Dissertations / Theses on the topic 'Retina face'

The mammalian immune system is equipped to both eliminate pathogenic microorganisms and tumors, while remaining in homeostasis with commensal species at mucosal surfaces and tolerant towards self. Suppressor regulatory T cells (Tregs) are a major sentinel of this immunological tolerance. Induced Tregs (iTregs) arise in the periphery following the integration of cues from the metabolites, cytokines, etc. which make up its milieu. Dysregulation of iTreg development, function or homing underlies the etiology of many autoimmune diseases and immunopathologies. The amelioration or prevention of multiple murine disease models by boosting Treg cell numbers foreshadows clinical efficacy of iTreg therapy, but an incomplete understanding of Treg development has thus far prevented successful translation. Therefore, we considered the basic biology of T cell fate decision making from two unique, but integrated angles. First, we show that the stimulation of PPARγ in human T cells upregulates RDH10, a molecule which catalyzes the rate limiting step in the oxidation of retinol to transcriptionally active all-trans retinoic acid (ATRA), a positive regulator of iTreg development. This functionally intact pathway endows T cells the ability to autonomously sense and respond to retinoid signals present during Treg development and at tissue sites. Next, we asked questions about how T cells sense nutrient and oxygen availability as they differentiate. Tregs lacking the serine/threonine kinase PINK1 have limited activation-induced phosphorylation of Akt and oxidative phosphorylation rates, and reduced suppressor function. Notably, the uncoupling of iTreg function from normal FoxP3 expression reinforces the recent hypothesis that the PI3K/Akt/mTORC1 axis and metabolic checkpoints are decisive players in the acquisition of suppressor activity. Ultimately, the studies described herein converge on Akt and metabolism, and contribute to our understanding of how T cells integrate diverse signals present during fate determinism, provoking future Treg based therapeutics.

Bien qu'ayant suscité des recherches depuis 30 ans, le problème de la reconnaissance de visages en contexte de vidéosurveillance, sachant qu'une seule image par individu est disponible pour l'enrôlement, n'est pas encore résolu. Dans ce contexte, les deux défis les plus difficiles à relever consistent à développer des algorithmes robustes aux variations d'illumination et aux variations de pose. De plus, il y a aussi une contrainte forte sur la complexité en temps et en occupation mémoire des algorithmes à mettre en oeuvre dans de tels systèmes. Le travail développé dans cette thèse apporte plusieurs avancées innovantes dans ce contexte de reconnaissance faciale en vidéosurveillance. Premièrement, une méthode de normalisation des variations d'illumination visant à simuler les performances de la rétine est proposée en tant que pré-traitement des images faciales. Deuxièmement, nous proposons un nouveau descripteur appelé POEM (Patterns of Oriented Edge Magnitudes) destiné à représenter les structures locales d'une image. Ce descripteur est discriminant, robuste aux variations extérieures (variations de pose, d'illumination, d'expression, d'âge que l'on rencontre souvent avec les visages). Troisièmement, un modèle statistique de reconnaissance de visages en conditions de pose variables, centré sur une modélisation de la manière dont l'apparence du visage évolue lorsque le point de vue varie, est proposé. Enfin, une nouvelle approche visant à modéliser les relations spatiales entre les composantes du visage est présentée. A l'exception de la dernière approche, tous les algorithmes proposés sont très rapides à calculer et sont donc adaptés à la contrainte de traitement temps réel des systèmes de vidéosurveillance<br>Although having been an active research topic for 30 years, recognizing a person from surveillance having seen only one image is unsolved. Within this context, the two greatest challenges are the variations of pose and illumination. Moreover, there are strict constraints upon the complexity in both terms of computational time and stockage requirements. The work developed throughout this dissertation gives several advantages in the context of real-time and unconstrained face recognition. Firstly, an illumination normalization method simulating the performance of human retina is proposed as preprocessing algorithm. Secondly, we propose novel features called POEM (Patterns of Oriented Edge Magnitudes) for representing a local image structure. This descriptor is discriminative and robust to exterior variations (variations of pose, illumination, expression and pose that we always see when dealing with face images). Thirdly, a statistical model for robust face recognition across poses, entered on modeling how facial patch appearance changes as the viewpoint varies, is proposed. Finally, a novel approach modeling the spatial relationships between face components is developed. Except the last algorithm, all proposed methods are very fast and are therefore suitable for the constraints upon real-time of surveillance applications

We have used the chicken retina as a model for investigating cell cycle regulation and cell fate commitment during central nervous system development. This thesis focuses on the characterization of and commitment to the horizontal cell fate in the retina. Horizontal cells are interneurons that provide intraretinal signal processing prior to information relay to the brain. We have identified molecular markers that selectively distinguish the three subtypes of horizontal cells, previously described in the chicken retina based on morphology. Subtype specific birth-dating revealed that horizontal cell subtypes are generated consecutively by biased progenitors that are sensitive to the inhibitory effects of follistatin. Follistatin stimulates proliferation in progenitors by repressing the differentiation signal of activin. Initially, injection of follistatin led to a decrease in committed horizontal cells but as the inhibitory effect dissipated it resulted in an increased number of horizontal cells. During development committed horizontal cell progenitors migrate to the vitreal side of the retina where they become arrested in G2-phase for approximately two days. When the arrest is overcome the horizontal cell progenitors undergo ectopic mitosis followed by migration to their designated layer. The G2-phase arrest is not triggered or maintained by any of the classic G2-arrest pathways such as DNA damage or stress. Nevertheless, we show that the cyclin B1-Cdk1 complex has a central role in maintaining this G2-phase arrest. Two transcription factors, FoxN4 and Ptf1a, are required for the generation of horizontal cells. We show that these factors are also sufficient to promote horizontal cell fate. Overexpression of FoxN4 and Ptf1a resulted in an overproduction of horizontal- and amacrine cells at the expense of ganglion- and photoreceptor cells. We identified Atoh7, a transcription factor required for the generation of ganglion cells, as a Ptf1a transcriptional target for downregulation. Our data support a common horizontal/amacrine lineage separated from the ganglion/photoreceptor lineage by the action of Ptf1a. In conclusion, these data describe several novel characteristics of horizontal cells enhancing our understanding of neural development and cell fate commitment.

Cette thèse porte sur l’étude de l’interface entre électrodes et cellules épithéliales de la rétine : l’épithélium pigmenté. Les cellules RPE (Retinal Pigment Epithelium) qui le constitue forment une monocouche qui à confluence est constituée de cellules de forme polygonale. Elles sont juxtaposées et en contact intime les unes avec les autres par la présence de jonctions serrées. Un épithélium pigmenté endommagé est souvent associé à des pathologies de la vision. La spectroscopie d’impédance est une méthode de mesure qui permet d’étudier de manière non destructive un milieu composé d’éléments diélectriques et conducteurs. Cette mesure s’applique particulièrement bien aux cellules épithéliales. On applique ceci à l’étude du tapis cellulaires. Les membranes cellulaires remplissent le rôle de milieu diélectrique alors que les milieux ioniques intra et extracellulaires peuvent être considérés conducteurs. On peut en première approche analyser le module de l’impédance mesurée à une fréquence donnée afin de suivre le développement des tissus. Par exemple dans le domaine des implants à électrodes les fréquences autour de 1 KHz sont couramment citées. On peut par la suite mesurer l’impédance dans une gamme de fréquence plus importante et appliquer un modèle composé de dipôles électriques aux mesures. L’analyse des paramètres extraits peut donner une interprétation plus fine de l’état du tapis cellulaire. Deux notions seront principalement abordées dans cette thèse. Tout d’abord l’étude de l’utilisation de l’élément à constante de phase (CPE) dans la représentation du tapis cellulaire. Ensuite dans le cadre de ce modèle on va étudier le tapis cellulaire face à différentes perturbations<br>This manuscript focuses on studying the interface between an electrode and epithelial cells of the retina: the Retinal Pigment Epithelium (RPE). The cells that are part of this epithelium develops until they form a monolayer of juxtaposed cells with close lateral contact involving the presence of tight junctions. A damaged epithelium is often associated with sight alterations.Impedance spectroscopy is a measurement method that allows to study materials containing both conducting and dielectric elements in a non–destructive way. We apply this technique to the RPE cells layer. Cells membranes are the dielectric part while the intra and extracellular mediums are the conductive parts of this material. In a first stage one can measure the impedance at a fixed frequency as a way to follow tissues development. As an example, the 1 KHz frequency is often considered in characterizing electrodes from implanted devices. One can also measure the impedance over a wider bandwidth and apply an electric model circuit to the data. The extracted parameters can give a better interpretation of the state of the cell layer. In this work, two part will be mainly investigated. First we will evaluate the use of a constant phase element in part of the electrical model describing the cell layer. Second, and considering the same model, we will observe the reaction of the model when the cells are subject to various perturbations

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico<br>A deficiÃncia de vitamina A (DVA) à considerada um importante problema de saÃde pÃblica em todo o mundo e o papel da DVA na integridade epitelial intestinal ainda nÃo està bem compreendido. O objetivo do trabalho foi investigar a associaÃÃo do retinol (vitamina A) e carotenÃides com a barreira funcional intestinal em crianÃas de uma comunidade urbana em Fortaleza, no Nordeste do Brasil. Participaram do estudo 102 crianÃas de 2 meses a 9 anos de idade. O estado nutricional das crianÃas foi avaliado atravÃs do escore âzâ de peso por altura (WHZ), mostrando que 19,6% (20/102) das crianÃas apresentaram desnutriÃÃo leve (âzâ escore de -1 a -2). Todas as crianÃas tiveram as concentraÃÃes de retinol determinadas e nenhuma estava severamente deficiente (< 0,35 ÂM); 2,9% (3/102) das crianÃas apresentaram nÃveis moderados de deficiÃncia de vitamina A (0,36 - 0,70 ÂM); 20,6% (21/102) apresentaram leve deficiÃncia (0,71 - 1,05 ÂM) e 76,5% (78/102) apresentaram concentraÃÃes suficientes de retinol no sangue (> 1,05 ÂM). A razÃo de lactulose/manitol (L/M) estava anormal em 49% (47/97) das crianÃas quando comparadas com crianÃas saudÃveis de uma mesma regiÃo geogrÃfica. Os carotenÃides, luteÃna, &#946;-criptoxantina e beta-caroteno no soro das crianÃas do Parque UniversitÃrio, apresentaram correlaÃÃes inversas significativas com a razÃo de L/M. As proteÃnas de fase aguda (proteÃna C reativa, CRP e glicoproteÃna &#945;1-Ãcida, AGP) apresentaram correlaÃÃes inversas com retinol. O retinol correlacionou-se significativamente com a proteÃna ligadora de retinol (RBP) e com a transtiretina (TTR). Esses dados sugerem que a alteraÃÃo na barreira funcional intestinal provavelmente ocorreu atravÃs do caminho paracelular com baixas concentraÃÃes de carotenÃides no soro. Os carotenÃides, precursores do retinol, poderiam assim promover um melhor marcador para a barreira funcional intestinal alterada do que as medidas de RBP ou retinol. As concentraÃÃes sanguÃneas de retinol correlacionaram-se com a RBP e TTR e correlacionaram-se inversamente com a AGP e com a CPR<br>Vitamin A deficiency (VAD) is considered an important public health problem worldwide and the role of VAD on intestinal epithelial integrity is not well understood. To investigate the association of retinol (vitamin A) and carotenoids with the intestinal barrier function from children in an urban community in Fortaleza, Northeastern Brazil, one hundred and two children from 2 months to 9 years old participated in the study. The nutritional status of these children, measured by weight for height z-score (WHZ), showed that 19.6% (20/102) of them had mild malnutrition (-1 to â2 z-score). All children had their serum retinol concentration measured and none were severely deficient (<= 0.35 ÂM), 2.9% (3/102) were moderately (0.36 â 0.70 ÂM), 20.6% (21/102) were mildly (0.71 â 1.05 ÂM) deficiencies; 76.5% (78/102) were vitamin A sufficient (> 1.05 ÂM). The lactulose:mannitol (L/M) ratio was abnormal in 49% (47/97) of children when compared to healthy children in the same geographic area. Serum carotenoids, lutein, beta-cryptoxanthin and beta-carotene showed significant inverse correlation with the L/M ratio. Acute phase proteins (C-reactive protein; CRP; and &#945;-acid glycoprotein; AGP) were significantly inversely correlated with retinol. Retinol was significantly correlated with retinol-binding protein (RBP), and with transthyretin (TTR). These data suggest a disruption of intestinal barrier function due to paracellular pathway with low serum concentrations of carotenoids. The retinol precursors, carotenoids, may provide a better marker for disrupted intestinal barrier function than measurements of RBP or retinol. Serum retinol concentrations correlate with RBP and TTR and inversely correlate with AGP and CRP

VIEIRA, Milena Morais. Retinol, proteínas transportadoras, carotenóides, proteínas de fase aguda e barreira funcional intestinal em crianças de uma comunidade urbana de Fortaleza. 2007. 175 f. Tese (Doutorado em Farmacologia) - Universidade Federal do Ceará, Fortaleza, 2007.<br>Submitted by denise santos (denise.santos@ufc.br) on 2012-09-05T11:46:58Z No. of bitstreams: 1 2007_tese_mmvieira.pdf: 1064195 bytes, checksum: b0e5a020136459b676d498d3c0e16e98 (MD5)<br>Approved for entry into archive by Eliene Nascimento(elienegvn@hotmail.com) on 2012-09-06T12:26:23Z (GMT) No. of bitstreams: 1 2007_tese_mmvieira.pdf: 1064195 bytes, checksum: b0e5a020136459b676d498d3c0e16e98 (MD5)<br>Made available in DSpace on 2012-09-06T12:26:23Z (GMT). No. of bitstreams: 1 2007_tese_mmvieira.pdf: 1064195 bytes, checksum: b0e5a020136459b676d498d3c0e16e98 (MD5) Previous issue date: 2007<br>Vitamin A deficiency (VAD) is considered an important public health problem worldwide and the role of VAD on intestinal epithelial integrity is not well understood. To investigate the association of retinol (vitamin A) and carotenoids with the intestinal barrier function from children in an urban community in Fortaleza, Northeastern Brazil, one hundred and two children from 2 months to 9 years old participated in the study. The nutritional status of these children, measured by weight for height z-score (WHZ), showed that 19.6% (20/102) of them had mild malnutrition (-1 to –2 z-score). All children had their serum retinol concentration measured and none were severely deficient (<= 0.35 µM), 2.9% (3/102) were moderately (0.36 – 0.70 µM), 20.6% (21/102) were mildly (0.71 – 1.05 µM) deficiencies; 76.5% (78/102) were vitamin A sufficient (> 1.05 µM). The lactulose:mannitol (L/M) ratio was abnormal in 49% (47/97) of children when compared to healthy children in the same geographic area. Serum carotenoids, lutein, beta-cryptoxanthin and beta-carotene showed significant inverse correlation with the L/M ratio. Acute phase proteins (C-reactive protein; CRP; and α-acid glycoprotein; AGP) were significantly inversely correlated with retinol. Retinol was significantly correlated with retinol-binding protein (RBP), and with transthyretin (TTR). These data suggest a disruption of intestinal barrier function due to paracellular pathway with low serum concentrations of carotenoids. The retinol precursors, carotenoids, may provide a better marker for disrupted intestinal barrier function than measurements of RBP or retinol. Serum retinol concentrations correlate with RBP and TTR and inversely correlate with AGP and CRP<br>A deficiência de vitamina A (DVA) é considerada um importante problema de saúde pública em todo o mundo e o papel da DVA na integridade epitelial intestinal ainda não está bem compreendido. O objetivo do trabalho foi investigar a associação do retinol (vitamina A) e carotenóides com a barreira funcional intestinal em crianças de uma comunidade urbana em Fortaleza, no Nordeste do Brasil. Participaram do estudo 102 crianças de 2 meses a 9 anos de idade. O estado nutricional das crianças foi avaliado através do escore “z” de peso por altura (WHZ), mostrando que 19,6% (20/102) das crianças apresentaram desnutrição leve (“z” escore de -1 a -2). Todas as crianças tiveram as concentrações de retinol determinadas e nenhuma estava severamente deficiente (< 0,35 µM); 2,9% (3/102) das crianças apresentaram níveis moderados de deficiência de vitamina A (0,36 - 0,70 µM); 20,6% (21/102) apresentaram leve deficiência (0,71 - 1,05 µM) e 76,5% (78/102) apresentaram concentrações suficientes de retinol no sangue (> 1,05 µM). A razão de lactulose/manitol (L/M) estava anormal em 49% (47/97) das crianças quando comparadas com crianças saudáveis de uma mesma região geográfica. Os carotenóides, luteína, β-criptoxantina e beta-caroteno no soro das crianças do Parque Universitário, apresentaram correlações inversas significativas com a razão de L/M. As proteínas de fase aguda (proteína C reativa, CRP e glicoproteína α1-ácida, AGP) apresentaram correlações inversas com retinol. O retinol correlacionou-se significativamente com a proteína ligadora de retinol (RBP) e com a transtiretina (TTR). Esses dados sugerem que a alteração na barreira funcional intestinal provavelmente ocorreu através do caminho paracelular com baixas concentrações de carotenóides no soro. Os carotenóides, precursores do retinol, poderiam assim promover um melhor marcador para a barreira funcional intestinal alterada do que as medidas de RBP ou retinol. As concentrações sanguíneas de retinol correlacionaram-se com a RBP e TTR e correlacionaram-se inversamente com a AGP e com a CPR

Estudou-se a cinética das transformações de fase em resfriamento contínuo e em tratamentos isotérmicos de cinco ligas de aços TRIP microligados com Nb, contendo teores variáveis de Mn e Si, através de ensaios dilatométricos, de caracterização morfológica dos produtos de transformação e de cálculos termodinâmicos e simulações numéricas usando os programas Thermocalc ® e Dictra®. Foram determinados os diagramas RC para a transformação da austenita, e foi estudada a influência da precipitação de ferrita pró-eutetóide e de bainita na fração volumétrica de austenita retida. Através dos diagramas de resfriamento contínuo foi possível delimitar a extensão do campo intercrítico dos cinco aços analisados, com determinação da janela de resfriamento e seus intervalos de temperaturas. Isso permitiu projetar os ciclos de resfriamento controlado a serem aplicados durante o processamento termomecânico dos Aços TRIP-D, TRIP-E e TRIP-H. Os cálculos pelo modelo numérico de redistribuição de carbono e de elementos substitucionais na interface ferrita/austenita, bem como as medidas de microanálise química por WDS e EDS permitiram verificar que a taxa de crescimento da ferrita pró-eutetóide é controlada pela difusão do carbono na austenita. Para tempos curtos de tratamento, o modelo de crescimento que melhor se ajusta é o do equilíbrio local com partição negligível de soluto. Verificou-se através de tratamentos isotérmicos no campo bainítico, que o silício atrasa a precipitação de carbonetos durante a reação bainítica, o que justifica o aumento da estabilidade da austenita retida no aço de maior Si (TRIP-H), quando comparado com o aço de menor Si (TRIP-E). Baseado nos resultados dos estudos das transformações de fase por resfriamento contínuo foram selecionadas as ligas TRIP-D, TRIP-E e TRIP-H, para simular dois esquemas de laminação controlada por meio de ensaios de torção a quente. Nesses ensaios foram variados o grau de deformação e a temperatura de acabamento, de modo a estudar os efeitos dos parâmetros de deformação mecânica na fração transformada dos diferentes constituintes microestruturais, e em particular na fração volumétrica de austenita retida. O primeiro ensaio refere-se à laminação controlada por recristalização estática (LCRE) e o segundo à laminação convencional (LCC), com temperatura de acabamento de 1030°C e 850°C, respectivamente. O resfriamento consistiu em dois tratamentos isotérmicos consecutivos: o primeiro no campo intercrítico (austenita + ferrita), e o segundo no campo bainítico. O aumento do grau de deformação na simulação por torção a quente da laminação controlada por recristalização estática, levou a um aumento da porcentagem de austenita retida obtida durante o resfriamento controlado (de 9 a 14,0 %). O acúmulo de energia de deformação abaixo da TNR na simulação do processo de laminação controlada convencional provocou uma diminuição da fração volumétrica de austenita retida bem como da concentração de carbono contido nela. Os perfis de Mn e C obtidos a partir de análises químicas com EDS e WDS em amostras do aço TRIP-E, deformadas com deformação total de 2,1 e deformação total de 2,8, mostram a contribuição do refinamento de grão para a difusão destes elementos na frente da interface ferrita/austenita, durante a precipitação de ferrita pró-eutetóide.<br>The phase transformation kinetics of five Nb microalloyed Si-Mn TRIP steels was studied under continuous cooling and isothermal treatments, using dilatometric techniques, morphologic characterization, Thermocalc computational thermodynamics and Dictra numerical simulation. WDS and EDS X-ray microanalysis and Dictra numerical modeling of C, Mn and Si distribution during transformation showed that the reaction is carbon diffusion controlled and growth occurs under local equilibrium with negligible partition. CCT diagrams for austenite transformation were determined and the effect of the amount of proeutectoid ferrite and bainite precipitation on the volume fraction of retained austenite was also estimated. The CCT diagrams allowed determining the boundaries of the critical zone and the processing window to obtain bainite plus austenite microstructures. Based on this information cooling cycles were selected to perform thermomechanical treatments. Three TRIP steels were selected to simulate, in a hot torsion testing machine, two different controlled rolling sequences: Recrystallization Controlled Rolling and Conventional Controlled Rolling. The influence of the degree of deformation and the finishing temperature on the amount of retained austenite was studied. After rolling the cooling cycle comprised two isothermal treatments, one in the austenite + ferrite field and the other in the bainitic field. Increasing the strain during simulation of Recrystallization Controlled Rolling led to an increase in the volume fraction of retained austenite to the range 9 to 14 %. The energy stored during simulation bellow TNR of the Conventional Controlled Rolling led to a decrease in the volume fraction and in the carbon content of retained austenite. The Mn and C contents measured by EDS and WDS analysis of TRIP-E steel, showed that grain refinement due to recrystallization contributes to diffusion of these elements in front of the ferrite/austenite interface during precipitation.

Au cours de ma thèse, mes projets de recherche ont visé à mieux comprendre les mécanismes moléculaires contrôlant la prolifération et la spécification des cellules progénitrices dans la rétine du xénope à travers trois projets principaux. Le réseau de régulation qui contrôle la spécification des cellules progénitrices vers les sous-types neuronaux est à ce jour très peu connu. C'est dans ce contexte que j'ai étudié le rôle du facteur de transcription à domaine bHLH, Ascl1, dans la détermination des sous-types rétiniens au cours du développement. Par des approches in vivo de gain et perte de fonction d'Ascl1, des expériences d'épistasie et la recherche de ses cibles transcriptionnelles, j'ai pu mettre en évidence qu'Ascl1 (i) est impliqué dans la genèse des neurones GABAergiques rétiniens, (ii) qu'il est épistatique sur des facteurs glutamatergiques tels que Neurog2, NeuroD1 ou Atoh7, (iii) que son activité GABAergique est conférée par son domaine basique de liaison à l'ADN et (iv) que cette activité implique la régulation directe du facteur de transcription Ptf1a. Ces données ajoutent donc une nouvelle pièce au réseau transcriptionnel gouvernant la spécification des sous-types GABAergiques au cours du développement de la rétine. La mise en place correcte des types et sous-types cellulaires de la rétine nécessite une coordination avec le moment de sortie du cycle cellulaire des progéniteurs rétiniens. Dans ce contexte, j'ai contribué à l'avancée d'un projet visant à étudier le réseau de signalisation contrôlant la prolifération des précurseurs de la rétine. Par des approches in vivo, génétiques et pharmacologiques, cette étude a montré que les voies Wnt et Hedgehog s'antagonisent pour réguler l'activité proliférative des cellules souches et progénitrices rétiniennes. Nos données préliminaires suggèrent que ces voies agissent de façon opposée à la fois sur la sortie et sur la cinétique du cycle cellulaire. Ce travail nous a conduit à proposer un modèle selon lequel ces voies Wnt et Hedgehog réguleraient la balance entre prolifération et différenciation dans la rétine post-embryonnaire. Enfin, dans le but d'élargir nos connaissances sur les réseaux de signalisation et les réseaux transcriptionnels impliqués dans le contrôle de la prolifération et de la détermination cellulaire dans la rétine, j'ai également contribué à la recherche de nouveaux marqueurs spécifiques des différentes populations cellulaires rétiniennes au travers d'un crible à grande échelle par hybridation in situ. De nombreux gènes spécifiquement exprimés dans les cellules souches ou les cellules progénitrices constituent des gènes candidats pour de futures approches fonctionnelles.

碩士<br>國立成功大學<br>電機工程學系<br>102<br>Face recognition has been an active research area due to its wide range of application in information security, video surveillance systems, human-computer interaction, and criminal verification. Illumination variation, facial expression, and pose variation remain a persistent challenge in face recognition. In the thesis, we proposed a face recognition system which can resolve the problem caused by illumination variation. In our method, Retinex algorithm is adopted to remove the shadow of face firstly, and Local binary pattern is used to describe face feature. We propose global and local discriminative features for face recognition under various facial conditions based on robust feature description and feature extraction. Experimental results demonstrate that our method can improve face recognition rate when amount of training images limited.

ARS2 is a stable component of the nuclear cap-binding complex (CBC) and is critical for RNA Polymerase II transcript processing. As such, ARS2 functions in numerous RNA Polymerase II transcript processing events, which happen co-transcriptionally from initiation to termination, and post-transcriptionally during maturation and export into the cytoplasm. Developmentally, ARS2 is essential for stem cell maintenance and differentiation during embryogenesis and in neural stem cells. Two major questions in the field were: 1) how does ARS2 function in stem cell maintenance and/or differentiation? and 2) how does ARS2 distinguish between disparate RNA classes and processing complexes? In chapter 2, I show that ARS2 is required for the proliferation and cell fate decisions of progenitors in the mouse retina. Specifically, ARS2 knockdown delays cell cycle progression and leads to premature cell cycle exit. Additionally, ARS2 knockdown increases the proportion of cells expressing rod photoreceptor marker Nrl, and decreases Müller glial marker expression. Similarly, knockdown of FLASH, an essential component for replication-dependent histone transcript processing and cell cycle progression, increases the proportion of cells expressing the Nrl reporter, suggesting ARS2’s role in histone processing is contributing to cell cycle progression and fate specification in the developing retina. In chapter 3, I used bioinformatics analysis and homology modeling to classify four structural domains of mammalian ARS2, including a newly identified RNA recognition motif (RRM), and performed mutagenesis to assess their functions. The unstructured C-terminus is required for interaction with the CBC, the Mid domain is implicated in binding DROSHA, which is required for microRNA biogenesis, while the zinc finger and RRM are involved in binding FLASH. Moreover, the zinc finger is required for interacting with RNA. Collectively, this work establishes a model where ARS2 acts as a scaffold, using multiple domains to interact with distinct processing complexes in a mutually exclusive manner. It is also the first study describing the requirements of ARS2 in the developing retina. Understanding the molecular mechanisms governing progenitor proliferation and cell fate specification is crucial in order to design therapies for retinal degenerative diseases.<br>Graduate<br>0487

Tese de Doutoramento em Medicina<br>During development of the mammalian eye, the first retinal ganglion cells (RGCs) that extend to the brain are located in the dorsocentral retina, in the mouse, during mid-embryogenesis. These RGCs extend to either ipsilateral or contralateral targets, but the ipsilateral projections from the central retina do not survive into postnatal periods. The function and means of disappearance of the transient ipsilateral projection are not known. We have followed the course of this transient early ipsilateral RGC cohort, paying attention to how far they extend, whether they enter target regions in the brain and if so, which ones, and the time course of their disappearance. Several different techniques were tested for labeling the axonal projection from the central retina. While the use of a viral vector and a conditional Brn3b knock-out mouse presented difficulties in specifc labeling of RGCs and of ipsi- or contralateral projections, respectively, both the application of the lipophilic tracer DiI and in utero electroporation of GFP into central retina allowed the analysis of the growth and position of the ipsilateral and contralateral retinal projections. The proportion of ipsi- versus contralateral projections was calculated at E13.5 and 15.5 using DiI. In utero electroporation of E12.5 retina with GFP constructs was used to label axons prospectively into postnatal ages. Our results show that the earliest ipsilateral axons are segregated from the laterally-positioned contralateral axons in the optic tract. In agreement with previous reports, we found that the number of central retina ipsilateral RGCs declines after E16.5. Nonetheless, some ipsilateral axons from the central retina enter the superior colliculus (SC) and arborize minimally, but very few enter the dorsal lateral geniculate nucleus (dLGN). To understand whether caspases are involved in the disappearance of the ipsilateral projection from the central retina, immunohistochemistry experiments were performed but without conclusive results. To identify candidate genes expressed in ipsilateral vs contralateral RGC axons in the central retina at E13.5, a technique that combines retrograde labeling with DiI, applied retrogradely, with immunohistochemistry was developed. To date, no molecular marker was found that selectively labeled the transient ipsilaterally-projecting RGC axons from central retina. The results of this work and the methods developed will be useful to better understand the elimination of transient axonal projections, and their role in establishing neuronal circuits.<br>Durante o desenvolvimento do olho, as primeiras células ganglionares da retina (CGR) que se extendem para o cérebro estão localizadas na retina dorsocentral dos murganhos. Apesar destas CGR projetarem tanto para alvos ipsilaterais como contralaterais, a projeção ipsilateral da retina central não sobrevive para o período pós-natal. A função e o contexto do desaparecimento da projeção transitória ipsilateral é desconhecida. Nesta tese, seguimos o percurso desta coorte de CGR transitória ipsilaterais, atendendo à sua extensão, a invasão de alvos, e desaparecimento. Foram testadas diferentes técnicas de marcação de projeções axonais da retina central. O uso de vetores víricos e de murganhos destituídos do gene Brn3b não marcou seletivamente uma coorte de CGR na retina central, enquanto as experiências com DiI e electroporação in utero da proteína fluorescente verde (PFV) permitiram a análise da projeção ipsilateral e contralateral da retina central, esta última de forma prospetiva. A proporção da projeção ipsi- vs contralateral marcada com DiI diminui do dia de gestação embrionária E13.5 ao E15.5. As experiências com DiI mostraram também a segregação lateral dos primeiros axónios ipsilaterais no trato óptico. A electroporação in utero de um plasmídeo de PFV foi usada para marcar os axónios em estadios temporais consecutivos até idades pósnatais. Em concordância com estudos anteriores verificámos um declínio acentuado do número de CGR ipsilaterais da retina central após E16.5. No entanto, alguns axónios ipsilaterais da retina central invadem o colículo superior e arborizam minimamente, com poucos axónios invadindo a componente dorsal do núcleo geniculado lateral com ramificações curtas. Para compreender se o desaparecimento da projeção ipsilateral da retina central está relacionada com a expressão axonal de caspases, foram realizadas análises imunohistoquímicas que não revelaram resultados conclusivos. Para testar a expressão diferencial de ‘genes candidatos’ nas CGR da retina central a E13.5, foi desenvolvida uma técnica que combina o uso do marcador biofílico DiI com imunohistoquímica. No entanto com esta técnica e em estudos anteriores não foram identificados marcadores moleculares que identifiquem exclusivamente a projeção transitória ipsilateral da retina central. Os resultados desta tese e os métodos desenvolvidos nela serão úteis para uma melhor compreensão da eliminação de projeções axonais transitórias com o objetivo final de compreender melhor a formação de circuitos neuronais.<br>The work on this thesis was supported by NIH R01 EY012736 and P30 EY019007 (Carol Mason); and the Portuguese Foundation for Science and Technology fellowship SFRH/BD/74926/2010, Fundação para a Ciência e Tecnologia (FCT, Portugal)/ European Regional Development Fund (FEDER) for the PhD scholarship and the Portuguese North Regional Operational Program (ON.2 SR&TD Integrated Program – NORTE-07-0124-FEDER-000021) under the National Strategic Reference Framework (QREN), through the FEDER); the Luso-American Development Foundation, and the MD-PhD Program, University of Minho.

O setor dos transportes representa uma forma de ligação entre estados. Este satisfaz as necessidades globais ao permitir a movimentação de pessoas e bens. Sendo essencial para o desenvolvimento económico, encontra-se muitas vezes associado ao comércio mundial, representando uma ferramenta essencial e estratégica para a evolução das nações. Contudo, os custos de transporte são variáveis com poder influenciador sobre valor das mercadorias transacionadas. Sendo este um risco constante, torna-se importante gerir corretamente a sua variação e saber agir com base nos acontecimentos. Focando a variação do preço dos combustíveis e o sector de transporte de mercadorias a atuar em Portugal, procurou-se saber se as empresas em causa possuem um modelo de gestão de riscos e se têm mecanismos de defesa face às oscilações do preço do petróleo e seus derivados. Com o objetivo de compreender como são geridas as empresas de transportes de mercadorias a operar em Portugal, foi elaborado um questionário que permitiu recolher informação necessária para apurar conclusões relevantes. Com as empresas da amostra classificadas de micro a grandes empresas, sediadas em Portugal continental e nas ilhas, um dos focos do estudo foi transmitir informação credível e fundamentada. No questionário são abordados assuntos como a existência, ou não, de um modelo de gestão de riscos, qual a expectativa de evolução dos riscos do negócio e quais são as ferramentas usadas na atenuação dos riscos face à variação do preço dos combustíveis. Os resultados revelam que a maioria das empresas possui mecanismos de defesa face às oscilações do preço do petróleo, todavia resta saber se estas estão a retirar o máximo proveito dos procedimentos usados ou se, por outro lado, estes não estão a ser usados da forma correta.