A statistical evaluation and analysis of mosquito repellent combination
- Authors: Asquith, Ilse Bernadette
- Date: 2004
- Subjects: Mosquitoes -- Control , Insect baits and repellents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10422 , http://hdl.handle.net/10948/d1015732
- Description: The present product development project was aimed at studying the synergism and/or antagonism amongst various known insect repellent actives with the view to formulating a multi-active repellent product with improved properties when compared to current single-active commercial products. Advanced statistical methods were used to identify synergism between individual active substances and to define a formulation as close as possible to the “ideal” formulation. Several mosquito repellent samples were prepared and sent to the South African Bureau of Standards (SABS) in Pretoria to test for their efficiency in repelling mosquitoes. From the results of the repellency tests of the various active combinations, three actives were identified that showed promising signs of synergism. These actives were then studied in further detail to determine their optimum combination. In addition, it was shown that when using a natural flavourant as promoter and incorporating a slow-release agent into formulations for aerosols and lotions, a product is obtained that gives comparable levels of efficiency to current commercial products, but at much reduced levels of active loading. Accelerated stability tests performed on the final combination of the three actives used in the final formulation showed no adverse reactions over a three-week study. These tests shall be repeated once the final application form (lotion, aerosol, etc) and product packing have been decided.
- Full Text:
- Date Issued: 2004
- Authors: Asquith, Ilse Bernadette
- Date: 2004
- Subjects: Mosquitoes -- Control , Insect baits and repellents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10422 , http://hdl.handle.net/10948/d1015732
- Description: The present product development project was aimed at studying the synergism and/or antagonism amongst various known insect repellent actives with the view to formulating a multi-active repellent product with improved properties when compared to current single-active commercial products. Advanced statistical methods were used to identify synergism between individual active substances and to define a formulation as close as possible to the “ideal” formulation. Several mosquito repellent samples were prepared and sent to the South African Bureau of Standards (SABS) in Pretoria to test for their efficiency in repelling mosquitoes. From the results of the repellency tests of the various active combinations, three actives were identified that showed promising signs of synergism. These actives were then studied in further detail to determine their optimum combination. In addition, it was shown that when using a natural flavourant as promoter and incorporating a slow-release agent into formulations for aerosols and lotions, a product is obtained that gives comparable levels of efficiency to current commercial products, but at much reduced levels of active loading. Accelerated stability tests performed on the final combination of the three actives used in the final formulation showed no adverse reactions over a three-week study. These tests shall be repeated once the final application form (lotion, aerosol, etc) and product packing have been decided.
- Full Text:
- Date Issued: 2004
The challenge of applying systematic conservation planning to the marine environment using expert knowledge (focus: Sparidae)
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
- Authors: Bause, Mariëtte
- Date: 2004
- Subjects: Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11064 , http://hdl.handle.net/10948/343 , Marine parks and reserves -- South Africa , Nature conservation -- South Africa , Fishery conservation -- South Africa , Sparidae
- Description: Although the marine environment has generally been considered to be less in need of attention from conservationists, politicians and managers than the terrestrial environment, there has been an increasing appreciation that there is little left in the marine environment that can be considered unaltered by humans. Conservation action is therefore urgently needed to protect marine populations, species and environments from anthropogenic pressures. Since overharvesting seems to be the main cause of the collapse in coastal ecosystems, areas need to be protected so that stocks can recover. However, the proclamation of such marine protected areas (MPAs) need to be well planned to ensure that species are well represented and that their biological requirements are met in the long term. While terrestrial conservation planners have started to incorporate biological, social and economic information into so-called systematic conservation plans, marine planners have been more hesitant to use these approaches due to the greater openness of the ocean (with the associated greater dispersal of marine organisms and propogules, lower levels of endemism, and lack of ownership) and the paucity of available information. The current study aimed to investigate the applicability of systematic approaches to the process of selecting sites for a network of potential replenishment zones for seabream species that could supplement protection already afforded by existing no-fishing reserves. Since many of these seabream species are popular targets in both the recreational and commercial linefishery sectors, they have been overexploited and are in need of additional protection. Information on these species and the diversity of their associated reefs were obtained through consultations with scientists, managers and resource-users (namely SCUBA divers, spearfishers as well as recreational and commercial fishers). These data were obtained during workshops where Participatory Rural Appraisal (PRA) scoring and mapping methods were applied. Although ordinal-scale, rather than interval-or ratio-scale data were obtained, these data could be used in an interactive selection process. Because these methods require relatively cheap materials and few personnel, they could be used to collect information where limited budgets are available. Quantitative targets for the protection of individual species were set on the basis of their status in the Marine Living Resource Act, since this reflected their different requirements for protection. A preliminary investigation indicated that the current no-fishing reserves effectively achieved most of these goals for seabream species. The selection of sites for the replenishment network was based on irreplaceability analyses, while decisions between sites with lower irreplaceability values were based on explicit design rules. A total of 26 sites were required to achieve targets for all species. These replenishment zones could potentially be established, managed and monitored by voluntary community groups. This study therefore indicated that systematic conservation planning can successfully be applied to the marine environment, while the involvement of stakeholders is crucial to ensure that conservation action is supported.
- Full Text:
- Date Issued: 2004
The execution of the financial management function in small to medium-sized building contractors as a means of promoting business sustainability
- Authors: Bekker, Jakobus Petrus
- Date: 2004
- Subjects: Contractors' operation -- Finance , Construction industry -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11004 , http://hdl.handle.net/10948/336 , Contractors' operation -- Finance , Construction industry -- Finance
- Description: The objective of this study was to investigate the extent to which small to medium-sized building contractors beneficially utilise the financial management function in their enterprises to improve and ensure business sustainability. Financial management focuses on the principles of decision-making, which requires action, without perfect knowledge of the outcome. To effectively execute the financial function, using the primary inputs in decision-making, financial management requires the ability to: understand and interpret financial statements and reports; make reasoned and objective decisions in controlling the operations of the enterprise; have a thorough knowledge of the internal functioning of the enterprise; and have a thorough knowledge of current and expected future economic conditions in the external environment. To do this, requires an effectively applied financial management function in the enterprises, which includes the utilisation of the financial management criteria to ensure business sustainability. However, without an appreciation of what financial management is, how important financial management is, and how financial management must be applied in the enterprise, small to medium-sized building contractors will find it difficult to effectively perform the financial management function and its different activities. It was therefore important to determine how well owners and construction managers of the average small to medium-sized building contractor deal with and utilise the financial management function in their enterprises. Consequently, a survey was carried out amongst small to medium-sized building contractors in the Nelson Mandela Metropolitan Municipal (NMMM) area, which revealed information that was used to come to certain conclusions: Firstly, it can be concluded that the financial management function is generally exercised superficially. This is supported by the responses of small to medium-sized building contractors, which implied that more than half the contractors do not fully perform financial management tasks. Secondly, it was concluded that the financial management criteria generally do not play a role in the business sustainability considerations of small to medium-sized building contractors. This is supported by the results, which imply that more than half the contractors do not fully utilise the financial management criteria.
- Full Text:
- Date Issued: 2004
- Authors: Bekker, Jakobus Petrus
- Date: 2004
- Subjects: Contractors' operation -- Finance , Construction industry -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11004 , http://hdl.handle.net/10948/336 , Contractors' operation -- Finance , Construction industry -- Finance
- Description: The objective of this study was to investigate the extent to which small to medium-sized building contractors beneficially utilise the financial management function in their enterprises to improve and ensure business sustainability. Financial management focuses on the principles of decision-making, which requires action, without perfect knowledge of the outcome. To effectively execute the financial function, using the primary inputs in decision-making, financial management requires the ability to: understand and interpret financial statements and reports; make reasoned and objective decisions in controlling the operations of the enterprise; have a thorough knowledge of the internal functioning of the enterprise; and have a thorough knowledge of current and expected future economic conditions in the external environment. To do this, requires an effectively applied financial management function in the enterprises, which includes the utilisation of the financial management criteria to ensure business sustainability. However, without an appreciation of what financial management is, how important financial management is, and how financial management must be applied in the enterprise, small to medium-sized building contractors will find it difficult to effectively perform the financial management function and its different activities. It was therefore important to determine how well owners and construction managers of the average small to medium-sized building contractor deal with and utilise the financial management function in their enterprises. Consequently, a survey was carried out amongst small to medium-sized building contractors in the Nelson Mandela Metropolitan Municipal (NMMM) area, which revealed information that was used to come to certain conclusions: Firstly, it can be concluded that the financial management function is generally exercised superficially. This is supported by the responses of small to medium-sized building contractors, which implied that more than half the contractors do not fully perform financial management tasks. Secondly, it was concluded that the financial management criteria generally do not play a role in the business sustainability considerations of small to medium-sized building contractors. This is supported by the results, which imply that more than half the contractors do not fully utilise the financial management criteria.
- Full Text:
- Date Issued: 2004
A critical analysis of the influence of the "Prevention of the illegal eviction from and unlawful occupation of Land Act 19 of 1998" on investment in residential income-producing property
- Authors: Botha, Brink
- Date: 2004
- Subjects: Rental housing -- Law and legislation -- South Africa , Eviction -- Law and legislation -- South Africa , Occupancy (Law) -- South Africa , Real estate investment -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11005 , http://hdl.handle.net/10948/321 , Rental housing -- Law and legislation -- South Africa , Eviction -- Law and legislation -- South Africa , Occupancy (Law) -- South Africa , Real estate investment -- Law and legislation -- South Africa
- Description: This research will focus on the influence of legislation (as indicated in this research) on the investment decision in residential income-producing property. Assumptions, as recorded in the hypothesis of this study, indicate that the legislation had a changing influence on the investment decision in residential income-producing property in comparison to the time period prior to the promulgation of the legislation. The research methodology will be based on a comparative analysis of the current legislation and the proposed Draft Amendment Bill. This analysis will be tested by means of a case study analysis incorporating a phenomenological study based on written data. The problems, sub-problems and hypothesis will be addressed and tested in this research in conjunction with the prescribed research methodology. This research is concluded by means of a synopsis and recommendations.
- Full Text:
- Date Issued: 2004
- Authors: Botha, Brink
- Date: 2004
- Subjects: Rental housing -- Law and legislation -- South Africa , Eviction -- Law and legislation -- South Africa , Occupancy (Law) -- South Africa , Real estate investment -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11005 , http://hdl.handle.net/10948/321 , Rental housing -- Law and legislation -- South Africa , Eviction -- Law and legislation -- South Africa , Occupancy (Law) -- South Africa , Real estate investment -- Law and legislation -- South Africa
- Description: This research will focus on the influence of legislation (as indicated in this research) on the investment decision in residential income-producing property. Assumptions, as recorded in the hypothesis of this study, indicate that the legislation had a changing influence on the investment decision in residential income-producing property in comparison to the time period prior to the promulgation of the legislation. The research methodology will be based on a comparative analysis of the current legislation and the proposed Draft Amendment Bill. This analysis will be tested by means of a case study analysis incorporating a phenomenological study based on written data. The problems, sub-problems and hypothesis will be addressed and tested in this research in conjunction with the prescribed research methodology. This research is concluded by means of a synopsis and recommendations.
- Full Text:
- Date Issued: 2004
An investigation into the captive spawning, egg characteristics and egg quality of the mud crab (Scylla serrata) in South Africa
- Authors: Churchill, Giles John
- Date: 2004
- Subjects: Scylla serrata , Crabs -- South Africa , Scylla serrata -- South Africa , Crabs -- Eggs -- Incubation , Crabs -- Spawning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5376 , http://hdl.handle.net/10962/d1015963
- Description: The source of a reliable supply of seed is one of the most important factors determining the success of aquaculture. At present mud crab culture is reliant on wild caught juveniles, which limits the expansion of mud crab farming globally. This, coupled with the paucity of knowledge of the spawning and egg characteristics of mud crabs, prompted the investigation into the captive spawning, incubation and egg quality of Scylla serrata in South Africa. A total of 112 mature females were caught from three estuaries in northern KwaZulu Natal and acclimated to captive conditions. Mature females were present in the estuaries throughout the year and ranged from 90 to 200 mm carapace width. Except for 40 crabs all the females spawned in captivity. On average spawning took place 38 ± 23 days after capture but was not dependent on crab size. Fecundity was significantly correlated to crab size (p = 0.026), with larger females producing more eggs. The average fecundity per batch was 5.79 ± 2.07 million eggs. Hatch success rate for all egg batches was high averaging 84 ± 6 %. Egg dropping occurred in all egg batches during incubation. On average 6.5 % of the egg mass was dropped during incubation. At the average temperature of 27⁰C eggs in the incubation system hatched within 292 ± 12 hours after extrusion. In-vitro incubation of eggs proved to be an ineffective means of incubating Scylla serrata eggs with a hatch success rate of only 25 ± 5 %. Egg quality was assessed both directly, using variables such as hatch success rate and hatch synchronicity and retrospectively by using stress tests and comparing survival of larvae from different coloured egg batches. Lipid class composition and fatty acid methyl ester content for 28 batches of eggs and 16 batches of larvae were analyzed. The biochemical composition of the egg was correlated to survival of larvae in the stress tests to ascertain if the lipid content of the eggs determines their quality. Stress tests were used to retrospectively assess egg quality. Four stressors were administered to newly hatched larvae and the LD50 values recorded. An average LD50 of 64 hours was recorded for the starvation tests, 40% for the salinity tests, 37 ppm for the formalin tests and 39.7 mg/l NH3 for the ammonia stress tests was recorded. Egg colour ranged from pale yellow to orange-red. Egg colour was not influenced by female size or the time the females spent in captivity prior to spawning. Egg colour can therefore not be used as an indicator of quality. The lipid profiles of newly extruded eggs had no effect on hatch synchronicity or hatch success rate. However, the stress tests identified female size (p ≤ 0.02), DHA content of the egg (p ≤ 0.02), Σ omega-3 fatty acids of eggs (p ≤ 0.02) and EPA content of eggs (p ≤ 0.007) as possible determinants of egg quality. Larger crabs tended to produce poorer quality eggs. Egg quality also decreased as the amount of DHA, EPA and the Σ omega-3 fatty acids decreased in the eggs. To summarize, the results of this study indicated that the following parameters affect egg quality - crab size, DHA, EPA and Σ omega-3 fatty acid content of eggs.
- Full Text:
- Date Issued: 2004
- Authors: Churchill, Giles John
- Date: 2004
- Subjects: Scylla serrata , Crabs -- South Africa , Scylla serrata -- South Africa , Crabs -- Eggs -- Incubation , Crabs -- Spawning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5376 , http://hdl.handle.net/10962/d1015963
- Description: The source of a reliable supply of seed is one of the most important factors determining the success of aquaculture. At present mud crab culture is reliant on wild caught juveniles, which limits the expansion of mud crab farming globally. This, coupled with the paucity of knowledge of the spawning and egg characteristics of mud crabs, prompted the investigation into the captive spawning, incubation and egg quality of Scylla serrata in South Africa. A total of 112 mature females were caught from three estuaries in northern KwaZulu Natal and acclimated to captive conditions. Mature females were present in the estuaries throughout the year and ranged from 90 to 200 mm carapace width. Except for 40 crabs all the females spawned in captivity. On average spawning took place 38 ± 23 days after capture but was not dependent on crab size. Fecundity was significantly correlated to crab size (p = 0.026), with larger females producing more eggs. The average fecundity per batch was 5.79 ± 2.07 million eggs. Hatch success rate for all egg batches was high averaging 84 ± 6 %. Egg dropping occurred in all egg batches during incubation. On average 6.5 % of the egg mass was dropped during incubation. At the average temperature of 27⁰C eggs in the incubation system hatched within 292 ± 12 hours after extrusion. In-vitro incubation of eggs proved to be an ineffective means of incubating Scylla serrata eggs with a hatch success rate of only 25 ± 5 %. Egg quality was assessed both directly, using variables such as hatch success rate and hatch synchronicity and retrospectively by using stress tests and comparing survival of larvae from different coloured egg batches. Lipid class composition and fatty acid methyl ester content for 28 batches of eggs and 16 batches of larvae were analyzed. The biochemical composition of the egg was correlated to survival of larvae in the stress tests to ascertain if the lipid content of the eggs determines their quality. Stress tests were used to retrospectively assess egg quality. Four stressors were administered to newly hatched larvae and the LD50 values recorded. An average LD50 of 64 hours was recorded for the starvation tests, 40% for the salinity tests, 37 ppm for the formalin tests and 39.7 mg/l NH3 for the ammonia stress tests was recorded. Egg colour ranged from pale yellow to orange-red. Egg colour was not influenced by female size or the time the females spent in captivity prior to spawning. Egg colour can therefore not be used as an indicator of quality. The lipid profiles of newly extruded eggs had no effect on hatch synchronicity or hatch success rate. However, the stress tests identified female size (p ≤ 0.02), DHA content of the egg (p ≤ 0.02), Σ omega-3 fatty acids of eggs (p ≤ 0.02) and EPA content of eggs (p ≤ 0.007) as possible determinants of egg quality. Larger crabs tended to produce poorer quality eggs. Egg quality also decreased as the amount of DHA, EPA and the Σ omega-3 fatty acids decreased in the eggs. To summarize, the results of this study indicated that the following parameters affect egg quality - crab size, DHA, EPA and Σ omega-3 fatty acid content of eggs.
- Full Text:
- Date Issued: 2004
Investigations into the nutritional requirements of juvenile dusky kob, Argyrosomus japonicus (Pisces sciaendae), under ambient culture conditions
- Authors: Daniel, Simon James
- Date: 2004
- Subjects: Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5197 , http://hdl.handle.net/10962/d1002602 , Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Description: The effect of dietary protein, protein and energy ratios, fish meal replacement by Soya bean meal and feeding frequency was investigated on the growth, feed efficiency and body composition, of juvenile dusky kob, Argyrosomus japonicus. The effect of dietary protein levels was investigated by comparing isocaloric diets containing 35, 40, 45 and 55% protein. Dietary protein inclusion level significantly affected specific growth rates, feed efficiency and body composition (in terms of fat deposition) and results show that a minimum of 45% and maximum of 52.3% dietary protein is optimal. The protein and energy requirements were investigated by comparing three protein levels (35,40 and 45%) with three lipid levels (6, 9 and 12%) in a 3x3 factorial design. A diet 45% protein and 9% lipid, with a P: E ratio of29 mglkJ and DE of 15.5 kJ/g resulted in an optimal specific growth rate (1.6± 0.2), feed efficiency (FCR= 1.7±0.44; PER= 1.36) and body composition for A. japonicus. To investigate the effect of partial fish meal replacement by Soya bean meal (SBM) in the diet, 20-50% of the protein from fish meal was substituted by protein from SBM, and were compared with a control diet containing only fish meal. No significant differences in the specific growth rates, feed efficiencies and the body composition were recorded for the fish fed the control diet and for fish fed the 20 and 30% SBM treatments. Results show that up to 30% of the protein from fish meal can be replaced with protein from SBM in the diet of this species. The effect of feeding frequency and gut evacuation time was investigated by comparing four feeding frequencies. Fish were fed to satiation either once, twice, three or four times a day. Feed intake was significantly affected by feeding frequency and fish fed 2, 3 and 4 meals a day ate significantly more food (p< 0.05) than the fish fed one meal a day. No significant differences (p> 0.05) in the specific growth rates, feed efficiencies and body composition were recorded for fish fed 2, 3 and 4 times a day. Feed intake was used to calculate an optimal daily ration and feeding two meals a day resulted in an optimal daily ration of 4% BW/day. A gut evacuation time of 7.25 hours indicates that fish fed twice a day probably had sufficient time to digest their food and evacuate their guts, resulting in the same daily feed intake as fish given 3 and 4 meals a day. Results conclude that under the present experimental conditions, a minimum daily ration of 4% BW/day, fed twice a day (in the morning and evening) is required for optimal growth (SGR= 1.33± 0.1), feed efficiency (FCR= 1.96± 0.4; PER= 1.44± 0.2) and body composition in juvenile dusky kob.
- Full Text:
- Date Issued: 2004
- Authors: Daniel, Simon James
- Date: 2004
- Subjects: Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5197 , http://hdl.handle.net/10962/d1002602 , Argyrosomus -- Nutrition -- Requirements , Sciaenidae -- Nutrition -- Requirements , Fishes -- Food , Fishes -- Growth , Fish culture , Fishes -- Nutrition -- Requirements
- Description: The effect of dietary protein, protein and energy ratios, fish meal replacement by Soya bean meal and feeding frequency was investigated on the growth, feed efficiency and body composition, of juvenile dusky kob, Argyrosomus japonicus. The effect of dietary protein levels was investigated by comparing isocaloric diets containing 35, 40, 45 and 55% protein. Dietary protein inclusion level significantly affected specific growth rates, feed efficiency and body composition (in terms of fat deposition) and results show that a minimum of 45% and maximum of 52.3% dietary protein is optimal. The protein and energy requirements were investigated by comparing three protein levels (35,40 and 45%) with three lipid levels (6, 9 and 12%) in a 3x3 factorial design. A diet 45% protein and 9% lipid, with a P: E ratio of29 mglkJ and DE of 15.5 kJ/g resulted in an optimal specific growth rate (1.6± 0.2), feed efficiency (FCR= 1.7±0.44; PER= 1.36) and body composition for A. japonicus. To investigate the effect of partial fish meal replacement by Soya bean meal (SBM) in the diet, 20-50% of the protein from fish meal was substituted by protein from SBM, and were compared with a control diet containing only fish meal. No significant differences in the specific growth rates, feed efficiencies and the body composition were recorded for the fish fed the control diet and for fish fed the 20 and 30% SBM treatments. Results show that up to 30% of the protein from fish meal can be replaced with protein from SBM in the diet of this species. The effect of feeding frequency and gut evacuation time was investigated by comparing four feeding frequencies. Fish were fed to satiation either once, twice, three or four times a day. Feed intake was significantly affected by feeding frequency and fish fed 2, 3 and 4 meals a day ate significantly more food (p< 0.05) than the fish fed one meal a day. No significant differences (p> 0.05) in the specific growth rates, feed efficiencies and body composition were recorded for fish fed 2, 3 and 4 times a day. Feed intake was used to calculate an optimal daily ration and feeding two meals a day resulted in an optimal daily ration of 4% BW/day. A gut evacuation time of 7.25 hours indicates that fish fed twice a day probably had sufficient time to digest their food and evacuate their guts, resulting in the same daily feed intake as fish given 3 and 4 meals a day. Results conclude that under the present experimental conditions, a minimum daily ration of 4% BW/day, fed twice a day (in the morning and evening) is required for optimal growth (SGR= 1.33± 0.1), feed efficiency (FCR= 1.96± 0.4; PER= 1.44± 0.2) and body composition in juvenile dusky kob.
- Full Text:
- Date Issued: 2004
Search algorithms on structured and unstructured data in a large database
- Du Plessis, Mathys Cornelius
- Authors: Du Plessis, Mathys Cornelius
- Date: 2004
- Subjects: Online algorithms , Database searching -- South Africa -- Port Elizabeth , Information retrieval -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11094 , http://hdl.handle.net/10948/d1019681
- Description: This project is concerned with the development of a search algorithm for a large archival database. The Port Elizabeth Genealogical Information System (PEGIS) contains a database consisting of almost 600000 individuals. The standard search algorithms are no longer sufficient to locate individuals in the database. A new algorithm was required that allows searches on any of the words or dates in the database, as well as a means to specify where in the desired record a word should occur. A ranking function of retrieved records was also required. A literature study on the field of Information Retrieval and on algorithms designed specifically for the PEGIS was done. These algorithms were adapted and hybridized to yield a search algorithm that allows for the boolean formulation of queries and the specification of the structure of search words in the desired records. The algorithm ranks retrieved records in assumed relevance to the user. The new algorithms were evaluated with regards to retrieval speed and accuracy and were found to be very effective.
- Full Text:
- Date Issued: 2004
- Authors: Du Plessis, Mathys Cornelius
- Date: 2004
- Subjects: Online algorithms , Database searching -- South Africa -- Port Elizabeth , Information retrieval -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11094 , http://hdl.handle.net/10948/d1019681
- Description: This project is concerned with the development of a search algorithm for a large archival database. The Port Elizabeth Genealogical Information System (PEGIS) contains a database consisting of almost 600000 individuals. The standard search algorithms are no longer sufficient to locate individuals in the database. A new algorithm was required that allows searches on any of the words or dates in the database, as well as a means to specify where in the desired record a word should occur. A ranking function of retrieved records was also required. A literature study on the field of Information Retrieval and on algorithms designed specifically for the PEGIS was done. These algorithms were adapted and hybridized to yield a search algorithm that allows for the boolean formulation of queries and the specification of the structure of search words in the desired records. The algorithm ranks retrieved records in assumed relevance to the user. The new algorithms were evaluated with regards to retrieval speed and accuracy and were found to be very effective.
- Full Text:
- Date Issued: 2004
An assessment of density estimation methods for forest ungulates
- Authors: Ellis, Amanda Morgan
- Date: 2004
- Subjects: Wildlife management -- South Africa -- Eastern Cape Animal populations -- Estimates Wildlife conservation -- South Africa -- Eastern Cape Game farms -- South Africa -- Eastern Cape Ungulates -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5829 , http://hdl.handle.net/10962/d1007830
- Description: The development of conservation and management programs for an animal population relies on a knowledge of the number of individuals in an area. In order to achieve reliable estimates, precise and accurate techniques for estimating population densities are needed. This study compared the use of direct and indirect methods of estimating kudu (Trage/aphus strepsiceras), bush buck (Trage/aphus scriptus), common duiker (Sy/vicapra grimmia), and blue duiker (Philantamba manticala) densities on Shamwari Game Reserve in the Eastern Cape Province, South Africa. These species prefer habitats of dense forest and bush for concealment and are therefore not easily counted in open areas. Herein direct observation counts were compared to indirect sampling via pellet group counts (clearance plots, line transects, variable-width transects, and strip transects). Clearance plots were examined every 2 weeks, while all other methods were conducted seasonally, from August 2002 until August 2003. The strip transect method provided the lowest density estimates (animals per hal ranging from 0.001 for bushbuck to 0.025 for common duiker, while direct observations yielded the highest estimates, ranging from 0.804 for bush buck to 4.692 for kudu. Also, a validation of methods was performed against a known population of kudu during which the DISTANCE method yielded the most accurate results, with an estimated density of 0.261 that was within the actual density of 0.246 to 0.282. In addition, the DISTANCE method was compared to helicopter counts ofkudu and its estimates were found to be approximately 2.6 times greater than the helicopter count results. When the assessment of the methods was made, the cost, manpower and effort requirements, coefficient of variation, and performance against a known population for each method were taken into consideration. Overall, the DISTANCE method performed the best with low cost, minimal manpower and effort requirements, and low coefficient of variation. On Shamwari Game Reserve, the DISTANCE method estimated 0.300 kudu, 0.108 bushbuck, 0.387 common duiker, and 0.028 blue duiker per ha, which, when extrapolated to the total number of animals present within subtropical thicket habitat, estimated 1973 kudu, 710 bush buck, 2545 common duiker, and 184 blue duiker.
- Full Text:
- Date Issued: 2004
- Authors: Ellis, Amanda Morgan
- Date: 2004
- Subjects: Wildlife management -- South Africa -- Eastern Cape Animal populations -- Estimates Wildlife conservation -- South Africa -- Eastern Cape Game farms -- South Africa -- Eastern Cape Ungulates -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5829 , http://hdl.handle.net/10962/d1007830
- Description: The development of conservation and management programs for an animal population relies on a knowledge of the number of individuals in an area. In order to achieve reliable estimates, precise and accurate techniques for estimating population densities are needed. This study compared the use of direct and indirect methods of estimating kudu (Trage/aphus strepsiceras), bush buck (Trage/aphus scriptus), common duiker (Sy/vicapra grimmia), and blue duiker (Philantamba manticala) densities on Shamwari Game Reserve in the Eastern Cape Province, South Africa. These species prefer habitats of dense forest and bush for concealment and are therefore not easily counted in open areas. Herein direct observation counts were compared to indirect sampling via pellet group counts (clearance plots, line transects, variable-width transects, and strip transects). Clearance plots were examined every 2 weeks, while all other methods were conducted seasonally, from August 2002 until August 2003. The strip transect method provided the lowest density estimates (animals per hal ranging from 0.001 for bushbuck to 0.025 for common duiker, while direct observations yielded the highest estimates, ranging from 0.804 for bush buck to 4.692 for kudu. Also, a validation of methods was performed against a known population of kudu during which the DISTANCE method yielded the most accurate results, with an estimated density of 0.261 that was within the actual density of 0.246 to 0.282. In addition, the DISTANCE method was compared to helicopter counts ofkudu and its estimates were found to be approximately 2.6 times greater than the helicopter count results. When the assessment of the methods was made, the cost, manpower and effort requirements, coefficient of variation, and performance against a known population for each method were taken into consideration. Overall, the DISTANCE method performed the best with low cost, minimal manpower and effort requirements, and low coefficient of variation. On Shamwari Game Reserve, the DISTANCE method estimated 0.300 kudu, 0.108 bushbuck, 0.387 common duiker, and 0.028 blue duiker per ha, which, when extrapolated to the total number of animals present within subtropical thicket habitat, estimated 1973 kudu, 710 bush buck, 2545 common duiker, and 184 blue duiker.
- Full Text:
- Date Issued: 2004
Synthesis and evaluation of PGM-selective ligands
- Gxoyiya, Babalwa Siliziwe Blossom
- Authors: Gxoyiya, Babalwa Siliziwe Blossom
- Date: 2013-05-28
- Subjects: Platinum group , Ligands , Ligands -- Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4450 , http://hdl.handle.net/10962/d1007849 , Platinum group , Ligands , Ligands -- Evaluation
- Description: A series of polydentate POM-selective, sulfur-containing amide ligands have been synthesized from ro-dibromoalkanes and mercaptoacetanilide, The resulting 3,6- dithiaoctanediamides and 3,7-dithianonanediamides, some of which contain a polymerisable group, were all characterized by high-resolution MS, IR, I Hand I3C NMR spectroscopic methods. Various approaches to the polymerisable ligands were explored, the most efficient proving to be the incorporation of an allyl ether moiety in the mercaptoacetanilide. The corresponding Pd(U) and Pt(II) complexes were also prepared from the metal chloride salts and characterized by elemental analysis and spectroscopic methods. The NMR data indicates that both the cis- and transcomplexes were formed, while the IR data indicates cis- coordination of the chlorine . ligands. Molecularly imprinted polymers (MIP's), prepared using platinum(II) mercaptoacetanilide and 3,6-dithiadiamide complexes, showed high selectivity for , , palladium(II) [in the presence of Pt(II), CoCII), Cu(II) and Ni(II)] as determined by . ICP-MS analysis. The more kinetically inert Pt(II) ions however, slowly displaced Pd(II), confirming the Pt(II) selectivity of the MIP's. Solvent extraction studies were conducted to explore the selectivity of the 3,6- dithiaoctanediamides and 3,7-dithianonanediamides for Pd(U) over CoCII), Cu(U) and Ni(II). The ICP-MS data indicate that, in general, equilibration was achieved within ten minutes and that the longer-chain amides were less selective than the shorter-chain analogues. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Gxoyiya, Babalwa Siliziwe Blossom
- Date: 2013-05-28
- Subjects: Platinum group , Ligands , Ligands -- Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4450 , http://hdl.handle.net/10962/d1007849 , Platinum group , Ligands , Ligands -- Evaluation
- Description: A series of polydentate POM-selective, sulfur-containing amide ligands have been synthesized from ro-dibromoalkanes and mercaptoacetanilide, The resulting 3,6- dithiaoctanediamides and 3,7-dithianonanediamides, some of which contain a polymerisable group, were all characterized by high-resolution MS, IR, I Hand I3C NMR spectroscopic methods. Various approaches to the polymerisable ligands were explored, the most efficient proving to be the incorporation of an allyl ether moiety in the mercaptoacetanilide. The corresponding Pd(U) and Pt(II) complexes were also prepared from the metal chloride salts and characterized by elemental analysis and spectroscopic methods. The NMR data indicates that both the cis- and transcomplexes were formed, while the IR data indicates cis- coordination of the chlorine . ligands. Molecularly imprinted polymers (MIP's), prepared using platinum(II) mercaptoacetanilide and 3,6-dithiadiamide complexes, showed high selectivity for , , palladium(II) [in the presence of Pt(II), CoCII), Cu(II) and Ni(II)] as determined by . ICP-MS analysis. The more kinetically inert Pt(II) ions however, slowly displaced Pd(II), confirming the Pt(II) selectivity of the MIP's. Solvent extraction studies were conducted to explore the selectivity of the 3,6- dithiaoctanediamides and 3,7-dithianonanediamides for Pd(U) over CoCII), Cu(U) and Ni(II). The ICP-MS data indicate that, in general, equilibration was achieved within ten minutes and that the longer-chain amides were less selective than the shorter-chain analogues. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
In vitro anti-HIV activities of Sutherlandia frutescens and Lobostemon trigonum extracts
- Authors: Harnett, Siobhán Margaret
- Date: 2004
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11072 , http://hdl.handle.net/10948/347 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Description: Currently, the approved anti-HIV drugs on the market only target the three HIV enzymes: reverse transcriptase, protease and more recently, integrase. Due to the limited nature of the current therapy, it is possible that a multi-drug resistant virus can emerge. The main concerns in developing countries however, are the expense and availability of the drugs and because of this, it is essential to investigate all alternatives. Traditional medicine offers many advantages as compared to allopathic treatment in so far as being relatively cheaper, accessible and it is broadly accepted in the population groups of the developing countries. Little is known though, of the exact efficacy and toxicity of these remedies so it is vital that these possible leads be investigated thoroughly. For the purpose of this study, two plants, Sutherlandia frutescens and Lobostemon trigonum were studied to ascertain their potential anti-HIV activity. Sutherlandia has received international attention as a possible cheap herbal remedy to improve the health of AIDS sufferers. Anecdotal evidence from health workers claim that HIV- infected patients on Sutherlandia treatment have shown improved CD4 counts, decreased viral loads and a general improvement in well-being. Extracts were prepared from dried leaves and flowers in methanol, ethanol, acetone, methylene dichloride or distilled water. Sulphated polysaccharides have been described extensively in literature with regards to their anti-HIV activity, so as a form of dereplication; an ethanol precipitation was performed on the aqueous extracts to remove sulphated polysaccharides. A toxicity study was performed on all crude extracts using uninfected peripheral mononuclear blood cells (PBMCs) isolated from whole blood. To measure anti-HIV activity, HIV-infected PBMCs were cultured with each of the crude extracts and cell viability measured using the tetrazolium salt, XTT. HIV-infected CEM-NKR-CCR5 cells were also used and supernatant from the viral studies was tested for the HIV antigen p24. xii Results varied greatly between assays but with the inclusion of a point-scale system to evaluate the extracts it was clear that overall the organic extracts of the Sutherlandia flowers, especially the acetone extract (SFA), showed great anti-HIV potential. SFA in every case decreased p24 levels and in the toxicity study did not decrease cell proliferation. With the HIV-infected PBMCs SFA actually helped improve cell proliferation despite the infection. To determine the specific anti- HIV activity, all crude extracts were tested for inhibition of HIV-I reverse transcriptase, the glycohydrolase enzymes: a-glucosidase, ß-glucosidase, ßglucuronidase, HIV-I integrase and HIV-II protease. No significant inhibition was seen with these experiments except for the HIV-I RT assay. The aqueous extract of the Lobostemon leaves produced an inhibitor of HIV-RT with a very low IC50 value of 0.049mg/ml. Some inhibitory effect was lost with the removal of the sulphated polysaccharides and the addition of BSA to the assay, but still 64% inhibition of the HIVRT remained, which confirmed that the inhibitor could be something novel, and not of the polysaccharide or tannin compounds.
- Full Text:
- Date Issued: 2004
- Authors: Harnett, Siobhán Margaret
- Date: 2004
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11072 , http://hdl.handle.net/10948/347 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , HIV infections -- Alternative treatment -- South Africa
- Description: Currently, the approved anti-HIV drugs on the market only target the three HIV enzymes: reverse transcriptase, protease and more recently, integrase. Due to the limited nature of the current therapy, it is possible that a multi-drug resistant virus can emerge. The main concerns in developing countries however, are the expense and availability of the drugs and because of this, it is essential to investigate all alternatives. Traditional medicine offers many advantages as compared to allopathic treatment in so far as being relatively cheaper, accessible and it is broadly accepted in the population groups of the developing countries. Little is known though, of the exact efficacy and toxicity of these remedies so it is vital that these possible leads be investigated thoroughly. For the purpose of this study, two plants, Sutherlandia frutescens and Lobostemon trigonum were studied to ascertain their potential anti-HIV activity. Sutherlandia has received international attention as a possible cheap herbal remedy to improve the health of AIDS sufferers. Anecdotal evidence from health workers claim that HIV- infected patients on Sutherlandia treatment have shown improved CD4 counts, decreased viral loads and a general improvement in well-being. Extracts were prepared from dried leaves and flowers in methanol, ethanol, acetone, methylene dichloride or distilled water. Sulphated polysaccharides have been described extensively in literature with regards to their anti-HIV activity, so as a form of dereplication; an ethanol precipitation was performed on the aqueous extracts to remove sulphated polysaccharides. A toxicity study was performed on all crude extracts using uninfected peripheral mononuclear blood cells (PBMCs) isolated from whole blood. To measure anti-HIV activity, HIV-infected PBMCs were cultured with each of the crude extracts and cell viability measured using the tetrazolium salt, XTT. HIV-infected CEM-NKR-CCR5 cells were also used and supernatant from the viral studies was tested for the HIV antigen p24. xii Results varied greatly between assays but with the inclusion of a point-scale system to evaluate the extracts it was clear that overall the organic extracts of the Sutherlandia flowers, especially the acetone extract (SFA), showed great anti-HIV potential. SFA in every case decreased p24 levels and in the toxicity study did not decrease cell proliferation. With the HIV-infected PBMCs SFA actually helped improve cell proliferation despite the infection. To determine the specific anti- HIV activity, all crude extracts were tested for inhibition of HIV-I reverse transcriptase, the glycohydrolase enzymes: a-glucosidase, ß-glucosidase, ßglucuronidase, HIV-I integrase and HIV-II protease. No significant inhibition was seen with these experiments except for the HIV-I RT assay. The aqueous extract of the Lobostemon leaves produced an inhibitor of HIV-RT with a very low IC50 value of 0.049mg/ml. Some inhibitory effect was lost with the removal of the sulphated polysaccharides and the addition of BSA to the assay, but still 64% inhibition of the HIVRT remained, which confirmed that the inhibitor could be something novel, and not of the polysaccharide or tannin compounds.
- Full Text:
- Date Issued: 2004
Sobriety of crisp and fuzzy topological spaces
- Authors: Jacot-Guillarmod, Paul
- Date: 2004
- Subjects: Topological spaces , Fuzzy sets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5414 , http://hdl.handle.net/10962/d1005228 , Topological spaces , Fuzzy sets
- Description: The objective of this thesis is a survey of crisp and fuzzy sober topological spaces. We begin by examining sobriety of crisp topological spaces. We then extend this to the L- topological case and obtain analogous results and characterizations to those of the crisp case. We then brie y examine semi-sobriety of (L;M)-topological spaces.
- Full Text:
- Date Issued: 2004
- Authors: Jacot-Guillarmod, Paul
- Date: 2004
- Subjects: Topological spaces , Fuzzy sets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5414 , http://hdl.handle.net/10962/d1005228 , Topological spaces , Fuzzy sets
- Description: The objective of this thesis is a survey of crisp and fuzzy sober topological spaces. We begin by examining sobriety of crisp topological spaces. We then extend this to the L- topological case and obtain analogous results and characterizations to those of the crisp case. We then brie y examine semi-sobriety of (L;M)-topological spaces.
- Full Text:
- Date Issued: 2004
The application of rheological techniques in the characterization of semisolids in the pharmaceutical industry
- Authors: Jaganath, Nelesh
- Date: 2004
- Subjects: Drugs -- Dosage forms , Rheology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10128 , http://hdl.handle.net/10948/380 , Drugs -- Dosage forms , Rheology
- Description: Rheological characterization of pharmaceutical semisolids is of importance as it provides fundamental information required for the assessment of some of the final properties of a product such as viscosity, elasticity, quality and storage stability. The effect of formulation variables on product characteristics such as consistency and correlation of consumer evaluation of consistency can also be attained. (Ramachandran et al., 1999) This study focussed on using rheological techniques to fully characterize the properties of various semisolid formulations being developed or produced at a South African-based generic pharmaceutical company. Various tests were employed to characterize the semisolid dosage forms (creams and ointments), including continuous shear tests such as flow and viscosity curves and yield point measurements, oscillatory tests such as amplitude and frequency sweeps, as well as step and temperature ramp tests. A method to determine justifiable and meaningful viscosity specifications was developed, where excellent reproducibility of results were obtained when compared to the single-point viscosity determinations usually used. An evaluation as to whether rheology can be utilized as an assessment tool for product stability revealed varying results, with the oscillation-frequency sweep test displaying modest predictive capabilities. Observable differences in rheological character were found when evaluating ointment formulations exhibiting deviating quality characteristics. When analysing the effect of varying processing parameters, namely, cooling rate and mixing speed, during the manufacture of a cream, statistically significant rheological differences were obtained, while a thorough characterization of a scale-up procedure was also achieved upon analysis of various rheological properties.
- Full Text:
- Date Issued: 2004
- Authors: Jaganath, Nelesh
- Date: 2004
- Subjects: Drugs -- Dosage forms , Rheology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10128 , http://hdl.handle.net/10948/380 , Drugs -- Dosage forms , Rheology
- Description: Rheological characterization of pharmaceutical semisolids is of importance as it provides fundamental information required for the assessment of some of the final properties of a product such as viscosity, elasticity, quality and storage stability. The effect of formulation variables on product characteristics such as consistency and correlation of consumer evaluation of consistency can also be attained. (Ramachandran et al., 1999) This study focussed on using rheological techniques to fully characterize the properties of various semisolid formulations being developed or produced at a South African-based generic pharmaceutical company. Various tests were employed to characterize the semisolid dosage forms (creams and ointments), including continuous shear tests such as flow and viscosity curves and yield point measurements, oscillatory tests such as amplitude and frequency sweeps, as well as step and temperature ramp tests. A method to determine justifiable and meaningful viscosity specifications was developed, where excellent reproducibility of results were obtained when compared to the single-point viscosity determinations usually used. An evaluation as to whether rheology can be utilized as an assessment tool for product stability revealed varying results, with the oscillation-frequency sweep test displaying modest predictive capabilities. Observable differences in rheological character were found when evaluating ointment formulations exhibiting deviating quality characteristics. When analysing the effect of varying processing parameters, namely, cooling rate and mixing speed, during the manufacture of a cream, statistically significant rheological differences were obtained, while a thorough characterization of a scale-up procedure was also achieved upon analysis of various rheological properties.
- Full Text:
- Date Issued: 2004
An investigation into the neuroprotective effects of melatonin in a model of rotenone-induced neurodegeneration
- Authors: Kadanthode, Rubina John
- Date: 2004
- Subjects: Melatonin , Nervous system -- Degeneration -- Treatment , Rotenone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3763 , http://hdl.handle.net/10962/d1003241 , Melatonin , Nervous system -- Degeneration -- Treatment , Rotenone
- Description: Parkinson’s disease, one of the most common neurodegenerative disorders associated with ageing, is characterised by abnormal and profound loss of nigrostriatal dopaminergic neurons. The cause of Parkinson’s disease is unknown, but epidemiological studies suggest an association with pesticides and other environmental toxins, and biochemical studies implicate oxidative damage and mitochondrial impairment, particularly at the level of complex I enzyme. Recently, rotenone, a commonly used organic pesticide and a classical inhibitor of mitochondrial complex I has been reported to reproduce the specific features of Parkinson’s disease in rodents. The mitochondrial respiratory chain is one of the most important sites of reactive oxygen species production under physiological conditions. Toxic free radicals have been implicated in a variety of neurodegenerative diseases as well as ageing itself. Melatonin, a secretory product of the pineal gland is a multifaceted free radical scavenger and natural antioxidant. In the present study, the neuroprotective effects of melatonin against the environmental neurotoxin, rotenone was investigated. Initial studies showed that inhibition of mitochondrial complex I enzyme by rotenone induced superoxide radical generation. Melatonin, administered to the rat in vivo and in vitro was able to offer neuroprotection by curtailing the production of superoxide radicals induced by rotenone. Mitochondria, being the major target of rotenone, the effects of melatonin were investigated at the mitochondrial level. Melatonin was able to increase the electron transport chain activity thus preventing the respiratory inhibition by rotenone. The pineal hormone also counteracted the action of rotenone on complex I enzyme. These results suggest melatonin’s ability to potentially limit the free radical generation and thereby modulate the mitochondrial functions. The detection and measurement of lipid peroxidation is the evidence most frequently cited to support the involvement of free radical reactions in toxicology and in human disease. Melatonin also offered significant protection in vivo and in vitro against rotenone induced lipid peroxidation. Since iron plays a major role in oxidative damage and in the progression of Parkinson’s disease, the effect of melatonin on both rotenone and iron induced lipid peroxidation was investigated, the results of which show that melatonin affords protection and this was suggested to be due to its interaction with the rotenone-iron complex that might have formed. Electrochemical studies were further used to characterise the interactions between melatonin, rotenone and iron (III). Melatonin was shown to bind with iron and thus reducing their toxicity. Histological studies were undertaken to assess the effects of melatonin on rotenone induced toxicity on the dopaminergic neurons in the rat brain. Rotenone treated brains showed extensive neuronal damage whereas with melatonin less damage was observed. Rotenone induces apoptosis via reactive oxygen species production and apoptotic cell death has been identified in PD brains. Furthermore, the apoptotic cell death was detected and quantified by the TUNEL staining. Rotenone treated sections showed signs of apoptosis whereas with melatonin, less apoptotic damage was observed. The findings of this study indicate that the neurohormone, melatonin may protect against rotenone-induced neurodegeneration. Since melatonin production falls substantially during ageing, the loss of this antioxidant is theorized to be instrumental in the degenerative processes associated with advanced age. Considering how devastating diseases such as Parkinson’s disease, are to a patient and the patient’s families, the discovery of protective agents are a matter of urgency. Further investigations using the pesticide model will help to determine the involvement of environmental exposure in the pathogenesis of human diseases as well as to test therapeutic strategies for the treatment of such diseases.
- Full Text:
- Date Issued: 2004
- Authors: Kadanthode, Rubina John
- Date: 2004
- Subjects: Melatonin , Nervous system -- Degeneration -- Treatment , Rotenone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3763 , http://hdl.handle.net/10962/d1003241 , Melatonin , Nervous system -- Degeneration -- Treatment , Rotenone
- Description: Parkinson’s disease, one of the most common neurodegenerative disorders associated with ageing, is characterised by abnormal and profound loss of nigrostriatal dopaminergic neurons. The cause of Parkinson’s disease is unknown, but epidemiological studies suggest an association with pesticides and other environmental toxins, and biochemical studies implicate oxidative damage and mitochondrial impairment, particularly at the level of complex I enzyme. Recently, rotenone, a commonly used organic pesticide and a classical inhibitor of mitochondrial complex I has been reported to reproduce the specific features of Parkinson’s disease in rodents. The mitochondrial respiratory chain is one of the most important sites of reactive oxygen species production under physiological conditions. Toxic free radicals have been implicated in a variety of neurodegenerative diseases as well as ageing itself. Melatonin, a secretory product of the pineal gland is a multifaceted free radical scavenger and natural antioxidant. In the present study, the neuroprotective effects of melatonin against the environmental neurotoxin, rotenone was investigated. Initial studies showed that inhibition of mitochondrial complex I enzyme by rotenone induced superoxide radical generation. Melatonin, administered to the rat in vivo and in vitro was able to offer neuroprotection by curtailing the production of superoxide radicals induced by rotenone. Mitochondria, being the major target of rotenone, the effects of melatonin were investigated at the mitochondrial level. Melatonin was able to increase the electron transport chain activity thus preventing the respiratory inhibition by rotenone. The pineal hormone also counteracted the action of rotenone on complex I enzyme. These results suggest melatonin’s ability to potentially limit the free radical generation and thereby modulate the mitochondrial functions. The detection and measurement of lipid peroxidation is the evidence most frequently cited to support the involvement of free radical reactions in toxicology and in human disease. Melatonin also offered significant protection in vivo and in vitro against rotenone induced lipid peroxidation. Since iron plays a major role in oxidative damage and in the progression of Parkinson’s disease, the effect of melatonin on both rotenone and iron induced lipid peroxidation was investigated, the results of which show that melatonin affords protection and this was suggested to be due to its interaction with the rotenone-iron complex that might have formed. Electrochemical studies were further used to characterise the interactions between melatonin, rotenone and iron (III). Melatonin was shown to bind with iron and thus reducing their toxicity. Histological studies were undertaken to assess the effects of melatonin on rotenone induced toxicity on the dopaminergic neurons in the rat brain. Rotenone treated brains showed extensive neuronal damage whereas with melatonin less damage was observed. Rotenone induces apoptosis via reactive oxygen species production and apoptotic cell death has been identified in PD brains. Furthermore, the apoptotic cell death was detected and quantified by the TUNEL staining. Rotenone treated sections showed signs of apoptosis whereas with melatonin, less apoptotic damage was observed. The findings of this study indicate that the neurohormone, melatonin may protect against rotenone-induced neurodegeneration. Since melatonin production falls substantially during ageing, the loss of this antioxidant is theorized to be instrumental in the degenerative processes associated with advanced age. Considering how devastating diseases such as Parkinson’s disease, are to a patient and the patient’s families, the discovery of protective agents are a matter of urgency. Further investigations using the pesticide model will help to determine the involvement of environmental exposure in the pathogenesis of human diseases as well as to test therapeutic strategies for the treatment of such diseases.
- Full Text:
- Date Issued: 2004
Age, growth and yield-per-recruit analysis of ndunduma Diplotaxodon limnothrissa (Teleostei: Cichlidae), in the southeastern arm of Lake Malawi
- Authors: Kanyerere, Geoffrey Zantute
- Date: 2004
- Subjects: Fishes -- Nyasa, Lake , Cichlids -- Nyasa, Lake , Fishes -- Growth -- Nyasa, Lake , Fishes -- Age -- Nyasa, Lake , Fishery resources -- Malawi , Fishery management -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5214 , http://hdl.handle.net/10962/d1005057 , Fishes -- Nyasa, Lake , Cichlids -- Nyasa, Lake , Fishes -- Growth -- Nyasa, Lake , Fishes -- Age -- Nyasa, Lake , Fishery resources -- Malawi , Fishery management -- Malawi
- Description: Diplotaxodon limnothrissa Turner (1995) is a widely distributed species occurring throughout Lake Malawi, extending from the surface to a depth of at least 220m. It is probably the most abundant cichlid in the lake with biomass estimates of around 87 000 tonnes in the pelagic zone alone. The species is exploited commercially in the southern part of the lake but since its inception the fishery has never been assessed. As such this study investigates some aspects of age and growth of the species besides applying a yield-per-recruit analysis to assess the status of the fishery. Analysis of sectioned sagittal otoliths revealed that D. limnothrissa is fast growing and relatively long-lived species, attaining ages in excess of 10 years. Growth in length was rapid in immature fish, with fish attaining almost half of their maximum size within their first year. Le ngth-at-age was described by the von Bertalanffy growth model with combined-sex growth described as Lt = 211.21(1-exp(- 0.24(t+1.36))) mm TL. Total, natural and fishing mortalities were estimated at 0.76 yr⁻¹, 0.31 yr⁻¹ and 0.45 yr⁻¹ respectively. Per-recruit analysis indicated that the D. limnothrissa stock in the southeast arm of the lake is fully exploited as indicated by the current spawner biomass-per-recruit ratios of 31-55% (SB/R)F=0. Modelling indicated that the current age-at-capture (2.67 years) is lower than the age at which yield is optimised (> 5 years) based on the F₀·₁ harvesting strategy. It is, therefore, recommended that the age-at-capture should be increased from 2.67 to 5 years to optimise yield.
- Full Text:
- Date Issued: 2004
- Authors: Kanyerere, Geoffrey Zantute
- Date: 2004
- Subjects: Fishes -- Nyasa, Lake , Cichlids -- Nyasa, Lake , Fishes -- Growth -- Nyasa, Lake , Fishes -- Age -- Nyasa, Lake , Fishery resources -- Malawi , Fishery management -- Malawi
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5214 , http://hdl.handle.net/10962/d1005057 , Fishes -- Nyasa, Lake , Cichlids -- Nyasa, Lake , Fishes -- Growth -- Nyasa, Lake , Fishes -- Age -- Nyasa, Lake , Fishery resources -- Malawi , Fishery management -- Malawi
- Description: Diplotaxodon limnothrissa Turner (1995) is a widely distributed species occurring throughout Lake Malawi, extending from the surface to a depth of at least 220m. It is probably the most abundant cichlid in the lake with biomass estimates of around 87 000 tonnes in the pelagic zone alone. The species is exploited commercially in the southern part of the lake but since its inception the fishery has never been assessed. As such this study investigates some aspects of age and growth of the species besides applying a yield-per-recruit analysis to assess the status of the fishery. Analysis of sectioned sagittal otoliths revealed that D. limnothrissa is fast growing and relatively long-lived species, attaining ages in excess of 10 years. Growth in length was rapid in immature fish, with fish attaining almost half of their maximum size within their first year. Le ngth-at-age was described by the von Bertalanffy growth model with combined-sex growth described as Lt = 211.21(1-exp(- 0.24(t+1.36))) mm TL. Total, natural and fishing mortalities were estimated at 0.76 yr⁻¹, 0.31 yr⁻¹ and 0.45 yr⁻¹ respectively. Per-recruit analysis indicated that the D. limnothrissa stock in the southeast arm of the lake is fully exploited as indicated by the current spawner biomass-per-recruit ratios of 31-55% (SB/R)F=0. Modelling indicated that the current age-at-capture (2.67 years) is lower than the age at which yield is optimised (> 5 years) based on the F₀·₁ harvesting strategy. It is, therefore, recommended that the age-at-capture should be increased from 2.67 to 5 years to optimise yield.
- Full Text:
- Date Issued: 2004
Changes in energy use patterns in the Bushbuckridge Lowveld of the Limpopo Province, South Africa: eleven years on
- Authors: Madubansi, Mainza
- Date: 2004
- Subjects: Energy consumption -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4756 , http://hdl.handle.net/10962/d1007139 , Energy consumption -- South Africa -- Limpopo
- Description: This research reports on the energy transition that has taken place in the Bushbuckridge district between 1991 and 2002. It is a follow up to a similar study that was done in 1991 investigating a number of aspects of energy use. It uses the 1991 study as a baseline and aims to explore how the passage of time, growth of the local population and changes in incomes and the availability of fuels have affected the patterns of fuel use in the region in the past eleven years. A structured interview approach was used for most aspects of the study. The interview schedule included sections on types, amounts and reasons for use and non-use of 13 different energy sources as well as data on income levels, household size and other economic parameters. Analysis of the consumption patterns of the different fuel types revealed that between the two survey periods, households in the sample settlements went through some pronounced changes in patterns of fuel use, particularly those that had acquired electricity. The introduction of electricity in the region had certainly played a major role in spurring the energy transition. Fuels that were previously used for lighting, powering entertainment appliances and refrigeration had been displaced by electricity. In terms of cooking and other thermal application, however, the vast majority of households in all the sample settlements continued using fuelwood and complemented it to a lesser extent with paraffin and electricity. In both surveys, the use or non-use of available fuels in the region was influenced by several factors. Common reasons for non-use of certain fuel types included expense, lack of appliances, the risk involved in using such fuels and the preference for other fuels. Reasons for use were mainly related to the low cost of the fuel and the fuel’s ability to meet particular end uses. Although incomes in the region had increased between 1991 and 2002, they were still below the poverty line. Activities from which households obtained their income remained the same. Old age pension, migrant wages and the informal sector remained the largest contributors of income to most households. Other indicators of relative wealth and poverty, like ownership of vehicles, bicycles and beds remained the same.
- Full Text:
- Date Issued: 2004
- Authors: Madubansi, Mainza
- Date: 2004
- Subjects: Energy consumption -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4756 , http://hdl.handle.net/10962/d1007139 , Energy consumption -- South Africa -- Limpopo
- Description: This research reports on the energy transition that has taken place in the Bushbuckridge district between 1991 and 2002. It is a follow up to a similar study that was done in 1991 investigating a number of aspects of energy use. It uses the 1991 study as a baseline and aims to explore how the passage of time, growth of the local population and changes in incomes and the availability of fuels have affected the patterns of fuel use in the region in the past eleven years. A structured interview approach was used for most aspects of the study. The interview schedule included sections on types, amounts and reasons for use and non-use of 13 different energy sources as well as data on income levels, household size and other economic parameters. Analysis of the consumption patterns of the different fuel types revealed that between the two survey periods, households in the sample settlements went through some pronounced changes in patterns of fuel use, particularly those that had acquired electricity. The introduction of electricity in the region had certainly played a major role in spurring the energy transition. Fuels that were previously used for lighting, powering entertainment appliances and refrigeration had been displaced by electricity. In terms of cooking and other thermal application, however, the vast majority of households in all the sample settlements continued using fuelwood and complemented it to a lesser extent with paraffin and electricity. In both surveys, the use or non-use of available fuels in the region was influenced by several factors. Common reasons for non-use of certain fuel types included expense, lack of appliances, the risk involved in using such fuels and the preference for other fuels. Reasons for use were mainly related to the low cost of the fuel and the fuel’s ability to meet particular end uses. Although incomes in the region had increased between 1991 and 2002, they were still below the poverty line. Activities from which households obtained their income remained the same. Old age pension, migrant wages and the informal sector remained the largest contributors of income to most households. Other indicators of relative wealth and poverty, like ownership of vehicles, bicycles and beds remained the same.
- Full Text:
- Date Issued: 2004
Biochemical characterization of plasmodium falciparum heat shock protein 70
- Matambo, Tonderayi Sylvester
- Authors: Matambo, Tonderayi Sylvester
- Date: 2004
- Subjects: Plasmodium falciparum , Malaria -- Prevention , Protein folding , Proteins -- Purification , Heat shock proteins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4134 , http://hdl.handle.net/10962/d1015767
- Description: Plamodium falciparum heat shock protein (PfHsp70) is believed to be involved in the cytoprotection of the malaria parasite through its action as a molecular chaperone. Bioinformatic analysis reveal that PfHsp70 consists of the three canonical Hsp70 domains; an ATPase domain of 45 kDa, Substrate binding domain of 15 kDa and a C-terminal domain of 10 kDa. At the C-terminus there is a GGMP repeat motif that is commonly found in Hsp70s of parasitic origins. Plasmodium falciparum genome is 80% A-T rich, making it difficult to recombinantly express its proteins in Escherhia coli (E. coli) as a result of rare codon usage. In this study we carried out experiments to improve expression in E. coli by inserting the PfHsp70 coding region into the pQE30 expression vector. However multiple bands were detected by Western analysis, probably due to the presence of rare codons. The RIG plasmid, which encodes tRNAs for rare codons in particular Arg (AGA/AGG), Ile (AUA) and Gly (GGA) was engineered into the E. coli strain resulting in production of full length PfHsp70. Purification was achieved through Ni²⁺ Chelating sepharose under denaturing conditions. PfHsp70 was found to have a very low basal ATPase activity of 0.262 ± 0.05 nmoles/min/mg of protein. In the presence of reduced and carboxymethylated lactalbumin (RCMLA) a 11-fold increase in ATPase activity was noted whereas in the presence of both RCMLA and Trypanosoma cruzi DnaJ (Tcj2) a 16-fold was achieved. For ATP hydrolysis kcat value of 0.003 min⁻¹ was obtained whereas for ADP release a greater kcat value of 0.8 min⁻¹ was obtained. These results indicated that rate of ATP hydrolysis maybe the rate-determining step in the ATPase cycle of PfHsp70.
- Full Text:
- Date Issued: 2004
- Authors: Matambo, Tonderayi Sylvester
- Date: 2004
- Subjects: Plasmodium falciparum , Malaria -- Prevention , Protein folding , Proteins -- Purification , Heat shock proteins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4134 , http://hdl.handle.net/10962/d1015767
- Description: Plamodium falciparum heat shock protein (PfHsp70) is believed to be involved in the cytoprotection of the malaria parasite through its action as a molecular chaperone. Bioinformatic analysis reveal that PfHsp70 consists of the three canonical Hsp70 domains; an ATPase domain of 45 kDa, Substrate binding domain of 15 kDa and a C-terminal domain of 10 kDa. At the C-terminus there is a GGMP repeat motif that is commonly found in Hsp70s of parasitic origins. Plasmodium falciparum genome is 80% A-T rich, making it difficult to recombinantly express its proteins in Escherhia coli (E. coli) as a result of rare codon usage. In this study we carried out experiments to improve expression in E. coli by inserting the PfHsp70 coding region into the pQE30 expression vector. However multiple bands were detected by Western analysis, probably due to the presence of rare codons. The RIG plasmid, which encodes tRNAs for rare codons in particular Arg (AGA/AGG), Ile (AUA) and Gly (GGA) was engineered into the E. coli strain resulting in production of full length PfHsp70. Purification was achieved through Ni²⁺ Chelating sepharose under denaturing conditions. PfHsp70 was found to have a very low basal ATPase activity of 0.262 ± 0.05 nmoles/min/mg of protein. In the presence of reduced and carboxymethylated lactalbumin (RCMLA) a 11-fold increase in ATPase activity was noted whereas in the presence of both RCMLA and Trypanosoma cruzi DnaJ (Tcj2) a 16-fold was achieved. For ATP hydrolysis kcat value of 0.003 min⁻¹ was obtained whereas for ADP release a greater kcat value of 0.8 min⁻¹ was obtained. These results indicated that rate of ATP hydrolysis maybe the rate-determining step in the ATPase cycle of PfHsp70.
- Full Text:
- Date Issued: 2004
Fishes in the Mngazi and Mngazana estuaries, with particular emphasis on the community structure and primary carbon sources
- Authors: Mbande, Sekiwe
- Date: 2004
- Subjects: Fishes -- South Africa -- Mngazi Estuary , Fishes -- South Africa -- Mngazana Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazi Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazana Estuary , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishes -- Physiology , Fishes -- Effect of water quality on , Fishes -- Effect of temperature on , Fishes -- Food , Fishes -- Effect of turbidity on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5700 , http://hdl.handle.net/10962/d1005386 , Fishes -- South Africa -- Mngazi Estuary , Fishes -- South Africa -- Mngazana Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazi Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazana Estuary , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishes -- Physiology , Fishes -- Effect of water quality on , Fishes -- Effect of temperature on , Fishes -- Food , Fishes -- Effect of turbidity on
- Description: The fish community structure of two contrasting estuaries, one with a well developed mangrove forest (Mngazana) and the other without mangroves (Mngazi) was compared. Both the Mngazi and Mngazana estuary fish communities were dominated by marine species, reflecting the importance of these systems as nursery areas for marine fishes. The Mngazi Estuary contained 18% more estuarine fishes in terms of catch per unit effort (CPUE) than the Mngazana Estuary. The reduced tidal influence due to the narrow mouth opening is a possible reason for the heightened CPUE of estuarine species in the Mngazi estuary. The recorded higher diversity of fish species in the Mngazana Estuary when compared with the Mngazi Estuary was attributed to the greater influence of the marine environment due to the wide permanently open mouth, as well as the presence of a variety of habitats in this system. In both estuaries tropical and temperate species were captured, confirming the transitional nature of their biogeographic location which is situated close to the boundary between the subtropical and warm temperate regions of the Southern African coastline. Contrary to previous studies, which recorded seasonal changes in the proportions of tropical and temperate species, the proportions of tropical species remained unchanged at approximately 70% during the January and June sampling occasions. Global warming as a possible reason for the increased dominance of tropical species is discussed. Although several studies in southern Africa have investigated estuarine food web structure, none have compared mangrove and non-mangrove estuaries. In this study, the primary sources of carbon utilised by the fish fauna in the Mngazi and Mngazana estuaries was investigated. The carbon isotopic values of fishes in both estuaries displayed a continuum rather than a tight clustering around particular energy sources. Most detritus feeders of the family Mugilidae (mullets) from both estuaries were relatively more enriched than other fish taxa. The isotopic values of the mullet species suggest a diet derived from relatively enriched carbon sources such as benthic microalgae, the eelgrass Zostera capensis and associated epiphytes. Based on the isotopic values, piscivorous fishes from both estuaries could not be linked to specific prey fish taxa, but clearly the mullet species were not their main food source. The invertebrate feeders that were found in both estuaries showed greater isotopic variations in the Mngazana Estuary than in the Mngazi Estuary, probably reflecting the higher diversity of habitats (carbon sources) and invertebrate prey species in the Mngazana system. Generally the isotopic signatures of fishes from the Mngazi Estuary were more enriched than those from the Mngazana Estuary, thus indicating the possible effect of δ¹³C depleted mangrove derived carbon in the latter system.
- Full Text:
- Date Issued: 2004
- Authors: Mbande, Sekiwe
- Date: 2004
- Subjects: Fishes -- South Africa -- Mngazi Estuary , Fishes -- South Africa -- Mngazana Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazi Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazana Estuary , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishes -- Physiology , Fishes -- Effect of water quality on , Fishes -- Effect of temperature on , Fishes -- Food , Fishes -- Effect of turbidity on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5700 , http://hdl.handle.net/10962/d1005386 , Fishes -- South Africa -- Mngazi Estuary , Fishes -- South Africa -- Mngazana Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazi Estuary , Fishes -- Effect of habitat modification on -- South Africa -- Mngazana Estuary , Estuarine fishes -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Fishes -- Physiology , Fishes -- Effect of water quality on , Fishes -- Effect of temperature on , Fishes -- Food , Fishes -- Effect of turbidity on
- Description: The fish community structure of two contrasting estuaries, one with a well developed mangrove forest (Mngazana) and the other without mangroves (Mngazi) was compared. Both the Mngazi and Mngazana estuary fish communities were dominated by marine species, reflecting the importance of these systems as nursery areas for marine fishes. The Mngazi Estuary contained 18% more estuarine fishes in terms of catch per unit effort (CPUE) than the Mngazana Estuary. The reduced tidal influence due to the narrow mouth opening is a possible reason for the heightened CPUE of estuarine species in the Mngazi estuary. The recorded higher diversity of fish species in the Mngazana Estuary when compared with the Mngazi Estuary was attributed to the greater influence of the marine environment due to the wide permanently open mouth, as well as the presence of a variety of habitats in this system. In both estuaries tropical and temperate species were captured, confirming the transitional nature of their biogeographic location which is situated close to the boundary between the subtropical and warm temperate regions of the Southern African coastline. Contrary to previous studies, which recorded seasonal changes in the proportions of tropical and temperate species, the proportions of tropical species remained unchanged at approximately 70% during the January and June sampling occasions. Global warming as a possible reason for the increased dominance of tropical species is discussed. Although several studies in southern Africa have investigated estuarine food web structure, none have compared mangrove and non-mangrove estuaries. In this study, the primary sources of carbon utilised by the fish fauna in the Mngazi and Mngazana estuaries was investigated. The carbon isotopic values of fishes in both estuaries displayed a continuum rather than a tight clustering around particular energy sources. Most detritus feeders of the family Mugilidae (mullets) from both estuaries were relatively more enriched than other fish taxa. The isotopic values of the mullet species suggest a diet derived from relatively enriched carbon sources such as benthic microalgae, the eelgrass Zostera capensis and associated epiphytes. Based on the isotopic values, piscivorous fishes from both estuaries could not be linked to specific prey fish taxa, but clearly the mullet species were not their main food source. The invertebrate feeders that were found in both estuaries showed greater isotopic variations in the Mngazana Estuary than in the Mngazi Estuary, probably reflecting the higher diversity of habitats (carbon sources) and invertebrate prey species in the Mngazana system. Generally the isotopic signatures of fishes from the Mngazi Estuary were more enriched than those from the Mngazana Estuary, thus indicating the possible effect of δ¹³C depleted mangrove derived carbon in the latter system.
- Full Text:
- Date Issued: 2004
Cleaning of fouled membranes using enzymes from a sulphidogenic bioreactor
- Authors: Melamane, Xolisa
- Date: 2004
- Subjects: Membrane filters , Membrane filters -- Fouling , Enzymes -- Biotechnology , Enzymes -- Purification , Water -- Purification -- Membrane filtration , Ultrafiltration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4133 , http://hdl.handle.net/10962/d1015764
- Description: Maintenance of membrane performance requires inevitable cleaning or defouling of fouled membranes. Membrane cleaning using enzymes such as proteases, lipases, α-glucosidases from a sulphidogenic bioreactor was investigated. At first, dilute and concentrated enzyme extract were prepared form the sulphidogenic pellet. Enzyme assays on 0.5 % azocaisen, 1 % triacetin and 1 mg/ml ρ-nitrophenyl-α-D-glucopyranoside were performed using the concentrated enzyme extract (0 – 200 mg/ml). For membrane fouling, an abattoir effluent was obtained from Ostritech Pty (Ltd), Grahamstown, South Africa. The effluent was characterised for presence of potential foulants such as lipids, proteins, amino acids and carbohydrates. Static fouling of polysulphone membranes (0.22 μm, 47 mm) was then performed using the abattoir effluent. Cleaning of the fouled membranes was also performed using at first the dilute and then the concentrated form (200 mg/ml) of enzyme extracts. Qualitative and quantitative biochemical analysis for proteins, lipids and carbohydrates was performed to ascertain the presence of foulants on polysulphone membranes and their removal by dilute or concentrated enzyme extracts. The ability of dilute enzyme extracts to remove proteins lipids, and carbohydrates fouling capillary UF membrane module; their ability to restore permeate fluxes and transmembrane pressure after cleaning/defouling was also investigated. Permeate volumes from this UF membrane module were analysed for protein, amino acids, lipids, and carbohydrates concentrations after fouling and defouling. Fouling was further characterized by standard blocking, cake filtration and pore blocking models using stirred UF cell and polyethersulphone membranes with MWCO of 30 000, 100 000 and 300 000. After characterization of fouling, polyethersulphone membranes with MWCO of 30 000 and 300 000 were defouled using the concentrated enzyme extract (100 mg ml). Enzyme activities at 200 mg/ml of enzyme concentration were 8.071 IU, 86.71 IU and 789.02 IU for proteases, lipases and α-glucosidases. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Proteins, lipids and carbohydrates fouling polysulphone membranes after a day were removed by 23.4 %, when a dilute enzyme was used. A concentrated enzyme extract of 200 mg/ml was able to remove proteins, lipids and carbohydrates up to 5 days of fouling by 100 %, 82 %, 71 %, 68 % and 76 % respectively. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 hour. Sulphidogenic proteases activity was 2.1 U/ml and flux Recovery (FR %) was 64. Characterization of fouling revealed that proteins and lipids were major foulants while low concentration of carbohydrates fouled polyethersulphone membranes. Fouling followed standard blocking for 10 minutes in all the membranes; afterwards fouling adopted cake filtration model for membranes with 30 000 MWCO and pore blocking model for membranes with 300 000 MWCO. A concentration of 100 mg/ml of enzyme extract was able to remove fouling from membranes with MWCO of 30 000. Defouling membranes that followed pore blocking model i.e. 300 000 MWCO was not successful due to a mass transfer problem. From the results of defouling of 30 000 and 300 000 MWCO it was concluded that defouling of cake layer fouling (30 000 MWCO) was successful while defouling of pore blocking fouling was unsuccessful due to a mass transfer problem. The ratio of enzymes present in the enzyme extract when calculated based on enzymatic activity for proteases, lipases and α-glucosidases was 1.1 %, 11 % and 87.9 %. It was hypothesized that apart from proteases, lipases, α and β-glucosidases; phosphatases, sulphatases, amonipeptidases etc. from a sulphidogenic bioreactor clean or defoul cake layer fouling by organic foulants and pore blocking fouling provided the mass transfer problem is solved. However, concentration of enzymes from a sulphidogenic bioreactor has not been optimized yet. Other methods of concentrating the enzyme extract can be investigated for example use of organic solvents.
- Full Text:
- Date Issued: 2004
- Authors: Melamane, Xolisa
- Date: 2004
- Subjects: Membrane filters , Membrane filters -- Fouling , Enzymes -- Biotechnology , Enzymes -- Purification , Water -- Purification -- Membrane filtration , Ultrafiltration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4133 , http://hdl.handle.net/10962/d1015764
- Description: Maintenance of membrane performance requires inevitable cleaning or defouling of fouled membranes. Membrane cleaning using enzymes such as proteases, lipases, α-glucosidases from a sulphidogenic bioreactor was investigated. At first, dilute and concentrated enzyme extract were prepared form the sulphidogenic pellet. Enzyme assays on 0.5 % azocaisen, 1 % triacetin and 1 mg/ml ρ-nitrophenyl-α-D-glucopyranoside were performed using the concentrated enzyme extract (0 – 200 mg/ml). For membrane fouling, an abattoir effluent was obtained from Ostritech Pty (Ltd), Grahamstown, South Africa. The effluent was characterised for presence of potential foulants such as lipids, proteins, amino acids and carbohydrates. Static fouling of polysulphone membranes (0.22 μm, 47 mm) was then performed using the abattoir effluent. Cleaning of the fouled membranes was also performed using at first the dilute and then the concentrated form (200 mg/ml) of enzyme extracts. Qualitative and quantitative biochemical analysis for proteins, lipids and carbohydrates was performed to ascertain the presence of foulants on polysulphone membranes and their removal by dilute or concentrated enzyme extracts. The ability of dilute enzyme extracts to remove proteins lipids, and carbohydrates fouling capillary UF membrane module; their ability to restore permeate fluxes and transmembrane pressure after cleaning/defouling was also investigated. Permeate volumes from this UF membrane module were analysed for protein, amino acids, lipids, and carbohydrates concentrations after fouling and defouling. Fouling was further characterized by standard blocking, cake filtration and pore blocking models using stirred UF cell and polyethersulphone membranes with MWCO of 30 000, 100 000 and 300 000. After characterization of fouling, polyethersulphone membranes with MWCO of 30 000 and 300 000 were defouled using the concentrated enzyme extract (100 mg ml). Enzyme activities at 200 mg/ml of enzyme concentration were 8.071 IU, 86.71 IU and 789.02 IU for proteases, lipases and α-glucosidases. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Proteins, lipids and carbohydrates fouling polysulphone membranes after a day were removed by 23.4 %, when a dilute enzyme was used. A concentrated enzyme extract of 200 mg/ml was able to remove proteins, lipids and carbohydrates up to 5 days of fouling by 100 %, 82 %, 71 %, 68 % and 76 % respectively. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 hour. Sulphidogenic proteases activity was 2.1 U/ml and flux Recovery (FR %) was 64. Characterization of fouling revealed that proteins and lipids were major foulants while low concentration of carbohydrates fouled polyethersulphone membranes. Fouling followed standard blocking for 10 minutes in all the membranes; afterwards fouling adopted cake filtration model for membranes with 30 000 MWCO and pore blocking model for membranes with 300 000 MWCO. A concentration of 100 mg/ml of enzyme extract was able to remove fouling from membranes with MWCO of 30 000. Defouling membranes that followed pore blocking model i.e. 300 000 MWCO was not successful due to a mass transfer problem. From the results of defouling of 30 000 and 300 000 MWCO it was concluded that defouling of cake layer fouling (30 000 MWCO) was successful while defouling of pore blocking fouling was unsuccessful due to a mass transfer problem. The ratio of enzymes present in the enzyme extract when calculated based on enzymatic activity for proteases, lipases and α-glucosidases was 1.1 %, 11 % and 87.9 %. It was hypothesized that apart from proteases, lipases, α and β-glucosidases; phosphatases, sulphatases, amonipeptidases etc. from a sulphidogenic bioreactor clean or defoul cake layer fouling by organic foulants and pore blocking fouling provided the mass transfer problem is solved. However, concentration of enzymes from a sulphidogenic bioreactor has not been optimized yet. Other methods of concentrating the enzyme extract can be investigated for example use of organic solvents.
- Full Text:
- Date Issued: 2004
A contribution to cabbage pest management by subsistence and small-scale farmers in the Eastern Cape, South Africa
- Authors: Mkize, Nolwazi
- Date: 2004
- Subjects: Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5659 , http://hdl.handle.net/10962/d1005342 , Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Description: The interaction between farmers, agricultural scientists and extension workers is sometimes overlooked in agricultural entomology. In an attempt to respond to this reality this study examines some foundation of this interaction in relation to the pest management practices of subsistence and small-scale farmers and also highlights the problems that might arise in the implementation of IPM. Problems involving pests occurrence; language barriers; beliefs, knowledge and perception about insects, and visual literacy are examined. The thesis has a two-fold focus, firstly the study of pests on cabbages of subsistence farmers in Grahamstown and secondly a broader focus on other aspects such as cultural entomology, perception of insects and visual literacy specifically in relation to Xhosa speaking people in the Eastern Cape. The most important crop for emergent farmers in the Eastern Cape are cabbages, which have a variety of pests of which diamondback moths and are the most important. Traditional pest management practices tend to influence the development of IPM programmes adopted by these farmers. Eastern Cape farmers apply periodic cropping systems, which had an effect on the population densities of diamondback moth (DBM), other lepidopteran pests and their parasitoids. Considering the maximum population densities of DBM, which were 0.2 - 2.9 larvae/plant, there were no major pest problems. The availability of parasitoids, even in highly disturbed and patchy environments, showed good potential for biological control. Since some extension officers cannot speak the local farmers’ language, a dictionary of insect names was formulated in their language (isiXhosa) to assist communication. Response-frequency distribution analysis showed that the dictionary is essentially complete. The literal translations of some names show that isiXhosa speakers often relate insects to people, or to their habitat or classify them according to their behaviour. Farmers from eight sites in the Eastern Cape were interviewed regarding their knowledge and perception of insect pests and their control thereof. To some extent, farmers still rely on cultural control and have beliefs about insects that reflected both reality and superstition. There is no difference between the Ciskei and Transkei regions regarding insect-related beliefs. Farmers generally lack an understanding of insect ecology. There is a need for farmers to be taught about insects to assist with the implementation of IPM. Leftover pesticides from commercial farms or detergents are sometimes used to manage the pests. When training illiterate or semi-literate farmers, it is important to understand their media literacy so as to design useful graphic and object training media. Generally farmers showed that they either understand graphic or object media depending on the features of the insects being looked at. These findings are discussed with regard to the potential development of IPM training material for subsistence and small-scale farmers in a community.
- Full Text:
- Date Issued: 2004
- Authors: Mkize, Nolwazi
- Date: 2004
- Subjects: Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5659 , http://hdl.handle.net/10962/d1005342 , Cabbage -- Diseases and pests , Insect pests -- Integrated control -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- South Africa -- Eastern Cape
- Description: The interaction between farmers, agricultural scientists and extension workers is sometimes overlooked in agricultural entomology. In an attempt to respond to this reality this study examines some foundation of this interaction in relation to the pest management practices of subsistence and small-scale farmers and also highlights the problems that might arise in the implementation of IPM. Problems involving pests occurrence; language barriers; beliefs, knowledge and perception about insects, and visual literacy are examined. The thesis has a two-fold focus, firstly the study of pests on cabbages of subsistence farmers in Grahamstown and secondly a broader focus on other aspects such as cultural entomology, perception of insects and visual literacy specifically in relation to Xhosa speaking people in the Eastern Cape. The most important crop for emergent farmers in the Eastern Cape are cabbages, which have a variety of pests of which diamondback moths and are the most important. Traditional pest management practices tend to influence the development of IPM programmes adopted by these farmers. Eastern Cape farmers apply periodic cropping systems, which had an effect on the population densities of diamondback moth (DBM), other lepidopteran pests and their parasitoids. Considering the maximum population densities of DBM, which were 0.2 - 2.9 larvae/plant, there were no major pest problems. The availability of parasitoids, even in highly disturbed and patchy environments, showed good potential for biological control. Since some extension officers cannot speak the local farmers’ language, a dictionary of insect names was formulated in their language (isiXhosa) to assist communication. Response-frequency distribution analysis showed that the dictionary is essentially complete. The literal translations of some names show that isiXhosa speakers often relate insects to people, or to their habitat or classify them according to their behaviour. Farmers from eight sites in the Eastern Cape were interviewed regarding their knowledge and perception of insect pests and their control thereof. To some extent, farmers still rely on cultural control and have beliefs about insects that reflected both reality and superstition. There is no difference between the Ciskei and Transkei regions regarding insect-related beliefs. Farmers generally lack an understanding of insect ecology. There is a need for farmers to be taught about insects to assist with the implementation of IPM. Leftover pesticides from commercial farms or detergents are sometimes used to manage the pests. When training illiterate or semi-literate farmers, it is important to understand their media literacy so as to design useful graphic and object training media. Generally farmers showed that they either understand graphic or object media depending on the features of the insects being looked at. These findings are discussed with regard to the potential development of IPM training material for subsistence and small-scale farmers in a community.
- Full Text:
- Date Issued: 2004
DRUBIS : a distributed face-identification experimentation framework - design, implementation and performance issues
- Authors: Ndlangisa, Mboneli
- Date: 2004
- Subjects: Principal components analysis , Human face recognition (Computer science) , Image processing , Biometric identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4704 , http://hdl.handle.net/10962/d1015768
- Description: We report on the design, implementation and performance issues of the DRUBIS (Distributed Rhodes University Biometric Identification System) experimentation framework. The Principal Component Analysis (PCA) face-recognition approach is used as a case study. DRUBIS is a flexible experimentation framework, distributed over a number of modules that are easily pluggable and swappable, allowing for the easy construction of prototype systems. Web services are the logical means of distributing DRUBIS components and a number of prototype applications have been implemented from this framework. Different popular PCA face-recognition related experiments were used to evaluate our experimentation framework. We extract recognition performance measures from these experiments. In particular, we use the framework for a more indepth study of the suitability of the DFFS (Difference From Face Space) metric as a means for image classification in the area of race and gender determination.
- Full Text:
- Date Issued: 2004
- Authors: Ndlangisa, Mboneli
- Date: 2004
- Subjects: Principal components analysis , Human face recognition (Computer science) , Image processing , Biometric identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4704 , http://hdl.handle.net/10962/d1015768
- Description: We report on the design, implementation and performance issues of the DRUBIS (Distributed Rhodes University Biometric Identification System) experimentation framework. The Principal Component Analysis (PCA) face-recognition approach is used as a case study. DRUBIS is a flexible experimentation framework, distributed over a number of modules that are easily pluggable and swappable, allowing for the easy construction of prototype systems. Web services are the logical means of distributing DRUBIS components and a number of prototype applications have been implemented from this framework. Different popular PCA face-recognition related experiments were used to evaluate our experimentation framework. We extract recognition performance measures from these experiments. In particular, we use the framework for a more indepth study of the suitability of the DFFS (Difference From Face Space) metric as a means for image classification in the area of race and gender determination.
- Full Text:
- Date Issued: 2004