28,766 research outputs found
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Measuring and Monitoring Cognition in the Postoperative Period
It is common for patients of all ages to experience some degree of cognitive disturbance following surgery. In most cases, impairment appears mild and is restricted to the acute post-operative period, resolving steadily and speedily. In a small number of cases, however, deficits may be more pronounced and/or endure for longer periods, significantly delaying recovery and increasing the risk of serious clinical complications. The ability to accurately measure postoperative cognition, and track recovery of function, is an important clinical task. This review explores practical and methodological issues that may confound this process, examining how best to obtain reliable and meaningful measures of cognition before and after surgery. It considers neuropsychological test selection, administration, analysis and interpretation and offers evidence-based practice points for clinicians and researchers
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Chronic disease self-management approaches within the complex organisational structure of a health care system
Self-management has the potential to reduce the burden of chronic disease — but it needs to be integrated into the health system
Identity and Search in Social Networks
Social networks have the surprising property of being "searchable": Ordinary
people are capable of directing messages through their network of acquaintances
to reach a specific but distant target person in only a few steps. We present a
model that offers an explanation of social network searchability in terms of
recognizable personal identities: sets of characteristics measured along a
number of social dimensions. Our model defines a class of searchable networks
and a method for searching them that may be applicable to many network search
problems, including the location of data files in peer-to-peer networks, pages
on the World Wide Web, and information in distributed databases.Comment: 4 page, 3 figures, revte
Deep Inelastic Lepton-Nucleon Scattering at HERA
Data from the HERA collider experiments, H1 and ZEUS, have been fundamental
to the rapid recent development of our understanding of the partonic
composition of the proton and of QCD. This report focuses on inclusive
measurements of neutral and charged current cross sections at HERA, using the
full available data taken to date. The present precision on the proton parton
densities and the further requirements for future measurements at the Tevatron
and LHC are explored. Emphasis is also placed on the region of very low
Bjorken-x and Q^2. In this region, the `confinement' transition takes place
from partons to hadrons as the relevant degrees of freedom and novel or exotic
QCD effects associated with large parton densities are most likely to be
observed. Finally, prospects for the second phase of HERA running are
discussed.Comment: 13 pages, 15 figures, to appear in Proceedings of the XXI
International Symposium on lepton and Photon Interactions at High Energies,
Fermilab, August 200
MOSFIRE Absorption Line Spectroscopy of z > 2 Quiescent Galaxies: Probing a Period of Rapid Size Growth
Using the MOSFIRE near-infrared multi-slit spectrograph on the Keck 1
Telescope, we have secured high signal-to-noise ratio absorption line spectra
for six massive galaxies with redshift 2 < z < 2.5. Five of these galaxies lie
on the red sequence and show signatures of passive stellar populations in their
rest-frame optical spectra. By fitting broadened spectral templates we have
determined stellar velocity dispersions and, with broad-band HST and Spitzer
photometry and imaging, stellar masses and effective radii. Using this enlarged
sample of galaxies we confirm earlier suggestions that quiescent galaxies at z
> 2 have small sizes and large velocity dispersions compared to local galaxies
of similar stellar mass. The dynamical masses are in very good agreement with
stellar masses (log Mstar/Mdyn = -0.02 +/- 0.03), although the average
stellar-to-dynamical mass ratio is larger than that found at lower redshift
(-0.23 +/- 0.05). By assuming evolution at fixed velocity dispersion, not only
do we confirm a surprisingly rapid rate of size growth but we also consider the
necessary evolutionary track on the mass-size plane and find a slope alpha =
dlogR / dlogM > ~2 inconsistent with most numerical simulations of minor
mergers. Both results suggest an additional mechanism may be required to
explain the size growth of early galaxies.Comment: Updated to match the published versio
Community Structure of the Physical Review Citation Network
We investigate the community structure of physics subfields in the citation
network of all Physical Review publications between 1893 and August 2007. We
focus on well-cited publications (those receiving more than 100 citations), and
apply modularity maximization to uncover major communities that correspond to
clearly-identifiable subfields of physics. While most of the links between
communities connect those with obvious intellectual overlap, there sometimes
exist unexpected connections between disparate fields due to the development of
a widely-applicable theoretical technique or by cross fertilization between
theory and experiment. We also examine communities decade by decade and also
uncover a small number of significant links between communities that are widely
separated in time.Comment: 14 pages, 7 figures, 8 tables. Version 2: various small additions in
response to referee comment
Scale-freeness for networks as a degenerate ground state: A Hamiltonian formulation
The origin of scale-free degree distributions in the context of networks is
addressed through an analogous non-network model in which the node degree
corresponds to the number of balls in a box and the rewiring of links to balls
moving between the boxes. A statistical mechanical formulation is presented and
the corresponding Hamiltonian is derived. The energy, the entropy, as well as
the degree distribution and its fluctuations are investigated at various
temperatures. The scale-free distribution is shown to correspond to the
degenerate ground state, which has small fluctuations in the degree
distribution and yet a large entropy. We suggest an implication of our results
from the viewpoint of the stability in evolution of networks.Comment: 7 pages, 3 figures. To appear in Europhysics lette
Stress-intensity factor calculations using the boundary force method
The Boundary Force Method (BFM) was formulated for the three fundamental problems of elasticity: the stress boundary value problem, the displacement boundary value problem, and the mixed boundary value problem. Because the BFM is a form of an indirect boundary element method, only the boundaries of the region of interest are modeled. The elasticity solution for the stress distribution due to concentrated forces and a moment applied at an arbitrary point in a cracked infinite plate is used as the fundamental solution. Thus, unlike other boundary element methods, here the crack face need not be modeled as part of the boundary. The formulation of the BFM is described and the accuracy of the method is established by analyzing a center-cracked specimen subjected to mixed boundary conditions and a three-hole cracked configuration subjected to traction boundary conditions. The results obtained are in good agreement with accepted numerical solutions. The method is then used to generate stress-intensity solutions for two common cracked configurations: an edge crack emanating from a semi-elliptical notch, and an edge crack emanating from a V-notch. The BFM is a versatile technique that can be used to obtain very accurate stress intensity factors for complex crack configurations subjected to stress, displacement, or mixed boundary conditions. The method requires a minimal amount of modeling effort
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