Dans les écosystèmes aquatiques, l'activité anthropique, mais aussi le contexte naturel induisent chez les organismes aquatiques des situations de stress multiples. Parmi les sources potentielles de perturbation, trois d'entre elles, d’origine chimique, ont été étudiées : contamination métallique, une contamination par un herbicide, par un mélange d’alkylphénols polyéthoxylés et enfin une contamination par un produit pétrolier. Cette démarche entre dans le cadre de la directive européenne REACh (Registration Evaluation Autorisation of CHemicals) mais aussi de la directive cadre eau DCE (directive 2000/60/CE) du parlement Européen et du Conseil établissant une politique communautaire dans le domaine de l'eau. Il s’agit en fait d'évaluer la pertinence d’une série d’indicateurs précoces de pollution (ex : biomarqueurs) afin de prédire l'effet des substances chimiques lors de contaminations chroniques ou ponctuelles du milieu aquatique. Une approche intégrée des interactions des substances ou produits sélectionnés sur la réponse génétique, protéique, cellulaire, histologique et individuelle chez la truite arc-en-ciel, Onchorynchus mykiss, a été entreprise en mésocosmes ouverts et dynamiques et en laboratoire. In vivo, une étude multimarqueurs sur des truites juvéniles femelles diploïdes a été menée à chaque exposition, de 21 ou 28 jours, et durant une période de « récupération » afin d'estimer les effets sur la physiologie des truitelles. Le mélange de nonylphénols polyéthoxylés et l’essence utilisés pour les expositions montrent ainsi des effets qui perdurent jusqu’à la fin de cette période de « récupération ». Les mésocosmes, utilisés lors de cette thèse, offrent des conditions favorables au maintien et à la croissance de truites juvéniles. (...) Dans une démarche de recherche de biomarqueurs d’effets chez une espèce modèle, transposer ces travaux chez des poissons (mâles et femelles) à des stades de développement différents pourrait ainsi permettre d’isoler les paramètres les plus pertinents, à chaque stade ou pour l’ensemble du cycle de l’espèce, afin d’apporter de nouveaux outils pour la surveillance des milieux aquatiques. / In the aquatic ecosystems, anthropic activity, but also natural environment induce several kind of stress in aquatic organisms. Among the potential sources of stress, three chemicals were studied here: a metal, a bipyridylium herbicide, a mixture of nonylphenol polyethoxylate and an oil product exposure. This study enters within the framework of the European directive REACh (Registration Evaluation Authorization of CHemicals) but also of the Directive Cadre Eau, DCE (directive 2000/60/CE) of the European Parliament. The aim is to evaluate the relevance of an early pollution indicator pool (biomarkers) in order to predict chemical substance effects during chronic exposure or after specific contaminations of the aquatic compartment. An integrated approach of the substance effects on the genetic, proteinic, cellular, histological and individual answers in the rainbow trout, Onchorynchus mykiss, were undertaken in open and dynamic mesocosms and also laboratory. In vivo, a multibiomarker study on female juvenile trout was done at each exposure, over 21 or 28 days, followed by a period of “recovery». The mixture of nonylphenol polyethoxylate and the gasoline used for the exposures thus show effects which perdurent until the end of this period of “recovery. The mesocosms used in this study offer favorable conditions for juvenile survival and growth. (...) In addition to the assessment of the measurement robustness and the biomarker relevance, we compared the data obtained in this study with the in vivo tests and those obtained using in vitro tests. This approach made possible to highlight coherent answers between in vitro the tests and in vivo markers. But in vitro tests are only one preliminary approach to quickly seek a specific toxic action. The modulation monitoring of key genes in the fish reproduction function, during a gasoline exposure, offers complementary informationabout the pollutant mode of action. We noted that the effects of the contamination on the hormonal rates were differed in time compared to the modulation of the gene transcription. In order to bring new tools for the monitoring, in a model species, of the aquatic environment,transposing this work in male and female fish at different developmental stages would enableisolating still most relevant parameters.

Se analizó la relación entre las variables de empatía, autoeficacia general y autoeficacia en situaciones sociales, así como entre sus dimensiones. La muestra estuvo conformada por 159 bomberos voluntarios (21.4% mujeres y 78.6% hombres), con una edad promedio de 36.08 años (DE = 10.90), pertenecientes a diversas bombas de Lima Metropolitana. Se les aplicó tres instrumentos: el Interpersonal Reactivity Index (IRI adaptado al español), Escala de Autoeficacia General y Escala de Autoeficacia en Situaciones Sociales. En relación a los resultados, se encontraron relaciones significativas entre la empatía y autoeficacia tanto general como en situaciones sociales. Específicamente, la dimensión Toma de Perspectiva de empatía presentó una correlación positiva, y de magnitud moderada con Autoeficacia General (rs = .44, p <. 01). Además, Toma de Perspectiva y las dimensiones de Autoeficacia para el control cognitivo (rs = .35, p <. 01) y Autoeficacia para habilidades de afrontamiento (rs = .31, p <. 01), presentan correlaciones positivas, y de magnitud moderada. Por el contrario, Distrés personal se asoció negativamente con todas las dimensiones de autoeficacia, respectivamente, (rs = -.28, p <. 01), (rs = -.27, p <. 01), (rs = .40, p <. 01), (rs = -.36, p <. 01). Adicionalmente, se encontró una relación negativa, y de magnitud moderada entre la edad y la dimensión Fantasía de empatía (rs = -.31, p <. 01). / The relationship between the variables of empathy, general self-efficacy and self-efficacy in social situations, as well as between their dimensions, was analyzed. The sample consisted of 159 volunteer firemen belonging to several fire stations of Metropolitan Lima. Of both sexes, being 21.4% women and 78.6% men, with an average age of 36.08 years (SD = 10.90). To which three instruments were applied: the Interpersonal Reactivity Index (IRI adapted to Spanish), the General Self-Efficacy Scale and the Self-Efficacy Scale in Social Situations. Regarding the results, it was found that, in general, significant relationships were found between empathy and self-efficacy, both general and social situations. Specifically, the Taking Empathy perspective dimension presented a positive correlation, and of moderate magnitude with General Self-efficacy (rs = .44, p <. 01). In addition, Perspective Taking and the dimensions of Self-efficacy for cognitive control (rs = .35, p <. 01) and Self-efficacy for coping skills (rs = .31, p <. 01), present positive correlations, and of magnitude moderate In contrast, personal distress was negatively associated with all self-efficacy dimensions, respectively, (rs = -.28, p <. 01), (rs = -.27, p <. 01), (rs = .40, p <. 01), (rs = -.36, p <. 01). Additionally, a negative relationship was found, with a moderate magnitude between age and the Fantasy of Empathy dimension (rs = -.31, p <. 01). / Tesis

Student Number : 0318213N - MCCP research report - School of Psychology - Faculty of Humanities / The following study aimed to assess coping strategies in adolescents following a suicide prevention program conducted by the South African Depression and Anxiety Group. The study aimed to assess whether there was a change in coping strategies in adolescents following the suicide prevention program. Suicide ideation was measured using the Positive and Negative Suicide Ideation Scale (PANSI) and Coping Strategies was measured using the Coping Across Situations Questionnaire (CASQ). Data was collected on 74 individuals in Grade 11 (26 males and 48 females). It was found that positive suicide ideation was not significantly different for males and females before the intervention, while females scored higher than males on the negative suicide ideation scale, indicating that females have more thoughts about suicide than males. There was no significant difference between positive and negative suicide ideation scores for both females and males following the suicide prevention program. The results further indicate that Active Coping; Internal Coping and Withdrawal Coping were not significantly different for boys and girls in the pretest, as well as in the post test. A negative relationship appears to exist between post PANSI negative ideation and Active Coping, which means that individuals who use more active coping have fewer thoughts about suicide. Active Coping is strongly related to Internal Coping and moderately related to Withdrawal Coping. Also, Internal coping is moderately related to Withdrawal Coping. The implications are that caregivers and professionals can begin to assess individual adolescent suicide ideation levels through an understanding of the individual’s coping strategy. Further research should be conducted in other socio-economic regions and rural and urban areas could be compared to get a holistic view of coping strategies and suicide ideation levels in South Africa, as a country.

L’illettrisme est passé en France de 6% des jeunes accueillis au service militaire en 1900 à plus de 9% en 2004. Différents dispositifs sont mis en place en faveur des salariés d’entreprise. Celui du secteur de la Propreté vise la « maîtrise des écrits professionnels ». Au sein de ce dispositif, qui permet de renforcer les savoirs de base des salariés, l’acquisition ou l’accroissement des capacités de lecture constitue le point commun de toutes les actions de formation examinées. Le dispositif d’accompagnement des formateurs met en évidence une professionnalisation des formateurs liée à l’obligation de formaliser des pratiques, aux réunions de confrontation des pratiques mises en place par l’OPCA et aux échanges documentaires entre les formateurs. L’analyse des pratiques des formateurs permet de dégager différentes stratégies pédagogiques dont la mesure des effets, avec le test ECCLA, montre que les progrès sont plus liés au niveau de départ, à la langue d’origine qu’aux différences entre les supports utilisés. Ces supports sont orientés soit vers l’activité professionnelle, soit vers l’activité quotidienne des personnes. / Illiteracy for young people accommodated in military service has increased from 6% to over 9% between 1900 and 2004 Various devices are in place for company employees. The hygiene sector aims at "master of professional writing." Within this device, which helps strengthen the basic knowledge of employees, acquisition or expansion of literacy is the common point of all training activities examined OU studied. The support device for trainers highlights a high professionalism of trainers linked to the obligation to formalize practices, confrontational meetings of practices implemented by the OPCA and document exchange among trainers. The analysis of the trainers’pratices can identify different instructional strategies in which the measure of the effect with the test Eccla shows that progress is more related to the starting level, language of origin and differences between the media used. These materials are geared either towards the profession, or towards the daily activity of people.

Considerando que o Exame Nacional do Ensino Médio influencia práticas de ensino, este trabalho tem como proposta verificar como Situações-problema (ZABALA e ARNAU, 2010) articuladas ao Ensino de Química podem promover o desenvolvimento de Competências e Habilidades exigidas pelo ENEM. Desenvolvemos e aplicamos uma sequência de atividades em um Cursinho Popular Comunitário. Os objetivos de trabalho consistiram em analisar as atividades procurando evidenciar as principais dificuldades conceituais e cognitivas dos alunos na resolução dos problemas, realizar um acompanhamento individual dos estudantes para verificar evoluções ou superações das dificuldades, contribuir com práticas pedagógicas no Ensino de Química, e desenvolver um estudo dos principais documentos oficiais. De forma contraditória as próprias questões do ENEM nem sempre desenvolvem Competências e Habilidades, apresentando um caráter conteudista. Assim, criamos e aplicamos situações que problematizaram o ensino. Os dados deste trabalho foram obtidos através da resolução de questões reelaboradas do próprio ENEM e outras criadas. Como análise de dados foi empregada a ferramenta Análise de Conteúdos proposta por Bardin (1977), apoiando-se em referenciais teóricos que investigam o desenvolvimento de habilidades cognitivas de alta e baixa ordem para a criação de categorias (MARCONDES E SUART (2008) e ZOLLER, (1993)). Os alunos apresentaram melhores rendimentos em questões de baixa ordem cognitiva que, segundo Zoller (1993), significa maior facilidade em recordar a informação, aplicar conhecimentos ou algoritmos memorizados. Quanto ao rendimento em questões que demandaram alta cognição, incialmente apresentou-se baixo, mas após a participação nas sequências de atividades, houve um aumento gradual e significativo. O que representou o domínio de investigação e resolução de problemas muitas vezes pouco familiares aos alunos e a tomada de decisões (ZOLLER, 1993). Acreditamos que conhecer o aluno de forma individualizada foi importante para que pudéssemos acompanhar suas dificuldades e avanços. Diversas foram as razões que comprometeram a resolução adequada dos problemas propostos, como o nível de envolvimento e compreensão dos alunos, a forma de aplicação dos conhecimentos adquiridos, e também, dificuldades conceituais e de raciocínios matemáticos. Apesar das dificuldades, ensinar por meio de competências e habilidades certamente correspondem à forma ideal de ensino. E como educadores temos a obrigação de enfrentar os desafios cotidianos da educação. / Considering that the National Examination of Secondary Education influences teaching practices, this work has as a proposal to verify as Problem Situations (ZABALA e ARNAU, 2010) articulated to the teaching of Chemistry can promote the development of Competences and Skills required by ENEM. We developed and aplied a sequence of activities in a Community Popular Course. The objectives of the study were to analyze the activities seeking to highlight the main conceptual and cognitive difficulties of the students in solving problems, to carry out an individual follow-up of the students to verify evolutions or overcome difficulties, to contribute with pedagogical practices in the teaching of Chemistry, and to develop a study of the main official documents. In a contradictory way the very issues of the E do not always develop Skills and Abilities, presenting a content character. Thus, we create and apply Situations that problematized the teaching. The data of this work were obtained through the resolution of reworked questions of the ENEM itself and other created ones. The data analysis tool was proposed by Bardin (1977), based on theoretical references that investigate the development of high and low order cognitive abilities for the creation of categories (MARCONDES AND SUART (2008) and ZOLLER, (1993)).According to Zoller (1993), the students presented better performance in questions of low order of cognition, which means that it is easier to remember the information, to apply memorized knowledge or algorithms. Concerning income in questions that demand high cognition, it was initially low, but after participation in the sequences of activities, there was a gradual and significant increase. What represented the domain of investigation and resolution of problems often unfamiliar to students and the decision-making (ZOLLER, 1993). We believe that knowing the student in an individualized way was important so that we could follow his difficulties and advances. There were several reasons that compromised the adequate resolution of the proposed problems, such as the level of student involvement and understanding, the application of acquired knowledge, and also conceptual difficulties and mathematical reasoning. Despite the difficulties, teaching through skills and abilities certainly correspond to the ideal form of teaching. And as educators we have an obligation to face the everyday challenges of education.

O presente trabalho consiste em uma pesquisa sobre como adolescentes jogam e resolvem situações-problemas relativas ao Sudoku. O objetivo foi analisar o raciocínio de escolares por meio de seu desempenho nesse jogo. Poucas são as pesquisas com jogos de regras para o desenvolvimento e aprendizagem de alunos de 9º ano do Ensino Fundamental II e, por isso, o desejo em pesquisar sobre o desenvolvimento do raciocínio por meio do jogo Sudoku com essa parcela da população escolar. O ponto diferenciador de nosso trabalho é a questão da dificuldade dos alunos em justificar suas respostas às situações- problema propostas. Para tanto, a professora-pesquisadora elaborou partidas de jogo Sudoku e situações-problema relativas ao mesmo jogo e as desenvolveu com 21 alunos de 9º ano do Ensino Fundamental II de uma escola pública do município de São Paulo. A coleta de dados foi realizada durante 15 aulas por meio de protocolos elaborados pela professora-pesquisadora. Na análise desses dados coletados, investigamos o desenvolvimento do raciocínio dos alunos ao longo dos encontros por meio de suas resoluções e da linguagem que utilizaram para justificar suas respostas aos jogos e aos Enigmas Sudoku propostos. A discussão dos resultados foi orientada principalmente pelos estudos de Jean Piaget quanto ao desenvolvimento e à aprendizagem e pelo estudo de Philippe Meirieu sobre como aprender por meio de situações-problema. Os alunos avançaram consideravelmente do primeiro encontro para o último em relação aos conceitos e procedimentos relativos aos jogos e às situações-problema e, além disso, desenvolveram sua justificação lógica, permitindo concluir que as experiências por que passaram ofereceram a oportunidade de tomarem consciência dos motivos que os orientaram em suas escolhas. Consideramos essa pesquisa relevante para o campo da Psicologia do Desenvolvimento e da Aprendizagem, pois, por meio de um jogo, aprendemos a trabalhar o raciocínio e uma forma de pensar, útil para a escola e para a vida / This work is a research about how teenagers play and solve problem situations related to Sudoku. The aim was to analyze the logic of students through their performance in that game. There are not so many researches on rule games for development and learning of students in 9th grade from Elementary School and, because of this, there was the desire to research the development of logic through Sudoku game with this part of the school population. The differentiator point of this work is the question of the students difficulty to justify their answers to the proposed problem situations. For that, the teacher-researcher elaborated Sudoku matches and problem situations related to the same game and developed them with 21 students in the 9th grade of the Elementary School in a public school in São Paulo city. The data collection was done during 15 classes by protocols elaborated by the teacher-researcher. In the analysis of the collected data, we investigated the development of the students´ logic during the encounters with the solutions and the language used to justify their answers in the proposed games and puzzles. The discussion of the results was oriented by the studies of Jean Piaget on development and learning and by the studies of Philippe Meirieu on how to learn with problem situations. The students had a considerable progress from the first encounter to the last one in relation to concepts and procedures related to the game and to the problem situations and, beyond that, they developed their logical justification, allowing us to conclude that the experiences that they had endured offered them an opportunity to be conscious of the reasons that oriented them on their choices. We consider this research relevant to the Developmental and Educational Psychology field because through a game we learned to work with logic and a way of thinking, useful for school and life

This diploma thesis addresses the issue of mutual attitudes among teachers and pupils at the upper-primary-schools. The thesis is based on the assumption that the teacher-student rapport is the significant determinant of the educational process. The aim of the thesis is to determine the factors and the ways of affecting mutual attitudes among pupils and teachers at upper- primary-schools. The theory section of the thesis focuses on the issues of attitudes and of the personality of a pupil and teacher at the upper-primary-school and on the interaction between them. The thesis describes the factors affecting mutual attitudes among pupils and teachers as well as the characterics of adolescent. It also describes the teacher's personality and his role in the educational process. The objective of the research section is to identify the characteristic features of mutual attitudes among teachers and pupils at the upper-primary-schools. The section also suggests the causes constituting specific attitudes among students and teachers at the upper-primary-schools. It seeks to determine whether the factors of teacher's age, gender, and specialization, and that of the pupil's gender are affecting the mutual attitudes among pupils and their teachers. Data will be obtained through the questionnaire survey of...

This research aims to explain teacher policy developments in England since the nineteenth century, using a historical approach. To this end, this research has demarcated the scope of teacher policy, in consideration of the main career phases of regular teachers, into three policy areas – initial teacher training, curriculum and teaching, and employment and professional development – and has divided the whole period of 1800-2008, in consideration of major political changes and the management of the research, into four periods of governments: early era governments (1800-1943), post-war era governments (1944-1979), Thatcherite governments (1979-1997), and New Labour governments (1997-2008). Teacher policy in each period has been explained in accordance with an analytical framework employing concepts of historical-institution legacies (HILs), interlinking-institution legacies (IILs), government strategies, political ideologies and socio-economic situations, devised largely on the basis of the perspectives of historical institutionalism and the statecentred approach. Teacher policy in the early era governments has been explained in terms of HILs developed to address the long-lived effects of early institutions on subsequent policies over time. The changing pattern of teacher policy during the period of government change in the last three periods has been explained in terms of IILs. This research suggests certain teacher policies in the early era governments have had a strong effect on subsequent policies, consistently or intermittently, in the form of revival. For example, apprenticeship instituted as an early form of school-based teacher training has reflected its legacy in subsequent policies such as SCITT and employment-based training. This research has found that, as IILs, striking changes in certain policies have already started before government change. Furthermore, this research argues that the three groups of governments have employed their own strategies under different political ideologies and socio-economic situations, and that most teacher policies have been made in line with their strategies.

Submitted by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-12-04T12:29:35Z No. of bitstreams: 1 JuarezMoreiradaSilvaJuniorTese2018.pdf: 3146246 bytes, checksum: c41051f9cb46fae388f3b273416604f1 (MD5) / Approved for entry into archive by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-12-04T12:29:51Z (GMT) No. of bitstreams: 1 JuarezMoreiradaSilvaJuniorTese2018.pdf: 3146246 bytes, checksum: c41051f9cb46fae388f3b273416604f1 (MD5) / Made available in DSpace on 2018-12-04T12:29:51Z (GMT). No. of bitstreams: 1 JuarezMoreiradaSilvaJuniorTese2018.pdf: 3146246 bytes, checksum: c41051f9cb46fae388f3b273416604f1 (MD5) Previous issue date: 2018-08-07 / The purpose of this research is to investigate learning situations and the fostering of autonomy in university classroom. The main objective of this thesis is to analyze which relationships exist between learning situations and the fostering of student autonomy. According to its objectives, it is a descriptive/analytical research. According to the data collection procedures, this study is a field research. Considering the nature of the data, it is qualitative. It was observed, based on participatory pedagogy, the learning situations proposed by the teacher, which are responsible by the interactions created and established in the classroom. This favored the analysis of evidence of fostering student autonomy taking into account four interrelated spheres: situated practice, overt instruction, critical schema and transformed practice. It should be emphasized that learning situations cannot be reduced and/or limited to problem situations and/or problematization of theme/content. From this result, it is concluded that the fostering of student autonomy must occur through the proposal, execution and efficient monitoring of the spheres that make up the learning situations; that is, it does not occur with the simple proposition of problem situations on scientific knowledge. It is understood that autonomy is a two-way process, it relates to the professor’s attitude as much as to the student’s, which are inserted in an educational context. Desiring the development of student autonomy requires the correct use of learning situations, as well as providing opportunities for the student to be responsible for his own individual and sociocultural learning, which will allow him, through interaction, to become an autonomous and conscious agent in social practices, through the domain of existing knowledge in society and the way to produce this knowledge. / A presente tese versa sobre situações de aprendizagem e promoção da autonomia na sala de aula universitária. Apresenta como objetivo geral analisar que relações existem entre situações de aprendizagem e promoção da autonomia do estudante. Trata-se de uma pesquisa de campo qualitativa, de natureza descritiva-analítica. Procurou-se observar, com base na pedagogia participativa, as situações de aprendizagem propostas pelo professor, as quais contribuem para as interações que se criam e se estabelecem no espaço sala de aula, o que favoreceu a análise de indícios de promoção da autonomia do estudante, levando-se em consideração quatro esferas inter-relacionadas: prática situada, instrução aberta, esquema crítico e prática transformada. Destaca-se que as situações de aprendizagem não podem ser reduzidas e/ou limitadas a situações-problema e ou problematização de tema/conteúdo. A partir desse resultado, conclui-se que a promoção da autonomia do estudante pode ocorrer mediante a proposta/execução/acompanhamento eficiente das esferas que compõem as situações de aprendizagem; isto é, não ocorre com a simples proposição de situações-problema sobre o conhecimento científico. Compreende-se que a autonomia é uma via de mão dupla, pois se relaciona com a atitude do professor quanto do estudante, os quais estão inseridos em um contexto educacional. Desejar o desenvolvimento da autonomia requer, além da correta utilização das situações de aprendizagem, ofertar ao estudante a oportunidade para que ele possa assumir a responsabilidade pelo seu aprendizado individual e sociocultural, o que lhe permitirá, por meio da interação, constituir-se em agente autônomo e consciente da sua prática social, por meio do domínio do conhecimento elaborado existente na sociedade, bem como do próprio modo de produzir esse conhecimento.

Le scanner a révolutionné la médecine permettant une accélération et une meilleure prise en charge du patient. La tomodensitométrie (TDM) s’accompagne d’un désavantage qui est l’augmentation du risque de cancer radio-induit des patients qui en bénéficient. La question se pose notamment aux urgences où l’emploi du scanner est de plus en plus prédominant, souvent après la réalisation d’une radiographie. Cette attitude, malgré tout justifiée dans la plupart des cas, peut s'avérer délétère. De ce fait les principes de radioprotection obligent à l’optimisation de la dose délivrée aux patients. L’inquiétude principale réside dans l’irradiation du thorax qui est la région la plus radiosensible du corps humain. Cela se traduit par une recherche continue d’un compromis entre l’obtention de la dose la plus basse possible tout en gardant une qualité d’image satisfaisante pour le diagnostic. Les dernières années des innovations technologiques ont été développées pour optimiser la dose au scanner ; la plus importante et la plus récente étant la reconstruction itérative (RI). La RI permet d’améliorer les index de qualité image avec une dose abaissée ou à dose équivalente reconstruite avec la classique rétroprojection filtrée, mais restituant enfin une qualité d’image modifiée. L’objectif de cette thèse était d’établir un protocole TDM du thorax délivrant une dose similaire à celle d’une radiographie du thorax de face et une de profil (ULD-CT_Ultra-low-dose-Computed Tomography) pour des indications de douleurs thoraciques en urgence sans injection de produit de contraste. La réaction des radiologues non habitués a été investiguée pour considérer la modification de l’image liée à la réduction de la dose et de l’emploi de la RI. Pour atteindre cet objectif les travaux de cette thèse se sont déroulés selon trois phases. La première phase représente une approche globale à la RI, testée sur fantômes pour optimiser les protocoles TDM de notre département. À partir des résultats obtenus, la deuxième phase a débuté. Des protocoles TDM thorax standard, à basse dose (LD-CT_Low-dose) et à très basse dose (ULD-CT) ont été testés sur des cadavres humains. La troisième phase a été caractérisée par l’application du protocole ULD-CT en pratique clinique aux urgences. Quatre articles scientifiques ont été rédigés pour représenter les trois phases de cette thèse. En conclusion, le protocole ULD-CT reconstruit avec des hauts niveaux de RI a délivré une dose inférieure à celle du niveau de référence diagnostique national pour une radiographie du thorax de face et une de profil. Ce type de protocole à très faible dose reconstruit avec RI est une alternative valable à la radiographie pour certaines indications sélectionnées pour l’exploration du thorax en urgence. En outre les radiologues malgré des remarques critiques sur la qualité d’image de l’ULD-CT ont toujours déclaré un niveau de confiance diagnostique élevé. / Computed Tomography (CT) improved patients' health care. However CT has a major drawback, which is the ionizing irradiation of the patient with an ensuing radiation-induced cancer risk. This issue is particularly observed in emergency settings, where the CT is increasingly becoming a dominant tool for the care decision-making, often after a radiographic study. Although this attitude is justified in the majority of the cases, it could be deleterious. Thus the principles of radiation safety obligate to the optimization of radiation dose delivered to the patients. The main problem is that the chest is the most radiation sensitive region of the human body. Hence the research of the better trade-off between the dose reduction and a diagnostic image quality is mandatory. Recently, several technological improvements have been developed to optimize the radiation dose at CT. The newest and most important innovation is the iterative reconstruction (IR). IR improves the quality image indexes of a CT image generated with a lowered dose or equivalent to that reconstructed with filtered back projection. Finally this reconstruction method renders a modified CT image. The goals of this PhD thesis were: i) to establish an unenhanced CT protocol, delivering a dose in the range of a radiographic study (ULD_ultra-low-dose-CT), for chest pain indications with no need of contrast media administration and ii) to investigate the reaction of unaccustomed radiologists to ULD-CT imaging. To accomplish these tasks the work of this thesis has been split in three phases. In the first phase a study approaching globally the IR was carried out testing several CT protocols on phantoms, in order to optimize the CT protocols of our institution. The outcomes of this study opened the second phase. A standard dose CT, a low-dose-CT and an ULD-CT protocols were acquired on the chest of human cadavers. The third phase was characterized by the application of ULD-CT in clinical practice in emergency settings. Four scientific articles were produced to communicate the results of this doctorate work. In conclusion, the ULD-CT protocol, reconstructed with high strengths of IR, conveyed a dose lower than the one of the national diagnostic reference level for a double projections chest X-ray. This ULD-CT protocol with IR is a valid alternative to the radiography for the study of the chest, for selected indications in emergency settings. Moreover, despite the radiologists were censorious about the ULD-CT image quality, they demonstrated always a high diagnostic confidence level.