1,368 research outputs found
Are group- and cluster-scale dark matter halos over-concentrated?
We investigate the relationship between the halo mass, M_200, and
concentration, c, for a sample of 26 group- and cluster-scale strong
gravitational lenses. In contrast with previous results, we find that these
systems are only ~ 0.1 dex more over-concentrated than similar-mass halos from
dark matter simulations; the concentration of a halo with M_200 = 10^14 M_sun
is log c = 0.78\pm0.05, while simulations of halos with this mass at similar
redshifts (z ~ 0.4) predict log c ~ 0.56 - 0.71. We also find that we are
unable to make informative inference on the slope of the M_200-c relation in
spite of our large sample size; we note that the steep slopes found in previous
studies tend to follow the slope in the covariance between M_200 and c,
indicating that these results may be measuring the scatter in the data rather
than the intrinsic signal. Furthermore, we conclude that our inability to
constrain the M_200-c slope is due to a limited range of halo masses, as
determined by explicitly modelling our halo mass distribution, and we suggest
that other studies may be producing biased results by using an incorrect
distribution for their halo masses.Comment: 8 pages; accepted to MNRA
Autoantibodies to BRAF, a new family of autoantibodies associated with rheumatoid arthritis
International audienceBRAF (v raf murine sarcoma viral oncogene homologue B1) is a serine-threonine kinase involved in the mitogen-activated protein kinase (MAPK) signalling pathway, known to be implicated in the production of pro-inflammatory cytokines.We have observed that sera from rheumatoid arthritis (RA) patients recognize the BRAF's catalytic domain, which encompasses amino acids 416 to 766. Here, we identify peptide targets of anti-BRAF autoantibodies and test whether anti-BRAF autoantibodies may interfere with BRAF kinase activity.METHODS:Anti-BRAF autoantibodies were detected by ELISA (enzyme-linked immunosorbent assay) in the serum of RA patients and controls, using 40 overlapping 20mer peptides encompassing the catalytic domain of BRAF as immunosorbents. To test whether autoantibodies to BRAF influence BRAF kinase activity, we developed an in vitro phosphorylation assay of MEK1 (mitogen extracellular regulated kinase), a major BRAF substrate. MEK1 phosphorylation by BRAF was tested in the presence of purified anti-BRAF autoantibodies from RA patients or control antibody.RESULTS:We found that one BRAF peptide, P25 (656 to 675), is specifically recognized by autoantibodies from RA patients. Of interest, anti-P25 autoantibodies are detected in 21% of anti-CCP (cyclic citrullinated peptides) negative RA patients. Anti-BRAF autoantibodies activate the in vitro phosphorylation of MEK1 mediated by BRAF.CONCLUSIONS:Anti-BRAF autoantibodies from RA patients preferentially recognize one BRAF peptide: P25. Autoantibody responses to P25 are detected in 21% of anti-CCP negative RA patients. Most anti-BRAF autoantibodies activate BRAF kinase activity
Partition du plan temps-fréquence et réallocation
Le problème que nous abordons est celui du découpage du plan temps-fréquence en vue d'obtenir une description simplifiée d'un signal multicomposante qui rende possible l'extraction de chacune de ses composantes et leur reconstruction. La solution proposée s'appuie sur une nouvelle extension de la méthode de réallocation, qui permet très naturellement d'extraire les différentes composantes à l'aide d'une technique de classification non supervisée. L'originalité de ce travail réside dans la manière dont on extrait l'information qui sert à construire la partition. A cette fin, on utilise non pas la distribution temps-fréquence elle-même, mais le champ de ses vecteurs de réallocation, ce qui apporte aussi un nouvel éclairage sur la question de ce qu'est une composante d'un signal
Composition of UHECR and the Pierre Auger Observatory Spectrum
We fit the recently published Pierre Auger ultra-high energy cosmic ray
spectrum assuming that either nucleons or nuclei are emitted at the sources. We
consider the simplified cases of pure proton, or pure oxygen, or pure iron
injection. We perform an exhaustive scan in the source evolution factor, the
spectral index, the maximum energy of the source spectrum Z E_{max}, and the
minimum distance to the sources. We show that the Pierre Auger spectrum agrees
with any of the source compositions we assumed. For iron, in particular, there
are two distinct solutions with high and low E_{max} (e.g. 6.4 10^{20} eV and 2
10^{19} eV) respectively which could be distinguished by either a large
fraction or the near absence of proton primaries at the highest energies. We
raise the possibility that an iron dominated injected flux may be in line with
the latest composition measurement from the Pierre Auger Observatory where a
hint of heavy element dominance is seen.Comment: 19 pages, 6 figures (33 panels)- Uses iopart.cls and iopart12.clo- In
version 2: addition of a few sentences and two reference
Testing a simple recipe for estimating galaxy masses from minimal observational data
The accuracy and robustness of a simple method to estimate the total mass
profile of a galaxy is tested using a sample of 65 cosmological
zoom-simulations of individual galaxies. The method only requires information
on the optical surface brightness and the projected velocity dispersion
profiles and therefore can be applied even in case of poor observational data.
In the simulated sample massive galaxies ( \kms) at
redshift have almost isothermal rotation curves for broad range of radii
(RMS for the circular speed deviations from a constant value over
). For such galaxies the method recovers the
unbiased value of the circular speed. The sample averaged deviation from the
true circular speed is less than with the scatter of
(RMS) up to . Circular speed estimates of massive
non-rotating simulated galaxies at higher redshifts ( and ) are also
almost unbiased and with the same scatter. For the least massive galaxies in
the sample ( \kms) at the RMS deviation is
and the mean deviation is biased low by about . We also derive the
circular velocity profile from the hydrostatic equilibrium (HE) equation for
hot gas in the simulated galaxies. The accuracy of this estimate is about RMS
for massive objects () and the HE
estimate is biased low by , which can be traced to the presence of
gas motions. This implies that the simple mass estimate can be used to
determine the mass of observed massive elliptical galaxies to an accuracy of
and can be very useful for galaxy surveys.Comment: 15 pages, 14 figures, 1 tabl
From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors
The Ettore Majorana paper - Theory of incomplete P triplets- published in
1931, focuses on the role of selection rules for the non-radiative decay of two
electron excitations in atomic spectra, involving the configuration interaction
between discrete and continuum channels. This work is a key step for
understanding the 1935 work of Ugo Fano on the asymmetric lineshape of two
electron excitations and the 1958 Herman Feshbach paper on the shape resonances
in nuclear scattering arising from configuration interaction between many
different scattering channels. The Feshbach resonances are today of high
scientific interest in many different fields and in particular for ultracold
gases and high Tc superconductivity.Comment: 13 pages, 7 figures. Journal of Superconductivity and Novel Magnetism
to be publishe
Investigation of the 6He cluster structures
The 4He+2n and t+t clustering of the 6He ground state were investigated by
means of the transfer reaction 6He(p,t)4He at 25 MeV/nucleon. The experiment
was performed in inverse kinematics at GANIL with the SPEG spectrometer coupled
to the MUST array. Experimental data for the transfer reaction were analyzed by
a DWBA calculation including the two neutrons and the triton transfer. The
couplings to the 6He --> 4He + 2n breakup channels were taken into account with
a polarization potential deduced from a coupled-discretized-continuum channels
analysis of the 6He+1H elastic scattering measured at the same time. The
influence on the calculations of the 4He+t exit potential and of the triton
sequential transfer is discussed. The final calculation gives a spectroscopic
factor close to one for the 4He+2n configuration as expected. The spectroscopic
factor obtained for the t+t configuration is much smaller than the theoretical
predictions.Comment: 10 pages, 11 figures, accepted in PR
The Sloan Lens ACS Survey. VII. Elliptical Galaxy Scaling Laws from Direct Observational Mass Measurements
We use a sample of 53 massive early-type strong gravitational lens galaxies
with well-measured redshifts (ranging from z=0.06 to 0.36) and stellar velocity
dispersions (between 175 and 400 km/s) from the Sloan Lens ACS (SLACS) Survey
to derive numerous empirical scaling relations. The ratio between central
stellar velocity dispersion and isothermal lens-model velocity dispersion is
nearly unity within errors. The SLACS lenses define a fundamental plane (FP)
that is consistent with the FP of the general population of early-type
galaxies. We measure the relationship between strong-lensing mass M_lens within
one-half effective radius (R_e/2) and the dimensional mass variable M_dim =
G^-1 sigma_e2^2 R_e/2 to be log_10 [M_lens/10^11 M_Sun] = (1.03 +/- 0.04)
log_10 [M_dim/10^11 M_Sun] + (0.54 +/- 0.02) (where sigma_e2 is the projected
stellar velocity dispersion within R_e/2). The near-unity slope indicates that
the mass-dynamical structure of massive elliptical galaxies is independent of
mass, and that the "tilt" of the SLACS FP is due entirely to variation in total
(luminous plus dark) mass-to-light ratio with mass. Our results imply that
dynamical masses serve as a good proxies for true masses in massive elliptical
galaxies. Regarding the SLACS lenses as a homologous population, we find that
the average enclosed 2D mass profile goes as log_10 [M(<R)/M_dim] = (1.10 +/-
0.09) log_10 [R/R_e] + (0.85 +/- 0.03), consistent with an isothermal (flat
rotation curve) model when de-projected into 3D. This measurement is
inconsistent with the slope of the average projected aperture luminosity
profile at a confidence level greater than 99.9%, implying a minimum
dark-matter fraction of f_DM = 0.38 +/- 0.07 within one effective radius.
(abridged)Comment: 13 pages emulateapj; accepted for publication in the Ap
Report on the first round of the Mock LISA Data Challenges
The Mock LISA Data Challenges (MLDCs) have the dual purpose of fostering the
development of LISA data analysis tools and capabilities, and demonstrating the
technical readiness already achieved by the gravitational-wave community in
distilling a rich science payoff from the LISA data output. The first round of
MLDCs has just been completed: nine data sets containing simulated
gravitational wave signals produced either by galactic binaries or massive
black hole binaries embedded in simulated LISA instrumental noise were released
in June 2006 with deadline for submission of results at the beginning of
December 2006. Ten groups have participated in this first round of challenges.
Here we describe the challenges, summarise the results, and provide a first
critical assessment of the entries.Comment: Proceedings report from GWDAW 11. Added author, added reference,
clarified some text, removed typos. Results unchanged; Removed author, minor
edits, reflects submitted versio
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