A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Large-scale wind disturbances promote tree diversity in a Central Amazon forest

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha-1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m2 ha-1). Highly impacted areas had tree density and basal area as low as 120 trees ha-1 and 14.9 m2 ha-1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level. © 2014 Marra et al

Cellulose acetate graft copolymers with nano-structured architectures: Synthesis and characterization

International audienceCellulose acetate is a very good film-forming polymer with major applications in cigarette filters, photographic films, cosmetics and pharmaceutics formulations and membrane separation processes. Nevertheless, its rigidity and relative hydrophobic character can be limiting drawbacks for some applications. In this work, new cellulose acetate materials with highly flexible and hydrophilic grafts were obtained with different hydrophilic/hydrophobic balances. Cellulose acetate was grafted with methyl diethylene glycol methacrylate (MDEGMA) from brominated macroinitiators by atom transfer radical polymerization (ATRP) in two steps. The first step consisted of introducing ATRP initiator groups on cellulose acetate by reacting hydroxyl side groups with 2-bromoisobutyryl bromide. A preliminary study was then carried out to determine the experimental conditions for the controlled ATRP of MDEGMA homopolymerization in a solvent (cyclopentanone) compatible with cellulose acetate grafting. In these conditions, the MDEGMA homopolymerization followed Hanns Fischer's kinetics model accounting for the radical persistent effect. The ATRP grafting was then investigated for two cellulose acetate macroinitiators differing in the number of their ATRP initiator groups. Two families of graft copolymers with nano-structured architectures were obtained. The first family corresponded to copolymers with a high number of short grafts. The copolymers of the second family had almost the same graft weight fractions but a small number of long grafts. The morphology of the graft copolymers was then investigated by synchrotron X-ray scattering. The most informative results showed that the phase segregation depended upon the number and length of the poly(MDEGMA) grafts. The copolymer with 44 wt.% of long grafts showed a segregated morphology of nano-domains with sharp interfaces and a radius of gyration of 11.5 nm (from Guinier's law). These cellulose acetate copolymers eventually led to strong films with potential applications in membrane separations