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No description available.

No description available.

No description available.

Nonlinear Dirac equations exhibiting soliton phenomena are studied. Conditions are derived for the existence of solitons and an analysis of their stability is presented. New results are obtained for models previously considered in the literature. A particular model is studied for which all stationary states are localized in a finite domain and have positive energy but indefinite charge. The electromagnetic field is introduced by minimal coupling and it is shown that the discrete nature of the electric charge, and of the angular momentum, follow from a many-body stability principle. This principle also implies the de Broglie frequency relation, and furnishes an expression for the fine structure constant. The resulting charged soliton is tentatively identified with the electron.

Problem: Many individuals with chronic illnesses such as stroke and ongoing activity limitations report self-perceived health related quality of life (HRQL) that is similar to that of healthy individuals. This phenomenon is termed response shift (RS). RS describes how people change: internal standards in assessing HRQL (recalibration), values (reprioritization), or how they define HRQL (reconceptualization), after an event such as stroke. Changes in HRQL post stroke may be inaccurate if RS is not taken into account. Increased knowledge of RS may affect the way in which HRQL measures are used, both clinically and in research. The overall objective was to assess RS in construct specific HRQL models post stroke: physical function, mental health, and participation. Methods: Data were analysed from the longitudinal study “Understanding Quality of Life Post-Stroke: A Study of Individuals and their Caregivers”. Six-hundred and seventy- eight persons with stroke at 1, 3, 6, and 12 months post stroke participated. Generic and stroke specific HRQL measures were collected. Descriptive analysis was completed with SAS, and identification of RS utilized structural equation modeling with LISREL. Results: Mean age of participants was 67 years (SD 14.8), and 45% were female. RS was identified in mental health using a framework which was developed for identifying RS statistically with multiple time points. RS was also identified in physical function where it had not been expected, possibly due to the self perceived nature of the response options. The effect size of change in physical function was affected by the presence of RS. The timing of RS in mental health and physical function was primarily around the 12 month time period, and predominantly recalibration RS. RS was also identified in participation. Conclusions: The framework that was developed was useful in identifying RS and incorporated important issues such as multiple testing and validation of the model. The presence of RS affects measurement of HRQL constructs post stroke; recalibration RS can be measured clinically with specific methods to account for RS. RS should also be measured in research studies to ensure accurate measurement of change. Future research should evaluate additional models in stroke and other populations.

There are several reasons for reducing particulate formation as a result of combustion processes and to date, a number of approaches have been proposed to numerically predict soot. There is a trade-off between accuracy and computational cost and processing time. Two equation semi-empirical models have been used, with some success, to reconcile the need for fast solution turn around and accuracy. However, these models do not account for the mass balance between the gas phase and soot. In this study, the effects of mass conservation of the soot precursors in the gas phase were investigated in an ethylene-air laminar flame simulation at atmospheric pressure. Soot formation was predicted with a two-equation model. Then the model was modified for predicting soot in a turbulent ethylene-air flame operating at 1 atm. The new model is a [2+1]-equation model which accounts for the mass conservation of soot precursors.

Baigiamajame darbe nagrinėjama paprastoji antros eilės diferencialinė lygtis. Jos sprendinių gavimui ir analizei naudojamas faktorizacijos metodas – ieškomosios funkcijos skaidymas dauginamaisiais bei kiti tradiciniai paprastųjų diferencialinių lygčių sprendimo metodai: nepriklausomo kintamojo keitimo metodas, konstantų varijavimo metodas. / In this work is analyzed second-order differential equation. I use factorization method and other traditional ordinary differential equations approaches as an example: independent variable exchange method, variation of constants method and direct integration, to find solutions of the equation.

The nonlinear interactions between long surface waves and interfacial waves in a two-layer fluid are studied theoretically. The fluid is density-stratified and the thicknesses of the top and bottom layers are both assumed to be shallow relative to the length of a typical surface wave and interfacial wave, respectively. A set of Boussinesq-type equations are derived for potential flow in this system. The equations are then analyzed for the dynamics of the nonlinear resonant interactions between a monochromatic surface wave and two oblique interfacial waves. The analysis uses a second order perturbation approach. Consequently, a set of coupled transient evolution equations of wave amplitudes is derived. Moreover, the effect of weak viscosity of the lower layer is incorporated in the problem and the influences of important parameters on surface and interfacial wave evolution (namely the directional angle of interfacial waves, density ratio of the layers, thickness of the fluid layers, surface wave frequency, surface wave amplitude, and lower layer viscosity) are investigated. The results of the parametric study are discussed and are generally in qualitative agreement with previous studies. In shallow water, a triad formed of surface waves (or interfacial waves) can be considered in near-resonant interaction. In contrast to the previous studies which limited the study to a triad (one surface wave and two interfacial waves or one interfacial and two surface waves), the problem is generalized by considering the nonlinear interactions between a triad of surface waves and three oblique pairs of interfacial waves. In this system, each surface wave is in near-resonance interaction with other surface waves and in exact resonance with a pair of oblique interfacial waves. Similarly, each interfacial wave is in near-resonance interaction with other interfacial waves which are propagating in the same direction. Inclusion of all the interactions considerably changes the pattern of evolution of waves and highlights the necessity of accounting for several wave harmonics. Effects of density ratio, depth ratio, and surface wave frequency on the evolution of waves are discussed. Finally, a formulation is derived for spatial evolution of one surface wave spectrum in nonlinear interaction with two oblique interfacial wave spectra. The two-layer Boussinesq-type equations are treated in frequency domain to study the nonlinear interactions of time-harmonic waves. Based on weakly two-dimensional propagation of each wave train, a parabolic approximation is applied to derive the formulation.

Background: The first aim of this thesis was to systematically review the evidence for the impact of interpersonal trauma in childhood on appraisals of auditory hallucinations in adulthood. Informed by this systematic review and cognitive models of psychosis, potential moderators of the relationship between trauma and distress were proposed. Hypotheses: It was hypothesised that the experience of interpersonal trauma in childhood would predict ‘self blaming’ and ‘danger to self’ appraisals made by voice hearers about their auditory hallucinations. It was predicted that these appraisals would interact with the use of avoidant and non avoidant coping strategies and that this would predict wellbeing. Method 1 and results: In order to measure voice appraisals, the Interpretation of Voices Inventory was adapted. It was completed by one hundred and thirteen voice hearing participants and confirmatory factor analysis was used to test the predicted factors. Most items covaried with their respective factors acceptably. A number of items did not load well and it was recommended that they be removed from the measure. The amended factor structure improved the fit of the measure to an acceptable standard. Method 2 and results: Sixty two participants completed additional measures of interpersonal trauma in childhood and wellbeing. Structural equation modeling provided support for a link between severity of childhood trauma and ‘danger to self’ appraisals. ‘Danger to self’ appraisals predicted the use of acceptance based coping and this predicted wellbeing. Independent of this model, interpersonal coping was shown to predict the use of psychological explanations for the experience of auditory hallucinations. Psychological explanations did not predict acceptance or wellbeing. Discussion: It may be clinically helpful to test acceptance based interventions using ‘danger to self’ appraisals as an outcome measure in the future. Possible factors that may have influenced the results were reflected on. The potentially negative impact of insight on wellbeing was discussed. Stigma was highlighted as a potential barrier to non avoidant coping