Essais de revégétalisation par des espèces locales d'anciens sites miniers de la région de Thio

Ces essais avaient pour but de tester certaines espèces locales pour restaurer d'anciens terrains miniers et d'analyser leur adaptabilité, leurs modalités d'implantation et leur durabilité pour obtenir une couverture dens

Les forêts de montagne de la Nouvelle-Calédonie

L'existence d'un gradient local de température plus prononcé près des montagnes isolées abaisse l'altitude moyenne de formation des masses nuageuses, créant ainsi des conditions propices au développement des forêts de montagne en Nouvelle-Calédonie à des altitudes inférieures à 1 600 m. Ces forêts sont d'une grande importance pour la biodiversité et la compréhension de la phytogéographie et phylogénie de certains groupes, comme celui des conifères ou ceux des genres Metrosideros (Myrtaceae) et Cunonia (Cunoniaceae). Elles constituent aussi des refuges pour la faune menacée et jouent un rôle de régulateur hydrologique non négligeable. Relativement bien protégées, elles sont peu menacées par l'exploitation forestière, un peu plus par les activités minières. Le plus grand risque semble, toutefois, être le réchauffement climatique global, qui pourrait entraîner une disparition des conditions écologiques particulières nécessaires à leur existence. (Résumé d'auteur

Strain gradient crystal plasticity with evolving length scale: Application to voided irradiated materials

International audienceA micromorphic crystal plasticity model is used to simulate slip band localization in single crystalsunder simple shear at finite deformations. Closed form analytical solutions are derived for singleslip in the case of positive, zero and negative strain hardening. Linear negative strain hardening,i.e. linear softening, leads to a constant localization slip band width, while non linear softening andsaturating behaviour results in an increasing band width. An enhanced model is therefore proposed inorder to maintain a bounded localization slip band width when considering an exponential softeningbehaviour. Analytical solutions are used to validate finite element computation of the same boundaryvalue problems. The enhanced micromorphic crystal plasticity model is then applied to predict theinteraction between localized slip bands and voids encountered in voided irradiated materials. For thatpurpose, periodic porous unit cells are loaded in simple shear with a strain gradient crystal plasticitymatrix material. The finite element simulation results show that, for a given void volume fraction, thelarger the voids, the wider the localization band. However, for a given void size, the larger the voidvolume fraction, the narrower the localization band. In addition a satisfactory qualitative agreementof the rotation and elongation of the voids with the experimental observations made in irradiatedmaterials is observed, where small voids are shown to remain ellipsoidal for larger shear strains thanlarge voids which deform into peanut-like shapes

Analysis of iatrogenic risk related to anticholinergic effects using two scales in acute geriatric inpatient unit

Anticholinergic medications are responsible for most frequent adverse drug effects. Two scales have been elaborated as tools for prescribers: the Anticholinergic Drug Scale (ADS) of Carnahan et al., and the Anticholinergic Risk Scale (ARS) of Rudolph et al. The objective of this study was to analyze the diagnostic performance of both scales for predicting signs related to an anticholinergic effect. Method: Medical records of 1379 patients aged 75 years or older hospitalized in a geriatric acute care unit between 2002 and 2005 were studied. The analyze was made retrospectively, but data were collected prospectively. Results: Risk of appearance of total anticholinergic signs (ADS : OR 1,45, CI 95% [1,03-2,03], p=0,037 and ARS : OR 1,98, CI 95% [1,19-3,28] p<0,01) and peripheral signs (ADS: OR 1,66, CI 95% [1,22-2,26], p<0,01 and ARS : OR 1,81, CI 95% [1,19-2,75], p<0,01) increased when score was >= 3 with both scales, which wasn\u27t the case for central signs. Conclusion: Both scales permitted to detect an increased risk of appearance of total and peripheral anticholinergic signs, but not the centrals as delirium. Interest of total anticholinergic burden remains to be demonstrated, especially for delirium risk assessment

Jamming at Zero Temperature and Zero Applied Stress: the Epitome of Disorder

We have studied how 2- and 3- dimensional systems made up of particles interacting with finite range, repulsive potentials jam (i.e., develop a yield stress in a disordered state) at zero temperature and applied stress. For each configuration, there is a unique jamming threshold, $\phi_c$, at which particles can no longer avoid each other and the bulk and shear moduli simultaneously become non-zero. The distribution of $\phi_c$ values becomes narrower as the system size increases, so that essentially all configurations jam at the same $\phi$ in the thermodynamic limit. This packing fraction corresponds to the previously measured value for random close-packing. In fact, our results provide a well-defined meaning for "random close-packing" in terms of the fraction of all phase space with inherent structures that jam. The jamming threshold, Point J, occurring at zero temperature and applied stress and at the random close-packing density, has properties reminiscent of an ordinary critical point. As Point J is approached from higher packing fractions, power-law scaling is found for many quantities. Moreover, near Point J, certain quantities no longer self-average, suggesting the existence of a length scale that diverges at J. However, Point J also differs from an ordinary critical point: the scaling exponents do not depend on dimension but do depend on the interparticle potential. Finally, as Point J is approached from high packing fractions, the density of vibrational states develops a large excess of low-frequency modes. All of these results suggest that Point J may control behavior in its vicinity-perhaps even at the glass transition.Comment: 21 pages, 20 figure

Factors associated with an increased risk of vertebral fracture in monoclonal gammopathies of undetermined significance

Monoclonal gammopathies of undetermined significance (MGUS) have been shown to be associated with an increased risk of fractures. This study describes prospectively the bone status of MGUS patients and determines the factors associated with vertebral fracture. We included prospectively 201 patients with MGUS, incidentally discovered, and with no known history of osteoporosis: mean age 66.6±12.5 years, 48.3% women, 51.7% immunoglobulin G (IgG), 33.3% IgM and 10.4% IgA. Light chain was kappa in 64.2% patients. All patients had spinal radiographs and bone mineral density measurement in addition to gammopathy assessment. At least one prevalent non-traumatic vertebral fracture was discovered in 18.4% patients and equally distributed between men and women. Fractured patients were older, had a lower bone density and had also more frequently a lambda light chain isotype. Compared with patients with κ light chain, the odds ratio of being fractured for patients with λ light chain was 4.32 (95% confidence interval 1.80-11.16; P=0.002). These results suggest a high prevalence of non-traumatic vertebral fractures in MGUS associated with lambda light chain isotype and not only explained by low bone density