Mechanical behavior of polycrystals: Coupled in situ DIC-EBSD analysis of pure copper under tensile test

Understanding the mechanisms at the microstructure scale is of great importance for modeling the behavior of materials at different scales. To this end, digital image correlation (DIC) is an effective measurement method for evaluating the strains generated by various loading conditions. The objective of this paper is to describe the experimental setup and the use of high resolution digital image correlation (HRDIC) during in situ Scanning Electron Microscope (SEM) tests in order to provide a coupling between polycrystalline modeling and experiment in the near future. The HRDIC technique is used to evaluate the tensile behavior of a pure copper polycrystal at room temperature. Several magnitudes are investigated in order to discuss the representativeness of the results with respect to the macroscopic scale. The selected image correlation parameters are discussed regarding the ability of the technique to define inter- and intra- granular strain heterogeneities. Finally, based on EBSD analyzes, the impact of grain orientation on the mechanical behavior is discussed. The Schmid factor, calculated from a macroscopic stress, appears to be the determining factor concerning the orientation of the location bands. On the other hand, it is not sufficient to define the mean strains in the grains

Towards an image quality criterion to optimize Digital image correlation. Use of an analytical model to optimize acquisition conditions

Digital image correlation (DIC) is expanding in many fields. In particular, it requires that the acquisition conditions and speckle be adapted to each application. A new methodology allowing to define the quality of the images in a fast and precise way is proposed. An analytical model based on mean intensity gradient of speckle pattern criterion and the standard deviation of displacement on images has been proposed. The model can be used on the whole image or by creating subsets in the image. Standard deviation maps of displacement are obtained. The methodology makes it possible to save a considerable amount of time compared to the full DIC calculation to optimize the image acquisition conditions, the speckle and the DIC parameters

Residual bodies activate Sertoli cell interleukin-1 alpha (IL-1α) release, which triggers IL-6 production by an autocrine mechanism, through the lipoxygenase pathway

International audienceInterleukin-1 (IL-1) and IL-6 are produced by Sertoli cells. As IL-1 stimulates IL-6 production in some tissues, the cascade of events that results in IL-6 secretion by Sertoli cells was studied. The addition of IL-1 alpha to Sertoli cells resulted in a time-dependent increase in IL-6 secretion. Incubation of Sertoli cells with two known stimulators of IL-1 production, lipopolysaccharide (LPS) and residual bodies, resulted in a significant increase in IL-1 release into the medium several hours before IL-6 release. That IL-1 is essential for IL-6 production from Sertoli cells was established by blocking the actions of LPS and residual bodies with an anti-IL-1 alpha antibody. An increase in the release of IL-1 before IL-6 was also observed in medium obtained from staged segments of intact seminiferous tubules; IL-1 reached a maximum level at stage VIII, when mature spermatozoa are released and residual bodies are formed and phagocytosed. The secretion of IL-6 was low during this stage and then increased progressively from stage IX onward, consistent with IL-1 stimulation of IL-6. The pathway of IL-1 alpha-induced release of IL-6 was studied in the presence of agents that influence arachidonic acid release and metabolism. IL-1 alpha was found to stimulate arachidonic acid release by Sertoli cells. Furthermore, a phospholipase A2 inhibitor, aristolochic acid, significantly decreased IL-1-, LPS-, and pyrularia pubera thionin-induced IL-6 secretion from Sertoli cells. Indomethacin, a specific inhibitor of the cyclooxygenase pathway, had no significant effect on basal, but enhanced IL-1- and LPS-stimulated IL-6 production. The involvement of arachidonic acid metabolites produced in the lipoxygenase pathway on the release of IL-6 was investigated indirectly, using nordihydroguaiaretic acid. This inhibitor reduced basal and IL-1 alpha- and LPS-stimulated IL-6 production. Ethacrynic acid, an inhibitor of peptido-leukotriene synthesis, also reduced basal IL-6 levels and blocked IL-1 alpha- as well as LPS-induced IL-6 secretion. It is concluded that IL-1 produced by Sertoli cells in response to LPS or residual bodies induces IL-6 through the lipoxygenase pathway

Ibuprofen disrupts steroidogenesis in the human fetal testis.

International audienc

Représentation et traitement pratique de la flexibilité dans les problèmes sous contraintes

* INRA - Unité de Biométrie, Centre de Toulouse (FRA) Diffusion du document : INRA - Unité de Biométrie, Centre de Toulouse (FRA)National audienceEn premier lieu, après un rapide rappel des principales définitions relatives aux CSP, nous donnons une description des applications nécessitant ou ayant nécessité une extension du formalisme classique. Différentes origines de la flexibilité sont ensuite recensées en s'appuyant sur ces applications ; on distingue principalement les causes suivantes : existence de préférences, nature imprécise et incertaine des connaissances, complexité d'un problème nécessitant une hiérarchisation et évolution dans le temps. Afin d'illustrer ces formes de flexibilité, nous présentons un problème typique d'emploi du temps. Nous abordons ensuite le problème du traitement de la flexibilité. Pour chacune des origines, nous discutons des énoncés de problèmes sous-jacents et des différentes approches envisageables. La conclusion donne une synthèse des besoins soulevés. Une série d'annexes est consacrée à la résolution de CSP flexibles. Après un rapide état de l'art, nous présentons les travaux réalisés par les membres du projet constituant des éléments de réponse pour le traitement de certains cas de flexibilité