En quoi les dispositifs territoriaux de la gestion de l’eau peuvent-ils être efficaces

Après trente ans de mise en oeuvre des dispositifs issus de la territorialisation de la politique de l’eau, le recul est suffisant pour interroger leur contribution à la préservation ou à l’amélioration de l’état écologique des hydrosystèmes, devenus un impératif européen depuis 2000. À partir de l’exemple de la gestion de la rivière Drôme, cet article nous explique le processus de territorialisation ainsi que les conditions de l’efficacité d’une politique environnementale à l’échelle locale

Optomechanically induced transparency

Coherent interaction of laser radiation with multilevel atoms and molecules can lead to quantum interference in the electronic excitation pathways. A prominent example observed in atomic three-level-systems is the phenomenon of electromagnetically induced transparency (EIT), in which a control laser induces a narrow spectral transparency window for a weak probe laser beam. The concomitant rapid variation of the refractive index in this spectral window can give rise to dramatic reduction of the group velocity of a propagating pulse of probe light. Dynamic control of EIT via the control laser enables even a complete stop, that is, storage, of probe light pulses in the atomic medium. Here, we demonstrate optomechanically induced transparency (OMIT)--formally equivalent to EIT--in a cavity optomechanical system operating in the resolved sideband regime. A control laser tuned to the lower motional sideband of the cavity resonance induces a dipole-like interaction of optical and mechanical degrees of freedom. Under these conditions, the destructive interference of excitation pathways for an intracavity probe field gives rise to a window of transparency when a two-photon resonance condition is met. As a salient feature of EIT, the power of the control laser determines the width and depth of the probe transparency window. OMIT could therefore provide a new approach for delaying, slowing and storing light pulses in long-lived mechanical excitations of optomechanical systems, whose optical and mechanical properties can be tailored in almost arbitrary ways in the micro- and nano-optomechanical platforms developed to date

Polarization imaging reflectometry in the wild

We present a novel approach for on-site acquisition of surface reflectance for planar, spatially varying, isotropic materials in uncontrolled outdoor environments. Our method exploits the naturally occuring linear polarization of incident illumination: by rotating a linear polarizing filter in front of a camera at 3 different orientations, we measure the linear polarization reflected off the sample and combine this information with multiview analysis and inverse rendering in order to recover per-pixel, high resolution reflectance maps. We exploit polarization both for diffuse/specular separation and surface normals estimation by combining polarization measurements from at least two near orthogonal views close to Brewster angle of incidence. We then use our estimates of surface normals and albedos in an inverse rendering framework to recover specular roughness. To the best of our knowledge, our method is the first to successfully extract a complete set of reflectance parameters with passive capture in completely uncontrolled outdoor environments

Penetration of human skin by the cercariae of Schistosoma mansoni : an investigation of the effect of multiple cercarial applications

It has previously been postulated that L-arginine emitted by penetrating Schistosoma mansoni cercariae serves as an intraspecific signal guiding other cercariae to the penetration site. It was suggested that penetrating in groups offers a selective advantage. If this hypothesis is correct and group penetration at one site on the host offers an advantage, it would follow that at such a site, successive groups of cercariae would be able to penetrate skin in either greater numbers or at a faster rate. This prediction was tested by the use of an in vitro model of cercarial penetration based on the Franz cell and using human skin. It was demonstrated that there was no increase in the percentage of cercariae able to penetrate the skin with subsequent exposures. Consequently, it seems unlikely that the release of L-arginine by cercariae during penetration could have evolved as a specific orientation system based on a selective advantage offered by group penetration.Peer reviewe

Dynamic capability development in multinational enterprises: Reconciling routine reconfiguration between the headquarters and subsidiaries

Research Summary Starting from the premise that firms need dynamic capabilities to adapt to changing environments, we discuss how multinational enterprises (MNEs) develop dynamic capabilities from internationalization. Unlike domestic firms that develop dynamic capabilities within one organizational system, MNEs are inherently multi-level systems with the headquarters and subsidiaries. In this paper, we focus on how internationalization depth and breadth function as sources of learning and unlearning in the headquarters and subsidiaries, and how this serves as the antecedent for routine reconfiguration and dynamic capability development in the MNE. We theorize that the headquarters\u27 and subsidiaries\u27 brokering capabilities are critical for reconciling routine reconfiguration at the two levels so that dynamic capability development can occur, and the MNE can adapt to environmental changes. Managerial Summary Our model of dynamic capability development in multinational enterprises (MNEs) via internationalization makes dynamic capabilities actionable for managers in three main ways. First, we emphasize both learning and unlearning from internationalization as important for both the subsidiaries and headquarters to reconfigure routines to adapt to changing environments. Second, the routine reconfiguration that occurs from the subsidiaries or the headquarters serves as the impetus for dynamic capability development in the MNE. Third, for dynamic capability development to occur in the MNE, both the headquarters and the subsidiaries must be able to reconcile routine reconfigurations via the headquarters\u27 and the subsidiaries\u27 brokering capabilities

The Transiting Exocomets in the HD 172555 System

The Earth is thought to have formed dry, in a part of the Solar Nebula deficient in organic material, and to have acquired its organics and water through bombardment by minor bodies. Observations of this process in well-dated systems can provide insight into the probable origin and composition of the bombarding parent bodies. Transiting cometary activity has previously been reported in Ca II for the late-A member of the 241 Myr old Pictoris Moving Group member, HD 172555(Kiefer et al. 2014). We present HST STIS and COS spectra of HD 172555 demonstrating that the star has chromospheric emission and variable in falling gas features in transitions of silicon and carbon ions at times when no Fe II absorption is seen in the UV data, and no Ca II absorption is seen in contemporary optical spectra. The lack of CO absorption and stable gas absorption at the system velocity is consistent with the absence of a cold Kuiper belt analog (Riviere-Marichalar et al. 2012) in this system. The presence of infall in some species at one epoch and others at different epochs suggests that, like Pictoris, there may be more than one family of exocomets. If perturbed into star-grazing orbits by the same mechanism as for Pic, these data suggest that the wide planet frequency among A-early F stars in the PMG is at least 37.5, well above the frequency estimated for young moving groups independent of host star spectral type

Evolution of elastic and mechanical properties during fault shear. The roles of clay content, fabric development, and porosity

Phyllosilicates weaken faults due to the formation of shear fabrics. Although the impacts of clay abundance and fabric on frictional strength, sliding stability, and porosity of faults are well studied, their influence on elastic properties is less known, though they are key factors for fault stiffness. We document the role that fabric and consolidation play in elastic properties and show that smectite content is the most important factor determining whether fabric or porosity controls the elastic response of faults. We conducted a suite of shear experiments on synthetic smectite-quartz fault gouges (10–100 wt% smectite) and sediment incoming to the Sumatra subduction zone. We monitored Vp, Vs, friction, porosity, shear and bulk moduli. We find that mechanical and elastic properties for gouges with abundant smectite are almost entirely controlled by fabric formation (decreasing mechanical and elastic properties with shear). Though fabrics control the elastic response of smectite-poor gouges over intermediate shear strains, porosity is the primary control throughout the majority of shearing. Elastic properties vary systematically with smectite content: High smectite gouges have values of Vp ~ 1,300–1,800 m/s, Vs ~ 900–1,100 m/s, K ~ 1–4 GPa, and G ~ 1–2 GPa, and low smectite gouges have values of Vp ~ 2,300–2,500 m/s, Vs ~ 1,200–1,300 m/s, K ~ 5–8 GPa, and G ~ 2.5–3 GPa. We find that, even in smectite-poor gouges, shear fabric also affects stiffness and elastic moduli, implying that while smectite abundance plays a clear role in controlling gouge properties, other fine-grained and platy clay minerals may produce similar behavior through their control on the development of fabrics and thin shear surfaces