Feasibility of Bioremediation of a Ground Water Polluted with Alkylpyridines   总被引：1，自引：0，他引：1  

Zeev Ronen  Jean-Marc Bollag  Cheng-Hsiung Hsu  James C. Young 《Ground water》1996,34(2):194-199

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Cation exchanged Fe(II) and Sr compared to other divalent cations (Ca, Mg) in the bure Callovian–Oxfordian formation: Implications for porewater composition modelling     

Christophe Tournassat  Catherine Lerouge  Philippe Blanc  Jocelyne Brendlé  Jean-Marc Greneche  Stéphane Touzelet  Eric C. Gaucher 《Applied Geochemistry》2008

Iron and Sr bearing phases were thoroughly investigated by means of spectrometric and microscopic techniques in Callovian–Oxfordian (COX) samples originating from the ANDRA Underground Research Laboratory (URL) in Bure (France). Strontium was found to be essentially associated with celestite, whereas Fe was found to be distributed over a wide range of mineral phases. Iron was mainly present as Fe(II) in the studied samples (∼93% from Mössbauer results). Most of the Fe(II) was found to be in pyrite, sideroplesite/ankerite and clay minerals. Iron(III), if present, was associated with clay minerals (probably illite, illite-smectite mixed layer minerals and chlorite). No Fe(III) oxy(hydro)xide could be detected in the samples. Strontianite was not observed either. Based on these observations, it is likely that the COX porewater is in equilibrium with the following carbonate minerals, calcite, dolomite and ankerite/sideroplesite, but not with strontianite. It is shown that this equilibrium information can be combined with clay cation exchange composition information in order to give direct estimates or constraints on the solubility products of the carbonate minerals dolomite, siderite and strontianite. As a consequence, an experimental method was developed to retrieve the cation exchanged Fe(II) in very well preserved COX samples.  相似文献   

Symplectic Integrators: Rotations and Roundoff Errors     

Jean-Marc Petit 《Celestial Mechanics and Dynamical Astronomy》1998,70(1):1-21

We investigate the numerical implementation of a symplectic integrator combined with a rotation (as in the case of an elongated rotating primary). We show that a straightforward implementation of the rotation as a matrix multiplication destroys the conservative property of the global integrator, due to roundoff errors. According to Blank et al. (1997), there exists a KAM-like theorem for twist maps, where the angle of rotation is a function of the radius. This theorem proves the existence of invariant tori which confine the orbit and prevent shifts in radius. We replace the rotation by a twist map or a combination of shears that display the same kind of behaviour and show that we are able not only to recover the conservative properties of the rotation, but also make it more efficient in term of computing time. Next we test the shear combination together with symplectic integrator of order 2, 4, and 6 on a Keplerian orbit. The resulting integrator is conservative down to the roundoff errors. No linear drift of the energy remains, only a divergence as the square root of the number of iterations is to be seen, as in a random walk. We finally test the three symplectic integrators on a real case problem of the orbit of a satellite around an elongated irregular fast rotating primary. We compare these integrators to the well-known general purpose, self-adaptative Bulirsch–Stoer integrator. The sixth order symplectic integrator is more accurate and faster than the Bulirsch–Stoer integrator. The second- and fourth- order integrators are faster, but of interest only when extreme speed is mandatory. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Accretion disc outbursts: a new version of an old model   总被引：1，自引：0，他引：1  

Jean-Marie Hameury  Kristen Menou  Guillaume Dubus  Jean-Pierre Lasota  & Jean-Marc Huré 《Monthly notices of the Royal Astronomical Society》1998,298(4):1048-1060

We have developed 1D time-dependent numerical models of accretion discs, using an adaptive grid technique and an implicit numerical scheme, in which the disc size is allowed to vary with time. The code fully resolves the cooling and heating fronts propagating in the disc. We show that models in which the radius of the outer edge of the disc is fixed produce incorrect results, from which probably incorrect conclusions about the viscosity law have been inferred. In particular we show that outside-in outbursts are possible when a standard bimodal behaviour of the Shakura–Sunyaev viscosity parameter α is used. We also discuss to what extent insufficient grid resolution has limited the predictive power of previous models. We find that the global properties (magnitudes, etc.) of transient discs can be addressed by codes using a high, but reasonable, number of fixed grid points. However, the study of the detailed physical properties of the transition fronts generally requires resolutions which are out of reach of fixed grid codes. It appears that most time-dependent models of accretion discs published in the literature have been limited by resolution effects, improper outer boundary conditions, or both.  相似文献   

The mesoscale variability in the Caribbean Sea. Part II: Energy sources   总被引：1，自引：0，他引：1  

Julien Jouanno  Julio Sheinbaum  Bernard Barnier  Jean-Marc Molines 《Ocean Modelling》2009,26(3-4):226-239

The processes which drive the production and the growth of the strong mesoscale eddy field in the Caribbean Sea are examined using a general circulation model. Diagnostics of the simulations suggest that:(1) The mean currents in the Caribbean Sea are intrinsically unstable. The nature of the instability and its strength vary spatially due to strong differences of current structure among basins.(2) The greatest and most energetic eddies of the Caribbean Sea originate in the Venezuela Basin by mixed barotropic-baroclinic instability of an intense jet, formed with waters mostly from the surface return flow of the Meridional Overturning Circulation and the North Equatorial Current which converge and accelerate through the Grenada Passage. The vertical shear of this inflow is enhanced by an eastward undercurrent, which flows along the south American Coast between 100 and 250 m depth. The shallow eddies (less than 200 m depth) formed in the vicinity of the Grenada Passage get rapidly deeper (down to 1000 m depth) and stronger by their interaction with the deep interior flow of the Subtropical Gyre, which enters through passages north of St. Lucia. These main eastern Caribbean inflows merge and form the southern Caribbean Current, whose baroclinic instability is responsible for the westward growth and strengthening of these eddies from the Venezuela to the Colombia Basin.(3) Eddies of lesser strength are produced in other regions of the Caribbean Sea. Their generation and growth is also linked with instability of the local currents. First, cyclones are formed in the cyclonic shear of the northern Caribbean Current, but appear to be rapidly dissipated or absorbed by the large anticyclones coming from the southern Caribbean. Second, eddies in the Cayman Sea, which impact the Yucatan region, are locally produced and enhanced by barotropic instability of the deep Cayman Current.(4) The role of the North Brazil Current (NBC) rings is mostly to act as a finite perturbation for the instability of the mean flow. Their presence near the Lesser Antilles is ubiquitous and they appear to be linked with most of the Caribbean eddies. There are some evidences that the frequency at which they form near the Grenada Passage is influenced by the frequency at which the NBC rings impinge the Lesser Antilles. But large Caribbean eddies also form without a close influence of any ring, and comparison between simulations shows that mean eddy kinetic energy and eddy population in the Caribbean Sea are not substantially different in absence or presence of NBC rings: their presence is not a necessary condition for the generation and growth of the Caribbean eddies.  相似文献   

Turbulent Structures in a Pine Forest with a Deep and Sparse Trunk Space: Stand and Edge Regions   总被引：1，自引：0，他引：1  

Sylvain Dupont  Mark R. Irvine  Jean-Marc Bonnefond  Eric Lamaud  Yves Brunet 《Boundary-Layer Meteorology》2012,143(2):309-336

Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may affect canopy-atmosphere exchanges through its action on the development of turbulent structures. Here we investigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterized by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the results of large-eddy simulations are used and analyzed together. In stand conditions, far from the edge, canopy-top structures appear strongly damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, autocorrelation and spectral analyses are not quite appropriate to characterize the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange region, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addition to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite direction and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region.  相似文献   

Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model     

Anne Marie Treguier  Claire Gourcuff  Pascale Lherminier  Herle Mercier  Bernard Barnier  Gurvan Madec  Jean-Marc Molines  Thierry Penduff  Lars Czeschel  Claus Böning 《Ocean Dynamics》2006,56(5-6):568-580

Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of the -coordinate overturning reveals model–data discrepancies: the vertical structure in the models does not change as much as the observed one. The East Greenland current variability is mainly wind-forced in the ATL6 model, while fluctuations due to eddies and instabilities explain a large part of the North Atlantic Current variability. The time-residual transport of dense water and heat due to eddy correlations between currents and properties is small across this section, which is normal to the direction of the main current.  相似文献   

Persistent multi-decadal Greenland temperature fluctuation through the last millennium     

Takuro Kobashi  Jeffrey P. Severinghaus  Jean-Marc Barnola  Kenji Kawamura  Tara Carter  Tosiyuki Nakaegawa 《Climatic change》2010,100(3-4):733-756

Future Greenland temperature evolution will affect melting of the ice sheet and associated global sea-level change. Therefore, understanding Greenland temperature variability and its relation to global trends is critical. Here, we reconstruct the last 1,000 years of central Greenland surface temperature from isotopes of N₂ and Ar in air bubbles in an ice core. This technique provides constraints on decadal to centennial temperature fluctuations. We found that northern hemisphere temperature and Greenland temperature changed synchronously at periods of ~20 years and 40–100 years. This quasi-periodic multi-decadal temperature fluctuation persisted throughout the last millennium, and is likely to continue into the future.  相似文献   

A method for regional climate change detection using smooth temporal patterns     

Aurélien Ribes  Jean-Marc Azaïs  Serge Planton 《Climate Dynamics》2010,35(2-3):391-406

This paper introduces an original method for climate change detection, called temporal optimal detection method. The method consists in searching for a smooth temporal pattern in the observations. This pattern can be either the response of the climate system to a specific forcing or to a combination of forcings. Many characteristics of this new method are different from those of the classical “optimal fingerprint” method. It allows to infer the spatial distribution of the detected signal, without providing any spatial guess pattern. The spatial properties of the internal climate variability doesn’t need to be estimated either. The estimation of such quantities being very challenging at regional scale, the proposed method is particularly well-suited for such scale. The efficiency of the method is illustrated by applying it on real homogenized datasets of temperatures and precipitation over France. A multimodel detection is performed in both cases, using an ensemble of atmosphere-ocean general circulation models for estimating the temporal patterns. Regarding temperatures, new results are highlighted, especially by showing that a change is detected even after removing the uniform part of the warming. The sensitivity of the method is discussed in this case, relatively to the computation of the temporal patterns and to the choice of the model. The method also allows to detect a climate change signal in precipitation. This change impacts the spatial distribution of the precipitation more than the mean over the domain. The ability of the method to provide an estimate of the spatial distribution of the change following the prescribed temporal patterns is also illustrated.  相似文献   

Diversité du métamorphisme éclogitique dans le massif ophiolitique du Monviso (Alpes occidentales,Italie)     

Stéphane Schwartz  Jean-Marc Lardeaux  Stéphane Guillot  Pierre Tricart 《Geodinamica Acta》2013,26(2-3):169-188

Résumé

Le complexe ophiolitique du Monviso représente un témoin essentiel de la lithosphère océanique subduite puis exhumée dans les Alpes occidentales. Ce complexe est classiquement subdivisé en unités lithologiques, qui ont toutes subi une évolution structurale caractérisée par la succession de trois événements dans des environnements (1) éclogitique, (2) schistes bleus puis (3) schistes verts. Cependant la quantification des conditions physiques du métamorphisme éclogitique au sein de trois unités à lithologies comparables (Viso Mozzo, Passo Gallarino et Lago Superiore), montrent clairement l’existence d’une hétérogénéité des conditions éclogitiques enregistrée par l’ensemble des unités, indépendamment de la chimie de la roche initiale. Les conditions estimées sont de 450 ± 40 °C et de 12 ± 3 kb pour l’unité du Viso Mozzo et du Passo Gallarino contre 580 ± 40°C et 19 ± 2 kb pour l’unité du Lago Superiore. De plus l’analyse structurale combinée révèle que c’est au cours de l’exhumation, dans les conditions du faciès des schistes bleus, que les différentes unités vont être juxtaposées et vont suivre une histoire tectono-métamorphique commune. Ces nouvelles données, impliquent une réinterprétation des modèles géodynamiques existants et couramment admis pour le Monviso. Ce dernier doit être considéré comme un complexe résultant de l’accrétion de différents morceaux d’une lithosphère océanique subduite, qui se sont détachés à différentes profondeurs pour venir se stocker à 25 km de profondeur dans les conditions du faciès des schistes bleus. © 2000 Éditions scientifiques et médicales Elsevier SAS  相似文献