44,849 research outputs found
Perturbative Wilson loops from unquenched Monte Carlo simulations at weak couplings
Perturbative expansions of several small Wilson loops are computed through
next-to-next-to-leading order in unquenched lattice QCD, from Monte Carlo
simulations at weak couplings. This approach provides a much simpler
alternative to conventional diagrammatic perturbation theory, and is applied
here for the first time to full QCD. Two different sets of lattice actions are
considered: one set uses the unimproved plaquette gluon action together with
the unimproved staggered-quark action; the other set uses the one-loop-improved
Symanzik gauge-field action together with the so-called ``asqtad''
improved-staggered quark action. Simulations are also done with different
numbers of dynamical fermions. An extensive study of the systematic
uncertainties is presented, which demonstrates that the small third-order
perturbative component of the observables can be reliably extracted from
simulation data. We also investigate the use of the rational hybrid Monte Carlo
algorithm for unquenched simulations with unimproved-staggered fermions. Our
results are in excellent agreement with diagrammatic perturbation theory, and
provide an important cross-check of the perturbation theory input to a recent
determination of the strong coupling by the HPQCD
collaboration.Comment: 14 pages, 8 figure
Capillary condensation in disordered porous materials: hysteresis versus equilibrium behavior
We study the interplay between hysteresis and equilibrium behavior in
capillary condensation of fluids in mesoporous disordered materials via a
mean-field density functional theory of a disordered lattice-gas model. The
approach reproduces all major features observed experimentally. We show that
the simple van der Waals picture of metastability fails due to the appearance
of a complex free-energy landscape with a large number of metastable states. In
particular, hysteresis can occur both with and without an underlying
equilibrium transition, thermodynamic consistency is not satisfied along the
hysteresis loop, and out-of-equilibrium phase transitions are possible.Comment: 4 pages, 4 figure
Asymptotic corrections to the eigenvalue density of the GUE and LUE
We obtain correction terms to the large N asymptotic expansions of the
eigenvalue density for the Gaussian unitary and Laguerre unitary ensembles of
random N by N matrices, both in the bulk of the spectrum and near the spectral
edge. This is achieved by using the well known orthogonal polynomial expression
for the kernel to construct a double contour integral representation for the
density, to which we apply the saddle point method. The main correction to the
bulk density is oscillatory in N and depends on the distribution function of
the limiting density, while the corrections to the Airy kernel at the soft edge
are again expressed in terms of the Airy function and its first derivative. We
demonstrate numerically that these expansions are very accurate. A matching is
exhibited between the asymptotic expansion of the bulk density, expanded about
the edge, and the asymptotic expansion of the edge density, expanded into the
bulk.Comment: 14 pages, 4 figure
Radio Galaxy Zoo: Knowledge Transfer Using Rotationally Invariant Self-Organising Maps
With the advent of large scale surveys the manual analysis and classification
of individual radio source morphologies is rendered impossible as existing
approaches do not scale. The analysis of complex morphological features in the
spatial domain is a particularly important task. Here we discuss the challenges
of transferring crowdsourced labels obtained from the Radio Galaxy Zoo project
and introduce a proper transfer mechanism via quantile random forest
regression. By using parallelized rotation and flipping invariant Kohonen-maps,
image cubes of Radio Galaxy Zoo selected galaxies formed from the FIRST radio
continuum and WISE infrared all sky surveys are first projected down to a
two-dimensional embedding in an unsupervised way. This embedding can be seen as
a discretised space of shapes with the coordinates reflecting morphological
features as expressed by the automatically derived prototypes. We find that
these prototypes have reconstructed physically meaningful processes across two
channel images at radio and infrared wavelengths in an unsupervised manner. In
the second step, images are compared with those prototypes to create a
heat-map, which is the morphological fingerprint of each object and the basis
for transferring the user generated labels. These heat-maps have reduced the
feature space by a factor of 248 and are able to be used as the basis for
subsequent ML methods. Using an ensemble of decision trees we achieve upwards
of 85.7% and 80.7% accuracy when predicting the number of components and peaks
in an image, respectively, using these heat-maps. We also question the
currently used discrete classification schema and introduce a continuous scale
that better reflects the uncertainty in transition between two classes, caused
by sensitivity and resolution limits
Do Primary Care Doctors Behave the Same in Antibiotic Prescribing for Upper Respiratory Tract Infections?
Purpose: To compare the extent of using an evidence-based approach in managing upper respiratory tract infections (URTIs) among primary care doctors from two different government clinic settings in Malaysia. Method: This is a cross sectional, prospective study carried out in a teaching university primary care centre in Kuala Lumpur (KL) where doctors are constantly exposed to continuing medical education (CME) and seven health clinics in Seremban, Malaysia where doctors have less exposure to CME in the year 2000. Twelve primary care practitioners in KL and 13 in Seremban participated in the study. Each practitioner was asked to record clinical data and prescriptions given to twenty consecutive patients with URTIs using a structured questionnaire for each patient. The extent of usage of an evidence-based approach in managing URTIs among practitioners was assessed
Are Doctors in the University-Based Primary Care Clinic More Evidence-Based?
Letter to the editor
How do Doctors Decide When to Prescribe Antibiotics in Upper Respiratory Tract Infections?
Purpose: To examine the predictive features which doctors use when prescribing antibiotics in upper respiratory tract infections (URTIs). Method: This is a cross sectional, prospective study done in a teaching university primary care centre in Kuala Lumpur from June to August 2000. Twelve primary care practitioners participated in the study. Each practitioner was asked to record clinical data and prescriptions given to twenty consecutive patients with URTIs using a structured questionnaire for each patient
Evaluation of tantalum for mercury containment in the SNAP-8 boiler
Corrosion testing of tantalum for mercury containment in SNAP 8 boile
RAMESES publication standards: realist syntheses
PMCID: PMC3558331This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
- …