Impacts des changements climatiques sur la gestion des barrages-réservoirs du bassin de la Seine - Premiers résultats du projet Climaware

International audienceLes projections climatiques établies par le GIECC indiquent que des changements significatifs dans les précipitations et les températures sont à attendre en Europe dans les prochaines décennies, ce qui devrait impacter la disponibilité en eau. Le projet européen Climaware (2010-2013, financé par IWRM-Net) a été monté pour développer des mesures d'adaptation telles que des instruments de gestion intégrée pour une gestion durable des ressources en eau tenant compte des changements climatiques. Au sein du projet, le cas d'étude sur la rivière Seine se concentre sur l'adaptation de la gestion de barrages (et éventuellement de la capacité de stockage) pour deux objectifs principaux : le soutien d'étiage et l'écrêtement de crues, avec des enjeux socio-économiques importants, en particulier dans la région parisienne. Les quatre grands barrages gérés par l'EPTB Seine Grands Lacs sont situés sur la partie amont du bassin sur quatre sous-bassins différents. Un modèle hydrologique semi-distribué a été développé pour simuler la transformation pluie-débit sur le bassin. Le modèle a été calé en utilisant les données de débits naturalisés sur 25 stations hydrométriques sur le bassin. Le modèle a ensuite été alimenté par des projections climatiques désagrégées issues de sept modèles climatiques différents. Les résultats indiquent que les débits d'étiage pourraient être significativement diminués sur le bassin d'ici à 2050. Ceci appelle à définir des stratégies de gestion adaptées. Plusieurs options seront testées pour tenir compte de ces modifications sur le bassin. / Climate projections established by the IPCC indicate that significant changes in precipitation and temperature are to be expected in Europe in the next decades, which should impact regional water availability. The Climaware European project (2010-2013, funded by IMWR-Net) was set up to develop adaptation measures such as integrated planning instruments for sustainable water resources management accounting for the impacts of climate change. Within the project, the Seine River case study focuses on the adaptation of dam management (and possibly dam storage capacity) for two main objectives: low-flow augmentation and flood alleviation, with important socio-economic stakes especially in the great Paris area. The four large reservoirs managed by the Seine Grands Lacs public basin authority, are situated on the upstream part of the basin on four different sub-basins. A semi-distributed hydrological model was developed to simulate the rainfall-runoff transformation on the basin. The model was calibrated using the naturalized flow data available on 25 gauging station across the basin. Then it was fed with climate projections downscaled from seven different climate models. Results indicate that low flows may be significantly reduced on the basin by 2050. This calls for defining adapted management strategies. Various options will be tested to account for these modifications on the basin

Two and three-dimensional oscillons in nonlinear Faraday resonance

We study 2D and 3D localised oscillating patterns in a simple model system exhibiting nonlinear Faraday resonance. The corresponding amplitude equation is shown to have exact soliton solutions which are found to be always unstable in 3D. On the contrary, the 2D solitons are shown to be stable in a certain parameter range; hence the damping and parametric driving are capable of suppressing the nonlinear blowup and dispersive decay of solitons in two dimensions. The negative feedback loop occurs via the enslaving of the soliton's phase, coupled to the driver, to its amplitude and width.Comment: 4 pages; 1 figur

Cymantrene–Triazole "Click" Products: Structural Characterization and Electrochemical Properties

We report the first known examples of triazole-derivatized cymantrene complexes (η5-[4-substituted triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I), obtained via a “click” chemical synthesis, bearing a phenyl, 3-aminophenyl, or 4-aminophenyl moiety at the 4-position of the triazole ring. Structural characterization data using multinuclear NMR, UV–vis, ATR-IR, and mass spectrometric methods are provided, as well as crystallographic data for (η5-[4-phenyltriazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I) and (η5-[4-(3-aminophenyl)triazol-1-yl]cyclopentadienyl)tricarbonylmanganese(I). Cyclic voltammetric characterization of the redox behavior of each of the three cymantrene–triazole complexes is presented together with digital simulations, in situ infrared spectroelectrochemistry, and DFT calculations to extract the associated kinetic and thermodynamic parameters. The trypanocidal activity of each cymantrene–triazole complex is also examined, and these complexes are found to be more active than cymantrene alone

Practical computational toolkits for dendrimers and dendrons structure design

Dendrimers and dendrons offer an excellent platform for developing novel drug delivery systems and medicines. The rational design and further development of these repetitively branched systems are restricted by difficulties in scalable synthesis and structural determination, which can be overcome by judicious use of molecular modelling and molecular simulations. A major difficulty to utilise in silico studies to design dendrimers lies in the laborious generation of their structures. Current modelling tools utilise automated assembly of simpler dendrimers or the inefficient manual assembly of monomer precursors to generate more complicated dendrimer structures. Herein we describe two novel graphical user interface (GUI) toolkits written in Python that provide an improved degree of automation for rapid assembly of dendrimers and generation of their 2D and 3D structures. Our first toolkit uses the RDkit library, SMILES nomenclature of monomers and SMARTS reaction nomenclature to generate SMILES and mol files of dendrimers without 3D coordinates. These files are used for simple graphical representations and storing their structures in databases. The second toolkit assembles complex topology dendrimers from monomers to construct 3D dendrimer structures to be used as starting points for simulation using existing and widely available software and force fields. Both tools were validated for ease-of-use to prototype dendrimer structure and the second toolkit was especially relevant for dendrimers of high complexity and size.Peer reviewe

Wave patterns generated by an axisymmetric obstacle in a two-layer flow

Gravity waves generated by a moving obstacle in a two-layer stratified fluid are investigated. The experimental configuration is three-dimensional with an axisymmetric obstacle which is towed in one of the two layers. The experimental method used in the present study is based on a stereoscopic technique allowing the 3D reconstruction of the interface between the two layers. Investigation into the wave pattern as a function of the Froude number, Fr, based on the relative density of the fluid layers and the velocity of the towed obstacle is presented. Specific attention is paid to the transcritical regime for which Fr is close to one. Potential energy trapped in the wave field patterns is also extracted from the experimental results and is analyzed as a function of both the Froude number, Fr, and the transcritical similarity parameter Γ. In particular, a remarkable increase in the potential energy around Fr = 1 is observed and a scaling allowing to assemble data resulting from different experimental parameters is proposed

Anomalous J/ψJ/\psi suppression in Pb-Pb interactions at 158 GeV per nucleon

The Drell-Yan and J/psi cross-sections measured in Pb-Pb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J/psi in Pb-Pb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions. (C) 1997 Elsevier Science B.V

Green electrochemical template synthesis of CoPt nanoparticles with tunable size, composition, and magnetism from microemulsions using an ionic liquid (bmimPF6)

Altres ajuts: Substrates have been prepared in IMB-CNM (CSIC),supported by the (CSIC) NGG-258 project.Electrodeposition from microemulsions using ionic liquids is revealed as a green method for synthesizing magnetic alloyed nanoparticles, avoiding the use of aggressive reducing agents. Microemulsions containing droplets of aqueous solution (electrolytic solution containing Pt(IV) and Co(II) ions) in an ionic liquid (bmimPF) define nanoreactors in which the electrochemical reduction takes place. Highly crystalline hcp alloyed CoPt nanoparticles, in the 10-120 nm range with a rather narrow size distribution, have been deposited on a conductive substrate. The relative amount of aqueous solution to ionic liquid determines the size of the nanoreactors, which serve as nanotemplates for the growth of the nanoparticles and hence determine their size and distribution. Further, the stoichiometry (PtCo) of the particles can be tuned by the composition of the electrolytic solution inside the droplets. The control of the size and composition of the particles allows tailoring the room-temperature magnetic behavior of the nanoparticles from superparaparamagnetic to hard magnetic (with a coercivity of H = 4100 Oe) in the as-obtained state. © 2014 American Chemical Society