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The processes underlying macroecological gradients in body size are widely debated, in part because their intraspecific variability remains poorly described even in well-studied taxa such as vertebrates. In this study, we investigated how climate, habitat, genetic lineage and sex explain body size variations in French populations of the European pond turtle (Emys orbicularis). We measured 7016 adult individuals captured in 41 populations, covering most of the species’ distribution in metropolitan France, including Corsica. Body size variation in our sample was wide and comparable to that found across the species’ worldwide range. Variation was similar in magnitude at regional and local levels, suggesting that body size is influenced by local factors as much as by regional factors such as climate or genetic lineage. Smaller sizes were associated with Mediterranean or altered oceanic climates, and with two lineages (E. o. galloitalica and E. o. galloitalica/E. o. orbicularis), while larger sizes were associated with northern environments and the orbicularis lineage. Body size variations recorded at local level reflect an adaptive response to environmental constraints, suggesting that habitat is also an important factor in understanding size variation.

International audience; Benthic diatoms are widely used as bio-indicators in water quality monitoring of rivers and streams, but less commonly in lentic waterbodies such as pools and lakes. Currently, a new method for assessing the ecological status of lakes is being tested in France to meet the requirements of the European Water Framework Directive (WFD) 2000/60/EC. This new method uses epilithic and epiphytic diatoms growing on stones and aquatic plants. Alternatively, freshwater turtles and the epizoic algae found on their carapaces may provide an excellent substrate for estimating water quality. Our study proposes an original diatom-based method for assessing the quality of water bodies in which turtles live. The main objective was to compare the Biological Diatom Index (BDI) values measured from epizoic diatom samples taken on the carapace of turtles with classical epilithic or epiphytic samples. Epizoic samples were taken from the carapaces of the turtle Emys orbicularis in two shallow French Mediterranean wetlands. Our results indicate that diatom assemblages differ slightly within the three substrates studied with limited variations in index value. However, some variability among epizoic samples from the same site suggests that several turtle individuals should be sampled for water quality biomonitoring.

Rheological measurements were made on concrete and mortars to characterize the shear thickening behavior of certain concrete mix designs. Shear thickening reduction levers were found by selecting and designing admixtures. Since the shear-thickening phenomena occur at the scale of the finest particles, industrial limestone fillers were studied that behave like cementitious materials. Theories based on previous academic works were relevant. The shear stress-dependent effects of shear thickening and size scaling were very helpful to distinguish between surface interactions, such as lubrication and volumetric contributions and also including the packing effects. The suspension viscosity curves vary accordingly to the Newtonian viscosity of the solvent medium. In both the shear thinning and shear thickening regimes, viscosity is controlled by adjusting the amount of two specific admixtures. The reduction of friction between polymer-coated materials appears to be a key phenomenon to delay onset shear thickening in industrial processes.

International audience; The shear rheology of a microcrystalline cellulose dissolved in a 9% NaOH aqueous solution was studied in the steady and oscillatory modes. The cellulose-(9% NaOH-H2O) mixtures show not to be true solutions. In the dilute regime, with cellulose concentration below 1%, the rheological behavior is typical of the one of suspensions. The formation of cellulose aggregates is favored when temperature is increased. In the semidilute regime, an irreversible aggregate-based gelation occurs, being faster with increasing temperature.

International audience; Calorimetry, small-angle X-ray scattering, and viscometry were used to study the structure of NaOH-water and cellulose-NaOH-water solutions in the range of 0-20% NaOH and 0-5% cellulose concentrations in the low-temperature region of -60 to 0 °C. Pure NaOH-water solutions show a pseudoeutectic behavior with three phases: free water that crystallizes and melts at a certain melting temperature which decreases with the increase of NaOH concentration; a NaOH hydrate that melts at -35 °C; water bound to hydrates that does not crystallize. The addition of cellulose does not change the amount of the free water. The cellulose chains are located in the hydrate region, one to two hydroxyl groups of the glucopyranose unit being bound to a soda hydrate.