Showing items 1 - 17 of 17

Your selections:

A dynamics based analysis of allosteric modulation in heat shock proteins

  • Authors: Penkler, David Lawrence
  • Date: 2019
  • Subjects: Heat shock proteins , Molecular chaperones , Allosteric regulation , Homeostasis , Protein kinases , Transcription factors , Adenosine triphosphatase , Cancer -- Chemotherapy , Molecular dynamics , High throughput screening (Drug development)
  • Language: English
  • Type: text , Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/115948 , vital:34273
  • Description: The 70 kDa and 90 kDa heat shock proteins (Hsp70 and Hsp90) are molecular chaperones that play central roles in maintaining cellular homeostasis in all organisms of life with the exception of archaea. In addition to their general chaperone function in protein quality control, Hsp70 and Hsp90 cooperate in the regulation and activity of some 200 known natively folded protein clients which include protein kinases, transcription factors and receptors, many of which are implicated as key regulators of essential signal transduction pathways. Both chaperones are considered to be large multi-domain proteins that rely on ATPase activity and co-chaperone interactions to regulate their conformational cycles for peptide binding and release. The unique positioning of Hsp90 at the crossroads of several fundamental cellular pathways coupled with its known association with diverse oncogenic peptide clients has brought the molecular chaperone under increasing interest as a potential anti-cancer target that is crucially implicated with all eight hallmarks of the disease. Current orthosteric drug discovery efforts aimed at the inhibition of the ATPase domain of Hsp90 have been limited due to high levels of associated toxicity. In an effort to circumnavigate this, the combined focus of research efforts is shifting toward alternative approaches such as interference with co-chaperone binding and the allosteric inhibition/activation of the molecular chaperone. The overriding aim of this thesis was to demonstrate how the computational technique of Perturbation response scanning (PRS) coupled with all-atom molecular dynamics simulations (MD) and dynamic residue interaction network (DRN) analysis can be used as a viable strategy to efficiently scan and accurately identify allosteric control element capable of modulating the functional dynamics of a protein. In pursuit of this goal, this thesis also contributes to the current understanding of the nucleotide dependent allosteric mechanisms at play in cellular functionality of both Hsp70 and Hsp90. All-atom MD simulations of E. coli DnaK provided evidence of nucleotide driven modulation of conformational dynamics in both the catalytically active and inactive states. PRS analysis employed on these trajectories demonstrated sensitivity toward bound nucleotide and peptide substrate, and provided evidence of a putative allosterically active intermediate state between the ATPase active and inactive conformational states. Simultaneous binding of ATP and peptide substrate was found to allosterically prime the chaperone for interstate conversion regardless of the transition direction. Detailed analysis of these allosterically primed states revealed select residue sites capable of selecting a coordinate shift towards the opposite conformational state. In an effort to validate these results, the predicted allosteric hot spot sites were cross-validated with known experimental works and found to overlap with functional sites implicated in allosteric signal propagation and ATPase activation in Hsp70. This study presented for the first time, the application of PRS as a suitable diagnostic tool for the elucidation and quantification of the allosteric potential of select residues to effect functionally relevant global conformational rearrangements. The PRS methodology described in this study was packaged within the Python programming environment in the MD-TASK software suite for command-line ease of use and made freely available. Homology modelling techniques were used to address the lack of experimental structural data for the human cytosolic isoform of Hsp90 and for the first time provided accurate full-length structural models of human Hsp90α in fully-closed and partially-open conformations. Long-range all-atom MD simulations of these structures revealed nucleotide driven modulation of conformational dynamics in Hsp90. Subsequent DRN and PRS analysis of these MD trajectories allowed for the quantification and elucidation of nucleotide driven allosteric modulation in the molecular chaperone. A detailed PRS analysis revealed allosteric inter-domain coupling between the extreme terminals of the chaperone in response to external force perturbations at either domain. Furthermore PRS also identified several individual residue sites that are capable of selecting conformational rearrangements towards functionally relevant states which may be considered to be putative allosteric target sites for future drug discovery efforts Molecular docking techniques were employed to investigate the modulation of conformational dynamics of human Hsp90α in response to ligand binding interactions at two identified allosteric sites at the C-terminal. High throughput screening of a small library of natural compounds indigenous to South Africa revealed three hit compounds at these sites: Cephalostatin 17, 20(29)-Lupene-3β isoferulate and 3'-Bromorubrolide F. All-atom MD simulations on these protein-ligand complexes coupled with DRN analysis and several advanced trajectory based analysis techniques provided evidence of selective allosteric modulation of Hsp90α conformational dynamics in response to the identity and location of the bound ligands. Ligands bound at the four-helix bundle presented as putative allosteric inhibitors of Hsp90α, driving conformational dynamics in favour of dimer opening and possibly dimer separation. Meanwhile, ligand interactions at an adjacent sub-pocket located near the interface between the middle and C-terminal domains demonstrated allosteric activation of the chaperone, modulating conformational dynamics in favour of the fully-closed catalytically active conformational state. Taken together, the data presented in this thesis contributes to the understanding of allosteric modulation of conformational dynamics in Hsp70 and Hsp90, and provides a suitable platform for future biochemical and drug discovery studies. Furthermore, the molecular docking and computational identification of allosteric compounds with suitable binding affinity for allosteric sites at the CTD of human Hsp90α provide for the first time “proof-of-principle” for the use of PRS in conjunction with MD simulations and DRN analysis as a suitable method for the rapid identification of allosteric sites in proteins that can be probed by small molecule interaction. The data presented in this section could pave the way for future allosteric drug discovery studies for the treatment of Hsp90 associated pathologies.
  • Full Text:
  • Date Issued: 2019

Nutritional quality of sausage made with edible meat waste and the perception of consumers on offal product in Eastern Cape Province, South Africa

  • Authors: Oluwasegun, Babatunde Alao
  • Date: 2019
  • Subjects: Meat -- Quality
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10353/19021 , vital:40094
  • Description: Meat processing at the abattoir provides meat by product and waste while, the major part of the muscle which constitutes a third is edible. The edible by products (EBP) of meat have a notable position in our day-to-day life and are used in diverse forms. However, the quality of offal meat may differ according to intrinsic and extrinsic attributes that may occasionally be shaped by the attitude of consumers towards the products. Therefore, the first objective of this thesis focused on features that might influence consumer preferences and their perception of offal meat. A total of 202 consumers from three Municipalities in Amathole District were randomly sampled using exponential nondiscriminative snowball sampling. Data were gathered through a structured questionnaire containing open ended and closed ended questions. The study showed that consumers were more influenced by the freshness, price and availability of the product and these factors are used to determine the purchase outlet. Differences were observed in the offal meat consumption between the age groups. Age groups 25-34 (29.7%) and 35-44 (27.4%) showed the highest offal meat consumption, while the decline was observed in age groups of 55-64 (11.9%), 65- 74 (5.9%) and 75-85 (0.01%) respectively. The most preferred purchase point for offal meat in this study was in butcheries. However, it was observed that the factors influencing offal consumption in Amathole District were similar to meat consumption except that, offals were mainly purchased at butcher shops. The second objective in this study was to determine the sensory characteristics and consumer acceptance of sausages with 10% fat, 30% edible meat waste and 50% edible meat waste. Sensory descriptive attributes such as appearance, texture, colour, taste, flavour and overall acceptance of the sausage were evaluated by sensory panel (n = 60). The sensory panel comprised of students from undergraduates, post-graduates, post-doctoral fellows and lecturers at the University of Fort Hare. The findings of the study indicated that 50% replacement of xiii edible meat waste was similar to the commercial 10% fat with regard to several sensory attributes and pooled liking. Therefore, the utilization of the edible meat waste in production of sausages has the potential to increase profitability in meat industry and minimise meat waste in the industry. However, the cooking method that was more acceptable to consumers in this study was using the microwave as compared to oven-grilling. Furthermore, the effects of different cooking methods (microwave and oven-grilling) on proximate and mineral composition of the formulated sausages were determined. However, the cooking process appeared to have a significant effect on most of the minerals in the sausage. The cooking methods had a significant effect at P <0.01 on the nutrients composition of the formulated sausage. It was observed that the nutritional values of the sausage was better preserved after the cooking process due to higher mean values obtained after cooking. The mean values for calcium (173.1, 221.76, 231.29), potassium (444.57, 158.58, 156.67), magnesium (84.43, 257.97, 127.27), zinc (52.94, 35.27, 27.13), copper (8.8, 7.07, 4.44), manganese (8.74, 0.65, 0.08), sodium (589.42, 604.45, 529.79) and iron (63.3, 85.38, 74.81) in cooked. And the mean values for calcium (286.18, 132.18, 114.79), potassium (206.64, 113.83, 207.81), magnesium (189.89, 33.97, 48.11), zinc (61.05, 28.09, 26.44), copper (2.92, 2.73, 3.89), manganese (1.42, 0.11, 0.35), sodium (566.47, 530.79, 527.35) and iron (77.56, 58.68, 45.42) in uncooked sausage varied greatly among the treatments. Although, the disparities in the mineral content may be attributed to the different edible meat waste from different parts of the cattle which are either from feedlot or pastured based. In regard to the results obtained from proximate and mineral composition, microwave cooking method was found to be the best cooking technique for healthy eating. Finally, the effect of frying with two different oils (sunflower oil and olive oil) on the fatty acid composition of sausage made with edible meat waste was examined. The results revealed that beef sausage containing 70% edible meat wastes and 30% beef (T1) had a higher fat content xiv (25.7%±0.83%) than other treatments. On the other hand, beef sausage fortified with 10% fat and 90% beef (T3) had the lowest fat content but highest FFDM (55.85±0.57%) and moisture content (69.15±0.62) than other treatments. Despite the increase in omega-3: omega-6 fatty acid ratio in the sausage treatments after cooking, the mean value of omega-3: omega-6 fatty acid ratio was greater than 1:5 (0.2) which is within the FAO/WHO recommended range. The omega-3: omega-6 association is well-known for its importance in the diet because it is a key factor for balanced eicosanoid production in the living organism. The significant reduction in saturated fatty acids after cooking showed that there could also be a positive influence on the human health if consumed. Therefore, it may be concluded from the findings of the study that sausage made with edible meat waste as fat replacer is safe for human consumption.
  • Full Text:
  • Date Issued: 2019

Fraction-specific geochemistry across the Asbestos Hills BIF of the Transvaal Supergroup, South Africa: implications for the origin of BIF and the history of atmospheric oxygen

  • Authors: Oonk, Paul Bernardus Hendrikus
  • Date: 2017
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10962/50721 , vital:26021
  • Description: Banded iron formations (BIF), deposited prior to and concurrent with the Great Oxidation Event (GOE) at ca. 2.4 Ga, record changes in oceanic and atmospheric chemistry during this critical time interval. Four previously unstudied drill-cores from the Griqualand West Basin, South Africa, capturing the rhythmically mesobanded, deep-water Kuruman BIF and the overlying granular, shallower Griquatown BIF, were sampled every ca. 10 m along core depth. Mineralogically, these BIFs consist of three iron-bearing fractions: (1) Fe-Ca-Mg-Mn carbonates, (2) magnetite with/without minor hematite and (3) Fe-silicates. These fractions are typically fine-grained on a sub-μm scale and their co-occurrence in varying amounts means that bulk-rock or microanalytical geochemical and stable isotope data are influenced by mineralogy.
  • Full Text:
  • Date Issued: 2017

Intimate strangers: encountering the foreign in urban spaces

  • Authors: Seshoka, Thabo Jerry
  • Date: 2017
  • Subjects: Urbanization -- South Africa -- Port Elizabeth -- History , Cities and towns -- South Africa -- Port Elizabeth -- History Architecture -- South Africa -- Port Elizabeth Cultural property -- South Africa -- Port Elizabeth
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: http://hdl.handle.net/10948/13746 , vital:27304
  • Description: The year 2015 marked a significant year in South African History and it ignited a deep desire in the hearts of locals in Port Elizabeth, Nelson Mandela Bay Metropolitan to question and engage with the city’s ambivalent heritage landscape and heritage discourse. The year 2015 was the year in which the country witnessed the rise community movements that called for the removal of Victorian and Apartheid era heritages across the country. The year also saw a rise in violent service delivery protests and a rise in the amount of xenophobic attacks across the county, including Port Elizabeth. In this thesis, positioned within the field of heritage studies (Anthropology) and employing the concept of the ubuhlanti (Kraal) as a tool to understand the former within a heritage framework. The thesis unpacks and demonstrate how the city centre of Port Elizabeth can be likened to the concept of the ubuhlanti. The ubuhlanti: an intimate community space, which has the potential to double up as an exclusionary space, excluding those who do not possess the necessary social capital to enter its centre.
  • Full Text:
  • Date Issued: 2017

Control and vulnerability : reflections on the nature of human agency and personhood

  • Authors: Paphitis, Sharli Anne
  • Date: 2015
  • Subjects: Self-control , Vulnerability (Personality trait) , Self (Philosophy) , Social psychology , Cognitive science , Frankfurt, Harry G., 1929- -- Criticism and interpretation , Watson, Gary, 1943- -- Criticism and interpretation , Mele, Alfred R., 1951- -- Criticism and interpretation , Nietzsche, Friedrich Wilhelm, 1844-1900 -- Criticism and interpretation
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2750 , http://hdl.handle.net/10962/d1018671
  • Description: Following the writings of philosophers such as Harry Frankfurt, Gary Watson, and Alfred Mele, in this thesis I defend some central claims of the self-control view of human agency. However, I not only defend, but also supplement this view in the following two ways. First, drawing on work by Mary Midgley and Sigmund Freud I advance the claim that self-control requires the experience of internal conflict between an agent’s motivations and intentions. Second, drawing on insights from Simone de Beauvoir and Friedrich Nietzsche, as well as recent research in social psychology and cognitive science, I will argue in this thesis that self-control and vulnerability are inextricably intertwined with one another, and that as a result both are to be seen as constitutive of human agency. While it is the capacity for self-control that marks us out as human agents, I argue that it is also our uniquely human vulnerability which distinguishes our agency from the kind of agency which we might attribute to other potential or actual forms of sentience. Further, while the concepts of human agency and personhood are typically conflated in the analytic tradition of philosophy, in this thesis I will show that there are good reasons for understanding these two concepts as subtly distinct from one another. The term personhood, I will argue, can fruitfully be understood in substantive rather than purely formal terms. A person, in the superlative sense, is to be understood as someone who exercises their agency well; and, as such, persons are answerable to a number of normative prescriptions. Following Midgley, Nietzsche and Martha Nussbaum, I argue against Frankfurt’s normative prescription for personhood in the form of what he calls ‘wholeheartedness’, and offer four normative prescriptions for personhood of my own.
  • Full Text:
  • Date Issued: 2015

A needs-ICTD strategy alignment framework foundation for the measurement of ICTD impact

  • Authors: Baduza, Gugulethu Qhawekazi
  • Date: 2014
  • Subjects: Siyakhula Living Lab SAP Research Needs assessment -- Information technology -- Social aspects -- South Africa -- Case studies Information technology -- South Africa -- Management -- Case studies Information technology -- Social aspects -- South Africa Rural development -- Economic aspects -- South Africa Rural development -- South Africa -- Sociological aspects Rural development projects -- South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1155 , http://hdl.handle.net/10962/d1011116
  • Description: Many Information and Communication Technologies for Development (ICTD) projects are established with the overall aim of positively developing the communities they are implemented in. However, the solutions that are provided are often commonly developed without the needs of these communities being sufficiently investigated beforehand. As a result the ICTD strategy of the project ends up not well aligned with the aims and targets of the needs of the community. As a result of this, an appropriate programme theory for the project and relevant impact indicators fail to be adequately developed. Consequently, when an impact assessment is conducted it is often found that the intended effects are not directly linked to the needs of the community or what the community had hoped to gain from the ICTD initiative. The purpose of this research serves to develop a needs-ICTD strategy alignment foundation that supports the identification and formulation of impact assessment indicators. Through this research, a framework is developed to support the alignment of ICTD strategy, the development and the promotion of contextual needs of rural communities and other frequently marginalized areas. The Needs-ICTD strategy alignment framework is composed of eight main components that describe the process that can be used to align ICTD strategy with community needs. These components include: collaboration between the internal and external stakeholders, the development of the community, conducting baseline studies, the needs assessment, the ICTD strategy, linking of the needs-ICTD strategy, and lastly the identification of impact indicators. An interpretive research approach is used to explore and inform the framework through a multi-case study investigation of the Siyakhula Living Lab and two projects in the Systems Application Products (SAP) Living Lab. Two main case study questions drive the exploration of the framework, that being: 1) How are the needs of the community elicited and how is the ICTD strategy aligned to the needs of the community? 2) And, why were the selected approaches chosen for aligning the needs of the community and ICTD strategy? Data for this research was collected qualitatively through interviews, document analysis and participant observation. Key findings indicate that the involvement of internal (local) stakeholders in the development and alignment of ICTD strategy to the needs of the community is still lacking. As a consequence, many community members end up not fully understanding the project objectives and how these objectives aims are to be achieved. The research also finds that ‘solution specific’ projects also fail communities as they focus specifically on one target group and repeatedly fail to assist the community holistically in supporting their information and their community development needs.
  • Full Text:
  • Date Issued: 2014

Language policy and planning in the Tshwane Metropolitan Municipality: the challenges of implementation

  • Authors: Seshoka, Keaobaka Omphile Precious
  • Date: 2013 , 2013-03-26
  • Subjects: Language policy -- South Africa -- City of Tshwane Metropolitan Municipality Language planning -- South Africa -- City of Tshwane Metropolitan Municipality Community development -- South Africa -- Gauteng Local government -- South Africa -- Gauteng Municipal services -- South Africa --Gauteng
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3554 , http://hdl.handle.net/10962/d1001519
  • Description: This study explores the challenges related to language policy and planning in the City of Tshwane Metropolitan municipality. The study sets to look at the at the challenges affecting successful implementation by the City of Tshwane Metropolitan Municipality as a state organ charged with local development and service delivery for the communities. In terms of the Municipal Systems Act of 2000 municipalities are expected to respond to the language use and preferences of their local communities by making sure that their language policies are fully implemented. The researcher highlights that in instances where municipalities communicate information they are required to make special provision for the speakers of African languages in the communities that they serve in the languages they best understand. This work looks at various statutory language policy documents in South Africa in particular, that give the task of language policy implementation to municipalities as they are the local extension of the national government. This study also argues that municipalities are critical to implementation of language policy. It further notes that in order for the full social, economic and political transformation to take place in municipalities they have to be transformed linguistically in a radical way whereby all the official languages play a major role in all these spheres than before. This view is held by many scholars and researchers in the areas of language policy and planning. This study highlights that the challenges to successful language planning and policy in the government sectors are due to lack of commitment by the government, language practitioners and planners and increased monolingualism in the municipality. The study further explores the language policy and plan of the City of Tshwane Metropolitan Municipality and the the strategies that can contribute to successful optimization of language resources of the Tshwane Metropolitan Municipality in order to give effect to the use of local languages as contained in policy documents and also establish how the city of Tshwane can better reinforce its strategies to implement this language plan and policy. The main focus area of this research is on the language policy and plan of the City of Tshwane Metropolitan Municipality and assesses whether the language practices in these institutions are reflective of their policy and plan. It is hoped that the study will be able to give policy makers and those tasked with implementation, especially at government municipalities’ strategies for improvement in the functionality and the implementation of their language policies and plans. It is also hoped that recommendations and challenges highlighted by this research will be of a better assistance on how to better reinforce strategies to implement the language plan and policy in the government sectors.
  • Full Text:
  • Date Issued: 2013

The lived experience of South African, black, Xhosa-speaking lesbians in Nelson Mandela Bay

  • Authors: Venter, Aneké
  • Date: 2013
  • Subjects: Lesbianism -- Psychological aspects , Lesbians -- Identity , Lesbians -- Social conditions , Coming out (Sexual orientation) -- South Africa -- Nelson Mandela Bay
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:9965 , http://hdl.handle.net/10948/d1020812
  • Description: The aim of the study was to gain a holistic understanding of the lived experiences of four South African, black, Xhosa-speaking lesbians in Nelson Mandela Bay. Contextual, exploratory, descriptive qualitative research based on a phenomenological approach was conducted and analysed through interpretative phenomenological analysis (IPA). A combination of purposive and snowball sampling was used to recruit participants and semistructured in-depth interviews were conducted with four South African adult, black, Xhosaspeaking females of homosexual orientation between the ages of 18 to 35 years. Findings indicate that the participants experience the following: (a) sexual development as a major influence on their sexual- and self-identity, (b) homosexual sexual orientation had a psychological impact on their lives, (c) they have a holistic understanding of who they are, and this understanding of themselves, has positively influenced their lives, (d) their homosexual sexual orientation has influenced the personal relationships in their lives in both positive and negative ways, (e) society has influenced their lives both positively and negatively because of their homosexual sexual orientation , (f) social networking can act as a risk to unintentional disclosure of homosexual sexual orientation and (g) they have experienced discrimination in various areas of their lives because of their homosexual sexual orientation. Some suggestions for future research included exploring lesbian stereotypes within the broader society, as well as inside the black lesbian community and examining the so-called differences between city and township lesbians with an emphasis on beliefs, attitudes, practices, subcultures and gender identity issues.
  • Full Text:
  • Date Issued: 2013

Investigation of photosensitising behaviour of Ni, Pd and Pt phthalocyanines towards phenolic pollutants

  • Authors: Ogunbayo, Taofeek Babatunde
  • Date: 2011
  • Subjects: Phthalocyanines Pollutants Photochemistry Photosensitizing compounds
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4321 , http://hdl.handle.net/10962/d1004979
  • Description: Syntheses of various octasubstituted open-shell (Ni(II), Pd(II) and Pt(II)) metallophthalocyanines and their metal-free analogues have been carried out. Spectroscopic characterizations, photophysical and photochemical studies were carried out to determine the effects of these metals on the molecules using the metal-free phthalocyanine analogues as benchmark. Metal-binding studies of few thio-derivatised phthalocyanines were done to increase the number of palladium metal on the phthalocyanine ligands and determine the effect of increasing number of this metal on phthalocyanine properties. Palladium (PdPc) and platinum phthalocyanines (PtPc) gave good triplet and singlet oxygen quantum yields making them suitable for further investigation in application as photosensitisers. Using 4-nitrophenol as model pollutant, photosensitization reactions were carried out under homogenous and heterogeneous conditions. The reactions were monitored using UV-vis spectroscopy. The MPcs were adsorbed on functionalized single wall carbon nanotube (SWCNT-COOH) to form heterogeneous photosensitizers with PtPc failing to adsorb on the SWCNT-COOH. Under the heterogeneous condition, all the PdPcs photosensitization kinetics was consistent with Langmuir-Hinshelwood reaction model. The best photosenstiser, β-palladium dodecylthio phthalocyanine was also deployed in sensitization of oxidation of 4-chlorophenol and pentachlorophenol under homogenous and heterogeneous conditions to establish the ability of the molecules to sensitize oxidation of wide range of phenolic pollutants. Identifications of the products of the reactions were conducted using gas chromatography and high pressure liquid chromatography (HPLC) hyphenated with mass analyzer (LC-MS). Mechanisms of all the reactions were investigated and all the complexes, in spite of reduced lifetime resulting from open-shell nature of the metals, sensitized the reactions through singlet oxygen mediated pathway. All the heterogeneous sensitisers were recyclable in the 4- nitrophenol oxidation but β-palladium dodecylthio phthalocyanine proved unrecyclable in the oxidation of pentachlorophenol.
  • Full Text:
  • Date Issued: 2011

The biotechnology of hard coal utilization as a bioprocess substrate

  • Authors: Mutambanengwe, Cecil Clifford Zvandada
  • Date: 2010
  • Subjects: Coal -- Biotechnology Acid mine drainage Coal mines and mining -- Environmental aspects
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3934 , http://hdl.handle.net/10962/d1003993
  • Description: The development of coal biotechnology, using hard coal as a substrate, has been impeded by its low reactivity in biological processes. As a result, the more successful application studies have focused on lignitic soft coals. However, new studies have reported using biologically or geologically oxidized hard coal as a functional substrate option for bioprocess applications on a large scale. This study undertook a preliminary investigation into the feasibility of environmental applications of coal biotechnology using oxidized hard coal substrates in both anaerobic and aerobic processes with carbon dioxide, sulfate and oxygen as terminal electron acceptors. A preliminary characterization of the oxidized hard coal substrates was undertaken to determine and predict their viability and behavior as electron donors and carbon sources for environmental bioprocess applications of direct interest to the coal mining industry. Both biologically and geologically oxidized coal substrates showed loss of up to 17% and 52% carbon respectively and incorporation of oxygen ranging from 0.9 – 24%. The latter substrate showed greater loss of carbon and increased oxygenation. The biologically and geologically oxidized hard coal substrates were shown to partition readily into 23% and 32% organic humic acid, a 0.1% fulvic acid fraction and 65% and 59% inorganic and humin fractions respectively. These organic components were shown to be potentially available for biological consumption. In the unmodified hard coal substrate, partitioning was not observed and it did not perform as a functional substrate for any of the bioprocesses investigated. Where carbon dioxide was used as a terminal electron acceptor, methane production ranging from 9 – 26 mg CH4.g substrate-1 was demonstrated from both oxidized coal substrates. Geologically oxidized coal produced 30% more methane than biologically oxidized coal. Methane yields from the geologically oxidized coal in the presence and absence of a co-substrate were 5 – 13-fold higher than previous studies that used hard coal for methanogenesis. Based on these results, and that the development and optimization of the biological oxidation process is currently ongoing, further applications investigated in this study were undertaken using geologically oxidized coal. It was shown using pyrolysis gas chromatography mass spectrometry that the methanogenic system was dependent on the presence of an effective co-substrate supporting the breakdown of the complex organic structures within the oxidized hard coal substrate. Also that the accumulation of aromatic intermediate breakdown compounds predominantly including toluene, furfural, styrene and 2-methoxy vinyl phenol appeared to become inhibitory to both methanogenic and sulfidogenic reactions. This was shown to be a more likely cause of reactor failure rather than substrate exhaustion over time. Evidence of a reductive degradation pathway of the complex organic structures within the oxidized hard coal substrates was shown through the production, accumulation and utilization of volatile fatty acids including acetic, formic, propionic, butyric and valeric acids. Comparative analysis of the volatile fatty acids produced in this system showed that geologically oxidized coal produced 20% more of the volatile fatty acids profiled and double the total concentration compared to the biologically oxidized coal. The use of geologically oxidized hard coal as a functional substrate for biological sulfate reduction was demonstrated in the neutralization of a simulated acid mine drainage wastewater in both batch and continuous process operations. Results showed an increase in pH from pH 4.0 to ~ pH 8.0 with sulfide production rates of ~ 86 mgL-1.day-1 in the batch reactions, while the pH increased to pH 9.0 and sulfide production rates of up to 450 mgL-1.day-1 were measured in the continuous process studies using sand and coal up-flow packed bed reactors. Again, the requirement for an effective co-substrate was demonstrated with lactate shown to function as a true co-substrate in this system. However, a low cost alternative to lactate would need to emerge if the process was to function in large-scale commercial environmental treatment applications. In this regard, the aerobic growth and production of Neosartorya fischeri biomass (0.64 g.biomass.g SOC-1) was demonstrated using oxidized hard coal and glutamate as a co-substrate. Both can be produced from wastes generated on coal mines, with the fungal biomass generated in potentially large volumes. Preliminary demonstration of the use of the fungal biomass as a carbon and electron donor source for biological sulfate reduction was shown and thus that this could serve as an effective substrate for anaerobic environmental treatment processes. Based on these findings, an Integrated Coal Bioprocess model was proposed using oxidized hard coal as a substrate for environmental remediation applications on coal mines. In this approach, potential applications included methane recovery from waste coal, use of waste coal in the treatment of acid mine drainage waste waters and the recovery and use of humic acids in the rehabilitation of open cast mining soils. This study provided a first report demonstrating the use of biologically and geologically oxidized hard coals as bioprocess substrates in environmental bioremediation applications. It also provided an indication that follow-up bioengineering studies to investigate scaled-up applications of these findings would be warranted.
  • Full Text:
  • Date Issued: 2010

Biological control initiatives against Lantana camara L. (Verbenaceae) in South Africa : an assessment of the present status of the programme, and an evaluation of Coelocephalapion camarae Kissinger (Coleoptera: Brentidae) and Falconia intermedia (Distant) (Heteroptera: Miridae), two new candidate natural enemies for release on the weed

  • Authors: Baars, Jan-Robert
  • Date: 2003
  • Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
  • Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
  • Full Text:
  • Date Issued: 2003

Pyrroloiminoquinone metabolites from South African Latrunculid sponges

  • Authors: Antunes, Edith Martins
  • Date: 2003
  • Subjects: Sponges -- South Africa PQQ (Biochemistry) Marine metabolites -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4340 , http://hdl.handle.net/10962/d1005001
  • Description: An in depth chemical investigation of the major and minor pyrroloiminoquinone metabolites produced by four species of endemic South African Latrunculid sponges, collected from Algoa Bay and the Tsitsikamma Marine Reserve off the south eastern coast of South Africa, yielded eleven new and twelve known pyrroloiminoquinone metabolites. The structures of the new metabolites were determined using standard spectroscopic techniques. Tsitsikamma pedunculata was shown to contain 7,8-dehydro-3-dihydro-discorhabdin C (2.1), 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C (2.2), discorhabdin S (2.3), 14-bromo-1-hydroxy-discorhabdin S (2.4), 1-bromo-2-hydroxy-4-debromo-discorhabdin S (2.5), and 2,4-debromo-3-dihydro-discorhabdin C (2.6), together with the known compounds 14-bromo-discorhabdin C (1.51), 14-bromo-3-dihydro-discorhabdin C (1.52) and 3-dihydro-discorhabdin C. The metabolites from T. pedunculata were characterised by the presence of a reduced C-3 carbonyl and bromination at C-14. Compounds isolated from a second Latrunculid sponge, Latrunculia lorii, ranged from a substituted bicyclic pyrrolecarboxylic acid, makaluvic acid A (1.47), to the simple tricyclic known pyrroloiminoquinones makaluvamine C (1.33) and damirone B (1.20) and the more complex discorhabdin D type metabolites, discorhabdin M (3.2), 1-amino discorhabdin D (3.3), 1-methoxy discorhabdin D (3.4) and 1-alanyl discorhabdin D (3.5). Discorhabdin G* (3.1) was also isolated and characterised. This is the first reported occurrence of the known compounds 1.20, 1.33 and 1.47 in a Latrunculia sponge. Discorhabdin and bis-pyrroloiminoquinone type compounds predominated in Tsitsikamma favus. Three known, tsitsikammamines A (1.71) and B (1.72), 1.52, and five new pyrroloiminoquinones, tsitsikammamine N-oxime (4.1), tsitsikammamine B N-oxime (4.2), 2.1, 2.4 and 2.6, were isolated from this sponge. A fourth Latrunculid sponge (Strongylodesma sp.) yielded three known compounds, discorhabdins A (1.57), D (1.61) and 1.53, and one new pyrroloiminoquinone 3.3. The dual role of these metabolites as cytotoxic agents and pigments resulted in an attempt to relate the photochemical properties of these metabolites to their cytotoxicity. The pyrroloiminoquinone metabolites studied exhibited moderate singlet oxygen quantum yields, while three compounds (1.57, 4.1 and 4.2) were shown to be capable of producing radicals at a wavelength of 532 nm. The possibility of a correlation between the electrochemical properties and anti-cancer (HCT-116) activity of selected pyrroloiminoquinones was explored. A study of the oesophageal and ovarian cytotoxicities of two pyrroloiminoquinones (1.57 and 1.72), together with an investigation into the intercalation and topoisomerase I inhibitory activity of the bis-pyrroloiminoquinones (1.71, 1.72, 4.1 and 4.2), are presented.
  • Full Text:
  • Date Issued: 2003

The effect of photoperiod on some aspects of reproduction in a Southern African rodent : the pouched mouse (Saccostomus Campestris)

  • Authors: Gray, Janine
  • Date: 2001
  • Subjects: Mice -- Reproduction Antechinus -- Africa, Southern
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5676 , http://hdl.handle.net/10962/d1005361
  • Description: The pouched mouse, Saccostomus campestris is widely distributed south of the Sahara, inhabiting both subtropical and tropical latitudes and a number of different biotic zones, where it breeds seasonally. In North temperate latitudes, reproduction in small mammals is controlled by photoperiod however this cue becomes less influential as latitude decreases towards the equator. The aim of the present study is to establish the role of photoperiod in the environmental control of reproduction in a seasonally breeding small mammal at low latitudes in a highly unpredictable environment. Spermatogenesis of domesticated and Fl-generation pouched mice was not inhibited by short daylength while decreasing daylength significantly affected the oestrous cycle of adult domesticated female pouched mice. Photoperiod had little effect on the oestrous cycle of F I-generation females while a possible inherent circannual endogenous rhythm controlled inhibition of reproduction in these females. Body mass of male and female juvenile pouched mice was consistently lower in short daylength and in juvenile female pouched mice the onset of fertility may be weight-dependent. The attainment of sexual maturity of domesticated and FIlF2-generation females was retarded but not halted in short daylength and females in long daylength reached puberty 7.8 - 10.2 days earlier. Short daylength also lengthened the interval between vaginal perforation and first oestrus. Puberty in juvenile females was age-dependent as both domesticated and FIlF2-generation males attained puberty at 50 days of age, although fewer males were fertile in long daylength than short daylength. Although litter size of pouched mice was smaller in short daylength for both domesticated and wildcaught females this was not due to a reduction in the ovulation rate. Domesticated females had significantly larger litters than wild-caught females. Male and female pouched mice have evolved different reproductive strategies as males become sexually mature at the same age irrespective of photoperiod and remain fertile throughout the year. In contrast, females tend to be more complex as juveniles delay reproductive maturity and adults become nonreproductive in short daylength. However, in the presence of a fertile male and if environmental conditions are favourable, in short daylength, females can become reproductively active within approximately 3 days. Thus, although the pouched mouse has adopted a purely opportunistic reproductive strategy, vestiges of photoresponsiveness are still present in the female. The seasonality exhibited in the wild is therefore due to the female. Pouched mice live in a highly unpredictable environment so the sole use of photoperiod to regulate reproduction would be disadvantageous.
  • Full Text:
  • Date Issued: 2001

Influence of macro- versus microcooling on the physiological and psychological performance of the human operator

  • Authors: Heyns, Gerhardus Johannes
  • Date: 1995
  • Subjects: Cold -- Physiological effect , Temperature -- Physiological effect , Body temperature -- Regulation , Heat -- Physiological effect
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5167 , http://hdl.handle.net/10962/d1016247
  • Description: This study evaluated the effect of a macro- versus a microcooling system on the cognitive, psychomotor and physiological performance of human operators. Male subjects (n = 24) were acclimatized for four days and then subjected to three different environmental conditions: hot ambient (40°C; 40% RH), microcooling and macrocooling. Each environmental condition was repeated twice; once under a rest condition and once while simulating a physical workload of 40 W. Four performance tests (reasoning, eye-hand coordination, memory, reaction time) were conducted once every hour for four hours. Five physiological measurements, viz rectal temperature, skin temperature, heart rate, total sweat loss and sweat rate, were taken. A significant difference existed between the physiological responses under the hot ambient condition and both cooling conditions. For all five physiological parameters he human operator benefitted substantially whatever the cooling condition. The psychological performance results indicated a greater benefit under the cooling conditions, though various external factors may have influenced responses. User perception showed that macrocooling was perceived to be the optimal method of cooling. The results showed that there was no difference in the extent to which both rectal temperature and heart rate (for rest and work conditions) decreased over the 4-hour study period with micro- and macrocooling. In the baseline hot environment both increase. Sweat rate was lowest when resting or working in a microcooled environment and at its highest in the hot baseline environment. Mean skin temperature was lowest (for rest and work conditions) with microcooling and highest in the hot baseline environment. Reaction time and memory/attention were the same under all three environmental conditions. Eye-hand coordination was better with cooling than without, but did not differ between the two cooling conditions. Reasoning ability was poorest under the hot baseline condition and best in the macrocooled environment. User perception showed that the subjects found macrocooling highly acceptable. Microcooling was found to be uncomfortable, particularly because cold air (18 - 21°C) entered the jacket at one point which caused numbness of the skin at that point. Jackets did not always fit subjects well and the umbilical cord restricted free movement.
  • Full Text:
  • Date Issued: 1995

"Us" and "them": disagreement over the meanings of terms, ambiguity, contestability and strategy in the Zimbabwean House of Assembly

  • Authors: Hasler, Arthur Richard Patrick
  • Date: 1989
  • Subjects: Politicians -- Zimbabwe -- Language , Zimbabwe -- Politics and government -- 1980- |xLanguage
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: vital:2083 , http://hdl.handle.net/10962/d1001600
  • Description: This is a study of how certain value loaded political terms are used in Zimbabwean Parliamentary debate. Before 1980 it is argued that aspects of lexical choice and an individual's sociopolitical position were extremely closely related, especially in the case of "white Rhodesians". There was also a marked lack of ambiguity in the use of value loaded terms at this time. In contemporary Zimbabwean House of Assembly, however, terms which became popularized when the new government came to power in 1980 are used with considerable ambiguity and contestability in order to further specific strategies. Though correlations between the choice of lexical units and individuals' positions in the social structure have been identified as "sociolinguistic variables" (Downes 1984, 75), it is argued that an analysis of this type of correlation should lead us to an analysis of how these lexical units or "terms" are used by individual speakers in a micro-political process. I hypothesize that the ambiguity and contestability which encompass certain key terms used in the Zimbabwean House contribute to their being used as strategies to achieve individual or party goals. I show that the terms are manipulated by individuals in various contexts, and that the normative connotations of terms, that is what the terms "ought" to mean, is not consistent with the ways in which they are used. This, in turn, has an effect on how people think the terms should be used. This process of language change exposes the interface between language usage and social life. Though not reducible to a single "correct" interpretation, it does provide rich material for the analysis of culture.
  • Full Text:
  • Date Issued: 1989

Oor die kortkuns van John Miles

  • Authors: De Beer, Marésa
  • Date: 1988
  • Subjects: Miles, John, 1938- -- Criticism and interpretation
  • Language: Afrikaans
  • Type: text , Thesis , Masters , MA
  • Identifier: vital:3569 , http://hdl.handle.net/10962/d1002092
  • Description: This thesis involves intensive analyses of some of the short-short stories in John Miles's Liefs nie op straat nie, in order to reveal the narrative strategies employed in each. In other words, it is geared to "the rules that govern ... textual actualization and, consequently, those rules that govern the way literary discourse functions as communication" (Riffaterre 1983: 158). Subsequently, attention is given to the interrelationship among the texts, the way in which they act upon one another and interact with the title of the volume, in order to establish the function of such relations. The following texts are analysed in consecutive chapters: "Lucy", "Lappies, kan jy my hoor, Lappies?", "Voorgevoel", "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?", "Hy staan by die deur en hy klop", "Gustav gaan speel", and "Liefs nie op straat nie". In a concluding chapter the implications of the title are discussed with reference to all the texts in the volume, including those not analysed individually. It is concluded that, on the one hand, the expectations raised by the title are ironicized because the title is never "completed" explicitly, and because that which, by implication, should not be seen in public ("op straat"), is specifically situated in the street and scrutinized in close-up. But on the other hand the title also evokes a peculiar mentality present in all the texts, either in the narrators, or in the characters, or in both. The discussion of "Lucy" is focussed mainly on the contrast and interaction between the world of the child and that of the adult and on the way in which this interaction is actualized within the text through the contrast in the experience of time, the use of "mémoire involontaire", "durée" and the contrasts between (and overlapping of) narrative perspective and focalization. In respect of "Lappies, kan jy my hoor, Lappies?" special attention is paid to similarities and contrasts between this text and the traditional suspense story, notably the way in which conventional techniques are employed to create suspense, as well as to generate an entire subtext which eventually "relocates" the text on the niveau of the murderer's psychological dilemma. In discussing "Voorgevoel" emphasis is not placed primarily on what is conveyed by the narrator, but on the way in which his intentions are subverted both by the window pane through which he is looking and by the narration as such. In this way he is foregrounded and revealed as narrator, just as the text is foregrounded and revealed as literature, with the emphasis, in both cases, not only on their defence mechanisms but also on their impotence. "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?" are grouped together in one chapter in order to illuminate the interaction between the two narratives in the first text, as well as the interaction between the two texts. Ultimately, they may be seen as three narratives juxtaposed through irony and relativism. The "triumph" of the "preferably not in public" mentality, both in the text and in society, is also illustrated by the interaction between the three narratives. In chapter, 5, in which "Hy staan by die deur en hy klop" is discussed, attention is focussed on the ironic function of the Biblical references, the contrast between Jan and the rest of society, and the way in which the "climax" is located within the Iserian "blank" in the text, so that the entire process of decoding is based on a filling in of that "blank" and its implications. "Gustav gaan speel" is based loosely on Barthes's lexia model, in order to determine the signifying process in the text, and also to demonstrate the way in which the text presupposes rereading. In the discussion of the title text it is revealed how the text is centered in the basic dichotomy between the narrator-as-writer and the journalist, and the way in which this polarity is relativized by the text as such. The text is demonstrated to be the credo of the volume as a whole as well as of the fiction of the Seventies in Afrikaans.
  • Full Text:
  • Date Issued: 1988

An analysis of Wesleyan missionary strategy in the eastern districts of the Cape Colony and "Caffreland" between 1823 and 1838, and an attempt to determine how far it reacted to government policies in the Cape

  • Authors: Duff, Allen Ernest George
  • Date: 1969
  • Subjects: Wesleyan Methodist Missionary Society , Missions -- South Africa -- Cape of Good Hope -- History -- Sources , Cape of Good Hope (South Africa) -- History -- 1795-1872
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:1250 , http://hdl.handle.net/10962/d1011606 , Wesleyan Methodist Missionary Society , Missions -- South Africa -- Cape of Good Hope -- History -- Sources , Cape of Good Hope (South Africa) -- History -- 1795-1872
  • Description: The purpose of this thesis has been to trace and examine the development of Wesleyan attitudes, and the actions which resulted therefrom towards the task of the evangelisation of the eastern districts of the Cape Colony and "Caffreland". These attitudes were conditioned throughout by the fact that they held certain religious principles as paramount. It is an attempt to clarify what was involved on the ecclesiastical side in this period of Wesleyan and South African history. A considerable amount of attention has been given, by various writers, to the history of the south-eastern area of South Africa in the first half of the nineteenth century. Some works have either been concerned with the more general history of the time or with the position of all the missionaries within the total political sphere. Others have concentrated on the Wesleyans particularly, either in a very general sense or in relation to one particular event, or the later decades or this half century. The period 1823 to 1833 was chosen because it covered the period of the origin of Wesleyan strategy and its first distinct phases. Where after it may be considered to have reached full maturity and become the basis of all future action in the succeeding decades. Wesleyan strategy was, to a large extent, a reaction to government policies and requires, throughout, such a consideration. The Wesleyan Missionary Society was chosen, not because on any denominational affiliations, but because of the part which it played in these areas during that time and has since played in the annuals of eastern Cape history. The approach has been to present the relevant documents in chronological order. This was done to emphasise the development over the years. Chapters have consequently been divided according to the stages or phases of this development. It has meant that subsidiary question which arise from this development have not been dealt with separately, but simply referred to as they occur. One point remains. Wesleyan correspondence from the Eastern Cape between 1837 and 1857 has disappeared from the archives of the Methodist Missionary Society in London. All attempts to trace these letters have proved futile. Consequently, it was necessary to reproduce a couple of quotes from letters contained in this correspondence which is referred to by D. Williams and C. Roxborough who had access to this material.
  • Full Text:
  • Date Issued: 1969
  • 1
  • Disclaimer
  • Privacy
  • Copyright
  • Contact