2,066 research outputs found
Plastic response of a 2D amorphous solid to quasi-static shear : I - Transverse particle diffusion and phenomenology of dissipative events
We perform extensive simulations of a 2D LJ glass subjected to quasi-static
shear deformation at T=0. We analyze the distribution of non-affine
displacements in terms of contributions of plastic, irreversible events, and
elastic, reversible motions. From this, we extract information about
correlations between plastic events and about the elastic non-affine noise.
Moreover, we find that non-affine motion is essentially diffusive, with a
clearly size-dependent diffusion constant. These results, supplemented by close
inspection of the evolving patterns of the non-affine tangent displacement
field, lead us to propose a phenomenology of plasticity in such amorphous
media. It can be schematized in terms of elastic loading and irreversible flips
of small, randomly located shear transformation zones, elastically coupled via
their quadrupolar fields
New Technologies, Workplace Organisation and the Age Structure of the Workforce: Firm-Level Evidence
This paper investigates the relationships between new technologies, innovative workplace practices and the age structure of the workforce in a sample of French manufacturing firms. We find evidence that the wage bill share of older workers is lower in innovative firms and that the opposite holds for younger workers. This age bias is also evidenced within occupational groups, thus suggesting that skills do not completely protect workers against the labour market consequences of ageing. More detailed analysis of employment inflows and outflows shows that new technologies essentially affect older workers through reduced hiring opportunities, whereas organisational innovations mainly increase their probability of exit. This suggests that some skill obsolescence may be at work in our sample.new work practices, technology, older workers, labour demand
Stability of hexagonal solidification patterns
We investigate the dynamics of cellular solidification patterns using
three-dimensional phase-field simulations. The cells can organize into stable
hexagonal patterns or exhibit unsteady evolutions. We identify the relevant
secondary instabilities of regular hexagonal arrays and find that the stability
boundaries depend significantly on the strength of crystalline anisotropy. We
also find multiplet states that can be reached by applying well-defined
perturbations to a pre-existing hexagonal array.Comment: Minor changes, mainly in introduction and conclusion, one reference
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Perturbation of Tunneling Processes by Mechanical Degrees of Freedom in Mesoscopic Junctions
We investigate the perturbation in the tunneling current caused by
non-adiabatic mechanical motion in a mesoscopic tunnel junction. A theory
introduced by Caroli et al. \cite{bi1,bi2,bi3} is used to evaluate second order
self-energy corrections for this non-equilibrium situation lacking
translational invariance. Inelastic signatures of the mechanical degrees of
freedom are found in the current-voltage characteristics. These give
rise to sharp features in the derivative spectrum, .Comment: 22 pages LaTeX + 3 uuencoded PS picture
Stability of critical bubble in stretched fluid of square-gradient density-functional model with triple-parabolic free energy
The square-gradient density-functional model with triple-parabolic free
energy, that was used previously to study the homogeneous bubble nucleation [J.
Chem. Phys. 129, 104508 (2008)], is used to study the stability of the critical
bubble nucleated within the bulk under-saturated stretched fluid. The stability
of the bubble is studied by solving the Schr\"odinger equation for the
fluctuation. The negative eigenvalue corresponds to the unstable growing mode
of the fluctuation. Our results show that there is only one negative eigenvalue
whose eigenfunction represents the fluctuation that corresponds to the
isotropically growing or shrinking nucleus. In particular, this negative
eigenvalue survives up to the spinodal point. Therefore the critical bubble is
not fractal or ramified near the spinodal.Comment: 9 pages, 8 figures, Journal of Chemical Physics accepted for
publicatio
Comment on ``Quasiparticle Spectra around a Single Vortex in a d-wave Superconductor''
In a recent Letter Morita, Kohmoto and Maki analyzed the structure of
quasiparticle states near a single vortex in a d-wave superconductor using an
approximate version of the Bogoliubov - de Gennes theory. Their principal
result is the existence of a bound state within the core region at finite
energy with full rotational symmetry, which they assert explains the recent
scanning tunneling microscopy results on YBCO single crystals. Here we argue
that the approximation used in this work is fundamentally inadequate for the
description of a d-wave vortex and that the obtained circular symmetry of the
local density of states is an unphysical artifact of this approximation.Comment: 1 page REVTeX, to appear in PR
Compton telescope with coded aperture mask: Imaging with the INTEGRAL/IBIS Compton mode
Compton telescopes provide a good sensitivity over a wide field of view in
the difficult energy range running from a few hundred keV to several MeV. Their
angular resolution is, however, poor and strongly energy dependent. We present
a novel experimental design associating a coded mask and a Compton detection
unit to overcome these pitfalls. It maintains the Compton performance while
improving the angular resolution by at least an order of magnitude in the field
of view subtended by the mask. This improvement is obtained only at the expense
of the efficiency that is reduced by a factor of two. In addition, the
background corrections benefit from the coded mask technique, i.e. a
simultaneous measurement of the source and background. This design is
implemented and tested using the IBIS telescope on board the INTEGRAL satellite
to construct images with a 12' resolution over a 29 degrees x 29 degrees field
of view in the energy range from 200 keV to a few MeV. The details of the
analysis method and the resulting telescope performance, particularly in terms
of sensitivity, are presented
Computational Methods for the Integrative Analysis of Genomics and Pharmacological Data
Since the pioneering NCI-60 panel of the late'80's, several major screenings of genetic profiling and drug testing in cancer cell lines have been conducted to investigate how genetic backgrounds and transcriptional patterns shape cancer's response to therapy and to identify disease-specific genes associated with drug response. Historically, pharmacogenomics screenings have been largely heterogeneous in terms of investigated cell lines, assay technologies, number of compounds, type and quality of genomic data, and methods for their computational analysis. The analysis of this enormous and heterogeneous amount of data required the development of computational methods for the integration of genomic profiles with drug responses across multiple screenings. Here, we will review the computational tools that have been developed to integrate cancer cell lines' genomic profiles and sensitivity to small molecule perturbations obtained from different screenings
Dry Friction due to Adsorbed Molecules
Using an adiabatic approximation method, which searches for Tomlinson
model-like instabilities for a simple but still realistic model for two
crystalline surfaces in the extremely light contact limit, with mobile
molecules present at the interface, sliding relative to each other, we are able
to account for the virtually universal occurrence of "dry friction." The model
makes important predictions for the dependence of friction on the strength of
the interaction of each surface with the mobile molecules.Comment: four pages of latex, figure provide
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