Constraints on grain size and stable iron phases in the uppermost Inner Core from multiple scattering modeling of seismic velocity and attenuation

International audienceWe propose to model the uppermost inner core as an aggregate of randomly oriented anisotropic ``patches''. A patch is defined as an assemblage of a possibly large number of crystals with identically oriented crystallographic axes. This simple model accounts for the observed velocity isotropy of short period body waves, and offers a reasonable physical interpretation for the scatterers detected at the top of the inner core. From rigorous multiple scattering modeling of seismic wave propagation through the aggregate, we obtain strong constraints on both the size and the elastic constants of iron patches. We perform a systematic search for iron models compatible with measured seismic velocities and attenuations. An iron model is characterized by its symmetry (cubic or hexagonal), elastic constants, and patch size. Independent of the crystal symmetry, we infer a most likely size of patch of the order of 400~m. Recent {\it bcc} iron models from the literature are in very good agreement with the most probable elastic constants of cubic crystals found in our inversion. Our study (1) suggests that the presence of melt may not be required to explain the low shear wavespeeds in the inner core and (2) supports the recent experimental results on the stability of cubic iron in the inner core, at least in its upper part

Effets de l'amnioinfusion en présence de liquide amniotique méconial épais sur les anomalies du rythme cardiaque foetal

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Amorphous magnesium silicate ultrasound-assisted precipitation in a mixing system: Population balance modelling and crystallization rates identification

International audienceNatural talc is a very interesting filler for plastic and rubber materials and paints because it enables polymer matrix properties to be improved. Nano-sized particles are required to get a good dispersion of the solid in the polymer matrix. However, at the moment the main drawback in the use of natural talc is that, with a conventional milling process, nanometric particle sizes are difficult and expensive to obtain. A process of magnesium silicate synthesis made by ultrasound-assisted precipitation has been developed in two steps. The first step consists of the synthesis of amorphous magnesium silicate by precipitation from sodium metasilicate and acid magnesium chloride. In the second step, the amorphous solid is transformed in a crystalline solid under pressure. In this study an ultrasound-assisted synthesis of amorphous magnesium silicate is proposed. Some process parameters (ultrasound power, initial reactants molalities and reactants flow rate) have effects on the particle-size distribution. The population balance is modelled and solved by moments method in the steady state to identify nucleation and growth rates and agglomeration kernel as a function of operating conditions and to understand how these conditions affect the particle-size distribution

Une ingénierie éducative innovante pour travailler des compétences en EDD dans le cadre d'un Observatoire Hommes Milieux

International audienceNous présentons un dispositif qui engage des relations entre chercheurs, enseignants et élèves dans un territoire partagé. Un Observatoire Hommes Milieux permet d'appréhender la complexité, l'incertitude, les savoirs en construction et la projection vers le(s) futur(s) possible(s), compétences centrales en éducation au développement durable. Des jeux de rôle ont été proposés à travers la co-construction de séquences pédagogiques par des chercheurs et des enseignants, et des dispositifs pédagogiques variés tels que des sorties, des débats et des rencontres avec des chercheurs et des acteurs du territoire. Les élèves se sont confrontés à une certaine complexité en manipulant des temporalités : observation de co-évolutions hommes-milieux dans le passé et projection dans le futur par exemple. En retour, les acquis de ce travail visaient à développer chez les élèves des capacités à réinvestir hors de l' école ce qu'ils ont vu en classe. C' est un enjeu fort de la contribution des activités scolaires à l' éducation citoyenne

Étude de la précipitation du silicate de magnésium amorphe assistée par ultrasons (synthèse, caractérisation et modélisation)

Le talc naturel est utilisé en tant que charge de haute performance des matrices polymères, car il permet d'améliorer leurs propriétés mécaniques. Pour cela, la dispersion de la charge dans la matrice doit être de qualité, ce qui implique que les particules soient nanométriques. Or, obtenir des particules nanométriques par broyage s'avère coûteux énergétiquement et économiquement. L'étude d'une opération de précipitation a conduit à la synthèse de silicate de magnésium amorphe constitué de particules primaires nanométriques. L'analyse de surface du solide par chromatographie gazeuse inverse a été employée afin de prédire les interactions entre le solide et la matrice polymère. La constante d'équilibre du solide amorphe et les vitesses de cristallisation ont pu être identifiées après modélisation des équilibres chimiques.Natural talc is used as an high performance filler in polymer matrices because it enables to improve mechanical properties. In order to improve these properties, a good-quality dispersion of the filler in the polymer matrix is necessary, that involves particles being nano-sized. However, getting nano-sized particles by milling processes is expensive and very energetic. The study of a precipitation operation has led to the synthesis of amorphous magnesium silicate whose primary particles are nano-sized. Solid surface analysis by inverse gas chromatography has been made in order to predict interactions between solid and polymer matrix. Equilibrium constant of amorphous solid and crystallization rates have been identified after modelling of chemical equilibria.TOULOUSE-INP (315552154) / SudocSudocFranceF

Firmware implementation of a recurrent neural network for the computation of the energy deposited in the liquid argon calorimeter of the ATLAS experiment

The ATLAS experiment measures the properties of particles that are products of proton-proton collisions at the LHC. The ATLAS detector will undergo a major upgrade before the high luminosity phase of the LHC. The ATLAS liquid argon calorimeter measures the energy of particles interacting electromagnetically in the detector. The readout electronics of this calorimeter will be replaced during the aforementioned ATLAS upgrade. The new electronic boards will be based on state-of-the-art field-programmable gate arrays (FPGA) from Intel allowing the implementation of neural networks embedded in firmware. Neural networks have been shown to outperform the current optimal filtering algorithms used to compute the energy deposited in the calorimeter. This article presents the implementation of a recurrent neural network (RNN) allowing the reconstruction of the energy deposited in the calorimeter on Stratix 10 FPGAs. The implementation in high level synthesis (HLS) language allowed fast prototyping but fell short of meeting the stringent requirements in terms of resource usage and latency. Further optimisations in Very High-Speed Integrated Circuit Hardware Description Language (VHDL) allowed fulfilment of the requirements of processing 384 channels per FPGA with a latency smaller than 125 ns.Comment: 13 pages, 8 figure

Multimethod Characterization of the French-Pyrenean Valley of Bagnères-de-Bigorre for Seismic-Hazard Evaluation: Observations and Models

International audienceA narrow rectilinear valley in the French Pyrenees, affected in the past by damaging earthquakes, has been chosen as a test site for soil response characteriza- tion. The main purpose of this initiative was to compare experimental and numerical approaches. A temporary network of 10 stations has been deployed along and across the valley during two years; parallel various experiments have been conducted, in particular ambient noise recording, and seismic profiles with active sources for struc- ture determination at the 10 sites. Classical observables have been measured for site amplification evaluation, such as spectral ratios of horizontal or vertical motions between site and reference stations using direct S waves and S coda, and spectral ratios between horizontal and vertical (H/V) motions at single stations using noise and S-coda records. Vertical shear-velocity profiles at the stations have first been obtained from a joint inversion of Rayleigh wave dispersion curves and ellipticity. They have subsequently been used to model the H/V spectral ratios of noise data from synthetic seismograms, the H/V ratio of S-coda waves based on equipartition theory, and the 3D seismic response of the basin using the spectral element method. General good agreement is found between simulations and observations. The 3D simulation reveals that topography has a much lower contribution to site effects than sedimentary filling, except at the narrow ridge crests. We find clear evidence of a basin edge effect, with an increase of the amplitude of ground motion at some distance from the edge inside the basin and a decrease immediately at the slope foot

Le jeu de rôle en EDD pour dépasser une pensée binaire : une étude de cas à l’école primaire

Le jeu de rôle est une forme de débat dans lequel les arguments sont fournis aux participants. Cet article repose sur l’analyse des échanges langagiers lors d’un jeu de rôle autour d’une problématique relative au territoire local dans une classe d’élèves français âgés de 8 à 10 ans. Nous identifions les accords et désaccords avec les diverses propositions afin d’établir leur degré de cohérence avec leur personnage. Les résultats témoignent d’un niveau d’argumentation élevé, d’une cohérence dans les arguments avancés ainsi que de l’émergence de nouvelles propositions. Le jeu de rôle semble remplir sa fonction d’appropriation d’arguments. Il rend compte également d’une possible construction de compétences écocitoyennes.Debating is a school practice mobilized in various contexts with varied stakes and renewed modalities in primary school French curriculum. We present the analysis of linguistic exchanges during a role-play with 8 to 10 years old pupils from the point of view of argumentation. We try to identify if pupils are capable of mobilizing arguments and if exchanged arguments are coherent with the character they represent. Results testify of a high argumentation level, of coherence in advanced arguments as well as an emergence of new proposals. If role-play fulfills its arguments appropriation function, it also conveys a possible thought emancipation

CSI 2264: Characterizing Accretion-Burst Dominated Light Curves for Young Stars in NGC 2264

Based on more than four weeks of continuous high cadence photometric monitoring of several hundred members of the young cluster NGC 2264 with two space telescopes, NASA's Spitzer and the CNES CoRoT (Convection, Rotation, and planetary Transits), we provide high quality, multi-wavelength light curves for young stellar objects (YSOs) whose optical variability is dominated by short duration flux bursts, which we infer are due to enhanced mass accretion rates. These light curves show many brief -- several hour to one day -- brightenings at optical and near-infrared (IR) wavelengths with amplitudes generally in the range 5-50% of the quiescent value. Typically, a dozen or more of these bursts occur in a thirty day period. We demonstrate that stars exhibiting this type of variability have large ultraviolet (UV) excesses and dominate the portion of the u-g vs. g-r color-color diagram with the largest UV excesses. These stars also have large Halpha equivalent widths, and either centrally peaked, lumpy Halpha emission profiles or profiles with blue-shifted absorption dips associated with disk or stellar winds. Light curves of this type have been predicted for stars whose accretion is dominated by Rayleigh-Taylor instabilities at the boundary between their magnetosphere and inner circumstellar disk, or where magneto-rotational instabilities modulate the accretion rate from the inner disk. Amongst the stars with the largest UV excesses or largest Halpha equivalent widths, light curves with this type of variability greatly outnumber light curves with relatively smooth sinusoidal variations associated with long-lived hot spots. We provide quantitative statistics for the average duration and strength of the accretion bursts and for the fraction of the accretion luminosity associated with these bursts.Comment: Accepted for publication in AJ. 39 pages; 6 tables; 25 figures, many of which are highly degraded to meet size limits. Please download the regular resolution version at http://web.ipac.caltech.edu/staff/amc/staufferetal2014.pd