Difficultés de réinsertion sociale des traumatisés crâniens graves : une altération des auto-présentations normatives

Les troubles cognitifs résultant d'un traumatisme crânien grave (T.C.G.) retentissent sur l'adapta­tion sociale et professionnelle des victimes. L'objectif de ce travail est de mettre en évidence et d'analyser les troubles fonctionnels responsables des problèmes d'insertion rencontrés par les traumatisés crâniens graves (patients T.C.G.). Nous émettons l'hypothèse que les difficultés rencontrées par ces patients proviennent d'une perception altérée des normes situationnelles et par conséquent d'une mise en œuvre défaillante des comportements adéquats à adopter. Pour tester cette hypothèse, nous avons étudié les capacités des patients T.C.G. à manipuler les stratégies d'auto-présentation en fonction de la désirabilité sociale d'un certain type de réponse (norme d'internalité) et de la nature des consignes administrées. Nous avons utilisé le questionnaire de « locus of control» de Dubois (1985) avec le paradigme d'auto-présentation (donner une bonne image de soi ou une mauvaise image de soi). Nous avons également utilisé le paradigme de « la petite annonce », les sujets devaient répondre à un questionnaire en orientant leurs réponses de manière à obtenir successivement deux postes bien différenciés (animateur et archiviste). Les tests d'intelligence sociale élaborés par O'Sullivan et Guilford (1978) ont complété notre protocole afin de mesurer les capacités des patients T.C.G. à reconnaître la structure des situations sociales. Les résultats mettent en évidence les difficultés rencontrées par les patients T.C.G. pour mettre en place les stratégies d'auto-présentation qui leur permettraient de s'adapter à une norme. Par exemple, ils présentent une perception altérée de la désirabilité du registre explicatif interne et des difficultés pour adapter leurs réponses en fonction des caractéristiques des postes à pourvoir. En raison des déficits des fonctions exécutives (touchant les activités d'analyse de la demande, de planification, de contrôle...), de l'anosognosie et des déficits métacognitifs, les traumatisés crâniens graves sont en échec pour analyser correctement les situations sociales et pour fournir un comportement adapté.Cognitive disorders resulting from a serious traumatic brain injury have some impact on the social and professional integration of the patients. The aim of this study is ta highlight and analyse the functional disorders responsible for the troubles encountered by the patients. We assessed that the encountered difficulties might came from an impaireel perception of situational standards and consequently from a mistaken irnplementation of the suitable behaviours to adopt. In order ta examine that theoty, we studied brain damaged people 's abilities ta handle self­presentation strategies in accordance with some types of expected social responses and granted instructions. We used the « Locus of control » questionnaire created by Dubois (1985) which includes the self-presentation model ; that is ta be favourably considered or not ta be favourably considered. We used as well the small ad paradigm ; the subjects had ta answer a questionnaire in such a way as ta successfully obtain two well-differentiated jobs either as an activity leader or as an archivist/ a librarian. The social tests of intelligence created by 0' Sullivan and Guilford were included in our experiment in order to evaluate the patients' capacities ta recognise the pattern of social situations. Our results point out that brain dama ged people have difficulties ta use the self-presentation strate gies, which would help them ta adapt ta a pattern (a norm). For example, they show an impaired perception of the expected pattern of internai explanation and show dijficulties to adapt their responses in accordance with the characteristics of the jobs offered. Due to the déficits in the functions of execution (reasoning, planning, controlling) in associative learning and in metacognition, brain dama ged patients fait ta analyse correctly social situations and ta react appropriately. A better-adapted understanding and mastering of their dijficulties of managing social situations should improve the patients' integration in their social and working environment

Improvements for imaging ceramics sintering in situ in ESEM

International audienceSintering of green samples of alumina produced by ice-templating was followed in situ in an environmental scanning electron microscope (ESEM) up to temperatures as high as 1375 degrees C. These alumina samples with well-defined architectures are of great interest in the field of materials science due to their high specific strength (especially in compression), low density and adaptable porosity. For the present study, they also have the advantage to exhibit an important topography, inducing interesting contrast when imaged in an ESEM. Improvements of the imaging conditions in the ESEM were essential to really follow the sintering process involving formation of necks between grains or shift of the centre of grains. This paper describes the improvements made and the results observed on the sintering process of alumina green samples processed by ice-templating

Deformation mechanism of cerium oxide nanocubes - an in situ transmission electron microscopy study

Cerium oxide nanoparticles are used in many industrial products, among which solid oxide fuel cell electrodes or catalysts. However, their mechanical properties are rarely taken into account and few studies dealt with the determination of their deformation mechanism [1, 2]. Please click Download on the upper right corner to see the full abstract

Electron microscopy contribution in the comprehension of interaction mechanisms between nanoparticles and biological cells

Parmi les nanoparticules aptes à accompagner la radiothérapie en clinique, les nanoparticules à base d oxyde de gadolinium paraissent pertinentes, de part leur multimodalité en imagerie et leur effet radiosensibilisant prouvé in vitro et in vivo. Cet effet de radiosensibilisation est exceptionnel notamment sur des cellules cancéreuses radiorésistantes de la lignée SQ20B (carcinome squameux tête et cou) et uniquement pour des doses modérées de nanoparticules (aux alentours de 0.6 mM en Gd). Les clichés de microscopie électronique ont montré que ce maximum de radiosensibilisation est dû à une internalisation maximale des particules dans le cytoplasme, notamment par macropinocytose. Ce mécanisme d internalisation est caractérisé par la formation de vésicules de grandes tailles, ou macropinosomes. Il se produit suivant deux étapes : la formation d agglomérats de nanoparticules à proximité de la membrane cellulaire puis la récupération de ceux-ci par les lamellipodes de la cellule. La première étape est fortement dépendante des caractéristiques physicochimiques des particules, plus particulièrement leur potentiel zêta qui détermine la taille de l agglomérat, et de la distance les séparant de la cellule. Dans des gammes de taille et de distance à la membrane optimales aux concentrations modérées, l agglomérat peut être récupéré par les lamellipodes de la cellule. Il s en suit une protubérance sur la membrane plasmique formant un macropinosome contenant les agglomérats de nanoparticules. Cet endosome précoce suivra ensuite le schéma d endocytose classique dans le cytoplasme en fusionnant avec des corps multivésiculaires, uniquement visible en microscopie électronique à transmission, pouvant contenir des enzymes de dégradation détruisant leur contenu. Ces enzymes rendent le pH acide à l intérieur de la vésicule. Plus les nanoparticules sont proches du noyau cellulaire plus leur effet radiosensibilisant sera efficace. Les espèces oxygénées réactives (ROS) et les électrons Auger et secondaires peuvent atteindre l ADN du noyau plus facilement. A faibles doses ( 0.7 mM) les nanoparticules forment une couronne autour de la membrane cellulaire agissant comme écran, empêchant ainsi les ROS et les électrons générés de pouvoir atteindre l ADN et induire des cassures, le noyau étant situé à quelques micromètres de la membrane cellulaire. Les résultats obtenus ouvrent la voie sur la nécessité de contrôler l'internalisation cellulaire des nanoparticules en contrôlant leur chimie, laissant envisager ainsi des opportunités prometteuses dans le domaine de la radiothérapie assistée par nanoparticules délivrant de faibles doses de radiation aux patients.Over the last few decades, nanoparticles have been studied in theranostic field with the objective of exhibiting a long circulation time through the body coupled to major accumulation in tumor tissues, rapid elimination, therapeutic potential and contrast properties. In this context, we developed sub-5 nm gadolinium-based nanoparticles that possess in vitro efficient radiosensitizing effects at moderate concentration when incubated with head and neck squamous cell carcinoma cells (SQ20B). Two main cellular internalization mechanisms were evidenced and quantified: passive diffusion and macro- pinocytosis. Whereas the amount of particles internalized by passive diffusion is not sufficient to induce in vitro a significant radiosensitizing effect, the cellular uptake by macropinocytosis leads to a successful radiotherapy in a limited range of particles incubation concentration. Macropinocytosis processes in two steps: formation of agglomerates at vicinity of the cell followed by their collect via the lamellipodia (i.e. the arms ) of the cell. The first step is strongly dependent on the physicochemical characteristics of the particles, especially their zeta potential that determines the size of the agglomerates and their distance from the cell. These results should permit to control the quantity of particles internalized in the cell cytoplasm, promising ambitious opportunities towards a particle-assisted radiotherapy using lower radiation doses.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

In situ nanocompression tests in an environmental TEM to study plasticity of cerium oxides

Cerium oxide plays an important role in several fields, among which catalysis, gas detection or fuel cells [1]. Cerium oxide nanoparticles are also used as superior abrasive particles in chemical mechanical planarization (CMP), which is a key process in semiconductor device fabrication [2]. Most of the current research focus on the synthesis of cerium oxide to optimize CMP, but analysing its deformation mechanisms is also a promising research direction [3]. Please click Additional Files below to see the full abstract

TEM observation and in situ compression tests of transition alumina prepared by high pressure compaction at room temperature

The behavior of ceramics at the nanometer scale strongly differs from the one of the corresponding bulk material. For instance, strong plastic deformation has recently been reported in isolated nanometer-sized alumina nanoparticles or MgO nanocubes, when tested in situ in a transmission electron microscope (TEM). This plastic behavior may also occur in a powder during the compaction process, even at room temperature. Controlling plastic deformation of nanoparticles during the ceramics processing might be a way to enhance their properties or to improve the processing route (compaction and sintering steps, for instance). We present here a comprehensive study of the mechanical behavior of transition alumina in the compacted powder. Please click Additional Files below to see the full abstract

Evidence for the formation of distorted nanodomains involved in the phase transformation of stabilized zirconia by coupling convergent beam electron diffraction and in situ TEM nanoindentation

International audienceThe transformation of zirconia from its tetragonal to its monoclinic phase is an important feature of the zirconia system. First found to be an advantage due to its important toughening effect, it can also be very detrimental when it occurs in the framework of low-temperature degradation, particularly in the case of biomaterial applications. One way to avoid or to control this phase transformation is to understand how it initiates and more particularly the stress states that can trigger it. A new technique available inside a transmission electron microscope seems to be particularly well suited for that type of study: convergent beam electron diffraction, a well-known technique to reveal stresses, was coupled to in situ transmission electron microscopy mechanical nanoindentation. The experiments reveal the presence of sheared nanoregions at grain boundaries. These could act as embryos for tetragonal-to-monoclinic phase transformations. This is an important first step in the understanding of the earliest stage of zirconia phase transformation

From dislocation nucleation to dislocation multiplication in ceramic nanoparticle

Magnesium oxide nanocubes are compressed along the [001] direction in situ in the transmission electron microscope. Incipient plasticity in the smaller samples is characterized by the nucleation of few 1/2{110} dislocations while a larger number of line defects is observed in larger nanocubes. Yield and flow stresses scattered stochastically above a minimum value varying as the inverse of the sample size. The upper bound is given by the reduced number of dislocation sources. Such size-dependent behaviour is justified by a detailed statistical analysis and is fully explained by the deformation mechanism

Accurate characterization of pure silicon-substituted hydroxyapatite powders synthesized by a new precipitation route

International audienceThis paper presents a new aqueous precipitation method to prepare silicon-substituted hydroxyapatites Ca10(PO4)6-y(SiO4)y(OH)2-y(VOH)2-y (SiHAs) and details the characterization of powders with varying Si content up to y = 1.25 mol molSiHA−1. X-ray diffraction, transmission electron microscopy, solid-state nuclear magnetic resonance and Fourier transform infrared spectroscopy were used to accurately characterize samples calcined at 400°C for 2 h and 1000°C for 15 h. This method allows the synthesis of monophasic SiHAs with controlled stoichiometry. The theoretical maximum limit of incorporation of Si into the hexagonal apatitic structure is y < 1.5. This limit depends on the OH content in the channel, which is a function of the Si content, temperature and atmosphere of calcination. These results, particularly those from infrared spectroscopy, raise serious reservations about the phase purity of previously prepared and biologically evaluated SiHA powders, pellets and scaffolds in the literature