Outside the world of music the transistor has supplanted the vacuum tube. Transistors do the same sort of job as vacuum tubes but they use germanium or silicon in their manufacture, thus the current is produced in a solid state, rather than a vacuum. Most electronic devices are built with solid state technology. Exceptions are some musical instrument amplifiers and some audiophile grade stereo gear. For the users of this equipment the transistor is unsatisfactory both spiritually and with respect to sound. The need for tubes has become specialized, to the point where designers are designing amplifiers to the specifications of available tubes. The relative scarcity of these gems makes the notion of manufacturing specific tubes under exacting conditions, in relatively small quantities, attractive. A place to make these glass jewels should respect their history, use, and the careful manufacturing techniques required to make them. It is the basilica of the church of the distorted guitar sound. / Master of Architecture

Yes / Springtails (Collembola) are unique in Hexapoda for bearing a ventral tube (collophore) on the first abdominal segment. Although numerous studies have been conducted on the functions of the ventral tube, its fine structure has not been thoroughly elucidated to date. In this paper, we observed the jumping behavior of the clover springtail Sminthurus viridis (Linnaeus, 1758) and dissected the ventral tube using light microscopy to elucidate the fine structure and the possible function of the ventral tube. The results show that a pair of eversible vesicles can be extended from the apical opening of the ventral tube. The eversible vesicles are furnished with numerous small papillae, and can be divided into a basal part and a distal part. The eversible vesicles have a central lumen connected to the tiny papillae and leading to the body cavity. The eversible vesicles can reach any part of the body, and may serve as following functions: (a) absorbing moisture; (b) uptaking water; (c) cleaning the body surface; and (d) fastening the body on a smooth surface.

Emissions of greenhouse and toxic gases from current combustion processes significantly contribute to the global climate crisis. Recent policies worldwide have shifted focus towards combating these emissions using clean and renewable energy sources. However, achieving carbon neutrality while meeting modern energy needs will require alternative carbon-free fuel sources for power generation turbine cycles. Ammonia-hydrogen blends have shown potential as carbon-free fuel sources, necessitating further investigation to accurately predict combustion properties like ignition delay times and species formation rates. These are critical for designing and constructing combustors for these power cycles. This thesis explores the combustion characteristics of ammonia-hydrogen blends experimentally to develop and improve computational chemical kinetic models. Using laser absorption spectroscopy, species time histories for ammonia (NH3), water (H2O), and nitric oxide (NO) were measured with quantum cascade lasers centered at 10.39 μm, 7.3 μm, and 5.15 μm, respectively. Data was collected during the decomposition of ammonia with a hydrogen content of 0%, 30%, and 50% at equivalence ratios of 0.6 in air. Experimental conditions were generated using the University of Central Florida's high-pressure shock tube for advanced research (HiPER-STAR), with reflected shock pressures of 5, 10, and 20 bar with temperatures ranging from 1300 to 2200 K. These findings will be used to develop chemical kinetic models to predict ammonia-hydrogen chemistry, thereby advancing the development of clean energy cycles.

Un grand nombre de maladies cardiaques apparaissent à la suite de problèmes développementaux dus à des mutations dans des gènes très conservés durant l'évolution. Il est donc crucial d'identifier les acteurs intervenants dans la cardiogenèse. Durant ma thèse, j'ai étudié la différenciation cardiaque, en utilisant la Drosophile comme modèle, avec comme objectifs d'identifier des nouveaux intervenants grâce à l'acquisition de données globales par une approche génomique tissue spécifique. J'ai tout d'abord mis au point un protocole permettant d'acquérir des données génomique spécifiquement dans le tube cardiaque de la Drosophile lors de la différenciation des cardiomyocytes. Ce fut une étape primordiale pour le reste de ma thèse. Ce protocole me permet d'isoler spécifiquement les cellules du système cardiaque.A partir de là, j'ai réalisé une cinétique transcriptomique qui a permis de mettre en évidence environ 1000 gènes différenciellement exprimés au cours de la différenciation cardiaque. Ensuite, En collaboration avec Delphine Potier, une thésarde bio-informaticienne de l'équipe, des modules Cis-régulateur (CRM) pouvant conduire à l'expression dans le tube cardiaque ont été prédits, ainsi que des facteurs de transcription putatifs régulant ces CRM. Ces nouveaux acteurs du réseau de régulation génique cardiaque sont en cours de validation.Dans un second temps, je me suis intéressé à un facteur de transcription à homéoboîte clé de la cardiogenèse : Abdominal-A (AbdA). AbdA est essentiel pour la différenciation de la partie postérieure du tube cardiaque, le cœur proprement dit, et à l'acquisition de sa fonction. Cependant, ses cibles ainsi que son action tissue spécifique sont encore inconnu à ce jourAfin d'apporter un élément de réponse, j'ai analysé le transcriptome consécutif à un Gain de Fonction de AbdA spécifiquement dans le système cardiaque ce qui m'a permis de mettre en évidence plus de 1000 gènes dérégulés par AbdA lors de la différenciation cardiaque. / Cardiac diseases generally arise from developmental disorders caused by mutations in genes that are highly conserved during evolution. It is therefore of prime interest to identify actors which participate to cardiogenesis. During my thesis, I have analyzed cardiac differentiation, using Drosophila as a model. My objective was to identify news actors of the cardiac Gene Regulatory Network (GRN) using a genomic approach and starting from tissue specific whole data acquisition.First, I have set a protocol to allow tissue specific genomic data acquisition during cardiac differentiation. It was a critical step for my thesis. This protocol allowed me to isolate specifically cardiac system cells.Using this protocol, I analyzed the transcriptome dynamics and determined that 1000 genes are dynamically expressed during cardiac differentiation.Next, in collaboration with Delphine Potier, a PhD student in bio-informatic in the team, cis-regulatory modules (CRM), which can drive expression in the cardiac tube, have been predicted, and also putative transcription factors regulating these CRM. These new cardiac GRN actors are currently tested in vivo.In a second time, I have analyzed the function of Abdominal-A (AbdA) a homeobox transcription factor which plays a key role during cardiogenesis. :. AbdA is crucial for the differentiation of the posterior part of the organ, called heart My aim was to identify cardiac specific AbdA targets.

As recentes técnicas miniaturizadas de preparo de amostra, microextração em fase sólida (SPME) e in tube SPME, apresentam uma série de vantagens em relação aos métodos clássicos de extração (extração líquido-líquido e extração em fase sólida), tais como: não requer instrumentação analítica sofisticada, utilização de pequenas quantidades de solventes orgânicos, rápido processo operacional, permite automação das análises, a reutilização das fases extratoras, e integra em um único sistema a extração, concentração e introdução da amostra no cromatográfico. Esta dissertação tem como objetivo a padronização, validação e comparação dos métodos SPME/LC-UV com dessorção off line e in tube SPME/LC-UV, para a análise dos antidepressivos da nova geração (mirtazapina, citalopram, paroxetina, duloxetina, fluoxetina e sertralina) em amostras de plasma para fins de monitorização terapêutica. As variáveis: fase extratora, pH da matriz, tempo e temperatura de extração e de dessorção e força iônica apresentaram grande influência na eficiência do processo SPME. O método SPME/LC-UV padronizado, apresentou limite de quantificação (LQ) de 25 a 50 ng mL-1, ampla faixa de linearidade (LQ ? 500 ng mL-1, r2 > 0,9970) e precisão inter ensaios com coeficientes de variação menor que 15% para todos os analitos. Apesar das baixas taxas de recuperação obtidas, de 8,1% (citalopram) a 17,1% (mirtazapina), o método SPME/LC-UV apresentou seletividade e sensibilidade analítica adequada. As variáveis: pH da matriz, fluxo e número de ciclos aspirar/dispensar e volume de amostra apresentaram grande influência na eficiência do processo in tube SPME. A etapa de precipitação de proteínas do plasma, anterior ao processo de extração, foi necessária para a eliminação dos compostos endógenos. O método in tube SPME/LC-UV padronizado apresentou seletividade adequada, precisão inter ensaios com coeficiente de variação menor que 10%, LQ de 20 a 50 ng mL-1, linearidade na faixa de concentração do LQ a 500 ng mL-1, com r2 > 0,9983 para todos os analitos e recuperação absoluta de 5,32% (mirtazapina) a 43,5% (sertralina). A técnica in tube SPME, quando comparada à SPME, permitiu a automação das análises, menor exposição do analista às amostras biológicas e solventes orgânicos, menor tempo de análise e menor volume de amostra de plasma. A eficácia dos métodos, SPME/LC-UV e in tube SPME/LC-UV, foi comprovada através das análises de amostras de plasma de pacientes em terapia com os antidepressivos, para fins de monitorização terapêutica. / The recent miniaturized sample techniques preparation, solid phase microextraction (SPME) and in tube SPME, present several advantages when compared with classic extraction methods (liquid-liquid extraction and solid phase extraction), such as: it does not require sophisticated analytical instrumentation, use small organic solvent amounts, fast operational process, automation of the analyses, reuse extraction phases, and incorporates, into a single procedure, sample extraction, concentration and sample introduction. The aim of this work is development, validation and comparison of methods SPME/LC-UV with off line desorption and in tube SPME/LC-UV, for analyses of antidepressants of the new generation (mirtazapine, citalopram, paroxetine, duloxetine, fluoxetine and sertraline) in plasma samples for therapeutic drug monitoring. Variables: extraction phase, matrix pH, time and temperature of extraction and desorption and ionic strength showed great influence in SPME process efficiency. The method SPME/LC-UV presented limit of quantification (LOQ) variety from 25 to 50 ng mL-1, wide range the of linearity (LOQ 500 ng mL-1, r2 > 0.9970) and interassays precision with coefficient of variation lower than 15% for all analytes. Although the low recovery, from 8.1% (citalopram) to 17.1% (mirtazapine), the method SPME/LC-UV presented adequate selectivity and analytical sensitivity. Variables: matrix pH, flow and number of aspirate/dispense cycles and sample volume showed great influence in the in tube SPME process efficiency. The protein precipitation of the plasma steps, previous to the extraction process, was necessary for the endogenous compounds elimination. The method in tube SPME/LC showed adequate selectivity, interassays precision with coefficient of variation lower than 10%, LOQ variety from 20 to 50 ng mL-1, linearity in range concentration from LOQ to 500 ng mL-1, with r2 > 0.9983 for all analytes and recovery from 5.32% (mirtazapine) to 43.5% (sertraline). The technique in tube SPME, compared with the SPME, permitted the automation of the analyses, minor exposition of the analyst to the biological samples and organic solvent, shorter analyses time and minor plasma sample volume. The effectiveness methods, SPME/LC-UV and in tube SPME/LC-UV, was proven through the analyses of plasma samples of patients in therapy with antidepressants, for therapeutic drug monitoring.

O presente trabalho descreve os processos de preparação do aluminato de bário e cálcio, material emissor de elétrons, empregados nos catodos do tipo impregnado para utilização em uma válvula de microondas do tipo TWT. Os catodos investigados constituem-se de uma pastilha de tungstênio porosa impregnada com aluminato de bário e cálcio com proporção molar 5:3:2. Para a síntese do aluminato, utilizaram-se três diferentes métodos: reação em estado sólido, precipitação e cristalização. A termogravimetria auxiliou na consolidação dos procedimentos de preparação dos aluminatos de modo a definir os parâmetros de pirólise/calcinação. Verificou-se que a técnica que apresentou melhores características de síntese foi o método da cristalização, pois esta apresentou uma menor temperatura de formação do aluminato (800ºC) em atmosfera oxidante (O2), quando comparada às técnicas de reação em estado sólido e de precipitação (temperatura de 1000ºC em atmosfera redutora – H2). Utilizou-se o conceito da distribuição da função trabalho prática (PWFD) de Miram para a caracterização termiônica dos catodos impregnados. Empregando-se este método, foi possível traçar o perfil termiônico do catodo com aluminato de bário e cálcio. As curvas PWFD apresentaram a função trabalho média do catodo aluminato de, aproximadamente, 2,00 eV. / In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pirolisys atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques – formation temperature is about 1000ºC in hydrogen atmosphere), whereas it presented the lower formation temperature (800ºC) in oxidizing atmosphere (O2). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV.

Les tubes à paroi mince en alliage à mémoire de forme Nickel-Titane (AMF NiTi) sont largement utilisés dans la fabrication de stents auto-expansibles. Leur fonctionnement repose sur la superélasticité (SE), comme de nombreuses autres applications des AMF NiTi dans le domaine biomédical. Le SE est un phénomène cristallographique réversible qui donne aux AMF la capacité de récupérer de grandes déformations par simple déchargement mécanique. En raison de la nature cristallographique du SE, les propriétés mécaniques liées à cet effet devraient être affectées par l'anisotropie inhérente du tube, qui émerge de son processus de fabrication. Cependant, le NiTi est encore souvent considéré comme isotrope dans la conception et l'optimisation de tels dispositifs. L'une des difficultés empêchant l'utilisation de modèles anisotropes est l'absence de caractérisations mécanique de l'anisotropie du tube NiTi. Le présent travail vise à effectuer une telle caractérisation pour un tube superélastique NiTi à paroi mince. Dans une campagne expérimentale, le comportement en traction du tube est analysé à différentes orientations et températures. La technique de corrélation d'image numérique (digital image correlation - DIC) est utilisée pour surveiller la distribution des déformations pendant les essais de traction. Les résultats montrent que toutes les propriétés analysées liées à la SE sont anisotropes. Toutes les dépendances d'orientation sont presque symétriques à 45° de l'axe du tube. Certaines propriétés dépendent également de la température, dépendance qui est également anisotrope. Une approche thermodynamique basée sur l'énergie libre de Gibbs est utilisée pour analyser ces dépendances d'orientation et de température. Avec cette analyse, il a été possible de relier l'hystérésis mécanique de la SE et les contributions irréversibles présentes dans le système. Enfin, l'influence de l'anisotropie sur la distribution des déformations est vérifiée. L'accent est mis sur l'analyse du phénomène de localisation de la déformation tout au long du chargement et du déchargement. L'inclinaison de la bande de localisation est caractérisée et évaluée avec une approche de plasticité. L'angle de la bande avant observé avec DIC est prédit en utilisant des données de vitesse de déformation globale. / Thin walled tubes of Nickel-Titanium shape memory alloys (NiTi SMA) are widely used in the fabrication of self-expandable stents. The operation of stents relies on the superelastic effect (SE), as many other applications of NiTi SMA in the biomedical field. The SE is a reversible crystallographic phenomenon that gives SMA the ability to recover large strains through simple unload. Due to the crystallographic nature of the SE, the mechanical properties related to this effect are expected to be affected by the inherent anisotropy of the tube, which emerges from its fabrication process. However, NiTi is still often treated as isotropic in the design and optimization of such devices. One of the difficulties preventing the use of anisotropic models is a lack of mechanical characterizations about the NiTi tube's anisotropy. The present work aims to perform such characterization for a thin walled NiTi superelastic tube. In an experimental campaign, the tensile behaviour of the tube is analysed at different orientations and temperatures. Digital Image Correlation (DIC) technique is used to monitor the strain distribution during tensile tests. Results show that all the analysed properties related with SE are anisotropic. All the orientation dependencies are nearly symmetrical to 45° from the tube's axis. Some properties are also dependent on temperature, a dependence that is also anisotropic. A thermodynamic approach based on the Gibbs free energy is used to analyse these orientation and temperature dependencies. With this analysis it was possible to relate the SE stress hysteresis and thermodynamic irreversible energy contributions. Finally, the influence of anisotropy on the strain distribution of tensile samples is verified. Focus is given to the analysis of the strain localization phenomenon throughout loading and unloading. The inclination of the localization front band is characterized and evaluated with a plasticity approach. The front angle observed with DIC is predicted using global strain rate data.

Ce travail a été effectué dans le cadre d’études de la miniaturisation d’un cryo-réfrigérateur de type tube à gaz pulsé (TGP) et particulièrement pour mieux comprendre l’écoulement et le transfert de chaleur dans un régénérateur, l’élément clé du TGP.Nous présentons les études numérique et expérimentale du facteur de frottement et du nombre de Nusselt pour les écoulements stationnaires et continus à nombre de Reynolds modéré O(1 − 100) au sein d’un régénérateur micro-fabriqué. L’influence de la porosité et de la géométrie est étudiée. La micro-structure précisément contrôlée représente des canaux incurvés de largeur de 10, 20 et 40 μm et de profondeur de 100 à 300 μm qui forment un réseau de colonnes ayant des profiles de losanges ou sinusoïdaux. Les micro-canaux sont gravés sur un substrat de silicium par la technologie DRIE. Une technologie d’implantation de thermomètres à l’intérieur de la micro-structure de régénérateur a été développée et mise en œuvre. Les performances des micro-régénérateurs ont été étudiées selon deux approches : la première se base sur le rapport des pertes de charges dans l’écoulement et de l’efficacité du transfert thermique (NPH/NTU) ; la deuxième, sur le coefficient de transfert de chaleur globale proposé par Bejan. L’étude numérique de ces deux critères montre tout le potentiel des micro-structures proposées. / This research is done in the framework of miniaturisation of pulse tube cryocoolers studies and especially to gain a better understanding of the mass flow and heat transfert in the regenerator, which is a crucial component of these type of cryocoolers.In this work we present a numerical and experimental study of the Darcy-Weisbach friction factor and Nusselt number for a continuous and steady flow at moderate Reynolds number O(1−100) in a micro-machined regenerators. The influence of porosity from 40 to 80 % and of the geometry parameters are studied. Well-controlled microstructures represent convoluted channels of 10, 20 or 40 μm width and 100 or 300 μm depth generated by rhombic- or sinusoidal-shaped columns.The channels are etched in Silicon wafers using DRIE MEMS technology. The thermometers are integrated inside the regenerator’s micro-structure to measure the temperature evolution. The efficiency of the regenerators is estimated using two different approaches : the first, as a ratio of pressure drop losses and heat transfer efficiency (NPH/NTU) ; the second, as a volumetric heat transfer density coefficient proposed by Bejan. The numerical study of the efficiency shows theinterest of proposed micro-structures.

The spatial and temporal patterning of sequence specific transcription factors (SSTFs) contributes to cell type specification and organ formation during embryogenesis. Homeodomain transcription factors are evolutionally conserved among invertebrate and vertebrate animals. They are responsible for body segmentation and organogenesis. Lbx1 and Pitx2 both are homeodomain transcription factors contributing to SSTF pattern formation during multiple organ formations. We studied how homeodomain transcription factors regulate SSTF and non-SSTF genes in a population-specific manner using the Lbx1[superscript EGFP] and Pitx2[superscript LacZ] mouse models. We have studied the role of Lbx1 in dorsal horn interneuron specification and Pitx2 in forelimb muscle formation. The two top non-SSTF target genes, NPY and Chmp2b, of Lbx1 are studied for expression pattern and potential neuronal function in neural tube. The T box, Hox gene families and Pax genes were identified as Pitx2 target genes via microarray analysis and their expression pattern were analyzed in forelimb. The expression domains of signaling molecules were altered in absence of Pitx2, suggesting that Pitx2 played a general role in pattern formation in forelimb mesenchyme. / Graduation date: 2013

Thesis (M.S.)--University of Michigan, 1984.