Philippe JEAN-PIERRE

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/1999
• Auteurs : J.L. ZaraderBruno GasPhilippe DrobinskiP. Dabas
• Organismes : Institut des Systèmes Intelligents et Robotique Sorbonne Université Institut des Systèmes Intelligents et Robotique Laboratoire de Météorologie Dynamique (UMR 8539)

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Jean-Philippe BoulangerChristophe Menkes
• Organismes : Laboratoire d'océanographie dynamique et de climatologie Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
• Publié dans Climate Dynamics le 30/10/2020

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Résumé : The TOPEX/POSEIDON sea level data have been shown to observe the sea surface height variability accurately over the globe and, more particularly, in the tropical Pacific, core region of the El Niño/Southern Oscillation. Various studies have already provided descriptions of long equatorial wave propagation as well as estimates of their reflection at both the eastern and western boundaries using TOPEX/POSEIDON data over short time periods. In this present work, we are first interested in computing long equatorial wave amplitudes over a much longer period (October 1992-May 1998) focusing on the Kelvin and first three largest Rossby waves. Secondly, we are examining qualitatively potential theories of ENSO in the light of observations of the strong 1997-1998 El Niño event. At the eastern boundary, Kelvin waves are observed to reflect into first (third) mode Rossby waves with a reflection efficiency of 75% (65%) of that of an infinite meridional wall. In the western Pacific Ocean, the reflection of the first Rossby wave does explain more than 90% of the Kelvin wave variance. The second Rossby wave is found not to be correlated to the Kelvin wave amplitude, and the third Rossby wave is highly correlated to the Kelvin signal although its contribution is weak. The investigation during the 1997-1998 event of two theories potentially important for ENSO (the delayed action oscillator mechanism and the recent theory of Picaut et al., 1997) led us to the following conclusions. The westerly wind anomalies observed in the western Pacific in December 1996 and March 1997 forced downwelling Kelvin waves which advected the eastern edge of the warm pool eastward and deepened the thermocline in the east Pacific. Both zonal advection and vertical processes are suggested to act constructively during the onset of positive anomalies in the central and eastern Pacific. From May to September 1997, downwelling Kelvin wave wind-forced in the central Pacific and reflected downwelling Rossby waves (reinforced by local easterly wind anomalies) acted against each other, and the 28°C isotherm was found to move slightly westward. In October 1997, strong westerly wind anomalies forced a strong downwelling Kelvin wave potentially responsible for the strong warming in the east Pacific. The 28°C isotherm reached the eastern boundary. At that time, the equatorial sea surface temperatures are zonally homogeneous. The strong downwelling Rossby waves reflected at the boundary could not act to terminate the warm event through zonal advection as suggested by Picaut et al. However the reflected upwelling Kelvin waves coming from the western boundary weakened the downwelling Kelvin signal in the central and east Pacific leading to a decrease of the sea surface temperature anomalies. Following this decrease, westerly wind anomalies in the central Pacific weakened, and upwelling Kelvin waves reinforced by easterly wind anomalies in the western Pacific propagated toward the eastern Pacific. As a conclusion, both theories must be considered simultaneously to understand the variability observed during the 1997-1998 El Niño event. However observations strongly suggest the delayed action oscillator mechanism to be the major process at work during the weakening of the warm 1997-1998 ENSO.

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• Type de publi. : Rapport
• Date de publi. : 01/01/1999
• Auteurs : Pierre AndriesPatrick Le TallecJean-Philippe PerlatBenoît Perthame
• Organismes : Multi-Models and Numerical Methods Multi-Models and Numerical Methods Multi-Models and Numerical Methods

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Résumé : In this paper we prove the entropy inequality for the Gaussian-BGK model of Boltzmann equation. This model, also called ellipsoidal statistical model, was introduced in order to fit realistic values of the transport coefficients (Prandtl number, second viscosity) in the Navier-Stokes approxima- tion, which cannot be achieved by the usual relaxation towards isotropic Maxwellians introduced in standard BGK models. Moreover, we introduce new entropic kinetic models for polyatomic gases which suppress the internal energy variable in the phase space by using two distribution functions (one for particles mass and one for their internal energy). This reduces the cost of their numerical solution while keeping a kinetic description well adapted to desequilibrium regions.

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Fichiers liés : RR-3716.pdf

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/1999
• Auteurs : Eric KerhervePhilippe NaudGeorges GermainJean-Marie PhamPierre Jarry
• Organismes : Laboratoire de l'intégration, du matériau au système Laboratoire de l'intégration, du matériau au système Laboratoire de l'intégration, du matériau au système

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Viviane LeboucherJames C. OrrPhilippe Jean-BaptisteMaurice ArnoldPatrick MonfrayN TisnératAlain PoissonJean-Claude Duplessy
• Organismes : Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] Géochrononologie Traceurs Archéométrie Laboratoire de Physique et Chimie Marines Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] Paléocéanographie
• Publié dans Radiocarbon le 27/10/2020

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Résumé : Accelerator mass spectrometry (AMS) radiocarbon measurements were made on 120 samples collected between Antarctica and South Africa along 30°E during the WOCE-France CIVA 1 campaign in February 1993. Our principal objective was to complement the Southern Ocean's sparse existing data set in order to improve the 14C benchmark used for validating ocean carbon-cycle models, which disagree considerably in this region. Measured 14C is consistent with the 0-S characteristics of CIVA1. Antarctic Intermediate Water (AAIW) forming north of the Polar Front (PF) is rich in'4C, whereas surface waters south of the PF are depleted in 14C. A distinct old 14C signal was found for the contribution of the Pacific Deep Water (PDW) to the return flow of Circumpolar Deep Waters (CDW). Comparison to previous measurements shows a 4C decrease in surface waters, consistent with northward displacement of surface waters, replacement by old deep waters upwelled at the Antarctic Divergence, and atmospheric decline in 14C. Conversely, an increase was found in deeper layers, in the AAIW. Large uncertainties, associated with previous methods for separating natural and bomb 14C when in the Southern Ocean south of 45°S, motivated us to develop a new approach that relies on a simple mixing model and on chlorofluorocarbon (CFC) measurements also taken during CIVA1. This approach leads to inventories for CIVA1 that are equal to or higher than those calculated with previous methods. Differences between old and new methods are especially high south of approximately 55°S, where bomb 14C inventories are relatively modest.

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Fichiers liés : oceanic-radiocarbon-between-antarctica-and-south-africa-along-woce-section-16-at-30-e-div.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Philippe BallonJean-Pierre Hamard
• Organismes : Écosystèmes forestiers et paysages Écosystèmes forestiers et paysages
• Publié dans Forêt de Gascogne le 14/05/2020

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Résumé : L'augmentation récente des populations de cervidés sur l'ensemble du territoire semble être à l'origine de la généralisation des phénomènes de dégâts en forêt. A la demande conjointe des Ministères de l'Agriculture et de l'Environnement, un observatoire des dégâts de cervidés en milieu forestier vient d'être mis en place. Pour cela, 5 départements représentatifs de la diversité des situations cynégétiques et forestières ont été choisis. D'ici la fin de l'année prochaine diverses analyses et études seront effectuées dans le département des Landes. Les études porteront sur l'évaluation de l'importance des dégâts de cervidés en forêt, le fonctionnement du plan de chasse, et la recherche de solutions.

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• Type de publi. : Rapport
• Date de publi. : 01/01/1999
• Auteurs : Françoise Simonot-LionJörn MiggeJean-Louis BoucheronPhilippe LemaireSamuel BoutinAttia MondherPatrick PalmieriYvon TrinquetThierry GautierJean-Pierre ElloyFranck Gasnier
• Organismes : Real time and interoperability Real time and interoperability Institut de Recherche en Informatique et Systèmes Aléatoires

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Résumé : L'objectif du langage AIL est de décrire une architecture véhicule depuis les prestations demandées jusqu'à l'implémentation, concrétisée par une ou plusieurs architectures opérationnelles résultantes. Ce document présente la spécification des classes d'objets ainsi que leurs relations pour la conception des architectures électroniques embarquées dans un véhicule automobile. La manipulation des objets est faite à l'aide du langage AIL (Architecture Implementation Language).

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Philippe DelayeAlain BlouinDenis DroletJean-Pierre MonchalinLouis-Anne de MontmorillonGérald Roosen
• Organismes : Laboratoire Charles Fabry de l'Institut d'Optique / Manolia Industrial Materials Institute (NRCC) Industrial Materials Institute (NRCC) Industrial Materials Institute (NRCC) Laboratoire Charles Fabry de l'Institut d'Optique / Manolia Laboratoire Charles Fabry de l'Institut d'Optique / Manolia
• Publié dans Applied Physics Letters le 01/11/2020

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Résumé : We describe both theoretically and experimentally a polarization independent interferometric adaptive photodetector based on photorefractive two-wave mixing. The configuration is based on the simultaneous recording of two independent gratings in a single photorefractive crystal. Applied to the detection of ultrasonic signals, this interferometric photodetector operates with depolarized beams issued from multimode fibers and gives a detection limit close to the ultimate.

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Fichiers liés : PhD1-33.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Catherine LeonCatherine VialChristian GachetPhilippe OhlmannBeatrice HechlerJean-Pierre CazenaveAnna LecchiMarco Cattaneo
• Organismes :
• Publié dans Thrombosis and Haemostasis le 22/10/2020

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Résumé : ADP is a key stimulus inducing platelet shape change and aggregation, a rise in internal calcium and inhibition of adenylyl cyclase. These signaling pathways are thought to be activated by three independent receptors, but to date only the P2Y1 receptor responsible for calcium mobilization and the ionotropic P2X1 receptor have been identified. We report here the characteristics of the P2Y1 receptor in a patient presenting a selective deficiency of ADP-induced aggregation. Cloning of the P2Y1 gene revealed that the patient's DNA and mRNA were normal. Pharmacological studies showed that the P2Y1 receptor was expressed and functional in patient's platelets. Hence, the P2Y, receptor is not the cause of the impaired ADP-induced platelet aggregation in this patient. The P2X1 mRNA was also found to be present and normal. These findings add evidence to previous observations suggesting that a third P2 receptor coupled to adenylyl cyclase may be involved in ADP-induced platelet aggregation.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Jean-Pierre HermierAlberto BramatiA. Z. KhouryElisabeth GiacobinoJean-Philippe PoizatTiejun ChangPhilippe Grangier
• Organismes : Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Kastler Brossel Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique
• Publié dans Journal of the Optical Society of America. A Optics, Image Science, and Vision le 30/10/2020

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Résumé : The transverse distribution of intensity noise in the far field of semiconductor lasers has been experimentally studied. For a single-mode edge-emitting laser, it has been found that a large amount of noise is present in higher-order nonlasing transverse modes parallel to the diode junction. In the case of a spatially multimode vertical-cavity surface-emitting laser, each mode exhibits a large noise, but these noises show strong anticorrelations.

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Fichiers liés : 00558800.pdf

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