17,778 research outputs found
Operational integrator
System operates in the nonreturn-to-zero mode, maintaining the increased bit density capability of this mode but with much higher noise immunity than conventional schemes offer. This integrator performs a mathematical integrating function on inputs from 100 Hz through 100 MHz
Scattering of vector mesons off nucleons
We construct a relativistic and unitary approach to 'high' energy pion- and
photon-nucleon reactions taking the , , ,
final states into account. Our scheme dynamically
generates the s- and d-wave nucleon resonances N(1535), N(1650) and N(1520) and
isobar resonances and in terms of quasi-local
interaction vertices. The description of photon-induced processes is based on a
generalized vector-meson dominance assumption which directly relates the
electromagnetic quasi-local 4-point interaction vertices to the corresponding
vertices involving the and fields. We obtain a satisfactory
description of the elastic and inelastic pion- and photon-nucleon scattering
data in the channels considered. The resulting s-wave - and
-nucleon scattering amplitudes are presented. Using these amplitudes we
compute the leading density modification of the and energy
distributions in nuclear matter. We find a repulsive energy shift for the
meson at small nuclear density but predict considerable strength in
resonance-hole like -meson modes. Compared to previous calculations our
result for the -meson spectral function shows a significantly smaller
in-medium effect. This reflects a fairly small coupling strength of the N(1520)
resonance to the channel.Comment: 78 pages, 19 figures, moderately revised version, accepted in Nucl.
Phys.
Saturation from nuclear pion dynamics
We construct an equation-of-state for nuclear matter based on the chiral
Lagrangian. The relevant scales are discussed and an effective chiral power
expansion scheme, which is constructed to work around the nuclear saturation
density, is presented. A realistic equation-of-state is obtained by adjusting
one free parameter, when the leading and subleading terms in the expansion are
included. The saturation mechanism is due to correlations induced by the
one-pion-exchange interaction. Furthermore, we find a substantial deviation
from the Fermi-gas estimate of the quark condensate in nuclear matter already
at the saturation density.Comment: revised version, with minor corrections, 13 pages, 3 Postscript
figure
From meson- and photon-nucleon scattering to vector mesons in nuclear matter
We present a relativistic and unitary approach to pion- and photon-nucleon
scattering taking into account the , , , ,
, and channels. Our scheme dynamically
generates the s- and d-wave nucleon resonances N(1535), N(1650), N(1520) and
N(1700) and isobar resonances and in terms of
quasi-local two-body interaction terms. We obtain a fair description of the
experimental data relevant for slow vector-meson propagation in nuclear matter.
The s-wave - and -meson nucleon scattering amplitudes, which
define the leading density modification of the - and -meson
spectral functions in nuclear matter, are predicted.Comment: 6 pages, 1 figure; contribution to the Int. Workshop XXX on Gross
Properties of Nuclei and Nuclear Excitations: Ultrarelativistic Heavy Ion
Collisions, Hirschegg, Jan. 13-19, 200
The Impact of Employer-Provided Health Insurance on Dynamic Employment Transitions
We estimate the impact of employer-provided health insurance (EPHI) on the job mobility of males over time using a dynamic empirical model that accounts for unobserved heterogeneity. Previous studies of job-lock reach different conclusions about possible distortions in labor mobility stemming from an employment-based health insurance system: a few authors find no evidence of job-lock, while most find reductions in the mobility of insured workers of between 20 and 40%. WE use data from the National Longitudinal Survey of Youth which describes the health insurance an individual holds, as well as whether he is offered insurance by his employer. This additional information allows us to model the latent individual characteristics that are correlated with the offer of EPHI, the acceptance of EPHI, and employment transitions. Our results provide an estimate of job-lock unbiased through correlation with positive job characteristics and individual specific turnover propensity. We find no evidence of job-lock among married males, and produce small estimates of job-lock among unmarried males of between 10 and 15%.
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