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Search Results: 1 - 10 of 198126 matches for " N. Barriere "
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Concept Clustering and Knowledge Integration from a Children's Dictionary
Caroline Barriere,Fred Popowich
Computer Science , 1997,
Abstract: Knowledge structures called Concept Clustering Knowledge Graphs (CCKGs) are introduced along with a process for their construction from a machine readable dictionary. CCKGs contain multiple concepts interrelated through multiple semantic relations together forming a semantic cluster represented by a conceptual graph. The knowledge acquisition is performed on a children's first dictionary. A collection of conceptual clusters together can form the basis of a lexical knowledge base, where each CCKG contains a limited number of highly connected words giving useful information about a particular domain or situation.
Soft gamma-ray optics: new Laue lens design and performance estimates
N. Barriere,L. Natalucci,N. Abrosimov,P. von Ballmoos,P. Bastie,P. Courtois,M. Jentschel,J. Knodlseder,J. Rousselle,P. Ubertini
Physics , 2009, DOI: 10.1117/12.826138
Abstract: Laue lenses are an emerging technology based on diffraction in crystals that allows the concentration of soft gamma rays. This kind of optics that works in the 100 keV - 1.5 MeV band can be used to realize an high-sensitivity and high-angular resolution telescope (in a narrow field of view). This paper reviews the recent progresses that have been done in the development of efficient crystals, in the design study and in the modelisation of the answer of Laue lenses. Through the example of a new concept of 20 m focal length lens focusing in the 100 keV - 600 keV band, the performance of a telescope based on a Laue lens is presented. This lens uses the most efficient mosaic crystals in each sub-energy range in order to yield the maximum reflectivity. Imaging capabilities are investigated and shows promising results.
Experimental and theoretical study of diffraction properties of various crystals for the realization of a soft gamma-ray Laue lens
Nicolas Barriere,Julien Rousselle,Peter von Ballmoos,Nikolai V. Abrosimov,Pierre Courtois,Pierre Bastie,Thierry Camus,Michael Jentschel,Vladimir N. Kurlov,Lorenzo Natalucci,Gilles Roudil,Nicolai Frisch Brejnholt,Denis Serre
Physics , 2009,
Abstract: Crystals are the elementary constituents of Laue lenses, an emerging technology which could allow the realization of a space borne telescope 10 to 100 times more sensitive than existing ones in the 100 keV - 1.5 MeV energy range. This study addresses the current endeavor to the development of efficient crystals for the realization of a Laue lens. In the theoretical part 35 candidate-crystals both pure and two-components are considered. Their peak reflectivity at 100 keV, 500 keV and 1 MeV is calculated assuming they are mosaic crystals. It results that a careful selection of crystals can allow a reflectivity above 30% over the whole energy range, and even reaching 40% in its lower part. Experimentally, we concentrated on three different materials (Si_{1-x}Ge_x with gradient of composition, mosaic Cu and Au) that have been measured both at ESRF and ILL using highly-monochromatic beams ranging from 300 keV up to 816 keV. The aim was to check their homogeneity, quality and angular spread (mosaicity). These crystals have shown outstanding performance such as reflectivity up to 31% at ~600 keV (Au) or 60% at 300 keV (SiGe) and angular spread as low as 15 arcsec for Cu, fulfilling very well the requirements for a Laue lens application. Unexpectedly, we also noticed important discrepancies with Darwin's model when a crystal is measured using various energies.
Study of Microwave Tomography Measurement Setup Configurations for Breast Cancer Detection Based on Breast Compression
Alvaro Diaz-Bolado,Paul-Andre Barriere,Jean-Jacques Laurin
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/701378
Abstract: Microwave tomography (MT) measurement setups for different configurations based on breast compression are compared to classical circular measurement setups. Configurations based on compression allow measuring the evanescent component of the scattered field and lead to a compact measurement setup that allows direct image comparison with a standard mammography system. The different configurations are compared based on the singular value decomposition (SVD) of the radiation operator for a 2D TM case. This analysis allows determining under which conditions the image quality obtained from the reconstructions can be enhanced. These findings are confirmed by a series of reconstructions of breast phantoms based on synthetic data obtained at a single frequency of operation. 1. Introduction Active microwave imaging for breast cancer detection has been an active research field in the past years [1]. Two different approaches have been considered, namely, radar-type approaches [2] and microwave tomography (MT) [3]. MT is used to estimate the complex permittivity distribution inside the object under test (OUT), by solving an inverse scattering problem when the object is illuminated under several different conditions and the scattered field is measured at different locations. In MT, detailed information of the OUT is obtained at the expense of solving a nonlinear and ill-posed inverse scattering problem [4]. A measurement setup in MT typically includes a series of receiving (Rx) and transmitting (Tx) antennas for measuring the scattered fields needed for the reconstruction algorithms. The antennas can be arranged in planar, cylindrical, or hemispherical surfaces. In the available clinical prototypes, the patient lies prone on a table with the breast pendant in a liquid [3, 5]. This configuration has been proposed for maximizing the comfort of the patient. In such a case, a cylindrical or hemispherical configuration is preferred since the antennas can be conformal with the shape of the breast and can accurately sample the scattered fields. However, compression of the breast may present several advantages over this classical configuration [6, 7]. The Tx and Rx antennas can be placed very close to the OUT, allowing the measurement of the evanescent scattered fields. Also, this procedure can lead to simplifications of the reconstruction algorithm since the thickness of the compressed breast is precisely known. Finally, because both MT and X-ray mammography can use the same compressed configuration a combined approach would take advantage of the benefits of both
Exploring plasma evolution during Sagittarius A* flares
Salome Dibi,Sera Markoff,Renaud Belmont,Julien Malzac,Nicolas M. Barriere,John A. Tomsick
Physics , 2015, DOI: 10.1093/mnras/stu599
Abstract: We present a new way of describing the flares from Sgr A* with a self-consistent calculation of the particle distribution. All relevant radiative processes are taken into account in the evolution of the electron distribution and resulting spectrum. We present spectral modelling for new X-ray flares observed by NuSTAR, together with older observations in different wavelengths, and discuss the changes in plasma parameters to produce a flare. We show that under certain conditions, the real particle distribution can differ significantly from standard distributions assumed in most studies. We conclude that the flares are likely generated by magnetized plasma consistent with our understanding of the accretion flow. Including non-thermal acceleration, injection, escape, and cooling losses produces a spectrum with a break between the infrared and the X-ray, allowing a better simultaneous description of the different wavelengths. We favour the non-thermal synchrotron interpretation, assuming the infrared flare spectrum used is representative. We also consider the effects on Sgr A*s quiescent spectrum in the case of a density increase due to the G2 encounter with Sgr A*.
SN 2010jl: Optical to hard X-ray observations reveal an explosion embedded in a ten solar mass cocoon
E. O. Ofek,A. Zoglauer,S. E. Boggs,N. M. Barriere,S. P. Reynolds,C. L. Fryer,F. A. Harrison,S. B. Cenko,S. R. Kulkarni,A. Gal-Yam,I. Arcavi,E. Bellm,J. S. Bloom,F. Christensen,W. W. Craig,W. Even,A. V. Filippenko,B. Grefenstette,C. J. Hailey,R. Laher,K. Madsen,E. Nakar,P. E. Nugent,D. Stern,M. Sullivan,J. Surace,W. W. Zhang
Physics , 2013, DOI: 10.1088/0004-637X/781/1/42
Abstract: (Abridged) Some supernovae (SNe) may be powered by the interaction of the SN ejecta with a large amount of circumstellar matter (CSM). Here we outline a method to measure the mass of the optically thick CSM around such SNe. We present observations of SN2010jl, including the first detection of a SN using NuSTAR. The total radiated luminosity of SN2010jl is extreme, at least 9e50 erg. By modeling the visible-light data, we robustly show that the mass of the circumstellar material within ~1e16 cm of the progenitor was in excess of 10 solar masses, likely ejected tens of years prior to the SN explosion. Our modeling suggests that the shock velocity during shock breakout was ~6000 km/s, decelerating to ~2600 km/s about two years after maximum light. Our late-time NuSTAR+XMM spectra of the SN presumably provide the first direct measurement of SN shock velocity two years after the SN maximum light -- measured to be in the range of 2000 to 4500 km/s if the ions and electrons are in equilibrium, and >~2000 km/s if they are not in equilibrium. This measurement is in agreement with the shock velocity predicted by our modeling of the optical data. We also show that the mean radial density distribution of the CSM roughly follows an r^-2 law. A possible explanation for the massive CSM with a wind-like profile is that they are the result of multiple pulsational pair instability events prior to the SN explosion, separated from each other by years.
Chandra Identification of Two AGN Discovered by INTEGRAL
John A. Tomsick,Roman Krivonos,Farid Rahoui,Marco Ajello,Jerome Rodriguez,Nicolas Barriere,Arash Bodaghee,Sylvain Chaty
Physics , 2015, DOI: 10.1093/mnras/stv325
Abstract: Here, we report on observations of two hard X-ray sources that were originally discovered with the INTEGRAL satellite: IGR J04059+5416 and IGR J08297-4250. We use the Chandra X-ray Observatory to localize the sources and then archival near-IR images to identify the counterparts. Both sources have counterparts in the catalog of extended 2 Micron All-Sky Survey sources, and the counterpart to IGR J04059+5416 has been previously identified as a galaxy. Thus, we place IGR J04059+5416 in the class of Active Galactic Nuclei (AGN), and we suggest that IGR J08297-4250 is also an AGN. If this identification is correct, the near-IR images suggest that the host galaxy of IGR J08297-4250 may be merging with a smaller nearby galaxy. For IGR J04059+5416, the 0.3-86 keV spectrum from Chandra and INTEGRAL is consistent with an absorbed power-law with a column density of N_H = 3.1(+2.0)(-1.5)e22 cm-2 and a photon index of Gamma = 1.4+/-0.7, and we suggest that it is a Seyfert galaxy. For IGR J08297-4250, the photon index is similar, Gamma = 1.5+/-0.8, but the source is highly absorbed (N_H = 6.1(+10.1)(-4.3)e23 cm-2).
Letter of Intent for Double-CHOOZ: a Search for the Mixing Angle Theta13
F. Ardellier,I. Barabanov,J. C. Barriere,M. Bauer,L. Bezrukov,C. Buck,C. Cattadori,B. Courty,M. Cribier,F. Dalnoki-Veress,N. Danilov,H. de Kerret,A. Di Vacri,A. Etenko,M. Fallot,Ch. Grieb,M. Goeger,A. Guertin,T. Kirchner,Y. S. Krylov,D. Kryn,C. Hagner,W. Hampel,F. X. Hartmann,P. Huber,J. Jochum,T. Lachenmaier,Th. Lasserre,Ch. Lendvai,M. Lindner,F. Marie,J. Martino,G. Mention,A. Milsztajn,J. P. Meyer,D. Motta,L. Oberauer,M. Obolensky,L. Pandola,W. Potzel,S. Schoenert,U. Schwan,T. Schwetz,S. Scholl,L. Scola,M. Skorokhvatov,S. Sukhotin,A. Letourneau,D. Vignaud,F. von Feilitzsch,W. Winter,E. Yanovich
Physics , 2004,
Abstract: Tremendous progress has been achieved in neutrino oscillation physics during the last few years. However, the smallness of the $\t13$ neutrino mixing angle still remains enigmatic. The current best constraint comes from the CHOOZ reactor neutrino experiment $\s2t13 < 0.2$ (at 90% C.L., for $\adm2=2.0 10^{-3} \text{eV}^2$). We propose a new experiment on the same site, Double-CHOOZ, to explore the range of $\s2t13$ from 0.2 to 0.03, within three years of data taking. The improvement of the CHOOZ result requires an increase in the statistics, a reduction of the systematic error below one percent, and a careful control of the cosmic ray induced background. Therefore, Double-CHOOZ will use two identical detectors, one at $\sim$150 m and another at 1.05 km distance from the nuclear cores. The plan is to start data taking with two detectors in 2008, and to reach a sensitivity of 0.05 in 2009, and 0.03 in 2011.
Initial Results from NuSTAR Observations of the Norma Arm
Arash Bodaghee,John A. Tomsick,Roman Krivonos,Daniel Stern,Franz E. Bauer,Nicolas Barriere,Steven E. Boggs,Finn E. Christensen,William W. Craig,Eric V. Gotthelf,Charles J. Hailey,Fiona A. Harrison,Jaesub Hong,Kaya Mori,William W. Zhang
Physics , 2014, DOI: 10.1088/0004-637X/791/1/68
Abstract: Results are presented for an initial survey of the Norma Arm gathered with the focusing hard X-ray telescope NuSTAR. The survey covers 0.2 deg$^2$ of sky area in the 3-79 keV range with a minimum and maximum raw depth of 15 ks and 135 ks, respectively. Besides a bright black-hole X-ray binary in outburst (4U 1630-47) and a new X-ray transient (NuSTAR J163433-473841), NuSTAR locates three sources from the Chandra survey of this region whose spectra are extended above 10 keV for the first time: CXOU J163329.5-473332, CXOU J163350.9-474638, and CXOU J163355.1-473804. Imaging, timing, and spectral data from a broad X-ray range (0.3-79 keV) are analyzed and interpreted with the aim of classifying these objects. CXOU J163329.5-473332 is either a cataclysmic variable or a faint low-mass X-ray binary. CXOU J163350.9-474638 varies in intensity on year-long timescales, and with no multi-wavelength counterpart, it could be a distant X-ray binary or possibly a magnetar. CXOU J163355.1-473804 features a helium-like iron line at 6.7 keV and is classified as a nearby cataclysmic variable. Additional surveys are planned for the Norma Arm and Galactic Center, and those NuSTAR observations will benefit from the lessons learned during this pilot study.
First Measurement of θ_13 from Delayed Neutron Capture on Hydrogen in the Double Chooz Experiment
Double Chooz Collaboration,Y. Abe,C. Aberle,J. C. dos Anjos,J. C. Barriere,M. Bergevin,A. Bernstein,T. J. C. Bezerra,L. Bezrukhov,E. Blucher,N. S. Bowden,C. Buck,J. Busenitz,A. Cabrera,E. Caden,L. Camilleri,R. Carr,M. Cerrada,P. -J. Chang,P. Chimenti,T. Classen,A. P. Collin,E. Conover,J. M. Conrad,J. I. Crespo-Anadón,K. Crum,A. Cucoanes,E. Damon,J. V. Dawson,S. Dazeley,D. Dietrich,Z. Djurcic,M. Dracos,V. Durand,J. Ebert,Y. Efremenko,M. Elnimr,A. Erickson,A. Etenko,M. Fallot,M. Fechner,F. von Feilitzsch,J. Felde,S. M. Fernandes,V. Fischer,D. Franco,A. J. Franke,M. Franke,H. Furuta,R. Gama,I. Gil-Botella,L. Giot,M. G?ger-Neff,L. F. G. Gonzalez,L. Goodenough,M. C. Goodman,J. TM. Goon,D. Greiner,N. Haag,S. Habib,C. Hagner,T. Hara,F. X. Hartmann,J. Haser,A. Hatzikoutelis,T. Hayakawa,M. Hofmann,G. A. Horton-Smith,A. Hourlier,M. Ishitsuka,J. Jochum,C. Jollet,C. L. Jones,F. Kaether,L. N. Kalousis,Y. Kamyshkov,D. M. Kaplan,T. Kawasaki,G. Keefer,E. Kemp,H. de Kerret,T. Konno,D. Kryn,M. Kuze,T. Lachenmaier,C. E. Lane,C. Langbrandtner,T. Lasserre,A. Letourneau,D. Lhuillier,H. P. Lima Jr,M. Lindner,J. M. López-Casta?o,J. M. LoSecco,B. K. Lubsandorzhiev,S. Lucht,D. McKee,J. Maeda,C. N. Maesano,C. Mariani,J. Maricic,J. Martino,T. Matsubara,G. Mention,A. Meregaglia,M. Meyer,T. Miletic,R. Milincic,H. Miyata,Th. A. Mueller,Y. Nagasaka,K. Nakajima,P. Novella,M. Obolensky,L. Oberauer,A. Onillon,A. Osborn,I. Ostrovskiy,C. Palomares,I. M. Pepe,S. Perasso,P. Perrin,P. Pfahler,A. Porta,W. Potzel
Statistics , 2013, DOI: 10.1016/j.physletb.2013.04.050
Abstract: The Double Chooz experiment has determined the value of the neutrino oscillation parameter $\theta_{13}$ from an analysis of inverse beta decay interactions with neutron capture on hydrogen. This analysis uses a three times larger fiducial volume than the standard Double Chooz assessment, which is restricted to a region doped with gadolinium (Gd), yielding an exposure of 113.1 GW-ton-years. The data sample used in this analysis is distinct from that of the Gd analysis, and the systematic uncertainties are also largely independent, with some exceptions, such as the reactor neutrino flux prediction. A combined rate- and energy-dependent fit finds $\sin^2 2\theta_{13}=0.097\pm 0.034(stat.) \pm 0.034 (syst.)$, excluding the no-oscillation hypothesis at 2.0 \sigma. This result is consistent with previous measurements of $\sin^2 2\theta_{13}$.
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