A geochemical and morphological investigation of placer gold grains from the southern Seward Peninsula, Alaska : implications for source and transport mechanisms
- Gauntlett, Ernest John Herbert
- Authors: Gauntlett, Ernest John Herbert
- Date: 2015
- Subjects: Placer deposits -- Alaska -- Seward Peninsula , Gold alloys , Gold mines and mining -- Alaska -- Seward Peninsula , Geochemical surveys -- Alaska -- Seward Peninsula , Trace elements -- Alaska -- Seward Peninsula , Drift -- Alaska -- Seward Peninsula , Gold -- Standards of fineness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5085 , http://hdl.handle.net/10962/d1018202
- Description: [Partial abstract]: This study presents the first detailed geochemical and morphological characterisation of gold grains from the southern Seward Peninsula, Alaska, a region with significant historical and on-going placer gold mining. Quantitative Au, Ag, Hg, and Cu data are presented for gold grains from eleven sites. Additionally, quantitative Te, W, As, and Sb trace element data are presented for gold grains from ten of the eleven sites. Although it is acknowledged that quantitative trace element analysis of gold grains is a relatively new endeavour, the limited trace element data obtained in this study suggest that trace element analysis could be useful for characterising gold sources on the southern Seward Peninsula. Major and minor element geochemical profiling is sufficient at differentiating between sites from regional provenance systems but insufficient at differentiating between sites within a single system. Differentiating among sites within a single system will likely require microchemical analysis of mineral inclusions and analysis of trace element signatures.
- Full Text:
- Date Issued: 2015
- Authors: Gauntlett, Ernest John Herbert
- Date: 2015
- Subjects: Placer deposits -- Alaska -- Seward Peninsula , Gold alloys , Gold mines and mining -- Alaska -- Seward Peninsula , Geochemical surveys -- Alaska -- Seward Peninsula , Trace elements -- Alaska -- Seward Peninsula , Drift -- Alaska -- Seward Peninsula , Gold -- Standards of fineness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5085 , http://hdl.handle.net/10962/d1018202
- Description: [Partial abstract]: This study presents the first detailed geochemical and morphological characterisation of gold grains from the southern Seward Peninsula, Alaska, a region with significant historical and on-going placer gold mining. Quantitative Au, Ag, Hg, and Cu data are presented for gold grains from eleven sites. Additionally, quantitative Te, W, As, and Sb trace element data are presented for gold grains from ten of the eleven sites. Although it is acknowledged that quantitative trace element analysis of gold grains is a relatively new endeavour, the limited trace element data obtained in this study suggest that trace element analysis could be useful for characterising gold sources on the southern Seward Peninsula. Major and minor element geochemical profiling is sufficient at differentiating between sites from regional provenance systems but insufficient at differentiating between sites within a single system. Differentiating among sites within a single system will likely require microchemical analysis of mineral inclusions and analysis of trace element signatures.
- Full Text:
- Date Issued: 2015
Towards a framework for building security operation centers
- Authors: Jacobs, Pierre Conrad
- Date: 2015
- Subjects: Security systems industry , Systems engineering , Expert systems (Computer science) , COBIT (Information technology management standard) , Computer security
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4710 , http://hdl.handle.net/10962/d1017932
- Description: In this thesis a framework for Security Operation Centers (SOCs) is proposed. It was developed by utilising Systems Engineering best practices, combined with industry-accepted standards and frameworks, such as the TM Forum’s eTOM framework, CoBIT, ITIL, and ISO/IEC 27002:2005. This framework encompasses the design considerations, the operational considerations and the means to measure the effectiveness and efficiency of SOCs. The intent is to provide guidance to consumers on how to compare and measure the capabilities of SOCs provided by disparate service providers, and to provide service providers (internal and external) a framework to use when building and improving their offerings. The importance of providing a consistent, measureable and guaranteed service to customers is becoming more important, as there is an increased focus on holistic management of security. This has in turn resulted in an increased number of both internal and managed service provider solutions. While some frameworks exist for designing, building and operating specific security technologies used within SOCs, we did not find any comprehensive framework for designing, building and managing SOCs. Consequently, consumers of SOCs do not enjoy a constant experience from vendors, and may experience inconsistent services from geographically dispersed offerings provided by the same vendor.
- Full Text:
- Date Issued: 2015
- Authors: Jacobs, Pierre Conrad
- Date: 2015
- Subjects: Security systems industry , Systems engineering , Expert systems (Computer science) , COBIT (Information technology management standard) , Computer security
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4710 , http://hdl.handle.net/10962/d1017932
- Description: In this thesis a framework for Security Operation Centers (SOCs) is proposed. It was developed by utilising Systems Engineering best practices, combined with industry-accepted standards and frameworks, such as the TM Forum’s eTOM framework, CoBIT, ITIL, and ISO/IEC 27002:2005. This framework encompasses the design considerations, the operational considerations and the means to measure the effectiveness and efficiency of SOCs. The intent is to provide guidance to consumers on how to compare and measure the capabilities of SOCs provided by disparate service providers, and to provide service providers (internal and external) a framework to use when building and improving their offerings. The importance of providing a consistent, measureable and guaranteed service to customers is becoming more important, as there is an increased focus on holistic management of security. This has in turn resulted in an increased number of both internal and managed service provider solutions. While some frameworks exist for designing, building and operating specific security technologies used within SOCs, we did not find any comprehensive framework for designing, building and managing SOCs. Consequently, consumers of SOCs do not enjoy a constant experience from vendors, and may experience inconsistent services from geographically dispersed offerings provided by the same vendor.
- Full Text:
- Date Issued: 2015
Present state of macrophytes and responses to management scenarios at the St. Lucia and Mfolozi estuaries
- Authors: Rautenbach, Kelly
- Date: 2015
- Subjects: Aquatic plants -- South Africa , Estuaries -- South Africa , Marine plants -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3195 , vital:20410
- Description: The St. Lucia Estuary, the largest estuary in South Africa, has been subject to many natural (a decade long drought) and anthropogenic impacts. A particular mouth manipulation activity, the artificial separation of the Mfolozi River and the St Lucia Estuary in 1952, was done to stop the perceived “silting up” of the estuary, but resulted in a decrease in freshwater supply. The changes in inflows (both fresh and marine) are controlled by management decisions and affect other system parameters such as salinity, water level and turbidity, which influence the distribution of biota. Therefore knowledge on the physico-chemical environment and eco-physiological tolerances of macrophytes will lead to informed future management decisions. The first of the three objectives carried out for this study determined the present state and distribution of the macrophytes of the St. Lucia and Mfolozi estuaries. The macrophyte habitats mapped in 2008 and 2013 were the submerged macrophytes, reeds and sedges, mangroves, grass and shrubs, salt marsh (succulent) and swamp forest. Results indicated that low salinity in the lakes and high water level in 2013 caused die-back or expansion of particular habitats. Submerged macrophytes, in particular Stuckenia pectinata, grows well in water with salinity <15 ppt, therefore this habitat increased by 412 ha (96%) in cover since 2008. Salt marsh decreased by 553 ha (57%) due to inundation. Since 2008 the reeds and sedges increased by 390 ha (in North Lake and the Narrows) due to the salinity decrease. In the Narrows the mangroves decreased by 28 ha (9%) in area cover. This was due to the drought that persisted for so many years, which caused low water levels and non-tidal conditions. The second objective was to determine the present state / health of the mangroves at four sites along the Narrows by assessing sediment condition and population structure of the trees. These results were compared to those obtained in 2010. The total density of Avicennia marina increased since 2010, however this was due to the large increase in seedlings at Site 1, the back channel site. The highest sediment salinity (26 ppt) and porewater salinity (29 ppt) was recorded for this site and these results show that this back channel site was strongly influenced by the open Mfolozi Estuary (increase in marine waters) and tidal conditions at the time of sampling in 2013. The total density of Bruguiera gymnorrhiza decreased, but an increase in adults was recorded at Site 2, the freshwater site. The soil collected from the Bruguiera quadrats was fresher and drier than that of the Avicennia quadrats of Site 2. Lack of seedlings (of both species) was due to the dense stands of Acrostichum aureum (mangrove fern) and Phragmites australis (common reed) and a thick, impenetrable mat of Avicennia pneumatophores. At Sites 3 and 4, the drier sites (where sediment moisture contents were the lowest for all sites at 43 and 42% respectively), seedling and sapling density was low, but adults increased in density since 2010. Recruitment and survival were impacted by the harsh environmental conditions that prevailed prior to 2013 (low water level and non-tidal influence), but adults survived. The results of the test that determined the percentage of aerenchyma of the pneumatophores indicated that waterlogging stress did not affect the aerenchyma of the pneumatophores. However the period of inundation was probably not significant enough to have affected the production of aerenchyma. The third objective formed part of an ongoing study by the Global Environmental Facility (GEF) on the feasibility of linking the Mfolozi River back to the St Lucia Estuary and the responses of these systems to different management scenarios: 1) the “do nothing” scenario; 2) maintain separate Mfolozi and St Lucia mouths representing an open mouth condition; and 3) actively facilitate a single mouth (therefore linking the Mfolozi and St Lucia mouths). Data gathered on the eco-physiological tolerances of the dominant macrophyte species was used to predict the response of the different habitats to these various management scenarios and the results indicated that the best management scenario would be to actively facilitate a single mouth (Scenario 3) as the estuary habitats would increase significantly because of preferred tidal and saline conditions, as this would represent more natural conditions. The results of the study will provide input to recommendations for future “adaptive management” strategies for the Global Environmental Facility (GEF) Project.
- Full Text:
- Date Issued: 2015
- Authors: Rautenbach, Kelly
- Date: 2015
- Subjects: Aquatic plants -- South Africa , Estuaries -- South Africa , Marine plants -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3195 , vital:20410
- Description: The St. Lucia Estuary, the largest estuary in South Africa, has been subject to many natural (a decade long drought) and anthropogenic impacts. A particular mouth manipulation activity, the artificial separation of the Mfolozi River and the St Lucia Estuary in 1952, was done to stop the perceived “silting up” of the estuary, but resulted in a decrease in freshwater supply. The changes in inflows (both fresh and marine) are controlled by management decisions and affect other system parameters such as salinity, water level and turbidity, which influence the distribution of biota. Therefore knowledge on the physico-chemical environment and eco-physiological tolerances of macrophytes will lead to informed future management decisions. The first of the three objectives carried out for this study determined the present state and distribution of the macrophytes of the St. Lucia and Mfolozi estuaries. The macrophyte habitats mapped in 2008 and 2013 were the submerged macrophytes, reeds and sedges, mangroves, grass and shrubs, salt marsh (succulent) and swamp forest. Results indicated that low salinity in the lakes and high water level in 2013 caused die-back or expansion of particular habitats. Submerged macrophytes, in particular Stuckenia pectinata, grows well in water with salinity <15 ppt, therefore this habitat increased by 412 ha (96%) in cover since 2008. Salt marsh decreased by 553 ha (57%) due to inundation. Since 2008 the reeds and sedges increased by 390 ha (in North Lake and the Narrows) due to the salinity decrease. In the Narrows the mangroves decreased by 28 ha (9%) in area cover. This was due to the drought that persisted for so many years, which caused low water levels and non-tidal conditions. The second objective was to determine the present state / health of the mangroves at four sites along the Narrows by assessing sediment condition and population structure of the trees. These results were compared to those obtained in 2010. The total density of Avicennia marina increased since 2010, however this was due to the large increase in seedlings at Site 1, the back channel site. The highest sediment salinity (26 ppt) and porewater salinity (29 ppt) was recorded for this site and these results show that this back channel site was strongly influenced by the open Mfolozi Estuary (increase in marine waters) and tidal conditions at the time of sampling in 2013. The total density of Bruguiera gymnorrhiza decreased, but an increase in adults was recorded at Site 2, the freshwater site. The soil collected from the Bruguiera quadrats was fresher and drier than that of the Avicennia quadrats of Site 2. Lack of seedlings (of both species) was due to the dense stands of Acrostichum aureum (mangrove fern) and Phragmites australis (common reed) and a thick, impenetrable mat of Avicennia pneumatophores. At Sites 3 and 4, the drier sites (where sediment moisture contents were the lowest for all sites at 43 and 42% respectively), seedling and sapling density was low, but adults increased in density since 2010. Recruitment and survival were impacted by the harsh environmental conditions that prevailed prior to 2013 (low water level and non-tidal influence), but adults survived. The results of the test that determined the percentage of aerenchyma of the pneumatophores indicated that waterlogging stress did not affect the aerenchyma of the pneumatophores. However the period of inundation was probably not significant enough to have affected the production of aerenchyma. The third objective formed part of an ongoing study by the Global Environmental Facility (GEF) on the feasibility of linking the Mfolozi River back to the St Lucia Estuary and the responses of these systems to different management scenarios: 1) the “do nothing” scenario; 2) maintain separate Mfolozi and St Lucia mouths representing an open mouth condition; and 3) actively facilitate a single mouth (therefore linking the Mfolozi and St Lucia mouths). Data gathered on the eco-physiological tolerances of the dominant macrophyte species was used to predict the response of the different habitats to these various management scenarios and the results indicated that the best management scenario would be to actively facilitate a single mouth (Scenario 3) as the estuary habitats would increase significantly because of preferred tidal and saline conditions, as this would represent more natural conditions. The results of the study will provide input to recommendations for future “adaptive management” strategies for the Global Environmental Facility (GEF) Project.
- Full Text:
- Date Issued: 2015
The biology, behaviour and survival of pupating false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a citrus pest in South Africa
- Authors: Love, Claire Natalie
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Larvae -- Behavior , Citrus -- Diseases and pests , Citrus -- Diseases and pests -- Biological control , Biological pest control agents , Entomopathogenic fungi , Insect nematodes , Pupae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5941 , http://hdl.handle.net/10962/d1018907
- Description: Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter.
- Full Text:
- Date Issued: 2015
- Authors: Love, Claire Natalie
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Larvae -- Behavior , Citrus -- Diseases and pests , Citrus -- Diseases and pests -- Biological control , Biological pest control agents , Entomopathogenic fungi , Insect nematodes , Pupae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5941 , http://hdl.handle.net/10962/d1018907
- Description: Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter.
- Full Text:
- Date Issued: 2015
Studies towards the development of novel antimalarial agents
- Authors: Adeyemi, Christiana Modupe
- Date: 2015
- Subjects: Antimalarials , Malaria , Drug resistance , Drug development , Enzyme inhibitors , Plasmodium
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54645 , vital:26596
- Description: Considerable efforts have been made in the modification of existing antimalarial drugs, and the support of incentive programmes have led to a drastic decrease in malaria cases reported by WHO during the past 6 years. However, the development of drug resistance threatens the eradication of this deadly disease and has prompted research on the synthesis of novel antimalarial drugs. Our research has involved the design and synthesis of novel benzylated phosphonate esters as potential 1-deoxy-D-xylose-5-phosphate reductoisomerase (DXR) inhibitors. A series of amidoalkylphosphonate esters were obtained by reacting various 3-subsituted anilines and heterocyclic amines with chloroalkanoyl chlorides and reacting the resulting chloroalkanamides with triethyl phosphite using Michaelis-Arbuzov methodology. Benzylation of the phosphonate esters afforded a series of novel N-benzylated derivatives in good yields and these compounds were fully characterised by NMR and HRMS methods. Several approaches to the introduction of a benzyl group at the C-2 position of the phosphonate ester derivatives have been explored, leading unexpectedly to the isolation of unprecedented tetrahydrofuranyl derivatives. Studies towards the preparation of potential bi-functional PfDXR / HIV-1 RT inhibitors have also been initiated. Preliminary in silico docking studies of selected non-benzylated and benzylated phosphonated derivatives into the Pf-DXR active-site has provided useful insight into the binding potential of these ligands. Bioassays have revealed a very low toxicity for all the synthesised phosphonated compounds and a number of these ligands also exhibit a promising inhibitory activity against the Plasmodium parasite.
- Full Text:
- Date Issued: 2015
- Authors: Adeyemi, Christiana Modupe
- Date: 2015
- Subjects: Antimalarials , Malaria , Drug resistance , Drug development , Enzyme inhibitors , Plasmodium
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54645 , vital:26596
- Description: Considerable efforts have been made in the modification of existing antimalarial drugs, and the support of incentive programmes have led to a drastic decrease in malaria cases reported by WHO during the past 6 years. However, the development of drug resistance threatens the eradication of this deadly disease and has prompted research on the synthesis of novel antimalarial drugs. Our research has involved the design and synthesis of novel benzylated phosphonate esters as potential 1-deoxy-D-xylose-5-phosphate reductoisomerase (DXR) inhibitors. A series of amidoalkylphosphonate esters were obtained by reacting various 3-subsituted anilines and heterocyclic amines with chloroalkanoyl chlorides and reacting the resulting chloroalkanamides with triethyl phosphite using Michaelis-Arbuzov methodology. Benzylation of the phosphonate esters afforded a series of novel N-benzylated derivatives in good yields and these compounds were fully characterised by NMR and HRMS methods. Several approaches to the introduction of a benzyl group at the C-2 position of the phosphonate ester derivatives have been explored, leading unexpectedly to the isolation of unprecedented tetrahydrofuranyl derivatives. Studies towards the preparation of potential bi-functional PfDXR / HIV-1 RT inhibitors have also been initiated. Preliminary in silico docking studies of selected non-benzylated and benzylated phosphonated derivatives into the Pf-DXR active-site has provided useful insight into the binding potential of these ligands. Bioassays have revealed a very low toxicity for all the synthesised phosphonated compounds and a number of these ligands also exhibit a promising inhibitory activity against the Plasmodium parasite.
- Full Text:
- Date Issued: 2015
Synthesis of silver nanoparticles and their role against human and Plasmodium falciparum leucine aminopeptidase
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
The development of biological tools to aid in the genetic investigation of the black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros mitochondrial genomes
- Authors: Parsons, Michelle
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/56059 , vital:26769
- Description: The black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros are found in South Africa. A decline in the populations of these species has resulted due to human activities such as habitat fragmentation and poaching. This has contributed to the loss of genetic diversity amongst the black and white rhinoceros. Conservation and anti-poaching efforts are needed to help maintain genetic diversity. These efforts could be improved through the development of non-invasive techniques to examine DNA from threatened animals. The aim of this research was to develop a molecular technique which would allow for the identification of the black and white rhinoceros and to develop a molecular technique which would allow for intraspecies genetic variation to be examined. DNA extractions were performed on matched faecal and tissue samples that were collected from two regions in South Africa. Polymerase chain reaction (PCR) primer sets were designed to investigate several regions of the rhinoceros mitochondrial genome. PCR optimisation was completed for the target regions. Sequencing was conducted on all final PCR products. The cytochrome c oxidase subunit 1 (COIi) gene allowed for the rhinoceros family to be identified. This region was digested with the HindIII restriction enzyme, which allowed for the specific identification of either the black or white rhinoceros. A subsequent region of the cytochrome c oxidase subunit 1 (COIii) as well as the D-loop, hypervariable regions (HV1 and HV2), cytochrome b (cytb) and 16s rRNA regions were investigated. These regions displayed potential for establishing geographic origin for black rhinoceros samples, whereas the D-loop and HV2 show potential for the white rhinoceros. The white rhinoceros displayed sequence variation in the HV2 and cytb region, while variation was observed in the COIi and HV1 for the black rhinoceros. All investigated target regions allowed for the rhinoceros family to be identified. The COI (COIi and COIii), HV2 and cytb regions allowed for the subspecies of rhinoceros to be identified, however the D-loop was not able to identify the white rhinoceros species. The 16s rRNA and HV1 regions allowed for the correct subspecies of rhinoceros to be identified, however as the primers were only compatible for the black rhinoceros therefore a subsequent investigation is required for the white rhinoceros. The establishment of this novel PCR based technique to identify white and black rhinoceros will allow for efficient species identification in wildlife forensic cases. A biological method was established to study intraspecies variation for the white and black rhinoceros; however the investigated target regions did not yield sufficient genetic variation. The core techniques developed in this study will be valuable for future studies that wish to investigate genetic variation in mammal species.
- Full Text:
- Date Issued: 2015
- Authors: Parsons, Michelle
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/56059 , vital:26769
- Description: The black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros are found in South Africa. A decline in the populations of these species has resulted due to human activities such as habitat fragmentation and poaching. This has contributed to the loss of genetic diversity amongst the black and white rhinoceros. Conservation and anti-poaching efforts are needed to help maintain genetic diversity. These efforts could be improved through the development of non-invasive techniques to examine DNA from threatened animals. The aim of this research was to develop a molecular technique which would allow for the identification of the black and white rhinoceros and to develop a molecular technique which would allow for intraspecies genetic variation to be examined. DNA extractions were performed on matched faecal and tissue samples that were collected from two regions in South Africa. Polymerase chain reaction (PCR) primer sets were designed to investigate several regions of the rhinoceros mitochondrial genome. PCR optimisation was completed for the target regions. Sequencing was conducted on all final PCR products. The cytochrome c oxidase subunit 1 (COIi) gene allowed for the rhinoceros family to be identified. This region was digested with the HindIII restriction enzyme, which allowed for the specific identification of either the black or white rhinoceros. A subsequent region of the cytochrome c oxidase subunit 1 (COIii) as well as the D-loop, hypervariable regions (HV1 and HV2), cytochrome b (cytb) and 16s rRNA regions were investigated. These regions displayed potential for establishing geographic origin for black rhinoceros samples, whereas the D-loop and HV2 show potential for the white rhinoceros. The white rhinoceros displayed sequence variation in the HV2 and cytb region, while variation was observed in the COIi and HV1 for the black rhinoceros. All investigated target regions allowed for the rhinoceros family to be identified. The COI (COIi and COIii), HV2 and cytb regions allowed for the subspecies of rhinoceros to be identified, however the D-loop was not able to identify the white rhinoceros species. The 16s rRNA and HV1 regions allowed for the correct subspecies of rhinoceros to be identified, however as the primers were only compatible for the black rhinoceros therefore a subsequent investigation is required for the white rhinoceros. The establishment of this novel PCR based technique to identify white and black rhinoceros will allow for efficient species identification in wildlife forensic cases. A biological method was established to study intraspecies variation for the white and black rhinoceros; however the investigated target regions did not yield sufficient genetic variation. The core techniques developed in this study will be valuable for future studies that wish to investigate genetic variation in mammal species.
- Full Text:
- Date Issued: 2015
Photodynamic antimicrobial chemotherapy activities of porphyrin- and phthalocyanine-platinum nanoparticle conjugates
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
Visualising M-learning system usage data
- Authors: Kamuhanda, Dany
- Date: 2015
- Subjects: Database management Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11015 , vital:26876
- Description: Data storage is an important practice for organisations that want to track their progress. The evolution of data storage technologies from manual methods of storing data on paper or in spreadsheets, to the automated methods of using computers to automatically log data into databases or text files has brought an amount of data that is beyond the level of human interpretation and comprehension. One way of addressing this issue of interpreting large amounts of data is data visualisation, which aims to convert abstract data into images that are easy to interpret. However, people often have difficulty in selecting an appropriate visualisation tool and visualisation techniques that can effectively visualise their data. This research proposes the processes that can be followed to effectively visualise data. Data logged from a mobile learning system is visualised as a proof of concept to show how the proposed processes can be followed during data visualisation. These processes are summarised into a model that consists of three main components: the data, the visualisation techniques and the visualisation tool. There are two main contributions in this research: the model to visualise mobile learning usage data and the visualisation of the usage data logged from a mobile learning system. The mobile learning system usage data was visualised to demonstrate how students used the mobile learning system. Visualisation of the usage data helped to convert the data into images (charts and graphs) that were easy to interpret. The evaluation results indicated that the proposed process and resulting visualisation techniques and tool assisted users in effectively and efficiently interpreting large volumes of mobile learning system usage data.
- Full Text:
- Date Issued: 2015
- Authors: Kamuhanda, Dany
- Date: 2015
- Subjects: Database management Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11015 , vital:26876
- Description: Data storage is an important practice for organisations that want to track their progress. The evolution of data storage technologies from manual methods of storing data on paper or in spreadsheets, to the automated methods of using computers to automatically log data into databases or text files has brought an amount of data that is beyond the level of human interpretation and comprehension. One way of addressing this issue of interpreting large amounts of data is data visualisation, which aims to convert abstract data into images that are easy to interpret. However, people often have difficulty in selecting an appropriate visualisation tool and visualisation techniques that can effectively visualise their data. This research proposes the processes that can be followed to effectively visualise data. Data logged from a mobile learning system is visualised as a proof of concept to show how the proposed processes can be followed during data visualisation. These processes are summarised into a model that consists of three main components: the data, the visualisation techniques and the visualisation tool. There are two main contributions in this research: the model to visualise mobile learning usage data and the visualisation of the usage data logged from a mobile learning system. The mobile learning system usage data was visualised to demonstrate how students used the mobile learning system. Visualisation of the usage data helped to convert the data into images (charts and graphs) that were easy to interpret. The evaluation results indicated that the proposed process and resulting visualisation techniques and tool assisted users in effectively and efficiently interpreting large volumes of mobile learning system usage data.
- Full Text:
- Date Issued: 2015
A comparison of open source and proprietary digital forensic software
- Authors: Sonnekus, Michael Hendrik
- Date: 2015
- Subjects: Computer crimes , Computer crimes -- Investigation , Electronic evidence , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4717 , http://hdl.handle.net/10962/d1017939
- Description: Scrutiny of the capabilities and accuracy of computer forensic tools is increasing as the number of incidents relying on digital evidence and the weight of that evidence increase. This thesis describes the capabilities of the leading proprietary and open source digital forensic tools. The capabilities of the tools were tested separately on digital media that had been formatted using Windows and Linux. Experiments were carried out with the intention of establishing whether the capabilities of open source computer forensics are similar to those of proprietary computer forensic tools, and whether these tools could complement one another. The tools were tested with regards to their capabilities to make and analyse digital forensic images in a forensically sound manner. The tests were carried out on each media type after deleting data from the media, and then repeated after formatting the media. The results of the experiments performed demonstrate that both proprietary and open source computer forensic tools have superior capabilities in different scenarios, and that the toolsets can be used to validate and complement one another. The implication of these findings is that investigators have an affordable means of validating their findings and are able to more effectively investigate digital media.
- Full Text:
- Date Issued: 2015
- Authors: Sonnekus, Michael Hendrik
- Date: 2015
- Subjects: Computer crimes , Computer crimes -- Investigation , Electronic evidence , Open source software
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4717 , http://hdl.handle.net/10962/d1017939
- Description: Scrutiny of the capabilities and accuracy of computer forensic tools is increasing as the number of incidents relying on digital evidence and the weight of that evidence increase. This thesis describes the capabilities of the leading proprietary and open source digital forensic tools. The capabilities of the tools were tested separately on digital media that had been formatted using Windows and Linux. Experiments were carried out with the intention of establishing whether the capabilities of open source computer forensics are similar to those of proprietary computer forensic tools, and whether these tools could complement one another. The tools were tested with regards to their capabilities to make and analyse digital forensic images in a forensically sound manner. The tests were carried out on each media type after deleting data from the media, and then repeated after formatting the media. The results of the experiments performed demonstrate that both proprietary and open source computer forensic tools have superior capabilities in different scenarios, and that the toolsets can be used to validate and complement one another. The implication of these findings is that investigators have an affordable means of validating their findings and are able to more effectively investigate digital media.
- Full Text:
- Date Issued: 2015