1,323 research outputs found
Enhancement of the superconducting transition temperature from the competition between electron-electron correlations and electron-phonon interactions
We uncover that the competition between electron-electron correlations and
electron-phonon interactions gives rise to unexpectedly huge enhancement of the
superconducting transition temperature, several hundreds percent larger (
200 K) than that of the case when only one of the two is taken into account
( 30 K). Our renormalization group analysis claims that this mechanism
for the enhancement of the critical temperature is not limited on
superconductivity but applied to various Fermi surface instabilities, proposing
an underlying universal structure, which turns out to be essentially identical
to that of a recent study [Phys. Rev. Lett. {\bf 108}, 046601 (2012)] on the
enhancement of the Kondo temperature in the presence of Rashba spin-orbit
interactions. We also discuss the stability of superconductivity against
nonmagnetic randomness
B --> pi and B --> K transitions in partially quenched chiral perturbation theory
We study the properties of the B-->pi and B-->K transition form factors in
partially quenched QCD by using the approach of partially quenched chiral
perturbation theory combined with the static heavy quark limit. We show that
the form factors change almost linearly when varying the value of the sea quark
mass, whereas the dependence on the valence quark mass contains both the
standard and chirally divergent (quenched) logarithms. A simple strategy for
the chiral extrapolations in the lattice studies with Nsea=2 is suggested. It
consists of the linear extrapolations from the realistically accessible quark
masses, first in the sea and then in the valence quark mass. From the present
approach, we estimate the uncertainty induced by such extrapolations to be
within 5%.Comment: Published versio
PIONIER: a visitor instrument for the VLTI
PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its
first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD
integrated optics combiner that can also be used in scanning mode. It provides
low spectral resolution in H and K band. PIONIER is designed for imaging with a
specific emphasis on fast fringe recording to allow closure-phases and
visibilities to be precisely measured. In this work we provide the detailed
description of the instrument and present its updated status.Comment: Proceedings of SPIE conference Optical and Infrared Interferometry II
(Conference 7734) San Diego 201
The diameter of the CoRoT target HD 49933. Combining the 3D limb darkening, asteroseismology, and interferometry
Context. The interpretation of stellar pulsations in terms of internal
structure depends on the knowledge of the fundamental stellar parameters.
Long-base interferometers permit us to determine very accurate stellar radii,
which are independent constraints for stellar models that help us to locate the
star in the HR diagram. Aims: Using a direct interferometric determination of
the angular diameter and advanced three-dimensional (3D) modeling, we derive
the radius of the CoRoT target HD 49933 and reduce the global stellar parameter
space compatible with seismic data. Methods: The VEGA/CHARA
spectro-interferometer is used to measure the angular diameter of the star. A
3D radiative hydrodynamical simulation of the surface is performed to compute
the limb darkening and derive a reliable diameter from visibility curves. The
other fundamental stellar parameters (mass, age, and Teff) are found by fitting
the large and small p-mode frequency separations using a stellar evolution
model that includes microscopic diffusion. Results: We obtain a limb-darkened
angular diameter of {\theta}LD = 0.445 \pm 0.012 mas. With the Hipparcos
parallax, we obtain a radius of R = 1.42 \pm 0.04 Rsun. The corresponding
stellar evolution model that fits both large and small frequency separations
has a mass of 1.20 \pm 0.08 Msun and an age of 2.7 Gy. The atmospheric
parameters are Teff = 6640 \pm 100 K, log g = 4.21 \pm 0.14, and [Fe/H] =
-0.38.Comment: 4 pages, 4 figure
Identification of distinct subgroups of Sj\uf6gren\u27s disease by cluster analysis based on clinical and biological manifestations: data from the cross-sectional Paris-Saclay and the prospective ASSESS cohorts
\ua9 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: Sj\uf6gren\u27s disease is a heterogenous autoimmune disease with a wide range of symptomsâincluding dryness, fatigue, and painâin addition to systemic manifestations and an increased risk of lymphoma. We aimed to identify distinct subgroups of the disease, using cluster analysis based on subjective symptoms and clinical and biological manifestations, and to compare the prognoses of patients in these subgroups. Methods: This study included patients with Sj\uf6gren\u27s disease from two independent cohorts in France: the cross-sectional Paris-Saclay cohort and the prospective Assessment of Systemic Signs and Evolution of Sj\uf6gren\u27s Syndrome (ASSESS) cohort. We first used an unsupervised multiple correspondence analysis to identify clusters within the Paris-Saclay cohort using 26 variables comprising patient-reported symptoms and clinical and biological manifestations. Next, we validated these clusters using patients from the ASSESS cohort. Changes in disease activity (measured by the European Alliance of Associations for Rheumatology [EULAR] Sj\uf6gren\u27s Syndrome Disease Activity Index [ESSDAI]), patient-acceptable symptom state (measured by the EULAR Sj\uf6gren\u27s Syndrome Patient Reported Index [ESSPRI]), and lymphoma incidence during follow-up were compared between clusters. Finally, we compared our clusters with the symptom-based subgroups previously described by Tarn and colleagues. Findings: 534 patients from the Paris-Saclay cohort (502 [94%] women, 32 [6%] men, median age 54 years [IQR 43â64]), recruited between 1999 and 2022, and 395 patients from the ASSESS cohort (370 [94%] women, 25 [6%] men, median age 53 years [43â63]), recruited between 2006 and 2009, were included in this study. In both cohorts, hierarchical cluster analysis revealed three distinct subgroups of patients: those with B-cell active disease and low symptom burden (BALS), those with high systemic disease activity (HSA), and those with low systemic disease activity and high symptom burden (LSAHS). During follow-up in the ASSESS cohort, disease activity and symptom states worsened for patients in the BALS cluster (67 [36%] of 186 patients with ESSPRI score <5 at month 60 vs 92 [49%] of 186 at inclusion; p<0\ub70001). Lymphomas occurred in patients in the BALS cluster (five [3%] of 186 patients; diagnosed a median of 70 months [IQR 42â104] after inclusion) and the HSA cluster (six [4%] of 158 patients; diagnosed 23 months [13â83] after inclusion). All patients from the Paris-Saclay cohort with a history of lymphoma were in the BALS and HSA clusters. This unsupervised clustering classification based on symptoms and clinical and biological manifestations did not correlate with a previous classification based on symptoms only. Interpretation: On the basis of symptoms and clinical and biological manifestations, we identified three distinct subgroups of patients with Sj\uf6gren\u27s disease with different prognoses. Our results suggest that these subgroups represent different heterogeneous pathophysiological disease mechanisms, stages of disease, or both. These findings could be of interest when stratifying patients in future therapeutic trials. Funding: Fondation pour la Recherche M\ue9dicale, French Ministry of Health, French Society of Rheumatology, Innovative Medicines Initiative 2 Joint Undertaking, Medical Research Council UK, and Foundation for Research in Rheumatology
Tevatron-for-LHC Report: Preparations for Discoveries
This is the "TeV4LHC" report of the "Physics Landscapes" Working Group,
focused on facilitating the start-up of physics explorations at the LHC by
using the experience gained at the Tevatron. We present experimental and
theoretical results that can be employed to probe various scenarios for physics
beyond the Standard Model.Comment: 222 pp., additional contribution added, typos/layout correcte
PIBF+ extracellular vesicles from mouse embryos affect IL-10 production by CD8+ cells
Earlier evidence suggests, that the embryo signals to the maternal immune system. Extracellular vesicles (EVs) are produced by all types of cells, and because they transport different kinds of molecules from one cell to the other, they can be considered as means of intercellular communication. The aim of this work was to test, whether the embryo is able to produce sufficient amounts of EVs to alter the function of peripheral lymphocytes. Embryo-derived EVs were identified by their Annexin V biding capacity, and sensitivity to Triton X dependent lysis, using flow cytometry. Transmission electron microscopy was used to detect EVs at the implantation site. Progesterone-induced blocking factor (PIBF) expression in embryo-derived EVs was demonstrated with immuno-electron microscopy. The % of IL-10 + murine lymphocytes was determined by flow cytometry. EVs were present in embryo culture media, but not in empty media. Mouse embryo-derived EVs adhere to the surface of both CD4+ and CD8+ murine peripheral T lymphocytes, partly, via phosphatidylserine binding. The number of IL-10+ murine peripheral CD8+ cells increases in the presence of embryo-derived EVS, and this effect is counteracted by pre-treatment of EVs with an anti-PIBF antibody, suggesting that the embryo communicates with the maternal immune system via EVs
Superconductivity in Fullerides
Experimental studies of superconductivity properties of fullerides are
briefly reviewed. Theoretical calculations of the electron-phonon coupling, in
particular for the intramolecular phonons, are discussed extensively. The
calculations are compared with coupling constants deduced from a number of
different experimental techniques. It is discussed why the A_3 C_60 are not
Mott-Hubbard insulators, in spite of the large Coulomb interaction. Estimates
of the Coulomb pseudopotential , describing the effect of the Coulomb
repulsion on the superconductivity, as well as possible electronic mechanisms
for the superconductivity are reviewed. The calculation of various properties
within the Migdal-Eliashberg theory and attempts to go beyond this theory are
described.Comment: 33 pages, latex2e, revtex using rmp style, 15 figures, submitted to
Review of Modern Physics, more information at
http://radix2.mpi-stuttgart.mpg.de/fullerene/fullerene.htm
A ten thousand frames per second readout MAPS for the EUDET beam telescope
Designed and manufactured in a commercial CMOS 0.35 ÎŒm OPTO process for equipping the EUDET beam telescope, MIMOSA26 is the first reticule size pixel sensor with digital output and integrated zero suppression. It features a matrix of pixels with 576 rows and 1152 columns, covering an active area of ~224 mm2. A single point resolution of about 4 ÎŒm was obtained with a pixel pitch of 18.4 ÎŒm. Its architecture allows a fast readout frequency of ~10 k frames/s. The paper describes the chip design, test and major characterisation outcome
Obscured Activity: AGN, Quasars, Starbursts and ULIGs observed by the Infrared Space Observatory
Some of the most active galaxies in the Universe are obscured by large
quantities of dust and emit a substantial fraction of their bolometric
luminosity in the infrared. Observations of these infrared luminous galaxies
with the Infrared Space Observatory (ISO) have provided a relatively unabsorbed
view to the sources fuelling this active emission. The improved sensitivity,
spatial resolution and spectroscopic capability of ISO over its predecessor
Infrared Astronomical Satellite (IRAS), has enabled significant advances in the
understanding of the infrared properties of active galaxies. ISO surveyed a
wide range of active galaxies which, in the context of this review, includes
those powered by intense bursts of star-formation as well as those containing a
dominant active galactic nucleus (AGN). Mid infrared imaging resolved for the
first time the dust enshrouded nuclei in many nearby galaxies, while a new era
in infrared spectroscopy was opened by probing a wealth of atomic, ionic and
molecular lines as well as broad band features in the mid and far infrared.
This was particularly useful since it resulted in the understanding of the
power production, excitation and fuelling mechanisms in the nuclei of active
galaxies including the intriguing but so far elusive ultraluminous infrared
galaxies. Detailed studies of various classes of AGN and quasars greatly
improved our understanding of the unification scenario. Far-infrared imaging
and photometry also revealed the presence of a new very cold dust component in
galaxies and furthered our knowledge of the far-infrared properties of faint
starbursts, ULIGs and quasars. We summarise almost nine years of key results
based upon ISO data spanning the full range of luminosity and type of active
galaxies.Comment: Accepted for publication in 'ISO science legacy - a compact review of
ISO major achievements', Space Science Reviews - dedicated ISO issue. To be
published by Springer in 2005. 62 pages (low resolution figures version).
Higher resolution PDFs available from
http://users.physics.uoc.gr/~vassilis/papers/VermaA.pdf or
http://www.iso.vilspa.esa.es/science/SSR/Verma.pd
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