Rapport relatif à la création du Conseil national du numérique

Rapport remis à Monsieur Eric Besson, Ministre chargé de l\u27Industrie, de l\u27Energie et de l\u27Economie numérique, par Pierre Kosciusko-Morizet, président de l\u27ASCEL (association de l\u27économie numérique), co-fondateur du site Priceminister.com, sur le futur Conseil national du numérique qui doit voir le jour au printemps 2011

A NMR and molecular dynamics study of CO2-bearing basaltic melts and glasses

International audienceThe presence of volatile, especially carbon dioxide (CO2), in silicate liquids is considered as a key parameter to magmatic degassing and eruptive processes. Unfortunately, due to experimental difficulties, our current knowledge on the CO2 effect on silicate melt structure is weak and relies on the observation of ex-situ recovered CO2-bearing glasses.In the present work, we confront the results obtained from NMR spectroscopic observations of glass synthesised at pressure between 0.5 and 3.0 GPa and theoretical investigations from first-principles molecular dynamics (FPMD) simulations conducted at 5.0 and 8.0 GPa on high temperature melt for a simplified basaltic composition.The results obtained on the aluminosilicate framework (molar fraction of silicon species and Al average coordination number) suggest that both ex-situ and in-situ results compare adequately. The results are in agreement with our current knowledge on the change in aluminosilicate melt/glass structure with changing intensive conditions. Increasing pressure from 0.5 to 8.0 GPa induces 1) an increase in the average Al coordination number from 4.1 to almost 5.0 and 2) an increase in the degree of polymerisation with NBO/Si changing from 1.30 to 0.80.The presence of CO2 does not seem to induce a dramatic change on both the average Al coordination number and the NBO/Si. FPMD simulations performed with 0 and 20 wt.% CO2 at 8.0 GPa result in a change from 4.84 to 4.96 for the average Al coordination number and in a change from 0.87 to 0.80 for the NBO/Si value, respectively.On the contrary, there is a lack of consistency in between the CO2 speciation obtained from NMR spectroscopy and from FPMD simulations. Whereas the analysis of glasses does not reveal the presence of CO2mol species, the FPMD simulation results suggests the existence of a small proportion of CO2mol. Further work with in-situ experimental approach is therefore required to explain the observed lack of consistency between the CO2 speciation in glass and in high temperature melt with basaltic composition

C-O-H fluid solubility in Haplo-basalt under reducing conditions: An experimental study

International audienceWe conducted an experimental study to constrain the C-H-O solubility and speciation in hydrous silicate melts equilibrated under reduced fO2 conditions. Haplo-basaltic glasses in the NCMAS-C-O-H system were synthesised using IHPV at 1250 °C, 200-300 MPa with variable applied fH2 so as to vary fO2. Recovered rapidly quenched glasses were characterized using various spectroscopic methods: Micro-FTIR, Raman and 13C-MAS NMR. Glass CO2 content changes from 680 to 1320 ppm between ΔFMQ-2.6 and ΔFMQ + 2.6 independently of H2O content changing from 1.3 to 4.0 wt.%. Recent thermodynamic modelling of isobaric CO2-H2O solubility fails to reproduce our CO2-H2O solubility trend under reducing conditions. The lower CO2 solubility in the melt as compared to more oxidized conditions is directly correlated to the decrease of fCO2 within the fluid phase under reducing conditions. Carbonate groups (CO32-), OH- and H2Omol are the volatile species in the glasses. No evidence for CH4, carbides or organic compounds was observed. 13C MAS NMR analysis suggests that several carbonate units are coexisting in the glasses. {1H} 13C-CPMAS NMR suggests that all CO32- units are surrounded by OH groups. Those environments appear to slightly change with changing fO2 conditions suggesting different degree of hydrogenation in the vicinity of the carbonate groups. Our data show that the presence of a significant amount of dissolved does not increase the solubility of species such as CO or CH4. In other words, such species remain insoluble in basaltic melts, as established under dry conditions. Altogether, our CO2 solubility results show that a wet but reduced basalt will degass more C-species than if oxidized, owing to the lower prevailing fCO2 and insoluble character of CO. The presence of an important fraction of CO in the fluid phase will have a large impact on the primitive atmospheric compositions of Mars and the Earth

A model for the activity of silica along the carbonatite-kimberlite-mellilitite-basanite melt compositional joint

International audienceCarbon dioxide and water, being present in the Earth’s mantle at concentration levels of tens to hundreds of ppm, greatly lower the peridotite solidus temperature and drastically modify the composition of produced melts. The presence of CO2 produces silica-poor, carbonate-rich liquids at the onset of melting, and these liquids shift toward silica rich compositions as the degree of melting increases. Numerous geochemical observations and experimental studies have revealed the complexity of the transition between carbonate-rich and silicate-rich melts. It is characterized by a strongly non-linear evolution and, under specific conditions, by immiscibility. To better constrain this transition, we have used the thermodynamic activity of silica as a probe of the mixing properties between molten carbonate and molten silicate. The activity of silica (image) was calculated for a large number of experimental liquids from two equilibria: olivine-orthopyroxene-melt and immiscible silicate-rich melt-carbonate-rich melt (491 data points ranging from 1 to 14 GPa and 1090 to 1800°C). We modeled image during incipient melting of the peridotite in presence of CO2 with a generalized Margules function. Our model well reproduces the silica activity–composition relationships of the experimental database, and can be used to predict the silica content of the melts coexisting with olivine and orthopyroxene. We show that water content and Ca/Mg ratio in the melts have an important influence on the image. In contrast to a recent empirical model (Dasgupta et al., 2013), the analysis of the experimental database reveals that the transition from carbonate to silicate melt with decreasing depth should occur abruptly in oceanic mantle. Our model predict that carbonatitic melts with ~ 5 wt.% SiO2 can be stabilized from ~ 150 km depth, at the onset of incipient melting by “redox melting”, up to ~ 75 km, above which the liquid evolves abruptly to a carbonated silicate composition (> ~ 25 wt.% SiO2). In the cratonic mantle lithosphere, our model predicts that carbonatitic melts are prevailing up to shallow depth, and conflicts the recent model (Russell et al., 2012) of CO2-saturation triggered by orthopyroxene assimilation during kimberlite ascent

Instrumenter la lecture savante de documents multimédia temporels

L’évolution des technologies de numérisation et de diffusion documentaires confronte le lettré à des contenus et des méthodes de travail qui excèdent le cadre théorique et technique hérité de la tradition de la lettre et de l’imprimé. Prenant acte du caractère matériel et spatial de l’activité critique, où la manipulation des connaissances est conjointe à la manipulation des objets qui les incarnent, cet article propose une réflexion sur la nécessité de prolonger l’action de l’ingénierie documentaire dans le champ des interfaces homme-machine. C’est en effet par l’espace – autant celui de son environnement que celui de l’écriture – que le lecteur se rend maître de la temporalité de ses documents et de son projet interprétatif même. Notre enjeu est alors de comprendre les fondements de l’activité critique pour esquisser des directions structurantes pour son instrumentation informatique. Suite à l’exposition de ces aspects théoriques, nous présenterons quelques outils et instruments articulés dans un environnement de lecture savante multimédia, actuellement en cours de développement et de test

CO 2 Solubility in Kimberlite melts CO 2 Solubility in Kimberlite melts

International audienceCarbon dioxide is the most abundant volatile in kimberlite melts and its solubility exerts a prime influence on the melt structure, buoyancy, transport rate and hence eruption dynamics. The actual primary composition of kimberlite magma is the matter of some debate but the solubility of CO2 in kimberlitic melts is also poorly constrained due to difficulties in quenching these compositions to a glass that retains the equilibrium CO2 content. In this study we used a range of synthetic, melt compositions with broadly kimberlitic to carbonatitic characteristics which can, under certain conditions, be quenched fast enough to produce a glass. These materials are used to determine the CO2 solubility as a function of chemical composition and pressure (0.05-1.5 GPa). Our results suggest that the solubility of CO2 decreases steadily with increasing amount of network forming cations from ~ 30 wt% CO2 at 12 wt% SiO2 down to ~ 3 wt% CO2 at 40 wt% SiO2. For low silica melts, CO2 solubility correlates non-linearly with pressure showing a sudden increase from 0.1 to 100 MPa and a smooth increase for pressure > 100 MPa. This peculiar pressure-solubility relationship in low silica melts implies that CO2 degassing must mostly occur within the last 3 km of ascent to the surface having potential links with the highly explosive nature of kimberlite magmas and some of the geo-morphological features of their root zone. We present an empirical CO2 solubility model covering a large range of melt composition from 11 to 55 wt% SiO2 spanning the transition from carbonatitic to kimberlitic at pressures from 1500 to 50 MPa

The effect of shape and cooking duration on preference and consumption of carrots in preadolescent children

Background and objectives : Vegetables are one of the most difficult categories of food to introduce in children’s diet (Cooke & Wardle, 2005) and children’s low consumption of vegetables is pointed as a major source of public health concern in many developed countries. A better understanding of children sensory preferences could help to improve children’s vegetables acceptance

The effect of sulfur on the glass transition temperature in anorthite-diopside eutectic glasses

International audienceThe effect of sulfur dissolved in anorthite-diopside eutectic (AD) glasses on the glasstransition temperature (Tg) has been investigated via Differential Scanning Calorimetricmeasurements (DSC) and Thermogravimetric Analysis (TGA) under moderately reducing tooxidizing conditions.In a series of AD glasses, we have measured the change in Tg as a function of S contentpresent as SO42- (HS- is also identified to a lesser extent) and H2O content. The AD glassesinvestigated have S contents ranging from 0 to 7519 ppm and H2O contents ranging from 0 to5.3 wt.%. In agreement with previous studies, increasing H2O content induces a strongexponential decrease in Tg: volatile free AD glass has a Tg at 758±13C and AD glass with5.18±0.48 wt.% H2O has a Tg at 450±11C. The change in Tg as a function of H2O is wellreproducedwith a third-order polynomial function and has been used to constrain Tg at anyH2O content. The effect of S on Tg is almost inexistent or towards a decrease in Tg withincreasing S content. For instance, at ~2.4 wt.% H2O, the addition of S induces a change inTg from 585±10°C with 0 ppm S to 523±3C with 2365±138 ppm S; a further increase in Sup to 7239±90 ppm S does not induce a dramatic change in Tg measured at 529±2C.The limited effect of S on the glass transition temperature contrasts with recent spectroscopicmeasurements suggesting that S dissolution as SO42- groups provokes an increase in thepolymerization degree. We propose an alternative view which reconciles the spectroscopicevidence with the Tg measurements. The dissolution of S as SO42- does not induce theformation of Si-O-Si molecular bonding through consumption of available non-bridgingoxygens (NBO) but instead we suggest that Si-O-S molecular bonds are formed which are not detectable by DSC measurements but mimic the increase in glass polymerization. Therefore, spectroscopic measurements must be used with caution in order to extract melt physicalproperties

Investigation of refractive index dynamics during in vitro embryo development using off-axis digital holographic microscopy

Funding: Engineering and Physical Sciences Research Council - EP/P030017/1, EP/R004854/1; Australian Research Council - FL210100099; National Health and Medical Research Council - APP2003786; Future Making Fellowship (University of Adelaide); Hospital Research Foundation (Mid-career fellowship C-MCF58-2019).Embryo quality is a crucial factor affecting live birth outcomes. However, an accurate diagnostic for embryo quality remains elusive in the in vitro fertilization clinic. Determining physical parameters of the embryo may offer key information for this purpose. Here, we demonstrate that digital holographic microscopy (DHM) can rapidly and non-invasively assess the refractive index of mouse embryos. Murine embryos were cultured in either low- or high-lipid containing media and digital holograms recorded at various stages of development. The phase of the recorded hologram was numerically retrieved, from which the refractive index of the embryo was calculated. We showed that DHM can detect spatio-temporal changes in refractive index during embryo development that are reflective of its lipid content. As accumulation of intracellular lipid is known to compromise embryo health, DHM may prove beneficial in developing an accurate, non-invasive, multimodal diagnostic.Publisher PDFPeer reviewe