62,056 research outputs found
Driven localized excitations in the acoustic spectrum of small nonlinear macroscopic and microscopic lattices
Both bright and dark traveling, locked, intrinsic localized modes (ILMs) have
been generated with a spatially uniform driver at a frequency in the acoustic
spectrum of a nonlinear micromechanical cantilever array. Complementary
numerical simulations show that a minimum density of modes, hence array size,
is required for the formation of such locked smoothly running excitations.
Additional simulations on a small 1-D antiferromagnetic spin system are used to
illustrate that such uniformly driven running ILMs should be a generic feature
of a nanoscale atomic lattice.Comment: Physical Review Letters, accepte
Step Bunching with Alternation of Structural Parameters
By taking account of the alternation of structural parameters, we study
bunching of impermeable steps induced by drift of adatoms on a vicinal face of
Si(001). With the alternation of diffusion coefficient, the step bunching
occurs irrespective of the direction of the drift if the step distance is
large. Like the bunching of permeable steps, the type of large terraces is
determined by the drift direction. With step-down drift, step bunches grows
faster than those with step-up drift. The ratio of the growth rates is larger
than the ratio of the diffusion coefficients. Evaporation of adatoms, which
does not cause the step bunching, decreases the difference. If only the
alternation of kinetic coefficient is taken into account, the step bunching
occurs with step-down drift. In an early stage, the initial fluctuation of the
step distance determines the type of large terraces, but in a late stage, the
type of large terraces is opposite to the case of alternating diffusion
coefficient.Comment: 8pages, 16 figure
On correlation functions of integrable models associated to the six-vertex R-matrix
We derive an analog of the master equation obtained recently for correlation
functions of the XXZ chain for a wide class of quantum integrable systems
described by the R-matrix of the six-vertex model, including in particular
continuum models. This generalized master equation allows us to obtain multiple
integral representations for the correlation functions of these models. We
apply this method to derive the density-density correlation functions of the
quantum non-linear Schrodinger model.Comment: 21 page
Toward a systems understanding of plant–microbe interactions
Plants are closely associated with microorganisms including pathogens and mutualists that influence plant fitness. Molecular genetic approaches have uncovered a number of signaling components from both plants and microbes and their mode of actions. However, signaling pathways are highly interconnected and influenced by diverse sets of environmental factors. Therefore, it is important to have systems views in order to understand the true nature of plant–microbe interactions. Indeed, systems biology approaches have revealed previously overlooked or misinterpreted properties of the plant immune signaling network. Experimental reconstruction of biological networks using exhaustive combinatorial perturbations is particularly powerful to elucidate network structure and properties and relationships among network components. Recent advances in metagenomics of microbial communities associated with plants further point to the importance of systems approaches and open a research area of microbial community reconstruction. In this review, we highlight the importance of a systems understanding of plant–microbe interactions, with a special emphasis on reconstruction strategies
Coupled forward-backward trajectory approach for non-equilibrium electron-ion dynamics
We introduce a simple ansatz for the wavefunction of a many-body system based
on coupled forward and backward-propagating semiclassical trajectories. This
method is primarily aimed at, but not limited to, treating nonequilibrium
dynamics in electron-phonon systems. The time-evolution of the system is
obtained from the Euler-Lagrange variational principle, and we show that this
ansatz yields Ehrenfest mean field theory in the limit that the forward and
backward trajectories are orthogonal, and in the limit that they coalesce. We
investigate accuracy and performance of this method by simulating electronic
relaxation in the spin-boson model and the Holstein model. Although this method
involves only pairs of semiclassical trajectories, it shows a substantial
improvement over mean field theory, capturing quantum coherence of nuclear
dynamics as well as electron-nuclear correlations. This improvement is
particularly evident in nonadiabatic systems, where the accuracy of this
coupled trajectory method extends well beyond the perturbative electron-phonon
coupling regime. This approach thus provides an attractive route forward to the
ab-initio description of relaxation processes, such as thermalization, in
condensed phase systems
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Surface damage resulting from rolling contact operating in magnetic field
This paper describes the effects of magnetic field in rolling contact tests of steel by using a two-disc configuration and the investigation of mechanisms involved.
Two contact conditions, namely pure rolling and rolling with 10% sliding were used together with 0.4 and 1.1 Tesla horizontal static magnetic fields created by permanent magnets. Results of optical and scanning electron microscope observations point out that finer wear particles and smoother worn surfaces are produced in the presence of a magnetic field. It is proposed that finer wear particles result from the movement of subsurface crack initiation towards the surface due to the action of magnetic field
The Other Side of the Trade Imbalance: What Will Japan Do?
With the mounting U.S. trade deficit, much attention has centered on the role of U.S. macroeconomic policy and economic structure as contributing factors. This paper contends that the economic structure and policies of Japan have also done much to contribute to the trade imbalance. Institutional features of Japan's macroeconomy and industrial structure which have promoted her large trade surplus are discussed and industrial policies evaluated. Given the nature and magnitude of the role played by Japan in causing the bilateral trade imbalance, the next question the paper addresses is how Japan might best act to alleviate this imbalance. This section of the paper examines fiscal, monetary and other policy initiatives Japan might take to reduce the trade imbalance. The evidence stresses the desirability of expanding Japan's services industries, particularly leisure-related services.
An Isomonodromy Cluster of Two Regular Singularities
We consider a linear matrix ODE with two coalescing regular
singularities. This coalescence is restricted with an isomonodromy condition
with respect to the distance between the merging singularities in a way
consistent with the ODE. In particular, a zero-distance limit for the ODE
exists. The monodromy group of the limiting ODE is calculated in terms of the
original one. This coalescing process generates a limit for the corresponding
nonlinear systems of isomonodromy deformations. In our main example the latter
limit reads as , where is the -th Painlev\'e equation. We
also discuss some general problems which arise while studying the
above-mentioned limits for the Painlev\'e equations.Comment: 44 pages, 8 figure
Off-Line, Multi-Detector Intensity Interferometers II: Implications and Applications
Intensity interferometry removes the stringent requirements on mechanical
precision and atmospheric corrections that plague all amplitude interferometry
techniques at the cost of severely limited sensitivity. A new idea we recently
introduced, very high redundancy, alleviates this problem. It enables the
relatively simple construction (~1cm mechanical precision) of a ground-based
astronomical facility able to transform a two-dimensional field of point-like
sources to a three-dimensional distribution of micro-arcsec resolved systems,
each imaged in several optical bands. Each system will also have its high
resolution residual timing, high quality (inside each band) spectra and light
curve, emergent flux, effective temperature, polarization effects and perhaps
some thermodynamic properties, all directly measured. All the above attributes
can be measured in a single observation run of such a dedicated facility. We
conclude that after three decades of abandonment optical intensity
interferometry deserves another review, also as a ground-based alternative to
the science goals of space interferometers.Comment: The article has been accepted for publication in MNRA
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