This thesis examines the structure and regulated expression of the gene encoding the neuroendocrine peptides neurotensin and neuromedin N (NT/N gene). Previous studies have shown that expression of NT/N mRNA and NT peptide in PC12 cells are strictly dependent on simultaneous exposure to combinations of nerve growth factor (NGF), glucocorticoids, activators of adenylate cyclase, and lithium ion. My objective was to characterize the cis-regulatory DNA sequences involved in regulated expression of this gene. The initial focus of this study was an analysis of the structure, tissue-specific expression, and exon evolution of the rat NT/N gene. Nucleotide sequence comparisons between the rat gene and the canine and bovine cDNA sequences indicated that the predicted structure of a 170 amino acid precursor protein is highly conserved. Furthermore, the close similarity between the two cDNAs suggested that identical precursor proteins are expressed in neural and endocrine tissues. RNA analysis revealed that the gene is transcribed to yield two distinct mRNAs, 1.0 kb and 1.5 kb in size. The two mRNA species differ only in the size of their 3' untranslated regions. Interestingly, the smaller mRNA is predominant in the gastrointestinal tract, while both mRNAs are equally abundant in all neural tissues examined, except the cerebellum, where no expression was observed. Transient transfection assays were used to delineate the rat NT/N gene cis-regulatory DNA sequences. Progressive deletion of the NT/N 5' flanking region revealed that sequences between -216 and +56 of the NT/N gene are sufficient to confer the full spectrum of responses of the endogenous gene to either of two reporter genes. A detailed mutational analysis of the NT/N control region indicated that it is composed of an array of inducible cis-regulatory elements, including an AP-1 site, two cAMP-responsive elements (CREs), and a glucocorticoid-responsive element (GRE). Specific mutations to the AP-1 site and either CRE suggested that these elements are functionally interdependent. I propose that this array of cis-regulatory sequences in the NT/N transcriptional control region serves to integrate multiple environmental stimuli into a unified transcriptional response. To further examine the role of the AP-1 site and CREs in the NT/N promoter, reporter genes containing either a single or multiple AP-1 or CRE sites were expressed in PC12 cells and protein kinase A-deficient PC12 cells treated with forskolin, NGF, and lithium, either individually, or in combination. The results indicated that lithium and NGF markedly activate promoters containing multiple AP-1 sites, but not a single site, and that these effects were additive. Both agents potentiated forskolin-induced activation of promoters containing a single or multiple CREs, but had no effect, individually. Also, in contrast to the activation of multiple AP-1 sites by lithium and NGF, activation of the NT/N promoter and promoters containing CREs is absolutely dependent on protein kinase A activity. These results suggested that promoters containing multiple AP-1 sites, or a single AP-1 site in the context of nearby active CREs, are selectively activated by lithium and NGF in PC12 cells. Based on the results of this thesis I have proposed a model to account for the complex transcriptional regulation of the NT/N gene in PC12 cells. I have also addressed the relevance of these findings to the mechanisms of phenotypic plasticity of embryonic neural crest cells, NGF-induced neuronal differentiation, and the pharmacological actions of lithium.

L'objet de la thèse était la commande d'un système de nano-positionnement par couranttunnel, avec application sur la plateforme expérimentale développée au laboratoire Gipsa-lab.Cette thèse s'inscrit dans le cadre de la commande des systèmes micro et nano-mécatronique,pour des applications en microscopie en champ proche ou dans des systèmes depositionnement ultra-précis. A l'échelle nanométrique, des problèmes de bruits de différentesnatures, vibrations, non-linéarités et instabilité influencent la précision et la qualité de mesuredu système. L'objectif était donc de pouvoir faire face à ces contraintes en utilisant destechniques modernes de commande robuste. Dans cette thèse, un système de mesure à couranttunnel a été modélisé et le problème de contrôle lié aux performances de mesure souhaitées aété formulé. Les performances souhaitées, à savoir la précision de la mesure et le rejet decertaines perturbations avec la robustesse adéquate, ont été atteints en utilisant des lois decommande robuste. Ces lois de commande ont été validées expérimentalement (àl'atmosphère ambiante) sur une plateforme du Gipsa-lab. À la fin de cette thèse, pour uneapplication de scanner de surface à l'échelle atomique, une modélisation dynamique MIMOdu système a été proposée et un régulateur MIMO afin de réduire l'erreur de positionnementdûe au couplage a été validé en simulations. / The objective of this thesis was to control the nano-positioning system using tunneling current with the real-time validation over an experimental platform developed in Gipsa-lab. This thesis lies in the domain of control for micro and nano-mechatronics systems for the applications of scanning probe microscopy and ultra-precise positioning. At nanometer scale, the problems of noise, vibrations, nonlinearity and instability influence the precision of the measurement. The objective was to deal with these constraints by using the modern techniques of robust control. In this thesis, a system of tunneling current measurement has been modelled and the control problem has been formulated in terms of desired measurement performances. Then, robust control design laws are analyzed in order to achieve better performances in terms of measurement precision and rejection of certain disturbances with robustness. These control laws are experimentally validated (at ambient atmosphere) for a platform of Gipsa-lab. At the end of this thesis, a dynamic modelling of MIMO system for an application of scanning the surface with an atomic resolution has been proposed and a MIMO controller in order to reduce the positioning error due to coupling has been validated in simulations.

In diverse eukaryotic organisms, double-stranded RNA (dsRNA) induces robust silencing of cellular RNA cognate to either strand of the input dsRNA; a phenomenon now known as RNA interference (RNAi). Within the RNAi pathway, small, 21 nucleotide (nt) duplexed RNA, dubbed small interfering RNAs (siRNAs), derived from the longer input dsRNA, guide the RNA induced silencing complex (RISC) to destroy its target RNA. Due to its ability to silence virtually any gene, whether endogenous or exogenous, in a variety of model organisms and systems, RNAi has become a valuable laboratory tool, and is even being heralded as a potential therapy for an array of human diseases. In order to understand this complex and unique pathway, we have undertaken the biochemical characterization of RNAi in the model insect, Drosophila melanogaster. To begin, we investigated the role of ATP in the RNAi pathway. Our data reveal several ATP-dependent steps and suggest that the RNAi reaction comprises as least five sequential stages: ATP-dependent processing of double-stranded RNA into siRNAs, ATP-independent incorporation of siRNAs into an inactive ~360 kDa protein/RNA complex, ATP-dependent unwinding of the siRNA duplex to generate an active complex, ATP-dependent activation of RISC following siRNA unwinding, and ATP-independent recognition and cleavage of the RNA target. In addition, ATP is used to maintain 5´ phosphates on siRNAs, and only siRNAs with these characteristic 5´ phosphates gain entry into the RNAi pathway. Next, we determined that RISC programmed exogenously with an siRNA, like that programmed endogenously with microRNAs (miRNAs), is an enzyme. However, while RISC behaves like a classical Michaelis-Menten enzyme in the presence of ATP, without ATP, multiple rounds of catalysis are limited by release of RISC-produced cleavage products. Kinetic analysis of RISC suggests that different regions of the siRNA play distinct roles in the cycle of target recognition, cleavage and product release. Bases near the siRNA 5´ end disproportionately contribute to target RNA-binding energy, whereas base pairs formed by the central and 3´ region of the siRNA provide helical geometry required for catalysis. Lastly, the position of the scissile phosphate is determined during RISC assembly, before the siRNA encounters its RNA target. In the course of performing the kinetic assessment of RISC, we observed that when siRNAs are designed with regard to 'functional asymmetry' (by unpairing the 5´ terminal nucleotide of the siRNA's guide strand, i.e. the strand anti-sense to the target RNA), not all of the RISC formed was active for target cleavage. We observed, somewhat paradoxically, that increased siRNA unwinding and subsequent accumulation of single-stranded RNA into RISC led to reduced levels of active RISC formation. This inactive RISC did not act as a competitor for the active fraction. In order to characterize this non-cleaving complex, we performed a series of protein-siRNA photo-crosslinking assays. From these assays we found that thermodynamic stability and termini structure plays a role in determining which proteins an siRNA will associate with, and how association occurs. Furthermore, we have found, by means of the photo-crosslinking assays, that siRNAs commingle with components of the miRNA pathway, particularly Ago1, suggesting overlapping functions or crosstalk for factors thought to be involved in separate, distinct pathways.

Transcription of the osteocalcin gene, which encodes a bone-specific 10 kDa protein, is controlled by the coordinated utilization of modularly organized basal and hormone-responsive enhancer elements. Activation of these sequences involves the interaction of specific transcription factors to these promoter elements. It is becoming increasingly accepted that nuclear architecture provides a basis for support of tightly regulated modulation of cell growth and tissue-specific transcription which is required for the onset and progression of differentiation. Thus packaging of DNA as chromatin can facilitate the cooperative interaction between activities of independent regulatory elements that contribute to the level of transcription. Here, we show that a specific nucleosomal organization supports the constitutive expression of the osteocalcin gene in ROS 17/2.8 rat osteosarcoma cells and that chromatin remodeling directly correlates with the developmentally regulated transcriptional activation of this gene in normal diploid osteoblasts. By combining DNase I, micrococcal nuclease, and specific restriction endonuclease digestion analysis, we observed that the presence of DNase I hypersensitive sites (proximal: -170 to -70, and distal: -600 to -400) and a selective nucleosome positioning over the osteocalcin gene promoter are directly associated with developmentally stage-specific transcriptional activation in bone-derived cells. In addition, we found that chromatin hyperacetylation prevents a key transition in the chromatin structure which is required for the formation of the distal DNase I hypersensitive site. This transition involves the interaction of specific nuclear factors and is necessary for the subsequent ligand-dependent binding of the vitamin D receptor complex. Finally, we have established a requirement for sequences residing in the proximal region of the osteocalcin gene promoter for both formation of the proximal hypersensitive site and basal transcriptional activity. Our approach was to assay nuclease accessibility in ROS 17/2.8 cell lines stably transfected with promoter deletion constructs driving expression of a CAT reporter gene.

[pt] Esta dissertação tem como objetivo analisar práticas pedagógicas no ensino de Design Gráfico baseadas nas Metodologias Ativas (MA). A pesquisa fez um mapeamento de tais metodologias, que foram originalmente concebidas para aplicação em áreas de conhecimento relacionadas às disciplinas exatas. Partindo da articulação das MA e práticas pedagógicas para o ensino de Design, foram estruturados, propostos e experimentados em sala de aula exercícios e dinâmicas relacionados às metodologia em questão. Realizou-se um estudo de campo de pesquisa-ação em disciplina projetual de Design ao longo de três semestres e, no último semestre, registrou-se o diário de bordo da disciplina, aula a aula, além da realização de entrevistas com professores de Design com o intuito de conhecer suas práticas pedagógicas. Também foram feitas entrevistas com alunos participantes, que foram gravadas e analisadas à luz da taxonomia do aprendizado significativo de Fink (2007). Os resultados foram registrados, classificados e documentados, e criou-se um instrumento de análise das práticas pedagógicas relatadas, cuja interpretação consolidada, no capítulo final, resultou na proposição e reflexão acerca das estratégias pedagógicas que se buscava atingir. / [en] This dissertation aims to analyze pedagogical practices in Graphic Design teaching based on active methodologies. The research mapped out such methodologies, which were originally designed for application in areas of knowledge related to exact subjects. Starting from the articulation of AM and pedagogical practices for the teaching of Design, exercises and dynamics related to the methodologies in question were structured, proposed and experienced in the classroom. An action-study field study was carried out in a projectual Design discipline over three semesters, and in the last semester a class diary was written, besides interviews with Design teachers on purpose to know their pedagogical practices. Student interviews were recorded and analyzed in light of Fink s (2007) taxonomy of significant learning. The results were recorded, classified and documented, and an instrument of analysis of the reported pedagogical practices was created, whose consolidated interpretation, in the final chapter, resulted in the proposals and reflections about the pedagogical strategies that were sought to achieve.

L’étude des ouvrages de physique publiés au 18e siècle montre que l’évolution depuis le 17e siècle est loin de se limiter à l’approfondissement des seules découvertes de Newton, comme on a souvent tendance à le présenter aujourd’hui. La physique mécaniste de Descartes, attaquée par Newton, va continuer de se développer avec l’aide de nombreux savants, en particulier de l’Académie des Sciences parisienne. Les débats entre cartésiens et newtoniens ne sont toujours pas éteints dans les années 1740. Ce véritable duel scientifique de plus d’un demi-siècle est au cœur d’une réflexion plus large sur la physique et s’exerce sur plusieurs plans : Mathématisation, Concepts, définitions, lois, rôle de l’expérience et des hypothéses, Problèmes philosophiques : les principes, la recherche des causes, les problèmes théologiques. L'objet de cette thèse est de montrer que la diversité des approches et des méthodes tout au long du premier 18e siècle va permettre l’émergence d’une nouvelle conception de la physique. Cette diversité se manifeste dans les écrits d’auteurs nombreux, les savants eux-mêmes, mais aussi ceux qu’on a appelés les transmetteurs, dont le rôle fut très important. / The study of books on physics published in the 18th century shows that the evolution since the 17th century is much more than just a furthering of the discoveries of Newton, as we often tend to present it these days. Descartes’s mechanistic physics, severely criticized by Newton, was to develop with help from many scientists, particularly from the Academy of Sciences in Paris. The discussions between Cartesians and Newtonians did not end in the 1740’s. This real scientific duel, which lasted over half a century, was the heart of a broader way of thinking about physics which operated on several levels: Mathématization, Concepts, définitions, laws, the role of experimentation and hypotheses, Philosophical problems: principles, the search of the causes, theological problems. The aim of this thesis is to show that the variety of the approaches and the methods throughout the early 18th century was to allow the creation of a new conception of physics. This variety appears in the works of many authors, who were either scientists themselves, or transmitters of science, who played a very important role, too.

Este trabalho aborda o uso de experimentação remota como forma de aprimorar a educação em sistemas de controle e automação. Para isto, uma arquitetura é proposta, onde experimentos reais podem ser combinados com partes simuladas (virtuais) criando um experimento de realidade mista. Um ambiente de ensino à distância, acessível na Internet, engloba o experimento remoto para proporcionar maiores recursos pedagógicos, guias e materiais educacionais teóricos aos estudantes. As diversas tecnologias, presentes no estado da arte, utilizadas para a elaboração da arquitetura são descritas e comparadas para facilitar o entendimento das escolhas realizadas. Trabalhos correlatos são apresentados para descrever o estado da arte dos laboratórios de experiências remotas de diversos tipos. Com base neste estudo, deficiências e vantagens são apontadas para a criação da arquitetura proposta. Para validar a arquitetura são propostos diversos estudos de caso com implementações utilizadas nos cursos de automação e controle da instituição na qual este trabalho está relacionado, ou ainda em cursos de educação à distância para atingir um público mais amplo. Esta dissertação está relacionada como resultado importante do consórcio internacional RExNet, financiado pelo projeto europeu Alfa, do qual a UFRGS faz parte. / This work aims to the use of remotely web-based experiments to improve the learning process of automation and control systems theory courses. An architecture combining virtual learning environments, remote experiments, students guide and experiments analysis is proposed based on a wide state of art study. The validation of the architecture uses state of art technologies and new simple developed programs to implement the case studies presented. All implementations presented in this work uses an Internet accessible virtual learning environment providing educational resources, guides and learning material to create a distance learning course associated with the remote mixed reality experiment. The experiment is integrated in the learning environment and support the mixture of real equipments combined with simulated ones (virtual). This mixture of equipments (components) is automatic controlled by the user and is a new developed technology called interchangeable components. The state of art section of this work presents, compare and describes several technologies used to implement the proposed architecture. Related work of remote experimentation and virtual learning environments is also presented. The architecture was elaborated based on appointed advantages and drawbacks of the related studies. This work is part of the RExNet consortium, supported by the European Alfa project.

Este estudo aborda a formação em psicologia em contexto de intervenção num projeto de extensão acadêmica. O contexto de pesquisa envolve experiências com um programa de trabalho educativo que atende jovens que cumprem medidas socioeducativa e/ou protetiva e equipes que operam essa política pública, conforme o Estatuto da Criança e do Adolescente. Esta demanda da comunidade, enunciada na universidade através da extensão acadêmica, diz de uma produção social contemporânea brasileira que força um encontro entre a vida destes jovens e os modos de formar-praticar psicologia neste contexto. A problematização do processo de formação em psicologia nessas práticas é construída com os conceitos de experimentação, enunciação coletiva e subjetivação, no diálogo com Gilles Deleuze, Félix Guattari e Michel Foucault. Ao criar um regime de visibilidade "do não saber o que fazer" que acompanha a formação e a produção de conhecimento, como paradoxo que inventa outros modos de formar-praticar psicologia, se dá também a interlocução com Jacques Rancière e sua obra "O mestre ignorante". Com a indagação filosófica e sob a orientação da pesquisa-intervenção, foi utilizada uma ferramenta metodológica construída na experiência do grupo de trabalho da psicologia (professora, bolsistas e estagiários) nessas atividades de extensão, com o uso de uma modalidade de escrita em ambiente à distância, através de listas de discussão. A relevância deste processo vincula-se diretamente a uma proposta pedagógica e metodológica própria ao contexto e objetivo do uso deste tipo de ferramenta numa experiência de formação em ensino superior orientada pelo Laboratório de Linguagem, Interação e Cognição (LELIC) da Faculdade de Educação da UFRGS. Esse modo de escrever, denominado de diário coletivo, tem como pragmática a enunciação coletiva de matérias de expressão que emergem no agenciamento de uma psicologia que inventa sua prática na relação com as micropolíticas juvenis. Com essa matéria de expressão foram produzidas cartografias de práticas institucionais e práticas de si de uma formação em psicologia orientada pelo princípio ético-estético-político. Ao cartografar o "não saber o que fazer" no processo de formar psicólogos encontra-se a potencia de um paradoxo que força o pensamento e inventa uma psicologia que forma e se forma na composição de cartografias de um língua menor da psicologia. Assim, é construído um diálogo com formulações teórico-metodológicas da psicologia brasileira que afirmam possibilidades de intervenção nas zonas de interferência da esquizo-análise. / This study approaches higher education in psychology in the context of an intervention in a higher academic extension project. The research context involves experiences with an educative work program that supports young people in fulfilling socioeducational and/or protective measures and the work groups that operates in this public policy, as praised by ECA (Child and Adolescent Statute). This community need, enunciated at the university through the academic extension program, describes a Brazilian social contemporary production that forces a meeting between the life of these young people and the ways to become and practice psychology at this field. The problematization of higher education psychology process in these practices is constructed with the concepts of experimentation, collective enunciation collective and subjectivation, in the dialogue with Gilles Deleuze, Félix Guatarri and Michel Foucault. In creating a visibility regime of "not knowing what to do", that follows the formation and production of knowledge, as a paradox that invents other ways of become and practice psychology, it gives also a interlocution with Jaques Rancière and his work "The ignorant Master". Within the philosophical question and under the intervention research orientation, it was used a methodological tool built upon the experience of the work group in psychology course (teachers, fellowship and internship students) on these extension activities, with the use of a written modality in distant environment, trough discussion lists. The relevance of this process is directly associated to a pedagogical and methodological proposal, specific to the context and aim of using this type of tool in an experience of higher education, oriented by Cognition, Interaction and Language Laboratory (CILL) of Education School of Federal University of Rio Grande do Sul. This way of writing, named collective diary, has as its pragmatic a collective enunciation of expressive materials that emerges in the assemblage of a psychology that invents its practices in the relation with youth micropolitics. With this expression material, institutional and self practice cartographies were produced, of a academic education in psychology orientated by the politic-aesthetic-ethic principle. In the act of cartograph the "not knowing what to do" in the process of academic education in psychology it finds the power of a paradox that forces the thinking and invents a psychology that educates and educates itself in the cartography composition of minor language in psychology. Thus, a dialogue is constructed with theoric-methodological formulations of Brazilian psychology that states possibilities of intervention in the interferences zones of schizoanalyses.

Esta tese pretende apresentar uma contribuição aos estudos em educação e, mais especificamente, para a formação de professores em serviço, por meio de um debate sobre as condições de criar e inventar, para além da reprodução de modelos. Essa discussão que, via de regra, já vem acontecendo há mais tempo, tem defendido a invenção do novo como ruptura dos modos dominantes de pensar e aprender que tendem a cópia e a reprodução. Já a tese explorou as possibilidades de invenção, dando-se na coexistência com os modelos instalados e vigentes de pensar e aprender, sem ruptura anunciada ou como pressuposto de partida, mas por interversões que desviam as linhas instituídas como rotinas e hábitos nos modos de ensinar e aprender em sala de aula. A problematização inicial é de natureza filosófica, mas a ciência, atualmente contagiada e desafiada nessa direção, permitiu que esse estudo se aproximasse do tênue e intenso fio que faz comunicar esses dois planos: o filosófico e o científico. As linhas de tensionamento para pensar a invenção em educação, e mais especificamente a invenção na sala de aula e na formação de professores, foram estudadas, para esta tese, a partir das produções filosóficas de Bergson, Deleuze e Guattari, e científicas com Prigogine. Essas linhas apresentam- -se, num sentido, como tendência a produzir um observador externo, explicador do mundo, sendo arrastado pelos contextos práticos e utilitários da vida cotidiana, podendo ser denominadas de tendência ao desenvolvimento. Em outro sentido, coexistente ao primeiro, as linhas em tensão apresentam-se em curva, fazendo da resistência uma tendência ao envolvimento, que, pelo contágio de si, e pela implicação, permitiria ultrapassar e inverter as tendências explicativas. As condições de produção desta tese, ENTRE essas duas linhas, são dadas pelo vínculo com um grupo de pesquisa em desenvolvimento no Laboratório de Estudos em Linguagem, Interação e Cognição - LELIC - da Faculdade de Educação da UFRGS, com o Projeto Civitas e pelos grupos de estudos com os professores em formação. Desse agenciamento "LELIC-Civitas-professores", que é o meio, o entrelinhas, entre-tempo, emerge um campo de experimentação e problematização das ideias e do pensamento. Assim, a tese explorou tanto a "invenção das condições de invenção" de um pesquisador, de uma sala de aula, de um professor, de um grupo, de uma rede, como as inversões que se produzem nas linhas que tendem a desviar, das mudanças contínuas e em devir, próprias da duração dessa invenção. O estudo das inversões passou por uma discussão sobre modos de simular e de pensar e prosseguiu nos capítulos finais da tese com a exploração do plano do conceito de interveRsão e dos diagramas de interveRsões. / This thesis intended to make a contribution to studies in education and more specifically to educate teachers in service, through a debate on how to create and invent, beyond the reproduction of models. This discussion, which as a rule has been going on, supports inventing new thoughts and rupturing with dominant modes of thinking and learning, which have a tendency to copy and to reproduce. This thesis, on the other hand, explored the possibilities for invention, which happens in coexistence with the traditional and current models to think and learn, without a rupture as such, but with inversions that deviate from the lines established as routines and habits and modes of teaching and learning in the classroom. The initial questioning is philosophical in nature, but science, currently infected and challenged in this direction, enabled this study to approach the delicate and heavy thread communicating the philosophical to the scientific level. The lines of tension to think the invention in education and more specifically the invention in the classroom and in teacher education were studied for this thesis from the philosophical productions of Bergson, Deleuze and Guattari, and the scientific productions of Prigogine. These lines present themselves in one sense as a tendency to make an outside observer, explainer of the world, drawn by the utilities and practical contexts of everyday life that can be called a trend towards development; in another sense, alongside the first one, tension lines present as curved lines that turn resistance into a trend to involvement that through contagion of self, and by implication, would help to overcome and reverse the explanatory trends. The conditions for the production of this thesis between these two lines are given by a link to a research group under development at the Laboratory for Studies in Language, Interaction and Cognition - LELIC, Faculty of Education at the UFRGS with the Civitas Project and groups of studies with teachers under education. From this agency 'LELIC-Civitas-teachers', which is the milieu, the intertwining agent, the time between, emerges a field of experimentation and questioning of ideas and thought. Therefore, this thesis explored both the 'invention of the conditions for invention' of a researcher, of a classroom, of a teacher, of a group, of a network, and the inversions that occur in those lines that tend to deviate from continuous changes and to become, throughout the duration of the invention. The study of inversions has gone through a discussion of ways to simulate and to think and continued in the final chapters of the thesis with the construction of the concept of interveRsion and interveRsion diagrams.

Submitted by João Vitor Granja de Almeida (joaov.granja@gmail.com) on 2015-06-26T14:17:01Z No. of bitstreams: 1 JoaoGranja_DissertacaoEPGE.pdf: 491088 bytes, checksum: 6b308d5edc8ccc344f8fbbfb2b5ced15 (MD5) / Approved for entry into archive by BRUNA BARROS (bruna.barros@fgv.br) on 2015-06-30T14:06:29Z (GMT) No. of bitstreams: 1 JoaoGranja_DissertacaoEPGE.pdf: 491088 bytes, checksum: 6b308d5edc8ccc344f8fbbfb2b5ced15 (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-07-03T17:33:40Z (GMT) No. of bitstreams: 1 JoaoGranja_DissertacaoEPGE.pdf: 491088 bytes, checksum: 6b308d5edc8ccc344f8fbbfb2b5ced15 (MD5) / Made available in DSpace on 2015-07-03T17:33:51Z (GMT). No. of bitstreams: 1 JoaoGranja_DissertacaoEPGE.pdf: 491088 bytes, checksum: 6b308d5edc8ccc344f8fbbfb2b5ced15 (MD5) Previous issue date: 2015-04-30 / Nesse artigo, eu desenvolvo e analiso um modelo de dois perí odos em que dois polí ticos competem pela preferência de um eleitor representativo, que sabe quão benevolente é um dos polí ticos mas é imperfeitamente informado sobre quão benevolente é o segundo polí tico. O polí tico conhecido é interpretado como um incumbente de longo prazo, ao passo que o polí tico desconhecido é interpretado como um desa fiante menos conhecido. É estabelecido que o mecanismo de provisão de incentivos inerente às elei cões - que surge através da possibilidade de não reeleger um incumbente - e considerações acerca de aquisi cão de informa cão por parte do eleitor se combinam de modo a determinar que em qualquer equilí brio desse jogo o eleitor escolhe o polí tico desconhecido no per íodo inicial do modelo - uma a cão à qual me refi ro como experimenta cão -, fornecendo assim uma racionaliza cão para a não reelei cão de incumbentes longevos. Especifi camente, eu mostro que a decisão do eleitor quanto a quem eleger no per odo inicial se reduz à compara cão entre os benefí cios informacionais de escolher o polí tico desconhecido e as perdas econômicas de fazê-lo. Os primeiros, que capturam as considera cões relacionadas à aquisi cão de informa cão, são mostrados serem sempre positivos, ao passo que as últimas, que capturam o incentivo à boa performance, são sempre não-negativas, implicando que é sempre ótimo para o eleitor escolher o polí tico desconhecido no per íodo inicial. / In this paper, I develop and analyze a two-period model where two politicians compete for the preference of a representative voter, who knows how benevolent one of the politicians is but is imperfectly informed about the benevolence of the second politician. The known politician is interpreted to be a long time incumbent, whilst the unknown politician is taken to represent a lesser known challenger. I show how the incentive provision mechanism inherent in elections - which arises through the possibility of voting an incumbent out of offi ce - and information acquisition considerations by the voter combine to determine that in any equilibrium of the game the voter chooses the unknown politician in the initial period of the model - an action referred to as experimentation -, thus providing a rationale for voting long time incumbents out of offi ce. Speci cally, I show that the voter's decision over whom to elect in the initial period boils down to a comparison of the informational benefi ts of choosing the unknown politician and the economic losses of doing so. The former, which captures information acquisition concerns, is shown to be positive, whereas the latter, which captures incentive provision, is shown to be non-positive, implying that it is always optimal for the voter to choose the unknown politician.