Structural–dynamical relationship in silica PEG hybrid gels

International audienceHybrid organic–inorganic materials have been prepared from mixtures of tetraethoxysilane and poly(ethylene glycol) (PEG) of low molecular mass. These materials are diphasic systems in which silica aggregates, controlling the mechanical properties, are wrapped around by the polymer phase. Strong correlations between the synthesis scheme, the structure and the properties of these materials are evidenced. Solid-state 29Si NMR points out the change of the silica morphology with the nature of the catalyst (acidic, [HCl] or nucleophilic, [NH4F]). In addition, these changes induce strong variations of the thermal properties of the PEG phase. The structural and dynamical inhomogeneities of the PEG are analyzed using 13C NMR and EPR spectroscopies. Near the SiO2 surfaces, hydrogen bonding hinders the motion of the PEG chains, while the bulk of the polymeric phase possesses the same properties as the polymer melt. Thermal analyses (DSC) disclose the difference between materials prepared with the various catalysts which are related to the degree of interpenetration between the two phases

Recognition and treatment of severe sepsis in the emergency department: retrospective study in two French teaching hospitals

Abstract Background Sepsis management in the Emergency Department remains a daily challenge. The Surviving Sepsis Campaign (SSC) has released three-hour bundle. The implementation of these bundles in European Emergency Departments remains poorly described. The main objective was to assess the compliance with the Severe Sepsis Campaign 3-h bundle (blood culture, lactate dosage, first dose of antibiotics and 30 ml/kg fluid challenge). Secondary objectives were the analysis of the delay of severe sepsis recognition and description of the population. Methods In accordance with STROBE statement, we performed a retrospective study in two French University Hospital Emergency Departments from February to August 2015. Patients admitted during the study period were screened using the electronic files of the hospital databases. Patient’s files were reviewed and included in the study if they met severe sepsis criteria. Demographics, comorbities, treatments were recorded. Delays from admission to severe sepsis diagnosis, fluid loading onset and antibiotics administration were calculated. Results One hundred thirty patients were included (76 men, mean age 71 ± 14 years). Blood culture, lactate dosage, antibiotics and 30 ml/kg fluid loading were performed within 3 hours in % [95% confidence interval] 100% [96–100%], 62% [54–70%], 49% [41–58%] and 19% [13–27%], respectively. 25 patients out of 130 (19% [13–27%]) fulfilled each criteria of the 3-h bundle. The mean fluid loading volume was 18 ± 11 ml/kg. Mean delay between presentation and severe sepsis diagnosis was 200 ± 263 min, from diagnosis to fluid challenge and first antibiotic dose, 10 ± 27 min and 20 ± 55 min, respectively. Conclusion Compliance with SSC 3-h bundle and delay between admission and sepsis recognition have to be improved. If confirmed by other studies, an improvement program might be deployed

Synchrotron DUV luminescence micro-imaging to identify and map historical organic coatings on wood

International audienceDeep ultraviolet (DUV) photoluminescence (PL) microimaging is an emerging approach to characterise materials from historical artefacts (see M. Thoury, J.-P. Echard, M. Réfrégiers, B. H. Berrie, A. Nevin, F. Jamme and L. Bertrand, Anal. Chem., 2011, 83, 1737–1745). Here we further assess the potential of the method to access a deeper understanding of multi-layered varnishes coating wooden violins and lutes. Cross-section micro samples from important 16th- to 18th-century instruments were investigated using synchrotron PL microimaging and microspectroscopy. Excitation was performed in the DUV and the near ultraviolet (NUV) regions, and emission recorded from the DUV to the visible region, at a submicrometric spatial resolution. Intercomparison of microspectroscopy and microimaging was made possible by radiometrically correcting PL spectra both in excitation and emission. Based on an optimised selection of emission and excitation bands, the specific PL features of the organic binding materials allowed a vastly enhanced discrimination between collagen-based sizing layers and oil/resin-based layers compared to epiluminescence microscopy. PL therefore appears to be a very promising analytical tool to provide new insights into the diversity of surface coating techniques used by instrument-makers. More generally, our results demonstrate the potential of synchrotron PL for studying complex heterogeneous materials beyond the core application of the technique to life sciences

Repression of early lateral root initiation events by transient water deficit in barley and maize

The formation of lateral roots (LRs) is a key driver of root system architecture and developmental plasticity. The first stage of LR formation, which leads to the acquisition of founder cell identity in the pericycle, is the primary determinant of root branching patterns. The fact that initiation events occur asynchronously in a very small number of cells inside the parent root has been a major difficulty in the study of the molecular regulation of branching patterns. Inducible systems that trigger synchronous lateral formation at predictable sites have proven extremely valuable in Arabidopsis to decipher the first steps of LR formation. Here, we present a LR repression system for cereals that relies on a transient water-deficit treatment, which blocks LR initiation before the first formative divisions. Using a time-lapse approach, we analysed the dynamics of this repression along growing roots and were able to show that it targets a very narrow developmental window of the initiation process. Interestingly, the repression can be exploited to obtain negative control root samples where LR initiation is absent. This system could be instrumental in the analysis of the molecular basis of drought-responsive as well as intrinsic pathways of LR formation in cereals

Cropping system diversification does not always beget weed diversity

International audienceCropping system (CS) diversification appears as a promising solution to increase CS sustainability. However, weed community response to different options of CS diversification remains poorly documented. Moreover, these effects are expected to be more pronounced in experimental than commercial farms because experimental farms explore more diverse combinations of farming practices. We hypothesized that (i) CS diversification would increase weed diversity at multiple spatio-temporal scales but that (ii) different options of CS diversification would select different weed communities and that (iii) responses could differ between experimental and commercial farms. Hence, weed density per species was measured over a 6-year time period in a CS experiment and in a farmers’ network (both resorting to diverse CSs that were numerically summarized to allow their comparison, i.e. different positions along gradients of tillage intensity, herbicide use, crop rotation length etc.). Weed density measures were used to compute weed diversity indices (taxonomic and functional, at annual and plurennial scales) and community weighted means on key response traits for each CS. All experimented alternative CSs (diversified crop sequences with coherent but different combinations of weed management tools) showed that diverse combinations of agronomic tools are available to increase weed diversity, as highlighted by a 3 and 2-fold increase in species richness at the annual and plurennial scales, respectively. In contrast, only one farmer CS (3-year rotation, low tillage intensity, intermediate herbicide reliance) showed significantly higher levels of weed diversity, possibly because the reduced tillage intensity was not compensated by other agronomic levers (e.g. increase of herbicide use and/or crop rotation diversity). Such outcomes were attributed to (i) reduced CS complexity in commercial compared to experimental farms and (ii) high herbicide reliance in commercial farms, irrespectively of CS complexity. Across both experimental and commercial farms, tillage, weed management and crop type appeared as the main factors structuring weed communities. Systems with reduced tillage were associated with a higher percentage of grasses and perennials. Systems with spring/summer crops and/or mechanical weeding were associated with a higher proportion of spring/summer and perennial species. These results suggest that solutions are readily available for farmers to implement sustainable weed management, but supports are required to address the factors hindering the adoption of these experimented CS in commercial conditions

Tanis (2020)

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Méthodes, leviers et stratégies de lutte

Partie 5International audienc