International audienc

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CARAIB, a mechanistic model of carbon assimilation in the biosphere estimates the net primary productivity (NPP) of the continental vegetation on a grid of 1 ø x 1 ø in latitude and longitude. The model considers the annual and diurnal cycles. It is based on the coupling of the three following submodels; a leaf assimilation model including estimates of stomatal conductance and leaf respiration, a canopy model describing principally the radiative transfer through the foliage, and a wood respiration model. Present-day climate and vegetation characteristics allow the discrimination between ecotypes. In particular, specific information on vegetation distribution and properties is successfully used at four levels; the leaf physiological level, the plant level, the ecosystem level, and the global level. The productivity determined by the C ARAIB model is compared with local measurements and empirical estimates showing a good agreement with a global value of 65 Gt C yr -1. The sensitivity of the model to the diurnal cycle and to the abundance of C4 species is also tested. The productivity slightly decreases (10%) when the diurnal cycle of the temperature is neglected. By contrast, neglecting the diurnal cycle of solar irradiance produces unrealistically high values of NPP. Even if the importance of this increase would presumably be reduced by the coupling of CARAIB with a nutrient cycle model, this test emphasizes the key role of the diurnal cycle in a mechanistic model of the NPP. Uncertainties on the abundance and spatial distribution of Ca plants may cause errors in the NPP estimates, however, as demonstrated by two sensitivity tests, these errors are certainly lower than 10% at the global scale as shown by two tests. tatively uses mechanistic models [Farquhar et al., 1980; Collatz et al., 1992] to predict the net primary productivity (NPP) at a global scale. Even if this scaling-up method rests upon many simplifications, it is a first step toward the modeling of CO2 assimilation by continental vegetation, and it gives results as realistic as those of previous estimations. Furthermore, improvements of this model are expected as physiological knowledge and scaling-up methodology progress. The sensitivity of the model to the diurnal cycle is tested. It is shown that ignoring this cycle may introduce important errors in NPP estimates.

Thin films of polypyrrole doped by polyanions have been deposited onto stainless steel and carbon fibers by anodic electropolymerization of pyrrole in the presence of an anionic polyelectrolyte in water. Films with a thickness smaller than 600 nm have been formed, which strongly adhere to the solid supports. The polymeric dopant has been selected for its ability to complex silver ions. Scanning electron microscopy, Rutherford backscattering analyses, and IR spectroscopy have confirmed that silver is actually immobilized in the films and provides them with an antibacterial activity against the Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus.

Since the end of the 20th century, the a-, band «-copper phthalocyanine (CuPc) blue pigments are widely used in modern artists' paints. The identification of the CuPc crystalline structure can provide useful technical and chronological information for the study of works of art. Although when a CuPc blue pigment is identified, its crystalline structure often remains unspecified despite the interest for conservation science. In this study, X-ray powder diffraction, attenuated total reflectance micro-Fourier transform infrared spectroscopy and micro-Raman spectroscopy analyses have been carried out on 15 dry pigment samples of CuPc and acrylic, vinylic, alkyd, arabic gum and oil-based artists' paints. By using the polymorphic markers underlined for dry pigments, the CuPc crystalline structure has been successfully identified for most of the analysed artists' paints. However, according to the analytical technique used and the investigated paint sample, the obtained results largely differ.