21,934 research outputs found
A FIRST DETERMINATION OF THE SURFACE DENSITY OF GALAXY CLUSTERS AT VERY LOW X--RAY FLUXES
We present the first results of a serendipitous search for clusters of
galaxies in deep ROSAT-PSPC pointed observations at high galactic latitude. The
survey is being carried out using a Wavelet based Detection Algorithm which is
not biased against extended, low surface brightness sources. A new
flux--diameter limited sample of 10 cluster candidates has been created from
surveyed area. Preliminary CCD observations have revealed
that a large fraction of these candidates correspond to a visible enhancement
in the galaxy surface density, and several others have been identified from
other surveys. We believe these sources to be either low--moderate redshift
groups or intermediate to high redshift clusters. We show X-ray and optical
images of some of the clusters identified to date. We present, for the first
time, the derived number density of the galaxy clusters to a flux limit of (0.5--2.0 keV). This extends the -- of previous cluster surveys by more than one decade in flux.
Results are compared to theoretical predictions for cluster number counts.Comment: uuencoded compressed Postscript, 7 pages including 4 figures.
Accepted for publication in Ap. J. Letters
Age-related differences in pointing accuracy in familiar and unfamiliar environments
This study aimed to investigate age-related differences in spatial mental representations of familiar and unfamiliar places. Nineteen young adults (aged 18\u201323) and 19 older adults (aged 60\u201374), all living in the same Italian town, completed a set of visuospatial measures and then pointed in the direction of familiar landmarks in their town and in the direction of landmarks in an unknown environment studied on a map. Results showed that older adults were less accurate in the visuospatial tasks and in pointing at landmarks in an unfamiliar environment, but performed as well as the young adults when pointing to familiar places. Pointing performance correlated with visuospatial tests accuracy in both familiar and unfamiliar environments, while only pointing in an unknown environment correlated with visuospatial working memory (VSWM).
The spatial representation of well-known places seems to be well preserved in older adults (just as well as in young adults), while it declines for unfamiliar environments. Spatial abilities sustain the mental representations of both familiar and unfamiliar environments, while the support of VSWM resources is only needed for the latter
Extended radio emission in BL Lac objects - I: the images
We have observed 28 sources selected from the 1Jy sample of BL Lac objects
(Stickel et al. 1991) with the Very Large Array (VLA) in A, B and D
configurations at 1.36, 1.66 and 4.85 GHz, and/or with the Westerbork Synthesis
Radio Telescope (WSRT) at 1.40 GHz. In this paper we present high sensitivity
images at arcsecond resolution of the 18 objects showing extended structure in
our images, and of another source from the FIRST (Faint Images of the Radio Sky
at Twenty-cm) survey (Becker et al. 1995). In general our high sensitivity
images reveal an amount of extended emission larger than previously reported.
In some objects the luminosity of the extended structure is comparable with
that of FR~II radio sources. A future paper will be devoted to the
interpretation of these results.Comment: 12 pages, 35 figures, to appear on A&A Supp. Ser., postscript file
with figures included available at
http://www.ira.noto.cnr.it/staff/carlo/ds1030.ps.g
Características do grão de algumas linhagens de soja de tegumento colorido.
bitstream/item/65447/1/CTAA-DOCUMENTOS-17-CARACTERISTICAS-DO-GRAO-DE-ALGUMAS-LINHAGENS-DE-SOJA-DE-TEGUMENTO-COLORIDO-FL-.pd
Theory of high-order harmonic generation from molecules by intense laser pulses
We show that high-order harmonics generated from molecules by intense laser
pulses can be expressed as the product of a returning electron wave packet and
the photo-recombination cross section (PRCS) where the electron wave packet can
be obtained from simple strong-field approximation (SFA) or from a companion
atomic target. Using these wave packets but replacing the PRCS obtained from
SFA or from the atomic target by the accurate PRCS from molecules, the
resulting HHG spectra are shown to agree well with the benchmark results from
direct numerical solution of the time-dependent Schr\"odinger equation, for the
case of H in laser fields. The result illustrates that these powerful
theoretical tools can be used for obtaining high-order harmonic spectra from
molecules. More importantly, the results imply that the PRCS extracted from
laser-induced HHG spectra can be used for time-resolved dynamic chemical
imaging of transient molecules with temporal resolutions down to a few
femtoseconds.Comment: 10 pages, 5 figure
X-ray observation of ULAS J1120+0641, the most distant quasar at z=7.08
We aim at probing the emission mechanism of the accreting super massive black
holes in the high redshift Universe. We study the X-ray spectrum of
ULAS1120+0641, the highest redshift quasar detected so far at z=7.085, which
has been deeply observed (340 ks) by XMM-Newton. Despite the long integration
time the spectral analysis is limited by the poor statistics, with only 150
source counts being detected. We measured the spectrum in the 2-80 keV
rest-frame (0.3-10 keV observed) energy band. Assuming a simple power law model
we find a photon index of 2.0+/-0.3 and a luminosity of 6.7+/-0.3 10^44 erg/s
in the 2-10 keV band, while the intrinsic absorbing column can be only loosely
constrained (NH< 1E23 cm^-2). Combining our data with published data we
calculate that the X-ray-to-optical spectral index alpha_OX is1.8+/-0.1, in
agreement with the alpha_OX-UV luminosity correlation valid for lower redshift
quasars. We expanded to high energies the coverage of the spectral energy
distribution of ULAS1120+0641. This is the second time that a z >6 quasar has
been investigated through a deep X-ray observation. In agreement with previous
studies of z~6 AGN samples, we do not find any hint of evolution in the
broadband energy distribution. Indeed from our dataset ULAS 1120+0641 is
indistinguishable from the population of optically bright quasar at lower
redshift.Comment: 5 pages, 4 figures, A&A in press; updated with the accepted versio
Soja na alimentação humana.
Características físicas, composição química e valor nutritivo. Obtenção e uso dos principais produtos de soja. Produtos não desengordurados. Produtos do óleo bruto. Produtos do farelo desengordurado cru. Produtos de tradição oriental.bitstream/item/65355/1/CTAA-DOCUMENTOS-01-SOJA-NA-ALIMENTACAO-HUMANA-LV-2005-00497.pd
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