Les interconnecteurs représentent une pièce maîtresse des piles à combustibles à oxyde solide (SOFC) car ils sont chargés de collecter et de délivrer les électrons produits lors de la réaction électrochimique du cœur de pile. Les matériaux d'interconnecteurs doivent donc être stables sous air et sous H2/H2O. Ce travail vise à étudier l'influence d'un mince revêtement d'oxydes d'éléments réactifs (La2O3, Y2O3) réalisé par MOCVD sur le comportement à haute température (800°C) de matériaux d'interconnecteurs métalliques, tels que les alliages Crofer22APU, Haynes230 et Fe30Cr. La réalisation de tests de longue durée (7 700 et 15 400 heures) s'est avérée être riche en enseignements. Le suivi cinétique, la caractérisation des couches d'oxyde et la détermination du paramètre ASR ont permis d'établir que la présence d'oxydes de type pérovskite (LaCrO3, YCrO3), formés lors de l'oxydation, permettaient d'améliorer sensiblement la conductivité électrique des matériaux d'interconnecteurs. Sous atmosphère anodique (H2/10%H2O), même si les éléments réactifs conservent leur effet bénéfique, les cinétiques de corrosion sont plus rapides. L'augmentation de la porosité de la couche, l'amélioration de l'adhérence et la diminution de la taille des grains d'oxyde portent à croire que la diffusion anionique devient prépondérante sous vapeur d'eau. Enfin, l'effet bénéfique d'une pré-oxydation courte à 1 000°C sur le comportement des alliages revêtus et non revêtus est établi. Des expériences de marquage isotopique sous 16O2/18O2 ont démontré que cette amélioration s'explique par un changement du mécanisme de diffusion, la pré-oxydation engendrant une diminution de la contribution cationique.

Elections are one of the most fundamental activities of a democratic society. As is the case in any other aspect of life, developments in technology have resulted changes in the voting procedure from using the traditional paper-based voting to voting by use of electronic means, or e-voting. E-voting involves using different forms of electronic means like / voting machines, voting via the Internet, telephone, SMS and digital interactive television. This thesis concerns voting by telephone, or televoting, it starts by giving a brief overview and evaluation of various models and technologies that are implemented within such systems. The aspects of televoting that have been investigated are technologies that provide a voice interface to the voter and conduct the voting process, namely the Election Markup Language (EML), Automated Speech Recognition (ASR) and Text-to-Speech (TTS).

Cantilevered reinforced concrete columns with a lap splice of the longitudinal reinforcement near the base can induce high moment demands on the splice region when lateral loads are present on the structure. Code design specifications typically require a conservative splice length to account for these high moment demands and their consequences of bond failure. The required splice length is calculated as a function of required development length, which is a function of the bond between the reinforcement and the surrounding concrete, and a factor depending on the section detailing. However, the effects of concrete deterioration due to alkali silica reaction (ASR) and/or delayed ettringite formation (DEF) may weaken the bond of the splice region enough to overcome the conservative splice length, potentially resulting in brittle failure of the column during lateral loading. This thesis presents the following results obtained from an experimental and analytical program. * Fabrication of large-scale specimens of typical column splice regions with concrete that is susceptible to ASR/DEF deterioration * Measurement of the large-scale specimen deterioration due to ASR/DEF accelerated deterioration * Analytical model of the column splice region based on flexure theory as a function of the development length of the reinforcement and a factor to account for deterioration of the bond due to ASR/DEF * Experimental behavior of two large-scale specimens that are not influenced by premature concrete deterioration due to ASR/DEF (control specimens). This experimental data is also used to calibrate the analytical model. The conclusions of the research are that the analytical model correlates well with the experimental behavior of the large-scale control specimens not influenced by ASR/DEF. The lap splice region behaved as expected and an over-strength in the splice region is evident. To account for ASR/DEF damage, the analytical model proposes a reduction factor to decrease the bond strength of the splice region to predict ultimate performance of the region with different levels of premature concrete deterioration.

Reinforced concrete bridge columns can deteriorate prematurely due to the alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF), causing internal expansion and cracking on the surface of the concrete. The performance of the longitudinal reinforcement lap splice in deteriorated concrete columns is the focus in this research. This thesis presents the results from the deterioration of large-scale specimens constructed and placed in an environment susceptible to ASR/DEF deterioration, the experimental results from four-point and three-point structural load tests, and an analytical model based on bending theory characterizing the specimen behavior during the structural load tests. Fourteen large-scale specimens were constructed, placed in an environment to accelerate the ASR/DEF deterioration mechanisms, and instrumented both internally and externally to measure the internal concrete expansions, and surface expansions and crack widths. In addition, two control specimens were constructed and kept in a laboratory, preventing ASR/DEF deterioration. Post-tensioning was used to simulate axial load on a bridge column. Structural load tests were performed on eight specimens with no ASR/DEF damage to late stage ASR and minimal DEF damage. Comparing the specimen behaviors during the loading testing, it was found that the yield strength increased about 5-15%, and post-cracking stiffness up to first yielding of the deteriorated specimens was about 25-35% stiffer than the control specimens. The increased specimen strength and stiffness likely occurred from volumetric expansion due to ASR/DEF damage which engaged the reinforcement, further confining the concrete and causing a beneficial increase in the axial post-tensioning load. The analytical model matched the control specimens well and matched the non-control specimens when the axial load was increased.

This research focuses on the characterization of damage accumulation in concrete specimens. Specifically, a nonlinear vibration technique is used to characterize the damage introduced by ongoing alkali-silica reactions (ASR). The nonlinear resonance testing consists of an analysis of the frequency response of concrete specimens subjected to impact loading. ASR introduces a third gel like phase, which can be expansive in the presence of moisture. The result of ASR is the formation of microcracks and debonding between aggregate and cement phases. Collectively, these changes act to increase the specimens' nonlinearity. As a result, it is found that the concrete samples exhibit nonlinear behavior; mainly a decrease in resonance frequency with an increasing level of excitation strain. The relationship between the amplitude of the response and the amount of frequency shift is used as a parameter to describe the nonlinearity of the specimen. The specimens used in this research are of varying reactivity with respect to ASR, which is induced in accordance with ASTM C 1293. The level of nonlinearity is used as a measure of damage caused by the progress of ASR throughout the one year test duration. These nonlinear resonance results are compared to the traditional measures of expansion described in the standard. The robustness and repeatability of the proposed technique is also investigated by repeated testing of samples assumed to be at a specific damage state. Finally, a petrographic staining technique is used to complement nonlinearity measurements and to further gain understanding of ASR. The results of this study show that the proposed nonlinear resonance methods are very sensitive to microstructural changes and have great potential for quantitative damage assessment in concrete.

This research project, funded by the Federal Highway Administration, entails the construction of an outdoor exposure site in order to evaluate various methods for mitigating alkali-silica reaction (ASR) in hardened concrete. The exposure site, built at the Concrete Durability Center at the University of Texas at Austin J.J. Pickle Research campus, included a series of bridge deck, column and slab elements. The specimens were cast in 2008, allowed to expand to predetermined expansion levels and then treated with various mitigation measures, after which the specimens were monitored for expansion, humidity, and deterioration. / text

The field of molecular evolution has benefited greatly from the use of ancestral sequence reconstruction as a methodology to better understand the molecular mechanisms associated with functional divergence. The method of ancestral sequence reconstruction has never been experimentally validated despite the method being exploited to generate high profile publications and gaining wider use in many laboratories. The failure to validate such a method is a consequence of 1) our inability to travel back in time to document evolutionary transitions and 2) the slow pace of natural evolutionary processes that prevent biologists from ‘witnessing’ evolution in action (pace viruses). In this thesis research, we have generated an experimentally known phylogeny of fluorescent proteins in order to benchmark ancestral sequence reconstruction methods. The tips/leaves of the fluorescent protein experimental phylogeny are used to determine the performances of various ASR methods. This is the first example of combining experimental phylogenetics and ancestral sequence reconstruction.

Elections are one of the most fundamental activities of a democratic society. As is the case in any other aspect of life, developments in technology have resulted changes in the voting procedure from using the traditional paper-based voting to voting by use of electronic means, or e-voting. E-voting involves using different forms of electronic means like / voting machines, voting via the Internet, telephone, SMS and digital interactive television. This thesis concerns voting by telephone, or televoting, it starts by giving a brief overview and evaluation of various models and technologies that are implemented within such systems. The aspects of televoting that have been investigated are technologies that provide a voice interface to the voter and conduct the voting process, namely the Election Markup Language (EML), Automated Speech Recognition (ASR) and Text-to-Speech (TTS).

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As plantas são organismos sésseis que continuamente enfrentam situações ambientais adversas, o que acarreta em reduções significativas da biomassa e da produtividade. O trabalho, aqui exposto, teve como objetivo avaliar o papel dos fatores de transcrição ASR (do ingles ABA, stress and ripening) na resposta a estresses abióticos em plantas de arroz. Também teve como objetivo avaliar as respostas de plantas de Arabidopsis thaliana ao estresse produzido nos momentos iniciais da exposição ao metal alumínio. O capítulo 1 da presente tese, compara a expressão de miRNAs entre plantas silenciadas para o gene ASR5 (ASR5_RNAi) e plantas não transformadas (controle). De um total de 279 miRNAs maduros identificados, distribuídos em 60 famílias, 159 foram diferencialmente expressos quando as duas bibliotecas foram comparadas. Uma correlação negativa entre o MIR167 e seu gene alvo (LOC_Os07g29820) também foi confirmada por PCR em tempo real. Este é o primeiro trabalho sugerindo o envolvimento das proteínas ASR na regulação da expressão de miRNAs em planta. O segundo capítulo apresenta o estudo das proteínas ASR na manutenção da homeostase do pH em plantas de arroz. Verificou-se uma diminuição do crescimento radicular em plantas silenciadas em solução ácida, quando comparadas com plantas não transformadas nas mesmas condições. Também foi analisada a viabilidade da ponta de raízes quanto ao dano causado pelo baixo pH e diferentes concentrações de Ca+2, demonstrando que a adição de CaCl2 é capaz de aliviar o efeito tóxico do excesso de protons H+. Diversos genes reprimidos nas plantas silenciadas e envolvidos no mecanismo de manutenção do pH em células vegetais, também foram investigados. O terceiro e último capítulo é dedicado ao estudo da resposta inicial de plantas de Arabidopsis thaliana ao estresse por alumínio. Plantas com 7 dias de idade foram expostas a uma concentração de 25 μM de AlCl3 durante 3 horas e modificações na abundância de proteínas foi investigada com a técnica de espectrometria de massa. Um total de 3.213 proteínas foram identificadas, sendo que destas, 293 apresentaram variação no nível de expressão. Diversas proteínas com expressão induzida são funcionalmente associadas com a detoxificação de espécies reativas de oxigênio (ROS), indicando que o tratamento ocasionou estresse oxidativo nas raízes de A. thaliana. Também foram identificadas uma proteína mitocondrial carreadora de substrato e uma acyl-CoA oxidase com possível papel nos mecanismos de defesa em resposta a alumínio e com potencial para futuros estudos funcionais na planta modelo. De uma maneira geral, os resultados aqui apresentados mostram, pela primeira vez, que ASR5 está envolvida na regulação de miRNAs e na homeostase do pH em plantas de arroz, além de identificar proteínas responsivas ao estresse por alumínio em A. thaliana. / Plants are sessile organisms that continuously face adverse environmental situations, leading to a significant reduction in biomass and yield. The aim of the present work was to further study the ASR (ABA, stress and ripening) transcription factors in rice plants. Moreover, the responses of Arabidopsis thaliana to aluminum stress were also analyzed. The chapter 1 of this thesis compares the expression of mature miRNAs in the ASR5 silenced plants (ASR5_RNAi) and in non-transformed plants (control). From a total of 279 mature miRNA of 60 families, 159 were differentially expressed. A negative correlation of MIR167 and its target gene (LOC_Os07g29820) was also confirmed by real time RT-qPCR. This is the first report showing the involvement of ASR proteins in miRNA gene expression regulation. The second chapter presents the study of participation of ASR proteins in the maintenance of pH homeostasis in rice plants. The evaluation of root growth in ASR5_RNAi plants upon acid solution showed inhibition of root growth when compared to non-transformed plants in the same condition. Root tip feasibility and damage caused by low pH and different concentrations of Ca+2 was also analyzed. The results indicate that addition of CaCl2 is capable of alleviating the toxic effects of H+ protons. Several genes downregulated in silenced plants and involved in pH maintenance in plant cells have also been investigated. This work demonstrates the importance of ASR transcription factors in a biological process not yet described. The third and final chapter describes the study of the initial response of Arabidopsis thaliana to aluminum stress. Seven-day old seedlings were treated with 25 μM AlCl3 for 3 hours and submitted to quantitative analyses by mass spectrometry. A total of 3,213 proteins were identified, from which 293 proteins were differentially responsive upon aluminum treatment. Several proteins with increased expression in response to the treatment are functionally associated with reactive oxygen species (ROS), indicating that the Al3+ exposure caused oxidative stress in the roots of A. thaliana. A mitochondrial substrate carrier (At1g78180) and an acyl-CoA oxidase (At3g51840) with a putative role in Al defense were also up-regulated and constitute interesting targets for functional studies of aluminum toxicity in the model plant. Overall, the results here presented show for the first time that ASR5 is involved in miRNA and pH homeostases regulation in rice plants and also identify proteins responsive to aluminum stress in A. thaliana.