5,905 research outputs found
Morphology and Redshifts of Extremely Red Galaxies in the GOODS/CDFS deep ISAAC field
We present the photometric redshift distribution of a sample of 198 Extremely
Red Galaxies (ERGs) with Ks3.92 (Vega), selected by Roche et al.
in 50.4 sq. arcmin of the Chandra Deep Field South (CDFS). The sample has been
obtained using ISAAC-VLT and ACS-HST GOODS public data. We also show the
results of a morphological study of the 72 brightest ERGs in the z band (z<25,
AB).Comment: 2 pages, 2 figures. To appear in the proceedings of the ESO/USM/MPE
Workshop "Multiwavelength Mapping of Galaxy Formation and Evolution", Venice,
October 13-16, 200
Quantum turbulence at finite temperature: the two-fluids cascade
To model isotropic homogeneous quantum turbulence in superfluid helium, we
have performed Direct Numerical Simulations (DNS) of two fluids (the normal
fluid and the superfluid) coupled by mutual friction. We have found evidence of
strong locking of superfluid and normal fluid along the turbulent cascade, from
the large scale structures where only one fluid is forced down to the vorticity
structures at small scales. We have determined the residual slip velocity
between the two fluids, and, for each fluid, the relative balance of inertial,
viscous and friction forces along the scales. Our calculations show that the
classical relation between energy injection and dissipation scale is not valid
in quantum turbulence, but we have been able to derive a temperature--dependent
superfluid analogous relation. Finally, we discuss our DNS results in terms of
the current understanding of quantum turbulence, including the value of the
effective kinematic viscosity
Transmission Resonance in an Infinite Strip of Phason-Defects of a Penrose Approximant Network
An exact method that analytically provides transfer matrices in finite
networks of quasicrystalline approximants of any dimensionality is discussed.
We use these matrices in two ways: a) to exactly determine the band structure
of an infinite approximant network in analytical form; b) to determine, also
analytically, the quantum resistance of a finite strip of a network under
appropriate boundary conditions. As a result of a subtle interplay between
topology and phase interferences, we find that a strip of phason-defects along
a special symmetry direction of a low 2-d Penrose approximant, leads to the
rigorous vanishing of the reflection coefficient for certain energies. A
similar behavior appears in a low 3-d approximant. This type of ``resonance" is
discussed in connection with the gap structure of the corresponding ordered
(undefected) system.Comment: 18 pages special macros jnl.tex,reforder.tex, eqnorder.te
Silicate absorption in heavily obscured galaxy nuclei
Spectroscopy at 8-13 microns with T-ReCS on Gemini-S is presented for 3
galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and
NGC 5506. In the galaxies with the deepest absorption bands, the silicate
profile towards the nuclei is well represented by the emissivity function
derived from the circumstellar emission from the red supergiant, mu Cephei
which is also representative of the mid-infrared absorption in the diffuse
interstellar medium in the Galaxy. There is spectral structure near 11.2
microns in NGC 3094 which may be due to a component of crystalline silicates.
In NGC 5506, the depth of the silicate absorption increases from north to south
across the nucleus, suggestive of a dusty structure on scales of 10s of
parsecs. We discuss the profile of the silicate absorption band towards galaxy
nuclei and the relationship between the 9.7 micron silicate and 3.4 micron
hydrocarbon absorption bands.Comment: 7 pages, accepted for publication in MNRA
The differential regulation of Lck kinase phosphorylation sites by CD45 is critical for T cell receptor signaling responses
SummaryThe molecular mechanisms whereby the CD45 tyrosine phosphatase (PTPase) regulates T cell receptor (TCR) signaling responses remain to be elucidated. To investigate this question, we have reconstituted CD45 (encoded by Ptprc)-deficient mice, which display severe defects in thymic development, with five different expression levels of transgenic CD45RO, or with mutant PTPase null or PTPase-low CD45R0. Whereas CD45 PTPase activity was absolutely required for the reconstitution of thymic development, only 3% of wild-type CD45 activity restored T cell numbers and normal cytotoxic T cell responses. Lowering the CD45 expression increased CD4 lineage commitment. Peripheral T cells with very low activity of CD45 phosphatase displayed reduced TCR signaling, whereas intermediate activity caused hyperactivation of CD4+ and CD8+ T cells. These results are explained by a rheostat mechanism whereby CD45 differentially regulates the negatively acting pTyr-505 and positively acting pTyr-394 p56lck tyrosine kinase phosphorylation sites. We propose that high wild-type CD45 expression is necessary to dephosphorylate p56lck pTyr-394, suppressing CD4 T+ cell lineage commitment and hyperactivity
Photodissociation of p-process nuclei studied by bremsstrahlung induced activation
A research program has been started to study experimentally the
near-threshold photodissociation of nuclides in the chain of cosmic heavy
element production with bremsstrahlung from the ELBE accelerator. An important
prerequisite for such studies is good knowledge of the bremsstrahlung
distribution which was determined by measuring the photodissociation of the
deuteron and by comparison with model calculations. First data were obtained
for the astrophysically important target nucleus 92-Mo by observing the
radioactive decay of the nuclides produced by bremsstrahlung irradiation at
end-point energies between 11.8 MeV and 14.0 MeV. The results are compared to
recent statistical model calculations.Comment: 6 pages, 8 figures, Proceedings Nuclear Physics in Astrophysics II,
May 16-20, 2005, Debrecen, Hungary. The original publication is available at
www.eurphysj.or
The evolution of Ks-selected galaxies in the GOODS/CDFS deep ISAAC field
We present estimated redshifts and derived properties for a sample of 1663
galaxies with Ks <= 22 (Vega), selected from 50.4 sq.arcmin of the GOODS/CDFS
field with deep ISAAC imaging, and make an extensive comparison of their
properties with those of the extremely red galaxies (ERGs) selected in the same
field. We study in detail the evolution of Ks-selected galaxies up to redshifts
z ~ 4 and clarify the role of ERGs within the total Ks-band galaxy population.
We compute the total Ks-band luminosity function (LF) and compare its evolution
with the ERG LF. Up to =2.5, the bright end of the Ks-band LF shows no
sign of decline, and is progressively well reproduced by the ERGs with
increasing redshift. We also explore the evolution of massive systems present
in our sample: up to 20%-25% of the population of local galaxies with assembled
stellar mass M>1x10^11 Msun has been formed before redshift z ~ 4, and contains
~ 45% to 70% of the stellar mass density of the Universe at that redshift.
Within our sample, the comoving number density of these massive systems is then
essentially constant down to redshift z ~ 1.5, by which point most of them have
apparently evolved into (I-Ks)-selected ERGs. The remaining massive systems
observed in the local Universe are assembled later, at redshifts z <= 1.5. Our
results therefore suggest a two-fold assembly history for massive galaxies, in
which galaxy/star formation proceeds very efficiently in high mass haloes at
very high redshift.Comment: Revised version accepted by MNRAS. 17 pages, 15 figure
Ultrastructural Distinctions Between Treatment Responders and Non-Responders in Schizophrenia: Postmortem Studies of the Striatum
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