The synthesis of fructooligosaccharides by the fructofuranosidase FopAp from Aspergillus niger
- Pindura, Mitchell Kingsley Chido
- Authors: Pindura, Mitchell Kingsley Chido
- Date: 2012
- Subjects: Aspergillus niger , Oligosaccharides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4158 , http://hdl.handle.net/10962/d1018267
- Description: Fructooligosaccharides (FOS) are short-chain fructans with a terminal glucose moiety and are found naturally in many plant species. Besides their wide use as an alternative sweetener in food and beverage industry, FOS have shown great potential as neutraceuticals against diabetes, colon cancer and bowel disease. The uses of FOS are dependent on the degree of polymerisation that they exhibit. β-fructofuranosidase (FFase) and fructosyltransferase (FTase) enzymes are capable of synthesing FOS from carbohydrate raw materials such as chicory and sugar beet. The aim of this study was to investigate the synthesis of FOS of a pre-defined chain length, from sucrose, by the enzyme FopAp; a β-fructofuranosidase from Aspergillus niger. ATCC 20611. The crude enzyme FopAp was successfully purified, with a yield of 78.20 %, by ammonium sulphate precipitation and anion exchange chromatography. Two protein fractions, named FA and FB were shown to exhibit FFase activity. SDS PAGE analysis revealed two proteins with molecular weights of 112 kDa and 78 kDa, which were identified as a FFase and a hydrolase. Temperature and pH optima of 20 ºC and 9, respectively, were observed for the transfructosylation activity in the FFase. The purified FFase exhibited a half life of 1.5 hrs under optimal conditions. Substrate kinetic studies indicated a high hydrolytic activity at low sucrose concentrations, with Vmax and Km of 1.25 μmol/ml/min and 3.28 mM, respectively. Analysis by response surface methodology identified temperature and pH to be significant factors for the production of kestose and nystose, at a 95 % level of confidence. These findings were confirmed by neural networks constructed to identify optimal conditions of FOS synthesis.FOS synthesis was found to be optimal between pH 6 and pH 9 at 25 ºC. The factor of reaction time was found to be insignificant within the selected experimental constraints, for both FOS species. The findings of this investigation are very important as the foundations of a commercially viable synthetic process for the production of FOS.
- Full Text:
- Authors: Pindura, Mitchell Kingsley Chido
- Date: 2012
- Subjects: Aspergillus niger , Oligosaccharides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4158 , http://hdl.handle.net/10962/d1018267
- Description: Fructooligosaccharides (FOS) are short-chain fructans with a terminal glucose moiety and are found naturally in many plant species. Besides their wide use as an alternative sweetener in food and beverage industry, FOS have shown great potential as neutraceuticals against diabetes, colon cancer and bowel disease. The uses of FOS are dependent on the degree of polymerisation that they exhibit. β-fructofuranosidase (FFase) and fructosyltransferase (FTase) enzymes are capable of synthesing FOS from carbohydrate raw materials such as chicory and sugar beet. The aim of this study was to investigate the synthesis of FOS of a pre-defined chain length, from sucrose, by the enzyme FopAp; a β-fructofuranosidase from Aspergillus niger. ATCC 20611. The crude enzyme FopAp was successfully purified, with a yield of 78.20 %, by ammonium sulphate precipitation and anion exchange chromatography. Two protein fractions, named FA and FB were shown to exhibit FFase activity. SDS PAGE analysis revealed two proteins with molecular weights of 112 kDa and 78 kDa, which were identified as a FFase and a hydrolase. Temperature and pH optima of 20 ºC and 9, respectively, were observed for the transfructosylation activity in the FFase. The purified FFase exhibited a half life of 1.5 hrs under optimal conditions. Substrate kinetic studies indicated a high hydrolytic activity at low sucrose concentrations, with Vmax and Km of 1.25 μmol/ml/min and 3.28 mM, respectively. Analysis by response surface methodology identified temperature and pH to be significant factors for the production of kestose and nystose, at a 95 % level of confidence. These findings were confirmed by neural networks constructed to identify optimal conditions of FOS synthesis.FOS synthesis was found to be optimal between pH 6 and pH 9 at 25 ºC. The factor of reaction time was found to be insignificant within the selected experimental constraints, for both FOS species. The findings of this investigation are very important as the foundations of a commercially viable synthetic process for the production of FOS.
- Full Text:
The synthesis of α-alkoxy and α-aminostannanes as precursors to Novel Chromium Fischer Carbenes
- Authors: Meyer, Annalene
- Date: 2012
- Subjects: Alkoxides , Organometallic compounds , Carbenes (Methylene compounds) , Chromium , Molybdenum , Tungsten , Organolithium compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4371 , http://hdl.handle.net/10962/d1005036 , Alkoxides , Organometallic compounds , Carbenes (Methylene compounds) , Chromium , Molybdenum , Tungsten , Organolithium compounds
- Description: The present study involves the use of main group organometallics: organostannanes and organolithiums as precursors to chromium Fischer carbene complexes. Fischer carbenes are well stabilized by the π‐donor substituents such as alkoxy and amino groups and low oxidation state metals such as Group 6 (Chromium, Molybdenum or Tungsten). Carbenes are an important intermediate in the synthesis of a range of compounds through cyclopropanations, insertions, coupling and photochemical reactions. Synthesis and successful characterisation of three α‐alkoxystannanes was achieved via nucleophilic addition of tributylstannyllithium to the respective aldehydes, followed by an immediate MOM protection of the resulting alcohol. Six α‐aminostanannes were synthesised, consisting of N‐BOC, N‐acetyl and N‐ethyl derivatives of pyrrolidine and piperidine, via α‐lithiation and subsequent tinlithium transmetallation in the presence of TMEDA. The ¹³C NMR analysis highlighted an interesting phenomenon of tin‐carbon coupling that revealed unique structural information of both types of stannanes. DFT analysis was completed on the series of stannanes; a predicted frequency analysis was obtained which complemented the experimental Infra‐red data in elucidation of the compounds. The α‐alkoxy and α‐aminostannanes provided stable precursors to the organolithiums required for the synthesis of the novel Fischer chromium carbenes. The organolithiums were obtained via tinlithium exchange at low temperatures, followed by the addition of chromium hexacarbonyl to form the acylpentacarbonyl‐chromate salt. Alkylation of this intermediate using a Meerwein salt, Me₃OBF₄, gave rise to the novel Fischer chromium carbene complexes. Fischer chromium carbenes derived from the two isomeric butyl and isobutyl stannanes and the two N‐ethyl α‐aminostannanes were successfully synthesised. The difficulty encountered in the purification of the Fischer carbene complexes hindered the full characterisation, due to the presence of a by‐product, tetrabutyltin.
- Full Text:
- Authors: Meyer, Annalene
- Date: 2012
- Subjects: Alkoxides , Organometallic compounds , Carbenes (Methylene compounds) , Chromium , Molybdenum , Tungsten , Organolithium compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4371 , http://hdl.handle.net/10962/d1005036 , Alkoxides , Organometallic compounds , Carbenes (Methylene compounds) , Chromium , Molybdenum , Tungsten , Organolithium compounds
- Description: The present study involves the use of main group organometallics: organostannanes and organolithiums as precursors to chromium Fischer carbene complexes. Fischer carbenes are well stabilized by the π‐donor substituents such as alkoxy and amino groups and low oxidation state metals such as Group 6 (Chromium, Molybdenum or Tungsten). Carbenes are an important intermediate in the synthesis of a range of compounds through cyclopropanations, insertions, coupling and photochemical reactions. Synthesis and successful characterisation of three α‐alkoxystannanes was achieved via nucleophilic addition of tributylstannyllithium to the respective aldehydes, followed by an immediate MOM protection of the resulting alcohol. Six α‐aminostanannes were synthesised, consisting of N‐BOC, N‐acetyl and N‐ethyl derivatives of pyrrolidine and piperidine, via α‐lithiation and subsequent tinlithium transmetallation in the presence of TMEDA. The ¹³C NMR analysis highlighted an interesting phenomenon of tin‐carbon coupling that revealed unique structural information of both types of stannanes. DFT analysis was completed on the series of stannanes; a predicted frequency analysis was obtained which complemented the experimental Infra‐red data in elucidation of the compounds. The α‐alkoxy and α‐aminostannanes provided stable precursors to the organolithiums required for the synthesis of the novel Fischer chromium carbenes. The organolithiums were obtained via tinlithium exchange at low temperatures, followed by the addition of chromium hexacarbonyl to form the acylpentacarbonyl‐chromate salt. Alkylation of this intermediate using a Meerwein salt, Me₃OBF₄, gave rise to the novel Fischer chromium carbene complexes. Fischer chromium carbenes derived from the two isomeric butyl and isobutyl stannanes and the two N‐ethyl α‐aminostannanes were successfully synthesised. The difficulty encountered in the purification of the Fischer carbene complexes hindered the full characterisation, due to the presence of a by‐product, tetrabutyltin.
- Full Text:
The treatment of brewery effluent using an integrated high rate algal ponding system
- Authors: Cilliers, Anneke
- Date: 2012
- Subjects: Water -- Purification -- South Africa , Algae -- Biotechnology , Algae culture , Algae -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5331 , http://hdl.handle.net/10962/d1005177 , Water -- Purification -- South Africa , Algae -- Biotechnology , Algae culture , Algae -- Economic aspects
- Description: The application of high rate algal ponds (HRAP) in the treatment of brewery effluent that met the South African Department of Water Affairs and Forestry's (DWAF) general limits for discharge into a natural water resource of 1998 were tested during a lO-month baseline phase, followed by an 11-month optimization phase. The objective of the baseline phase was to monitor the seasonal performance of HRAPs. The hydraulic retention time (HRT) fluctuated between 11.16 d and 12.00 d in HRAPs. The chemical oxygen demand (COD) increased from 130.12 ± 6.94 mg/L (post-AD), to 171.21 ± 7.99 mg/L (post-HRAP) . The presence of algal cells and evaporation contributed towards an increase in post-HRAP COD. The ammonia (NH₄-N) concentration decreased from 46.59 ± 2.47 mg/L (post-AD), to 1.08 ± 0.12 mg/L (post-HRAP). The nitrite (NO₂- N) concentration remained below 1.00 mg/L in post-pilot plant AD, post-PFP and post-HRAP effluent. The phosphate (PO₄-P) concentration decreased from 29.81 ± 1.39 mg/L (post-AD) to 17.30 ± 1.16 mg/L PO₄-P. The objective of the optimization phase was to manipulate the HRT to achieve the maximum treatment rate that met the DWAF general limits for discharge into a natural water resource of 1998. Nitrogen (as NH₄-N, NO₃-N, NO₂-N) removal efficiency was used as an indicator of nutrient removal success. HRT was influenced by season. The optimal HRT for autumn was 4.30 d at a temperature of 20.53ºC in HRAP A2 (heated) and 18.96ºC in HRAP B2 (ambient). The optimal HRT for summer was 2.74 d at 29.90ºC in HRAP A2 (heated) and 26.36ºC in HRAP B2 (ambient). The COD decreased from 152.33 ± 4.85 mg/L (post-AD) to 95 .00 ± 3.75 mg/L (post-HRAP A2), and to 100.82 ± 5.93 mg/L (post-HRAP B2). The incoming NH₄-N concentration decreased from 42.53 ± 1.38 mg/ L (post-AD), to 1.70 ± 0.81 mg/ L (post-HRAP) . The nitrate (NO₃-N) concentration post-HRAP was 12 - 14 mg/L. The main methods for NH₄-N removal were probably NH₄-N volatilization through algal uptake. HRAPs were able to lower nitrogen and phosphorous concentrations to within the DWAF limits under normal operating conditions. It is recommended that HRAP treated brewery wastewater be used for irrigation after salt removal, or alternatively, for groundwater recharge . Regulatory exemptions would be required for higher than permitted COD and EC concentrations to enable these actions.
- Full Text:
- Authors: Cilliers, Anneke
- Date: 2012
- Subjects: Water -- Purification -- South Africa , Algae -- Biotechnology , Algae culture , Algae -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5331 , http://hdl.handle.net/10962/d1005177 , Water -- Purification -- South Africa , Algae -- Biotechnology , Algae culture , Algae -- Economic aspects
- Description: The application of high rate algal ponds (HRAP) in the treatment of brewery effluent that met the South African Department of Water Affairs and Forestry's (DWAF) general limits for discharge into a natural water resource of 1998 were tested during a lO-month baseline phase, followed by an 11-month optimization phase. The objective of the baseline phase was to monitor the seasonal performance of HRAPs. The hydraulic retention time (HRT) fluctuated between 11.16 d and 12.00 d in HRAPs. The chemical oxygen demand (COD) increased from 130.12 ± 6.94 mg/L (post-AD), to 171.21 ± 7.99 mg/L (post-HRAP) . The presence of algal cells and evaporation contributed towards an increase in post-HRAP COD. The ammonia (NH₄-N) concentration decreased from 46.59 ± 2.47 mg/L (post-AD), to 1.08 ± 0.12 mg/L (post-HRAP). The nitrite (NO₂- N) concentration remained below 1.00 mg/L in post-pilot plant AD, post-PFP and post-HRAP effluent. The phosphate (PO₄-P) concentration decreased from 29.81 ± 1.39 mg/L (post-AD) to 17.30 ± 1.16 mg/L PO₄-P. The objective of the optimization phase was to manipulate the HRT to achieve the maximum treatment rate that met the DWAF general limits for discharge into a natural water resource of 1998. Nitrogen (as NH₄-N, NO₃-N, NO₂-N) removal efficiency was used as an indicator of nutrient removal success. HRT was influenced by season. The optimal HRT for autumn was 4.30 d at a temperature of 20.53ºC in HRAP A2 (heated) and 18.96ºC in HRAP B2 (ambient). The optimal HRT for summer was 2.74 d at 29.90ºC in HRAP A2 (heated) and 26.36ºC in HRAP B2 (ambient). The COD decreased from 152.33 ± 4.85 mg/L (post-AD) to 95 .00 ± 3.75 mg/L (post-HRAP A2), and to 100.82 ± 5.93 mg/L (post-HRAP B2). The incoming NH₄-N concentration decreased from 42.53 ± 1.38 mg/ L (post-AD), to 1.70 ± 0.81 mg/ L (post-HRAP) . The nitrate (NO₃-N) concentration post-HRAP was 12 - 14 mg/L. The main methods for NH₄-N removal were probably NH₄-N volatilization through algal uptake. HRAPs were able to lower nitrogen and phosphorous concentrations to within the DWAF limits under normal operating conditions. It is recommended that HRAP treated brewery wastewater be used for irrigation after salt removal, or alternatively, for groundwater recharge . Regulatory exemptions would be required for higher than permitted COD and EC concentrations to enable these actions.
- Full Text:
The trophic ecology of parrotfish of Zanzibar application of stable isotope analysis
- Plass-Johnson, Jeremiah Grahm
- Authors: Plass-Johnson, Jeremiah Grahm
- Date: 2012
- Subjects: Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5789 , http://hdl.handle.net/10962/d1005477 , Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Description: Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.
- Full Text:
- Authors: Plass-Johnson, Jeremiah Grahm
- Date: 2012
- Subjects: Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5789 , http://hdl.handle.net/10962/d1005477 , Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Description: Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.
- Full Text:
The valuation of amounts for the purpose of inclusion in gross income
- Authors: Spearman, Tarryn Leigh
- Date: 2012
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:887 , http://hdl.handle.net/10962/d1001641
- Description: The present research investigates the valuation of amounts for the purpose of inclusion in gross income. Because the gross income definition in section 1 of the Income Tax Act includes "amounts in cash or otherwise", valuations are often required in order to establish a value in money terms for amounts received or accrued in a form otherwise than in cash. The basis on which these valuations are made can vary and the courts have frequently been called upon to decide on the correct method of valuation. There has been an ongoing debate in the courts as to whether a strict objective approach or a more flexible subjective approach should be adopted when valuing an amount in a form other than cash, which was finally settled in the decision by the Supreme Court of Appeal in CIR v Brummeria Renaissance (Pty) Ltd, which held that an objective approach must be followed. The present research will demonstrate how the strict rule of interpretation tends to result in purely objective valuations as it requires that the ordinary grammatical meaning of words be applied and does not allow the court to consider the purpose of the legislation or introduce any subjectivity based on the circumstances of each individual taxpayer and the facts of each particular case, which a purposive interpretation approach does. The purposive approach to interpretation is therefore more closely aligned with the subjective approach to valuation. Both the objective and subjective approaches to valuation have advantages and disadvantages, which are addressed in the research. The need for certainty in taxation was articulated as early as 1776 by Adam Smith in his Wealth of Nations. The objective approach appears to create a level of consistency as all income received by a taxpayer is effectively taxed as if received by a third party in an arm’s length transaction. The approach has led to unfair decisions at odds with economic reality and generally accepted accounting principles, which could be challenged on the basis of a lack of equity and fairness as required by the Constitution of the Republic of South Africa. The research demonstrates that an objective method of valuation is neither fully objective nor appropriate in certain circumstances, while a subjective approach may be more appropriate as it ensures that each taxpayer’s individual rights are protected. Although the subjective approach successfully addresses the issue of fairness, it threatens to introduce an unacceptable level of inconsistency and is, in reality, not always administratively feasible. The present research concludes that a trade-off between fairness and consistency is often necessary.
- Full Text:
- Authors: Spearman, Tarryn Leigh
- Date: 2012
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:887 , http://hdl.handle.net/10962/d1001641
- Description: The present research investigates the valuation of amounts for the purpose of inclusion in gross income. Because the gross income definition in section 1 of the Income Tax Act includes "amounts in cash or otherwise", valuations are often required in order to establish a value in money terms for amounts received or accrued in a form otherwise than in cash. The basis on which these valuations are made can vary and the courts have frequently been called upon to decide on the correct method of valuation. There has been an ongoing debate in the courts as to whether a strict objective approach or a more flexible subjective approach should be adopted when valuing an amount in a form other than cash, which was finally settled in the decision by the Supreme Court of Appeal in CIR v Brummeria Renaissance (Pty) Ltd, which held that an objective approach must be followed. The present research will demonstrate how the strict rule of interpretation tends to result in purely objective valuations as it requires that the ordinary grammatical meaning of words be applied and does not allow the court to consider the purpose of the legislation or introduce any subjectivity based on the circumstances of each individual taxpayer and the facts of each particular case, which a purposive interpretation approach does. The purposive approach to interpretation is therefore more closely aligned with the subjective approach to valuation. Both the objective and subjective approaches to valuation have advantages and disadvantages, which are addressed in the research. The need for certainty in taxation was articulated as early as 1776 by Adam Smith in his Wealth of Nations. The objective approach appears to create a level of consistency as all income received by a taxpayer is effectively taxed as if received by a third party in an arm’s length transaction. The approach has led to unfair decisions at odds with economic reality and generally accepted accounting principles, which could be challenged on the basis of a lack of equity and fairness as required by the Constitution of the Republic of South Africa. The research demonstrates that an objective method of valuation is neither fully objective nor appropriate in certain circumstances, while a subjective approach may be more appropriate as it ensures that each taxpayer’s individual rights are protected. Although the subjective approach successfully addresses the issue of fairness, it threatens to introduce an unacceptable level of inconsistency and is, in reality, not always administratively feasible. The present research concludes that a trade-off between fairness and consistency is often necessary.
- Full Text:
Third crime unlucky
- Authors: Cartwright, Robert Oliver
- Date: 2012
- Subjects: South African fiction (English) -- 21st century , Creative writing (Higher education) , Creative writing -- Fiction
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5987 , http://hdl.handle.net/10962/d1015729
- Description: This is a contemporary mystery novel set in the Eastern Cape. A town’s airstrip, situated between the golf club and the military base, acts as host to the local flying club and an active skydiving school. An amateur investigator uses unorthodox methods and the help of friends to find the cause of aeroplane fires and sabotage. His investigations lead him via geological research and insurance reports into contact with members of the aviation, property development and military fields.
- Full Text:
- Authors: Cartwright, Robert Oliver
- Date: 2012
- Subjects: South African fiction (English) -- 21st century , Creative writing (Higher education) , Creative writing -- Fiction
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5987 , http://hdl.handle.net/10962/d1015729
- Description: This is a contemporary mystery novel set in the Eastern Cape. A town’s airstrip, situated between the golf club and the military base, acts as host to the local flying club and an active skydiving school. An amateur investigator uses unorthodox methods and the help of friends to find the cause of aeroplane fires and sabotage. His investigations lead him via geological research and insurance reports into contact with members of the aviation, property development and military fields.
- Full Text:
Ties that bind
- Authors: Tshisela, Namhla
- Date: 2012
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:20988 , http://hdl.handle.net/10962/5913
- Description: This collection of short stories about contemporary black South African women reveals their hopes and anxieties, and explores their relationships with themselves, their families, and the people around them. It sets out to challenge stereotypes about black women being browbeaten in a country riddled by poverty and disease by portraying women successfully forging their identities in society.
- Full Text:
- Authors: Tshisela, Namhla
- Date: 2012
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:20988 , http://hdl.handle.net/10962/5913
- Description: This collection of short stories about contemporary black South African women reveals their hopes and anxieties, and explores their relationships with themselves, their families, and the people around them. It sets out to challenge stereotypes about black women being browbeaten in a country riddled by poverty and disease by portraying women successfully forging their identities in society.
- Full Text:
Touching Brýnstone
- Authors: Woudstra, Ruth
- Date: 2012
- Subjects: South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century , South African poetry (English) -- 21st century , Creative writing (Higher education) , Diaries -- Authorship , English language -- Writing
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2504 , http://hdl.handle.net/10962/d1015032
- Description: Touching Brýnstone is the story of Beth, a young journalist who is troubled by misfortunes in her family and work circumstances. In a Pretoria library she is seduced by a book that consoles her and progressively becomes a fetish object. It sparks a journey to Japan, where she arrives to teach English. She is intent on meeting the author, whom she confounds with protagonist and book. This Bildungsroman is an exploration of the complex relationship between inner and outer self, and the struggle towards wholeness. Beth must find a way out of the obsession so that she can return to South Africa with an enriched insight into her shadow self.
- Full Text:
- Authors: Woudstra, Ruth
- Date: 2012
- Subjects: South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century , South African poetry (English) -- 21st century , Creative writing (Higher education) , Diaries -- Authorship , English language -- Writing
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2504 , http://hdl.handle.net/10962/d1015032
- Description: Touching Brýnstone is the story of Beth, a young journalist who is troubled by misfortunes in her family and work circumstances. In a Pretoria library she is seduced by a book that consoles her and progressively becomes a fetish object. It sparks a journey to Japan, where she arrives to teach English. She is intent on meeting the author, whom she confounds with protagonist and book. This Bildungsroman is an exploration of the complex relationship between inner and outer self, and the struggle towards wholeness. Beth must find a way out of the obsession so that she can return to South Africa with an enriched insight into her shadow self.
- Full Text:
Trophic ecology of breeding northern rockhopper penguins, Eudyptes Moseleyi, at Tristan da Cunha, South Atlantic Ocean
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
Understanding the biomolecular interactions involved in dimerisation of the Saccharomyces cerevisiae eukaryotic translation initiation factor 5A
- Authors: Charlton, Jane Laura
- Date: 2012
- Subjects: Proteins -- Synthesis -- Research , Saccharomyces cerevisiae -- Research , Dimers , Dimers -- Research , Eukaryotic cells -- Research , Yeast -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4057 , http://hdl.handle.net/10962/d1004118 , Proteins -- Synthesis -- Research , Saccharomyces cerevisiae -- Research , Dimers , Dimers -- Research , Eukaryotic cells -- Research , Yeast -- Research
- Description: Translation initiation factor 5A (IF5A) is an essential, highly conserved protein found within all eukaryotic (eIF5A) and archaeal (aIF5A) cells. The IF5A protein is unique in that it contains the amino acid hypusine; a two-step post translational modification of a single, conserved lysine residue. Although hypusination of eIF5A is vital for eukaryotic cell viability, the primary role of the protein and its hypusine side chain remain a mystery. eIF5A, initially identified as a translation initiation factor, is not required for global protein synthesis leading to the prevailing proposal that eIF5A is purely involved in the translation of a select subset of mRNAs. Recently a number of mutational studies have focused on the conserved, hypusine-containing loop region of eIF5A where specific residues have been found to be essential for activity without affecting hypusination. It has been postulated that eIF5A exists as a dimer (40 kDa) under native conditions and that these residues may be at the interface of dimerisation. The aim of this research was therefore to conduct a mutational analysis of the loop region in support of this hypothesis. A functional analysis of the Saccharomyces cerevisiae eIF5A mutant proteins K48D, G50A, H52A and K56A revealed that these substitutions impaired growth to varying degrees in vivo with G50A and K48D mutant proteins displaying the most convincing defects. Gel filtration profiles gave unexpected results determining eIF5A mutant and wild type proteins to have a native molecular weight of 30 to 31 kDa, suggesting that the eIF5A oligomeric state may be transitory and subject to certain conditions. The inconclusive results obtained from using gel filtration studies led to an investigation into the feasibility of producing native, hypusinated peptides for future structural studies using nuclear magnetic resonance. Hypusinated and unhypusinated eIF5A were successfully separated into their domains making this a possibility. Finally, this study proposes a role for eIF5A in eukaryotic IRES-driven translation initiation.
- Full Text:
- Authors: Charlton, Jane Laura
- Date: 2012
- Subjects: Proteins -- Synthesis -- Research , Saccharomyces cerevisiae -- Research , Dimers , Dimers -- Research , Eukaryotic cells -- Research , Yeast -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4057 , http://hdl.handle.net/10962/d1004118 , Proteins -- Synthesis -- Research , Saccharomyces cerevisiae -- Research , Dimers , Dimers -- Research , Eukaryotic cells -- Research , Yeast -- Research
- Description: Translation initiation factor 5A (IF5A) is an essential, highly conserved protein found within all eukaryotic (eIF5A) and archaeal (aIF5A) cells. The IF5A protein is unique in that it contains the amino acid hypusine; a two-step post translational modification of a single, conserved lysine residue. Although hypusination of eIF5A is vital for eukaryotic cell viability, the primary role of the protein and its hypusine side chain remain a mystery. eIF5A, initially identified as a translation initiation factor, is not required for global protein synthesis leading to the prevailing proposal that eIF5A is purely involved in the translation of a select subset of mRNAs. Recently a number of mutational studies have focused on the conserved, hypusine-containing loop region of eIF5A where specific residues have been found to be essential for activity without affecting hypusination. It has been postulated that eIF5A exists as a dimer (40 kDa) under native conditions and that these residues may be at the interface of dimerisation. The aim of this research was therefore to conduct a mutational analysis of the loop region in support of this hypothesis. A functional analysis of the Saccharomyces cerevisiae eIF5A mutant proteins K48D, G50A, H52A and K56A revealed that these substitutions impaired growth to varying degrees in vivo with G50A and K48D mutant proteins displaying the most convincing defects. Gel filtration profiles gave unexpected results determining eIF5A mutant and wild type proteins to have a native molecular weight of 30 to 31 kDa, suggesting that the eIF5A oligomeric state may be transitory and subject to certain conditions. The inconclusive results obtained from using gel filtration studies led to an investigation into the feasibility of producing native, hypusinated peptides for future structural studies using nuclear magnetic resonance. Hypusinated and unhypusinated eIF5A were successfully separated into their domains making this a possibility. Finally, this study proposes a role for eIF5A in eukaryotic IRES-driven translation initiation.
- Full Text:
Using co-located radars and instruments to analyse ionespheric events over South Africa
- Authors: Athieno, Racheal
- Date: 2012
- Subjects: Ionosphere -- Research -- South Africa , Space environment -- Research -- South Africa , Meteorology -- Research -- South Africa , Ionosondes -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5493 , http://hdl.handle.net/10962/d1005279 , Ionosphere -- Research -- South Africa , Space environment -- Research -- South Africa , Meteorology -- Research -- South Africa , Ionosondes -- Research -- South Africa
- Description: Space weather and its effect on technological systems are important for scientific research. Developing an understanding of the behaviour, sources and effects of ionospheric events form a basis for improving space weather prediction. This thesis attempts to use co-located radars and instruments for the analysis of ionospheric events over South Africa. The HF Doppler radar, ionosonde, Global Positioning System (GPS) and GPS ionospheric scintillation monitor (GISTM) receivers are co-located in Hermanus (34.4°S, 19.2°E), one of the observatories for the space science directorate of the South African National Space Agency (SANSA). Data was obtained from these radars and instruments and analysed for ionospheric events. Only the Hermanus station was selected for this analysis, because it is currently the only South African station that hosts all the mentioned radars and instruments. Ionospheric events identified include wave-like structures, Doppler spread, sudden frequency deviations and ionospheric oscillations associated with geomagnetic pulsations. For the purpose of this work, ionospheric events are defined as any unusual structures observed on the received signal and inferred from observations made by the HF Doppler radar. They were identified by visual inspection of the Doppler shift spectrograms. The magnitude and nature of the events vary, depending on their source and were observed by all, some or one instrument. This study suggests that the inclusion of a wider data coverage and more stations in South Africa merit consideration, especially since plans are underway to host a co-located radar network similar to that in Hermanus at at least three additional observatory sites in South Africa. This study lays a foundation for multi-station co-located radar and instrument observation and analysis of ionospheric events which should enhance the accuracy of space weather and HF communication prediction.
- Full Text:
- Authors: Athieno, Racheal
- Date: 2012
- Subjects: Ionosphere -- Research -- South Africa , Space environment -- Research -- South Africa , Meteorology -- Research -- South Africa , Ionosondes -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5493 , http://hdl.handle.net/10962/d1005279 , Ionosphere -- Research -- South Africa , Space environment -- Research -- South Africa , Meteorology -- Research -- South Africa , Ionosondes -- Research -- South Africa
- Description: Space weather and its effect on technological systems are important for scientific research. Developing an understanding of the behaviour, sources and effects of ionospheric events form a basis for improving space weather prediction. This thesis attempts to use co-located radars and instruments for the analysis of ionospheric events over South Africa. The HF Doppler radar, ionosonde, Global Positioning System (GPS) and GPS ionospheric scintillation monitor (GISTM) receivers are co-located in Hermanus (34.4°S, 19.2°E), one of the observatories for the space science directorate of the South African National Space Agency (SANSA). Data was obtained from these radars and instruments and analysed for ionospheric events. Only the Hermanus station was selected for this analysis, because it is currently the only South African station that hosts all the mentioned radars and instruments. Ionospheric events identified include wave-like structures, Doppler spread, sudden frequency deviations and ionospheric oscillations associated with geomagnetic pulsations. For the purpose of this work, ionospheric events are defined as any unusual structures observed on the received signal and inferred from observations made by the HF Doppler radar. They were identified by visual inspection of the Doppler shift spectrograms. The magnitude and nature of the events vary, depending on their source and were observed by all, some or one instrument. This study suggests that the inclusion of a wider data coverage and more stations in South Africa merit consideration, especially since plans are underway to host a co-located radar network similar to that in Hermanus at at least three additional observatory sites in South Africa. This study lays a foundation for multi-station co-located radar and instrument observation and analysis of ionospheric events which should enhance the accuracy of space weather and HF communication prediction.
- Full Text:
Videographic analysis of the Coelacanth, Latimeria Chalumnae, and associated habitats in the Isimangaliso Wetland Park, KwaZulu-Natal, South Africa
- Thornycroft, Rosanne Elizabeth
- Authors: Thornycroft, Rosanne Elizabeth
- Date: 2012
- Subjects: Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5333 , http://hdl.handle.net/10962/d1005179 , Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Description: Videography is a valuable tool in biological and ecological studies. Using video footage obtained during previous coelacanth surveys, this thesis investigated coelacanths and their associated habitats in the submarine canyons of iSimangaliso Wetland Park, South Africa. This thesis aimed to (1) describe the biological habitats within the submarine canyons, (2) determine coelacanth distribution within these habitats, and (3) assess the use of computer-aided identification to successfully identify individual coelacanths. Seven different habitat types were noted with the most distinctive being the canyon margins that consisted of dense agglomerations of gorgonians, wire and whip corals, and sponges. Results suggested that although substratum type has a great influence on invertebrate community structure in the canyons, depth is the principal factor. Coelacanths were associated with cave habitats within the steep rocky canyon walls. Habitat analyses allowed predictive classification tree models to be constructed. Depth, underlying percentage of rock, and percentage cover of gorgonians and sponges were the most important variables for determining coelacanth presence and absence. The overall correct classification rate for the model was estimated at 96.6%, correctly predicting coelacanth absence (> 99%) better than presence (60%). Because coelacanths have a unique spot pattern it was possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator the software accurately identified between 56 and 92% of the individuals. Identification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs. Each of the sections presented in this thesis represent a possible step towards analysing coelacanth-related habitats, locating and then analysing new habitats. Steps include first locating a population and then performing a habitat analysis. Coelacanth location within the different habitats can then be determined allowing the development of predictive models to potentially identify possible locations of new populations. The final step is to identify individual fish within the population for assessing demographic parameters and population monitoring.
- Full Text:
- Authors: Thornycroft, Rosanne Elizabeth
- Date: 2012
- Subjects: Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5333 , http://hdl.handle.net/10962/d1005179 , Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Description: Videography is a valuable tool in biological and ecological studies. Using video footage obtained during previous coelacanth surveys, this thesis investigated coelacanths and their associated habitats in the submarine canyons of iSimangaliso Wetland Park, South Africa. This thesis aimed to (1) describe the biological habitats within the submarine canyons, (2) determine coelacanth distribution within these habitats, and (3) assess the use of computer-aided identification to successfully identify individual coelacanths. Seven different habitat types were noted with the most distinctive being the canyon margins that consisted of dense agglomerations of gorgonians, wire and whip corals, and sponges. Results suggested that although substratum type has a great influence on invertebrate community structure in the canyons, depth is the principal factor. Coelacanths were associated with cave habitats within the steep rocky canyon walls. Habitat analyses allowed predictive classification tree models to be constructed. Depth, underlying percentage of rock, and percentage cover of gorgonians and sponges were the most important variables for determining coelacanth presence and absence. The overall correct classification rate for the model was estimated at 96.6%, correctly predicting coelacanth absence (> 99%) better than presence (60%). Because coelacanths have a unique spot pattern it was possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator the software accurately identified between 56 and 92% of the individuals. Identification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs. Each of the sections presented in this thesis represent a possible step towards analysing coelacanth-related habitats, locating and then analysing new habitats. Steps include first locating a population and then performing a habitat analysis. Coelacanth location within the different habitats can then be determined allowing the development of predictive models to potentially identify possible locations of new populations. The final step is to identify individual fish within the population for assessing demographic parameters and population monitoring.
- Full Text:
Water quality dynamics in an experimental serial-use raceway and its effects on growth of South African abalone, Haliotis midae
- Authors: Naylor, Matthew Aubrey
- Date: 2012
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Effect of water quality on , Abalones -- Nutrition -- South Africa , Abalones -- Feeding and feeds , Abalones -- Growth , Fish culture -- Water reuse
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5335 , http://hdl.handle.net/10962/d1005181 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Effect of water quality on , Abalones -- Nutrition -- South Africa , Abalones -- Feeding and feeds , Abalones -- Growth , Fish culture -- Water reuse
- Description: An understanding of species specific water quality requirements is essential for efficient production of aquaculture products, an aspect not well documented for the land-based culture of the South African abalone, Haliotis midae. In order for the industry to remain competitive in international markets, efficient use of water supplies and the development of water reuse technology is needed. This study assessed the changes in water quality between tanks in a tiered serial-use raceway in relation to accumulated biomass and water flow and estimated the flow index (FI) (L h⁻¹ kg⁻¹) at which growth becomes significantly affected. The effect of dietary protein level, supplementation of pure oxygen and addition of sodium hydroxide (NaOH⁻) on water quality and fundamental production parameters in the serial-use raceways was also assessed. The serial-use raceways were used as a tool to create a range of water quality conditions at which the growth, feed conversion ratio (FCR) and condition factor (CF) of "cocktail" size (60 – 70 mm) H. midae could be monitored. The metabolic activity of the abalone resulted in a deterioration in water quality between tanks in series. pH (r² = 0.99; p < 0.001) and dissolved oxygen concentration (r² = 0.99; p < 0.001) were positively correlated with flow index (pH = 7.38 FI°·°² ; dissolved oxygen = 6.92 FI°·°⁴), while free ammonia nitrogen (FAN) (r² = 0.99, p < 0.001) and nitrite (NO²⁻ - N) (r² = 0.93, p < 0.001) were negatively correlated with flow index (FAN = 8.02 FI⁻°·⁷¹). Nitrite concentrations increased over time indicating colonisation of Nitrosomonas bacteria on the basket surfaces. A flow index of 7.2 – 9.0 L h⁻¹ kg⁻¹ was estimated as the minimum to avoid significant reductions in weight and shell length gain and increases in FCR values. Total ammonia nitrogen (TAN) and FAN concentrations were significantly correlated to dietary protein (P) (t = 6.63, p < 0.0001 and t = 6.41, p < 0.0001, respectively) and flow index (t = 5.42, p < 0.0001 and t = 3.9, p < 0.0002, respectively) and could be estimated using the models TAN = 9.73 P – 110.3 log (FI), and FAN = 0.132 P – 1.10 log (FI). Mean FAN concentrations were 67 and 41 % lower in tanks fed a diet containing 22 and 26 % protein respectively, when compared to tanks fed a 33 % protein diet. Supplementation with pure oxygen (103 ± 8 % saturation) improved shell length gain (t = 3.45, p = 0.026) in abalone exposed to high FAN (2.43 ± 1.1 μg L⁻¹) and low pH (7.6 ± 0.13), relative to a treatment with no oxygen supplementation (92 ± 6 % saturation). Addition of a sodium hydroxide solution resulted in elevated mean pH in treatment raceways when compared to control raceways. The increased pH resulted in significantly higher weight gain (g abalone⁻¹) (F₁·₁₂ = 4.51; p = 0.055) and shell length gain (mm abalone⁻¹) (F₁·₁₂ = 4.56; p = 0.054) at an α-error level of < 5.5 %. In two trials, weight gain and shell length gain were significantly correlated to pH (p < 0.001), and multiple regression of pH, dissolved oxygen and FAN consistently revealed pH to be the best predictor of growth. It is therefore suggested that decreasing pH is the first limiting water quality variable for abalone in serial-use raceways. As a decrease in water pH is linked to respiration by the abalone and subsequent increase in dissolved carbon dioxide (CO₂) concentration, future studies should examine the effects of CO₂ on H. midae metabolic rate, calcification rate and health. The results of this study will contribute toward our understanding of the specific water quality requirements for H. midae in commercial aquaculture systems, and influence the design and management procedures for abalone water reuse systems.
- Full Text:
- Authors: Naylor, Matthew Aubrey
- Date: 2012
- Subjects: Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Effect of water quality on , Abalones -- Nutrition -- South Africa , Abalones -- Feeding and feeds , Abalones -- Growth , Fish culture -- Water reuse
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5335 , http://hdl.handle.net/10962/d1005181 , Haliotis midae -- South Africa , Abalone culture -- South Africa , Abalones -- Effect of water quality on , Abalones -- Nutrition -- South Africa , Abalones -- Feeding and feeds , Abalones -- Growth , Fish culture -- Water reuse
- Description: An understanding of species specific water quality requirements is essential for efficient production of aquaculture products, an aspect not well documented for the land-based culture of the South African abalone, Haliotis midae. In order for the industry to remain competitive in international markets, efficient use of water supplies and the development of water reuse technology is needed. This study assessed the changes in water quality between tanks in a tiered serial-use raceway in relation to accumulated biomass and water flow and estimated the flow index (FI) (L h⁻¹ kg⁻¹) at which growth becomes significantly affected. The effect of dietary protein level, supplementation of pure oxygen and addition of sodium hydroxide (NaOH⁻) on water quality and fundamental production parameters in the serial-use raceways was also assessed. The serial-use raceways were used as a tool to create a range of water quality conditions at which the growth, feed conversion ratio (FCR) and condition factor (CF) of "cocktail" size (60 – 70 mm) H. midae could be monitored. The metabolic activity of the abalone resulted in a deterioration in water quality between tanks in series. pH (r² = 0.99; p < 0.001) and dissolved oxygen concentration (r² = 0.99; p < 0.001) were positively correlated with flow index (pH = 7.38 FI°·°² ; dissolved oxygen = 6.92 FI°·°⁴), while free ammonia nitrogen (FAN) (r² = 0.99, p < 0.001) and nitrite (NO²⁻ - N) (r² = 0.93, p < 0.001) were negatively correlated with flow index (FAN = 8.02 FI⁻°·⁷¹). Nitrite concentrations increased over time indicating colonisation of Nitrosomonas bacteria on the basket surfaces. A flow index of 7.2 – 9.0 L h⁻¹ kg⁻¹ was estimated as the minimum to avoid significant reductions in weight and shell length gain and increases in FCR values. Total ammonia nitrogen (TAN) and FAN concentrations were significantly correlated to dietary protein (P) (t = 6.63, p < 0.0001 and t = 6.41, p < 0.0001, respectively) and flow index (t = 5.42, p < 0.0001 and t = 3.9, p < 0.0002, respectively) and could be estimated using the models TAN = 9.73 P – 110.3 log (FI), and FAN = 0.132 P – 1.10 log (FI). Mean FAN concentrations were 67 and 41 % lower in tanks fed a diet containing 22 and 26 % protein respectively, when compared to tanks fed a 33 % protein diet. Supplementation with pure oxygen (103 ± 8 % saturation) improved shell length gain (t = 3.45, p = 0.026) in abalone exposed to high FAN (2.43 ± 1.1 μg L⁻¹) and low pH (7.6 ± 0.13), relative to a treatment with no oxygen supplementation (92 ± 6 % saturation). Addition of a sodium hydroxide solution resulted in elevated mean pH in treatment raceways when compared to control raceways. The increased pH resulted in significantly higher weight gain (g abalone⁻¹) (F₁·₁₂ = 4.51; p = 0.055) and shell length gain (mm abalone⁻¹) (F₁·₁₂ = 4.56; p = 0.054) at an α-error level of < 5.5 %. In two trials, weight gain and shell length gain were significantly correlated to pH (p < 0.001), and multiple regression of pH, dissolved oxygen and FAN consistently revealed pH to be the best predictor of growth. It is therefore suggested that decreasing pH is the first limiting water quality variable for abalone in serial-use raceways. As a decrease in water pH is linked to respiration by the abalone and subsequent increase in dissolved carbon dioxide (CO₂) concentration, future studies should examine the effects of CO₂ on H. midae metabolic rate, calcification rate and health. The results of this study will contribute toward our understanding of the specific water quality requirements for H. midae in commercial aquaculture systems, and influence the design and management procedures for abalone water reuse systems.
- Full Text:
Web-based visualisation techniques for reporting zoonotic outbreaks
- Authors: Ncube, Sinini Paul
- Date: 2012
- Subjects: Zoonoses -- Reporting , Communicable diseases -- Reporting , Communication in medicine , Medical telematics , Internet , Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4664 , http://hdl.handle.net/10962/d1006672 , Zoonoses -- Reporting , Communicable diseases -- Reporting , Communication in medicine , Medical telematics , Internet , Information visualization
- Description: Zoonotic diseases are diseases that are transmitted from animals or vectors to humans and vice versa. The public together with veterinarian authorities should readily access disease information as it is vital in rapidly controlling resultant zoonotic outbreak threats through improved awareness. Currently, the reporting of disease information in South Africa is predominantly limited to traditional methods of Information Communication Technologies (ICTs) like faxes, monthly newspaper reports, radios, phones and televisions. Although these are effective ways of communication, their disadvantage is that the information that most of them offer can only be accessed at specific times during a crisis. New technologies like the internet have become the most efficient way of distributing information in near-real-time. Many developed countries have used web-based reporting platforms to deliver timely information through temporal and geographic visualisation techniques. There has been an attempt in the use of web-based reporting in South Africa but most of these sites are characterised by heavy text which makes them time consuming to use or maintain. As a result most sites have not been updated or have ceased to exist because of the work load involved. The success of web reporting mechanisms in developed countries offers evidence that web-based reporting systems when appropriately visualised can improve the easy understanding of information and efficiency in the analysis of that data. In this thesis, a web-based reporting prototype was proposed after gathering information from different sources: literature related to disease reporting and the visualisation of infectious diseases; the exploration of the currently deployed web systems; and the investigation of user requirements from relevant parties. The proposed prototype system was then developed using Adobe Flash tools, Java and MySQL languages. A focus group then reviewed the developed system to ascertain that the relevant requirements had been incorporated and to obtain additional ideas about the system. This led to the proposal of a new prototype system that can be used by the authorities concerned as a plan to develop a fully functional disease reporting system for South Africa.
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- Authors: Ncube, Sinini Paul
- Date: 2012
- Subjects: Zoonoses -- Reporting , Communicable diseases -- Reporting , Communication in medicine , Medical telematics , Internet , Information visualization
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4664 , http://hdl.handle.net/10962/d1006672 , Zoonoses -- Reporting , Communicable diseases -- Reporting , Communication in medicine , Medical telematics , Internet , Information visualization
- Description: Zoonotic diseases are diseases that are transmitted from animals or vectors to humans and vice versa. The public together with veterinarian authorities should readily access disease information as it is vital in rapidly controlling resultant zoonotic outbreak threats through improved awareness. Currently, the reporting of disease information in South Africa is predominantly limited to traditional methods of Information Communication Technologies (ICTs) like faxes, monthly newspaper reports, radios, phones and televisions. Although these are effective ways of communication, their disadvantage is that the information that most of them offer can only be accessed at specific times during a crisis. New technologies like the internet have become the most efficient way of distributing information in near-real-time. Many developed countries have used web-based reporting platforms to deliver timely information through temporal and geographic visualisation techniques. There has been an attempt in the use of web-based reporting in South Africa but most of these sites are characterised by heavy text which makes them time consuming to use or maintain. As a result most sites have not been updated or have ceased to exist because of the work load involved. The success of web reporting mechanisms in developed countries offers evidence that web-based reporting systems when appropriately visualised can improve the easy understanding of information and efficiency in the analysis of that data. In this thesis, a web-based reporting prototype was proposed after gathering information from different sources: literature related to disease reporting and the visualisation of infectious diseases; the exploration of the currently deployed web systems; and the investigation of user requirements from relevant parties. The proposed prototype system was then developed using Adobe Flash tools, Java and MySQL languages. A focus group then reviewed the developed system to ascertain that the relevant requirements had been incorporated and to obtain additional ideas about the system. This led to the proposal of a new prototype system that can be used by the authorities concerned as a plan to develop a fully functional disease reporting system for South Africa.
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Why do learners and teachers experience problems with the concept of zero?
- Authors: Jooste, Zonia
- Date: 2012
- Subjects: Numbers, Divisibility of -- Study and teaching (Primary) -- South Africa Numbers, Divisibility of -- Study and teaching (Secondary) -- South Africa Mathematics teachers -- Training of -- South Africa -- Eastern Cape Mathematics teachers -- Training of -- South Africa -- Western Cape Education, Primary -- Curricula -- South Africa Education, Secondary -- Curricula -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1906 , http://hdl.handle.net/10962/d1006764
- Description: The controversy around the inclusion of zero in the number system has been widely documented. Influential mathematicians in various ancient cultures did not accept zero as a number. The idea of the empty set was too abstract and they could not conceptualise division by zero. Surprisingly, understanding of the concept is still a matter of concern today. In spite of expansive reports on and recommendations for developing conceptualisation of the concept, learners and teachers still experience problems similar to those that ancient mathematicians struggled with. The study was initiated by an observation of Grade 7 learners' inability to solve the problems 4 × 0 and 0 ÷ 7 effectively or at all. I investigated why Grade 3 to 6 learners and mathematics teachers on a BEd (in-service) course and an accredited ACE course experience problems with the concept of zero. I was especially interested in the understanding of multiplication and division by zero. I investigated teachers' knowledge of zero's characteristics as a number, the history of zero and how they teach the concept, in order to support my assumptions. The data production process was performed over a period of two years. It involved a multi-case opportunity sample approach embedded in the empirical field that formed the backdrop of my involvement as mathematics education specialist in schools in the Western and Eastern Cape. The interpretative orientation of the study allowed me to conduct inquiries that served to confirm or challenge my assumptions and enabled me to construct generalisations that depict learners' and teachers' knowledge construction. The qualitative data analysis informed the presentation and discussion of the findings. The single most important message conveyed to readers of this study is that the value of zero as a number, its importance in the number system, its properties and its behaviour in calculations, should not be underrated. Teaching of this abstract concept requires competent teachers who are able to mediate understanding in the most effective and innovative manner. Professional development programmes should orchestrate this competence and curriculum developers and textbook authors should acknowledge the significance of learning and teaching the concept of zero.
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- Authors: Jooste, Zonia
- Date: 2012
- Subjects: Numbers, Divisibility of -- Study and teaching (Primary) -- South Africa Numbers, Divisibility of -- Study and teaching (Secondary) -- South Africa Mathematics teachers -- Training of -- South Africa -- Eastern Cape Mathematics teachers -- Training of -- South Africa -- Western Cape Education, Primary -- Curricula -- South Africa Education, Secondary -- Curricula -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1906 , http://hdl.handle.net/10962/d1006764
- Description: The controversy around the inclusion of zero in the number system has been widely documented. Influential mathematicians in various ancient cultures did not accept zero as a number. The idea of the empty set was too abstract and they could not conceptualise division by zero. Surprisingly, understanding of the concept is still a matter of concern today. In spite of expansive reports on and recommendations for developing conceptualisation of the concept, learners and teachers still experience problems similar to those that ancient mathematicians struggled with. The study was initiated by an observation of Grade 7 learners' inability to solve the problems 4 × 0 and 0 ÷ 7 effectively or at all. I investigated why Grade 3 to 6 learners and mathematics teachers on a BEd (in-service) course and an accredited ACE course experience problems with the concept of zero. I was especially interested in the understanding of multiplication and division by zero. I investigated teachers' knowledge of zero's characteristics as a number, the history of zero and how they teach the concept, in order to support my assumptions. The data production process was performed over a period of two years. It involved a multi-case opportunity sample approach embedded in the empirical field that formed the backdrop of my involvement as mathematics education specialist in schools in the Western and Eastern Cape. The interpretative orientation of the study allowed me to conduct inquiries that served to confirm or challenge my assumptions and enabled me to construct generalisations that depict learners' and teachers' knowledge construction. The qualitative data analysis informed the presentation and discussion of the findings. The single most important message conveyed to readers of this study is that the value of zero as a number, its importance in the number system, its properties and its behaviour in calculations, should not be underrated. Teaching of this abstract concept requires competent teachers who are able to mediate understanding in the most effective and innovative manner. Professional development programmes should orchestrate this competence and curriculum developers and textbook authors should acknowledge the significance of learning and teaching the concept of zero.
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Women leadership: a case study in the Otjozondjupa Region, Namibia
- Authors: Araes, Cornelia
- Date: 2012
- Subjects: Women -- Education (Primary) -- Namibia Leadership in women -- Education (Primary) -- Namibia Management -- Education (Primary) -- Namibia Educational leadership -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1825 , http://hdl.handle.net/10962/d1003711
- Description: Empowerment of women in leadership and in particular, school leadership has been the focus of the Namibian government and the country since independence in 1990. Different policies and laws, post‐independence, make provision for women empowerment and leadership in a range of organisations and institutions throughout the country. However, reports on gender equity in leadership positions suggest that Namibia is not really moving towards these policy goals at a sufficiently quick pace. A lot still needs to be achieved in terms of transforming the gender stereotyping in Namibia, which still suffers from the legacy of gender discrimination of the apartheid era. Modern‐day academic authors and journalists portray an increasing interest in an awareness of the advantages of women leadership. Women are increasingly perceived to have leadership styles more suitable for contemporary conditions than men. It is against this backdrop that this study sought to investigate women leadership in the Otjiwarongo circuit in the Otjozondjupa educational region in Namibia. The study used a qualitative, interpretive research paradigm. It adopted a case study approach. The primary participants consisted of four women principals in the Otjiwarongo circuit and the secondary participants included four women education officers from the same circuit. Semi‐structured interviews, a focus group interview and observation were applied as methods for collecting data and the data collection period was just over six weeks. Data analysis was done through coding and identification of categories. The findings revealed that women principals possessed the qualities of commitment, good communication and are passionate about their work, which are qualities normally associated with effective leadership. In terms of their role in their schools, they emerged as democratic leaders who involved all stakeholders in the decision making process through consensus. In addition, they demonstrated distributive and servant leadership in their interactions with stakeholders. The main challenge to the leadership position of these women principals seemed to be the stereotypical view held, that as women, they had to work twice as hard as men at leading schools. The study recommended that people oriented leadership styles, such as the ones enacted by the women principals in this study, are highly recommended for effective leadership in the 21st century.
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- Authors: Araes, Cornelia
- Date: 2012
- Subjects: Women -- Education (Primary) -- Namibia Leadership in women -- Education (Primary) -- Namibia Management -- Education (Primary) -- Namibia Educational leadership -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1825 , http://hdl.handle.net/10962/d1003711
- Description: Empowerment of women in leadership and in particular, school leadership has been the focus of the Namibian government and the country since independence in 1990. Different policies and laws, post‐independence, make provision for women empowerment and leadership in a range of organisations and institutions throughout the country. However, reports on gender equity in leadership positions suggest that Namibia is not really moving towards these policy goals at a sufficiently quick pace. A lot still needs to be achieved in terms of transforming the gender stereotyping in Namibia, which still suffers from the legacy of gender discrimination of the apartheid era. Modern‐day academic authors and journalists portray an increasing interest in an awareness of the advantages of women leadership. Women are increasingly perceived to have leadership styles more suitable for contemporary conditions than men. It is against this backdrop that this study sought to investigate women leadership in the Otjiwarongo circuit in the Otjozondjupa educational region in Namibia. The study used a qualitative, interpretive research paradigm. It adopted a case study approach. The primary participants consisted of four women principals in the Otjiwarongo circuit and the secondary participants included four women education officers from the same circuit. Semi‐structured interviews, a focus group interview and observation were applied as methods for collecting data and the data collection period was just over six weeks. Data analysis was done through coding and identification of categories. The findings revealed that women principals possessed the qualities of commitment, good communication and are passionate about their work, which are qualities normally associated with effective leadership. In terms of their role in their schools, they emerged as democratic leaders who involved all stakeholders in the decision making process through consensus. In addition, they demonstrated distributive and servant leadership in their interactions with stakeholders. The main challenge to the leadership position of these women principals seemed to be the stereotypical view held, that as women, they had to work twice as hard as men at leading schools. The study recommended that people oriented leadership styles, such as the ones enacted by the women principals in this study, are highly recommended for effective leadership in the 21st century.
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μCloud : a P2P cloud platform for computing service provision
- Authors: Fouodji Tasse, Ghislain
- Date: 2012 , 2012-08-22
- Subjects: Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4663 , http://hdl.handle.net/10962/d1006669 , Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Description: The advancements in virtualization technologies have provided a large spectrum of computational approaches. Dedicated computations can be run on private environments (virtual machines), created within the same computer. Through capable APIs, this functionality is leveraged for the service we wish to implement; a computer power service (CPS). We target peer-to-peer systems for this service, to exploit the potential of aggregating computing resources. The concept of a P2P network is mostly known for its expanded usage in distributed networks for sharing resources like content files or real-time data. This study adds computing power to the list of shared resources by describing a suitable service composition. Taking into account the dynamic nature of the platform, this CPS provision is achieved using a self stabilizing clustering algorithm. So, the resulting system of our research is based around a hierarchical P2P architecture and offers end-to-end consideration of resource provisioning and reliability. We named this system μCloud and characterizes it as a self-provisioning cloud service platform. It is designed, implemented and presented in this dissertation. Eventually, we assessed our work by showing that μCloud succeeds in providing user-centric services using a P2P computing unit. With this, we conclude that our system would be highly beneficial in both small and massively deployed environments. , KMBT_223 , Adobe Acrobat 9.51 Paper Capture Plug-in
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- Authors: Fouodji Tasse, Ghislain
- Date: 2012 , 2012-08-22
- Subjects: Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4663 , http://hdl.handle.net/10962/d1006669 , Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Description: The advancements in virtualization technologies have provided a large spectrum of computational approaches. Dedicated computations can be run on private environments (virtual machines), created within the same computer. Through capable APIs, this functionality is leveraged for the service we wish to implement; a computer power service (CPS). We target peer-to-peer systems for this service, to exploit the potential of aggregating computing resources. The concept of a P2P network is mostly known for its expanded usage in distributed networks for sharing resources like content files or real-time data. This study adds computing power to the list of shared resources by describing a suitable service composition. Taking into account the dynamic nature of the platform, this CPS provision is achieved using a self stabilizing clustering algorithm. So, the resulting system of our research is based around a hierarchical P2P architecture and offers end-to-end consideration of resource provisioning and reliability. We named this system μCloud and characterizes it as a self-provisioning cloud service platform. It is designed, implemented and presented in this dissertation. Eventually, we assessed our work by showing that μCloud succeeds in providing user-centric services using a P2P computing unit. With this, we conclude that our system would be highly beneficial in both small and massively deployed environments. , KMBT_223 , Adobe Acrobat 9.51 Paper Capture Plug-in
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