High performance nonwovens in technical textile applications
- Authors: Ogunleye, Christopher Olarinde
- Date: 2013
- Subjects: Nonwoven fabrics , Textile fabrics -- Technological innovations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10356 , http://hdl.handle.net/10948/d1021011
- Description: The aim of this research was to establish the optimum processing conditions and parameters for producing nonwoven fabrics best suited for application in disposable and protective wear for surgical gowns, drapes and laboratory coats. Carded and crosslapped webs, of three basic weights (80, 120, and 150g/m2), from greige (unscoured and unbleached) cotton, viscose and polyester fibres, were hydroentangled, using three different waterjet pressures (60, 100 and 120 bars), on a Fleissner Aquajet hydroentanglement machine. An antibacterial agent (Ruco-Coat FC 9005) and a fluorochemical water repellent agent (Ruco Bac-AGP), were applied in one bath using the pad-dry-cure technique, to impart both antibacterial and water repellent properties to the fabrics, SEM photomicrographs indicating that the finished polymers were evenly dispersed on the fabric surface. The effect of waterjet pressure, fabric weight and type and treatment on the structure of the nonwoven produced, was evaluated by measuring the relevant characteristics of the fabrics. As expected, there was an interrelationship between fabric weight, thickness, and density, the fabric thickness and mass density increasing with fabric weight. An increase in waterjet pressure decreased the fabric thickness and increased the fabric density. The water repellent and antibacterial treatment increased the fabric weight and thickness. The antimicrobial activity of the fabrics was assessed by determining the percentage reduction in Staphylococcus aureus and Escherichia coli bacteria population. The maximum percent reduction at 24hrs contact time for both bacteria ranged from 99.5 to 99.6 percent for all the fabric types. The standard spray test ratings for the three treated fabrics ranged from 80-90 percent, whereas that of the untreated water repellent fabric was zero, while the contact angles for all the fabric types exceeded 90 degrees, indicating good resistance to wetting. It was found that the tensile strength of the fabric in the cross-machine direction was higher than that in the machine direction, for both the treated and untreated fabrics, with the tensile strengths in both the MD and CD of the treated fabrics were greater than that of the untreated fabrics, the reverse being true for the extension at break. An increase in waterjet pressure increased the tensile strength but decreased the extension at break, for both the treated and untreated fabrics. The finishing treatment decreased the mean pore size of all the fabrics, the mean pore size decreasing with an increase in fabric weight and waterjet pressure. An increase in waterjet pressure and fabric weight decreased the air and water vapour permeability, as did the finishing treatment, although the differences were not always statistically significant. The polyester fabrics had the highest water and air permeability. Hence low weight fabrics of 80 g/m2, which were hydroentangled at low water jet pressures of 60 bars, were suitable for use in this study due to their higher air and water vapour permeability as well as higher pore size distribution. These group of fabrics thus meet the requirements for surgical gowns, drapes, nurses’ uniforms and laboratory coats.
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- Date Issued: 2013
Improving decision making through analysing the economic impact of budget allocation at the city of Cape Town
- Authors: Kaiser, Gisela Noelle
- Date: 2013
- Subjects: Cape Town (South Africa) -- Politics and government , City planning -- South Africa --Cape Town , Budget -- South Africa -- Cape Town , Local government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9684 , http://hdl.handle.net/10948/d1008305 , Cape Town (South Africa) -- Politics and government , City planning -- South Africa --Cape Town , Budget -- South Africa -- Cape Town , Local government
- Description: Local government is at the forefront of engagement between the government and South Africa’s people, delivering basic services to communities. Following the transition to a democratic government in 1994, the country was demarcated in a manner that provides complete coverage by local government. Annually, managing the administration of service delivery implementation at local government level costs the country many billions. Much of the revenue used by local government in providing services is derived from income from sale of basic services and property rates, augmented by allocations from national and provincial government, equitably shared amongst municipalities. Local government has autonomy in its operations, but is strictly governed by a collection of cascading legislation, introduced to protect the interests of the people. The primary objective of the research was to investigate the efficacy of budget expenditure in local government, in particular the City of Cape Town as a metropolitan municipality. With an annual budget approaching R30 billion, the aim was to establish how the budget was determined and allocated to the service menu provided by the City, and to investigate whether better methods of allocating expenditure could be developed. A mixed research methodology was followed, relying on quantitative methods for analysing survey data statistically, while providing for detailed qualitative methods in interviewing and studying the specific case in detail. The theoretical perspective most suited to this research was found to be that of pragmatism, for its flexibility of interpretation, practicality and space for multiple perspectives. A constructivist epistemology was adopted to provide for the interplay between object and subject in constructing meaning. This research focused on examination of applicable legislation, secondary data in reports, and statistical analysis of opinion surveys of municipal officials involved in budgeting at different levels and interviews with key stakeholders. The findings indicate that budget allocation can be improved upon in a number of ways, despite complying with a myriad of restrictive and onerous regulations applicable to local government. It was found that the administration is fragmented in its operations and that the structure of necessity favours isolated service delivery rather than integration. Further, that compliance impacts negatively on time spent in planning and pursuit of strategic intent to the extent that Reporting often becomes a more important deliverable than basic services. The size of the City hinders common understanding, and introducing any change in political vision requires particular attention.
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- Date Issued: 2013
International joint ventures and firm value: an empirical study of South African partner firms
- Authors: Mangwengwende, Tadiwanashe Mukudzeyi
- Date: 2013
- Subjects: Joint ventures Joint ventures -- South Africa Business enterprises -- Valuation International business enterprises
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1033 , http://hdl.handle.net/10962/d1004174
- Description: This study investigates international equity joint ventures (IJVs) and South African partner firm value creation at formation. In addition, it tests whether four contentious formation characteristics, namely, the geographical location of the IJV partner, the level of economic development in the IJV partner’s home country, the level of equity held by the South African firm and the industry of the South African firm, can explain when South African IJVs are value enhancing and when they are value diminishing. IJVs are a popular business mode and an important channel for infrastructure and skills investment in developing countries. However, despite their popularity and potential social benefits, these IJVs are predominantly created by the decisions of private firms to collaborate with foreign firms and governments. Consequently the preservation and development of the IJV investment channel is dependent on the encouragement of private firm IJV participation. It is at uncovering potential tools to encourage IJV participation by South African firms that IJV firm value creation becomes important because it stands as a motivator for South African firms’ involvement in IJVs. Existing literature on IJVs and partner firm value has presented conflicting evidence with support for the views that they are value enhancing, value diminishing or of no immediate consequence to their partners’ firm value. Consequently, previous research offers limited firm value support for IJVs. For South African firms considering joint ventures and national policy makers determined to promote IJVs there is a need for an investigation of South African partner IJV firm value effects. Moreover, it is also necessary to test potential explanatory variables that may help to explain when the IJVs are value enhancing and when they are not as this will inform IJV contract negotiations and how limited national government resources are used to promote IJVs. In order to assess firm value creation for South African firms this study performed event studies on IJV formation announcements from 1998 to 2011 using daily share returns from the Johannesburg Securities Exchange taking care to incorporate recent developments in the event study methodology. The study found that while the market responds to IJV announcements, its responses do not, on average, reflect that IJVs are firm value enhancing for their South African partners at formation. This stands in contrast to considerable empirical literature and IJV firm value creation theory. In addition, factoring in formation characteristics, argued to potentially help explain cases of value creation and destruction from IJVs, provided limited explanation for positive and negative wealth effectsfor South African firms entering IJVs. This result has important value for IJV participants, national economic policy makers and IJV researchers. For IJV participants and national policy makers, the results caution unfettered entry/support for IJVs and challenge the role of equity distribution in determining the value of the IJV to its partner firms. For IJV researchers, the results present new evidence questioning IJV firm value creation at formation and provide a potential explanation for the conflict in previous IJV research. The study makes four key contributions to the existing knowledge of IJV firm value creation. Firstly, it assesses IJV wealth effects for the hitherto untested South African IJVs. Secondly, in doing so it adds a new data set (South African IJVs) to the current IJV literature. Thirdly, in reviewing the literature on IJV firm value creation the study presents a disaggregated model of IJV firm value creation from which to develop IJV research and potentially solve the persistent conflict in empirical results on IJV partner wealth effects. Finally, it informs future South African IJV agreements by uncovering factors that influence and do not influence partner wealth effects for South African firms.
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- Date Issued: 2013
Invasion of Lantana into India: analyzing introduction, spread, human adaptations and management
- Authors: Hari Krishnan, Ramesh Kannan
- Date: 2013
- Subjects: Lantana -- India Weeds -- Control -- India Plant introduction -- India Natural resources -- India Botany, Economic -- India Botany -- Social aspects -- India
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4728 , http://hdl.handle.net/10962/d1001756
- Description: Objectives and Research Questions 1. To reconstruct the history of invasion of Lantana in India from where, by who, and when was Lantana species introduced into India?, given its long history in the country, is it still spreading or has it become more or less stable? 2. To study the human adaptation to Lantana invasion: socioeconomic causes and consequences of the use of Lantana as an alternative source of livelihood for forest dependent communities in southern India; how have local communities adapted to the invasion?; what are the key determinants that may have driven communities to use Lantana?; what are the economic consequences of the use of Lantana by local communities? 3. To critically review local practices and forest policy for the management of Lantana in southern India.; how has the use of Lantana by local communities impacted its local regeneration?; does the use of Lantana in local context have implications for its management?; what has been the role of the Forest Department and its policies in managing Lantana?
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- Date Issued: 2013
Investigation into causes of service delivery protests in municipalities :a case study of Nelson Mandela Bay Municipality
- Authors: Shaidi, Elisante Walter
- Date: 2013
- Subjects: Municipal government|zSouth Africa -- Port Elizabeth , Municipal government
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:8245 , http://hdl.handle.net/10948/d1011153 , Municipal government|zSouth Africa -- Port Elizabeth , Municipal government
- Description: This study investigates the causes of the service delivery protests in South African municipalities that occurred between 2005 to 2013. In a sense, the recent widespread service delivery protests which, in many instances, have turned violent, have sounded an alarm that cannot be ignored. The study is premised on the fact that no political democracy can survive and flourish if the mass of its people remain in poverty, and in a state of inequality and unemployed without tangible prospects for a better life. In this regard, the presence of service delivery protests, especially violent ones, is a threat to South Africa’s young democracy and its sustainability. This study is based on the assumption that the Nelson Mandela Bay Metropolitan Municipality, like other municipalities in South Africa, could be confronted with the possibility of further violent service delivery protests if the current causes were not scientifically investigated and solutions found. The study adopted a hypothesis with a view that South African municipalities could succeed in rendering effective public services if matters of poor public participation, corruption, service delivery inhibiting systemic factors, a cumbersome legislative environment, political infighting, poor intergovernmental fiscal regime and the low capacity of municipalities were adequately addressed. The study proposed to provide a brief literature review on the emergence of service delivery protests against the backdrop of a theoretical investigation on the new local government developmental mandate. The empirical survey and research methodology employed in the study is described, followed by the operationalisation of the survey questionnaire used for gathering field data. The research findings of the empirical survey are then statistically analysed, interpreted and reported. Some of the findings on the causes of service delivery protests includes slow pace of service delivery, especially in the delivery of sustainable human settlements, poor public participation and other underpinning systemic factors. Recommendations flowing from, inter alia, the results of the empirical study, are presented on how the existing status quo can be changed to enhance service delivery and development. If adopted, these recommendations will enable the Nelson Mandela Bay Municipality, as a development agent, to fulfil its developmental mandate thereby addressing the causes of the service delivery protests currently facing it.
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- Date Issued: 2013
Investigation into the technical feasibility of biological treatment of precious metal refining wastewater
- Authors: Moore, Bronwyn Ann
- Date: 2013
- Subjects: Sewage -- Purification -- Biological treatment -- South Africa Sewage -- Purification -- Activated sludge process -- South Africa Water reuse -- South Africa Flotation -- South Africa Platinum mines and mining -- Waste disposal -- South Africa Platinum mines and mining -- Economic aspects -- South Africa Mine water -- Environmental aspects -- South Africa Platinum mines and mining -- Waste minimization -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3888 , http://hdl.handle.net/10962/d1002013
- Description: The hydrometallurgical refining of platinum group metals results in large volumes of liquid waste that requires suitable treatment before any disposal can be contemplated. The wastewater streams are characterized by extremes of pH, high inorganic ion content (such as chloride), significant residual metal loads and small amounts of entrained organic compounds. Historically these effluents were housed in evaporation reservoirs, however lack of space and growing water demands have led Anglo Platinum to consider treatment of these effluents. The aim of this study was to investigate whether biological wastewater treatment could produce water suitable for onsite reuse. Bench-scale activated sludge and anaerobic digestion for co-treatment of an acidic refinery waste stream with domestic wastewater were used to give preliminary data. Activated sludge showed better water treatment at lab scale in terms of removal efficiencies of ammonia (approximately 25%, cf. 20% in anaerobic digestion) and COD (70% cf. 43% in digestion) and greater robustness when biomass health was compared. Activated sludge was consequently selected for a pilot plant trial. The pilot plant was operated on-site and performed comparably with the bench-scale system, however challenges in the clarifier design led to losses of biomass and poor effluent quality (suspended solids washout). The pilot plant was unable to alter the pH of the feed, but a two week maturation period resulted in the pH increasing from 5.3 to 7.0. Tests on algal treatment as an alternative or follow-on unit operation to activated sludge showed it not to be a viable process. The activated sludge effluent was assessed for onsite reuse in flotation and it was found that there was no significant difference between its flotation performance and that of the process water currently used, indicating the effluent generated by the biological treatment system can be used successfully for flotation. Flotation is the method whereby minerals refining operations recover minerals of interest from ore through the addition of chemicals and aeration of the ore slurry. Target minerals adhere to the bubbles and can be removed from the process.
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- Date Issued: 2013
Low symmetry metallophthalocyanines and their nanoparticle conjugates for photodynamic antimicrobial chemotherapy
- Authors: Masilela, Nkosiphile
- Date: 2013
- Subjects: Nanoparticles Anti-infective agents Chemotherapy Photochemotherapy Quantum dots Gold Silver , Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4278 , http://hdl.handle.net/10962/d1001906
- Description: This thesis reports on the syntheses of novel low symmetrically substituted Zn, Sn, Ge and Ti MPc complexes containing a single carboxylic or cysteinyl group available for attachments to MNPs. The complexes were extensively characterized by various techniques to ensure their purity. Various metallic nanoparticles consisting of silver (AgNPs), gold (AuNPs) as well as quantum dots (QDs) were successfully prepared and conjugated to the low symmetry phthalocyanine complexes. The conjugates were successfully characterized using many techniques. The Q-band maxima of the MPcs were observed at completely different wavelength regions depending on the nature of the substituents and the central metal used. Blue shifting of the Q band in the absorption spectra was observed for the complexes in the presence of AuNPs, while aggregation was observed in the presence of quantum dots. The complexes were successfully electrospun into polymer fibers for the antimicrobial inhibition of bacteria. The photophysical and photochemical properties of these complexes were extensively investigated. Higher triplet and singlet oxygen quantum yields were achieved for the Ge Pc complexes, with all the complexes giving reasonable singlet oxygen quantum yields. An enhancement in triplet and singlet oxygen quantum yields was observed for all the complexes in the presence of metal nanoparticles. However, the singlet oxygen quantum yields decreased for all the complexes when incorporated into electrospun fibers. The antimicrobial behaviour of the complexes was investigated against Bacillus Subtilis and Staphylococcus Aureus in solution and in the fiber matrix. High antimicrobial inhibitions were observed for the Ge complexes followed by the ZnPc derivatives. All the low symmetry ZnPc derivatives were conjugated to AgNPs and their antimicrobial behaviour was compared to their symmetrical counterparts. The best antimicrobial inhibition behaviour was observed for the low symmetry Pcs when compared to their symmetrical counterparts. In the absence and in the presence of AgNPs, axially ligated SiPc also showed better antimicrobial activity when it was compared to the unsubstituted ZnPc complex.
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- Date Issued: 2013
M-health user experience framework for the public healthcare sector
- Authors: Ouma, Stella
- Date: 2013
- Subjects: Communication in public health , Public health -- South Africa , Wireless communication systems in medical care
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9827 , http://hdl.handle.net/10948/d1020793
- Description: The public healthcare sectors within developing nations face a lot of challenges because of constrained resources available to them. The South African public healthcare sector is no different. Although it serves the majority of the South African population, most of the financial resources are directed towards the private sector, which serves very few individuals when compared to the public healthcare sector. Apart from that, other challenges that the National Department of Health has to deal with include the lack of sufficiently trained healthcare employees who can work on the different levels of the public healthcare sector, as well as the burden of diseases such as HIV and Aids, tuberculosis and other chronic diseases. In order to improve service delivery, the National Department of Health is introducing Information and Communications Technology interventions that can increase efficiency and reduce costs, thereby improving the quality of service delivery. This research delivers an m-health application user experience framework to be proposed to the National Department of Health in South Africa, in order to assist in scaling up of m-health applications. The m-health applications that can benefit the South African population if scaled up successfully include those that can be used in remote data collection, treatment and compliance, accessing patients records, remote monitoring, communication and training for healthcare workers and applications that can be used for education and awareness. The study focused on three domains: the Human-Computer Interaction domain, public healthcare domain and Health Informatics domain. The proposed framework was realized by investigating mobile user experience components, mobile health requirements and the South African public healthcare domain components that contribute to the m-health user experience framework. This research was conducted through the interpretivist philosophy. Due to the exploratory nature of the study, an application of qualitative methodology was used. The conceptual theoretical framework was validated through a single case study approach by m-health user experience experts, who reside in South Africa. Data were analysed inductively. An m-health user experience framework was provided at the end of the study. An m-health user experience framework can assist the National Department of Health to look into design issues, address m-health requirements and put the domain needs in place, thus enabling the Department to successfully scale up implementations of m-health applications nationwide.
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- Date Issued: 2013
Microcystin enhances the fitness of microcystin producing cyanobacteria at high light intensities by either preventing or retarding photoinhibition
- Authors: Phelan, Richard Reginald
- Date: 2013
- Subjects: Microcystins , Microcystis , Cyanobacterial toxins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10354 , http://hdl.handle.net/10948/d1020957
- Description: Several genera of cyanobacteria produce microcystin, a monocyclic peptide, with a unique chemical structure. To date, there have been over a 100 different structural variants of microcystin which have been identified. Microcystin production is affected by numerous environmental factors. However, the primary modulating factor for intracellular microcystin quota is the intracellular N:C ratio. No clearly defined biological role has been described for microcystin. Proposed roles for microcystin include defence against plankton grazers, metal chelation, an infochemical and a protectant against oxidative stress. There is sufficient evidence to support a biological role for microcystin in photosynthesis: microcystin is predominantly located in the thylakoid membranes, the microcystin gene cluster is differentially expressed as a function of light and a growth advantage for the microcystin producer in saturating light intensities. The purpose of this study is to investigate a possible biological role for microcystin in preventing photoinhibition and thus explaining the growth advantage observed in toxin-producers over non-toxin-producers. The uptake of exogenous microcystin was observed in Synechocystis PCC 6803 which was internalized and located in the thylakoid membranes and caused the inhibition of photosynthesis. Microcystin variants and increasing concentrations of microcystin-LR had no effect on the fluidity of the thylakoid membranes. The exposure of thylakoid membranes from Synechocystis PCC 6803 to physiologically relevant concentrations of different microcystin variants resulted in the inhibition of photosystem II activity but not photosystem I activity. The inhibition of photosystem II was variant dependent and concentration dependent for microcystin-LR and microcystin-RR. Chlorophyll a fluorescence data showed that photosystem II inhibition was caused by the inhibition of the oxygen evolving complex. Furthermore, a completion study revealed that the microcystin-producing Microcystis PCC 7806 had a competitive advantage over the non-microcystin producing ΔmcyA mutant of Microcystis PCC 7806 at high light intensities. The data indicates that microcystin protects the toxin-producer by either retarding or preventing photoinhibition and thus identifying the first data supported function for microcystin in cyanobacteria.
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- Date Issued: 2013
Modulation of Plasmodium falciparum chaperones PfHsp70-1 and PfHsp70-x by small molecules
- Authors: Cockburn, Ingrid Louise
- Date: 2013
- Subjects: Plasmodium falciparum Heat shock proteins Molecular chaperones Homeostasis Protein folding Malaria Antimalarials Escherichia coli
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3887 , http://hdl.handle.net/10962/d1001747
- Description: The heat shock proteins of ~ 70 kDa (Hsp70s) are a conserved group of molecular chaperones important in maintaining the protein homeostasis in cells, carrying out functions including refolding of misfolded or unfolded proteins. Hsp70s function in conjunction with a number of other proteins including Hsp40 cochaperones. Central to the regulation Hsp70 activity is the Hsp70 ATPase cycle, involving ATP hydrolysis by Hsp70, and stimulation of this ATP hydrolysis by Hsp40. PfHsp70-1, the major cytosolic Hsp70 in the malaria parasite, Plasmodium falciparum, and PfHsp70-x, a novel malarial Hsp70 recently found to be exported to the host cell cytosol during the erythrocytic stages of the P. falciparum lifecycle, are both thought to play important roles in the malaria parasite’s survival and virulence, and thus represent novel antimalarial targets. Modulation of the function of these proteins by small molecules could thus lead to the development of antimalarials with novel targets and mechanisms. In the present study, malarial Hsp70s (PfHsp70-1 and PfHsp70-x), human Hsp70 (HSPA1A), malarial Hsp40 (PfHsp40) and human Hsp40 (Hsj1a) were recombinantly produced in Escherichia coli. In a characterisation of the chaperone activity of recombinant PfHsp70-x, the protein was found to have a basal ATPase activity (15.7 nmol ATP/min/mg protein) comparable to that previously described for PfHsp70-1, and an aggregation suppression activity significantly higher than that of PfHsp70-1. In vitro assays were used to screen five compounds of interest (lapachol, bromo-β-lapachona and malonganenones A, B and C) belonging to two compound classes (1,4 naphthoquinones and prenylated alkaloids) for modulatory effects on PfHsp70-1, PfHsp70-x and HsHsp70. A wide range of effects by compounds on the chaperone activities of Hsp70s was observed, including differential effects by compounds on different Hsp70s despite high conservation (≥ 70 % sequence identity) between the Hsp70s. The five compounds were shown to interact with all three Hsp70s in in vitro binding studies. Differential modulation by compounds was observed between the Hsj1a-stimulated ATPase activities of different Hsp70s, suggestive of not only a high degree of specificity of compounds to chaperone systems, but also distinct interactions between different Hsp70s and Hjs1a. The effects of compounds on the survival of P. falciparum parasites as well as mammalian cells was assessed. Bromo-β-lapachona was found to have broad effects across all systems, modulating the chaperone activities of all three Hsp70s, and showing significant toxicity toward both P. falciparum parasites and mammalian cells in culture. Malonganenone A was found to modulate only the malarial Hsp70s, not human Hsp70, showing significant toxicity toward malarial parasites (IC₅₀ ~ 0.8 μM), and comparatively low toxicity toward mammalian cells, representing therefore a novel starting point for a new class of antimalarials potentially targeting a new antimalarial drug target, Hsp70.
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- Date Issued: 2013
Molecular signaling in colorectal carcinogenesis : the roles and relationships of beta-catenin, PPARgamma and COX-2
- Authors: Fredericks, Ernst
- Date: 2013
- Subjects: Colon (Anatomy) -- Cancer , Cyclooxygenase 2 , Peroxisomes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10357 , http://hdl.handle.net/10948/d1021014
- Description: Colorectal cancer (CRC) is a common disease with significant morbidity and mortality. In spite of significant advances in understanding the molecular signaling in this disorder, unanswered questions remain. Cyclooxygenase-2 (COX-2) and β-catenin have established roles in colorectal carcinogenesis, with both being upregulated early in the disease course. The role of peroxisome proliferator-activated receptor γ (PPARγ) is less clear, but has been shown to be downregulated in colon cancer models. Butyrate, a short chain fatty acid, produced by colon microbiota and transported into the colonocyte by transporter proteins, appears to be important in early carcinogenesis. The butyrate concentration is reduced in CRC and so are its transporters. Interleukin-17 (IL-17) plays a role in colitis-associated colorectal cancer (CAC), but its function in sporadic CRC is less clear. Similarly, Protein kinase C (PKC) has proven involvement in many solid tumours, including CRC, but its exact mechanistic role is still speculative. AIM: To investigate the role and possible signaling pathways of the major role players, β-catenin, COX-2 and PPARγ in early CRC. Further, to elucidate the mechanistic pathways of butyrate and its transporters, IL-17 and PKC in CRC. METHOD: Informed consent was obtained for all patients. Patients were recruited in various disease categories, including normal, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and CRC. Colon biopsy specimens were obtained during colonoscopy and used for immunohistochemistry (IHC) and gene expression analysis of the above genes by quantitative polymerase chain reaction (qPCR). RESULTS: β-catenin mRNA and protein expression was increased in CRC and the IBD groups compared to the normal group, while it was reduced in the IBS groups. COX-2 mRNA expression showed a steady increase from normal, through IBS, IBD and CRC groups to a statistically significant degree. The COX-2 protein expression, however, did not match the mRNA expression with increased COX-2 protein expression in normal and IBS groups and reduced expression in IBD and CRC groups. PPARγ mRNA expression was unchanged in IBD and CRC groups, but significantly increased in the IBS group compared to normal. Butyrate transporter, SLC16A1 mRNA was significantly reduced in CRC, but also in the IBS groups, which was unexpected. In the IBD group, SLC16A1 mRNA was unchanged in Crohn’s disease (CD) but significantly reduced in ulcerative colitis (UC). Similarly, SLC5A8 mRNA expression was significantly reduced in the CRC as well as the IBS groups. In the IBD groups, SLC5A8 was unchanged in UC but significantly increased in CD. IL-17 mRNA expression was significantly reduced in CRC and IBS groups, but unchanged in the IBD groups. PKCε mRNA was significantly increased in CRC as expected. In the IBD groups, PKCε mRNA was unchanged in CD but significantly increased in UC. In the IBS groups, PKCε mRNA in constipation –IBS (C-IBS) was significantly reduced, but unchanged in diarrhoea – IBS (D-IBS). CONCLUSIONS: β-catenin mRNA and protein expression was increased in CRC and the CRC promoting IBD groups. COX-2 protein expression was incongruent with the COX-2 mRNA expression and this may reflect homeostatic control mechanisms. High COX-2 mRNA expression in CRC and CRC promoting IBD groups may be a secondary phenomenon reflecting the inflammatory milieu, rather than a true carcinogenesis-related event. PPARγ does not appear to play a central role in early colon carcinogenesis, in spite of available literature suggesting otherwise. Butyrate transporters showed inconsistent results and for now no firm conclusions can be drawn from this. IL-17 may play a role in CAC as confirmed in this and other studies, but its role in sporadic CRC is tenuous and requires further investigation. Likewise for PKCε, upregulation is associated with increased tumourigenecity as shown in this study, however, the mechanistic pathway(s) involved is still speculative and requires further study.
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- Date Issued: 2013
Monitoring carbon stocks in the sub-tropical thicket biome using remote sensing and GIS techniques : the case of the Great Fish River Nature Reserve and its environs, Eastern Cape province, South Africa
- Authors: Nyamugama, Adolph
- Date: 2013
- Subjects: Fragmented landscapes -- South Africa -- Eastern Cape -- Remote sensing , Environmental degradation -- South Africa -- Eastern Cape , Remote sensing , Geographic information systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10672 , http://hdl.handle.net/10948/d1020303
- Description: The subtropical thicket biome in the Eastern Cape Province of South Africa has been heavily degraded and transformed due overutilization during the last century. The highly degraded and transformed areas exhibit a significant loss of above ground carbon stocks (AGC) and loss of SOC content. Information about land use /cover change and fragmentation dynamics is a prerequisite for measuring carbon stock changes. The main aim of this study is to assess the trends of land use/cover change, fragmentation dynamics, model the temporal changes of AGC stocks in the Great Fish River Nature Reserve and its environs from 1972 to 2010, quantify and map the spatial distribution of SOC concentrations in the partial subtropical thicket cover in the Great Fish River Nature Reserve and environs (communal rangelands). Multi-temporal analyses based on 1972 Landsat MSS, 1982 and 1992 Landsat TM, 2002 Landsat ETM and 2010 SPOT 5 High Resolution images were used for land use/cover change detection and fragmentation analysis. Object oriented post-classification comparison was applied for land use/cover change detection analysis. Fragmentation dynamics analysis was carried out by computing and analyzing landscape metrics in land use/cover classes. Landscape fragmentation analyses revealed that thicket vegetation has increasingly become fragmented, characterized by smaller less linked patches of intact thicket cover. Landscape metrics for intact thicket and degraded thicket classes reflected fragmentation, as illustrated by the increase in the Number of Patches (NP), Patch Density (PD), Landscape Shape Index (LSI), and a decrease in Mean Patch Size (MPS). The use of remote sensing techniques and landscape metrics was vital for the understanding of the dynamics of land use/cover change and fragmentation. Baseline land use/cover maps produced for 1972, 1982, 1992 2002 and 2010 and fragmentation analyses were then used for analyzing carbon stock changes in the study area. To model the temporal changes of AGC stocks in the Great Fish River Nature Reserve and its environs from 1972 to 2010, a method based on the integration of RS and GIS was employed for the estimation of AGC stocks in a time series. A non-linear regression model was developed using NDVI values generated from SPOT 5 HRG satellite imagery of 2010 as the independent variable and AGC stock estimates from field plots as the dependent variable. The regression model was used to estimate AGC stocks for the entire study area on the 2010 SPOT 5 HRG and also extrapolated to the 1972 Landsat MSS, 1982 and 1992 Landsat TM, and 2002 Landsat ETM. The AGC stocks for the period 1972 -1982, 1982-1992, 1992-200) and 2002-2010 were compared by means of change detection analysis. The comparison of AGC stocks was carried out at subtropical thicket class level. The results showed a decline of AGC stocks in all the classes from 1972 to 2010. Degraded and transformed thicket classes had the highest AGC stock losses. The decline of AGC stocks was attributed to thicket transformation and degradation which were caused by anthropogenic activities. To map and quantify SOC concentration in partial (fractional) thicket vegetation cover, the spectral reflectance of both thicket vegetation and bare-soils was measured in situ. Soil samples were collected from the sampling sites and transported to the laboratory for spectral reflectance and SOC measurements. Thicket vegetation and bare soil reflectance were measured using spectroscopy both in situ and under laboratory conditions. Their respective endmembers were extracted from ASTER imagery using the Pixel Purity Index (PPI). The endmembers were validated with in situ and laboratory thicket and bare-soil reflectance signatures. The spectral unmixing technique was applied to ASTER imagery to discriminate pure pixels of thicket vegetation and bare-soils; a residual spectral image was produced. The Residual Spectral Unmixing (RSU) procedure was applied to the residual spectral image to produce an RSU soil spectrum image. Partial Least Squares Regression (PSLR) model was developed using spectral signatures of a residual soil spectrum image as the independent variable and SOC concentration measured from soil samples as the dependent variable. The PSLR prediction model was used to predict SOC concentration on the RSU soil spectral image. The predicted SOC concentration was then validated with SOC concentration measured from the field plots. A Strong correlation (R2 = 0.82) was obtained between the predicted SOC concentration and the SOC concentration measured from field samples. The PSLR was then used to generate a map of SOC concentration for the Great Fish River Nature Reserve and its environs. Areas with very low SOC concentrations were found in the degraded communal villages, as opposed to the higher SOC values in the protected area. The results confirmed that RS techniques are key to estimating and mapping the spatial distribution of SOC concentration in partial subtropical thicket vegetation. Partial thicket vegetation has a huge influence on the soil spectra; it can influence the prediction of SOC concentration. The use of the RSU approach eliminates partial thicket vegetation cover from bare soil spectra. The residual soil spectrum image contains enough information for the mapping of SOC concentration. The technique has the potential to augment the applicability of airborne imaging spectroscopy for soil studies in the sub-tropical thicket biome and similar environments.
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- Date Issued: 2013
Nonlinear effects with a focus on cross phase modulation and its impact on wavelength division multiplexing optical fibre networks
- Authors: Gamatham, Romeo Reginald Gunther
- Date: 2013
- Subjects: Wavelength division multiplexing , Optical communications , Fiber optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/6302 , vital:21071
- Description: The demand for faster data transmission is ever increasing. Wavelength division multiplexing (WDM) presents as a viable solution to increase the data transmission rate significantly. WDM systems are based on the ability to transmit multiple wavelengths simultaneously down the fibre. Unlike time division multiplexing (TDM) systems, WDM systems do not increase the data transfer by increasing the transmission rate of a single channel. In WDM systems the data rate per channel remains the same, only multiple channels carry data across the link. Dense wavelength division multiplexing (DWDM) promises even more wavelengths packed together in the same fibre. This multiplication of channels increases the bandwidth capacity rapidly. Networks are looking into making use of technology that will ensure no electronic signal regeneration at any point within the DWDM network. Examples are; reconfigurable optical add/drop multiplexers (ROADM) and optical cross connect (OXC) units. These components essentially enable network operators to split, combine and multiplex optical signals carried by optical fibre. WDM allows network operators to increase the capacity of existing networks without expensive re-cabling. This provides networks with the flexibility to be upgraded to larger bandwidths and for reconfiguration of network services. Further, WDM technology opens up an opportunity of marketing flexibility to network operators, where operators not only have the option to rent out cables and fibres but wavelengths as well. Cross phase modulation (XPM) poses a problem to WDM networks. The refractive index experienced by a neighbouring optical signal, not only depends on the signal’s intensity but on the intensity of the co-propagating signal as well. This effect leads to a phase change and is known as XPM. This work investigates the characteristics of XPM. It is shown that, in a two channel WDM network, a probe signal’s SOP can be steered by controlling a high intensity pump signal’s SOP. This effect could be applied to make a wavelength converter. Experimental results show that the degree of polarization (DOP) of a probe signal degrades according to a mathematical model found in literature. The pump and probe signals are shown to experience maximum interaction, for orthogonal probe-pump SOP vector orientations. This may be problematic to polarization mode dispersion compensators. Additionally, experimental results point out that the SOP of a probe signal is much more active in the presence of a high intensity pump, as compared to the single signal transmission scenario.
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- Date Issued: 2013
Novel applications of Morita-Baylis-Hillman methodology in organic synthesis
- Authors: Mciteka, Lulama Patrick
- Date: 2013 , 2013-04-22
- Subjects: Organic compounds -- Synthesis -- Research Asymmetric synthesis Asymmetry (Chemistry) Chemical reactions -- Research Camphor -- Research AZT (Drug) -- Research Chemical inhibitors -- Research Chemistry -- Methodology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4439 , http://hdl.handle.net/10962/d1007598
- Description: The overall approach in the present investigation has been to explore applications of the Morita-Baylis-Hillman (MBH) reaction in asymmetric synthesis and in the continuation of systems with medicinal potential. To this end, a series of varied camphor-derived acrylate esters was prepared to serve as chiral substrates in asymmetric Morita-Baylis- Hillman reactions. Reduction of N-substituted camphor-10-sulfonamides afforded the 3- exo-hydroxy derivatives as the major products. Acylation of the corresponding sodium alkoxides gave the desired 3-exo-acrylate esters, isolation of which was complicated by concomitant formation of hydrochlorinated and diastereomeric competition products. Bulky camphorsulfonamides containing alkyl, dialkyl, aromatic and adamantyl groups were selected as N-substituents with the view of achieving stereoselective outcome in subsequent MBH reactions. The synthesis of novel camphor-derived Morita-Baylis-Hillman adducts using various pyridine-carboxaldehydes proceeded with exceptionally high yields with diastereoselectivities ranging from 7-33 % d.e. Both 1D and 2D NMR and HRMS techniques were employed to confirm the structures and an extensive study of the electropositive fragmentation patterns of a number of camphor-derived chiral acrylate esters was conducted. Attention has also been given to the application of MBH methodology in the construction of heterocyclic ‘cinnamate-like’ AZT conjugates which were designed to serve as dualaction HIV-1 integrase-reverse transcriptase (IN-RT) inhibitors. A number of pyridine carboxaldehyde-derived MBH adducts were synthesized using methyl, ethyl and t-butyl acrylates in the presence of 3-hydroxyquinuclidine (3-HQ) as catalyst. The yields for these reactions were excellent. The resulting MBH adducts were acetylated and subjected to aza-Michael addition using propargylamine. The resulting alkylamino compounds were then used in ‘Click reactions’ to form the targeted AZT-conjugates in moderate to excellent yield. In silico docking of computer modelled AZT-conjugates into the HIV-1 integrase and reverse transcriptase enzyme-active sites and potential hydrogen-bonding interaction with active-site amino acid residues were identified. The electrospray MS fragmentations of the AZT and the novel AZT-conjugates were also investigated and common fragmentation pathways were identified.
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- Date Issued: 2013
Numerical relativity on cosmological past null cones
- Authors: Van der Walt, Petrus Johannes
- Date: 2013
- Subjects: Cosmology Numerical calculations General relativity (Physics) -- Mathematics Einstein field equations Gravity Gravitational waves Horizon
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5396 , http://hdl.handle.net/10962/d1002959
- Description: The observational approach to cosmology is the endeavour to reconstruct the geometry of the Universe using only data that is theoretically verifiable within the causal boundaries of a cosmological observer. Using this approach, it was shown in [36] that given ideal cosmological observations, the only essential assumption necessary to determine the geometry of the Universe is a theory of gravity. Assuming General Relativity, the full set of Einstein field equations (EFEs) can be used to reconstruct the geometry of the Universe using direct observations on the past null cone (PNC) as initial conditions. Observationally and theoretically this is a very ambitious task and therefore, current developments have been restricted to spherically symmetric dust models while only relaxing the usual assumption of homogeneity in the radial direction. These restricted models are important for the development of theoretical foundations and also useful as verification models since they avoid the circularity of verifying what has already been assumed. The work presented in this thesis is the development of such a model where numerical relativity (NR) is used to simulate the observable universe. Similar to the work of Ellis and co-workers [36], a reference frame based on the PNC is used. The reference frame used here, however, is based on that of the characteristic formalism of NR, which has developed for calculating the propagation of gravitational waves. This provides a formalism that is well established in NR, making the use of existing algorithms possible. The Bondi-Sachs coordinates of the characteristic formalism is, however, not suitable for calculations beyond the observer apparent horizon (AH) since the diameter distance used as a radial coordinate becomes multi-valued when the cosmological PNC reconverges in the history of a universe, smaller in the past. With this taken into consideration, the Bondi-Sachs characteristic formalism is implemented for cosmology and the problem approaching the AH is investigated. Further developments address the limitations approaching the AH by introducing a metric based on the Bondi-Sachs metric where the radial coordinate is replaced with an affine parameter. The model is derived with a cosmological constant Λ incorporated into the EFEs where Λ is taken as a parameter of the theory of gravity rather than as a matter source term. Similar to the conventional characteristic formalism, this model consists of a system of differential equations for numerically evolving the EFEs as a characteristic initial value problem (CIVP). A numerical code implemented for the method has been found to be second order convergent. This code enables simulations of different models given identical data on the initial null cone and provides a method to investigate their physical consistency within the causally connected region of our current PNC. These developments closely follow existing 3D schemes developed for gravitational wave simulations, which should make it natural to extend the affine CIVP beyond spherical symmetric simulations. The developments presented in this thesis is an extended version of two papers published earlier.
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- Date Issued: 2013
On the implementation effectiveness and efficiency of ecological interventions in operational contexts : the case of Working for Water
- Authors: McConnachie, Matthew Morgan
- Date: 2013
- Subjects: Working for Water Programme Alien plants -- South Africa -- Eastern Cape Alien plants -- Control -- South Africa -- Eastern Cape Alien plants -- Control -- Cost effectiveness -- South Africa -- Eastern Cape Conservation of natural resources -- South Africa -- Eastern Cape Acacia mearnsii -- South Africa -- Eastern Cape Poverty -- South Africa -- Eastern Cape Revegetation -- South Africa -- Eastern Cape Restoration ecology -- South Africa -- Eastern Cape Environmental degradation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4729 , http://hdl.handle.net/10962/d1001956
- Description: There is little understanding of the implementation efficiency and effectiveness of restoring plant invaded landscapes within operational contexts. South Africa's Working for Water (WfW) programme is arguably the most ambitious alien plant control programme in the world, yet little is known about its cost-effectiveness and the challenges it faces in linking poverty and environmental objectives. My first aim was to assess the cost-effectiveness of invasive plant removal, and the factors that underpin its effectiveness over large spatial and temporal scales. The second aim was to compare the accuracy of evidence-based findings with managers' experience-based beliefs, and to assess whether managers are willing to change their beliefs after being exposed to it. The third aim was to assess the costs and benefits of removal versus removal followed by active native re-vegetation. My final aim is to assess the challenges and lessons learnt by managers linking ecological restoration with poverty alleviation objectives, specifically within the public works model. My study area was focused primarily on two WfW river catchment projects in the western region of the Eastern Cape province. I adopted an interdisciplinary approach drawing from a range of methods such as observational studies, statistical modelling and interviews with managers. The key findings were that control efforts in the two catchment projects are largely inadequate owing to many sites being re-invaded and not enough resources being allocated to the catchments. It would take between 54 and 695 years to clear the respective catchments. In terms of cost-effectiveness, my results exceeded previous estimates by 1.5 to 8.6 times for each catchment project. After being exposed to the evidence-based findings, the managers did not change their beliefs when it came to forecasting the future effectiveness. I found that active native re-vegetation after removal of invasive plants is very costly and that priority should be given to understanding the effectiveness of the removal treatments on native species recovery. The managers cited significant challenges in effectively and efficiently meeting the programmes dual objectives. Based on a broader review of the public works literature I recommend WfW re-examine the type of public works they currently use.
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- Date Issued: 2013
Pedagogical ways-of-knowing in the design studio
- Authors: Kethro, Philippa
- Date: 2013
- Subjects: Graphic arts -- Education (Higher) Interior decoration -- Education (Higher) Fashion design -- Education (Higher) Industrial design -- Education (Higher) Aesthetics, Modern Art -- Philosophy Education, Higher -- Aims and objectives Interaction analysis in education Visual literacy Critical realism Communication and education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1840 , http://hdl.handle.net/10962/d1004338
- Description: This research addresses the effect of pedagogical ways-of-knowing in higher education design programmes such as Graphic Design, Interior Design, Fashion, and Industrial Design. One problematic aspect of design studio pedagogy is communication between teachers and students about the aesthetic visual meaning of the students’ designed objects. This problematic issue involves ambiguous and divergent ways-of-knowing the design meaning of these objects. The research focus is on the design teacher role in design studio interactions, and regards pedagogical ways-of-knowing as the ways in which teachers expect students to know visual design meaning. This pedagogical issue is complicated by the fact that there is no agreed-upon corpus of domain knowledge in design, so visual meaning depends greatly on the social knowledge retained by students and teachers. The thesis pursues an explanation of pedagogical ways-of-knowing that is approached through the philosophy of critical realism. How it is that particular events and experiences come to occur in a particular way is the general focus of critical realist philosophy. A critical realist approach to explanation is the use of abductive inference, or inference as to how it is that puzzling empirical circumstances emerge. An abductive strategy aims to explain how such circumstances emerge by considering them in a new light. This is done in this study by applying Luhmann’s theory of the emergence of cognition in communication to teacher ways-of-knowing in the design studio. Through the substantive use of Luhmann’s theory, an abductive conjecture of pedagogical ways-of-knowing is mounted. This conjecture is brought to bear on an examination of research data, in order to explain how pedagogical ways of-knowing constrain or enable the emergence of shared visual design meaning in the design studio. The abductive analysis explains three design pedagogical ways-of-knowing: design inquiry, design representation and design intent. These operate as macro relational mechanisms that either enable or constrain the emergence of shared visual design meaning in the design studio. The mechanism of relation is between design inquiry, design representation and design intent as historical knowing structures, and ways-of-knowing in respect of each of these knowing structures. For example, design inquiry as an historical knowing structure has over time moved from ways-of-knowing such as rationalistic problem solving to direct social observation and later to interpretive cultural analysis. The antecedence of these ways-of-knowing is important because communication about visual meaning depends upon prior knowledge, and teachers may then reproduce past ways-of-knowing. The many ways-of-knowing that respectively relate to design inquiry, design representation and design intent are shown to be communicatively formed and recursive over time. From a Luhmannian perspective, these ways-of-knowing operate as variational distinctions that indicate or relate to the knowing structures of design inquiry, design representation and design intent. This is the micro-level operation of pedagogical ways-of-knowing as relational mechanisms in design studio communication. Design teachers’ own ways-of-knowing may then embrace implicit way-of-knowing distinctions that indicate the knowledge structures of design inquiry, design representation and design intent. This implicit indication by distinction is the relational mechanism that may bring design teachers’ expectation that this and not that visual design meaning should apply in communication about any student’s designed object. Such an expectation influences communication between teachers and students about the potential future meaning of students’ designs. Consequently, shared visual design meaning may or may not emerge. The research explanation brings the opportunity for design teachers to make explicit the often implicit way-of-knowing distinctions they use, and to relate these distinctions to the knowing structures thus indicated. The study then offers a new perspective on the old design pedagogical problem of design studio conflict over the meaning of students’ designs. Options for applying this research explanation in design studio interactions between students and teachers are therefore suggested.
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- Date Issued: 2013
Petrogenesis and metallogenesis of the Panzhihua Fe-Ti oxide ore-bearing mafic layered intrusion, SW China
- Authors: Howarth, Geoffrey Hamilton
- Date: 2013
- Subjects: Petrogenesis Metallogeny Intrusions (Geology) -- China -- Panzhihua Metallogenic provinces -- China -- Panzhihua Igneous rocks -- China -- Panzhihua Geochemistry Iron Titanium Oxides Ores Magmas
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4915 , http://hdl.handle.net/10962/d1001810
- Description: The Panzhihua intrusion is one of several large Fe-Ti oxide ore bearing intrusions related to the major flood volcanism of the Emeishan Large Igneous Province (ELIP), SW China. The Panzhihua intrusion in particular has recently become the focus of numerous studies owing to the excellent exposure in large open pit mining operations. The formation of Fe-Ti oxide ore layers has been the focus of these studies and has become a somewhat controversial topic with three separate models currently proposed for ore formation. The gabbroic Panzhihua intrusion extends for ± 19 km along strike, has a maximum thickness of 3000 m and hosts extensive (up to 60 m thick) Fe-Ti oxide ore layers in the lower portions of the intrusion. The intrusion has been divided into five zones: marginal zone (MGZ), lower zone (LZ), middle zone A (MZa), middle zone b (MZb) and the upper zone (UZ). The gabbroic rocks are comprised of plagioclase, clinopyroxene and interstitial Fe-Ti oxides with minor olivine. Apatite is present within the MZb only and shows no correlation with Fe-Ti oxide ore layers. Fe-Ti oxides are present throughout the stratigraphy of the intrusion. This is unlike typical layered intrusions where significant Fe-enrichment through fractionation of Fe-poor silicate phases (i.e. plagioclase) is required before Fe-Ti oxide saturation. There are no oxide-free cumulate rocks at the Panzhihua intrusion, implying either an evolved parent magma or very high Fe content of the source rocks. I present here new mineral composition data, whole-rock major and trace element geochemistry along with whole-rock Sr-Nd isotopes and PGEs in order to constrain the evolution of the Panzhihua parent magma en route from source to chamber and the formation of Fe-Ti oxide ore layers. Furthermore an initial pilot study using O-isotope data is conducted on Ti-magnetite and plagioclase separates from gabbroic vs. ore rocks. Results are coupled with detailed thermodynamic modeling using the software PELE in order to further constrain Fe-Ti oxide ore layer formation. The intrusion is characterised by extreme depletion of PGEs relative to the coeval flood basalts and picrites. High Cu/Pd and Pd/Pt imply two separate stages of S-saturated and S-undersaturated depletion of PGEs. Pd is highly compatible in sulphide and is quickly scavenged by sulphide liquids resulting in an increase in Cu/Pd of the residual liquid. Furthermore decoupling of Pd and Pt can be achieved by either late stage hydrothermal alteration or through S-undersaturated stage of PGE depletion where Pt is scavenged by Pt-rich alloys or oxide minerals. I show that the latter is more likely. Fractionation modeling suggests that the Panzhihua parent magma formed at depth from original picritic magma. This is consistent with several other recent studies on other layered intrusions of the ELIP. Sr-Nd isotopic ratios indicate very little crustal contamination has occurred en route to the current chamber. Sr and Nd concentrations of footwall rocks are too low to produce any significant change in initial Sr and Nd isotopic ratios of the intruding basaltic magmas, indicating that crustal contamination will not be indicated by Sr-Nd isotopic ratios. Gradational change in the Sr-Nd isotope ratios across the MGZ provides strong evidence for formation in an open system by multiple replenishments of progressively less contaminated magmas from depth. Contamination is difficult to constrain but must be occurring prior to emplacement at the current level (low Sr and Nd contents of footwall). A gradational upward decrease in highly incompatible element across the MGZ can then be explained by continuous magma flow, which effectively removes the evolved intercumulus liquids from the growing cumulate pile at the base of the chamber. The initial stages of formation of the Panzhihua intrusion are interpreted to result from prolonged low volume pulses of magma into a slowly opening chamber. The timing of Fe-Ti oxide crystallisation is fundamental in the understanding of the petrogenesis of ore layers. Distinct geochemical variation in whole-rock Fe2O3/TiO2 and Zr/Nb indicates that Timagnetite is the dominant oxide within the lower ± 270 m of the intrusion whereas above this level both Ti-magnetite and ilmenite are present as cumulus phases. This is interpreted to indicate a variation in the fO2 where the lower intrusion crystallises at higher fO2 relative to that above this level. Silicates within the ore layers, in particular plagioclase, are highly embayed and resorped where in contact with Fe-Ti oxides. This characteristic of the silicate grains implies early crystallisation prior to Fe-Ti oxides with subsequent disequilibrium conditions resulting in resorption. Furthermore distinct reaction rims of kaersutite amphibole, Fo-enriched olivine, An-enriched plagioclase and pleonaste are observed. The abundance of amphibole suggests H2O involvement in this reaction and consumption of silicates. A model for parent magma crystallisation at various H2O contents indicates that plagioclase crystallisation temperature is very sensitive to H2O content of the parent magma. Plagioclase crystallises early for “dry” compositions but significantly later for “wet” compositions. Fe-Ti oxide ore layers are generally well layered, contain gabbroic xenoliths and are observed raversing/cross-cutting the cumulate stratigraphy. I present here a new model for ore layer formation in order to account for these distinct features of the ore layers. A model invoking multiple replenishments of magma with variable oxide microphenocryst content, H2O content and volume is proposed. Magma evolving in the plumbing system and fed to the Panzhihua chamber is variably enriched in H2O, which results in significantly different crystallisation paths. High H2O magmas (> 2 wt %) crystallise Fe-Ti oxides early whereas low H2O magmas (< 1 wt %) crystallise oxides late. Early pulses of H2O-poor magma crystallise a sequence of plag+cpx+Fe-Ti oxide (±ol). Later pulses of H2Orich magma subsequently intrude the partially crystallised cumulate sequence incorporating and consuming previously crystallised silicates with subsequent early crystallisation of Ti-magnetite and formation of ore layers. H2O-rich magmas likely have suspended Ti-magnetite microphenocrysts as well, which crystallise at depth in the plumbing system. This model can account for the various characteristic features of the Fe-Ti oxide ore layers at the Panzhihua intrusion as well as other Fe-Ti oxide ore bearing intrusions in the region.
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- Date Issued: 2013
Phototransformation of pollutants using lutetium and zinc phthalocyanines anchored on electrospun polymer fibers
- Authors: Zugle, Ruphino
- Date: 2013
- Subjects: Electrospinning Phthalocyanines Lutetium Zinc Polymers Dysprosium Pollutants Air Pollution Photochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4286 , http://hdl.handle.net/10962/d1002962
- Description: Novel lanthanide phthalocyanines containing dysprosium, erbium and lutetium as central metals were synthesized using phthalonitrile:metal salt ratio of 4:1 or lower phthalonitrile content as well as using unmetallated phthalocyanine. They were characterized using various spectroscopic and elemental analyses. Dysprosium bis-phthalocyanine was obtained while monomers were obtained for erbium and lutetium phthalocyanines. Theopen-shelldysprosiumbis-phthalocyanine and the monomeric complex of the open-shell erbium were neither fluorescent nor showed the ability to generate singlet oxygen. The triplet states of all the lutetium phthalocyanines were found to be populated with high triplet quantum yields and corresponding high singlet oxygen quantum yields. The fluorescence quantum yields of the lutetium phthalocyanines were however found to be very low. The lutetium phthalocyanines together with unsubstituted zinc phthalocyanine and its derivatives were successfully incorporated into electrospun polymer fibers either by covalent linkage or sorption forces. Spectral characteristics of the functionalized electrospun polymer fibers indicated that the phthalocyanines were bound and their integrity maintained within the fiber matrices. Most importantly the fluorescence and photoactivity of the phthalocyanines were equally maintained within the electrospun fibers. The functionalized electrospun polymer fibers especially those containing the zinc phthalocyanines could qualitatively detect nitrogen dioxide, a known environmental air pollutant. Also all the functionalized electrospun polystyrene and polysulfone fibers containing lutetium and zinc phthalocyanines could be applied for the photoconversion of 4-chlorophenol, 4-nitrophenol and methyl orange. Those of polystyrene could be re-used. Polyacrylic acid and polyurethane functionalized electrospun fibers were found not to be suitable for photocatalytic applications in aqueous medium. 4-Chlorophenol was found to be more susceptible to photodegradation while methyl orange very difficult to degrade.
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- Date Issued: 2013
Politics, polemics and practice: a history of narratives about, and responses to, AIDS in South Africa, 1980-1995
- Authors: Tsampiras, Carla
- Date: 2013
- Subjects: AIDS (Disease) -- Government policy -- South Africa AIDS (Disease) -- Political aspects -- South Africa -- History AIDS (Disease) -- South Africa -- Public opinion -- History AIDS (Disease) -- Social aspects -- South Africa -- History South Africa -- Politics and government -- 20th century African National Congress Health Policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2517 , http://hdl.handle.net/10962/d1001653
- Description: The ongoing urgency of addressing AIDS in South Africa has kept academics and activists focussed primarily on the immediate crises of AIDS ‘in the present’. This thesis, covering the period 1980 – 1995, examines narratives about, and responses to, AIDS ‘in the past’ and explores the interplay between these narratives and elites in medical and political communities trying to address AIDS during a period of political transition. The thesis begins by examining the hegemonic medico-scientific narratives about AIDS that featured in the South African Medical Journal, an important site of enquiry as AIDS was primarily conceived of as a ‘medical issue’. The SAMJ narratives, which often relied on constructed ‘AIDS avatars’, framed understandings of the syndrome and influenced responses to it by medical and political communities. The first community that the thesis explores is the African National Congress (ANC) in exile, which had to address AIDS in exile communities and prepare health strategies for ‘the new South Africa’. Secondly, the thesis analyses government responses to AIDS and argues that four phases of response can be identified. These phases were characterised by minimum concerns about obtaining information and providing health advice; efforts to gather infection data while exploiting political and public fear; attempts to extend health education and (belatedly) encourage broader engagement; and finally, consultative, democratic ideals. The thesis then examines the National Medical and Dental Association (NAMDA) a progressive medical organisation that worked with the ANC on influential health (and AIDS) strategies. NAMDA members ‘crossed over’ between various medical and political communities and both reinforced and challenged hegemonic AIDS narratives. Finally, the thesis moves from the abstract, via the practical, to the personal and concludes with a detailed account of the experiences of two sexuality activists at the intersections of these communities and narratives. By focussing on these medical and political communities, and analysing the relationships between these communities, the existing AIDS narratives, and individuals, the thesis also reveals the constructions of morality, ‘race’, gender, and sexuality that infused them. In doing this it shows how polemic and politics combined to influence practical responses to, and personal experiences of, AIDS.
- Full Text:
- Date Issued: 2013