Gazing at Exhibit A
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229643 , vital:49696 , xlink:href="http://liminalities.net/9-1/exhibit.pdf"
- Description: Brett Bailey recently toured a new work in Europe and South Africa, called The Exhibit Series (2010-2013). In different countries the work has appeared under different titles—Exhibit A and Exhibit B, while Exhibit C will be produced in 2014. These productions replicate and parody ethnographic spectacles of the nineteenth century, interrogating European colonial atrocities in Africa, as well as contemporary xenophobia. They consist of a series of installations housed in individual rooms that audience members enter one by one. Inside these rooms one is confronted by beautifully arranged spectacles referencing historical atrocities committed in Namibia by German speaking peoples, as well as atrocities under the Belgian and French colonial regimes in the two Congos. The “exhibits” also include references to more recent incidents of European racism against migrants from Africa. The work has been both applauded and derided. In Berlin, for example, activists called it “a human zoo” and protested that this was “the wrong way to discuss a violent colonial history,”1 while others have called the work “haunting”, praising the production for its “dignity” and “beauty.”2
- Full Text:
- Date Issued: 2013
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229643 , vital:49696 , xlink:href="http://liminalities.net/9-1/exhibit.pdf"
- Description: Brett Bailey recently toured a new work in Europe and South Africa, called The Exhibit Series (2010-2013). In different countries the work has appeared under different titles—Exhibit A and Exhibit B, while Exhibit C will be produced in 2014. These productions replicate and parody ethnographic spectacles of the nineteenth century, interrogating European colonial atrocities in Africa, as well as contemporary xenophobia. They consist of a series of installations housed in individual rooms that audience members enter one by one. Inside these rooms one is confronted by beautifully arranged spectacles referencing historical atrocities committed in Namibia by German speaking peoples, as well as atrocities under the Belgian and French colonial regimes in the two Congos. The “exhibits” also include references to more recent incidents of European racism against migrants from Africa. The work has been both applauded and derided. In Berlin, for example, activists called it “a human zoo” and protested that this was “the wrong way to discuss a violent colonial history,”1 while others have called the work “haunting”, praising the production for its “dignity” and “beauty.”2
- Full Text:
- Date Issued: 2013
The Monkey Cage
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229763 , vital:49708 , xlink:href="https://hdl.handle.net/10520/EJC149510"
- Full Text:
- Date Issued: 2013
- Authors: Krueger, Anton
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/229763 , vital:49708 , xlink:href="https://hdl.handle.net/10520/EJC149510"
- Full Text:
- Date Issued: 2013
Rhodes University Research Report 2013
- Rhodes University, Roberts, Jaine, Mantolo, Thumeka, Jacob, Patricia, Macgregor, Jill, Dore, Sally
- Authors: Rhodes University , Roberts, Jaine , Mantolo, Thumeka , Jacob, Patricia , Macgregor, Jill , Dore, Sally
- Date: 2013
- Language: English
- Type: Text
- Identifier: http://hdl.handle.net/10962/59330 , vital:27549
- Description: From Foreword by Dr Saleem Badat: Rhodes University has positioned itself as a research university that, alongside excellence in undergraduate teaching, also takes scholarship seriously. This has strongly shaped the intellectual identity of the university and, today, research income and expenditure are significant components of the university’s finances. Rhodes University values the scholar-teacher model of combining research with teaching and learning, and other scholarly activities. This has a strong influence on the quality of intellectual endeavour at the University, and is critical in advancing the University’s pursuit of a strong postgraduate trajectory. This is an opportunity to briefly reflect on research at Rhodes over the eight years of my Vice-Chancellorship. It is gratifying to see that scholarship and publishing has continued to blossom at Rhodes, and has also occurred over a wider academic base, and that there has also been increased enrolments of postgraduates, as part of overall University strategy. Postgraduate enrolments increased from 24% (1 397) in 2006 to 30% (2 302) in 2013, with considerable increases in the numbers of Masters and Doctoral students. Between 2006 and 2013, Honours and Postgraduate Diploma graduations increased from 453 to 719, Masters graduations increased by 73% (from 171 to 296) and Doctoral graduations by 70% (from 46 to 78). Concomitantly, there was an increase in the numbers of black and women PhD graduates. The number of Postdoctoral Fellows at Rhodes rose from 19 in 2007 to 68 in 2013, an increase of 258%. , A publication of the Rhodes University Research Office, compiled and edited by Jaine Roberts, Thumeka Mantolo, Patricia Jacob and Jill Macgregor. Design and Layout: Sally Dore
- Full Text:
- Date Issued: 2013
- Authors: Rhodes University , Roberts, Jaine , Mantolo, Thumeka , Jacob, Patricia , Macgregor, Jill , Dore, Sally
- Date: 2013
- Language: English
- Type: Text
- Identifier: http://hdl.handle.net/10962/59330 , vital:27549
- Description: From Foreword by Dr Saleem Badat: Rhodes University has positioned itself as a research university that, alongside excellence in undergraduate teaching, also takes scholarship seriously. This has strongly shaped the intellectual identity of the university and, today, research income and expenditure are significant components of the university’s finances. Rhodes University values the scholar-teacher model of combining research with teaching and learning, and other scholarly activities. This has a strong influence on the quality of intellectual endeavour at the University, and is critical in advancing the University’s pursuit of a strong postgraduate trajectory. This is an opportunity to briefly reflect on research at Rhodes over the eight years of my Vice-Chancellorship. It is gratifying to see that scholarship and publishing has continued to blossom at Rhodes, and has also occurred over a wider academic base, and that there has also been increased enrolments of postgraduates, as part of overall University strategy. Postgraduate enrolments increased from 24% (1 397) in 2006 to 30% (2 302) in 2013, with considerable increases in the numbers of Masters and Doctoral students. Between 2006 and 2013, Honours and Postgraduate Diploma graduations increased from 453 to 719, Masters graduations increased by 73% (from 171 to 296) and Doctoral graduations by 70% (from 46 to 78). Concomitantly, there was an increase in the numbers of black and women PhD graduates. The number of Postdoctoral Fellows at Rhodes rose from 19 in 2007 to 68 in 2013, an increase of 258%. , A publication of the Rhodes University Research Office, compiled and edited by Jaine Roberts, Thumeka Mantolo, Patricia Jacob and Jill Macgregor. Design and Layout: Sally Dore
- Full Text:
- Date Issued: 2013
Falcipains as malarial drug targets
- Authors: Kanzi, Aquillah Mumo
- Date: 2013
- Subjects: Malaria Malaria -- Chemotherapy Plasmodium falciparum Antimalarials -- Development Cysteine proteinases Cysteine proteinases -- Inhibitors Papain Drug development Bioinformatics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3897 , http://hdl.handle.net/10962/d1003842
- Description: Malaria is an infectious disease caused by parasites of the Plasmodium genus with mortality rates of more than a million annually, hence a major global public health concern. Plasmodium falciparum (P. falciparum) accounts for over 90% of malaria incidence. Increased resistance to antimalarial drugs by the Plasmodium parasite, coupled with the lack of an effective malaria vaccine necessitates the urgent need for new research avenues to develop novel and more potent antimalarial drugs. This study focused on falcipains, a group of P. falciparum cysteine proteases that belong to the clan CA and papain family C1, that have emerged as potential drug targets due to their involvement in a range of crucial functions in the P. falciparum life cycle. Recently, falcipain-2 has been validated as a drug target but little is known of its Plasmodium orthologs. Currently, there are several falcipain inhibitors that have been identified, most of which are peptide based but none has proceeded to drug development due to associated poor pharmacological profiles and susceptibility to degradation by host cysteine proteases. Non-peptides inhibitors have been shown to be more stable in vivo but limited information exists. In vivo studies on falcipain-2 and falcipain-3 inhibitors have also been complicated by varying outcomes, thus a good understanding of the structural variations of falcipain Plasmodium orthologs at the active site could go a long way to ease in vivo results interpretation and effective inhibitor design. In this study, we use bioinformatics approaches to perform comparative sequence and structural analysis and molecular docking to characterize protein-inhibitor interactions of falcipain homologs at the active site. Known FP-2 and FP-3 small molecule nonpeptide inhibitors were used to identify residue variations and their effect on inhibitor binding. This was done with the aim of screening a collection of selected non-peptide compounds of South African natural origin to identify possible new inhibitor leads. Natural compounds with high binding affinities across all Plasmodium orthologs were identified. These compounds were then used to search the ZINC database for similar compounds which could have better binding affinities across all selected falcipain homologs. Compounds with high binding affinities across all Plasmodium orthologs were found.
- Full Text:
- Date Issued: 2013
- Authors: Kanzi, Aquillah Mumo
- Date: 2013
- Subjects: Malaria Malaria -- Chemotherapy Plasmodium falciparum Antimalarials -- Development Cysteine proteinases Cysteine proteinases -- Inhibitors Papain Drug development Bioinformatics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3897 , http://hdl.handle.net/10962/d1003842
- Description: Malaria is an infectious disease caused by parasites of the Plasmodium genus with mortality rates of more than a million annually, hence a major global public health concern. Plasmodium falciparum (P. falciparum) accounts for over 90% of malaria incidence. Increased resistance to antimalarial drugs by the Plasmodium parasite, coupled with the lack of an effective malaria vaccine necessitates the urgent need for new research avenues to develop novel and more potent antimalarial drugs. This study focused on falcipains, a group of P. falciparum cysteine proteases that belong to the clan CA and papain family C1, that have emerged as potential drug targets due to their involvement in a range of crucial functions in the P. falciparum life cycle. Recently, falcipain-2 has been validated as a drug target but little is known of its Plasmodium orthologs. Currently, there are several falcipain inhibitors that have been identified, most of which are peptide based but none has proceeded to drug development due to associated poor pharmacological profiles and susceptibility to degradation by host cysteine proteases. Non-peptides inhibitors have been shown to be more stable in vivo but limited information exists. In vivo studies on falcipain-2 and falcipain-3 inhibitors have also been complicated by varying outcomes, thus a good understanding of the structural variations of falcipain Plasmodium orthologs at the active site could go a long way to ease in vivo results interpretation and effective inhibitor design. In this study, we use bioinformatics approaches to perform comparative sequence and structural analysis and molecular docking to characterize protein-inhibitor interactions of falcipain homologs at the active site. Known FP-2 and FP-3 small molecule nonpeptide inhibitors were used to identify residue variations and their effect on inhibitor binding. This was done with the aim of screening a collection of selected non-peptide compounds of South African natural origin to identify possible new inhibitor leads. Natural compounds with high binding affinities across all Plasmodium orthologs were identified. These compounds were then used to search the ZINC database for similar compounds which could have better binding affinities across all selected falcipain homologs. Compounds with high binding affinities across all Plasmodium orthologs were found.
- Full Text:
- Date Issued: 2013
The influence of students' perceived happiness on their entrepreneurial intention at a higher educational institution in South Africa
- Authors: Mamoudou, Hamadou
- Date: 2013
- Subjects: Entrepreneurship -- Study and teaching , ntrepreneurship
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9319 , http://hdl.handle.net/10948/d1020764
- Description: Like most developing countries, South Africa is characterised by high rates of unemployment in general and even more so among the youth and graduates. One solution to this unemployment problem is encouraging people to become entrepreneurs. Most findings reveal however that entrepreneurial activities among the youth in general and university graduates in particular are low. Since entrepreneurial intention is the main precursor of future entrepreneurial actions, a secondary research was undertaken in this study to discover which factors influence entrepreneurial intention in order to increase students’ future entrepreneurial behaviour. Various determinants of entrepreneurial intention were found in the literature, but none of the previous studies investigated the influence of happiness on entrepreneurial intention, despite the growing importance of research on happiness. Consequently, the primary objective of this study was to identify and empirically test the possible influence of various determinants of students’ Perceived happiness on their Entrepreneurial intention at a higher educational institution in South Africa. The comprehensive literature review that was undertaken revealed eleven independent variables that could potentially influence students’ Perceived happiness. These independent variables were regrouped under two main categories, namely sociodemographic factors and psychological factors. Socio-demographic factors included: Perception of wealth, Satisfaction with health, Perception of employment, Leisure, Social relationships and Religion. On the other hand, psychological factors included: Extroversion, Neuroticism, Optimism, Self-esteem and Goals achievement. The independent variables, the mediating variable (Perceived happiness), as well as the dependent variable (Entrepreneurial intention) were clearly defined and operationalised and a hypothesised model, suggesting the hypotheses between the variables was built. During the creation of the measuring instrument, items were sourced from both reliable and valid scales used in previous studies, as well as self-generated items. The respondents of this study were identified through the simple random sampling technique and an electronic questionnaire was sent to each one of them. In total, 806 usable questionnaires were returned and data was subjected to several statistical analyses. An exploratory factor analysis was conducted to assess the validity of the measuring instrument, whereas reliability was gauged by calculating Cronbach’s alpha coefficients. These two tests allowed the extraction of the dependent variable (Entrepreneurial intention), the mediating variable (Perceived happiness) and seven independent variables, namely Perception of wealth, Perception of employment, Leisure, Religion, Extroversion, Neuroticism and finally Goals achievement. Pearson’s correlation coefficients were calculated in order to assess the degree of correlation or association that existed between the variables investigated in the present study. Multiple regressions analyses were used to test the influence of the independent variables on the mediating variable, whereas simple regression analysis was used to assess the influence of the mediating variable on the dependent variable. Additionally, a series of multiple regression analyses was conducted in order to verify the mediating effect of Perceived happiness between all the independent variables and Entrepreneurial intention. The following independent variables were identified as influencing the mediating variable Perceived happiness, namely: Perception of employment; Leisure; Religion; Extroversion; Neuroticism; and Goals achievement. The results of the series of multiple regression analyses revealed that Perceived happiness had a positive influence on Entrepreneurial intention. However, Perceived happiness did not mediate the relationships between the independent variables and Entrepreneurial intention. Thus, the following independent variables were identified as having a direct influence on the dependent variable Entrepreneurial intention, namely: Perception of wealth; Religion; Perception of employment; Extroversion; and Goals achievement. In order to investigate the influence of various demographic variables on the independent, the mediating and the dependent variables, an analysis of variance (ANOVA) was performed. The demographic variables Gender, Population group, Year of study and Faculty had influences on the dependent variable, Entrepreneurial intention, whereas only Population group and Faculty had influences on the mediating variables, Perceived happiness. By empirically investigating the influence of students’ Perceived happiness on their Entrepreneurial intention, this study has expended the limits of knowledge on both happiness and entrepreneurial intention research. It has made a significant contribution towards understanding the factors influencing students’ Perceived happiness and their Entrepreneurial intention. In addition, practical suggestions and recommendations towards increasing students’ levels of Perceived happiness and aspirations to become entrepreneurs after completing their studies have been proposed to students, lecturers and university management.
- Full Text:
- Date Issued: 2013
- Authors: Mamoudou, Hamadou
- Date: 2013
- Subjects: Entrepreneurship -- Study and teaching , ntrepreneurship
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9319 , http://hdl.handle.net/10948/d1020764
- Description: Like most developing countries, South Africa is characterised by high rates of unemployment in general and even more so among the youth and graduates. One solution to this unemployment problem is encouraging people to become entrepreneurs. Most findings reveal however that entrepreneurial activities among the youth in general and university graduates in particular are low. Since entrepreneurial intention is the main precursor of future entrepreneurial actions, a secondary research was undertaken in this study to discover which factors influence entrepreneurial intention in order to increase students’ future entrepreneurial behaviour. Various determinants of entrepreneurial intention were found in the literature, but none of the previous studies investigated the influence of happiness on entrepreneurial intention, despite the growing importance of research on happiness. Consequently, the primary objective of this study was to identify and empirically test the possible influence of various determinants of students’ Perceived happiness on their Entrepreneurial intention at a higher educational institution in South Africa. The comprehensive literature review that was undertaken revealed eleven independent variables that could potentially influence students’ Perceived happiness. These independent variables were regrouped under two main categories, namely sociodemographic factors and psychological factors. Socio-demographic factors included: Perception of wealth, Satisfaction with health, Perception of employment, Leisure, Social relationships and Religion. On the other hand, psychological factors included: Extroversion, Neuroticism, Optimism, Self-esteem and Goals achievement. The independent variables, the mediating variable (Perceived happiness), as well as the dependent variable (Entrepreneurial intention) were clearly defined and operationalised and a hypothesised model, suggesting the hypotheses between the variables was built. During the creation of the measuring instrument, items were sourced from both reliable and valid scales used in previous studies, as well as self-generated items. The respondents of this study were identified through the simple random sampling technique and an electronic questionnaire was sent to each one of them. In total, 806 usable questionnaires were returned and data was subjected to several statistical analyses. An exploratory factor analysis was conducted to assess the validity of the measuring instrument, whereas reliability was gauged by calculating Cronbach’s alpha coefficients. These two tests allowed the extraction of the dependent variable (Entrepreneurial intention), the mediating variable (Perceived happiness) and seven independent variables, namely Perception of wealth, Perception of employment, Leisure, Religion, Extroversion, Neuroticism and finally Goals achievement. Pearson’s correlation coefficients were calculated in order to assess the degree of correlation or association that existed between the variables investigated in the present study. Multiple regressions analyses were used to test the influence of the independent variables on the mediating variable, whereas simple regression analysis was used to assess the influence of the mediating variable on the dependent variable. Additionally, a series of multiple regression analyses was conducted in order to verify the mediating effect of Perceived happiness between all the independent variables and Entrepreneurial intention. The following independent variables were identified as influencing the mediating variable Perceived happiness, namely: Perception of employment; Leisure; Religion; Extroversion; Neuroticism; and Goals achievement. The results of the series of multiple regression analyses revealed that Perceived happiness had a positive influence on Entrepreneurial intention. However, Perceived happiness did not mediate the relationships between the independent variables and Entrepreneurial intention. Thus, the following independent variables were identified as having a direct influence on the dependent variable Entrepreneurial intention, namely: Perception of wealth; Religion; Perception of employment; Extroversion; and Goals achievement. In order to investigate the influence of various demographic variables on the independent, the mediating and the dependent variables, an analysis of variance (ANOVA) was performed. The demographic variables Gender, Population group, Year of study and Faculty had influences on the dependent variable, Entrepreneurial intention, whereas only Population group and Faculty had influences on the mediating variables, Perceived happiness. By empirically investigating the influence of students’ Perceived happiness on their Entrepreneurial intention, this study has expended the limits of knowledge on both happiness and entrepreneurial intention research. It has made a significant contribution towards understanding the factors influencing students’ Perceived happiness and their Entrepreneurial intention. In addition, practical suggestions and recommendations towards increasing students’ levels of Perceived happiness and aspirations to become entrepreneurs after completing their studies have been proposed to students, lecturers and university management.
- Full Text:
- Date Issued: 2013
Synthesis and characterisation of oxorhenium(V) and tricarbonylrhenium(I) complexes with biologically active N, O and N, S-Donor ligands
- Authors: Mukiza, Janvier
- Date: 2013
- Subjects: Rhenium , Rhenium compounds , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10437 , http://hdl.handle.net/10948/d1020769
- Description: This study investigated the synthesis of rhenium(I) and rhenium(V) complexes with a variety of multidentate NS, NSO, NO and SO-donor ligands. It also investigated the synthesis of dinuclear dihalogeno- and trihalogeno-bridged rhenium(I) complexes based on the fac-[Re(CO)3]+ core. The reactions of hydrated folic acid with [Re(CO)5X] (X = Cl, Br) were studied, and the complexes [Re(CO)3(H2O)3]+[Re2(μ-X)3CO)6]−.5H2O [X= Br (1), Cl(2)] were isolated. The reaction of orotic acid potassium salt [Re(CO)5Br] was performed, and the complex [Re2(μ-Br)2(CO)8] was isolated. The reaction of bis(piperidin-1- yl)methanone with [Re(CO)5Cl] followed by recrystallisation of the resulting precipitate in dichloromethane/acetontrile resulted in the complex [Re2(μ- Cl)2(CO)6(MeCN)2]. The X-ray crystal structures show that all these complexes display a distorted octahedral geometry around the central rhenium atoms. The reactions of aroylhydrazone-based ligands such as 3-((pyridin- 2yl)methyleneamino)-2,3-dihydro-2-pyridin-2yl)quinazolin-4-(1H)-one (Hppq) and N-(di(pyridin-2-yl)methylene)benzohydrazide (Hdpmb) with [Re(CO)5Cl] were studied and led to the formation of the complexes [Re(CO)3Cl(Hdpmb)] and [Re(CO)3Cl(Hppq)]. The Hdpmb and Hppq coordinated to the fac-[Re(CO)3]+ core as neutral bidentate chalates via the pyridinic nitrogens (for Hdpmb) and via imino and pyridinic nitrogens for Hppq. The X-ray crystal structures show that the geometry around the rhenium in both complexes is a distorted octahedral. The treatment of the dithizone (H2dz) ligand with rhenium(V) precursors containing a triphenylphosphine group (PPh3) led to the decomposition of dithizone. The decomposition product reacted with the triphenylphosphine group and generated a new ligand triphenylphosphazeno-N-phenylmethanethiohydrazide (H2L). The reaction of trans-[ReOX3(PPh3)2] (X = Cl, Br) with dithizone (H2dz) led to the complex [ReO(dz)2][ReO(HL)2]. The reaction of trans-[ReOI2(OEt)(PPh3)2] with H2dz led to the same product. The reaction of cis-[ReO2I(PPh3)2] with H2dz in methanol led to [ReO(dz)2][ReO(HL)2](MeOH)2 in which methanol bonded to HLvia hydrogen bonds. The H2dz was doubly deprotonated and coordinated to the [ReO]3+ moiety via a thiolate sulfur and deprotonated hydrazinic nitrogen to yield [ReO(dz)2]−, while the H2L was singly deprotonated and coordinated to [ReO]3+ moiety via the neutral sulfur atom and deprotonated hydrazinic nitrogen to yield [ReO(HL)2]+. The X-ray crystal structure show that in both [ReO(HL)2]+ and [ReO(dz)2]−, the rhenium atoms are five-coordinated and adopt a distorted squarebased pyramidal geometry. The reaction of thiosemicarbazones such as salcylidene-4- phenylthiosemicarbazide (H3salpt) with cis-[ReO2I(PPh3)2] was investigated and led to the complex [ReO(Hsalpt)(H2salpt)]. The X-ray study reveals that Hsalpt is present as a tridentate chelate coordinating via the thiolate sulfur, imino nitrogen and phenolic oxygen, while H2salpt coordinates as a bidentate chelate via the thiolate sulfur and imino nitrogen atoms. The geometry around rhenium is distorted octahedral. The coordination mode of the benzoylthiourea derivatives 4-tert-butyl-N- (diphenylcarbamothioyl)benzamide (Htpb) and N-(diethylcarbamothioyl)benzamide (Heb) to the [Re2O3]4+ and fac-[Re(CO)3]+ cores were investigated. The reaction of [Re(CO)5Cl] in presence of sodium acetate with Htpb led to the dimeric complex [Re(CO)3(tpb)]2 in which the tpb coordinated to the fac-[Re(CO)3]+ core via the ketonic oxygen and bridging thiolate sulfur. The same reaction with Heb led to the monomeric complex [Re(CO)3(eb)(Heb)], in which the eb coordinates to the fac-[Re(CO)3]+core via thiolate sulfur and ketonic oxygen with Heb binding via the neutral sulfur atom. The reaction of Heb with cis-[ReO2I(PPh3)2] at room temperature with excess of sodium acetate led to the dimeric complex (μ-O)[ReO(eb)2]2 in which Heb is present as a monoanionic (deprotonated) bidentate with coordination through the thiolate sulfur and ketonic oxygen.
- Full Text:
- Date Issued: 2013
- Authors: Mukiza, Janvier
- Date: 2013
- Subjects: Rhenium , Rhenium compounds , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10437 , http://hdl.handle.net/10948/d1020769
- Description: This study investigated the synthesis of rhenium(I) and rhenium(V) complexes with a variety of multidentate NS, NSO, NO and SO-donor ligands. It also investigated the synthesis of dinuclear dihalogeno- and trihalogeno-bridged rhenium(I) complexes based on the fac-[Re(CO)3]+ core. The reactions of hydrated folic acid with [Re(CO)5X] (X = Cl, Br) were studied, and the complexes [Re(CO)3(H2O)3]+[Re2(μ-X)3CO)6]−.5H2O [X= Br (1), Cl(2)] were isolated. The reaction of orotic acid potassium salt [Re(CO)5Br] was performed, and the complex [Re2(μ-Br)2(CO)8] was isolated. The reaction of bis(piperidin-1- yl)methanone with [Re(CO)5Cl] followed by recrystallisation of the resulting precipitate in dichloromethane/acetontrile resulted in the complex [Re2(μ- Cl)2(CO)6(MeCN)2]. The X-ray crystal structures show that all these complexes display a distorted octahedral geometry around the central rhenium atoms. The reactions of aroylhydrazone-based ligands such as 3-((pyridin- 2yl)methyleneamino)-2,3-dihydro-2-pyridin-2yl)quinazolin-4-(1H)-one (Hppq) and N-(di(pyridin-2-yl)methylene)benzohydrazide (Hdpmb) with [Re(CO)5Cl] were studied and led to the formation of the complexes [Re(CO)3Cl(Hdpmb)] and [Re(CO)3Cl(Hppq)]. The Hdpmb and Hppq coordinated to the fac-[Re(CO)3]+ core as neutral bidentate chalates via the pyridinic nitrogens (for Hdpmb) and via imino and pyridinic nitrogens for Hppq. The X-ray crystal structures show that the geometry around the rhenium in both complexes is a distorted octahedral. The treatment of the dithizone (H2dz) ligand with rhenium(V) precursors containing a triphenylphosphine group (PPh3) led to the decomposition of dithizone. The decomposition product reacted with the triphenylphosphine group and generated a new ligand triphenylphosphazeno-N-phenylmethanethiohydrazide (H2L). The reaction of trans-[ReOX3(PPh3)2] (X = Cl, Br) with dithizone (H2dz) led to the complex [ReO(dz)2][ReO(HL)2]. The reaction of trans-[ReOI2(OEt)(PPh3)2] with H2dz led to the same product. The reaction of cis-[ReO2I(PPh3)2] with H2dz in methanol led to [ReO(dz)2][ReO(HL)2](MeOH)2 in which methanol bonded to HLvia hydrogen bonds. The H2dz was doubly deprotonated and coordinated to the [ReO]3+ moiety via a thiolate sulfur and deprotonated hydrazinic nitrogen to yield [ReO(dz)2]−, while the H2L was singly deprotonated and coordinated to [ReO]3+ moiety via the neutral sulfur atom and deprotonated hydrazinic nitrogen to yield [ReO(HL)2]+. The X-ray crystal structure show that in both [ReO(HL)2]+ and [ReO(dz)2]−, the rhenium atoms are five-coordinated and adopt a distorted squarebased pyramidal geometry. The reaction of thiosemicarbazones such as salcylidene-4- phenylthiosemicarbazide (H3salpt) with cis-[ReO2I(PPh3)2] was investigated and led to the complex [ReO(Hsalpt)(H2salpt)]. The X-ray study reveals that Hsalpt is present as a tridentate chelate coordinating via the thiolate sulfur, imino nitrogen and phenolic oxygen, while H2salpt coordinates as a bidentate chelate via the thiolate sulfur and imino nitrogen atoms. The geometry around rhenium is distorted octahedral. The coordination mode of the benzoylthiourea derivatives 4-tert-butyl-N- (diphenylcarbamothioyl)benzamide (Htpb) and N-(diethylcarbamothioyl)benzamide (Heb) to the [Re2O3]4+ and fac-[Re(CO)3]+ cores were investigated. The reaction of [Re(CO)5Cl] in presence of sodium acetate with Htpb led to the dimeric complex [Re(CO)3(tpb)]2 in which the tpb coordinated to the fac-[Re(CO)3]+ core via the ketonic oxygen and bridging thiolate sulfur. The same reaction with Heb led to the monomeric complex [Re(CO)3(eb)(Heb)], in which the eb coordinates to the fac-[Re(CO)3]+core via thiolate sulfur and ketonic oxygen with Heb binding via the neutral sulfur atom. The reaction of Heb with cis-[ReO2I(PPh3)2] at room temperature with excess of sodium acetate led to the dimeric complex (μ-O)[ReO(eb)2]2 in which Heb is present as a monoanionic (deprotonated) bidentate with coordination through the thiolate sulfur and ketonic oxygen.
- Full Text:
- Date Issued: 2013
Rhenium (I), (III) and (V) complexes with potentially multidentate N, O-Donor ligands
- Authors: Habarurema, Gratien
- Date: 2013
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10441 , http://hdl.handle.net/10948/d1020952
- Description: This study investigates the coordination modes of potential multidentate N,O-donor Schiff base ligands to the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The project is aimed at the synthesis of tridentate, tetradentate and pentadentate Schiff bases ligands derived from the condensation reactions of benzaldehyde with different primary amines. The structures of these Schiff bases and their complexes were confirmed by using physical characterization methods, namely melting points, UV-Visible, UV-emission, 1H NMR and IR spectroscopy, X-ray diffractometry and elemental analysis. To further understand the coordination chemistry of rhenium, the prepared diiminediphenol N2O2-donor Schiff base ligand N N′-o-phenylene-bis(salicylaldimine) (H2salphen) was reacted with trans-[ReOCl3(PPh3)2] to yield cis-[ReCl2(ophsal)(PPh3)], whereas its reaction with trans-[ReOBr3(PPh3)2] resulted in the formation of the cis-[ReBr2(aphsal)(PPh3)].2CH3CN complex. In the above complexes the H2salphen ligand was cleaved leading to the coordinated tridentate ophsal NO2- and aphsal N2O-donor ligands. The reaction of H3aphsal with trans-[ReOBr3(PPh3)2] in toluene led to an unexpected compound, trans- [{[ReBr(aphsal)(PPh3)2]Br}{[ReBr(aphsal)(PPh3)2](ReO4)}] with an imido [ReNR]3+core. The ligand aphsal was coordinated tridentately with the doubly deprotonated amino nitrogen leading to Re(V)-imido complexes. The reaction of 2-((Z)-(2-aminoethylimino)methyl)phenol (H3amphol) with [Re(CO)5Cl] led to the rhenium(I) product fac-[Re(CO)3(H3amphol)] with H3amphol coordinated as a monoanionic tridentate chelate through its phenolate oxygen and amino nitrogen atoms. The X-ray crystal structures showed that all complexes display a distorted octahedral geometry around the central rhenium atom. The reaction of 2,6-bis(2-hydroxyphenylimino)pyridine (H2hpp) with cis-[ReO2I(PPh3)2] resulted in the reduced Re(III) product trans-[Re(hpp)(PPh3)2]I, while trans-[Re(hpp)(PPh3)2](ReO4) was isolated from its reaction with trans-[ReOCl3(PPh3)2]. The H2hpp ligand acts as a pentadentate N3O2-donor ligand where the two phenolic protons undergo deprotonation and its three nitrogens act as neutral donor atoms. Both compounds resulted from a disproportionation reaction characterized by the produced perrhenate counter-ion. The complex fac-[Re(CO)3(H2hpp)Cl] was prepared from [Re(CO)5Cl] and H2hpp in toluene. The H2hpp ligand acted as a neutral bidentate N,N-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, two neutral nitrogen atoms and a chloride ligand. The reactions of the potentially tetradentate ligand N,N'-ethylenebis(salicylideneimine) (H2salen) with different rhenium(V) precursors resulted in the formation of two dimeric oxorhenium (V) compounds. In the reaction of H2salen with trans-[ReOCl3(PPh3)2] in ethanol, the highly unusual distorted dimeric complex (μ-salen)[ReOCl2(PPh3)]2 was isolated, in which salen2- is coordinated as a tetradentate to two oxorhenium(V) centres, and salen2- is present as a bidentate monoanionic ligand on each rhenium center. The reaction of cis- [ReO2I(PPh3)2] with H2salen led to the formation of the neutral dimeric oxorhenium(V) complex (μ-O)[ReO(salen)]2 in which the tetradentate chelate salen acts as a tetradentate dianionic ligand through its phenolate oxygens and nitrogen atoms of the azomethine groups. In its reaction with H2hmp the compound (μ-O)[ReO(hmp)]2 was isolated. In this product the pentadentate ligand H2hmp coordinated as tetradentate via its phenolic oxygen and nitrogen atoms. The reaction of the potentially tetradentate N1,N2-bis(aminobenzylidene)-1,2-ethylenediamine (H2amben) with trans-[ReOCl3(PPh3)2] led to the formation of the monocationic square-pyramidal complex salt [ReO(amben)](ReO4.
- Full Text:
- Date Issued: 2013
- Authors: Habarurema, Gratien
- Date: 2013
- Subjects: Rhenium , Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10441 , http://hdl.handle.net/10948/d1020952
- Description: This study investigates the coordination modes of potential multidentate N,O-donor Schiff base ligands to the [ReVO]3+ and fac-[ReI(CO)3]+ cores. The project is aimed at the synthesis of tridentate, tetradentate and pentadentate Schiff bases ligands derived from the condensation reactions of benzaldehyde with different primary amines. The structures of these Schiff bases and their complexes were confirmed by using physical characterization methods, namely melting points, UV-Visible, UV-emission, 1H NMR and IR spectroscopy, X-ray diffractometry and elemental analysis. To further understand the coordination chemistry of rhenium, the prepared diiminediphenol N2O2-donor Schiff base ligand N N′-o-phenylene-bis(salicylaldimine) (H2salphen) was reacted with trans-[ReOCl3(PPh3)2] to yield cis-[ReCl2(ophsal)(PPh3)], whereas its reaction with trans-[ReOBr3(PPh3)2] resulted in the formation of the cis-[ReBr2(aphsal)(PPh3)].2CH3CN complex. In the above complexes the H2salphen ligand was cleaved leading to the coordinated tridentate ophsal NO2- and aphsal N2O-donor ligands. The reaction of H3aphsal with trans-[ReOBr3(PPh3)2] in toluene led to an unexpected compound, trans- [{[ReBr(aphsal)(PPh3)2]Br}{[ReBr(aphsal)(PPh3)2](ReO4)}] with an imido [ReNR]3+core. The ligand aphsal was coordinated tridentately with the doubly deprotonated amino nitrogen leading to Re(V)-imido complexes. The reaction of 2-((Z)-(2-aminoethylimino)methyl)phenol (H3amphol) with [Re(CO)5Cl] led to the rhenium(I) product fac-[Re(CO)3(H3amphol)] with H3amphol coordinated as a monoanionic tridentate chelate through its phenolate oxygen and amino nitrogen atoms. The X-ray crystal structures showed that all complexes display a distorted octahedral geometry around the central rhenium atom. The reaction of 2,6-bis(2-hydroxyphenylimino)pyridine (H2hpp) with cis-[ReO2I(PPh3)2] resulted in the reduced Re(III) product trans-[Re(hpp)(PPh3)2]I, while trans-[Re(hpp)(PPh3)2](ReO4) was isolated from its reaction with trans-[ReOCl3(PPh3)2]. The H2hpp ligand acts as a pentadentate N3O2-donor ligand where the two phenolic protons undergo deprotonation and its three nitrogens act as neutral donor atoms. Both compounds resulted from a disproportionation reaction characterized by the produced perrhenate counter-ion. The complex fac-[Re(CO)3(H2hpp)Cl] was prepared from [Re(CO)5Cl] and H2hpp in toluene. The H2hpp ligand acted as a neutral bidentate N,N-donor chelate. The metal is coordinated to three carbonyl donors in a facial orientation, two neutral nitrogen atoms and a chloride ligand. The reactions of the potentially tetradentate ligand N,N'-ethylenebis(salicylideneimine) (H2salen) with different rhenium(V) precursors resulted in the formation of two dimeric oxorhenium (V) compounds. In the reaction of H2salen with trans-[ReOCl3(PPh3)2] in ethanol, the highly unusual distorted dimeric complex (μ-salen)[ReOCl2(PPh3)]2 was isolated, in which salen2- is coordinated as a tetradentate to two oxorhenium(V) centres, and salen2- is present as a bidentate monoanionic ligand on each rhenium center. The reaction of cis- [ReO2I(PPh3)2] with H2salen led to the formation of the neutral dimeric oxorhenium(V) complex (μ-O)[ReO(salen)]2 in which the tetradentate chelate salen acts as a tetradentate dianionic ligand through its phenolate oxygens and nitrogen atoms of the azomethine groups. In its reaction with H2hmp the compound (μ-O)[ReO(hmp)]2 was isolated. In this product the pentadentate ligand H2hmp coordinated as tetradentate via its phenolic oxygen and nitrogen atoms. The reaction of the potentially tetradentate N1,N2-bis(aminobenzylidene)-1,2-ethylenediamine (H2amben) with trans-[ReOCl3(PPh3)2] led to the formation of the monocationic square-pyramidal complex salt [ReO(amben)](ReO4.
- Full Text:
- Date Issued: 2013
Low symmetry metallophthalocyanines and their nanoparticle conjugates for photodynamic antimicrobial chemotherapy
- Authors: Masilela, Nkosiphile
- Date: 2013
- Subjects: Nanoparticles Anti-infective agents Chemotherapy Photochemotherapy Quantum dots Gold Silver , Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4278 , http://hdl.handle.net/10962/d1001906
- Description: This thesis reports on the syntheses of novel low symmetrically substituted Zn, Sn, Ge and Ti MPc complexes containing a single carboxylic or cysteinyl group available for attachments to MNPs. The complexes were extensively characterized by various techniques to ensure their purity. Various metallic nanoparticles consisting of silver (AgNPs), gold (AuNPs) as well as quantum dots (QDs) were successfully prepared and conjugated to the low symmetry phthalocyanine complexes. The conjugates were successfully characterized using many techniques. The Q-band maxima of the MPcs were observed at completely different wavelength regions depending on the nature of the substituents and the central metal used. Blue shifting of the Q band in the absorption spectra was observed for the complexes in the presence of AuNPs, while aggregation was observed in the presence of quantum dots. The complexes were successfully electrospun into polymer fibers for the antimicrobial inhibition of bacteria. The photophysical and photochemical properties of these complexes were extensively investigated. Higher triplet and singlet oxygen quantum yields were achieved for the Ge Pc complexes, with all the complexes giving reasonable singlet oxygen quantum yields. An enhancement in triplet and singlet oxygen quantum yields was observed for all the complexes in the presence of metal nanoparticles. However, the singlet oxygen quantum yields decreased for all the complexes when incorporated into electrospun fibers. The antimicrobial behaviour of the complexes was investigated against Bacillus Subtilis and Staphylococcus Aureus in solution and in the fiber matrix. High antimicrobial inhibitions were observed for the Ge complexes followed by the ZnPc derivatives. All the low symmetry ZnPc derivatives were conjugated to AgNPs and their antimicrobial behaviour was compared to their symmetrical counterparts. The best antimicrobial inhibition behaviour was observed for the low symmetry Pcs when compared to their symmetrical counterparts. In the absence and in the presence of AgNPs, axially ligated SiPc also showed better antimicrobial activity when it was compared to the unsubstituted ZnPc complex.
- Full Text:
- Date Issued: 2013
- Authors: Masilela, Nkosiphile
- Date: 2013
- Subjects: Nanoparticles Anti-infective agents Chemotherapy Photochemotherapy Quantum dots Gold Silver , Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4278 , http://hdl.handle.net/10962/d1001906
- Description: This thesis reports on the syntheses of novel low symmetrically substituted Zn, Sn, Ge and Ti MPc complexes containing a single carboxylic or cysteinyl group available for attachments to MNPs. The complexes were extensively characterized by various techniques to ensure their purity. Various metallic nanoparticles consisting of silver (AgNPs), gold (AuNPs) as well as quantum dots (QDs) were successfully prepared and conjugated to the low symmetry phthalocyanine complexes. The conjugates were successfully characterized using many techniques. The Q-band maxima of the MPcs were observed at completely different wavelength regions depending on the nature of the substituents and the central metal used. Blue shifting of the Q band in the absorption spectra was observed for the complexes in the presence of AuNPs, while aggregation was observed in the presence of quantum dots. The complexes were successfully electrospun into polymer fibers for the antimicrobial inhibition of bacteria. The photophysical and photochemical properties of these complexes were extensively investigated. Higher triplet and singlet oxygen quantum yields were achieved for the Ge Pc complexes, with all the complexes giving reasonable singlet oxygen quantum yields. An enhancement in triplet and singlet oxygen quantum yields was observed for all the complexes in the presence of metal nanoparticles. However, the singlet oxygen quantum yields decreased for all the complexes when incorporated into electrospun fibers. The antimicrobial behaviour of the complexes was investigated against Bacillus Subtilis and Staphylococcus Aureus in solution and in the fiber matrix. High antimicrobial inhibitions were observed for the Ge complexes followed by the ZnPc derivatives. All the low symmetry ZnPc derivatives were conjugated to AgNPs and their antimicrobial behaviour was compared to their symmetrical counterparts. The best antimicrobial inhibition behaviour was observed for the low symmetry Pcs when compared to their symmetrical counterparts. In the absence and in the presence of AgNPs, axially ligated SiPc also showed better antimicrobial activity when it was compared to the unsubstituted ZnPc complex.
- Full Text:
- Date Issued: 2013
Photophysicochemical properties of aluminium phthalocyanine-platinum conjugates
- Authors: Malinga, Nduduzo Nkanyiso
- Date: 2013 , 2013-04-05
- Subjects: Phthalocyanines , Photochemistry , Photochemotherapy , Aluminium , Platinum , Nanoparticles , Cancer -- Photochemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4285 , http://hdl.handle.net/10962/d1002954 , Phthalocyanines , Photochemistry , Photochemotherapy , Aluminium , Platinum , Nanoparticles , Cancer -- Photochemotherapy
- Description: The combination of chemotherapy and photodynamic therapy was investigated by synthesis and characterization of octacarboxy phthalocyanine covalent conjugates with platinum complexes. This work presents the synthesis, characterization and photophysicochemical properties of aluminium (diaquaplatinum) octacarboxyphthalocyanine and aluminium (diammine) octacarboxyphthalocyanine. The conjugates were prepared by conjugating aluminium octacarboxy phthalocyanine with potassium tetrachloro platinate to yield aluminium tetrakis and trikis (diaquaplatinum) octacarboxy phthalocyanine. The aluminium octacarboxy phthalocyanine was also conjugated with cis-diamminedichloroplatinum to yield aluminium bis and tris (diaquaplatinum) octacarboxy phthalocyanine. From the characterization of the conjugates it was discovered that the aluminium (diaquaplatinum) octacarboxy phthalocyanine had formed platinum nanoparticles with the Pc acting as a capping agent. The triplet lifetimes decreased with the increasing number of platinum complexesconjugated to the Pc. The heavy atom effect improved the overall photophysicochemical properties.
- Full Text:
- Date Issued: 2013
- Authors: Malinga, Nduduzo Nkanyiso
- Date: 2013 , 2013-04-05
- Subjects: Phthalocyanines , Photochemistry , Photochemotherapy , Aluminium , Platinum , Nanoparticles , Cancer -- Photochemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4285 , http://hdl.handle.net/10962/d1002954 , Phthalocyanines , Photochemistry , Photochemotherapy , Aluminium , Platinum , Nanoparticles , Cancer -- Photochemotherapy
- Description: The combination of chemotherapy and photodynamic therapy was investigated by synthesis and characterization of octacarboxy phthalocyanine covalent conjugates with platinum complexes. This work presents the synthesis, characterization and photophysicochemical properties of aluminium (diaquaplatinum) octacarboxyphthalocyanine and aluminium (diammine) octacarboxyphthalocyanine. The conjugates were prepared by conjugating aluminium octacarboxy phthalocyanine with potassium tetrachloro platinate to yield aluminium tetrakis and trikis (diaquaplatinum) octacarboxy phthalocyanine. The aluminium octacarboxy phthalocyanine was also conjugated with cis-diamminedichloroplatinum to yield aluminium bis and tris (diaquaplatinum) octacarboxy phthalocyanine. From the characterization of the conjugates it was discovered that the aluminium (diaquaplatinum) octacarboxy phthalocyanine had formed platinum nanoparticles with the Pc acting as a capping agent. The triplet lifetimes decreased with the increasing number of platinum complexesconjugated to the Pc. The heavy atom effect improved the overall photophysicochemical properties.
- Full Text:
- Date Issued: 2013
Synthesis of fluorescent polymers with pendant triazole-substituted coumarin side-chains via a combination of click chemistry and raft-mediated polymerization
- Authors: Wali, Nwabisa Whitney
- Date: 2013
- Subjects: Fluorescent polymers , Polymerization , Macromolecules -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10432 , http://hdl.handle.net/10948/d1020142
- Description: This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.
- Full Text:
- Date Issued: 2013
- Authors: Wali, Nwabisa Whitney
- Date: 2013
- Subjects: Fluorescent polymers , Polymerization , Macromolecules -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10432 , http://hdl.handle.net/10948/d1020142
- Description: This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.
- Full Text:
- Date Issued: 2013
Effects of crop rotation and tillage system on the control of ryegrass (lolium multiflorum X perenne) in wheat (triticum aestivum) in the Swartland production area of South Africa's Western Cape Province
- Authors: Nteyi, Sinovuyo Mava
- Date: 2013
- Subjects: Cropping systems , Conservation tillage -- South Africa -- Western Cape , Ryegrasses
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10738 , http://hdl.handle.net/10948/d1020990
- Description: A major challenge facing agriculture today is to sustain the productivity of agricultural systems with the reduction of weed invasion. The Swartland region in the Western Cape (South Africa) is intensively cropped, producing wheat (Triticum aestivum) as the major crop. As a result of the weedy ryegrass invasion the wheat yield is reduced. In addition, ryegrass has developed resistance to grass herbicides (graminicides). This situation has increased the need to use alternative practices for controlling the invasion of ryegrass in wheat fields. In this regard, crop rotation and tillage systems were proposed as techniques to suppress the ryegrass invasion. This could thus maintain a sustainable long-term wheat production system with less application of herbicides, decreased input costs and increased total grain yield. Against this background, the effects of crop rotation and tillage were determined on ryegrass seedling emergence in a field and shade netting experiment, while seed dormancy was determined in the laboratory. The objectives were to compare the wheat production of two crop rotations with mono-cropped wheat and assess the impact on the ryegrass population in no-till and minimum tillage systems. Analyses of variance on data sets of ryegrass seeds from 2009, 2010 and 2011 were used to determine germination and dormancy percentages in laboratory experiments. The performance of laboratory treatments was evaluated on the basis of germination percentage of seeds. In the field and shade netting experiments, analyses of variance for data from 2007, 2011 and 2012 were used to determine crop rotation x tillage system response. Field and shade netting performance were evaluated on the basis of ryegrass population inhibition and stimulation respectively. Ryegrass seeds from 2009 and 2010 showed higher germination percentages (80 per cent and 73 per cent) than 2011 (42 per cent). Primary dormancy prevented high germination of newly harvested seeds as dormancy release increase with age of the seed. Results of field and shade netting experiments showed stimulation of the ryegrass weed population in wheat monoculture under minimum tillage. However, when wheat was rotated with leguminous crops under both tillage systems (minimum-till and no-till) ryegrass was significantly inhibited. It was concluded that the critical period for weed competition is the first six weeks after planting. Results from this study provide a basis for producers of cereals to make good decisions with regards to timing weed control measures. It is essential to use competitive crop sequences which will inhibit weeds. The challenge is getting this practice adopted and implemented by producers as it will promote conservation agriculture within the region. This study promotes long-term sustainable wheat production systems with an efficient weed management programme that is environmentally friendly using less herbicides within the Swartland region.
- Full Text:
- Date Issued: 2013
- Authors: Nteyi, Sinovuyo Mava
- Date: 2013
- Subjects: Cropping systems , Conservation tillage -- South Africa -- Western Cape , Ryegrasses
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10738 , http://hdl.handle.net/10948/d1020990
- Description: A major challenge facing agriculture today is to sustain the productivity of agricultural systems with the reduction of weed invasion. The Swartland region in the Western Cape (South Africa) is intensively cropped, producing wheat (Triticum aestivum) as the major crop. As a result of the weedy ryegrass invasion the wheat yield is reduced. In addition, ryegrass has developed resistance to grass herbicides (graminicides). This situation has increased the need to use alternative practices for controlling the invasion of ryegrass in wheat fields. In this regard, crop rotation and tillage systems were proposed as techniques to suppress the ryegrass invasion. This could thus maintain a sustainable long-term wheat production system with less application of herbicides, decreased input costs and increased total grain yield. Against this background, the effects of crop rotation and tillage were determined on ryegrass seedling emergence in a field and shade netting experiment, while seed dormancy was determined in the laboratory. The objectives were to compare the wheat production of two crop rotations with mono-cropped wheat and assess the impact on the ryegrass population in no-till and minimum tillage systems. Analyses of variance on data sets of ryegrass seeds from 2009, 2010 and 2011 were used to determine germination and dormancy percentages in laboratory experiments. The performance of laboratory treatments was evaluated on the basis of germination percentage of seeds. In the field and shade netting experiments, analyses of variance for data from 2007, 2011 and 2012 were used to determine crop rotation x tillage system response. Field and shade netting performance were evaluated on the basis of ryegrass population inhibition and stimulation respectively. Ryegrass seeds from 2009 and 2010 showed higher germination percentages (80 per cent and 73 per cent) than 2011 (42 per cent). Primary dormancy prevented high germination of newly harvested seeds as dormancy release increase with age of the seed. Results of field and shade netting experiments showed stimulation of the ryegrass weed population in wheat monoculture under minimum tillage. However, when wheat was rotated with leguminous crops under both tillage systems (minimum-till and no-till) ryegrass was significantly inhibited. It was concluded that the critical period for weed competition is the first six weeks after planting. Results from this study provide a basis for producers of cereals to make good decisions with regards to timing weed control measures. It is essential to use competitive crop sequences which will inhibit weeds. The challenge is getting this practice adopted and implemented by producers as it will promote conservation agriculture within the region. This study promotes long-term sustainable wheat production systems with an efficient weed management programme that is environmentally friendly using less herbicides within the Swartland region.
- Full Text:
- Date Issued: 2013
A study of maximum and minimum operators with applications to piecewise linear payoff functions
- Authors: Seedat, Ebrahim
- Date: 2013
- Subjects: Options (Finance) Piecewise linear topology Geometry, Affine Riesz spaces Lattice theory Algebra, Boolean Pricing , Max and min operators
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:931 , http://hdl.handle.net/10962/d1001457
- Description: The payoff functions of contingent claims (options) of one variable are prominent in Financial Economics and thus assume a fundamental role in option pricing theory. Some of these payoff functions are continuous, piecewise-defined and linear or affine. Such option payoff functions can be analysed in a useful way when they are represented in additive, Boolean normal, graphical and linear form. The issue of converting such payoff functions expressed in the additive, linear or graphical form into an equivalent Boolean normal form, has been considered by several authors for more than half-a-century to better-understand the role of such functions. One aspect of our study is to unify the foregoing different forms of representation, by creating algorithms that convert a payoff function expressed in graphical form into Boolean normal form and then into the additive form and vice versa. Applications of these algorithms are considered in a general theoretical sense and also in the context of specific option contracts wherever relevant. The use of these algorithms have yielded easy computation of the area enclosed by the graph of various functions using min and max operators in several ways, which, in our opinion, are important in option pricing. To summarise, this study effectively dealt with maximum and minimum operators from several perspectives
- Full Text:
- Date Issued: 2013
- Authors: Seedat, Ebrahim
- Date: 2013
- Subjects: Options (Finance) Piecewise linear topology Geometry, Affine Riesz spaces Lattice theory Algebra, Boolean Pricing , Max and min operators
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:931 , http://hdl.handle.net/10962/d1001457
- Description: The payoff functions of contingent claims (options) of one variable are prominent in Financial Economics and thus assume a fundamental role in option pricing theory. Some of these payoff functions are continuous, piecewise-defined and linear or affine. Such option payoff functions can be analysed in a useful way when they are represented in additive, Boolean normal, graphical and linear form. The issue of converting such payoff functions expressed in the additive, linear or graphical form into an equivalent Boolean normal form, has been considered by several authors for more than half-a-century to better-understand the role of such functions. One aspect of our study is to unify the foregoing different forms of representation, by creating algorithms that convert a payoff function expressed in graphical form into Boolean normal form and then into the additive form and vice versa. Applications of these algorithms are considered in a general theoretical sense and also in the context of specific option contracts wherever relevant. The use of these algorithms have yielded easy computation of the area enclosed by the graph of various functions using min and max operators in several ways, which, in our opinion, are important in option pricing. To summarise, this study effectively dealt with maximum and minimum operators from several perspectives
- Full Text:
- Date Issued: 2013
Development and validation of in-process control test kits for biodiesel production
- Authors: Fibi, Pumza Oscarine
- Date: 2013
- Subjects: Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10416 , http://hdl.handle.net/10948/d1012645 , Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Description: The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.
- Full Text:
- Date Issued: 2013
- Authors: Fibi, Pumza Oscarine
- Date: 2013
- Subjects: Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10416 , http://hdl.handle.net/10948/d1012645 , Biodiesel fuels -- South Africa , Biomass energy -- South Africa
- Description: The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.
- Full Text:
- Date Issued: 2013
Novel applications of Morita-Baylis-Hillman methodology in organic synthesis
- Authors: Mciteka, Lulama Patrick
- Date: 2013 , 2013-04-22
- Subjects: Organic compounds -- Synthesis -- Research Asymmetric synthesis Asymmetry (Chemistry) Chemical reactions -- Research Camphor -- Research AZT (Drug) -- Research Chemical inhibitors -- Research Chemistry -- Methodology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4439 , http://hdl.handle.net/10962/d1007598
- Description: The overall approach in the present investigation has been to explore applications of the Morita-Baylis-Hillman (MBH) reaction in asymmetric synthesis and in the continuation of systems with medicinal potential. To this end, a series of varied camphor-derived acrylate esters was prepared to serve as chiral substrates in asymmetric Morita-Baylis- Hillman reactions. Reduction of N-substituted camphor-10-sulfonamides afforded the 3- exo-hydroxy derivatives as the major products. Acylation of the corresponding sodium alkoxides gave the desired 3-exo-acrylate esters, isolation of which was complicated by concomitant formation of hydrochlorinated and diastereomeric competition products. Bulky camphorsulfonamides containing alkyl, dialkyl, aromatic and adamantyl groups were selected as N-substituents with the view of achieving stereoselective outcome in subsequent MBH reactions. The synthesis of novel camphor-derived Morita-Baylis-Hillman adducts using various pyridine-carboxaldehydes proceeded with exceptionally high yields with diastereoselectivities ranging from 7-33 % d.e. Both 1D and 2D NMR and HRMS techniques were employed to confirm the structures and an extensive study of the electropositive fragmentation patterns of a number of camphor-derived chiral acrylate esters was conducted. Attention has also been given to the application of MBH methodology in the construction of heterocyclic ‘cinnamate-like’ AZT conjugates which were designed to serve as dualaction HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. A number of pyridine carboxaldehyde-derived MBH adducts were synthesized using methyl, ethyl and t-butyl acrylates in the presence of 3-hydroxyquinuclidine (3-HQ) as catalyst. The yields for these reactions were excellent. The resulting MBH adducts were acetylated and subjected to aza-Michael addition using propargylamine. The resulting alkylamino compounds were then used in ‘Click reactions’ to form the targeted AZT-conjugates in moderate to excellent yield. In silico docking of computer modelled AZT-conjugates into the HIV-1 integrase and reverse transcriptase enzyme-active sites and potential hydrogen-bonding interaction with active-site amino acid residues were identified. The electrospray MS fragmentations of the AZT and the novel AZT-conjugates were also investigated and common fragmentation pathways were identified.
- Full Text:
- Date Issued: 2013
- Authors: Mciteka, Lulama Patrick
- Date: 2013 , 2013-04-22
- Subjects: Organic compounds -- Synthesis -- Research Asymmetric synthesis Asymmetry (Chemistry) Chemical reactions -- Research Camphor -- Research AZT (Drug) -- Research Chemical inhibitors -- Research Chemistry -- Methodology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4439 , http://hdl.handle.net/10962/d1007598
- Description: The overall approach in the present investigation has been to explore applications of the Morita-Baylis-Hillman (MBH) reaction in asymmetric synthesis and in the continuation of systems with medicinal potential. To this end, a series of varied camphor-derived acrylate esters was prepared to serve as chiral substrates in asymmetric Morita-Baylis- Hillman reactions. Reduction of N-substituted camphor-10-sulfonamides afforded the 3- exo-hydroxy derivatives as the major products. Acylation of the corresponding sodium alkoxides gave the desired 3-exo-acrylate esters, isolation of which was complicated by concomitant formation of hydrochlorinated and diastereomeric competition products. Bulky camphorsulfonamides containing alkyl, dialkyl, aromatic and adamantyl groups were selected as N-substituents with the view of achieving stereoselective outcome in subsequent MBH reactions. The synthesis of novel camphor-derived Morita-Baylis-Hillman adducts using various pyridine-carboxaldehydes proceeded with exceptionally high yields with diastereoselectivities ranging from 7-33 % d.e. Both 1D and 2D NMR and HRMS techniques were employed to confirm the structures and an extensive study of the electropositive fragmentation patterns of a number of camphor-derived chiral acrylate esters was conducted. Attention has also been given to the application of MBH methodology in the construction of heterocyclic ‘cinnamate-like’ AZT conjugates which were designed to serve as dualaction HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. A number of pyridine carboxaldehyde-derived MBH adducts were synthesized using methyl, ethyl and t-butyl acrylates in the presence of 3-hydroxyquinuclidine (3-HQ) as catalyst. The yields for these reactions were excellent. The resulting MBH adducts were acetylated and subjected to aza-Michael addition using propargylamine. The resulting alkylamino compounds were then used in ‘Click reactions’ to form the targeted AZT-conjugates in moderate to excellent yield. In silico docking of computer modelled AZT-conjugates into the HIV-1 integrase and reverse transcriptase enzyme-active sites and potential hydrogen-bonding interaction with active-site amino acid residues were identified. The electrospray MS fragmentations of the AZT and the novel AZT-conjugates were also investigated and common fragmentation pathways were identified.
- Full Text:
- Date Issued: 2013
A marine chemical ecology study of the sea hare, Bursatella leachii in South Africa
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: D'Souza, Nicole
- Date: 2013 , 2013-03-22
- Subjects: Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4283 , http://hdl.handle.net/10962/d1002952 , Sea hares (Mollusks) -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Ecology -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Behavior -- South Africa -- Kenton-on-Sea , Sea hares (Mollusks) -- Defenses -- Behavior -- South Africa -- Kenton-on-Sea
- Description: The large cosmopolitan sea hare Bursatella leachii is a common resident in Eastern Cape river mouths during summer and late autumn where they congregate in beds of Zostera capensis to breed. In this thesis, the previously known toxic formamide marine secondary metabolite (-)-bursatellin (2.2), which may deter predators of South African specimens of the globally distributed sea hare Bursatella leachii, was isolated and identified (Chapter 2). There have been no previous chemical ecology studies of B. leachii and the latter half of this thesis is devoted to chemical ecology studies of this organism. Interestingly, the isolation of the (-)-diastereomer of 2.2 from specimens of B. leachii collected from the Kariega River mouth (near Kenton-on-Sea) suggests that the South African specimens of this species are similar to specimens collected from Puerto Rico and from the Mediterranean Sea. Two different chromatographic techniques for isolating 2.2 were compared in order to maximize the amount of 2.2 isolated from the Kariega River mouth sea hares. The doubling of selected resonances observed in both the ¹H and ¹³C NMR spectra of the bursatellin isolated in this study suggest one of three possibilities; either firstly, the presence of closely related compound(s), secondly, the presence of diastereomers or thirdly the presence of rotamers. Through NMR kinetic studies, we were able to establish that the presence of rotamers was very unlikely due to no change in the relative ratio (3:1) of the ¹H NMR signals with an increase in temperature. Although the attempted synthesis of the acetate derivative (2.28), as a means of separating a diastereomeric mixture was successful, the chromatographic separation of the proposed acetylated diastereomers was not successful. Preparation of the camphanate ester derivatives (e.g. 2.30) proved to be unsuccessful. Five B. leachii specimens were dissected, their organs separated and individually extracted with methanol. The methanol extracts were individually chromatographed on HP-20 media, and the distribution of bursatellin determined by isolation and NMR. It was evident from this investigation that the distribution of 2.2 within individual B. leachii specimens was found to be highest within the B. leachii ink gland. The lower amounts of 2.2 contained in the digestive system, relative to other organs, was hypothesized to occur because 2.2 is sequestered from the diet of the sea hare and efficiently moved from the gut to various organs around the body where it is stored. The absence of 2.2 from the skin was surprising and may be a result of a smaller mass of skin relative to other organs coupled with the limitations of the chromatographic separation techniques employed. Surprisingly, no bursatellin was found within juvenile sea hares. Chapter three discusses the isolation of ilimaquinone (3.1) and pelorol (3.19) from the sponge Hippospongia metachroma and the structure elucidation of each compound using computer modeling to illustrate the conformation. It was deemed necessary to isolate these well known and abundant bioactive marine natural products from a sponge as standard compounds in the bioassays given the paucity of 2.2 available for this study. Chapter four describes the assays used to test the biological activity of the bursatellin 2.2 compared to the generally bioactive ilimaquinone and the structurally related and commercially available broad spectrum antibiotic chloramphenicol. B. leachii, a shell-less marine mollusc inhabits a variety of intertidal habitats and, therefore, is exposed to several different predators, yet does not appear to have any specific predators. Potential predators of this sea hare in the Kariega Estuary could be fish and amphipods which are found in close proximity to these sea hares. Results of the assays showed that at roughly natural concentrations, (calculated from the isolated chromatographic yield) feeding was deterred by the fish and amphipods, which implied that 2.2 may confer a defensive role within the organism. The relatively high concentration present within the ink gland of B. leachii may support this hypothesis. Surprisingly, given its structural similarity to chloramphenicol, 2.3 did not show any antimicrobial action against five of the six bacterial strains against which it was screened [chloramphenicol inhibited the growth of all the bacterial strains at very low concentrations (0.25 mg/mL)]. Bursatellin was found to be only active against Staphylococus aureus at high concentrations ca. 2 mg/mL when compared to chloramphenicol. Neither bursatellin nor chloramphenicol showed anti-fungal activity. Although this study suggests that the sea hares may use chemical defences in addition to opaline ink to defend themselves, they also live within the seagrass Z. capensis, which possibly provides the sea hare with a cryptic form of physical defence against several predators that are unable to swim freely within the weed beds in the littoral zone of the estuary. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
Application of lie group analysis to mathematical models in epidemiology
- Authors: Otieno, Andrew Alex Omondi
- Date: 2013
- Subjects: Epidemiology -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18486 , http://hdl.handle.net/11260/100
- Description: Lie group analysis is arguably the most systematic vehicle for finding exact solutions of differential equations. Using this approach one has at one's disposal a variety of algorithms that make the solution process of many differential equations algorithmic. Vital properties of a given differential equation can often be inferred from the symmetries admitted by the equation. However, Lie group analysis has not enjoyed wide-spread application to systems of first-order ordinary differential equations. This is because such systems typically admit an infinite number of Lie point symmetries, and there is no systematic way to find even a single nontrivial one-dimensional Lie symmetry algebra. In the few applications available, the approach has been to circumvent the problem by transforming a given system of first-order ordinary differential equations into one in which at least one of the equations is of order two or greater. It is therefore fair to say that the full power of Lie group analysis has not been sufficiently harnessed in the solution of systems of first-order ordinary differential equations. In this dissertation we review some applications of Lie group analysis to systems of first order ordinary differential equations. We shed light on the integration procedure for first-order systems of ordinary differential equations admitting a solvable Lie algebra. We do this via instructive examples drawn from mathematical epidemiology models. In particular we revisit the work of Nucci and Torrisi [54] and improve the exposition of the Lie-symmetry-inspired solution of a mathematical model which describes a HIV transmission. To aid implementation of the integration strategy for systems of ordinary differential equations, we have developed ad-hoc routines for finding particular types of admitted symmetries and checking if a given symmetry is indeed admitted by a system of ordinary differential equations.
- Full Text:
- Date Issued: 2013
- Authors: Otieno, Andrew Alex Omondi
- Date: 2013
- Subjects: Epidemiology -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:18486 , http://hdl.handle.net/11260/100
- Description: Lie group analysis is arguably the most systematic vehicle for finding exact solutions of differential equations. Using this approach one has at one's disposal a variety of algorithms that make the solution process of many differential equations algorithmic. Vital properties of a given differential equation can often be inferred from the symmetries admitted by the equation. However, Lie group analysis has not enjoyed wide-spread application to systems of first-order ordinary differential equations. This is because such systems typically admit an infinite number of Lie point symmetries, and there is no systematic way to find even a single nontrivial one-dimensional Lie symmetry algebra. In the few applications available, the approach has been to circumvent the problem by transforming a given system of first-order ordinary differential equations into one in which at least one of the equations is of order two or greater. It is therefore fair to say that the full power of Lie group analysis has not been sufficiently harnessed in the solution of systems of first-order ordinary differential equations. In this dissertation we review some applications of Lie group analysis to systems of first order ordinary differential equations. We shed light on the integration procedure for first-order systems of ordinary differential equations admitting a solvable Lie algebra. We do this via instructive examples drawn from mathematical epidemiology models. In particular we revisit the work of Nucci and Torrisi [54] and improve the exposition of the Lie-symmetry-inspired solution of a mathematical model which describes a HIV transmission. To aid implementation of the integration strategy for systems of ordinary differential equations, we have developed ad-hoc routines for finding particular types of admitted symmetries and checking if a given symmetry is indeed admitted by a system of ordinary differential equations.
- Full Text:
- Date Issued: 2013
Budget control analysis of logistics companies in Port Elizabeth
- Authors: Phipps, Kaaren Maree
- Date: 2013
- Subjects: Budget -- South Africa -- Port Elizabeth , Budget baselines -- South Africa -- Port Elizabeth , Budget process -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:8946 , http://hdl.handle.net/10948/d1021027
- Description: The treatise analyses the issues around budgets and examines budget expenditure control procedures. The research method selected has been formulated from the research onion process (Saunders, Lewis and Thornhill 2009). This methodology first identifies the research approach, research strategy, timelines and data collection methods. As part of the research process, a quantitative approach has been taken and a survey was carried out in relation to the collection of quantitative data for the purposes of the treatise research. The final analysis of the survey results is reflected in the conclusion of the research findings. Budget expenditure control procedures provide a company with a method of control for managing actual spending against the budget. Most companies have a refined practice of budget preparation, and in the larger companies, these are implemented across all departments and carried out by respective managers. Once the budget is in place, it is the responsibility of the managers to ensure that those having expenditure authorisation adhere to it. If control procedures are well managed, this allows for improved efficiency in operations and can lead to benefits in budget performance. Control procedures that are inefficient and poorly managed will inhibit budget objectives being achieved. The control procedures for budget expenditure can be formulated and applied to optimise budget performance and to control budget variance. Formal budget expenditure control procedures, as part of a company’s budget strategy, can provide managers with an effective business tool that improves current budget spending control procedures. This will then result in the identification of potential efficiency gains and improve budget performance.
- Full Text:
- Date Issued: 2013
- Authors: Phipps, Kaaren Maree
- Date: 2013
- Subjects: Budget -- South Africa -- Port Elizabeth , Budget baselines -- South Africa -- Port Elizabeth , Budget process -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:8946 , http://hdl.handle.net/10948/d1021027
- Description: The treatise analyses the issues around budgets and examines budget expenditure control procedures. The research method selected has been formulated from the research onion process (Saunders, Lewis and Thornhill 2009). This methodology first identifies the research approach, research strategy, timelines and data collection methods. As part of the research process, a quantitative approach has been taken and a survey was carried out in relation to the collection of quantitative data for the purposes of the treatise research. The final analysis of the survey results is reflected in the conclusion of the research findings. Budget expenditure control procedures provide a company with a method of control for managing actual spending against the budget. Most companies have a refined practice of budget preparation, and in the larger companies, these are implemented across all departments and carried out by respective managers. Once the budget is in place, it is the responsibility of the managers to ensure that those having expenditure authorisation adhere to it. If control procedures are well managed, this allows for improved efficiency in operations and can lead to benefits in budget performance. Control procedures that are inefficient and poorly managed will inhibit budget objectives being achieved. The control procedures for budget expenditure can be formulated and applied to optimise budget performance and to control budget variance. Formal budget expenditure control procedures, as part of a company’s budget strategy, can provide managers with an effective business tool that improves current budget spending control procedures. This will then result in the identification of potential efficiency gains and improve budget performance.
- Full Text:
- Date Issued: 2013
A Comparative study of two copper(II) based metal-organic frameworks : Cu2¼(OH)½B4C•8H2O and Cu2Na(OH)B4C•7H2O
- Authors: Coombes, Matthew
- Date: 2013
- Subjects: Copper , Organometallic compounds , Supramolecular organometallic chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4533 , http://hdl.handle.net/10962/d1016245
- Description: This study focussed on two copper(II)-containing metal-organic frameworks (MOFs): Cu2Na(OH)B4C•7H2O and Cu2¼(OH)½B4C•8H2O (B4C = 1,2,4,5- benzenetetracarboxylate). They are both covalent, three-dimensional metalorganic framework polymers containing voids filled with water molecules. Both were characterised by elemental analysis, infrared spectroscopy, X-ray powder diffractometry (both in situ and regular), thermogravimetric analysis, differential scanning calorimetry and X-ray photoelectron spectroscopy. These two MOFs are essentially identical, with the only difference being the substitution of sodium by copper at every 4th site (disordered throughout the crystal). The guest inclusion properties of both MOFs were studied and compared. Although both structures collapse on dehydration, it was observed that Cu2Na(OH)B4C•7H2O is able to take up signifcant amounts of water, methanol and ethanol. All these processes are fully reversible. Car-Parrinello molecular dynamics studies suggest that it is a strong interaction between the oxygen atoms on these molecules with the sodium cation of the MOF that is responsible for this signifcant uptake. In contrast, Cu2¼ (OH)½ B4C•8H2O, the MOF without a sodium cation, did not demonstrate any methanol or ethanol uptake, but was able to take up some water. The uptake of water, however, is not a fully reversible process. The absence of sodium likely results in insuffcient energy to draw methanol and ethanol into the framework, while a subtle rotation of a carboxylate group on dehydration decreases the ability of the framework to form hydrogen bonds, thus reducing the ability to take up water. A series of hydrothermal syntheses were performed in order to develop a method of synthesis superior to the current gel-based synthesis that requires several months and has poor yields. The hydrothermal products were characterized by elemental analysis, infrared spectroscopy, X-ray powder diffractometry, thermogravimetric analysis and differential scanning calorimetry. It was shown that the MOF Cu2Na(OH)B4C•7H2O may be synthesised in almost 100% yield by using a temperature of 120°C over a period of 72 hours. It was not possible to synthesise Cu2¼ (OH)½ B4C•8H2O in a 100% yield - it was only obtained as a minor product.
- Full Text:
- Date Issued: 2013
- Authors: Coombes, Matthew
- Date: 2013
- Subjects: Copper , Organometallic compounds , Supramolecular organometallic chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4533 , http://hdl.handle.net/10962/d1016245
- Description: This study focussed on two copper(II)-containing metal-organic frameworks (MOFs): Cu2Na(OH)B4C•7H2O and Cu2¼(OH)½B4C•8H2O (B4C = 1,2,4,5- benzenetetracarboxylate). They are both covalent, three-dimensional metalorganic framework polymers containing voids filled with water molecules. Both were characterised by elemental analysis, infrared spectroscopy, X-ray powder diffractometry (both in situ and regular), thermogravimetric analysis, differential scanning calorimetry and X-ray photoelectron spectroscopy. These two MOFs are essentially identical, with the only difference being the substitution of sodium by copper at every 4th site (disordered throughout the crystal). The guest inclusion properties of both MOFs were studied and compared. Although both structures collapse on dehydration, it was observed that Cu2Na(OH)B4C•7H2O is able to take up signifcant amounts of water, methanol and ethanol. All these processes are fully reversible. Car-Parrinello molecular dynamics studies suggest that it is a strong interaction between the oxygen atoms on these molecules with the sodium cation of the MOF that is responsible for this signifcant uptake. In contrast, Cu2¼ (OH)½ B4C•8H2O, the MOF without a sodium cation, did not demonstrate any methanol or ethanol uptake, but was able to take up some water. The uptake of water, however, is not a fully reversible process. The absence of sodium likely results in insuffcient energy to draw methanol and ethanol into the framework, while a subtle rotation of a carboxylate group on dehydration decreases the ability of the framework to form hydrogen bonds, thus reducing the ability to take up water. A series of hydrothermal syntheses were performed in order to develop a method of synthesis superior to the current gel-based synthesis that requires several months and has poor yields. The hydrothermal products were characterized by elemental analysis, infrared spectroscopy, X-ray powder diffractometry, thermogravimetric analysis and differential scanning calorimetry. It was shown that the MOF Cu2Na(OH)B4C•7H2O may be synthesised in almost 100% yield by using a temperature of 120°C over a period of 72 hours. It was not possible to synthesise Cu2¼ (OH)½ B4C•8H2O in a 100% yield - it was only obtained as a minor product.
- Full Text:
- Date Issued: 2013
Assessing the entrepreneurial attributes of undergraduate business students at Nelson Mandela Metropolitan University
- Authors: Saunders, Shelley
- Date: 2013
- Subjects: Entrepreneurship -- South Africa -- Port Elizabeth , Business students -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9316 , http://hdl.handle.net/10948/d1020129
- Description: To improve and develop South Africa’s entrepreneurial activity, it is vital that the population acquires certain attributes which are common among individuals who exhibit entrepreneurial behaviour. As the occurrence of entrepreneurial attributes increases in the population, so too will the probability of entrepreneurial behaviour and entrepreneurial activity. A possible first step in ensuring that a population possesses the necessary attributes is to assess the current levels of development of these entrepreneurial attributes among students of business. Underdeveloped attributes can then be identified, and steps taken to bring about improvements. The primary objective of this study was to assess the entrepreneurial attributes of undergraduate business students at the Nelson Mandela Metropolitan University. In order to achieve this objective an in-depth analysis of secondary sources was conducted. The nature of entrepreneurship was defined and its importance highlighted. Furthermore, the status of entrepreneurship both globally and nationally was elaborated on. Entrepreneurship education was also addressed, and its role in developing entrepreneurial attributes was discussed. The 16 entrepreneurial attributes associated with successful entrepreneurs were described. The most commonly used intentions-based models were also discussed. In line with the intentions-based theories, the greater the perception of possessing the attributes associated with a successful entrepreneur by an individual, the greater the belief by that individual that he or she has the capacity and competence to become an entrepreneur, which in turn will influence their entrepreneurial intentions. Against the background of the literature overview, several hypotheses were formulated and subjected to empirical testing. A quantitative research approach was selected, the sample consisting of all undergraduate business students studying at three South African universities as well as two international universities. Convenience sampling was implemented in this study. The validity of the measuring instrument was determined by means of a factor analysis, and the reliability by means of calculating Cronbach alpha coefficients. The statistical techniques used to analyse the data included calculating descriptive statistics (the mean, standard deviation and frequency distributions), t-tests and Cohen’s d, a multivariate analysis of variance (MANOVA), an analysis of variance (ANOVA), Chi-squared statistic, and Cramer’s V. The results of the study show that NMMU students regarded the attributes Commitment, High energy level, Planning and perseverance and Overcoming failure as the four most-developed attributes, while they regarded Continuous learning, Knowledge-seeking, Initiative and responsibility and Communication ability as the least-developed. With the exception of the attributes Commitment and Overcoming failure, the level of development of the entrepreneurial attributes of NMMU students showed significant improvement between the 2001 and the 2010 studies. With the exception of Continuous learning, no significant differences were reported in the levels of development of the various entrepreneurial attributes between students at NMMU and students at the other South African universities participating in the study. When comparing the significant differences in the level of development of the 16 entrepreneurial attributes between NMMU and the international universities, a large practical significance was found for the attributes High energy level, Continuous learning and Knowledge seeking. For the attributes Planning and perseverance, Communication ability, Overcoming failure, Initiative and responsibility, High energy level, Creativity and flexibility, Knowledge seeking, Continuous learning, Financial proficiency and Business knowledge, students with entrepreneurial intentions reported significantly higher mean scores than students without entrepreneurial intentions. In other words, students with higher levels of development of these attributes are more likely to have entrepreneurial intentions. It was also found that significant differences in the levels of development of entrepreneurial attributes were reported for the demographic variables Levels of study, Gender and Age. No significant differences were found to exist between the demographic variables Level of study, Gender and Self-employment status of parents and the Entrepreneurial intention of NMMU students. This study has contributed to the field of entrepreneurship research by identifying several entrepreneurial attributes that are more likely to be found in students with entrepreneurial intentions than those without them. This study has also shown that certain demographic factors are related to the levels of development of certain entrepreneurial attributes, as well as to entrepreneurial intentions. Furthermore, through the assessment of entrepreneurial attributes of NMMU students and by making comparisons with other universities, this study has contributed to entrepreneurship education at NMMU as well as to entrepreneurship education in South Africa and abroad. Educators of entrepreneurship have been given insights into the levels of development of several entrepreneurial attributes among their students. In addition, recommendations have been made on how to improve the levels of development of the attributes investigated in this study.
- Full Text:
- Date Issued: 2013
- Authors: Saunders, Shelley
- Date: 2013
- Subjects: Entrepreneurship -- South Africa -- Port Elizabeth , Business students -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:9316 , http://hdl.handle.net/10948/d1020129
- Description: To improve and develop South Africa’s entrepreneurial activity, it is vital that the population acquires certain attributes which are common among individuals who exhibit entrepreneurial behaviour. As the occurrence of entrepreneurial attributes increases in the population, so too will the probability of entrepreneurial behaviour and entrepreneurial activity. A possible first step in ensuring that a population possesses the necessary attributes is to assess the current levels of development of these entrepreneurial attributes among students of business. Underdeveloped attributes can then be identified, and steps taken to bring about improvements. The primary objective of this study was to assess the entrepreneurial attributes of undergraduate business students at the Nelson Mandela Metropolitan University. In order to achieve this objective an in-depth analysis of secondary sources was conducted. The nature of entrepreneurship was defined and its importance highlighted. Furthermore, the status of entrepreneurship both globally and nationally was elaborated on. Entrepreneurship education was also addressed, and its role in developing entrepreneurial attributes was discussed. The 16 entrepreneurial attributes associated with successful entrepreneurs were described. The most commonly used intentions-based models were also discussed. In line with the intentions-based theories, the greater the perception of possessing the attributes associated with a successful entrepreneur by an individual, the greater the belief by that individual that he or she has the capacity and competence to become an entrepreneur, which in turn will influence their entrepreneurial intentions. Against the background of the literature overview, several hypotheses were formulated and subjected to empirical testing. A quantitative research approach was selected, the sample consisting of all undergraduate business students studying at three South African universities as well as two international universities. Convenience sampling was implemented in this study. The validity of the measuring instrument was determined by means of a factor analysis, and the reliability by means of calculating Cronbach alpha coefficients. The statistical techniques used to analyse the data included calculating descriptive statistics (the mean, standard deviation and frequency distributions), t-tests and Cohen’s d, a multivariate analysis of variance (MANOVA), an analysis of variance (ANOVA), Chi-squared statistic, and Cramer’s V. The results of the study show that NMMU students regarded the attributes Commitment, High energy level, Planning and perseverance and Overcoming failure as the four most-developed attributes, while they regarded Continuous learning, Knowledge-seeking, Initiative and responsibility and Communication ability as the least-developed. With the exception of the attributes Commitment and Overcoming failure, the level of development of the entrepreneurial attributes of NMMU students showed significant improvement between the 2001 and the 2010 studies. With the exception of Continuous learning, no significant differences were reported in the levels of development of the various entrepreneurial attributes between students at NMMU and students at the other South African universities participating in the study. When comparing the significant differences in the level of development of the 16 entrepreneurial attributes between NMMU and the international universities, a large practical significance was found for the attributes High energy level, Continuous learning and Knowledge seeking. For the attributes Planning and perseverance, Communication ability, Overcoming failure, Initiative and responsibility, High energy level, Creativity and flexibility, Knowledge seeking, Continuous learning, Financial proficiency and Business knowledge, students with entrepreneurial intentions reported significantly higher mean scores than students without entrepreneurial intentions. In other words, students with higher levels of development of these attributes are more likely to have entrepreneurial intentions. It was also found that significant differences in the levels of development of entrepreneurial attributes were reported for the demographic variables Levels of study, Gender and Age. No significant differences were found to exist between the demographic variables Level of study, Gender and Self-employment status of parents and the Entrepreneurial intention of NMMU students. This study has contributed to the field of entrepreneurship research by identifying several entrepreneurial attributes that are more likely to be found in students with entrepreneurial intentions than those without them. This study has also shown that certain demographic factors are related to the levels of development of certain entrepreneurial attributes, as well as to entrepreneurial intentions. Furthermore, through the assessment of entrepreneurial attributes of NMMU students and by making comparisons with other universities, this study has contributed to entrepreneurship education at NMMU as well as to entrepreneurship education in South Africa and abroad. Educators of entrepreneurship have been given insights into the levels of development of several entrepreneurial attributes among their students. In addition, recommendations have been made on how to improve the levels of development of the attributes investigated in this study.
- Full Text:
- Date Issued: 2013
Contributions of inshore and offshore sources of primary production to the foodweb, and the trophic connectivity between various habitats along a depth-gradient, in Sodwana Bay, Kwazulu-Natal, South Africa
- Authors: Parkinson, Matthew Cameron
- Date: 2013
- Subjects: Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5179 , http://hdl.handle.net/10962/d1001630 , Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
- Description: Sodwana Bay, situated within the iSimangaliso Wetland Park, is ecologically important as it contains high-latitude corals and the most southerly known population of coelacanths. This thesis utilised stable isotope and lipid analyses to investigate the trophic ecology of the area, in particular, understanding the relative contribution of inshore and offshore primary production to consumers inhabiting intertidal and shallow subtidal, coral reef, deep reef, canyon head and pelagic habitats. Seaweeds, excluding certain species of red seaweeds with highly depleted carbon signatures, and phytoplankton, such as diatoms, were found to be the principal sources of primary production for all consumers. Offshore production was typified by dinoflagellates. Particulate organic matter (POM) was spatio-temporally variable. Three distinct productivity periods related to nutrient cycling were noted with enriched carbon signatures and higher organic matter loads associated with warmer water. Inshore primary production was an important source of carbon to consumers in all habitats with the exception of zooplankton that were more reliant on pelagic primary production. Benthic invertebrates reflected a gradient in the utilisation of inshore production, due to the reduced availability of this source further offshore. Consumers at the furthest sites offshore were found to include a substantial quantity of inshore-derived production in their diets. Fishes, which are more mobile, were found to incorporate a similar proportion of inshore production into their diets regardless of where they were collected from.
- Full Text:
- Date Issued: 2013
- Authors: Parkinson, Matthew Cameron
- Date: 2013
- Subjects: Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5179 , http://hdl.handle.net/10962/d1001630 , Marine ecology -- South Africa -- Sodwana Bay , Food chains (Ecology) -- South Africa -- Sodwana Bay , Coastal ecology -- South Africa -- Sodwana Bay , Stable isotopes , Dinoflagellates , Marine algae
- Description: Sodwana Bay, situated within the iSimangaliso Wetland Park, is ecologically important as it contains high-latitude corals and the most southerly known population of coelacanths. This thesis utilised stable isotope and lipid analyses to investigate the trophic ecology of the area, in particular, understanding the relative contribution of inshore and offshore primary production to consumers inhabiting intertidal and shallow subtidal, coral reef, deep reef, canyon head and pelagic habitats. Seaweeds, excluding certain species of red seaweeds with highly depleted carbon signatures, and phytoplankton, such as diatoms, were found to be the principal sources of primary production for all consumers. Offshore production was typified by dinoflagellates. Particulate organic matter (POM) was spatio-temporally variable. Three distinct productivity periods related to nutrient cycling were noted with enriched carbon signatures and higher organic matter loads associated with warmer water. Inshore primary production was an important source of carbon to consumers in all habitats with the exception of zooplankton that were more reliant on pelagic primary production. Benthic invertebrates reflected a gradient in the utilisation of inshore production, due to the reduced availability of this source further offshore. Consumers at the furthest sites offshore were found to include a substantial quantity of inshore-derived production in their diets. Fishes, which are more mobile, were found to incorporate a similar proportion of inshore production into their diets regardless of where they were collected from.
- Full Text:
- Date Issued: 2013