Study of the potential for existing bathythermic string drifters

Evaluation report on the use of subsurface temperature buoy data and on their ability to provide suitable measurements in the ocean boundary laye

Aging in the glass phase of a 2D random periodic elastic system

Using RG we investigate the non-equilibrium relaxation of the (Cardy-Ostlund) 2D random Sine-Gordon model, which describes pinned arrays of lines. Its statics exhibits a marginal ($\theta=0$) glass phase for $T<T_g$ described by a line of fixed points. We obtain the universal scaling functions for two-time dynamical response and correlations near $T_g$ for various initial conditions, as well as the autocorrelation exponent. The fluctuation dissipation ratio is found to be non-trivial and continuously dependent on $T$.Comment: 5 pages, RevTex, Modified Versio

Notre expérience du couple métal-métal (MoM) dans le resurfaçage (RTH) et les prothèses totales de hanche avec tête de grand diamètre (PTH-GD) présentant un suivi minimum de 10 ans : À propos de 215 cas.

peer reviewedIntroduction : Au début des années 2000, le couple métal-métal (MoM) a connu un regain d’intérêt pour les prothèses de resurfaçage (PR) ainsi que pour les prothèses totales de hanche (PTH) utilisant des megatêtes (> 36 mm) (MT). Depuis 2011, il n’a cessé d’alimenter les débats suite au taux d’échecs à court et moyen termes anormalement élevé dans certains études. Des prothèses particulières ont dès 2010 jeté le discrédit sur ce couple dans son ensemble, imposant un suivi radio-clinique et biologique attentif de ces patients. Matériel et méthodes : Entre 2003 et 2009, 215 prothèses MoM ont été implantées dans notre service. Nous avons revu avec un recul d’au-moins 10 ans (10 – 21 ans ; moyenne 15,2 ans) 142 patients porteurs d’implants DUROM (68 MT, 74 PR), 60 patients porteurs d’implants BHR (15 MT, 45 PR) et 13 patients porteurs d’implants ASR (12 MT, 1 PR). 38 patients perdus de vue ou décédés d’une cause sans relation avec les implants (27 DUROM, 8 BHR et 3 ASR) mais présentant un suivi minimum de 10 ans ont été inclus dans l’étude. Nous avons établi pour chaque groupe de prothèse le score de Harris (HHS) en préopératoire et au dernier suivi , le taux de survie des implants ainsi qu’un historique détaillé des complications ayant mené à une reprise chirurgicale. Résultats : Pour le groupe DUROM, les HHS étaient de 52,9 en préopératoire et 96,5 ; au dernier suivi, nous dénombrons 14 reprises, 7 sur méga-tête (10,3 %) et 7 sur resurfaçage (9,5 %). Pour le groupe BHR, les HHS étaient de 52,4 en préopératoire et 96,2 ; au dernier suivi, nous dénombrons 6 reprises, 1 sur méga-tête (6,7 %) et 5 sur resurfaçage (11,1 %). Pour le groupe ASR, les HHS étaient de 51,3 en préopératoire et 93,1 ; au dernier suivi, nous dénombrons 2 reprises sur méga-tête (15,4 %) et pas de reprise de notre unique resurfaçage (0,0 %). Les principales causes de reprise sont pour les PR une cobaltémie élevée sans symptôme clinique (2 cas), un descellement cotyloïdien (3 cas), un conflit antérieur (3 cas) et un cas de luxation ; pour les MT un descellement (3 cas), une infection (3 cas) et la présence d’une pseudotumeur (2 cas). Les autres indications de reprises étaient des ossifications hétérotopiques, une bursite trochantérienne, une fracture périprothétique ainsi qu’une suspicion d’allergie au métal. Discussion : Les résultats de notre étude semblent montrer un faible pourcentage d’échec lié spécifiquement à l’utilisation du couple MoM à grand diamètre : 3 % (7/215 cas). Selon notre expérience, toute une classe d’implants qui aurait pu conserver une place dans des indications bien spécifiques s’est vue condamnée probablement à tort. Conclusion : Il semble important d’étudier ces implants non pas en tant que classe globale mais en séparant resurfaçaces, mégatêtes et fabricants en raison de la spécificité des métallurgies

Broad relaxation spectrum and the field theory of glassy dynamics for pinned elastic systems

We study thermally activated, low temperature equilibrium dynamics of elastic systems pinned by disorder using one loop functional renormalization group (FRG). Through a series of increasingly complete approximations, we investigate how the field theory reveals the glassy nature of the dynamics, in particular divergent barriers and barrier distributions controling the spectrum of relaxation times. A naive single relaxation time approximation for each wavevector is found to be unsatisfactory. A second approximation based on a random friction model, yields a size (L) dependent log-normal distribution of relaxation times (mean barriers ~L^\theta and variance ~ L^{\theta/2}) and a procedure to estimate dynamical scaling functions. Finally, we study the full structure of the running dynamical effective action within the field theory. We find that relaxation time distributions are non-trivial (broad but not log-normal) and encoded in a closed hierarchy of FRG equations. A thermal boundary layer ansatz (TBLA) appears as a consistent solution. It extends the one discovered in the statics which was shown to embody droplet thermal fluctuations. Although perturbative control remains a challenge, the structure of the dynamical TBLA which encodes barrier distributions opens the way for deeper understanding of the field theory approach to glasses

Semi-empirical dissipation source functions for ocean waves: Part I, definition, calibration and validation

New parameterizations for the spectra dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is non-zero only when a non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced to represent the dissipation of short waves due to longer breaking waves. Several degrees of freedom are introduced in the wave breaking and the wind-wave generation term of Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from gentle swells to major hurricanes, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations yield the best overall results to date. Perspectives for further improvement are also given.Comment: revised version for Journal of Physical Oceanograph

The Next Generation Virgo Cluster Survey. X. Properties of Ultra-Compact Dwarfs in the M87, M49 and M60 Regions

We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive, red-sequence galaxies M87, M49 and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color-color diagrams ($u^*iK_s$ or $u^*gz$). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ~3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters, and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ~85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.Comment: 37 pages, 40 figures. To appear in The Astrophysical Journa

The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87

The origin of ultra-compact dwarfs (UCDs)--objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies--has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme GCs, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs (rh >~10 pc) and 911 GCs associated with central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M_star > ~2X10^6 M_sun and 92% are as blue as the classic blue GCs, nearly triple the sample of previous confirmed Virgo UCDs, providing by far the best opportunity for studying the global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of the blue GCs in the inner ~ 70 kpc and as steep as that of the red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than the GCs, and the blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have a radially increasing orbital anisotropy profile, and are tangentially-biased at radii < ~ 40 kpc and radially-biased further out. In contrast, the blue GCs become more tangentially-biased at larger radii beyond ~ 40 kpc; (4) GCs with M_star > 2X10^6 M_sun have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially-biased orbital structure of UCDs at large radii is in general agreement with the "tidally threshed dwarf galaxy" scenario.Comment: 27 pages, 21 figures. To appear in The Astrophysical Journa

On the origin of heavy-tail statistics in equations of the Nonlinear Schrödinger type

We study the formation of extreme events in incoherent systems described by the Nonlinear Schrödinger type of equations. We consider an exact identity that relates the evolution of the normalized fourth-order moment of the probability density function of the wave envelope to the rate of change of the width of the Fourier spectrum of the wave field. We show that, given an initial condition characterized by some distribution of the wave envelope, an increase of the spectral bandwidth in the focusing/defocusing regime leads to an increase/decrease of the probability of formation of rogue waves. Extensive numerical simulations in 1D+1 and 2D+1 are also performed to confirm the results