity of their respective impacts to beaches, and how long it would take the ecosystem to recover should the threat be removed. The scoring was based on the collective expert opinion of the scientific community working on sandy beaches, at a workshop during the VIth International Sandy Beach Symposium 2012. To standardize the scores and ensure broad applicability, a base case scenario of a pristine beach was established, and maximum theoretical scores were provided for this context. The method for integrating these scores into a spatial, cumulative threat assessment was then determined. In Chapter 5, the maximum theoretical scores (from Chapter 4) were down-scaled to suit the current threat regime to the South African sandy beaches, and the cumulative threat assessment methodology was applied. From this analysis, the most threatened beaches in South Africa, and the most important threats were highlighted. A decision-support tool for managers was derived from the site-specific cumulative threat-impact scores, based first on the degree of permanent habitat transformation, and second on the cumulative impact of other stressors where the impacts these stressors have could potentially be mitigated or ameliorated. Part 3 concerns conservation of beaches explicitly. It addresses how much of which valued features of beaches is required to ensure their long-term persistence, and the design of a network of beaches in South Africa that are of ecological importance and should be set aside as reserves. Conservation targets are set in Chapter 6, using species-area curves to determine a baseline percentage-area required to protect sandy beach habitats, which is modified using heuristic principles based on habitat rarity and threat status (from a recent national assessment). A fixed target was applied to all species, also modified by heuristic principles, and another fixed target was applied to key assemblages and processes.
- Full Text:
- Date Issued: 2012
- Authors: Harris, Linda Rozanne
- Date: 2012
- Subjects: Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology , PhD Thesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10688 , http://hdl.handle.net/10948/d1007920 , Seashore -- South Africa , Bathing beaches -- South Africa , Shorelines -- South Africa , Conservation biology
- Description: An ecosytem-based spatial conservation plan for the South African sandy beaches. Sandy beaches are valuable ecosystems. They support a collection of species that is unique, comprising many endemic species, and provide a number of key ecosystem goods and services, including scenic vistas for human recreation, nesting sites for turtles and birds, and important areas for biogeochemical recycling, water filtration and purification. However, sandy beaches have not been well understood or appreciated as ecosystems, and consequently have a legacy of poor coastal management. In many instances this has lead to a "tyranny of small decisions", where multiple, seemingly insignificant management decisions and actions have resulted in complete transformation and degradation of the shoreline in several places. In addition to inappropriate management strategies, beaches are also poorly represented in conservation areas. Further, where they are recognised as being "conserved" in marine protected areas, this often is a false sense of protection because the far more sensitive dune portion of the littoral active zone is invariably not included in the reserve. In short, there is a need for a new way to approach sandy beach conservation and management that includes the system (dunes, intertidal beaches and surf zones) as a whole. On one hand, the approach should make provision for use of the abundant natural resources and opportunities associated with sandy shores in ways that are sustainable and contribute to biodiversity stewardship - through ecosystem-based management and marine spatial planning. But, on the other hand, it must simultaneously contribute to securing a sufficient amount of the key ecological attributes of beaches (habitats, biodiversity and processes) in a network of reserves, to ensure that the ecosystem, natural resources, and services all persist in perpetuity - through systematic conservation planning. The aim of this Thesis is to integrate these into a single approach, which I call ecosystem-based spatial conservation planning for sandy beaches, using the South African sandy shores as a case study. To achieve this broad aim, the Thesis is divided into three parts. Part 1 deals with establishing baseline information by quantifying spatial patterns in sandy beach habitats (Chapter 1), biodiversity, key assemblages and processes, and outstanding physical features (Chapter 2). First, mapping sandy beach habitats is a challenge given the vast, linear extent of shorelines and significant resources required to complete the project. Therefore, a novel approach was derived using statistical techniques (conditional inference trees) to identify physical features of beaches that can be observed on Google Earth (or similar) imagery, and that can provide good predictions of beach morphodynamic (habitat) types. Based on the results of this analysis, sandy beaches (and all other coastal habitat types) were mapped digitally in ArcGIS. Second, spatial patterns in sandy beach biodiversity (vertebrates, macrofauna, microflora and foredune plants) were mapped by compiling existing data on the distributions of key species that have been well studied or mapped previously (vertebrates and foredune plants), and by niche modelling (macrofauna and microflora). For the latter, data from all previous sandy-beach sampling events in South Africa were compiled from published and unpublished sources, and supplemented with additional sampling of 23 beaches along the national shoreline, targeting macrofauna and phytoplankton. Altogether, the macrofauna database comprised data from 135 sites and 186 sampling events, and the microflora (phytoplankton and microphytobenthos) database comprised data from 73 sites and 510 samples. The probabilistic distribution of each "resident" species (present at 10 or more sites) was modelled in MaxEnt version 3.3.3k, probability thresholds were determined statistically (to convert the data into predicted presence-absence), and displayed as a digital map. A composite biodiversity map was compiled, and key trends in species richness and endemism along the national shoreline were quantified. To supplement biodiversity proper, additional valued-features of sandy beaches were mapped, including: important assemblages; unique habitat features; and sites associated with key ecological processes. Part 2 considers threats to sandy beaches in the context of deriving an appropriate management strategy that seeks to provide for use of the coast, but in a way that has least overall impact to the ecosystem. A method for assessing cumulative threats to sandy beaches is adapted from an existing framework (Chapter 4). This entailed compiling a list of threats to beaches, and scoring these (out of 10) in terms of the severity of their respective impacts to beaches, and how long it would take the ecosystem to recover should the threat be removed. The scoring was based on the collective expert opinion of the scientific community working on sandy beaches, at a workshop during the VIth International Sandy Beach Symposium 2012. To standardize the scores and ensure broad applicability, a base case scenario of a pristine beach was established, and maximum theoretical scores were provided for this context. The method for integrating these scores into a spatial, cumulative threat assessment was then determined. In Chapter 5, the maximum theoretical scores (from Chapter 4) were down-scaled to suit the current threat regime to the South African sandy beaches, and the cumulative threat assessment methodology was applied. From this analysis, the most threatened beaches in South Africa, and the most important threats were highlighted. A decision-support tool for managers was derived from the site-specific cumulative threat-impact scores, based first on the degree of permanent habitat transformation, and second on the cumulative impact of other stressors where the impacts these stressors have could potentially be mitigated or ameliorated. Part 3 concerns conservation of beaches explicitly. It addresses how much of which valued features of beaches is required to ensure their long-term persistence, and the design of a network of beaches in South Africa that are of ecological importance and should be set aside as reserves. Conservation targets are set in Chapter 6, using species-area curves to determine a baseline percentage-area required to protect sandy beach habitats, which is modified using heuristic principles based on habitat rarity and threat status (from a recent national assessment). A fixed target was applied to all species, also modified by heuristic principles, and another fixed target was applied to key assemblages and processes.
- Full Text:
- Date Issued: 2012
An evaluation of programming assistance tools to support the learning of IT programming: a case study in South African secondary schools
- Authors: Koorsse, Melisa
- Date: 2012
- Subjects: Computer science , Computer literacy , Computer programming
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10472 , http://hdl.handle.net/10948/d1010581 , Computer science , Computer literacy , Computer programming
- Description: Worldwide, there is a decline in interest in the computer science profession and in the subject at secondary school level. Novice programmers struggle to understand introductory programming concepts and this difficulty of learning to program is contributing to the lack of interest in the field of computer science. Information Technology (IT) learners in South African secondary schools are novice programmers, introduced to introductory programming concepts in the subject which also includes topics on hardware and system software, e-communication, social and ethical issues, spreadsheets and databases. The difficulties faced by IT learners are worsened by the lack of suitably qualified teachers, a saturated learning programme that allocates very little time to the understanding of complex programming concepts and limited class time where practical examples can be implemented with the support of the IT teacher. This research proposes that IT learners could be supported by a programming assistance tool (PAT). A PAT is a software program that can be used by novice programmers to learn how to program and/or improve their understanding of programming concepts. PATs use different techniques to assist novice programmers. The main objective of this research was to determine whether the use of a PAT impacted IT learners’ understanding of programming concepts and motivation towards programming. The literature study and feedback from IT learners and teachers were used to identify novice programming difficulties and IT learner programming difficulties, respectively. Selection criteria were derived from the programming difficulties identified. The selection criteria were grouped into three categories, namely, programming concepts, programming knowledge and programming skills. Existing PATs were evaluated using the selection criteria and three PATs, namely, RoboMind, Scratch and B#, were selected as suitable for use by IT learners. RoboMind was adapted in this research study, allowing it to support the Delphi programming language. The three PATs were evaluated by participating IT learners at four schools. The findings of this research provided no conclusive evidence that IT learners who used a PAT had a significantly better understanding of programming concepts and motivation towards programming than learners who did not use a PAT. IT learner feedback was used to identify the strengths and shortcomings of the three PATs and to provide recommendations for the development of PATs specifically to support IT learners. This research study has provided several theoretical and practical contributions, including the research design, selection criteria, adaptations to RoboMind and the evaluation of the three PATs. In addition, IT teachers and learners have been made aware of PATs and the support that can be provided by these PATs. IT teachers have also been provided with a means of selecting PATs applicable to the IT curriculum. All the research contributions have formed the basis for future work, such as improving and extending RoboMind’s functionality and support of programming concepts, the refinement of the selection criteria and, ultimately, the development of a new PAT, specifically designed to support IT learner understanding of programming concepts and motivation towards programming.
- Full Text:
- Date Issued: 2012
- Authors: Koorsse, Melisa
- Date: 2012
- Subjects: Computer science , Computer literacy , Computer programming
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10472 , http://hdl.handle.net/10948/d1010581 , Computer science , Computer literacy , Computer programming
- Description: Worldwide, there is a decline in interest in the computer science profession and in the subject at secondary school level. Novice programmers struggle to understand introductory programming concepts and this difficulty of learning to program is contributing to the lack of interest in the field of computer science. Information Technology (IT) learners in South African secondary schools are novice programmers, introduced to introductory programming concepts in the subject which also includes topics on hardware and system software, e-communication, social and ethical issues, spreadsheets and databases. The difficulties faced by IT learners are worsened by the lack of suitably qualified teachers, a saturated learning programme that allocates very little time to the understanding of complex programming concepts and limited class time where practical examples can be implemented with the support of the IT teacher. This research proposes that IT learners could be supported by a programming assistance tool (PAT). A PAT is a software program that can be used by novice programmers to learn how to program and/or improve their understanding of programming concepts. PATs use different techniques to assist novice programmers. The main objective of this research was to determine whether the use of a PAT impacted IT learners’ understanding of programming concepts and motivation towards programming. The literature study and feedback from IT learners and teachers were used to identify novice programming difficulties and IT learner programming difficulties, respectively. Selection criteria were derived from the programming difficulties identified. The selection criteria were grouped into three categories, namely, programming concepts, programming knowledge and programming skills. Existing PATs were evaluated using the selection criteria and three PATs, namely, RoboMind, Scratch and B#, were selected as suitable for use by IT learners. RoboMind was adapted in this research study, allowing it to support the Delphi programming language. The three PATs were evaluated by participating IT learners at four schools. The findings of this research provided no conclusive evidence that IT learners who used a PAT had a significantly better understanding of programming concepts and motivation towards programming than learners who did not use a PAT. IT learner feedback was used to identify the strengths and shortcomings of the three PATs and to provide recommendations for the development of PATs specifically to support IT learners. This research study has provided several theoretical and practical contributions, including the research design, selection criteria, adaptations to RoboMind and the evaluation of the three PATs. In addition, IT teachers and learners have been made aware of PATs and the support that can be provided by these PATs. IT teachers have also been provided with a means of selecting PATs applicable to the IT curriculum. All the research contributions have formed the basis for future work, such as improving and extending RoboMind’s functionality and support of programming concepts, the refinement of the selection criteria and, ultimately, the development of a new PAT, specifically designed to support IT learner understanding of programming concepts and motivation towards programming.
- Full Text:
- Date Issued: 2012
An investigation into the antidiabetic and catalytic properties of oxovanadium(IV) complexes
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
An investigation into the control of audio streaming across networks having diverse quality of service mechanisms
- Authors: Foulkes, Philip James
- Date: 2012
- Subjects: Streaming audio -- Testing Data transmission systems -- Testing Computer networks -- Management Computer networks -- Evaluation Computer network protocols -- Standards
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4607 , http://hdl.handle.net/10962/d1004865
- Description: The transmission of realtime audio data across digital networks is subject to strict quality of service requirements. These networks need to be able to guarantee network resources (e.g., bandwidth), ensure timely and deterministic data delivery, and provide time synchronisation mechanisms to ensure successful transmission of this data. Two open standards-based networking technologies, namely IEEE 1394 and the recently standardised Ethernet AVB, provide distinct methods for achieving these goals. Audio devices that are compatible with IEEE 1394 networks exist, and audio devices that are compatible with Ethernet AVB networks are starting to come onto the market. There is a need for mechanisms to provide compatibility between the audio devices that reside on these disparate networks such that existing IEEE 1394 audio devices are able to communicate with Ethernet AVB audio devices, and vice versa. The audio devices that reside on these networks may be remotely controlled by a diverse set of incompatible command and control protocols. It is desirable to have a common network-neutral method of control over the various parameters of the devices that reside on these networks. As part of this study, two Ethernet AVB systems were developed. One system acts as an Ethernet AVB audio endpoint device and another system acts as an audio gateway between IEEE 1394 and Ethernet AVB networks. These systems, along with existing IEEE 1394 audio devices, were used to demonstrate the ability to transfer audio data between the networking technologies. Each of the devices is remotely controllable via a network neutral command and control protocol, XFN. The IEEE 1394 and Ethernet AVB devices are used to demonstrate the use of the XFN protocol to allow for network neutral connection management to take place between IEEE 1394 and Ethernet AVB networks. User control over these diverse devices is achieved via the use of a graphical patchbay application, which aims to provide a consistent user interface to a diverse range of devices.
- Full Text:
- Date Issued: 2012
- Authors: Foulkes, Philip James
- Date: 2012
- Subjects: Streaming audio -- Testing Data transmission systems -- Testing Computer networks -- Management Computer networks -- Evaluation Computer network protocols -- Standards
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4607 , http://hdl.handle.net/10962/d1004865
- Description: The transmission of realtime audio data across digital networks is subject to strict quality of service requirements. These networks need to be able to guarantee network resources (e.g., bandwidth), ensure timely and deterministic data delivery, and provide time synchronisation mechanisms to ensure successful transmission of this data. Two open standards-based networking technologies, namely IEEE 1394 and the recently standardised Ethernet AVB, provide distinct methods for achieving these goals. Audio devices that are compatible with IEEE 1394 networks exist, and audio devices that are compatible with Ethernet AVB networks are starting to come onto the market. There is a need for mechanisms to provide compatibility between the audio devices that reside on these disparate networks such that existing IEEE 1394 audio devices are able to communicate with Ethernet AVB audio devices, and vice versa. The audio devices that reside on these networks may be remotely controlled by a diverse set of incompatible command and control protocols. It is desirable to have a common network-neutral method of control over the various parameters of the devices that reside on these networks. As part of this study, two Ethernet AVB systems were developed. One system acts as an Ethernet AVB audio endpoint device and another system acts as an audio gateway between IEEE 1394 and Ethernet AVB networks. These systems, along with existing IEEE 1394 audio devices, were used to demonstrate the ability to transfer audio data between the networking technologies. Each of the devices is remotely controllable via a network neutral command and control protocol, XFN. The IEEE 1394 and Ethernet AVB devices are used to demonstrate the use of the XFN protocol to allow for network neutral connection management to take place between IEEE 1394 and Ethernet AVB networks. User control over these diverse devices is achieved via the use of a graphical patchbay application, which aims to provide a consistent user interface to a diverse range of devices.
- Full Text:
- Date Issued: 2012
An investigation into the impact of fairtrade in South Africa
- Authors: Jari, Bridget
- Date: 2012
- Subjects: Competition, Unfair -- Research -- South Africa Price maintenance -- Research -- South Africa Fair trade associations -- South Africa Sustainable development -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1006 , http://hdl.handle.net/10962/d1002741
- Description: World international trade is moving towards more free trade, through globalization and trade liberalization. These moves are guided by trade theories which state that on an aggregated level, nations involved in free trade should benefit, and further that free trade is fair. However, in practice, contradictory views have been raised, stating that free trade may not necessarily be benefiting all participants equally. Rather, other nations, especially developing nations, have become worse-off after opening up their markets for free trade. On the other hand, many developed nations have benefited substantially from free trade. Among other factors, the difference in benefits is believed to have been influenced by the types of commodities being traded (where developing nations mainly trade in primary goods and developed nations in anufactured goods) and unequal power relations (some nations for example, the EU and the US, still adopt protectionism in their agricultural sector). In order to address market imbalances resulting from free trade, Fairtrade has arisen. Fairtrade aims to improve international trading conditions in order to benefit small-scale farmers and farm workers in the developing nations. The Fairtrade organization further claims that its principles are in line with sustainable development. However, Fairtrade suffers a credibility gap because there is a lack of independent research to support their claims. To date in South Africa, there is little research examining the claims of the Fairtrade organization. In order to contribute to the Fairtrade discussion in South Africa, this study has investigated the validity of Fairtrade‘s claims that it contributes towards sustainable development. The study utilised primary data, which was collected from ten commercial farms and two small-scale farmer cooperatives located in the Eastern Cape and Western Cape provinces that are/were Fairtrade certified. The main reason for including commercial farmers and small-scale farmer cooperatives in the study was for comparing relative impacts in the two Fairtrade structures. The data was then analysed using a sustainable livelihoods framework, which was developed in the study. The study focussed on investigating the impact of Fairtrade tools, which are minimum prices, premiums, pre-financing and support for long-term relationships, on its intended beneficiaries. Minimum prices offered to producers cover production costs and are above market prices, and Fairtrade premiums are to be invested in developmental projects. Therefore, examining the influence of Fairtrade tools on individuals and communities provides an overview of how Fairtrade influences development. The results of the study show that sampled Fairtrade beneficiaries in South Africa have witnessed substantial positive changes as a result of Fairtrade. The Fairtrade initiative has managed to empower small-scale producers and farm workers, as well as leverage development opportunities for their wider communities. It has supported organizational development in the supply chain, facilitated investment in community development projects and in business-related training. Producers, both commercial and small-scale producers, managed to access a market that offers stable prices, and have gained from minimum prices. Furthermore, small-scale farmers have been allowed an opportunity to expand their business into export markets, and enjoyed an increase in incomes. Fairtrade benefits further trickle down to non-Fairtrade community members, in the form of employment creation and community development. Despite positive effects, Fairtrade producers faced challenges, including high Fairtrade administration costs and a small market for Fairtrade commodities. The study concludes that in the face of challenges, Fairtrade brings economic, social and environmental benefits, but as compared to economic and social development, the impact on environmental development is rather limited. Even though that is the case, Fairtrade offers valuable development opportunities to producers in South Africa.
- Full Text:
- Date Issued: 2012
- Authors: Jari, Bridget
- Date: 2012
- Subjects: Competition, Unfair -- Research -- South Africa Price maintenance -- Research -- South Africa Fair trade associations -- South Africa Sustainable development -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1006 , http://hdl.handle.net/10962/d1002741
- Description: World international trade is moving towards more free trade, through globalization and trade liberalization. These moves are guided by trade theories which state that on an aggregated level, nations involved in free trade should benefit, and further that free trade is fair. However, in practice, contradictory views have been raised, stating that free trade may not necessarily be benefiting all participants equally. Rather, other nations, especially developing nations, have become worse-off after opening up their markets for free trade. On the other hand, many developed nations have benefited substantially from free trade. Among other factors, the difference in benefits is believed to have been influenced by the types of commodities being traded (where developing nations mainly trade in primary goods and developed nations in anufactured goods) and unequal power relations (some nations for example, the EU and the US, still adopt protectionism in their agricultural sector). In order to address market imbalances resulting from free trade, Fairtrade has arisen. Fairtrade aims to improve international trading conditions in order to benefit small-scale farmers and farm workers in the developing nations. The Fairtrade organization further claims that its principles are in line with sustainable development. However, Fairtrade suffers a credibility gap because there is a lack of independent research to support their claims. To date in South Africa, there is little research examining the claims of the Fairtrade organization. In order to contribute to the Fairtrade discussion in South Africa, this study has investigated the validity of Fairtrade‘s claims that it contributes towards sustainable development. The study utilised primary data, which was collected from ten commercial farms and two small-scale farmer cooperatives located in the Eastern Cape and Western Cape provinces that are/were Fairtrade certified. The main reason for including commercial farmers and small-scale farmer cooperatives in the study was for comparing relative impacts in the two Fairtrade structures. The data was then analysed using a sustainable livelihoods framework, which was developed in the study. The study focussed on investigating the impact of Fairtrade tools, which are minimum prices, premiums, pre-financing and support for long-term relationships, on its intended beneficiaries. Minimum prices offered to producers cover production costs and are above market prices, and Fairtrade premiums are to be invested in developmental projects. Therefore, examining the influence of Fairtrade tools on individuals and communities provides an overview of how Fairtrade influences development. The results of the study show that sampled Fairtrade beneficiaries in South Africa have witnessed substantial positive changes as a result of Fairtrade. The Fairtrade initiative has managed to empower small-scale producers and farm workers, as well as leverage development opportunities for their wider communities. It has supported organizational development in the supply chain, facilitated investment in community development projects and in business-related training. Producers, both commercial and small-scale producers, managed to access a market that offers stable prices, and have gained from minimum prices. Furthermore, small-scale farmers have been allowed an opportunity to expand their business into export markets, and enjoyed an increase in incomes. Fairtrade benefits further trickle down to non-Fairtrade community members, in the form of employment creation and community development. Despite positive effects, Fairtrade producers faced challenges, including high Fairtrade administration costs and a small market for Fairtrade commodities. The study concludes that in the face of challenges, Fairtrade brings economic, social and environmental benefits, but as compared to economic and social development, the impact on environmental development is rather limited. Even though that is the case, Fairtrade offers valuable development opportunities to producers in South Africa.
- Full Text:
- Date Issued: 2012
Assessing the effect of a laundry detergent ingredient (LAS) on organisms of a rural South African river
- Authors: Gordon, Andrew K
- Date: 2012
- Subjects: Detergent pollution of rivers, lakes, etc. -- Research -- South Africa -- Eastern Cape Water -- Pollution -- Research -- South Africa -- Eastern Cape Stream health -- Research -- South Africa -- Eastern Cape Stream ecology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6042 , http://hdl.handle.net/10962/d1006201
- Description: Powdered laundry detergents are consumed in high volumes worldwide. Post use, they are directed toward water resources via wastewater treatment works or, as is the situation in many rural areas of South Africa, they enter the environment directly as a result of laundry washing activity undertaken alongside surface waters. Within wastewater treatment works, the main ingredient in powdered laundry detergents, the narcotic toxin linear alkylbenzene sulfonate (LAS), is mostly removed, rendering the waste stream a negligible risk to the aquatic biota of receiving waters. In contrast, the biological and ecological impacts of direct LAS input to the aquatic environment, as a consequence of near-stream laundry washing, are yet to be fully realised. Consequently, this thesis posed two research questions: 1) 'What are the LAS concentrations in a small rural South African river'? and 2) 'Is the in-stream biological community negatively affected at these concentrations?' The chosen study area, the community of Balfour in the Eastern Cape Province, is like many rural areas of South Africa where inadequate provision of piped water to homesteads necessitates laundry washing alongside the nearby Balfour River. The first research question was addressed in two ways: by predicting LAS concentrations in Balfour River water by assessing detergent consumption and laundry washing behaviour of residents living alongside the river; and measuring actual in- stream LAS concentrations on different days of the week and during different seasons. Results indicated that LAS concentrations were highly variable temporally and spatially. High peak concentrations of LAS occurred infrequently and were limited to the immediate vicinity of near-stream laundry washing activity with the highest measured concentration being 342 μg.L ⁻¹ and the average 21 μg.L ⁻¹ over the sampling period. The second research question was addressed by integrating the chemical evidence, determined from the first research question, with the biological evidence of stress responses measured in macroinvertebrates collected downstream of near-stream laundry washing activity on the Balfour River. Predicted and measured LAS exposure concentrations from the Balfour River were compared to a water quality guideline for LAS (304 μg.L ⁻¹), specifically derived in this thesis. Biological stress responses were measured at different levels of organisation: two sub-cellular responses (lipid peroxidation and cholinesterase activity); three measures of macroinvertebrate tolerance to water quality impairment; five measures of community composition; three measures of community richness; and a surrogate measure of ecosystem function (functional feeding groups). Weight-of-evidence methodology was utilised to assess, integrate and interpret the chemical and biological evidence, and at its conclusion, determined no effect on the in-stream biological community of the Balfour River downstream of laundry washing activity.
- Full Text:
- Date Issued: 2012
- Authors: Gordon, Andrew K
- Date: 2012
- Subjects: Detergent pollution of rivers, lakes, etc. -- Research -- South Africa -- Eastern Cape Water -- Pollution -- Research -- South Africa -- Eastern Cape Stream health -- Research -- South Africa -- Eastern Cape Stream ecology -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6042 , http://hdl.handle.net/10962/d1006201
- Description: Powdered laundry detergents are consumed in high volumes worldwide. Post use, they are directed toward water resources via wastewater treatment works or, as is the situation in many rural areas of South Africa, they enter the environment directly as a result of laundry washing activity undertaken alongside surface waters. Within wastewater treatment works, the main ingredient in powdered laundry detergents, the narcotic toxin linear alkylbenzene sulfonate (LAS), is mostly removed, rendering the waste stream a negligible risk to the aquatic biota of receiving waters. In contrast, the biological and ecological impacts of direct LAS input to the aquatic environment, as a consequence of near-stream laundry washing, are yet to be fully realised. Consequently, this thesis posed two research questions: 1) 'What are the LAS concentrations in a small rural South African river'? and 2) 'Is the in-stream biological community negatively affected at these concentrations?' The chosen study area, the community of Balfour in the Eastern Cape Province, is like many rural areas of South Africa where inadequate provision of piped water to homesteads necessitates laundry washing alongside the nearby Balfour River. The first research question was addressed in two ways: by predicting LAS concentrations in Balfour River water by assessing detergent consumption and laundry washing behaviour of residents living alongside the river; and measuring actual in- stream LAS concentrations on different days of the week and during different seasons. Results indicated that LAS concentrations were highly variable temporally and spatially. High peak concentrations of LAS occurred infrequently and were limited to the immediate vicinity of near-stream laundry washing activity with the highest measured concentration being 342 μg.L ⁻¹ and the average 21 μg.L ⁻¹ over the sampling period. The second research question was addressed by integrating the chemical evidence, determined from the first research question, with the biological evidence of stress responses measured in macroinvertebrates collected downstream of near-stream laundry washing activity on the Balfour River. Predicted and measured LAS exposure concentrations from the Balfour River were compared to a water quality guideline for LAS (304 μg.L ⁻¹), specifically derived in this thesis. Biological stress responses were measured at different levels of organisation: two sub-cellular responses (lipid peroxidation and cholinesterase activity); three measures of macroinvertebrate tolerance to water quality impairment; five measures of community composition; three measures of community richness; and a surrogate measure of ecosystem function (functional feeding groups). Weight-of-evidence methodology was utilised to assess, integrate and interpret the chemical and biological evidence, and at its conclusion, determined no effect on the in-stream biological community of the Balfour River downstream of laundry washing activity.
- Full Text:
- Date Issued: 2012
Assessing the impacts of invasive non-native African sharptooth catfish Clarias Gariepinus
- Authors: Kadye, Wilbert Takawira
- Date: 2012
- Subjects: Catfishes -- South Africa -- Eastern Cape Biological invasions -- South Africa -- Great Fish River Biological invasions -- South Africa -- Sundays River Clarias gariepinus Freshwater ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5227 , http://hdl.handle.net/10962/d1005070
- Description: Invasive species are of particular concern as they have the potential to alter community structure and food web relationships within their invaded habitats. African sharptooth catfish Clarias gariepinus, a generalist predator, was introduced through an inter-basin water transfer scheme into the Great Fish and Sundays Rivers, Eastern Cape, South Africa, where it threatens the native riverine biota. This thesis assessed its impact from a trophic perspective. Patterns in catfish distribution and abundance revealed an upstream to downstream gradient that was associated with spatial distribution of most species within the mainstream, and a mainstream to tributary gradient that was associated with the spatial distribution of native minnows. The catfish was predicted to occur widely within the mainstem habitats and to decrease progressively along the mainstrem to tributary gradient with the physico-chemical environment being a good proxy for predicting both its occurrence and abundance. The results suggest the catfish proliferated within mainstem habitats where invasion resistance was possibly reduced due to alteration of flow. Population dynamics and size structuring of two native cyprinid minnows Pseudobarbus afer and Barbus anoplus, threatened by catfish, were examined within uninvaded headwater streams in relation to their proximate physical habitats. Their habitats were characterised by seasonal variation in physico-chemical conditions and a spatial variation in substrata compositions. No evidence of differences was found between seasons for density and capture probability for either species. The population size and density for P. afer was found to increase with increasing proportion of boulders. In comparison, B. anoplus population size and probability of capture increased with increasing proportion of bedrock and bank vegetation, respectively. Size structuring was explained predominantly by seasonality and habitat variables for P. afer and B. anoplus, respectively. Stable isotope ratios of carbon and nitrogen were used to compare the spatial variation in both the community-wide and catfish-specific niches and to estimate catfish prey sources from different habitats within the invaded systems. Aquatic community and catfish niches were statistically different among localities, suggesting that each locality had a distinct community-wide trophic structure. Dispersion metrics indicated no evidence of differences in the clustering among individuals, but provided evidence of differences in path trajectories for the comparisons of catfish populations that suggested dietary plasticity within different localities. Dietary studies revealed both ontogenetic shift and omnivory that suggested that catfish may exhibit less pronounced top-down effects within its invaded habitats. Manipulative experiments were used to test the response of benthic macroinvertebrates within two rivers that were differentially impacted by catfish as a presstype disturbance. Macroinvertebrates were non-responsive to catfish presence within a system where catfish had previously been established. In contrast, excluding catfish in this system indicated a response that suggested the importance of refuge within invaded habitats and the possible recovery pattern of certain macroinvertebrate taxa. By comparison, introduction of catfish within previously uninvaded localities provided evidence of direct catfish impact through elimination of conspicuous taxa. Acoustic telemetry was used to investigate catfish movement patterns within an invaded lentic habitat and provided evidence that habitat utilisation was non-random. The shallow and structured river mouth habitat, which was most utilised, was probably the most ideal for its breeding and feeding. This inferred potential overlap with native species and suggested the risk of predation and competitive interference. Catfish also exhibited both nocturnal and diurnal activity patterns that were probably related to feeding.
- Full Text:
- Date Issued: 2012
- Authors: Kadye, Wilbert Takawira
- Date: 2012
- Subjects: Catfishes -- South Africa -- Eastern Cape Biological invasions -- South Africa -- Great Fish River Biological invasions -- South Africa -- Sundays River Clarias gariepinus Freshwater ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5227 , http://hdl.handle.net/10962/d1005070
- Description: Invasive species are of particular concern as they have the potential to alter community structure and food web relationships within their invaded habitats. African sharptooth catfish Clarias gariepinus, a generalist predator, was introduced through an inter-basin water transfer scheme into the Great Fish and Sundays Rivers, Eastern Cape, South Africa, where it threatens the native riverine biota. This thesis assessed its impact from a trophic perspective. Patterns in catfish distribution and abundance revealed an upstream to downstream gradient that was associated with spatial distribution of most species within the mainstream, and a mainstream to tributary gradient that was associated with the spatial distribution of native minnows. The catfish was predicted to occur widely within the mainstem habitats and to decrease progressively along the mainstrem to tributary gradient with the physico-chemical environment being a good proxy for predicting both its occurrence and abundance. The results suggest the catfish proliferated within mainstem habitats where invasion resistance was possibly reduced due to alteration of flow. Population dynamics and size structuring of two native cyprinid minnows Pseudobarbus afer and Barbus anoplus, threatened by catfish, were examined within uninvaded headwater streams in relation to their proximate physical habitats. Their habitats were characterised by seasonal variation in physico-chemical conditions and a spatial variation in substrata compositions. No evidence of differences was found between seasons for density and capture probability for either species. The population size and density for P. afer was found to increase with increasing proportion of boulders. In comparison, B. anoplus population size and probability of capture increased with increasing proportion of bedrock and bank vegetation, respectively. Size structuring was explained predominantly by seasonality and habitat variables for P. afer and B. anoplus, respectively. Stable isotope ratios of carbon and nitrogen were used to compare the spatial variation in both the community-wide and catfish-specific niches and to estimate catfish prey sources from different habitats within the invaded systems. Aquatic community and catfish niches were statistically different among localities, suggesting that each locality had a distinct community-wide trophic structure. Dispersion metrics indicated no evidence of differences in the clustering among individuals, but provided evidence of differences in path trajectories for the comparisons of catfish populations that suggested dietary plasticity within different localities. Dietary studies revealed both ontogenetic shift and omnivory that suggested that catfish may exhibit less pronounced top-down effects within its invaded habitats. Manipulative experiments were used to test the response of benthic macroinvertebrates within two rivers that were differentially impacted by catfish as a presstype disturbance. Macroinvertebrates were non-responsive to catfish presence within a system where catfish had previously been established. In contrast, excluding catfish in this system indicated a response that suggested the importance of refuge within invaded habitats and the possible recovery pattern of certain macroinvertebrate taxa. By comparison, introduction of catfish within previously uninvaded localities provided evidence of direct catfish impact through elimination of conspicuous taxa. Acoustic telemetry was used to investigate catfish movement patterns within an invaded lentic habitat and provided evidence that habitat utilisation was non-random. The shallow and structured river mouth habitat, which was most utilised, was probably the most ideal for its breeding and feeding. This inferred potential overlap with native species and suggested the risk of predation and competitive interference. Catfish also exhibited both nocturnal and diurnal activity patterns that were probably related to feeding.
- Full Text:
- Date Issued: 2012
Bayliss-Hillman adducts as scaffolds for the construction of novel compounds with medicinal potential
- Authors: Idahosa, Kenudi Christiana
- Date: 2012
- Subjects: Antimalarials -- Research Malaria -- Chemotherapy -- Research AIDS (Disease) -- Treatment -- Research AIDS (Disease) -- Chemotherapy -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4410 , http://hdl.handle.net/10962/d1006763
- Description: This project has focused on exploring the application of Baylis-Hillman (BH) {a.k.a. Morita-Baylis-Hillman (MBH)} scaffolds in the construction of various compounds with medicinal potential. A series of 2-nitrobenzaldehydes has been treated under BH conditions, with two different activated alkenes, viz., (MVK) and methyl acrylate, using (DABCO) or (3-HQ) as catalyst. While most of the BH reactions were carried out at room temperature, some reactions were conducted using microwave irradiation. The resulting BH adducts have been subjected to dehydration, conjugate addition and allylic substitution to obtain appropriate intermediates, which have been used in turn, to synthesize possible lead compounds, viz., cinnamate esters as HIV-1 integrase inhibitors, 3-(aminomethyl)quinolines and quinolones as anti-malarials and cinnamate ester-AZT conjugates as dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Conjugate addition reactions of methyl acrylate-derived BH β-hydroxy esters with the amines, piperidine, propargylamine and 2-amino-5-(diethylamino)pentane, has afforded a range of products as diastereomeric mixtures in moderate to excellent yields. Catalytic hydrogenation of the aminomethy β-hydroxy esters derivatives, using a palladium-oncarbon (Pd-C) catalyst, has afforded the corresponding, novel 3-aminomethyl-2- quinolone derivatives in moderate yields. Effective allylic substitution reactions of the MVK-derived BH β-hydroxy ketones (via a conjugate addition-elimination pathway) using in situ-generated HCl has afforded the corresponding α-chloromethyl derivatives, which have been reacted with various amines, including piperidine, piperazine, propargylamine and 2-amino-5-(diethylamino)pentane, to yield α-aminomethyl derivatives. Catalytic hydrogenation of selected α-aminomethyl derivatives, using a Pd-C catalyst, has afforded the corresponding, novel 3- (aminomethyl)-2-methylquinoline derivatives in low to moderate yields. A bioassay, conducted on a 6-hydroxy-2-methyl-3-[(piperidin-1-yl)methyl]quinoline isolated early in the study indicated anti-malarial activity and prompted further efforts in the synthesis of analogous compounds. Reaction of the methyl acrylate-derived BH adducts with POCl3 has provided access to α-(chloromethyl)cinnamate ester derivatives, which have been aminated to afford α- (aminomethyl)cinnamate ester derivatives as potential HIV-1 integrase inhibitors. The α- (propargylaminomethyl)cinnamates were used, in turn, as substrates for the “click chemistry” reaction with 3'-azido-3'-deoxythymidine (AZT– an azide and an established reverse transcriptase HIV-1 inhibitor) to afford cinnamate ester-AZT conjugates as potential dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Computer modelling and docking studies of a cinnamate ester-AZT conjugate into the HIV-1 integrase and reverse transcriptase active-sites revealed potential hydrogen-bonding interactions with amino acid residues within the receptor cavities. The isolated products have been appropriately characterized using IR, 1- and 2-D NMR and HRMS techniques, while elucidation of the stereochemistry of the double bond in the BH-derived halomethyl derivatives has been assigned on the basis of NOE, computer modelling and X-ray crystallographic data.
- Full Text:
- Date Issued: 2012
- Authors: Idahosa, Kenudi Christiana
- Date: 2012
- Subjects: Antimalarials -- Research Malaria -- Chemotherapy -- Research AIDS (Disease) -- Treatment -- Research AIDS (Disease) -- Chemotherapy -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4410 , http://hdl.handle.net/10962/d1006763
- Description: This project has focused on exploring the application of Baylis-Hillman (BH) {a.k.a. Morita-Baylis-Hillman (MBH)} scaffolds in the construction of various compounds with medicinal potential. A series of 2-nitrobenzaldehydes has been treated under BH conditions, with two different activated alkenes, viz., (MVK) and methyl acrylate, using (DABCO) or (3-HQ) as catalyst. While most of the BH reactions were carried out at room temperature, some reactions were conducted using microwave irradiation. The resulting BH adducts have been subjected to dehydration, conjugate addition and allylic substitution to obtain appropriate intermediates, which have been used in turn, to synthesize possible lead compounds, viz., cinnamate esters as HIV-1 integrase inhibitors, 3-(aminomethyl)quinolines and quinolones as anti-malarials and cinnamate ester-AZT conjugates as dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Conjugate addition reactions of methyl acrylate-derived BH β-hydroxy esters with the amines, piperidine, propargylamine and 2-amino-5-(diethylamino)pentane, has afforded a range of products as diastereomeric mixtures in moderate to excellent yields. Catalytic hydrogenation of the aminomethy β-hydroxy esters derivatives, using a palladium-oncarbon (Pd-C) catalyst, has afforded the corresponding, novel 3-aminomethyl-2- quinolone derivatives in moderate yields. Effective allylic substitution reactions of the MVK-derived BH β-hydroxy ketones (via a conjugate addition-elimination pathway) using in situ-generated HCl has afforded the corresponding α-chloromethyl derivatives, which have been reacted with various amines, including piperidine, piperazine, propargylamine and 2-amino-5-(diethylamino)pentane, to yield α-aminomethyl derivatives. Catalytic hydrogenation of selected α-aminomethyl derivatives, using a Pd-C catalyst, has afforded the corresponding, novel 3- (aminomethyl)-2-methylquinoline derivatives in low to moderate yields. A bioassay, conducted on a 6-hydroxy-2-methyl-3-[(piperidin-1-yl)methyl]quinoline isolated early in the study indicated anti-malarial activity and prompted further efforts in the synthesis of analogous compounds. Reaction of the methyl acrylate-derived BH adducts with POCl3 has provided access to α-(chloromethyl)cinnamate ester derivatives, which have been aminated to afford α- (aminomethyl)cinnamate ester derivatives as potential HIV-1 integrase inhibitors. The α- (propargylaminomethyl)cinnamates were used, in turn, as substrates for the “click chemistry” reaction with 3'-azido-3'-deoxythymidine (AZT– an azide and an established reverse transcriptase HIV-1 inhibitor) to afford cinnamate ester-AZT conjugates as potential dual-action HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. Computer modelling and docking studies of a cinnamate ester-AZT conjugate into the HIV-1 integrase and reverse transcriptase active-sites revealed potential hydrogen-bonding interactions with amino acid residues within the receptor cavities. The isolated products have been appropriately characterized using IR, 1- and 2-D NMR and HRMS techniques, while elucidation of the stereochemistry of the double bond in the BH-derived halomethyl derivatives has been assigned on the basis of NOE, computer modelling and X-ray crystallographic data.
- Full Text:
- Date Issued: 2012
Biological synthesis of metallic nanoparticles and their interactions with various biomedical targets
- Authors: Sennuga, Afolake Temitope
- Date: 2012
- Subjects: Nanoparticles Biosynthesis Nanotechnology Biomineralization Morphology Ceruloplasmin Ribonucleases Adenosine triphosphatase Acetylcholinesterase Platinum Gold Silver
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4009 , http://hdl.handle.net/10962/d1004069
- Description: The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology. In this study, a comparative biological synthesis, characterization and biomedical effects of metallic nanoparticles of platinum, gold and silver were investigated. Metallic nanoparticles were biologically synthesized using cage-like (apoferritin), barrel-like (GroEL) and non-caged (ribonuclease) proteins. Nanoparticles generated were characterized using common techniques such as UV-visible spectroscopy, scanning and transmission electron microscopy, inductively coupled optical emission spectroscopy, Fourier transform infra-red spectroscopy and energy dispersion analysis of X-rays (EDAX). Nanoparticles synthesised biologically using apoferritin, GroEL and RNase with exhibited similar chemical and physical properties as thoses nanoparticles generated chemically. In addition, the metallic nanoparticles fabricated within the cage-like and barrel-like cavities of apoferritin and GroEL respectively, resulted in nanoparticles with relatively uniform morphology as opposed to those obtained with the non-caged ribonuclease. The enzymatic (ferroxidase) activity of apoferritin was found to be greatly enhanced with platinum (9-fold), gold (7-fold) and silver (54-fold) nanoparticles. The ATPase activity of GroEL was inhibited by silver nanoparticles (64%), was moderately activated by gold nanoparticles (47%) and considerably enhanced by platinum nanoparticles (85%). The hydrolytic activity of RNase was however, lowered by these metallic nanoparticles (90% in Ag nanoparticles) and to a higher degree with platinum (95%) and gold nanoparticles (~100%). The effect of synthesized nanoparticles on the respective enzyme activities of these proteins was also investigated and the potential neurotoxic property of these particles was also determined by an in vitro interaction with acetylcholinesterase. Protein encapsulated nanoparticles with apoferrtin and GroEL showed a decreased inhibition of acetylcholinesterase (<50%) compared with nanoparticles attached to ribonuclease (>50%). Thus, it can be concluded that the cavities of apoferitin and GroEL acted as nanobiofactories for the synthesis and confinement of the size and shape of nanoparticles. Furthermore, the interior of these proteins provided a shielding effect for these nanoparticles and thus reduced/prevented their possible neurotoxic effect and confirmed safety in their method of production and application. The findings from this study would prove beneficial in the application of these nanoparticles as a potential drug/drug delivery vehicle for the prevention, treatment/management of diseases associated with these enzymes/proteins.
- Full Text:
- Date Issued: 2012
- Authors: Sennuga, Afolake Temitope
- Date: 2012
- Subjects: Nanoparticles Biosynthesis Nanotechnology Biomineralization Morphology Ceruloplasmin Ribonucleases Adenosine triphosphatase Acetylcholinesterase Platinum Gold Silver
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4009 , http://hdl.handle.net/10962/d1004069
- Description: The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology. In this study, a comparative biological synthesis, characterization and biomedical effects of metallic nanoparticles of platinum, gold and silver were investigated. Metallic nanoparticles were biologically synthesized using cage-like (apoferritin), barrel-like (GroEL) and non-caged (ribonuclease) proteins. Nanoparticles generated were characterized using common techniques such as UV-visible spectroscopy, scanning and transmission electron microscopy, inductively coupled optical emission spectroscopy, Fourier transform infra-red spectroscopy and energy dispersion analysis of X-rays (EDAX). Nanoparticles synthesised biologically using apoferritin, GroEL and RNase with exhibited similar chemical and physical properties as thoses nanoparticles generated chemically. In addition, the metallic nanoparticles fabricated within the cage-like and barrel-like cavities of apoferritin and GroEL respectively, resulted in nanoparticles with relatively uniform morphology as opposed to those obtained with the non-caged ribonuclease. The enzymatic (ferroxidase) activity of apoferritin was found to be greatly enhanced with platinum (9-fold), gold (7-fold) and silver (54-fold) nanoparticles. The ATPase activity of GroEL was inhibited by silver nanoparticles (64%), was moderately activated by gold nanoparticles (47%) and considerably enhanced by platinum nanoparticles (85%). The hydrolytic activity of RNase was however, lowered by these metallic nanoparticles (90% in Ag nanoparticles) and to a higher degree with platinum (95%) and gold nanoparticles (~100%). The effect of synthesized nanoparticles on the respective enzyme activities of these proteins was also investigated and the potential neurotoxic property of these particles was also determined by an in vitro interaction with acetylcholinesterase. Protein encapsulated nanoparticles with apoferrtin and GroEL showed a decreased inhibition of acetylcholinesterase (<50%) compared with nanoparticles attached to ribonuclease (>50%). Thus, it can be concluded that the cavities of apoferitin and GroEL acted as nanobiofactories for the synthesis and confinement of the size and shape of nanoparticles. Furthermore, the interior of these proteins provided a shielding effect for these nanoparticles and thus reduced/prevented their possible neurotoxic effect and confirmed safety in their method of production and application. The findings from this study would prove beneficial in the application of these nanoparticles as a potential drug/drug delivery vehicle for the prevention, treatment/management of diseases associated with these enzymes/proteins.
- Full Text:
- Date Issued: 2012
Characterisation and optimisation of waterjet impact forces and energy parameters during hydroentanglement
- Authors: Moyo, Doice
- Date: 2012
- Subjects: Textile chemistry , Nonwoven fabrics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10453 , http://hdl.handle.net/10948/d1020134
- Description: Hydroentanglement is an important technique of bonding fibres to produce nonwovens using high velocity waterjets as the primary bonding tool. The work reported in this thesis addresses the gap in scientific knowledge and understanding, both theoretical and experimental, related to the impact forces and energy of the waterjets used in the hydroentanglement process. The current study focused on the impact forces and energy involved in, and the optimisation of, the hydroentanglement process. The results of the experimentally measured waterjet impact forces have been used to characterise the waterjets as well as to verify empirically the theoretical models currently available for explaining the mechanics of the hydroentanglement process. Since the process of supplying pressurised waterjets consumes a great deal of energy, the study of energy consumption and efficiency of the system has been critical. A method was proposed and used to determine the coefficients of velocity and water discharge of an industrial machine set-up, helping explain the mechanism of energy transfer during hydroentanglement and to concurrently optimise the process. Furthermore, a response surface experimental design was used to optimise the hydroentanglement of viscose and Polylactic acid (PLA) fibres into nonwovens. The selected Box-Behnken design, with four factors, namely the waterjet force, machine processing speed, input weight and fibre type, was employed to investigate the multivariate process factors and their interactive effects on physical and mechanical properties of nonwovens. Two sets of experiments, the later for validation, were performed to study the energy transfer efficiency. The results of the relative energy transfer to bond the fibrous web showed that it was possible to produce nonwovens using lower input energy without compromising the quality of the products. The optimum waterjet pressure and machine speed used to produce the Abstract nonwoven with the highest tensile strength for the least amount of energy supplied were identified.
- Full Text:
- Date Issued: 2012
- Authors: Moyo, Doice
- Date: 2012
- Subjects: Textile chemistry , Nonwoven fabrics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10453 , http://hdl.handle.net/10948/d1020134
- Description: Hydroentanglement is an important technique of bonding fibres to produce nonwovens using high velocity waterjets as the primary bonding tool. The work reported in this thesis addresses the gap in scientific knowledge and understanding, both theoretical and experimental, related to the impact forces and energy of the waterjets used in the hydroentanglement process. The current study focused on the impact forces and energy involved in, and the optimisation of, the hydroentanglement process. The results of the experimentally measured waterjet impact forces have been used to characterise the waterjets as well as to verify empirically the theoretical models currently available for explaining the mechanics of the hydroentanglement process. Since the process of supplying pressurised waterjets consumes a great deal of energy, the study of energy consumption and efficiency of the system has been critical. A method was proposed and used to determine the coefficients of velocity and water discharge of an industrial machine set-up, helping explain the mechanism of energy transfer during hydroentanglement and to concurrently optimise the process. Furthermore, a response surface experimental design was used to optimise the hydroentanglement of viscose and Polylactic acid (PLA) fibres into nonwovens. The selected Box-Behnken design, with four factors, namely the waterjet force, machine processing speed, input weight and fibre type, was employed to investigate the multivariate process factors and their interactive effects on physical and mechanical properties of nonwovens. Two sets of experiments, the later for validation, were performed to study the energy transfer efficiency. The results of the relative energy transfer to bond the fibrous web showed that it was possible to produce nonwovens using lower input energy without compromising the quality of the products. The optimum waterjet pressure and machine speed used to produce the Abstract nonwoven with the highest tensile strength for the least amount of energy supplied were identified.
- Full Text:
- Date Issued: 2012