The AGNS and their host galaxies as seen in the mid-infrared     

O. Laurent  I.F. Mirabel  P. Gallais  M. Sauvage  L. Vigroux  C. Cesarsky  V. Charmandaris 《Astrophysics and Space Science》1999,266(1-2):175-180

We present a new diagnostic diagram based on ISOCAMspectra (5-16 m) to distinguish the emission inducedby the active galactic nucleus (AGN) from that associated with thestar formation activity. This diagnostic based on the mid-IRcontinuum and the Unidentified Infrared Band (UIB) intensity allowsus to estimate the relative importance of the three components (HIIregions, diffuse/photo-dissociation regions (PDRs), and AGN) contained ingalaxy mid-infrared emission. In AGN spectra, we confirm the absenceof UIBs presumably photodissociated by the X-UV radiation field. Inaddition, a non-negligible continuum below 9 m commonlyassociated with emission from hot dust is present in AGNs. Adiagnostic diagram derived from these two results can be used fordetecting obscured AGNs embedded in a large concentration of dust.  相似文献   

Strain analysis of a shear zone in a granodiorite—reply     

J.P. Burg  Ph. Laurent 《Tectonophysics》1979,60(3-4):313-315

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Spatial Variability of Trends in the Rainfall-Runoff Relationship: A Mesoscale Study in the Mosel Basin     

Laurent Pfister  Gilles Drogue  Abdelkhalak El Idrissi  Jean-François Iffly  Christelle Poirier  Lucien Hoffmann 《Climatic change》2004,66(1-2):67-87

The spatial variability of observed trends in rainfall structure over the last 5 decades and its effects on the spatial variability of maximum daily water levels in the Grand-Duchy of Luxembourg (Europe) were investigated in 9 sub-basins of the Mosel river. Over the past 25 years, an increase in westerly atmospheric circulation types during winter months has caused an increase in winter rainfall totals, duration and intensity. More specifically, the spatial variability of trends having affected winter rainfall totals, duration and intensity have led to spatially varying positive trends in maximum daily water levels. Observed trends in rainfall characteristics and maximum daily water levels during winter show closely linked spatial patterns that are strongly related to the topography of the study area.  相似文献   

Mid-latitude Southern Indian Ocean response to Northern Hemisphere Heinrich events     

Marie Alexandrine Sicre  Laurent Labeyrie  Ullah Ezat  Josette Duprat  Jean Louis Turon  Sabine Schmidt  Elisabeth Michel  Alain Mazaud 《Earth and Planetary Science Letters》2005,240(3-4):724-731

The lack of temporal resolution and accurate chronology of Southern Ocean marine cores has hampered comparison of glacial millennial-scale oscillations between the Southern Ocean, Antarctic ice and other records from both hemispheres. In this study, glacial climate variability is investigated over the last 50 ka using a multi-proxy approach. A precise chrono-stratigraphy was developed on the high-sedimentation rate core MD94-103 (Indian Southern Ocean, 45°35′S 86°31′E, 3560 m water depth) by geomagnetic synchronization between the later core and NAPIS75, and ¹⁴C dates. High-resolution time-series of δ¹⁸O in planktonic foraminifera Globigerina bulloides and Neogloboquadrina pachyderma, and sea surface temperatures (SSTs) estimated from the alkenone U^K′₃₇ index and foraminifera assemblages have been generated. Temporal evolution of the two temperature proxy records is notably different during the last glacial period. While foraminifera data indicate a consistent cooling towards the last glacial maximum, anomalous warm glacial alkenone temperatures suggest a strong advection of warm “detrital” alkenones by surface waters of the Agulhas current. Superimposed to this general trend, during Heinrich events, foraminiferal SSTs point to warmer surface waters, while concurrent alkenone SSTs exhibit apparent coolings probably caused by enhanced local alkenone production. By analogy to modern observations, possible influence of ENSO-like conditions on the subantarctic Southern Ocean SSTs is discussed.  相似文献   

Spécificités hydrogéologiques des hautes vallées alpines: Exemple de la Haute-Sarine (Suisse)     

Julien Vaudan  Aurèle Parriaux  Laurent Tacher  Gianni della Valle 《Eclogae Geologicae Helvetiae》2005,98(3):371-383

The alpine valley of the Haute-Sarine is on several accounts representative of the alluvial aquifers of mountain by its very environment and its hydrogeologic characteristics. The investigations and the analysis carried out within the framework of this study enabled us to improve knowledge on the Quaternary filling of the valley and to highlight the preferential supplies of the aquifer by infiltration of the river and precipitations and also by the underground contributions of evaporitic karsts. We also could note the opulence of groundwater resources of the Haute-Sarine both from the qualitative and the quantitative points of view. The knowledge of these typical characteristics of alluvial aquifers of high altitude allowed finally the development of a concept of management and protection of groundwater resources that falls under a sustainable development policy of the groundwater storage in the alpine areas. Manuscrit re?u le 4 février 2003 Révision acceptée le 30 mars 2005  相似文献   

Surface chemistry of disordered mackinawite (FeS)   总被引：1，自引：0，他引：1  

Mariëtte Wolthers  Laurent Charlet  David Rickard 《Geochimica et cosmochimica acta》2005,69(14):3469-3481

Disordered mackinawite, FeS, is the first formed iron sulfide in ambient sulfidic environments and has a highly reactive surface. In this study, the solubility and surface chemistry of FeS is described. Its solubility in the neutral pH range can be described by K_s^app = {Fe²⁺} · {H₂S(aq)} · {H⁺}⁻² = 10^+4.87±0.27. Acid-base titrations show that the point of zero charge (PZC) of disordered mackinawite lies at pH ∼7.5. The hydrated disordered mackinawite surface can be best described by strongly acidic mono-coordinated and weakly acidic tricoordinated sulfurs. The mono-coordinated sulfur site determines the acid-base properties at pH < PZC and has a concentration of 1.2 × 10⁻³ mol/g FeS. At higher pH, the tricoordinated sulfur, which has a concentration of 1.2 × 10⁻³ mol/g FeS, determines surface charge changes. Total site density is 4 sites nm⁻². The acid-base titration data are used to develop a surface complexation model for the surface chemistry of FeS.  相似文献   

New insight on aliphatic linkages in the macromolecular organic fraction of Orgueil and Murchison meteorites through ruthenium tetroxide oxidation     

Laurent Remusat  Sylvie Derenne  François Robert 《Geochimica et cosmochimica acta》2005,69(17):4377-4386

Ruthenium tetroxide oxidation was used to examine the macromolecular insoluble organic matter (IOM) from the Orgueil and Murchison meteorites and especially to characterize the aliphatic linkages. Already applied to various terrestrial samples, ruthenium tetroxide is a selective oxidant which destroys aromatic units, converting them into CO₂, and yields aliphatic and aromatic acids. In our experiment on chondritic IOM, it produces mainly short aliphatic diacids and polycarboxylic aromatic acids. Some short hydroxyacids are also detected.Aliphatic diacids are interpreted as aliphatic bridges between aromatic units in the chemical structure, and polycarboxylic aromatic acids are the result of the fusion of polyaromatic units. The product distribution shows that aliphatic links are short with numerous substitutions. No indigenous monocarboxylic acid was detected, showing that free aliphatic chains must be very short (less than three carbon atoms). The hydroxyacids are related to the occurrence of ester and ether functional groups within the aliphatic bridges between the aromatic units. This technique thus allows us to characterize in detail the aliphatic linkages of the IOMs, and the derived conclusions are in agreement with spectroscopic, pyrolytic, and degradative results previously reported.Compared to terrestrial samples, the aliphatic part of chondritic IOM is shorter and highly substituted. Aromatic units are smaller and more cross-linked than in coals, as already proposed from NMR data. Orgueil and Murchison IOM exhibit some tiny differences, especially in the length of aliphatic chains.  相似文献   

Modeling endogenous learning and imperfect competition effects in climate change economics     

Laurent Viguier  Leonardo Barreto  Alain Haurie  Socrates Kypreos  Peter Rafaj 《Climatic change》2006,79(1-2):121-141

In this two-part paper we evaluate the effect of “endogenizing” technological learning and strategic behavior of agents in economic models used to assess climate change policies. In the first part we show the potential impact of R&D policies or demonstration and deployment (D&D) programs in the context of stringent stabilization scenarios. In the second part we show how game-theoretic methods can be implemented in climate change economic models to take into account three types of strategic interactions: (i) the market power of the countries benefiting from very low abatement costs on international markets for CO₂ emissions, (ii) the strategic behavior of governments in the domestic allocation of CO₂ emissions quotas, and (iii) the non-cooperative behavior of countries and regions in the burden sharing of CO₂ concentration stabilization. The two topics of endogenous learning and game-theoretic approach to economic modeling are two manifestations of the need to take into account the strategic behavior of agents in the evaluation of climate change policies. In the first case an R&D policy or a demonstration and deployment (D&D) program are put in place in order to attain a cost reduction through the learning effect; in the second case the agents (countries) reply optimally to the actions decided by the other agents by exploiting their strategic advantages. Simulations based on integrated assessment models illustrate the approaches. These studies have been conducted under the Swiss NCCR-Climate program.  相似文献   

Atmospheric GCM response to an idealized anomaly of the Mediterranean sea surface temperature     

Laurent Z. X. Li 《Climate Dynamics》2006,27(5):543-552

The atmospheric response to an idealized 2 K cooling of the Mediterranean Sea is studied in a general circulation model (GCM). In the downstream region, from the eastern Mediterranean basin to the whole Asian continent (following the sub-tropical jet-stream), a baroclinic response is produced with high pressure near the surface and low pressure in the upper layers. It is the direct response to the Mediterranean cooling and it needs only a few days to be established. Teleconnections with strong zonal characteristics are found following the sub-tropical jet-stream to the North Pacific and North America, propagating further across the North Atlantic towards Northern Europe. Two remarkable remote features are the deepening of the Aleutian Low in the North Pacific and the weakening of the Icelandic Low in the North Atlantic. These two teleconnections form and grow in several days in the North Pacific and several tens of days in the North Atlantic. Both have a quasi-barotropic vertical structure. It is believed that they are the consequence of complex interactions between the mean flow and the transient eddies in the atmosphere.  相似文献   

Plate Motion of India and Interseismic Strain in the Nepal Himalaya from GPS and DORIS Measurements   总被引：3，自引：0，他引：3  

Pierre Bettinelli  Jean-Philippe Avouac  Mireille Flouzat  François Jouanne  Laurent Bollinger  Pascal Willis  Gyani Raja Chitrakar 《Journal of Geodesy》2006,80(8-11):567-589

We analyse geodetically estimated deformation across the Nepal Himalaya in order to determine the geodetic rate of shortening between Southern Tibet and India, previously proposed to range from 12 to 21 mm yr^?1. The dataset includes spirit-levelling data along a road going from the Indian to the Tibetan border across Central Nepal, data from the DORIS station on Everest, which has been analysed since 1993, GPS campaign measurements from surveys carried on between 1995 and 2001, as well as data from continuous GPS stations along a transect at the logitude of Kathmandu operated continuously since 1997. The GPS data were processed in International Terrestrial Reference Frame 2000 (ITRF2000), together with the data from 20 International GNSS Service (IGS) stations and then combined using quasi- observation combination analysis (QOCA). Finally, spatially complementary velocities at stations in Southern Tibet, initially determined in ITRF97, were expressed in ITRF2000. After analysing previous studies by different authors, we determined the pole of rotation of the Indian tectonic plate to be located in ITRF2000 at 51.409±1.560° N and ?10.915±5.556°E, with an angular velocity of 0.483±0.015°. Myr^?1. Internal deformation of India is found to be small, corresponding to less than about 2 mm yr^?1 of baseline change between Southern India and the Himalayan piedmont. Based on an elastic dislocation model of interseismic strain and taking into account the uncertainty on India plate motion, the mean convergence rate across Central and Eastern Nepal is estimated to 19±2.5 mm yr^?1, (at the 67% confidence level). The main himalayan thrust (MHT) fault was found to be locked from the surface to a depth of about 20 km over a width of about 115 km. In these regions, the model parameters are well constrained, thanks to the long and continuous time-series from the permanent GPS as well as DORIS data. Further west, a convergence rate of 13.4±5 mm yr^?1, as well as a fault zone, locked over 150 km, are proposed. The slight discrepancy between the geologically estimated deformation rate of 21±1.5 mm yr^?1 and the 19±2.5 mm yr^?1 geodetic rate in Central and Eastern Nepal, as well as the lower geodetic rate in Western Nepal compared to Eastern Nepal, places bounds on possible temporal variations of the pattern and rate of strain in the period between large earthquakes in this region.  相似文献