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Sustainable, environmentally friendly, and renewable energy sources are urgently needed as concerns about carbon emissions and the depletion of fossil fuels are becoming worrying. It is vital to explore cost-effective and environmentally sustainable energy sources to ensure adequate provision for the ever-increasing energy demand. Supercapacitor devices enable storage of energy and its delivery at high power over a short period. These devices have the advantage of being manufactured at low cost, being safe to use, and having a long-life cycle. This study investigated the effect of incorporating a carbon-based material (graphene foam) within a ternary transition-metals hydroxide (Nickel, Cobalt, and Manganese) to obtain its optimal electrochemical properties for supercapacitors applications. It involved a low-cost and environmentally sustainable synthesis method whereby a constant quantity of the ternary metal hydroxides (NiCoMnTH) was loaded onto various amounts of graphene foam (GF). Typical energy storage characterisation techniques were performed on the synthesised material. The physical characterisation provided results regarding the structural, morphological and surface particularities of the different nanostructured materials. The electrochemical characterisation (EC) allowed the evaluation of the materials' electrochemical behaviours and performances. The EC results also revealed the optimised composite, which demonstrated outstanding electrochemical performances. The integration of graphene foam within the pristine material enhanced its surface area improving its specific capacity to about 178,6 mAh g-1. This specific capacity was close to the triple of the initial value having a specific capacity value equivalent to 76,2 mAh g-1 when evaluated in the same configuration and under the same settings. The improved nanomaterial was then utilised as a positive electrode material for the design of a novel hybrid device. The hybrid device was assembled with the optimised material (NiCoMnTH/GF) on the positive end and activated carbon on the negative end. The device demonstrated a sustaining specific capacity of 23,4 mAh g-1at a specific current of 0,5 A g-1. The device also yielded sustaining specific energy and power densities of values of 22,32 Wh kg-1 and 439,7 W kg-1 respectively at the same specific current. The battery-supercapacitor materials combination developed a synergetic effect on the electrochemical properties, thereby enhancing the specific energy and power densities. After a 15000 cycles stability test, the device displayed an outstanding Coulombic efficiency of 99,9 % and capacity retention of 80 % within a potential range of 1,6 V at a specific current of 3 A g−1. These results have demonstrated the prodigious electrochemical potentials of the as-prepared novel nanomaterial and its capability to be utilised as a positive electrode for energy storage applications. / Dissertation (MSc (Chemical Technology))--University of Pretoria, 2020. / National Research Foundation / Chemical Engineering / MSc (Chemical Technology) / Unrestricted

Title: The knowledge, attitudes and use of performance enhancing substances and supplements among male High-school first and second team athletes in the metropolitan area of Cape Town, South Africa. Objective: Pressure to perform and to achieve success is to many high school athletes the overbearing goal and reality. Many are willing to use substances to achieve their goals even at the expense of their health and wellbeing. Four objectives emanated from this research: To determine the most frequently used sport performance enhancing substances and supplements (PESS) by male high school athletes; to evaluate the prevalence and use of PESS; to determine the main sources of information on PESS to determine the knowledge and lastly to determine the perceptions and attitudes of male high school athletes on PESS usage. Design: This study used a prospective cross sectional survey design. A self-administered questionnaire was employed to assess the participant’s knowledge, perceptions, attitude toward and use of PESS. The selected sample was male athletes in high schools in the central metropolitan area in Cape Town that were involved in competitive sports at the first and second team level. Results: One hundred and twenty two male athletes from four schools in the central metropolitan area of Cape Town participated. No serious PESS use was found. The main first choice of reported sources of information regarding PESS was pharmacists (21.3%), biokineticists (16.4%) and the internet (16.4%). The participants’ knowledge, perception and attitude toward the use of PESS was found to be poor. Conclusion: Most athletes reported to gather information from pharmacists (21.3%) and biokineticists which is encouraging since it is expected of these professionals to provide sound advice. It is suggested to create awareness among such professionals regarding use of PESS by this population and to incorporate organizations such as SAIDS and WADA as part of this dissemination of knowledge. The knowledge, perceptions and attitude toward PESS use by male high school athletes appears to be lacking thus indicating the need for more education on PESS.

Open water in sea ice, such as leads and polynyas, plays a crucial role in determining the formation of deep- and bottom-water, as well as their long-term global properties and circulation. Ocean general circulation models (GCMs) designed for studies of the long-term thermohaline circulation have typically coarse resolution, making it inevitable to parameterize subgrid-scale features such as leads and convective plumes. In this study, a hierarchy of higher-resolution sea-ice models is developed to reduce uncertainties due to coarse resolution, while keeping the ocean component at coarse resolution to maintain the efficiency of the GCM to study the long-term deep-ocean properties and circulation. The higher-resolved sea-ice component is restricted to the Southern Ocean. Compared with the coarse sea-ice model, the intermediate, higher-resolution version yields more detailed coastal polynyas, a realistically sharp ice edge, and an overall enhanced lead fraction. The latter gives enhanced rates of Antarctic Bottom Water formation through enhanced near-boundary convection. Sensitivity experiments revealed coastal katabatic winds accounted for in the higher resolution version, are the main reason for producing such an effect. For a more realistic coastline, satellite passive-microwave data for fine-grid land/ice-shelf – seaice/ ocean boundary were used. With a further enhancement of the resolution of the Southern Ocean’s sea-ice component, a grid spacing of 22 km is reached. This is about the size of the pixel resolution of satellite-passive microwave data from which ice concentration is retrieved. This product is used in this study to validate the sea-ice component of the global ocean GCM. The overall performance of the high-resolution sea-ice component is encouraging, particularly the representation of the crucial coastal polynyas. Enhancing the resolution of the convection parameterization reduces spurious coarse-grid polynyas. Constraining the upper-ocean temperature and modifying the plume velocity removes unrealistic small-scale convection within the ice pack. The observed highfrequency variability along the ice edge is to some extent captured by exposing the ice pack to upper-ocean currents that mimic tidal variability. While these measures improve several characteristics of the Southern Ocean sea-ice pack, they deteriorate the global deepocean properties and circulation, calling for further refinements and tuning to arrive at presently observed conditions.

No / Student self-assessment is widely reported to offer numerous advantages to the learner. It is a popular practice for empowering students and the advantages are claimed to incorporate increased dialogue between students and teachers and the development of skills that encompass critical awareness and reflectivity. It is, potentially, a process that may enable health care practitioners to be lifelong learners, equipped with the skills for autonomy in learning and professional practice. As such it might be viewed as an essential element of the curriculum. This paper reports on a study designed to evaluate the implementation of self-assessment among student health care practitioners. The pilot study examined the impact of self-assessment on learning and how the process was perceived by students and staff. Findings indicated that a varied approach had been taken to its implementation, which had significant repercussions in the way in which it was perceived by students. Similarly, there was a varied approach taken by students to the process of self-assessment and this had significant repercussions for its overall value as a learning tool. The outcomes of this study provide a sound rational for maintaining and expanding the practice of student self-assessment and important lessons for the process of doing so.

MSc (Med), Biokinetics, Faculty of Health Sciences, University of the Witwatersrand / Introduction: Performance enhancing substance (PES) use is a major concern currently facing adolescent sport. The youth have become more competitive in sport, with some using substances and supplements to improve their performance. Unfortunately, some of these adolescent athletes are using substances that are both harmful to their health and prohibited. Aim of study: To establish the attitudes and perceptions towards and the use of PES, including prohibited substances and food supplements, by adolescent male athletes, in selected Johannesburg boys’ high schools. Method: The study design was a cross-sectional study using a self-administered questionnaire. Male adolescent high school learners involved in 1st and 2nd team competitive high school sport in seven Johannesburg boys’ high schools were invited to volunteer to participate in the study. Questionnaires were completed under conditions similar to an examination, where participants were not allowed to communicate with each other. Demographic data was analysed using descriptive statistics. Results: The sample size was 100. Results indicated that the prevalence of PES use amongst the participants was 30%. The use of prohibited substances was found, including growth hormone (5%), anabolic androgenic steroids (4%), and adrenaline (4%). Food supplement use was also found in this sample, including creatine (32%), protein (61%), carbohydrate (54%), caffeine (57%) and vitamin (61%) supplementation. Most of the participants (83%) that used PES started using them when they were over 15 years old. The majority of the participants (42%) played rugby as their main high school sport. Conclusion: The findings indicate that there was generally a low prevalence of ergogenic substance use in Johannesburg boys’ high school sport for performance enhancement. Substances such as anabolic androgenic steroids (4%) and growth hormone (5%) were found to be used by the learners. The anti-doping attitude of the learners may be improved by education programmes, which aim to decrease the prevalence of prohibited PES use in adolescent sport.

We propose a scheme for outsourcing Private Information Retrieval (PIR) to untrusted servers while protecting the privacy of the database owner as well as that of the database clients. We observe that by layering PIR on top of an Oblivious RAM (ORAM) data layout, we provide the ability for the database owner to perform private writes, while database clients can perform private reads from the database even while the owner is offline. We can also enforce pricing and access control on a per-record basis for these reads. This extends the usual ORAM model by allowing multiple database readers without requiring trusted hardware; indeed, almost all of the computation in our scheme during reads is performed by untrusted cloud servers. Built on top of a simple ORAM protocol, we implement a real system as a proof of concept. Our system privately updates a 1 MB record in a 16 GB database with an average end-to-end overhead of 1.22 seconds and answers a PIR query within 3.5 seconds over a 2 GB database. We make an observation that the database owner can always conduct a private read as an ordinary database client, and the private write protocol does not have to provide a "read" functionality as a standard ORAM protocol does. Based on this observation, we propose a second construction with the same privacy guarantee, but much faster. We also implement a real system for this construction, which privately writes a 1 MB record in a 1 TB database with an amortized end-to-end response time of 313 ms. Our first construction demonstrates the fact that a standard ORAM protocol can be used for outsourcing PIR computations in a privacy-friendly manner, while our second construction shows that an ad-hoc modification of the standard ORAM protocol is possible for our purpose and allows more efficient record updates.

Cryptographic credentials allow user authorizations to be granted and verified. and have such applications as e-Passports, e-Commerce, and electronic cash. This thesis proposes a privacy protecting approach of binding biometrically derived keys to cryptographic credentials to prevent unauthorized lending. Our approach builds on the 2011 work of Adams, offering additional benefits of privacy protection of biometric information, generality on biometric modalities, and performance. Our protocol integrates into Brands’ Digital Credential scheme, and the Anonymous Credentials scheme of Camenisch and Lysyanskaya. We describe a detailed integration with the Digital Credential Scheme and sketch the integration into the Anonymous Credentials scheme. Security proofs for non-transferability, correctness of ownership, and unlinkability are provided for the protocol’s instantiation into Digital Credentials. Our approach uses specialized biometric devices in both the issue and show protocols. These devices are configured with our proposed primitive, the fuzzy ex-tractor indistinguishability adaptor which uses a traditional fuzzy extractor to create and regenerate cryptographic keys from biometric data and IND-CCA2 secure en-cryption protect the generated public data against multiplicity attacks. Pedersen commitments are used to hold the key at issue and show time, and A zero-knowledge proof of knowledge is used to ensure correspondence of key created at issue-time and regenerated at show-time. The above is done in a manner which preserves biometric privacy, as and delivers non-transferability of digital credentials. The biometric itself is not stored or divulged to any of the parties involved in the protocol. Privacy protection in multiple enrollments scenarios is achieved by the fuzzy extractor indistinguishability adapter. The zero knowledge proof of knowledge is used in the showing protocol to prove knowledge of values without divulging them.

Numerous studies have investigated the relationship between physical activity and physiological health (e.g., Burke et al., 2006; Irwin, 2004). Less attention has been paid to the contribution of physical activity on psychological well-being (Fox et al., 2000), and more specifically eudaimonic well-being, which reflects optimal psychological functioning and development at ones maximum potential (Ryff, 1989, 1995). This study investigated the role that health-enhancing physical activity (HEPA; any form of physical activity that benefits health and functional capacity; Miilunpalo et al., 2000) plays in eudaimonic well-being, which Ryff conceptualizes in terms of six dimensions: (1) Autonomy (i.e., being self-determined and independent); (2) Environmental Mastery (i.e., having a sense of mastery and competence in managing the environment); (3) Personal Growth (i.e., having a feeling of continued development); (4) Positive Relations with Others (i.e., having warm, satisfying, and trusting relationships with others); (5) Purpose in Life (i.e., having goals and a sense of direction in life); and, (6) Self-acceptance (i.e., possessing a positive attitude toward the self).<p> Employing Ryffs (1989, 1995) perspective of eudaimonic well-being, this study explored whether or not experiencing eudaimonia during HEPA moderates the relationship between HEPA and eudaimonic well-being. Additionally, it explored whether or not the relationship between experiencing eudaimonia during HEPA and eudaimonic well-being is mediated by basic need satisfaction. Undergraduate university students (N = 524; Mage = 20.7 years) completed an online survey including the Scales of Psychological Well-Being (Ryff & Keyes, 1995), the Short Questionnaire to Assess Health-enhancing Physical Activity (Wendel-Vos et al., 2003), the Hedonic and Eudaimonic Motives for Activity scale (Huta & Ryan, 2008), and the Psychological Need Satisfaction in Exercise Scale (Wilson, Rogers, et al., 2006). While level of HEPA was not significantly related to eudaimonic well-being (r = .05, p = .24), experiencing hedonia during HEPA (i.e., enjoying oneself, experiencing pleasure; r = .40, p < .01), experiencing eudaimonia during HEPA (r = .37, p < .01), and basic need satisfaction (r = .46, p < .01) were significantly related to eudaimonic well-being. Although experiencing eudaimonia during HEPA did not moderate the relationship between HEPA and eudaimonic well-being, experiencing eudaimonia during HEPA accounted for a significant 2.2% unique variance in eudaimonic well-being beyond HEPA and experiencing hedonia during HEPA (the full model accounted for a significant 18.2% of the variance in eudaimonic well-being).<p> Furthermore, the data were consistent with a model of partial mediation in that basic need satisfaction partially accounted for the relationship between experiencing eudaimonia during HEPA and eudaimonic well-being, supporting the proposition put forth by Ryan et al. (2008) that positive psychological well-being is a result of eudaimonic living that facilitates the satisfaction of our basic psychological needs. Findings from this study suggest that what appears to be significant in the relationship between HEPA and eudaimonic well-being is not the level of activity, but rather what is experienced during the activity. Future research may explore the directionality of the relationship by examining the extent to which eudaimonic well-being influences what is experienced during activity.