56 research outputs found
350 Micron Dust Emission from High Redshift Objects
We report observations of a sample of high redshift sources (1.8<z<4.7),
mainly radio-quiet quasars, at 350 microns using the SHARC bolometer camera at
the Caltech Submillimeter Observatory. Nine sources were detected (>4-sigma)
and upper limits were obtained for 11 with 350 micron flux density limits
(3-sigma) in the range 30-125mJy. Combining published results at other
far-infrared and millimeter wavelengths with the present data, we are able to
estimate the temperature of the dust, finding relatively low values, averaging
50K. From the spectral energy distribution, we derive dust masses of a few 10^8
M_sun and luminosities of 4-33x10^{12} L_sun (uncorrected for any
magnification) implying substantial star formation activity. Thus both the
temperature and dust masses are not very different from those of local
ultraluminous infrared galaxies. For this redshift range, the 350 micron
observations trace the 60-100 micron rest frame emission and are thus directly
comparable with IRAS studies of low redshift galaxies.Comment: 5 pages, 2 PS figures. Accepted for publication in Astrophysical
Journal Letter
Opiate Receptors in the Rat Brain Specific Labeling of Multiple Membrane Components with [3H]Etorphine?
The evolution of clusters in the CLEF cosmological simulation: X-ray structural and scaling properties
We present results from a study of the X-ray cluster population that forms
within the CLEF cosmological hydrodynamics simulation, a large N-body/SPH
simulation of the Lambda CDM cosmology with radiative cooling, star formation
and feedback. The scaled projected temperature and entropy profiles at z=0 are
in good agreement with recent high-quality observations of cool core clusters,
suggesting that the simulation grossly follows the processes that structure the
intracluster medium (ICM) in these objects. Cool cores are a ubiquitous
phenomenon in the simulation at low and high redshift, regardless of a
cluster's dynamical state. This is at odds with the observations and so
suggests there is still a heating mechanism missing from the simulation. Using
a simple, observable measure of the concentration of the ICM, which correlates
with the apparent mass deposition rate in the cluster core, we find a large
dispersion within regular clusters at low redshift, but this diminishes at
higher redshift, where strong "cooling-flow" systems are absent in our
simulation. Consequently, our results predict that the normalisation and
scatter of the luminosity-temperature relation should decrease with redshift;
if such behaviour turns out to be a correct representation of X-ray cluster
evolution, it will have significant consequences for the number of clusters
found at high redshift in X-ray flux-limited surveys.Comment: 20 pages, 21 figures, MNRAS, accepted with minor modifications to
original manuscrip
AMBER : a near infrared focal instrument for the VLTI
10 pagesInternational audienceAMBER is the General User near-infrared focal instrument of the Very Large Telescope interferometer. Its specifications are based on three key programs on Young Stellar Objects, Active Galactic Nuclei central regions, masses and spectra of hot Extra Solar Planets. It has an imaging capacity because it combines up to three beams and very high accuracy measurement are expected from the spatial filtering of beams by single mode fibers and the comparison of measurements made simultaneously in different spectral channels
An asymmetry detected in the disk of Kappa CMa with the AMBER/VLTI
International audienceAims. We study the geometry and kinematics of the circumstellar environment of the Be star Kappa CMa in the Br gamma emission line and its nearby continuum. Methods. We use the VLTI/AMBER instrument operating in the K band which provides a spatial resolution of about 6 mas with a spectral resolution of 1500 to study the kinematics within the disk and to infer its rotation law. In order to obtain more kinematical constraints we also use an high spectral resolution Pa beta line profile obtain in December 2005 at the Observatorio do Pico do Dios, Brazil and we compile V/R line profile variations and spectral energy distribution data points from the literature. Results. Using differential visibilities and differential phases across the Br gamma line we detect an asymmetry in the disk. Moreover, we found that kappa CMa seems difficult to fit within the classical scenario for Be stars, illustrated recently by alpha Arae observations, i.e. a fast rotating B star close to its breakup velocity surrounded by a Keplerian circumstellar disk with an enhanced polar wind. Finally we discuss the possibility for kappa CMa to be a critical rotator with a Keplerian rotating disk and try to see if the detected asymmetry can be interpreted within the "one-armed" viscous disk framework
The chromatin remodeler p400 ATPase facilitates Rad51-mediated repair of DNA double-strand breaks
DNA damage signaling and repair take place in a chromatin context. Consequently, chromatin-modifying enzymes, including adenosine triphosphate–dependent chromatin remodeling enzymes, play an important role in the management of DNA double-strand breaks (DSBs). Here, we show that the p400 ATPase is required for DNA repair by homologous recombination (HR). Indeed, although p400 is not required for DNA damage signaling, DNA DSB repair is defective in the absence of p400. We demonstrate that p400 is important for HR-dependent processes, such as recruitment of Rad51 to DSB (a key component of HR), homology-directed repair, and survival after DNA damage. Strikingly, p400 and Rad51 are present in the same complex and both favor chromatin remodeling around DSBs. Altogether, our data provide a direct molecular link between Rad51 and a chromatin remodeling enzyme involved in chromatin decompaction around DNA DSBs
Essai d\u27\ue9levage en captivit\ue9 \ue9troite du Li\ue8vre commun, Lepus europaeus Pallas, 1778
Volume: 38Start Page: 333End Page: 33
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