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An ion imprinted polymer for the determination of Ni (II) ions from mine tailing samples

  • Authors: Rammika, Modise
  • Date: 2011
  • Subjects: Imprinted polymers , Metal ions , Polymerization , Mineral industries -- Waste disposal
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4323 , http://hdl.handle.net/10962/d1004981 , Imprinted polymers , Metal ions , Polymerization , Mineral industries -- Waste disposal
  • Description: A Ni(II)-dimethylglyoxime ion imprinted polymer {Ni(II)-DMG IIP} was synthesized by the trapping method using the bulk polymerisation format. The structures of the imprinted and non-imprinted polymer were evaluated by infrared spectroscopy and the morphology was observed by scanning electron microscopy. The Ni(II)-DMG IIP was optimised for pH, mass, time and by the uniform design experimental method for the molar ratios of monomer to crosslinker to porogen and template to ligands as well as keeping these parameters constant and varying the quantities of initiator, 2,2'-azobisisobutyronitrile (AIBN). The optimum pH was 8.5, optimum mass was 50 mg, optimum time was 1 min and the optimum molar ratios of crosslinker to monomer, monomer to template and nickel(II) sulfate hexahydrate (NiSO₄.6H₂O) to 4-vinylpyridine to dimethylglyoxime were found to be 3.3:1.0, 0.6:1.0 and 1.0:0.6:3.6 respectively with 30 mg and 8 mL as the optimum amounts of initiator and porogen respectively. Through this optimisation, recovery of Ni(II) was increased from 98 to 100%. Selectivity of the ion imprinted polymer was evaluated by analysing, using an inductively coupled plasma-optical emission spectrometer, for Ni(II) ions that were spiked with varying concentrations of Co(II), Cu(II), Zn(II), Pd(II), Fe(II), Ca(II), Mg(II), Na(I) and K(I) in aqueous samples. Selectivity studies also confirmed that the ion imprinted polymer had very good selectivity characterised by % RSD of less than 5 %. Co(II) was the only ion found to slightly interfere with the determination of Ni(II). The limits of detection and quantification were found to be 3x10⁻⁴ μg/mL and 9x10⁻⁴ μg/mL respectively. The method was evaluated by a custom solution of ground water certified reference material (SEP-3) and sandy soil reference material (BCR-142R) and the concentrations of Ni(II) obtained were not significantly different to the certified ones. The Ni(II)-DMG IIP was then evaluated in aqueous and soil samples where recoveries of 93 to 100% and 98 to 99% respectively were obtained with enrichment factors ranging from 2 to 18 in aqueous and 27 to 40 in soil samples. Finally, the Ni(II)-DMG IIP was used to analyse mine tailings samples and Ni(II) recovery of 99% was obtained with an enrichment factor of 2.
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An organisation development intervention in a secondary school in the Erongo region of Namibia

  • Authors: Steenkamp, Angeline Anna
  • Date: 2011
  • Subjects: School management and organization -- Namibia -- Erongo Organizational change -- Namibia -- Erongo Curriculum planning -- Namibia -- Erongo
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1683 , http://hdl.handle.net/10962/d1003566
  • Description: The challenge for Namibia is to translate Vision 2030 into realistic and implementable programmes and to develop and adopt a set of interventions which will raise the quality of education. The quality of education currently on offer varies from school to school and, indeed, from class to class (Namibia. MoE, 2006, p. 1). The National Standards and Performance Indicators (ETSIP, 2006) for schools in Namibia and the Education and Training Sector Improvement Programme (ETSIP), have been developed to address the quality of education across the country, and to make provision for school managers to be trained. Organisation Development is a planned change approach which focuses on the change processes of the organisation, by opening up communication, decreasing internal destructiveness – such as win-lose conflicts – and by increasing creativity in problem solving. It is based on the values and assumptions about people and their organisations. OD promotes interdependence and interconnectedness, involvement in problem solving and decision making. OD is a process for teaching people how to solve problems, take advantage of opportunities, and learn how to do better over time. OD was introduced to Evergreen Senior Secondary School in the form of a Survey Data Feedback (SDF) where data was collected, analysed and fed back to the participants. The case study involved 20 staff members made up of the principal, two head of departments and 17 teachers. Formal and focus-group interviews, as well as observation, were used to collect data. What was derived from the data was that the OD approach was something new to the participants, and served as an eye-opener. Further, it became evident from the data that participants had high hopes that OD would bring about immediate visible changes regarding the operation of their organisation. It is essential to remind participants that OD is a long-term change process, and not a “quick fix”.
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Analysis of volatility spillover effects between the South African, regional and world equity markets

  • Authors: Mumba, Mabvuto
  • Date: 2011
  • Subjects: Financial crises International finance Stocks -- Prices -- Africa Stocks -- Prices -- South Africa Capital market -- Africa Capital market -- South Africa Foreign exchange rates Africa -- Economic conditions South Africa -- Economic conditions
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:957 , http://hdl.handle.net/10962/d1002691
  • Description: The current study examines the extent and magnitude by which global and regional shocks are transmitted to the volatility of returns in the stock markets of South Africa, Egypt, Nigeria, Botswana, Mauritius and Egypt. This is done so as to make inferences on the level of the domestic market‟s integration into the regional and world capital markets. By applying multivariate and univariate GARCH models, using weekly data from June 1995 to May 2010, the main empirical findings are threefold. Firstly, the volatility analytical framework finds statistically significant and time-varying volatility spillover effects from the regional and global markets to the South African market. Global shocks are generally stronger and account for up to 23.9 percent of the volatility of South Africa‟s equity market compared to weaker regional factors which account for less than 1 percent of domestic variance. Only in countries with strong bilateral trade and economic links with South Africa, such as Botswana and Namibia, is it found that regional factors are more dominant than global factors for domestic volatility. Compared to the other African markets, the joint influence of foreign shocks on domestic volatility is highest in South Africa and Egypt, two of Africa‟s largest and most developed markets. The results further demonstrate that for all the African markets the explanatory power of both regional and global factors for domestic volatility is not constant over time and tends to increase during turbulent market periods. Secondly, the analysis of the determinants of South frica‟s second moment linkages with the global market suggests that the volatility of the exchange rate plays a cardinal role in influencing the magnitude by which global shocks affect domestic volatility. The increased global integration in the second moments cannot be attributed to either increased trade integration, convergence in inflation rates or to convergence in interest rates between South Africa and the global markets. Lastly, tests were conducted to examine whether there have been contagion effects from the regional and global markets to South Africa from the 1997 Asian crisis and the 2007/8 global financial crisis. The results show no evidence of contagion during either the East Asian currency crisis or the recent global financial crisis to South Africa, while some African markets, such as Egypt, Mauritius and Botswana, exhibit contagion effects from either crisis. Overall, the empirical findings generally support the view that African markets are segmented both at the regional and global levels as domestic volatility is more influenced by local idiosyncratic shocks (the proportion not attributable to either global and regional factors). However, the volatility of South Africa, and to a lesser extent Egypt, remains relatively more open to global influence. This implies that the potential for gains from international portfolio diversification and the scope for success of policies aimed at the stabilisation of equity markets in these markets exist.
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Angel networks as a business start-up financing option in South Africa

  • Authors: Sibanda, Zenzo
  • Date: 2011
  • Subjects: Angels (Investors) -- South Africa Small business -- Finance -- South Africa New business enterprises -- Finance -- South Africa Venture capital -- South Africa Microfinance -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1164 , http://hdl.handle.net/10962/d1002780
  • Description: The following study is about business angels financing small business start-ups. It explores the aspect of starting up an entrepreneurial venture in which the entrepreneur seeks to secure start-up finance from lenders, raising the various issues that are known to characterise this engagement between the entrepreneur and the lender. Using the phenomenological paradigm, the study seeks to determine the awareness of small scale financing by entrepreneurs in South Africa, to determine the most commonly used source of start-up business funding in South Africa, to assess the extent to which business angel financing could be used to finance businesses in South Africa and to determine the factors impacting the use of business angel financing in South Africa. From these objectives, the study will also seek to determine the extent to which business angel networks could facilitate the financing of business start-ups. Small businesses invariably come up in different policy spheres as the main avenues to social and economic construction across national and regional lines. The importance of a successful business start up to a growing economy should not be underestimated. In line with this is the particular factor of gaining access to start up capital, which continues to emerge as a leading contributor to the success or failure of business start ups. Studies continue to verify that the most common challenge faced by most emerging entrepreneurs is start-up capital, either in the lack of this capital, the unfavourable conditions surrounding its availability, the lack of assets to serve as collateral for its use or the ambiguous flow of crucial information between lenders and providers of finance in the funding relationship (Abor and Biekpe, 2006: 69;Hernandez-Trillo, Pagan and Paxton, 2005: 435, ISPESE, 2005: 7, CDE, 2004: 5; Musengi 2003: 11). Roger Sorheim (2005: 179) refers to business angels as private individuals who offer risk capital to unlisted companies that are struggling to obtain start up capital to finance their business ideas. Business angels are further defined as high net-worth bearers of substantial private capital who predominantly invest in the early stage of high risk high potential return business ventures with a positive further growth potential. Business angel finance is typically a ‘once-off’ early stage form of small firm financing compared to the more frequent later stage venture capitalist funding. Studies show that business angels represent an underutilised wealth creation mechanism when it comes to small firm start-ups as most business angels contribute expertise in addition to finance to the start-ups they get involved in. This brings valuable business insight to the commercialisation of a good business idea. The business angel network exposes a range of potentially viable business prospects to willing investors by facilitating the flow of information about entrepreneurs and their businesses, thereby eliminating ambiguity, information asymmetry and transaction costs (Aernoudt and Erikson, 2002: 178; Van Osnabrugge and Robinson, 2000:374; Macht, 2006:1; Ehlrich, De Noble, Moore and Weaver, 1994:70; Sorheim, 2005:179). To achieve a holistic approach to a phenomenon which appears to be relatively new in South African business circles, the study will follow a qualitative approach in which two categories of populations will be used, one of small business operators and the other of business angels in South Africa. In the study, 20 small business operators and five business angels in Grahamstown will be approached using the convenience and snowballing sampling methods respectively. Face-to-face semi-structured interviews will be used as a data collection method and content analysis will be used as a data analysis tool (Collis and Hussey, 2003:156, Driver, Wood, Segal and Herrington, 2001:32, National Small Business Act ). There has been very limited research on business angels in the South African context, therefore the study would significantly contribute in entrepreneurship, government and small business development circles as it brings about attention to what the researcher predicts is an underutilised business start-up financing option.
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Application of catalysts and nanomaterials in the design of an electrochemical sensor for ochratoxin A

  • Authors: Flanagan, Shane Patrick
  • Date: 2011 , 2010-12-06
  • Subjects: Ochratoxins , Filamentous fungi , Electrochemical sensors , Nanostructured materials , Catalysts , Food contamination
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4121 , http://hdl.handle.net/10962/d1013328
  • Description: Ochratoxin A is the most potent chlorinated derivative of the ochratoxin group, consisting of a 5'-chlorinated dihydroisocoumarin moiety linked by an amide bond to l-phenylalanine. Produced as a secondary fungal metabolite by several species of Aspergillus and Penicillium, ochratoxin A has been shown to readily contaminate a large variety of commodities including cereals, groundnuts, dried fruit, spices and coffee. This has led to widespread contamination of ochratoxin in wine, beer, milk and meat products. As ochratoxin A is a potent nephrotoxin exhibiting teratogenic and carcinogenic properties, the development of a rapid screening platform for the cost effective control of ochratoxin A content in foodstuffs is therefore required. The evaluation of metallophthalocyanine and carbon nanotube electrode modification toward the development of a nanostructured biosensor capable of enhancing the electrochemical detection of ochratoxin A in complex media is presented. Cyclic voltammetry at a glassy carbon electrode allowed for the optimization of detection parameters including pH and type of supporting electrolyte. Britton-Robinson buffer was found to be the most suitable supporting electrolyte in terms of sensitivity and reproducibility obtaining a LOD of 0.28 μM as determined by differential pulse voltammetry. Subsequent analysis determined the dependence of OTA oxidation on pH in acidic media which proceeds with the transfer of two electrons to form a quinone/hydroquinone couple shown to adsorb to the electrode surface. Passivation of the electrode through adsorption of oxidation products was shown to severely limit the detection of OTA upon successive detection cycles. Comparison of various metallophthalocyanine modifiers showed an increase in sensitivity toward the detection of OTA at phthalocyanine complexes with metal based redox processes. However with the exception of NiPc and CoTCPc complexes, phthalocyanine modification was limited by the increase in deviation of current response and extent of fouling. NiPc modification showed an increase in sensitivity by two fold with fouling characteristics comparable to an unmodified electrode while low improvements in fouling was observed at CoTCPc modified electrodes with sensitivity in detection comparable to an unmodified electrode.Modification of the electrode with multi- and single walled carbon nanotubes produced a significant increase in sensitivity toward the detection of ochratoxin A. The electrocatalytic activity of nanotube modifiers was attributed to the increase in surface area and to the addition of oxygenated functional groups upon acid treatment as confirmed by Raman spectroscopy. Acid functionalization of the carbon nanotubes for a period of two hours produced the greatest increase in sensitivity obtaining a respective LOD of 0.09 μM and 0.03 μM for analysis of ochratoxin A at multi- and single walled carbon nanotube modified electrodes. Centrifugal purification of carbon nanotubes was deemed necessary to improve the electrocatalytic activity of the nanotube modifiers through the removal of carbonaceous impurities as visualized by atomic force microscopy. Furthermore, a crude lipase preparation, lipase A, was investigated as a potential biological recognition element for selective detection of ochratoxin A in complex media. Lipase A enabled the hydrolysis of ochratoxin A to the electroactive species ochratoxin α as confirmed by thin layer chromatography and voltammetric analysis. Additional isolation of a pure hydrolase from the lipase A preparation is required prior to utilization within a nanostructured biosensor platform capable of detecting ochratoxin A in complex media.
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Application of macroinvertebrate based biomonitoring approaches to assess anthropogenic impacts in the Swartkops River, South Africa

  • Authors: Odume, Oghenekaro Nelson
  • Date: 2011
  • Subjects: Water -- Pollution -- South Africa -- Swartkops River Water quality biological assessment -- South Africa -- Swartkops River Environmental monitoring -- South Africa -- Swartkops River Aquatic invertebrates -- Effect of water pollution on -- South Africa -- Swartkops River
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:6040 , http://hdl.handle.net/10962/d1006199
  • Description: A growing human population accompanied by urbanisation and industrialisation have led to over exploitation and pollution of freshwater resources and have consequently impacted on aquatic ecosystem health. The Swartkops River in the Eastern Cape of South Africa is no exception. It drains a heavily industrialised catchment which has led to deterioration of its water quality due to pollution. Integrated water resources management (IWRM) requires the concurrent sustainable use of water resources and the protection of aquatic ecosystem health. Macroinvertebrates are well known for their ability to reflect the health of the environment in which they live, thus they were used to assess anthropogenic impacts in the Swartkops River for this study. Macroinvertebrate based biomonitoring approaches, including the South African Scoring System version 5 (SASS5); a multimetric approach involving 19 metrics; Chironomidae community assessments and screening of morphological deformities in Chironomidae larvae, were applied at four selected sampling sites to assess environmental water quality in the Swartkops River. Macroinvertebrates were sampled us ing the SASS5 protocols. Chironomidae were mounted and identified as far as practically possible using available keys. Mentum, ligula, mandible, paraligula and antenna in Chironomidae larvae were screened for deformities. Physical and chemical water quality variables were measured at each of the selected sampling sites. All data were subjected to relevant statistical analyses. Of the four sites sampled during the study period, results revealed that water quality at site 1 was the least impacted with highest SASS5 scores, average score per taxa (ASPT) values, richness, diversity, equitability and Ephemeroptera –Plecoptera-Trichoptera (EPT) richness, as well as least incidences of chironomid deformities. Water quality at site 2 was considered the next least impacted with higher SASS5 scores, A SPT values, richness, diversity and equitability, and lower incidences of deformities compared to sites 3 and 4. SASS5 scores and ASPT values revealed that both sites 3 and 4 were critically modified but the multimetric analysis, Chironomidae community assessment and incidences of deformities in Chironomidae larvae indicated that site 3 is the most impacted of the four sampling sites, with least species diversity, richness, equitability and highest incidences of deformities. The study revealed the importance of multicriteria approach to environmental biomonitoring as an integrated water resources management tool, and based on the results, site 3, as the most impacted, could be prioritised for restoration intervention.
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Assessment of organochlorine pesticide residues in fish samples from the Okavango Delta, Botswana

  • Authors: Mpofu, Christopher
  • Date: 2011 , 2011-02-28
  • Subjects: Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4404 , http://hdl.handle.net/10962/d1006707 , Pesticides , Organochlorine compounds , Freshwater fishes -- Effect of pesticides on -- Botswana -- Okavango River Delta , Water -- Pesticide content -- Botswana -- Okavango River Delta , Catfishes -- Botswana -- Okavango River Delta , Tigerfish -- Botswana -- Okavango River Delta , Redbreast tilapia -- Botswana -- Okavango River Delta
  • Description: This thesis presents an evaluation of the dispersive solid-phase extraction (d-SPE) method referred to as the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the determination of four organochlorine pesticide residues in fish samples. The pesticides investigated in this study were o, p′-DDT, p, p′-DDE, aldrin and dieldrin. The combined use of Gas Chromatography with an Electron Capture Detector (GC-ECD) and sensitive Time of Flight (TOF) mass detector facilitated the identification of the target analytes. In the absence of certified reference material, the overall analytical procedure was validated by systematic recovery experiments on spiked samples at three levels of 2, 5 and 10 ng/g. The targeted compounds were successfully extracted and their recovery ranged from 76 to 96% with relative standard deviations of less than 13%. The optimum QuEChERS conditions were 2g of fish powder, 10 ml acetonitrile and 1 min shaking time. The optimal conditions were applied to assess the levels of chlorinated pesticides in blunt-tooth catfish (Clarias ngamensis), tigerfish (Hydrocynus vittatus), Oreochromis andersonii and red-breasted tilapia (Tilapia rendalli) from the Okavango Delta, Botswana. Dieldrin, p, p′-DDE and aldrin were detected in all the analysed samples with a concentration range of 0.04 – 0.29, 0.07 – 0.33, 0.04 – 0.28 and 0.03 – 0.24 ng/g per dry weight in O. andersonii, C. ngamensis, T. rendalli and H. vittatus respectively. These concentrations were below the US-EPA 0.1 μg/g allowable limit in edible fish and the Australian Maximum Residue Limit (MRL) of 50 - 1000 ng/g in fresh fish. DDT was not detected in all the fish species investigated. The mean lipid content recorded in the fish samples were 1.24, 2.16, 2.18 and 4.21% for H. vittatus, T. rendalli, O. andersonni and C. ngamensis respectively. No systematic trend was observed between fish age and pesticide levels in fish. Acetylcholinesterase (AChE) activity assays were performed to assess the effects of organochlorine pesticides in Clarias ngamensis. The enzyme activity recorded in Clarias ngamensis from the Okavango Delta and the reference site was 12.31 μmol of acetylcholine iodide hydrolysed/min/g brain tissue. The enzyme activity remained the same indicating no enzyme inhibition. The conclusions drawn from this study are that the QuEChERS method is applicable for the determination of organochlorine pesticide residues in fish matrices. The fish from the Okavango Delta are safe for human consumption.
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Bayesian logistic regression models for credit scoring

  • Authors: Webster, Gregg
  • Date: 2011
  • Subjects: Bayesian statistical decision theory Credit scoring systems Regression analysis Logistic regression analysis Monte Carlo method Markov processes Financial institutions
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:5574 , http://hdl.handle.net/10962/d1005538
  • Description: The Bayesian approach to logistic regression modelling for credit scoring is useful when there are data quantity issues. Data quantity issues might occur when a bank is opening in a new location or there is change in the scoring procedure. Making use of prior information (available from the coefficients estimated on other data sets, or expert knowledge about the coefficients) a Bayesian approach is proposed to improve the credit scoring models. To achieve this, a data set is split into two sets, “old” data and “new” data. Priors are obtained from a model fitted on the “old” data. This model is assumed to be a scoring model used by a financial institution in the current location. The financial institution is then assumed to expand into a new economic location where there is limited data. The priors from the model on the “old” data are then combined in a Bayesian model with the “new” data to obtain a model which represents all the available information. The predictive performance of this Bayesian model is compared to a model which does not make use of any prior information. It is found that the use of relevant prior information improves the predictive performance when the size of the “new” data is small. As the size of the “new” data increases, the importance of including prior information decreases
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Becoming African: debating post-apartheid white South African identities

  • Authors: Matthews, Sally
  • Date: 2011
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/142409 , vital:38077 , DOI: 10.1080/14725843.2011.530440
  • Description: The post-apartheid era necessitates the rethinking of white identities in South Africa. One way in which some white South Africans are seeking to redefine themselves is through describing themselves as African. However, claims by white South Africans that they too are Africans have been met with mixed responses from black South Africans. In this article I use contributions to an online university students' forum to explore ways in which some white South Africans are embracing an African identity and to consider ways in which some black South Africans are responding to white South Africans' shifting identities. I use contributions to this forum as a starting point to think about the possibilities and limitations that the embracing of an African identity has for the development of what Frankenberg calls ‘anti-racist forms of whiteness’ among white South Africans.
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Being Indian, being MK: an exploration of the experiences and ethnic identities of Indian South African Umkhonto we Sizwe members

  • Authors: Lalla, Varsha
  • Date: 2011
  • Subjects: Umkhonto we Sizwe (South Africa) -- Research Political activists -- Research -- South Africa East Indians -- Politics and government -- Research -- South Africa Ethnicity -- Political aspects -- South Africa -- Research
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2792 , http://hdl.handle.net/10962/d1003002
  • Description: Umkhonto we Sizwe (MK) was a military organization dominated by black Africans. Although it is not generally associated with Indian South Africans, who form a minority in the country, there were Indian MK members. This thesis explores the way in which Indian MK members reconciled aspects of their ethnic identity with their membership of MK. It explores the experiences of two generations of members: those born between 1929 and 1944 and those born between 1960 and 1969. In particular it looks at whether they experienced tensions between their ethnic and political identities. It explores what set these Indian South Africans apart from the rest of the Indian South African community that did not join MK. It also looks at what significant differences there were between different generations of Indian MK members. The research results show that the first generation MK members believe that their MK activities were „the highest form of passive resistance‟. An explanation for this way of referring to their activities could be that this was a way of reconciling tensions between their ethnic and political identities. The first generation was also very critical of the Indian SA community. This could be because they still feel part of this community despite having a strong political consciousness that is different from most of the community. It was found that some of the features that set Indian MK members apart from other Indian South Africans were that they were not raised in very religious households and occupied a fairly low rather than „middle man‟ economic position. In addition, members of the first generation of MK members were raised in comparatively multi-racial areas. Both generations made the decision to join MK because of Indian role models. There were some marked differences between the two generations of MK veterans. Most notably, the younger did not see their activities as in line with passive resistance and they also displayed more ambivalence about their ethnic identities.
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Being moved by a way the world is not

  • Authors: Jones, Ward E
  • Date: 2011
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/275631 , vital:55064 , xlink:href="https://doi.org/10.1007/s11229-009-9522-z"
  • Description: At the end of Lecture 3 of The Empirical Stance, Bas van Fraassen suggests that we see the change of view involved in scientific revolutions as being, at least in part, emotional. In this paper, I explore one plausible way of cashing out this suggestion. Someone’s emotional approval of a description of the world, I argue, thereby shows that she takes herself to have reason to take that description seriously. This is true even if she is convinced—as a scientific community is when it considers alternative theories—that this description is false, that it is not the way the world is.
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Biological control of Pereskia aculeata Miller (Cactaceae)

  • Authors: Paterson, Iain Douglas
  • Date: 2011
  • Subjects: Pereskia -- Biological control -- South Africa Cactus -- Biological control -- South Africa Invasive plants -- Biological control -- South Africa Curculionidae -- South Africa Pyralidae -- South Africa Insects as biological pest control agents -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5825 , http://hdl.handle.net/10962/d1007653
  • Description: Pereskia aculeata Miller (Cactaceae) is an environmental weed that is damaging to natural ecosystems in South Africa. The plant is native to Central and South America and was first recorded in South Africa in a botanical garden in 1858. In this thesis, research into the biological control of P. aculeata was conducted with the intention of improving the control of the weed. A pre-release study of the relationship between P. aculeata density and native plant biodiversity indicated that P. aculeata has a negative impact on native biodiversity. The native plant biodiversity associated with different P. aculeata densities was used to determine threshold values and goals for the control of the weed. A threshold value of 50% P. aculeata density was calculated, indicating that P. aculeata density must be maintained below 50% in order to conserve native plant biodiversity. The ultimate goal of the control programme should be to maintain P. aculeata densities below 30%. At these densities there was no significant difference in native plant biodiversity from if the weed were absent from the ecosystem. The biological control agent, Phenrica guérini Bechyne (Chrysomelidae), has been released in South Africa but the potential of the agent to impact P. aculeata is not known and no post release evaluation has been conducted. Impact assessment studies indicate that P. guérini does not impact P. aculeata, even at high densities, but the results of greenhouse experiments should be interpreted with caution because of problems with extrapolation into the field. Although observations in the field suggest that P. guérini has reduced P. aculeata densities at one site, it is clear that new biological control agents are needed to reduce the weed to acceptable levels. Identifying the origin of the South African P. aculeata population was believed to be important to the biological control programme due to the disjunct native distribution and intraspecific variation of the species. Natural enemies associated with plant genotypes in different parts of the native distribution may have developed specialised relationships with certain intraspecific variants of the plant, resulting in differences in agent efficacy on certain host plant genotypes. A molecular study indicated that the closest relatives to the South African weed population found in the native distribution were in Rio de Janeiro Province, Brazil. A bioassay experiment in which fitness related traits of the biological control agent, P. guérini, were measured on various P. aculeata genotypes was conducted to determine the importance of host plant intraspecific variation. There was little variation in fitness traits between genotypes and no evidence of intraspecific host plant specialization. Although intraspecific variation had no effect on agent efficacy in the case of P. guérini, it is possible that other natural enemies may be more specialized. Genotype matching is expected to be more important when natural enemies likely to be specialised to individual genotypes are considered for biological control. Potential biological control agents were prioritized from data collected on surveys in the native distribution. The most promising of these, based on the presence of feeding, incidence, predicted host range, climatic matching, genotype matching and mode of damage, are two species of Curculionidae, the current biological control agent P. guérini and the stem boring moth, Maracayia chiorisalis Walker (Crambidae). The two curculionid species and M. chlorisalis should be considered priorities for host specificity studies. Releases of P. guérini and any new biological control agents should be made at sites where the pre-release study was conducted so that post-release evaluation data can be compared with the pre-release data and the impact of biological control can be evaluated. Retrospective analyses of biological control programmes provide important ways of improving aspects of biological control programmes, such as methods of agent selection. The evaluation of success in biological control programmes is essential for retrospective analyses because factors that have lead to successes or failures can be analysed. Retrospective analyses of biological control programmes, such as this thesis, may improve weed management, thereby contributing to the conservation of natural resources.
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Biomechanical, physiological and perceptual responses of three different athlete groups to the cycle-run transition

  • Authors: Cripwell, Devin Matthew
  • Date: 2011
  • Subjects: Biomechanics -- Research , Human mechanics -- Research , Cycling -- Physiological aspects -- Research , Running -- Physiological aspects -- Research , Exercise -- Physiological aspects -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5106 , http://hdl.handle.net/10962/d1005184 , Biomechanics -- Research , Human mechanics -- Research , Cycling -- Physiological aspects -- Research , Running -- Physiological aspects -- Research , Exercise -- Physiological aspects -- Research
  • Description: The transition from cycling to running has been identified as one of the key determinants of success in triathlon, as it has been suggested that the cycle may affect subsequent running efficiency such that running performance is significantly altered or reduced. It is also suggested that athletes more adapted to the transition itself, rather than purely running or cycling, may be more efficient during the post-cycle running bout. The current study sought to investigate the effects of prior cycling on subsequent selected biomechanical, physiological and perceptual responses of three different athlete groups. Subjects were selected on the basis of their sporting background, and were divided into three groups – triathletes, cyclists and runners. Experimentation required subjects to perform a seven minute treadmill running protocol at 15km.h⁻¹, during which biomechanical (EMG, Stride rate, Stride length, Vertical acceleration), physiological (HR, VO₂, EE) and perceptual (RPE) responses were recorded. After resting, subjects were required to perform a twenty minute stationary cycle at 70% of maximal aerobic power (previously determined), immediately followed by a second seven minute treadmill running protocol during which the same data were collected and compared to those collected during the first run. Biomechanical responses indicate that the cycle protocol had no effect on the muscle activity or vertical acceleration responses of any of the three subject groups, while the triathlete group significantly altered their gait responses in order to preserve running economy. The triathlete group was the least affected when considering the physiological responses, as running economy was preserved for this group. The runner and cyclist groups were significantly affected by the transition, as running economy decreased significantly for these groups. Perceptual responses indicate that athletes more experienced with the transition may find the transition from cycling to running to be easier than those inexperienced in this transition. It is apparent that a high intensity cycle protocol has limited statistical impact on selected biomechanical responses, while physiological and perceptual responses were altered, during a subsequent run, regardless of athlete type. That said, the ability of transition-trained athletes to transition comfortably between disciplines was highlighted, which may have important performance implications.
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Biphenyl sorption to different soil clay minerals

  • Authors: Tandlich, Roman , Baláž, Štefan
  • Date: 2011
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/76869 , vital:30632 , https://doi.org/10.5897/AJAR10.1012
  • Description: Only limited information is available in the literature on the role of soil mineral surfaces in the sorption of hydrophobic organic pollutants. This knowledge gap is addressed through the assessment of biphenyl sorption to kaolinite, illite and bentonite; using the batch equilibration technique with incubations lasting 6 or 21 days at 28 ± 2°C in the dark [RT1]. Sorption of biphenyl onto kaolinite followed the Freundlich sorption isotherm, whereas linear sorption isotherms were observed on illite and bentonite [RT2]. The biphenyl sorption partition coefficient on kaolinite ranged from 0.1 to 9.1 cm3.g-1 after 6 days and no sorption was observed after 21 days. This could have been caused by a completely reversible sorption or a loss of binding capacity after 21 days [RT3]. The respective values of the biphenyl sorption partition coefficient on illite and bentonite ranged from 20.3 ± 0.3 to 120 ± 8 cm3.g-1.Sorption equilibrium on the internal clay surfaces was reached after 6 days, as indicated by the sorption data for illite and bentonite [RT4]. Access of biphenyl molecules to the internal clay surfaces is a function of the ionic strength of soil solution and the soil organic matter is the dominant site for biphenyl sorption after 6 to 21 days.
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Bluetooth audio and video streaming on the J2ME platform

  • Authors: Sahd, Curtis Lee
  • Date: 2011 , 2010-09-09
  • Subjects: Bluetooth technology , Mobile communication systems , Communication -- Technological innovations , Communication -- Network analysis , Wireless communication systems , L2TP (Computer network protocol) , Computer network protocols , Streaming audio , Streaming video
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4633 , http://hdl.handle.net/10962/d1006521 , Bluetooth technology , Mobile communication systems , Communication -- Technological innovations , Communication -- Network analysis , Wireless communication systems , L2TP (Computer network protocol) , Computer network protocols , Streaming audio , Streaming video
  • Description: With the increase in bandwidth, more widespread distribution of media, and increased capability of mobile devices, multimedia streaming has not only become feasible, but more economical in terms of space occupied by the media file and the costs involved in attaining it. Although much attention has been paid to peer to peer media streaming over the Internet using HTTP and RTSP, little research has focussed on the use of the Bluetooth protocol for streaming audio and video between mobile devices. This project investigates the feasibility of Bluetooth as a protocol for audio and video streaming between mobile phones using the J2ME platform, through the analysis of Bluetooth protocols, media formats, optimum packet sizes, and the effects of distance on transfer speed. A comparison was made between RFCOMM and L2CAP to determine which protocol could support the fastest transfer speed between two mobile devices. The L2CAP protocol proved to be the most suitable, providing average transfer rates of 136.17 KBps. Using this protocol a second experiment was undertaken to determine the most suitable media format for streaming in terms of: file size, bandwidth usage, quality, and ease of implementation. Out of the eight media formats investigated, the MP3 format provided the smallest file size, smallest bandwidth usage, best quality and highest ease of implementation. Another experiment was conducted to determine the optimum packet size for transfer between devices. A tradeoff was found between packet size and the quality of the sound file, with highest transfer rates being recorded with the MTU size of 668 bytes (136.58 KBps). The class of Bluetooth transmitter typically used in mobile devices (class 2) is considered a weak signal and is adversely affected by distance. As such, the final investigation that was undertaken was aimed at determining the effects of distance on audio streaming and playback. As can be expected, when devices were situated close to each other, the transfer speeds obtained were higher than when devices were far apart. Readings were taken at varying distances (1-15 metres), with erratic transfer speeds observed from 7 metres onwards. This research showed that audio streaming on the J2ME platform is feasible, however using the currently available class of Bluetooth transmitter, video streaming is not feasible. Video files were only playable once the entire media file had been transferred.
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Challenging the forked tongue of multilingualism: scholarship in African languages at SA Universities with specific reference to Rhodes

  • Authors: Kaschula, Russell H
  • Date: 2011
  • Language: English
  • Type: Text
  • Identifier: vital:586 , http://hdl.handle.net/10962/d1018946 , https://orcid.org/0000-0002-5481-6748
  • Description: [From the text] Effective multilingualism will aid SA in creating Social Cohesion (cultural, linguistic), a National Government initiative forming part of language planning. Languages should be seen as part of our environment and “resource package” within an intercultural paradigm. All students exiting School and University must be proficient in an African language and English or Afrikaans.
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Characterization and electrocatalytic applications of metallophthalocyanine-single walled carbon nanotube conjugates

  • Authors: Mugadza, Tawanda
  • Date: 2011 , 2011-03-30
  • Subjects: Phthalocyanines Pesticides Nanotubes Electrocatalysis Electrochemistry Transmission electron microscopy
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4419 , http://hdl.handle.net/10962/d1006855
  • Description: Metallophthalocyanine-single walled carbon nanotube conjugates were successfully synthesized and applied in the electrochemical characterizations of pesticides (amitrole and diuron) and 2-mercaptoethanol (2-ME). The formation of conjugates was confirmed through the use of the following analytical techniques: UV-vis, FTIR, Raman and XRD spectroscopies, atomic force and transmission electron microscopies and voltammetry. Chemically linking SWCNT to MPcs created platforms that offered efficient transfer of electrons and this was confirmed through electrochemical impedance studies (EIS) and voltammetry as shown by lower ΔEp values observed in conjugates. Carboxy carrying MPcs have very poor electron transfer kinetics (both tetrasubstituted and low symmetry), but the presence of SWCNTs activates their catalysis. All electrochemical studies were done at pH 4. Cyclic voltammetry, rotating disk linear sweep voltammetry, chronoamperometry and EIS were used in the electrochemical characterization of 2-ME and the pesticides on poly-Ni(OH)TAPc and MPc-SWCNT modified glassy carbon electrodes (GCEs). High Tafel slopes were observed for the pesticides relative to 2-ME, an indication of the passivating nature of their oxidation products. However, conjugates showed very high resistances to passivation and were easily regenerated by shaking in methanol. Improved catalysis of the conjugates is also indicated by the high catalytic rate constants for the analytes, observed on these electrodes. Conjugates of low symmetry MPcs with SWCNTs gave the highest catalytic rate constants, confirming better catalysis on these electrode surfaces. The nature of SWCNT functionalization also affected catalysis, with amine functionalized SWCNTs inducing better catalytic properties into the MPcs than carboxylic acid terminated CNTs. The presence of amine functionalized SWCNTs activates the catalysis of non-catalytic carboxy-carrying MPcs and this is more pronounced in conjugates of tetrasubstituted MPcs relative to those of low symmetry Pcs. Ethylene amine (EA) functionalized SWCNTs reduced redox overpotentials of the MPcs more than the phenyl-amine (PA) functionalized counterparts. Poly-NiTAPc was successfully converted to poly-Ni(OH)TAPc through cyclisation in pH 4 buffer and showed very good catalytic properties towards diuron, relative to the former.
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Characterization of stratified L-topological spaces by convergence of stratified L-filters

  • Authors: Orpen, David Lisle
  • Date: 2011
  • Subjects: Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5402 , http://hdl.handle.net/10962/d1005216 , Topology , Generalized spaces , Filters (Mathematics) , Topological spaces
  • Description: For the case where L is an ecl-premonoid, we explore various characterizations of SL-topological spaces, in particular characterization in terms of a convergence function lim: FS L(X) ! LX. We find we have to introduce a new axiom , L on the lim function in order to completely describe SL-topological spaces, which is not required in the case where L is a frame. We generalize the classical Kowalski and Fischer axioms to the lattice context and examine their relationship to the convergence axioms. We define the category of stratified L-generalized convergence spaces, as a generalization of the classical convergence spaces and investigate conditions under which it contains the category of stratified L-topological spaces as a reflective subcategory. We investigate some subcategories of the category of stratified L-generalized convergence spaces obtained by generalizing various classical convergence axioms.
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Co-utilisation of microalgae for wastewater treatment and the production of animal feed supplements

  • Authors: Johnson, Hailey E
  • Date: 2011
  • Subjects: Microalgae -- Biotechnology , Algae culture , Algae products , Waste products as feed , Sewage -- Purification , Organic wastes -- Recycling , Food industry and trade -- Waste disposal , Agriculture -- Waste disposal
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3940 , http://hdl.handle.net/10962/d1003999 , Microalgae -- Biotechnology , Algae culture , Algae products , Waste products as feed , Sewage -- Purification , Organic wastes -- Recycling , Food industry and trade -- Waste disposal , Agriculture -- Waste disposal
  • Description: Microalgae have a variety of commercial applications, the oldest of which include utilisation as a food source and for use in wastewater treatment. These applications, however, are seldom combined due to toxicity concerns, for ethical reasons, and generally the requirement for cultivation of a single algae species for use as a feed supplement. These problems might be negated if a “safer” wastewater such as that from agricultural and/or commercial food production facilities were to be utilised and if a stable algae population can be maintained. In this investigation preliminary studies were carried out using an Integrated Algae Pond System (IAPS) for domestic wastewater treatment to determine the species composition in the associated High Rate Algae Ponds (HRAPs). The effect of different modes of operation, continuous versus batch, on nutrient removal, productivity and species composition was also investigated. Furthermore, indigenous species in the HRAP were isolated and molecularly identified as, Chlorella, Micractinium, Scenedesmus and Pediastrum. Additionally, the effect of the nor amino acid, 2-hydroxy-4-(methylthio)-butanoic acid (HMTBA) and its Cu-chelated derivative, on the growth and biochemical composition of Chlorella, Micractinium, Scenedesmus, Pediastrum and Spirulina was investigated. Species composition in the HRAP was stable under continuous operation with Micractinium dominating > 90% of the algae population. Under batch operation the population dynamic shifted; Chlorella outcompeted Micractinium possibly due to nutrient depletion and selective grazing pressures caused by proliferation of Daphnia. Higher species diversity was observed during batch mode as slower growing algae were able to establish in the HRAP. Nutrient removal efficiency and biomass productivity was higher in continuous mode, however lower nutrient levels were obtained in batch operation. HMTBA did not significantly affect growth rate, however treatment with 10 mg.L-1 resulted in slightly increased growth rate in Micractinium and increased final biomass concentrations in Chlorella, Micractinium and Spirulina (although this was not statistically significant for Micractinium and Spirulina), which are known mixotrophic species. Algae treated with Cu-HMTBA, showed reduced final biomass concentration with 10 mg.L-1, caused by Cu toxicity. Biochemical composition of the algae was species-specific and differed through the growth cycle, with high protein observed during early growth and high carbohydrate during late growth/early stationary phase. Additionally, 0.1 mg.L-1 HMTBA and Cu-HMTBA significantly reduced protein content in Chlorella, Micractinium, Scenedesmus and Pediastrum. In conclusion, operation of the HRAP in continuous culture provided suitable wastewater treatment with high productivity of an ideal species, Micractinium, for use in animal feed supplementation. This species had 40% protein content during growth (higher than the other species tested) and dominated the HRAP at > 90% of the algae population during continuous mode. Addition of HMTBA (> 1 mg.L-1) to algae cultivation systems and those treating wastewater, has the potential to improve productivity and the value of the biomass by enhancing protein content. Overall, the co-utilisation of microalgae for wastewater treatment and the generation of a biomass rich in protein, for incorporation into formulated animal feed supplements, represents a closed ecosystem which conserves nutrients and regenerates a most valuable resource, water.
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Cointegration in equity markets: a comparison between South African and major developed and emerging markets

  • Authors: Petrov, Pavel
  • Date: 2011
  • Subjects: Cointegration Stock exchanges -- South Africa Stock exchanges -- Developing countries Stock exchanges -- Developed countries South Africa -- Economic conditions Portfolio management -- South Africa Econometrics Autoregression (Statistics)
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:5575 , http://hdl.handle.net/10962/d1005539
  • Description: Cointegration has important implications for portfolio diversification. One of these is that in order to spread risk it is advisable to invest in markets that are not cointegrated. Over the last several decades communication technology has made the world a smaller place and hence cointegration in equity markets has become more prevalent. The bulk of research into cointegration focuses on developed and Asian markets, with little research been done on African markets. This study compares the Engle-Granger and Johansen tests for cointegration and uses them to calculate the level of cointegration between South African and other global equity markets. Each market is compared pair-wise with South Africa and the results have been that in general South Africa is cointegrated with other emerging markets but not really with African nor developed markets. Short-run analysis with the error correction was carried out and showed that in general markets respond slowly to any disequilibrium. Innovation accounting methods showed that the country placed first in Cholesky ordering dominates the other one. Multivariate cointegration was carried out using three selections of 4, 6 and 8 market portfolios. One of the markets was SA and the others were all chosen based on the criteria that they are not pair-wise cointegrated with SA. The level of cointegration varied depending on the portfolios, as did the error correction rates, impulse responses and variance decomposition. The one constant was that the USA dominated any portfolio where it was introduced. Recommendations were finally made about which market portfolio an investor should consider as most favourable.
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