L'instrument EUSO-Balloon est un prototype pour le télescope JEM-EUSO, destiné à observer pour la première fois depuis l’espace les gerbes atmosphériques induites par les rayons cosmiques d'ultra-haute énergie. Le principe de détection repose sur la mesure des photons émis par la fluorescence de l’atmosphère terrestre lors du développement des gerbes. EUSO-Balloon, un télescope UV embarqué à bord d’un ballon stratosphérique, a pour but de prouver la pertinence des concepts instrumentaux développés dans le cadre du projet JEM-EUSO. Cette thèse est dédiée en grande partie à l’assemblage, l’intégration et les tests du module de photo-détection d’EUSO-Balloon. Il s’agit d’un ensemble de 36 tubes photomultiplicateurs multi-anodes, pour un total de 2304 pixels, et d’une électronique de lecture permettant d’imager le développement, s’effectuant à la vitesse de la lumière, des gerbes atmosphériques. Cette caméra permet ainsi de réaliser des images de 2,5 microsecondes avec une sensibilité au photo-électron unique. Il aura été démontré que la mesure de l’efficacité de photo-détection de la caméra est réalisable avec une précision inférieure à 5% pour la tension de polarisation adaptée. EUSO-Balloon a effectué son premier vol en août 2014 lors duquel il a été prouvé, grâce à l’utilisation d’événements simulés par tirs lasers, qu’il est possible d’imager le développement de gerbes atmosphériques depuis le proche espace. Les données enregistrées permettent de réaliser une étude sur le bruit de fond UV produit par l’atmosphère terrestre. L’ensemble du travail d’assemblage, d’intégration et de test permet d’envisager les développements pour les futures missions. / The EUSO-Balloon instrument is a prototype for the JEM-EUSO telescope, intended to observe for the first time from space the extensive air showers (EAS) induced by the ultra-high energy cosmic rays. The detection technique relies on the measurement of the photons produced by the fluorescence of the Earth’s atmosphere when EAS develop. EUSO-Balloon, a UV telescope payload of a stratospheric balloon, has the objective to prove the relevance of the concepts developed for the JEM-EUSO project. An important part of this thesis is devoted to the assembly, the integration and the test of the EUSO-Balloon’s photo-detection module. It is an array of 36 multi-anodes photo-multiplier tubes, for a total of 2,304 pixels, and of a readout electronics able to image the development at the speed of the light of the EAS. It has a framing time of 2.5 microseconds with a single photo-electron sensitivity. It has been proved that the photo-detection efficiency of this camera can be measured with an accuracy better than 5% for the proper polarization voltage. The first flight of EUSO-Balloon happened in August 2014 and proved, with the use of laser induced events, that air showers can be imaged for the near space. Data acquired during this flight allow to study the UV background originating from the Earth’s atmosphere. The assembly, integration and test work provided during this project leads the development of future missions.

Background: There are treatments available to manage overweight and obesity (O&O). Intragastric balloons (IGB) are one option; they fill the stomach, increasing the sensation of satiety, limiting the amount of food to be ingested, and thus leading to weight loss. However, data suggest that patients regain weight long-term after an IGB treatment. As IGB is a relatively recent procedure for O&O, there is limited information about patient care practices alongside treatment, and whether could explain success or failure to maintain weight loss long-term.  Objective: The aim of the study was to explore clinical dietitians’ perspectives on patient care practices alongside IGB procedures. Method: Six semi-structured qualitative interviews were recorded, transcribed, and explored using qualitative content analysis method, which resulted in three categories. Results: The results showed that the clinical dietitians had many practices in place to condition patients before treatment. Screening the patient, balloon role information, and setting realistic expectations were considered essential practices. The involvement of a multi-disciplinary team was viewed as a critical factor to ensure engagement and follow-up with patients. The findings showed a high level of variability of frequency and contact during treatment and after balloon removal. Developing patients’ self-efficacy through practices like motivational coaching, dietary education, and behavioural therapy were also common practices.  Conclusion: Although similar practice patterns were identified, the findings highlighted a high level of variability in practices between respondents’ workplaces. This study was a first attempt to explore dietitians’ perceptions on patient care practices in relation to IGB-treatments, and it is too early to determine whether differences in practices have any impact on long-term weight loss maintenance. These could be the focus of new studies. / Bakgrund: Olika behandlingar är tillgängliga för att hantera övervikt och fetma. Intragastriska ballonger (IGB) är ett alternativ; de fyller magen, ökar mättnadskänslan, begränsar mängden av mat som kan intas och leder därmed till viktminskning. Data tyder dock på att patienter långsiktigt går upp i vikt långsiktigt efter IGB-behandling. Eftersom IGB behandlingar är en relativt ny procedur för övervikt och fetma, finns det bara begränsad information om patientvårdsprocesser som används i samband med behandlingen, och om skillnader i dessa skulle kunna förklara framgång eller misslyckande med att upprätthålla viktminskning långsiktigt. Syfte: Syftet med studien var att utforska dietisters perspektiv på patientvårdsprocesser och stödmetoder i samband med IGB-behandlingar. Metod: Sex semi-strukturerade kvalitativa intervjuer spelades in, transkriberades och analyserades enligt kvalitativ innehållsanalysmetoden, vilket resulterade i tre kategorier. Resultat: Resultaten visade att dietister använde många processer/metoder för att förbereda patienten innan behandling. Patientundersökning, ballongsinformation och att sätta realistiska förväntningar ansågs vara väsentliga metoder. Engagemang av ett multidisciplinärt team sågs som en kritisk faktor för att säkerställa engagemang och uppföljning med patienten. Resultaten visade en stor variation av frekvens och kontakt från vårdpersonalen under och efter IGB-behandling. Att utveckla patientens förmåga att ta eget ansvar med metoder som motiverande samtal, kostundervisning och beteendeterapi var också vanliga. Slutsats: Även om liknande processer/metoder identifierades, resultaten visade en stor variation i praktiken mellan respondenternas arbetsplatser. Studien var ett första försök att undersöka dietisters uppfattningar om patientvårdsprocesser i samband med IGB-behandling, och det är för tidigt att avgöra om skillnader i metoderna har någon inverkan på patienternas viktminskning underhåll långsiktigt. Dessa kan vara i fokus för nya studier.

Master of Science / Department of Psychological Sciences / Michael Young / When making decisions, the probability and magnitude of errors can play a major role in changing preferences. Electroencephalography (EEG) research examining the error-related negativity (ERN) and the associated feedback-related negativity (FRN) has indicated that the amplitude of each component may predict subsequent behavioral change. The current study used a version of the Balloon Analogue Risk Task (BART) that involves outcomes that are dynamically changing over time. As the balloon grows, more points are available but the probability of the balloon popping (netting zero points) is higher; the participant decides when to stop the balloon’s expansion to maximize points. The BART was adapted to facilitate the study of the FRN in dynamic environments. The purpose of Experiment 1 was to determine the effect of error magnitude on FRN amplitude during popped (incorrect) trials, whereas Experiment 2 was aimed at determining the effect of error magnitude on FRN amplitude during cashed-in (correct) trials. It was hypothesized that larger errors (i.e., the balloon popping after waiting a long time to cash-in) would result in a larger FRN than smaller errors. In Experiment 1, error magnitude did not contribute to the amplitude of the FRN. In Experiment 2, the masked points possible condition was a replication of Experiment 1. In the unmasked points possible condition, the number of points that could have been earned for each balloon was presented before participants found out how many points were earned. It was expected that there would be a larger FRN magnitude after cashed-in trials in the unmasked points possible condition compared to the masked points possible condition based on the magnitude of the error. In Experiment 2, the amplitude of the FRN was affected by the magnitude of the error on cashed-in trials in the unmasked condition, but not the masked condition. These results are seemingly at odds, and cannot be assimilated into any currently extant model of the FRN. An explanation relying on the motivational importance of errors is discussed.

An experiential thesis, this document begins at dawn, travels through storms and calm air and ends at night in Argentina. It details the circumstances and influences leading to my thesis exhibition at the Anderson Gallery, including an artist’s statement told through a creative reading of Ray Bradbury’s “All Summer in a Day” and the excitement I found in an out-of-print text on scuba diving.

abstract: The development of new Ultra-Violet/Visible/IR range (UV/Vis/IR) astronomical instrumentation that use novel approaches for imaging and increase the accessibility of observing time for more research groups is essential for rapid innovation within the community. Unique focal planes that are rapid-prototyped, low cost, and provide high resolution are key. In this dissertation the emergent designs of three unique focal planes are discussed. These focal planes were each designed for a different astronomical platform: suborbital balloon, suborbital rocket, and ground-based observatory. The balloon-based payload is a hexapod-actuated focal plane that uses tip-tilt motion to increase angular resolution through the removal of jitter – known as the HExapod Resolution-Enhancement SYstem (HERESY), the suborbital rocket imaging payload is a Jet Propulsion Laboratory (JPL) delta-doped charge-coupled device (CCD) packaged to survive the rigors of launch and image far-ultra-violet (FUV) spectra, and the ground-based observatory payload is a star centroid tracking modification to the balloon version of HERESY for the tip-tilt correction of atmospheric turbulence. The design, construction, verification, and validation of each focal plane payload is discussed in detail. For HERESY’s balloon implementation, pointing error data from the Stratospheric Terahertz Observatory (STO) Antarctic balloon mission was used to form an experimental lab test setup to demonstrate the hexapod can eliminate jitter in flight-like conditions. For the suborbital rocket focal plane, a harsh set of unit-level tests to ensure the payload could survive launch and space conditions, as well as the characterization and optimization of the JPL detector, are detailed. Finally, a modification of co-mounting a fast-read detector to the HERESY focal plane, for use on ground-based observatories, intended to reduce atmospherically induced tip-tilt error through the centroid tracking of bright natural guidestars, is described. / Dissertation/Thesis / Doctoral Dissertation Exploration Systems Design 2019

Traditional methods of studying underground coal mine explosions are limited to observations and data collected during experimental explosions. These experiments are expensive, time-consuming, and require major facilities, such as the Lake Lynn Experimental Mine. The development of computational fluid dynamics (CFD) modeling of explosions can help minimize the need for large-scale testing. This thesis utilized the commercial CFD software, SC/Tetra, to examine three case studies. The first case study modeled the combustion of methane in a scaled shock tube, measuring approximately 1 foot by 1 foot, by 20.5 feet long, with a methane cloud of 2.5 feet in length, at a concentration of 9% methane. The numerical results from the CFD model were in good agreement with experimental data gathered, with all pressure peaks within 0.25 psi of the recorded pressure data. However, the model had an extensive run-time of 16 hours to reach the peak pressures. The second case study modeled the same explosion, but utilized a total pressure boundary condition at the location of the membrane, instead of the combustion of methane. A pressure-time curve was assigned to this boundary, recreating the release of pressure by the explosion. This was made possible with the knowledge of the experimental data. The numerical results from the CFD model were in excellent agreement with experimental data gathered, with all pressure peaks within 0.07 psi of the recorded pressure data. Alternatively, this model had a run-time of 40 minutes. The third case study modeled a methane explosion in a large shock tube, measuring 8 feet by 8 feet, by 40 feet long, with a methane cloud of 4 feet in length, at a concentration of 9% methane. The bursting balloon technique was employed, which did not model the combustion of methane, but instead the equivalent energy release. The numerical results from the CFD model were in good agreement with the experimental data gathered, with all pressure peaks within 0.025 psi of the recorded pressure data. Additionally, the numerical results modeled the negative pressure phenomenon observed in the experimental results, caused by suction or negative pressure created by the blast wave, immediately following the positive wave. This model had a run-time of 20 minutes. The results of this researched provided validation that there are alternative ways to successfully model methane explosion, without having to model the chemical reactions involved in the combustion of methane, providing quicker run-times and in this case, more accurate results.

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Abstract: Background: At present, device closure of interatrial communication has become a well established technique in order to adequately treat severe left-to-right shunt associated with ASDs. During the traditional procedure, fluoroscopy with the waist of a compliant balloon is used to determine the appropriate size of the closure device and defect sizing. Choice of adequate closure device using transthoracic echocardiography (TTE) has been hitherto unreported. Methods & Materials: Between December 2002 and October 2004, 40 patients (15 males, 25 females, mean age; 11.7 ¡Ó 7.8 years ) with secundum ASDs underwent transcatheter closure at our institution. In group 1, 30 patients had the procedure by balloon sizing and TTE sizing. In 10 patients (group 2), TTE sizing was used as the sole too l for selecting device size and the device size was chosen to be based on the Amplatzer septal occluder ( ASO ) size and TTE size ratio in group 1. The procedure was performed under continuous transoesophageal echocardiographic monitor with general anesthesia. Results: The correlation was found between TTE and stretched balloon sizing diameter SBD ( y= 1.2645x-1.4465; R²=0.9861 ), and between TTE size and ASO size ( y = 1.3412x-1.2864; R²=0.9929 ) in group 1. In group 2, statistical correlation between TTE and ASO ( y=1.3419x-0.1172; R²=0.9934 ) was also found. Good linear regression between TTE size and ASO chosen size was noted in group 1 and group 2 (R²=0.99).In group 2, successful device implantation was accomplished in all patients whose device size was chosen to be based on the ASO and TTE ratio in group 1. Conclusions: TTE sizing is a safe and ideal method to measure interatrial defect and choose the occluding device respectively. With our experience, the sizing based on the TTE is generally easier than measurement from the balloon sizing.

<p>Paper A: In this paper, the development and implementation of a contact algorithm based on C2-continuous surface representations is discussed. In 3D contact simulations involving models with arbitrarily curved surfaces (as in the case of vessel walls), the discretization of the contact surfaces by means of facet-based techniques could lead to numerical instabilities and finally loss of quadratic convergence. These instabilities arise mainly due to the sliding of contractor (slave) nodes over the boundaries of target (master) contact facets, where jumps of the normal vector are experienced. The paper addresses successfully this problem, by discretization of the target surfaces by means of C2-continuous parameterization schemes. Initially, the uniform cubic B-spline surfaces are introduced. Next, in an attempt for more accurate representations of the geometric models of the contact surfaces, a new parameterization based on the expression of cubic B-splines is developed. The two approaches are implemented into a finite element framework and more specifically, into the multipurpose finite element analysis program FEAP. The special merits of the developed algorithms and the advantages of the smooth surfaces over facet-based approaches are exhibited through a classical contact mechanics problem, considering incompressibility, finite deformations and large slidings. Next, a simulation of balloon angioplasty with stenting is presented, where the contact between both medical devices (balloon and stent) with the arterial wall is modeled. The arterial wall is modeled in this first approach, as hyperelastic, homogeneous, isotropic, while a cylindrically orthotropic model is developed to capture the nonlinear, anisotropic behavior of the balloon catheter under pressure. Two stents with the same geometry but different strut thickness, are studied. Both are considered elasto-plastic. The performed simulations point out the outcome of the balloon angioplasty and stenting in terms of luminal gain and mechanical strains. Finally, a comparison between the two stent configurations is presented.</p><p>Paper B: The second paper makes use of the contact tool developed in Paper A and focuses on the changes of the mechanical environment of the arterial wall due to stenting, as a function of a set of stent design parameters. In particular, Paper B presents a detailed geometric and material model of a postmortem human iliac artery, composed by distinct tissue components, each associated with specific mechanical properties. The constitutive formulation for the artery considers anisotropic, highly nonlinear mechanical characteristics under supraphysiological loadings. The material and structural parameters of the arterial model are obtained through uniaxial tensile tests on stripes extracted from the several arterial tissues that form the stenosis, axially and circumferentially oriented. Through cooperation with a well-established stent manufacturing company, an iliac stent was acquired. The dimensions of the stent are measured under a reflected-light microscope, while it is parameterized in such a way as to enable new designs to be simply generated through variations of its geometric parameters. The 3D balloon-stent-artery interaction is simulated by making use of the smooth contact surfaces with C2-continuity, as previously mentioned. Next, scalar quantities attempt to characterize the arterial wall changes after stenting, in form of contact forces induced by the stent struts, stresses within the individual components and luminal change. These numerically derived quantities allow the determination of the most appropriate stent configuration for an individual stenosis. Therefore, the proposed methodology has the potential to provide a scientific basis for optimizing treatment procedures, stent material and geometries on a patient-specific level.</p>

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