Neste trabalho foi estudado o crescimento de fibras da matriz LiLa(WO4)2 (LLW) pura e co-dopada com íons Yb3+ e Er3+ via micro pulling-down. Foram crescidas fibras homogêneas e transparentes de LiLa(WO4)2:Yb3+:Er3+ com teor de dopante de 2, 5, 7, 10 e 15 mol% de Yb3+, todas co-dopadas com teor de 0,5 mol% de Er3+, com 1mm de diâmetro e até 22 mm de comprimento. Partindo-se da dopagem de 20 mol% não foi possível o crescimento de fibras com a mesma qualidade das demais, ocorrendo segregação e, possivelmente, formação de fase secundária. A temperatura de fusão dos compostos diminui com a adição de Yb3+, indo de 1020°C para o LLW puro, para 991°C com dopagem de 20 mol%. Para a análise de espectroscopia de emissão, as fibras foram excitadas com laser na região do infravermelho em 972 nm, sendo observada a emissão dos íons Er3+ via conversão ascendente. Foram observadas emissões referentes às transições 4S3/2 → 4I15/2 (centroide em 550 nm), 2H11/2 → 4I15/2 (527 nm) e 4F9/2 → 4I15/2 (653 nm); sendo a primeira a mais intensa. A eficiência de emissão aumentou de ~7% para a fibra pura, para 36% na fibra com 15 mol% de Yb3+. Foi encontrado que, para a maior intensidade de emissão, a quantidade ideal de Yb3+ deve ser de 11,5 mol%. / In the current work, was studied the growth of pure and Yb3+ and Er3+-doped LiLa(WO4)2 (LLW) by micro pulling-down technique. Were grown homogeneous and transparent fibers of Yb3+:Er3+:LiLa(WO4)2 with a dopant content of 2, 5, 7, 10 and 15 mol% of Yb3+, all co-doped with 0.5 mol% Er3+, 1 mm diameter and up to 22 mm length. It was not possible grow fibers with 20 mol% of Yb3+ due segregation and, possibly, formation of secondary phases. Noticed the melting temperature of the doped compounds decreases with the addition of Yb3+, from 1020 °C (pure LLW) to 991 °C (20 mol% Yb-doped). For emission studies, the fibers were excited in the infrared region at 972 nm and up conversion emission of Er3+ ions was registered. Emissions referring to transitions 4S3/2 → 4I15/2 (centroid at 550 nm), 2H11/2 → 4I15/2 (527 nm) and 4F9/2 → 4I15/2 (653 nm) were observed; the first one being the most intense. Emission efficiency increased from ~ 7% in pure fiber to 36% in doped fiber with 15 mol% of Yb3+. It was found that, for the highest emission intensity, the ideal amount of Yb3+ should be 11.5 mol%.

Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2012

Orientador: Henrique Ferreira / Resumo: Xanthomonas citri subsp. citri (X. citri) é o agente etiológico do cancro cítrico, uma doença que ataca todas as variedades comerciais de citros, causando prejuízos econômicos em vários países produtores. Em áreas endêmicas, o cancro cítrico é controlado principalmente por aplicação de bactericidas cúpricos. Compostos alternativos para controlar a doença são desejáveis, pois os bactericidas cúpricos causam impactos ambientais e podem induzir resistência em X. citri. Um passo importante para a descoberta e avaliação de novos compostos para controle de X. citri é a caracterização de genes/proteínas que são alvos em potencial. O gene mreB codifica para uma proteína que é uma actina bacteriana com papel-chave na determinação da morfologia celular. Esses genes foram caracterizados em algumas bactérias, nas quais foi demonstrado que são essenciais. Não existem relatos da caracterização de mreB em X. citri. A proteína MreB e a actina tem baixa similaridade de sequência, apesar de serem homólogos funcionais. Essas características fazem de MreB um alvo interessante para novos compostos antibacterianos. Os objetivos deste trabalho foram descrever a função e determinar a localização subcelular de MreB em X. citri. Para estudar a função de MreB, duas estratégias foram usadas para deletar o gene mreB em X. citri. Entretanto, não foi possível obter mutantes deletados para mreB nem na ausência, nem na presença de complementação. Esse resultado evidenciou que mreB é essencial para X. citri e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Xanthomonas citri subsp. citri (X. citri) is the etiological agent of Citrus canker, a widespread plant disease that attacks all varieties of commercial citrus plants, causing economic loss worldwide. In endemic areas, citrus canker is controlled mainly by the application of cupric bactericides. Alternative compounds to control this pathogen are desirable, since copper based bactericides have negative environmental impact and induce resistance in X. citri. An important step for the discovery and evaluation of new compounds to control X. citri is the characterization of genes/proteins that are potential targets. The mreB gene codes for a protein that is a bacterial actin homologue with a key role in rod shape morphogenesis. This gene was characterized in some bacteria, in which it was shown to be essential. There are no reports of characterization of mreB in X. citri. MreB and actin have a weak sequence similarity, despite being functional homologues. These characteristics make MreB an interesting target for new antibacterial chemical compounds. The objectives of this work were to study the function and subcellular localization of MreB in X. citri. To study the function of MreB in X. citri, two strategies were used to delete the mreB gene. However, neither strategy produced deleted mutants. This result confirmed that mreB is essential to X. citri and showed that the complementation method used was not adequate to ensure the viability of X. citri. To investigate MreB subcellula... (Complete abstract click electronic access below) / Mestre

Cette thèse a permis d’évaluer l’effet des changements de morphologie d’un matériau cimentaire soumis à un traitement thermique jusqu’à T (≤ 400°C). Pour cela, nous avons caractérisé expérimentalement le comportement mécanique (en compression uniaxiale, compression hydrostatique avec ou sans déviateur), poro-mécanique (modules d’incompressibilité Kb, Ks et coefficient de Biot b) et hydraulique (perméabilité au gaz), d’un mortier modèle E/C=0,5 suite à un cycle de chauffage/refroidissement. Les essais mécaniques multiaxiaux sont couplés aux mesures de perméabilité, qui servent d’indicateur de la progression de la fissuration du matériau sous contrainte. Nous avons également mis au point un essai original, permettant de quantifier le volume de l’espace poreux interconnecté sous chargement hydrostatique Pc. La création de porosité occluse sous l’effet d’un accroissement du confinement est confirmée, et ainsi la diminution de la rigidité de la matrice solide Ks avec Pc après traitement thermique T>200°C. Nous avons également identifié un effet bouchon (aucun passage de gaz) lors d’un chargement couplé, thermique et en compression hydrostatique du mortier mais aussi de bétons industriels (CERIB et ANDRA). Afin d’analyser l’évolution des propriétés mécaniques et poro-élastiques après traitement thermique, un modèle prédictif thermo-élasto-plastique avec endommagement isotrope et une approche micro-mécanique descriptive, intégrant la présence de micro-fissures, y sont couplés / This work investigates the effects of morphological changes of a cement-based material subjected to heat treatment (up to 400°C). For a model W/C=0.5 mortar, we have characterized experimentally hydraulic behaviour (gas permeability), mechanical behaviour (in uniaxial compression, hydrostatic compression with or without deviatoric stress) and poro-mechanical behaviour (incompressibility moduli Kb, Ks and Biot’s coefficient b) after a heating/cooling cycle. We have also developed an original experiment aimed at quantifying the accessible pore space volume under hydrostatic compression. The creation of occluded porosity under high confinement is confirmed, which justifies the observed decrease of solid matrix rigidity Ks under high confinement. A gas retention phenomenon was identified under simultaneous thermal and hydrostatic loadings for mortar, and industrial concretes (provided by CERIB and ANDRA). A predictive thermo-elasto-plastic model with isotropic damage and a micro-mechanical approach, which represents micro-cracking, are coupled in order to analyze or predict the evolution of mechanical and poro-elastic properties after heat cycling

Les miARN sont de petits ARN non codant dont la taille varie entre 21-24 nucléotides. Ils jouent un rôle de régulateurs post-transcriptionnels en utilisant leur complémentarité de séquence avec l’ARN messager (ARNm) cible afin d’induire sa répression. Grâce à la protéine Argonaute 2 (Ago2) dans laquelle les miARN sont incorporés formant ainsi le complexe miRISC, des cofacteurs sont recrutés afin d’induire la dégradation ou le blocage de la traduction de l’ARNm cible. Initialement connus pour réguler leurs cibles dans le cytoplasme, les miARN sont de plus en plus décrits comme étant des régulateurs de l’expression génique au niveau nucléaire. Dans ce travail, nous avons démontré la présence, au sein du noyau, d’un nouveau mécanisme de régulation post-transcriptionel par les miARN dont les facteurs majeurs sont Sfpq et Pspc1 / Micro-RNA, nuclear regulation, gene silencing, SfpqThere is a growing body of evidence about the presence and the activity of the miRISC in the nucleus of mammalian cells. Here we show by quantitative proteomic analysis that Ago2 interacts with the complex formed by Sfpq, Pspc1 and NonO in a RNA-dependent fashion. Sfpq mediates the interaction between miRISC with Pspc1 and NonO in the nucleoplasm. By HITS-CLIP coupled with transcriptomic analysis, we demonstrated that Sfpq specifically controls the downregulation of a subset of crucial let-7a-target mRNAs in stem cells, including Lin28a, Prtg, and Igf2bp1. Sfpq directly binds to specific sequence in the 3'UTR to promote the recruitment of selected nucleoplasmic miRNAs and triggers the decay, as we show for Lin28a mRNA. These results extend the miRNA-mediated post-transcriptional gene silencing into the nucleus and indicate that a dual strategy

Orientador: Antonio Olavo Cardoso Jorge / Coorientador: João Manoel Theotonio dos Santos / Banca: Luciane Dias Oliveira / Banca: Graziella Nuernberg Back Brito / Resumo: A resistência adquirida pelas bactérias aos antibióticos de amplo espectro tornou-se uma ameaça à saúde global. A necessidade de encontrar fármacos que consigam combater micro-organismos multirresistentes tem se tornado um grande desafio. Neste cenário, as plantas medicinais são promissoras por terem propriedades antimicrobianas eficazes, devido à presença de compostos fitoquímicos com atividades biológicas diversas. O objetivo desse estudo foi avaliar a ação antimicrobiana dos extratos glicólicos de Hamamelis virginiana (hamamélis) e de Persea americana (abacateiro) sobre cepas multirresistentes de Klebsiella pneumoniae e Pseudomonas aeruginosa. A avaliação da atividade antimicrobiana dos extratos vegetais foi realizada em sete cepas clínicas de K. pneumoniae e de P. aeruginosa, em comparação com uma cepa de referência de K. pneumoniae (ATCC 4352) e de P. aeruginosa (ATCC 15442). Para a determinação das concentrações inibitórias mínimas (CIM) e bactericida mínima (CBM) dos extratos de abacateiro e de hamamélis foi utilizado o método de microdiluição em caldo, segundo NCCLS. Após obtenção destes resultados, foi verificada a ação dos extratos sobre biofilmes monomicrobianos de oito cepas de K. pneumoniae e de P. aeruginosa (1 cepa ATCC e 7 cepas clínicas resistentes). Após o período de 48 horas para a formação do biofilme, os extratos foram adicionados separadamente, pelo período de cinco minutos, na concentração efetiva pré-determinada (CBM) e concentrações superiores. Poster... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract : The resistance created by bacteria to broad-spectrum antibiotics has become a threat to global health. The need to find drugs that can combat multidrug-resistant microorganisms has become a major challenge. In this scenario, medicinal plants are promising because they have effective antimicrobial properties due to the presence of phytochemical compounds with diverse biological activities. The objective of this study was to evaluate the antimicrobial action of the glycolic extracts of Hamamelis virginiana (hamamelis) and Persea americana (avocado) on multiresistant strains of Klebsiella pneumoniae and Pseudomonas aeruginosa. The evaluation of the antimicrobial activity of the plant extracts was carried out in seven clinical strains of K. pneumoniae and P. aeruginosa, compared to an strain of K. pneumoniae (ATCC 4352) and P. aeruginosa (ATCC 15442). The broth microdilution method, according to NCCLS, was used to determine the minimum inhibitory (MIC) and bactericidal (MBM) concentrations of the extracts of avocado and witch hazel. After obtaining these results, the extracts on monomicrobial biofilms of eight strains of K. pneumoniae and P. aeruginosa (1 strain ATCC and 7 resistant clinical strains) were verified. After the 48 hour period for biofilm formation, the extracts were removed, with a five-minute interval, in the effective exercise session (MBC) and in the upper sets. Afterwards, the biofilms were washed and measured by two different testicles, in which the biofilm biomass was evaluated by the violet glass and the viability of the microorganisms by the MTT test. The experiments were performed with n = 10, using two replicates for each strain / extract. The data were analyzed statistically by the ANOVA method, complemented by the Tukey test, with a significance level of 5% (p≤0.05). The results demonstrated an antibacterial activity of both extracts against the standard strain and as the clinical .... / Mestre

Cette thèse est consacrée à l’étude d’une technique innovante de lyse de microorganismes, fondée sur l’utilisation d’impulsions haute tension en milieu aqueux. Cette technique se distingue de l’électroporation qui exploite le champ électrique produit pour dégrader la membrane cellulaire ; dans notre étude les impulsions haute tension permettent la formation d’arcs électriques produisant de multiples phénomènes physico-chimiques qui peuvent entraîner la lyse des microorganismes.L’efficacité du procédé a été évalué sur les microorganismes suivants : des microalgues productrices d’huile (Nannochloropsis gaditana et Phaeodactylum tricornutum) et des bactéries couramment utilisées comme modèles de laboratoire (Escherishia coli et Bacillus subtilis). Dans ces travaux, nous avons montré que les ondes de pression produites sont principalement responsables de la lyse.En fin d’étude, des perspectives sont explorées en vue du développement de systèmes autonomes soit dans le cadre de la bioproduction, soit dans le cadre de l’analyse cellulaire. / This thesis focuses on the study of an innovative technology for microorganisms lysis, based on high voltage pulses generated in an aqueous medium. This technology is different from electroporation which operates thanks to the electric field for damaging cell membranes ; in our study high voltage pulses generate an electric arc leading to various physicochemical phenomena supposed to lyse microorganisms.The technology efficiency is evaluated with the following microorganims : some lipid producting microalgae (Nannochloropsis gaditana and Phaeodactylum tricornutum) and classical laboratory model bacteria (Escherishia coli and Bacillus subtilis). In this work, we found that generated shock waves are mainly responsible of the cells lysis.At the end, the development of self-functioning devices is investigated either for bioproduction or for cell analysis.

Pour résoudre la limitation inhérente au procédé d’impression laser LIFT, une approche utilisant une double impulsion (DP-LIFT) a été développée au cours de cette thèse. Dans ce processus, une irradiation laser de durée de quelques dizaines de microsecondes crée un bain de métal en fusion et une seconde impulsion ultra-brève induit le mouvement du fluide, la formation d’un jet ou d’une goutte et le transfert du métal liquide. Cette thèse présente une étude expérimentale détaillée sur le processus DP-LIFT. L'influence des paramètres des deux irradiations laser a été étudiée en s’appyuant sur un ensemble de méthodes d'observation. Pour étudier l’influence de ces paramètres sur la dynamique de l’éjection, un modèle basé sur la conservation de l’énergie a été utilisé. De plus, nous avons démontré que, pour certaines configurations des diamètres respectifs des deux spots lasers, des nanojets focalisés étaient générés. Enfin, en conservant une épaisseur fixe du film métallique, des gouttelettes uniques, sans débris, d'un diamètre allant de 670 nm à 6,0 µm ont été imprimées avec une reproductibilité élevée. des matrices de piliers ont également été imprimées pour démontrer le potentiel de la méthode LIFT à double impulsion pour la fabrication de micro-structures 3D / To solve the inherent limitation of Laser-induced Forward Transfer (LIFT), a double pulse LIFT (DP-LIFT) approach has been developed in this thesis. In this process, a first long pulse laser irradiation creates a melted metal pool and a second ultrashort pulse induces the fluid motion and initiates the jetting transfer. This thesis provides a detailed experimental study on the DP-LIFT process. The influence of double pulse parameters on the jetting phenomena has been carefully studied by means of various observation methods. To predict the jetting behaviors, an energy balanced model has been used. Moreover, we demonstrated that for some configurations of the respective diameters of the two lasers, focused nanojets are generated from the melting pool. Finally, from a fixed thickness of the donor film, debris-free single droplets with diameters ranging from 670 nm to 6.0 µm have been printed with high reproducibility. 2.5 D pillars matrix are printed to demonstrate the potential of the double pulse LIFT method for the fabrication of 3D micro-structures.

Ce travail de thèse explore l’excitation électrique de micro-OLEDs en régime d’impulsion afin d’évaluer la possibilité d’atteindre le seuil laser dans les diodes laser organiques qui restent encore à démontrer. Ils’agit d’identifier des solutions scientifiques et techniques ouvrant la voie vers des densités d’excitations électriques équivalentes aux seuils laser observés en pompage optique. Dans la littérature, les seuils les plus bas sont équivalents à des densités de courant entre 0.72 et 4kA/cm² si on suppose une efficacité quantique externe de 1%. De telles densités de courant imposent un régime d’excitation électrique impulsionnel pour s’affranchir des risques de destructions par effet thermique et des pertes par annihilation singulet-triplet dès lors que l’on travaille avec des durées d’impulsion de l’ordre de la nanoseconde. Et pour espérer des réponses électriques et optiques efficaces à de telles durées d’impulsions, il est proposé ici de combiner l’électronique hyperfréquence et l’optoélectronique organique. A cet effet, un modèle électrique équivalent de l’OLED permettant d’accéder à son temps de réponse en mode tout-ou-rien est développé. De plus, des électrodes spécifiques sont dimensionnées et structurées sous forme de lignes coplanaires d’impédance caractéristique 50Ω afin de maîtriser l’impédance du circuit d’excitation et d’assurer le transfert du maximum d’énergie de l’impulsion d’excitation vers celui-ci. Après dépôts de l’hétéro-structure organique basée sur le système hôte-dopant Alq3:DCM, les composants ainsi réalisés sont caractérisés électriquement et optiquement avec différentes techniques par analyse vectorielle, en régime continu et en régime d’impulsion. En régime d’impulsion de très courtes durées (2.5~20ns) et à faible taux de répétition (100Hz), des temps de réponse de 330ps etdes densités de courant maximales entre 4 et 6kA/cm² ont été mesurés alors que le maximum de luminance culmine à 4.11x10⁶ cd/m². / This thesis explores the pulsed electrical excitation of micro-OLEDs in order to evaluate the possibility of reaching the laser threshold in organic laser diodes that have not yet be demonstrated. The main goal is the identification of the scientific and technical solutions towards high electrical excitation current densities equivalent to the laser thresholds observed under optical pumping. In the literature, the lowest reported thresholds are equivalent to current densities between 0.72 and 4kA/cm², assuming an external quantum efficiency of 1%. Such current densities imply a pulsed electrical excitation regime to prevent the risks of device breakdown by Joule heating effects and to avoid losses by excitons annihilation processes, as long as the pulses duration are in nanosecond range. To expect efficient electrical and optical responses to such pulse durations, it is suggested to combine microwave electronics and organic optoelectronics. For this purpose, an equivalent electrical model of the organic light emitting device, allowing access to its on-off mode time response, is developed. Additionally, specific electrodes are designed and patterned in the coplanar waveguide configuration with characteristic impedance of 50Ω, inorder to control the impedance of the excitation circuit and to ensure the maximum energy transfer of the excitation pulse to the device. After deposition of organic hetero-structure based on the Alq3:DCM host-guest system, the device is characterized electrically and optically with different techniques by vector network analysis, in continuous mode and in pulse mode. In pulse excitation regime with very short pulses durations (2.5~20ns) and low repetition rate (100Hz), time response of 330ps and maximum current densities between 4 and 6kA/cm² are recorded while the maximum of luminance peaks at 4.11x10⁶ cd/m².

Cette thèse a pour objet de coupler la microfluidique et la microthermique pour réaliser des dispositifs miniaturisés de mesure et de contrôle de température. Nous avons utilisé les faibles constantes de temps des échanges thermiques aux échelles micrométriques et la capacité d'intégration offerte par la microfluidique, pour développer de nouveaux outils afin d'explorer d'autres domaines scientifiques. Dans le domaine de la physique, nous avons fabriqué un micro-conductimètre thermique afin d'étudier certaines des propriétés thermiques des nanofluides. Dans le domaine de la thermochimie nous avons mis au point un microcalorimètre à flux continu intégrable dans un laboratoire sur puce. Les possibilités offertes par la rapidité des transferts thermiques aux échelles micrométriques nous ont permis de développer des dispositifs de contrôle de température appliqués à la biologie cellulaire. Ce type de dispositif permet de confiner une colonie de cellules et d'effectuer des changements de température du milieu, en quelques secondes. Nous avons ainsi la possibilité de contrôler l'activité de protéines thermosensibles et d'étudier certaines propriétés du cytosquelette de S.Pombe. Les caractéristiques de ce type de dispositif ouvrent la voie à de nouvelles recherches en biologie cellulaire, particulièrement sur le rôle de protéines d'intérêt thérapeutique rendues préalablement thermosensibles.