62,507 research outputs found
Newtonian limit of String-Dilaton Gravity
We study the weak-field limit of string-dilaton gravity and derive
corrections to the Newtonian potential which strength directly depends on the
self interaction potential and the nonminimal coupling of the dilaton scalar
field. We discuss also possible astrophysical applications of the results, in
particular the flat rotation curves of spiral galaxies.Comment: 11 pages, LATEX file, to appear in IJMP
Identifying the challenges and facilitators of implementing a COPD care bundle.
BACKGROUND: Care bundles have been shown to improve outcomes, reduce hospital readmissions and reduce length of hospital stay; therefore increasing the speed of uptake and delivery of care bundles should be a priority in order to deliver more timely improvements and consistent high-quality care. Previous studies have detailed the difficulties of obtaining full compliance to bundle elements but few have described the underlying reasons for this. In order to improve future implementation this paper investigates the challenges encountered by clinical teams implementing a chronic obstructive pulmonary disease (COPD) care bundle and describes actions taken to overcome these challenges. METHODS: An initial retrospective documentary analysis of data from seven clinical implementation teams was undertaken to review the challenges faced by the clinical teams. Three focus groups with healthcare professionals and managers explored solutions to these challenges developed during the project. RESULTS: Documentary analysis identified 28 challenges which directly impacted implementation of the COPD care bundle within five themes; staffing, infrastructure, process, use of improvement methodology and patient and public involvement. Focus groups revealed that the five most significant challenges for all groups were: staff too busy, staff shortages, lack of staff engagement, added workload of the bundle and patient coding issues. The participants shared facilitating factors used to overcome issues including: shifting perceptions to improve engagement, further education sessions to increase staff participation and gaining buy-in from managers through payment frameworks. CONCLUSIONS: Maximising the impact of a care bundle relies on its successful and timely implementation. Teams implementing the COPD care bundle encountered challenges that were common to all teams and sites. Understanding and learning from the challenges faced by previous endeavours and identifying the facilitators to overcoming these barriers provides an opportunity to mitigate issues that waste time and resources, and ensures that training can be tailored to the anticipated challenges
Weakly coupled quantum spin singlets in BaCrO
Using single crystal inelastic neutron scattering with and without
application of an external magnetic field and powder neutron diffraction, we
have characterized magnetic interactions in BaCrO. Even without
field, we found that there exist three singlet-to-triplet excitation modes in
scattering plane. Our complete analysis shows that the three modes
are due to spatially anisotropic interdimer interactions that are induced by
local distortions of the tetrahedron of oxygens surrounding the Jahn-Teller
active Cr. The strong intradimer coupling of meV
and weak interdimer interactions ( meV) makes
BaCrO a good model system for weakly-coupled quantum spin
dimers
Tree Amplitudes and Two-loop Counterterms in D=11 Supergravity
We compute the tree level 4-particle bosonic scattering amplitudes in D=11
supergravity. By construction, they are part of a linearized supersymmetry-,
coordinate- and 3-form gauge-invariant. While this on-shell invariant is
nonlocal, suitable SUSY-preserving differentiations turn it into a local one
with correct dimension to provide a natural lowest (two-loop) order counterterm
candidate. Its existence shows explicitly that no symmetries protect this
ultimate supergravity from the nonrenormalizability of its lower-dimensional
counterparts.Comment: 14 page
Checking the transverse Ward-Takahashi relation at one loop order in 4-dimensions
Some time ago Takahashi derived so called {\it transverse} relations relating
Green's functions of different orders to complement the well-known
Ward-Green-Takahashi identities of gauge theories by considering wedge rather
than inner products. These transverse relations have the potential to determine
the full fermion-boson vertex in terms of the renormalization functions of the
fermion propagator. He & Yu have given an indicative proof at one-loop level in
4-dimensions. However, their construct involves the 4th rank Levi-Civita tensor
defined only unambiguously in 4-dimensions exactly where the loop integrals
diverge. Consequently, here we explicitly check the proposed transverse
Ward-Takahashi relation holds at one loop order in -dimensions, with
.Comment: 20 pages, 3 figures This version corrects and clarifies the previous
result. This version has been submitted for publicatio
General features of Bianchi-I cosmological models in Lovelock gravity
We derived equations of motion corresponding to Bianchi-I cosmological models
in the Lovelock gravity. Equations derived in the general case, without any
specific ansatz for any number of spatial dimensions and any order of the
Lovelock correction. We also analyzed the equations of motion solely taking
into account the highest-order correction and described the drastic difference
between the cases with odd and even numbers of spatial dimensions. For
power-law ansatz we derived conditions for Kasner and generalized Milne regimes
for the model considered. Finally, we discuss the possible influence of matter
in the form of perfect fluid on the solutions obtained.Comment: extended version of published Brief Repor
Information-theory-based solution of the inverse problem in classical statistical mechanics
We present a procedure for the determination of the interaction potential
from the knowledge of the radial pair distribution function. The method,
realized inside an inverse Monte Carlo simulation scheme, is based on the
application of the Maximum Entropy Principle of information theory and the
interaction potential emerges as the asymptotic expression of the transition
probability. Results obtained for high density monoatomic fluids are very
satisfactory and provide an accurate extraction of the potential, despite a
modest computational effort.Comment: 9 pages, 2 figure
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