ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Electrostatic approach is considered for mitigation of communication attenuation during the testing of laser powered directed energy weapon. Mitigation analysis is carried out for two target materials Al and Ti. Plasma parameters are obtained using one dimensional coupled analysis of laser-target interaction. Influence of laser beam frequency on plasma parameters is addressed. Sheath thickness is obtained using transient sheath calculations. It is found that uninterrupted telemetry can be achieved | using a maximum bias voltage of 10 kV, through Al plasma for fluences below 5 J/cm² and through Ti plasma for fluences below 2 J/cm².

BACKGROUND: Left ventricular outflow tract (LVOT) obstruction and paravalvular leak (PVL) are relatively uncommon, but are serious complications of prosthetic valve replacement. CASE PRESENTATION: We present a case that displays the unique therapeutic challenges of treating a patient who developed both LVOT obstruction and mitral PVL after undergoing surgical aortic and mitral valve replacement (MVR). We also describe the use of alcohol septal ablation and albumin-glutaraldehyde (BioGlue) for septal ablation to percutaneously treat the patient's LVOT obstruction, followed by use of an Amplatzer vascular plug for percutaneous closure of an antero-medial mitral PVL associated with severe regurgitation. CONCLUSION: Percutaneous interventional management of these entities may be considered as an initial therapeutic option, especially in high-risk patients with significant morbidity and mortality of repeat surgical operations.

published_or_final_version / Chemistry / Master / Master of Philosophy

Two-dimensional numerical simulations of ablatively accelerated thin-shells subject to Rayleigh-Taylor instability are presented. Results for both single wavelength and multiwavelength perturbations show that the nonlinear effects of the instability are evident mainly in the "bubble" rather than the "spike." Approximate roles for predicting the dominant nonlinear mode-mode interactions, which limit shell performance, are also discussed. The work concludes with a discussion of recommendations for future work in this area.

UA Open Access Publishing Fund / Resistant hypertension is associated with chronic activation of the sympathetic nervous system resulting in various comorbidities. The prevalence of resistant hypertension is often under estimated due to various reasons. Activation of sympathetic nervous system at the renal- as well as systemic- level contributes to the increased level of catecholamines and resulting increase in the blood pressure. This increased activity was demonstrated by increased muscle sympathetic nerve activity and renal and total body noradrenaline spillover. Apart from the hypertension, it is hypothesized to be associated with insulin resistance, congestive heart failure and obstructive sleep apnea. Renal denervation is a novel procedure where the sympathetic afferent and efferent activity is reduced by various techniques and has been used successfully to treat drug-resistant hypertension improvement of various metabolic derangements. Renal denervation has the unique advantage of offering the denervation at the renal level, thus mitigating the systemic side effects. Renal denervation can be done by various techniques including radiofrequency ablation, ultrasound guided ablation and chemical ablation. Various trials evaluated the role of renal denervation in the management of resistant hypertension and have found promising results. More studies are underway to evaluate the role of renal denervation in patients presenting with resistant hypertension in different scenarios. Appropriate patient selection might be the key in determining the effectiveness of the procedure.

Previous work demonstrates conflicting evidence regarding the influence of snowmelt timing on forest net ecosystem exchange (NEE). Based on 15years of eddy covariance measurements in Colorado, years with earlier snowmelt exhibited less net carbon uptake during the snow ablation period, which is a period of high potential for productivity. Earlier snowmelt aligned with colder periods of the seasonal air temperature cycle relative to later snowmelt. We found that the colder ablation-period air temperatures during these early snowmelt years lead to reduced rates of daily NEE. Hence, earlier snowmelt associated with climate warming, counterintuitively, leads to colder atmospheric temperatures during the snow ablation period and concomitantly reduced rates of net carbon uptake. Using a multilinear-regression (R-2=0.79, P<0.001) relating snow ablation period mean air temperature and peak snow water equivalent (SWE) to ablation-period NEE, we predict that earlier snowmelt and decreased SWE may cause a 45% reduction in midcentury ablation-period net carbon uptake.

Liver cancer is a major cause of death worldwide and the impact that it has is set to increase in the coming decades. More than half a million cases are diagnosed each year and it is likely many more sufferers are dying unidentified in parts of the world with poor healthcare. Survival rates for untreated cases after diagnosis are low with few patients living beyond one year. A key cause for low survival rates being that the standard treatment is surgical resection; fewer than one quarter of patients are suitable for invasive surgery and five year survival rates rarely exceeds 66 %. RadioFrequency Ablation (RFA) is a minimally invasive technique which utilises the electrically resistive property of tissue to deposit heat energy locally in the vicinity of the tips of an RFA needle. Heat is transferred away through the tissue by conduction, convection of large blood vessels, and bulk flow of blood in smaller vessels. Liver cells, both cancerous and benign, when exposed to the resultant abnormally high temperatures die considerably more rapidly than in cases of natural hyperthermia. It is thus the radiotherapist’s objective to place the RFA needle in a position that maximises destruction of tumour cells, but minimises the collateral damage of surrounding healthy cells. The learning curve of this nontrivial task is reflected unfavourably in the statistics that relate patient survival rate to clinician experience. In this thesis two mathematical models are presented that could be combined into a ‘global’ model of the effects of RFA. To predict cell death in these conditions under RFA, the O’NeillModel is presented in which cells are accounted for by one of three states: alive, vulnerable, and dead. A mechanistic interpretation of the O’Neill Model is attained through comparison to a model from the literature. A known, but little investigated occurrence of tissue swelling in the annular region peripheral to the ablation volume is modelled in a novel way through equations from the literature that track ion transport across the cell membrane; the O’Neill Model for cell death is also incorporated into this model of oedema.

Microwave spectroscopy is a gas phase technique typically geared toward measuring the rotational transitions of Molecules. The information contained in this type of spectroscopy pertains to a molecules structure, both geometric and electronic, which give insight into a molecule's chemistry. Typically this type of spectroscopy is high resolution, but narrowband ≤1 MHz in frequency. This is achieved by tuning a cavity, exciting a molecule with electromagnetic radiation in the microwave region, turning the electromagnetic radiation o, and measuring a signal from the molecular relaxation in the form of a free induction decay (FID). The FID is then Fourier transformed to give a frequency of the transition. "Fast passage" is defined as a sweeping of frequencies through a transition at a time much shorter (≤10 s) than the molecular relaxation (≈100 s). Recent advancements in technology have allowed for the creation of these fast frequency sweeps, known as "chirps", which allow for broadband capabilities. This work presents the design, construction, and implementation of one such novel, high-resolution microwave spectrometer with broadband capabilities. The manuscript also provides the theory, technique, and motivations behind building of such an instrument. In this manuscript it is demonstrated that, although a gas phase technique, solids, liquids, and transient species may be studied with the spectrometer with high sensitivity, making it a viable option for many molecules wanting to be rotationally studied. The spectrometer has a relative correct intensity feature that, when coupled with theory, may ease the difficulty in transition assignment and facilitate dynamic chemical studies of the experiment. Molecules studied on this spectrometer have, in turn, been analyzed and assigned using common rotational spectroscopic analysis. Detailed theory on the analysis of these molecules has been provided. Structural parameters such as rotational constants and centrifugal distortion constants have been determined and reported for most molecules in the document. Where possible, comparisons have been made amongst groups of similar molecules to try and get insight into the nature of the bonds those molecules are forming. This has been achieved the the comparisons of nuclear electric quadrupole and nuclear magnetic coupling constants, and the results therein have been determined and reported.

Modification of nanostructures via laser processing is of great interest for a wide range of applications such as aerospace and the storage of nuclear waste. The primary goal of this dissertation is to improve the understanding of nanostructures through two primary routes: the modification of aerogels and pulsed laser ablation in ethanol. A new class of materials, patterned aerogels, was fabricated by photopolymerizing selected regions of homogeneous aerogel monoliths using visible light. The characterization and fabrication of functionally graded, cellular and compositionally anisotropic aerogels and ceramics is discussed. Visible light was utilized due to it’s minimal absorption and scattering by organic molecules and oxide nanoparticles within wet gels. This allowed for the fabrication of deeply penetrating, well resolved patterns. Similarly, nanoporous monoliths with a typical aerogel core and a mechanically robust exterior ceramic layer were synthesized from silica aerogels cross-linked with polyacrylonitrile. Simple variations of the exposure geometry allowed fabrication of a wide variety of anisotropic materials without requiring layering or bonding. Nanoparticle solutions were prepared by laser ablation of metal foils (Fe and Mo) in ethanol. Ablation of Fe generated Fe3O4 and Fe3C nanoparticles which were superparamagnetic with a saturation magnetization Ms = 124 emu/g. Zero field cooled (ZFC) measurements collected at an applied field of 50 Oe displayed a maximum magnetic susceptibility at 120 K with a broad distribution. Field cooled (FC) measurements showed a thermal hysteresis indicative of temperature dependent magnetic viscosity. Pulsed laser ablation of a Mo foil in ethanol generated inhomogeneous nanoparticles where Mo and MoC coexisted within the same aggregate. Formation of these unique nanoparticles is likely due to phase separation that occurs when a high temperature carbide phase cools after the laser pulse terminates. Similarly, magnetic nanoparticle suspensions were generated by pulsed laser ablation of Fe and Mo in ethanol. The formation of several carbide phases with no discernable alloy formation was seen. A decrease in magnetization with a decrease in Fe concentration was seen which was reconciled with the decreased Fe content in the system. However, at Fe concentrations below ~ 40%, an increase in Ms and Hc was observed which was reconciled with the disappearance of the ε–Fe3C. TEM analysis showed the formation of core-shell nanoparticles and Energy Filtered TEM showed the distribution of Fe-based nanoparticles in the suspensions.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.