Reviewing the definition of the natural resource curse and analysing its occurence post-1990
- Authors: Mwansa, Mumamba Chitumwa
- Date: 2014
- Subjects: Resource curse , Natural resources -- Management , Economic development , National income
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1100 , http://hdl.handle.net/10962/d1013243
- Description: That countries with high natural resource abundance should experience slower economic growth than those with low resource abundance seems contrary to what would be expected, considering the developmental head-start such resources afford. Yet Sachs and Warner (1997) found that economies with a high share of natural resource exports in national income in 1970 tended to experience slower economic growth in the two decades that followed. This finding, that natural resources are a “curse” rather than a blessing, has become generally accepted. This thesis sought to test whether the conclusion drawn from their data – that higher natural resource abundance leads to slower economic growth – is still correct. It sought to test their findings first by correcting for their use of resource intensity (natural resources share of exports) as a proxy for abundance. Using measures of resource abundance for 1995 as a proxy for abundance in previous decades, it was found that higher resource abundance was not associated with lower economic growth in the 1970s and 1980s. This finding is contrary to that of Sachs and Warner (1997, 2001). Secondly, this thesis tested whether the natural resource curse effect was still present for the period 1995–2010. This was done by observing the effect of both resource abundance and resource intensity on economic growth during 1995–2010. In both cases no resource curse effect was found, for this more recent period. The resource curse had disappeared regardless of whether one uses Sachs and Warner’s (1997, 2001) measure of resource intensity or a measure of resource abundance. Natural resources should therefore no longer be considered a “curse”. In explaining the difference for the impact of resource intensity between the 1970-90 period measured by Sachs and Warner (1997, 2001) and the more recent period 1995-2010 it was found that the Dutch Disease effect has decreased significantly since the 1970s and 1980s. This could partly explain why the resource curse has disappeared when measured in terms of resource intensity. Thus it was concluded that the natural resource curse existed in the period 1970-90 only when measured in terms of resource intensity but not when measured relative to resource abundance. The negative effects of natural resources on economic growth have disappeared in terms of both resource intensity and resource abundance in the more recent time period.
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Road to redemption
- Authors: Singh, Anirood
- Date: 2014
- Subjects: Creative writing (Higher education) -- Research -- South Africa , Creative writing -- Fiction , South African fiction (English) -- Study and teaching (Higher) , South African fiction (English) -- 21st century , Detective and mystery stories, South African (English)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5977 , http://hdl.handle.net/10962/d1013035
- Description: Lurching from day-today in the months before South Africa becomes a republic, booze-befuddled Indian private investigator Rohit Biswas does not ponder how he can secure his daughter's future after he became a widower and lost his job as police detective when he killed a man who fatally stabbed his wife. Salvation appears when a rich client hires the PI to find evidence proving his son did not rape and murder a white socialite. Fighting against seeming impossible odds in colonial-apartheid Durban and a sanctions-busting conspiracy, Biswas secures his client's acquittal. In the process he defies karma and redeems himself.
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Sarkaiym
- Authors: Sutherns, Michael Courtney
- Date: 2014
- Subjects: Creative writing (Higher education) -- Research -- South Africa , Creative writing -- Fiction , South African fiction (English) -- Study and teaching (Higher) , South African fiction (English) -- 21st century
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5976 , http://hdl.handle.net/10962/d1012998
- Description: The kingdom of Sansland situated on the Azanian Peninsula has been ruled by Sorricians, the sky people, ever since they landed on terra firma centuries ago. The indigenous population are forced to engage directly in the social and economic perpetuation of their own domination beneath the Sorrician heel. Until revolution flares in the antipodes, and soon, even the gods themselves seem to take an interest in the inevitable course of events. But all is not what it seems. The revolution appears to proceed too rapidly. The kingdom’s trade infrastructure collapses too easily. The Sorrician rulers are inexplicably and unrealistically confident in their ability to repel an attack on the capital. It will take a man of conscience, a regular soldier and a boy priest to restore appearances back to reality.
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Saving and investment in South Africa: a causality study
- Authors: Mngqibisa, Vuyisa
- Date: 2014
- Subjects: Saving and investment -- South Africa Investments -- South Africa Credit -- South Africa Finance, Personal -- South Africa Portfolio management -- South Africa Investment analysis -- South Africa Error analysis (Mathematics)
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1086 , http://hdl.handle.net/10962/d1011887
- Description: This study aims to investigate the relationship between private saving and investment for South Africa using a Vector Error Correction Framework. Saving and investment are considered to be important factors for sustainable economic growth in the country, particularly as these variables have been recorded at significantly lower levels than those of other developing nations. By examining the direction of causality between saving and investment, the most suitable policy measures can be used in stimulating either savings or investment, and as a result aggregate growth. The study found a positive two-way causality to exist between these two variables, proving that both saving and investment-led policies are necessary in raising saving and investment levels. With the inclusion of credit extension as the third variable used to remove any variable bias, the study not only found credit extension to Granger cause private saving, but the reverse relationship was found to be present as well. This relationship was however found to be negative, confirming that lower borrowing constraints may have a negative effect on saving levels. The negative relationship between credit supply and private saving (substitution effect) proves that credit supply will only yield a positive result for savings if channelled through investment expenditure.
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Screening of entomopathogenic fungi against citrus mealybug (Planococcus citri (Risso)) and citrus thrips (Scirtothrips aurantii (Faure))
- Authors: FitzGerald, Véronique Chartier
- Date: 2014
- Subjects: Entomopathogenic fungi , Citrus mealybug -- South Africa -- Eastern Cape , Citrus thrips -- South Africa -- Eastern Cape , Citrus -- Diseases and pests , Citrus mealybug -- Biological control , Citrus thrips -- Biological control , Biological pest control agents , Scanning electron microscopy , Mycoses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4166 , http://hdl.handle.net/10962/d1020887
- Description: Mealybugs (Planococcus citri) and thrips (Scirtothrips aurantii) are common and extremely damaging citrus crop pests which have proven difficult to control via conventional methods, such as chemical pesticides and insect growth regulators. The objective of this study was to determine the efficacy of entomopathogenic fungi against these pests in laboratory bioassays. Isolates of Metarhizium anisopliae and Beauveria bassiana from citrus orchards in the Eastern Cape, South Africa were maintained on Sabouraud Dextrose 4% Agar supplemented with Dodine, chloramphenicol and rifampicin at 25°C. Infectivity of the fungal isolates was initially assessed using 5th instar false codling moth, Thaumatotibia leucotreta, larvae. Mealybug bioassays were performed in 24 well plates using 1 x 107 ml-1 conidial suspensions and kept at 26°C for 5 days with a photoperiod of 12 L:12 D. A Beauveria commercial product and an un-inoculated control were also screened for comparison. Isolates GAR 17 B3 (B. bassiana) and FCM AR 23 B3 (M. anisopliae) both resulted in 67.5% mealybug crawler mortality and GB AR 23 13 3 (B. bassiana) resulted in 64% crawler mortality. These 3 isolates were further tested in dose-dependent assays. Probit analyses were conducted on the dose-dependent assays data using PROBAN to determine LC₅₀ values. For both the mealybug adult and crawlers FCM AR 23 B3 required the lowest concentration to achieve LC₅₀ at 4.96 x 10⁶ conidia ml-1 and 5.29 x 10⁵ conidia ml-1, respectively. Bioassays on adult thrips were conducted in munger cells with leaf buds inoculated with the conidial suspensions. Isolate GAR 17 B3 had the highest mortality rate at 70% on thrips while FCM AR 23 B3 resulted in 60% mortality. Identification of the isolates, FCM AR 23 B3, GAR 17 B3 and GB AR 23 13 3, were confirmed to be correct using both microscopic and molecularly techniques. ITS sequences were compared to other sequences from GenBank and confirmed phylogenetically using MEGA6. Mealybug infection was investigated using scanning electron microscopy, mycosis was confirmed but the infection process could not be followed due to the extensive waxy cuticle. These results indicate that there is potential for the isolates FCM AR 23 B3 and GAR 17 B3 to be developed as biological control agents for the control of citrus mealybug and thrips. Further research would be required to determine their ability to perform under field conditions.
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Secrets I keep
- Authors: Thurgood, Mikaila Rae
- Date: 2014
- Subjects: South African fiction (English) -- 21st century , Creative writing (Higher education) -- Research -- South Africa , Creative writing -- Fiction , South African fiction (English) -- Study and teaching (Higher)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5981 , http://hdl.handle.net/10962/d1015638
- Description: My mother had many failings. Her inability to cook. Her inability to work. Her inability to love. But her two biggest failings...those were the ones that had the potential to ruin my entire life, to ruin my brother’s life, to tear a family apart. More than anything, it was her inability to act. Claire is a young woman working in Johannesburg as a PA. She has few friends barring her au pair flatmate Beth and work colleague Marge. Her nights are spent trying to overcome the trauma of her past to find sexual fulfilment in a shallow world of one night stands. Whether she can set herself on a path towards a more normal life comes down to one crucial thing – forgiveness.
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Sediment linkages in a small catchment in the Mount Fletcher southern Drakensberg region, South Africa
- Authors: Mzobe, Pearl Nonjabulo
- Date: 2014
- Subjects: Soil erosion -- South Africa -- Mount Fletcher , Soil conservation -- South Africa -- Mount Fletcher , Soil degradation -- South Africa -- Mount Fletcher , Food security -- South Africa , Wetland management -- South Africa -- Mount Fletcher , Watersheds -- South Africa -- Mount Fletcher
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:4879 , http://hdl.handle.net/10962/d1013224
- Description: Soil erosion is a persistent problem that requires continued control efforts as agricultural land loses productivity and communities dependent on the land become increasingly vulnerable to decreased food security. The negative effects of soil erosion in Khamopele River catchment, in the Mount Fletcher southern Drakensberg region of South Africa, are manifest in extensive gullying and wetland loss. Soil erosion has resulted in siltation in a recently constructed dam and the alteration of aquatic habitats. This research was undertaken to identify the sources of eroded sediment in the small upper catchments of the Mzimvubu River catchment to inform broader catchment management strategies. The scale of erosion was quantified using field surveys of gully extent and form. Environmental magnetic tracing techniques were used to determine the sources of eroded sediment in Khamopele River and upper Tina River catchments. The radionuclide ¹³⁷Cs was used to determine soil loss over a 55 year period in Khamopele River catchment. The Landscape Connectivity framework was used to describe the sediment source, pathway and sink interactions at sample area level. Results indicated that historical and contemporary land management practices such as uncontrolled grazing, grassland burning and furrows promoted soil erosion in the catchment. Soil erosion was most pronounced in the Taung sample area where there was extensive gullying, tunnelling and subsurface erosion. Environmental magnetic tracing results indicated that there were clear differences in source areas. Despite its prevalence in the area, gully erosion was not shown to be a major source of sediment to downstream sinks. Topsoil and hillslope derived sediment were shown to be mobile in the catchment, suggesting that sheet erosion processes were dominant in the catchment. Radionuclide tracing studies showed that at least 20 cm of soil had been eroded from the Khamopele River catchment surface since 1956. This research has shown that it is possible to distinguish source areas of erosion in the catchment by matching catchment mineral magnetic signatures to those in sink areas. This means that rehabilitation projects can use resources efficiently as the areas needing the most attention can be identified.
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Shembe religion's integration of African traditional religion and Christianity : a sociological case study
- Authors: Shange, Nombulelo Tholithemba
- Date: 2014
- Subjects: Shembe Church Christianity and other religions -- South Africa -- Inanda Christianity and culture -- South Africa -- Inanda Independent churches -- South Africa -- Inanda Religious tolerance -- South Africa -- Inanda South Africa -- Religious life and customs
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3365 , http://hdl.handle.net/10962/d1011819
- Description: The Shembe Church's integration of African Traditional Religion and Christianity has been met by many challenges. This merger has been rejected by both African traditionalists and Christians. The Shembe Church has been met by intolerance even though the movement in some ways creates multiculturalism between different people and cultures. This thesis documents the Shembe Church's ideas and practices; it discusses how the Shembe Church combines two ideologies that appear to be at odds with each other. In looking at Shembe ideas and practices, the thesis discusses African religion-inspired rituals like ukusina, ancestral honouring, animal sacrificing and virgin testing. The thesis also discusses the heavy Christian influence within the Shembe Church; this is done by looking at the Shembe Church's use of The Bible and Moses' Laws which play a crucial role in the Church. The challenges the Shembe Church faces are another main theme of the thesis. The thesis looks at cases of intolerance and human rights violations experienced by Shembe members. This is done in part by looking at the living conditions at eBuhleni, located at Inanda, KZN. The thesis also analyses individual Shembe member's experiences and discusses how some members of the Shembe church experience the acceptance of the Shembe religion in South African society. This thesis concludes by trying to make a distinction between intolerance and controversy. I try to highlight the idea that what many Shembe followers see as discrimination and intolerance towards them is sometimes a difference in opinion from other cultural groups. Sometimes these differences are not geared towards criticising other religious groups or perpetuating intolerance.
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Social learning in community based natural resource management project (CBNRM) : a case study of Chipembere gardening project in Zimbabwe.
- Authors: Mukwambo, Robson
- Date: 2014
- Subjects: Social learning -- Zimbabwe , Social learning -- Case studies , Vegetable gardening -- Zimbabwe , Economic development projects -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2014 , http://hdl.handle.net/10962/d1016363
- Description: This investigation of social learning processes in the Chipembere gardening project was conducted in Rockvale village one in Sebakwe communal area in the Midlands province of Zimbabwe. In essence, the study sought to explore how the Chipembere gardening project as a community-based natural resource management initiative (CBNRM), was reflecting and supporting social learning processes of change. It also sought to enrich and deepen an organizational understanding of social learning and to generate ideas and draw recommendations that could be used to strengthen learning in other CBNRM projects. The research was undertaken as a qualitative case study with data generated through semi-structured interviews with individuals and groups. It also included an analysis of project documents and an extended period of participant observation on site and in the gardening activities. Data were indexed and coded for generating analytical memos that were used to extract and represent the scope of social learning interations within the developing project. The study found that within the Chipembere gardening project a wide range of learning interactions were significant in shaping the developing project. Furthermore, these interactions were earmarked as the major drivers of social learning processes within the project. The study concluded that the social learning interactions amongst the gardeners in the Chipembere community garden were instrumental in fostering change that enhanced community livelinhoods and wellbeing.
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Some general convergence theorems on fixed points
- Authors: Panicker, Rekha Manoj
- Date: 2014
- Subjects: Fixed point theory , Convergence , Coincidence theory (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5426 , http://hdl.handle.net/10962/d1013112
- Description: In this thesis, we first obtain coincidence and common fixed point theorems for a pair of generalized non-expansive type mappings in a normed space. Then we discuss two types of convergence theorems, namely, the convergence of Mann iteration procedures and the convergence and stability of fixed points. In addition, we discuss the viscosity approximations generated by (ψ ,ϕ)-weakly contractive mappings and a sequence of non-expansive mappings and then establish Browder and Halpern type convergence theorems on Banach spaces. With regard to iteration procedures, we obtain a result on the convergence of Mann iteration for generalized non-expansive type mappings in a Banach space which satisfies Opial's condition. And, in the case of stability of fixed points, we obtain a number of stability results for the sequence of (ψ,ϕ)- weakly contractive mappings and the sequence of their corresponding fixed points in metric and 2-metric spaces. We also present a generalization of Fraser and Nadler type stability theorems in 2-metric spaces involving a sequence of metrics.
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South African International Relations (Ir) and the China-Africa relationship: a critical reflection
- Authors: Walker, Timothy Charles
- Date: 2014
- Subjects: South Africa -- Relations -- China , China -- Relations -- South Africa , International relations -- Philosophy , Critical theory
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2885 , http://hdl.handle.net/10962/d1015518
- Description: South African International Relations (IR) is a prominent source of China-Africa research and analysis, producing reports, journal articles and books that seek to illuminate the emerging relationship between China and Africa. It plays an important role in the framing of the relationship, as well as how it is perceived outside of the discipline. However, critical concerns have been raised about the context within which South African IR operates. It is therefore important that IR research, including its assumptions, dominant concepts, professed values and aspirations to studying the China-Africa relationship, be critically examined. The aim of this thesis is to contribute to critical thinking in South African IR by opening up for future discussion the new directions and possibilities for China-Africa IR. Utilising a critique located in Critical International Relations Theory (CIRT), this thesis critically reflects upon both the context of South African IR’s China-Africa research and the perspectives it has produced. The thesis argues that in spite of many descriptive and empirical studies, China- Africa research is theoretically underdeveloped in South African IR. Further, it argues that theoretical work is marginalised despite the fact that both historical and contemporary research relies on concepts drawn from IR theory. South African IR’s focus on policy relevance is advanced as a reason for the prevalence of theoretical underdevelopment. This thesis concludes by reviewing arguments for the improved use of IR theory in China-Africa IR, which will lead to a better understanding of this important relationship.
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Strength training and cardiovascular risk post-menses, with particular emphasis on the plasma lipoproteins: a controlled trial
- Authors: Viljoen, Janet Erica
- Date: 2014
- Subjects: Weight training for women -- Physiological aspects , Exercise for women -- Physiological aspects , Middle-aged women -- Health and hygiene , Cardiovascular system -- Diseases , Hypercholesteremia , Blood lipoproteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5155 , http://hdl.handle.net/10962/d1013578
- Description: Introduction: Cardiovascular disease affects a greater proportion of females than it does males, and is responsible for an estimated 52 percent of female deaths per annum, globally. Due to the loss of oestrogen associated with the menopause, post-menopausal females are at elevated risk for hypercholesterolaemia which is a primary risk factor for cardiovascular disease. It has not yet been conclusively established whether resistance training can be used to ameliorate hypercholesterolaemia. Aim: This randomized controlled trial investigated what effect 12 weeks of progressive resistance training would have on plasma lipoproteins in a sample of post-menopausal females. Methods: Caucasian women (n=30 intervention and n=18 control) between the ages of 55 and 65 years who were not taking hormone replacement therapy were recruited. Participants did not smoke, were sedentary, were not taking any form of cholesterol-lowering medication, had at least one cholesterol abnormality at baseline but were otherwise healthy and able to participate in a strength training programme. Following extensive medical pre-screening, information dissemination and voluntary consent, the sample was divided into two groups. The exercise sample undertook 12 weeks of resistance training on five days of the week. The control group received no intervention. Measurements were obtained at baseline and every four weeks thereafter and included measures of strength, biochemistry (oestradiol, testosterone, full blood lipid profile, glycated haemoglobin and sex hormone binding globulin), anthropometry, morphology and self-reports (dietary intake, energy expenditure and the profile of mood states questionnaire). Results: There was no change to low density lipoprotein cholesterol, high density lipoprotein cholesterol, triglyceride content or total cholesterol as a result of the intervention. Back, chest and leg strength increased significantly (p<0.01) (increases of 51 percent, 35 percent and 43 percent respectively from baseline); waist circumference dropped (p<0.01) by 5 percent overall and diastolic blood pressure decreased significantly (-9 percent, p<0.01) in the exercise cohort but no change was noted in the matched control. Dietary intake, energy expenditure and body mass remained unchanged in both samples. Morphology (sum of skinfolds, estimated body fat content and girth measures) did not change and nor did other biochemical measures (HbA1c and sex hormone binding globulin) or hormone levels (oestradiol and testosterone). Despite the lack of overall change, an important finding was noted in individual results where a clear indication of ‘responders’ and ‘non-responders’ emerged. Conclusion: Overall mean results suggest that 12 weeks resistance training undertaken five days of the week was ineffective in reducing hypercholesterolaemia in this sample. Despite there being no identifying characteristics determined in this sample, evidence of responders and non-responders to the intervention indicates that reliance on mean data may not be sufficient when analysing data from exercise interventions. Therefore, while progressive resistance training had a positive effect on strength, waist circumference and diastolic blood pressure, it did not positively influence the plasma lipoproteins in this cohort of post-menopausal women. , Maiden name: Kelly, Janet Erica
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Structural bioinformatics analysis of the Hsp40 and Hsp70 molecular chaperones from humans
- Authors: Adeyemi, Samson Adebowale
- Date: 2014
- Subjects: Structural bioinformatics , Molecular chaperones , Heat shock proteins , Protein-protein interactions , Biomolecules
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4171 , http://hdl.handle.net/10962/d1020962
- Description: HSP70 is one of the most important families of molecular chaperone that regulate the folding and transport of client proteins in an ATP dependent manner. The ATPase activity of HSP70 is stimulated through an interaction with its family of HSP40 co-chaperones. There is evidence to suggest that specific partnerships occur between the different HSP40 and HSP70 isoforms. While some of the residues involved in the interaction are known, many of the residues governing the specificity of HSP40-HSP70 partnerships are not precisely defined. It is not currently possible to predict which HSP40 and HSP70 isoforms will interact. We attempted to use bioinformatics to identify residues involved in the specificity of the interaction between the J domain from HSP40 and the ATPase domain from the HSP70 isoforms from humans. A total of 49 HSP40 and 13 HSP70 sequences from humans were retrieved and used for subsequent analyses. The HSP40 J domains and HSP70 ATPase domains were extracted using python scripts and classified according to the subcellular localization of the proteins using localization prediction programs. Motif analysis was carried out using the full length HSP40 proteins and Multiple Sequence Alignment (MSA) was performed to identify conserved residues that may contribute to the J domain – ATPase domain interactions. Phylogenetic inference of the proteins was also performed in order to study their evolutionary relationship. Homology models of the J domains and ATPase domains were generated. The corresponding models were docked using HADDOCK server in order to analyze possible putative interactions between the partner proteins using the Protein Interactions Calculator (PIC). The level of residue conservation was found to be higher in Type I and II HSP40 than in Type III J proteins. While highly conserved residues on helixes II and III could play critical roles in J domain interactions with corresponding HSP70s, conserved residues on helixes I and IV seemed to be significant in keeping the J domain in its right orientation for functional interactions with HSP70s. Our results also showed that helixes II and III formed the interaction interface for binding to HSP70 ATPase domain as well as the linker residues. Finally, data based docking procedures, such as applied in this study, could be an effective method to investigate protein-protein interactions complex of biomolecules.
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Synthesis and characterization of NaYGdF4 upconversion nanoparticles and an investigation of their effects on the spectroscopic properties of two phthalocyanine dyes
- Authors: Taylor, Jessica Mary
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54621 , vital:26594
- Description: Sphere and star shaped NaYGdF4:Yb/Er(Tm) upconversion nanoparticles were successfully synthesized utilizing a methanol assisted thermal decomposition approach and their chemical, spectroscopic and fluorescence properties were fully characterized. In addition, their influence on the spectroscopic and fluorescence properties of two phthalocyanines (Pcs) (unsubstituted tetrathiophenoxy phthalocyanine (H2Pc) and aluminium octacarboxy phthalocyanine (Cl)AlOCPc) was investigated. Upconversion nanoparticles were found to produce characteristic upconversion fluorescence emissions in the blue, green, red and NIR regions and were also shown to possess paramagnetic properties. Simple mixing with an H2Pc in toluene was found to exert no change on the spectroscopic or fluorescence properties of the Pc while covalent conjugation to a (Cl)AlOCPc resulted in a large Q band blue shift accompanied by a decrease in fluorescence lifetimes in DMSO. The red light excitation mediated singlet oxygen generation of the H2Pc mixed with upconversion nanoparticles was investigated and singlet oxygen fluorescence lifetimes were found to decrease in the presence of the nanoparticles. Upconversion mediated singlet oxygen generation, by way of resonance energy transfer to the Pc, was also attempted using 972 nm excitation; however, no singlet oxygen was detected utilizing singlet oxygen NIR emission detection. Pending further work using alternative singlet oxygen detection methods, this suggests that while upconversion nanoparticles possess excellent fluorescent imaging capabilities, they are relatively inefficient in inducing singlet oxygen production simply when mixed with phthalocyanines. Despite this, by combining phthalocyanines and upconversion nanoparticles, we present a system capable of: multimodal imaging, using both upconversion and phthalocyanines emissions, singlet oxygen generation, via direct excitation of the phthalocyanine with red laser light, and, possibly, magnetic resonance imaging, as a result of doping the upconversion nanoparticles with Gd3+ ions.
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Synthesis and structure-activity relationship studies of 1,4-naphthoquinone derivatives as potential anti-trypanosomal agents
- Authors: Chakaingesu, Chikomborero
- Date: 2014
- Subjects: African trypanosomiasis , Trypanosoma brucei , Naphthoquinone , Protozoan diseases , Drugs -- Structure-activity relationships , Millennium Development Goals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3873 , http://hdl.handle.net/10962/d1020959
- Description: Human African Trypanosomiasis (HAT) is an infectious, vector-borne protozoal disease which is amongst the so-called neglected diseases. In 2000, at a summit of the United Nations, eight Millennium Development Goals (MDGs) were set, to be achieved by 2015. MDG 6 states “to combat HIV/AIDS, malaria & other diseases”. With just under 2 years to go before the end of 2015, HAT is still thriving in developing countries. The drugs currently used for the treatment of HAT are in short supply, have severe side effects and those used to treat late stages of the disease are very difficult to administer. The aforementioned challenges call for research into this neglected disease in order to develop new, safe and easy-to-use medicines. Naphthoquinones are a class of compounds shown to possess anti-parasitic activity, amongst a variety of other biological activities, and therefore this pharmacophore was selected for this study. The purpose of this study was to synthesise derivatives of 2,3-dichloro-1,4- naphthoquinone to be tested for anti-trypanosomal activity and thereafter conduct structureactivity relationship studies. A series of reactions were carried out using thiophenol, phenol and aniline nucleophiles to synthesise thioether (-S-), ether (-O-) and amino (-NH-) derivatives of 2,3-dichloro-1,4-naphthoquinone with various halogen or methyl substituents. Purification of the products was carried out by recrystallisation. Nuclear magnetic resonance (NMR), infra-red (IR) and high pressure liquid chromatography coupled to an electro-spray ionisation mass spectrometer (HPLC-ESI-MS) were the analytical methods used for structural confirmation of the products. There were eighteen 1,4-naphthoquinone derivatives that were successfully synthesised using ethanolic solutions. Unfortunately, attempts to synthesise 1,4-naphthoquinones in reactions involving 2-(trifluoro-methyl)aniline and 2-isopropyl-5-methylphenol were unsuccessful, presumably due to steric hindrance by the bulky ortho-substituents. Although the aims of the synthetic procedures were to obtain both mono- and disubstituted products by nucleophilic displacement of the chlorine atom(s) of 2,3-dichloro-1,4- naphthoquinone, only monosubstituted products were obtained from substitution with aniline and phenol nucleophiles. Thiol nucleophiles, however, selectively yielded disubstituted products only. Synthesised naphthoquinone derivatives were tested against Trypanosoma brucei and calculation of the EC₅₀ values from the obtained dose-response curves was carried out using the four parametric equation. All the 1,4-naphthoquinones showed a degree of potency, except compounds 1b, 3c and 3e, which had little or lack of potency. Structure-activity relationship studies (SARs and QSARs) were carried out to determine which structural features or functional group substituents of the naphthoquinone derivatives contribute or take away from the desired anti-trypanosomal activity. It was found that compounds with the best in vitro anti-trypanosomal potencies in the series of analogous 1,4-naphthoquinone derivatives had EC₅₀ values in the range 2.137 to 2.884 μM. The most potent compound in the series was 2-chloro-3-(4-(trifluoromethyl)phenylamino)-1,4- naphthoquinone 1e; but it was 142-fold less potent than the reference standard of melarsoprol.
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Synthesis of chromium carbene scaffolds for use in medicinal chemistry
- Authors: Rafael, Christopher Carlos Ferreira
- Date: 2014
- Subjects: Carbenes (Methylene compounds) , Pharmaceutical chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4456 , http://hdl.handle.net/10962/d1010863 , Carbenes (Methylene compounds) , Pharmaceutical chemistry
- Description: This study involves using methyllithium to synthesize Fischer carbene complexes as precursors for metal templated α,β-unsaturated complexes with potential as acceptors in the Baylis Hillman reaction as well as in Dötz benzannulation. Fischer carbene complexes contain low oxidation state metal centers, are electrophilic in nature and are stabilized by π-donating substituents such as alkoxy and amino groups. The increased electron withdrawing nature of the metal carbonyl moiety was expected to improve the rates of reaction compared to organic carbonyls. Four Fischer carbenes were synthesized via nucleophilic addition of MeLi to chromium and tungsten hexacarbonyl at low temperatures followed by alkylation using either a Meerwein salt (Me₃OBF₄) to give the desired Fischer metal methyl methoxy carbenes or Et₄NBr/alkylhalide to make the corresponding ethoxy and allyloxy carbenes. Characterization was by means of ¹³C NMR, ¹H NMR, and IR. In silico studies were carried out looking at the effect of substituents on the carbene bond. Synthesis of α,β-unsaturated complexes was effected via the aldol condensation route and found to be unfavorable using enolizable aldehydes, although the use of two aryl aldehydes resulted in successful preparation of two α,β-unsaturated complexes. Difficulty in the purification of these complexes hindered their full characterization. Computational studies looked at the effect of substituents on the system as well as variation of the metal from Cr to Mo and W. Synthesis of Baylis Hillman adducts using α,β-unsaturated complexes as acceptors was unsuccessful due to the ease of product oxidization. One potential product was obtained in its crude form although purification was not possible due to oxidation. Computational studies suggested that the oxygen on the ligand negatively impacts the stability of these Fischer carbene derived Baylis Hillman adducts promoting intramolecular oxidation of the metal. The α,β-unsaturated complexes and Baylis Hillman adducts were considered to be candidates to undergo Dötz benzannulation methodology. The use of the α,β-unsaturated complexes in this reaction was generally unsuccessful, both in the microwave and in conventional reflux conditions. Computational studies of these compounds were carried out to facilitate understanding of their stability and configuration.
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Synthesis of silver nanoparticles and their role against a thiazolekinase enzyme from Plasmodium falciparum
- Authors: Yao, Jia
- Date: 2014
- Subjects: Silver , Nanoparticles , Thiazoles , Plasmodium falciparum , Antimalarials , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4168 , http://hdl.handle.net/10962/d1020894
- Description: Malaria, a mosquito-borne infectious disease, caused by the protozoan Plasmodium genus, is the greatest health challenges worldwide. The plasmodial vitamin B1 biosynthetic enzyme PfThzK diverges significantly, both structurally and functionally from its counterpart in higher eukaryotes, thereby making it particularly attractive as a biomedical target. In the present study, PfThzK was recombinantly produced as 6×His fusion protein in E. coli BL21, purified using nickel affinity chromatography and size exclusion chromatography resulting in 1.03% yield and specific activity 0.28 U/mg. The enzyme was found to be a monomer with a molecular mass of 34 kDa. Characterization of the PfThzK showed an optimum temperature and pH of 37°C and 7.5 respectively, and it is relatively stable (t₁/₂=2.66 h). Ag nanoparticles were synthesized by NaBH₄/tannic acid, and characterized by UV-vis spectroscopy and transmission electron microscopy. The morphologies of these Ag nanoparticles (in terms of size) synthesized by tannic acid appeared to be more controlled with the size of 7.06±2.41 nm, compared with those synthesized by NaBH₄, with the sized of 12.9±4.21 nm. The purified PfThzK was challenged with Ag NPs synthesized by tannic acid, and the results suggested that they competitively inhibited PfThzK (89 %) at low concentrations (5-10 μM) with a Ki = 6.45 μM.
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Synthetic analogues of marine bisindole alkaloids as potent selective inhibitors of MRSA pyruvate kinase
- Authors: Veale, Clinton Gareth Lancaster
- Date: 2014 , 2014-04-02
- Subjects: Alkaloids , Pyruvate kinase , Staphylococcus aureus , Antibiotics , Sponges -- South Africa , Imidazoles , Biological assay , Antibacterial agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4563 , http://hdl.handle.net/10962/d1020893
- Description: Globally, methicillin resistant Staphylococcus aureus (MRSA) has become increasingly difficult to manage in the clinic and new antibiotics are required. The structure activity relationship (SAR) study presented in this thesis forms part of an international collaborative effort to identify potent and selective inhibitors of an MRSA pyruvate kinase (PK) enzyme target. In earlier work the known marine natural product bromodeoxytopsentin (1.6), isolated from a South African marine sponge Topsentia pachastrelloides, exhibited selective and significant inhibition of MRSA PK (IC₅₀ 60 nM). Accordingly bromodeoxytopsentin provided the initial chemical scaffold around which our SAR study was developed. Following a comprehensive introduction, providing the necessary background to the research described in subsequent Chapters, this thesis has been divided into three major parts. Part one (Chapter 2) documents the synthesis of two natural imidazole containing topsentin analogues 1.40, 1.46, five new synthetic analogues 1.58—1.61, 2.104. In the process we developed a new method for the synthesis of topsentin derivatives via selenium dioxide mediated oxidation of N-Boc protected 3-acetylindoles to yield glyoxal intermediates which were subsequently cyclized and deprotected to yield the desired products. Interestingly we were able to demonstrate a delicate relationship between the relative equivalents of selenium dioxide and water used during the oxidation step, careful manipulation of which was required to prevent the uncontrolled formation of side products. Synthetic compounds 1.40, 1.46, 1.58—1.61 were found to be potent inhibitors of MRSA PK (IC₅₀ 238, 2.1, 23, 1.4, 6.3 and 3.2 nM respectively) with 1000-10000 fold selectivity for MRSA PK over four human orthologs. In the second part of this thesis (Chapter 3) we report the successful synthesis of a cohort of previously unknown thiazole containing bisindole topsentin analogues 1.62—1.68 via a Hantzsch thiazole synthesis. Bioassay results revealed that these compounds were only moderate inhibitors of MRSA PK (IC₅₀ 5.1—20 μM) which suggested that inhibitory activity was significantly reduced upon substitution of the central imidazole ring of topsentin type analogues with a thiazole type ring. In addition in Chapter 3 we describe unsuccessful attempts to regiospecifically synthesize oxazole and imidazole topsentin analogues through a similar Hantzsch method. As a consequence of our efforts in this regard we investigated three key reactions in depth, namely the synthesis of 2.2, 3.38, 3.40, 3.41 via α-bromination of 3-acetylindole and the synthesis of indolyl-3-carbonylnitriles 2.13, 3.45—3.47 and α-oxo-1H-indole-3-thioacetamides 3.48—3.51. The investigation of the latter led to the isolation and elucidation of two anomalous N,N-dimethyl-1H-indole-3-carboxamides 3.52 and 3.53. Finally the third part of this thesis (Chapter 4) deals with in silico assessment of the binding of both the imidazole and thiazole containing bisindole alkaloids to the MRSA PK protein which initially guided our SAR studies. In this chapter we reveal that there appears to be no correlation between in silico binding predictions and in vitro MRSA PK inhibitory bioassay data. Superficially it seems that binding energy as determined by the docking program used for these studies correlated with the size of the indole substituents and did not reflect IC₅₀ MRSA PK inhibitory data. Although this led us to computationally explore possible alternative binding sites no clear alternative has been identified.
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Taxonomy and life history of the zebra seabream, Diplodus cervinus (Perciformes: Sparidae), in southern Angola
- Authors: Winkler, Alexander Claus
- Date: 2014
- Subjects: Diplodus -- Classification Fish populations -- Angola Diplodus -- Angola Diplodus -- South Africa Diplodus -- Morphology Fisheries -- Angola Sparidae
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:5361 , http://hdl.handle.net/10962/d1012062
- Description: The zebra sea bream, Diplodus cervinus (Sparidae) is an inshore fish comprised of two boreal subspecies from the Gulf of Oman and the Mediterranean / north eastern Atlantic and one austral subspecies from South Africa and southern Angola. The assumption of a single austral subspecies has, however, been questioned due to mounting molecular and morphological evidence suggesting that the cool Benguela current is a vicariant barrier that has separated many synonymous inshore fish species between South Africa and southern Angola. The aims of this thesis are to conduct a comparative morphological analysis of Diplodus cervinus in southern Angola and South Africa in order to classify the southern Angolan population and then to conduct a life history assessment to assess the life history impact of allopatry on this species between the two regions. Results of the morphological findings of the present study (ANOSIM, p < 0.05, Rmeristic = 0.42) and (Rmorphometric = 0.30) along with a concurrent molecular study (FST = 0.4 – 0.6), identified significant divergence between specimens from South Africa (n = 25) and southern Angola (n = 37) and supported stock separation and possibly sub-speciation, depending on the classification criteria utilised. While samples from the two boreal subspecies were not available for the comparative morphological or molecular analysis, comparisons of the colouration patterns between the three subspecies, suggested similarity between the southern Angola and the northern Atlantic / Mediterranean populations. In contrast, the colouration patterns between the southern Angolan and South African specimens differed substantially, further supporting the morphological and molecular results. The distinct morphological divergence between the southern Angolan and South African populations was not reflected within the life history traits of both populations. A combination of methods, including length/age frequency analyses, adult sex ratios and histological analysis was used to determine that this species is a rudimentary hermaphrodite in southern Angola. Peak spawning season was observed between June and July. The overall sex ratio (M: F) was 1:1.52 with females dominating smaller younger size classes and 50% maturity was attained at 210 mm FL and 4.6 years. Females [L(t) = 287.5(1-e⁻°·¹⁸⁽t⁻²·⁸⁴⁾)] grew significantly faster (LRT, p < 0.05) than males [L(t) = 380.19(1-e⁻°·°⁶⁽t⁻⁷·¹²⁾)]. The higher maximum age of the southern Angolan population of D. cervinus (43 years) was older than that of South African individuals sampled in the tsitsikamma national park. The similarities in the life history of the two austral populations are probably a consequence of similar selective pressures in the similar warmtemperate habitats. Evidence to support the above comments was found in the feeding study which showed that the South African and Angolan populations were almost identical, with both populations feeding primarily on amphipods and polychaete worms throughout ontogeny. In contrast, the diet of their boreal conspecifics from the Mediterranean was different, where larger individuals tended to select larger, and more robust, prey items. The life history differences observed between the boreal and austral populations can be attributed to either sampling bias or environmental factors. Sampling biases included the use of different age and growth estimation techniques, while the environmental factors would include differential selective pressures most likely driven by different resource availability and exploitation. The present study provides crucial baseline life history information of a potentially exploitable species off southern Angola as well as information on the life history plasticity of the species. Unfortunately, the current lack of uniformity in the methods used to estimate life history parameters between studies conducted on the boreal and austral populations have complicated our understanding of the evolution of various life history trends in sparid fish. From a management perspective however, the results from the present study can be used to propose management strategies for an emerging trap fishery in southern Angola. Using a balanced exploitation fishery approach (harvesting up to the size-at-100% maturity), the size of the fish traps entrance was calculated based the morphological information from this and other small sparid species that are targeted and was estimated to be 62 mm.
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Teachers' perceptions of behavioural problems manifested by Grade 11 and 12 learners in three Namibian schools
- Authors: Akawa, Ester Anna Nelago
- Date: 2014
- Subjects: Education, Secondary -- Namibia School children -- Namibia -- Attitudes Learning disabilities -- Social aspects Behavior disorders in children -- Education (Secondary) -- Namibia Children with social disabilities -- Education (Secondary) -- Namibia Emotional problems of children -- Education (Secondary) -- Namibia Teachers -- Job stress -- Namibia
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1962 , http://hdl.handle.net/10962/d1010868
- Description: In Namibia today few learners with behavioural and learning problems are within special schools as most are placed within the mainstream school system. Placing these learners within the mainstream system is part of the policy of Inclusive Education (IE) because it argues that this would benefit these learners and also save resources. IE is concerned with addressing barriers to learning and behavioural problems are regarded as one of these barriers. IE argues for a series of new approaches to the diagnosis and response to learners with behavioural problems. This poses challenges for teachers in mainstream schools. Teachers are at the forefront of this situation as they are usually the first to observe and experience the behavioural problems in the schools and are expected to respond appropriately. They find this situation both challenging and problematic. This research explores a sample of teachers’ perceptions of learners’ behavioural problems. To collect in-depth information, this study followed a qualitative approach with a case study design. The data were collected through semi-structured interviews, supplemented with observation and document analysis. The study consisted of fifteen respondents: three principals, three teacher counsellors and nine teachers from the three selected schools. This study illuminates the types of behaviour that teachers encounter, the impact of these behaviours, the factors seen as contributing to these behaviours, and how teachers and the school system deal with these behaviours. In addition the study applies Bronfenbrenner’s bioecological model (1992) to explain how the behaviours manifested by Grade 11 and 12 learners, and identified as problematic by teachers, are part of an interconnected nested social system. The results from the study indicate the manifestation of behavioural problems to be common occurrences in secondary schools are evident, amongst others, through fighting, bullying, substance abuse, truancy, and disrespect of teachers and authority. The teachers pointed to the prevalence of these problems as well as the serious impact such problems have on these learners, their fellow learners, and on the teachers. The teachers identified a complex array of what they saw as contributing factors located within the school, peer groups, family and home circumstances, the local community, as well within the national education policy, the economy and society. The study points to some specific, as well as broader, lessons and opportunities for action both for those managing the education system at the national level and for schools and teachers.
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