Multiscale morphology of the galaxy distribution     

Enn Saar  Vicent J. Martínez  Jean-Luc Starck  David L. Donoho 《Monthly notices of the Royal Astronomical Society》2007,374(3):1030-1044

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Split Comet C/2001 A2 (LINEAR)     

Jehin  Emmanuel  Boehnhardt  Hermann  Sekanina  Zdenek  Bonfils  Xavier  Schütz  Oliver  Beuzit  Jean-Luc  Billeres  Malvina  Garradd  Gordon J.  Leisy  Pierre  Marchis  Franck  Más  Antonio  Origlia  Livia  Scarpa  Daniel  Thomas  Daniel  Tozzi  Gian Paolo 《Earth, Moon, and Planets》2002,90(1-4):147-151

Comet C/2001 A2 experienced several splitting events duringits 2001 perihelion passage. The first break-upevent was observed in March 2001 (IAUC 7616).In this paper we report the first results of ourextensive imaging and spectroscopic monitoring campaignwith ESO telescopes over several weeks before andafter the perihelion passage on May 25 2001.  相似文献   

Seismic Empirical Relations for the Tellian Atlas, North Africa, and their Usefulness for Seismic Risk Assessment     

Noureddine Beghoul  Jean-Luc Chatelain  Mohamed-Salah Boughacha  Hadj Benhallou  Rida Dadou  Amira Mezioud-Saïch 《Pure and Applied Geophysics》2010,167(3):277-321

Seismic events that occurred during the past half century in the Tellian Atlas, North Africa, are used to establish fundamental seismic empirical relations, tying earthquake magnitude to source parameters (seismic moment, fault plane area, maximal displacement along the fault, and fault plane length). Those empirical relations applied to the overall seismicity from 1716 to present are used to transform the magnitude (or intensity) versus time distribution into (1) cumulative seismic moment versus time, and (2) cumulative displacements versus time. Both of those parameters as well as the computed seismic moment rate, the strain rate along the Tellian Atlas strike, and various other geological observations are consistent with the existence, in the Tellian Atlas, of three distinct active tectonic blocks. These blocks are seismically decoupled from each other, thus allowing consideration of the seismicity as occurring in three different distinct seismotectonic blocks. The cumulative displacement versus time from 1900 to present for each of these tectonic blocks presents a remarkable pattern of recurrence time intervals and precursors associated with major earthquakes. Indeed, most major earthquakes that occurred in these three blocks might have been predicted in time. The Tellian Atlas historical seismicity from the year 881 to the present more substantially confirms these observations, in particular for the western block of the Tellian Atlas. Theoretical determination of recurrence time intervals for the Tellian Atlas large earthquakes using Molnar and Kostrov formalisms is also consistent with these observations. Substantial observations support the fact that the western and central Tellian Atlas are currently at very high seismic risk, in particular the central part. Indeed, most of the accumulated seismic energy in the central Tellian Atlas crust has yet to be released, despite the occurrence of the recent destructive May 2003 Boumerdes earthquake (M _w = 6.8). The accumulated seismic energy is equivalent to a magnitude 7.6 earthquake. In situ stress and geodetic measurements, as well as other geophysical field data measurements, are now required to practically check the validity of those observations.  相似文献   

Analytical model of the long-period forced longitude librations of Mercury     

Marie Yseboodt  Jean-Luc Margot 《Icarus》2010,207(2):536-544

The shaking of Mercury’s orbit by the planets forces librations in longitude in addition to those at harmonics of the orbital period that have been used to detect Mercury’s molten core. We extend the analytical formulation of Peale et al. (Peale, S.J., Margot, J.L., Yseboodt, M. [2009]. Icarus 199, 1-8) in order to provide a convenient means of determining the amplitudes and phases of the forced librations without resorting to numerical calculations. We derive an explicit relation between the amplitude of each forced libration and the moment of inertia parameter (B-A)/C_m. Far from resonance with the free libration period, the libration amplitudes are directly proportional to (B-A)/C_m. Librations with periods close to the free libration period of ∼12 years may have measurable (∼arcsec) amplitudes. If the free libration period is sufficiently close to Jupiter’s orbital period of 11.86 years, the amplitude of the forced libration at Jupiter’s period could exceed the 35 arcsec amplitude of the 88-day forced libration. We also show that the planetary perturbations of the mean anomaly and the longitude of pericenter of Mercury’s orbit completely determine the libration amplitudes.While these signatures do not affect spin rate at a detectable level (as currently measured by Earth-based radar), they have a much larger impact on rotational phase (affecting imaging, altimetry, and gravity sensors). Therefore, it may be important to consider planetary perturbations when interpreting future spacecraft observations of the librations.  相似文献   

Stratigraphy in the Mawrth Vallis region through OMEGA, HRSC color imagery and DTM     

D. Loizeau  N. Mangold  V. Ansan  J.-P. Bibring  Y. Langevin  G. Neukum 《Icarus》2010,205(2):396-418

The Mawrth Vallis region contains an extensive (at least 300 km × 400 km) and thick (?300 m), finely layered (at meter scale), clay-rich unit detected by OMEGA. We use OMEGA, HRSC DTMs derived from stereoscopic imagery, HRSC color imagery and high resolution imagery such as MOC, CTX and HiRISE to characterize the geometry and the composition of the clay-rich unit at the regional scale. Our results show that the clay-bearing unit can be divided into sub-units on the basis of differences in color and composition. In false-color visible imagery, alternating white/bluish and orange/red colored units correspond to a compositional succession of, respectively, Al- and Fe- or Mg-phyllosilicate rich material. Geological cross-sections are presented along the principal outcrops of the region in order to define the stratigraphy of these sub-units. This method shows that the dips of the sub-units are frequently close to the slopes of the present topography, except for scarps visible at the dichotomy boundary, inside impact craters walls, and outcrops inside Mawrth Vallis. In addition to the Al- and Fe- or Mg-phyllosilicate rich sub-units, an altered surface is identified as the lower basement unit. We propose two possible end-member scenarios to explain the derived stratigraphy: (1) alteration of volcaniclastic, aeolian or aqueous layered deposits of various compositions by groundwater, resulting in distinct altered rocks; or (2) Alteration coeval with the deposition of sediments under varying chemical conditions, in wet pedodiagenetic environment.  相似文献   

New experimental determination of Li and B partition coefficients during upper mantle partial melting   总被引：1，自引：1，他引：0  

Luisa Ottolini  Didier Laporte  Nicola Raffone  Jean-Luc Devidal  Brieuc Le Fèvre 《Contributions to Mineralogy and Petrology》2009,157(3):313-325

Despite the growing interest for Li and B as geochemical tracers, especially for material transfer from subducting slabs to overlying peridotites, little is known about the behaviour of these two elements during partial melting of mantle sources. In particular, mineral/melt partition coefficients for B and to a lesser extent Li are still a matter of debate. In this work, we re-equilibrated a synthetic basalt doped with ~10 ppm B and ~6 ppm Li with an olivine powder from a spinel lherzolite xenolith at 1 GPa–1,330°C, and we analyzed Li and B in the run products by secondary ion mass spectrometry (SIMS). In our experiment, B behaved as a highly incompatible element with mineral/melt partition coefficients of the order of 10⁻² (D ^ol/melt = 0.008 (0.004–0.013); D ^opx/melt = 0.024 (0.015–0.033); D ^cpx/melt = 0.041 (0.021–0.061)), and Li as a moderately incompatible element (D ^ol/melt = 0.427 (0.418–0.436); D ^opx/melt = 0.211 (0.167–0.256); D ^cpx/melt = 0.246 (0.229–0.264)). Our partition coefficients for Li are in good agreement with previous determinations. In the case of B, our partition coefficients are equal within error to those reported by Brenan et al. (1998) for all the mineral phases analyzed, but are lower than other coefficients from literature for some of the phases (up to 5 times for cpx). Our measurements complement the data set of Ds for modelling partial melting of the upper mantle and basalt generation, and confirm that, in this context, B is more incompatible than previously anticipated.  相似文献   

MuSET: A multiparameter and high precision sensor for downhole spontaneous electrical potential measurements     

Philippe A. Pezard  Stéphanie Gautier  Tanguy Le Borgne  Bruno Legros  Jean-Luc Deltombe 《Comptes Rendus Geoscience》2009,341(10-11):957-964

On the basis of an existing multiparameter borehole fluid sensor (p, T, Cw, pH, Eh), a new downhole tool designed for 200 bars and 75 °C was developed to measure the spontaneous electrical potential in situ with great precision (better than a μV). To this end, the new sensor is based on the use of unpolarizable Pb/PbCl₂ electrodes either at the surface or downhole. In situ testing has demonstrated a capacity to identify several subsurface sources of natural electrical potential such as diffusion ones (membrane potential in the presence of clays, Fickian processes due to pore fluid salinity gradients), or else the electrokinetic mechanisms with gradients in pore fluid pressure. As a consequence, Multi-Sensors Electrical Tool (MuSET) might be used as an “electrical flowmeter” sensitive to both horizontal and vertical fluid flow in a vertical borehole.  相似文献   

A Model of PCB Bioaccumulation in the Sea Bass Food Web from the Seine Estuary (Eastern English Channel)     

V. Loizeau  A. Abarnou  P. Cugier  A. Jaouen-Madoulet  A. -M. Le Guellec  A. Menesguen 《Marine pollution bulletin》2001,43(7-12):242-255

A bioaccumulation model was developed to simulate the PCB contamination in the sea bass food web from the Seine Estuary. The model relies upon a contaminant mass balance budget for each biological species. Biological processes determine the extent of bioaccumulation: respiration and feeding rates control the uptake of contaminants whereas excretion, spawning, and growth act on the chemicals removal. A step-by-step modelling approach was followed. A first version was a steady-state model validated for the bioaccumulation processes. In the second version seasonal variation was taken into account, and finally in the third version, the model was coupled with a population dynamics model to describe PCB contamination in each age class.  相似文献   

Deformation and dynamic recrystallization of K feldspar augen in orthogneiss from Montagne Noire,Occitania, Southern France     

Jean-Luc Vidal  Ladislas Kubin  Pierre Debat  Jean-Claude Soula 《Lithos》1980,13(3):247-255

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The problem of regionalization among geographers: the case of Switzerland     

Jean-Luc Piveteau 《Geoforum》1975,6(2)

The lack of any unified view amongst geographers in their conceptions of the articulation of Swiss space is evidence, in the dialectical sense, of the complexity of the reality. It is also, however, a sympton of methodological uncertainty. The purpose of this article is an analysis of this malaise, usually passed over in silence.The evolution of geography during the last hundred years cannot be easily defined, but against a general trend opposed approaches have always been present.The manner of conceiving Swiss space is still affected by the changes in the physiognomy of the country, but the analysis of reality and reality itself are out of phase.It appears possible that the presuppositions admitted by authors or the intellectual paths followed by them in regionalisation should be considered and treated as one of the fundamentals of all studies concerned with the organisation of space.  相似文献