1,471 research outputs found
Three-body decays: structure, decay mechanism and fragment properties
We discuss the three-body decay mechanisms of many-body resonances. R-matrix
sequential description is compared with full Faddeev computation. The role of
the angular momentum and boson symmetries is also studied. As an illustration
we show the computed -particle energy distribution after the decay of
12C(1^+) resonance at 12.7 MeV.Comment: 4 pages, 3 figures. Proceedings of the workshop "Critical Stability
of Few-Body Quantum Systems" 200
Effect of psychosocial factors on low back pain in industrial workers
Aim: To test the hypothesis that workplace psychosocial factors such as demand, control, support, job satisfaction and job appreciation can predict the future onset of disabling low back pain (LBP). Methods: The present study involved a prospective cohort of 4500 Iranian industrial workers. Data were gathered by means of a self-reported questionnaire about LBP, as well as working life exposure, lifestyle factors, social exposures, co-morbidity, life events and psychosomatic complaints in 2004. All new episodes of disabling LBP resulting in medically certified sick leave during the 1-year follow-up registered by occupational health clinic inside the factory. Results: The participation rate was good (85). A total of 744 subjects reported current LBP (point prevalence cases). A total of 52 (<2) new episodes of disabling LBP were observed during the 1-year follow-up (incident cases). Male employees reported higher demands, lower control and lower support than female employees. Employees with high demands, low control, job strain, low job satisfaction and low job appreciation showed increased odds ratios, and these results were statistically significant. Conclusions: Few prospective studies in this field have been published, but all of them are related to industrialized countries. This prospective study suggests the aetiological role of job strain for LBP. The findings of this study indicate a substantial potential for disease prevention and health promotion at the workplace. Ă© The Author 2008. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved
Analytical approximation of the stress-energy tensor of a quantized scalar field in static spherically symmetric spacetimes
Analytical approximations for and of a
quantized scalar field in static spherically symmetric spacetimes are obtained.
The field is assumed to be both massive and massless, with an arbitrary
coupling to the scalar curvature, and in a zero temperature vacuum state.
The expressions for and are divided into
low- and high-frequency parts. The contributions of the high-frequency modes to
these quantities are calculated for an arbitrary quantum state. As an example,
the low-frequency contributions to and are
calculated in asymptotically flat spacetimes in a quantum state corresponding
to the Minkowski vacuum (Boulware quantum state). The limits of the
applicability of these approximations are discussed.Comment: revtex4, 17 pages; v2: three references adde
Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions
Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated consistently, and applied to Li. The same two-body
interactions between the three particles are used to calculate the ground state
structure and the final state of the reaction processes. We reproduce the
available momentum distributions from Li fragmentation, together with
the size and energy of Li, with a neutron-core relative state containing
a -state admixture of 20\%-30\%. The available fragmentation data strongly
suggest an -state in Li at about 50 keV, and indicate a -state
around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file
attached at the end of the LaTeX file). To be published in Phys. Rev.
Higher-order squeezing for the codirectional Kerr nonlinear coupler
In this Letter we study the evolution of the higher-order squeezing, namely,
th-order single-mode squeezing, sum- and difference-squeezing for the
codirectional Kerr nonlinear coupler. We show that the amount of squeezing
decreases when , i.e. the squeezing order, increases. For specific values of
the interaction parameters squeezing factors exhibit a series of
revival-collapse phenomena, which become more pronounced when the value of
increases. Sum-squeezing can provide amounts of squeezing greater than those
produced by the th higher-order () squeezing for the same values of
interaction parameters and can map onto amplitude-squared squeezing. Further,
we prove that the difference-squeezing is not relevant measure for obtaining
information about squeezing from this device.Comment: 13 pages, 3 figure
Vortex Dynamics and Defects in Simulated Flux Flow
We present the results of molecular dynamic simulations of a two-dimensional
vortex array driven by a uniform current through random pinning centers at zero
temperature. We identify two types of flow of the driven array near the
depinning threshold. For weak disorder the flux array contains few dislocation
and moves via correlated displacements of patches of vortices in a {\it
crinkle} motion. As the disorder strength increases, we observe a crossover to
a spatially inhomogeneous regime of {\it plastic} flow, with a very defective
vortex array and a channel-like structure of the flowing regions. The two
regimes are characterized by qualitatively different spatial distribution of
vortex velocities. In the crinkle regime the distribution of vortex velocities
near threshold has a single maximum that shifts to larger velocities as the
driving force is increased. In the plastic regime the distribution of vortex
velocities near threshold has a clear bimodal structure that persists upon
time-averaging the individual velocities. The bimodal structure of the velocity
distribution reflects the coexistence of pinned and flowing regions and is
proposed as a quantitative signature of plastic flow.Comment: 12 pages, 13 embedded PostScript figure
Quantum properties of the codirectional three-mode Kerr nonlinear coupler
We investigate the quantum properties for the codirectional three-mode Kerr
nonlinear coupler. We investigate single-, two- and three-mode quadrature
squeezing, Wigner function and purity. We prove that this device can provide
richer nonclassical effects than those produced by the conventional coupler,
i.e. the two-mode Kerr coupler. We show that it can provide squeezing and the
quadrature squeezing exhibiting leaf-revival-collapse phenomenon in dependence
on the values of the interaction parameters. In contrast to the conventional
Kerr coupler two different forms of cat states can be simultaneously generated
in the waveguides. We deduce conditions required for the complete
disentanglement between the components of the system.Comment: 23 pages, 6 figure
Effect of FET geometry on charge ordering of transition metal oxides
We examine the effect of an FET geometry on the charge ordering phase diagram
of transition metal oxides using numerical simulations of a semiclassical model
including long-range Coulomb fields, resulting in nanoscale pattern formation.
We find that the phase diagram is unchanged for insulating layers thicker than
approximately twice the magnetic correlation length. For very thin insulating
layers, the onset of a charge clump phase is shifted to lower values of the
strength of the magnetic dipolar interaction, and intermediate diagonal stripe
and geometric phases can be suppressed. Our results indicate that, for
sufficiently thick insulating layers, charge injection in an FET geometry can
be used to experimentally probe the intrinsic charge ordering phases in these
materials.Comment: 4 pages, 4 postscript figure
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
Corporate financing decisions: UK survey evidence
Despite theoretical developments in recent years, our understanding of corporate capital structure remains incomplete. Prior empirical research has been dominated by archival regression studies which are limited in their ability to fully reflect the diversity found in practice. The present paper reports on a comprehensive survey of corporate financing decision-making in UK listed companies. A key finding is that firms are heterogeneous in their capital structure policies. About half of the firms seek to maintain a target debt level, consistent with trade-off theory, but 60 per cent claim to follow a financing hierarchy, consistent with pecking order theory. These two theories are not viewed by respondents as either mutually exclusive or exhaustive. Many of the theoretical determinants of debt levels are widely accepted by respondents, in particular the importance of interest tax shield, financial distress, agency costs and also, at least implicitly, information asymmetry. Results also indicate that cross-country institutional differences have a significant impact on financial decisions
- âŠ