Melting of Fe–Ni–Si and Fe–Ni–S alloys at megabar pressures: implications for the core–mantle boundary temperature     

Guillaume Morard  Denis Andrault  Nicolas Guignot  Julien Siebert  Gaston Garbarino  Daniele Antonangeli 《Physics and Chemistry of Minerals》2011,38(10):767-776

High pressure melting behavior of three Fe-alloys containing 5 wt% Ni and (1) 10 wt% Si, (2) 15 wt% Si or (3) 12 wt% S was investigated up to megabar pressures by in situ X-ray diffraction and laser-heated diamond anvil cell techniques. We observe a decrease in melting temperature with increasing Si content over the entire investigated pressure range. This trend is used to discuss the melting curve of pure Fe. Moreover, our measurements of eutectic melting in the Fe–Fe₃S system show a change in slope around 50 GPa concomitant with the fcc–hcp phase transition in pure solid iron. Extrapolations of our melting curve up to the core–mantle boundary pressure yield values of 3,600–3,750 K for the freezing temperature of plausible outer core compositions.  相似文献   

Signification des sables tertiaires de l’Ardenne méridionale : du nouveau sur la capture de la Meuse lorraine     

Guillaume Pierre 《Geodinamica Acta》2013,26(1):45-54

Résumé

La question de la capture de la Meuse lorraine est abordée par le biais de l’étude des sables tertiaires qui jalonnent les plateaux de l’Ardenne méridionale. Toujours polygéniques, ces sables ont une histoire plus ou moins longue qui débute à l’Éocène où l’altération poussée du socle produit un épais manteau sableux. Certains gisements in situ fossilisés sont restés quasiment intacts (Régniowez) tandis que d’autres (Doisches) portent la marque de remaniements successifs (marins et/ou continentaux) qui se suivent jusqu’au Miocène sans que leur filiation avec le matériau d’origine, attestée par la nature de leurs barylites, ne se perde. Comme les sables fluviatiles miocènes (in fine) du plateau ardennais ne portent pas la signature minéralogique d’une Meuse lorraine, à l’inverse de la Traînée mosane (datée du Miocène moyen), la capture se trouve à la fois confirmée et datée. L’ancien réseau de la Meuse lorraine, quant à lui, n’a pu se mettre en place qu’après l’Oligocène, époque à laquelle un glacis incliné de l’Ardenne vers le Bassin parisien fonctionnait encore. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献   

Confirming regional 1 cm differential geoid accuracy from airborne gravimetry: the Geoid Slope Validation Survey of 2011   总被引：3，自引：3，他引：0  

Dru A. Smith  Simon A. Holmes  Xiaopeng Li  Sébastien Guillaume  Yan Ming Wang  Beat Bürki  Daniel R. Roman  Theresa M. Damiani 《Journal of Geodesy》2013,87(10-12):885-907

A terrestrial survey, called the Geoid Slope Validation Survey of 2011 (GSVS11), encompassing leveling, GPS, astrogeodetic deflections of the vertical (DOV) and surface gravity was performed in the United States. The general purpose of that survey was to evaluate the current accuracy of gravimetric geoid models, and also to determine the impact of introducing new airborne gravity data from the ‘Gravity for the Redefinition of the American Vertical Datum’ (GRAV-D) project. More specifically, the GSVS11 survey was performed to determine whether or not the GRAV-D airborne gravimetry, flown at 11 km altitude, can reduce differential geoid error to below 1 cm in a low, flat gravimetrically uncomplicated region. GSVS11 comprises a 325 km traverse from Austin to Rockport in Southern Texas, and includes 218 GPS stations ( $\sigma _{\Delta h }= 0.4$ cm over any distance from 0.4 to 325 km) co-located with first-order spirit leveled orthometric heights ( $\sigma _{\Delta H }= 1.3$ cm end-to-end), including new surface gravimetry, and 216 astronomically determined vertical deflections $(\sigma _{\mathrm{DOV}}= 0.1^{\prime \prime })$ . The terrestrial survey data were compared in various ways to specific geoid models, including analysis of RMS residuals between all pairs of points on the line, direct comparison of DOVs to geoid slopes, and a harmonic analysis of the differences between the terrestrial data and various geoid models. These comparisons of the terrestrial survey data with specific geoid models showed conclusively that, in this type of region (low, flat) the geoid models computed using existing terrestrial gravity, combined with digital elevation models (DEMs) and GRACE and GOCE data, differential geoid accuracy of 1 to 3 cm (1 $\sigma )$ over distances from 0.4 to 325 km were currently being achieved. However, the addition of a contemporaneous airborne gravity data set, flown at 11 km altitude, brought the estimated differential geoid accuracy down to 1 cm over nearly all distances from 0.4 to 325 km.  相似文献   

Finding Science with Science: Evaluating a Domain and Scientific Ontology User Interface for the Discovery of Scientific Resources     

Kristin Stock  Vera Karasova  Anne Robertson  Guillaume Roger  Mark Small  Mohamed Bishr  Jens Ortmann  Tim Stojanovic  Femke Reitsma  Lukasz Korczynski  Boyan Brodaric  Zoe Gardner 《Transactions in GIS》2013,17(4):612-639

Current approaches to the discovery of scientific resources (publications, data sets and web services) are dominated by keyword search. These approaches do not allow scientists to search on the deeper semantics of scientific resources, or to discover resources on the basis of the scientific approaches taken. This article evaluates a user interface that allows users to discover scientific resources through structured knowledge in the form of ontologies describing the domain and the scientific knowledge inherent within the scientific resource, and also through informal user tags. These combined capabilities provide scientists with new and powerful options for resource discovery. A qualitative user evaluation explored how scientists felt about the approach for resource discovery in the context of their scientific work. The study showed that marine scientists were enthusiastic about the capabilities of such an approach and appreciated the ability to browse the visual structure of the knowledge and query on scientific method but, overall, preferred the use of tags over ontologies. The exploratory nature of the user study was used to identify future directions for such improvements.  相似文献   

Source to sink relations between the Tian Shan and Junggar Basin (northwest China) from Late Palaeozoic to Quaternary: evidence from detrital U‐Pb zircon geochronology     

Wei Yang  Marc Jolivet  Guillaume Dupont‐Nivet  Zhaojie Guo  Zhicheng Zhang  Chaodong Wu 《Basin Research》2013,25(2):219-240

The tectonic evolution of the Tian Shan, as for most ranges in continental Asia is dominated by north‐south compression since the Cenozoic India‐Asia collision. However, precollision governing tectonic processes remain enigmatic. An excellent record is provided by thick Palaeozoic – Cenozoic lacustrine to fluvial depositional sequences that are well preserved in the southern margin of the Junggar Basin and exposed along a foreland basin associated to the Late Cenozoic rejuvenation of the Tian Shan ranges. U/Pb (LA‐ICP‐MS) dating of detrital zircons from 14 sandstone samples from a continuous series ranging in age from latest Palaeozoic to Quaternary is used to investigate changes in sediment provenance through time and to correlate them with major tectonic phases in the range. Samples were systematically collected along two nearby sections in the foreland basin. The results show that the detrital zircons are mostly magmatic in origin, with some minor input from metamorphic zircons. The U‐Pb detrital zircon ages range widely from 127 to 2856 Ma and can be divided into four main groups: 127–197 (sub‐peak at 159 Ma), 250–379 (sub‐peak at 318 Ma), 381–538 (sub‐peak at 406 Ma) and 543–2856 Ma (sub‐peak at 912 Ma). These groups indicate that the zircons were largely derived from the Tian Shan area to the south since a Late Carboniferous basin initiation. The provenance and basin‐range pattern evolution of the southern margin of Junggar Basin can be generally divided into four stages: (1) Late Carboniferous – Early Triassic basin evolution in a half‐graben or post‐orogenic extensional context; (2) From Middle Triassic to Upper Jurassic times, the southern Junggar became a passively subsiding basin until (3) being inverted during Lower Cretaceous – Palaeogene; (4) During the Neogene, a piedmont developed along the northern margin of the North Tian Shan block and Junggar Basin became a true foreland basin.  相似文献   

D/O and D/H ratios in the local interstellar medium from FUSE observations     

Guillaume Hébrard 《Astrophysics and Space Science》2004,289(3-4):225-228

Since HI, OI, and DI have nearly the same ionization potential, the deuterium-to-oxygen ratio (D/O) is an important tracer of the D/H ratio and of its putative spatial variations. D/O is indeed very sensitive to astration, both because of deuterium destruction and oxygen production. Moreover, D/O measurements are less subject to systematic errors than D/H.A survey of D/O in the interstellar medium is performed by the Deuterium Working Group of the FUSE PI Team. The first results show that D/O is a better D/H proxy than D/N, and that D/O is homogeneous in the local interstellar medium, at least within about 100pc. The stability of D/O appears as a strong argument which supports both D/H and O/H spatial stability in the local interstellar medium.  相似文献   

Wolf–Rayet stars in M33 – I. Optical spectroscopy using CFHT-MOS     

Jay B. Abbott  Paul A. Crowther †  Laurent Drissen †  Luc Dessart †  Pierre Martin  Guillaume Boivin 《Monthly notices of the Royal Astronomical Society》2004,350(2):552-564

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Erratum to: Uncovering consistencies in Indian rainfall trends observed over the last half century     

Guillaume Lacombe  Matthew McCartney 《Climatic change》2016,136(2):339-351

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A high-precision digital astrogeodetic traverse in an area of steep geoid gradients close to the coast of Perth,Western Australia     

P. Schack  C. Hirt  M. Hauk  W. E. Featherstone  T. J. Lyon  S. Guillaume 《Journal of Geodesy》2018,92(10):1143-1153

We present results from a new vertical deflection (VD) traverse observed in Perth, Western Australia, which is the first of its kind in the Southern Hemisphere. A digital astrogeodetic QDaedalus instrument was deployed to measure VDs with \({\sim }\)0.2\(''\) precision at 39 benchmarks with a \({{\sim }}1~\hbox {km}\) spacing. For the conversion of VDs to quasigeoid height differences, the method of astronomical–topographical levelling was applied, based on topographical information from the Shuttle Radar Topography Mission. The astronomical quasigeoid heights are in 20–30 mm (RMS) agreement with three independent gravimetric quasigeoid models, and the astrogeodetic VDs agree to 0.2–0.3\(''\) (north–south) and 0.6–0.9\(''\) (east–west) RMS. Tilt-like biases of \({\sim }1\,\,\hbox {mm}\) over \({\sim }1\,\,\hbox {km}\) are present for all quasigeoid models within \({\sim }20\,\,\hbox {km}\) of the coastline, suggesting inconsistencies in the coastal zone gravity data. The VD campaign in Perth was designed as a low-cost effort, possibly allowing replication in other Southern Hemisphere countries (e.g., Asia, Africa, South America and Antarctica), where VD data are particularly scarce.  相似文献   

On several numerical strategies to solve Richards’ equation in heterogeneous media with finite volumes     

Bassetto  Sabrina  Cancès  Clément  Enchéry  Guillaume  Tran  Quang-Huy 《Computational Geosciences》2022,26(5):1297-1322

Computational Geosciences - We propose several numerical approaches building on upstream mobility two-point flux approximation finite volumes to solve Richards’ equation in domains made of...  相似文献