1,314 research outputs found
System-adapted correlation energy density functionals from effective pair interactions
We present and discuss some ideas concerning an ``average-pair-density
functional theory'', in which the ground-state energy of a many-electron system
is rewritten as a functional of the spherically and system-averaged pair
density. These ideas are further clarified with simple physical examples. We
then show that the proposed formalism can be combined with density functional
theory to build system-adapted correlation energy functionals. A simple
approximation for the unknown effective electron-electron interaction that
enters in this combined approach is described, and results for the He series
and for the uniform electron gas are briefly reviewed.Comment: to appear in Phil. Mag. as part of Conference proceedings for the
"Electron Correlations and Materials Properties", Kos Greece, July 5-9, 200
The 'top 100' drugs and classes in England An updated 'starter formulary' for trainee prescribers.
AIMS: Prescribing is a complex skill required of doctors and, increasingly, other healthcare professionals. Use of a personal formulary can help to develop this skill. In 2006-9, we developed a core list of the 100 most commonly prescribed drugs. Our aim in the present study was to update this 'starter formulary' to ensure its continued relevance for prescriber training. METHODS: We analysed large contemporary primary and secondary care datasets to identify the most frequently prescribed medicinal products. Items were classified into natural groups, broadly following their British National Formulary classification. The resulting drug groups were included in the core list if they comprised ≥0.1% prescriptions in both settings or ≥0.2-0.3% prescriptions in one setting. Drugs from emergency guidelines that did not qualify by prescribing frequency completed the list. RESULTS: Over 1 billion primary care items and approximately 1.8 million secondary care prescriptions were analysed. The updated list comprises 81 drug groups commonly prescribed in both settings; 6 from primary care; 7 from secondary care; and 6 from emergency guidelines. 88% of the formulary was unchanged. Notable changes include entry of newer anti-epileptics and dipeptidyl peptidase-4 inhibitors and exit of phenytoin and thiazolidinediones. CONCLUSIONS: The relative stability of the core drug list over 9 years and the current update ensure that learning based on this list remains relevant to practice. Trainee prescribers may be encouraged to use this 'starter formulary' to develop a sound basis of prescribing knowledge and skills that they can subsequently apply more widely
The orientation and kinematics of inner tidal tails around dwarf galaxies orbiting the Milky Way
Using high-resolution collisionless N-body simulations we study the
properties of tidal tails formed in the immediate vicinity of a two-component
dwarf galaxy evolving in a static potential of the Milky Way (MW). The stellar
component of the dwarf is initially in the form of a disk and the galaxy is
placed on an eccentric orbit motivated by CDM-based cosmological simulations.
We measure the orientation, density and velocity distribution of the stars in
the tails. Due to the geometry of the orbit, in the vicinity of the dwarf,
where the tails are densest and therefore most likely to be detectable, they
are typically oriented towards the MW and not along the orbit. We report on an
interesting phenomenon of `tidal tail flipping': on the way from the pericentre
to the apocentre the old tails following the orbit are dissolved and new ones
pointing towards the MW are formed over a short timescale. We also find a tight
linear relation between the velocity of stars in the tidal tails and their
distance from the dwarf. Using mock data sets we demonstrate that if dwarf
spheroidal (dSph) galaxies in the vicinity of the MW are tidally affected their
kinematic samples are very likely contaminated by tidally stripped stars which
tend to artificially inflate the measured velocity dispersion. The effect is
stronger for dwarfs on their way from the peri- to the apocentre due to the
formation of new tidal tails after pericentre. Realistic mass estimates of dSph
galaxies thus require removal of these stars from kinematic samples.Comment: 8 pages, 7 figures, accepted for publication in MNRA
Fitting a 3D Morphable Model to Edges: A Comparison Between Hard and Soft Correspondences
We propose a fully automatic method for fitting a 3D morphable model to
single face images in arbitrary pose and lighting. Our approach relies on
geometric features (edges and landmarks) and, inspired by the iterated closest
point algorithm, is based on computing hard correspondences between model
vertices and edge pixels. We demonstrate that this is superior to previous work
that uses soft correspondences to form an edge-derived cost surface that is
minimised by nonlinear optimisation.Comment: To appear in ACCV 2016 Workshop on Facial Informatic
Evaluating the feasibility of using candidate DNA barcodes in discriminating species of the large Asteraceae family
<p>Abstract</p> <p>Background</p> <p>Five DNA regions, namely, <it>rbcL</it>, <it>matK</it>, ITS, ITS2, and <it>psbA-trnH</it>, have been recommended as primary DNA barcodes for plants. Studies evaluating these regions for species identification in the large plant taxon, which includes a large number of closely related species, have rarely been reported.</p> <p>Results</p> <p>The feasibility of using the five proposed DNA regions was tested for discriminating plant species within Asteraceae, the largest family of flowering plants. Among these markers, ITS2 was the most useful in terms of universality, sequence variation, and identification capability in the Asteraceae family. The species discriminating power of ITS2 was also explored in a large pool of 3,490 Asteraceae sequences that represent 2,315 species belonging to 494 different genera. The result shows that ITS2 correctly identified 76.4% and 97.4% of plant samples at the species and genus levels, respectively. In addition, ITS2 displayed a variable ability to discriminate related species within different genera.</p> <p>Conclusions</p> <p>ITS2 is the best DNA barcode for the Asteraceae family. This approach significantly broadens the application of DNA barcoding to resolve classification problems in the family Asteraceae at the genera and species levels.</p
Urological referral of asymptomatic men in general practice in England
The Prostate Cancer Risk Management Programme (PCRMP) launched in November 2002 provides guidelines for general practitioners (GPs) on age-specific prostate-specific antigen (PSA) cutoff levels in asymptomatic men. The impact of the PCRMP on GP referrals is unknown. This study investigates whether there was a change in the proportion of asymptomatic men with raised PSA levels (⩾3 ng ml−1) who were referred to urologists since the launch of the guidelines. Sixty-nine general practices in four areas of England and the main pathology laboratory in each area, which had participated in our previous research, were asked to provide data. Forty-eight practices (70%) provided retrospective data on urological referrals in men who had a PSA test taken in the periods 1 December 2001 to 31 May 2002 (pre-launch) and 1 December 2003 to 31 May 2004 (post-launch). Data on referrals were completed for 709 (79%) out of 898 and 1040 (90%) out of 1157 raised records pre- and post-launch, respectively. The percentage of men with raised PSA levels who were asymptomatic was similar in both time periods (19–20%) and the proportion referred to urologists according to the PCRMP guidelines did not increase significantly over time (24% pre-launch and 29% post-launch, P=0.42). The referral rate was lower than expected if the guidelines had been followed. The influence of the guidelines seems to have been low. At the time of data collection, 56% (112 out of 200) of GP partners reported that they were aware of receiving the PCRMP pack. To ensure future, effective implementation of guidelines requires evaluation
Development and implementation of the Structured Training Trainer Assessment Report (STTAR) in the English National Training Programme for laparoscopic colorectal surgery
Background: There is a lack of educational tools available for surgical teaching critique, particularly for advanced laparoscopic surgery. The aim was to develop and implement a tool that assesses training quality and structures feedback for trainers in the English National Training Programme for laparoscopic colorectal surgery. Methods: Semi-structured interviews were performed and analysed, and items were extracted. Through the Delphi process, essential items pertaining to desirable trainer characteristics, training structure and feedback were determined. An assessment tool (Structured Training Trainer Assessment Report—STTAR) was developed and tested for feasibility, acceptability and educational impact. Results: Interview transcripts (29 surgical trainers, 10 trainees, four educationalists) were analysed, and item lists created and distributed for consensus opinion (11 trainers and seven trainees). The STTAR consisted of 64 factors, and its web-based version, the mini-STTAR, included 21 factors that were categorised into four groups (training structure, training behaviour, trainer attributes and role modelling) and structured around a training session timeline (beginning, middle and end). The STTAR (six trainers, 48 different assessments) demonstrated good internal consistency (α = 0.88) and inter-rater reliability (ICC = 0.75). The mini-STTAR demonstrated good inter-item reliability (α = 0.79) and intra-observer reliability on comparison of 85 different trainer/trainee combinations (r = 0.701, p = <0.001). Both were found to be feasible and acceptable. The educational report for trainers was found to be useful (4.4 out of 5). Conclusions: An assessment tool that evaluates training quality was developed and shown to be reliable, acceptable and of educational value. It has been successfully implemented into the English National Training Programme for laparoscopic colorectal surgery
Ordering phenomena in quasi one-dimensional organic conductors
Low-dimensional organic conductors could establish themselves as model
systems for the investigation of the physics in reduced dimensions. In the
metallic state of a one-dimensional solid, Fermi-liquid theory breaks down and
spin and charge degrees of freedom become separated. But the metallic phase is
not stable in one dimension: as the temperature is reduced, the electronic
charge and spin tend to arrange themselves in an ordered fashion due to strong
correlations. The competition of the different interactions is responsible for
which broken-symmetry ground state is eventually realized in a specific
compound and which drives the system towards an insulating state.
Here we review the various ordering phenomena and how they can be identified
by optic and magnetic measurements. While the final results might look very
similar in the case of a charge density wave and a charge-ordered metal, for
instance, the physical cause is completely different. When density waves form,
a gap opens in the density of states at the Fermi energy due to nesting of the
one-dimension Fermi surface sheets. When a one-dimensional metal becomes a
charge-ordered Mott insulator, on the other hand, the short-range Coulomb
repulsion localizes the charge on the lattice sites and even causes certain
charge patterns.
We try to point out the similarities and conceptional differences of these
phenomena and give an example for each of them. Particular emphasis will be put
on collective phenomena which are inherently present as soon as ordering breaks
the symmetry of the system.Comment: Review article Naturwissenschaften 200
The Social Life of Time and Methods: Studying London’s Temporal Architectures
This paper contributes to work on the social life of time. It focuses on how time is doubled; produced by and productive of the relations and processes it operates through. In particular, it explores the methodological implications of this conception of time for how social scientists may study the doubledness of time. It draws on an allied move within the social sciences to see methods as themselves doubled; as both emerging from and constitutive of the social worlds that they seek to understand. We detail our own very different methodological experiments with studying the social life of time in London, engaging interactive documentary to elucidate nonlinear imaginaries of space-time in London’s pop-up culture (Ella Harris) and encountering time on a series of walks along a particular stretch of road in south east London (Beckie Coleman). While clearly different projects in terms of their content, ambition and scope, in bringing these projects together we show the ability of our methods to grasp and perform from multiple angles and scales what Sharma calls ‘temporal architectures’. Temporal architectures, composed of elements including the built environment, commodities, services, technologies and labour, are infrastructures that enable social rhythms and temporal logics and that can entail a politicized valuing of the time of certain groups over others. We aim to contribute to an expanded and enriched conceptualisation of methods for exploring time, considering what our studies might offer to work on the doubled social life of time and methods, and highlighting in particular their implications for an engagement with a politics of time and temporality
Low oxygen tension primes aortic endothelial cells to the reparative effect of tissue-protective cytokines
Erythropoietin (EPO) has both erythropoietic and tissue-protective properties. The EPO analogues carbamylated EPO (CEPO) and pyroglutamate helix B surface peptide (pHBSP) lack the erythropoietic activity of EPO but retain the tissue-protective properties that are mediated by a heterocomplex of EPO receptor (EPOR) and the β common receptor (βCR). We studied the action of EPO and its analogues in a model of wound healing where a bovine aortic endothelial cells (BAECs) monolayer was scratched and the scratch closure was assessed over 24 h under different oxygen concentrations. We related the effects of EPO and its analogues on repair to their effect on BAECs proliferation and migration (evaluated using a micro-Boyden chamber). EPO, CEPO and pHBSP enhanced scratch closure only at lower oxygen (5%), while their effect at atmospheric oxygen (21%) was not significant. The mRNA expression of EPOR was doubled in 5% compared to 21% oxygen, and this was associated with increased EPOR assessed by immunofluorescence and Western blot. By contrast βCR mRNA levels were similar in 5% and 21% oxygen. EPO and its analogues increased both BAECs proliferation and migration, suggesting that both may be involved in the reparative process. The priming effect of low oxygen tension on the action of tissue-protective cytokines may be of relevance to vascular disease, including atherogenesis and restenosis
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