Efficacy of two medical plant extracts and metformin in the prevention of diet induced fatty liver
- Tshidino, Shonisani Cathphonia
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
Comparative performance of natural and synthetic fibre nonwoven geotextiles
- Tshifularo, Cyrus Alushavhiwi
- Authors: Tshifularo, Cyrus Alushavhiwi
- Date: 2017
- Subjects: Geotextiles Textile fabrics , Textile fibers -- Testing Textile industry -- Quality control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21362 , vital:29504
- Description: The aim of this work was to establish a range of suitable process parameters which can be utilized to produce needlepunched nonwoven fabrics for geotextile applications. Nonwoven fabrics were produced from 100% PP, a blend of 50/50% PP/kenaf and 100% kenaf fibres. The depths of needle penetration of 4, 7 and 10 mm, stroke frequencies of 250, 350 and 450 strokes/min and mass per unit area of 300, 600 and 900 g/m2 were utilized for producing the fabrics, on a Dilo loom. The effect of depth of needle penetration, stroke frequency and mass per unit area on the fabric properties, namely, tensile strength, puncture resistance, pore size, water permeability and transmissivity were analysed. In addition, the effect of chemicals, namely, 10% ammonium hydroxide (NH4OH), 10% sodium chloride (NaCl) and 3% sulphuric acid (H2SO4) solutions on degradation of the fabric was also studied. The results have shown that density, thickness and nominal weight of the needlepunched nonwoven fabrics were related to each other and they were influenced by stroke frequency, depth of needle penetration and feed rate of the needlepunching process. The increase in nominal weight of the fabrics also increases thickness and density of the fabrics. The tensile strength and puncture resistance of the fabrics increased with the increases in stroke frequency, depth of needle penetration and fabric mass per unit area. However, lower tensile strength and puncture resistance were achieved in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area. Bigger pores were resulted in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area, however, pore size decreased with increases in stroke frequency, depth of needle penetration and mass per unit area. Water permeability depends on the pore size, properties of the fibres, stroke frequency, depth of needle penetration and mass per unit area. Higher tensile strength and higher puncture resistance were achieved in the needlepunched nonwoven fabrics produced from 100% PP fibres, therefore, they are suitable for some load-bearing geotextile applications, such as reinforcement and separation. However, higher water permeability was achieved in the fabrics produced from 100% kenaf fibres, therefore, they are ideal for geotextile applications where good water permeability is required. Higher values for transmissivity were obtained in the fabrics produced from a blend of 50/50% PP/kenaf fibres, therefore they are suitable for drainage applications. The fabrics produced from a blend of 50/50% PP/kenaf fibres achieved better values of tensile strength, puncture resistance, pore size and water permeability in comparison to that produced from 100% PP and 100% kenaf fibres. However, better tensile strength and puncture resistance were achieved in the fabrics produced from 100% PP fibres and bigger pore size and higher water permeability were achieved in the fabrics produced from 100% kenaf fibres. Therefore, it can be suggested that the nonwoven fabrics produced from a blend of 50/50% PP/kenaf fibres can fulfil almost all requirements of geotextile applications, such as, filtration, separation, reinforcement and drainage. The fabrics produced from 100% PP fibres were not damaged or deteriorated when treated with all the three chemicals due to chemical inertness of polypropylene. However, the fabrics produced from a blend of 50/50% PP/kenaf and 100% kenaf fibres were damaged and deteriorated when treated with H2SO4.
- Full Text:
- Date Issued: 2017
- Authors: Tshifularo, Cyrus Alushavhiwi
- Date: 2017
- Subjects: Geotextiles Textile fabrics , Textile fibers -- Testing Textile industry -- Quality control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21362 , vital:29504
- Description: The aim of this work was to establish a range of suitable process parameters which can be utilized to produce needlepunched nonwoven fabrics for geotextile applications. Nonwoven fabrics were produced from 100% PP, a blend of 50/50% PP/kenaf and 100% kenaf fibres. The depths of needle penetration of 4, 7 and 10 mm, stroke frequencies of 250, 350 and 450 strokes/min and mass per unit area of 300, 600 and 900 g/m2 were utilized for producing the fabrics, on a Dilo loom. The effect of depth of needle penetration, stroke frequency and mass per unit area on the fabric properties, namely, tensile strength, puncture resistance, pore size, water permeability and transmissivity were analysed. In addition, the effect of chemicals, namely, 10% ammonium hydroxide (NH4OH), 10% sodium chloride (NaCl) and 3% sulphuric acid (H2SO4) solutions on degradation of the fabric was also studied. The results have shown that density, thickness and nominal weight of the needlepunched nonwoven fabrics were related to each other and they were influenced by stroke frequency, depth of needle penetration and feed rate of the needlepunching process. The increase in nominal weight of the fabrics also increases thickness and density of the fabrics. The tensile strength and puncture resistance of the fabrics increased with the increases in stroke frequency, depth of needle penetration and fabric mass per unit area. However, lower tensile strength and puncture resistance were achieved in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area. Bigger pores were resulted in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area, however, pore size decreased with increases in stroke frequency, depth of needle penetration and mass per unit area. Water permeability depends on the pore size, properties of the fibres, stroke frequency, depth of needle penetration and mass per unit area. Higher tensile strength and higher puncture resistance were achieved in the needlepunched nonwoven fabrics produced from 100% PP fibres, therefore, they are suitable for some load-bearing geotextile applications, such as reinforcement and separation. However, higher water permeability was achieved in the fabrics produced from 100% kenaf fibres, therefore, they are ideal for geotextile applications where good water permeability is required. Higher values for transmissivity were obtained in the fabrics produced from a blend of 50/50% PP/kenaf fibres, therefore they are suitable for drainage applications. The fabrics produced from a blend of 50/50% PP/kenaf fibres achieved better values of tensile strength, puncture resistance, pore size and water permeability in comparison to that produced from 100% PP and 100% kenaf fibres. However, better tensile strength and puncture resistance were achieved in the fabrics produced from 100% PP fibres and bigger pore size and higher water permeability were achieved in the fabrics produced from 100% kenaf fibres. Therefore, it can be suggested that the nonwoven fabrics produced from a blend of 50/50% PP/kenaf fibres can fulfil almost all requirements of geotextile applications, such as, filtration, separation, reinforcement and drainage. The fabrics produced from 100% PP fibres were not damaged or deteriorated when treated with all the three chemicals due to chemical inertness of polypropylene. However, the fabrics produced from a blend of 50/50% PP/kenaf and 100% kenaf fibres were damaged and deteriorated when treated with H2SO4.
- Full Text:
- Date Issued: 2017
Method development for chemolysis of waste tyres and characterization of the components
- Authors: Tsipa, Phuti Cedric
- Date: 2018
- Subjects: Composite materials , Rubber Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36694 , vital:34044
- Description: Chemolysis method for degradation and extraction of waste tyres for production of oil was developed. This method consist of three different solvent systems; firstly, the selective solvent system capable of extracting the process oil used in the production of tyres. This solvent system follows a phase transfer catalysis reaction, which is a reaction with a solvent consisting of two phases. Second system is a Destructive solvent system, which is capable of breaking down the polymer chains within the rubber matrix. It follows phase transfer catalysis reaction. Lastly, the collecting/wash solvent system, which is capable of collecting the remaining extracts in the residual crumb. Three products where obtained from this method: Liquid (oil), Gas and Solid (char), with the oil plus char being the focus of this study. Characterizations were carried out to obtain the quality of the oil recovered. Various analytical techniques were used to achieve the aims and objectives of this study, this involved Fourier Transform Infra-red spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) spectroscopy, High-resolution Thermogravimetric analysis (Hi-resTM TGA), Gas Chromatography coupled to Mass spectroscopy (GC-MS) and Simulated Distillation D86 (SIMDIST D86). Hydrocarbon compounds and market value acids where identified with reference to standards ran on the GC-MS. Market value acids were quantified to obtain the exact amount present in the extracted oil, the amounts for dodecanoic acid, hexadecanoic acid, heptadecanoic acid and octadecanoic acid were 0.73%, 5.1%, 0.49% and 9.98% respectively. Approximately 15% of this market value acid are present in the extracted oil. Internal GC-MS library and Retention Index (RI) methods with the help of NIST library were also used for compounds identification. A total of 53 compounds were successfully identified. SIMDIST D86 analysis showed that the petroleum fractions present in the total extracted oil were Heavy naphtha 0.73%, Kerosene 3.23%, Distillate fuel oil 6.27%, Light vacuum gas oil 57.93% and Heavy vacuum gas oil 31.83%. Hi-resTM TGA was used to characterize the char recovered for thermal properties. Chemolysis char showed relatively similar thermal stability compared to commercial N115 carbon black. The chemolysis method of oil extraction from waste tyres reported in this thesis shows promise in terms of both the routine of execution, quantification of market value constituents of the oil and chemical details of both the tyre derived oil and char.
- Full Text:
- Date Issued: 2018
- Authors: Tsipa, Phuti Cedric
- Date: 2018
- Subjects: Composite materials , Rubber Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36694 , vital:34044
- Description: Chemolysis method for degradation and extraction of waste tyres for production of oil was developed. This method consist of three different solvent systems; firstly, the selective solvent system capable of extracting the process oil used in the production of tyres. This solvent system follows a phase transfer catalysis reaction, which is a reaction with a solvent consisting of two phases. Second system is a Destructive solvent system, which is capable of breaking down the polymer chains within the rubber matrix. It follows phase transfer catalysis reaction. Lastly, the collecting/wash solvent system, which is capable of collecting the remaining extracts in the residual crumb. Three products where obtained from this method: Liquid (oil), Gas and Solid (char), with the oil plus char being the focus of this study. Characterizations were carried out to obtain the quality of the oil recovered. Various analytical techniques were used to achieve the aims and objectives of this study, this involved Fourier Transform Infra-red spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) spectroscopy, High-resolution Thermogravimetric analysis (Hi-resTM TGA), Gas Chromatography coupled to Mass spectroscopy (GC-MS) and Simulated Distillation D86 (SIMDIST D86). Hydrocarbon compounds and market value acids where identified with reference to standards ran on the GC-MS. Market value acids were quantified to obtain the exact amount present in the extracted oil, the amounts for dodecanoic acid, hexadecanoic acid, heptadecanoic acid and octadecanoic acid were 0.73%, 5.1%, 0.49% and 9.98% respectively. Approximately 15% of this market value acid are present in the extracted oil. Internal GC-MS library and Retention Index (RI) methods with the help of NIST library were also used for compounds identification. A total of 53 compounds were successfully identified. SIMDIST D86 analysis showed that the petroleum fractions present in the total extracted oil were Heavy naphtha 0.73%, Kerosene 3.23%, Distillate fuel oil 6.27%, Light vacuum gas oil 57.93% and Heavy vacuum gas oil 31.83%. Hi-resTM TGA was used to characterize the char recovered for thermal properties. Chemolysis char showed relatively similar thermal stability compared to commercial N115 carbon black. The chemolysis method of oil extraction from waste tyres reported in this thesis shows promise in terms of both the routine of execution, quantification of market value constituents of the oil and chemical details of both the tyre derived oil and char.
- Full Text:
- Date Issued: 2018
Developing a socio- ecological framework for the restoration of estuaries using the Swartkops Estuary as a case study
- Authors: Tsipa, Vusumzi
- Date: 2022-04
- Subjects: Estuarine ecology -- South Africa -- Swartkops River Estuary , Ecosystem
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59622 , vital:62208
- Description: The aim of this study was to develop and test a socio-ecological systems framework for the restoration of estuaries in South Africa using the Swartkops Estuary as a case study. This necessitated a review of existing SES frameworks that have been developed for use in other disciplines. As part of the newly developed framework, the Swartkops estuary condition was assessed using the Estuary Health Index to understand the present ecological state (PES) of the estuary following from the last assessment done in 2013/2014. The Estuary Health Index is a nationally accepted method of measuring the health of South African estuaries. The state of the societal system was assessed through field observations, engagements with estuary users on-site, insights provided by the Zwartkops Conservancy, and from recent literature. The potential for restoration of habitats for the purpose of carbon storage was also assessed as part of this study. The suitability of disturbed habitats for stimulating future salt marsh growth was investigated since an important incentive for restoration is blue carbon storage. This is important as blue carbon ecosystems offer great potential as a climate change mitigation measure through their ability to sequester carbon. This was done by evaluating plant cover and sediment characteristics at sites along the length of the estuary representing disturbed and undisturbed areas. The estuarine health score for the Swartkops Estuary was found to be 47 out of 100 translating to a PES Category D (largely modified estuary). The main problem in the estuary is water quality along with habitat loss and resource exploitation. The three Wastewater Treatment Works (WWTWs) located upstream of the estuary are the main drivers behind the decline in estuary health in addition to other threats to the water quality which are stormwater run-off inputs from the Motherwell canal and Markman canal. This study showed that the health of the estuary is on a negative trajectory towards a largely degraded estuary. Fishing, bait collection and the use of spiritual sites are the dominant vii ecosystem services used at the estuary. Through the assessment of the state of the societal system, the estuary was highlighted to be a major food source for many people living close to the estuary through subsistence fishing and bait collection for selling to recreational fishers. The estuary is also a health hazard to the very same people that depend on it for survival because of the poor water quality particularly high metal inputs from past and present nearby industrial activities. Restoration plans need to be developed in consideration of the estuary status quo that includes the societal system and the ecosystem services provided by the estuary. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Tsipa, Vusumzi
- Date: 2022-04
- Subjects: Estuarine ecology -- South Africa -- Swartkops River Estuary , Ecosystem
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59622 , vital:62208
- Description: The aim of this study was to develop and test a socio-ecological systems framework for the restoration of estuaries in South Africa using the Swartkops Estuary as a case study. This necessitated a review of existing SES frameworks that have been developed for use in other disciplines. As part of the newly developed framework, the Swartkops estuary condition was assessed using the Estuary Health Index to understand the present ecological state (PES) of the estuary following from the last assessment done in 2013/2014. The Estuary Health Index is a nationally accepted method of measuring the health of South African estuaries. The state of the societal system was assessed through field observations, engagements with estuary users on-site, insights provided by the Zwartkops Conservancy, and from recent literature. The potential for restoration of habitats for the purpose of carbon storage was also assessed as part of this study. The suitability of disturbed habitats for stimulating future salt marsh growth was investigated since an important incentive for restoration is blue carbon storage. This is important as blue carbon ecosystems offer great potential as a climate change mitigation measure through their ability to sequester carbon. This was done by evaluating plant cover and sediment characteristics at sites along the length of the estuary representing disturbed and undisturbed areas. The estuarine health score for the Swartkops Estuary was found to be 47 out of 100 translating to a PES Category D (largely modified estuary). The main problem in the estuary is water quality along with habitat loss and resource exploitation. The three Wastewater Treatment Works (WWTWs) located upstream of the estuary are the main drivers behind the decline in estuary health in addition to other threats to the water quality which are stormwater run-off inputs from the Motherwell canal and Markman canal. This study showed that the health of the estuary is on a negative trajectory towards a largely degraded estuary. Fishing, bait collection and the use of spiritual sites are the dominant vii ecosystem services used at the estuary. Through the assessment of the state of the societal system, the estuary was highlighted to be a major food source for many people living close to the estuary through subsistence fishing and bait collection for selling to recreational fishers. The estuary is also a health hazard to the very same people that depend on it for survival because of the poor water quality particularly high metal inputs from past and present nearby industrial activities. Restoration plans need to be developed in consideration of the estuary status quo that includes the societal system and the ecosystem services provided by the estuary. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Comparison of the population growth potential of South African loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles
- Authors: Tucek, Jenny Bianka
- Date: 2014
- Subjects: Sea turtles -- Population viability analysis -- South Africa , Migratory animals -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5032 , vital:20793
- Description: A beach conservation programme protecting nesting loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles in South Africa was started in 1963. As initial numbers of nesting females were low for both species (107 loggerheads and 24 leatherbacks) it was proposed that the protection of eggs, hatchlings and nesting females along the nesting beach would induce population growth and prohibit local extinction. Today, 50 years later, the loggerhead population exceeds 650 females per annum, whereas the leatherback population counts about 65 nesting females per year. The trend for leatherback turtles is that the population has been stable for about 30 years whereas loggerheads are increasing exponentially. Thus, this thesis investigated several life-history traits to explain the differing responses to the ongoing beach conservation programme. Reproductive output and success were assessed for both species; it was hypothesised that environmental conditions are sub-optimal for leatherback turtles to reproduce successfully. It was ascertained that nesting loggerhead females deposit larger clutches than leatherbacks (112 ± SD 20 eggs and 100 ± SD 23 eggs, respectively), but that annual reproductive output per individual leatherback female exceeds that of loggerhead turtles (±700 eggs and ±448 eggs, respectively) because they exhibit a higher intra-seasonal nesting frequency (leatherbacks n = 7 and loggerheads n = 4 from Nel et al. 2013). Emergence success (i.e. the percentage of hatchlings produced) per nest was similar for both species (loggerhead 73.6 ± SD 27.68 % and leatherback turtles 73.8 ± SD 22.70 %), but as loggerhead turtles nest in greater numbers, i.e. producing more hatchlings per year, the absolute population growth potential favours the loggerhead turtle. The second factor investigated was sex ratio because sea turtles display temperature-dependent sex determination (TSD) where extreme incubation temperatures can skew the sex ratio (i.e. feminising or masculinising a clutch). It was suspected that leatherback turtles are male-biased as this is the southern-most rookery (for both species). Further, leatherback nests are generally closer to the high tide mark, which might induce a cooling effect. Standard histological techniques were applied to sex hatchlings and a generalized linear model (GLM) was used to approximate annual sex ratio. Loggerhead sex ratio (2009 - 2011) was estimated at 86.9 ± SE 0.35 % female-biased; however, sufficient replication for the leatherback population was only obtained for season 2010, which indicated a 97.1 % (95 % CI 93.3 - 98.7) female bias. Both species are, thus, highly female-biased, and current sex ratio for leatherback turtles is not prohibiting population growth. Current sex ratios, however, are not necessarily indicative of sex ratios in the past which would have induced present population growth. Thus, to account for present population growth profiles, sex ratios from the past needed to be ascertained. Annual sex ratios (1997 - 2011) were modelled from historical air and sea surface temperatures (SSTs) but no significant change over time was obtained for either loggerhead or leatherback turtles (linear regression; p ≥ 0.45). The average sex ratio over this 15-year period for the South African loggerhead turtle was approximated at 77.1 ± SE 3.36 % female-biased, whereas leatherbacks exhibited a 99.5 ± SE 0.24 % female bias. Re-analysing data from the mid-80s by Maxwell et al. (1988) also indicated a 77.4 % female bias for the South African loggerhead population. It is, therefore, highly likely that sex ratios of the South African loggerhead and leatherback sea turtle populations have been stable for at least three decades and are not accountable for the differing population growth profiles as they are displayed today. Another possibility that could explain the opposed population growth profiles is the time taken for animals to replace themselves, i.e. age at maturity. It was suspected that age at maturity for the South African loggerhead turtle is comparable with that for leatherbacks. Using data from a 30-year mutilation tagging experiment (i.e. notching), age at first reproduction for South African loggerhead females was estimated. Results ranged broadly but a mean of 36.2 ± SD 7.71 years was obtained using a Gaussian distribution. Age at reproduction of the South African leatherback turtle was not determined but the literature suggests a much younger age of 13.3 - 26.8 years (Zug & Parham 1996, Dutton et al. 2005, Avens et al. 2009, Jones et al. 2011). Therefore, population growth would favour leatherback turtles as they exhibit a much shorter generation time. Finally, it was concluded that all life-history parameters investigated favour leatherback turtles, yet loggerheads are displaying population growth. However, as there were no obvious constraints to population growth on the nesting beach, it is suspected that population growth of the South African leatherback turtle is either unobserved (due to inadequate monitoring not capturing sufficient numbers of nesting events to establish a trend) or that population growth is prohibited by some offshore factor such as industrial fisheries (or some other driver not yet identified). Monitoring should, thus, be expanded and offshore mortality monitored as the leatherback population nesting in South Africa is still critically endangered with nesting numbers dangerously low.
- Full Text:
- Date Issued: 2014
- Authors: Tucek, Jenny Bianka
- Date: 2014
- Subjects: Sea turtles -- Population viability analysis -- South Africa , Migratory animals -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5032 , vital:20793
- Description: A beach conservation programme protecting nesting loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles in South Africa was started in 1963. As initial numbers of nesting females were low for both species (107 loggerheads and 24 leatherbacks) it was proposed that the protection of eggs, hatchlings and nesting females along the nesting beach would induce population growth and prohibit local extinction. Today, 50 years later, the loggerhead population exceeds 650 females per annum, whereas the leatherback population counts about 65 nesting females per year. The trend for leatherback turtles is that the population has been stable for about 30 years whereas loggerheads are increasing exponentially. Thus, this thesis investigated several life-history traits to explain the differing responses to the ongoing beach conservation programme. Reproductive output and success were assessed for both species; it was hypothesised that environmental conditions are sub-optimal for leatherback turtles to reproduce successfully. It was ascertained that nesting loggerhead females deposit larger clutches than leatherbacks (112 ± SD 20 eggs and 100 ± SD 23 eggs, respectively), but that annual reproductive output per individual leatherback female exceeds that of loggerhead turtles (±700 eggs and ±448 eggs, respectively) because they exhibit a higher intra-seasonal nesting frequency (leatherbacks n = 7 and loggerheads n = 4 from Nel et al. 2013). Emergence success (i.e. the percentage of hatchlings produced) per nest was similar for both species (loggerhead 73.6 ± SD 27.68 % and leatherback turtles 73.8 ± SD 22.70 %), but as loggerhead turtles nest in greater numbers, i.e. producing more hatchlings per year, the absolute population growth potential favours the loggerhead turtle. The second factor investigated was sex ratio because sea turtles display temperature-dependent sex determination (TSD) where extreme incubation temperatures can skew the sex ratio (i.e. feminising or masculinising a clutch). It was suspected that leatherback turtles are male-biased as this is the southern-most rookery (for both species). Further, leatherback nests are generally closer to the high tide mark, which might induce a cooling effect. Standard histological techniques were applied to sex hatchlings and a generalized linear model (GLM) was used to approximate annual sex ratio. Loggerhead sex ratio (2009 - 2011) was estimated at 86.9 ± SE 0.35 % female-biased; however, sufficient replication for the leatherback population was only obtained for season 2010, which indicated a 97.1 % (95 % CI 93.3 - 98.7) female bias. Both species are, thus, highly female-biased, and current sex ratio for leatherback turtles is not prohibiting population growth. Current sex ratios, however, are not necessarily indicative of sex ratios in the past which would have induced present population growth. Thus, to account for present population growth profiles, sex ratios from the past needed to be ascertained. Annual sex ratios (1997 - 2011) were modelled from historical air and sea surface temperatures (SSTs) but no significant change over time was obtained for either loggerhead or leatherback turtles (linear regression; p ≥ 0.45). The average sex ratio over this 15-year period for the South African loggerhead turtle was approximated at 77.1 ± SE 3.36 % female-biased, whereas leatherbacks exhibited a 99.5 ± SE 0.24 % female bias. Re-analysing data from the mid-80s by Maxwell et al. (1988) also indicated a 77.4 % female bias for the South African loggerhead population. It is, therefore, highly likely that sex ratios of the South African loggerhead and leatherback sea turtle populations have been stable for at least three decades and are not accountable for the differing population growth profiles as they are displayed today. Another possibility that could explain the opposed population growth profiles is the time taken for animals to replace themselves, i.e. age at maturity. It was suspected that age at maturity for the South African loggerhead turtle is comparable with that for leatherbacks. Using data from a 30-year mutilation tagging experiment (i.e. notching), age at first reproduction for South African loggerhead females was estimated. Results ranged broadly but a mean of 36.2 ± SD 7.71 years was obtained using a Gaussian distribution. Age at reproduction of the South African leatherback turtle was not determined but the literature suggests a much younger age of 13.3 - 26.8 years (Zug & Parham 1996, Dutton et al. 2005, Avens et al. 2009, Jones et al. 2011). Therefore, population growth would favour leatherback turtles as they exhibit a much shorter generation time. Finally, it was concluded that all life-history parameters investigated favour leatherback turtles, yet loggerheads are displaying population growth. However, as there were no obvious constraints to population growth on the nesting beach, it is suspected that population growth of the South African leatherback turtle is either unobserved (due to inadequate monitoring not capturing sufficient numbers of nesting events to establish a trend) or that population growth is prohibited by some offshore factor such as industrial fisheries (or some other driver not yet identified). Monitoring should, thus, be expanded and offshore mortality monitored as the leatherback population nesting in South Africa is still critically endangered with nesting numbers dangerously low.
- Full Text:
- Date Issued: 2014
Factors influencing first-year students’ career decisions to pursue an IT career
- Authors: Twani, Malibongwe
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54135 , vital:46306
- Description: The process of deciding on a career is a dauntingand life-changing decision,which all scholarshave had to make. Various factors influence a first-year student’s career choice decision and selected field of study. Career decision-making,as a field of study, has been extensivelyresearched,globally. The research studies focusingon IT career choicesof studentshave indicated that scholars choosing careers in Information Technology (IT) are influenced by factors such as salaries, knowledge of career opportunities, the reputation of IT-related fields in society and by parents, teachers and role models. Recent research indicates that exposure to new technologies and programming concepts at the school level can influence a scholar’s IT career choice. Theories relating to career choice have focused on the characteristics of individuals and their environment. Career choice models have identified factors that influenced a student’s career choice.In South Africahowever,there have been limited studies investigating the factors influencing students’ career decisions in choosing careers in Computer Science (CS), Information Systems (IS) and Information Technology (IT)using mixed-methods.This study aims to investigate the factors that influence first-year students’ decisionsin choosing an IT career at the Nelson Mandela University.The research study pursueda pragmatisticapproach,using a mixed-methods approach. In investigating theories andfactors that influence students’ decisionsin choosing IT careers,the study used systematic literature reviews. The decision-making theories and factorsin theliterature review facilitated the creation of the conceptual framework for IT career decision making. A questionnaire was developed and distributed amongst ITand Non-ITfirst-year studentsin 2021. Fourhundredand eightparticipants completed the survey. The data obtained from the survey were statistically analysed, includingdescriptive analysis andExploratory Factor Analysis(EFA). Additionally, inferential statistics were used namely; Correlations, t-test, Confirmatory Factor Analysis(CFA)and Structural Equation Modelling(SEM). The study results wereinterpreted andcompared with iiiotherrelevantstudies. Recommendations were madeto address the factorsthat influencefirst-year students’ IT career decisions.The study highlighted that high academic confidence and personal attributes amongststudents,whowereinvolved at an early age in programming and using computers,chose IT as a career. The study showed significant statistical differences betweenIT and Non-IT groups in perceptions about the IT industry and identifying job title descriptions.Additionally, a significant statistical difference between languages and genders was identified in understanding careers. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Twani, Malibongwe
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54135 , vital:46306
- Description: The process of deciding on a career is a dauntingand life-changing decision,which all scholarshave had to make. Various factors influence a first-year student’s career choice decision and selected field of study. Career decision-making,as a field of study, has been extensivelyresearched,globally. The research studies focusingon IT career choicesof studentshave indicated that scholars choosing careers in Information Technology (IT) are influenced by factors such as salaries, knowledge of career opportunities, the reputation of IT-related fields in society and by parents, teachers and role models. Recent research indicates that exposure to new technologies and programming concepts at the school level can influence a scholar’s IT career choice. Theories relating to career choice have focused on the characteristics of individuals and their environment. Career choice models have identified factors that influenced a student’s career choice.In South Africahowever,there have been limited studies investigating the factors influencing students’ career decisions in choosing careers in Computer Science (CS), Information Systems (IS) and Information Technology (IT)using mixed-methods.This study aims to investigate the factors that influence first-year students’ decisionsin choosing an IT career at the Nelson Mandela University.The research study pursueda pragmatisticapproach,using a mixed-methods approach. In investigating theories andfactors that influence students’ decisionsin choosing IT careers,the study used systematic literature reviews. The decision-making theories and factorsin theliterature review facilitated the creation of the conceptual framework for IT career decision making. A questionnaire was developed and distributed amongst ITand Non-ITfirst-year studentsin 2021. Fourhundredand eightparticipants completed the survey. The data obtained from the survey were statistically analysed, includingdescriptive analysis andExploratory Factor Analysis(EFA). Additionally, inferential statistics were used namely; Correlations, t-test, Confirmatory Factor Analysis(CFA)and Structural Equation Modelling(SEM). The study results wereinterpreted andcompared with iiiotherrelevantstudies. Recommendations were madeto address the factorsthat influencefirst-year students’ IT career decisions.The study highlighted that high academic confidence and personal attributes amongststudents,whowereinvolved at an early age in programming and using computers,chose IT as a career. The study showed significant statistical differences betweenIT and Non-IT groups in perceptions about the IT industry and identifying job title descriptions.Additionally, a significant statistical difference between languages and genders was identified in understanding careers. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
Using mobile information visualisation to support the analysis of telecommunication service ultilisation
- Authors: Twigg, Gianni Gurshwin
- Date: 2012
- Subjects: Telecommunication , Visualization , Technology -- Social aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10497 , http://hdl.handle.net/10948/d1020831
- Description: Telecommunication service utilisation (TSU) focuses on how customers make use of telecommunication services and can provide valuable information for decision making for improved customer service delivery. When a telecommunication service provider consults with customers, large amounts of static documentation on TSU data are compiled. Compiling this documentation for in-field investigation is manually intensive and the documentation does not effectively support decision making. Existing systems for visualising TSU data do not efficiently support in-field investigation of TSU and lack dynamic interaction. This highlights the need to investigate a solution to better support in-field investigation of TSU. This research followed a Design Science Research methodology to develop and evaluate a solution to solve the problem identified. The use of tablet devices for in-field investigation of TSU was identified as a suitable solution. Mobile information visualisation (MIV) techniques were investigated to determine appropriate display and interaction techniques for the visualisation of TSU data on a tablet device. An existing visualisation framework for TSU was identified and extended to incorporate touch-based interactions. Three service usage views were identified for visualising TSU, namely a Trend, Network and Detail Usage View. A Dashboard View was also identified to provide a quick reference view of the different views. A prototype called MobiTel was developed on a tablet device. MobiTel incorporated the identified information visualisation techniques. MobiTel was evaluated using an expert review and a user study to determine its usability and usefulness. The results indicated that MobiTel was perceived as being useful for in-field investigation and that the participants perceived the prototype to be easy to use and learn. The user study also indicated that the participants were satisfied with MobiTel. This research has determined that MIV techniques can be used for in-field investigation of TSU. Design recommendations were devised for designing an interactive mobile prototype for visualising service usage information. Future work will involve using map-based visualisation for visualising TSU data on different customer sites.
- Full Text:
- Date Issued: 2012
- Authors: Twigg, Gianni Gurshwin
- Date: 2012
- Subjects: Telecommunication , Visualization , Technology -- Social aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10497 , http://hdl.handle.net/10948/d1020831
- Description: Telecommunication service utilisation (TSU) focuses on how customers make use of telecommunication services and can provide valuable information for decision making for improved customer service delivery. When a telecommunication service provider consults with customers, large amounts of static documentation on TSU data are compiled. Compiling this documentation for in-field investigation is manually intensive and the documentation does not effectively support decision making. Existing systems for visualising TSU data do not efficiently support in-field investigation of TSU and lack dynamic interaction. This highlights the need to investigate a solution to better support in-field investigation of TSU. This research followed a Design Science Research methodology to develop and evaluate a solution to solve the problem identified. The use of tablet devices for in-field investigation of TSU was identified as a suitable solution. Mobile information visualisation (MIV) techniques were investigated to determine appropriate display and interaction techniques for the visualisation of TSU data on a tablet device. An existing visualisation framework for TSU was identified and extended to incorporate touch-based interactions. Three service usage views were identified for visualising TSU, namely a Trend, Network and Detail Usage View. A Dashboard View was also identified to provide a quick reference view of the different views. A prototype called MobiTel was developed on a tablet device. MobiTel incorporated the identified information visualisation techniques. MobiTel was evaluated using an expert review and a user study to determine its usability and usefulness. The results indicated that MobiTel was perceived as being useful for in-field investigation and that the participants perceived the prototype to be easy to use and learn. The user study also indicated that the participants were satisfied with MobiTel. This research has determined that MIV techniques can be used for in-field investigation of TSU. Design recommendations were devised for designing an interactive mobile prototype for visualising service usage information. Future work will involve using map-based visualisation for visualising TSU data on different customer sites.
- Full Text:
- Date Issued: 2012
The survival of micro -enteprises in Kampala, Uganda :a substainable livelihoods approach
- Authors: Twinorugyendo,Penninah
- Date: 2016
- Subjects: Microfinance -- Uganda -- Kampala New Business Enterprises -- Uganda -- Kampala -- Finance , Small business -- Uganda -- Kampala
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45333 , vital:38571
- Description: This purpose of this thesis was to explain the resilience of certain micro-enterprises (MEs) in Kampala, Uganda – by focusing on their vulnerability, the assets that they brought to bear on the situation, the role of non-governmental organizations and government institutions in supporting MEs, and the strategies used by ME owners, themselves. As such, it adopts the Sustainable-Livelihoods approach – an approach that has not been used in Kampala before. Thus, it makes a valuable contribution to the field. Designed as a qualitative study, it used in-depth interviews and focus-group discussions. The major findings on vulnerability were linked to: the rising cost of materials; unfair licensing; the struggle to win tenders; local and foreign competition; and the disruption of utilities. The assets used to sustain the welfare of the MEs included: making use of a range of skill-acquisition strategies; leveraging networks; and pooling resources. Financial assets used by MEs revolved around informal savings and credit schemes; but the support given to the MEs through government agencies and NGOs was difficult to assess. Several important strategies were used by ME owners. One of these involved linking with formal construction companies. In addition, temporary workshops constructed out of wood-and-iron, were common. This increased mobility and allowed the re-use of materials. Furthermore, MEs manufactured their own tools, developed new marketing techniques, and diversified their income-generating activities. The significance of this study is two-pronged. It demonstrates that the resilience of MEs does depend on their own positive qualities, but also on an increasingly business-friendly national and international economic environment.
- Full Text:
- Date Issued: 2016
- Authors: Twinorugyendo,Penninah
- Date: 2016
- Subjects: Microfinance -- Uganda -- Kampala New Business Enterprises -- Uganda -- Kampala -- Finance , Small business -- Uganda -- Kampala
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45333 , vital:38571
- Description: This purpose of this thesis was to explain the resilience of certain micro-enterprises (MEs) in Kampala, Uganda – by focusing on their vulnerability, the assets that they brought to bear on the situation, the role of non-governmental organizations and government institutions in supporting MEs, and the strategies used by ME owners, themselves. As such, it adopts the Sustainable-Livelihoods approach – an approach that has not been used in Kampala before. Thus, it makes a valuable contribution to the field. Designed as a qualitative study, it used in-depth interviews and focus-group discussions. The major findings on vulnerability were linked to: the rising cost of materials; unfair licensing; the struggle to win tenders; local and foreign competition; and the disruption of utilities. The assets used to sustain the welfare of the MEs included: making use of a range of skill-acquisition strategies; leveraging networks; and pooling resources. Financial assets used by MEs revolved around informal savings and credit schemes; but the support given to the MEs through government agencies and NGOs was difficult to assess. Several important strategies were used by ME owners. One of these involved linking with formal construction companies. In addition, temporary workshops constructed out of wood-and-iron, were common. This increased mobility and allowed the re-use of materials. Furthermore, MEs manufactured their own tools, developed new marketing techniques, and diversified their income-generating activities. The significance of this study is two-pronged. It demonstrates that the resilience of MEs does depend on their own positive qualities, but also on an increasingly business-friendly national and international economic environment.
- Full Text:
- Date Issued: 2016
A comparison of conventional and ultrasonic seams in swimwear
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
- Authors: Tyalana, Nommiselo
- Date: 2018
- Subjects: Textile finishing , Textile finishing agents Seams (Sewing) Textile fabrics Textile fibers Textile design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36727 , vital:34048
- Description: Ultrasonic welding technology is a relatively new technology in apparel construction, this research forms part of a study to assess its effectiveness as a joining technology that can be used in ladies swimwear. The ultimate aim was to determine whether the ultrasonic welding joining technique could be successfully used in assembling ladies swimwear garments, comprising only synthetic fibres, namely polyester/Lycra, polyamide/Lycra, polyamide/Lycra power-net and polyamide/Lycra mesh warp knitted fabrics. These specific swimwear fabrics were selected since they comprise 100% thermoplastic synthetic fibres, considered ideal for ultrasonic welding. This study essentially compares and contrasts the performance of two seam joining techniques: namely conventional sewing and ultrasonic welding, in terms of seam strength, when used in the above mentioned four fabrics. Conventionally sewn and ultrasonically welded seams were produced, straight and curved, in both the wale and course directions of the fabrics. The conventionally sewn seams were produced using two sewing machines; namely an overlocker, also known as a mock safety sewing machine, and a cover seam machines. All conventionally sewn seams were stitched and tested under similar conditions. The ultrasonic welded seams were produced using three different wheels, a Medium Male Knurled pattern wheel, a Staggered Triple Stitch pattern wheel and a Single Stitch pattern wheel. The amplitude and speed of the welding machine, during the ultrasonic seaming, were kept constant, except when welding the polyamide/Lycra power-net and the polyamide/Lycra mesh fabrics when the pressure had to be drastically reduced in order to avoid excessively softened seams. The results of the study are presented in the form of line charts, scatter charts and tables. The ultrasonic welded seams, joined with the Medium Male Knurled wheel, exhibited surface waviness, as opposed to those joined with the Staggered Triple Stitch wheel which were smooth. It was found that, in terms of seam strength, the ultrasonic seams produced with the Single Stitch and Medium Male Knurled pattern wheels out performed those produced with the Staggered Triple Stitch wheels. The polyester/Lycra fabric was found easier to handle during the ultrasonic seaming process than the polyamide/Lycra fabric, although the strength of the ultrasonic seams in the polyester/Lycra fabric did not differ consistently from those of the polyamide/Lycra fabric. It was found that the conventional sewn seams were consistently stronger, and had a better appearance, than the ultrasonic welded seams. Although some promising results were obtained, in terms of the strength of the ultrasonic welded seams, the results overall were far too variable, inconsistent and unsatisfactory for this technique of seaming to be recommended at this stage for any of the swimwear fabrics covered. Further, more in depth, studies are required in order to gain a better understating of the effect of the various ultrasonic seaming parameters, as well as fabric parameters on ultrasonic seam strength and consistency.
- Full Text:
- Date Issued: 2018
Biospeciation and antidiabetic effects of oxidovanadium(IV) complexes
- Authors: Ugirinema, Vital
- Date: 2014
- Subjects: Vanadium compounds , Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10442 , http://hdl.handle.net/10948/d1020973
- Description: The syntheses of bis(1R-imidazole-2/4-carboxylato)oxidovanadium(IV) complexes was successfully carried out and the complexes were isolated in the solid state. The coordinated water was confirmed by elemental analyses, and single crystal XRD. The complexes were therefore distorted octahedral rather than square planar due to the coordination of water at the sixth position. The reaction of the vanadyl ion (VO2+) with imidazole-4-carboxylic acid (Im4COOH), imidazole-2-carboxylic acid (Im2COOH) and methylimidazole-2-carboxylic acid (MeIm2COOH), respectively, in the presence of small bioligands (bL) [oxalate (Ox), lactate (Lact), and phosphate (Phos)] and high molecular weight (HMM) human serum proteins [albumin (HSA) and transferrin (hTf)] were studied in aqueous solution using potentiometric acid base titrations under oxygen and carbon dioxide–free conditions. The data obtained from these titrations was used to calculate the binary and ternary stability constants using the programme HYPERQUAD. The overall stability constants for VO2+-L-Ox system (log β1111 = 18.9, 18.79 and 19.86), VO2+-L-Lact system (log β1111 = 21.83, 20.98 and 22.86), and VO2+-L-Phos system (log β1111 = 27.35, 24.16 and 27.42) (for L= Im4COOH, Im2COOH and MeIm2COOH, respectively) were obtained. The species distribution diagrams showed that under physiological pH the following ternary and quaternary species; [(VO)L(bL)], and [VO(L)(bL)(OH)], would dominate provided that the competition with serum proteins is not too strong. These species were also confirmed by HPLC, LC-MS and EPR. The overall stability constants for the VO2+-L-HSA system (log β2,1,1,0 = 24.3, 23.7 and 24.7), and for the VO2+-L-hTf system (log β2,2,1,0 = 31.1, 30.8, 36.4 for L = Im4COOH, Im2COOH and MeIm2COOH, respectively), suggesting stronger binding of transferrin. The formation constants for the formation of binary (VO(IV) and the proteins) were 9.1 and 13 for log β11, and 20.9 and 25.2 for β12, for human serum albumin and human serum transferrin respectively. The species distribution diagrams for the proteins (HMM) with oxidovanadium(IV) under physiological pH was dominated by VO(HMM)2, VOL(HMM) for unsubstituted Im4COOH and Im2COOH, however, for the N-substituted MeIm2COOH, the species distribution diagrams under physiological pH, were dominated by VOL2, VO(HMM)2 and VO2L2(HMM). These species were further confirmed by HPLC, MALDI-TOF-MS and EPR. The glucose stimulated insulin secretion (GSIS) action of the complexes was investigated using INS-1E cells at 1μM concentration which was established through cytotoxicity studies via the MTT assay. The vanadium salt (VOSO4), cationic vanadium(IV) complex ([VO(MeImCH2OH)2]2+) were also included in the GSIS study in addition to the three neutral complexes [VO(Im4COO)2, VO(Im2COO)2 and VO(MeIm2COO)2] for comparison. The neutral complexes, especially VO(MeIm2COO)2, showed promising results in the stimulation of insulin secretion than the cationic complex and the vanadium salt.
- Full Text:
- Date Issued: 2014
- Authors: Ugirinema, Vital
- Date: 2014
- Subjects: Vanadium compounds , Diabetes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10442 , http://hdl.handle.net/10948/d1020973
- Description: The syntheses of bis(1R-imidazole-2/4-carboxylato)oxidovanadium(IV) complexes was successfully carried out and the complexes were isolated in the solid state. The coordinated water was confirmed by elemental analyses, and single crystal XRD. The complexes were therefore distorted octahedral rather than square planar due to the coordination of water at the sixth position. The reaction of the vanadyl ion (VO2+) with imidazole-4-carboxylic acid (Im4COOH), imidazole-2-carboxylic acid (Im2COOH) and methylimidazole-2-carboxylic acid (MeIm2COOH), respectively, in the presence of small bioligands (bL) [oxalate (Ox), lactate (Lact), and phosphate (Phos)] and high molecular weight (HMM) human serum proteins [albumin (HSA) and transferrin (hTf)] were studied in aqueous solution using potentiometric acid base titrations under oxygen and carbon dioxide–free conditions. The data obtained from these titrations was used to calculate the binary and ternary stability constants using the programme HYPERQUAD. The overall stability constants for VO2+-L-Ox system (log β1111 = 18.9, 18.79 and 19.86), VO2+-L-Lact system (log β1111 = 21.83, 20.98 and 22.86), and VO2+-L-Phos system (log β1111 = 27.35, 24.16 and 27.42) (for L= Im4COOH, Im2COOH and MeIm2COOH, respectively) were obtained. The species distribution diagrams showed that under physiological pH the following ternary and quaternary species; [(VO)L(bL)], and [VO(L)(bL)(OH)], would dominate provided that the competition with serum proteins is not too strong. These species were also confirmed by HPLC, LC-MS and EPR. The overall stability constants for the VO2+-L-HSA system (log β2,1,1,0 = 24.3, 23.7 and 24.7), and for the VO2+-L-hTf system (log β2,2,1,0 = 31.1, 30.8, 36.4 for L = Im4COOH, Im2COOH and MeIm2COOH, respectively), suggesting stronger binding of transferrin. The formation constants for the formation of binary (VO(IV) and the proteins) were 9.1 and 13 for log β11, and 20.9 and 25.2 for β12, for human serum albumin and human serum transferrin respectively. The species distribution diagrams for the proteins (HMM) with oxidovanadium(IV) under physiological pH was dominated by VO(HMM)2, VOL(HMM) for unsubstituted Im4COOH and Im2COOH, however, for the N-substituted MeIm2COOH, the species distribution diagrams under physiological pH, were dominated by VOL2, VO(HMM)2 and VO2L2(HMM). These species were further confirmed by HPLC, MALDI-TOF-MS and EPR. The glucose stimulated insulin secretion (GSIS) action of the complexes was investigated using INS-1E cells at 1μM concentration which was established through cytotoxicity studies via the MTT assay. The vanadium salt (VOSO4), cationic vanadium(IV) complex ([VO(MeImCH2OH)2]2+) were also included in the GSIS study in addition to the three neutral complexes [VO(Im4COO)2, VO(Im2COO)2 and VO(MeIm2COO)2] for comparison. The neutral complexes, especially VO(MeIm2COO)2, showed promising results in the stimulation of insulin secretion than the cationic complex and the vanadium salt.
- Full Text:
- Date Issued: 2014
Evaluating the effectiveness of public participation in the environmental impact assessment process in South Africa
- Authors: Uithaler, Eldrid Marlon
- Date: 2015
- Subjects: Environmental impact analysis -- South Africa , Environmental policy -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5928 , vital:21015
- Description: This research is based on reflections of various practitioners and their views on how public participation processes may or may not contribute to effective EIA decisions. It is therefore grounded in what is described as practitioner-based research. To study comparative development activities effectively, one must draw on many disciplines and construct a balanced understanding of historical and contemporary development processes. No single conventional disciplinary area of research is able to integrate the issues of public participation, EIA and decision-making in the context of the current development debate. The emergence of Trans-disciplinary areas of research allows for such integration. The Africa Earth Observatory Network (AEON) institute creates the space for this study to achieve an integrated response to the question of the effectiveness of public participation in EIA and decision-making. This further creates the opportunity to contribute and expand the growing body of knowledge and literature of public participation in the earth stewardship science discipline. Making use of triangulation, this study fulfils four major tasks: firstly, an assessment is made on the historical and theoretical importance, process and outcome of both EIA and public participation internationally and in South Africa. Secondly, three prominent case studies (i) the Coega IDZ, (ii) the Pondoland N2 Toll Road, and (iii) the anticipated Hydraulic Fracturing in the Karoo each focusses on concerns of an environmental, socio-economic, and political nature to assess if the public participation process has had influence, if any, on the final decisions for these projects to go-ahead. Thirdly, a survey was conducted to establish the views and perceptions of practitioners in the EIA and public participation domain on the effectiveness of public participation in EIA processes. Lastly, face-to-face interviews were conducted with various ‘pracademics’, i.e. consultants, practitioners, government, and non-governmental officials to establish their views on how public participation may or may not influence EIA decisions. Utilising the International Association for Public Participation’s (IAP2) participation spectrum as an evaluation tool, this research explores thirteen key criteria normally attributed to effective public participation. This provides a scale (inform, involve, consult, collaborate) to assess whether public participation in EIA in South Africa is least effective (inform) or most effective (collaborate). My research confirms that in South Africa an enabling environment to address impacts on our environment is emerging. One of the main challenges remains putting in place robust, clear and effective regulations, models or approaches that provide for effective public participation and decision-making in EIAs. My research also suggests that the legislation on which EIA is based cannot by itself guarantee the effectiveness of public participation processes. In practice, EIA is an institutional process of power division between different actors, and the practitioner or ‘pracademic’ has to play a more fundamental role to ensure effectiveness and fairness in the public participation process. Academic commentators should therefore call for new approaches that emphasise collaborative interaction between decision-makers and the public as well as deliberation amongst participants.
- Full Text:
- Date Issued: 2015
- Authors: Uithaler, Eldrid Marlon
- Date: 2015
- Subjects: Environmental impact analysis -- South Africa , Environmental policy -- Citizen participation
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/5928 , vital:21015
- Description: This research is based on reflections of various practitioners and their views on how public participation processes may or may not contribute to effective EIA decisions. It is therefore grounded in what is described as practitioner-based research. To study comparative development activities effectively, one must draw on many disciplines and construct a balanced understanding of historical and contemporary development processes. No single conventional disciplinary area of research is able to integrate the issues of public participation, EIA and decision-making in the context of the current development debate. The emergence of Trans-disciplinary areas of research allows for such integration. The Africa Earth Observatory Network (AEON) institute creates the space for this study to achieve an integrated response to the question of the effectiveness of public participation in EIA and decision-making. This further creates the opportunity to contribute and expand the growing body of knowledge and literature of public participation in the earth stewardship science discipline. Making use of triangulation, this study fulfils four major tasks: firstly, an assessment is made on the historical and theoretical importance, process and outcome of both EIA and public participation internationally and in South Africa. Secondly, three prominent case studies (i) the Coega IDZ, (ii) the Pondoland N2 Toll Road, and (iii) the anticipated Hydraulic Fracturing in the Karoo each focusses on concerns of an environmental, socio-economic, and political nature to assess if the public participation process has had influence, if any, on the final decisions for these projects to go-ahead. Thirdly, a survey was conducted to establish the views and perceptions of practitioners in the EIA and public participation domain on the effectiveness of public participation in EIA processes. Lastly, face-to-face interviews were conducted with various ‘pracademics’, i.e. consultants, practitioners, government, and non-governmental officials to establish their views on how public participation may or may not influence EIA decisions. Utilising the International Association for Public Participation’s (IAP2) participation spectrum as an evaluation tool, this research explores thirteen key criteria normally attributed to effective public participation. This provides a scale (inform, involve, consult, collaborate) to assess whether public participation in EIA in South Africa is least effective (inform) or most effective (collaborate). My research confirms that in South Africa an enabling environment to address impacts on our environment is emerging. One of the main challenges remains putting in place robust, clear and effective regulations, models or approaches that provide for effective public participation and decision-making in EIAs. My research also suggests that the legislation on which EIA is based cannot by itself guarantee the effectiveness of public participation processes. In practice, EIA is an institutional process of power division between different actors, and the practitioner or ‘pracademic’ has to play a more fundamental role to ensure effectiveness and fairness in the public participation process. Academic commentators should therefore call for new approaches that emphasise collaborative interaction between decision-makers and the public as well as deliberation amongst participants.
- Full Text:
- Date Issued: 2015
Growth and characterization of ZnO nanorods using chemical bath deposition
- Authors: Urgessa, Zelalem Nigussa
- Date: 2012
- Subjects: Zinc oxide , Photoluminescence , Semiconductor nanocrystals , Semiconductors -- Materials , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10559 , http://hdl.handle.net/10948/d1021124 , http://hdl.handle.net/10948/d1021119
- Description: Semiconductor devices are commonplace in every household. One application of semiconductors in particular, namely solid state lighting technology, is destined for a bright future. To this end, ZnO nanostructures have gained substantial interest in the research community, in part because of its requisite large direct band gap. Furthermore, the stability of the exciton (binding energy 60 meV) in this material, can lead to lasing action based on exciton recombination and possibly exciton interaction, even above room temperature. Therefore, it is very important to realize controllable growth of ZnO nanostructures and investigate their properties. The main motivation for this thesis is not only to successfully realize the controllable growth of ZnO nanorods, but also to investigate the structure, optical and electrical properties in detail by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy (steady state and time resolved) and X-ray diffraction (XRD). Furthermore, strong rectification in the ZnO/p-Si heterojunction is demonstrated. Nanorods have been successfully synthesized on silicon by a two-step process, involving the pre-coating of the substrate by a seed layer, followed by the chemical bath deposition of the nanorods. ZnO seed layers with particle sizes of about 5 nm are achieved by the thermal decomposition of zinc acetate dihydrate dissolved in ethanol. The effects of the seed layer density on the distribution, alignment and uniformity of subsequently grown nanorods were studied. The aspect ratio, orientation and distribution of nanorods are shown to be well controlled through adjusting the density of the ZnO nanoparticles pre-coated onto the substrates. It is shown that the seed layer is a prerequisite for the growth of well aligned ZnO nanorods on lattice mismatched Si substrate. The influence of various nanorod growth parameters on the morphology, optical and electrical properties of the nanorods were also systematically studied. These include the oxygen to zinc molar ratio, the pH of the growth solution, the concentration of the reactants, the growth temperature and growth time, different hydroxide precursors and the addition of surface passivating agents to the growth solution. By controlling these xii parameters different architectures of nanostructures, like spherical particles, well aligned nanorods, nanoflowers and thin films of different thicknesses are demonstrated. A possible growth mechanism for ZnO nanostructures in solution is proposed. XRD indicated that all the as-grown nanostructures produced above 45 C crystallize in the wurtzite structure and post growth annealing does not significantly enhance the crystalline quality of the material. In material grown at lower temperature, traces of zinc hydroxide were observed. The optical quality of the nanostructures was investigated using both steady-state PL and time-resolved (TR) PL from 4 K to room temperature. In the case of as-grown samples, both UV and defect related emissions have been observed for all nanostructures. The effect of post-growth annealing on the optical quality of the nanostructures was carefully examined. The effect of annealing in different atmospheres was also investigated. Regardless of the annealing environment annealing at a temperature as low as 300 C enhances the UV emission and suppresses defect related deep level emission. However, annealing above 500 C is required to out-diffuse hydrogen, the presence of which is deduced from the I4 line in the low temperature PL spectra of ZnO. TRPL was utilized to investigate lifetime decay profiles of nanorods upon different post growth treatments. The bound exciton lifetime strongly depends on the post-growth annealing temperature: the PL decay time is much faster for as grown rods, confirming the domination of surface assisted recombination. In general, the PL analysis showed that the PL of nanorods have the same characteristics as that of bulk ZnO, except for the stronger contribution from surface related bound excitons in the former case. Surface adsorbed impurities causing depletion and band bending in the near surface region is implied from both time resolved and steady state PL. Finally, although strong rectification in the ZnO/p-Si heterojunction is illustrated, no electroluminescence has been achieved. This is explained in terms of the band offset between ZnO and Si and interfacial states. Different schemes are proposed to improve the performance of ZnO/Si heterojunction light emitting devices.
- Full Text:
- Date Issued: 2012
- Authors: Urgessa, Zelalem Nigussa
- Date: 2012
- Subjects: Zinc oxide , Photoluminescence , Semiconductor nanocrystals , Semiconductors -- Materials , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10559 , http://hdl.handle.net/10948/d1021124 , http://hdl.handle.net/10948/d1021119
- Description: Semiconductor devices are commonplace in every household. One application of semiconductors in particular, namely solid state lighting technology, is destined for a bright future. To this end, ZnO nanostructures have gained substantial interest in the research community, in part because of its requisite large direct band gap. Furthermore, the stability of the exciton (binding energy 60 meV) in this material, can lead to lasing action based on exciton recombination and possibly exciton interaction, even above room temperature. Therefore, it is very important to realize controllable growth of ZnO nanostructures and investigate their properties. The main motivation for this thesis is not only to successfully realize the controllable growth of ZnO nanorods, but also to investigate the structure, optical and electrical properties in detail by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy (steady state and time resolved) and X-ray diffraction (XRD). Furthermore, strong rectification in the ZnO/p-Si heterojunction is demonstrated. Nanorods have been successfully synthesized on silicon by a two-step process, involving the pre-coating of the substrate by a seed layer, followed by the chemical bath deposition of the nanorods. ZnO seed layers with particle sizes of about 5 nm are achieved by the thermal decomposition of zinc acetate dihydrate dissolved in ethanol. The effects of the seed layer density on the distribution, alignment and uniformity of subsequently grown nanorods were studied. The aspect ratio, orientation and distribution of nanorods are shown to be well controlled through adjusting the density of the ZnO nanoparticles pre-coated onto the substrates. It is shown that the seed layer is a prerequisite for the growth of well aligned ZnO nanorods on lattice mismatched Si substrate. The influence of various nanorod growth parameters on the morphology, optical and electrical properties of the nanorods were also systematically studied. These include the oxygen to zinc molar ratio, the pH of the growth solution, the concentration of the reactants, the growth temperature and growth time, different hydroxide precursors and the addition of surface passivating agents to the growth solution. By controlling these xii parameters different architectures of nanostructures, like spherical particles, well aligned nanorods, nanoflowers and thin films of different thicknesses are demonstrated. A possible growth mechanism for ZnO nanostructures in solution is proposed. XRD indicated that all the as-grown nanostructures produced above 45 C crystallize in the wurtzite structure and post growth annealing does not significantly enhance the crystalline quality of the material. In material grown at lower temperature, traces of zinc hydroxide were observed. The optical quality of the nanostructures was investigated using both steady-state PL and time-resolved (TR) PL from 4 K to room temperature. In the case of as-grown samples, both UV and defect related emissions have been observed for all nanostructures. The effect of post-growth annealing on the optical quality of the nanostructures was carefully examined. The effect of annealing in different atmospheres was also investigated. Regardless of the annealing environment annealing at a temperature as low as 300 C enhances the UV emission and suppresses defect related deep level emission. However, annealing above 500 C is required to out-diffuse hydrogen, the presence of which is deduced from the I4 line in the low temperature PL spectra of ZnO. TRPL was utilized to investigate lifetime decay profiles of nanorods upon different post growth treatments. The bound exciton lifetime strongly depends on the post-growth annealing temperature: the PL decay time is much faster for as grown rods, confirming the domination of surface assisted recombination. In general, the PL analysis showed that the PL of nanorods have the same characteristics as that of bulk ZnO, except for the stronger contribution from surface related bound excitons in the former case. Surface adsorbed impurities causing depletion and band bending in the near surface region is implied from both time resolved and steady state PL. Finally, although strong rectification in the ZnO/p-Si heterojunction is illustrated, no electroluminescence has been achieved. This is explained in terms of the band offset between ZnO and Si and interfacial states. Different schemes are proposed to improve the performance of ZnO/Si heterojunction light emitting devices.
- Full Text:
- Date Issued: 2012
Comparison of in vitro activities of selected Ganoderma species in relation to skin diseases
- Authors: Van Aardt, Robin Kaylah
- Date: 2022-12
- Subjects: Ganoderma diseases of plants -- South Africa , Macrophages
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61143 , vital:69766
- Description: Ganoderma species of macrofungi have been reported to have a multitude of medicinal properties, however, there is limited information on this genus in South Africa. The goal of this study was to compare biological activities of selected Ganoderma spp. in relation to skin diseases with emphasis on the antibacterial, antioxidant, anti-inflammatory and cytotoxic in vitro activities. Ethanolic and aqueous extracts prepared from six samples of G. lucidum [two commercial products (MG-LZ8 and Medi Mushroom Reishi extract), polar, antler, fruiting body and mycelium] and ten cultivated Ganoderma spp. were screened for bioactivities. Antibacterial activity was assessed using the 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium (INT) assay against skin pathogens (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae). Cytotoxicity was determined using bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst/ PI) staining on the B16F10 melanoma cell line. The 2,2-Diphenyl-1- picrylhydrazyl (DPPH) and Ferric reducing ability of plasma (FRAP) assays were used to investigate antioxidant activity. Immune modulatory effects included detection of phagocytic activity and phenotypic changes of RAW 264.7 murine macrophage cells. The phenotypic macrophage polarisation of the extracts on RAW 264.7 murine macrophage cells was tested by treating the cells with the extracts and measuring the fluorescence of cell surface markers. CD86 was used as indicator for the M1 phenotype and CD206 as a general marker for M2 phenotypes. The commercially available and cultivated G. lucidum extracts did not show antibacterial activity within the 0-2mg/mL concentration range tested. The commercially available MG-LZ8 G. lucidum extract expressed cytotoxic activity with an IC50 value of 21.26 µg/mL while the ethanolic conk fruiting body and mycelial G. lucidum extract showed a significant reduction in live cells, indicating anti-proliferative activity. G. destructans mycelial ethanol extract displayed anti-proliferative activity at a concentration of 200 μg/mL which shows great potential as a mycelial extract. All the G. lucidum extracts exhibited free radical scavenging abilities with the Ganoderma spp. showing little to no measurable activity. G. lucidum and Ganoderma spp extracts had similar responses without inflammatory activity for the concentration ranges tested. The extracts did not increase macrophage phagocytic activity using the pHrodo™ Green E. coli iii BioParticles™ Conjugate. G. lucidum and Ganoderma spp. extracts induced macrophage polarisation toward the M2 phenotype, with the G. lucidum antler and conk fruiting body extracts displaying significant activity. This study illustrates one of the first investigations of the bioactivity of indigenous Ganoderma spp.; G. destructans type and G. eickeri, spp. nov. identified by Coeztee et al (2015). , Thesis (MSc) -- Faculty of Science, School of Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2022-12
- Authors: Van Aardt, Robin Kaylah
- Date: 2022-12
- Subjects: Ganoderma diseases of plants -- South Africa , Macrophages
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61143 , vital:69766
- Description: Ganoderma species of macrofungi have been reported to have a multitude of medicinal properties, however, there is limited information on this genus in South Africa. The goal of this study was to compare biological activities of selected Ganoderma spp. in relation to skin diseases with emphasis on the antibacterial, antioxidant, anti-inflammatory and cytotoxic in vitro activities. Ethanolic and aqueous extracts prepared from six samples of G. lucidum [two commercial products (MG-LZ8 and Medi Mushroom Reishi extract), polar, antler, fruiting body and mycelium] and ten cultivated Ganoderma spp. were screened for bioactivities. Antibacterial activity was assessed using the 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium (INT) assay against skin pathogens (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae). Cytotoxicity was determined using bisBenzamide H 33342 trihydrochloride/propidium iodide (Hoechst/ PI) staining on the B16F10 melanoma cell line. The 2,2-Diphenyl-1- picrylhydrazyl (DPPH) and Ferric reducing ability of plasma (FRAP) assays were used to investigate antioxidant activity. Immune modulatory effects included detection of phagocytic activity and phenotypic changes of RAW 264.7 murine macrophage cells. The phenotypic macrophage polarisation of the extracts on RAW 264.7 murine macrophage cells was tested by treating the cells with the extracts and measuring the fluorescence of cell surface markers. CD86 was used as indicator for the M1 phenotype and CD206 as a general marker for M2 phenotypes. The commercially available and cultivated G. lucidum extracts did not show antibacterial activity within the 0-2mg/mL concentration range tested. The commercially available MG-LZ8 G. lucidum extract expressed cytotoxic activity with an IC50 value of 21.26 µg/mL while the ethanolic conk fruiting body and mycelial G. lucidum extract showed a significant reduction in live cells, indicating anti-proliferative activity. G. destructans mycelial ethanol extract displayed anti-proliferative activity at a concentration of 200 μg/mL which shows great potential as a mycelial extract. All the G. lucidum extracts exhibited free radical scavenging abilities with the Ganoderma spp. showing little to no measurable activity. G. lucidum and Ganoderma spp extracts had similar responses without inflammatory activity for the concentration ranges tested. The extracts did not increase macrophage phagocytic activity using the pHrodo™ Green E. coli iii BioParticles™ Conjugate. G. lucidum and Ganoderma spp. extracts induced macrophage polarisation toward the M2 phenotype, with the G. lucidum antler and conk fruiting body extracts displaying significant activity. This study illustrates one of the first investigations of the bioactivity of indigenous Ganoderma spp.; G. destructans type and G. eickeri, spp. nov. identified by Coeztee et al (2015). , Thesis (MSc) -- Faculty of Science, School of Biochemistry and Microbiology, 2023
- Full Text:
- Date Issued: 2022-12
The kinetics and associated reactions of ruthenium(VIII)
- Authors: Van Aswegen, Werner
- Date: 2009
- Subjects: Ruthenium , Ruthenium compounds , Alcohols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10392 , http://hdl.handle.net/10948/1130 , http://hdl.handle.net/10948/d1008611 , Ruthenium , Ruthenium compounds , Alcohols
- Description: This study investigated the reduction reaction of ruthenium tetroxide by various aliphatic alcohols in acidic medium. UV-Vis spectroscopy still plays an essential role in the analysis and study of volatile ruthenium tetroxide and was used in this study to collect kinetic data. This data was analyzed using graphical and computational methods, such as Mauser diagrams and kinetic simulation software. From the results obtained it is proposed that the reaction occurs by the following two-step reaction model: Ru(VIII) k1 Ru(VI) Ru(VI) k2 k-2 Ru(III) Molar extinction coefficients and conditional rate constants were calculated using kinetic simulating software and a hydride transfer mechanism was proposed. The temperature dependence of this reduction reaction was also investigated and thermodynamic parameters calculated. Ruthenium concentrations were determined using a method employing UV-Vis spectroscopy. The method proved to be a reliable, sensitive and simple technique.
- Full Text:
- Date Issued: 2009
- Authors: Van Aswegen, Werner
- Date: 2009
- Subjects: Ruthenium , Ruthenium compounds , Alcohols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10392 , http://hdl.handle.net/10948/1130 , http://hdl.handle.net/10948/d1008611 , Ruthenium , Ruthenium compounds , Alcohols
- Description: This study investigated the reduction reaction of ruthenium tetroxide by various aliphatic alcohols in acidic medium. UV-Vis spectroscopy still plays an essential role in the analysis and study of volatile ruthenium tetroxide and was used in this study to collect kinetic data. This data was analyzed using graphical and computational methods, such as Mauser diagrams and kinetic simulation software. From the results obtained it is proposed that the reaction occurs by the following two-step reaction model: Ru(VIII) k1 Ru(VI) Ru(VI) k2 k-2 Ru(III) Molar extinction coefficients and conditional rate constants were calculated using kinetic simulating software and a hydride transfer mechanism was proposed. The temperature dependence of this reduction reaction was also investigated and thermodynamic parameters calculated. Ruthenium concentrations were determined using a method employing UV-Vis spectroscopy. The method proved to be a reliable, sensitive and simple technique.
- Full Text:
- Date Issued: 2009
Phenotypic plasticity of metabolic rate in an afrotropical bird species (Euplectes orix) across a temperature gradient
- Van de Ven, Tanja Maria Francisca Nicole
- Authors: Van de Ven, Tanja Maria Francisca Nicole
- Date: 2012
- Subjects: Phenotypic plasticity , Evolutionary genetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10718 , http://hdl.handle.net/10948/d1012659 , Phenotypic plasticity , Evolutionary genetics
- Description: Avian species are known to have the capacity to respond to environmental changes through physiological adjustments. The process whereby organisms adjust their phenotype without genetic change is termed phenotypic plasticity and it is mostly observed to be a phenotypic improvement to ecological challenges. Metabolic rate (MR), which is the rate of energy expenditure in a species, is a highly flexible physiological parameter which results in a great diversity of avian standardised metabolic rates. Like birds from high latitudes, Afrotropical bird species are expected to have the capacity to adjust their energy expenditure to match the availability of resources. Previous studies on the flexibility of physiological parameters in birds have focused on the magnitude of change of physiological adjustments and the cues inducing these changes. Comparative research has furthermore investigated metabolic rates across aridity, altitude, latitude and temperature gradients. Recently, a clear dichotomy has become evident with elevated metabolic rates observed in high latitude birds in winter and a down-regulation of metabolic rates observed in birds exposed to low latitude mild winters. In this study, the shape of the reaction norm, the magnitude, the reversibility, the direction and the rate of change of two physiological parameters, basal metabolic rate (BMR) and summit metabolic rate (Msum), were investigated in a coastal and an inland population of Southern Red Bishops (Euplectes orix) through seasonal acclimatisation and laboratory acclimation. Summer and winter basal metabolic rates as well as body mass, were highly flexible traits in free-ranging coastal and inland Red Bishops. Birds acclimatised to a mild coastal climate in winter exhibited reduced basal and summit metabolic rates, whereas birds originating from a more variable inland climate increased basal metabolic rate in winter, but did not show increases of Msum in winter. Red Bishops responded to short term thermal acclimation under laboratory conditions by gradually changing body mass. Acclimation periods of 21 days revealed a negative relationship between body mass and acclimation air temperature. Peak responses of basal metabolic rate to ambient temperature change were observed in both coastal and inland birds between two and eight days after the change in acclimation air temperature. The influences of seasonal acclimatisation on energy expenditure differed between coastal and inland birds, however, during laboratory acclimation individuals from the two populations showed no difference in response. Within the individuals of the coastal and inland Southern Red Bishops, phenotypic flexibility is observed in body mass, basal metabolic rate and summit metabolic rate as a response to environmental changes. This flexibility is thought to increase thermoregulatory capacities of the Southern Red Bishop in different habitats and climates.
- Full Text:
- Date Issued: 2012
- Authors: Van de Ven, Tanja Maria Francisca Nicole
- Date: 2012
- Subjects: Phenotypic plasticity , Evolutionary genetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10718 , http://hdl.handle.net/10948/d1012659 , Phenotypic plasticity , Evolutionary genetics
- Description: Avian species are known to have the capacity to respond to environmental changes through physiological adjustments. The process whereby organisms adjust their phenotype without genetic change is termed phenotypic plasticity and it is mostly observed to be a phenotypic improvement to ecological challenges. Metabolic rate (MR), which is the rate of energy expenditure in a species, is a highly flexible physiological parameter which results in a great diversity of avian standardised metabolic rates. Like birds from high latitudes, Afrotropical bird species are expected to have the capacity to adjust their energy expenditure to match the availability of resources. Previous studies on the flexibility of physiological parameters in birds have focused on the magnitude of change of physiological adjustments and the cues inducing these changes. Comparative research has furthermore investigated metabolic rates across aridity, altitude, latitude and temperature gradients. Recently, a clear dichotomy has become evident with elevated metabolic rates observed in high latitude birds in winter and a down-regulation of metabolic rates observed in birds exposed to low latitude mild winters. In this study, the shape of the reaction norm, the magnitude, the reversibility, the direction and the rate of change of two physiological parameters, basal metabolic rate (BMR) and summit metabolic rate (Msum), were investigated in a coastal and an inland population of Southern Red Bishops (Euplectes orix) through seasonal acclimatisation and laboratory acclimation. Summer and winter basal metabolic rates as well as body mass, were highly flexible traits in free-ranging coastal and inland Red Bishops. Birds acclimatised to a mild coastal climate in winter exhibited reduced basal and summit metabolic rates, whereas birds originating from a more variable inland climate increased basal metabolic rate in winter, but did not show increases of Msum in winter. Red Bishops responded to short term thermal acclimation under laboratory conditions by gradually changing body mass. Acclimation periods of 21 days revealed a negative relationship between body mass and acclimation air temperature. Peak responses of basal metabolic rate to ambient temperature change were observed in both coastal and inland birds between two and eight days after the change in acclimation air temperature. The influences of seasonal acclimatisation on energy expenditure differed between coastal and inland birds, however, during laboratory acclimation individuals from the two populations showed no difference in response. Within the individuals of the coastal and inland Southern Red Bishops, phenotypic flexibility is observed in body mass, basal metabolic rate and summit metabolic rate as a response to environmental changes. This flexibility is thought to increase thermoregulatory capacities of the Southern Red Bishop in different habitats and climates.
- Full Text:
- Date Issued: 2012
Exploring plants as medicine: an in vitro approach
- Authors: Van de Venter, Maryna
- Subjects: Medicinal plants , Oncology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55562 , vital:52968
- Description: Introduction: Plants as medicine Archaeological evidence for the use of plants as medicine dates as far back as 60,000 years ago from the area now known as Iraq, and 8,000 years ago from China. The first written records are from the Sumerians from 5,000 BC and the Ancient Egyptians from 1,500 BC. Two well-known plants that were already used in that time are the opium poppy, and cannabis. The first pharmaceutical medicine was only developed in 1804 when the German Friedrich Sertürner isolated morphine from the opium poppy (Pan et al 2014).
- Full Text:
- Authors: Van de Venter, Maryna
- Subjects: Medicinal plants , Oncology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55562 , vital:52968
- Description: Introduction: Plants as medicine Archaeological evidence for the use of plants as medicine dates as far back as 60,000 years ago from the area now known as Iraq, and 8,000 years ago from China. The first written records are from the Sumerians from 5,000 BC and the Ancient Egyptians from 1,500 BC. Two well-known plants that were already used in that time are the opium poppy, and cannabis. The first pharmaceutical medicine was only developed in 1804 when the German Friedrich Sertürner isolated morphine from the opium poppy (Pan et al 2014).
- Full Text:
Alternative pine species/hybrids for the Cape timber growing regions of South Africa
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
- Authors: Van der Hoef, André
- Date: 2020
- Subjects: Species -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/47613 , vital:40258
- Description: Pinus radiata has been the preferred commercial sawtimber species for the Cape forestry region for many years. Since the introduction of Fusarium circinatum, and the susceptibility of P. radiata to this disease, the sustainable production of this pine species for the Cape has been negatively impacted due to poor survival in the nursery and in field plantings. For this reason, a number of additional pine species and hybrids have been established in the Cape region of South Africa since 2006 to identify taxa that would perform as well as or better than P. radiata. Three research trials were implemented on contrasting sites that contained eight common species/hybrids treatments that included P. elliottii, P. elliottii x P. caribaea, P. radiata, P. patula x P. greggii var. australis, P. patula x P. oocarpa, P. patula x P. tecunumanii (HE), P. patula x P. tecunumanii (LE) and P. tecunumanii (HE) x P. oocarpa were established at Witelsbos, Kruisfontein and Garcia across diverse soil types, drainage and climate conditions in the Cape. Survival, growth data and tree morphology (forking, foxtails, broken tops and stem form) were assessed at five years of age and individual tree volume was calculated. Five year results indicate that on the waterlogged site at Witelsbos P. elliottii and its hybrid with P. caribaea was best in terms of productivity, at the dry site of Garcia, P. taeda and P. elliottii demonstrated promise, and at Kruisfontein, the most fertile site, P. elliottii x P. caribaea, P. patula x P. tecunumanii (LE) and P. maximinoi were found to be promising alternatives to P. radiata. Wood properties were assessed at Kruisfontein at six-years of age. Basic density and Modulus of Elasticity (MOE) were found to be significantly different for the various species/hybrids. Pinus patula x P. tecunumanii (LE), P. patula x P. greggii (S), P. maximinoi and P. patula x P. tecunumanii (HE) were all significantly better than P. radiata, which would suggest that these taxa would have similar or superior wood strength over P. radiata, the preferred sawtimber species for the Cape region. Only P. tecunumanii (HE) x P. oocarpa had a higher basic density than P. radiata, but not significantly different. Species that had similar basic density were P. patula x P. greggii (S), P. taeda and P. tecunumanii (LE) x P. caribaea. Although P. elliottii x P. caribaea had the highest volume at Witelsbos and Kruisfontein, the timber qualities were the worst, suggesting that some breeding is needed to improve this hybrid to be an acceptable sawtimber species. From this study, several potential alternative species/hybrids have been identified that are tolerant to the F. circinatum pathogen and have acceptable growth and wood properties, compared to P. radiata.
- Full Text:
- Date Issued: 2020
An enterprise architecture for environmental information management and reporting
- Authors: Van der Hoogen, Anthea
- Date: 2013
- Subjects: Business enterprises -- Information technology -- Management , Sustainable development reporting , Environmental reporting
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10499 , http://hdl.handle.net/10948/d1021040
- Description: Organisations globally are communicating their environmental sustainability impact to stakeholders by means of the widely used sustainability report. A key benefit of environmental sustainability reporting is that organisations can gain a positive reputation when these reports are presented to stakeholders. Organisations in South Africa are faced with many challenges regarding managing sustainability information and producing an environmental sustainability report. Two of the primary challenges are the many diverse standards for sustainability reporting and data quality issues. Information Technology (IT) can be used to support and improve the process of sustainability reporting but it is important to align the environmental sustainability strategies with the strategies of business and also with the IT strategy to avoid silos of information and reporting. Enterprise Architecture (EA) can be used to solve alignment problems since it supports business-IT alignment. EA is defined by the International Standards Organisation (ISO) as “The fundamental concepts or properties of a system in its environment embodied in its elements, relationships, and in the principles of its design and evolution”. It can be argued, therefore, that EA can be used to support environmental sustainability information management and the reporting process by means of its support of improved business-IT alignment and ultimately integrated systems. The main objective of this study is to investigate how EA can be used to support environmental information management (EIM) and reporting. A survey study of thirty one prominent South African organisations was undertaken in order to investigate the status of their EA adoption and environmental reporting and EIM processes. An EA for EIM Toolkit and a set of guidelines are proposed which can provide support for EIM through the use of EA. These guidelines were proposed based on best-practice for each of the three process levels of an organisation, namely, the strategic level, the operational level and the technological level. The toolkit and guidelines were derived from theory and the results of the industry survey were then validated by an in-depth analysis of a case study consisting of multiple cases with key employees of seven South African organisations which have proved to be successful at EA and EIM and reporting. The results of the case study show that the EA for EIM Toolkit and related guidelines can assist organisations to align their environmental sustainability strategies with their organisational and IT strategies.
- Full Text:
- Date Issued: 2013
- Authors: Van der Hoogen, Anthea
- Date: 2013
- Subjects: Business enterprises -- Information technology -- Management , Sustainable development reporting , Environmental reporting
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10499 , http://hdl.handle.net/10948/d1021040
- Description: Organisations globally are communicating their environmental sustainability impact to stakeholders by means of the widely used sustainability report. A key benefit of environmental sustainability reporting is that organisations can gain a positive reputation when these reports are presented to stakeholders. Organisations in South Africa are faced with many challenges regarding managing sustainability information and producing an environmental sustainability report. Two of the primary challenges are the many diverse standards for sustainability reporting and data quality issues. Information Technology (IT) can be used to support and improve the process of sustainability reporting but it is important to align the environmental sustainability strategies with the strategies of business and also with the IT strategy to avoid silos of information and reporting. Enterprise Architecture (EA) can be used to solve alignment problems since it supports business-IT alignment. EA is defined by the International Standards Organisation (ISO) as “The fundamental concepts or properties of a system in its environment embodied in its elements, relationships, and in the principles of its design and evolution”. It can be argued, therefore, that EA can be used to support environmental sustainability information management and the reporting process by means of its support of improved business-IT alignment and ultimately integrated systems. The main objective of this study is to investigate how EA can be used to support environmental information management (EIM) and reporting. A survey study of thirty one prominent South African organisations was undertaken in order to investigate the status of their EA adoption and environmental reporting and EIM processes. An EA for EIM Toolkit and a set of guidelines are proposed which can provide support for EIM through the use of EA. These guidelines were proposed based on best-practice for each of the three process levels of an organisation, namely, the strategic level, the operational level and the technological level. The toolkit and guidelines were derived from theory and the results of the industry survey were then validated by an in-depth analysis of a case study consisting of multiple cases with key employees of seven South African organisations which have proved to be successful at EA and EIM and reporting. The results of the case study show that the EA for EIM Toolkit and related guidelines can assist organisations to align their environmental sustainability strategies with their organisational and IT strategies.
- Full Text:
- Date Issued: 2013
A value alignment smart city stakeholder model
- Van der Hoogen, Anthea Vivian
- Authors: Van der Hoogen, Anthea Vivian
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54129 , vital:46309
- Description: The concept of a Smart City has evolved over the last three decades and has attracted the increasing interest of the scientific research community. Unfortunately, many Smart City projects and initiatives do not provide the value expected by all the stakeholders. Many of the reasons for this relate to a lack of data management, data integration, data access and stakeholder participation. People are an integral part of any city’s ecosystem, and the Smart City concept was introduced to address the challenges of an ever-growing global population leading to the risk of depletion of economic, environmental and social resources. The problem addressed in this study is based on the challenges preventing the creation of the value of smart cities or stakeholders. Limited research has been published on the status of Smart City initiatives or on the impact of various success factors on the potential value creation for stakeholders including citizens. Studies on initiatives in developing countries, such as South Africa are even less. Whilst some challenges and constraints related to smart cities in Africa have been reported, there are no studies reporting on initiatives across the data value chain that consider all types of stakeholders, nor the impact of these initiatives. This study addressed this gap in research and designed a theoretical Value Alignment Smart City Stakeholder (VASCS) Model based on a Systematic Literature Review and a review of related theories. The model has important components that should form part of any Smart City project or Smart City initiative. These five main components are: 1) nine Smart City dimensions with related success factors; 2) four stakeholder roles (enablers, providers, utilisers and users); 3) the data value chain; and 4) the five phases of stakeholder benefits/value realisation that can be linked to; 5) stakeholder value alignment. This study applied the VASCS Model to Smart City initiatives in two case studies in the Eastern Cape Province of South Africa, which were the Nelson Mandela Bay and Buffalo City to investigate and understand the status of such initiatives and the alignment of value thereof. The stakeholder interviews were conducted in two rounds with various stakeholders of Smart City initiatives, referred to as cases in the two case studies. An expert review of the VASCS Model was conducted with eight experts in the field of Information Systems and Smart Cities. The findings of this review served to confirm the components of the model, with only minor improvements recommended. It was confirmed that all of the components need to be considered in planning Smart City projects. The first round consisted of six interviews with enablers and providers and the second round consisted of 22 interviews with users, utilisers and citizens. The interviews investigated the value and impact experienced by stakeholders of these initiatives, with a particular focus on the users, utilisers and citizens of the cases. The interview data was transcribed and qualitatively analysed by using Atlas.tiand Excel. The data was analysed according to the Technological, Organisational and Environmental theory constructs and other identified themes. The interview analysis findings revealed several drivers for these initiatives, which were primarily cost reduction, integration and quality assurance. The results also highlighted access to resources, such as technical skills as a challenge. Another challenge identified was connectivity related to access to data and the digital and physical divide that can impact decision making. The main benefits of Smart City initiatives highlighted were the provision of infrastructure, education and training and digitalisation. The theoretical contribution of this study is the VASCS Model, which can assist other researchers and practitioners with knowledge of the factors, drivers, challenges and value obtained in Smart City initiatives. The model has two supplementary components: A Stakeholder Classification Model and a Smart City Success Factor Evaluation Template. The practical contribution of this study is the potential use of the VASCS Model by practitioners, city management, researchers and other stakeholders, who can use the model, with the related model and template for planning and evaluating Smart City initiatives. The model can be used to classify the digital activities according to a Smart City’s success factors while evaluating the value created by these activities. The impact of these initiatives can then be assessed through value realisation and alignment for stakeholders. The scientific contribution is the adoption of the model to the cases in the Eastern Cape. To reveal in depth, rich, interview findings that provide important lessons learnt relating to the value created for the stakeholders and the addition of these findings to the body of knowledge. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Van der Hoogen, Anthea Vivian
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54129 , vital:46309
- Description: The concept of a Smart City has evolved over the last three decades and has attracted the increasing interest of the scientific research community. Unfortunately, many Smart City projects and initiatives do not provide the value expected by all the stakeholders. Many of the reasons for this relate to a lack of data management, data integration, data access and stakeholder participation. People are an integral part of any city’s ecosystem, and the Smart City concept was introduced to address the challenges of an ever-growing global population leading to the risk of depletion of economic, environmental and social resources. The problem addressed in this study is based on the challenges preventing the creation of the value of smart cities or stakeholders. Limited research has been published on the status of Smart City initiatives or on the impact of various success factors on the potential value creation for stakeholders including citizens. Studies on initiatives in developing countries, such as South Africa are even less. Whilst some challenges and constraints related to smart cities in Africa have been reported, there are no studies reporting on initiatives across the data value chain that consider all types of stakeholders, nor the impact of these initiatives. This study addressed this gap in research and designed a theoretical Value Alignment Smart City Stakeholder (VASCS) Model based on a Systematic Literature Review and a review of related theories. The model has important components that should form part of any Smart City project or Smart City initiative. These five main components are: 1) nine Smart City dimensions with related success factors; 2) four stakeholder roles (enablers, providers, utilisers and users); 3) the data value chain; and 4) the five phases of stakeholder benefits/value realisation that can be linked to; 5) stakeholder value alignment. This study applied the VASCS Model to Smart City initiatives in two case studies in the Eastern Cape Province of South Africa, which were the Nelson Mandela Bay and Buffalo City to investigate and understand the status of such initiatives and the alignment of value thereof. The stakeholder interviews were conducted in two rounds with various stakeholders of Smart City initiatives, referred to as cases in the two case studies. An expert review of the VASCS Model was conducted with eight experts in the field of Information Systems and Smart Cities. The findings of this review served to confirm the components of the model, with only minor improvements recommended. It was confirmed that all of the components need to be considered in planning Smart City projects. The first round consisted of six interviews with enablers and providers and the second round consisted of 22 interviews with users, utilisers and citizens. The interviews investigated the value and impact experienced by stakeholders of these initiatives, with a particular focus on the users, utilisers and citizens of the cases. The interview data was transcribed and qualitatively analysed by using Atlas.tiand Excel. The data was analysed according to the Technological, Organisational and Environmental theory constructs and other identified themes. The interview analysis findings revealed several drivers for these initiatives, which were primarily cost reduction, integration and quality assurance. The results also highlighted access to resources, such as technical skills as a challenge. Another challenge identified was connectivity related to access to data and the digital and physical divide that can impact decision making. The main benefits of Smart City initiatives highlighted were the provision of infrastructure, education and training and digitalisation. The theoretical contribution of this study is the VASCS Model, which can assist other researchers and practitioners with knowledge of the factors, drivers, challenges and value obtained in Smart City initiatives. The model has two supplementary components: A Stakeholder Classification Model and a Smart City Success Factor Evaluation Template. The practical contribution of this study is the potential use of the VASCS Model by practitioners, city management, researchers and other stakeholders, who can use the model, with the related model and template for planning and evaluating Smart City initiatives. The model can be used to classify the digital activities according to a Smart City’s success factors while evaluating the value created by these activities. The impact of these initiatives can then be assessed through value realisation and alignment for stakeholders. The scientific contribution is the adoption of the model to the cases in the Eastern Cape. To reveal in depth, rich, interview findings that provide important lessons learnt relating to the value created for the stakeholders and the addition of these findings to the body of knowledge. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
Vergelyking van Tilapia (Oreochromis Mossambicus)en Koi (Ciprinus Carpio) in verskillende produksiestelsels
- Authors: Van der Merwe, Johan Philip
- Date: 2002
- Subjects: Fish culture
- Language: Afrikaans
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10967 , http://hdl.handle.net/10948/114 , Fish culture
- Description: Die studie was uitgevoer om te bepaal of warmwaterspesies soos tilapia (Oreochromis mossambicus) en koi (Ciprinus carpio) gebruik kan word as deel van 'n roterende akwakultuur produksie sisteem in die Wes-Kaap. Drie produksiestelsels (drywende hokstelsel; gronddamme en hersirkuleringseenheid) was ge-evalueer vir beide tilapia en koi produksie. Twee verskillende diëte (tilapia, 32% proteien, 'n lae waarde dieet en koi, 32% proteien, 'n hoë waarde dieet) was ook ge-evalueer vir die effek op koi produksie. Tilapia- en koi vingerlinge was teen dieselfde lading (250/hok) in elke produksiestelsel geplaas. By die begin van die proewe het die tilapia vingerlinge 'n gemiddelde gewig van 60-80g en die koi vingerlinge 'n gemiddelde lengte van 30-40 mm gehad. Die visse is twee keer per dag gevoer en data is op 'n maandelikse basis oor 'n periode van 84 dae versamel. Produksie data vir die tilapia versamel was: 1) die gemiddelde daaglikse toename, 2) die totale voer verbruik, 3) water temperature en 4) mortaliteite is daagliks aangeteken. Die produksie data versamel vir koi wat twee verskillende diëte ontvang het in drie verskillende produksiestelsels was: 1) die gemiddelde daaglikse toename in lengte, 2) die totale voer verbruik, 3) water temperature en 4) mortaliteite is daagliks aangeteken. Die resultate van die tilapia studie het aangedui dat tilapia in die hersirkuleeringseenheid het deurgaans 'n swaarder gewig gehad (p<0.05) as die van die drywende hokstelsel en gronddam stelsel. Terwyl die gronddam stelsel weer 'n swaarder gewig gehad het as die drywende hokstelsel behalwe vir April (171,67 / 39,49 vs 159,33 / 22,15). Nieteenstaande die verskil in begin gewig en eind gewig in die guns van die tilapia in die hersirkuleringseenheid teenoor die ander twee stelsels het die GDT tussen die drywende hokstelsel en die hersirkuleringseenheid nie noemenswaardig verskil nie (1,20 / 0,15 vs 1,40 / 0,24). Die tilapia in die gronddamme het egter swakker (p<0,05) gewigstoename van 0,72 / 0,32 g gehad teenoor die tilapia in die drywende hokstesel 1,40 / 0,24 g en 1,20 / 0,15 g van die tilapia in die hersirkuleringseenheid. Tilapia in die gronddamme het dus ongeveer 45% swakker gemiddelde gewigstoename getoon as die van die drywende hokstelsel en hersirkuleringseenheid. Die produksiestelsel het 'n hoogs betekenisvolle invloed (p<0,001) op die groeipotensiaal van tilapia gehad in hierdie studie. Die gemiddelde totale hoeveelheid voer verbruik was nie statisties verskillend tussen die drywende hokstelsel en gronddam stelsel nie (29,83 / 2,66 vs 30,83 / 5,42), maar wel (p<0,05) vir die hersirkuleringseenheid (29,94 / 0,88). Die VOV het nie verskil tussen die drywende hokstelsel en hersirkuleringeenheid, maar daar was wel 'n verskil (p<0,05) tussen hierdie twee stelsels en die van die gronddamme. Die totale gemiddelde mortaliteite van tilapia was die hoogste (p<0,05) vir die drywende hokstelsel in vergelyking met die gronddamme en hersirkuleringseenheid. Die drywende hokstelsel het 14,67 / 14,61% meer mortaliteite gehad as die gronddamme en hersirkuleringeenheid. Die koi studie se resultate dui aan dat die tipe stelsel het 'n hoogs betekenisvolle (p<0,001) invloed gehad op die gemiddelde toename in lengte van die koi vis vir die somerseisoen. Die tipe dieet het geen invloed op die toename in lengte van koi vis vir al drie die stelsels ge-evalueer, maar die interaksie tussen dieet en die tipe stelsel was wel betekenisvol (p<0.05). Die interaksie tussen die tipe dieet en die tipe stelsel was die hoogste vir die groddamme 136,41 / 32,46 mm en 136,25 / 33,08 mm vir beide tilapia en die koi diëte gevoer. Die gemiddelde totale voer wat deur koi visse in die drie stelsels verbruik is, het wel statisties van mekaar verskil (p<0,05). Koi visse in die gronddam stelsel het meer voer verbruik vir beide die tilapia- en koi dieet (31,03 / 2,01 en 29,67 / 3,57) in vergelyking met die (26,35 / 2,44 ; 26,98 / 0,49 en 5,50 # 0,52 en 6,13 / 0,22) vir die drywende hokke en hersirkuleringseenheid stelsels onderskiedelik. Die % mortaliteite was betekenisvol (p<0,05) vir die verskillende stelsels. Koi visse in die hersirkuleringseenheid het die hoogste mortaliteite gehad vir beide die tilapia en die koi diëte (65,50 / 18,07% en 79,50 / 38,27%) terwyl koi visse in die gronddamme die laagste mortaliteite ondervind het (1,20 / 1,20% en 2,33 / 4,89%) vir beide die tilapia en koi diëte. Die koi in die gronddam stelsel het die beste resultate gelewer en dit is ook moontlik om koi 'n lae waarde dieet te voer sonder nadelige effekte op produksie.
- Full Text:
- Date Issued: 2002
- Authors: Van der Merwe, Johan Philip
- Date: 2002
- Subjects: Fish culture
- Language: Afrikaans
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10967 , http://hdl.handle.net/10948/114 , Fish culture
- Description: Die studie was uitgevoer om te bepaal of warmwaterspesies soos tilapia (Oreochromis mossambicus) en koi (Ciprinus carpio) gebruik kan word as deel van 'n roterende akwakultuur produksie sisteem in die Wes-Kaap. Drie produksiestelsels (drywende hokstelsel; gronddamme en hersirkuleringseenheid) was ge-evalueer vir beide tilapia en koi produksie. Twee verskillende diëte (tilapia, 32% proteien, 'n lae waarde dieet en koi, 32% proteien, 'n hoë waarde dieet) was ook ge-evalueer vir die effek op koi produksie. Tilapia- en koi vingerlinge was teen dieselfde lading (250/hok) in elke produksiestelsel geplaas. By die begin van die proewe het die tilapia vingerlinge 'n gemiddelde gewig van 60-80g en die koi vingerlinge 'n gemiddelde lengte van 30-40 mm gehad. Die visse is twee keer per dag gevoer en data is op 'n maandelikse basis oor 'n periode van 84 dae versamel. Produksie data vir die tilapia versamel was: 1) die gemiddelde daaglikse toename, 2) die totale voer verbruik, 3) water temperature en 4) mortaliteite is daagliks aangeteken. Die produksie data versamel vir koi wat twee verskillende diëte ontvang het in drie verskillende produksiestelsels was: 1) die gemiddelde daaglikse toename in lengte, 2) die totale voer verbruik, 3) water temperature en 4) mortaliteite is daagliks aangeteken. Die resultate van die tilapia studie het aangedui dat tilapia in die hersirkuleeringseenheid het deurgaans 'n swaarder gewig gehad (p<0.05) as die van die drywende hokstelsel en gronddam stelsel. Terwyl die gronddam stelsel weer 'n swaarder gewig gehad het as die drywende hokstelsel behalwe vir April (171,67 / 39,49 vs 159,33 / 22,15). Nieteenstaande die verskil in begin gewig en eind gewig in die guns van die tilapia in die hersirkuleringseenheid teenoor die ander twee stelsels het die GDT tussen die drywende hokstelsel en die hersirkuleringseenheid nie noemenswaardig verskil nie (1,20 / 0,15 vs 1,40 / 0,24). Die tilapia in die gronddamme het egter swakker (p<0,05) gewigstoename van 0,72 / 0,32 g gehad teenoor die tilapia in die drywende hokstesel 1,40 / 0,24 g en 1,20 / 0,15 g van die tilapia in die hersirkuleringseenheid. Tilapia in die gronddamme het dus ongeveer 45% swakker gemiddelde gewigstoename getoon as die van die drywende hokstelsel en hersirkuleringseenheid. Die produksiestelsel het 'n hoogs betekenisvolle invloed (p<0,001) op die groeipotensiaal van tilapia gehad in hierdie studie. Die gemiddelde totale hoeveelheid voer verbruik was nie statisties verskillend tussen die drywende hokstelsel en gronddam stelsel nie (29,83 / 2,66 vs 30,83 / 5,42), maar wel (p<0,05) vir die hersirkuleringseenheid (29,94 / 0,88). Die VOV het nie verskil tussen die drywende hokstelsel en hersirkuleringeenheid, maar daar was wel 'n verskil (p<0,05) tussen hierdie twee stelsels en die van die gronddamme. Die totale gemiddelde mortaliteite van tilapia was die hoogste (p<0,05) vir die drywende hokstelsel in vergelyking met die gronddamme en hersirkuleringseenheid. Die drywende hokstelsel het 14,67 / 14,61% meer mortaliteite gehad as die gronddamme en hersirkuleringeenheid. Die koi studie se resultate dui aan dat die tipe stelsel het 'n hoogs betekenisvolle (p<0,001) invloed gehad op die gemiddelde toename in lengte van die koi vis vir die somerseisoen. Die tipe dieet het geen invloed op die toename in lengte van koi vis vir al drie die stelsels ge-evalueer, maar die interaksie tussen dieet en die tipe stelsel was wel betekenisvol (p<0.05). Die interaksie tussen die tipe dieet en die tipe stelsel was die hoogste vir die groddamme 136,41 / 32,46 mm en 136,25 / 33,08 mm vir beide tilapia en die koi diëte gevoer. Die gemiddelde totale voer wat deur koi visse in die drie stelsels verbruik is, het wel statisties van mekaar verskil (p<0,05). Koi visse in die gronddam stelsel het meer voer verbruik vir beide die tilapia- en koi dieet (31,03 / 2,01 en 29,67 / 3,57) in vergelyking met die (26,35 / 2,44 ; 26,98 / 0,49 en 5,50 # 0,52 en 6,13 / 0,22) vir die drywende hokke en hersirkuleringseenheid stelsels onderskiedelik. Die % mortaliteite was betekenisvol (p<0,05) vir die verskillende stelsels. Koi visse in die hersirkuleringseenheid het die hoogste mortaliteite gehad vir beide die tilapia en die koi diëte (65,50 / 18,07% en 79,50 / 38,27%) terwyl koi visse in die gronddamme die laagste mortaliteite ondervind het (1,20 / 1,20% en 2,33 / 4,89%) vir beide die tilapia en koi diëte. Die koi in die gronddam stelsel het die beste resultate gelewer en dit is ook moontlik om koi 'n lae waarde dieet te voer sonder nadelige effekte op produksie.
- Full Text:
- Date Issued: 2002