3. Electronic Theses and Dissertations (ETDs)

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Wear Reduction and Media Density Optimization for the Single Stage Pipe Densifier at Sishen Iron Ore’s Beneficiation Plants
(University of the Witwatersrand, Johannesburg, 0202-02) Botha, Simone; Kabezya, Kitungwa
The depleting high-grade iron ore mining supply at Sishen Mine in the Northern Cape, South Africa, has given rise to its beneficiation plants operating at higher media densities to upgrade lower-grade ore. In this study, densification was numerically modelled using an MPPIC model and experimentally tested using a 200-mm diameter centrifugal densifier from two local suppliers – Multotec and HMA. Shear stress, wear rate, separation efficiency and media losses were measured at increasing operating densities and differing vortex finder sizes. Optimum operating conditions were established. It was found that a feed density of 3.60 t/m3 and a shear stress of 9.70 e-3 N/m3 at the inlet using a vortex finder diameter size of 30 mm exhibited favourable performance in terms of media densification and downstream recovery. The practical significance of this is proven in terms of wear rate and its predictability to provide a consistent overflow of below 1.20 t/m3 media to the recovery circuit. Furthermore, information about ideal operating conditions in terms of inlet pressure and controls to identify premature failures were established.
A study of the physiology of pepsinogen in the human with special reference to its disturbance in diseases of the upper gastro-intestinal tract
(University of the Witwatersrand, Johannesburg, 1953) Hirschowitz, Basil Isaac; Jones, F. Avery
This study was originally undertaken to determine the clinical value of estimating pepsinogen in the urine in cases of peptic ulcer because recent publications had shown that uropepsin (urinary pepsinogen) excretion in ulcers differed from normal controls. Briefly, the state of knowledge of pepsinogen when this study was undertaken was as follows: pepsinogen was discovered by Langley in 1881 and eventually isolated in 1958 by Herriot who described its physico-chemical properties. It was known to be formed in the stomach wall and mainly secreted into the stomach where it was irreversibly changed into pepsin in the presence or hydrochloric acid. None was reabsorbed and this pepsin was destroyed in the alkaline small intestine. Some pepsinogen diffused directly into the blood stream from the peptic cells and as far as could be ascertained was lost, till it appeared in the urine - a fact discovered by Brucke in 1861. Its transport to and the mechanism of its excretion by the kidney were the subject of hypothetical discussion only. In disease urinary pepsinogen had been studied for some time and the final conclusions were that it was increased in ulcers, especially duodenal ulcers and decreased or absent in pernicious anaemia. It was apparent early in this study that investigation of urinary pepsinogen alone would be of little value in advancing the knowledge of the normal and abnormal physiology of pepsinogen in the human. The investigation was then extended to study the pathological disturbances of urinary pepsinogen more closely, and if possible to determine what happened to pepsinogen between the stomach and the urine. This latter project became possible after the development of a technique not previously described for determining blood pepsinogen and it was found that pepsinogen diffuses from the peptic cells into the blood, and circulate as free pepsinogen in the plasma. From the plasma it is freely diffused through the body and filtered through the glomerular membrane and then reabsorbed in the tubules of the kidney to the extent of 65 - 95%. This new concept of pepsinogen excretion by the kidney calls for a re-orientation of the conclusions previously held of the significance of the urinary pepsinogen in disease, In this report, an attempt is made to present the whole cycle of pepsinogen metabolsim from its formation in the stomach to its appearance in the urine, with-normal and abnormal variations, as a unified concept. While in places comments or conclusions may appear dogmatic, it is realized that this study has produced more questions than answers. It is hoped, however, that a small contribution will have been effected by this work towards a better understanding of the direction of further advances in the knowledge of the aetiology and pathological behaviour of peptic ulcers.
Pegmatite investigations in the Karibib district, South West Africa
(University of the Witwatersrand, Johannesburg, 1963) Roering, Christian
The outer pegmatitie zone of variable thickness which is essentially a very coarse-grained granite consisting of larger perthite phenocrysts lying in a matrix of albite, quartz and muscovite. The inner portions of this zone may reveal a great enrichment of perthite, so much so, that it may grade into a giant perthite zone, e. g. Rubicon main ore-body; Karlsbrunn close to the Li-bearing ore zones. This outer portion of the pegmatite may also reveal a subdivision into two distinct units: an outermost zone of albite-quartz-muscovite and an inner zone of albite-perthite-quartz-muscovite. This sequence of essentially granitic crystallization is often abruptly broken by the appearance of a zone consisting essentially of cleavelandite with minor quartz and muscovite. This zone is characterized by the appearance of numerous accessory minerals often in economic quantities, e. g. beryl, columbite-tantalite-frondellite, topaz and apatite. The zone is generally of the order 1-5 feet depending on the original size of the pegmatitie and the degree of fractionation. That it is not a late replacement unit is confirmed by observations at Rubicon where corroded crystals of beryl belonging to this zone are found lying in a matrix of lepidolite and albite which is the next unit to form. The lepidolite-albite zone in fact replaces the beryl-bearing zone. The striking symmetry alone of the Rubicon body testifies to this zone preceeding in crystallization sequence the Li-ore zones. The significant fact about this zone is that it marks a distinct break in the crystallization history of the pegmatite, i. e. it marks the change from crystallization of essentially granitic components to the formation of late phase constituents, viz. Li-bearing and associated minerals. It possibly marks the break from magmatic crystallization to late-magmatic conditions when pneumatogenic and even hydrothermal processes begin to operate. The next group of minerals to form are noticeably rich in Li and are frequently associated with sugary albite. The major minerals are petalite, lepidolite and albite, while minor amounts of amblygonite also occur. There is a definite spacial relationship sequence in the formation of these minerals. Petalite crystallizes first and collects in the upper part of this unit generally forming a hood. Amblygonite, albite, quartz, may occur at the same time. Immediately below this petalite hood, and at a somewhat later stage, fine-grained lepidolite crystallizes together with albite and minor quartz. The final phase to form at this general stage is sugary albite which collects at the bottom of the still non-crystalline portion of the magma chamber. The sugary albite phase is able to behave diapirically and can intrude, brecciate, and replace any of the previously crystallized zonal constituents. Each successive stage here can assume corrosive relationships to previously consolidated units. No assessment is made as to the amount of replacement that may take place as the criterion commonly used for such diagnosis are somewhat subjective. During this entire process of complex diffusions and crystallization, silica is apparently being concentrated in the residual fractions of the pegmatite magma. The next zone to form is a cleavelandite-rich rock confined to the quartz core margin. This cleavelandite is able to vein and brecciate and corrode the immediately adjacent lying lepidolite and is often associated with minerals such as beryl, columbite, tantalite, tourmaline, topaz and apatitie. Amblygonite may also belong to this stage of mineralization though in general it tends to be associated close in time with the petalite stage of mineralization. The final stage of the crystallization sequence is the quartz core. Quartz veinlets emanating from the core have been observed to cut across adjacent lepidllite-rich and amblygonite-albite zones. Euhedral crystals of columbite and beryl at the core margin are completely surrounded by quartz. These observations may suggest that quartz, although concentrated in the centre of the dyke, probably existed in some unconsolidated state (e. g. a gel as Brotzen (1959) has suggested). The development of a gas phase at certain stages of the pegmatites consolidation history possibly accounts for the vertical fractionation found in these pegmatites. Finally details of the more important pegmatite minerals are given together with chemical analyses.
The Quantitative Hydrogeological Mapping of Zebediela Estates, Central Transvaal
(University of the Witwatersrand, Johannesburg, 1970-05) Pretorius, Desmond Aubrey
The groundwater system on zebediela Estates, situated along the northern edge of the Springbok Flats in the Central Transvaal, has been studied by physiographic, geologic , geophysical, geochemical, and hydrologic methods . Emphasis has been placed on the subsurface mapping of the spatial distribution patterns of a nvn1ber of hydrogeologic parameters, and computer-based polynomial trend surface analysis has been employed to facilitate the interpretation of the maps. The computer has also been used to determine the general statistics of the frequency distributions of the various parameters and to platform sequential multiple linear regression analysis in an attempt to determine the relationships between the variables . Data arrays of observations, computations, and interpretations have been disp layed in 38 tables in the text and 21 appendices to the text . The distr ibution patterns , in one and two dimensions, have been portrayed in 8 text figures and 117 maps, separate from the t ext. The area studied covers approximate ly 23 square mil es, in which 556, 000 orange trees have been planted on 5800 acres . An average annual amount of 2400 million gallons of water is required to maintain t he operation, and 560 million gallons of this quantity are withdrawn, on the average, each year from boreholes tapping the groundwater resources of the Estates . Up to April, 1969, 315 holes had been drilled, and 151 had become producers at one time or another. In 19 years of exploitation between 1950 and 1968, 10, 600 million gallons of groundwater were withdrawn, at an average rate of 13 million gallons per year per production borehole. The study has shown that the groundwater system supplying this substantial quantity of water consists of two main elements - a piedmont alluvial slope, in which stream channels and paleochannels on coalescing alluvial fans are acting as conduits for the transmistion of water from the intake areas; and an underlying bedrock storage reservoir composed of aquifers of the Transvaal and Karroo sequences . The Malmani dolomite aquifers and the Stormberg basalt aquifers are superior to those of the Wolkberg quartzites, shales, and lavas, and the Stormberg Cave sandstones. It has been possible to distinguish two cycles of Karoo basalts, each of which shows differentiation . The upper cycle is far more important as an aquifer than the lower cycle. The piedmont slope is composed of portions of three alluvial fans , the spines of which have a general southeasterly trend towards the junction of the Nkumpi and Olifant rivers in the valley-flat environment well to the south of the Estates . The upland areas above the apices of the fans embrace the mountain ranges which form the northern rim of the Transvaal Basin, and these uplands have suffered right-lateral movements along extensive east-northeast-trending transcurrent faults which must have continued to be active into recent times in order to displace the stream course on the fans. The fan-head section and portion of the midfan section of the Nkumpi fan, in which the Gompies River is situated, occur over the east-central, eastern, and southeastern parts of the property, and, where underlain by the upper basalt aquifers, constitute the most important source of groundwater on Zebediela Estates. The whole of the fan-head and mid-fan sections of the Mamukebe fan are located in the riorthern, west-central, western, and southwestern localities of the area studied. The fan is much smaller than either of the others, and is underlain by Wolkberg rocks, Cave sandstones, and lower basalts. Its overall groundwater potential is consequently lower than that of either of the other two components of the piedmont slope. Only a very restricted portion of the fan-head section of the Mogoto fan occurs in the extreme northwestern corner of the Estates, where it is underlain by the dolomite aquifer, Its groundwater parameters are consequently very favourable, but the true potential of this fan lies beyond the western boundary of the property. The average yield of boreholes in the upper basalt is 3600 gallons per hour; in the lower basalt, 2000 g.p.h.; in the sandstone, 1500 g.p.h.; in the dolomite, 11,200 g.p.h.; and in the quartzites, 1500 g.p.h. The average yield for all boreholes on the Estates is 4100 gallons per hour. All of these figures are appreciably higher than those for equivalent formations elsewhere in South Africa, testifying to the impoi,tance of the piedmont alluvial slope environment in the overall groundwater system at Zebediela. The average annual recharge of the groundwater reservoirs from all sources has been estimated at 700 million gallons. With the average annual withdrawal being of the order of 560 million gallons, the possibility exists that production from the aquifers can be increased by 25 per cent, without fear of serious, permanent deterioration in the performance of the groundwater system. However, excessive exploitation in times of low recharge might lead to the development of quality h.azards with respect to sodiuum, ehloride, and bicarbonate over the upperbasalts. This possibility does not exist for the remaining aquifers, particularly those in the dolomite, from which relatively pure water is drawn. An added problem in the recharge of the upper basalt aquifer is the contamination of t he groundwater in storage by lithium, brought into the Zebediela groundwater- system by the Nkumpi River, which transmits the element from the granite terrain to the north of the mountainous rim of the Springbok Flats. A new model of groundwater exploration has been devised, based on optimum drilling sites being located where coincidence takes place of piedmont stream channel conduits, dolomite or upper basalt aquifers, and transcurrent fault aquicludes, Results obtained from the employment of this model during two years of drilling subsequent to its development in a preliminary form produced an increase of 14 per cent in the average yield of all boreholes drilled.
Bub's cookbook: a new village in crown mines
(University of the Witwatersrand, Johannesburg, 1979-10) Mendelowitz, Colin J.; Tindale, Donald
A new village in Crown Mines using the existing historical architectural language.
Experimental heat transfer coefficients for the cooling of oil in horizontal internal forced convective transitional flow
(University of the Witwatersrand, Johannesburg, 1981) Rogers, Douglas Gordon; Van der Merwe, D.F.
A study of the finite element method, with reference to the Adina finite element package
(University of the Witwatersrand, Johannesburg, 1983) Constancon, Charles Peter
This dissertation presents a theoretical and practical study of the finite element met hod using the ADINA finite element program. The package was applied to the analysis of three different problems, namely: A nonlinear static analysis; a free vibration analysis and a themal analysis. The first two analyses were supplemented with experimental results for the purpose of comparison whilst the last was compared with a closed form analytic solution. The first problem consisted of a materially nonlinear static analysis of a cast iron sheave wheel. The sheave was physically loaded with a rope up to failure of the rim. Strain gauges monitored strain at twenty-four locations. In order to simulate the nonlinear properties of the east iron, a Drucker Prager yield criterion was utilised and accordingly, a subroutine describing the elasto-plastic constitutive laws was interfaced with the ADINA package. Owing to self-imposed limitations on computer resources, the sheave was modelled as a two-dimensional body. The results correlated well in the linear region but deviated when plastic deformation was pronounced. It is suspected that this was due to a combination of approximations in modelling the geometry and the material. In the free vibration analysis, a simple portal frame was built in order to compare its natural mode shapes and frequencies with those obtained from a finite element simulation. This comparison proved satisfactory. The thermal analysis was executed primarily to test and gain first hand experience with the ADINAT package. A two-dimensional flat plate subjected to a sinusoidal temperature load was simulated. Although the application was simple, the accuracy of the FEM results confirmed that the package was operating correctly. In all these exercises ADINA package performed satisfactorily. Experience show that the programme was not user-friendly, however this is not considered a drawback in a research environment.
Translating terms of affection and abuse from German to English with special reference to animal metaphors
(University of the Witwatersrand, Johannesburg, 1987) Conze, Ingola; Taylor, Oakshott
Mathematical representation and analysis of articular surfaces: application to the functional anatomy and palaeo-anthropology of the ankle joint
(University of the Witwatersrand, Johannesburg, 1990) Webb, Christie Peter; Tobias, Phillip Vallentine
This thesis is a study of quantifiable variation in the geometric shape of the superior articular surface of the talus of higher primates, with special reference to fossil tali of Plio-Pleistocene hominids. (Abbreviation abstract).
The theory and practice of community participation in provision of urban structure
(University of the Witwatersrand, Johannesburg, 1993) Abbott, John; McCutcheon, Robert
The thesis develops a new approach to community participation, for application to infrastructure provision projects in developing countries, based upon social surveys and case studies of negotiations in five South African communities. Existing approaches to community participation are analysed and shown to be unsuitable for infrastructure provision. The thesis compares the characteristics of infrastructure projects with those of other types of development projects and demonstrates how these characteristics can be used to situate a given project within a project environment defined in terms of two variables: the openness of government to community involvement in decision-making, and project complexity. Social surveys carried out in Soweto and KwaThandeka showed the centrality of infrastructure to social change in South Africa. Existing urban management systems were unable to cope with the stresses placed upon them. Four facets of urban management were identified as being under stress: institutional capacity, legitimacy, affordability, and user convenience. These stresses change the nature of infrastructure provision from the supply of end products into a complex process. Central to this process are: an increased number of actors influencing decisions, the enhanced role of technical professionals, and the social implications of different levels of service. The case-study of KwaThandeka included a study of the negotiation process with the provincial administration. This research led to the development of a performance specification for comparing social, economic and technical measures of value. A new conceptual framework for community participation was derived, based upon the different actors involved in the decision-making process and the different needs of each of those actors. Three case studies from Natal identified different implementation strategies for community participation. Communities were found to have three distinct needs: involvement in the political process; involvement in technical decision-making; and representation as consumers of services. An analytical tool was developed to assist project managers in understanding the relationships between actors in a project. The thesis shows how technical project management can be integrated into the participation process. The success of community participation can be evaluated by assessing the degree of consensus achieved between actors, and the intensity of community involvement.
Man-The-Shaman is it the Whole Story? A Feminist Perspective on the San Rock Art of Southern Africa
(University of the Witwatersrand, Johannesburg, 1995-06) Stevenson, Judith S.
Ethnographic accounts show that both shamanic and gender rituals play a critical role in San culture. Although 30% of the women and 50% of the men become shamans, the literature investigating San rock art frequently defines 'Man-the-Shaman' and minimizes the feasibility of female depictions of this important social role. Prior rock art research has tended to separate shamanic and gender processes to the impoverishment of both. This dissertation investigates the symbolic connections between these two social spheres, and argues that they are inseparable. Through this examination of gender and shamanic roles in San society this dissertation argues that metaphors reflect these two social spheres. It also argues that metaphors are a way of life which are expressed both in reality and non-reality. With these points in mind, it investigates the role of men and women as related to San rock art through social roles.
Surface Brillouin scattering studies of high-temperature elasticity
(University of the Witwatersrand, Johannesburg, 1999-03) Stoddart, Paul Randall; Comins, J. Darrel
A novel technique has been developed for studying the elastic proper ties of opaque solids at high temperatures. The method is based on surface Brillouin scattering (SBS) and has the advantages of being contact-free and non-destructive. The elastic constants can be extracted from SBS measurements of the directional dependence of the surface wave velocities. An optical furnace was designed to provide the special scattering geometry required for these measurements. The technique has been evaluated on silicon and a single-crystal nickel-based superalloy, with measurements up to 800°C and 200°C respectively. Above these temperatures, measurements were precluded by a marked deterioration in the surface quality. The elastic constants for silicon compare favourably with the established ultrasonic values, particularly in terms of the changes as a function of temperature. Additional measurement were performed on silicon at temperatures up to 900°C in order to examine the well-known central mode feature. These results shed light on a major outstanding problem in SBS, because they reveal the presence of a second quasielastic mode that may be associated with scattering from diffusive excitations. Further measurements at high and low temperatures are proposed to confirm the mechanism. Silicon was also used as a test system to clarify certain aspects of the theory and practice of SBS that have not been properly dealt with before, such as the effects of surface anisotropy and of the extended collection aperture. This indicates that SBS provides effective elastic constants for the outer 300 nm of the sample surface and thus may be influenced by surface damage and surface contamination. In the case of the superalloy, the difficulties encountered in gathering data at higher temperatures suggests that modifications to the furnace arrangement are required. The larger relative error in the velocities also created problems in the extraction of the elastic constants. This difficulty was satisfactorily overcome by using the longitudinal threshold in the Lamb shoulder to fix the value of c₁₁. Although the work described here has been limited to temperatures below 900°C, it is clear that SBS provides a powerful method for probing the elastic properties of opaque solids at elevated temperatures.
Impacts of Acid Mine Drainage on the Kromdraaispruit System
(University of the Witwatersrand, Johannesburg, 2000-07) Kyeyune, Silvia Kataliwa; Limpitlaw, Daniel
The area of study, the Kromdraaispruit system, is located in the Mpumalanga Province of South Africa. The system consists of both a stream and a wetland, which are receiving environments of treated acid mine drainage emanating from the flooded underground coal workings. The mine management noted that, even after the water from the underground workings had passed through the liming plant, acidic seeps 200m downstream were polluting it. Sampling of the Kromdraaispruit system was done over a 12-month period. Different parameters including pH, EC, Total Dissolved Solids (TDS), Suspended Solids, Total Alkalinity (TAIK), Acidity, Chloride, Sulphate, Calcium, Magnesium, Sodium, Potassium, Iron, Manganese and Aluminium were analysed. The analysis revealed an acid mine drainage problem with maximum measured concentrations of >2000 mg/l S02, 15.84 mg/l Mn, 580.90 mg/l Ca, 49.14 mg/l Mg, 13.41 mg/l K and 98.25 mg/l Fe. The lowest pH in the region was pH 2.97 from the seeps around the liming plant area. Using different modelling packages like ILWIS and STASOFT, it was found that, compared to the acidic seep, the groundwater intercepting the stream at four points, one point along the liming plant stream and three in the wetland, did not have as big an impact on the concentration of some determinants like pH. In the Kromdraaispruit wetland, the wetland sediments act as a sink for contaminants, generally improving the quality of the water flowing through it. The concentration of some determinants passing through the wetland, such as SO, Mn, Ca, Mg, K and TDS, decreased. It was also noted that the efficiency of the wetland was greatly reduced by the high discharge of accumulated salts that simply flushed through it. In most cases, determinants like SO, Mn, AI, Ca, TDS, EC and pH decreased, but not to concentrations complying with the permissible levels stipulated by the Department of Water Affairs and Forestry. Due to the addition of lime downstream of the liming plant, a suspension of “yellow buoy” formed in the wetland. This decreased the potential of the wetland to reduce pollution. Soils were collected at different sites around the study area during the rainy and dry seasons. Laboratory analysis involved determination of total anions and cations, Sodium Adsorption Ratio (SAR), saturation, pH, electrical conductivity (EC) and the concentrations of Ca, Mg, K, Na, SO, F, CI, NO, NO and available PO. From the results obtained it was noted that the soils did not contribute to nor ameliorate acid mine drainage in the Kromdraaispruit system. This is because South Africa is an arid region and migration of ions in the soil to cause any significant impacts is slow. This study discusses the implications of these observations for the monitoring and management of the polluted system.
Validating the corporate entrepreneurial assessment instrument in South Africa
(University of the Witwatersrand, Johannesburg, 2005) Alcock, Simon
The Corporate Entrepreneurship Assessment Instrument (CEAI) was developed in North America to measure the attractiveness of the internal environment of companies to corporate entrepreneurs. The objective of this research was to validate the Corporate Entrepreneurship Assessment Instrument in South Africa. Data from a study of South African middle managers was analysed to assess the CEAI’s reliability and validity. While the CEAI is reasonably reliable, there are problems with its validity in South Africa. Some of the factors of the CEAI were correlated, contradicting one of the assumptions made by the original authors. Some items did not appear to contribute significantly to any of the factors, while others were ambiguous. The data was examined further, and several options for improving the CEAI were proposed. These included changing the number of factors, changing the number of items in each factor, rewording or removing some of the items, and adding new items.
The role of increased gastrointestinal alcohol production in patients with the metabolic syndrome: Implications for the pathogenesis of non-alcoholic fatty liver disease
(University of the Witwatersrand, Johannesburg, 2006) Menezes, Colin Nigel; Immelman, Ronnie; Raal, Derick
Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease with hepatic histology that resembles alcoholic liver disease. It is a frequent cause of chronic liver disease and is attracting increasing scientific attention worldwide. I explored the possibility that increased gastrointestinal alcohol production may have a role as a “second hit” in the pathogenesis of NAFLD in study subjects with the metabolic syndrome. In an attempt to investigate this hypothesis, this study looked at blood, urine and breath levels of alcohol in patients with the metabolic syndrome versus matched age and ethnic group healthy controls. Of the twenty study subjects, 80% had dyslipidaemia, 60% had hypertension and 70% had type 2 diabetes mellitus. Their mean BMI was 35.1±8.2 kg/m² (mean ± SD, P < 0.0001 versus controls). The serum aminotransferases were significantly elevated in the study subjects, their ALT levels being 57.4±44.79 U/L versus 17.4±4.60 U/L in the controls (95% CI 18.02 – 61.42, P < 0.001), and their AST levels 52.5±36.21 U/L versus 23.4±4.86 U/L in the controls (95% CI 11.99 – 46.20, P < 0.01). Seventy five percent of the study group had sonar features suggestive of fatty liver disease. Two adipocytokines, adiponectin and leptin, mediators of insulin resistance, an important factor in the development and progression of NAFLD, were also measured. Adiponectin levels were significantly lower (6875 ng/L versus 15475 ng/L; median value, P < 0.01), and leptin concentration levels significantly higher (13.56 ng/L versus 3.05 ng/L; median value, P < 0.05) in the study subjects than in the control group. Alcohol was detected in 60% of the study subjects, of which 35% tested positive for ethanol, 55% tested positive for methanol, and 30% tested positive for both ethanol and methanol. This was a statistically significant result, as none of the control group tested positive for any of the alcohols. The ethanol concentration in the study subjects’ blood was 7.14±3.28 mg% (mean ± SD), in their urine 3.71± 12.87 mg% (mean ± SD) whilst none was detected in their breath. The methanol concentration in the study subjects’ blood was 16.17±17.95 mg% (mean ± SD), in their urine 6.8± 13.58 mg% (mean ± SD) while their breath level was 2.05±3.19 mg (mean ± SD). This study therefore suggests that endogenous alcohol production may be indeed be involved in the pathogenesis of NAFLD in subjects with the metabolic syndrome. Not only ethanol but also methanol was detected in the subjects tested. endogenous alcohol may therefore be responsible for the ‘second hit’ theory in the pathogenesis of NAFLD, and it is likely that formaldehyde, the metabolite of methanol may be a more potent toxin of the patocyte injury as opposed to acetaldehyde, the metabolite of ethanol. The most likely source of the alcohol is from intestinal bacterial flora. These findings provide further insight into the pathogenesis of NALFD, suggesting other therapeutic alternatives such as the use of antibiotics and probiotics as a potential treatment strategy for NAFLD.
The impact of brand equity and product augmentation on purchasing industrial commodities.
(University of the Witwatersrand, Johannesburg, 2006) Alexander, Nicholas Stewart
The purpose of this research was to establish the impact of brand equity and product augmentation on purchase decisions involving industrial commodities. The field of investigation was that of industrial tyres in the South African open cast mining industry and the sample was extracted from buying centre members who purchased tyres for earthmoving equipment for use on coal mines in the Mpumalanga Province of South Africa. Literature pertaining to commodity products, brand concepts and consumer brands forms the basis of the literature review; whereafter specific study on industrial branding and the buying centre were explored. The research method used was a conjoint analysis experiment which was constructed following a series of pilot studies to determine the key factors in industrial tyre procurement. The findings were that brand was indeed considered of primary importance in tyre procurement, demonstrated by each buying centres' willingness to pay a premium price for their preferred brand of tyre. Product durability and price were second and third in importance respectively. The augmented product attributes of delivery lead time and technical support were considered least important of the five attributes. These results have important implications for mining company procurement departments as well as tyre suppliers. Mining companies may be paying premium prices for tyres which are a considerable cost element in running expenses for heavy machinery. On the other hand, well known tyre supply companies may be able to expand their market share and improve profitability through the use of this information.
Financial derivatives in the South African mining industry
(University of the Witwatersrand, Johannesburg, 2006) Josef, Avichay
The purpose of this research was to identify factors which influence the decision to use financial derivatives in the South African mining industry and then to establish their importance to the industry.The research incorporated both qualitative and quantitative primary research phases. The qualitative survey formed the questionnaire framework for the quantitative phase. The quantitative survey formed the bulk of the analysis, and both mean rank tests and factor analysis were employed to interpret the data. Thirteen factors, influencing the decision to use financial derivatives, were identified. However, statistically significant mean rank tests (where p < 0.05) indicated that, out of the initial thirteen factors, the South African mining industry viewed the following to be the most important: 1. Change the Volatility of Cash Flows 2. Improve Value of the Firm 3. Change the Volatility of Accounting Earnings 4. The Size of the Firm 5. The Perceptions of Derivatives Use by Investors, Regulators and the Public It was also found that combinations of factors, rather than individual factors, influence the decision to use derivatives. Therefore, a factor analysis was conducted to identify these various combinations. The analysis yielded seven broadly defined combinations of factors which incorporated the top five factors and were able to explain most of the variance observed from the original thirteen factors. These seven combinations were:  Perceptions and External Finances  Cost of Capital and the Value of the Firm  Volatility of Accounting Earnings  Size of Firm  Availability of Information  Financial Distress  Political and Country Instability Furthermore, outputs indicated that the use of financial derivatives and the relative importance of factors in terms of derivative usage may be influenced by factors other than those discussed in this research.
Standard Bank's entry strategy into Africa
(University of the Witwatersrand, Johannesburg, 2006) Armstrong, Gareth
Emerging markets offer atractive business opportunities to international companies. This is due to their high margins, as a result of the risk-reward trade-off and the large customer base that can realise economies of scale in a short period of time. Concomitantly, South African banks are following their clients into Africa in order to provide them with corporate financial servies. In addition, a largely under-serviced local population provides an ongoing customer base for retail banking offerings. Standard Bank has the largest presence of any South African bank in Africa, conducting business, as it does, in seventeen African countries. The current research has identified economic and political factors in emerging markets that are likely to have the most significant impact on Standard Bank's operations in Africa. Additionally, the implication that these conditions hold for the choice of entry strategy was also investigated. The finidngs indicated that Standard Bank's corporate strategy for Africa plays a larger role than do the emerging market conditions when deciding on acquisition versus greenfield entry into a particular markets. Standard Bank also derives a first-mover advantage (FMA) in both the corprate and retail banking spaces in new markets.
The effect of all-trans retinoic acid on the migration of avian neural crest cells in vitro an in vivo
(University of the Witwatersrand, Johannesburg, 2007-02-15T11:43:45Z) Tshabalala, Vincent Abie Thabiso
Retinoic acid, the active metabolite of Vitamin A is known to play a major role in embryonic growth and differentiation during development. It has been shown that either excess or deficiency of retinoic acid during embryogenesis can be teratogenic. In order to study the teratogenic effects of retinoic acid, the aim of the present study was therefore to investigate the effect of all-trans retinoic acid on the migration and fate of neural crest cells in vitro and in vivo. In addition, the study investigated the effect of retinoic acid on the cytoskeletal elements of neural crest cells and on Rac and Rho, two members of the Rho family of GTPases. The neural tubes containing neural crest cells of quail embryos were removed at cranial levels and cultured on fibronectin as a substrate. The neural tubes were cultured in either Dulbecco’s minimal essential medium (DMEM) or in DMEM+Dimethylsulphoxide (DMSO) as controls. In order to test the effect of retinoic acid, the neural tubes were cultured in 10⁻⁵M all-trans retinoic acid (RA) which was reconstituted in DMSO. The distance of migration of the cultured quail neural crest cells was measured and compared between the controls and the experimentals. To study the effect of RA on the cell actin cytoskeleton in vitro, cultured neural crest cells were stained with rhodamine phalloidin. In addition, following 24 hours of culture, the quail neural crest cells were brought into suspension and micro-injected into 36 hour-old chick hosts. While the migration of neural crest cells was extensive in the control cultures in vitro, migration was inhibited in the retinoic acid-treated neural crest cells. In addition, retinoic-acid treated neural crest cells showed pigmentation and neuronal processes earlier than did the control neural crest cells. Retinoic acid-treated neural crest cells showed a disarray of the cytoskeletal elements as they were devoid of stress fibres and focal adhesions. In addition, retinoic acid appears to decrease the expression of Rac and Rho of cultured quail neural crest cells. Following micro-injection of cultured control and RA-treated quail neural crest into the cranial region of chick hosts, the control cells populated the beak area, whereas the retinoic acid-treated quail neural crest cells migrated to the retina of the eye, a region they normally do not populate. These results suggest that retinoic acid disturbs the migration of neural crest cells. It appears to do this by affecting the cytoskeletal elements of neural crest cells and the genes that are involved in forming these elements.
Strategy communication effectiveness in the South African banking industry.
(University of the Witwatersrand, Johannesburg, 2008) Alagbaoso, Manessah O.; Christie, Peter
In the business environment of South African banking industry, informed and committed employees are a source of competitive advantage. More than ever before, organisations’ strategies need to be effectively communicated, understood at all levels, and effectively implemented. The purpose of this study is to examine factors responsible for the effective communication of strategy between the head office and the network of a South African banking organization using the face-to-face medium. The data for this study was collected via a questionnaire and statistically analysed using Descriptive Statistics, Factor Analysis, Cluster Analysis and Analysis of Variance (ANOVA). A five-factor solution was obtained and the factors are: 1. Interpersonal Communication; 2. Change and Improvement; 3. Employee Involvement in Strategy Formulation; 4. Stability; and 5. Vertical Communication. Of these five factors, the first three are deemed significantly important to strategy communication effectiveness and factors one and five are specifically important to effective strategy communication through the use of the face-to-face medium. The Cluster Analysis resulted in six clusters named: 1. Best of both worlds; 2. Specialists; 3. Elitists; 4. Bureaucrats; 5. Salesmen; and 6. Ostriches. The research confirmed the importance of the involvement of all levels of managers in strategy formulation and the predominant use of the face-to-face medium for effective strategy communication. Other key recommendations include the use of managers that have been in the organisation for more than six months and less than ten years for policies related to strategy communication, and the specific use of middle managers to oversee policies related to strategy communication using the face-to-face medium.