A retrospective assessment of the Port Alfred linefishery with respect to the changes in the South African fisheries management environment
- Authors: Donovan, Bruce
- Date: 2013-07-18
- Subjects: Fishery management -- South Africa -- Port Alfred , Fisheries -- South Africa -- Port Alfred , South Africa. Marine & Coastal Management , Coastal zone management -- South Africa -- Port Alfred , Fishing -- South Africa -- Port Alfred , Fisheries -- Environmental aspects -- South Africa -- Port Alfred , Fish stock assessment -- South Africa -- Port Alfred , Fishing surveys -- South Africa -- Port Alfred , Marine fishes -- South Africa -- Port Alfred
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5353 , http://hdl.handle.net/10962/d1008298 , Fishery management -- South Africa -- Port Alfred , Fisheries -- South Africa -- Port Alfred , South Africa. Marine & Coastal Management , Coastal zone management -- South Africa -- Port Alfred , Fishing -- South Africa -- Port Alfred , Fisheries -- Environmental aspects -- South Africa -- Port Alfred , Fish stock assessment -- South Africa -- Port Alfred , Fishing surveys -- South Africa -- Port Alfred , Marine fishes -- South Africa -- Port Alfred
- Description: Since the study on the Port Alfred/Kenton-on-Sea/Boknes linefishery by Hecht and Tilney (1989) there have been substantive changes to the linefish management environment in South Africa. Using the Port Alfred linefishery as a model, the aim of this study was to evaluate the effectiveness of the linefish management regulations that were implemented by Marine and Coastal Management (MCM) since 1992, and to assess the behaviour and 'status' of the fishery in response to these changes. Changes to both the licensing structure and catch regulations have had a significant effect on the functioning of many aspects of the Port Alfred linefishery (fishing effort, catch composition, cpue) as well as on the structure of the fishery and its socio-economic profile. Overall commercial cpue decreased from 1985 to 1998. Since 1998 there has been a significant increase in cpue (from 2.3 Kg.fisher⁻¹ hour⁻¹ to a peak of 4.8 Kg.fisher⁻¹.hour⁻¹ in 2005. This was attributed to good catches of geelbek, particularly in 2005, 2007 and 2008 (during these years geelbek contributed an average of 35% to the total landings in comparison to a mean contribution of II % between 1985 and 2004). However, size spectra analysis suggests that the increase in overall cpue since 1998 misrepresents the actual status of the fishery. If geelbek is excluded from the analysis on the grounds that it is the only species in the fishery that is highly migratory, susceptible to recruitment fluctuations and it does not contribute to the catches on a year round basis, then the results suggest that the fishery is still in a declining phase despite the 80% reduction in commercial effort and numerous stricter catch regulations (e.g. size/bag limits). Furthermore, the cpue of silver kob, which has been the "mainstay" species of the fishery, has consistently declined over the last 23 year period (from 1.69 Kg.fisher⁻1 .hour1 in 1986 to 0.86 Kg.fisher⁻1.hour⁻1in 2007). The substantial reduction in commercial effort in the fishery from 33 vessels in 2001 to 13 in 2002 resulted in a shift from commercial to recreational fishing. The number of active commercial vessels in Port Alfred alone decreased from 29 in 1989 (Hecht 1993) to four in 2008. During the same timeframe, the number of regularly active recreational vessels had almost doubled (16 in 1989 to 26 in 2008). Despite the greater number of recreational boats in the fishery they only landed approximately half the average yearly tonnage of the commercial vessels (21,5 and 44,7 tonnes,annum-I , respectively) between 2006 and 2008, This was ascribed to the differences in catch regulations for the two sectors, Furthermore, it was speculated that increasing operating costs and narrowing profit margins have contributed to lower levels of compliance in both the commercial and recreational sectors since 2006, For example, 16% of silver kob landed during 2006-08 were under the minimum size, Despite the changes made to the regulations since 1998 and the 60,6% reduction In legislated commercial effort in the fishery between 2001 and 2002 it was concluded that the fishery has continued to decline, Except for the good recruitment of geelbek (which may be due to regulatory changes made in 1992) the changes in the management environment have had no measurable positive effect on this fishery, It is recommended that commercial effort should not be allowed to increase beyond the current number of active boats, that there should be an area restriction on all commerciallinefish vessels, that the current recreational bag limit for silver kob should be re-assessed, there should also be a concerted and nationally funded effort to educate recreational anglers about the merits of catch and release, and the frequency of catch inspections of both sectors should be increased, , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Donovan, Bruce
- Date: 2013-07-18
- Subjects: Fishery management -- South Africa -- Port Alfred , Fisheries -- South Africa -- Port Alfred , South Africa. Marine & Coastal Management , Coastal zone management -- South Africa -- Port Alfred , Fishing -- South Africa -- Port Alfred , Fisheries -- Environmental aspects -- South Africa -- Port Alfred , Fish stock assessment -- South Africa -- Port Alfred , Fishing surveys -- South Africa -- Port Alfred , Marine fishes -- South Africa -- Port Alfred
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5353 , http://hdl.handle.net/10962/d1008298 , Fishery management -- South Africa -- Port Alfred , Fisheries -- South Africa -- Port Alfred , South Africa. Marine & Coastal Management , Coastal zone management -- South Africa -- Port Alfred , Fishing -- South Africa -- Port Alfred , Fisheries -- Environmental aspects -- South Africa -- Port Alfred , Fish stock assessment -- South Africa -- Port Alfred , Fishing surveys -- South Africa -- Port Alfred , Marine fishes -- South Africa -- Port Alfred
- Description: Since the study on the Port Alfred/Kenton-on-Sea/Boknes linefishery by Hecht and Tilney (1989) there have been substantive changes to the linefish management environment in South Africa. Using the Port Alfred linefishery as a model, the aim of this study was to evaluate the effectiveness of the linefish management regulations that were implemented by Marine and Coastal Management (MCM) since 1992, and to assess the behaviour and 'status' of the fishery in response to these changes. Changes to both the licensing structure and catch regulations have had a significant effect on the functioning of many aspects of the Port Alfred linefishery (fishing effort, catch composition, cpue) as well as on the structure of the fishery and its socio-economic profile. Overall commercial cpue decreased from 1985 to 1998. Since 1998 there has been a significant increase in cpue (from 2.3 Kg.fisher⁻¹ hour⁻¹ to a peak of 4.8 Kg.fisher⁻¹.hour⁻¹ in 2005. This was attributed to good catches of geelbek, particularly in 2005, 2007 and 2008 (during these years geelbek contributed an average of 35% to the total landings in comparison to a mean contribution of II % between 1985 and 2004). However, size spectra analysis suggests that the increase in overall cpue since 1998 misrepresents the actual status of the fishery. If geelbek is excluded from the analysis on the grounds that it is the only species in the fishery that is highly migratory, susceptible to recruitment fluctuations and it does not contribute to the catches on a year round basis, then the results suggest that the fishery is still in a declining phase despite the 80% reduction in commercial effort and numerous stricter catch regulations (e.g. size/bag limits). Furthermore, the cpue of silver kob, which has been the "mainstay" species of the fishery, has consistently declined over the last 23 year period (from 1.69 Kg.fisher⁻1 .hour1 in 1986 to 0.86 Kg.fisher⁻1.hour⁻1in 2007). The substantial reduction in commercial effort in the fishery from 33 vessels in 2001 to 13 in 2002 resulted in a shift from commercial to recreational fishing. The number of active commercial vessels in Port Alfred alone decreased from 29 in 1989 (Hecht 1993) to four in 2008. During the same timeframe, the number of regularly active recreational vessels had almost doubled (16 in 1989 to 26 in 2008). Despite the greater number of recreational boats in the fishery they only landed approximately half the average yearly tonnage of the commercial vessels (21,5 and 44,7 tonnes,annum-I , respectively) between 2006 and 2008, This was ascribed to the differences in catch regulations for the two sectors, Furthermore, it was speculated that increasing operating costs and narrowing profit margins have contributed to lower levels of compliance in both the commercial and recreational sectors since 2006, For example, 16% of silver kob landed during 2006-08 were under the minimum size, Despite the changes made to the regulations since 1998 and the 60,6% reduction In legislated commercial effort in the fishery between 2001 and 2002 it was concluded that the fishery has continued to decline, Except for the good recruitment of geelbek (which may be due to regulatory changes made in 1992) the changes in the management environment have had no measurable positive effect on this fishery, It is recommended that commercial effort should not be allowed to increase beyond the current number of active boats, that there should be an area restriction on all commerciallinefish vessels, that the current recreational bag limit for silver kob should be re-assessed, there should also be a concerted and nationally funded effort to educate recreational anglers about the merits of catch and release, and the frequency of catch inspections of both sectors should be increased, , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
A biochemical study of the antidiabetic and anticogulant effects of Tulbaghia Violacea
- Authors: Davison, Candice
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10311 , http://hdl.handle.net/10948/1523 , Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Description: Secondary metabolites derived from plants, especially those used by traditional healers, are at the forefront of new drug development in combating diseases such as cancer and diabetes. Garlic is employed in indigenous medicine all over the world for the treatment of a variety of diseases. Dietary garlic has been recognized for its beneficial health effects. In particular, garlic consumption has been correlated with (i) reduction of risk factors for cardiovascular diseases and cancer, (ii) stimulation of immune function, (iii) enhanced detoxification of foreign compounds, (iv) hepatoprotection, (v) antimicrobial effects, (vi) antioxidant effects, and most importantly (vii) its hypoglycemic and anticoagulant properties. Due to these beneficial properties, garlic and its closely related genera which includes Tulbaghia violacea, may be useful as coadjuvant therapy in the treatment of type 2 diabetes and some of its physiological complications. The aim of this study was to determine if T. violacea has antidiabetic and anticoagulant properties. This was performed in vitro using both aqueous and organic extracts of the roots, leaves and bulbs. An organic extract was able to improve glucose-stimulated insulin secretion (GSIS) in INS-1 pancreatic β-cells and glucose uptake in Chang liver cells. The BO extract had no effect on the glucose uptake in 3T3-L1 an adipose cell line and reduced glucose utilisation in C2C12, a skeletal muscle cell line. Some of the properties displayed by T. violacea in this study are consistent with those found in similar studies with garlic extracts. It was observed that the BO extract increased the membrane potential and Glut-2 expression in INS-1 cells cultured at hyperglycemic levels, however, at normoglycemic levels a reduction was observed. The oxygen consumption increased at both glycemic levels due to treatment with the BO extract. Platelets were exposed to the extracts to determine their effects upon platelet aggregation, adhesion and protein secretion. Since the BO extract displayed the highest potential at inhibiting platelet aggregation and adhesion. A rat model was used in ex vivo studies to determine if the extract exhibited the same effect in a physiological model. It was noted that the BO extract exhibited a higher degree of inhibition on platelet aggregation and adhesion than the positive control, aspirin. The BO extract reduced clotting times in the prothrombin time (PT) test, but prolonged the clotting time in the actived partial thromboplastin time (APTT) assay in the ex vivo model; however, it had no affect on these clotting assays in the in vitro model using human blood. The BO extract increased the D-dimer and Fibrinogen-C levels in the in vitro model, but had no effect on the D-dimer concentrations and lowered the Fibrinogen-C levels in the ex vivo model. The active compounds in the extract remain to be elucidated.
- Full Text:
- Date Issued: 2010
- Authors: Davison, Candice
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10311 , http://hdl.handle.net/10948/1523 , Medicinal plants -- South Africa , Diabetes -- Alternative treatment -- South Africa , Violaceae -- Therapeutic use -- South Africa , Anticoagulants (Medicine) , Plants -- Analysis
- Description: Secondary metabolites derived from plants, especially those used by traditional healers, are at the forefront of new drug development in combating diseases such as cancer and diabetes. Garlic is employed in indigenous medicine all over the world for the treatment of a variety of diseases. Dietary garlic has been recognized for its beneficial health effects. In particular, garlic consumption has been correlated with (i) reduction of risk factors for cardiovascular diseases and cancer, (ii) stimulation of immune function, (iii) enhanced detoxification of foreign compounds, (iv) hepatoprotection, (v) antimicrobial effects, (vi) antioxidant effects, and most importantly (vii) its hypoglycemic and anticoagulant properties. Due to these beneficial properties, garlic and its closely related genera which includes Tulbaghia violacea, may be useful as coadjuvant therapy in the treatment of type 2 diabetes and some of its physiological complications. The aim of this study was to determine if T. violacea has antidiabetic and anticoagulant properties. This was performed in vitro using both aqueous and organic extracts of the roots, leaves and bulbs. An organic extract was able to improve glucose-stimulated insulin secretion (GSIS) in INS-1 pancreatic β-cells and glucose uptake in Chang liver cells. The BO extract had no effect on the glucose uptake in 3T3-L1 an adipose cell line and reduced glucose utilisation in C2C12, a skeletal muscle cell line. Some of the properties displayed by T. violacea in this study are consistent with those found in similar studies with garlic extracts. It was observed that the BO extract increased the membrane potential and Glut-2 expression in INS-1 cells cultured at hyperglycemic levels, however, at normoglycemic levels a reduction was observed. The oxygen consumption increased at both glycemic levels due to treatment with the BO extract. Platelets were exposed to the extracts to determine their effects upon platelet aggregation, adhesion and protein secretion. Since the BO extract displayed the highest potential at inhibiting platelet aggregation and adhesion. A rat model was used in ex vivo studies to determine if the extract exhibited the same effect in a physiological model. It was noted that the BO extract exhibited a higher degree of inhibition on platelet aggregation and adhesion than the positive control, aspirin. The BO extract reduced clotting times in the prothrombin time (PT) test, but prolonged the clotting time in the actived partial thromboplastin time (APTT) assay in the ex vivo model; however, it had no affect on these clotting assays in the in vitro model using human blood. The BO extract increased the D-dimer and Fibrinogen-C levels in the in vitro model, but had no effect on the D-dimer concentrations and lowered the Fibrinogen-C levels in the ex vivo model. The active compounds in the extract remain to be elucidated.
- Full Text:
- Date Issued: 2010
A bioinorganic investigation of some metal complexes of the Schiff base, N,N'-bis(3-methoxysalicylaldimine)propan-2-ol
- Authors: Mopp, Estelle
- Date: 2010 , 2012-04-13
- Subjects: Schiff bases , Bioinorganic chemistry , Metal complexes , Transition metal complexes , Transition metals , Cancer -- Chemotherapy , Ligands -- Toxicity , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4413 , http://hdl.handle.net/10962/d1006768 , Schiff bases , Bioinorganic chemistry , Metal complexes , Transition metal complexes , Transition metals , Cancer -- Chemotherapy , Ligands -- Toxicity , Antineoplastic agents
- Description: This thesis includes the synthesis, characterisation, antioxidant and antimicrobial activities of Cu(II)-, Co(II)- and Co(III) complexes with N,N'-bis(3- methoxysalicylaldimine)propan-2-ol, 2-OH-oVANPN. The Schiff base ligand, 2-OHoVANPN, is derived from o-vanillin and 1,3-diaminopropan-2-ol. The o-vanillin condensed with 1,3-diaminopropan-2-ol in a 2:1 molar ratio yields this potential tetraor pentadentate ligand. The complexes synthesized are tetra (or penta or hexa) coordinated. Formation of the complexes is symbolized as follows:- MX₂ + 2-OH-oVANPN (2:1) -> [M(2-OH-oVANPN)Xn] + HnX MX₂ + 2-OH-oVANPN (2:1) -> [Mn(2-OH-oVANPN)OH] + H₂X₂ MX₂ + (o-vanillin : diaminopropanol) (1:1) -> [M(1:1)X₂] MX₂ + (o-vanillin : diaminopropanol) (1:1) -> [M₃(1:1)X₄] M = Cu(II), Co(II) or Co(III); X = Cl; n = 1, 2. Their structural features have been deduced from their elemental analytical data, IR spectral data, and electronic spectral data. With the exception of {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆}(A4), the Cu(II) complexes were monomeric with 2-OH-oVANPN acting as a tetradentate ligand. A binuclear Co(II) complex, [Co₂(C₁₉H₁₉N₂O₅)(OH)] (B1), was synthesised and the rest of the Co(II) and Co(III) complexes were monomeric with chloride ions coordinating to the metal centre in some cases. Electronic data suggest that the cobalt(II) complexes have octahedral geometries and the copper(II) complexes have square planar structures – Co(III) is likely to be octahedral. Thermal analyses, which included the copper-block-method for determining sublimation temperatures, revealed that some copper(II) and cobalt(II) complexes are hygroscopic and sublime at 200 °C and below. DSC analyses of the Cu(II) complexes gave exotherms around 300 °C for complexes K[Cu(C₁₉H₂₀N₂O₅)(OH)]·2H₂O (A1) and [Cu(C₁₁H15N₂O₃)(Cl)₂]·2H₂O (A2) and above 400 °C for [Cu(C₁₁H₁₆N₂O₃)(Cl)₂] (A3) and {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆} (A4). Antioxidant studies were carried out against the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·). The cobalt(II) complex, [Co₂(C₁₉H₁₉N₂O₅)(OH)] (B1), which was synthesized in the presence of KOH, had no antioxidant activity, whilst the other cobalt(II) complexes, [Co(C₁₇H₁₇N₂O₅(Cl))]·1½H₂O (B2), [Co(C₁₉H₂₂N₂O₅) (Cl)₂]·5½H₂O (B3) and [Co(C₁₉H₂₂N₂O₅)(Cl)₂]·5½H₂O (B4), which were synthesised in the absence of KOH, demonstrated antioxidant activity. The latter complexes are candidates for cancer cell line testing, while [Cu(C₁₁H₁₆N₂O₃)(Cl)₂] (A3), {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆} (A4), [Co(C₁₉H₂₁N₂O₅)(Cl)₂ ]·5H₂O (C2) and [Co(C₁₉H₂₀N₂O₅)(Cl)]·3H₂O (C3) may show anticancer activity through possible hydrolysis products. Most of the complexes synthesized displayed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans. The results indicated that complexes [Cu(C₁₁H₁₆N₂O₃)(Cl)₂](A3), [Co(C₁₉H₂₂N₂O₅)(Cl)₂]·5½H₂O (B3) and [Co(C₁₉H₂₁N₂O₅)(Cl)₂ ]·5H₂O (C2) are active against the Gram-negative Ps. aeruginosa and that the ligand, 2-OH-oVANPN, did not have any activity. The same trend was observed with 2-OH-oVANPN, {Cu₃(C₁₁H₁₄N₂O₃)(Cl)4(H₂O)₆} (A4) and [Co(C₁₉H₂₀N₂O₅)(Cl)]·3H₂O (C3) against the Gram-positive S. aureus. As for activity against E. coli and C. albicans, some complexes showed more activity than the ligand. There is an observed trend here that the metal complexes are more active (toxic) than the corresponding ligand, which is in agreement with Tweedy’s chelation theory.
- Full Text:
- Date Issued: 2010
- Authors: Mopp, Estelle
- Date: 2010 , 2012-04-13
- Subjects: Schiff bases , Bioinorganic chemistry , Metal complexes , Transition metal complexes , Transition metals , Cancer -- Chemotherapy , Ligands -- Toxicity , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4413 , http://hdl.handle.net/10962/d1006768 , Schiff bases , Bioinorganic chemistry , Metal complexes , Transition metal complexes , Transition metals , Cancer -- Chemotherapy , Ligands -- Toxicity , Antineoplastic agents
- Description: This thesis includes the synthesis, characterisation, antioxidant and antimicrobial activities of Cu(II)-, Co(II)- and Co(III) complexes with N,N'-bis(3- methoxysalicylaldimine)propan-2-ol, 2-OH-oVANPN. The Schiff base ligand, 2-OHoVANPN, is derived from o-vanillin and 1,3-diaminopropan-2-ol. The o-vanillin condensed with 1,3-diaminopropan-2-ol in a 2:1 molar ratio yields this potential tetraor pentadentate ligand. The complexes synthesized are tetra (or penta or hexa) coordinated. Formation of the complexes is symbolized as follows:- MX₂ + 2-OH-oVANPN (2:1) -> [M(2-OH-oVANPN)Xn] + HnX MX₂ + 2-OH-oVANPN (2:1) -> [Mn(2-OH-oVANPN)OH] + H₂X₂ MX₂ + (o-vanillin : diaminopropanol) (1:1) -> [M(1:1)X₂] MX₂ + (o-vanillin : diaminopropanol) (1:1) -> [M₃(1:1)X₄] M = Cu(II), Co(II) or Co(III); X = Cl; n = 1, 2. Their structural features have been deduced from their elemental analytical data, IR spectral data, and electronic spectral data. With the exception of {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆}(A4), the Cu(II) complexes were monomeric with 2-OH-oVANPN acting as a tetradentate ligand. A binuclear Co(II) complex, [Co₂(C₁₉H₁₉N₂O₅)(OH)] (B1), was synthesised and the rest of the Co(II) and Co(III) complexes were monomeric with chloride ions coordinating to the metal centre in some cases. Electronic data suggest that the cobalt(II) complexes have octahedral geometries and the copper(II) complexes have square planar structures – Co(III) is likely to be octahedral. Thermal analyses, which included the copper-block-method for determining sublimation temperatures, revealed that some copper(II) and cobalt(II) complexes are hygroscopic and sublime at 200 °C and below. DSC analyses of the Cu(II) complexes gave exotherms around 300 °C for complexes K[Cu(C₁₉H₂₀N₂O₅)(OH)]·2H₂O (A1) and [Cu(C₁₁H15N₂O₃)(Cl)₂]·2H₂O (A2) and above 400 °C for [Cu(C₁₁H₁₆N₂O₃)(Cl)₂] (A3) and {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆} (A4). Antioxidant studies were carried out against the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·). The cobalt(II) complex, [Co₂(C₁₉H₁₉N₂O₅)(OH)] (B1), which was synthesized in the presence of KOH, had no antioxidant activity, whilst the other cobalt(II) complexes, [Co(C₁₇H₁₇N₂O₅(Cl))]·1½H₂O (B2), [Co(C₁₉H₂₂N₂O₅) (Cl)₂]·5½H₂O (B3) and [Co(C₁₉H₂₂N₂O₅)(Cl)₂]·5½H₂O (B4), which were synthesised in the absence of KOH, demonstrated antioxidant activity. The latter complexes are candidates for cancer cell line testing, while [Cu(C₁₁H₁₆N₂O₃)(Cl)₂] (A3), {Cu₃(C₁₁H₁₄N₂O₃)(Cl)₄(H₂O)₆} (A4), [Co(C₁₉H₂₁N₂O₅)(Cl)₂ ]·5H₂O (C2) and [Co(C₁₉H₂₀N₂O₅)(Cl)]·3H₂O (C3) may show anticancer activity through possible hydrolysis products. Most of the complexes synthesized displayed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus niger and Candida albicans. The results indicated that complexes [Cu(C₁₁H₁₆N₂O₃)(Cl)₂](A3), [Co(C₁₉H₂₂N₂O₅)(Cl)₂]·5½H₂O (B3) and [Co(C₁₉H₂₁N₂O₅)(Cl)₂ ]·5H₂O (C2) are active against the Gram-negative Ps. aeruginosa and that the ligand, 2-OH-oVANPN, did not have any activity. The same trend was observed with 2-OH-oVANPN, {Cu₃(C₁₁H₁₄N₂O₃)(Cl)4(H₂O)₆} (A4) and [Co(C₁₉H₂₀N₂O₅)(Cl)]·3H₂O (C3) against the Gram-positive S. aureus. As for activity against E. coli and C. albicans, some complexes showed more activity than the ligand. There is an observed trend here that the metal complexes are more active (toxic) than the corresponding ligand, which is in agreement with Tweedy’s chelation theory.
- Full Text:
- Date Issued: 2010
A comparison of ecosystem health and services provided by subtropical thicket in and around the Bathurst commonage
- Authors: Stickler, Meredith Mercedes
- Date: 2010
- Subjects: Ecosystem services -- South Africa -- Bathurst , Ecosystem management , Commons -- South Africa -- Bathurst , Natural resources, Communal -- South Africa -- Bathurst , Land use, Rural -- South Africa -- Eastern Cape , Ecosystem health -- South Africa -- Bathurst
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4766 , http://hdl.handle.net/10962/d1007169 , Ecosystem services -- South Africa -- Bathurst , Ecosystem management , Commons -- South Africa -- Bathurst , Natural resources, Communal -- South Africa -- Bathurst , Land use, Rural -- South Africa -- Eastern Cape , Ecosystem health -- South Africa -- Bathurst
- Description: Municipal commonage in South Africa offers previously disadvantaged, landless residents access to both direct ecosystem goods and services (EGS) that provide additional income options and indirect social and cultural services. Given that EGS production is a function of ecosystem health, it is imperative that commonage land be managed to maximize current local benefit streams while ensuring future options through the maintenance of natural ecosystem functions. The payments for ecosystem services (PES) model potentially offers an opportunity for contributing to local economic development while providing fiscal incentives for environmentally sustainable natural resource management. PES depends on the demonstration of quantifiable changes in EGS delivery due to improvement in or maintenance of high ecosystem health that are a verifiable result of modifications in management behavior. This thesis therefore compared spatial variations in (i) ecosystem health and (ii) nine direct and indirect EGS values derived from natural resources on the Bathurst municipal commonage and neighboring Waters Meeting Nature Reserve (NR) to explore how different land use intensities affect ecosystem health and the resulting provision of EGS. The results indicate that the total economic value of annually produced EGS on the study site is nearly R 9.8 million (US$ 1.2 million), with a standing stock of natural capital worth some R 28 million (US$ 3.4 million). Nearly 45% of the total annual production is attributed to Waters Meeting NR, with roughly 34% from the low use zone of the commonage and the remaining 22% from the high use zone. Of the total annual production value on the study site, roughly 59% is derived from indirect (non-consumptive) uses of wildlife for the study site as a whole, though this proportion varies from 25% in the high use zone of the commonage to 94% on Waters Meeting NR. The two largest annual production values on the study site derive from ecotourism (R 3.5 million, US$ 0.4 million) and livestock production (R 2.6 million, US$ 0.3 million), suggesting that while increased production of indirect EGS could generate significant additional revenues, especially on Waters Meeting NR and in the low use zone of the commonage, direct (consumptive) EGS will likely remain an important component of land use on the commonage. A PES project to support the adoption of silvo-pastoral practices could provide positive incentives for improved land use practices on the commonage and potentially be financed by conservation-friendly residents of the Kowie River catchment and/or increased ecotourism revenues from Waters Meeting NR. Allowing carefully designed and monitored local access to natural resources within Waters Meeting NR could also reduce pressure on commonage resources. Together, these approaches could lead to a more sustainable subtropical thicket landscape and ensure that critical natural resources remain available to support local livelihoods in the long-term.
- Full Text:
- Date Issued: 2010
- Authors: Stickler, Meredith Mercedes
- Date: 2010
- Subjects: Ecosystem services -- South Africa -- Bathurst , Ecosystem management , Commons -- South Africa -- Bathurst , Natural resources, Communal -- South Africa -- Bathurst , Land use, Rural -- South Africa -- Eastern Cape , Ecosystem health -- South Africa -- Bathurst
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4766 , http://hdl.handle.net/10962/d1007169 , Ecosystem services -- South Africa -- Bathurst , Ecosystem management , Commons -- South Africa -- Bathurst , Natural resources, Communal -- South Africa -- Bathurst , Land use, Rural -- South Africa -- Eastern Cape , Ecosystem health -- South Africa -- Bathurst
- Description: Municipal commonage in South Africa offers previously disadvantaged, landless residents access to both direct ecosystem goods and services (EGS) that provide additional income options and indirect social and cultural services. Given that EGS production is a function of ecosystem health, it is imperative that commonage land be managed to maximize current local benefit streams while ensuring future options through the maintenance of natural ecosystem functions. The payments for ecosystem services (PES) model potentially offers an opportunity for contributing to local economic development while providing fiscal incentives for environmentally sustainable natural resource management. PES depends on the demonstration of quantifiable changes in EGS delivery due to improvement in or maintenance of high ecosystem health that are a verifiable result of modifications in management behavior. This thesis therefore compared spatial variations in (i) ecosystem health and (ii) nine direct and indirect EGS values derived from natural resources on the Bathurst municipal commonage and neighboring Waters Meeting Nature Reserve (NR) to explore how different land use intensities affect ecosystem health and the resulting provision of EGS. The results indicate that the total economic value of annually produced EGS on the study site is nearly R 9.8 million (US$ 1.2 million), with a standing stock of natural capital worth some R 28 million (US$ 3.4 million). Nearly 45% of the total annual production is attributed to Waters Meeting NR, with roughly 34% from the low use zone of the commonage and the remaining 22% from the high use zone. Of the total annual production value on the study site, roughly 59% is derived from indirect (non-consumptive) uses of wildlife for the study site as a whole, though this proportion varies from 25% in the high use zone of the commonage to 94% on Waters Meeting NR. The two largest annual production values on the study site derive from ecotourism (R 3.5 million, US$ 0.4 million) and livestock production (R 2.6 million, US$ 0.3 million), suggesting that while increased production of indirect EGS could generate significant additional revenues, especially on Waters Meeting NR and in the low use zone of the commonage, direct (consumptive) EGS will likely remain an important component of land use on the commonage. A PES project to support the adoption of silvo-pastoral practices could provide positive incentives for improved land use practices on the commonage and potentially be financed by conservation-friendly residents of the Kowie River catchment and/or increased ecotourism revenues from Waters Meeting NR. Allowing carefully designed and monitored local access to natural resources within Waters Meeting NR could also reduce pressure on commonage resources. Together, these approaches could lead to a more sustainable subtropical thicket landscape and ensure that critical natural resources remain available to support local livelihoods in the long-term.
- Full Text:
- Date Issued: 2010
A framework for mobile SOA using compression
- Authors: Saunders, Evan
- Date: 2010
- Subjects: Service-oriented architecture (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10459 , http://hdl.handle.net/10948/1500 , Service-oriented architecture (Computer science)
- Description: The widely accepted standards of Service-Oriented Architecture (SOA) have changed the way many organisations conduct their everyday business. The significant popularity of mobile devices has seen a rapid increase in the rate of mobile technology enhancements, which have become widely used for communication, as well as conducting everyday tasks. An increased requirement in many businesses is for staff not to be tied down to the office. Consequently, mobile devices play an important role in achieving the mobility and information access that people desire. Due to the popularity and increasing use of SOA and mobile devices, Mobile Service-Oriented Architecture (Mobile SOA) has become a new industry catch-phrase. Many challenges, however, exist within the Mobile SOA environment. These issues include limitations on mobile devices, such as a reduced screen size, lack of processing power, insufficient processing memory, limited battery life, poor storage capacity, unreliable network connections, limited bandwidth available and high transfer costs. This research aimed to provide an elegant solution to the issues of a mobile device, which hinders the performance of Mobile SOA. The main objective of this research was to improve the effectiveness and efficiency of Mobile SOA. In order to achieve this goal, a framework was proposed, which supported intelligent compression of files used within a Web Service. The proposed framework provided a set of guidelines that facilitate the quick development of a system. A proof-of-concept prototype was developed, based on these guidelines and the framework design principles. The prototype provided practical evidence of the effectiveness of implementing a system based on the proposed framework. An analytical evaluation was conducted to determine the effectiveness of the prototype within the Mobile SOA environment. A performance evaluation was conducted to determine efficiency it provides. Additionally, the performance evaluation highlighted the decrease in file transfer time, as well as the significant reduction in transfer costs. The analytical and performance evaluations demonstrated that the prototype optimises the effectiveness and efficiency of Mobile SOA. The framework could, thus, be used to facilitate efficient file transfer between a Server and (Mobile) Client.
- Full Text:
- Date Issued: 2010
- Authors: Saunders, Evan
- Date: 2010
- Subjects: Service-oriented architecture (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10459 , http://hdl.handle.net/10948/1500 , Service-oriented architecture (Computer science)
- Description: The widely accepted standards of Service-Oriented Architecture (SOA) have changed the way many organisations conduct their everyday business. The significant popularity of mobile devices has seen a rapid increase in the rate of mobile technology enhancements, which have become widely used for communication, as well as conducting everyday tasks. An increased requirement in many businesses is for staff not to be tied down to the office. Consequently, mobile devices play an important role in achieving the mobility and information access that people desire. Due to the popularity and increasing use of SOA and mobile devices, Mobile Service-Oriented Architecture (Mobile SOA) has become a new industry catch-phrase. Many challenges, however, exist within the Mobile SOA environment. These issues include limitations on mobile devices, such as a reduced screen size, lack of processing power, insufficient processing memory, limited battery life, poor storage capacity, unreliable network connections, limited bandwidth available and high transfer costs. This research aimed to provide an elegant solution to the issues of a mobile device, which hinders the performance of Mobile SOA. The main objective of this research was to improve the effectiveness and efficiency of Mobile SOA. In order to achieve this goal, a framework was proposed, which supported intelligent compression of files used within a Web Service. The proposed framework provided a set of guidelines that facilitate the quick development of a system. A proof-of-concept prototype was developed, based on these guidelines and the framework design principles. The prototype provided practical evidence of the effectiveness of implementing a system based on the proposed framework. An analytical evaluation was conducted to determine the effectiveness of the prototype within the Mobile SOA environment. A performance evaluation was conducted to determine efficiency it provides. Additionally, the performance evaluation highlighted the decrease in file transfer time, as well as the significant reduction in transfer costs. The analytical and performance evaluations demonstrated that the prototype optimises the effectiveness and efficiency of Mobile SOA. The framework could, thus, be used to facilitate efficient file transfer between a Server and (Mobile) Client.
- Full Text:
- Date Issued: 2010
A proxy approach to protocol interoperability within digital audio networks
- Authors: Igumbor, Osedum Peter
- Date: 2010
- Subjects: Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4601 , http://hdl.handle.net/10962/d1004852 , Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Description: Digital audio networks are becoming the preferred solution for the interconnection of professional audio devices. Prominent amongst their advantages are: reduced noise interference, signal multiplexing, and a reduction in the number of cables connecting networked devices. In the context of professional audio, digital networks have been used to connect devices including: mixers, effects units, preamplifiers, breakout boxes, computers, monitoring controllers, and synthesizers. Such networks are governed by protocols that define the connection management rocedures, and device synchronization processes of devices that conform to the protocols. A wide range of digital audio network control protocols exist, each defining specific hardware requirements of devices that conform to them. Device parameter control is achieved by sending a protocol message that indicates the target parameter, and the action that should be performed on the parameter. Typically, a device will conform to only one protocol. By implication, only devices that conform to a specific protocol can communicate with each other, and only a controller that conforms to the protocol can control such devices. This results in the isolation of devices that conform to disparate protocols, since devices of different protocols cannot communicate with each other. This is currently a challenge in the professional music industry, particularly where digital networks are used for audio device control. This investigation seeks to resolve the issue of interoperability between professional audio devices that conform to different digital audio network protocols. This thesis proposes the use of a proxy that allows for the translation of protocol messages, as a solution to the interoperability problem. The proxy abstracts devices of one protocol in terms of another, hence allowing all the networked devices to appear as conforming to the same protocol. The proxy receives messages on behalf of the abstracted device, and then fulfills them in accordance with the protocol that the abstracted device conforms to. Any number of protocol devices can be abstracted within such a proxy. This has the added advantage of allowing a common controller to control devices that conform to the different protocols.
- Full Text:
- Date Issued: 2010
- Authors: Igumbor, Osedum Peter
- Date: 2010
- Subjects: Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4601 , http://hdl.handle.net/10962/d1004852 , Digital communications , Local area networks (Computer networks) , Computer sound processing , Computer networks , Computer network protocols
- Description: Digital audio networks are becoming the preferred solution for the interconnection of professional audio devices. Prominent amongst their advantages are: reduced noise interference, signal multiplexing, and a reduction in the number of cables connecting networked devices. In the context of professional audio, digital networks have been used to connect devices including: mixers, effects units, preamplifiers, breakout boxes, computers, monitoring controllers, and synthesizers. Such networks are governed by protocols that define the connection management rocedures, and device synchronization processes of devices that conform to the protocols. A wide range of digital audio network control protocols exist, each defining specific hardware requirements of devices that conform to them. Device parameter control is achieved by sending a protocol message that indicates the target parameter, and the action that should be performed on the parameter. Typically, a device will conform to only one protocol. By implication, only devices that conform to a specific protocol can communicate with each other, and only a controller that conforms to the protocol can control such devices. This results in the isolation of devices that conform to disparate protocols, since devices of different protocols cannot communicate with each other. This is currently a challenge in the professional music industry, particularly where digital networks are used for audio device control. This investigation seeks to resolve the issue of interoperability between professional audio devices that conform to different digital audio network protocols. This thesis proposes the use of a proxy that allows for the translation of protocol messages, as a solution to the interoperability problem. The proxy abstracts devices of one protocol in terms of another, hence allowing all the networked devices to appear as conforming to the same protocol. The proxy receives messages on behalf of the abstracted device, and then fulfills them in accordance with the protocol that the abstracted device conforms to. Any number of protocol devices can be abstracted within such a proxy. This has the added advantage of allowing a common controller to control devices that conform to the different protocols.
- Full Text:
- Date Issued: 2010
A spectroscopic study of the electronic effects on copper (II) and copper (I) complexes of ligands derived from various substituted benzyaldehyde- and cinnamaldehyde- based schiff bases
- Authors: Magwa, Nomampondo Penelope
- Date: 2010 , 2010-03-19
- Subjects: Copper -- Analysis , Schiff bases , Organometallic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4407 , http://hdl.handle.net/10962/d1006712 , Copper -- Analysis , Schiff bases , Organometallic compounds
- Description: Several Schiff base ligands, N, N‟-(aryl)benzyaldiimine ligands (R-BEN); N, N‟-(aryl)benzyaldiamine dihydrochloride ligands (R-BENH•2HCl); N, N‟-(aryl)benzyaldiamine ligands (R-BENH); N, N‟-bis(cinnamaldiimine) ligands (R-CA2EN) were synthesized for the investigation of the electronic effect of the substituents at para-position of the Schiff base ligands and their copper complexes. The synthesis of Schiff bases was carried out by reacting a series of para-substituted benzyaldehyde, and para-substituted cinnamaldehyde with ethylenediamine. The imine group of Schiff bases, N, N‟-(aryl)benzyaldiimine ligands and N, N‟-bis(cinnamaldiimine)ligands were reduced to corresponding amines with sodium borohydride in methanol These ligands, N, N‟-(aryl)benzyaldiamine ligands (H-BENH), N, N‟-bis(cinnamaldiimine)ligands (CA2EN) were reacted with copper(II) dihalide and copper(I) monohalide ions respectively to form complexes. The ligands and their complexes were analysed using elemental analyses, FT-IR spectroscopy (mid-IR), UV/vis in aprotic and protic solvents,while mass spectrometry, 1H-NMR and 13C-NMR were used to further analyse the ligands. By using substituent parameters, both the single and dual substituent parameters with the spectroscopic data obtained from the spectroscopic techiques mentioned above, it was hoped to monitor and determine whether the electronic effects (resonance or inductive effcets) was predominantly within the Schiff base ligands and copper complexes. The NMR studies with dual substituent parameters suggest that the effects of the substituents are transimitted through the ligands, via resonance effects and that the phenyl group is nonplanar with the azomethine in N, N‟-(aryl)benzyaldiimine ligands. The presence of an extra double bond in Schiff base {(N, N‟-bis(cinnamaldiimine) ligand)} altered the electron density. The UV/vis studies showed that the symmetry of the N, N‟-bis(4-R-benzyl)-1, 2-diaminoethanedihalidecopper(II) complexes were predominantly tetrahedral for both chloro and bromo complexes. The correlation studies from mid-infrared were beneficial in monitoring the effect experienced by N, N‟-(aryl)benzaldiimine ligands, the studies suggest that the inductive effect is more pronounced at the C=N.
- Full Text:
- Date Issued: 2010
- Authors: Magwa, Nomampondo Penelope
- Date: 2010 , 2010-03-19
- Subjects: Copper -- Analysis , Schiff bases , Organometallic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4407 , http://hdl.handle.net/10962/d1006712 , Copper -- Analysis , Schiff bases , Organometallic compounds
- Description: Several Schiff base ligands, N, N‟-(aryl)benzyaldiimine ligands (R-BEN); N, N‟-(aryl)benzyaldiamine dihydrochloride ligands (R-BENH•2HCl); N, N‟-(aryl)benzyaldiamine ligands (R-BENH); N, N‟-bis(cinnamaldiimine) ligands (R-CA2EN) were synthesized for the investigation of the electronic effect of the substituents at para-position of the Schiff base ligands and their copper complexes. The synthesis of Schiff bases was carried out by reacting a series of para-substituted benzyaldehyde, and para-substituted cinnamaldehyde with ethylenediamine. The imine group of Schiff bases, N, N‟-(aryl)benzyaldiimine ligands and N, N‟-bis(cinnamaldiimine)ligands were reduced to corresponding amines with sodium borohydride in methanol These ligands, N, N‟-(aryl)benzyaldiamine ligands (H-BENH), N, N‟-bis(cinnamaldiimine)ligands (CA2EN) were reacted with copper(II) dihalide and copper(I) monohalide ions respectively to form complexes. The ligands and their complexes were analysed using elemental analyses, FT-IR spectroscopy (mid-IR), UV/vis in aprotic and protic solvents,while mass spectrometry, 1H-NMR and 13C-NMR were used to further analyse the ligands. By using substituent parameters, both the single and dual substituent parameters with the spectroscopic data obtained from the spectroscopic techiques mentioned above, it was hoped to monitor and determine whether the electronic effects (resonance or inductive effcets) was predominantly within the Schiff base ligands and copper complexes. The NMR studies with dual substituent parameters suggest that the effects of the substituents are transimitted through the ligands, via resonance effects and that the phenyl group is nonplanar with the azomethine in N, N‟-(aryl)benzyaldiimine ligands. The presence of an extra double bond in Schiff base {(N, N‟-bis(cinnamaldiimine) ligand)} altered the electron density. The UV/vis studies showed that the symmetry of the N, N‟-bis(4-R-benzyl)-1, 2-diaminoethanedihalidecopper(II) complexes were predominantly tetrahedral for both chloro and bromo complexes. The correlation studies from mid-infrared were beneficial in monitoring the effect experienced by N, N‟-(aryl)benzaldiimine ligands, the studies suggest that the inductive effect is more pronounced at the C=N.
- Full Text:
- Date Issued: 2010
An evaluation of the impact of corruption, economic status and political influence on the Malawian construction industry
- Authors: Phiri, Mulima Anaclet
- Date: 2010
- Subjects: Construction industry -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9688 , http://hdl.handle.net/10948/1155 , Construction industry -- Malawi
- Description: The key objectives of this MSc (Construction Management) dissertation are to evaluate the negative impact of: corruption; political influence, and the poor economy on the construction industry; in order to gain insight regarding the management of the sector to achieve the desired project deliverables, which are: • Achievement of a functional fit for purpose built environment, which is to the clients’ requirements; • Achievement of a Financially viable product in line with the clients’ budget; • Achievement of a successful and timely completion, and • Achievement of the required quality standard of the final product. To achieve the above mentioned project deliverables, the study entailed the following prominent findings: • There is a need to manage political greed in the distribution of development projects, and functionality of the product to suit the client / community; • There is a need to manage, mitigate and combat corruption in order to diminish the dominance of unscrupulous contractors over others, and to achieve clients’ desired quality standards; • There is a requirement to manage the construction policy formulation process and governance of laws and regulations to revamp the retrogression of the industry, and • There is a requirement to manage project cost to significantly boost the ailing economy. In conclusion, the study evaluates the Malawi construction industry status and improvements there on. The management of the industry’s phenomena and mind set is of paramount importance to the success of the findings in this study. Recommendations to improve the status quo relative to the findings are: to train all active stakeholders in construction management courses; a national initiative to sensitise the community regarding the powers granted to them, as an electorate of the stakeholders; to change the phenomenon of and mindset relative to bribes, and finally to derive a passion for construction and for the associated built environment.
- Full Text:
- Date Issued: 2010
- Authors: Phiri, Mulima Anaclet
- Date: 2010
- Subjects: Construction industry -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9688 , http://hdl.handle.net/10948/1155 , Construction industry -- Malawi
- Description: The key objectives of this MSc (Construction Management) dissertation are to evaluate the negative impact of: corruption; political influence, and the poor economy on the construction industry; in order to gain insight regarding the management of the sector to achieve the desired project deliverables, which are: • Achievement of a functional fit for purpose built environment, which is to the clients’ requirements; • Achievement of a Financially viable product in line with the clients’ budget; • Achievement of a successful and timely completion, and • Achievement of the required quality standard of the final product. To achieve the above mentioned project deliverables, the study entailed the following prominent findings: • There is a need to manage political greed in the distribution of development projects, and functionality of the product to suit the client / community; • There is a need to manage, mitigate and combat corruption in order to diminish the dominance of unscrupulous contractors over others, and to achieve clients’ desired quality standards; • There is a requirement to manage the construction policy formulation process and governance of laws and regulations to revamp the retrogression of the industry, and • There is a requirement to manage project cost to significantly boost the ailing economy. In conclusion, the study evaluates the Malawi construction industry status and improvements there on. The management of the industry’s phenomena and mind set is of paramount importance to the success of the findings in this study. Recommendations to improve the status quo relative to the findings are: to train all active stakeholders in construction management courses; a national initiative to sensitise the community regarding the powers granted to them, as an electorate of the stakeholders; to change the phenomenon of and mindset relative to bribes, and finally to derive a passion for construction and for the associated built environment.
- Full Text:
- Date Issued: 2010
An ion imprinted polymer for the selective extraction of mercury (II) ions in aqueous media
- Authors: Batlokwa, Bareki Shima
- Date: 2010 , 2013-07-18
- Subjects: Mercury , Metal ions , Imprinted polymers , Polymerization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4294 , http://hdl.handle.net/10962/d1004541 , Mercury , Metal ions , Imprinted polymers , Polymerization
- Description: This thesis presents the application of an imprinted mercury(lI) polymer that we synthesized by copolymerizing the functional and cross-linking monomers, N'-[3-(Trimethoxysilyl)propyl] diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS) in the presence of mercury (II) ions as template. A bulk polymerization method following a double-imprinting procedure and employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer was employed in the synthesis. The imprinted polymer particles were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and their average size determined by screen analysis using standard test sieves. The relative selective coefficients (k') of the imprinted polymer evaluated from selective binding studies between Hg ²⁺and Cu²⁺ or Hg²⁺ and Cd²⁺, were 10588 and 3147, respectively. These values indicated highly favored Hg²⁺ extractions over the two competing ions. Application of the polymer to various real water samples (tap, sea, river, pulverized coal solution, treated and untreated sewerage from the vicinity of Grahamstown in South Africa) showed high extraction efficiencies (EEs) of Hg²⁺ ions; (over 84% in all cases) as evaluated from the detected unextracted Hg²⁺ ions by inductively coupled plasma optical emission spectroscopy (ICP-OES). The limit of detection (LOD, 3ơ) of the method was evaluated to be 0.036 ng ml⁻¹ and generally the data (n=10) had percentage relative standard deviation (%RSD) of less than 4%. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre-concentration of mercury(lI) ions in aqueous environments. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2010
- Authors: Batlokwa, Bareki Shima
- Date: 2010 , 2013-07-18
- Subjects: Mercury , Metal ions , Imprinted polymers , Polymerization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4294 , http://hdl.handle.net/10962/d1004541 , Mercury , Metal ions , Imprinted polymers , Polymerization
- Description: This thesis presents the application of an imprinted mercury(lI) polymer that we synthesized by copolymerizing the functional and cross-linking monomers, N'-[3-(Trimethoxysilyl)propyl] diethylenetriamine (TPET) and tetraethylorthosilicate (TEOS) in the presence of mercury (II) ions as template. A bulk polymerization method following a double-imprinting procedure and employing hexadecyltrimethylammonium bromide (CTAB), as a second template to improve the efficiency of the polymer was employed in the synthesis. The imprinted polymer particles were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and their average size determined by screen analysis using standard test sieves. The relative selective coefficients (k') of the imprinted polymer evaluated from selective binding studies between Hg ²⁺and Cu²⁺ or Hg²⁺ and Cd²⁺, were 10588 and 3147, respectively. These values indicated highly favored Hg²⁺ extractions over the two competing ions. Application of the polymer to various real water samples (tap, sea, river, pulverized coal solution, treated and untreated sewerage from the vicinity of Grahamstown in South Africa) showed high extraction efficiencies (EEs) of Hg²⁺ ions; (over 84% in all cases) as evaluated from the detected unextracted Hg²⁺ ions by inductively coupled plasma optical emission spectroscopy (ICP-OES). The limit of detection (LOD, 3ơ) of the method was evaluated to be 0.036 ng ml⁻¹ and generally the data (n=10) had percentage relative standard deviation (%RSD) of less than 4%. These findings indicate that the double-imprinted polymer has potential to be used as an efficient extraction material for the selective pre-concentration of mercury(lI) ions in aqueous environments. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2010
Analysis of the anti-cancer activity of novel indigenous algal compounds in breast cancer: towards the development of a model for screening anti-cancer stem cell activity
- Authors: Lawson, Jessica Clair
- Date: 2010
- Subjects: Breast -- Cancer , Breast -- Cancer -- Chemotherapy , Breast -- Cancer -- Treatment , Red algae , Brown algae , Algae -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3925 , http://hdl.handle.net/10962/d1003984 , Breast -- Cancer , Breast -- Cancer -- Chemotherapy , Breast -- Cancer -- Treatment , Red algae , Brown algae , Algae -- Biotechnology
- Description: Breast cancer, the most common malignancy diagnosed in women, is one of the leading causes of death in women worldwide. In South Africa only 32% of women diagnosed with advanced breast cancer survive more than five years. The search for new chemotherapeutic agents capable of effectively treating breast cancer is therefore essential. Recent evidence supporting the cancer stem cell theory of cancer development for breast cancer challenges the current theories of cancer development and hence treatment. Cancer stem cells are a small subpopulation of tumour cells that possess properties of both cancer cells and stem cells and are believed to be the tumour-initiating population of many cancers. Cancer stem cells are inherently resistant to many chemotherapeutic agents and in this way have been associated with repopulation of tumours after chemotherapy. This phenomenon is proposed as a possible mechanism for cancer relapse after treatment. Cancer stem cells have also been implicated in metastasis, the major cause of mortality in cancer patients. Therefore, any treatment that is capable of targeting and removing breast cancer stem cells may have the theoretical potential to effectively treat breast cancer. However, there are currently no such treatments available for clinical use. We were provided access to a library of novel indigenous small molecules isolated from red and brown algae found off the Eastern Cape of South Africa. The aim of this project was to analyse the anti-cancer and anti-cancer stem cell properties of the compounds in this library and to identify „hit‟ compounds which could form the basis for future development into new anti-cancer drugs. Ten novel compounds of algal origin were tested for cytotoxicity, by determining their ability to inhibit the growth of MCF12A breast epithelial cells and MCF7 breast cancer cells using the colorimetric MTT [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] cell proliferation assay. All but one of the compounds tested exhibited cytotoxicity towards the MCF7 cancer cell line, with IC50 values (the concentration of the compound that leads to a 50% inhibition in cell growth) of between 3 μM and 90 μM. The chemotherapeutic drug paclitaxel was used as a positive control. Four of the compounds (RUMB-001, RUMB-002, RUMB-007 and RUMB-010/saragaquinoic acid) were significantly more toxic to the MCF7 cancer cell line, than the „normal‟ MCF12A breast cells and were selected as priority compounds for further analyses. In addition, two other compounds were selected as priority compounds, one highly cytotoxic towards both MCF12A and MCF7 cell lines (RUMB-015) and one which was non toxic to either cell line (RUMB-017/018). Preliminary studies into the mechanism of cytotoxicity using Western blot analysis for poly (ADP-ribose) polymerase (PARP) cleavage and Hoechst 33342 immunostaining in MCF-7 cells were largely unsuccessful. The Hoechst 33342 immunostaining assay did provide tentative evidence that selected priority compounds were capable of inducing apoptosis, although these assays will need to be repeated using a less subjective assay to confirm the results. The priority compounds were subsequently investigated for their cytotoxic effect on the cancer stem cell-enriched side population in MCF7 cells. The ability of the priority compounds to selectively target the cancer stem cell containing side population was assessed using two complementary flow cytometry-based techniques – namely the Hoechst 33342-exclusion assay, and fluorescent immunostaining for the expression of the putative cancer stem cell marker, ABCG2+. The ABCG2+ staining assay was a novel technique developed during the course of this study. It remains to be fully validated, but it may provide a new and reliable way to identify and analyse cancer stem cell containing side population cells. The MCF7 cells were treated with the compounds and the proportion of putative cancer stem cells compared with the size of the population in untreated cells was assessed. Three compounds (RUMB-010, RUMB-015 and RUMB-017/018) capable of reducing the proportion of side population cells within the MCF7 cell line were identified. Taking these data together, we identified two potential „hit‟ compounds which should be prioritised for future research. These are compounds RUMB-010/sargaquinoic acid and RUMB-017/018. RUMB-010 is of interest as it was shown to target the putative cancer stem cell population, in addition to the bulk MCF7 tumour line, but was relatively less toxic to the „normal‟ MCF12A cell line. RUMB-017/018 is of interest due to the ability to selectively target the cancer stem cell enriched side population, while having little effect on the normal (MCF12A) or bulk tumour (MCF7) cell lines tested. These compounds will be important as „hit‟ compounds for drug development and as tool compounds to study cancer and cancer stem cell biology.
- Full Text:
- Date Issued: 2010
- Authors: Lawson, Jessica Clair
- Date: 2010
- Subjects: Breast -- Cancer , Breast -- Cancer -- Chemotherapy , Breast -- Cancer -- Treatment , Red algae , Brown algae , Algae -- Biotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3925 , http://hdl.handle.net/10962/d1003984 , Breast -- Cancer , Breast -- Cancer -- Chemotherapy , Breast -- Cancer -- Treatment , Red algae , Brown algae , Algae -- Biotechnology
- Description: Breast cancer, the most common malignancy diagnosed in women, is one of the leading causes of death in women worldwide. In South Africa only 32% of women diagnosed with advanced breast cancer survive more than five years. The search for new chemotherapeutic agents capable of effectively treating breast cancer is therefore essential. Recent evidence supporting the cancer stem cell theory of cancer development for breast cancer challenges the current theories of cancer development and hence treatment. Cancer stem cells are a small subpopulation of tumour cells that possess properties of both cancer cells and stem cells and are believed to be the tumour-initiating population of many cancers. Cancer stem cells are inherently resistant to many chemotherapeutic agents and in this way have been associated with repopulation of tumours after chemotherapy. This phenomenon is proposed as a possible mechanism for cancer relapse after treatment. Cancer stem cells have also been implicated in metastasis, the major cause of mortality in cancer patients. Therefore, any treatment that is capable of targeting and removing breast cancer stem cells may have the theoretical potential to effectively treat breast cancer. However, there are currently no such treatments available for clinical use. We were provided access to a library of novel indigenous small molecules isolated from red and brown algae found off the Eastern Cape of South Africa. The aim of this project was to analyse the anti-cancer and anti-cancer stem cell properties of the compounds in this library and to identify „hit‟ compounds which could form the basis for future development into new anti-cancer drugs. Ten novel compounds of algal origin were tested for cytotoxicity, by determining their ability to inhibit the growth of MCF12A breast epithelial cells and MCF7 breast cancer cells using the colorimetric MTT [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] cell proliferation assay. All but one of the compounds tested exhibited cytotoxicity towards the MCF7 cancer cell line, with IC50 values (the concentration of the compound that leads to a 50% inhibition in cell growth) of between 3 μM and 90 μM. The chemotherapeutic drug paclitaxel was used as a positive control. Four of the compounds (RUMB-001, RUMB-002, RUMB-007 and RUMB-010/saragaquinoic acid) were significantly more toxic to the MCF7 cancer cell line, than the „normal‟ MCF12A breast cells and were selected as priority compounds for further analyses. In addition, two other compounds were selected as priority compounds, one highly cytotoxic towards both MCF12A and MCF7 cell lines (RUMB-015) and one which was non toxic to either cell line (RUMB-017/018). Preliminary studies into the mechanism of cytotoxicity using Western blot analysis for poly (ADP-ribose) polymerase (PARP) cleavage and Hoechst 33342 immunostaining in MCF-7 cells were largely unsuccessful. The Hoechst 33342 immunostaining assay did provide tentative evidence that selected priority compounds were capable of inducing apoptosis, although these assays will need to be repeated using a less subjective assay to confirm the results. The priority compounds were subsequently investigated for their cytotoxic effect on the cancer stem cell-enriched side population in MCF7 cells. The ability of the priority compounds to selectively target the cancer stem cell containing side population was assessed using two complementary flow cytometry-based techniques – namely the Hoechst 33342-exclusion assay, and fluorescent immunostaining for the expression of the putative cancer stem cell marker, ABCG2+. The ABCG2+ staining assay was a novel technique developed during the course of this study. It remains to be fully validated, but it may provide a new and reliable way to identify and analyse cancer stem cell containing side population cells. The MCF7 cells were treated with the compounds and the proportion of putative cancer stem cells compared with the size of the population in untreated cells was assessed. Three compounds (RUMB-010, RUMB-015 and RUMB-017/018) capable of reducing the proportion of side population cells within the MCF7 cell line were identified. Taking these data together, we identified two potential „hit‟ compounds which should be prioritised for future research. These are compounds RUMB-010/sargaquinoic acid and RUMB-017/018. RUMB-010 is of interest as it was shown to target the putative cancer stem cell population, in addition to the bulk MCF7 tumour line, but was relatively less toxic to the „normal‟ MCF12A cell line. RUMB-017/018 is of interest due to the ability to selectively target the cancer stem cell enriched side population, while having little effect on the normal (MCF12A) or bulk tumour (MCF7) cell lines tested. These compounds will be important as „hit‟ compounds for drug development and as tool compounds to study cancer and cancer stem cell biology.
- Full Text:
- Date Issued: 2010
Application of multiserver queueing to call centres
- Authors: Majakwara, Jacob
- Date: 2010
- Subjects: Call centers , ERLANG (Computer program language) , Queuing theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5578 , http://hdl.handle.net/10962/d1015461
- Description: The simplest and most widely used queueing model in call centres is the M/M/k system, sometimes referred to as Erlang-C. For many applications the model is an over-simplification. Erlang-C model ignores among other things busy signals, customer impatience and services that span multiple visits. Although the Erlang-C formula is easily implemented, it is not easy to obtain insight from its answers (for example, to find an approximate answer to questions such as "how many additional agents do I need if the arrival rate doubles?"). An approximation of the Erlang-C formula that gives structural insight into this type of question would be of use to better understand economies of scale in call centre operations. Erlang-C based predictions can also turn out highly inaccurate because of violations of underlying assumptions and these violations are not straightforward to model. For example, non-exponential service times lead one to the M/G/k queue which, in stark contrast to the M/M/k system, is difficult to analyse. This thesis deals mainly with the general M/GI/k model with abandonment. The arrival process conforms to a Poisson process, service durations are independent and identically distributed with a general distribution, there are k servers, and independent and identically distributed customer abandoning times with a general distribution. This thesis will endeavour to analyse call centres using M/GI/k model with abandonment and the data to be used will be simulated using EZSIM-software. The paper by Brown et al. [3] entitled "Statistical Analysis of a Telephone Call Centre: A Queueing-Science Perspective," will be the basis upon which this thesis is built.
- Full Text:
- Date Issued: 2010
- Authors: Majakwara, Jacob
- Date: 2010
- Subjects: Call centers , ERLANG (Computer program language) , Queuing theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5578 , http://hdl.handle.net/10962/d1015461
- Description: The simplest and most widely used queueing model in call centres is the M/M/k system, sometimes referred to as Erlang-C. For many applications the model is an over-simplification. Erlang-C model ignores among other things busy signals, customer impatience and services that span multiple visits. Although the Erlang-C formula is easily implemented, it is not easy to obtain insight from its answers (for example, to find an approximate answer to questions such as "how many additional agents do I need if the arrival rate doubles?"). An approximation of the Erlang-C formula that gives structural insight into this type of question would be of use to better understand economies of scale in call centre operations. Erlang-C based predictions can also turn out highly inaccurate because of violations of underlying assumptions and these violations are not straightforward to model. For example, non-exponential service times lead one to the M/G/k queue which, in stark contrast to the M/M/k system, is difficult to analyse. This thesis deals mainly with the general M/GI/k model with abandonment. The arrival process conforms to a Poisson process, service durations are independent and identically distributed with a general distribution, there are k servers, and independent and identically distributed customer abandoning times with a general distribution. This thesis will endeavour to analyse call centres using M/GI/k model with abandonment and the data to be used will be simulated using EZSIM-software. The paper by Brown et al. [3] entitled "Statistical Analysis of a Telephone Call Centre: A Queueing-Science Perspective," will be the basis upon which this thesis is built.
- Full Text:
- Date Issued: 2010
Artificial neural networks as simulators for behavioural evolution in evolutionary robotics
- Pretorius, Christiaan Johannes
- Authors: Pretorius, Christiaan Johannes
- Date: 2010
- Subjects: Neural networks (Computer science) , Robotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10462 , http://hdl.handle.net/10948/1476 , Neural networks (Computer science) , Robotics
- Description: Robotic simulators for use in Evolutionary Robotics (ER) have certain challenges associated with the complexity of their construction and the accuracy of predictions made by these simulators. Such robotic simulators are often based on physics models, which have been shown to produce accurate results. However, the construction of physics-based simulators can be complex and time-consuming. Alternative simulation schemes construct robotic simulators from empirically-collected data. Such empirical simulators, however, also have associated challenges, such as that some of these simulators do not generalize well on the data from which they are constructed, as these models employ simple interpolation on said data. As a result of the identified challenges in existing robotic simulators for use in ER, this project investigates the potential use of Artificial Neural Networks, henceforth simply referred to as Neural Networks (NNs), as alternative robotic simulators. In contrast to physics models, NN-based simulators can be constructed without needing an explicit mathematical model of the system being modeled, which can simplify simulator development. Furthermore, the generalization capabilities of NNs suggest that NNs could generalize well on data from which these simulators are constructed. These generalization abilities of NNs, along with NNs’ noise tolerance, suggest that NNs could be well-suited to application in robotics simulation. Investigating whether NNs can be effectively used as robotic simulators in ER is thus the endeavour of this work. Since not much research has been done in employing NNs as robotic simulators, many aspects of the experimental framework on which this dissertation reports needed to be carefully decided upon. Two robot morphologies were selected on which the NN simulators created in this work were based, namely a differentially steered robot and an inverted pendulum robot. Motion tracking and robotic sensor logging were used to acquire data from which the NN simulators were constructed. Furthermore, custom code was written for almost all aspects of the study, namely data acquisition for NN training, the actual NN training process, the evolution of robotic controllers using the created NN simulators, as well as the onboard robotic implementations of evolved controllers. Experimental tests performed in order to determine ideal topologies for each of the NN simulators developed in this study indicated that different NN topologies can lead to large differences in training accuracy. After performing these tests, the training accuracy of the created simulators was analyzed. This analysis showed that the NN simulators generally trained well and could generalize well on data not presented during simulator construction. In order to validate the feasibility of the created NN simulators in the ER process, these simulators were subsequently used to evolve controllers in simulation, similar to controllers developed in related studies. Encouraging results were obtained, with the newly-evolved controllers allowing real-world experimental robots to exhibit obstacle avoidance and light-approaching behaviour with a reasonable degree of success. The created NN simulators furthermore allowed for the successful evolution of a complex inverted pendulum stabilization controller in simulation. It was thus clearly established that NN-based robotic simulators can be successfully employed as alternative simulation schemes in the ER process.
- Full Text:
- Date Issued: 2010
- Authors: Pretorius, Christiaan Johannes
- Date: 2010
- Subjects: Neural networks (Computer science) , Robotics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10462 , http://hdl.handle.net/10948/1476 , Neural networks (Computer science) , Robotics
- Description: Robotic simulators for use in Evolutionary Robotics (ER) have certain challenges associated with the complexity of their construction and the accuracy of predictions made by these simulators. Such robotic simulators are often based on physics models, which have been shown to produce accurate results. However, the construction of physics-based simulators can be complex and time-consuming. Alternative simulation schemes construct robotic simulators from empirically-collected data. Such empirical simulators, however, also have associated challenges, such as that some of these simulators do not generalize well on the data from which they are constructed, as these models employ simple interpolation on said data. As a result of the identified challenges in existing robotic simulators for use in ER, this project investigates the potential use of Artificial Neural Networks, henceforth simply referred to as Neural Networks (NNs), as alternative robotic simulators. In contrast to physics models, NN-based simulators can be constructed without needing an explicit mathematical model of the system being modeled, which can simplify simulator development. Furthermore, the generalization capabilities of NNs suggest that NNs could generalize well on data from which these simulators are constructed. These generalization abilities of NNs, along with NNs’ noise tolerance, suggest that NNs could be well-suited to application in robotics simulation. Investigating whether NNs can be effectively used as robotic simulators in ER is thus the endeavour of this work. Since not much research has been done in employing NNs as robotic simulators, many aspects of the experimental framework on which this dissertation reports needed to be carefully decided upon. Two robot morphologies were selected on which the NN simulators created in this work were based, namely a differentially steered robot and an inverted pendulum robot. Motion tracking and robotic sensor logging were used to acquire data from which the NN simulators were constructed. Furthermore, custom code was written for almost all aspects of the study, namely data acquisition for NN training, the actual NN training process, the evolution of robotic controllers using the created NN simulators, as well as the onboard robotic implementations of evolved controllers. Experimental tests performed in order to determine ideal topologies for each of the NN simulators developed in this study indicated that different NN topologies can lead to large differences in training accuracy. After performing these tests, the training accuracy of the created simulators was analyzed. This analysis showed that the NN simulators generally trained well and could generalize well on data not presented during simulator construction. In order to validate the feasibility of the created NN simulators in the ER process, these simulators were subsequently used to evolve controllers in simulation, similar to controllers developed in related studies. Encouraging results were obtained, with the newly-evolved controllers allowing real-world experimental robots to exhibit obstacle avoidance and light-approaching behaviour with a reasonable degree of success. The created NN simulators furthermore allowed for the successful evolution of a complex inverted pendulum stabilization controller in simulation. It was thus clearly established that NN-based robotic simulators can be successfully employed as alternative simulation schemes in the ER process.
- Full Text:
- Date Issued: 2010
Assessing the diet of the Cape leopard (panthera pardus) in the Cederberg and Gamka mountains, South Africa
- Authors: Rautenbach, Therèsè
- Date: 2010
- Subjects: Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10699 , http://hdl.handle.net/10948/1078 , Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Description: As limited prey availability and persecution by humans in response to livestock predation are key conservation concerns for the Cape leopard (Martins & Martins 2006), the present study aimed to provide more information regarding their feeding habits. The first objective was to determine whether the Cape leopard was subject to a change in their prey base and how they responded to the change. This was established by comparison of their current diet in the Cederberg and Gamka Mountains, determined by using scat analysis techniques, with a previous dietary assessment (Norton et al. 1986). The second aim was to provide a preliminary assessment of the prey preference of the Cape leopard and examine the utility of camera trap surveys to determine leopard prey preference. Leopard diet in the Cederberg and Gamka Mountains consisted largely of small- (1-10 kg) and medium-sized (10-40 kg) mammals; rock hyraxes (Procavia capensis) and klipspringers (Oreotragus oreotragus) were key prey items. In terms of regional variation in leopard diet, there was a significant difference in the average weight of prey utilized in the Cederberg and Gamka Mountains. Despite the importance of prey availability of suitable size, their flexibility in terms of prey size utilization reflected their ability to switch to smaller prey to fulfil their dietary requirements, when prey is limited. The study suggested a dietary shift, with significant variation in prey species utilization in both regions. The shift did not appear to be in response to prey scarcity, but rather a reduction in key prey species, particularly the rock hyrax. The shift involved an increase in the number of species utilized, and only a very small increase in livestock predation in both areas. There was however no significant variation in prey size category utilization. This demonstrated their dietary flexibility, as well as the importance of suitable prey sizes rather than the presence of specific prey species to fulfil their dietary requirements. The camera trap survey revealed a strong correlation between the number of camera trap days and the number of photographs taken of identifiable species. Variation of this correlation between different habitats supported the notion that individual images are a better unit to determine sampling efficiency than trap days. The camera trap survey also showed that small rodent availability was underestimated by camera trap surveillance, which resulted in poor prey preference estimation. It was therefore suggested that camera trap surveys be restricted to the surveillance of larger prey species (> 1 kg). By excluding small rodents from the analysis, prey preference could be estimated for other species and prey size categories. Small- and medium-sized mammals were significantly preferred, whereas large mammals were significantly avoided by the Cape leopard.
- Full Text:
- Date Issued: 2010
- Authors: Rautenbach, Therèsè
- Date: 2010
- Subjects: Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10699 , http://hdl.handle.net/10948/1078 , Leopard -- South Africa , Animal feeding -- South Africa , Predation (Biology)
- Description: As limited prey availability and persecution by humans in response to livestock predation are key conservation concerns for the Cape leopard (Martins & Martins 2006), the present study aimed to provide more information regarding their feeding habits. The first objective was to determine whether the Cape leopard was subject to a change in their prey base and how they responded to the change. This was established by comparison of their current diet in the Cederberg and Gamka Mountains, determined by using scat analysis techniques, with a previous dietary assessment (Norton et al. 1986). The second aim was to provide a preliminary assessment of the prey preference of the Cape leopard and examine the utility of camera trap surveys to determine leopard prey preference. Leopard diet in the Cederberg and Gamka Mountains consisted largely of small- (1-10 kg) and medium-sized (10-40 kg) mammals; rock hyraxes (Procavia capensis) and klipspringers (Oreotragus oreotragus) were key prey items. In terms of regional variation in leopard diet, there was a significant difference in the average weight of prey utilized in the Cederberg and Gamka Mountains. Despite the importance of prey availability of suitable size, their flexibility in terms of prey size utilization reflected their ability to switch to smaller prey to fulfil their dietary requirements, when prey is limited. The study suggested a dietary shift, with significant variation in prey species utilization in both regions. The shift did not appear to be in response to prey scarcity, but rather a reduction in key prey species, particularly the rock hyrax. The shift involved an increase in the number of species utilized, and only a very small increase in livestock predation in both areas. There was however no significant variation in prey size category utilization. This demonstrated their dietary flexibility, as well as the importance of suitable prey sizes rather than the presence of specific prey species to fulfil their dietary requirements. The camera trap survey revealed a strong correlation between the number of camera trap days and the number of photographs taken of identifiable species. Variation of this correlation between different habitats supported the notion that individual images are a better unit to determine sampling efficiency than trap days. The camera trap survey also showed that small rodent availability was underestimated by camera trap surveillance, which resulted in poor prey preference estimation. It was therefore suggested that camera trap surveys be restricted to the surveillance of larger prey species (> 1 kg). By excluding small rodents from the analysis, prey preference could be estimated for other species and prey size categories. Small- and medium-sized mammals were significantly preferred, whereas large mammals were significantly avoided by the Cape leopard.
- Full Text:
- Date Issued: 2010
Bioaccumulation and ecotoxicology of b-methylamino-l-alanine (BMAA) in model crop plants
- Niyonzima, Francois Niyongabo
- Authors: Niyonzima, Francois Niyongabo
- Date: 2010
- Subjects: Cyanobacteria , Environmental toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10312 , http://hdl.handle.net/10948/1475 , Cyanobacteria , Environmental toxicology
- Description: Cyanobacteria are known to produce a variety of toxic compounds. β-N-methylamino-L-alanine (BMAA) is one of the neurotoxins produced by most cyanobacteria. BMAA has been implicated in amyotrophic lateral sclerosis / Parkinsonism dementia complex (ALS / PDC) and was suggested to contribute to this pathology after biomagnification and slow release of BMAA from a protein associated form. The uptake and accumulation of BMAA by the aquatic macrophyte Ceratophyllum demersum has recently been shown, but the consumption of aquatic macrophytes by humans is not typical. The uptake by, and accumulation in, crop plants (Nasturtium officinale and Daucus carota) was therefore investigated so as to establish the existence of any risk to humans from the consumption of plants irrigated with water from dams with high cyanobacterial biomass and therefore high BMAA levels. After the exposure to the BMAA through the growth medium, BMAA had no effect on growth and development of N. officinale and D. carota. The uptake and bioaccumulation of BMAA was observed in N. officinale and D. carota, and was found to be concentration-dependent. Both free and bound cellular BMAA was detected following BMAA exposure through the growth medium. The photosynthetic apparatus of N. officinale was not significantly damaged. The uptake and accumulation of BMAA in edible terrestrial plants may constitute another route of human exposure to BMAA; it may now be prudent to avoid spray irrigation of edible plants with waters from dams with high cyanobacterial biomass and therefore high BMAA levels. After uptake by plants, the cyanotoxins may induce oxidative stress. A recent study showed that BMAA has a significant inhibitory effect on the oxidative stress enzymes in C. demersum. Therefore, the toxicological effects on selected plants were investigated by a range of biochemical enzyme assays in order to establish the plant stress response to exogenous BMAA. The inhibition of antioxidant enzymes upon exposure of N. officinale to BMAA through the growth medium was observed. The inhibition of antioxidant defence enzymes by BMAA correlated with the BMAA bioaccumulation in N. officinale. Further investigations are needed to analyze the uptake, accumulation, and ecotoxicology of BMAA in other crop plants, and to examine the fate of BMAA in these plants particularly its distribution and metabolism.
- Full Text:
- Date Issued: 2010
- Authors: Niyonzima, Francois Niyongabo
- Date: 2010
- Subjects: Cyanobacteria , Environmental toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10312 , http://hdl.handle.net/10948/1475 , Cyanobacteria , Environmental toxicology
- Description: Cyanobacteria are known to produce a variety of toxic compounds. β-N-methylamino-L-alanine (BMAA) is one of the neurotoxins produced by most cyanobacteria. BMAA has been implicated in amyotrophic lateral sclerosis / Parkinsonism dementia complex (ALS / PDC) and was suggested to contribute to this pathology after biomagnification and slow release of BMAA from a protein associated form. The uptake and accumulation of BMAA by the aquatic macrophyte Ceratophyllum demersum has recently been shown, but the consumption of aquatic macrophytes by humans is not typical. The uptake by, and accumulation in, crop plants (Nasturtium officinale and Daucus carota) was therefore investigated so as to establish the existence of any risk to humans from the consumption of plants irrigated with water from dams with high cyanobacterial biomass and therefore high BMAA levels. After the exposure to the BMAA through the growth medium, BMAA had no effect on growth and development of N. officinale and D. carota. The uptake and bioaccumulation of BMAA was observed in N. officinale and D. carota, and was found to be concentration-dependent. Both free and bound cellular BMAA was detected following BMAA exposure through the growth medium. The photosynthetic apparatus of N. officinale was not significantly damaged. The uptake and accumulation of BMAA in edible terrestrial plants may constitute another route of human exposure to BMAA; it may now be prudent to avoid spray irrigation of edible plants with waters from dams with high cyanobacterial biomass and therefore high BMAA levels. After uptake by plants, the cyanotoxins may induce oxidative stress. A recent study showed that BMAA has a significant inhibitory effect on the oxidative stress enzymes in C. demersum. Therefore, the toxicological effects on selected plants were investigated by a range of biochemical enzyme assays in order to establish the plant stress response to exogenous BMAA. The inhibition of antioxidant enzymes upon exposure of N. officinale to BMAA through the growth medium was observed. The inhibition of antioxidant defence enzymes by BMAA correlated with the BMAA bioaccumulation in N. officinale. Further investigations are needed to analyze the uptake, accumulation, and ecotoxicology of BMAA in other crop plants, and to examine the fate of BMAA in these plants particularly its distribution and metabolism.
- Full Text:
- Date Issued: 2010
Bioethanol production from waste paper through fungal biotechnology
- Authors: Voigt, Paul George
- Date: 2010
- Subjects: Biomass energy , Cellulose -- Biodegradation , Waste paper -- Recycling , Biomass chemicals -- Economic aspects , Renewable energy sources , Fungi -- Biotechnology , Enzymes -- Biotechnology
- Language: English
- Type: Thesis , MSc , Masters
- Identifier: vital:3861 , http://hdl.handle.net/10962/d1013447
- Description: Bioethanol is likely to be a large contributor to the fuel sector of industry in the near future. Current research trends are geared towards utilizing food crops as substrate for bioethanol fermentation; however, this is the source of much controversy. Utilizing food crops for fuel purposes is anticipated to cause massive food shortages worldwide. Cellulose is the most abundant renewable resource on earth and is subject to a wide array of scientific study in order to utilize the glucose contained within it. Waste paper has a high degree of cellulose associated with it, which makes it an ideal target for cellulose biotechnology with the ultimate end goal of bioethanol production. This study focussed on producing the necessary enzymes to hydrolyse the cellulose found in waste paper and using the sugars produced to produce ethanol. The effects of various printing inks had on the production of sugars and the total envirorunental impact of the effluents produced during the production line were also examined. It was found that the fungus Trichoderma longibrachiatum DSM 769 grown in Mandel's medium with waste newspaper as the sole carbon source at 28 °C for 6 days produced extracellular cellulase enzymes with an activity of 0.203 ± 0.009 FPU.ml⁻¹, significantly higher activity as compared to other paper sources. This extracellular cellulase was used to hydrolyse waste newspaper and office paper, with office paper yielding the highest degree of sugar production with an end concentration of 5.80 ± 0.19 g/1 at 40 °C. Analysis by HPLC showed that although glucose was the major product at 4.35 ± 0.12 g/1, cellobiose was also produced in appreciable amounts (1.97 ± 0.71 g/1). The sugar solution was used as a substrate for Saccharomyces cerevisiae DSM 1333 and ethanol was produced at a level of 1.79 ± 0.26 g/1, the presence of which was confirmed by a 600 MHz NMR spectrum. It was found that cellobiose was not fermented by this strain of S. cerevisiae. Certain components of inks (the PAHs phenanthrene and naphthalene) were found to have a slight inhibitory effect (approximately 15% decrease) on the cellulase enzymes at very high concentrations (approximately 600 μg/1 in aqueous medium), while anthracene had no effect. Whole newsprint ink was shown not to sorb glucose. The environmental analysis of the effluents produced showed that in order for the effluents to be discharged into an aqueous ecosystem they would have to be diluted up to 200 times. They were also shown to have the potential to cause severe machinery damage if reused without proper treatment.
- Full Text:
- Date Issued: 2010
- Authors: Voigt, Paul George
- Date: 2010
- Subjects: Biomass energy , Cellulose -- Biodegradation , Waste paper -- Recycling , Biomass chemicals -- Economic aspects , Renewable energy sources , Fungi -- Biotechnology , Enzymes -- Biotechnology
- Language: English
- Type: Thesis , MSc , Masters
- Identifier: vital:3861 , http://hdl.handle.net/10962/d1013447
- Description: Bioethanol is likely to be a large contributor to the fuel sector of industry in the near future. Current research trends are geared towards utilizing food crops as substrate for bioethanol fermentation; however, this is the source of much controversy. Utilizing food crops for fuel purposes is anticipated to cause massive food shortages worldwide. Cellulose is the most abundant renewable resource on earth and is subject to a wide array of scientific study in order to utilize the glucose contained within it. Waste paper has a high degree of cellulose associated with it, which makes it an ideal target for cellulose biotechnology with the ultimate end goal of bioethanol production. This study focussed on producing the necessary enzymes to hydrolyse the cellulose found in waste paper and using the sugars produced to produce ethanol. The effects of various printing inks had on the production of sugars and the total envirorunental impact of the effluents produced during the production line were also examined. It was found that the fungus Trichoderma longibrachiatum DSM 769 grown in Mandel's medium with waste newspaper as the sole carbon source at 28 °C for 6 days produced extracellular cellulase enzymes with an activity of 0.203 ± 0.009 FPU.ml⁻¹, significantly higher activity as compared to other paper sources. This extracellular cellulase was used to hydrolyse waste newspaper and office paper, with office paper yielding the highest degree of sugar production with an end concentration of 5.80 ± 0.19 g/1 at 40 °C. Analysis by HPLC showed that although glucose was the major product at 4.35 ± 0.12 g/1, cellobiose was also produced in appreciable amounts (1.97 ± 0.71 g/1). The sugar solution was used as a substrate for Saccharomyces cerevisiae DSM 1333 and ethanol was produced at a level of 1.79 ± 0.26 g/1, the presence of which was confirmed by a 600 MHz NMR spectrum. It was found that cellobiose was not fermented by this strain of S. cerevisiae. Certain components of inks (the PAHs phenanthrene and naphthalene) were found to have a slight inhibitory effect (approximately 15% decrease) on the cellulase enzymes at very high concentrations (approximately 600 μg/1 in aqueous medium), while anthracene had no effect. Whole newsprint ink was shown not to sorb glucose. The environmental analysis of the effluents produced showed that in order for the effluents to be discharged into an aqueous ecosystem they would have to be diluted up to 200 times. They were also shown to have the potential to cause severe machinery damage if reused without proper treatment.
- Full Text:
- Date Issued: 2010
Brood cycles in queenless colonies of Apis mellifera capensis
- Authors: Crous, Kendall Lauren
- Date: 2010
- Subjects: Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5652 , http://hdl.handle.net/10962/d1005335 , Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Description: In a honeybee colony, the loss of a queen is considered to be a serious occurrence and, if a new queen is not produced, ultimately doomed. However, in colonies of Apis mellifera capensis (Cape honeybees), numerous pathways are available for a colony which unexpectedly losses a queen. At the onset of this experiment, four colonies of A. m. capensis were dequeened. Following this photographs of all brood frames in each colony were taken and the contents of the cells analysed. Cells were chosen at random but once selected were repeatedly analysed for the duration of the experiment. The contents of a total of 44 888 individual cells were analysed. Any queen cells constructed during the sampling period were removed, maintaining a queenless state. In each colony, as predicted, the removal of the queen evoked a variety of responses in an attempt to rectify the sudden loss. However, ultimately three of the four colonies absconded, leaving little by way of stores. Three of the four colonies initially attempted to rear a new queen while one colony was immediately invaded by a presumed foreign queen and hence any attempt at queen cell construction ceased. An increased number of queen cells in the swarm position were recorded in all colonies. The invasion of a colony by a foreign queen was considered to be a new pathway available for queenless colonies of A.m capensis. Worker policing and suspected brood cannibalism was prevalent in all sampled colonies yet in addition, the transfer of eggs and larvae from cell to cell was also observed which may have increased the suspected cases of policing and cannibalism. It was unclear whether an egg or larva had been consumed or simply moved to another cell on the brood frame. All colonies contained eggs from laying workers to varying degrees, based on the length of each individual sampling period which varied between colonies due to differences in absconding dates. A steady breakdown in the effectiveness of the division of labour amongst the worker bees was observed in each of the colonies highlighting the vital role of a queen. This breakdown was clearly seen in the reduction in general housekeeping within a colony. An increase in stores indicated a possible increase in the number of forager bees, thereby reducing the number of worker bees available for other duties. Pathways available to broodright colonies and strategies used following sudden queen loss are discussed.
- Full Text:
- Date Issued: 2010
- Authors: Crous, Kendall Lauren
- Date: 2010
- Subjects: Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5652 , http://hdl.handle.net/10962/d1005335 , Cape honeybee , Bee culture -- Queen rearing , Bees -- Breeding
- Description: In a honeybee colony, the loss of a queen is considered to be a serious occurrence and, if a new queen is not produced, ultimately doomed. However, in colonies of Apis mellifera capensis (Cape honeybees), numerous pathways are available for a colony which unexpectedly losses a queen. At the onset of this experiment, four colonies of A. m. capensis were dequeened. Following this photographs of all brood frames in each colony were taken and the contents of the cells analysed. Cells were chosen at random but once selected were repeatedly analysed for the duration of the experiment. The contents of a total of 44 888 individual cells were analysed. Any queen cells constructed during the sampling period were removed, maintaining a queenless state. In each colony, as predicted, the removal of the queen evoked a variety of responses in an attempt to rectify the sudden loss. However, ultimately three of the four colonies absconded, leaving little by way of stores. Three of the four colonies initially attempted to rear a new queen while one colony was immediately invaded by a presumed foreign queen and hence any attempt at queen cell construction ceased. An increased number of queen cells in the swarm position were recorded in all colonies. The invasion of a colony by a foreign queen was considered to be a new pathway available for queenless colonies of A.m capensis. Worker policing and suspected brood cannibalism was prevalent in all sampled colonies yet in addition, the transfer of eggs and larvae from cell to cell was also observed which may have increased the suspected cases of policing and cannibalism. It was unclear whether an egg or larva had been consumed or simply moved to another cell on the brood frame. All colonies contained eggs from laying workers to varying degrees, based on the length of each individual sampling period which varied between colonies due to differences in absconding dates. A steady breakdown in the effectiveness of the division of labour amongst the worker bees was observed in each of the colonies highlighting the vital role of a queen. This breakdown was clearly seen in the reduction in general housekeeping within a colony. An increase in stores indicated a possible increase in the number of forager bees, thereby reducing the number of worker bees available for other duties. Pathways available to broodright colonies and strategies used following sudden queen loss are discussed.
- Full Text:
- Date Issued: 2010
Collaborative monitoring in ecosystem management in South Africa's communal lands
- Authors: Bolus, Cosman
- Date: 2010
- Subjects: Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4743 , http://hdl.handle.net/10962/d1006948 , Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Description: Internationally there is an increasing focus on involving local communities in natural resource management and monitoring. Monitoring methods which are professionally driven appear to be inadequate to deal with the monitoring of natural resource use and biodiversity conservation, globally. This is especially evident in areas such as South African rural communal land. Two community based natural resource management (CBNRM) programmes in areas which are communally governed in the Eastern Cape, South Africa, namely Nqabara and Machubeni, were used as part of this research study. This thesis identified and tested potentially simple and cost effective monitoring methods related to the utilization of the local rangelands and indigenous forests. The criteria that were tested include 1) appropriateness and effectiveness in measuring change, and 2) contribution to building adaptive capacity among local land managers through learning. The criteria were assessed using a scoring system for each monitoring method in order to evaluate their strengths and weaknesses . This was done by using both quantitative and qualitative data. Contribution to building adaptive capacity was assessed by evaluating technical capacity gained, local ecological knowledge contributed and learning by participants. This was done using qualitative data. The results show that the monitoring methods had different strengths and weaknesses in relation to the criteria, making them more appropriate for different priorities such as effectively measuring change or building adaptive capacity. It is argued that an adaptive approach is a useful component in the participatory monitoring process. An adaptive framework was developed from lessons learnt in this study for collaborative monitoring. Challenges such as low literacy levels and adequate training still need to be addressed to strengthen efforts towards participatory monitoring. Factors such as incentives, conflict and local values may negatively affect the legitimacy and sustainability of participatory monitoring and therefore also need to be addressed.
- Full Text:
- Date Issued: 2010
- Authors: Bolus, Cosman
- Date: 2010
- Subjects: Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4743 , http://hdl.handle.net/10962/d1006948 , Conservation of natural resources -- South Africa , Natural resources -- South Africa -- Management , Community development -- South Africa -- Citizen participation , Conservation of natural resources -- Social aspects -- South Africa
- Description: Internationally there is an increasing focus on involving local communities in natural resource management and monitoring. Monitoring methods which are professionally driven appear to be inadequate to deal with the monitoring of natural resource use and biodiversity conservation, globally. This is especially evident in areas such as South African rural communal land. Two community based natural resource management (CBNRM) programmes in areas which are communally governed in the Eastern Cape, South Africa, namely Nqabara and Machubeni, were used as part of this research study. This thesis identified and tested potentially simple and cost effective monitoring methods related to the utilization of the local rangelands and indigenous forests. The criteria that were tested include 1) appropriateness and effectiveness in measuring change, and 2) contribution to building adaptive capacity among local land managers through learning. The criteria were assessed using a scoring system for each monitoring method in order to evaluate their strengths and weaknesses . This was done by using both quantitative and qualitative data. Contribution to building adaptive capacity was assessed by evaluating technical capacity gained, local ecological knowledge contributed and learning by participants. This was done using qualitative data. The results show that the monitoring methods had different strengths and weaknesses in relation to the criteria, making them more appropriate for different priorities such as effectively measuring change or building adaptive capacity. It is argued that an adaptive approach is a useful component in the participatory monitoring process. An adaptive framework was developed from lessons learnt in this study for collaborative monitoring. Challenges such as low literacy levels and adequate training still need to be addressed to strengthen efforts towards participatory monitoring. Factors such as incentives, conflict and local values may negatively affect the legitimacy and sustainability of participatory monitoring and therefore also need to be addressed.
- Full Text:
- Date Issued: 2010
Comparison of A₄ neutrino mass models
- Barry, James Munnik Hamilton
- Authors: Barry, James Munnik Hamilton
- Date: 2010
- Subjects: Neutrinos -- Mass , Standard model (Nuclear physics) , Particles (Nuclear physics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5554 , http://hdl.handle.net/10962/d1015271
- Description: The present neutrino oscillation data are compatible with tri-bimaximal mixing, to leading order. The addition of an A₄ family symmetry and extended Higgs sector to the Standard Model can generate this mixing pattern, assuming the correct vacuum expectation value alignment of Higgs scalars. The effect of deviating this alignment is studied, for different types of A₄ models, with a phenomenological emphasis: the effect of perturbations on the model predictions for the neutrino oscillation and neutrino mass observables. The standard theoretical description of neutrino oscillations is presented, along with a summary of the past, present and future experimental efforts aimed at measuring the neutrino mixing parameters. Additionally, the current constraints on the sum of absolute neutrino masses and the amplitude for neutrinoless double beta decay, which is yet to be observed, are discussed. These constraints provide a model-independent test of family symmetery models. The Standard Model is reviewed, and extensions to the Standard Model such as the seesaw mechanism(s) are discussed: these are designed to endow neutrinos with mass, and can be incorporated into A₄ symmetry models. Models with different A₄ particle assignments are analysed for deviations from tribimaximal mixing. There are nine models presented in Chapter 5, with lepton doublets transforming as 3 (underlined) and right-handed charged leptons transforming as 1, 1', 1" (all underlined) ; five of these include right-handed neutrinos transforming as 3 (underlined) and make use of the seesaw mechanism. Chapter 6 contains the analysis of six models that assign all leptons to the 3 (underlined) representation, with four of these utilising the seesaw mechanism. The models are tested for any degree of fine tuning of the parameters that define the mass matrices. The effect of perturbations on the mixing angle observables, in particular sin² ∅₁₃ and sin² ∅₂₃, is studied, as well as the effect on the Jarlskog invariant, Jcp. Investigations of the (Mee)- ∑Mv parameter space allow for comparison with current data, and can lead to the possible exclusion of a particular model by constraints from future data.
- Full Text:
- Date Issued: 2010
- Authors: Barry, James Munnik Hamilton
- Date: 2010
- Subjects: Neutrinos -- Mass , Standard model (Nuclear physics) , Particles (Nuclear physics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5554 , http://hdl.handle.net/10962/d1015271
- Description: The present neutrino oscillation data are compatible with tri-bimaximal mixing, to leading order. The addition of an A₄ family symmetry and extended Higgs sector to the Standard Model can generate this mixing pattern, assuming the correct vacuum expectation value alignment of Higgs scalars. The effect of deviating this alignment is studied, for different types of A₄ models, with a phenomenological emphasis: the effect of perturbations on the model predictions for the neutrino oscillation and neutrino mass observables. The standard theoretical description of neutrino oscillations is presented, along with a summary of the past, present and future experimental efforts aimed at measuring the neutrino mixing parameters. Additionally, the current constraints on the sum of absolute neutrino masses and the amplitude for neutrinoless double beta decay, which is yet to be observed, are discussed. These constraints provide a model-independent test of family symmetery models. The Standard Model is reviewed, and extensions to the Standard Model such as the seesaw mechanism(s) are discussed: these are designed to endow neutrinos with mass, and can be incorporated into A₄ symmetry models. Models with different A₄ particle assignments are analysed for deviations from tribimaximal mixing. There are nine models presented in Chapter 5, with lepton doublets transforming as 3 (underlined) and right-handed charged leptons transforming as 1, 1', 1" (all underlined) ; five of these include right-handed neutrinos transforming as 3 (underlined) and make use of the seesaw mechanism. Chapter 6 contains the analysis of six models that assign all leptons to the 3 (underlined) representation, with four of these utilising the seesaw mechanism. The models are tested for any degree of fine tuning of the parameters that define the mass matrices. The effect of perturbations on the mixing angle observables, in particular sin² ∅₁₃ and sin² ∅₂₃, is studied, as well as the effect on the Jarlskog invariant, Jcp. Investigations of the (Mee)- ∑Mv parameter space allow for comparison with current data, and can lead to the possible exclusion of a particular model by constraints from future data.
- Full Text:
- Date Issued: 2010
Comparison of the neuroprotective potential of theanine and minocycline
- Authors: Mpofu, Tariro Ann-Maureen
- Date: 2010 , 2010-09-20
- Subjects: Nervous system -- Degeneration -- Treatment , Tetracyclines , Antibiotics -- Side effects , Theanine -- Evaluation , Drugs -- Administration , Cerebrovascular disease -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3775 , http://hdl.handle.net/10962/d1003253 , Nervous system -- Degeneration -- Treatment , Tetracyclines , Antibiotics -- Side effects , Theanine -- Evaluation , Drugs -- Administration , Cerebrovascular disease -- Prevention
- Description: Stroke is one of the most common causes of disability and death worldwide. The most commonly experienced stroke in the clinical setting is focal ischaemia in which the middle cerebral artery (MCA) is occluded and leads to a complex series of various pathophysiological pathways that ultimately lead to neuronal cell death. Several studies have been conducted on various therapeutic agents in the search for a neuroprotective drug and various animal models have been used to carry out this research. While theanine, a component of green tea and minocycline, a tetracycline antibiotic, have been shown to possess some neuroprotective properties, the mechanisms by which these two agents carry out these effects still remains unclear. The objectives of this study were to investigate the mechanisms by which these drugs carry out these neuroprotective effects and their neuroprotective ability in a MCA occlusion model of focal ischaemia. Ischaemia leads to oxidative stress due to the imbalance of free radicals and the endogenous antioxidant defence system. An antioxidant assay using the stable 2, 2-diphenyl-1-picrylhydrazyl (DPPH●) radical was used to assess the antiradical properties of each drug. It was found that minocycline showed superior antioxidant activity in vitro when compared to theanine. Further studies on the drugs‟ ability to attenuate the Fenton reaction (in which iron catalyses the formation of reactive species) were elucidated using electrochemical analysis, UV/VIS studies, ferrozine and ferritin assays. It was found that minocycline, in contrast to theanine, was able to bind to iron ions and thus potentially prevent the participation of iron in metal catalysed radical reaction. The antioxidant activity of both drugs was further investigated by assessing their effect on cyanide-induced superoxide generation and quinolinic acid (QA)-induced lipid peroxidation (LP). Experimental evidence shows that both drugs had no significant effect on the generation of superoxide in vitro and that there was a significant decrease in LP for minocycline in vitro and theanine in vivo. The metal binding and antioxidant properties were postulated to be a possible mechanism through which these agents reduced lipid peroxidation. A study was conducted to determine the effects of the drugs on the biosynthesis of the neurotoxin, QA and it was found that minocycline increases the levels of holoenzyme activity of tryptophan-2, 3-dioxygenase (TDO) in vitro and that theanine reduces the levels of the same enzyme in vivo after treatment for 10 days. TDO is the enzyme that converts tryptophan to other products that enable enzymatic activity to change it to QA. Minocycline was thought to bring about this effect as it has been shown from preceding experimental studies that it is an effective reducing agent. Theanine on the other hand is hypothesised to bring about a reduction in holoenzyme activity by changing the binding of tryptophan to the enzyme or affecting the radicals that participate in the enzymatic degradation of tryptophan. A focal ischaemic model of stroke was induced by occluding the MCA. Histological examination of the hippocampus post -ischaemia shows a reduction in the size of the infarct after pre-treatment with minocycline only. A further study into the effects of the drugs on the generation of superoxide and on the levels of the endogenous glutathione after a stroke was carried out. Pre-treatment of the animals with either theanine or minocycline showed no significant effects on the generation of the radical species or of the endogenous antioxidant which ruled out these as a mechanism of neuroprotection of both drugs, post-ischaemia.The findings of this study provide novel information on the possible mechanisms by which both theanine and minocycline act to bring about neuroprotection. In particular in this study, pre-treatment with minocycline has shown promise in the focal ischaemic model of stroke.
- Full Text:
- Date Issued: 2010
- Authors: Mpofu, Tariro Ann-Maureen
- Date: 2010 , 2010-09-20
- Subjects: Nervous system -- Degeneration -- Treatment , Tetracyclines , Antibiotics -- Side effects , Theanine -- Evaluation , Drugs -- Administration , Cerebrovascular disease -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3775 , http://hdl.handle.net/10962/d1003253 , Nervous system -- Degeneration -- Treatment , Tetracyclines , Antibiotics -- Side effects , Theanine -- Evaluation , Drugs -- Administration , Cerebrovascular disease -- Prevention
- Description: Stroke is one of the most common causes of disability and death worldwide. The most commonly experienced stroke in the clinical setting is focal ischaemia in which the middle cerebral artery (MCA) is occluded and leads to a complex series of various pathophysiological pathways that ultimately lead to neuronal cell death. Several studies have been conducted on various therapeutic agents in the search for a neuroprotective drug and various animal models have been used to carry out this research. While theanine, a component of green tea and minocycline, a tetracycline antibiotic, have been shown to possess some neuroprotective properties, the mechanisms by which these two agents carry out these effects still remains unclear. The objectives of this study were to investigate the mechanisms by which these drugs carry out these neuroprotective effects and their neuroprotective ability in a MCA occlusion model of focal ischaemia. Ischaemia leads to oxidative stress due to the imbalance of free radicals and the endogenous antioxidant defence system. An antioxidant assay using the stable 2, 2-diphenyl-1-picrylhydrazyl (DPPH●) radical was used to assess the antiradical properties of each drug. It was found that minocycline showed superior antioxidant activity in vitro when compared to theanine. Further studies on the drugs‟ ability to attenuate the Fenton reaction (in which iron catalyses the formation of reactive species) were elucidated using electrochemical analysis, UV/VIS studies, ferrozine and ferritin assays. It was found that minocycline, in contrast to theanine, was able to bind to iron ions and thus potentially prevent the participation of iron in metal catalysed radical reaction. The antioxidant activity of both drugs was further investigated by assessing their effect on cyanide-induced superoxide generation and quinolinic acid (QA)-induced lipid peroxidation (LP). Experimental evidence shows that both drugs had no significant effect on the generation of superoxide in vitro and that there was a significant decrease in LP for minocycline in vitro and theanine in vivo. The metal binding and antioxidant properties were postulated to be a possible mechanism through which these agents reduced lipid peroxidation. A study was conducted to determine the effects of the drugs on the biosynthesis of the neurotoxin, QA and it was found that minocycline increases the levels of holoenzyme activity of tryptophan-2, 3-dioxygenase (TDO) in vitro and that theanine reduces the levels of the same enzyme in vivo after treatment for 10 days. TDO is the enzyme that converts tryptophan to other products that enable enzymatic activity to change it to QA. Minocycline was thought to bring about this effect as it has been shown from preceding experimental studies that it is an effective reducing agent. Theanine on the other hand is hypothesised to bring about a reduction in holoenzyme activity by changing the binding of tryptophan to the enzyme or affecting the radicals that participate in the enzymatic degradation of tryptophan. A focal ischaemic model of stroke was induced by occluding the MCA. Histological examination of the hippocampus post -ischaemia shows a reduction in the size of the infarct after pre-treatment with minocycline only. A further study into the effects of the drugs on the generation of superoxide and on the levels of the endogenous glutathione after a stroke was carried out. Pre-treatment of the animals with either theanine or minocycline showed no significant effects on the generation of the radical species or of the endogenous antioxidant which ruled out these as a mechanism of neuroprotection of both drugs, post-ischaemia.The findings of this study provide novel information on the possible mechanisms by which both theanine and minocycline act to bring about neuroprotection. In particular in this study, pre-treatment with minocycline has shown promise in the focal ischaemic model of stroke.
- Full Text:
- Date Issued: 2010
Constraints and challenges faced by small, medium and micro enterprise contractors in Malawi
- Authors: Chilipunde, Rodrick Lengama
- Date: 2010
- Subjects: Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9686 , http://hdl.handle.net/10948/1220 , Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Description: Small, medium and micro enterprises (SMMEs) are an important sector of any construction economy. The need for efficient SMMEs is well documented and cannot be over-emphasised. SMMEs are vital in their contribution to employment creation and value reorientation. However, their in process operations are not well understood and have rarely been addressed. The aim of this research was therefore to establish a base level of understanding of the operational core-face of SMMEs in Malawi. The methodology used included an extensive literature review and field survey conducted on 52 SMMEs. The field survey used the questionnaire instrument and random sampling. The critical findings from the literature were that there are binding constraints in the operations of SMMEs. The field survey confirmed the issues raised in the literature and posited the operational challenges as lack of finance, training and business skills; limited skills in Construction Information Technology (IT), and prevalence of unethical conduct amongst some of the stakeholders. The findings make an invaluable contribution to the search for solutions to the problems faced by construction SMMEs in Malawi and provide insight for further research in institutional weaknesses and policy issues regarding in this part of the world. The implications of the findings are that unless the limitations named above are resolved, SMMEs in Malawi will continue to experience poor growth and competitiveness. The recommendations include the developing of training programmes in business management, introduction of sector specific financing programmes and the provision of an appropriate regulatory and legislative framework. By establishing the core issues affecting the operations of SMMEs in the Malawian construction industry, the research has contributed to the enhancement of the understanding of this elusive subject.
- Full Text:
- Date Issued: 2010
- Authors: Chilipunde, Rodrick Lengama
- Date: 2010
- Subjects: Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9686 , http://hdl.handle.net/10948/1220 , Small business -- Malawi -- Management , Contractors' operations -- Malawi , Small business -- Malawi -- Finance
- Description: Small, medium and micro enterprises (SMMEs) are an important sector of any construction economy. The need for efficient SMMEs is well documented and cannot be over-emphasised. SMMEs are vital in their contribution to employment creation and value reorientation. However, their in process operations are not well understood and have rarely been addressed. The aim of this research was therefore to establish a base level of understanding of the operational core-face of SMMEs in Malawi. The methodology used included an extensive literature review and field survey conducted on 52 SMMEs. The field survey used the questionnaire instrument and random sampling. The critical findings from the literature were that there are binding constraints in the operations of SMMEs. The field survey confirmed the issues raised in the literature and posited the operational challenges as lack of finance, training and business skills; limited skills in Construction Information Technology (IT), and prevalence of unethical conduct amongst some of the stakeholders. The findings make an invaluable contribution to the search for solutions to the problems faced by construction SMMEs in Malawi and provide insight for further research in institutional weaknesses and policy issues regarding in this part of the world. The implications of the findings are that unless the limitations named above are resolved, SMMEs in Malawi will continue to experience poor growth and competitiveness. The recommendations include the developing of training programmes in business management, introduction of sector specific financing programmes and the provision of an appropriate regulatory and legislative framework. By establishing the core issues affecting the operations of SMMEs in the Malawian construction industry, the research has contributed to the enhancement of the understanding of this elusive subject.
- Full Text:
- Date Issued: 2010