6,456 research outputs found
Reflected Backward Stochastic Difference Equations and Optimal Stopping Problems under g-expectation
In this paper, we study reflected backward stochastic difference equations
(RBSDEs for short) with finitely many states in discrete time. The general
existence and uniqueness result, as well as comparison theorems for the
solutions, are established under mild assumptions. The connections between
RBSDEs and optimal stopping problems are also given. Then we apply the obtained
results to explore optimal stopping problems under -expectation. Finally, we
study the pricing of American contingent claims in our context.Comment: 29 page
The Grushko decomposition of a finite graph of finite rank free groups: an algorithm
A finitely generated group admits a decomposition, called its Grushko
decomposition, into a free product of freely indecomposable groups. There is an
algorithm to construct the Grushko decomposition of a finite graph of finite
rank free groups. In particular, it is possible to decide if such a group is
free.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol9/paper41.abs.htm
Impact of a case-management intervention for reducing emergency attendance on primary care: randomised control trial
BACKGROUND:
The impact on primary care workload of case-management interventions to reduce emergency department (ED) attendances is unknown.
AIM:
To examine the impact of a telephone-based case-management intervention targeting people with high ED attendance on primary care use.
DESIGN AND SETTING:
A single-site data extract from a larger randomised control trial, using the patient-level data from primary care electronic health records (2015–2020), was undertaken.
METHOD:
A total of 363 patients at high risk of ED usage were randomised to receive a 6-month case-management intervention (253 patients) or standard care (110 patients). Poisson regression models were used to calculate monthly rates of primary care use over time for the 2 years post-randomisation, comparing both arms. Usage was subclassified into face-to-face, telephone, letter, and community and secondary care referrals, stratified by patient demographics.
RESULTS:
No significant difference was found in the mean annual rate of primary care events between the intervention and control arms (P = 0.70). Secondary care referrals saw a 26% reduction in the mean annual referral rate (incident rate ratio [IRR] 0.74, 95% confidence interval [CI] = 0.64 to 0.86, P<0.001) and letters sent increased by 6% in the intervention arm compared with the control arm (IRR 1.06, 95% CI = 1.01 to 1.11, P = 0.01). In the case-managed arm, in patients aged ≥80 years there was a 33% increase in primary care usage (IRR 1.33, 95% CI = 1.28 to 1.40, P<0.001); with a corresponding 10% decrease in patients aged <80 years when compared with controls (IRR 0.90, 95% CI = 0.87 to 0.92, P<0.001).
CONCLUSION:
A targeted case-management intervention to reduce ED attendances did not increase overall primary care use. Redistribution of usage is seen among some patient groups, particularly older people, which may have important implications for primary healthcare planning
The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters
Spectroscopic and photometric data for likely member stars of five Galactic
globular clusters (M3, M53, M71, M92, and NGC 5053) and three open clusters
(M35, NGC 2158, and NGC 6791) are processed by the current version of the SEGUE
Stellar Parameter Pipeline (SSPP), in order to determine estimates of
metallicities and radial velocities for the clusters. These results are then
compared to values from the literature. We find that the mean metallicity
() and mean radial velocity () estimates for each cluster are
almost all within 2{\sigma} of the adopted literature values; most are within
1{\sigma}. We also demonstrate that the new version of the SSPP achieves small,
but noteworthy, improvements in estimates at the extrema of the
cluster metallicity range, as compared to a previous version of the pipeline
software. These results provide additional confidence in the application of the
SSPP for studies of the abundances and kinematics of stellar populations in the
Galaxy.Comment: 98 pages, 31 figures; accepted for publication in A
A Survey of CN and CH Variations in Galactic Globular Clusters from SDSS Spectroscopy
We present a homogeneous survey of the CN and CH bandstrengths in eight
Galactic globular clusters observed during the course of the Sloan Extension
for Galactic Understanding and Exploration (SEGUE) sub-survey of the SDSS. We
confirm the existence of a bimodal CN distribution among RGB stars in all of
the clusters with metallicity greater than [Fe/H] = -1.7; the lowest
metallicity cluster with an observed CN bimodality is M53, with [Fe/H] ~ -2.1.
There is also some evidence for individual CN groups on the subgiant branches
of M92, M2, and M13, and on the red giant branches of M92 and NGC 5053.
Finally, we quantify the correlation between overall cluster metallicity and
the slope of the CN bandstrength-luminosity plot as a means of further
demonstrating the level of CN-enrichment in cluster giants. Our results agree
well with previous studies reported in the literature.Comment: AJ submitted; 80 pages, 22 figure
Multi-Element Abundance Measurements from Medium-Resolution Spectra. II. Catalog of Stars in Milky Way Dwarf Satellite Galaxies
We present a catalog of Fe, Mg, Si, Ca, and Ti abundances for 2961 red giant
stars that are likely members of eight dwarf satellite galaxies of the Milky
Way (MW): Sculptor, Fornax, Leo I, Sextans, Leo II, Canes Venatici I, Ursa
Minor, and Draco. For the purposes of validating our measurements, we also
observed 445 red giants in MW globular clusters and 21 field red giants in the
MW halo. The measurements are based on Keck/DEIMOS medium-resolution
spectroscopy combined with spectral synthesis. We estimate uncertainties in
[Fe/H] by quantifying the dispersion of [Fe/H] measurements in a sample of
stars in monometallic globular clusters. We estimate uncertainties in Mg, Si,
Ca, and Ti abundances by comparing our medium-resolution spectroscopic
measurements to high-resolution spectroscopic abundances of the same stars. For
this purpose, our DEIMOS sample included 132 red giants with published
high-resolution spectroscopy in globular clusters, the MW halo field, and dwarf
galaxies. The standard deviations of the differences in [Fe/H] and [alpha/Fe]
(the average of [Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe]) between the two samples
is 0.15 and 0.16, respectively. This catalog represents the largest sample of
multi-element abundances in dwarf galaxies to date. The next papers in this
series draw conclusions on the chemical evolution, gas dynamics, and star
formation histories from the catalog presented here. The wide range of dwarf
galaxy luminosity reveals the dependence of dwarf galaxy chemical evolution on
galaxy stellar mass.Comment: 26 pages, 22 figures, 4 machine-readable tables (available in the
source file; click "Other formats"); accepted for publication in ApJ
Supplements; updated acknowledgments in v
Do adults with high functioning autism or Asperger Syndrome differ in empathy and emotion recognition?
The present study examined whether adults with high functioning autism (HFA) showed greater difficulties in (i) their self-reported ability to empathise with others and/or (ii) their ability to read mental states in others’ eyes than adults with Asperger syndrome (AS). The Empathy Quotient (EQ) and ‘Reading the Mind in the Eyes’ Test (Eyes Test) were compared in 43 adults with AS and 43 adults with HFA. No significant difference was observed on EQ score between groups, while adults with AS performed significantly better on the Eyes Test than those with HFA. This suggests that adults with HFA may need more support, particularly in mentalizing and complex emotion recognition, and raises questions about the existence of subgroups within autism spectrum conditions
Single-particle motional oscillator powered by laser
An ion, atom, molecule or macro-particle in a trap can exhibit large motional
oscillations due to the Doppler-affected radiation pressure by a laser,
blue-detuned from an absorption line of a particle. This oscillator can be
nearly thresholdless, but under certain conditions it may exhibit huge
hysteretic excitation. Feasible applications include a "Foucault pendulum" in a
trap, a rotation sensor, single atom spectroscopy, isotope separation, etc.Comment: 9 pages, 1 fig; v2: the latest revision for Optics Expres
Testing stellar population synthesis models with Sloan Digital Sky Survey colors of M31's globular clusters
Accurate stellar population synthesis models are vital in understanding the
properties and formation histories of galaxies. In order to calibrate and test
the reliability of these models, they are often compared with observations of
star clusters. However, relatively little work has compared these models in the
ugriz filters, despite the recent widespread use of this filter set. In this
paper, we compare the integrated colors of globular clusters in the Sloan
Digital Sky Survey (SDSS) with those predicted from commonly used simple
stellar population (SSP) models. The colors are based on SDSS observations of
M31's clusters and provide the largest population of star clusters with
accurate photometry available from the survey. As such, it is a unique sample
with which to compare SSP models with SDSS observations. From this work, we
identify a significant offset between the SSP models and the clusters' g-r
colors, with the models predicting colors which are too red by g-r\sim0.1. This
finding is consistent with previous observations of luminous red galaxies in
the SDSS, which show a similar discrepancy. The identification of this offset
in globular clusters suggests that it is very unlikely to be due to a minority
population of young stars. The recently updated SSP model of Maraston &
Stromback better represents the observed g-r colors. This model is based on the
empirical MILES stellar library, rather than theoretical libraries, suggesting
an explanation for the g-r discrepancy.Comment: 8 pages, 4 figures, accepted for publication in Ap
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