Perceptions of commerce graduates from a selected higher education institution
- Authors: Kaliika, Michael
- Date: 2012
- Subjects: Education, Higher -- Curricula -- South Africa -- Evaluation Business education -- Curricula -- South Africa -- Evaluation Business education graduates -- South Africa -- Attitudes
- Type: Thesis , Masters , MCom
- Identifier: vital:1188 , http://hdl.handle.net/10962/d1004358
- Description: The role of higher education in developing human capital and contributing to economic growth, competitive advantage and societal progress of any country is well documented. The direct link between the economic performance of a country and the level of education of its citizens cannot be repudiated. Furthermore, the demands of a growing economy, governmental pressure and the competitive international business environment have put pressure on South African businesses. This is aggravated by a “skills crisis” and the need to deliver more goods and services to increasingly more diverse customers. There is consensus amongst experts that the shortage of skills and high-level managerial human resources in South Africa constitute a major threat to the country’s future economic development and productivity growth. As the business world becomes increasingly sophisticated and challenging, so does the need to continuously review and assess the business qualifications that equip managers to cope with the challenges facing them. The competencies that come with a Commerce degree are relevant in every corner of society from managing successful private companies, public organisations, for governments to be able to contribute to the greatest good of society, to socially effective not- for- profit organisations. Despite the importance of a degree in Commerce there are some criticisms about the degree and Commerce graduates. The problem statement of this study is therefore vested in the continuum of praise and criticisms of Commerce graduates and the Commerce curriculum and, the reported imbalances between higher education institutions and the needs of the labour market. The question is whether such praise and criticisms are justified and whether higher education institutions specifically meet the requirements and expectations of both the graduates themselves and of business practice. The primary research objective of this study was, therefore, to obtain the opinions of Commerce graduates and Commerce graduate employers on the overall perception of Commerce graduates produced by a prominent HEI in the Eastern Cape Province in South iv Africa. To achieve this objective and based on in-depth analysis of secondary sources, two independent empirical surveys, aimed at two population strata were conducted, namely: • The Commerce graduates with known email addresses (N = 1 870) were extracted from the HEI’s alumni database. A total of 231 usable questionnaires were received from these Commerce graduates. • The employers with known addresses (N = 85) were extracted from the selected HEIs Career Centre database. A total of 47 usable questionnaires were received from the employers of the Commerce graduates. The main findings in this research pertain to aspects concerning core courses in the Commerce curriculum offered by the selected HEI, management skills and traits as required in the work environment, commerce curriculum outcomes and perceived experience as a student in the Faculty of Commerce at the selected HEI and Employer perceptions on the profile of the Commerce graduate. In this regard, the main findings are therefore summarised below: • Both graduates and employers assigned high relative importance scores to seventeen of the 19 core courses, supporting the multi-functionary interdisciplinary approach to the Commerce curriculum. Concerns were expressed by the Commerce graduates with the quality of tuition they had received in most of the core courses. Likewise, employers were not always satisfied with the Commerce graduates’ proficiency in some of the core courses, relative to the importance of core courses for running a business. • The Commerce graduates and employers strongly endorsed and supported the importance of the 43 management skills and traits in the work environment. Commerce graduates expressed concerns about the extent to which their management skills and traits had been developed through tuition. Concerns about the proficiency of the Commerce graduates in all the management skills and traits, relative to the importance in the work place, were conveyed by the employers. • On average the perceptions on the outcome of studies in the Faculty of Commerce were very highly regarded by the Commerce graduates. The highest mean score was for the item “Studying in the Faculty of Commerce contributed to an increase in my knowledge and abilities.”• The perceived experience of Commerce graduates as students in the Faculty of Commerce at the selected HEI was very highly regarded, implying that the selected HEI was meeting the expectations of its Commerce graduates. • Employer perceptions of what would constitute an ideal Commerce graduate were not fully met by the profile of the actual Commerce graduate from the selected HEI.
- Full Text:
- Date Issued: 2012
- Authors: Kaliika, Michael
- Date: 2012
- Subjects: Education, Higher -- Curricula -- South Africa -- Evaluation Business education -- Curricula -- South Africa -- Evaluation Business education graduates -- South Africa -- Attitudes
- Type: Thesis , Masters , MCom
- Identifier: vital:1188 , http://hdl.handle.net/10962/d1004358
- Description: The role of higher education in developing human capital and contributing to economic growth, competitive advantage and societal progress of any country is well documented. The direct link between the economic performance of a country and the level of education of its citizens cannot be repudiated. Furthermore, the demands of a growing economy, governmental pressure and the competitive international business environment have put pressure on South African businesses. This is aggravated by a “skills crisis” and the need to deliver more goods and services to increasingly more diverse customers. There is consensus amongst experts that the shortage of skills and high-level managerial human resources in South Africa constitute a major threat to the country’s future economic development and productivity growth. As the business world becomes increasingly sophisticated and challenging, so does the need to continuously review and assess the business qualifications that equip managers to cope with the challenges facing them. The competencies that come with a Commerce degree are relevant in every corner of society from managing successful private companies, public organisations, for governments to be able to contribute to the greatest good of society, to socially effective not- for- profit organisations. Despite the importance of a degree in Commerce there are some criticisms about the degree and Commerce graduates. The problem statement of this study is therefore vested in the continuum of praise and criticisms of Commerce graduates and the Commerce curriculum and, the reported imbalances between higher education institutions and the needs of the labour market. The question is whether such praise and criticisms are justified and whether higher education institutions specifically meet the requirements and expectations of both the graduates themselves and of business practice. The primary research objective of this study was, therefore, to obtain the opinions of Commerce graduates and Commerce graduate employers on the overall perception of Commerce graduates produced by a prominent HEI in the Eastern Cape Province in South iv Africa. To achieve this objective and based on in-depth analysis of secondary sources, two independent empirical surveys, aimed at two population strata were conducted, namely: • The Commerce graduates with known email addresses (N = 1 870) were extracted from the HEI’s alumni database. A total of 231 usable questionnaires were received from these Commerce graduates. • The employers with known addresses (N = 85) were extracted from the selected HEIs Career Centre database. A total of 47 usable questionnaires were received from the employers of the Commerce graduates. The main findings in this research pertain to aspects concerning core courses in the Commerce curriculum offered by the selected HEI, management skills and traits as required in the work environment, commerce curriculum outcomes and perceived experience as a student in the Faculty of Commerce at the selected HEI and Employer perceptions on the profile of the Commerce graduate. In this regard, the main findings are therefore summarised below: • Both graduates and employers assigned high relative importance scores to seventeen of the 19 core courses, supporting the multi-functionary interdisciplinary approach to the Commerce curriculum. Concerns were expressed by the Commerce graduates with the quality of tuition they had received in most of the core courses. Likewise, employers were not always satisfied with the Commerce graduates’ proficiency in some of the core courses, relative to the importance of core courses for running a business. • The Commerce graduates and employers strongly endorsed and supported the importance of the 43 management skills and traits in the work environment. Commerce graduates expressed concerns about the extent to which their management skills and traits had been developed through tuition. Concerns about the proficiency of the Commerce graduates in all the management skills and traits, relative to the importance in the work place, were conveyed by the employers. • On average the perceptions on the outcome of studies in the Faculty of Commerce were very highly regarded by the Commerce graduates. The highest mean score was for the item “Studying in the Faculty of Commerce contributed to an increase in my knowledge and abilities.”• The perceived experience of Commerce graduates as students in the Faculty of Commerce at the selected HEI was very highly regarded, implying that the selected HEI was meeting the expectations of its Commerce graduates. • Employer perceptions of what would constitute an ideal Commerce graduate were not fully met by the profile of the actual Commerce graduate from the selected HEI.
- Full Text:
- Date Issued: 2012
Perceptions of rural consumers and the quality of mutton at purchase points in the Eastern Cape Province, South Africa
- Authors: Rani, Zikhona Theodora
- Date: 2012
- Subjects: Meat -- Quality , Mutton -- Quality , Consumers' preferences , Quality of products , Consumers -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11823 , http://hdl.handle.net/10353/d1007562 , Meat -- Quality , Mutton -- Quality , Consumers' preferences , Quality of products , Consumers -- South Africa -- Eastern Cape
- Description: The objective of the study was to determine perceptions of rural consumers on mutton quality, and the quality of mutton at purchase points in the Eastern Cape Province, South Africa. The study was conducted in five different municipalities (Buffalo City, Nkonkobe, Ngqushwa, Lukhanje and Amahlathi). A survey was conducted where a sample of 215 consumers were randomly selected and interviewed, either at point of purchase or as they left the shops. The survey was not limited to the shoppers only but also extended to households from the villages. Questions on some of the most important meat quality cues were compiled. The physico-chemical quality of mutton purchased from different shops was also determined. Forty different shops and butcheries selling mutton from all the selected municipalities were visited. Different parts of mutton samples were bought. Physico-chemical qualities of mutton such as colour (L* - lightness, b* - redness and a* - yellowness) and meat pH measurements were taken at points of purchase. Cooking loss and tenderness evaluations were later done at the Meat Science laboratory at the University of Fort Hare. The results indicated that price was one of the major factors affecting the purchasing decisions of consumers. Thirty four percent of the consumers preferred mutton as compared to other protein sources, even though they were not buying this type of meat because it was not affordable to them. Both male and female consumers suggested that more sheep farmers need to be established in order to reduce the levels of imported mutton into South Africa. They also highlighted that selection programmes that will result in efficient sheep production and reduced mutton prices need to be implemented. Meat at points of purchase was affected by season resulting in lower lightness (L*24.7±0.49) values in winter and higher (L* 32.2±0.49) in Spring. The class of shop did not have an effect on meat quality attributes. Trotter had high values of lightness (L*30.4±2.78a), redness (a*30.4±2.78a), yellowness (13.1±1.08a), pH (6.3±0.12a), tenderness (24.9±3.69b) and cooking loss (39.5±4.38ab). The number of days from when the meat was put on the shelves to the time when it was purchased for consumption (days to purchase) had a significant (P<0.05) negative correlation with the Warner Braztler Shear Force (WBSF)values and lightness of the meat. Significant negative (P < 0.05) correlations between pH and colour of the meat (L*, a* and b*) were also observed. It was concluded that rural consumers perceive the quality of mutton as the best and that the physico-chemical quality of meat purchased from different shops was different, largely based on the part of meat, meat storage conditions and not necessarily on the class of the shop.
- Full Text:
- Date Issued: 2012
- Authors: Rani, Zikhona Theodora
- Date: 2012
- Subjects: Meat -- Quality , Mutton -- Quality , Consumers' preferences , Quality of products , Consumers -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11823 , http://hdl.handle.net/10353/d1007562 , Meat -- Quality , Mutton -- Quality , Consumers' preferences , Quality of products , Consumers -- South Africa -- Eastern Cape
- Description: The objective of the study was to determine perceptions of rural consumers on mutton quality, and the quality of mutton at purchase points in the Eastern Cape Province, South Africa. The study was conducted in five different municipalities (Buffalo City, Nkonkobe, Ngqushwa, Lukhanje and Amahlathi). A survey was conducted where a sample of 215 consumers were randomly selected and interviewed, either at point of purchase or as they left the shops. The survey was not limited to the shoppers only but also extended to households from the villages. Questions on some of the most important meat quality cues were compiled. The physico-chemical quality of mutton purchased from different shops was also determined. Forty different shops and butcheries selling mutton from all the selected municipalities were visited. Different parts of mutton samples were bought. Physico-chemical qualities of mutton such as colour (L* - lightness, b* - redness and a* - yellowness) and meat pH measurements were taken at points of purchase. Cooking loss and tenderness evaluations were later done at the Meat Science laboratory at the University of Fort Hare. The results indicated that price was one of the major factors affecting the purchasing decisions of consumers. Thirty four percent of the consumers preferred mutton as compared to other protein sources, even though they were not buying this type of meat because it was not affordable to them. Both male and female consumers suggested that more sheep farmers need to be established in order to reduce the levels of imported mutton into South Africa. They also highlighted that selection programmes that will result in efficient sheep production and reduced mutton prices need to be implemented. Meat at points of purchase was affected by season resulting in lower lightness (L*24.7±0.49) values in winter and higher (L* 32.2±0.49) in Spring. The class of shop did not have an effect on meat quality attributes. Trotter had high values of lightness (L*30.4±2.78a), redness (a*30.4±2.78a), yellowness (13.1±1.08a), pH (6.3±0.12a), tenderness (24.9±3.69b) and cooking loss (39.5±4.38ab). The number of days from when the meat was put on the shelves to the time when it was purchased for consumption (days to purchase) had a significant (P<0.05) negative correlation with the Warner Braztler Shear Force (WBSF)values and lightness of the meat. Significant negative (P < 0.05) correlations between pH and colour of the meat (L*, a* and b*) were also observed. It was concluded that rural consumers perceive the quality of mutton as the best and that the physico-chemical quality of meat purchased from different shops was different, largely based on the part of meat, meat storage conditions and not necessarily on the class of the shop.
- Full Text:
- Date Issued: 2012
Perceptions of scarce skills in the department of Infrastructure and Engineering : Nelson Mandela Bay Municipality
- Oshoniyi, Oluwaseun Abodunrin
- Authors: Oshoniyi, Oluwaseun Abodunrin
- Date: 2012
- Subjects: Labor supply -- South Africa , Professional employees -- South Africa. , Professional employees -- Supply and demand -- South Africa , Occupational training -- South Africa , South Africa -- Economic policy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8488 , http://hdl.handle.net/10948/d1019843
- Description: The scarcity of skills is a global phenomenon, affecting the capacity building, economic growth and development components of all nations. The African continent has been affected by skills shortages, emanating from certain socio-economic factors. This resulted in the ‘brain drain’, emigration and absorption of skilled talent to developed countries, in search of a better standard of living and employment opportunities. The issue of scarce skills in South Africa was identified by the Government in 2006, due to an identified shortage of expertise and proficiencies, required to fill numerous vacant positions within the local government to meet service delivery needs. The identification of skills shortages led to the formulation of macro-economic policies to address the issue of scarce skills and the identification of the most affected professions, which included, inter alia, engineers; technicians; project managers; and architects. Despite the implementation of these policies, underlying factors compound the issue, complicating and limiting remedial efforts. The South African Government is faced with the challenge of providing quality basic services for the public, especially at the local level. The country has since 2010 experienced multiple incidents of service delivery protests, predominantly in the under-developed communities. The Eastern Cape is no exception, as the Nelson Mandela Bay area has experienced protests, concerning poor service delivery, primarily in Walmer Township. The provision of basic services, are of dire necessity to the communities, as the Eastern Cape is one of the poorest provinces in South Africa. The educational system at primary and secondary levels is faced with challenges in the Eastern Cape province. These challenges are the shortage of teachers; poor infrastructure; and teacher absenteeism. This compounds the issue of scarce skills acquisition and development; the volume of skilled, expert and proficient talent available to the municipality, to fill in vacancies, gaps and areas with shortfalls and deficits within the entity, is reduced and minimal, underscoring the depth of the entrenchment of this scarcity of skills issue. The primary focus of the study is to expose the factors contributing to skills shortages and the implications, apropos service delivery, from the municipal workers’ perceptions. The study highlights and describes the factors affecting scarce skills acquisition and development in South Africa, along with providing a background of the Eastern Cape and demonstrating that the shortage of skills, within the Infrastructure and Engineering Department of the Nelson Mandela Bay Municipality, has an impact on the production, efficacy and efficiency of services for communities. The study also emphasises the essentiality of quality leadership and management within the organisation, a pivotal aspect in ensuring the municipality performs at optimal level, meeting organisational goals. This is a critical issue, as the study revealed that sound management and leadership is lacking within the municipality, affecting quality of the service delivery output. The findings of this study further revealed that adequate training and development is lacking in the municipality. This is hampering skills development, outstandingly with regard to technical skills talents, as their training needs are not met.
- Full Text:
- Date Issued: 2012
- Authors: Oshoniyi, Oluwaseun Abodunrin
- Date: 2012
- Subjects: Labor supply -- South Africa , Professional employees -- South Africa. , Professional employees -- Supply and demand -- South Africa , Occupational training -- South Africa , South Africa -- Economic policy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:8488 , http://hdl.handle.net/10948/d1019843
- Description: The scarcity of skills is a global phenomenon, affecting the capacity building, economic growth and development components of all nations. The African continent has been affected by skills shortages, emanating from certain socio-economic factors. This resulted in the ‘brain drain’, emigration and absorption of skilled talent to developed countries, in search of a better standard of living and employment opportunities. The issue of scarce skills in South Africa was identified by the Government in 2006, due to an identified shortage of expertise and proficiencies, required to fill numerous vacant positions within the local government to meet service delivery needs. The identification of skills shortages led to the formulation of macro-economic policies to address the issue of scarce skills and the identification of the most affected professions, which included, inter alia, engineers; technicians; project managers; and architects. Despite the implementation of these policies, underlying factors compound the issue, complicating and limiting remedial efforts. The South African Government is faced with the challenge of providing quality basic services for the public, especially at the local level. The country has since 2010 experienced multiple incidents of service delivery protests, predominantly in the under-developed communities. The Eastern Cape is no exception, as the Nelson Mandela Bay area has experienced protests, concerning poor service delivery, primarily in Walmer Township. The provision of basic services, are of dire necessity to the communities, as the Eastern Cape is one of the poorest provinces in South Africa. The educational system at primary and secondary levels is faced with challenges in the Eastern Cape province. These challenges are the shortage of teachers; poor infrastructure; and teacher absenteeism. This compounds the issue of scarce skills acquisition and development; the volume of skilled, expert and proficient talent available to the municipality, to fill in vacancies, gaps and areas with shortfalls and deficits within the entity, is reduced and minimal, underscoring the depth of the entrenchment of this scarcity of skills issue. The primary focus of the study is to expose the factors contributing to skills shortages and the implications, apropos service delivery, from the municipal workers’ perceptions. The study highlights and describes the factors affecting scarce skills acquisition and development in South Africa, along with providing a background of the Eastern Cape and demonstrating that the shortage of skills, within the Infrastructure and Engineering Department of the Nelson Mandela Bay Municipality, has an impact on the production, efficacy and efficiency of services for communities. The study also emphasises the essentiality of quality leadership and management within the organisation, a pivotal aspect in ensuring the municipality performs at optimal level, meeting organisational goals. This is a critical issue, as the study revealed that sound management and leadership is lacking within the municipality, affecting quality of the service delivery output. The findings of this study further revealed that adequate training and development is lacking in the municipality. This is hampering skills development, outstandingly with regard to technical skills talents, as their training needs are not met.
- Full Text:
- Date Issued: 2012
Perceptions on knowledge and understanding acquired by secondary school learners from sex education to reduce sex-related problems in the Libode District in the Eastern Cape : Implications for school management
- Authors: Gcelu, Ntombizandile
- Date: 2012
- Subjects: Sex education -- Learners -- Education (Secondary)
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18452 , http://hdl.handle.net/11260/d1007758
- Description: The study investigates whether knowledge and understanding acquired by secondary school learners from sex education in schools contribute to meaningful reduction of sex-related problems amongst them. The study was undertaken in the Eastern Cape in the Libode District (Nonesi Circuit). Data was collected from one hundred and thirty learners of five junior secondary schools of the Libode District (Nonesi Circuit).The respondents were learners with ages varying between 12 and 18 years, grades 7-9 (females and males). A quantitative approach and qualitative approach (mixed-method approach) was used. A survey design in the form of questionnaire was selected in the study. Nonesi circuit has a population of twenty junior secondary schools with a total enrolment of 2500 learners. Out of this population, a sample of five junior secondary schools was used. The five junior secondary schools were selected purposively. The sample consisted of twenty-six learners from each junior secondary school. Questionnaires were personally distributed, administered and collected by myself in the five junior secondary schools. The study findings revealed that learners understand the knowledge they acquired from sex education to prevent pregnancy and sex related diseases. The study also showed that knowledge and understanding acquired by learners from sex education is not effective enough to empower them to prevent pregnancy and sex-related diseases. The study highlighted the point that secondary school learners know and use other available sources of information on sex education after school to empower them to reduce pregnancy and sex- related diseases. It also revealed that learners know but do not take responsibility for their own lives regarding prevention of sex-related diseases.
- Full Text:
- Date Issued: 2012
- Authors: Gcelu, Ntombizandile
- Date: 2012
- Subjects: Sex education -- Learners -- Education (Secondary)
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18452 , http://hdl.handle.net/11260/d1007758
- Description: The study investigates whether knowledge and understanding acquired by secondary school learners from sex education in schools contribute to meaningful reduction of sex-related problems amongst them. The study was undertaken in the Eastern Cape in the Libode District (Nonesi Circuit). Data was collected from one hundred and thirty learners of five junior secondary schools of the Libode District (Nonesi Circuit).The respondents were learners with ages varying between 12 and 18 years, grades 7-9 (females and males). A quantitative approach and qualitative approach (mixed-method approach) was used. A survey design in the form of questionnaire was selected in the study. Nonesi circuit has a population of twenty junior secondary schools with a total enrolment of 2500 learners. Out of this population, a sample of five junior secondary schools was used. The five junior secondary schools were selected purposively. The sample consisted of twenty-six learners from each junior secondary school. Questionnaires were personally distributed, administered and collected by myself in the five junior secondary schools. The study findings revealed that learners understand the knowledge they acquired from sex education to prevent pregnancy and sex related diseases. The study also showed that knowledge and understanding acquired by learners from sex education is not effective enough to empower them to prevent pregnancy and sex-related diseases. The study highlighted the point that secondary school learners know and use other available sources of information on sex education after school to empower them to reduce pregnancy and sex- related diseases. It also revealed that learners know but do not take responsibility for their own lives regarding prevention of sex-related diseases.
- Full Text:
- Date Issued: 2012
Performance of defensive shares on the JSE during financial crisis: evidence from analysis of returns and volatility
- Authors: Arguile, Wayne Peter
- Date: 2012
- Subjects: Industries -- South Africa -- Finance Industries -- South Africa -- Statistics Johannesburg Stock Exchange Rational expectations (Economic theory)
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1001 , http://hdl.handle.net/10962/d1002736
- Description: This study analyses whether historically defensive sectors on the JSE have – with respect to the market – proven to be defensive during the recent global financial crisis. By withstanding the shocks of market volatility, defensive industries (such as pharmaceuticals and consumer staples) are renowned for their consistent performance throughout the business cycle. Using daily data for the period 2000–2009, the study compares the descriptive statistics of sector returns before and during the crisis. The volatility of each sector relative to the market index is calculated using the CAPM beta and a simplified volatility ratio. The same comparison is extended to the conditional volatilities of each of the sectors, which is estimated using the GARCH model and two of its extensions: the EGARCH and GJR GARCH models. While no sector experienced a positive mean return during the financial crisis, Healthcare, Consumer Goods, Consumer Services and Industrials all proved less volatile than the market. Surprisingly, Telecommunications proved more volatile than the market and experienced leverage effects during the financial crisis. Since the timing of a recession is difficult to predict, defensive securities were found to be a useful investment tool for protection against adverse movements in the stock market.
- Full Text:
- Date Issued: 2012
- Authors: Arguile, Wayne Peter
- Date: 2012
- Subjects: Industries -- South Africa -- Finance Industries -- South Africa -- Statistics Johannesburg Stock Exchange Rational expectations (Economic theory)
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1001 , http://hdl.handle.net/10962/d1002736
- Description: This study analyses whether historically defensive sectors on the JSE have – with respect to the market – proven to be defensive during the recent global financial crisis. By withstanding the shocks of market volatility, defensive industries (such as pharmaceuticals and consumer staples) are renowned for their consistent performance throughout the business cycle. Using daily data for the period 2000–2009, the study compares the descriptive statistics of sector returns before and during the crisis. The volatility of each sector relative to the market index is calculated using the CAPM beta and a simplified volatility ratio. The same comparison is extended to the conditional volatilities of each of the sectors, which is estimated using the GARCH model and two of its extensions: the EGARCH and GJR GARCH models. While no sector experienced a positive mean return during the financial crisis, Healthcare, Consumer Goods, Consumer Services and Industrials all proved less volatile than the market. Surprisingly, Telecommunications proved more volatile than the market and experienced leverage effects during the financial crisis. Since the timing of a recession is difficult to predict, defensive securities were found to be a useful investment tool for protection against adverse movements in the stock market.
- Full Text:
- Date Issued: 2012
Peri-urban agriculture and population growth : the case of Asmara, Eritrea
- Authors: Fessahaie, Tesfamichael
- Date: 2012
- Subjects: Urban agriculture -- Eritrea -- Asmara , Cities and towns -- Eritrea -- Asmara -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10668 , http://hdl.handle.net/10948/d109790
- Description: The aim of this thesis is to provide a differentiated view of peri-urban agriculture in the context of urban population growth in Asmara, Eritrea. Peri-urban agriculture is viewed as a distinct type of broader urban agriculture, and in this case is not as subsistence-orientated as other branches of it. Urban population growth is comprised of three elements, namely, natural population increase, rural-urban migration and outward movement of people to the urban periphery linked to urban expansion. Each receives extensive treatment. Asmara is the capital city of Eritrea and using Weeks (2004:473) phrase can be termed as a “primate city”. As such, it exerts a major influence on the political, economic and cultural life of the country, but has never been subjected to this type of research. The analytical framework that is adopted is that of urban population growth. In order to operationalize it, theoretical insights into each of its three branches were applied. For example, the informalisation of the economy in developing cities was used to explain the operation of peri-urban agriculture in the context of natural population growth. An adaption of the original Harris-Todaro Model by Fields (2004) was used for the migrants, and the Mosaic Model by Bryant and Johnson (1992) for those facing urban encroachment. Primary data were collected in the field by the author with the help of research assistants. This was supplemented by secondary data which involved reports commissioned by the Ministry of Agriculture and the Ministry of Public Works. Focus Group discussions were also held to supplement the data with information, views and insights that do not emerge in one-to-one interviews. This thesis demonstrates that those respondents operating within the context of natural population growth make a viable living from peri-urban agriculture, but that they also recognise that there are considerable challenges to be faced. Three sub-groups of farmers are identified. Of these, poultry farmers are the most vulnerable because of the high costs of the inputs, the uncertainty associated with avian „flu and an undeveloped distribution network. The vegetable producers, on the other hand, have a sophisticated marketing network, but low levels of education, high household numbers and an impending shortage of land and water. The agriculturalists that have migrated to Asmara seem to have created sustainable occupations for themselves over a number of years. However, 75 percent of them felt that migration to Asmara was not worthwhile. This negative view is explained in terms of the struggle it has taken to maintain such a living and the growing shortage of land. This set of farmers achieves lower production levels than its city-reared counterparts, carries considerable expenses and has to hire its land. The farmers who have had to cope with urban encroachment fall into two classes. The first has chosen to remain in peri-urban agriculture despite feeling the pressure to scale down activities and thus have a lower income. The majority of this group are dairy farmers who have to trade off increasing costs of cattle feed against shrinking grazing land. They are unwilling to take the initiative to solve their land problems, but look to the authorities to do so. The second class of respondents in this category have abandoned their agricultural holdings. The majority of these agriculturalists are poultry farmers living in the Eastern side of the city. A shortage of agricultural land, high population densities and high costs of inputs make poultry farming difficult. This thesis, therefore, presents a multifaceted view of peri-urban agriculture. While each set of farmers has to cope with its own particular circumstances, there is a common factor. This is the tension between preserving agricultural land on the urban fringe and the need to expand the city to accommodate its inhabitants.
- Full Text:
- Date Issued: 2012
- Authors: Fessahaie, Tesfamichael
- Date: 2012
- Subjects: Urban agriculture -- Eritrea -- Asmara , Cities and towns -- Eritrea -- Asmara -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10668 , http://hdl.handle.net/10948/d109790
- Description: The aim of this thesis is to provide a differentiated view of peri-urban agriculture in the context of urban population growth in Asmara, Eritrea. Peri-urban agriculture is viewed as a distinct type of broader urban agriculture, and in this case is not as subsistence-orientated as other branches of it. Urban population growth is comprised of three elements, namely, natural population increase, rural-urban migration and outward movement of people to the urban periphery linked to urban expansion. Each receives extensive treatment. Asmara is the capital city of Eritrea and using Weeks (2004:473) phrase can be termed as a “primate city”. As such, it exerts a major influence on the political, economic and cultural life of the country, but has never been subjected to this type of research. The analytical framework that is adopted is that of urban population growth. In order to operationalize it, theoretical insights into each of its three branches were applied. For example, the informalisation of the economy in developing cities was used to explain the operation of peri-urban agriculture in the context of natural population growth. An adaption of the original Harris-Todaro Model by Fields (2004) was used for the migrants, and the Mosaic Model by Bryant and Johnson (1992) for those facing urban encroachment. Primary data were collected in the field by the author with the help of research assistants. This was supplemented by secondary data which involved reports commissioned by the Ministry of Agriculture and the Ministry of Public Works. Focus Group discussions were also held to supplement the data with information, views and insights that do not emerge in one-to-one interviews. This thesis demonstrates that those respondents operating within the context of natural population growth make a viable living from peri-urban agriculture, but that they also recognise that there are considerable challenges to be faced. Three sub-groups of farmers are identified. Of these, poultry farmers are the most vulnerable because of the high costs of the inputs, the uncertainty associated with avian „flu and an undeveloped distribution network. The vegetable producers, on the other hand, have a sophisticated marketing network, but low levels of education, high household numbers and an impending shortage of land and water. The agriculturalists that have migrated to Asmara seem to have created sustainable occupations for themselves over a number of years. However, 75 percent of them felt that migration to Asmara was not worthwhile. This negative view is explained in terms of the struggle it has taken to maintain such a living and the growing shortage of land. This set of farmers achieves lower production levels than its city-reared counterparts, carries considerable expenses and has to hire its land. The farmers who have had to cope with urban encroachment fall into two classes. The first has chosen to remain in peri-urban agriculture despite feeling the pressure to scale down activities and thus have a lower income. The majority of this group are dairy farmers who have to trade off increasing costs of cattle feed against shrinking grazing land. They are unwilling to take the initiative to solve their land problems, but look to the authorities to do so. The second class of respondents in this category have abandoned their agricultural holdings. The majority of these agriculturalists are poultry farmers living in the Eastern side of the city. A shortage of agricultural land, high population densities and high costs of inputs make poultry farming difficult. This thesis, therefore, presents a multifaceted view of peri-urban agriculture. While each set of farmers has to cope with its own particular circumstances, there is a common factor. This is the tension between preserving agricultural land on the urban fringe and the need to expand the city to accommodate its inhabitants.
- Full Text:
- Date Issued: 2012
Peripheral vision field fatigue during simulated driving : the effects of time on task and time of day on selected psychophysiological, performance and subjective responses
- Authors: Robertson, Jade Kelly
- Date: 2012 , 2012-09-22
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5141 , http://hdl.handle.net/10962/d1007136 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Description: Worldwide, motor accidents are responsible for a large number of deaths and disabilities (Connor et al., 2001), and one of the major causes of motor accidents is driver fatigue. Although majority of drivers are aware of the dangers of fatigued driving, accidents related to this continues to contribute to a large percentage of all accidents, between 5 and 50% (Nilsson et al., 1997; Williamson et al., 2011). The purpose of the research was to establish the effect that fatigue renders on an individual’s peripheral visual field and to determine whether a decrement in driving performance occurs at the same rate as a decrement in peripheral visual performance. Fatigue was induced through time of day as well as time on task. Sixteen students from Rhodes University were recruited, subject to no previous sleep disorders, among other criteria. Each participant was required to partake in two conditions, namely a day condition (09h00–11h00) and a night condition (23h00– 01h00). Each condition consisted of a 90 minute dual task; the primary task was a tracking task, in which participants were instructed to track a white line as accurately as possible. A secondary peripheral response task was introduced, in which participants were instructed to respond as quickly as possible to the peripheral stimuli, by pressing one of two clickers located on the steering wheel. The peripheral stimuli were located at 20º, 30º and 40º visual angle. Psychophysiological, performance and subjective measures were obtained before, during and after the main task. The pre- and post-tests included core body temperature, critical flicker fusion frequency threshold, a digit span memory test, Wits Sleepiness Scale and a NASA-TLX questionnaire. The psychophysiological and performance measures of heart rate, heart rate variability, blink frequency, blink duration, lane deviation, number of saccades towards peripheral stimuli, response time to peripheral stimuli and the percentage of missed peripheral responses were all recorded throughout the 90 minute main dual task. The results revealed significant differences (p<0.05) for heart rate variability, number of saccades towards peripheral stimuli and the Wits Sleepiness Scale, with regard to time of day. For time on task, significant effects were established for lane deviation, response time to peripheral stimuli, percentage of missed peripheral responses, heart rate, heart rate variability, blink frequency, blink duration, critical flicker fusion frequency threshold, core body temperature and the Wits Sleepiness Scale. Eccentricity was analysed and found to be significant for response time to peripheral stimuli, as well as for the percentage of missed peripheral responses; there was a significant increase in both measures with an increase in the stimuli eccentricity. No significances were established for time of day or between the pre- and post-tests conducted for the digit span memory performance; however, a significant interactional effect between the two was established. When assessing the percentage rate of decrement of driving performance compared to the percentage rate in the decrement of the missed peripheral responses, it was found that the percentage rate of decrement was equal for both measures. Thus from this research it can be seen that, concurrent with a decrement in driving performance, there are adverse effects on an individuals' peripheral vision, which have great implications for the safety of workers in industry and transport, as well as motorists. It was also established that time on task is possibly a more appropriate variable to consider than time of day, when implementing work schedules and rest breaks in industry, transport and fields alike, as more significant findings were seen for time on task compared to time of day. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
- Authors: Robertson, Jade Kelly
- Date: 2012 , 2012-09-22
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5141 , http://hdl.handle.net/10962/d1007136 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue , Peripheral vision
- Description: Worldwide, motor accidents are responsible for a large number of deaths and disabilities (Connor et al., 2001), and one of the major causes of motor accidents is driver fatigue. Although majority of drivers are aware of the dangers of fatigued driving, accidents related to this continues to contribute to a large percentage of all accidents, between 5 and 50% (Nilsson et al., 1997; Williamson et al., 2011). The purpose of the research was to establish the effect that fatigue renders on an individual’s peripheral visual field and to determine whether a decrement in driving performance occurs at the same rate as a decrement in peripheral visual performance. Fatigue was induced through time of day as well as time on task. Sixteen students from Rhodes University were recruited, subject to no previous sleep disorders, among other criteria. Each participant was required to partake in two conditions, namely a day condition (09h00–11h00) and a night condition (23h00– 01h00). Each condition consisted of a 90 minute dual task; the primary task was a tracking task, in which participants were instructed to track a white line as accurately as possible. A secondary peripheral response task was introduced, in which participants were instructed to respond as quickly as possible to the peripheral stimuli, by pressing one of two clickers located on the steering wheel. The peripheral stimuli were located at 20º, 30º and 40º visual angle. Psychophysiological, performance and subjective measures were obtained before, during and after the main task. The pre- and post-tests included core body temperature, critical flicker fusion frequency threshold, a digit span memory test, Wits Sleepiness Scale and a NASA-TLX questionnaire. The psychophysiological and performance measures of heart rate, heart rate variability, blink frequency, blink duration, lane deviation, number of saccades towards peripheral stimuli, response time to peripheral stimuli and the percentage of missed peripheral responses were all recorded throughout the 90 minute main dual task. The results revealed significant differences (p<0.05) for heart rate variability, number of saccades towards peripheral stimuli and the Wits Sleepiness Scale, with regard to time of day. For time on task, significant effects were established for lane deviation, response time to peripheral stimuli, percentage of missed peripheral responses, heart rate, heart rate variability, blink frequency, blink duration, critical flicker fusion frequency threshold, core body temperature and the Wits Sleepiness Scale. Eccentricity was analysed and found to be significant for response time to peripheral stimuli, as well as for the percentage of missed peripheral responses; there was a significant increase in both measures with an increase in the stimuli eccentricity. No significances were established for time of day or between the pre- and post-tests conducted for the digit span memory performance; however, a significant interactional effect between the two was established. When assessing the percentage rate of decrement of driving performance compared to the percentage rate in the decrement of the missed peripheral responses, it was found that the percentage rate of decrement was equal for both measures. Thus from this research it can be seen that, concurrent with a decrement in driving performance, there are adverse effects on an individuals' peripheral vision, which have great implications for the safety of workers in industry and transport, as well as motorists. It was also established that time on task is possibly a more appropriate variable to consider than time of day, when implementing work schedules and rest breaks in industry, transport and fields alike, as more significant findings were seen for time on task compared to time of day. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
Persepectives on market processes followed in setting South African water services tariffs
- Authors: Norden, Ryan Henri
- Date: 2012
- Subjects: Water-supply -- South Africa -- Costs , Water utilities -- Rates -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9019 , http://hdl.handle.net/10948/d1018929
- Description: South Africa’s private sector and the practice of using market processes are often dismissed by the government as service providing options, because they increase costs and fail the poor population. There is some substance to the government’s position, given that there is a natural monopoly advantage in water service provision. Under these circumstances it could be expected that a single firm would emerge as dominant in the provision of these services to urban customers. Were this firm a private one, and unregulated, it could be expected to practice exploitative pricing, make excess profits, and undersupply waste water management service. A private firm would also not provide services to the poor unless their service was subsidised. However most of these deficiencies can be regulated (as shown in Chapter Four), and also occur under public sector provision (as shown in Chapter Five) Are the private sector failures sufficient reason to abandon the market and private sector as mechanisms to deliver water service in South Africa? This dissertation finds little use is made of market processes and the private sector in water service provision (Chapter One), despite there being legal provision for such involvement (Chapter Two). It also finds that public water service providers are not subject to competition policy and consumer protection provisions, whereas private sector providers would be (Chapter Three). The administration of questionnaires to municipalities and the Department of Water Affairs (DWA) show that the various water service providers often operate under unique circumstances, making it difficult to extrapolate management insights from one municipality to another (Chapter Six). A case study on Nelson Mandela Bay Municipal tariff setting reveals a mismatch between economic principle and policy practice, and suggests that economic principle plays a lesser role in the design of tariff structures than other factors (Chapter Seven). Given the problems that are occurring in public sector water service provision, the dissertation concludes the case for dismissing private sector or public utility models for water service delivery may be weaker than is believed by the South African government.
- Full Text:
- Date Issued: 2012
- Authors: Norden, Ryan Henri
- Date: 2012
- Subjects: Water-supply -- South Africa -- Costs , Water utilities -- Rates -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9019 , http://hdl.handle.net/10948/d1018929
- Description: South Africa’s private sector and the practice of using market processes are often dismissed by the government as service providing options, because they increase costs and fail the poor population. There is some substance to the government’s position, given that there is a natural monopoly advantage in water service provision. Under these circumstances it could be expected that a single firm would emerge as dominant in the provision of these services to urban customers. Were this firm a private one, and unregulated, it could be expected to practice exploitative pricing, make excess profits, and undersupply waste water management service. A private firm would also not provide services to the poor unless their service was subsidised. However most of these deficiencies can be regulated (as shown in Chapter Four), and also occur under public sector provision (as shown in Chapter Five) Are the private sector failures sufficient reason to abandon the market and private sector as mechanisms to deliver water service in South Africa? This dissertation finds little use is made of market processes and the private sector in water service provision (Chapter One), despite there being legal provision for such involvement (Chapter Two). It also finds that public water service providers are not subject to competition policy and consumer protection provisions, whereas private sector providers would be (Chapter Three). The administration of questionnaires to municipalities and the Department of Water Affairs (DWA) show that the various water service providers often operate under unique circumstances, making it difficult to extrapolate management insights from one municipality to another (Chapter Six). A case study on Nelson Mandela Bay Municipal tariff setting reveals a mismatch between economic principle and policy practice, and suggests that economic principle plays a lesser role in the design of tariff structures than other factors (Chapter Seven). Given the problems that are occurring in public sector water service provision, the dissertation concludes the case for dismissing private sector or public utility models for water service delivery may be weaker than is believed by the South African government.
- Full Text:
- Date Issued: 2012
Perspectives on China's rise in Namibia: the effects on foreign policy and domestic politics
- Amadhila, Nelago Ndapandula Ndanyanyukwa
- Authors: Amadhila, Nelago Ndapandula Ndanyanyukwa
- Date: 2012
- Subjects: Namibia -- Relations -- China China -- Relations -- Namibia Namibia -- Politics and government -- Chinese influences Namibia -- Economic conditions -- Chinese influences
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2758 , http://hdl.handle.net/10962/d1002968
- Description: This thesis analyses the different levels at which China’s presence in Namibia affects Namibia’s domestic politics and foreign policy from a constructivist viewpoint. Constructivist theory is used to examine the different perceptions of the Chinese in Namibia and how these inform Namibian politics and Sino-Namibian relations. These perceptions are formed at different levels of society in formal and informal relations, state-to-state, state-to-business,business-to-business and individual-to-group relations. The way in which perceptions of Chinese involvement in Namibia at the grassroots level of society differ from those at the top increasingly has an effect on domestic Namibian politics and, as such, Sino-Namibian relations. This identifies official and non-official perceptions of China’s political, economic and social presence to determine the effects of grassroots on China vis-à-vis official perceptions in Namibian politics and the effects of grassroots views on Namibian politics and on official views and state behaviour towards China and China’s presence in the country.
- Full Text:
- Date Issued: 2012
- Authors: Amadhila, Nelago Ndapandula Ndanyanyukwa
- Date: 2012
- Subjects: Namibia -- Relations -- China China -- Relations -- Namibia Namibia -- Politics and government -- Chinese influences Namibia -- Economic conditions -- Chinese influences
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2758 , http://hdl.handle.net/10962/d1002968
- Description: This thesis analyses the different levels at which China’s presence in Namibia affects Namibia’s domestic politics and foreign policy from a constructivist viewpoint. Constructivist theory is used to examine the different perceptions of the Chinese in Namibia and how these inform Namibian politics and Sino-Namibian relations. These perceptions are formed at different levels of society in formal and informal relations, state-to-state, state-to-business,business-to-business and individual-to-group relations. The way in which perceptions of Chinese involvement in Namibia at the grassroots level of society differ from those at the top increasingly has an effect on domestic Namibian politics and, as such, Sino-Namibian relations. This identifies official and non-official perceptions of China’s political, economic and social presence to determine the effects of grassroots on China vis-à-vis official perceptions in Namibian politics and the effects of grassroots views on Namibian politics and on official views and state behaviour towards China and China’s presence in the country.
- Full Text:
- Date Issued: 2012
PhDs by publications
- Niven, Penelope, Grant, Carolyn
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
- Authors: Niven, Penelope , Grant, Carolyn
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/281108 , vital:55693 , xlink:href="https://doi.org/10.1080/13562517.2012.640086"
- Description: PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers’ experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an overarching thesis. The writers argue that whilst it can be a pragmatic choice for some, PhDs by publications are more likely to be highly complex meta-narratives and that an overview of past research is fraught with theoretical, conceptual and epistemological challenges in the quest for coherence. They claim that the nomenclature ‘PhDs by publications’ or ‘through publications’ is misleading: in the epistemological space of Humanities or Education studies, this mode of doctoral research is more accurately represented as a ‘PhD with or alongside publications’. They conclude that the particular affordance of the model is that it privileges accounts of the process of knowledge building and of descriptions of the gradual emergence of ‘doctoralness’ in the person of the researcher.
- Full Text:
- Date Issued: 2012
Phenotypic plasticity of metabolic rate in an afrotropical bird species (Euplectes orix) across a temperature gradient
- Van de Ven, Tanja Maria Francisca Nicole
- Authors: Van de Ven, Tanja Maria Francisca Nicole
- Date: 2012
- Subjects: Phenotypic plasticity , Evolutionary genetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10718 , http://hdl.handle.net/10948/d1012659 , Phenotypic plasticity , Evolutionary genetics
- Description: Avian species are known to have the capacity to respond to environmental changes through physiological adjustments. The process whereby organisms adjust their phenotype without genetic change is termed phenotypic plasticity and it is mostly observed to be a phenotypic improvement to ecological challenges. Metabolic rate (MR), which is the rate of energy expenditure in a species, is a highly flexible physiological parameter which results in a great diversity of avian standardised metabolic rates. Like birds from high latitudes, Afrotropical bird species are expected to have the capacity to adjust their energy expenditure to match the availability of resources. Previous studies on the flexibility of physiological parameters in birds have focused on the magnitude of change of physiological adjustments and the cues inducing these changes. Comparative research has furthermore investigated metabolic rates across aridity, altitude, latitude and temperature gradients. Recently, a clear dichotomy has become evident with elevated metabolic rates observed in high latitude birds in winter and a down-regulation of metabolic rates observed in birds exposed to low latitude mild winters. In this study, the shape of the reaction norm, the magnitude, the reversibility, the direction and the rate of change of two physiological parameters, basal metabolic rate (BMR) and summit metabolic rate (Msum), were investigated in a coastal and an inland population of Southern Red Bishops (Euplectes orix) through seasonal acclimatisation and laboratory acclimation. Summer and winter basal metabolic rates as well as body mass, were highly flexible traits in free-ranging coastal and inland Red Bishops. Birds acclimatised to a mild coastal climate in winter exhibited reduced basal and summit metabolic rates, whereas birds originating from a more variable inland climate increased basal metabolic rate in winter, but did not show increases of Msum in winter. Red Bishops responded to short term thermal acclimation under laboratory conditions by gradually changing body mass. Acclimation periods of 21 days revealed a negative relationship between body mass and acclimation air temperature. Peak responses of basal metabolic rate to ambient temperature change were observed in both coastal and inland birds between two and eight days after the change in acclimation air temperature. The influences of seasonal acclimatisation on energy expenditure differed between coastal and inland birds, however, during laboratory acclimation individuals from the two populations showed no difference in response. Within the individuals of the coastal and inland Southern Red Bishops, phenotypic flexibility is observed in body mass, basal metabolic rate and summit metabolic rate as a response to environmental changes. This flexibility is thought to increase thermoregulatory capacities of the Southern Red Bishop in different habitats and climates.
- Full Text:
- Date Issued: 2012
- Authors: Van de Ven, Tanja Maria Francisca Nicole
- Date: 2012
- Subjects: Phenotypic plasticity , Evolutionary genetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10718 , http://hdl.handle.net/10948/d1012659 , Phenotypic plasticity , Evolutionary genetics
- Description: Avian species are known to have the capacity to respond to environmental changes through physiological adjustments. The process whereby organisms adjust their phenotype without genetic change is termed phenotypic plasticity and it is mostly observed to be a phenotypic improvement to ecological challenges. Metabolic rate (MR), which is the rate of energy expenditure in a species, is a highly flexible physiological parameter which results in a great diversity of avian standardised metabolic rates. Like birds from high latitudes, Afrotropical bird species are expected to have the capacity to adjust their energy expenditure to match the availability of resources. Previous studies on the flexibility of physiological parameters in birds have focused on the magnitude of change of physiological adjustments and the cues inducing these changes. Comparative research has furthermore investigated metabolic rates across aridity, altitude, latitude and temperature gradients. Recently, a clear dichotomy has become evident with elevated metabolic rates observed in high latitude birds in winter and a down-regulation of metabolic rates observed in birds exposed to low latitude mild winters. In this study, the shape of the reaction norm, the magnitude, the reversibility, the direction and the rate of change of two physiological parameters, basal metabolic rate (BMR) and summit metabolic rate (Msum), were investigated in a coastal and an inland population of Southern Red Bishops (Euplectes orix) through seasonal acclimatisation and laboratory acclimation. Summer and winter basal metabolic rates as well as body mass, were highly flexible traits in free-ranging coastal and inland Red Bishops. Birds acclimatised to a mild coastal climate in winter exhibited reduced basal and summit metabolic rates, whereas birds originating from a more variable inland climate increased basal metabolic rate in winter, but did not show increases of Msum in winter. Red Bishops responded to short term thermal acclimation under laboratory conditions by gradually changing body mass. Acclimation periods of 21 days revealed a negative relationship between body mass and acclimation air temperature. Peak responses of basal metabolic rate to ambient temperature change were observed in both coastal and inland birds between two and eight days after the change in acclimation air temperature. The influences of seasonal acclimatisation on energy expenditure differed between coastal and inland birds, however, during laboratory acclimation individuals from the two populations showed no difference in response. Within the individuals of the coastal and inland Southern Red Bishops, phenotypic flexibility is observed in body mass, basal metabolic rate and summit metabolic rate as a response to environmental changes. This flexibility is thought to increase thermoregulatory capacities of the Southern Red Bishop in different habitats and climates.
- Full Text:
- Date Issued: 2012
Photocatalytic activity and antibacterial properties of Ag/N-doped TiO2 nanoparticles on PVAE-CS nanofibre support
- Authors: Ocwelwang, Atsile Rosy
- Date: 2012
- Subjects: Nanocomposites (Materials) , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11337 , http://hdl.handle.net/10353/d1006794 , Nanocomposites (Materials) , Nanofibers , Electrospinning
- Description: Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.
- Full Text:
- Date Issued: 2012
- Authors: Ocwelwang, Atsile Rosy
- Date: 2012
- Subjects: Nanocomposites (Materials) , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11337 , http://hdl.handle.net/10353/d1006794 , Nanocomposites (Materials) , Nanofibers , Electrospinning
- Description: Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.
- Full Text:
- Date Issued: 2012
Photoconductive spectroscopy of GaSb thin films
- Authors: Shura, Megersa Wodajo
- Date: 2012
- Subjects: Photoelectron spectroscopy , Photoconductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10549 , http://hdl.handle.net/10948/d1019937
- Description: In this study, we have investigated the photo-response of gallium antimonide (GaSb) by measuring the spectral, injection level, as well as the temperature dependence of the steady-state photoconductivity of epitaxial films. By combining the various photo-response measurements with-galvanometric measurements, the effective excess carrier lifetimes could be calculated and described in terms of the various experimental variables considered. From a comparison of the measured and theoretical carrier lifetimes, a clear discrepancy was found for the injection dependent results. This inconsistency between the expected and measured behaviours was resolved using a two-layer model to describe the photo-conductive response of the thin film. In this model, the generation/recombination processes are considered for the bulk as well as for a depleted near-surface region. By combining these two contributions when calculating the total excess photocurrent, the various experimental results could be successfully described. The photo-response measurements revealed that the main contribution to the photocurrent came from the near-surface region, where the bandto- band and Auger recombination transitions are reduced. From the simulation of the injection level dependence of the excess carrier lifetime, some of the near-surface characteristics, such as the position of the surface Fermi-level and the surface recombination velocity, could be determined. In the case of p-type GaSb, the room temperature surface Fermi-level was found to be pinned (290±20) meV above the valence band maximum, whereas the n-type material had a pinning position of (150±20) meV above the valence band maximum. These pinning positions were shown to be independent of the doping density and relatively insensitive to the surface treatments considered. The presence of a near-surface depletion region, as well as the position of the surface Fermi-level, was corroborated by Raman spectroscopy. From a comparison of the phonon mode and the phonon-hole plasmon coupled mode, a surface Fermi-level position of (300 ± 30) meV was deduced for p-type GaSb. Finally, the effect various surface treatments have on the photo-response, and related surface properties, were investigated. Removal of the native oxide (HCl:H2O) followed by sulphur passivation (Na2S:9H2O) results in a slight decrease in the surface Fermi-level position. Aging studies however revealed that the surface characteristics reverted back to the untreated values following a few days in air. Coating the GaSb surfaces with a thin ZnS layer was found to have little effect on the surface potential, resulting only in a slight increase in the near-surface donor density. The sensitivity of the measured photocurrent to surface treatments and changes in the ambient with cooling, further validate the importance of considering the surface potential and the related space-charge when describing the photoconductive response of GaSb thin films.
- Full Text:
- Date Issued: 2012
- Authors: Shura, Megersa Wodajo
- Date: 2012
- Subjects: Photoelectron spectroscopy , Photoconductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10549 , http://hdl.handle.net/10948/d1019937
- Description: In this study, we have investigated the photo-response of gallium antimonide (GaSb) by measuring the spectral, injection level, as well as the temperature dependence of the steady-state photoconductivity of epitaxial films. By combining the various photo-response measurements with-galvanometric measurements, the effective excess carrier lifetimes could be calculated and described in terms of the various experimental variables considered. From a comparison of the measured and theoretical carrier lifetimes, a clear discrepancy was found for the injection dependent results. This inconsistency between the expected and measured behaviours was resolved using a two-layer model to describe the photo-conductive response of the thin film. In this model, the generation/recombination processes are considered for the bulk as well as for a depleted near-surface region. By combining these two contributions when calculating the total excess photocurrent, the various experimental results could be successfully described. The photo-response measurements revealed that the main contribution to the photocurrent came from the near-surface region, where the bandto- band and Auger recombination transitions are reduced. From the simulation of the injection level dependence of the excess carrier lifetime, some of the near-surface characteristics, such as the position of the surface Fermi-level and the surface recombination velocity, could be determined. In the case of p-type GaSb, the room temperature surface Fermi-level was found to be pinned (290±20) meV above the valence band maximum, whereas the n-type material had a pinning position of (150±20) meV above the valence band maximum. These pinning positions were shown to be independent of the doping density and relatively insensitive to the surface treatments considered. The presence of a near-surface depletion region, as well as the position of the surface Fermi-level, was corroborated by Raman spectroscopy. From a comparison of the phonon mode and the phonon-hole plasmon coupled mode, a surface Fermi-level position of (300 ± 30) meV was deduced for p-type GaSb. Finally, the effect various surface treatments have on the photo-response, and related surface properties, were investigated. Removal of the native oxide (HCl:H2O) followed by sulphur passivation (Na2S:9H2O) results in a slight decrease in the surface Fermi-level position. Aging studies however revealed that the surface characteristics reverted back to the untreated values following a few days in air. Coating the GaSb surfaces with a thin ZnS layer was found to have little effect on the surface potential, resulting only in a slight increase in the near-surface donor density. The sensitivity of the measured photocurrent to surface treatments and changes in the ambient with cooling, further validate the importance of considering the surface potential and the related space-charge when describing the photoconductive response of GaSb thin films.
- Full Text:
- Date Issued: 2012
Photooxidation of 4-chlorophenol sensitized by lutetium tetraphenoxy phthalocyanine anchored on electrospun polystyrene polymer fiber
- Zugle, Ruphino, Antunes, Edith M, Khene, Samson M, Nyokong, Tebello
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
- Authors: Zugle, Ruphino , Antunes, Edith M , Khene, Samson M , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245787 , vital:51405 , xlink:href="https://doi.org/10.1016/j.poly.2011.11.005"
- Description: An electrospun polystyrene (PS) fiber incorporating tetraphenoxy phthalocyanine complex of lutetium (LuTPPc/PS) as a photosensitizer was applied for the degradation of 4-chlorophenol in aqueous solution in the presence of visible light. The photocatalytic activity of the LuTPPc in the fiber was compared to that of zinc phthalocyanine (ZnPc) incorporated into the PS fiber, and the former showed higher activity. UV–Vis spectral changes of sample solutions indicated transformation of the analyte with first order kinetics and half-lives that are within one and half hours for LuTPPc/PS. Products identified from the spectral changes and gas chromatography were benzoquinone, hydroquinone and 4,4′-dihydroxydiphenol suggesting that the photodegradation of 4-chlorophenol was through both Types I and II mechanisms.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety
- Yaşa, Göknur, Erdoğmuş, Ali, Uğur, Ahmet Lütf, Şener, M Kasım, Avcıata, Ulvi, Nyokong, Tebello
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
- Authors: Yaşa, Göknur , Erdoğmuş, Ali , Uğur, Ahmet Lütf , Şener, M Kasım , Avcıata, Ulvi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244360 , vital:51250 , xlink:href="https://doi.org/10.1142/S1088424612500940"
- Description: The synthesis, photophysical and photochemical properties of nonperipherally (a) mercaptoquinoline substituted Zn(II), TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1 H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.
- Full Text:
- Date Issued: 2012
Photophysical and photochemical studies of sulfur containing phthalocyanine derivatives in the presence of folic acid
- Nombona, Nolwazi, Nyokong, Tebello
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/243180 , vital:51124 , xlink:href="https://doi.org/10.1016/j.ica.2012.03.051"
- Description: The syntheses of zinc and magnesium 9,16,23-tris-(5-trifluoromethyl-2-mercaptopyridine)-2-(carboxy)phthalocyaninato complexes are described for the first time. The photophysical and photochemical parameters of these molecules in the absence or presence of folic acid are compared to the corresponding oxygen bridged complexes and to 2,9,17,23-tetrakis-[(1,6-hexanedithiol)phthalocyaninato]zinc(II), [8,15,22-tris-(naptho)-2-(amidoethanethiol)phthalocyaninato]zinc(II) and zinc phthalocyanine tetrasulfonate. In the absence of folic acid, the complexes show relatively good triplet quantum yields (ranging from 0.52 to 0.88) in DMSO with reasonable triplet lifetime between 140 and 470 μs. The complexes showed high singlet oxygen quantum yield values ranging from 0.27 to 0.66 in the absence of folic acid. In the presence of folic acid, the triplet quantum yield values were between 0.37 and 0.75 and the lifetimes were significantly reduced (70–320 μs).
- Full Text:
- Date Issued: 2012
Photophysicochemical and photodynamic studies of phthalocyanines conjugated to selected drug delivery agents
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
Photophysicochemical studies of phenylthio phthalocyanines interaction with gold nanoparticles and applications in dye sensitised solar cells and optical limiting
- Authors: Forteath, Shaun
- Date: 2012
- Subjects: Phthalocyanines , Nanoparticles , Photochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4334 , http://hdl.handle.net/10962/d1004995 , Phthalocyanines , Nanoparticles , Photochemistry
- Description: The syntheses, spectroscopic characterisation, photophysical and photochemical studies have been conducted for a variety of phenylthio substituted phthalocyanines (Pcs). Comparisons have been made taking into consideration the influence of the central metal ion, solvent properties and substituent type. The optical limiting properties were also determined for all the Pcs synthesised. A low-symmetry metallophthalocyanine complex was similarly characterised and the photoelectrochemical parameters determined when used as a sensitiser of nanoporous ZnO. The symmetric analogue was conjugated to gold nanoparticles to determine the influence of interactions on its photophysical properties and distinct differences occurred in the absorption and fluorescence spectra suggesting successful formation of conjugates.
- Full Text:
- Date Issued: 2012
- Authors: Forteath, Shaun
- Date: 2012
- Subjects: Phthalocyanines , Nanoparticles , Photochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4334 , http://hdl.handle.net/10962/d1004995 , Phthalocyanines , Nanoparticles , Photochemistry
- Description: The syntheses, spectroscopic characterisation, photophysical and photochemical studies have been conducted for a variety of phenylthio substituted phthalocyanines (Pcs). Comparisons have been made taking into consideration the influence of the central metal ion, solvent properties and substituent type. The optical limiting properties were also determined for all the Pcs synthesised. A low-symmetry metallophthalocyanine complex was similarly characterised and the photoelectrochemical parameters determined when used as a sensitiser of nanoporous ZnO. The symmetric analogue was conjugated to gold nanoparticles to determine the influence of interactions on its photophysical properties and distinct differences occurred in the absorption and fluorescence spectra suggesting successful formation of conjugates.
- Full Text:
- Date Issued: 2012
Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives
- Iqbal, Zafar, Ogunsipe, Abimbola, Nyokong, Tebello, Lyubimtsev, Alexey, Hanack, Michael, Ziegler, Thomas
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
- Authors: Iqbal, Zafar , Ogunsipe, Abimbola , Nyokong, Tebello , Lyubimtsev, Alexey , Hanack, Michael , Ziegler, Thomas
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244416 , vital:51255 , xlink:href="https://doi.org/10.1142/S1088424612500630"
- Description: The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen.
- Full Text:
- Date Issued: 2012
Physico-chemical and microalgal characteristics of the Goukamma Estuary
- Authors: Kaselowski, Tanja
- Date: 2012
- Subjects: Estuarine ecology , Estuaries -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10623 , http://hdl.handle.net/10948/d1011130 , Estuarine ecology , Estuaries -- South Africa
- Description: Estuaries are intrinsically complex and dynamic ecosystems that display marked spatial and temporal variability. Because estuaries are situated at the receiving end of catchment activities, they are at particular risk of alterations to their natural complexity. The overarching objective of this study was to gain an overview of the abiotic conditions and biotic response of the Goukamma Estuary, a small temporarily open/closed estuary (TOCE) which is situated in a relatively undisturbed catchment in the Southern Cape. Physico-chemical properties drive estuarine ecology, and together with biological indicators, are commonly assessed to determine the present status of an estuary. During the study, physico-chemical parameters reflected great spatial and temporal variability in response to the mouth state over a 13 month period. Parameters ranged within expected limits, as proposed by the conceptual model for water quality of TOCE’s (Snow and Taljaard 2007). Of particular importance was the prominent occurrence of salinity stratification and hypoxic conditions (dissolved oxygen [DO] < 3 mg l-1) during both open and closed mouth states. Data indicated that in the wide and shallow lower reaches, weak stratification gradients were present and oxygenated conditions (DO > 6 mg l-1) were maintained throughout the water column mainly by wind and tidal action. However, stratification increased towards the deeper, channel-like middle and upper reaches of the estuary, followed by a significant reduction in bottom DO concentrations and development of hypoxia and anoxia. Bottom water hypoxia commonly occurs in microtidal estuaries due to the limited influence of mixing forces, mainly by wind and tidal action. The Goukamma Estuary is a channel-like microtidal estuary where stratification effectively limited oxygenation of the bottom water which resulted in frequent occurrence of bottom water hypoxia. During June 2010 when the highest local rainfall (75 mm) was recorded for the region, salinity and DO data showed that this amount of rainfall was insignificant as it did not replenish the water column of oxygen. Only the surface 0.5 m layer was fresh and oxygenated while below this, the water column was completely hypoxic. In an unimpacted state, the Goukamma Estuary is a blackwater system and is expected to be nutrient poor; however, farming activities in the catchment have resulted in elevated nutrient concentrations. This study showed that significantly higher nutrient concentrations were measured in the middle and upper reaches of the estuary, adjacent to cattle farms situated in the floodplain of these reaches. Nutrient concentrations represented mesotrophic (dissolved inorganic nitrogen [DIN] > 500 μg l-1) to eutrophic conditions (dissolved inorganic phosphorus [DIP] > 25 μg l-1). Nutrient input stimulated phytoplankton to attain a significantly high biomass, ranging between 0.3 – 112 μg l-1 (~ 7.7 ± 1.3 μg l-1; n = 128) and 0.8 – 289 μg l-1 (~ 21.1 ± 4.4 μg l-1; n = 80) during the open and closed states, respectively. High organic loads are associated with high oxygen demands which consequently result in hypoxia following decomposition. Exacerbated by natural salinity stratification which effectively limits oxygenation of the water column, unnaturally high nutrient concentrations and coinciding organic loads place the estuary at particular risk of degradation. This study captured key patterns and processes by quantifying salinity, oxygen and nutrient concentrations in addition to biological indicators (phytoplankton biomass and community composition). Considering possible budget constraints, it is recommended that monthly salinity and oxygen concentrations should be monitored as well as seasonal nutrient concentrations. It is also recommended that riparian buffer zones should be established in the middle and upper reaches of the estuary, as these vegetation buffers have been well documented to contribute to nutrient attenuation and improved water quality from agricultural run-off.
- Full Text:
- Date Issued: 2012
- Authors: Kaselowski, Tanja
- Date: 2012
- Subjects: Estuarine ecology , Estuaries -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10623 , http://hdl.handle.net/10948/d1011130 , Estuarine ecology , Estuaries -- South Africa
- Description: Estuaries are intrinsically complex and dynamic ecosystems that display marked spatial and temporal variability. Because estuaries are situated at the receiving end of catchment activities, they are at particular risk of alterations to their natural complexity. The overarching objective of this study was to gain an overview of the abiotic conditions and biotic response of the Goukamma Estuary, a small temporarily open/closed estuary (TOCE) which is situated in a relatively undisturbed catchment in the Southern Cape. Physico-chemical properties drive estuarine ecology, and together with biological indicators, are commonly assessed to determine the present status of an estuary. During the study, physico-chemical parameters reflected great spatial and temporal variability in response to the mouth state over a 13 month period. Parameters ranged within expected limits, as proposed by the conceptual model for water quality of TOCE’s (Snow and Taljaard 2007). Of particular importance was the prominent occurrence of salinity stratification and hypoxic conditions (dissolved oxygen [DO] < 3 mg l-1) during both open and closed mouth states. Data indicated that in the wide and shallow lower reaches, weak stratification gradients were present and oxygenated conditions (DO > 6 mg l-1) were maintained throughout the water column mainly by wind and tidal action. However, stratification increased towards the deeper, channel-like middle and upper reaches of the estuary, followed by a significant reduction in bottom DO concentrations and development of hypoxia and anoxia. Bottom water hypoxia commonly occurs in microtidal estuaries due to the limited influence of mixing forces, mainly by wind and tidal action. The Goukamma Estuary is a channel-like microtidal estuary where stratification effectively limited oxygenation of the bottom water which resulted in frequent occurrence of bottom water hypoxia. During June 2010 when the highest local rainfall (75 mm) was recorded for the region, salinity and DO data showed that this amount of rainfall was insignificant as it did not replenish the water column of oxygen. Only the surface 0.5 m layer was fresh and oxygenated while below this, the water column was completely hypoxic. In an unimpacted state, the Goukamma Estuary is a blackwater system and is expected to be nutrient poor; however, farming activities in the catchment have resulted in elevated nutrient concentrations. This study showed that significantly higher nutrient concentrations were measured in the middle and upper reaches of the estuary, adjacent to cattle farms situated in the floodplain of these reaches. Nutrient concentrations represented mesotrophic (dissolved inorganic nitrogen [DIN] > 500 μg l-1) to eutrophic conditions (dissolved inorganic phosphorus [DIP] > 25 μg l-1). Nutrient input stimulated phytoplankton to attain a significantly high biomass, ranging between 0.3 – 112 μg l-1 (~ 7.7 ± 1.3 μg l-1; n = 128) and 0.8 – 289 μg l-1 (~ 21.1 ± 4.4 μg l-1; n = 80) during the open and closed states, respectively. High organic loads are associated with high oxygen demands which consequently result in hypoxia following decomposition. Exacerbated by natural salinity stratification which effectively limits oxygenation of the water column, unnaturally high nutrient concentrations and coinciding organic loads place the estuary at particular risk of degradation. This study captured key patterns and processes by quantifying salinity, oxygen and nutrient concentrations in addition to biological indicators (phytoplankton biomass and community composition). Considering possible budget constraints, it is recommended that monthly salinity and oxygen concentrations should be monitored as well as seasonal nutrient concentrations. It is also recommended that riparian buffer zones should be established in the middle and upper reaches of the estuary, as these vegetation buffers have been well documented to contribute to nutrient attenuation and improved water quality from agricultural run-off.
- Full Text:
- Date Issued: 2012