A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
- Authors: Phelan, Richard Reginald
- Date: 2009
- Subjects: Microcystis aeruginosa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10320 , http://hdl.handle.net/10948/1285 , Microcystis aeruginosa
- Description: Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.
- Full Text:
- Date Issued: 2009
A preliminary investigation and photographic atlas of nodules found in the Bokkelveld group (Gydo formation), Steytlerville district, South Africa
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
- Authors: Browning, Claire
- Date: 2009
- Subjects: Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10656 , http://hdl.handle.net/10948/927 , Gydo formation -- South Africa , Formations (Geology) -- South Africa -- Western Cape , Formations (Geology) -- South Africa -- Eastern Cape , Groups (Stratigraphy) -- South Africa -- Western Cape , Geology -- Stratigraphic , Bokkeveld group (South Africa)
- Description: Nodules within the lower Bokkeveld shales often contain well-preserved invertebrate fossil material. The aim of this study was to describe some characteristics seen at various scales (macro-, micro- and ultra -) within nodules that might contribute to an understanding of aspects of nodule formation and the reasons for the excellent preservation of the fossil material within these nodules. Detailed, high quality macro-photographs were taken of sliced and whole nodule surfaces and a catalogue was produced to tentatively identify fossils present and illustrate the variations seen within nodules. Selected nodules were then subjected to petrographic, ultra-structural (SEM) and some chemical (EDS, XRD & XRF) analysis to investigate the possible reasons for these variations. The chemical results have indicated that nodules are enriched with quartz compared to the surrounding shale. Quartz is also the dominant mineral replacing trilobite carapace material within nodules, while trilobite material within shales is replaced with equal proportions of hematite, biotite and quartz. It appears that the higher resistance of quartz to weathering is the dominant factor leading to the preservation of both nodules within the shales and trilobite material within the nodules examined. A comparison with some Western Cape nodules highlighted possible variations in overall nodule chemical composition along strike. Western Cape nodules are predominantly composed of apatite whereas the Cockscomb nodules are mainly composed of quartz. This quartz-apatite compositional variation in nodules occurring within a single formation has been reported from nodules found in the Armorican Massif of France which are very similar in a number of respects to the Bokkeveld nodules described in this study. Based on various features of the fossils present and the structure of nodules they were probably formed during early diagenesis within an epeiric marine deposit greatly affected by sea level fluctuations.
- Full Text:
- Date Issued: 2009
A resource allocation system for invasive alien plant control on the St. Francis Conservancy
- Authors: Reeves, Brian
- Date: 2009
- Subjects: Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10634 , http://hdl.handle.net/10948/1073 , Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Description: Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.
- Full Text:
- Date Issued: 2009
- Authors: Reeves, Brian
- Date: 2009
- Subjects: Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10634 , http://hdl.handle.net/10948/1073 , Alien plants -- Control -- South Africa , Plant invasions -- South Africa
- Description: Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.
- Full Text:
- Date Issued: 2009
A Speciation study of the chloro-hydroxo complexes of Pt(II)
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
- Authors: Davis, John Christopher
- Date: 2009
- Subjects: Platinum , Platinum -- Separation , Platinum compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10388 , http://hdl.handle.net/10948/1213 , Platinum , Platinum -- Separation , Platinum compounds
- Description: In this study a method was developed to identify and quantify platinum(II) complexes of the type [PtCl4-n(OH)n]2- and [PtCl4-n(H2O)n]2-n. Separation of the various species was achieved with the aid of a hyphenated reversed phase HPLC-ICP-MS technique coupled with an ion-pairing reagent, HMHDCl2. The adsorption of HMHD2+ onto a C-18 column was investigated by generating a series of breakthrough curves. It was found that the selectivity for high charge density anions originates from its low surface coverage relative to TBA+, which on the other hand could not separate Pt(II) complexes. The peaks in the chromatographic traces were assigned by following the stepwise ligand substitution of [PtCl4]2- in hydroxide medium with UV/Vis spectrophotometry and HPLC-ICP-MS simultaneously. A computer program was written by the author to analyse chromatographic data by deconvoluting the chromatogram into its individual components and calculating the mole fraction of each component. The validity of the consecutive pseudo-first order model was validated by constructing 3D Mauser diagrams with the raw spectrophotometric data (A1 vs A2 vs A3). Additional software was used to simulate the raw spectrophotometric data and processed chromatographic data. The pseudo-first order rate constants obtained in both cases were in agreement with each other. Hence, peaks were assigned to [PtCl4]2-, [PtCl3(OH)]2-, [PtCl2(OH)2]2-, [PtCl3(H2O)]-. The molar extinction coefficient spectra of [PtCl3(OH)]2- and [PtCl2(OH)2]2- were obtained by simulating the spectrophotometric data at wavelengths from 280 to 450 nm. The reaction of [PtCl4]2- with sodium hydroxide was investigated with UV/Vis spectrophotometry at 25 °C. A rate constant consisting of a first and second order term was obtained. The first order term agreed with what has been reported in the literature for aquation of [PtCl4]2- at 25 degrees C. The influence of temperature was established by conducting the experiment at different temperatures. It was found that the reaction proceeds essentially via aquation at elevated temperatures.
- Full Text:
- Date Issued: 2009
An investigation into a natural language interface for contact centers
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
An investigation of the factors influencing vegetation stress in a part of the Keiskamma catchment, Eastern Cape : a remote sensing and GIS approach
- Haindongo, Priscilla Nauwanga
- Authors: Haindongo, Priscilla Nauwanga
- Date: 2009
- Subjects: Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10652 , http://hdl.handle.net/10948/975 , Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Description: Vegetation stress as a form of degradation is a widespread problem in many catchments in the Eastern Cape province. The Keiskamma is one of the catchments where considerable parts of the thicket biome are stressed. This necessitates an assessment of the status of the thicket biome by way of detecting vegetation stress in the area. The underpinnings of vegetation stress are investigated in this study. As a basic method to evaluate the thicket condition, remotely sensed data were acquired. High resolution ASTER imagery for the Keiskamma area at two different dates (2001 and 2005) was used to compute SVI and NDVI as indicators of vegetation stress conditions. A Digital Elevation Model (DEM) was used to derive slope angle and aspect. By way of digitizing from ortho-photo maps, various land-use types were mapped using Arc View GIS. The relationship between land use, terrain, soil erosion and vegetation stress was established. Field based techniques comprising stomatal conductance measurements were used and compared to remotely sensed data. The SVI and NDVI resultant images expressed similarities in areas depicting vegetation stress conditions at both epochs. A strong linear regression between NDVI and stomatal conductance measurements (mmol/m²) serve to confirm that the NDVI is a reliable indicator of vegetation stress condition. Slope angle and aspect were found to have a significant influence on vegetation stress conditions. Similarly variations in soil moisture and soil surface condition have strong implications for vegetation stress. Amongst other land-use types, abandoned lands were found to have the lowest NDVI values implying an association with the worst vegetation stress scenarios. It was concluded that an element of persistent stress conditions exists amongst the thicket vegetation of the Keiskamma catchment. This was mainly due to land use activities in the area.
- Full Text:
- Date Issued: 2009
- Authors: Haindongo, Priscilla Nauwanga
- Date: 2009
- Subjects: Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10652 , http://hdl.handle.net/10948/975 , Plants, Effect of stress on -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Vegetation and climate -- South Africa -- Eastern Cape , Ecology -- South Africa -- Eastern Cape -- Remote sensing
- Description: Vegetation stress as a form of degradation is a widespread problem in many catchments in the Eastern Cape province. The Keiskamma is one of the catchments where considerable parts of the thicket biome are stressed. This necessitates an assessment of the status of the thicket biome by way of detecting vegetation stress in the area. The underpinnings of vegetation stress are investigated in this study. As a basic method to evaluate the thicket condition, remotely sensed data were acquired. High resolution ASTER imagery for the Keiskamma area at two different dates (2001 and 2005) was used to compute SVI and NDVI as indicators of vegetation stress conditions. A Digital Elevation Model (DEM) was used to derive slope angle and aspect. By way of digitizing from ortho-photo maps, various land-use types were mapped using Arc View GIS. The relationship between land use, terrain, soil erosion and vegetation stress was established. Field based techniques comprising stomatal conductance measurements were used and compared to remotely sensed data. The SVI and NDVI resultant images expressed similarities in areas depicting vegetation stress conditions at both epochs. A strong linear regression between NDVI and stomatal conductance measurements (mmol/m²) serve to confirm that the NDVI is a reliable indicator of vegetation stress condition. Slope angle and aspect were found to have a significant influence on vegetation stress conditions. Similarly variations in soil moisture and soil surface condition have strong implications for vegetation stress. Amongst other land-use types, abandoned lands were found to have the lowest NDVI values implying an association with the worst vegetation stress scenarios. It was concluded that an element of persistent stress conditions exists amongst the thicket vegetation of the Keiskamma catchment. This was mainly due to land use activities in the area.
- Full Text:
- Date Issued: 2009
Characterization of hydrogen and helium implanted silicon carbide
- Authors: O'Connell, Jacques Herman
- Date: 2009
- Subjects: Silicon carbide , Hydrogen , Helium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10539 , http://hdl.handle.net/10948/979 , Silicon carbide , Hydrogen , Helium
- Description: This dissertation focuses on the characterization of hydrogen implanted 3C-SiC and helium implanted 6H-SiC and the interaction of silver and palladium with the SiC. The main technique used for the analysis of the implanted SiC was transmission electron microscopy (TEM), although scanning electron microscopy (SEM) and nanoindentation hardness testing were also used. Both H and He implantations were done at an ion energy of 100 keV and the total dose for both species was 1017 ions/cm2. Specimens were annealed at 1000 °C for 20 min in an inert atmosphere. The observed depth of ion damage agreed closely with that predicted by TRIM 2008. The damaged region in the He implanted specimens had a high density of small bubbles but no cracks were observed. Severe cracking was observed along the damaged region in the H implanted specimens. A second phase hexagonal (4H-SiC) was detected in two grains in the 3C-SiC and some grown in voids were also observed. The wettability of SiC by a 2:1 by volume mixture of Ag and Pd is extremely low but is significantly increased through the addition of Si to the mixture. The Si containing metal mixture was found to migrate along the grain boundaries of polycrystalline 3CSiC while sealing the point of entry. Pd attacks SiC and severe etching was observed on the surface of 6H-SiC. An epitaxially orientated Pd2Si inclusion was observed in the 6H-SiC. No effect of implantation damage on the interaction of Pd and Ag with SiC was observed. Pd etched the surface of the He implanted 6H-SiC down through the damaged region with no evidence of implantation damage left after 67 hours of annealing and thus no conclusions could be drawn. The metal mixture interacted with the non implanted surface of the H implanted 3C-SiC after dissolving the Si substrate and therefore the effect of the ion damage on the interaction could not be investigated. Nanoindentation hardness measurements showed a marked increase in hardness of He implanted 6H-SiC annealed for 20 min at 1000 °C over that of as implanted and virgin material. There was also a large decrease in hardness corresponding to the depth of the ion damage.
- Full Text:
- Date Issued: 2009
- Authors: O'Connell, Jacques Herman
- Date: 2009
- Subjects: Silicon carbide , Hydrogen , Helium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10539 , http://hdl.handle.net/10948/979 , Silicon carbide , Hydrogen , Helium
- Description: This dissertation focuses on the characterization of hydrogen implanted 3C-SiC and helium implanted 6H-SiC and the interaction of silver and palladium with the SiC. The main technique used for the analysis of the implanted SiC was transmission electron microscopy (TEM), although scanning electron microscopy (SEM) and nanoindentation hardness testing were also used. Both H and He implantations were done at an ion energy of 100 keV and the total dose for both species was 1017 ions/cm2. Specimens were annealed at 1000 °C for 20 min in an inert atmosphere. The observed depth of ion damage agreed closely with that predicted by TRIM 2008. The damaged region in the He implanted specimens had a high density of small bubbles but no cracks were observed. Severe cracking was observed along the damaged region in the H implanted specimens. A second phase hexagonal (4H-SiC) was detected in two grains in the 3C-SiC and some grown in voids were also observed. The wettability of SiC by a 2:1 by volume mixture of Ag and Pd is extremely low but is significantly increased through the addition of Si to the mixture. The Si containing metal mixture was found to migrate along the grain boundaries of polycrystalline 3CSiC while sealing the point of entry. Pd attacks SiC and severe etching was observed on the surface of 6H-SiC. An epitaxially orientated Pd2Si inclusion was observed in the 6H-SiC. No effect of implantation damage on the interaction of Pd and Ag with SiC was observed. Pd etched the surface of the He implanted 6H-SiC down through the damaged region with no evidence of implantation damage left after 67 hours of annealing and thus no conclusions could be drawn. The metal mixture interacted with the non implanted surface of the H implanted 3C-SiC after dissolving the Si substrate and therefore the effect of the ion damage on the interaction could not be investigated. Nanoindentation hardness measurements showed a marked increase in hardness of He implanted 6H-SiC annealed for 20 min at 1000 °C over that of as implanted and virgin material. There was also a large decrease in hardness corresponding to the depth of the ion damage.
- Full Text:
- Date Issued: 2009
Complexes of the ReO³⁺/Re(CO)₃cores with multidentate N,O-Donor chelates
- Authors: Potgieter, Kim Carey
- Date: 2009
- Subjects: Rhenium , Schiff bases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10387 , http://hdl.handle.net/10948/1225 , Rhenium , Schiff bases
- Description: This study investigates the coordination modes of multidentate N,O-donor ligands toward the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with 4-aminoantipyrine (H2pap) were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The X-ray crystal structures show that both complexes display a distorted octahedral geometry around the central rhenium atom, and are mirror images of each other. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The attempted synthesis of the potentially hexadentate Schiff base ligand 1,2-bis(2-{(Z)- [(2-hydroxyphenyl)imido]methyl}phenoxy)benzene from the condensation reaction of 2- (2-((2-aminophenoxy)methyl)benzyloxy)benzenamine and salicylaldehyde produced the zwitterion derivative (H2ono) of 2-{(Z)-[2-(hydroxyphenyl)imino]methyl}phenol. The tridentate Schiff bases (Z)-2-(2-aminobenzylideneamino)phenol (H3onn) and (Z)-2-(2- (methylthio)benzylideneamino)phenol (Hons) were prepared in a similar manner. The reaction of H2ono with trans-[ReOBr3(PPh3)2] surprisingly led to the isolation of the rhenium(III) complex [ReBr(PPh3)2(ono)], in which ono acts as a dianionic tridentate ligand. The reaction of H3onn with trans-[ReOBr3(PPh3)2] produced the imidorhenium(V) complex salt [ReBr(PPh3)2(onn)]Br, in which onn is coordinated as a trianionic tridentate imidoiminophenolate. The reaction of Hons with [Re(CO)5Br] led to the further decomposition of the Hons ligand, and the rhenium(I) product fac- [Re(CO)3(ons)(Hno)] (Hno = 2-aminophenol) was isolated, with ons coordinated as a monoanionic bidentate chelate (with a free SCH3 group), and Hno present as a neutral monodentate ligand with coordination through the amino nitrogen atom. Abstract Nelson Mandela Metropolitan University vi The reactions of the potentially hexadentate ligand N,N’-{ethane-1,2- diylbis[nitrilomethylidenebenzene-1,2-diyl]}bis(2-aminobenzeneimine) (H2ted) with rhenium(V) starting materials resulted in the decomposition of the H2ted molecule to give different coordinated multidentate ligands coordinated to the rhenium(V) centers. In the reaction of H2ted with trans-[ReOBr3(PPh3)2] in ethanol, the highly unusual ‘3+3’ complex cation [Re(tnn)(Htnn)]Br2 was isolated, in which tnn is coordinated as a tridentate imido-imino-amine, and Htnn is present as a tridentate monoanionic amidoimino- amine chelate (H2tnn = N-(2-aminophenylmethylidene)ethane-1,2-diamine). With trans-[ReO2(py)4]Cl as starting material, the neutral complex [ReO(dne)] was found, in which the tetradentate chelate dne acts as a triamido-imine. The reaction of cis- [ReO2I(PPh3)2] with H2ted led to the formation of the monocationic complex salt [ReO(ane)]PF6, with ane acting as a tetradentate dianionic diamidodiimine (H2ane = N,N’-bis[(2-aminophenyl)methylidene] ethane-1,2-diamine). The seven-coordinate rhenium(III) complex cation [Re(dhp)(PPh3)2]+ (H2dhp = 2,6-bis(2- hydroxyphenyliminomethyl)pyridine) was isolated as the iodide salt from the reaction of cis-[ReO2I(PPh3)2] with H2dhp in ethanol and as the perrhenate salt from the reaction of trans-[ReOBr3(PPh3)2] with H2dhp in methanol. Both products result from a disproportionation reaction with perrhenate also being produced in the process. The complex fac-[Re(CO)3(H2dhp)Br] was prepared from [Re(CO)5Br] and H2dhp in toluene, where the H2dhp ligand acts as a neutral bidentate NN-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, to a neutral imino nitrogen, a pyridinic nitrogen and a bromide.
- Full Text:
- Date Issued: 2009
- Authors: Potgieter, Kim Carey
- Date: 2009
- Subjects: Rhenium , Schiff bases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10387 , http://hdl.handle.net/10948/1225 , Rhenium , Schiff bases
- Description: This study investigates the coordination modes of multidentate N,O-donor ligands toward the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with 4-aminoantipyrine (H2pap) were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The X-ray crystal structures show that both complexes display a distorted octahedral geometry around the central rhenium atom, and are mirror images of each other. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The attempted synthesis of the potentially hexadentate Schiff base ligand 1,2-bis(2-{(Z)- [(2-hydroxyphenyl)imido]methyl}phenoxy)benzene from the condensation reaction of 2- (2-((2-aminophenoxy)methyl)benzyloxy)benzenamine and salicylaldehyde produced the zwitterion derivative (H2ono) of 2-{(Z)-[2-(hydroxyphenyl)imino]methyl}phenol. The tridentate Schiff bases (Z)-2-(2-aminobenzylideneamino)phenol (H3onn) and (Z)-2-(2- (methylthio)benzylideneamino)phenol (Hons) were prepared in a similar manner. The reaction of H2ono with trans-[ReOBr3(PPh3)2] surprisingly led to the isolation of the rhenium(III) complex [ReBr(PPh3)2(ono)], in which ono acts as a dianionic tridentate ligand. The reaction of H3onn with trans-[ReOBr3(PPh3)2] produced the imidorhenium(V) complex salt [ReBr(PPh3)2(onn)]Br, in which onn is coordinated as a trianionic tridentate imidoiminophenolate. The reaction of Hons with [Re(CO)5Br] led to the further decomposition of the Hons ligand, and the rhenium(I) product fac- [Re(CO)3(ons)(Hno)] (Hno = 2-aminophenol) was isolated, with ons coordinated as a monoanionic bidentate chelate (with a free SCH3 group), and Hno present as a neutral monodentate ligand with coordination through the amino nitrogen atom. Abstract Nelson Mandela Metropolitan University vi The reactions of the potentially hexadentate ligand N,N’-{ethane-1,2- diylbis[nitrilomethylidenebenzene-1,2-diyl]}bis(2-aminobenzeneimine) (H2ted) with rhenium(V) starting materials resulted in the decomposition of the H2ted molecule to give different coordinated multidentate ligands coordinated to the rhenium(V) centers. In the reaction of H2ted with trans-[ReOBr3(PPh3)2] in ethanol, the highly unusual ‘3+3’ complex cation [Re(tnn)(Htnn)]Br2 was isolated, in which tnn is coordinated as a tridentate imido-imino-amine, and Htnn is present as a tridentate monoanionic amidoimino- amine chelate (H2tnn = N-(2-aminophenylmethylidene)ethane-1,2-diamine). With trans-[ReO2(py)4]Cl as starting material, the neutral complex [ReO(dne)] was found, in which the tetradentate chelate dne acts as a triamido-imine. The reaction of cis- [ReO2I(PPh3)2] with H2ted led to the formation of the monocationic complex salt [ReO(ane)]PF6, with ane acting as a tetradentate dianionic diamidodiimine (H2ane = N,N’-bis[(2-aminophenyl)methylidene] ethane-1,2-diamine). The seven-coordinate rhenium(III) complex cation [Re(dhp)(PPh3)2]+ (H2dhp = 2,6-bis(2- hydroxyphenyliminomethyl)pyridine) was isolated as the iodide salt from the reaction of cis-[ReO2I(PPh3)2] with H2dhp in ethanol and as the perrhenate salt from the reaction of trans-[ReOBr3(PPh3)2] with H2dhp in methanol. Both products result from a disproportionation reaction with perrhenate also being produced in the process. The complex fac-[Re(CO)3(H2dhp)Br] was prepared from [Re(CO)5Br] and H2dhp in toluene, where the H2dhp ligand acts as a neutral bidentate NN-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, to a neutral imino nitrogen, a pyridinic nitrogen and a bromide.
- Full Text:
- Date Issued: 2009
Detecting changes in elephant body condition in relation to resource quality
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
- Authors: De Klerk, Christelle
- Date: 2009
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10704 , http://hdl.handle.net/10948/939 , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: Elephants, as megaherbivores, are known to have extensive impacts on vegetation, especially in enclosed areas. This raises the issue that elephants in enclosed areas may become limited by resource availability. Resource limitation is generally expressed via density dependence, but elephants, due to their slow demography, may not be affected by initial changes in resource availability. This highlights the need for a more sensitive measure of resource limitation to allow for the detection of energy stress within a population before changes in vital rates occur. This study investigated visual changes in elephant body condition in relation to resource availability in a number of Eastern Cape reserves to assess whether body condition could be used to detect life stages, as well as seasons and sites which may be resource limited. Elephant life stages were divided into energy stressed (newly weaned calves, lactating females, and old females) and non-energy stressed classes (sub-adults and non-lactating females) to determine whether energy stressed life stages were more vulnerable to resource limitation. In the AENP it was found that lactating and old females exhibited significantly poorer body condition than non-energy stressed individuals, but that weaned calves had body conditions similar to non-energy stressed individuals. Comparisons between seasons revealed that all life stages exhibited better condition in winter than summer or spring, with lactating females showing little recovery of condition over time. Seasonal body conditions were correlated with rainfall recorded in the Addo Elephant National Park. Comparisons of elephant body condition between sites (n = 6) revealed that body condition varied across sites, with poorer body condition associated with areas of higher elephant density and low rainfall during the study period. Comparisons with faecal dietary quality data both between sites and seasons indicated that body condition also responded to changes in the availability of protein and neutral detergent fibre (NDF) of plant resources, with higher protein and lower values associated with better condition. Based on condition estimates of elephants occurring in the Addo Main Camp, it was established that this population is experiencing nutritional stress, with energy stressed individuals exhibiting the lowest body conditions. This was supported by dietary quality measures. Our findings suggest that elephant body condition is a good measure for detecting resource limitation, both within populations and between seasons, and that elephant body condition respond to relatively small changes in resource conditions, thus making it an effective measure for the detection of nutritional stress. Additionally, our findings show that energy stressed individuals, particularly lactating and old females are more vulnerable to resource limitation. This demonstrates the importance of monitoring these life stages for the detection of density dependence within populations. Finally, our data suggest that threshold values of faecal dietary quality may exist at which body condition within a population begins to deteriorate, making it possible to determine the condition of a population through values obtained in faecal samples.
- Full Text:
- Date Issued: 2009
Detection of contaminants in wool bales using nuclear techniques
- Authors: Rapakgadi, Jim
- Date: 2009
- Subjects: Wool scouring , Mohair , X-rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10448 , http://hdl.handle.net/10948/993 , Wool scouring , Mohair , X-rays
- Description: To improve the quality and the marketability of wool and mohair, it is important to encourage, ensure and preferable certify that the baled fibre is free of contaminants. Anything other than the fibre that is within the bale can be classified as contaminants; this may be in the form of metal and wooden objects, plastic materials, paints, and vegetable matter such as grass and seed. The internationally accepted method for detecting and classifying these contaminants are highly labour intensive and costly. The ultimate goal of the present research is to develop a non-invasive and nondestructive technique that can be used to detect contaminants, particularly plastic (polymer) materials within wool and mohair bales. Such a technique can be implemented in the wool industry and also could be applied to other fibres, such as cotton. The immediate objective of this study was to evaluate the capability and the limitation of X-rays as a technique to detect such contaminants. It was found that X-rays were suitable for detecting foreign objects, or contaminants, such as metals, but not for detecting plastic materials, such as polypropylene and polyethylene.
- Full Text:
- Date Issued: 2009
- Authors: Rapakgadi, Jim
- Date: 2009
- Subjects: Wool scouring , Mohair , X-rays
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10448 , http://hdl.handle.net/10948/993 , Wool scouring , Mohair , X-rays
- Description: To improve the quality and the marketability of wool and mohair, it is important to encourage, ensure and preferable certify that the baled fibre is free of contaminants. Anything other than the fibre that is within the bale can be classified as contaminants; this may be in the form of metal and wooden objects, plastic materials, paints, and vegetable matter such as grass and seed. The internationally accepted method for detecting and classifying these contaminants are highly labour intensive and costly. The ultimate goal of the present research is to develop a non-invasive and nondestructive technique that can be used to detect contaminants, particularly plastic (polymer) materials within wool and mohair bales. Such a technique can be implemented in the wool industry and also could be applied to other fibres, such as cotton. The immediate objective of this study was to evaluate the capability and the limitation of X-rays as a technique to detect such contaminants. It was found that X-rays were suitable for detecting foreign objects, or contaminants, such as metals, but not for detecting plastic materials, such as polypropylene and polyethylene.
- Full Text:
- Date Issued: 2009
Development of biological control strategies against sirex noctilio (Fabricius) on Sappi Forests (Ltd) Landholdings in the summer rainfall regions of South Africa
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
Ecosystem health of the Nelson Mandela Bay sandy beaches
- Authors: Yani, Vuyolwethu Veronica
- Date: 2009
- Subjects: Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10600 , http://hdl.handle.net/10948/1075 , Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Description: An investigation of ecosystem functioning of sandy beaches in the Nelson Mandela Bay Municipality (NMBM) was carried out with the aim of describing their type and pollution status. Water salinity, temperature, pH, beach slope, water inorganic nutrient concentrations, urea, and chlorophyll-a concentration as well as the composition of zooplankton, phytoplankton, meiofauna, benthic microalgae and bacteria were examined at thirteen beaches. The beaches were classified into three types: short beaches; long beaches with surf diatoms; and long beaches that import biomass (without surf diatoms). Of the thirteen beaches, five were non-polluted and eight polluted with polluting human activities in and around them. Most beaches were dominated by fine sand except for St. Georges Strand where the particles were medium to fine sand and Maitland’s River Beach, Bluewater Bay and Sardinia Bay that had coarse sand. Nutrient concentrations ranged from 1.98 ± 0.10 μM to 19.30 ± 3.02 μM nitrate; 4.88 ± 1.00 μM to 11.97 ± 1.00 μM ammonium; 0.67 ± 0.00 μM to 2.31 ±1.00 μM soluble reactive phosphorus; and 0.00 to 0.03 ± 0.00 μg l-1 urea-N. Chlorophyll-a concentrations ranged from 0.04 ± 0.02 to 1.57 ± 0.11 μg l-1. Chlorophyll-a concentrations were negatively correlated to ammonium for all beach types (short beaches: r = 0.94; long importing beaches: r = 0.95 and surf diatom beaches: 0.94) and to nitrate for short and long importing beaches (short: r = 0.97 and long importing: r = 0.85). By contrast, a positive correlation was found between observed between chlorophyll-a concentrations and urea for surf diatom beaches (r = 0.93) and for long importing beaches (r = 0.73). Chlorophyll-a concentrations were negatively correlated to short beaches (r = 0.99) and long importing beaches (r = 0.76). The E. coli and total coliforms in all the sampled beaches were within the recommended South African water quality guidelines for contact recreation as specified by DWAF (1995) except at New Brighton Beach (2 419 total coliforms/100 ml and 1 853 E. coli cells/100 ml) and St. Georges Strand (274 total coliforms/100 ml). Diatoms dominated the phytoplankton and benthic microflora; calanoid copepods dominated the zooplankton and deposit-feeding nematodes dominated the meiofauna in all the beaches with no changes found at polluted beaches.
- Full Text: false
- Date Issued: 2009
- Authors: Yani, Vuyolwethu Veronica
- Date: 2009
- Subjects: Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10600 , http://hdl.handle.net/10948/1075 , Seashore ecology -- South Africa -- Eastern Cape , Sand dune ecology -- South Africa -- Eastern Cape , Coastal ecology -- South Africa -- Eastern Cape , Beaches -- South Africa -- Eastern Cape
- Description: An investigation of ecosystem functioning of sandy beaches in the Nelson Mandela Bay Municipality (NMBM) was carried out with the aim of describing their type and pollution status. Water salinity, temperature, pH, beach slope, water inorganic nutrient concentrations, urea, and chlorophyll-a concentration as well as the composition of zooplankton, phytoplankton, meiofauna, benthic microalgae and bacteria were examined at thirteen beaches. The beaches were classified into three types: short beaches; long beaches with surf diatoms; and long beaches that import biomass (without surf diatoms). Of the thirteen beaches, five were non-polluted and eight polluted with polluting human activities in and around them. Most beaches were dominated by fine sand except for St. Georges Strand where the particles were medium to fine sand and Maitland’s River Beach, Bluewater Bay and Sardinia Bay that had coarse sand. Nutrient concentrations ranged from 1.98 ± 0.10 μM to 19.30 ± 3.02 μM nitrate; 4.88 ± 1.00 μM to 11.97 ± 1.00 μM ammonium; 0.67 ± 0.00 μM to 2.31 ±1.00 μM soluble reactive phosphorus; and 0.00 to 0.03 ± 0.00 μg l-1 urea-N. Chlorophyll-a concentrations ranged from 0.04 ± 0.02 to 1.57 ± 0.11 μg l-1. Chlorophyll-a concentrations were negatively correlated to ammonium for all beach types (short beaches: r = 0.94; long importing beaches: r = 0.95 and surf diatom beaches: 0.94) and to nitrate for short and long importing beaches (short: r = 0.97 and long importing: r = 0.85). By contrast, a positive correlation was found between observed between chlorophyll-a concentrations and urea for surf diatom beaches (r = 0.93) and for long importing beaches (r = 0.73). Chlorophyll-a concentrations were negatively correlated to short beaches (r = 0.99) and long importing beaches (r = 0.76). The E. coli and total coliforms in all the sampled beaches were within the recommended South African water quality guidelines for contact recreation as specified by DWAF (1995) except at New Brighton Beach (2 419 total coliforms/100 ml and 1 853 E. coli cells/100 ml) and St. Georges Strand (274 total coliforms/100 ml). Diatoms dominated the phytoplankton and benthic microflora; calanoid copepods dominated the zooplankton and deposit-feeding nematodes dominated the meiofauna in all the beaches with no changes found at polluted beaches.
- Full Text: false
- Date Issued: 2009
Efficacy of selected Kenyan medicinal plants used in the treatment and management of Type II Diabetes
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
- Authors: Karachi, Jacqueline
- Date: 2009
- Subjects: Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10327 , http://hdl.handle.net/10948/1049 , Diabetes -- Alternative treatment -- Kenya , Medicinal plants -- Kenya
- Description: In Kenya, the prevalence of diabetes is estimated at 3-10 percent of the population. These figures could be higher because most type 2 diabetics are diagnosed many years after onset. Out of this number, 15 percent are people below 30 years of age who need prompt education to avoid complications that are associated with diabetes (DMI centre, 2004). Due to inadequate or lack of proper information, most patients especially those with type 2 diabetes are diagnosed through complications. Untreated or poorly managed diabetes is now the leading cause of eye disease and kidney failure in the world. Diabetes is the largest cause of kidney failure in the developed world, and is the fourth leading cause of global death by disease in the world (IDF, 2007). At the Kenyatta National Hospital in Nairobi, Kenya, it is the leading cause of all non-accident related amputations. It is with such statistics in mind and the grim reality of poor and inadequate health services that this research is based. The wide use of selected medicinal plants for the treatment and management of diabetes warrants the further study of these plants for potential use and commercialization. The data obtained can also be invaluable for use and reference when using these plants for medicinal purposes. The medicinal plant studied in the research is widely used in Kenya by many communities and was chosen based on ethno-pharmacological references using traditional medicinal practitioners as well as patient’s recommendations. Different in vitro and in vivo assays were studied to try and elucidate the mechanisms of action as well as the organs targeted during treatment using this plant.
- Full Text:
- Date Issued: 2009
Habitat and foraging models as aids in the identification of priority areas for mitigating actions to reduce the incidence of electrocutions of the threatened Cape Griffon Gyps coprotheres in the Eastern Cape
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009
In vitro effects of endogenous and exogenous cannabinoids on insulin resistance and secretion
- Authors: Gallant, Megan
- Date: 2009
- Subjects: Cannabinoids , Cannabis , Insulin resistance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10324 , http://hdl.handle.net/10948/1076 , Cannabinoids , Cannabis , Insulin resistance
- Description: Type 2 diabetes mellitus results from a combination of insulin resistance and impaired insulin secretion. The aim of this study is to investigate the effect of endogenous and exogenous cannabinoids on insulin resistant cell lines, viz skeletal muscle (C2C12) and fat (3T3-L1), and to investigate the effects of these cannabinoids on insulin secretion in pancreatic β-cells (INS 1). Insulin resistance was induced in the cells using 20 ng/mL TNF-α (3T3-L1) and 100 nM insulin (C2C12). Insulin resistant cells were exposed to cannabinoids for 48 hours after which glucose uptake, RT-PCR and Western blot analysis was performed. Additionally, adipokine assays were performed on the 3T3-L1 cells. The insulin resistant 3T3-L1 and C2C12 cells had reduced glucose uptake, decreased IRS-1 and Glut-4 expression indicative of an insulin resistant state. The extract and THC significantly enhanced glucose uptake, IRS-1 and Glut-4 in 3T3-L1 and C2C12 cells. The extract and THC thus have the potential to be an insulin sensitizing agent. Interleukin-6 was significantly decreased by THC. INS 1 cells, cultured under normoglycemic conditions, were exposed to cannabinoids for 48 hours after which glucose-stimulated insulin secretion, radioimmunoassay, oxygen consumption, RT-PCR and Western blot analysis was performed. Insulin stimulatory index was not significantly affected after cannabinoid exposure, except by THC. The cannabinoids decreased insulin content, in a concentration dependent manner, but the inhibition mechanism remains elusive. The cannabinoid Treated cells showed insulin gene expression levels similar to the control, while only THC proved effective in significantly stimulating Glut-2 gene expression. Oxygen consumption studies showed levels lower than the control cells. Most of the cannabinoids inhibited insulin secretion under normoglycemia except THC, while the cannabinoids exhibited the potential to improve insulin resistant adipocyte and myocytes response to glucose and gene regulation.
- Full Text:
- Date Issued: 2009
- Authors: Gallant, Megan
- Date: 2009
- Subjects: Cannabinoids , Cannabis , Insulin resistance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10324 , http://hdl.handle.net/10948/1076 , Cannabinoids , Cannabis , Insulin resistance
- Description: Type 2 diabetes mellitus results from a combination of insulin resistance and impaired insulin secretion. The aim of this study is to investigate the effect of endogenous and exogenous cannabinoids on insulin resistant cell lines, viz skeletal muscle (C2C12) and fat (3T3-L1), and to investigate the effects of these cannabinoids on insulin secretion in pancreatic β-cells (INS 1). Insulin resistance was induced in the cells using 20 ng/mL TNF-α (3T3-L1) and 100 nM insulin (C2C12). Insulin resistant cells were exposed to cannabinoids for 48 hours after which glucose uptake, RT-PCR and Western blot analysis was performed. Additionally, adipokine assays were performed on the 3T3-L1 cells. The insulin resistant 3T3-L1 and C2C12 cells had reduced glucose uptake, decreased IRS-1 and Glut-4 expression indicative of an insulin resistant state. The extract and THC significantly enhanced glucose uptake, IRS-1 and Glut-4 in 3T3-L1 and C2C12 cells. The extract and THC thus have the potential to be an insulin sensitizing agent. Interleukin-6 was significantly decreased by THC. INS 1 cells, cultured under normoglycemic conditions, were exposed to cannabinoids for 48 hours after which glucose-stimulated insulin secretion, radioimmunoassay, oxygen consumption, RT-PCR and Western blot analysis was performed. Insulin stimulatory index was not significantly affected after cannabinoid exposure, except by THC. The cannabinoids decreased insulin content, in a concentration dependent manner, but the inhibition mechanism remains elusive. The cannabinoid Treated cells showed insulin gene expression levels similar to the control, while only THC proved effective in significantly stimulating Glut-2 gene expression. Oxygen consumption studies showed levels lower than the control cells. Most of the cannabinoids inhibited insulin secretion under normoglycemia except THC, while the cannabinoids exhibited the potential to improve insulin resistant adipocyte and myocytes response to glucose and gene regulation.
- Full Text:
- Date Issued: 2009
Investigation of the microstructure of nuclear grade matrix graphite
- Authors: Downey, Justin Michael
- Date: 2009
- Subjects: Graphite -- South Africa , Microstructure , Nanostructured materials -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10540 , http://hdl.handle.net/10948/944 , Graphite -- South Africa , Microstructure , Nanostructured materials -- South Africa
- Description: This dissertation focuses on the investigation of the microstructures of two nuclear grade matrix graphites. These graphites were intended for use in the core components of a high temperature test reactor (HTTR) of the pebble bed modular reactor (PBMR) design. The graphites were provided in the form of fuel spheres and a reflector block. The techniques used in the analysis of the materials include fracturing, etching, scanning electron microscopy (SEM), nano-indentation, x-ray diffraction (XRD) and transmission electron microscopy (TEM). The microstructures of the materials were characterized successfully. The fuel sphere material consisted of a high concentration of curved graphite flakes and grains in contact with turbostratic matrix graphite. The well graphitized flakes and grains were polycrystalline in nature. Delamination cracks were prevalent in the graphite crystallites. There was no significant difference in the microstructures of the center, interior and surface regions of the fuel sphere material. No evidence of amorphous carbon or resin residues was found. The reflector material consisted of a low concentration of graphite crystallites embedded within turbostratic matrix graphite. Delamination cracks were observed within the graphite crystallites, and many cavities were present in the material. TEM observation also revealed the presence of diamond crystallites. It was concluded that the fuel sphere graphite was most probably suitable for use as is, provided that the material also possessed other required properties for use in a HTTR. The reflector material however was considered to be unsuitable for use in a HTTR. It was thus suggested that the reflector material could be made more suitable by sufficient graphitization of the turbostratic graphite which formed the bulk of the material.
- Full Text:
- Date Issued: 2009
- Authors: Downey, Justin Michael
- Date: 2009
- Subjects: Graphite -- South Africa , Microstructure , Nanostructured materials -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10540 , http://hdl.handle.net/10948/944 , Graphite -- South Africa , Microstructure , Nanostructured materials -- South Africa
- Description: This dissertation focuses on the investigation of the microstructures of two nuclear grade matrix graphites. These graphites were intended for use in the core components of a high temperature test reactor (HTTR) of the pebble bed modular reactor (PBMR) design. The graphites were provided in the form of fuel spheres and a reflector block. The techniques used in the analysis of the materials include fracturing, etching, scanning electron microscopy (SEM), nano-indentation, x-ray diffraction (XRD) and transmission electron microscopy (TEM). The microstructures of the materials were characterized successfully. The fuel sphere material consisted of a high concentration of curved graphite flakes and grains in contact with turbostratic matrix graphite. The well graphitized flakes and grains were polycrystalline in nature. Delamination cracks were prevalent in the graphite crystallites. There was no significant difference in the microstructures of the center, interior and surface regions of the fuel sphere material. No evidence of amorphous carbon or resin residues was found. The reflector material consisted of a low concentration of graphite crystallites embedded within turbostratic matrix graphite. Delamination cracks were observed within the graphite crystallites, and many cavities were present in the material. TEM observation also revealed the presence of diamond crystallites. It was concluded that the fuel sphere graphite was most probably suitable for use as is, provided that the material also possessed other required properties for use in a HTTR. The reflector material however was considered to be unsuitable for use in a HTTR. It was thus suggested that the reflector material could be made more suitable by sufficient graphitization of the turbostratic graphite which formed the bulk of the material.
- Full Text:
- Date Issued: 2009
Modelling of size-based portfolios using a mixture of normal distributions
- Authors: Janse Van Rensburg, Stéfan
- Date: 2009
- Subjects: Capital assets pricing model
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10569 , http://hdl.handle.net/10948/985 , Capital assets pricing model
- Description: From option pricing using the Black and Scholes model, to determining the signi cance of regression coe cients in a capital asset pricing model (CAPM), the assumption of normality was pervasive throughout the eld of nance. This was despite evidence that nancial returns were non-normal, skewed and heavy- tailed. In addition to non-normality, there remained questions about the e ect of rm size on returns. Studies examining these di erences were limited to ex- amining the mean return, with respect to an asset pricing model, and did not consider higher moments. Janse van Rensburg, Sharp and Friskin (in press) attempted to address both the problem of non-normality and size simultaneously. They (Janse van Rens- burg et al in press) tted a mixture of two normal distributions, with common mean but di erent variances, to a small capitalisation portfolio and a large cap- italisation portfolio. Comparison of the mixture distributions yielded valuable insight into the di erences between the small and large capitalisation portfolios' risk. Janse van Rensburg et al (in press), however, identi ed several shortcom- ings within their work. These included data problems, such as survivorship bias and the exclusion of dividends, and the questionable use of standard statistical tests in the presence of non-normality. This study sought to correct the problems noted in the paper by Janse van Rensburg et al (in press) and to expand upon their research. To this end survivorship bias was eliminated and an e ective dividend was included into the return calculations. Weekly data were used, rather than the monthly data of Janse van Rensburg et al (in press). More portfolios, over shorter holding periods, were considered. This allowed the authors to test whether Janse van Rensburg et al's (in press) ndings remained valid under conditions di erent to their original study. Inference was also based on bootstrapped statistics, in order to circumvent problems associated with non-normality. Additionally, several di erent speci cations of the normal mixture distribution were considered, as opposed to only the two-component scale mixture. In the following, Chapter 2 provided a literature review of previous studies on return distributions and size e ects. The data, data preparation and portfolio formation were discussed in Chapter 3. Chapter 4 gave an overview of the statistical methods and tests used throughout the study. The empirical results of these tests, prior to risk adjustment, were presented in Chapter 5. The impact of risk adjustment on the distribution of returns was documented in Chapter 6. The study ended, Chapter 7, with a summary of the results and suggestions for future research.
- Full Text:
- Date Issued: 2009
- Authors: Janse Van Rensburg, Stéfan
- Date: 2009
- Subjects: Capital assets pricing model
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10569 , http://hdl.handle.net/10948/985 , Capital assets pricing model
- Description: From option pricing using the Black and Scholes model, to determining the signi cance of regression coe cients in a capital asset pricing model (CAPM), the assumption of normality was pervasive throughout the eld of nance. This was despite evidence that nancial returns were non-normal, skewed and heavy- tailed. In addition to non-normality, there remained questions about the e ect of rm size on returns. Studies examining these di erences were limited to ex- amining the mean return, with respect to an asset pricing model, and did not consider higher moments. Janse van Rensburg, Sharp and Friskin (in press) attempted to address both the problem of non-normality and size simultaneously. They (Janse van Rens- burg et al in press) tted a mixture of two normal distributions, with common mean but di erent variances, to a small capitalisation portfolio and a large cap- italisation portfolio. Comparison of the mixture distributions yielded valuable insight into the di erences between the small and large capitalisation portfolios' risk. Janse van Rensburg et al (in press), however, identi ed several shortcom- ings within their work. These included data problems, such as survivorship bias and the exclusion of dividends, and the questionable use of standard statistical tests in the presence of non-normality. This study sought to correct the problems noted in the paper by Janse van Rensburg et al (in press) and to expand upon their research. To this end survivorship bias was eliminated and an e ective dividend was included into the return calculations. Weekly data were used, rather than the monthly data of Janse van Rensburg et al (in press). More portfolios, over shorter holding periods, were considered. This allowed the authors to test whether Janse van Rensburg et al's (in press) ndings remained valid under conditions di erent to their original study. Inference was also based on bootstrapped statistics, in order to circumvent problems associated with non-normality. Additionally, several di erent speci cations of the normal mixture distribution were considered, as opposed to only the two-component scale mixture. In the following, Chapter 2 provided a literature review of previous studies on return distributions and size e ects. The data, data preparation and portfolio formation were discussed in Chapter 3. Chapter 4 gave an overview of the statistical methods and tests used throughout the study. The empirical results of these tests, prior to risk adjustment, were presented in Chapter 5. The impact of risk adjustment on the distribution of returns was documented in Chapter 6. The study ended, Chapter 7, with a summary of the results and suggestions for future research.
- Full Text:
- Date Issued: 2009
Production of biologically active recombinant HIV-1 protease and intehrase for the purpose of screening medicianl plant extracts
- Authors: Bosch, Janine
- Date: 2009
- Subjects: Medicinal plants -- South Africa , HIV infections -- Alternative treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10325 , http://hdl.handle.net/10948/1056 , Medicinal plants -- South Africa , HIV infections -- Alternative treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: Human immunodeficiency virus (HIV) and its gradual weakening of the immune system is an ever growing threat. Acquired immune deficiency syndrome (AIDS), the final stage of HIV, renders a person vulnerable to various opportunistic infections, which in the end lead to death. Apart from intensive vaccine studies, treatment research mainly focuses on preventing the individual HIV enzymes (reverse transcriptase, integrase and protease) from performing their functions. Entry inhibitors, however, block viral entry into the cell, while antisense drugs lock onto the viral genome to keep it from functioning. In this study production of active recombinant HIV-1 protease and integrase was attempted for future drug screening programs. HIV-1 protease was cloned into a pET28b(+) vector and expressed in ROSETTA(DE3)pLysS cells. The protein was purified using a nickel-affinity column utilizing the hexa-histidine tag encoded by the vector. Gel filtration chromatography was attempted after refolding of the protease, but protease yield seemed to decrease with the additional purification step. Partially purified protease was characterized with kinetic studies. Kinetic parameters of HIV-1 protease were determined to be Km = 592 μM, Vmax = 0.59 μM/min and kcat = 31 s-1. HIV-1 integrase, which was cloned into a pET15b vector, was expressed in E. coli BL21(DE3) cells. The coding sequence had been mutated to introduce the amino acid substitutions F185K and C280S, increasing solubility of the protein. The first step in purification of this protein was nickel-affinity chromatography, after which cation exchange chromatography was attempted. HIV-1 integrase concentration was low throughout experiments and no clear elution from the cation exchange column could be observed. A non-radioactive enzyme linked HIV-1 integrase assay failed to detect integrase activity. Modifications to future studies of the integrase are suggested in the chapter involved.
- Full Text:
- Date Issued: 2009
- Authors: Bosch, Janine
- Date: 2009
- Subjects: Medicinal plants -- South Africa , HIV infections -- Alternative treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10325 , http://hdl.handle.net/10948/1056 , Medicinal plants -- South Africa , HIV infections -- Alternative treatment -- South Africa , Materia medica, Vegetable -- South Africa
- Description: Human immunodeficiency virus (HIV) and its gradual weakening of the immune system is an ever growing threat. Acquired immune deficiency syndrome (AIDS), the final stage of HIV, renders a person vulnerable to various opportunistic infections, which in the end lead to death. Apart from intensive vaccine studies, treatment research mainly focuses on preventing the individual HIV enzymes (reverse transcriptase, integrase and protease) from performing their functions. Entry inhibitors, however, block viral entry into the cell, while antisense drugs lock onto the viral genome to keep it from functioning. In this study production of active recombinant HIV-1 protease and integrase was attempted for future drug screening programs. HIV-1 protease was cloned into a pET28b(+) vector and expressed in ROSETTA(DE3)pLysS cells. The protein was purified using a nickel-affinity column utilizing the hexa-histidine tag encoded by the vector. Gel filtration chromatography was attempted after refolding of the protease, but protease yield seemed to decrease with the additional purification step. Partially purified protease was characterized with kinetic studies. Kinetic parameters of HIV-1 protease were determined to be Km = 592 μM, Vmax = 0.59 μM/min and kcat = 31 s-1. HIV-1 integrase, which was cloned into a pET15b vector, was expressed in E. coli BL21(DE3) cells. The coding sequence had been mutated to introduce the amino acid substitutions F185K and C280S, increasing solubility of the protein. The first step in purification of this protein was nickel-affinity chromatography, after which cation exchange chromatography was attempted. HIV-1 integrase concentration was low throughout experiments and no clear elution from the cation exchange column could be observed. A non-radioactive enzyme linked HIV-1 integrase assay failed to detect integrase activity. Modifications to future studies of the integrase are suggested in the chapter involved.
- Full Text:
- Date Issued: 2009
Purification and characterization of serine proteinase inhibitors from two South African indigenous plants, Acacia karoo and Acacia schweinfurthii
- Authors: Odei-Addo, Frank
- Date: 2009
- Subjects: Proteinase -- Inhibitors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10319 , http://hdl.handle.net/10948/1291 , Proteinase -- Inhibitors
- Description: Serine proteases are known to perform a wide range of functions essential to life; however there has to be some form of control mechanism in place. One of the many control mechanisms is their specific inhibition by protein proteinase inhibitors. Proteinase inhibitors in plants, present in their seeds, participate in defense mechanisms and their production is induced by herbivory or wounding. Plant proteinase inhibitors have been reported to inhibit a variety of serine proteinases, including enzymes of the blood coagulation cascade. In this study, various indigenous seed extracts were screened for potential serine proteinase inhibition. Acacia schweinfurthii was selected as a potential inhibitor that inhibited trypsin and factor X. The AS inhibitor was successfully purified to homogeneity by precipitating with 80 percent (v/v) acetone and the sequential chromatographic steps including ion-exchange chromatography, size exclusion chromatography, affinity purification on a trypsin-agarose column and RP-HPLC. Reducing SDS-PAGE conditions revealed an inhibitor of two polypeptide chains A and B of approximate molecular weights 16 and 10 kDa, respectively, and under non-reducing conditions, 25 kDa was observed. The inhibitor was shown to inhibit trypsin, chymotrypsin and factor X indicating the dynamic nature of the reactive site. An enzyme: inhibitor ratio of 1:1, and a Ki of 3.45nM was determined for the AS inhibitor on trypsin, and the inhibitor also weakly inhibit chymotrypsin. AS inhibitor and STI inhibited factor X with a Ki values of 13.7nM and 77.5μM respectively. Amino acid analysis revealed Mmin values of the A- and B- chain of 15,000 and 7,800, respectively. The effect of seed extracts on the activated partial thrombin time (APTT) and prothrombin time (PT) was tested. No prolongation of the PT was obtained. For the crude extracts of AK and AS, IC200 values of 4.6 and 189.62 μg/mL, were respectively obtained. For the purified fractions of STI, AS and AK, IC200 values of 51.5, 114.31 and 893.8 μg/ml were observed, respectively. Keywords: proteinase inhibitors, Acacia species, trypsin inhibitor, FX inhibitor.
- Full Text:
- Date Issued: 2009
- Authors: Odei-Addo, Frank
- Date: 2009
- Subjects: Proteinase -- Inhibitors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10319 , http://hdl.handle.net/10948/1291 , Proteinase -- Inhibitors
- Description: Serine proteases are known to perform a wide range of functions essential to life; however there has to be some form of control mechanism in place. One of the many control mechanisms is their specific inhibition by protein proteinase inhibitors. Proteinase inhibitors in plants, present in their seeds, participate in defense mechanisms and their production is induced by herbivory or wounding. Plant proteinase inhibitors have been reported to inhibit a variety of serine proteinases, including enzymes of the blood coagulation cascade. In this study, various indigenous seed extracts were screened for potential serine proteinase inhibition. Acacia schweinfurthii was selected as a potential inhibitor that inhibited trypsin and factor X. The AS inhibitor was successfully purified to homogeneity by precipitating with 80 percent (v/v) acetone and the sequential chromatographic steps including ion-exchange chromatography, size exclusion chromatography, affinity purification on a trypsin-agarose column and RP-HPLC. Reducing SDS-PAGE conditions revealed an inhibitor of two polypeptide chains A and B of approximate molecular weights 16 and 10 kDa, respectively, and under non-reducing conditions, 25 kDa was observed. The inhibitor was shown to inhibit trypsin, chymotrypsin and factor X indicating the dynamic nature of the reactive site. An enzyme: inhibitor ratio of 1:1, and a Ki of 3.45nM was determined for the AS inhibitor on trypsin, and the inhibitor also weakly inhibit chymotrypsin. AS inhibitor and STI inhibited factor X with a Ki values of 13.7nM and 77.5μM respectively. Amino acid analysis revealed Mmin values of the A- and B- chain of 15,000 and 7,800, respectively. The effect of seed extracts on the activated partial thrombin time (APTT) and prothrombin time (PT) was tested. No prolongation of the PT was obtained. For the crude extracts of AK and AS, IC200 values of 4.6 and 189.62 μg/mL, were respectively obtained. For the purified fractions of STI, AS and AK, IC200 values of 51.5, 114.31 and 893.8 μg/ml were observed, respectively. Keywords: proteinase inhibitors, Acacia species, trypsin inhibitor, FX inhibitor.
- Full Text:
- Date Issued: 2009
Purification and partial characterisation of cathepsin D from ostrich skeletal muscle, and its activity during meat maturation
- Authors: Krause, Jason
- Date: 2009
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10313 , http://hdl.handle.net/10948/1461 , Proteolytic enzymes , Ostrich products industry
- Description: Cathepsin D, a muscle proteinase, participates in lysosomally mediated protein degradation in vivo. This enzyme has been proposed to play a significant role in the postmortem proteolysis process apparently associated with tenderisation. The lack of data on the postmortem characteristics of ostrich meat, especially on the ageing process and its influence on meat tenderness, called for an investigation into this process. There is no data available for purified ostrich cathepsin D, and the aim of this study was, therefore, to isolate, purify and characterise cathepsin D from ostrich skeletal muscle and subsequently investigate the possible role that it may have in the tenderisation process of meat. Cathepsin D was successfully isolated and purified from ostrich skeletal muscle using pepstatin A-agarose chromatography. The purified enzyme was composed of two subunits (14 and 29kDa). The amino acid composition as well as the N-terminal amino acid sequence of both subunits were determined. Kinetic parameters (Km and Vm), thermodynamic parameters (Ea, ∆H, ∆S and ∆G) and functional characteristics (effect of pH, temperature and various inhibitors on cathepsin D activity) were determined and are reported in this study. Ostrich muscle cathepsin D showed a pH optimum of 4 and a temperature optimum of 45°C. The activity of cathepsin D was strongly inhibited by pepstatin A and DTT. Purified ostrich cathepsin D displayed kinetic and functional properties similar to previously reported values from various species. The effect of storage on the activity of cathepsin D was investigated over a 30 day period. It was established that substantial postmortem cathepsin D activity remained throughout the storage period, to implicate cathepsin D, fulfilling a possible role in meat maturation.
- Full Text:
- Date Issued: 2009
- Authors: Krause, Jason
- Date: 2009
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10313 , http://hdl.handle.net/10948/1461 , Proteolytic enzymes , Ostrich products industry
- Description: Cathepsin D, a muscle proteinase, participates in lysosomally mediated protein degradation in vivo. This enzyme has been proposed to play a significant role in the postmortem proteolysis process apparently associated with tenderisation. The lack of data on the postmortem characteristics of ostrich meat, especially on the ageing process and its influence on meat tenderness, called for an investigation into this process. There is no data available for purified ostrich cathepsin D, and the aim of this study was, therefore, to isolate, purify and characterise cathepsin D from ostrich skeletal muscle and subsequently investigate the possible role that it may have in the tenderisation process of meat. Cathepsin D was successfully isolated and purified from ostrich skeletal muscle using pepstatin A-agarose chromatography. The purified enzyme was composed of two subunits (14 and 29kDa). The amino acid composition as well as the N-terminal amino acid sequence of both subunits were determined. Kinetic parameters (Km and Vm), thermodynamic parameters (Ea, ∆H, ∆S and ∆G) and functional characteristics (effect of pH, temperature and various inhibitors on cathepsin D activity) were determined and are reported in this study. Ostrich muscle cathepsin D showed a pH optimum of 4 and a temperature optimum of 45°C. The activity of cathepsin D was strongly inhibited by pepstatin A and DTT. Purified ostrich cathepsin D displayed kinetic and functional properties similar to previously reported values from various species. The effect of storage on the activity of cathepsin D was investigated over a 30 day period. It was established that substantial postmortem cathepsin D activity remained throughout the storage period, to implicate cathepsin D, fulfilling a possible role in meat maturation.
- Full Text:
- Date Issued: 2009