Measuring the industry maturity of the South African export table grape industry
- Authors: De Bruyn, Corean
- Date: 2019
- Subjects: Exports -- South Africa , Fruit trade -- South Africa Agriculture -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/39403 , vital:35243
- Description: Despite the fact that the South African export table grape industry is more than a century old, studies which focus on the development of the industry have not previously been conducted. The main aim of this study was to measure the phase of maturity of the South African export table grape industry. The industry life cycle model was a main focus point to measure the maturity of the South African export table grape industry and as such has been used to analyse the dynamics of the South African export table grape industry. An expansive literature study was conducted to identify as many variables as possible that serve as indicators of the phase of maturity. A measuring instrument, in the form of a questionnaire, was developed, based on these identified variables. A randomly selected sample of 214 export table grape producers completed the questionnaire. Five main export table grape regions are present in South Africa, namely, the Hex River Valley region, the Berg River region, the Olifants River region, the Orange River region and the Northern Province region. An exploratory factor analysis was used to disentangle and reduce the large number of variables. From the factor analysis, four distinct factors emerged, namely: Manufacturing and Distribution, Demand, Research and Development, and Buyer Segments. Cronbach’s coefficient alpha was employed to confirm the reliability and internal consistency of the measuring instrument. The mean scores and standard deviations were used to determine the strength of direction of each of the four variables, followed by a t-test to determine the differences in development between the five regions. Finally, the Pearson’s Product Moment Correlations were calculated for investigating the correlations between the variables used. The findings indicated that, among the five-export table grape regions in South Africa, Manufacturing and Distribution have evolved beyond the introductory phase, but that there is still considerable scope for growth in all the regions. Additionally, there are significant differences between the five regions, thereby indicating that the industry exhibits uneven development with some of the regions being further along the path of development. Demand delivered the second highest mean score and the smallest variation among the five regions. This indicates that export table grapes from South African producers have a loyal customer base. The mean score, however, still indicated that the industry as a whole is in the growth phase of development. Research and Development delivered the highest mean score, thereby signifying the industry’s commitment to research and development. This once again points to an industry being in the growth phase of development. The average mean score delivered by Buyer Segments indicates that the market has begun to fragment. This provides opportunities to create and exploit niche marks. This too conforms to the characteristics of the growth phase in the industry life cycle model. In essence, the current study provided useful information regarding the evolution of the South African export table grape industry. Moreover, a foundation has been laid for further research to be conducted in the industry life cycle of the South African export table grape industry.
- Full Text:
- Date Issued: 2019
- Authors: De Bruyn, Corean
- Date: 2019
- Subjects: Exports -- South Africa , Fruit trade -- South Africa Agriculture -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/39403 , vital:35243
- Description: Despite the fact that the South African export table grape industry is more than a century old, studies which focus on the development of the industry have not previously been conducted. The main aim of this study was to measure the phase of maturity of the South African export table grape industry. The industry life cycle model was a main focus point to measure the maturity of the South African export table grape industry and as such has been used to analyse the dynamics of the South African export table grape industry. An expansive literature study was conducted to identify as many variables as possible that serve as indicators of the phase of maturity. A measuring instrument, in the form of a questionnaire, was developed, based on these identified variables. A randomly selected sample of 214 export table grape producers completed the questionnaire. Five main export table grape regions are present in South Africa, namely, the Hex River Valley region, the Berg River region, the Olifants River region, the Orange River region and the Northern Province region. An exploratory factor analysis was used to disentangle and reduce the large number of variables. From the factor analysis, four distinct factors emerged, namely: Manufacturing and Distribution, Demand, Research and Development, and Buyer Segments. Cronbach’s coefficient alpha was employed to confirm the reliability and internal consistency of the measuring instrument. The mean scores and standard deviations were used to determine the strength of direction of each of the four variables, followed by a t-test to determine the differences in development between the five regions. Finally, the Pearson’s Product Moment Correlations were calculated for investigating the correlations between the variables used. The findings indicated that, among the five-export table grape regions in South Africa, Manufacturing and Distribution have evolved beyond the introductory phase, but that there is still considerable scope for growth in all the regions. Additionally, there are significant differences between the five regions, thereby indicating that the industry exhibits uneven development with some of the regions being further along the path of development. Demand delivered the second highest mean score and the smallest variation among the five regions. This indicates that export table grapes from South African producers have a loyal customer base. The mean score, however, still indicated that the industry as a whole is in the growth phase of development. Research and Development delivered the highest mean score, thereby signifying the industry’s commitment to research and development. This once again points to an industry being in the growth phase of development. The average mean score delivered by Buyer Segments indicates that the market has begun to fragment. This provides opportunities to create and exploit niche marks. This too conforms to the characteristics of the growth phase in the industry life cycle model. In essence, the current study provided useful information regarding the evolution of the South African export table grape industry. Moreover, a foundation has been laid for further research to be conducted in the industry life cycle of the South African export table grape industry.
- Full Text:
- Date Issued: 2019
Mechanism of action of non-synonymous single nucleotide variations associated with α-carbonic anhydrase II deficiency:
- Sanyanga, Taremekedzwa A, Nizami, Bilal, Tastan Bishop, Özlem
- Authors: Sanyanga, Taremekedzwa A , Nizami, Bilal , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162655 , vital:40970 , https://doi.org/10.3390/molecules24213987
- Description: Human carbonic anhydrase II (CA-II) is a Zinc (Zn 2+ ) metalloenzyme responsible for maintenance of acid-base balance within the body through the reversible hydration of CO 2 to produce protons (H + ) and bicarbonate (BCT). Due to its importance, alterations to the amino acid sequence of the protein as a result of single nucleotide variations (nsSNVs) have detrimental effects on homeostasis. Six pathogenic CA-II nsSNVs, K18E, K18Q, H107Y, P236H, P236R and N252D were identified, and variant protein models calculated using homology modeling. The effect of each nsSNV was analyzed using motif analysis, molecular dynamics (MD) simulations, principal component (PCA) and dynamic residue network (DRN) analysis. Motif analysis identified 11 functionally important motifs in CA-II.
- Full Text:
- Date Issued: 2019
- Authors: Sanyanga, Taremekedzwa A , Nizami, Bilal , Tastan Bishop, Özlem
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/162655 , vital:40970 , https://doi.org/10.3390/molecules24213987
- Description: Human carbonic anhydrase II (CA-II) is a Zinc (Zn 2+ ) metalloenzyme responsible for maintenance of acid-base balance within the body through the reversible hydration of CO 2 to produce protons (H + ) and bicarbonate (BCT). Due to its importance, alterations to the amino acid sequence of the protein as a result of single nucleotide variations (nsSNVs) have detrimental effects on homeostasis. Six pathogenic CA-II nsSNVs, K18E, K18Q, H107Y, P236H, P236R and N252D were identified, and variant protein models calculated using homology modeling. The effect of each nsSNV was analyzed using motif analysis, molecular dynamics (MD) simulations, principal component (PCA) and dynamic residue network (DRN) analysis. Motif analysis identified 11 functionally important motifs in CA-II.
- Full Text:
- Date Issued: 2019
Mechanisms and modes of β-N-methylamino-lalanine neurotoxicity: the basis for designing therapies
- Authors: Van Onselen, Rianita
- Date: 2019
- Subjects: Cyanobacteria , Amino acids -- Toxicology , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/32971 , vital:32483
- Description: Since the discovery of the non-canonical amino acid β-N-methylamino-L-alanine (BMAA) and the demonstration of its acute neurotoxicity in chicks and rats, it has been postulated that BMAA might contribute to the development of neurodegenerative diseases worldwide due to its presence in numerous aquatic and terrestrial food webs. This hypothesized link was widely criticized because of the inability to reproduce symptoms in a BMAA-exposed animal model that resembled the symptoms observed in humans, and for the inability to achieve significant levels of toxicity in in vitro models via the postulated mechanisms of toxicity. The most widely described mechanism of BMAA toxicity was excitotoxicity by over-excitation of ionotropic and/or metabotropic glutamate receptors following activation by BMAA. However, the excitotoxic potency of BMAA is much lower than those of other known excitotoxins and it was not known whether BMAA could accumulate in significant concentrations in synapses to cause the said excitotoxicity. Therefore, uptake of BMAA into synaptic vesicles from where it can be released into synapses in high concentrations, was investigated and it was found that, unlike the uptake that was observed for glutamate, BMAA was not taken up into synaptic vesicles. This discovery suggests that BMAA is not released into synapses via synaptic vesicles and that excitotoxicity is an unlikely mechanism of BMAA toxicity in mammalian systems. Misincorporation of BMAA into proteins in the place of L-serine was suggested to be an important mechanism of BMAA toxicity that could lead to protein misfolding and the subsequent protein aggregates that are typically found in the central nervous system (CNS) of neurodegenerative disease patients. However, previous studies in prokaryotes and in a rat pheochromocytoma PC12 cell line showed that misincorporation of BMAA does not occur to any significant extent. However, these studies were criticized for not using human-derived model systems to show that misincorporation does not occur, and it was argued that due to differences in mitochondrial protein synthesis mechanisms, misincorporation of BMAA into human proteins could not be ruled out as a possible mechanism of toxicity. Therefore, misincorporation of BMAA was investigated in a number of human-derived non-neuronal cell lines and directly compared to the misincorporation of other known amino acid analogues. No evidence of misincorporation of BMAA into these cell lines was obtained and therefore it was concluded that misincorporation of BMAA into proteins does not occur in human-derived cell models. Although misincorporation of BMAA into proteins was refuted as a mechanism of toxicity, the strong interactions between BMAA and proteins that require extensive purification procedures to remove the associated BMAA, could not be discounted as a possible contributor to the toxicity of BMAA. Cell-free interactions between BMAA and enzymes, which resulted in reduced activity, were described previously but the nature of these interactions was never determined. Therefore, the direct interactions between BMAA and a range of commercial proteins and melanin (that is known to also have a strong affinity for BMAA) were investigated in an attempt to describe the nature of these interactions. It was discovered that BMAA has a high affinity for hydroxyl groups, and that if these hydroxyl groups in the form of hydroxyl containing amino acid residues occurred in important regulatory or active sites of proteins, BMAA reduced the enzyme activity. Catalase was subsequently selected as an important enzyme required for the maintenance of the delicate reactive oxygen species (ROS) balance in the CNS, to test the effect of BMAA on the activity of the enzyme. BMAA inhibited a human commercial extract of catalase in a cell free system, and this inhibition appeared to be non-competitive in nature. Subsequently, catalase in an extract from a human cell line was also shown to be inhibited by BMAA and it was concluded that this BMAA induced inhibition of catalase could be an important contributor to the toxicity of BMAA in in vivo systems. The affinity of BMAA for hydroxyl groups, especially the reactive L-tyrosine side chain hydroxyl, was recognized as a possible mechanism that can be utilized to protect against the toxicity of BMAA. It was subsequently shown that excess concentrations of L-serine and L-tyrosine could protect against the BMAA-induced enzyme inhibition and improper folding of proteins in a cell-free system. By administering an equimolar concentration of either L-phenylalanine (the soluble precursor of L-tyrosine) or L-serine an hour before administration of BMAA in a rat model, the BMAA-induced neurotoxicity was greatly reduced, especially by treatment with L-phenylalanine, which resulted in a decrease of between 60-70% in the observed neuropathologies. It was recognized that the protection offered by L-phenylalanine was greater than would be expected if protection was by virtue of direct hydroxyl binding alone and it was subsequently hypothesized that the conversion of L-phenylalanine to dopamine could have contributed to the observed protection. Subsequently, the possible protection offered by dopamine, administered as L-DOPA, against BMAA neurotoxicity was investigated in the same neonatal rat model and compared to the protection offered by L-tyrosine. It was discovered that dopamine protected against the BMAAinduced neuronal cell losses in the hippocampus, striatum and spinal cord but it was not as efficient as L-tyrosine in protection against the BMAA-induced proteinopathies, suggesting two distinct mechanisms of BMAA toxicity, one of which is a depletion of dopamine, which had not been previously described. Finally, the nature of the BMAA-induced dopamine depletion was investigated by administering BMAA in combination with other dopaminergic modifiers viz. apomorphine (a D1/D2 receptor agonist), a dopamine transporter inhibitor (GBR12783) and reserpine (a vesicular monoamine transporter -VMAT2- inhibitor) to the neonatal rat model in an attempt to describe how BMAA functions as a dopaminergic toxin. Based on these results it was concluded that BMAA inhibits uptake of dopamine into synaptic vesicles by inhibiting VMAT2-mediated uptake of dopamine, which causes neuronal loss in the hippocampus, striatum and substantia nigra pars compacta, and that the BMAA-induced inhibition of catalase contributes significantly to the toxicity of BMAA by causing an accumulation of hydrogen peroxide in the hippocampus, striatum and spinal cord, which results in extensive neuronal damage in these areas. This work was the first to thoroughly investigate the mechanisms that explain the observed pathologies caused by BMAA in an in vivo model, and was the first to suggest that BMAA can reduce the dopamine in the CNS by inhibiting VMAT2-mediated uptake of dopamine into synaptic vesicles, and increase damage by reactive oxygen species by inhibiting catalase. BMAA is therefore a multimechanistic and multimodal.
- Full Text:
- Date Issued: 2019
- Authors: Van Onselen, Rianita
- Date: 2019
- Subjects: Cyanobacteria , Amino acids -- Toxicology , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/32971 , vital:32483
- Description: Since the discovery of the non-canonical amino acid β-N-methylamino-L-alanine (BMAA) and the demonstration of its acute neurotoxicity in chicks and rats, it has been postulated that BMAA might contribute to the development of neurodegenerative diseases worldwide due to its presence in numerous aquatic and terrestrial food webs. This hypothesized link was widely criticized because of the inability to reproduce symptoms in a BMAA-exposed animal model that resembled the symptoms observed in humans, and for the inability to achieve significant levels of toxicity in in vitro models via the postulated mechanisms of toxicity. The most widely described mechanism of BMAA toxicity was excitotoxicity by over-excitation of ionotropic and/or metabotropic glutamate receptors following activation by BMAA. However, the excitotoxic potency of BMAA is much lower than those of other known excitotoxins and it was not known whether BMAA could accumulate in significant concentrations in synapses to cause the said excitotoxicity. Therefore, uptake of BMAA into synaptic vesicles from where it can be released into synapses in high concentrations, was investigated and it was found that, unlike the uptake that was observed for glutamate, BMAA was not taken up into synaptic vesicles. This discovery suggests that BMAA is not released into synapses via synaptic vesicles and that excitotoxicity is an unlikely mechanism of BMAA toxicity in mammalian systems. Misincorporation of BMAA into proteins in the place of L-serine was suggested to be an important mechanism of BMAA toxicity that could lead to protein misfolding and the subsequent protein aggregates that are typically found in the central nervous system (CNS) of neurodegenerative disease patients. However, previous studies in prokaryotes and in a rat pheochromocytoma PC12 cell line showed that misincorporation of BMAA does not occur to any significant extent. However, these studies were criticized for not using human-derived model systems to show that misincorporation does not occur, and it was argued that due to differences in mitochondrial protein synthesis mechanisms, misincorporation of BMAA into human proteins could not be ruled out as a possible mechanism of toxicity. Therefore, misincorporation of BMAA was investigated in a number of human-derived non-neuronal cell lines and directly compared to the misincorporation of other known amino acid analogues. No evidence of misincorporation of BMAA into these cell lines was obtained and therefore it was concluded that misincorporation of BMAA into proteins does not occur in human-derived cell models. Although misincorporation of BMAA into proteins was refuted as a mechanism of toxicity, the strong interactions between BMAA and proteins that require extensive purification procedures to remove the associated BMAA, could not be discounted as a possible contributor to the toxicity of BMAA. Cell-free interactions between BMAA and enzymes, which resulted in reduced activity, were described previously but the nature of these interactions was never determined. Therefore, the direct interactions between BMAA and a range of commercial proteins and melanin (that is known to also have a strong affinity for BMAA) were investigated in an attempt to describe the nature of these interactions. It was discovered that BMAA has a high affinity for hydroxyl groups, and that if these hydroxyl groups in the form of hydroxyl containing amino acid residues occurred in important regulatory or active sites of proteins, BMAA reduced the enzyme activity. Catalase was subsequently selected as an important enzyme required for the maintenance of the delicate reactive oxygen species (ROS) balance in the CNS, to test the effect of BMAA on the activity of the enzyme. BMAA inhibited a human commercial extract of catalase in a cell free system, and this inhibition appeared to be non-competitive in nature. Subsequently, catalase in an extract from a human cell line was also shown to be inhibited by BMAA and it was concluded that this BMAA induced inhibition of catalase could be an important contributor to the toxicity of BMAA in in vivo systems. The affinity of BMAA for hydroxyl groups, especially the reactive L-tyrosine side chain hydroxyl, was recognized as a possible mechanism that can be utilized to protect against the toxicity of BMAA. It was subsequently shown that excess concentrations of L-serine and L-tyrosine could protect against the BMAA-induced enzyme inhibition and improper folding of proteins in a cell-free system. By administering an equimolar concentration of either L-phenylalanine (the soluble precursor of L-tyrosine) or L-serine an hour before administration of BMAA in a rat model, the BMAA-induced neurotoxicity was greatly reduced, especially by treatment with L-phenylalanine, which resulted in a decrease of between 60-70% in the observed neuropathologies. It was recognized that the protection offered by L-phenylalanine was greater than would be expected if protection was by virtue of direct hydroxyl binding alone and it was subsequently hypothesized that the conversion of L-phenylalanine to dopamine could have contributed to the observed protection. Subsequently, the possible protection offered by dopamine, administered as L-DOPA, against BMAA neurotoxicity was investigated in the same neonatal rat model and compared to the protection offered by L-tyrosine. It was discovered that dopamine protected against the BMAAinduced neuronal cell losses in the hippocampus, striatum and spinal cord but it was not as efficient as L-tyrosine in protection against the BMAA-induced proteinopathies, suggesting two distinct mechanisms of BMAA toxicity, one of which is a depletion of dopamine, which had not been previously described. Finally, the nature of the BMAA-induced dopamine depletion was investigated by administering BMAA in combination with other dopaminergic modifiers viz. apomorphine (a D1/D2 receptor agonist), a dopamine transporter inhibitor (GBR12783) and reserpine (a vesicular monoamine transporter -VMAT2- inhibitor) to the neonatal rat model in an attempt to describe how BMAA functions as a dopaminergic toxin. Based on these results it was concluded that BMAA inhibits uptake of dopamine into synaptic vesicles by inhibiting VMAT2-mediated uptake of dopamine, which causes neuronal loss in the hippocampus, striatum and substantia nigra pars compacta, and that the BMAA-induced inhibition of catalase contributes significantly to the toxicity of BMAA by causing an accumulation of hydrogen peroxide in the hippocampus, striatum and spinal cord, which results in extensive neuronal damage in these areas. This work was the first to thoroughly investigate the mechanisms that explain the observed pathologies caused by BMAA in an in vivo model, and was the first to suggest that BMAA can reduce the dopamine in the CNS by inhibiting VMAT2-mediated uptake of dopamine into synaptic vesicles, and increase damage by reactive oxygen species by inhibiting catalase. BMAA is therefore a multimechanistic and multimodal.
- Full Text:
- Date Issued: 2019
Medicinal Plants Used to Treat and Manage Respiratory Infections in the Limpopo Province, South Africa: Phytotherapeutic Study of Bapedi Traditional Healers’ Practices
- Authors: Semenya, Sebua Silas
- Date: 2019
- Subjects: Medicinal plants Respiratory infections -- Alternative treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15716 , vital:40512
- Description: There is paucity of data on South African traditional healers’ (THs) phytotherapeutic practices regarding respiratory infections (RIs). Several people in South Africa are contracting RIs due to prevalence of risk factors. This situation is exacerbated by limited modern health care facilities and associated personnel in some provinces in the country. The primary objectives of this study were twofold. First purpose was to execute a comprehensive social and ethnobotanical surveys aimed at (a) establishing the types of RIs treated by THs and diagnosis techniques used, (b) plants used as therapies for RIs and associated indigenous knowledge practices, (c) source/s of plants used as medicines, (d) harvesting practices, current local availability status, conservation status and threats of indigenous plants as well as the level of conservation knowledge possessed by THs. The second objective was to assess the therapeutic value of the four most frequently used plant species by THs by (a) analysing the phytochemical profile of the plant extracts, (b) their antioxidant activities, and (c) their antibacterial activities. Information linked to the social and ethnobotanical surveys was gathered via a semi-structured questionnaires, supplemented by field observations during face-to-face interview with 240 conveniently selected THs practicing in the municipalities of Capricorn, Sekhukhune and Waterberg districts of the Limpopo Province, South Africa. Data were generally analysed using Microsoft Excel and Statistical Package for the Social Sciences (SPSS). In addition to these softwares, ethnobotanical data were analysed via quantitative ethnobotanical indexes namely use mention (UM), fidelity level (FL), use value (UV) and preference ranking (PR). For laboratory experiments, qualitative phytochemical constitutes of the crude extracts were determined using the standard screening methods. The antioxidant activities of acetone, dichlomethane, hexane, methanol and water crude extracts were evaluated using qualitative and quantitative 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assays. Antibacterial activities of these extracts was assessed using microdilution and bioautography assays. Six types of RIs; tuberculosis (84.1%), sore throat (65%), asthma (58.3%), sinusitis (55%), pneumonia (53.3%) and rhinitis (43.7%) were treated by THs practicing as herbalists (58.7%), herbalists and diviners (40.5%), and diviners (0.4%). The identification of these RIs was based on the patients’ presentation of certain clinical symptoms, with THs practicing both herbalism and divination additionally using bone casting. There was a broad overlap between the clinical signs used to diagnose most of the RIs, and the specificity of symptoms followed when ascertaining an individual infection was low. A total of 224 plant species (83% indigenous and 16.9% exotics) belonging to 177 genera and 85 botanical families, mainly the Fabaceae (25 spp.) and Asteraceae (16 spp.) were used by THs as herbal medicines for the aforesaid RIs and perceived related symptoms (RSs). Most of the documented plant species were used for tuberculosis (82.1%) and asthma (46.4%). Roots (64%) and leaves (13%) formed an important mainstay for medicinal recipes preparations. Different routes of administering these recipes were noted, with oral (75.6%) and nasal (18.8%) being the most preferred. The most widely used species by THs to treat and manage all the six RIs with high UM, FL, UV and PR values included Clerodendrum ternatum, Cryptocarya transvaalensis, Enicostema axillare, Lasiosiphon caffer and Stylochaeton natalensis. Overall larger numbers of species used by Bapedi THs including the mentioned ones are recorded for the first time in scientific literature as remedies for RIs and RSs, thus reflecting a need for more similar studies amongst other ethnic groups of South Africa and elsewhere. The phytochemical screening of four most used plants C. ternatum, C. transvaalensis, E. axillare and L. caffer crude extracts revealed the presence of alkaloids, anthraquinones, cardiac glycosides, flavonoids, phlobatannin, saponins, steroids, tannins and terpenes. All plants including those that did not display any antioxidant activities using qualitative DPPH assay displayed a certain level of scavenging activity when quantified, with the mentioned extracts from E. axillare (water and hexane), L. caffer (water and acetone) and C. ternatum (acetone) showing excellent activity almost comparable to a standard antioxidant drug (ascorbic acid). Plant extracts from all used solvents were active against Mycobacterium smegmatis, Klebsiella pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa with miniumum bactericidal concentration values ranging between 0.019 and 2.5 mg/ml depending on the plant species. Some of plant extracts exhibited minimum inhibitory concentration values ranging between 0.63 to 2.5 mg/ml. This study showed that most of the diagnosis methods used by Bapedi THs and their herbal medicines have the potential to contribute towards the management and treatment of RIs and RSs. iii | Page Future endeavour should be focused on the following: (a) possibility of collaboration between questioned THs and local western health care practitioners in the treatment of these diseases, and (b) isolation, purification and characterization of the biologically active compounds from extract of the above-stated plants, amongst other inquiries.
- Full Text:
- Date Issued: 2019
- Authors: Semenya, Sebua Silas
- Date: 2019
- Subjects: Medicinal plants Respiratory infections -- Alternative treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15716 , vital:40512
- Description: There is paucity of data on South African traditional healers’ (THs) phytotherapeutic practices regarding respiratory infections (RIs). Several people in South Africa are contracting RIs due to prevalence of risk factors. This situation is exacerbated by limited modern health care facilities and associated personnel in some provinces in the country. The primary objectives of this study were twofold. First purpose was to execute a comprehensive social and ethnobotanical surveys aimed at (a) establishing the types of RIs treated by THs and diagnosis techniques used, (b) plants used as therapies for RIs and associated indigenous knowledge practices, (c) source/s of plants used as medicines, (d) harvesting practices, current local availability status, conservation status and threats of indigenous plants as well as the level of conservation knowledge possessed by THs. The second objective was to assess the therapeutic value of the four most frequently used plant species by THs by (a) analysing the phytochemical profile of the plant extracts, (b) their antioxidant activities, and (c) their antibacterial activities. Information linked to the social and ethnobotanical surveys was gathered via a semi-structured questionnaires, supplemented by field observations during face-to-face interview with 240 conveniently selected THs practicing in the municipalities of Capricorn, Sekhukhune and Waterberg districts of the Limpopo Province, South Africa. Data were generally analysed using Microsoft Excel and Statistical Package for the Social Sciences (SPSS). In addition to these softwares, ethnobotanical data were analysed via quantitative ethnobotanical indexes namely use mention (UM), fidelity level (FL), use value (UV) and preference ranking (PR). For laboratory experiments, qualitative phytochemical constitutes of the crude extracts were determined using the standard screening methods. The antioxidant activities of acetone, dichlomethane, hexane, methanol and water crude extracts were evaluated using qualitative and quantitative 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assays. Antibacterial activities of these extracts was assessed using microdilution and bioautography assays. Six types of RIs; tuberculosis (84.1%), sore throat (65%), asthma (58.3%), sinusitis (55%), pneumonia (53.3%) and rhinitis (43.7%) were treated by THs practicing as herbalists (58.7%), herbalists and diviners (40.5%), and diviners (0.4%). The identification of these RIs was based on the patients’ presentation of certain clinical symptoms, with THs practicing both herbalism and divination additionally using bone casting. There was a broad overlap between the clinical signs used to diagnose most of the RIs, and the specificity of symptoms followed when ascertaining an individual infection was low. A total of 224 plant species (83% indigenous and 16.9% exotics) belonging to 177 genera and 85 botanical families, mainly the Fabaceae (25 spp.) and Asteraceae (16 spp.) were used by THs as herbal medicines for the aforesaid RIs and perceived related symptoms (RSs). Most of the documented plant species were used for tuberculosis (82.1%) and asthma (46.4%). Roots (64%) and leaves (13%) formed an important mainstay for medicinal recipes preparations. Different routes of administering these recipes were noted, with oral (75.6%) and nasal (18.8%) being the most preferred. The most widely used species by THs to treat and manage all the six RIs with high UM, FL, UV and PR values included Clerodendrum ternatum, Cryptocarya transvaalensis, Enicostema axillare, Lasiosiphon caffer and Stylochaeton natalensis. Overall larger numbers of species used by Bapedi THs including the mentioned ones are recorded for the first time in scientific literature as remedies for RIs and RSs, thus reflecting a need for more similar studies amongst other ethnic groups of South Africa and elsewhere. The phytochemical screening of four most used plants C. ternatum, C. transvaalensis, E. axillare and L. caffer crude extracts revealed the presence of alkaloids, anthraquinones, cardiac glycosides, flavonoids, phlobatannin, saponins, steroids, tannins and terpenes. All plants including those that did not display any antioxidant activities using qualitative DPPH assay displayed a certain level of scavenging activity when quantified, with the mentioned extracts from E. axillare (water and hexane), L. caffer (water and acetone) and C. ternatum (acetone) showing excellent activity almost comparable to a standard antioxidant drug (ascorbic acid). Plant extracts from all used solvents were active against Mycobacterium smegmatis, Klebsiella pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa with miniumum bactericidal concentration values ranging between 0.019 and 2.5 mg/ml depending on the plant species. Some of plant extracts exhibited minimum inhibitory concentration values ranging between 0.63 to 2.5 mg/ml. This study showed that most of the diagnosis methods used by Bapedi THs and their herbal medicines have the potential to contribute towards the management and treatment of RIs and RSs. iii | Page Future endeavour should be focused on the following: (a) possibility of collaboration between questioned THs and local western health care practitioners in the treatment of these diseases, and (b) isolation, purification and characterization of the biologically active compounds from extract of the above-stated plants, amongst other inquiries.
- Full Text:
- Date Issued: 2019
Memory of a dead river
- Authors: Mayo, Thandokazi
- Date: 2019
- Subjects: Short stories, South African (English) , South African (English)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/92364 , vital:30716
- Description: My thesis is a collection of short stories that tap into cultural, literal references, both oral andvisual, and also draws on images I have seen and have struggled to get out of my head. The collection draws on Alissa Nutting’s distorted realism and Noy Holland’s evocative imagery to make even the most mundane things feel like something out of the ordinary. An unreal way of looking at real things. The stories are interrelated only insofar as they seek to normalise or neutralise the peculiarity of society’s seemingly outdated people who come from the rural areas. Their faces, their stories, their general mannerisms. To capture the tone of their emotions, their small plights, and to give an in-depth look into how where you are affects the very shape of your face.
- Full Text:
- Date Issued: 2019
- Authors: Mayo, Thandokazi
- Date: 2019
- Subjects: Short stories, South African (English) , South African (English)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/92364 , vital:30716
- Description: My thesis is a collection of short stories that tap into cultural, literal references, both oral andvisual, and also draws on images I have seen and have struggled to get out of my head. The collection draws on Alissa Nutting’s distorted realism and Noy Holland’s evocative imagery to make even the most mundane things feel like something out of the ordinary. An unreal way of looking at real things. The stories are interrelated only insofar as they seek to normalise or neutralise the peculiarity of society’s seemingly outdated people who come from the rural areas. Their faces, their stories, their general mannerisms. To capture the tone of their emotions, their small plights, and to give an in-depth look into how where you are affects the very shape of your face.
- Full Text:
- Date Issued: 2019
Mental health practitioners’ perceptions of utilising animal-assisted interventions
- Authors: Scheepers, Jessica
- Date: 2019
- Subjects: Animals -- Therapeutic use , Pets -- Therapeutic use Human-animal relationships Psychiatry -- Practice Mental health counseling
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/43512 , vital:36903
- Description: Clarity in recognising the individuals or circumstances where interaction with animals is possibly beneficial and suitable, is essential for both the individuals and the animals. The present research study attempted to document the intervention factors when local mental health practitioners utilise animal-assisted interventions (AAIs). This study was undertaken to explore and describe the factors mental health practitioners perceive as important when utilising AAIs for clients. In doing so the researcher was able to identify and describe the characteristics of clients considered by mental health practitioners for utilising AAIs, also the psychopathological conditions for which mental health practitioners utilise AAIs and the non-psychopathological applications. Additionally, the researcher identified and described the types and characteristics of the animals that are utilised in AAIs by mental health practitioners. The current study utilised a qualitative research approach employing non-probability purposive sampling. Semi-structured interviews were conducted with six female mental health practitioners. All participants had implemented AAIs and were able to speak English fluently. Interviews were conducted in English and continued until data saturation was reached. Findings in the current study demonstrate that local mental health practitioners have numerous considerations that pertain to the client including the human attributes that influence the selection of AAI, an appropriate climate (weather during outdoor therapy), and the medical conditions that may influence the implementation of AAIs. The current research also found that there is a broad scope for psychopathological applications of AAIs. Finally, there are several considerations pertaining to the animal that is used for the AAI, including trustworthiness/predictability, relevant attributes, skills/training the animal requires, a suitable environment, and fatigue/therapy exhaustion that may occur during AAIs. Limitations to the current study were identified - including limitations to the methodology employed and only female participants - and recommendations were made for further research.
- Full Text:
- Date Issued: 2019
- Authors: Scheepers, Jessica
- Date: 2019
- Subjects: Animals -- Therapeutic use , Pets -- Therapeutic use Human-animal relationships Psychiatry -- Practice Mental health counseling
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/43512 , vital:36903
- Description: Clarity in recognising the individuals or circumstances where interaction with animals is possibly beneficial and suitable, is essential for both the individuals and the animals. The present research study attempted to document the intervention factors when local mental health practitioners utilise animal-assisted interventions (AAIs). This study was undertaken to explore and describe the factors mental health practitioners perceive as important when utilising AAIs for clients. In doing so the researcher was able to identify and describe the characteristics of clients considered by mental health practitioners for utilising AAIs, also the psychopathological conditions for which mental health practitioners utilise AAIs and the non-psychopathological applications. Additionally, the researcher identified and described the types and characteristics of the animals that are utilised in AAIs by mental health practitioners. The current study utilised a qualitative research approach employing non-probability purposive sampling. Semi-structured interviews were conducted with six female mental health practitioners. All participants had implemented AAIs and were able to speak English fluently. Interviews were conducted in English and continued until data saturation was reached. Findings in the current study demonstrate that local mental health practitioners have numerous considerations that pertain to the client including the human attributes that influence the selection of AAI, an appropriate climate (weather during outdoor therapy), and the medical conditions that may influence the implementation of AAIs. The current research also found that there is a broad scope for psychopathological applications of AAIs. Finally, there are several considerations pertaining to the animal that is used for the AAI, including trustworthiness/predictability, relevant attributes, skills/training the animal requires, a suitable environment, and fatigue/therapy exhaustion that may occur during AAIs. Limitations to the current study were identified - including limitations to the methodology employed and only female participants - and recommendations were made for further research.
- Full Text:
- Date Issued: 2019
Mental health, where are we now?: a sociological analysis of the integration of mental health into primary healthcare in the Kingdom of Eswatini
- Authors: Dlamini, Zenanile Zoe
- Date: 2019
- Subjects: Mental health services -- Eswatini , Psychiatric hospitals -- Eswatini , Primary health care -- Eswatini , Mentally ill -- Services for -- Eswatini , Mental health policy -- Eswatini
- Language: English
- Type: text , Thesis , Masters , MSocSci
- Identifier: http://hdl.handle.net/10962/96269 , vital:31256
- Description: This is a qualitative study exploring the integration of mental health into primary healthcare in the Kingdom of Eswatini. Primary healthcare forms the basis of any healthcare service provision. Primary Healthcare for mental health is an essential component of any well-functioning health system. Making mental healthcare available in primary healthcare allows for early detection and early treatment while it is still easier and cheaper. Purposive sampling was used to recruit nursesand a government official in the Hhohho region in the Kingdom of Eswatini.The study found that there are major challenges in the primary health care clinics, and this negatively affects the WHO (2001) proposal on mental health integration into primary health care. This finding is similar to other low-income countries’ challenges in mental health integration into primary health care. The impact of neo-liberal policies on healthcare in Eswatini is explored and it is clear these policies impact the ability of the Ministry of Health to provide health care. The study also drew on the symbolic interaction perspective to understand the meanings that nurses attach to mental illness and their experiences mental health care.
- Full Text:
- Date Issued: 2019
- Authors: Dlamini, Zenanile Zoe
- Date: 2019
- Subjects: Mental health services -- Eswatini , Psychiatric hospitals -- Eswatini , Primary health care -- Eswatini , Mentally ill -- Services for -- Eswatini , Mental health policy -- Eswatini
- Language: English
- Type: text , Thesis , Masters , MSocSci
- Identifier: http://hdl.handle.net/10962/96269 , vital:31256
- Description: This is a qualitative study exploring the integration of mental health into primary healthcare in the Kingdom of Eswatini. Primary healthcare forms the basis of any healthcare service provision. Primary Healthcare for mental health is an essential component of any well-functioning health system. Making mental healthcare available in primary healthcare allows for early detection and early treatment while it is still easier and cheaper. Purposive sampling was used to recruit nursesand a government official in the Hhohho region in the Kingdom of Eswatini.The study found that there are major challenges in the primary health care clinics, and this negatively affects the WHO (2001) proposal on mental health integration into primary health care. This finding is similar to other low-income countries’ challenges in mental health integration into primary health care. The impact of neo-liberal policies on healthcare in Eswatini is explored and it is clear these policies impact the ability of the Ministry of Health to provide health care. The study also drew on the symbolic interaction perspective to understand the meanings that nurses attach to mental illness and their experiences mental health care.
- Full Text:
- Date Issued: 2019
Mesoscale alongshore and cross-shore transport and settlement of invertebrate larvae on the south east coast of South Africa
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
Methodological Survey of Simplified TD-DFT Methods for Fast and Accurate Interpretation of UV−Vis−NIR Spectra of Phthalocyanines
- Martynov, Alexander G, Mack, John, May, Aviwe K, Nyokong, Tebello, Gorbunova, Yulia G, Tsivadze, Aslan Yu
- Authors: Martynov, Alexander G , Mack, John , May, Aviwe K , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186915 , vital:44547 , xlink:href="https://doi.org/10.1021/acsomega.8b03500"
- Description: A methodological survey of density functional theory (DFT) methods for the prediction of UV−visible (vis)−near-infrared (NIR) spectra of phthalocyanines is reported. Four methods, namely, full time-dependent (TD)-DFT and its Tamm−Dancoff approximation (TDA), together with their simplified modifications (sTD-DFT and sTDA, respectively), were tested by using the examples of unsubstituted and alkoxy-substituted metal-free ligands and zinc complexes. The theoretical results were compared with experimental data derived from UV−visible absorption and magnetic circular dichroism spectroscopy. Seven popular exchange-correlation functionals (BP86, B3LYP, TPSSh, M06, CAM-B3LYP, LC-BLYP, and ωB97X) were tested within these four approaches starting at a relatively modest level using 6-31G(d) basis sets and gas-phase BP86/def2-SVP optimized geometries. A gradual augmentation of the computational levels was used to identify the influence of starting geometry, solvation effects, and basis sets on the results of TD-DFT and sTD-DFT calculations. It was found that although these factors do influence the predicted energies of the vertical excitations, they do not affect the trends predicted in the spectral properties across series of structurally related substituted free bases and metallophthalocyanines. The best accuracy for the gas-phase vertical excitations was observed in the lower-energy Q-band region for calculations that made use of range-separated hybrids for both full and simplified TD-DFT approaches. The CAMB3LYP functional provided particularly accurate results in the context of the sTD-DFT approach. The description of the higherenergy B-band region is considerably less accurate, and this demonstrates the need for further advances in the accuracy of theoretical calculations. Together with a general increase in accuracy, the application of simplified TD-DFT methods affords a 2−3 orders of magnitude speedup of the calculations in comparison to the full TD-DFT approach. It is anticipated that this approach will be widely used on desktop computers during the interpretation of UV−vis−NIR spectra of phthalocyanines and related macrocycles in the years ahead.
- Full Text:
- Date Issued: 2019
- Authors: Martynov, Alexander G , Mack, John , May, Aviwe K , Nyokong, Tebello , Gorbunova, Yulia G , Tsivadze, Aslan Yu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186915 , vital:44547 , xlink:href="https://doi.org/10.1021/acsomega.8b03500"
- Description: A methodological survey of density functional theory (DFT) methods for the prediction of UV−visible (vis)−near-infrared (NIR) spectra of phthalocyanines is reported. Four methods, namely, full time-dependent (TD)-DFT and its Tamm−Dancoff approximation (TDA), together with their simplified modifications (sTD-DFT and sTDA, respectively), were tested by using the examples of unsubstituted and alkoxy-substituted metal-free ligands and zinc complexes. The theoretical results were compared with experimental data derived from UV−visible absorption and magnetic circular dichroism spectroscopy. Seven popular exchange-correlation functionals (BP86, B3LYP, TPSSh, M06, CAM-B3LYP, LC-BLYP, and ωB97X) were tested within these four approaches starting at a relatively modest level using 6-31G(d) basis sets and gas-phase BP86/def2-SVP optimized geometries. A gradual augmentation of the computational levels was used to identify the influence of starting geometry, solvation effects, and basis sets on the results of TD-DFT and sTD-DFT calculations. It was found that although these factors do influence the predicted energies of the vertical excitations, they do not affect the trends predicted in the spectral properties across series of structurally related substituted free bases and metallophthalocyanines. The best accuracy for the gas-phase vertical excitations was observed in the lower-energy Q-band region for calculations that made use of range-separated hybrids for both full and simplified TD-DFT approaches. The CAMB3LYP functional provided particularly accurate results in the context of the sTD-DFT approach. The description of the higherenergy B-band region is considerably less accurate, and this demonstrates the need for further advances in the accuracy of theoretical calculations. Together with a general increase in accuracy, the application of simplified TD-DFT methods affords a 2−3 orders of magnitude speedup of the calculations in comparison to the full TD-DFT approach. It is anticipated that this approach will be widely used on desktop computers during the interpretation of UV−vis−NIR spectra of phthalocyanines and related macrocycles in the years ahead.
- Full Text:
- Date Issued: 2019
Methods for understanding social-ecological systems: a review of place-based studies
- de Vos, Alta, Biggs, Reinette, Preiser, Rika
- Authors: de Vos, Alta , Biggs, Reinette , Preiser, Rika
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415909 , vital:71299 , xlink:href="https://doi.org/10.5751/ES-11236-240416"
- Description: In recent years, social-ecological systems (SES) have emerged as a prominent analytical framing with which to investigate pressing sustainability issues associated with the Anthropocene era. Despite the growth of SES research, the lack of a delineated set of methods commonly contributes to disorientation for those entering into a field where methodological pluralism is the norm. We conduct a review of SES research, focusing particularly on methods used in this field. Our results reflect the rapid growth in SES research relative to other publications in relevant subject areas, and suggest a maturation of the field. Whilst institutions investigating SES have been mostly based in the global north, focal SES has been more globally distributed, although key regions, especially island regions, remain poorly studied. Key problems addressed in the studies related to policy, trade, conservation, adaptation, land use change, water, forests, sustainability, urban problems, and governance and institutions. We identified 311 methods, which we grouped into 27 method categories that can serve as a guide to SES research methods for newcomers to the field. We also performed an exploratory assessment of the ability of these methods to account for key features of SES as complex adaptive systems. We found that methods do better at accounting for the relational and context-dependent nature of SES, and least well with complex causality. Our study highlights the plurality of methods used in SES research, and helps highlight key areas in need of further methodological development.
- Full Text:
- Date Issued: 2019
- Authors: de Vos, Alta , Biggs, Reinette , Preiser, Rika
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415909 , vital:71299 , xlink:href="https://doi.org/10.5751/ES-11236-240416"
- Description: In recent years, social-ecological systems (SES) have emerged as a prominent analytical framing with which to investigate pressing sustainability issues associated with the Anthropocene era. Despite the growth of SES research, the lack of a delineated set of methods commonly contributes to disorientation for those entering into a field where methodological pluralism is the norm. We conduct a review of SES research, focusing particularly on methods used in this field. Our results reflect the rapid growth in SES research relative to other publications in relevant subject areas, and suggest a maturation of the field. Whilst institutions investigating SES have been mostly based in the global north, focal SES has been more globally distributed, although key regions, especially island regions, remain poorly studied. Key problems addressed in the studies related to policy, trade, conservation, adaptation, land use change, water, forests, sustainability, urban problems, and governance and institutions. We identified 311 methods, which we grouped into 27 method categories that can serve as a guide to SES research methods for newcomers to the field. We also performed an exploratory assessment of the ability of these methods to account for key features of SES as complex adaptive systems. We found that methods do better at accounting for the relational and context-dependent nature of SES, and least well with complex causality. Our study highlights the plurality of methods used in SES research, and helps highlight key areas in need of further methodological development.
- Full Text:
- Date Issued: 2019
Micro-structures, mineralogy, and chemistry of peritidal tufa stromatolites along the Eastern Cape coast
- Edwards, Mark Joseph Kalahari, Rishworth, Gavin M
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
Microalgae as indicators of environmental change in the St Lucia estuarine system
- Authors: Nunes, Monique
- Date: 2019
- Subjects: Microalgae -- South Africa -- St Lucia estuarine
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31165 , vital:31333
- Description: The St Lucia system represents 56% of the estuarine habitat area in South Africa. This dynamic estuarine lake responds to a complex interaction of climatic and anthropogenic drivers. There has been a long history of human interventions and the extended drought (2002-2012) led to major changes. In 1952, the inlet shared between the estuarine system and the Mfolozi River was artificially separated, which significantly reduced freshwater inflow. The systems were separated because of the silt load from the expanding agricultural activities in the Mfolozi River catchment. The drought prompted a critical review of re-establishing the historic connection, and in July 2012, the beach spillway was excavated marking the start of restoring connectivity. Increased rainfall coupled with the partial re-connection with the agriculturally-impacted Mfolozi River shifted the St Lucia estuarine system to a new wet phase. This study investigated the microalgal dynamics of the estuarine system as it transitioned to this new wet phase. Results showed that the phytoplankton and microphytobenthos (MPB) biomass was low (< 5 ug l-1 and < 60 mg m-2 respectively) throughout the system due to nutrient and light availability, water residence time and sediment type. The increased freshwater inflow from the Mfolozi River was limited to the Narrows and available nutrients promoted the growth of cyanobacteria and dinophytes in the water column. Of interest was the presence of the potentially harmful algal species Prorocentrum minimum. A weekly study investigated the relationship between freshwater inflow, phytoplankton succession and the introduction and persistence of harmful microalgal species in the lower reaches. The increased freshwater inflow received from the Mfolozi River has led to a system in a constant state of flux. The changes in salinity, light availability and water residence time, shifted the phytoplankton functional group structure to one where chlorophytes and euglenoids were dominant. The persistence of the nutrient tolerant euglenoids highlighted the influence of the nutrient-enriched freshwater inflow on the phytoplankton functional groups. However, the relative abundance of all functional groups remained low due to the rapid change in environmental conditions. The next step was to test the use of an artificial substrate as a monitoring method to detect nutrient induced change. Findings from the 28-day study showed that epilithic diatom communities growing on glass slides were good indicators of nutrient enrichment. The epilithic algal biomass increased significantly from 1.5 mg m-2 (Day 14) to 6 mg m-2 (Day 21), following peak river inflow. In contrast, the phytoplankton and MPB showed no discernible increase in biomass. Epilithic diatom community diversity, richness and evenness scores declined due to the increasing relative abundance of a single nutrient tolerant species, Cocconeis placentula var. euglypta. The use of diatoms as indicators of change depends on the accuracy of identification to species level. This can be a slow process requiring a high level of taxonomic expertise. Considering that molecular phylogenetic methods are readily used to produce a reliable taxonomic list, the suitability of DNA metabarcoding for diatom monitoring in the St Lucia Estuary was tested. Comparisons between the molecular and morphological method indicated that the diatom taxonomic composition was similar at 9 to 27% for genus level and 2 to 9% at species level. The low taxonomic similarity was related to the large number of unclassified DNA representative sequences included in the molecular inventory due to the incomplete DNA library database. However, the available operational taxonomic units (OTUs) from the molecular method did provide an effective alternative to determine the relevant community diversity estimates required for the application of the South African Estuarine Health Index (EHI). This research has highlighted the dynamic nature of the St Lucia estuarine system and the effectiveness of the microalgal communities to differentiate between the cyclical climatic phases and anthropogenic stressors such as nutrient enrichment.
- Full Text:
- Date Issued: 2019
- Authors: Nunes, Monique
- Date: 2019
- Subjects: Microalgae -- South Africa -- St Lucia estuarine
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31165 , vital:31333
- Description: The St Lucia system represents 56% of the estuarine habitat area in South Africa. This dynamic estuarine lake responds to a complex interaction of climatic and anthropogenic drivers. There has been a long history of human interventions and the extended drought (2002-2012) led to major changes. In 1952, the inlet shared between the estuarine system and the Mfolozi River was artificially separated, which significantly reduced freshwater inflow. The systems were separated because of the silt load from the expanding agricultural activities in the Mfolozi River catchment. The drought prompted a critical review of re-establishing the historic connection, and in July 2012, the beach spillway was excavated marking the start of restoring connectivity. Increased rainfall coupled with the partial re-connection with the agriculturally-impacted Mfolozi River shifted the St Lucia estuarine system to a new wet phase. This study investigated the microalgal dynamics of the estuarine system as it transitioned to this new wet phase. Results showed that the phytoplankton and microphytobenthos (MPB) biomass was low (< 5 ug l-1 and < 60 mg m-2 respectively) throughout the system due to nutrient and light availability, water residence time and sediment type. The increased freshwater inflow from the Mfolozi River was limited to the Narrows and available nutrients promoted the growth of cyanobacteria and dinophytes in the water column. Of interest was the presence of the potentially harmful algal species Prorocentrum minimum. A weekly study investigated the relationship between freshwater inflow, phytoplankton succession and the introduction and persistence of harmful microalgal species in the lower reaches. The increased freshwater inflow received from the Mfolozi River has led to a system in a constant state of flux. The changes in salinity, light availability and water residence time, shifted the phytoplankton functional group structure to one where chlorophytes and euglenoids were dominant. The persistence of the nutrient tolerant euglenoids highlighted the influence of the nutrient-enriched freshwater inflow on the phytoplankton functional groups. However, the relative abundance of all functional groups remained low due to the rapid change in environmental conditions. The next step was to test the use of an artificial substrate as a monitoring method to detect nutrient induced change. Findings from the 28-day study showed that epilithic diatom communities growing on glass slides were good indicators of nutrient enrichment. The epilithic algal biomass increased significantly from 1.5 mg m-2 (Day 14) to 6 mg m-2 (Day 21), following peak river inflow. In contrast, the phytoplankton and MPB showed no discernible increase in biomass. Epilithic diatom community diversity, richness and evenness scores declined due to the increasing relative abundance of a single nutrient tolerant species, Cocconeis placentula var. euglypta. The use of diatoms as indicators of change depends on the accuracy of identification to species level. This can be a slow process requiring a high level of taxonomic expertise. Considering that molecular phylogenetic methods are readily used to produce a reliable taxonomic list, the suitability of DNA metabarcoding for diatom monitoring in the St Lucia Estuary was tested. Comparisons between the molecular and morphological method indicated that the diatom taxonomic composition was similar at 9 to 27% for genus level and 2 to 9% at species level. The low taxonomic similarity was related to the large number of unclassified DNA representative sequences included in the molecular inventory due to the incomplete DNA library database. However, the available operational taxonomic units (OTUs) from the molecular method did provide an effective alternative to determine the relevant community diversity estimates required for the application of the South African Estuarine Health Index (EHI). This research has highlighted the dynamic nature of the St Lucia estuarine system and the effectiveness of the microalgal communities to differentiate between the cyclical climatic phases and anthropogenic stressors such as nutrient enrichment.
- Full Text:
- Date Issued: 2019
Microstructural evolution of welded creep aged 12% cr martensitic stainless steel
- Authors: Marx, Genevéve
- Date: 2019
- Subjects: Stainless steel -- Welding
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30766 , vital:31128
- Description: Tempered martensite ferritic (TMF) steels with 9-12% Cr additions are used extensively for high-pressure steam pipes in coal-fired power plants. They operate at temperatures above 500ºC and are consequently susceptible to creep damage. Due to economic reasons, welding must be performed on service exposed materials when a component needs to be replaced. Fusion welding results in the formation of different microstructural regions within the weldment. The primary failure mechanism of TMF steel welded components is Type IV cracking that results from accelerated void formation in the fine-grained heat affected zone (FGHAZ) during creep. Short-term creep-tests performed across weldments made on new and service exposed steels have shown that the weldment consistently fails in the FGHAZ of the service exposed material. This observation has not yet been fully explained since not much is known about the microstructural evolution of creep aged material during welding. Thus, further investigation on the microstructure of welded creep aged material is warranted. The main aim of this thesis was to investigate the microstructural evolution when welding upon creep aged 9-12% Cr martensitic steels using advanced electron microscopy techniques. X20CrMoV12-1 (12% Cr) in the virgin and long-term service-exposed state were investigated. GleebleTM weld simulation of the FGHAZ was performed on the materials. Detailed microstructural investigations were conducted on the parent and simulated FGHAZ materials to analyse the voids, dislocation density, micro-grains, and precipitates (M23C6, MX, Laves, Z-phase) in the materials. Light Microscopy (LM) and Scanning Electron Microscopy (SEM) was used to examine the voids. Twin-jet electropolished specimens were prepared for precipitate, micro-grain and substructure analyses using Transmission Kikuchi Diffraction (TKD) combined with Energy Dispersive Spectrometry (EDS), Concentric Backscatter (CBS) imaging, Energy-Filtered Transmission Electron Microscopy (EFTEM), and Annular Dark-Field Scanning Transmission Electron Microscopy (ADF-STEM) combined with EDS. The precipitates were extracted from the iron matrix using Bulk Replication and further investigated using EFTEM and STEM-EDS.
- Full Text:
- Date Issued: 2019
- Authors: Marx, Genevéve
- Date: 2019
- Subjects: Stainless steel -- Welding
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/30766 , vital:31128
- Description: Tempered martensite ferritic (TMF) steels with 9-12% Cr additions are used extensively for high-pressure steam pipes in coal-fired power plants. They operate at temperatures above 500ºC and are consequently susceptible to creep damage. Due to economic reasons, welding must be performed on service exposed materials when a component needs to be replaced. Fusion welding results in the formation of different microstructural regions within the weldment. The primary failure mechanism of TMF steel welded components is Type IV cracking that results from accelerated void formation in the fine-grained heat affected zone (FGHAZ) during creep. Short-term creep-tests performed across weldments made on new and service exposed steels have shown that the weldment consistently fails in the FGHAZ of the service exposed material. This observation has not yet been fully explained since not much is known about the microstructural evolution of creep aged material during welding. Thus, further investigation on the microstructure of welded creep aged material is warranted. The main aim of this thesis was to investigate the microstructural evolution when welding upon creep aged 9-12% Cr martensitic steels using advanced electron microscopy techniques. X20CrMoV12-1 (12% Cr) in the virgin and long-term service-exposed state were investigated. GleebleTM weld simulation of the FGHAZ was performed on the materials. Detailed microstructural investigations were conducted on the parent and simulated FGHAZ materials to analyse the voids, dislocation density, micro-grains, and precipitates (M23C6, MX, Laves, Z-phase) in the materials. Light Microscopy (LM) and Scanning Electron Microscopy (SEM) was used to examine the voids. Twin-jet electropolished specimens were prepared for precipitate, micro-grain and substructure analyses using Transmission Kikuchi Diffraction (TKD) combined with Energy Dispersive Spectrometry (EDS), Concentric Backscatter (CBS) imaging, Energy-Filtered Transmission Electron Microscopy (EFTEM), and Annular Dark-Field Scanning Transmission Electron Microscopy (ADF-STEM) combined with EDS. The precipitates were extracted from the iron matrix using Bulk Replication and further investigated using EFTEM and STEM-EDS.
- Full Text:
- Date Issued: 2019
Mineralogical, geochemical and lead isotopic analysis of the lead mineralization of the Skorpion Deposit, south western Namibia
- Authors: Uazeua, Kakunauua
- Date: 2019
- Subjects: Zinc ores -- Namibia , Formations (Geology) -- Namibia , Mineralogy -- Namibia , Lead -- Metallurgy -- Namibia , Lead -- Isotopes -- Namibia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68391 , vital:29250
- Description: The Skorpion none-sulphide Zinc Deposit is located in the para-autochtonous Port Nolloth Zone of the Gariep Belt, which overlays the Lower-Proterozoic Orange River Group basement rocks (Corrans et al., 1993). Situated in close proximity to the larger Rosh Pinah Zn-Pb deposit, the Skorpion Deposit contained a resource of 24.6 Mt at 10.6 % Zn and unquantified Cu and Pb prior to mining. To date, zinc has been the only metal exploited, with minor amounts of copper as a by-product. This study aims at understanding the mineralogical composition of the Skorpion lead mineralization and understanding the relationship between lead and the major metals such as zinc and copper in order to form a basis for further work that could determine the potential of processing lead as a by-product. As part of the study, work was also done on lead isotopes mainly with the aim of understanding the mineralization genesis and to determine the differences between the Skorpion and Rosh Pinah deposit which rationalize the inferior economic potential of the Skorpion lead mineralization. Results of the study have shown that majority of the lead mineralization is hosted by the felsic metavolcanics as galena and subordinately in the metasiliciclastics as pyromorphite, a lead manganese phosphate. In terms of the mineral textures, the lead minerals appear to be mainly secondary phases that have been remobilized and reprecipitated around pyrite, within pyrite cracks and intergrown with minerals such as chalcocite and greenockite. Lead has been mainly concentrated along fault zones. The elevated pyromorphite concentrations tend to occur within gossanous zones in close association with iron and manganese oxides. These textures represent supergene enrichment of a sulphide proto ore. However, contrary to copper and zinc mineralization, lead was not remobilized far from the proto ore merely as a function of its poor mobility in acidic fluids (Reddy et al., 1995). This substantiates the concentration of secondary lead in the felsic metavolcanics and to a much lesser extent, in the metasiliciclastics. Both secondary zinc and copper were reprecipitated in the metasiliciclastics, further away from the sulphide proto ore, hosted mainly by the felsic metavolcanics. The average lead isotope ratios of 206Pb/204Pb (17.26), 207Pb/204Pb (15.60) and 208Pb/204Pb (37.42) resemble results provided by Frimmel (2004) for both the Skorpion and Rosh Pinah deposits. For the Skorpion samples from Frimmel (2004) had the following average ratios: 206Pb/204Pb (17.29), 207Pb/204Pb (15.59) and 208Pb/204Pb (37.51). The Rosh Pinah samples had the following average ratios: 206Pb/204Pb (17.17), 207Pb/204Pb (15.61) and 208Pb/204Pb (37.45). These results indicate lead derivation from the lower 2.0 Ga Eburnean pre-Gariep basement in agreement with and Frimmel et al. (2004). The host felsic metavolcanics might have been derived from melting of the basement rocks during the formation of the Adamastor Ocean. In comparison to the Rosh Pinah deposit lead isotope signatures, the Skorpion lead isotopes overlap with the Rosh Pinah deposit isotopes, but have a much narrower range. This is an indication of a much shorter lived and potentially faster mineralization event contrary to the SEDEX type Rosh Pinah deposit. The smaller tonnage of the Skorpion deposit, its inferior lead concentrations and the elevated radiogenic lead isotopes point toward a VMS deposit which was formed in a small graben fed by shallow conduits during a short lived mineralization event. Sedimentary rocks covered the forming deposit at a fast rate and impaired the deposit advancement. The interaction between the upper crustal rocks and the mineralizing fluids is what may have resulted in the elevated radiogenic lead signature. In contrast to this, SEDEX deposits such as the Rosh Pinah Deposit, are generally fed by deep seated conduits that allow more longer lived leaching of metals from the underlying basement rocks and generally allow minor influence from upper crustal rocks.
- Full Text:
- Date Issued: 2019
- Authors: Uazeua, Kakunauua
- Date: 2019
- Subjects: Zinc ores -- Namibia , Formations (Geology) -- Namibia , Mineralogy -- Namibia , Lead -- Metallurgy -- Namibia , Lead -- Isotopes -- Namibia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/68391 , vital:29250
- Description: The Skorpion none-sulphide Zinc Deposit is located in the para-autochtonous Port Nolloth Zone of the Gariep Belt, which overlays the Lower-Proterozoic Orange River Group basement rocks (Corrans et al., 1993). Situated in close proximity to the larger Rosh Pinah Zn-Pb deposit, the Skorpion Deposit contained a resource of 24.6 Mt at 10.6 % Zn and unquantified Cu and Pb prior to mining. To date, zinc has been the only metal exploited, with minor amounts of copper as a by-product. This study aims at understanding the mineralogical composition of the Skorpion lead mineralization and understanding the relationship between lead and the major metals such as zinc and copper in order to form a basis for further work that could determine the potential of processing lead as a by-product. As part of the study, work was also done on lead isotopes mainly with the aim of understanding the mineralization genesis and to determine the differences between the Skorpion and Rosh Pinah deposit which rationalize the inferior economic potential of the Skorpion lead mineralization. Results of the study have shown that majority of the lead mineralization is hosted by the felsic metavolcanics as galena and subordinately in the metasiliciclastics as pyromorphite, a lead manganese phosphate. In terms of the mineral textures, the lead minerals appear to be mainly secondary phases that have been remobilized and reprecipitated around pyrite, within pyrite cracks and intergrown with minerals such as chalcocite and greenockite. Lead has been mainly concentrated along fault zones. The elevated pyromorphite concentrations tend to occur within gossanous zones in close association with iron and manganese oxides. These textures represent supergene enrichment of a sulphide proto ore. However, contrary to copper and zinc mineralization, lead was not remobilized far from the proto ore merely as a function of its poor mobility in acidic fluids (Reddy et al., 1995). This substantiates the concentration of secondary lead in the felsic metavolcanics and to a much lesser extent, in the metasiliciclastics. Both secondary zinc and copper were reprecipitated in the metasiliciclastics, further away from the sulphide proto ore, hosted mainly by the felsic metavolcanics. The average lead isotope ratios of 206Pb/204Pb (17.26), 207Pb/204Pb (15.60) and 208Pb/204Pb (37.42) resemble results provided by Frimmel (2004) for both the Skorpion and Rosh Pinah deposits. For the Skorpion samples from Frimmel (2004) had the following average ratios: 206Pb/204Pb (17.29), 207Pb/204Pb (15.59) and 208Pb/204Pb (37.51). The Rosh Pinah samples had the following average ratios: 206Pb/204Pb (17.17), 207Pb/204Pb (15.61) and 208Pb/204Pb (37.45). These results indicate lead derivation from the lower 2.0 Ga Eburnean pre-Gariep basement in agreement with and Frimmel et al. (2004). The host felsic metavolcanics might have been derived from melting of the basement rocks during the formation of the Adamastor Ocean. In comparison to the Rosh Pinah deposit lead isotope signatures, the Skorpion lead isotopes overlap with the Rosh Pinah deposit isotopes, but have a much narrower range. This is an indication of a much shorter lived and potentially faster mineralization event contrary to the SEDEX type Rosh Pinah deposit. The smaller tonnage of the Skorpion deposit, its inferior lead concentrations and the elevated radiogenic lead isotopes point toward a VMS deposit which was formed in a small graben fed by shallow conduits during a short lived mineralization event. Sedimentary rocks covered the forming deposit at a fast rate and impaired the deposit advancement. The interaction between the upper crustal rocks and the mineralizing fluids is what may have resulted in the elevated radiogenic lead signature. In contrast to this, SEDEX deposits such as the Rosh Pinah Deposit, are generally fed by deep seated conduits that allow more longer lived leaching of metals from the underlying basement rocks and generally allow minor influence from upper crustal rocks.
- Full Text:
- Date Issued: 2019
Mineralogy and geochemistry of permian black shales and carbonate concretions in the lower ECCA formations of the Steytlerville- Jansenville area, southern Karoo basin
- Authors: Maake, Laurentias Tebatso
- Date: 2019
- Subjects: Black shales -- South Africa -- Jansenville , Geochemistry Chemistry, Analytic Mineralogy -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/40643 , vital:36206
- Description: The Lower Permian Ecca Group formations of the Karoo Basin of South Africa have recently been identified as a target for shale gas exploration. These units, named the Prince Albert, Whitehill and Collingham formations, comprise organic-rich shales with occasional associated carbonate deposits, and siliciclastic facies. Mineralogical and geochemical investigations were conducted into carbonaceous shales and associated sedimentary rocks in the Jansenville area of the southern Karoo Basin with the ultimate aim to decipher the paleoenvironment and post-depositional conditions of these shales and their associated features such as prominent intra-formational carbonate deposits. Sediments of the main Karoo Basin were deposited from ~350 Ma to ~182 Ma, the end of sedimentation being marked by eruption of basaltic lava. This period, which began with the Dwyka continental glaciation, included tectonism of the Cape Fold Belt, the end-Permian mass extinction at ~250 Ma, and major intrusion of dolerite associated with the lavas of the Karoo Large Igneous Province. Subsequent to this, the basin experienced faulting associated with Gondwana breakup, uplift and intrusion of small volume kimberlite and melilite magmas, and erosion resulting in formation of a major escarpment. Each episode was imprinted upon the Karoo rocks and to a greater or lesser extent erases the signature of older episodes. To decipher the depositional paleoenvironment and post-depositional conditions of the black shales and the dolomite concretions posed a challenge due to deformation, orogeny, metamorphism, and weathering and erosion. Therefore, deep borehole core-logging and sampling was generally preferred over surface fieldwork, and trace elements backed up by scanning electron microscopy-based petrography was the method most relied upon to decipher the redox conditions of the black shales and the intra-formational carbonates. Relevant sections from three SOEKOR boreholes SP1/69, AB1/65 and QU1/65 were logged and carbonate concretions localities studied in four field locations. Samples collected from the core and field localities were prepared for thin section optical, SEM petrographical analysis, mineral identification, modal estimation by XRD, major, and trace element analysis by XRF and Laser Ablation-ICPMS, and acid leaching of a sample subset to determine the degree of pyritization (DOP). Logging of the SOEKOR boreholes indicates that in the western part of the basin all three lower Ecca formations, namely the Prince Albert, Whitehill and Collingham, overlie the tillites of the Dwyka Group, whereas near East London only the Whitehill Formation is present. Dwyka diamictites occur in all the studied boreholes overlying the crystalline basement in AB 1/65 and QU 1/65 boreholes whereas in the SP 1/69 the tillites rest above the quartzite of Witteberg Group of the Cape Supergroup. The shale consists of discontinuous, wavy and straight parallel laminae. Parallel, discontinuous and elongate micro-lenses of very fine-grained quartz are diagnostic and suggest late-stage silicification. Thin laminae of black shale are interlaminated with grey clay. The black shales are composed of quartz and clay minerals (illite and chlorite) as the major crystalline minerals with minor quantities of sulphides and heavy minerals. Organic matter occurs as unstructured, anhedral patches of amorphous material. It contains abundant small (~10nm) and less common larger (~100 nm) pores of subsphaeroidal shape. Carbonates occur as cementation and concretions. Heavy minerals identified by SEM include detrital zircon, thorite, titanite, authigenic fluorite, galena, sphene, and sphalerite and apatite, monazite and epidote-group minerals that appear to be of later stage metamorphic origin, some a product of hydrothermal feldspar alteration. Zircon and monazite show evidence of partial corrosion and/or new overgrowth. Titanite occurs in greater abundance in the SP1/69 section than other boreholes, where it exhibits a porphyroblastic texture suggesting secondary growth. These features all suggest modification of detrital minerals by metamorphic fluids and therefore some possible modification of bulk geochemical composition. Pyrite is abundant, commonly occurring as framboidal and occasional euhedral grains. Pyrite-bearing, calcite veins are common in the Whitehill Formation. Some pyrite is metamorphosed to pyrrhotite in the shales adjacent to dolerite intrusions. The carbonate deposits in the lower Ecca occur mostly as large concretions of 0.5-2.5 m in diameter at intensely faulted areas, and as laterally continuous beds at less intensely faulted areas. They consist of dominant dolomite with calcite (differentiated by thin section staining) and minor associated quartz veins, and appear to have formed in an early diagenetic stage of the black shale. Five different dolomite-rock textures were identified indicating varying crystal growth conditions. Calcite cementation types accompany these dolomite textures. The major types include mosaic, sparry and bladed/prismatic calcite cement. Calcite occurs mainly as cement in pores and grain replacement, as well as crudely radial septerian veins. XRD indicates that the carbonate concretions are made up of more than 90% dolomite, especially within the intensely folded areas. The remaining 10% consist of post-depositional quartz veins and secondary calcite associated with the quartz veins. In one locality (VAAL) the carbonate samples are dominates by bladed/prismatic calcite. The black shales in this study have similar geochemical signature to previously analysed samples from the Karoo Basin and to black shales worldwide. The geochemical signature results from the combined input of detrital sedimentary materials as well as enrichment or depletions acquired from pore water, biological activity and during diagenesis. Positive correlation of K2O, Na2O with Al2O3 suggests control by the detrital contribution. CaO and P2O5, have a negative correlation with Al2O3 suggesting a biogenic source. Elemental ratios suggest that the sediments derive from felsic source rock, most likely Cape Supergroup and underlying crystalline basement. These shales exhibit different degrees of trace-element enrichment relative to global average shale, the approximate order being Pb> V> Zn> Cr> Cu> Co > Ni. Assessment of selected trace elements, V/(V+Ni), V/Cr, Ni/Co and EF Mn ratios describes the paleoenvironment of these sediments to have been partially oxygenated before sulphate reduction interface. The pyrite size distribution, DOP, Fe and S correlation points to an organic matter limited environment, where the main sulphur sink is pyrite rather than organic matter. The DOP and Fe/Al indicated that the sediments became anoxic at the sediment-water interface (early diagenetic stages). V/Cr assessment of the dolomite concretions suggested partially oxygenated environment corresponding to the black shale deposition. The occurrence of concretions at the base of the Whitehill Formation, which has the highest TOC content of 14% compared to other associated formations, is evidence that organic matter preservation was important to their origins. The parameters used here to assess the redox conditions of the black shales and the dolomite concretions in this region of the Karoo Basin suggest a normal marine redox environment, rather than the anoxic Black Sea-type environment. The conditions that affected the lower Ecca formations varied from semi-oxygenated to oxygen depletion environment. The oxygen depletion environment occurred during the deposition of the Whitehill Formation of which organic matter preservation was favoured..
- Full Text:
- Date Issued: 2019
- Authors: Maake, Laurentias Tebatso
- Date: 2019
- Subjects: Black shales -- South Africa -- Jansenville , Geochemistry Chemistry, Analytic Mineralogy -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/40643 , vital:36206
- Description: The Lower Permian Ecca Group formations of the Karoo Basin of South Africa have recently been identified as a target for shale gas exploration. These units, named the Prince Albert, Whitehill and Collingham formations, comprise organic-rich shales with occasional associated carbonate deposits, and siliciclastic facies. Mineralogical and geochemical investigations were conducted into carbonaceous shales and associated sedimentary rocks in the Jansenville area of the southern Karoo Basin with the ultimate aim to decipher the paleoenvironment and post-depositional conditions of these shales and their associated features such as prominent intra-formational carbonate deposits. Sediments of the main Karoo Basin were deposited from ~350 Ma to ~182 Ma, the end of sedimentation being marked by eruption of basaltic lava. This period, which began with the Dwyka continental glaciation, included tectonism of the Cape Fold Belt, the end-Permian mass extinction at ~250 Ma, and major intrusion of dolerite associated with the lavas of the Karoo Large Igneous Province. Subsequent to this, the basin experienced faulting associated with Gondwana breakup, uplift and intrusion of small volume kimberlite and melilite magmas, and erosion resulting in formation of a major escarpment. Each episode was imprinted upon the Karoo rocks and to a greater or lesser extent erases the signature of older episodes. To decipher the depositional paleoenvironment and post-depositional conditions of the black shales and the dolomite concretions posed a challenge due to deformation, orogeny, metamorphism, and weathering and erosion. Therefore, deep borehole core-logging and sampling was generally preferred over surface fieldwork, and trace elements backed up by scanning electron microscopy-based petrography was the method most relied upon to decipher the redox conditions of the black shales and the intra-formational carbonates. Relevant sections from three SOEKOR boreholes SP1/69, AB1/65 and QU1/65 were logged and carbonate concretions localities studied in four field locations. Samples collected from the core and field localities were prepared for thin section optical, SEM petrographical analysis, mineral identification, modal estimation by XRD, major, and trace element analysis by XRF and Laser Ablation-ICPMS, and acid leaching of a sample subset to determine the degree of pyritization (DOP). Logging of the SOEKOR boreholes indicates that in the western part of the basin all three lower Ecca formations, namely the Prince Albert, Whitehill and Collingham, overlie the tillites of the Dwyka Group, whereas near East London only the Whitehill Formation is present. Dwyka diamictites occur in all the studied boreholes overlying the crystalline basement in AB 1/65 and QU 1/65 boreholes whereas in the SP 1/69 the tillites rest above the quartzite of Witteberg Group of the Cape Supergroup. The shale consists of discontinuous, wavy and straight parallel laminae. Parallel, discontinuous and elongate micro-lenses of very fine-grained quartz are diagnostic and suggest late-stage silicification. Thin laminae of black shale are interlaminated with grey clay. The black shales are composed of quartz and clay minerals (illite and chlorite) as the major crystalline minerals with minor quantities of sulphides and heavy minerals. Organic matter occurs as unstructured, anhedral patches of amorphous material. It contains abundant small (~10nm) and less common larger (~100 nm) pores of subsphaeroidal shape. Carbonates occur as cementation and concretions. Heavy minerals identified by SEM include detrital zircon, thorite, titanite, authigenic fluorite, galena, sphene, and sphalerite and apatite, monazite and epidote-group minerals that appear to be of later stage metamorphic origin, some a product of hydrothermal feldspar alteration. Zircon and monazite show evidence of partial corrosion and/or new overgrowth. Titanite occurs in greater abundance in the SP1/69 section than other boreholes, where it exhibits a porphyroblastic texture suggesting secondary growth. These features all suggest modification of detrital minerals by metamorphic fluids and therefore some possible modification of bulk geochemical composition. Pyrite is abundant, commonly occurring as framboidal and occasional euhedral grains. Pyrite-bearing, calcite veins are common in the Whitehill Formation. Some pyrite is metamorphosed to pyrrhotite in the shales adjacent to dolerite intrusions. The carbonate deposits in the lower Ecca occur mostly as large concretions of 0.5-2.5 m in diameter at intensely faulted areas, and as laterally continuous beds at less intensely faulted areas. They consist of dominant dolomite with calcite (differentiated by thin section staining) and minor associated quartz veins, and appear to have formed in an early diagenetic stage of the black shale. Five different dolomite-rock textures were identified indicating varying crystal growth conditions. Calcite cementation types accompany these dolomite textures. The major types include mosaic, sparry and bladed/prismatic calcite cement. Calcite occurs mainly as cement in pores and grain replacement, as well as crudely radial septerian veins. XRD indicates that the carbonate concretions are made up of more than 90% dolomite, especially within the intensely folded areas. The remaining 10% consist of post-depositional quartz veins and secondary calcite associated with the quartz veins. In one locality (VAAL) the carbonate samples are dominates by bladed/prismatic calcite. The black shales in this study have similar geochemical signature to previously analysed samples from the Karoo Basin and to black shales worldwide. The geochemical signature results from the combined input of detrital sedimentary materials as well as enrichment or depletions acquired from pore water, biological activity and during diagenesis. Positive correlation of K2O, Na2O with Al2O3 suggests control by the detrital contribution. CaO and P2O5, have a negative correlation with Al2O3 suggesting a biogenic source. Elemental ratios suggest that the sediments derive from felsic source rock, most likely Cape Supergroup and underlying crystalline basement. These shales exhibit different degrees of trace-element enrichment relative to global average shale, the approximate order being Pb> V> Zn> Cr> Cu> Co > Ni. Assessment of selected trace elements, V/(V+Ni), V/Cr, Ni/Co and EF Mn ratios describes the paleoenvironment of these sediments to have been partially oxygenated before sulphate reduction interface. The pyrite size distribution, DOP, Fe and S correlation points to an organic matter limited environment, where the main sulphur sink is pyrite rather than organic matter. The DOP and Fe/Al indicated that the sediments became anoxic at the sediment-water interface (early diagenetic stages). V/Cr assessment of the dolomite concretions suggested partially oxygenated environment corresponding to the black shale deposition. The occurrence of concretions at the base of the Whitehill Formation, which has the highest TOC content of 14% compared to other associated formations, is evidence that organic matter preservation was important to their origins. The parameters used here to assess the redox conditions of the black shales and the dolomite concretions in this region of the Karoo Basin suggest a normal marine redox environment, rather than the anoxic Black Sea-type environment. The conditions that affected the lower Ecca formations varied from semi-oxygenated to oxygen depletion environment. The oxygen depletion environment occurred during the deposition of the Whitehill Formation of which organic matter preservation was favoured..
- Full Text:
- Date Issued: 2019
Mining: A laminated, dialectic methodology for identifying not-yet-obvious green skills demand
- Authors: Rosenberg, Eureta
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436077 , vital:73225 , ISBN 9780429279362 , https://www.taylorfrancis.com/chapters/edit/10.4324/9780429279362-13/synthesis-elaboration-critical-realist-methodology-green-skills-research-eureta-rosenberg
- Description: This chapter shares insights about green skills demand research in South Africa, based on a 2015 study in coal mining. One purpose of that study was to develop methodology for green skills demand determination, and the chapter shares selected features of the multi-layered and multi-method research process used, including an extended contextual driver analysis and a value chain analysis. Some findings about what green skills are needed in coal mining are shared to contextualise and illustrate methodological insights. This chapter highlights the fact that whether or not a skill is scarce can be contested, and demonstrates how a laminated methodology can guide credible conclusions in such cases. It also introduces the value of ‘absenting absences’, a dialectic process that surfaced skills needs that are not-yet-obvious, but essential if mining is to achieve transformation towards sustainability.
- Full Text:
- Date Issued: 2019
- Authors: Rosenberg, Eureta
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436077 , vital:73225 , ISBN 9780429279362 , https://www.taylorfrancis.com/chapters/edit/10.4324/9780429279362-13/synthesis-elaboration-critical-realist-methodology-green-skills-research-eureta-rosenberg
- Description: This chapter shares insights about green skills demand research in South Africa, based on a 2015 study in coal mining. One purpose of that study was to develop methodology for green skills demand determination, and the chapter shares selected features of the multi-layered and multi-method research process used, including an extended contextual driver analysis and a value chain analysis. Some findings about what green skills are needed in coal mining are shared to contextualise and illustrate methodological insights. This chapter highlights the fact that whether or not a skill is scarce can be contested, and demonstrates how a laminated methodology can guide credible conclusions in such cases. It also introduces the value of ‘absenting absences’, a dialectic process that surfaced skills needs that are not-yet-obvious, but essential if mining is to achieve transformation towards sustainability.
- Full Text:
- Date Issued: 2019
Mobile money adoption: a case study of Zimbaweans residing in South Africa
- Authors: Chimusoro, Anna
- Date: 2019
- Subjects: Mobile commerce Financial institutions
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/13326 , vital:39634
- Description: A mobile phone has become an essential tool for both social and economic development in various countries around the world. For Zimbabweans residing in South Africa, a mobile phone is a lifeline to support family and relatives back home through Eco-cash mobile money service. With the assistance of mobile commerce applications, consumers are able to use their devices for financial transactions, taking pictures, videos and accessing social networks. As such, a mobile phone can be used for a myriad of functions other than communication purposes. These innovative technological developments in the telecommunications sector have also empowered businesses to improve on their efficiency and effectiveness. However, the challenge remains for consumers to adopt these innovations. Therefore, the purpose of this study was to determine the factors influencing the adoption of mobile money (Eco-cash) by Zimbabweans residing in South Africa. The study also established if perceived usefulness, perceived ease of use, perceived risk, perceived trust, social influence and facilitating conditions influence the intention to adopt mobile money (Eco-cash). The research adopted the TAM, extended TAM and UTAUT constructs to develop a theoretical model. A quantitative, descriptive research approach was applied to the study. Both primary and secondary sources were utilised in the collection of data. A self-administered questionnaire was distributed to a sample of 377 respondents through convenience and snowballing sampling methods in East London. Statistical Package for Social Sciences (SPSS) version 25 software packages was utilised to analyse the data. Analysis of Variance (ANOVA) and multiple linear regression analysis (MLR) statistical techniques were employed to interpret the findings. The study found significant relationships on perceived ease of use, perceived trust, perceived risk, perceived usefulness, social influence and user intention. No significant relationship was found between facilitating conditions and user intention. The study recommends that MNOs design mobile money systems that are user-friendly and simple to use. Furthermore, MNOs and mobile money agents can offer value added services to attract more consumers to use their services.
- Full Text:
- Date Issued: 2019
- Authors: Chimusoro, Anna
- Date: 2019
- Subjects: Mobile commerce Financial institutions
- Language: English
- Type: Thesis , Masters , MCom (Business Management)
- Identifier: http://hdl.handle.net/10353/13326 , vital:39634
- Description: A mobile phone has become an essential tool for both social and economic development in various countries around the world. For Zimbabweans residing in South Africa, a mobile phone is a lifeline to support family and relatives back home through Eco-cash mobile money service. With the assistance of mobile commerce applications, consumers are able to use their devices for financial transactions, taking pictures, videos and accessing social networks. As such, a mobile phone can be used for a myriad of functions other than communication purposes. These innovative technological developments in the telecommunications sector have also empowered businesses to improve on their efficiency and effectiveness. However, the challenge remains for consumers to adopt these innovations. Therefore, the purpose of this study was to determine the factors influencing the adoption of mobile money (Eco-cash) by Zimbabweans residing in South Africa. The study also established if perceived usefulness, perceived ease of use, perceived risk, perceived trust, social influence and facilitating conditions influence the intention to adopt mobile money (Eco-cash). The research adopted the TAM, extended TAM and UTAUT constructs to develop a theoretical model. A quantitative, descriptive research approach was applied to the study. Both primary and secondary sources were utilised in the collection of data. A self-administered questionnaire was distributed to a sample of 377 respondents through convenience and snowballing sampling methods in East London. Statistical Package for Social Sciences (SPSS) version 25 software packages was utilised to analyse the data. Analysis of Variance (ANOVA) and multiple linear regression analysis (MLR) statistical techniques were employed to interpret the findings. The study found significant relationships on perceived ease of use, perceived trust, perceived risk, perceived usefulness, social influence and user intention. No significant relationship was found between facilitating conditions and user intention. The study recommends that MNOs design mobile money systems that are user-friendly and simple to use. Furthermore, MNOs and mobile money agents can offer value added services to attract more consumers to use their services.
- Full Text:
- Date Issued: 2019
Model for the alleviation of poverty in South Africa
- Authors: Visagie, Jana
- Date: 2019
- Subjects: Poverty -- South Africa , Poverty -- Prevention
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/45701 , vital:38956
- Description: The existence of extreme poverty in an affluent world is morally unacceptable and action needs to be taken. The reduction of economic and social inequality within countries and between countries, as well as the honouring of human rights, is of utmost importance, but the eradication of poverty must take priority One of the main problems with poverty is that poverty impedes human flourishing). People are hungry and constantly live in pain and anguish while education is hampered. People do not develop fully on cognitive and physical levels as poverty allows the exploitation of the poor and their bodies. Feelings of shame and worthlessness are established for reasons people cannot control. To contribute to the ongoing attempts to reduce poverty, it is necessary to have an understanding as to why people remain poor in an affluent world and what can be done to address the causes of poverty. Unless a global culture of ethics and value alignment is pursued for the reduction of poverty, there will be devastating effects for the future Underwriting lasting escapes from chronic poverty demands more investment in education, employment and human development potentials and in the related infrastructure that permits people to enhance their living standards while developing their resilience to handle setbacks and the effects of climate change.ffects include, for example, disaster-risk management, global healthcare and social cohesion. These investment efforts 9 have the ability to generate a virtuous cycle of poverty reduction, national economic growth and enlarged individual opportunity This could diminish the inequalities that decelerate human development. The lack of practical and outcome-based poverty reduction models affords this research with a unique opportunity to fulfil the need and to contribute to the body of knowledge regarding the reduction of poverty towards 2030.
- Full Text:
- Date Issued: 2019
- Authors: Visagie, Jana
- Date: 2019
- Subjects: Poverty -- South Africa , Poverty -- Prevention
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/45701 , vital:38956
- Description: The existence of extreme poverty in an affluent world is morally unacceptable and action needs to be taken. The reduction of economic and social inequality within countries and between countries, as well as the honouring of human rights, is of utmost importance, but the eradication of poverty must take priority One of the main problems with poverty is that poverty impedes human flourishing). People are hungry and constantly live in pain and anguish while education is hampered. People do not develop fully on cognitive and physical levels as poverty allows the exploitation of the poor and their bodies. Feelings of shame and worthlessness are established for reasons people cannot control. To contribute to the ongoing attempts to reduce poverty, it is necessary to have an understanding as to why people remain poor in an affluent world and what can be done to address the causes of poverty. Unless a global culture of ethics and value alignment is pursued for the reduction of poverty, there will be devastating effects for the future Underwriting lasting escapes from chronic poverty demands more investment in education, employment and human development potentials and in the related infrastructure that permits people to enhance their living standards while developing their resilience to handle setbacks and the effects of climate change.ffects include, for example, disaster-risk management, global healthcare and social cohesion. These investment efforts 9 have the ability to generate a virtuous cycle of poverty reduction, national economic growth and enlarged individual opportunity This could diminish the inequalities that decelerate human development. The lack of practical and outcome-based poverty reduction models affords this research with a unique opportunity to fulfil the need and to contribute to the body of knowledge regarding the reduction of poverty towards 2030.
- Full Text:
- Date Issued: 2019
Modeling top-down and bottom-up drivers of a regime shift in invasive aquatic plant stable states
- Strange, Emily F, Landi, Pietro, Hill, Jaclyn M, Coetzee, Julie A
- Authors: Strange, Emily F , Landi, Pietro , Hill, Jaclyn M , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444732 , vital:74263 , https://doi.org/10.3389/fpls.2019.00889
- Description: The evidence for alternate stable states characterized by dominance of either floating or submerged plant dominance is well established. Inspired by an existing model and controlled experiments, we conceptually describe a dynamic that we have observed in the field using a simple model, the aim of which was to investigate key interactions of the shift between invasive floating and invasive submerged plant dominance, driven by the rapid decomposition of floating plants as a consequence of herbivory by biological control agents. This study showed that the rate of switch between floating and submerged invasive plant dominance, and the point in time at which the switch occurs, is dependent on the nutrient status of the water and the density of biological control agents on floating plant populations. Therefore, top-down invasive plant biological control efforts using natural enemies can affect systems on a wider scale than the intended agent – plant level, and can be significantly altered by bottom-up changes to the system, i.e., nutrient loading. The implications of this are essential for understanding the multiple roles invasive plants and their control have upon ecosystem dynamics. The results emphasize the importance of multi-trophic considerations for future invasive plant management and offer evidence for new pathways of invasion. The model outputs support the conclusion that, after the shift and in the absence of effective intervention, a submerged invasive stable state will persist.
- Full Text:
- Date Issued: 2019
- Authors: Strange, Emily F , Landi, Pietro , Hill, Jaclyn M , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444732 , vital:74263 , https://doi.org/10.3389/fpls.2019.00889
- Description: The evidence for alternate stable states characterized by dominance of either floating or submerged plant dominance is well established. Inspired by an existing model and controlled experiments, we conceptually describe a dynamic that we have observed in the field using a simple model, the aim of which was to investigate key interactions of the shift between invasive floating and invasive submerged plant dominance, driven by the rapid decomposition of floating plants as a consequence of herbivory by biological control agents. This study showed that the rate of switch between floating and submerged invasive plant dominance, and the point in time at which the switch occurs, is dependent on the nutrient status of the water and the density of biological control agents on floating plant populations. Therefore, top-down invasive plant biological control efforts using natural enemies can affect systems on a wider scale than the intended agent – plant level, and can be significantly altered by bottom-up changes to the system, i.e., nutrient loading. The implications of this are essential for understanding the multiple roles invasive plants and their control have upon ecosystem dynamics. The results emphasize the importance of multi-trophic considerations for future invasive plant management and offer evidence for new pathways of invasion. The model outputs support the conclusion that, after the shift and in the absence of effective intervention, a submerged invasive stable state will persist.
- Full Text:
- Date Issued: 2019
Modelling storm-time TEC changes using linear and non-linear techniques
- Authors: Uwamahoro, Jean Claude
- Date: 2019
- Subjects: Magnetic storms , Astronomy -- Computer programs , Imaging systems in astronomy , Ionospheric storms , Electrons -- Measurement , Magnetosphere -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/92908 , vital:30762
- Description: Statistical models based on empirical orthogonal functions (EOF) analysis and non-linear regression analysis (NLRA) were developed for the purpose of estimating the ionospheric total electron content (TEC) during geomagnetic storms. The well-known least squares method (LSM) and Metropolis-Hastings algorithm (MHA) were used as optimization techniques to determine the unknown coefficients of the developed analytical expressions. Artificial Neural Networks (ANNs), the International Reference Ionosphere (IRI) model, and the Multi-Instrument Data Analysis System (MIDAS) tomographic inversion algorithm were also applied to storm-time TEC modelling/reconstruction for various latitudes of the African sector and surrounding areas. This work presents some of the first statistical modeling of the mid-latitude and low-latitude ionosphere during geomagnetic storms that includes solar, geomagnetic and neutral wind drivers.Development and validation of the empirical models were based on storm-time TEC data derived from the global positioning system (GPS) measurements over ground receivers within Africa and surrounding areas. The storm criterion applied was Dst 6 −50 nT and/or Kp > 4. The performance evaluation of MIDAS compared with ANNs to reconstruct storm-time TEC over the African low- and mid-latitude regions showed that MIDAS and ANNs provide comparable results. Their respective mean absolute error (MAE) values were 4.81 and 4.18 TECU. The ANN model was, however, found to perform 24.37 % better than MIDAS at estimating storm-time TEC for low latitudes, while MIDAS is 13.44 % more accurate than ANN for the mid-latitudes. When their performances are compared with the IRI model, both MIDAS and ANN model were found to provide more accurate storm-time TEC reconstructions for the African low- and mid-latitude regions. A comparative study of the performances of EOF, NLRA, ANN, and IRI models to estimate TEC during geomagnetic storm conditions over various latitudes showed that the ANN model is about 10 %, 26 %, and 58 % more accurate than EOF, NLRA, and IRI models, respectively, while EOF was found to perform 15 %, and 44 % better than NLRA and IRI, respectively. It was further found that the NLRA model is 25 % more accurate than the IRI model. We have also investigated for the first time, the role of meridional neutral winds (from the Horizontal Wind Model) to storm-time TEC modelling in the low latitude, northern and southern hemisphere mid-latitude regions of the African sector, based on ANN models. Statistics have shown that the inclusion of the meridional wind velocity in TEC modelling during geomagnetic storms leads to percentage improvements of about 5 % for the low latitude, 10 % and 5 % for the northern and southern hemisphere mid-latitude regions, respectively. High-latitude storm-induced winds and the inter-hemispheric blows of the meridional winds from summer to winter hemisphere have been suggested to be associated with these improvements.
- Full Text:
- Date Issued: 2019
- Authors: Uwamahoro, Jean Claude
- Date: 2019
- Subjects: Magnetic storms , Astronomy -- Computer programs , Imaging systems in astronomy , Ionospheric storms , Electrons -- Measurement , Magnetosphere -- Observations
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/92908 , vital:30762
- Description: Statistical models based on empirical orthogonal functions (EOF) analysis and non-linear regression analysis (NLRA) were developed for the purpose of estimating the ionospheric total electron content (TEC) during geomagnetic storms. The well-known least squares method (LSM) and Metropolis-Hastings algorithm (MHA) were used as optimization techniques to determine the unknown coefficients of the developed analytical expressions. Artificial Neural Networks (ANNs), the International Reference Ionosphere (IRI) model, and the Multi-Instrument Data Analysis System (MIDAS) tomographic inversion algorithm were also applied to storm-time TEC modelling/reconstruction for various latitudes of the African sector and surrounding areas. This work presents some of the first statistical modeling of the mid-latitude and low-latitude ionosphere during geomagnetic storms that includes solar, geomagnetic and neutral wind drivers.Development and validation of the empirical models were based on storm-time TEC data derived from the global positioning system (GPS) measurements over ground receivers within Africa and surrounding areas. The storm criterion applied was Dst 6 −50 nT and/or Kp > 4. The performance evaluation of MIDAS compared with ANNs to reconstruct storm-time TEC over the African low- and mid-latitude regions showed that MIDAS and ANNs provide comparable results. Their respective mean absolute error (MAE) values were 4.81 and 4.18 TECU. The ANN model was, however, found to perform 24.37 % better than MIDAS at estimating storm-time TEC for low latitudes, while MIDAS is 13.44 % more accurate than ANN for the mid-latitudes. When their performances are compared with the IRI model, both MIDAS and ANN model were found to provide more accurate storm-time TEC reconstructions for the African low- and mid-latitude regions. A comparative study of the performances of EOF, NLRA, ANN, and IRI models to estimate TEC during geomagnetic storm conditions over various latitudes showed that the ANN model is about 10 %, 26 %, and 58 % more accurate than EOF, NLRA, and IRI models, respectively, while EOF was found to perform 15 %, and 44 % better than NLRA and IRI, respectively. It was further found that the NLRA model is 25 % more accurate than the IRI model. We have also investigated for the first time, the role of meridional neutral winds (from the Horizontal Wind Model) to storm-time TEC modelling in the low latitude, northern and southern hemisphere mid-latitude regions of the African sector, based on ANN models. Statistics have shown that the inclusion of the meridional wind velocity in TEC modelling during geomagnetic storms leads to percentage improvements of about 5 % for the low latitude, 10 % and 5 % for the northern and southern hemisphere mid-latitude regions, respectively. High-latitude storm-induced winds and the inter-hemispheric blows of the meridional winds from summer to winter hemisphere have been suggested to be associated with these improvements.
- Full Text:
- Date Issued: 2019