A refined genetic model for the Laisvall and Vassbo Mississippi Valley-type sandstone-hosted deposits,Sweden: constraints from paragenetic studies,organic geochemistry,and S,C, N,and Sr isotope data     

Nicolas J. Saintilan  Jorge E. Spangenberg  Elias Samankassou  Kalin Kouzmanov  Massimo Chiaradia  Michael B. Stephens  Lluís Fontboté 《Mineralium Deposita》2016,51(5):639-664

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The role of Atlantic Multi-decadal Oscillation in the global mean temperature variability     

Petr Chylek  James D. Klett  Manvendra K. Dubey  Nicolas Hengartner 《Climate Dynamics》2016,47(9-10):3271-3279

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Spectral Characterization of Colored Dissolved Organic Matter for Productive Inland Waters and Its Source Analysis     

SONG Kaishan  LI Lin  Lenore TEDESCO  Nicolas CLERCIN  LI Linhai  SHI Kun 《中国地理科学(英文版)》2015,(3):295-308

This study examined the spatiotemporal dynamics of colored dissolved organic matter(CDOM) and spectral slope(S), and further to analyze its sources in three productive water supplies(Eagle Creek, Geist and Morse reservoirs) from Indiana, USA. The results showed that he absorption coefficient aCDOM(440) ranged from 0.37 m–1 to 3.93 m–1 with an average of 1.89 ± 0.76 m–1(±SD) for the aggregated dataset, and S varied from 0.0048 nm–1 to 0.0239 nm–1 with an average of 0.0108 ± 0.0040 nm–1. A significant relationship between S and aCDOM(440) can be fitted with a power equation(S = 0.013 × aCDOM(440)–0.42, R2 = 0.612), excluding data from Geist Reservoir during high flow(12 April 2010) and the Morse Reservoir on 25 June 2010 due to a T-storm achieves even higher determination coefficient(R2 = 0.842). Correlation analysis indicated that aCDOM(440) has strong association with inorganic suspended matter(ISM) concentration(0.231 < R2 < 0.786) for each of the field surveys, and this trend followed the aggregated datasets(R2 = 0.447, p < 0.001). In contrast, chlorophyll-a was only correlated with aCDOM(440) in summer and autumn(0.081 < R2 < 0.763), indicating that CDOM is mainly from terrigenous sources in early spring and that phytoplankton contributed during the algal blooming season. The S value was used to characterize CDOM origin. The results indicate that the CDOM source is mainly controlled by hydrological variations, while phytoplankton originated organic matter also closely linked with CDOM dynamics in three productive reservoirs.  相似文献   

Hydrochemical response of a fractured carbonate aquifer to stress variations: application to leakage detection of the Vouglans arch dam lake (Jura,France)   总被引：1，自引：0，他引：1  

Catherine Bertrand  Yves Guglielmi  Sophie Denimal  Jacques Mudry  Guilhem Deveze  Nicolas Carry 《Environmental Earth Sciences》2015,74(12):7671-7683

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SARAL/AltiKa Global Statistical Assessment and Cross-Calibration with Jason-2     

Pierre Prandi  Sabine Philipps  Vincent Pignot  Nicolas Picot 《Marine Geodesy》2015,38(3):297-312

The CNES/ISRO mission SARAL/AltiKa was successfully launched on 25 February 2013. It reached its nominal orbit on 13 March 2013. AltiKa is the first altimeter using the Ka-band frequency. This article presents the results of the calibration and validation activities perfromed on the first year of the SARAL/AltiKa mission. The main objective of the article is to assess the SARAL/AltiKa data quality and to estimate the altimeter system performance using GDR products. To achieve this goal, we present mono-mission metrics and compare them with Jason-2 over the same period. Even if these missions do not have the same ground track, precise comparisons are still possible. They allow assessing parameter discrepancies and SSH consistency between both missions in order to detect geographically correlated biases, jumps or drifts. These results show that SARAL/AltiKa data quality is excellent: ocean data coverage is greater than 99.5%, standard deviation at cross-overs is 5.4 cm. The mission therefore fulfills the requirements of high precision altimetry and can be used (in conjunction with Jason-2) to monitor the global mean sea level, ensuring the continuity of the record over ERS/Envisat historical ground track. Possible improvements and open issues are also identified, foreseeing an even better mission performance.  相似文献   

A computer simulation study of natural silicate melts. Part II: High pressure properties     

Bertrand Guillot  Nicolas Sator 《Geochimica et cosmochimica acta》2007,71(18):4538-4556

The thermodynamic, structural and transport properties of natural silicate melts under pressure are investigated by molecular dynamics simulation with the help of a force field recently introduced by us [Guillot B. and Sator N. (2007) A computer simulation study of natural silicate melts. Part I: low pressure properties. Geochim. Cosmochim. Acta71, 1249-1265]. It is shown that the simulation reproduces accurately the bulk moduli of a large variety of silicate liquids as evaluated from ultrasonic studies. The equations of state (EOS) of the simulated melts are in good agreement with the density data on mid-ocean ridge basalt, komatiite, peridotite and fayalite as obtained either by sink/float experiments or by shock-wave compression. From the structural point of view it is shown that the population of ^[5]Al and ^[6]Al species increases rapidly upon initial compression (0-50 kbar) whereas for Si these highly coordinated species are found in a significant abundance (>5%) only above ∼50 kbar for ^[5]Si and ∼100-150 kbar for ^[6]Si. This increase of the coordination of network formers is not the only response of the melt structure to the densification: there is also a large redistribution of the T-O-T (T = Si, Al) bond angles with the pressure and noticeably upon initial compression in rhyolitic and basaltic liquids. Furthermore, a detailed analysis of the population of bridging oxygens (BO) and nonbridging oxygens (NBO) points out that the polymerization of the melt generally increases when the pressure increases, the magnitude of this polymerization enhancement being all the more important that the melt is depolymerized at low pressure. The role of triclusters (threefold coordinated oxygens to network former cations) is particularly emphasized in acidic and basaltic liquids. The pressure-induced redistribution of the oxygen atoms through the melt structure is also stressed. Finally, the simulation predicts a nonmonotonic behavior of the diffusivity of network former ions when the pressure increases, a feature with depends on the melt composition. This could have a counterpart in the electrical conductivity at sufficiently high temperature when the viscosity of the liquid is low.  相似文献   

From land to sea: provenance,composition, and preservation of organic matter in a marine sediment record from the North-East Greenland shelf spanning the Younger Dryas–Holocene     

Nanna Andreasen  Rebecca Jackson  Arka Rudra  Henrik Nøhr-Hansen  Hamed Sanei  Jørgen Bojesen-Koefoed  Marit-Solveig Seidenkrantz  Christof Pearce  Nicolas Thibault  Sofia Ribeiro 《Boreas: An International Journal of Quaternary Research》2023,52(4):459-475

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected-light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land-derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land-derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies.  相似文献   

Environmental change in subtropical South America for the last two millennia as shown by lacustrine pigments     

Lisa Coianiz  Daniel Ariztegui  Eduardo L. Piovano  Andrea Lami  Piero Guilizzoni  Stefano Gerli  Nicolas Waldmann 《Journal of Paleolimnology》2015,53(2):233-250

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Comet McNaught (260P/2012 K2): spin axis orientation and rotation period     

Federico Manzini  Virginio Oldani  Roberto Crippa  José Borrero  Erik Bryssink  Martin Mobberley  Joel Nicolas 《Astrophysics and Space Science》2014,351(2):435-450

Extensive observations of comet 260P/McNaught were carried out between August 2012 and January 2013. The images obtained were used to analyze the comet’s inner coma morphology at resolutions ranging from 250 to about 1000 km/pixel. A deep investigation of the dust features in the inner coma allowed us to identify only a single main active source on the comet’s nucleus, at an estimated latitude of ?50^°±15^°. A thorough analysis of the appearance and of the motion of the morphological structures, supported by graphic simulations of the geometrical conditions of the observations, allowed us to determine a pole orientation located within a circular spot of a 15^°-radius centered at RA=60^°, Dec=0^°. The rotation of the nucleus seems to occur on a single axis and is not chaotic, furthermore no precession effects could be estimated from our measurements. The comet’s spin axis never reached the plane of the sky from October 2012 to January 2013; during this period it did not change its direction significantly (less than 30^°), thus giving us the opportunity to observe mainly structures such as bow-shaped jets departing from the single active source located on the comet’s nucleus. Only during the months of August 2012 and January 2013 the polar axis was directed towards the Earth at an angle of about 45^° from the plane of the sky; this made it possible to observe the development of faint structures like fragments of shells or spirals. A possible rotation period of 0.340±0.01 days was estimated by means of differential photometric analysis.  相似文献   

SPIRE point source photometry: within the Herschel interactive processing environment (HIPE)     

Chris Pearson  Tanya Lim  Chris North  George Bendo  Luca Conversi  Darren Dowell  Matt Griffin  Terry Jin  Nicolas Laporte  Andreas Papageorgiou  Bernhard Schulz  Dave Shupe  Anthony J. Smith  Kevin Xu 《Experimental Astronomy》2014,37(2):175-194

The different algorithms appropriate for point source photometry on data from the SPIRE instrument on-board the Herschel Space Observatory, within the Herschel Interactive Processing Environment (HIPE) are compared. Point source photometry of a large ensemble of standard calibration stars and dark sky observations is carried out using the 4 major methods within HIPE: SUSSEXtractor, DAOphot, the SPIRE Timeline Fitter and simple Aperture Photometry. Colour corrections and effective beam areas as a function of the assumed source spectral index are also included to produce a large number of photometric measurements per individual target, in each of the 3 SPIRE bands (250, 350, 500μm), to examine both the accuracy and repeatability of each of the 4 algorithms. It is concluded that for flux densities down to the level of 30mJy that the SPIRE Timeline Fitter is the method of choice. However, at least in the 250 and 350μm bands, all 4 methods provide photometric repeatability better than a few percent down to at approximately 100mJy. The DAOphot method appears in many cases to have a systematic offset of ～8 % in all SPIRE bands which may be indicative of a sub-optimal aperture correction. In general, aperture photometry is the least reliable method, i.e. largest scatter between observations, especially in the longest wavelength band. At the faintest fluxes, <30mJy, SUSSEXtractor or DAOphot provide a better alternative to the Timeline Fitter.  相似文献