35,235 research outputs found
Simple Coherent Polarization Manipulation Scheme for Generating High Power Radially Polarized Beam
We present a simple novel scheme that converts a Gaussian beam into an
approximated radially polarized beam using coherent polarization manipulation
together with Poynting walk-off in birefringent crystals. Our scheme alleviates
the interferometric stability required by previous schemes that implemented
this coherent mode summation using Mach-Zehnder-like interferometers. A
symmetrical arrangement of two walk-off crystals with a half-wave plate, allows
coherence control even when the laser has short temporal coherence length. We
generated 14 watts of radially polarized beam from an Ytterbium fiber laser,
only limited by the available fiber laser power.Comment: Submitting for publicatio
molecular ions can exist in strong magnetic fields
Using the variational method it is shown that for magnetic fields G there can exist a molecular ion .Comment: LaTeX, 7 pp, 1 table, 4 figures. Title modified. Consideration of the
longitudinal size of the system was adde
Early life growth patterns persist for 12 years and impact pulmonary outcomes in cystic fibrosis
BACKGROUND:
In children with cystic fibrosis (CF), recovery from growth faltering within 2 years of diagnosis (Responders) is associated with better growth and less lung disease at age 6 years. This study examined whether these benefits are sustained through 12 years of age.
METHODS:
Longitudinal growth from 76 children with CF enrolled in the Wisconsin CF Neonatal Screening Project was examined and categorized into 5 groups: R12, R6, and R2, representing Responders who maintained growth improvement to age 12, 6, and 2 years, respectively, and I6 and N6, representing Non-responders whose growth did and did not improve during ages 2-6 years, respectively. Lung disease was evaluated by % predicted forced expiratory volume in one second (FEV1) and chest radiograph (CXR) scores.
RESULTS:
Sixty-two percent were Responders. Within this group, 47% were R12, 28% were R6, and 25% were R2. Among Non-responders, 76% were N6. CF children with meconium ileus (MI) had worse lung function and CXR scores compared to other CF children. Among 53 children with pancreatic insufficiency without MI, R12 had significantly better FEV1 (97-99% predicted) and CXR scores during ages 6-12 years than N6 (89-93% predicted). Both R6 and R2 experienced a decline in FEV1 by ages 10-12 years.
CONCLUSIONS:
Early growth recovery in CF is critical, as malnutrition during infancy tends to persist and catch-up growth after age 2 years is difficult. The longer adequate growth was maintained after early growth recovery, the better the pulmonary outcomes at age 12 years
Binary Neutron Stars in General Relativity: Quasi-Equilibrium Models
We perform fully relativistic calculations of binary neutron stars in
quasi-equilibrium circular orbits. We integrate Einstein's equations together
with the relativistic equation of hydrostatic equilibrium to solve the initial
value problem for equal-mass binaries of arbitrary separation. We construct
sequences of constant rest mass and identify the innermost stable circular
orbit and its angular velocity. We find that the quasi-equilibrium maximum
allowed mass of a neutron star in a close binary is slightly larger than in
isolation.Comment: 4 pages, 3 figures, RevTe
Precautionary Measures for Credit Risk Management in Jump Models
Sustaining efficiency and stability by properly controlling the equity to
asset ratio is one of the most important and difficult challenges in bank
management. Due to unexpected and abrupt decline of asset values, a bank must
closely monitor its net worth as well as market conditions, and one of its
important concerns is when to raise more capital so as not to violate capital
adequacy requirements. In this paper, we model the tradeoff between avoiding
costs of delay and premature capital raising, and solve the corresponding
optimal stopping problem. In order to model defaults in a bank's loan/credit
business portfolios, we represent its net worth by Levy processes, and solve
explicitly for the double exponential jump diffusion process and for a general
spectrally negative Levy process.Comment: 31 pages, 4 figure
Quasi-Local Energy Flux of Spacetime Perturbation
A general expression for quasi-local energy flux for spacetime perturbation
is derived from covariant Hamiltonian formulation using functional
differentiability and symplectic structure invariance, which is independent of
the choice of the canonical variables and the possible boundary terms one
initially puts into the Lagrangian in the diffeomorphism invariant theories.
The energy flux expression depends on a displacement vector field and the
2-surface under consideration. We apply and test the expression in Vaidya
spacetime. At null infinity the expression leads to the Bondi type energy flux
obtained by Lindquist, Schwartz and Misner. On dynamical horizons with a
particular choice of the displacement vector, it gives the area balance law
obtained by Ashtekar and Krishnan.Comment: 8 pages, added appendix, version to appear in Phys. Rev.
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