Plusieurs laboratoires et centres techniques ont commencé à travailler sur la possibilité de réaliser des composés multimatériaux via la Métallurgie des Poudres. Dans un tel cas, ce procédé permet d'éviter le problème de l'assemblage et d'obtenir une production aux cotes. Les compressions dynamique (CGV) et conventionnelle sont deux voies possibles qui pourront être comparées grâce à une presse de laboratoire instrumentée pour l'analyse des phénomènes. Pour certaines poudres, la CGV permet d'améliorer les propriétés à vert et de modifier favorablement les conditions de frittage. La compression est suivie d'un frittage conventionnel. Différents types de poudres (poudres métalliques, poudres dures mais également des poudres céramiques) sont utilisés dans ce projet permettant ainsi de proposer de nombreuses applications. Cette présentation montre les premiers résultats obtenus par le groupe de recherche.

This paper describes a method for producing model composites by the powder metallurgy route in order to control the spatial distribution of the reinforcement in a metallic matrix. The materials are fabricated by successive steps including mixing and extrusion. They are then characterized in 3D by X-ray tomography.

Background. We investigated whether schizophrenic subjects are impaired in non-routine behaviour because of the dysfunction of a general executive component labelled, in neuropsychological terms, the supervisory system.

Methods. A specific verbal sequencing test was designed for this purpose. Subjects had to perform sequential reasoning with verbal material. Each test sequence consisted of a series of words presented in jumbled order. The construction of some sequences had to be done using familiar routine associations (valid conditions). In contrast, some other sequences required the overriding selection of familiar routine associations, which were inappropriate within the general context of the task (invalid conditions). Twenty verbal sequences (10 valid–10 invalid) were administered. Thirty-seven DMS-IV schizophrenic patients and 21 normal volunteers matched for age and educational level were recruited.

Results. Compared to the control group the schizophrenic group was impaired in both valid and invalid conditions. The number of ‘capture errors’ specific to supervisory system failure was significantly higher in the schizophrenic group and only the schizophrenic patients had significantly fewer correct sequences in invalid conditions than in valid conditions. Poor performance in invalid conditions alone was observed only among the schizophrenic subjects without a general cognitive defect.

Conclusions. These findings suggest that sequencing procedures requiring an executive input are impaired in schizophrenia.

The studied transformation is associated with the decomposition reaction of brucite-type hydroxides into the corresponding oxide. It is shown, by various techniques (X-ray and neutron diffraction, Raman Spectroscopy, proton conductivity) that some modifications take place in the hydroxide structure before its transformation into the oxide structure,i.e., at a temperature lower than the transformation temperature. A mechanism is proposed to account for the experimental data.