7,911 research outputs found
Effectiveness of anonymised information sharing and use in health service, police, and local government partnership for preventing violence related injury: experimental study and time series analysis
Objective: To evaluate the effectiveness of anonymised information sharing to prevent injury related to violence. Design: Experimental study and time series analysis of a prototype community partnership between the health service, police, and local government partners designed to prevent violence. Setting: Cardiff, Wales, and 14 comparison cities designated "most similar" by the Home Office in England and Wales. Intervention After a 33 month development period, anonymised data relevant to violence prevention (precise violence location, time, days, and weapons) from patients attending emergency departments in Cardiff and reporting injury from violence were shared over 51 months with police and local authority partners and used to target resources for violence prevention. Main outcome measures: Health service records of hospital admissions related to violence and police records of woundings and less serious assaults in Cardiff and other cities after adjustment for potential confounders. Results: Information sharing and use were associated with a substantial and significant reduction in hospital admissions related to violence. In the intervention city (Cardiff) rates fell from seven to five a month per 100 000 population compared with an increase from five to eight in comparison cities (adjusted incidence rate ratio 0.58, 95% confidence interval 0.49 to 0.69). Average rate of woundings recorded by the police changed from 54 to 82 a month per 100 000 population in Cardiff compared with an increase from 54 to 114 in comparison cities (adjusted incidence rate ratio 0.68, 0.61 to 0.75). There was a significant increase in less serious assaults recorded by the police, from 15 to 20 a month per 100 000 population in Cardiff compared with a decrease from 42 to 33 in comparison cities (adjusted incidence rate ratio 1.38, 1.13 to 1.70). Conclusion: An information sharing partnership between health services, police, and local government in Cardiff, Wales, altered policing and other strategies to prevent violence based on information collected from patients treated in emergency departments after injury sustained in violence. This intervention led to a significant reduction in violent injury and was associated with an increase in police recording of minor assaults in Cardiff compared with similar cities in England and Wales where this intervention was not implemented
Coupled Cluster Channels in the Homogeneous Electron Gas
We discuss diagrammatic modifications to the coupled cluster doubles (CCD)
equations, wherein different groups of terms out of rings, ladders,
crossed-rings and mosaics can be removed to form approximations to the coupled
cluster method, of interest due to their similarity with various types of
random phase approximations. The finite uniform electron gas is benchmarked for
14- and 54-electron systems at the complete basis set limit over a wide density
range and performance of different flavours of CCD are determined. These
results confirm that rings generally overcorrelate and ladders generally
undercorrelate; mosaics-only CCD yields a result surprisingly close to CCD. We
use a recently developed numerical analysis [J. J. Shepherd and A. Gr\"uneis,
Phys. Rev. Lett. 110, 226401 (2013)] to study the behaviours of these methods
in the thermodynamic limit. We determine that the mosaics, on forming the
Brueckner Hamltonian, open a gap in the effective one-particle eigenvalues at
the Fermi energy. Numerical evidence is presented which shows that methods
based on this renormalisation have convergent energies in the thermodynamic
limit including mosaic-only CCD, which is just a renormalised MP2. All other
methods including only a single channel, namely ladder-only CCD, ring-only CCD
and crossed-ring-only CCD, appear to yield divergent energies; incorporation of
mosaic terms prevents this from happening.Comment: 9 pages, 4 figures, 1 table. Comments welcome: [email protected]
Range Separated Brueckner Coupled Cluster Doubles Theory
We introduce a range-separation approximation to coupled cluster doubles
(CCD) theory that successfully overcomes limitations of regular CCD when
applied to the uniform electron gas. We combine the short-range ladder channel
with the long-range ring channel in the presence of a Bruckner renormalized
one-body interaction and obtain ground-state energies with an accuracy of 0.001
a.u./electron across a wide range of density regimes. Our scheme is
particularly useful in the low-density and strongly-correlated regimes, where
regular CCD has serious drawbacks. Moreover, we cure the infamous
overcorrelation of approaches based on ring diagrams (i.e. the particle-hole
random phase approximation). Our energies are further shown to have appropriate
basis set and thermodynamic limit convergence, and overall this scheme promises
energetic properties for realistic periodic and extended systems which existing
methods do not possess.Comment: 5 pages, 3 figs. Now with supplementary info. Comments welcome:
[email protected]
Geochemical evidence for basement control of the west Cumberland haematite mineralization
A geochemical investigation of the West Cumberland meta somatic haematite deposits and related vein deposits in the central Lake District was carried out to establish the origin of the mineralizing fluids. Ore samples we re analysed for a variety of major and trace elements and were found to contain a simple geochemical assemblage characterised by the abundance of arsenic and locally barium. The lack of regional variation in ore geochemistry and the equally uniform mineralogy suggests that the replacement and vein deposits are cogenetic and belong to the same metallogenic province. Minor differences which do exist can be explained, by wallrock - ore fluid interactions. In the Eskdale area the veins are associated with a particular phase of the host granite containing an abundance of free haematite. Relative trace element enrichments in the ores are matched by sympathetic depletions in the adjacent haematized granite. The implied geochemical relationship is verified by a spatial correlation between areas of mineralization and. the distribution of concealed granite in the basement; as indicated by the gravity pattern. A more detailed gravity interpretation in the West Cumberland area shows that the zone of maximum mineralization in the limestones occurs directly above the faulted margin of a concealed, granite shelf extending outwards from the Ennerdale granophyre. Based on the combined/geological, geochemical and fluid, inclusion evidence a new model of haematite ore genesis is proposed which envisages the convective circulation of hot saline brines in the granite basement with the concomitant leaching of iron and its re deposition at higher levels as epigenetic haematite mineralization. The hypothesis is consistent with the known distribution of ore bodies and the observed spatial variation for arsenic and copper in the West Cumberland orefield. Baritic ores are related to the mixing of the ore fluids with formational waters from the Permo-Triassics
Thinking territory historically.
BACKGROUND:
While the randomised controlled trial (RCT) is generally regarded as the design of
choice for assessing the effects of health care, within the social sciences there is
considerable debate about the relative suitability of RCTs and non-randomised
studies (NRSs) for evaluating public policy interventions.
// OBJECTIVES:
To determine whether RCTs lead to the same effect size and variance as NRSs of
similar policy interventions; and whether these findings can be explained by other
factors associated with the interventions or their evaluation.
// METHODS:
Analyses of methodological studies, empirical reviews, and individual health and
social services studies investigated the relationship between randomisation and
effect size of policy interventions by:
1) Comparing controlled trials that are identical in all respects other than the use of
randomisation by 'breaking' the randomisation in a trial to create non-randomised
trials (re-sampling studies).
2) Comparing randomised and non-randomised arms of controlled trials mounted
simultaneously in the field (replication studies).
3) Comparing similar controlled trials drawn from systematic reviews that include
both randomised and non-randomised studies (structured narrative reviews and
sensitivity analyses within meta-analyses).
4) Investigating associations between randomisation and effect size using a pool of
more diverse RCTs and NRSs within broadly similar areas (meta-epidemiology).
// RESULTS:
Prior methodological reviews and meta-analyses of existing reviews comparing
effects from RCTs and nRCTs suggested that effect sizes from RCTs and nRCTs
may indeed differ in some circumstances and that these differences may well be
associated with factors confounded with design.
Re-sampling studies offer no evidence that the absence of randomisation directly
influences the effect size of policy interventions in a systematic way. No consistent
explanations were found for randomisation being associated with changes in effect
sizes of policy interventions in field trials
The effect of heating rates on low temperature hexane air combustion
Combustion of hydrocarbon fuels is traditionally separated into slow reaction, cool flame, and ignition regimes based on pressure and temperature. Standard tests, such as the ASTM E659, are used to determine the lowest temperature required to ignite a specific fuel mixed with air at atmospheric pressure. It is expected that the initial pressure and the rate at which the mixture is heated also influences the limiting temperature and the type of combustion. This study investigates the effect of heating rate, between 4 and 15 K/min, and initial pressure, in the range of 25–100 kPa, on ignition of n-hexane air mixtures. Mixtures with equivalence ratio ranging from Φ = 0.6 to Φ = 1.2 were investigated. The problem is also modeled computationally using an extension of Semenov’s classical autoignition theory with a detailed chemical mechanism. Experiments and simulations both show that in the same reactor either a slow reaction or an ignition event can take place depending on the heating rate. Analysis of the detailed chemistry demonstrates that a mixture which approaches the ignition region slowly undergoes a significant modification of its composition. This change in composition induces a progressive shift of the explosion limit until the mixture is no longer flammable. A mixture that approaches the ignition region sufficiently rapidly undergoes only a moderate amount of thermal decomposition and explodes quite violently
The effect of heating rates on low temperature hexane air combustion
Combustion of hydrocarbon fuels is traditionally separated into slow reaction, cool flame, and ignition regimes based on pressure and temperature. Standard tests, such as the ASTM E659, are used to determine the lowest temperature required to ignite a specific fuel mixed with air at atmospheric pressure. It is expected that the initial pressure and the rate at which the mixture is heated also influences the limiting temperature and the type of combustion. This study investigates the effect of heating rate, between 4 and 15 K/min, and initial pressure, in the range of 25–100 kPa, on ignition of n-hexane air mixtures. Mixtures with equivalence ratio ranging from Φ = 0.6 to Φ = 1.2 were investigated. The problem is also modeled computationally using an extension of Semenov’s classical autoignition theory with a detailed chemical mechanism. Experiments and simulations both show that in the same reactor either a slow reaction or an ignition event can take place depending on the heating rate. Analysis of the detailed chemistry demonstrates that a mixture which approaches the ignition region slowly undergoes a significant modification of its composition. This change in composition induces a progressive shift of the explosion limit until the mixture is no longer flammable. A mixture that approaches the ignition region sufficiently rapidly undergoes only a moderate amount of thermal decomposition and explodes quite violently
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