Restitution : seeing past loss and abandonment
- Authors: Greenway, Paul Wayne
- Date: 2013
- Subjects: Digitally printed materials Bereavement in art
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2389 , http://hdl.handle.net/10962/d1001579
- Description: This dissertation is concerned with loss and abandonment, and together with the practical component, titled Restitution, forms part of a Master of Fine Art degree submission. Both loss and abandonment can take many forms, from the straightforward deterioration, departure or removal of objects to the more complex deterioration of memory, responsibility and dignity. It seems though, that the question, “What has been lost?” is one that is always asked once it is too late. The loss becomes irretrievable and one is left only with fragments and traces. In Chapter 1 issues of liminality and the precariousness of being between states is addressed. Dignity of the ‘other’, in this case the deceased pauper, is interrogated especially with reference to complicity, forensic investigation and the forensic aesthetic. Chapter 2 outlines photographic representation, with attention given to posthumous portraiture, the punctum and memory in the service of permanence and authenticity. Chapter 3 considers the ambition and purpose of the artist through a critique centred on contemporary photographic artist, Sally Mann. Throughout the thesis and exhibition, I am concerned with loss as it relates physically to objects. Metaphorically, I investigate loss and abandonment in relation to dignity and responsibility. In so doing I view death as being the ultimate form of loss, as there is physical loss of the body, as one part of the whole that makes up ‘the person’, as well as the psychological and emotional loss that attends the passing of life. The delayed burial of the deceased therefore is seen to be evidence of abandonment at its extreme. I end by positioning my conclusion around a stop animation series in which I dug a grave and buried a pauper at Mayfield cemetery.
- Full Text:
- Date Issued: 2013
- Authors: Greenway, Paul Wayne
- Date: 2013
- Subjects: Digitally printed materials Bereavement in art
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2389 , http://hdl.handle.net/10962/d1001579
- Description: This dissertation is concerned with loss and abandonment, and together with the practical component, titled Restitution, forms part of a Master of Fine Art degree submission. Both loss and abandonment can take many forms, from the straightforward deterioration, departure or removal of objects to the more complex deterioration of memory, responsibility and dignity. It seems though, that the question, “What has been lost?” is one that is always asked once it is too late. The loss becomes irretrievable and one is left only with fragments and traces. In Chapter 1 issues of liminality and the precariousness of being between states is addressed. Dignity of the ‘other’, in this case the deceased pauper, is interrogated especially with reference to complicity, forensic investigation and the forensic aesthetic. Chapter 2 outlines photographic representation, with attention given to posthumous portraiture, the punctum and memory in the service of permanence and authenticity. Chapter 3 considers the ambition and purpose of the artist through a critique centred on contemporary photographic artist, Sally Mann. Throughout the thesis and exhibition, I am concerned with loss as it relates physically to objects. Metaphorically, I investigate loss and abandonment in relation to dignity and responsibility. In so doing I view death as being the ultimate form of loss, as there is physical loss of the body, as one part of the whole that makes up ‘the person’, as well as the psychological and emotional loss that attends the passing of life. The delayed burial of the deceased therefore is seen to be evidence of abandonment at its extreme. I end by positioning my conclusion around a stop animation series in which I dug a grave and buried a pauper at Mayfield cemetery.
- 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
Reflections on the appropriate use of unjustly conferred privilege:
- Authors: Matthews, Sally
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142714 , vital:38104 , DOI: 10.3167/th.2013.6013502
- Description: What ought beneficiaries of injustice to do with the privileges unjustly conferred upon them? This article examines how those who have been privileged as a consequence of injustice can best contribute to struggles for justice. In particular, I ask whether we ought to renounce privileges which have been unjustly conferred, or whether it may be better to use such privileges in ways that help bring about justice. The article engages in particular with feminist literature on the topic of privilege, building on arguments provided in this literature to argue that in many cases the best contribution the privileged can make to struggles for justice, is to use unjustly conferred privileges in a way that ultimately undermines the unjust systems and structures that conferred them. I tentatively outline some ways in which the privileged can develop the sensibilities which will allow them to use their privilege in this way.
- Full Text:
- Date Issued: 2013
- Authors: Matthews, Sally
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142714 , vital:38104 , DOI: 10.3167/th.2013.6013502
- Description: What ought beneficiaries of injustice to do with the privileges unjustly conferred upon them? This article examines how those who have been privileged as a consequence of injustice can best contribute to struggles for justice. In particular, I ask whether we ought to renounce privileges which have been unjustly conferred, or whether it may be better to use such privileges in ways that help bring about justice. The article engages in particular with feminist literature on the topic of privilege, building on arguments provided in this literature to argue that in many cases the best contribution the privileged can make to struggles for justice, is to use unjustly conferred privileges in a way that ultimately undermines the unjust systems and structures that conferred them. I tentatively outline some ways in which the privileged can develop the sensibilities which will allow them to use their privilege in this way.
- Full Text:
- Date Issued: 2013
Reflections on the appropriate use of unjustly conferred privilege:
- Authors: Matthews, Sally
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142314 , vital:38068 , DOI: 10.3167/th.2013.6013502
- Description: What ought beneficiaries of injustice to do with the privileges unjustly conferred upon them? This article examines how those who have been privileged as a consequence of injustice can best contribute to struggles for justice. In particular, I ask whether we ought to renounce privileges which have been unjustly conferred, or whether it may be better to use such privileges in ways that help bring about justice. The article engages in particular with feminist literature on the topic of privilege, building on arguments provided in this literature to argue that in many cases the best contribution the privileged can make to struggles for justice, is to use unjustly conferred privileges in a way that ultimately undermines the unjust systems and structures that conferred them. I tentatively outline some ways in which the privileged can develop the sensibilities which will allow them to use their privilege in this way.
- Full Text:
- Date Issued: 2013
- Authors: Matthews, Sally
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/142314 , vital:38068 , DOI: 10.3167/th.2013.6013502
- Description: What ought beneficiaries of injustice to do with the privileges unjustly conferred upon them? This article examines how those who have been privileged as a consequence of injustice can best contribute to struggles for justice. In particular, I ask whether we ought to renounce privileges which have been unjustly conferred, or whether it may be better to use such privileges in ways that help bring about justice. The article engages in particular with feminist literature on the topic of privilege, building on arguments provided in this literature to argue that in many cases the best contribution the privileged can make to struggles for justice, is to use unjustly conferred privileges in a way that ultimately undermines the unjust systems and structures that conferred them. I tentatively outline some ways in which the privileged can develop the sensibilities which will allow them to use their privilege in this way.
- 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
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
The screening and characterisation of compounds for modulators of heat shock protein (Hsp90) in a breast cancer cell model
- Authors: Moyo, Buhle
- Date: 2013 , 2013-07-18
- Subjects: Heat shock proteins Breast -- Cancer Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Treatment Cancer cells Naphthoquinone PQQ (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4060 , http://hdl.handle.net/10962/d1004129
- Description: Breast cancer is a leading cause of cancer death in Africa. Hsp90 has been identified as a target for anti-cancer treatments as its inhibition results in the disruption and ubiquitin–proteasome degradation of activated oncoproteins. Currently, there are no US Food and Drug Administration approved Hsp90 inhibitor drugs and existing Hsp90 inhibitors such as geldanamycin and novobiocin are hepatotoxic and display a low affinity for Hsp90, respectively. Therefore, there is a need for the development of Hsp90 inhibitors with improved inhibitory properties. In this study twelve natural compounds bearing a quinone nucleus were screened and characterised for the modulation of Hsp90. The compounds analysed formed three series; the sargaquinoic acid (SQA), naphthoquinone, and pyrroloiminoquinone alkaloid series. Certain compounds exhibited half maximal inhibitory concentrations of between 3.32 μM and 12.4 μM, while others showed no antiproliferative activity at concentrations of up to 500 μM in the MDA-MB-231 breast adenocarcinoma cell line. Immunofluorescence and Western analyses indicated that the modulation of Hsp90 and partner proteins by SQA was more similar to that of novobiocin. Isothermal titration calorimetry analyses suggested that SQA interacted with Hsp90β with a low affinity, and saturation-transfer difference nuclear magnetic resonance confirmed that this interaction with Hsp90β occurred through the methyl moiety bound to 1, 4 benzoquinone of SQA. Pulldown assays indicated SQA disrupted the association between Hsp90 and Hop dose-dependently, more similarly to novobiocin. Immunofluorescence and Western analyses performed on naphthoquinone and pyrroloiminoquinone alkaloid compounds indicated modulation of Hsp90 and Hsp90 partner proteins by the compounds. Naphthoquinone compounds were prioritised for analysis for binding to Hsp90β over the pyrroloiminoquinone alkaloid compounds. Lapachol interacted with Hsp90β with a low affinity however; this interaction was thought to be too weak to disrupt the association of Hsp90 and Hop. The remaining naphthoquinone compounds showed no interaction with Hsp90β, thus allowing the determination of a preliminary structure-activity relationship for these compounds. To the best of our knowledge, this is the first study to describe a systematic subcellular analysis of the effects of geldanamycin and novobiocin in comparison to sargaquinoic acid and compounds of the naphthoquinone and pyrroloquinoline scaffold on Hsp90 and its partner proteins. , Microsoft� Word 2010 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: Moyo, Buhle
- Date: 2013 , 2013-07-18
- Subjects: Heat shock proteins Breast -- Cancer Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Treatment Cancer cells Naphthoquinone PQQ (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4060 , http://hdl.handle.net/10962/d1004129
- Description: Breast cancer is a leading cause of cancer death in Africa. Hsp90 has been identified as a target for anti-cancer treatments as its inhibition results in the disruption and ubiquitin–proteasome degradation of activated oncoproteins. Currently, there are no US Food and Drug Administration approved Hsp90 inhibitor drugs and existing Hsp90 inhibitors such as geldanamycin and novobiocin are hepatotoxic and display a low affinity for Hsp90, respectively. Therefore, there is a need for the development of Hsp90 inhibitors with improved inhibitory properties. In this study twelve natural compounds bearing a quinone nucleus were screened and characterised for the modulation of Hsp90. The compounds analysed formed three series; the sargaquinoic acid (SQA), naphthoquinone, and pyrroloiminoquinone alkaloid series. Certain compounds exhibited half maximal inhibitory concentrations of between 3.32 μM and 12.4 μM, while others showed no antiproliferative activity at concentrations of up to 500 μM in the MDA-MB-231 breast adenocarcinoma cell line. Immunofluorescence and Western analyses indicated that the modulation of Hsp90 and partner proteins by SQA was more similar to that of novobiocin. Isothermal titration calorimetry analyses suggested that SQA interacted with Hsp90β with a low affinity, and saturation-transfer difference nuclear magnetic resonance confirmed that this interaction with Hsp90β occurred through the methyl moiety bound to 1, 4 benzoquinone of SQA. Pulldown assays indicated SQA disrupted the association between Hsp90 and Hop dose-dependently, more similarly to novobiocin. Immunofluorescence and Western analyses performed on naphthoquinone and pyrroloiminoquinone alkaloid compounds indicated modulation of Hsp90 and Hsp90 partner proteins by the compounds. Naphthoquinone compounds were prioritised for analysis for binding to Hsp90β over the pyrroloiminoquinone alkaloid compounds. Lapachol interacted with Hsp90β with a low affinity however; this interaction was thought to be too weak to disrupt the association of Hsp90 and Hop. The remaining naphthoquinone compounds showed no interaction with Hsp90β, thus allowing the determination of a preliminary structure-activity relationship for these compounds. To the best of our knowledge, this is the first study to describe a systematic subcellular analysis of the effects of geldanamycin and novobiocin in comparison to sargaquinoic acid and compounds of the naphthoquinone and pyrroloquinoline scaffold on Hsp90 and its partner proteins. , Microsoft� Word 2010 , Adobe Acrobat 9.54 Paper Capture Plug-in
- 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
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
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
An investigation into control mechanisms of driving performance : resource depletion and effort-regulation
- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
- Full Text:
- Date Issued: 2013
- Authors: Louw, Tyron Linton
- Date: 2013
- Subjects: Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5101 , http://hdl.handle.net/10962/d1001842 , Automobile driving simulators , Automobile driving -- Psychological aspects , Automobile driving -- Physiological aspects , Traffic accidents , Traffic safety , Fatigue
- Description: Driver fatigue is a complex phenomenon that has a range of causal factors including sleeprelated and task-related factors. These manifest as different safety and performance outcomes. Extensive research has been applied to linking these factors to performance impairment. However, little research focuses on the mechanisms by which this link exists. This research project therefore focuses on the processes underlying how driving performance is controlled and maintained during the development on non-sleep-related driver fatigue. The main aim was to establish whether progressive impairment of driving control over a prolonged drive could be attributed to a depletion of attentional resources, as proposed by Resource Theory, or to a withdrawal of effort, as proposed by Effort-Regulation Theory. As a multicomponent skill, driving requires perception, cognition and motor output. The secondary aim of this research was therefore to assess whether a prolonged drive impairs stage-specific information processing. Participants (n=24) in three experimental groups performed a 90-minute simulated drive wherein they were expected to keep the bonnet of a car on a lane (tracking task). The three groups differed in terms of lane width: small, medium and large, corresponding to low, medium, and high task-demand, respectively. To assess the impacts of this task on stagespecific information processing, participants performed a set of resource specific tests before and after the prolonged drive. Each task had two difficulty variations to ensure that performance decrement was due not only to the task-characteristic, but specifically to resource depletion. The tests probing information processing were: a modified Fitts' tapping task for motor programming, a digit recall task for perception, and an object recognition reading task for cognition. Performance was measured as lateral deviation of the car. Physiological measures included heart rate frequency (HR) and various time- and frequencydomain heart rate variability (HRV) parameters, eye blink frequency and duration. The Borg CR-10 scale was used to evaluate subjective effort and fatigue during the task. Driving control declined over time and was supplemented by HR, HRV, blink frequency and duration, indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Driving control declined to a greater extent in the large road width group and reflected a lower parasympathetic activity, whereas the inverse was observed for the small road width group. Resource tests reveal a non-specific impairment of information processing following the prolonged drive. However, this was accompanied by an increase in parasympathetic activity. Overall, results indicate that Effort-Regulation Theory better accounts for the impairment of driving control in prolonged driving than does Resource Theory. This suggests that the impact of fatigue is guided more by task goals and intrinsic motivation than by the manner in which the fatigue state developed. Moreover, performance impairment by effort-regulation is dependant more on time on task than on task-demand
- 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
Afro-communitarianism and the nature of reconciliation
- Authors: Oelofsen, Rianna
- Date: 2013
- Subjects: Ubuntu (Philosophy) Reconciliation -- South Africa Communitarianism -- Africa Philosophy, African
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2736 , http://hdl.handle.net/10962/d1006809
- Description: In this dissertation I sketch a conception of personhood as understood from within an Afrocommunitarian worldview, and argue that this understanding of personhood has implications for understanding the concept of reconciliation. Understanding ‘being human’ as a collective, communal enterprise has implications for how responsibility, justice, forgiveness and humanization (all cognate concepts of reconciliation) are conceptualized. In line with this understanding of reconciliation and its cognate concepts, I argue that the humanization of self and other (according to the Afrocommunitarian understanding of personhood) is required for addressing the ‘inferiority’ and concurrent ‘superiority’ racial complexes as diagnosed by Franz Fanon and Steve Biko. These complexes reach deeply within individual and collective psyches and political identities, and I argue that political solutions to protracted conflict (in South Africa and other racially charged contexts) which do not address these deeply entrenched pathologies will be inadequate according to an Afrocommunitarian framework.
- Full Text:
- Date Issued: 2013
- Authors: Oelofsen, Rianna
- Date: 2013
- Subjects: Ubuntu (Philosophy) Reconciliation -- South Africa Communitarianism -- Africa Philosophy, African
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2736 , http://hdl.handle.net/10962/d1006809
- Description: In this dissertation I sketch a conception of personhood as understood from within an Afrocommunitarian worldview, and argue that this understanding of personhood has implications for understanding the concept of reconciliation. Understanding ‘being human’ as a collective, communal enterprise has implications for how responsibility, justice, forgiveness and humanization (all cognate concepts of reconciliation) are conceptualized. In line with this understanding of reconciliation and its cognate concepts, I argue that the humanization of self and other (according to the Afrocommunitarian understanding of personhood) is required for addressing the ‘inferiority’ and concurrent ‘superiority’ racial complexes as diagnosed by Franz Fanon and Steve Biko. These complexes reach deeply within individual and collective psyches and political identities, and I argue that political solutions to protracted conflict (in South Africa and other racially charged contexts) which do not address these deeply entrenched pathologies will be inadequate according to an Afrocommunitarian framework.
- Full Text:
- Date Issued: 2013
Incidence of Staphylococcus species in bovine milk: their antimicrobial sensitivity in selected antibiotics and Usnea barbata lichen extracts
- Idamokoro, Emrobowansan Monday
- Authors: Idamokoro, Emrobowansan Monday
- Date: 2013
- Subjects: Staphylococcus , Microbial sensitivity tests , Traditional medicine , Lichens -- Analysis , Mastitis , Antibiotics in agriculture
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11829 , http://hdl.handle.net/10353/d1016193 , Staphylococcus , Microbial sensitivity tests , Traditional medicine , Lichens -- Analysis , Mastitis , Antibiotics in agriculture
- Description: This study was done in order to assess the incidence of Staphylococcus species from milk of cows with subclinical mastitis and their antimicrobial sensitivity in some selected antibiotics and Usnea barbata lichen extracts. The study was conducted in two different commercial dairy farms. Staphylococcus species isolates were identified using several biochemical tests which included Gram’s staining test, catalase test and oxidase test. A commercial API® staph kit (bioMerieux, France) was used to confirm the bacterial organisms to their species level. The antimicrobial sensitivity of individual species was determined according to the Clinical Laboratory Standard Institute (CLSI) for the selected antibiotics. Agar well diffusion method and the broth micro-dilution technique were used to determine the sensitivity of Staphylococcus species in U. barbata extracts. A total of 467 milk samples were screened for bacterial identification from the two farms. Fifteen different Staphylococcus species isolates were identified from all milk samples that were examined. The most frequently isolated species included Staphylococcus xylosus (54.34%), Staphylococcus hominis (24.78%), Staphylococcus aureus (16.38%), Staphylococcus saprophyticus (16.12%) and Staphylococcus haemolyticus (11.63%). Most Staphylococcus species were resistant to Penicillin (75.35%), Nalidixic acid (72.55%) and Ampicillin (63%). Furthermore, the bacterial sensitivity evaluation of U. barbata lichen extracted with methanol and ethyl-acetate against selected Staphylococcus species isolates showed 92.31% and 53.85% susceptibility, respectively. The minimum inhibitory concentration (MIC) of the methanol and ethyl-acetate extracts ranged between 0.0390 to 10 mg/ml. There was a relatively high incidence of Staphylococcus species identified in milk of cows with subclinical mastitis from both farms. Conversely, Staphylococcus species isolates were resistant to antibiotics (mostly penicillin and ampicillin) commonly used in the farms. Furthermore, the study investigated the antimicrobial sensitivity of U. barbata extract in-vitro which may validate its use in traditional medicine for treatment of cows with mastitis.
- Full Text:
- Date Issued: 2013
- Authors: Idamokoro, Emrobowansan Monday
- Date: 2013
- Subjects: Staphylococcus , Microbial sensitivity tests , Traditional medicine , Lichens -- Analysis , Mastitis , Antibiotics in agriculture
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11829 , http://hdl.handle.net/10353/d1016193 , Staphylococcus , Microbial sensitivity tests , Traditional medicine , Lichens -- Analysis , Mastitis , Antibiotics in agriculture
- Description: This study was done in order to assess the incidence of Staphylococcus species from milk of cows with subclinical mastitis and their antimicrobial sensitivity in some selected antibiotics and Usnea barbata lichen extracts. The study was conducted in two different commercial dairy farms. Staphylococcus species isolates were identified using several biochemical tests which included Gram’s staining test, catalase test and oxidase test. A commercial API® staph kit (bioMerieux, France) was used to confirm the bacterial organisms to their species level. The antimicrobial sensitivity of individual species was determined according to the Clinical Laboratory Standard Institute (CLSI) for the selected antibiotics. Agar well diffusion method and the broth micro-dilution technique were used to determine the sensitivity of Staphylococcus species in U. barbata extracts. A total of 467 milk samples were screened for bacterial identification from the two farms. Fifteen different Staphylococcus species isolates were identified from all milk samples that were examined. The most frequently isolated species included Staphylococcus xylosus (54.34%), Staphylococcus hominis (24.78%), Staphylococcus aureus (16.38%), Staphylococcus saprophyticus (16.12%) and Staphylococcus haemolyticus (11.63%). Most Staphylococcus species were resistant to Penicillin (75.35%), Nalidixic acid (72.55%) and Ampicillin (63%). Furthermore, the bacterial sensitivity evaluation of U. barbata lichen extracted with methanol and ethyl-acetate against selected Staphylococcus species isolates showed 92.31% and 53.85% susceptibility, respectively. The minimum inhibitory concentration (MIC) of the methanol and ethyl-acetate extracts ranged between 0.0390 to 10 mg/ml. There was a relatively high incidence of Staphylococcus species identified in milk of cows with subclinical mastitis from both farms. Conversely, Staphylococcus species isolates were resistant to antibiotics (mostly penicillin and ampicillin) commonly used in the farms. Furthermore, the study investigated the antimicrobial sensitivity of U. barbata extract in-vitro which may validate its use in traditional medicine for treatment of cows with mastitis.
- Full Text:
- Date Issued: 2013
Phytochemical analyses and Brine shrimp (Artemia Salina) lethality studies on Syzygium cordatum
- Authors: Chiguvare, Herbert
- Date: 2013
- Subjects: Artemia , Crustacea , Chromatographic analysis , Medicinal plants , Essences and essential oils , Traditional medicine
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11336 , http://hdl.handle.net/10353/d1004352 , Artemia , Crustacea , Chromatographic analysis , Medicinal plants , Essences and essential oils , Traditional medicine
- Description: Syzygium cordatum Hoscht ex. C Krauss, also known as water berry, is normally used by the people of South Africa for respiratory ailments including tuberculosis, stomach complaints, treatment of wounds and as emetics. An extract of the leaves can be used as a purgative for diarrhoea treatment. The leaves of Syzygium cordatum Myrtaceae were obtained from the Eastern Cape Province of South Africa, air dried and sequential solvent extraction was done to obtain various non volatile crude extracts. The volatile extract, that is the essential oil was extracted from the leaves using hydrodistillation and analysis of compounds was done by GC/MS for composition. 32 compounds were obtained from the fresh leaves and 18 compounds were obtained from the dry leaves. The fresh oil contains caryophyllene (11.8 percent) and caryophyllene oxide (11.1 percent) as the main sesquiterpene component. α-Pinene(5.0 percent) was the only monoterpene compound identified in the fresh oil in substantial amount. The dry leaves oil had copanene (17.0 percent), β-Caryophellene (26.0 percent), cubenol (6.5 percent) and caryophellene oxide (14.2 percent) as the dominant constituent of the oil. Summary of the classes of compounds in the oil revealed that the chemical profile of both oils were dominated by sesquiterpenoid compounds. This is the first time that terpenoids compounds are being identified in both the fresh and dry leaf oil of S. cordatum. Hexane leaf extract was selected due to the interest in the terpenoid compounds. Column chromatography of the hexane crude gave five (5) of which two are fully reported. The isolates were fully elucidated using spectroscopic methods to be β-Sitosterol (HC3) and Friedela-3-one (HC1A/HC1D). Cytotoxicity analysis was carried out on the crude using the Brine shrimps assay. Isolates 1C and1D showed significant lethality using the brine shrimps assay with lethality values (LC50) of 4.105mg/ml for HC1C and 4.11mg/ml for 1D/1A respectively.
- Full Text:
- Date Issued: 2013
- Authors: Chiguvare, Herbert
- Date: 2013
- Subjects: Artemia , Crustacea , Chromatographic analysis , Medicinal plants , Essences and essential oils , Traditional medicine
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11336 , http://hdl.handle.net/10353/d1004352 , Artemia , Crustacea , Chromatographic analysis , Medicinal plants , Essences and essential oils , Traditional medicine
- Description: Syzygium cordatum Hoscht ex. C Krauss, also known as water berry, is normally used by the people of South Africa for respiratory ailments including tuberculosis, stomach complaints, treatment of wounds and as emetics. An extract of the leaves can be used as a purgative for diarrhoea treatment. The leaves of Syzygium cordatum Myrtaceae were obtained from the Eastern Cape Province of South Africa, air dried and sequential solvent extraction was done to obtain various non volatile crude extracts. The volatile extract, that is the essential oil was extracted from the leaves using hydrodistillation and analysis of compounds was done by GC/MS for composition. 32 compounds were obtained from the fresh leaves and 18 compounds were obtained from the dry leaves. The fresh oil contains caryophyllene (11.8 percent) and caryophyllene oxide (11.1 percent) as the main sesquiterpene component. α-Pinene(5.0 percent) was the only monoterpene compound identified in the fresh oil in substantial amount. The dry leaves oil had copanene (17.0 percent), β-Caryophellene (26.0 percent), cubenol (6.5 percent) and caryophellene oxide (14.2 percent) as the dominant constituent of the oil. Summary of the classes of compounds in the oil revealed that the chemical profile of both oils were dominated by sesquiterpenoid compounds. This is the first time that terpenoids compounds are being identified in both the fresh and dry leaf oil of S. cordatum. Hexane leaf extract was selected due to the interest in the terpenoid compounds. Column chromatography of the hexane crude gave five (5) of which two are fully reported. The isolates were fully elucidated using spectroscopic methods to be β-Sitosterol (HC3) and Friedela-3-one (HC1A/HC1D). Cytotoxicity analysis was carried out on the crude using the Brine shrimps assay. Isolates 1C and1D showed significant lethality using the brine shrimps assay with lethality values (LC50) of 4.105mg/ml for HC1C and 4.11mg/ml for 1D/1A respectively.
- 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.
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- Date Issued: 2013