16,837 research outputs found
Predictive validity of the HCR-20 for inpatient aggression:the effect of intellectual disability on accuracy
BackgroundPeople with intellectual disability (ID) account for a large proportion of aggressive incidents in secure and forensic psychiatric services. Although the Historical, Clinical, Risk Management 20 (HCR-20) has good predictive validity in inpatient settings, it does not perform equally in all groups and there is little evidence for its efficacy in those with ID.MethodA pseudo-prospective cohort study of the predictive efficacy of the HCR-20 for those with ID (n = 109) was conducted in a UK secure mental health setting using routinely collected risk data. Performance of the HCR-20 in the ID group was compared with a comparison group of adult inpatients without an ID (n = 504). Analysis controlled for potential covariates including security level, length of stay, gender and diagnosis.ResultsThe HCR-20 total score was a significant predictor of any aggression and of physical aggression for both groups, although the area under the curve values did not reach the threshold for a large effect size. The clinical subscale performed significantly better in those without an ID compared with those with. The ID group had a greater number of relevant historical and risk management items. The clinicians' summary judgment significantly predicted both types of aggressive outcomes in the ID group, but did not predict either in those without an ID.ConclusionsThis study demonstrates that, after controlling for a range of potential covariates, the HCR-20 is a significant predictor of inpatient aggression in people with an ID and performs as well as for a comparison group of mentally disordered individuals without ID. The potency of HCR-20 subscales and items varied between the ID and comparison groups suggesting important target areas for improved prediction and risk management interventions in those with ID
The influence of baryons on the mass distribution of dark matter halos
Using a set of high-resolution N-body/SPH cosmological simulations with
identical initial conditions but run with different numerical setups, we
investigate the influence of baryonic matter on the mass distribution of dark
halos when radiative cooling is NOT included. We compare the concentration
parameters of about 400 massive halos with virial mass from \Msun to
\Msun. We find that the concentration parameters for the
total mass and dark matter distributions in non radiative simulations are on
average larger by ~3% and 10% than those in a pure dark matter simulation. Our
results indicate that the total mass density profile is little affected by a
hot gas component in the simulations. After carefully excluding the effects of
resolutions and spurious two-body heating between dark matter and gas
particles, we conclude that the increase of the dark matter concentration
parameters is due to interactions between baryons and dark matter. We
demonstrate this with the aid of idealized simulations of two-body mergers. The
results of individual halos simulated with different mass resolutions show that
the gas profiles of densities, temperature and entropy are subjects of mass
resolution of SPH particles. In particular, we find that in the inner parts of
halos, as the SPH resolution increases the gas density becomes higher but both
the entropy and temperature decrease.Comment: 8 pages, 6 figures, 1 table, ApJ in press (v652n1); updated to match
with the being published versio
Barrier and internal wave contributions to the quantum probability density and flux in light heavy-ion elastic scattering
We investigate the properties of the optical model wave function for light
heavy-ion systems where absorption is incomplete, such as Ca
and O around 30 MeV incident energy. Strong focusing effects
are predicted to occur well inside the nucleus, where the probability density
can reach values much higher than that of the incident wave. This focusing is
shown to be correlated with the presence at back angles of a strong enhancement
in the elastic cross section, the so-called ALAS (anomalous large angle
scattering) phenomenon; this is substantiated by calculations of the quantum
probability flux and of classical trajectories. To clarify this mechanism, we
decompose the scattering wave function and the associated probability flux into
their barrier and internal wave contributions within a fully quantal
calculation. Finally, a calculation of the divergence of the quantum flux shows
that when absorption is incomplete, the focal region gives a sizeable
contribution to nonelastic processes.Comment: 16 pages, 15 figures. RevTeX file. To appear in Phys. Rev. C. The
figures are only available via anonynous FTP on
ftp://umhsp02.umh.ac.be/pub/ftp_pnt/figscat
HST images and properties of the most distant radio galaxies
We present Hubble Space Telescope images of 11 high redshift radio galaxies
(between and ). The galaxies were observed with the WFPC2 camera
in a broad band filter (F606W or F707W, roughly equivalent to V or R-band), for
2 orbits each. We find that on the scale of the HST observations there is a
wide variety of morphological structures of the hosting galaxies: most objects
have a clumpy, irregular appearance, consisting of a bright nucleus and a
number of smaller components, suggestive of merging systems. Some observed
structures could be due (at least partly) to the presence of dust distributed
through the galaxies. The UV continuum emission is generally elongated and
aligned with the axis of the radio sources, however the characteristics of the
``alignment effect'' differ from case to case, suggesting that the phenomenon
cannot be explained by a single physical mechanism. We compare the properties
of our radio galaxies with those of the
UV dropout galaxies and conclude that (i) the most massive radio galaxies may
well evolve from an aggregate of UV dropout galaxies and (ii) high redshift
radio galaxies probably evolve into present day brightest cluster galaxies.Comment: 22 pages, 30 figures, accepted by A&
The late-type stellar content of the Fornax and Sculptor dwarf galaxies
A field of area 0.13 square degrees has been surveyed for late-type stars in each of the Fornax and Sculptor dwarf elliptical galaxies. JHK photometric data have been obtained for most of the stars found. In Fornax, we have positively identified 25 C stars and one M giant. In Sculptor, two relatively blue C stars and a small number of possible M giants have been identified. In contrast to the Magellanic Clouds, there are no M6-M9 giants in Fornax or Sculptor.
The mean value and the variance of the bolometric luminosity function for the Fornax C stars are — 4.66 ± 0.47, quite similar to the values for the Magellanic Cloud C stars. The colors of the Fornax
C stars overlap those of the C stars in the Magellanic Clouds but are bluer in the mean. The large dispersion in the color-magnitude diagram of the Fornax C stars is interpreted as arising from a significant spread in age and/or metallicity in the stellar population of Fornax.
The C stars found in Sculptor are quite similar in color and luminosity to the C stars in the globular cluster ω Centauri and are at the faint end of the luminosity distribution of C stars found in the
Magellanic Clouds and Fornax.
The ratio of cool C stars to M stars, as determined from identical survey techniques, increases dramatically along the sequence Milky Way, LMC, SMC, and Fornax. This increase, together with systematic changes in the colors of the C and M stars, can be understood as arising from a systematic decrease in the mean metallicity of the galaxies on this sequence. The lack of concurrent significant changes in M_(bol)(mean) or M_(bol)(max) of the carbon stars may not be consistent with current theories of C star formation and evolution.
The new data for Sculptor, as well as those previously published, point to a stellar population, and possibly a star-formation history, qualitatively similar to that of ω Cen. A sharp discontinuity between Fornax and Sculptor in some of the properties which characterize the late-type stellar population of these two systems stands in contrast to a rather smooth gradation in the same properties for Fornax and galaxies more massive than it. We speculate that this discontinuity could have arisen if Sculptor were stripped of its gas component at a much earlier time than Fornax
Tracking Down a Critical Halo Mass for Killing Galaxies through the Growth of the Red-Sequence
Red-sequence galaxies record the history of terminated star-formation in the
Universe and can thus provide important clues to the mechanisms responsible for
this termination. We construct composite samples of published cluster and field
galaxy photometry in order to study the build-up of galaxies on the
red-sequence, as parameterised by the dwarf-to-giant ratio (DGR). We find that
the DGR in clusters is higher than that of the field at all redshifts, implying
that the faint end of the red-sequence was established first in clusters. We
find that the DGR evolves with redshift for both samples, consistent with the
``down-sizing'' picture of star formation. We examine the predictions of
semi-analytic models for the DGR and find that neither the magnitude of its
environmental dependence nor its evolution is correctly predicted in the
models. Red-sequence DGRs are consistently too high in the models, the most
likely explanation being that the strangulation mechanism used to remove hot
gas from satellite galaxies is too efficient. Finally we present a simple toy
model including a threshold mass, below which galaxies are not strangled, and
show that this can predict the observed evolution of the field DGR.Comment: MNRAS letters accepted. 5 pages, 1 figur
Trend in ice moistening the stratosphere – constraints from isotope data of water and methane
Water plays a major role in the chemistry and radiative budget of the stratosphere. Air enters the stratosphere predominantly in the tropics, where the very low temperatures around the tropopause constrain water vapour mixing ratios to a few parts per million. Observations of stratospheric water vapour show a large positive long-term trend, which can not be explained by change in tropopause temperatures. Trends in the partitioning between vapour and ice of water entering the stratosphere have been suggested to resolve this conundrum. We present measurements of stratospheric H_(2)O, HDO, CH_4 and CH_(3)D in the period 1991–2007 to evaluate this hypothesis. Because of fractionation processes during phase changes, the hydrogen isotopic composition of H_(2)O is a sensitive indicator of changes in the partitioning of vapour and ice. We find that the seasonal variations of H_(2)O are mirrored in the variation of the ratio of HDO to H_(2)O with a slope of the correlation consistent with water entering the stratosphere mainly as vapour. The variability in the fractionation over the entire observation period is well explained by variations in H_(2)O. The isotopic data allow concluding that the trend in ice arising from particulate water is no more than (0.01±0.13) ppmv/decade in the observation period. Our observations suggest that between 1991 and 2007 the contribution from changes in particulate water transported through the tropopause plays only a minor role in altering in the amount of water entering the stratosphere
Providing Self-Aware Systems with Reflexivity
We propose a new type of self-aware systems inspired by ideas from
higher-order theories of consciousness. First, we discussed the crucial
distinction between introspection and reflexion. Then, we focus on
computational reflexion as a mechanism by which a computer program can inspect
its own code at every stage of the computation. Finally, we provide a formal
definition and a proof-of-concept implementation of computational reflexion,
viewed as an enriched form of program interpretation and a way to dynamically
"augment" a computational process.Comment: 12 pages plus bibliography, appendices with code description, code of
the proof-of-concept implementation, and examples of executio
Effect of positron-atom interactions on the annihilation gamma spectra of molecules
Calculations of gamma spectra for positron annihilation on a selection of
molecules, including methane and its fluoro-substitutes, ethane, propane,
butane and benzene are presented. The annihilation gamma spectra characterise
the momentum distribution of the electron-positron pair at the instant of
annihilation. The contribution to the gamma spectra from individual molecular
orbitals is obtained from electron momentum densities calculated using modern
computational quantum chemistry density functional theory tools. The
calculation, in its simplest form, effectively treats the low-energy
(thermalised, room-temperature) positron as a plane wave and gives annihilation
gamma spectra that are about 40% broader than experiment, although the main
chemical trends are reproduced. We show that this effective "narrowing" of the
experimental spectra is due to the action of the molecular potential on the
positron, chiefly, due to the positron repulsion from the nuclei. It leads to a
suppression of the contribution of small positron-nuclear separations where the
electron momentum is large. To investigate the effect of the nuclear repulsion,
as well as that of short-range electron-positron and positron-molecule
correlations, a linear combination of atomic orbital description of the
molecular orbitals is employed. It facilitates the incorporation of correction
factors which can be calculated from atomic many-body theory and account for
the repulsion and correlations. Their inclusion in the calculation gives gamma
spectrum linewidths that are in much better agreement with experiment.
Furthermore, it is shown that the effective distortion of the electron momentum
density, when it is observed through positron annihilation gamma spectra, can
be approximated by a relatively simple scaling factor.Comment: 26 pages, 12 figure
Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario
We present an entirely analytic model for a preheated, polytropic
intergalactic medium in hydrostatic equilibrium within a NFW dark halo
potential in which the evolution of the halo structure between major merger
events proceeds inside-out by accretion. This model is used to explain, within
a standard CDM cosmogony, the observed X-ray properties of nearby
relaxed, non-cooling flow groups and clusters of galaxies. We find that our
preferred solution to the equilibrium equations produces scaling relations in
excellent agreement with observations, while simultaneously accounting for the
typical structural characteristics of the distribution of the diffuse baryons.
In the class of preheating models, ours stands out because it offers a unified
description of the intrahalo medium for galaxy systems with total masses above
\sm 2\times 10^{13}\msun, does not produce baryonic configurations with large
isentropic cores, and reproduces faithfully the observed behavior of the gas
entropy at large radii. All this is achieved with a moderate level of energy
injection of about half a keV, which can be easily accommodated within the
limits of the total energy released by the most commonly invoked feedback
mechanisms, as well as with a polytropic index of 1.2, consistent with both
many observational determinations and predictions from high-resolution
gas-dynamical simulations of non-cooling flow clusters. More interestingly, our
scheme offers a physical motivation for the adoption of this specific value of
the polytropic index, as it is the one that best ensures the conservation after
halo virialization of the balance between the total specific energies of the
gas and dark matter components for the full range of masses investigated.Comment: 18 pages, 11 figures, accepted for publication in the Astrophysical
Journa
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