741 research outputs found
Proton Wires in an Electric Field: the Impact of Grotthuss Mechanism on Charge Translocation
We present the results of the modeling of proton translocation in finite
H-bonded chains in the framework of two-stage proton transport model. We
explore the influence of reorientation motion of protons, as well as the effect
of electric field and proton correlations on system dynamics. An increase of
the reorientation energy results in the transition of proton charge from the
surrounding to the inner water molecules in the chain. Proton migration along
the chain in an external electric field has a step-like character, proceeding
with the occurrence of electric field threshold-type effects and drastic
redistribution of proton charge. Electric field applied to correlated chains
induces first a formation of ordered dipole structures for lower field
strength, and than, with a further field strength increase, a stabilization of
states with Bjerrum D-defects. We analyze the main factors responsible for the
formation/annihilation of Bjerrum defects showing the strong influence of the
complex interplay between reorientation energy, electric field and temperature
in the dynamics of proton wire.Comment: 28 pages, 9 figure
Lifetimes of states in 19Ne above the 15 O + alpha breakup threshold
The 15O(alpha,gamma)19Ne reaction plays a role in the ignition of Type I
x-ray bursts on accreting neutron stars. The lifetimes of states in 19Ne above
the 15O + alpha threshold of 3.53 MeV are important inputs to calculations of
the astrophysical reaction rate. These levels in 19Ne were populated in the
3He(20Ne,alpha)19Ne reaction at a 20Ne beam energy of 34 MeV. The lifetimes of
six states above the threshold were measured with the Doppler shift attenuation
method (DSAM). The present measurements agree with previous determinations of
the lifetimes of these states and in some cases are considerably more precise
Ultrastructure of the first component of human complement: electron microscopy of the crosslinked complex.
Two Mode Quantum Systems: Invariant Classification of Squeezing Transformations and Squeezed States
A general analysis of squeezing transformations for two mode systems is given
based on the four dimensional real symplectic group Sp(4,\Re)\/. Within the
framework of the unitary metaplectic representation of this group, a
distinction between compact photon number conserving and noncompact photon
number nonconserving squeezing transformations is made. We exploit the
Sp(4,\Re)-SO(3,2)\/ local isomorphism and the U(2)\/ invariant squeezing
criterion to divide the set of all squeezing transformations into a two
parameter family of distinct equivalence classes with representative elements
chosen for each class. Familiar two mode squeezing transformations in the
literature are recognized in our framework and seen to form a set of measure
zero. Examples of squeezed coherent and thermal states are worked out. The need
to extend the heterodyne detection scheme to encompass all of U(2)\/ is
emphasized, and known experimental situations where all U(2)\/ elements can
be reproduced are briefly described.Comment: Revtex 37 pages, Latex figures include
Lifetime of 19Ne*(4.03 MeV)
The Doppler-shift attenuation method was applied to measure the lifetime of
the 4.03 MeV state in 19Ne. Utilizing a 3He-implanted Au foil as a target, the
state was populated using the 20Ne(3He,alpha)19Ne reaction in inverse
kinematics at a 20Ne beam energy of 34 MeV. De-excitation gamma rays were
detected in coincidence with alpha particles. At the 1 sigma level, the
lifetime was determined to be 11 +4, -3 fs and at the 95.45% confidence level
the lifetime is 11 +8, -7 fs.Comment: 6 pages, submitted to Phys. Rev.
On Bures fidelity of displaced squeezed thermal states
Fidelity plays a key role in quantum information and communication theory.
Fidelity can be interpreted as the probability that a decoded message possesses
the same information content as the message prior to coding and transmission.
In this paper, we give a formula of Bures fidelity for displaced squeezed
thermal states directly by the displacement and squeezing parameters and
birefly discuss how the results can apply to quantum information theory.Comment: 10 pages with RevTex require
Ultra-high brilliance multi-MeV -ray beam from non-linear Thomson scattering
We report on the generation of a narrow divergence (
mrad), multi-MeV ( MeV) and ultra-high brilliance ( photons s mm mrad 0.1\% BW) -ray
beam from the scattering of an ultra-relativistic laser-wakefield accelerated
electron beam in the field of a relativistically intense laser (dimensionless
amplitude ). The spectrum of the generated -ray beam is
measured, with MeV resolution, seamlessly from 6 MeV to 18 MeV, giving clear
evidence of the onset of non-linear Thomson scattering. The photon source has
the highest brilliance in the multi-MeV regime ever reported in the literature
Self-energy limited ion transport in sub-nanometer channels
The current-voltage characteristics of the alpha-Hemolysin protein pore
during the passage of single-stranded DNA under varying ionic strength, C, are
studied experimentally. We observe strong blockage of the current, weak
super-linear growth of the current as a function of voltage, and a minimum of
the current as a function of C. These observations are interpreted as the
result of the ion electrostatic self-energy barrier originating from the large
difference in the dielectric constants of water and the lipid bilayer. The
dependence of DNA capture rate on C also agrees with our model.Comment: more experimental material is added. 4 pages, 7 figure
A Magnetic Flux Tube Oscillation Model for QPOs in SGR Giant Flares
Giant flares from soft gamma-ray repeaters (SGRs) are one of the most violent
phenomena in neutron stars. Quasi-periodic oscillations (QPOs) with frequencies
ranging from 18 to 1840 Hz have been discovered in the tails of giant flares
from two SGRs, and were ascribed to be seismic vibrations or torsional
oscillations of magnetars. Here we propose an alternative explanation for the
QPOs in terms of standing sausage mode oscillations of flux tubes in the
magnetar coronae. We show that most of the QPOs observed in SGR giant flares
could be well accounted for except for those with very high frequencies (625
and 1840 Hz).Comment: 15 pages,1 figures,1 table, accepted for publication in The
Astrophysical Journa
Multiplicity Distributions of Squeezed Isospin States
Multiplicity distributions of neutral and charged particles arising from
squeezed coherent states are investigated. Projections onto global isospin
states are considered. We show how a small amount of squeezing can
significantly change the multiplicity distributions. The formalism is proposed
to describe the phenomenological properties of neutral and charged particles
anomalously produced in hadronic and nuclear collisions at very high energies.Comment: 17 pages, 6 figures sent upon request ([email protected]
- …