This thesis explores the role of mood in adherence to changes in behaviour required for weight maintenance following weight loss in an obese sample. Significant increases in physical activity are necessary for successful weight maintenance, yet this change in lifestyle remains challenging for many. Anecdotally, the importance of being in the 'right mood' to make lifestyle changes is frequently reported. A systematic review of the weight maintenance literature revealed that a number of behaviour change techniques were associated with effective weight maintenance interventions. Therefore, the current randomised control study employed relevant behaviour change techniques within two goal setting interventions to improve either daily steps walked or mood compared to a control group in a weight loss programme cohort. The number of daily steps walked and mood were evaluated and the following questions were addressed: 1) In an obese population enrolled in a weight loss programme, do goal-setting interventions increase the number of steps walked compared to those in a control group? 2) Does the mood score differ for those participants in the mood improvement intervention group compared to those in the steps-walked intervention or control groups? 3) Does weight change differ for those individuals who have shown mood improvement compared to those whose mood is unchanged/worsened? The primary outcomes of steps walked, mood and weight were recorded immediately after intervention and again after unsupervised follow up 6-months later. The results showed that all groups increased the number of steps walked but not significantly so. This increase was greatest for the steps-walked group during the active intervention period but greatest for the mood intervention group during the unsupervised follow-up period. Mood improved significantly for all groups and was associated with significantly increased weight loss at follow-up. A trend for increased steps walked being associated with improved mood was observed in the 6-month follow up period. These findings highlight the links between mood and continued participation in lifestyle behaviour changes required for weight maintenance. Future research priorities are outlined for this field.

Cette thèse présente l'étude des photodiodes à avalanche de structure SAGM, à zone d'avalanche en Al(Ga)InAs et à zone d'absorption en GaInAs réalisées sur substrat InP. Ces APD visent deux types d'applications: les télécommunications optiques pour les réseaux métro/accès à 10Gb/s et la détection en espace libre pour la profilométrie de type LIDAR. Tout d'abord, la mesure des coefficients d'ionisation de différents composés Aluminium a orienté notre choix du matériau d'avalanche vers l'AlInAs qui possède le rapport des coefficients d'ionisation le plus élevé. Ensuite, les mesures et les simulations du courant d'obscurité nous ont permis d'une part de déterminer son origine et de le réduire, et d'autre part, d'établir un modèle de la photodiode (courant d'obscurité, gain et bande passante) que nous avons validé grâce à l'étude de différentes structures verticales et de différentes géométries de diodes. Enfin, la caractérisation des APD réalisées a démontré simultanément un faible courant d'obscurité multiplié lobs.M = 2nA, une responsivité élevée R0(M = 1) = 0,9A.W-1 à 1,55µm, un faible facteur d'excès de bruit f(M = 10) = 3,5 et un produit gainxbande passante élevé G x B = 150GHz qui placent nos composants au meilleur niveau de l'état de l'art. Les mesures du taux d'erreur et de la sensibilité de photorécepteurs utilisant nos diodes valident l'amélioration qu'apportent ces APD par rapport à la concurrence. De plus, les premières mesures de sensibilité en espace libre confirment l'intérêt porté à ce type de photodiodes. / This thesis presents the study of SAGM avalanche photodiodes, with a thin Al(Ga)InAs avalanche layer and a GaInAs absorption layer, grown on InP substrate. These APDs target two applications : optical telecommunications for 10Gb/s metro/access networks and free space detection for LIDAR profilometry. First, the ionization coefficients measurements on several Aluminium compound materials lead us to choose AlInAs as avalanche material because of its high ionization coefficients ratio. Then dark current measurements and simulations allow us on one hand, to find its origin and to reduce its level, and on the other hand, to make out a photodiode model (dark current, multiplication factor and bandwidth) which was validated through the study of various APD vertical structures and diode geometries. Finally, the APDs characterization simultaneously demonstrates a low multiplied dark current Id,M = 2nA, a high responsivity R0(M = 1) = 0,9A.W-1 at 1,55µm, a low excess noise factor f(M = 10) = 3,5 and a high gain×bandwidth product G × B = 150GHz, which put our components at the best state of the art level. System measurements such as bit error rate or sensitivity carried out on photoreceivers using our diodes validate the improvement brought by these APDs compared to competitors. Moreover, the early free space sensitivity measurements confirm the interest showed to this kind of photodiodes.

Recently, there is great interest in achieving higher-level integration, higher data rates, and reduced overall costs. At millimeter-wave (mm-wave) bands, the wavelength is small enough to realize an antenna-on-chip (AoC), which is an ideal solution for high compactness and lower costs. However, the main drawback of AoC is the low resistivity (10 Ω-cm) Si substrate used in the standard CMOS technology, which absorbs most radio-frequency (RF) power that was supposed to be radiated by the on-chip antenna. Moreover, due to the high relative permittivity (11.9) and relatively large electrical thickness of the Si, higher order surface wave modes get excited, which further degrade the antenna radiation performance. In order to alleviate the above-mentioned issues with the low gain of AoC, a combination of an artificial magnetic conductor (AMC) surface, a high dielectric constant superstrate, and a Fresnel lens is presented in this work. The AMC is realized in standard CMOS technology along with the AoC, whereas the superstrate and lens are part of a smart packaging solution. The AMC surface can change wave propagation characteristics at the operating frequency to achieve in-phase reflection, resulting in gain enhancement by reducing the loss in the substrate. The high dielectric constant superstrate behaves as an impedance transformer between the Si substrate and air, thus enhancing the coupling to air. Finally, the Fresnel lens enhances the gain by focusing the electromagnetic (EM) radiation beam at the boresight. For AoC realization, a standard 0.18 μm CMOS process was utilized. A coplanar waveguide (CPW) fed monopole on-chip antenna at 71 GHz, along with the corresponding driving circuit, was designed and fabricated. The AMC enhances the gain by 3 dB. Since the chip needs to be packaged anyways, in this work, we optimize the package to provide further gain enhancement. This smart package, comprising a superstrate and a Fresnel lens, provides a gain enhancement of 16 dB. The overall combination of the optimized AMC surface, superstrate layer, and lens package can provide a gain enhancement of around 19 dB. Furthermore, the package has been realized through additive manufacturing techniques that ensure lower costs for the overall system.

In this study, the response of a liquid-fueled resonant pulse combustor to changes in liquid fuel composition was investigated. Experiments were performed with gasoline- ethanol, gasoline-diesel, and gasoline-heptane mixtures selected to produce meaningful variations in the ignition delay time. A review of ignition quality tester (IQT) data provided an expected increase in the overall delay for gasoline-ethanol mixtures with increasing ethanol concentrations, and a decrease for gasoline-diesel mixtures with increasing diesel concentrations in the mixture. By taking the phase of the ion signal as an indicator of heat release timing, the experimental results showed an agreement of gasoline-ethanol cases with the IQT data with a near linear increase with increasing ethanol concentrations. However, for gasoline-diesel, there exit no linear relation with the IQT data. For the case of gasoline-heptane mixtures, the results showed a linear decrease in delay with increasing heptane concentrations. Furthermore, it was shown that small changes in the physical properties of the fuel can significantly in sequence the cold-start operation of the combustor and alter the coupling between the unsteady heat release and resonant acoustic pressure wave during resonant operation. Dynamic combustion chamber pressure, stagnation temperature and pressure are recorded after a fixed warm-up time to characterize the performance and operation of the device. Results are interpreted in the context of fuel sensitivity and performance optimization of a resonant pulse combustor for pressure gain turbine applications.

<p>Pressure gain combustion is beneficial for engine cycle efficiency, compactness, and less emissions. In this disseration, two classes of fluid expansions systems were developed to harness power from the high-speed flow delivered by the pressure gain combustor: a compact expansion system and an efficiency expansion system. In addition, a new class of pressure probes for expansion systems is developed.</p> <p>A numerical methodology is carried out to design and characterize these expansion devices and measurement systems via steady and unsteady Reynolds Averaged Navier stokes simulations. Firstly, the compact expansion system is achieved by developing a supersonic axial turbine. Performance of the supersonic axial turbine exposed to fluctuations from a nozzle downstream of a rotating detonation combustor is assessed with an increased level of complexity, including time-resolved stator, time-resolved rotor, and time-resolved turbine stage characterization. Power extraction, damping of fluctuations, and loss budgeting are evaluated. Unsteady heat transfer assessment is performed to investigate the convective heat flux distribution and decomposition. A performance map is constructed to explore the operating limit. Afterwards, the efficient expansion system is achieved by retrofitting an existing subsonic axial turbine. Without redesigning turbine airfoils, the stator endwall contour was modified to integrate the subsonic axial turbine to a diffuser and a rotating detonation combustor. Performance of the retrofitted subsonic axial turbine exposed to fluctuations form a diffuser is evaluated at several frequencies, amplitudes and inlet Mach numbers, with an increased level of model fidelity, including unsteady stator alone, unsteady turbine stage with a reduced model, full unsteady turbine stage assessment. Turbine efficiency, damping of oscillations, and loss budgeting are assessed. A multi-step optimization strategy is utilized to enhance turbine efficiency by improving the endwall contouring. A performance map is created to examine the operating range. Finally, a new type of pressure probes was developed and angular calibration was performed. A whisker-inspired design enabled the reduction of the vortex shedding effect.</p>

Reports have linked atypical antipsychotics (AAPs) with weight gain. The polymorphic CYP2D6 involved in metabolism has been associated with medication morbidity. Eleven subjects receiving olanzapine were genotyped for CYP2D6 to examine the relationship between 2D6 and AAP weight gain. Using a linear regression, the dependent variable was percent change in body mass index (BMI). Genotype, dose and duration of treatment were independent. Genotype was significant (P < 0.0097) for those with a *1/*3 or *4 genotype experiencing a larger percent BMI change than those with a *1/*1 genotype. This may be due to increased olanzapine concentrations leading to increased exposure, which may trigger AAP weight gain.

Child care providers in Mississippi are required by the Mississippi Health Department to obtain food manager’s training and certification. The TummySafe© program satisfies this requirement and is offered in a self-paced computer delivered version and a traditional classroom version. This research explores participant changes in attitude and self-reported behaviors in the two methods of curriculum delivery as well as the correlation of knowledge change with attitude and self-reported behavior change. A quasi-experimental, pre-test/post-test design was used. Attitude change was not significantly different in the two methods. Traditional participants reported a higher change in self-reported behaviors than computer delivered participants. Both attitude and self-reported behavior change were positively correlated with knowledge gain.

This qualitative study included women who had gone through the menopausal transition and had experienced obesity, and it focused on their weight histories and experiences across the life course. The goal of this research was to add to the body of knowledge concerning weight gain by applying a novel middle range theory (story theory). Story theory was used to collect and interpret from women’s life course stories the critical themes and patterns of their weight gain. Oral accounts were elicited during personal interviews from a convenience sample of ten women recruited from a weight loss and exercise program in Central Florida. Literature focusing on the prevalence of obesity, contributing factors and associated complications, as well as treatment approaches is extensive. A variety of approaches have been proposed to identify factors that contribute to the development of obesity across the lifespan. Ultimately, the goal of these studies is to understand risk factors for weight gain along with corresponding prevention and management strategies. A particular life course approach focuses on critical periods across the life span that may be associated with risk for the development of obesity. For women, puberty, pregnancy and menopause are noted to be critical for weight change in the life course as they are associated with hormonal changes and changes in body composition including fat mass. Story theory was chosen to conceptualize and guide participants through a personal interview in order to share their weight experiences along their life course. Content analysis procedures were used to analyze the data in order to identify themes and corresponding verbatim exemplars. A re-constructed composite story was developed that included excerpts from the participants’ stories in order to reveal contextualized results. Themes that were identified relative to participants’ experiences with their weight included: changes associated with emotional and iv physical health; eating patterns associated with multiple and/or changing roles/relationships; and, changes in the environment. An interpretation of the predominant pattern of weight gain included: changes in eating and physical activity that occur during multiple and simultaneous transitional life experiences, primarily in adulthood. The findings suggest that transitional experiences in women's lives - physiological, developmental, relational or environmental - were critical in that they presented risk for behavior changes related to eating and physical activity. The results of this study and the use of story theory have implications for providing individualized, patient-centered lifestyle recommendations for the prevention of unhealthy weight gain

<p> The characteristics of small-signal gain in a TE CO₂ laser amplifier are investigated using a new technique based on gain measurements of the sequence, hot and regular CO₂ laser bands. This new technique enables us, for the first time, to determine accurately the rotational and vibrational temperatures characterizing the CO₂ laser system. The gain ratio of the sequence band to the regular band provides a simple and accurate determination of the ν₃ mode vibrational temperature. The variation of this ν₃ mode vibrational temperature with discharge energy enables us to determine the net pumping efficiency to the ν₃ mode levels as a function of input energy. It is found that the ν₃ mode vibrational temperature saturates at high input energy. This saturation sets an upper limit to the gain attainable in TE CO₂ laser amplifiers. Once this saturation occurs, increasing background gas temperature causes a reduction in gain at high input energy. </p> <p> As we can measure all the characteristic temperatures relevant to the gain medium, a comparison between the calculated and experimental gain can be carried out with no adjustable parameters. The result of such a direct comparison confirms both the validity of the conventional "mode temperature" model for CO₂ laser dynamics and the validity of our measurement technique for vibrational temperatures. </p> <p> The results of the present study have shown the existence of a de-excitation mechanism occurring in the discharge, which reduces drastically the pumping efficiency to the ν₃ mode at high discharge energy. It is therefore essential to incorporate such a de-excitation mechanism in the accurate modeling of CO₂ laser dynamics. The present study contributes to a better understanding of CO₂ laser dynamics at high discharge energies. </p> / Thesis / Master of Science (MSc)

A model relating the gain of a Nd³⁺ -glass laser amplifier to its input pumping energy is developed in this thesis. This model, which is based on the Nd³⁺ rate equations, is tested experimentally, using a giant pulse as the input to the amplifier. The results of these experiments conform well to the model. / Thesis / Master of Science (MSc)