pinecone/core-2020-05-10-deduplication huggingface dataset:
Carbon dioxide in silica-undersaturated melt Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

International audienceSilica undersaturated melts such as nephelinites are very peculiar magmatic materials. Their occurrence on Earth is often associated with carbonatite melts. These low-silica melts can dissolve a large quantity of CO2 and are rich in alkalis. However, the way CO2 dissolves into these melts and the effect of different alkali elements are poorly constrained. We present experimental results on the CO2 solubility and speciation in synthetic nephelinite in the NKCMAS system, equilibrated at high-pressure (50-300 MPa), high-temperature (1250°C) with an excess C-O-H fluid phase. The nephelinitic glasses with 20 mol.% total alkali oxides were synthesized with varying K2O/(K2O+Na2O) ratio (denoted as #K) in order to investigate the differential effect of those two alkali cations on CO2 solubility and speciation. All experiments were conducted under oxidizing conditions (>NNO+3) resulting in binary fluid phase compositions with CO2 and H2O species. The CO2 content and speciation were investigated using Micro-Raman and Solid State NMR spectroscopies for 13C nucleus. We observe an increase in CO2 content as a function of pressure, consistent with previous studies but CO2 solubility is much higher than in alkali-poorer melts. The CO2 content is above 1 wt.% at 50 MPa and increases up to 4.5 wt.% at 300 MPa. The progressive replacement of Na by K (#K between 0 and 1) induces an increase in CO2 content. At 50 MPa, the CO2 solubility is ∼1.75 wt.% in the K-free glass (#K = 0) and increases up to ∼3.0 wt.% CO2 in Na-free glass (#K = 1). The change in CO2 solubility as a function of #K is discussed in terms of carbonatite genesis. The 13C NMR spectra show that carbonate (CO32-) environments can be attributed to carbonate species associated to non-bridging oxygen in agreement with the depolymerized nature of the investigated compositions. Two singular additional carbonated species were also identified with 13C NMR signatures at 161 and 165 ppm. Those species are assigned to isolated K+ ... CO32- ... H+ and Na+ ... CO32- ... H+ carbonate species. The presence of such isolated carbonate species is interpreted as possible precursors to carbonatitic melt genesis
Periglacial morphogenesis in the Paris Basin: insight from geophysical survey and consequences for the fate of soil pollution.

International audienceGeophysical survey by of the Pierrelaye-Bessancourt area revealed conductive polygon patterns of 20-30 m diameter detected between 0.5 and 1.7 m depth. The patterns are formed by greenish glauconite and carbonated sand hollows where clay-rich pedological horizons bend downward, forming narrow tongs extending up to 2-3 m depth. Such structures were interpreted as a buried polygonal ice-wedge network. Geometrical relationships between the lithological units allowed the identification of successive landscape events and a landscape chronology. The sequence started during the Saalian glaciation with (1) development of patterned grounds by thermokarstic cryoturbation; (2) consecutive deflation/erosion during post-permafrost aridity; (3) loess and eolian sand deposits; (4) weathering of the former deposits with development of pedogenic horizons during the Eemian interglacial; (5) recurrent cryoturbation and thermal cracking leading to infolding of the pedogenic horizons during the Pleniglacial optimum (Weichselian); (5) finally erosion that levelled the periglacial microreliefs, leading to the modern landscape. In this agricultural area, urban waste water has been spread and has led to high levels of metal pollution in the surface horizons of the soils. The polygonal cryogenic structures have major impacts on soil hydrology and dispersion/distribution of heavy metals toward the geological substrate
The H2O solubility of alkali basaltic melts: an experimental study

International audienceExperiments were conducted to determine the water solubility of alkali basalts from Etna, Stromboli and Vesuvius volcanoes, Italy. The basaltic melts were equilibrated at 1,200°C with pure water, under oxidized conditions, and at pressures ranging from 163 to 3,842 bars. Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model for the water solubility of basalts of varying alkalinity and fO2 to be derived: $$ {\text{H}}_{ 2} {\text{O}}\left( {{\text{wt}}\% } \right) = {\text{ H}}_{ 2} {\text{O}}_{\text{MORB}} \left( {{\text{wt}}\% } \right) + \left( {5.84 \times 10^{ - 5} *{\text{P}} - 2.29 \times 10^{ - 2} } \right) \times \left( {{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}} \right)\left( {{\text{wt}}\% } \right) + 4.67 \times 10^{ - 2} \times \Updelta {\text{NNO}} - 2.29 \times 10^{ - 1} $$ where H2OMORB is the water solubility at the calculated P, using the model of Dixon et al. (1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents, whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using standard thermodynamic considerations yields values close to previous findings if room temperature water species are used. When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation of the partial molar volume of total water using H2O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm3/mol in reasonable agreement with estimates obtained from density measurements
Timing of initiation of extension in the Tianshan, based on structural, geochemical and geochronological analyses of bimodal volcanism and olistostrome in the Bogda Shan (NW China)

International audienceThis paper describes an olistostrome formation and accompanied bimodal volcanic rocks occurring in the Baiyanggou area, south of Bogda Shan. The main lithotectonic units consist of olistostrome, volcanic rocks and turbidite. The olistostrome is tectonically underlain by Upper Carboniferous limestone and sandstone along a NEE-trending detachment fault. Paleo-growth fault is locally observed. The olistostrome unit includes plenty of blocks of limestone, sandstone, rhyolite and volcaniclastic rocks, and a matrix of graywacke. Limestone blocks are dated as Pennsylvanian-Bashkirian in age by the coral and brachiopod fossils that are extensively recognized in the Upper Carboniferous strata. The volcanic unit consists of pillowed and massive basalt and rhyolite, the latter occur as an 8- to 10-meter-thick layer above the olistostrome unit. The turbidite unit is mainly composed of chert, siliceous mudstone and sandstone, within which the Bouma sequence can be locally recognized. Meter-wide gabbro and diabase dykes intrude these three units. Geochemically, rhyolites are characterized by high ACNK value of >1.1, depletion of Ba, Nb and Sm, and enrichment in Rb, Th and Zr. Basaltic rocks are rich in K2O, they show a LREE-enriched pattern and depletion in Ba, Nb and Zr, and enrichment in Ti, Ce and Hf, similar to continental rift-type tholeiite series. A gabbro porphyrite intruding the olistostrome was dated at 288 ± 3 Ma by a sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb method, and a rhyolite at 297 ± 2 Ma by a laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) zircon U-Pb method. The Baiyanggou olistostrome and accompanying bimodal volcanic series are linked to an extensional setting that developed in the south of the Bogda Shan. Several lines of evidence, e.g. occurrence of large-scale strike-slip shear zones, large number of mantle-derived magmatic rocks and available geochronological data, demonstrate a significant geodynamic change from convergence to extension in the Chinese Tianshan belt, even in the whole Central Asian Orogenic Belt. The extension in the Chinese Tianshan belt is initiated at ca. 300 Ma, i.e. around Carboniferous-Permian boundary times, and the peak period of intra-plate magmatism occurred in the interval of 300-250 Ma
Status of Virgo detector

International audienceThe commissioning of the Virgo gravitational wave detector has restarted after several major hardware upgrades carried out during winter 2005. Now Virgo is fully operative and its sensitivity greatly improved and continually improving. A program of short scientific data taking has already started and Virgo is moving towards a period of continuous data taking, which should start at the end of May 2007. The actual status of the Virgo detector is reported, describing the actual detector sensitivity as well as the limiting noises and the mid-term plans
Asteroid occultations today and tomorrow: toward the GAIA era

International audienceContext: Observation of star occultations is a powerful tool to determine shapes and sizes of asteroids. This is key information necessary for studying the evolution of the asteroid belt and to calibrate indirect methods of size determination, such as the models used to analyze thermal infrared observations. Up to now, the observation of asteroid occultations is an activity essentially secured by amateur astronomers equipped with small, portable equipments. However, the accuracy of the available ephemeris prevents accurate predictions of the occultation events for objects smaller than ~100 km. Aims: We investigate current limits in predictability and observability of asteroid occultations, and we study their possible evolution in the future, when high accuracy asteroid orbits and star positions (such as those expected from the mission Gaia of the European Space Agency) will be available. Methods: We use a simple model for asteroid ephemeris uncertainties and numerical algorithms for estimating the limits imposed by the instruments, assuming realistic CCD performances and asteroid size distribution, to estimate the expected occultation rate under different conditions. Results: We show that high accuracy ephemerides which will be available in the future will extend toward much smaller asteroids the possibility of observing asteroid occultations, greatly increasing the number of events and objects involved. A complete set of size measurements down to ~10 km main belt asteroids could be obtained in a few years, provided that a small network of ground-based 1m telescopes are devoted to occultation studies
Dinoflagellate cyst population evolution throughout past interglacials: Key features along the Iberian margin and insights from the new IODP Site U1385 (Exp 339)

International audienceIODP 339 Site U1385 ("Shackleton site", e.g. Hodell et al., 2013a), from the SW Iberianmargin, offers the opportunity to study marine microfossil population dynamics bycomparing several past interglacials and to test natural shifts of species that occurred acrossthese warm periods, in a subtropical context. Here, more specifically, we present resultsobtained for the dinoflagellate cyst (dinocyst) population integrated at a regional scalethanks to the addition of data from proximal sites from southern Iberian margin. Whenpossible, observations made using the dinocyst bio-indicator are compared to additionalproxies from the same records in order to test the synchronicity of the marine biotaresponse. Pollen data available for some of the compiled marine sequences also offer theopportunity to directly compare marine biota with terrestrial ecosystem responses. Thisspatio-temporal compilation reveals that, over the last 800 ka, surface waters around Iberiawere tightly coupled to (rapid) climate changes and were characterised by coherent dinocystassemblage patterns, highlighting a permanent connection between Atlantic andMediterranean waters as evidenced through a continuous exchange of dinocyst populations.Some index species well illustrate the evolution of the regional hydrographic context alongtime, as for instance Spiniferites and Impagidinium species, together with Lingulodiniummachaerophorum, Bitectatodinium tepikiense and heterotrophic brown cysts. Theyconstitute key bio-indicators in context of natural environmental shifts at long and shorttimescales
Minimal predicted distance: a kinematic cue to investigate collision avoidance between walkers

International audienceCollision-free navigation requires avoiding static and moving obstacles as well as other humans. Our objective was to identify the conditions that lead to avoidance manoeuvres in locomotor trajectories of two walkers. Based on the assumption of a reciprocal interaction, we suggested a mutual variable, the Minimum Predicted Distance (MPD), which emphasises the risk of collision and describes the general collision avoidance behaviour. We concluded that walkers are able to accurately predict crossing distances and to react accordingly. The avoidance is performed with anticipation, i.e., maneuvers are ended time before interaction ended. However, our analysis focused on the mutual aspects of interaction. Future work is still required to investigate the nature of each walker reactions to avoid collision
A stochastic model of transport in three-dimensional porous media

International audienceModeling of solute transport remains a key issue in the area of groundwater contamination. The fundamental processes of solute transport are advection and dispersion and an accurate description is needed for all modeling studies. The most common approach (advection-dispersion equation) considers an average advective flow rate and a Fickian-like dispersion. Here we propose a more accurate approach: advection is a function of the dispersive behavior of the solute and of medium characteristics. This method provides useful insight for the dispersion process in general. The aim of this article is to present the mathematical background of the random walk model and a simple numerical application
Ram extrusion force for a frictional plastic material: model prediction and application to cement paste

the original publication is available at http://www.springerlink.com/content/pn3034u81144458g/International audienceWe developed a model to predict the ram extrusion force of frictional plastic materials such as cement-based pastes. The extrusion of cement-based materials has already been studied, but the interaction between shaping force and paste behaviour still have to be understood. Our model is based on the plastic frictional behaviour of cement-based materials and integrates the physical mechanisms that govern material extrusion flow and extrusion force increase. When the process starts, a pressure gradient is created in the extruder due to wall friction of the paste that is submitted to plug flow. It induces a consolidation of the material. As a result, a large increase of extrusion force appears. A Coulomb law is used to model cement-based materials, which is considered as consolidating granular media. Such modelling is compared with experimental results. Tests were carried out on extrudible cement pastes. Modelling and experimental results are in good agreement
Impact of episodic vertical fluxes on sea surface pC02

International audienceEpisodic events like hurricanes, storms and frontal- and eddy-driven upwelling can alter the partial pressure of CO<sub>2</sub> (pCO<sub>2</sub>) at the sea surface by entraining subsurface waters into the surface mixed layer (ML) of the ocean. Since pCO<sub>2</sub> is a function of total dissolved inorganic carbon (DIC), temperature (T), salinity and alkalinity, it responds to the combined impacts of physical, chemical and biological changes. Here, we present an analytical framework for assessing the relative magnitude and sign in the short-term perturbation of surface pCO<sub>2</sub> arising from vertical mixing events. Using global, monthly, climatological datasets, we assess the individual, as well as integrated, contribution of various properties to surface pCO<sub>2</sub> in response to episodic mixing. The response depends on the relative vertical gradients of properties beneath the ML. Many areas of the ocean exhibit very little sensitivity to mixing owing to the compensatory effects of DIC and T on pCO<sub>2</sub>, whereas others, such as the eastern upwelling margins, have the potential to generate large positive/negative anomalies in surface pCO<sub>2</sub>. The response varies seasonally and spatially and becomes more intense in subtropical and subpolar regions during summer. Regions showing a greater pCO<sub>2</sub> response to vertical mixing are likely to exhibit higher spatial variability in surface pCO<sub>2</sub> on time scales of days
Thalassobaculum salexigens sp. nov., a new member of the family Rhodospirillaceae from the NW Mediterranean Sea, and emended description of the genus Thalassobaculum

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/00001/11201/7846.pdfInternational audienceA novel Gram-negative bacteria, named CZ41_10a(T), was isolated from coastal surface waters of the north-western Mediterranean Sea. Cells were motile, pleomorphic rods, 1.6 mum long and 0.7 mum wide and formed cream colonies on marine agar medium. The G+C content of the genomic DNA was 65 mol%. Phylogenetic analysis of 16S rRNA gene sequences placed the new isolate in the genus Thalassobaculum, a member of the family Rhodospirillaceae, class Alphaproteobacteria. Unlike Thalassobaculum litoreum CL-GR58(T), its closest relative, strain CZ41_10a(T) was unable to grow anaerobically and did not exhibit nitrate reductase activity. On the basis of DNA-DNA hybridization, fatty acid content and physiological and biochemical characteristics, this isolate represents a novel species for which the name Thalassobaculum salexigens sp. nov. is proposed. The type strain is CZ41_10a(T) (=DSM 19539(T)=CIP 109604(T)=MOLA [corrected] 84(T)). An emended description of the genus Thalassobaculum is also given
Reshaping and capturing Leidenfrost drops with a magnet

International audienceLiquid oxygen, which is paramagnetic, also undergoes Leidenfrost effect at room temperature. In this article, we first study the deformation of oxygen drops in a magnetic field and show that it can be described via an effective capillary length, which includes the magnetic force. In a second part, we describe how these ultra-mobile drops passing above a magnet significantly slow down and can even be trapped. The critical velocity below which a drop is captured is determined from the deformation induced by the field. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4796133
Regularized direct and indirect symmetric variational BIE formulations for three-dimensional elasticity.

This paper deals with symmetric variational regularized BIE formulations for the mixed elastostatic boundary-value problem. A direct version (i.e. in terms of unknown boundary displacement and tractions) is first established. The formulation expresses the stationarity of an augmented potential energy functional, thus being truly a variational BIE formulation. Then an indirect version (in terms of unknown fictitious densities) is established from the direct one. Both are expressed using at most weakly singular integrals followed by regular integrals, by means of a combined use of indirect regularization and Stokes theorem. The displacements and tractions are required to be C0,α continuous and piecewise continuous respectively, thus conventional BEM interpolation of any degree may be used. These formulations provide a basis for the numerical solution of 3D elastic problems. The numerical evaluation of the singular integrals that arise in the process is discussed. The formulations presented here provide some understanding of the underlying principles as well as a sound working base for Galerkin boundary element analysis of elastic problems
Using E-Exercise Bases in Mathematics: Case Studies at University

En open access sur http://www.springerlink.com/content/k2k616x254q34236/?p=fa97ce28e2884c20834f83d7d8f92a2e&pi=1International audienceE-Exercise Bases (EEB) are now used in the teaching of mathematics, especially at university. We discuss here the consequences of their use on the students' activity during computer lab sessions. Results stem from observations of several teaching designs organised in different French universities with three e-exercise bases. The analysis focuses on new tasks and on specific solving strategies, which appear using these resources. Moreover, specific didactic contract clauses are studied
spMC: an R-package for 3D lithological reconstructions based on spatial Markov chains

The paper presents the spatial Markov Chains (spMC) R-package and a case study of subsoil simulation/prediction located in a plain site of Northeastern Italy. spMC is a quite complete collection of advanced methods for data inspection, besides spMC implements Markov Chain models to estimate experimental transition probabilities of categorical lithological data. Furthermore, simulation methods based on most known prediction methods (as indicator Kriging and CoKriging) were implemented in spMC package. Moreover, other more advanced methods are available for simulations, e.g. path methods and Bayesian procedures, that exploit the maximum entropy. Since the spMC package was developed for intensive geostatistical computations, part of the code is implemented for parallel computations via the OpenMP constructs. A final analysis of this computational efficiency compares the simulation/prediction algorithms by using different numbers of CPU cores, and considering the example data set of the case study included in the package. (C) 2016 Elsevier Ltd. All rights reserved
Tree Species Classification Based on 3D Bark Texture Analysis

International audienceTerrestrialLaserScanning(TLS)techniqueistodaywidelyusedingroundplotstoacquire3Dpointcloudsfromwhichforestin-ventoryattributesarecalculated.Inthecaseofmixedplantingswherethe3Dpointcloudscontaindatafromseveraldifferenttreespecies,itisimportanttobeabletoautomaticallyrecognizethetreespeciesinordertoanalyzethedataofeachofthespeciesseparately.AlthoughautomatictreespeciesrecognitionfromTLSdataisanimportantproblem,ithasreceivedverylittleattentionfromthescientificcommunity.InthispaperweproposeamethodforclassifyingfivedifferenttreespeciesusingTLSdata.Ourmethodisbasedontheanalysisofthe3Dgeometrictextureofthebarkinordertocomputeroughnessmeasuresandshapecharacteris-ticsthatarefedasinputtoaRandomForestclassifiertoclassifythetreespecies.Themethodhasbeenevaluatedonatestsetcomposedof265samples(53samplesofeachofthe5species)andtheresultsobtainedareveryencouraging
Tools for incorporating a D-wave contribution in Skyrme energy density functionals

The possibility of adding a D-wave term to the standard Skyrme effective interaction has been widely considered in the past. Such a term has been shown to appear in the next-to-next-to-leading order of the Skyrme pseudo-potential. The aim of the present article is to provide the necessary tools to incorporate this term in a fitting procedure: first, a mean-field equation written in spherical symmetry in order to describe spherical nuclei and second, the response function to detect unphysical instabilities. With these tools it will be possible to build a new fitting procedure to determine the coupling constants of the new functional