39 research outputs found
Identification sans contrainte de stationnarité d'un modèle AR d'une texture
Un problème classique en analyse d'image est d'obtenir une modélisation caractéristique d'images texturées. L'utilisation d'un modèle AR-2D fournit souvent des solutions efficaces. Cependant, l'identification des coefficients d'un tel modèle est assujettie à l'hypothèse de stationnarité du signal. Pour résoudre ce problème, nous considérons la distribution spatiale du signal générateur utilisé avec le modèle AR-2D. L'originalité de ce travail vient d'une identification simultanée des paramètres du modèle et des échantillons du générateur, ceci par un processus neuronal. Ainsi, comme résultats nouveaux, nous proposons une méthode permettant de représenter une texture par un couple d'attributs, un modèle AR-2D et une distribution spatiale du signal générateur
Sculpting the disk around T Cha: an interferometric view
(Abridged) Circumstellar disks are believed to be the birthplace of planets
and are expected to dissipate on a timescale of a few Myr. The processes
responsible for the removal of the dust and gas will strongly modify the radial
distribution of the dust and consequently the SED. In particular, a young
planet will open a gap, resulting in an inner disk dominating the near-IR
emission and an outer disk emitting mostly in the far-IR. We analyze a full set
of data (including VLTI/Pionier, VLTI/Midi, and VLT/NaCo/Sam) to constrain the
structure of the transition disk around TCha. We used the Mcfost radiative
transfer code to simultaneously model the SED and the interferometric
observations. We find that the dust responsible for the emission in excess in
the near-IR must have a narrow temperature distribution with a maximum close to
the silicate sublimation temperature. This translates into a narrow inner dusty
disk (0.07-0.11 AU). We find that the outer disk starts at about 12 AU and is
partially resolved by the Pionier, Sam, and Midi instruments. We show that the
Sam closure phases, interpreted as the signature of a candidate companion, may
actually trace the asymmetry generated by forward scattering by dust grains in
the upper layers of the outer disk. These observations help constrain the
inclination and position angle of the outer disk. The presence of matter inside
the gap is difficult to assess with present-day observations. Our model
suggests the outer disk contaminates the interferometric signature of any
potential companion that could be responsible for the gap opening, and such a
companion still has to be unambiguously detected. We stress the difficulty to
observe point sources in bright massive disks, and the consequent need to
account for disk asymmetries (e.g. anisotropic scattering) in model-dependent
search for companions.Comment: Removed the word "first" in the abstract of the paper: "obtained with
the first 4-telescope combiner (VLTI/Pionier)
The VLTI / PIONIER near-infrared interferometric survey of southern T Tauri stars. I. First results
Context : The properties of the inner disks of bright Herbig AeBe stars have
been studied with near infrared (NIR) interferometry and high resolution
spectroscopy. The continuum and a few molecular gas species have been studied
close to the central star; however, sensitivity problems limit direct
information about the inner disks of the fainter T Tauri stars.
Aims : Our aim is to measure some of the properties of the inner regions of
disks surrounding southern T Tauri stars.
Methods : We performed a survey with the PIONIER recombiner instrument at
H-band of 21 T Tauri stars. The baselines used ranged from 11 m to 129 m,
corresponding to a maximum resolution of 3mas (0.45 au at 150 pc).
Results : Thirteen disks are resolved well and the visibility curves are
fully sampled as a function of baseline in the range 45-130 m for these 13
objects. A simple qualitative examination of visibility profiles allows us to
identify a rapid drop-off in the visibilities at short baselines in 8 resolved
disks. This is indicative of a significant contribution from an extended
contribution of light from the disk. We demonstrate that this component is
compatible with scattered light, providing strong support to a prediction made
by Pinte et al. (2008). The amplitude of the drop-off and the amount of dust
thermal emission changes from source to source suggesting that each disk is
different. A by-product of the survey is the identification of a new
milli-arcsec separation binary: WW Cha. Spectroscopic and interferometric data
of AK Sco have also been fitted with a binary and disk model.
Conclusions : Visibility data are reproduced well when thermal emission and
scattering form dust are fully considered. The inner radii measured are
consistent with the expected dust sublimation radii. Modelling of AK Sco
suggests a likely coplanarity between the disk and the binary's orbital planeComment: 19 pages, 11 figure
Subcutaneous phaeohyphomycosis due to Phialemoniopsis ocularis successfully treated by voriconazole
International audienceWe report a case of subcutaneous infection in a 67 year-old Cambodian man who presented with a 5-month history of swelling of the right foot. Histopathology was compatible with phaeohyphomycosis and the hyphomycete Phialemoniopsis ocularis was identified by the means of morphological and molecular techniques. The patient responded well to a 6-month oral treatment with voriconazole alone
A Spitzer Survey of Protoplanetary Disk Dust in the Young Serpens Cloud: How do Dust Characteristics Evolve with Time?
We present Spitzer IRS mid-infrared (5-35 micron) spectra of a complete
flux-limited sample (> 3 mJy at 8 micron) of young stellar object (YSO)
candidates selected on the basis of their infrared colors in the Serpens
Molecular Cloud. Spectra of 147 sources are presented and classified.
Background stars (with slope consistent with a reddened stellar spectrum and
silicate features in absorption), galaxies (with redshifted PAH features) and a
planetary nebula (with high ionization lines) amount to 22% of contamination in
this sample, leaving 115 true YSOs. Sources with rising spectra and ice
absorption features, classified as embedded Stage I protostars, amount to 18%
of the sample. The remaining 82% (94) of the disk sources are analyzed in terms
of spectral energy distribution shapes, PAHs and silicate features. The
presence, strength and shape of these silicate features are used to infer disk
properties for these systems. About 8% of the disks have 30/13 micron flux
ratios consistent with cold disks with inner holes or gaps, and 3% of the disks
show PAH emission. Comparison with models indicates that dust grains in the
surface of these disks have sizes of at least a few \mu\m. The 20 micron
silicate feature is sometimes seen in absence of the 10 micron feature, which
may be indicative of very small holes in these disks. No significant difference
is found in the distribution of silicate feature shapes and strengths between
sources in clusters and in the field. Moreover, the results in Serpens are
compared with other well-studied samples: the c2d IRS sample distributed over 5
clouds and a large sample of disks in the Taurus star-forming region. The
remarkably similar distributions of silicate feature characteristics in samples
with different environment and median ages - if significant - imply that the
dust population in the disk surface results from an equilibrium between dust
growth and destructive collision processes that are maintained over a few
million years for any YSO population irrespective of environment.Comment: accepted by Ap
IRIM at TRECVID2009: High Level Feature Extraction
International audienceThe IRIM group is a consortium of French teams working on Multimedia Indexing and Retrieval. This paper describes our participation to the TRECVID 2009 High Level Features detection task. We evaluated a large number of different descriptors (on TRECVID 2008 data) and tried different fusion strategies, in particular hierarchical fusion and genetic fusion. The best IRIM run has a Mean Inferred Average Precision of 0.1220, which is significantly above TRECVID 2009 HLF detection task median performance. We found that fusion of the classification scores from different classifier types improves the performance and that even with a quite low individual performance, audio descriptors can help
Évaluation et prospective de la démographie médicale en chirurgie orthopédique et traumatologique (quels chirurgiens pour quelle chirurgie ?)
PARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF
Le système expert NEREIS des annélides polychètes de France (ordre des Phyllodocida, Amphinomida, Spintherida et Eunicida)
La Faune de France des annélides polychètes errantes de Fauvel (1923) ne comporte que 15 familles (Histribdellidae et Ichthyotomidae exclues). Actuellement, on compte 37 familles présentes sur les côtes de France; il a donc été nécessaire de réviser la clé de détermination des familles pour réaliser un logiciel permettant un diagnostic rapide des taxa. Le générateur utilisé, Xi Plus, est édité par Syspertec