530 research outputs found
Superconducting ground state study of valence skip compound AgSnSe
The valence-skipped superconductors are natural candidates for unconventional
superconductivity, as they can exhibit a negative effective, attractive
interaction for electron-pairing. This work reports comprehensive XRD,
magnetization, specific heat and muon spin rotation and relaxation measurements
(SR) on a valence-skipped compound: AgSnSe. The temperature dependence
of the electronic specific heat () and of the upper critical field
() provide evidence of two-gap superconductivity, which is also
confirmed by our transverse-field SR measurements. Our zero-field SR
measurements suggest preserved time-reversal symmetry in the superconducting
ground state of AgSnSe.Comment: 8 pages, 6 figure
EDGE: The direct link between mass growth history and the extended stellar haloes of the faintest dwarf galaxies
Ultra-faint dwarf galaxies (UFDs) are commonly found in close proximity to
the Milky Way and other massive spiral galaxies. As such, their projected
stellar ellipticity and extended light distributions are often thought to owe
to tidal forces. In this paper, we study the projected stellar ellipticities
and faint stellar outskirts of tidally isolated ultra-faints drawn from the
'Engineering Dwarfs at Galaxy Formation's Edge' (EDGE) cosmological simulation
suite. Despite their tidal isolation, our simulated dwarfs exhibit a wide range
of projected ellipticities (), with many possessing
anisotropic extended stellar haloes that mimic tidal tails, but owe instead to
late-time accretion of lower mass companions. Furthermore, we find a strong
causal relationship between ellipticity and formation time of an UFD, which is
robust to a wide variation in the feedback model. We show that the distribution
of projected ellipticities in our suite of simulated EDGE dwarfs matches well
with that of 21 Local Group dwarf galaxies. Given the ellipticity in EDGE
arises from an ex-situ accretion origin, the agreement in shape indicates the
ellipticities of some observed dwarfs may also originate from a similar
non-tidal scenario. The orbital parameters of these observed dwarfs further
support that they are not currently tidally disrupting. If the baryonic content
in these galaxies is still tidally intact, then the same may be true for their
dark matter content, making these galaxies in our Local Group pristine
laboratories for testing dark matter and galaxy formation models.Comment: 10 pages, 4 figures; submitted to MNRA
Radiation hardness qualification of PbWO4 scintillation crystals for the CMS Electromagnetic Calorimeter
This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2010 IOPEnsuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered
Successful treatment of recalcitrant cutaneous sarcoidosis with fumaric acid esters
BACKGROUND: Sarcoidosis is a multisystem disease of unknown origin characterized by the formation of noncaseating granulomas, in particular in the lungs, lymph nodes, eyes, and skin. Systemic treatment for cutaneous sarcoidosis can be used for large disfiguring lesions, generalized involvement, or recalcitrant lesions that did not respond to topical therapy. CASE PRESENTATIONS: We report three patients with recalcitrant cutaneous sarcoidosis who were treated with oral fumaric acid esters (FAE). Three female patients presented with cutaneous sarcoidosis that have proved to be refractory to various therapies, including corticosteroids and chloroquine. We treated the patients with FAE in tablet form using two formulations differing in strength (Fumaderm(® )initial, Fumaderm(®)). Dosage of FAE was performed according to the standard therapy regimen for psoriasis patients. After treatment with FAE (4–12 months), a complete clearance of skin lesions was achieved in the three patients. The side effects observed in this trial correspond to the well-known spectrum of adverse effects of FAE (flush, minor gastrointestinal complaints, lymphopenia). CONCLUSIONS: On the basis of our findings FAE therapy seems to be a safe and effective regimen for patients with recalcitrant cutaneous sarcoidosis. Nevertheless further investigations are necessary to confirm our preliminary results
The Double Star Plasma Electron and Current Experiment
The Double Star Project is a collaboration between Chinese and European space agencies, in which two Chinese magnetospheric research spacecraft, carrying Chinese and European instruments, have been launched into equatorial (on 29 December 2003) and polar (on 25 July 2004) orbits designed to enable complementary studies with the Cluster spacecraft. The two Double Star spacecraft TC-1 and TC-2 each carry a Double Star Plasma Electron and Current Experiment (PEACE) instrument. These two instruments were based on Cluster Flight Spare equipment, but differ from Cluster instruments in two important respects. Firstly, a Double Star PEACE instrument has only a single sensor, which must be operated in a manner not originally envisaged in the Cluster context in order to sample the full range of energies. Secondly, the DPU hardware was modified and major changes of onboard software were implemented, most notably a completely different approach to data compression has been adopted for Double Star, which allows high resolution 3-dimensional distributions to be transmitted almost every spin, a significant improvement over Cluster. This paper describes these instruments, and includes examples of data collected in various magnetospheric regions encountered by the spacecraft which have been chosen to illustrate the power of combined Double Star and Cluster measurements
Intercalibration of the barrel electromagnetic calorimeter of the CMS experiment at start-up
Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated
Smaller than expected bright-spot offsets in Spitzer phase curves of the hot Jupiter Qatar-1b
We present \textit{Spitzer} full-orbit thermal phase curves of the hot
Jupiter Qatar-1b, a planet with the same equilibrium temperature---and
intermediate surface gravity and orbital period---as the well-studied planets
HD 209458b and WASP-43b. We measure secondary eclipse of at
m and at m, corresponding to dayside
brightness temperatures of ~K and ~K,
respectively, consistent with a vertically isothermal dayside. The respective
nightside brightness temperatures are ~K and
~K, in line with a trend that hot Jupiters all have similar
nightside temperatures. We infer a Bond albedo of and a
moderate day-night heat recirculation efficiency, similar to HD 209458b.
General circulation models for HD 209458b and WASP-43b predict that their
bright-spots should be shifted east of the substellar point by tens of degrees,
and these predictions were previously confirmed with \textit{Spitzer}
full-orbit phase curve observations. The phase curves of Qatar-1b are likewise
expected to exhibit eastward offsets. Instead, the observed phase curves are
consistent with no offset: at m and
at m. The discrepancy in circulation
patterns between these three otherwise similar planets points to the importance
of secondary parameters like rotation rate and surface gravity, and the
presence or absence of clouds, in determining atmospheric conditions on hot
Jupiters.Comment: 14 pages, 8 figures. Accepted for publication in A
EDGE: The direct link between mass growth history and the extended stellar haloes of the faintest dwarf galaxies
Ultra-faint dwarf galaxies (UFDs) are commonly found in close proximity to the Milky Way and other massive spiral galaxies. As such, their projected stellar ellipticity and extended light distributions are often thought to owe to tidal forces. In this paper, we study the projected stellar ellipticities and faint stellar outskirts of tidally isolated ultra-faints drawn from the ‘Engineering Dwarfs at Galaxy Formation’s Edge’ (EDGE) cosmological simulation suite. Despite their tidal isolation, our simulated dwarfs exhibit a wide range of projected ellipticities (0.03 < ε < 0.85), with many possessing anisotropic extended stellar haloes that mimic tidal tails, but owe instead to late-time accretion of lower mass companions. Furthermore, we find a strong causal relationship between ellipticity and formation time of a UFD, which is robust to a wide variation in the feedback model. We show that the distribution of projected ellipticities in our suite of simulated EDGE dwarfs matches well with a sample of 19 Local Group dwarf galaxies and a sample of 11 isolated dwarf galaxies. Given ellipticity in EDGE arises from an ex-situ accretion origin, the agreement in shape indicates the ellipticities of some observed dwarfs may also originate from a non-tidal scenario. The orbital parameters of these observed dwarfs further support that they are not currently tidally disrupting. If the baryonic content in these galaxies is still tidally intact, then the same may be true for their dark matter content, making these galaxies in our Local Group pristine laboratories for testing dark matter and galaxy formation models
X-ray emission from the Sombrero galaxy: discrete sources
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival
Chandra observations with a total exposure of ~200 ks. With a detection limit
of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30
kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler
et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS
observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray
binaries (LMXBs). We quantify the differential luminosity functions (LFs) for
both the detected GC and field LMXBs, whose power-low indices (~1.1 for the
GC-LF and ~1.6 for field-LF) are consistent with previous studies for
elliptical galaxies. With precise sky positions of the GCs without a detected
X-ray source, we further quantify, through a fluctuation analysis, the GC LF at
fainter luminosities down to 1E35 erg/s. The derived index rules out a
faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent
findings in several elliptical galaxies and the bulge of M31. On the other
hand, the 2-6 keV unresolved emission places a tight constraint on the field
LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101
sources in the halo of Sombrero. The presence of these sources cannot be
interpreted as galactic LMXBs whose spatial distribution empirically follows
the starlight. Their number is also higher than the expected number of cosmic
AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray
surveys. We suggest that either the cosmic X-ray background is unusually high
in the direction of Sombrero, or a distinct population of X-ray sources is
present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
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