558 research outputs found
Alien Registration- Michaud, Peter (Eagle Lake, Aroostook County)
https://digitalmaine.com/alien_docs/33041/thumbnail.jp
Does Academic Medicine Matter?
The authors discuss a new systematic review that found no difference in health outcomes between academic and nonacademic health care settings
Stellar Models with Enhanced Abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in Turn, at Constant Helium and Iron Abundances
Recent work has shown that most globular clusters have at least two
chemically distinct components, as well as cluster-to-cluster differences in
the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order
to investigate the implications of variations in the abundances of these and
other metals for H-R diagrams and predicted ages, grids of evolutionary
sequences have been computed for scaled solar and enhanced alpha-element
mixtures, and for mixtures in which the assumed [m/Fe] value for each of the
metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by
0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages
from 6 to 14 Gyr, have been computed for -3.0 < [Fe/H] < -0.6, with helium
abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded
versions of the Victoria stellar structure program and the Regina interpolation
code, respectively. Turnoff luminosity versus age relations from isochrones are
found to depend almost entirely on the importance of the CNO-cycle, and thereby
mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do
not contribute significantly to the opacities at low temperatures and
densities, variations in their abundances do not impact the Teff scale of red
giants. The latter is a strong function of the abundances of only Mg and Si
(and Fe, possibly to a lesser extent), because they are so abundant and because
they are strong sources of opacity at low temperatures. For these reasons, Mg
and Si also have important effects on the temperatures of main-sequence stars.
Due to their low abundances, Na, Ca, and Ti are of little consequence for
stellar models. The effects of varying the adopted solar metals mix and the
helium abundance at a fixed [Fe/H] are also briefly discussed.Comment: 27 pages, 18 figures; accepted and tentatively scheduled for
publication in ApJ, volume 755 (Aug 10, 2012 issue
Fiducial Stellar Population Sequences for the VJKs Photometric System
We have obtained broad-band near-infrared photometry for seven Galactic star
clusters (M92, M15, M13, M5, NGC1851, M71 and NGC6791) using the WIRCam
wide-field imager on the Canada-France-Hawaii Telescope, supplemented by images
of NGC1851 taken with HAWK-I on the VLT. In addition, 2MASS observations of the
[Fe/H] ~ 0.0 open cluster M67 were added to the cluster database. From the
resultant (V-J)-V and (V-Ks)-V colour-magnitude diagrams (CMDs), fiducial
sequences spanning the range in metallicity, -2.4 < [Fe/H] < +0.3, have been
defined which extend (for most clusters) from the tip of the red-giant branch
(RGB) to ~ 2.5 magnitudes below the main-sequence turnoff. These fiducials
provide a valuable set of empirical isochrones for the interpretation of
stellar population data in the 2MASS system. We also compare our newly derived
CMDs to Victoria isochrones that have been transformed to the observed plane
using recent empirical and theoretical colour-Teff relations. The models are
able to reproduce the entire CMDs of clusters more metal rich than [Fe/H] ~
-1.4 quite well, on the assumption of the same reddenings and distance moduli
that yield good fits of the same isochrones to Johnson-Cousins BV(RI)C
photometry. However, the predicted giant branches become systematically redder
than the observed RGBs as the cluster metallicity decreases. Possible
explanations for these discrepancies are discussed.Comment: 18 pages, 20 figures, Accepted for publication in A
Asteroseismology of the Transiting Exoplanet Host HD 17156 with HST FGS
Observations conducted with the Fine Guidance Sensor on Hubble Space
Telescope (HST) providing high cadence and precision time-series photometry
were obtained over 10 consecutive days in December 2008 on the host star of the
transiting exoplanet HD 17156b. During this time 10^12 photons (corrected for
detector deadtime) were collected in which a noise level of 163 parts per
million per 30 second sum resulted, thus providing excellent sensitivity to
detection of the analog of the solar 5-minute p-mode oscillations. For HD 17156
robust detection of p-modes supports determination of the stellar mean density
of 0.5301 +/- 0.0044 g/cm^3 from a detailed fit to the observed frequencies of
modes of degree l = 0, 1, and 2. This is the first star for which direct
determination of the mean stellar density has been possible using both
asteroseismology and detailed analysis of a transiting planet light curve.
Using the density constraint from asteroseismology, and stellar evolution
modeling results in M_star = 1.285 +/- 0.026 solar, R_star = 1.507 +/- 0.012
solar, and a stellar age of 3.2 +/- 0.3 Gyr.Comment: Accepted by ApJ; 16 pages, 18 figure
An Examination of Recent Transformations to the BV(RI)_C Photometric System from the Perspective of Stellar Models for Old Stars
Isochrones for ages > 4 Gyr and metallicities in the range -2.5 < [Fe/H] <
+0.3 that take the diffusion of helium and recent advances in stellar physics
into account are compared with observations in the Johnson-Cousins BV(RI)_C
photometric system for several open and globular star clusters. The adopted
color-Teff relations include those which we have derived from the latest MARCS
model atmospheres and empirical transformations for dwarf and subgiant stars
given by Casagrande et al (2010, A&A, 512, 54; CRMBA). Those reported by
VandenBerg & Clem (2003, AJ, 126, 778) have also been considered, mainly to
resolve some outstanding questions concerning them. Remarkably, when the
subdwarfs in the CRMBA data set that have sigma_pi/pi < 0.15 are superimposed
on a set of 12 Gyr isochrones spanning a wide range in [Fe/H], the inferred
metallicities and effective temperatures agree, in the mean, with those given
by CRMBA to within +/- 0.05 dex and +/- 10 K, respectively. Thus the hot Teff
scale derived by CRMBA is nearly identical with that predicted by stellar
models and consequently, there is excellent consistency between theory and
observations on the H-R diagram and the different color-magnitude diagrams
considered in this investigation. To obtain similar consistency, the colors
obtained from the MARCS and VandenBerg & Clem B-V vs. Teff relations for
metal-poor dwarf stars should be adjusted to the red by 0.02-0.03 mag. In
general, isochrones that employ the CRMBA transformations provide reasonably
good fits to our BV(RI)_C photometry for main-sequence stars in the globular
clusters 47 Tuc, M3, M5, M92 and NGC 1851 - but not the cluster giants (when
adopting the synthetic MARCS colors). We speculate that differences between the
actual heavy-element mixtures and those assumed in the theoretical models may
be the primary cause of this difficulty.Comment: To appear in 2010, AJ, 140, 102
Fresh Chicken as Main Risk Factor for Campylobacteriosis, Denmark
Increased consumption of fresh poultry in Denmark has contributed substantially to the increasing incidence of human campylobacteriosis
F.A.R.O.G. FORUM, Vol. 5 No. 3
https://digitalcommons.library.umaine.edu/francoamericain_forum/1016/thumbnail.jp
Le FORUM, Vol. 35 No. 1
https://digitalcommons.library.umaine.edu/francoamericain_forum/1029/thumbnail.jp
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