A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. / High purity natural type Il a diamond specimens were used in this study. Conducting layers in the surfaces of these diamonds were generated using low-ion dose multiple implantation-annealing steps. The implantation energies and the ion-doses were spread evenly to intermix the point-defects, thereby increasing the probability of interstitialvacancy recombinations and promoting dopant-interstitial-vacancy combination resulting in activated dopant sites in the implanted layers. The process used to prepare our samples is known as cold-implantation-rapid-annealing (CIRA). Carbon-ion and boron-ion implantation was used to prepare the diamond specimens, and de-conductivity measurements in the temperature range of 1.5-300 K were made following each CIRA sequence. An electrical conductivity crossover from the Mott variable range hopping (VRH) to the Efros-Shklovskii VRH conduction was observed when the temperature of insulating samples was lowered. The conductivity crossover temperature Tcross decreases with increasing concentration of the boron-ion dose in the implanted layers, indicating the narrowing of the Coulomb gap in the single-particle density of states near the Fermi energy. (Abbreviation abstract) / Andrew Chakane 2019

by Leung Chi Hung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Leung Chi Hung. / Acknowledgments --- p.i / Abstract --- p.ii-iii / Table of Contents --- p.iv-v / Figures Caption --- p.vi-xii / Tables Caption --- p.xiii / Chapter 1. --- Introduction / Chapter 1.1 --- "Magnetoresistance (MR),Giant Magnetoresistance (GMR),Colossal Magnetoresistance (CMR) and Their Applications" --- p.1-1 / Chapter 1.2 --- Colossalmagnetoresistance Effect in LCMO --- p.1-5 / Chapter 1.3 --- Significance of Ultra-Sharp Metal-Semiconductor Transition LCMO Thin Film --- p.1-12 / Chapter 1.4 --- The Use of Silver in the YBCO --- p.1-14 / Chapter 1.5 --- Previews --- p.1-15 / Chapter 1.6 --- References --- p.1-17 / Chapter 2. --- Epitixial Growth of Single-Crystal LCMO Thin Film by FTS method / Chapter 2.1 --- Facing-Target Sputtering Method --- p.2-1 / Chapter 2.2 --- Fabrication of LCMO Targets --- p.2-4 / Chapter 2.3 --- Deposition of the LCMO Thin Film / Chapter 2.3.1 --- Deposition Condition --- p.2-6 / Chapter 2.3.2 --- Deposition Process --- p.2-9 / Chapter 2.4 --- X-ray Diffraction Studies and Surface Morphology --- p.2-11 / Chapter 2.5 --- M-S Transition of LCMO Thm Film --- p.2-15 / Chapter 2.6 --- Discussions --- p.2-19 / Chapter 3. --- The Role of Silver in LCMO / Chapter 3.1 --- Reaction between Ag and LCMO --- p.3-1 / Chapter 3.2 --- Grain Size and Transition Temperature in Bulk LCMO --- p.3-9 / Chapter 3.3 --- Improving the Sharpness of Metal - Semiconductor Transition and Crystallinity of LCMO Film --- p.3-15 / Chapter 3.4 --- Stabilization of the LCMO Structure --- p.3-21 / Chapter 3.5 --- Discussions --- p.3-25 / Chapter 4 --- Epitaxial Growth of the Ultra-Sharp Metal-Semiconductor Transition LCMO Thin Film / Chapter 4.1 --- Synthesis Process of the Ultra-Sharp Metal-Semiconductor Transition LCMO Thin Films --- p.4-1 / Chapter 4.2 --- Resistivity and Magnetoresistance --- p.4-6 / Chapter 4.3 --- Thermal Annealing Effects / Chapter 4.3.1 --- Oxygen Annealing Effect --- p.4-15 / Chapter 4.3.1 --- High Pressure Annealing Effect --- p.4-20 / Chapter 4.3.2 --- Vacuum Annealing Effect --- p.4-23 / Chapter 4.4 --- Surface Morphology and Characterization --- p.4-27 / Chapter 4.5 --- Discussions --- p.4-37

We study dynamic phase transitions in the constant-volume and constant- pressure ensembles of two different systems: a one-dimensional system of diffusive hard particles and a three-dimensional glass-former of nearly-hard repulsive particles. The dynamic transitions are observed using ensembles of trajectories biased with respect to their dynamic activity, biasing to greater or lower activities than equilibrium allows us to sample different dynamic phases. We perform finite-size scaling of the transitions with respect to sys- tem size and observation time, and compare them to first-order phase tran- sitions. The two ensembles are not equivalent in the one-dimensional model. We compare our results to analytic predictions for diffusive systems in both the active and inactive phases, there are structural signatures for both dy- namic regimes. The active phases show hyperuniform ordering and the inac- tive regimes show jamming behaviour, local jamming in the constant-volume ensemble is achieved through phase separation. In the three-dimensional sys- tem we observe a dynamic transition to a glassy inactive phase, there is no obvious structural change and the structural relaxation time increases sig- nificantly. We take configurations from the active and inactive phases and subject them to a jamming protocol in order to compare the final density of the jammed packings. Previous work shows that the inactive phase of glass-forming systems have a different distribution of vibrational modes and a higher compressibility, this suggests that the jamming behaviour should differ between the two phases. We show that jammed packings generated from inactive configurations are denser than those generated from active configurations.

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Vita. / Digitized by Kansas Correctional Industries

Severe dehydration is lethal for most biological species, however there are a number of organisms which have evolved mechanisms to avoid damage during dehydration. One of these mechanisms is the accumulation of small solutes (e.g. sugars), which have been shown to preserve membranes by inhibiting deleterious phase changes at low hydration. Specifically, sugars reduce the gel to fluid phase transition temperatures of model lipid/water mixtures. However, there is debate about the precise mechanism, the resolution of which hinges on the location of the sugars. An experimental investigation into the effects of small solutes on the phase behaviour of phospholipid membranes is presented in order help identify the mechanisms by which solutes facilitate desiccation tolerance. Differential Scanning Calorimetry (DSC) was used to determine the first comprehensive phase diagram for the synthetic phospholipid DPPC over a wide range of hydration and solute molar ratios between 0.1 and 1.0 sugars per lipid. Over the same range of hydrations and solute concentrations Small Angle X-Ray Scattering (SAXS) was used to measure the structural parameters of the membrane bilayers necessary to determine both the phase of the membrane lipids and the location of the solutes. SAXS was also used to conduct the first comprehensive study of the effect of solutes on the kinetics of the fluid - gel transition of DPPC over a range of both hydration and solute concentration. Finally, contrast variation Small Angle Neutron Scattering (SANS) was used to quantitatively determine the location of the solutes. Data from these complimentary techniques are presented which show a monotonic relationship between both transition temperature and repeat spacing with respect to solute concentration. This relationship exists between solute:lipid molar ratios between 0.1 to approximately 0.5, after which higher concentrations of solute are shown to have no further effect on either the bilayer repeat spacing or transition temperature. It is proposed that the exclusion of small solutes into sugar/water micro-phases external to the bilayer can account for this behaviour. A theoretical model previously used to describe membrane phase behaviour at low hydrations is modified to account for the presence of solutes between membrane bilayers. This model is shown to be in quantitative agreement with the experimental data up until approximately 0.5 sucrose molecules per lipid, the point of solute exclusion. Once exclusion is taken into account, the model is quantitative over the whole range of sugar concentrations.

<p>The aims of this study was to examine the perceived transition demands, resources, barriers, coping strategies, and consequences for two cases of transition, one successful and one unsuccessful transition – from junior to senior level in swimming. A qualitative study was executed on two swimmers from southern of Sweden. The instrument was a semi structured interview guide with the Sport Transition Career model as framework. The results showed that the athlete copes better with a balance between resources and demands exist and has a successful transition from junior to senior level. An unsuccessful transition were more likely to occur when the athlete had poor resources (internal and external), and the intervention with a therapist became ineffective. A further study is needed to find out if there are differences between the resources and the demands and the coping skills between female and male athletes.</p>

<p>The purpose of the study was to investigate what factors affect the young athletes in the transition from junior to senior sport. The study’s secondary purpose was to find out what the athletes do to cope with the transitions and the final purpose was to revile what indicates the end of the transition to the athletes. The interview guide had three parts with questions about background information, personal experience related to the transition from junior to senior sport and finally the transition’s effect on the athlete’s career, life outside sport and lessons drawn from the experience. The study consisted of nine interviews, with four male and five female athletes. The data was analysed by using sentence categorisation. Quotations were used to underline the results. The results were divided into several categories, namely: demands, resources, barriers, coping, indicators and long-term effects. The results implicate that the participants felt that it was a big step to take that involved changes in demands both in the sport and in the life outside sport. The participants also felt that social demands, demands on the self, school and planning caused the biggest barriers during the transition. The results also imply that the resource most commonly mentioned by the participants were social factors (such as team cohesion) followed by individual factors. The coping strategies mainly involved mental strategies while the long-term effects show effects of evolving mental skills. Finally the indicators most commonly mentioned were objective and involved an increase in responsibility and better statistics. It is discussed in which way the results of this study can be further strengthened by the results of earlier studies and theories.</p>

No description available.

The aims of this study was to examine the perceived transition demands, resources, barriers, coping strategies, and consequences for two cases of transition, one successful and one unsuccessful transition – from junior to senior level in swimming. A qualitative study was executed on two swimmers from southern of Sweden. The instrument was a semi structured interview guide with the Sport Transition Career model as framework. The results showed that the athlete copes better with a balance between resources and demands exist and has a successful transition from junior to senior level. An unsuccessful transition were more likely to occur when the athlete had poor resources (internal and external), and the intervention with a therapist became ineffective. A further study is needed to find out if there are differences between the resources and the demands and the coping skills between female and male athletes.