Time filter

Source Type

Soucail G.,Toulouse University Midi-Pyrenees | Soucail G.,CNRS Institute for research in astrophysics and planetology
Astronomy and Astrophysics | Year: 2012

Context. The cluster Abell 2163 is a merging system of several subclusters with complex dynamics. It presents exceptional X-rays properties (high temperature and luminosity), suggesting that it is a very massive cluster. Recent 2D analysis of the gas distribution has revealed a complex and multiphase structure. Aims. This paper presents a wide-field weak lensing study of the dark matter distribution in the cluster in order to provide an alternative vision of the merging status of the cluster. The 2D mass distribution was built and compared to the galaxies and gas distributions. Methods. A Bayesian method, implemented in the Im2shape software, was used to fit the shape parameters of the faint background galaxies and to correct for PSF smearing. A careful color selection on the background galaxies was applied to retrieve the weak lensing signal. Shear signal was measured out to more than 2 Mpc (≈ 12′ from the center). The radial shear profile was fit with different parametric mass profiles. The 2D mass map was built from the shear distribution and used to identify the different mass components. Results. The 2D mass map agrees with the galaxy distribution, while the total mass inferred from weak lensing shows a strong discrepancy to the X-ray deduced mass. Regardless of the method used, the virial mass M 200 falls in the range 8 to 14 × 10 14 h 70 -1 M ⊙ inside the virial radius (∼2.0 h 70 -1 Mpc), a value that is two times less than the mass deduced from X-rays. The central mass clump appears bimodal in the dark matter distribution, with a mass ratio ∼3:1 between the two components. The infalling clump A2163-B is detected in weak lensing as an independent entity. All these results are interpreted in the context of a multiple merger seen less than 1 Gyr after the main crossover. © 2012 ESO.

Paletou F.,Toulouse University Midi-Pyrenees | Paletou F.,CNRS Institute for research in astrophysics and planetology
Astronomy and Astrophysics | Year: 2012

The general context of this study is the post-processing of multiline spectropolarimetric observations of stars, and in particular the numerical analysis techniques aiming at detecting and characterizing polarized signatures. Using real observational data, we compare and clarify several points concerning various methods of analysis. We applied and compared the results of simple line addition, least-squares deconvolution, and denoising by principal component analysis to polarized stellar spectra available from the TBLegacy database of the Narval spectropolarimeter. This comparison of various approaches of distinct sophistication levels allows us to make a safe choice for the next implementation of on-line post-processing of our unique database for the stellar physics community. © 2012 ESO.

Earthquake precursors are now regularly described but often detected only after a major or moderate seismic event. Presence and influence of fluids in the seismogenic processes are often observed at the time of earthquake studies. Even today, the understanding of the physical processes involved in the source region is a real challenge for seismic hazard assessment. Here, the aftershock sequence of the ML = 5.2, 1996 Saint-Paul-de-Fenouillet (Eastern Pyrenees, France) earthquake is first re-examined with P-wave cross-correlations, resulting in extracting three multiplets and in determining new locations. Multiplets and spatio-temporal distribution analysis of the aftershocks allow for quantifying the hydraulic diffusivity D at a maximum value of 5 m2/s and the permeability K at 10- 15 m2 in the upper Pyrenean crust. Second, a model is established in order to explain the hydrogeochemical transient anomalies, which occurred during the 15 day-period preceding the 1996 earthquake. These anomalies consist on a temporal and spatial sequence of gas emissions in the epicentral area and on chloride and lead concentration variations in a bottled mineral water 25 km north to the main shock epicenter. The proposed model processed in a standard elastic half-space, consists of creep on a low-angle crustal normal-fault, generating volumetric strain field changes over a distance of 25 km from the epicentral area. This model is able to constrain not only the mechanisms and the locations of the geochemical anomalies, but also their timing and probable casual links to the triggering of the impending major event. Also, the active extension proposed here is compatible with seismological observations in the Pyrenees. Thus, the possibility of such creep, which can be considered as a slow-slip event, is discussed in the Pyrenean tectonic and geological context. The model is discussed and compared to previous proposed models on precursor processes of earthquakes, especially concerning the preparation zone concept. Finally, a complete seismic scenario over the period beginning 15 days before the quake and ending 5 days after is proposed and discussed. © 2009 Elsevier B.V. All rights reserved.

Fournier J.-P.,McGill University | Azoulay L.,Toulouse University Midi-Pyrenees | Yin H.,McGill University | Montastruc J.-L.,McGill University | And 2 more authors.
JAMA Internal Medicine | Year: 2015

IMPORTANCE Tramadol is a weak opioid analgesic whose use has increased rapidly, and it has been associated with adverse events of hypoglycemia. OBJECTIVE To assess whether tramadol use, when compared with codeine use, is associated with an increased risk of hospitalization for hypoglycemia. DESIGN, SETTING, AND PARTICIPANTS A nested case-control analysiswas conducted within the United Kingdom Clinical Practice Research Datalink linked to the Hospital Episodes Statistics database of all patients newly treated with tramadol or codeine for noncancer pain between 1998 and 2012. Cohort and case-crossover analyses were also conducted to assess consistency of the results. MAIN OUTCOMES AND MEASURES Cases of hospitalization for hypoglycemiawere matched with up to 10 controls on age, sex, and duration of follow-up. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated comparing use of tramadol with codeine. A cohort analysis, with high-dimensional propensity score-adjusted hazard ratios (HRs) and 95%CIs, was performed comparing tramadol with codeine in the first 30 days after treatment initiation. Finally, a case-crossover analysis was also performed, in which exposure to tramadol in a 30-day risk period immediately before the hospitalization for hypoglycemia was compared with 11 consecutive 30-day control periods. Odds ratios and 95%CIs were estimated using conditional logistic regression analysis. RESULTS The cohort included 334 034 patients, of whom 1105 were hospitalized for hypoglycemia during follow-up (incidence, 0.7 per 1000 per year) and matched to 11 019 controls. Compared with codeine, tramadol use was associated with an increased risk of hospitalization for hypoglycemia (OR, 1.52 [95%CI, 1.09-2.10]), particularly elevated in the first 30 days of use (OR, 2.61 [95%CI, 1.61-4.23]). This 30-day increased risk was confirmed in the cohort (HR, 3.60 [95%CI, 1.56-8.34]) and case-crossover analyses (OR, 3.80 [95%CI, 2.64-5.47]). CONCLUSIONS AND RELEVANCE The initiation of tramadol therapy is associated with an increased risk of hypoglycemia requiring hospitalization. Additional studies are needed to confirm this rare but potentially fatal adverse event.. Copyright © 2015 American Medical Association. All rights reserved.

Kessler W.S.,National Oceanic and Atmospheric Administration | Cravatte S.,Ird Institute Of Recherche Pour Le Developpement | Cravatte S.,Toulouse University Midi-Pyrenees
Journal of Geophysical Research: Oceans | Year: 2013

The mean absolute geostrophic circulation of the Coral Sea is constructed from climatological hydrographic data referenced to a 1000 m velocity field derived from Argo float drift. Two branches of the South Equatorial Current (SEC) enter the Coral Sea between New Caledonia and the Solomon Islands: the broad, upper thermocline North Vanuatu Jet (NVJ), and the narrow North Caledonian Jet (NCJ) extending to at least 1500 m. Most of this incoming flow leaves to the Solomon Sea. Four distinct pathways through the Coral Sea are traced by their water properties: (1) The NCJ crosses the Sea to the coast of Australia and turns north at densities sigma 25-27.4 as the main source of the Gulf of Papua (GPC) western boundary current, eventually feeding the New Guinea Coastal Undercurrent; (2) part of the shallow NVJ turns into the Solomon Sea in midbasin, carrying high-salinity water above sigma 25.5; (3) another part of the NVJ continues to Australia, then turns north to join the GPC, extending it to the surface; (4) a shallow finger of NVJ water, traced by low oxygen above sigma 25, turns south along the coast, beginning the East Australian Current (EAC) at 15°S. Total transport from the Coral to the Tasman Sea is small and shallow; instead, most of the EAC is fed from south of New Caledonia, consistent with the Island Rule. However, large transport fractions occur in narrow jets close to coastlines and reefs and are not well sampled, precluding a quantitative estimate of meridional redistribution of the incoming SEC. Key Points Argo float drift references Coral Sea climatological geostrophic currents Interior and boundary current transports largely explained by the Island Rule Three distinct pathways carry the SEC through the Coral Sea to the equator © 2013 The Authors.

Discover hidden collaborations