Queer transgressions : the choreographing of a male homosexual presence with reference to selected choreographers
- Authors: De Boer, Kyle Dylan
- Date: 2011
- Subjects: Queer theory , Gender identity in dance , Homosexuality in dance , Homosexuality and dance , Male homosexuality , Dance -- South Africa , Choreographers -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2161 , http://hdl.handle.net/10962/d1009442
- Description: Queer Transgressions: The choreographing of a male homosexual presence with reference to selected choreographers explores queer identity and in particular representations of a male homosexual presence in dance. Within the methodological framework of dance studies and queer theory I explore the ―self fashioning‖ of my male homosexual presence in dance. This is achieved by critically deconstructing my choreographic process when making choreography. Therefore this thesis is informed by both academic research and my self-reflexive experience of choreography and dance performance. The deconstruction of my autobiography and choreographic process is discussed with reference to both international and South African queer choreographers. This means that by accounting for my own experiences and approaches toward representing a male homosexual presence in dance, I explore the history and engagements of other queer choreographers also creating such representations. I therefore examine the works of selected choreographers and chart the development of the representation of a male homosexual presence in dance. By exploring the choreographic process of other queer choreographers I identify choreographic tactics that queer choreographers are using when making work. From this point of departure I shift the focus away from international queer choreographers and provide insight into the choreographic processes of South African queer choreographers. By accounting for the works and choreographic processes of South African choreographers, I provide a context in which my choreographic explorations on the subject matter can take place. This choreographic exploration manifests itself through a self-reflexive/autobiographic account on the research and practice of my choreographic process. During my choreographic exploration I set the challenge to both engage with and explore further, established ―queering tactics. This is done with the intention to reveal and create representations of a male homosexual presence in dance.
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- Date Issued: 2011
Race, class and inequality: an exploration of the scholarship of Professor Bernard Magubane
- Authors: Tanyanyiwa, Precious
- Date: 2011
- Subjects: Magubane, Bernard -- Knowledge and learning , South Africa -- Race relations , Sociology -- South Africa , Race -- South Africa , Equality -- South Africa , Research -- South Africa , South Africa -- Social policy , Social classes -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3324 , http://hdl.handle.net/10962/d1003112 , Magubane, Bernard -- Knowledge and learning , South Africa -- Race relations , Sociology -- South Africa , Race -- South Africa , Equality -- South Africa , Research -- South Africa , South Africa -- Social policy , Social classes -- South Africa
- Description: This thesis begins with the assumption that the theory of academic dependency provides an adequate framework within which the relationship between social science communities in the North and South can be understood. Present problems of social scientists in the South have very often been attributed to this dependence and it has been concluded that academic dependence has resulted in an uncritical and imitative approach to ideas and concepts from the West (Alatas, 2000). This dependence has also resulted in the general regression among social scientists based in the South and in a marginalisation of their works within the social science community no matter how significant and original they may be. The problematic invisibility of the works of prominent South African scholars is a dimension of a wider crisis of academic dependence, if unchecked this current trend will also reinforce academic dependence. From the nature of the problems generated by academic dependence, it is obvious that there is a need for an intellectual emancipation movement. This movement may take different forms that may range from but are not limited to a commitment to endogeneity which involves among other things, knowledge production that takes South African local conditions seriously enough to be the basis for the development of distinct conceptual ideas and theories. This requires transcending the tendency to use ‘the local’ primarily as a tool for data collection and theoretical framing done from the global north. Secondly, there is a need to take the local, indigenous, ontological narratives seriously enough to serve as source codes for works of distinct epistemological value and exemplary ideas within the global project of knowledge production. Endogeneity in the context of African knowledge production should also involve an intellectual standpoint derived from a rootedness in the African conditions; a centring of African ontological discourses and experiences as the basis of intellectual work (Adesina, 2008: 135). In this study, it is suggested that the recommendations highlighted above can only succeed if scholars make an effort to actually engage with locally produced knowledge. There is therefore a need to make greater efforts to know each other’s work on Africa. This demand is not to appease individual egos but it is essential for progress in scientific work. African communities will benefit from drawing with greater catholicity from the well–spring of knowledge about Africa generated by Africans. In the South African context, transcending academic dependence in the new generation of young academics requires engagement with the work of our local scholars who have devoted their lives to knowledge production. This thesis explores the scholarship of Professor Bernard Magubane by engaging with his works on race, class and inequality by locating his works within the wider debates on race, class and inequality in South Africa. The specific contributions of Professor Magubane to the enterprise of knowledge production are identified and discussed in relation to his critique of Western social science in its application to Africa. The making of Professor Magubane’s life, his career, scholarship and biography details are analysed with the intention of showing their influence on Magubane as a Scholar. The examination of Professor Magubane’s intellectual and biographical accounts help to explain the details, contexts and implications of his theoretical paradigm shifts. This helps prove that Professor Magubane’s experiences and theoretical positions were socially and historically constituted. The research from which this thesis derives is part of an NRF-funded project, on Endogeneity and Modern Sociology in South Africa, under the direction of Professor Jimi Adesina.
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- Date Issued: 2011
Raw phones: the domestication of mobile phones amongst young adults in Hooggenoeg, Grahamstown
- Authors: Schoon, Alette Jeanne
- Date: 2011
- Subjects: Cell phones -- Social aspects -- South Africa -- Grahamstown Communication -- Sex differences -- South Africa -- Grahamstown Social media -- South Africa -- Grahamstown Interpersonal communication -- Technological innovations -- Social aspects -- South Africa -- Grahamstown Communication and culture -- South Africa -- Grahamstown Online social networks -- Social aspects -- South Africa -- Grahamstown Mobile communication systems -- Social aspects -- South Africa -- Grahamstown Identity (Psychology) in youth Colored people (South Africa) -- Social life and customs -- South Africa -- Grahamstown Colored people (South Africa) -- Ethnic identity -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3482 , http://hdl.handle.net/10962/d1002937
- Description: This dissertation examines the meanings that young adults give to their mobile phones in the township of Hooggenoeg in Grahamstown in the Eastern Cape. The research was predominantly conducted through individual interviews with nine young adults as well as two small gender-based focus groups. Participant observation as well as a close reading of the popular mobile website Outoilet also contributed to the study. Drawing on Silverstone, Hirsch and Morley’s (1992) work into the meanings attributed to the mobile phone through the domestication processes of appropriation, objectification, incorporation and conversion, the study argues for the heterogeneous roles defined for mobile phones as they are integrated into different cultural contexts. The term ‘raw phones’ in the thesis title refers to a particular cultural understanding of respectability in mainly working-class ‘coloured’¹ communities in South Africa, as described by Salo (2007) and Ross (2010), in which race, class and gender converge in the construction of the respectable person’s opposite – a lascivious, almost certainly female, dependent, black and primitive ‘raw’ Other. The study argues that in Hooggenoeg, the mobile phone becomes part of semantic processes that define both respectability and ‘rawness’ , thus helping to reproduce social relations in this community along lines of race, class and gender. A major focus of the study is the instant messaging application MXit, and how it assists in the social production of space, by helping to constitute both private and dispersed network spaces of virtual communication, in a setting where social life is otherwise very public, and social networks outside of cyberspace are densely contiguous and localised. In contrast, gossip mobile website Outoilet seems to intensify this contiguous experience of space. My findings contest generalised claims, predominantly from the developed world, which assert that the mobile phone promotes mobility and an individualised society, and show that in particular contexts it may in fact promote immobility and create a collective sociability.
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- Date Issued: 2011
Regional application of the Pitman monthly rainfall-runoff model in Southern Africa incorporating uncertainty
- Authors: Kapangaziwiri, Evison
- Date: 2011
- Subjects: Water supply -- Africa, Southern Water supply -- Measurement -- Africa, Southern Hydrology -- Mathematical models -- Africa, Southern Hydrologic models Rain and rainfall -- Mathematical models -- Africa, Southern Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6037 , http://hdl.handle.net/10962/d1006178
- Description: Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework. , iText 1.4.6 (by lowagie.com)
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- Date Issued: 2011
Relational processes enabling the balancing of academic work and motherhood: a grounded theory study with academic women at a South African university
- Authors: Poulos, Tessa
- Date: 2011
- Subjects: Working mothers -- South Africa -- Grahamstown Women in education -- South Africa -- Grahamstown Work and family -- South Africa -- Grahamstown Rhodes University -- Employees Motherhood -- South Africa -- Grahamstown Sex role in the work environment -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3038 , http://hdl.handle.net/10962/d1002547
- Description: Through the use of contextual data, this research study aims to explicate a theory about the experiences of academic women, who are also mothers, employed at a South African University. The research is interpretive in nature as it explores the women's accounts of the conflicts they face in striving to satisfy the demands of both their scholarly work and family responsibilities within multiple intersecting factors related to their personal/familial circumstances, and the strategic processes they engage in to manage the balance between these competing roles. The study followed a constructivist grounded theory design in an attempt to test the hypothesis (emerging from a prior pilot study) that the most significant enabling factors at work in the lives of these women comprise various relational support processes. The findings indicate that balancing academic work and mothering is a delicate activity that is sensitive to a number of facilitating as well as hindering factors. The participants revealed that they experience work-family role-conflict as a result of competing desires to dedicate themselves fully to both of these roles. The relational factors most prominently cited as being critical to enabling a work-family balance include the presence of a supportive partner, a support structure in the home in the form of an employed domestic helper, and the support derived from a 'shared experience' with other working mothers. Non-relational factors emanating from the unique quality of life afforded to mothers by employment within the particular case institution also emerged as being significantly enabling of a work-family balance for this group of academic mothers.
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- Date Issued: 2011
Representing conflict: an analysis of The Chronicle's coverage of the Gukurahundi conflict in Zimbabwe between 1983 and 1986
- Authors: Santos, Phillip
- Date: 2011
- Subjects: The Chronicle (Zimbabwe) Zimbabwe -- History -- 1980- Zimbabwe -- Politics and government -- 1980- Mass media -- Political aspects -- Zimbabwe Mass media -- Moral and ethical aspects -- Zimbabwe Journalistic ethics -- Zimbabwe Journalism -- Objectivity -- Zimbabwe War in mass media -- Zimbabwe Violence in mass media -- Zimbabwe Mass media and peace -- Zimbabwe Discourse analysis
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3481 , http://hdl.handle.net/10962/d1002936
- Description: This research is premised on the understanding that media texts are discourses and that all discourses are functional, that is, they refer to things, issues and events, in meaningful and goal oriented ways. Nine articles are analysed to explicate the sorts of discourses that were promoted by The Chronicle during the Gukurahundi conflict in Zimbabwe between 1982 and 1986. It is argued that discourses in the news media are shaped by the role(s), the type(s) of journalism assumed by such media, and by the political environment in which the news media operate. The interplay between the roles, types of journalism practised, and the effect the political environment has on news discourses is assessed within the context of conflictual situations. This is done using insights from the theoretical position of peace journalism and its critique of professional or mainstream journalism as promoting war/violence journalism. Using the case of The Chronicle's reportage of the Gukurahundi conflict in Zimbabwe, it is concluded that, in performing the collaborative role, state owned/controlled media assume characteristics of war/violence journalism. On the other hand, it is concluded that The Chronicle developed practices consistent with peace journalism when it both espoused the facilitative role and journalistic objectivity. These findings undermine the conventional view among proponents of peace journalism that in times of conflict, the news media should be interventionist in favour of peace and that they should abandon the journalistic norm of objectivity which they argue, promotes war/violence journalism.
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- Date Issued: 2011
Responses of intertidal macroalgae and associated fauna to interactive processes acting over multiple spatial scales
- Authors: Mostert, Bruce Petrus
- Date: 2011 , 2010-12-01
- Subjects: Biodiversity -- South Africa , Spatial ecology , Marine algae -- South Africa , Marine organisms -- Effect of water pollution on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5890 , http://hdl.handle.net/10962/d1013370
- Description: The decrease of biological diversity from low latitudes near the equator towards high latitudes is one of the most fundamental patterns noted in ecology. These trends have been the subject of numerous terrestrial and marine studies and have caused the proposal of several explanatory hypotheses. No single hypothesis has adequately accounted for these observed trends. Furthermore, large-scale patterns are frequently modified by processes acting at meso- to small-scales. It is imperative to understand the interaction of these processes to elucidate the mechanisms controlling the structure of intertidal assemblages. The main aim of this thesis was to test the influence of multiple processes at a range of spatial scales on biogenic engineers. Biogenic engineers, such as macroalgae, have been reported to be strongly influenced by processes such as grazing, biogeography and upwelling and subsequent effects are expected to be linked to their associated assemblages. I used infaunal assemblages associated with macroalgae as a model system to understand the interactive effects of meso-scale upwelling in conjunction with large-scale factors (regional and biogeographic). Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis, inhabiting different but overlapping home ranges were used in this study. Smaller scale, physical attributes and the associated fauna of these algal species were compared. The effects of meso- to large-scale physical gradients on marine organisms have been investigated in many instances and resultant gradients in physical variables observed. This study was undertaken to investigate morphological trends exhibited by Hypnea spicifera and Champia lumbricalis to compare possible similarities between coastlines and to determine if inferred meso- to large-scale processes influence physical trends in a similar manner despite the coastlines being affected by different hydrodynamic processes. The macroalgae were located in two distinctly different upwelling regimes, Hypnea spicifera on the east and south coasts and Champia lumbricalis on the west coast. Upwelling (delivery of nutrients and primary production) was not found to be an important factor in determining the physical characteristics of macroalgae but there were clear patterns linked to latitude. Mean percentage cover of Hypnea spicifera was positively correlated with distance along the east and south coasts. Mean mass and mean surface area of H. spicifera were, however, negatively correlated with distance from Port St Johns. Mean frond length showed a negative trend but this relationship was not statistically significant. On the west coast, there was a significant increase in mean frond length from north to south for Champia lumbricalis. Mean surface area and mean mass of C. lumbricalis exhibited non-significant negative trends from north to south while there was a non-significant positive trend for mean percentage cover. Following the “Productivity Hypothesis”, these patterns from north to south along the coastlines of South Africa could have important implications for biodiversity associated with these algae. Many previous studies have focussed on the effects of upwelling on species (i.e. effects of nutrients and temperature) but have failed to separate this effect from large scale effects such as biogeography and latitudinal gradients. I tested the influence meso-scale upwelling, large-scale biogeographic processes and latitudinal gradients with two different species of macroalgae one on the east and south coasts of South Africa and the other on the west coast. Hypnea spicifera inhabits the east and south coasts of South Africa spanning two biogeographic provinces and is generally affected by relatively weak upwelling, whereas Champia lumbricalis inhabits the west coast spanning one biogeographic province which is subjected to intense persistent upwelling year round. Within the east and west coast biogeographic provinces there are, however, regions with both upwelling and non-upwelling. On the east and south coasts, entire assemblages differed significantly among the three Regions (St Lucia, Port Alfred and Knysna, while assemblages between upwelling/non-upwelling areas were not different. Assemblages on the different shores differed significantly from each other. There were no significant effects of region or upwelling for the number of individuals of Crustacea or Polychaeta, while Mollusca showed a significant effect of region. The number of individuals of other taxa showed a significant interaction of region and upwelling. Region had a significant effect on number of species of molluscs and other taxa, while there was no effect for either region or upwelling for the Crustacea or Polychaeta. In general different factors were shown to be important (region and shore) while upwelling was rarely important. On the west coast assemblages associated with C. lumbricalis were not influenced by region or upwelling but there were significant differences between shores. Region, upwelling ad shore did not affect number of individuals. There was a significant interaction of region and upwelling for the number of species of crustaceans, while numbers of species of Mollusca, Polychaeta and other taxa showed no effects. In general, regional factors strongly influenced most organisms, while upwelling played a minor role. Hypotheses about differences between upwelling and non-upwelling regions in terms of species abundances and composition due to the input of cold nutrient rich water were not supported. A link between the effects of larger-scale biogeographic factors and their influence on habitat forming taxa and the resultant effects on associated infauna would be a likely explanation for the patterns observed in this study. Diversity of assemblages is known to be influenced by the structural complexity of a habitat, increasing complexity increases the amount of available niches therefore potentially increasing the number of species found within that habitat. Three species of macroalgae, Hypnea spicifera, Champia lumbricalis and Bifurcaria brassicaeformis were selected on the basis of being structurally similar and having their distributional ranges overlap in order to elucidate the effects of structure and macroalgal species on associated assemblages. Hypnea spicifera is different in terms of surface area and biomass from Champia lumbricalis and Bifurcaria brassicaeformis. Assemblages of species found on the three rhodophytes showed both shore and the species of alga had significant effects on composition. Only numbers of individuals of molluscs were affected by the species of alga. Crustacea and Polychaeta showed an interaction of the species of alga with shore. In the case of this study, it is likely that the three species of macroalgae mitigate biological stressors such as predation and physical stressors such as wave exposure and desiccation. In general, meso-scale upwelling is suggested to be marginalised when considering the structuring of assemblages associated with macroalgae, while large scale biogeography has more of an influence. Within shores, assemblages were also strongly influenced by smaller-scale factors such as differences in the structure and species of alga. This study indicates the importance of investigating patterns across a range of spatial scales to gain a comprehensive understanding of factors influencing intertidal organisms.
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- Date Issued: 2011
Risk-based assessment of environmental asbestos contamination in the Northern Cape and North West provinces of South Africa
- Authors: Jones, Robert Ryan
- Date: 2011
- Subjects: Asbestos industry -- Health aspects -- South Africa -- Northern Cape Asbestos industry -- Health aspects -- South Africa -- North West Environmental risk assessment -- South Africa-- Northern Cape Environmental risk assessment -- North West Asbestos -- Toxicology -- South Africa -- Northern Cape Asbestos -- Toxicology -- South Africa -- North West Tailings (Metallurgy) -- Waste disposal -- South Africa -- Northern Cape Tailings (Metallurgy) -- Waste disposal -- South Africa -- North West
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4780 , http://hdl.handle.net/10962/d1012612
- Description: The commercial mining of asbestos occurred in four Provinces of South Africa (Northern Cape, North West, Limpopo and Mpumalanga). It was initiated in the late 1800's and lasted for over a hundred years into the beginning of this century. As a producer of amphibole asbestos, South Africa far outpaced every other country being responsible for 97% of global production. The last crocidolite mine closed in 1996 and chrysotile in 2002. Anecdotal information concerning environmental contamination as a result of the former mining activities and the improper disposal of mine waste tailings has been reported by a variety of authors. Few comprehensive or systematic surveys have been conducted to date to document this issue and very little quantifiable research has been completed on the communities located in close proximity to the former mine sites to determine the extent of contamination. In 2004-2006 communities were surveyed within the Northern Cape and North West Provinces to determine the extent and severity of environmental contamination. This research developed and applied a methodology to select those communities suspected of environmental contamination, a targeted survey methodology, and a protocol for rapid sample laboratory analysis. A total of 41 communities were initially predicted by the model to be suspected for environmental asbestos contamination. Based on the inclusion of local knowledge, a final 36 communities were selected for a screening-level field assessment, 34 of which were found to contain environmental asbestos contamination at rates ranging from 20 to 100% of the surveyed locations. A total of 1 843 samples of soil and building material were collected in the screening level assessment. One community (Ga-Mopedi) was selected as being representative of the total cohort and a more detailed house to house survey was completed. A total of 1 486 samples were collected during the detailed survey. Results of the detailed survey revealed 26.2% of the homes were contaminated with asbestos containing soil and/or building material. A theoretical quantitative cumulative exposure assessment was developed to estimate the disease burden within the study area population of 126,130 individuals within the surveyed communities resulting in a predicted range of 25-52.4 excess deaths per year from lung cancer and mesothelioma due solely to environmental exposures to asbestos pollution.
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- Date Issued: 2011
Sedimentology of plio-pleistocene gravel barrier deposits in the palaeo-Orange River mouth, Namibia : depositional history and diamond mineralisation
- Authors: Spaggiari, Renato Igino
- Date: 2011 , 2013-08-19
- Subjects: Diamond mines and mining -- Namibia Sediments (Geology) -- South Africa and Namibia -- Orange River Estuary Diamond deposits -- Namibia Orange River Estuary (Namibia and South Africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4927 , http://hdl.handle.net/10962/d1004636
- Description: The largest known marine diamond placer, the Namibian mega-placer, lies along the Atlantic coast of south-western Africa from the Orange River mouth 1,000 km northwards to the Namibian-Angolan border. The most economically viable portion of the Namibian mega-placer (>75 million carats recovered at >95% gem quality) comprises onshore and offshore marine deposits that are developed within ∼100km of the Orange River outfall. For much of the Cainozoic, this long-lived fluvial system has been the main conduit transporting diamonds from kimberlitic and secondary sources in the cratonic hinterland of southern Africa to the Atlantic shelf that has been neutrally buoyant over this period. Highly energetic marine processes, driven in part, by southerly winds with an attendant northward-directed longshore drift, have generated terminal placers that are preserved both onshore and offshore. This study, through detailed field sedimentological and diamond analyses, investigates the development and mineralisation of gravel barrier deposits within the ancestral Orange River mouth area during a major ∼30 m regional transgression ('30 m Package') in the Late Pliocene. At that time, diamond supply from this fluvial conduit was minimal, yet the corresponding onshore marine deposits to the north of the Orange River mouth were significantly diamond enriched, enabling large-scale alluvial diamond mining to take place for over 75 years. Of the entire coastline of south-western Africa, the most complete accumulation of the '30 m Package' is preserved within the palaeo-Orange River mouth as barrier spit and barrier beach deposits. Arranged vertically and laterally in a 16m thick succession, these are deposits of: (1) intertidal beach, (2) lagoon and washover, (3) tidal inlet and spit recurve and (4) storm-dominated subtidal settings. These were parts of larger barrier features, the bulk of which are preserved as highstand deposits that are diamond-bearing with varying, but generally low grades (<13 stones (diamonds) per hundred tons, spht). Intertidal beach and spit recurve deposits have higher economic grades (12-13 spht) due to the energetic sieving and mobile trapping mechanisms associated with their emplacement. In contrast, the less reworked and more sandy subtidal, tidal inlet and washover deposits have un-economic grades (<2 spht). Despite these low grades, the barrier deposits have the largest average stone (diamond) size (1-2 carats/stone, cts/stn) of the entire Namibian mega-placer, given their proximity to the ancestral Orange River outfall. This study demonstrates that barrier shoreline evolution at the fluvial/marine interface was controlled by: (1) a strong and coarse fluvial sediment supply that sustained shoreline growth on a highly energetic coast, (2) accommodation space facilitating sediment preservation and (3) short-duration, high-frequency sea-level cycles superimposed on the∼30 m regional transgression, promoting hierarchal stacking of progradational deposits. During these sea-level fluctuations, diamonds were 'farmed' from older, shelf sequences in the offshore and driven landward to accumulate in '30 m Package' highstand barrier deposits. In spite of the large supply of diamonds, their retention in these deposits was poor due to an incompetent footwall of ancestral Orange River mouth sediment and the inherent cobble-boulder size of the barrier gravels. Thus the principal process controlling diamond entrapment in these barrier deposits was kinetic sieving in a coarse-grained framework. Consequently, at the marine/fluvial interface and down-drift for ∼5 km, larger diamonds (1-2 cts/stn) were retained in low-grade (<2 spht), coarse-gravel barrier shorelines. Smaller diamonds (mostly < I cts/stn) were rejected into the northward-driven littoral sediments and further size-sorted along ∼95 km of Namibian coast to accumulate in finer, high-grade beach placers (> 100 spht) where bedrock footwall promoted such high concentrations. The gravel-dominated palaeo-Orange River mouth is considered to be the ' heart' of the Namibian mega-placer, controlling sediment and diamond supply to the littoral zone further north. Although coarse gravel is retained at the river mouth, the incompetence of this highly energetic setting to trap diamonds renders it sub-economic. This ineffectiveness at the fluvial/marine interface is thus fundamental in enriching the coastal tract farther down-drift and developing highly economic coastal placers along the Atlantic coast of south-western Africa. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Date Issued: 2011
Seductive Manoeuvres: an analysis of the use of feminist performance strategies as a means of staging alternative sexualities in two dance theatre works
- Authors: Barnard, Joni
- Date: 2011
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/76823 , vital:30627
- Description: Located within the discipline of Performance Studies, this thesis seeks to validate performance and theatre, specifically dance theatre, as legitimate fields of research and enquiry that can enrich the polemics surrounding discourse, representation, the body and identity. Within this thesis I explore and analyse the creative processes and performance strategies used in two dance theatres works: Acty Tang’s Chaste (2007) and my own work entitled Displayed and Framed (2008) and how these strategies support the staging of alternative sexualities. I argue that the staging of alternative sexualities calls for an alternative approach to the performance strategies utilised in the production of space, the representations of the body and the use of text in both works. Each work offers a particular exploration of gender and sexuality in the attempt to represent alternative identities, alternative bodies and alternative sexualities. In this thesis I identify the endeavour to stage ‘otherness’ as a feminist endeavour and thus identify the performance strategies utilised in each work as feminist performance strategies. Through my analysis I wish to highlight the ways in which a feminist approach can contribute to and enrich both the staging of and understanding of alternative sexualities. In both Chaste (2007) and Displayed and Framed (2008), the choreographers of each work are also performers in their own work in an endeavour to explore and represent their own identity. The analysis of my own work requires that I play the multiple roles of choreographer, performer and researcher. In this analysis I provide accounts of my own experiences, processes and struggles of creating Displayed and Framed (2008) which are analysed in conjunction with my readings of Chaste (2007) and Tang’s personal experiences in creating the work. Thus this thesis explores the value of reflection and self reflectivity in the processes of creating performance.
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- Date Issued: 2011
Sign language in South Africa language planning and policy challenges
- Authors: Ganiso, Mirriam Nosiphiwo
- Date: 2011
- Subjects: Sign language -- Study and teaching -- South Africa Deaf -- Education -- South Africa Deaf -- Means of communication
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3588 , http://hdl.handle.net/10962/d1002163
- Description: This thesis sets out to undertake research into the very important topic of sign language and its usage, particularly in the Western Cape Province of South Africa. Three schools are used in this study. Interviews and questionnaires were used to conduct research with teachers, students and deaf teacher assistants within this context. The analysis of this data is presented in Chapter five of this thesis.
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- Date Issued: 2011
Solid-phase extraction based sample preparation for the determination of drug and organic pollutant residue
- Authors: Pule, Bellah Oreeditse
- Date: 2011 , 2011-02-08
- Subjects: Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4406 , http://hdl.handle.net/10962/d1006711 , Food contamination , Drugs -- Analysis , Pharmaceutical chemistry , Extraction (Chemistry) , Sorbents
- Description: This thesis presents solid phase extraction (SPE) methodologies based on mixed-mode polymeric sorbents; a mixed mode strong anion exchanger (Agilent SampliQ SAX) and a mixed mode strong cation exchanger (Agilent SampliQ SCX). Furthermore, dispersive-SPE based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method was assessed for applicability in the determination of drug residues. The mixed-mode polymeric sorbents were evaluated for the simultaneous fractionation of drugs that exhibit diverse polarities with acidic, basic and neutral functionalities in biological matrices (plasma and urine). The polymeric skeleton of these sorbents entails an exchanger group and therefore provides two retention mechanisms, strong cation or anion exchange retention mechanisms with hydrophobic interactions. It was demonstrated that with a sequential elution protocol for sample clean-up analytes were fractionated into acidic, basic and neutral classes. The SAX was employed for analysis of ketoprofen, naproxen (acidic drugs), nortriptyline (basic) and secobarbital (neutral) from urine sample. The SCX was used for fractionating phenobarbital, p-toluamide (acidic), amphetamine, m-toluidine (basic) and acetaminophen (neutral drug) from plasma sample. QuEChERS method was employed for quantitative determination of 16 polycyclic aromatic hydrocarbons (PAHs) from fish fillets and soil; 9 sulfonamides (SAs) from chicken muscles and acrylamide (AA) in cooking oil. The analyte recoveries ranged from 79.6 - 109% with RSDs ranging from 0.06 - 1.9% at three different fortification levels. Good linearity (r2 > 0.9990) was attained for most analytes. The limits of detection and quantification ranged from 0.03 - 0.84 μg/ml and 0.81 - 1.89 μg/ml respectively for analytes in biological samples. LODs and LOQs for analytes in food and environmental samples ranged from 0.02 to 0.39 and 0.25 to 1.30 ng/g respectively.
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- Date Issued: 2011
South African money market volatility, asymmetry and retail interest pass-through
- Authors: Fadiran, Gideon Oluwatobi
- Date: 2011
- Subjects: Money market -- South Africa Interest rates -- South Africa Monetary policy -- South Africa Econometric models Banks and banking -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:993 , http://hdl.handle.net/10962/d1002728
- Description: The purpose of this paper is to examine the interest rate transmission mechanism for South Africa as an emerging economy in a pre-repo and repo system. It explains how the money market rate is transmitted to the retail interest rates both in the long-run and short-run and tests the symmetric and asymmetric interest rate pass-through using the Scholnick (1996) ECM and the Wang and Lee (2009) ECM-EGARCH (1, 1)-M methodology. This permitted the examination of the impact of interest rate volatility, along with the leverage effect. An incomplete pass-through is found in the short-run. From the entire sample period, a symmetric adjustment is found in the deposit rate, which had upward rigidity adjustment, while an asymmetric adjustment is found in the lending rate, with a downward rigidity adjustment. All the adjustments supported the collusive pricing arrangements. According to the conditional variance estimation of the ECM-EGARCH (1, 1), negative volatility impact and leverage effect are present and influential only in the deposit interest rate adjustment process in South Africa.
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- Date Issued: 2011
SphereZyme (TM) technology for enhanced enzyme immobilisation application in biosensors
- Authors: Molawa, Letshego Gloria
- Date: 2011
- Subjects: Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3989 , http://hdl.handle.net/10962/d1004048 , Immobilized enzymes , Hydrolases , Hydrolysis , SphereZyme , Biosensors , Proteolytic enzymes
- Description: Self-immobilisation enzyme technologies, such as SphereZyme™, suffer from the lack of applicability to hydrolyse large substrates. Solid support immobilisation is usually a method of choice, to produce a stable biocatalyst for large substrates hydrolysis in the industry. In order to investigate this limitation, a commercial protease called Alcalase® was chosen as a model enzyme due to its natural activity (hydrolysis of large substrates-proteins). Prior to immobilising through the SphereZyme™ technology, Alcalase® was partially purified through dialysis followed by CM Sepharose™ FF cation exchanger. Sample contaminants, such as salts and stabilisers can inhibit protein crosslinking by reacting with glutaraldehyde. Alcalase® was successfully separated into 3 proteases with the major peak correlating to a positive control run on native PAGE, indicating that it was likely subtilisin Carlsberg. A 16% alkaline protease activity for azo-casein hydrolysis was retained when 5% v/v PEI: 25% v/v glutaraldehyde solution was used as a crosslinking agent in Alcalase® SphereZyme™ production. An increase in activity was also observed for monomeric substrates (PNPA) where the highest was 55%. The highest % activities maintained when 0.33 M EDA: 25% v/v glutaraldehyde solution was initially used as crosslinking agent were 4.5% and 1.6% for monomeric and polymeric substrates, respectively. PEI is a hydrophilic branched polymer with an abundance of amine groups compared to EDA. A comparison study of immobilisation efficiencies of SphereZyme™, Eupergit® and Dendrispheres was also performed for large substrate biocatalysis. The two latter technologies are solid-support immobilisation methods. Dendrispheres reached its maximum loading capacity in the first 5 minute of the one hour binding time. Twenty minutes was chosen as a maximum binding time since there was constant protein maintained on the solid support and no enzyme loss was observed during the 1 hour binding time. PEI at pH 11.5, its native pH, gave the highest immobilisation yield and specific activity over the PEI pH range of 11.5 to 7. SphereZyme™ had the highest ratio for azocasein hydrolysis followed by Dendrispheres and Eupergit®. The SphereZyme™ was also shown to be applicable to biosensors for phenol detection. Different modifications of glassy carbon electrode (GCE) were evaluated as a benchmark for the fabrication of SphereZyme™ modified phenol biosensor. GCE modified with laccase SphereZyme™ entrapped in cellulose membrane was the best modification due to the broad catechol range (<0.950 mM), high correlation coefficient (R2, 0.995) and relative high sensitivity factor (0.305 μA.mM-1). This type of biosensor was also shown to be electroactive at pH 7.0 for which its control, free laccase, lacked electroactivity. From the catalytic constants calculated, GCE modified with laccase SphereZyme™ entrapped in cellulose membrane also gave the highest effectiveness factor (Imax/Km app) of 1.84 μA.mM-1. The modified GCE with Alcalase® SphereZyme™ was relatively more sensitive than GCE modified with free Alcalase®.
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- Date Issued: 2011
Staged authenticities an exploration of the representations of AmaXhosa culture within the main programme of the National Arts Festival, 2009
- Authors: Reeve, Zoë Rose Louise Patricia
- Date: 2011
- Subjects: Standard Bank National Arts Festival Performing arts festivals -- South Africa -- Grahamstown Xhosa (African people) -- Music -- Social aspects Performing arts festivals -- Social aspects -- South Africa -- Grahamstown Cultural property -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2146 , http://hdl.handle.net/10962/d1002378
- Description: This thesis investigates the presentation of AmaXhosa traditional dancing and music on the stages of the National Arts Festival (NAF), Main Programme, of South Africa in 2009. Four productions featuring AmaXhosa traditional dancing and music, as well as a fine art exhibition, are analysed to determine how the AmaXhosa culture is being portrayed, what is considered authentic and how these productions may affect the memory of the AmaXhosa nation. In an attempt to understand the position of these productions within the NAF the South African cultural context as well as the NAF is examined. The post-apartheid, post-rainbow nation, South African cultural context is discussed and how the NAF could contribute towards creating a more unified South African identity. Incorporated and inscribed memory categories are related to how one could determine authenticity in traditional indigenous productions. A cautionary note on incorporated memory is linked to efficacy, while a loss of incorporated memory within the AmaXhosa society may result in ritual acts being orientated towards entertainment. If the private culture is consistently displayed in the public realm then it is inevitable that the ways in which the AmaXhosa recollect their history will be altered. The contribution of the transitional spaces of theatres and proscenium arch stages to the choreography and incorporated memory of the performers relates to the collective recollection of the AmaXhosa. Bearing this in mind, this thesis suggests that the NAF is playing a dual role in the evolution of the AmaXhosa. It is both positively contributing to the economic upliftment of a sector of the population and exposing people to this rich and multilayered culture. However, it is also impacting the efficacy of the private culture and fracturing the traditional knowledge of the AmaXhosa by assisting in the inscription of their performance forms. , This thesis consists of three parts (1 pdf document and two video mp4 files)
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- Date Issued: 2011
Stewardship as an educational process of social learning and change: two case studies conducted in the Western Cape
- Authors: Walker, Clara Isabella
- Date: 2011
- Subjects: Environmental education -- South Africa -- Western Cape Conservation of natural resources -- South Africa -- Western Cape Natural resources -- South Africa -- Western Cape -- Management Social learning -- South Africa -- Western Cape Sustainable development -- South Africa -- Western Cape Cape Nature Stewardship Programme (South Africa) Biodiversity Stewardship Programme (South Africa)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1772 , http://hdl.handle.net/10962/d1003657
- Description: Stewardship in South Africa, as it is being implemented within the framework of the Biodiversity Stewardship Programme (BSP), is an attempt by conservation agencies to engage landowners in the voluntary securing of parcels of biodiverse land, through signing a contract for a certain time period, not to develop the landscape in ways that will impact negatively on the biodiversity of the area in question. The focus of this study is the relationship between biodiversity stewardship and social learning, as I hope to ascertain how stewardship practices are helping to resolve the current problems of biodiversity loss in the Western Cape. The overall aim of this research is to gain an understanding of how, in its capacity as a conservation education process, the Cape Nature Stewardship Programme can foster social learning amongst the landowners involved in its implementation, by leading them to a better understanding of their environmental responsibilities. Data was generated through the use of interviews and informal discussions with participants together with document analysis, such as brochures, pamphlets and presentations. My approach to the analysis of my data was two-phased. In the first phase, I analysed the data generated from the interview process and from reviewing the documents the stewardship officials supplied me with. The second phase involved looking into the results of the two case studies, and formulating analytical statements which were then used to review the case evidence within a social learning perspective, derived from Wals (2007). In constructing an analytical framework for the interpretation of my data, I drew heavily on Wals' (2007) notion of social learning occurring in sequential activities. I used this insight as a lens through which to trace the educational effects of the implementation of the CNSP in the two case study areas.The research highlighted evidence that Stewardship initiatives should be based on the foundation of social learning and invest time and effort in building an environmental knowledge capital amongst the landowners involved. By equipping them with these necessary conservation skills, one creates a 'community of practice' where those individuals adopt a sustainability habitus contributing towards a change and environmental understanding and practises in field.
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- Date Issued: 2011
Stories from forest, river and mountain : exploring children's cultural environmental narratives and their role in the transmission of cultural connection to and protection of biodiversity
- Authors: Alexander, Jamie Kim
- Date: 2011
- Subjects: Children and the environment -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape -- Citizen participation , Environmental education -- South Africa -- Eastern Cape , Human ecology -- South Africa -- Eastern Cape , Oral tradition -- South Africa -- Eastern Cape , Social learning -- South Africa -- Eastern Cape , Traditional ecological knowledge -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:6061 , http://hdl.handle.net/10962/d1015267
- Description: Preservationist conservation created a legacy of national parks and protected areas that were surrounded by local people dispossessed of their land and denied the rights to use the resources they had previously relied upon. Although conservation is now shifting towards a more participatory approach, research gaps still exist in determining the meaning of 'the environment' and the role of local means of conservation in rural communities in South Africa. This study focused on children's cultural environmental narratives from two rural villages in the Eastern Cape, South Africa. Children from grades 4, 7 and 10 were involved in the study, and adult family members, local experts and village elders were included in the study to allow for comparison between children's and adult's narratives and to realise what Local Ecological Knowledge (LEK) was being passed on. This thesis considers children's use of the environment for play and their sense of place as key methods in ascertaining children's environmental narratives and perceptions. At both field sites, local experts and community elders possessed a wealth of cultural environmental narratives, but these narratives were not necessarily being passed on. Changing household structures and other socio-economic factors influence cultural environmental practices, which in turn have an impact on the cultural environmental narratives being passed down. In many cases, parents' safety fears strongly impacted upon children's access to the environment, resulting in gendered environmental knowledge. The study compared differing vegetation types and degrees of environmental access. The differing environments produced similar cultural environmental narratives, leading to new understandings in community environment relationships. Children living near the state administered forest had significantly less environmental knowledge, bringing about questions of sustainable bio-cultural diversity in the future. The recognition of cultural environmental values is especially important in the rural areas of South Africa, where unemployment and increased poverty levels have led to greater dependence on natural resources for social, economic and cultural purposes. It is proposed that local cultural environmental narratives and landscape perceptions be included into community conservation and environmental education policies and programmes to provide local solutions to the problem of biodiversity conservation in local contexts.
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- Date Issued: 2011
Structural and functional characterisation of the protein inhibitor of activated STAT3 (PIAS3)
- Authors: Mautsa, Nicodemus
- Date: 2011
- Subjects: Cytokines Immune response Proteins Cancer cells -- Growth -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3991 , http://hdl.handle.net/10962/d1004050
- Description: The signal transducer and activator of transcription (STAT) and protein inhibitor of STAT(PIAS) system represent an elegant regulatory mechanism of transcriptional control IN mammalian cytokine signalling. Abnormal activation of the system is associated with immune disorders and a large group of diverse tumours. PIAS3 is a multiple domain protein with distinct functions involved in regulation of cytokine-mediated gene activation pathways.Its over-expression significantly inhibits cell growth and renders cancer cells more sensitive to drugs. The objective of this study was to structurally and biochemically characterise the function of the PIAS3 protein using in silico, in vivo and in vitro analysis approaches.The conservation pattern of the PIAS protein family and critical conserved residues in the PINIT (Proline, Isoleucine, Asparagine, Isoleucine, Tyrosine) domain were identified. The PINIT domain model was generated based on the PINIT domain structure of yeast PIAS3 homologue Siz1 and structural determinants in the PIAS3-STAT3 interaction were evaluated.Guided by the in silico findings, in vivo analysis of the localisation of the PIAS3, mutantderivatives of PIAS3 (PIAS3-L97A, PIAS3-R99N, PIAS3-R99Q), PINIT and acidic domain was conducted. PIAS3 was completely localised in the nucleus while PIAS3 mutants appeared to exhibit diffuse cytoplasmic distribution. The PINIT domain was predominantly localised in the nucleus with some apparent perinuclear staining while the acidic domain exhibited a predominantly perinuclear staining pattern. Further analysis of the PINIT domain and the effect of the mutants on PIAS3-STAT3 interaction were assessed by in vitro analysis. Guided by in silico analysis, the PINIT domain and mutant derivatives of PINIT domain (PINIT-L97A, PINIT-R99N, and PINIT-R99Q) were heterologously expressed in Escherichia coli and subsequently purified using a combination of immobilized metal affinity and size exclusion based chromatography. The size and structural elements of the PINIT domain and its mutants were characterised. The 23 kDa PINIT domain was found to exist as a monomer in solution and its secondary structure was shown to consist of 66 % β-sheets by fourier transformed infrared spectroscopy consistent with the generated homology model.Using surface plasmonresonance spectroscopy (SPR) the PINIT domain was shown to bind to STAT3 in a specific concentration dependent manner. Recombinant PINIT-L97A,PINITR99N and PINIT-R99Q mutants, which exhibited similar structural integrity to the wildtype, were found to abrogate binding to STAT3. These findings suggest that these residues form part of a potential binding surface for stat3. In conclusion, this study has provided evidence that the PINIT domain is an important determinant of PIAS3 interaction with STAT3 and that the interaction is mediated by defined conserved residues directly involved in the PINITSTAT3 interaction.
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- Date Issued: 2011
Studies in marine quinone chemistry
- Authors: Sunassee, Suthananda Naidu
- Date: 2011
- Subjects: Quinone Marine natural products Marine invertebrates Marine pharmacology Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4355 , http://hdl.handle.net/10962/d1005020
- Description: This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer
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- Date Issued: 2011
Studies in South African marine molluscan chemistry
- Authors: Bromley, Candice Leigh
- Date: 2011
- Subjects: Mollusks -- South Africa , Marine invertebrates -- South Africa , Marine metabolites -- South Africa , Chemical oceanography -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4356 , http://hdl.handle.net/10962/d1005021
- Description: This thesis investigates the variability occurring in the secondary metabolites produced by three South African marine molluscs. Chapter Two discusses the isolation and spectroscopic structure elucidation of the metabolites isolated from two Siphonaria species. The re-investigation of Siphonaria capensis yielded siphonarienfuranone (2.2) as the only common polypropionate isolated from both the 1998 and 2009 collections of S. capensis from the same areas suggesting possible seasonal or genetic variation in polypropionate production. The sterol cholest-7-en-3,5,7- triol (2.33) was also isolated form the 2009 collection of S. capensis and this is the first time this compound has been isolated from a Siphonaria species. The second species, Siphonaria oculus is closely related to S. capensis and the investigation into the former’s secondary metaboliteproduction revealed 2.2 as a major metabolite suggesting an inter-species overlap in polypropionate production. Three new polypropionate metabolites, 2.35, 2.36 and 2.37 were also isolated from S. oculus. An unsuccessful attempt was made to establish the absolute configuration of 2.37 using the modified Mosher’s method and the limited amount of 2.37 available prevented any further attempts at resolving the absolute configuration of this compound. The 1H NMR analysis of the defensive mucus collected directly from S. oculus revealed the presence of the acyclic polypropionate 2.37 as a minor metabolite. The absence of characteristic signals for the furanone containing compounds 2.2, 2.35 and 2.36, might suggest that these compounds cyclise from a hypothetical acyclic precursor (2.38) during standard work up of bulk acetone extracts of Siphonaria species. Chapter Three discusses the re-isolation and spectroscopic structure elucidation of the metabolites isolated from the nudibranch, Leminda millecra. Three known natural products, millecrone A (3.1), 8-hydroxycalamenene (3.6) and cubebenone (3.8) were re-isolated from our 2010 collection of L. millecra, as well as the new minor metabolite 8-acetoxycalamenene (3.16). The cytotoxic prenylated toluquinones and toluhydroquinones (3.9-3.15) initially isolated from the 1998 collection of L. millecra were not found in the 2010 collection supporting the hypothesis that these compounds may be of fungal origin. L. millecra clearly shows variability in the compounds sequestered by this species with millecrone A (3.1) being the only common metabolite in the three investigations of L. millecra to date. An unsuccessful attempt was made to establish the absolute configuration of 3.1, 3.6 and 3.8 through initial LAH reduction of the ketone moiety contained in 3.1 and 3.8 and esterification of the resultant diastereomeric alcohol mixtures and the phenol functionality in 3.6 with (1S)-camphanic chloride. Crystallisation of the (S)- camphanate esters of 3.6 and 3.8 for X-ray analysis were unsuccessful, while the unexpected conjugate addition of a hydride in 3.1 resulted in complex diastereomeric mixtures which could not be separated by HPLC.
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- Date Issued: 2011