Perceptions and practices of small-scale piggery farmers towards animal welfare in the Nelson Mandela Bay Metropole
- Authors: Maqhajana, Mzwanele
- Date: 2016
- Subjects: Animal welfare -- South Africa -- Nelson Mandela Bay Municipality , Farms, Small -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8079 , vital:24719
- Description: There has been an increasing concern about animal welfare in small-scale farming as the farmers' agricultural practices shift towards intensive agriculture. It has become important to comprehend how small-scale farmers perceive and practice animal welfare relative to production and market integration. To solve the research problem, the research emphasis was on assessing the following practices; procedures adopted by the small-scale farmers, welfare levels verses industry equirements for market integration; determinants affecting small-scale perceptions and attitudes towards animal welfare and how has animal welfare affected farm development and production. The research focus for this study was to investigate the linkage between perceptions and this process. In order to achieve a more in-depth understanding of the study while also ensuring its validity and correctness a triangulation research method was applied, which consisted of a quantitative and qualitative method approach. The focus groups and structured research interview questions were used as the main data collections instruments. The study consisted of sixty-two piggery small-scale farmers from three areas of the Nelson Mandela Bay metropole. The study found that there was a disparity between the perceptions and practice of small-scale farmers. Farmers perceived their practices as acceptable. However, on most of the farms the pigs were farmed in an unhygienic environment, had limited handling facilities, the farmers had unconventional methods to handle the pigs; there was poor support from technical services, many of the farmers never administered animal welfare evaluations and applied questionable feeding practices. The study also indicated that less than 15% had suitable facilities to accommodate suitable reproduction and piglet care. The researcher recommended the following interventions to improve animal welfare approaches with small-scale farmers in the Nelson Mandela Bay metropole: Training and information campaigns to improve small-scale piggery farmers' perception and knowledge of animal welfare, as well as market standards and requirements. Strengthening the relationship between the small-scale piggery farmers and animal welfare stakeholders. Including active engagement between small scale piggery farmers and the Department of Rural Development, Agrarian Reform and Urban Agriculture Unit of the Nelson Mandela Bay Municipality. Encouraging farmers to strive for stronger markets to facilitate better income and care of animals.
- Full Text:
- Date Issued: 2016
- Authors: Maqhajana, Mzwanele
- Date: 2016
- Subjects: Animal welfare -- South Africa -- Nelson Mandela Bay Municipality , Farms, Small -- South Africa -- Nelson Mandela Bay Municipality
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8079 , vital:24719
- Description: There has been an increasing concern about animal welfare in small-scale farming as the farmers' agricultural practices shift towards intensive agriculture. It has become important to comprehend how small-scale farmers perceive and practice animal welfare relative to production and market integration. To solve the research problem, the research emphasis was on assessing the following practices; procedures adopted by the small-scale farmers, welfare levels verses industry equirements for market integration; determinants affecting small-scale perceptions and attitudes towards animal welfare and how has animal welfare affected farm development and production. The research focus for this study was to investigate the linkage between perceptions and this process. In order to achieve a more in-depth understanding of the study while also ensuring its validity and correctness a triangulation research method was applied, which consisted of a quantitative and qualitative method approach. The focus groups and structured research interview questions were used as the main data collections instruments. The study consisted of sixty-two piggery small-scale farmers from three areas of the Nelson Mandela Bay metropole. The study found that there was a disparity between the perceptions and practice of small-scale farmers. Farmers perceived their practices as acceptable. However, on most of the farms the pigs were farmed in an unhygienic environment, had limited handling facilities, the farmers had unconventional methods to handle the pigs; there was poor support from technical services, many of the farmers never administered animal welfare evaluations and applied questionable feeding practices. The study also indicated that less than 15% had suitable facilities to accommodate suitable reproduction and piglet care. The researcher recommended the following interventions to improve animal welfare approaches with small-scale farmers in the Nelson Mandela Bay metropole: Training and information campaigns to improve small-scale piggery farmers' perception and knowledge of animal welfare, as well as market standards and requirements. Strengthening the relationship between the small-scale piggery farmers and animal welfare stakeholders. Including active engagement between small scale piggery farmers and the Department of Rural Development, Agrarian Reform and Urban Agriculture Unit of the Nelson Mandela Bay Municipality. Encouraging farmers to strive for stronger markets to facilitate better income and care of animals.
- Full Text:
- Date Issued: 2016
An investigation of alternative separation strategies for common chemical mixtures by means of host-guest chemistry protocols with host compounds N,N′- bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine and N,N’-bis(5-phenyl-10,11- dihydro-5-dibenzo[a,d]cycloheptenyl)ethylenediamine
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
The application of GIS and remote sensing to assess the effect of periodic flooding on communities along the Juskeiriver: A case study of Alexandria Township, Johannesburg, South Africa
- Authors: Mawasha, Tshepo Sylvester
- Date: 2016
- Subjects: Remote sensing Geographic information systems -- South Africa , Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45613 , vital:38918
- Description: Floods are water induced disasters that led to temporary induction of dry and cause serious damages in the affected location such as loss of valuable assets, lives and destruction of infrastructure. Flooding had become common in Alexandra Township during rainfall season and the recorded impact of periodic flooding on communities is increasing at an alarming rate. This study seeks to identify populations vulnerable to flooding and to map-out areas at high risk of flood disasters, using GIS and RS as a tool. For GIS application different types of maps were produced, namely, flood vulnerability, hazards, risk and risk index map highlighting areas at risk of being affected by flooding. Flood risk index maps identify three categories of risk zones; low and high risk zone. The household units within each of the risk zones was calculated and the total was estimated to be 762 for low-risk and 32 486 for high risk zone. The SRTM Digital Elevation Model (DEM) and multi-temporal Satellite Probatoire d’Observation de la Terra (SPOT) satellite images for 1997, 2006 and 2013 of the area was used for land-use and land-cover (LULC) change analyses using maximum-likelihood post-classification comparison. Results reveal that tremendous urban development had taken place in the study area along the Jukskei River area for the past sixteen years. It was observed that there was a sharp decrease in vegetation from 237ha (1997) to 134ha (2006) to 68ha (2013). This may had a negative impact on the environment around this area by decreasing surface runoff. The trend however, shows that bare surface and vegetation land-cover class has no potential to recover. Questionnaires aimed at all the residents in the study area were used to assess the effect of periodic flooding on communities. Community leader and City of Johannesburg Disaster Management Unit (CoJDMU) interviews were also conducted to get more insight about floods management in the study area. Finally, strategies for alleviating flood risk in the study area were discussed and some recommendations were made to help the government and municipal authorities to improve and development sustainable flood mitigation measures.
- Full Text:
- Date Issued: 2016
- Authors: Mawasha, Tshepo Sylvester
- Date: 2016
- Subjects: Remote sensing Geographic information systems -- South Africa , Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/45613 , vital:38918
- Description: Floods are water induced disasters that led to temporary induction of dry and cause serious damages in the affected location such as loss of valuable assets, lives and destruction of infrastructure. Flooding had become common in Alexandra Township during rainfall season and the recorded impact of periodic flooding on communities is increasing at an alarming rate. This study seeks to identify populations vulnerable to flooding and to map-out areas at high risk of flood disasters, using GIS and RS as a tool. For GIS application different types of maps were produced, namely, flood vulnerability, hazards, risk and risk index map highlighting areas at risk of being affected by flooding. Flood risk index maps identify three categories of risk zones; low and high risk zone. The household units within each of the risk zones was calculated and the total was estimated to be 762 for low-risk and 32 486 for high risk zone. The SRTM Digital Elevation Model (DEM) and multi-temporal Satellite Probatoire d’Observation de la Terra (SPOT) satellite images for 1997, 2006 and 2013 of the area was used for land-use and land-cover (LULC) change analyses using maximum-likelihood post-classification comparison. Results reveal that tremendous urban development had taken place in the study area along the Jukskei River area for the past sixteen years. It was observed that there was a sharp decrease in vegetation from 237ha (1997) to 134ha (2006) to 68ha (2013). This may had a negative impact on the environment around this area by decreasing surface runoff. The trend however, shows that bare surface and vegetation land-cover class has no potential to recover. Questionnaires aimed at all the residents in the study area were used to assess the effect of periodic flooding on communities. Community leader and City of Johannesburg Disaster Management Unit (CoJDMU) interviews were also conducted to get more insight about floods management in the study area. Finally, strategies for alleviating flood risk in the study area were discussed and some recommendations were made to help the government and municipal authorities to improve and development sustainable flood mitigation measures.
- Full Text:
- Date Issued: 2016
Foraging ecology of gentoo penguins pygoscelis papua at the Falkland Islands
- Authors: Handley, Jonathan Murray
- Date: 2017
- Subjects: Gentoo penguin -- Food -- Falkland Islands Gentoo penguin -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/14113 , vital:27431
- Description: Marine top predators often occupy broad geographical ranges that encompass varied habitats. Therefore, a pre-requisite towards conserving these animals is to determine the components of their realized niche, and investigate whether a species is a specialist or a generalist. For generalist species, it is also necessary to understand if local specialisation occurs. Uncovering these components can allow us to build models of a species realized niche that may then be used to infer habitat use in unsampled locations. However, fully understanding the components of a marine top predators realized niche is challenging owing to the limited opportunity for in situ observations. Overcoming these limitations is a key step in marine top predator research. It will enhance our understanding of trophic coupling in marine systems, and aid in the development of tools to better study these predators in their dynamic environment. Seabirds, penguins (Spheniscids) in particular, are a group of animals for which investigating their realized niche is of vital importance. This is because numerous species face growing uncertainty in the Anthropocene, and in a time of rapid environmental change there is furthermore a need to better understand the potential use of these birds as indicators of ecosystem health. The aim of this thesis, therefore, is to investigate the foraging ecology of gentoo penguins (Pygoscelis papua) at the Falkland Islands. At the Falkland Islands, limited historical information exists regarding this species foraging ecology, with most information coming from a single location at the Falklands. As the Falkland Islands have the world’s largest population of gentoo penguins, elucidating factors influencing this population will have global relevance. Furthermore, historical information indicated potential competition with fisheries, and with prospecting for hydrocarbons and an inshore fishery, there is a need to understand the distribution of these birds across the islands. Penguins are also well suited to carry biologging devices allowing for in situ observations of inter and intraspecific interactions, as well as habitat specific interactions. In this study, I sampled birds over three breeding seasons, from four breeding colonies - chosen for their varied surrounding at sea habitat - across the Falkland Islands. I investigated the diet with stomach content and stable isotope analysis, the at-sea distribution with GPS and time depth recorders, and how these birds behaved at sea using custom made animal-borne camera loggers. Furthermore, I developed a method to recognise prey encounter events from back mounted accelerometers, using a supervised machine learning approach. As part of the first species specific description of diet at this scale for the Falklands, I revealed six key prey items for the birds: rock cod (Patagonotothen spp.), lobster krill (Munida spp.), Falkland herring (Sprattus fuegensis), Patagonian squid (Doryteuthis gahi), juvenile fish (likely all nototheniids), and southern blue whiting (Micromesistius australis). The use of animal-borne camera loggers verified that not only do gentoo penguins consume a diverse array of prey items, but they adopted various methods to capture and pursue prey, with evidence of birds following optimal foraging theory. Prey composition varied significantly between study sites with the at-sea distribution and habitat use of penguins reflecting that of local prey. Birds from colonies close to gently sloping, shallow waters, foraged primarily in a benthic manner and had larger niche widths. However, those at a colony surrounded by steeply sloping, deeper waters, typically foraged in a pelagic manner. Contrasting diet patterns were also prevalent from stable isotope data, and the niche widths of birds relating to both stomach content and stable isotope data were larger at colonies where benthic foraging was prevalent. Therefore, it was clear that surrounding bathymetry played a key role in shaping this species’ foraging ecology, and that at the population level at the Falkland Islands birds are generalists. However, at individual colonies some specialisation occurs to take advantage of locally available prey. I developed habitat distribution models - via boosted regression trees – which transferred well in time but poorly across space. Reasons for poor model transfer might relate to the generalist foraging nature of these birds and the reduced availability of environmental predictors owing to the limited range of these birds. I furthermore developed a method to identify prey encounter events that can also, to a degree, distinguish between prey items. This method will be a promising approach to refine habitat distribution models in future. These habitat distribution models could potentially contribute to marine spatial planning at the Falkland Islands. Footage from animal-borne camera loggers clearly showed that prey behaviour can significantly influence trophic coupling in marine systems and should be accounted for in studies using marine top predators as samplers of mid to lower trophic level species. Ultimately, flexibility in foraging strategies and inter-colony variation will play a critical role when assessing factors such as interspecific competition or overlap with anthropogenic activities.
- Full Text:
- Date Issued: 2017
- Authors: Handley, Jonathan Murray
- Date: 2017
- Subjects: Gentoo penguin -- Food -- Falkland Islands Gentoo penguin -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/14113 , vital:27431
- Description: Marine top predators often occupy broad geographical ranges that encompass varied habitats. Therefore, a pre-requisite towards conserving these animals is to determine the components of their realized niche, and investigate whether a species is a specialist or a generalist. For generalist species, it is also necessary to understand if local specialisation occurs. Uncovering these components can allow us to build models of a species realized niche that may then be used to infer habitat use in unsampled locations. However, fully understanding the components of a marine top predators realized niche is challenging owing to the limited opportunity for in situ observations. Overcoming these limitations is a key step in marine top predator research. It will enhance our understanding of trophic coupling in marine systems, and aid in the development of tools to better study these predators in their dynamic environment. Seabirds, penguins (Spheniscids) in particular, are a group of animals for which investigating their realized niche is of vital importance. This is because numerous species face growing uncertainty in the Anthropocene, and in a time of rapid environmental change there is furthermore a need to better understand the potential use of these birds as indicators of ecosystem health. The aim of this thesis, therefore, is to investigate the foraging ecology of gentoo penguins (Pygoscelis papua) at the Falkland Islands. At the Falkland Islands, limited historical information exists regarding this species foraging ecology, with most information coming from a single location at the Falklands. As the Falkland Islands have the world’s largest population of gentoo penguins, elucidating factors influencing this population will have global relevance. Furthermore, historical information indicated potential competition with fisheries, and with prospecting for hydrocarbons and an inshore fishery, there is a need to understand the distribution of these birds across the islands. Penguins are also well suited to carry biologging devices allowing for in situ observations of inter and intraspecific interactions, as well as habitat specific interactions. In this study, I sampled birds over three breeding seasons, from four breeding colonies - chosen for their varied surrounding at sea habitat - across the Falkland Islands. I investigated the diet with stomach content and stable isotope analysis, the at-sea distribution with GPS and time depth recorders, and how these birds behaved at sea using custom made animal-borne camera loggers. Furthermore, I developed a method to recognise prey encounter events from back mounted accelerometers, using a supervised machine learning approach. As part of the first species specific description of diet at this scale for the Falklands, I revealed six key prey items for the birds: rock cod (Patagonotothen spp.), lobster krill (Munida spp.), Falkland herring (Sprattus fuegensis), Patagonian squid (Doryteuthis gahi), juvenile fish (likely all nototheniids), and southern blue whiting (Micromesistius australis). The use of animal-borne camera loggers verified that not only do gentoo penguins consume a diverse array of prey items, but they adopted various methods to capture and pursue prey, with evidence of birds following optimal foraging theory. Prey composition varied significantly between study sites with the at-sea distribution and habitat use of penguins reflecting that of local prey. Birds from colonies close to gently sloping, shallow waters, foraged primarily in a benthic manner and had larger niche widths. However, those at a colony surrounded by steeply sloping, deeper waters, typically foraged in a pelagic manner. Contrasting diet patterns were also prevalent from stable isotope data, and the niche widths of birds relating to both stomach content and stable isotope data were larger at colonies where benthic foraging was prevalent. Therefore, it was clear that surrounding bathymetry played a key role in shaping this species’ foraging ecology, and that at the population level at the Falkland Islands birds are generalists. However, at individual colonies some specialisation occurs to take advantage of locally available prey. I developed habitat distribution models - via boosted regression trees – which transferred well in time but poorly across space. Reasons for poor model transfer might relate to the generalist foraging nature of these birds and the reduced availability of environmental predictors owing to the limited range of these birds. I furthermore developed a method to identify prey encounter events that can also, to a degree, distinguish between prey items. This method will be a promising approach to refine habitat distribution models in future. These habitat distribution models could potentially contribute to marine spatial planning at the Falkland Islands. Footage from animal-borne camera loggers clearly showed that prey behaviour can significantly influence trophic coupling in marine systems and should be accounted for in studies using marine top predators as samplers of mid to lower trophic level species. Ultimately, flexibility in foraging strategies and inter-colony variation will play a critical role when assessing factors such as interspecific competition or overlap with anthropogenic activities.
- Full Text:
- Date Issued: 2017
The FAST fabric objective measurement properties of commercial worsted apparel fabrics available in South Africa
- Authors: Das, Sweta
- Date: 2018
- Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/17814 , vital:28458
- Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
- Full Text:
- Date Issued: 2018
- Authors: Das, Sweta
- Date: 2018
- Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/17814 , vital:28458
- Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
- Full Text:
- Date Issued: 2018
An exploration of the Participatory Guarantee System (PGS) facilitating the growth and certification of small-scale organic farmers: Giyani, Garden Route and Overberg case studies
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
The hypolithic invertebrate community in the eastern Karoo: the role of rock size, microclimate and recolonization
- Authors: Van der Westhuizen, Tara
- Date: 2019
- Subjects: Habitat (Ecology) -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo Invertebrates Ecosystem management -- South Africa -- Karoo Soil microbial ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44191 , vital:37128
- Description: Hypolithic habitats are important for the persistence of fauna that utilize these habitats as refuges and resource patches. Little is known, however, about the composition and structure of this community in the semi-arid Karoo. The current study therefore aims to explore the patterns and processes behind hypolithic communities, through determining the effect of rock size and baboon presence on the hypolithic community, the influence of rock size on the microclimate experienced under rocks, as well as determining the short- (over five days) and long- (over 12 months) term colonisation of the hypolithic habitat following a rock rolling disturbance, in a semi-arid Karoo environment. The hypolithic fauna encountered, and the temperature and moisture content experienced under a range of rock sizes were measured. Additionally, hypolithic fauna under rocks that were rolled to mimic rock rolling by baboons were sampled after a set period (i.e. over five days and 12 months). Large rocks were found to provide a more stable microclimate than small rocks. The probability of hypolithic fauna presence was influenced by rock size and season, and hypolithic fauna abundance (except in the dry season), richness, body size and biomass did not correlate with rock size. Additionally, the probability of detecting hypolithic fauna under intermediate sized and larger rocks was greater in the presence of baboons than in the absence of baboons, and in the presence of baboons hypolithic fauna richness increased with rock size. Furthermore, it was shown that hypolithic fauna abundance and biomass did not differ under rolled rocks over a short- (i.e. over five days) or long- (i.e. over 12 months) term period. The short-term colonisation of hypolithic habitats was not influenced by season or rock density. Lastly, most of the change in hypolithic community composition (over 12 months) occurred in the first three months and thereafter the hypolithic community composition approached pre-disturbance levels in month 12. The hypolithic habitat was shown to be influenced by a variety of conditions and processes affecting hypolithic community composition and structure. This study therefore contributes to our understanding of the hypolithic invertebrate community in the eastern Karoo, and the influence of rock size, baboon presence, microclimate and colonisation on hypolithic community composition and structure.
- Full Text:
- Date Issued: 2019
- Authors: Van der Westhuizen, Tara
- Date: 2019
- Subjects: Habitat (Ecology) -- South Africa -- Karoo , Biotic communities -- South Africa -- Karoo Invertebrates Ecosystem management -- South Africa -- Karoo Soil microbial ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44191 , vital:37128
- Description: Hypolithic habitats are important for the persistence of fauna that utilize these habitats as refuges and resource patches. Little is known, however, about the composition and structure of this community in the semi-arid Karoo. The current study therefore aims to explore the patterns and processes behind hypolithic communities, through determining the effect of rock size and baboon presence on the hypolithic community, the influence of rock size on the microclimate experienced under rocks, as well as determining the short- (over five days) and long- (over 12 months) term colonisation of the hypolithic habitat following a rock rolling disturbance, in a semi-arid Karoo environment. The hypolithic fauna encountered, and the temperature and moisture content experienced under a range of rock sizes were measured. Additionally, hypolithic fauna under rocks that were rolled to mimic rock rolling by baboons were sampled after a set period (i.e. over five days and 12 months). Large rocks were found to provide a more stable microclimate than small rocks. The probability of hypolithic fauna presence was influenced by rock size and season, and hypolithic fauna abundance (except in the dry season), richness, body size and biomass did not correlate with rock size. Additionally, the probability of detecting hypolithic fauna under intermediate sized and larger rocks was greater in the presence of baboons than in the absence of baboons, and in the presence of baboons hypolithic fauna richness increased with rock size. Furthermore, it was shown that hypolithic fauna abundance and biomass did not differ under rolled rocks over a short- (i.e. over five days) or long- (i.e. over 12 months) term period. The short-term colonisation of hypolithic habitats was not influenced by season or rock density. Lastly, most of the change in hypolithic community composition (over 12 months) occurred in the first three months and thereafter the hypolithic community composition approached pre-disturbance levels in month 12. The hypolithic habitat was shown to be influenced by a variety of conditions and processes affecting hypolithic community composition and structure. This study therefore contributes to our understanding of the hypolithic invertebrate community in the eastern Karoo, and the influence of rock size, baboon presence, microclimate and colonisation on hypolithic community composition and structure.
- Full Text:
- Date Issued: 2019
A Statistical assessment of available solar resource across multiple sites in South Africa
- Authors: Eastwood, Kirstie
- Date: 2019
- Subjects: Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39907 , vital:35505
- Description: Around the globe, fossil fuels remain the primary source of energy at around 78% of the world’s total energy consumption. However, the associated carbon emissions, environmental impact, the depletion of fossil fuels and price and cost volatility are factors influencing the growing popularity of research into renewable energy. Solar power is acknowledged as the fastest-growing renewable energy, but the uncertainty surrounding the long-term projections of solar irradiance available for energy conversion is a hindrance when discussing the financial risk with potential investors. This study investigates the quality of freely available solar resource data in South Africa as well as proposes techniques for potential solar farm site comparisons. Tolerance intervals derived within a Bayesian framework provide information on the future available solar resource across multiple sites. These techniques capture the inherent variability in the available solar resource which equips investors with statistical methods that lead to the better understanding of the solar resource and thus aids in better decision-making.
- Full Text:
- Date Issued: 2019
- Authors: Eastwood, Kirstie
- Date: 2019
- Subjects: Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39907 , vital:35505
- Description: Around the globe, fossil fuels remain the primary source of energy at around 78% of the world’s total energy consumption. However, the associated carbon emissions, environmental impact, the depletion of fossil fuels and price and cost volatility are factors influencing the growing popularity of research into renewable energy. Solar power is acknowledged as the fastest-growing renewable energy, but the uncertainty surrounding the long-term projections of solar irradiance available for energy conversion is a hindrance when discussing the financial risk with potential investors. This study investigates the quality of freely available solar resource data in South Africa as well as proposes techniques for potential solar farm site comparisons. Tolerance intervals derived within a Bayesian framework provide information on the future available solar resource across multiple sites. These techniques capture the inherent variability in the available solar resource which equips investors with statistical methods that lead to the better understanding of the solar resource and thus aids in better decision-making.
- Full Text:
- Date Issued: 2019
An investigation into the use of a ceramifiable Ethylene Vinyl Acetate (EVA) co-polymer formulation to aid flame retardency in electrical cables
- Authors: Bambalaza, Sonwabo Elvis
- Date: 2014
- Subjects: Vinyl acetate , Polymeric composites , Inorganic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10433 , http://hdl.handle.net/10948/d1020159
- Description: The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
- Full Text:
- Date Issued: 2014
- Authors: Bambalaza, Sonwabo Elvis
- Date: 2014
- Subjects: Vinyl acetate , Polymeric composites , Inorganic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10433 , http://hdl.handle.net/10948/d1020159
- Description: The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
- Full Text:
- Date Issued: 2014
Efficacy of selected Kenyan medicinal plants used in the treatment and management of Type II Diabetes
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
An investigation into the effect of carbon type addictives on the negative electrode during the partial state of charge capacity cycling of lead acid batteries
- Authors: Snyders, Charmelle
- Date: 2011
- Subjects: Lead-acid batteries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10379 , http://hdl.handle.net/10948/1494 , Lead-acid batteries
- Description: It is well known that a conventional lead acid cell that is exposed to a partial state of charge capacity cycling (PSoCCC) would experience a build-up of irreversible PbSO4 on the negative electrode. This results into a damaged negative electrode due to excessive PbSO4 formation by the typical visual “Venetian Blinds” effect of the active material. This displays the loss of adhesion of the active material with the electrode’s grids thereby making large sections of the material ineffective and reducing the cells useful capacity during high current applications. The addition of certain graphites to the negative paste mix had proven to be successful to reduce this effect. In the first part of the study, the physical and chemical properties of the various additives that are added to the negative electrode paste mix were comparatively studied. This was done to investigate any significant differences between various suppliers that could possibly influence the electrochemical characteristics of the Pb-acid battery performance. This comparative study was done by using the following analytical techniques; BET surface area, laser diffraction particle size, PXRD, TGA-MS and SEM. The study showed that there were no significant differences between the additives supplied from different suppliers except for some anomalies in the usefulness of techniques such as N2 adsorption to study the BET surface area of BaSO4. In order to reduce the sulphation effect from occurring within the Pb-acid battery a number of adjustments are made to the electrode active material. For example, Pb-acid battery manufacturers make use of an inert polymer based material, known as Polymat, to cover the electrode surfaces as part of their continuous electrode pasting process. It is made from a non woven polyester fiber that is applied to the pasted electrodes during the continuous pasting process. In this study the Polymat pasted electrodes has demonstrated a better physical adhesion of the active material to the grid support thereby maintaining the active material’s physical integrity. This however did not reduce the sulphation effect due to the high rate partial state of capacity cycling (HRPSoCCC) test but reduced the physical damage due to the irreversible active material blistering effect. The study investigated what effect the Polymat on the electrodes has on the III battery’s Cold Cranking Ability (CCA) at -18 degree C, the HRPSoCCC cycling and its active material utilization. The study showed that there was little or no differences in the CCA and HRPSoCCC capabilities of cells made with the Polymat when compared to cells without the Polymat, with significant improvement in active material’s adhesion and integrity to the grid wire. This was confirmed by PXRD and SEM analysis. Negative electrodes were made with four types of graphites (natural, flake, expanded and nano fibre) added to the negative paste mixture in order to reduce the effect of sulphation. The study looked at using statistical design of experiment (DoE) principles to investigate the variables (additives) such as different graphites, BaSO4 and Vanisperse to the negative electrode paste mixture where upon measuring the responses (electrochemical tests) a set of controlled experiments were done to study the extent of the variables interaction, dependency and independency on the cells electrochemical properties. This was especially in relation to the improvement of the battery’s ability to work under HRPSoCCC. The statistical analysis showed that there was a notable significant influence of the amounts of vanisperse, BaSO4 and their respective interactions on a number of electrochemical responses, such as the Peukert constant (n), CCA discharge time, material utilization at different discharge rates and the ability to capacity cycle under the simulated HRPSoCCC testing. The study did not suggest an optimized concentration of the additives, but did give an indication that there was a statistical significant trend in certain electrochemical responses with an interaction between the amounts of the additives BaSO4 and Vanisperse. The study also showed that the addition of a small amount of Nano carbon can significantly change the observed crystal morphology of the negative active material and that an improvement in the number of capacity cycles can be achieved during the HRPSoCCC test when compared to the other types of graphite additives.
- Full Text:
- Date Issued: 2011
- Authors: Snyders, Charmelle
- Date: 2011
- Subjects: Lead-acid batteries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10379 , http://hdl.handle.net/10948/1494 , Lead-acid batteries
- Description: It is well known that a conventional lead acid cell that is exposed to a partial state of charge capacity cycling (PSoCCC) would experience a build-up of irreversible PbSO4 on the negative electrode. This results into a damaged negative electrode due to excessive PbSO4 formation by the typical visual “Venetian Blinds” effect of the active material. This displays the loss of adhesion of the active material with the electrode’s grids thereby making large sections of the material ineffective and reducing the cells useful capacity during high current applications. The addition of certain graphites to the negative paste mix had proven to be successful to reduce this effect. In the first part of the study, the physical and chemical properties of the various additives that are added to the negative electrode paste mix were comparatively studied. This was done to investigate any significant differences between various suppliers that could possibly influence the electrochemical characteristics of the Pb-acid battery performance. This comparative study was done by using the following analytical techniques; BET surface area, laser diffraction particle size, PXRD, TGA-MS and SEM. The study showed that there were no significant differences between the additives supplied from different suppliers except for some anomalies in the usefulness of techniques such as N2 adsorption to study the BET surface area of BaSO4. In order to reduce the sulphation effect from occurring within the Pb-acid battery a number of adjustments are made to the electrode active material. For example, Pb-acid battery manufacturers make use of an inert polymer based material, known as Polymat, to cover the electrode surfaces as part of their continuous electrode pasting process. It is made from a non woven polyester fiber that is applied to the pasted electrodes during the continuous pasting process. In this study the Polymat pasted electrodes has demonstrated a better physical adhesion of the active material to the grid support thereby maintaining the active material’s physical integrity. This however did not reduce the sulphation effect due to the high rate partial state of capacity cycling (HRPSoCCC) test but reduced the physical damage due to the irreversible active material blistering effect. The study investigated what effect the Polymat on the electrodes has on the III battery’s Cold Cranking Ability (CCA) at -18 degree C, the HRPSoCCC cycling and its active material utilization. The study showed that there was little or no differences in the CCA and HRPSoCCC capabilities of cells made with the Polymat when compared to cells without the Polymat, with significant improvement in active material’s adhesion and integrity to the grid wire. This was confirmed by PXRD and SEM analysis. Negative electrodes were made with four types of graphites (natural, flake, expanded and nano fibre) added to the negative paste mixture in order to reduce the effect of sulphation. The study looked at using statistical design of experiment (DoE) principles to investigate the variables (additives) such as different graphites, BaSO4 and Vanisperse to the negative electrode paste mixture where upon measuring the responses (electrochemical tests) a set of controlled experiments were done to study the extent of the variables interaction, dependency and independency on the cells electrochemical properties. This was especially in relation to the improvement of the battery’s ability to work under HRPSoCCC. The statistical analysis showed that there was a notable significant influence of the amounts of vanisperse, BaSO4 and their respective interactions on a number of electrochemical responses, such as the Peukert constant (n), CCA discharge time, material utilization at different discharge rates and the ability to capacity cycle under the simulated HRPSoCCC testing. The study did not suggest an optimized concentration of the additives, but did give an indication that there was a statistical significant trend in certain electrochemical responses with an interaction between the amounts of the additives BaSO4 and Vanisperse. The study also showed that the addition of a small amount of Nano carbon can significantly change the observed crystal morphology of the negative active material and that an improvement in the number of capacity cycles can be achieved during the HRPSoCCC test when compared to the other types of graphite additives.
- Full Text:
- Date Issued: 2011
Detecting changes in elephant body condition in relation to resource quality
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
Growth of the South African abalone (Haliotis Midae) on three diets, under commercial conditions
- Authors: Makhande, Emmanuel Denis
- Date: 2008
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10706 , http://hdl.handle.net/10948/755 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Description: Haliotis midae is the cornerstone of the South African abalone fishery. For more than a decade, the wild abalone stock of South Africa has suffered decline due to over-exploitation and illegal activities such as poaching. Prior to 1970, no regulations were in place concerning the annual landings. As a result the fishery was exploited as if it were an infinite resource. It is this initial uncontrolled harvesting (regardless of age) and poaching that has driven the abalone resource decline. Due to the slow growth rate exhibited by abalone as a species, natural replenishment of wild stock following exploitation and poaching was far below the rate of exploitation of this resource. Studies on the growth of abalone have mainly been conducted under laboratory conditions. The purpose of this study was to measure the growth of abalone, fed different diets, under commercial culture conditions. Three food types were used namely; commercial pellets, seaweed (Ulva spp.) and dried kelp bars (Ecklonia maxima). Four diets were obtained from the three food types namely; combination of commercial pellets and seaweed (Diet A), commercial pellets only (Diet B), seaweed only (Diet C) and dried kelp bars only (Diet D). The food types used in this study represent both artificial (Commercial pellets) and natural feeds (seaweed and kelp) used in commercial abalone culture. The growth of two cohorts (40-50 mm and 50-60 mm) was followed over a 426 day period, with data for the first 183 days being used for statistical analysis to determine performance of a given diet. The best growth rates were found in abalone fed Diet A (40-50 mm: 2.64 mm.month-1; 50-60 mm 2.78: mm.month-1) and B (40-50 mm: 2.20 mm.month-1; 50-60 mm: 2.35: mm.month-1). These (Diets A and B) gave higher growth rates when compared to Diets C and D (natural diets), whose growth rates ranged between 0.50 mm.month-1 and 1.71 mm.month-1 for both cohorts. Also observed in this study was that, the mixture of formulated diet and seaweed gave better growth than formulated diet given exclusively.
- Full Text:
- Date Issued: 2008
- Authors: Makhande, Emmanuel Denis
- Date: 2008
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10706 , http://hdl.handle.net/10948/755 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Nutrition -- South Africa , Abalones -- Physiology -- South Africa
- Description: Haliotis midae is the cornerstone of the South African abalone fishery. For more than a decade, the wild abalone stock of South Africa has suffered decline due to over-exploitation and illegal activities such as poaching. Prior to 1970, no regulations were in place concerning the annual landings. As a result the fishery was exploited as if it were an infinite resource. It is this initial uncontrolled harvesting (regardless of age) and poaching that has driven the abalone resource decline. Due to the slow growth rate exhibited by abalone as a species, natural replenishment of wild stock following exploitation and poaching was far below the rate of exploitation of this resource. Studies on the growth of abalone have mainly been conducted under laboratory conditions. The purpose of this study was to measure the growth of abalone, fed different diets, under commercial culture conditions. Three food types were used namely; commercial pellets, seaweed (Ulva spp.) and dried kelp bars (Ecklonia maxima). Four diets were obtained from the three food types namely; combination of commercial pellets and seaweed (Diet A), commercial pellets only (Diet B), seaweed only (Diet C) and dried kelp bars only (Diet D). The food types used in this study represent both artificial (Commercial pellets) and natural feeds (seaweed and kelp) used in commercial abalone culture. The growth of two cohorts (40-50 mm and 50-60 mm) was followed over a 426 day period, with data for the first 183 days being used for statistical analysis to determine performance of a given diet. The best growth rates were found in abalone fed Diet A (40-50 mm: 2.64 mm.month-1; 50-60 mm 2.78: mm.month-1) and B (40-50 mm: 2.20 mm.month-1; 50-60 mm: 2.35: mm.month-1). These (Diets A and B) gave higher growth rates when compared to Diets C and D (natural diets), whose growth rates ranged between 0.50 mm.month-1 and 1.71 mm.month-1 for both cohorts. Also observed in this study was that, the mixture of formulated diet and seaweed gave better growth than formulated diet given exclusively.
- Full Text:
- Date Issued: 2008
The mining and visualisation of application services data
- Authors: Knoetze, Ronald Morgan
- Date: 2005
- Subjects: Data mining -- South Africa , Computer algorithms , Network performance (Telecommunication) -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10480 , http://hdl.handle.net/10948/451 , Data mining -- South Africa , Computer algorithms , Network performance (Telecommunication) -- Research -- South Africa
- Description: Many network monitoring tools do not provide sufficiently in-depth and useful reports on network usage, particularly in the domain of application services data. The optimisation of network performance is only possible if the networks are monitored effectively. Techniques that identify patterns of network usage can assist in the successful monitoring of network performance. The main goal of this research was to propose a model to mine and visualise application services data in order to support effective network management. To demonstrate the effectiveness of the model, a prototype, called NetPatterns, was developed using data for the Integrated Tertiary Software (ITS) application service collected by a network monitoring tool on the NMMU South Campus network. Three data mining algorithms for application services data were identified for the proposed model. The data mining algorithms used are classification (decision tree), clustering (K-Means) and association (correlation). Classifying application services data serves to categorise combinations of network attributes to highlight areas of poor network performance. The clustering of network attributes serves to indicate sparse and dense regions within the application services data. Association indicates the existence of any interesting relationships between different network attributes. Three visualisation techniques were selected to visualise the results of the data mining algorithms. The visualisation techniques selected were the organisation chart, bubble chart and scatterplots. Colour and a variety of other visual cues are used to complement the selected visualisation techniques. The effectiveness and usefulness of NetPatterns was determined by means of user testing. The results of the evaluation clearly show that the participants were highly satisfied with the visualisation of network usage presented by NetPatterns. All participants successfully completed the prescribed tasks and indicated that NetPatterns is a useful tool for the analysis of network usage patterns.
- Full Text:
- Date Issued: 2005
- Authors: Knoetze, Ronald Morgan
- Date: 2005
- Subjects: Data mining -- South Africa , Computer algorithms , Network performance (Telecommunication) -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10480 , http://hdl.handle.net/10948/451 , Data mining -- South Africa , Computer algorithms , Network performance (Telecommunication) -- Research -- South Africa
- Description: Many network monitoring tools do not provide sufficiently in-depth and useful reports on network usage, particularly in the domain of application services data. The optimisation of network performance is only possible if the networks are monitored effectively. Techniques that identify patterns of network usage can assist in the successful monitoring of network performance. The main goal of this research was to propose a model to mine and visualise application services data in order to support effective network management. To demonstrate the effectiveness of the model, a prototype, called NetPatterns, was developed using data for the Integrated Tertiary Software (ITS) application service collected by a network monitoring tool on the NMMU South Campus network. Three data mining algorithms for application services data were identified for the proposed model. The data mining algorithms used are classification (decision tree), clustering (K-Means) and association (correlation). Classifying application services data serves to categorise combinations of network attributes to highlight areas of poor network performance. The clustering of network attributes serves to indicate sparse and dense regions within the application services data. Association indicates the existence of any interesting relationships between different network attributes. Three visualisation techniques were selected to visualise the results of the data mining algorithms. The visualisation techniques selected were the organisation chart, bubble chart and scatterplots. Colour and a variety of other visual cues are used to complement the selected visualisation techniques. The effectiveness and usefulness of NetPatterns was determined by means of user testing. The results of the evaluation clearly show that the participants were highly satisfied with the visualisation of network usage presented by NetPatterns. All participants successfully completed the prescribed tasks and indicated that NetPatterns is a useful tool for the analysis of network usage patterns.
- Full Text:
- Date Issued: 2005
Defect Classification in Photovoltaic Modules through Thermal Infrared Imaging using Machine Learning
- Dunderdale, Christopher, Clohessy, C M
- Authors: Dunderdale, Christopher , Clohessy, C M
- Date: 2020
- Subjects: Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48280 , vital:40838
- Description: As the global energy demand continues to soar, solar energy has become an attractive and environmentally conscious method to meet this demand. This study examines the use of machine learning techniques for defect detection and classification in photovoltaic systems using thermal infrared images. A deep learning and feature-based approach is also investigated for the purpose of detecting and classifying defective photovoltaic modules. The VGG-16 and MobileNet deep learning models are shown to provide good performance for the classification of defects. The scale invariant feature transform (SIFT) descriptor, combined with the random forest and support vector machine classifier, is also used to discriminate between defective and non-defective photovoltaic modules in a South African setting. The successful implementation of this approach has significant potential for cost reduction in defect classification over currently available methods.
- Full Text:
- Date Issued: 2020
- Authors: Dunderdale, Christopher , Clohessy, C M
- Date: 2020
- Subjects: Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48280 , vital:40838
- Description: As the global energy demand continues to soar, solar energy has become an attractive and environmentally conscious method to meet this demand. This study examines the use of machine learning techniques for defect detection and classification in photovoltaic systems using thermal infrared images. A deep learning and feature-based approach is also investigated for the purpose of detecting and classifying defective photovoltaic modules. The VGG-16 and MobileNet deep learning models are shown to provide good performance for the classification of defects. The scale invariant feature transform (SIFT) descriptor, combined with the random forest and support vector machine classifier, is also used to discriminate between defective and non-defective photovoltaic modules in a South African setting. The successful implementation of this approach has significant potential for cost reduction in defect classification over currently available methods.
- Full Text:
- Date Issued: 2020
The diet of the Subantarctic (A. Tropicalis) and Antarctic (A. Gazella) Fur seal at Marion Island
- Mgibantaka, Nonkoliso Felicia
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
- Authors: Mgibantaka, Nonkoliso Felicia
- Date: 2013
- Subjects: Southern fur seals -- Feeding and feeds -- Antarctica , Seals (Animals) -- Antarctica , Marine ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10729 , http://hdl.handle.net/10948/d1021104
- Description: Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.
- Full Text:
- Date Issued: 2013
Development of polypropylene – waste tyre crumbs based tpe's with the aid of vistamaxxtm as a compatibiliser
- Authors: Masele, Siyamtanda
- Date: 2019
- Subjects: Polymers , Polymerization Crumb rubber Rubber
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42589 , vital:36670
- Description: Polypropylene (PP) is a semi crystalline thermoplastic polymer and one of the most commonly used polyolefins. It is well known for its poor impact resistance; hence, for industries such as the automotive and packaging, reinforced PP is widely used. In general plastic waste disposal is a global crisis raising environmental and human health concerns, with PP being the highest consumed polymer globally; hence a push in the reuse and recycling of PP. Recycled polypropylene has limited uses for industrial applications due to its highly reduced properties owing to the recycling process which inhabits cutting of chains lengths, broadened molecular weight distributions and compromised crystallinity. Several studies have investigated the use of reinforcing fillers and modifiers in order to improve properties of PP. Inorganic materials and minerals such as CaCO3, Mica, Talc and glass fibre are used as fillers to improve mechanical properties (tensile and hardness), but still lacks in improving the impact resistance. Thermoplastic elastomers (TPE) are typically used where elastomer and thermoplastics fail as individual components. This is because they have the benefit of thermoplastic properties at hypo ambient condition and elastomer properties such as good impact and elongation at sub-zero conditions. The study took a route of using PP and waste tyre crumb rubber (CR) material to prepare potentially low-cost waste based TPE’s, which would then inherit both properties of PP and the rubber component. VistamaxxTM 6202 (EPR), a commercial name for ethylene-propylene monomer (EPR), was used as a compatibiliser to improve interaction between PP and CR and to contribute towards the overall improvement of various properties such as mechanical properties. VistamaxxTM has a low glass transition temperature (Tg, = -30 ºC), which is important for low temperature applications such as cold storage; it also has a very high elongation and as a result contributed significantly to the overall properties when used in TPE blends. The study highlighted differences between two TPE compounding formulation pathways; namely master-batch (MB) and design of experiments (DoE). The MB formulations were blends that were prepared by a conventional way of compounding; where a pre-mixed CR/EPR blend, in the ratio of 80(CR):20(EPR), was used to form a master-batch. Results showed that there are some similarities between TPEs prepared in different ways, which suggests that the ultimate properties such as thermal stability are in fact more PP matrix based. Thermal analyses results revealed that when high amount of CR was added to the TPE blends, there was a substantial amount of residue mainly due to inherent carbon black. The degree of crystallinity of the blends decreased with increased amounts of CR irrespective of whether it was the MB or DoE blends. The MB TPE blends demonstrated that hardness is not linked to the amount of the MB nor the crystallinity of blends. Meanwhile, tensile elongation and tensile stress were affected by crystallinity. On the other hand, the impact strength findings showed that the amount of MB in TPE blends reached a threshold at 30%. The DoE based TPE blends demonstrated that the optimum mechanical properties are observed when components of the blends are incorporated individually during compounding. This was observed for impact strength, tensile stress as well as elongation at break. The results showed that the incorporation of EPR should be at least 20% for good impact and elongation properties; however, for tensile and hardness, the PP matrix must be high. The study also showed that, for better mechanical properties it was more suitable to use the blends formulated with DoE, because the master-batch approach limited the improving of the mechanical properties by an addition of up to 30% of both the CR and EPR. The storage modulus as well as the tan delta for both MB and DoE decreased when the elastomeric phases were added on both methods, whereas tan delta Tg values decreased as more of the elastomeric phase was added. Evidence from morphology studies showed that the majority of TPE blends suffer from inadequate distribution and adhesion between PP and elastomer; resulting in poor mechanical properties. Furthermore, a threshold of matrix invasion is observed from 30% and above of CR in the blend, where lack of in capsulated lamps of CR were observed hindering the stress induced crystallization and relaxation of the PP phase. The latter was observed irrespective of the type of blend, which strongly suggests and highlights the limits of blending PP with elastomers. Study demonstrated the ability of VistamaxxTM to be utilized as a binding material for PP and CR and displaying the challenges that might arise when used as a master-batch with crumb rubber.
- Full Text:
- Date Issued: 2019
- Authors: Masele, Siyamtanda
- Date: 2019
- Subjects: Polymers , Polymerization Crumb rubber Rubber
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/42589 , vital:36670
- Description: Polypropylene (PP) is a semi crystalline thermoplastic polymer and one of the most commonly used polyolefins. It is well known for its poor impact resistance; hence, for industries such as the automotive and packaging, reinforced PP is widely used. In general plastic waste disposal is a global crisis raising environmental and human health concerns, with PP being the highest consumed polymer globally; hence a push in the reuse and recycling of PP. Recycled polypropylene has limited uses for industrial applications due to its highly reduced properties owing to the recycling process which inhabits cutting of chains lengths, broadened molecular weight distributions and compromised crystallinity. Several studies have investigated the use of reinforcing fillers and modifiers in order to improve properties of PP. Inorganic materials and minerals such as CaCO3, Mica, Talc and glass fibre are used as fillers to improve mechanical properties (tensile and hardness), but still lacks in improving the impact resistance. Thermoplastic elastomers (TPE) are typically used where elastomer and thermoplastics fail as individual components. This is because they have the benefit of thermoplastic properties at hypo ambient condition and elastomer properties such as good impact and elongation at sub-zero conditions. The study took a route of using PP and waste tyre crumb rubber (CR) material to prepare potentially low-cost waste based TPE’s, which would then inherit both properties of PP and the rubber component. VistamaxxTM 6202 (EPR), a commercial name for ethylene-propylene monomer (EPR), was used as a compatibiliser to improve interaction between PP and CR and to contribute towards the overall improvement of various properties such as mechanical properties. VistamaxxTM has a low glass transition temperature (Tg, = -30 ºC), which is important for low temperature applications such as cold storage; it also has a very high elongation and as a result contributed significantly to the overall properties when used in TPE blends. The study highlighted differences between two TPE compounding formulation pathways; namely master-batch (MB) and design of experiments (DoE). The MB formulations were blends that were prepared by a conventional way of compounding; where a pre-mixed CR/EPR blend, in the ratio of 80(CR):20(EPR), was used to form a master-batch. Results showed that there are some similarities between TPEs prepared in different ways, which suggests that the ultimate properties such as thermal stability are in fact more PP matrix based. Thermal analyses results revealed that when high amount of CR was added to the TPE blends, there was a substantial amount of residue mainly due to inherent carbon black. The degree of crystallinity of the blends decreased with increased amounts of CR irrespective of whether it was the MB or DoE blends. The MB TPE blends demonstrated that hardness is not linked to the amount of the MB nor the crystallinity of blends. Meanwhile, tensile elongation and tensile stress were affected by crystallinity. On the other hand, the impact strength findings showed that the amount of MB in TPE blends reached a threshold at 30%. The DoE based TPE blends demonstrated that the optimum mechanical properties are observed when components of the blends are incorporated individually during compounding. This was observed for impact strength, tensile stress as well as elongation at break. The results showed that the incorporation of EPR should be at least 20% for good impact and elongation properties; however, for tensile and hardness, the PP matrix must be high. The study also showed that, for better mechanical properties it was more suitable to use the blends formulated with DoE, because the master-batch approach limited the improving of the mechanical properties by an addition of up to 30% of both the CR and EPR. The storage modulus as well as the tan delta for both MB and DoE decreased when the elastomeric phases were added on both methods, whereas tan delta Tg values decreased as more of the elastomeric phase was added. Evidence from morphology studies showed that the majority of TPE blends suffer from inadequate distribution and adhesion between PP and elastomer; resulting in poor mechanical properties. Furthermore, a threshold of matrix invasion is observed from 30% and above of CR in the blend, where lack of in capsulated lamps of CR were observed hindering the stress induced crystallization and relaxation of the PP phase. The latter was observed irrespective of the type of blend, which strongly suggests and highlights the limits of blending PP with elastomers. Study demonstrated the ability of VistamaxxTM to be utilized as a binding material for PP and CR and displaying the challenges that might arise when used as a master-batch with crumb rubber.
- Full Text:
- Date Issued: 2019
The effects of terpenoids on the expression and function of cytokines and adipokines in pre-adipocytes and differentiated adipocytes
- Authors: Bloom, Carri-Ann
- Date: 2017
- Subjects: Terpenes , Cytokines , Fat cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/9208 , vital:26479
- Description: CURRENTLY UNDER EMBARGO UNTIL THE 26/4/2019: Type 2 diabetes is a metabolic disorder characterised by inflammation, insulin resistance and the inability of pancreatic β-cells to secrete enough insulin to produce a physiological effect. Obesity and high levels of triacylglycerol’s are associated with the development of Type 2 diabetes. Adipose tissue is an active endocrine organ that secretes various protein and peptide hormones, known as adipokines, which mediate important metabolic functions. In an insulin resistant and hyperglycaemic state, levels of anti-inflammatory adipokines, adiponectin, are reduced, whereas levels of pro-inflammatory cytokines, interleukin-6 and interleukin-1β, are elevated; this results in a shift from an anti- to a pro-inflammatory state that is accompanied by dysfunction and apoptosis of the pancreatic β-cells. Cannabis sativa L. has been traditionally used as an anti-inflammatory agent in Southern Africa, specifically treating snakebites, fever and malaria. Δ9-tetrahydrocannabinol is the main psychoactive compound derived from C. sativa, whereas the other major cannabinoids, cannabinol and cannabidiol, have shown anti-inflammatory and sedative properties respectively. Marrubiin is a compound derived from the plant Leonotis leonurus L. and has been traditionally used as an anti-inflammatory and anti-diabetic agent. To determine the effects of these compounds in a hyperglycaemic state, pre- and differentiated mouse adipocytes (3T3-L1 cells) were exposed for seven and fourteen days to the following treatments: Δ9-tetrahydrocannabinol, cannabidiol, cannabinol, marrubiin, anandamide (an endogenous endocannabinoid) and cannabis extract, individually and in combination, under normal glucose and hyperglycaemic conditions. Levels of adiponectin, interleukin-6, leptin, tumour-necrosis factor-α and interleukin-1β were quantified using mouse enzyme-linked immunosorbent assay kits and Oil Red O staining was carried out to determine lipid distribution and lipid droplet characteristics. Results indicate that various cannabinoids, in combination, mediate an anti-inflammatory effect by decreasing the expression of various pro-inflammatory cytokines, which may have allowed for a shift from a pro- to an anti-inflammatory state by these compounds, and may also contribute to the reduction of lipid, which may be used as a supplementary option to current diabetic treatment regimes.
- Full Text: false
- Date Issued: 2017
- Authors: Bloom, Carri-Ann
- Date: 2017
- Subjects: Terpenes , Cytokines , Fat cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/9208 , vital:26479
- Description: CURRENTLY UNDER EMBARGO UNTIL THE 26/4/2019: Type 2 diabetes is a metabolic disorder characterised by inflammation, insulin resistance and the inability of pancreatic β-cells to secrete enough insulin to produce a physiological effect. Obesity and high levels of triacylglycerol’s are associated with the development of Type 2 diabetes. Adipose tissue is an active endocrine organ that secretes various protein and peptide hormones, known as adipokines, which mediate important metabolic functions. In an insulin resistant and hyperglycaemic state, levels of anti-inflammatory adipokines, adiponectin, are reduced, whereas levels of pro-inflammatory cytokines, interleukin-6 and interleukin-1β, are elevated; this results in a shift from an anti- to a pro-inflammatory state that is accompanied by dysfunction and apoptosis of the pancreatic β-cells. Cannabis sativa L. has been traditionally used as an anti-inflammatory agent in Southern Africa, specifically treating snakebites, fever and malaria. Δ9-tetrahydrocannabinol is the main psychoactive compound derived from C. sativa, whereas the other major cannabinoids, cannabinol and cannabidiol, have shown anti-inflammatory and sedative properties respectively. Marrubiin is a compound derived from the plant Leonotis leonurus L. and has been traditionally used as an anti-inflammatory and anti-diabetic agent. To determine the effects of these compounds in a hyperglycaemic state, pre- and differentiated mouse adipocytes (3T3-L1 cells) were exposed for seven and fourteen days to the following treatments: Δ9-tetrahydrocannabinol, cannabidiol, cannabinol, marrubiin, anandamide (an endogenous endocannabinoid) and cannabis extract, individually and in combination, under normal glucose and hyperglycaemic conditions. Levels of adiponectin, interleukin-6, leptin, tumour-necrosis factor-α and interleukin-1β were quantified using mouse enzyme-linked immunosorbent assay kits and Oil Red O staining was carried out to determine lipid distribution and lipid droplet characteristics. Results indicate that various cannabinoids, in combination, mediate an anti-inflammatory effect by decreasing the expression of various pro-inflammatory cytokines, which may have allowed for a shift from a pro- to an anti-inflammatory state by these compounds, and may also contribute to the reduction of lipid, which may be used as a supplementary option to current diabetic treatment regimes.
- Full Text: false
- Date Issued: 2017
Evaluation of noise levels of micro-wind turbines using a randomised experiment
- Authors: Clohessy, Chantelle May
- Date: 2012
- Subjects: Wind turbines -- Noise , Wind turbines -- valuation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10508 , http://hdl.handle.net/10948/d1015974
- Description: One of the biggest environmental concerns of a wind turbine is the wind turbine noise (Prospathopoulos and Voutsinas, 2007). This study assesses the noise impacts of wind turbines on the environment by comparing the micro-wind turbine noise to traditional accepted surrounding sounds. The collection of the sound level data was done by using a randomised experiment. The sound level data was then fitted to a General Linear Model to determine the relationship between the sound levels generated at a given site to the time of day, wind speed, wind direction and distance from the sound source. An additional study was conducted to determine the relationship between wind speed and the sound levels of wind turbines. The distribution of frequency components of wind turbine sound was also determined.
- Full Text:
- Date Issued: 2012
- Authors: Clohessy, Chantelle May
- Date: 2012
- Subjects: Wind turbines -- Noise , Wind turbines -- valuation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10508 , http://hdl.handle.net/10948/d1015974
- Description: One of the biggest environmental concerns of a wind turbine is the wind turbine noise (Prospathopoulos and Voutsinas, 2007). This study assesses the noise impacts of wind turbines on the environment by comparing the micro-wind turbine noise to traditional accepted surrounding sounds. The collection of the sound level data was done by using a randomised experiment. The sound level data was then fitted to a General Linear Model to determine the relationship between the sound levels generated at a given site to the time of day, wind speed, wind direction and distance from the sound source. An additional study was conducted to determine the relationship between wind speed and the sound levels of wind turbines. The distribution of frequency components of wind turbine sound was also determined.
- Full Text:
- Date Issued: 2012
Optimization of a manufacturing process for atrazine with a focus on waste minimization
- Authors: Mtyopo, Mteteleli Bethwell
- Date: 2004
- Subjects: Waste minimization , Atrazine -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10976 , http://hdl.handle.net/10948/259 , Waste minimization , Atrazine -- Environmental aspects
- Description: Chemical synthesis is not complete without waste treatment. There is no chemical process that does not produce waste. The untreated effluent discharged by chemical industries poses a major environmental concern. This dissertation describes the results of an investigation carried out on the formation of by-products (impurities) during the synthesis of atrazine by neutralization of the reaction mixture during the actual synthesis procedure, and prior to disposal using carbon dioxide or hydrochloric acid. The main objectives for the said investigation were: {u100083} To optimise the reaction parameters to obtain a higher yield and purity of atrazine. {u100083} To evaluate the use of carbon dioxide and hydrochloric acid to neutralise the reaction mixture. {u100083} To study the solids present in the effluent. Synthetic reactions were carried out in the presence of an organic solvent, methyl isobutyl ketone (MIBK). The synthesis of atrazine was optimised in terms of addition sequence and rates of amine reagents and base (proton acceptor) additions by means of bench scale reactions. It was found that addition of a neutralising step (hydrochloric acid or carbon dioxide) to neutralise the basic reaction mixture prior to and after addition of the secondary amine and the base minimizes the formation of by-products. Of particular importance in ensuring high yields and selectivity to the atrazine product was temperature control, pH control, reagent ratios, addition rates and mixing. The latter was important in view of the rapid reaction of amine/NaOH with cyanuric chloride, as well as the possible reaction of mono-i, the reaction intermediate, with IPA in cases of excesses of reagent. Under optimum conditions, an atrazine composition of >97% was achieved where the resultant product was well within stipulated product specifications.
- Full Text:
- Date Issued: 2004
- Authors: Mtyopo, Mteteleli Bethwell
- Date: 2004
- Subjects: Waste minimization , Atrazine -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10976 , http://hdl.handle.net/10948/259 , Waste minimization , Atrazine -- Environmental aspects
- Description: Chemical synthesis is not complete without waste treatment. There is no chemical process that does not produce waste. The untreated effluent discharged by chemical industries poses a major environmental concern. This dissertation describes the results of an investigation carried out on the formation of by-products (impurities) during the synthesis of atrazine by neutralization of the reaction mixture during the actual synthesis procedure, and prior to disposal using carbon dioxide or hydrochloric acid. The main objectives for the said investigation were: {u100083} To optimise the reaction parameters to obtain a higher yield and purity of atrazine. {u100083} To evaluate the use of carbon dioxide and hydrochloric acid to neutralise the reaction mixture. {u100083} To study the solids present in the effluent. Synthetic reactions were carried out in the presence of an organic solvent, methyl isobutyl ketone (MIBK). The synthesis of atrazine was optimised in terms of addition sequence and rates of amine reagents and base (proton acceptor) additions by means of bench scale reactions. It was found that addition of a neutralising step (hydrochloric acid or carbon dioxide) to neutralise the basic reaction mixture prior to and after addition of the secondary amine and the base minimizes the formation of by-products. Of particular importance in ensuring high yields and selectivity to the atrazine product was temperature control, pH control, reagent ratios, addition rates and mixing. The latter was important in view of the rapid reaction of amine/NaOH with cyanuric chloride, as well as the possible reaction of mono-i, the reaction intermediate, with IPA in cases of excesses of reagent. Under optimum conditions, an atrazine composition of >97% was achieved where the resultant product was well within stipulated product specifications.
- Full Text:
- Date Issued: 2004