The purpose of this study was to evaluate the efficacy of a cognitive and metacognitive intervention program (Caribbean Quest; CQ), on improving cognitive and social self-concepts (i.e., evaluative self-perceptions, including self-efficacy beliefs), executive function (EF), and attention. The effect of motivation on cognitive training derived benefits also was assessed. Motivation was examined both in terms of motivation specific to engagement in the CQ intervention (i.e., state motivation) and children’s intrinsic motivation for learning situations in general. In addition, the relationship between age, motivation, and self-concept was investigated. Participants included fifty-five male children, ranging in age from 6 to 12 years, with teacher reported deficits in EF and attention (29 controls, M = 8.38 years; 26 intervention, M = 8.35 years). The CQ intervention was delivered to children at school by trained educational assistants (EAs). On average, children completed 12 hours of intervention over 6 weeks. During CQ training sessions, EAs provided support to children in their game play, helping them to monitor their performance and utilize cognitive and metacognitive strategies. Each participant completed a battery of tests before and after the intervention, including measures of cognitive function, self-concept, working memory (WM), sustained attention, and intrinsic motivation. Teachers also provided ratings of children’s intrinsic motivation. Following CQ sessions, children’s state motivation was assessed. Pre- and post-test analyses did not reveal significant intervention effects for self-concept. However, given known developmental differences in self-evaluations for children less than eight years of age as compared to children aged eight years and older, self-concept was analyzed separately within younger and older age groups. Results indicated that children younger than eight years of age showed significant improvements on cognitive and social self-concept compared to the control group, suggesting that self-concept may be more amenable to change in younger children. Transfer effects of cognitive training to neuropsychological measures of WM and attention were not significant, although findings trended in the direction of higher benefit for the intervention group. For participants in the intervention group, child-reported intrinsic motivation, but not teacher-reported or state motivation, predicted the extent of change on the self-concept questionnaire and the sustained attention task. Results indicated cognitive self-concept and state motivation increased with age for the younger group of children; for the older group of children, state motivation decreased with age. In sum, results support the use of a cognitive and metacognitive training intervention for improving cognitive and social self-concepts in younger boys with EF and attention deficits. These findings highlight the importance of motivation as a key determinant of change and training derived gains. Future studies should further explore the relationship between motivation and training derived gains to better understand factors that might limit or enhance the effectiveness of cognitive intervention, as well as examine the value of concurrently targeting motivational factors in cognitive intervention. / Graduate

Poor management of nitrogen (N) fertilisers and water in agro-ecosystems reduces yield, quality and N-use efficiency, and leads to pollution. The objective of this study was to improve irrigation and N management for planted pastures through adaptive management with simple tools and modelling. Field experiments were conducted in 2007 and 2008 at Cedara (KwaZulu Natal) and Hatfield (Gauteng) using annual ryegrass as a case study under a range of N and irrigation application strategies. Collected data sets were also used to calibrate and validate the SWB-Pro (simple) and SWB-Sci (detailed) model versions. After validation, the model was used to develop irrigation calendars and strategies, and estimate irrigation requirements for annual ryegrass. The highest forage yields were produced when N application rates ranged between 30 to 60 kg N ha-1 for each growth cycle, except for the first 2-3 growth cycles when there was high soil N carryover from the previous season. The current farmers’ recommendation (fixed N application rate of 50 kg ha-1 per growth cycle) maximised biomass but reduced pasture quality. Adaptive strategies based on nitrate concentration in wetting front detectors at different depths, reduced fertiliser N application by 28–32% and reduced potentially leachable residual soil N, while improving forage quality without yield reduction. The rate 30-40 kg N ha-1 per growth cycle provided a compromise between forage yield and quality. The SWB model performed well in simulating ryegrass growth, leaf area index, forage yield, root zone soil water deficit, daily evapotranspiration, biomass N uptake and soil nitrate. Site specific and monthly variable irrigation calendars were developed using the SWB-Pro model, for four major milk producing areas of South Africa. The simpler monthly irrigation calendars can be used in the absence of irrigation monitoring tools or more accurate site specific calendars. The SWB-Pro model requires relatively few and simple inputs. However, irrigation monitoring/scheduling with the aid of real time modelling or measurements is better than calendars developed using the SWB-Pro model with long-term historical weather data. The SWB-Sci model showed ways of improving water use efficiency using ‘room for rain’ and ‘mildly deficit irrigation’ approaches in high rainfall areas. Scenario modelling demonstrated that the best management strategy of achieving maximum yield together with low N leaching is by integrating N and water management. This integrated management can be based on the wetness of the soil and nitrate concentration in the deep root zone using wetting front detectors. The model can be used to generate monitoring protocols such as depth of wetting front detector placement and selecting N thresholds to be used for adaptive management. Setting approximate thresholds for wetting depth and nitrate concentration is a first step in implementing an adaptive management strategy. However, the challenge is to find monitoring tools which allow effective implementation of the strategy. In this study, the wetting front detector proved to be a robust, on-farm water and nitrate monitoring tool which is relatively simple and cost effective. Should it become widely adopted, farmers are expected to improve these thresholds as more experience is gained. The SWB model could also be used to evaluate alternative thresholds for adaptive N and water management. / Thesis (PhD)--University of Pretoria, 2012. / Plant Production and Soil Science / unrestricted

Recent advances in space geodetic techniques such as Very Long Baseline Interferometry, Global Navigation Satellite Services, Satellite Laser Ranging and advanced numerical weather prediction model simulations, provide huge tropospheric data sets with improved spatial temporal resolution. These data sets exhibit unique fluctuations that have a spatial-temporal structure which are thought to mimic the complex behaviour of the atmosphere. As a result, the analysis of non-stationary structure in the tropospheric parameters derived from geodetic and numerical model simulations could be used to probe the extent of universality in the dynamics of the atmosphere, with applications in space geodesy. In order to identify the physical causes of variability of tropospheric parameters, parametric and nonparametric data analyses strategies which are investigated and reported in this thesis, are used to inform on the geophysical signals embedded in the data structure. In the first task of this research work, it is shown that the fluctuations of atmospheric water vapour over southern Africa are non-linear and non-stationary. Secondly, the tropospheric data sets are transformed to stationarity and the stochastic behaviour of water vapour fluctuations are assessed by use of an automatic algorithm that estimates the model parameters. By using a data adaptive modelling algorithm, an autoregressive-movingaverage model was found to sufficiently characterise the derived stationary water vapour fluctuations. Furthermore, the non-linear and non-stationary properties of tropospheric delay due to water vapour were investigated by use of robust and tractable non-linear approaches such as detrended fluctuation analysis, independent component analysis, wavelet transform and empirical mode decomposition. The use of non-linear approaches to data analysis is objective and tractable because they allow data to speak for themselves during analysis and also because of the non-linear components embedded in the atmosphere system. In the thesis, we establish that the non-linear and non-stationary properties in the tropospheric data sets (i.e., tropospheric delay due to water vapour and delay gradients) could be triggered from strongly non-linear stochastic processes that have a local signature (e.g. local immediate topography, weather and associated systems) and/or exogenous. In addition, we explore and report on the presence of scaling properties (and therefore memory) in tropospheric parameters. This self-similar behaviour exhibit spatial-temporal dependence and could be associated with geophysical processes that drive atmosphere dynamics. Satellite Laser Ranging data are very sensitive to atmospheric conditions, which causes a delay of the laser pulse, hence an apparent range increase. A test for non-linearity is applied within specialised software for these data; it is found that the range residuals (i.e., the observed minus computed residuals) are improved when possible non-linearity of the locally measured meteorological parameters as applied to a range delay model are considered. / Thesis (PhD)--University of Pretoria, 2011. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

This study focused on two central themes. The first addressed the vulnerability of farmers to climate change at household and regional levels. The second theme analysed determinants of adaptation measures and factors influencing the perceptions of climate change in the Nile Basin of Ethiopia. Three approaches are employed to address the above themes. The first approach is the vulnerability to expected poverty approach. It is based on estimating the probability that a given shock or set of shocks moves consumption by households below a given minimum level (such as a consumption poverty line) or forces the consumption level to stay below the given minimum requirement if it is already below this level. This is adopted to assess vulnerability at household level. Secondly, the method of principal component analysis (PCA) is employed to create vulnerability indices to conduct a comparative analysis of the vulnerability across regional states. Lastly, the Heckman selection probit model is used to analyse the two-step process of adaptation, which consists of perceiving a change in climate followed by taking appropriate adaptation measures in response. Results indicate that vulnerability is highly sensitive to a minimum income requirement (poverty line) that farm households require to survive on a daily basis. For example, when the daily minimum income is fixed at US$0.3 per day, only 7 percent of farmers are vulnerable to future climate change, whereas at a minimum income level of US$2 per day, 93 percent of the farmers are vulnerable to climate extremes. Therefore, policies should encourage income generation and asset holding, both of which will enable consumption smoothing during and immediately after harsh climatic events. Results further show that the relatively least-developed, semi-arid and arid regions namely, Afar and Somali, are highly vulnerable to climate change. The large Oromia region, which is characterised both by areas of good agricultural production in the highlands and midlands and by recurrent droughts, especially in the lowlands, is also vulnerable. Furthermore, the Tigray region, which experiences recurring droughts, is also vulnerable to the negative impacts of climate change in comparison with the other regions. Integrated rural development policies, aimed at alleviating poverty with special emphasis on the relatively less-developed regions of the country (i.e., Afar and Somali), can play a double role in reducing poverty and in increasing adaptive capacity to climate change. The study also reveals that experienced farmers, more educated farmers, better-off farmers, better-informed farmers, farmers who access extension and credit services and those with stronger social networks are more likely to perceive climate change and adapt. Government policies and investment strategies that support the provision of and access to education; credit; extension services on crop and livestock production; information on climate and adaptation measures across different agro-ecologies and encourage informal social networks are necessary to better adapt to climate change in Ethiopia. / Thesis (PhD)--University of Pretoria, 2010. / Agricultural Economics, Extension and Rural Development / unrestricted

With the advent of an effective and safe vaccine against measles, the control of measles has been astounding. In several countries the success of immunisation have led to the attempt to eliminate measles transmission entirely, through the use of vaccination strategies originally developed in the polio eradication programme. These strategies are to increase and maintain high routine coverage, to conduct periodic supplemental mass immunisation campaigns and case based, laboratory confirmed surveillance. In South Africa, measles mass vaccination was added to the existing polio mass vaccination campaigns in 1996 and 1997, and the combined strategies were formulated for the South African context in this document. This document is targeted at decision makers in the national and provincial Departments of Health, to enable a coordinated and effective South African measles elimination programme. / Dissertation (MMed)--University of Pretoria, 2013. / Immunology / unrestricted

No description available.

This thesis provides a discussion on some analytical and empirical models of online auctions. The objective is to provide an alternative framework for analyzing online auctions, and to characterize the distribution of intermediate prices. Chapter 1 provides a mathematical formulation of the eBay auction format and background to the data used in the empirical analysis. Chapter 2 analyzes policies for optimally disposing inventory using online auctions. It is assumed a seller has a fixed number of items to sell using a sequence of, possibly overlapping, single-item auctions. The decision the seller must make is when to start each auction. The decision involves a trade-off between a holding cost for each period an item remains unsold, and a cannibalization effect among competing auctions. Consequently the seller must trade-off the expected marginal gain for the ongoing auctions with the expected marginal cost of the unreleased items by further deferring their release. The problem is formulated as a discrete time Markov Decision Problem. Conditions are derived to ensure that the optimal release policy is a control limit policy in the current price of the ongoing auctions. Chapter 2 focuses on the two item case which has sufficient complexity to raise challenging questions. An underlying assumption in Chapter 2 is that the auction dynamics can be captured by a set of transition probabilities. Chapter 3 shows with two fixed bidding strategies how the transition probabilities can be derived for a given auction format and bidder arrival process. The two specific bidding strategies analyzed are when bidders bid: 1) a minimal increment, and 2) their true valuation. Chapters 4 and 5 provides empirical analyzes of 4,000 eBay auctions conducted by Dell. Chapter 4 provides a statistical model where over discrete time periods, prices of online auctions follow a zero-inflated gamma distribution. Chapter 5 provides an analysis of the 44,000 bids placed in the auctions, based on bids following a gamma distribution. Both models presented in Chapters 4 and 5 are based on conditional probabilities given the price and elapsed time of an auction, and certain parameters of the competing auctions. Chapter 6 concludes the thesis with a discussion of the main results and possible extensions. / Business, Sauder School of / Graduate

The goal of this study was to gather information from Aboriginal offenders and develop a categorical map that describes the factors that help and hinder maintaining a crime free life after incarceration. The critical incident technique was utilized to examine 42 Aboriginal offenders’ journeys from prison to the community. Three hundred and forty-one incidents collapsed into nine major categories representing themes that were helpful in maintaining a crime free life: 1) transformation of self; 2) cultural and traditional experiences; 3) healthy relationships; 4) having routine and structure in daily living; 5) freedom from prison; 6) purpose and fulfillment in life; 7) attempting to live alcohol and drug free; 8) professional support and programming; and 9) learning to identify and express oneself. Seventy-eight incidents formed four categories representing obstacles that interfere with maintaining a crime free life: 1) self; 2) unhealthy relationships; 3) substance use; and 4) lack of opportunity and professional support. The findings were compared and contrasted to two major theories in the literature: desistance and the risk-needs-responsivity principle. Most of the categories were well substantiated in the literature contributing knowledge to theory, policy, practice, and the community. Information obtained from this study provides an increased understanding of the needs of Aboriginal offenders and offers guidance concerning useful strategies to incorporate into their wellness plans when entering the community, most notably respecting Aboriginal culture and traditional practices. The findings also add awareness of those circumstances, issues, and problems that arise during transition that may be harmful or create obstacles to a successful transition. / Education, Faculty of / Educational and Counselling Psychology, and Special Education (ECPS), Department of / Graduate

This thesis proposes a classification system of risk mitigation strategies based on literature search and industry interviews. Following that, a list of generic properties was generated to describe individual strategies. In parallel, populating the properties of a large number of identified strategies was attempted. The practical implications are discussed mainly focusing on knowledge management for risk mitigation strategies. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Spelling is one of the most important components of writing at single-word level and is regarded as a vital part of written communication. Also spelling is seen as an important tool in writing. Without the ability to spell as a broader aspect of writing, a person could not be called literate in the conventional sense of the word. Although the spelling is so important, learners in the foundation phase especially in grade three commit interlingual spelling errors. This means that at this stage learners transfer patterns of the mother tongue to the second language. By so doing that they write English words as the way they are pronounced in their mother tongue. Hence this study investigated grade three teachers’ strategies to help English second language learners overcome interlingual spelling errors. In exploring these strategies this study adopted a qualitative approach in order to ensure reliability and validity of the study. The data gathering instruments used included semi-structured interviews, classroom observations and document analysis. One primary school in Mdantsane a township in East London District was purposively selected to form the context of the study. The medium of instruction in this school is isiXhosa in the foundation phase and English is taught as a subject. Two teachers and their classes participated in this study. The findings of the study revealed that different factors contribute to interlingual spelling errors. These factors are status of the parent (they were illiterate), pronunciation, language borrowing and language transfer. It is also revealed that teachers have a limited number of strategies to teach learners overcome interlingual spelling errors instead they use strategies to teach spelling generally.