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International audience; In this article, the Optimal Reciprocal Collision Avoidance (ORCA) algorithm is modified to make it work for speed constrained aircraft. The adaptation of ORCA to aircraft conflict resolution shows that when the speed norm is constrained, aircraft flying within the same speed range with small angle converging trajectories tend to remain on parallel tracks, preventing a resolution of the conflict. The ORCA algorithm is slightly modified to avoid this behavior. In the new algorithm called CSORCA (Constant Speed Optimal Reciprocal Collision Avoidance), the directions of the semi-plane used to calculate the conflict free maneuvers are modified when the relative speed vector is in the semi-circular part of the conflicting area. After explaining the reasons that make the original algorithm fail in the constant speed environment, the modification made on the algorithm is detailed and its impact on a simple example is shown. The new strategy is also compared to an Add-Up strategy close to the Airborne Separation Assurance System (ASAS) strategy found in the literature. Hundreds of fast time simulations are then performed to compare the two versions of the algorithm for different traffic densities in the horizontal plane. In these simulations the speed norm is first constrained. The aircraft can only change direction with a limited turning rate. Simulations with released speed constraints are then performed to compare the behavior of both algorithms in a more general environment. In all the scenarios tested, CSORCA is more efficient than ORCA to solve conflicts.

EASPEBIOmEAGROSUP; Pedogenic carbonates (calcretes) have often been proposed as possible markers of the pedogenetic processes in soils under semi-arid climate. However, precise chronological constraints on, their formation are required in order to investigate the climatic and paleo-environmental conditions that prevailed during and after their formation, and to improve our understanding of the, physical and chemical conditions that promoted their development and preservation. Moreover, these authigenic calcium carbonate precipitates provide us with an interesting test of the U-Th radioactive disequilibrium dating method, the reliability of which has been demonstrated extensively in aragonitic corals and calcitic continental speleothems, but which remains much more questionable in highly porous, chemically and mineralogically complex media such as soil profiles. We report here U-238-U-234-Th-230 radioactive disequilibrium analyses measured by Thermo-Ionization Mass Spectrometry in calcretes from two sites in southwest India. Since calcretes are impure carbonates mixed with various amounts of parent rock and weathered minerals, all ages must be computed using the isochron technique, involving the extraction of several coeval subsamples from the same soil horizon and U-Th analyses after total dissolution (TSD) method, in order to correct for the detrital component. Th-232 is usually used as index of the detrital contamination, and the isochron age is derived from the isotopic composition (Th-230/U-238; U-234/U-238) of the pure authigenic carbonate end-member of the mixing line. Our results show that each set of samples taken from decimetric blocks is characterized by a well-defined isochron line in a 3-D Osmond diagram (Th-232/U-238; Th-230/U-238; U-234/U-238). The regression lines obtained for most of the samples show probabilities of fit satisfying the mathematical assumptions of the isochron model (in most cases 0.05), and mean square weighted deviations (MSWD) values around 1. The compositions of the end-members are highly variable between the different isochrons, both for the carbonate phase, indicating various ages of cristallisation, and for the detrital phase, indicating various origins and compositions. Notably, our data demonstrate that the detrital component is in all cases out of secular equilibrium, by contrast with the standard paradigm of "dirty carbonate" dating, which is based on the assumption of average continental crust Th/U elemental ratio, and secular equilibrium values of the ((Th-230/U-238) and (U-234/U-238) ratios. At the first site (Coimbatore), we obtain U-Th ages between 304 +/- 38 ka and 44 +/- 2.9 ka (2 sigma) from the base to the top of the profile. These suggest discontinuous precipitation of the different fades in good agreement with micro morphological observations. At the second study site (Gundlupet), the carbonate nodules sampled from two different profiles, yield consistent ages of 200 ka, which suggests that precipitation of nodular carbonate occurred across the entire pediment toposequence during a single event. Surprisingly, in mere contradiction with the standard model of impure carbonate dating, two puzzling samples display "vertical isochrons", i.e., variable Th-232/U-238 without any variation of the Th-230/U-238 and U-234/U-238 ratios. Such patterns require extremely high Th-232/U-238 ratios, in an as yet unidentified detrital phase. Taken at face value, these results suggest that no clear correlation can be inferred between the precipitation of these pedogenic carbonates and major orbitally-driven climate variations recorded in other archives during the last glacial/interglacial cycles.

Resume La methadone est utilisee dans de nombreux pays comme traitement antalgique des douleurs liees au cancer. Nous rapportons le cas d’un patient ayant bien repondu a la methode d’analgesie autocontrolee preconisee comme methode d’equilibration par le protocole de l’Afssaps 2010.

We present monthly resolved records of strontium/calcium (Sr/Ca) and oxygen isotope (δ18O) ratios from well-preserved fossil corals drilled during the Integrated Ocean Drilling Program (IODP) Expedition 310 “Tahiti Sea Level” and reconstruct sea surface conditions in the central tropical South Pacific Ocean during two time windows of the last deglaciation. The two Tahiti corals examined here are uranium/thorium (U/Th)-dated at 12.4 and 14.2 ka, which correspond to the Younger Dryas (YD) cold reversal and the Bolling–Allerod (B–A) warming of the Northern Hemisphere, respectively. The coral Sr/Ca records indicate that annual average sea surface temperature (SST) was 2.6–3.1 °C lower at 12.4 ka and 1.0–1.6 °C lower at 14.2 ka relative to the present, with no significant changes in the amplitude of the seasonal SST cycle. These cooler conditions were accompanied by seawater δ18O (δ18Osw) values higher by ~ 0.8‰ and ~ 0.6‰ relative to the present at 12.4 and 14.2 ka, respectively, implying more saline conditions in the surface waters. Along with previously published coral Sr/Ca records from the island [Cohen and Hart (2004), Deglacial sea surface temperatures of the western tropical Pacific: A new look at old coral. Paleoceanography 19, PA4031, doi:10.1029/2004PA001084], our new Tahiti coral records suggest that a shift toward lower SST by ~ 1.5 °C occurred from 13.1 to 12.4 ka, which was probably associated with a shift toward higher δ18Osw by ~ 0.2‰. Along with a previously published coral Sr/Ca record from Vanuatu [Correge et al. (2004), Interdecadal variation in the extent of South Pacific tropical waters during the Younger Dyras event. Nature 428, 927–929], the Tahiti coral records provide new evidence for a pronounced cooling of the western to central tropical South Pacific during the Northern Hemisphere YD event.

Detection and precise quantification of the different carbonate minerals is crucial in selecting coral reef samples prior to geochemical and radiochronological measurements, thus helping to interpret changes in the mineralogical composition of geological formations made of reef material and associated sediments such as periplatform oozes. While powder X-ray diffraction (XRD) is a widely used method for mineralogical analysis, precise and accurate quantification of mineral abundance requires a thorough calibration of the instrument and method by means of gravimetric standards. In this study, we optimize a calibration method for the quantitative determination of four widespread Ca and Mg carbonates: calcite, aragonite, magnesian calcite (Mg-calcite) and dolomite. To detect and quantify very low calcite contents, which provide a crucial screening criterion for coral radiochronology, we perform a detailed survey of analytical precision and limits using two different XRD facilities. Detection and quantification limits (≈ 0.18% and ≈ 0.9% calcite in a calcite–aragonite mixture, respectively) are shown to be similar between the two instruments. The reproducibility of measurements clearly demonstrates that it is preferable to use peak area rather than peak height alone to obtain a precise quantification of the abundances of various carbonate minerals.