3,086 research outputs found
The HCR-20 as a measure of reliable and clinically significant change in violence risk among secure psychiatric inpatients
Objective Periodic structured violence risk assessment is the principle method underlying treatment planning for mentally disordered offenders but little is known about how risk changes over time. We aimed to determine whether hospitalised patients underwent reliable clinical change in assessed risk. Method We used a pseudo-prospective longitudinal study design. Demographic, clinical and risk assessment data of adult inpatients (N=480) who had been routinely assessed with the HCR-20 on two to four occasions over a mean period of 17 months (SD=2) were collated. Linear mixed models regression was conducted to determine change over time on total, subscale, and individual item scores, and relative change between clinical and demographic groups. The Reliable Change Index was calculated to examine whether change was greater than that expected by measurement error; clinically significant change was defined as the extent to which HCR-20 scores reduced below previously reported scores for patients not requiring hospitalisation. Results HCR-20 total score (Estimate −0.42, 95% CI=−0.84, −0.01, p<.05; d=.20) and clinical score (Estimate=−0.42, 95% CI=−0.64, −0.20, p<.001; d=.36) reduced over assessments. Significant differences in change were evident between clinically and demographically defined groups. A maximum of 3% of individuals showed clinically significant reliable reductions in HCR-20 total scores. The scores of patients whose overall level of risk was judged to have decreased did not reduce between assessments. Conclusion Violence risk changes very little over the course of treatment although there is some variation between groups. Most change cannot be demonstrated to be reliable or clinically significant. Important clinical management decisions should not depend solely on evidence from changes in HCR-20 risk assessment
Population III star formation in a Lambda CDM universe, II: Effects of a photodissociating background
We examine aspects of primordial star formation in the presence of a
molecular hydrogen-dissociating ultraviolet background. We compare a set of AMR
hydrodynamic cosmological simulations using a single cosmological realization
but with a range of ultraviolet background strengths in the Lyman-Werner band.
This allows us to study the effects of Lyman-Werner radiation on suppressing H2
cooling at low densities as well as the high-density evolution of the
collapsing core in a self-consistent cosmological framework. We find that the
addition of a photodissociating background results in a delay of the collapse
of high density gas at the center of the most massive halo in the simulation
and, as a result, an increase in the virial mass of this halo at the onset of
baryon collapse. We find that, contrary to previous results, Population III
star formation is not suppressed for J, but occurs even with
backgrounds as high as J. We find that H2 cooling leads to collapse
despite the depressed core molecular hydrogen fractions due to the elevated H2
cooling rates at K. We observe a relationship between the
strength of the photodissociating background and the rate of accretion onto the
evolving protostellar cloud core, with higher LW background fluxes resulting in
higher accretion rates. Finally, we find that the collapsing halo cores in our
simulations do not fragment at densities below cm
regardless of the strength of the LW background, suggesting that Population III
stars forming in halos with T K may still form in isolation.Comment: 46 pages, 14 figures (9 color). Accepted by the Astrophysical
Journal, some minor revision
Population III Star Formation in a Lambda WDM Universe
In this paper we examine aspects of primordial star formation in a gravitino
warm dark matter universe with a cosmological constant. We compare a set of
simulations using a single cosmological realization but with a wide range of
warm dark matter particle masses which have not yet been conclusively ruled out
by observations. The addition of a warm dark matter component to the initial
power spectrum results in a delay in the collapse of high density gas at the
center of the most massive halo in the simulation and, as a result, an increase
in the virial mass of this halo at the onset of baryon collapse. Both of these
effects become more pronounced as the warm dark matter particle mass becomes
smaller. A cosmology using a gravitino warm dark matter power spectrum assuming
a particle mass of m_{WDM} ~ 40keV is effectively indistinguishable from the
cold dark matter case, whereas the m_{WDM} ~ 15 keV case delays star formation
by approx. 10^8 years. There is remarkably little scatter between simulations
in the final properties of the primordial protostar which forms at the center
of the halo, possibly due to the overall low rate of halo mergers which is a
result of the WDM power spectrum. The detailed evolution of the collapsing halo
core in two representative WDM cosmologies is described. At low densities
(n_{b} <= 10^5 cm^{-3}), the evolution of the two calculations is qualitatively
similar, but occurs on significantly different timescales, with the halo in the
lower particle mass calculation taking much longer to evolve over the same
density range and reach runaway collapse. Once the gas in the center of the
halo reaches relatively high densities (n_{b} >= 10^5 cm^{-3}) the overall
evolution is essentially identical in the two calculations.Comment: 36 pages, 12 figures (3 color). Astrophysical Journal, accepte
How short should short-term risk assessment be? Determining the optimum interval for START reassessment in a secure mental health service
The Short-Term Assessment of Risk and Treatability (START) guides assessment of potential adverse outcomes. Assessment is recommended every 3 months but there is no evidence for this interval. We aimed to inform whether earlier reassessment was warranted. We collated START assessments for N = 217 adults in a secure mental health hospital, and subsequent aggressive, self-harm, self-neglect and victimization incidents. We used receiver operating characteristic analysis to assess predictive validity; survival function analysis to examine differences between low-, medium-, and high-risk groups; and hazard function analysis to determine the optimum interval for reassessment. The START predicted aggression and self-harm at 1, 2 and 3 months. At-risk individuals engaged in adverse outcomes earlier than low-risk patients. About half warranted reassessment before 3 months due to engagement in risk behaviour before that point despite a low-risk rating, or because of non-engagement by that point despite an elevated risk rating. Risk assessment should occur at appropriate intervals so that management strategies can be individually tailored. Assessment at 3-month intervals is supported by the evidence. START assessments should be revisited earlier if risk behaviours are not prevented; teams should constantly re-evaluate the need for restrictive practices
Uncertainties in Galactic Chemical Evolution Models
We use a simple one-zone galactic chemical evolution model to quantify the uncertainties generated by the input parameters in numerical predictions for a galaxy with properties similar to those of the Milky Way. We compiled several studies from the literature to gather the current constraints for our simulations regarding the typical value and uncertainty of the following seven basic parameters: the lower and upper mass limits of the stellar initial mass function (IMF), the slope of the high-mass end of the stellar IMF, the slope of the delay-time distribution function of Type Ia supernovae (SNe Ia), the number of SNe Ia per M ⊙ formed, the total stellar mass formed, and the final mass of gas. We derived a probability distribution function to express the range of likely values for every parameter, which were then included in a Monte Carlo code to run several hundred simulations with randomly selected input parameters. This approach enables us to analyze the predicted chemical evolution of 16 elements in a statistical manner by identifying the most probable solutions, along with their 68% and 95% confidence levels. Our results show that the overall uncertainties are shaped by several input parameters that individually contribute at different metallicities, and thus at different galactic ages. The level of uncertainty then depends on the metallicity and is different from one element to another. Among the seven input parameters considered in this work, the slope of the IMF and the number of SNe Ia are currently the two main sources of uncertainty. The thicknesses of the uncertainty bands bounded by the 68% and 95% confidence levels are generally within 0.3 and 0.6 dex, respectively. When looking at the evolution of individual elements as a function of galactic age instead of metallicity, those same thicknesses range from 0.1 to 0.6 dex for the 68% confidence levels and from 0.3 to 1.0 dex for the 95% confidence levels. The uncertainty in our chemical evolution model does not include uncertainties relating to stellar yields, star formation and merger histories, and modeling assumptions
The prediction and management of aquatic nitrogen pollution across Europe: an introduction to the Integrated Nitrogen in European Catchments project (INCA)
Excess nitrogen in soils, fresh water, estuarine and marine systems contributes to nutrient enrichment in key ecosystems throughout Europe, often leading to detrimental environmental impacts, such as soil acidification or the eutrophication of water bodies. The Integrated Nitrogenmodel for European Catchments (INCA) project aims to develop a generic version of the Integrated Nitrogen in Catchments (INCA) model to simulate the retention and transport of nitrogen within river systems, thereby providing a tool to aid the understanding of nitrogen dynamics and for river-basin management/policy-making. To facilitate the development of the model, 10 partners have tested the INCA model with data collected in study sites located in eight European countries as part of the INCA project. This paper summarises the key nitrogen issues within Europe, describes the main aims and methodology of the INCA project, and sets the project in the context of the current major research initiatives at a European level.</p> <p style='line-height: 20px;'><b>Keywords: </b>Europe, European Union, nitrogen, nitrate, ammonium, river basin management, modelling, water chemistry, acidification, eutrophication, Water Framework Directive, INCA
Positron detection in silica monoliths for miniaturised quality control of PET radiotracers
We demonstrate the use of the miniaturised Medipix positron sensor for detection of the clinical PET radiotracer, [⁶⁸Ga]gallium-citrate, on a silica-based monolith, towards microfluidic quality control. The system achieved a far superior signal-to-noise ratio compared to conventional sodium iodide-based radio-HPLC detection and allowed real-time visualisation of positrons in the monolith
Population III star formation in a Lambda CDM universe, I: The effect of formation redshift and environment on protostellar accretion rate
(abridged) We perform 12 extremely high resolution adaptive mesh refinement
cosmological hydrodynamic simulations of Population III star formation in a
Lambda CDM universe, varying the box size and large-scale structure, to
understand systematic effects in the formation of primordial protostellar
cores. We find results that are qualitatively similar to those observed
previously. We observe that the threshold halo mass for formation of a
Population III protostar does not evolve significantly with time in the
redshift range studied (33 > z > 19) but exhibits substantial scatter due to
different halo assembly histories: Halos which assembled more slowly develop
cooling cores at lower mass than those that assemble more rapidly, in agreement
with Yoshida et al. (2003). We do, however, observe significant evolution in
the accretion rates of Population III protostars with redshift, with objects
that form later having higher maximum accretion rates, with a variation of two
orders of magnitude (10^-4 - 10^-2 Msolar/year). This can be explained by
considering the evolving virial properties of the halos with redshift and the
physics of molecular hydrogen formation at low densities. Our result implies
that the mass distribution of Population III stars inferred from their
accretion rates may be broader than previously thought, and may evolve with
redshift. Finally, we observe that our collapsing protostellar cloud cores do
not fragment, consistent with previous results, which suggests that Population
III stars which form in halos of mass 10^5 - 10^6 Msun always form in
isolation.Comment: Accepted by The Astrophysical Journal. Some minor changes. 65 pages,
3 tables, 21 figures (3 color). To appear in January 1, 2007 issu
The Santa Fe Light Cone Simulation Project: I. Confusion and the WHIM in Upcoming Sunyaev-Zel'dovich Effect Surveys
We present the first results from a new generation of simulated large sky
coverage (~100 square degrees) Sunyaev-Zeldovich effect (SZE) cluster surveys
using the cosmological adaptive mesh refinement N-body/hydro code Enzo. We have
simulated a very large (512^3h^{-3}Mpc^3) volume with unprecedented dynamic
range. We have generated simulated light cones to match the resolution and
sensitivity of current and future SZE instruments. Unlike many previous studies
of this type, our simulation includes unbound gas, where an appreciable
fraction of the baryons in the universe reside.
We have found that cluster line-of-sight overlap may be a significant issue
in upcoming single-dish SZE surveys. Smaller beam surveys (~1 arcmin) have more
than one massive cluster within a beam diameter 5-10% of the time, and a larger
beam experiment like Planck has multiple clusters per beam 60% of the time. We
explore the contribution of unresolved halos and unbound gas to the SZE
signature at the maximum decrement. We find that there is a contribution from
gas outside clusters of ~16% per object on average for upcoming surveys. This
adds both bias and scatter to the deduced value of the integrated SZE, adding
difficulty in accurately calibrating a cluster Y-M relationship.
Finally, we find that in images where objects with M > 5x10^{13} M_{\odot}
have had their SZE signatures removed, roughly a third of the total SZE flux
still remains. This gas exists at least partially in the Warm Hot Intergalactic
Medium (WHIM), and will possibly be detectable with the upcoming generation of
SZE surveys.Comment: 14 pages, 13 figures, version accepted to ApJ. Major revisions mad
On the Discovery of Monocular Rivalry by Tscherning in 1898:Translation and Review
Monocular rivalry was named by Breese in 1899. He made prolonged observation of superimposed orthogonal gratings; they fluctuated in clarity with either one or the other grating occasionally being visible alone. A year earlier, Tscherning observed similar fluctuations with a grid of vertical and horizontal lines and with other stimuli; we draw attention to his prior account. Monocular rivalry has since been shown to occur with a wide variety of superimposed patterns with several independent rediscoveries of it. We also argue that Helmholtz described some phenomenon other than monocular rivalry in 1867
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