114 research outputs found
Memberships and CM Diagrams of the Open Cluster NGC 7243
The results of astrometric and photometric investigations of the open cluster
NGC 7243 are presented. Proper motions of 2165 stars with root-mean-square
error of 1.1 mas/yr were obtained by means of PDS scanning of astrometric
plates covering the time interval of 97 years. A total of 211 cluster members
down to V=15.5 mag have been identified. V and B magnitudes have been
determined for 2118 and 2110 stars respectively. Estimations of mass (348Mo < M
< 522Mo), age (t=2.5x10^8 yr), distance (r=698 pc) and reddening (E(B-V)=0.24)
of the cluster NGC 7243 have been made.Comment: 24 pages, 15 figures. Submitted to Astronomy and Astrophysic
New membership determination and proper motions of NGC 1817. Parametric and non-parametric approach
We have calculated proper motions and re-evaluated the membership
probabilities of 810 stars in the area of two NGC objects, NGC 1817 and NGC
1807. We have obtained absolute proper motions from 25 plates in the reference
system of the Tycho-2 Catalogue. The plates have a maximum epoch difference of
81 years; and they were taken with the double astrograph at Zo-Se station of
Shanghai Observatory, which has an aperture of 40 cm and a plate scale of 30
arcsec/mm. The average proper motion precision is 1.55 mas/yr. These proper
motions are used to determine the membership probabilities of stars in the
region, based on there being only one very extended physical cluster: NGC 1817.
With that aim, we have applied and compared parametric and non-parametric
approaches to cluster/field segregation. We have obtained a list of 169
probable member stars.Comment: 11 pages, 8 figures, A&A in pres
Early-type stars in the young open cluster IC1805. II. The probably single stars HD15570 and HD15629, and the massive binary/triple system HD15558
Aims: We address the issue of the multiplicity of the three brightest
early-type stars of the young open cluster IC1805, namely HD15570, HD15629 and
HD15558. Methods: For the three stars, we measured the radial velocity by
fitting Gaussian curves to line profiles in the optical domain. In the case of
the massive binary HD15558, we also used a spectral disentangling method to
separate the spectra of the primary and of the secondary in order to derive the
radial velocities of the two components. These measurements were used to
compute orbital solutions for HD15558. Results: For HD15570 and HD15629, the
radial velocities do not present any significant trend attributable to a binary
motion on time scales of a few days, nor from one year to the next. In the case
of HD15558 we obtained an improved SB1 orbital solution with a period of about
442 days, and we report for the first time on the detection of the spectral
signature of its secondary star. We derive spectral types O5.5III(f) and O7V
for the primary and the secondary of HD15558. We tentatively compute a first
SB2 orbital solution although the radial velocities from the secondary star
should be considered with caution. The mass ratio is rather high, i.e. about 3,
and leads to very extreme minimum masses, in particular for the primary object.
Minimum masses of the order of 150 \pm 50 and 50 \pm 15 M_\odot are found
respectively for the primary and the secondary. Conclusions: We propose that
HD15558 could be a triple system. This scenario could help to reconcile the
very large minimum mass derived for the primary object with its spectral type.
In addition, considering new and previously published results, we find that the
binary frequency among O-stars in IC1805 has a lower limit of 20%, and that
previously published values (80%) are probably overestimated.Comment: 12 pages, including 6 figures (+ 4 pages of online material),
accepted for publication by A&
Kinematic parameters and membership probabilities of open clusters in the Bordeaux PM2000 catalogue
We derive lists of proper-motions and kinematic membership probabilities for
49 open clusters and possible open clusters in the zone of the Bordeaux PM2000
proper motion catalogue (). We test
different parametrisations of the proper motion and position distribution
functions and select the most successful one. In the light of those results, we
analyse some objects individually. The segregation between cluster and field
member stars, and the assignment of membership probabilities, is accomplished
by applying a new and fully automated method based on both parametrisations of
the proper motion and position distribution functions, and genetic algorithm
optimization heuristics associated with a derivative-based hill climbing
algorithm for the likelihood optimization. We present a catalogue comprising
kinematic parameters and associated membership probability lists for 49 open
clusters and possible open clusters in the Bordeaux PM2000 catalogue region. We
note that this is the first determination of proper motions for five open
clusters. We confirm the non-existence of two kinematic populations in the
region of 15 previously suspected non-existent objects.Comment: 14 pages, 6 figures, 4 tables. Accepted for publication in Astronomy
& Astrophysic
Determinants of health after hospital discharge: rationale and design of the Vanderbilt Inpatient Cohort Study (VICS)
BACKGROUND: The period following hospital discharge is a vulnerable time for patients when errors and poorly coordinated care are common. Suboptimal care transitions for patients admitted with cardiovascular conditions can contribute to readmission and other adverse health outcomes. Little research has examined the role of health literacy and other social determinants of health in predicting post-discharge outcomes. METHODS: The Vanderbilt Inpatient Cohort Study (VICS), funded by the National Institutes of Health, is a prospective longitudinal study of 3,000 patients hospitalized with acute coronary syndromes or acute decompensated heart failure. Enrollment began in October 2011 and is planned through October 2015. During hospitalization, a set of validated demographic, cognitive, psychological, social, behavioral, and functional measures are administered, and health status and comorbidities are assessed. Patients are interviewed by phone during the first week after discharge to assess the quality of hospital discharge, communication, and initial medication management. At approximately 30 and 90 days post-discharge, interviewers collect additional data on medication adherence, social support, functional status, quality of life, and health care utilization. Mortality will be determined with up to 3.5Â years follow-up. Statistical models will examine hypothesized relationships of health literacy and other social determinants on medication management, functional status, quality of life, utilization, and mortality. In this paper, we describe recruitment, eligibility, follow-up, data collection, and analysis plans for VICS, as well as characteristics of the accruing patient cohort. DISCUSSION: This research will enhance understanding of how health literacy and other patient factors affect the quality of care transitions and outcomes after hospitalization. Findings will help inform the design of interventions to improve care transitions and post-discharge outcomes
X-ray Source Populations in the Region of the Open Clusters NGC 6633 and IC 4756
Using deep exposures (~10^5 s) with the ROSAT HRI, we have performed
flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open
stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources
respectively. Our primary aim is to search for so-far unrecognised cluster
members. We propose identifications or classifications (cluster member, field
star, extragalactic field object) for the X-ray sources, based on published
membership lists, and on X-ray:optical flux ratios and optical
colour--magnitude diagrams. Results of simulating the expected X-ray-emitting
source populations are compared with the ROSAT measurements and with the
expected capabilities of the XMM mission. The simulations provide a novel
method of comparing the activity levels of NGC 6633 and IC 4756 with that of
the Hyades. The measurements and simulations confirm that cluster members are
the major class of X-ray emitter in these fields at flux levels f_x >
10^{-14}/erg/cm^2/s (0.1--2.4 keV), contributing ~40 per cent of the total
X-ray sources. We find 6 possible new members in NGC 6633, and 4 candidates in
IC 4756; all require further observation to establish membership probability.Comment: 12 pages, 4 figure
Adults with childhood-onset chronic conditions admitted to US pediatric and adult intensive care units
PURPOSE: To compare demographics, intensive care units (ICU) admission characteristics, and ICU outcomes among adults with childhood-onset chronic conditions (COCC) admitted to U.S. pediatric and adult ICUs. MATERIALS AND METHODS: Retrospective cross-sectional analyses of 6,088 adults aged 19â40 years admitted in 2008 to 70 pediatric ICUs that participated in the Virtual Pediatric Intensive Care Unit Performance Systems and 50 adult ICUs that participated in Project IMPACT. RESULTS: COCC were present in 53% of young adults admitted to pediatric units, compared to 9% of those in adult units. The most common COCC in both groups were congenital cardiac abnormalities, cerebral palsy, and chromosomal abnormalities. Adults with COCC admitted to pediatric units were significantly more likely to be younger, have lower functional status, and be non-trauma patients than those in adult units. The median ICU length-of-stay was 2 days and the intensive care unit mortality rate was 5% for all COCC patients with no statistical difference between pediatric or adult units. CONCLUSIONS: There are marked differences in characteristics between young adults with COCC admitted to PICUs and adult ICUs. Barriers to accommodating these young adults may be reasons why many such adults have not transitioned from pediatric to adult critical care
Ground-based CCD astrometry with wide field imagers. III. [email protected] proper-motion catalog of the globular cluster omega Centauri
Omega Centauri is the most well studied Globular Cluster because of its
numerous puzzling features. Intensive spectroscopic follow-up observing
campaigns targeting stars at different positions on the color-magnitude diagram
promises to clarify some of these peculiarities. To able to target cluster
members reliably during spectroscopic surveys and both spatial and radial
distributions in the cluster outskirts without including field stars, a high
quality proper-motion catalog of omega Cen and membership probability
determination are required. The only available wide field proper-motion catalog
of omega Cen is derived from photographic plates, and only for stars brighter
than B~16. Using ESO archive data, we create a new, CCD-based, proper-motion
catalog for this cluster, extending to B~20. We used the high precision
astrometric software developed specifically for data acquired by [email protected]
telescope and presented in the first paper of this series. We achieved a good
cluster-field separation with a temporal base-line of only four years. We
corrected our photometry for sky-concentration effects. We provide calibrated
photometry for UBVRI wide-band data plus narrow-band filter data centered on
H_alpha for almost 360 000 stars. We can confirm that the omega Cen metal-poor
and the metal-rich components have the same proper motion, and demonstrate that
the metal-intermediate component in addition exhibits the same mean motion as
the other RGB stars. We provided membership probability determination for
published omega Cen variable star catalogs. Our catalog extends the
proper-motion measurements to fainter than the cluster turn-off luminosity, and
covers a wide area (~33'x33') around the center of omega Cen. Our catalog is
now electronically available to the astronomical community.Comment: 21 pages, 15 figures (8 in low resolution), shortened abstract,
revised version, accepted (October 3rd, 2008) for publication in A&
Using data-driven rules to predict mortality in severe community acquired pneumonia
Prediction of patient-centered outcomes in hospitals is useful for performance benchmarking, resource allocation, and guidance regarding active treatment and withdrawal of care. Yet, their use by clinicians is limited by the complexity of available tools and amount of data required. We propose to use Disjunctive Normal Forms as a novel approach to predict hospital and 90-day mortality from instance-based patient data, comprising demographic, genetic, and physiologic information in a large cohort of patients admitted with severe community acquired pneumonia. We develop two algorithms to efficiently learn Disjunctive Normal Forms, which yield easy-to-interpret rules that explicitly map data to the outcome of interest. Disjunctive Normal Forms achieve higher prediction performance quality compared to a set of state-of-the-art machine learning models, and unveils insights unavailable with standard methods. Disjunctive Normal Forms constitute an intuitive set of prediction rules that could be easily implemented to predict outcomes and guide criteria-based clinical decision making and clinical trial execution, and thus of greater practical usefulness than currently available prediction tools. The Java implementation of the tool JavaDNF will be publicly available. © 2014 Wu et al
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Recalibration of the delirium prediction model for ICU patients (PRE-DELIRIC): a multinational observational study
Purpose
Recalibration and determining discriminative power, internationally, of the existing delirium prediction model (PRE-DELIRIC) for intensive care patients.
Methods
A prospective multicenter cohort study was performed in eight intensive care units (ICUs) in six countries. The ten predictors (age, APACHE-II, urgent and admission category, infection, coma, sedation, morphine use, urea level, metabolic acidosis) were collected within 24 h after ICU admission. The confusion assessment method for the intensive care unit (CAM-ICU) was used to identify ICU delirium. CAM-ICU screening compliance and inter-rater reliability measurements were used to secure the quality of the data.
Results
A total of 2,852 adult ICU patients were screened of which 1,824 (64 %) were eligible for the study. Main reasons for exclusion were length of stay <1 day (19.1 %) and sustained coma (4.1 %). CAM-ICU compliance was mean (SD) 82 ± 16 % and inter-rater reliability 0.87 ± 0.17. The median delirium incidence was 22.5 % (IQR 12.8â36.6 %). Although the incidence of all ten predictors differed significantly between centers, the area under the receiver operating characteristic (AUROC) curve of the eight participating centers remained good: 0.77 (95 % CI 0.74â0.79). The linear predictor and intercept of the prediction rule were adjusted and resulted in improved re-calibration of the PRE-DELIRIC model.
Conclusions
In this multinational study, we recalibrated the PRE-DELIRIC model. Despite differences in the incidence of predictors between the centers in the different countries, the performance of the PRE-DELIRIC-model remained good. Following validation of the PRE-DELIRIC model, it may facilitate implementation of strategies to prevent delirium and aid improvements in delirium management of ICU patients
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