904 research outputs found
La restauration Ă©cologique du fleuve RhĂŽne sous le double regard du sociologue et de l'Ă©cologue
ActĂ© en 1998, le Programme dĂ©cennal de restauration hydraulique et Ă©cologique du RhĂŽne s'est fixĂ© comme objectif principal d'augmenter les dĂ©bits rĂ©servĂ©s dans les bras court-circuitĂ©s du fleuve. Cet objectif Ă©tait initialement pensĂ© comme une action de restauration Ă©cologique de milieux naturels fortement perturbĂ©s. Un processus concomitant de concertations a plusieurs fois dĂ©placĂ© l'intĂ©rĂȘt initial vers des projets d'Ă©laboration d'un territoire fluvial, puis d'un outil de gestion contre les crues. L'approche interdisciplinaire appliquĂ©e, entre sociologie et Ă©cologie, interroge la capacitĂ© d'une telle action environnementale Ă aboutir Ă des rĂ©sultats hybrides, relevant Ă la fois de l'amĂ©lioration d'un Ă©cosystĂšme fluvial et d'un processus de gouvernance. / A ten-year physical and ecological restoration programme was defined for the Rhone River in 1998. Initially, one of its main objectives was to increase the minimum flow in several by-passed sections, with the clear goal of improving the fluvial habitat and the general ecological functioning of the river. A complex consultation process which brought together the hydropower industry, regional civil organisations, and local civil representatives was adopted to define more precisely the local measures to be taken. In the course of this process, the programme underwent a progressive change from purely ecological to more socially motivated outcomes such as improving amenity values and flood defence. We studied how increasing the minimum flow is a topic that can or cannot be discussed by the actors during the consultation process. For example, there is less discussion about the ecological value than about the economic value of the restoration programme between the hydropower industry and the local elected members. But, the various actors readily debate with the scientists about floods and sedimentary transport, linked with local knowledge. We applied a multidisciplinary approach, involving sociology and ecological sciences, to question the restoration programme and to analyse its hybrid results in terms of both the ecological and amenity values and at the same time to understand the governance process
Les demandes sociales de restauration des riviĂšres et leurs traductions scientifiques et politiques
La restauration des riviĂšres n'est pas qu'une prĂ©occupation des experts et des Ă©cologistes. Une rĂ©trospective des demandes sociales en faveur d'une prĂ©servation et d'une rĂ©habilitation des cours d'eau montre que celles-ci ont Ă©tĂ© portĂ©es par des intĂ©rĂȘts multiples et parfois contradictoires. La fin du 19Ăšme siĂšcle et dĂ©but du 20Ăšme est marquĂ©e par des prĂ©occupations de dĂ©peuplement des cours d'eau, la pĂ©riode de reconstruction d'aprĂšs guerre met l'accent sur la qualitĂ© de l'eau brute Ă des fins d'adduction et de distribution d'eau, depuis les annĂ©es 70 le courant Ă©cologiste trouve de nombreux relais dans la population Ă travers les activitĂ©s de nature revendiquĂ©e par les classes moyennes comme partie intĂ©grante de leur qualitĂ© de vie. Ces trois exemples montrent en outre que les prĂ©occupations sociales sont diversement interprĂ©tĂ©es par les scientifiques et les politiques qui contribuent Ă modifier leur expression en agissant sur les connaissances et les moyens d'action ou la rĂ©glementation. A travers ces quelques exemples nous montrons que les questions de mise en oeuvre de la directive cadre s'apprĂ©hendent mieux en tenant compte des aspirations sociales qui ont conduit Ă l'adoption de cette directive / River restoration does not only concern experts and ecologists. Social demands in favour of river protection and enhancement have been historically diverse and contradictory. Three examples are analysed to support this point. Implementing the new framework directive requires to take into account which social expectations were at stake while the directive was adopte
The Strong Levinson Theorem for the Dirac Equation
We consider the Dirac equation in one space dimension in the presence of a
symmetric potential well. We connect the scattering phase shifts at E=+m and
E=-m to the number of states that have left the positive energy continuum or
joined the negative energy continuum respectively as the potential is turned on
from zero.Comment: Submitted to Physical Review Letter
Regards sociologiques croisés sur les processus de création au théùtre
International audienc
Synthesis process and hydrodynamic behavior of a new filtration material for passive wastewater dephosphatation
International audienceThe preparation optimization of a filter material intended to be used as a phosphate sorbent in flow-through conditions is investigated. The mixing of ferrihydrite (Fh) and pozzolana (Pz) using a âdry contact methodâ is found to be the most efficient and leads to the formation of a micrometric thick Fh coating deposited into the honeycombed structure of Pz. The maximal Fh content of ~ 8.5 wt.% is significantly higher than the quantity deposited on other classical substrates such as sand. The phosphate sorption kinetics and isotherms, under dynamic conditions in batch experiments, are best described by pseudo-second-order and Freundlich models respectively. Moreover, under static conditions, sorption kinetics reveals intra-aggregate diffusion process. Phosphate ion retention in packed columns, and especially the breakthrough point, can be adequately predicted when coupling the classical convection dispersion equation and the surface complexation model. Breakthrough curves of phosphate ions are strongly dependent on flow rate; which is important for future industrial applications. Finally, and unexpectedly, a high value of phosphate adsorption capacity (80 mg PO4 gâ 1) is observed when phosphate-containing wastewater is used as feed solution. This is mostly explained by soluble calcium ions, which favors the phosphate fixation onto the filter material surfac
Quantized conductance in a one-dimensional ballistic oxide nanodevice
Electric-field effect control of two-dimensional electron gases (2-DEG) has
enabled the exploration of nanoscale electron quantum transport in
semiconductors. Beyond these classical materials, transition metal-oxide-based
structures have d-electronic states favoring the emergence of novel quantum
orders absent in conventional semiconductors. In this context, the
LaAlO3/SrTiO3 interface that combines gate-tunable superconductivity and
sizeable spin-orbit coupling is emerging as a promising platform to realize
topological superconductivity. However, the fabrication of nanodevices in which
the electronic properties of this oxide interface can be controlled at the
nanoscale by field-effect remains a scientific and technological challenge.
Here, we demonstrate the quantization of conductance in a ballistic quantum
point contact (QPC), formed by electrostatic confinement of the LaAlO3/SrTiO3
2-DEG with a split-gate. Through finite source-drain voltage, we perform a
comprehensive spectroscopic investigation of the 3d energy levels inside the
QPC, which can be regarded as a spectrometer able to probe Majorana states in
an oxide 2-DEG
Ising model in small-world networks
The Ising model in small-world networks generated from two- and
three-dimensional regular lattices has been studied. Monte Carlo simulations
were carried out to characterize the ferromagnetic transition appearing in
these systems. In the thermodynamic limit, the phase transition has a
mean-field character for any finite value of the rewiring probability p, which
measures the disorder strength of a given network. For small values of p, both
the transition temperature and critical energy change with p as a power law. In
the limit p -> 0, the heat capacity at the transition temperature diverges
logarithmically in two-dimensional (2D) networks and as a power law in 3D.Comment: 6 pages, 7 figure
Ensemble-based data assimilation for operational flood forecasting â On the merits of state estimation for 1D hydrodynamic forecasting through the example of the âAdour Maritimeâ river
This study presents the implementation and the merits of an Ensemble Kalman Filter (EnKF) algorithm with an inflation procedure on the 1D shallow water model MASCARET in the framework of operational flood forecasting on the âAdour Maritimeâ river (South West France). In situ water level observations are sequentially assimilated to correct both water level and discharge. The stochastic estimation of the background error statistics is achieved over an ensemble of MASCARET integrations with perturbed hydrological boundary conditions. It is shown that the geometric characteristics of the network as well as the hydrological forcings and their temporal variability have a significant impact on the shape of the univariate (water level) and multivariate (water level and discharge) background error covariance functions and thus on the EnKF analysis. The performance of the EnKF algorithm is examined for observing system simulation experiments as well as for a set of eight real flood events (2009â2014). The quality of the ensemble is deemed satisfactory as long as the forecast lead time remains under the transfer time of the network, when perfect hydrological forcings are considered. Results demonstrate that the simulated hydraulic state variables can be improved over the entire network, even where no data are available, with a limited ensemble size and thus a computational cost compatible with operational constraints. The improvement in the water level Root-Mean-Square Error obtained with the EnKF reaches up to 88% at the analysis time and 40% at a 4-h forecast lead time compared to the standalone model
Competition between electron pairing and phase coherence in superconducting interfaces
In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spinâorbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high- energy dxz/dyz bands in the quantum well, more apt to host superconductivity
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