861 research outputs found

    A New Family of Planets ? "Ocean Planets"

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    A new family of planets is considered which is between rochy terrestrial planets and gaseous giant ones: "Ocean-Planets". We present the possible formation, composition and internal models of these putative planets, including that of their ocean, as well as their possible Exobiology interest. These planets should be detectable by planet detection missions such as Eddington and Kepler, and possibly COROT (lauch scheduled in 2006). They would be ideal targets for spectroscopic missions such as Darwin/TPF.Comment: 15 pages, 3 figures submitted to Icarus notes (10 july 2003

    Scanning electron microscope study of two African populations of Radopholus similis (Nematoda : Pratylenchidae) and proposal of R. citrophilus as a junior synonym of R. similis

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    Les structures cuticulaires de #Radopholus similis provenant de CÎte d'Ivoire et de Guinée Bissau ont été étudiées en microscopie électronique à balayage. Les résultats montrent que les structures cuticulaires sont identiques dans les deux populations et exhibent une variabilité supérieure à celle observée dans les populations américaines de #R. similis et de #R. citrophilus qui est proposé comme un synonyme mineur de #R. similis. Des données additionnelles sont apportées sur la forme de la queue et les champs latéraux chez la femelle, et sur la forme de la région céphalique et de la bursa chez le mùle. (Résumé d'auteur

    Mesures de facteurs spectroscopiques de 61Ni par réaction (d, p) en régime sous-coulombien

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    Nous avons utilisé la réaction (d, p) en régime sous-coulombien pour mesurer les facteurs spectroscopiques de deux états excités par transferts l = 0 et l = 2 dans 61Ni au voisinage de 4,8 MeV. Nos résultats confirment que la rÚgle de somme pour le remplissage des couches 3s1/2 et 2d n'est satisfaite qu'à 50 % dans 61Ni

    Phase field modeling of electrochemistry I: Equilibrium

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    A diffuse interface (phase field) model for an electrochemical system is developed. We describe the minimal set of components needed to model an electrochemical interface and present a variational derivation of the governing equations. With a simple set of assumptions: mass and volume constraints, Poisson's equation, ideal solution thermodynamics in the bulk, and a simple description of the competing energies in the interface, the model captures the charge separation associated with the equilibrium double layer at the electrochemical interface. The decay of the electrostatic potential in the electrolyte agrees with the classical Gouy-Chapman and Debye-H\"uckel theories. We calculate the surface energy, surface charge, and differential capacitance as functions of potential and find qualitative agreement between the model and existing theories and experiments. In particular, the differential capacitance curves exhibit complex shapes with multiple extrema, as exhibited in many electrochemical systems.Comment: v3: To be published in Phys. Rev. E v2: Added link to cond-mat/0308179 in References 13 pages, 6 figures in 15 files, REVTeX 4, SIUnits.sty. Precedes cond-mat/030817

    DĂ©pouillement et analyse de spectres Ă  l'aide d'un ordinateur IBM 1800

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    On décrit briÚvement un systÚme d'analyse de résultats d'expériences à basse énergie. Un dialogue utilisateur-ordinateur améliore fortement la rapidité et la facilité des analyses

    Impact du Petit Age Glaciaire sur les plaines alluviales méditerranéenne françaises : apport de la géoarchéologie à l'évolution du bassin du Roussillon

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    International audienceDans la zone méditerranéenne, le Petit Age Glaciaire est enregistrée par le systÚme fluvial sous le nom bien connu de "Younger Infill". Selon des résultats récents obtenus dans le bassin du Roussillon, nous proposons une premiÚre esquisse pour le moment, a savoir les causes et les conséquences de cet épisode climatique, basé à la fois sur des données géoarchéologiques et d'archives

    Un nouveau vaccin injectable contre la maladie de Newcastle préparé en cultures de cellules bovines

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    Provost A., Valette L. R., Papageorgiou C. Un nouveau vaccin injectable contre la maladie de Newcastle préparé en cultures de cellules bovines. In: Bulletin de l'Académie Vétérinaire de France tome 115 n°9, 1962. pp. 399-402

    Modeling diffusion of intracellular metabolites in the mouse brain up to very high diffusion-weighting: Diffusion in long fibers (almost) accounts for non-monoexponential attenuation

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    Purpose: To investigate how intracellular metabolites diffusion measured in vivo up to very high q/b in the mouse brain can be explained in terms of simple geometries. / Methods: 10 mice were scanned using our new STE‐LASER sequence, at 11.7 Tesla (T), up to qmax = 1 Όm−1 at diffusion time td = 63.2 ms, corresponding to bmax = 60 ms/”mÂČ. We model cell fibers as randomly oriented cylinders, with radius a and intracellular diffusivity urn:x-wiley:07403194:media:mrm26548:mrm26548-math-0004, and fit experimental data as a function of q to estimate urn:x-wiley:07403194:media:mrm26548:mrm26548-math-0005 and a. / Results: Randomly oriented cylinders account well for measured attenuation, giving fiber radii and urn:x-wiley:07403194:media:mrm26548:mrm26548-math-0006 in the expected ranges (0.5–1.5 ”m and 0.30–0.45 ”m2/ms, respectively). The only exception is N‐acetyl‐aspartate (NAA) (extracted a∌0), which we show to be compatible with a small fraction of the NAA pool being confined in highly restricted compartments (with short T2). / Conclusion: The non‐monoexponential signal attenuation of intracellular metabolites in the mouse brain can be described by diffusion in long and thin cylinders, yielding realistic Dintra and fiber diameters. However, this simple model may require small “corrections” for NAA, in the form of a small fraction of the NAA signal originating from a highly restricted compartment

    Advanced concepts and methods for very high intensity accelerators

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    AbstractFor very high intensity accelerators, not only beam power but also space charge is a concern. Both aspects should be taken into consideration for any analysis of accelerators aiming at comparing their performances and pointing out the challenging sections. As high beam power is an issue from the lowest energy, careful and exhaustive beam loss predictions have to be done. High space charge implies lattice compactness making the implementation of beam diagnostics very problematic, so a clear strategy for beam diagnostic has to be defined. Beam halo is no longer negligible. Its dynamics is different from that of the core and plays a significant role in the particle loss process. Therefore, beam optimization must take the halo into account and beam characterization must be able to describe the halo part in addition to the core one. This paper presents the advanced concepts and methods for beam analysis, beam loss prediction, beam optimization, beam diagnostic, and beam characterization especially dedicated to very high intensity accelerators. Examples of application of these concepts are given in the case of the IFMIF accelerators
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