244 research outputs found
Interferometric radii of bright Kepler stars with the CHARA Array: {\theta} Cygni and 16 Cygni A and B
We present the results of long-baseline optical interferometry observations
using the Precision Astronomical Visual Observations (PAVO) beam combiner at
the Center for High Angular Resolution Astronomy (CHARA) Array to measure the
angular sizes of three bright Kepler stars: {\theta} Cygni, and both components
of the binary system 16 Cygni. Supporting infrared observations were made with
the Michigan Infrared Combiner (MIRC) and Classic beam combiner, also at the
CHARA Array. We find limb-darkened angular diameters of 0.753+/-0.009 mas for
{\theta} Cyg, 0.539+/-0.007 mas for 16 Cyg A and 0.490+/-0.006 mas for 16 Cyg
B. The Kepler Mission has observed these stars with outstanding photometric
precision, revealing the presence of solar-like oscillations. Due to the
brightness of these stars the oscillations have exceptional signal-to-noise,
allowing for detailed study through asteroseismology, and are well constrained
by other observations. We have combined our interferometric diameters with
Hipparcos parallaxes, spectrophotometric bolometric fluxes and the
asteroseismic large frequency separation to measure linear radii ({\theta} Cyg:
1.48+/-0.02 Rsun, 16 Cyg A: 1.22+/-0.02 Rsun, 16 Cyg B: 1.12+/-0.02 Rsun),
effective temperatures ({\theta} Cyg: 6749+/-44 K, 16 Cyg A: 5839+/-42 K, 16
Cyg B: 5809+/-39 K), and masses ({\theta} Cyg: 1.37+/-0.04 Msun, 16 Cyg A:
1.07+/-0.05 Msun, 16 Cyg B: 1.05+/-0.04 Msun) for each star with very little
model dependence. The measurements presented here will provide strong
constraints for future stellar modelling efforts.Comment: 9 pages, 4 figures, and 5 tables, accepted for publication in Monthly
Notices of the Royal Astronomical Societ
Mean angular diameters, distances and pulsation modes of the classical Cepheids FF Aql and T Vul - CHARA/FLUOR near-infrared interferometric observations
We report the first angular diameter measurements of two classical Cepheids,
FF Aql and T Vul, that we have obtained with the FLUOR instrument installed at
the CHARA interferometric array. We obtain average limb-darkened angular
diameters of \theta_LD = 0.878 +/- 0.013 mas and \theta_LD = 0.629 +/- 0.013
mas, respectively for FF Aql and T Vul. Combining these angular diameters with
the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6 +/- 2.2
Rsol and R = 35.6 +/- 4.4 Rsol, respectively. The comparison with empirical and
theoretical Period-Radius relations leads to the conclusion that these Cepheids
are pulsating in their fundamental mode. The knowledge of the pulsation mode is
of prime importance to calibrate the Period-Luminosity relation with a uniform
sample of fundamental mode Cepheids
Fundamental Properties of Stars using Asteroseismology from Kepler & CoRoT and Interferometry from the CHARA Array
We present results of a long-baseline interferometry campaign using the PAVO
beam combiner at the CHARA Array to measure the angular sizes of five
main-sequence stars, one subgiant and four red giant stars for which solar-like
oscillations have been detected by either Kepler or CoRoT. By combining
interferometric angular diameters, Hipparcos parallaxes, asteroseismic
densities, bolometric fluxes and high-resolution spectroscopy we derive a full
set of near model-independent fundamental properties for the sample. We first
use these properties to test asteroseismic scaling relations for the frequency
of maximum power (nu_max) and the large frequency separation (Delta_nu). We
find excellent agreement within the observational uncertainties, and
empirically show that simple estimates of asteroseismic radii for main-sequence
stars are accurate to <~4%. We furthermore find good agreement of our measured
effective temperatures with spectroscopic and photometric estimates with mean
deviations for stars between T_eff = 4600-6200 K of -22+/-32 K (with a scatter
of 97K) and -58+/-31 K (with a scatter of 93 K), respectively. Finally we
present a first comparison with evolutionary models, and find differences
between observed and theoretical properties for the metal-rich main-sequence
star HD173701. We conclude that the constraints presented in this study will
have strong potential for testing stellar model physics, in particular when
combined with detailed modelling of individual oscillation frequencies.Comment: 18 pages, 12 figures, 7 tables; accepted for publication in Ap
The radius and effective temperature of the binary Ap star beta CrB from CHARA/FLUOR and VLT/NACO observations
The prospects for using asteroseismology of rapidly oscillating Ap (roAp)
stars are hampered by the large uncertainty in fundamental stellar parameters.
Results in the literature for the effective temperature (Teff) often span a
range of 1000 K. Our goal is to reduce systematic errors and improve the Teff
calibration of Ap stars based on new interferometric measurements. We obtained
long-baseline interferometric observations of beta CrB using the CHARA/FLUOR
instrument. To disentangle the flux contributions of the two components of this
binary star, we obtained VLT/NACO adaptive optics images. We determined limb
darkened angular diameters of 0.699+-0.017 mas for beta CrB A (from
interferometry) and 0.415+-0.017 mas for beta CrB B (from surface brightness-
color relations), corresponding to radii of 2.63+-0.09 Rsun (3.4 percent
uncertainty) and 1.56+-0.07 Rsun (4.5 percent). The combined bolometric flux of
the A and B components was determined from satellite UV data, spectrophotometry
in the visible and broadband data in the infrared. The flux from the B
component constitutes 16+-4 percent of the total flux and was determined by
fitting an ATLAS9 model atmosphere to the broad-band NACO J and K magnitudes.
Combining the flux of the A component with its measured angular diameter, we
determine the effective temperature Teff(A) = 7980+-180 K (2.3 percent). Our
new interferometric and imaging data enable a nearly model-independent
determination of the effective temperature of beta CrB A. Including our recent
study of alpha Cir, we now have direct Teff measurements of two of the
brightest roAp stars, providing a strong benchmark for an improved calibration
of the Teff scale for Ap stars. This will support the use of potentially strong
constraints imposed by asteroseismic studies of roAp stars.Comment: 7 pages, accepted by A&
Asteroseismology and interferometry of the red giant star epsilon Oph
The GIII red giant star epsilon Oph has been found to exhibit several modes
of oscillation by the MOST mission. We interpret the observed frequencies of
oscillation in terms of theoretical radial p-mode frequencies of stellar
models. Evolutionary models of this star, in both shell H-burning and core
He-burning phases of evolution, are constructed using as constraints a
combination of measurements from classical ground-based observations (for
luminosity, temperature, and chemical composition) and seismic observations
from MOST. Radial frequencies of models in either evolutionary phase can
reproduce the observed frequency spectrum of epsilon Oph almost equally well.
The best-fit models indicate a mass in the range of 1.85 +/- 0.05 Msun with
radius of 10.55 +/- 0.15 Rsun. We also obtain an independent estimate of the
radius of epsilon Oph using high accuracy interferometric observations in the
infrared K' band, using the CHARA/FLUOR instrument. The measured limb darkened
disk angular diameter of epsilon Oph is 2.961 +/- 0.007 mas. Together with the
Hipparcos parallax, this translates into a photospheric radius of 10.39 +/-
0.07 Rsun. The radius obtained from the asteroseismic analysis matches the
interferometric value quite closely even though the radius was not constrained
during the modelling.Comment: 11 pages, accepted for publication in Astronomy & Astrophysic
Fundamental properties of the Population II fiducial stars HD 122563 and Gmb 1830 from CHARA interferometric observations
We have determined the angular diameters of two metal-poor stars, HD 122563
and Gmb 1830, using CHARA and Palomar Testbed Interferometer observations. For
the giant star HD 122563, we derive an angular diameter theta_3D = 0.940 +-
0.011 milliarcseconds (mas) using limb-darkening from 3D convection simulations
and for the dwarf star Gmb 1830 (HD 103095) we obtain a 1D limb-darkened
angular diameter theta_1D = 0.679 +- 0.007 mas. Coupling the angular diameters
with photometry yields effective temperatures with precisions better than 55 K
(Teff = 4598 +- 41 K and 4818 +- 54 K --- for the giant and the dwarf star,
respectively). Including their distances results in very well-determined
luminosities and radii (L = 230 +- 6 L_sun, R = 23.9 +- 1.9 R_sun and L = 0.213
+- 0.002 L_sun, R = 0.664 +- 0.015 R_sun, respectively). We used the CESAM2k
stellar structure and evolution code in order to produce models that fit the
observational data. We found values of the mixing-length parameter alpha (which
describes 1D convection) that depend on the mass of the star. The masses were
determined from the models with precisions of <3% and with the well-measured
radii excellent constraints on the surface gravity are obtained (log g = 1.60
+- 0.04, 4.59 +- 0.02, respectively). The very small errors on both log g and
Teff provide stringent constraints for spectroscopic analyses given the
sensitivity of abundances to both of these values. The precise determination of
Teff for the two stars brings into question the photometric scales for
metal-poor stars.Comment: accepted A&A, 8 dbl-column pages, incl. 7 tables and 4 figure
A Tale of Two Herbig Ae stars -MWC275 and AB Aurigae: Comprehensive Models for SED and Interferometry
We present comprehensive models for the Herbig Ae stars MWC275 and AB Aur
that aim to explain their spectral energy distribution (from UV to millimeter)
and long baseline interferometry (from near-infrared to millimeter)
simultaneously. Data from the literature, combined with new mid-infrared (MIR)
interferometry from the Keck Segment Tilting Experiment, are modeled using an
axisymmetric Monte Carlo radiative transfer code. Models in which most of the
near-infrared (NIR) emission arises from a dust rim fail to fit the NIR
spectral energy distribution (SED) and sub-milli-arcsecond NIR CHARA
interferometry. Following recent work, we include an additional gas emission
component with similar size scale to the dust rim, inside the sublimation
radius, to fit the NIR SED and long-baseline NIR interferometry on MWC275 and
AB Aur. In the absence of shielding of star light by gas, we show that the
gas-dust transition region in these YSOs will have to contain highly refractory
dust, sublimating at ~1850K. Despite having nearly identical structure in the
thermal NIR, the outer disks of MWC275 and AB Aur differ substantially. In
contrast to the AB Aur disk, MWC275 lacks small grains in the disk atmosphere
capable of producing significant 10-20micron emission beyond ~7AU, forcing the
outer regions into the "shadow" of the inner diskComment: Accepted for publication in Ap
Effect of a peer-educational intervention on provider knowledge and reported performance in family planning services: a cluster randomized trial
<p>Abstract</p> <p>Background</p> <p>Peer education is an interactive method of teaching or learning which is widely used for educating school and college students, in a variety of different forms. However, there are few studies on its effectiveness for in-service education. The aim of this study was to evaluate the effect of an educational programme including peer discussions, based on a needs assessment, on the providers' knowledge and reported performance in family planning services.</p> <p>Methods</p> <p>An educational programme was designed and applied in a random selection of half of in-charges of the 74 family health units (intervention group) in Tabriz at a regular monthly meeting. The other half constituted the control group. The programme included eight pages of written material and a two-hour, face-to-face discussion session with emphasis on the weak areas identified through a needs assessment questionnaire. The educated in-charges were requested to carry out a similar kind of programme with all peers at their health facilities within one month. All in-charges received one self-administered questionnaire containing knowledge questions one month after the in-charge education (follow-up I: 61 responses), and another one containing knowledge and self-reported performance questions 26 months later (follow-up II: 61 responses). Also, such tests were done for the peers facilitated by the in-charges one (105 responses) and 27 months (114 responses) after the peer discussions. Multiple linear regression was used for comparing mean total scores, and Chi square for comparing proportions between control and intervention groups, after defining facility as the unit of randomization.</p> <p>Results</p> <p>The mean total percentage scores of knowledge (percent of maximal possible score) in the intervention group were significantly higher than in the control group, both at follow-up I (63%) and at follow-up II (57%); with a difference of 16 (95% CI: 11, 22) and 5 (95% CI: 0.4, 11) percentage units, respectively. Only two of the nine reported performance items were significantly different among the non in-charges in the intervention group at follow-up II.</p> <p>Conclusions</p> <p>The educational programme including peer discussions using existing opportunities with no need for additional absence from the workplace might be a useful complement to formal large group education for the providers.</p
N-Glycosylation of ß4 Integrin Controls the Adhesion and Motility of Keratinocytes
α6ß4 integrin is an essential component of hemidesmosomes and modulates cell migration in wound healing and cancer invasion. To elucidate the role of N-glycosylation on ß4 integrin, we investigated keratinocyte adhesion and migration through the re-expression of wild-type or N-glycosylation-defective ß4 integrin (ΔNß4) in ß4 integrin null keratinocytes. N-glycosylation of ß4 integrin was not essential for the heterodimer formation of ß4 integrin with α6 integrin and its expression on a cell surface, but N-glycosylation was required for integrin-mediated cell adhesion and migration. Concomitantly with the reduction of ß4 integrin in the membrane microdomain, the intracellular signals of Akt and ERK activation were decreased in cells expressing ΔNß4 integrin. Forced cross-linking of ß4 integrin rescued the decreased ERK activation in ΔNß4 integrin-expressing cells to a similar extent in wild-type ß4 integrin-expressing cells. Surprisingly, compared with cells expressing wild-type ß4 integrin, an alternation in N-glycan structures expressed on epidermal growth factor receptor (EGFR), and the induction of a stronger association between EGFR and ß4 integrin were observed in ΔNß4 integrin-expressing cells. These results clearly demonstrated that N-glycosylation on ß4 integrin plays an essential role in keratinocyte cellular function by allowing the appropriate complex formation on cell surfaces
Genome-Wide Profiling of Histone H3 Lysine 4 and Lysine 27 Trimethylation Reveals an Epigenetic Signature in Prostate Carcinogenesis
BACKGROUND: Increasing evidence implicates the critical roles of epigenetic regulation in cancer. Very recent reports indicate that global gene silencing in cancer is associated with specific epigenetic modifications. However, the relationship between epigenetic switches and more dynamic patterns of gene activation and repression has remained largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: Genome-wide profiling of the trimethylation of histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3) was performed using chromatin immunoprecipitation coupled with whole genome promoter microarray (ChIP-chip) techniques. Comparison of the ChIP-chip data and microarray gene expression data revealed that loss and/or gain of H3K4me3 and/or H3K27me3 were strongly associated with differential gene expression, including microRNA expression, between prostate cancer and primary cells. The most common switches were gain or loss of H3K27me3 coupled with low effect on gene expression. The least prevalent switches were between H3K4me3 and H3K27me3 coupled with much higher fractions of activated and silenced genes. Promoter patterns of H3K4me3 and H3K27me3 corresponded strongly with coordinated expression changes of regulatory gene modules, such as HOX and microRNA genes, and structural gene modules, such as desmosome and gap junction genes. A number of epigenetically switched oncogenes and tumor suppressor genes were found overexpressed and underexpressed accordingly in prostate cancer cells. CONCLUSIONS/SIGNIFICANCE: This work offers a dynamic picture of epigenetic switches in carcinogenesis and contributes to an overall understanding of coordinated regulation of gene expression in cancer. Our data indicate an H3K4me3/H3K27me3 epigenetic signature of prostate carcinogenesis
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