A Social Media Method for Eliciting Millennials’ Worldviews on the Coastal and Marine Environment
- Authors: Okuah, Obrukevwe Anehwe
- Date: 2020
- Subjects: Millennialism -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/48588 , vital:40893
- Description: A lack of involvement by participants with traditional data collection methods for research has led to insufficient data regarding millennials’ worldviews on the coastal and marine environment. Understanding millennial worldviews could provide insights for policy interventions for sustainable use of the marine and coastal environment. The aim of this research is to design, develop and evaluate an appropriate social media method to elicit millennials’ worldviews on the coastal and marine environment. The methodology used for the research was Design Science Research (DSR), which is a legitimate approach to conducting research in the field of Information Systems. The methods used were a literature review, interviews with social media experts and Social Media Influencers (SMIs), and a focus group discussion with researchers from the field of social sciences. The proposed artefact (the method) can be used to provide guidance to researchers for engaging and eliciting opinions and worldviews of millennials on social media. The method includes a Social Media Influencer Model that illustrates the relationship between SMIs’ characteristics and techniques for engaging the public, and a Social Media Analytics (SMA) Process model that can guide researchers through the steps of eliciting worldviews from the public. Although there are several SMA techniques that can be used, the proposed method uses sentiment analysis as an SMA technique for deriving sentiments from social media data. The method was evaluated by researchers who require a social media method for eliciting millennials worldviews. The findings confirmed some of the techniques identified in literature as well as some additional techniques and processes. It was also evident that using this method could assist researchers for data collection and specifically to obtain worldviews on the marine and coastal environment. The contribution of this study is an artefact that fulfils the need for a social media method for data collection that is more convenient for researchers and millennials and can guide researchers through the steps of eliciting worldviews from the public.
- Full Text:
- Date Issued: 2020
- Authors: Okuah, Obrukevwe Anehwe
- Date: 2020
- Subjects: Millennialism -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/48588 , vital:40893
- Description: A lack of involvement by participants with traditional data collection methods for research has led to insufficient data regarding millennials’ worldviews on the coastal and marine environment. Understanding millennial worldviews could provide insights for policy interventions for sustainable use of the marine and coastal environment. The aim of this research is to design, develop and evaluate an appropriate social media method to elicit millennials’ worldviews on the coastal and marine environment. The methodology used for the research was Design Science Research (DSR), which is a legitimate approach to conducting research in the field of Information Systems. The methods used were a literature review, interviews with social media experts and Social Media Influencers (SMIs), and a focus group discussion with researchers from the field of social sciences. The proposed artefact (the method) can be used to provide guidance to researchers for engaging and eliciting opinions and worldviews of millennials on social media. The method includes a Social Media Influencer Model that illustrates the relationship between SMIs’ characteristics and techniques for engaging the public, and a Social Media Analytics (SMA) Process model that can guide researchers through the steps of eliciting worldviews from the public. Although there are several SMA techniques that can be used, the proposed method uses sentiment analysis as an SMA technique for deriving sentiments from social media data. The method was evaluated by researchers who require a social media method for eliciting millennials worldviews. The findings confirmed some of the techniques identified in literature as well as some additional techniques and processes. It was also evident that using this method could assist researchers for data collection and specifically to obtain worldviews on the marine and coastal environment. The contribution of this study is an artefact that fulfils the need for a social media method for data collection that is more convenient for researchers and millennials and can guide researchers through the steps of eliciting worldviews from the public.
- Full Text:
- Date Issued: 2020
A study of contaminants in fish in South Africa : linking science, management and society
- Authors: Ramparsad, Kerina
- Date: 2020
- Subjects: Estuarine fishes -- Contamination -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48609 , vital:40895
- Description: Contaminants in fish is a concern globally and locally. Fish have the propensity to accumulate contaminants to levels that may pose a threat to human health and disrupt ecosystem function. The purpose for investigating contaminants in this study for fish provides the public with information on the potential human health risks from the contaminated fish we consume. This study also investigated contaminants in estuarine fish and sediment, and is important to monitor as these components of ecosystems can indicate contamination in estuaries. Effective methods to determine contaminants in fish and sediment included the Direct Mercury Analyser 80 for mercury, Gas Chromatography for fatty acids and polychlorinated biphenyls and Inductively Coupled Plasma for aluminium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, vanadium and zinc. Basic statistical tools, geochemical techniques, a bioaccumulation model and human health risk assessment tools provided by the United States Environmental Protection Agency were used to interpret the data. Ultimately consumption advice was developed from the risk assessment results and showed predatory fish such as swordfish and bluenose species are recommended to be avoided while yellow tail, red roman, mackerel, fish fingers and canned tuna are some of the fish that can be eaten 10-14 times per month that would not cause potential health risks. It was found that estuarine ambassid fish investigated in this study were not suitable for contaminant monitoring. There were no clear spatial and seasonal trends observed in the estuaries suggesting that ambassid fish efficiently assimilate contaminants. There was little evidence that contaminants were transferred from sediment to ambassid fish in the eThekwini estuaries. Therefore, their use is limited as a cost-effective estuarine contaminant monitoring tool. Each estuary investigated is unique and requires its own management plan.
- Full Text:
- Date Issued: 2020
- Authors: Ramparsad, Kerina
- Date: 2020
- Subjects: Estuarine fishes -- Contamination -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48609 , vital:40895
- Description: Contaminants in fish is a concern globally and locally. Fish have the propensity to accumulate contaminants to levels that may pose a threat to human health and disrupt ecosystem function. The purpose for investigating contaminants in this study for fish provides the public with information on the potential human health risks from the contaminated fish we consume. This study also investigated contaminants in estuarine fish and sediment, and is important to monitor as these components of ecosystems can indicate contamination in estuaries. Effective methods to determine contaminants in fish and sediment included the Direct Mercury Analyser 80 for mercury, Gas Chromatography for fatty acids and polychlorinated biphenyls and Inductively Coupled Plasma for aluminium, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, vanadium and zinc. Basic statistical tools, geochemical techniques, a bioaccumulation model and human health risk assessment tools provided by the United States Environmental Protection Agency were used to interpret the data. Ultimately consumption advice was developed from the risk assessment results and showed predatory fish such as swordfish and bluenose species are recommended to be avoided while yellow tail, red roman, mackerel, fish fingers and canned tuna are some of the fish that can be eaten 10-14 times per month that would not cause potential health risks. It was found that estuarine ambassid fish investigated in this study were not suitable for contaminant monitoring. There were no clear spatial and seasonal trends observed in the estuaries suggesting that ambassid fish efficiently assimilate contaminants. There was little evidence that contaminants were transferred from sediment to ambassid fish in the eThekwini estuaries. Therefore, their use is limited as a cost-effective estuarine contaminant monitoring tool. Each estuary investigated is unique and requires its own management plan.
- Full Text:
- Date Issued: 2020
A study on certain factors that may affect the economic viability of backgrounding beef weaner calves on pastures in the Southern Cape area of South Africa
- Authors: Terblanche, Ian
- Date: 2020
- Subjects: Calves -- Weaning -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/47623 , vital:40259
- Description: The backgrounding of beef weaner calves from pastures has the potential to be developed as an intensive beef enterprise that can increase the income of smaller farms, given that these farms have the ability to produce good quality pastures. This study was conducted to verify the inputs that impact on the viability of pasture backgrounding systems in an attempt to provide beef producers with better information for decision making. The scientific research was conducted with the registered Kromme Rhee Bonsmara herd at the Kromme Rhee research farm of the Western Cape Department of Agriculture. The farm is situated at 18º50’E and 33º51’S in the Stellenbosch area and has an altitude of 177 m above sea level. The area is situated in the winter rainfall region of the Western Cape with an annual rainfall of 670 mm. The average summer temperature ranges between 15-35 ºC and winter temperature between 10-17 ºC. The aim of this study was to develop growth curves representing the growth of Bonsmara animals for use by beef producers in predicting future live weight of animals in a pasture backgrounding system. Dry matter (DM) intake was measured at various live weight stages in order to determine whether a prediction model could be established to represent the DM intake of growing Bonsmara cattle on pastures. Results were used as inputs to determine whether backgrounding on pastures was economically viable. Animals were weighed at monthly intervals. Weighings commenced from birth and continued for a period of 797 days, repeated with two production year groups. One group consisted of 18 heifers and 12 bulls that were weighed from birth till an average age of 759 days. The other group consisted of four heifers and seven bulls and was weighed from birth untill an average age of 892 days. Roughage supplementation was done with lucerne hay in periods of pasture shortfalls, while a protein and energy lick were supplied continuously. A feeding trial with 10 weaned heifers and 10 bull calves of the same year group was conducted to determine the average feed intake per individual animal over a thirteen-month period that commenced after weaning. Two groups of five Bonsmara bull calves and two groups of five Bonsmara heifers were grouped according to age and gender. The feed intake of the growing calves was recorded for different live weight categories. The animals received lucerne (Medicago sativa) hay on an ad lib basis, while a concentrate supplement was supplied at 2 kg per animal per day up until live weights of 350 kg for heifers and 380 kg for bulls was achieved. The lucerne based diet was formulated to simulate a diet for growing animals on pasture with additional supplementation. Group feed intake values of the four groups of animals were measured at about 20-day intervals over the trial period of 369 days. The feed waste was dried and weighed back to calculate a waste percentage to be used as a correction factor. The Gompertz growth function was used to develop growth curves for male and female Bonsmara animals. Results indicated a significant difference between the mature weight of males and females (P <0.05). In both year groups the nonlinear Gompertz growth model predicted heavier mature weight for males compared to females. Mature weights of bulls were respectively 44.4% and 68.5% higher than that of heifers over the two year period. Days at maximum growth occurred later for males than for females (P <0.05) and the maturing rate of males and females did not differ significantly. Individual average feed intakes were calculated from the group fed animals over the duration of the rearing period. The data revealed that feed intake for bulls can be predicted by the linear model, DMI= 0.16531 + 0.0235306 x live weight (P ≤0.001; R 2 = 78.25). The feed intake of heifers can be predicted by the linear model, DMI= -1.41991 + 0.0283891 x live weight (P ≤0.001; R 2= 76.25). Analysis of variance detected no difference between the percentage feed intake of heifers (2.46%) and bulls (2.40%), over the experimental period. Prices of different live weight groupings were analysed over seven years to establish whether cyclical price trends can be observed across years and seasonal price trends within years. Within years prices were found to differ between months. For all calf weight groups, the lowest prices occurred in the months of March, April, May, June and July which showed price indices significantly different (P <0.05) from indices of the months of October, November and December when highest prices occurred, confirming seasonality in weaner calf prices. Price indices were developed for use as an input in the economic viability assessment. A brief literature review on the production and quality of four common pastures in the Southern Cape was done to gather information for compiling pasture budgets for use in determining the economic viability of pasture backgrounding. The economic viability of backgrounding on pastures was evaluated on a gross margin level and illustrated for three pasture systems namely irrigated oats as a winter pasture, irrigated lucerne as a spring pasture and dryland P. clandestinum /E. plana /mixed grass also as a low-cost spring pasture. All three pasture systems showed a positive economic viability for the decision parameters used in the illustration. The gross margin of backgrounding on the oats pasture system was more sensitive to a small decrease in the predicted price or the predicted live weight and therefore a riskier option than backgrounding on the other two systems. Outputs from the gross margin analyses were used in partial budgeting to illustrate a robust decision support framework that beef farmers can use for making decisions whether to sell weaners straight after weaning as opposed to selling after a period of backgrounding on pastures. Overall results indicate that backgrounding of calves on pastures has the potential to be a viable beef enterprise on smaller farms in the region. Keywords: beef production; Gompertz growth curves, feed intake; pasture backgrounding; gross margin; partial budgets.
- Full Text:
- Date Issued: 2020
- Authors: Terblanche, Ian
- Date: 2020
- Subjects: Calves -- Weaning -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/47623 , vital:40259
- Description: The backgrounding of beef weaner calves from pastures has the potential to be developed as an intensive beef enterprise that can increase the income of smaller farms, given that these farms have the ability to produce good quality pastures. This study was conducted to verify the inputs that impact on the viability of pasture backgrounding systems in an attempt to provide beef producers with better information for decision making. The scientific research was conducted with the registered Kromme Rhee Bonsmara herd at the Kromme Rhee research farm of the Western Cape Department of Agriculture. The farm is situated at 18º50’E and 33º51’S in the Stellenbosch area and has an altitude of 177 m above sea level. The area is situated in the winter rainfall region of the Western Cape with an annual rainfall of 670 mm. The average summer temperature ranges between 15-35 ºC and winter temperature between 10-17 ºC. The aim of this study was to develop growth curves representing the growth of Bonsmara animals for use by beef producers in predicting future live weight of animals in a pasture backgrounding system. Dry matter (DM) intake was measured at various live weight stages in order to determine whether a prediction model could be established to represent the DM intake of growing Bonsmara cattle on pastures. Results were used as inputs to determine whether backgrounding on pastures was economically viable. Animals were weighed at monthly intervals. Weighings commenced from birth and continued for a period of 797 days, repeated with two production year groups. One group consisted of 18 heifers and 12 bulls that were weighed from birth till an average age of 759 days. The other group consisted of four heifers and seven bulls and was weighed from birth untill an average age of 892 days. Roughage supplementation was done with lucerne hay in periods of pasture shortfalls, while a protein and energy lick were supplied continuously. A feeding trial with 10 weaned heifers and 10 bull calves of the same year group was conducted to determine the average feed intake per individual animal over a thirteen-month period that commenced after weaning. Two groups of five Bonsmara bull calves and two groups of five Bonsmara heifers were grouped according to age and gender. The feed intake of the growing calves was recorded for different live weight categories. The animals received lucerne (Medicago sativa) hay on an ad lib basis, while a concentrate supplement was supplied at 2 kg per animal per day up until live weights of 350 kg for heifers and 380 kg for bulls was achieved. The lucerne based diet was formulated to simulate a diet for growing animals on pasture with additional supplementation. Group feed intake values of the four groups of animals were measured at about 20-day intervals over the trial period of 369 days. The feed waste was dried and weighed back to calculate a waste percentage to be used as a correction factor. The Gompertz growth function was used to develop growth curves for male and female Bonsmara animals. Results indicated a significant difference between the mature weight of males and females (P <0.05). In both year groups the nonlinear Gompertz growth model predicted heavier mature weight for males compared to females. Mature weights of bulls were respectively 44.4% and 68.5% higher than that of heifers over the two year period. Days at maximum growth occurred later for males than for females (P <0.05) and the maturing rate of males and females did not differ significantly. Individual average feed intakes were calculated from the group fed animals over the duration of the rearing period. The data revealed that feed intake for bulls can be predicted by the linear model, DMI= 0.16531 + 0.0235306 x live weight (P ≤0.001; R 2 = 78.25). The feed intake of heifers can be predicted by the linear model, DMI= -1.41991 + 0.0283891 x live weight (P ≤0.001; R 2= 76.25). Analysis of variance detected no difference between the percentage feed intake of heifers (2.46%) and bulls (2.40%), over the experimental period. Prices of different live weight groupings were analysed over seven years to establish whether cyclical price trends can be observed across years and seasonal price trends within years. Within years prices were found to differ between months. For all calf weight groups, the lowest prices occurred in the months of March, April, May, June and July which showed price indices significantly different (P <0.05) from indices of the months of October, November and December when highest prices occurred, confirming seasonality in weaner calf prices. Price indices were developed for use as an input in the economic viability assessment. A brief literature review on the production and quality of four common pastures in the Southern Cape was done to gather information for compiling pasture budgets for use in determining the economic viability of pasture backgrounding. The economic viability of backgrounding on pastures was evaluated on a gross margin level and illustrated for three pasture systems namely irrigated oats as a winter pasture, irrigated lucerne as a spring pasture and dryland P. clandestinum /E. plana /mixed grass also as a low-cost spring pasture. All three pasture systems showed a positive economic viability for the decision parameters used in the illustration. The gross margin of backgrounding on the oats pasture system was more sensitive to a small decrease in the predicted price or the predicted live weight and therefore a riskier option than backgrounding on the other two systems. Outputs from the gross margin analyses were used in partial budgeting to illustrate a robust decision support framework that beef farmers can use for making decisions whether to sell weaners straight after weaning as opposed to selling after a period of backgrounding on pastures. Overall results indicate that backgrounding of calves on pastures has the potential to be a viable beef enterprise on smaller farms in the region. Keywords: beef production; Gompertz growth curves, feed intake; pasture backgrounding; gross margin; partial budgets.
- Full Text:
- Date Issued: 2020
A trait-based approach to identify indicators for measuring rocky reef ecosystem condition in South Africa
- Authors: Smit, Kaylee
- Date: 2020
- Subjects: Environmental management -- Evaluation , Environmental monitoring -- Methodology Marine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49292 , vital:41618
- Description: An important yet challenging task for effective ecosystem-based management of marine ecosystems is the reliable measurement and monitoring of changes in ecosystem condition. In South Africa, the National Biodiversity Assessment (NBA) has relied on cumulative pressure mapping, based on the calculation of cumulative impact scores, as a proxy for measures of marine ecosystem condition. While this method is practical for broad scale assessments where ecological data are lacking, there is a need to groundtruth this approach at local scales using in-situ data. The aim of this thesis was to identify potential indicators that can be used to measure the ecosystem condition of subtidal rocky reefs on the East coast of South Africa to groundtruth national pressure-based condition assessments. This thesis constituted the first attempt to conduct a comprehensive assessment of rocky reef ecosystem condition to validate national pressure-based assessments in South Africa. Based on a comprehensive literature review, a traits-based approach was selected to ensure that ecosystem structure and function were included in condition measurements. Fish and benthic community data were collected using baited remote underwater stereo-video systems (144 video samples) from the Natal Shelf ecoregion. Sampling spanned a gradient of low to high human pressures, which incorporated an effective Marine Protected Area (to define reference conditions), as well as areas exposed to intermediate levels of human pressures and a highly impacted area offshore of a large metropolitan port city. Structural and functional indicators were compared among localities and suitable functional indicators were aggregated into multimetric indices (MMIs) to provide an integrated measurement of ecosystem condition. Approximately 840 benthic biota and 10 400 fish (representing 176 identified fish species) were counted. Results showed that functional indicators, particularly size-based ones, were more effective at detecting changes in ecosystem condition compared with structural indicators based on taxonomy. Reefs in good ecological condition had a higher biomass of target species and a higher proportion of large predatory fish with more adults, compared with impacted areas. Benthic communities, however, appeared less responsive to cumulative pressures. The MMIs, using fish and benthic community data, were used to compare condition categories with those from the NBA. Results showed that the pressure-based assessments provided a reasonable proxy of broad patterns of rocky reef ecosystem condition. However, fine-scale discrepancies between results from the data-driven approach versus the proxy method suggested that broad-scale proxies might overestimate condition in some areas and underestimate it in others. To build on these results, the applicability of structural and functional indicators and MMIs were tested using an independent stereo-BRUVs dataset from the Agulhas Shelf ecoregion. Findings showed that not all MPAs were in good ecological condition compared with adjacent impacted areas, as was estimated by the NBA. However, there is a need to improve the quality of trait data and to test indicators and indices in other ecoregions, ecosystem types and in response to a broader range of improved pressure data. Furthermore, there is a need to apply innovative research to guide the calculation of thresholds for condition categories to advance condition assessments.
- Full Text:
- Date Issued: 2020
- Authors: Smit, Kaylee
- Date: 2020
- Subjects: Environmental management -- Evaluation , Environmental monitoring -- Methodology Marine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49292 , vital:41618
- Description: An important yet challenging task for effective ecosystem-based management of marine ecosystems is the reliable measurement and monitoring of changes in ecosystem condition. In South Africa, the National Biodiversity Assessment (NBA) has relied on cumulative pressure mapping, based on the calculation of cumulative impact scores, as a proxy for measures of marine ecosystem condition. While this method is practical for broad scale assessments where ecological data are lacking, there is a need to groundtruth this approach at local scales using in-situ data. The aim of this thesis was to identify potential indicators that can be used to measure the ecosystem condition of subtidal rocky reefs on the East coast of South Africa to groundtruth national pressure-based condition assessments. This thesis constituted the first attempt to conduct a comprehensive assessment of rocky reef ecosystem condition to validate national pressure-based assessments in South Africa. Based on a comprehensive literature review, a traits-based approach was selected to ensure that ecosystem structure and function were included in condition measurements. Fish and benthic community data were collected using baited remote underwater stereo-video systems (144 video samples) from the Natal Shelf ecoregion. Sampling spanned a gradient of low to high human pressures, which incorporated an effective Marine Protected Area (to define reference conditions), as well as areas exposed to intermediate levels of human pressures and a highly impacted area offshore of a large metropolitan port city. Structural and functional indicators were compared among localities and suitable functional indicators were aggregated into multimetric indices (MMIs) to provide an integrated measurement of ecosystem condition. Approximately 840 benthic biota and 10 400 fish (representing 176 identified fish species) were counted. Results showed that functional indicators, particularly size-based ones, were more effective at detecting changes in ecosystem condition compared with structural indicators based on taxonomy. Reefs in good ecological condition had a higher biomass of target species and a higher proportion of large predatory fish with more adults, compared with impacted areas. Benthic communities, however, appeared less responsive to cumulative pressures. The MMIs, using fish and benthic community data, were used to compare condition categories with those from the NBA. Results showed that the pressure-based assessments provided a reasonable proxy of broad patterns of rocky reef ecosystem condition. However, fine-scale discrepancies between results from the data-driven approach versus the proxy method suggested that broad-scale proxies might overestimate condition in some areas and underestimate it in others. To build on these results, the applicability of structural and functional indicators and MMIs were tested using an independent stereo-BRUVs dataset from the Agulhas Shelf ecoregion. Findings showed that not all MPAs were in good ecological condition compared with adjacent impacted areas, as was estimated by the NBA. However, there is a need to improve the quality of trait data and to test indicators and indices in other ecoregions, ecosystem types and in response to a broader range of improved pressure data. Furthermore, there is a need to apply innovative research to guide the calculation of thresholds for condition categories to advance condition assessments.
- Full Text:
- Date Issued: 2020
Alternative pine species/hybrids for the Cape timber growing regions of South Africa
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
An investigation of the morphological and electrochemical properties of anode titanate materials used in li-ion batteries
- Authors: Gelant, Charmaine
- Date: 2020
- Subjects: Electrodes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48346 , vital:40851
- Description: The chemistry involved in the synthesis of lithium titanium oxide (Li4Ti5O12) for lithium ion battery applications is critical for understanding and optimizing the most cost-efficient manufacturing route. This study investigates the sol-gel synthesis technique of Li4Ti5O12 using triethanolamine (TEOA) as complexing agent by means of in-situ Powder X-ray Diffraction (PXRD). The influence of doping with various metals such as Al3+, Mg2+ , Co3+ and Ni2+ that were made as precursors was considered for comparison purposes due to literature showing improved electrochemical performance using the molecular formula of Li4Ti4.95M0.05O12. The in-situ PXRD technique was used to identify the phase changes that occurred in the thermal synthesis process from the sol-gel precursors to the final crystalline oxides. The materials’ decomposition mechanisms were characterized by thermal gravimetric analysis (TGA) as the precursors were gradually heated to obtain the final oxides. BET surface area analysis and scanning electron microscopy (SEM) were used in order to obtain a morphological understanding of the materials during the synthetic route at specific temperature regions. The in-situ studies have shown that the precursor materials are amorphous at room temperature to about 550 °C, after which the spinel and anatase formed, with relatively small crystallites and a large surface area. The study also showed that a crystalline intermediate phase formed at around 150-200 °C, which then disappeared above 250 °C and was speculated to be a titanium acid (H2Ti2O5.H2O). Upon further heating above 250 °C, the anatase phase converted to the high temperature stable TiO2 phase, rutile, also with an increased formation of the expected LTO spinel phase around 850 °C. Keeping the material at 850 °C, isothermally, did show further conversion of the rutile into the desired spinel phase Li4Ti5O12 (LTO) with an increase in the crystallite size and a decrease in surface area. SEM analysis of the material at 850 °C did show some extensive sintering of the particles with some samples indicating the presence of an additional β-Li2TiO3 phase that formed at the high temperatures. Upon cooling, the βLi2TiO3 phase showed a distinctive powder diffraction pattern besides the typical spinel II LTO phase. The study showed that in comparison to the oxide formed at 850 °C, a mixed phase material of the spinel LTO, anatase and rutile could be achieved at temperatures close to 650 °C with very small crystallites and a relatively large surface area that showed desirable electrochemical properties. Suitable Li-ion coin cells were built with the undoped spinel and doped materials that were isothermally made at 650 °C and 850 °C, whereby their electrochemical properties were tested in the form of cell capacity, electrochemical impedance spectroscopy (EIS) and differential capacity (dQ/dV) studies. The cells made with the materials at 850 °C provided reasonable capacity where the dQ/dV plots did show a single step redox reaction at around 1.5V vs Li/Li+ . These were compared to cells made with commercially available LTO and highlighted the importance of high surface area and small particle size of the active material in order to achieve acceptable electrochemical performances. The cells with the materials made at 650 °C showed to have good capacity upon the first discharge with a number of irreversible phase transitions that were subsequently not observed upon recharging. The dQ/dV graphs showed that the phase transitions were unique to the mixed phase composition of the material made at low temperatures and the cells made with the doped spinel materials were on average better performing than the undoped LTO material. Subsequent grinding steps of the active material made at 850 °C improved the capacity performance of the cells but were still lower when compared to the commercially available material. Hence, significantly longer grinding and processing time would be required to achieve battery active materials that are acceptable for commercial use. This study highlights the importance of understanding the phase transitions that occur during the synthesis route of making battery active material, where doping with different elements and using lower temperatures during synthesis could lead to electroactive materials that do not require additional excessive processing steps such as grinding.
- Full Text:
- Date Issued: 2020
- Authors: Gelant, Charmaine
- Date: 2020
- Subjects: Electrodes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48346 , vital:40851
- Description: The chemistry involved in the synthesis of lithium titanium oxide (Li4Ti5O12) for lithium ion battery applications is critical for understanding and optimizing the most cost-efficient manufacturing route. This study investigates the sol-gel synthesis technique of Li4Ti5O12 using triethanolamine (TEOA) as complexing agent by means of in-situ Powder X-ray Diffraction (PXRD). The influence of doping with various metals such as Al3+, Mg2+ , Co3+ and Ni2+ that were made as precursors was considered for comparison purposes due to literature showing improved electrochemical performance using the molecular formula of Li4Ti4.95M0.05O12. The in-situ PXRD technique was used to identify the phase changes that occurred in the thermal synthesis process from the sol-gel precursors to the final crystalline oxides. The materials’ decomposition mechanisms were characterized by thermal gravimetric analysis (TGA) as the precursors were gradually heated to obtain the final oxides. BET surface area analysis and scanning electron microscopy (SEM) were used in order to obtain a morphological understanding of the materials during the synthetic route at specific temperature regions. The in-situ studies have shown that the precursor materials are amorphous at room temperature to about 550 °C, after which the spinel and anatase formed, with relatively small crystallites and a large surface area. The study also showed that a crystalline intermediate phase formed at around 150-200 °C, which then disappeared above 250 °C and was speculated to be a titanium acid (H2Ti2O5.H2O). Upon further heating above 250 °C, the anatase phase converted to the high temperature stable TiO2 phase, rutile, also with an increased formation of the expected LTO spinel phase around 850 °C. Keeping the material at 850 °C, isothermally, did show further conversion of the rutile into the desired spinel phase Li4Ti5O12 (LTO) with an increase in the crystallite size and a decrease in surface area. SEM analysis of the material at 850 °C did show some extensive sintering of the particles with some samples indicating the presence of an additional β-Li2TiO3 phase that formed at the high temperatures. Upon cooling, the βLi2TiO3 phase showed a distinctive powder diffraction pattern besides the typical spinel II LTO phase. The study showed that in comparison to the oxide formed at 850 °C, a mixed phase material of the spinel LTO, anatase and rutile could be achieved at temperatures close to 650 °C with very small crystallites and a relatively large surface area that showed desirable electrochemical properties. Suitable Li-ion coin cells were built with the undoped spinel and doped materials that were isothermally made at 650 °C and 850 °C, whereby their electrochemical properties were tested in the form of cell capacity, electrochemical impedance spectroscopy (EIS) and differential capacity (dQ/dV) studies. The cells made with the materials at 850 °C provided reasonable capacity where the dQ/dV plots did show a single step redox reaction at around 1.5V vs Li/Li+ . These were compared to cells made with commercially available LTO and highlighted the importance of high surface area and small particle size of the active material in order to achieve acceptable electrochemical performances. The cells with the materials made at 650 °C showed to have good capacity upon the first discharge with a number of irreversible phase transitions that were subsequently not observed upon recharging. The dQ/dV graphs showed that the phase transitions were unique to the mixed phase composition of the material made at low temperatures and the cells made with the doped spinel materials were on average better performing than the undoped LTO material. Subsequent grinding steps of the active material made at 850 °C improved the capacity performance of the cells but were still lower when compared to the commercially available material. Hence, significantly longer grinding and processing time would be required to achieve battery active materials that are acceptable for commercial use. This study highlights the importance of understanding the phase transitions that occur during the synthesis route of making battery active material, where doping with different elements and using lower temperatures during synthesis could lead to electroactive materials that do not require additional excessive processing steps such as grinding.
- Full Text:
- Date Issued: 2020
Analysis of the effectiveness of Tulbaghia Violacea extracts as devulcanizing agents for synthetic CIS-1,4-polyisoprene vulcanizates
- Authors: Gxakuma, Lutho
- Date: 2020
- Subjects: Plant extracts , Plant products -- South Africa Medicinal plants -- South Africa Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49093 , vital:41600
- Description: Tulbaghia violacea is an indigenous plant commonly known as wild garlic, wilde knoffel in Afrikaans, isihaqa in Zulu or itswele lomlambo in Xhosa. Its leaves and bulbs are widely used as herbal remedies for various ailments and its medicinal uses include fever and colds, asthma, tuberculosis and stomach problems. Like all other members of the Alliacea family, Tulbaghia violacea produces a distinctive garlic-like odour when its leaves or rhizomes are damaged, resulting in the release of cysteine-derived sulphur compounds which include the oil-soluble organo-sulphur compounds and water-soluble cysteine derivatives. Chemically synthesized sulphur containing compounds have been reported to be effective devulcanizing agents and many industries prefer to perform devulcanization using them. Most commonly applied devulcanizing agents include disulphides, thiophenols and their zinc salts, and mercaptans which are mixed with the rubber scrap powder under specific reaction conditions. In this study, instead of performing devulcanization by using industrial synthesized sulphur containing compounds, the effectiveness of the extracts of organo-sulphur containing compounds from Tulbaghia violacea are evaluated as potential devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizates. This is a new, cheap and greener practice of rubber devulcanization. Diallyl disulphide, which is one of the organo-sulphur containing compounds present in Tulbaghia violacea, is the devulcanizing agent of interest to this study. The organo-sulphur containing compounds were extracted from the bulbs, roots and leaves of the plant using the soxhlet and ultrasonic bath extraction method. The solvent system used in the soxhlet extraction method was 2% of 2-propanol in n-hexane whereas in ultrasonic bath extraction method the solvent system used was 100% ethanol. An essential oil extract was obtained from the plant organs. The yield of the essential oil extracts obtained using the soxhlet extraction method was higher compared to the yield of the essential oil extracts obtained using the ultrasonic bath extraction method. According to the Fourier-Transform Infrared spectroscopy, the organo-sulphur containing compounds were present in the essential oil extracts of the plant. The essential oil extracts that were extracted using the soxhlet extraction method were chosen for further analysis. It was found out that the allyl sulphide and diallyl disulphide have the same retention time from the High Performance Liquid Chromatography (using a normal phase column). The Differential Scanning Calorimeter indicated that the allyl sulphide was not present in the essential oil extracts whereas the diallyl disulphide was present in the essential oil extract of the roots and leaves. The High Performance Liquid Chromatography was used to quantify the presence of the diallyl disulphide in the essential oil extract of roots and leaves. The quantity of diallyl disulphide was 23% in the dry mass of the essential oil extract of roots. In the essential oil extract of leaves the diallyl disulphide was very low concentrated and the High Performance Liquid Chromatography was less sensitive to detect it. According to the Thermogravimetric Analyser, it was found that the essential oil extracts begin to degrade at 120 °C and experience a multistage degradation. The softening temperature of the essential oil extracts was 60 °C from the Simultaneous Differential Scanning Calorimeter-Thermogravimetric Analyser. Conventional vulcanization of synthetic cis-1,4-polyisoprene was prepared with the vulcanization ingredients of zinc oxide, sulphur, stearic acid and N-tert-butyl-2-benzothiazole sulphenamide. The vulcanized synthetic cis-1,4-polyisoprene produced, under the heating temperature of 160 °C, was mixed with the essential oil extracts using the internal mixer at 60 °C and the two-roll mill. The overall torque, tan delta and the total crosslink density were the properties of interest of synthetic cis-1,4-polyisoprene vulcanizate in this study. The devulcanization temperature for the treated synthetic cis-1,4-polyisoprene vulcanizate with the essential oil extracts was optimized using the Dynamic Moving Die Rheometer and Dynamic Rubber Process Analyser. The amount of essential oil extracts at which they are effective devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizate was also optimized. During optimization a change on the latter mentioned properties of synthetic cis-1,4-polyisoprene vulcanizate was observed, indicating that the essential oil extracts have an effect as potential devulcanizing agents. The essential oil extracts increased the tan delta and reduced the overall torque, and total crosslink density of synthetic cis-1,4-polyisoprene vulcanizate as expected from devulcanizing agents. 200 °C was a preferable devulcanization temperature whereas essential oil extracts were effective as devulcanizing agent at 1.4%. However, the essential oil extracts influenced the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate during the mixing process in the internal mixer at 60 °C, which was before heating at 200 °C. The essential oil extracts had a higher influence on the overall torque of synthetic cis-1,4-polyisoprene vulcanizate under heating at 200 °C whereas at 60 °C, during the mixing process, they had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate. The essential oil extract of leaves had a higher influence on the overall torque whereas the essential oil extract of bulbs had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 200 °C. The essential oil extract of roots shown a greater influence on the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 60 °C during the mixing process. The effect of the essential oil extracts on the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate was also investigated using the Modulated Differential Scanning Calorimetry method. The essential oil extract of bulbs and roots influenced the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate by reducing it whereas the essential oil extract of leaves caused a temperature shift of the reversing heat capacity curve from the Modulated Differential Scanning Calorimeter thermogram of synthetic cis-1,4-polyisoprene vulcanizate. Therefore, the results indicated that the essential oil extracts of Tulbaghia violacea have an effect as an alternative potential devulcanizing agents for conventional vulcanized synthetic cis-1,4-polyisoprene whether the diallyl disulphide compound is present or not in them.
- Full Text:
- Date Issued: 2020
- Authors: Gxakuma, Lutho
- Date: 2020
- Subjects: Plant extracts , Plant products -- South Africa Medicinal plants -- South Africa Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49093 , vital:41600
- Description: Tulbaghia violacea is an indigenous plant commonly known as wild garlic, wilde knoffel in Afrikaans, isihaqa in Zulu or itswele lomlambo in Xhosa. Its leaves and bulbs are widely used as herbal remedies for various ailments and its medicinal uses include fever and colds, asthma, tuberculosis and stomach problems. Like all other members of the Alliacea family, Tulbaghia violacea produces a distinctive garlic-like odour when its leaves or rhizomes are damaged, resulting in the release of cysteine-derived sulphur compounds which include the oil-soluble organo-sulphur compounds and water-soluble cysteine derivatives. Chemically synthesized sulphur containing compounds have been reported to be effective devulcanizing agents and many industries prefer to perform devulcanization using them. Most commonly applied devulcanizing agents include disulphides, thiophenols and their zinc salts, and mercaptans which are mixed with the rubber scrap powder under specific reaction conditions. In this study, instead of performing devulcanization by using industrial synthesized sulphur containing compounds, the effectiveness of the extracts of organo-sulphur containing compounds from Tulbaghia violacea are evaluated as potential devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizates. This is a new, cheap and greener practice of rubber devulcanization. Diallyl disulphide, which is one of the organo-sulphur containing compounds present in Tulbaghia violacea, is the devulcanizing agent of interest to this study. The organo-sulphur containing compounds were extracted from the bulbs, roots and leaves of the plant using the soxhlet and ultrasonic bath extraction method. The solvent system used in the soxhlet extraction method was 2% of 2-propanol in n-hexane whereas in ultrasonic bath extraction method the solvent system used was 100% ethanol. An essential oil extract was obtained from the plant organs. The yield of the essential oil extracts obtained using the soxhlet extraction method was higher compared to the yield of the essential oil extracts obtained using the ultrasonic bath extraction method. According to the Fourier-Transform Infrared spectroscopy, the organo-sulphur containing compounds were present in the essential oil extracts of the plant. The essential oil extracts that were extracted using the soxhlet extraction method were chosen for further analysis. It was found out that the allyl sulphide and diallyl disulphide have the same retention time from the High Performance Liquid Chromatography (using a normal phase column). The Differential Scanning Calorimeter indicated that the allyl sulphide was not present in the essential oil extracts whereas the diallyl disulphide was present in the essential oil extract of the roots and leaves. The High Performance Liquid Chromatography was used to quantify the presence of the diallyl disulphide in the essential oil extract of roots and leaves. The quantity of diallyl disulphide was 23% in the dry mass of the essential oil extract of roots. In the essential oil extract of leaves the diallyl disulphide was very low concentrated and the High Performance Liquid Chromatography was less sensitive to detect it. According to the Thermogravimetric Analyser, it was found that the essential oil extracts begin to degrade at 120 °C and experience a multistage degradation. The softening temperature of the essential oil extracts was 60 °C from the Simultaneous Differential Scanning Calorimeter-Thermogravimetric Analyser. Conventional vulcanization of synthetic cis-1,4-polyisoprene was prepared with the vulcanization ingredients of zinc oxide, sulphur, stearic acid and N-tert-butyl-2-benzothiazole sulphenamide. The vulcanized synthetic cis-1,4-polyisoprene produced, under the heating temperature of 160 °C, was mixed with the essential oil extracts using the internal mixer at 60 °C and the two-roll mill. The overall torque, tan delta and the total crosslink density were the properties of interest of synthetic cis-1,4-polyisoprene vulcanizate in this study. The devulcanization temperature for the treated synthetic cis-1,4-polyisoprene vulcanizate with the essential oil extracts was optimized using the Dynamic Moving Die Rheometer and Dynamic Rubber Process Analyser. The amount of essential oil extracts at which they are effective devulcanizing agents for synthetic cis-1,4-polyisoprene vulcanizate was also optimized. During optimization a change on the latter mentioned properties of synthetic cis-1,4-polyisoprene vulcanizate was observed, indicating that the essential oil extracts have an effect as potential devulcanizing agents. The essential oil extracts increased the tan delta and reduced the overall torque, and total crosslink density of synthetic cis-1,4-polyisoprene vulcanizate as expected from devulcanizing agents. 200 °C was a preferable devulcanization temperature whereas essential oil extracts were effective as devulcanizing agent at 1.4%. However, the essential oil extracts influenced the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate during the mixing process in the internal mixer at 60 °C, which was before heating at 200 °C. The essential oil extracts had a higher influence on the overall torque of synthetic cis-1,4-polyisoprene vulcanizate under heating at 200 °C whereas at 60 °C, during the mixing process, they had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate. The essential oil extract of leaves had a higher influence on the overall torque whereas the essential oil extract of bulbs had a higher influence on the tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 200 °C. The essential oil extract of roots shown a greater influence on the overall torque and tan delta of synthetic cis-1,4-polyisoprene vulcanizate at 60 °C during the mixing process. The effect of the essential oil extracts on the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate was also investigated using the Modulated Differential Scanning Calorimetry method. The essential oil extract of bulbs and roots influenced the reversing heat capacity of synthetic cis-1,4-polyisoprene vulcanizate by reducing it whereas the essential oil extract of leaves caused a temperature shift of the reversing heat capacity curve from the Modulated Differential Scanning Calorimeter thermogram of synthetic cis-1,4-polyisoprene vulcanizate. Therefore, the results indicated that the essential oil extracts of Tulbaghia violacea have an effect as an alternative potential devulcanizing agents for conventional vulcanized synthetic cis-1,4-polyisoprene whether the diallyl disulphide compound is present or not in them.
- Full Text:
- Date Issued: 2020
Applied phylogeography : mapping the genetic resource of Honeybush across the Cape Floristic Region
- Authors: Galuszynski, Nicholas C
- Date: 2020
- Subjects: Phylogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46771 , vital:39655
- Description: Aim: Honeybush tea is a herbal infusion made from members of the Cape Floristic Region (CFR) endemic Cyclopia Vent. Consting of 21 extant species, six are anthropogenically redistributed across the CFR for Honeybush cultivation. However, with no information regarding the distribution and levels of genetic diversity among wild Honeybush populations, anthropogenic translocation of cultivated genotypes may risk disrupting natural genetic diversity patterns. In this thesis, an applied phylogeographic approach is used to provide baseline insights into the spatial structuring of Honeybush genetic diversity. Location: The Cape Floristic Region (CFR), located along the southern Cape of South Africa. Methods: Spatial structuring of evolutionary lineages within Cyclopia are explored at a genus level using data generated from the combination of Anchored Hybrid Enrichment library preparation and high through put sequencing. A High Resolution Melt analysis (HRM) toolkit is then developed to screen haplotype variation across three non-coding chloroplast loci. This HRM toolkit coupled with haplotype confirmation Sanger sequencing is then applied to describe the spatial structuring of genetic diversity in wild populations for two Honeybush species (C. intermedia and C. subternata) and to compare genetic diversity among wild and cultivated populations of three Honeybush species (C. intermedia, C. subternata, and C. longifolia). A reanalysis of published phylogeographic data focusing on CFR plant taxa is used to test if phylogeographic breaks occur across the boundaries among adjacent Centers of Endemism (CoEs). Finally, the low-copy nuclear data set generated via AHE and high throughput sequencing is summarized. Results: Phylogeographic structuring was detected at the inter- and intraspecific levels in Cyclopia. The genus level analysis revealed a strong phylogenetic split between western CFR and eastern CFR endemic species in the nuclear and chloroplast genomes. At the intraspecific level, HRM proved to be a high throughput and accurate tool for haplotype detection, revealing phylogeographic structuring of genetic diversity in C.intermediaand C.subternata. This genetic diversity and structuring was not detected in cultivated Honeybush populations, which appear to have originated from a small number of founding individuals and have experienced a genetic bottleneck. Spatial structuring of genetic lineages is common among CFR plant taxa and the reanalysis of existing data found a significant trend for phylogeographic breaks tooccuracrosstheboundariesamongadjacentCoEs. Finally, over200000baseswere sequenced across 445 low-copy nuclear loci for 14 Cyclopia species. Conclusions: This thesis provides important baseline information on the spatial distribution of wild Honeybush genetic diversity. Phylogeographic structuring is present in wild Honeybush populations. This however is not accounted for in cultivated populations, which may place wild genetic diversity at risk of being disrupted if geneflow among wild and cultivated populations occurs. The results from this thesis should therefore be used to develop precautionary guidelines for the anthropogenic redistribution of Honeybush genetic material for cultivation. Furthermore, the novel insights into regional patterns of phylogeohraphic structuring of plant populations should encourage more efficient and hypothesis driven sampling designs in future phylogeographic work in the CFR. The high throughput sequence data generated in this thesis should transform Cyclopia to a model organism for the study of molecular evolution in the CFR.
- Full Text:
- Date Issued: 2020
- Authors: Galuszynski, Nicholas C
- Date: 2020
- Subjects: Phylogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46771 , vital:39655
- Description: Aim: Honeybush tea is a herbal infusion made from members of the Cape Floristic Region (CFR) endemic Cyclopia Vent. Consting of 21 extant species, six are anthropogenically redistributed across the CFR for Honeybush cultivation. However, with no information regarding the distribution and levels of genetic diversity among wild Honeybush populations, anthropogenic translocation of cultivated genotypes may risk disrupting natural genetic diversity patterns. In this thesis, an applied phylogeographic approach is used to provide baseline insights into the spatial structuring of Honeybush genetic diversity. Location: The Cape Floristic Region (CFR), located along the southern Cape of South Africa. Methods: Spatial structuring of evolutionary lineages within Cyclopia are explored at a genus level using data generated from the combination of Anchored Hybrid Enrichment library preparation and high through put sequencing. A High Resolution Melt analysis (HRM) toolkit is then developed to screen haplotype variation across three non-coding chloroplast loci. This HRM toolkit coupled with haplotype confirmation Sanger sequencing is then applied to describe the spatial structuring of genetic diversity in wild populations for two Honeybush species (C. intermedia and C. subternata) and to compare genetic diversity among wild and cultivated populations of three Honeybush species (C. intermedia, C. subternata, and C. longifolia). A reanalysis of published phylogeographic data focusing on CFR plant taxa is used to test if phylogeographic breaks occur across the boundaries among adjacent Centers of Endemism (CoEs). Finally, the low-copy nuclear data set generated via AHE and high throughput sequencing is summarized. Results: Phylogeographic structuring was detected at the inter- and intraspecific levels in Cyclopia. The genus level analysis revealed a strong phylogenetic split between western CFR and eastern CFR endemic species in the nuclear and chloroplast genomes. At the intraspecific level, HRM proved to be a high throughput and accurate tool for haplotype detection, revealing phylogeographic structuring of genetic diversity in C.intermediaand C.subternata. This genetic diversity and structuring was not detected in cultivated Honeybush populations, which appear to have originated from a small number of founding individuals and have experienced a genetic bottleneck. Spatial structuring of genetic lineages is common among CFR plant taxa and the reanalysis of existing data found a significant trend for phylogeographic breaks tooccuracrosstheboundariesamongadjacentCoEs. Finally, over200000baseswere sequenced across 445 low-copy nuclear loci for 14 Cyclopia species. Conclusions: This thesis provides important baseline information on the spatial distribution of wild Honeybush genetic diversity. Phylogeographic structuring is present in wild Honeybush populations. This however is not accounted for in cultivated populations, which may place wild genetic diversity at risk of being disrupted if geneflow among wild and cultivated populations occurs. The results from this thesis should therefore be used to develop precautionary guidelines for the anthropogenic redistribution of Honeybush genetic material for cultivation. Furthermore, the novel insights into regional patterns of phylogeohraphic structuring of plant populations should encourage more efficient and hypothesis driven sampling designs in future phylogeographic work in the CFR. The high throughput sequence data generated in this thesis should transform Cyclopia to a model organism for the study of molecular evolution in the CFR.
- Full Text:
- Date Issued: 2020
Applying high-resolution remote sensing to quantify baboon damage at a sub-compartment level in pine stands in the Mpumalanga escarpment region of South Africa
- Authors: Ferreira, Regardt
- Date: 2020
- Subjects: Environmental sciences -- Remote sensing , Geographic information systems Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49082 , vital:41599
- Description: Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Ferreira, Regardt
- Date: 2020
- Subjects: Environmental sciences -- Remote sensing , Geographic information systems Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49082 , vital:41599
- Description: Managing risk in intensively managed monoculture plantation forests is an essential task to ensure sustainable yield and a continuous flow of forest products. However, since risks can be either biotic or abiotic, not all of them have a predictable pattern of spread, which can cause severe losses if management does not have the chance to implement mitigation action. Monitoring the change in forest health is vital as this provides the opportunity for preventative management and quantifies the amount of damage that management has to deal with. To provide this window of opportunity for appropriate action, constant monitoring is required. Until recently, forest health was measured through field surveys which provided adequate data. This procedure, however, is time consuming. Remote sensing has become very popular as a monitoring tool, due to its ability to provide assessment data in a fraction of the time. In this study, baboon damage in plantations along the Mpumalanga escarpment area of South Africa was monitored using remote sensing methods. While there are many methods of forest health monitoring using remote sensing, some approaches are less suitable as they either monitor damage caused at a plantation level, use lower spatial resolution (>10m) datasets or map damage using one available time period. The purpose of this study was first to establish the impact of baboon damage through time, using Sentinel-2 satellite imagery with all vegetation indices available, and the Extreme Gradient Boosting (XGboost) algorithm. The second part focused on analysing the damage at a tree level using PlanetScope imagery using a deep Learning approach. Overall, the study found that the use of Sentinel-2 data and PlanetScope data could accurately distinguish between the varying severity of baboon damage, achieving an accuracy of 95% and 82%. The processing time of the deep learning Artificial Neural Network (ANN) was greatly affected by the number of hidden layers and neurons used. Implementation of techniques used in this study has the potential to improve the accuracy of forest health monitoring in compartment forestry in South Africa.
- Full Text:
- Date Issued: 2020
Assessing the Social Sustainability of Wind Energy in the Karoo
- Authors: Hechter, J P
- Date: 2020
- Subjects: Wind power -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48378 , vital:40854
- Description: Background: In an ecologically conscious world, the need for sustainable development and the need to produce alternative energy is at the forefront of discussions. South Africa has been witnessing to a surge in wind energy developments in recent years. Although, environmental impacts often enjoy more emphasis, social impacts are equally important. Recently social sustainability was seen as an integral part of sustainable development for the future and can no longer be ignored. Wind energy is pathway towards sustainable development but can have detrimental impacts on social sustainability. On the one hand wind energy is said to impact culture, sense of places and cause unrest in a community, however, on the other hand it is said to be socially sustainable to the point where wind energy is incorporated into local culture and not to mention the employment opportunities it can create. This is particularly important for vulnerable communities found in the Karoo, where unemployment is very high. Purpose/ Aim: The aim of this study was to assess the social sustainability of a wind energy project in the Karoo by constructing a theoretical assessment model designed to produce appropriate and specific social indicators. Methodology: A literature review was undertaken to gain insights into the social sustainability of wind energy which also served as the theoretical backbone for the model and assessment parameters. The assessment model produced 10 indicators which was used as interview schedule with key stakeholders in the study area. A total of 31 qualitative interviews were conducted and produced a good data set. Findings: The results from this study show that here was no significant negative impact reported with regards to social sustainability. The wind developer is committed to the community based on the various social initiative funded by it. Although a definite positive impact and improvement in terms of social sustainability is evident in the area, there is still a long way to go as many outcomes set by the wind developer is yet to achieved.
- Full Text:
- Date Issued: 2020
- Authors: Hechter, J P
- Date: 2020
- Subjects: Wind power -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48378 , vital:40854
- Description: Background: In an ecologically conscious world, the need for sustainable development and the need to produce alternative energy is at the forefront of discussions. South Africa has been witnessing to a surge in wind energy developments in recent years. Although, environmental impacts often enjoy more emphasis, social impacts are equally important. Recently social sustainability was seen as an integral part of sustainable development for the future and can no longer be ignored. Wind energy is pathway towards sustainable development but can have detrimental impacts on social sustainability. On the one hand wind energy is said to impact culture, sense of places and cause unrest in a community, however, on the other hand it is said to be socially sustainable to the point where wind energy is incorporated into local culture and not to mention the employment opportunities it can create. This is particularly important for vulnerable communities found in the Karoo, where unemployment is very high. Purpose/ Aim: The aim of this study was to assess the social sustainability of a wind energy project in the Karoo by constructing a theoretical assessment model designed to produce appropriate and specific social indicators. Methodology: A literature review was undertaken to gain insights into the social sustainability of wind energy which also served as the theoretical backbone for the model and assessment parameters. The assessment model produced 10 indicators which was used as interview schedule with key stakeholders in the study area. A total of 31 qualitative interviews were conducted and produced a good data set. Findings: The results from this study show that here was no significant negative impact reported with regards to social sustainability. The wind developer is committed to the community based on the various social initiative funded by it. Although a definite positive impact and improvement in terms of social sustainability is evident in the area, there is still a long way to go as many outcomes set by the wind developer is yet to achieved.
- Full Text:
- Date Issued: 2020
Biology, stock assessment and angler attitudes towards the introduction of slot size limits for a recreationally important species Sparodon durbanensis (Sparidae) in South Africa
- Authors: Hewett, Kyle
- Date: 2020
- Subjects: Sparidae -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48389 , vital:40855
- Description: Sparodon durbanensis (white musselcracker) is an endemic fish species in the Family Sparidae found in shallow (< 20 m) coastal waters from the Western Cape to KwaZulu-Natal. It is large-growing, late-maturing, long-lived and is a popular target species in the South African marine shore-based line and spear fisheries. Management regulations for the species have remained the same for over two decades despite anecdotal information of population declines. However, since the last life history-information for S. durbanensis was collected in the late 1980s, there is a paucity of contemporary information needed to inform wise management. The aim of this study was to collect contemporary socio-ecological information on the species and its fishery in order to better inform the management of the species. In order to do this, the growth-rate of historical and contemporary samples of Sparodon durbanensis was compared, a length-based stock assessment was performed and the knowledge and attitudes of anglers towards the introduction of improved regulations were investigated. The growth-rate was compared using otolith width as a proxy for fish growth. It was found that the growth-rate had remained relatively stable between 1963 and 2010, suggesting that S. durbanensis may be resilient to the increasing levels of environmental variability observed throughout its range and that the historical growth parameters determined for this species may remain applicable for contemporary stock assessment. The batch fecundity was determined for 50 mm size classes and used to estimate the percentage cumulative population batch fecundity using historical 803 mm FL (904 mm TL) and contemporary 776 mm FL (874 mm TL) length structure, respectively. Based on these observations a suitable harvest slot limit of 600-850 mm TL was suggested. A Length-Based Spawning Potential Ratio (SPR) model was used to provide the first formal stock assessment for S. durbanensis. The input parameters of M/k=1.44, L∞=1021 mm FL, L50=350 mm FL and L95=800 mm FL and length composition data comprising of 134 lengths obtained from a collection of competitive angling catches, estimated a SPR of 41%, which is above the 40% target reference point. A total of 126 online and face– to-face, replica questionnaires were completed by spearfishermen and recreational shore anglers. Responses indicated that anglers that target S. durbanensis are generally a specialized group who are knowledgeable about the biology and ecology of the species and are passionate about the conservation of the species. Participants indicated that Marine Protected Areas are likely the most effective regulation in the current suite of regulations used to manage the fishery and suggested that poor law enforcement was the major factor inhibiting the efficacy of fishery regulations. New proposed regulations, such as a harvest slot limit (and particularly the one between 600-850 mm TL) for S. durbanensis, was well supported, however participants suggested that non-compliance was a concern. Although, the SPR remained above the 40% target reference point, further declines in the stock status should be prevented through the implementation of a 600-850 mm TL harvest slot limit. Based on the findings of this study, this limit should provide protection against both growth and recruitment overfishing by providing protection to sexually immature, fast growing fish and to large adults that contribute the greatest proportion to population replenishment.
- Full Text:
- Date Issued: 2020
- Authors: Hewett, Kyle
- Date: 2020
- Subjects: Sparidae -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48389 , vital:40855
- Description: Sparodon durbanensis (white musselcracker) is an endemic fish species in the Family Sparidae found in shallow (< 20 m) coastal waters from the Western Cape to KwaZulu-Natal. It is large-growing, late-maturing, long-lived and is a popular target species in the South African marine shore-based line and spear fisheries. Management regulations for the species have remained the same for over two decades despite anecdotal information of population declines. However, since the last life history-information for S. durbanensis was collected in the late 1980s, there is a paucity of contemporary information needed to inform wise management. The aim of this study was to collect contemporary socio-ecological information on the species and its fishery in order to better inform the management of the species. In order to do this, the growth-rate of historical and contemporary samples of Sparodon durbanensis was compared, a length-based stock assessment was performed and the knowledge and attitudes of anglers towards the introduction of improved regulations were investigated. The growth-rate was compared using otolith width as a proxy for fish growth. It was found that the growth-rate had remained relatively stable between 1963 and 2010, suggesting that S. durbanensis may be resilient to the increasing levels of environmental variability observed throughout its range and that the historical growth parameters determined for this species may remain applicable for contemporary stock assessment. The batch fecundity was determined for 50 mm size classes and used to estimate the percentage cumulative population batch fecundity using historical 803 mm FL (904 mm TL) and contemporary 776 mm FL (874 mm TL) length structure, respectively. Based on these observations a suitable harvest slot limit of 600-850 mm TL was suggested. A Length-Based Spawning Potential Ratio (SPR) model was used to provide the first formal stock assessment for S. durbanensis. The input parameters of M/k=1.44, L∞=1021 mm FL, L50=350 mm FL and L95=800 mm FL and length composition data comprising of 134 lengths obtained from a collection of competitive angling catches, estimated a SPR of 41%, which is above the 40% target reference point. A total of 126 online and face– to-face, replica questionnaires were completed by spearfishermen and recreational shore anglers. Responses indicated that anglers that target S. durbanensis are generally a specialized group who are knowledgeable about the biology and ecology of the species and are passionate about the conservation of the species. Participants indicated that Marine Protected Areas are likely the most effective regulation in the current suite of regulations used to manage the fishery and suggested that poor law enforcement was the major factor inhibiting the efficacy of fishery regulations. New proposed regulations, such as a harvest slot limit (and particularly the one between 600-850 mm TL) for S. durbanensis, was well supported, however participants suggested that non-compliance was a concern. Although, the SPR remained above the 40% target reference point, further declines in the stock status should be prevented through the implementation of a 600-850 mm TL harvest slot limit. Based on the findings of this study, this limit should provide protection against both growth and recruitment overfishing by providing protection to sexually immature, fast growing fish and to large adults that contribute the greatest proportion to population replenishment.
- Full Text:
- Date Issued: 2020
Coherent detection of data and timing signals over optical fiber for telescope networks
- Authors: Nfanyana, Ketshabile
- Date: 2020
- Subjects: Fiber optics , Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49226 , vital:41612
- Description: Telescope networks are increasingly being developed with networks such as the SKA telescope demanding the use of high-end technology to be incorporated. These networks require accurate clock signals to be transported to antennas as well as massive data to be transported from individual parabolic array antennas to a central computer for data analysis. To achieve this, optical fiber technology forms the backbone of these networks, proving high speed transmission and required bandwidth. For a distributed telescope network, coherent detection technology serves as the ideal optical fiber technology candidate for transport of information to a correlator. Use of this technology constitutes too many benefits. Sensitivity of the system is improved, and advanced modulation formats can be employed thereby improving spectral efficiency. Furthermore, coherent detection allows for digital signal processing algorithms to be employed for equalization of transmission impairments such as chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise and nonlinear effects in the electrical domain. CD equalization is performed in the time or frequency domain using digital filters which suppress the fibers dispersion effectively. PMD equalization is usually performed in the time domain through the use of adaptive filters which employ algorithms such as least mean squares (LMS) and constant modulus algorithm (CMA). These algorithms further equalize residual CD. In mitigation of phase noise (carrier phase recovery), feed-forward and feedback carrier phase algorithms are used. Fiber nonlinearities and other impairments are compensated using the digital backpropagation algorithm which solves for the Manakov equation and nonlinear Schrödinger equation (NLSE). Distribution of stable clock signals to individual antennas is an important aspect of telescope networks. Clock signals are used to drive the digitizers and time stamping of received antenna information. These clock signals can be distributed using coherent detection technology by phase modulating the clock so as to provide inherent phase modulation robustness to noise through the fiber. In this thesis, we present coherent detection of non-return-to-zero pseudorandom binary sequence (PRBS-7) using binary phase shift keying (BPSK) through 26.6 km non-zero dispersion shifted fiber (NZDSF) at 10 Gbps. Digital signal processing for equalization of CD and PMD was performed offline using MATLAB software. For residual CD and PMD equalization, the LMS algorithm was used. The performance of the system, bit error rate (BER), was compared with that of an intensity modulated on-off keying (OOK) signal at the same bit rate. Basing on receiver sensitivity performance of OOK at 10-9 bit error rate, BPSK achieved superior performance with receiver sensitivity improvements of 18.37 dB and 13.89 dB attained for back-to-back and transmission over fiber, respectively. Phase modulation transmission of a 4 GHz clock signal was also conducted. Frequency instability, Allan variance and phase noise, of phase modulated clock was compared with that of intensity modulated clock. Moreover, we present an all optical clock generation scheme using frequency heterodyning technique. Allan variance values in the range of 10-10 were attained. The frequency instability of this clock generation scheme was quantified using the spectrum analyzer method. Furthermore, an all-photonic technique for data latency tracking of 5G networks over optical fiber is presented. The technique is spectrally efficient and is able to track latency down to the nano second timescale.
- Full Text:
- Date Issued: 2020
- Authors: Nfanyana, Ketshabile
- Date: 2020
- Subjects: Fiber optics , Very large array telescopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49226 , vital:41612
- Description: Telescope networks are increasingly being developed with networks such as the SKA telescope demanding the use of high-end technology to be incorporated. These networks require accurate clock signals to be transported to antennas as well as massive data to be transported from individual parabolic array antennas to a central computer for data analysis. To achieve this, optical fiber technology forms the backbone of these networks, proving high speed transmission and required bandwidth. For a distributed telescope network, coherent detection technology serves as the ideal optical fiber technology candidate for transport of information to a correlator. Use of this technology constitutes too many benefits. Sensitivity of the system is improved, and advanced modulation formats can be employed thereby improving spectral efficiency. Furthermore, coherent detection allows for digital signal processing algorithms to be employed for equalization of transmission impairments such as chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise and nonlinear effects in the electrical domain. CD equalization is performed in the time or frequency domain using digital filters which suppress the fibers dispersion effectively. PMD equalization is usually performed in the time domain through the use of adaptive filters which employ algorithms such as least mean squares (LMS) and constant modulus algorithm (CMA). These algorithms further equalize residual CD. In mitigation of phase noise (carrier phase recovery), feed-forward and feedback carrier phase algorithms are used. Fiber nonlinearities and other impairments are compensated using the digital backpropagation algorithm which solves for the Manakov equation and nonlinear Schrödinger equation (NLSE). Distribution of stable clock signals to individual antennas is an important aspect of telescope networks. Clock signals are used to drive the digitizers and time stamping of received antenna information. These clock signals can be distributed using coherent detection technology by phase modulating the clock so as to provide inherent phase modulation robustness to noise through the fiber. In this thesis, we present coherent detection of non-return-to-zero pseudorandom binary sequence (PRBS-7) using binary phase shift keying (BPSK) through 26.6 km non-zero dispersion shifted fiber (NZDSF) at 10 Gbps. Digital signal processing for equalization of CD and PMD was performed offline using MATLAB software. For residual CD and PMD equalization, the LMS algorithm was used. The performance of the system, bit error rate (BER), was compared with that of an intensity modulated on-off keying (OOK) signal at the same bit rate. Basing on receiver sensitivity performance of OOK at 10-9 bit error rate, BPSK achieved superior performance with receiver sensitivity improvements of 18.37 dB and 13.89 dB attained for back-to-back and transmission over fiber, respectively. Phase modulation transmission of a 4 GHz clock signal was also conducted. Frequency instability, Allan variance and phase noise, of phase modulated clock was compared with that of intensity modulated clock. Moreover, we present an all optical clock generation scheme using frequency heterodyning technique. Allan variance values in the range of 10-10 were attained. The frequency instability of this clock generation scheme was quantified using the spectrum analyzer method. Furthermore, an all-photonic technique for data latency tracking of 5G networks over optical fiber is presented. The technique is spectrally efficient and is able to track latency down to the nano second timescale.
- Full Text:
- Date Issued: 2020
Comprehensive characterization of the antidiabetic potential of selected plants and macrofungi from Africa using an in vitro target-directed screening platform and cellomics
- Authors: Pringle, Nadine Alex
- Date: 2020
- Subjects: Hypoglycemic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46750 , vital:39653
- Description: Several synthetic antidiabetic drugs have been developed to date, however, most are accompanied by adverse side-effects while remaining expensive and largely inaccessible to the vast majority of those who need it. To provide enough scientific evidence to support the inclusion of more affordable African antidiabetic medicinal plants and macrofungi into healthcare programs, this study sought out to develop a comprehensive in vitro antidiabetic target-directed screening platform incorporating high content screening and analysis/ cellomics. To test the success of this model, the potential antidiabetic mechanisms of five plants (Aspalathus linearis, Brachylaena discolor, Carpobrotus deliciosus, Sutherlandia frutescens and Tarchonanthus camphoratus) and two macrofungal species (Ganoderma lucidum and Hericium erinaceus) were explored. The screening model consisted of approximately 22 assays exploring the antidiabetic effects of selected aqueous and ethanolic extracts in five well-characterised antidiabetic targets: the intestine, liver, skeletal muscle, adipose tissue/ obesity and pancreatic β-cells. These targets were further categorised and scored under three mechanistic classes/ therapeutic targets (postprandial hyperglycaemia; insulin resistance and inflammation; pancreatic β-cell function) to elucidate their potential mechanisms of action and select appropriate animal models for future studies. Almost any normal or diabetic rodent model would be suitable to explore the antidiabetic potential of extracts such as A. linearis, B. discolor ethanol, C. deliciosus ethanol or T. camphoratus which obtained high cumulative scores under postprandial hyperglycaemia while high fat diet and genetic models of obesity appear more suited towards extracts such as H. erinaceus aqueous that obtained their highest cumulative score under insulin resistance. In general, a combination of rodent models ranging from non-obese models to models of obesity and β-cell destruction presenting symptoms from all three mechanistic classes should be considered due to the pleiotropic nature of the tested extracts, however, establishing appropriate experimental designs is crucial. To demonstrate the versatility of the screening platform and emphasise the importance of in vitro screening pertaining to diabetic complications, a more detailed biochemical investigation into the potential therapeutic benefits of A. linearis in the treatment of diabetic wounds was conducted. Several properties supporting the therapeutic potential of rooibos were highlighted with the green and fermented extracts presenting distinctly different characteristics. The pro-inflammatory nature of fermented rooibos may have therapeutic value for wounds characterised with a delayed initial inflammatory phase, such as early diabetic wounds while the green extract appears more suited to wounds burdened with excessive inflammation as it attenuated COX-2 levels and effectively protected fibroblasts against oxidative stress. To date, this appears to be the most comprehensive antidiabetic screening platform in existence and consequently provides the only feasible solution that will enable natural product antidiabetic research to progress to the point where natural products can be commercialised and incorporated into meaningful healthcare programs. Future research should be focussed towards further expanding this model by incorporating additional targets, more sophisticated cell culturing techniques, multiplexed high content screening assays and carrying out combination treatments that explore the antidiabetic effects of two or more crude extracts to establish whether they are capable of acting in a synergistic manner.
- Full Text:
- Date Issued: 2020
- Authors: Pringle, Nadine Alex
- Date: 2020
- Subjects: Hypoglycemic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46750 , vital:39653
- Description: Several synthetic antidiabetic drugs have been developed to date, however, most are accompanied by adverse side-effects while remaining expensive and largely inaccessible to the vast majority of those who need it. To provide enough scientific evidence to support the inclusion of more affordable African antidiabetic medicinal plants and macrofungi into healthcare programs, this study sought out to develop a comprehensive in vitro antidiabetic target-directed screening platform incorporating high content screening and analysis/ cellomics. To test the success of this model, the potential antidiabetic mechanisms of five plants (Aspalathus linearis, Brachylaena discolor, Carpobrotus deliciosus, Sutherlandia frutescens and Tarchonanthus camphoratus) and two macrofungal species (Ganoderma lucidum and Hericium erinaceus) were explored. The screening model consisted of approximately 22 assays exploring the antidiabetic effects of selected aqueous and ethanolic extracts in five well-characterised antidiabetic targets: the intestine, liver, skeletal muscle, adipose tissue/ obesity and pancreatic β-cells. These targets were further categorised and scored under three mechanistic classes/ therapeutic targets (postprandial hyperglycaemia; insulin resistance and inflammation; pancreatic β-cell function) to elucidate their potential mechanisms of action and select appropriate animal models for future studies. Almost any normal or diabetic rodent model would be suitable to explore the antidiabetic potential of extracts such as A. linearis, B. discolor ethanol, C. deliciosus ethanol or T. camphoratus which obtained high cumulative scores under postprandial hyperglycaemia while high fat diet and genetic models of obesity appear more suited towards extracts such as H. erinaceus aqueous that obtained their highest cumulative score under insulin resistance. In general, a combination of rodent models ranging from non-obese models to models of obesity and β-cell destruction presenting symptoms from all three mechanistic classes should be considered due to the pleiotropic nature of the tested extracts, however, establishing appropriate experimental designs is crucial. To demonstrate the versatility of the screening platform and emphasise the importance of in vitro screening pertaining to diabetic complications, a more detailed biochemical investigation into the potential therapeutic benefits of A. linearis in the treatment of diabetic wounds was conducted. Several properties supporting the therapeutic potential of rooibos were highlighted with the green and fermented extracts presenting distinctly different characteristics. The pro-inflammatory nature of fermented rooibos may have therapeutic value for wounds characterised with a delayed initial inflammatory phase, such as early diabetic wounds while the green extract appears more suited to wounds burdened with excessive inflammation as it attenuated COX-2 levels and effectively protected fibroblasts against oxidative stress. To date, this appears to be the most comprehensive antidiabetic screening platform in existence and consequently provides the only feasible solution that will enable natural product antidiabetic research to progress to the point where natural products can be commercialised and incorporated into meaningful healthcare programs. Future research should be focussed towards further expanding this model by incorporating additional targets, more sophisticated cell culturing techniques, multiplexed high content screening assays and carrying out combination treatments that explore the antidiabetic effects of two or more crude extracts to establish whether they are capable of acting in a synergistic manner.
- Full Text:
- Date Issued: 2020
Conservation biology of an apex predator in the Anthropocene : poaching, pastoralism and lions in multi-use landscapes, South-Eastern Africa
- Authors: Everatt, Kristoffer T
- Date: 2020
- Subjects: Conservation biology -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48290 , vital:40839
- Description: Many of the world’s apex predators are experiencing catastrophic declines as a result of competition with humans. Understanding the mechanisms and ecosystem impacts of apex predator declines is a fundamental ecological question crucial to conserving the Earth’s biodiversity and functioning ecosystems. In this thesis I used the African lion Panthera leo, as a model species to investigate the impacts of anthropogenic pressures on the conservation and ecology of an apex predator. Specifically, I investigated the relative and cumulative influences of pastoralism and poaching on lion occurrence, population connectivity, ecological role, space use, prey selection and viability across a 73 000 km2 multi-use landscape in southern Africa. Using landscape occupancy spoor surveys, I tested the hypotheses that lions were most limited by either interference or by exploitative competition with humans and identified thresholds of lion tolerance to human activities. My results showed that lions occupied only a fraction of the landscape and were limited by a combination of interference and exploitative competition with humans. Interference competition with pastoralism however was the biggest driver limiting lion occupancy, creating a clear disturbance threshold for lions cumulating in their near complete loss from the landscape. I employed call-up surveys, pride monitoring and mortality analysis to investigate the numerical impacts of anthropogenic pressures on the viability of a lion sub-population. I found that persecution by pastoralists was the greatest source of lion mortalities across the landscape. However, the targeted poaching of lions for body parts had emerged as the greatest threat to lions in a nominally protected National Park where I documented a steep population decline and collapse of lion prides. I used GPS tracking and diet analysis of lions at the human-wildlands interface to test if lions foraged optimally or were constrained by competition with humans. I fount that individual lions appeared to select for prey and habitat optimally, while also showing some level of risk avoidance towards anthropogenic pressures. I then considered landscape resistances to test if sink habitats may provide connectivity between sources or act as ecological traps. I found that potential connectivity for lions between the region’s two source populations was limited by a loss of habitat and prey. Furthermore, the impacts of by-catch in snares risked transforming the few remaining potential conservation corridors into ecological traps. Finally, I examined interactions between lions and syntopic mesopredators across gradients of anthropogenic pressures to test if the functional role of lions was affected by human pressures. I found that lions showed limited suppression of mesopredators, however, anthropogenic pressures increased lion’s interactions with syntopic predators. As an apex predator, lions have evolved limited capacity to mitigate top-down competitive pressures, however, like many of the world’s apex predators, they are becoming increasingly limited by anthropogenic pressures. This study provides a predictive understanding of an apex predator’s ecological responses to top-down anthropogenic pressures which can be applied globally to the question of conservation in the Anthropocene.
- Full Text:
- Date Issued: 2020
- Authors: Everatt, Kristoffer T
- Date: 2020
- Subjects: Conservation biology -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48290 , vital:40839
- Description: Many of the world’s apex predators are experiencing catastrophic declines as a result of competition with humans. Understanding the mechanisms and ecosystem impacts of apex predator declines is a fundamental ecological question crucial to conserving the Earth’s biodiversity and functioning ecosystems. In this thesis I used the African lion Panthera leo, as a model species to investigate the impacts of anthropogenic pressures on the conservation and ecology of an apex predator. Specifically, I investigated the relative and cumulative influences of pastoralism and poaching on lion occurrence, population connectivity, ecological role, space use, prey selection and viability across a 73 000 km2 multi-use landscape in southern Africa. Using landscape occupancy spoor surveys, I tested the hypotheses that lions were most limited by either interference or by exploitative competition with humans and identified thresholds of lion tolerance to human activities. My results showed that lions occupied only a fraction of the landscape and were limited by a combination of interference and exploitative competition with humans. Interference competition with pastoralism however was the biggest driver limiting lion occupancy, creating a clear disturbance threshold for lions cumulating in their near complete loss from the landscape. I employed call-up surveys, pride monitoring and mortality analysis to investigate the numerical impacts of anthropogenic pressures on the viability of a lion sub-population. I found that persecution by pastoralists was the greatest source of lion mortalities across the landscape. However, the targeted poaching of lions for body parts had emerged as the greatest threat to lions in a nominally protected National Park where I documented a steep population decline and collapse of lion prides. I used GPS tracking and diet analysis of lions at the human-wildlands interface to test if lions foraged optimally or were constrained by competition with humans. I fount that individual lions appeared to select for prey and habitat optimally, while also showing some level of risk avoidance towards anthropogenic pressures. I then considered landscape resistances to test if sink habitats may provide connectivity between sources or act as ecological traps. I found that potential connectivity for lions between the region’s two source populations was limited by a loss of habitat and prey. Furthermore, the impacts of by-catch in snares risked transforming the few remaining potential conservation corridors into ecological traps. Finally, I examined interactions between lions and syntopic mesopredators across gradients of anthropogenic pressures to test if the functional role of lions was affected by human pressures. I found that lions showed limited suppression of mesopredators, however, anthropogenic pressures increased lion’s interactions with syntopic predators. As an apex predator, lions have evolved limited capacity to mitigate top-down competitive pressures, however, like many of the world’s apex predators, they are becoming increasingly limited by anthropogenic pressures. This study provides a predictive understanding of an apex predator’s ecological responses to top-down anthropogenic pressures which can be applied globally to the question of conservation in the Anthropocene.
- Full Text:
- Date Issued: 2020
Continuous flow synthesis of 5-formyl-2,4- dimethyl-1h-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib anti-cancer drug
- Authors: Gqokoma, Zizo
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48356 , vital:40852
- Description: The present trend in the pharmaceutical industry is towards adapting continuous flow processing with the main driving force behind this being the need to reduce environmental and economic costs. Continuous flow systems have proven to produce better quality products at lower costs, time and energy. As a result, this technique has diversified and expanded to provide novel, and practical solutions to not only organic synthesis but also renewable fuels and material science. The focus of this research work was to exploit continuous flow systems, to develop a continuous flow process that is energy and time effective, using commercial micro reactors to synthesize 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib, an anti-cancer drug. In this thesis, a successful study on the individual translation of a 5 step batch synthesis of 5- formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid into optimised continuous flow syntheses is demonstrated. A comprehensive literature review and background on cancer, and an introduction to pyrrole rings, their role in disease treatments in addition to a brief introduction to continuous flow technology with its advantages, and comparison to classical batch methods are provided in the first chapter. Chapter two is detailing the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis of the four intermediates towards the target compound in this work proved to be far superior compared to their batch syntheses; excellent improvements in reaction yields and selectivity in addition to tremendously shorter reaction times were observed. This is expounded in chapter three with detailed discussions of the results attained during the continuous flow optimisation of each step within the scope of this research, are provided. The concluding remarks, the impact of this study and future work are elucidated in chapter four.
- Full Text:
- Date Issued: 2020
- Authors: Gqokoma, Zizo
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48356 , vital:40852
- Description: The present trend in the pharmaceutical industry is towards adapting continuous flow processing with the main driving force behind this being the need to reduce environmental and economic costs. Continuous flow systems have proven to produce better quality products at lower costs, time and energy. As a result, this technique has diversified and expanded to provide novel, and practical solutions to not only organic synthesis but also renewable fuels and material science. The focus of this research work was to exploit continuous flow systems, to develop a continuous flow process that is energy and time effective, using commercial micro reactors to synthesize 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid, a key intermediate towards the synthesis of sunitinib, an anti-cancer drug. In this thesis, a successful study on the individual translation of a 5 step batch synthesis of 5- formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid into optimised continuous flow syntheses is demonstrated. A comprehensive literature review and background on cancer, and an introduction to pyrrole rings, their role in disease treatments in addition to a brief introduction to continuous flow technology with its advantages, and comparison to classical batch methods are provided in the first chapter. Chapter two is detailing the experimental procedures utilised for both batch and continuous flow syntheses. The continuous flow synthesis of the four intermediates towards the target compound in this work proved to be far superior compared to their batch syntheses; excellent improvements in reaction yields and selectivity in addition to tremendously shorter reaction times were observed. This is expounded in chapter three with detailed discussions of the results attained during the continuous flow optimisation of each step within the scope of this research, are provided. The concluding remarks, the impact of this study and future work are elucidated in chapter four.
- Full Text:
- Date Issued: 2020
Continuous flow synthesis of imatinib intermediates
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
- Authors: Rupapa, Harold Takunda
- Date: 2020
- Subjects: Flow chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47464 , vital:39993
- Description: In this thesis, an alternative approach using continuous flow chemistry towards imatinib intermediates is described; an important drug in the treatment of acute myeloid leukemia. Various protocols that describe the multistep batch organic synthesis of imatinib are outlined. Many of the batch synthetic protocols require long reaction times in the multistep synthesis towards the various imatinib intermediates. A broad description into the cancer epidemic such as myeloid leukemia, the cost of drug manufacture and the effect that the high cost of manufacture has on the accessibility to such treatment in Africa is outlined. Use of continuous flow reactors, the exploitation of various technologies and their advantages on organic synthesis compared to batch synthesis are also described. The batch reaction conditions needed for the multistep transformation towards imatinib were adapted to a continuous flow set up. The optimization investigation shows an improvement in the conversion in the various steps. The flow synthesis of the enaminone provided a conversion of 99% when in o-xylene and the ability to use backpressure regulators assisted the investigation at high temperatures. Solution-phase flow synthesis of the guanidinium nitrate, which gave low yields in batch, also showed an improvement in conversion, where in 30 minutes a conversion of 99% was confirmed by altering the co-solvent mixture. The cycloaddition reaction of the enaminone and the guanidinium nitrate salt, achieved 90% conversion to the 2-aminopyridine core at 180 oC. The nitro group reduction was achieved in the presence of a greener catalyst, namely iron pentanedionate, in the presence of hydrazine hydrate. The effect of temperature, molar equivalence and solvent on reaction conversions could be observed in these steps. The thesis is concluded in chapter 4, with the conclusion and recommendations for future work towards a scalable continuous flow synthesis of the imatinib intermediates.
- Full Text:
- Date Issued: 2020
Contributions to the systematics and ecology of Tulista Raf(Asphodelaceae subfam. Alooideae)
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020
- Authors: Molteno, Steven Martin
- Date: 2020
- Subjects: Plant ecology -- South Africa , Plant ecology -- Comparative method Biodiversity , Species diversity
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49182 , vital:41608
- Description: The subject of this study is the taxonomy, morphology, distribution and ecology of Tulista Raf. (Asphodelaceae subfam. Alooideae), a genus of succulent plants that are endemic to South Africa. A lack of clarity on the taxonomy of this genus, coupled with an incomplete understanding of the distribution, ecology and habitat preferences of the constituent species, risks hampering the conservation of Tulista species, two of which are endangered species. The purpose of this study is therefore to address the need for a more detailed and consistent treatment of Tulista taxonomy and morphology, complemented by a study of the plants’ distribution and ecology. The work first provides a review of the relevant taxonomy and nomenclature, concluding with the presentation of the validly published names referring to Tulista. A detailed morphometric study resulted in strong support for one species, Tulista marginata (Lam.) G.D.Rowley, as well as for a grouping comprising Tulista pumila (L.) G.D.Rowley and Tulista minor (Aiton) Gideon F.Sm. & Molteno, with further moderate support for the distinction between the latter two species. The fourth out of the currently recognised species, Tulista kingiana (Poelln.) Gideon F.Sm. & Molteno, was only weakly characterised by the morphometric results, which suggested that its closest morphological affinity may be with hybrid plants that are sometimes found near T. marginata populations. The characterisation of some more controversial taxa was not supported in the results. Some changes to the circumscription of currently recognised Tulista species are also suggested by the results. In addition, field work conducted during the course of the study resulted in an expanded set of distribution data for the genus, together with certain habitat variables identified as potentially significant for the distribution and ecology of Tulista species.
- Full Text:
- Date Issued: 2020
Creating Citizen-Science for Groundwater Monitoring prior to potential Shale Gas Development in Cradock (South-Eastern Karoo, South Africa)
- Authors: Dhliwayo, Nyaradzo
- Date: 2020
- Subjects: Natural gas -- Prospecting -- Environmental aspects -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48224 , vital:40526
- Description: Citizen Science is an integral tool for community engagement in scientific project design, implementation, data interpretation and reporting, in the quest to promote local capacity development as well as scientific knowledge. Based on the relevance of public engagement in aspects of the natural environment and associated scientific issues associated with the risks and opportunities of potential Shale Gas Development (SGD), a Citizen-Science (CS) study was designed in the Eastern Karoo region of South Africa linked to a Shale Gas Baseline Study initiated by the Africa Earth Observatory Network (AEON). As the pilot area of the baseline study, the town of Cradock was chosen to be the study area for this research; and CS was used to facilitate the identification of the Cradock community’s abilities to monitor the effects of potential SGD in this region. The development of new knowledge, skills and support, as well as a deeper understanding of the community’s role in Citizen Science studies, was also facilitated by this process. This study demonstrates the feasibility of integrating Citizen Science into existing community structures in Africa, thereby encouraging community engagement in the developmental programmes through participatory methods. Using a collaborative Action-Research Approach, consistent community roundtable meetings and key informant interviews served as invaluable platforms for the establishment of a 7-member community working group, that played the liaison role between the researcher and the Cradock community in the CS implementation process. Coupled with this was the recruitment and the training of eight young citizens in conducting a hydro-census and groundwater sampling for six boreholes within the identified Cradock commonage farms, as well as two boreholes on the farm of an identified emergent farmer. The engagements between the researcher, AEON scientists, the community working group and the community at large, enabled the successful implementation of CS training in two groundwater monitoring aspects and the testing of eleven water quality parameters. The training process was combined with the design and the development of a customised ‘Xoras’ Online Application, which was used to capture and share the hydro-census data recorded. Experiential learning in hydro-census and groundwater sampling resulted subsequently in an increased understanding and awareness of these aspects (Figure A). Even if SGD does not materialise in the South-Eastern Karoo, CS training will enable communities in the Shale-Gas Development precincts to participate in local decision-making forums on ground water, health, or on any related regional development projects. It is anticipated that the adoption of CS will ix promote future community engagements, especially about water across this water-scarce region, allowing for greater community-voice representation in resource-policy decisions related to potential Shale-Gas and related natural resource industries in the Karoo.
- Full Text:
- Date Issued: 2020
- Authors: Dhliwayo, Nyaradzo
- Date: 2020
- Subjects: Natural gas -- Prospecting -- Environmental aspects -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48224 , vital:40526
- Description: Citizen Science is an integral tool for community engagement in scientific project design, implementation, data interpretation and reporting, in the quest to promote local capacity development as well as scientific knowledge. Based on the relevance of public engagement in aspects of the natural environment and associated scientific issues associated with the risks and opportunities of potential Shale Gas Development (SGD), a Citizen-Science (CS) study was designed in the Eastern Karoo region of South Africa linked to a Shale Gas Baseline Study initiated by the Africa Earth Observatory Network (AEON). As the pilot area of the baseline study, the town of Cradock was chosen to be the study area for this research; and CS was used to facilitate the identification of the Cradock community’s abilities to monitor the effects of potential SGD in this region. The development of new knowledge, skills and support, as well as a deeper understanding of the community’s role in Citizen Science studies, was also facilitated by this process. This study demonstrates the feasibility of integrating Citizen Science into existing community structures in Africa, thereby encouraging community engagement in the developmental programmes through participatory methods. Using a collaborative Action-Research Approach, consistent community roundtable meetings and key informant interviews served as invaluable platforms for the establishment of a 7-member community working group, that played the liaison role between the researcher and the Cradock community in the CS implementation process. Coupled with this was the recruitment and the training of eight young citizens in conducting a hydro-census and groundwater sampling for six boreholes within the identified Cradock commonage farms, as well as two boreholes on the farm of an identified emergent farmer. The engagements between the researcher, AEON scientists, the community working group and the community at large, enabled the successful implementation of CS training in two groundwater monitoring aspects and the testing of eleven water quality parameters. The training process was combined with the design and the development of a customised ‘Xoras’ Online Application, which was used to capture and share the hydro-census data recorded. Experiential learning in hydro-census and groundwater sampling resulted subsequently in an increased understanding and awareness of these aspects (Figure A). Even if SGD does not materialise in the South-Eastern Karoo, CS training will enable communities in the Shale-Gas Development precincts to participate in local decision-making forums on ground water, health, or on any related regional development projects. It is anticipated that the adoption of CS will ix promote future community engagements, especially about water across this water-scarce region, allowing for greater community-voice representation in resource-policy decisions related to potential Shale-Gas and related natural resource industries in the Karoo.
- Full Text:
- Date Issued: 2020
Data transport over optical fibre for ska using advanced modulation flexible spectrum technology
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
- Authors: Dlamini, Phumla Patience
- Date: 2020
- Subjects: Fiber optics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50666 , vital:42329
- Description: Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
- Full Text:
- Date Issued: 2020
Database and guide for Lesotho wool and mohair production and quality
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020
- Authors: Maqalika, Papali Elizabeth
- Date: 2020
- Subjects: Mohair -- Dissertations -- Lesotho , Wool -- Dissertations -- Lesotho Textile fabrics -- Lesotho Textile industry -- Lesotho
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49148 , vital:41605
- Description: Lesotho produces significant quantities of Merino apparel wool and mohair, both of a quality that allows them to compete on the global market and to make a significant contribution to the economy of the country. Nevertheless, very little production and quality data and trends of these fibres have been documented. This is a serious disadvantage in terms of international trading and benchmarking as well as attempts to improve the production and quality of Lesotho wool and mohair. In the light of the aforementioned, the available production and quality data of the past 10 years have been captured and analysed for trends and also benchmarking, where considered applicable. The main focus is on fibre diameter (fineness), staple length, and yield since they largely determine fibre quality, application and price. Some quality related tests were undertaken to fill certain important gaps in the available data. In addition, prickle and medullation were evaluated on representative wool and mohair samples, respectively, because they represent important quality measures for apparel wool and mohair, respectively. It was found that Lesotho wool and mohair are of a fairly good and internationally competitive quality, with the wool having an average fibre diameter (MFD) of ≈20μm, an average staple length of about 64mm, an average VM level of about 4%, an average yield of about 57%, and the annual production being about 4 million kilograms greasy. The average staple length of the mohair was about 140mm, average MFD about 29μm and the average medullation, which unless otherwise specified, refers to the objectionable medullated fibres (kemp type) including the flat medullated fibre, relatively high at about 5.7%. The latter is certainly an area of concern which needs attention and improvement. It was found that the prickle level (Comfort Factor), of some of the wools tested was of such a level as to make the wool suitable for wearing against the skin. With respect to mohair, there is considerable scope to substantially reduce the level of objectionable medullated (kemp style) fibre level through the appropriate breeding interventions. Production of both wool and mohair has increased slightly over the ten years covered by this study. It also became apparent that Lesotho wool and mohair quality and production are greatly influenced by the farming practices and climatic conditions. Greater adoption of the merino sheep breed, sheds/barns and sheep coats are suggested as ways to reduce mortality rate (due to extremely cold temperatures), improve quality and increase yield and production. Some farming practices such as the lack of barns, supplementary feeding and veterinary care present constraints in terms of production of both wool and mohair. The districts in the Highlands region had the highest production of mostly wool, this being ascribed to better pastures, climatic and other conditions conducive to wool and mohair production. Both wool and mohair are considered to have potential for improved quality and production, which could be affected by appropriate interventions by the Small Agricultural and Development Project (SADP) and others through National Wool and Mohair Growers Association (NWMGA). Nevertheless, since the wool and mohair growers (farmers) do not form part of these and other interventions, they do not readily adopt the various strategies and decisions and do not receive the associated benefits immediately. It is therefore advised that local farmers, relevant educators and researchers be represented in policy and other decision making forums. In this way, educational campaigns will be demand driven with greater chance of adoption and success.
- Full Text:
- Date Issued: 2020