Ecological engineering: an assessment of the ecological impact of Reno mattress structures used in erosion control in the Keurbooms Estuary, South Africa
- Authors: De Villiers, Nina
- Date: 2020
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Keurboomstrand , Coast changes -- South Africa -- Keurboomstrand , Shore protection -- South Africa -- Keurboomstrand , Coastal engineering-- South Africa -- Keurboomstrand , Coastal zone management-- South Africa -- Keurboomstrand , Estuarine ecology-- South Africa -- Keurboomstrand , Eelgrass -- South Africa -- Keurboomstrand , Reno Mattresses
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166138 , vital:41332
- Description: Global climate changes have been associated with ocean warming and sea-level rise. Armouring of coastlines has become common practice with the increasing threat of coastal erosion. The transformation of soft sediment habitats to hard, artificial habitats because of coastline armouring can lead to changes in species diversity, composition and distribution. It is, therefore, essential to assess changes to habitats from coastal development as well as the ecological impact erosion control structures have within coastal systems. Ecological engineering attempts to combine engineering principals and ecological processes to reduce environmental impacts from coastal development and the implementation of artificial structures. Estuaries are particularly vulnerable to anthropogenic impacts through development, and are extremely important systems offering nursery and foraging grounds for many species. These systems are, however, particularly vulnerable to anthropogenic impacts from urbanisation and development. Within South Africa many estuaries are being transformed by the addition of artificial structures to combat erosion, one such structure is the Reno mattress (a flattened wire box filled with rocks). This study compared the fish diversity and abundances of existing Reno mattress structures and natural eelgrass (Zostera capensis) habitat in the Keurbooms Estuary, South Africa. Benthic invertebrates were sampled using standard core sampling and an adapted suction sampling approach within the two habitats. The non-destructive method of mini Baited Remote Underwater Video Systems (BRUVs) was used to sample fish. Seasonal benthic invertebrate and fish abundances and assemblages were assessed from winter 2018 to spring 2019 with greater abundances of both recorded in summer. Significantly greater abundances, diversity, and richness of fish were found in the Reno mattress habitat compared to Z. capensis. Invertebrate taxa displayed some overlap between habitats, however, three higher taxonomic groups were only recorded within Reno mattress habitat and one only within the eelgrass habitat. Fish assemblages differed significantly between the two established habitats. A Before-After-Control-Impact (BACI) investigation was used to assess the ecological impact of newly installed Reno mattresses in the Keurbooms Estuary. Zostera capensis extent was sampled by determining the percentage cover of 0.5 m X 0.5 m quadrats and measurements of eelgrass blades. Percentage cover and blade length decreased during the installation of Reno mattress, but then recovered shortly after completion of the installation. Abundances, richness and diversity of invertebrates and fish were found to be similar before and after the installation which suggests that the installation had no net negative impact on the site. The Reno mattresses were found to attract fauna typical of rocky shore environments as well as a few invasive alien invertebrate species. This study noted that a hybrid habitat of Reno mattress and eelgrass was created and may in fact provide the positives of both to a system. In any coastal development it will be important to balance the demands of a growing population and the protection of natural habitats. The results of this study suggest that complex artificial structures such as Reno mattresses do provide habitat for fish and invertebrates. However, the use of these structures should be in combination with natural vegetation (e.g. as a hybrid habitat) and not one that replaces intertidal and subtidal natural habitat especially eelgrass. There is limited information regarding the ecological impacts of using Reno mattresses in estuaries and this study provides new information on their ecological efficacy that should be valuable for future coastal erosion control practices.
- Full Text:
- Date Issued: 2020
- Authors: De Villiers, Nina
- Date: 2020
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Keurboomstrand , Coast changes -- South Africa -- Keurboomstrand , Shore protection -- South Africa -- Keurboomstrand , Coastal engineering-- South Africa -- Keurboomstrand , Coastal zone management-- South Africa -- Keurboomstrand , Estuarine ecology-- South Africa -- Keurboomstrand , Eelgrass -- South Africa -- Keurboomstrand , Reno Mattresses
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166138 , vital:41332
- Description: Global climate changes have been associated with ocean warming and sea-level rise. Armouring of coastlines has become common practice with the increasing threat of coastal erosion. The transformation of soft sediment habitats to hard, artificial habitats because of coastline armouring can lead to changes in species diversity, composition and distribution. It is, therefore, essential to assess changes to habitats from coastal development as well as the ecological impact erosion control structures have within coastal systems. Ecological engineering attempts to combine engineering principals and ecological processes to reduce environmental impacts from coastal development and the implementation of artificial structures. Estuaries are particularly vulnerable to anthropogenic impacts through development, and are extremely important systems offering nursery and foraging grounds for many species. These systems are, however, particularly vulnerable to anthropogenic impacts from urbanisation and development. Within South Africa many estuaries are being transformed by the addition of artificial structures to combat erosion, one such structure is the Reno mattress (a flattened wire box filled with rocks). This study compared the fish diversity and abundances of existing Reno mattress structures and natural eelgrass (Zostera capensis) habitat in the Keurbooms Estuary, South Africa. Benthic invertebrates were sampled using standard core sampling and an adapted suction sampling approach within the two habitats. The non-destructive method of mini Baited Remote Underwater Video Systems (BRUVs) was used to sample fish. Seasonal benthic invertebrate and fish abundances and assemblages were assessed from winter 2018 to spring 2019 with greater abundances of both recorded in summer. Significantly greater abundances, diversity, and richness of fish were found in the Reno mattress habitat compared to Z. capensis. Invertebrate taxa displayed some overlap between habitats, however, three higher taxonomic groups were only recorded within Reno mattress habitat and one only within the eelgrass habitat. Fish assemblages differed significantly between the two established habitats. A Before-After-Control-Impact (BACI) investigation was used to assess the ecological impact of newly installed Reno mattresses in the Keurbooms Estuary. Zostera capensis extent was sampled by determining the percentage cover of 0.5 m X 0.5 m quadrats and measurements of eelgrass blades. Percentage cover and blade length decreased during the installation of Reno mattress, but then recovered shortly after completion of the installation. Abundances, richness and diversity of invertebrates and fish were found to be similar before and after the installation which suggests that the installation had no net negative impact on the site. The Reno mattresses were found to attract fauna typical of rocky shore environments as well as a few invasive alien invertebrate species. This study noted that a hybrid habitat of Reno mattress and eelgrass was created and may in fact provide the positives of both to a system. In any coastal development it will be important to balance the demands of a growing population and the protection of natural habitats. The results of this study suggest that complex artificial structures such as Reno mattresses do provide habitat for fish and invertebrates. However, the use of these structures should be in combination with natural vegetation (e.g. as a hybrid habitat) and not one that replaces intertidal and subtidal natural habitat especially eelgrass. There is limited information regarding the ecological impacts of using Reno mattresses in estuaries and this study provides new information on their ecological efficacy that should be valuable for future coastal erosion control practices.
- Full Text:
- Date Issued: 2020
Effect of the nature of nanoparticles on the photophysicochemical properties and photodynamic antimicrobial chemotherapy of phthalocyanines
- Authors: Magadla, Aviwe
- Date: 2020
- Subjects: Nanoparticles , Phthalocyanines , Anti-infective agents -- Therapeutic use , Photochemotherapy , Photochemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123107 , vital:35406
- Description: In this work, the syntheses and characterisation of Zn monocaffeic acid tri–tert–butyl phthalocyanine (1), Zn monocarboxyphenoxy tri– tert–butylphenoxyl phthalocyanine (2), tetrakis phenoxy N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (3) and tetrakis N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (5) are presented. Complexes 3 and 5 were further quartenised with 1,3- propanesultone to form corresponding complexes (4) and (6), respectively. Complexes 1 and 2 were covalently linked to amino functionalised nanoparticles (NPs). Complexes 3, 4, 5 and 6 where linked to oleic acid/oleylamine capped (OLA/OLM) silver-iron dimers (Ag-Fe3O4 OLA/OLM) and silver-iron core shell (Ag@Fe3O4 OLA/OLM) NPs via interaction between the nanoparticles and the imino group on the phthalocyanines. The phthalocyanine-NP conjugates afforded an increase in triplet quantum yields with a corresponding decrease in fluorescence quantum yield as compared to the phthalocyanine complexes alone. Complexes 3, 4 and their conjugates were then used for photodynamic antimicrobial chemotherapy on E. coli. The zwitterionic photosensitiser 4 and its conjugates showed better efficiency for photodynamic antimicrobial chemotherapy compared to their neutral counterparts.
- Full Text:
- Date Issued: 2020
- Authors: Magadla, Aviwe
- Date: 2020
- Subjects: Nanoparticles , Phthalocyanines , Anti-infective agents -- Therapeutic use , Photochemotherapy , Photochemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123107 , vital:35406
- Description: In this work, the syntheses and characterisation of Zn monocaffeic acid tri–tert–butyl phthalocyanine (1), Zn monocarboxyphenoxy tri– tert–butylphenoxyl phthalocyanine (2), tetrakis phenoxy N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (3) and tetrakis N,N-dimethyl-4-(methylimino) phthalocyanine indium (III) chloride (5) are presented. Complexes 3 and 5 were further quartenised with 1,3- propanesultone to form corresponding complexes (4) and (6), respectively. Complexes 1 and 2 were covalently linked to amino functionalised nanoparticles (NPs). Complexes 3, 4, 5 and 6 where linked to oleic acid/oleylamine capped (OLA/OLM) silver-iron dimers (Ag-Fe3O4 OLA/OLM) and silver-iron core shell (Ag@Fe3O4 OLA/OLM) NPs via interaction between the nanoparticles and the imino group on the phthalocyanines. The phthalocyanine-NP conjugates afforded an increase in triplet quantum yields with a corresponding decrease in fluorescence quantum yield as compared to the phthalocyanine complexes alone. Complexes 3, 4 and their conjugates were then used for photodynamic antimicrobial chemotherapy on E. coli. The zwitterionic photosensitiser 4 and its conjugates showed better efficiency for photodynamic antimicrobial chemotherapy compared to their neutral counterparts.
- Full Text:
- Date Issued: 2020
Effectiveness of different interventions to reduce occupational sitting among office administrators at Rhodes University
- Authors: Malesa, Thato
- Date: 2020
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering , Compliance
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166403 , vital:41360
- Description: Background: Sitting for prolonged periods is common in the working environment. Office workers are exposed to long periods of sitting time at work. Research has reported associations between prolonged sitting and negative health implications. As such studies have proposed different interventions aimed at reducing sitting times in the workplace. The aim of the current study was to evaluate the effectiveness of two different interventions, physical intervention (sit-stand worktables) and personal intervention (instruction to stretch) on compliance and reducing occupational sitting behaviour. The study also aimed to investigate the effectiveness of interventions in improving or impairing mood. Methods: The study took the form of a fieldbased study atRhodes University, Makhanda, South Africa. Fifteen full–time office workers in different divisions participated in the study. Participants were randomly allocated to either the physical or personal intervention group. In both intervention groups, partic ipants were prompted to stand for five minutes every hour during the workday to either work in a standing position or perform stretches. Over the course of the experiment, desk occupancy, sitting/standing time and mood effect were recorded in both intervention groups Both intervention groups were monitored for a period of three months (58 days). Results: The study found that the physical intervention group was an effective approach to reduce prolonged sitting in the workplace in comparison to the personal intervention group. Over the course of the experiment, there was sustain usage of interventions in both groups, however, in the physical intervention group desk usage decreased overtime. The findings of the study also show that some participants were more compliant with the study procedures than others. It was also found that mood improved upon introducing interventions in the workplace. However, with the outcomes of the results, the study acknowledges that several factors emerged which are likely to impact compliance, which future studies may investigate. Conclusion: Although sit-stand worktables are expensive, it seems like introducing them was successful in reducing sitting time and changing sitting behaviour in comparison to an intervention that instruct s individuals to stand up and stretch.
- Full Text:
- Date Issued: 2020
- Authors: Malesa, Thato
- Date: 2020
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering , Compliance
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166403 , vital:41360
- Description: Background: Sitting for prolonged periods is common in the working environment. Office workers are exposed to long periods of sitting time at work. Research has reported associations between prolonged sitting and negative health implications. As such studies have proposed different interventions aimed at reducing sitting times in the workplace. The aim of the current study was to evaluate the effectiveness of two different interventions, physical intervention (sit-stand worktables) and personal intervention (instruction to stretch) on compliance and reducing occupational sitting behaviour. The study also aimed to investigate the effectiveness of interventions in improving or impairing mood. Methods: The study took the form of a fieldbased study atRhodes University, Makhanda, South Africa. Fifteen full–time office workers in different divisions participated in the study. Participants were randomly allocated to either the physical or personal intervention group. In both intervention groups, partic ipants were prompted to stand for five minutes every hour during the workday to either work in a standing position or perform stretches. Over the course of the experiment, desk occupancy, sitting/standing time and mood effect were recorded in both intervention groups Both intervention groups were monitored for a period of three months (58 days). Results: The study found that the physical intervention group was an effective approach to reduce prolonged sitting in the workplace in comparison to the personal intervention group. Over the course of the experiment, there was sustain usage of interventions in both groups, however, in the physical intervention group desk usage decreased overtime. The findings of the study also show that some participants were more compliant with the study procedures than others. It was also found that mood improved upon introducing interventions in the workplace. However, with the outcomes of the results, the study acknowledges that several factors emerged which are likely to impact compliance, which future studies may investigate. Conclusion: Although sit-stand worktables are expensive, it seems like introducing them was successful in reducing sitting time and changing sitting behaviour in comparison to an intervention that instruct s individuals to stand up and stretch.
- Full Text:
- Date Issued: 2020
Efficacy of the rind physiological disorder oleocellosis control measures in lemon fruit (Citrus limon) under shade netting
- Authors: Njili, Zamazima
- Date: 2020
- Subjects: Citrus fruits--Storage--Diseases and injuries , Citrus--Diseases and pests Citrus fruit industry Citrus products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49237 , vital:41613
- Description: Lemon growers aim to produce fruit with no blemishes on the rind. Fruit without blemishes is regarded as high value fruit required for the export market. Leakage of phytotoxic oil from the rind tissues damages them and results in the development of oleocellosis symptoms. Four experiments were conducted to investigate methods of avoiding and controlling the development of oleocellosis during harvest and post-harvest handling. The first experiment indicated that the rind oil release pressure (RORP) test is the method most effective at predicting oleocellosis incidents. The experiment also suggested that fruit not exposed to the sun are the most susceptible to oleocellosis due to low temperatures that cause high turgidity. Oleocellosis results when turgid fruit is mishandled. A cultivar experiment was carried out to ascertain the lemon cultivar most susceptible to oleocellosis. The results show that the Limoneira cultivar is the most susceptible to oleocellosis and 2PH seedless is the least susceptible cultivar when compared to other lemon cultivars such as Lisbon, Eureka and Genoa. When the use of shade netting was tested to determine its effect on oleocellosis severity, it was found that using shade netting did not have an effect. Fruit grown under shade netting had the same colour and average diameter as fruit grown in an open orchard. In the same experiment, mature fruit were shown to be more susceptible to oleocellosis than immature fruit. The final part of the project investigated harvesting and post-harvest practices to determine those that cause oleocellosis the most. It was found that fruit after degreening had greater oleocellosis due to exposure to moisture conditions and rough handling. Another practice that results in oleocellosis occurs before waxing when the fruit was roughly transferred from the bins into the packline. The third oleocellosis inducing practice was moving fruit along the conveyor belt while it is turgid. Improvement of handling procedures to reduce oleocellosis can increase export volume and result in higher value of fruit per carton.
- Full Text:
- Date Issued: 2020
- Authors: Njili, Zamazima
- Date: 2020
- Subjects: Citrus fruits--Storage--Diseases and injuries , Citrus--Diseases and pests Citrus fruit industry Citrus products
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/49237 , vital:41613
- Description: Lemon growers aim to produce fruit with no blemishes on the rind. Fruit without blemishes is regarded as high value fruit required for the export market. Leakage of phytotoxic oil from the rind tissues damages them and results in the development of oleocellosis symptoms. Four experiments were conducted to investigate methods of avoiding and controlling the development of oleocellosis during harvest and post-harvest handling. The first experiment indicated that the rind oil release pressure (RORP) test is the method most effective at predicting oleocellosis incidents. The experiment also suggested that fruit not exposed to the sun are the most susceptible to oleocellosis due to low temperatures that cause high turgidity. Oleocellosis results when turgid fruit is mishandled. A cultivar experiment was carried out to ascertain the lemon cultivar most susceptible to oleocellosis. The results show that the Limoneira cultivar is the most susceptible to oleocellosis and 2PH seedless is the least susceptible cultivar when compared to other lemon cultivars such as Lisbon, Eureka and Genoa. When the use of shade netting was tested to determine its effect on oleocellosis severity, it was found that using shade netting did not have an effect. Fruit grown under shade netting had the same colour and average diameter as fruit grown in an open orchard. In the same experiment, mature fruit were shown to be more susceptible to oleocellosis than immature fruit. The final part of the project investigated harvesting and post-harvest practices to determine those that cause oleocellosis the most. It was found that fruit after degreening had greater oleocellosis due to exposure to moisture conditions and rough handling. Another practice that results in oleocellosis occurs before waxing when the fruit was roughly transferred from the bins into the packline. The third oleocellosis inducing practice was moving fruit along the conveyor belt while it is turgid. Improvement of handling procedures to reduce oleocellosis can increase export volume and result in higher value of fruit per carton.
- Full Text:
- Date Issued: 2020
Elucidation of the effect of cannabinoids on ER stress to determine their molecular mechanism of action in breast cancer cells
- Authors: De la Harpe, Amy
- Date: 2020
- Subjects: Endoplasmic reticulum -- Pathophysiology , Breast -- Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48213 , vital:40525
- Description: Endoplasmic reticulum (ER) stress is defined as an imbalance between the ER’s protein-folding load and folding capacity. ER stress is induced by various physiological conditions and subsequently triggers the activation of the unfolded protein response (UPR) to re-establish homeostasis and promote cell survival. However, under severe or chronic stress, apoptosis is induced. Normal cells generally do not experience ER stress; however, stressful conditions in the tumour micro-environment facilitates chronic ER stress and UPR activation, which plays a pivotal role in tumour survival. Exacerbation of pre-existing ER stress can trigger cancer cell death, with a minimal effect on normal cells. Currently, no high-throughput method exists to detect and quantify ER stress in cell lines. This study showed that Thioflavin T, a fluorescent dye that binds to misfolded protein aggregates, can be used for the high-throughput detection of ER stress, and provides several advantages over currently used methods. Current literature suggests that cannabinoid treatment may induce cancer cell death via ER stress, however little is known about the mechanism of induction. This study proposed a mechanism that occurs via the influx of Ca2+ via the vanilloid receptor 1 (TRPV1), and subsequent ROS production, which affects protein folding. ER stress was induced using various cannabinoids and measured using Thioflavin T and western blot analysis. The effect of cannabinoid treatment on ROS production and the intracellular Ca2+ concentration was measured. Cannabidiol (CBD) was the most potent ER stress inducer, significantly increasing Ca2+ and ROS accumulation; however, the level of accumulated Ca2+ across cell lines varied, which may be due to the differences in the TRPV1 expression and localization. Concomitant treatment of CBD with an antioxidant significantly increased cell viability and decreased ER stress induction in the MCF7 cell line. Concomitant treatment with a TRPV1 antagonist increased viability in this cell line. In conclusion, the results suggested that CBD may induce ER stress via Ca2+ influx through the TRPV1 receptor, thereby elevating intracellular ROS levels and disrupting protein folding.
- Full Text:
- Date Issued: 2020
- Authors: De la Harpe, Amy
- Date: 2020
- Subjects: Endoplasmic reticulum -- Pathophysiology , Breast -- Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48213 , vital:40525
- Description: Endoplasmic reticulum (ER) stress is defined as an imbalance between the ER’s protein-folding load and folding capacity. ER stress is induced by various physiological conditions and subsequently triggers the activation of the unfolded protein response (UPR) to re-establish homeostasis and promote cell survival. However, under severe or chronic stress, apoptosis is induced. Normal cells generally do not experience ER stress; however, stressful conditions in the tumour micro-environment facilitates chronic ER stress and UPR activation, which plays a pivotal role in tumour survival. Exacerbation of pre-existing ER stress can trigger cancer cell death, with a minimal effect on normal cells. Currently, no high-throughput method exists to detect and quantify ER stress in cell lines. This study showed that Thioflavin T, a fluorescent dye that binds to misfolded protein aggregates, can be used for the high-throughput detection of ER stress, and provides several advantages over currently used methods. Current literature suggests that cannabinoid treatment may induce cancer cell death via ER stress, however little is known about the mechanism of induction. This study proposed a mechanism that occurs via the influx of Ca2+ via the vanilloid receptor 1 (TRPV1), and subsequent ROS production, which affects protein folding. ER stress was induced using various cannabinoids and measured using Thioflavin T and western blot analysis. The effect of cannabinoid treatment on ROS production and the intracellular Ca2+ concentration was measured. Cannabidiol (CBD) was the most potent ER stress inducer, significantly increasing Ca2+ and ROS accumulation; however, the level of accumulated Ca2+ across cell lines varied, which may be due to the differences in the TRPV1 expression and localization. Concomitant treatment of CBD with an antioxidant significantly increased cell viability and decreased ER stress induction in the MCF7 cell line. Concomitant treatment with a TRPV1 antagonist increased viability in this cell line. In conclusion, the results suggested that CBD may induce ER stress via Ca2+ influx through the TRPV1 receptor, thereby elevating intracellular ROS levels and disrupting protein folding.
- Full Text:
- Date Issued: 2020
Evaluation of an NADPH-dependent assay for inhibition screening of Salmonella enterica DOXP Reguctoisomerase for identification of novel drug hit compounds
- Authors: Ngcongco, Khanyisile
- Date: 2020
- Subjects: 1-Deoxy-D-xylulose 5-phosphate , Antibiotics , Drug development , Salmonella , Enterobacteriaceae , Vaccines , Plasmodium falciparum , Mycobacterium tuberculosis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167132 , vital:41440
- Description: Invasive non-typhoidal Salmonella, caused by the intracellular pathogen Salmonella enterica, has emerged as a major cause of bloodstream infections. It remains a neglected infection responsible for many deaths in Africa, as it fails to receive the level of support that is given to most better known infections. There are currently no vaccines against invasive non-typhoidal Salmonella. First-line antibiotics have been used for treatment, however, the rise in the resistance of the bacteria against these antibiotics has made treatment of invasive salmonellosis into a clinical problem. Therefore, the discovery of new compounds for the development of antibiotic drugs is required. Central metabolic pathways can be a useful source for identifying drug targets and among these is the non-mevalonate pathway, one of the pathways used for the biosynthesis of isoprenoid precursors. The second step of the non-mevalonate pathway involves the NADPH-dependent reduction of 1-deoxy-D-xylulose 5-phosphate (DOXP) into 2-C-methyl-D-erythritol 4-phosphate (MEP). 1-Deoxy-D-xylulose 5-phosphate (DOXP) reductoisomerase plays a vital role in the catalysis of this reaction and requires NADPH and divalent metal cations as co-factors for its activity. In this investigation recombinant DOXP reductoisomerase from Salmonella enterica, Plasmodium falciparum and Mycobacterium tuberculosis were biochemically characterized as potential targets for developing drugs that could be used as treatment of the disease. The expression and nickel-chelate affinity purification of S. enterica DOXP reductoisomerase in a fully functional native state was successfully achieved. However, the expression and purification of P. falciparum DXR and M. tuberculosis DXR was unsuccessful due to the formation of insoluble inclusion bodies. Although alternative purification strategies were explored, including dialysis and slow dilution, these proteins remained insoluble, making their functional analysis not possible. An NADPH-dependent enzyme assay was used to determine the activity of S. enterica DXR. This assay monitors the reduction of DOXP to MEP by measuring the absorbance at 340 nm, which reflects the concentration of NADPH. An alternative assay, resazurin reduction, which monitors the NADPH-dependent reduction of resazurin to resorufin, was explored for detecting enzyme activity. The recombinant S. enterica DOXP reductoisomerase had a specific activity of 0.126 ± 0.0014 μmol/min/mg protein and a Km and Vmax of 881 μM and 0.249 μmol/min/mg respectively. FR900098, a derivative of fosmidomycin, is a well-known inhibitor of DXR, however, the sensitivity of S. enterica DXR towards FR900098 has not yet been reported. The NADPH dependent enzyme and resazurin reduction assays were used to determine whether FR900098 has enzyme inhibitory effects against S. enterica DXR. Upon confirming that FR900098 is able to inhibit S. enterica DXR, FR900098 was used as a control compound in the screening of novel compounds. The S. enterica DXR enzyme was screened for inhibition by the collection of compounds from the Pathogen Box. Compounds that exhibited the desired inhibitory activity, referred to as ‘hits’ were selected for further investigation. These hits were confirmed using the NADPH-dependent enzyme assay, resulting in the identification of two different DXR inhibitor compounds, MMV002816, also known as diethylcarbamazine, and MMV228911. The inhibitory concentration (IC50) values of FR900098, MMV002816 and MMV228911 against S. enterica DXR were 1.038 μM, 2.173 μM and 6.861 μM respectively. The binding mode of these compounds to S. enterica DXR could lead to the discovery of novel druggable sites on the enzyme and stimulate the development of new antibiotics that can be used for treating Salmonella infections.
- Full Text:
- Date Issued: 2020
- Authors: Ngcongco, Khanyisile
- Date: 2020
- Subjects: 1-Deoxy-D-xylulose 5-phosphate , Antibiotics , Drug development , Salmonella , Enterobacteriaceae , Vaccines , Plasmodium falciparum , Mycobacterium tuberculosis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167132 , vital:41440
- Description: Invasive non-typhoidal Salmonella, caused by the intracellular pathogen Salmonella enterica, has emerged as a major cause of bloodstream infections. It remains a neglected infection responsible for many deaths in Africa, as it fails to receive the level of support that is given to most better known infections. There are currently no vaccines against invasive non-typhoidal Salmonella. First-line antibiotics have been used for treatment, however, the rise in the resistance of the bacteria against these antibiotics has made treatment of invasive salmonellosis into a clinical problem. Therefore, the discovery of new compounds for the development of antibiotic drugs is required. Central metabolic pathways can be a useful source for identifying drug targets and among these is the non-mevalonate pathway, one of the pathways used for the biosynthesis of isoprenoid precursors. The second step of the non-mevalonate pathway involves the NADPH-dependent reduction of 1-deoxy-D-xylulose 5-phosphate (DOXP) into 2-C-methyl-D-erythritol 4-phosphate (MEP). 1-Deoxy-D-xylulose 5-phosphate (DOXP) reductoisomerase plays a vital role in the catalysis of this reaction and requires NADPH and divalent metal cations as co-factors for its activity. In this investigation recombinant DOXP reductoisomerase from Salmonella enterica, Plasmodium falciparum and Mycobacterium tuberculosis were biochemically characterized as potential targets for developing drugs that could be used as treatment of the disease. The expression and nickel-chelate affinity purification of S. enterica DOXP reductoisomerase in a fully functional native state was successfully achieved. However, the expression and purification of P. falciparum DXR and M. tuberculosis DXR was unsuccessful due to the formation of insoluble inclusion bodies. Although alternative purification strategies were explored, including dialysis and slow dilution, these proteins remained insoluble, making their functional analysis not possible. An NADPH-dependent enzyme assay was used to determine the activity of S. enterica DXR. This assay monitors the reduction of DOXP to MEP by measuring the absorbance at 340 nm, which reflects the concentration of NADPH. An alternative assay, resazurin reduction, which monitors the NADPH-dependent reduction of resazurin to resorufin, was explored for detecting enzyme activity. The recombinant S. enterica DOXP reductoisomerase had a specific activity of 0.126 ± 0.0014 μmol/min/mg protein and a Km and Vmax of 881 μM and 0.249 μmol/min/mg respectively. FR900098, a derivative of fosmidomycin, is a well-known inhibitor of DXR, however, the sensitivity of S. enterica DXR towards FR900098 has not yet been reported. The NADPH dependent enzyme and resazurin reduction assays were used to determine whether FR900098 has enzyme inhibitory effects against S. enterica DXR. Upon confirming that FR900098 is able to inhibit S. enterica DXR, FR900098 was used as a control compound in the screening of novel compounds. The S. enterica DXR enzyme was screened for inhibition by the collection of compounds from the Pathogen Box. Compounds that exhibited the desired inhibitory activity, referred to as ‘hits’ were selected for further investigation. These hits were confirmed using the NADPH-dependent enzyme assay, resulting in the identification of two different DXR inhibitor compounds, MMV002816, also known as diethylcarbamazine, and MMV228911. The inhibitory concentration (IC50) values of FR900098, MMV002816 and MMV228911 against S. enterica DXR were 1.038 μM, 2.173 μM and 6.861 μM respectively. The binding mode of these compounds to S. enterica DXR could lead to the discovery of novel druggable sites on the enzyme and stimulate the development of new antibiotics that can be used for treating Salmonella infections.
- Full Text:
- Date Issued: 2020
Evaluation of Baited Remote Underwater Video Systems (BRUVS) for monitoring fish communities in Lake Malawi/Niassa
- Authors: Van Wyk, Angus
- Date: 2020
- Subjects: Underwater videography -- Malawi , Chambo -- Malawi -- Monitoring , Fishes -- Malawi -- Monitoring , Oreochromis lidole -- Malawi -- Monitoring
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145546 , vital:38448
- Description: Baited Remote Underwater Video systems (BRUVS) have become a well-established in-situ monitoring technique in clearwater aquatic ecosystems. The relatively low cost, nondestructive and non-extractive nature of this technique permits BRUVS to be employed in a wide range of habitats. To date, the vast majority of studies using BRUVS technology have been conducted in marine habitats. Subsequently, BRUVS applications in freshwater habitats are scant, and techniques are not well developed. The primary objective of this thesis was to address this knowledge gap and develop standard operating procedures for BRUVS employment in Lake Malawi/Niassa and explore the potential of BRUVS as a monitoring tool for fish communities in the African Great Lakes. Eight easily identifiable species groups, representative of Lake Malawi/Niassa inshore fish communities, were used to develop the technique. The optimal BRUVS deployment time to obtain 95 % species accumulation was achieved in a 15-minute recording period. Power analysis, using a pre-determined 80 % power, a confidence interval of 95 % and a significance level of < 0.05 was used to determine annual sampling effort requirements for each species group. The power analysis was performed to detect a 10 % change in abundance over a hypothetical 10-year monitoring scenario. In areas where fish abundance was lower, the sampling effort required to monitor key fisheries species was significantly higher. For example, Chambo, the local Oreochromis (Nyasalapia) species flock, required an annual sampling effort of 120 deployments in Malawi compared to 56 in Mozambique ( < 0.05). Chambo had a higher detection probability in areas of lesser fishing pressure and were found in higher abundances in deeper, less accessible habitats. Deep-water (> 20 m) and rocky habitats were most important in explaining Chambo abundance and detection probability. The size-structure of Chambo in Lake Malawi/Niassa reflects size-specific depth and habitat migrations. Larger Chambo were observed aggregating in waters deeper than 20 m and a broader size range of individuals were observed utilising structured habitat. The effects of fishing are apparent in the size-structure of Chambo in the areas sampled. In study areas exposed to greater levels of fishing pressure – such as Malawi, the BRUVS detected significantly fewer individuals within sexually mature size classes, and the average size was smaller than in areas with less exploitation.
- Full Text:
- Date Issued: 2020
- Authors: Van Wyk, Angus
- Date: 2020
- Subjects: Underwater videography -- Malawi , Chambo -- Malawi -- Monitoring , Fishes -- Malawi -- Monitoring , Oreochromis lidole -- Malawi -- Monitoring
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145546 , vital:38448
- Description: Baited Remote Underwater Video systems (BRUVS) have become a well-established in-situ monitoring technique in clearwater aquatic ecosystems. The relatively low cost, nondestructive and non-extractive nature of this technique permits BRUVS to be employed in a wide range of habitats. To date, the vast majority of studies using BRUVS technology have been conducted in marine habitats. Subsequently, BRUVS applications in freshwater habitats are scant, and techniques are not well developed. The primary objective of this thesis was to address this knowledge gap and develop standard operating procedures for BRUVS employment in Lake Malawi/Niassa and explore the potential of BRUVS as a monitoring tool for fish communities in the African Great Lakes. Eight easily identifiable species groups, representative of Lake Malawi/Niassa inshore fish communities, were used to develop the technique. The optimal BRUVS deployment time to obtain 95 % species accumulation was achieved in a 15-minute recording period. Power analysis, using a pre-determined 80 % power, a confidence interval of 95 % and a significance level of < 0.05 was used to determine annual sampling effort requirements for each species group. The power analysis was performed to detect a 10 % change in abundance over a hypothetical 10-year monitoring scenario. In areas where fish abundance was lower, the sampling effort required to monitor key fisheries species was significantly higher. For example, Chambo, the local Oreochromis (Nyasalapia) species flock, required an annual sampling effort of 120 deployments in Malawi compared to 56 in Mozambique ( < 0.05). Chambo had a higher detection probability in areas of lesser fishing pressure and were found in higher abundances in deeper, less accessible habitats. Deep-water (> 20 m) and rocky habitats were most important in explaining Chambo abundance and detection probability. The size-structure of Chambo in Lake Malawi/Niassa reflects size-specific depth and habitat migrations. Larger Chambo were observed aggregating in waters deeper than 20 m and a broader size range of individuals were observed utilising structured habitat. The effects of fishing are apparent in the size-structure of Chambo in the areas sampled. In study areas exposed to greater levels of fishing pressure – such as Malawi, the BRUVS detected significantly fewer individuals within sexually mature size classes, and the average size was smaller than in areas with less exploitation.
- Full Text:
- Date Issued: 2020
Exploring Quinolinyl-Thiazolidinedione hybrid compounds as potential anti-tubercular agents
- Authors: Mtshare, Thanduxolo Elihle
- Date: 2020
- Subjects: Quinoline , Mycobacterium tuberculosis , Tuberculosis -- Chemotherapy , Plasmodium falciparum , Thiazolidinedione
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143314 , vital:38232
- Description: Tuberculosis (TB) is an infectious disease caused by the pathogen, Mycobacterium tuberculosis. According to the World Health Organization, TB is the ninth leading cause of death worldwide ranking above HIV/AIDS. This high mortality rate of TB begs the questions about the efficiency of the current therapy and raises an urgent need to create novel anti-tuberculosis agents which will aid in curbing this burden. Quinoline containing compounds have remarkable biological activities across a wide spectrum of diseases including anti-tuberculosis. On the other hand, thiazolidinedione containing compounds possess a broad spectrum of biological properties. In this study, we rationally designed compounds containing these pharmacophoric units and investigated them for their potential biological activity against Mycobacterium tuberculosis. Considering antimalarial activity of quinoline-based compounds, the compounds achieved were also cross-screened for their activity against the Plasmodium falciparum parasite, a causative agent of malaria. In all the synthesized compounds, compound 2.6a, 2.6b and 2.7b emerged as most active compounds against the H37Rv strain with MIC₉₀ values ranging in between of 1.08 – 17.1 μM. In addition, none of the compounds showed any inhibitory activities against the 3D7 strain of P. falciparum parasite. All the compounds prepared in this study showed no significant human cytotoxic effects as measured by HeLa cell line.
- Full Text:
- Date Issued: 2020
- Authors: Mtshare, Thanduxolo Elihle
- Date: 2020
- Subjects: Quinoline , Mycobacterium tuberculosis , Tuberculosis -- Chemotherapy , Plasmodium falciparum , Thiazolidinedione
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/143314 , vital:38232
- Description: Tuberculosis (TB) is an infectious disease caused by the pathogen, Mycobacterium tuberculosis. According to the World Health Organization, TB is the ninth leading cause of death worldwide ranking above HIV/AIDS. This high mortality rate of TB begs the questions about the efficiency of the current therapy and raises an urgent need to create novel anti-tuberculosis agents which will aid in curbing this burden. Quinoline containing compounds have remarkable biological activities across a wide spectrum of diseases including anti-tuberculosis. On the other hand, thiazolidinedione containing compounds possess a broad spectrum of biological properties. In this study, we rationally designed compounds containing these pharmacophoric units and investigated them for their potential biological activity against Mycobacterium tuberculosis. Considering antimalarial activity of quinoline-based compounds, the compounds achieved were also cross-screened for their activity against the Plasmodium falciparum parasite, a causative agent of malaria. In all the synthesized compounds, compound 2.6a, 2.6b and 2.7b emerged as most active compounds against the H37Rv strain with MIC₉₀ values ranging in between of 1.08 – 17.1 μM. In addition, none of the compounds showed any inhibitory activities against the 3D7 strain of P. falciparum parasite. All the compounds prepared in this study showed no significant human cytotoxic effects as measured by HeLa cell line.
- Full Text:
- Date Issued: 2020
Finite precision arithmetic in Polyphase Filterbank implementations
- Authors: Myburgh, Talon
- Date: 2020
- Subjects: Radio interferometers , Interferometry , Radio telescopes , Gate array circuits , Floating-point arithmetic , Python (Computer program language) , Polyphase Filterbank , Finite precision arithmetic , MeerKAT
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146187 , vital:38503
- Description: The MeerKAT is the most sensitive radio telescope in its class, and it is important that systematic effects do not limit the dynamic range of the instrument, preventing this sensitivity from being harnessed for deep integrations. During commissioning, spurious artefacts were noted in the MeerKAT passband and the root cause was attributed to systematic errors in the digital signal path. Finite precision arithmetic used by the Polyphase Filterbank (PFB) was one of the main factors contributing to the spurious responses, together with bugs in the firmware. This thesis describes a software PFB simulator that was built to mimic the MeerKAT PFB and allow investigation into the origin and mitigation of the effects seen on the telescope. This simulator was used to investigate the effects in signal integrity of various rounding techniques, overflow strategies and dual polarisation processing in the PFB. Using the simulator to investigate a number of different signal levels, bit-width and algorithmic scenarios, it gave insight into how the periodic dips occurring in the MeerKAT passband were the result of the implementation using an inappropriate rounding strategy. It further indicated how to select the best strategy for preventing overflow while maintaining high quantization effciency in the FFT. This practice of simulating the design behaviour in the PFB independently of the tools used to design the DSP firmware, is a step towards an end-to-end simulation of the MeerKAT system (or any radio telescope using nite precision digital signal processing systems). This would be useful for design, diagnostics, signal analysis and prototyping of the overall instrument.
- Full Text:
- Date Issued: 2020
- Authors: Myburgh, Talon
- Date: 2020
- Subjects: Radio interferometers , Interferometry , Radio telescopes , Gate array circuits , Floating-point arithmetic , Python (Computer program language) , Polyphase Filterbank , Finite precision arithmetic , MeerKAT
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146187 , vital:38503
- Description: The MeerKAT is the most sensitive radio telescope in its class, and it is important that systematic effects do not limit the dynamic range of the instrument, preventing this sensitivity from being harnessed for deep integrations. During commissioning, spurious artefacts were noted in the MeerKAT passband and the root cause was attributed to systematic errors in the digital signal path. Finite precision arithmetic used by the Polyphase Filterbank (PFB) was one of the main factors contributing to the spurious responses, together with bugs in the firmware. This thesis describes a software PFB simulator that was built to mimic the MeerKAT PFB and allow investigation into the origin and mitigation of the effects seen on the telescope. This simulator was used to investigate the effects in signal integrity of various rounding techniques, overflow strategies and dual polarisation processing in the PFB. Using the simulator to investigate a number of different signal levels, bit-width and algorithmic scenarios, it gave insight into how the periodic dips occurring in the MeerKAT passband were the result of the implementation using an inappropriate rounding strategy. It further indicated how to select the best strategy for preventing overflow while maintaining high quantization effciency in the FFT. This practice of simulating the design behaviour in the PFB independently of the tools used to design the DSP firmware, is a step towards an end-to-end simulation of the MeerKAT system (or any radio telescope using nite precision digital signal processing systems). This would be useful for design, diagnostics, signal analysis and prototyping of the overall instrument.
- Full Text:
- Date Issued: 2020
Flammability of indigenous and invasive alien woody plants in coastal fynbos and thicket
- Msweli, Samukelisiwe Tholakele, Potts, Alastair J
- Authors: Msweli, Samukelisiwe Tholakele , Potts, Alastair J
- Date: 2020
- Subjects: Forest fires -- Environmental aspects , Forest fires -- Prevention and control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45875 , vital:39313
- Description: Globally, extreme fires have become more common in wildland-urban interface areas, and more recently, along the southern Cape coast of South Africa. The 2017 Knysna fires prompted greater understanding of the flammability of, and the fire risk posed by, different vegetation groups, which is essential to develop fire risk mitigation strategies. In this study, I experimentally assessed flammability of 30 woody plant species from the vegetation groups indigenous fynbos, thicket, and invasive alien plants (IAPs) that occur along the southern Cape coast. Live plant shoots were sampled across varying fire weather conditions and burnt experimentally to measure flammability in relation to fire weather conditions, fuel moisture, and fuel load. Flammability measures considered were: burn intensity, completeness of burn, time-to-ignition, and the likelihood of spontaneous ignition. I further assessed the flammability of partially dried plant material as a crude proxy for drought effects, to ascertain whether drying of fuels would differentially affect the flammability of the vegetation groups. I used generalized linear mixed-effects models to assess flammability measures in relation to the predictor variables: fire weather, fuel moisture, fuel load, vegetation groups, and species (as a random factor). Results showed that increasing severity of fire weather significantly increased flammability through increasing burn intensity, increasing completeness of burn, increasing the likelihood of spontaneous ignition, and also reducing time-to-ignition. Increasing fuel moisture significantly decreased burn intensity, completeness of burn, and the likelihood of spontaneous ignition. Fuel load significantly increased burn intensity and time-to-ignition. Flammability was highest in IAPs, intermediate in fynbos, and lowest in thicket. IAPs and fynbos showed significantly higher ignitability, and thus present risks under moderate and high fire weather conditions, whereas thicket presents lower risks under low and moderate fire weather conditions. The drying out of fuels considerably increased flammability equally in the three vegetation groups, and by implication, fire risk due to an increase in dead:live ratio. Flammability was furthermore assessed in relation to fuel traits, i.e. the proportion of fine fuels, coarse fuels, and dead fuels, fuel bed porosity, fuel load, and fuel moisture, using multiple regression analysis and stepwise selection of factors. This revealed that fuel moisture was the most important factor affecting flammability in terms of all the flammability measures. Results further showed that the increase in v the proportions of fine fuels increased flammability by increasing completeness of burn. Lastly, vegetation groups were compared (using Kruskal Wallis) in terms of their flammability and fuel traits. I found that fynbos and IAPs exhibited greater flammability on account of higher completeness of burn and more rapid ignition than thicket species, but no clear distinction was evident between fynbos and IAPs. Fynbos’ high flammability was attributed to high proportions of fine and porous fuels. Thicket’s low flammability was attributed to high proportions of coarse and dense fuels. Little distinction in fuel traits could be made between fynbos and IAPs, except that fynbos had a greater proportion of fine fuels. There is a potential risk posed by the IAPs in terms of increased flammability and fire severity, on an indigenous landscape that is invaded. Fire managers need to encourage the prioritization of the management of IAPs that present high flammability as an attempt to reduce fire risk along the southern Cape coast of South Africa.
- Full Text:
- Date Issued: 2020
- Authors: Msweli, Samukelisiwe Tholakele , Potts, Alastair J
- Date: 2020
- Subjects: Forest fires -- Environmental aspects , Forest fires -- Prevention and control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45875 , vital:39313
- Description: Globally, extreme fires have become more common in wildland-urban interface areas, and more recently, along the southern Cape coast of South Africa. The 2017 Knysna fires prompted greater understanding of the flammability of, and the fire risk posed by, different vegetation groups, which is essential to develop fire risk mitigation strategies. In this study, I experimentally assessed flammability of 30 woody plant species from the vegetation groups indigenous fynbos, thicket, and invasive alien plants (IAPs) that occur along the southern Cape coast. Live plant shoots were sampled across varying fire weather conditions and burnt experimentally to measure flammability in relation to fire weather conditions, fuel moisture, and fuel load. Flammability measures considered were: burn intensity, completeness of burn, time-to-ignition, and the likelihood of spontaneous ignition. I further assessed the flammability of partially dried plant material as a crude proxy for drought effects, to ascertain whether drying of fuels would differentially affect the flammability of the vegetation groups. I used generalized linear mixed-effects models to assess flammability measures in relation to the predictor variables: fire weather, fuel moisture, fuel load, vegetation groups, and species (as a random factor). Results showed that increasing severity of fire weather significantly increased flammability through increasing burn intensity, increasing completeness of burn, increasing the likelihood of spontaneous ignition, and also reducing time-to-ignition. Increasing fuel moisture significantly decreased burn intensity, completeness of burn, and the likelihood of spontaneous ignition. Fuel load significantly increased burn intensity and time-to-ignition. Flammability was highest in IAPs, intermediate in fynbos, and lowest in thicket. IAPs and fynbos showed significantly higher ignitability, and thus present risks under moderate and high fire weather conditions, whereas thicket presents lower risks under low and moderate fire weather conditions. The drying out of fuels considerably increased flammability equally in the three vegetation groups, and by implication, fire risk due to an increase in dead:live ratio. Flammability was furthermore assessed in relation to fuel traits, i.e. the proportion of fine fuels, coarse fuels, and dead fuels, fuel bed porosity, fuel load, and fuel moisture, using multiple regression analysis and stepwise selection of factors. This revealed that fuel moisture was the most important factor affecting flammability in terms of all the flammability measures. Results further showed that the increase in v the proportions of fine fuels increased flammability by increasing completeness of burn. Lastly, vegetation groups were compared (using Kruskal Wallis) in terms of their flammability and fuel traits. I found that fynbos and IAPs exhibited greater flammability on account of higher completeness of burn and more rapid ignition than thicket species, but no clear distinction was evident between fynbos and IAPs. Fynbos’ high flammability was attributed to high proportions of fine and porous fuels. Thicket’s low flammability was attributed to high proportions of coarse and dense fuels. Little distinction in fuel traits could be made between fynbos and IAPs, except that fynbos had a greater proportion of fine fuels. There is a potential risk posed by the IAPs in terms of increased flammability and fire severity, on an indigenous landscape that is invaded. Fire managers need to encourage the prioritization of the management of IAPs that present high flammability as an attempt to reduce fire risk along the southern Cape coast of South Africa.
- Full Text:
- Date Issued: 2020
Fluid characteristics in hydrothermal veins of the Twangiza-Namoya Gold Belt, South Kivu and Maniema Provinces, DRC
- Authors: Reid, Wesson Kyle
- Date: 2020
- Subjects: Gold ores -- Geology -- Kivu (Congo : Region) , Mineralogy -- Congo (Democratic Republic) , Hydrothermal deposits -- Congo (Democratic Republic) , Quartz -- Congo (Democratic Republic)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167314 , vital:41467
- Description: This study evaluates fluid variations in hydrothermal quartz veins from gold deposits in Kamiuga, Lugushwa and Namoya, located in the Twangiza-Namoya Gold Belt (TNGB) of the Kibara Belt in the eastern Democratic Republic of the Congo (DRC. Petrographic, fluid inclusion (FI) microthermometric observations and Raman spectroscopy provided qualitative and quantitative fluid composition data on the hydrothermal and magmatic fluids and their evolution during mineral precipitation. The formational fluids, based on genetically specific characteristics, were categorized into six distinct FI Types. Type 1 to 4 FIs are common in all TNGB fluids. Type 1 and 2 FIs are high salinity halite bearing FIs that indicate formation fluids that are predominantly metamorphic-sedimentary in source. CO2 vapour-bearing and the aqueous-saline CO2 liquid-bearing Type 3 FIs commonly contain CH4 and/or N2. Type 4 FIs are saline aqueous and commonly co-genetic with Type 1 and 2 FIs. Type 5 CO2-rich FIs contain either sulphide crystals, amorphous or crystalline carbon. Type 3 and 5 FIs indicate fluid sources rich in organic materials. Type 6 single aqueous-liquid phase FIs have no apour bubble, lacked a visible phase change on heating and were not thermometrically evaluated. The data indicated a high correlation between fluid composition and gold grades. High Au grade veins correlate with CO2 bearing Type 3 and 5 FIs -predominantly liquid-bearing CO2 fluids and quartz veins and fluids that contain increased organic material and sulphides. The polyphase quartz veins show highly variable homogenisation and formational temperatures exceeding 400°C. Formation conditions indicate high trapping temperatures in relation to the pressures at which fluids were captured. The high depth-temperature gradients are likely associated with mesothermal orogenic go ld deposition. Mineralisation is interpreted to have taken place as a result of mobilisation of fluids during the Pan African orogeny. Based on fluid petrography and microthermometry, gold mineralisation is most likely associated with secondary fluid influx from metamorphic sedimentary sourrces such as metapelites. The correlation between high gold grades and secondary fluids containing sulphides, high depth-temperature gradients, elevated CO2, CH4 and organic materials suggest black shales as a possible primary fluid and gold source. The development of variable and multiple fluid influx events and interactions with host rocks and imported materials resulted in complex polyphase quartz veins; the product of which created viable gold deposits throughout the TNGB. The six FI Types provides evidence of the diversity in the formation and evolution of gold deposits in the TNGB.
- Full Text:
- Date Issued: 2020
- Authors: Reid, Wesson Kyle
- Date: 2020
- Subjects: Gold ores -- Geology -- Kivu (Congo : Region) , Mineralogy -- Congo (Democratic Republic) , Hydrothermal deposits -- Congo (Democratic Republic) , Quartz -- Congo (Democratic Republic)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167314 , vital:41467
- Description: This study evaluates fluid variations in hydrothermal quartz veins from gold deposits in Kamiuga, Lugushwa and Namoya, located in the Twangiza-Namoya Gold Belt (TNGB) of the Kibara Belt in the eastern Democratic Republic of the Congo (DRC. Petrographic, fluid inclusion (FI) microthermometric observations and Raman spectroscopy provided qualitative and quantitative fluid composition data on the hydrothermal and magmatic fluids and their evolution during mineral precipitation. The formational fluids, based on genetically specific characteristics, were categorized into six distinct FI Types. Type 1 to 4 FIs are common in all TNGB fluids. Type 1 and 2 FIs are high salinity halite bearing FIs that indicate formation fluids that are predominantly metamorphic-sedimentary in source. CO2 vapour-bearing and the aqueous-saline CO2 liquid-bearing Type 3 FIs commonly contain CH4 and/or N2. Type 4 FIs are saline aqueous and commonly co-genetic with Type 1 and 2 FIs. Type 5 CO2-rich FIs contain either sulphide crystals, amorphous or crystalline carbon. Type 3 and 5 FIs indicate fluid sources rich in organic materials. Type 6 single aqueous-liquid phase FIs have no apour bubble, lacked a visible phase change on heating and were not thermometrically evaluated. The data indicated a high correlation between fluid composition and gold grades. High Au grade veins correlate with CO2 bearing Type 3 and 5 FIs -predominantly liquid-bearing CO2 fluids and quartz veins and fluids that contain increased organic material and sulphides. The polyphase quartz veins show highly variable homogenisation and formational temperatures exceeding 400°C. Formation conditions indicate high trapping temperatures in relation to the pressures at which fluids were captured. The high depth-temperature gradients are likely associated with mesothermal orogenic go ld deposition. Mineralisation is interpreted to have taken place as a result of mobilisation of fluids during the Pan African orogeny. Based on fluid petrography and microthermometry, gold mineralisation is most likely associated with secondary fluid influx from metamorphic sedimentary sourrces such as metapelites. The correlation between high gold grades and secondary fluids containing sulphides, high depth-temperature gradients, elevated CO2, CH4 and organic materials suggest black shales as a possible primary fluid and gold source. The development of variable and multiple fluid influx events and interactions with host rocks and imported materials resulted in complex polyphase quartz veins; the product of which created viable gold deposits throughout the TNGB. The six FI Types provides evidence of the diversity in the formation and evolution of gold deposits in the TNGB.
- Full Text:
- Date Issued: 2020
Formulation and evaluation of liposomal films for buccal delivery of antiretroviral drug
- Authors: Okafor, Nnamdi Ikemefuna
- Date: 2020
- Subjects: Liposomes , Highly active antiretroviral therapy , Antiretroviral agents , HIV infections -- Prevention
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/117161 , vital:34485
- Description: The human immune deficiency virus (HIV) infection has been ranked as one of the most devastating microbial infections in the world. This status is a result of the HIV rapid genetic variation, which limits discovery of a vaccine. Use application of antiretroviral therapy (ARVT) in treatment of the disease caused by the HIV infection (known as acquired immunodeficiency syndrome, HIV-AIDS) is frequently compromised by several factors such as the low bioavailability and severe adverse effects associated with the existing antiretroviral drugs (ARVDs). This underlines the need for controlling the pharmacokinetics profiles of ARVD using effective vehicles that can modify drug biodistribution. The same is true for many other conditions, where delivery systems can determine the success or failure of treatment by controlling pharmacokinetic and dynamic properties. The mucosal linings of the oral cavities in addition offer adorable route of administration for systematic drug delivery, improving drug therapeutic performance and often preferred by clinicians and patients. Liposomes are tiny spherical sacs of phospholipid molecules enclosing water droplets, formed (artificially) to carry drugs or other substances into the tissues by crossing and targeting to specific organelles. This work therefore focused on preparation of liposomes and liposomal buccal films (BFs) for potential buccal delivery of efavirenz, an ARVD model endowed with poor solubility and several side effects. The liposomes were prepared by thin film hydration method using crude soybean lecithin (CL) and cholesterol. Efavirenz loaded liposomes were evaluated for particle size, Zeta potential (ZP), morphology, encapsulation efficiency (EE%) and release kinetics studies. The physiochemical properties of the liposomes were also evaluated using Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), energy dispersity spectroscopy (EDS), and Fourier transform infrared (FTIR), while the formulation with the best encapsulation efficiency was used as the solvent medium for the buccal film formation. The buccal films were prepared using solvent casting method, where the liposomal suspension was used as the dispersing medium. The films were optimized for physical properties (thickness, weight variation and folding endurance) using digital Vernier calliper and digital weighing balance. The physiochemical properties of the selected BFs films made of Carbopol (CP) and its combination with Pluronic F127 (PF127) were further characterized using XRD, DSC, FTIR, Transmission Electron Microscopy (TEM), EDS and Scanning Electron Microscopy (SEM). The permeation study of the selected BFs was investigated using Franz diffusion cell. The BFs composed of CP alone or its combination with PF127 demonstrated much better bio-adhesive properties than the films made of other polymers (like Hydroxyl propyl methyl cellulose, HPMC) alone or in combination with PF127. The developed liposome formulation showed high encapsulation 98.8 ± 0.01 % in CL to cholesterol mass ratio of 1:1 and total lipid to drug mass ratio of 2:1. The average particle size 104.82 ± 2.29 nm and Zeta potential -50.33 ± 0.95 mV of these liposomes were found to be attractive for targeted delivery to the HIV infected cells. The CP based BFs (without and with PF127) exhibited good film thickness 0.88 ± 0.10 and 0.76 ± 0.14 mm, with weight uniformity 68.22 ± 1.04 and 86.28 ± 2. 16 mg, satisfactory flexibility values 258 and 321, and slightly acidic pH 6.43 ± 0.76 and 6.32 ± 0.01. The swelling percentage was found to be 50 % for CP film alone and 78 % for CP film with PF127. The cumulative amount of drug that permeated through the buccal epithelium over 24 hours was about 66 % from CP film alone and 75 % from CP film with PF127. Since no evidence of the liposomal encapsulation of EFV have been reported to our knowledge, we find the insights from the present study valuable as a set of preliminary data to encourage further investigations of the encapsulation and delivery of EFV like antiretrovirals for enhanced solubility, site targeting and prolonged release using crude soybean lecithin and mucoadhesive polymers, which holds some added economical values as naturally occurring lipid and polymeric mixtures as a promising delivery systems for buccal delivery of ARVDs.
- Full Text:
- Date Issued: 2020
- Authors: Okafor, Nnamdi Ikemefuna
- Date: 2020
- Subjects: Liposomes , Highly active antiretroviral therapy , Antiretroviral agents , HIV infections -- Prevention
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/117161 , vital:34485
- Description: The human immune deficiency virus (HIV) infection has been ranked as one of the most devastating microbial infections in the world. This status is a result of the HIV rapid genetic variation, which limits discovery of a vaccine. Use application of antiretroviral therapy (ARVT) in treatment of the disease caused by the HIV infection (known as acquired immunodeficiency syndrome, HIV-AIDS) is frequently compromised by several factors such as the low bioavailability and severe adverse effects associated with the existing antiretroviral drugs (ARVDs). This underlines the need for controlling the pharmacokinetics profiles of ARVD using effective vehicles that can modify drug biodistribution. The same is true for many other conditions, where delivery systems can determine the success or failure of treatment by controlling pharmacokinetic and dynamic properties. The mucosal linings of the oral cavities in addition offer adorable route of administration for systematic drug delivery, improving drug therapeutic performance and often preferred by clinicians and patients. Liposomes are tiny spherical sacs of phospholipid molecules enclosing water droplets, formed (artificially) to carry drugs or other substances into the tissues by crossing and targeting to specific organelles. This work therefore focused on preparation of liposomes and liposomal buccal films (BFs) for potential buccal delivery of efavirenz, an ARVD model endowed with poor solubility and several side effects. The liposomes were prepared by thin film hydration method using crude soybean lecithin (CL) and cholesterol. Efavirenz loaded liposomes were evaluated for particle size, Zeta potential (ZP), morphology, encapsulation efficiency (EE%) and release kinetics studies. The physiochemical properties of the liposomes were also evaluated using Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), energy dispersity spectroscopy (EDS), and Fourier transform infrared (FTIR), while the formulation with the best encapsulation efficiency was used as the solvent medium for the buccal film formation. The buccal films were prepared using solvent casting method, where the liposomal suspension was used as the dispersing medium. The films were optimized for physical properties (thickness, weight variation and folding endurance) using digital Vernier calliper and digital weighing balance. The physiochemical properties of the selected BFs films made of Carbopol (CP) and its combination with Pluronic F127 (PF127) were further characterized using XRD, DSC, FTIR, Transmission Electron Microscopy (TEM), EDS and Scanning Electron Microscopy (SEM). The permeation study of the selected BFs was investigated using Franz diffusion cell. The BFs composed of CP alone or its combination with PF127 demonstrated much better bio-adhesive properties than the films made of other polymers (like Hydroxyl propyl methyl cellulose, HPMC) alone or in combination with PF127. The developed liposome formulation showed high encapsulation 98.8 ± 0.01 % in CL to cholesterol mass ratio of 1:1 and total lipid to drug mass ratio of 2:1. The average particle size 104.82 ± 2.29 nm and Zeta potential -50.33 ± 0.95 mV of these liposomes were found to be attractive for targeted delivery to the HIV infected cells. The CP based BFs (without and with PF127) exhibited good film thickness 0.88 ± 0.10 and 0.76 ± 0.14 mm, with weight uniformity 68.22 ± 1.04 and 86.28 ± 2. 16 mg, satisfactory flexibility values 258 and 321, and slightly acidic pH 6.43 ± 0.76 and 6.32 ± 0.01. The swelling percentage was found to be 50 % for CP film alone and 78 % for CP film with PF127. The cumulative amount of drug that permeated through the buccal epithelium over 24 hours was about 66 % from CP film alone and 75 % from CP film with PF127. Since no evidence of the liposomal encapsulation of EFV have been reported to our knowledge, we find the insights from the present study valuable as a set of preliminary data to encourage further investigations of the encapsulation and delivery of EFV like antiretrovirals for enhanced solubility, site targeting and prolonged release using crude soybean lecithin and mucoadhesive polymers, which holds some added economical values as naturally occurring lipid and polymeric mixtures as a promising delivery systems for buccal delivery of ARVDs.
- Full Text:
- Date Issued: 2020
Functional conversion of commercial buildings in South Africa
- Authors: Kuliti, Gerald
- Date: 2020
- Subjects: Commercial buildings -- South Africa , Buildings -- Conservation and restoration Buildings -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46075 , vital:39485
- Description: In the major cities of South Africa, there is a prevalence of originally built commercial buildings that are being converted into residential apartments or other industrial economic spaces. These secondary users refurbish the original structures to accommodate their new specialised requirements and this mostly happens after the buildings have been lying vacant for a long period of time. The study by Y.Long et al. (2011) narrates the changes in land use, identification of driving forces and the mapping of areas that are experiencing intense land use transformation. Properties that were developed for a focused particular use, were found to have been redeveloped within a few years for other functions. Subjects that were included in the sample were selected to meet specific criteria. The stakeholders had to meet the following criteria to be included in the sample: They were registered professionals in the built environment such as: Architecture, Engineering (civil, electrical, mechanical and structural), Quantity Surveying, Town Planning, Construction Management and Estate management The method that was used to collect data was self-completion questionnaire that was given out by electronic mail. After the data was collected, it was organised and analysed. For the analysis of closed-ended questions, an online programme called QuestionPro, was used, data was analysed by using descriptive statistics and frequency tables were drawn and from these, the data was presented in pie diagrams and bar graphs. While it is necessary to expand the horizons of the ever-growing global population, it is imperative that all stakeholders in the building industry work together to find sustainable solutions to residential and industrial development.
- Full Text:
- Date Issued: 2020
- Authors: Kuliti, Gerald
- Date: 2020
- Subjects: Commercial buildings -- South Africa , Buildings -- Conservation and restoration Buildings -- Maintenance and repair
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46075 , vital:39485
- Description: In the major cities of South Africa, there is a prevalence of originally built commercial buildings that are being converted into residential apartments or other industrial economic spaces. These secondary users refurbish the original structures to accommodate their new specialised requirements and this mostly happens after the buildings have been lying vacant for a long period of time. The study by Y.Long et al. (2011) narrates the changes in land use, identification of driving forces and the mapping of areas that are experiencing intense land use transformation. Properties that were developed for a focused particular use, were found to have been redeveloped within a few years for other functions. Subjects that were included in the sample were selected to meet specific criteria. The stakeholders had to meet the following criteria to be included in the sample: They were registered professionals in the built environment such as: Architecture, Engineering (civil, electrical, mechanical and structural), Quantity Surveying, Town Planning, Construction Management and Estate management The method that was used to collect data was self-completion questionnaire that was given out by electronic mail. After the data was collected, it was organised and analysed. For the analysis of closed-ended questions, an online programme called QuestionPro, was used, data was analysed by using descriptive statistics and frequency tables were drawn and from these, the data was presented in pie diagrams and bar graphs. While it is necessary to expand the horizons of the ever-growing global population, it is imperative that all stakeholders in the building industry work together to find sustainable solutions to residential and industrial development.
- Full Text:
- Date Issued: 2020
Generation of a virtual library of terpenes using graph theory, and its application in exploration of the mechanisms of terpene biosynthesis
- Authors: Dendera, Washington
- Date: 2020
- Subjects: Terpenes , Plants -- Metabolism , Computational biology , Bioinformatics , Organic compounds -- Synthesis , Monoterpenes , Molecular biology -- Computer simulation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123453 , vital:35439
- Description: Terpenes form a large group of organic compounds which have proven to be of use to many living organisms being used by plants for metabolism (Pichersky and Gershenzon, 1934; McGarvey and Croteau, 1995; Gershenzon and Dudareva, 2007), defence or as a means to attract pollinators and also used by humans in medical, pharmaceutical and food industry (Bicas, Dionísio and Pastore, 2009; Marmulla and Harder, 2014; Kandi et al., 2015). Following on literature methods to generate chemical libraries using graph theoretic techniques, complete libraries of all possible terpene isomers have been constructed with the goal of construction of derivative libraries of possible carbocation intermediates which are important in the elucidation of mechanisms in the biosynthesis of terpenes. Virtual library generation of monoterpenes was first achieved by generating graphs of order 7, 8, 9 and 10 using the Nauty and Traces suite. These were screened and processed with a set of collated Python scripts written to recognize the graphs in text format and translate them to molecules, minimizing through Tinker whilst discarding graphs that violate chemistry laws. As a result of the computational time required only order 7 and order 10 graphs were processed. Out of the 873 graphs generated from order seven, 353 were converted to molecules and from the 11,7 million produced from order 10 half were processed resulting in the production of 442928 compounds (repeats included). For screening, 55 366 compounds were docked in the active site of limonene synthase; of these 2355 ligands had a good Vina docking score with a binding energy of between -7.0 and -7.4 kcal.mol-1. When these best docked molecules were overlaid in the active site a map of possible ligand positions within the active site of limonene synthase was traced out.
- Full Text:
- Date Issued: 2020
- Authors: Dendera, Washington
- Date: 2020
- Subjects: Terpenes , Plants -- Metabolism , Computational biology , Bioinformatics , Organic compounds -- Synthesis , Monoterpenes , Molecular biology -- Computer simulation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123453 , vital:35439
- Description: Terpenes form a large group of organic compounds which have proven to be of use to many living organisms being used by plants for metabolism (Pichersky and Gershenzon, 1934; McGarvey and Croteau, 1995; Gershenzon and Dudareva, 2007), defence or as a means to attract pollinators and also used by humans in medical, pharmaceutical and food industry (Bicas, Dionísio and Pastore, 2009; Marmulla and Harder, 2014; Kandi et al., 2015). Following on literature methods to generate chemical libraries using graph theoretic techniques, complete libraries of all possible terpene isomers have been constructed with the goal of construction of derivative libraries of possible carbocation intermediates which are important in the elucidation of mechanisms in the biosynthesis of terpenes. Virtual library generation of monoterpenes was first achieved by generating graphs of order 7, 8, 9 and 10 using the Nauty and Traces suite. These were screened and processed with a set of collated Python scripts written to recognize the graphs in text format and translate them to molecules, minimizing through Tinker whilst discarding graphs that violate chemistry laws. As a result of the computational time required only order 7 and order 10 graphs were processed. Out of the 873 graphs generated from order seven, 353 were converted to molecules and from the 11,7 million produced from order 10 half were processed resulting in the production of 442928 compounds (repeats included). For screening, 55 366 compounds were docked in the active site of limonene synthase; of these 2355 ligands had a good Vina docking score with a binding energy of between -7.0 and -7.4 kcal.mol-1. When these best docked molecules were overlaid in the active site a map of possible ligand positions within the active site of limonene synthase was traced out.
- Full Text:
- Date Issued: 2020
Gentrification in the Nelson Mandela Bay central business district
- Mageda, Nomthandazo Christellene
- Authors: Mageda, Nomthandazo Christellene
- Date: 2020
- Subjects: Gentrification , Urban renewal-- South Africa -- Nelson Mandela Metropolitan Municipality Neighborhoods -- South Africa -- Nelson Mandela Metropolitan Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46119 , vital:39498
- Description: Gentrification is the process by which middle-class residents settle inner city neighborhood previously occupied by working-class. Gentrification has long been viewed as a consumption phenomenon, which is triggered by the urge of a certain fraction of a middle class – gentrifies – to create and maintain distinction. The research is designed as a socio-economic account to discuss the development in the NMB CBD area. In my research I examine the multiscalar forces affecting neighborhood change. This study will also examine the elements affecting and also the benefits of the gentrification process using quantitative methods. The CBD of the NMB represents certain universalities of gentrification in an old city. Today the city is no longer the regular of development but instead its progenitor. Adopting the language of “urbanization” and “cities of the future” will be considered in gearing the economic development arm. It does so by an extensive mapping of gentrification processes in Port Elizabeth. It also contains a smaller study on gentrification in Cape Town and also on an international level. The outcomes provide telling insights into gentrification as a generic process affecting not just low income areas (classical gentrification) and high income areas (super-gentrification), but also a wide-ranging spectrum of medium-income areas (ordinary gentrification). This study examines the interdependent variables of gentrification, going beyond a profitable analysis and incorporating the voice of all the actors involved in the process of gentrification, using quantitative analysis. By taking into account all perspectives, this study permits a holistic understanding of the social costs and benefits associated with gentrification. As multifaceted as gentrification is, it is becoming more pervasive in cities globally, a holistic tally of the social costs and benefits of revitalization projects becoming imperative. The study concludes with discussions of the contributions, limitations, recommendations for the NMB CBD and other cities that are considering revitalizing their urban cores and implications for future research.
- Full Text:
- Date Issued: 2020
- Authors: Mageda, Nomthandazo Christellene
- Date: 2020
- Subjects: Gentrification , Urban renewal-- South Africa -- Nelson Mandela Metropolitan Municipality Neighborhoods -- South Africa -- Nelson Mandela Metropolitan Municipality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46119 , vital:39498
- Description: Gentrification is the process by which middle-class residents settle inner city neighborhood previously occupied by working-class. Gentrification has long been viewed as a consumption phenomenon, which is triggered by the urge of a certain fraction of a middle class – gentrifies – to create and maintain distinction. The research is designed as a socio-economic account to discuss the development in the NMB CBD area. In my research I examine the multiscalar forces affecting neighborhood change. This study will also examine the elements affecting and also the benefits of the gentrification process using quantitative methods. The CBD of the NMB represents certain universalities of gentrification in an old city. Today the city is no longer the regular of development but instead its progenitor. Adopting the language of “urbanization” and “cities of the future” will be considered in gearing the economic development arm. It does so by an extensive mapping of gentrification processes in Port Elizabeth. It also contains a smaller study on gentrification in Cape Town and also on an international level. The outcomes provide telling insights into gentrification as a generic process affecting not just low income areas (classical gentrification) and high income areas (super-gentrification), but also a wide-ranging spectrum of medium-income areas (ordinary gentrification). This study examines the interdependent variables of gentrification, going beyond a profitable analysis and incorporating the voice of all the actors involved in the process of gentrification, using quantitative analysis. By taking into account all perspectives, this study permits a holistic understanding of the social costs and benefits associated with gentrification. As multifaceted as gentrification is, it is becoming more pervasive in cities globally, a holistic tally of the social costs and benefits of revitalization projects becoming imperative. The study concludes with discussions of the contributions, limitations, recommendations for the NMB CBD and other cities that are considering revitalizing their urban cores and implications for future research.
- Full Text:
- Date Issued: 2020
Get sleep or get stumped: sleep behaviour in elite South African cricket players during competition
- Authors: McEwan, Kayla
- Date: 2020
- Subjects: Sleep -- Physiological aspects , Cricket players -- Health and hygiene , Cricket players -- South Africa -- Health and hygiene , Cricket -- Health aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147950 , vital:38696
- Description: Introduction: Good sleep behaviour is associated with achieving optimal athletic performance and reducing the risk of injury. Elite cricket players have unique physical and cognitive demands, and must accommodate for congested competition and travel schedules (all of which increase the risk of disruptive sleep). Further, the political pressures and socioeconomic barriers in South African cricket could affect the sleep of the country’s elite players. Previous research in cricket has focussed on the impact that nutrition, equipment specifications, movement physiology and psychology could elicit on performance (where many professional teams hire support staff to supervise these disciplines); however, there is limited empirical application of sleep research in elite cricket players. Therefore, this study aimed to characterise the sleep behaviours of elite South African cricket players during periods of competition and investigate the relationship between pre-match sleep and cricket performance. Methods: A longitudinal field-based investigation was implemented to monitor the sleep behaviour of 26 elite South African cricket players (age: 28.6 ± 4.0 years; height: 1.8 ± 0.1 m; weight: 85.7 ± 10.8 kg; elite experience: 3.7 ± 4.0 years) during home and away competitive tours. The Morningness-Eveningness Questionnaire and Athlete Sleep Behaviour Questionnaire were administered to identify chronotype and poor sleep behaviours. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post-match. Linear mixed model regression was used to compare differences in sleep variables between time-periods, match venues, player roles, match formats, sleep medication and racial groups. Spearman’s correlation (rs) was used to assess the relationship of substance use (alcohol and caffeine), age, elite experience and match performance with selected sleep indices. Statistical significance for all measures was accepted at p < 0.05. Hedge’s (g) were used as the measure of effect size. Results: Light-emitting technology use, effects of travel, late evening alcohol consumption and muscle soreness were the main factors that impacted sleep. Post-match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post-travel (07:53 ± 01:07; g = 1.19 [0.81;1.57]) and pre-match (08:43 ± 01:03; g = 1.97 [1.55;2.39]) total sleep time. Post-travel sleep onset latency and sleep efficiency were significantly (p < 0.05) shorter (g = 0.74 [0.29;1.29]) and higher (g = 1.35 [0.76;1.94]) at home than away. Although not significant (p > 0.05), allrounders took longer to fall asleep (g = 0.90 [0.23;1.57]), obtained less total sleep (0.76 [0.29;1.42]) and had lower morning freshness scores (g = 1.10 [0.42;1.78]) the night before a match compared to batsmen. Wake after sleep onset and get up time were moderately longer (g = 0.61 [0.22;1.26]) and later (g = 0.62 [0.27;1.17]) before. Twenty20 matches compared to One-Day International matches respectively. Further, sleep duration significantly declined from pre-match to post-match during the multi-day Test format (p = 0.04, g= 0.75 [0.40;1.12]). Late alcohol consumption was significantly (p < 0.05) correlated with a decrease in total sleep time, regardless of match venue (home: rs (49) = -0.69; away: rs (27) = -0.57). During the away condition, an increase in age was significantly associated with longer wake after sleep onset durations (rs (13) = 0.52, p = 0.0003), while greater elite experience was significantly associated with longer total sleep time (rs (72) = 0.36, p = 0.02). The non-sleep medication group took significantly longer to fall asleep compared to the sleep medication group during the first week of the away condition (p = 0.02, g = 0.75 [0.25;1.26]) particularly on nights following transmeridian travel. Although not significant ( p > 0.05), Asian/Indian players had moderately longer sleep onset latencies (g = 1.07 [0.66;1.47]), wake after sleep onset durations (g = 0.86 [0.42;1.29]), and lower subjective sleep quality (g = 0.86 [0.46;1.26]) and morning freshness scores (g = 0.89 [0.47;1.27]) compared to Whites. Similarly, Black Africans had moderately lower subjective sleep quality scores compared to Whites (g = 0.71 [0.43;0.97]). Longer sleep onset latencies and shorter total sleep times were significantly (p < 0.05) associated with poorer One-Day International (rs (28) = -0.57) and Test (rs (12) = 0.59) batting performances respectively. Higher subjective sleep quality scores were significantly associated with better Twenty20 bowling economies (rs (8) = -0.52). Discussion: There was no evidence of poor pre-match sleep behaviour, irrespective of venue; however, the most apparent disruption to sleep occurred post-match (similar to that found in other team-sports). Most disparities in sleep between match venues existed post-travel, with better sleep behaviour observed during the home condition. The differences in sleep patterns found in all three match formats were expected given the variations in format scheduling and duration. Although sleep medication was shown to promote better sleep, its long-term effectiveness was limited. The results promote the implementation of practical strategies aimed to reduce bedtime light-emitting technology use, late evening alcohol consumption and muscle pain. Inter-individual sleep behaviour was found between player roles, age, experience level and race. Moderate associations existed between sleep and markers of batting performance, specifically for the longer, strategic formats of the game. Conclusion: The current study provided new insight of the sleep behaviour in elite South African cricket players during competition. Individualized sleep monitoring practices are encouraged, with specific supervision over older, less experienced players as well as the racial minorities and allrounders of the team. The poor post-match sleep behaviour, together with the sleep and performance correlations, provide ideal opportunities for future interventions to focus on match recovery and the use sleep monitoring as a competitive advantage.
- Full Text:
- Date Issued: 2020
- Authors: McEwan, Kayla
- Date: 2020
- Subjects: Sleep -- Physiological aspects , Cricket players -- Health and hygiene , Cricket players -- South Africa -- Health and hygiene , Cricket -- Health aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/147950 , vital:38696
- Description: Introduction: Good sleep behaviour is associated with achieving optimal athletic performance and reducing the risk of injury. Elite cricket players have unique physical and cognitive demands, and must accommodate for congested competition and travel schedules (all of which increase the risk of disruptive sleep). Further, the political pressures and socioeconomic barriers in South African cricket could affect the sleep of the country’s elite players. Previous research in cricket has focussed on the impact that nutrition, equipment specifications, movement physiology and psychology could elicit on performance (where many professional teams hire support staff to supervise these disciplines); however, there is limited empirical application of sleep research in elite cricket players. Therefore, this study aimed to characterise the sleep behaviours of elite South African cricket players during periods of competition and investigate the relationship between pre-match sleep and cricket performance. Methods: A longitudinal field-based investigation was implemented to monitor the sleep behaviour of 26 elite South African cricket players (age: 28.6 ± 4.0 years; height: 1.8 ± 0.1 m; weight: 85.7 ± 10.8 kg; elite experience: 3.7 ± 4.0 years) during home and away competitive tours. The Morningness-Eveningness Questionnaire and Athlete Sleep Behaviour Questionnaire were administered to identify chronotype and poor sleep behaviours. Players completed an altered version of the Core Consensus Sleep Diary every morning post-travel, pre-match and post-match. Linear mixed model regression was used to compare differences in sleep variables between time-periods, match venues, player roles, match formats, sleep medication and racial groups. Spearman’s correlation (rs) was used to assess the relationship of substance use (alcohol and caffeine), age, elite experience and match performance with selected sleep indices. Statistical significance for all measures was accepted at p < 0.05. Hedge’s (g) were used as the measure of effect size. Results: Light-emitting technology use, effects of travel, late evening alcohol consumption and muscle soreness were the main factors that impacted sleep. Post-match total sleep time (06:31 ± 01:09) was significantly (p < 0.05) shorter compared to post-travel (07:53 ± 01:07; g = 1.19 [0.81;1.57]) and pre-match (08:43 ± 01:03; g = 1.97 [1.55;2.39]) total sleep time. Post-travel sleep onset latency and sleep efficiency were significantly (p < 0.05) shorter (g = 0.74 [0.29;1.29]) and higher (g = 1.35 [0.76;1.94]) at home than away. Although not significant (p > 0.05), allrounders took longer to fall asleep (g = 0.90 [0.23;1.57]), obtained less total sleep (0.76 [0.29;1.42]) and had lower morning freshness scores (g = 1.10 [0.42;1.78]) the night before a match compared to batsmen. Wake after sleep onset and get up time were moderately longer (g = 0.61 [0.22;1.26]) and later (g = 0.62 [0.27;1.17]) before. Twenty20 matches compared to One-Day International matches respectively. Further, sleep duration significantly declined from pre-match to post-match during the multi-day Test format (p = 0.04, g= 0.75 [0.40;1.12]). Late alcohol consumption was significantly (p < 0.05) correlated with a decrease in total sleep time, regardless of match venue (home: rs (49) = -0.69; away: rs (27) = -0.57). During the away condition, an increase in age was significantly associated with longer wake after sleep onset durations (rs (13) = 0.52, p = 0.0003), while greater elite experience was significantly associated with longer total sleep time (rs (72) = 0.36, p = 0.02). The non-sleep medication group took significantly longer to fall asleep compared to the sleep medication group during the first week of the away condition (p = 0.02, g = 0.75 [0.25;1.26]) particularly on nights following transmeridian travel. Although not significant ( p > 0.05), Asian/Indian players had moderately longer sleep onset latencies (g = 1.07 [0.66;1.47]), wake after sleep onset durations (g = 0.86 [0.42;1.29]), and lower subjective sleep quality (g = 0.86 [0.46;1.26]) and morning freshness scores (g = 0.89 [0.47;1.27]) compared to Whites. Similarly, Black Africans had moderately lower subjective sleep quality scores compared to Whites (g = 0.71 [0.43;0.97]). Longer sleep onset latencies and shorter total sleep times were significantly (p < 0.05) associated with poorer One-Day International (rs (28) = -0.57) and Test (rs (12) = 0.59) batting performances respectively. Higher subjective sleep quality scores were significantly associated with better Twenty20 bowling economies (rs (8) = -0.52). Discussion: There was no evidence of poor pre-match sleep behaviour, irrespective of venue; however, the most apparent disruption to sleep occurred post-match (similar to that found in other team-sports). Most disparities in sleep between match venues existed post-travel, with better sleep behaviour observed during the home condition. The differences in sleep patterns found in all three match formats were expected given the variations in format scheduling and duration. Although sleep medication was shown to promote better sleep, its long-term effectiveness was limited. The results promote the implementation of practical strategies aimed to reduce bedtime light-emitting technology use, late evening alcohol consumption and muscle pain. Inter-individual sleep behaviour was found between player roles, age, experience level and race. Moderate associations existed between sleep and markers of batting performance, specifically for the longer, strategic formats of the game. Conclusion: The current study provided new insight of the sleep behaviour in elite South African cricket players during competition. Individualized sleep monitoring practices are encouraged, with specific supervision over older, less experienced players as well as the racial minorities and allrounders of the team. The poor post-match sleep behaviour, together with the sleep and performance correlations, provide ideal opportunities for future interventions to focus on match recovery and the use sleep monitoring as a competitive advantage.
- Full Text:
- Date Issued: 2020
Grandmothers’ perceptions regarding breastfeeding following training for breastfeeding support in Nelson Mandela Bay Health District: a qualitative study
- Authors: Manyange, Rumbidzai Lynda
- Date: 2020
- Subjects: Breastfeeding promotion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46441 , vital:39583
- Description: Rationale: Although there has been active promotion of breastfeeding for the past decades in South Africa, there has been inadequate support from multiple role players. Strategies that do not engage important family members, such as grandmothers in supporting breastfeeding are likely to fail. In many African countries, grandmothers often make critical decisions about early child feeding practices, particularly for first-time mothers. Despite the influence grandmothers have, limited studies have been done in South Africa to assess whether it is possible to change breastfeeding outcomes by empowering grandmothers as well as including them in intervention programmes. Nelson Mandela University, in collaboration with the United Nations Children Education Fund (UNICEF) and a local Non-Governmental Organisation (NGO), recently launched a breastfeeding support programme, Sakha Esethu. The aim was to capacitate both primary and secondary caregivers to enable them to provide optimal breastfeeding support for mothers in various communities. However, it was important to explore the perceptions of grandmothers regarding breastfeeding to assess whether improved breastfeeding knowledge will translate into changed perceptions and therefore improved support for exclusive breastfeeding in communities in Nelson Mandela Bay. Aim: The study aimed to describe and explore the perceptions of grandmothers regarding breastfeeding after participating in a breastfeeding support programme in Nelson Mandela Bay health district (NMBHD). Methodology: The study followed a descriptive-exploratory, contextual study design with a qualitative approach. The four ethical principles that guided the study were: autonomy, non-maleficence, beneficence and justice. The researcher conducted five focus group discussions (FGD) at ECD centres in NMBHD, where 34 grandmothers participated in the study. Participants were chosen using a purposively sampling technique and data was collected using FGD interviews. Verbatim transcription was done after every FGD and data was analysed using the eight steps of Tesch’s analysis technique. An independent coder with experience in qualitative data analysis assisted to verify the codes generated. vi Results: Four major themes and eleven subthemes emerged through data analysis. The identified themes were: (1)Participant knowledge regarding breastfeeding. Participants reflected on poor knowledge on the perceived maternal benefits of breastfeeding, variance on the optimal duration of breastfeeding and recognised myths and cultural taboos related to breastfeeding, such as the use of traditional mixes, “dirty” breastmilk and perceived milk insufficiency; (2) Views on complementary feeding. The subthemes that emerged included: Participants shared their views on the age of introduction for complementary foods and feeding practices for infants; (3) Challenges related to breastfeeding. The challenges identified included: challenges for working mothers and those attending school, lack of family support and societal support for EBF, lack of support from healthcare professionals relating to initiation and continuation of breastfeeding and difficulties coping with breast health. (4) Participants enthused about the impact of being supported to optimise breastfeeding.Participants were able to share on the camaraderie benefits experienced from the Sakha Esethu group as well as on the support grandmothers can provide. Conclusion and Recommendations: This study confirmed that participation of grandmothers in the Sakha Esethu programme had an impact on changes in grandmothers’ perceptions regarding breastfeeding. However, the programme can be further improved by placing more emphasis on aspects i.e. maternal benefits of breastfeeding, during mentor training. Furthermore, there is a need to strengthen healthcare worker support and training, especially with regards to adapting counselling strategies to include breastfeeding challenges and cultural beliefs.
- Full Text:
- Date Issued: 2020
- Authors: Manyange, Rumbidzai Lynda
- Date: 2020
- Subjects: Breastfeeding promotion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46441 , vital:39583
- Description: Rationale: Although there has been active promotion of breastfeeding for the past decades in South Africa, there has been inadequate support from multiple role players. Strategies that do not engage important family members, such as grandmothers in supporting breastfeeding are likely to fail. In many African countries, grandmothers often make critical decisions about early child feeding practices, particularly for first-time mothers. Despite the influence grandmothers have, limited studies have been done in South Africa to assess whether it is possible to change breastfeeding outcomes by empowering grandmothers as well as including them in intervention programmes. Nelson Mandela University, in collaboration with the United Nations Children Education Fund (UNICEF) and a local Non-Governmental Organisation (NGO), recently launched a breastfeeding support programme, Sakha Esethu. The aim was to capacitate both primary and secondary caregivers to enable them to provide optimal breastfeeding support for mothers in various communities. However, it was important to explore the perceptions of grandmothers regarding breastfeeding to assess whether improved breastfeeding knowledge will translate into changed perceptions and therefore improved support for exclusive breastfeeding in communities in Nelson Mandela Bay. Aim: The study aimed to describe and explore the perceptions of grandmothers regarding breastfeeding after participating in a breastfeeding support programme in Nelson Mandela Bay health district (NMBHD). Methodology: The study followed a descriptive-exploratory, contextual study design with a qualitative approach. The four ethical principles that guided the study were: autonomy, non-maleficence, beneficence and justice. The researcher conducted five focus group discussions (FGD) at ECD centres in NMBHD, where 34 grandmothers participated in the study. Participants were chosen using a purposively sampling technique and data was collected using FGD interviews. Verbatim transcription was done after every FGD and data was analysed using the eight steps of Tesch’s analysis technique. An independent coder with experience in qualitative data analysis assisted to verify the codes generated. vi Results: Four major themes and eleven subthemes emerged through data analysis. The identified themes were: (1)Participant knowledge regarding breastfeeding. Participants reflected on poor knowledge on the perceived maternal benefits of breastfeeding, variance on the optimal duration of breastfeeding and recognised myths and cultural taboos related to breastfeeding, such as the use of traditional mixes, “dirty” breastmilk and perceived milk insufficiency; (2) Views on complementary feeding. The subthemes that emerged included: Participants shared their views on the age of introduction for complementary foods and feeding practices for infants; (3) Challenges related to breastfeeding. The challenges identified included: challenges for working mothers and those attending school, lack of family support and societal support for EBF, lack of support from healthcare professionals relating to initiation and continuation of breastfeeding and difficulties coping with breast health. (4) Participants enthused about the impact of being supported to optimise breastfeeding.Participants were able to share on the camaraderie benefits experienced from the Sakha Esethu group as well as on the support grandmothers can provide. Conclusion and Recommendations: This study confirmed that participation of grandmothers in the Sakha Esethu programme had an impact on changes in grandmothers’ perceptions regarding breastfeeding. However, the programme can be further improved by placing more emphasis on aspects i.e. maternal benefits of breastfeeding, during mentor training. Furthermore, there is a need to strengthen healthcare worker support and training, especially with regards to adapting counselling strategies to include breastfeeding challenges and cultural beliefs.
- Full Text:
- Date Issued: 2020
Growth and photosynthetic responses of Acacia (Vachellia) seedlings to atmospheric CO2 increased from glacial to current concentrations: underlying mechanisms and ecological implications
- Authors: Anderson, Bruce Maurice
- Date: 2020
- Subjects: Acacia vachellia , Acacia vachellia -- Growth , Acacia -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138182 , vital:37604
- Description: The African Acacia species Vachellia karroo, V. robusta, V. nilotica, and V. tortilis are some of the most invasive species implicated in bush encroachment and woody thickening of historically open savannas in southern Africa. This is partially explained by historic increases in atmospheric CO2 concentrations, which are proposed to have promoted the growth and survivorship of C3 tree seedlings relative to C4 grasses. However, the uniformity of CO2 responsiveness and differences among Vachellia species remain largely undetermined. Here we investigate the growth and photosynthetic responses of four Vachellia species, all implicated in woody encroachment, but originating from distinct climatic niches. Exposing these species to a range of sub-ambient CO2 concentrations (12 – 40 Pa) showed that V. karroo, V. robusta, V. nilotica and V. tortilis all responded strongly and fairly consistently to increasing CO2 concentrations, acting as a ‘functional type’ despite being selected from different geographic regions and having different climatic niches. Combined average net CO2 assimilation rates increased by 130% despite significant, but low levels of down-regulation and decreased stomatal conductance. The increased photosynthetic rates stimulated growth and biomass production in all compartments, with no significant differences in interspecific above and below ground allocation. Growth rates and dry biomass increased by 50% and 186%, respectively, while leaf level water use efficiency (ratio of net CO2 assimilation rate to transpiration rate) increased by an average of 218%. When this was scaled to the whole plant level, this stimulation was decreased to 80%. The decrease was the result of the CO2 stimulated increase in canopy areas, which increased leaf area for water loss. The seedlings’ total number of spinescent physical defenses, as well as the average mass and spine mass fraction also increased with rising CO2. These thicker spines could act as better deterrents against vertebrate browsers. Spine density was unchanged, however, showing that the increased spine numbers were associated with larger seedlings at higher CO2 rather than an increase in the number of spines per stem length. The stimulatory effects of increasing CO2 concentrations since the last glacial maximum and resultant increases in seedling growth and biomass are likely to have had important consequences for the survival and establishment of Acacia seedlings. Tolerance of drought and disturbance has been related to seedling size, hence stimulating the growth rate could confer disturbance tolerance and this tolerance would develop more rapidly with increasing CO2 concentrations. Furthermore, increased nitrogen and water use efficiency have the potential to support seedling establishment in environments where these resources would otherwise be limited at lower atmospheric CO2 concentrations. Resulting in a larger proportion of CO2 fertilization responsive woody seedlings surviving the seedling size classes, and persisting within historically open savannas. Where interspecific differences occurred they are likely to have arisen from adaptation to specific climates where these species are native and selection would have been driven by factors such climate, resource availability, levels of disturbance and competitive interactions. V. karroo had the highest growth rates and strong CO2 driven increases in biomass accumulation, despite having the lowest inherent photosynthetic rates. V. karroo also had the lowest increase in water use efficiency and high transpiration rates could potentially increase access to soil nutrients through mass flow. This species had the highest mean spine mass and showed significant increases in spine mass fraction at elevated CO2 concentrations, which may be important for deterring herbivores. V. robusta’s distribution to the mesic east coast of Africa suggests that water is an important limitation to its distribution. Hence, the CO2 stimulated increase in water use efficiency at both leaf and whole canopy level allows speculation that this may be an important driver of this species’ range expansion, which might continue if increasing levels of CO2 continue to promote water use efficiency. V. nilotica occupies a broad range of habitats, inhabiting large areas of the subtropics both north and south of the equator, with the strongest climatic correlates being the precipitation of the wettest quarter followed by high temperature seasonality. In response to increasing CO2, V. nilotica showed overall strong increases in growth, water use efficiency, and physical defenses. These responses may explain why V. nilotica has been such a successful encroacher in a broad range of habitats where limitations are likely to include multiple climatic factors and disturbances. V. tortilis has the widest distribution of all the species studied, covering broad ranges of Africa and only being excluded from the wettest parts of the equator and driest parts of the deserts. In these experiments this species showed the lowest biomass responsiveness to CO2, but had especially large increases in water use efficiency at both the leaf and canopy level. This may have been an important driver for this species’ encroachment into the more arid parts of its distribution, however this link will need to be verified with further experimentation.
- Full Text:
- Date Issued: 2020
- Authors: Anderson, Bruce Maurice
- Date: 2020
- Subjects: Acacia vachellia , Acacia vachellia -- Growth , Acacia -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/138182 , vital:37604
- Description: The African Acacia species Vachellia karroo, V. robusta, V. nilotica, and V. tortilis are some of the most invasive species implicated in bush encroachment and woody thickening of historically open savannas in southern Africa. This is partially explained by historic increases in atmospheric CO2 concentrations, which are proposed to have promoted the growth and survivorship of C3 tree seedlings relative to C4 grasses. However, the uniformity of CO2 responsiveness and differences among Vachellia species remain largely undetermined. Here we investigate the growth and photosynthetic responses of four Vachellia species, all implicated in woody encroachment, but originating from distinct climatic niches. Exposing these species to a range of sub-ambient CO2 concentrations (12 – 40 Pa) showed that V. karroo, V. robusta, V. nilotica and V. tortilis all responded strongly and fairly consistently to increasing CO2 concentrations, acting as a ‘functional type’ despite being selected from different geographic regions and having different climatic niches. Combined average net CO2 assimilation rates increased by 130% despite significant, but low levels of down-regulation and decreased stomatal conductance. The increased photosynthetic rates stimulated growth and biomass production in all compartments, with no significant differences in interspecific above and below ground allocation. Growth rates and dry biomass increased by 50% and 186%, respectively, while leaf level water use efficiency (ratio of net CO2 assimilation rate to transpiration rate) increased by an average of 218%. When this was scaled to the whole plant level, this stimulation was decreased to 80%. The decrease was the result of the CO2 stimulated increase in canopy areas, which increased leaf area for water loss. The seedlings’ total number of spinescent physical defenses, as well as the average mass and spine mass fraction also increased with rising CO2. These thicker spines could act as better deterrents against vertebrate browsers. Spine density was unchanged, however, showing that the increased spine numbers were associated with larger seedlings at higher CO2 rather than an increase in the number of spines per stem length. The stimulatory effects of increasing CO2 concentrations since the last glacial maximum and resultant increases in seedling growth and biomass are likely to have had important consequences for the survival and establishment of Acacia seedlings. Tolerance of drought and disturbance has been related to seedling size, hence stimulating the growth rate could confer disturbance tolerance and this tolerance would develop more rapidly with increasing CO2 concentrations. Furthermore, increased nitrogen and water use efficiency have the potential to support seedling establishment in environments where these resources would otherwise be limited at lower atmospheric CO2 concentrations. Resulting in a larger proportion of CO2 fertilization responsive woody seedlings surviving the seedling size classes, and persisting within historically open savannas. Where interspecific differences occurred they are likely to have arisen from adaptation to specific climates where these species are native and selection would have been driven by factors such climate, resource availability, levels of disturbance and competitive interactions. V. karroo had the highest growth rates and strong CO2 driven increases in biomass accumulation, despite having the lowest inherent photosynthetic rates. V. karroo also had the lowest increase in water use efficiency and high transpiration rates could potentially increase access to soil nutrients through mass flow. This species had the highest mean spine mass and showed significant increases in spine mass fraction at elevated CO2 concentrations, which may be important for deterring herbivores. V. robusta’s distribution to the mesic east coast of Africa suggests that water is an important limitation to its distribution. Hence, the CO2 stimulated increase in water use efficiency at both leaf and whole canopy level allows speculation that this may be an important driver of this species’ range expansion, which might continue if increasing levels of CO2 continue to promote water use efficiency. V. nilotica occupies a broad range of habitats, inhabiting large areas of the subtropics both north and south of the equator, with the strongest climatic correlates being the precipitation of the wettest quarter followed by high temperature seasonality. In response to increasing CO2, V. nilotica showed overall strong increases in growth, water use efficiency, and physical defenses. These responses may explain why V. nilotica has been such a successful encroacher in a broad range of habitats where limitations are likely to include multiple climatic factors and disturbances. V. tortilis has the widest distribution of all the species studied, covering broad ranges of Africa and only being excluded from the wettest parts of the equator and driest parts of the deserts. In these experiments this species showed the lowest biomass responsiveness to CO2, but had especially large increases in water use efficiency at both the leaf and canopy level. This may have been an important driver for this species’ encroachment into the more arid parts of its distribution, however this link will need to be verified with further experimentation.
- Full Text:
- Date Issued: 2020
Household and business recycling programs as green strategies for waste management in East London, South Africa
- Authors: Fotoyi, Tenjiwe
- Date: 2020
- Subjects: Refuse and refuse disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18687 , vital:42706
- Description: Municipalities in South Africa generate enormous waste which is disposed of in a few landfill sites which, in turn, have a limited life span. Household recycling is one important mechanism that can be used to reduce the amount of waste that reaches overfilled landfill sites. The city of East London is running out of land to dispose waste, and their landfill sites, in particular, are filing up fast. Most of the waste generated, is recyclable, however recycling in the city remains fragmented, and is moving very slowly. This is because of the lack of a co-ordinated approach between the BCMM and the local communities, across the many suburbs of East London. Considering that urban areas have limited space, effective and efficient use of current landfills is of strategic importance. This research therefore will examine ways of improving recycling in East London, addressing challenges facing current recycling. Data for this study was collected from the random administration of 100 questionnaires on different categories of respondents in the study area. The study revealed that by the introduction of the “Hand-on-waste” programme, the waste management personnel have taken the first step towards household waste recycling. However, the level of awareness and knowledge of the public on domestic recycling was quite poor, if residents are given the necessary encouragement, motivation and recycling infrastructure waste minimisation would be achieved
- Full Text:
- Date Issued: 2020
- Authors: Fotoyi, Tenjiwe
- Date: 2020
- Subjects: Refuse and refuse disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18687 , vital:42706
- Description: Municipalities in South Africa generate enormous waste which is disposed of in a few landfill sites which, in turn, have a limited life span. Household recycling is one important mechanism that can be used to reduce the amount of waste that reaches overfilled landfill sites. The city of East London is running out of land to dispose waste, and their landfill sites, in particular, are filing up fast. Most of the waste generated, is recyclable, however recycling in the city remains fragmented, and is moving very slowly. This is because of the lack of a co-ordinated approach between the BCMM and the local communities, across the many suburbs of East London. Considering that urban areas have limited space, effective and efficient use of current landfills is of strategic importance. This research therefore will examine ways of improving recycling in East London, addressing challenges facing current recycling. Data for this study was collected from the random administration of 100 questionnaires on different categories of respondents in the study area. The study revealed that by the introduction of the “Hand-on-waste” programme, the waste management personnel have taken the first step towards household waste recycling. However, the level of awareness and knowledge of the public on domestic recycling was quite poor, if residents are given the necessary encouragement, motivation and recycling infrastructure waste minimisation would be achieved
- Full Text:
- Date Issued: 2020
Hydrogeochemistry of shallow karoo basin aquifers in the border-kei region flanking the Indian Ocean, Eastern Cape, South Africa
- Authors: Jeppesen, Keegan
- Date: 2020
- Subjects: Water chemistry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48401 , vital:40856
- Description: As the potential for shale gas exploitation becomes a real possibility across parts of the Karoo in South Africa, and groundwater is one of the systems that could become heavily stressed if the shale gas industry becomes operational, it is important therefore to gain a better understanding into the hydrogeochemical systems and processes that occur within the Karoo Basin. Groundwater systems are very complex and are heavily relied upon in many areas across the Karoo that are surface water deficient. Groundwater is used domestically, for irrigation and livestock as well as in industry. A hydrogeochemical baseline investigation was undertaken in the shallow Karoo Basin aquifers (< 100 m) of the Border-Kei region with in the Eastern Cape of South Africa, which flanks the Indian Ocean. Since it has been suggested that seawater might be used as a potential fracking fluid, it is important to also establish baseline data linked to potential seawater salinisation in the coastal aquifers. This was achieved by sampling water from both 35 production and 3 non-production boreholes (by making use of a bailer and discrete interval sampler). Water from all 38 samples was analysed for major anions and cations, trace elements as well as for δ 18O and δ 2H stable isotopes. Results indicate that the majority of the groundwater in the study area falls within acceptable limits for domestic use, and although slightly saline, is exploitable for other uses as well. It was also found that dolerite dykes that have intruded into the Karoo Basin sediments have slight effects on the groundwater chemistry, but that these effects are also masked by the water-rock interactions occurring with the aquifer. It was also determined with major ions and stable isotopes that although the coastal aquifers do have saline signatures (EC > 200 mS/m) this is not due to salinisation via seawater intrusion. It is instead postulated that the salinity arises from marine aerosols that have introduced NaCl onto the soil layer, and which then leaches into the groundwater system through precipitation or irrigation. In the event of shale gas extraction through fracking or the expansion of rural and urban centres, this project serves as a preliminary hydrogeochemical baseline before any of these processes proceed within the Karoo Basin.
- Full Text:
- Date Issued: 2020
- Authors: Jeppesen, Keegan
- Date: 2020
- Subjects: Water chemistry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48401 , vital:40856
- Description: As the potential for shale gas exploitation becomes a real possibility across parts of the Karoo in South Africa, and groundwater is one of the systems that could become heavily stressed if the shale gas industry becomes operational, it is important therefore to gain a better understanding into the hydrogeochemical systems and processes that occur within the Karoo Basin. Groundwater systems are very complex and are heavily relied upon in many areas across the Karoo that are surface water deficient. Groundwater is used domestically, for irrigation and livestock as well as in industry. A hydrogeochemical baseline investigation was undertaken in the shallow Karoo Basin aquifers (< 100 m) of the Border-Kei region with in the Eastern Cape of South Africa, which flanks the Indian Ocean. Since it has been suggested that seawater might be used as a potential fracking fluid, it is important to also establish baseline data linked to potential seawater salinisation in the coastal aquifers. This was achieved by sampling water from both 35 production and 3 non-production boreholes (by making use of a bailer and discrete interval sampler). Water from all 38 samples was analysed for major anions and cations, trace elements as well as for δ 18O and δ 2H stable isotopes. Results indicate that the majority of the groundwater in the study area falls within acceptable limits for domestic use, and although slightly saline, is exploitable for other uses as well. It was also found that dolerite dykes that have intruded into the Karoo Basin sediments have slight effects on the groundwater chemistry, but that these effects are also masked by the water-rock interactions occurring with the aquifer. It was also determined with major ions and stable isotopes that although the coastal aquifers do have saline signatures (EC > 200 mS/m) this is not due to salinisation via seawater intrusion. It is instead postulated that the salinity arises from marine aerosols that have introduced NaCl onto the soil layer, and which then leaches into the groundwater system through precipitation or irrigation. In the event of shale gas extraction through fracking or the expansion of rural and urban centres, this project serves as a preliminary hydrogeochemical baseline before any of these processes proceed within the Karoo Basin.
- Full Text:
- Date Issued: 2020