6,988 research outputs found
Detailed study of B037 based on {\sl HST} images
B037 is of interest because it is both the most luminous and the most highly
reddened cluster known in M31. Images of deep observations and of highly
spatial resolutions with the Advanced Camera for Surveys on the {\sl HST}
firstly show that this cluster is crossed by a dust lane. Photometric data in
the F606W and F814W filters obtained in this paper provide that, colors of
() in the dust lane are redder mags than ones in
the other regions of B037. The {\sl HST} images show that, this dust lane seems
to be contained in B037, not from the M31 disk or the Milky Way. As we know,
the formation of dust requires gas with a rather high metallicity. However,
B037 has a low metallicity to be . So, it seems
improbable that the observed dust lane is physically associated with B037. It
is clear that the origin of this dust lane is worthy of future study. In
addition, based on these images, we present the precise variation of
ellipticity and position angle, and of surface brightness profile, and
determine the structural parameters of B037 by fitting a single-mass isotropic
King model. In the F606W filter, we derive the best-fitting scale radius,
r_0=0.56\pm0.02\arcsec~(=2.16\pm0.08~\rm{pc}), a tidal radius,
r_t=8.6\pm0.4\arcsec~(=33.1\pm1.5~\rm{pc}), and a concentration index . In the F814W filter, we derive
r_0=0.56\pm0.01\arcsec~(=2.16\pm0.04~\rm{pc}),
r_t=8.9\pm0.3\arcsec~(=34.3\pm1.2~\rm{pc}), and . The extinction-corrected central surface brightness is
in the F606W filter, and in the F814W filter, respectively.Comment: Accepted for Publication in RAA, 13 pages, 5 figures and 7 table
Old Metal-rich Globular Cluster Populations: Peak Color and Peak Metallicity Trends with Mass of Host Spheroids
We address the problem of the factors contributing to a peak color trend of
old metal-rich globular cluster (MRGC) populations with mass of their hosts,
early-type galaxies and spheroidal subsystems of spiral ones (spheroids). The
color-mass trend is often converted to a metallicity-mass trend under the
assumption that age effects are small or negligible. While direct estimates of
the ages of MRGC populations neither can rule out nor reliably support the
populations' age trend, key data on timing of the formation of spheroids and
other indirect evidence imply it in the sense: the more massive spheroid the
older on average its MRGC population. We show that the contribution of an
allowable age trend of the MRGC populations to their peak color trend can
achieve up to ~50 % or so. In this event the comparable value of the color
trend, ~30 %, is due to alpha-element ratio systematic variations of the order
of Delta[alpha/Fe] ~ 0.1 to 0.2 dex because of a correlation between the
[alpha/Fe] ratios and age. Hence a systematic variation of exactly [Fe/H]
ratios may turn out to be less significant among the contributors, and its
range many times lower, i.e. of the order of Delta[Fe/H] ~ 0.1 or even none,
than the corresponding range deduced by assuming no age trend.Comment: 5 pages, 1 figure, accepted for publication in Astronomische
Nachrichte
Age and mass studies for young star clusters in M31 from SEDs-fit
In this paper, we present photometry for young star clusters in M31, which
are selected from Caldwell et al. These star clusters have been observed as
part of the Beijing--Arizona--Taiwan--Connecticut (BATC) Multicolor Sky Survey
from 1995 February to 2008 March. The BATC images including these star clusters
are taken with 15 intermediate-band filters covering 3000--10000 \AA. Combined
with photometry in the {\sl GALEX} far- and near-ultraviolet, broad-band
, SDSS , and infrared of Two Micron All Sky Survey,
we obtain their accurate spectral energy distributions (SEDs) from 1538-20000
\AA. We derive these star clusters' ages and masses by comparing their SEDs
with stellar population synthesis models. Our results are in good agreement
with previous determinations. The mean value of age and mass of young clusters
( Gyr) is about 385 Myr and , respectively. There
are two distinct peaks in the age distribution, a highest peak at age 60
Myr and a secondary peak around 250 Myr, while the mass distribution shows a
single peak around . A few young star clusters have two-body
relaxation times greater than their ages, indicating that those clusters have
not been well dynamically relaxed and therefore have not established the
thermal equilibrium. There are several regions showing aggregations of young
star clusters around the 10 kpc ring and the outer ring, indicating that the
distribution of the young star clusters is well correlated with M31's
star-forming regions. The young massive star clusters (age Myr and
mass ) show apparent concentration around the ring
splitting region, suggesting a recent passage of a satellite galaxy (M32)
through M31 disk.Comment: Accepted for Publication in AJ, 15 pages, 14 figures and 4 table
Age and structure parameters of a remote M31 globular cluster B514 based on HST, 2MASS, GALEX and BATC observations
B514 is a remote M31 globular cluster which locating at a projected distance
of R_p~55 kpc. Deep observations with the Advanced Camera for Surveys (ACS) on
the Hubble Space Telescope (HST) are used to provide the accurate integrated
light and star counts of B514. By coupling analysis of the distribution of the
integrated light with star counts, we are able to reliably follow the profile
of the cluster out to ~40". Based on the combined profile, we study in detail
its surface brightness distribution in F606W and F814W filters, and determine
its structural parameters by fitting a single-mass isotropic King model. The
results showed that, the surface brightness distribution departs from the
best-fit King model for r>10". B514 is quite flatted in the inner region, and
has a larger half-light radius than majority of normal globular clusters of the
same luminosity. It is interesting that, in the M_V versus log R_h plane, B514
lies nearly on the threshold for ordinary globular clusters as defined by
Mackey & van den Bergh. In addition, B514 was observed as part of the
Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey, using 13
intermediate-band filters covering a wavelength range of 3000--8500 \AA. Based
on aperture photometry, we obtain its SEDs as defined by the 13 BATC filters.
We determine the cluster's age and mass by comparing its SEDs (from 2267 to
20000{\AA}, comprising photometric data in the near-ultraviolet of GALEX, 5
SDSS bands, 13 BATC intermediate-band, and 2MASS near-infrared JHKs} filters)
with theoretical stellar population synthesis models, resulting in age of
Gyr. This age confirms the previous suggestion that B514 is an old
GC in M31. B514 has a mass of , and is a
medium-mass globular cluster in M31.Comment: Accepted for Publication in AJ, 18 pages, 6 figures and 9 table
Why physicians are lousy gatekeepers: Sicklisting decisions when patients have private information on symptoms
In social insurance systems that grant workers paid sick leave, physicians act as gatekeepers, supposedly granting sickness certificates to the sick and not to shirkers. Previous research has emphasized the physician's superior ability to judge patients' need of treatment and potential collusion with the patient vis‐á‐vis an insurer. What is less well understood is the role of patients' private information. We explore the case where patients have private information about the presence of nonverifiable symptoms. Anyone can then claim to experience such symptoms, reducing physicians' ability to distinguish between sick patients and shirkers. Doubting a patients' reported symptoms may prevent good medical treatment of the truly sick. We show that for all parameter values, the Bayesian Nash equilibrium is that some physicians trust all claims of nonverifiable symptoms, sicklisting shirkers as well as sick; for many values, every physician is trusting. In particular, if physician strategies are observable by patients, extremely strong gatekeeping preferences are required to make physicians mistrust. To limit unwarranted sicklisting, policies reducing the benefits of shirking for healthy workers may be better suited than attempts to convince physicians to be strict.publishedVersio
The M33 Globular Cluster System with PAndAS Data: The Last Outer Halo Cluster?
We use CFHT/MegaCam data to search for outer halo star clusters in M33 as
part of the Pan-Andromeda Archaeological Survey (PAndAS). This work extends
previous studies out to a projected radius of 50 kpc and covers over 40 square
degrees. We find only one new unambiguous star cluster in addition to the five
previously known in the M33 outer halo (10 kpc <= r <= 50 kpc). Although we
identify 2440 cluster candidates of various degrees of confidence from our
objective image search procedure, almost all of these are likely background
contaminants, mostly faint unresolved galaxies. We measure the luminosity,
color and structural parameters of the new cluster in addition to the five
previously-known outer halo clusters. At a projected radius of 22 kpc, the new
cluster is slightly smaller, fainter and redder than all but one of the other
outer halo clusters, and has g' ~ 19.9, (g'-i') ~ 0.6, concentration parameter
c ~ 1.0, a core radius r_c ~ 3.5 pc, and a half-light radius r_h ~ 5.5 pc. For
M33 to have so few outer halo clusters compared to M31 suggests either tidal
stripping of M33's outer halo clusters by M31, or a very different, much calmer
accretion history of M33.Comment: 37 pages, 9 figures. Accepted by the Astrophysical Journa
Continuous monitoring of the isotopic composition of surface water vapor at Lhasa, southern Tibetan Plateau
The stable isotopes (δ18O and δD) of water vapor are used to characterize continuous variations in large-scale and boundary-layer atmospheric processes. We presented continuous measurements of δ18O in surface water vapor at Lhasa, southern Tibetan Plateau, from October 2018 to September 2019 to investigate how large-scale and local atmospheric processes influence variations in water vapor δ18O at different time scales. The water vapor δ18O measurements reveal different seasonal characteristics and diurnal patterns. At the seasonal scale, δ18O exhibits a W-shape with two maxima in May–June and October as well as two minima in July–August and February. The diurnal variations in the water vapor δ18O and meteorological data throughout the year present distinct occurrences of maxima and minima during different periods. We found that the significant seasonal variability is mainly associated with the transition between the Indian summer monsoon and the westerlies, which transport distinct moisture to the southern Tibetan Plateau. The local temperature, specific humidity and boundary layer height impact the diurnal variations in water vapor δ18O to some extent with remarkable seasonal differences.publishedVersio
Optimization and evaluation of a coarse-grained model of protein motion using X-ray crystal data
Simple coarse-grained models, such as the Gaussian Network Model, have been
shown to capture some of the features of equilibrium protein dynamics. We
extend this model by using atomic contacts to define residue interactions and
introducing more than one interaction parameter between residues. We use
B-factors from 98 ultra-high resolution X-ray crystal structures to optimize
the interaction parameters. The average correlation between GNM fluctuation
predictions and the B-factors is 0.64 for the data set, consistent with a
previous large-scale study. By separating residue interactions into covalent
and noncovalent, we achieve an average correlation of 0.74, and addition of
ligands and cofactors further improves the correlation to 0.75. However,
further separating the noncovalent interactions into nonpolar, polar, and mixed
yields no significant improvement. The addition of simple chemical information
results in better prediction quality without increasing the size of the
coarse-grained model.Comment: 18 pages, 4 figures, 1 supplemental file (cnm_si.tex
Quality of Life Changes Following Peripheral Blood Stem Cell Transplantation and Participation in a Mixed-Type, Moderate-intensity, Exercise Program
Summary:The purpose of this investigation was to evaluate the impact of undertaking peripheral blood stem cell transplantation (PBST) on quality of life (QoL), and to determine the effect of participating in a mixed-type, moderate-intensity exercise program on QoL. It was also an objective to determine the relationship between peak aerobic capacity and QoL in PBST patients. QoL was assessed via the CARES questionnaire and peak aerobic capacity by a maximal graded treadmill test, pretransplant (PI), post transplant (PII) and following a 12-week intervention period (PIII). At PII, 12 patients were divided equally into a control or exercise intervention group. Undergoing a PBST was associated with a statistically but not clinically significant decline in QoL (P<0.05). Following the intervention, exercising patients demonstrated an improved QoL when compared with pretransplant ratings (P<0.01) and nonexercising transplant patients (P<0.05). Moreover, peak aerobic capacity and QoL were correlated (P<0.05). The findings demonstrated that exercise participation following oncology treatment is associated with a reduction in the number and severity of endorsed problems, which in turn leads to improvements in global, physical and psychosocial QoL. Furthermore, a relationship between fitness and QoL exists, with those experiencing higher levels of fitness also demonstrating higher QoL.Bone Marrow Transplantation (2004) 33, 553-558. doi:10.1038/sj.bmt.1704378 Published online 12 January 200
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