A comparative study of the comfort related properties of commercial apparel fabrics containing natural and man-made fibres
- Authors: Stoffberg, Marguerite Ester
- Date: 2013
- Subjects: Textile fabrics , Materials -- Thermal properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10455 , http://hdl.handle.net/10948/d1020931
- Description: The relationship between the fabric parameters, as independent variables, and the comfort related properties, as dependent variables, of commercial suiting fabrics, containing both natural and man-made fibres, have been studied. The fabric parameters measured in the study were mass, thickness, density, and air permeability. The comfort related properties, tested on a Permetest instrument, included water vapour permeability, water vapour resistance, and thermal resistance, with the moisture permeability index being derived. A total of 26 commercial suiting fabrics, covering a wide range of mass, as well as different fibre types and blends and fabric structures, was tested. The fibres covered, included wool, polyester, viscose, and cotton, while the fabric structures covered were 1x1 plain weave, 2x1 twill and 2x2 twill weave. The objectives of this study were to determine the empirical relationships between the measured fabric properties and the measured comfort related properties, and to determine the role, if any, of fibre type and fabric structure, since many claims are made in practice concerning the relative advantages, in terms of comfort, of a specific fibre type or blend, or fabric structure, over others, some of which being supported by research results. Since the fabrics covered, were commercial and were not engineered so that the different fabric parameters (independent variables) and fibre type and blend, as well as fabric structure could be varied independently of each other, the effects of the various fabric parameters on the fabric comfort related properties were determined and quantified by multiple regression analyses (multi-linear and multi-quadratic), and the best fit regression equations, and contribution of each parameter to the overall fit established. It was found that fabric thickness and fabric mass had the largest effect on the comfort related properties as measured here, fabric mass determining, to a large extent, water vapour permeability, and fabric thickness, thermal resistance. The rest of the fabric parameters included in the study had only a relatively small effect on the measured comfort related properties. The influence of fabric parameters, with particular reference to mass and thickness, on the measured comfort related properties, were much greater than that of fibre type or blend, or fabric structure. It was, therefore, concluded from this study, that the fabric parameters, as opposed to the intrinsic characteristics of a particular fibre, whether natural or man-made, largely determined those fabric comfort related properties measured here.
- Full Text:
- Date Issued: 2013
- Authors: Stoffberg, Marguerite Ester
- Date: 2013
- Subjects: Textile fabrics , Materials -- Thermal properties
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10455 , http://hdl.handle.net/10948/d1020931
- Description: The relationship between the fabric parameters, as independent variables, and the comfort related properties, as dependent variables, of commercial suiting fabrics, containing both natural and man-made fibres, have been studied. The fabric parameters measured in the study were mass, thickness, density, and air permeability. The comfort related properties, tested on a Permetest instrument, included water vapour permeability, water vapour resistance, and thermal resistance, with the moisture permeability index being derived. A total of 26 commercial suiting fabrics, covering a wide range of mass, as well as different fibre types and blends and fabric structures, was tested. The fibres covered, included wool, polyester, viscose, and cotton, while the fabric structures covered were 1x1 plain weave, 2x1 twill and 2x2 twill weave. The objectives of this study were to determine the empirical relationships between the measured fabric properties and the measured comfort related properties, and to determine the role, if any, of fibre type and fabric structure, since many claims are made in practice concerning the relative advantages, in terms of comfort, of a specific fibre type or blend, or fabric structure, over others, some of which being supported by research results. Since the fabrics covered, were commercial and were not engineered so that the different fabric parameters (independent variables) and fibre type and blend, as well as fabric structure could be varied independently of each other, the effects of the various fabric parameters on the fabric comfort related properties were determined and quantified by multiple regression analyses (multi-linear and multi-quadratic), and the best fit regression equations, and contribution of each parameter to the overall fit established. It was found that fabric thickness and fabric mass had the largest effect on the comfort related properties as measured here, fabric mass determining, to a large extent, water vapour permeability, and fabric thickness, thermal resistance. The rest of the fabric parameters included in the study had only a relatively small effect on the measured comfort related properties. The influence of fabric parameters, with particular reference to mass and thickness, on the measured comfort related properties, were much greater than that of fibre type or blend, or fabric structure. It was, therefore, concluded from this study, that the fabric parameters, as opposed to the intrinsic characteristics of a particular fibre, whether natural or man-made, largely determined those fabric comfort related properties measured here.
- Full Text:
- Date Issued: 2013
A contribution to the theory of prime modules
- Authors: Ssevviiri, David
- Date: 2013
- Subjects: Modules (Algebra) , Radical theory , Rings (Algebra)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10510 , http://hdl.handle.net/10948/d1019923
- Description: This thesis is aimed at generalizing notions of rings to modules. In par-ticular, notions of completely prime ideals, s-prime ideals, 2-primal rings and nilpotency of elements of rings are respectively generalized to completely prime submodules and classical completely prime submodules, s-prime submodules, 2-primal modules and nilpotency of elements of modules. Properties and rad-icals that arise from each of these notions are studied.
- Full Text:
- Date Issued: 2013
- Authors: Ssevviiri, David
- Date: 2013
- Subjects: Modules (Algebra) , Radical theory , Rings (Algebra)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10510 , http://hdl.handle.net/10948/d1019923
- Description: This thesis is aimed at generalizing notions of rings to modules. In par-ticular, notions of completely prime ideals, s-prime ideals, 2-primal rings and nilpotency of elements of rings are respectively generalized to completely prime submodules and classical completely prime submodules, s-prime submodules, 2-primal modules and nilpotency of elements of modules. Properties and rad-icals that arise from each of these notions are studied.
- Full Text:
- Date Issued: 2013
A framework for co-located collaborative business process modelling using touch technologies
- Authors: Snyman, Irene
- Date: 2013
- Subjects: Reengineering (Management) , Information technology
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10498 , http://hdl.handle.net/10948/d1021015
- Description: In recent years the field of Business Process Modelling (BPM) has gained increasing attention from both the business and research communities. One of the primary drivers for BPM is the improved understanding of Business Processes (BPs) and the competitive advantage gained over competitors. In addition, BPM can improve communication in an organisation and facilitate increased support for change management. BPM is a collaborative activity that needs to be carried out in a team environment, and Collaborative Business Process Modelling (CBPM) promotes improved readability, accuracy and quality of process models as well as a reduced workload for modellers. In spite of the increased popularity of CBPM, there is limited research related to the collaborative nature of the modelling tasks performed by modellers and specifically to the synchronisation of shared process models. In addition, tools and techniques to support CBPM do not support this synchronisation effectively or efficiently. This study proposes a conceptual framework for CBPM using touch technologies in a colocated collaborative environment. The main research problem addressed by this study is that modellers experience difficulties conducting BPM activities in a co-located collaborative environment. In order to address the research problem and clarify and elaborate on the problems of CBPM, a two-fold approach was undertaken. Firstly, after an in-depth literature review, a BPM survey was designed and then sent to modellers in South African Information Technology (IT) consulting companies in order to provide a more in-depth understanding of the status and challenges of CBPM in IT consulting organisations. The results revealed that available BPM software do not adequately cater for CBPM and software tools do not enforce versioning and synchronisation. In addition, hardware constraints were reported as well as problems with integrating different parts of the process model that the modellers were working on. The results of the survey also showed that the positive aspects of CBPM are that ideas could be shared and overall there is a better understanding of the BPs being modelled. The second part of the problem elaboration consisted of usability field studies with participants from both education and industry using a traditional popular BPM software tool, Enterprise Architect (EA). Whilst several benefits of CBPM were confirmed, several challenges were encountered, particularly with regard to the integration and synchronisation of models. To overcome the problems of CBPM, a framework was developed that allows for co-located CBPM using tablet PCs. The framework includes a developed prototype of the BPMTouch software which runs on tablet PCs, as well as some theoretical aspects of CBPM. The BPMTouch software supports effective and efficient CBPM and the synchronisation of process models since it allows multiple modellers to work together on one BP model, with each modeller using his/her own tablet. If one modeller makes changes to the model, the changes are immediately reflected on the tablets of the other modellers since the changes to the model are updated in real time. Modellers cannot draw on the same model simultaneously, however, everyone can see what the active modeller (active participant with the green flag) is doing. Other participants can then become the active modeller and make changes to the model once the flag has been released and re-allocated. The results from the field studies, industry surveys and usability evaluations were all incorporated into the BPMTouch software tool design and into the aspects of CBPM in order to assist with the process of co-located CBPM using touch technologies. Usability evaluations were carried out in which industry and student participants used BPMTouch to create an integrated model and simultaneously and synchronously create a process model. The evaluations of the BPMTouch prototype revealed that participants prefer this system over traditional BPM software since the BPMTouch removes the need for post modelling integration. The theoretical contribution of the framework consists of aspects proposing that organisations should take the potential benefits and challenges of CBPM into consideration and address the Critical Success Factors (CSFs) before embarking on a CBPM project. These aspects can help with decisions relating to CBPM. The use of this framework can improve the quality of process models, reduce the workload of modellers and in this way increase the success rate of CBPM projects.
- Full Text:
- Date Issued: 2013
- Authors: Snyman, Irene
- Date: 2013
- Subjects: Reengineering (Management) , Information technology
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10498 , http://hdl.handle.net/10948/d1021015
- Description: In recent years the field of Business Process Modelling (BPM) has gained increasing attention from both the business and research communities. One of the primary drivers for BPM is the improved understanding of Business Processes (BPs) and the competitive advantage gained over competitors. In addition, BPM can improve communication in an organisation and facilitate increased support for change management. BPM is a collaborative activity that needs to be carried out in a team environment, and Collaborative Business Process Modelling (CBPM) promotes improved readability, accuracy and quality of process models as well as a reduced workload for modellers. In spite of the increased popularity of CBPM, there is limited research related to the collaborative nature of the modelling tasks performed by modellers and specifically to the synchronisation of shared process models. In addition, tools and techniques to support CBPM do not support this synchronisation effectively or efficiently. This study proposes a conceptual framework for CBPM using touch technologies in a colocated collaborative environment. The main research problem addressed by this study is that modellers experience difficulties conducting BPM activities in a co-located collaborative environment. In order to address the research problem and clarify and elaborate on the problems of CBPM, a two-fold approach was undertaken. Firstly, after an in-depth literature review, a BPM survey was designed and then sent to modellers in South African Information Technology (IT) consulting companies in order to provide a more in-depth understanding of the status and challenges of CBPM in IT consulting organisations. The results revealed that available BPM software do not adequately cater for CBPM and software tools do not enforce versioning and synchronisation. In addition, hardware constraints were reported as well as problems with integrating different parts of the process model that the modellers were working on. The results of the survey also showed that the positive aspects of CBPM are that ideas could be shared and overall there is a better understanding of the BPs being modelled. The second part of the problem elaboration consisted of usability field studies with participants from both education and industry using a traditional popular BPM software tool, Enterprise Architect (EA). Whilst several benefits of CBPM were confirmed, several challenges were encountered, particularly with regard to the integration and synchronisation of models. To overcome the problems of CBPM, a framework was developed that allows for co-located CBPM using tablet PCs. The framework includes a developed prototype of the BPMTouch software which runs on tablet PCs, as well as some theoretical aspects of CBPM. The BPMTouch software supports effective and efficient CBPM and the synchronisation of process models since it allows multiple modellers to work together on one BP model, with each modeller using his/her own tablet. If one modeller makes changes to the model, the changes are immediately reflected on the tablets of the other modellers since the changes to the model are updated in real time. Modellers cannot draw on the same model simultaneously, however, everyone can see what the active modeller (active participant with the green flag) is doing. Other participants can then become the active modeller and make changes to the model once the flag has been released and re-allocated. The results from the field studies, industry surveys and usability evaluations were all incorporated into the BPMTouch software tool design and into the aspects of CBPM in order to assist with the process of co-located CBPM using touch technologies. Usability evaluations were carried out in which industry and student participants used BPMTouch to create an integrated model and simultaneously and synchronously create a process model. The evaluations of the BPMTouch prototype revealed that participants prefer this system over traditional BPM software since the BPMTouch removes the need for post modelling integration. The theoretical contribution of the framework consists of aspects proposing that organisations should take the potential benefits and challenges of CBPM into consideration and address the Critical Success Factors (CSFs) before embarking on a CBPM project. These aspects can help with decisions relating to CBPM. The use of this framework can improve the quality of process models, reduce the workload of modellers and in this way increase the success rate of CBPM projects.
- Full Text:
- Date Issued: 2013
A mathematical investigation of the effects of sexual orientation and HIV status on HPV transmission and vaccination
- Authors: Holtzhausen, Tresia Louisa
- Date: 2013
- Subjects: Virus diseases -- Mathematical models , Cervix uteri -- Cancer -- Treatment , Sexual orientation , Immune response -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3946 , vital:20494
- Description: The effect of the inclusion of sexual behaviour, particularly three sexual orientation classes, on the transmission dynamics of HPV and cervical cancer incidence was investigated. A comprehensive literature review of mathematical models of HPV transmission and the natural history of cervical cancer was concluded. A mathematical model using ordinary differential equations was developed, which incorporated the three sexual orientation classes, and a sexual mixing algorithm for modelling the transmission dynamics. Reproduction numbers, determined through a simplified version of the developed model, indicated that the bisexual population could form a bridge between the heterosexual and homosexual population. The level of interaction is determined by the selection preferences of a bisexual individual to form a partnership with an individual of the same or opposite sex. The model was simulated, with parameters based on a South African population and HPV type 16/18, to investigate the effects of HIV status, sexual orientation and various vaccination strategies on HPV transmission and cervical cancer incidence. The results indicated that HIV status is a significant factor when determining cervical cancer incidence. The results regarding vaccination strategies agreed with results from the literature review with a two sex before sexual debut and catch up program the most effective, noting that with increased vaccination coverage of females the marginal impact on cervical cancer incidence of this approach diminished.
- Full Text:
- Date Issued: 2013
- Authors: Holtzhausen, Tresia Louisa
- Date: 2013
- Subjects: Virus diseases -- Mathematical models , Cervix uteri -- Cancer -- Treatment , Sexual orientation , Immune response -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3946 , vital:20494
- Description: The effect of the inclusion of sexual behaviour, particularly three sexual orientation classes, on the transmission dynamics of HPV and cervical cancer incidence was investigated. A comprehensive literature review of mathematical models of HPV transmission and the natural history of cervical cancer was concluded. A mathematical model using ordinary differential equations was developed, which incorporated the three sexual orientation classes, and a sexual mixing algorithm for modelling the transmission dynamics. Reproduction numbers, determined through a simplified version of the developed model, indicated that the bisexual population could form a bridge between the heterosexual and homosexual population. The level of interaction is determined by the selection preferences of a bisexual individual to form a partnership with an individual of the same or opposite sex. The model was simulated, with parameters based on a South African population and HPV type 16/18, to investigate the effects of HIV status, sexual orientation and various vaccination strategies on HPV transmission and cervical cancer incidence. The results indicated that HIV status is a significant factor when determining cervical cancer incidence. The results regarding vaccination strategies agreed with results from the literature review with a two sex before sexual debut and catch up program the most effective, noting that with increased vaccination coverage of females the marginal impact on cervical cancer incidence of this approach diminished.
- Full Text:
- Date Issued: 2013
A model for supporting environmental awereness in higher education using social media
- Authors: Tlebere, Thabo Eugene
- Date: 2013
- Subjects: Social media , Environmental education , Universities and colleges
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10496 , http://hdl.handle.net/10948/d1020820
- Description: University sustainability is a field of research that has been gaining increased interest in recent years. The reduction of environmental impact has become a strategic objective of universities globally. Universities have been prompted to take necessary action to ensure that their environmental impact is at a minimum. The environmental component of sustainability deals with the current conservation of the earth’s natural resources so that future generations can also have access to them. Human beings, due to their increasing needs, are accountable for the exploitation of natural resources. They are regarded as the main contributors to imbalances in the natural systems. Environmental concerns such as global warming, deforestations, disposal of wastes, and ozone reduction are the outcomes of the damage caused by humans on the environment. The aim of environmental education is to acquire remediation of the environment by making individuals aware of the environment and by educating them about how to live a more sustainable lifestyle. Environmental awareness is perceived as knowledge of the factors that affect the environment and having sensitivity towards the environment. Higher Education Institutions (HEIs) bear the responsibility of educating individuals about environmental issues since they provide education to future leaders in society who may have an influence on future conditions in the environment. Social media are capable of delivering information to a large spectrum of audiences at a low cost. The Pew Internet American Life Project reported that the number of adults who utilise social media has increased by 57 percent from 2005 to 2011. Several environmental activist organisations utilise social media to carry out environmental awareness campaigns. In this study two environmental awareness campaigns which were powered by social media were conducted to improve environmental awareness of individuals in a higher education environment. A Social media Model for ENvironmental Awareness (SMENA) was developed to facilitate the environmental awareness campaigns. The SMENA includes a website, social media as well as theoretical guidelines for creating environmental awareness campaigns, and for using social media for environmental awareness campaigns. A case study at the Nelson Mandela Metropolitan University (NMMU) was used to empirically evaluate SMENA. Students at the Department of Computer Sciences of NMMU were exposed to information about environmental issues through social media with the intention of improving their environmental knowledge and awareness. The SMENA website usability was rated positively and students enjoyed the blogs and information distributed by means of social media. The results of the study intervention were positive and showed that social media can be used to improve the environmental knowledge of students. This study provides a valuable contribution to both the field of environmental education and social media usage and acceptance. The guidelines and requirements for using social media to improve environmental awareness provided in this study can be used to assist educators and university management with addressing the problems of reducing environmental impact.
- Full Text:
- Date Issued: 2013
- Authors: Tlebere, Thabo Eugene
- Date: 2013
- Subjects: Social media , Environmental education , Universities and colleges
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10496 , http://hdl.handle.net/10948/d1020820
- Description: University sustainability is a field of research that has been gaining increased interest in recent years. The reduction of environmental impact has become a strategic objective of universities globally. Universities have been prompted to take necessary action to ensure that their environmental impact is at a minimum. The environmental component of sustainability deals with the current conservation of the earth’s natural resources so that future generations can also have access to them. Human beings, due to their increasing needs, are accountable for the exploitation of natural resources. They are regarded as the main contributors to imbalances in the natural systems. Environmental concerns such as global warming, deforestations, disposal of wastes, and ozone reduction are the outcomes of the damage caused by humans on the environment. The aim of environmental education is to acquire remediation of the environment by making individuals aware of the environment and by educating them about how to live a more sustainable lifestyle. Environmental awareness is perceived as knowledge of the factors that affect the environment and having sensitivity towards the environment. Higher Education Institutions (HEIs) bear the responsibility of educating individuals about environmental issues since they provide education to future leaders in society who may have an influence on future conditions in the environment. Social media are capable of delivering information to a large spectrum of audiences at a low cost. The Pew Internet American Life Project reported that the number of adults who utilise social media has increased by 57 percent from 2005 to 2011. Several environmental activist organisations utilise social media to carry out environmental awareness campaigns. In this study two environmental awareness campaigns which were powered by social media were conducted to improve environmental awareness of individuals in a higher education environment. A Social media Model for ENvironmental Awareness (SMENA) was developed to facilitate the environmental awareness campaigns. The SMENA includes a website, social media as well as theoretical guidelines for creating environmental awareness campaigns, and for using social media for environmental awareness campaigns. A case study at the Nelson Mandela Metropolitan University (NMMU) was used to empirically evaluate SMENA. Students at the Department of Computer Sciences of NMMU were exposed to information about environmental issues through social media with the intention of improving their environmental knowledge and awareness. The SMENA website usability was rated positively and students enjoyed the blogs and information distributed by means of social media. The results of the study intervention were positive and showed that social media can be used to improve the environmental knowledge of students. This study provides a valuable contribution to both the field of environmental education and social media usage and acceptance. The guidelines and requirements for using social media to improve environmental awareness provided in this study can be used to assist educators and university management with addressing the problems of reducing environmental impact.
- Full Text:
- Date Issued: 2013
An economic analysis of an intensive sheep production system on cultivated pastures in South Africa, incorporating creep feeding- and accelerated breeding practices
- Authors: Terblanche, Stefan
- Date: 2013
- Subjects: Pastures -- Irrigation -- South Africa , Sheep -- Productivity -- South Africa , Sheep -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10737 , http://hdl.handle.net/10948/d1020939
- Description: The South African sheep industry has experienced an increase in the price of meat and wool over the past several years. This has led to an interest in intensification of sheep production off planted pastures. Due to this phenomenon an economic viability study was done on the intensification of sheep production on cultivated pastures under irrigation. When intensifying sheep production, certain management practices need to be incorporated in order to enhance the output obtained per hectare and to overcome the higher input cost of production. Management practices that could be included are creep feeding, accelerated breeding and feedlotting of lambs after weaning. In order to determine the economic viability of such a system, certain production parameters need to be obtained for producing sheep intensively from cultivated pastures. Three studies were conducted to obtain the required production parameters; these were then followed by an economic evaluation incorporating the parameters obtained from the studies. All the studies were conducted at Kromme Rhee and Langgewens, two research farms of the Department of Agriculture in the Western Cape.
- Full Text:
- Date Issued: 2013
- Authors: Terblanche, Stefan
- Date: 2013
- Subjects: Pastures -- Irrigation -- South Africa , Sheep -- Productivity -- South Africa , Sheep -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10737 , http://hdl.handle.net/10948/d1020939
- Description: The South African sheep industry has experienced an increase in the price of meat and wool over the past several years. This has led to an interest in intensification of sheep production off planted pastures. Due to this phenomenon an economic viability study was done on the intensification of sheep production on cultivated pastures under irrigation. When intensifying sheep production, certain management practices need to be incorporated in order to enhance the output obtained per hectare and to overcome the higher input cost of production. Management practices that could be included are creep feeding, accelerated breeding and feedlotting of lambs after weaning. In order to determine the economic viability of such a system, certain production parameters need to be obtained for producing sheep intensively from cultivated pastures. Three studies were conducted to obtain the required production parameters; these were then followed by an economic evaluation incorporating the parameters obtained from the studies. All the studies were conducted at Kromme Rhee and Langgewens, two research farms of the Department of Agriculture in the Western Cape.
- Full Text:
- Date Issued: 2013
An enterprise architecture for environmental information management and reporting
- Authors: Van der Hoogen, Anthea
- Date: 2013
- Subjects: Business enterprises -- Information technology -- Management , Sustainable development reporting , Environmental reporting
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10499 , http://hdl.handle.net/10948/d1021040
- Description: Organisations globally are communicating their environmental sustainability impact to stakeholders by means of the widely used sustainability report. A key benefit of environmental sustainability reporting is that organisations can gain a positive reputation when these reports are presented to stakeholders. Organisations in South Africa are faced with many challenges regarding managing sustainability information and producing an environmental sustainability report. Two of the primary challenges are the many diverse standards for sustainability reporting and data quality issues. Information Technology (IT) can be used to support and improve the process of sustainability reporting but it is important to align the environmental sustainability strategies with the strategies of business and also with the IT strategy to avoid silos of information and reporting. Enterprise Architecture (EA) can be used to solve alignment problems since it supports business-IT alignment. EA is defined by the International Standards Organisation (ISO) as “The fundamental concepts or properties of a system in its environment embodied in its elements, relationships, and in the principles of its design and evolution”. It can be argued, therefore, that EA can be used to support environmental sustainability information management and the reporting process by means of its support of improved business-IT alignment and ultimately integrated systems. The main objective of this study is to investigate how EA can be used to support environmental information management (EIM) and reporting. A survey study of thirty one prominent South African organisations was undertaken in order to investigate the status of their EA adoption and environmental reporting and EIM processes. An EA for EIM Toolkit and a set of guidelines are proposed which can provide support for EIM through the use of EA. These guidelines were proposed based on best-practice for each of the three process levels of an organisation, namely, the strategic level, the operational level and the technological level. The toolkit and guidelines were derived from theory and the results of the industry survey were then validated by an in-depth analysis of a case study consisting of multiple cases with key employees of seven South African organisations which have proved to be successful at EA and EIM and reporting. The results of the case study show that the EA for EIM Toolkit and related guidelines can assist organisations to align their environmental sustainability strategies with their organisational and IT strategies.
- Full Text:
- Date Issued: 2013
- Authors: Van der Hoogen, Anthea
- Date: 2013
- Subjects: Business enterprises -- Information technology -- Management , Sustainable development reporting , Environmental reporting
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10499 , http://hdl.handle.net/10948/d1021040
- Description: Organisations globally are communicating their environmental sustainability impact to stakeholders by means of the widely used sustainability report. A key benefit of environmental sustainability reporting is that organisations can gain a positive reputation when these reports are presented to stakeholders. Organisations in South Africa are faced with many challenges regarding managing sustainability information and producing an environmental sustainability report. Two of the primary challenges are the many diverse standards for sustainability reporting and data quality issues. Information Technology (IT) can be used to support and improve the process of sustainability reporting but it is important to align the environmental sustainability strategies with the strategies of business and also with the IT strategy to avoid silos of information and reporting. Enterprise Architecture (EA) can be used to solve alignment problems since it supports business-IT alignment. EA is defined by the International Standards Organisation (ISO) as “The fundamental concepts or properties of a system in its environment embodied in its elements, relationships, and in the principles of its design and evolution”. It can be argued, therefore, that EA can be used to support environmental sustainability information management and the reporting process by means of its support of improved business-IT alignment and ultimately integrated systems. The main objective of this study is to investigate how EA can be used to support environmental information management (EIM) and reporting. A survey study of thirty one prominent South African organisations was undertaken in order to investigate the status of their EA adoption and environmental reporting and EIM processes. An EA for EIM Toolkit and a set of guidelines are proposed which can provide support for EIM through the use of EA. These guidelines were proposed based on best-practice for each of the three process levels of an organisation, namely, the strategic level, the operational level and the technological level. The toolkit and guidelines were derived from theory and the results of the industry survey were then validated by an in-depth analysis of a case study consisting of multiple cases with key employees of seven South African organisations which have proved to be successful at EA and EIM and reporting. The results of the case study show that the EA for EIM Toolkit and related guidelines can assist organisations to align their environmental sustainability strategies with their organisational and IT strategies.
- Full Text:
- Date Issued: 2013
An investigation of short-chain fatty acid profiles and influential gastrointenstinal microbiota associated with irritable bowel syndrome
- Authors: Theunissen, Reza
- Date: 2013
- Subjects: Fatty acids in human nutrition , Gastrointestinal system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10352 , http://hdl.handle.net/10948/d1020943
- Description: Microbiota are present in large numbers and as a diverse population within the gastrointestinal tract. There are approximately 400 different species of microbiota which may be beneficial, harmful or both, but each play an important role in the regulation and modulation of the hosts’ bowel processes (McOrist et al. 2008; Dethlefsen et al. 2008). Many of these colon microbiota allow for saccharolytic fermentation of non-digestible dietary fibres and carbohydrates into by-products and intermediates, followed by a subsequent conversion into short chain fatty acids (SCFAs) (mainly n-butyric acid, propionic acid and acetic acid) each of which play an important role in maintaining colon homeostasis (Topping & Clifton 2001). A balance of ‘good’ microbiota (e.g., Bacteroides spp./ Bifidobacteria spp.) and ‘bad’ microbiota (e.g., Veilonellae) and the optimal production of various SCFAs within the gut could possibly allow for proper functioning of the large intestine and assist in decreasing the onset of various colonic disorders such as Irritable Bowel Syndrome (IBS). The sample group for the study consists of male and female patients, with an average age of 40 to 50 years old, whom of which have been diagnosed with either constipation IBS (C-IBS) or diarrhoea IBS (D-IBS) via the Rome III criteria system for IBS diagnosis. DNA and SCFA extractions were optimised for human stool, colonic fluid and tissue biopsy sample obtained from the aforementioned patients. Optimization steps allowed for starting material with high analysis integrity. Different methods of microbiota analysis, such as ARISA, were investigated; however, real-time qPCR was selected as the best method to identify and quantify specific microbiota. Extracted SCFAs were separated via gas chromatography and identified and quantified via Mass Spectrometry. Significant changes in microbial content and SCFA profiles were found to be associated with healthy and IBS patients. Results obtained would however be influenced by external factors typical of clinical studies of this nature. This study allows for opportunities for future research into understanding IBS.
- Full Text:
- Date Issued: 2013
- Authors: Theunissen, Reza
- Date: 2013
- Subjects: Fatty acids in human nutrition , Gastrointestinal system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10352 , http://hdl.handle.net/10948/d1020943
- Description: Microbiota are present in large numbers and as a diverse population within the gastrointestinal tract. There are approximately 400 different species of microbiota which may be beneficial, harmful or both, but each play an important role in the regulation and modulation of the hosts’ bowel processes (McOrist et al. 2008; Dethlefsen et al. 2008). Many of these colon microbiota allow for saccharolytic fermentation of non-digestible dietary fibres and carbohydrates into by-products and intermediates, followed by a subsequent conversion into short chain fatty acids (SCFAs) (mainly n-butyric acid, propionic acid and acetic acid) each of which play an important role in maintaining colon homeostasis (Topping & Clifton 2001). A balance of ‘good’ microbiota (e.g., Bacteroides spp./ Bifidobacteria spp.) and ‘bad’ microbiota (e.g., Veilonellae) and the optimal production of various SCFAs within the gut could possibly allow for proper functioning of the large intestine and assist in decreasing the onset of various colonic disorders such as Irritable Bowel Syndrome (IBS). The sample group for the study consists of male and female patients, with an average age of 40 to 50 years old, whom of which have been diagnosed with either constipation IBS (C-IBS) or diarrhoea IBS (D-IBS) via the Rome III criteria system for IBS diagnosis. DNA and SCFA extractions were optimised for human stool, colonic fluid and tissue biopsy sample obtained from the aforementioned patients. Optimization steps allowed for starting material with high analysis integrity. Different methods of microbiota analysis, such as ARISA, were investigated; however, real-time qPCR was selected as the best method to identify and quantify specific microbiota. Extracted SCFAs were separated via gas chromatography and identified and quantified via Mass Spectrometry. Significant changes in microbial content and SCFA profiles were found to be associated with healthy and IBS patients. Results obtained would however be influenced by external factors typical of clinical studies of this nature. This study allows for opportunities for future research into understanding IBS.
- Full Text:
- Date Issued: 2013
Analysis of temporal and spatial variations in water storage by means of gravimetric and hydrologic methods in the region around the South African gravimetric observation station
- Authors: Mahed, Gaathier
- Date: 2013
- Subjects: Ground water -- South Africa , Geology -- South Africa , Hydrogeology -- South Africa , Water-supply -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6714 , vital:21137
- Description: This work examines the use of gravity data and its application to subsurface water reservoirs in the immediate vicinity of the South African Geodynamic Observatory, Sutherland (SAGOS), situated in a semi-arid region of the Karoo region of South Africa, and underlain by the Karoo sedimentary rocks intruded by dolerite dykes and sills. SAGOS houses the only supergravity metre (SG) in Africa, and this thesis sets out to test its use in monitoring groundwater dynamics using hydrological and gravity data. The main aim of this work is the application of the SG data, in conjunction with hydrological data, to better understand episodic recharge of subsurface reservoirs. The importance of water as a resource, globally and specifically the Karoo, is reviewed in conjunction with supply and demand of water. This is to contextualise the socio-economic, technical as well as policy issues related to water resource management. Applicable technologies for water resource management and efficient water use are highlighted and the application of gravity to hydrology is introduced, including satellite as well as ground based tools. In addition, arid zone hydrology as well as recharge and its mechanisms are analysed in order to better understand these processes when examined from gravity measurements. Issues related to understanding flow within the vadose zone as well as in secondary aquifers are examined, and gravity residuals and subsurface hydrology are highlighted. Thereafter, a conceptual groundwater flow modelof the study area is developed using multiple tools. First, the geology around SAGOS was mapped using SPOT 5 imagery and then ground truthed. Second, stable isotopes and water chemistry analysis was undertaken on water samples from selected boreholes. The results allude to preferential flow acting as the main mechanism for groundwater recharge. Follow-up pump-tests illustrate that fracture connectivity is greatest at close proximity to the dyke. Soil mapping, using aerial photography was also undertaken. Duplex soils, enriched with clay at depth, dominate the study area. Using in-situ infiltration tests, it is shown that the alluvium, which lines the river beds, has a higher hydraulic conductivity than the other soils, confirming that these streams act as preferential conduits for subsurface recharge. Precipitation events were correlated against gravity residuals at 4 wells, over different time periods. The results are examined using time series analyses. Gravity residuals from well SA BK07, over a period of 24 hours after the rainfall event, delineate instances of negative correlations, as well as strong positive correlations (of up to 0.9). On the whole however, correlations between gravity and groundwater at SA BK07 are variable and weak, and in conjunction with water level measurements and water chemistry, the data suggest that this well is located in a dynamic conduit (throughflow) and not in a permanent groundwater reservoir. By contrast, other wells show strong positive correlations between gravity residuals and water levels following episodic recharge events for a later time series. Correlations between the water levels and gravity residuals in wells SA BK04, SA BK05 and SA BK 01 are in excess of 0.7 for specific rainfall events. In summary, the results suggests that gravity is an excellent tool for measuring episodic groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater losses/gains in arid and semi-arid areas. Recommendations for future work are highlighted at the end; these include the possible use of hydrological modelling of reservoirs at various scales and then comparing these results to the SG as well as GOCE and GRACE satellites data, and then improving numerical modelling of the groundwater dynamics for sites like Sutherland and the surrounding arid Karoo region, where sparse water shortages, and potential pollution related to fracking for shale-gas, are likely to compete with established water needs for farming and human consumption. It is also suggested that the gravity modelling be examined to better understand site specific scenarios and thus aid in improving the processing of the gravity signal.
- Full Text:
- Date Issued: 2013
- Authors: Mahed, Gaathier
- Date: 2013
- Subjects: Ground water -- South Africa , Geology -- South Africa , Hydrogeology -- South Africa , Water-supply -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6714 , vital:21137
- Description: This work examines the use of gravity data and its application to subsurface water reservoirs in the immediate vicinity of the South African Geodynamic Observatory, Sutherland (SAGOS), situated in a semi-arid region of the Karoo region of South Africa, and underlain by the Karoo sedimentary rocks intruded by dolerite dykes and sills. SAGOS houses the only supergravity metre (SG) in Africa, and this thesis sets out to test its use in monitoring groundwater dynamics using hydrological and gravity data. The main aim of this work is the application of the SG data, in conjunction with hydrological data, to better understand episodic recharge of subsurface reservoirs. The importance of water as a resource, globally and specifically the Karoo, is reviewed in conjunction with supply and demand of water. This is to contextualise the socio-economic, technical as well as policy issues related to water resource management. Applicable technologies for water resource management and efficient water use are highlighted and the application of gravity to hydrology is introduced, including satellite as well as ground based tools. In addition, arid zone hydrology as well as recharge and its mechanisms are analysed in order to better understand these processes when examined from gravity measurements. Issues related to understanding flow within the vadose zone as well as in secondary aquifers are examined, and gravity residuals and subsurface hydrology are highlighted. Thereafter, a conceptual groundwater flow modelof the study area is developed using multiple tools. First, the geology around SAGOS was mapped using SPOT 5 imagery and then ground truthed. Second, stable isotopes and water chemistry analysis was undertaken on water samples from selected boreholes. The results allude to preferential flow acting as the main mechanism for groundwater recharge. Follow-up pump-tests illustrate that fracture connectivity is greatest at close proximity to the dyke. Soil mapping, using aerial photography was also undertaken. Duplex soils, enriched with clay at depth, dominate the study area. Using in-situ infiltration tests, it is shown that the alluvium, which lines the river beds, has a higher hydraulic conductivity than the other soils, confirming that these streams act as preferential conduits for subsurface recharge. Precipitation events were correlated against gravity residuals at 4 wells, over different time periods. The results are examined using time series analyses. Gravity residuals from well SA BK07, over a period of 24 hours after the rainfall event, delineate instances of negative correlations, as well as strong positive correlations (of up to 0.9). On the whole however, correlations between gravity and groundwater at SA BK07 are variable and weak, and in conjunction with water level measurements and water chemistry, the data suggest that this well is located in a dynamic conduit (throughflow) and not in a permanent groundwater reservoir. By contrast, other wells show strong positive correlations between gravity residuals and water levels following episodic recharge events for a later time series. Correlations between the water levels and gravity residuals in wells SA BK04, SA BK05 and SA BK 01 are in excess of 0.7 for specific rainfall events. In summary, the results suggests that gravity is an excellent tool for measuring episodic groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater losses/gains in arid and semi-arid areas. Recommendations for future work are highlighted at the end; these include the possible use of hydrological modelling of reservoirs at various scales and then comparing these results to the SG as well as GOCE and GRACE satellites data, and then improving numerical modelling of the groundwater dynamics for sites like Sutherland and the surrounding arid Karoo region, where sparse water shortages, and potential pollution related to fracking for shale-gas, are likely to compete with established water needs for farming and human consumption. It is also suggested that the gravity modelling be examined to better understand site specific scenarios and thus aid in improving the processing of the gravity signal.
- Full Text:
- Date Issued: 2013
Anchovy and Sardine in Algoa Bay and their relationship with response variables in two threatened avian predators
- Authors: Potter, Cara-Paige
- Date: 2013
- Subjects: Fishes -- Predators of -- South Africa -- Algoa Bay , Anchovies -- South Africa , Sardines -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10730 , http://hdl.handle.net/10948/d1021130
- Description: Huge populations of sardine and anchovy exist in the four major upwelling systems around the world. These fish are both important ecologically and economically. Pelagic fish dominate the mid trophic level and can exert both a top-down control of zooplankton and a bottom-up control on predatory fish and marine top predators. They also make up a substantial contribution of the world catches in seas around the world where they co-exist in upwelling areas. The fluctuations of sardine and anchovy are largely influenced by recruitment from the larval stage and by the physical environmental forces that determine the planktonic compositions upon which they feed. In southern Africa, the biology and behaviour of two threatened seabird species, African penguins (Spheniscus demersus) and Cape gannets (Morus capensis), are directly influenced by the availability of sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus). This study aimed to provide further insight into the fluctuations of sardine and anchovy in relation to the variability of environmental factors such as wind, sea surface temperature, rainfall and plankton abundance, focusing specifically on Algoa Bay in the Eastern Cape, South Africa. Algoa Bay is particularly important as it is home to the world’s largest African penguin colony and the world’s largest gannetry. Therefore, to further investigate the populations of these two seabird species, the fluctuations of their food source were studied.
- Full Text:
- Date Issued: 2013
- Authors: Potter, Cara-Paige
- Date: 2013
- Subjects: Fishes -- Predators of -- South Africa -- Algoa Bay , Anchovies -- South Africa , Sardines -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10730 , http://hdl.handle.net/10948/d1021130
- Description: Huge populations of sardine and anchovy exist in the four major upwelling systems around the world. These fish are both important ecologically and economically. Pelagic fish dominate the mid trophic level and can exert both a top-down control of zooplankton and a bottom-up control on predatory fish and marine top predators. They also make up a substantial contribution of the world catches in seas around the world where they co-exist in upwelling areas. The fluctuations of sardine and anchovy are largely influenced by recruitment from the larval stage and by the physical environmental forces that determine the planktonic compositions upon which they feed. In southern Africa, the biology and behaviour of two threatened seabird species, African penguins (Spheniscus demersus) and Cape gannets (Morus capensis), are directly influenced by the availability of sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus). This study aimed to provide further insight into the fluctuations of sardine and anchovy in relation to the variability of environmental factors such as wind, sea surface temperature, rainfall and plankton abundance, focusing specifically on Algoa Bay in the Eastern Cape, South Africa. Algoa Bay is particularly important as it is home to the world’s largest African penguin colony and the world’s largest gannetry. Therefore, to further investigate the populations of these two seabird species, the fluctuations of their food source were studied.
- Full Text:
- Date Issued: 2013
Assemblage dynamics of larval fishes associated with various shallow water nursery habitats in Algoa Bay, South Africa
- Authors: Pattrick, Paula
- Date: 2013
- Subjects: Spawning -- South Africa -- Algoa Bay , Fishes -- Larvae -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10727 , http://hdl.handle.net/10948/d1021042
- Description: The success of the larval stage in fishes plays a critical role in structuring adult fish populations. It is well understood that juveniles of many marine fish species are closely associated with nearshore and coastal habitats that serve as nursery areas while adult assemblages are more widely distributed. The larval phase however, particularly pertaining to nursery habitat use, remains poorly understood in South Africa. A mixed-method, larval and juvenile fish study was conducted in the warm-temperate shallow coastal waters of Algoa Bay, South Africa. Two years (2010 – 2012) of seasonal sampling at 27 stations at various habitat types revealed distinct spatio-temporal patterns in larval fish composition and abundance. In total, 164 species from 50 families were collected in the nearshore (<30 m), over reef and sand, in the surf zone and large estuarine habitats in Algoa Bay. Engraulidae dominated the larval fish catch in the nearshore (38.4 percent) and over the selected reef and sand habitats (37.8 percent). Cynoglossidae (28.1 percent) and Sparidae (8.4 percent) were the second and third most abundant fish families in the nearshore. In subtidal reef and sand habitats, Gobiidae (23.4 percent) and Clupeidae (9.2 percent) were the second and third most abundant families respectively. Sparidae dominated (71.4 percent) surf zones followed by Soleidae (10.8 percent) and Mugilidae (5.3 percent), while in the mouth area of two permanently open estuaries in Algoa Bay, Gobiidae (35.9 percent) Sparidae (30.1 percent) and Mugilidae (12.4 percent) dominated. Several species from the Blenniidae, Gobiesocidae, Gobiidae, Scorpaenidae and Tripterygiidae fish families complete their pelagic larval phase in the reef habitats in Algoa Bay. These reef habitats therefore serve as important nursery areas for the larvae of benthic species. The sand and nearshore habitats serve as nursery areas for Clupeidae and Engraulidae. Highest densities of Carangidae, Sciaenidae and Sparidae larvae were observed at the subtidal reef habitats indicating that this area is important for accumulation of the early developmental stages of these fishes. The nearshore serves as an important accumulation habitat for species in the Haemulidae and Soleidae families whose juveniles are known to recruit into estuarine nursery areas. The nearshore therefore is a specific area of presettlement buildup of larvae prior to settlement of larvae or juveniles in estuarine nursery areas. Cynoglossidae larvae are also using the nearshore as an accumulation area prior to settlement and recruitment into adult populations occurring in shallow water habitats. In the surf zone, not only are estuary-dependent fish species utilizing this habitat as a nursery area, but marinespecies whose adults are either associated with rocky shores or surf zones are similarly using these areas as nursery habitats. In addition, estuary-dependent fish species which spawn in the marine environment are actively recruiting into estuarine nursery areas on both tides. Active recruitment against the outgoing ebb tide flow was a conclusive finding in this study. These larvae and juveniles are actively swimming against the ebb tide in the shallower, slower-flowing marginal areas where current flow is reduced. Strong environmental gradients on multiple temporal and spatial scales occur in Algoa Bay. Seasonal patterns were evident in larval densities, richness and diversity. Peaks in density, richness and diversity occurred during spring and summer (September to February) associated with increasing water temperatures and a high productivity providing a good food environment for larval fishes. Thereafter densities declined steadily as a result of natural mortality, settlement or adult spawning activity, until autumn when numbers dropped suddenly as the surviving larvae moved to settlement habitats. The relationship between larval fish and environmental variables provides information useful to determine distributions. Therefore the Bay is particularly suited for modelling larval fish distributions. Using generalized linear models, larval fish density in the nearshore of Algoa Bay responded to different ocean features to varying degrees. Larval fish density responded positively to both upwelling and when warm water plumes, originating from an Agulhas Current meander, entered Algoa Bay. On subtidal reefs, habitat complexity played an important role in determining larval fish composition and diversity. The less structurally complex, reefassociated sand habitats, yielded higher species richness and diversity than the high and low profile reef habitats. Therefore, it is likely that the importance of less structurally complex habitats has been overlooked relative to other habitats in terms of their function for larval fishes. In the surf zone, wave period and wave height, which can be related to exposure, were the most significant environmental factors influencing larval fish assemblages. Greatest species diversity was observed in the surf zone habitats heavily influenced by wave action in the windward sector of Algoa Bay. The identification of spawning areas and the mapping of distributions of early developmental stages of fishes are important in providing data pertaining to the protection of these habitats. This is particularly relevant as a new marine protected area MPA)is planned for the eastern sector of Algoa Bay. Results from retrogressive plots indicate that the spawning locations of several species of coastal and pelagic fishes are occurring outside of the Bay, with the bay therefore serving as an accumulation area. Furthermore, distribution modelling results demonstrate that the early developmental stages of fishes in the shallow coastal habitats of Algoa Bay exhibit high spatial variability in their distributions. Results presented in this thesis help fill the knowledge gaps critical to the understanding of larval fish nursery areas of several economically and ecologically important fish species in Algoa Bay.
- Full Text:
- Date Issued: 2013
- Authors: Pattrick, Paula
- Date: 2013
- Subjects: Spawning -- South Africa -- Algoa Bay , Fishes -- Larvae -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10727 , http://hdl.handle.net/10948/d1021042
- Description: The success of the larval stage in fishes plays a critical role in structuring adult fish populations. It is well understood that juveniles of many marine fish species are closely associated with nearshore and coastal habitats that serve as nursery areas while adult assemblages are more widely distributed. The larval phase however, particularly pertaining to nursery habitat use, remains poorly understood in South Africa. A mixed-method, larval and juvenile fish study was conducted in the warm-temperate shallow coastal waters of Algoa Bay, South Africa. Two years (2010 – 2012) of seasonal sampling at 27 stations at various habitat types revealed distinct spatio-temporal patterns in larval fish composition and abundance. In total, 164 species from 50 families were collected in the nearshore (<30 m), over reef and sand, in the surf zone and large estuarine habitats in Algoa Bay. Engraulidae dominated the larval fish catch in the nearshore (38.4 percent) and over the selected reef and sand habitats (37.8 percent). Cynoglossidae (28.1 percent) and Sparidae (8.4 percent) were the second and third most abundant fish families in the nearshore. In subtidal reef and sand habitats, Gobiidae (23.4 percent) and Clupeidae (9.2 percent) were the second and third most abundant families respectively. Sparidae dominated (71.4 percent) surf zones followed by Soleidae (10.8 percent) and Mugilidae (5.3 percent), while in the mouth area of two permanently open estuaries in Algoa Bay, Gobiidae (35.9 percent) Sparidae (30.1 percent) and Mugilidae (12.4 percent) dominated. Several species from the Blenniidae, Gobiesocidae, Gobiidae, Scorpaenidae and Tripterygiidae fish families complete their pelagic larval phase in the reef habitats in Algoa Bay. These reef habitats therefore serve as important nursery areas for the larvae of benthic species. The sand and nearshore habitats serve as nursery areas for Clupeidae and Engraulidae. Highest densities of Carangidae, Sciaenidae and Sparidae larvae were observed at the subtidal reef habitats indicating that this area is important for accumulation of the early developmental stages of these fishes. The nearshore serves as an important accumulation habitat for species in the Haemulidae and Soleidae families whose juveniles are known to recruit into estuarine nursery areas. The nearshore therefore is a specific area of presettlement buildup of larvae prior to settlement of larvae or juveniles in estuarine nursery areas. Cynoglossidae larvae are also using the nearshore as an accumulation area prior to settlement and recruitment into adult populations occurring in shallow water habitats. In the surf zone, not only are estuary-dependent fish species utilizing this habitat as a nursery area, but marinespecies whose adults are either associated with rocky shores or surf zones are similarly using these areas as nursery habitats. In addition, estuary-dependent fish species which spawn in the marine environment are actively recruiting into estuarine nursery areas on both tides. Active recruitment against the outgoing ebb tide flow was a conclusive finding in this study. These larvae and juveniles are actively swimming against the ebb tide in the shallower, slower-flowing marginal areas where current flow is reduced. Strong environmental gradients on multiple temporal and spatial scales occur in Algoa Bay. Seasonal patterns were evident in larval densities, richness and diversity. Peaks in density, richness and diversity occurred during spring and summer (September to February) associated with increasing water temperatures and a high productivity providing a good food environment for larval fishes. Thereafter densities declined steadily as a result of natural mortality, settlement or adult spawning activity, until autumn when numbers dropped suddenly as the surviving larvae moved to settlement habitats. The relationship between larval fish and environmental variables provides information useful to determine distributions. Therefore the Bay is particularly suited for modelling larval fish distributions. Using generalized linear models, larval fish density in the nearshore of Algoa Bay responded to different ocean features to varying degrees. Larval fish density responded positively to both upwelling and when warm water plumes, originating from an Agulhas Current meander, entered Algoa Bay. On subtidal reefs, habitat complexity played an important role in determining larval fish composition and diversity. The less structurally complex, reefassociated sand habitats, yielded higher species richness and diversity than the high and low profile reef habitats. Therefore, it is likely that the importance of less structurally complex habitats has been overlooked relative to other habitats in terms of their function for larval fishes. In the surf zone, wave period and wave height, which can be related to exposure, were the most significant environmental factors influencing larval fish assemblages. Greatest species diversity was observed in the surf zone habitats heavily influenced by wave action in the windward sector of Algoa Bay. The identification of spawning areas and the mapping of distributions of early developmental stages of fishes are important in providing data pertaining to the protection of these habitats. This is particularly relevant as a new marine protected area MPA)is planned for the eastern sector of Algoa Bay. Results from retrogressive plots indicate that the spawning locations of several species of coastal and pelagic fishes are occurring outside of the Bay, with the bay therefore serving as an accumulation area. Furthermore, distribution modelling results demonstrate that the early developmental stages of fishes in the shallow coastal habitats of Algoa Bay exhibit high spatial variability in their distributions. Results presented in this thesis help fill the knowledge gaps critical to the understanding of larval fish nursery areas of several economically and ecologically important fish species in Algoa Bay.
- Full Text:
- Date Issued: 2013
Assessing soil carbon and carbon dioxide effluxes under different vegetation cover conditions in the Eastern Cape Province, South Africa
- Authors: Zengeni, Rebecca
- Date: 2013
- Subjects: Soils -- Carbon content -- Measurement , Carbon dioxide mitigation -- South Africa , Greenhouse gas mitigation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10665 , http://hdl.handle.net/10948/d1018676
- Description: Albany thicket is prevalent in the Eastern Cape Province of South Africa. Its spread has diminished through overgrazing and heavy browsing by animals, land clearance and urban expansion. The result is highly degraded land characterized by invasion of alien species. There is a wealth of documented evidence on the high carbon sequestration ability of thicket biome, but not much has been done to assess its effect on carbon dioxide emissions from the soil. Given that the concentration of atmospheric greenhouse gases has been constantly rising since the industrial era, it is imperative to assess the influence of thicket biome as a source or sink of these gases. There is evidence of shifts in the climate in southern Africa as reflected by changes in rainfall patterns, increased temperatures, recurrent droughts and fires. As such, the historical rainfall variability in an Albany thicket region and its interaction with the temporal land use / cover changes was studied. This served to give some background information about the study area for more detailed study on C and carbon dioxide effluxes in thicket vegetation under different levels of degradation. This study thus aimed to determine the influence of thicket vegetation at various levels of degradation on soil carbon and carbon dioxide fluxes. The impact of plant photosynthetic pathway on soil C residence time and gas effluxes were analysed to elucidate on the land-use and cover patterns occurring in the area. All this was done to shed some light on the role of soil and thicket vegetation on carbon dioxide emissions and C storage in the spectrum of a shifting climate. The main area of research was Amakhala reserve in an Albany thicket in Eastern Cape Province; and it concentrated on three land cover types namely intact thicket, degraded thicket and grassland. The objectives mentioned above were achieved by assessing historical rainfall variability from 1970 to 2010 through trend and time series analysis at nine rainfall stations located at Amakhala reserve, Grahamstown, Bathurst, Port Alfred, Uitenhage and Port Elizabeth. The land use changes that have occurred in the Albany thicket region covering Amakhala reserve, Grahamstown, Bathurst and Port Alfred were also assessed for 1989, 1999 and 2009 through satellite image analysis with Idrisi Andes GIS software; then their interaction with rainfall variability were determined. To elucidate on the vegetation species composition and land use / cover changes that have occurred in the study area, plant biomass as well carbon (C) and nitrogen (N) isotope measurements were done. Plant biomass was assessed for the dominant species through use of pre-existing allometric equations that required data on plant basal diameter, canopy area, stem numbers and height. The plant carbon was then estimated through use of a conversion factor of 0.48 on above-ground biomass, while soil organic C was determined through the modified Walkely - Black method. Carbon and N isotope ratios were determined from the foliar material of three replicate samples of dominant plant species then analyzed through mass spectrometry. Soil carbon dioxide effluxes were then monitored in each of the intact thicket (IT), degraded thicket (DT) and grassland (G) over a 10 month period; by measuring the net carbon dioxide exchange rate (NCER) through the dynamic chamber method. An automated carbon dioxide exchange analyzer, coupled to a soil temperature probe and photosynthetic active radiation (PAR) sensor was used; with NCER measurements taken every 20-30 days. Soil temperature, moisture, penetration resistance and PAR readings were taken during each assay and later used to interpret the NCER. Results showed that long term variability in annual rainfall had a declining trend at Grahamstown (r = -0.59), Uitenhage and Bathurst stations (r = -0.32 at both stations), but was not significant at Amakhala, Port Alfred and Port Elizabeth stations. Most reductions in rainfall occurred in the 1980s and 1990s with the autumn, winter and summer rainfalls, the daily rainfall index and the daily rainfall subclasses of 10 mm and above showing a similar trend. The land use change detection gave a significant increase in proportion of degraded and transformed (moderately degraded) land between 1989 and 2009 with most of the increases occurring from 1989 to 1999, while farmland area decreased by 1.8 percent over the years. Thus the Albany region had over 30 percent of its land occupied by transformed vegetation, with heavy browsing and uncontrolled grazing being attributed to the destruction of pristine vegetation. Land-use change to game ranching and goat pastoralism was attributed to the reduction in farmland. Rainfall variability – land use change linkages were most significant in 1999 that recorded the least rainfall and had the lowest mean, maximum and sum of the NDVI. Grahamstown had the most significant rainfall-NDVI trends as it had the lowest NDVIs in 1999 when rainfall was lowest, the highest NDVI in 1989 when rainfall was highest and moderate NDVIs in 2009 when rainfall was moderate. Vegetation at the IT was characterized by a dense thicket with diverse growth forms of canopy trees, woody shrubs, succulent shrubs and ephemerals which mostly had the C3 type of pathway. This was in contrast with the IT soil isotopy that showed more positive C isotope ratios, indicating a switch between C3 and CAM photosynthesis in original vegetation. Most of the canopy trees had disappeared in the DT to be replaced by herbs, shrubs and grasses. As such, there was a huge difference in isotope ratios between DT plants and soils with the plants having mostly C3 metabolism while the soil showed a predominance of CAM plants in previous vegetation, indicating significant changes in land cover. The G site mostly comprised the grasses Themeda triandra and Panicum maximum and a few herbs. It maintained a dominance of C4 metabolism in both plants and soils showing very little change in species composition over the years. Because of the higher species diversity at IT, its soil organic C was quite high reaching levels of 3.4 percent (i.e. 3.4 t C / ha) in the top 10 cm then decreasing with depth (p < 0.001); but was moderate at DT (1.1-1.3 percent) and very low at G ( 0.5 percent C) (p < 0.001). In the same manner above-ground biomass was highest at IT i.e. 330 000 kg/ha; but was only 22 000 kg/ha in DT and as low as 6 700 kg/ha in G vegetation. High biomass at IT was mostly attributed to the succulent shrub Portulacaria afra and the canopy trees Euclea undulate, Rhus longispina and Schotia afra. This above-ground biomass translated to biomass C amounts of 158 000 kg/ha at IT, 10 600 kg/ha at DT and 3 200 kg/ha at G. Thus the IT had the highest while G the least and DT moderate plant and soil C sequestration ability. In all, the conversion of IT to DT led to a net loss of 147 000 Kg of biomass C / ha and 12 000kg less organic C / ha of land. Soil carbon dioxide effluxes were however variable between seasons as they were affected by differences in soil properties and seasonal weather patterns. High soil moisture levels (up to 16 percent gravimetric moisture) resulted in reduced soil penetration resistance (1 to 4 Kg/cm2) which raised effluxes at G and DT sites (up to 1.2 μmols m-2 sec-1) in winter, while low moisture (2 percent) resulted in hard dry soil (14 Kgm-2 penetration resistance) with suppressed CO2 effluxes in spring (0.2 μmols m-2 sec-1) especially in DT and G soils. Rising temperature generally caused accelerated gas emissions but only when moisture was not limiting (as was the case in IT). Thus the high summer temperatures (up to 40oC) gave lower effluxes especially in DT and G (< 1 μm-2sec-1) due to limited moisture supply (< 10 percent); while the Autumn period that had very high temperature (up to 48 oC) and good moisture (up to 16 percent) saw accelerated soil CO2 emissions (averaging 2 μmols m-2 sec-1) from all cover types. The high biomass and litter fall at IT served as ready substrate for soil respiration as long as moisture was not limiting and temperatures were favourable, while reduced cover at DT resulted in poor moisture conservation and creation of hard dry soils in spring and summer with reduced respiration. It was concluded that the DT had high CO2 effluxes in winter and reduced emissions in summer; while the opposite was true for the IT. All the cover types had minimal CO2 effluxes in spring and accelerated emissions in autumn. The grassland on the other hand was a fairly moderate source or sink of CO2 in most seasons compared with the other two covers. It was observed that an environment of good moisture and low-moderate temperatures (such as that in the winter) minimises effluxes while maintaining good plant productivity. It was concluded that thicket vegetation is a good sink of carbon that should be preserved in its natural condition to optimize its carbon sequestration potential. All three land covers served as sources or sinks of CO2 depending on soil and seasonal conditions. Thus high moisture and low penetration resistance generally increased effluxes of thicket ecosystems. The effect of increasing temperature on effluxes was only significant when moisture was not limiting. Conditions of good moisture and low-moderate temperatures gave reasonable amounts of effluxes while maintaining good plant productivity. Though the dry soil conditions significantly reduced effluxes in all land covers; they were not desirable since they decreased plant productivity and ultimately its C sequestration potential. Moreover, prolonged dry conditions only serve to exacerbate recovery of thicket plants as they increase mortality of canopy species in degraded and transformed areas in comparison with intact thicket.
- Full Text:
- Date Issued: 2013
- Authors: Zengeni, Rebecca
- Date: 2013
- Subjects: Soils -- Carbon content -- Measurement , Carbon dioxide mitigation -- South Africa , Greenhouse gas mitigation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10665 , http://hdl.handle.net/10948/d1018676
- Description: Albany thicket is prevalent in the Eastern Cape Province of South Africa. Its spread has diminished through overgrazing and heavy browsing by animals, land clearance and urban expansion. The result is highly degraded land characterized by invasion of alien species. There is a wealth of documented evidence on the high carbon sequestration ability of thicket biome, but not much has been done to assess its effect on carbon dioxide emissions from the soil. Given that the concentration of atmospheric greenhouse gases has been constantly rising since the industrial era, it is imperative to assess the influence of thicket biome as a source or sink of these gases. There is evidence of shifts in the climate in southern Africa as reflected by changes in rainfall patterns, increased temperatures, recurrent droughts and fires. As such, the historical rainfall variability in an Albany thicket region and its interaction with the temporal land use / cover changes was studied. This served to give some background information about the study area for more detailed study on C and carbon dioxide effluxes in thicket vegetation under different levels of degradation. This study thus aimed to determine the influence of thicket vegetation at various levels of degradation on soil carbon and carbon dioxide fluxes. The impact of plant photosynthetic pathway on soil C residence time and gas effluxes were analysed to elucidate on the land-use and cover patterns occurring in the area. All this was done to shed some light on the role of soil and thicket vegetation on carbon dioxide emissions and C storage in the spectrum of a shifting climate. The main area of research was Amakhala reserve in an Albany thicket in Eastern Cape Province; and it concentrated on three land cover types namely intact thicket, degraded thicket and grassland. The objectives mentioned above were achieved by assessing historical rainfall variability from 1970 to 2010 through trend and time series analysis at nine rainfall stations located at Amakhala reserve, Grahamstown, Bathurst, Port Alfred, Uitenhage and Port Elizabeth. The land use changes that have occurred in the Albany thicket region covering Amakhala reserve, Grahamstown, Bathurst and Port Alfred were also assessed for 1989, 1999 and 2009 through satellite image analysis with Idrisi Andes GIS software; then their interaction with rainfall variability were determined. To elucidate on the vegetation species composition and land use / cover changes that have occurred in the study area, plant biomass as well carbon (C) and nitrogen (N) isotope measurements were done. Plant biomass was assessed for the dominant species through use of pre-existing allometric equations that required data on plant basal diameter, canopy area, stem numbers and height. The plant carbon was then estimated through use of a conversion factor of 0.48 on above-ground biomass, while soil organic C was determined through the modified Walkely - Black method. Carbon and N isotope ratios were determined from the foliar material of three replicate samples of dominant plant species then analyzed through mass spectrometry. Soil carbon dioxide effluxes were then monitored in each of the intact thicket (IT), degraded thicket (DT) and grassland (G) over a 10 month period; by measuring the net carbon dioxide exchange rate (NCER) through the dynamic chamber method. An automated carbon dioxide exchange analyzer, coupled to a soil temperature probe and photosynthetic active radiation (PAR) sensor was used; with NCER measurements taken every 20-30 days. Soil temperature, moisture, penetration resistance and PAR readings were taken during each assay and later used to interpret the NCER. Results showed that long term variability in annual rainfall had a declining trend at Grahamstown (r = -0.59), Uitenhage and Bathurst stations (r = -0.32 at both stations), but was not significant at Amakhala, Port Alfred and Port Elizabeth stations. Most reductions in rainfall occurred in the 1980s and 1990s with the autumn, winter and summer rainfalls, the daily rainfall index and the daily rainfall subclasses of 10 mm and above showing a similar trend. The land use change detection gave a significant increase in proportion of degraded and transformed (moderately degraded) land between 1989 and 2009 with most of the increases occurring from 1989 to 1999, while farmland area decreased by 1.8 percent over the years. Thus the Albany region had over 30 percent of its land occupied by transformed vegetation, with heavy browsing and uncontrolled grazing being attributed to the destruction of pristine vegetation. Land-use change to game ranching and goat pastoralism was attributed to the reduction in farmland. Rainfall variability – land use change linkages were most significant in 1999 that recorded the least rainfall and had the lowest mean, maximum and sum of the NDVI. Grahamstown had the most significant rainfall-NDVI trends as it had the lowest NDVIs in 1999 when rainfall was lowest, the highest NDVI in 1989 when rainfall was highest and moderate NDVIs in 2009 when rainfall was moderate. Vegetation at the IT was characterized by a dense thicket with diverse growth forms of canopy trees, woody shrubs, succulent shrubs and ephemerals which mostly had the C3 type of pathway. This was in contrast with the IT soil isotopy that showed more positive C isotope ratios, indicating a switch between C3 and CAM photosynthesis in original vegetation. Most of the canopy trees had disappeared in the DT to be replaced by herbs, shrubs and grasses. As such, there was a huge difference in isotope ratios between DT plants and soils with the plants having mostly C3 metabolism while the soil showed a predominance of CAM plants in previous vegetation, indicating significant changes in land cover. The G site mostly comprised the grasses Themeda triandra and Panicum maximum and a few herbs. It maintained a dominance of C4 metabolism in both plants and soils showing very little change in species composition over the years. Because of the higher species diversity at IT, its soil organic C was quite high reaching levels of 3.4 percent (i.e. 3.4 t C / ha) in the top 10 cm then decreasing with depth (p < 0.001); but was moderate at DT (1.1-1.3 percent) and very low at G ( 0.5 percent C) (p < 0.001). In the same manner above-ground biomass was highest at IT i.e. 330 000 kg/ha; but was only 22 000 kg/ha in DT and as low as 6 700 kg/ha in G vegetation. High biomass at IT was mostly attributed to the succulent shrub Portulacaria afra and the canopy trees Euclea undulate, Rhus longispina and Schotia afra. This above-ground biomass translated to biomass C amounts of 158 000 kg/ha at IT, 10 600 kg/ha at DT and 3 200 kg/ha at G. Thus the IT had the highest while G the least and DT moderate plant and soil C sequestration ability. In all, the conversion of IT to DT led to a net loss of 147 000 Kg of biomass C / ha and 12 000kg less organic C / ha of land. Soil carbon dioxide effluxes were however variable between seasons as they were affected by differences in soil properties and seasonal weather patterns. High soil moisture levels (up to 16 percent gravimetric moisture) resulted in reduced soil penetration resistance (1 to 4 Kg/cm2) which raised effluxes at G and DT sites (up to 1.2 μmols m-2 sec-1) in winter, while low moisture (2 percent) resulted in hard dry soil (14 Kgm-2 penetration resistance) with suppressed CO2 effluxes in spring (0.2 μmols m-2 sec-1) especially in DT and G soils. Rising temperature generally caused accelerated gas emissions but only when moisture was not limiting (as was the case in IT). Thus the high summer temperatures (up to 40oC) gave lower effluxes especially in DT and G (< 1 μm-2sec-1) due to limited moisture supply (< 10 percent); while the Autumn period that had very high temperature (up to 48 oC) and good moisture (up to 16 percent) saw accelerated soil CO2 emissions (averaging 2 μmols m-2 sec-1) from all cover types. The high biomass and litter fall at IT served as ready substrate for soil respiration as long as moisture was not limiting and temperatures were favourable, while reduced cover at DT resulted in poor moisture conservation and creation of hard dry soils in spring and summer with reduced respiration. It was concluded that the DT had high CO2 effluxes in winter and reduced emissions in summer; while the opposite was true for the IT. All the cover types had minimal CO2 effluxes in spring and accelerated emissions in autumn. The grassland on the other hand was a fairly moderate source or sink of CO2 in most seasons compared with the other two covers. It was observed that an environment of good moisture and low-moderate temperatures (such as that in the winter) minimises effluxes while maintaining good plant productivity. It was concluded that thicket vegetation is a good sink of carbon that should be preserved in its natural condition to optimize its carbon sequestration potential. All three land covers served as sources or sinks of CO2 depending on soil and seasonal conditions. Thus high moisture and low penetration resistance generally increased effluxes of thicket ecosystems. The effect of increasing temperature on effluxes was only significant when moisture was not limiting. Conditions of good moisture and low-moderate temperatures gave reasonable amounts of effluxes while maintaining good plant productivity. Though the dry soil conditions significantly reduced effluxes in all land covers; they were not desirable since they decreased plant productivity and ultimately its C sequestration potential. Moreover, prolonged dry conditions only serve to exacerbate recovery of thicket plants as they increase mortality of canopy species in degraded and transformed areas in comparison with intact thicket.
- Full Text:
- Date Issued: 2013
Atmospheric pressure metal-organic vapour phase epitaxial growth of InAs/GaSb strained layer superlattices
- Authors: Miya, Senzo Simo
- Date: 2013
- Subjects: Gallium arsenide semiconductors , Organometallic compounds , Compound semiconductors , Metal organic chemical vapor deposition , Superlattices as materials , Epitaxy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10557 , http://hdl.handle.net/10948/d1020866
- Description: The importance of infrared (IR) technology (for detection in the 3-5 μm and 8-14 μm atmospheric windows) has spread from military applications to civilian applications since World War II. The commercial IR detector market in these wavelength ranges is dominated by mercury cadmium telluride (MCT) alloys. The use of these alloys has, however, been faced with technological difficulties. One of the materials that have been tipped to be suitable to replace MCT is InAs/InxGa1-xSb strained layer superlattices (SLS’s). Atmospheric pressure metal-organic vapour phase epitaxy (MOVPE) has been used to grow InAs/GaSb strained layer superlattices (SLS’s) at 510 °C in this study. This is a starting point towards the development of MOVPE InAs/InxGa1-xSb SLS’s using the same system. Before the SLS’s could be attempted, the growth parameters for GaSb were optimised. Growth parameters for InAs were taken from reports on previous studies conducted using the same reactor. Initially, trimethylgallium, a source that has been used extensively in the same growth system for the growth of GaSb and InxGa1-xSb was intended to be used for gallium species. The high growth rates yielded by this source were too large for the growth of SLS structures, however. Thus, triethylgallium (rarely used for atmospheric pressure MOVPE) was utilized. GaSb layers (between 1 and 2 μm thick) were grown at two different temperatures (550 °C and 510 °C) with a varying V/III ratio. A V/III ratio of 1.5 was found to be optimal at 550 °C. However, the low incorporation efficiency of indium into GaSb at this temperature was inadequate to obtain InxGa1-xSb with an indium mole fraction (x) of around 0.3, which had previously been reported to be optimal for the performance of InAs/InxGa1-xSb SLS’s, due to the maximum splitting of the valence mini bands for this composition. The growth temperature was thus lowered to 510 °C. This resulted in an increase in the optimum V/III ratio to 1.75 for GaSb and yielded much higher incorporation efficiencies of indium in InxGa1-xSb. However, this lower growth temperature also produced poorer surface morphologies for both the binary and ternary layers, due to the reduced surface diffusion of the adsorbed species. An interface control study during the growth of InAs/GaSb SLS’s was subsequently conducted, by investigating the influence of different gas switching sequences on the interface type and quality. It was noted that the growth of SLS’s without any growth interruptions at the interfaces leads to tensile strained SLS’s (GaAs-like interfaces) with a rather large lattice mismatch. A 5 second flow of TMSb over the InAs surface and a flow of H2 over GaSb surface yielded compressively strained SLS’s. Flowing TMIn for 1 second and following by a flow of TMSb for 4 seconds over the GaSb surface, while flowing H2 for 5 seconds over the InAs surface, resulted in SLS’s with GaAs-like interfacial layers and a reduced lattice mismatch. Temperature gradients across the surface of the susceptor led to SLS’s with different structural quality. High resolution x-ray diffraction (HRXRD) was used to determine the thicknesses as well as the type of interfacial layers. The physical parameters of the SLS’s obtained from simulating the HRXRD spectra were comparable to the parameters obtained from cross sectional transmission electron microscopy (XTEM) images. The thicknesses of the layers and the interface type played a major role in determining the cut-off wavelength of the SLS’s.
- Full Text:
- Date Issued: 2013
- Authors: Miya, Senzo Simo
- Date: 2013
- Subjects: Gallium arsenide semiconductors , Organometallic compounds , Compound semiconductors , Metal organic chemical vapor deposition , Superlattices as materials , Epitaxy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10557 , http://hdl.handle.net/10948/d1020866
- Description: The importance of infrared (IR) technology (for detection in the 3-5 μm and 8-14 μm atmospheric windows) has spread from military applications to civilian applications since World War II. The commercial IR detector market in these wavelength ranges is dominated by mercury cadmium telluride (MCT) alloys. The use of these alloys has, however, been faced with technological difficulties. One of the materials that have been tipped to be suitable to replace MCT is InAs/InxGa1-xSb strained layer superlattices (SLS’s). Atmospheric pressure metal-organic vapour phase epitaxy (MOVPE) has been used to grow InAs/GaSb strained layer superlattices (SLS’s) at 510 °C in this study. This is a starting point towards the development of MOVPE InAs/InxGa1-xSb SLS’s using the same system. Before the SLS’s could be attempted, the growth parameters for GaSb were optimised. Growth parameters for InAs were taken from reports on previous studies conducted using the same reactor. Initially, trimethylgallium, a source that has been used extensively in the same growth system for the growth of GaSb and InxGa1-xSb was intended to be used for gallium species. The high growth rates yielded by this source were too large for the growth of SLS structures, however. Thus, triethylgallium (rarely used for atmospheric pressure MOVPE) was utilized. GaSb layers (between 1 and 2 μm thick) were grown at two different temperatures (550 °C and 510 °C) with a varying V/III ratio. A V/III ratio of 1.5 was found to be optimal at 550 °C. However, the low incorporation efficiency of indium into GaSb at this temperature was inadequate to obtain InxGa1-xSb with an indium mole fraction (x) of around 0.3, which had previously been reported to be optimal for the performance of InAs/InxGa1-xSb SLS’s, due to the maximum splitting of the valence mini bands for this composition. The growth temperature was thus lowered to 510 °C. This resulted in an increase in the optimum V/III ratio to 1.75 for GaSb and yielded much higher incorporation efficiencies of indium in InxGa1-xSb. However, this lower growth temperature also produced poorer surface morphologies for both the binary and ternary layers, due to the reduced surface diffusion of the adsorbed species. An interface control study during the growth of InAs/GaSb SLS’s was subsequently conducted, by investigating the influence of different gas switching sequences on the interface type and quality. It was noted that the growth of SLS’s without any growth interruptions at the interfaces leads to tensile strained SLS’s (GaAs-like interfaces) with a rather large lattice mismatch. A 5 second flow of TMSb over the InAs surface and a flow of H2 over GaSb surface yielded compressively strained SLS’s. Flowing TMIn for 1 second and following by a flow of TMSb for 4 seconds over the GaSb surface, while flowing H2 for 5 seconds over the InAs surface, resulted in SLS’s with GaAs-like interfacial layers and a reduced lattice mismatch. Temperature gradients across the surface of the susceptor led to SLS’s with different structural quality. High resolution x-ray diffraction (HRXRD) was used to determine the thicknesses as well as the type of interfacial layers. The physical parameters of the SLS’s obtained from simulating the HRXRD spectra were comparable to the parameters obtained from cross sectional transmission electron microscopy (XTEM) images. The thicknesses of the layers and the interface type played a major role in determining the cut-off wavelength of the SLS’s.
- Full Text:
- Date Issued: 2013
Characterisation and biotic classification of Eastern Cape mixed substrate shores
- Authors: Garner, Cornelia Johanna
- Date: 2013
- Subjects: Coastal sediments -- South Africa -- Eastern Cape , Coastal biodiversity --- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10641 , http://hdl.handle.net/10948/d1020825
- Description: A significant proportion of the South African coastline is composed of both soft (mostly sand) and hard (mostly bedrock) substrata, i.e. “mixed”. This study described and classified macrobenthic assemblages of 20 Eastern Cape mixed substrate shores that differed in shore topography and the extent and position of intertidal rock and sand. A stratified random approach was used. Species richness, composition, abundance and environmental variables were determined. Commonly used beach indices were calculated. A total of 78 macrofaunal and 172 macroalgal species from rock substrate assemblages and 205 macrofauna species from sediment were recorded. Total species richness and richness per substratum exceeded that of sandy beaches devoid of rock and rocky shores with no sand. Rhodophyta were the most diverse and abundant algae, dominating all low-elevation rock surfaces as midlittoral and infralittoral turfs. Chlorophyta diversity was higher than at rocky shores, contributing more to cover-abundance at study sites and in microhabitats with an increased sand load. Sessile macrofauna species richness and abundance was lower than that of rocky shores. Polychaetes and crustaceans were the most diverse and abundant beach infauna. Species richness of both substrates declined from the low shore towards the high shore, but abundance trends varied substantially. The presence and extent of an intertidal biotope/subzone at either substrate depended on substrate availability.The supralittoral fringe in both substrate types was most often affected. Zonal overlap was evident on rock substrate: assemblages of raised midlittoral rock surfaces were enriched by species from lower surfaces sometimes leading to elimination of character taxa. Classification and ordination identified three potential mixed substrate shore biotic types: Biotic type A (Jania-Corallina- Polysiphonia turf) was characterised by robustly-textured algal turfs, a lowered predominance and diversity of polychaetes and an increase in crustacean abundance and diversity in sediment. Biotic type B (Polysiphonia-Tayloriella-Caulacanthus turf) had intermediately and biotic type C (Arthrocardia-Laurencia turf) the most sheltered eulittoral zones and beaches. DCCA identified the major environmental parameters affecting the macrobiota as: the level of wave energy, geological control of waves by hard substrate, sediment grain size and sediment inundation. A strong cross-shore wave attenuation results in sheltered sediments and midshore rock surfaces. Beach macrofauna were highly variable and diverse, which directly opposes previous perceptions about the sediment-bound biota of mixed substrate shores. The hierarchical cluster analysis produced a biotic classification of mixed substrate shores that was indicative of a biotic response to the total effects of leading environmental parameters. Macrobenthos of rock surfaces and sediment therefore showed potential to be used as an alternative or complementary to physical characteristics in classifying mixed substrate shores.
- Full Text:
- Date Issued: 2013
- Authors: Garner, Cornelia Johanna
- Date: 2013
- Subjects: Coastal sediments -- South Africa -- Eastern Cape , Coastal biodiversity --- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10641 , http://hdl.handle.net/10948/d1020825
- Description: A significant proportion of the South African coastline is composed of both soft (mostly sand) and hard (mostly bedrock) substrata, i.e. “mixed”. This study described and classified macrobenthic assemblages of 20 Eastern Cape mixed substrate shores that differed in shore topography and the extent and position of intertidal rock and sand. A stratified random approach was used. Species richness, composition, abundance and environmental variables were determined. Commonly used beach indices were calculated. A total of 78 macrofaunal and 172 macroalgal species from rock substrate assemblages and 205 macrofauna species from sediment were recorded. Total species richness and richness per substratum exceeded that of sandy beaches devoid of rock and rocky shores with no sand. Rhodophyta were the most diverse and abundant algae, dominating all low-elevation rock surfaces as midlittoral and infralittoral turfs. Chlorophyta diversity was higher than at rocky shores, contributing more to cover-abundance at study sites and in microhabitats with an increased sand load. Sessile macrofauna species richness and abundance was lower than that of rocky shores. Polychaetes and crustaceans were the most diverse and abundant beach infauna. Species richness of both substrates declined from the low shore towards the high shore, but abundance trends varied substantially. The presence and extent of an intertidal biotope/subzone at either substrate depended on substrate availability.The supralittoral fringe in both substrate types was most often affected. Zonal overlap was evident on rock substrate: assemblages of raised midlittoral rock surfaces were enriched by species from lower surfaces sometimes leading to elimination of character taxa. Classification and ordination identified three potential mixed substrate shore biotic types: Biotic type A (Jania-Corallina- Polysiphonia turf) was characterised by robustly-textured algal turfs, a lowered predominance and diversity of polychaetes and an increase in crustacean abundance and diversity in sediment. Biotic type B (Polysiphonia-Tayloriella-Caulacanthus turf) had intermediately and biotic type C (Arthrocardia-Laurencia turf) the most sheltered eulittoral zones and beaches. DCCA identified the major environmental parameters affecting the macrobiota as: the level of wave energy, geological control of waves by hard substrate, sediment grain size and sediment inundation. A strong cross-shore wave attenuation results in sheltered sediments and midshore rock surfaces. Beach macrofauna were highly variable and diverse, which directly opposes previous perceptions about the sediment-bound biota of mixed substrate shores. The hierarchical cluster analysis produced a biotic classification of mixed substrate shores that was indicative of a biotic response to the total effects of leading environmental parameters. Macrobenthos of rock surfaces and sediment therefore showed potential to be used as an alternative or complementary to physical characteristics in classifying mixed substrate shores.
- Full Text:
- Date Issued: 2013
Clarifying the influence of human-environment interaction in nature-based adventure tourism in the Tsitsikamma, South Africa
- Authors: Giddy, Julia K
- Date: 2013
- Subjects: Human ecology -- South Africa -- Tsitsikammaberge , Tourism -- South Africa -- Tsitsikammaberge
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10674 , http://hdl.handle.net/10948/d1020782
- Description: Adventure tourism (AT), defined as “a broad spectrum of outdoor touristic activities,often commercialized and involving an interaction with the natural environment away from the participants’ home range and containing elements of risk,” (Hall, 1992, p. 143) is currently one of the fastest growing sub-sectors of the tourism industry (Buckley 2010). Because it has emerged relatively recently as a field of study, a number of scholars have called for ongoing research in the area, see Swarbrooke (2003), Pomfret (2006), Buckley (2010), Rogerson (2007), and Williams & Soutar (2005). Much of this research, to date, has focused on marketing, injury caused by AT participation, environmental impacts, and the broad notion of “risk” associated with AT. The problem is that little of this work has focused on the significance of the environment in adventure tourism – an important element inherent in its definition. Thus, this thesis aims to move beyond a general risk-based analysis of AT, and focus on the role of the environment. This is done through a human-environment interaction approach undertaken in Tsitsikamma Village where five adventure tourist operations are based. The first step in operationalizing this approach was to develop a conceptual framework that integrated adventure tourism into a general framework on humanenvironment interaction. The second step was to use a research instrument which enabled one to examine the influence of the environment on human motivations and adventure tourism experiences, and not only the influence of humans on the environment. The former was accomplished through questionnaires based on external, environmental elements that attract adventure tourists as well as inherent personality traits impel such tourists to participate in AT. The latter, based on interviews and participant perceptions, sought to establish the significance of impacts on the environment as well as initiatives taken by AT companies to minimize environmental damage. The findings show that although risk/thrill does play a role, AT motivations and experiences are complex and multidimensional. The environment does significantly influence both motivations and even more so AT experiences. Furthermore, there are distinct differences between the motivations and experiences of participants in different types of AT activities, indicating that generalizing the industry as whole neglects these significant differences. In terms of influences on the environment, the results show that most AT operators in the Tsitsikamma have some consideration for environmental protection and take some initiatives to minimize environmental damage, though the degree to which this occurs differs significantly. Furthermore, activity participants do not believe that the activities have a strong negative impact on the environment, though the majority acknowledge small impacts. The types of impacts observed by participants vary significantly between companies. This thesis demonstrates the manner in which the two-way relationship between humans and the environment manifests itself in the commercial AT industry. The result is a well-rounded examination of the influence of human-environment interaction on AT participants.
- Full Text:
- Date Issued: 2013
- Authors: Giddy, Julia K
- Date: 2013
- Subjects: Human ecology -- South Africa -- Tsitsikammaberge , Tourism -- South Africa -- Tsitsikammaberge
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10674 , http://hdl.handle.net/10948/d1020782
- Description: Adventure tourism (AT), defined as “a broad spectrum of outdoor touristic activities,often commercialized and involving an interaction with the natural environment away from the participants’ home range and containing elements of risk,” (Hall, 1992, p. 143) is currently one of the fastest growing sub-sectors of the tourism industry (Buckley 2010). Because it has emerged relatively recently as a field of study, a number of scholars have called for ongoing research in the area, see Swarbrooke (2003), Pomfret (2006), Buckley (2010), Rogerson (2007), and Williams & Soutar (2005). Much of this research, to date, has focused on marketing, injury caused by AT participation, environmental impacts, and the broad notion of “risk” associated with AT. The problem is that little of this work has focused on the significance of the environment in adventure tourism – an important element inherent in its definition. Thus, this thesis aims to move beyond a general risk-based analysis of AT, and focus on the role of the environment. This is done through a human-environment interaction approach undertaken in Tsitsikamma Village where five adventure tourist operations are based. The first step in operationalizing this approach was to develop a conceptual framework that integrated adventure tourism into a general framework on humanenvironment interaction. The second step was to use a research instrument which enabled one to examine the influence of the environment on human motivations and adventure tourism experiences, and not only the influence of humans on the environment. The former was accomplished through questionnaires based on external, environmental elements that attract adventure tourists as well as inherent personality traits impel such tourists to participate in AT. The latter, based on interviews and participant perceptions, sought to establish the significance of impacts on the environment as well as initiatives taken by AT companies to minimize environmental damage. The findings show that although risk/thrill does play a role, AT motivations and experiences are complex and multidimensional. The environment does significantly influence both motivations and even more so AT experiences. Furthermore, there are distinct differences between the motivations and experiences of participants in different types of AT activities, indicating that generalizing the industry as whole neglects these significant differences. In terms of influences on the environment, the results show that most AT operators in the Tsitsikamma have some consideration for environmental protection and take some initiatives to minimize environmental damage, though the degree to which this occurs differs significantly. Furthermore, activity participants do not believe that the activities have a strong negative impact on the environment, though the majority acknowledge small impacts. The types of impacts observed by participants vary significantly between companies. This thesis demonstrates the manner in which the two-way relationship between humans and the environment manifests itself in the commercial AT industry. The result is a well-rounded examination of the influence of human-environment interaction on AT participants.
- Full Text:
- Date Issued: 2013
Commercialisation of emerging famers in the Eastern Cape province: identification of limiting factors that inhibit the progression from subsistence to commercial farming
- Authors: Khapayi, Musa
- Date: 2013
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10593 , http://hdl.handle.net/10948/d1020067
- Description: The broad objective of the study was to investigate the limiting factors that prevent a breakthrough of emerging farmers to commercial agricultural farming industry. The research objectives were to describe the demographic characteristics such as age, education, farming skills and experience; determine the required support services needed; and inform the limiting factors that prevent breakthrough of emerging farmers to enter commercial agricultural industry. The study was conducted in King William’s Town area through structured questionnaires administered by the researcher. A sample of 50 emerging farmers was drawn in the area. The majority of households in the area depend on subsistence farming for household survival. Results indicated that emerging farmers are faced with poor physical infrastructure such as implements to better their production as well as low education levels which results as an inability to interpret market information to be used in production planning. It is also clear that the farmers face a lack of market infrastructure, poor roads, lack of market information, lack of transportation to markets and high transportation costs. The majority of the farmers were old and the youth was not engaged in agriculture. The findings showed that there is an insufficient role from government with regards to emerging farmer support and providing the required infrastructure to access markets or improving rural infrastructure. As a result the majority of the farmers are trapped in a cycle of poverty. The following policy recommendations are suggested: Financial services such as credit must be made available to emerging farmers at reasonable interest rates such as low interest rate subsidies to emerging farmers up until commercialisation. The requirements for emerging farmers to access loans, funding or credit should be restructured or adjusted to the ability of the farmer to repay the credit rather than the availability of title deeds or assets as collateral. Extension officers should regularly visit the localities were emerging farmers are farming have a better understanding of their farming areas, farming methods and improve their communication with the farmers. Lastly the land reform initiatives should be re-organised or developed if necessary to ensure efficient re-allocation of land. The policies should be developed to focus on both the individual farm plots and the collective rights.
- Full Text:
- Date Issued: 2013
- Authors: Khapayi, Musa
- Date: 2013
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10593 , http://hdl.handle.net/10948/d1020067
- Description: The broad objective of the study was to investigate the limiting factors that prevent a breakthrough of emerging farmers to commercial agricultural farming industry. The research objectives were to describe the demographic characteristics such as age, education, farming skills and experience; determine the required support services needed; and inform the limiting factors that prevent breakthrough of emerging farmers to enter commercial agricultural industry. The study was conducted in King William’s Town area through structured questionnaires administered by the researcher. A sample of 50 emerging farmers was drawn in the area. The majority of households in the area depend on subsistence farming for household survival. Results indicated that emerging farmers are faced with poor physical infrastructure such as implements to better their production as well as low education levels which results as an inability to interpret market information to be used in production planning. It is also clear that the farmers face a lack of market infrastructure, poor roads, lack of market information, lack of transportation to markets and high transportation costs. The majority of the farmers were old and the youth was not engaged in agriculture. The findings showed that there is an insufficient role from government with regards to emerging farmer support and providing the required infrastructure to access markets or improving rural infrastructure. As a result the majority of the farmers are trapped in a cycle of poverty. The following policy recommendations are suggested: Financial services such as credit must be made available to emerging farmers at reasonable interest rates such as low interest rate subsidies to emerging farmers up until commercialisation. The requirements for emerging farmers to access loans, funding or credit should be restructured or adjusted to the ability of the farmer to repay the credit rather than the availability of title deeds or assets as collateral. Extension officers should regularly visit the localities were emerging farmers are farming have a better understanding of their farming areas, farming methods and improve their communication with the farmers. Lastly the land reform initiatives should be re-organised or developed if necessary to ensure efficient re-allocation of land. The policies should be developed to focus on both the individual farm plots and the collective rights.
- Full Text:
- Date Issued: 2013
Cretaceous dyke swarms and brittle deformation structures in the upper continental crust flanking the Atlantic and Indian margins of Southern Africa, and their relationship to Gondwana break-up
- Authors: Muedi, Thomas Tshifhiwa
- Date: 2013
- Subjects: Dikes (Geology) -- Africa, Southern , Joints (Geology) -- Africa, Southern , Gondwana (Continent)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10675 , http://hdl.handle.net/10948/d1020896
- Description: Permanent brittle deformation of rocks of the upper crust is often manifested in the growth of fractures, or sliding along fractures, which may subsequently be intruded by magma and other fluids. The brittle deformation structures described here include faults, joints and dykes. Brittle deformation structures along passive continental margins result from continental fragmentation and related uplift, as is seen around the southern African margins in response to Gondwana break-up. In many cases the fragmentation is accompanied by significant magmatic events, for example the Cretaceous mafic dyke swarms that form major components of the South Atlantic Large Igneous Province (LIP) and originated during the break-up of West Gondwana (Africa and South America). The magmatic events accompanying the break-up of Gondwana resulted in crustal extension and the formation of joint systems and dyke swarms that exhibit distinct geometric features that appear to display fractal patterns. This work analyses the relationship between the Henties Bay-Outjo Dyke Swarm (HOD) on the west coast of Namibia, and the Ponta Grossa Dyke Swarm (PG) on the coast of Brazil, both of which formed ca. ~130 Ma, to test for their co-linearity and fractal geometry before and during West Gondwana break-up. This was achieved by reconstructing Gondwana‘s plates that contained the PG and HOD swarms, using ArcGIS and Gplates software. The dyke analyses was complemented with a comparative study of joints of the Table Mountain Group quartzites (TMG, ca. 400 Ma) in the Western Cape Province and Golden Valley Sill (GVS, ca. 180 Ma) in the Eastern Cape Province, to compare their fractal patterns and possible relationship. Mapping of joints was carried out in the field with the use of a compass and GPS. The HOD trend is positioned largely NNE > NE, but a NW dyke trend is also common. The dominant joints in the TMG trend NNW > WSW and the GVS joints trend WNW > NNE and others. The GVS and HOD orientations appear strongly correlated, while TMG shows no simple orientation correlation with GVS and HOD. The lack of correlation is attributed to the TMG‘s formation in different host-rocks with variable anisotropy and/or the presence of different mechanical processes acting at a different time in geological history. All mapped dykes and joints were analysed to test for fractal geometry. The fractal dimension results of about 18605 HOD dykes from microscopic to mega scale (0.1 mm – 100 km) shows fractal patterns that range between Df = 1.1 to 1.9; and the fractal dimension of about 1716 joints in the TMG and about 1026 joints in the GVS at all scales range between ca. Df = 1.6 to 1.9. The similarity of the fractal patterns indicates that joints and dykes may have formed in response to similar tectonic stress events; and similar orientations may indicate that joints pre-dated the dyke intrusions. However, the data also indicate that dykes are not always related to pre-existing joints.
- Full Text:
- Date Issued: 2013
- Authors: Muedi, Thomas Tshifhiwa
- Date: 2013
- Subjects: Dikes (Geology) -- Africa, Southern , Joints (Geology) -- Africa, Southern , Gondwana (Continent)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10675 , http://hdl.handle.net/10948/d1020896
- Description: Permanent brittle deformation of rocks of the upper crust is often manifested in the growth of fractures, or sliding along fractures, which may subsequently be intruded by magma and other fluids. The brittle deformation structures described here include faults, joints and dykes. Brittle deformation structures along passive continental margins result from continental fragmentation and related uplift, as is seen around the southern African margins in response to Gondwana break-up. In many cases the fragmentation is accompanied by significant magmatic events, for example the Cretaceous mafic dyke swarms that form major components of the South Atlantic Large Igneous Province (LIP) and originated during the break-up of West Gondwana (Africa and South America). The magmatic events accompanying the break-up of Gondwana resulted in crustal extension and the formation of joint systems and dyke swarms that exhibit distinct geometric features that appear to display fractal patterns. This work analyses the relationship between the Henties Bay-Outjo Dyke Swarm (HOD) on the west coast of Namibia, and the Ponta Grossa Dyke Swarm (PG) on the coast of Brazil, both of which formed ca. ~130 Ma, to test for their co-linearity and fractal geometry before and during West Gondwana break-up. This was achieved by reconstructing Gondwana‘s plates that contained the PG and HOD swarms, using ArcGIS and Gplates software. The dyke analyses was complemented with a comparative study of joints of the Table Mountain Group quartzites (TMG, ca. 400 Ma) in the Western Cape Province and Golden Valley Sill (GVS, ca. 180 Ma) in the Eastern Cape Province, to compare their fractal patterns and possible relationship. Mapping of joints was carried out in the field with the use of a compass and GPS. The HOD trend is positioned largely NNE > NE, but a NW dyke trend is also common. The dominant joints in the TMG trend NNW > WSW and the GVS joints trend WNW > NNE and others. The GVS and HOD orientations appear strongly correlated, while TMG shows no simple orientation correlation with GVS and HOD. The lack of correlation is attributed to the TMG‘s formation in different host-rocks with variable anisotropy and/or the presence of different mechanical processes acting at a different time in geological history. All mapped dykes and joints were analysed to test for fractal geometry. The fractal dimension results of about 18605 HOD dykes from microscopic to mega scale (0.1 mm – 100 km) shows fractal patterns that range between Df = 1.1 to 1.9; and the fractal dimension of about 1716 joints in the TMG and about 1026 joints in the GVS at all scales range between ca. Df = 1.6 to 1.9. The similarity of the fractal patterns indicates that joints and dykes may have formed in response to similar tectonic stress events; and similar orientations may indicate that joints pre-dated the dyke intrusions. However, the data also indicate that dykes are not always related to pre-existing joints.
- Full Text:
- Date Issued: 2013
Designing multi-touch tabletop interaction techniques to support co-located Group Information Management
- Authors: Ditta, Mohammed Ali
- Date: 2013
- Subjects: Groupware (Computer software) , Teams in the workplace -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10493 , http://hdl.handle.net/10948/d1020639
- Description: Co-located group information management (GIM) is a form of groupware with the aim of enabling users to collaboratively find, store, maintain, organise and share personal and/or group information in support of a group activity. Existing systems aimed at partially supporting GIM activities have been implemented on single user devices. These systems make use of asynchronous communication that may hinder collaboration by misinterpretation, information leaks, etc. Few systems exist, with limited functionality, that support co-located GIM. Multi-touch tabletop interaction has given rise to a new approach for supporting Computer Supported Cooperative Work (CSCW). Multi-touch tabletops allow multiple users to naturally interact with a computer device using a shared display and gesture interaction. The tabletop environment also enables users to sit in a natural environment and synchronously communicate without bulky desktops or laptops. Multi-touch tabletops provide the hardware necessary to support co-located GIM. Existing multi-touch interaction techniques were analysed and proved insufficient to support the advanced functional requirements of GIM. The goal of this research was therefore to support co-located GIM by designing new multi-touch tabletop interaction techniques. An architecture was proposed to support co-located GIM with new multi-touch interaction techniques. A software prototype was developed based on the proposed architecture to facilitate the main activities of GIM and to collaboratively compile documents. The prototype was named CollaGIM (Colla – collaborative, GIM – group information management). CollaGIM supports the main activities of GIM using natural gesture interaction on a multi-touch tabletop. An evaluation of the software was conducted by means of a user study where 15 teams of two people participated. High task success rates and user satisfaction results were achieved, which showed that CollaGIM was capable of supporting co-located GIM using the new multi-touch tabletop interaction techniques. CollaGIM also positively supported collaboration between users.
- Full Text:
- Date Issued: 2013
- Authors: Ditta, Mohammed Ali
- Date: 2013
- Subjects: Groupware (Computer software) , Teams in the workplace -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10493 , http://hdl.handle.net/10948/d1020639
- Description: Co-located group information management (GIM) is a form of groupware with the aim of enabling users to collaboratively find, store, maintain, organise and share personal and/or group information in support of a group activity. Existing systems aimed at partially supporting GIM activities have been implemented on single user devices. These systems make use of asynchronous communication that may hinder collaboration by misinterpretation, information leaks, etc. Few systems exist, with limited functionality, that support co-located GIM. Multi-touch tabletop interaction has given rise to a new approach for supporting Computer Supported Cooperative Work (CSCW). Multi-touch tabletops allow multiple users to naturally interact with a computer device using a shared display and gesture interaction. The tabletop environment also enables users to sit in a natural environment and synchronously communicate without bulky desktops or laptops. Multi-touch tabletops provide the hardware necessary to support co-located GIM. Existing multi-touch interaction techniques were analysed and proved insufficient to support the advanced functional requirements of GIM. The goal of this research was therefore to support co-located GIM by designing new multi-touch tabletop interaction techniques. An architecture was proposed to support co-located GIM with new multi-touch interaction techniques. A software prototype was developed based on the proposed architecture to facilitate the main activities of GIM and to collaboratively compile documents. The prototype was named CollaGIM (Colla – collaborative, GIM – group information management). CollaGIM supports the main activities of GIM using natural gesture interaction on a multi-touch tabletop. An evaluation of the software was conducted by means of a user study where 15 teams of two people participated. High task success rates and user satisfaction results were achieved, which showed that CollaGIM was capable of supporting co-located GIM using the new multi-touch tabletop interaction techniques. CollaGIM also positively supported collaboration between users.
- Full Text:
- Date Issued: 2013
Development and validation of in-process control test kits for biodiesel production
- Authors: Fibi, Pumza Oscarine
- Date: 2013
- Subjects: Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10416 , http://hdl.handle.net/10948/d1012645 , Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Description: The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.
- Full Text:
- Date Issued: 2013
- Authors: Fibi, Pumza Oscarine
- Date: 2013
- Subjects: Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10416 , http://hdl.handle.net/10948/d1012645 , Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Description: The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.
- Full Text:
- Date Issued: 2013
Diet and foraging distribution of gentoo penguins pygoscelis papua at Cow Bay, Falkland Islands
- Authors: Handley, Jonathan Murray
- Date: 2013
- Subjects: Gentoo penguin -- Food -- Falkland Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10724 , http://hdl.handle.net/10948/d1020377
- Description: Knowledge of diet and distribution in marine top predators is critical in interpreting their ecological role. Furthermore, this information is required for effective management and conservation of these species. For gentoo penguins at the Falkland Islands a previous overlap in dietary items with commercial fisheries was recognised. Despite this the at-sea distribution has been poorly studied and only at a few localities. Therefore, this thesis looks to broaden the knowledge of foraging ecology for gentoo penguins at another site in the archipelago, Cow Bay. The aim was firstly, through stomach content analysis, to determine if diet changed over a large temporal scale (2002/03/04 – 2011/12/13), and between the chick guard and crèche periods of chick rearing. Secondly, through GPS loggers, to assess distribution at sea during the incubation and chick guard periods (2012/13). Additionally, foraging ecology between genders was investigated. Gentoo penguins at Cow Bay foraged primarily on fish (66-99 percent) throughout the entire study period. The principle prey item by mass was Patagonotothen spp., considered previously as discard by fisheries but now an important commercial resource, for all periods (47-78 percent) except that of the 2012/13 crèche period (19 percent). During this period Sprattus fugensis made up the bulk of the diet (52 percent). Cephalopods, particularly Loligo gahi (1-24 percent), were also prominent in the diet and crustaceans contributed negligibly. The diet indicated that gentoo penguins are capable of both a benthic and pelagic feeding strategy which likely reflects changes in local prey abundance. Birds typically conducted foraging activities during daylight hours with greater trip duration, path length, maximum distance and area utilised during the incubation period than the guard. All trips were confined to the continental shelf and within the boundaries of a marine management zone, the Falkland Islands Interim Conservation Zone (FICZ). Males and females fed on the same size and composition of prey items. Trip duration, path length and maximum distance from the colony were not significantly different, although males foraged in a slightly larger area than females marginally to the north. As at-sea distribution was confined within the FICZ this management area provides protection to food resources of gentoo penguins breeding at Cow Bay. At this site, the population is increasing, likely associated with increased prey availability as evidenced by record catches of Patagonotothen spp. in recent years at the Falkland Islands. Continued long term monitoring of gentoo penguin diet and fishery yields to allow detection of possible competition in the future is recommended. As marine sentinels, on-going monitoring of gentoo penguin populations at the Falkland Islands is likely to provide early warning signs of reduced prey availability.
- Full Text:
- Date Issued: 2013
- Authors: Handley, Jonathan Murray
- Date: 2013
- Subjects: Gentoo penguin -- Food -- Falkland Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10724 , http://hdl.handle.net/10948/d1020377
- Description: Knowledge of diet and distribution in marine top predators is critical in interpreting their ecological role. Furthermore, this information is required for effective management and conservation of these species. For gentoo penguins at the Falkland Islands a previous overlap in dietary items with commercial fisheries was recognised. Despite this the at-sea distribution has been poorly studied and only at a few localities. Therefore, this thesis looks to broaden the knowledge of foraging ecology for gentoo penguins at another site in the archipelago, Cow Bay. The aim was firstly, through stomach content analysis, to determine if diet changed over a large temporal scale (2002/03/04 – 2011/12/13), and between the chick guard and crèche periods of chick rearing. Secondly, through GPS loggers, to assess distribution at sea during the incubation and chick guard periods (2012/13). Additionally, foraging ecology between genders was investigated. Gentoo penguins at Cow Bay foraged primarily on fish (66-99 percent) throughout the entire study period. The principle prey item by mass was Patagonotothen spp., considered previously as discard by fisheries but now an important commercial resource, for all periods (47-78 percent) except that of the 2012/13 crèche period (19 percent). During this period Sprattus fugensis made up the bulk of the diet (52 percent). Cephalopods, particularly Loligo gahi (1-24 percent), were also prominent in the diet and crustaceans contributed negligibly. The diet indicated that gentoo penguins are capable of both a benthic and pelagic feeding strategy which likely reflects changes in local prey abundance. Birds typically conducted foraging activities during daylight hours with greater trip duration, path length, maximum distance and area utilised during the incubation period than the guard. All trips were confined to the continental shelf and within the boundaries of a marine management zone, the Falkland Islands Interim Conservation Zone (FICZ). Males and females fed on the same size and composition of prey items. Trip duration, path length and maximum distance from the colony were not significantly different, although males foraged in a slightly larger area than females marginally to the north. As at-sea distribution was confined within the FICZ this management area provides protection to food resources of gentoo penguins breeding at Cow Bay. At this site, the population is increasing, likely associated with increased prey availability as evidenced by record catches of Patagonotothen spp. in recent years at the Falkland Islands. Continued long term monitoring of gentoo penguin diet and fishery yields to allow detection of possible competition in the future is recommended. As marine sentinels, on-going monitoring of gentoo penguin populations at the Falkland Islands is likely to provide early warning signs of reduced prey availability.
- Full Text:
- Date Issued: 2013