324 research outputs found
Multi-site campaign on the open cluster M67. I. Observations and photometric reductions
We report on an ambitious multi-site campaign aimed at detecting stellar
variability, particularly solar-like oscillations, in the red giant stars in
the open cluster M67 (NGC 2682). During the six-week observing run, which
comprised 164 telescope nights, we used nine 0.6-m to 2.1-m class telescopes
located around the world to obtain uninterrupted time-series photometry. We
outline here the data acquisition and reduction, with emphasis on the
optimisation of the signal-to-noise of the low amplitude (50-500 micromag)
solar-like oscillations. This includes a new and efficient method for obtaining
the linearity profile of the CCD response at ultra high precision (~10 parts
per million). The noise in the final time series is 0.50 mmag per minute
integration for the best site, while the noise in the Fourier spectrum of all
sites combined is 20 micromag. In addition to the red giant stars, this data
set proves to be very valuable for studying high-amplitude variable stars such
as eclipsing binaries, W UMa systems and delta Scuti stars.Comment: 12 pages, 13 figures, accepted by MNRA
Multisite campaign on the open cluster M67. III. Delta Scuti pulsations in the blue stragglers
We have made an asteroseismic analysis of the variable blue stragglers in the
open cluster M67. The data set consists of photometric time series from eight
sites using nine 0.6-2.1 meter telescopes with a time baseline of 43 days. In
two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41
and 26) detected in delta Scuti stars belonging to a stellar cluster, and EW
Cnc has the second highest number of frequencies detected in any delta Scuti
star. We have computed a grid of pulsation models that take the effects of
rotation into account. The distribution of observed and theoretical frequencies
show that in a wide frequency range a significant fraction of the radial and
non-radial low-degree modes are excited to detectable amplitudes. Despite the
large number of observed frequencies we cannot constrain the fundamental
parameters of the stars. To make progress we need to identify the degrees of
some of the modes either from multi-colour photometry or spectroscopy.Comment: 15 pages, 14 figs, one appendix. Part three in a series of papers
describing results from an extensive multi-site campaign on the open cluster
M6
A meta‐analysis of change in applicants' perceptions of fairness
Using an event‐triggered multi‐stage framework, this random‐effects meta‐analysis examined the changes in applicants' perceptions of fairness between consecutive stages and throughout the entire personnel selection process. We integrated findings of studies with at least two measurement points, resulting in 45 effect sizes (overall N = 3,038). Trajectories of perceptions of fairness decreased nonlinearly across the process, with a steeper decrease for people who held high levels of initial fairness expectations. Unjust treatment produced a decrease in perceptions of fairness from pretest to posttest and an increase from posttest to postdecision. Furthermore, the length of the time interval moderated the changes in fairness perceptions between the posttest and postdecision stage. Practical implications and an agenda for future research are discussed
Asteroseismology of Eclipsing Binary Stars in the Kepler Era
Eclipsing binary stars have long served as benchmark systems to measure
fundamental stellar properties. In the past few decades, asteroseismology - the
study of stellar pulsations - has emerged as a new powerful tool to study the
structure and evolution of stars across the HR diagram. Pulsating stars in
eclipsing binary systems are particularly valuable since fundamental properties
(such as radii and masses) can determined using two independent techniques.
Furthermore, independently measured properties from binary orbits can be used
to improve asteroseismic modeling for pulsating stars in which mode
identifications are not straightforward. This contribution provides a review of
asteroseismic detections in eclipsing binary stars, with a focus on space-based
missions such as CoRoT and Kepler, and empirical tests of asteroseismic scaling
relations for stochastic ("solar-like") oscillations.Comment: 28 pages, 12 figures, 2 tables; Proceedings of the AAS topical
conference "Giants of Eclipse" (AASTCS-3), July 28 - August 2 2013, Monterey,
C
Kepler observations of variability in B-type stars
The analysis of the light curves of 48 B-type stars observed by Kepler is
presented. Among these are 15 pulsating stars, all of which show low
frequencies characteristic of SPB stars. Seven of these stars also show a few
weak, isolated high frequencies and they could be considered as SPB/beta Cep
hybrids. In all cases the frequency spectra are quite different from what is
seen from ground-based observations. We suggest that this is because most of
the low frequencies are modes of high degree which are predicted to be unstable
in models of mid-B stars. We find that there are non-pulsating stars within the
beta Cep and SPB instability strips. Apart from the pulsating stars, we can
identify stars with frequency groupings similar to what is seen in Be stars but
which are not Be stars. The origin of the groupings is not clear, but may be
related to rotation. We find periodic variations in other stars which we
attribute to proximity effects in binary systems or possibly rotational
modulation. We find no evidence for pulsating stars between the cool edge of
the SPB and the hot edge of the delta Sct instability strips. None of the stars
show the broad features which can be attributed to stochastically-excited modes
as recently proposed. Among our sample of B stars are two chemically peculiar
stars, one of which is a HgMn star showing rotational modulation in the light
curve.Comment: 19 pages, 11 figures, 4 table
Meta-analysis of genome-wide association studies of asthma in ethnically diverse North American populations.
Asthma is a common disease with a complex risk architecture including both genetic and environmental factors. We performed a meta-analysis of North American genome-wide association studies of asthma in 5,416 individuals with asthma (cases) including individuals of European American, African American or African Caribbean, and Latino ancestry, with replication in an additional 12,649 individuals from the same ethnic groups. We identified five susceptibility loci. Four were at previously reported loci on 17q21, near IL1RL1, TSLP and IL33, but we report for the first time, to our knowledge, that these loci are associated with asthma risk in three ethnic groups. In addition, we identified a new asthma susceptibility locus at PYHIN1, with the association being specific to individuals of African descent (P = 3.9 × 10(-9)). These results suggest that some asthma susceptibility loci are robust to differences in ancestry when sufficiently large samples sizes are investigated, and that ancestry-specific associations also contribute to the complex genetic architecture of asthma
Voreloxin, a first-in-class anticancer quinolone derivative, acts synergistically with cytarabine in vitro and induces bone marrow aplasia in vivo
Exposure to Moderate Air Pollution during Late Pregnancy and Cord Blood Cytokine Secretion in Healthy Neonates
Ambient air pollution can alter cytokine concentrations as shown in vitro and following short-term exposure to high air pollution levels in vivo. Exposure to pollution during late pregnancy has been shown to affect fetal lymphocytic immunophenotypes. However, effects of prenatal exposure to moderate levels of air pollutants on cytokine regulation in cord blood of healthy infants are unknown.
In a birth cohort of 265 healthy term-born neonates, we assessed maternal exposure to particles with an aerodynamic diameter of 10 µm or less (PM₁₀), as well as to indoor air pollution during the last trimester, specifically the last 21, 14, 7, 3 and 1 days of pregnancy. As a proxy for traffic-related air pollution, we determined the distance of mothers' homes to major roads. We measured cytokine and chemokine levels (MCP-1, IL-6, IL-10, IL-1ß, TNF-α and GM-CSF) in cord blood serum using LUMINEX technology. Their association with pollution levels was assessed using regression analysis, adjusted for possible confounders.
Mean (95%-CI) PM₁₀ exposure for the last 7 days of pregnancy was 18.3 (10.3-38.4 µg/m³). PM₁₀ exposure during the last 3 days of pregnancy was significantly associated with reduced IL-10 and during the last 3 months of pregnancy with increased IL-1ß levels in cord blood after adjustment for relevant confounders. Maternal smoking was associated with reduced IL-6 levels. For the other cytokines no association was found.
Our results suggest that even naturally occurring prenatal exposure to moderate amounts of indoor and outdoor air pollution may lead to changes in cord blood cytokine levels in a population based cohort
KIC 3858884: a hybrid {\delta} Sct pulsator in a highly eccentric eclipsing binary
The analysis of eclipsing binaries containing non-radial pulsators allows: i)
to combine two different and independent sources of information on the internal
structure and evolutionary status of the components, and ii) to study the
effects of tidal forces on pulsations. KIC 3858884 is a bright Kepler target
whose light curve shows deep eclipses, complex pulsation patterns with
pulsation frequencies typical of {\delta} Sct, and a highly eccentric orbit. We
present the result of the analysis of Kepler photometry and of high resolution
phaseresolved spectroscopy. Spectroscopy yielded both the radial velocity
curves and, after spectral disentangling, the primary component effective
temperature and metallicity, and line-of-sight projected rotational velocities.
The Kepler light curve was analyzed with an iterative procedure devised to
disentangle eclipses from pulsations which takes into account the visibility of
the pulsating star during eclipses. The search for the best set of binary
parameters was performed combining the synthetic light curve models with a
genetic minimization algorithm, which yielded a robust and accurate
determination of the system parameters. The binary components have very similar
masses (1.88 and 1.86 Msun) and effective temperatures (6800 and 6600 K), but
different radii (3.45 and 3.05 Rsun). The comparison with the theoretical
models evidenced a somewhat different evolutionary status of the components and
the need of introducing overshooting in the models. The pulsation analysis
indicates a hybrid nature of the pulsating (secondary) component, the
corresponding high order g-modes might be excited by an intrinsic mechanism or
by tidal forces.Comment: 18 pages, 14 figures, accepted for publication on Astronomy &
Astrophysic
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