Dispersal of sterile false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), for a sterile insect technique programme on citrus
- Authors: Wagenaar, Gideon Daniel
- Date: 2015
- Subjects: Cryptophlebia leucotreta , Insect pests -- Control -- South Africa , Citrus -- Diseases and pests -- Control -- South Africa , Insect sterilization
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4977 , vital:20774
- Description: The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is an important pest of citrus in South Africa and challenging to manage due to its inconspicuous nature. An effective method currently being employed for the area-wide suppression of the FCM is the Sterile Insect Technique (SIT) and the effective dispersal of sterile moths is very important for success with SIT. This study was conducted in the Addo area of the Sundays River Valley (Eastern Cape) where the programme is commercially used. In this study, sterile male moths were released in different orchards on a citrus farm, and in nearby veld at different times of the year, and their dispersal was monitored through the use of pheromone traps. Various climatic factors were monitored. This provided insight into the local dispersal of sterile male FCM adults in response to abiotic cues (particularly climatic factors). The movement of the FCM in four citrus cultivars, namely lemons, navel and Valencia oranges and mandarins and in the nearby veld (open field), was determined at six different stages of the year. Results clearly indicated that sterile FCM movement is concentrated within citrus orchards, as very few moths were trapped beyond 30 m from the release point, particularly in navel and Valencia orchards. Of the climatic factors measured, minimum and maximum temperatures had the most significant influence on FCM dispersal, and based on the results, various recommendations are made for the releases of sterile FCM in an area-wide SIT management programmes on citrus. A better understanding of the dispersal capabilities of the FCM in an agricultural system, under different conditions and at different times of the year, is invaluable not only in improving release strategies in an SIT programme but in planning future control strategies against the FCM.
- Full Text:
- Date Issued: 2015
- Authors: Wagenaar, Gideon Daniel
- Date: 2015
- Subjects: Cryptophlebia leucotreta , Insect pests -- Control -- South Africa , Citrus -- Diseases and pests -- Control -- South Africa , Insect sterilization
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4977 , vital:20774
- Description: The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is an important pest of citrus in South Africa and challenging to manage due to its inconspicuous nature. An effective method currently being employed for the area-wide suppression of the FCM is the Sterile Insect Technique (SIT) and the effective dispersal of sterile moths is very important for success with SIT. This study was conducted in the Addo area of the Sundays River Valley (Eastern Cape) where the programme is commercially used. In this study, sterile male moths were released in different orchards on a citrus farm, and in nearby veld at different times of the year, and their dispersal was monitored through the use of pheromone traps. Various climatic factors were monitored. This provided insight into the local dispersal of sterile male FCM adults in response to abiotic cues (particularly climatic factors). The movement of the FCM in four citrus cultivars, namely lemons, navel and Valencia oranges and mandarins and in the nearby veld (open field), was determined at six different stages of the year. Results clearly indicated that sterile FCM movement is concentrated within citrus orchards, as very few moths were trapped beyond 30 m from the release point, particularly in navel and Valencia orchards. Of the climatic factors measured, minimum and maximum temperatures had the most significant influence on FCM dispersal, and based on the results, various recommendations are made for the releases of sterile FCM in an area-wide SIT management programmes on citrus. A better understanding of the dispersal capabilities of the FCM in an agricultural system, under different conditions and at different times of the year, is invaluable not only in improving release strategies in an SIT programme but in planning future control strategies against the FCM.
- Full Text:
- Date Issued: 2015
A natural user interface architecture using gestures to facilitate the detection of fundamental movement skills
- Authors: Amanzi, Richard
- Date: 2015
- Subjects: Human activity recognition , Human-computer interaction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6204 , vital:21055
- Description: Fundamental movement skills (FMSs) are considered to be one of the essential phases of motor skill development. The proper development of FMSs allows children to participate in more advanced forms of movements and sports. To be able to perform an FMS correctly, children need to learn the right way of performing it. By making use of technology, a system can be developed that can help facilitate the learning of FMSs. The objective of the research was to propose an effective natural user interface (NUI) architecture for detecting FMSs using the Kinect. In order to achieve the stated objective, an investigation into FMSs and the challenges faced when teaching them was presented. An investigation into NUIs was also presented including the merits of the Kinect as the most appropriate device to be used to facilitate the detection of an FMS. An NUI architecture was proposed that uses the Kinect to facilitate the detection of an FMS. A framework was implemented from the design of the architecture. The successful implementation of the framework provides evidence that the design of the proposed architecture is feasible. An instance of the framework incorporating the jump FMS was used as a case study in the development of a prototype that detects the correct and incorrect performance of a jump. The evaluation of the prototype proved the following: - The developed prototype was effective in detecting the correct and incorrect performance of the jump FMS; and - The implemented framework was robust for the incorporation of an FMS. The successful implementation of the prototype shows that an effective NUI architecture using the Kinect can be used to facilitate the detection of FMSs. The proposed architecture provides a structured way of developing a system using the Kinect to facilitate the detection of FMSs. This allows developers to add future FMSs to the system. This dissertation therefore makes the following contributions: - An experimental design to evaluate the effectiveness of a prototype that detects FMSs - A robust framework that incorporates FMSs; and - An effective NUI architecture to facilitate the detection of fundamental movement skills using the Kinect.
- Full Text:
- Date Issued: 2015
- Authors: Amanzi, Richard
- Date: 2015
- Subjects: Human activity recognition , Human-computer interaction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6204 , vital:21055
- Description: Fundamental movement skills (FMSs) are considered to be one of the essential phases of motor skill development. The proper development of FMSs allows children to participate in more advanced forms of movements and sports. To be able to perform an FMS correctly, children need to learn the right way of performing it. By making use of technology, a system can be developed that can help facilitate the learning of FMSs. The objective of the research was to propose an effective natural user interface (NUI) architecture for detecting FMSs using the Kinect. In order to achieve the stated objective, an investigation into FMSs and the challenges faced when teaching them was presented. An investigation into NUIs was also presented including the merits of the Kinect as the most appropriate device to be used to facilitate the detection of an FMS. An NUI architecture was proposed that uses the Kinect to facilitate the detection of an FMS. A framework was implemented from the design of the architecture. The successful implementation of the framework provides evidence that the design of the proposed architecture is feasible. An instance of the framework incorporating the jump FMS was used as a case study in the development of a prototype that detects the correct and incorrect performance of a jump. The evaluation of the prototype proved the following: - The developed prototype was effective in detecting the correct and incorrect performance of the jump FMS; and - The implemented framework was robust for the incorporation of an FMS. The successful implementation of the prototype shows that an effective NUI architecture using the Kinect can be used to facilitate the detection of FMSs. The proposed architecture provides a structured way of developing a system using the Kinect to facilitate the detection of FMSs. This allows developers to add future FMSs to the system. This dissertation therefore makes the following contributions: - An experimental design to evaluate the effectiveness of a prototype that detects FMSs - A robust framework that incorporates FMSs; and - An effective NUI architecture to facilitate the detection of fundamental movement skills using the Kinect.
- Full Text:
- Date Issued: 2015
Towards measuring corporate sustainability in the Nelson Mandela Bay automotive manufacturing sector
- Authors: Adams, Abulele
- Date: 2015
- Subjects: Sustainability -- South Africa -- Port Elizabeth Sustainable development -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18465 , vital:28648
- Description: This study explored the methods available for measuring corporate sustainability and created an instrument to measure corporate sustainability in the Nelson Mandela Bay (NMB) automotive manufacturing sector. The instrument was created based on three components of sustainability which are environment, society and economy. The study went a step further and added a fourth dimension, current trends to design a measuring instrument. The instrument was then applied on participating companies and further refined to improve it. A total of 16 multi-dimensional indicators to measure corporate sustainability were created and applied to 12 companies in the automotive manufacturing sector. The indicators were used to create a composite corporate sustainability index which can be used to compare the corporate sustainability performance of companies. These indicators were created based on theoretical research and fist hand experience observing the automotive manufacturing sector in the NMB. The indicators were applied to companies as a pilot to test whether they are feasible. Following this, the indicators were refined, improved and applied to more companies to measure corporate sustainability performance. The results of the study were the measuring instrument created, the creation of a composite index as well as the application of the instrument on 12 companies to determine whether the instrument was refined enough to detect differences in the corporate sustainability performance of companies. The results are discussed and further recommendations are made for improvements in the creation and application of the instrument to measure corporate sustainability in the NMB automotive manufacturing sector.
- Full Text:
- Date Issued: 2015
Towards measuring corporate sustainability in the Nelson Mandela Bay automotive manufacturing sector
- Authors: Adams, Abulele
- Date: 2015
- Subjects: Sustainability -- South Africa -- Port Elizabeth Sustainable development -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18465 , vital:28648
- Description: This study explored the methods available for measuring corporate sustainability and created an instrument to measure corporate sustainability in the Nelson Mandela Bay (NMB) automotive manufacturing sector. The instrument was created based on three components of sustainability which are environment, society and economy. The study went a step further and added a fourth dimension, current trends to design a measuring instrument. The instrument was then applied on participating companies and further refined to improve it. A total of 16 multi-dimensional indicators to measure corporate sustainability were created and applied to 12 companies in the automotive manufacturing sector. The indicators were used to create a composite corporate sustainability index which can be used to compare the corporate sustainability performance of companies. These indicators were created based on theoretical research and fist hand experience observing the automotive manufacturing sector in the NMB. The indicators were applied to companies as a pilot to test whether they are feasible. Following this, the indicators were refined, improved and applied to more companies to measure corporate sustainability performance. The results of the study were the measuring instrument created, the creation of a composite index as well as the application of the instrument on 12 companies to determine whether the instrument was refined enough to detect differences in the corporate sustainability performance of companies. The results are discussed and further recommendations are made for improvements in the creation and application of the instrument to measure corporate sustainability in the NMB automotive manufacturing sector.
- Full Text:
- Date Issued: 2015
A multiscale remote sensing assessment of subtropical indigenous forests along the wild coast, South Africa
- Authors: Blessing, Sithole Vhusomuzi
- Date: 2015
- Subjects: Forests and forestry -- South Africa -- Remote sensing , Forest conservation , Remote sensing , Geographic information systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10677 , http://hdl.handle.net/10948/d1021169
- Description: The subtropical forests located along South Africa’s Wild Coast region, declared as one of the biodiversity hotspots, provide benefits to the local and national economy. However, there is evidence of increased pressure exerted on the forests by growing population and reduced income from activities not related to forest products. The ability of remote sensing to quantify subtropical forest changes over time, perform species discrimination (using field spectroscopy) and integrating field spectral and multispectral data were all assessed in this study. Investigations were conducted at pixel, leaf and sub-pixel levels. Both per-pixel and sub-pixel classification methods were used for improved forest characterisation. Using SPOT 6 imagery for 2013, the study determined the best classification algorithm for mapping sub-tropical forest and other land cover types to be the maximum likelihood classifier. Maximum likelihood outperformed minimum distance, spectral angle mapper and spectral information divergence algorithms, based on overall accuracy and Kappa coefficient values. Forest change analysis was made based on spectral measurements made at top of the atmosphere (TOC) level. When applied to the 2005 and 2009 SPOT 5 images, subtropical forest changes between 2005-2009 and 2009-2013 were quantified. A temporal analysis of forest cover trends in the periods 2005-2009 and 2009-2013 identified a decreasing trend of -3648.42 and -946.98 ha respectively, which translated to 7.81 percent and 2.20 percent decrease. Although there is evidence of a trend towards decreased rates of forest loss, more conservation efforts are required to protect the Wild Coast ecosystem. Using field spectral measurements data, the hierarchical method (comprising One-way ANOVA with Bonferroni correction, Classification and Regression Trees (CART) and Jeffries Matusita method) successfully selected optimal wavelengths for species discrimination at leaf level. Only 17 out of 2150 wavelengths were identified, thereby reducing the complexities related to data dimensionality. The optimal 17 wavelength bands were noted in the visible (438, 442, 512 and 695 nm), near infrared (724, 729, 750, 758, 856, 936, 1179, 1507 and 1673 nm) and mid-infrared (2220, 2465, 2469 and 2482 nm) portions of the electromagnetic spectrum. The Jeffries-Matusita (JM) distance method confirmed the separability of the selected wavelength bands. Using these 17 wavelengths, linear discriminant analysis (LDA) classified subtropical species at leaf level more accurately than partial least squares discriminant analysis (PLSDA) and random forest (RF). In addition, the study integrated field-collected canopy spectral and multispectral data to discriminate proportions of semi-deciduous and evergreen subtropical forests at sub-pixel level. By using the 2013 land cover (using MLC) to mask non-forested portions before sub-pixel classification (using MTMF), the proportional maps were a product of two classifiers. The proportional maps show higher proportions of evergreen forests along the coast while semi-deciduous subtropical forest species were mainly on inland parts of the Wild Coast. These maps had high accuracy, thereby proving the ability of an integration of field spectral and multispectral data in mapping semi-deciduous and evergreen forest species. Overall, the study has demonstrated the importance of the MLC and LDA and served to integrate field spectral and multispectral data in subtropical forest characterisation at both leaf and top-of-atmosphere levels. The success of both the MLC and LDA further highlighted how essential parametric classifiers are in remote sensing forestry applications. Main subtropical characteristics highlighted in this study were species discrimination at leaf level, quantifying forest change at pixel level and discriminating semi-deciduous and evergreen forests at sub-pixel level.
- Full Text:
- Date Issued: 2015
- Authors: Blessing, Sithole Vhusomuzi
- Date: 2015
- Subjects: Forests and forestry -- South Africa -- Remote sensing , Forest conservation , Remote sensing , Geographic information systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10677 , http://hdl.handle.net/10948/d1021169
- Description: The subtropical forests located along South Africa’s Wild Coast region, declared as one of the biodiversity hotspots, provide benefits to the local and national economy. However, there is evidence of increased pressure exerted on the forests by growing population and reduced income from activities not related to forest products. The ability of remote sensing to quantify subtropical forest changes over time, perform species discrimination (using field spectroscopy) and integrating field spectral and multispectral data were all assessed in this study. Investigations were conducted at pixel, leaf and sub-pixel levels. Both per-pixel and sub-pixel classification methods were used for improved forest characterisation. Using SPOT 6 imagery for 2013, the study determined the best classification algorithm for mapping sub-tropical forest and other land cover types to be the maximum likelihood classifier. Maximum likelihood outperformed minimum distance, spectral angle mapper and spectral information divergence algorithms, based on overall accuracy and Kappa coefficient values. Forest change analysis was made based on spectral measurements made at top of the atmosphere (TOC) level. When applied to the 2005 and 2009 SPOT 5 images, subtropical forest changes between 2005-2009 and 2009-2013 were quantified. A temporal analysis of forest cover trends in the periods 2005-2009 and 2009-2013 identified a decreasing trend of -3648.42 and -946.98 ha respectively, which translated to 7.81 percent and 2.20 percent decrease. Although there is evidence of a trend towards decreased rates of forest loss, more conservation efforts are required to protect the Wild Coast ecosystem. Using field spectral measurements data, the hierarchical method (comprising One-way ANOVA with Bonferroni correction, Classification and Regression Trees (CART) and Jeffries Matusita method) successfully selected optimal wavelengths for species discrimination at leaf level. Only 17 out of 2150 wavelengths were identified, thereby reducing the complexities related to data dimensionality. The optimal 17 wavelength bands were noted in the visible (438, 442, 512 and 695 nm), near infrared (724, 729, 750, 758, 856, 936, 1179, 1507 and 1673 nm) and mid-infrared (2220, 2465, 2469 and 2482 nm) portions of the electromagnetic spectrum. The Jeffries-Matusita (JM) distance method confirmed the separability of the selected wavelength bands. Using these 17 wavelengths, linear discriminant analysis (LDA) classified subtropical species at leaf level more accurately than partial least squares discriminant analysis (PLSDA) and random forest (RF). In addition, the study integrated field-collected canopy spectral and multispectral data to discriminate proportions of semi-deciduous and evergreen subtropical forests at sub-pixel level. By using the 2013 land cover (using MLC) to mask non-forested portions before sub-pixel classification (using MTMF), the proportional maps were a product of two classifiers. The proportional maps show higher proportions of evergreen forests along the coast while semi-deciduous subtropical forest species were mainly on inland parts of the Wild Coast. These maps had high accuracy, thereby proving the ability of an integration of field spectral and multispectral data in mapping semi-deciduous and evergreen forest species. Overall, the study has demonstrated the importance of the MLC and LDA and served to integrate field spectral and multispectral data in subtropical forest characterisation at both leaf and top-of-atmosphere levels. The success of both the MLC and LDA further highlighted how essential parametric classifiers are in remote sensing forestry applications. Main subtropical characteristics highlighted in this study were species discrimination at leaf level, quantifying forest change at pixel level and discriminating semi-deciduous and evergreen forests at sub-pixel level.
- Full Text:
- Date Issued: 2015
An assessment of the in vitro neuroprotective potential of selected Algerian and South African medicinal plant extracts
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
- Authors: Fewell, William
- Date: 2015
- Subjects: Medicinal plants -- South Africa , Nervous system -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/8608 , vital:26411
- Description: It is estimated by the World Health Organization (WHO) that by 2040 neurodegenerative disorders will collectively surpass cancer as the primary cause of death in industrialised countries (WHO,2006). Natural flora represents one of the most important therapeutic sources in modern drug discovery, however only a limited number of plant species have been screened for their neuroprotective value. The neuroprotective potential of eleven Algerian and two South African medicinal plant extracts were assessed in this study, aiming to identify promising candidates for future research. Neurodegenerative disorders such as Parkinson’s disease are characterised by distinct biochemical features, including protein misfolding/-aggregation, excessive oxidative stress and apoptotic cell death. As such, medicinal plant extracts were screened for biological properties directly relevant to neurodegeneration. The capacity to induce autophagy was also investigated as mounting evidence suggests that activation of this pathway may reduce abnormal protein aggregation and promote neuronal survival.
- Full Text: false
- Date Issued: 2015
A model for mobile, context-aware in-car communication systems to reduce driver distractions
- Authors: Tchankue-Sielinou, Patrick
- Date: 2015
- Subjects: Automobiles -- Safety measures , Context-aware computing , Mobile communication systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4144 , vital:20556
- Description: Driver distraction remains a matter of concern throughout the world as the number of car accidents caused by distracted driving is still unacceptably high. Industry and academia are working intensively to design new techniques that will address all types of driver distraction including visual, manual, auditory and cognitive distraction. This research focuses on an existing technology, namely in-car communication systems (ICCS). ICCS allow drivers to interact with their mobile phones without touching or looking at them. Previous research suggests that ICCS have reduced visual and manual distraction. Two problems were identified in this research: existing ICCS are still expensive and only available in limited models of car. As a result of that, only a small number of drivers can obtain a car equipped with an ICCS, especially in developing countries. The second problem is that existing ICCS are not aware of the driving context, which plays a role in distracting drivers. This research project was based on the following thesis statement: A mobile, context-aware model can be designed to reduce driver distraction caused by the use of ICCS. A mobile ICCS is portable and can be used in any car, addressing the first problem. Context-awareness will be used to detect possible situations that contribute to distracting drivers and the interaction with the mobile ICCS will be adapted so as to avert calls and text messages. This will address the second problem. As the driving context is dynamic, drivers may have to deal with critical safety-related tasks while they are using an existing ICCS. The following steps were taken in order to validate the thesis statement. An investigation was conducted into the causes and consequences of driver distraction. A review of literature was conducted on context-aware techniques that could potentially be used. The design of a model was proposed, called the Multimodal Interface for Mobile Info-communication with Context (MIMIC) and a preliminary usability evaluation was conducted in order to assess the feasibility of a speech-based, mobile ICCS. Despite some problems with the speech recognition, the results were satisfying and showed that the proposed model for mobile ICCS was feasible. Experiments were conducted in order to collect data to perform supervised learning to determine the driving context. The aim was to select the most effective machine learning techniques to determine the driving context. Decision tree and instance-based algorithms were found to be the best performing algorithms. Variables such as speed, acceleration and linear acceleration were found to be the most important variables according to an analysis of the decision tree. The initial MIMIC model was updated to include several adaptation effects and the resulting model was implemented as a prototype mobile application, called MIMIC-Prototype.
- Full Text:
- Date Issued: 2015
- Authors: Tchankue-Sielinou, Patrick
- Date: 2015
- Subjects: Automobiles -- Safety measures , Context-aware computing , Mobile communication systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4144 , vital:20556
- Description: Driver distraction remains a matter of concern throughout the world as the number of car accidents caused by distracted driving is still unacceptably high. Industry and academia are working intensively to design new techniques that will address all types of driver distraction including visual, manual, auditory and cognitive distraction. This research focuses on an existing technology, namely in-car communication systems (ICCS). ICCS allow drivers to interact with their mobile phones without touching or looking at them. Previous research suggests that ICCS have reduced visual and manual distraction. Two problems were identified in this research: existing ICCS are still expensive and only available in limited models of car. As a result of that, only a small number of drivers can obtain a car equipped with an ICCS, especially in developing countries. The second problem is that existing ICCS are not aware of the driving context, which plays a role in distracting drivers. This research project was based on the following thesis statement: A mobile, context-aware model can be designed to reduce driver distraction caused by the use of ICCS. A mobile ICCS is portable and can be used in any car, addressing the first problem. Context-awareness will be used to detect possible situations that contribute to distracting drivers and the interaction with the mobile ICCS will be adapted so as to avert calls and text messages. This will address the second problem. As the driving context is dynamic, drivers may have to deal with critical safety-related tasks while they are using an existing ICCS. The following steps were taken in order to validate the thesis statement. An investigation was conducted into the causes and consequences of driver distraction. A review of literature was conducted on context-aware techniques that could potentially be used. The design of a model was proposed, called the Multimodal Interface for Mobile Info-communication with Context (MIMIC) and a preliminary usability evaluation was conducted in order to assess the feasibility of a speech-based, mobile ICCS. Despite some problems with the speech recognition, the results were satisfying and showed that the proposed model for mobile ICCS was feasible. Experiments were conducted in order to collect data to perform supervised learning to determine the driving context. The aim was to select the most effective machine learning techniques to determine the driving context. Decision tree and instance-based algorithms were found to be the best performing algorithms. Variables such as speed, acceleration and linear acceleration were found to be the most important variables according to an analysis of the decision tree. The initial MIMIC model was updated to include several adaptation effects and the resulting model was implemented as a prototype mobile application, called MIMIC-Prototype.
- Full Text:
- Date Issued: 2015
Hydrothermal co-liquefaction of microalgae biomass and coal
- Authors: Charlie, David
- Date: 2015
- Subjects: Microalgae -- Biotechnology Biomass chemicals , Biomass energy
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/50087 , vital:42035
- Description: In this research, the objective was to investigate under the chosen liquefaction conditions whether co-liquefaction of coal and microalgae biomass as agglomerates does possess a distinct advantage over the individual liquefaction of microalgae and coal. This was initially done by preparing dry micro algal biomass, followed by the preparation of coal fines and finally coal-algae as agglomerates. The agglomerates were prepared by continuously adsorbing wet concentrated microalgae slurry/solution onto the dry coal fines in order to prepare different ratios of coal-algae agglomerate(s). Ultimate analysis of the starting material (coal fines and the microalgae) as well the agglomerates then followed. According to research, wet microalgae biomass has the potential of acting as a hydrogen donor. By preparing the agglomerates, the rationale was to promote hydrogen supply from the micro algal biomass that has high hydrogen content to the coal with lower hydrogen content. The resulting product was then expected to have fairly higher hydrogen content. However, this was not observed or evident from the elemental analysis results. The results (elemental composition) showed no difference between the agglomerates and the coal. Based on the observed ultimate analysis results, liquefaction experiments were conducted to determine whether hydrogen transfer and the expected synergistic effect between micro algal biomass and coal would occur. The crude oil product was recovered and simulated distillation technique was used for the characterization of the crude oil product. The results we in agreement that higher yields can be achieved during co-liquefaction as compared to the individual liquefaction. A possible synergistic effect that was investigated in this research existed. Liquefaction results provided evidence of higher yields recovery from the agglomerates compared to those of coal fines and microalgae biomass. Although there was higher recovery on the agglomerates, there appears to be a downward trend (decrease) in product recovery with higher loadings of micro algal biomass on to the coal. This means that higher loading of micro algal biomass tend to suppress liquefaction of coal, thus resulting in lower product recovery. While lower loadings tend to effectively facilitate the liquefaction of coal, thus proving that the proposed synergistic effect between the two does exist. Overall product recovery (yields) of the agglomerates is higher compared to the individual recovery of coal fines and microalgae biomass. This was followed by mass balancing to determine the overall conversion. Higher conversions were achieved on the agglomerates compared to coal. This could mean that microalgae have the potential to facilitate the liquefaction of coal and improve its conversion. The observed trend results in improved conversion as well as higher oil yields (simulated distillation results). Overall, the mass balancing provided insightful information regarding the coal-microalgae interaction based on the conversion, and this further corresponds or supports the simulated distillation results. This research paper provides evidence of the synergistic effect that exists between micro algal biomass and coal.
- Full Text:
- Date Issued: 2015
- Authors: Charlie, David
- Date: 2015
- Subjects: Microalgae -- Biotechnology Biomass chemicals , Biomass energy
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/50087 , vital:42035
- Description: In this research, the objective was to investigate under the chosen liquefaction conditions whether co-liquefaction of coal and microalgae biomass as agglomerates does possess a distinct advantage over the individual liquefaction of microalgae and coal. This was initially done by preparing dry micro algal biomass, followed by the preparation of coal fines and finally coal-algae as agglomerates. The agglomerates were prepared by continuously adsorbing wet concentrated microalgae slurry/solution onto the dry coal fines in order to prepare different ratios of coal-algae agglomerate(s). Ultimate analysis of the starting material (coal fines and the microalgae) as well the agglomerates then followed. According to research, wet microalgae biomass has the potential of acting as a hydrogen donor. By preparing the agglomerates, the rationale was to promote hydrogen supply from the micro algal biomass that has high hydrogen content to the coal with lower hydrogen content. The resulting product was then expected to have fairly higher hydrogen content. However, this was not observed or evident from the elemental analysis results. The results (elemental composition) showed no difference between the agglomerates and the coal. Based on the observed ultimate analysis results, liquefaction experiments were conducted to determine whether hydrogen transfer and the expected synergistic effect between micro algal biomass and coal would occur. The crude oil product was recovered and simulated distillation technique was used for the characterization of the crude oil product. The results we in agreement that higher yields can be achieved during co-liquefaction as compared to the individual liquefaction. A possible synergistic effect that was investigated in this research existed. Liquefaction results provided evidence of higher yields recovery from the agglomerates compared to those of coal fines and microalgae biomass. Although there was higher recovery on the agglomerates, there appears to be a downward trend (decrease) in product recovery with higher loadings of micro algal biomass on to the coal. This means that higher loading of micro algal biomass tend to suppress liquefaction of coal, thus resulting in lower product recovery. While lower loadings tend to effectively facilitate the liquefaction of coal, thus proving that the proposed synergistic effect between the two does exist. Overall product recovery (yields) of the agglomerates is higher compared to the individual recovery of coal fines and microalgae biomass. This was followed by mass balancing to determine the overall conversion. Higher conversions were achieved on the agglomerates compared to coal. This could mean that microalgae have the potential to facilitate the liquefaction of coal and improve its conversion. The observed trend results in improved conversion as well as higher oil yields (simulated distillation results). Overall, the mass balancing provided insightful information regarding the coal-microalgae interaction based on the conversion, and this further corresponds or supports the simulated distillation results. This research paper provides evidence of the synergistic effect that exists between micro algal biomass and coal.
- Full Text:
- Date Issued: 2015
Environmental flows, health and importance of macrophytes in the estuaries of water management area 11
- Authors: Cowie, Meredith
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7930 , vital:24324
- Description: Estuaries require sufficient quantity, quality and appropriate timing of freshwater inflow, referred to as environmental flow requirements, to ensure adequate health and functioning. In South Africa the environmental flow requirements of estuaries is determined using Resource Directed Measures (RDM). The present health and importance of an estuary must be considered when determining the ecological flow required to maintain an estuary in its desired state. An Estuarine Health Index that quantifies changes in abiotic and biotic components from natural conditions to present day is used. Health of biotic components is assessed according to changes in species richness, abundance and community composition. There has, however, been debate regarding the calculation of these attributes. In particular, for macrophytes, the inclusion of all habitat within the Estuarine Functional Zone (i.e. 5 m topographical contour) would affect the health and changes over time determined in past assessments. This is due to different areas being included as different areas would be included The aim of this study was to test the validity and suggest improvements to South Africa’s RDM macrophyte health score determination. The health of macrophytes were assessed at varying levels of intensity from desktop studies to thorough field studies. Rapid field studies provided a visual estimate of macrophyte health; while the intermediate and comprehensive assessments quantified change by mapping the distribution of macrophyte habitats from aerial photographs. These approaches were applied to the 64 estuaries within the Mvoti-Mzimkulu Water Management Area (WMA 11), situated in KwaZulu-Natal (KZN) on the subtropical east coast. Historically, these estuaries have supported restricted macrophyte habitats. Consequently, estuaries that presently or historically supported range limited habitats such as mangroves and swamp forest are considered important. Submerged macrophytes are scarce in KZN estuaries due to siltation and low turbidity and thus estuaries supporting this macrophyte habitat are also important. Based on available literature important estuaries were highlighted and selected for field studies. Transects spanning from the estuary water channel to the boundary of the EFZ provided a generalised distribution of KZN vegetation along an elevation gradient. The transition from estuarine to terrestrial vegetation can be used to improve the current EFZ boundaries, as estuarine area has been found to occur outside of the 5 m contour in some estuaries. Results from the desktop assessment indicated that most of the estuaries are moderately modified. There was a 50 % similarity in the macrophyte health scores determined by the desktop assessment to the 2011 National Biodiversity Assessment (NBA). Field studies mostly confirmed the desktop assessment aside from seven estuaries that had different scores. There has been a significant loss of macrophyte habitat with 100% loss of certain habitats from 9 of the 22 estuaries for which there were field assessments. Submerged macrophytes were not found at any of the estuaries that were assessed in the field. Black mangroves, Bruguiera gymnorrhiza (L.) Lam., were rediscovered at Ngane Estuary, however the few individuals could not be considered a ‘mappable’ community (i.e. <0.5 ha). Mtamvuna and Mkomazi estuaries both supported small stands of mangroves that, compared to data from 2006, appeared healthy. Macrophyte habitats and surrounding coastal forest matched the species composition described in the Vegetation Map of South Africa. The freshwater mangrove or Powder puff tree, Barringtonia racemosa (L.) Roxb, was not abundant in the estuaries. It was only found at four (Damba, Fafa, Little Amanzimtoti and Mvoti) of the estuaries that were assessed in the field. Important estuaries, from a botanical perspective, included some of the larger estuaries such as Mgeni, Durban Bay and Sipingo. Smaller, healthier estuaries that presently support mangrove and swamp forest habitat were also identified as important from a botanical perspective. Macrophyte habitats have mainly been lost due to non-flow related pressures. Sugarcane cultivation occurred within the floodplain of 25% of the estuaries. Nutrient enrichment was evident for 12.5% of the estuaries and reed encroachment was evident for 27% of estuaries for which there were field assessments. Development, aside from the N2 road bridges, was evident for 40% of the estuaries assessed in the field. Invasive plant species, including aquatic invasive plants, were present in all estuaries assessed in the field. The extent of invasive plant species was related to the degree of disturbance and surrounding land use pressures. The Mkomazi and Mvoti estuaries that were assessed at a comprehensive level, as they have earmarked for further water abstraction, had the poorest macrophyte health scores. The macrophyte health of these estuaries was much lower than previously determined by the NBA. The decline in health was attributed to the removal of macrophyte habitat for sugarcane cultivation and development as well as displacement by invasive plant species. The areas covered by the macrophyte habitats also differed from the NBA highlighting the importance of updated mapping and ground truthing. Largely differing macrophyte health scores were produced when attributes were calculated using different combinations of macrophyte habitats. Results indicate that only macrophyte habitats and no other floodplain vegetation should be included when calculating abundance. All macrophyte habitats, physical habitats and floodplain should be incorporated when calculating community composition. The minimum of these attributes is used as the overall macrophyte health score as a precautionary approach is followed. Scoring of health is subjective and the only benchmark for determining the most appropriate method is comparion with previous RDM studies. This study illustrates the need for a standardised RDM scoring method that is presented in a manner that ensures the same results irregardless of the speciliast conducting the study. The updated estuary health and importance scores for WMA 11 are necessary to inform management, particularly as few of the estuaries receive formal protection. In conclusion, this study contributed to the limited knowledge of the estuaries of WMA 11 and assisted in determining appropriate methods for assessing the health and importance of estuary macrophytes.
- Full Text:
- Date Issued: 2015
- Authors: Cowie, Meredith
- Date: 2015
- Subjects: Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Aquatic plants -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7930 , vital:24324
- Description: Estuaries require sufficient quantity, quality and appropriate timing of freshwater inflow, referred to as environmental flow requirements, to ensure adequate health and functioning. In South Africa the environmental flow requirements of estuaries is determined using Resource Directed Measures (RDM). The present health and importance of an estuary must be considered when determining the ecological flow required to maintain an estuary in its desired state. An Estuarine Health Index that quantifies changes in abiotic and biotic components from natural conditions to present day is used. Health of biotic components is assessed according to changes in species richness, abundance and community composition. There has, however, been debate regarding the calculation of these attributes. In particular, for macrophytes, the inclusion of all habitat within the Estuarine Functional Zone (i.e. 5 m topographical contour) would affect the health and changes over time determined in past assessments. This is due to different areas being included as different areas would be included The aim of this study was to test the validity and suggest improvements to South Africa’s RDM macrophyte health score determination. The health of macrophytes were assessed at varying levels of intensity from desktop studies to thorough field studies. Rapid field studies provided a visual estimate of macrophyte health; while the intermediate and comprehensive assessments quantified change by mapping the distribution of macrophyte habitats from aerial photographs. These approaches were applied to the 64 estuaries within the Mvoti-Mzimkulu Water Management Area (WMA 11), situated in KwaZulu-Natal (KZN) on the subtropical east coast. Historically, these estuaries have supported restricted macrophyte habitats. Consequently, estuaries that presently or historically supported range limited habitats such as mangroves and swamp forest are considered important. Submerged macrophytes are scarce in KZN estuaries due to siltation and low turbidity and thus estuaries supporting this macrophyte habitat are also important. Based on available literature important estuaries were highlighted and selected for field studies. Transects spanning from the estuary water channel to the boundary of the EFZ provided a generalised distribution of KZN vegetation along an elevation gradient. The transition from estuarine to terrestrial vegetation can be used to improve the current EFZ boundaries, as estuarine area has been found to occur outside of the 5 m contour in some estuaries. Results from the desktop assessment indicated that most of the estuaries are moderately modified. There was a 50 % similarity in the macrophyte health scores determined by the desktop assessment to the 2011 National Biodiversity Assessment (NBA). Field studies mostly confirmed the desktop assessment aside from seven estuaries that had different scores. There has been a significant loss of macrophyte habitat with 100% loss of certain habitats from 9 of the 22 estuaries for which there were field assessments. Submerged macrophytes were not found at any of the estuaries that were assessed in the field. Black mangroves, Bruguiera gymnorrhiza (L.) Lam., were rediscovered at Ngane Estuary, however the few individuals could not be considered a ‘mappable’ community (i.e. <0.5 ha). Mtamvuna and Mkomazi estuaries both supported small stands of mangroves that, compared to data from 2006, appeared healthy. Macrophyte habitats and surrounding coastal forest matched the species composition described in the Vegetation Map of South Africa. The freshwater mangrove or Powder puff tree, Barringtonia racemosa (L.) Roxb, was not abundant in the estuaries. It was only found at four (Damba, Fafa, Little Amanzimtoti and Mvoti) of the estuaries that were assessed in the field. Important estuaries, from a botanical perspective, included some of the larger estuaries such as Mgeni, Durban Bay and Sipingo. Smaller, healthier estuaries that presently support mangrove and swamp forest habitat were also identified as important from a botanical perspective. Macrophyte habitats have mainly been lost due to non-flow related pressures. Sugarcane cultivation occurred within the floodplain of 25% of the estuaries. Nutrient enrichment was evident for 12.5% of the estuaries and reed encroachment was evident for 27% of estuaries for which there were field assessments. Development, aside from the N2 road bridges, was evident for 40% of the estuaries assessed in the field. Invasive plant species, including aquatic invasive plants, were present in all estuaries assessed in the field. The extent of invasive plant species was related to the degree of disturbance and surrounding land use pressures. The Mkomazi and Mvoti estuaries that were assessed at a comprehensive level, as they have earmarked for further water abstraction, had the poorest macrophyte health scores. The macrophyte health of these estuaries was much lower than previously determined by the NBA. The decline in health was attributed to the removal of macrophyte habitat for sugarcane cultivation and development as well as displacement by invasive plant species. The areas covered by the macrophyte habitats also differed from the NBA highlighting the importance of updated mapping and ground truthing. Largely differing macrophyte health scores were produced when attributes were calculated using different combinations of macrophyte habitats. Results indicate that only macrophyte habitats and no other floodplain vegetation should be included when calculating abundance. All macrophyte habitats, physical habitats and floodplain should be incorporated when calculating community composition. The minimum of these attributes is used as the overall macrophyte health score as a precautionary approach is followed. Scoring of health is subjective and the only benchmark for determining the most appropriate method is comparion with previous RDM studies. This study illustrates the need for a standardised RDM scoring method that is presented in a manner that ensures the same results irregardless of the speciliast conducting the study. The updated estuary health and importance scores for WMA 11 are necessary to inform management, particularly as few of the estuaries receive formal protection. In conclusion, this study contributed to the limited knowledge of the estuaries of WMA 11 and assisted in determining appropriate methods for assessing the health and importance of estuary macrophytes.
- Full Text:
- Date Issued: 2015
On the characterisation of photovoltaic device parameters using light beam induced current measurements
- Bezuidenhout, Lucian John-Ross
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2015
- Subjects: Solar cells--Materials , Semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10551 , http://hdl.handle.net/10948/d1020282
- Description: Light Beam Induced Current (LBIC) measurement is a non-destructive technique used to perform localized characterization of solar cells using a light beam as a probe. The technique allows the determination of local photo response of a cell, the electrical parameters and defects that occur in the individual solar cell. The semiconductor materials used to create solar cells are not always defect free and these defects reduce the electrical performance of the device. It is therefore important to use a system that will allow the characterization and extract the solar cell parameters as can be done using the LBIC system. By analysing these parameters and cell defects, further studies can be done to enhance the cell’s lifetime and hence its efficiency. Light beam induced current (LBIC) is a technique that focuses light onto a solar cell device and thus creating a photo-generated current that can be measured in the external circuit for analyses. By scanning this beam probe across a solar cell while measuring the current-voltage characteristics, a map of various parameters can be obtained. This thesis presents the design of the LBIC system, the software interfacing of the data acquisition system and local photo-response within different solar cell technologies. In addition, this thesis represent two curve fitting algorithms namely: the Gradient Descent Optimisation and the Differential Evolution used for the extraction of solar cell device parameters. The algorithms are based on the one-diode solar cell model and make use of the light generated current-voltage (I-V) data obtained from the LBIC system. Different solar cell technologies namely; single crystalline (c-Si) and multicrystalline silicon (mc-Si) was used for analysis. LBIC maps and I-V characteristics of both technologies was obtained. The LBIC maps shows performance degrading defects present in the bulk and the surface of the solar cells as a function of spatial distribution. These localised defects acts as trapping mechanism for the charge carriers and therefore limits recombination within the solar cell and thus decreasing the performance of the solar cell device. The resulting I-V characteristics obtained from the LBIC system were used to determine the performance parameters using the two algorithms. The resultant effect of these parameters on the performance of the solar cells was observed. The overall results showed that LBIC is a useful tool for identifying and characterising defects in solar cells.
- Full Text:
- Date Issued: 2015
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2015
- Subjects: Solar cells--Materials , Semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10551 , http://hdl.handle.net/10948/d1020282
- Description: Light Beam Induced Current (LBIC) measurement is a non-destructive technique used to perform localized characterization of solar cells using a light beam as a probe. The technique allows the determination of local photo response of a cell, the electrical parameters and defects that occur in the individual solar cell. The semiconductor materials used to create solar cells are not always defect free and these defects reduce the electrical performance of the device. It is therefore important to use a system that will allow the characterization and extract the solar cell parameters as can be done using the LBIC system. By analysing these parameters and cell defects, further studies can be done to enhance the cell’s lifetime and hence its efficiency. Light beam induced current (LBIC) is a technique that focuses light onto a solar cell device and thus creating a photo-generated current that can be measured in the external circuit for analyses. By scanning this beam probe across a solar cell while measuring the current-voltage characteristics, a map of various parameters can be obtained. This thesis presents the design of the LBIC system, the software interfacing of the data acquisition system and local photo-response within different solar cell technologies. In addition, this thesis represent two curve fitting algorithms namely: the Gradient Descent Optimisation and the Differential Evolution used for the extraction of solar cell device parameters. The algorithms are based on the one-diode solar cell model and make use of the light generated current-voltage (I-V) data obtained from the LBIC system. Different solar cell technologies namely; single crystalline (c-Si) and multicrystalline silicon (mc-Si) was used for analysis. LBIC maps and I-V characteristics of both technologies was obtained. The LBIC maps shows performance degrading defects present in the bulk and the surface of the solar cells as a function of spatial distribution. These localised defects acts as trapping mechanism for the charge carriers and therefore limits recombination within the solar cell and thus decreasing the performance of the solar cell device. The resulting I-V characteristics obtained from the LBIC system were used to determine the performance parameters using the two algorithms. The resultant effect of these parameters on the performance of the solar cells was observed. The overall results showed that LBIC is a useful tool for identifying and characterising defects in solar cells.
- Full Text:
- Date Issued: 2015
Tetrol and derivatives: synthesis, host-guest properties and racemate resolutions
- Authors: Pohl, Pieter Lourens
- Date: 2015
- Subjects: Chemistry, Organic , Chirality , Asymmetric synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2879 , vital:20359
- Description: In this study, we investigated the potential of a novel chiral host compound (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives for use in racemate resolution using host-guest chemistry. The parent TETROL molecule is composed of a butane chain bearing a hydroxy functionality on each carbon, and two phenyl rings on each of the terminal carbons. The two internal carbon atoms are chiral. The syntheses of TETROL and derivatives were carried out by modifying the diester of naturally-occurring optically active tartaric acid using a variety of aromatic Grignard reagents. These included phenyl, anisyl, tolyl and naphthyl groups, as well as aromatic rings bearing fluoro and trifluoromethyl substitutents. The substituents on the aromatic rings were located in the ortho, meta or para positions. The so-obtained potential host compounds were investigated for their inclusion abilities by recrystallizing them from a number of potential chiral guest compounds such as 2- and 3-methylcyclohexanone, camphor, i-propanol and 2-butanol, as well as various achiral organic compounds. Host:guest ratios were determined by means of 1H-NMR spectroscopy. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. X-Ray data of the inclusion complexes indicated that a pair of 1,3-intramolecular hydrogen bonds was a significant stabilizing factor of the geometries of all the hosts. The guest was always held in the host crystal by means of a hydrogen bond with the host, where the host functioned as the hydrogen bond donor and the guest as the acceptor. There were a number of other inter- and intra-molecular contacts that further stabilized the inclusion complexes. A surprising feature of the inclusion of 3-methylcyclohexanone, as elucidated by X-ray analysis, was that its methyl group adopted the axial orientation, the higher energy conformation for these kinds of molecules, and a 3-alkylketone effect was proposed to be one of the reasons for this observation. Thermal data was used to assess the relative thermal stabilities of the complexes, and the results compared with features of the X-ray structures, in order to determine whether thermal stability is related in some way to the nature of the guest packing in the host crystal. the case of the racemic guests, complexes obtained were analysed using chiral GC-MS. TETROL preferred the R-enantiomers of 2- and 3-methylcyclohexanone (21.7% and 16.7% e.e.). The S-enantiomer of camphor was favoured but the e.e. was low (3.8%). p-AnisylTETROL had a preference for the S-enantiomer in the case of 2- and 3-methylcyclohexanone as well as 2-butanol (44.3%, 20.4% and 1.7% e.e., respectively). p-TolylTETROL could only successfully resolve 2-butanol (23.5% e.e. in favour of the R-enantiomer). o-TolylTETROL preferred the R-enantiomers of methyl phenyl sulfoxide (29.2% e.e.) and 2-butanol (21.5% e.e.). Overall, TETROL and its derivatives exhibited the ability to resolve racemic mixtures to some extent.
- Full Text:
- Date Issued: 2015
- Authors: Pohl, Pieter Lourens
- Date: 2015
- Subjects: Chemistry, Organic , Chirality , Asymmetric synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2879 , vital:20359
- Description: In this study, we investigated the potential of a novel chiral host compound (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives for use in racemate resolution using host-guest chemistry. The parent TETROL molecule is composed of a butane chain bearing a hydroxy functionality on each carbon, and two phenyl rings on each of the terminal carbons. The two internal carbon atoms are chiral. The syntheses of TETROL and derivatives were carried out by modifying the diester of naturally-occurring optically active tartaric acid using a variety of aromatic Grignard reagents. These included phenyl, anisyl, tolyl and naphthyl groups, as well as aromatic rings bearing fluoro and trifluoromethyl substitutents. The substituents on the aromatic rings were located in the ortho, meta or para positions. The so-obtained potential host compounds were investigated for their inclusion abilities by recrystallizing them from a number of potential chiral guest compounds such as 2- and 3-methylcyclohexanone, camphor, i-propanol and 2-butanol, as well as various achiral organic compounds. Host:guest ratios were determined by means of 1H-NMR spectroscopy. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. X-Ray data of the inclusion complexes indicated that a pair of 1,3-intramolecular hydrogen bonds was a significant stabilizing factor of the geometries of all the hosts. The guest was always held in the host crystal by means of a hydrogen bond with the host, where the host functioned as the hydrogen bond donor and the guest as the acceptor. There were a number of other inter- and intra-molecular contacts that further stabilized the inclusion complexes. A surprising feature of the inclusion of 3-methylcyclohexanone, as elucidated by X-ray analysis, was that its methyl group adopted the axial orientation, the higher energy conformation for these kinds of molecules, and a 3-alkylketone effect was proposed to be one of the reasons for this observation. Thermal data was used to assess the relative thermal stabilities of the complexes, and the results compared with features of the X-ray structures, in order to determine whether thermal stability is related in some way to the nature of the guest packing in the host crystal. the case of the racemic guests, complexes obtained were analysed using chiral GC-MS. TETROL preferred the R-enantiomers of 2- and 3-methylcyclohexanone (21.7% and 16.7% e.e.). The S-enantiomer of camphor was favoured but the e.e. was low (3.8%). p-AnisylTETROL had a preference for the S-enantiomer in the case of 2- and 3-methylcyclohexanone as well as 2-butanol (44.3%, 20.4% and 1.7% e.e., respectively). p-TolylTETROL could only successfully resolve 2-butanol (23.5% e.e. in favour of the R-enantiomer). o-TolylTETROL preferred the R-enantiomers of methyl phenyl sulfoxide (29.2% e.e.) and 2-butanol (21.5% e.e.). Overall, TETROL and its derivatives exhibited the ability to resolve racemic mixtures to some extent.
- Full Text:
- Date Issued: 2015
Biomass potential and nutrient export of mature pinus radiata in the southern Cape region of South Africa
- Authors: Van Zyl, Salmon Johannes
- Date: 2015
- Subjects: Pinus radiata -- South Africa , Forest biomass -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4321 , vital:20584
- Description: South Africa lags behind the rest of the world with regard to the availability of allometric biomass information. There is a complete lack of site specific allometric data for Pinus radiata in the southern Cape region, impeding investment in the renewable energy sector. This shortcoming was addressed by developing up-scalable, single tree biomass models. These models quantify the aboveground biomass of rotation age P. radiata grown in the southern Cape across a range of site conditions. The models use diameter at breast height (DBH) to predict the aboveground component biomass. A nutrient loss risk potential was assigned to each biomass component. Nineteen trees were destructively harvested using a full fresh weight sampling approach. Basic density was determined using a water displacement method, while Newton’s volume equation was used for stemwood volume determination. Log linear models were simultaneously regressed through seemingly unrelated regression (SUR) using the “Systemfit” R statistical package to force component additivity. A categorical variable was applied to the models, grouping the data into two Site Index (SI) based categories, namely “Low” SI and “Medium to High” SI, to account for inter-site variability. The corrected Akaike Information Criteria (AICc) and coefficient of determination (R2) was used to determine the goodness of fit of the models. The McElroy R2 for the SUR system was 0.95. Biomass models were developed that are able to predict various tree component masses at high levels of certainty within site and stand attribute ranges similar to this study. The importance of accurate, site specific wood basic density was demonstrated by its substantial weighting on stem and hence total biomass. Results showed that the stemwood mean basic density range was between 503 kg m-3 and 517 kg m-3 for the “Low” SI sites and 458 kg m-3 for the “Medium to High” SI sites. Site quality can have a major impact on the models, particularly on poorer sites where stemwood production is proportionally less than other tree components. Total aboveground biomass was estimated to range between 58.61 odt ha-1 and 70.85 odt ha-1 for “Low” SI sites, and 185.31 odt ha-1 to 266.58 odt ha-1 for “Medium to High” SI sites. Stemwood biomass accounted for 65% of the total aboveground biomass for “Low” SI sites and 70% for “Medium to High” SI sites.
- Full Text:
- Date Issued: 2015
- Authors: Van Zyl, Salmon Johannes
- Date: 2015
- Subjects: Pinus radiata -- South Africa , Forest biomass -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4321 , vital:20584
- Description: South Africa lags behind the rest of the world with regard to the availability of allometric biomass information. There is a complete lack of site specific allometric data for Pinus radiata in the southern Cape region, impeding investment in the renewable energy sector. This shortcoming was addressed by developing up-scalable, single tree biomass models. These models quantify the aboveground biomass of rotation age P. radiata grown in the southern Cape across a range of site conditions. The models use diameter at breast height (DBH) to predict the aboveground component biomass. A nutrient loss risk potential was assigned to each biomass component. Nineteen trees were destructively harvested using a full fresh weight sampling approach. Basic density was determined using a water displacement method, while Newton’s volume equation was used for stemwood volume determination. Log linear models were simultaneously regressed through seemingly unrelated regression (SUR) using the “Systemfit” R statistical package to force component additivity. A categorical variable was applied to the models, grouping the data into two Site Index (SI) based categories, namely “Low” SI and “Medium to High” SI, to account for inter-site variability. The corrected Akaike Information Criteria (AICc) and coefficient of determination (R2) was used to determine the goodness of fit of the models. The McElroy R2 for the SUR system was 0.95. Biomass models were developed that are able to predict various tree component masses at high levels of certainty within site and stand attribute ranges similar to this study. The importance of accurate, site specific wood basic density was demonstrated by its substantial weighting on stem and hence total biomass. Results showed that the stemwood mean basic density range was between 503 kg m-3 and 517 kg m-3 for the “Low” SI sites and 458 kg m-3 for the “Medium to High” SI sites. Site quality can have a major impact on the models, particularly on poorer sites where stemwood production is proportionally less than other tree components. Total aboveground biomass was estimated to range between 58.61 odt ha-1 and 70.85 odt ha-1 for “Low” SI sites, and 185.31 odt ha-1 to 266.58 odt ha-1 for “Medium to High” SI sites. Stemwood biomass accounted for 65% of the total aboveground biomass for “Low” SI sites and 70% for “Medium to High” SI sites.
- Full Text:
- Date Issued: 2015
Perspectives of stakeholders on engagement around benefits and use of the Wilderness and Swartvlei lakes
- Authors: Roos, Aneri
- Date: 2015
- Subjects: Lake ecology -- South Africa , Environmental management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6588 , vital:21121
- Description: The objective of this research was to determine how stakeholder engagement impacts on the use and sharing of ecosystem service benefits derived from large lake systems. The Wilderness and Swartvlei lake systems, which form an integral part of the Wilderness Section of the Garden Route National Park (GRNP), were chosen as the study area. The park is juxtaposed with urban and other land uses making it one of the most integrated urban conservation areas in South Africa. The park is an open-access park with only enclosed areas being the camping and chalet areas that borders onto the Touw River Estuary. A major contribution of this research was that it classified stakeholder groups into ten meta-identities (associations, businesses, charity organisations, conservancies, government departments, informal groupings, learning/educational institutions, multiple stakeholder projects, spiritual groupings and sports clubs) and that through an iterative research approach it stimulated dialogue between individuals across the various meta-identities. Engagement is a way of allowing stakeholders to develop a sense of ownership through the decision-making process. This could also lead to a higher level of trust and cooperation. The main insights drawn from this research were that, history is important; engagement is characterised by an on-going blame-game (at least in part as a result of this particular history); meta-identities share some values, but differ in how they see the world; there is a concern over social issues (widespread concern, but few mechanisms to address the issue); management agencies are stewards of the feedbacks between social and ecological systems (responsible for regulating flows of benefits), but in open-access systems cannot do so on their own; all meta-identities are keen to contribute and this can, with appropriate facilitation, be harnessed towards collective action. Stakeholders associated with all ten meta-identities identified provisioning and cultural services as a benefit derived from the lakes. No regulating or supporting services were identified as benefits. This could indicate a gap in awareness of the importance of these services. A category that emerged from this study is the importance of employment opportunities linked to the management of natural resources. The study showed that engagement does not occur around the benefits that can be derived from the lakes, but rather around the issues that have a direct or indirect influence on the ecosystem services and therefore the suite of benefits that would be available for sharing. The issues could be divided into two broad themes; social issues and developmental pressures. The social issues pose an indirect threat to the lakes while the developmental pressures pose a direct threat. As the mandates across agencies differ, with the municipalities concerned with the social issues and SANParks with the pressures, the importance of communication and cooperative governance was highlighted.
- Full Text:
- Date Issued: 2015
- Authors: Roos, Aneri
- Date: 2015
- Subjects: Lake ecology -- South Africa , Environmental management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/6588 , vital:21121
- Description: The objective of this research was to determine how stakeholder engagement impacts on the use and sharing of ecosystem service benefits derived from large lake systems. The Wilderness and Swartvlei lake systems, which form an integral part of the Wilderness Section of the Garden Route National Park (GRNP), were chosen as the study area. The park is juxtaposed with urban and other land uses making it one of the most integrated urban conservation areas in South Africa. The park is an open-access park with only enclosed areas being the camping and chalet areas that borders onto the Touw River Estuary. A major contribution of this research was that it classified stakeholder groups into ten meta-identities (associations, businesses, charity organisations, conservancies, government departments, informal groupings, learning/educational institutions, multiple stakeholder projects, spiritual groupings and sports clubs) and that through an iterative research approach it stimulated dialogue between individuals across the various meta-identities. Engagement is a way of allowing stakeholders to develop a sense of ownership through the decision-making process. This could also lead to a higher level of trust and cooperation. The main insights drawn from this research were that, history is important; engagement is characterised by an on-going blame-game (at least in part as a result of this particular history); meta-identities share some values, but differ in how they see the world; there is a concern over social issues (widespread concern, but few mechanisms to address the issue); management agencies are stewards of the feedbacks between social and ecological systems (responsible for regulating flows of benefits), but in open-access systems cannot do so on their own; all meta-identities are keen to contribute and this can, with appropriate facilitation, be harnessed towards collective action. Stakeholders associated with all ten meta-identities identified provisioning and cultural services as a benefit derived from the lakes. No regulating or supporting services were identified as benefits. This could indicate a gap in awareness of the importance of these services. A category that emerged from this study is the importance of employment opportunities linked to the management of natural resources. The study showed that engagement does not occur around the benefits that can be derived from the lakes, but rather around the issues that have a direct or indirect influence on the ecosystem services and therefore the suite of benefits that would be available for sharing. The issues could be divided into two broad themes; social issues and developmental pressures. The social issues pose an indirect threat to the lakes while the developmental pressures pose a direct threat. As the mandates across agencies differ, with the municipalities concerned with the social issues and SANParks with the pressures, the importance of communication and cooperative governance was highlighted.
- Full Text:
- Date Issued: 2015
Efficiency evaluation of South Africa tertiary education institutions using data envelopment analysis
- Authors: Chitekedza, Ignatious
- Date: 2015
- Subjects: Data envelopment analysis -- South Africa , Principal components analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4764 , vital:20674
- Description: With an increasing number of students enrolling at higher education institutions in South Africa, it has become important to investigate whether these institutions are using their resources adequately. This study uses data envelopment analysis (DEA) to estimate the efficiency of 23 South African tertiary education institutions based on both teaching and research outputs. Using DEA we are able to rank South African universities according to their use of resources in these two areas. These rankings can identify institutions which are performing well and also those which require improvement. The effect that merging institutions has on this efficiency is also determined. Owing to the limited sample size, variable reduction techniques, including the efficiency contribution measure (ECM) and principal components analysis (PCA-DEA), were used to improve the discrimination of the analysis.
- Full Text:
- Date Issued: 2015
- Authors: Chitekedza, Ignatious
- Date: 2015
- Subjects: Data envelopment analysis -- South Africa , Principal components analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4764 , vital:20674
- Description: With an increasing number of students enrolling at higher education institutions in South Africa, it has become important to investigate whether these institutions are using their resources adequately. This study uses data envelopment analysis (DEA) to estimate the efficiency of 23 South African tertiary education institutions based on both teaching and research outputs. Using DEA we are able to rank South African universities according to their use of resources in these two areas. These rankings can identify institutions which are performing well and also those which require improvement. The effect that merging institutions has on this efficiency is also determined. Owing to the limited sample size, variable reduction techniques, including the efficiency contribution measure (ECM) and principal components analysis (PCA-DEA), were used to improve the discrimination of the analysis.
- Full Text:
- Date Issued: 2015
Studies on flax/polypropylene-reinforced composites for automotive applications
- Authors: Biyana, Nobuhle Yvonne
- Date: 2015
- Subjects: Polypropylene fibers , Fibrous composites , Reinforced plastics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10456 , http://hdl.handle.net/10948/d1021150
- Description: The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.
- Full Text:
- Date Issued: 2015
- Authors: Biyana, Nobuhle Yvonne
- Date: 2015
- Subjects: Polypropylene fibers , Fibrous composites , Reinforced plastics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10456 , http://hdl.handle.net/10948/d1021150
- Description: The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.
- Full Text:
- Date Issued: 2015
In vivo and In vitro investigations to elucidate the associations of B-N-methylamino-L-alanine with proteins
- Authors: Van Onselen, Rianita
- Date: 2015
- Subjects: Cyanobacteria , Bioaccumulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4923 , vital:20767
- Description: The cyanobacterially synthesized non-canonical amino acid β-N-methylamino-ʟ-alanine (BMAA) has been proposed to be a causative agent in the development of sporadic neurodegenerative diseases. This neurotoxin bioaccumulates and biomagnifies with increasing trophic levels in ecosystems by associating with proteins. It has been suggested that these associations with host proteins also serve as a reservoir from where BMAA is slowly released with normal protein catabolism, resulting in a continuous low level exposure. However, the nature of these associations remains poorly defined. The widely accepted hypothesis regarding the nature of these associations is that BMAA associates with proteins through primary incorporation into proteins with specific replacement of serine. In addition to excitotoxicity, BMAA misincorporation has been proposed as a potential mechanism of toxicity because of its link to protein tangle diseases. Interactions between BMAA and proteins that are not the result of misincorporation, have also been observed. However, the nature of these non-primary associations has not been investigated. This study focussed on establishing whether BMAA is misincorporated into host proteins with consequent toxicity, and on elucidating the nature of the BMAA-protein associations not linked to primary incorporation. In comparative studies between BMAA and canavanine, an arginine analogue known to misincorporate, exposure to BMAA did not result in any toxicity in prokaryotes or in an undifferentiated eukaryotic mammalian cell line, in contrast to what was observed upon canavanine exposure. Differentiation of the cell line with nerve growth factor to express glutamate receptors resulted in marked toxicity upon BMAA exposure, highlighting excitoxicity as the main mechanism of BMAA toxicity. Furthermore, it was demonstrated that BMAA interacts with free amino acids and proteins in the absence of de novo protein synthesis, causing enzyme inhibition and protein misfolding. It was concluded that BMAA does not interact with proteins through primary incorporation and that the observed associations are the result of an interaction between BMAA and amino acid side chains to form covalent bonds.
- Full Text:
- Date Issued: 2015
- Authors: Van Onselen, Rianita
- Date: 2015
- Subjects: Cyanobacteria , Bioaccumulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4923 , vital:20767
- Description: The cyanobacterially synthesized non-canonical amino acid β-N-methylamino-ʟ-alanine (BMAA) has been proposed to be a causative agent in the development of sporadic neurodegenerative diseases. This neurotoxin bioaccumulates and biomagnifies with increasing trophic levels in ecosystems by associating with proteins. It has been suggested that these associations with host proteins also serve as a reservoir from where BMAA is slowly released with normal protein catabolism, resulting in a continuous low level exposure. However, the nature of these associations remains poorly defined. The widely accepted hypothesis regarding the nature of these associations is that BMAA associates with proteins through primary incorporation into proteins with specific replacement of serine. In addition to excitotoxicity, BMAA misincorporation has been proposed as a potential mechanism of toxicity because of its link to protein tangle diseases. Interactions between BMAA and proteins that are not the result of misincorporation, have also been observed. However, the nature of these non-primary associations has not been investigated. This study focussed on establishing whether BMAA is misincorporated into host proteins with consequent toxicity, and on elucidating the nature of the BMAA-protein associations not linked to primary incorporation. In comparative studies between BMAA and canavanine, an arginine analogue known to misincorporate, exposure to BMAA did not result in any toxicity in prokaryotes or in an undifferentiated eukaryotic mammalian cell line, in contrast to what was observed upon canavanine exposure. Differentiation of the cell line with nerve growth factor to express glutamate receptors resulted in marked toxicity upon BMAA exposure, highlighting excitoxicity as the main mechanism of BMAA toxicity. Furthermore, it was demonstrated that BMAA interacts with free amino acids and proteins in the absence of de novo protein synthesis, causing enzyme inhibition and protein misfolding. It was concluded that BMAA does not interact with proteins through primary incorporation and that the observed associations are the result of an interaction between BMAA and amino acid side chains to form covalent bonds.
- Full Text:
- Date Issued: 2015
An exposition of Hilbert C-modules
- Authors: Sokopo, Bulelani Joab
- Date: 2015
- Subjects: Mathematics Algebra , Functions, Continuous Mathematical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50008 , vital:41974
- Description: In trying to prove that derivations of type I AW -algebras are inner, I. Kaplansky introduced and developed the basics of the concept of Hilbert C- modules. He sought to generalize the idea of a Hilbert space by replacing the field C of all complex numbers with a general (commutative and unital) C-algebra. Twenty years later, the concept was broadened and expanded to non-commutative C-algebras by W. L. Paschke and M. A. Rieffel in their papers on inner product modules over B-algebras and induced representations of C-algebras, respectively. Since then, the theory of Hilbert C-modules has grown rapidly. It was used by G. G. Kasparov as the framework for his bivariant K-theory. More recently, Hilbert C-modules have formed the technical basis for the C*-algebraic approach to quantum group theory. The aim of this dissertation is to provide as detailed an account as possible of the theory of Hilbert C-modules, as given in a book of E. C. Lance, up to and including the KSGNS construction. The KSGNS construction, named after Kasparov, Stinespring, Gelfand, Naimark and Segal, is a generalization to Hilbert C-modules of the familiar GNS construction for C-algebras. The result by Kaplansky that all derivations of a type I AW-algebra are inner is given as an application in the final chapter of the dissertation.
- Full Text:
- Date Issued: 2015
- Authors: Sokopo, Bulelani Joab
- Date: 2015
- Subjects: Mathematics Algebra , Functions, Continuous Mathematical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50008 , vital:41974
- Description: In trying to prove that derivations of type I AW -algebras are inner, I. Kaplansky introduced and developed the basics of the concept of Hilbert C- modules. He sought to generalize the idea of a Hilbert space by replacing the field C of all complex numbers with a general (commutative and unital) C-algebra. Twenty years later, the concept was broadened and expanded to non-commutative C-algebras by W. L. Paschke and M. A. Rieffel in their papers on inner product modules over B-algebras and induced representations of C-algebras, respectively. Since then, the theory of Hilbert C-modules has grown rapidly. It was used by G. G. Kasparov as the framework for his bivariant K-theory. More recently, Hilbert C-modules have formed the technical basis for the C*-algebraic approach to quantum group theory. The aim of this dissertation is to provide as detailed an account as possible of the theory of Hilbert C-modules, as given in a book of E. C. Lance, up to and including the KSGNS construction. The KSGNS construction, named after Kasparov, Stinespring, Gelfand, Naimark and Segal, is a generalization to Hilbert C-modules of the familiar GNS construction for C-algebras. The result by Kaplansky that all derivations of a type I AW-algebra are inner is given as an application in the final chapter of the dissertation.
- Full Text:
- Date Issued: 2015
The metabolism and environmental fate of the cyanobacterial neurotoxin Beta-N-methylamino-L-alanine
- Authors: Downing, Simoné
- Date: 2015
- Subjects: Cyanobacteria , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4225 , vital:20569
- Description: The neurotoxic amino acid β-‐N-‐methylamino-Lalanine (BMAA)is present in environmentally ubiquitous cyanobacteria and bioaccumulates and biomagnifies within the environment. The implication of BMAA in the development of neurodegenerative disease has raised concerns over the potential risk of human exposure to this neurotoxin, and has focussed attention on identifying possible routes of exposure that include direct contact with cyanobacteria and the ingestion of BMAA-‐containing plant and animal products.
- Full Text:
- Date Issued: 2015
- Authors: Downing, Simoné
- Date: 2015
- Subjects: Cyanobacteria , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4225 , vital:20569
- Description: The neurotoxic amino acid β-‐N-‐methylamino-Lalanine (BMAA)is present in environmentally ubiquitous cyanobacteria and bioaccumulates and biomagnifies within the environment. The implication of BMAA in the development of neurodegenerative disease has raised concerns over the potential risk of human exposure to this neurotoxin, and has focussed attention on identifying possible routes of exposure that include direct contact with cyanobacteria and the ingestion of BMAA-‐containing plant and animal products.
- Full Text:
- Date Issued: 2015
Factors affecting the success of reseeding rehabilitation in the semi-arid Karoo, South Africa
- Authors: Matthee, Willem
- Date: 2015
- Subjects: Ecological disturbances -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Environmental degradation -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2889 , vital:20360
- Description: Due to overgrazing, mining and other anthropogenic disturbances, large sections of the Karoo region have been degraded, resulting in areas with low vegetation cover, where erosion rates are high and vegetation is dominated by unpalatable species. These areas have low and unpredictable rainfall, with slow to non-existent autogenic recovery, and this often forces landowners to implement reseeding rehabilitation in an attempt to increase both overall vegetation cover and the relative abundance of palatable plants. Landowners use soil preparation treatments, which include creating micro-catchments, ripping, mulching and brush packing, to supplement land rehabilitation. This study investigated the significance of initial rainfall, mean monthly rainfall, soil preparation techniques, slope, existing vegetation cover, litter, mulch and stone cover in determining the success of reseeding rehabilitation. Rainfall had the most significant influence, where long-lived shrubs established best under low initial rainfall and high mean monthly rainfall, and grasses established best after receiving high initial rainfall. Micro-catchments proved the most successful soil preparation technique for the establishment of long-lived shrubs, while ripping and mulching impacted negatively on grass establishment. A combination of mulch and micro-catchments aided Osteospermum sinuatum establishment in soils where soil shrinkage cracks occurred. Temperature influenced seed germination and drought tolerance of Lessertia annularis, Fingerhuthia africana and O. sinuatum, with higher germination success of O. sinuatum under temperatures simulating summer, and of F. africana under temperatures simulating winter. L. annularis germination had a faster growth rate and higher survival when germinated under autumn/spring temperatures. Landowners are advised to sow seeds of more than one species during rehabilitation, to include micro-catchments as soil preparation treatment, and to sow seeds during a time when rainfall is predicted to be high.
- Full Text:
- Date Issued: 2015
- Authors: Matthee, Willem
- Date: 2015
- Subjects: Ecological disturbances -- South Africa -- Karoo , Arid regions -- South Africa -- Karoo , Environmental degradation -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/2889 , vital:20360
- Description: Due to overgrazing, mining and other anthropogenic disturbances, large sections of the Karoo region have been degraded, resulting in areas with low vegetation cover, where erosion rates are high and vegetation is dominated by unpalatable species. These areas have low and unpredictable rainfall, with slow to non-existent autogenic recovery, and this often forces landowners to implement reseeding rehabilitation in an attempt to increase both overall vegetation cover and the relative abundance of palatable plants. Landowners use soil preparation treatments, which include creating micro-catchments, ripping, mulching and brush packing, to supplement land rehabilitation. This study investigated the significance of initial rainfall, mean monthly rainfall, soil preparation techniques, slope, existing vegetation cover, litter, mulch and stone cover in determining the success of reseeding rehabilitation. Rainfall had the most significant influence, where long-lived shrubs established best under low initial rainfall and high mean monthly rainfall, and grasses established best after receiving high initial rainfall. Micro-catchments proved the most successful soil preparation technique for the establishment of long-lived shrubs, while ripping and mulching impacted negatively on grass establishment. A combination of mulch and micro-catchments aided Osteospermum sinuatum establishment in soils where soil shrinkage cracks occurred. Temperature influenced seed germination and drought tolerance of Lessertia annularis, Fingerhuthia africana and O. sinuatum, with higher germination success of O. sinuatum under temperatures simulating summer, and of F. africana under temperatures simulating winter. L. annularis germination had a faster growth rate and higher survival when germinated under autumn/spring temperatures. Landowners are advised to sow seeds of more than one species during rehabilitation, to include micro-catchments as soil preparation treatment, and to sow seeds during a time when rainfall is predicted to be high.
- Full Text:
- Date Issued: 2015
The antifungal activity of an aqueous Tulbaghia violacea plant extract against Aspergillus flavus
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2015
- Subjects: Medicinal plants , Antifungal agents , Fungi -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5858 , vital:21001
- Description: Phytochemical analysis of both HEA1 and the crude plant extract showed the presence of phenolics, tannins and saponins. Saponins were the predominant secondary metabolites and were mostly abundant in the plant extract and to a lesser extent in the active compound. Steroidal saponins, tannins and phenolics were also detected in the plant extract, but only the phenolics were detected in the active compound. The results of the phytochemical analysis showed that those compounds that were not present in the active compound could be removed from the crude extract during the TLC purification process. Investigation on the mechanism of action of the crude plant extract on the sterol production by A. flavus showed that the plant extract affected ergosterol biosynthesis by causing an accumulation of oxidosqualene in the ergosterol biosynthetic pathway resulting in a decline in ergosterol production. An oscillatory response in lanosterol production was observed in the presence of the plant extract, which may be an adaptation mechanism of A. flavus to unfavourable conditions and compensation for the loss of enzyme activity which may have occurred as a result of the accumulation of oxidosqualene. The antifungal activity of the plant extract on ergosterol production by A. flavus may also be due to saponins which target the cell membrane and ergosterol production in fungi. The effect of the plant extract on the fungal cell wall of A. flavus also showed that the plant extract caused a decline in β-(1, 3) glucan production by inhibiting β-glucan synthase. The plant extract also affected the chitin synthesis pathway of A. flavus, by causing a decline in chitin production, which was due to the inhibition of chitin synthase. Investigation of chitinase production using 4MU substrates showed that the plant extract caused an accumulation of chitobioses, by activating chitobiosidases and endochitinases. A decline in N-acetylglucosaminidase activity in the presence of the plant extract was observed and this prevented the formation of N-acetylglucosamine. The accumulation of chitobiosidase and endochitinase may be as a result of autolysis that may be triggered by A. flavus as a survival mechanism in the presence of the plant extract and as a compensatory mechanism for the loss of β-glucans and chitin. The antifungal effect of the plant extract on various components of the cell wall of A. flavus, makes T. violacea aqueous plant extract an ideal chemotherapeutic agent against both human and plant pathogens of Aspergillus. The broad spectrum of antifungal activity of T. violacea against A. flavus also eliminates any chances of the fungus developing resistance towards it and would make it a candidate for use as a potential antifungal agent. Further identification and possible chemical synthesis is needed to shed light on the safety and efficacy of the active compound for further development as a chemotherapeutic agent.
- Full Text:
- Date Issued: 2015
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2015
- Subjects: Medicinal plants , Antifungal agents , Fungi -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5858 , vital:21001
- Description: Phytochemical analysis of both HEA1 and the crude plant extract showed the presence of phenolics, tannins and saponins. Saponins were the predominant secondary metabolites and were mostly abundant in the plant extract and to a lesser extent in the active compound. Steroidal saponins, tannins and phenolics were also detected in the plant extract, but only the phenolics were detected in the active compound. The results of the phytochemical analysis showed that those compounds that were not present in the active compound could be removed from the crude extract during the TLC purification process. Investigation on the mechanism of action of the crude plant extract on the sterol production by A. flavus showed that the plant extract affected ergosterol biosynthesis by causing an accumulation of oxidosqualene in the ergosterol biosynthetic pathway resulting in a decline in ergosterol production. An oscillatory response in lanosterol production was observed in the presence of the plant extract, which may be an adaptation mechanism of A. flavus to unfavourable conditions and compensation for the loss of enzyme activity which may have occurred as a result of the accumulation of oxidosqualene. The antifungal activity of the plant extract on ergosterol production by A. flavus may also be due to saponins which target the cell membrane and ergosterol production in fungi. The effect of the plant extract on the fungal cell wall of A. flavus also showed that the plant extract caused a decline in β-(1, 3) glucan production by inhibiting β-glucan synthase. The plant extract also affected the chitin synthesis pathway of A. flavus, by causing a decline in chitin production, which was due to the inhibition of chitin synthase. Investigation of chitinase production using 4MU substrates showed that the plant extract caused an accumulation of chitobioses, by activating chitobiosidases and endochitinases. A decline in N-acetylglucosaminidase activity in the presence of the plant extract was observed and this prevented the formation of N-acetylglucosamine. The accumulation of chitobiosidase and endochitinase may be as a result of autolysis that may be triggered by A. flavus as a survival mechanism in the presence of the plant extract and as a compensatory mechanism for the loss of β-glucans and chitin. The antifungal effect of the plant extract on various components of the cell wall of A. flavus, makes T. violacea aqueous plant extract an ideal chemotherapeutic agent against both human and plant pathogens of Aspergillus. The broad spectrum of antifungal activity of T. violacea against A. flavus also eliminates any chances of the fungus developing resistance towards it and would make it a candidate for use as a potential antifungal agent. Further identification and possible chemical synthesis is needed to shed light on the safety and efficacy of the active compound for further development as a chemotherapeutic agent.
- Full Text:
- Date Issued: 2015
Evaluating the effectiveness of public participation in the environmental impact assessment process in South Africa
- Authors: Uithaler, Eldrid Marlon
- Date: 2015
- Subjects: Environmental impact analysis -- South Africa , Environmental policy -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5928 , vital:21015
- Description: This research is based on reflections of various practitioners and their views on how public participation processes may or may not contribute to effective EIA decisions. It is therefore grounded in what is described as practitioner-based research. To study comparative development activities effectively, one must draw on many disciplines and construct a balanced understanding of historical and contemporary development processes. No single conventional disciplinary area of research is able to integrate the issues of public participation, EIA and decision-making in the context of the current development debate. The emergence of Trans-disciplinary areas of research allows for such integration. The Africa Earth Observatory Network (AEON) institute creates the space for this study to achieve an integrated response to the question of the effectiveness of public participation in EIA and decision-making. This further creates the opportunity to contribute and expand the growing body of knowledge and literature of public participation in the earth stewardship science discipline. Making use of triangulation, this study fulfils four major tasks: firstly, an assessment is made on the historical and theoretical importance, process and outcome of both EIA and public participation internationally and in South Africa. Secondly, three prominent case studies (i) the Coega IDZ, (ii) the Pondoland N2 Toll Road, and (iii) the anticipated Hydraulic Fracturing in the Karoo each focusses on concerns of an environmental, socio-economic, and political nature to assess if the public participation process has had influence, if any, on the final decisions for these projects to go-ahead. Thirdly, a survey was conducted to establish the views and perceptions of practitioners in the EIA and public participation domain on the effectiveness of public participation in EIA processes. Lastly, face-to-face interviews were conducted with various ‘pracademics’, i.e. consultants, practitioners, government, and non-governmental officials to establish their views on how public participation may or may not influence EIA decisions. Utilising the International Association for Public Participation’s (IAP2) participation spectrum as an evaluation tool, this research explores thirteen key criteria normally attributed to effective public participation. This provides a scale (inform, involve, consult, collaborate) to assess whether public participation in EIA in South Africa is least effective (inform) or most effective (collaborate). My research confirms that in South Africa an enabling environment to address impacts on our environment is emerging. One of the main challenges remains putting in place robust, clear and effective regulations, models or approaches that provide for effective public participation and decision-making in EIAs. My research also suggests that the legislation on which EIA is based cannot by itself guarantee the effectiveness of public participation processes. In practice, EIA is an institutional process of power division between different actors, and the practitioner or ‘pracademic’ has to play a more fundamental role to ensure effectiveness and fairness in the public participation process. Academic commentators should therefore call for new approaches that emphasise collaborative interaction between decision-makers and the public as well as deliberation amongst participants.
- Full Text:
- Date Issued: 2015
- Authors: Uithaler, Eldrid Marlon
- Date: 2015
- Subjects: Environmental impact analysis -- South Africa , Environmental policy -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5928 , vital:21015
- Description: This research is based on reflections of various practitioners and their views on how public participation processes may or may not contribute to effective EIA decisions. It is therefore grounded in what is described as practitioner-based research. To study comparative development activities effectively, one must draw on many disciplines and construct a balanced understanding of historical and contemporary development processes. No single conventional disciplinary area of research is able to integrate the issues of public participation, EIA and decision-making in the context of the current development debate. The emergence of Trans-disciplinary areas of research allows for such integration. The Africa Earth Observatory Network (AEON) institute creates the space for this study to achieve an integrated response to the question of the effectiveness of public participation in EIA and decision-making. This further creates the opportunity to contribute and expand the growing body of knowledge and literature of public participation in the earth stewardship science discipline. Making use of triangulation, this study fulfils four major tasks: firstly, an assessment is made on the historical and theoretical importance, process and outcome of both EIA and public participation internationally and in South Africa. Secondly, three prominent case studies (i) the Coega IDZ, (ii) the Pondoland N2 Toll Road, and (iii) the anticipated Hydraulic Fracturing in the Karoo each focusses on concerns of an environmental, socio-economic, and political nature to assess if the public participation process has had influence, if any, on the final decisions for these projects to go-ahead. Thirdly, a survey was conducted to establish the views and perceptions of practitioners in the EIA and public participation domain on the effectiveness of public participation in EIA processes. Lastly, face-to-face interviews were conducted with various ‘pracademics’, i.e. consultants, practitioners, government, and non-governmental officials to establish their views on how public participation may or may not influence EIA decisions. Utilising the International Association for Public Participation’s (IAP2) participation spectrum as an evaluation tool, this research explores thirteen key criteria normally attributed to effective public participation. This provides a scale (inform, involve, consult, collaborate) to assess whether public participation in EIA in South Africa is least effective (inform) or most effective (collaborate). My research confirms that in South Africa an enabling environment to address impacts on our environment is emerging. One of the main challenges remains putting in place robust, clear and effective regulations, models or approaches that provide for effective public participation and decision-making in EIAs. My research also suggests that the legislation on which EIA is based cannot by itself guarantee the effectiveness of public participation processes. In practice, EIA is an institutional process of power division between different actors, and the practitioner or ‘pracademic’ has to play a more fundamental role to ensure effectiveness and fairness in the public participation process. Academic commentators should therefore call for new approaches that emphasise collaborative interaction between decision-makers and the public as well as deliberation amongst participants.
- Full Text:
- Date Issued: 2015