Este trabalho tem por objetivo estudar as interações superfíciais de cristais líquidos em uma interface cristal líquido-polímero, com a utilização de filmes poliméricos contendo cadeias laterais com corante azo. Nesse estudo foi utilizado um fotopolímero, onde pode se promover o ordenamento dos grupos laterais ao longo de uma direção preferencial através de um processo de isomerização trans-cis. Através da irradiação do filme de polímero com luz polarizada é possível promover a formação de uma anisotropia óptica no filme. A intensidade deste efeito pode ser controlada através da energia incidente e da concentração dos grupos laterais corante azo presentes no polímero. Neste trabalho foi realizado um estudo sistemático da orientação induzida ao cristal líquido nemático por um filme contendo corante azo no grupo lateral. Os aspectos investigados são: a estabilidade térmica e temporal do alinhamento induzido ao cristal líquido; a competição entre dois efeitos de orientação induzidos ao cristal líquido, o esfregamento e o fotoalinhamento; a influência da cncentração dos grupos laterais e da energia de irradiação. Para caracterizar as interações entre o cristal líquido e o filme polimérico foram empregadas técnicas ópticas que permitiram a determinação das intensidades de ancoramento azimutal e zenital em função da concentração de grupos laterais e da energia de irradiação. Mostramos ser possível um ancoramento azimutal que pode ter sua intensidade controlada pela concentração dos grupos laterais, pelo tempo de irradiação com luz polarizada, ou ainda pela potência do laser de excitação, e um ancoramento zenital bastante fraco, que praticamente não é afetado pelo processo de foto-isomerização. / The aim of this work is to study the superficial interactions of liquid crystals in an interface liquid Crystal-polymer, with the use of polymer films containing azo-dyes groups as side chain. In this study a photopolymer was used, where the ordering of the side group can be promoted along a preferential direction through a trans-cis isomerization process. Through the irradiation of the polymeric film with polarized light it is possible to promote the formation of an optical anisotropy in the film. The intensity of this effect can be controlled through the incident energy and the concentration of the azo-dye side groups presents in the polymer. In this work a systematic study of the orientation induced to the nematic liquid crystal by a polymeric film containing azo-dye groups in the side group was performed. The investigated aspects are: -The thermal and temporary stability of the alignment induced to the liquid crystal; -The competition among two orientation effects induced to the liquid crystal, the rubbing and the photo alignment; -The influence of the concentration of the side groups and of the irradiation energy. To characterize the interactions between the liquid crystal and the polymeric film we used optical techniques that allowed the determination of the azimuthal and zenithal anchoring strengths as a function of the concentration of side groups and of the irradiation energy. We showed to be possible an azimuthal anchoring that can have its intensity controlled by the concentration of the side groups, and the irradiation time with polarized light, or still for the power of the excitation laser, and a zenithal anchoring quite weak, that practically is not affected by the process of photo isomerization.

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Les troubles alimentaires à l’adolescence se retrouvent dans divers contextes socio-économiques et constituent une importante question de santé publique au Brésil. Néanmoins, les liens entre la famile, l’alimentation et les troubles alimentaires sont encore peu explorés, spécifiquement au Nord-Est du Brésil. Notre objectif est d’analyser la place de la nourriture dans les relations familiales d’adolescentes brésiliennes anorexiques et boulimiques. Nous avons utilisé une méthode qualitative, exploratoire, auprès d’un échantillon de vingt-six sujets, dont huit familles, quatre anorexiques, quatre boulimiques, âgées de 12 à 18 ans, huit mères, quatre pères, cinq grand-mères et une soeur dans deux services de santé publique, CETRATA et PRONUTRA à Fortaleza-Ceará, au Nord-Est du Brésil. Nous les avons ensuite interrogés grâce à l’outil de photo-elicitation. La photographie d’un repas familial prise par l’adolescente a servi de base à l’entretien semi-structuré. L’analyse des entretiens a été réalisée à l’aide de l’Interpretative Phenomenological Analysis (IPA). L’analyse des résultats a permis d’analyser deux facteurs importants : la relation duelle parent-adolescente et le fonctionnement du groupe familial. Les résultats mettent en lumière un contrôle paternel très important dans la gestion de l’alimentation dans le groupe anorexie. La nourriture est apparue comme un moyen trouvé par l’adolescente anorexique et boulimique pour élaborer leurs situations de perte et de deuil. L’adolescente réorganise ses liens affectifs dans un mouvement paradoxal de demande de contrôle par l’autre, qu’elle-même contrôle en retour. Il semble y avoir, spécifiquement, dans l’anorexie, une délégation de la part des parents de soin aux personnes tierces, représentées par la famille élargie et les personnes appartenant aux systèmes extrafamiliaux. Différents conflits entre les sous-systèmes autour de la nourriture ont une fonction structurante pour le système familial, même s’il s’agit de le maintenir dans un état dysfonctionnel. Ces conflits affaiblissent la cohésion familiale dans l’anorexie et la boulimie. Un affaiblissement des règles et une informalité autour de l’organisation d’un repas sont apparus comme une manière d’échapper à la rigidité des rôles que le trouble alimentaire de la fille impose aux parents. Il semblerait que le mode d’organisation de repas familiaux ne reflète pas nécessairement le mode de fonctionnement de la famille. L’un des résultats les plus importants que notre étude sont conflits transgénérationnels.Nous avons trouvé des divergences entre la génération des parents et celle des grand-mères concernant la façon d’éduquer l’enfant et la transmission de rituels. Ces divergences semblent donc affaiblir le sentiment d’appartenance de l’adolescente à la famille à travers la nourriture. L’ensemble de nos résultats montrent la nécessité de travailler autour du processus séparation-individuation de l’adolescente brésilienne anorexique et boulimique de manière à concilier l’identité individuelle et familiale et favoriser son autonomisation. / Eating disorders in adolescence occur in various socioeconomic contexts in Brazil and are thus an important public health issue there. Nevertheless, the link between family, food and eating disorders has been very little explored, especially in northeastern Brazil. Our main goal was to examine the role of food in family relationships of Brazilian teenagers with anorexia and bulimia. We used an exploratory qualitative method to analyze interviews with 8 families and twenty-six individuals: four adolescents with anorexia and four others with bulimia, aged 12 to 18 years, with eight mothers, four fathers, five grandmothers, and one sister of a teenager with bulimia, referred through two public health centers (CETRATA and PRONUTRA) in Fortaleza-Ceara, in northeastern Brazil. Applying the technique of photoelicitation, we used a photograph of a family meal taken by the adolescent as the basis for the semi-structured interviews, analyzed with Interpretative Phenomenological Analysis (IPA). The results revealed two important superordinate themes: the parent-teenager relationship and the functioning of the family group. Results highlighted important paternal control in anorexia nervosa. Food appeared to be a means enabling adolescents with anorexia and bulimia to deal their situations of loss and grief. They appear to reorganize their emotional ties in a paradoxical movement by which they request to be controlled by another, who in turn they control. In anorexia, in particular, parents appear to delegate to third parties (the extended family and persons belonging to non-family systems) the role of monitoring the girl’s food supply. Different types of conflict around food between the subsystems, including that of siblings, seem to be necessary to maintain the family system, albeit dysfunctionally, and they weaken family cohesion. Loosening of the rules and informality around organization of meals has emerged as a way to escape the rigidity of the roles that daughters’ eating disorders impose on parents. One of the most important results of our study is the existence of transgenerational conflicts. We found divergences between the parents’ generation and that of the grandmothers concerning the ways of raising children and transmitting rituals. These divergences thus seem to weaken these teenaged girls’ feelings of belonging to the family through food. Overall, the results show the need for work around the separation-individuation process in Brazilian girls with anorexia and bulimia to help reconcile their individual and family identities and to promote their autonomy.

Spider-silk is known as one of the stronger natural materials, unfortunately it is impossible to farm spiders due to their territorial and cannibalistic nature. To address this issue, researchers have studied spider-silk to discover how it is produced in nature. From their results, spider-silk is composed of large sized proteins produced in two different cell types. Using this knowledge, researchers created transgenic organisms capable of producing spider-silk proteins in large quantities. Using these proteins, several groups have created fibers, films, hydrogels, and adhesives with robust and versatile properties. Wet-spinning is a technique commonly used to create fibers from spider-silk proteins. These fibers unfortunately do not compare to the mechanical properties of natural silk. To address this researchers have used a method known as electrospinning to create spider-silk fibers with substantially smaller diameters. In doing so, these electrospun fibers have increased surface area and enhanced mechanical properties. Using this method, our group has modified the electrospinner to be able to produce continuous fine diameter yarns composed of hundreds of nanofibers with mechanical properties surpassing that of natural silk. Fibers aside, spider-silk proteins can be used to create a variety of different biocompatible materials. To further enhance these materials, our group has utilized a technique traditionally used for observation. This technique employs a high intensity light source to initiate cross-links within the proteins. With this method, our spider-silk protein materials have increased their mechanical properties by a factor of seven. These materials can further be modified through post-treatments, resulting in tunable materials with diverse and robust mechanical properties.

As a part of the Tourist Information Provider (TIP) system, this project focuses on creating a photo gallery service in the TIP system, which allows users to share, browse and categorize their photos. The core of this project is to provide users a location-based photo browsing. The system provides photos which are taken in the current user's location. We considered privacy control on photos that users uploaded. A photo owner is able to sign an access level to each of their photos and permit different users to access them. We also considered reusing resources. The system allows a user to use an URL of a photo in the system in stead of uploading the photo from the local computer. The system also provides a URL of each photo in order to use the photo on other web places, e.g., Blogs. We use tags and photo metadata Eixf to categorize photos.

De par leur diversité et leur large gamme d'applications, les polymères se sont imposés dans notre environnement. Dans le cas d'applications techniques ces matériaux peuvent être exposés à des environnements agressifs conduisant à une altération de leurs propriétés. Les effets de cette dégradation sont reliés à la notion de durée de vie, c'est-à-dire au temps nécessaire pour qu'une propriété atteigne un seuil en dessous duquel le matériau devient inutilisable. Le suivi du vieillissement des matériaux polymères présente donc des enjeux importants. La spectroscopie de fluorescence est une technique qui permet d'apporter certaines réponses à ce problème. Dans le cadre de cette étude, l'accent a été porté sur l'utilisation de la spectroscopie de fluorescence pour l'étude des phénomènes intervenant lors de l'irradiation UV ou de la sollicitation mécanique d'un polymère. Dans le cas du polyéthylène haute densité, l'absence de signal fluorescent intrinsèque impose l'ajout d'un colorant. Ce colorant donnant une réponse en fluorescence dépendant de son microenvironnement, toutes modifications des chaînes du polymère engendrent un déplacement du pic de fluorescence de la sonde. Ce travail peut être séparé en deux grandes parties indépendantes, d'un coté l'influence du vieillissement UV sur la réponse fluorescente et de l'autre l'influence d'une sollicitation mécanique. Dans la première partie, l'utilisation de techniques complémentaires telles que l'IRTF ou l'AED a permis de corréler les différents résultats avec les mécanismes de vieillissement connus du polyéthylène. Les résultats obtenus dans cette partie montrent la grande sensibilité de la spectroscopie de fluorescence aux réarrangements microstructuraux intervenant dans le matériau. Dans la seconde partie, la dépendance entre la contrainte appliquée au matériau et la longueur d'onde de fluorescence a permis a partir de modèles simples d'évaluer les contraintes internes qui se développent au cours d'une sollicitation cyclique.

The emergence of organic semiconductors is exciting since it promises to open up for straightforward and low-cost fabrication of a wide range of efficient and novel electronic devices. However, in order for this promise to become reality it is critical that new and functional fabrication techniques are developed. This thesis demonstrates the conceptualization, development, realization and implementation of a particularly straightforward and scalable fabrication process: the photo-induced and resist-free imprint patterning technique.Initial experiments revealed that some members of a group of carbon-cage molecular semiconductors – termed fullerenes – can be photochemically modified into dimeric or polymeric structures during exposure to laser light, and, importantly, that the exposed fullerene material retains its good electron-transport property while its solubility in common organic solvents is drastically lowered. With this information at hand, it was possible to design and create well-defined patterns in a solution-deposited fullerene film by exposing selected film areas to laser light and then developing the entire film in a tuned developer solution. An electronically active fullerene pattern emerges at the locations defined by the incident laser beam, and the patterning technique was successfully utilized for the fabrication of arrays of efficient field-effect transistors.In a later stage, the capacity of the photo-induced and resist-free imprint technique was demonstrated to encompass the fabrication of ubiquitous and useful CMOS circuits. These are based on a combination of p-type and n-type transistors, and a blend between a p-type organic semiconductor and an n-type fullerene compound was designed so that the latter dominated. By solution-depositing the blend film on an array of transistor structures, exposing selected transistors to laser light, and then developing the entire transistor array in a developer solution, it was possible to establish a desired combination of (non-exposed) p-type transistors and (exposed) n-type transistors. We finally utilized this combination of transistors for the fabrication of a CMOS circuit in the form of well a-functional organic inverter stage.

Photon mass attenuation coefficients are indispensable input parameters for use in several disciplines. They are of value for medical diagnostics, radiation therapy, material science, etc. Currently, photon mass attenuation coefficients derived from model calculations are widely used. This project directly measured the photon mass attenuation coefficients of water and a number of water based solutions. These measurements were made using a High Purity Germanium (HPGe) detector allowing for increased resolution beyond traditional techniques. Four sources were used (\Ba, \Eu, \Cs, \Am) producing multiple photons of interest over the range of 40 keV to 1.4 MeV, allowed for simultaneous collection of data and a refining of uncertainties beyond past techniques. Direct measurements using a new liquid technique supported the validity of Bragg's additive law, allowing for the mass attenuation coefficient of a constituent element to be calculated from a set of independent measurements. This technique allows materials not easily directly measured to be determined without an overburdening increase in uncertainty. The same direct measurements showed a deviation from the currently relied upon National Institute of Standards and Technology (NIST) database - XCOM. Investigations of the deviation and surrounding references showed XCOM being at most accurate to 5 \% relative uncertainty.

Semi-insulating gallium arsenide (SI-GaAs) has gained great interest in recent years due to its wide application in optoelectronic devices and high-speed integrated circuits. An important feature of SI-GaAs is the high density of deep-level defect states, which control the electrical properties of the substrate by compensating the shallow defects. Over the years, deep-level transient spectroscopy (DLTS) and its variations have been the most effective tools employed for the characterization of deep-level defects. However, most of these techniques require a contact probe and tend to be quite restrictive in their applications’ scope. In this thesis deep-level photo-thermal spectroscopy (DLPTS), an all-optical rate-window-based technique, is presented as a novel noncontact technique for the characterization of deep-level defects in SI-GaAs. The signal-generation mechanism for DLPTS is the super-bandgap excitation of carriers, and the sub-bandgap detection of the defect’s thermal-emission process. Combined with the rate-window detection utilizing lock-in amplifiers, DLPTS measurements are performed in three different modalities: temperature-scan, pulse-rate scan, and time-scan. This work demonstrates that each mode provides unique information about the defect configuration, and, in combination, the modes offer a powerful tool for the study of defect properties and optoelectronic processes in SI-GaAs. A hierarchical carrier-emission theory is proposed to explain the thermal broadening (nonexponentiality) in photo-thermal spectra. The model is studied comparatively with the Gaussian distribution of activation energies, and their similarities demonstrate an ergodic equivalence of random energy distribution and the constrained hierarchical emission process. In addition, a rate-window gated photo-carrier radiometry (PCR) technique is developed. The original diffusion-based PCR theory is modified to reflect the signal domination by trap emission and capture rates in the absence of diffusion. Defect luminescence is collected and analyzed using photo-thermal temperature spectra and resonant detection combined with frequency scans. The study results in the identification of five radiative defect states and the defect-photoluminescence quantum efficiency.

No description available.