On the universal outcome of star formation: is there a link between stars and brown dwarfs?     

Pavel Kroupa †  Jerome Bouvier  Gaspard Duchêne  Estelle Moraux 《Monthly notices of the Royal Astronomical Society》2003,346(2):354-368

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Sensitivity to stress of the estuarine bivalve Macoma balthica from areas between the Netherlands and its southern limits (Gironde)     

H. Hummel  C. Amiard-Triquet  G. Bachelet  M. Desprez  J. Marchand  B. Sylvand  J.C. Amiard  H. Rybarczyk  R.H. Bogaards  J. Sinke  Y. De Wit  L. De Wolf 《Journal of Sea Research》1996,35(4):315-321

Variation in the sensitivity to stress of Macoma balthica was measured in several French and Dutch estuaries. For adult and juvenile Macoma balthica exposed to copper under conditions of starvation, differences in mortality rate, condition, glycogen, burrowing rate and copper content were assessed. No significant differences were observed between adults and juveniles; the influence of treatment and origin was always evident. Animals from the most southern estuaries, Loire and Gironde, near to the species's southern limit of distribution, showed, in the field, the strongest deviations for the ecophysiological traits measured, and were in the experiments the most sensitive to stress.  相似文献   

Preliminary Results from a New 157 nm Laser Ablation ICP-MS Instrument: New Opportunities in the Analysis of Solid Samples     

Philippe Telouk  Estelle F. Rose-Koga  Francis Albarede 《Geostandards and Geoanalytical Research》2003,27(1):5-11

Preliminary results are given from an excimer 157 nm laser ablation multiple-collector inductively coupled plasma-mass spectrometer (LA-MC-ICP-MS), used for the isotopic measurements of solid materials. Elements of geological interest with different volatilities such as Pb and U (e.g. zircon geochronology) and Cu and Zn (as examples of geochemical/biochemical tracers) were analysed. The range of ablation rates of 20-150 nm s^-1 enabled us to ablate the sample down to a depth of 45 μm for a 50 μm diameter pit. The Cu and Zn isotopic measurements gave values that were very stable with, on average, a 0.01 % standard error, comparable with that achieved in liquid mode measurements.  相似文献   

Clinoform nucleation and growth in coarse-grained deltas, Loreto basin, Baja California Sur, Mexico: a response to episodic accelerations in fault displacement   总被引：1，自引：0，他引：1  

Estelle Mortimer  Sanjeev Gupta†  Patience Cowie 《Basin Research》2005,17(3):337-359

We investigate the controls on the architecture of coarse‐grained delta progradational units (PUs) in the Pliocene Loreto basin (Baja California Sur, Mexico), a half‐graben located on the western margin of the Gulf of California. Dorsey et al. (1997b) argued that delta progradation and transgression cycles in the basin were driven by episodic fault‐controlled subsidence along the basin‐bounding Loreto fault. Here we test this hypothesis by a detailed analysis of the sedimentary architecture of 11 exceptionally well‐exposed, vertically arranged fluvio‐deltaic PUs, each of which shows lateral facies transition from proximal alluvial facies palaeo‐seaward into distal pro‐delta facies. Of these 11 PUs, seven exhibit a lateral transition from a shoal water to Gilbert‐delta facies associations as they are traced palaeo‐seaward. This transition is characterised by down‐transport development of foresets, which grow in height up to 35 m. Foreset units thicken in a basinward direction, with initially an oblique topset–foreset geometry that becomes increasingly sigmoidal. Each delta is capped by a shell bed that records drowning of the delta top. This systematic transition in delta architecture records increasing water depth through time during individual episodes of progradation. A mechanism that explains this transition is an accelerating rate of fault‐controlled subsidence during each PU. During episodes of low slip rate, shoal‐water deltas prograde across the submerged topography of the underlying delta unit. As displacement rate accelerates, increasing bathymetry at the delta front leads to steepening of foresets and initiation of Gilbert deltas. Subsequent delta drowning results from sediment starvation at the shoreline at high slip rates because of sediment trapping upstream. The observed delta architecture suggests that the long‐term (>100 kyr) history of slip on the Loreto fault was characterised by repetitive episodes of accelerating displacement accumulation. Such episodic fault behaviour is most likely to be because of variations in temporal and spatial strain partitioning between the Loreto fault and other faults in the Gulf of California. A physical explanation for the acceleration phenomenon involves evolving frictional properties on the episodically active Loreto fault.  相似文献   

Climatic change and great lakes levels the impact on shipping     

D. Marchand  M. Sanderson  D. Howe  C. Alpaugh 《Climatic change》1988,12(2):107-133

This paper represents an attempt to combine the output of several models that deal with future climatic, hydrologic and economic conditions in the Great Lakes and makes some predictions about the possible impact of one scenario of 2 × CO₂ climate on Great Lakes shipping. It is realized that there is a great deal of uncertainty in all the models and that improvements are continually being made. Data from a General Circulation Model of future temperature and precipitation in the Great Lakes basin, a Great Lakes levels and flows model from the Canada Centre for Inland Waters and an International Joint Commision's Great Lakes economic model modified by the University of Wisconsin were used. The 1900–1976 period of lake levels and flows was used. The hydrologic model indicated that future mean lake levels may be reduced by one-half meter, and that the extreme low levels of the mid 1960's could occur 77% of the time in the future. No ice cover is predicted for any lake except Erie, permitting an eleven month shipping season. Five scenarios of future impact on shipping were evaluated. It was found that mean annual shipping costs may increase by 30% and the frequency of years when costs exceed those of the period of low lake levels (1963–65) could rise to 97%. Possible policy options in a future with climatically induced lower lake levels could include regulation to keep levels artificially high by diversions into the system, or increased dredging of the connecting channels.  相似文献   

Phosphorus oxynitride PON, a silica analogue: structure and compression of the cristobalite-like phase; P –T phase diagram     

J. M. Léger  J. Haines  C. Chateau  G. Bocquillon  M. W. Schmidt  S. Hull  F. Gorelli  A. Lesauze  R. Marchand 《Physics and Chemistry of Minerals》2001,28(6):388-398

 The structure of the cristobalite-like polymorph of phosphorus oxynitride PON has been refined using neutron powder diffraction data. It is tetragonal, space group I&4macr;2d, Z=4. The four P–(O,N) distances are equal but the tetrahedron is compressed along c. In AX₂ or ABX₄ compounds, the tetragonal I&4macr;2d or I&4macr; structure is obtained when the average ratio of the cation to anion radius is below 1.186, whereas the tetragonal P4₁2₁2 or orthorhombic C222₁ structure is obtained at low temperatures for larger ratios. The cell parameters of this PON polymorph have been determined as a function of hydrostatic pressure by in situ angle dispersive X-ray powder diffraction in a diamond-anvil cell. Under truly hydrostatic pressure, a strong anisotropic behavior is observed with the c parameter being nearly incompressible. Very slight anisotropic stress strongly modifies the high-pressure behavior. According to the pressure-temperature conditions of treatment, three phases, cristobalite-, moganite-, and quartz-like, have been obtained by quenching experiments, and the P–T phase diagram of PON was derived. The high-pressure behavior of the α-quartz, moganite, and cristobalite-like polymorphs of PON and SiO₂ is discussed. Received: 7 August 2000 / Accepted: 21 January 2001  相似文献   

Découverte d'un granite ≪ charnockitique ≫ au sein de ≪ gneiss œillés ≫ Perspectives nouvelles sur l'origine de certaines leptynites du Massif Armoricain Méridional (France)     

B. Lasnier  A. Leyreloup  J. Marchand 《Contributions to Mineralogy and Petrology》1973,41(2):131-144

The authors describe from the South of Brittany (inverted limb of the “overthrust nappe of Champtoceaux”, near Nantes) an example of a relic massif of “charnockitised” granite, within augen gneisses and blastomylonitic leptynites. The granite is characterised by the presence of coronas of almandite + orthoclase between biotite (ores) and plagioclase, indicating that it was affected by a pre-deformation granulitic phase of metamorphism before its retromorphism in the amphibolite and greenschist facies, a similar history is recorded in associated metabasites. The progressive transformation of granite to augen gneisses and leptynites is a new observation of importance concerning the origin of leptynites.   相似文献   

Levels of PCBs and DDTs in mussels from the N.W. Mediterranean     

M Marchand  D Vas  E.K Duursma 《Marine pollution bulletin》1976,7(4):65-69

The concentration of synthetic chlorinated hydrocarbons has been monitored in mussels collected on the north-west Mediterranean coast. DDT and PCB contamination is widespread in this region and the results suggest that the mussels are directly exposed to DDT. Seasonal changes in fat content of the mussels and the (unknown) rates of chlorinated hydrocarbon accumulation and excretion make the detailed interpretation of data difficult and limit the value of mussels as bio-indicators of pollution.  相似文献   

The Monitor project: rotation of low-mass stars in the open cluster NGC 2516     

Jonathan Irwin  Simon Hodgkin  Suzanne Aigrain  Leslie Hebb  Jerome Bouvier  Cathie Clarke  Estelle Moraux  D. M. Bramich 《Monthly notices of the Royal Astronomical Society》2007,377(2):741-758

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The Monitor project: JW 380 – a 0.26-, 0.15-M_⊙, pre-main-sequence eclipsing binary in the Orion nebula cluster     

Jonathan Irwin  Suzanne Aigrain  Simon Hodgkin  Keivan G. Stassun  Leslie Hebb  Mike Irwin  Estelle Moraux  Jerome Bouvier  Aude Alapini  Richard Alexander  D. M. Bramich  Jon Holtzman  Eduardo L. Martín  Mark J. McCaughrean  Frédéric Pont  P. E. Verrier  María Rosa Zapatero Osorio 《Monthly notices of the Royal Astronomical Society》2007,380(2):541-550

We present a general recipe for constructing N -body realizations of galaxies comprising near spherical and disc components. First, an exact spherical distribution function for the spheroids (halo and bulge) is determined, such that it is in equilibrium with the gravitational monopole of the disc components. Second, an N -body realization of this model is adapted to the full disc potential by growing the latter adiabatically from its monopole. Finally, the disc is sampled with particles drawn from an appropriate distribution function, avoiding local-Maxwellian approximations. We performed test simulations and find that the halo and bulge radial density profile very closely match their target model, while they become slightly oblate due to the added disc gravity. Our findings suggest that vertical thickening of the initially thin disc is caused predominantly by spiral and bar instabilities, which also result in a radial re-distribution of matter, rather than scattering off interloping massive halo particles.  相似文献