4,332 research outputs found
Positronium collisions with rare-gas atoms
We calculate elastic scattering of positronium (Ps) by the Xe atom using the
recently developed pseudopotential method [I. I. Fabrikant and G. F. Gribakin,
Phys. Rev. A 90, 052717 (2014)] and review general features of Ps scattering
from heavier rare-gas atoms: Ar, Kr, and Xe. The total scattering cross section
is dominated by two contributions: elastic scattering and Ps ionization
(breakup). To calculate the Ps ionization cross sections we use the
binary-encounter method for Ps collisions with an atomic target. Our results
for the ionization cross section agree well with previous calculations carried
out in the impulse approximation. Our total Ps-Xe cross section, when plotted
as a function of the projectile velocity, exhibits similarity with the
electron-Xe cross section for the collision velocities higher than 0.8 a.u.,
and agrees very well with the measurements at Ps velocities above 0.5 a.u.Comment: 7 pages, 7 figures, submitted to J. Phys.
Virtual Data in CMS Analysis
The use of virtual data for enhancing the collaboration between large groups
of scientists is explored in several ways:
- by defining ``virtual'' parameter spaces which can be searched and shared
in an organized way by a collaboration of scientists in the course of their
analysis;
- by providing a mechanism to log the provenance of results and the ability
to trace them back to the various stages in the analysis of real or simulated
data;
- by creating ``check points'' in the course of an analysis to permit
collaborators to explore their own analysis branches by refining selections,
improving the signal to background ratio, varying the estimation of parameters,
etc.;
- by facilitating the audit of an analysis and the reproduction of its
results by a different group, or in a peer review context.
We describe a prototype for the analysis of data from the CMS experiment
based on the virtual data system Chimera and the object-oriented data analysis
framework ROOT. The Chimera system is used to chain together several steps in
the analysis process including the Monte Carlo generation of data, the
simulation of detector response, the reconstruction of physics objects and
their subsequent analysis, histogramming and visualization using the ROOT
framework.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 9 pages, LaTeX, 7 eps figures. PSN
TUAT010. V2 - references adde
Novel electrocardiographic criteria for the diagnosis of arrhythmogenic right ventricular cardiomyopathy
Aims: In order to improve the electrocardiographic (ECG) diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC), we evaluated novel quantitative parameters of the QRS complex and the value of bipolar chest leads (CF leads) computed from the standard 12 leads.
Methods and results: We analysed digital 12-lead ECGs in 44 patients with ARVC, 276 healthy subjects including 44 age and sex-matched with the patients and 36 genotyped members of ARVC families. The length and area of the terminal S wave in V1 to V3 were measured automatically using a common for all 12 leads QRS end. T wave negativity was assessed in V1 to V6 and in the bipolar CF leads computed from the standard 12 leads. The length and area of the terminal S wave were significantly shorter, whereas the S wave duration was significantly longer in ARVC patients compared with matched controls. Among members of ARVC families, those with mutations (n = 15) had shorter QRS length in V2 and V3 and smaller QRS area in lead V2 compared with those without mutations (n = 20). In ARVC patients, the CF leads were diagnostically superior to the standard unipolar precordial leads. Terminal S wave duration in V1 >48 ms or major T wave negativity in CF leads separated ARVC patients from matched controls with 90% sensitivity and 86% specificity.
Conclusion: The terminal S wave length and area in the right precordial leads are diagnostically useful and suitable for automatic analysis in ARVC. The CF leads are diagnostically superior to the unipolar precordial leads
Geothermal probabilistic cost study
A tool is presented to quantify the risks of geothermal projects, the Geothermal Probabilistic Cost Model (GPCM). The GPCM model was used to evaluate a geothermal reservoir for a binary-cycle electric plant at Heber, California. Three institutional aspects of the geothermal risk which can shift the risk among different agents was analyzed. The leasing of geothermal land, contracting between the producer and the user of the geothermal heat, and insurance against faulty performance were examined
Laparoscopic Sacropexy: A Retrospective Analysis of the Subjective Outcome in 310 Cases
Background and Objective. The aim of this study was to assess the subjective outcome following laparoscopic sacropexy. Methods. We performed a retrospective cohort study among women treated for descensus with laparoscopic sacropexy between January 2000 and December 2007. 310 patients received questionnaires during followup assessing major pre- and postoperative symptoms and overall satisfaction. Results. 214 (69%) patients responded to the questionnaire. Mean followup was 24.5 months. The number of patients with back or lower abdominal pain, foreign body sensation in the vagina and prolapse-related symptoms, urinary symptoms, vaginal and bladder infections, and the need for pessary usage decreased significantly postsurgically. Bowel symptoms increased slightly but not significantly. Two years after surgery, nearly 2 thirds of the women were satisfied or very satisfied with the outcome. Conclusion. Laparoscopic sacropexy is an effective treatment of descensus, with favorable or satisfactory subjective outcomes
Addressing the clumsiness loophole in a Leggett-Garg test of macrorealism
The rise of quantum information theory has lent new relevance to experimental
tests for non-classicality, particularly in controversial cases such as
adiabatic quantum computing superconducting circuits. The Leggett-Garg
inequality is a "Bell inequality in time" designed to indicate whether a single
quantum system behaves in a macrorealistic fashion. Unfortunately, a violation
of the inequality can only show that the system is either (i)
non-macrorealistic or (ii) macrorealistic but subjected to a measurement
technique that happens to disturb the system. The "clumsiness" loophole (ii)
provides reliable refuge for the stubborn macrorealist, who can invoke it to
brand recent experimental and theoretical work on the Leggett-Garg test
inconclusive. Here, we present a revised Leggett-Garg protocol that permits one
to conclude that a system is either (i) non-macrorealistic or (ii)
macrorealistic but with the property that two seemingly non-invasive
measurements can somehow collude and strongly disturb the system. By providing
an explicit check of the invasiveness of the measurements, the protocol
replaces the clumsiness loophole with a significantly smaller "collusion"
loophole.Comment: 7 pages, 3 figure
Results on the Wess-Zumino consistency condition for arbitrary Lie algebras
The so-called covariant Poincare lemma on the induced cohomology of the
spacetime exterior derivative in the cohomology of the gauge part of the BRST
differential is extended to cover the case of arbitrary, non reductive Lie
algebras. As a consequence, the general solution of the Wess-Zumino consistency
condition with a non trivial descent can, for arbitrary (super) Lie algebras,
be computed in the small algebra of the 1 form potentials, the ghosts and their
exterior derivatives. For particular Lie algebras that are the semidirect sum
of a semisimple Lie subalgebra with an ideal, a theorem by Hochschild and Serre
is used to characterize more precisely the cohomology of the gauge part of the
BRST differential in the small algebra. In the case of an abelian ideal, this
leads to a complete solution of the Wess-Zumino consistency condition in this
space. As an application, the consistent deformations of 2+1 dimensional
Chern-Simons theory based on iso(2,1) are rediscussed.Comment: 39 pages Latex file, 1 eps figure, typos and proof of lemma 5
correcte
Nature of 45 degree vortex lattice reorientation in tetragonal superconductors
The transformation of the vortex lattice in a tetragonal superconductor which
consists of its 45 degree reorientation relative to the crystal axes is studied
using the nonlocal London model. It is shown that the reorientation occurs as
two successive second order (continuous) phase transitions. The transition
magnetic fields are calculated for a range of parameters relevant for
borocarbide superconductors in which the reorientation has been observed
The Phase Transition to a Square Vortex Lattice in Type-II Superconductors with Fourfold Anisotropy
We investigate the stability of the square vortex lattice which has been
recently observed in experiments on the borocarbide family of superconductors.
Taking into account the tetragonal symmetry of these systems, we add fourfold
symmetric fourth-derivative terms to the Ginzburg-Landau(GL) free energy. At
these terms may be treated perturbatively to lowest order to locate
the transition from a distorted hexagonal to a square vortex lattice. We also
solve for this phase boundary numerically in the strongly type-II limit,
finding large corrections to the lowest-order perturbative results. We
calculate the relative fourfold anisotropy for field in the plane
to be 4.5% at the temperature, , where the transition occurs at
for field along the axis. This is to be compared to the 3.6%
obtained in the perturbative calculation. Furthermore, we find that the phase
boundary in the phase diagram has positive slope near .Comment: 15 pages including 2 figures, LaTe
Four-fold basal plane anisotropy of the nonlocal magnetization of YNi2B2C
Studies of single crystal YNi2B2C have revealed a four-fold anisotropy of the
equilibrium magnetization in the square crystallographic basal plane. This pi/2
periodicity occurs deep in the superconductive mixed state. In this crystal
symmetry, an ordinary superconductive mass anisotropy (as in usual London
theory) allows only a constant, isotropic response. In contrast, the
experimental results are well described by generalized London theory
incorporating non-local electrodynamics, as needed for this clean,
intermediate-k superconductor.Comment: 4 pages, 4 figure
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