Compressibility of Ca3Al2Si3O12 perovskite up to 55 GPa     

Steeve Gréaux  Denis Andrault  Laurent Gautron  Nathalie Bolfan-Casanova  Mohamed Mezouar 《Physics and Chemistry of Minerals》2014,41(6):419-429

Compressibility of perovskite-structured Ca₃Al₂Si₃O₁₂ grossular (GrPv) was investigated at high pressure and high temperature by means of angle-dispersive powder X-ray diffraction using a laser-heated diamond anvil cell. We observed the Pbnm orthorhombic distortion for the pure phase above 50 GPa, whereas below this pressure, Al-bearing CaSiO₃ perovskite coexists with an excess of corundum. GrPv has a bulk modulus (K ₀ = 229 ± 5 GPa; \(K_{0}^{{\prime }}\) fixed to 4) almost similar to that reported for pure CaSiO₃ perovskite. Its unit-cell volume extrapolated to ambient conditions (V ₀ = 187.1 ± 0.4 Å³) is found to be ~2.5 % larger than for the Al-free phase. We observe an increasing unit-cell anisotropy with increasing pressure, which could have implications for the shear properties of Ca-bearing perovskite in cold slabs subducted into the Earth’s mantle.  相似文献   

Advanced methods in landslide modelling     

Giulio Iovine  Denis Cohen 《Natural Hazards》2014,72(1):1-4

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Lake Shira Level Changes in Late Holocene     

Andrey DARIN  Ivan KALUGIN  Natalya MAKSIMOVA  Tatiana MARKOVICH  Yakov RAKSHUN  Dmitryi SOROKOLETOV  Fedor DARIN  Denis RAGOZIN 《《地质学报》英文版》2014,88(Z1):3-4

正1 Introduction Meromictic Shira Lake is a good represfor detail climate modeling due to its locainformation and annually laminated bottomsediment column of 155 cm in length wahammer corer in the deepest(24 m)central in 2009.2 Sample Preparations and Measuring  相似文献   

Katy?     

Denis Wood 《The Cartographic journal》2014,51(2):179-186

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Velocity and abundance precisions for future high‐resolution spectroscopic surveys: A study for 4MOST     

E. Caffau  A. Koch  L. Sbordone  P. Sartoretti  C.J. Hansen  F. Royer  N. Leclerc  P. Bonifacio  N. Christlieb  H.‐G. Ludwig  E.K. Grebel  R.S. de Jong  C. Chiappini  J. Walcher  S. Mignot  S. Feltzing  M. Cohen  I. Minchev  A. Helmi  T. Piffl  E. Depagne  O. Schnurr 《Astronomische Nachrichten》2013,334(3):197-216

In preparation for future, large‐scale, multi‐object, high‐resolution spectroscopic surveys of the Galaxy, we present a series of tests of the precision in radial velocity and chemical abundances that any such project can achieve at a 4 m class telescope. We briefly discuss a number of science cases that aim at studying the chemo‐dynamical history of the major Galactic components (bulge, thin and thick disks, and halo) – either as a follow‐up to the Gaia mission or on their own merits. Based on a large grid of synthetic spectra that cover the full range in stellar parameters of typical survey targets, we devise an optimal wavelength range and argue for a moderately high‐resolution spectrograph. As a result, the kinematic precision is not limited by any of these factors, but will practically only suffer from systematic effects, easily reaching uncertainties <1km s^–1. Under realistic survey conditions (namely, considering stars brighter than r = 16 mag with reasonable exposure times) we prefer an ideal resolving power of R ∼20 000 on average, for an overall wavelength range (with a common two‐arm spectrograph design) of [395;456.5] nm and [587;673] nm. We show for the first time on a general basis that it is possible to measure chemical abundance ratios to better than 0.1 dex for many species (Fe, Mg, Si, Ca, Ti, Na, Al, V, Cr, Mn, Co, Ni, Y, Ba, Nd, Eu) and to an accuracy of about 0.2 dex for other species such as Zr, La, and Sr. While our feasibility study was explicitly carried out for the 4MOST facility, the results can be readily applied to and used for any other conceptual design study for high‐resolution spectrographs. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Anchors for the cosmic distance scale: the Cepheid QZ Normae in the open cluster NGC 6067     

D. Majaess  L. Sturch  C. Moni Bidin  M. Soto  W. Gieren  R. Cohen  F. Mauro  D. Geisler  C. Bonatto  J. Borissova  D. Minniti  D. Turner  D. Lane  B. Madore  G. Carraro  L. Berdnikov 《Astrophysics and Space Science》2013,347(1):61-70

Cepheids are key to establishing the cosmic distance scale. Therefore it’s important to assess the viability of QZ Nor, V340 Nor, and GU Nor as calibrators for Leavitt’s law via their purported membership in the open cluster NGC 6067. The following suite of evidence confirms that QZ Nor and V340 Nor are members of NGC 6067, whereas GU Nor likely lies in the foreground: (i) existing radial velocities for QZ Nor and V340 Nor agree with that established for the cluster ( $-39.4\pm0.2(\sigma_{\bar {x}}) \pm1.2 (\sigma)~\mbox{km/s}$ ) to within 1 km/s, whereas GU Nor exhibits a markedly smaller value; (ii) a steep velocity-distance gradient characterizes the sight-line toward NGC 6067, thus implying that objects sharing common velocities are nearly equidistant; (iii) a radial profile constructed for NGC 6067 indicates that QZ Nor is within the cluster bounds, despite being 20′ from the cluster center; (iv) new BVJH photometry for NGC 6067 confirms the cluster lies d=1.75±0.10 kpc distant, a result that matches Wesenheit distances computed for QZ Nor/V340 Nor using the Benedict et al. (Astron. J. 133:1810, 2007, HST parallaxes) calibration. QZ Nor is a cluster Cepheid that should be employed as a calibrator for the cosmic distance scale.  相似文献   

Satellite-based peatland mapping: Potential of the MODIS sensor     

Dirk Pflugmacher  Olga N. Krankina  Warren B. Cohen 《Global and Planetary Change》2007,56(3-4):248

Peatlands play a major role in the global carbon cycle but are largely overlooked in current large-scale vegetation mapping efforts. In this study, we investigated the potential of the Moderate Resolution Imaging Spectroradiometer (MODIS) to capture the extent and distribution of peatlands in the St. Petersburg region of Russia by analyzing the relationships between peatland cover fractions derived from reference maps and  1-km resolution MODIS Nadir BRDF-Adjusted Reflectance (NBAR) data from year 2002.First, we characterized and mapped 50 peatlands from forest inventory and peat deposit inventory data. The peatlands represent three major nutritional types (oligotrophic, mesotrophic, eutrophic) and different sizes (0.6–7800 ha). In addition, parts of 6 peatlands were mined for peat and these were mapped separately. The reference maps provided information on peatland cover for 1105 MODIS pixels. We performed regression analysis on 50% of the pixels and reserved the remainder for model validation. Canonical correlation analysis on the MODIS reflectance bands and the peatland cover fractions produced a multi-spectral peatland cover index (PCI), which served as the predictor in a reduced major axis (RMA) regression model. The results suggest a high potential for mapping peatlands with MODIS. The RMA regression models explained much of the variance in the PCI (r² = 0.74 for mined and r² = 0.81 for unmined peatlands). Model validation showed high correlation between observed versus predicted peatland cover (mined: r = 0.87; unmined: r = 0.92). We used the models to derive peatland cover estimates for the St. Petersburg region and compared the results to current MODIS land cover maps.  相似文献   

Rotating micro-structures in Antarctic cold basal ice: implications for glacier flow and its interpretation     

Denis Samyn  Sean J. Fitzsimons  Reginald D. Lorrain 《International Journal of Earth Sciences》2010,99(8):1849-1857

Structural analyses were conducted in the basal zone of an Antarctic glacier. The studied basal ice sequence was retrieved from a 20-m-long subglacial tunnel dug at the margin of the glacier and is at the temperature of −17°C. For the first time, rotating clast systems embedded within debris-rich ice were thin-sectioned using specially designed cutting techniques. The observed structures reflect the occurrence of pervasive shearing at the base of the glacier, and can be used as shear sense indicators. In addition, some of these structures provide evidence for the presence of thin liquid films at the time of formation despite the marked freezing temperature of the ice. It is showed here that cautious analysis of deformation structures present in debris-bearing ice may bring insights not only into the flow dynamics of the embedding matrix, but also into the behaviour of the interstitial fluid network at the base of cold glaciers and ice sheets.  相似文献   

Geochemical study of clays used as barriers in landfills   总被引：1，自引：0，他引：1  

AbdelIllah Bezzar  Denis François  Fouad Ghomari 《Comptes Rendus Geoscience》2010,342(9):695-700

This is a hydraulic and geochemical study on 2 materials: natural clay (AN) and a regenerated material made up of a sand-bentonite (SB) mixture. The hydraulic part allowed us to conclude that a 10% industrial bentonite content mixed with sand offers hydraulic properties that are similar to those of AN material and are lower than the required standards. The geochemical properties of both AN and SB matrixes are comparable with those of some of the synthetic leachates studied. Furthermore, the Langmuir model helped us to identify the adsorption capacities of both matrixes with the following selectivities: Pb > Cu > Cd > Zn.  相似文献   

PHYSIOLOGICAL INHIBITORY EFFECT OF OCS IN ARACHIDONIC ACID-RICH PARIETOCHLORIS INCISA （TREBOUXIOPHYCEAE, CHLOROPHYTA）   总被引：2，自引：0，他引：2  

刘建国  张成武ZviCohen AmosRichmond 《中国海洋湖沼学报》2002,20(3):248-255

Parietochloris incisa is an arachidonic acid-rich snow green alga. The main physiological profiles, such as ash free dry weight (AFDW), chlorophyll, carotenoid, protein and total fatty acids (TFA), in this alga exposed to old culture supernatant (OCS) at the decline phase or its crude ethyl acetate extracts (CEAE) were investigated by using tubular photobioreactors of different diameters. Results showed that both OCS and CEAE had strong inhibitory effect on the above physiological parameters. The longer the culture was exposed to OCS and the more CEAE were added into the algal culture, the more the above physiological properties were inhibited. Arachidonic acid (AA), the dominant component of fatty acids in this alga, was also seriously inhibited with respect to total TFA, AFDW of cell mass, or culture volume, due to a prebable reduction of enzymes activities catalyzing chain elongation from C18:1ω9 to AA. These results incontestably evidenced that some CEAE dissolving substances existing in OCS, like auto-inhibitors, inhibited P. incisa growth through feedback. Hence, any efficient removal of auto-inhibitors from algal culture to decrease their bioactivity could be good for maximal production of desired products like AA.  相似文献