839 research outputs found
Exploration of the BaSeL stellar library for 9 F-type stars COROT potential targets
The Basel Stellar Library (BaSeL models) is constituted of the merging of
various synthetic stellar spectra libraries, with the purpose of giving the
most comprehensive coverage of stellar parameters. It has been corrected for
systematic deviations detected in respect to UBVRIJHKLM photometry at solar
metallicity, and can then be considered as the state-of-the-art knowledge of
the broad band content of stellar spectra. In this paper, we consider a sample
of 9 F-type stars with detailed spectroscopic analysis to investigate the Basel
Stellar Library in two photometric systems simultaneously, Johnson (B-V, U-B)
and Stromgren (b-y, m_1, and c_1). The sample corresponds to potential targets
of the central seismology programme of the COROT space experiment, which have
been recently observed at OHP. The atmospheric parameters T_eff, [Fe/H], and
log g obtained from the BaSeL models are compared with spectroscopic
determinations as well as with results of other photometric calibrations. For a
careful interpretation of the BaSeL solutions, we computed confidence regions
around the best ^2-estimates and projected them on T_eff-[Fe/H],
T_eff-log g, and log g-[Fe/H] diagrams. (Abridged)Comment: 16 pages, LaTeX2e; version accepted for publication in the new A&A
Journal: minor changes + figures in black and white for better readabilit
Uncertainty-principle noise in vacuum-tunneling transducers
The fundamental sources of noise in a vacuum-tunneling probe used as an
electromechanical transducer to monitor the location of a test mass are
examined using a first-quantization formalism. We show that a tunneling
transducer enforces the Heisenberg uncertainty principle for the position and
momentum of a test mass monitored by the transducer through the presence of two
sources of noise: the shot noise of the tunneling current and the momentum
fluctuations transferred by the tunneling electrons to the test mass. We
analyze a number of cases including symmetric and asymmetric rectangular
potential barriers and a barrier in which there is a constant electric field.
Practical configurations for reaching the quantum limit in measurements of the
position of macroscopic bodies with such a class of transducers are studied
New frontiers at the interface of general relativity and quantum optics
In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel\u27s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose-Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall. © 2009 Springer Science+Business Media B.V
Evaluation of C-reactive protein and its kinetics as a prognostic indicator in canine leptospirosis.
OBJECTIVE
To evaluate C-reactive protein at presentation and during hospitalisation in dogs with acute kidney injury resulting from leptospirosis to compare C-reactive protein at presentation in dogs with acute kidney injury of different aetiology and to study its correlation with markers of inflammation, azotaemia and survival.
MATERIALS AND METHODS
Prospective observational study of 41 dogs with acute kidney injury secondary to leptospirosis and 15 control dogs with acute kidney injury of different aetiology. C-reactive protein was measured at presentation in both groups and daily for 7 days in a subgroup of 28 dogs with leptospirosis. The associations of C-reactive protein with neutrophil count, albumin, urea, creatinine and survival were analysed.
RESULTS
C-reactive protein was increased at presentation in all dogs with leptospirosis but was not significantly different from dogs with acute kidney injury of different cause. It was associated with markers of inflammation (neutrophil count, albumin) but not with azotaemia (creatinine, urea). It decreased gradually from presentation to day 4, with significantly lower concentrations in survivors than non-survivors. Initial C-reactive protein was only weakly associated with outcome, but its average concentration from presentation to day 2 was more strongly associated. Absolute and relative changes in C-reactive protein during hospitalisation and creatinine at presentation were not associated with survival.
CLINICAL SIGNIFICANCE
Serial assessment of C-reactive protein may improve outcome prediction in dogs with leptospirosis compared with a single measurement at presentation or with markers of renal function
The Evolution of Massive Stars. I. Red Supergiants in the Magellanic Clouds
We investigate the red supergiant (RSG) content of the SMC and LMC using
multi-object spectroscopy on a sample of red stars previously identified by
{\it BVR} CCD photometry. We obtained high accuracy ( km s) radial
velocities for 118 red stars seen towards the SMC and 167 red stars seen
towards the LMC, confirming most of these (89% and 95%, respectively) as red
supergiants (RSGs). Spectral types were also determined for most of these RSGs.
We find that the distribution of spectral types is skewed towards earlier type
at lower metallicities: the average (median) spectral type is K5-7 I in the
SMC, M1 I in the LMC, and M2 I in the Milky Way. We argue that RSGs in the
Magellanic Clouds are 100deg (LMC) and 300deg (SMC) cooler than Galactic RSGs
of the same spectral type. We compare the distribution of RSGs in the H-R
diagram to that of various stellar evolutionary models; we find that none of
the models produce RSGs as cool and luminous as what is actually observed. In
all of our H-R diagrams, however, there is an elegant sequence of decreasing
effective temperatures with increasing luminosities; explaining this will be an
important test of future stellar evolutionary models.Comment: Version with eps figures embedded can be obtained from
ftp://ftp.lowell.edu/pub/massey/rsgs.ps.gz Accepted by the Astronomical
Journa
The age of the oldest globular clusters
The age of three of the oldest clusters -- M15, M68, M92 -- has been
redetermined. We use the latest EOS and opacity data available for calculating
both isochrones and zero age horizontal branches and employ the brightness
difference between turn-off and horizontal branch to determine the cluster age.
Our best ages for all three clusters are about 13 Gyr, and even smaller ages
are possible. Our results help to reconcile cluster ages with recent results on
the age of the universe determined from the Hubble constant.Comment: submitted to The Astrophysical Journal Letter
Treatment of ovarian cancer with surgery, short-course chemotherapy and whole abdominal radiation
Background The primary aim was to induce a high number of pCR in early (FIGO IC, JIB + C)-and advanced (FIGO ffl—IV)—stage ovarian cancer with a surgery plus 4 cycles of cisplatin and meiphalan (PAMP) regimen. The second objective was to prevent relapse with WAR in patients in remission after chemotherapy. Patients and methods 218 eligible patients were treated after staging laparotomy with cisplatin 80 mg/sqm iv. on day 1 and melphalan 12 mg/sqm i.v. on day 2 q 4 weeks. Response was verified by second-look laparotomy. WAR was carried out with the open field technique on a linear accele rator (daily dose: 1.3 Gy, total dose: 29.9 Gy) in patients with pathological or clinicaJ CR or pathological PR with microscopical residual disease. Results 146/218 patients (67%, 95% CI: 61%-73%) responded to PAMIP: 56 (26%) achieved pCR, 24 (11%), cCR, 56 (26%) pPR and 10 (5%) cPR (c=clinical, p=pathological). Multivariate analyses revealed that in advanced stages (92 cases in remission), the achievement of pCR was the most important factor for longer time to failure (TIF) and survival. Only 5 1/118 (43%) patients in remission received WAR Early-stage patients <=55 years were more likely to have WAR than patients older than 55 years (77% vs. 23%; p= 0.02). Advanced-stage patients with cCR were less likely to be irradiated than patients with pCR or pPR (10% vs. 51%; p= 0.003). Toxicity of PAMP was acceptable with 10% of WHO grade 4 hematologic toxicity. Acute hematological toxicity of WAR caused interruption (3 3%) or incompleteness (3 3%) of irradiation in the majority of patients. Conclusions PAMP is an effective treatment for advanced ovarian cancer with a 67% response rate after 4 cycles. For the majority of patients in remission, WAR as a consolidation treatment was hardly feasible. For these patients new treatment modalities to consolidate remission are neede
The Kinematics of Thick Disks in External Galaxies
We present kinematic measurements of the thick and thin disks in two edge-on
galaxies. We have derived stellar rotation curves at and above the galaxies'
midplanes using Ca II triplet features measured with the GMOS spectrograph on
Gemini North. In one galaxy, FGC 1415, the kinematics above the plane show
clear rotation that lags that of the midplane by ~20-50%, similar to the
behavior seen in the Milky Way. However, the kinematics of the second galaxy,
FGC 227, are quite different. The rotation above the plane is extremely slow,
showing <25% of the rotation speed of the stars at the midplane. We decompose
the observed rotation curves into a superposition of thick and thin disk
kinematics, using 2-dimensional fits to the galaxy images to determine the
fraction of thick disk stars at each position. We find that the thick disk of
FGC 1415 rotates at 30-40% of the rotation speed of the thin disk. In contrast,
the thick disk of FGC 227 is very likely counter-rotating, if it is rotating at
all. These observations are consistent with the velocity dispersion profiles we
measure for each galaxy. The detection of counter-rotating thick disks
conclusively rules out models where the thick disk forms either during
monolithic collapse or from vertical heating of a previous thin disk. Instead,
the data strongly support models where the thick disk forms from direct
accretion of stars from infalling satellites.Comment: 13 pages, 10 figures. Accepted for publication in Ap
The Star Formation Epoch of the Most Massive Early-Type Galaxies
We present new Keck spectroscopy of early-type galaxies in three galaxy
clusters at z~0.5. We focus on the fundamental plane (FP) relation, and combine
the kinematics with structural parameters determined from HST images. The
galaxies obey clear FP relations, which are offset from the FP of the nearby
Coma cluster due to passive evolution of the stellar populations. The z~0.5
data are combined with published data for 11 additional clusters at
0.18<z<1.28, to determine the evolution of the mean M/L(B) ratio of cluster
galaxies with masses M>10^11 M_sun, as implied by the FP. We find
dlog(M/L(B))/dz = -0.555+-0.042, stronger evolution than was previously
inferred from smaller samples. The observed evolution depends on the
luminosity-weighted mean age of the stars in the galaxies, the initial mass
function (IMF), selection effects due to progenitor bias, and other parameters.
Assuming a normal IMF but allowing for various other sources of uncertainty we
find z* = 2.01+-0.20 for the luminosity-weighted mean star formation epoch. The
main uncertainty is the slope of the IMF in the range 1-2 Solar masses: we find
z* = 4.0 for a top-heavy IMF with slope x=0. The M/L(B) ratios of the cluster
galaxies are compared to those of recently published samples of field
early-type galaxies at 0.32<z<1.14. Assuming that progenitor bias and the IMF
do not depend on environment we find that the present-day age of stars in
massive field galaxies is 4.1 +- 2.0 % (~0.4 Gyr) less than that of stars in
massive cluster galaxies, consistent with most, but not all, previous studies
of local and distant early-type galaxies. This relatively small age difference
is surprising in the context of expectations from ``standard'' hierarchical
galaxy formation models. [ABRIDGED]Comment: Accepted for publication in ApJ. Minor corrections to match published
versio
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