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Comparative study of the effect of silver nanoparticles on the hexokinase activity from human and Trypanosoma brucei

Impact of batting skill on pacing during repeated sprints between the wickets.

  • Authors: Elliott, Andrea
  • Date: 2014
  • Subjects: Cricket -- Batting -- Research , Sprinting -- Research , Cricket players , Exercise -- Physiological aspects -- Research , Sports -- Physiological aspects -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5153 , http://hdl.handle.net/10962/d1013546
  • Description: Introduction: With batting in cricket, there is no known end point, making the allocation of resources and the development of a suitable pacing strategy more difficult. How batsmen allocate resources and pace themselves when repeatedly sprinting between the wickets is therefore not known. According to the ‘anticipatory feedback’ model, the level of expertise/experience has a substantial influence on the development of a suitable pacing strategy. Skilled or experienced batsmen may therefore have a greater ability to develop and implement a pacing strategy compared to that of novice or less-skilled batsmen. Purpose: To assess whether the absence of a known end point at the beginning of repeated sprint bouts between the wickets effects how batsmen pace themselves comparing skilled and less-skilled batsmen. Methods: Twenty-four male cricketers from a university league were selected. Twelve skilled batsmen (players in the top five batting order), and 12 less-skilled batsmen (players in the bottom five batting order) completed three experimental. All trials required batsmen to complete the same number of shuttle sprints (14 shuttles and therefore 28 runs), while only the information provided before each trial differed. Control Trial: This trial is also referred to as the ‘informed’ trial as the batsmen are aware of the exercise requirements (end point). Unknown Trial: The batsmen were not informed of the exercise end point and were required to run on command for an indefinite period (28 runs). Deceptive Trial: Batsmen’ were incorrectly informed with regards to the number of sprints (told they were only doing 14 runs when in fact they were doing 28 runs). Muscle activity, sprint times and RPE measures were obtained during all three trials and compared. Results: Significant (p<0.05) group effects were apparent for sprint times and, ‘central’ and ‘local’ RPE. Specifically, skilled batsmen obtained the faster mean sprint times, and less-skilled batsmen reported the higher mean ‘central’ and ‘local’ RPE values in all three experimental trials. There were no significant group effects for muscle activation. Skilled batsmen did however have lower muscle activation compared to less-skilled batsmen in all three trials. Furthermore, general trends revealed that sprint times and muscle activation decreased over time (from shuttle 1 to shuttle 14), and RPE (‘central’ and ‘local’) ratings increased, regardless of the experimental trials. Skilled batsmen performed the best in all three trials. This was determined by the attainment of faster sprint times, lower muscle activation and low RPE ratings in each of the three trials. The assessment of the relationship of the dependent variables measured in each trial, did however suggest that skilled batsmen performed best in the deceptive trial while less-skilled batsmen performed best in the control trial. Skilled batsmen thus showed superior performance when trial requirements were unclear. Less-skilled batsmen however, were seen to experience decrements in performance when information regarding the end point was unknown or misleading. Conclusion: It can thus be concluded that previous experience facilitates in the obtainment of improved sprint times between the wickets, especially when the exact end point is unknown.
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  • Date Issued: 2014

Lignocellulosic waste degradation using enzyme synergy with commercially available enzymes and Clostridium cellulovorans XylanaseA and MannanaseA

  • Authors: Morrison, David Graham
  • Date: 2014
  • Subjects: Lignocellulose -- Biodegradation , Enzymes -- Biotechnology , Agricultural wastes as fuel , Polysaccharides -- Biotechnology , Sugar -- Inversion , Clostridium , Xylanases , Monomers
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4119 , http://hdl.handle.net/10962/d1013292
  • Description: The launch of national and international initiatives to reduce pollution, reliance on fossil fuels and increase the beneficiation of agricultural wastes has prompted research into sugar monomer production from lignocellulosic wastes. These sugars can subsequently be used in the production of biofuels and environmentally degradable plastics. This study investigated the use of synergistic combinations of commercial and pure enzymes to lower enzyme costs and loadings, while increasing enzyme activity in the hydrolysis of agricultural waste. Pineapple pomace was selected due to its current underutilisation and the substantial quantities of it produced annually, as a by-product of pineapple canning. One of the primary costs in beneficiating agricultural wastes, such as pineapple pomace, is the high cost of enzyme solutions used to generate reducing sugars. This can be lowered through the use of synergistic combinations of enzymes. Studies related to the inclusion of hemicellulose degrading enzymes with commercial enzyme solutions have been limited and investigation of these solutions in select combinations, together with pineapple pomace substrate, allows for novel research. The use of synergistic combinations of purified cellulosomal enzymes has previously been shown to be effective at releasing reducing sugars from agricultural wastes. For the present study, MannanaseA and XylanaseA from Clostridium cellulovorans were heterologously expressed in Escherichia coli BL21 (DE3) cells and purified with immobilised metal affinity chromatography. These enzymes, in addition to two commercially available enzyme solutions (Celluclast 1.5L® and Pectinex® 3XL), were assayed on defined polysaccharides that are present in pineapple pomace to determine their substrate specificities. The degree(s) of synergy and specific activities of selected combinations of these enzymes were tested under both simultaneous and sequential conditions. It was observed that several synergistic combinations of enzyme solutions in select ratios, such as C20P60X20 (20% cellulose, 60% pectinase and 20% xylanse), C20P40X40 (20% cellulose, 40% pectinase and 40% xylanase) and C20P80 (20% cellulose, 80% pectinase) with pineapple pomace could both decrease the protein loading, while raising the level of activity compared to individual enzyme solutions. The highest quantity of reducing sugars to protein weight used on pineapple pomace was recorded at 3, 9 and 18 hours with combinations of Pectinex® 3XL and Celluclast 1.5L®, but for 27 h it was combinations of both these commercial solutions with XynA. The contribution of XynA was significant as C20P60X20 displayed the second highest reducing sugar production of 1.521 mg/mL, at 36 h from 12.875 μg/mL of protein, which was the second lowest protein loading. It was also shown that certain enzyme combinations, such as Pectinex® 3XL, Celluclast 1.5L® and XynA, did not generate synergy when combined in solution at the initial stages of hydrolysis, and instead generated a form of competition called anti-synergy. This was due to Pectinex® 3XL which had anti-synergy relationships in select combinations with the other enzyme solutions assayed. It was also observed that the degree of synergy and specific activity for a combination changed over time. Some solutions displayed the highest levels of synergy at the commencement of hydrolysis, namely Celluclast 1.5L®, ManA and XynA. Other combinations exhibited the highest levels of synergy at the end of the assay period, such as Pectinex® 3XL and Celluclast 1.5L®. Whether greater synergy was generated at the start or end of hydrolysis was a function of the stability of the enzymes in solution and whether enzyme activity increased substrate accessibility or generated competition between enzymes in solution. Sequential synergy studies demonstrated an anti-synergy relationship between Pectinex® 3XL and XynA or ManA, as well as Pectinex® 3 XL and Celluclast 1.5L®. It was found that under sequential synergy conditions with Pectinex® 3 XL, XynA and ManA, that anti-synergy could be negated and high degrees of synergy attained when the enzymes were added in specific loading orders and not inhibited by the presence of other active enzymes. The importance of loading order was demonstrated under sequential synergy conditions when XynA was added before ManA followed by Pectinex® 3 XL, which increased the activity and synergy of the solution by 50%. This equates to a 60% increase in reducing sugar release from the same concentrations of enzymes and emphasises the importance of removing anti-synergy relationships from combinations of enzymes. It can be concluded that a C20P60X20 combination (based on activity) can both synergistically increase the reducing sugar production and lower the protein loading required for pineapple pomace hydrolysis. This study also highlights the importance of reducing anti-synergy in customised enzyme cocktails and how sequential synergy can demonstrate the order in which a lignocellulosic waste is degraded.
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  • Date Issued: 2014

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

Geochemical exploration in arid and semi-arid environments

  • Authors: Van Berkel, Ferdinand
  • Date: 1983 , 2013-04-02
  • Subjects: Geochemical prospecting , Arid regions
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4920 , http://hdl.handle.net/10962/d1004389 , Geochemical prospecting , Arid regions
  • Description: Anomalous element distributions within the regolith result from chemical adjustments of the earth's surface to prevailing climatic conditions. Because of the lack of moisture in the arid environment, chemical equilibrium related to paleoclimates is largely maintained. Mechanical or clastic dispersion dominates arid weathering and hence the exploration approach is largely dictated by the degree of preservation of the paleoregolith. Arid environment geochemists thus have to contend with surface materials ranging from laterite and calcrete in areas where the imprint of aridity is minimal, to more conventional sample media such as bedrock, stream sediment and lithic soils in actively dissecting areas. Extraction techniques are designed specifically to isolate clastic dispersion trains. Thick mantles of aeolian and water-borne overburden characterise desert lowlands and are a challenge to the exploration geochemist. Techniques showing the most promise in these areas include groundwater geochemistry, vapour geochemistry, surface microlayer geochemistry, geobotany and biogeochemistry which attempt to isolate gaseous and weak hydromorphic, ore-related trace-element dispersions. Termite mound sampling yields convincing results and appears to be an under-utilised geochemical approach. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
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  • Date Issued: 1983
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