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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Effects of gender, age, season on the mineral profiles of impala on the Experimental Farm in Messina (Aepyceros melampus) (Lichtenstein, 1812)

Laaka, Nchaupe Bright January 2014 (has links)
The purpose of this study was to provide baseline data on the mineral status of impala and to investigate the possibility of using impala as sentinel species for monitoring important elements that may affect livestock and wildlife production in southern Africa. Approximately 27 impala were sampled at the Messina Experimental Farm. Animals of different sexes, age groups and anatomical locations were sampled. Specific tissues sampled were: liver, thyroid gland, kidney fat and kidney and approximately 100g of each tissue was collected. The study examines direct cause and effect by taking a holistic approach, which includes examining exposures according to age, sex and body burden. In order to review and summarize the health state of sampled areas in terms of exposure to environmental heavy metal contaminants. Impala (Aepyceros melampus) were used as indicator species in this study. / Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Animal and Wildlife Sciences / MScAgric / Unrestricted

Vegetal BM 297 ATO as a potential food grade coating material for microencapsulation of Bifidobacterium lactis Bb12 probiotic strain under supercritical conditions

Labuschagne, Markus Christof January 2014 (has links)
The use of probiotics administered either in a direct clinical sense or indirectly as a food additive has grown greatly in recent years due to the new 'healthy living' trend. The global market for probiotics was worth R186.2 billion in 2013, showing a growth of 4.3% compounded per annum over a period of five years. Probiotics are however sensitive to different environmental factors such as light, moisture and oxidation in addition to the stresses encountered during processing. The shelf of probiotics in foodstuffs and pharmaceuticals are limited, which lead to increased costs to the manufacturer in having to incorporate enough cultures to account for losses, or a decreased benefit to the consumer in not receiving the required amount of cells needed for health benefits to be actualized. Microencapsulation is a technique used to protect probiotic cells against harsh conditions encountered both in the environment during storage and transport, and in the human body after consumption. This leads to higher numbers of viable probiotic cells being available to the consumer after consumption and decreased costs to the manufacturer as less cells need to be added. Current microencapsulation techniques are plagued with problems such as the inability to be produced at an industrial scale, the use of toxic solvents which kill the probiotic cells and contribute to pollution and the need for FDA approval of the pharmaceutical grade excipients they use. A novel encapsulation technique using the Particles from a Gas Saturated Solution (PGSS) system has been developed by the Council for Scientific and Industrial Research (CSIR), which does not require organic solvents and uses carbon dioxide in a supercritical state to create microcapsules. There is very limited knowledge on the use of lipid based food grade excipients for use in probiotic microencapsulation for food applications. The combination of these ideas could result in a novel method of protecting sensitive food additives, in addition to creating a platform for new techniques in the pharmaceutical and food industries. Bifidobacteria were successfully encapsulated using the novel PGSS method. Two lipid based excipients, Compritol E 472 ATO and Vegetal BM 297 ATO were tested to determine if they could be used in the microencapsulation of bifidobacteria. Results showed that the temperature needed to successfully liquefy the Compritol resulted in high losses of cells. It was decided to continue the study with only Vegetal BM 297 ATO which resulted in much lower losses of probiotic cells. The results demonstrated that the cells were successfully encapsulated inside Vegetal BM 297 ATO microparticles. The particles contained high numbers of cells and the process did not cause any morphological changes on the probiotic cells. The process was optimized by changing the reaction formulation and mixing chamber parameters until an encapsulation efficiency (EE) of 88% was attained. The Vegetal microparticles containing the bifidobacteria were a very desirable size for use in the food industry. This was the first time the use of a lipid based food grade excipient in microencapsulation of probiotics using a PGSS procedure was demonstrated. This result leads to further testing of the Vegetal BM 297 ATO microparticles containing bifidobacteria in in vitro gastrointestinal environments. It was found that the Vegetal BM 297 ATO matrix provided a protective effect on the cells during simulated gastrointestinal transit. There were more viable cultures in the sample containing encapsulated cells after exposure to simulated gastric fluid (SGF) and subsequently simulated intestinal fluid (SIF). The cells were released from the Vegetal BM 297 ATO matrix over 7 hours after an initial decrease in numbers. The viable numbers of non-encapsulated cells continuously decreased while the encapsulated cells continuously increased over time during exposure. The microparticles were subsequently tested to see if they increased the shelf life of bifidobacteria under different storage conditions. It was found that during refrigerated storage the microparticles did not increase the shelf life of bifidobacteria, but that it had a slight protective effect when stored at room temperature. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Microbiology and Plant Pathology / MSc / Unrestricted

The pathogenicity and host specificity of Penicillium spp. on pome and citrus fruit

Louw, Johannes Petrus January 2014 (has links)
Penicillium includes some of the most concerning postharvest pathogens of pome and citrus fruit. The pathogenicity and aggressiveness of selected Penicillium spp. previously isolated from South African and European Union fruit export chains were investigated on pome and citrus fruit. New insight and findings were documented in this study. Penicillium digitatum, the most aggressive pathogen on citrus, was also identified the most aggressive on „Beurre Bosc‟, „Beurre Hardy‟ and „Sempre Rosemarie‟ pears. It was also the third most aggressive species on „Granny Smith‟ and „Cripps Pink‟ apples. To our knowledge this is the first report where P. digitatum has been described as an aggressive pathogen on certain pome fruit cultivars. The most concerning species in terms of decay on the evaluated apple cultivars („Royal Gala‟, „Granny Smith‟, „Golden Delicious‟, „Topred‟ and „Cripps Pink‟) and two pear cultivars („Packham‟s Triumph‟ and „Forelle‟) were P. expansum and P. crustosum respectively. New reports concerning spoilage caused by these species were noted on citrus. Penicillium expansum decay and tissue-response lesions were noted on „Nules Clementine‟, „Owari Satsuma‟, „Delta Valencia‟, „Midknight Valencia‟ and „Eureka‟ seeded. Penicillium crustosum caused decay and tissue-response lesions on „Nules Clementine‟, „Nova‟, „Owari Satsuma‟, „Delta Valencia‟, „Cambria Navel‟, „Eureka‟ seeded and „Star Ruby‟. In contrast to more aggressive infections and large surface lesions, some tissue-response lesions sporulated despite their small size, thus allowing the species to complete their life cycle. The second most aggressive species affecting citrus was P. italicum. Pathogenicity of P. solitum was also confirmed on some apple and pear cultivars, although a broader cultivar range and higher level of aggression was observed on pears. Penicillium brevicompactum was only found to be pathogenic on pears. New information regarding host-Penicillium interactions, the potential of cross-infection and the impact each species may have on fruit moving through the market chain was added. Future studies should examine the link between host susceptibility as influenced by maturity and the pathogenic potential of non-host pathogens. Further research is needed to elaborate on the pathogenicity of P. digitatum on pome fruit. Information on market-end losses, the causal agents involved, and inoculum levels and sources may prove beneficial in solving industry problems at the retail-end. / Dissertation (MScAgric)--University of Pretoria, 2014. / lk2014 / Microbiology and Plant Pathology / MScAgric / Unrestricted

Assessment of rationality review in the Jurisprudence of the constitutional court

Mafuraha, Emanuel January 2014 (has links)
Read abstract in the document / Dissertation (LLM)--University of Pretoria, 2014. / lk2014 / Public Law / LLM / Unrestricted

Production and characterization of transgenic Arabidopsis and soybean (Glycine max (L.) Merrill.) plants over-expressing oryzacystatin I (OC-I)

Makgopa, M.E. (Matome Eugene) January 2014 (has links)
In legumes, drought causes early senescence due to loss of the symbiotic relationship between the plant and the rhizobacterium. Senescence is characterized by increases in proteolytic enzymes required for protein recycling to other plant tissues. Transgenic soybean plants over-expressing a cysteine protease inhibitor (OC-I) were successfully generated and characterized. Plants of transgenic lines had differential transgene expression. Transgenic plants had lower protease activity determined by both an in-gel assay and in a fluoremetric assay using SDS-PAGE and fluorogenic protease substrate, respectively. Transgenic Arabidopsis plants over-expressing OC-I, generated by floral dip method, were more drought-tolerant compared to non-transgenic Arabidopsis plants. Seeds of different transgenic soybean lines had a lower germination rate and these transgenic lines had fewer leaves and shorter stems. Under drought stress, plants of transgenic lines performed better than wild-type non-transgenic plants with CO2 assimilation (photosynthesis) and better instantaneous water-use efficiencies (IWUE). In particular, plants of one transgenic line (line 57) appeared to be more drought-tolerant when compared to plants of all other tested lines. These transgenic plants retained more soil water and also had fewer leaves when compared to wild-type non-transgenic plants. Results obtained in this study have provided evidence that preventing cysteine protease activity by over-expressing a protease inhibitor causes phenotypic changes of the plant demonstrating an important role of cysteine proteases in plant growth and development and plant stress. Future work will focus on identifying these OC-I sensitive proteases and investigating their individual function in plant growth and development and stress. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Plant Science / PhD / Unrestricted

Female customers’ expectations and satisfaction regarding custom - made apparel

Makopo, Mirriam Motlatsi Hedwig January 2014 (has links)
Today’s marketplace is characterised by fierce competition and customer satisfaction has increasingly become important as a key element and strategy for businesses to remain competitive (Gocek and Beceren, 2012; Rad, 2011; Wang and Ji, 2009; Kincade, Giddings and Chen-Yu, 1998; Matzler and Hinterhuber, 1998). A business needs to satisfy its customers against its competitors, in order to increase its medium and long term profitability (Peter and Olson in Gocek and Berecen, 2012). Customer satisfaction will lead to a return of sales, customer loyalty and customer retention. However, providing customer satisfaction requires an understanding of the customer’s perception of quality. Consumers who wear custom-made apparel are a market segment with specific preferences that need to be satisfied. Prior to acquisition, consumers form certain quality standards and then purchase apparel products to satisfy these standards (Kincade et al., 1998). Apparel quality evaluation can be very complex as consumers use specific product dimensions, which differ in their importance by product and the individual consumer. Since custom-made apparel products do not exist at the time of ordering, the complexity can intensify because evaluation of the quality can only take place when the product is complete and during wear and care. Inability to evaluate apparel quality before purchase could later lead to customer dissatisfaction (Kincade et al., 1998). Customer dissatisfaction resulting from failure of the apparel product to meet customers’ expectations could have negative impact on customer loyalty, customer retention and profitability. Although several studies on apparel quality have been undertaken, only a few of them (De Klerk and Lubbe, 2008; De Klerk and Tselepis, 2007; De klerk and Lubbe, 2004; Tselepis and De Klerk, 2004; North, De Vos and Kotze, 2003) were in the context of South Africa, of which none specifically focused on custom-made apparel. Therefore, an empirical research study on the female custom-made apparel customers’ expectations and satisfaction regarding custom-made apparel was conducted. The aim of the study was to explore and describe how female custom-made apparel customers evaluate the quality of custom-made apparel. The study further describes how female custom-made apparel customers appraise the performance of custom-made apparel, the emotions they experience following appraisals, the coping strategies used by the dissatisfied customers, as well as the consequent post-purchasing behaviours of satisfied customers. The expectancy-disconfirmation paradigm and the cognitive appraisal theory were chosen as theoretical perspectives to compile a conceptual framework for the study. The research is exploratory and descriptive, as it delves into an area of study on which no previous research could be traced in South Africa. A quantitative research style was employed. A survey was conducted by using a self-administered structured questionnaire to collect data. The theoretical background from the literature review was used to compile the questionnaire. In addition, the results of the one-on-one interviews conducted with twelve participants were used to facilitate the development of the questionnaire before it was finalised. The questionnaire included statements on a four-point Likert-type scale and a nominal Yes/No scale, which assessed the customers’ expectations and satisfaction. Prior to data collection, the questionnaire was pilot-tested on a sample of fifteen respondents and necessary adjustments were made. A non-probability purposive sampling method, combined with a snowballing technique was used to recruit respondents for the study. With the assistance of some fieldworkers and the designers who provide custom-made apparel, data were collected from 209 females, who resided in the East, South and West regions of Pretoria (Tshwane). The respondents were either satisfied or dissatisfied with their latest custom-made garment/outfit. Data were captured and analysed by descriptive statistical methods. The findings revealed that the sensory, comfort, durability and emotional dimensions are significant in determining the quality of custom-made apparel. However, the respondents were not that satisfied with the performance of some of the dimensions they rated as important, especially the sensory and the emotional dimensions. More than three quarters of the respondents who were dissatisfied with the performance of their garments/outfits blamed the custom-made apparel businesses and they believed that the designers who made their garments/outfits could have prevented the poor performance. In a similar pattern, the satisfied respondents mostly praised the custom-made apparel businesses for the satisfactory performance of their outfits. Many of the dissatisfied respondents never contacted the designers to obtain redress. Instead, most of them spread negative-word-of-mouth and stopped to patronise their businesses. The findings suggest that external attribution of blame for the product’s poor performance alone does not necessarily lead to direct complaint behavioural outcomes like contacting the business to seek redress. The entire appraisal process, including personal and situational factors played a role in determining the subsequent behavioural outcomes. The study recommends that custom-made apparel businesses encourage customer feedback, in order to get the opportunity to rectify problems and to retain existing customers, while attracting new ones. Small businesses that provide custom-made apparel have a niche to offer their customers what large manufacturers cannot. If properly managed, custom-made apparel businesses could provide employment in the informal sector of South Africa, where fewer jobs are available. The findings of the study contribute to existing theory on the subject of South African female apparel customers, particularly the female custom-made apparel customer. / Dissertation (MA)--University of Pretoria, 2014. / lk2014 / Consumer Science / MA / Unrestricted

Characterising four Cowpea (Vigna unguiculata (L.) Walp.) Mozambican landraces deposited in a seed bank for drought tolerance

Martins, C.M. January 2014 (has links)
Cowpea production is severely affected by environmental stress factors, particularly drought. More drought-tolerant crops are therefore urgently required for future improvement of food production in Mozambique. To increase high productivity and sustainability of cowpea there is a need to establish an active local breeding program, this should also include screening and characterisation of germplasm to select for more drought-tolerant cowpea landraces. This study has been therefore conducted in a temperature-controlled greenhouse at the University of Pretoria and in an open-sided tunnel house in Mozambique. The overall aim of the research work was to identify the most drought-tolerant cowpea landrace currently deposited in the Mozambican gene bank. Results of this study showed that tested Mozambican cowpea landraces have a different degree of drought tolerance with one Mozambican cowpea landrace, Timbawene moteado, better performing under drought conditions. In particular, plants of this landrace had more vigorous growth better overcoming a drought period with fast recovery and re-growth after drought exposure. Plants also maintained high rates of photosynthetic CO2 assimilation when exposed to drought and used better assimilated carbon to generate biomass than the other tested cowpea landraces. Protein and chlorophyll degradation was further less affected and had only a slight increase in proteolytic activity under drought with the proline content significantly increasing under drought. In contrast, plants of the landrace Massava nhassenje were the most drought-sensitive plants with low water-use efficiency and low CO2 assimilation as well as the lowest shoot biomass accumulation and high protease activity under drought. This study has overall demonstrated that the Mozambican cowpea germplasm deposited in the seed bank is diverse and contains characteristics that could be useful for a national breeding program. Shoot biomass, were thereby valuable traits which could be easily measured in Mozambique in a tunnel house experiment. This study might serve as a basis to screen a greater number of landraces to identify a greater number of landraces as useful additions in an active local cowpea breeding program. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Plant Science / PhD / Unrestricted

Comparison of Sampling Methods for Kriging Models

Beckley, Michaela Claire January 2014 (has links)
This study aims to generate from a three-dimensional data set of carbon dioxide ux in the Southern Ocean, a sample set for use with Kriging in order to generate estimated carbon dioxide ux values across the complete three-dimensional data set. In order to determine which sampling strategies are to be used with the three-dimensional data set, a number of a-priori and a-posteriori sampling methods are tested on a two-dimensional subset. These various sampling methods are used to determine whether or not the estimated error variance generated by Kriging is a good substitute for the true error as a measure of error. Carbon dioxide is a well known "greenhouse gas" and is partially responsible for climate change. However, some anthropogenic carbon dioxide is absorbed by the oceans and as such, the oceans currently play a mitigating role in climate change by acting as a sink for carbon dioxide. It has been suggested that if the production of carbon dioxide continues unabated that the oceans may become a source rather than a sink for carbon dioxide. This would mean that the oceanic carbon dioxide ux (exchange of carbon dioxide between the atmosphere and the surface of the ocean) would invert. As such, modelling of the carbon dioxide ux is of clear importance. Additionally as the Southern Ocean is highly undersampled, a sampling strategy for this ocean which would allow for high levels of accuracy with small sample sizes would be ideal. Kriging is a geostatistical weighted interpolation technique. The weights are based on the covariance structure of the data and the distances between points. In addition to an estimate at a point, Kriging also produces an estimated error variance which can be used as an indication of uncertainty. This study made use of model data for carbon dioxide ux in the Southern i Ocean. This data covers a year by making use of averaged data for 5 day intervals. This results in a three-dimensional data set covering latitude, longitude and time. This study used this data to generate a covariance structure for the data after the removal of trend and using this covariance structure, tested various sampling strategies in two dimensions, sampling approximately 10% of the two-dimensional data subset. These sampling strategies made use of either the estimated error variance or the true error and included two simple heuristics, genetic algorithms, the Updated Kriging Variance Algorithm and Random Sampling. Two of the genetic algorithms tested were selected to maximise the error measure of interest, in order to determine the full range of errors that could be generated. The percentage absolute errors obtained across these methods ranged from 2:1% to 64:4%. Based on these strategies, the estimated error variance was determined to not be an accurate surrogate for true error and that in cases where absolute error is available, such as data minimisation, absolute error should be used as the measure of error. However, if no data is available then it does provide an easy to calculate measure of error. This study also concluded that Addition of a Point at Point of Maximum Absolute Error does provide a good validation sampling method to which other methods may be compared. Additionally, based on true errors and computational requirements, three methods were selected to be implemented on a three-dimensional subset of the data. These methods were Random Sampling, Addition of a Point at Point of Maximum Absolute Error and Addition of a Point at Point of Maximum Estimated Error Variance. Each of these methods for sampling were performed twice on the data, sampling up to approximately 5% of the data. Random Sampling produced percentage absolute errors of 21:02% and 20:98%, Addition of a Point at Point of Maximum Estimated Error Variance produced errors of 18:54% and 18:55% while Addition of a Point at Point of Maximum Absolute Error was able to produce percentage absolute errors of 14:33% and 14:32%. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Mechanical and Aeronautical Engineering / MSc / Unrestricted

A study on interest rate basis - risk models after the 2008 liquidity crunch

Mentis, Petros January 2014 (has links)
In this dissertation we take a look at the rise of interest rate basis spreads in the market following the liquidity and credit crunch of 2008. We show that post 2008 the valuation of all interest rate instruments of a single yield curve for a particular currency is no longer a feasible approach and the assumption of no arbitrage between di erent tenors is no longer applicable. Following that a closer look is taken into the cause of such widening basis spreads and the impact they have had on the market with a focus on reconstituting the no arbitrage argument and looking at a post crisis multiple curve framework following an axiomatic approach as introduced by Henrard [37] and further explored by Bianchetti and Morini [6, 50]. A bottom-up market approach is taken by Ametrano [2] and the two approaches are shown to be equivalent in result. An analogy is made to quanto style cross currency swap adjustments observed by the aforementioned authors as well as Michaud and Upper [47], and Tuckman and Por rio [57]. We proceed to look at the approaches taken by authors such as Henrard [36, 37] in ex- tending the Black and Stochastic Alpha Beta Rho models to include basis spreads and Kijima et al. [42] who extend a model introduced by Boenkost and Schmidt [11] and put forward a quadratic Gaussian model and a Vasicek model. Mercurio [46] puts forward an extension to the LIBOR Market Model (also referred to as the Brace-Gatarek-Musiela model) under both forward measures and spot measures. Finally we consider the rise of using overnight index swaps in construction OIS discount curves and their application in the valuation of interest rate derivatives in the presence of collateral as well as reconciling the spread between OIS and vanilla interest rate swaps with credit risk measures. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Mathematics and Applied Mathematics / MSc / Unrestricted

Employment equity : the implimentation and application of affirmative action in the workplace

Mhambi, Masonwabe Honest January 2014 (has links)
Dissertation (LLM)--University of Pretoria, 2014. / lk2014 / Mercantile Law / LLM / Unrestricted

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