HYDROGEN EMBRITTLEMENT IN Al-Li-Cu-Mg ALLOYS (8090-T651)

This paper describes the hydrogen embrittlement (HE) of an Al-Li alloy aged at 190°C and with different durations of ageing (10, 15, 20 and 30 hr). Two techniques were employed to measure HE : a) cathodic polarization in a molten salts bath with -3 V/Ag on tensile specimens ; b) gaseous hydrogenation on disks. Hydrogen charging was achieved at 190°C. The results show that HE is important when the alloy is in the over-aged condition

Crystalline and electronic structure of Pu–Ce and Pu–Ce–Ga alloys stabilized in the δ phase

International audienceIn the actinides series (which corresponds to the progressive filling of the 5f sub-shell), plutonium lies at the changeover for the behavior of the 5f electrons between the light actinides (up to Np) with delocalized 5f states, and the heavy actinides (from Am on) with localized 5f states. At this boundary, the expanded δ-phase exhibits an intermediate and thus controversial behavior of its 5f electrons. This high temperature δ-phase can be stabilized at and below room temperature by alloying with so-called deltagen solutes Ga, Al, Ce and Am. In this work, some Pu–Ce and Pu–Ce–Ga alloys were studied using several techniques (dilatometry, X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS), electrical resistivity and magnetic susceptibility). It is found that the mechanism of δ-Pu stabilization is far from straightforward as both Pu 5f and Ce 4f electronic states are involved, inducing complex crystalline organization while no clear localization of the 5f states can be deduced from experimental results. Ternary Pu–Ce–Ga alloys show cooperative deltagen effects of Ce and Ga

Cytokin in action is linked to oxidative stress as shown by proteome analysis in ArabidopsisArabidopsis

International audienc

Cytokin in action is linked to oxidative stress as shown by proteome analysis in ArabidopsisArabidopsis

International audienc

Link between cytokinins, oxidative stress and jasmonic acid as revealed by proteome analysis in ArabidopsisArabidopsis

International audienc

Link between cytokinins, oxidative stress and jasmonic acid as revealed by proteome analysis in ArabidopsisArabidopsis

International audienc

Convergent evolution of endosymbiont differentiation in dalbergioid and inverted repeat-lacking clade legumes mediated by nodule-specific cysteine-rich peptides

Nutritional symbiotic interactions require the housing of large numbers of microbial symbionts, which produce essential compounds for the growth of the host. In the legume-rhizobium nitrogen-fixing symbiosis, thousands of rhizobium microsymbionts, called bacteroids, are confined intracellularly within highly specialized symbiotic host cells. In Inverted Repeat-Lacking Clade (IRLC) legumes such as Medicago spp., the bacteroids are kept under control by an arsenal of nodule-specific cysteine-rich (NCR) peptides, which induce the bacteria in an irreversible, strongly elongated, and polyploid state. Here, we show that in Aeschynomene spp. legumes belonging to the more ancient Dalbergioid lineage, bacteroids are elongated or spherical depending on the Aeschynomene spp. and that these bacteroids are terminally differentiated and polyploid, similar to bacteroids in IRLC legumes. Transcriptome, in situ hybridization, and proteome analyses demonstrated that the symbiotic cells in the Aeschynomene spp. nodules produce a large diversity of NCR-like peptides, which are transported to the bacteroids. Blocking NCR transport by RNA interference-mediated inactivation of the secretory pathway inhibits bacteroid differentiation. Together, our results support the view that bacteroid differentiation in the Dalbergioid clade, which likely evolved independently from the bacteroid differentiation in the IRLC clade, is based on very similar mechanisms used by IRLC legumes