Philippe JEAN-PIERRE

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Jean‐françois CantaloubePierre GallianPhilippe BiaginiHoussam AttouiJacqueline EscherJean‐pierre ZappitelliYves DelordPhilippe de MiccoXavier de Lamballerie
• Organismes : Virologie UMR1161
• Publié dans Transfusion le 25/10/2020

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Francois FerriereNaim KhanJean-Philippe MeynielPierre Deschaux
• Organismes : Université de Limoges
• Publié dans Developmental and Comparative Immunology le 01/11/2020

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Catherine BirckLionel MoureyPatrice GouetBéatrice FabryJörg SchumacherPhilippe RousseauDaniel KahnJean-Pierre Samama
• Organismes : Institut de pharmacologie et de biologie structurale
• Publié dans Structure le 31/10/2020

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Résumé : Background: A variety of bacterial adaptative cellular responses to environmental stimuli are mediated by two-component signal transduction pathways. In these phosphorelay cascades, histidine kinases transphosphorylate a conserved aspartate in the receiver domain, a conserved module in the response regulator superfamily. The main effect of this phosphorylation is to alter the conformation of the response regulator in order to modulate its biological function. The response regulator FixJ displays a typical modular arrangement, with a phosphorylatable N-terminal receiver domain and a C-terminal DNA-binding domain. In the symbiotic bacterium Sinorhizobium meliloti, phosphorylation of this response regulator activates transcription of nitrogen-fixation genes. Results: The crystal structures of the phosphorylated and of the unphosphorylated N-terminal receiver domain of FixJ (FixJN) were solved at 2.3 Å and 2.4 Å resolution, respectively. They reveal the environment of the phosphoaspartate in the active site and the specific conformational changes leading to activation of the response regulator. Phosphorylation of the conserved aspartate induces major structural changes in the β4-α4 loop, and in the signaling surface α4-β5 that mediates dimerization of the phosphorylated full-length response regulator. A site-directed mutant at this protein-protein interface decreases the affinity of the phosphorylated response regulator for the fixK promoter tenfold. Conclusions: The cascade of phosphorylation-induced conformational changes in FixJN illustrates the role of conserved residues in stabilizing the phosphoryl group in the active site, triggering the structural transition and achieving the post-phosphorylation signaling events. We propose that these phosphorylation-induced conformational changes underly the activation of response regulators in general.

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Fichiers liés : birck-structure99.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : Pierre CabanesBashkim VrekajJean-Luc LamboleyPhilippe LenhardtClaire BalandierGuillaume BonnetVangjel DimoJulien EspagneÉric FouacheLami KoçoSkënder MuçajPellumb NaipiPatrick NeuryYann PépinIris PojaniFrançois QuantinAltin Skenderaj
• Organismes : Institut national de recherches archéologiques préventives
• Publié dans Bulletin de Correspondance Hellénique le 26/10/2020

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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. : 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. : 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 : Philippe BiaginiPierre GallianHoussam AttouiJean-François CantaloubePhilippe de MiccoXavier de Lamballerie
• Organismes : Virologie UMR1161
• Publié dans Journal of General Virology le 01/11/2020

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• Type de publi. : Chapître d'ouvrage
• Date de publi. : 01/01/1999
• Auteurs : Philippe Sénac
• Organismes : France, Amériques, Espagne, Sociétés, Pouvoirs, Acteurs

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/1999
• Auteurs : L. JouniauxJean-Pierre PozziJean BerthierPhilippe Massé
• Organismes : Géophysique expérimentale (IPGS) Laboratoire de géologie de l'ENS Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information
• Publié dans Journal of Geophysical Research : Solid Earth le 27/10/2020

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Résumé : Detection of changes in the flow rate of expelled fluids in accretionary prisms by monitoring of electric and magnetic fields is discussed. A numerical model of the electric and magnetic fields associated with fluid flow variations at the Nankai Trough is presented which gives a numerical solution of the coupled system of electric convection currents and conduction currents that directly determines the magnetic anomaly itself. Measurements in a borehole located between two vents are shown to be well adapted to detection of fluid flow variations using the vertical gradient of the electric potential and the horizontal magnetic field. The vertical electric field is about 10 mV/km up to 500 m depth where there is a lithologic reflector and about 50 mV/km below this reflector. The horizontal gradient of the magnetic field is 2 nT/km at the seafloor. Modelization with a lower fault conductivity and a larger décollement thickness has also been modeled. The vertical gradient of the horizontal magnetic field is ~5 to 15 nT/km. A variation of 3 mV and 1.5 to 3 nT at 600 m depth in a borehole could reveal a fluid flow rate variation of 20%, which is a reasonable fluid flow change based on some observations at short-scale time. Since a 1.5 to 3 nT anomaly seems easier to detect than a 3 mV anomaly, it is likely that the variation of the magnetic field would more sensitively reveal fluid flow variations. When monitoring the magnetic field at the seafloor, a change of 0.4 nT/km in the horizontal gradient could reveal a fluid flow rate variation of 20%.

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Fichiers liés : 1999JB900102.pdf

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