1,185 research outputs found
Measuring the black hole spin direction in 3D Cartesian numerical relativity simulations
We show that the so-called flat-space rotational Killing vector method for
measuring the Cartesian components of a black hole spin can be derived from the
surface integral of Weinberg's pseudotensor over the apparent horizon surface
when using Gaussian normal coordinates in the integration. Moreover, the
integration of the pseudotensor in this gauge yields the Komar angular momentum
integral in a foliation adapted to the axisymmetry of the spacetime. As a
result, the method does not explicitly depend on the evolved lapse and
shift on the respective timeslice, as they are fixed to Gaussian
normal coordinates, while leaving the coordinate labels of the spatial metric
and the extrinsic curvature unchanged. Such gauge fixing
endows the method with coordinate invariance, which is not present in integral
expressions using Weinberg's pseudotensor, as they normally rely on the
explicit use of Cartesian coordinates
Interference between the halves of a double-well trap containing a Bose-Einstein condensate
Interference between the halves of a double-well trap containing a
Bose-Einstein condensate is studied. It is found that when the atoms in the two
wells are initially in the coherent state, the intensity exhibits collapses and
revivals, but it does not for the initial Fock states. Whether the initial
states are in the coherent states or in a Fock states, the fidelity time has
nothing to do with collision. We point out that interference and its fidelity
can be adjusted experimentally by properly preparing the number and initial
states of the system.Comment: 10 pages, 3 figures, accepted by Phy. rev.
Neutrinos with Lorentz-violating operators of arbitrary dimension
The behavior of fermions in the presence of Lorentz and CPT violation is
studied. Allowing for operators of any mass dimension, we classify all
Lorentz-violating terms in the quadratic Lagrange density for free fermions.
The result is adapted to obtain the effective hamiltonian describing the
propagation and mixing of three flavors of left-handed neutrinos in the
presence of Lorentz violation involving operators of arbitrary mass dimension.
A characterization of the neutrino coefficients for Lorentz violation is
provided via a decomposition using spin-weighted spherical harmonics. The
restriction of the general theory to various special cases is discussed,
including among others the renormalizable limit, the massless scenario,
flavor-blind and oscillation-free models, the diagonalizable case, and several
isotropic limits. The formalism is combined with existing data on neutrino
oscillations and kinematics to extract a variety of measures of coefficients
for Lorentz and CPT violation. For oscillations, we use results from the
short-baseline experiments LSND and MiniBooNE to obtain explicit sensitivities
to effects from flavor-mixing Lorentz-violating operators up to mass dimension
10, and we present methods to analyze data from long-baseline experiments. For
propagation, we use time-of-flight measurements from the supernova SN1987A and
from a variety of experiments including MINOS and OPERA to constrain
oscillation-free Lorentz-violating operators up to mass dimension 10, and we
discuss constraints from threshold effects in meson decays and Cherenkov
emission.Comment: 35 pages two-column REVTe
Filled Landau levels in neutral quantum gases
We consider the signatures of the Integer Quantum Hall Effect in a degenerate
gas of electrically neutral atomic fermions. An effective magnetic field is
achieved by applying two incident light beams with a high orbital angular
momentum. We show how states corresponding to completely filled Landau levels
are obtained and discuss various possibilities to measure the incompressible
nature of the trapped two-dimensional gasComment: Minor corrections. Phys. Rev. A, 053632 (2005). High resolution
figures can be obtained from the author
Ferromagnetic resonance force microscopy on a thin permalloy film
Ferromagnetic Resonance Force Microscopy (FMRFM) offers a means of performing
local ferromagnetic resonance. We have studied the evolution of the FMRFM force
spectra in a continuous 50 nm thick permalloy film as a function of probe-film
distance and performed numerical simulations of the intensity of the FMRFM
probe-film interaction force, accounting for the presence of the localized
strongly nonuniform magnetic field of the FMRFM probe magnet. Excellent
agreement between the experimental data and the simulation results provides
insight into the mechanism of FMR mode excitation in an FMRFM experiment.Comment: 9 pages, 2 figure
PMU31 early cost-effectiveness analysis of continuous monitoring of lung-aeration with electrical impedance tomography in preterm neonates with respiratory distress syndrome
Objectives
Respiratory distress syndrome (RDS) is relatively common in preterm neonates due to lung immaturity. Clinical management by respiratory support is associated with high complications rates. Guidance on appropriate lung-aeration is limited using conventional thorax X-ray monitoring. Electrical impedance tomography (EIT) allows radiation-free, continuous lung-aeration monitoring to guide effective respiratory support. EIT produces dynamic images of air volume changes whereas X-ray shows 2-D structure. Clinicians expect EIT implementation to reduce the number of patients requiring mechanical ventilation, overall complication rates and hospitalisation length. We conducted an early cost-effectiveness analysis of EIT-monitoring in preterm neonates with RDS versus standard care in the Netherlands.
Methods
A decision-analytic model was constructed comparing costs and effects of conventional X-ray versus EIT-monitoring for preterm neonates with RDS from the healthcare perspective with a time horizon of two years. Input parameters were based on literature and cost databases. The effects of EIT-monitoring were based on consensus by 6 clinical experts for two scenarios, (1) a conservative scenario assuming only a decrease of patients on mechanical ventilation under EIT-monitoring, and (2) an optimistic scenario including scenario (1) and assuming an additional 10% relative complication rate decrease in comparison to standard care. Main outcomes were total average costs per patient, number of patients with bronchopulmonary dysplasia (BPD), and mortality. One-way sensitivity analyses were conducted.
Results
EIT-monitoring was estimated to be cost-saving in both scenarios, mainly due to a shorter average hospital length of stay. Total incremental costs per patient for EIT-monitored care versus standard care were -€929 and -€10,706 for scenario (1) and (2), respectively. The number of patients with BPD and deaths were reduced. Results were robust to changes in input parameters.
Conclusions
EIT lung-aeration monitoring in preterm neonates is expected to result in cost-savings and lower mortality and BPD rates, in comparison to standard care, in a Dutch hospital setting.
Copyright © 2019 Published by Elsevier Inc
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