Study of degradation phenomena of a polymer after irradiation

Certains polymères ont la particularité de présenter des propriétés barrières remarquables à la fois aux gaz et à la vapeur d'eau et sont alors des solutions de choix pour des applications d'emballage notamment dans le domaine alimentaire et pharmaceutique. Il est cependant parfois nécessaire de recourir à un traitement physique pour pouvoir renforcer les propriétés mécaniques d'un emballage plastique. En particulier, les rayonnements ionisants (électrons accélérés et rayons gamma), qui sont de plus en plus utilisés à l'échelle industrielle, permettent de déclencher des réactions de réticulation et de greffage. Or, ces phénomènes peuvent s'accompagner d'autres réactions non souhaitées pouvant conduire à des produits indésirables d'un point de vue esthétique, potentiellement toxique ou pour les propriétés intrinsèques des matériaux.Dans un contexte où la législation impose une connaissance approfondie des produits mis sur le marché, les effets d'un rayonnement ionisant sur un polymère de grand intérêt industriel ont été étudiés. Les modifications structurales ont été caractérisées par un large panel de techniques analytiques (RMN 13C-PDN, microspectroscopie IR, XPS, ToF-SIMS, etc), les variations de propriétés physiques ont été suivies et enfin, des solutions pour limiter les effets indésirables post-irradiation ont été étudiées.Some polymers exhibit outstanding barrier properties to both gas and water vapor and are then good candidates for packaging applications particularly in the food and pharmaceutical field. However, for some applications, it is necessary to apply a physical treatment in order to enhance the mechanical properties of plastic packaging. In particular, ionizing radiation (accelerated electrons and gamma rays), which are increasingly used in industrial scale, can trigger crosslinking and grafting reactions. However, these phenomena may be accompanied by other undesirable reactions which could lead to undesirable aesthetic or toxic products or could affect intrinsic properties of the materials.In a very demanding legislation, the effects of ionizing radiation on a polymer of great industrial interest were studied. The structural changes were characterized by a wide range of analytical techniques (NMR 13C-DNP, IR microspectroscopy, XPS, ToF-SIMS, etc), changes in physical properties were followed and finally, solutions to limit the undesirable effects created by irradiation were investigated

Exploration strategies in visual search : effect of motivation on attention

L’objectif de ce travail de thèse est de voir dans quelle mesure la motivation participe à l’engagement des processus attentionnels pour la sélection et le traitement des informations lors d’une activité de recherche visuelle. Lorsque la recherche visuelle est orientée par un but (comme une consigne) le comportement visuel d’exploration est modifié (sélection et traitement des informations). La recherche d’information suppose également un engagement de l’individu pour atteindre le but fixé en mettant en place des comportements adaptés. Cet engagement traduit une motivation qui est ici appréhendée au travers de la théorie de l’assignation d’objectif (Locke & Latham, 1990, 2002; Latham & Locke, 2007). Une tâche de recherche visuelle d’une cible spécifique, nommée par sa catégorie sur-ordonnée parmi des distracteurs de catégorie sémantique différente, associée à une consigne spécifique (de vitesse, de précision ou de faire de son mieux) ont été utilisées pour répondre aux objectifs de recherche. Les objectifs des travaux présentés ici étaient de (1) rendre compte de l’effet de l’assignation d’objectif sur le comportement de recherche, (2) étudier la relation entre l’objectif assigné et la spécificité de la tâche et (3) observer l’effet du contexte sémantique sur l’assignation d’objectif. Les trois expériences menées ont permis de mettre en évidence une relation entre la motivation et l’attention sur le comportement visuel de recherche. Ce travail de thèse ouvre sur des perspectives de recherche dans des situations plus écologiques comme les sites web ou les jeux vidéo.The aim of this study was to explore the link between motivation and attentional processes in regards to selection and information processes during visual-search task. When the visual search is goal driven (i.e., with an instruction) visual search behavior is changed (selection and information processes). During visual search, the individual need to be committed in order to reach the assigned goal by using a strategic behavior. This commitment could be defined as motivation as described in the Goal Setting theory (Locke & Latham, 1990, 2002; Latham & Locke, 2007). A visual search task was designed in which participants had to find a specific word, denominated by its super-ordinated category, among distractors. A specific instruction (speed, accuracy or do your best) was added in order to specify the goal of the search. The aims of this work were to (1) reveal the effect of the goal setting on search behavior, (2) study the relationship between the goal setting and the characteristic of the task and (3) observe the effect of semantic context on goal setting. The three experiments allow us to observe a relationship between motivation and attention on visual search behavior. This research concludes on the possibilities to lead more experiments on ecological environment like websites or video games

When Canary Primes Yellow: Effects of Semantic Memory on Overt Attention

This study explored how overt attention is influenced by the colour that is primed when a target word is read during a lexical visual search task. Prior studies have shown that attention can be influenced by conceptual or perceptual overlap between a target word and distractor pictures: attention is attracted to pictures that have the same form (rope―snake) or colour (green―frog) as the spoken target word or is drawn to an object from the same category as the spoken target word (trumpet―piano). The hypothesis for this study was that attention should be attracted to words displayed in the colour that is primed by reading a target word (for example, yellow for canary). An experiment was conducted in which participants' eye movements were recorded whilst they completed a lexical visual search task. The primary finding was that participants' eye movements were mainly directed towards words displayed in the colour primed by reading the target word, even though this colour was not relevant to completing the visual search task. This result is discussed in terms of top-down guidance of overt attention in visual search for words

Erreurs diagnostiques en médecine d'urgence (étude rétrospective de 50 dossiers d'erreurs diagnostiques au Service d'accueil des urgences du CHU de Toulouse-Purpan)

TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE3-BU Santé-Allées (315552109) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

L'assignation d'un objectif de performances a-t-elle un impact sur les processus attentionnels lors de la recherche d'informations

National audienceno abstrac

Quand canari amorce jaune : effet sur l'orientation de l'attention

National audienceno abstrac

Stratégies de résolution au MFFT : Apport de l'oculométrie cognitive

National audienceno abstrac

Recherche d'informations : assignation d'objectifs et distance sémantique

National audienceno abstrac

A FTIR/chemometrics approach to characterize the gamma radiation effects on iodine/epoxy-paint interactions in Nuclear Power Plants

International audienceThe effects of radiation on polymeric materials are a topic of concern in a wide range of industries including the sterilization, and the nuclear power industry. While much work has concentrated on systems like polyolefins that are radiation sterilized, some work has been done on epoxy systems. The epoxy system studied is an epoxy/amine paint which is representative of the paint that covers the inner surfaces of the French nuclear reactor containment buildings. In case of a severe accident on a Nuclear Power Plant, fission products can be released from the nuclear fuel to the reactor containment building. Among them, volatile iodine (I 2) can be produced and can interact with the epoxy-paint. This paint is also subjected to gamma radiation damages (due to the high dose in the containment coming from radio-nuclides released from the fuel). So the epoxy-paint studied was exposed to gamma radiation under air atmosphere after being loaded with I 2 or not. The aim of this study is to characterize by FTIR spectroscopy the iodine-paint interactions, then to identify the radiation damages on the epoxy-paint, and to check their effects on these iodine-paint interactions. This work shows the potential of multi-block analysis method (ANOVA-PCA and COMDIM = AComDim) for such a study as it allows to identify the nature of iodine/epoxy-paint interactions and to characterize the gamma radiation damages on the epoxy-paint. AComDim method conduces to the extraction of Common Components to different tables and highlights factors of influence and their interactions

Tracking pores during solidification of a Ni-based superalloy using 4D synchrotron microtomography

International audienc