Identification of SNPs within the CYP2A6 enzyme of TNBC cell lines and the resulting change in activity
- Dingle, Laura Margaret Kirkpatrick
- Authors: Dingle, Laura Margaret Kirkpatrick
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64349 , vital:28536
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Dingle, Laura Margaret Kirkpatrick
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64349 , vital:28536
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Impacts of African elephant feeding on white rhinoceros foraging opportunities
- Authors: Prinsloo, Dominique
- Date: 2017
- Subjects: Herbivores -- Ecology -- South Africa , Grassland ecology -- South Africa Animal-plant relationships -- South Africa Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13768 , vital:27306
- Description: In this study, I investigated the interaction between two megaherbivores, the African elephant and white rhinoceros, that has the potential to impact grazing lawns of which white rhino are the creators and maintainers and elephants are potentially the modifiers. I hypothesized that as elephants browse, they discard a variety of coarse woody debris onto the ground; should this woody debris (of varying amounts and sizes) fall onto grazing lawns, white rhino either move them, consume grass around the woody debris or abandon the lawn entirely. If high levels of woody debris are deposited here, grazing by white rhino is likely to be prevented, at which time I predicted that mesoherbivores would have a competitive advantage in accessing forage that white rhino cannot. I examined the mechanistic links between different levels of elephant-deposited woody debris and grass response at a point scale and feeding patch spatial scale of grazing lawns in an African savanna. In addition, I assessed the response of mesoherbivores in terms of vigilance behaviour with increasing levels of predation risk posed by increasing levels of woody debris. I present the first evidence of an indirect effect of elephant on white rhino foraging behaviour. I demonstrate how increasing levels of woody debris lead to a decreasing probability of foraging by white rhino. I also demonstrate how the probability of foraging by mesoherbivores increases as the amount of forage increases. However, since this study took place during a severe drought where resources are extremely limited, I was unable to properly separate the effects of elephant-deposited woody debris from the severe lack of rainfall on grass response and subsequently herbivore foraging behaviour. Due possibly to the drought, mesoherbivores responded less or not at all to risk factors such as woody debris therefore woody debris was not a predictor of vigilance behaviour in my study. This study contributes to our understanding of how the impacts of elephants, as ecosystem engineers, have cascading effects on savanna ecosystems. My study showed that elephant impact mediates the foraging behaviour of white rhino during a drought. However, under average rainfall periods, my original hypothesized effect of the indirect impacts of elephants on white rhino foraging and grazing lawn dynamics could still hold. This key hypothesis that I was unable to test under ‘normal’ conditions due to the drought is still valid and functionally important for understanding the ecosystem processes driving grazing lawn formation, persistence and composition in African savannas where elephants and white rhinos coexist.
- Full Text:
- Date Issued: 2017
- Authors: Prinsloo, Dominique
- Date: 2017
- Subjects: Herbivores -- Ecology -- South Africa , Grassland ecology -- South Africa Animal-plant relationships -- South Africa Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13768 , vital:27306
- Description: In this study, I investigated the interaction between two megaherbivores, the African elephant and white rhinoceros, that has the potential to impact grazing lawns of which white rhino are the creators and maintainers and elephants are potentially the modifiers. I hypothesized that as elephants browse, they discard a variety of coarse woody debris onto the ground; should this woody debris (of varying amounts and sizes) fall onto grazing lawns, white rhino either move them, consume grass around the woody debris or abandon the lawn entirely. If high levels of woody debris are deposited here, grazing by white rhino is likely to be prevented, at which time I predicted that mesoherbivores would have a competitive advantage in accessing forage that white rhino cannot. I examined the mechanistic links between different levels of elephant-deposited woody debris and grass response at a point scale and feeding patch spatial scale of grazing lawns in an African savanna. In addition, I assessed the response of mesoherbivores in terms of vigilance behaviour with increasing levels of predation risk posed by increasing levels of woody debris. I present the first evidence of an indirect effect of elephant on white rhino foraging behaviour. I demonstrate how increasing levels of woody debris lead to a decreasing probability of foraging by white rhino. I also demonstrate how the probability of foraging by mesoherbivores increases as the amount of forage increases. However, since this study took place during a severe drought where resources are extremely limited, I was unable to properly separate the effects of elephant-deposited woody debris from the severe lack of rainfall on grass response and subsequently herbivore foraging behaviour. Due possibly to the drought, mesoherbivores responded less or not at all to risk factors such as woody debris therefore woody debris was not a predictor of vigilance behaviour in my study. This study contributes to our understanding of how the impacts of elephants, as ecosystem engineers, have cascading effects on savanna ecosystems. My study showed that elephant impact mediates the foraging behaviour of white rhino during a drought. However, under average rainfall periods, my original hypothesized effect of the indirect impacts of elephants on white rhino foraging and grazing lawn dynamics could still hold. This key hypothesis that I was unable to test under ‘normal’ conditions due to the drought is still valid and functionally important for understanding the ecosystem processes driving grazing lawn formation, persistence and composition in African savannas where elephants and white rhinos coexist.
- Full Text:
- Date Issued: 2017
Improving the cold tolerance of false codling moth, thaumatotibia leucotreta, for better performance in a sterile insect release programme
- Authors: Daniel, Claire Ashleigh
- Date: 2017
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction -- Effect of temperature on , Cryptophlebia leucotreta -- Biological control -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Insecticides , Citrus fruit industry -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5271 , vital:20803
- Description: The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a major pest of citrus and other important crops in Sub-Saharan Africa. The introduction of a sterile insect technique (SIT) programme for FCM in South Africa has proven to be very effective in the control of FCM. The objective was to flood citrus orchards with large numbers of sterile males resulting in a ratio of at least 10 sterile to 1 wild moth, increasing the probability of a female moth mating with a sterile male. This target is often achieved and the programme is generally successful, however there are some challenges regarding this programme. The mass rearing environment, artificial diet, handling methods and irradiation have an impact on sterile insect quality as environmental differences between the rearing facility and field, influences the insect phenotype and competitiveness. This is evident as wild male moths can theoretically actively fly at a temperature of 12°C and laboratory-reared sterilized moths, due to the radiation treatment, appear unable to fly below 20°C. As a consequence, sterile males are out-competed by wild males during the cooler months of the year. This is detrimental to the SIT programme as FCM do not undergo diapause, meaning they are active during winter and will still reproduce. Therefore, to maximize the effect of the SIT programme, it is vital to increase the flight ability of mass reared sterile males at lower temperatures. Various studies have shown that by adding cryoprotectants to the basic laboratory diets increases the cold tolerance of certain insects and thus may allow them to be mobile at lower temperatures, however it imperative that any chemical used to augment the commercial diet of the insect has no negative effects on the insect physiology and development. To investigate this detail for FCM, five generations of FCM were reared on diets augmented with various known insect cryoprotectants. These augmented FCM were subsequently used in experiments designed to determine firstly, if the cryoprotectants had a positive result on the cold tolerance of the FCM, and secondly, if they had any adverse effects on other physiological aspects such as duration of development. Laboratory trials indicated that the flight ability of male FCM was improved when larvae were reared on diets augmented with trehalose and cholesterol (with an average of 40 % of cholesterol and trehalose augmented males that flew at 15 °C where 0 % of the control flew). Results obtained during the field trials support the laboratory results as there was a significant increase in the number of trehalose augmented moths caught in the field during March and July (winter). Results also showed potential for cholesterol to be used as an additive. Other important findings show that both cholesterol and trehalose have no negative impacts on developmental rate, pupal size, and egg production and viability. Trehalose was found to increase the pupal mass of male and female FCM, as well as the number of eggs laid per female. Cholesterol was found to increase developmental rate and the number of eggs laid. The main findings of this study were that diet additives could improve the massrearing of FCM for SIT and the competitiveness of the males, especially at lower temperatures. However, the additives were expensive and cost could well be a constraint to the wide scale implementation of the new technology.
- Full Text:
- Date Issued: 2017
- Authors: Daniel, Claire Ashleigh
- Date: 2017
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction -- Effect of temperature on , Cryptophlebia leucotreta -- Biological control -- South Africa , Citrus -- Diseases and pests -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Insecticides , Citrus fruit industry -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5271 , vital:20803
- Description: The false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a major pest of citrus and other important crops in Sub-Saharan Africa. The introduction of a sterile insect technique (SIT) programme for FCM in South Africa has proven to be very effective in the control of FCM. The objective was to flood citrus orchards with large numbers of sterile males resulting in a ratio of at least 10 sterile to 1 wild moth, increasing the probability of a female moth mating with a sterile male. This target is often achieved and the programme is generally successful, however there are some challenges regarding this programme. The mass rearing environment, artificial diet, handling methods and irradiation have an impact on sterile insect quality as environmental differences between the rearing facility and field, influences the insect phenotype and competitiveness. This is evident as wild male moths can theoretically actively fly at a temperature of 12°C and laboratory-reared sterilized moths, due to the radiation treatment, appear unable to fly below 20°C. As a consequence, sterile males are out-competed by wild males during the cooler months of the year. This is detrimental to the SIT programme as FCM do not undergo diapause, meaning they are active during winter and will still reproduce. Therefore, to maximize the effect of the SIT programme, it is vital to increase the flight ability of mass reared sterile males at lower temperatures. Various studies have shown that by adding cryoprotectants to the basic laboratory diets increases the cold tolerance of certain insects and thus may allow them to be mobile at lower temperatures, however it imperative that any chemical used to augment the commercial diet of the insect has no negative effects on the insect physiology and development. To investigate this detail for FCM, five generations of FCM were reared on diets augmented with various known insect cryoprotectants. These augmented FCM were subsequently used in experiments designed to determine firstly, if the cryoprotectants had a positive result on the cold tolerance of the FCM, and secondly, if they had any adverse effects on other physiological aspects such as duration of development. Laboratory trials indicated that the flight ability of male FCM was improved when larvae were reared on diets augmented with trehalose and cholesterol (with an average of 40 % of cholesterol and trehalose augmented males that flew at 15 °C where 0 % of the control flew). Results obtained during the field trials support the laboratory results as there was a significant increase in the number of trehalose augmented moths caught in the field during March and July (winter). Results also showed potential for cholesterol to be used as an additive. Other important findings show that both cholesterol and trehalose have no negative impacts on developmental rate, pupal size, and egg production and viability. Trehalose was found to increase the pupal mass of male and female FCM, as well as the number of eggs laid per female. Cholesterol was found to increase developmental rate and the number of eggs laid. The main findings of this study were that diet additives could improve the massrearing of FCM for SIT and the competitiveness of the males, especially at lower temperatures. However, the additives were expensive and cost could well be a constraint to the wide scale implementation of the new technology.
- Full Text:
- Date Issued: 2017
In silico analysis of plasmodium falciparum Hsp70-x for potential binding sites and hits
- Authors: Amusengeri, Arnold
- Date: 2017
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59136 , vital:27435
- Description: Restricted access-thesis embargoed for 1 year - release date April 2019
- Full Text:
- Date Issued: 2017
- Authors: Amusengeri, Arnold
- Date: 2017
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59136 , vital:27435
- Description: Restricted access-thesis embargoed for 1 year - release date April 2019
- Full Text:
- Date Issued: 2017
Incidence of norovirus from pig faecal samples in the Eastern Cape South Africa
- Authors: Taku, Ongeziwe
- Date: 2017
- Subjects: Viral gastroenteritis Virus diseases Swine -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12374 , vital:39257
- Description: Norovirus is one of the causative agents of gastroenteritis in humans and belongs to the Caliciviridae family. Gastroenteritis is a common disease which has emerged as a worldwide health problem and it induces high number of diarrheal episodes in children and adults. Communal location such as schools, homes, day-care, cruise ships and hospitals have high risk of Norovirus infection. Besides humans, Norovirus have been found in farm animals including pigs; porcine Norovirus has been reported to be genetically related to human Norovirus which raise concerns about potential zoonotic spread and pigs may serve as reservoirs of human Norovirus strains. This current study assessed the occurrence of Norovirus infection amongst pigs in selected commercial pig farms in the Eastern Cape, South Africa. One hundred and twenty (120) RNA samples isolated from faecal samples of pigs were amplified using the RT-PCR and Nested PCR assay targeting the RdRp gene. Out of the one hundred and twenty RNA samples analysed, only five (4.2 percent) were positive for Norovirus. All positive isolates were sequenced (ABI 310 prism sequencer), edited and analysed phylogenetically using the Geneious version 9.1.5 software. Phylogenetic analysis of the generated sequences from the positive samples was performed with reference sequences obtained from the GenBank. Out of the five positive isolates analysed, four nucleotide sequences (FH14, FH20, FH13 and TS05) showed high similarity with Caliciviruses (non-human) and FHO5 showed high similarity to human Norovirus and clustered with human Norovirus GII. These findings revealed low prevalence of Norovirus in the Eastern Cape Province. Notwithstanding the low prevalence of Norovirus in the study communities, it is still of serious health concern.
- Full Text:
- Date Issued: 2017
- Authors: Taku, Ongeziwe
- Date: 2017
- Subjects: Viral gastroenteritis Virus diseases Swine -- Diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12374 , vital:39257
- Description: Norovirus is one of the causative agents of gastroenteritis in humans and belongs to the Caliciviridae family. Gastroenteritis is a common disease which has emerged as a worldwide health problem and it induces high number of diarrheal episodes in children and adults. Communal location such as schools, homes, day-care, cruise ships and hospitals have high risk of Norovirus infection. Besides humans, Norovirus have been found in farm animals including pigs; porcine Norovirus has been reported to be genetically related to human Norovirus which raise concerns about potential zoonotic spread and pigs may serve as reservoirs of human Norovirus strains. This current study assessed the occurrence of Norovirus infection amongst pigs in selected commercial pig farms in the Eastern Cape, South Africa. One hundred and twenty (120) RNA samples isolated from faecal samples of pigs were amplified using the RT-PCR and Nested PCR assay targeting the RdRp gene. Out of the one hundred and twenty RNA samples analysed, only five (4.2 percent) were positive for Norovirus. All positive isolates were sequenced (ABI 310 prism sequencer), edited and analysed phylogenetically using the Geneious version 9.1.5 software. Phylogenetic analysis of the generated sequences from the positive samples was performed with reference sequences obtained from the GenBank. Out of the five positive isolates analysed, four nucleotide sequences (FH14, FH20, FH13 and TS05) showed high similarity with Caliciviruses (non-human) and FHO5 showed high similarity to human Norovirus and clustered with human Norovirus GII. These findings revealed low prevalence of Norovirus in the Eastern Cape Province. Notwithstanding the low prevalence of Norovirus in the study communities, it is still of serious health concern.
- Full Text:
- Date Issued: 2017
Influence of sedimentological and hydrological processes on the distribution of the Spartina maritima salt marsh in the Keurbooms Estuary, Western Cape
- Authors: Mfikili, Athi Nkosibonile
- Date: 2017
- Subjects: Salt marshes -- South Africa -- Western Cape Estuarine hydrology -- South Africa -- Western Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13004 , vital:27143
- Description: Salt marshes are some of the most productive ecosystems in the world and have been the centre of attention over the past few decades, due to their decline as a result of global climate change and anthropogenic impacts. The growth of salt marshes is determined by substrate type, soil conductivity and elevation. The permanently open Keurbooms Estuary along the south-east coast of South Africa is subjected to occasional fluvial flooding and its intertidal area lacks well developed salt marshes, with Spartina maritima restricted to the lower reaches of the Bitou tributary and a few sections of the Keurbooms tributary. Presumeably because of fine sediment habitat in the confluence and lower Bitou tributary. The salinity of the estuarine water ranges between 0.1 – 26.9 and 3.2 – 35.3 in the Bitou and Keurbooms tributaries respectively. A typical salt wedge salinity pattern is common in the Keurbooms tributary where saline water often intrudes underneath the freshwater, especially during high river flows. The following hypotheses were developed and tested in this study: The limited spatial distribution of S. maritima in the Keurbooms Estuary is due to limited availability of fine sediment habitat; and the source of the fine sediment in the estuary is the Bitou tributary rather than the Keurbooms tributary or the sea. It was further postulated that after sediment characteristics, floods are the major hydrological driver determining the distribution of S. maritima in the Keurbooms Estuary. The results of the surveys of the estuarine channel bottom sediments showed that the Keurbooms tributary was mostly characterized by the sand-size sediment fraction derived from the feldspathic and sandstone with evidence of fine sediment fractions restricted to the upper reaches at the confluence with Whiskey Creek. The Bitou was almost always composed of coarse sized sediments in the upper reaches, fine sediment deposits in the middle and lower reaches and medium sorted sand with almost no clay or calcium carbonate in the estuarine component below the confluence of the tributaries. These findings were further supported by the surface sediment deposited within the S. maritima intertidal salt marsh, which showed finer sediment deposits in the Bitou marsh compared to the Keurbooms marsh surface. Similar results were also found in the sediment cores, with the Keurbooms marsh sediment becoming finer with increasing depth whereas fine sediments reduced with depth in the Bitou marsh. The results of the sediment mineralogy indicated that the increased concentrations of clay minerals in the S. maritima surface sediments are derived from the Bokkeveld shale, siltstone and clay slate exposed above the N2 Bridge in the Keurbooms Estuary. GIS mapping shows that S. maritima has been declining over the past two decades, with rapid decreases especially evident after big flooding events. The GIS mapping also indicates that the patches of the S. maritima in the Keurbooms tributary are more exposed to big floods than the Bitou marsh. Despite showing an overall decline, S. maritima area coverage remained more consistent in the lower reaches of the Bitou tributary than in the Keurbooms tributary. Despite the larger and more persistent area cover, the S. maritima plants were shorter and less dense than the plants growing in the sandy substrate. The black/grey colouration of soil with increasing depth in the Bitou tributary was an indication of the reduced state of the soil caused by prolonged waterlogged conditions. The roots of S. maritima in both tributaries were mostly restricted to the sub-surface substrate layer (i.e. 0 – 0.25 m), although the Bitou populations showed more vegetative propagation than the Keurbooms populations. This mechanism of reproduction was also demonstrated during the transplant experiment which showed a greater number of new stem production in the fine sediment substrates compared to the sandy silt substrates. Although accretion rates were not determined in this study, the short-term sediment deposition rates revealed that sedimentation is active in the marshes of the Keurbooms Estuary. Therefore, in spite of showing a decline in area cover, the production of viable seed and observed vegetative propagation suggest that the S. maritima is likely to colonize open stable intertidal mudflats / sandflats, thus maintaining its distribution as an intertidal species in the salt marshes of the Keurbooms Estuary.
- Full Text:
- Date Issued: 2017
- Authors: Mfikili, Athi Nkosibonile
- Date: 2017
- Subjects: Salt marshes -- South Africa -- Western Cape Estuarine hydrology -- South Africa -- Western Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13004 , vital:27143
- Description: Salt marshes are some of the most productive ecosystems in the world and have been the centre of attention over the past few decades, due to their decline as a result of global climate change and anthropogenic impacts. The growth of salt marshes is determined by substrate type, soil conductivity and elevation. The permanently open Keurbooms Estuary along the south-east coast of South Africa is subjected to occasional fluvial flooding and its intertidal area lacks well developed salt marshes, with Spartina maritima restricted to the lower reaches of the Bitou tributary and a few sections of the Keurbooms tributary. Presumeably because of fine sediment habitat in the confluence and lower Bitou tributary. The salinity of the estuarine water ranges between 0.1 – 26.9 and 3.2 – 35.3 in the Bitou and Keurbooms tributaries respectively. A typical salt wedge salinity pattern is common in the Keurbooms tributary where saline water often intrudes underneath the freshwater, especially during high river flows. The following hypotheses were developed and tested in this study: The limited spatial distribution of S. maritima in the Keurbooms Estuary is due to limited availability of fine sediment habitat; and the source of the fine sediment in the estuary is the Bitou tributary rather than the Keurbooms tributary or the sea. It was further postulated that after sediment characteristics, floods are the major hydrological driver determining the distribution of S. maritima in the Keurbooms Estuary. The results of the surveys of the estuarine channel bottom sediments showed that the Keurbooms tributary was mostly characterized by the sand-size sediment fraction derived from the feldspathic and sandstone with evidence of fine sediment fractions restricted to the upper reaches at the confluence with Whiskey Creek. The Bitou was almost always composed of coarse sized sediments in the upper reaches, fine sediment deposits in the middle and lower reaches and medium sorted sand with almost no clay or calcium carbonate in the estuarine component below the confluence of the tributaries. These findings were further supported by the surface sediment deposited within the S. maritima intertidal salt marsh, which showed finer sediment deposits in the Bitou marsh compared to the Keurbooms marsh surface. Similar results were also found in the sediment cores, with the Keurbooms marsh sediment becoming finer with increasing depth whereas fine sediments reduced with depth in the Bitou marsh. The results of the sediment mineralogy indicated that the increased concentrations of clay minerals in the S. maritima surface sediments are derived from the Bokkeveld shale, siltstone and clay slate exposed above the N2 Bridge in the Keurbooms Estuary. GIS mapping shows that S. maritima has been declining over the past two decades, with rapid decreases especially evident after big flooding events. The GIS mapping also indicates that the patches of the S. maritima in the Keurbooms tributary are more exposed to big floods than the Bitou marsh. Despite showing an overall decline, S. maritima area coverage remained more consistent in the lower reaches of the Bitou tributary than in the Keurbooms tributary. Despite the larger and more persistent area cover, the S. maritima plants were shorter and less dense than the plants growing in the sandy substrate. The black/grey colouration of soil with increasing depth in the Bitou tributary was an indication of the reduced state of the soil caused by prolonged waterlogged conditions. The roots of S. maritima in both tributaries were mostly restricted to the sub-surface substrate layer (i.e. 0 – 0.25 m), although the Bitou populations showed more vegetative propagation than the Keurbooms populations. This mechanism of reproduction was also demonstrated during the transplant experiment which showed a greater number of new stem production in the fine sediment substrates compared to the sandy silt substrates. Although accretion rates were not determined in this study, the short-term sediment deposition rates revealed that sedimentation is active in the marshes of the Keurbooms Estuary. Therefore, in spite of showing a decline in area cover, the production of viable seed and observed vegetative propagation suggest that the S. maritima is likely to colonize open stable intertidal mudflats / sandflats, thus maintaining its distribution as an intertidal species in the salt marshes of the Keurbooms Estuary.
- Full Text:
- Date Issued: 2017
Inhalable particulate systems for anti-tubercular drug delivery
- Nkanga, Christian Isalomboto
- Authors: Nkanga, Christian Isalomboto
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37966 , vital:24720
- Description: Tuberculosis (TB) is a deadly infectious microbial disease that is currently dominating public health concerns. Among the pharmacological issues in the management of TB are the poor bioavailability of some anti-TB drugs, mostly due to the fast first-pass metabolism, and high drug load needed for combination therapy. These result in a lengthy treatment with several adverse effects causing decreased patient compliance. These factors often lead to the therapeutic failure and promote the development of drug resistant strains, justifying the urgent need for new therapeutic strategies. Liposomes are lipid-based particulate vehicles known to be the most clinically appointed drug carriers currently. Liposomal systems are reported to be rapidly engulfed by macrophages - where the mycobacterium often resides. This makes liposomes appropriate vehicles for targeted anti-TB drug delivery. Many research groups have reported the potential of liposomes systems to deliver anti-TB drugs. However, the costly formulation status of liposomes, due the use of expensive synthetic or highly purified natural phospholipids, is a limitation to the treatment of a poverty related infectious disease like TB. The aim of this study was to design and develop liposomes for pulmonary delivery of anti-TB drugs using crude soybean lecithin (CL) and its purirified version. CL is an FDA- approved naturally occurring phospholipid mixture that is quite cheap and readily available. Various liposome batches were prepared using a film hydration method and characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Liposomes composed of CL and cholesterol (Chol) in a 3:1 mass ratio were selected for drug encapsulation based on the following characteristics: polydispersity index (PDI, 0.28), mean particles sizes (PS, 502 nm) and zeta potential (ZP, -56 mV). Isoniazid (INH) was encapsulated as a model drug using a freeze-thaw loading technique and an HPLC method was validated for quantitative analysis. The physicochemical properties of INH-loaded liposomes were comprehensively investigated using thermal, microscopy and spectroscopic techniques. This formulation showed a high encapsulation efficiency (%EE) of 78%, much better than the liposomes made from purified lecithin, 20%. Other characteristics of INH- loaded liposomes, which make them attractive for pulmonary TB therapy, are presented in this dissertation. These include a controlled release of 50% of the encapsulated INH over 12 hours. Finally, rifampicin (RIF) was added as a hydrophobic model drug and several evaluations were conducted on these dual drug-loaded liposomes. Of particular interest, it was noted that the dual drug-loaded liposomes made of CL alone showed the highest %EE (59% for INH and 90% for RIF) compared to those containing Chol or those made of purified lecithin. Surprisingly, the average PS of the dual CL-based liposomes (1114 nm) was in the size range reported for optimum deep lung deposition and macrophage uptake. In addition, the mean ZP of these liposomes (-63 mV) seems to be favourable for their shelf stability and internalization by macrophages. Overall, these findings show that the dual CL-based liposomes developed would be promising for macrophage-targeting pulmonary delivery of anti-TB drugs.
- Full Text:
- Date Issued: 2017
- Authors: Nkanga, Christian Isalomboto
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37966 , vital:24720
- Description: Tuberculosis (TB) is a deadly infectious microbial disease that is currently dominating public health concerns. Among the pharmacological issues in the management of TB are the poor bioavailability of some anti-TB drugs, mostly due to the fast first-pass metabolism, and high drug load needed for combination therapy. These result in a lengthy treatment with several adverse effects causing decreased patient compliance. These factors often lead to the therapeutic failure and promote the development of drug resistant strains, justifying the urgent need for new therapeutic strategies. Liposomes are lipid-based particulate vehicles known to be the most clinically appointed drug carriers currently. Liposomal systems are reported to be rapidly engulfed by macrophages - where the mycobacterium often resides. This makes liposomes appropriate vehicles for targeted anti-TB drug delivery. Many research groups have reported the potential of liposomes systems to deliver anti-TB drugs. However, the costly formulation status of liposomes, due the use of expensive synthetic or highly purified natural phospholipids, is a limitation to the treatment of a poverty related infectious disease like TB. The aim of this study was to design and develop liposomes for pulmonary delivery of anti-TB drugs using crude soybean lecithin (CL) and its purirified version. CL is an FDA- approved naturally occurring phospholipid mixture that is quite cheap and readily available. Various liposome batches were prepared using a film hydration method and characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Liposomes composed of CL and cholesterol (Chol) in a 3:1 mass ratio were selected for drug encapsulation based on the following characteristics: polydispersity index (PDI, 0.28), mean particles sizes (PS, 502 nm) and zeta potential (ZP, -56 mV). Isoniazid (INH) was encapsulated as a model drug using a freeze-thaw loading technique and an HPLC method was validated for quantitative analysis. The physicochemical properties of INH-loaded liposomes were comprehensively investigated using thermal, microscopy and spectroscopic techniques. This formulation showed a high encapsulation efficiency (%EE) of 78%, much better than the liposomes made from purified lecithin, 20%. Other characteristics of INH- loaded liposomes, which make them attractive for pulmonary TB therapy, are presented in this dissertation. These include a controlled release of 50% of the encapsulated INH over 12 hours. Finally, rifampicin (RIF) was added as a hydrophobic model drug and several evaluations were conducted on these dual drug-loaded liposomes. Of particular interest, it was noted that the dual drug-loaded liposomes made of CL alone showed the highest %EE (59% for INH and 90% for RIF) compared to those containing Chol or those made of purified lecithin. Surprisingly, the average PS of the dual CL-based liposomes (1114 nm) was in the size range reported for optimum deep lung deposition and macrophage uptake. In addition, the mean ZP of these liposomes (-63 mV) seems to be favourable for their shelf stability and internalization by macrophages. Overall, these findings show that the dual CL-based liposomes developed would be promising for macrophage-targeting pulmonary delivery of anti-TB drugs.
- Full Text:
- Date Issued: 2017
Integration of Eucalyptus coppice regeneration with mechanical harvesting in South Africa
- Schwegman, Kylle, Ackerman, S A
- Authors: Schwegman, Kylle , Ackerman, S A
- Date: 2017
- Subjects: Eucalyptus -- Regeneration Harvesting machinery
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21131 , vital:29443
- Description: In South Africa, ca. 530 000 ha of the plantation area is planted to Eucalyptus spp. which are native to Australia. Commercially grown hardwoods account for 40.5% of the total area planted to trees, yet contribute more than 70% of the timber to the pulpwood market. This is largely attributed to the superior quality of fibre and pulping properties associated with eucalypt plantations, increases in global short-fibre pulp demands. This as well as the ability to reduce the temporary unplanted period and associated re-establishment costs when choosing to regenerate a stand through coppice management. With the unlikelihood of additional eucalypts being introduced into South Africa, and a reduction in genetic gains from 3rd-4th generation tree breading programmes, most of the eucalypts currently planted will be managed for at least one coppice rotation before replanting with improved genetic material if available. This together with the increased use of mechanised silvicultural and harvesting operations, concerns have been raised as to whether the integration of Eucalyptus coppice regeneration and mechanical harvesting in South Africa is both possible and financially viable for the forest industry to practise. The need for integration becomes more important as often mechanised systems have smaller tolerance levels when compared to manual systems. The first trial was situated in Zululand and was implemented to determine the type and severity of stump damage, coppicing potential and coppice growth over the rotation, associated with four types of harvesting and extraction systems on coppice regeneration. Results obtained from these four treatments (harvesting systems that ranged from manual to fully mechanised cut-to-length systems), found that irrespective of the harvesting system used, more damage occurred to the top than bottom half of the stump, with a significant decrease in coppice regrowth with increasing stump damage. Most damage and least coppice regrowth occurred in the extraction rows where the damage recorded could be attributed to vehicle movement, tear-outs and/or log stripping. There was no significant difference between the harvesting systems in terms of stump mortality, final stem stocking and rotation-end volume. Although this trial indicates that the harvesting systems tested had no impact on tree production the severity of damage and/or difference may have been masked by the excellent coppice potential of the species used for this trial (E. grandis x E. urophylla). Based on the results obtained in the first trial, and using five existing data sets, each data set consisted of four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or) where possible to determine the cost benefits associated with each treatment at various levels of stocking over a full rotation period. BOP (best operating practice) and Or (original stocking) refers to treatments with two stems stump-1, and s (single stem) refers to one stem stump-1. Within each of the four treatment sub-sets, treatments with three levels of stump survival were sought (60%; 80%; 100%), in order to assess financial viability of harvesting different coppice regimes (one coppice stem and two coppiced stems stump-1) using a fully mechanised cut-to-length harvesting system was tested. No differences were found between one coppice stem and two coppiced stems stump-1 in terms of financial returns (internal rate of return). Of the four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or), treatments which had two coppice stems stump-1 lead to increased harvesting cost, while coppice stumps with one stem favours mechanised harvesting and reduced harvesting costs. The final trial, which was also implemented in Zululand, tested the timing of reduction of one coppice stem stump-1 at various stump and stem densities in order to develop an appropriate coppice regime that could favour fully mechanised CTL harvesting systems. Although significant differences were detected at 23 months between the additional control (current recommendation) and the various Reduction_ht (3.5 m, 4.5 m, and 6.5 m) treatments for Dbh, Ba, and Stocking. It is likely that these differences may become less with time due to the decrease in absolute and relative differences between the various treatments with time. This thesis indicates that it is possible to successfully integrate eucalypt coppice regeneration and fully mechanised CTL harvesting. As the results obtained showed that despite the harvesting-associated damage found, no significant difference occurred between the harvesting systems tested in terms of stump mortality, stem stocking (after the final reduction) and rotation-end volume. With regards to the financial implications (using internal rates of return - IRR) associated with harvesting coppice stands of one or two stems stump-1, no clear cost-benefits were found between either of these two treatment scenarios. As those factors that contribute to increased volumes per hectare (increased stem numbers and the retention of two stems stump-1), tend to become normalised across a treatment sub-set, this results in increased harvesting costs with a reduction in the IRR. Coppice management regimes need to be investigated that favour fully mechanised CTL harvesting systems (fewer stems to harvest, but with increased volumes per stem). This includes a reduction to one stem stump-1, as opposed to the current recommendations where some stumps have two stems, such as was tested in the final trial. Although initial results were promising, rotation-end data would be needed to determine any longer term impacts from carrying out an early thinning of coppice shoots to one stem stump-1. Future research needs to be carried out to: determine the influence of mechanised harvesting and extraction for difference species of eucalypts, especially for those that do not coppice as well as the species tested in these trials (Eucalyptus grandis x Eucalyptus urophylla), develop harvesting productivity and/or volume models for coppiced stands of one and two stems stump-1 for different Eucalyptus spp., determine financial returns using specifically designed coppice management regimes which optimise the integration of both mechanical harvesting and silvicultural perations.
- Full Text:
- Date Issued: 2017
- Authors: Schwegman, Kylle , Ackerman, S A
- Date: 2017
- Subjects: Eucalyptus -- Regeneration Harvesting machinery
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21131 , vital:29443
- Description: In South Africa, ca. 530 000 ha of the plantation area is planted to Eucalyptus spp. which are native to Australia. Commercially grown hardwoods account for 40.5% of the total area planted to trees, yet contribute more than 70% of the timber to the pulpwood market. This is largely attributed to the superior quality of fibre and pulping properties associated with eucalypt plantations, increases in global short-fibre pulp demands. This as well as the ability to reduce the temporary unplanted period and associated re-establishment costs when choosing to regenerate a stand through coppice management. With the unlikelihood of additional eucalypts being introduced into South Africa, and a reduction in genetic gains from 3rd-4th generation tree breading programmes, most of the eucalypts currently planted will be managed for at least one coppice rotation before replanting with improved genetic material if available. This together with the increased use of mechanised silvicultural and harvesting operations, concerns have been raised as to whether the integration of Eucalyptus coppice regeneration and mechanical harvesting in South Africa is both possible and financially viable for the forest industry to practise. The need for integration becomes more important as often mechanised systems have smaller tolerance levels when compared to manual systems. The first trial was situated in Zululand and was implemented to determine the type and severity of stump damage, coppicing potential and coppice growth over the rotation, associated with four types of harvesting and extraction systems on coppice regeneration. Results obtained from these four treatments (harvesting systems that ranged from manual to fully mechanised cut-to-length systems), found that irrespective of the harvesting system used, more damage occurred to the top than bottom half of the stump, with a significant decrease in coppice regrowth with increasing stump damage. Most damage and least coppice regrowth occurred in the extraction rows where the damage recorded could be attributed to vehicle movement, tear-outs and/or log stripping. There was no significant difference between the harvesting systems in terms of stump mortality, final stem stocking and rotation-end volume. Although this trial indicates that the harvesting systems tested had no impact on tree production the severity of damage and/or difference may have been masked by the excellent coppice potential of the species used for this trial (E. grandis x E. urophylla). Based on the results obtained in the first trial, and using five existing data sets, each data set consisted of four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or) where possible to determine the cost benefits associated with each treatment at various levels of stocking over a full rotation period. BOP (best operating practice) and Or (original stocking) refers to treatments with two stems stump-1, and s (single stem) refers to one stem stump-1. Within each of the four treatment sub-sets, treatments with three levels of stump survival were sought (60%; 80%; 100%), in order to assess financial viability of harvesting different coppice regimes (one coppice stem and two coppiced stems stump-1) using a fully mechanised cut-to-length harvesting system was tested. No differences were found between one coppice stem and two coppiced stems stump-1 in terms of financial returns (internal rate of return). Of the four treatment sub-sets (4m_8m_s; 2m_8m_s; 4m_8m_BOP; 2m_8m_Or), treatments which had two coppice stems stump-1 lead to increased harvesting cost, while coppice stumps with one stem favours mechanised harvesting and reduced harvesting costs. The final trial, which was also implemented in Zululand, tested the timing of reduction of one coppice stem stump-1 at various stump and stem densities in order to develop an appropriate coppice regime that could favour fully mechanised CTL harvesting systems. Although significant differences were detected at 23 months between the additional control (current recommendation) and the various Reduction_ht (3.5 m, 4.5 m, and 6.5 m) treatments for Dbh, Ba, and Stocking. It is likely that these differences may become less with time due to the decrease in absolute and relative differences between the various treatments with time. This thesis indicates that it is possible to successfully integrate eucalypt coppice regeneration and fully mechanised CTL harvesting. As the results obtained showed that despite the harvesting-associated damage found, no significant difference occurred between the harvesting systems tested in terms of stump mortality, stem stocking (after the final reduction) and rotation-end volume. With regards to the financial implications (using internal rates of return - IRR) associated with harvesting coppice stands of one or two stems stump-1, no clear cost-benefits were found between either of these two treatment scenarios. As those factors that contribute to increased volumes per hectare (increased stem numbers and the retention of two stems stump-1), tend to become normalised across a treatment sub-set, this results in increased harvesting costs with a reduction in the IRR. Coppice management regimes need to be investigated that favour fully mechanised CTL harvesting systems (fewer stems to harvest, but with increased volumes per stem). This includes a reduction to one stem stump-1, as opposed to the current recommendations where some stumps have two stems, such as was tested in the final trial. Although initial results were promising, rotation-end data would be needed to determine any longer term impacts from carrying out an early thinning of coppice shoots to one stem stump-1. Future research needs to be carried out to: determine the influence of mechanised harvesting and extraction for difference species of eucalypts, especially for those that do not coppice as well as the species tested in these trials (Eucalyptus grandis x Eucalyptus urophylla), develop harvesting productivity and/or volume models for coppiced stands of one and two stems stump-1 for different Eucalyptus spp., determine financial returns using specifically designed coppice management regimes which optimise the integration of both mechanical harvesting and silvicultural perations.
- Full Text:
- Date Issued: 2017
Interactions between two biological control agents released on Pereskia aculeata Miller (Cactaceae), in South Africa
- Authors: Mnqeta, Zezethu
- Date: 2017
- Subjects: Pereskia aculeata -- Biological control , Cactus -- Biological control -- South Africa , Alien plants -- Biological control -- South Africa , Flea beetles -- South Africa , Coreidae -- South Africa , Insects as biological pest control agents -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7949 , vital:21327
- Description: Pereskia aculeata Miller (Cactaceae) is an alien invasive plant introduced into South Africa from Brazil, which has negative impacts on native biodiversity in South Africa. Phenrica guerini Bechyne (Chrysomelidae) and Catorhintha schaffneri Brailovsky & Garcia (Coreidae) are two biological control agents released against P. aculeata in South Africa. Phenrica guerini was first released against P. aculeata, in 1991, followed by C. schaffneri in 2014. The overall aim of this study was to improve the biological control programme against P. aculeata in order to decrease its density to a level where it does not threaten the native biodiversity of South Africa. The first part of this study evaluated the efficacy of P. guerini on P. aculeata at Port Alfred (Eastern Cape) to better understand the role of P. guerini in the biological control of P. aculeata. An insecticide exclusion experiment was conducted over 100 days. Plots with P. guerini had a mean of 187 (SE ± 62) fewer leaves/m2 than plots without P. guerini. The agent reduced percentage cover in plots with P. guerini, with a mean of 19.42% (SE ± 3.15) lower cover than plots without P. guerini. Although P. guerini had an impact on P. aculeata at Port Alfred previous studies have indicated that a reduction to below 50% cover is required for native biodiversity to recover and the agent only reduced cover to 62% at Port Alfred. Phenrica guerini has therefore not reduced percentage cover sufficiently to completely control the weed. The data collected from Port Alfred was compared to the performance of the agent nationwide. Although P. guerini was found at far more sites than previously recorded, there were very few sites with comparable levels of damage to Port Alfred. This evidence suggests that P. guerini is not sufficiently damaging to reduce P. aculeata to acceptable levels and other biological control agents should be considered.Interactions between two biological control agents can have complex and unexpected impacts for a biological control programme. The second part of this study was to investigate interactions between C. schaffneri and P. guerini under laboratory conditions to test whether the two agents, individually or jointly, enhanced or reduced their impact on P. aculeata. Potted P. aculeata plants were exposed to one of four treatments: control (no agents), P. guerini only, C. schaffneri only and both species in combination. Four stocking densities, ranging from 2 to 12 insects per plant were used. Catorhintha schaffneri alone at high densities was more damaging than all other treatments with a significantly greater reduction in the mean number of leaves, 11.7 (SE ± 1.29), and shoot lengths, 2.17cm (SE ± O. 75). Even at lower density treatments, the combination of the two agents was not significantly more damaging than C. schaffneri alone and C. schaffneri was always more damaging than P. guerini alone. Mortality of P. guerini was significantly higher than C. schaffneri at the highest stocking density when in combination. Phenrica guerini contributes towards the biological control of P. aculeata at some sites in South Africa but not enough to completely control the weed. The antagonistic interaction between P. guerini and C. schaffneri suggests that these agents should not be released together because this would impact negatively on the overall biocontrol programme against P. aculeata. Catorhintha schaffneri should be released at sites were P. guerini is not present and evaluations of the success of this agent in the field should be conducted. Extrapolation of laboratory-based studies into the field is often challenging so mass-rearing of P. guerini should continue until there is convincing proof that C. schaffneri alone is more effective than P. guerini in the field.
- Full Text:
- Date Issued: 2017
- Authors: Mnqeta, Zezethu
- Date: 2017
- Subjects: Pereskia aculeata -- Biological control , Cactus -- Biological control -- South Africa , Alien plants -- Biological control -- South Africa , Flea beetles -- South Africa , Coreidae -- South Africa , Insects as biological pest control agents -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7949 , vital:21327
- Description: Pereskia aculeata Miller (Cactaceae) is an alien invasive plant introduced into South Africa from Brazil, which has negative impacts on native biodiversity in South Africa. Phenrica guerini Bechyne (Chrysomelidae) and Catorhintha schaffneri Brailovsky & Garcia (Coreidae) are two biological control agents released against P. aculeata in South Africa. Phenrica guerini was first released against P. aculeata, in 1991, followed by C. schaffneri in 2014. The overall aim of this study was to improve the biological control programme against P. aculeata in order to decrease its density to a level where it does not threaten the native biodiversity of South Africa. The first part of this study evaluated the efficacy of P. guerini on P. aculeata at Port Alfred (Eastern Cape) to better understand the role of P. guerini in the biological control of P. aculeata. An insecticide exclusion experiment was conducted over 100 days. Plots with P. guerini had a mean of 187 (SE ± 62) fewer leaves/m2 than plots without P. guerini. The agent reduced percentage cover in plots with P. guerini, with a mean of 19.42% (SE ± 3.15) lower cover than plots without P. guerini. Although P. guerini had an impact on P. aculeata at Port Alfred previous studies have indicated that a reduction to below 50% cover is required for native biodiversity to recover and the agent only reduced cover to 62% at Port Alfred. Phenrica guerini has therefore not reduced percentage cover sufficiently to completely control the weed. The data collected from Port Alfred was compared to the performance of the agent nationwide. Although P. guerini was found at far more sites than previously recorded, there were very few sites with comparable levels of damage to Port Alfred. This evidence suggests that P. guerini is not sufficiently damaging to reduce P. aculeata to acceptable levels and other biological control agents should be considered.Interactions between two biological control agents can have complex and unexpected impacts for a biological control programme. The second part of this study was to investigate interactions between C. schaffneri and P. guerini under laboratory conditions to test whether the two agents, individually or jointly, enhanced or reduced their impact on P. aculeata. Potted P. aculeata plants were exposed to one of four treatments: control (no agents), P. guerini only, C. schaffneri only and both species in combination. Four stocking densities, ranging from 2 to 12 insects per plant were used. Catorhintha schaffneri alone at high densities was more damaging than all other treatments with a significantly greater reduction in the mean number of leaves, 11.7 (SE ± 1.29), and shoot lengths, 2.17cm (SE ± O. 75). Even at lower density treatments, the combination of the two agents was not significantly more damaging than C. schaffneri alone and C. schaffneri was always more damaging than P. guerini alone. Mortality of P. guerini was significantly higher than C. schaffneri at the highest stocking density when in combination. Phenrica guerini contributes towards the biological control of P. aculeata at some sites in South Africa but not enough to completely control the weed. The antagonistic interaction between P. guerini and C. schaffneri suggests that these agents should not be released together because this would impact negatively on the overall biocontrol programme against P. aculeata. Catorhintha schaffneri should be released at sites were P. guerini is not present and evaluations of the success of this agent in the field should be conducted. Extrapolation of laboratory-based studies into the field is often challenging so mass-rearing of P. guerini should continue until there is convincing proof that C. schaffneri alone is more effective than P. guerini in the field.
- Full Text:
- Date Issued: 2017
Invasion status and potential impacts of bluegill Lepomis macrochirus Rafinesque, 1819 in the Kariega River, Eastern Cape, South Africa
- Authors: Ndaleni, Phumza Malibongwe
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7586 , vital:21276
- Description: The impact of alien invasive species is one of the greatest threats to biodiversity globally. All of the major drainages of South Africa are invaded by non-native fishes, yet little information is available on their impact. This thesis focusses on providing a better understanding of the potential impacts of bluegill Lepomis macrochirus Rafinesque, 1819, a species introduced into South Africa from the USA in 1938. The study assesses the distribution, establishment success and feeding ecology of L. macrochirus in an invaded South African River system in order to better understand and document its potential impacts. Specifically; this thesis (1) assesses the distribution and relative abundance of L. macrochirus in the Kariega System of the Eastern Cape, (2) determines the diet of the species in one of the major impoundments of the system, and (3) uses an experimental comparative functional response approach to assess whether this species has heightened predatory capabilities when compared with fishes with which it cooccurs. Ninety-six sites in the Kariega River system were sampled from the headwaters down to the estuary. Small native fish species (Enteromius anoplus and Enteromius pallidus) occurred mostly in the upper reaches, while in the middle and lower reaches, the centrarchid alien largemouth bass Micropterus salmoides and bluegill L. mocrochirus dominated. There was overlap between the centrarchids and introduced banded tilapia Tilapia sparrmanii and southern mouthbrooder Pseudocrenilabrus philander, but never with small-bodied native species. The stomach contents of L. macrochirus were examined during winter and summer and prey were identified to family level. Crustaceans and insects were an important component in their diet, but in summer fish eggs were common. Comparisons of bluegill diet with published literature indicated that there was potential for competition with largemouth bass, banded tilapia and southern mouthbrooder. Feeding experiments were conducted to compare the functional responses of these four species using a common prey item. Banded tilapia had significantly lower attack rates than the other species with no significant difference observed in other species. Bluegill has a similar impact to that of banded tilapia and southern mouthbrooder, but lower than that of largemouth bass. Results of the present study highlight that L. macrochirus introduced into dams will likely result in both upstream and downstream invasion of river systems. It is likely that this species does not, however, have as much of a predatory impact as M. salmoides in that its predatory capacity is relatively reduced and more comparable to South African native cichlids. These results are discussed within the context of invasion success/failure in other regions of southern Africa.
- Full Text:
- Date Issued: 2017
- Authors: Ndaleni, Phumza Malibongwe
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7586 , vital:21276
- Description: The impact of alien invasive species is one of the greatest threats to biodiversity globally. All of the major drainages of South Africa are invaded by non-native fishes, yet little information is available on their impact. This thesis focusses on providing a better understanding of the potential impacts of bluegill Lepomis macrochirus Rafinesque, 1819, a species introduced into South Africa from the USA in 1938. The study assesses the distribution, establishment success and feeding ecology of L. macrochirus in an invaded South African River system in order to better understand and document its potential impacts. Specifically; this thesis (1) assesses the distribution and relative abundance of L. macrochirus in the Kariega System of the Eastern Cape, (2) determines the diet of the species in one of the major impoundments of the system, and (3) uses an experimental comparative functional response approach to assess whether this species has heightened predatory capabilities when compared with fishes with which it cooccurs. Ninety-six sites in the Kariega River system were sampled from the headwaters down to the estuary. Small native fish species (Enteromius anoplus and Enteromius pallidus) occurred mostly in the upper reaches, while in the middle and lower reaches, the centrarchid alien largemouth bass Micropterus salmoides and bluegill L. mocrochirus dominated. There was overlap between the centrarchids and introduced banded tilapia Tilapia sparrmanii and southern mouthbrooder Pseudocrenilabrus philander, but never with small-bodied native species. The stomach contents of L. macrochirus were examined during winter and summer and prey were identified to family level. Crustaceans and insects were an important component in their diet, but in summer fish eggs were common. Comparisons of bluegill diet with published literature indicated that there was potential for competition with largemouth bass, banded tilapia and southern mouthbrooder. Feeding experiments were conducted to compare the functional responses of these four species using a common prey item. Banded tilapia had significantly lower attack rates than the other species with no significant difference observed in other species. Bluegill has a similar impact to that of banded tilapia and southern mouthbrooder, but lower than that of largemouth bass. Results of the present study highlight that L. macrochirus introduced into dams will likely result in both upstream and downstream invasion of river systems. It is likely that this species does not, however, have as much of a predatory impact as M. salmoides in that its predatory capacity is relatively reduced and more comparable to South African native cichlids. These results are discussed within the context of invasion success/failure in other regions of southern Africa.
- Full Text:
- Date Issued: 2017
Investigating adaptation strategies to climate change by smallholder farmers : evidence from, Lesotho
- Authors: Morahanye, Mokhantso Lilian
- Date: 2017
- Subjects: Climatic changes -- South Africa Farms, Small -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5807 , vital:29397
- Description: In Lesotho, agriculture is the dominant activity and involves crop and livestock production, range management and forestry activities. The current climatic variability in the country has caused decline in food production as result of increased dry spells, frequency of droughts and erratic rainfall. These climatic events are expected to have a significant impact on the livelihoods of the smallholder farmers. In combatting the harmful effects of climate change, smallholder farmers in Lesotho have employed various adaptation strategies based on their local knowledge and limited means. While these strategies may not be optimal they obviously constitute the basis for potentially effective improved technologies which can be developed and communicated through an efficient extension system, hence the need to precisely identify them and understand the factors that affect their choice. The main objective of this study was therefore, to identify the adaptation strategies and investigate the factors influencing smallholder farmers’ choice of those adaptation strategies. The study made use of multi-stage stratified sampling technique to select 160 respondents across four agro-ecological zones (lowlands, highlands, foothills and Senqu River Valley) in Leribe and Mohales’Hoek districts of Lesotho. Primary data for the study were collected using semi - structured questionnaire assisted with interview schedules administered on the respondents. Data collected were analysed using descriptive statistics and the multinomial logistics regression model. The results show that there are more males than females, majority of the respondents’ attained primary education, and older people dominate the smallholder farming system. The adaptation strategies used in MNL model were soil and water management, crop management and livestock management. The results further revealed that soil and water management strategies were the most adopted climate change strategies amongst smallholder farmers. It is understood that marital status, age and gender, income, land tenure, crop grown, extension services, and agro-ecological zones are the determinant factors influencing the choice of the adaptation strategies. This study concludes by recommending that smallholder farmers should be sensitised about climate change and both government and non-government organisations working on climate change related issues should direct their attention to rural communities to ensure effective response to climate change.
- Full Text:
- Date Issued: 2017
- Authors: Morahanye, Mokhantso Lilian
- Date: 2017
- Subjects: Climatic changes -- South Africa Farms, Small -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5807 , vital:29397
- Description: In Lesotho, agriculture is the dominant activity and involves crop and livestock production, range management and forestry activities. The current climatic variability in the country has caused decline in food production as result of increased dry spells, frequency of droughts and erratic rainfall. These climatic events are expected to have a significant impact on the livelihoods of the smallholder farmers. In combatting the harmful effects of climate change, smallholder farmers in Lesotho have employed various adaptation strategies based on their local knowledge and limited means. While these strategies may not be optimal they obviously constitute the basis for potentially effective improved technologies which can be developed and communicated through an efficient extension system, hence the need to precisely identify them and understand the factors that affect their choice. The main objective of this study was therefore, to identify the adaptation strategies and investigate the factors influencing smallholder farmers’ choice of those adaptation strategies. The study made use of multi-stage stratified sampling technique to select 160 respondents across four agro-ecological zones (lowlands, highlands, foothills and Senqu River Valley) in Leribe and Mohales’Hoek districts of Lesotho. Primary data for the study were collected using semi - structured questionnaire assisted with interview schedules administered on the respondents. Data collected were analysed using descriptive statistics and the multinomial logistics regression model. The results show that there are more males than females, majority of the respondents’ attained primary education, and older people dominate the smallholder farming system. The adaptation strategies used in MNL model were soil and water management, crop management and livestock management. The results further revealed that soil and water management strategies were the most adopted climate change strategies amongst smallholder farmers. It is understood that marital status, age and gender, income, land tenure, crop grown, extension services, and agro-ecological zones are the determinant factors influencing the choice of the adaptation strategies. This study concludes by recommending that smallholder farmers should be sensitised about climate change and both government and non-government organisations working on climate change related issues should direct their attention to rural communities to ensure effective response to climate change.
- Full Text:
- Date Issued: 2017
Investigation of the potency of topical corticosteroids using the vasoconstrictor assay
- Authors: Zvidzayi, Kudzayi Michael
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65279 , vital:28717
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Zvidzayi, Kudzayi Michael
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65279 , vital:28717
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
Ionospheric disturbances during magnetic storms at SANAE
- Authors: Hiyadutuje, Alicreance
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54956 , vital:26639
- Description: The coronal mass ejections (CMEs) and solar flares associated with extreme solar activity may strike the Earth's magnetosphere and give rise to geomagnetic storms. During geomagnetic storms, the polar plasma dynamics may influence the middle and low-latitude ionosphere via travelling ionospheric disturbances (TIDs). These are wave-like electron density disturbances caused by atmospheric gravity waves propagating in the ionosphere. TIDs focus and defocus SuperDARN signals producing a characteristic pattern of ground backscattered power (Samson et al., 1989). Geomagnetic storms may cause a decrease of total electron content (TEC), i.e. a negative storm effect, or/and an increase of TEC, i.e. a positive storm effect. The aim of this project was to investigate the ionospheric response to strong storms (Dst < -100 nT) between 2011 and 2015, using TEC and scintillation measurements derived from GPS receivers as well as SuperDARN power, Doppler velocity and convection maps. In this study the ionosphere's response to geomagnetic storms is determined by the magnitude and time of occurrence of the geomagnetic storm. The ionospheric TEC results of this study show that most of the storm effects observed were a combination of both negative and positive per storm per station (77.8%), and only 8.9% and 13.3% of effects on TEC were negative and positive respectively. The highest number of storm effects occurred in autumn (36.4%), while 31.6%, 28.4% and 3.6% occurred in winter, spring and summer respectively. During the storms studied, 71.4% had phase scintillation in the range of 0.7 - 1 radians, and only 14.3% of the storms had amplitude scintillations near 0.4. The storms studied at SANAE station generated TIDs with periods of less than an hour and amplitudes in the range 0.2 - 5 TECU. These TIDs were found to originate from the high-velocity plasma flows, some of which are visible in SuperDARN convection maps. Early studies concluded that likely sources of these disturbances correspond to ionospheric current surges (Bristow et al., 1994) in the dayside auroral zone (Huang et al., 1998).
- Full Text:
- Date Issued: 2017
- Authors: Hiyadutuje, Alicreance
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54956 , vital:26639
- Description: The coronal mass ejections (CMEs) and solar flares associated with extreme solar activity may strike the Earth's magnetosphere and give rise to geomagnetic storms. During geomagnetic storms, the polar plasma dynamics may influence the middle and low-latitude ionosphere via travelling ionospheric disturbances (TIDs). These are wave-like electron density disturbances caused by atmospheric gravity waves propagating in the ionosphere. TIDs focus and defocus SuperDARN signals producing a characteristic pattern of ground backscattered power (Samson et al., 1989). Geomagnetic storms may cause a decrease of total electron content (TEC), i.e. a negative storm effect, or/and an increase of TEC, i.e. a positive storm effect. The aim of this project was to investigate the ionospheric response to strong storms (Dst < -100 nT) between 2011 and 2015, using TEC and scintillation measurements derived from GPS receivers as well as SuperDARN power, Doppler velocity and convection maps. In this study the ionosphere's response to geomagnetic storms is determined by the magnitude and time of occurrence of the geomagnetic storm. The ionospheric TEC results of this study show that most of the storm effects observed were a combination of both negative and positive per storm per station (77.8%), and only 8.9% and 13.3% of effects on TEC were negative and positive respectively. The highest number of storm effects occurred in autumn (36.4%), while 31.6%, 28.4% and 3.6% occurred in winter, spring and summer respectively. During the storms studied, 71.4% had phase scintillation in the range of 0.7 - 1 radians, and only 14.3% of the storms had amplitude scintillations near 0.4. The storms studied at SANAE station generated TIDs with periods of less than an hour and amplitudes in the range 0.2 - 5 TECU. These TIDs were found to originate from the high-velocity plasma flows, some of which are visible in SuperDARN convection maps. Early studies concluded that likely sources of these disturbances correspond to ionospheric current surges (Bristow et al., 1994) in the dayside auroral zone (Huang et al., 1998).
- Full Text:
- Date Issued: 2017
Linking livelihood and ecosystem change in two dryland sites in Southern Africa over a period of 30 years
- Authors: Masunungure, Current
- Date: 2017
- Subjects: Marwendo Village (Zimbabwe) -- Social conditions , Tshivhulani Village (South Africa) -- Social conditions , Marwendo Village (Zimbabwe) -- Environmental conditions , Tshivhulani Village (South Africa) -- Environmental conditions , Climatic changes -- South Africa -- Tshivhulani Village , Climatic changes -- Zimbabwe -- Marwendo Village
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4819 , vital:20732
- Description: The ongoing and rapid change (from global to local level) in climate, populations, governments, cultures, environment, land use and economies are critical issues, especially for poor rural communities found in the dryland parts of southern Africa. The manifestations of change can combine to increase rural livelihood vulnerability, through the erosion of assets and insecurity, but can at the same time create new opportunities. Studies that consider the complex nature of change across scales and how it affects changes in livelihoods, ecosystems and responses at local level, are increasingly needed. This study, carried out in two purposefully selected study sites in the communal drylands of south-eastern Zimbabwe (Marwendo village) and Limpopo province in South Africa (Tshivhulani village), examined the complex nature of change across scales by assessing the way in which change at the global scale results in localised trends, shocks and stressors, and its impacts on livelihoods and ecosystems and responses over the past 30 years. The study applies social-ecological system thinking in understanding human-environment change. Particular emphasis was put on the role of social protection and natural resources in responding to change, shocks and stressors. The study employed a mixed method approach to gather data which included a household survey, life history interviews, transect walks, focus group discussions as well as secondary sources of information. The results of the study illustrate that shocks and stressors are common in both villages and are likely to increase in severity and frequency with ongoing and rapid human-environmental change, especially climate change. The local responses to change, shocks and stressors are primarily reactive and mainly intensify exploitation of existing natural resources and social protection as safety-nets. In Marwendo village, the villagers relied more on the use and sale of natural resource products readily available to them, whereas in Tshivhulani village they mainly tend to rely on social grants. Thus, in the future, households’ vulnerability might increase, and may be worse in Marwendo village, since important components of current livelihoods remain natural resource-based and climate sensitive. In Tshivhulani village, livelihoods characterised by high dependence on social grants can have severe consequences for households as children get older or elderly members die and grants cease to be available. Social grants therefore only really offer a temporary relief. This coupled with environmentally destructive practices such as brick-moulding in Marwendo village and uncontrolled settlements in Tshivhulani village may reinforce the negative impacts of change and thus undermine sustainable adaptation. The study concludes that multiple lenses for understanding the links between livelihood and ecosystem vulnerability in the context of the ongoing and rapid change are essential, and these provide insights into how different policy options for livelihood improvement and social protection might be appropriate for reducing household and ecosystem vulnerabilities in the future.
- Full Text:
- Date Issued: 2017
- Authors: Masunungure, Current
- Date: 2017
- Subjects: Marwendo Village (Zimbabwe) -- Social conditions , Tshivhulani Village (South Africa) -- Social conditions , Marwendo Village (Zimbabwe) -- Environmental conditions , Tshivhulani Village (South Africa) -- Environmental conditions , Climatic changes -- South Africa -- Tshivhulani Village , Climatic changes -- Zimbabwe -- Marwendo Village
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4819 , vital:20732
- Description: The ongoing and rapid change (from global to local level) in climate, populations, governments, cultures, environment, land use and economies are critical issues, especially for poor rural communities found in the dryland parts of southern Africa. The manifestations of change can combine to increase rural livelihood vulnerability, through the erosion of assets and insecurity, but can at the same time create new opportunities. Studies that consider the complex nature of change across scales and how it affects changes in livelihoods, ecosystems and responses at local level, are increasingly needed. This study, carried out in two purposefully selected study sites in the communal drylands of south-eastern Zimbabwe (Marwendo village) and Limpopo province in South Africa (Tshivhulani village), examined the complex nature of change across scales by assessing the way in which change at the global scale results in localised trends, shocks and stressors, and its impacts on livelihoods and ecosystems and responses over the past 30 years. The study applies social-ecological system thinking in understanding human-environment change. Particular emphasis was put on the role of social protection and natural resources in responding to change, shocks and stressors. The study employed a mixed method approach to gather data which included a household survey, life history interviews, transect walks, focus group discussions as well as secondary sources of information. The results of the study illustrate that shocks and stressors are common in both villages and are likely to increase in severity and frequency with ongoing and rapid human-environmental change, especially climate change. The local responses to change, shocks and stressors are primarily reactive and mainly intensify exploitation of existing natural resources and social protection as safety-nets. In Marwendo village, the villagers relied more on the use and sale of natural resource products readily available to them, whereas in Tshivhulani village they mainly tend to rely on social grants. Thus, in the future, households’ vulnerability might increase, and may be worse in Marwendo village, since important components of current livelihoods remain natural resource-based and climate sensitive. In Tshivhulani village, livelihoods characterised by high dependence on social grants can have severe consequences for households as children get older or elderly members die and grants cease to be available. Social grants therefore only really offer a temporary relief. This coupled with environmentally destructive practices such as brick-moulding in Marwendo village and uncontrolled settlements in Tshivhulani village may reinforce the negative impacts of change and thus undermine sustainable adaptation. The study concludes that multiple lenses for understanding the links between livelihood and ecosystem vulnerability in the context of the ongoing and rapid change are essential, and these provide insights into how different policy options for livelihood improvement and social protection might be appropriate for reducing household and ecosystem vulnerabilities in the future.
- Full Text:
- Date Issued: 2017
Maize stalk fibre reinforced natural rubber/tyre-tread reclaimed rubber composites
- Authors: Mente, Pumza
- Date: 2017
- Subjects: Polymeric composites Rubber
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19332 , vital:28852
- Description: This research project focuses on the production of reclaimed rubber composites reinforced with natural fibres obtained from agricultural waste. The prepared natural fibre composites were characterized through evaluation of curing characteristics, tensile properties, thermal properties, dynamic mechanical properties and electron microscopy imaging. Untreated composites generally showed poor properties which were attributed to poor compatibility and fibre agglomeration. Various treatments were then employed in attempts to improve the composite properties. Fibre treatments used were water treatment and silane treatments using two different silane coupling agents. Torque, reaction rate and tensile modulus were observed to increase with addition of reclaimed rubber and natural fibres. Tensile strength and elongation at break increased with addition of natural rubber. An increase in thermal stability was observed with addition of reclaimed rubber. Dynamic mechanical analysis (DMA) results have shown that addition of reclaimed rubber resulted to an increase in glass transition temperature. Scanning electron microscopy (SEM) images of tensile fractured composites showed evidence of fibre pull-outs from the matrix. Removal of lignin from treated natural fibres was evident from thermogravimetric analysis (TGA) for all fibre treatments. There were no noticeable improvements in composites properties with use of fibre treatments and there were no statistical differences observed among the different fibre treatments. Generally, the composites prepared showed high stiffness and low tensile strength.
- Full Text:
- Date Issued: 2017
- Authors: Mente, Pumza
- Date: 2017
- Subjects: Polymeric composites Rubber
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19332 , vital:28852
- Description: This research project focuses on the production of reclaimed rubber composites reinforced with natural fibres obtained from agricultural waste. The prepared natural fibre composites were characterized through evaluation of curing characteristics, tensile properties, thermal properties, dynamic mechanical properties and electron microscopy imaging. Untreated composites generally showed poor properties which were attributed to poor compatibility and fibre agglomeration. Various treatments were then employed in attempts to improve the composite properties. Fibre treatments used were water treatment and silane treatments using two different silane coupling agents. Torque, reaction rate and tensile modulus were observed to increase with addition of reclaimed rubber and natural fibres. Tensile strength and elongation at break increased with addition of natural rubber. An increase in thermal stability was observed with addition of reclaimed rubber. Dynamic mechanical analysis (DMA) results have shown that addition of reclaimed rubber resulted to an increase in glass transition temperature. Scanning electron microscopy (SEM) images of tensile fractured composites showed evidence of fibre pull-outs from the matrix. Removal of lignin from treated natural fibres was evident from thermogravimetric analysis (TGA) for all fibre treatments. There were no noticeable improvements in composites properties with use of fibre treatments and there were no statistical differences observed among the different fibre treatments. Generally, the composites prepared showed high stiffness and low tensile strength.
- Full Text:
- Date Issued: 2017
MEQSILHOUETTE: a mm-VLBI observation and signal corruption simulator
- Authors: Blecher, Tariq
- Date: 2017
- Subjects: Large astronomical telescopes , Very long baseline interferometry , MEQSILHOUETTE (Software) , Event horizon telescope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/40713 , vital:25019
- Description: The Event Horizon Telescope (EHT) aims to resolve the innermost emission of nearby supermassive black holes, Sgr A* and M87, on event horizon scales. This emission is predicted to be gravitationally lensed by the black hole which should produce a shadow (or silhouette) feature, a precise measurement of which is a test of gravity in the strong-field regime. This emission is also an ideal probe of the innermost accretion and jet-launch physics, offering the new insights into this data-limited observing regime. The EHT will use the technique of Very Long Baseline Interferometry (VLBI) at (sub)millimetre wavelengths, which has a diffraction limited angular resolution of order ~ 10 µ-arcsec. However, this technique suffers from unique challenges, including scattering and attenuation in the troposphere and interstellar medium; variable source structure; as well as antenna pointing errors comparable to the size of the primary beam. In this thesis, we present the meqsilhouette software package which is focused towards simulating realistic EHT data. It has the capability to simulate a time-variable source, and includes realistic descriptions of the effects of the troposphere, the interstellar medium as well as primary beams and associated antenna pointing errors. We have demonstrated through several examples simulations that these effects can limit the ability to measure the key science parameters. This simulator can be used to research calibration, parameter estimation and imaging strategies, as well as gain insight into possible systematic uncertainties.
- Full Text:
- Date Issued: 2017
- Authors: Blecher, Tariq
- Date: 2017
- Subjects: Large astronomical telescopes , Very long baseline interferometry , MEQSILHOUETTE (Software) , Event horizon telescope
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/40713 , vital:25019
- Description: The Event Horizon Telescope (EHT) aims to resolve the innermost emission of nearby supermassive black holes, Sgr A* and M87, on event horizon scales. This emission is predicted to be gravitationally lensed by the black hole which should produce a shadow (or silhouette) feature, a precise measurement of which is a test of gravity in the strong-field regime. This emission is also an ideal probe of the innermost accretion and jet-launch physics, offering the new insights into this data-limited observing regime. The EHT will use the technique of Very Long Baseline Interferometry (VLBI) at (sub)millimetre wavelengths, which has a diffraction limited angular resolution of order ~ 10 µ-arcsec. However, this technique suffers from unique challenges, including scattering and attenuation in the troposphere and interstellar medium; variable source structure; as well as antenna pointing errors comparable to the size of the primary beam. In this thesis, we present the meqsilhouette software package which is focused towards simulating realistic EHT data. It has the capability to simulate a time-variable source, and includes realistic descriptions of the effects of the troposphere, the interstellar medium as well as primary beams and associated antenna pointing errors. We have demonstrated through several examples simulations that these effects can limit the ability to measure the key science parameters. This simulator can be used to research calibration, parameter estimation and imaging strategies, as well as gain insight into possible systematic uncertainties.
- Full Text:
- Date Issued: 2017
Microencapsulation of anti-tuberculosis drugs using sporopollenin
- Authors: Mhlana, Kanyisile
- Date: 2017
- Subjects: Mycobacterium tuberculosis -- South Africa -- Prevention Microencapsulation , Plant spores
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13912 , vital:27357
- Description: In this thesis, we explore the benefits of microencapsulating isoniazid and pyrazinamide within sporopollenin exine capsules derived from Lycopodium clavatum. Sporopollenin is a natural biopolymer, which is extracted from the outer shell of pollen grains. These hollow microcapsules can encapsulate and release drug actives in a controlled manner and possess many other advantages such as homogeneity in morphology and size, resilience to both strong acids and bases, they have antioxidant properties as well as UV protection to protect the material inside the microcapsule. Compared to artificial microcapsules, sporopollenin’s muco-adhesion to intestinal tissues contributes greatly to the extended contact of the sporopollenin with the intestines leading to an increased efficiency of delivery of drugs. The hollow microcapsules can be easily filled with a solution of the active or active in a liquid form by simply mixing both together. The drug actives are released in the human body depending on pH factors. Active release can otherwise have controlled by adding a coating on the shell, or co-encapsulation with the active inside the shell so that high drug concentrations are delivered to the site of infection. Encapsulation of the drug active will possibly improve therapeutic abilities of the drugs; simplify the treatment of TB-HIV coinfections by eliminating troublesome drug-drug interactions and drastically reduce or eliminates side effects. The SECs were loaded using a passive filling method. The drug active (0.1 g) was dissolved in a solvent and mixed with the SECs (0.1 g) for 10 minutes. After mixing for 10 minutes, the solvent was removed by a rotary evaporator and dried to a constant mass. The surface of the sporopollenin exines were analysed on a FTIR to observe if there are any drug deposits on the surface of the SECs. The loading efficiency and drug release percentage was determined by using calibrations curves and analysed on a UV-vis spectrophotometer. Further work has been proposed in which to characterize the SECs further and producing coated tablets from loaded SECs.
- Full Text:
- Date Issued: 2017
- Authors: Mhlana, Kanyisile
- Date: 2017
- Subjects: Mycobacterium tuberculosis -- South Africa -- Prevention Microencapsulation , Plant spores
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13912 , vital:27357
- Description: In this thesis, we explore the benefits of microencapsulating isoniazid and pyrazinamide within sporopollenin exine capsules derived from Lycopodium clavatum. Sporopollenin is a natural biopolymer, which is extracted from the outer shell of pollen grains. These hollow microcapsules can encapsulate and release drug actives in a controlled manner and possess many other advantages such as homogeneity in morphology and size, resilience to both strong acids and bases, they have antioxidant properties as well as UV protection to protect the material inside the microcapsule. Compared to artificial microcapsules, sporopollenin’s muco-adhesion to intestinal tissues contributes greatly to the extended contact of the sporopollenin with the intestines leading to an increased efficiency of delivery of drugs. The hollow microcapsules can be easily filled with a solution of the active or active in a liquid form by simply mixing both together. The drug actives are released in the human body depending on pH factors. Active release can otherwise have controlled by adding a coating on the shell, or co-encapsulation with the active inside the shell so that high drug concentrations are delivered to the site of infection. Encapsulation of the drug active will possibly improve therapeutic abilities of the drugs; simplify the treatment of TB-HIV coinfections by eliminating troublesome drug-drug interactions and drastically reduce or eliminates side effects. The SECs were loaded using a passive filling method. The drug active (0.1 g) was dissolved in a solvent and mixed with the SECs (0.1 g) for 10 minutes. After mixing for 10 minutes, the solvent was removed by a rotary evaporator and dried to a constant mass. The surface of the sporopollenin exines were analysed on a FTIR to observe if there are any drug deposits on the surface of the SECs. The loading efficiency and drug release percentage was determined by using calibrations curves and analysed on a UV-vis spectrophotometer. Further work has been proposed in which to characterize the SECs further and producing coated tablets from loaded SECs.
- Full Text:
- Date Issued: 2017
Microstructure and properties of zirconium silicide surface layers on zirlo for improved nuclear fuel cladding
- Authors: Ngongo, Sinoyolo
- Date: 2017
- Subjects: Zirconium alloys Zirconium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/20098 , vital:29107
- Description: Zirconium alloys have important applications as nuclear reactor fuel cladding material. In this study the microstructure and properties of zirconium silicide synthesized by heating ZIRLO (which is an alloy of zirconium and niobium) in contact with silicon powder has been investigated. The silicide acts as a coating layer to protect the ZIRLO from oxidation which is associated with hydrogen pick-up. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the morphology and crystal structure of the silicides respectively. Heating of ZIRLO with silicon powder was carried out in a Webb 89 Vacuum Furnace for various temperatures (1000–1400 °C) and times (4–8 hours) in an argon atmosphere or under vacuum, which resulted in the diffusion of silicon into the ZIRLO and the formation of zirconium silicide layers. The sample heat treated for 8 hours at 1000 °C did not show any evidence of inter-diffusion between the ZIRLO and silicon, this suggests that a temperature of 1000 °C is not sufficient to facilitate the formation of a silicide layer. The formation of the silicide layer was however observed after heat treatments at 1200 °C and 1400 °C using SEM and TEM. The silicide formed at 1200 °C as a layer on the ZIRLO sample and voids were observed in this layer, most likely due to the Kirkendall effect which occurs in solid state diffusion. The results suggest that Zr has a larger flux than Si as the voids formed in the ZIRLO. The temperature of 1400 °C appears to exceed the ideal required for silicide formation on the surface of ZIRLO, since the silicon infiltrated very far into the ZIRLO and in fact reacted with the entire ZIRLO sample. Both these samples were heat treated for 8 hours in an argon atmosphere. Silicide layers without voids were obtained in the case where ZIRLO and Si were heat treated for 8 and 4 hours at 1200 °C in an argon atmosphere and under vacuum respectively. The average penetration rate, calculated from the aforementioned heat treatments, of Si into Zr was calculated to be 4.5 μm/hour. The diffusion coefficient of Si in Zr was also estimated and it differs by about a factor of 104 from the reported value Zr into Si diffusion coefficient.
- Full Text:
- Date Issued: 2017
- Authors: Ngongo, Sinoyolo
- Date: 2017
- Subjects: Zirconium alloys Zirconium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/20098 , vital:29107
- Description: Zirconium alloys have important applications as nuclear reactor fuel cladding material. In this study the microstructure and properties of zirconium silicide synthesized by heating ZIRLO (which is an alloy of zirconium and niobium) in contact with silicon powder has been investigated. The silicide acts as a coating layer to protect the ZIRLO from oxidation which is associated with hydrogen pick-up. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the morphology and crystal structure of the silicides respectively. Heating of ZIRLO with silicon powder was carried out in a Webb 89 Vacuum Furnace for various temperatures (1000–1400 °C) and times (4–8 hours) in an argon atmosphere or under vacuum, which resulted in the diffusion of silicon into the ZIRLO and the formation of zirconium silicide layers. The sample heat treated for 8 hours at 1000 °C did not show any evidence of inter-diffusion between the ZIRLO and silicon, this suggests that a temperature of 1000 °C is not sufficient to facilitate the formation of a silicide layer. The formation of the silicide layer was however observed after heat treatments at 1200 °C and 1400 °C using SEM and TEM. The silicide formed at 1200 °C as a layer on the ZIRLO sample and voids were observed in this layer, most likely due to the Kirkendall effect which occurs in solid state diffusion. The results suggest that Zr has a larger flux than Si as the voids formed in the ZIRLO. The temperature of 1400 °C appears to exceed the ideal required for silicide formation on the surface of ZIRLO, since the silicon infiltrated very far into the ZIRLO and in fact reacted with the entire ZIRLO sample. Both these samples were heat treated for 8 hours in an argon atmosphere. Silicide layers without voids were obtained in the case where ZIRLO and Si were heat treated for 8 and 4 hours at 1200 °C in an argon atmosphere and under vacuum respectively. The average penetration rate, calculated from the aforementioned heat treatments, of Si into Zr was calculated to be 4.5 μm/hour. The diffusion coefficient of Si in Zr was also estimated and it differs by about a factor of 104 from the reported value Zr into Si diffusion coefficient.
- Full Text:
- Date Issued: 2017
Mineralogical and geochemical constraints on the origin, alteration history and metallogenic significance of the Manganore iron-formation, Northern Cape Province, South Africa
- Authors: Papadopoulos, Vlassis
- Date: 2017
- Subjects: Banded iron formation , Transvaal Supergroup (South Africa) , Groups (Stratigraphy) South Africa , Lithostratigraphy , Petrology South Africa , Geochemistry South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65189 , vital:28702
- Description: The Manganore iron-formation (MIF) of the Transvaal Supergroup is host to the most important high-grade iron ore bodies in South Africa. Prevailing models for ore genesis invoke supergene processes performing during a long period of erosion, oxidation and weathering under tropical lateritic conditions while the role of potential hydrothermal processes is not addressed. Lack of detailed petrographical and geochemical data necessitated reexamination of the MIF through new and existing drill core exploration material. Thorough petrographical investigation revealed a multi-event complex alteration history involving hydrothermal activity. Iron and silica mobility during alteration is demonstrated by a series of replacement, overprinting, crosscutting textures, extensive silicification and hematitization. Metasomatized textures such as pseudomorphs of primary magnetite, carbonate minerals and chert pods/lenses point to an alteration occurring in layer- controlled fronts and link stratigraphically the MIF to Kuruman and Griquatown iron- formations. Whole-rock geochemical data verify textural observations suggesting strong enrichment of iron or silica in meter-scale horizons, expressed by different generations of quartz and hematite. High-grade iron ore is highly enriched in TiO2 and Al2O3 compared to the protolith while both BIF and iron ore display highly increased concentrations of trace elements (transition metals and HFSE). Oxygen isotopes from different quartz textures reveal little to none isotopic exchangement during alteration whereas O isotopes from hematite are in concert to values from literature and suggest two different generations of hematite. A total of 20 minerals apart from quartz and hematite were documented. An earlier alkali/HFSE alteration event that is believed to have affected the overlying Gamagara shales is recorded in the BIF by the presence of muscovite, apatite, rutile, zircon and xenotime. A later and possibly ongoing event of succeeding hydrothermal pulses involves mainly sulphates (gypsum, baryte, celestine), pyrite, carbonates (siderite, calcite) and silicates (berthierine and tourmaline). Alkali-bearing brines persistently exploit the BIF mainly through karstification-related secondary porosity, are evidently carrying iron and are proposed to participate in or control the iron enrichment by facilitating removal of silica. The source of metals, sulfur and carbon is attributed to the underlying Campbellrand dolomites and especially to the upper Gamogaan Formation. The unconformable contact between BIF and the overlying shales is suggested as a suitable fluid conduit for the development of the observed BIF and shale-derived high-grade hematite iron ore.
- Full Text:
- Date Issued: 2017
- Authors: Papadopoulos, Vlassis
- Date: 2017
- Subjects: Banded iron formation , Transvaal Supergroup (South Africa) , Groups (Stratigraphy) South Africa , Lithostratigraphy , Petrology South Africa , Geochemistry South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65189 , vital:28702
- Description: The Manganore iron-formation (MIF) of the Transvaal Supergroup is host to the most important high-grade iron ore bodies in South Africa. Prevailing models for ore genesis invoke supergene processes performing during a long period of erosion, oxidation and weathering under tropical lateritic conditions while the role of potential hydrothermal processes is not addressed. Lack of detailed petrographical and geochemical data necessitated reexamination of the MIF through new and existing drill core exploration material. Thorough petrographical investigation revealed a multi-event complex alteration history involving hydrothermal activity. Iron and silica mobility during alteration is demonstrated by a series of replacement, overprinting, crosscutting textures, extensive silicification and hematitization. Metasomatized textures such as pseudomorphs of primary magnetite, carbonate minerals and chert pods/lenses point to an alteration occurring in layer- controlled fronts and link stratigraphically the MIF to Kuruman and Griquatown iron- formations. Whole-rock geochemical data verify textural observations suggesting strong enrichment of iron or silica in meter-scale horizons, expressed by different generations of quartz and hematite. High-grade iron ore is highly enriched in TiO2 and Al2O3 compared to the protolith while both BIF and iron ore display highly increased concentrations of trace elements (transition metals and HFSE). Oxygen isotopes from different quartz textures reveal little to none isotopic exchangement during alteration whereas O isotopes from hematite are in concert to values from literature and suggest two different generations of hematite. A total of 20 minerals apart from quartz and hematite were documented. An earlier alkali/HFSE alteration event that is believed to have affected the overlying Gamagara shales is recorded in the BIF by the presence of muscovite, apatite, rutile, zircon and xenotime. A later and possibly ongoing event of succeeding hydrothermal pulses involves mainly sulphates (gypsum, baryte, celestine), pyrite, carbonates (siderite, calcite) and silicates (berthierine and tourmaline). Alkali-bearing brines persistently exploit the BIF mainly through karstification-related secondary porosity, are evidently carrying iron and are proposed to participate in or control the iron enrichment by facilitating removal of silica. The source of metals, sulfur and carbon is attributed to the underlying Campbellrand dolomites and especially to the upper Gamogaan Formation. The unconformable contact between BIF and the overlying shales is suggested as a suitable fluid conduit for the development of the observed BIF and shale-derived high-grade hematite iron ore.
- Full Text:
- Date Issued: 2017
Mineralogical variation in the basal Upper Zone, Bushveld Igneous Complex, South Africa: implications for ore genesis and mineral extraction
- Van Huyssteen, Darryn Ashley
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017
- Authors: Van Huyssteen, Darryn Ashley
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5060 , vital:20762
- Full Text:
- Date Issued: 2017