Evolution du Facteur de résistance hygrothermique transitoire en fonction des séquences d'empilement pour des composites stratifiés sous des conditions d'environnement cycliques

Exposé à des conditions d'environnement cycliques, les composites à matrices polymères sont capables d'absorber une quantité d'humidité durant de longues années de service. Suite à ce type d'environnement, il se développe des contraintes hygrothermiques extrêmement critiques aux bords et aux interfaces fibres/résines. Au cours des premiers temps de la diffusion d'humidité, les contraintes hygrothermiques sont assez importantes dans la direction transversale, où elles peuvent engendrées un délaminage par gonflement entre les plis formants le stratifié. Pour avoir une idée sur la probabilité d'endommagement des plaques stratifiées sous des contraintes hygrothermiques transitoires, on a adopté le critère de rupture de Tsai-Wu. Le critère de sécurité sera vérifier en évaluant le facteur de résistance (R) pour chaque séquence d'empilement aux bords de la plaque stratifiée

Temporal Dissociation between Myeloperoxidase (MPO)-Modified LDL and MPO Elevations during Chronic Sleep Restriction and Recovery in Healthy Young Men

OBJECTIVES: Many studies have evaluated the ways in which sleep disturbances may influence inflammation and the possible links of this effect to cardiovascular risk. Our objective was to investigate the effects of chronic sleep restriction and recovery on several blood cardiovascular biomarkers. METHODS AND RESULTS: Nine healthy male non-smokers, aged 22-29 years, were admitted to the Sleep Laboratory for 11 days and nights under continuous electroencephalogram polysomnography. The study consisted of three baseline nights of 8 hours sleep (from 11 pm to 7 am), five sleep-restricted nights, during which sleep was allowed only between 1 am and 6 am, and three recovery nights of 8 hours sleep (11 pm to 7 am). Myeloperoxidase-modified low-density lipoprotein levels increased during the sleep-restricted period indicating an oxidative stress. A significant increase in the quantity of slow-wave sleep was measured during the first recovery night. After this first recovery night, insulin-like growth factor-1 levels increased and myeloperoxidase concentration peaked. CONCLUSIONS: We observed for the first time that sleep restriction and the recovery process are associated with differential changes in blood biomarkers of cardiovascular disease

Lichenological exploration of Algeria: historical overview and annotated bibliography, 1799-2013

yesDespite more than two centuries of almost uninterrupted surveys and studies of Algerian lichenology, the history and lichen diversity of Algeria are still poorly understood. During the preparation of a forthcoming checklist of Algerian lichens it was considered necessary to provide the present historical overview of lichenological exploration of the country from 1799 to 2013, supported by a reasonably comprehensive annotated bibliography of 171 titles