Contribution to the understanding of tribological properties of graphite intercalation compounds with metal chloride

Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gaps in their structure through which interlayer interactions are weak. The controlled variation of the distances and interactions between graphene layers by intercalation of electrophilic species in graphite is used in order to explore more deeply the friction reduction properties of low-dimensional compounds. Three graphite intercalation compounds with antimony pentachloride, iron trichloride and aluminium trichloride are studied. Their tribological properties are correlated to their structural parameters, and the interlayer interactions are deduced from ab initio bands structure calculations

Autism as a disorder of neural information processing: directions for research and targets for therapy

The broad variation in phenotypes and severities within autism spectrum disorders suggests the involvement of multiple predisposing factors, interacting in complex ways with normal developmental courses and gradients. Identification of these factors, and the common developmental path into which theyfeed, is hampered bythe large degrees of convergence from causal factors to altered brain development, and divergence from abnormal brain development into altered cognition and behaviour. Genetic, neurochemical, neuroimaging and behavioural findings on autism, as well as studies of normal development and of genetic syndromes that share symptoms with autism, offer hypotheses as to the nature of causal factors and their possible effects on the structure and dynamics of neural systems. Such alterations in neural properties may in turn perturb activity-dependent development, giving rise to a complex behavioural syndrome many steps removed from the root causes. Animal models based on genetic, neurochemical, neurophysiological, and behavioural manipulations offer the possibility of exploring these developmental processes in detail, as do human studies addressing endophenotypes beyond the diagnosis itself

Atomic scale simulations provide insights on swelling induced by irradiations

International audienceRationale of the responses of materials to irradiation is commonly based on separate post-mortem analysis of experiments and primary damage states obtained by atomistic simulations of displacement cascades.We developed in recent years an atomic scale methodology that gives access to irradiation doses for materials in which displacements cascades boil down to point defects only. Irradiation dose is obtained by accumulation of these point defects mimicking time-consuming cascades overlap. Such methodology proved to be very efficient in providing atomic scale explanations of irradiation effects in term of swelling for different materials such as graphite or urania.We show for example in irradiated graphite [1] that the well-known anisotropic volume change characterized by a shrinking in basal plane and a swelling in the c-axis is not related only to the widening of graphene interlayer caused by interstitials. It relies also to wrinkling of graphene layers with same physical laws as for rippling of carpets or curtains. In irradiated urania [2], we also bring an atomic scale explanation to the well-known dilatation-contraction peak observed in the early stage of irradiations. It is related to the transformation of Frank loops which significantly contribute to the swelling into perfect dislocations which release strain