Development of an enzyme-synergy based bioreactor system for the beneficiation of apple pomace lignocellulosic waste
- Authors: Abboo, Sagaran
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/315 , vital:19947
- Description: Due to the finite supply of non-renewable fossil fuels, agro-industrial wastes are identified as alternate, renewable sources for energy supply. Large amounts of fruit waste are generated in South Africa due to fruit juice and wine processing from apples, grapes and citrus fruit. Apple pomace is the solid residue that is left over after juice, cider and wine processing and constitutes between 25-30% of the total fruit. On a global scale millions of tonnes of apple pomace are produced; between 2006-2007 over 46 million tonnes were produced. In South Africa a total production of 244 469 tonnes were produced during the 2011- 2012 season. Initially, apple pomace was regarded as a waste by-product used for animal feed and compost in soil, however presently it is considered a source of dietary fiber and natural antioxidants like polyphenols. In addition, apple pomace has a high carbohydrate content and can be enzymatically hydrolysed to produce sugar monomers which, in turn, can be fermented by yeasts to produce bioethanol. The polyphenols present in apple pomace can be used for their health properties, and the bioethanol can be used as a replacement for fossil fuel. Apple pomace is lignocellulosic in nature and consists of hemicellulose, cellulose, lignin and pectin. A combination of enzymes such as cellulases, hemicellulases, pectinases and lignases are required to operate in synergy for the degradation of lignocellulosic biomass. This is due to the recalcitrant nature of lignocellulose. This study investigated the degradation of apple pomace using a combination of commercially obtained enzyme cocktails viz. Viscozyme L , Celluclast 1.5L and Novozyme 188. The commercial enzymes Viscozyme L and Celluclast 1.5L were added in a ratio of 1:1 (50%:50%). The final concentrations of the enzymes were 0.019 mg/ml each. Novozyme 188 was added to provide a final concentration of 0.0024 mg/ml. A novel cost effective 20L bioreactor was designed, constructed and implemented for the degradation of apple pomace to produce value added products. The hydrolysis of the apple pomace was performed initially in 1 L flasks (batch fed) and, once optimized, scaled up to a 20 L bioreactor in batch mode. The bioreactors were operated at room temperature (22 ± 2ºC) and in an unbuffered system. The sugars released were detected and quantified using an optimized validated HPLC method established in this study. The sugars released in the bioreactors were mainly glucose, galactose, arabinose, cellobiose and fructose. The polyphenols released in this study were gallic acid, catechin, epicatechin, chlorogenic acid, rutin and phloridzin, which have a number of health benefits. The simultaneous analyses of the polyphenols were performed using a newly developed and validated HPLC method established in this study. This method was developed to detect nine polyphenols simultaneously. The two HPLC methods developed and validated in this study for the analysis of sugars and polyphenols demonstrated good accuracy, precision, reproducibility, linearity, robustness and sensitivity. Both analytical methods were validated according to the International Convention on Harmonization (ICH). The HPLC parameters for sugar analysis were: refractive index (RI) as the detection mode, the stationary phase was a ligand-exchange sugar column (Shodex SP0810) and an aqueous mobile phase in isocratic mode was used. The HPLC method for polyphenols employed UV diode array detection (DAD) as the detection mode, a reverse phase column as the stationary phase and a mobile phase of consisting of 0.01 M phosphoric acid in water and 100% methanol using gradient elution mode. The highest concentrations of sugars released in the novel 20 L bioreactor with 20% apple pomace (w/v) substrate loading were as follow: glucose (6.5 mg/ml), followed by galactose (2.1 mg/ml), arabinose (1.4 mg/ml), cellobiose (0.7 mg/ml) and fructose (0.5 mg/ml). The amounts of polyphenols released at 20% (w/v) apple pomace substrate were epicatechin (0.01 mg/ml), catechin (0.002 mg/ml), rutin (0.03 mg/ml), chlorogenic acid (0.002 mg/ml) and gallic acid 0.01 (mg/ml). Two mathematical models were developed in this study for kinetic analysis of lignocellulose (apple pomace) hydrolysis in the novel 20 L bioreactor, using the experimental data generated by the above HPLC analyses. The first model, modelling with regression, defines the hydrolysis of the sugars glucose, galactose, cellobiose and arabinose produced in the novel 20 L bioreactor at 5%, 10%, 15% and 20% (w/v) substrate concentrations. The regression model describes the sugars produced in the 20 L bioreactor by minimizing the error of the sugars released by finding a value for K which minimises the function which computes the sum of squares of errors between the solution curves and the data points. The second, more complex, model developed in this study used a system of differential equations model (ODE). This model solved the system by using a numerical method, such as the Runge-Kutta method, then fitted the solution curves to the data. Both models simulated (and had the ability to predict) the production of sugars in the novel 20 L bioreactor for apple pomace hydrolysis. These two models also revealed the time at which the maximum amount of sugars were released, which revealed the optimum time to run the 20 L bioreactor in order to be more cost effective. The optimum time for maximum glucose (the main sugar used in fermentation for biofuel production) release was determined to be around 60 h. The ODE model, in addition, determined the rate at which the substrate became depleted, as well as the rate at which the enzymes became deactivated for the various substrate loadings in the 20 L bioreactor. A third model was developed to determine the optimal running cost of the bioreactor which incorporated the substrate loading and the amount of glucose (g/L) produced. The novel 20 L bioreactor constructed from cost effective materials demonstrated that agro-industrial waste can be converted to value-added products by lignocellolytic enzymes. The sugars released from apple pomace can be used in biofuel production and the polyphenols as food supplements and nutraceuticals for health benefits. This novel study contributes to agro-industrial waste beneficiation via fuel production. In addition, using agro-industrial waste for the generation of value added products (instead of mere disposal) will help prevent environmental pollution.
- Full Text:
- Date Issued: 2016
- Authors: Abboo, Sagaran
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/315 , vital:19947
- Description: Due to the finite supply of non-renewable fossil fuels, agro-industrial wastes are identified as alternate, renewable sources for energy supply. Large amounts of fruit waste are generated in South Africa due to fruit juice and wine processing from apples, grapes and citrus fruit. Apple pomace is the solid residue that is left over after juice, cider and wine processing and constitutes between 25-30% of the total fruit. On a global scale millions of tonnes of apple pomace are produced; between 2006-2007 over 46 million tonnes were produced. In South Africa a total production of 244 469 tonnes were produced during the 2011- 2012 season. Initially, apple pomace was regarded as a waste by-product used for animal feed and compost in soil, however presently it is considered a source of dietary fiber and natural antioxidants like polyphenols. In addition, apple pomace has a high carbohydrate content and can be enzymatically hydrolysed to produce sugar monomers which, in turn, can be fermented by yeasts to produce bioethanol. The polyphenols present in apple pomace can be used for their health properties, and the bioethanol can be used as a replacement for fossil fuel. Apple pomace is lignocellulosic in nature and consists of hemicellulose, cellulose, lignin and pectin. A combination of enzymes such as cellulases, hemicellulases, pectinases and lignases are required to operate in synergy for the degradation of lignocellulosic biomass. This is due to the recalcitrant nature of lignocellulose. This study investigated the degradation of apple pomace using a combination of commercially obtained enzyme cocktails viz. Viscozyme L , Celluclast 1.5L and Novozyme 188. The commercial enzymes Viscozyme L and Celluclast 1.5L were added in a ratio of 1:1 (50%:50%). The final concentrations of the enzymes were 0.019 mg/ml each. Novozyme 188 was added to provide a final concentration of 0.0024 mg/ml. A novel cost effective 20L bioreactor was designed, constructed and implemented for the degradation of apple pomace to produce value added products. The hydrolysis of the apple pomace was performed initially in 1 L flasks (batch fed) and, once optimized, scaled up to a 20 L bioreactor in batch mode. The bioreactors were operated at room temperature (22 ± 2ºC) and in an unbuffered system. The sugars released were detected and quantified using an optimized validated HPLC method established in this study. The sugars released in the bioreactors were mainly glucose, galactose, arabinose, cellobiose and fructose. The polyphenols released in this study were gallic acid, catechin, epicatechin, chlorogenic acid, rutin and phloridzin, which have a number of health benefits. The simultaneous analyses of the polyphenols were performed using a newly developed and validated HPLC method established in this study. This method was developed to detect nine polyphenols simultaneously. The two HPLC methods developed and validated in this study for the analysis of sugars and polyphenols demonstrated good accuracy, precision, reproducibility, linearity, robustness and sensitivity. Both analytical methods were validated according to the International Convention on Harmonization (ICH). The HPLC parameters for sugar analysis were: refractive index (RI) as the detection mode, the stationary phase was a ligand-exchange sugar column (Shodex SP0810) and an aqueous mobile phase in isocratic mode was used. The HPLC method for polyphenols employed UV diode array detection (DAD) as the detection mode, a reverse phase column as the stationary phase and a mobile phase of consisting of 0.01 M phosphoric acid in water and 100% methanol using gradient elution mode. The highest concentrations of sugars released in the novel 20 L bioreactor with 20% apple pomace (w/v) substrate loading were as follow: glucose (6.5 mg/ml), followed by galactose (2.1 mg/ml), arabinose (1.4 mg/ml), cellobiose (0.7 mg/ml) and fructose (0.5 mg/ml). The amounts of polyphenols released at 20% (w/v) apple pomace substrate were epicatechin (0.01 mg/ml), catechin (0.002 mg/ml), rutin (0.03 mg/ml), chlorogenic acid (0.002 mg/ml) and gallic acid 0.01 (mg/ml). Two mathematical models were developed in this study for kinetic analysis of lignocellulose (apple pomace) hydrolysis in the novel 20 L bioreactor, using the experimental data generated by the above HPLC analyses. The first model, modelling with regression, defines the hydrolysis of the sugars glucose, galactose, cellobiose and arabinose produced in the novel 20 L bioreactor at 5%, 10%, 15% and 20% (w/v) substrate concentrations. The regression model describes the sugars produced in the 20 L bioreactor by minimizing the error of the sugars released by finding a value for K which minimises the function which computes the sum of squares of errors between the solution curves and the data points. The second, more complex, model developed in this study used a system of differential equations model (ODE). This model solved the system by using a numerical method, such as the Runge-Kutta method, then fitted the solution curves to the data. Both models simulated (and had the ability to predict) the production of sugars in the novel 20 L bioreactor for apple pomace hydrolysis. These two models also revealed the time at which the maximum amount of sugars were released, which revealed the optimum time to run the 20 L bioreactor in order to be more cost effective. The optimum time for maximum glucose (the main sugar used in fermentation for biofuel production) release was determined to be around 60 h. The ODE model, in addition, determined the rate at which the substrate became depleted, as well as the rate at which the enzymes became deactivated for the various substrate loadings in the 20 L bioreactor. A third model was developed to determine the optimal running cost of the bioreactor which incorporated the substrate loading and the amount of glucose (g/L) produced. The novel 20 L bioreactor constructed from cost effective materials demonstrated that agro-industrial waste can be converted to value-added products by lignocellolytic enzymes. The sugars released from apple pomace can be used in biofuel production and the polyphenols as food supplements and nutraceuticals for health benefits. This novel study contributes to agro-industrial waste beneficiation via fuel production. In addition, using agro-industrial waste for the generation of value added products (instead of mere disposal) will help prevent environmental pollution.
- Full Text:
- Date Issued: 2016
Measuring the performance of the banking sector in Zimbabwe
- Authors: Abel, Sanderson
- Date: 2016
- Subjects: Banks and banking -- Zimbabwe , Bank profits -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5110 , vital:20806
- Description: The measurement of the banking sector performance in Zimbabwe is motivated by the unique developments that typified the sector during the period 2009-2014 after emerging from an economic crisis. The Zimbabwean economy returned to stability and growth in 2009, after a decade long economic decline. Economic stability brought about growth in deposits, loans, assets, capitalization and profits during this period. The banking sector has been accused of excessive profiteering through overpricing their products, which culminated in the intervention by the authorities in the sector. The interest rates spread, fees and other charges were presumed to be high which motivated the need to understand whether the banking sector is efficient or inefficient given the high interest rate spreads between the deposit rates and lending rates. Furthermore the high interest rates have raised the question of whether banks were exploiting their market power to price their products highly or whether their prices were determined by the dictates of market forces. Continued profitability of the sector also called for an investigation into what was driving the persistence of profitability over time. The primary objective of this research was to measure the performance of the banking sector during the period 2009-2014. The study contributes to the empirical literature by measuring and assessing the drivers of banking sector competition, efficiency and profitability and applying them at much disaggregated levels. This study also contributes to the debate on the relationships among the performance measures of competition, profitability and efficiency. The study adopted a number of methods which contributes to the array of tools central banks can employ to measure bank performance. The study employed a number of methodologies to measure the competition, efficiency and profitability performance of the banking sector. Competition was estimated using the new empirical industrial organisation methods of Panza and Rose (1987) and the Lerner (1934) Index was used. Cost and revenue efficiency was estimated using the two step methods of Data Envelopment Analysis followed by the Tobit regression method. An assessment of the persistence and drivers of profitability was measured using the Generalised Method of Moments. This study shows that the banking sector was operating under monopolistic competition market structure. This implies that banks held some market power as a result of product differentiation due to unique features such as brands, image and advertising, among others. The study indicates that competition increased during the period 2009-2014. Market power/competition in the banking sector during the study period was driven by capital adequacy, non-performing loans, liquidity risk, cost-income ratio, economic growth and government policy on pricing of bank products. The study suggests that the banking sector experienced an average inefficiency level of approximately 35 per cent in relationship with the best performing institutions in the sample. As a result of stability experienced in the economy, the average revenue and cost efficiency increased between 2009 and 2014. The study further established that the discord around the implementation of the indigenisation and empowerment law, coupled with the government intervention in the banking sector had a negative impact on the banking sector efficiency. It also found that efficiency is determined by market power, capital adequacy, cost income ratio, economic growth, inflation, market share and profitability. The Granger Causality test between cost efficiency and market power suggests that causality is bidirectional. On the other hand granger causality between revenue efficiency and market power is unidirectional and positive, running from revenue efficiency to market power. The result implies that policy measures should bring a balance between increasing competition and improving the revenue efficiency. The study shows that the banking sector was profitable during the period 2009 to 2014. The profitability was a reflection of a stable macroeconomic environment, typified by low inflation levels, despite the crises during this period. It further reveals that the banking sector‟s profitability persisted over time, reflecting the regulatory structure of the sector. The study established that profitability was determined by market power, non-performing loans, liquidity risk, capital adequacy, bank size and cost efficiency. This implies profitability was driven by bank specific determinants. There are a number of policy implications derived from the study. Regulatory measures such as forced consolidations can lead to excessive market power by the banking institution; hence it should be moderated. Banks should enhance credit risk because NPLs has been dragging profits. Banks should take advantage of the various measures introduced, such as the setting up of the special purpose vehicle and credit reference bureau. The government should avoid tampering with market forces as this reduces competition, efficiency and profitability and put in place measures that grow the economy as it increases the efficiency and profitability of the banking sector.
- Full Text:
- Date Issued: 2016
- Authors: Abel, Sanderson
- Date: 2016
- Subjects: Banks and banking -- Zimbabwe , Bank profits -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/5110 , vital:20806
- Description: The measurement of the banking sector performance in Zimbabwe is motivated by the unique developments that typified the sector during the period 2009-2014 after emerging from an economic crisis. The Zimbabwean economy returned to stability and growth in 2009, after a decade long economic decline. Economic stability brought about growth in deposits, loans, assets, capitalization and profits during this period. The banking sector has been accused of excessive profiteering through overpricing their products, which culminated in the intervention by the authorities in the sector. The interest rates spread, fees and other charges were presumed to be high which motivated the need to understand whether the banking sector is efficient or inefficient given the high interest rate spreads between the deposit rates and lending rates. Furthermore the high interest rates have raised the question of whether banks were exploiting their market power to price their products highly or whether their prices were determined by the dictates of market forces. Continued profitability of the sector also called for an investigation into what was driving the persistence of profitability over time. The primary objective of this research was to measure the performance of the banking sector during the period 2009-2014. The study contributes to the empirical literature by measuring and assessing the drivers of banking sector competition, efficiency and profitability and applying them at much disaggregated levels. This study also contributes to the debate on the relationships among the performance measures of competition, profitability and efficiency. The study adopted a number of methods which contributes to the array of tools central banks can employ to measure bank performance. The study employed a number of methodologies to measure the competition, efficiency and profitability performance of the banking sector. Competition was estimated using the new empirical industrial organisation methods of Panza and Rose (1987) and the Lerner (1934) Index was used. Cost and revenue efficiency was estimated using the two step methods of Data Envelopment Analysis followed by the Tobit regression method. An assessment of the persistence and drivers of profitability was measured using the Generalised Method of Moments. This study shows that the banking sector was operating under monopolistic competition market structure. This implies that banks held some market power as a result of product differentiation due to unique features such as brands, image and advertising, among others. The study indicates that competition increased during the period 2009-2014. Market power/competition in the banking sector during the study period was driven by capital adequacy, non-performing loans, liquidity risk, cost-income ratio, economic growth and government policy on pricing of bank products. The study suggests that the banking sector experienced an average inefficiency level of approximately 35 per cent in relationship with the best performing institutions in the sample. As a result of stability experienced in the economy, the average revenue and cost efficiency increased between 2009 and 2014. The study further established that the discord around the implementation of the indigenisation and empowerment law, coupled with the government intervention in the banking sector had a negative impact on the banking sector efficiency. It also found that efficiency is determined by market power, capital adequacy, cost income ratio, economic growth, inflation, market share and profitability. The Granger Causality test between cost efficiency and market power suggests that causality is bidirectional. On the other hand granger causality between revenue efficiency and market power is unidirectional and positive, running from revenue efficiency to market power. The result implies that policy measures should bring a balance between increasing competition and improving the revenue efficiency. The study shows that the banking sector was profitable during the period 2009 to 2014. The profitability was a reflection of a stable macroeconomic environment, typified by low inflation levels, despite the crises during this period. It further reveals that the banking sector‟s profitability persisted over time, reflecting the regulatory structure of the sector. The study established that profitability was determined by market power, non-performing loans, liquidity risk, capital adequacy, bank size and cost efficiency. This implies profitability was driven by bank specific determinants. There are a number of policy implications derived from the study. Regulatory measures such as forced consolidations can lead to excessive market power by the banking institution; hence it should be moderated. Banks should enhance credit risk because NPLs has been dragging profits. Banks should take advantage of the various measures introduced, such as the setting up of the special purpose vehicle and credit reference bureau. The government should avoid tampering with market forces as this reduces competition, efficiency and profitability and put in place measures that grow the economy as it increases the efficiency and profitability of the banking sector.
- Full Text:
- Date Issued: 2016
Molecular studies on cholera and non-cholera causing vibrio pathogens isolated from some water resources and aquatic animals in Eastern Cape Province, South Africa
- Authors: Abioye, Oluwatayo Emmanuel
- Date: 2018
- Subjects: Vibrio cholerae -- Pathogens Vibrio cholerae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9154 , vital:34283
- Description: The global socioeconomic and disease burdens of cholera; a disease caused by Vibrio cholerae have been ongoing since it was first reported in India in 1563. Unfortunately, emerging non-cholera causing Vibrio pathogens have been contributing to the malady of Vibrio genus globally in the recent years. The history of cholera outbreaks in South Africa have been well documented but information regarding other non-cholera Vibrio pathogens, is deficient in the literature. This study evaluated the statuses of aquatic animals including crustaceans, molluscs, and fish as important reservoirs of six key pathogenic Vibrio spp. in some important water resources and fish markets in the Eastern Cape, South Africa, between December 2016 and November 2017. Physiochemical parameters that are vital for water quality assessment were determined for all the water sampling points using standard methods. The parameters include pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, temperature, total dissolved solids, turbidity and biological oxygen demand (BOD5). Vibrio spp. densities in water and aquatic animal samples were determined using membrane filtration and Most Probable NumberPolymerase chain reaction (MPN-PCR) methods respectively. Presumptive Vibrio spp. were recovered from the samples by direct plating of water samples and aliquots of aquatic animal homogenates on thiosulfate-citrate-bile salts-sucrose (TCBS) agar. Where necessary, samples were enriched using alkaline peptone water (APW) for optimum isolation of the targeted Vibrio spp. Presumptive isolates were identified and delineated into the six targeted pathogenic Vibrio spp. using PCR method. The antibiogram fingerprint of selected Vibrio spp. against a panel 18 panels of antibacterial agents were also carried out. Multiple antibiotic resistance phenotypes (MARPs) per set of isolates from water sampling sites and aquatic animal types were determined. Finally, multiple antibiotic resistance indices (MARI) for isolates recovered from the samples were determined. All experiments were done in replicate and data compared using one-way analysis of variance and one-tail t-test as appropriate. Correlation and regression analysis were also carried out as appropriate. Uncontrolled agricultural, industrial and domestic wastewater influxes, as well as run-off intrusions into the water resources investigated, were observed throughout the sampling season. The physicochemical qualities of the water resources varied with seasons. While pH observed for all the water sampling sites complied with South Africa and international standards, most sampling sites did not comply with set standards for one or more of the remaining physicochemical parameters. The parameters that frequently exhibited significant correlation and regression with Vibrio spp. densities were TDS, TSS, turbidity and temperature. The densities of Vibrio spp. in the samples studied varied with season and the highest density per sample types were observed in the summer. The prevalence of Vibrio spp. in freshwater, brackish water and aquatic animal samples were 79 percent, 78 percent and 86 percent respectively. The respective prevalence of V. cholerae, V. mimicus, V. fluvialis, V.alginolyticus, V. vulnificus and V. parahaemolyticus in freshwater samples (18 percent, 3 percent, ~1 percent, ~1 percent, <1 percent, < percent), brackish water(12 percent, 3 percent, 28 percent,~1 percent, ~1 percent, 9 percent) and aquatic animals (9 percent, 1 percent, 17 percent, 1 percent, 1 percent, 17 percent) were observed. All isolates from all the sample types showed very high antibiotic resistance against ampicillin and polymyxin B. Furthermore, MARPs were observed among isolates from the three sample types. Multiple antibiotic resistance indices (MARI) above 0.2 was observed at one site on Kowie River, three on Kubusi River and one on Buffalo River. The findings of this study suggest that most South Africa water-bodies especially freshwater resources are not well protected. This need to be addressed in a country like South Africa where availability of the freshwater resource for human activities is a critical issue. Base on the prevalence of pathogenic Vibrio spp. especially MARPs and sites that exhibited above 0.2 threshold for MARI, environmental base Vibrio species monitoring programs are recommended.
- Full Text:
- Date Issued: 2018
- Authors: Abioye, Oluwatayo Emmanuel
- Date: 2018
- Subjects: Vibrio cholerae -- Pathogens Vibrio cholerae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9154 , vital:34283
- Description: The global socioeconomic and disease burdens of cholera; a disease caused by Vibrio cholerae have been ongoing since it was first reported in India in 1563. Unfortunately, emerging non-cholera causing Vibrio pathogens have been contributing to the malady of Vibrio genus globally in the recent years. The history of cholera outbreaks in South Africa have been well documented but information regarding other non-cholera Vibrio pathogens, is deficient in the literature. This study evaluated the statuses of aquatic animals including crustaceans, molluscs, and fish as important reservoirs of six key pathogenic Vibrio spp. in some important water resources and fish markets in the Eastern Cape, South Africa, between December 2016 and November 2017. Physiochemical parameters that are vital for water quality assessment were determined for all the water sampling points using standard methods. The parameters include pH, electrical conductivity (EC), total dissolved solids (TDS), salinity, temperature, total dissolved solids, turbidity and biological oxygen demand (BOD5). Vibrio spp. densities in water and aquatic animal samples were determined using membrane filtration and Most Probable NumberPolymerase chain reaction (MPN-PCR) methods respectively. Presumptive Vibrio spp. were recovered from the samples by direct plating of water samples and aliquots of aquatic animal homogenates on thiosulfate-citrate-bile salts-sucrose (TCBS) agar. Where necessary, samples were enriched using alkaline peptone water (APW) for optimum isolation of the targeted Vibrio spp. Presumptive isolates were identified and delineated into the six targeted pathogenic Vibrio spp. using PCR method. The antibiogram fingerprint of selected Vibrio spp. against a panel 18 panels of antibacterial agents were also carried out. Multiple antibiotic resistance phenotypes (MARPs) per set of isolates from water sampling sites and aquatic animal types were determined. Finally, multiple antibiotic resistance indices (MARI) for isolates recovered from the samples were determined. All experiments were done in replicate and data compared using one-way analysis of variance and one-tail t-test as appropriate. Correlation and regression analysis were also carried out as appropriate. Uncontrolled agricultural, industrial and domestic wastewater influxes, as well as run-off intrusions into the water resources investigated, were observed throughout the sampling season. The physicochemical qualities of the water resources varied with seasons. While pH observed for all the water sampling sites complied with South Africa and international standards, most sampling sites did not comply with set standards for one or more of the remaining physicochemical parameters. The parameters that frequently exhibited significant correlation and regression with Vibrio spp. densities were TDS, TSS, turbidity and temperature. The densities of Vibrio spp. in the samples studied varied with season and the highest density per sample types were observed in the summer. The prevalence of Vibrio spp. in freshwater, brackish water and aquatic animal samples were 79 percent, 78 percent and 86 percent respectively. The respective prevalence of V. cholerae, V. mimicus, V. fluvialis, V.alginolyticus, V. vulnificus and V. parahaemolyticus in freshwater samples (18 percent, 3 percent, ~1 percent, ~1 percent, <1 percent, < percent), brackish water(12 percent, 3 percent, 28 percent,~1 percent, ~1 percent, 9 percent) and aquatic animals (9 percent, 1 percent, 17 percent, 1 percent, 1 percent, 17 percent) were observed. All isolates from all the sample types showed very high antibiotic resistance against ampicillin and polymyxin B. Furthermore, MARPs were observed among isolates from the three sample types. Multiple antibiotic resistance indices (MARI) above 0.2 was observed at one site on Kowie River, three on Kubusi River and one on Buffalo River. The findings of this study suggest that most South Africa water-bodies especially freshwater resources are not well protected. This need to be addressed in a country like South Africa where availability of the freshwater resource for human activities is a critical issue. Base on the prevalence of pathogenic Vibrio spp. especially MARPs and sites that exhibited above 0.2 threshold for MARI, environmental base Vibrio species monitoring programs are recommended.
- Full Text:
- Date Issued: 2018
The coordination chemistry of Rhenium(V) with multidentate no-donor ligands
- Authors: Abrahams, Abubak'r
- Date: 2009
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10370 , http://hdl.handle.net/10948/912 , Rhenium , Ligands
- Description: The neutral distorted octahedral complexes [ReOCl(L)] {H2L = N,N-bis(2- hydroxybenzyl)-2-(2-aminoethyl)dimethylamine (H2had), N,N-bis(2-hydroxybenzyl) aminomethylpyridine (H2hap); N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)pyridine (H2hae)} were prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H2L in ethanol. The X-ray structure determinations of [ReOCl(had)] and [ReOCl(hap)] were performed, and in both complexes the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen. Treatment of trans-[ReO2(py)4]I with two equivalents and one equivalent each of H2had in acetone afforded the iodide salts of the oxypyridinium-ammonium zwitterions N1-(2-hydroxybenzyl)-N2,N2- dimethyl-N1-((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [Hhpd]+ and N2,N2- dimethyl-N1-bis((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [dod]+ respectively. In [Hhpd]I, one of the 2-hydroxyphenyl groups of H2had is substituted by an oxypyridinium group, and in [dod]I, both 2-hydroxyphenyl groups are converted. The X-ray crystal structure determination of the starting material H2had, [Hhpd]I and [dod]I reveals trigonal pyramidal geometries around the central amino nitrogen. The complex salt [ReO(bsa)]PF6 (H2bsa=bis(N-methylsalicylicylideneiminopropyl) amine) was prepared from the reaction of cis-[ReO2I(PPh3)2] with H2bsa in toluene. The dianionic pentadentate ligand bsa is coordinated to the ReO3+ moiety via one secondary amino and two imino nitrogens, and two anionic phenolate oxygens. The complex was characterized by spectroscopy and analytical data, and the structure has been determined by single-crystal X-ray diffraction analysis. The complex exhibits a distorted octahedral geometry around the central rhenium(V) ion, with the basal plane being defined by a phenolate oxygen, two imino nitrogens and the secondary amino. ix A. Abrahams Nelson Mandela Metropolitan University The reaction of a two-fold molar excess of the potentially NN-donor ligand 2,2’- dipyridylamine (dpa) with trans-[ReO(OEt)Cl2(PPh3)2] in ethanol led to the isolation of [ReOCl2(OEt)(dpa)]. The X-ray crystal structure shows that the NN-chelated dpa is coordinated in the equatorial plane cis to the oxo and ethoxo groups, which are in trans positions relative to each other. The treatment of trans- [ReOCl3(PPh3)2] with a tenfold molar excess of dpa in ethanol at the refluxing temperature yielded the trans-dioxo complex [ReO2(dpa)2]Cl, but with a twofold molar excess only (μ-O)[{ReOCl2(dpa)}2] was isolated. Repeating the latter reaction with (n-Bu4N)[ReOCl4] as starting material in ethanol at room temperature a dark green product, also with the formulation (μ-O)[{ReOCl2(dpa)}2], was isolated. The reaction of equimolar quantities of bis(pyridin-2-yl)methyl)amine (HBPA) with (n-Bu4N)[ReOCl4] in acetone at room temperature led to the isolation of the sixcoordinate rhenium(V) complex [ReOCl(H2O)(BPA)]Cl. IR, NMR and X-ray crystallographic results indicate that BPA is coordinated as a tridentate uninegative chelate, with deprotonation of the amine nitrogen. The water molecule is coordinated trans to the oxo group, with the Re=O and Re-OH2 bond distances equal to 1.663(9) and 2.21(1) Å respectively. Complexes of the general formula [ReOX2{(C5H4N)CH(O)CH2(C5H4N)}] (X = Cl, I) were prepared by the reactions of trans-[ReOCl3(PPh3)2] and trans- [ReOI2(OEt)(PPh3)2] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. Experimental evidence shows that the coordinated DPE ligand has undergone addition of water at the ethylenic carbons, and that the (C5H4N)CH(O)CH2(C5H4N) moiety acts as a uninegative tridentate NON-donor ligand. The X-ray crystal structures of both complexes show a distorted octahedral geometry around the rhenium(V) centre. The treatment of trans-[ReOCl3(PPh3)2] with H2dbd in a 2:1 molar ratio in acetonitrile led to the isolation of the ligand-bridged dimer (μ-dbd)[ReOCl2(PPh3)]2. The X-ray crystal structure of the complex reveals a dinuclear structure in which two rhenium(V) ions are bridged by the dbd ligand. Each rhenium ion is in a x A. Abrahams Nelson Mandela Metropolitan University distorted octahedral geometry. The basal plane is defined by a phosphorus atom of the PPh3 group, two chlorides cis to each other, and a pyridyl nitrogen atom of dbd. The oxo group and alcoholate oxygen of dbd lie in trans axial positions. The complexes cis-[ReOX2(msa)(PPh3)] (X = Cl, Br, I) were prepared from trans- [ReOCl3(PPh3)2], trans-[ReOBr3(PPh3)2] or trans-[ReOI2(OEt)(PPh3)2] with 2-(1- iminoethyl)phenol (Hmsa) in acetonitrile. An X-ray crystallographic study shows that the bonding distances and angles in the comlexes are nearly identical, and that the two halides in each complex are coordinated cis to each other in the equatorial plane cis to the oxo group. The oxo-bridged dinuclear rhenium(V) complex [(μ-O){ReOCl(amp)}2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] and 6-amino-3-methyl-1-phenyl- 4-azahept-2-ene-1-one (Hamp) in acetone. The characterization of the complex by elemental analysis, infrared and 1H NMR spectroscopy and X-ray crystallography shows that amp is coordinated as a monoanionic NNO-donor chelate as an amino-amido ketone. However, the reaction of the similar ligand 7- amino-4,7-dimethyl-5-aza-3-octen-2-one (Hada) with [Re(CO)5Br] produced the product fac-[Re(CO)3Br(Hada)], with Hada coordinated as a neutral NN-donor amino-imino-ketone.
- Full Text:
- Date Issued: 2009
- Authors: Abrahams, Abubak'r
- Date: 2009
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10370 , http://hdl.handle.net/10948/912 , Rhenium , Ligands
- Description: The neutral distorted octahedral complexes [ReOCl(L)] {H2L = N,N-bis(2- hydroxybenzyl)-2-(2-aminoethyl)dimethylamine (H2had), N,N-bis(2-hydroxybenzyl) aminomethylpyridine (H2hap); N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)pyridine (H2hae)} were prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H2L in ethanol. The X-ray structure determinations of [ReOCl(had)] and [ReOCl(hap)] were performed, and in both complexes the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen. Treatment of trans-[ReO2(py)4]I with two equivalents and one equivalent each of H2had in acetone afforded the iodide salts of the oxypyridinium-ammonium zwitterions N1-(2-hydroxybenzyl)-N2,N2- dimethyl-N1-((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [Hhpd]+ and N2,N2- dimethyl-N1-bis((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [dod]+ respectively. In [Hhpd]I, one of the 2-hydroxyphenyl groups of H2had is substituted by an oxypyridinium group, and in [dod]I, both 2-hydroxyphenyl groups are converted. The X-ray crystal structure determination of the starting material H2had, [Hhpd]I and [dod]I reveals trigonal pyramidal geometries around the central amino nitrogen. The complex salt [ReO(bsa)]PF6 (H2bsa=bis(N-methylsalicylicylideneiminopropyl) amine) was prepared from the reaction of cis-[ReO2I(PPh3)2] with H2bsa in toluene. The dianionic pentadentate ligand bsa is coordinated to the ReO3+ moiety via one secondary amino and two imino nitrogens, and two anionic phenolate oxygens. The complex was characterized by spectroscopy and analytical data, and the structure has been determined by single-crystal X-ray diffraction analysis. The complex exhibits a distorted octahedral geometry around the central rhenium(V) ion, with the basal plane being defined by a phenolate oxygen, two imino nitrogens and the secondary amino. ix A. Abrahams Nelson Mandela Metropolitan University The reaction of a two-fold molar excess of the potentially NN-donor ligand 2,2’- dipyridylamine (dpa) with trans-[ReO(OEt)Cl2(PPh3)2] in ethanol led to the isolation of [ReOCl2(OEt)(dpa)]. The X-ray crystal structure shows that the NN-chelated dpa is coordinated in the equatorial plane cis to the oxo and ethoxo groups, which are in trans positions relative to each other. The treatment of trans- [ReOCl3(PPh3)2] with a tenfold molar excess of dpa in ethanol at the refluxing temperature yielded the trans-dioxo complex [ReO2(dpa)2]Cl, but with a twofold molar excess only (μ-O)[{ReOCl2(dpa)}2] was isolated. Repeating the latter reaction with (n-Bu4N)[ReOCl4] as starting material in ethanol at room temperature a dark green product, also with the formulation (μ-O)[{ReOCl2(dpa)}2], was isolated. The reaction of equimolar quantities of bis(pyridin-2-yl)methyl)amine (HBPA) with (n-Bu4N)[ReOCl4] in acetone at room temperature led to the isolation of the sixcoordinate rhenium(V) complex [ReOCl(H2O)(BPA)]Cl. IR, NMR and X-ray crystallographic results indicate that BPA is coordinated as a tridentate uninegative chelate, with deprotonation of the amine nitrogen. The water molecule is coordinated trans to the oxo group, with the Re=O and Re-OH2 bond distances equal to 1.663(9) and 2.21(1) Å respectively. Complexes of the general formula [ReOX2{(C5H4N)CH(O)CH2(C5H4N)}] (X = Cl, I) were prepared by the reactions of trans-[ReOCl3(PPh3)2] and trans- [ReOI2(OEt)(PPh3)2] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. Experimental evidence shows that the coordinated DPE ligand has undergone addition of water at the ethylenic carbons, and that the (C5H4N)CH(O)CH2(C5H4N) moiety acts as a uninegative tridentate NON-donor ligand. The X-ray crystal structures of both complexes show a distorted octahedral geometry around the rhenium(V) centre. The treatment of trans-[ReOCl3(PPh3)2] with H2dbd in a 2:1 molar ratio in acetonitrile led to the isolation of the ligand-bridged dimer (μ-dbd)[ReOCl2(PPh3)]2. The X-ray crystal structure of the complex reveals a dinuclear structure in which two rhenium(V) ions are bridged by the dbd ligand. Each rhenium ion is in a x A. Abrahams Nelson Mandela Metropolitan University distorted octahedral geometry. The basal plane is defined by a phosphorus atom of the PPh3 group, two chlorides cis to each other, and a pyridyl nitrogen atom of dbd. The oxo group and alcoholate oxygen of dbd lie in trans axial positions. The complexes cis-[ReOX2(msa)(PPh3)] (X = Cl, Br, I) were prepared from trans- [ReOCl3(PPh3)2], trans-[ReOBr3(PPh3)2] or trans-[ReOI2(OEt)(PPh3)2] with 2-(1- iminoethyl)phenol (Hmsa) in acetonitrile. An X-ray crystallographic study shows that the bonding distances and angles in the comlexes are nearly identical, and that the two halides in each complex are coordinated cis to each other in the equatorial plane cis to the oxo group. The oxo-bridged dinuclear rhenium(V) complex [(μ-O){ReOCl(amp)}2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] and 6-amino-3-methyl-1-phenyl- 4-azahept-2-ene-1-one (Hamp) in acetone. The characterization of the complex by elemental analysis, infrared and 1H NMR spectroscopy and X-ray crystallography shows that amp is coordinated as a monoanionic NNO-donor chelate as an amino-amido ketone. However, the reaction of the similar ligand 7- amino-4,7-dimethyl-5-aza-3-octen-2-one (Hada) with [Re(CO)5Br] produced the product fac-[Re(CO)3Br(Hada)], with Hada coordinated as a neutral NN-donor amino-imino-ketone.
- Full Text:
- Date Issued: 2009
Decentralization and quality assurance in the Ugandan primary education sector
- Authors: Abu-Baker, Mutaaya Sirajee
- Date: 2018
- Subjects: Schools -- Decentralization -- Uganda , Education, Primary -- Uganda , Educational change -- Uganda
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/57390 , vital:26897
- Description: The study presented in this thesis is a case study analysis of decentralization and quality assurance in a decentralized set up of the Ugandan Primary Schooling. The research looked at how the monitoring and evaluation informed the policy formulation process to regulate quality assurance in a decentralized governance of primary education. The Study was positioned in the critical realist paradigm, interpretive in orientation and used both coding and thematic techniques to understand the teachers’, SMC members’, and officers’ (at district and ministry levels) experiences and perceptions of quality assurance in a decentralized set up. Data was gathered using interviews, document analysis and observation methods. The findings indicated that the study was affected by eleven themes: Management System and Leadership, Human Resource Management, Finance Administration and Management, Parenting and Nutrition, Politics, Motivation, Social Structures and Patterns, Legislative Process and Policies, Infrastructure Development and Management, Community Involvement in Education and Curriculum and Professionalism. The monitoring and evaluation system had a framework in which it operates, though there was no quality assurance policy to guide the provision of quality education. The study finally indicated that there are more threats in a decentralized set up that put Quality in danger. Secondly, there was absence of supervision/inspection in schools as there was no evidence to prove this due to absence of reports. However, document analysis indicated visits of officers to schools. Records management was a problem to schools. Decentralization was adopted at different levels by different countries to address specific problems identified in view of service delivery. Finally, though monitoring and evaluation results informed the policy and decision makers, there was no quality assurance policy to guide the provision of quality education in institutions.
- Full Text:
- Date Issued: 2018
- Authors: Abu-Baker, Mutaaya Sirajee
- Date: 2018
- Subjects: Schools -- Decentralization -- Uganda , Education, Primary -- Uganda , Educational change -- Uganda
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/57390 , vital:26897
- Description: The study presented in this thesis is a case study analysis of decentralization and quality assurance in a decentralized set up of the Ugandan Primary Schooling. The research looked at how the monitoring and evaluation informed the policy formulation process to regulate quality assurance in a decentralized governance of primary education. The Study was positioned in the critical realist paradigm, interpretive in orientation and used both coding and thematic techniques to understand the teachers’, SMC members’, and officers’ (at district and ministry levels) experiences and perceptions of quality assurance in a decentralized set up. Data was gathered using interviews, document analysis and observation methods. The findings indicated that the study was affected by eleven themes: Management System and Leadership, Human Resource Management, Finance Administration and Management, Parenting and Nutrition, Politics, Motivation, Social Structures and Patterns, Legislative Process and Policies, Infrastructure Development and Management, Community Involvement in Education and Curriculum and Professionalism. The monitoring and evaluation system had a framework in which it operates, though there was no quality assurance policy to guide the provision of quality education. The study finally indicated that there are more threats in a decentralized set up that put Quality in danger. Secondly, there was absence of supervision/inspection in schools as there was no evidence to prove this due to absence of reports. However, document analysis indicated visits of officers to schools. Records management was a problem to schools. Decentralization was adopted at different levels by different countries to address specific problems identified in view of service delivery. Finally, though monitoring and evaluation results informed the policy and decision makers, there was no quality assurance policy to guide the provision of quality education in institutions.
- Full Text:
- Date Issued: 2018
Graphene quantum dots and their metallophthalocyanines nanoconjugates as novel photoluminescent nanosensors
- Authors: Achadu, Ojodomo John
- Date: 2018
- Subjects: Quantum dots , Graphene , Phthalocyanines , Nanoconjugates , Novel photoluminescent nanosensors , Metallophthalocyanines
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/60719 , vital:27821
- Description: The fabrication and application of graphene quantum dots (GQDs)-based photoluminescent probes for the detection of analytes is presented. GQDs were functionalized with complexes such as metallophthalocyanines (MPcs), metal nanoparticles (Au@Ag NPs), 2,2,6,6-tetramethyl(piperidin-1-yl)oxyl (TEMPO), maleimide and thymine for the sensing of target analytes such as ascorbic acid (AA), biothiols (cysteine, homocysteine and glutathione) and mercury ion (Hg²+). The design strategy and approach was based on the quenching of the fluorescence of the GQDs upon functionalization with the above-mentioned complexes, which could be restored in the presence of the target analytes (due to their specific interaction affinity with the complexes). For the detection of AA, GQDs were covalently and/or non-covalently conjugated to TEMPO-bearing complexes to form GQDs-4A-TEMPO and GQDs-TEMPO-MPc systems with nanomolar limits of detection. For the detection of biothiols, Au@Ag NPs and maleimide-bearing complexes (MPc), which have specific affinity to interact with biothiols, were deployed. Hg²+ detection involved the use of GQDs and/or MPcs with thiol and thymine groups, respectively. In addition, a smart sensing platform was designed for the dual detection of biothiols and Hg²+ using supramolecular hybrid of polyethyleneimine functionalized-GQDs and MPc-Au@Ag conjugate. The probe could detect, in a sequential manner, Hg²+ and biothiols with high sensitivity. Results obtained from the LODs of the probes showed that GQDs sensing performances could be enhanced in the presence of MPcs. The probes designed in this work were successfully deployed in the assays of the target analytes in real samples and the recoveries obtained confirmed the analytical applicability of the probes.
- Full Text:
- Date Issued: 2018
- Authors: Achadu, Ojodomo John
- Date: 2018
- Subjects: Quantum dots , Graphene , Phthalocyanines , Nanoconjugates , Novel photoluminescent nanosensors , Metallophthalocyanines
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/60719 , vital:27821
- Description: The fabrication and application of graphene quantum dots (GQDs)-based photoluminescent probes for the detection of analytes is presented. GQDs were functionalized with complexes such as metallophthalocyanines (MPcs), metal nanoparticles (Au@Ag NPs), 2,2,6,6-tetramethyl(piperidin-1-yl)oxyl (TEMPO), maleimide and thymine for the sensing of target analytes such as ascorbic acid (AA), biothiols (cysteine, homocysteine and glutathione) and mercury ion (Hg²+). The design strategy and approach was based on the quenching of the fluorescence of the GQDs upon functionalization with the above-mentioned complexes, which could be restored in the presence of the target analytes (due to their specific interaction affinity with the complexes). For the detection of AA, GQDs were covalently and/or non-covalently conjugated to TEMPO-bearing complexes to form GQDs-4A-TEMPO and GQDs-TEMPO-MPc systems with nanomolar limits of detection. For the detection of biothiols, Au@Ag NPs and maleimide-bearing complexes (MPc), which have specific affinity to interact with biothiols, were deployed. Hg²+ detection involved the use of GQDs and/or MPcs with thiol and thymine groups, respectively. In addition, a smart sensing platform was designed for the dual detection of biothiols and Hg²+ using supramolecular hybrid of polyethyleneimine functionalized-GQDs and MPc-Au@Ag conjugate. The probe could detect, in a sequential manner, Hg²+ and biothiols with high sensitivity. Results obtained from the LODs of the probes showed that GQDs sensing performances could be enhanced in the presence of MPcs. The probes designed in this work were successfully deployed in the assays of the target analytes in real samples and the recoveries obtained confirmed the analytical applicability of the probes.
- Full Text:
- Date Issued: 2018
Contributions to the study of a class of optimal control problems on the orthogonal groups SO(3) and SO(4)
- Authors: Adams, Ross Montague
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64826 , vital:28608
- Description: In this thesis we investigate a class of invariant optimal control problems, and their associated quadratic Hamilton-Poisson systems, on the orthogonal groups SO(3) and SO(4). Specifically, we are concerned with the class of left-invariant control affine systems. We begin by classifying all cost-extended systems on SO(3) under cost equivalence. (Cost-extended systems are closely related to optimal control problems.) A classification of all quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space so(3)*, under affine equivalence, is also obtained. For the normal forms obtained in our classification (of Hamilton-Poisson systems) we investigate the (Lyapunov) stability nature of the equilibria using spectral and energy-Casimir methods. For a subclass of these systems, we obtain analytic expressions for the integral curves of the associated Hamiltonian vector fields in terms of (basic) Jacobi elliptic functions. The explicit relationship between the classification of cost-extended systems on SO(3) and the classification of quadratic Hamilton- Poisson systems on so(3)* is provided. On SO(4), a classification of all left-invariant control affine systems under L-equivalence is obtained. We then determine which of these representatives are controllable, thus obtaining a classification under detached feedback equivalence. We also obtain a partial classification of quadratic Hamilton-Poisson systems on the Lie-Poisson space so(4)*. An investigation of the stability nature of the equilibria for a subclass of these systems is also done. Several illustrative examples of optimal control problems on the orthogonal group SO(3) are provided. More specifically, we consider an optimal control problem corresponding to a representative of our classification (of cost-extended system) for each possible number of control inputs. For each of these problems, we obtain explicit expressions for the extremal trajectories on the homogeneous space S2 by projecting the extremal trajectories on the group SO(3). The examples provided show how our classifications of cost-extended systems and Hamilton-Poisson systems can be used to obtain the optimal controls and the extremal trajectories corresponding to a large class of optimal control problems on SO(3). An example of a four-input optimal control problem on SO(4) is also provided. This example is provided to show how the solutions of certain problems on SO(4) can be related to the solutions of certain optimal control problems on SO(3).
- Full Text:
- Date Issued: 2015
- Authors: Adams, Ross Montague
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64826 , vital:28608
- Description: In this thesis we investigate a class of invariant optimal control problems, and their associated quadratic Hamilton-Poisson systems, on the orthogonal groups SO(3) and SO(4). Specifically, we are concerned with the class of left-invariant control affine systems. We begin by classifying all cost-extended systems on SO(3) under cost equivalence. (Cost-extended systems are closely related to optimal control problems.) A classification of all quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space so(3)*, under affine equivalence, is also obtained. For the normal forms obtained in our classification (of Hamilton-Poisson systems) we investigate the (Lyapunov) stability nature of the equilibria using spectral and energy-Casimir methods. For a subclass of these systems, we obtain analytic expressions for the integral curves of the associated Hamiltonian vector fields in terms of (basic) Jacobi elliptic functions. The explicit relationship between the classification of cost-extended systems on SO(3) and the classification of quadratic Hamilton- Poisson systems on so(3)* is provided. On SO(4), a classification of all left-invariant control affine systems under L-equivalence is obtained. We then determine which of these representatives are controllable, thus obtaining a classification under detached feedback equivalence. We also obtain a partial classification of quadratic Hamilton-Poisson systems on the Lie-Poisson space so(4)*. An investigation of the stability nature of the equilibria for a subclass of these systems is also done. Several illustrative examples of optimal control problems on the orthogonal group SO(3) are provided. More specifically, we consider an optimal control problem corresponding to a representative of our classification (of cost-extended system) for each possible number of control inputs. For each of these problems, we obtain explicit expressions for the extremal trajectories on the homogeneous space S2 by projecting the extremal trajectories on the group SO(3). The examples provided show how our classifications of cost-extended systems and Hamilton-Poisson systems can be used to obtain the optimal controls and the extremal trajectories corresponding to a large class of optimal control problems on SO(3). An example of a four-input optimal control problem on SO(4) is also provided. This example is provided to show how the solutions of certain problems on SO(4) can be related to the solutions of certain optimal control problems on SO(3).
- Full Text:
- Date Issued: 2015
Maintenance management systems of on-campus student hostels at Nigerian universities
- Authors: Adamu, Anita Dzikwi
- Date: 2015
- Subjects: School buildings -- Maintenance and repair , Dormitories -- Nigeria , Nigeria -- Student housing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9710 , http://hdl.handle.net/10948/d1020168
- Description: Most universities have long recognised the importance and contribution of on-campus hostels to the learning process. In so doing, most of these institutions have provided and maintained building facilities for academic purposes (teaching and research). Hostels are integral components of most campuses of Nigerian universities, and they are part of the built assets of the institutions in terms of both administration and maintenance management. Currently, there is little understanding of the maintenance management systems of on-campus hostel buildings in both the public and the private universities. Moreover, there is a dearth of research evidence demonstrating that there is an appreciable difference in the maintenance management systems of the Federal, State and private universities in Nigeria. This research aimed at establishing an understanding of maintenance management systems of on-campus hostel buildings at Nigerian universities owned by the Federal and State governments and the Private Sector, relative to stipulated criteria for best practice.The qualitative method of research inquiry that is rooted in the phenomenological paradigm was employed in the investigations. The research activities included a comprehensive review of the related literature and study of selected cases. The North-central geopolitical zone of Nigeria was the selected geographical scope of this research. Ten universities were purposefully selected for the study, and they include three Federal, four state and three private universities. The nature and differences in the research questions necessitated generating different forms of data. The questions that were related to the maintenance management systems for the hostels in place at the universities were addressed with the outcomes of interviews with the hostel managers. The questions that were about the structures and current conditions of the hostel buildings at the three categories of universities were addressed with data that were generated from condition assessments of the facilities and physical observations with the aid of cameras. The study reveals apparent deteriorated and unhealthy conditions of most of the on-campus hostels at the public universities, while those of the private universities are satisfactory. The research also found that the maintenance management systems in use at all the universities are reactive and lack proper planning and coordination of maintenance activities. There is no significant difference in the maintenance management systems of hostels at the public and the private universities and the systems have major negative impact on the conditions of the buildings and their performances. The research has developed a conceptual model for the study of maintenance management informed by the theoretical framework. The model considered the impact of the external environmental factors on the management and maintenance of the hostels. Secondly, the interrelationships of strategic and performance management with maintenance management in developing an effective maintenance management system were established. The study has achieved its aim of establishing an understanding of maintenance management systems of on-campus hostel buildings at Nigerian universities owned by the Federal and, State governments and the Private Sector. The maintenance management model developed in the study is recommended to maintenance management departments as a guide for effective maintenance of the built facilities in their institutions.
- Full Text:
- Date Issued: 2015
- Authors: Adamu, Anita Dzikwi
- Date: 2015
- Subjects: School buildings -- Maintenance and repair , Dormitories -- Nigeria , Nigeria -- Student housing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9710 , http://hdl.handle.net/10948/d1020168
- Description: Most universities have long recognised the importance and contribution of on-campus hostels to the learning process. In so doing, most of these institutions have provided and maintained building facilities for academic purposes (teaching and research). Hostels are integral components of most campuses of Nigerian universities, and they are part of the built assets of the institutions in terms of both administration and maintenance management. Currently, there is little understanding of the maintenance management systems of on-campus hostel buildings in both the public and the private universities. Moreover, there is a dearth of research evidence demonstrating that there is an appreciable difference in the maintenance management systems of the Federal, State and private universities in Nigeria. This research aimed at establishing an understanding of maintenance management systems of on-campus hostel buildings at Nigerian universities owned by the Federal and State governments and the Private Sector, relative to stipulated criteria for best practice.The qualitative method of research inquiry that is rooted in the phenomenological paradigm was employed in the investigations. The research activities included a comprehensive review of the related literature and study of selected cases. The North-central geopolitical zone of Nigeria was the selected geographical scope of this research. Ten universities were purposefully selected for the study, and they include three Federal, four state and three private universities. The nature and differences in the research questions necessitated generating different forms of data. The questions that were related to the maintenance management systems for the hostels in place at the universities were addressed with the outcomes of interviews with the hostel managers. The questions that were about the structures and current conditions of the hostel buildings at the three categories of universities were addressed with data that were generated from condition assessments of the facilities and physical observations with the aid of cameras. The study reveals apparent deteriorated and unhealthy conditions of most of the on-campus hostels at the public universities, while those of the private universities are satisfactory. The research also found that the maintenance management systems in use at all the universities are reactive and lack proper planning and coordination of maintenance activities. There is no significant difference in the maintenance management systems of hostels at the public and the private universities and the systems have major negative impact on the conditions of the buildings and their performances. The research has developed a conceptual model for the study of maintenance management informed by the theoretical framework. The model considered the impact of the external environmental factors on the management and maintenance of the hostels. Secondly, the interrelationships of strategic and performance management with maintenance management in developing an effective maintenance management system were established. The study has achieved its aim of establishing an understanding of maintenance management systems of on-campus hostel buildings at Nigerian universities owned by the Federal and, State governments and the Private Sector. The maintenance management model developed in the study is recommended to maintenance management departments as a guide for effective maintenance of the built facilities in their institutions.
- Full Text:
- Date Issued: 2015
Plastochron index - an indicator of plant structure and function a case study using Pisum sativum L
- Ade-Ademilua, Omobolanle Elizabeth
- Authors: Ade-Ademilua, Omobolanle Elizabeth
- Date: 2006
- Subjects: Plant anatomy Plant physiology Peas -- Anatomy Peas -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4183 , http://hdl.handle.net/10962/d1003751
- Description: The use of chronological age for example, using days after sowing (DAS), or days after germination (DAG) as a time variable may result in the inherent variability between plants resulting in differences which can be large enough to obscure subtle developmental trends that become evident among plants sown at the same time. An alternative to DAS or DAG is the plastochron index (PI), first used by Erickson and Michelini (1957) as a morphological time scale and numerical index; which to according to the authors suggested and represented a more accurate reflection of the developmental status of a plant. The research presented in this thesis was therefore aimed specifically at utilizing the index in qualitative and quantitative analyses, to confirm its usefulness in analyzing and predicting plant growth and development. Specifically this research focused on investigating various morphological and physiological events that together, hopefully, would serve as a template for the prediction of the growth, development and reactions of Pisum sativum L. to different growth conditions. In Chapter 3, the use of the average length of the first pair of leaflets on each node as a suitable parameter for calculating PI in P. sativum is suggested. The results presented in Chapter 3 suggest that plant age is best expressed using the plastochron index, as this reflects the time interval between the initiations of successive pairs of leaflets. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2005) A re-evaluation of plastochron index in peas - a case for using leaflet length. South African Journal of Botany 71: 76-80”. The PI formula developed was subsequently used in this research to conduct qualitative and quantitative investigations of plant growth and development in which all data and observations were related directly to the plastochron index. In Chapter 4, the sink to source transition in Pisum sativum L. leaves at different plastochron ages in nodulating plants was investigated using the phloem-mobile fluorescent marker, 5,6-carboxyfluorescein (5,6-CF). The results demonstrated that young leaves remained strong sinks up until LPI 0, after which sink-source transition occurred up to LPI 1.8 and leaflets transitioned to strong source systems by LPI 2.0. A well-developed cross-connected phloem system between paired leaflets in peas, and the petiole and the stem vascular supply was observed. The data presented in the second part of Chapter 4 suggest that the phloem transport between leaflet pairs is independent of the sink/source state of the leaflets, or of movement along the source to sink gradient. The data support the presence of a modular transport system which may ensure re-allocation and balancing between leaflets of the same physiological age and photosynthetic and transport status, thereby load-balancing the local transport system, before exporting to other younger (sink) regions. The investigation of leaf development using the plastochron index (Chapter 5) revealed that the formation of air spaces in the palisade and spongy mesophyll, one of the preparatory events for transition from sink to source state in developing leaves, occurs between LPI 0 and LPI 1 in pea leaflets. Results of the anatomical and ultrastructural study related to PI are presented in Chapter 5. The density of wall ingrowths in transfer cells of minor veins increased with LPI and appeared to be associated with the probable transition to source state and the related potential increase in the production of assimilates for export. The onset of wall ingrowth development in leaflets at LPI 0 provided evidence that sink-to-source transition commences at LPI 0 in P. sativum. Presumably-functional plasmodesmata as well as a few mature sieve elements were evident in class IV veins in the apical region of young and older leaflets at LPI 0. The number of mature sieve elements per vein however, increased with increasing LPI. Most class V veins were still undergoing division at LPI 0 and their sieve elements did not show signs of maturity until LPI 1. The increase in the number of mature metaphloem sieve elements in young, supposedly importing tissue at LPI 0 to older, supposedly exporting tissues at LPI 2 is evidence of the association between phloem maturation and transition from importing to exporting status. In Chapter 6, I report on the effects of elevated CO[subscript 2] on the growth and leaf development of nodulating and non-nodulating Pisum sativum L var. Greenfeast grown under controlled environment of the same nitrogen (6mM) and nitrogen- free nutrient solution conditions. Shortterm exposure to elevated CO[subscript 2] induced rapid plant growth, irrespective of treatment. However, long-term elevated CO[subscript 2] treatment did not affect rate of leaf appearance (RLA) in nodulated plants, irrespective of mineral N supply but enhanced RLA in non- nodulating plants supplied with mineral N. Supplied N resulted in a significant increase in leaflet elongation rate (LfER) under both ambient and elevated CO[subscript 2], but LfER was not significantly affected by nodulation but was increased by high CO[subscript 2]. This suggested that the growth of nodulating P. sativum L may not be significantly affected under CO[subscript 2] levels as high as 1000 μmol mol[superscript -1]. The data suggest that elevated CO[subscript 2] will enhance canopy size, provided adequate soil N is available and more so in non-nodulating plants. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2004) The effects of elevated CO[subscript 2] and nitrogen availability supersedes the need for nodulation in peas grown under controlled environmental conditions. South African Journal of Botany 70: 816 – 823”. This thesis demonstrates that the similarity in the qualitative analyses results obtained from plants from different CO[subscript 2], nitrogen and nodulation treatment conditions, highlights the fact that plants of same PI value are at the same developmental state, irrespective of the growth condition. Furthermore, changes in plant structure and function observed under different growth conditions can be related simply to changes in plastochron index. The work presented in this thesis demonstrate that changes in plant structure and function analyzed are related to changes in PI. An important finding of this thesis is that with the use of PI, results can be compiled as a template for predicting the structure- function state of pea plants at any plastochron age, under any growth conditions, before using small representative sample populations.
- Full Text:
- Date Issued: 2006
- Authors: Ade-Ademilua, Omobolanle Elizabeth
- Date: 2006
- Subjects: Plant anatomy Plant physiology Peas -- Anatomy Peas -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4183 , http://hdl.handle.net/10962/d1003751
- Description: The use of chronological age for example, using days after sowing (DAS), or days after germination (DAG) as a time variable may result in the inherent variability between plants resulting in differences which can be large enough to obscure subtle developmental trends that become evident among plants sown at the same time. An alternative to DAS or DAG is the plastochron index (PI), first used by Erickson and Michelini (1957) as a morphological time scale and numerical index; which to according to the authors suggested and represented a more accurate reflection of the developmental status of a plant. The research presented in this thesis was therefore aimed specifically at utilizing the index in qualitative and quantitative analyses, to confirm its usefulness in analyzing and predicting plant growth and development. Specifically this research focused on investigating various morphological and physiological events that together, hopefully, would serve as a template for the prediction of the growth, development and reactions of Pisum sativum L. to different growth conditions. In Chapter 3, the use of the average length of the first pair of leaflets on each node as a suitable parameter for calculating PI in P. sativum is suggested. The results presented in Chapter 3 suggest that plant age is best expressed using the plastochron index, as this reflects the time interval between the initiations of successive pairs of leaflets. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2005) A re-evaluation of plastochron index in peas - a case for using leaflet length. South African Journal of Botany 71: 76-80”. The PI formula developed was subsequently used in this research to conduct qualitative and quantitative investigations of plant growth and development in which all data and observations were related directly to the plastochron index. In Chapter 4, the sink to source transition in Pisum sativum L. leaves at different plastochron ages in nodulating plants was investigated using the phloem-mobile fluorescent marker, 5,6-carboxyfluorescein (5,6-CF). The results demonstrated that young leaves remained strong sinks up until LPI 0, after which sink-source transition occurred up to LPI 1.8 and leaflets transitioned to strong source systems by LPI 2.0. A well-developed cross-connected phloem system between paired leaflets in peas, and the petiole and the stem vascular supply was observed. The data presented in the second part of Chapter 4 suggest that the phloem transport between leaflet pairs is independent of the sink/source state of the leaflets, or of movement along the source to sink gradient. The data support the presence of a modular transport system which may ensure re-allocation and balancing between leaflets of the same physiological age and photosynthetic and transport status, thereby load-balancing the local transport system, before exporting to other younger (sink) regions. The investigation of leaf development using the plastochron index (Chapter 5) revealed that the formation of air spaces in the palisade and spongy mesophyll, one of the preparatory events for transition from sink to source state in developing leaves, occurs between LPI 0 and LPI 1 in pea leaflets. Results of the anatomical and ultrastructural study related to PI are presented in Chapter 5. The density of wall ingrowths in transfer cells of minor veins increased with LPI and appeared to be associated with the probable transition to source state and the related potential increase in the production of assimilates for export. The onset of wall ingrowth development in leaflets at LPI 0 provided evidence that sink-to-source transition commences at LPI 0 in P. sativum. Presumably-functional plasmodesmata as well as a few mature sieve elements were evident in class IV veins in the apical region of young and older leaflets at LPI 0. The number of mature sieve elements per vein however, increased with increasing LPI. Most class V veins were still undergoing division at LPI 0 and their sieve elements did not show signs of maturity until LPI 1. The increase in the number of mature metaphloem sieve elements in young, supposedly importing tissue at LPI 0 to older, supposedly exporting tissues at LPI 2 is evidence of the association between phloem maturation and transition from importing to exporting status. In Chapter 6, I report on the effects of elevated CO[subscript 2] on the growth and leaf development of nodulating and non-nodulating Pisum sativum L var. Greenfeast grown under controlled environment of the same nitrogen (6mM) and nitrogen- free nutrient solution conditions. Shortterm exposure to elevated CO[subscript 2] induced rapid plant growth, irrespective of treatment. However, long-term elevated CO[subscript 2] treatment did not affect rate of leaf appearance (RLA) in nodulated plants, irrespective of mineral N supply but enhanced RLA in non- nodulating plants supplied with mineral N. Supplied N resulted in a significant increase in leaflet elongation rate (LfER) under both ambient and elevated CO[subscript 2], but LfER was not significantly affected by nodulation but was increased by high CO[subscript 2]. This suggested that the growth of nodulating P. sativum L may not be significantly affected under CO[subscript 2] levels as high as 1000 μmol mol[superscript -1]. The data suggest that elevated CO[subscript 2] will enhance canopy size, provided adequate soil N is available and more so in non-nodulating plants. This section of the research has been published as “Ade-Ademilua OE, Botha CEJ (2004) The effects of elevated CO[subscript 2] and nitrogen availability supersedes the need for nodulation in peas grown under controlled environmental conditions. South African Journal of Botany 70: 816 – 823”. This thesis demonstrates that the similarity in the qualitative analyses results obtained from plants from different CO[subscript 2], nitrogen and nodulation treatment conditions, highlights the fact that plants of same PI value are at the same developmental state, irrespective of the growth condition. Furthermore, changes in plant structure and function observed under different growth conditions can be related simply to changes in plastochron index. The work presented in this thesis demonstrate that changes in plant structure and function analyzed are related to changes in PI. An important finding of this thesis is that with the use of PI, results can be compiled as a template for predicting the structure- function state of pea plants at any plastochron age, under any growth conditions, before using small representative sample populations.
- Full Text:
- Date Issued: 2006
Enhancing the role of the Kaizen suggestion tool in South African lean automotive companies of the Eastern Cape
- Authors: Adedeji, Adeyemi Charles
- Date: 2011
- Subjects: Lean manufacturing , Manufacturing processes , Production management -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:8644 , http://hdl.handle.net/10948/d1008157 , Lean manufacturing , Manufacturing processes , Production management -- Mathematical models
- Description: The Toyota manufacturing system, aptly referred to as Lean manufacturing, has received a reasonable appreciation and awareness over the past decade in South African industry. This production phenomenon constitutes an organizational culture that encourages world-class production success through the liberation of factory resources, while employees are empowered and encouraged to contribute ideas for the improvement of processes and products. However, despite lean awareness and the crucial role of employee participation in the suggestion of ideas in world-class organizations, the performance level of lean manufacturing in South African industry is largely devoid of the Kaizen suggestion tool, particularly in the automotive companies of the Eastern Cape. The aim of this research was to proffer appropriate recommendations, improved awareness, understanding and practice for the improvement of the Kaizen suggestion principle in the automotive companies of the Eastern Cape. The research primarily focused on the ‘management/employees’ paradigm within the organisational context. The methodology employed in the study included a thorough review of the relevant literature and a questionnaire, which was developed and administered to both the management and employees of the thirty automotive components suppliers in Eastern Cape. The target companies constituted the units of analyses and therefore provided the opportunity for a detailed investigation of the links between management and employees as well as a submission of ideas for operational and organisational processes as established in the literature review. Epistemologically, the research is objectivist and paradigmically, positivist. However, some qualitative aspects of the data were relevant to the study and, therefore, were used in a complementary manner. The case approach utilized mixed methods by applying a range of data collection techniques and evidence from multiple sources while the sampling technique was sequential, involving both purposive and stratified random sampling. The study reveals the apparent lack of a systematic mechanism for the practice and administration of the Kaizen suggestion tools in most Eastern Cape automotive companies. This demerit is found to have negatively affected maximum employee participation and involvement in organizational decision making within the Province. The study has established a basic level of awareness and understanding among employees / employers relations that the Kaizen suggestion scheme is a vital tool for delivering strategic objectives in the management of decision making and organizational growth. The study strongly advocates the inclusion of employee suggestion systems as part of the organizational process.
- Full Text:
- Date Issued: 2011
- Authors: Adedeji, Adeyemi Charles
- Date: 2011
- Subjects: Lean manufacturing , Manufacturing processes , Production management -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:8644 , http://hdl.handle.net/10948/d1008157 , Lean manufacturing , Manufacturing processes , Production management -- Mathematical models
- Description: The Toyota manufacturing system, aptly referred to as Lean manufacturing, has received a reasonable appreciation and awareness over the past decade in South African industry. This production phenomenon constitutes an organizational culture that encourages world-class production success through the liberation of factory resources, while employees are empowered and encouraged to contribute ideas for the improvement of processes and products. However, despite lean awareness and the crucial role of employee participation in the suggestion of ideas in world-class organizations, the performance level of lean manufacturing in South African industry is largely devoid of the Kaizen suggestion tool, particularly in the automotive companies of the Eastern Cape. The aim of this research was to proffer appropriate recommendations, improved awareness, understanding and practice for the improvement of the Kaizen suggestion principle in the automotive companies of the Eastern Cape. The research primarily focused on the ‘management/employees’ paradigm within the organisational context. The methodology employed in the study included a thorough review of the relevant literature and a questionnaire, which was developed and administered to both the management and employees of the thirty automotive components suppliers in Eastern Cape. The target companies constituted the units of analyses and therefore provided the opportunity for a detailed investigation of the links between management and employees as well as a submission of ideas for operational and organisational processes as established in the literature review. Epistemologically, the research is objectivist and paradigmically, positivist. However, some qualitative aspects of the data were relevant to the study and, therefore, were used in a complementary manner. The case approach utilized mixed methods by applying a range of data collection techniques and evidence from multiple sources while the sampling technique was sequential, involving both purposive and stratified random sampling. The study reveals the apparent lack of a systematic mechanism for the practice and administration of the Kaizen suggestion tools in most Eastern Cape automotive companies. This demerit is found to have negatively affected maximum employee participation and involvement in organizational decision making within the Province. The study has established a basic level of awareness and understanding among employees / employers relations that the Kaizen suggestion scheme is a vital tool for delivering strategic objectives in the management of decision making and organizational growth. The study strongly advocates the inclusion of employee suggestion systems as part of the organizational process.
- Full Text:
- Date Issued: 2011
Anti-diabetic and phytochemical analysis of sutherlandia frutescens extracts
- Authors: Adefuye, Ogheneochuko Janet
- Date: 2016
- Subjects: Medicinal plants -- Africa , Traditional medicine -- Africa , Herbs -- Therapeutic use -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/3549 , vital:20441
- Description: In Africa, the importance of medicinal plants in folklore medicine and their contribution to primary healthcare is well recognized. Across the continent, local herbal mixtures still provide the only therapeutic option for about 80% of the population. The vast floral diversity and the intrinsic ethnobotanical knowledge has been the backbone of localized traditional herbal medical practices. In Africa, an estimated 5400 of the 60000 described plant taxa possess over 16300 therapeutic uses. Similarly, with a therapeutic flora comprising of approximately 650 species, herbal medical practitioners in South Africa, make use of a plethora of plants to treat different human diseases and infections. Over the years, studies have identified numerous plant species with potential against chronic metabolic diseases including type 2 diabetes mellitus (T2DM). Globally, the incidence and prevalence of T2DM have reached epidemic proportions affecting people of all ages, nationalities and ethnicity. Considered the fourth leading cause of deaths by disease, T2DM is a global health crisis with an estimated diagnosis and mortality frequency of 1 every 5 seconds and 1 every 7 seconds respectively. Though the exact pathophysiology of T2DM is not entirely understood, initial peripheral insulin resistance in adipose tissue, liver, and skeletal muscle with subsequent pancreatic β-cell dysfunction resulting from an attempt to compensate for insulin resistance is a common feature of the disease. The current approach to treating T2DM is the use of oral antidiabetic agents (OAAs), insulin, and incretin-based drugs in an attempt to achieve glycaemic control and maintain glucose homeostasis. However, conventional anti-T2DM drugs have been shown to have limited efficacies and serious adverse effects. Hence, the need for newer, more efficacious and safer anti-T2DM agents. Sutherlandia frutescens subsp. microphylla is a flowering shrub of the pea family (Fabaceae/Leguminaceae) found mainly in the Western Cape and Karoo regions of Southern Africa. Concoctions of various parts of the plant are used in the management of different ailments including T2DM. However, despite extensive biological and pharmacological studies, few analyses exist of the chemical constituents of S. frutescens and no Triple Time of Flight Liquid Chromatography with Mass Spectrometry (Triple TOF LC/MS/MS) analysis has been performed. The initial aim of this study was to investigate the phytochemical profile of hot aqueous, cold aqueous, 80% ethanolic, 100% ethanolic, 80% methanolic and 100% methanolic extracts of a single source S. frutescens plant material using colorimetric and spectrophotometric analysis. The hot aqueous extractant was found to be the best extractant for S. frutescens, yielding 1.99 g of crude extract from 16 g fresh powdered plant material. This data suggests that application of heat and water as the extractant (hot aqueous) could play a vital role in extraction of bioactive compounds from S. frutescens and also justifies the traditional use of a tea infusion of S. frutescens. Colorimetric analysis revealed the presence of flavonoids, flavonols, tannins, and phenols in all extracts with varying intensity. The organic extracts 100% methanol, 80% and 100% ethanol exhibited high color intensity (+++) for flavonoids and flavonols respectively, while all the extracts exhibited a moderate color intensity (++) for tannins and phenols. Spectrophotometric analysis of S. frutescens extracts revealed that all the organic extracts contained a significantly higher concentration (in mg/g of extract) of flavonols and tannins when compared to the aqueous extracts. All extracts contained approximately equal levels of phenols. These data confirm the presence of all four groups of bioactive phytocompounds in the S. frutescens extracts used in this study, and also confirm that different solvent extractants possess the capability to differentially extract specific groups of phytocompounds. in individual extracts. Further comparison of these compounds with online databases of anti-diabetic phytocompounds led to the preliminary identification of 10 possible anti-diabetic compounds; α-Pinene, Limonene, Sabinene, Carvone, Myricetin, Rutin, Stigmasterol, Emodin, Sarpagine and Hypoglycin B in crude and solid phase extraction (SPE) fractions of S. frutesecens. Furthermore, using two hepatic cell lines (Chang and HepG2) as an in-vtro model system, the anti-T2DM properties of crude aqueous and organic extracts of S. frutescents was investigated and compared. Both aqueous and organic extracts of S. frutescens were found to decrease gluconeogenesis, increase glucose uptake and decrease lipid accumulation (Triacylglycerol, Diacylglycerol, and Monoacylglycerol) in Chang and HepG2 hepatic cell cultures made insulin resistant (IR) following exposure to high concentration of insulin and fructose. Using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), the aqueous and organic extracts of S. frutescens were confirmed to regulate the expression of Vesicle-associated membrane protein 3 (VAMP3), Mitogen-activated protein kinase 8 (MAPK8), and Insulin receptor substrate 1 (IRS1) in insulin resistant hepatic cells. IR-mediated downregulation of VAMP3, MAPK8, and IRS1 mRNA in IR HepG2 hepatic cell cultures was reversed in the presence of aqueous and organic extracts of S. frutescens. The hot aqueous extract displayed the highest activity in all the assays, while all the organic extracts displayed similar potency. In conclusion, this study reports that aqueous and organic extracts of S. frutescens possess numerous anti-diabetic compounds that can be further investigated for the development of new, more efficacious and less toxic anti-diabetic agents. The presence of multiple compounds in a single extract does suggest a synergistic or combinatorial therapeutic effect. These findings support the burgeoning body of in-vivo and in-vitro literature evidence on the anti-diabetic properties of S. frutescens and its use in folklore medicine.
- Full Text:
- Date Issued: 2016
- Authors: Adefuye, Ogheneochuko Janet
- Date: 2016
- Subjects: Medicinal plants -- Africa , Traditional medicine -- Africa , Herbs -- Therapeutic use -- Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/3549 , vital:20441
- Description: In Africa, the importance of medicinal plants in folklore medicine and their contribution to primary healthcare is well recognized. Across the continent, local herbal mixtures still provide the only therapeutic option for about 80% of the population. The vast floral diversity and the intrinsic ethnobotanical knowledge has been the backbone of localized traditional herbal medical practices. In Africa, an estimated 5400 of the 60000 described plant taxa possess over 16300 therapeutic uses. Similarly, with a therapeutic flora comprising of approximately 650 species, herbal medical practitioners in South Africa, make use of a plethora of plants to treat different human diseases and infections. Over the years, studies have identified numerous plant species with potential against chronic metabolic diseases including type 2 diabetes mellitus (T2DM). Globally, the incidence and prevalence of T2DM have reached epidemic proportions affecting people of all ages, nationalities and ethnicity. Considered the fourth leading cause of deaths by disease, T2DM is a global health crisis with an estimated diagnosis and mortality frequency of 1 every 5 seconds and 1 every 7 seconds respectively. Though the exact pathophysiology of T2DM is not entirely understood, initial peripheral insulin resistance in adipose tissue, liver, and skeletal muscle with subsequent pancreatic β-cell dysfunction resulting from an attempt to compensate for insulin resistance is a common feature of the disease. The current approach to treating T2DM is the use of oral antidiabetic agents (OAAs), insulin, and incretin-based drugs in an attempt to achieve glycaemic control and maintain glucose homeostasis. However, conventional anti-T2DM drugs have been shown to have limited efficacies and serious adverse effects. Hence, the need for newer, more efficacious and safer anti-T2DM agents. Sutherlandia frutescens subsp. microphylla is a flowering shrub of the pea family (Fabaceae/Leguminaceae) found mainly in the Western Cape and Karoo regions of Southern Africa. Concoctions of various parts of the plant are used in the management of different ailments including T2DM. However, despite extensive biological and pharmacological studies, few analyses exist of the chemical constituents of S. frutescens and no Triple Time of Flight Liquid Chromatography with Mass Spectrometry (Triple TOF LC/MS/MS) analysis has been performed. The initial aim of this study was to investigate the phytochemical profile of hot aqueous, cold aqueous, 80% ethanolic, 100% ethanolic, 80% methanolic and 100% methanolic extracts of a single source S. frutescens plant material using colorimetric and spectrophotometric analysis. The hot aqueous extractant was found to be the best extractant for S. frutescens, yielding 1.99 g of crude extract from 16 g fresh powdered plant material. This data suggests that application of heat and water as the extractant (hot aqueous) could play a vital role in extraction of bioactive compounds from S. frutescens and also justifies the traditional use of a tea infusion of S. frutescens. Colorimetric analysis revealed the presence of flavonoids, flavonols, tannins, and phenols in all extracts with varying intensity. The organic extracts 100% methanol, 80% and 100% ethanol exhibited high color intensity (+++) for flavonoids and flavonols respectively, while all the extracts exhibited a moderate color intensity (++) for tannins and phenols. Spectrophotometric analysis of S. frutescens extracts revealed that all the organic extracts contained a significantly higher concentration (in mg/g of extract) of flavonols and tannins when compared to the aqueous extracts. All extracts contained approximately equal levels of phenols. These data confirm the presence of all four groups of bioactive phytocompounds in the S. frutescens extracts used in this study, and also confirm that different solvent extractants possess the capability to differentially extract specific groups of phytocompounds. in individual extracts. Further comparison of these compounds with online databases of anti-diabetic phytocompounds led to the preliminary identification of 10 possible anti-diabetic compounds; α-Pinene, Limonene, Sabinene, Carvone, Myricetin, Rutin, Stigmasterol, Emodin, Sarpagine and Hypoglycin B in crude and solid phase extraction (SPE) fractions of S. frutesecens. Furthermore, using two hepatic cell lines (Chang and HepG2) as an in-vtro model system, the anti-T2DM properties of crude aqueous and organic extracts of S. frutescents was investigated and compared. Both aqueous and organic extracts of S. frutescens were found to decrease gluconeogenesis, increase glucose uptake and decrease lipid accumulation (Triacylglycerol, Diacylglycerol, and Monoacylglycerol) in Chang and HepG2 hepatic cell cultures made insulin resistant (IR) following exposure to high concentration of insulin and fructose. Using real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), the aqueous and organic extracts of S. frutescens were confirmed to regulate the expression of Vesicle-associated membrane protein 3 (VAMP3), Mitogen-activated protein kinase 8 (MAPK8), and Insulin receptor substrate 1 (IRS1) in insulin resistant hepatic cells. IR-mediated downregulation of VAMP3, MAPK8, and IRS1 mRNA in IR HepG2 hepatic cell cultures was reversed in the presence of aqueous and organic extracts of S. frutescens. The hot aqueous extract displayed the highest activity in all the assays, while all the organic extracts displayed similar potency. In conclusion, this study reports that aqueous and organic extracts of S. frutescens possess numerous anti-diabetic compounds that can be further investigated for the development of new, more efficacious and less toxic anti-diabetic agents. The presence of multiple compounds in a single extract does suggest a synergistic or combinatorial therapeutic effect. These findings support the burgeoning body of in-vivo and in-vitro literature evidence on the anti-diabetic properties of S. frutescens and its use in folklore medicine.
- Full Text:
- Date Issued: 2016
The design of quantum dots and their conjugates as luminescent probes for analyte sensing
- Authors: Adegoke, Oluwasesan
- Date: 2014
- Subjects: Quantum dots Anolytes Luminescent probes Luminescence spectroscopy Phthalocyanines Nanoparticles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4457 , http://hdl.handle.net/10962/d1010866
- Description: The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan
- Date: 2014
- Subjects: Quantum dots Anolytes Luminescent probes Luminescence spectroscopy Phthalocyanines Nanoparticles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4457 , http://hdl.handle.net/10962/d1010866
- Description: The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
- Full Text:
- Date Issued: 2014
Evaluation of some pharmaceutical and personal care products and pesticide residues in selected wastewater treatment plants and receiving watersheds in Eastern Cape, South Africa
- Ademoyegun, Olufemi Temitope
- Authors: Ademoyegun, Olufemi Temitope
- Date: 2017
- Subjects: Emerging contaminants in water -- South Africa -- Eastern Cape Water treatment plants -- Waste disposal -- South Africa -- Eastern Cape Organic compounds -- Environmental aspects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/2922 , vital:28138
- Description: Emerging organic contaminants (EOCs) have been the focus of global environmental research for over three decades. EOCs have caused widespread concern due to their extensive use. As EOCs were designed to correct, enhance or protect a specific physiological, their target effects in humans and/or farm stocks are relatively well known and documented. However, there is limited knowledge about their unintended effects in the environment. To address the occurrence, distribution and fate of EOCs in the environment, efficient and reliable analytical methods are needed. The relatively low concentration, high polarity, and thermal lability of some EOCs, together with their interaction with complex environmental matrices, make their analysis challenging. Sample preparation followed by GC or HPLC separation and mass spectrometry (MS) detection has become the standard approach for evaluating EOCs in environmental samples. Physicochemical properties of EOCs range from highly water-soluble (hydrophylic) to highly water-insoluble (hydrophobic). Two groups of these EOCs were considered for study in this work. Pharmaceutical and personal care products (PPCPs) were comprehensively studied in five wastewater treatment plants and their receiving watersheds in Amathole districts in Eastern C ape, South Africa. PPCPs have been widely reported in wastewater influents, effluents, receiving rivers and biosolids, but reports of their occurrence in all these matrixes have been limited by the difficulty of analysis. Therefore, a comprehensive validation of methods was carried out on the influents, effluents, sludge and soil from the irrigated golf course where the effluent of one of the study sites was being used for over three decades now for irrigation. In all, thirteen PPCPs from five therapeutic groups were selected for study in this work because of their administering rate and availability of analytical instrument. Good limit of detection (LOD) and limit of quantification (LOQ) were achieved for the method used. The LOD for the aqueous Three different technologies were employed for the treatment of wastewater in the five selected wastewater treatment plants (WWTPs) and study was carried out to evaluate their ability to eliminate the selected compounds from the influents to the effluents using statistical analysis (ANOVA) at p<0.05 on the percentage removal rate across the three plants. The results had shown eight of the compounds having no significant difference among the treatment operations, whereas the remaining five compounds varied significantly among the treatment technologies under investigation. Principal component analysis was performed on the concentration of PPCPs, their removal rate and also on the physicochemical and treatment operation parameters. Hydraulic retention time (HRT) had correlation coefficient, r = 0.90 with the concentration of PPCPs and removal rates. Furthermore, occurrences, seasonal variation, mean concentration distribution pattern of the compounds, and temporal evaluation of the mean concentration of the pharmaceutical compounds in the five WWTPs during one year of sampling were considered. The results revealed that five products which were diclofenac, ibuprofen, paracetamol, triclosan and diethyl toluamide (DDET) were predominant among the PPCPs in all the WWTPs. The removal efficiency was highest in caffeine with 96 percent, and the lowest was obtained with carbamazepine (4 percent). Risk quotient of the concentration of PPCPs in the effluents and receiving waters was determined to assess their chronic toxicity at three trophic levels: fish, algae and matrixes studied ranged from 0.01 μg/L to 0.25 μg/L, and the LOQ from 0.02 μg/L to 0.78 μg/L. In the solid matrixes, LOD varied from 0.01 ng/g to 0.65 ng/g, and the LOQ between 0.08 ng/g and 5.17 ng/g. Better recovery efficiency was obtained with this mixture of solvents, acetone: dichloromethane (1:1), for the recovery of the five therapeutic groups in the solid matrixes using ultrasonication- assisted techniques. The results show percentage recovery values ranging from 68.8 percent to 107.5 percent diaphian. According to the environmental risk assessment results, ibuprofen and triclosan were found to be the most critical compounds due to their high risk quotient values. These findings will, therefore, help in the future evaluation of the efficiency of different treatment technologies in the removal of various PPCPs from the wastewater and their sustainable management in the aquatic resources in Eastern Cape, South Africa. For the lipophilic organochlorine pesticides (OCPs), the limits of detection (LODs) of the tested congeners varied from 0.04 ng/g (α-BHC) to 0.49 ng/g (endosulfan sulfate) and the limits of quantification ranging from 0.22 ng/g (aldrin) to 2.17 ng/g (δ-BHC).
- Full Text:
- Date Issued: 2017
- Authors: Ademoyegun, Olufemi Temitope
- Date: 2017
- Subjects: Emerging contaminants in water -- South Africa -- Eastern Cape Water treatment plants -- Waste disposal -- South Africa -- Eastern Cape Organic compounds -- Environmental aspects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/2922 , vital:28138
- Description: Emerging organic contaminants (EOCs) have been the focus of global environmental research for over three decades. EOCs have caused widespread concern due to their extensive use. As EOCs were designed to correct, enhance or protect a specific physiological, their target effects in humans and/or farm stocks are relatively well known and documented. However, there is limited knowledge about their unintended effects in the environment. To address the occurrence, distribution and fate of EOCs in the environment, efficient and reliable analytical methods are needed. The relatively low concentration, high polarity, and thermal lability of some EOCs, together with their interaction with complex environmental matrices, make their analysis challenging. Sample preparation followed by GC or HPLC separation and mass spectrometry (MS) detection has become the standard approach for evaluating EOCs in environmental samples. Physicochemical properties of EOCs range from highly water-soluble (hydrophylic) to highly water-insoluble (hydrophobic). Two groups of these EOCs were considered for study in this work. Pharmaceutical and personal care products (PPCPs) were comprehensively studied in five wastewater treatment plants and their receiving watersheds in Amathole districts in Eastern C ape, South Africa. PPCPs have been widely reported in wastewater influents, effluents, receiving rivers and biosolids, but reports of their occurrence in all these matrixes have been limited by the difficulty of analysis. Therefore, a comprehensive validation of methods was carried out on the influents, effluents, sludge and soil from the irrigated golf course where the effluent of one of the study sites was being used for over three decades now for irrigation. In all, thirteen PPCPs from five therapeutic groups were selected for study in this work because of their administering rate and availability of analytical instrument. Good limit of detection (LOD) and limit of quantification (LOQ) were achieved for the method used. The LOD for the aqueous Three different technologies were employed for the treatment of wastewater in the five selected wastewater treatment plants (WWTPs) and study was carried out to evaluate their ability to eliminate the selected compounds from the influents to the effluents using statistical analysis (ANOVA) at p<0.05 on the percentage removal rate across the three plants. The results had shown eight of the compounds having no significant difference among the treatment operations, whereas the remaining five compounds varied significantly among the treatment technologies under investigation. Principal component analysis was performed on the concentration of PPCPs, their removal rate and also on the physicochemical and treatment operation parameters. Hydraulic retention time (HRT) had correlation coefficient, r = 0.90 with the concentration of PPCPs and removal rates. Furthermore, occurrences, seasonal variation, mean concentration distribution pattern of the compounds, and temporal evaluation of the mean concentration of the pharmaceutical compounds in the five WWTPs during one year of sampling were considered. The results revealed that five products which were diclofenac, ibuprofen, paracetamol, triclosan and diethyl toluamide (DDET) were predominant among the PPCPs in all the WWTPs. The removal efficiency was highest in caffeine with 96 percent, and the lowest was obtained with carbamazepine (4 percent). Risk quotient of the concentration of PPCPs in the effluents and receiving waters was determined to assess their chronic toxicity at three trophic levels: fish, algae and matrixes studied ranged from 0.01 μg/L to 0.25 μg/L, and the LOQ from 0.02 μg/L to 0.78 μg/L. In the solid matrixes, LOD varied from 0.01 ng/g to 0.65 ng/g, and the LOQ between 0.08 ng/g and 5.17 ng/g. Better recovery efficiency was obtained with this mixture of solvents, acetone: dichloromethane (1:1), for the recovery of the five therapeutic groups in the solid matrixes using ultrasonication- assisted techniques. The results show percentage recovery values ranging from 68.8 percent to 107.5 percent diaphian. According to the environmental risk assessment results, ibuprofen and triclosan were found to be the most critical compounds due to their high risk quotient values. These findings will, therefore, help in the future evaluation of the efficiency of different treatment technologies in the removal of various PPCPs from the wastewater and their sustainable management in the aquatic resources in Eastern Cape, South Africa. For the lipophilic organochlorine pesticides (OCPs), the limits of detection (LODs) of the tested congeners varied from 0.04 ng/g (α-BHC) to 0.49 ng/g (endosulfan sulfate) and the limits of quantification ranging from 0.22 ng/g (aldrin) to 2.17 ng/g (δ-BHC).
- Full Text:
- Date Issued: 2017
The development of a cultural family business model of good governance for Greek family businesses in South Africa
- Adendorff, Christian Michael
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
Genetic diversity, resistance profile of hiv and risk assessment of mother-to-child transmission in pregnant women on antiretroviral therapy in the Eastern Cape, South Africa
- Authors: Adeniyi, Oladele Vincent
- Date: 2019
- Subjects: Antiretroviral agents , HIV infections -- Treatment -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15120 , vital:40183
- Description: Despite the initiation of life-long ART in HIV-infected pregnant women, the rate and determinants of infant HIV transmission are not known, especially in the poor resource settings of the Eastern Cape, South Africa. Maternal anti-retroviral therapy (ART) is crucial for elimination of mother-to-child transmission (MTCT) of HIV. However, the inevitable risks of emergence of HIV drug resistance poses significant threat to achieving this goal of HIV-free generation and keeping mothers alive. Also, it is unclear if women with high viral load at delivery have acquired clinically relevant mutations, which could confer resistance to the ART, thus, further increasing the risks of motherto-child transmission of HIV-drug resistance strains. In addition to the gaps identified in the prevention of mother-to-child transmission (PMTCT) context, the understanding of regional epidemics is crucial to the broader epidemiological profiling of HIV infections in the country. Despite the rapid influx of foreign nationals to South African and Eastern Cape Province, there has not been any molecular epidemiological studies profiling the HIV diversity in the Eastern Cape.
- Full Text:
- Date Issued: 2019
- Authors: Adeniyi, Oladele Vincent
- Date: 2019
- Subjects: Antiretroviral agents , HIV infections -- Treatment -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/15120 , vital:40183
- Description: Despite the initiation of life-long ART in HIV-infected pregnant women, the rate and determinants of infant HIV transmission are not known, especially in the poor resource settings of the Eastern Cape, South Africa. Maternal anti-retroviral therapy (ART) is crucial for elimination of mother-to-child transmission (MTCT) of HIV. However, the inevitable risks of emergence of HIV drug resistance poses significant threat to achieving this goal of HIV-free generation and keeping mothers alive. Also, it is unclear if women with high viral load at delivery have acquired clinically relevant mutations, which could confer resistance to the ART, thus, further increasing the risks of motherto-child transmission of HIV-drug resistance strains. In addition to the gaps identified in the prevention of mother-to-child transmission (PMTCT) context, the understanding of regional epidemics is crucial to the broader epidemiological profiling of HIV infections in the country. Despite the rapid influx of foreign nationals to South African and Eastern Cape Province, there has not been any molecular epidemiological studies profiling the HIV diversity in the Eastern Cape.
- Full Text:
- Date Issued: 2019
Design of Immunobiosensors for Detection of Tumor-Associated Anti-P53 Autoantibodies: Method Development
- Authors: Adeniyi, Omotayo Kayode
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
- Description: Introduction -- Experimental -- Label-Free Impedimetric Sensing of Anti-P53ab... -- Fluorescent detection of Anti-P53ab -- Peroxidase-like activity of Fe3O4@SiNP-APTES-Au@Pd... -- Colorimetric detection of Anti-P53ab , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
- Full Text:
- Date Issued: 2020
- Authors: Adeniyi, Omotayo Kayode
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
- Description: Introduction -- Experimental -- Label-Free Impedimetric Sensing of Anti-P53ab... -- Fluorescent detection of Anti-P53ab -- Peroxidase-like activity of Fe3O4@SiNP-APTES-Au@Pd... -- Colorimetric detection of Anti-P53ab , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
- Full Text:
- Date Issued: 2020
Active learning strategies used by teachers during English reading comprehension lessons in six selected primary schools in Nigeria
- Adepoju, Adetokunboh Abayomi
- Authors: Adepoju, Adetokunboh Abayomi
- Date: 2018
- Subjects: Education, Primary -- Nigeria Learning strategies -- Nigeria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8485 , vital:32838
- Description: Reading is an integral part of education from which one gets access to information. Unfortunately, reading ability among primary school pupils, the foundation level of education, is at its lowest ebb. These pupils when they get to secondary schools eventually fail external examinations-a situation which according to National Examination Council, is caused by inappropriate teaching methods. Consequent upon this, this study assessed active learning strategies used by teacher during English reading comprehension lessons in six selected primary schools in Nigeria. The main research question was: How do teachers employ active learning strategies in teaching English reading comprehension? The study adopted qualitative approach and case study design. With the use of purposive sampling technique to select six head teachers, six primary VI teachers, two members of the School Basic Committee, the Director Local Government Education Authority and six focus groups. The study used interviews, documents and focus group interview as research instruments to collect data. Data were analysed based on interpretivism paradigm which interpreted participants’ views according to the word view of the participants. The study found out that teachers have good knowledge of active learning strategies and use them in teaching English reading comprehension lessons but are faced with some daunting challenges such as non-availability of instructional materials, lack of library, lack of qualified teachers and lack of time. The study concluded that students fail woefully in English reading comprehension because teachers do not use appropriate teaching techniques. The study recommend that teachers must use active learning strategies effectively and more often during English reading comprehension, more time should be allocated for English reading comprehension, effective use of instructional materials should be considered and the government should employ specialist teachers to teach English reading comprehension.
- Full Text:
- Date Issued: 2018
- Authors: Adepoju, Adetokunboh Abayomi
- Date: 2018
- Subjects: Education, Primary -- Nigeria Learning strategies -- Nigeria
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8485 , vital:32838
- Description: Reading is an integral part of education from which one gets access to information. Unfortunately, reading ability among primary school pupils, the foundation level of education, is at its lowest ebb. These pupils when they get to secondary schools eventually fail external examinations-a situation which according to National Examination Council, is caused by inappropriate teaching methods. Consequent upon this, this study assessed active learning strategies used by teacher during English reading comprehension lessons in six selected primary schools in Nigeria. The main research question was: How do teachers employ active learning strategies in teaching English reading comprehension? The study adopted qualitative approach and case study design. With the use of purposive sampling technique to select six head teachers, six primary VI teachers, two members of the School Basic Committee, the Director Local Government Education Authority and six focus groups. The study used interviews, documents and focus group interview as research instruments to collect data. Data were analysed based on interpretivism paradigm which interpreted participants’ views according to the word view of the participants. The study found out that teachers have good knowledge of active learning strategies and use them in teaching English reading comprehension lessons but are faced with some daunting challenges such as non-availability of instructional materials, lack of library, lack of qualified teachers and lack of time. The study concluded that students fail woefully in English reading comprehension because teachers do not use appropriate teaching techniques. The study recommend that teachers must use active learning strategies effectively and more often during English reading comprehension, more time should be allocated for English reading comprehension, effective use of instructional materials should be considered and the government should employ specialist teachers to teach English reading comprehension.
- Full Text:
- Date Issued: 2018
Psychological capital and emotional intelligence as moderators of the relationship between occupational stress and organisational citizenship behaviour among graduate employees in Nigeria
- Authors: Aderibigbe, John Kolawole
- Date: 2017
- Subjects: Psychology, Industrial Emotional intelligence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8642 , vital:33250
- Description: The study investigated psychological capital and emotional intelligence as moderators of the relationship between occupational stress and organisational citizenship behaviour among graduate employees in Nigeria, using the explanatory cross-sectional (survey) research design and three sampling techniques (The Two-stage Cluster Sampling Method, The Convenience Sampling Method and The Purposive Sampling Technique) to sample 1532 male and female graduate employees in Nigeria. A structured validated questionnaire was used to collect data from the respondents. Six hypotheses were stated and tested in the study towards propounding a model, using Pearson Correlation Analysis, Multiple Regression Analysis and Structural Equation Modelling. The results show that there is a weak positive relationship between occupational stress and organisational citizenship behaviour, r = 0.070, p<0.01; there is a significant positive relationship between psychological capital and organisational citizenship behaviour, r = 0.588, p<0.01; there is a significant positive relationship between emotional intelligence and organisational citizenship behaviour, r = 0.473, p<0.01; psychological capital is a significant moderator of the relationship between occupational stress and organisational citizenship behaviour, F (2,1529) = 8.514; R2= 0.011; p <.05; emotional intelligence is a significant moderator of the relationship between occupational stress and organisational citizenship behaviour, F (2,1529) = 5.945; R2= 0.008; p <.05; psychological capital and emotional intelligence are significant joint moderators of the relationship between occupational stress and organisational citizenship behaviour, F (1,1530) = 221.240; R2= 0.186; p <.05; psychological capital has a direct and significant positive effect on organisational citizenship behaviour, R= 0.657, p<.001; emotional intelligence has a direct and significant positive effect on organisational citizenship behaviour, R= 0.183, p<.001; psychological capital has a direct and significant positive effect on occupational stress, R= 0.100, p<.001; emotional intelligence has a direct and significant positive effect on psychological capital, R= 0.547, p<.001. Based on the results, the study concludes that psychological capital and emotional intelligence are significant joint moderators of the relationship between occupational stress and organisational citizenship behaviour. The proposed model was, therefore, empirically confirmed. The researcher recommends that the empirical model of effective management of occupational stress and organisational citizenship behaviour, which has been propounded in the study, should be adopted and applied by teachers, lecturers, seminar facilitators, workshop trainers, supervisors and managers during their coaching or training sessions.
- Full Text:
- Date Issued: 2017
- Authors: Aderibigbe, John Kolawole
- Date: 2017
- Subjects: Psychology, Industrial Emotional intelligence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8642 , vital:33250
- Description: The study investigated psychological capital and emotional intelligence as moderators of the relationship between occupational stress and organisational citizenship behaviour among graduate employees in Nigeria, using the explanatory cross-sectional (survey) research design and three sampling techniques (The Two-stage Cluster Sampling Method, The Convenience Sampling Method and The Purposive Sampling Technique) to sample 1532 male and female graduate employees in Nigeria. A structured validated questionnaire was used to collect data from the respondents. Six hypotheses were stated and tested in the study towards propounding a model, using Pearson Correlation Analysis, Multiple Regression Analysis and Structural Equation Modelling. The results show that there is a weak positive relationship between occupational stress and organisational citizenship behaviour, r = 0.070, p<0.01; there is a significant positive relationship between psychological capital and organisational citizenship behaviour, r = 0.588, p<0.01; there is a significant positive relationship between emotional intelligence and organisational citizenship behaviour, r = 0.473, p<0.01; psychological capital is a significant moderator of the relationship between occupational stress and organisational citizenship behaviour, F (2,1529) = 8.514; R2= 0.011; p <.05; emotional intelligence is a significant moderator of the relationship between occupational stress and organisational citizenship behaviour, F (2,1529) = 5.945; R2= 0.008; p <.05; psychological capital and emotional intelligence are significant joint moderators of the relationship between occupational stress and organisational citizenship behaviour, F (1,1530) = 221.240; R2= 0.186; p <.05; psychological capital has a direct and significant positive effect on organisational citizenship behaviour, R= 0.657, p<.001; emotional intelligence has a direct and significant positive effect on organisational citizenship behaviour, R= 0.183, p<.001; psychological capital has a direct and significant positive effect on occupational stress, R= 0.100, p<.001; emotional intelligence has a direct and significant positive effect on psychological capital, R= 0.547, p<.001. Based on the results, the study concludes that psychological capital and emotional intelligence are significant joint moderators of the relationship between occupational stress and organisational citizenship behaviour. The proposed model was, therefore, empirically confirmed. The researcher recommends that the empirical model of effective management of occupational stress and organisational citizenship behaviour, which has been propounded in the study, should be adopted and applied by teachers, lecturers, seminar facilitators, workshop trainers, supervisors and managers during their coaching or training sessions.
- Full Text:
- Date Issued: 2017
Design of immunosensor for the detection of C-reactive protein using oriented antibody immobilization
- Authors: Adesina, Abiola Olanike
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
- Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
- Full Text:
- Date Issued: 2020
- Authors: Adesina, Abiola Olanike
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
- Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
- Full Text:
- Date Issued: 2020
Apparent digestibility coefficients of feed ingredients and essential amino acid requirements of dusky kob (Argyrosomus japonicus)
- Authors: Adesola, Abidemi Adejoke
- Date: 2017
- Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/32140 , vital:24014
- Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
- Full Text:
- Date Issued: 2017
- Authors: Adesola, Abidemi Adejoke
- Date: 2017
- Subjects: Amino acids in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/32140 , vital:24014
- Description: Important to the evaluation of potential feed ingredients for inclusion in fish diets should be their digestibility and amino acid requirement so that feeds can be formulated on a digestible basis rather than a gross nutrient basis. This thesis established techniques for faecal collection, the validity of digestibility markers, it determined apparent digestibility coefficients for various novel feed ingredients, and it established the optimal lysine requirement for Argyrosomus japonicus, which was used to estimate each of the essential amino acid requirements by using the ideal protein concept. There were no significant differences in dry matter apparent digestibility coefficients when faeces were collected by stripping (77.0 %), dissection (80.1 %) or settlement (83.5 %). Faecal collection by the settlement method produced the most reliable digestibility data. Apparent digestibility coefficients for dry matter, crude protein and energy calculated using acid-insoluble ash were higher (84.0 %, 93.2 % and 93.0 %, respectively) than those using chromic oxide (55.7 %, 79.1 % and 78.2 %) and titanium dioxide (58.6 %, 79.7 % and 80.5 %). The magnitude of variation in digestibility coefficients obtained using acid-insoluble ash was always lower than that obtained with the other markers. Therefore, acid-insoluble ash was preferred as a dietary marker. Using the above protocol, protein and amino acid digestibility of some animal and plant protein ingredients were evaluated in a series of experiments. The first trial compared the apparent digestibility coefficients of some animal products included as single protein source in the test diets. Apparent protein digestibility values were 84.5 %, 83.8 %, 85.8 % and 83.1 % for fishmeal-prime, fishmeal-standard, poultry meal and pork meal, respectively. Apparent digestibility coefficients for poultry meal were comparable to those of fishmeal, which indicate its potential as a substitute for fishmeal in the diets of A. japonicus. The second trial determined the apparent coefficients of plant and animal protein sources included at 30 % into a practical reference diet (70 %). Apparent protein digestibility ranged from 92.4 % in sunflower meal to 85.5 % in corn gluten meal. Soybean meal is a promising feed ingredient in A. japonicus due to the high apparent digestibility of its protein (92.0 %) and essential amino acid digestibility (mean average 91.4 %). A fundamental assumption in fish feed formulation is that the digestibility of nutrients is additive, i.e., digestibility of a nutrient in one ingredient does not interact with the digestibility of the same nutrient in another ingredient. In the third trial, additivity of feed ingredients was tested using pork meal and poultry meal. The results indicate that the apparent digestibility coefficient of animal protein ingredients could be calculated from compound diets to accurately determine protein and amino acid digestibility in A. japonicus, and possibly other carnivorous fish species. Dietary essential amino acid requirements were determined for juvenile A. japonicus in two trials. A dose-response study was conducted using crystalline lysine to determine the optimal requirement of dietary lysine for A. japonicus. Optimal dietary lysine was estimated at 31.7 g kg-¹ dry diet, corresponding to 73.5 g kg-¹ of dietary protein, based on specific growth rate and broken-line segmented regression analyses. Dietary requirements for other essential amino acids ranged from 22 g kg-¹ (histidine) to 71 g kg-¹ (leucine) crude protein. The results of the present study provided a research tool that could be used to assess and verify the conclusions of earlier dietary work on A. japonicus and in further studies to develop least cost diet formulations for this species. The study also adds to the knowledge of the nutritional requirements of A. japonicus by providing information on the digestibility of plants and animal protein ingredients. It also contributes to future dietary research for this species because this study determines, for the first time, the most suitable methods for investigating the digestibility of raw materials for A. japonicus.
- Full Text:
- Date Issued: 2017