Philippe JEAN-PIERRE

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Max Max LesaffreF. JeanFrançois RamazAlbert-Claude BoccaraMichel GrossPhilippe DelayeGérald Roosen
• Organismes : Institut Langevin - Ondes et Images (UMR7587) Institut Langevin - Ondes et Images (UMR7587) Institut Langevin - Ondes et Images (UMR7587) Institut Langevin - Ondes et Images (UMR7587) Laboratoire Kastler Brossel Laboratoire Charles Fabry de l'Institut d'Optique / Manolia Laboratoire Charles Fabry de l'Institut d'Optique / Manolia
• Publié dans Optics Express le 27/10/2020

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Résumé : The measurement of optical contrasts within thick biological tissues can be performed with the hybrid technique of acousto-optic imaging, but it has been shown that an acquisition rate in the 1−10kHz range is required for a good efficiency. This comes from the interferometric nature of the signal, blurred by speckle decorrelation in a time c, due to a decrease of the speckle pattern contrast at the exit of the sample. An holographic setup that associates a fast and large area single photodetector and a photorefractive crystal, can measure in real-time the acousto-optic signal: this is the so-called self-adaptive wavefront holography technique. Nevertheless, it is essential to size the photorefractive response time (PR) of the crystal with c in order to optimize the signal-to-noise ratio of the measurement. This time mainly depends on the overall light intensity within the crystal. We have developed an original in situ method to determine PR with the combination of acoustic pulses and a frequency de-tuning of the reference beam. We can measure precisely this time but also monitor it according to a theoretical model that we have previously described. We are able to adapt the response time of the setup to the decorrelation time of the medium under study

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Fichiers liés : PhD1-59.pdf

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/2007
• Auteurs : Philippe MontraversJean-Paul MiraJean-Pierre GangneuxO. LeroyO. Lortholary
• Organismes : Service d'anesthésie - réanimation chirurgicale Service de Réanimation Médicale Signalisation et Réponses aux Agents Infectieux et Chimiques Service de Parasitologie-Mycologie [Rennes] Centre d'infectiologie Necker-Pasteur [CHU Necker]

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Olivier BockMarie-Noëlle BouinAndrea WalpersdorfJean-Philippe LaforeSerge JanicotFrancoise GuichardAnna Agusti-Panareda
• Organismes : Service d'aéronomie Laboratoire de Géophysique Interne et Tectonophysique Centre national de recherches météorologiques Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques
• Publié dans Quarterly Journal of the Royal Meteorological Society le 27/10/2020

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Résumé : This study aims at assessing the consistency between different precipitable water vapour (PWV) datasets over Africa (between 35°N and 10°S). This region is characterized by large spatial and temporal variability of humidity but also by the scarcity of its operational observing network, limiting our knowledge of the hydrological cycle. We intercompare data from observing techniques such as ground-based Global Positioning System (GPS), radiosondes, AERONET sun photometers and SSM/I, as well as reanalyses from European Centre for Medium-Range Weather Forecasts (ERA-40) and National Center for Environmental Prediction (NCEP2). The GPS data, especially, are a new source of PWV observation in this region. PWV estimates from nine ground-based GPS receivers of the international GPS network data are used as a reference dataset to which the others are compared. Good agreement is found between observational techniques, though dry biases of 12-14% are evidenced in radiosonde data at three sites. Reasonable agreement is found between the observational datasets and ERA-40 (NCEP2) reanalyses with maximum bias 9% (14%) and standard deviation 17% (20%). Since GPS data were not assimilated in the ERA-40 and NCEP2 reanalyses, they allow for a fully independent validation of the reanalyses. They highlight limitations in the reanalyses, especially at time-scales from sub-daily to periods of a few days. This work also demonstrates the high potential of GPS PWV estimates over Africa for the analysis of the hydrological cycle, at time-scales ranging between sub-diurnal to seasonal. Such observations can help studying atmospheric processes targeted by the African Monsoon Multidisciplinary Analysis project

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/2007
• Auteurs : François CaylaJean Jacques GonzalezPierre FretonPhilippe Teulet
• Organismes : LAboratoire PLasma et Conversion d'Energie Arc Electrique et Procédés Plasmas Thermiques Arc Electrique et Procédés Plasmas Thermiques Arc Electrique et Procédés Plasmas Thermiques

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• Type de publi. : Communication dans un congrès
• Date de publi. : 01/01/2007
• Auteurs : Ivan FaveroAlice BerthelotGuillaume CassaboisChristophe VoisinClaude DelalandePhilippe RoussignolRobson FerreiraJ.-M. Gérard
• Organismes : Laboratoire Pierre Aigrain Laboratoire Pierre Aigrain Laboratoire Pierre Aigrain Laboratoire Pierre Aigrain Laboratoire Pierre Aigrain Laboratoire Pierre Aigrain Nanophysique et Semiconducteurs

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Résumé : The temperature-induced broadening of the optical spectrum is a major issue of the quantum dot optical properties. Temperature-dependent measurements have shown that the line-shape can be described by the superposition of the so-called zero-phonon line and broad side-bands extending on several meV [1]. These side-bands arise from the radiative recombination of electron-hole pairs assisted by the emission and the absorption of acoustic phonons and are quantitatively interpreted in the framework of the Huang-Rhys theory. However, within this theoretical treatment, the zero-phonon line does not show any broadening with temperature in strong contrast with the literature which shows a wide dispersion of the data on the temperature dependence of this zero-phonon line-width [2-5]. We show here that the thermal activation of the processes leading to spectral diffusion in the motional narrowing regime [6] results in a Lorentzian zero-phonon line with a width that increases linearly with temperature. This extrinsic dephasing process is studied by systematic measurements of the linewidth for single quantum dots in the motional narrowing regime, i.e. with a zero-phonon line that keeps a Lorentzian profile in the investigated range of experimental parameters. This contribution to the temperature dependence of the zero-phonon line-width relies on an interaction between acoustic phonons and carriers outside the QDs in contrast with previous models where acoustic phonons interact with carriers inside the dot. Our original model provides a unified interpretation to the published data on the temperature dependence of the zero-phonon line. [1]L. Besombes, K. Kheng, L. Marsal, and H. Mariette, Phys. Rev. B 65, 121314 (2002). [2]C. Kammerer, C. Voisin, G. Cassabois, C. Delalande, Ph. Roussignol, F. Klopf, J. P. Reithmaier, A. Forchel, and J. M. G\'{e}rard, Phys. Rev. B 66, 041306 (2002). [3]B. Urbaszek, E. J. McGhee, M. Kruger, R. J. Warburton, K. Karrai, T. Amand, B. D. Gerardot, P. M. Petroff, and J. M. Garcia, Phys. Rev. B 69, 035304 (2004). [4]G. Ortner, D. R. Yakovlev, M. Bayer, S. Rudin, T. L. Reinecke, S. Fafard, Z. Wasilewski, and A. Forchel, Phys. Rev. B 70, 201301 (2004). [5]P. Borri, W. Langbein, U. Woggon, V. Stavarache, D. Reuter, and A. D. Wieck, Phys. Rev. B 71, 115328 (2005). [6]A. Berthelot, I. Favero, G. Cassabois, C. Voisin, C. Delalande, Ph. Roussignol, R. Ferreira, and J. M. G\'{e}rard, Nature Phys. 2, 759 (2006).

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Philippe RenaultJean-Louis SoletDaouda SissokoElsa BalleydierSophie LarrieuLaurent FilleulChristian LassalleJulien ThiriaEmmanuelle RachouHenriette de ValkDaniele IlefMartine LedransIsabelle QuatresousPhilippe QuénelVincent Pierre
• Organismes : Cellule InterRégionale d'Epidémiologie Réunion Mayotte Indian Ocean Regional Office [Saint-Denis, La Réunion] Cellule InterRégionale d'Epidémiologie Réunion Mayotte Laboratoire de Biotechnologie et Microbiologie Appliquée Institut de Veille Sanitaire Epidémiologie, santé publique et développement Cire Aquitaine Association Nationale de Prévention en Alcoologie et Addictologie [Saint-Denis, La Réunion] Direction Régionale des Affaires Sanitaires et Sociales de La Réunion Observatoire régional de la santé La Réunion Institut de Veille Sanitaire Cellule Interrégionale d'Epidémiologie Institut de Veille Sanitaire "Personal Protection Against Vectors" working group Cellule interrégionale d'épidémiologie Antilles-Guyane Institut de Veille Sanitaire Cellule InterRégionale d'Epidémiologie Réunion Mayotte
• Publié dans American Journal of Tropical Medicine and Hygiene le 25/10/2020

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Résumé : In January 2005, an epidemic of chikungunya fever broke out in the Comoro Islands and lasted until May 2005. In April, cases were also reported in Mayotte and Mauritius. On Réunion Island, the first cases were reported at the end of April. Surveillance of this epidemic required an adaptive system, which at first was based on active and retrospective case detection around the cases reported, then relied on a sentinel network when the incidence increased. Emerging and severe forms of infection were investigated. Death certificates were monitored. By April 2006, the surveillance estimate was 244,000 cases of chikungunya virus infection, including 123 severe cases and 41 of maternoneonatal transmission, with an overall attack rate of 35%. Chikungunya infection was mentioned on 203 death certificates and significant mortality was observed. This epidemic highlighted the need for a mutual strategy of providing information on arboviral diseases and their prevention and control between countries in the southwestern Indian Ocean.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Jozefien GoossensPhilippe Leclaire​Xiaodong XuChrist GlorieuxLoïc MartinezAntonella SolaCristina SiligardiValeria CannilloTom van Der DonckJean-Pierre Celis
• Organismes : Laboratorium voor Akoestiek en Thermische Fysica Laboratorium voor Akoestiek en Thermische Fysica Laboratorium voor Akoestiek en Thermische Fysica Laboratorium voor Akoestiek en Thermische Fysica Equipe Circuit Instrumentation et Modélisation Electronique Department of Materials and Environmental Engineering Department of Materials and Environmental Engineering Department of Materials and Environmental Engineering Department MTM Department MTM
• Publié dans Journal of Applied Physics le 02/11/2020

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Résumé : The potential and limitations of Rayleigh wave spectroscopy to characterize the elastic depth profile of heterogeneous functional gradient materials are investigated by comparing simulations of the surface acoustic wave dispersion curves of different profile-spectrum pairs. This inverse problem is shown to be quite ill posed. The method is then applied to extract information on the depth structure of a glass-ceramic ͑ alumina͒ functionally graded material from experimental data. The surface acoustic wave analysis suggests the presence of a uniform coating region consisting of a mixture of Al2O3 and glass, with a sharp transition between the coating and the substrate. This is confirmed by scanning electron microscope with energy dispersive x-ray analysis.

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Fichiers liés : GLXG.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Jean-Philippe PréauxPierre de La Harpe
• Organismes : Institut de Mathématiques de Marseille Section de mathématiques [Genève]
• Publié dans Annales de la Faculté des Sciences de Toulouse. Mathématiques. le 29/10/2020

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Guillaume CharpiatPierre MaurelJean-Philippe PonsRenaud KerivenOlivier C Faugeras
• Organismes : Spatio-Temporal Activity Recognition Systems Computer and biological vision Vision, Action et Gestion d'informations en Santé Computer and biological vision imagine [Marne-la-Vallée] Centre Scientifique et Technique du Bâtiment Computer and biological vision Centre d'Enseignement et de Recherche en Technologies de l'Information et Systèmes Computer and biological vision Mathematical and Computational Neuroscience Computer and biological vision
• Publié dans International Journal of Computer Vision le 01/11/2020

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Résumé : This paper tackles an important aspect of the variational problem underlying active contours: optimization by gradient flows. Classically, the definition of a gradient depends directly on the choice of an inner product structure. This consideration is largely absent from the active contours literature. Most authors, explicitely or implicitely, assume that the space of admissible deformations is ruled by the canonical L 2 inner prod-uct. The classical gradient flows reported in the literature are relative to this particular choice. Here, we investigate the relevance of using (i) other inner products, yielding other gradient descents, and (ii) other minimizing flows not deriving from any inner product. In particular, we show how to induce different de-grees of spatial consistency into the minimizing flow, in order to decrease the probability of getting trapped into irrelevant local minima. We report numerical experiments indicating that the sensitivity of the active contours method to initial conditions, which seriously limits its applicability and efficiency, is alleviated by our application-specific spatially coherent minimizing flows. We show that the choice of the inner product can be seen as a prior on the deformation fields and we present an extension of the definition of the gradient toward more general priors.

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Fichiers liés : gradients.pdf

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• Type de publi. : Article dans une revue
• Date de publi. : 01/01/2007
• Auteurs : Moulay-Rachid BabaaJean-Louis BantigniesLaurent AlvarezPhilippe ParentFrançois Le NormandMike GulasJeannot Mané-ManéPoncharal PhilippeBryan Doyle
• Organismes : Laboratoire des colloïdes, verres et nanomatériaux Laboratoire des colloïdes, verres et nanomatériaux Laboratoire des colloïdes, verres et nanomatériaux Laboratoire de Chimie Physique - Matière et Rayonnement Institut de Physique et Chimie des Matériaux de Strasbourg Institut de Physique et Chimie des Matériaux de Strasbourg Institut de Physique et Chimie des Matériaux de Strasbourg Laboratoire des colloïdes, verres et nanomatériaux
• Publié dans Journal of Nanoscience and Nanotechnology le 25/10/2020

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Résumé : Functionalization of multi-walled carbon nanotubes (MWNTs) surface by sulfonated poly (ether ether ketone) SPEEK chains using a direct attachment reaction was investigated. A two step method was performed. MWNTs were oxidized by a nitric acid treatment to generate carboxyl groups on their surface. The grafting reaction of sulfonated groups of SPEEK with carboxyl groups present on the surface of oxidized MWNTs readily proceeds by using hexane diamine as an interlinking molecule. Transmission electron microscopy (TEM) shows that tubes are wrapped by polymer chains. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) at the C K-edge, O K-edge, and N K-edge and X-ray photoelectron spectroscopy (XPS) were used to give evidence of covalent functionalization of MWNTs by SPEEK macromolecules.

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Fichiers liés : babaa2007.pdf

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