Stark-Effect Scattering in Rough Quantum Wells

A scattering mechanism stemming from the Stark-shift of energy levels by electric fields in semiconductor quantum wells is identified. This scattering mechanism feeds off interface roughness and electric fields, and modifies the well known 'sixth-power' law of electron mobility degradation. This work first treats Stark-effect scattering in rough quantum wells as a perturbation for small electric fields, and then directly absorbs it into the Hamiltonian for large fields. The major result is the existence of a window of quantum well widths for which the combined roughness scattering is minimum. Carrier scattering and mobility degradation in wide quantum wells are thus expected to be equally severe as in narrow wells due to Stark-effect scattering in electric fields.Comment: 4 pages, 2 figures with png forma

Dislocation scattering in a two-dimensional electron gas

A theory of scattering by charged dislocation lines in a two-dimensional electron gas (2DEG) is developed. The theory is directed towards understanding transport in AlGaN/GaN high-electron-mobility transistors (HEMT), which have a large number of line dislocations piercing through the 2DEG. The scattering time due to dislocations is derived for a 2DEG in closed form. This work identifies dislocation scattering as a mobility-limiting scattering mechanism in 2DEGs with high dislocation densities. The insensitivity of the 2DEG (as compared to bulk) to dislocation scattering is explained by the theory.Comment: 6 pages, 3 figure

Utilising a Combined Exercise and Counselling Program to Examine the Relationship Between Emotional Self-Efficacy and Physiological Improvements in Breast Cancer Survivors

Breast cancer diagnosis in women has increased in recent years, though medical progress has helped more patients become survivors rather than victims. With cancer diagnosis and treatment, however, comes a host of psychological and physical side effects that must be addressed. Research has found exercise and counselling may decrease the detrimental effects of breast cancer, but programs have typically utilised these modalities separately. As psychosocial issues appear correlated with physical health, it is imperative to examine the mind-body connection and explore the benefits of a combination exercise and counselling program. One psychological variable of interest is emotional self-efficacy, which relates to how capable one is of recognising and regulating emotions and may influence overall well-being and survival. This study explored if participation in such a program improved emotional self-efficacy and physiological health, and if self-efficacy levels correlated with other variables. A 20-week intervention was utilised, consisting of two phases. During the first eight weeks, participants (n=19) were randomised among four groups: exercise-only (Ex; n=5), counselling-only (C; n=5), exercise and counselling (ExC; n=5), or usual care control (UsC; n=4). After these 8 weeks in separate intervention groups, all women were enrolled in exercise and counselling for the remaining 12 weeks of the 20-week study. Emotional self-efficacy and physiological parameters (cardiorespiratory endurance, upper and lower body strength, and flexibility) were assessed at baseline, 8 weeks, and 20 weeks. Non-parametric testing was utilised to examine betweengroup and within-group changes in the variables of interest. Results indicated all groups were balanced at baseline for all parameters except age and radiation treatment. Eight-week findings indicated C, E, and ExC all improved emotional self-efficacy when compared to UsC (p=0.052), with the greatest score improvement observed in ExC (median=17.3). This finding suggests a program utilising both exercise and counselling may be most beneficial for improving selfefficacy. Additionally, both Ex and ExC improved in the physiological variables of interest compared to C and UsC, though only the increase in upper-body strength reached statistical significance (p=0.010). At the end of the 20 weeks, once all participants had undertaken at least 12 weeks of exercise and counselling, no significant differences remained between groups. These results indicate a catch-up effect occurred, with 12 weeks of exercise and counselling sufficient to produce beneficial changes. No correlations were observed between adherence and emotional self-efficacy, while negative correlations were observed between baseline emotional self-efficacy scores and both overall self-efficacy changes and flexibility changes. No adverse effects or new or worsened cases of lymphoedema resulted from participation in the 20-week program. Results from this study suggested combining exercise and counselling benefits both physical and psychosocial parameters, improving emotional self-efficacy more than exercise or counselling alone, with significant improvements achieved in a short time. Additionally, those with low emotional self-efficacy may have the most to gain from such an intervention. Findings from this study increased knowledge on the efficiency of a combined exercise and counselling program on addressing both physical and psychological side-effects of breast cancer. These findings can provide guidance for the implementation of such programs in the healthcare setting. Assisting post-treatment breast cancer patients to strengthen both their minds and bodies may help improve their overall quality of life and, ultimately, survivorship. This thesis is submitted in partial fulfilment of the requirement for the degree of Master of Health Sciences of the University of Notre Dame Australia, Fremantle Campus, School of Health Science

Study of structural and electrical properties of few double perovskite compounds

A detail structure and electrical characterization of a few double perovskite and their perovskite counterpart have been performed. All the compounds are synthesized by wet chemical route known as sol-gel process. The samples are found to be in single phase and stoichiometric. The information about the molecular bonding is obtained from the FTIR spectra. The calculated band gap from UV-Visible spectra characterises the semiconducting and insulating nature of the material. The morphology of the materials has been studied through FESEM and finally the dielectric spectroscopy has been carried out for all compounds