496 research outputs found
Positive correlation of employment and psychological well-being for veterans with major abdominal surgery
Background
Intestinal stomas (ostomies) have been associated negatively with multiple aspects of health-related quality of life. This article examines the relationship between employment status and psychological well-being (PWB) in veterans who underwent major bowel procedures with or without ostomy.
Methods
Veterans from 3 Veterans Affairs (VA) medical centers were surveyed using the City of Hope ostomy-specific questionnaire and the Short Form 36 item Veteranâs version (SF-36V). Response rate was 48% (511 of 1,063). Employment and PWB relationship was assessed using multiple regression with age, income, SF-36V physical component summary (PCS), and employment status as independent variables.
Results
Employed veterans reported higher PWB compared with unemployed veterans (P = .003). Full-time workers also reported higher PWB than part-time or unemployed workers (P = .001). Ostomy was not an independent predictor of PWB.
Conclusions
Employment among veterans after major abdominal surgery may have intrinsic value for PWB. Patients should be encouraged to return to work, or do volunteer work after recovery
project: III. Gas mass fraction shape in high redshift clusters
We study the gas mass fraction, behavior in
project. The typical shape of high redshift galaxy
clusters follows the global shape inferred at low redshift quite well. This
result is consistent with the gravitational instability picture leading to self
similar structures for both the dark and baryonic matter. However, the mean
XMM$ clusters, the apparent gas
fraction at the virial radius is consistent with a non-evolving universal value
in a high matter density model and not with a concordance.Comment: Accepted, A&A, in pres
Fluctuation-Dissipation theorems and entropy production in relaxational systems
We show that for stochastic dynamical systems out of equilibrium the
violation of the fluctuation-dissipation equality is bounded by a function of
the entropy production. The result applies to a much wider situation than `near
equilibrium', comprising diffusion as well as glasses and other macroscopic
systems far from equilibrium. For aging systems this bounds the age-frequency
regimes in which the susceptibilities satisfy FDT in terms of the rate of decay
of the H-function, a question intimately related to the reading of a
thermometer placed in contact with the system.Comment: 4 pages, RevTex; formula and reference added plus various minor
changes in the tex
The Mass and Structure of the Pleiades Star Cluster from 2MASS
We present the results of a large scale search for new members of the
Pleiades star cluster using 2MASS near-infrared photometry and proper motions
derived from POSS plates digitized by the USNO PMM program. The search extends
to a 10 degree radius around the cluster, well beyond the presumed tidal
radius, to a limiting magnitude of R ~ 20, corresponding to ~ 0.07 M_sun at the
distance and age of the Pleiades. Multi-object spectroscopy for 528 candidates
verifies that the search was extremely effective at detecting cluster stars in
the 1 - 0.1 M_sun mass range using the distribution of H_alpha emission
strengths as an estimate of sample contamination by field stars.
When combined with previously identified, higher mass stars, this search
provides a sensitive measurement of the stellar mass function and dynamical
structure of the Pleiades. The degree of tidal elongation of the halo agrees
well with current N body simulation results. Tidal truncation affects masses
below ~ 1 M_sun. The cluster contains a total mass ~ 800 M_sun. Evidence for a
flatter mass function in the core than in the halo indicates the depletion of
stars in the core with mass less than ~ 0.5 M_sun, relative to stars with mass
\~1 - 0.5 M_sun, and implies a preference for very low mass objects to populate
the halo or escape. The overall mass function is best fitted with a lognormal
form that becomes flat at ~ 0.1 M_sun. Whether sufficient dynamical evaporation
has occurred to detectably flatten the initial mass function, via preferential
escape of very low mass stars and brown dwarfs, is undetermined, pending better
membership information for stars at large radial distances.Comment: 19 pages, 14 figures, 2 tables, accepted by AJ, to appear April 200
Optimal learning rules for familiarity detection
It has been suggested that the mammalian memory system has both familiarity and recollection components. Recently, a high-capacity network to store familiarity has been proposed. Here we derive analytically the optimal learning rule for such a familiarity memory using a signalto- noise ratio analysis. We find that in the limit of large networks the covariance rule, known to be the optimal local, linear learning rule for pattern association, is also the optimal learning rule for familiarity discrimination. The capacity is independent of the sparseness of the patterns, as long as the patterns have a fixed number of bits set. The corresponding information capacity is 0.057 bits per synapse, less than typically found for associative networks
Albedo and Reflection Spectra of Extrasolar Giant Planets
We generate theoretical albedo and reflection spectra for a full range of
extrasolar giant planet (EGP) models, from Jovian to 51-Pegasi class objects.
Our albedo modeling utilizes the latest atomic and molecular cross sections, a
Mie theory treatment of extinction by condensates, a variety of particle size
distributions, and an extension of the Feautrier radiative transfer method
which allows for a general treatment of the scattering phase function. We find
that due to qualitative similarities in the compositions and spectra of objects
within each of five broad effective temperature ranges, it is natural to
establish five representative EGP albedo classes: a ``Jovian'' class (T K; Class I) with tropospheric ammonia clouds, a ``water
cloud'' class (T K; Class II) primarily affected by
condensed HO, a ``clear'' class (T K; Class III)
which lacks clouds, and two high-temperature classes: Class IV (900 K
T 1500 K) for which alkali metal absorption
predominates, and Class V (T 1500 K and/or low surface
gravity ( 10 cm s)) for which a high silicate layer
shields a significant fraction of the incident radiation from alkali metal and
molecular absorption. The resonance lines of sodium and potassium are expected
to be salient features in the reflection spectra of Class III, IV, and V
objects. We derive Bond albedos and effective temperatures for the full set of
known EGPs and explore the possible effects of non-equilibrium condensed
products of photolysis above or within principal cloud decks. As in Jupiter,
such species can lower the UV/blue albedo substantially, even if present in
relatively small mixing ratios.Comment: revised LaTeX manuscript accepted to Ap.J.; also available at
http://jupiter.as.arizona.edu/~burrows/paper
Astrocladistics of the Jovian Trojan swarms
The Jovian Trojans are two swarms of small objects that share Jupiter's orbit, clustered around the leading and trailing Lagrange points, L4 and L5. In this work, we investigate the Jovian Trojan population using the technique of astrocladistics, an adaptation of the 'tree of life' approach used in biology. We combine colour data from WISE, SDSS, Gaia DR2, and MOVIS surveys with knowledge of the physical and orbital characteristics of the Trojans, to generate a classification tree composed of clans with distinctive characteristics. We identify 48 clans, indicating groups of objects that possibly share a common origin. Amongst these are several that contain members of the known collisional families, though our work identifies subtleties in that classification that bear future investigation. Our clans are often broken into subclans, and most can be grouped into 10 superclans, reflecting the hierarchical nature of the population. Outcomes from this project include the identification of several high priority objects for additional observations and as well as providing context for the objects to be visited by the forthcoming Lucy mission. Our results demonstrate the ability of astrocladistics to classify multiple large and heterogeneous composite survey data sets into groupings useful for studies of the origins and evolution of our Solar system
The K2-HERMES Survey: Age and Metallicity of the Thick Disc
Asteroseismology is a promising tool to study Galactic structure and
evolution because it can probe the ages of stars. Earlier attempts comparing
seismic data from the {\it Kepler} satellite with predictions from Galaxy
models found that the models predicted more low-mass stars compared to the
observed distribution of masses. It was unclear if the mismatch was due to
inaccuracies in the Galactic models, or the unknown aspects of the selection
function of the stars. Using new data from the K2 mission, which has a
well-defined selection function, we find that an old metal-poor thick disc, as
used in previous Galactic models, is incompatible with the asteroseismic
information. We show that spectroscopic measurements of [Fe/H] and
[/Fe] elemental abundances from the GALAH survey indicate a mean
metallicity of for the thick disc. Here is the
effective solar-scaled metallicity, which is a function of [Fe/H] and
[/Fe]. With the revised disc metallicities, for the first time, the
theoretically predicted distribution of seismic masses show excellent agreement
with the observed distribution of masses. This provides an indirect
verification of the asteroseismic mass scaling relation is good to within five
percent. Using an importance-sampling framework that takes the selection
function into account, we fit a population synthesis model of the Galaxy to the
observed seismic and spectroscopic data. Assuming the asteroseismic scaling
relations are correct, we estimate the mean age of the thick disc to be about
10 Gyr, in agreement with the traditional idea of an old -enhanced
thick disc.Comment: 21 pages, submitted to MNRA
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