Anti-diabetic and phytochemical analysis of sutherlandia frutescens extracts
- Authors: Adefuye, Ogheneochuko Janet
- Date: 2016
- Subjects: Medicinal plants -- Africa , Traditional medicine -- Africa , Herbs -- Therapeutic use -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/3549 , vital:20441
- Description: In Africa, the importance of medicinal plants in folklore medicine and their contribution to primary healthcare is well recognized. Across the continent, local herbal mixtures still provide the only therapeutic option for about 80% of the population. The vast floral diversity and the intrinsic ethnobotanical knowledge has been the backbone of localized traditional herbal medical practices. In Africa, an estimated 5400 of the 60000 described plant taxa possess over 16300 therapeutic uses. Similarly, with a therapeutic flora comprising of approximately 650 species, herbal medical practitioners in South Africa, make use of a plethora of plants to treat different human diseases and infections. Over the years, studies have identified numerous plant species with potential against chronic metabolic diseases including type 2 diabetes mellitus (T2DM). Globally, the incidence and prevalence of T2DM have reached epidemic proportions affecting people of all ages, nationalities and ethnicity. Considered the fourth leading cause of deaths by disease, T2DM is a global health crisis with an estimated diagnosis and mortality frequency of 1 every 5 seconds and 1 every 7 seconds respectively. Though the exact pathophysiology of T2DM is not entirely understood, initial peripheral insulin resistance in adipose tissue, liver, and skeletal muscle with subsequent pancreatic β-cell dysfunction resulting from an attempt to compensate for insulin resistance is a common feature of the disease. The current approach to treating T2DM is the use of oral antidiabetic agents (OAAs), insulin, and incretin-based drugs in an attempt to achieve glycaemic control and maintain glucose homeostasis. However, conventional anti-T2DM drugs have been shown to have limited efficacies and serious adverse effects. Hence, the need for newer, more efficacious and safer anti-T2DM agents. Sutherlandia frutescens subsp. microphylla is a flowering shrub of the pea family (Fabaceae/Leguminaceae) found mainly in the Western Cape and Karoo regions of Southern Africa. Concoctions of various parts of the plant are used in the management of different ailments including T2DM. However, despite extensive biological and pharmacological studies, few analyses exist of the chemical constituents of S. frutescens and no Triple Time of Flight Liquid Chromatography with Mass Spectrometry (Triple TOF LC/MS/MS) analysis has been performed. The initial aim of this study was to investigate the phytochemical profile of hot aqueous, cold aqueous, 80% ethanolic, 100% ethanolic, 80% methanolic and 100% methanolic extracts of a single source S. frutescens plant material using colorimetric and spectrophotometric analysis. The hot aqueous extractant was found to be the best extractant for S. frutescens, yielding 1.99 g of crude extract from 16 g fresh powdered plant material. This data suggests that application of heat and water as the extractant (hot aqueous) could play a vital role in extraction of bioactive compounds from S. frutescens and also justifies the traditional use of a tea infusion of S. frutescens. Colorimetric analysis revealed the presence of flavonoids, flavonols, tannins, and phenols in all extracts with varying intensity. The organic extracts 100% methanol, 80% and 100% ethanol exhibited high color intensity (+++) for flavonoids and flavonols respectively, while all the extracts exhibited a moderate color intensity (++) for tannins and phenols. Spectrophotometric analysis of S. frutescens extracts revealed that all the organic extracts contained a significantly higher concentration (in mg/g of extract) of flavonols and tannins when compared to the aqueous extracts. All extracts contained approximately equal levels of phenols. These data confirm the presence of all four groups of bioactive phytocompounds in the S. frutescens extracts used in this study, and also confirm that different solvent extractants possess the capability to differentially extract specific groups of phytocompounds. in individual extracts. Further comparison of these compounds with online databases of anti-diabetic phytocompounds led to the preliminary identification of 10 possible anti-diabetic compounds; α-Pinene, Limonene, Sabinene, Carvone, Myricetin, Rutin, Stigmasterol, Emodin, Sarpagine and Hypoglycin B in crude and solid phase extraction (SPE) fractions of S. frutesecens. Furthermore, using two hepatic cell lines (Chang and HepG2) as an in-vtro model system, the anti-T2DM properties of crude aqueous and organic extracts of S. frutescents was investigated and compared. Both aqueous and organic extracts of S. frutescens were found to decrease gluconeogenesis, increase glucose uptake and decrease lipid accumulation (Triacylglycerol, Diacylglycerol, and Monoacylglycerol) in Chang and HepG2 hepatic cell cultures made insulin resistant (IR) following exposure to high concentration of insulin and fructose. Using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), the aqueous and organic extracts of S. frutescens were confirmed to regulate the expression of Vesicle-associated membrane protein 3 (VAMP3), Mitogen-activated protein kinase 8 (MAPK8), and Insulin receptor substrate 1 (IRS1) in insulin resistant hepatic cells. IR-mediated downregulation of VAMP3, MAPK8, and IRS1 mRNA in IR HepG2 hepatic cell cultures was reversed in the presence of aqueous and organic extracts of S. frutescens. The hot aqueous extract displayed the highest activity in all the assays, while all the organic extracts displayed similar potency. In conclusion, this study reports that aqueous and organic extracts of S. frutescens possess numerous anti-diabetic compounds that can be further investigated for the development of new, more efficacious and less toxic anti-diabetic agents. The presence of multiple compounds in a single extract does suggest a synergistic or combinatorial therapeutic effect. These findings support the burgeoning body of in-vivo and in-vitro literature evidence on the anti-diabetic properties of S. frutescens and its use in folklore medicine.
- Full Text:
- Date Issued: 2016
- Authors: Adefuye, Ogheneochuko Janet
- Date: 2016
- Subjects: Medicinal plants -- Africa , Traditional medicine -- Africa , Herbs -- Therapeutic use -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/3549 , vital:20441
- Description: In Africa, the importance of medicinal plants in folklore medicine and their contribution to primary healthcare is well recognized. Across the continent, local herbal mixtures still provide the only therapeutic option for about 80% of the population. The vast floral diversity and the intrinsic ethnobotanical knowledge has been the backbone of localized traditional herbal medical practices. In Africa, an estimated 5400 of the 60000 described plant taxa possess over 16300 therapeutic uses. Similarly, with a therapeutic flora comprising of approximately 650 species, herbal medical practitioners in South Africa, make use of a plethora of plants to treat different human diseases and infections. Over the years, studies have identified numerous plant species with potential against chronic metabolic diseases including type 2 diabetes mellitus (T2DM). Globally, the incidence and prevalence of T2DM have reached epidemic proportions affecting people of all ages, nationalities and ethnicity. Considered the fourth leading cause of deaths by disease, T2DM is a global health crisis with an estimated diagnosis and mortality frequency of 1 every 5 seconds and 1 every 7 seconds respectively. Though the exact pathophysiology of T2DM is not entirely understood, initial peripheral insulin resistance in adipose tissue, liver, and skeletal muscle with subsequent pancreatic β-cell dysfunction resulting from an attempt to compensate for insulin resistance is a common feature of the disease. The current approach to treating T2DM is the use of oral antidiabetic agents (OAAs), insulin, and incretin-based drugs in an attempt to achieve glycaemic control and maintain glucose homeostasis. However, conventional anti-T2DM drugs have been shown to have limited efficacies and serious adverse effects. Hence, the need for newer, more efficacious and safer anti-T2DM agents. Sutherlandia frutescens subsp. microphylla is a flowering shrub of the pea family (Fabaceae/Leguminaceae) found mainly in the Western Cape and Karoo regions of Southern Africa. Concoctions of various parts of the plant are used in the management of different ailments including T2DM. However, despite extensive biological and pharmacological studies, few analyses exist of the chemical constituents of S. frutescens and no Triple Time of Flight Liquid Chromatography with Mass Spectrometry (Triple TOF LC/MS/MS) analysis has been performed. The initial aim of this study was to investigate the phytochemical profile of hot aqueous, cold aqueous, 80% ethanolic, 100% ethanolic, 80% methanolic and 100% methanolic extracts of a single source S. frutescens plant material using colorimetric and spectrophotometric analysis. The hot aqueous extractant was found to be the best extractant for S. frutescens, yielding 1.99 g of crude extract from 16 g fresh powdered plant material. This data suggests that application of heat and water as the extractant (hot aqueous) could play a vital role in extraction of bioactive compounds from S. frutescens and also justifies the traditional use of a tea infusion of S. frutescens. Colorimetric analysis revealed the presence of flavonoids, flavonols, tannins, and phenols in all extracts with varying intensity. The organic extracts 100% methanol, 80% and 100% ethanol exhibited high color intensity (+++) for flavonoids and flavonols respectively, while all the extracts exhibited a moderate color intensity (++) for tannins and phenols. Spectrophotometric analysis of S. frutescens extracts revealed that all the organic extracts contained a significantly higher concentration (in mg/g of extract) of flavonols and tannins when compared to the aqueous extracts. All extracts contained approximately equal levels of phenols. These data confirm the presence of all four groups of bioactive phytocompounds in the S. frutescens extracts used in this study, and also confirm that different solvent extractants possess the capability to differentially extract specific groups of phytocompounds. in individual extracts. Further comparison of these compounds with online databases of anti-diabetic phytocompounds led to the preliminary identification of 10 possible anti-diabetic compounds; α-Pinene, Limonene, Sabinene, Carvone, Myricetin, Rutin, Stigmasterol, Emodin, Sarpagine and Hypoglycin B in crude and solid phase extraction (SPE) fractions of S. frutesecens. Furthermore, using two hepatic cell lines (Chang and HepG2) as an in-vtro model system, the anti-T2DM properties of crude aqueous and organic extracts of S. frutescents was investigated and compared. Both aqueous and organic extracts of S. frutescens were found to decrease gluconeogenesis, increase glucose uptake and decrease lipid accumulation (Triacylglycerol, Diacylglycerol, and Monoacylglycerol) in Chang and HepG2 hepatic cell cultures made insulin resistant (IR) following exposure to high concentration of insulin and fructose. Using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), the aqueous and organic extracts of S. frutescens were confirmed to regulate the expression of Vesicle-associated membrane protein 3 (VAMP3), Mitogen-activated protein kinase 8 (MAPK8), and Insulin receptor substrate 1 (IRS1) in insulin resistant hepatic cells. IR-mediated downregulation of VAMP3, MAPK8, and IRS1 mRNA in IR HepG2 hepatic cell cultures was reversed in the presence of aqueous and organic extracts of S. frutescens. The hot aqueous extract displayed the highest activity in all the assays, while all the organic extracts displayed similar potency. In conclusion, this study reports that aqueous and organic extracts of S. frutescens possess numerous anti-diabetic compounds that can be further investigated for the development of new, more efficacious and less toxic anti-diabetic agents. The presence of multiple compounds in a single extract does suggest a synergistic or combinatorial therapeutic effect. These findings support the burgeoning body of in-vivo and in-vitro literature evidence on the anti-diabetic properties of S. frutescens and its use in folklore medicine.
- Full Text:
- Date Issued: 2016
Scalable chemistry involving diazonium salts
- Authors: Akwi, Faith Mary
- Date: 2016
- Subjects: Azo compounds -- Synthesis , Chemical processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6909 , vital:21162
- Description: Herein an alternative approach aimed at reducing the cost of numbering up technique as a scale up strategy for chemical processes from the laboratory bench top to the industry is explored. The effect of increasing channel size on the reaction conversion of the synthesis of azo compounds is investigated. This was achieved via a systematic investigative understanding of the synthesis in microreactors where a proof of concept study was performed to determine the optimum reaction parameters in azo coupling reactions involving couplers with aminated or hydroxylated groups in Little Things Factory-MS microreactors (Channel diameter: 1.0 mm) It was found that at slightly alkaline conditions (pH 8.55) and at a temperature of 25 °C, excellent conversions were attained in the azo coupling reaction of the diazonium salt solution of 2,4-dimethylaniline to 2-naphthol. On the other hand, the azo coupling reaction of the diazonium salt solution of p-nitroaniline to diphenylamine was found to thrive at a pH of 5.71 and at a temperature of 25 °C. Using, these optimized reaction parameters, the in-situ and reactive quench of diazonium salts in LTF-MS microreactors was investigated where it was found that at a flow rate of 0.2 ml/min, 0.03 ml/min and 0.07 ml/min of diazotizable amine & HCl, sodium nitrite and coupler solutions respectively, a conversion of 98% is achieved in approximately 2.4 minutes. A library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic aromatic systems. The scaled up synthesis of these compounds in a homemade PTFE tubing (ID 1.5 mm) reactor system was thereafter investigated and comparable conversions were observed. Capitalizing on the benefits of a large surface area and the short molecular diffusion distances observed in microreactors, in-situ phase transfer catalyzed azo coupling reaction of diphenylamine to p-nitroaniline was also explored. In this investigation a rapid and easy optimization protocol that yielded a 99%, 22% and 33% conversion of diphenylamine, carbazole and triphenylamine respectively in approximately 2.4 minutes using Chemtrix microreactors was established. On increasing the microreactor channel internal diameter in the scaled up synthesis approach, it was found that a 0.5 mm increase in channel internal diameter does result in lower reaction conversions.
- Full Text:
- Date Issued: 2016
- Authors: Akwi, Faith Mary
- Date: 2016
- Subjects: Azo compounds -- Synthesis , Chemical processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6909 , vital:21162
- Description: Herein an alternative approach aimed at reducing the cost of numbering up technique as a scale up strategy for chemical processes from the laboratory bench top to the industry is explored. The effect of increasing channel size on the reaction conversion of the synthesis of azo compounds is investigated. This was achieved via a systematic investigative understanding of the synthesis in microreactors where a proof of concept study was performed to determine the optimum reaction parameters in azo coupling reactions involving couplers with aminated or hydroxylated groups in Little Things Factory-MS microreactors (Channel diameter: 1.0 mm) It was found that at slightly alkaline conditions (pH 8.55) and at a temperature of 25 °C, excellent conversions were attained in the azo coupling reaction of the diazonium salt solution of 2,4-dimethylaniline to 2-naphthol. On the other hand, the azo coupling reaction of the diazonium salt solution of p-nitroaniline to diphenylamine was found to thrive at a pH of 5.71 and at a temperature of 25 °C. Using, these optimized reaction parameters, the in-situ and reactive quench of diazonium salts in LTF-MS microreactors was investigated where it was found that at a flow rate of 0.2 ml/min, 0.03 ml/min and 0.07 ml/min of diazotizable amine & HCl, sodium nitrite and coupler solutions respectively, a conversion of 98% is achieved in approximately 2.4 minutes. A library of azo compounds was thus generated under these reaction conditions from couplers with aminated or hydroxylated aromatic aromatic systems. The scaled up synthesis of these compounds in a homemade PTFE tubing (ID 1.5 mm) reactor system was thereafter investigated and comparable conversions were observed. Capitalizing on the benefits of a large surface area and the short molecular diffusion distances observed in microreactors, in-situ phase transfer catalyzed azo coupling reaction of diphenylamine to p-nitroaniline was also explored. In this investigation a rapid and easy optimization protocol that yielded a 99%, 22% and 33% conversion of diphenylamine, carbazole and triphenylamine respectively in approximately 2.4 minutes using Chemtrix microreactors was established. On increasing the microreactor channel internal diameter in the scaled up synthesis approach, it was found that a 0.5 mm increase in channel internal diameter does result in lower reaction conversions.
- Full Text:
- Date Issued: 2016
A framework for grain commodity trading decision support in South Africa
- Authors: Ayankoya, Kayode Anthony
- Date: 2016
- Subjects: Grain trade -- South Africa Commodity exchanges -- South Africa Food industry and trade -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11437 , vital:26925
- Description: In several countries around the world, grain commodities are traded as assets on stock exchanges. This indicate that the market and effectively the prices of the grain commodities in such countries, are controlled by several local and international economic, political and social factors that are rapidly changing. As a result, the prices of some grain commodities are volatile and trading in such commodities are prone to price-related risks. There are different trading strategies for minimising price-related risks and maximising profits. But empirical research suggests that making the right decision for effective grain commodities trading has been a difficult task for stakeholders due to high volatility of grain commodities prices. Studies have shown that this is more challenging among grain commodities farmers because of their lack of skills and the time to sift through and make sense of the datasets on the plethora of factors that influence the grain commodities market. This thesis focused on providing an answer for the main research problem that grain farmers in South Africa do not take full advantage of all the available strategies for trading their grain commodities because of the complexities associated with monitoring the large datasets that influence the grain commodities market. The main objective set by this study is to design a framework that can be followed to collect, integrate and analyse datasets that influence trading decisions of grain farmers in South Africa about grain commodities. This study takes advantage of the developments in Big Data and Data Science to achieve the set objective using the Design Science Research (DSR) methodology. The prediction of future prices of grain commodities for the different trading strategies was identified as an important factor for making better decisions when trading grain commodities and the key factors that influence the prices were identified. This was followed by a critical review of the literature to determine how the concepts of Big Data and Data Science can be leveraged for an effective grain commodities trading decision support. This resulted in a proposed framework for grain commodities trading. The proposed framework suggested an investigation of the factors that influence the prices of grain commodities as the basis for acquiring the relevant datasets. The proposed framework suggested the adoption of the Big Data approach in acquiring, preparing and integrating relevant datasets from several sources. Furthermore, it was suggested that algorithmic models for predicting grain commodities prices can be developed on top of the data layer of the proposed framework to provide real-time decision support. The proposed framework suggests the need for a carefully designed visualisation of the result and the collected data that promotes user experience. Lastly, the proposed framework included a technology consideration component to support the Big Data and Data Science approach of the framework. To demonstrate that the proposed framework addressed the main problem of this research, datasets from several sources on trading white maize in South Africa and the factors that influence market were streamed, integrated and analysed. Backpropagation Neural Network algorithm was used for modelling the prices of white maize for spot and futures trading strategies were predicted. There are other modelling techniques such as the Box-Jenkins statistical time series analysis methodology. But, Neural Networks was identified as more suitable for time series data with complex patterns and relationships. A demonstration system was setup to provide effective decision support by using near real-time data to provide a dynamic predictive analytics for the spot and December futures contract prices of white maize in South Africa. Comparative analysis of predictions made using the model from the proposed framework to actual data indicated a significant degree of accuracy. A further evaluation was carried out by asking experienced traders to make predictions for the spot and December futures contract prices of white maize. The result of the exercise indicated that the predictions from the developed model were much closer to the actual prices. This indicated that the proposed framework is technically capable and generally useful. It also shows that the proposed framework can be used to provide decision support about trading grain commodities to stakeholders with lesser skills, experience and resources. The practical contribution of this thesis is that relevant datasets from several sources can be streamed into an integrated data source in real-time, which can be used as input for a real-time learning algorithmic model for predicting grain commodities prices. This will make it possible for a predictive analytics that responds to market volatility thereby providing an effective decision support for grain commodities trading. Another practical contribution of this thesis is a proposed framework that can be followed for developing a Decision Support System for trading in grain commodities. This thesis made theoretical contributions by building on the information processing theory and the decision making theory. The theoretical contribution of this thesis consists of the identification of Big Data approach, tools and techniques for eradicating uncertainty and equivocality in grain commodities trading decision making process.
- Full Text:
- Date Issued: 2016
- Authors: Ayankoya, Kayode Anthony
- Date: 2016
- Subjects: Grain trade -- South Africa Commodity exchanges -- South Africa Food industry and trade -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/11437 , vital:26925
- Description: In several countries around the world, grain commodities are traded as assets on stock exchanges. This indicate that the market and effectively the prices of the grain commodities in such countries, are controlled by several local and international economic, political and social factors that are rapidly changing. As a result, the prices of some grain commodities are volatile and trading in such commodities are prone to price-related risks. There are different trading strategies for minimising price-related risks and maximising profits. But empirical research suggests that making the right decision for effective grain commodities trading has been a difficult task for stakeholders due to high volatility of grain commodities prices. Studies have shown that this is more challenging among grain commodities farmers because of their lack of skills and the time to sift through and make sense of the datasets on the plethora of factors that influence the grain commodities market. This thesis focused on providing an answer for the main research problem that grain farmers in South Africa do not take full advantage of all the available strategies for trading their grain commodities because of the complexities associated with monitoring the large datasets that influence the grain commodities market. The main objective set by this study is to design a framework that can be followed to collect, integrate and analyse datasets that influence trading decisions of grain farmers in South Africa about grain commodities. This study takes advantage of the developments in Big Data and Data Science to achieve the set objective using the Design Science Research (DSR) methodology. The prediction of future prices of grain commodities for the different trading strategies was identified as an important factor for making better decisions when trading grain commodities and the key factors that influence the prices were identified. This was followed by a critical review of the literature to determine how the concepts of Big Data and Data Science can be leveraged for an effective grain commodities trading decision support. This resulted in a proposed framework for grain commodities trading. The proposed framework suggested an investigation of the factors that influence the prices of grain commodities as the basis for acquiring the relevant datasets. The proposed framework suggested the adoption of the Big Data approach in acquiring, preparing and integrating relevant datasets from several sources. Furthermore, it was suggested that algorithmic models for predicting grain commodities prices can be developed on top of the data layer of the proposed framework to provide real-time decision support. The proposed framework suggests the need for a carefully designed visualisation of the result and the collected data that promotes user experience. Lastly, the proposed framework included a technology consideration component to support the Big Data and Data Science approach of the framework. To demonstrate that the proposed framework addressed the main problem of this research, datasets from several sources on trading white maize in South Africa and the factors that influence market were streamed, integrated and analysed. Backpropagation Neural Network algorithm was used for modelling the prices of white maize for spot and futures trading strategies were predicted. There are other modelling techniques such as the Box-Jenkins statistical time series analysis methodology. But, Neural Networks was identified as more suitable for time series data with complex patterns and relationships. A demonstration system was setup to provide effective decision support by using near real-time data to provide a dynamic predictive analytics for the spot and December futures contract prices of white maize in South Africa. Comparative analysis of predictions made using the model from the proposed framework to actual data indicated a significant degree of accuracy. A further evaluation was carried out by asking experienced traders to make predictions for the spot and December futures contract prices of white maize. The result of the exercise indicated that the predictions from the developed model were much closer to the actual prices. This indicated that the proposed framework is technically capable and generally useful. It also shows that the proposed framework can be used to provide decision support about trading grain commodities to stakeholders with lesser skills, experience and resources. The practical contribution of this thesis is that relevant datasets from several sources can be streamed into an integrated data source in real-time, which can be used as input for a real-time learning algorithmic model for predicting grain commodities prices. This will make it possible for a predictive analytics that responds to market volatility thereby providing an effective decision support for grain commodities trading. Another practical contribution of this thesis is a proposed framework that can be followed for developing a Decision Support System for trading in grain commodities. This thesis made theoretical contributions by building on the information processing theory and the decision making theory. The theoretical contribution of this thesis consists of the identification of Big Data approach, tools and techniques for eradicating uncertainty and equivocality in grain commodities trading decision making process.
- Full Text:
- Date Issued: 2016
Ecological principles for honeybush (Cyclopia spp.) conservation and cultivation
- Authors: Beyers, Andrea
- Date: 2016
- Subjects: Fynbos -- South Africa , Rooibos tea industry -- South Africa , Herbal teas -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5723 , vital:20975
- Description: Market demand for the fynbos-derived honeybush (Cyclopia spp.) tea is on the rise, and there is an urgent need for better conservation of wild Cyclopia populations and for a shift to sustainable cultivation. Rooibos is another popular fynbos product that underwent exponential market growth over the last two decades but this resulted in large-scale conversion of pristine mountain fynbos to intensively-used crop lands. Adopting a conservation agriculture approach in expanding indigenous products will help in conserving biodiversity and ecosystem processes in this global biodiversity hotspot. Conservation agriculture of indigenous fynbos products grown in the Cape Floristic Region (CFR) should follow five main principles in order to maximise biodiversity conservation alongside agriculture. These principles are: 1) maintain high diversity at all levels, 2) conserve soil structure and processes, 3) conserve and restore natural ecosystem processes, 4) promote ecosystem stability and self-perpetuation, and 5) maintain natural areas as sources of ecosystem components. Given the negative ecological consequences of the industrialisation of the rooibos industry, it would be in the interest of biodiversity conservation, and even of agriculture, to apply these principles to honeybush cultivation. In order to prevent further fynbos habitat loss, cultivation of honeybush could be catalysed on old fields rather than in ploughed or cleared fynbos. Here I compare germination, growth and survival of two species (Cyclopia intermedia E.Mey. and C. subternata Vogel) between different land use types (ploughed lands, old fields and intact fynbos) and treatments (cleared and uncleared) in the Langkloof, Eastern Cape, over one year. Plots of each land use type were subject to each of these two treatments, although the ploughed plot constituted only a cleared treatment. Growth was highest on ploughed land, while survival and growth were lowest in uncleared fynbos. Cleared fynbos had the lowest germination success in both species, with the other sites and treatments coming out roughly the same. These results show that although ploughed lands give highest yields, growth and survival on old fields without ploughing is comparable with that on ploughed lands and is therefore a feasible alternative. Understanding the recruitment dynamics of honeybush is imperative for adequate conservation of wild populations. Furthermore, understanding this ecological aspect of the genus will help in developing the honeybush industry as a sustainable, agroecological market that uses semi-natural populations for production. Although Cyclopia species are early-successional species that germinate after fire, recruitment of Cyclopia pubescens Eckl. & Zeyh. continues throughout the inter-fire period. Cyclopia pubescens populations near Port Elizabeth were described according to their age structure and plant densities to discern possible density-dependent recruitment effects. Results showed that dense stands for the most part do not support high post-fire recruitment. This gives insight into suitable planting densities for new or restore populations and into management guidelines for remnant populations of threatened species. This thesis highlights important issues facing the honeybush industry. Mainstreaming biodiversity conservation into honeybush production is achievable, given that the industry is still relatively young, but this will require further research and strong market leadership.
- Full Text:
- Date Issued: 2016
- Authors: Beyers, Andrea
- Date: 2016
- Subjects: Fynbos -- South Africa , Rooibos tea industry -- South Africa , Herbal teas -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5723 , vital:20975
- Description: Market demand for the fynbos-derived honeybush (Cyclopia spp.) tea is on the rise, and there is an urgent need for better conservation of wild Cyclopia populations and for a shift to sustainable cultivation. Rooibos is another popular fynbos product that underwent exponential market growth over the last two decades but this resulted in large-scale conversion of pristine mountain fynbos to intensively-used crop lands. Adopting a conservation agriculture approach in expanding indigenous products will help in conserving biodiversity and ecosystem processes in this global biodiversity hotspot. Conservation agriculture of indigenous fynbos products grown in the Cape Floristic Region (CFR) should follow five main principles in order to maximise biodiversity conservation alongside agriculture. These principles are: 1) maintain high diversity at all levels, 2) conserve soil structure and processes, 3) conserve and restore natural ecosystem processes, 4) promote ecosystem stability and self-perpetuation, and 5) maintain natural areas as sources of ecosystem components. Given the negative ecological consequences of the industrialisation of the rooibos industry, it would be in the interest of biodiversity conservation, and even of agriculture, to apply these principles to honeybush cultivation. In order to prevent further fynbos habitat loss, cultivation of honeybush could be catalysed on old fields rather than in ploughed or cleared fynbos. Here I compare germination, growth and survival of two species (Cyclopia intermedia E.Mey. and C. subternata Vogel) between different land use types (ploughed lands, old fields and intact fynbos) and treatments (cleared and uncleared) in the Langkloof, Eastern Cape, over one year. Plots of each land use type were subject to each of these two treatments, although the ploughed plot constituted only a cleared treatment. Growth was highest on ploughed land, while survival and growth were lowest in uncleared fynbos. Cleared fynbos had the lowest germination success in both species, with the other sites and treatments coming out roughly the same. These results show that although ploughed lands give highest yields, growth and survival on old fields without ploughing is comparable with that on ploughed lands and is therefore a feasible alternative. Understanding the recruitment dynamics of honeybush is imperative for adequate conservation of wild populations. Furthermore, understanding this ecological aspect of the genus will help in developing the honeybush industry as a sustainable, agroecological market that uses semi-natural populations for production. Although Cyclopia species are early-successional species that germinate after fire, recruitment of Cyclopia pubescens Eckl. & Zeyh. continues throughout the inter-fire period. Cyclopia pubescens populations near Port Elizabeth were described according to their age structure and plant densities to discern possible density-dependent recruitment effects. Results showed that dense stands for the most part do not support high post-fire recruitment. This gives insight into suitable planting densities for new or restore populations and into management guidelines for remnant populations of threatened species. This thesis highlights important issues facing the honeybush industry. Mainstreaming biodiversity conservation into honeybush production is achievable, given that the industry is still relatively young, but this will require further research and strong market leadership.
- Full Text:
- Date Issued: 2016
The management of chacma baboons and humans in a peri-urban environment: a case study from Nelson Mandela Metropolitan University's George Campus
- Authors: Botes, Peet
- Date: 2016
- Subjects: Human-animal relationships , Animal behavior , Human beings , Bestiality
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/5135 , vital:20812
- Description: Conflicts between humans and baboons (Papio ursinus) have become a significant management challenge on Nelson Mandela Metropolitan University’s (NMMUs) George Campus, which is located in peri-urban George in the Garden Route, of the Western Cape of South Africa. Current management policy, although required to be ‘scientifically’ based, largely relies on studies done outside the Garden Route. This study addresses the question of how the management of human-baboon relations could be improved on the campus. A case study was undertaken which aimed at addressing the cohabitation of baboons and humans on the NMMU campus, specifically human-baboon resource selection and interaction. The research methodology and the related analytical tools were primarily quantitative but were supplemented by some qualitative data drawn from interviews. Data collected was used to determine landscape features acting as Keystone Resource Areas (KRAs) for both humans and baboons on the campus. Relationships between the frequency and location of negative interactions, and resident-baboon distribution on the campus were also determined. Two key findings emerged from the research. First, residences, non-residence buildings and waste disposal stations act as KRAs for both humans and baboons. Second, the frequency of negative interaction correlates with the time spent by residents and baboons at residences, where common negative interactions between baboons and humans are known to occur. It is postulated that cohabitation on the NMMU George Campus is causing the habituation of baboons, a loss of fear of humans and association of humans with high energy foods. As a result, present cohabitation contributes to negative human-baboon relations in the George area. To ensure sustainable co-existence between humans and baboons on the George Campus, management should implement zonation and wildlife monitoring to reverse the loss of baboon fear of humans and better limit the availability of human-derived foods. In addition, management should consider giving stakeholders co-management roles to foster and facilitate knowledge and responsibility partnerships, and subsequently correct any misunderstandings related to human-baboon relations on the campus. Recommendations for further research include sampling beyond campus boundaries to compensate for regional variations in baboon behaviour and the biophysical environment.
- Full Text:
- Date Issued: 2016
- Authors: Botes, Peet
- Date: 2016
- Subjects: Human-animal relationships , Animal behavior , Human beings , Bestiality
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/5135 , vital:20812
- Description: Conflicts between humans and baboons (Papio ursinus) have become a significant management challenge on Nelson Mandela Metropolitan University’s (NMMUs) George Campus, which is located in peri-urban George in the Garden Route, of the Western Cape of South Africa. Current management policy, although required to be ‘scientifically’ based, largely relies on studies done outside the Garden Route. This study addresses the question of how the management of human-baboon relations could be improved on the campus. A case study was undertaken which aimed at addressing the cohabitation of baboons and humans on the NMMU campus, specifically human-baboon resource selection and interaction. The research methodology and the related analytical tools were primarily quantitative but were supplemented by some qualitative data drawn from interviews. Data collected was used to determine landscape features acting as Keystone Resource Areas (KRAs) for both humans and baboons on the campus. Relationships between the frequency and location of negative interactions, and resident-baboon distribution on the campus were also determined. Two key findings emerged from the research. First, residences, non-residence buildings and waste disposal stations act as KRAs for both humans and baboons. Second, the frequency of negative interaction correlates with the time spent by residents and baboons at residences, where common negative interactions between baboons and humans are known to occur. It is postulated that cohabitation on the NMMU George Campus is causing the habituation of baboons, a loss of fear of humans and association of humans with high energy foods. As a result, present cohabitation contributes to negative human-baboon relations in the George area. To ensure sustainable co-existence between humans and baboons on the George Campus, management should implement zonation and wildlife monitoring to reverse the loss of baboon fear of humans and better limit the availability of human-derived foods. In addition, management should consider giving stakeholders co-management roles to foster and facilitate knowledge and responsibility partnerships, and subsequently correct any misunderstandings related to human-baboon relations on the campus. Recommendations for further research include sampling beyond campus boundaries to compensate for regional variations in baboon behaviour and the biophysical environment.
- Full Text:
- Date Issued: 2016
Optimisation of clearcoat viscosity
- Authors: Bukula, Nwabisa Asanda
- Date: 2016
- Subjects: Coating processes , Automobiles -- Bodies -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4814 , vital:20707
- Description: Modern automobiles are painted with basecoat, technology which is either metallic, solid colour or pearlescent. This requires protection from chemicals, scratching, weathering and UV light by applying a protective top coat (clearcoat) over the basecoat. For the clearcoat to cure into a hard protective shell it undergoes an irreversible crosslinking process. This usually takes place over the first four to five hours, depending on the formulation and weather conditions. The speed of crosslinking can be enhanced by temperature. Pot life is important as it can affect the overall quality of the painted surface. If crosslinking occurs too quickly, before the clearcoat is applied onto the surface, the clearcoat cannot be used to produce a good quality finish. The “expired” mixture is thus discarded. If used, the quality of the finished product cannot be guaranteed to last, and the paintwork may have to be redone. This often means removing the underlying paint and primer as well with the clearcoat film. Besides the time lost, the discarded clearcoat mixture often lands in the landfill, polluting ground water and the environment. It is thus important from the point of view of both the environment preservation and waste management, that as much clearcoat as possible is used without being wasted. It was proven in an earlier study (BSc Hon Formulation Science Treatise, 2011) that adding eugenol to a clearcoat mixture after crosslinking had started could reduce its viscosity, which is an indicator of crosslinking progress. Crosslinking subsequently resumed at a lower rate than in traditional blends. If stored away from oxygen and high temperatures, this blend could maintain optimum viscosity indefinitely. In this follow up study an optimum formulation was developed using D - optimal experimental design. It sought to extend the pot life to avoid waste to spray painters while saving the environment from pollution. The formulation that gave the desired viscosity after five hours of pot life was adopted. It was hypothesised that the optimum formulated clearcoat mixture would have a longer pot life than its traditional counterparts, and that it would perform just as well as the traditional clearcoat mixtures. To study the rate of crosslinking (disappearance of functional groups and appearance of the urethane bond), FTIR spectrometry was performed on a mixture produced from the optimized formula in comparison to that of a traditional mixture (the control). The rate of disappearance of functional groups was found to be lower in the eugenol mixture than in the control mixture. After six hours, eugenol was added into the control mixture, and this seemed to reduce the viscosity with the re-emergence of functional groups in the mixture. After 24 hours of crosslinking, an FTIR scan was done on the solid sample and this revealed that the eugenol mixture had crosslinked fully, with no detectable functional groups in the sample.
- Full Text:
- Date Issued: 2016
- Authors: Bukula, Nwabisa Asanda
- Date: 2016
- Subjects: Coating processes , Automobiles -- Bodies -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4814 , vital:20707
- Description: Modern automobiles are painted with basecoat, technology which is either metallic, solid colour or pearlescent. This requires protection from chemicals, scratching, weathering and UV light by applying a protective top coat (clearcoat) over the basecoat. For the clearcoat to cure into a hard protective shell it undergoes an irreversible crosslinking process. This usually takes place over the first four to five hours, depending on the formulation and weather conditions. The speed of crosslinking can be enhanced by temperature. Pot life is important as it can affect the overall quality of the painted surface. If crosslinking occurs too quickly, before the clearcoat is applied onto the surface, the clearcoat cannot be used to produce a good quality finish. The “expired” mixture is thus discarded. If used, the quality of the finished product cannot be guaranteed to last, and the paintwork may have to be redone. This often means removing the underlying paint and primer as well with the clearcoat film. Besides the time lost, the discarded clearcoat mixture often lands in the landfill, polluting ground water and the environment. It is thus important from the point of view of both the environment preservation and waste management, that as much clearcoat as possible is used without being wasted. It was proven in an earlier study (BSc Hon Formulation Science Treatise, 2011) that adding eugenol to a clearcoat mixture after crosslinking had started could reduce its viscosity, which is an indicator of crosslinking progress. Crosslinking subsequently resumed at a lower rate than in traditional blends. If stored away from oxygen and high temperatures, this blend could maintain optimum viscosity indefinitely. In this follow up study an optimum formulation was developed using D - optimal experimental design. It sought to extend the pot life to avoid waste to spray painters while saving the environment from pollution. The formulation that gave the desired viscosity after five hours of pot life was adopted. It was hypothesised that the optimum formulated clearcoat mixture would have a longer pot life than its traditional counterparts, and that it would perform just as well as the traditional clearcoat mixtures. To study the rate of crosslinking (disappearance of functional groups and appearance of the urethane bond), FTIR spectrometry was performed on a mixture produced from the optimized formula in comparison to that of a traditional mixture (the control). The rate of disappearance of functional groups was found to be lower in the eugenol mixture than in the control mixture. After six hours, eugenol was added into the control mixture, and this seemed to reduce the viscosity with the re-emergence of functional groups in the mixture. After 24 hours of crosslinking, an FTIR scan was done on the solid sample and this revealed that the eugenol mixture had crosslinked fully, with no detectable functional groups in the sample.
- Full Text:
- Date Issued: 2016
Foraging ecology of the gentoo penguin, pygoscelis papua, at Marion Island
- Authors: Carpenter-Kling, Tegan
- Date: 2016
- Subjects: Gentoo penguin -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4912 , vital:20766
- Description: The distribution and subsequent availability of marine predators’ prey is highly variable and is linked to fluctuating oceanographic parameters. It is well documented that annual breeding success of seabirds is related to the temporal availability of prey. Knowledge of a seabird’s diet and at sea distribution is therefore critical in deducing the effect of a fluctuating environment on a seabirds’ population and, furthermore, to understand seabirds role in the environment. The gentoo penguin population at sub-Antarctic Marion Island experienced a decline of 52% between 1994 and 2012. It has been speculated that long term changes in the local marine environment, due to a southward shift of the sub-Antarctic Front (SAF), and subsequent changes in prey availability is the ultimate causal factor. Therefore, this thesis investigates the temporal variation in the diet these birds over three years, through the use of stomach content samples. It then investigates whether the composition of the diet has changed over the long term (approximately 18 years). Additionally, the at sea distribution of these birds was investigated using temperature-depth recorders (TDRs) and global positioning system (GPS) devices. This study represents the first to investigate variation in the diet over three years and over the long term. It is also the first study to track these birds fine scale movement. Over three years, the diet exhibited a high degree of variability. The birds primarily foraged on the fish, Lepidonotothen larseni and the crustaceans, Nauticaris marionis and Euphausia vallentiniy. Over three years, L. larseni became increasingly more important during the breeding season. This was attributed to an increase in availability of these fish during this time, as this time corresponded to the transition of these fish from the larval pelagic phase to the benthic adult phase. Furthermore, the proportions of N. marionis and E. vallentini in the diet varied significantly among years. This variation is possibly a result of the highly variable latitudinal position of the SAF. The diet changed over the long term. There was significantly less N. marionis and more E. vallentini in the diet during more recent years. The long term southward shift of the SAF is considered to be a leading cause of these significant changes in the diet. The shallow inter-island shelf between Marion and Prince Edward Island was an important foraging area possibly due to predictable prey resources. In addition, these birds exhibited an important and possibly unique foraging strategy. They performed short self-maintenance trips where after they return to land to roost for the night. The following day these trips were followed by a longer foraging trip that was followed by chick provisioning. This strategy is unique among seabirds longer trips are associated with self-maintenance and not chick provisioning. This study has provided important knowledge of the foraging ecology of the gentoo penguin at sub-Antarctic Marion Island. It highlights the necessity for continuation of diet and tracking studies of these birds if we are to fully understand the ultimate factors that are causing the decline in their breeding success and population numbers.
- Full Text:
- Date Issued: 2016
- Authors: Carpenter-Kling, Tegan
- Date: 2016
- Subjects: Gentoo penguin -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4912 , vital:20766
- Description: The distribution and subsequent availability of marine predators’ prey is highly variable and is linked to fluctuating oceanographic parameters. It is well documented that annual breeding success of seabirds is related to the temporal availability of prey. Knowledge of a seabird’s diet and at sea distribution is therefore critical in deducing the effect of a fluctuating environment on a seabirds’ population and, furthermore, to understand seabirds role in the environment. The gentoo penguin population at sub-Antarctic Marion Island experienced a decline of 52% between 1994 and 2012. It has been speculated that long term changes in the local marine environment, due to a southward shift of the sub-Antarctic Front (SAF), and subsequent changes in prey availability is the ultimate causal factor. Therefore, this thesis investigates the temporal variation in the diet these birds over three years, through the use of stomach content samples. It then investigates whether the composition of the diet has changed over the long term (approximately 18 years). Additionally, the at sea distribution of these birds was investigated using temperature-depth recorders (TDRs) and global positioning system (GPS) devices. This study represents the first to investigate variation in the diet over three years and over the long term. It is also the first study to track these birds fine scale movement. Over three years, the diet exhibited a high degree of variability. The birds primarily foraged on the fish, Lepidonotothen larseni and the crustaceans, Nauticaris marionis and Euphausia vallentiniy. Over three years, L. larseni became increasingly more important during the breeding season. This was attributed to an increase in availability of these fish during this time, as this time corresponded to the transition of these fish from the larval pelagic phase to the benthic adult phase. Furthermore, the proportions of N. marionis and E. vallentini in the diet varied significantly among years. This variation is possibly a result of the highly variable latitudinal position of the SAF. The diet changed over the long term. There was significantly less N. marionis and more E. vallentini in the diet during more recent years. The long term southward shift of the SAF is considered to be a leading cause of these significant changes in the diet. The shallow inter-island shelf between Marion and Prince Edward Island was an important foraging area possibly due to predictable prey resources. In addition, these birds exhibited an important and possibly unique foraging strategy. They performed short self-maintenance trips where after they return to land to roost for the night. The following day these trips were followed by a longer foraging trip that was followed by chick provisioning. This strategy is unique among seabirds longer trips are associated with self-maintenance and not chick provisioning. This study has provided important knowledge of the foraging ecology of the gentoo penguin at sub-Antarctic Marion Island. It highlights the necessity for continuation of diet and tracking studies of these birds if we are to fully understand the ultimate factors that are causing the decline in their breeding success and population numbers.
- Full Text:
- Date Issued: 2016
Higher order modulation formats for high speed optical communication systems with digital signal processing aided receiver
- Chabata, Tichakunda Valentine
- Authors: Chabata, Tichakunda Valentine
- Date: 2016
- Subjects: Optical communications , Modulation (Electronics) , Signal processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4775 , vital:20677
- Description: The drastic increase in the number of internet users and the general convergence of all other communication systems into an optical system have brought a sharp rise in demand for bandwidth and calls for high capacity transmission networks. Large unamplified transmission reach is another contributor in reducing deployment costs of an optical communication system. Spectrally efficient modulation formats are suggested as a solution to overcome the problems associated with limited channels and bandwidth of dense wavelength division multiplexing (DWDM) optical communication systems. Higher order modulation formats which are considered to be spectrally efficient and can increase the transmission capacity by transmitting more information in the amplitude, phase, polarization or a combination of all was studied. Different detection technologies are to be implemented to suit a particular higher order modulation format. In this research multilevel modulation formats, different detection technologies and a digital signal processing aided receiver were studied in a practical optical transmission system. The work in this thesis started with the implementation of the traditional amplitude shift keying (ASK) modulation and a differential phase shift keying (DPSK) modulation systems as they form the basic building block in the design of higher order modulation formats. Results obtained from using virtual photonics instruments (VPI)simulation software, receiver sensitivity for 10Gbpsnon-return-to-zero (NRZ), amplitude phase shift keying (ASK) and DPSK signals were measured to be -22.7 dBm and -22.0 dBm respectively. Performance comparison for the two modulation formats were done over different transmission distances. ASK also known as On-Off keying (OOK) performed better for shorter lengths whereas DPSK performed better for longer lengths of up to90km.Experimental results on a 10 Gbps NRZ- ASK signal gave a receiver sensitivity of -21.1 dBm from digital signal processing (DSP) aided receiver against -19.8 dBm from the commercial bit error ratio tester (BERT) yielding a small difference of 1.3 dB hence validating the reliability and accuracy of the digital signal processing (DSP) assisted receiver. Traditional direct detection scheme and coherent detection scheme performances were evaluated again on a 10 Gbps NRZ ASK signal. Coherent detection that can achieve a large unamplified transmission reach and has a higher passive optical splitting ratio was first evaluated using the VPI simulation software. Simulation results gave a receiver sensitivity of -30.4 dBm forcoherent detection and -18.3 dBm for direct detection, yielding a gain in receiver sensitivity of 12.1 dB. The complex coherently detected signal, from the experimental setup gave a receiver sensitivity of -20.6 dBm with a gain in receiver sensitivity of 3.5 dBm with respect to direct detection. A multilevel pulse amplitude modulation (4-PAM) that doubles the data rate per channel from10 Gbps to 20 Gbps by transmitting more information in the amplitude of the carrier signal was implemented. This was achieved by modulating the optical amplitude with an electrical four level amplitude shift keyed (ASK) signal. A receiver consisting of a single photodiode, three decision circuits and a decoding logic circuit was used to receive and extract the original transmitted data. A DSP aided receiver was used to evaluate the link performance. A receiver sensitivity of -12.8 dBm is attained with a dispersion penalty of about 7.2 dB after transmission through 25 km of G.652 fibre.
- Full Text:
- Date Issued: 2016
- Authors: Chabata, Tichakunda Valentine
- Date: 2016
- Subjects: Optical communications , Modulation (Electronics) , Signal processing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/4775 , vital:20677
- Description: The drastic increase in the number of internet users and the general convergence of all other communication systems into an optical system have brought a sharp rise in demand for bandwidth and calls for high capacity transmission networks. Large unamplified transmission reach is another contributor in reducing deployment costs of an optical communication system. Spectrally efficient modulation formats are suggested as a solution to overcome the problems associated with limited channels and bandwidth of dense wavelength division multiplexing (DWDM) optical communication systems. Higher order modulation formats which are considered to be spectrally efficient and can increase the transmission capacity by transmitting more information in the amplitude, phase, polarization or a combination of all was studied. Different detection technologies are to be implemented to suit a particular higher order modulation format. In this research multilevel modulation formats, different detection technologies and a digital signal processing aided receiver were studied in a practical optical transmission system. The work in this thesis started with the implementation of the traditional amplitude shift keying (ASK) modulation and a differential phase shift keying (DPSK) modulation systems as they form the basic building block in the design of higher order modulation formats. Results obtained from using virtual photonics instruments (VPI)simulation software, receiver sensitivity for 10Gbpsnon-return-to-zero (NRZ), amplitude phase shift keying (ASK) and DPSK signals were measured to be -22.7 dBm and -22.0 dBm respectively. Performance comparison for the two modulation formats were done over different transmission distances. ASK also known as On-Off keying (OOK) performed better for shorter lengths whereas DPSK performed better for longer lengths of up to90km.Experimental results on a 10 Gbps NRZ- ASK signal gave a receiver sensitivity of -21.1 dBm from digital signal processing (DSP) aided receiver against -19.8 dBm from the commercial bit error ratio tester (BERT) yielding a small difference of 1.3 dB hence validating the reliability and accuracy of the digital signal processing (DSP) assisted receiver. Traditional direct detection scheme and coherent detection scheme performances were evaluated again on a 10 Gbps NRZ ASK signal. Coherent detection that can achieve a large unamplified transmission reach and has a higher passive optical splitting ratio was first evaluated using the VPI simulation software. Simulation results gave a receiver sensitivity of -30.4 dBm forcoherent detection and -18.3 dBm for direct detection, yielding a gain in receiver sensitivity of 12.1 dB. The complex coherently detected signal, from the experimental setup gave a receiver sensitivity of -20.6 dBm with a gain in receiver sensitivity of 3.5 dBm with respect to direct detection. A multilevel pulse amplitude modulation (4-PAM) that doubles the data rate per channel from10 Gbps to 20 Gbps by transmitting more information in the amplitude of the carrier signal was implemented. This was achieved by modulating the optical amplitude with an electrical four level amplitude shift keyed (ASK) signal. A receiver consisting of a single photodiode, three decision circuits and a decoding logic circuit was used to receive and extract the original transmitted data. A DSP aided receiver was used to evaluate the link performance. A receiver sensitivity of -12.8 dBm is attained with a dispersion penalty of about 7.2 dB after transmission through 25 km of G.652 fibre.
- Full Text:
- Date Issued: 2016
Continuous flow synthesis of silicon compounds as feedstock for solar-grade silicon production
- Authors: Chigondo, Fidelis
- Date: 2016
- Subjects: Silicon -- Synthesis , Homogeneous catalysis
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4529 , vital:20613
- Description: This thesis describes the key steps in the production of high purity (solar-grade) silicon from metallurgical-grade silicon for use in the production of photovoltaic cells as alternative renewable, environmentally benign and cheap energy source. The initial part of the project involves the development and optimization of a small chemical production platform system capable of producing alkoxysilanes from metallurgical-grade silicon as green precursors to solar-grade silicon production. Specifically, the main aim of the study was to synthesize trialkoxysilanes in continuous flow mode, although the synthesis on monosilane was also done in batch mode. The alkoxylation reaction was carried out in a traditional slurry phase batch reactor, packed bed flow tubular reactor and also attempted in a continuous flow falling film tubular reactor. The effect of key parameters which affect the silicon conversion and selectivity for the desired trialkoxysilane were investigated and optimized using ethanol as a reagent model. The synthesis was then extended to the other alcohols namely methanol, n-propanol and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included: CuCl, Cu(OH)2, CuO and CuSO4. CuCl and Cu(OH)2 showed comparable activity in the batch mode but the former was more efficient in the packed bed flow tubular reactor. Cu(OH)2 could be used as a non-halide catalyst but its activity is limited to short reaction cycles (<10 h). The uncatalysed reaction resulted in negligible reaction rates in both types of reactors. High temperature catalyst pre-heating (>500 oC) resulted in a lower rate of reaction and selectivity than when slightly lower temperatures are used (<350 oC) in both reactors, although much difference was noticed in the packed bed flow tubular reactor. Synthesis in the batch reactor needed longer silicon-catalyst activation time, higher pre-heating temperature and higher catalyst amounts as compare to the packed bed flow tubular reactor. Reaction temperature and alcohol flow rate influenced the reaction in both methods. The optimum reaction temperature range and alcohol flow rate was comparable in both reactors (230 to 240 oC) and 0.1mL/min respectively. The effect of alcohol R-group (C1 to C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length in both methods. Ethanol showed highest selectivity (>95% in batch and >97% in flow) and conversion (about 88% in batch and about 64% in flow) as compared to all other alcohols studied showing that it could be the most efficient alkoxylation alcohol for this reaction. Overally, the packed bed flow tubular reactor resulted in higher selectivity to trialkoxysilanes than the batch system. Performing the reaction under pressure resulted in increased conversion but selectivity to the desire trialkoxysilane diminished. Synthesis in a continuous flow falling film tubular reactor was not successful as it resulted in very poor conversion and selectivity. Monosilane was successfully synthesized from the disproportionation of triethoxysilane using homogeneous and heterogeneous catalysts in batch mode. The results obtained from homogeneous catalysis showed that the reaction can be conducted at room temperature. The heterogeneous catalysis method resulted in slow conversion at room temperature but mild heating up to 55 oC greatly improved the reaction. Conducting the reaction under neat conditions produced comparable results to reactions which were carried out using solvents. The disproportionation reaction was best described by the first order kinetic model. The results obtained in this research indicate that the packed bed flow tubular reactor can be utilized with future modifications for continuous flow synthesis of alkoxysilanes as feedstock for the solar-grade silicon production.
- Full Text:
- Date Issued: 2016
- Authors: Chigondo, Fidelis
- Date: 2016
- Subjects: Silicon -- Synthesis , Homogeneous catalysis
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: http://hdl.handle.net/10948/4529 , vital:20613
- Description: This thesis describes the key steps in the production of high purity (solar-grade) silicon from metallurgical-grade silicon for use in the production of photovoltaic cells as alternative renewable, environmentally benign and cheap energy source. The initial part of the project involves the development and optimization of a small chemical production platform system capable of producing alkoxysilanes from metallurgical-grade silicon as green precursors to solar-grade silicon production. Specifically, the main aim of the study was to synthesize trialkoxysilanes in continuous flow mode, although the synthesis on monosilane was also done in batch mode. The alkoxylation reaction was carried out in a traditional slurry phase batch reactor, packed bed flow tubular reactor and also attempted in a continuous flow falling film tubular reactor. The effect of key parameters which affect the silicon conversion and selectivity for the desired trialkoxysilane were investigated and optimized using ethanol as a reagent model. The synthesis was then extended to the other alcohols namely methanol, n-propanol and n-butanol. Copper catalysts which were tested in the alkoxylation reaction included: CuCl, Cu(OH)2, CuO and CuSO4. CuCl and Cu(OH)2 showed comparable activity in the batch mode but the former was more efficient in the packed bed flow tubular reactor. Cu(OH)2 could be used as a non-halide catalyst but its activity is limited to short reaction cycles (<10 h). The uncatalysed reaction resulted in negligible reaction rates in both types of reactors. High temperature catalyst pre-heating (>500 oC) resulted in a lower rate of reaction and selectivity than when slightly lower temperatures are used (<350 oC) in both reactors, although much difference was noticed in the packed bed flow tubular reactor. Synthesis in the batch reactor needed longer silicon-catalyst activation time, higher pre-heating temperature and higher catalyst amounts as compare to the packed bed flow tubular reactor. Reaction temperature and alcohol flow rate influenced the reaction in both methods. The optimum reaction temperature range and alcohol flow rate was comparable in both reactors (230 to 240 oC) and 0.1mL/min respectively. The effect of alcohol R-group (C1 to C4) on the reaction revealed that conversion and selectivity generally decrease with an increase in carbon chain length in both methods. Ethanol showed highest selectivity (>95% in batch and >97% in flow) and conversion (about 88% in batch and about 64% in flow) as compared to all other alcohols studied showing that it could be the most efficient alkoxylation alcohol for this reaction. Overally, the packed bed flow tubular reactor resulted in higher selectivity to trialkoxysilanes than the batch system. Performing the reaction under pressure resulted in increased conversion but selectivity to the desire trialkoxysilane diminished. Synthesis in a continuous flow falling film tubular reactor was not successful as it resulted in very poor conversion and selectivity. Monosilane was successfully synthesized from the disproportionation of triethoxysilane using homogeneous and heterogeneous catalysts in batch mode. The results obtained from homogeneous catalysis showed that the reaction can be conducted at room temperature. The heterogeneous catalysis method resulted in slow conversion at room temperature but mild heating up to 55 oC greatly improved the reaction. Conducting the reaction under neat conditions produced comparable results to reactions which were carried out using solvents. The disproportionation reaction was best described by the first order kinetic model. The results obtained in this research indicate that the packed bed flow tubular reactor can be utilized with future modifications for continuous flow synthesis of alkoxysilanes as feedstock for the solar-grade silicon production.
- Full Text:
- Date Issued: 2016
The role of cancer procoagulant on the MTOR pathway
- Authors: Chiuswa, Chengetanai
- Date: 2016
- Subjects: Cancer -- Research , Neovascularization , Biochemistry , Blood coagulation factors -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7303 , vital:21316
- Description: Cancer procoagulant (CP) is a cysteine protease found in tumour cells and amnion chorion membranes. The main function of CP is not yet known, but it has potential roles in tumour growth and metastasis. Initially, CP was believed to increase coagulation in cancer patients; however, research has shown that increase in CP concentration does not correlate with an increase in coagulation. The location of CP in amnion chorion membranes and tumour cells only led to the hypothesis that CP might be involved in inducing blood vessel and or lymph vessel formation. CP was shown to induce lymphangiogenesis (lymph vessel formation) in human telomerase reverse transcriptase-human dermal endothelial cells (hTERT-HDLEC) (Tshaka, 2011). CP-induced tube formation was inhibited by rapamycin; indicating that CP may be signalling via the mammalian target of rapamycin (mTOR) pathway. The aim of this study was to investigate the effect of CP on the mTOR signalling pathway using human umbilical endothelial vein cells (HUVECs) as a model. CP was isolated from amnion chorion membranes and purified using two anion exchange chromatography steps. Purified CP (2 μg/ml) was used to induce tube formation in endothelial cells (HUVECs) seeded on growth factor reduced (GFR) Matrigel. In addition, the 2 μg/ml CP was used to treat cultured HUVECs. Sodium dodecyl sulphate polyacrylamide electrophoresis (SDS-PAGE) and western blotting were used to determine phosphorylation levels of protein kinase B (Akt) and ribosomal protein S6 kinase (S6K). CP was successfully isolated and purified using anion exchange chromatography. The effect of CP on tube formation was not significant relative to the control in the HUVEC cell line. The role of CP on Akt and S6K phosphorylation still needs to be verified by using sensitive methods of quantification such as enhanced chemiluminescence (ECL) and enzyme linked immunosorbent assay (ELISA). The levels of CP activity were shown to be higher in early tumour growth than in advanced cancer suggesting that certain physiological factors could be increasing CP activity during early tumour growth. This study investigated the effect of cobalt chloride on CP activity in breast cancer cell lines. Cobalt chloride reduced CP activity in MCF-7 and promoted CP activity in MDA-MB-231.
- Full Text:
- Date Issued: 2016
- Authors: Chiuswa, Chengetanai
- Date: 2016
- Subjects: Cancer -- Research , Neovascularization , Biochemistry , Blood coagulation factors -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7303 , vital:21316
- Description: Cancer procoagulant (CP) is a cysteine protease found in tumour cells and amnion chorion membranes. The main function of CP is not yet known, but it has potential roles in tumour growth and metastasis. Initially, CP was believed to increase coagulation in cancer patients; however, research has shown that increase in CP concentration does not correlate with an increase in coagulation. The location of CP in amnion chorion membranes and tumour cells only led to the hypothesis that CP might be involved in inducing blood vessel and or lymph vessel formation. CP was shown to induce lymphangiogenesis (lymph vessel formation) in human telomerase reverse transcriptase-human dermal endothelial cells (hTERT-HDLEC) (Tshaka, 2011). CP-induced tube formation was inhibited by rapamycin; indicating that CP may be signalling via the mammalian target of rapamycin (mTOR) pathway. The aim of this study was to investigate the effect of CP on the mTOR signalling pathway using human umbilical endothelial vein cells (HUVECs) as a model. CP was isolated from amnion chorion membranes and purified using two anion exchange chromatography steps. Purified CP (2 μg/ml) was used to induce tube formation in endothelial cells (HUVECs) seeded on growth factor reduced (GFR) Matrigel. In addition, the 2 μg/ml CP was used to treat cultured HUVECs. Sodium dodecyl sulphate polyacrylamide electrophoresis (SDS-PAGE) and western blotting were used to determine phosphorylation levels of protein kinase B (Akt) and ribosomal protein S6 kinase (S6K). CP was successfully isolated and purified using anion exchange chromatography. The effect of CP on tube formation was not significant relative to the control in the HUVEC cell line. The role of CP on Akt and S6K phosphorylation still needs to be verified by using sensitive methods of quantification such as enhanced chemiluminescence (ECL) and enzyme linked immunosorbent assay (ELISA). The levels of CP activity were shown to be higher in early tumour growth than in advanced cancer suggesting that certain physiological factors could be increasing CP activity during early tumour growth. This study investigated the effect of cobalt chloride on CP activity in breast cancer cell lines. Cobalt chloride reduced CP activity in MCF-7 and promoted CP activity in MDA-MB-231.
- Full Text:
- Date Issued: 2016
A study of lanthanide complexes with di-2-pyridyl ligands
- Authors: Coetzee, Louis-Charl Cloete
- Date: 2016
- Subjects: Rare earth metals
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4731 , vital:20659
- Description: The ligands di(2-pyridyl) ketone (DPK) and cis-1,2 di(2-pyridyl) ethylene (DPE) are N,N,Odonor ligands that can undergo nucleophilic addition and become more flexible for coordination. The reaction between the lanthanide thiocyanate salt and DPK gave rise to seven novel complexes of the general formula [Ln(NCS)3(DPKOH)3], where Ln = La, Ce, Nd, Eu, Tb, Dy and Ho. 1H NMR spectroscopy verified that the ligand underwent nucleophilic addition upon coordination. This was further confirmed using UV-Vis spectroscopy which showed a shift in the absorption bands due to conjugation of electrons within the pyridyl ring upon coordination. UV-Vis spectroscopy was also utilised to test the covalent character of the neodymium and holmium complexes. X-ray diffraction and IR spectroscopy showed that three DPK ligands coordinated bidentately through a pyridinic nitrogen and a hydroxyl oxygen, while three isothiocyanato molecules completed the coordination environment around each metal. Furthermore, X-ray diffraction also revealed that these complexes are isostructural, ninecoordinate and the polyhedron which encloses each ion is of trigonal tricapped prismatic shape with D3h symmetry. Micro-analysis on all the complexes, except lanthanum and holmium confirmed the molecular formulae produced from the crystallographic data of each complex. The reaction between the lanthanide thiocyanate salt and DPE produced poor quality crystals which could not be detected by X-ray diffraction. The lanthanide salts used for this reaction were lanthanum, neodymium, europium, dysprosium and holmium. Upon coordination, conductivity measurements detected the presence of lanthanide ions in each solution. 1H NMR and IR spectroscopic studies showed that the ethylenic moiety of DPE underwent nucleophilic addition upon coordination. UV-Vis spectroscopy further confirmed nucleophilic addition upon coordination due to shifts in absorption bands. IR spectroscopy verified the possibility of a bidentate coordination to each metal through a pyridinic nitrogen and a hydroxyl oxygen as well as a monodentate coordination through isothiocyanato ligands. A micro-analysis on all the complexes provided the molecular formulae that can best fit each complex. The effect of the solvent molecules on the bonding parameters of the lanthanum complex was investigated. An analysis of the results produced from crystallographic data revealed the presence of intermolecular forces which interacted and stabilised the complex.
- Full Text:
- Date Issued: 2016
- Authors: Coetzee, Louis-Charl Cloete
- Date: 2016
- Subjects: Rare earth metals
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/4731 , vital:20659
- Description: The ligands di(2-pyridyl) ketone (DPK) and cis-1,2 di(2-pyridyl) ethylene (DPE) are N,N,Odonor ligands that can undergo nucleophilic addition and become more flexible for coordination. The reaction between the lanthanide thiocyanate salt and DPK gave rise to seven novel complexes of the general formula [Ln(NCS)3(DPKOH)3], where Ln = La, Ce, Nd, Eu, Tb, Dy and Ho. 1H NMR spectroscopy verified that the ligand underwent nucleophilic addition upon coordination. This was further confirmed using UV-Vis spectroscopy which showed a shift in the absorption bands due to conjugation of electrons within the pyridyl ring upon coordination. UV-Vis spectroscopy was also utilised to test the covalent character of the neodymium and holmium complexes. X-ray diffraction and IR spectroscopy showed that three DPK ligands coordinated bidentately through a pyridinic nitrogen and a hydroxyl oxygen, while three isothiocyanato molecules completed the coordination environment around each metal. Furthermore, X-ray diffraction also revealed that these complexes are isostructural, ninecoordinate and the polyhedron which encloses each ion is of trigonal tricapped prismatic shape with D3h symmetry. Micro-analysis on all the complexes, except lanthanum and holmium confirmed the molecular formulae produced from the crystallographic data of each complex. The reaction between the lanthanide thiocyanate salt and DPE produced poor quality crystals which could not be detected by X-ray diffraction. The lanthanide salts used for this reaction were lanthanum, neodymium, europium, dysprosium and holmium. Upon coordination, conductivity measurements detected the presence of lanthanide ions in each solution. 1H NMR and IR spectroscopic studies showed that the ethylenic moiety of DPE underwent nucleophilic addition upon coordination. UV-Vis spectroscopy further confirmed nucleophilic addition upon coordination due to shifts in absorption bands. IR spectroscopy verified the possibility of a bidentate coordination to each metal through a pyridinic nitrogen and a hydroxyl oxygen as well as a monodentate coordination through isothiocyanato ligands. A micro-analysis on all the complexes provided the molecular formulae that can best fit each complex. The effect of the solvent molecules on the bonding parameters of the lanthanum complex was investigated. An analysis of the results produced from crystallographic data revealed the presence of intermolecular forces which interacted and stabilised the complex.
- Full Text:
- Date Issued: 2016
The effect of silica on the reduction of precipitated iron-based fischer-tropsch catalysts
- Authors: Coombes, Matthew
- Date: 2016
- Subjects: Fischer-Tropsch process Reduction (Chemistry) , Catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14873 , vital:27888
- Description: Iron Fischer-Tropsch (FT) catalysts are typically prepared as iron oxides which are reduced to FT-active iron metal and iron carbide prior to FT synthesis. The iron oxides contain a variety of different chemical and structural promoters to alter FT-activity. Silica is a common structural promoter which stabilises the formation of small crystallites and provides mechanical integrity to the catalyst. However, silica inhibits the reduction of the oxide precursor to the FT-active phases. This ultimately affects catalyst activity and product selectivity. It has been proposed that the silica interacts with the iron to form encapsulating shells of fayalite (Fe2SiO4), or fayalite rafts between the iron oxide and the silica support. In this study, six silica-promoted iron oxide samples were prepared using a simple co-precipitation technique. Samples contain varying amounts of silica, and the samples are named 100/x Fe/SiO2, where x is the weight of silica for 100 weight iron, with x taking on values of 0, 10, 25, 50, 100 and 200. The resulting iron oxides were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRPD), M¨ossbauer spectroscopy (MS), magnetic susceptibility measurements (MM), Raman spectroscopy, thermal gravimetric analysis (TGA) and nitrogen physisorption. Their reduction in a hydrogen atmosphere was investigated using temperature programmed reduction (TPR), in situ XRPD and TEM. The reduction in hydrogen of 100/0 Fe/SiO2 and 100/10 Fe/SiO2 was also studied using in situ gas flow TEM cells. These cells allow the samples to be studied in the electron microscope at temperature and pressure conditions approaching those experienced in a real reactor environment. In the absence of a silica promoter (100/0 Fe/SiO2), hematite particles are formed with mean particle diameters of 39 ± 12 and 52.7 ± 0.2 nm determined using TEM and XRPD respectively. MM data reveals a magnetic transition (Morin transition) at≈230 K, consistent with a mean particle size of≈50 nm. In a hydrogen atmosphere, the hematite reduces to metallic iron via a two-step process viz. hematite → magnetite → iron. The final iron particles have an average crystallite size of 68.0 ± 0.2 nm. The presence of lower amounts of silica in the samples 100/10 Fe/SiO2, 100/25 Fe/SiO2 and 100/50 Fe/SiO2 results in the formation of silicasubstituted 2-line ferrihydrite particles. Bands in the Raman spectra of these samples shift on increasing silica content, which indicates an increasing number of Fe-O-Si bonds within the ferrihydrite framework. MM reveals typical superparamagnetic (SPM) behaviour above a blocking temperature in the range 39 - 68 K which gives mean particle sizes of 4.2, 3.6 and 3.5 nm for 100/10 Fe/SiO2, 100/25 Fe/SiO2 and 100/50 Fe/SiO2 respectively, in good agreement with particle sizes determined using TEM (3.1±0.4, 2.4±0.3 and 2.4±0.3 nm respectively). MS data at 300 K and 4.2 K were fitted with distributions of ∆EQ and Bhf respectively. The median values of Bhf decrease with increasing silica content, indicating greater degrees of distortion in the Fe3+ environments induced by increased silica substitution. The reduction to metallic iron occurs via a three-step process viz. hematite → magnetite → wu¨stite → iron, with the silica stabilising the wu¨stite phase. The increasing amount of Fe-O-Si bonds on increasing silica content shifts reduction to higher temperatures broadens each reduction step as a result of local Fe-O-Si concentration variations. Fractions of each sample are not completely reduced even at 1000°C, with the relative proportion increasing with increasing silica content. In situ gas flow TEM studies reveal that the mechanism of reduction involves the liberation of atomic iron atoms from the silica-substituted iron oxides which agglomerate and grow into final iron particles. This leaves a poorly crystalline Fe-O-Si bonded framework behind. STEM-EDS and STEM-EELS reveal low concentrations of silicon at the surface of the resulting iron particles, however they do not form encapsulating shells of fayalite as previously suggested. The majority of the silica remains in the Fe-O-Si material which may crystallise into separate fayalite particles at elevated temperature. The presence of silica in high proportions (100/100 Fe/SiO2 and 100/200 Fe/SiO2) results in the formation of a two-phase system consisting of silicasubstituted 2-line ferrihydrite particles which are encapsulated in an ironinfused amorphous silica network. As with the other silica-bearing samples, there is an increase in Fe-O-Si bonds and an increase in the degree of distortion at Fe3+ sites with increasing silica content. The large amount of silica suppresses the blocking temperature of the SPM crystallites. In a hydrogen atmosphere, the reduction to metallic iron follows the same three step process as the other silica-bearing samples. Reduction temperatures are further shifted to higher values and given reduction steps are considerably broader with increasing silica content. The fraction of iron not fully reduced also increases. Iron particle diameters are very small, since encapsulation by the silica matrix prevents growth of particles.
- Full Text:
- Date Issued: 2016
- Authors: Coombes, Matthew
- Date: 2016
- Subjects: Fischer-Tropsch process Reduction (Chemistry) , Catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/14873 , vital:27888
- Description: Iron Fischer-Tropsch (FT) catalysts are typically prepared as iron oxides which are reduced to FT-active iron metal and iron carbide prior to FT synthesis. The iron oxides contain a variety of different chemical and structural promoters to alter FT-activity. Silica is a common structural promoter which stabilises the formation of small crystallites and provides mechanical integrity to the catalyst. However, silica inhibits the reduction of the oxide precursor to the FT-active phases. This ultimately affects catalyst activity and product selectivity. It has been proposed that the silica interacts with the iron to form encapsulating shells of fayalite (Fe2SiO4), or fayalite rafts between the iron oxide and the silica support. In this study, six silica-promoted iron oxide samples were prepared using a simple co-precipitation technique. Samples contain varying amounts of silica, and the samples are named 100/x Fe/SiO2, where x is the weight of silica for 100 weight iron, with x taking on values of 0, 10, 25, 50, 100 and 200. The resulting iron oxides were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRPD), M¨ossbauer spectroscopy (MS), magnetic susceptibility measurements (MM), Raman spectroscopy, thermal gravimetric analysis (TGA) and nitrogen physisorption. Their reduction in a hydrogen atmosphere was investigated using temperature programmed reduction (TPR), in situ XRPD and TEM. The reduction in hydrogen of 100/0 Fe/SiO2 and 100/10 Fe/SiO2 was also studied using in situ gas flow TEM cells. These cells allow the samples to be studied in the electron microscope at temperature and pressure conditions approaching those experienced in a real reactor environment. In the absence of a silica promoter (100/0 Fe/SiO2), hematite particles are formed with mean particle diameters of 39 ± 12 and 52.7 ± 0.2 nm determined using TEM and XRPD respectively. MM data reveals a magnetic transition (Morin transition) at≈230 K, consistent with a mean particle size of≈50 nm. In a hydrogen atmosphere, the hematite reduces to metallic iron via a two-step process viz. hematite → magnetite → iron. The final iron particles have an average crystallite size of 68.0 ± 0.2 nm. The presence of lower amounts of silica in the samples 100/10 Fe/SiO2, 100/25 Fe/SiO2 and 100/50 Fe/SiO2 results in the formation of silicasubstituted 2-line ferrihydrite particles. Bands in the Raman spectra of these samples shift on increasing silica content, which indicates an increasing number of Fe-O-Si bonds within the ferrihydrite framework. MM reveals typical superparamagnetic (SPM) behaviour above a blocking temperature in the range 39 - 68 K which gives mean particle sizes of 4.2, 3.6 and 3.5 nm for 100/10 Fe/SiO2, 100/25 Fe/SiO2 and 100/50 Fe/SiO2 respectively, in good agreement with particle sizes determined using TEM (3.1±0.4, 2.4±0.3 and 2.4±0.3 nm respectively). MS data at 300 K and 4.2 K were fitted with distributions of ∆EQ and Bhf respectively. The median values of Bhf decrease with increasing silica content, indicating greater degrees of distortion in the Fe3+ environments induced by increased silica substitution. The reduction to metallic iron occurs via a three-step process viz. hematite → magnetite → wu¨stite → iron, with the silica stabilising the wu¨stite phase. The increasing amount of Fe-O-Si bonds on increasing silica content shifts reduction to higher temperatures broadens each reduction step as a result of local Fe-O-Si concentration variations. Fractions of each sample are not completely reduced even at 1000°C, with the relative proportion increasing with increasing silica content. In situ gas flow TEM studies reveal that the mechanism of reduction involves the liberation of atomic iron atoms from the silica-substituted iron oxides which agglomerate and grow into final iron particles. This leaves a poorly crystalline Fe-O-Si bonded framework behind. STEM-EDS and STEM-EELS reveal low concentrations of silicon at the surface of the resulting iron particles, however they do not form encapsulating shells of fayalite as previously suggested. The majority of the silica remains in the Fe-O-Si material which may crystallise into separate fayalite particles at elevated temperature. The presence of silica in high proportions (100/100 Fe/SiO2 and 100/200 Fe/SiO2) results in the formation of a two-phase system consisting of silicasubstituted 2-line ferrihydrite particles which are encapsulated in an ironinfused amorphous silica network. As with the other silica-bearing samples, there is an increase in Fe-O-Si bonds and an increase in the degree of distortion at Fe3+ sites with increasing silica content. The large amount of silica suppresses the blocking temperature of the SPM crystallites. In a hydrogen atmosphere, the reduction to metallic iron follows the same three step process as the other silica-bearing samples. Reduction temperatures are further shifted to higher values and given reduction steps are considerably broader with increasing silica content. The fraction of iron not fully reduced also increases. Iron particle diameters are very small, since encapsulation by the silica matrix prevents growth of particles.
- Full Text:
- Date Issued: 2016
Towards an industrial ecology for the Nelson Mandela Bay: Metropolitan area
- Authors: Dalindyebo, Litha
- Date: 2016
- Subjects: Industrial ecology -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/9263 , vital:26556
- Description: The aim of this study is to formulate a model of industrial ecology for wider application in the Nelson Mandel Bay (NMB) Metropole. To achieve this aim, the following objectives will be pursued: • A theoretical investigation of the concept of industrial ecology – in an attempt to establish its meaning, as well as the implications thereof. • A theoretical investigation of the operational implications of industrial ecology, including existing methodologies, such as Material Flow Analysis (MFA) and Life Cycle Assessment (LCA) that can be applied, in order to develop a system of industrial ecology between different companies. • The formulation of a methodology for application to the case study. • Presenting and discussing the research results produced by the application of the industrial ecology related methodology to the case study. • To present a synthesis of the research results of this study. This objective includes a critical evaluation of the research methodology and results, as well as some recommendations for the facilitation of industrial ecology. The methodology of the research involved conducting semi structured interviews, conducting a Material Flow Analysis and Life Cycle Analysis using SIMAPRO software. There interview with Goodyear management took place (see Appendix A), while the management at Sovereign Foods agreed to an interview however they didn’t honour the agreement. During the interview at Goodyear understanding of the operational process was achieved by conducting the interviews. The three areas that were discussed during the interview process were: 1. How the boiler works; 2. Current Air-Emission results; and 3. The process of steam generation. An MFA and an LCA on the production process of comparing the boiler functionality was conducted, so that there is an adequate understanding of the environmental performance of the two different boilers. The results of the MFA are presented as follows, namely: the goal and scope definition and the inventory results. Coal boiler versus fluidised boiler data where modelled. The modelling is done on comparing the flow of chemicals during steam production process, and which chemicals have a significant environmental impact. The LCA results looked at the basis of the symbiotic approach by identifying sustainable choices of design, production and consumption. The findings of this research have been obtained from the investigation of industrial ecology framework planning at Goodyear SA and Sovereign Foods. The findings have revealed that there is a synergy that exists between the two case-study areas. However, this is based on Goodyear changing the technology of the boiler they use (a boiler creates steam for the tyre-building process). The company will be required to use a fluidised boiler, instead of the current coal boiler. The use of the fluidised boiler will ensure that all waste streams at Goodyear will be reused and recycled, thereby creating the framework for industrial ecology. The results that are firstly drawn out of SIMAPRO is the Life Cycle Inventory. In this research, there is a flow of 1437 chemical materials and substances in the production of steam using both coal boiler and fluidized boiler. Due to the number of substance flow elements, the research has presented only the significant substances that influence the environmental performance of steam production using the two different feeder materials, which are coal and chicken matter (see Figure 4.4). In the coal boiler process, sulfur comprises the largest amount of chemical substance. The other top five chemical components that contribute to the steam production process are: nickel, chromium, arsenic and iodosulfuron-methyl-sodium. The scale of figure 4.4 is reduced to show the various number of chemical flows found in the steam production process through SIMAPRO software. The Life Cycle Assessment (LCA) results were presented looking at namely the following characterization, normalization, weighting, single score and damage assessment (see Figure 4.7 – 4.10 p87 – p90). The figures are presented as taken directly from the reports drawn from the SIMAPRO software. Figure 4.7 gives the characterisation results up to 100%, where 0% has a minimal environmental effect; whereas 100% has the most significant environmental effect. Oxidation of coal is compared versus the oxidation of chicken matter, the coal boiler process has higher environmental impacts. Figure 4.8 shows the normalisation results of the coal boiler versus the fluidised boiler for the functional unit steam production. The environmental degradation under normalisation between the two boilers are measured, based on three parameters, namely: human health, ecosystems and resources. In all three parameters that are measured under normalisation, the production of steam using the coal boiler has the highest impacts. The weighting results in Figure 4.9 show a mirror image of the normalisation results. Finally, a gap analysis of the theoretical requirements for industrial ecology is displayed versus what currently exists in the case study area. The gap analysis will assist in the development of recommendations. These will be presented in the next chapter. A gap analysis of findings is discussed leading into the synthesis. The value of this research is that the baseline data of planning for an industrial ecology create a platform that can be used for implementing an industrial ecology between Goodyear SA and Sovereign Foods. This will, in time, have wider applications for the entire NMB metropole.
- Full Text:
- Date Issued: 2016
- Authors: Dalindyebo, Litha
- Date: 2016
- Subjects: Industrial ecology -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/9263 , vital:26556
- Description: The aim of this study is to formulate a model of industrial ecology for wider application in the Nelson Mandel Bay (NMB) Metropole. To achieve this aim, the following objectives will be pursued: • A theoretical investigation of the concept of industrial ecology – in an attempt to establish its meaning, as well as the implications thereof. • A theoretical investigation of the operational implications of industrial ecology, including existing methodologies, such as Material Flow Analysis (MFA) and Life Cycle Assessment (LCA) that can be applied, in order to develop a system of industrial ecology between different companies. • The formulation of a methodology for application to the case study. • Presenting and discussing the research results produced by the application of the industrial ecology related methodology to the case study. • To present a synthesis of the research results of this study. This objective includes a critical evaluation of the research methodology and results, as well as some recommendations for the facilitation of industrial ecology. The methodology of the research involved conducting semi structured interviews, conducting a Material Flow Analysis and Life Cycle Analysis using SIMAPRO software. There interview with Goodyear management took place (see Appendix A), while the management at Sovereign Foods agreed to an interview however they didn’t honour the agreement. During the interview at Goodyear understanding of the operational process was achieved by conducting the interviews. The three areas that were discussed during the interview process were: 1. How the boiler works; 2. Current Air-Emission results; and 3. The process of steam generation. An MFA and an LCA on the production process of comparing the boiler functionality was conducted, so that there is an adequate understanding of the environmental performance of the two different boilers. The results of the MFA are presented as follows, namely: the goal and scope definition and the inventory results. Coal boiler versus fluidised boiler data where modelled. The modelling is done on comparing the flow of chemicals during steam production process, and which chemicals have a significant environmental impact. The LCA results looked at the basis of the symbiotic approach by identifying sustainable choices of design, production and consumption. The findings of this research have been obtained from the investigation of industrial ecology framework planning at Goodyear SA and Sovereign Foods. The findings have revealed that there is a synergy that exists between the two case-study areas. However, this is based on Goodyear changing the technology of the boiler they use (a boiler creates steam for the tyre-building process). The company will be required to use a fluidised boiler, instead of the current coal boiler. The use of the fluidised boiler will ensure that all waste streams at Goodyear will be reused and recycled, thereby creating the framework for industrial ecology. The results that are firstly drawn out of SIMAPRO is the Life Cycle Inventory. In this research, there is a flow of 1437 chemical materials and substances in the production of steam using both coal boiler and fluidized boiler. Due to the number of substance flow elements, the research has presented only the significant substances that influence the environmental performance of steam production using the two different feeder materials, which are coal and chicken matter (see Figure 4.4). In the coal boiler process, sulfur comprises the largest amount of chemical substance. The other top five chemical components that contribute to the steam production process are: nickel, chromium, arsenic and iodosulfuron-methyl-sodium. The scale of figure 4.4 is reduced to show the various number of chemical flows found in the steam production process through SIMAPRO software. The Life Cycle Assessment (LCA) results were presented looking at namely the following characterization, normalization, weighting, single score and damage assessment (see Figure 4.7 – 4.10 p87 – p90). The figures are presented as taken directly from the reports drawn from the SIMAPRO software. Figure 4.7 gives the characterisation results up to 100%, where 0% has a minimal environmental effect; whereas 100% has the most significant environmental effect. Oxidation of coal is compared versus the oxidation of chicken matter, the coal boiler process has higher environmental impacts. Figure 4.8 shows the normalisation results of the coal boiler versus the fluidised boiler for the functional unit steam production. The environmental degradation under normalisation between the two boilers are measured, based on three parameters, namely: human health, ecosystems and resources. In all three parameters that are measured under normalisation, the production of steam using the coal boiler has the highest impacts. The weighting results in Figure 4.9 show a mirror image of the normalisation results. Finally, a gap analysis of the theoretical requirements for industrial ecology is displayed versus what currently exists in the case study area. The gap analysis will assist in the development of recommendations. These will be presented in the next chapter. A gap analysis of findings is discussed leading into the synthesis. The value of this research is that the baseline data of planning for an industrial ecology create a platform that can be used for implementing an industrial ecology between Goodyear SA and Sovereign Foods. This will, in time, have wider applications for the entire NMB metropole.
- Full Text:
- Date Issued: 2016
The effect of Acacia karroo tree density on grass species composition, forage yield and quality in different rainfall regimes in the Eastern Cape, South Africa
- Authors: De Ridder, Cornelius Henry
- Date: 2016
- Subjects: Grasses -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/2858 , vital:20357
- Description: It is widely believed that Acacia karroo Hayne trees compete with and negatively affect the production of grasses in their immediate surroundings. This perception formed as a result of observations by farmers of their veld as well as some research. The complexity of plant interactions in different conditions required that research be done to better explain the extent of grass and tree interactions. In response to this need, the effect of a range of Acacia karroo densities on grass production was tested in areas of differing rainfall. Results emphasize the complexity of such plant interactions but highlight rainfall as influencing the effect of tree density on grass production and grass quality. Study sites were chosen with significant differences in tree density and rainfall and this was found to be concomitant with significant differences in grass yield and crude protein (p < 0.001). Grass yield (mass produced) was negatively correlated with tree density (p < 0.001) and was affected by rainfall. High tree density reduced grass yield at the lower rainfall sites, but a reduction in yield was only recorded during dry conditions in the higher rainfall areas. By contrast, the crude protein content of grasses was positively correlated to tree density (p < 0.001). However, as with yield, rainfall played an important part in the strength of the correlation. Soil properties such as temperature (-) (p = 0.011), phosphorus content (+) (p = 0.006), calcium concentration (+) (p = 0.005), acid saturation (-) (p = 0.018), and soil pH (+) (p = 0.008) were also significantly correlated to tree density. Tree density enriched the soil, subsequently benefitting grass quality. The study sites investigated, had different plant communities and environmental conditions with Cradock, Kubusi Drift and Kei Mouth having unique communities and conditions while Adelaide and Cathcart could not be separated in either. Cradock was the driest site and the vegetation was dominated by both grasses and karroid shrubs, differing in pattern and process from the other sites. The Kubusi Drift site had high tree densities, to the extent that the trees altered the grass species composition. The effects of rainfall on grass yield and quality exceeded that of community composition differences.
- Full Text:
- Date Issued: 2016
- Authors: De Ridder, Cornelius Henry
- Date: 2016
- Subjects: Grasses -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/2858 , vital:20357
- Description: It is widely believed that Acacia karroo Hayne trees compete with and negatively affect the production of grasses in their immediate surroundings. This perception formed as a result of observations by farmers of their veld as well as some research. The complexity of plant interactions in different conditions required that research be done to better explain the extent of grass and tree interactions. In response to this need, the effect of a range of Acacia karroo densities on grass production was tested in areas of differing rainfall. Results emphasize the complexity of such plant interactions but highlight rainfall as influencing the effect of tree density on grass production and grass quality. Study sites were chosen with significant differences in tree density and rainfall and this was found to be concomitant with significant differences in grass yield and crude protein (p < 0.001). Grass yield (mass produced) was negatively correlated with tree density (p < 0.001) and was affected by rainfall. High tree density reduced grass yield at the lower rainfall sites, but a reduction in yield was only recorded during dry conditions in the higher rainfall areas. By contrast, the crude protein content of grasses was positively correlated to tree density (p < 0.001). However, as with yield, rainfall played an important part in the strength of the correlation. Soil properties such as temperature (-) (p = 0.011), phosphorus content (+) (p = 0.006), calcium concentration (+) (p = 0.005), acid saturation (-) (p = 0.018), and soil pH (+) (p = 0.008) were also significantly correlated to tree density. Tree density enriched the soil, subsequently benefitting grass quality. The study sites investigated, had different plant communities and environmental conditions with Cradock, Kubusi Drift and Kei Mouth having unique communities and conditions while Adelaide and Cathcart could not be separated in either. Cradock was the driest site and the vegetation was dominated by both grasses and karroid shrubs, differing in pattern and process from the other sites. The Kubusi Drift site had high tree densities, to the extent that the trees altered the grass species composition. The effects of rainfall on grass yield and quality exceeded that of community composition differences.
- Full Text:
- Date Issued: 2016
Investigating the effects of mopane worms (Imbrasia belina) on nutrients, Venetia-Limpopo Nature Reserve, South Africa
- De Swardt, Donovan Barry, O’Connor, Tim
- Authors: De Swardt, Donovan Barry , O’Connor, Tim
- Date: 2016
- Subjects: Herbivores -- Ecology -- South Africa -- Limpopo , Phytophagous insects -- South Africa -- Limpopo , Mopane worm -- South Africa -- Limpopo , Soil fertility -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/9273 , vital:26558
- Description: Ecologists have long been aware that large mammalian herbivores can alter ecosystem functioning in various ways, for example through changing where they defecate and urinate, which consequently affects nutrient cycling. The effects of herbivorous insects on ecosystems, however, have received limited attention until recently. Insects are capable of mass outbreaks, they can consume large volumes of vegetative material and can deposit large quantities of dung (frass), one example being the mopane worm, Imbrasia belina. This study looked at the effect of mopane worm frass on soil fertility in the mopane veld of the Venetia-Limpopo Nature Reserve and neighbouring Haakdoring farm. It found that mopane worms are capable of altering soil nutrient dynamics beneath the trees where they are browsing in three ways. Firstly, they increase the potential amount of nutrients deposited when compared with that deposited through conventional leaf litter. Secondly, they alter the rate of nutrient recycling by depositing nutrients in frass which decomposes more rapidly than conventional leaf litter. Lastly, they increase the amounts of potassium and phosphorus in the soil. While there is no conclusive data from this study that the mopane veld would become extinct if mopane worms were harvested to extinction, it has shown that there is relatively little evidence on how herbivorous insects could affect ecosystem functioning in the landscapes in which they occur. Further research is recommended that investigates how mopane worms influence soil fertility in more detail and over multiple geographical locations.
- Full Text:
- Date Issued: 2016
- Authors: De Swardt, Donovan Barry , O’Connor, Tim
- Date: 2016
- Subjects: Herbivores -- Ecology -- South Africa -- Limpopo , Phytophagous insects -- South Africa -- Limpopo , Mopane worm -- South Africa -- Limpopo , Soil fertility -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/9273 , vital:26558
- Description: Ecologists have long been aware that large mammalian herbivores can alter ecosystem functioning in various ways, for example through changing where they defecate and urinate, which consequently affects nutrient cycling. The effects of herbivorous insects on ecosystems, however, have received limited attention until recently. Insects are capable of mass outbreaks, they can consume large volumes of vegetative material and can deposit large quantities of dung (frass), one example being the mopane worm, Imbrasia belina. This study looked at the effect of mopane worm frass on soil fertility in the mopane veld of the Venetia-Limpopo Nature Reserve and neighbouring Haakdoring farm. It found that mopane worms are capable of altering soil nutrient dynamics beneath the trees where they are browsing in three ways. Firstly, they increase the potential amount of nutrients deposited when compared with that deposited through conventional leaf litter. Secondly, they alter the rate of nutrient recycling by depositing nutrients in frass which decomposes more rapidly than conventional leaf litter. Lastly, they increase the amounts of potassium and phosphorus in the soil. While there is no conclusive data from this study that the mopane veld would become extinct if mopane worms were harvested to extinction, it has shown that there is relatively little evidence on how herbivorous insects could affect ecosystem functioning in the landscapes in which they occur. Further research is recommended that investigates how mopane worms influence soil fertility in more detail and over multiple geographical locations.
- Full Text:
- Date Issued: 2016
Site Fidelity of southern right (Eubalaena australis) and humpback whales (Megaptera novaeangliae) in Algoa Bay, South Africa
- Authors: Drost, Eduard F
- Date: 2016
- Subjects: Marine mammals -- South Africa -- Algoa Bay Southern right whale -- South Africa -- Algoa Bay Humpback whale -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21735 , vital:29742
- Description: Mysticetes, or baleen whales, make up one of two sub-orders of the Order Cetacea within the Class Mammalia (Drikamer et al, 2013). It contains three families, each characterized by baleen plates (Drikamer et al, 2013). These baleen plates consist of keratin that replaced the tooth structures for feeding in these mammals (Drikamer et al, 2013). Other biological characteristics of these animals include paired external nares (blowholes), a sternum consisting of a single bone, symmetrical skull and the most conspicuous of all, the body length of between ten to thirty metres (Drikamer et al, 2013). It is thought that the size characteristic was probably the main factor when categorising them as cetaceans, with the Latin word ‘Cetus’ referring to ‘sea monster’ (Carnaby, 2006). In this literature review, the focus will fall on two species of mysticetes from separate families, namely that of the southern right whale, Eubalaena australis of the Balaenidae family, and the humpback whale, Megaptera novaeangliae of the Balaenopteridae family. Emphasis in this review will fall on the aspect of site fidelity of the mother-calf pairs.
- Full Text:
- Date Issued: 2016
- Authors: Drost, Eduard F
- Date: 2016
- Subjects: Marine mammals -- South Africa -- Algoa Bay Southern right whale -- South Africa -- Algoa Bay Humpback whale -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21735 , vital:29742
- Description: Mysticetes, or baleen whales, make up one of two sub-orders of the Order Cetacea within the Class Mammalia (Drikamer et al, 2013). It contains three families, each characterized by baleen plates (Drikamer et al, 2013). These baleen plates consist of keratin that replaced the tooth structures for feeding in these mammals (Drikamer et al, 2013). Other biological characteristics of these animals include paired external nares (blowholes), a sternum consisting of a single bone, symmetrical skull and the most conspicuous of all, the body length of between ten to thirty metres (Drikamer et al, 2013). It is thought that the size characteristic was probably the main factor when categorising them as cetaceans, with the Latin word ‘Cetus’ referring to ‘sea monster’ (Carnaby, 2006). In this literature review, the focus will fall on two species of mysticetes from separate families, namely that of the southern right whale, Eubalaena australis of the Balaenidae family, and the humpback whale, Megaptera novaeangliae of the Balaenopteridae family. Emphasis in this review will fall on the aspect of site fidelity of the mother-calf pairs.
- Full Text:
- Date Issued: 2016
Site Fidelity of southern right (Eubalaena australis) and humpback whales (Megaptera novaeangliae) in Algoa Bay, South Africa
- Authors: Drost, Eduard F
- Date: 2016
- Subjects: Southern right whale -- South Africa -- Algoa BaySH Humpback whale -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21732 , vital:29743
- Description: The site fidelity of humpback and southern right whales in Algoa Bay was investigated as a baseline study to examine the importance of this area for the future conservation of these species. An absence of whales since the 1980’s from Algoa Bay and more frequent sightings of southern right and humpback whales during a survey conducted between 2008 and 2011 in Algoa Bay led to the present photo-identification study. Data were collected from boat-based surveys along the coastline in 2015 and 2016 and data from a previous boat-based study during 2008-2011 assessing the occurrence of all cetaceans in Algoa Bay were added. A cumulative number of 96 individual southern right whales and 184 individual humpback whales were identified from callosity patterns and dorsal fins, respectively, over this period in Algoa Bay. A low resighting rate for both species was observed within (6.25 for southern right whales & 6.98% for humpback whales) and between years (1.04% for southern right whales & 9.24% for humpback whales) with mainly individual adult humpback whales being resighted. In contrast, all southern right whale resightings were confirmed to be mother-calf pair individuals. The timing of monthly sightings and resightings of mother-calf pair individuals in the bay may suggest that this area may serve as a fairly new nursery area for southern right whales and as a possible migratory corridor for humpback whales during their migrations to and from their breeding grounds. The sighting distribution within the bay suggest that mother-calf pairs are located closer inshore and further away from the shipping activities on the eastern side of the bay in the proximity of two operational ports. This forms an important baseline for future monitoring to assess the effect of increased shipping activity in the bay on the breeding behaviour of the whales. The site fidelity of humpback and southern right whales in Algoa Bay was investigated as a baseline study to examine the importance of this area for the future conservation of these species. An absence of whales since the 1980’s from Algoa Bay and more frequent sightings of southern right and humpback whales during a survey conducted between 2008 and 2011 in Algoa Bay led to the present photo-identification study. Data were collected from boat-based surveys along the coastline in 2015 and 2016 and data from a previous boat-based study during 2008-2011 assessing the occurrence of all cetaceans in Algoa Bay were added. A cumulative number of 96 individual southern right whales and 184 individual humpback whales were identified from callosity patterns and dorsal fins, respectively, over this period in Algoa Bay. A low resighting rate for both species was observed within (6.25 for southern right whales & 6.98% for humpback whales) and between years (1.04% for southern right whales & 9.24% for humpback whales) with mainly individual adult humpback whales being resighted. In contrast, all southern right whale resightings were confirmed to be mother-calf pair individuals. The timing of monthly sightings and resightings of mother-calf pair individuals in the bay may suggest that this area may serve as a fairly new nursery area for southern right whales and as a possible migratory corridor for humpback whales during their migrations to and from their breeding grounds. The sighting distribution within the bay suggest that mother-calf pairs are located closer inshore and further away from the shipping activities on the eastern side of the bay in the proximity of two operational ports. This forms an important baseline for future monitoring to assess the effect of increased shipping activity in the bay on the breeding behaviour of the whales.
- Full Text: false
- Date Issued: 2016
- Authors: Drost, Eduard F
- Date: 2016
- Subjects: Southern right whale -- South Africa -- Algoa BaySH Humpback whale -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21732 , vital:29743
- Description: The site fidelity of humpback and southern right whales in Algoa Bay was investigated as a baseline study to examine the importance of this area for the future conservation of these species. An absence of whales since the 1980’s from Algoa Bay and more frequent sightings of southern right and humpback whales during a survey conducted between 2008 and 2011 in Algoa Bay led to the present photo-identification study. Data were collected from boat-based surveys along the coastline in 2015 and 2016 and data from a previous boat-based study during 2008-2011 assessing the occurrence of all cetaceans in Algoa Bay were added. A cumulative number of 96 individual southern right whales and 184 individual humpback whales were identified from callosity patterns and dorsal fins, respectively, over this period in Algoa Bay. A low resighting rate for both species was observed within (6.25 for southern right whales & 6.98% for humpback whales) and between years (1.04% for southern right whales & 9.24% for humpback whales) with mainly individual adult humpback whales being resighted. In contrast, all southern right whale resightings were confirmed to be mother-calf pair individuals. The timing of monthly sightings and resightings of mother-calf pair individuals in the bay may suggest that this area may serve as a fairly new nursery area for southern right whales and as a possible migratory corridor for humpback whales during their migrations to and from their breeding grounds. The sighting distribution within the bay suggest that mother-calf pairs are located closer inshore and further away from the shipping activities on the eastern side of the bay in the proximity of two operational ports. This forms an important baseline for future monitoring to assess the effect of increased shipping activity in the bay on the breeding behaviour of the whales. The site fidelity of humpback and southern right whales in Algoa Bay was investigated as a baseline study to examine the importance of this area for the future conservation of these species. An absence of whales since the 1980’s from Algoa Bay and more frequent sightings of southern right and humpback whales during a survey conducted between 2008 and 2011 in Algoa Bay led to the present photo-identification study. Data were collected from boat-based surveys along the coastline in 2015 and 2016 and data from a previous boat-based study during 2008-2011 assessing the occurrence of all cetaceans in Algoa Bay were added. A cumulative number of 96 individual southern right whales and 184 individual humpback whales were identified from callosity patterns and dorsal fins, respectively, over this period in Algoa Bay. A low resighting rate for both species was observed within (6.25 for southern right whales & 6.98% for humpback whales) and between years (1.04% for southern right whales & 9.24% for humpback whales) with mainly individual adult humpback whales being resighted. In contrast, all southern right whale resightings were confirmed to be mother-calf pair individuals. The timing of monthly sightings and resightings of mother-calf pair individuals in the bay may suggest that this area may serve as a fairly new nursery area for southern right whales and as a possible migratory corridor for humpback whales during their migrations to and from their breeding grounds. The sighting distribution within the bay suggest that mother-calf pairs are located closer inshore and further away from the shipping activities on the eastern side of the bay in the proximity of two operational ports. This forms an important baseline for future monitoring to assess the effect of increased shipping activity in the bay on the breeding behaviour of the whales.
- Full Text: false
- Date Issued: 2016
The ecology of hard substrate communities around Sardinia Bay in the warm-temperate Agulhas Bioregion
- Authors: Evans, Adrian G , Nel, Ronel
- Date: 2016
- Subjects: Aquatic biodiversity -- South Africa -- Nelson Mandela Bay Municipality , Marine ecology -- South Africa -- Nelson Mandela Bay Municipality , Seashore biology -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6782 , vital:21141
- Description: Hard substrates in the marine environment are an important ecosystem of great scientific and economic value. Hard substrates provide suitable habitat for a diverse assemblage of benthic organisms. This thesis investigated the ecology of benthic hard substrate communities along a section of wave-exposed coastline, including the Sardinia Bay Marine Protected Area (MPA), in the warm-temperate Agulhas bioregion of South Africa. The effect of physical variables on benthic communities, including both the intertidal and shallow subtidal, was quantitatively assessed across (Chapter 3) and along (Chapter 4) the shore to provide a model of zonation for this bioregion and a baseline of community patters and biodiversity, as this information was lacking especially for the Sardinia Bay MPA. The zones described in Chapter 3 were in agreement with previous trends described for this bioregion with the addition of different biotopes in the upper Balanoid and deeper subtidal zones as well as the addition of an intermediate/transition zone in the subtidal between the algal dominated shallow subtidal and deeper subtidal, which has an increased abundance of sessile invertebrates. Disturbance is an important process in structuring benthic communities, and its role in structuring shallow benthic communities was investigated using a disturbance simulation experiment across a wave-exposure gradient (Chapter 5). Communities were found to change along the exposure gradient and monitoring the undisturbed communities showed that large waves caused disturbances across all the exposures. The recovery process was similar across all exposures mainly through lateral vegetative growth and regrowth from basal parts with communities in disturbed quadrats recovering to resemble the surrounding undisturbed community. Recruitment did not have a significant effect in the recovery process and community composition was therefore a result of the effects of the physical environment along the exposure gradient. Lastly this thesis investigated the indirect effects of protection in the small Sardinia Bay MPA (Chapter 6). Despite the small size of the MPA this study found differences in diversity and abundance between communities inside and outside the MPA. These differences in benthic biota infer indirect effects of protection that are probably due to the increase in abundance of exploited fish inside the MPA. Lower abundances of red algae, macroinvertebrates and diversity inside the MPA in the shallow depth category was attributed to the higher abundance of the generalist fish species that concentrate in the shallows. Significantly lower abundances of Chordata in the shallow and medium depth categories inside the MPA was attributed to predation by the benthic carnivorous species as ascidians are included in the diet of these species. This chapter also compared the effectiveness of destructive (scraped quadrats) and non-destructive (visually assessed quadrats) sampling methods. Scraped quadrats were found to be more effective in detecting changes across the MPA compared to visually assessed quadrats. Destructive methods sample the entire assemblage, to a higher taxonomic level, and measure abundance using biomass. It was concluded that biomass is a better metric when comparing communities across protection or other treatments as it provides better biological information of the community.
- Full Text:
- Date Issued: 2016
- Authors: Evans, Adrian G , Nel, Ronel
- Date: 2016
- Subjects: Aquatic biodiversity -- South Africa -- Nelson Mandela Bay Municipality , Marine ecology -- South Africa -- Nelson Mandela Bay Municipality , Seashore biology -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6782 , vital:21141
- Description: Hard substrates in the marine environment are an important ecosystem of great scientific and economic value. Hard substrates provide suitable habitat for a diverse assemblage of benthic organisms. This thesis investigated the ecology of benthic hard substrate communities along a section of wave-exposed coastline, including the Sardinia Bay Marine Protected Area (MPA), in the warm-temperate Agulhas bioregion of South Africa. The effect of physical variables on benthic communities, including both the intertidal and shallow subtidal, was quantitatively assessed across (Chapter 3) and along (Chapter 4) the shore to provide a model of zonation for this bioregion and a baseline of community patters and biodiversity, as this information was lacking especially for the Sardinia Bay MPA. The zones described in Chapter 3 were in agreement with previous trends described for this bioregion with the addition of different biotopes in the upper Balanoid and deeper subtidal zones as well as the addition of an intermediate/transition zone in the subtidal between the algal dominated shallow subtidal and deeper subtidal, which has an increased abundance of sessile invertebrates. Disturbance is an important process in structuring benthic communities, and its role in structuring shallow benthic communities was investigated using a disturbance simulation experiment across a wave-exposure gradient (Chapter 5). Communities were found to change along the exposure gradient and monitoring the undisturbed communities showed that large waves caused disturbances across all the exposures. The recovery process was similar across all exposures mainly through lateral vegetative growth and regrowth from basal parts with communities in disturbed quadrats recovering to resemble the surrounding undisturbed community. Recruitment did not have a significant effect in the recovery process and community composition was therefore a result of the effects of the physical environment along the exposure gradient. Lastly this thesis investigated the indirect effects of protection in the small Sardinia Bay MPA (Chapter 6). Despite the small size of the MPA this study found differences in diversity and abundance between communities inside and outside the MPA. These differences in benthic biota infer indirect effects of protection that are probably due to the increase in abundance of exploited fish inside the MPA. Lower abundances of red algae, macroinvertebrates and diversity inside the MPA in the shallow depth category was attributed to the higher abundance of the generalist fish species that concentrate in the shallows. Significantly lower abundances of Chordata in the shallow and medium depth categories inside the MPA was attributed to predation by the benthic carnivorous species as ascidians are included in the diet of these species. This chapter also compared the effectiveness of destructive (scraped quadrats) and non-destructive (visually assessed quadrats) sampling methods. Scraped quadrats were found to be more effective in detecting changes across the MPA compared to visually assessed quadrats. Destructive methods sample the entire assemblage, to a higher taxonomic level, and measure abundance using biomass. It was concluded that biomass is a better metric when comparing communities across protection or other treatments as it provides better biological information of the community.
- Full Text:
- Date Issued: 2016
A web-based repository for student mobility data in Africa
- Authors: Ferreira, Darren Bradley
- Date: 2016
- Subjects: Student mobility Students, Transfer of -- South Africa -- Psychological aspects , Education, Higher Foreign study
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/12605 , vital:27098
- Description: The number of international students studying abroad has doubled since the year 2000 and there are nearly five million students that are enrolled outside their country of origin. Over the past ten years new insights and approaches to the internationalisation of higher education have arisen which has influenced global research and education. Student mobility data is a component of internationalisation data. internationally mobile students are defined as students who have crossed international borders from their countries with the objective to study. Currently, there are several international organisations and projects that manage student mobility data from various Higher Education Institutions (HEIs) across the globe and report on this data. Two of these organisations are the Open Doors Report and Project Atlas. The organisations collect Data for Africa, although it is not as detailed and useful as the data provided about other countries. Since the number of students studying abroad has doubled since the year 2000, the amount of student mobility data kept by data collection agencies and HEIs has also increased. The data collected is not always accurate and this poses a data management problem. This study conducted a survey sent to international offices at various HEIs in South Africa and Africa. The survey investigates the current state of student mobility data management in HEIs. The survey results revealed that the international offices are currently dissatisfied with student mobility data management and will be willing to provide international student data to an African data repository. This study proposes the design and development of a web-based student mobility data repository, known as the African International Portal (AIP). The study identified design guidelines and requirements for a web-based data repository. The requirements, design and design guidelines were used to guide the development of the prototype. Heuristic evaluations were conducted on the prototype in order to identify any major usability problems. Findings revealed that the overall perceptions of the prototype were positive and can be attributed to the design considerations and guidelines used during the development phase. The prototype was evaluated using a full usability evaluation that determined the usefulness, effectiveness and efficiency of the prototype when users are in the process of managing student mobility data. The results indicate that the participants found the AIP to be an effective, efficient and a satisfactory means of managing student mobility data.
- Full Text:
- Date Issued: 2016
- Authors: Ferreira, Darren Bradley
- Date: 2016
- Subjects: Student mobility Students, Transfer of -- South Africa -- Psychological aspects , Education, Higher Foreign study
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/12605 , vital:27098
- Description: The number of international students studying abroad has doubled since the year 2000 and there are nearly five million students that are enrolled outside their country of origin. Over the past ten years new insights and approaches to the internationalisation of higher education have arisen which has influenced global research and education. Student mobility data is a component of internationalisation data. internationally mobile students are defined as students who have crossed international borders from their countries with the objective to study. Currently, there are several international organisations and projects that manage student mobility data from various Higher Education Institutions (HEIs) across the globe and report on this data. Two of these organisations are the Open Doors Report and Project Atlas. The organisations collect Data for Africa, although it is not as detailed and useful as the data provided about other countries. Since the number of students studying abroad has doubled since the year 2000, the amount of student mobility data kept by data collection agencies and HEIs has also increased. The data collected is not always accurate and this poses a data management problem. This study conducted a survey sent to international offices at various HEIs in South Africa and Africa. The survey investigates the current state of student mobility data management in HEIs. The survey results revealed that the international offices are currently dissatisfied with student mobility data management and will be willing to provide international student data to an African data repository. This study proposes the design and development of a web-based student mobility data repository, known as the African International Portal (AIP). The study identified design guidelines and requirements for a web-based data repository. The requirements, design and design guidelines were used to guide the development of the prototype. Heuristic evaluations were conducted on the prototype in order to identify any major usability problems. Findings revealed that the overall perceptions of the prototype were positive and can be attributed to the design considerations and guidelines used during the development phase. The prototype was evaluated using a full usability evaluation that determined the usefulness, effectiveness and efficiency of the prototype when users are in the process of managing student mobility data. The results indicate that the participants found the AIP to be an effective, efficient and a satisfactory means of managing student mobility data.
- Full Text:
- Date Issued: 2016
Trends in the game industry in the Eastern Cape
- Authors: Ferreira, Janene
- Date: 2016
- Subjects: Game farms -- South Africa -- Eastern Cape -- Management , Wildlife management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/5451 , vital:20846
- Description: The game industry has become one of the fastest-growing industries in South Africa and consequently, during recent years, a growing number of stock farms have been converted to game farms. All forms of utilization within the game industry play a vital role with regards to sustainability and simultaneously contributing a significant boost to the national economy. It is therefore important to ensure that game ranchers are as well-informed as possible in their decision-making, as well as in assessing their outputs and endeavours. However, the information available on the game industry in the Eastern Cape is limited. This research study therefore focuses on the emerging trends in the game industry in the province. The objectives of the research are to examine various pertinent factors associated with the game industry, investigate the trends and discuss whether these trends have any implications for future purposes. The research commenced with a literature review, as well as information from earlier survey studies of the Eastern Cape game industry. For the current study, a replicate survey was conducted throughout the Eastern Cape, involving as many game ranchers as possible, and data were collected by means of self-administered questionnaires. The dilemma confronting the black wildebeest in the Eastern Cape was thoroughly investigated, together with farmers’ opinions and trends for the future of the species. It was important to include this particular aspect in the research, as at the time of the survey, widespread concerns were expressed with regards to new legislation which emerged during that time. The research cast light on several aspects associated with the industry which could positively assist game ranchers towards improved management and planning, as well as provide guidelines for future development purposes. Furthermore, the research identified crucial issues that should receive immediate attention from stakeholders across the industry as well as government.
- Full Text:
- Date Issued: 2016
- Authors: Ferreira, Janene
- Date: 2016
- Subjects: Game farms -- South Africa -- Eastern Cape -- Management , Wildlife management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/5451 , vital:20846
- Description: The game industry has become one of the fastest-growing industries in South Africa and consequently, during recent years, a growing number of stock farms have been converted to game farms. All forms of utilization within the game industry play a vital role with regards to sustainability and simultaneously contributing a significant boost to the national economy. It is therefore important to ensure that game ranchers are as well-informed as possible in their decision-making, as well as in assessing their outputs and endeavours. However, the information available on the game industry in the Eastern Cape is limited. This research study therefore focuses on the emerging trends in the game industry in the province. The objectives of the research are to examine various pertinent factors associated with the game industry, investigate the trends and discuss whether these trends have any implications for future purposes. The research commenced with a literature review, as well as information from earlier survey studies of the Eastern Cape game industry. For the current study, a replicate survey was conducted throughout the Eastern Cape, involving as many game ranchers as possible, and data were collected by means of self-administered questionnaires. The dilemma confronting the black wildebeest in the Eastern Cape was thoroughly investigated, together with farmers’ opinions and trends for the future of the species. It was important to include this particular aspect in the research, as at the time of the survey, widespread concerns were expressed with regards to new legislation which emerged during that time. The research cast light on several aspects associated with the industry which could positively assist game ranchers towards improved management and planning, as well as provide guidelines for future development purposes. Furthermore, the research identified crucial issues that should receive immediate attention from stakeholders across the industry as well as government.
- Full Text:
- Date Issued: 2016