1,230 research outputs found
Laser-induced currents along molecular wire junctions
The treatment of the previous paper is extended to molecular wires.
Specifically, the effect of electron-vibrational interactions on the electronic
transport induced by femtosecond laser fields along unbiased
molecular nanojunctions is investigated. For this, the photoinduced vibronic
dynamics of trans-polyacetylene oligomers coupled to macroscopic metallic leads
is followed in a mean-field mixed quantum-classical approximation. A reduced
description of the dynamics is obtained by introducing projective lead-molecule
couplings and deriving an effective Schr\"odinger equation satisfied by the
orbitals in the molecular region. Two possible rectification mechanisms are
identified and investigated. The first one relies on near-resonance
photon-absorption and is shown to be fragile to the ultrafast electronic
decoherence processes introduced by the wire's vibrations. The second one
employs the dynamic Stark effect and is demonstrated to be highly efficient and
robust to electron-vibrational interactions.Comment: 14 pages, 10 figures. Accepted in J. Chem. Phy
Observation of a New Mechanism of Spontaneous Generation of Magnetic Flux in a Superconductor
We report the discovery of a new mechanism of spontaneous generation of a
magnetic flux in a superconductor cooled through . The sign of the
spontaneous flux changes randomly from one cooldown to the next, and follows a
Gaussian distribution. The width of the distribution increases with the size of
the temperature gradient in the sample. Our observations appear inconsistent
with the well known mechanisms of flux generation. The dependence on the
temperature gradient suggests that the flux may be generated through an
instability of the thermoelectric superconducting-normal quasiparticle
counterflow
Human rights violations in organ procurement practice in China
Over 90% of the organs transplanted in China before 2010 were procured from prisoners. Although Chinese officials announced in December 2014 that the country would completely cease using organs harvested from prisoners, no regulatory adjustments or changes in China’s organ donation laws followed. As a result, the use of prisoner organs remains legal in China if consent is obtained
The 'New Economy' and the Old Problems. Prospects for Fast Growth in Postsocialist Countries
Event Horizons in Numerical Relativity I: Methods and Tests
This is the first paper in a series on event horizons in numerical
relativity. In this paper we present methods for obtaining the location of an
event horizon in a numerically generated spacetime. The location of an event
horizon is determined based on two key ideas: (1) integrating backward in time,
and (2) integrating the whole horizon surface. The accuracy and efficiency of
the methods are examined with various sample spacetimes, including both
analytic (Schwarzschild and Kerr) and numerically generated black holes. The
numerically evolved spacetimes contain highly distorted black holes, rotating
black holes, and colliding black holes. In all cases studied, our methods can
find event horizons to within a very small fraction of a grid zone.Comment: 22 pages, LaTeX with RevTeX 3.0 macros, 20 uuencoded gz-compressed
postscript figures. Also available at http://jean-luc.ncsa.uiuc.edu/Papers/
Submitted to Physical Review
American Association for Public Opinion Research Constituency, Party, and Representation in Congress
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Quantum Driven Dissipative Parametric Oscillator in a Blackbody Radiation Field
We consider the general open system problem of a charged quantum oscillator
confined in a harmonic trap, whose frequency can be arbitrarily modulated in
time, that interacts with both an incoherent quantized (blackbody) radiation
field and with an arbitrary coherent laser field. We assume that the oscillator
is initially in thermodynamic equilibrium with its environment, a
non-factorized initial density matrix of the system and the environment, and
that at the modulation of the frequency, the coupling to the incoherent
and the coherent radiation are switched on. The subsequent dynamics, induced by
the presence of the blackbody radiation and the laser field, is studied in the
framework of the influence functional approach. This approach allows
incorporating, in \emph{analytic closed formulae}, the non-Markovian character
of the oscillator-environment interaction at any temperature as well the
non-Markovian character of the blackbody radiation and its zero-point
fluctuations. Expressions for the time evolution of the covariance matrix
elements of the quantum fluctuations and the reduced density-operator are
obtained.Comment: 11 pages. It matches the published versio
Homodyne detection for measuring internal quantum correlations of optical pulses
A new method is described for determining the quantum correlations at
different times in optical pulses by using balanced homodyne detection. The
signal pulse and sequences of ultrashort test pulses are superimposed, where
for chosen distances between the test pulses their relative phases and
intensities are varied from measurement to measurement. The correlation
statistics of the signal pulse is obtained from the time-integrated difference
photocurrents measured.Comment: 7 pages, A4.sty include
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