The removal and recovery of toxic and valuable metals from aqueous solutions by the yeast Saccharomyces cerevisiae
- Authors: Wilhelmi, Brendan Shane
- Date: 1998
- Subjects: Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4002 , http://hdl.handle.net/10962/d1004062 , Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
- Description: This project considered the use of the yeast Saccharomyces cerevisiae as a biosorbent for the removal and recovery of a range of metals from contaminated waters. S. cerevisiae, as a biosorbent, has the potential to provide a cost effective, selective and highly efficient purification system. Initial studies focused on metal accumulation by an immobilized baker's S. cerevisiae biosorbent. The parameters affecting metal uptake were investigated, these included metal concentration, time and solution pH. Metal uptake was rapid. Gold and cobalt reached saturation within 5 min of contact with the biosorbent in batch reactors. Copper, zinc, nickel, cadmium and chromium reached saturation within 30 min of contact. Metal accumulation was pH dependent and was generally unaffected at a solution pH ≥ 4, and was substantially decreased at pH ≤ 2. The exception was gold which was preferentially accumulated at a solution pH of 2. The immobilized baker's yeast accumulated metals with maximum binding capacities in the order of gold > cadmium > cobalt > zinc > copper > chromium > nickel. A rapid method to assess metal recovery was developed. Bioaccumulated metal was efficiently recovered using dilute mineral acids. Copper recovery of ≥ 80 % was achieved by decreasing the solution pH of the reaction mixture to 2 with the addition of nominal quantities of HCl, H₂SO₄ or RNO₃. Adsorption-desorption over 8 cycles had no apparent adverse effect on metal uptake or recovery in batch reactors. Transmission electron microscopy showed no evidence of damage to cells used in copper adsorption-desorption investigations. Biosorption columns were investigated as bioreactors due to their application potential. The metals investigated were effectively removed from solution. At a saturation threshold, metal uptake declined rapidly. Most metals investigated were desorbed from the columns by eluting with 0.1 M HCl. Initially recoveries of copper, cobalt and cadmium were as high as 100%. Desorbed copper, zinc, cadmium, nickel and cobalt were concentrated in 10 to 15 ml of eluent, representing up to a 40 fold decrease in solution volume. Cadmium, nickel and zinc uptake increased with the second application to the columns. Initial accumulation of gold and chromium was 42.2 μmol/g and 28.6 μmol/g, however, due to the low recoveries of these two metals, a second application was not investigated. Copper was applied to a single column for 8 consecutive adsorption-desorption cycles. Uptake increased from an initial 31.3 μmol/g to 47.8 μmol/g at cycle 7. The potential for selective metal recovery was demonstrated using two biosorption columns in series. Copper was accumulated and recovered most efficiently. Zinc, cobalt and cadmium were displaced to the second column. Copper bound preferentially to zinc at a ratio of 6:1. Copper bound preferentially to cobalt at a ratio of 4:1. Cadmium was only displaced at a ratio of 2:1. The successful transfer of the bioremediation technology from the laboratory to an industrial application has yet to be realized. Bioremediation of a Plaatjiesvlei Black Mountain mine effluent, which contained copper, zinc, lead and iron, was investigated in this project. The removal of the metals was most effective at pH 4. A combined strategy of pH adjustment and bioremediation using immobilized S. cerevisiae decreased the copper concentration by 92.5%, lead was decreased by 90% and zinc was decreased by 60%. Iron was mostly precipitated from solution at pH ≥ 4. An ageing pond at the mine with conditions such as; pH, water volume and metal concentration, which were more conducive to biological treatment was subsequently identified. The investigation indicated a possible application of the biomass as a supplement to chemical remediation. The metal removal capability of a waste brewer's yeast was subsequently investigated. A yeast conditioning step increased metal uptake up to 100% and enhanced reproducibility. Metal removal from solution was rapid and pH dependent. The metals were efficiently removed from solution at pH ≥ 4. Uptake was substantially inhibited at pH ≤ 3. The waste brewer's yeast accumulated metals with maximum binding capacities in the order of copper (25.4 μmol/g) > lead (19.4 μmol/g) > iron (15.6 μmol/g) > zinc (12.5 μmol/g). No correlation between cell physiology and metal uptake was observed. Uptake of the four metals was confirmed by energy dispersive X-ray microanalysis. The interference of lead, zinc and iron on copper uptake by the waste brewer's yeast, and the interference of copper on the uptake of lead, zinc and iron was investigated. Maximum copper uptake was not decreased in the presence of lead. The Bmax remained constant at approximately 25 μmol/g. The dissociation constants increased with increasing lead concentrations. Lead bioaccumulation was significantly decreased in the presence of copper. The type of inhibition was dependent on the initial copper concentrations. Zinc had a slight synergistic effect on copper uptake. The copper Bmax increased from 30.8 μmol/g in a single-ion system to 34.5 μmol/g in the presence of 200 μmol/l of zinc. Zinc uptake was severely inhibited in the presence of copper. The maximum uptake and dissociation constant values were decreased in the presence of copper, which suggested an uncompetitive inhibition. The affinity of copper was substantially higher than zinc. The presence of higher levels of copper than zinc in the yeast cells was confirmed by energy dispersive microanalysis. Copper uptake was decreased in the presence of iron, with the copper Bmax being decreased from 25.4 μmol/g in a single-ion system to 20.1 μmol/g in the presence of 200 μmol/l iron. Iron Bmax values remained constant at 16.0 μmol/g. Combined biosorption and EDXA results suggested the iron bound at a higher affinity than copper to the cell wall. Total copper removal was higher as larger quantities of copper were deposited in the cell cytoplasm. Metal removal from the Plaatjiesvlei effluent by free cell suspensions of the waste brewer's yeast was satisfactory. Copper levels were decreased by 96%, iron by 42%, lead 25% and zinc 2%. Waste brewer's yeast is a cheap source of biomass in South Africa, and could potentially provide the basis for the development of an innovative purification system for metal-contaminated waters.
- Full Text:
- Date Issued: 1998
- Authors: Wilhelmi, Brendan Shane
- Date: 1998
- Subjects: Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4002 , http://hdl.handle.net/10962/d1004062 , Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
- Description: This project considered the use of the yeast Saccharomyces cerevisiae as a biosorbent for the removal and recovery of a range of metals from contaminated waters. S. cerevisiae, as a biosorbent, has the potential to provide a cost effective, selective and highly efficient purification system. Initial studies focused on metal accumulation by an immobilized baker's S. cerevisiae biosorbent. The parameters affecting metal uptake were investigated, these included metal concentration, time and solution pH. Metal uptake was rapid. Gold and cobalt reached saturation within 5 min of contact with the biosorbent in batch reactors. Copper, zinc, nickel, cadmium and chromium reached saturation within 30 min of contact. Metal accumulation was pH dependent and was generally unaffected at a solution pH ≥ 4, and was substantially decreased at pH ≤ 2. The exception was gold which was preferentially accumulated at a solution pH of 2. The immobilized baker's yeast accumulated metals with maximum binding capacities in the order of gold > cadmium > cobalt > zinc > copper > chromium > nickel. A rapid method to assess metal recovery was developed. Bioaccumulated metal was efficiently recovered using dilute mineral acids. Copper recovery of ≥ 80 % was achieved by decreasing the solution pH of the reaction mixture to 2 with the addition of nominal quantities of HCl, H₂SO₄ or RNO₃. Adsorption-desorption over 8 cycles had no apparent adverse effect on metal uptake or recovery in batch reactors. Transmission electron microscopy showed no evidence of damage to cells used in copper adsorption-desorption investigations. Biosorption columns were investigated as bioreactors due to their application potential. The metals investigated were effectively removed from solution. At a saturation threshold, metal uptake declined rapidly. Most metals investigated were desorbed from the columns by eluting with 0.1 M HCl. Initially recoveries of copper, cobalt and cadmium were as high as 100%. Desorbed copper, zinc, cadmium, nickel and cobalt were concentrated in 10 to 15 ml of eluent, representing up to a 40 fold decrease in solution volume. Cadmium, nickel and zinc uptake increased with the second application to the columns. Initial accumulation of gold and chromium was 42.2 μmol/g and 28.6 μmol/g, however, due to the low recoveries of these two metals, a second application was not investigated. Copper was applied to a single column for 8 consecutive adsorption-desorption cycles. Uptake increased from an initial 31.3 μmol/g to 47.8 μmol/g at cycle 7. The potential for selective metal recovery was demonstrated using two biosorption columns in series. Copper was accumulated and recovered most efficiently. Zinc, cobalt and cadmium were displaced to the second column. Copper bound preferentially to zinc at a ratio of 6:1. Copper bound preferentially to cobalt at a ratio of 4:1. Cadmium was only displaced at a ratio of 2:1. The successful transfer of the bioremediation technology from the laboratory to an industrial application has yet to be realized. Bioremediation of a Plaatjiesvlei Black Mountain mine effluent, which contained copper, zinc, lead and iron, was investigated in this project. The removal of the metals was most effective at pH 4. A combined strategy of pH adjustment and bioremediation using immobilized S. cerevisiae decreased the copper concentration by 92.5%, lead was decreased by 90% and zinc was decreased by 60%. Iron was mostly precipitated from solution at pH ≥ 4. An ageing pond at the mine with conditions such as; pH, water volume and metal concentration, which were more conducive to biological treatment was subsequently identified. The investigation indicated a possible application of the biomass as a supplement to chemical remediation. The metal removal capability of a waste brewer's yeast was subsequently investigated. A yeast conditioning step increased metal uptake up to 100% and enhanced reproducibility. Metal removal from solution was rapid and pH dependent. The metals were efficiently removed from solution at pH ≥ 4. Uptake was substantially inhibited at pH ≤ 3. The waste brewer's yeast accumulated metals with maximum binding capacities in the order of copper (25.4 μmol/g) > lead (19.4 μmol/g) > iron (15.6 μmol/g) > zinc (12.5 μmol/g). No correlation between cell physiology and metal uptake was observed. Uptake of the four metals was confirmed by energy dispersive X-ray microanalysis. The interference of lead, zinc and iron on copper uptake by the waste brewer's yeast, and the interference of copper on the uptake of lead, zinc and iron was investigated. Maximum copper uptake was not decreased in the presence of lead. The Bmax remained constant at approximately 25 μmol/g. The dissociation constants increased with increasing lead concentrations. Lead bioaccumulation was significantly decreased in the presence of copper. The type of inhibition was dependent on the initial copper concentrations. Zinc had a slight synergistic effect on copper uptake. The copper Bmax increased from 30.8 μmol/g in a single-ion system to 34.5 μmol/g in the presence of 200 μmol/l of zinc. Zinc uptake was severely inhibited in the presence of copper. The maximum uptake and dissociation constant values were decreased in the presence of copper, which suggested an uncompetitive inhibition. The affinity of copper was substantially higher than zinc. The presence of higher levels of copper than zinc in the yeast cells was confirmed by energy dispersive microanalysis. Copper uptake was decreased in the presence of iron, with the copper Bmax being decreased from 25.4 μmol/g in a single-ion system to 20.1 μmol/g in the presence of 200 μmol/l iron. Iron Bmax values remained constant at 16.0 μmol/g. Combined biosorption and EDXA results suggested the iron bound at a higher affinity than copper to the cell wall. Total copper removal was higher as larger quantities of copper were deposited in the cell cytoplasm. Metal removal from the Plaatjiesvlei effluent by free cell suspensions of the waste brewer's yeast was satisfactory. Copper levels were decreased by 96%, iron by 42%, lead 25% and zinc 2%. Waste brewer's yeast is a cheap source of biomass in South Africa, and could potentially provide the basis for the development of an innovative purification system for metal-contaminated waters.
- Full Text:
- Date Issued: 1998
The analysis of a computer music network and the implementation of essential subsystems
- Authors: Wilks, Antony John
- Date: 1995
- Subjects: Computer networks , Computer music , MIDI (Standard)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4666 , http://hdl.handle.net/10962/d1006682 , Computer networks , Computer music , MIDI (Standard)
- Description: The inability to share resources in commercial and institutional computer music studios results in non-optimal resource utilisation. The use of computers to process, store and communicate data can be extended within these studios, to provide the capability of sharing resources amongst their users. This thesis describes a computer music network which was designed for this purpose. Certain devices had to be custom built for the implementation of the network. The thesis discusses the design and construction of these devices.
- Full Text:
- Date Issued: 1995
- Authors: Wilks, Antony John
- Date: 1995
- Subjects: Computer networks , Computer music , MIDI (Standard)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4666 , http://hdl.handle.net/10962/d1006682 , Computer networks , Computer music , MIDI (Standard)
- Description: The inability to share resources in commercial and institutional computer music studios results in non-optimal resource utilisation. The use of computers to process, store and communicate data can be extended within these studios, to provide the capability of sharing resources amongst their users. This thesis describes a computer music network which was designed for this purpose. Certain devices had to be custom built for the implementation of the network. The thesis discusses the design and construction of these devices.
- Full Text:
- Date Issued: 1995
A review of the Kalahari group: an aid to Kimberlite exploration in this medium
- Authors: Williams, Clint
- Date: 2003 , 2013-05-23
- Subjects: Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4916 , http://hdl.handle.net/10962/d1003216 , Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Description: The Kalahari Group sediments cover vast portions of the Archean Kaapvaal and Congo cratons that are considered highly prospective for economic kimberlites. In southern Africa, the term Kalahari refers to a structural basin, a group of Cretaceous to recent terrestrial continental sediments and an ill-defined desert, all of which have been grouped together as the Mega Kalahari by Thomas and Shaw (1993). The Mega Kalahari grouping includes sediments stretching from South Africa in the south to the Democratic Republic of Congo in the north, and from eastern Namibia to western Zimbabwe. This sand sea, at 2.5 million km², is the largest on earth and presents significant obstacles and challenges to the kimberlite explorationist attempting to locate bedrock-hosted diamondiferous kimberlite bodies. The Mega Kalahari sediments represent an ancient depositional environment with a complex history in which the stratigraphy and age of the deposits are not particularly well constrained or understood. Low fossil content, limited exposure, poor differentiation of the dominant surficial Kalahari Sand and a limited comprehension of an extensive duricrust suite has delayed the understanding of the sedimentological and environmental history of the basin. This sequence of sediments has accumulated and evolved through fluvio-deltaic, aeolian and groundwater processes, with characteristics due to primary deposition and subsequent modification being difficult to distinguish. Deposition in the Kalahari Basin has been subject to tectonic influences, changes in drainage directions and source areas of sediments, river capture and numerous large and small climatic fluctuations both in the basin and surrounding areas. It bears the imprint of recurring cycles during which the same sediments were reworked, sometimes by different agencies, all of which exacerbate attempts to correlate sedimentary units across the sequence. The Mega Kalahari is a series of contiguous Phanerozoic sedimentary basins situated within the African Superswell. The Superswell has dominated the gross geomorphology of southern Africa and contributed significantly to the present character of the Mega Kalahari and the evolution of the drainage systems. Overall, the tectonic framework established in southern Africa by the division of Gondwanaland led to the creation of a dual drainage system, with the hingeline acting as a watershed between a coastally-orientated exoreic system and an endoreic system draining into the interior. Deposition of sediments started in the late Cretaceous. Neo-tectonic activity expressed in the rifting in central Botswana, further influenced sedimentation rates and exerted a strong control over paleo-drainage directions. This revIew presents the complexities of the Kalahari cover sequence. The most Important geomorphological and sedimentary factors to be considered when designing and implementing kimberlite exploration programs within the Mega Kalahari environment are outlined and discussed. New data from exploration drilling programs are presented on the thickness of the Kalahari within portions of northern Namibia, western Zambia and Botswana. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
- Authors: Williams, Clint
- Date: 2003 , 2013-05-23
- Subjects: Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4916 , http://hdl.handle.net/10962/d1003216 , Kimberlite -- Kalahari Desert , Sedimentation and deposition -- Kalahari Desert
- Description: The Kalahari Group sediments cover vast portions of the Archean Kaapvaal and Congo cratons that are considered highly prospective for economic kimberlites. In southern Africa, the term Kalahari refers to a structural basin, a group of Cretaceous to recent terrestrial continental sediments and an ill-defined desert, all of which have been grouped together as the Mega Kalahari by Thomas and Shaw (1993). The Mega Kalahari grouping includes sediments stretching from South Africa in the south to the Democratic Republic of Congo in the north, and from eastern Namibia to western Zimbabwe. This sand sea, at 2.5 million km², is the largest on earth and presents significant obstacles and challenges to the kimberlite explorationist attempting to locate bedrock-hosted diamondiferous kimberlite bodies. The Mega Kalahari sediments represent an ancient depositional environment with a complex history in which the stratigraphy and age of the deposits are not particularly well constrained or understood. Low fossil content, limited exposure, poor differentiation of the dominant surficial Kalahari Sand and a limited comprehension of an extensive duricrust suite has delayed the understanding of the sedimentological and environmental history of the basin. This sequence of sediments has accumulated and evolved through fluvio-deltaic, aeolian and groundwater processes, with characteristics due to primary deposition and subsequent modification being difficult to distinguish. Deposition in the Kalahari Basin has been subject to tectonic influences, changes in drainage directions and source areas of sediments, river capture and numerous large and small climatic fluctuations both in the basin and surrounding areas. It bears the imprint of recurring cycles during which the same sediments were reworked, sometimes by different agencies, all of which exacerbate attempts to correlate sedimentary units across the sequence. The Mega Kalahari is a series of contiguous Phanerozoic sedimentary basins situated within the African Superswell. The Superswell has dominated the gross geomorphology of southern Africa and contributed significantly to the present character of the Mega Kalahari and the evolution of the drainage systems. Overall, the tectonic framework established in southern Africa by the division of Gondwanaland led to the creation of a dual drainage system, with the hingeline acting as a watershed between a coastally-orientated exoreic system and an endoreic system draining into the interior. Deposition of sediments started in the late Cretaceous. Neo-tectonic activity expressed in the rifting in central Botswana, further influenced sedimentation rates and exerted a strong control over paleo-drainage directions. This revIew presents the complexities of the Kalahari cover sequence. The most Important geomorphological and sedimentary factors to be considered when designing and implementing kimberlite exploration programs within the Mega Kalahari environment are outlined and discussed. New data from exploration drilling programs are presented on the thickness of the Kalahari within portions of northern Namibia, western Zambia and Botswana. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
Petrogenesis of the New Amalfi sheet a highly differentiated Karoo intrusion
- Authors: Williams, Craig Milton
- Date: 1995
- Subjects: Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4985 , http://hdl.handle.net/10962/d1005597 , Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
- Description: The New Amalfi Sheet is a highly differentiated tholeiitic intrusion which is situated between the towns of Matatiele and Swartberg in East Griqualand. It lies within the Central area of the Karoo Igneous Province. Rock types range from dolerites at the base and top through to a highly differentiated granophyre which is found as a 'sandwich horizon' within the top half of the sheet. The most evolved granophyre represents 15.86% of the initial liquid, which was found to be very similar in composition to the average Lesotho-type magma of Marsh and Eales (1984). The paragenetic sequence was found to be chromite → olivine → plagioclase → pigeonite and augite. Cumulus magnetite and ilmenite enter the paragenetic sequence together with immiscible sulphide droplets after 35% crystallization. In the late stages of crystallization, augite changes composition towards ferrohedenbergite. The reappearance of iron-rich olivine coincides with the disappearance of pigeonite and apatite appears as a cumulus phase for the first time after 70% crystallization. Granophyric intergrowth, which contains coarse perthitic Kfeldspar, becomes the most abundant modal entity within the most evolved granophyres. Differentiation was dominated by fractionation of plagioclase and pyroxene, with subordinate olivine and opaque-oxide fractionation. A minor amount of assimilation of country rock occurred within the topmost granophyres. The intrusion has been dated, using the Rb-Sr isochron method, at 178.37 ± 5.52 Ma. Extensive subsolidus deuteric alteration has resulted in the formation of a complete series of hydrothermally altered clinopyroxenes which are enriched in CaO but depleted in TiO₂ compared to the unaltered magmatic clinopyroxenes. It has also resulted in the formation of abundant vermiform ilmenite in the most evolved rocks, recognized by the fact that this phase is enriched in MnO compared to magmatic ilmenites. The very iron-rich orthopyroxene, ferrohypersthene, was found to have crystallized, during cooling of the sheet from the intercumulus liquid. Olivine in the dolerite re-equilibrated with the intercumulus liquid, becoming more iron-rich in composition.
- Full Text:
- Date Issued: 1995
- Authors: Williams, Craig Milton
- Date: 1995
- Subjects: Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4985 , http://hdl.handle.net/10962/d1005597 , Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
- Description: The New Amalfi Sheet is a highly differentiated tholeiitic intrusion which is situated between the towns of Matatiele and Swartberg in East Griqualand. It lies within the Central area of the Karoo Igneous Province. Rock types range from dolerites at the base and top through to a highly differentiated granophyre which is found as a 'sandwich horizon' within the top half of the sheet. The most evolved granophyre represents 15.86% of the initial liquid, which was found to be very similar in composition to the average Lesotho-type magma of Marsh and Eales (1984). The paragenetic sequence was found to be chromite → olivine → plagioclase → pigeonite and augite. Cumulus magnetite and ilmenite enter the paragenetic sequence together with immiscible sulphide droplets after 35% crystallization. In the late stages of crystallization, augite changes composition towards ferrohedenbergite. The reappearance of iron-rich olivine coincides with the disappearance of pigeonite and apatite appears as a cumulus phase for the first time after 70% crystallization. Granophyric intergrowth, which contains coarse perthitic Kfeldspar, becomes the most abundant modal entity within the most evolved granophyres. Differentiation was dominated by fractionation of plagioclase and pyroxene, with subordinate olivine and opaque-oxide fractionation. A minor amount of assimilation of country rock occurred within the topmost granophyres. The intrusion has been dated, using the Rb-Sr isochron method, at 178.37 ± 5.52 Ma. Extensive subsolidus deuteric alteration has resulted in the formation of a complete series of hydrothermally altered clinopyroxenes which are enriched in CaO but depleted in TiO₂ compared to the unaltered magmatic clinopyroxenes. It has also resulted in the formation of abundant vermiform ilmenite in the most evolved rocks, recognized by the fact that this phase is enriched in MnO compared to magmatic ilmenites. The very iron-rich orthopyroxene, ferrohypersthene, was found to have crystallized, during cooling of the sheet from the intercumulus liquid. Olivine in the dolerite re-equilibrated with the intercumulus liquid, becoming more iron-rich in composition.
- Full Text:
- Date Issued: 1995
The suitability of Alagoasa extrema Jacoby (Coleoptera: Chrysomelidae: Alticinae), as a biological control agent for Lantana camara L. in South Africa
- Authors: Williams, Hester Elizabeth
- Date: 2003
- Subjects: Lantana camara , Lantana camara -- South Africa , Biological pest control agents -- South Africa , Chrysomelidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5783 , http://hdl.handle.net/10962/d1005471 , Lantana camara , Lantana camara -- South Africa , Biological pest control agents -- South Africa , Chrysomelidae
- Description: Lantana camara Linnaeus (Verbenaceae), commonly known as lantana, is a highly invasive weed in many parts of the world. In South Africa it is naturalized in several provinces where it invades pastures, riverbanks, mountain slopes and valleys and commercial and natural forests, forming dense, impenetrable thickets. Chemical and mechanical control methods are expensive, labour intensive and provide only temporary relief as cleared areas are rapidly reinfested by seedlings and coppice growth. A biological control programme was initiated in South Africa in the 1960s, but despite the establishment of 11 agent species, it was considered to have had limited success. Several factors are thought to restrict the impact of the biocontrol agents. Firstly, L. camara occurs in a range of climatic regions, some of which are unsuitable for the establishment of agent species of tropical and subtropical origin. Secondly, L. camara is the result of hybridization between several Lantana species, forming a complex of hybridized and hybridizing varieties in the field, which match none of the Lantana species in the region of origin. This causes partial insect-host incompatibility, displayed as varietal preference. Thirdly, parasitism appears to have significantly reduced the effectiveness of several natural enemies. In spite of all these constraints, biological control has reduced invasion by L. camara by 26%. However, the weed is still very damaging and additional natural enemies are required to reduce infestations further. A flea-beetle species, Alagoasa extrema Jacoby (Coleoptera: Chrysomelidae), was collected from several sites in the humid subtropical and tropical regions of Mexico, and imported into quarantine in South Africa and studied as a potential biocontrol agent for L. camara. Favourable biological characteristics of this beetle included long-lived adults, several overlapping generations per year, and high adult and larval feeding rates. Observations from the insect’s native range and studies in South Africa suggest that A. extrema would probably be more suited to the subtropical, rather than the temperate areas in South Africa. Laboratory impact studies indicated that feeding damage by A. extrema larvae, over a period spanning the larval stage (16 to 20 days), reduced the above-ground biomass of L. camara plants by up to 29%. Higher larval populations resulted in a higher reduction of biomass. Varietal preference and suitability studies indicated that A. extrema exhibits a degree of varietal preference under laboratory conditions, with one of the white pink L. camara varieties proving the most suitable host. This variety is one of the most damaging varieties in South Africa and is particularly widespread in Mpumalanga Province. Although A. extrema proved to be damaging to L. camara, laboratory host range trials showed it to be an oligophagous species, capable of feeding and developing on several non-target species, especially two native Lippia species (Verbenaceae). The host suitability of these species was marginally lower than that of L. camara and the potential risk to these indigenous species was deemed to be too high to warrant release. It was therefore recommended that A. extrema not be considered for release in South Africa.
- Full Text:
- Date Issued: 2003
- Authors: Williams, Hester Elizabeth
- Date: 2003
- Subjects: Lantana camara , Lantana camara -- South Africa , Biological pest control agents -- South Africa , Chrysomelidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5783 , http://hdl.handle.net/10962/d1005471 , Lantana camara , Lantana camara -- South Africa , Biological pest control agents -- South Africa , Chrysomelidae
- Description: Lantana camara Linnaeus (Verbenaceae), commonly known as lantana, is a highly invasive weed in many parts of the world. In South Africa it is naturalized in several provinces where it invades pastures, riverbanks, mountain slopes and valleys and commercial and natural forests, forming dense, impenetrable thickets. Chemical and mechanical control methods are expensive, labour intensive and provide only temporary relief as cleared areas are rapidly reinfested by seedlings and coppice growth. A biological control programme was initiated in South Africa in the 1960s, but despite the establishment of 11 agent species, it was considered to have had limited success. Several factors are thought to restrict the impact of the biocontrol agents. Firstly, L. camara occurs in a range of climatic regions, some of which are unsuitable for the establishment of agent species of tropical and subtropical origin. Secondly, L. camara is the result of hybridization between several Lantana species, forming a complex of hybridized and hybridizing varieties in the field, which match none of the Lantana species in the region of origin. This causes partial insect-host incompatibility, displayed as varietal preference. Thirdly, parasitism appears to have significantly reduced the effectiveness of several natural enemies. In spite of all these constraints, biological control has reduced invasion by L. camara by 26%. However, the weed is still very damaging and additional natural enemies are required to reduce infestations further. A flea-beetle species, Alagoasa extrema Jacoby (Coleoptera: Chrysomelidae), was collected from several sites in the humid subtropical and tropical regions of Mexico, and imported into quarantine in South Africa and studied as a potential biocontrol agent for L. camara. Favourable biological characteristics of this beetle included long-lived adults, several overlapping generations per year, and high adult and larval feeding rates. Observations from the insect’s native range and studies in South Africa suggest that A. extrema would probably be more suited to the subtropical, rather than the temperate areas in South Africa. Laboratory impact studies indicated that feeding damage by A. extrema larvae, over a period spanning the larval stage (16 to 20 days), reduced the above-ground biomass of L. camara plants by up to 29%. Higher larval populations resulted in a higher reduction of biomass. Varietal preference and suitability studies indicated that A. extrema exhibits a degree of varietal preference under laboratory conditions, with one of the white pink L. camara varieties proving the most suitable host. This variety is one of the most damaging varieties in South Africa and is particularly widespread in Mpumalanga Province. Although A. extrema proved to be damaging to L. camara, laboratory host range trials showed it to be an oligophagous species, capable of feeding and developing on several non-target species, especially two native Lippia species (Verbenaceae). The host suitability of these species was marginally lower than that of L. camara and the potential risk to these indigenous species was deemed to be too high to warrant release. It was therefore recommended that A. extrema not be considered for release in South Africa.
- Full Text:
- Date Issued: 2003
Spatial and temporal occurrence of forensically important South African blowflies (Diptera: Calliphorida)
- Authors: Williams, Kirstin Alexa
- Date: 2003
- Subjects: Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5617 , http://hdl.handle.net/10962/d1003217 , Blowflies -- South Africa , Forensic entomology
- Description: Forensic entomology is an emergjng field in South Africa. Little is known about South African blowflies and factors that affect their use in a forensic context. This work provides a review and synthesis of previous work in South Africa and supplements some of the background and basic knowledge required for forensic entomology in South Africa. The seasonal occurrence of eight forensicaIIy important blowfly species was quantified by fortnightly trapping in Grahamstown, South Africa. The spatial distribution of each species was related to seasonal occurrence and habitat preference. Seasonal distributions of blowflies in carcasses in South Africa were obtained from the literature and compared to the seasonal trapping. By mapping South African locality records of forensicaIIy important blowflies and analyzing these records in a modified Principal Components Analysis of climatic data, the potential geographic distributions of each fly species was modeIIed. Most species were widespread, but Calliphora croceipalpis, Jaennicke, 1867, was found in cold places. This information is important for determining where certain species are likely to occur in forensic investigations. Nocturnal oviposition was examined in both field and laboratory experiments. Lucilia species could oviposit nocturnaIIy in the field, while Lucilia species, Chrysomya chloropyga, (Weidemann, 1818) and C. putoria (Weidemann, 1830) could oviposit nocturnaIIy in the laboratory. These findings are important factors in affecting the precision of estimates of a post mortem interval (PM!) by up to 12 hours. The thermophysiological ranges of four species of adult blowflies were determined by measuring onset temperatures of four significant behaviours: onset of neural activity; onset of coordinated movement; shade-seeking and death. There was a sexual size dimorphism in Lucilia species, Chrysomya chloropyga and Calliphora croceipalpis with females being larger than males. Chrysomya megacephala (Fabricius, 1794) had an unexpectedly high death threshold, while Calliphora croceipalpis had the lowest death threshold of the flies tested. These points were related to the seasonal and geographic occurrence of each species, to nocturnal activity and placed in a forensic context.
- Full Text:
- Date Issued: 2003
- Authors: Williams, Kirstin Alexa
- Date: 2003
- Subjects: Blowflies -- South Africa , Forensic entomology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5617 , http://hdl.handle.net/10962/d1003217 , Blowflies -- South Africa , Forensic entomology
- Description: Forensic entomology is an emergjng field in South Africa. Little is known about South African blowflies and factors that affect their use in a forensic context. This work provides a review and synthesis of previous work in South Africa and supplements some of the background and basic knowledge required for forensic entomology in South Africa. The seasonal occurrence of eight forensicaIIy important blowfly species was quantified by fortnightly trapping in Grahamstown, South Africa. The spatial distribution of each species was related to seasonal occurrence and habitat preference. Seasonal distributions of blowflies in carcasses in South Africa were obtained from the literature and compared to the seasonal trapping. By mapping South African locality records of forensicaIIy important blowflies and analyzing these records in a modified Principal Components Analysis of climatic data, the potential geographic distributions of each fly species was modeIIed. Most species were widespread, but Calliphora croceipalpis, Jaennicke, 1867, was found in cold places. This information is important for determining where certain species are likely to occur in forensic investigations. Nocturnal oviposition was examined in both field and laboratory experiments. Lucilia species could oviposit nocturnaIIy in the field, while Lucilia species, Chrysomya chloropyga, (Weidemann, 1818) and C. putoria (Weidemann, 1830) could oviposit nocturnaIIy in the laboratory. These findings are important factors in affecting the precision of estimates of a post mortem interval (PM!) by up to 12 hours. The thermophysiological ranges of four species of adult blowflies were determined by measuring onset temperatures of four significant behaviours: onset of neural activity; onset of coordinated movement; shade-seeking and death. There was a sexual size dimorphism in Lucilia species, Chrysomya chloropyga and Calliphora croceipalpis with females being larger than males. Chrysomya megacephala (Fabricius, 1794) had an unexpectedly high death threshold, while Calliphora croceipalpis had the lowest death threshold of the flies tested. These points were related to the seasonal and geographic occurrence of each species, to nocturnal activity and placed in a forensic context.
- Full Text:
- Date Issued: 2003
Macroinvertebrate community and species responses to chlorinated sewage effluent in the Umsunduze and Umbilo rivers, Kwa Zulu-Natal, South Africa
- Authors: Williams, Margot Lluttrell
- Date: 1997
- Subjects: Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5727 , http://hdl.handle.net/10962/d1005413 , Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Description: Chlorine has a wide variety of applications in water treatment. Because of its disinfectant efficacy, it is used world wide for the treatment of potable water, sewage, swimming pools and for the control of nuisance organisms in cooling towers. A problem arises when such chlorinated water enters the natural environment, as chlorine's greatest advantage, i.e. its germicidal capacity, becomes its greatest disadvantage. In particular, the discharge of heated, chlorinated water from cooling towers and chlorinated, treated sewage into rivers have severe consequences for the riverine flora and fauna. This study focused on the effects of chlorinated, treated sewage effluent on the community structure of benthic macroinvertebrates in two rivers in KwaZulu-Natal viz. the Umsunduze River in the Pietermaritzburg area, and the Umbilo River in the Durban area. The study was conducted in three phases. The first two phases comprised a toxicological investigation of the effects of chlorine on a selected riverine macroinvertebrate, and the third phase comprised an ecotoxicological investigation of the effects of chlorinated treated sewage on benthic macroinvertebrate community structure. The first phase of the study involved the development of an artificial stream system which would be suitable for determining the response of a selected macroinvertebrate species to chlorine. Chlorine is both reactive and volatile, so this necessitated the development of a specialised flow-through system with apparatus which would allow continuous dosing of a sodium hypochlorite solution. The system was set up at the Process Evaluation Facility at Wiggins Waterworks, Durban, where raw water from lnanda Dam was used. The second phase involved the use of this artificial stream system to conduct acute 96 h toxicity tests. Baetid mayfly nymphs (Baetis harrisoni Barnard) were selected as the test organisms after a preliminary investigation found them to be suitable for survival under laboratory conditions. For comparative purposes, tests were run first on B. harrisoni from a relatively uncontaminated stream in a residential area of Westville, then on specimens from the severely impacted Umbilo River. The LC₅₀ of chlorine for organisms from both sources was found to be in the region of 0.004 mg/l (free chlorine). This value was well below the general effluent standard of 0.1 mg/l in effect at the time. The recommended acute environmental guideline is 0.001 mg/l. The third phase of the study involved field validation of the toxicity test results. It was hypothesised that since the LC₅₀ for free chlorine was 0.004 mg/l, B. harrisoni would not be found downstream from a point source of chlorinated effluent where the concentration of free chlorine ranged from 0.06 to 0.2 mg/l, and that the macroinvertebrate community structure would also be altered. In order to test these hypotheses, benthic macro invertebrate community structure was investigated at several sites up- and downstream from the outlets of the Darvill Wastewater Works in the Umsunduze River and the Umbilo Sewage Purification Works in the Umbilo River. In addition, in order to differentiate between the effects of chlorinated and unchlorinated treated sewage, a section of the Umbilo River (upstream from the chlorinated discharge) was exposed to unchlorinated, treated sewage. In this way, a limited "before and after" sewage and an "upstream and downstream" from sewage investigation could be carried out. Organisms were collected from riffles (and from pools in the Umbilo River) and the samples were then sorted and organisms were identified to species level, where possible, otherwise to genus or family. Changes in community composition were shown graphically as pie charts of relative proportions of organisms found at each site, graphs of the average number of taxa at each site; and graphs of the average number of individuals at each site; Data from the Umbilo River were also analysed using TWINSPAN (Two-way indicator species analysis). In both the Umsunduze and the Umbilo rivers, the deleterious effects of the chlorinated effluent were clearly evident. At Umsunduze Site 3 and Umbilo Site 5 (both immediately downstream from the chlorinated effluent) both the number of taxa and number of individuals were substantially reduced, sometimes to zero. Where organisms were found at the next sites downstream (Sites 4 and 6 respectively), the samples were dominated by Chironomus. In contrast, the unchlorinated effluent in the Umbilo River caused very little difference in community structure. As predicted, B. harrisoni was not found in downstream samples in which chlorine was present, yet appeared to be relatively unaffected by the unchlorinated effluent, suggesting that chlorine, rather than the effluent was responsible for its absence at downstream sites. In conclusion, it would appear that while treated sewage effluent certainly causes changes in macroinvertebrate community structure, chlorination of this effluent leads to large scale destruction of the riverine community. This in turn delays the recovery process of the river, rendering a longer stretch unfit for use. The consequences of this delayed recovery are that the failure to meet the water quality requirements of the natural environment results in those of the other water users (agriculture, industry, domestic and recreation) not being met. This reduces the natural capacity of the riverine community to process organic waste and recover from the discharge of sewage effluent. Chlorination increases the distance of impaired water quality and environmental integrity which result from organically enriched treated sewage effluent. The results of the study indicated that the draft water quality guidelines for aquatic ecosystems, derived from inadequate data, and calculated with a safety factor, were the correct order of magnitude. The approach followed in the study will be useful in the development and refinement of water quality guidelines for aquatic ecosystems.
- Full Text:
- Date Issued: 1997
- Authors: Williams, Margot Lluttrell
- Date: 1997
- Subjects: Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5727 , http://hdl.handle.net/10962/d1005413 , Sewage -- Environmental aspects -- South Africa -- KwaZulu-Natal , Sewage -- Purification -- Chlorination -- South Africa -- KwaZulu-Natal , Baetis -- South Africa -- KwaZulu-Natal , Mayflies -- South Africa -- KwaZulu-Natal , Chlorine -- Environmental aspects -- South Africa -- KwaZulu-Natal
- Description: Chlorine has a wide variety of applications in water treatment. Because of its disinfectant efficacy, it is used world wide for the treatment of potable water, sewage, swimming pools and for the control of nuisance organisms in cooling towers. A problem arises when such chlorinated water enters the natural environment, as chlorine's greatest advantage, i.e. its germicidal capacity, becomes its greatest disadvantage. In particular, the discharge of heated, chlorinated water from cooling towers and chlorinated, treated sewage into rivers have severe consequences for the riverine flora and fauna. This study focused on the effects of chlorinated, treated sewage effluent on the community structure of benthic macroinvertebrates in two rivers in KwaZulu-Natal viz. the Umsunduze River in the Pietermaritzburg area, and the Umbilo River in the Durban area. The study was conducted in three phases. The first two phases comprised a toxicological investigation of the effects of chlorine on a selected riverine macroinvertebrate, and the third phase comprised an ecotoxicological investigation of the effects of chlorinated treated sewage on benthic macroinvertebrate community structure. The first phase of the study involved the development of an artificial stream system which would be suitable for determining the response of a selected macroinvertebrate species to chlorine. Chlorine is both reactive and volatile, so this necessitated the development of a specialised flow-through system with apparatus which would allow continuous dosing of a sodium hypochlorite solution. The system was set up at the Process Evaluation Facility at Wiggins Waterworks, Durban, where raw water from lnanda Dam was used. The second phase involved the use of this artificial stream system to conduct acute 96 h toxicity tests. Baetid mayfly nymphs (Baetis harrisoni Barnard) were selected as the test organisms after a preliminary investigation found them to be suitable for survival under laboratory conditions. For comparative purposes, tests were run first on B. harrisoni from a relatively uncontaminated stream in a residential area of Westville, then on specimens from the severely impacted Umbilo River. The LC₅₀ of chlorine for organisms from both sources was found to be in the region of 0.004 mg/l (free chlorine). This value was well below the general effluent standard of 0.1 mg/l in effect at the time. The recommended acute environmental guideline is 0.001 mg/l. The third phase of the study involved field validation of the toxicity test results. It was hypothesised that since the LC₅₀ for free chlorine was 0.004 mg/l, B. harrisoni would not be found downstream from a point source of chlorinated effluent where the concentration of free chlorine ranged from 0.06 to 0.2 mg/l, and that the macroinvertebrate community structure would also be altered. In order to test these hypotheses, benthic macro invertebrate community structure was investigated at several sites up- and downstream from the outlets of the Darvill Wastewater Works in the Umsunduze River and the Umbilo Sewage Purification Works in the Umbilo River. In addition, in order to differentiate between the effects of chlorinated and unchlorinated treated sewage, a section of the Umbilo River (upstream from the chlorinated discharge) was exposed to unchlorinated, treated sewage. In this way, a limited "before and after" sewage and an "upstream and downstream" from sewage investigation could be carried out. Organisms were collected from riffles (and from pools in the Umbilo River) and the samples were then sorted and organisms were identified to species level, where possible, otherwise to genus or family. Changes in community composition were shown graphically as pie charts of relative proportions of organisms found at each site, graphs of the average number of taxa at each site; and graphs of the average number of individuals at each site; Data from the Umbilo River were also analysed using TWINSPAN (Two-way indicator species analysis). In both the Umsunduze and the Umbilo rivers, the deleterious effects of the chlorinated effluent were clearly evident. At Umsunduze Site 3 and Umbilo Site 5 (both immediately downstream from the chlorinated effluent) both the number of taxa and number of individuals were substantially reduced, sometimes to zero. Where organisms were found at the next sites downstream (Sites 4 and 6 respectively), the samples were dominated by Chironomus. In contrast, the unchlorinated effluent in the Umbilo River caused very little difference in community structure. As predicted, B. harrisoni was not found in downstream samples in which chlorine was present, yet appeared to be relatively unaffected by the unchlorinated effluent, suggesting that chlorine, rather than the effluent was responsible for its absence at downstream sites. In conclusion, it would appear that while treated sewage effluent certainly causes changes in macroinvertebrate community structure, chlorination of this effluent leads to large scale destruction of the riverine community. This in turn delays the recovery process of the river, rendering a longer stretch unfit for use. The consequences of this delayed recovery are that the failure to meet the water quality requirements of the natural environment results in those of the other water users (agriculture, industry, domestic and recreation) not being met. This reduces the natural capacity of the riverine community to process organic waste and recover from the discharge of sewage effluent. Chlorination increases the distance of impaired water quality and environmental integrity which result from organically enriched treated sewage effluent. The results of the study indicated that the draft water quality guidelines for aquatic ecosystems, derived from inadequate data, and calculated with a safety factor, were the correct order of magnitude. The approach followed in the study will be useful in the development and refinement of water quality guidelines for aquatic ecosystems.
- Full Text:
- Date Issued: 1997
Energetic and kinematic responses to morphology-normalised speeds of walking and running
- Authors: Williams, Martin Andrew
- Date: 1989
- Subjects: Running -- Physiological aspects , Walking -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5166 , http://hdl.handle.net/10962/d1016240
- Description: This study investigated the influence of human morphology upon selected physiological, biomechanical and psychological responses to horizontal locomotion. In so doing, it was possible to evaluate the effectiveness with which morphology-normalised speeds of walking and running reduced the between-subject variability that is inherent in human locomotor responses. Twenty caucasian males were divided into two groups on the basis of stature - ten subjects in each of a "short" category (<170cm) and a "tall" category (>185cm). All subjects were habituated to treadmill locomotion prior to exposure to three walking treatments (0.83, 1.39 and 1.94m.s⁻¹) and three running treatments (2.50, 3.06 and 3.61m.s⁻¹). During each of these five-minute locomotor conditions, energetic (V02), kinematic (cadence and stride length) and psychophysical (central and local RPE) data were captured. From these data, lines of best fit were calculated for each subject, allowing for a prediction of the abovementioned locomotor variables from known absolute rates of progression. Using suitable regression equations, subject responses to morphology-normalised speeds of walking and running were effectively extrapolated. When the rate of progression was expressed in absolute terms (m.s⁻¹), significant differences (P <0.05) were found between the stature-related groups with respect to both energetic and kinematic locomotor responses. Such differences were successfully eliminated when use was made of locomotor speeds relativised on the basis of morphology. This study concludes that the use of appropriately prescribed morphology-normalised rates of progression are effective in reducing the variability in locomotor responses between subjects differing significantly in stature.
- Full Text:
- Date Issued: 1989
- Authors: Williams, Martin Andrew
- Date: 1989
- Subjects: Running -- Physiological aspects , Walking -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5166 , http://hdl.handle.net/10962/d1016240
- Description: This study investigated the influence of human morphology upon selected physiological, biomechanical and psychological responses to horizontal locomotion. In so doing, it was possible to evaluate the effectiveness with which morphology-normalised speeds of walking and running reduced the between-subject variability that is inherent in human locomotor responses. Twenty caucasian males were divided into two groups on the basis of stature - ten subjects in each of a "short" category (<170cm) and a "tall" category (>185cm). All subjects were habituated to treadmill locomotion prior to exposure to three walking treatments (0.83, 1.39 and 1.94m.s⁻¹) and three running treatments (2.50, 3.06 and 3.61m.s⁻¹). During each of these five-minute locomotor conditions, energetic (V02), kinematic (cadence and stride length) and psychophysical (central and local RPE) data were captured. From these data, lines of best fit were calculated for each subject, allowing for a prediction of the abovementioned locomotor variables from known absolute rates of progression. Using suitable regression equations, subject responses to morphology-normalised speeds of walking and running were effectively extrapolated. When the rate of progression was expressed in absolute terms (m.s⁻¹), significant differences (P <0.05) were found between the stature-related groups with respect to both energetic and kinematic locomotor responses. Such differences were successfully eliminated when use was made of locomotor speeds relativised on the basis of morphology. This study concludes that the use of appropriately prescribed morphology-normalised rates of progression are effective in reducing the variability in locomotor responses between subjects differing significantly in stature.
- Full Text:
- Date Issued: 1989
On the design and monitoring of photovoltaic systems for rural homes
- Authors: Williams, Nathaniel John
- Date: 2011
- Subjects: Photovoltaic cells , Dwellings -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10516 , http://hdl.handle.net/10948/1308 , Photovoltaic cells , Dwellings -- Power supply
- Description: It is estimated that 1.6 billion people today live without access to electricity. Most of these people live in remote rural areas in developing countries. One economic solution to this problem is the deployment of small domestic photovoltaic (PV) systems called solar home systems (SHS). In order to improve the performance and reduce the life cycle cost of these systems, accurate monitoring data of real SHSs is required. To this end, two SHSs typical of those found in the field were designed and installed, one in a rural area of the Eastern Cape of South Africa and the other in the laboratory. Monitoring systems were designed to record energy ows in the system and important environmental parameters. A novel technique was developed to correct for measurement errors occurring during the utilization of pulse width modulation charge control techniques. These errors were found to be as large as 47.6 percent. Simulations show that correction techniques produce measurement errors that are up to 20 times smaller than uncorrected values, depending upon the operating conditions. As a tool to aid in the analysis of monitoring data, a PV performance model was developed. The model, used to predict the maximum power point (MPP) power of a PV array, was able to predict MPP energy production to within 0.2 percent over the course of three days. Monitoring data from the laboratory system shows that the largest sources of energy loss are charge control, module under performance relative to manufacturer specifications and operation of the PV array away from MPP. These accounted for losses of approximately 18-27 percent, 15 percent and 8-11 percent of rated PV energy under standard test conditions, respectively. Energy consumed by loads on the systems was less than 50 percent of rated PV energy for both the remote and laboratory systems. Performance ratios (PR) for the laboratory system ranged from 0.38 to 0.49 for the three monitoring periods. The remote system produced a PR of 0.46. In both systems the PV arrays appear to have been oversized. This was due to overestimation of the energy requirements of the loads on the systems. In the laboratory system, the loads consisting of three compact fluorescent lamps and one incandescent lamp, were used to simulate a typical SHS load pro le and collectively consumed only 85 percent of their rated power. The 8 predicted load profile for the remote system proved to be signi cantly overestimated. The results of the monitoring project demonstrate the importance of acquiring an accurate estimation of the energy demand from loads on the system. Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding. Significant under-performance of the PV module used in the laboratory system, underlines the importance of measuring module IV curves and verifying manufacturer specifications before system deployment. It was also found that signi cant PV array performance gains could be obtained by the use of maximum power point tracking charge controllers. Increased PV array performance leads to smaller arrays and reduced system cost.
- Full Text:
- Date Issued: 2011
- Authors: Williams, Nathaniel John
- Date: 2011
- Subjects: Photovoltaic cells , Dwellings -- Power supply
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10516 , http://hdl.handle.net/10948/1308 , Photovoltaic cells , Dwellings -- Power supply
- Description: It is estimated that 1.6 billion people today live without access to electricity. Most of these people live in remote rural areas in developing countries. One economic solution to this problem is the deployment of small domestic photovoltaic (PV) systems called solar home systems (SHS). In order to improve the performance and reduce the life cycle cost of these systems, accurate monitoring data of real SHSs is required. To this end, two SHSs typical of those found in the field were designed and installed, one in a rural area of the Eastern Cape of South Africa and the other in the laboratory. Monitoring systems were designed to record energy ows in the system and important environmental parameters. A novel technique was developed to correct for measurement errors occurring during the utilization of pulse width modulation charge control techniques. These errors were found to be as large as 47.6 percent. Simulations show that correction techniques produce measurement errors that are up to 20 times smaller than uncorrected values, depending upon the operating conditions. As a tool to aid in the analysis of monitoring data, a PV performance model was developed. The model, used to predict the maximum power point (MPP) power of a PV array, was able to predict MPP energy production to within 0.2 percent over the course of three days. Monitoring data from the laboratory system shows that the largest sources of energy loss are charge control, module under performance relative to manufacturer specifications and operation of the PV array away from MPP. These accounted for losses of approximately 18-27 percent, 15 percent and 8-11 percent of rated PV energy under standard test conditions, respectively. Energy consumed by loads on the systems was less than 50 percent of rated PV energy for both the remote and laboratory systems. Performance ratios (PR) for the laboratory system ranged from 0.38 to 0.49 for the three monitoring periods. The remote system produced a PR of 0.46. In both systems the PV arrays appear to have been oversized. This was due to overestimation of the energy requirements of the loads on the systems. In the laboratory system, the loads consisting of three compact fluorescent lamps and one incandescent lamp, were used to simulate a typical SHS load pro le and collectively consumed only 85 percent of their rated power. The 8 predicted load profile for the remote system proved to be signi cantly overestimated. The results of the monitoring project demonstrate the importance of acquiring an accurate estimation of the energy demand from loads on the system. Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding. Significant under-performance of the PV module used in the laboratory system, underlines the importance of measuring module IV curves and verifying manufacturer specifications before system deployment. It was also found that signi cant PV array performance gains could be obtained by the use of maximum power point tracking charge controllers. Increased PV array performance leads to smaller arrays and reduced system cost.
- Full Text:
- Date Issued: 2011
Investigating household energy conservation behaviours in Johannesburg, South Africa
- Authors: Williams, Stephanie
- Date: 2019
- Subjects: Environmental behavior -- South Africa , Energy conservation -- Psychological aspects -- South Africa , Energy consumption -- Psychological aspects -- South Africa , South Africans -- Energy consumption
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94101 , vital:31000
- Description: Behavioural change is increasingly anticipated as an important pathway towards the reduction of the human footprint on the environment. Monitoring resource consumption at the household scale is essential as a basis for evaluating current performance and supports the understanding of how behaviour change interventions can be implemented. Yet, there are comparatively fewer studies on pro-environmental behaviour (PEB) in developing country contexts than in developed countries. Further, where research efforts have been made in developing countries, these have mainly focussed on low-income households. This means the extant literature on PEB is limited across a geographic and economic gradient, making generalisations about PEB problematic and limiting the scope for thinking about interventions for promoting pro-environmental behaviour in developing countries. In response to this, the study focuses on high-income households in Johannesburg, South Africa. Overall, the findings show a high level of heterogeneity in reported pro-environmental energy use behaviour, attributed to a suit of socio-demographic and value factors. Mainly, age, number of dependents, household size. Valuing leisure time were negatively correlated to energy use behaviours, while valuing environmental quality positively correlated to energy use behaviours. The provision of information energy-saving interventions yielded positive behavioural change as shown by reduced energy consumption of up to 12% in the Treatment group. However, no significant correlations were found between energy reduction and socio-demographic and personal value factors, which can be attributed to a different cultural context. The study discusses the implications of the findings on debates around pro-environmental behaviour and factors influencing pro-environmental behaviour, and provides further recommendations for future energy policies related to the household sector.
- Full Text:
- Date Issued: 2019
- Authors: Williams, Stephanie
- Date: 2019
- Subjects: Environmental behavior -- South Africa , Energy conservation -- Psychological aspects -- South Africa , Energy consumption -- Psychological aspects -- South Africa , South Africans -- Energy consumption
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94101 , vital:31000
- Description: Behavioural change is increasingly anticipated as an important pathway towards the reduction of the human footprint on the environment. Monitoring resource consumption at the household scale is essential as a basis for evaluating current performance and supports the understanding of how behaviour change interventions can be implemented. Yet, there are comparatively fewer studies on pro-environmental behaviour (PEB) in developing country contexts than in developed countries. Further, where research efforts have been made in developing countries, these have mainly focussed on low-income households. This means the extant literature on PEB is limited across a geographic and economic gradient, making generalisations about PEB problematic and limiting the scope for thinking about interventions for promoting pro-environmental behaviour in developing countries. In response to this, the study focuses on high-income households in Johannesburg, South Africa. Overall, the findings show a high level of heterogeneity in reported pro-environmental energy use behaviour, attributed to a suit of socio-demographic and value factors. Mainly, age, number of dependents, household size. Valuing leisure time were negatively correlated to energy use behaviours, while valuing environmental quality positively correlated to energy use behaviours. The provision of information energy-saving interventions yielded positive behavioural change as shown by reduced energy consumption of up to 12% in the Treatment group. However, no significant correlations were found between energy reduction and socio-demographic and personal value factors, which can be attributed to a different cultural context. The study discusses the implications of the findings on debates around pro-environmental behaviour and factors influencing pro-environmental behaviour, and provides further recommendations for future energy policies related to the household sector.
- Full Text:
- Date Issued: 2019
The petrology of the basalts of the Dordabis Formation in the vicinity of Dordabis in central S.W.A./Namibia|
- Authors: Williams-Jones, Ian Eric
- Date: 1985 , 2013-03-14
- Subjects: Basalt -- Namibia , Petrology -- Namibia , Geochemistry -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5062 , http://hdl.handle.net/10962/d1013277
- Description: The late Proterozoic volcanic and sedimentary sequence in the Dordabis area SWA/Namibia has been named the Dordabis Formation and subdivided, on the basis of field, petrological and petrographic evidence, into the Opdam and Bitterwater Members. Relict phases including augite and minor plagioclase only occur in the Bitterwater metalavas, as recrystallisation is complete in the Opdam metal avas. The composition of the relict feldspars ranges from labradorite in the ophitic basalts to oligoclase in the blastoporphyritic metalavas. The feldspars in the Opdam member are albitic in composition (An content 0,0 to 1,7) . Epidote compositions are typical of those occurring in metabasic rocks. Samples with high-iron whole-rock compositions are accompanied by high concentrations of Fe3+ in concomitant epidotes. Sixty three samples were analysed using X-ray fluorescence spectrometry to determine concentrations of major and 16 trace elements. Although greenschist facies metamorphism, metasomatism and shearing have produced scatter in the more mobile element concentrations, variation trends in other elements closely resemble modelled low-pressure fractional crystallisation trends. The Dordabis metalavas are petrologically classified as sub-alkaline, tholeiitic continental basalts. Low K/Rb ratios and low ratios of less incompatible to more incompatible elements probably reflect a source that has either been metasomati ca lly enriched or that has undergone little previous partial melting. Overlapping whole-rock variation trends indicate that the generally more evolved Opdam and primitive tholeiitic Bittenwater lavas are cogenetic. A comparison of the Dordabis Formation with the Sinclair Sequence and the Koras Group shows that their ages, petrology, petrography, associ a ted sedimentary suites and depositional environments are similar. It is concluded that they may possibly be coeval equivalents.
- Full Text:
- Date Issued: 1985
- Authors: Williams-Jones, Ian Eric
- Date: 1985 , 2013-03-14
- Subjects: Basalt -- Namibia , Petrology -- Namibia , Geochemistry -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5062 , http://hdl.handle.net/10962/d1013277
- Description: The late Proterozoic volcanic and sedimentary sequence in the Dordabis area SWA/Namibia has been named the Dordabis Formation and subdivided, on the basis of field, petrological and petrographic evidence, into the Opdam and Bitterwater Members. Relict phases including augite and minor plagioclase only occur in the Bitterwater metalavas, as recrystallisation is complete in the Opdam metal avas. The composition of the relict feldspars ranges from labradorite in the ophitic basalts to oligoclase in the blastoporphyritic metalavas. The feldspars in the Opdam member are albitic in composition (An content 0,0 to 1,7) . Epidote compositions are typical of those occurring in metabasic rocks. Samples with high-iron whole-rock compositions are accompanied by high concentrations of Fe3+ in concomitant epidotes. Sixty three samples were analysed using X-ray fluorescence spectrometry to determine concentrations of major and 16 trace elements. Although greenschist facies metamorphism, metasomatism and shearing have produced scatter in the more mobile element concentrations, variation trends in other elements closely resemble modelled low-pressure fractional crystallisation trends. The Dordabis metalavas are petrologically classified as sub-alkaline, tholeiitic continental basalts. Low K/Rb ratios and low ratios of less incompatible to more incompatible elements probably reflect a source that has either been metasomati ca lly enriched or that has undergone little previous partial melting. Overlapping whole-rock variation trends indicate that the generally more evolved Opdam and primitive tholeiitic Bittenwater lavas are cogenetic. A comparison of the Dordabis Formation with the Sinclair Sequence and the Koras Group shows that their ages, petrology, petrography, associ a ted sedimentary suites and depositional environments are similar. It is concluded that they may possibly be coeval equivalents.
- Full Text:
- Date Issued: 1985
Some aspects of the chemistry of zirconium compounds relating to their combination with collagen
- Williams-Wynn, David Ernest Arthur
- Authors: Williams-Wynn, David Ernest Arthur
- Date: 1960
- Subjects: Zirconium compounds , Collagen
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4513 , http://hdl.handle.net/10962/d1013456
- Description: [Summary] Some properties of zirconium compounds in aqueous solution have been determined using physico-chemical techniques. Zirconium oxychloride was used as the source of zirconium in all detailed investigations; zirconium sulphate was used in a few cases for comparative purposes. The Stokes diaphragm cell method has been used to determine the diffusion coefficient of zirconium in hydrochloric acid solution. It was found that the diffusion coefficient fell progressively with time, a limiting value being reached 4 to 5 weeks after dissolving the salt, and it was demonstrated that particles in the aged solutions were more homogeneous than in freshly prepared solutions. The limiting values were concentration dependent; dilute solutions had a lower diffusion coefficient than the more concentrated solutions when measured at the natural pH. In the presence of added acid the rate of diffusion was increased until a limiting value was reached in 0.5 M acid. The addition of alkali or complexing acids reduced the rate of diffusion.
- Full Text:
- Date Issued: 1960
- Authors: Williams-Wynn, David Ernest Arthur
- Date: 1960
- Subjects: Zirconium compounds , Collagen
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4513 , http://hdl.handle.net/10962/d1013456
- Description: [Summary] Some properties of zirconium compounds in aqueous solution have been determined using physico-chemical techniques. Zirconium oxychloride was used as the source of zirconium in all detailed investigations; zirconium sulphate was used in a few cases for comparative purposes. The Stokes diaphragm cell method has been used to determine the diffusion coefficient of zirconium in hydrochloric acid solution. It was found that the diffusion coefficient fell progressively with time, a limiting value being reached 4 to 5 weeks after dissolving the salt, and it was demonstrated that particles in the aged solutions were more homogeneous than in freshly prepared solutions. The limiting values were concentration dependent; dilute solutions had a lower diffusion coefficient than the more concentrated solutions when measured at the natural pH. In the presence of added acid the rate of diffusion was increased until a limiting value was reached in 0.5 M acid. The addition of alkali or complexing acids reduced the rate of diffusion.
- Full Text:
- Date Issued: 1960
Spatio-temporal variation of the land surface parameters in Temperature, in King Williams Town, Eastern Cape Province, South Africa
- Authors: Willie, Yanga Adrian
- Date: 2020
- Subjects: Environmental sciences
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12106 , vital:39152
- Description: The world is currently experiencing unprecedented urban growth. The influx of people into urban areas from rural areas is motivated by both economic and social factors such as increased employment opportunities. The latter is a result of, in part, industrialization, and the perceived higher standard of living that is often associated with access to better infrastructure. Surface Heat Island (SHI) is a phenomenon whereby urban areas experience higher surface temperatures than the surrounding rural areas. The presence of the SHI in urban areas has a negative impact not only on city dwellers, but also on the environment and the economy. The development of SHI is often associated with patterns of land use and land cover in urban areas. Numerous methods exist that can be used to study SHI’s. Literature suggests that Land Surface Temperature (LST), derived from satellite imagery, is a proven method that produces reliable results. The aim of this study was to evaluate the SHI in King Williams Town by studying the relationship between land surface temperatures, land cover and land cover indices. The derived indices are the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built up Index (NDBI). These indices were selected because they are representative of the land cover scheme used in the research study. This study was conducted in the King Williams town area between the years 1995 and 2018 the land surface temperature was derived from Landsat ETM + high thermal band data. The findings from this study provide an idea on the correlation between satellite derived land surface temperature and the land modification which occurred during the urbanization of King Williams Town during a 23 year period between1995 and 2018. The built up land category was the most influential in the development of high land surface temperature levels , vegetation had an opposite effect as a series of data sets illustrated that vegetated areas had a iv cooling effect on the surface. Water bodies in the study area had an insignificant effect on the Surface temperature levels while the grass lands weren’t as cooling as the vegetation but provided a cooling environment in the study area .The spatial distribution of areas of high surface temperature (hot spots) was discovered to be concentrated in the urban areas of the study area which is in the northwest region of the study area and correlates to the land cover and land cover indices associated with built up and artificial surfaces. The cooler areas or patches of land with lower values of land surface temperature were distributed on the outskirts of the study area away from the CBD and residential areas. This was the case because of the high concentration of vegetation and thicker grass lands in those regions.
- Full Text:
- Date Issued: 2020
- Authors: Willie, Yanga Adrian
- Date: 2020
- Subjects: Environmental sciences
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12106 , vital:39152
- Description: The world is currently experiencing unprecedented urban growth. The influx of people into urban areas from rural areas is motivated by both economic and social factors such as increased employment opportunities. The latter is a result of, in part, industrialization, and the perceived higher standard of living that is often associated with access to better infrastructure. Surface Heat Island (SHI) is a phenomenon whereby urban areas experience higher surface temperatures than the surrounding rural areas. The presence of the SHI in urban areas has a negative impact not only on city dwellers, but also on the environment and the economy. The development of SHI is often associated with patterns of land use and land cover in urban areas. Numerous methods exist that can be used to study SHI’s. Literature suggests that Land Surface Temperature (LST), derived from satellite imagery, is a proven method that produces reliable results. The aim of this study was to evaluate the SHI in King Williams Town by studying the relationship between land surface temperatures, land cover and land cover indices. The derived indices are the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built up Index (NDBI). These indices were selected because they are representative of the land cover scheme used in the research study. This study was conducted in the King Williams town area between the years 1995 and 2018 the land surface temperature was derived from Landsat ETM + high thermal band data. The findings from this study provide an idea on the correlation between satellite derived land surface temperature and the land modification which occurred during the urbanization of King Williams Town during a 23 year period between1995 and 2018. The built up land category was the most influential in the development of high land surface temperature levels , vegetation had an opposite effect as a series of data sets illustrated that vegetated areas had a iv cooling effect on the surface. Water bodies in the study area had an insignificant effect on the Surface temperature levels while the grass lands weren’t as cooling as the vegetation but provided a cooling environment in the study area .The spatial distribution of areas of high surface temperature (hot spots) was discovered to be concentrated in the urban areas of the study area which is in the northwest region of the study area and correlates to the land cover and land cover indices associated with built up and artificial surfaces. The cooler areas or patches of land with lower values of land surface temperature were distributed on the outskirts of the study area away from the CBD and residential areas. This was the case because of the high concentration of vegetation and thicker grass lands in those regions.
- Full Text:
- Date Issued: 2020
The role of Hsp90/Hsp70 organising protein (Hop) in the Proliferation, Survival and Migration of Breast Cancer Cells.
- Authors: Willmer, Tarryn
- Date: 2012
- Subjects: Cancer -- Treatment , Heat shock proteins , Cancer cells , Breast -- Cancer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4130 , http://hdl.handle.net/10962/d1015720
- Description: Hop (the Hsp90/Hsp70 organising protein) is a co-chaperone that acts as an adapter between the major molecular chaperones Hsp90 and Hsp70 during the cellular assembly of the Hsp90 complex. The Hsp90 complex regulates the stability and conformational maturation of a range of important cellular proteins, many of which are deregulated in cancer. In this study, we hypothesised that Hop knockdown inhibits proliferation and migration of cancer cells. We characterised the expression of Hop in cell models of different cancerous status, and provided evidence that Hop was upregulated in tumour cells compared to normal cell counterparts. Using an RNA interference approach, a 60-90% knockdown of Hop was achieved for up to 144 hours in the MDA-MB-231 and Hs578T breast cancer cell lines. Hop knockdown resulted in downregulation of the Hsp90 client proteins, Akt and Stat3, as well as a change in the expression of other Hsp90 co-chaperones, p23, Cdc37 and Aha1, while no change in the levels of Hsp90 or Hsp70 was observed. Silencing of Hop impaired cell proliferation in Hs578T cells but an increase in proliferation in MDA-MB-231, suggesting that the role of Hop in cancer cell proliferation was dependent on type of cancer cell. Hop knockdown in Hs578T and MDA-MB- 231 cells did not lead to any significant changes in the half maximal inhibitory concentrations (IC50) of selected small molecule inhibitors (paclitaxel, geldanamycin and novobiocin) in these cell lines after 72 hours. Hop knockdown cells were however, more sensitive than control cells to the Hsp90 inhibitors geldanamycin and novobiocin at earlier time points and in the presence of the drug transporter inhibitor, verapamil. Hop knockdown caused a decrease in cell migration as measured by the wound healing assay in both Hs578T and MDA-MB-231 cells. Hop was present in purified pseudopodia fractions of migrating cells, and immunofluorescence analysis showed that Hop colocalised with actin at the leading edges of pseudopodia, points of adhesion and at intercellular junctions of cells that have been stimulated to migrate with the chemokine stromal derived factor-1. Hop was able to bind to actin in vitro using actin cosedimentation assays, and silencing of Hop dramatically reduced the capacity of Hs578T cells to form pseudopodia. These results establish a correlation between Hop and actin dynamics, pseudopodia formation and migration in the context of Hop silencing, and collectively suggest that Hop plays a role in cancer cell migration. This study presents experimental evidence for a promising alternative to targeting Hsp90 and Hsp70 chaperones, a novel drug target in cancer therapy.
- Full Text:
- Date Issued: 2012
- Authors: Willmer, Tarryn
- Date: 2012
- Subjects: Cancer -- Treatment , Heat shock proteins , Cancer cells , Breast -- Cancer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4130 , http://hdl.handle.net/10962/d1015720
- Description: Hop (the Hsp90/Hsp70 organising protein) is a co-chaperone that acts as an adapter between the major molecular chaperones Hsp90 and Hsp70 during the cellular assembly of the Hsp90 complex. The Hsp90 complex regulates the stability and conformational maturation of a range of important cellular proteins, many of which are deregulated in cancer. In this study, we hypothesised that Hop knockdown inhibits proliferation and migration of cancer cells. We characterised the expression of Hop in cell models of different cancerous status, and provided evidence that Hop was upregulated in tumour cells compared to normal cell counterparts. Using an RNA interference approach, a 60-90% knockdown of Hop was achieved for up to 144 hours in the MDA-MB-231 and Hs578T breast cancer cell lines. Hop knockdown resulted in downregulation of the Hsp90 client proteins, Akt and Stat3, as well as a change in the expression of other Hsp90 co-chaperones, p23, Cdc37 and Aha1, while no change in the levels of Hsp90 or Hsp70 was observed. Silencing of Hop impaired cell proliferation in Hs578T cells but an increase in proliferation in MDA-MB-231, suggesting that the role of Hop in cancer cell proliferation was dependent on type of cancer cell. Hop knockdown in Hs578T and MDA-MB- 231 cells did not lead to any significant changes in the half maximal inhibitory concentrations (IC50) of selected small molecule inhibitors (paclitaxel, geldanamycin and novobiocin) in these cell lines after 72 hours. Hop knockdown cells were however, more sensitive than control cells to the Hsp90 inhibitors geldanamycin and novobiocin at earlier time points and in the presence of the drug transporter inhibitor, verapamil. Hop knockdown caused a decrease in cell migration as measured by the wound healing assay in both Hs578T and MDA-MB-231 cells. Hop was present in purified pseudopodia fractions of migrating cells, and immunofluorescence analysis showed that Hop colocalised with actin at the leading edges of pseudopodia, points of adhesion and at intercellular junctions of cells that have been stimulated to migrate with the chemokine stromal derived factor-1. Hop was able to bind to actin in vitro using actin cosedimentation assays, and silencing of Hop dramatically reduced the capacity of Hs578T cells to form pseudopodia. These results establish a correlation between Hop and actin dynamics, pseudopodia formation and migration in the context of Hop silencing, and collectively suggest that Hop plays a role in cancer cell migration. This study presents experimental evidence for a promising alternative to targeting Hsp90 and Hsp70 chaperones, a novel drug target in cancer therapy.
- Full Text:
- Date Issued: 2012
Periglacial landforms of the Ahlmannryggen and Jutulsessen areas of western Dronning Maud land, Antarctica
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
Optimisation of an in vitro model for anti-diabetic screening
- Authors: Wilson, Gayle Pamela
- Date: 2006
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10308 , http://hdl.handle.net/10948/428 , Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: The need for alternative strategies for the prevention and treatment of diabetes is growing rapidly as type II diabetes is reaching epidemic status in our society. This need was the basis for the creation of this study, as it was necessary to start looking towards medicinal plants as potential antidiabetic treatment and no comprehensive in vitro model existed. In creating a model for determining the effects of alternative traditional medicines as antidiabetic potentiates, it was necessary that two metabolic pathways, namely glucose uptake and insulin secretion, which play a significant role in glucose homeostasis, be at the centre of our investigations. The objective of this project was to optimize the methodology required to screen and ultimately determine the effectiveness of the plant extracts Kankerbos and MRC2003, as antidiabetic potentiates, through observing their effects on glucose utilisation and insulin secretion. If these medicinal plants are going to make a positive contribution to the health of type II diabetic South Africans, then the determination of their efficacy is essential. The cell lines used in this study included 3T3-L1 preadipocytes, Chang liver, C2C12 muscle and INS-1 rat pancreatic cells. Each cell line represents a different in vivo organ that is known to have an influence on glucose homeostasis in our bodies, each with its own unique metabolic pathways and mechanisms of activity, thereby making each one a vital component in the study. The positive controls for the two models were insulin and metformin (glucose utilisation) and glibenclamide (insulin secretion). Insulin was shown to provide a significant increase in the amount of glucose taken up in C2C12 muscle and Chang liver cells for acute conditions. Chronic treatments with metformin provided a significant increase in glucose utilised by Chang liver cells. Glibenclamide was an effective positive control for stimulating insulin secretion by INS-1 cells under acute conditions as there was a significant increase in the amount of insulin secreted. MRC2003 did not show any significant antidiabetic activity. Sutherlandia frutescens (Kankerbos) showed biological activities comparable to some of the more recognized antidiabetic compounds throughout the study. With regards to the glucose utilisation model, Kankerbos was seen to have both acute and chronic effects in different cell lines. In the C2C12 muscle cell line, Kankerbos significantly increased glucose uptake when they were exposed to acute conditions. Kankerbos also had a significant effect on the Chang liver cells as it was observed that under both acute and chronic conditions, this plant extract induced the uptake of glucose into these cells. With respect to the insulin secretion model involving INS-1 cells, no significant effect was seen during acute exposure with Kankerbos treatment. However during chronic exposure, an increase in insulin secretion was initiated by this plant extract. Overall, the results of this study suggest that Kankerbos has a twofold mechanism of action for its glucose-lowering effects. Given that Kankerbos is widely available in South Africa, this study was valuable as it provided an indication that Kankerbos has antidiabetic activities and could possibly be used as an alternative antidiabetic medication.
- Full Text:
- Date Issued: 2006
- Authors: Wilson, Gayle Pamela
- Date: 2006
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10308 , http://hdl.handle.net/10948/428 , Hypoglycemic agents , Diabetes -- Treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: The need for alternative strategies for the prevention and treatment of diabetes is growing rapidly as type II diabetes is reaching epidemic status in our society. This need was the basis for the creation of this study, as it was necessary to start looking towards medicinal plants as potential antidiabetic treatment and no comprehensive in vitro model existed. In creating a model for determining the effects of alternative traditional medicines as antidiabetic potentiates, it was necessary that two metabolic pathways, namely glucose uptake and insulin secretion, which play a significant role in glucose homeostasis, be at the centre of our investigations. The objective of this project was to optimize the methodology required to screen and ultimately determine the effectiveness of the plant extracts Kankerbos and MRC2003, as antidiabetic potentiates, through observing their effects on glucose utilisation and insulin secretion. If these medicinal plants are going to make a positive contribution to the health of type II diabetic South Africans, then the determination of their efficacy is essential. The cell lines used in this study included 3T3-L1 preadipocytes, Chang liver, C2C12 muscle and INS-1 rat pancreatic cells. Each cell line represents a different in vivo organ that is known to have an influence on glucose homeostasis in our bodies, each with its own unique metabolic pathways and mechanisms of activity, thereby making each one a vital component in the study. The positive controls for the two models were insulin and metformin (glucose utilisation) and glibenclamide (insulin secretion). Insulin was shown to provide a significant increase in the amount of glucose taken up in C2C12 muscle and Chang liver cells for acute conditions. Chronic treatments with metformin provided a significant increase in glucose utilised by Chang liver cells. Glibenclamide was an effective positive control for stimulating insulin secretion by INS-1 cells under acute conditions as there was a significant increase in the amount of insulin secreted. MRC2003 did not show any significant antidiabetic activity. Sutherlandia frutescens (Kankerbos) showed biological activities comparable to some of the more recognized antidiabetic compounds throughout the study. With regards to the glucose utilisation model, Kankerbos was seen to have both acute and chronic effects in different cell lines. In the C2C12 muscle cell line, Kankerbos significantly increased glucose uptake when they were exposed to acute conditions. Kankerbos also had a significant effect on the Chang liver cells as it was observed that under both acute and chronic conditions, this plant extract induced the uptake of glucose into these cells. With respect to the insulin secretion model involving INS-1 cells, no significant effect was seen during acute exposure with Kankerbos treatment. However during chronic exposure, an increase in insulin secretion was initiated by this plant extract. Overall, the results of this study suggest that Kankerbos has a twofold mechanism of action for its glucose-lowering effects. Given that Kankerbos is widely available in South Africa, this study was valuable as it provided an indication that Kankerbos has antidiabetic activities and could possibly be used as an alternative antidiabetic medication.
- Full Text:
- Date Issued: 2006
A preliminary appraisal of the mineral potential of Venda based on a reconnaissance geochemical soil sampling survey and literature review
- Wilson, Michael George Carey
- Authors: Wilson, Michael George Carey
- Date: 1990
- Subjects: Mines and mineral resources -- South Africa -- Venda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4994 , http://hdl.handle.net/10962/d1005606 , Mines and mineral resources -- South Africa -- Venda
- Description: A reconnaissance soil sampling survey was carried out over Venda by Cycad (Pty) Ltd and the samples were analysed for 36 elements using XRF techniques, by Anglo American Research Laboratories in Johanuesburg. The data resulting from this survey forms the basis for the present interpretive study. Initially the sample positions were co-ordinated, then the geological, soil and sample types were allocated to each point. Twelve lithological groupings were chosen which incorporated most of the available data, retained significant geological characteristics and consisted of statistically significant sample populations. Statistical manipulation was undertaken for each of the lithological groups. Using a final population of 5768 samples, means were determined and anomalous values were identified using a threshold of mean plus two standard deviations. Due to time and budgetary constraints, 24 of the 36 elements were chosen for statisical manipulation and fourteen of these, with particular economic significance, were chosen for plotting, wherever significant numbers of anomalies were present. The element overlays were plotted so as to coincide with 18 of the 25, 1:50 000 topographic sheets covering Venda , the remaining 7 having inadequate sample coverage to yield meaningful contours. In this way a total of 175 element overlay sheets were plotted, each showing contoured element levels, with selected anomalous values. The treatment of the vast body of information made available by the Cycad sampling programme has thus been selective and has continually been aimed at highlighting and concentrating attention on the areas of greatest indicated mineralization potential, rather than on specific anomalies. In this regard it is felt that the present study has been successful, in spite of limited sample coverage in some areas. Combining the results of this study with a modern tectonically-based appraisal of mineralization potential and a knowledge of the local geology and previously known mineralization gleaned from an extensive literature review, the following types of mineralization are considered to have the highest potential in Venda: i) Nickel-copper-platinum mineralization as well as magnesite, in the olivine dolerite sills which intrude the base of the Karoo Sequence in Northern Venda. ii) Coal in the basal Karoo Sequence sediments in a broad zone from Jazz 715 MS in the west, and along the Klein Tshipise fault from Amonda 159 MT to the Mutale Copper Fields then east of these to the Kruger National Park. Where intrusives invade these lower Karoo sed iments the potential exists for amorphous graphite. iii) Hydrothermal copper and possibly gold and silver concentrations, in Nzhelele and Sibasa Formation rocks, particularly those associated with faults known to have been active in post-Soutpansberg times. iv) Sediment-hosted massive sulphide deposits (Cu-Pb -Zn) close to basin margin faults, near intersections with cross cutting faults that have resulted in localized basin formation. These are most likely in the Soutpansberg sediments. v) Martle, flake-graphite and late stage skarn mineralization (including lead, zinc, gold and tungsten), in calcareous rocks of the Gumbu Formation.
- Full Text:
- Date Issued: 1990
- Authors: Wilson, Michael George Carey
- Date: 1990
- Subjects: Mines and mineral resources -- South Africa -- Venda
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4994 , http://hdl.handle.net/10962/d1005606 , Mines and mineral resources -- South Africa -- Venda
- Description: A reconnaissance soil sampling survey was carried out over Venda by Cycad (Pty) Ltd and the samples were analysed for 36 elements using XRF techniques, by Anglo American Research Laboratories in Johanuesburg. The data resulting from this survey forms the basis for the present interpretive study. Initially the sample positions were co-ordinated, then the geological, soil and sample types were allocated to each point. Twelve lithological groupings were chosen which incorporated most of the available data, retained significant geological characteristics and consisted of statistically significant sample populations. Statistical manipulation was undertaken for each of the lithological groups. Using a final population of 5768 samples, means were determined and anomalous values were identified using a threshold of mean plus two standard deviations. Due to time and budgetary constraints, 24 of the 36 elements were chosen for statisical manipulation and fourteen of these, with particular economic significance, were chosen for plotting, wherever significant numbers of anomalies were present. The element overlays were plotted so as to coincide with 18 of the 25, 1:50 000 topographic sheets covering Venda , the remaining 7 having inadequate sample coverage to yield meaningful contours. In this way a total of 175 element overlay sheets were plotted, each showing contoured element levels, with selected anomalous values. The treatment of the vast body of information made available by the Cycad sampling programme has thus been selective and has continually been aimed at highlighting and concentrating attention on the areas of greatest indicated mineralization potential, rather than on specific anomalies. In this regard it is felt that the present study has been successful, in spite of limited sample coverage in some areas. Combining the results of this study with a modern tectonically-based appraisal of mineralization potential and a knowledge of the local geology and previously known mineralization gleaned from an extensive literature review, the following types of mineralization are considered to have the highest potential in Venda: i) Nickel-copper-platinum mineralization as well as magnesite, in the olivine dolerite sills which intrude the base of the Karoo Sequence in Northern Venda. ii) Coal in the basal Karoo Sequence sediments in a broad zone from Jazz 715 MS in the west, and along the Klein Tshipise fault from Amonda 159 MT to the Mutale Copper Fields then east of these to the Kruger National Park. Where intrusives invade these lower Karoo sed iments the potential exists for amorphous graphite. iii) Hydrothermal copper and possibly gold and silver concentrations, in Nzhelele and Sibasa Formation rocks, particularly those associated with faults known to have been active in post-Soutpansberg times. iv) Sediment-hosted massive sulphide deposits (Cu-Pb -Zn) close to basin margin faults, near intersections with cross cutting faults that have resulted in localized basin formation. These are most likely in the Soutpansberg sediments. v) Martle, flake-graphite and late stage skarn mineralization (including lead, zinc, gold and tungsten), in calcareous rocks of the Gumbu Formation.
- Full Text:
- Date Issued: 1990
Associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in ECD centres in the Nelson Mandela Bay Municipality
- Authors: Wilson, Teresa Margaret
- Date: 2020
- Subjects: Nutrition--Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46344 , vital:39602
- Description: Introduction: Childhood overweight and obesity is an escalating global health issue. In Africa, overweight and obesity prevalence in children has nearly doubled since 2000(World Health Organisation, 2018).TheSANHANES-1 study (2013) identified that overweight and obesity in were most prevalent in urban informal areas of South Africa, with approximately a quarter of the children classified as overweight or obese (Shisana et al., 2013).In the Nelson Mandela Bay Municipality(NMBM), a double burden of disease was identified in the lower socio-economic population (Phekana et al., 2016). This study and others recommended further study into the contributing factors and behaviours which play a role in the development of overweight and obesity in children. These include household dietary intake, family history of lifestyle diseases, as well as the children’s and parental physical activity and sedentary time (Zhang et al.,2016).Aim: The aim of the study was to determine the associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in NMBM to describe underlying causes of childhood overweight and obesity.Methods: A cross-sectional design, using a quantitative approach, was used for this study(Ethics approval: H18-HEA-DIET-004). The study population included adult parents and/or caregivers of children from urban areas of Nelson Mandela Bay Municipality attending crèches and schools in these areas, in the age group from birth to 96 months (8 years). Randomised cluster sampling of crèches and schools from an existing database of anthropometrical data of children attending these crèches and schools in the area was done and a final sample of n=155obtained. With the assistance of a trained fieldworker, respondents completed a questionnaire detailing the family history of lifestyle diseases, physical activity levels and sedentary screen time behaviours, and a graphical adjusted version of a household dietary diversity questionnaire. Data about children’s activity levels in the preschool/creche environment was collected by the fieldworker by assessing the ECD centres’daily activity schedules. The anthropometric data of the children of the respondents was accessed from an existing database of these measurements. The data was described using means and standard deviations. Inferential statistics determined any existing associations between these underlying influences of childhood obesity.Results: Only 2% (n=3) of the children were underweight and 12% (n=9) were at risk of becoming underweight as classified by WAZ. HAZ scores identified26% (n=40) of the children at risk of becoming stunted, and 6% (n=9) of the children were already stunted. WHZ classified5% (n=8)of the children as overweight and 5% (n=8)as obese. A further 22% (n=34) of the children were at risk of becoming overweight.BMI/age classificationidentified25% (n=38) of the children as overweight and a further 12% (n=19) as obese. Out of the sample, 12%(n=17) of mothers and 8% (n=7) of fathers were categorised as overweight-to-obese according to the SA specific waist circumference(WC)cut-offs. Out of the children, 15% (n=22) have at least one parent who was overweight-to-obese. Traditional WC categories were classified48% (n=67) of the mothers as overweight-to-obese and at high risk for metabolic syndrome. Of all the lifestyle diseases, hypertension was the most prevalent with 29% (n=41) of households having at least one parent with hypertension. Parental physical activity was grossly overestimated, and the results found to be invalid. The Diet Variety and Frequency score resulted in a mean of 65.00 (n=154, SD=27.37) out of a possible 100 for the households in this sample, and junk food was consumed on three to four occasions per day in 32% (n=49) of households. There were no significant associations found between the parents’ variables and underweight children. Statistically small to medium effect associations were found between parental weight (both SA specific and traditional categories) and overweight children (classified by WHZ and BMI/age). Conclusions and recommendations: The prevalence of overweight and obesity among children in the NMBM was high. The only possible underlying cause of childhood overweight and obesity in pre-school children in the NMBM that could be determined by this study was parents’ weight classified by WC. However, it must be reiterated that due to the cross-sectional nature of the study, an association does not immediately mean causation, and the results are not adequate to rule out other underlying factors influencing childhood obesity. It is recommended that the results of the study are used to incentivise the final implementation of all the intervention targets laid out in the Strategic Plan for the Prevention and Control of Obesity in South Africa 2015-2020 in NMB, and for the development of the future obesity strategy after 2020. The results have shown the necessity for future health interventions to be targeted at the family as a unit.
- Full Text:
- Date Issued: 2020
- Authors: Wilson, Teresa Margaret
- Date: 2020
- Subjects: Nutrition--Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46344 , vital:39602
- Description: Introduction: Childhood overweight and obesity is an escalating global health issue. In Africa, overweight and obesity prevalence in children has nearly doubled since 2000(World Health Organisation, 2018).TheSANHANES-1 study (2013) identified that overweight and obesity in were most prevalent in urban informal areas of South Africa, with approximately a quarter of the children classified as overweight or obese (Shisana et al., 2013).In the Nelson Mandela Bay Municipality(NMBM), a double burden of disease was identified in the lower socio-economic population (Phekana et al., 2016). This study and others recommended further study into the contributing factors and behaviours which play a role in the development of overweight and obesity in children. These include household dietary intake, family history of lifestyle diseases, as well as the children’s and parental physical activity and sedentary time (Zhang et al.,2016).Aim: The aim of the study was to determine the associations between family history of diseases of lifestyle, lifestyle behaviour and anthropometric nutritional status of pre-school children in NMBM to describe underlying causes of childhood overweight and obesity.Methods: A cross-sectional design, using a quantitative approach, was used for this study(Ethics approval: H18-HEA-DIET-004). The study population included adult parents and/or caregivers of children from urban areas of Nelson Mandela Bay Municipality attending crèches and schools in these areas, in the age group from birth to 96 months (8 years). Randomised cluster sampling of crèches and schools from an existing database of anthropometrical data of children attending these crèches and schools in the area was done and a final sample of n=155obtained. With the assistance of a trained fieldworker, respondents completed a questionnaire detailing the family history of lifestyle diseases, physical activity levels and sedentary screen time behaviours, and a graphical adjusted version of a household dietary diversity questionnaire. Data about children’s activity levels in the preschool/creche environment was collected by the fieldworker by assessing the ECD centres’daily activity schedules. The anthropometric data of the children of the respondents was accessed from an existing database of these measurements. The data was described using means and standard deviations. Inferential statistics determined any existing associations between these underlying influences of childhood obesity.Results: Only 2% (n=3) of the children were underweight and 12% (n=9) were at risk of becoming underweight as classified by WAZ. HAZ scores identified26% (n=40) of the children at risk of becoming stunted, and 6% (n=9) of the children were already stunted. WHZ classified5% (n=8)of the children as overweight and 5% (n=8)as obese. A further 22% (n=34) of the children were at risk of becoming overweight.BMI/age classificationidentified25% (n=38) of the children as overweight and a further 12% (n=19) as obese. Out of the sample, 12%(n=17) of mothers and 8% (n=7) of fathers were categorised as overweight-to-obese according to the SA specific waist circumference(WC)cut-offs. Out of the children, 15% (n=22) have at least one parent who was overweight-to-obese. Traditional WC categories were classified48% (n=67) of the mothers as overweight-to-obese and at high risk for metabolic syndrome. Of all the lifestyle diseases, hypertension was the most prevalent with 29% (n=41) of households having at least one parent with hypertension. Parental physical activity was grossly overestimated, and the results found to be invalid. The Diet Variety and Frequency score resulted in a mean of 65.00 (n=154, SD=27.37) out of a possible 100 for the households in this sample, and junk food was consumed on three to four occasions per day in 32% (n=49) of households. There were no significant associations found between the parents’ variables and underweight children. Statistically small to medium effect associations were found between parental weight (both SA specific and traditional categories) and overweight children (classified by WHZ and BMI/age). Conclusions and recommendations: The prevalence of overweight and obesity among children in the NMBM was high. The only possible underlying cause of childhood overweight and obesity in pre-school children in the NMBM that could be determined by this study was parents’ weight classified by WC. However, it must be reiterated that due to the cross-sectional nature of the study, an association does not immediately mean causation, and the results are not adequate to rule out other underlying factors influencing childhood obesity. It is recommended that the results of the study are used to incentivise the final implementation of all the intervention targets laid out in the Strategic Plan for the Prevention and Control of Obesity in South Africa 2015-2020 in NMB, and for the development of the future obesity strategy after 2020. The results have shown the necessity for future health interventions to be targeted at the family as a unit.
- Full Text:
- Date Issued: 2020
Identification of potential novel roles for Hsp70/Hsp90 organising protein (Hop) using proteomic analysis in human cells
- Authors: Wingate, Ianthe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64758 , vital:28598
- Description: Expected release date-May 2018
- Full Text:
- Date Issued: 2016
- Authors: Wingate, Ianthe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64758 , vital:28598
- Description: Expected release date-May 2018
- Full Text:
- Date Issued: 2016
Implementing non-photorealistic rendering enhancements with real-time performance
- Authors: Winnemöller, Holger
- Date: 2002 , 2013-05-09
- Subjects: Computer animation , Computer graphics , Real-time data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4580 , http://hdl.handle.net/10962/d1003135 , Computer animation , Computer graphics , Real-time data processing
- Description: We describe quality and performance enhancements, which work in real-time, to all well-known Non-photorealistic (NPR) rendering styles for use in an interactive context. These include Comic rendering, Sketch rendering, Hatching and Painterly rendering, but we also attempt and justify a widening of the established definition of what is considered NPR. In the individual Chapters, we identify typical stylistic elements of the different NPR styles. We list problems that need to be solved in order to implement the various renderers. Standard solutions available in the literature are introduced and in all cases extended and optimised. In particular, we extend the lighting model of the comic renderer to include a specular component and introduce multiple inter-related but independent geometric approximations which greatly improve rendering performance. We implement two completely different solutions to random perturbation sketching, solve temporal coherence issues for coal sketching and find an unexpected use for 3D textures to implement hatch-shading. Textured brushes of painterly rendering are extended by properties such as stroke-direction and texture, motion, paint capacity, opacity and emission, making them more flexible and versatile. Brushes are also provided with a minimal amount of intelligence, so that they can help in maximising screen coverage of brushes. We furthermore devise a completely new NPR style, which we call super-realistic and show how sample images can be tweened in real-time to produce an image-based six degree-of-freedom renderer performing at roughly 450 frames per second. Performance values for our other renderers all lie between 10 and over 400 frames per second on homePC hardware, justifying our real-time claim. A large number of sample screen-shots, illustrations and animations demonstrate the visual fidelity of our rendered images. In essence, we successfully achieve our attempted goals of increasing the creative, expressive and communicative potential of individual NPR styles, increasing performance of most of them, adding original and interesting visual qualities, and exploring new techniques or existing ones in novel ways. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002
- Authors: Winnemöller, Holger
- Date: 2002 , 2013-05-09
- Subjects: Computer animation , Computer graphics , Real-time data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4580 , http://hdl.handle.net/10962/d1003135 , Computer animation , Computer graphics , Real-time data processing
- Description: We describe quality and performance enhancements, which work in real-time, to all well-known Non-photorealistic (NPR) rendering styles for use in an interactive context. These include Comic rendering, Sketch rendering, Hatching and Painterly rendering, but we also attempt and justify a widening of the established definition of what is considered NPR. In the individual Chapters, we identify typical stylistic elements of the different NPR styles. We list problems that need to be solved in order to implement the various renderers. Standard solutions available in the literature are introduced and in all cases extended and optimised. In particular, we extend the lighting model of the comic renderer to include a specular component and introduce multiple inter-related but independent geometric approximations which greatly improve rendering performance. We implement two completely different solutions to random perturbation sketching, solve temporal coherence issues for coal sketching and find an unexpected use for 3D textures to implement hatch-shading. Textured brushes of painterly rendering are extended by properties such as stroke-direction and texture, motion, paint capacity, opacity and emission, making them more flexible and versatile. Brushes are also provided with a minimal amount of intelligence, so that they can help in maximising screen coverage of brushes. We furthermore devise a completely new NPR style, which we call super-realistic and show how sample images can be tweened in real-time to produce an image-based six degree-of-freedom renderer performing at roughly 450 frames per second. Performance values for our other renderers all lie between 10 and over 400 frames per second on homePC hardware, justifying our real-time claim. A large number of sample screen-shots, illustrations and animations demonstrate the visual fidelity of our rendered images. In essence, we successfully achieve our attempted goals of increasing the creative, expressive and communicative potential of individual NPR styles, increasing performance of most of them, adding original and interesting visual qualities, and exploring new techniques or existing ones in novel ways. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002