Hydrological proceses, chemical variability, and multiple isotopestracing of water flow paths in the Kudumela Wetland- Limpopo Province, South Africa
- Authors: Mekiso, Feleke Abiyo
- Date: 2011
- Subjects: Kudumela Wetland -- South Africa -- Limpopo , Wetland hydrology -- South Africa -- Limpopo , Wetlands -- South Africa -- Limpopo , Wetland conservation -- South Africa -- Limpopo , Wetland management -- South Africa -- Limpopo , Isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6027 , http://hdl.handle.net/10962/d1006153 , Kudumela Wetland -- South Africa -- Limpopo , Wetland hydrology -- South Africa -- Limpopo , Wetlands -- South Africa -- Limpopo , Wetland conservation -- South Africa -- Limpopo , Wetland management -- South Africa -- Limpopo , Isotopes
- Description: The hydrology of the Kudumela Wetland, Limpopo Province of South Africa was studied from November 2005 to April 2007, involving both fieldwork and laboratory analyses. This study presents the results of an investigation of the hydrology of the Kudumela Wetland in South Africa, and its contribution to dry season flow in the Mohlapitsi and Olifants Rivers. Initially, 40 Piezometers were installed along seven transects and water levels monitored in order to understand water table level characteristics (fluctuations) with time. Water levels in transects one, three, the right bank portion of transect four and transect six showed fluctuations. Transect two, the left bank portion of transect four and transect five did not show significant temporal changes. The relationships between piezometer water levels, rainfall in the study area and stream flow observed at a river gauging station are not clear. The river within the wetland is a gaining stream because the water table level elevation is above that of the river. This indicates that the wetland is feeding the river. The northern part of the wetland (T1 and T2) is affected by artificial drains and most of the piezometers closest to the river channel showed the lowest variations. The relationships between rainfall, groundwater, and surface water at this site shows that stream flow did not respond quickly to precipitation as expected, even in months when rainfall increased (for example, 74 and 103mm during 08/02/06 and 18/02/06 respectively), and the groundwater levels did not show fluctuations, indicating that groundwater responds gradually to precipitation, and that the relationship between rainfall, groundwater and surface water is complex. The environmental stable isotopes (deuterium and oxygen-18) and the radioactive isotope (tritium) were analyzed, along with field observations of electrical conductivity (EC), pH, total alkalinity (Talka) and some major and minor dissolved ion analyses for tracing water dynamics in the study area. A total of 39 water samples was taken and analyzed from boreholes, auger holes, right bank and left bank drains, various points along the river and springs in four sampling visits to the wetland. The results did not clearly provide a temporal record of isotope and chemical variations in the various sources. Results from the most extensive sampling survey in April 2007 provide the most comprehensive overview of hydrological relationships. Clustering of the stable isotope data suggests that the water samples of upstream and downstream river, auger holes further south and most drains clustered together suggesting a common water source and almost all samples fall above the global (GMWL) and local (Pretoria MWL) meteoric water lines, while some fall between the global and Pretoria meteoric water lines. Six representative water samples were analyzed for major ion concentration. Both cation (Ca, Mg, K, and Na) and anion (HCO3, SO4, Cl, and NO3) analyses in November 2007 confirmed conclusions reached from field observations. The analysis shows that a single type of water (Ca, Mg-HCO3) is involved in the study area. In almost all major ion plots, the right bank drains, upstream river and downstream river samples grouped together in a single cluster. As the means for reliable river flow measurements were not available, except for the gauging station at the outlet of the valley, rough, semi-quantitative estimates were made during several field visits. These, suggest considerable losses of river flow into the gravel/boulder beds at and below a gabion dam at the head of the valley. Three major and several other left bank springs and right bank drains at transects T1 and T2 contributed to the river flow at all times. Along with the isotopic and chemical evidence, these observations have lead to a hypothesis that river water enters the wetland and flows back to the Mohlapitsi River through boulder beds underlying the wetland and through drains on the surface of the argillaceous aquitard covering the more conductive boulder beds. Deeper dolomitic groundwater does not appear to contribute to the water balance at least in the northern half of the wetland. Although environmental isotope and hydrochemistry results may not unequivocally prove this hypothesis they do not contradict it.
- Full Text:
- Date Issued: 2011
- Authors: Mekiso, Feleke Abiyo
- Date: 2011
- Subjects: Kudumela Wetland -- South Africa -- Limpopo , Wetland hydrology -- South Africa -- Limpopo , Wetlands -- South Africa -- Limpopo , Wetland conservation -- South Africa -- Limpopo , Wetland management -- South Africa -- Limpopo , Isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6027 , http://hdl.handle.net/10962/d1006153 , Kudumela Wetland -- South Africa -- Limpopo , Wetland hydrology -- South Africa -- Limpopo , Wetlands -- South Africa -- Limpopo , Wetland conservation -- South Africa -- Limpopo , Wetland management -- South Africa -- Limpopo , Isotopes
- Description: The hydrology of the Kudumela Wetland, Limpopo Province of South Africa was studied from November 2005 to April 2007, involving both fieldwork and laboratory analyses. This study presents the results of an investigation of the hydrology of the Kudumela Wetland in South Africa, and its contribution to dry season flow in the Mohlapitsi and Olifants Rivers. Initially, 40 Piezometers were installed along seven transects and water levels monitored in order to understand water table level characteristics (fluctuations) with time. Water levels in transects one, three, the right bank portion of transect four and transect six showed fluctuations. Transect two, the left bank portion of transect four and transect five did not show significant temporal changes. The relationships between piezometer water levels, rainfall in the study area and stream flow observed at a river gauging station are not clear. The river within the wetland is a gaining stream because the water table level elevation is above that of the river. This indicates that the wetland is feeding the river. The northern part of the wetland (T1 and T2) is affected by artificial drains and most of the piezometers closest to the river channel showed the lowest variations. The relationships between rainfall, groundwater, and surface water at this site shows that stream flow did not respond quickly to precipitation as expected, even in months when rainfall increased (for example, 74 and 103mm during 08/02/06 and 18/02/06 respectively), and the groundwater levels did not show fluctuations, indicating that groundwater responds gradually to precipitation, and that the relationship between rainfall, groundwater and surface water is complex. The environmental stable isotopes (deuterium and oxygen-18) and the radioactive isotope (tritium) were analyzed, along with field observations of electrical conductivity (EC), pH, total alkalinity (Talka) and some major and minor dissolved ion analyses for tracing water dynamics in the study area. A total of 39 water samples was taken and analyzed from boreholes, auger holes, right bank and left bank drains, various points along the river and springs in four sampling visits to the wetland. The results did not clearly provide a temporal record of isotope and chemical variations in the various sources. Results from the most extensive sampling survey in April 2007 provide the most comprehensive overview of hydrological relationships. Clustering of the stable isotope data suggests that the water samples of upstream and downstream river, auger holes further south and most drains clustered together suggesting a common water source and almost all samples fall above the global (GMWL) and local (Pretoria MWL) meteoric water lines, while some fall between the global and Pretoria meteoric water lines. Six representative water samples were analyzed for major ion concentration. Both cation (Ca, Mg, K, and Na) and anion (HCO3, SO4, Cl, and NO3) analyses in November 2007 confirmed conclusions reached from field observations. The analysis shows that a single type of water (Ca, Mg-HCO3) is involved in the study area. In almost all major ion plots, the right bank drains, upstream river and downstream river samples grouped together in a single cluster. As the means for reliable river flow measurements were not available, except for the gauging station at the outlet of the valley, rough, semi-quantitative estimates were made during several field visits. These, suggest considerable losses of river flow into the gravel/boulder beds at and below a gabion dam at the head of the valley. Three major and several other left bank springs and right bank drains at transects T1 and T2 contributed to the river flow at all times. Along with the isotopic and chemical evidence, these observations have lead to a hypothesis that river water enters the wetland and flows back to the Mohlapitsi River through boulder beds underlying the wetland and through drains on the surface of the argillaceous aquitard covering the more conductive boulder beds. Deeper dolomitic groundwater does not appear to contribute to the water balance at least in the northern half of the wetland. Although environmental isotope and hydrochemistry results may not unequivocally prove this hypothesis they do not contradict it.
- Full Text:
- Date Issued: 2011
The zoogeography of the cetaceans in Algoa Bay
- Authors: Melly, Brigitte Leigh
- Date: 2011
- Subjects: Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4858 , http://hdl.handle.net/10962/d1005534 , Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
- Description: The most recent study on cetaceans in Algoa Bay, South Africa, was conducted over 14 years ago. Consequently, knowledge of the cetacean species visiting this bay is currently based on incidental observations and stranding data. A number of developments in recent years: a deepwater port, proposed oil refinery, increased boating and fishing (commercial and recreational), a proposed Marine Protected Area, and the release of a whale-watching permit, all of which may impact these animals in some way, highlight the need for a baseline study on cetaceans. Therefore, the aim of this study was to determine the spatial and temporal distribution, and habitat preference of cetaceans in Algoa Bay. Boat-based surveys were conducted monthly between March 2009 and July 2010. At each sighting the GPS location, species, group size and composition, and behaviour were recorded. Using GIS, the sighting data was related to data layers of geographical variables such as sea surface temperature, depth and sea-floor substrate. Approximately 365 hours of search effort were completed over 57 surveys, with a total of 346 sightings. Species observed were: southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera brydei), Indian Ocean bottlenose dolphins (Tursiops aduncus), Indo-Pacific humpback dolphins (Sousa chinensis), and longbeaked common dolphins (Delphinus capensis). Southern right whales were observed during austral winter, utilising the shallow, protected areas of the bay as a mating and nursery ground. Humpback whales were also recorded extensively during winter, in more offshore waters, with a significant number of mother-calf pairs sighted. Bryde’s whales were recorded in offshore waters during summer and autumn, where they were primarily observed travelling and foraging. Bottlenose dolphins were the most prolific species sighted. They were recorded year-round throughout the inshore waters of the bay, with large group sizes (up to 500 animals), and displayed a wide variety of behaviours. Humpback dolphins were observed in extremely shallow and inshore waters (mean bottom depth of 6.6 m) along the south-west corner of the bay, in small groups of approximately three individuals. Common dolphins were the least observed species, and were mainly observed foraging in large groups of up to 800 individuals. The results of this study indicate how cetaceans utilise the bay in significantly different ways. Geographical and anthropogenic factors have influenced the spatial and temporal distribution of these animals and have resulted in habitat preferences, as well as potential key habitats, in the bay. Thus, this study has provided baseline information for future research and for better informed conservation and management strategies in Algoa Bay.
- Full Text:
- Date Issued: 2011
- Authors: Melly, Brigitte Leigh
- Date: 2011
- Subjects: Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4858 , http://hdl.handle.net/10962/d1005534 , Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
- Description: The most recent study on cetaceans in Algoa Bay, South Africa, was conducted over 14 years ago. Consequently, knowledge of the cetacean species visiting this bay is currently based on incidental observations and stranding data. A number of developments in recent years: a deepwater port, proposed oil refinery, increased boating and fishing (commercial and recreational), a proposed Marine Protected Area, and the release of a whale-watching permit, all of which may impact these animals in some way, highlight the need for a baseline study on cetaceans. Therefore, the aim of this study was to determine the spatial and temporal distribution, and habitat preference of cetaceans in Algoa Bay. Boat-based surveys were conducted monthly between March 2009 and July 2010. At each sighting the GPS location, species, group size and composition, and behaviour were recorded. Using GIS, the sighting data was related to data layers of geographical variables such as sea surface temperature, depth and sea-floor substrate. Approximately 365 hours of search effort were completed over 57 surveys, with a total of 346 sightings. Species observed were: southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera brydei), Indian Ocean bottlenose dolphins (Tursiops aduncus), Indo-Pacific humpback dolphins (Sousa chinensis), and longbeaked common dolphins (Delphinus capensis). Southern right whales were observed during austral winter, utilising the shallow, protected areas of the bay as a mating and nursery ground. Humpback whales were also recorded extensively during winter, in more offshore waters, with a significant number of mother-calf pairs sighted. Bryde’s whales were recorded in offshore waters during summer and autumn, where they were primarily observed travelling and foraging. Bottlenose dolphins were the most prolific species sighted. They were recorded year-round throughout the inshore waters of the bay, with large group sizes (up to 500 animals), and displayed a wide variety of behaviours. Humpback dolphins were observed in extremely shallow and inshore waters (mean bottom depth of 6.6 m) along the south-west corner of the bay, in small groups of approximately three individuals. Common dolphins were the least observed species, and were mainly observed foraging in large groups of up to 800 individuals. The results of this study indicate how cetaceans utilise the bay in significantly different ways. Geographical and anthropogenic factors have influenced the spatial and temporal distribution of these animals and have resulted in habitat preferences, as well as potential key habitats, in the bay. Thus, this study has provided baseline information for future research and for better informed conservation and management strategies in Algoa Bay.
- Full Text:
- Date Issued: 2011
SphereZyme (TM) technology for enhanced enzyme immobilisation application in biosensors
- Authors: Molawa, Letshego Gloria
- Date: 2011
- Subjects: Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3989 , http://hdl.handle.net/10962/d1004048 , Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Description: Self-immobilisation enzyme technologies, such as SphereZyme™, suffer from the lack of applicability to hydrolyse large substrates. Solid support immobilisation is usually a method of choice, to produce a stable biocatalyst for large substrates hydrolysis in the industry. In order to investigate this limitation, a commercial protease called Alcalase® was chosen as a model enzyme due to its natural activity (hydrolysis of large substrates-proteins). Prior to immobilising through the SphereZyme™ technology, Alcalase® was partially purified through dialysis followed by CM Sepharose™ FF cation exchanger. Sample contaminants, such as salts and stabilisers can inhibit protein crosslinking by reacting with glutaraldehyde. Alcalase® was successfully separated into 3 proteases with the major peak correlating to a positive control run on native PAGE, indicating that it was likely subtilisin Carlsberg. A 16% alkaline protease activity for azo-casein hydrolysis was retained when 5% v/v PEI: 25% v/v glutaraldehyde solution was used as a crosslinking agent in Alcalase® SphereZyme™ production. An increase in activity was also observed for monomeric substrates (PNPA) where the highest was 55%. The highest % activities maintained when 0.33 M EDA: 25% v/v glutaraldehyde solution was initially used as crosslinking agent were 4.5% and 1.6% for monomeric and polymeric substrates, respectively. PEI is a hydrophilic branched polymer with an abundance of amine groups compared to EDA. A comparison study of immobilisation efficiencies of SphereZyme™, Eupergit® and Dendrispheres was also performed for large substrate biocatalysis. The two latter technologies are solid-support immobilisation methods. Dendrispheres reached its maximum loading capacity in the first 5 minute of the one hour binding time. Twenty minutes was chosen as a maximum binding time since there was constant protein maintained on the solid support and no enzyme loss was observed during the 1 hour binding time. PEI at pH 11.5, its native pH, gave the highest immobilisation yield and specific activity over the PEI pH range of 11.5 to 7. SphereZyme™ had the highest ratio for azocasein hydrolysis followed by Dendrispheres and Eupergit®. The SphereZyme™ was also shown to be applicable to biosensors for phenol detection. Different modifications of glassy carbon electrode (GCE) were evaluated as a benchmark for the fabrication of SphereZyme™ modified phenol biosensor. GCE modified with laccase SphereZyme™ entrapped in cellulose membrane was the best modification due to the broad catechol range (<0.950 mM), high correlation coefficient (R2, 0.995) and relative high sensitivity factor (0.305 μA.mM-1). This type of biosensor was also shown to be electroactive at pH 7.0 for which its control, free laccase, lacked electroactivity. From the catalytic constants calculated, GCE modified with laccase SphereZyme™ entrapped in cellulose membrane also gave the highest effectiveness factor (Imax/Km app) of 1.84 μA.mM-1. The modified GCE with Alcalase® SphereZyme™ was relatively more sensitive than GCE modified with free Alcalase®.
- Full Text:
- Date Issued: 2011
- Authors: Molawa, Letshego Gloria
- Date: 2011
- Subjects: Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3989 , http://hdl.handle.net/10962/d1004048 , Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Description: Self-immobilisation enzyme technologies, such as SphereZyme™, suffer from the lack of applicability to hydrolyse large substrates. Solid support immobilisation is usually a method of choice, to produce a stable biocatalyst for large substrates hydrolysis in the industry. In order to investigate this limitation, a commercial protease called Alcalase® was chosen as a model enzyme due to its natural activity (hydrolysis of large substrates-proteins). Prior to immobilising through the SphereZyme™ technology, Alcalase® was partially purified through dialysis followed by CM Sepharose™ FF cation exchanger. Sample contaminants, such as salts and stabilisers can inhibit protein crosslinking by reacting with glutaraldehyde. Alcalase® was successfully separated into 3 proteases with the major peak correlating to a positive control run on native PAGE, indicating that it was likely subtilisin Carlsberg. A 16% alkaline protease activity for azo-casein hydrolysis was retained when 5% v/v PEI: 25% v/v glutaraldehyde solution was used as a crosslinking agent in Alcalase® SphereZyme™ production. An increase in activity was also observed for monomeric substrates (PNPA) where the highest was 55%. The highest % activities maintained when 0.33 M EDA: 25% v/v glutaraldehyde solution was initially used as crosslinking agent were 4.5% and 1.6% for monomeric and polymeric substrates, respectively. PEI is a hydrophilic branched polymer with an abundance of amine groups compared to EDA. A comparison study of immobilisation efficiencies of SphereZyme™, Eupergit® and Dendrispheres was also performed for large substrate biocatalysis. The two latter technologies are solid-support immobilisation methods. Dendrispheres reached its maximum loading capacity in the first 5 minute of the one hour binding time. Twenty minutes was chosen as a maximum binding time since there was constant protein maintained on the solid support and no enzyme loss was observed during the 1 hour binding time. PEI at pH 11.5, its native pH, gave the highest immobilisation yield and specific activity over the PEI pH range of 11.5 to 7. SphereZyme™ had the highest ratio for azocasein hydrolysis followed by Dendrispheres and Eupergit®. The SphereZyme™ was also shown to be applicable to biosensors for phenol detection. Different modifications of glassy carbon electrode (GCE) were evaluated as a benchmark for the fabrication of SphereZyme™ modified phenol biosensor. GCE modified with laccase SphereZyme™ entrapped in cellulose membrane was the best modification due to the broad catechol range (<0.950 mM), high correlation coefficient (R2, 0.995) and relative high sensitivity factor (0.305 μA.mM-1). This type of biosensor was also shown to be electroactive at pH 7.0 for which its control, free laccase, lacked electroactivity. From the catalytic constants calculated, GCE modified with laccase SphereZyme™ entrapped in cellulose membrane also gave the highest effectiveness factor (Imax/Km app) of 1.84 μA.mM-1. The modified GCE with Alcalase® SphereZyme™ was relatively more sensitive than GCE modified with free Alcalase®.
- Full Text:
- Date Issued: 2011
The development of an in vitro system for the production of drug metabolites using microsomal enzymes from bovine liver
- Authors: Morrison, Roxanne
- Date: 2011
- Subjects: Drugs -- Metabolism , Xenobiotics -- Metabolism , Metabolites , Drugs -- Testing , Toxicity testing -- In vitro , Doping in horse racing -- Control -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4087 , http://hdl.handle.net/10962/d1007698 , Drugs -- Metabolism , Xenobiotics -- Metabolism , Metabolites , Drugs -- Testing , Toxicity testing -- In vitro , Doping in horse racing -- Control -- Research
- Description: Drug metabolism is a specialised subset of xenobiotic metabolism, pertaining to the breakdown and elimination of pharmaceutical drugs. The enzymes involved in these pathways are the cytochrome P450 family of isozymes. Metabolism is an important factor in determining the pharmacological effects of drugs. The main aim of this study was to develop a system whereby the major metabolites of drugs can be produced in vitro. An in vitro system was developed and optimised using commercially prepared microsomes from rat liver and coumarin (by monitoring its conversion to 7-hydroxycoumarin) as a model. The optimum running conditions for the incubations were 50 μM coumarin, 50 μg protein/ml microsomes, 1 mM NADP⁺, 5 mM G6P and 1U/ml G6PDH incubated for 30 minutes at 38℃. The HPLC method for the detection of coumarin and 7-hydroxycoumarin was also validated with respect to linearity, reproducibility, precision, accuracy and lower limits of detection and quantification. The system developed was then tested using microsomes prepared from fresh bovine liver on these ten drugs of interest in doping control in horse racing: diazepam, nordiazepam, oxazepam, promazine, acepromazine, chlorpromazine, morphine, codeine, etoricoxib and lumiracoxib. The bovine liver microsomes were prepared using differential centrifugation and had activity on a par with the commercial preparations. This in vitro system metabolised the drugs and produced both phase I and II metabolites, similar to those observed in humans and horses in vivo. For example, the major metabolites of the benzodiazepine drug, diazepam, nordiazepam, temazepam and oxazepam as well as the glucuronidated phase II products were all found after incubations with the bovine liver microsomes. The metabolism of the drugs was also investigated in silico using the computational procedure, MetaSite. MetaSite was able to successfully predict known metabolites for most of the drugs studied. Differences were observed from the in vitro incubations and this is most likely due to MetaSite using only human cytochrome P450s for analysis.
- Full Text:
- Date Issued: 2011
- Authors: Morrison, Roxanne
- Date: 2011
- Subjects: Drugs -- Metabolism , Xenobiotics -- Metabolism , Metabolites , Drugs -- Testing , Toxicity testing -- In vitro , Doping in horse racing -- Control -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4087 , http://hdl.handle.net/10962/d1007698 , Drugs -- Metabolism , Xenobiotics -- Metabolism , Metabolites , Drugs -- Testing , Toxicity testing -- In vitro , Doping in horse racing -- Control -- Research
- Description: Drug metabolism is a specialised subset of xenobiotic metabolism, pertaining to the breakdown and elimination of pharmaceutical drugs. The enzymes involved in these pathways are the cytochrome P450 family of isozymes. Metabolism is an important factor in determining the pharmacological effects of drugs. The main aim of this study was to develop a system whereby the major metabolites of drugs can be produced in vitro. An in vitro system was developed and optimised using commercially prepared microsomes from rat liver and coumarin (by monitoring its conversion to 7-hydroxycoumarin) as a model. The optimum running conditions for the incubations were 50 μM coumarin, 50 μg protein/ml microsomes, 1 mM NADP⁺, 5 mM G6P and 1U/ml G6PDH incubated for 30 minutes at 38℃. The HPLC method for the detection of coumarin and 7-hydroxycoumarin was also validated with respect to linearity, reproducibility, precision, accuracy and lower limits of detection and quantification. The system developed was then tested using microsomes prepared from fresh bovine liver on these ten drugs of interest in doping control in horse racing: diazepam, nordiazepam, oxazepam, promazine, acepromazine, chlorpromazine, morphine, codeine, etoricoxib and lumiracoxib. The bovine liver microsomes were prepared using differential centrifugation and had activity on a par with the commercial preparations. This in vitro system metabolised the drugs and produced both phase I and II metabolites, similar to those observed in humans and horses in vivo. For example, the major metabolites of the benzodiazepine drug, diazepam, nordiazepam, temazepam and oxazepam as well as the glucuronidated phase II products were all found after incubations with the bovine liver microsomes. The metabolism of the drugs was also investigated in silico using the computational procedure, MetaSite. MetaSite was able to successfully predict known metabolites for most of the drugs studied. Differences were observed from the in vitro incubations and this is most likely due to MetaSite using only human cytochrome P450s for analysis.
- Full Text:
- Date Issued: 2011
Responses of intertidal macroalgae and associated fauna to interactive processes acting over multiple spatial scales
- Authors: Mostert, Bruce Petrus
- Date: 2011 , 2010-12-01
- Subjects: Biodiversity -- South Africa , Spatial ecology , Marine algae -- South Africa , Marine organisms -- Effect of water pollution on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5890 , http://hdl.handle.net/10962/d1013370
- Description: The decrease of biological diversity from low latitudes near the equator towards high latitudes is one of the most fundamental patterns noted in ecology. These trends have been the subject of numerous terrestrial and marine studies and have caused the proposal of several explanatory hypotheses. No single hypothesis has adequately accounted for these observed trends. Furthermore, large-scale patterns are frequently modified by processes acting at meso- to small-scales. It is imperative to understand the interaction of these processes to elucidate the mechanisms controlling the structure of intertidal assemblages. The main aim of this thesis was to test the influence of multiple processes at a range of spatial scales on biogenic engineers. Biogenic engineers, such as macroalgae, have been reported to be strongly influenced by processes such as grazing, biogeography and upwelling and subsequent effects are expected to be linked to their associated assemblages. I used infaunal assemblages associated with macroalgae as a model system to understand the interactive effects of meso-scale upwelling in conjunction with large-scale factors (regional and biogeographic). Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis, inhabiting different but overlapping home ranges were used in this study. Smaller scale, physical attributes and the associated fauna of these algal species were compared. The effects of meso- to large-scale physical gradients on marine organisms have been investigated in many instances and resultant gradients in physical variables observed. This study was undertaken to investigate morphological trends exhibited by Hypnea spicifera and Champia lumbricalis to compare possible similarities between coastlines and to determine if inferred meso- to large-scale processes influence physical trends in a similar manner despite the coastlines being affected by different hydrodynamic processes. The macroalgae were located in two distinctly different upwelling regimes, Hypnea spicifera on the east and south coasts and Champia lumbricalis on the west coast. Upwelling (delivery of nutrients and primary production) was not found to be an important factor in determining the physical characteristics of macroalgae but there were clear patterns linked to latitude. Mean percentage cover of Hypnea spicifera was positively correlated with distance along the east and south coasts. Mean mass and mean surface area of H. spicifera were, however, negatively correlated with distance from Port St Johns. Mean frond length showed a negative trend but this relationship was not statistically significant. On the west coast, there was a significant increase in mean frond length from north to south for Champia lumbricalis. Mean surface area and mean mass of C. lumbricalis exhibited non-significant negative trends from north to south while there was a non-significant positive trend for mean percentage cover. Following the “Productivity Hypothesis”, these patterns from north to south along the coastlines of South Africa could have important implications for biodiversity associated with these algae. Many previous studies have focussed on the effects of upwelling on species (i.e. effects of nutrients and temperature) but have failed to separate this effect from large scale effects such as biogeography and latitudinal gradients. I tested the influence meso-scale upwelling, large-scale biogeographic processes and latitudinal gradients with two different species of macroalgae one on the east and south coasts of South Africa and the other on the west coast. Hypnea spicifera inhabits the east and south coasts of South Africa spanning two biogeographic provinces and is generally affected by relatively weak upwelling, whereas Champia lumbricalis inhabits the west coast spanning one biogeographic province which is subjected to intense persistent upwelling year round. Within the east and west coast biogeographic provinces there are, however, regions with both upwelling and non-upwelling. On the east and south coasts, entire assemblages differed significantly among the three Regions (St Lucia, Port Alfred and Knysna, while assemblages between upwelling/non-upwelling areas were not different. Assemblages on the different shores differed significantly from each other. There were no significant effects of region or upwelling for the number of individuals of Crustacea or Polychaeta, while Mollusca showed a significant effect of region. The number of individuals of other taxa showed a significant interaction of region and upwelling. Region had a significant effect on number of species of molluscs and other taxa, while there was no effect for either region or upwelling for the Crustacea or Polychaeta. In general different factors were shown to be important (region and shore) while upwelling was rarely important. On the west coast assemblages associated with C. lumbricalis were not influenced by region or upwelling but there were significant differences between shores. Region, upwelling ad shore did not affect number of individuals. There was a significant interaction of region and upwelling for the number of species of crustaceans, while numbers of species of Mollusca, Polychaeta and other taxa showed no effects. In general, regional factors strongly influenced most organisms, while upwelling played a minor role. Hypotheses about differences between upwelling and non-upwelling regions in terms of species abundances and composition due to the input of cold nutrient rich water were not supported. A link between the effects of larger-scale biogeographic factors and their influence on habitat forming taxa and the resultant effects on associated infauna would be a likely explanation for the patterns observed in this study. Diversity of assemblages is known to be influenced by the structural complexity of a habitat, increasing complexity increases the amount of available niches therefore potentially increasing the number of species found within that habitat. Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis were selected on the basis of being structurally similar and having their distributional ranges overlap in order to elucidate the effects of structure and macroalgal species on associated assemblages. Hypnea spicifera is different in terms of surface area and biomass from Champia lumbricalis and Bifurcaria brassicaeformis. Assemblages of species found on the three rhodophytes showed both shore and the species of alga had significant effects on composition. Only numbers of individuals of molluscs were affected by the species of alga. Crustacea and Polychaeta showed an interaction of the species of alga with shore. In the case of this study, it is likely that the three species of macroalgae mitigate biological stressors such as predation and physical stressors such as wave exposure and desiccation. In general, meso-scale upwelling is suggested to be marginalised when considering the structuring of assemblages associated with macroalgae, while large scale biogeography has more of an influence. Within shores, assemblages were also strongly influenced by smaller-scale factors such as differences in the structure and species of alga. This study indicates the importance of investigating patterns across a range of spatial scales to gain a comprehensive understanding of factors influencing intertidal organisms.
- Full Text:
- Date Issued: 2011
- Authors: Mostert, Bruce Petrus
- Date: 2011 , 2010-12-01
- Subjects: Biodiversity -- South Africa , Spatial ecology , Marine algae -- South Africa , Marine organisms -- Effect of water pollution on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5890 , http://hdl.handle.net/10962/d1013370
- Description: The decrease of biological diversity from low latitudes near the equator towards high latitudes is one of the most fundamental patterns noted in ecology. These trends have been the subject of numerous terrestrial and marine studies and have caused the proposal of several explanatory hypotheses. No single hypothesis has adequately accounted for these observed trends. Furthermore, large-scale patterns are frequently modified by processes acting at meso- to small-scales. It is imperative to understand the interaction of these processes to elucidate the mechanisms controlling the structure of intertidal assemblages. The main aim of this thesis was to test the influence of multiple processes at a range of spatial scales on biogenic engineers. Biogenic engineers, such as macroalgae, have been reported to be strongly influenced by processes such as grazing, biogeography and upwelling and subsequent effects are expected to be linked to their associated assemblages. I used infaunal assemblages associated with macroalgae as a model system to understand the interactive effects of meso-scale upwelling in conjunction with large-scale factors (regional and biogeographic). Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis, inhabiting different but overlapping home ranges were used in this study. Smaller scale, physical attributes and the associated fauna of these algal species were compared. The effects of meso- to large-scale physical gradients on marine organisms have been investigated in many instances and resultant gradients in physical variables observed. This study was undertaken to investigate morphological trends exhibited by Hypnea spicifera and Champia lumbricalis to compare possible similarities between coastlines and to determine if inferred meso- to large-scale processes influence physical trends in a similar manner despite the coastlines being affected by different hydrodynamic processes. The macroalgae were located in two distinctly different upwelling regimes, Hypnea spicifera on the east and south coasts and Champia lumbricalis on the west coast. Upwelling (delivery of nutrients and primary production) was not found to be an important factor in determining the physical characteristics of macroalgae but there were clear patterns linked to latitude. Mean percentage cover of Hypnea spicifera was positively correlated with distance along the east and south coasts. Mean mass and mean surface area of H. spicifera were, however, negatively correlated with distance from Port St Johns. Mean frond length showed a negative trend but this relationship was not statistically significant. On the west coast, there was a significant increase in mean frond length from north to south for Champia lumbricalis. Mean surface area and mean mass of C. lumbricalis exhibited non-significant negative trends from north to south while there was a non-significant positive trend for mean percentage cover. Following the “Productivity Hypothesis”, these patterns from north to south along the coastlines of South Africa could have important implications for biodiversity associated with these algae. Many previous studies have focussed on the effects of upwelling on species (i.e. effects of nutrients and temperature) but have failed to separate this effect from large scale effects such as biogeography and latitudinal gradients. I tested the influence meso-scale upwelling, large-scale biogeographic processes and latitudinal gradients with two different species of macroalgae one on the east and south coasts of South Africa and the other on the west coast. Hypnea spicifera inhabits the east and south coasts of South Africa spanning two biogeographic provinces and is generally affected by relatively weak upwelling, whereas Champia lumbricalis inhabits the west coast spanning one biogeographic province which is subjected to intense persistent upwelling year round. Within the east and west coast biogeographic provinces there are, however, regions with both upwelling and non-upwelling. On the east and south coasts, entire assemblages differed significantly among the three Regions (St Lucia, Port Alfred and Knysna, while assemblages between upwelling/non-upwelling areas were not different. Assemblages on the different shores differed significantly from each other. There were no significant effects of region or upwelling for the number of individuals of Crustacea or Polychaeta, while Mollusca showed a significant effect of region. The number of individuals of other taxa showed a significant interaction of region and upwelling. Region had a significant effect on number of species of molluscs and other taxa, while there was no effect for either region or upwelling for the Crustacea or Polychaeta. In general different factors were shown to be important (region and shore) while upwelling was rarely important. On the west coast assemblages associated with C. lumbricalis were not influenced by region or upwelling but there were significant differences between shores. Region, upwelling ad shore did not affect number of individuals. There was a significant interaction of region and upwelling for the number of species of crustaceans, while numbers of species of Mollusca, Polychaeta and other taxa showed no effects. In general, regional factors strongly influenced most organisms, while upwelling played a minor role. Hypotheses about differences between upwelling and non-upwelling regions in terms of species abundances and composition due to the input of cold nutrient rich water were not supported. A link between the effects of larger-scale biogeographic factors and their influence on habitat forming taxa and the resultant effects on associated infauna would be a likely explanation for the patterns observed in this study. Diversity of assemblages is known to be influenced by the structural complexity of a habitat, increasing complexity increases the amount of available niches therefore potentially increasing the number of species found within that habitat. Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis were selected on the basis of being structurally similar and having their distributional ranges overlap in order to elucidate the effects of structure and macroalgal species on associated assemblages. Hypnea spicifera is different in terms of surface area and biomass from Champia lumbricalis and Bifurcaria brassicaeformis. Assemblages of species found on the three rhodophytes showed both shore and the species of alga had significant effects on composition. Only numbers of individuals of molluscs were affected by the species of alga. Crustacea and Polychaeta showed an interaction of the species of alga with shore. In the case of this study, it is likely that the three species of macroalgae mitigate biological stressors such as predation and physical stressors such as wave exposure and desiccation. In general, meso-scale upwelling is suggested to be marginalised when considering the structuring of assemblages associated with macroalgae, while large scale biogeography has more of an influence. Within shores, assemblages were also strongly influenced by smaller-scale factors such as differences in the structure and species of alga. This study indicates the importance of investigating patterns across a range of spatial scales to gain a comprehensive understanding of factors influencing intertidal organisms.
- Full Text:
- Date Issued: 2011
Assessment of organochlorine pesticide residues in fish samples from the Okavango Delta, Botswana
- Authors: Mpofu, Christopher
- Date: 2011 , 2011-02-28
- Subjects: Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4404 , http://hdl.handle.net/10962/d1006707 , Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
- Description: This thesis presents an evaluation of the dispersive solid-phase extraction (d-SPE) method referred to as the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the determination of four organochlorine pesticide residues in fish samples. The pesticides investigated in this study were o, p′-DDT, p, p′-DDE, aldrin and dieldrin. The combined use of Gas Chromatography with an Electron Capture Detector (GC-ECD) and sensitive Time of Flight (TOF) mass detector facilitated the identification of the target analytes. In the absence of certified reference material, the overall analytical procedure was validated by systematic recovery experiments on spiked samples at three levels of 2, 5 and 10 ng/g. The targeted compounds were successfully extracted and their recovery ranged from 76 to 96% with relative standard deviations of less than 13%. The optimum QuEChERS conditions were 2g of fish powder, 10 ml acetonitrile and 1 min shaking time. The optimal conditions were applied to assess the levels of chlorinated pesticides in blunt-tooth catfish (Clarias ngamensis), tigerfish (Hydrocynus vittatus), Oreochromis andersonii and red-breasted tilapia (Tilapia rendalli) from the Okavango Delta, Botswana. Dieldrin, p, p′-DDE and aldrin were detected in all the analysed samples with a concentration range of 0.04 – 0.29, 0.07 – 0.33, 0.04 – 0.28 and 0.03 – 0.24 ng/g per dry weight in O. andersonii, C. ngamensis, T. rendalli and H. vittatus respectively. These concentrations were below the US-EPA 0.1 μg/g allowable limit in edible fish and the Australian Maximum Residue Limit (MRL) of 50 - 1000 ng/g in fresh fish. DDT was not detected in all the fish species investigated. The mean lipid content recorded in the fish samples were 1.24, 2.16, 2.18 and 4.21% for H. vittatus, T. rendalli, O. andersonni and C. ngamensis respectively. No systematic trend was observed between fish age and pesticide levels in fish. Acetylcholinesterase (AChE) activity assays were performed to assess the effects of organochlorine pesticides in Clarias ngamensis. The enzyme activity recorded in Clarias ngamensis from the Okavango Delta and the reference site was 12.31 μmol of acetylcholine iodide hydrolysed/min/g brain tissue. The enzyme activity remained the same indicating no enzyme inhibition. The conclusions drawn from this study are that the QuEChERS method is applicable for the determination of organochlorine pesticide residues in fish matrices. The fish from the Okavango Delta are safe for human consumption.
- Full Text:
- Date Issued: 2011
- Authors: Mpofu, Christopher
- Date: 2011 , 2011-02-28
- Subjects: Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4404 , http://hdl.handle.net/10962/d1006707 , Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
- Description: This thesis presents an evaluation of the dispersive solid-phase extraction (d-SPE) method referred to as the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the determination of four organochlorine pesticide residues in fish samples. The pesticides investigated in this study were o, p′-DDT, p, p′-DDE, aldrin and dieldrin. The combined use of Gas Chromatography with an Electron Capture Detector (GC-ECD) and sensitive Time of Flight (TOF) mass detector facilitated the identification of the target analytes. In the absence of certified reference material, the overall analytical procedure was validated by systematic recovery experiments on spiked samples at three levels of 2, 5 and 10 ng/g. The targeted compounds were successfully extracted and their recovery ranged from 76 to 96% with relative standard deviations of less than 13%. The optimum QuEChERS conditions were 2g of fish powder, 10 ml acetonitrile and 1 min shaking time. The optimal conditions were applied to assess the levels of chlorinated pesticides in blunt-tooth catfish (Clarias ngamensis), tigerfish (Hydrocynus vittatus), Oreochromis andersonii and red-breasted tilapia (Tilapia rendalli) from the Okavango Delta, Botswana. Dieldrin, p, p′-DDE and aldrin were detected in all the analysed samples with a concentration range of 0.04 – 0.29, 0.07 – 0.33, 0.04 – 0.28 and 0.03 – 0.24 ng/g per dry weight in O. andersonii, C. ngamensis, T. rendalli and H. vittatus respectively. These concentrations were below the US-EPA 0.1 μg/g allowable limit in edible fish and the Australian Maximum Residue Limit (MRL) of 50 - 1000 ng/g in fresh fish. DDT was not detected in all the fish species investigated. The mean lipid content recorded in the fish samples were 1.24, 2.16, 2.18 and 4.21% for H. vittatus, T. rendalli, O. andersonni and C. ngamensis respectively. No systematic trend was observed between fish age and pesticide levels in fish. Acetylcholinesterase (AChE) activity assays were performed to assess the effects of organochlorine pesticides in Clarias ngamensis. The enzyme activity recorded in Clarias ngamensis from the Okavango Delta and the reference site was 12.31 μmol of acetylcholine iodide hydrolysed/min/g brain tissue. The enzyme activity remained the same indicating no enzyme inhibition. The conclusions drawn from this study are that the QuEChERS method is applicable for the determination of organochlorine pesticide residues in fish matrices. The fish from the Okavango Delta are safe for human consumption.
- Full Text:
- Date Issued: 2011
A review of the performance of Botswana citizen building contractors
- Authors: Muche, Freeman Hansungule
- Date: 2011
- Subjects: Contractors , Building -- Botswana , Construction industry -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9685 , http://hdl.handle.net/10948/1336 , Contractors , Building -- Botswana , Construction industry -- Botswana
- Description: Botswana was left underdeveloped in 1966 when it gained its independence from Great Britain. However, with the discovery of diamonds in the late 1970s, the economy of the country changed and two decades later the construction industry had experienced phenomenal growth. A growth propelled by the dominance of foreign contractors and the few citizen contractors available at the time resulted in a competitive environment in the industry. However, citizen contractors were unable to compete on the same level with their foreign counterparts, which was attributable to various factors such as a lack of resources and of business and technical experience. Being a major player in the construction industry, and realising the need to equip and encourage its own base of citizen contractors to actively participate in construction activities, the government of Botswana adopted new measures and policies that were meant to address the imbalances in the construction industry much to the advantage of citizen contractors. The rationale behind this study is to investigate the performance of citizen building contractors following the introduction of preferential procurement policies by the government of Botswana. This research study adopted the descriptive and analytical survey method which entailed the use of questionnaires and a review of the related literature for gathering relevant data. The sample strata included building contractors, consultants, and clients in the Botswana construction industry in Gaborone, Francistown, Selebi-phikwe, Maun, Serowe, and Lobatse. The empirical findings revealed that there is indeed a need to review some of the government assistance programs for citizen contractors in order to avoid the abuse of government resources and to further increase the citizen contractor’s knowledge base, skills, resources and capacity through mentorship and workshops. vi It is therefore incumbent upon government to protect those beneficiaries who genuinely require such assistance by critical assessment of the ineffective policies for the benefit of the whole industry
- Full Text:
- Date Issued: 2011
- Authors: Muche, Freeman Hansungule
- Date: 2011
- Subjects: Contractors , Building -- Botswana , Construction industry -- Botswana
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9685 , http://hdl.handle.net/10948/1336 , Contractors , Building -- Botswana , Construction industry -- Botswana
- Description: Botswana was left underdeveloped in 1966 when it gained its independence from Great Britain. However, with the discovery of diamonds in the late 1970s, the economy of the country changed and two decades later the construction industry had experienced phenomenal growth. A growth propelled by the dominance of foreign contractors and the few citizen contractors available at the time resulted in a competitive environment in the industry. However, citizen contractors were unable to compete on the same level with their foreign counterparts, which was attributable to various factors such as a lack of resources and of business and technical experience. Being a major player in the construction industry, and realising the need to equip and encourage its own base of citizen contractors to actively participate in construction activities, the government of Botswana adopted new measures and policies that were meant to address the imbalances in the construction industry much to the advantage of citizen contractors. The rationale behind this study is to investigate the performance of citizen building contractors following the introduction of preferential procurement policies by the government of Botswana. This research study adopted the descriptive and analytical survey method which entailed the use of questionnaires and a review of the related literature for gathering relevant data. The sample strata included building contractors, consultants, and clients in the Botswana construction industry in Gaborone, Francistown, Selebi-phikwe, Maun, Serowe, and Lobatse. The empirical findings revealed that there is indeed a need to review some of the government assistance programs for citizen contractors in order to avoid the abuse of government resources and to further increase the citizen contractor’s knowledge base, skills, resources and capacity through mentorship and workshops. vi It is therefore incumbent upon government to protect those beneficiaries who genuinely require such assistance by critical assessment of the ineffective policies for the benefit of the whole industry
- Full Text:
- Date Issued: 2011
A platform for computer-assisted multilingual literacy development
- Authors: Mudimba, Bwini Chizabubi
- Date: 2011
- Subjects: FundaWethu , Language acquisition -- Computer-assisted instruction , Language arts (Elementary) -- Computer-assisted instruction , Language and education , Education, Bilingual , Computer-assisted instruction , Educational technology , Computers and literacy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4600 , http://hdl.handle.net/10962/d1004850 , FundaWethu , Language acquisition -- Computer-assisted instruction , Language arts (Elementary) -- Computer-assisted instruction , Language and education , Education, Bilingual , Computer-assisted instruction , Educational technology , Computers and literacy
- Description: FundaWethu is reading software that is designed to deliver reading lessons to Grade R-3 (foundation phase) children who are learning to read in a multilingual context. Starting from a premise that the system should be both educative and entertaining, the system allows literacy researchers or teachers to construct rich multimedia reading lessons, with text, pictures (possibly animated), and audio files. Using the design-based research methodology which is problem driven and iterative, we followed a user-centred design process in creating FundaWethu. To promote sustainability of the software, we chose to bring teachers on board as “co-designers” using the lesson authoring tool. We made the authoring tool simple enough for use by non computer specialists, but expressive enough to enable a wide range of beginners reading exercises to be constructed in a number of different languages (indigenous South African languages in particular). This project therefore centred on the use of designbased research to build FundaWethu, the design and construction of FundaWethu and the usability study carried out to determine the adequacy of FundaWethu.
- Full Text:
- Date Issued: 2011
- Authors: Mudimba, Bwini Chizabubi
- Date: 2011
- Subjects: FundaWethu , Language acquisition -- Computer-assisted instruction , Language arts (Elementary) -- Computer-assisted instruction , Language and education , Education, Bilingual , Computer-assisted instruction , Educational technology , Computers and literacy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4600 , http://hdl.handle.net/10962/d1004850 , FundaWethu , Language acquisition -- Computer-assisted instruction , Language arts (Elementary) -- Computer-assisted instruction , Language and education , Education, Bilingual , Computer-assisted instruction , Educational technology , Computers and literacy
- Description: FundaWethu is reading software that is designed to deliver reading lessons to Grade R-3 (foundation phase) children who are learning to read in a multilingual context. Starting from a premise that the system should be both educative and entertaining, the system allows literacy researchers or teachers to construct rich multimedia reading lessons, with text, pictures (possibly animated), and audio files. Using the design-based research methodology which is problem driven and iterative, we followed a user-centred design process in creating FundaWethu. To promote sustainability of the software, we chose to bring teachers on board as “co-designers” using the lesson authoring tool. We made the authoring tool simple enough for use by non computer specialists, but expressive enough to enable a wide range of beginners reading exercises to be constructed in a number of different languages (indigenous South African languages in particular). This project therefore centred on the use of designbased research to build FundaWethu, the design and construction of FundaWethu and the usability study carried out to determine the adequacy of FundaWethu.
- Full Text:
- Date Issued: 2011
Investigating the role of heat shock proteins (Hsps) 40, 70 and 90 in the life cycle of Theiler's murine encephalomyelitis virus (TMEV)
- Mutsvunguma, Lorraine Zvichapera
- Authors: Mutsvunguma, Lorraine Zvichapera
- Date: 2011
- Subjects: Heat shock proteins , Picornaviruses , Encephalomyelitis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3966 , http://hdl.handle.net/10962/d1004025 , Heat shock proteins , Picornaviruses , Encephalomyelitis
- Description: Introduction: Picornaviruses are a family of RNA viruses which are economically and clinically significant. Like many other viruses, picornaviruses utilise host cell machinery to facilitate their replication and assembly, including heat shock proteins (Hsps). The aim of this research was to investigate the role of Hsp40, Hsp70 and Hsp90 during picornavirus infection using the cardiovirus, Theiler’s murine encephalomyelitis virus (TMEV), as a study model. Methodology: Picornavirus VP1 capsid proteins were analysed by multiple sequence alignment and multiple structural comparisons. Protein domain architecture was used to analyse Hsp90 cellular and viral client proteins. Effects of Hsp90 inhibitors, novobiocin and geldanamycin, on TMEV growth in BHK-21 cells was observed over a 48hr period. Localisation of Hsp40, Hsp90 and Hsp70 in TMEV-infected BHK-21 cells was investigated by indirect immunofluorescence and confocal microscopy. Results and Discussion: VP1 proteins of picornaviruses are highly divergent within the family at the amino acid level, which might be linked to the protein’s function in determining virus tropism and antibody neutralisation. An eight-stranded anti-parallel beta-barrel structure was found conserved in the VP1 protein structures which might be linked to the highly conserved picornavirus capsid assembly process. Absence of a common protein domain between Hsp90 viral and cellular client proteins that might be functionally connected to Hsp90, suggests that Hsp90 most likely recognises surface features rather than sequence motifs/patterns. The Hsp90 inhibitors, novobiocin and geldanamycin, had a negative effect on virus growth as virus-induced cytopathic effect was not observed in treated cell after 48hrs. TMEV 2C protein was detected by Western analysis in infected cell lysates treated with geldanamycin but not novobiocin, suggesting novobiocin affects the translation or processing of TMEV 2C. Immunofluorescence analysis of TMEV-infected cells showed a relocalisation of Hsp40 into the nucleus during infection. Overlap of Hsp40 and TMEV P1 was observed in the perinuclear region, suggesting colocalisation between these proteins. Hsp70 converged around the replication complex during infection but did not overlap with TMEV 2C. Hsp90 concentrated in the region of the replication complex where it overlapped with TMEV 2C and this redistribution was found to be dependent on the stage of infection. The overlap between Hsp90 and TMEV 2C signals observed, suggested colocalisation between the two proteins. Conclusion: This study identified Hsp90, Hsp70 and Hsp40 as possible host factors required in TMEV replication.
- Full Text:
- Date Issued: 2011
- Authors: Mutsvunguma, Lorraine Zvichapera
- Date: 2011
- Subjects: Heat shock proteins , Picornaviruses , Encephalomyelitis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3966 , http://hdl.handle.net/10962/d1004025 , Heat shock proteins , Picornaviruses , Encephalomyelitis
- Description: Introduction: Picornaviruses are a family of RNA viruses which are economically and clinically significant. Like many other viruses, picornaviruses utilise host cell machinery to facilitate their replication and assembly, including heat shock proteins (Hsps). The aim of this research was to investigate the role of Hsp40, Hsp70 and Hsp90 during picornavirus infection using the cardiovirus, Theiler’s murine encephalomyelitis virus (TMEV), as a study model. Methodology: Picornavirus VP1 capsid proteins were analysed by multiple sequence alignment and multiple structural comparisons. Protein domain architecture was used to analyse Hsp90 cellular and viral client proteins. Effects of Hsp90 inhibitors, novobiocin and geldanamycin, on TMEV growth in BHK-21 cells was observed over a 48hr period. Localisation of Hsp40, Hsp90 and Hsp70 in TMEV-infected BHK-21 cells was investigated by indirect immunofluorescence and confocal microscopy. Results and Discussion: VP1 proteins of picornaviruses are highly divergent within the family at the amino acid level, which might be linked to the protein’s function in determining virus tropism and antibody neutralisation. An eight-stranded anti-parallel beta-barrel structure was found conserved in the VP1 protein structures which might be linked to the highly conserved picornavirus capsid assembly process. Absence of a common protein domain between Hsp90 viral and cellular client proteins that might be functionally connected to Hsp90, suggests that Hsp90 most likely recognises surface features rather than sequence motifs/patterns. The Hsp90 inhibitors, novobiocin and geldanamycin, had a negative effect on virus growth as virus-induced cytopathic effect was not observed in treated cell after 48hrs. TMEV 2C protein was detected by Western analysis in infected cell lysates treated with geldanamycin but not novobiocin, suggesting novobiocin affects the translation or processing of TMEV 2C. Immunofluorescence analysis of TMEV-infected cells showed a relocalisation of Hsp40 into the nucleus during infection. Overlap of Hsp40 and TMEV P1 was observed in the perinuclear region, suggesting colocalisation between these proteins. Hsp70 converged around the replication complex during infection but did not overlap with TMEV 2C. Hsp90 concentrated in the region of the replication complex where it overlapped with TMEV 2C and this redistribution was found to be dependent on the stage of infection. The overlap between Hsp90 and TMEV 2C signals observed, suggested colocalisation between the two proteins. Conclusion: This study identified Hsp90, Hsp70 and Hsp40 as possible host factors required in TMEV replication.
- Full Text:
- Date Issued: 2011
Microwave Mediated synthesis of cyclic compounds
- Authors: Ndebvu, Rumbidzayi
- Date: 2011
- Subjects: Cyclic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18488 , http://hdl.handle.net/11260/d1007382
- Description: The scope of microwave induced synthesis of various cyclic compounds was investigated and considerably expanded. The advantages of this synthetic method were clearly demonstrated when compared to conventional heating methods of organic synthesis. The exposure of organic compounds to continual Ultraviolet (UV) radiation damages the materials and reduces their chemical and physical properties and in most cases irreversibly and this is not only a concern for industry but for consumers as well. Particularly prevalent are incidences of skin cancer now linked to UV radiation. Research efforts are directed towards finding cheap and efficient UV-absorbers to protect such light sensitive materials. Phenyl salicylates and hydroxybenzophenones constitute families of UV-absorber compounds, and this has necessitated this research. The condensation of differently substituted phenols with salicylic acid, catalyzed by either phosphoric acid (PPA), POCl3/ZnCl2 or ZnCl2 afforded the anticipated phenolic type UV -absorber molecules such as phenyl salicylate, 4-hydroxyphenyl-2-hydroxybenzoate, 2,3-dihydroxyphenyl-2-hydroxyphenylbenzoate, 3-hydroxyphenyl-2-hydroxybenzoate, (2,4-dihydroxyphenyl)(2-hydroxyphenyl)methanone, (2,3-dihydroxyphenyl)(2-hydroxyphenyl) methanone and 1,3-dihydroxyxanthone. PPA proved to be a more efficient catalyst for the condensation of salicylic acid with phenol, hydroquinone, pyrogallol and catechol while POCl3/ZnCl2 gave higher yields for resorcinol and phloroglucinol. In all cases, ZnCl2 alone did not show significant yield enhancement. The second part of this research work describes a convenient one-pot synthesis of NMethyl-2-pyrrolidone (NMP) an important industrial solvent by a conventional heating process and by microwave irradiation. The intermediate N-Methyl-hydroxybutyramide formed from the exothermic reaction of =-butyrolactone with aqueous monomethylamine, underwent an intramolecular condensation reaction catalyzed by highly active copper powder to form the anticipated product in very good yields.
- Full Text:
- Date Issued: 2011
- Authors: Ndebvu, Rumbidzayi
- Date: 2011
- Subjects: Cyclic compounds -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18488 , http://hdl.handle.net/11260/d1007382
- Description: The scope of microwave induced synthesis of various cyclic compounds was investigated and considerably expanded. The advantages of this synthetic method were clearly demonstrated when compared to conventional heating methods of organic synthesis. The exposure of organic compounds to continual Ultraviolet (UV) radiation damages the materials and reduces their chemical and physical properties and in most cases irreversibly and this is not only a concern for industry but for consumers as well. Particularly prevalent are incidences of skin cancer now linked to UV radiation. Research efforts are directed towards finding cheap and efficient UV-absorbers to protect such light sensitive materials. Phenyl salicylates and hydroxybenzophenones constitute families of UV-absorber compounds, and this has necessitated this research. The condensation of differently substituted phenols with salicylic acid, catalyzed by either phosphoric acid (PPA), POCl3/ZnCl2 or ZnCl2 afforded the anticipated phenolic type UV -absorber molecules such as phenyl salicylate, 4-hydroxyphenyl-2-hydroxybenzoate, 2,3-dihydroxyphenyl-2-hydroxyphenylbenzoate, 3-hydroxyphenyl-2-hydroxybenzoate, (2,4-dihydroxyphenyl)(2-hydroxyphenyl)methanone, (2,3-dihydroxyphenyl)(2-hydroxyphenyl) methanone and 1,3-dihydroxyxanthone. PPA proved to be a more efficient catalyst for the condensation of salicylic acid with phenol, hydroquinone, pyrogallol and catechol while POCl3/ZnCl2 gave higher yields for resorcinol and phloroglucinol. In all cases, ZnCl2 alone did not show significant yield enhancement. The second part of this research work describes a convenient one-pot synthesis of NMethyl-2-pyrrolidone (NMP) an important industrial solvent by a conventional heating process and by microwave irradiation. The intermediate N-Methyl-hydroxybutyramide formed from the exothermic reaction of =-butyrolactone with aqueous monomethylamine, underwent an intramolecular condensation reaction catalyzed by highly active copper powder to form the anticipated product in very good yields.
- Full Text:
- Date Issued: 2011
Mohair and wool fibre surface structure and lustre determination
- Ndlovu, Ntombizikhona Beaulah
- Authors: Ndlovu, Ntombizikhona Beaulah
- Date: 2011
- Subjects: Mohair and wool fibre -- Lustre
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18484 , http://hdl.handle.net/11260/d1006641
- Description: Textiles have always been one of the essential materials for people and have a great variety of uses such as in clothing, agriculture, medical, automotive and aerospace applications. The sort of properties needed for any type of fabric basically depend on the structure of the fibre surface. Of many geometric attributes that can be used to describe the surface appearance of a fibre, yarn, or fabric sample, one of the more common is lustre. Mohair and wool fibre surface structure have been studied using optical microscopy and Atomic Force Microscopy (AFM). Optical microscopy was also used to take fibre diameter measurements. Another technique, goniophotometry, was used to make quantitative lustre measurements of mohair and wool fibres. The surface structure of mohair has got a faint pattern of scales where the scales are generally unpronounced or flat and relatively long. Wool has got a scaly surface structure where the scales overlap leading to interlocking of fibres. The scale configuration on the surface of mohair and wool fibres also differs. A qualitative connection between fibre lustre and the fibre surface structure was found. Because of its smooth surface relative to that of wool, mohair reflects a greater amount of incident light specularly whereas wool reflects most of the incident light diffusely. In general, mohair fibres have a higher lustre than wool due to its less prominent cuticle structure found on its surface. Furthermore, mohair fibres with the smallest diameters give an even higher lustre.
- Full Text:
- Date Issued: 2011
- Authors: Ndlovu, Ntombizikhona Beaulah
- Date: 2011
- Subjects: Mohair and wool fibre -- Lustre
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18484 , http://hdl.handle.net/11260/d1006641
- Description: Textiles have always been one of the essential materials for people and have a great variety of uses such as in clothing, agriculture, medical, automotive and aerospace applications. The sort of properties needed for any type of fabric basically depend on the structure of the fibre surface. Of many geometric attributes that can be used to describe the surface appearance of a fibre, yarn, or fabric sample, one of the more common is lustre. Mohair and wool fibre surface structure have been studied using optical microscopy and Atomic Force Microscopy (AFM). Optical microscopy was also used to take fibre diameter measurements. Another technique, goniophotometry, was used to make quantitative lustre measurements of mohair and wool fibres. The surface structure of mohair has got a faint pattern of scales where the scales are generally unpronounced or flat and relatively long. Wool has got a scaly surface structure where the scales overlap leading to interlocking of fibres. The scale configuration on the surface of mohair and wool fibres also differs. A qualitative connection between fibre lustre and the fibre surface structure was found. Because of its smooth surface relative to that of wool, mohair reflects a greater amount of incident light specularly whereas wool reflects most of the incident light diffusely. In general, mohair fibres have a higher lustre than wool due to its less prominent cuticle structure found on its surface. Furthermore, mohair fibres with the smallest diameters give an even higher lustre.
- Full Text:
- Date Issued: 2011
Assessing the statistical methodologies of business research in the South African context
- Authors: Ndou, Aifheli Amos
- Date: 2011
- Subjects: Statistics -- South Africa , Commercial statistics -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:8631 , http://hdl.handle.net/10948/1484 , Statistics -- South Africa , Commercial statistics -- South Africa
- Description: The aim of the study is to establish an acceptable classification scheme for the statistical methods used in business research. The approach compares the statistical component of the research and evaluates how it has changed over time and across different journals. If, as expected, the statistical expertise has changed, the change would be identified with the view to recommending curriculum changes for Statistics Departments of South African tertiary institutions.
- Full Text:
- Date Issued: 2011
- Authors: Ndou, Aifheli Amos
- Date: 2011
- Subjects: Statistics -- South Africa , Commercial statistics -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:8631 , http://hdl.handle.net/10948/1484 , Statistics -- South Africa , Commercial statistics -- South Africa
- Description: The aim of the study is to establish an acceptable classification scheme for the statistical methods used in business research. The approach compares the statistical component of the research and evaluates how it has changed over time and across different journals. If, as expected, the statistical expertise has changed, the change would be identified with the view to recommending curriculum changes for Statistics Departments of South African tertiary institutions.
- Full Text:
- Date Issued: 2011
The medicinal chemistry of cyclo(D-Phe-2Cl-Pro) and cyclo(Phe-4F-Pro)
- Authors: Ndung'u, Susan Wanjiru
- Date: 2011
- Subjects: Peptide drugs , Cyclic peptides , Pharmaceutical chemistry , Peptides -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7083 , vital:21223
- Description: Although peptides and proteins are considered as lead compounds for the discovery and development of new therapeutic agents, poor metabolic and physical properties have limited their optimisation as drug candidates (Adessi & Soto, 2002). Research by medicinal chemists however, generated the discovery of structural similarities between some peptides and diketopiperazines and the common occurrence of such compounds in natural products. This discovery initiated the synthesis of diketopiperazines from amino acids in an attempt to bypass the previously mentioned limitations of using peptides as drug candidates (Dinsmore & Beshore, 2002). Diketopiperazines (DKPs) are the simplest form of cyclic dipeptides, and a class of unexplored bioactive peptides that have great potential for the future. The compounds are relatively simple to synthesise and are prevalent in nature (Prasad, 1995). The DKP backbone is rigid and therefore poses conformational constraint on the compounds. This rigidity allows for simple conformational analysis of the compounds and also gives insight into the conformational requirements for interaction with the targets involved in their biological activity. The reduced conformational freedom also increases the receptor specificity and thus the compounds are proposed to have less unfavourable effects (Anteunis, 1978). The aim of the study was to synthesise compounds that would exhibit metabolic stability, receptor specificity and enhanced lipophilicity which would increase the bioavailability of the compounds. This was to be achieved by the introduction of fluorine and chlorine elements into the DKPs. The structure of the DKPs would be altered which in turn would improve the physicochemical properties and the biological activity of the compounds (Naumann, 1999). Cyclo(D-Phe-2Cl-Pro) and cyclo(Phe-4F-Pro) were synthesised using the method of Milne et al. (1992) and by boiling the linear counterparts under reflux in sec-butanol-toluene. The structures of the synthesised DKPs were elucidated using mass spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy and molecular modeling. Qualitative analysis and evaluation of the physicochemical properties of the DKPs were performed using high-performance liquid chromatography, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and x-ray powder diffraction. The study aimed to determine the biological activity of cyclo(D-Phe-2Cl-Pro) and cyclo(Phe-4F-Pro) with respect to their anticancer, antimicrobial, haematological and antidiabetic effects. The anticancer results obtained indicated that the percentage inhibition produced by both DKPs were lower than those proposed by Graz et al. (2000) for proline-containing DKPs where, a greater than 50% inhibition was observed for cyclo(Phe-Pro). Antimicrobial studies revealed that both DKPs demonstrated marginal effects on Gram-positive and Gram-negative organisms but showed significant effects against C. albicans. The haematological studies revealed that cyclo(D-Phe-2Cl-Pro) at a screening concentration of 12.5 mM, significantly decreased the levels of D-dimer (P < 0.0001). The antidiabetics studies showed limited activity of the DKPs in inhibiting the activity of α-glucosidase and α-amylase enzymes.
- Full Text:
- Date Issued: 2011
- Authors: Ndung'u, Susan Wanjiru
- Date: 2011
- Subjects: Peptide drugs , Cyclic peptides , Pharmaceutical chemistry , Peptides -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/7083 , vital:21223
- Description: Although peptides and proteins are considered as lead compounds for the discovery and development of new therapeutic agents, poor metabolic and physical properties have limited their optimisation as drug candidates (Adessi & Soto, 2002). Research by medicinal chemists however, generated the discovery of structural similarities between some peptides and diketopiperazines and the common occurrence of such compounds in natural products. This discovery initiated the synthesis of diketopiperazines from amino acids in an attempt to bypass the previously mentioned limitations of using peptides as drug candidates (Dinsmore & Beshore, 2002). Diketopiperazines (DKPs) are the simplest form of cyclic dipeptides, and a class of unexplored bioactive peptides that have great potential for the future. The compounds are relatively simple to synthesise and are prevalent in nature (Prasad, 1995). The DKP backbone is rigid and therefore poses conformational constraint on the compounds. This rigidity allows for simple conformational analysis of the compounds and also gives insight into the conformational requirements for interaction with the targets involved in their biological activity. The reduced conformational freedom also increases the receptor specificity and thus the compounds are proposed to have less unfavourable effects (Anteunis, 1978). The aim of the study was to synthesise compounds that would exhibit metabolic stability, receptor specificity and enhanced lipophilicity which would increase the bioavailability of the compounds. This was to be achieved by the introduction of fluorine and chlorine elements into the DKPs. The structure of the DKPs would be altered which in turn would improve the physicochemical properties and the biological activity of the compounds (Naumann, 1999). Cyclo(D-Phe-2Cl-Pro) and cyclo(Phe-4F-Pro) were synthesised using the method of Milne et al. (1992) and by boiling the linear counterparts under reflux in sec-butanol-toluene. The structures of the synthesised DKPs were elucidated using mass spectrometry, nuclear magnetic resonance spectroscopy, infrared spectroscopy and molecular modeling. Qualitative analysis and evaluation of the physicochemical properties of the DKPs were performed using high-performance liquid chromatography, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and x-ray powder diffraction. The study aimed to determine the biological activity of cyclo(D-Phe-2Cl-Pro) and cyclo(Phe-4F-Pro) with respect to their anticancer, antimicrobial, haematological and antidiabetic effects. The anticancer results obtained indicated that the percentage inhibition produced by both DKPs were lower than those proposed by Graz et al. (2000) for proline-containing DKPs where, a greater than 50% inhibition was observed for cyclo(Phe-Pro). Antimicrobial studies revealed that both DKPs demonstrated marginal effects on Gram-positive and Gram-negative organisms but showed significant effects against C. albicans. The haematological studies revealed that cyclo(D-Phe-2Cl-Pro) at a screening concentration of 12.5 mM, significantly decreased the levels of D-dimer (P < 0.0001). The antidiabetics studies showed limited activity of the DKPs in inhibiting the activity of α-glucosidase and α-amylase enzymes.
- Full Text:
- Date Issued: 2011
Statistical comparison of international size-based equity index using a mixture distribution
- Authors: Ngundze, Unathi
- Date: 2011
- Subjects: Mixture distributions (Probability theory) , Finance -- Statistics , Investment analysis , Portfolio management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10576 , http://hdl.handle.net/10948/d1012367 , Mixture distributions (Probability theory) , Finance -- Statistics , Investment analysis , Portfolio management
- Description: Investors and financial analysts spend an inordinate amount of time, resources and effort in an attempt to perfect the science of maximising the level of financial returns. To this end, the field of distribution modelling and analysis of firm size effect is important as an investment analysis and appraisal tool. Numerous studies have been conducted to determine which distribution best fits stock returns (Mandelbrot, 1963; Fama, 1965 and Akgiray and Booth, 1988). Analysis and review of earlier research has revealed that researchers claim that the returns follow a normal distribution. However, the findings have not been without their own limitations in terms of the empirical results in that many also say that the research done does not account for the fat tails and skewness of the data. Some research studies dealing with the anomaly of firm size effect have led to the conclusion that smaller firms tend to command higher returns relative to their larger counterparts with a similar risk profile (Banz, 1981). Recently, Janse van Rensburg et al. (2009a) conducted a study in which both non- normality of stock returns and firm size effect were addressed simultaneously. They used a scale mixture of two normal distributions to compare the stock returns of large capitalisation and small capitalisation shares portfolios. The study concluded that in periods of high volatility, the small capitalisation portfolio is far more risky than the large capitalisation portfolio. In periods of low volatility they are equally risky. Janse van Rensburg et al. (2009a) identified a number of limitations to the study. These included data problems, survivorship bias, exclusion of dividends, and the use of standard statistical tests in the presence of non-normality. They concluded that it was difficult to generalise findings because of the use of only two (limited) portfolios. In the extension of the research, Janse van Rensburg (2009b) concluded that a scale mixture of two normal distributions provided a more superior fit than any other mixture. The scope of this research is an extension of the work by Janse van Rensburg et al. (2009a) and Janse van Rensburg (2009b), with a view to addressing several of the limitations and findings of the earlier studies. The Janse van rensburg (2009b) study was based on data from the Johannesburg Stock Exchange (JSE); this study seeks to compare their research by looking at the New York Stock Exchange (NYSE) to determine if similar results occur in developed markets. For analysis purposes, this study used the statistical software package R (R Development Core Team 2008) and its package mixtools (Young, Benaglia, Chauveau, Elmore, Hettmansperg, Hunter, Thomas, Xuan 2008). Some computation was also done using Microsoft Excel. This dissertation is arranged as follows: Chapter 2 is a literature review of some of the baseline studies and research that supports the conclusion that earlier research finding had serious limitations. Chapter 3 describes the data used in the study and gives a breakdown of portfolio formation and the methodology used in the study. Chapter 4 provides the statistical background of the methods used in this study. Chapter 5 presents the statistical analysis and distribution fitting of the data. Finally, Chapter 6 gives conclusions drawn from the results obtained in the analysis of data as well as recommendations for future work.
- Full Text:
- Date Issued: 2011
- Authors: Ngundze, Unathi
- Date: 2011
- Subjects: Mixture distributions (Probability theory) , Finance -- Statistics , Investment analysis , Portfolio management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10576 , http://hdl.handle.net/10948/d1012367 , Mixture distributions (Probability theory) , Finance -- Statistics , Investment analysis , Portfolio management
- Description: Investors and financial analysts spend an inordinate amount of time, resources and effort in an attempt to perfect the science of maximising the level of financial returns. To this end, the field of distribution modelling and analysis of firm size effect is important as an investment analysis and appraisal tool. Numerous studies have been conducted to determine which distribution best fits stock returns (Mandelbrot, 1963; Fama, 1965 and Akgiray and Booth, 1988). Analysis and review of earlier research has revealed that researchers claim that the returns follow a normal distribution. However, the findings have not been without their own limitations in terms of the empirical results in that many also say that the research done does not account for the fat tails and skewness of the data. Some research studies dealing with the anomaly of firm size effect have led to the conclusion that smaller firms tend to command higher returns relative to their larger counterparts with a similar risk profile (Banz, 1981). Recently, Janse van Rensburg et al. (2009a) conducted a study in which both non- normality of stock returns and firm size effect were addressed simultaneously. They used a scale mixture of two normal distributions to compare the stock returns of large capitalisation and small capitalisation shares portfolios. The study concluded that in periods of high volatility, the small capitalisation portfolio is far more risky than the large capitalisation portfolio. In periods of low volatility they are equally risky. Janse van Rensburg et al. (2009a) identified a number of limitations to the study. These included data problems, survivorship bias, exclusion of dividends, and the use of standard statistical tests in the presence of non-normality. They concluded that it was difficult to generalise findings because of the use of only two (limited) portfolios. In the extension of the research, Janse van Rensburg (2009b) concluded that a scale mixture of two normal distributions provided a more superior fit than any other mixture. The scope of this research is an extension of the work by Janse van Rensburg et al. (2009a) and Janse van Rensburg (2009b), with a view to addressing several of the limitations and findings of the earlier studies. The Janse van rensburg (2009b) study was based on data from the Johannesburg Stock Exchange (JSE); this study seeks to compare their research by looking at the New York Stock Exchange (NYSE) to determine if similar results occur in developed markets. For analysis purposes, this study used the statistical software package R (R Development Core Team 2008) and its package mixtools (Young, Benaglia, Chauveau, Elmore, Hettmansperg, Hunter, Thomas, Xuan 2008). Some computation was also done using Microsoft Excel. This dissertation is arranged as follows: Chapter 2 is a literature review of some of the baseline studies and research that supports the conclusion that earlier research finding had serious limitations. Chapter 3 describes the data used in the study and gives a breakdown of portfolio formation and the methodology used in the study. Chapter 4 provides the statistical background of the methods used in this study. Chapter 5 presents the statistical analysis and distribution fitting of the data. Finally, Chapter 6 gives conclusions drawn from the results obtained in the analysis of data as well as recommendations for future work.
- Full Text:
- Date Issued: 2011
Application of macroinvertebrate based biomonitoring approaches to assess anthropogenic impacts in the Swartkops River, South Africa
- Authors: Odume, Oghenekaro Nelson
- Date: 2011
- Subjects: Water -- Pollution -- South Africa -- Swartkops River Water quality biological assessment -- South Africa -- Swartkops River Environmental monitoring -- South Africa -- Swartkops River Aquatic invertebrates -- Effect of water pollution on -- South Africa -- Swartkops River
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6040 , http://hdl.handle.net/10962/d1006199
- Description: A growing human population accompanied by urbanisation and industrialisation have led to over exploitation and pollution of freshwater resources and have consequently impacted on aquatic ecosystem health. The Swartkops River in the Eastern Cape of South Africa is no exception. It drains a heavily industrialised catchment which has led to deterioration of its water quality due to pollution. Integrated water resources management (IWRM) requires the concurrent sustainable use of water resources and the protection of aquatic ecosystem health. Macroinvertebrates are well known for their ability to reflect the health of the environment in which they live, thus they were used to assess anthropogenic impacts in the Swartkops River for this study. Macroinvertebrate based biomonitoring approaches, including the South African Scoring System version 5 (SASS5); a multimetric approach involving 19 metrics; Chironomidae community assessments and screening of morphological deformities in Chironomidae larvae, were applied at four selected sampling sites to assess environmental water quality in the Swartkops River. Macroinvertebrates were sampled us ing the SASS5 protocols. Chironomidae were mounted and identified as far as practically possible using available keys. Mentum, ligula, mandible, paraligula and antenna in Chironomidae larvae were screened for deformities. Physical and chemical water quality variables were measured at each of the selected sampling sites. All data were subjected to relevant statistical analyses. Of the four sites sampled during the study period, results revealed that water quality at site 1 was the least impacted with highest SASS5 scores, average score per taxa (ASPT) values, richness, diversity, equitability and Ephemeroptera –Plecoptera-Trichoptera (EPT) richness, as well as least incidences of chironomid deformities. Water quality at site 2 was considered the next least impacted with higher SASS5 scores, A SPT values, richness, diversity and equitability, and lower incidences of deformities compared to sites 3 and 4. SASS5 scores and ASPT values revealed that both sites 3 and 4 were critically modified but the multimetric analysis, Chironomidae community assessment and incidences of deformities in Chironomidae larvae indicated that site 3 is the most impacted of the four sampling sites, with least species diversity, richness, equitability and highest incidences of deformities. The study revealed the importance of multicriteria approach to environmental biomonitoring as an integrated water resources management tool, and based on the results, site 3, as the most impacted, could be prioritised for restoration intervention.
- Full Text:
- Date Issued: 2011
- Authors: Odume, Oghenekaro Nelson
- Date: 2011
- Subjects: Water -- Pollution -- South Africa -- Swartkops River Water quality biological assessment -- South Africa -- Swartkops River Environmental monitoring -- South Africa -- Swartkops River Aquatic invertebrates -- Effect of water pollution on -- South Africa -- Swartkops River
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6040 , http://hdl.handle.net/10962/d1006199
- Description: A growing human population accompanied by urbanisation and industrialisation have led to over exploitation and pollution of freshwater resources and have consequently impacted on aquatic ecosystem health. The Swartkops River in the Eastern Cape of South Africa is no exception. It drains a heavily industrialised catchment which has led to deterioration of its water quality due to pollution. Integrated water resources management (IWRM) requires the concurrent sustainable use of water resources and the protection of aquatic ecosystem health. Macroinvertebrates are well known for their ability to reflect the health of the environment in which they live, thus they were used to assess anthropogenic impacts in the Swartkops River for this study. Macroinvertebrate based biomonitoring approaches, including the South African Scoring System version 5 (SASS5); a multimetric approach involving 19 metrics; Chironomidae community assessments and screening of morphological deformities in Chironomidae larvae, were applied at four selected sampling sites to assess environmental water quality in the Swartkops River. Macroinvertebrates were sampled us ing the SASS5 protocols. Chironomidae were mounted and identified as far as practically possible using available keys. Mentum, ligula, mandible, paraligula and antenna in Chironomidae larvae were screened for deformities. Physical and chemical water quality variables were measured at each of the selected sampling sites. All data were subjected to relevant statistical analyses. Of the four sites sampled during the study period, results revealed that water quality at site 1 was the least impacted with highest SASS5 scores, average score per taxa (ASPT) values, richness, diversity, equitability and Ephemeroptera –Plecoptera-Trichoptera (EPT) richness, as well as least incidences of chironomid deformities. Water quality at site 2 was considered the next least impacted with higher SASS5 scores, A SPT values, richness, diversity and equitability, and lower incidences of deformities compared to sites 3 and 4. SASS5 scores and ASPT values revealed that both sites 3 and 4 were critically modified but the multimetric analysis, Chironomidae community assessment and incidences of deformities in Chironomidae larvae indicated that site 3 is the most impacted of the four sampling sites, with least species diversity, richness, equitability and highest incidences of deformities. The study revealed the importance of multicriteria approach to environmental biomonitoring as an integrated water resources management tool, and based on the results, site 3, as the most impacted, could be prioritised for restoration intervention.
- Full Text:
- Date Issued: 2011
Characterization of stratified L-topological spaces by convergence of stratified L-filters
- Authors: Orpen, David Lisle
- Date: 2011
- Subjects: Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5402 , http://hdl.handle.net/10962/d1005216 , Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
- Description: For the case where L is an ecl-premonoid, we explore various characterizations of SL-topological spaces, in particular characterization in terms of a convergence function lim: FS L(X) ! LX. We find we have to introduce a new axiom , L on the lim function in order to completely describe SL-topological spaces, which is not required in the case where L is a frame. We generalize the classical Kowalski and Fischer axioms to the lattice context and examine their relationship to the convergence axioms. We define the category of stratified L-generalized convergence spaces, as a generalization of the classical convergence spaces and investigate conditions under which it contains the category of stratified L-topological spaces as a reflective subcategory. We investigate some subcategories of the category of stratified L-generalized convergence spaces obtained by generalizing various classical convergence axioms.
- Full Text:
- Date Issued: 2011
- Authors: Orpen, David Lisle
- Date: 2011
- Subjects: Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5402 , http://hdl.handle.net/10962/d1005216 , Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
- Description: For the case where L is an ecl-premonoid, we explore various characterizations of SL-topological spaces, in particular characterization in terms of a convergence function lim: FS L(X) ! LX. We find we have to introduce a new axiom , L on the lim function in order to completely describe SL-topological spaces, which is not required in the case where L is a frame. We generalize the classical Kowalski and Fischer axioms to the lattice context and examine their relationship to the convergence axioms. We define the category of stratified L-generalized convergence spaces, as a generalization of the classical convergence spaces and investigate conditions under which it contains the category of stratified L-topological spaces as a reflective subcategory. We investigate some subcategories of the category of stratified L-generalized convergence spaces obtained by generalizing various classical convergence axioms.
- Full Text:
- Date Issued: 2011
Neuronal nitric oxide synthase : a biomarker for Alzheimers disease : interaction of neuronal nitric oxide synthase with beta-amyloid peptides in the brain
- Authors: Padayachee, Eden Rebecca
- Date: 2011 , 2013-07-19
- Subjects: Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4086 , http://hdl.handle.net/10962/d1007677 , Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Description: High levels of the amino acid arginine and low levels of the product citrulline in the cerebrospinal fluid of Alzheimer's patients could mean that there is a decrease in the enzymes that metabolize this amino acid. One such enzyme is neuronal nitric oxide synthase (nNOS). In this study, neuronal nitric oxide synthase (nNOS), sourced from bovine brain was extracted and concentrated using two methods of precipitation: poly (ethylene glycol) 20 000 (PEG) and ammonium sulphate [(NH₄)₂S0₄). These two techniques gave no increase in yield nor fold purification and hence were abandoned in favour of ion exchange chromatography by DEAE-Sepharose. The enzyme was then successfully purified by anion-exchange and after dialysis produced a 38% yield and three fold purification and yielded the highest specific activity of 2.27 U/mg. Neuronal nitric oxide synthase (nNOS) was a heterodimeric protein with a total molecular mass of ± 225 kDa (95 and 130 kDa monomers). The temperature and pH optima of the enzyme were 40⁰C and 6.5, respectively. The kinetic parameters (KM and Vmax) of nNOS were 70 μM and 0.332 μmol.min⁻¹, respectively. Moreover neuronal nitric oxide synthase (nNOS) was relatively stable at 40⁰C (t½ = 3 h). It was also confirmed that β-amyloid peptides inhibited nNOS when bound to the enzyme and that nNOS behaved as a catalyst in fibril formation through association-dissociation between enzyme and β-amyloid peptide. It was further shown that Aβ₁₇₋₂₈ inhibited nNOS the most with a Ki of 1.92 μM and also had the highest Stern-Volmer value (Ksv) of 0.11 μM⁻¹ indicating tight binding affinity to nNOS and easier accessibility to fluor molecules during binding. Congo red, turbidity, thioflavin-T assays and transmission electron microscopy were successfully used to detect and visualize the presence of fibrils by studying the process of fibrillogenesis. Computerized molecular modeling successfully studied protein dynamics and conformational changes of nNOS. These results correlated with resonance energy transfer (FRET) results which revealed the distance of tryptophan residues from the arginine bound at enzyme active site. Both the aforementioned techniques revealed that in the natural state of the enzyme with arginine bound at the active site, the tryptophan residues (TRP₆₂₅ and TRP₇₂₁) were positioned at the surface of the enzyme 28 Å away from the active site. When the amyloid peptide (Aβ₁₇₋₂₈) was bound to the active site, these same two amino acids moved 14 Å closer to the active site. A five residue hydrophobic fragment Aβ₁₇₋₂₁ [Leu₁₇ - Val₁₈ - Phe₁₉ - Phe₂₀ - Ala₁] within Aβ₁₇₋₂₈ was shown by computer modeling to be critical to the binding of the peptide to the active site of nNOS.
- Full Text:
- Date Issued: 2011
- Authors: Padayachee, Eden Rebecca
- Date: 2011 , 2013-07-19
- Subjects: Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4086 , http://hdl.handle.net/10962/d1007677 , Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Description: High levels of the amino acid arginine and low levels of the product citrulline in the cerebrospinal fluid of Alzheimer's patients could mean that there is a decrease in the enzymes that metabolize this amino acid. One such enzyme is neuronal nitric oxide synthase (nNOS). In this study, neuronal nitric oxide synthase (nNOS), sourced from bovine brain was extracted and concentrated using two methods of precipitation: poly (ethylene glycol) 20 000 (PEG) and ammonium sulphate [(NH₄)₂S0₄). These two techniques gave no increase in yield nor fold purification and hence were abandoned in favour of ion exchange chromatography by DEAE-Sepharose. The enzyme was then successfully purified by anion-exchange and after dialysis produced a 38% yield and three fold purification and yielded the highest specific activity of 2.27 U/mg. Neuronal nitric oxide synthase (nNOS) was a heterodimeric protein with a total molecular mass of ± 225 kDa (95 and 130 kDa monomers). The temperature and pH optima of the enzyme were 40⁰C and 6.5, respectively. The kinetic parameters (KM and Vmax) of nNOS were 70 μM and 0.332 μmol.min⁻¹, respectively. Moreover neuronal nitric oxide synthase (nNOS) was relatively stable at 40⁰C (t½ = 3 h). It was also confirmed that β-amyloid peptides inhibited nNOS when bound to the enzyme and that nNOS behaved as a catalyst in fibril formation through association-dissociation between enzyme and β-amyloid peptide. It was further shown that Aβ₁₇₋₂₈ inhibited nNOS the most with a Ki of 1.92 μM and also had the highest Stern-Volmer value (Ksv) of 0.11 μM⁻¹ indicating tight binding affinity to nNOS and easier accessibility to fluor molecules during binding. Congo red, turbidity, thioflavin-T assays and transmission electron microscopy were successfully used to detect and visualize the presence of fibrils by studying the process of fibrillogenesis. Computerized molecular modeling successfully studied protein dynamics and conformational changes of nNOS. These results correlated with resonance energy transfer (FRET) results which revealed the distance of tryptophan residues from the arginine bound at enzyme active site. Both the aforementioned techniques revealed that in the natural state of the enzyme with arginine bound at the active site, the tryptophan residues (TRP₆₂₅ and TRP₇₂₁) were positioned at the surface of the enzyme 28 Å away from the active site. When the amyloid peptide (Aβ₁₇₋₂₈) was bound to the active site, these same two amino acids moved 14 Å closer to the active site. A five residue hydrophobic fragment Aβ₁₇₋₂₁ [Leu₁₇ - Val₁₈ - Phe₁₉ - Phe₂₀ - Ala₁] within Aβ₁₇₋₂₈ was shown by computer modeling to be critical to the binding of the peptide to the active site of nNOS.
- Full Text:
- Date Issued: 2011
Investigations of the assessment of bioequivalence of topical clotrimazole products using a dermatopharmacokinetic approach
- Authors: Parfitt, Natalie Rae
- Date: 2011 , 2010-07-05
- Subjects: Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3840 , http://hdl.handle.net/10962/d1007659 , Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Description: The specialised nature of the stratum corneum makes it an efficient barrier to foreign substances, including drug molecules. Therefore, cutaneous drug absorption is a slow and complex process of which stratum corneum penetration is the rate limiting step. The rate and extent of stratum corneum penetration by a drug compound depends greatly on the presence of penetration enhancing/retarding excipients and therefore the clinical outcomes of a product rely greatly on the components and quality of the formulation. Hence, establishing bioequivalence between topical products is crucial to ensure that patients receiving multisource drug products are assured of the same efficacy and safety as the brand product. Since locally acting topical formulations do not target the systemic circulation, conventional methods of assessing bioequivalence using plasma levels are not appropriate. Consequently, the current regulatory guidelines require comparative clinical trials to be carried out to show bioequivalence between topical products. As these studies are very expensive and time consuming, the development of a more direct and relatively rapid and inexpensive method for determining bioequivalence between topical products is required. Clotrimazole is an anti-fungal agent where the target site of action is in the stratum corneum. In this work, tape stripping, which involves the sampling of stratum corneum, was investigated as a tool for the determination of bioequivalence between topical clotrimazole products. The tape stripping method involved the analysis of each tape strip individually and standardization of stratum corneum thickness between subjects was carried out using TEWL measurements. This approach provided detailed information regarding the amount of clotrimazole present in the stratum corneum as well as the extent of drug penetration. Prior to the tape stripping studies an HPLC method was developed for the quantitative analysis of clotrimazole from the tape strip samples. This method was shown to be accurate and reproducible across the required range. It was also shown to be selective for clotrimazole in the presence of possible interfering substances such as those present in the tape adhesive and also skin components. The bioequivalence studies were conducted using a single “uptake” time point. In order to determine an appropriate dose duration for these studies a novel approach was employed, involving a preliminary dose duration study. For the bioequivalence investigations, Canesten® Topical cream was used as both test and reference products to determine if the method was capable of showing bioequivalence. Subsequently, Canesten® Topical cream was also compared to a 1% gel formulation to determine if the method could detect formulation differences. The conventional BE limits of 0.8 – 1.25 were used for the assessment of BE, however, the clinical relevance of using these limits for dermal studies is debatable since they are derived from oral pharmacokinetic studies. Therefore, the data from the tape stripping investigations were also assessed using more realistic limits of 0.75 – 1.33 and even 0.7 – 1.44. In addition to the tape stripping studies a novel method of determining the amount of drug present in the stratum corneum, the “Residual Method”, was investigated. This method involved assaying the amount of clotrimazole found in the residual formulation after a specified dose duration had elapsed and subtracting that amount from the amount of clotrimazole initially applied. The results of tape stripping investigations showed that, if the study is sufficiently powered, tape stripping may be used to determine bioequivalence according to the conventional limits, as well as possibly detect formulation differences between different clotrimazole products. Bioequivalence assessment using the widened intervals showed that fewer subjects were required to achieve a sufficient statistical power. The variability associated with this method was acceptable and tape stripping may therefore have the potential to be used as a BE tool in a regulatory setting for clotrimazole or other antifungal topical formulations. The “Residual Method” also showed promising results as a bioequivalence tool, but further investigation and extensive validation of this method is required before it can be suggested as a regulatory method. The results of these studies have clearly indicated that tape stripping has the potential to be used as an alternative to comparative clinical trails for the assessment of bioequivalence between clotrimazole formulations and also to assess bioequivalence between other antifungal products.
- Full Text:
- Date Issued: 2011
- Authors: Parfitt, Natalie Rae
- Date: 2011 , 2010-07-05
- Subjects: Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3840 , http://hdl.handle.net/10962/d1007659 , Dermatopharmacology , Drugs -- Therapeutic equivalency , Antifungal agents , Therapeutics, Cutaneous and external
- Description: The specialised nature of the stratum corneum makes it an efficient barrier to foreign substances, including drug molecules. Therefore, cutaneous drug absorption is a slow and complex process of which stratum corneum penetration is the rate limiting step. The rate and extent of stratum corneum penetration by a drug compound depends greatly on the presence of penetration enhancing/retarding excipients and therefore the clinical outcomes of a product rely greatly on the components and quality of the formulation. Hence, establishing bioequivalence between topical products is crucial to ensure that patients receiving multisource drug products are assured of the same efficacy and safety as the brand product. Since locally acting topical formulations do not target the systemic circulation, conventional methods of assessing bioequivalence using plasma levels are not appropriate. Consequently, the current regulatory guidelines require comparative clinical trials to be carried out to show bioequivalence between topical products. As these studies are very expensive and time consuming, the development of a more direct and relatively rapid and inexpensive method for determining bioequivalence between topical products is required. Clotrimazole is an anti-fungal agent where the target site of action is in the stratum corneum. In this work, tape stripping, which involves the sampling of stratum corneum, was investigated as a tool for the determination of bioequivalence between topical clotrimazole products. The tape stripping method involved the analysis of each tape strip individually and standardization of stratum corneum thickness between subjects was carried out using TEWL measurements. This approach provided detailed information regarding the amount of clotrimazole present in the stratum corneum as well as the extent of drug penetration. Prior to the tape stripping studies an HPLC method was developed for the quantitative analysis of clotrimazole from the tape strip samples. This method was shown to be accurate and reproducible across the required range. It was also shown to be selective for clotrimazole in the presence of possible interfering substances such as those present in the tape adhesive and also skin components. The bioequivalence studies were conducted using a single “uptake” time point. In order to determine an appropriate dose duration for these studies a novel approach was employed, involving a preliminary dose duration study. For the bioequivalence investigations, Canesten® Topical cream was used as both test and reference products to determine if the method was capable of showing bioequivalence. Subsequently, Canesten® Topical cream was also compared to a 1% gel formulation to determine if the method could detect formulation differences. The conventional BE limits of 0.8 – 1.25 were used for the assessment of BE, however, the clinical relevance of using these limits for dermal studies is debatable since they are derived from oral pharmacokinetic studies. Therefore, the data from the tape stripping investigations were also assessed using more realistic limits of 0.75 – 1.33 and even 0.7 – 1.44. In addition to the tape stripping studies a novel method of determining the amount of drug present in the stratum corneum, the “Residual Method”, was investigated. This method involved assaying the amount of clotrimazole found in the residual formulation after a specified dose duration had elapsed and subtracting that amount from the amount of clotrimazole initially applied. The results of tape stripping investigations showed that, if the study is sufficiently powered, tape stripping may be used to determine bioequivalence according to the conventional limits, as well as possibly detect formulation differences between different clotrimazole products. Bioequivalence assessment using the widened intervals showed that fewer subjects were required to achieve a sufficient statistical power. The variability associated with this method was acceptable and tape stripping may therefore have the potential to be used as a BE tool in a regulatory setting for clotrimazole or other antifungal topical formulations. The “Residual Method” also showed promising results as a bioequivalence tool, but further investigation and extensive validation of this method is required before it can be suggested as a regulatory method. The results of these studies have clearly indicated that tape stripping has the potential to be used as an alternative to comparative clinical trails for the assessment of bioequivalence between clotrimazole formulations and also to assess bioequivalence between other antifungal products.
- Full Text:
- Date Issued: 2011
The effectiveness of livestock guarding dogs for livestock production and conservation in Namibia
- Authors: Potgieter, Gail Christine
- Date: 2011
- Subjects: Livestock protection dogs -- Namibia , Herding dogs -- Namibia , Livestock -- Predators of -- Control -- Namibia , Livestock -- Losses -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10680 , http://hdl.handle.net/10948/1666 , Livestock protection dogs -- Namibia , Herding dogs -- Namibia , Livestock -- Predators of -- Control -- Namibia , Livestock -- Losses -- Namibia
- Description: The use of livestock guarding dogs (LGDs) to mitigate farmer-predator conflict in Namibia was evaluated. As farmer-predator conflict has two sides, LGDs were evaluated in terms of livestock production and conservation. The main objectives in terms of livestock production were to document: 1) the perceived ability of LGDs to reduce livestock losses in a cost-effective manner; 2) the farmers’ satisfaction with LGD performance; and 3) factors influencing LGD behaviour. The main objectives in terms of conservation were to record: 1) predator killing by farmers relative to LGD introduction; 2) direct impacts of LGDs on target (damage-causing) species; and 3) the impact of LGDs on non-target species. This evaluation was conducted on LGDs bred by the Cheetah Conservation Fund (CCF) and placed on farms in Namibia. The data were collected during face-to-face interviews with farmers using LGDs. Historical data from the CCF programme were used in conjunction with a complete survey of the farmers in the CCF LGD programme during 2009-2010. In terms of livestock production, 91 percent of the LGDs (n = 65) eliminated or reduced livestock losses. Subsequently, 73 percent of the farmers perceived their LGDs as economically beneficial, although a cost-benefit analysis showed that only 59 percent of the LGDs were cost-effective. Farmers were generally satisfied with the performance of their LGDs. However, farmer satisfaction was more closely linked to good LGD behaviour than the perceived reduction in livestock losses. The most commonly-reported LGD behavioural problems (n = 195) were staying at home rather than accompanying the livestock (21 percent) and chasing wildlife (19 percent). LGD staying home behaviour was linked to a lack of care on subsistence farms, as high quality dog food was not consistently provided. Care for LGDs declined with LGD age on subsistence, but not commercial, farms. In terms of conservation, predator-killing farmers killed fewer individuals in the year since LGD introduction than previously; this result was only significant for black-backed jackal Canis mesomelas. However, 37 LGDs killed jackals, nine killed baboons Papio ursinus, three killed caracals Caracal caracal and one killed a cheetah Acinonyx jubatus (n = 83). Farmers and LGDs combined killed significantly more jackals in the survey year than the same farmers (n = 36) killed before LGD introduction. Conversely, five farmers killed 3.2 ± 2.01 cheetahs each in the year before LGD introduction, whereas LGDs and these farmers combined killed only 0.2 ± 0.2 cheetahs per farm in the survey year. Only 16 LGDs (n = 83) killed non-target species. The high LGD success rate in terms of livestock production was facilitated by livestock husbandry practices in the study area. In terms of conservation, LGDs were more beneficial for apex predators than for mesopredators and had a minor impact on non-target species.
- Full Text:
- Date Issued: 2011
- Authors: Potgieter, Gail Christine
- Date: 2011
- Subjects: Livestock protection dogs -- Namibia , Herding dogs -- Namibia , Livestock -- Predators of -- Control -- Namibia , Livestock -- Losses -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10680 , http://hdl.handle.net/10948/1666 , Livestock protection dogs -- Namibia , Herding dogs -- Namibia , Livestock -- Predators of -- Control -- Namibia , Livestock -- Losses -- Namibia
- Description: The use of livestock guarding dogs (LGDs) to mitigate farmer-predator conflict in Namibia was evaluated. As farmer-predator conflict has two sides, LGDs were evaluated in terms of livestock production and conservation. The main objectives in terms of livestock production were to document: 1) the perceived ability of LGDs to reduce livestock losses in a cost-effective manner; 2) the farmers’ satisfaction with LGD performance; and 3) factors influencing LGD behaviour. The main objectives in terms of conservation were to record: 1) predator killing by farmers relative to LGD introduction; 2) direct impacts of LGDs on target (damage-causing) species; and 3) the impact of LGDs on non-target species. This evaluation was conducted on LGDs bred by the Cheetah Conservation Fund (CCF) and placed on farms in Namibia. The data were collected during face-to-face interviews with farmers using LGDs. Historical data from the CCF programme were used in conjunction with a complete survey of the farmers in the CCF LGD programme during 2009-2010. In terms of livestock production, 91 percent of the LGDs (n = 65) eliminated or reduced livestock losses. Subsequently, 73 percent of the farmers perceived their LGDs as economically beneficial, although a cost-benefit analysis showed that only 59 percent of the LGDs were cost-effective. Farmers were generally satisfied with the performance of their LGDs. However, farmer satisfaction was more closely linked to good LGD behaviour than the perceived reduction in livestock losses. The most commonly-reported LGD behavioural problems (n = 195) were staying at home rather than accompanying the livestock (21 percent) and chasing wildlife (19 percent). LGD staying home behaviour was linked to a lack of care on subsistence farms, as high quality dog food was not consistently provided. Care for LGDs declined with LGD age on subsistence, but not commercial, farms. In terms of conservation, predator-killing farmers killed fewer individuals in the year since LGD introduction than previously; this result was only significant for black-backed jackal Canis mesomelas. However, 37 LGDs killed jackals, nine killed baboons Papio ursinus, three killed caracals Caracal caracal and one killed a cheetah Acinonyx jubatus (n = 83). Farmers and LGDs combined killed significantly more jackals in the survey year than the same farmers (n = 36) killed before LGD introduction. Conversely, five farmers killed 3.2 ± 2.01 cheetahs each in the year before LGD introduction, whereas LGDs and these farmers combined killed only 0.2 ± 0.2 cheetahs per farm in the survey year. Only 16 LGDs (n = 83) killed non-target species. The high LGD success rate in terms of livestock production was facilitated by livestock husbandry practices in the study area. In terms of conservation, LGDs were more beneficial for apex predators than for mesopredators and had a minor impact on non-target species.
- Full Text:
- Date Issued: 2011
Solid-phase extraction based sample preparation for the determination of drug and organic pollutant residue
- Authors: Pule, Bellah Oreeditse
- Date: 2011 , 2011-02-08
- Subjects: Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4406 , http://hdl.handle.net/10962/d1006711 , Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Description: This thesis presents solid phase extraction (SPE) methodologies based on mixed-mode polymeric sorbents; a mixed mode strong anion exchanger (Agilent SampliQ SAX) and a mixed mode strong cation exchanger (Agilent SampliQ SCX). Furthermore, dispersive-SPE based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method was assessed for applicability in the determination of drug residues. The mixed-mode polymeric sorbents were evaluated for the simultaneous fractionation of drugs that exhibit diverse polarities with acidic, basic and neutral functionalities in biological matrices (plasma and urine). The polymeric skeleton of these sorbents entails an exchanger group and therefore provides two retention mechanisms, strong cation or anion exchange retention mechanisms with hydrophobic interactions. It was demonstrated that with a sequential elution protocol for sample clean-up analytes were fractionated into acidic, basic and neutral classes. The SAX was employed for analysis of ketoprofen, naproxen (acidic drugs), nortriptyline (basic) and secobarbital (neutral) from urine sample. The SCX was used for fractionating phenobarbital, p-toluamide (acidic), amphetamine, m-toluidine (basic) and acetaminophen (neutral drug) from plasma sample. QuEChERS method was employed for quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) from fish fillets and soil; 9 sulfonamides (SAs) from chicken muscles and acrylamide (AA) in cooking oil. The analyte recoveries ranged from 79.6 - 109% with RSDs ranging from 0.06 - 1.9% at three different fortification levels. Good linearity (r2 > 0.9990) was attained for most analytes. The limits of detection and quantification ranged from 0.03 - 0.84 μg/ml and 0.81 - 1.89 μg/ml respectively for analytes in biological samples. LODs and LOQs for analytes in food and environmental samples ranged from 0.02 to 0.39 and 0.25 to 1.30 ng/g respectively.
- Full Text:
- Date Issued: 2011
- Authors: Pule, Bellah Oreeditse
- Date: 2011 , 2011-02-08
- Subjects: Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4406 , http://hdl.handle.net/10962/d1006711 , Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Description: This thesis presents solid phase extraction (SPE) methodologies based on mixed-mode polymeric sorbents; a mixed mode strong anion exchanger (Agilent SampliQ SAX) and a mixed mode strong cation exchanger (Agilent SampliQ SCX). Furthermore, dispersive-SPE based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method was assessed for applicability in the determination of drug residues. The mixed-mode polymeric sorbents were evaluated for the simultaneous fractionation of drugs that exhibit diverse polarities with acidic, basic and neutral functionalities in biological matrices (plasma and urine). The polymeric skeleton of these sorbents entails an exchanger group and therefore provides two retention mechanisms, strong cation or anion exchange retention mechanisms with hydrophobic interactions. It was demonstrated that with a sequential elution protocol for sample clean-up analytes were fractionated into acidic, basic and neutral classes. The SAX was employed for analysis of ketoprofen, naproxen (acidic drugs), nortriptyline (basic) and secobarbital (neutral) from urine sample. The SCX was used for fractionating phenobarbital, p-toluamide (acidic), amphetamine, m-toluidine (basic) and acetaminophen (neutral drug) from plasma sample. QuEChERS method was employed for quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) from fish fillets and soil; 9 sulfonamides (SAs) from chicken muscles and acrylamide (AA) in cooking oil. The analyte recoveries ranged from 79.6 - 109% with RSDs ranging from 0.06 - 1.9% at three different fortification levels. Good linearity (r2 > 0.9990) was attained for most analytes. The limits of detection and quantification ranged from 0.03 - 0.84 μg/ml and 0.81 - 1.89 μg/ml respectively for analytes in biological samples. LODs and LOQs for analytes in food and environmental samples ranged from 0.02 to 0.39 and 0.25 to 1.30 ng/g respectively.
- Full Text:
- Date Issued: 2011