Biradical character of D-rich carriers in the insoluble organic matter of carbonaceous chondrites: A relic of the protoplanetary disk chemistry     

Olivier Delpoux  Hervé Vezin  Sylvie Derenne 《Geochimica et cosmochimica acta》2011,75(1):326-7965

The insoluble organic matter (IOM) of the Orgueil meteorite contains deuterium-rich radicals detectable by Electron Paramagnetic Resonance (EPR) techniques (Gourier et al., 2008). However the structure of these deuterium carriers remains poorly constrained. In this work, their electronic structure is deduced from the measurement of the spin states S by transient nutation in pulsed-EPR. It is shown that these deuterium-rich radicals are dominated by biradicaloids (species with S = 0 ground state and thermally accessible S = 1 state) and biradicals (species with S = 1 ground state) representing ∼61% and ∼31% of the radicals in the IOM of Orgueil, respectively, while single radicals (S = 1/2) contribute only to ∼8%. This is definitely different from mature terrestrial IOMs, which are known to contain almost exclusively S = 1/2 radicals. A structural model is proposed, whereby the occurrence of dominant biradicaloids and biradicals is the direct consequence of the structure of the IOM, made of a network of small aromatic moieties linked by branched and short aliphatic units. This implies that the formation of stable biradicaloids and biradicals by C-H breaking and their deuterium enrichment are produced after the formation of the IOM in the primitive solar system. These results reinforce the idea that the formation of the IOM and the deuterium-rich hotspots are the product of ion chemistry in the solar disk.  相似文献   

Microstructure and hydraulic conductivity of a compacted lime-treated soil   总被引：1，自引：0，他引：1  

Olivier Cuisinier  Jean-Claude Auriol  Tangi Le Borgne  Dimitri Deneele 《Engineering Geology》2011,(3):187

Under a given compaction energy and procedure, it is known that maximum dry density of a soil is lowered due to lime addition. This modification of maximum dry density could alter the hydraulic conductivity of the soil. The main object of this study was to assess the impact of lime-stabilization on a silt soil microstructure and then on saturated hydraulic conductivity. An investigation at the microscopic level with mercury intrusion porosimetry showed that lime treatment induced the formation of a new small class, with a diameter lower than 3 × 10³ Å in the compacted soil. This class is responsible for the difference in dry density between the treated and the untreated sample after compaction. It is shown that this small pores class was not altered by the compaction water content, the compaction procedure or the dry density. As in untreated soils, only the larger pores were modified by the compaction water content and the compaction procedure in the lime treated samples. The hydraulic conductivity appeared to be only related to the largest pores volume of the tested silt, regardless of lime treatment. Therefore, this study demonstrated that even if addition of lime resulted in a dramatic change of the maximum dry density of the tested silty soil, its effect on hydraulic conductivity is limited.  相似文献   

Diet of Haplognathia ruberrima (Gnathostomulida) in a Caribbean marine mangrove          下载免费PDF全文

Pierre‐Yves Pascal  Claude Bellemare  Wolfgang Sterrer  Henricus T. S. Boschker  Silvina Gonzalez‐Rizzo  Olivier Gros 《Marine Ecology》2015,36(2):246-257

Haplognathia ruberrima is a cosmopolitan gnathostomulid species found in sulfur bacterial mats in mangroves in Guadeloupe (French West Indies). Haplognathia ruberrima presents a δ¹³C value lower than all measured meiofaunal grazers and lower than the available measured food sources of this environment. This low δ¹³C value can not be due to specific ingestion of ¹³C‐depleted methanogenic bacteria because abundances of those bacteria are reduced in surficial and deep sediments as revealed by δ¹³C of bacterial fatty acid. According to scanning electron microscope observations, no bacterial ectosymbionts were observed at the surface of the gnathostomulids, and transmission electron microscope views revealed the absence of bacterial endosymbionts. Energy‐dispersive X‐ray spectroscopy analysis detected low levels of sulfur (0.32%±0.8) in biological tissues of H. ruberrima, confirming the absence of thioautotrophic bacterial symbionts in these animals. Consequently, the low δ¹³C value of H. ruberrima can not be due to the presence of sulfur‐oxidizing symbionts but more probably to the selective and exclusive consumption of free‐living, sulfur‐oxidizing bacteria.  相似文献   

Integrative taxonomic description of Plakina kanaky,a new polychromatic sponge species from New Caledonia (Porifera: Homoscleromorpha)          下载免费PDF全文

César Ruiz  Julijana Ivanišević  Pierre Chevaldonné  Alexander V. Ereskovsky  Nicole Boury‐Esnault  Jean Vacelet  Olivier P. Thomas  Thierry Pérez 《Marine Ecology》2015,36(4):1129-1143

Four similar sponges of different colors, all unknown to science, were collected in submarine caves of New Caledonia. We aimed at determining whether the four chromotypes represented different species or phenotypic variations of a unique new species. We used an integrative taxonomic approach combining morphologic, molecular and metabolomic analyses. The main traits that define these specimens are a skeleton made of monolophose, trilophose and tetralophose calthrops only, high chemical diversity and a high abundance and diversity of prokaryotic symbionts. The symbiotic community includes two unique prokaryote morphotypes, which are described for the first time in Homoscleromorpha, and appeared to be vertically transmitted. Although several features slightly differ among chromotypes, the most parsimonious conclusion was to propose a single new species Plakina kanaky sp. nov. Our phylogenetic analysis indicated the paraphyly of the Plakina genus, with P. kanaky sp. nov. belonging to a clade that includes Plakina jani and Plakina trilopha. The present work demonstrates that integrative taxonomy should be used in order to revise the entire Plakinidae family and especially the non‐monophyletic genus Plakina.  相似文献   

Intentional contamination of water distribution networks: developing indicators for sensitivity and vulnerability assessments     

Amir?NafiEmail author  Eric?Crastes  Rehan?Sadiq  Denis?Gilbert  Olivier?Piller 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(2):527-544

Performing a comprehensive risk analysis is primordial to ensure a reliable and sustainable water supply. Though the general framework of risk analysis is well established, specific adaptation seems needed for systems such as water distribution networks (WDN). Understanding of vulnerabilities of WDN against deliberate contamination and consumers’ sensitivity against contaminated water use is very vital to inform decision-maker. This paper presents an innovative step-by-step methodology for developing comprehensive indicators to perform sensitivity, vulnerability and criticality analyses in case of absence of early warning system (EWS). The assessment and the aggregation of these indicators with specific fuzzy operators allow identifying the most critical points in a WDN. Intentional intrusion of contaminants at these points can potentially harm both the consumers as well as water infrastructure. The implementation of the developed methodology has been demonstrated through a case study of a French WDN unequipped with sensors.  相似文献   

Does stress transmission in forelands depend on structural style? Distinctive stress magnitudes during Sevier thin‐skinned and Laramide thick‐skinned layer‐parallel shortening in the Bighorn Basin (USA) revealed by stylolite and calcite twinning paleopiezometry     

Nicolas Beaudoin  Olivier Lacombe  Marie‐Elonore David  Daniel Koehn 《地学学报》2020,32(3):225-233

The Sheep Mountain‐Little Sheep Mountain Anticlines, Bighorn Basin (USA) formed as basement‐cored Laramide structures in the formerly undeformed foreland of the thin‐skinned Sevier orogen. We take advantage of the well‐constrained microstructural network there to reconstruct differential stress magnitudes that prevailed during both Sevier and Laramide layer‐parallel shortening (LPS), before the onset of large‐scale folding. Differential stress magnitudes determined from tectonic stylolites are compared and combined to previous stress estimates from calcite twinning paleopiezometry in the same formations. During stress loading related to LPS, differential stress magnitudes transmitted from the distant Sevier thin‐skinned orogen into the sedimentary cover of the Bighorn basin (11–43 MPa) are higher than the differential stress magnitudes accompanying the early stage of LPS related to the thick‐skinned Laramide deformation (2–19 MPa). This study illustrates that the tectonic style of an orogen affects the transmission of early orogenic stress into the stable continental interior.  相似文献   

Glacial flood pulse effects on benthic fauna in equatorial high‐Andean streams          下载免费PDF全文

Sophie Cauvy‐Fraunié  Patricio Andino  Rodrigo Espinosa  Roger Calvez  Fabien Anthelme  Dean Jacobsen  Olivier Dangles 《水文研究》2014,28(6):3008-3017

Equatorial glacier‐fed streams present unique hydraulic patterns when compared to glacier‐fed observed in temperate regions as the main variability in discharge occurs on a daily basis. To assess how benthic fauna respond to these specific hydraulic conditions, we investigated the relationships between flow regime, hydraulic conditions (boundary Reynolds number, Re*), and macroinvertebrate communities (taxon richness and abundance) in a tropical glacier‐fed stream located in the high Ecuadorian Andes (> 4000 m). Both physical and biotic variables were measured under four discharge conditions (base‐flow and glacial flood pulses of various intensities), at 30 random points, in two sites whose hydraulic conditions were representative to those found in other streams of the study catchment. While daily glacial flood pulses significantly increased hydraulic stress in the benthic habitats (appearance of Re* > 2000), low stress areas still persisted even during extreme flood events (Re* < 500). In contrast to previous research in temperate glacier‐fed streams, taxon richness and abundance were not significantly affected by changes in hydraulic conditions induced by daily glacial flood pulses. However, we found that a few rare taxa, in particular rare ones, preferentially occurred in highly stressed hydraulic habitats. Monte‐Carlo simulations of benthic communities under glacial flood reduction scenarios predicted that taxon richness would be significantly reduced by the loss of high hydraulic stress habitats following glacier shrinking. This pioneer study on the relationship between hydraulic conditions and benthic diversity in an equatorial glacial stream evidenced unknown effects of climate change on singular yet endangered aquatic systems. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Intra-interstadial environmental changes in Last Glacial loess revealed by molluscan assemblages from the Upper Palaeolithic site of Amiens-Renancourt 1 (Somme,France)     

Olivier Moine  Pierre Antoine  Sylvie Coutard  Gilles Guérin  Christine Hatté  Clément Paris  Ségolène Saulnier-Copard 《第四纪科学杂志》2021,36(8):1322-1340

The Amiens-Renancourt 1 site recently yielded one of the most important Upper Palaeolithic human occupations of northern France by the number of flint artefacts and especially by the presence of Venus figurines. All the material comes from a single archaeological layer located in a tundra gley bracketed by loess units. A multi-proxy study combining a detailed stratigraphy, luminescence and radiocarbon datings and high-resolution (5 cm per sample) grain size and molluscan analyses was therefore carried out to reconstruct and date the associated environmental changes and to determine the exact context of the human occupation. The chronological frame thus established supports the correlations of the archaeology-bearing tundra gley and of an underlying arctic brown soil with Greenland interstadials GI-4 and GI-3. Composition changes in the molluscan population enabled the identification of transitional and optimum phases and sub-phases within these two pedogenetic horizons. A conceptual correlation model linking molluscan phases with millennial-scale variations of Greenland ice-core and Sieben Hengste speleothem climate records is proposed. The Human occupation appears contemporaneous to the end of the stadial–interstadial transition of GI-3. Synchronous in Amiens-Renancourt 1 and Nussloch, subsequent micro-gleys may also result from a regional/global forcing. Such a level of detail is unprecedented in a loess sequence.  相似文献   

An ESA NEOCC Effort to Eliminate High Palermo Scale Virtual Impactors     

Marco Micheli  Detlef Koschny  Gerhard Drolshagen  Olivier Hainaut  Fabrizio Bernardi 《Earth, Moon, and Planets》2014,113(1-4):1-13

In this work we summarize the initial results of a targeted effort of the ESA NEO Coordination Centre to obtain additional observational data in order to eliminate or reduce the impact probability estimate of a subset of the known near-Earth objects representing the highest fraction of the total known impact risk, as measured by the Palermo Scale.  相似文献   

Calderas,landslides and paleo-canyons on Piton de la Fournaise volcano (La Réunion Island,Indian Ocean)     

Olivier Merle  Philippe Mairine  Laurent Michon  Patrick Bachèlery  Magali Smietana 《Journal of Volcanology and Geothermal Research》2010,189(1-2):131-142

Based upon a re-interpretation of previous data and a new field campaign, a structural evolution is proposed for the early history of Piton de la Fournaise volcano from 500,000 to 50,000 years. Conceptually, it is shown that the formation of a caldera in which lava flows are contained inside the caldera depression, gives time for erosion to excavate deep canyons on the external slopes of the volcano, for example, the Rivière des Remparts, the Rivière Langevin and the Rivière de l'Est canyons on Piton de la Fournaise volcano. These canyons are infilled when lavas, filling the caldera and overflowing its rim, are able again to flow on the external slopes of the volcano. In the past, this excavating/infilling process has occurred twice following the formation of the Rivière des Remparts and Morne Langevin calderas. The formation of the third caldera, the Plaine des Sables caldera, was followed by the excavation of the current canyons. In addition to this process, two large landslides have been documented in the field. The first, which happened about 300,000 years ago, is apparently the first episode of the break up of Piton de la Fournaise volcano, predating the formation of the four large calderas. The second landslide, which occurred 150,000 years ago and is considered to be less extensive, has carried away the entire southern flank of the Rivière des Remparts caldera.  相似文献