-The effect of damping in the wave turbulence regime for thin vibrating plates is studied. An experimental method, allowing measurements of dissipation in the system at all scales, is first introduced. Practical experimental devices for increasing the dissipation are used. The main observable consequence of increasing the damping is a significant modification in the slope of the power spectral density, so that the observed power laws are not in a pure inertial regime. However, the system still displays a turbulent behavior with a cut-off frequency that is determined by the injected power which does not depend on damping. By using the measured damping power-law in numerical simulations, similar conclusions are drawn out.Introduction. -Wave (or weak) turbulence theory (WTT) aims at describing the long time behavior of weakly non linear systems with energy exchanges between scales. It predicts for long time broadband KolmogorovZakharov spectra, by analogy with hydrodynamic turbulence [1][2][3]. A large number of situations have been studied over the years starting from the initial context of water waves [4][5][6][7], to nonlinear optics [8] or Alfven Waves in plasmas [9] for instance.Wave turbulence for elastic vibrating plates has been investigated theoretically in 2006 [10], rapidly followed by two experimental works [11,12]. The theoretical analysis considers the dynamics in the framework of the von Kármán equations. For a thin plate of thickness h, Poisson ratio ν, density ρ and Young's modulus E, it yields [13]

International audienceWe experimentally study resonant interactions of oblique surface gravity waves in a large basin. Our results strongly extend previous experimental results performed mainly for perpendicular or collinear wave trains. We generate two oblique waves crossing at an acute angle, while we control their frequency ratio, steepnesses and directions. These mother waves mutually interact and give birth to a resonant wave whose properties (growth rate, resonant response curve and phase locking) are fully characterized. All our experimental results are found in good quantitative agreement with four-wave interaction theory with no fitting parameter. Off-resonance experiments are also reported and the relevant theoretical analysis is conducted and validated

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The majority of patients with migraine headaches are treated in non-specialized institutions though data on treatment outcomes are largely derived from tertiary care centers. The current non-interventional study explores efficacy and tolerability outcomes of patients with episodic migraines receiving topiramate as preventive agent in a general practice setting. A total of 366 patients (87% female, mean age 41.8 ± 11.6 years) were eligible for migraine prevention and treated with flexible dose topiramate for 6 months (core phase), and optionally for a total of 12 months (follow-up phase). Overall, 261 patients (77.7% of safety analysis set, SAF) completed the core phase. Reasons for discontinuation included adverse events (2.1%), lost to follow-up (1.8%), other reasons (1.5%), and end of therapy (0.3%) though in the majority of patients who discontinued no reasons were listed. The median daily dose at endpoint was 50 mg/day (range, 25–187.5 mg/day). The median days with migraine headaches decreased from 6.0 to 1.2 days (p < 0.001), median pain intensity score decreased from 17.0 to 3.2 points (p < 0.001). In women with reported menstruation-associated migraine, the median number of migraine attacks decreased from 4.0 to 0.9 (p < 0.001). Absenteeism as well as triptan use decreased significantly, and significant improvements in activities of daily living and quality of life were reported. The most frequently reported AEs were paraesthesia (4.2%) and nausea (3%). Results suggest that migraine prevention with topiramate in a general practice is generally well tolerated and associated with a significant improvement in migraine headaches and related functional impairment.

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-Tidally modulated shoreface (TMS) corresponds to peculiar costal environments. The general morphology and the expressed bedforms are provided by the interplay of both waves and tides. The recognition of TMS in the fossil record still remains a difficult task. The study of one mega-tidal modern TMS in the north of France (Berck-Plage) provides new key criteria to identify this kind of coastal system in the rock record. Field investigation and digital mapping were realized at lowest tide during spring tide under fair-weather condition. The intertidal zone is characterized by a succession of several sand banks shore parallel separated by topographic lows that are defined as ridges and runnels. Seven distinct dominant bedforms are recognized: 3D current ripples, 3D asymmetrical ripples, 2D symmetrical ripples, 2D small symmetrical dunes, 2D large symmetrical dunes, 3D symmetrical dunes and plane beds. The upper stage plane bedding mainly composed the ridges while the six other bedforms are commonly found within the runnels or on the flanks of the ridges. Comparison of the bedforms of Berck-Plage with previous experimental studies on bedforms genesis proves that the necessary flow parameters for generating these bedforms belong to an oscillatory flow except for the 3D current ripples, which are formed by a unidirectional flow. This study confirms the dominance of oscillatory structures through the intertidal zone in a mega-tidal context and show that wave processes are more powerful than tide processes for bedform generation although during fair weather conditions. Based on the timing of genesis, the description and the repeated pattern of distribution of bedforms between two ridges is highlighted thus helping to propose a theoretical facies sequence for an intertidal zone characterized by ridges and runnels applicable to ancient sedimentary successions.Keywords: waves / tides / ridge and runnel / bedforms / stratigraphy / Berck-Plage / France Résumé -Structures sédimentaires d'une zone intertidale en barre et bâches dominée par la houle (Berck-Plage ; Nord de la France) : implications pour le registre sédimentaire ancien. Les plages et avant-plages sous l'influence de la houle et modulées par l'action de la marée, correspondent à des environnements côtiers particuliers. Leurs géomorphologies générales ainsi que les structures sédimentaires associées résultent de l'action combinée de la houle et de la marée. L'identification de ces environnements atypiques dans des successions sédimentaires anciennes demeure difficile. L'analyse d'un environnement mégatidal semi-diurne actuel dans le Nord de la France (Berck-Plage) a permis de fournir de nouveaux critères de reconnaissance pour ce type de système côtier hybride dans le fossile. Une étude de terrain ainsi qu'une cartographie numérique ont été réalisées à marée basse au cours d'une marée de vives-eaux. La zone intertidale est caractérisée par une succession de plusieurs bancs de sables parallèles à la côte et qui sont définies comme des barres (topographie po...

We experimentally study the properties of nonlinear surface gravity waves in a large scale basin. We consider two different configurations: a one-dimensional (1D) monochromatic wave forcing, and a two-dimensional (2D) forcing with bichromatic waves satisfying resonant-wave interaction conditions. For the 1D forcing, we find a discrete wave energy spectrum dominated at high frequencies by bound waves whose amplitudes decrease as a power law of the frequency. Bound waves (e.g. to the carrier) are harmonics superimposed on the carrier wave propagating with the same phase velocity as the one of the carrier. When a narrow frequency random modulation is applied to this carrier, the high-frequency part of the wave energy spectrum becomes continuous with the same frequency-power law. Similar results are found for the 2D forcing when a random modulation is also applied to both carrier waves. Our results thus show that all these nonlinear gravity wave spectra are dominated at high frequencies by the presence of bound waves, even in the configuration where resonant interactions occur. Moreover, in all these configurations, the power-law exponent of the spectrum is found to depend on the forcing amplitude with the same trend as the one found in previous gravity wave turbulence experiments. Such set of bound waves may thus explain this dependence that was previously poorly understood.

When a vortex refracts surface waves, the momentum flux carried by the waves changes direction and the waves induce a reaction force on the vortex. We study experimentally the resulting vortex distortion. Incoming surface gravity waves impinge on a steady vortex of velocity U0 driven magnetohydrodynamically at the bottom of a fluid layer. The waves induce a shift of the vortex center in the direction transverse to wave propagation, together with a decrease in surface vorticity. We interpret these two phenomena in the framework introduced by Craik and Leibovich (1976): we identify the dimensionless Stokes drift S = Us/U0 as the relevant control parameter, Us being the Stokes drift velocity of the waves. We propose a simple vortex line model which indicates that the shift of the vortex center originates from a balance between vorticity advection by the Stokes drift and self-advection of the vortex. The decrease in surface vorticity is interpreted as a consequence of vorticity expulsion by the fast Stokes drift, which confines it at depth. This purely hydrodynamic process is analogous to the magnetohydrodynamic expulsion of magnetic field by a rapidly moving conductor through the electromagnetic skin effect. We study vorticity expulsion in the limit of fast Stokes drift and deduce that the surface vorticity decreases as 1/S, a prediction which is compatible with the experimental data. Such wave-induced vortex distortions have important consequences for the nonlinear regime of wave refraction: the refraction angle rapidly decreases with wave intensity. Top-view of the experimental cell, containing a height H = 3.6 cm of copper-sulfate solution. The wavemaker is a vertically oscillating cylinder touching the free-surface. A current I running between two coaxial electrodes interacts with the vertical field of a permanent magnet to produce an azimuthal Lorentz force driving the vortex. PTV in the dashed-green domain gives access to the wave-field and surface mean-flow. b. An azimuthal vortex (green) refracts surface waves by an angle θ. Because of refraction, the radiation pressure forces due to the incoming and outgoing waves do not compensate (thin red arrows). Instead, there is a net recoil force on the vortex (thick red arrow).