5,372 research outputs found
Recollections of My Research in Developing the Heart-Lung Machine at Jefferson Medical College
A personal memoir written by Dr. Bernard J. Miller about his introduction to and interest in medical research as well as his experiences working on the heart-lung machine. He focuses specifically on his working relationship with John H. Gibbon, Jr., the development of a viable oxygenator and ventilator, and early testing of the machine on animal
Physical Optics of Invertebrate Eyes
Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E
Modeling kicks from the merger of generic black-hole binaries
Recent numerical relativistic results demonstrate that the merger of
comparable-mass spinning black holes has a maximum ``recoil kick'' of up to
\sim 4000 \kms. However the scaling of these recoil velocities with mass
ratio is poorly understood. We present new runs showing that the maximum
possible kick perpendicular to the orbital plane does not scale as
(where is the symmetric mass ratio), as previously proposed, but is more
consistent with , at least for systems with low orbital precession.
We discuss the effect of this dependence on galactic ejection scenarios and
retention of intermediate-mass black holes in globular clusters.Comment: 5 pages, 1 figure, 3 tables. Version published in Astrophys. J. Let
Nucleon electroweak form factors in a meson-cloud model
The meson-cloud model of the nucleon consisting of a system of three valence
quarks surrounded by a meson cloud is applied to study the electroweak
structure of the proton and neutron. The electroweak nucleon form factors are
calculated within a light-front approach, by obtaining an overall good
description of the experimental data. Charge densities as a function of the
transverse distance with respect to the direction of the three-momentum
transfer are also discussed.Comment: Prepared for Proceedings of NSTAR2007, Workshop on the physics of
excited nucleons, Bonn (Germany), 5-8 September 200
Role of Corticosteroids in Bone Loss During Space Flight
The primary objective of this research project is to test the hypothesis that corticosteroids contribute to the adverse skeletal effects of space flight. To achieve this objective, serum corticosteroids, which are known to increase during space flight, must be maintained at normal physiologic levels in flight rats by a combination of adrenalectomy and corticosteroid supplementation via implanted hormone pellets. Bone analyses in these animals will then be compared to those of intact flight rats that, based on past experience, will undergo corticosteroid excess and bone loss during space flight. The results will reveal whether maintaining serum corticosteroids at physiologic levels in flight rats affects the skeletal abnormalities that normally develop during space flight. A positive response to this question would indicate that the bone loss and decreased bone formation associated with space flight are mediated, at least in part, by corticosteroid excess
Contributors to the March Issue/Notes
Notes by Robert E. Richardson, Bernard F. Grainey, Leo L. Linck, Joseph J. Miller, Jr., James E. Diver, William B. Mooney, John M. Speca, Timothy M. Green, and Daniel D. Dahill
Strong-Isospin Violation in the Neutron-Proton Mass Difference from Fully-Dynamical Lattice QCD and PQQCD
We determine the strong-isospin violating component of the neutron-proton
mass difference from fully-dynamical lattice QCD and partially-quenched QCD
calculations of the nucleon mass, constrained by partially-quenched chiral
perturbation theory at one-loop level. The lattice calculations were performed
with domain-wall valence quarks on MILC lattices with rooted staggered
sea-quarks at a lattice spacing of b=0.125 fm, lattice spatial size of L=2.5 fm
and pion masses ranging from m_pi ~ 290 MeV to ~ 350 MeV. At the physical value
of the pion mass, we predict M_n - M_p |(d-u) = 2.26 +- 0.57 +- 0.42 +- 0.10
MeV where the first error is statistical, the second error is due to the
uncertainty in the ratio of light-quark masses, eta=m_u/m_d, determined by
MILC, and the third error is an estimate of the systematic due to chiral
extrapolation.Comment: 14 pages, 11 figure
Vector and Axial Form Factors Applied to Neutrino Quasielastic Scattering
We calculate the quasielastic cross sections for neutrino scattering on
nucleons using up to date fits to the nucleon elastic electromagnetic form
factors GEp, GEn, GMp, GMn, and weak form factors. We show the extraction of Fa
for neutrino experiments. We show how well \minerva, a new approved experiment
at FNAL, can measure Fa. We show the that Fa has a different contribution to
the anti-neutrino cross section, and how the anti-neutrino data can be used to
check Fa extracted from neutrino scattering.Comment: Presented by Howard Budd at NuInt04, Mar. 2004, Laboratori Nazionali
del Gran Sasso - INFN - Assergi, Ital
The Effect of Coherent Structures on Stochastic Acceleration in MHD Turbulence
We investigate the influence of coherent structures on particle acceleration
in the strongly turbulent solar corona. By randomizing the Fourier phases of a
pseudo-spectral simulation of isotropic MHD turbulence (Re ), and
tracing collisionless test protons in both the exact-MHD and phase-randomized
fields, it is found that the phase correlations enhance the acceleration
efficiency during the first adiabatic stage of the acceleration process. The
underlying physical mechanism is identified as the dynamical MHD alignment of
the magnetic field with the electric current, which favours parallel
(resistive) electric fields responsible for initial injection. Conversely, the
alignment of the magnetic field with the bulk velocity weakens the acceleration
by convective electric fields - \bfu \times \bfb at a non-adiabatic stage of
the acceleration process. We point out that non-physical parallel electric
fields in random-phase turbulence proxies lead to artificial acceleration, and
that the dynamical MHD alignment can be taken into account on the level of the
joint two-point function of the magnetic and electric fields, and is therefore
amenable to Fokker-Planck descriptions of stochastic acceleration.Comment: accepted for publication in Ap
A General Formula for Black Hole Gravitational Wave Kicks
Although the gravitational wave kick velocity in the orbital plane of
coalescing black holes has been understood for some time, apparently
conflicting formulae have been proposed for the dominant out-of-plane kick,
each a good fit to different data sets. This is important to resolve because it
is only the out-of-plane kicks that can reach more than 500 km/s and can thus
eject merged remnants from galaxies. Using a different ansatz for the
out-of-plane kick, we show that we can fit almost all existing data to better
than 5 %. This is good enough for any astrophysical calculation, and shows that
the previous apparent conflict was only because the two data sets explored
different aspects of the kick parameter space.Comment: 14 pages
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