2,410 research outputs found
Non equilibrium dynamics below the super-roughening transition
The non equilibrium relaxational dynamics of the solid on solid model on a
disordered substrate and the Sine Gordon model with random phase shifts is
studied numerically. Close to the super-roughening temperature our
results for the autocorrelations, spatial correlations and response function as
well as for the fluctuation dissipation ratio (FDR) agree well with the
prediction of a recent one loop RG calculation, whereas deep in the glassy low
temperature phase substantial deviations occur. The change in the low
temperature behavior of these quantities compared with the RG predictions is
shown to be contained in a change of the functional temperature dependence of
the dynamical exponent , which relates the age of the system with a
length scale : changes from a linear -dependence close
to to a 1/T-behavior far away from . By identifying spatial domains
as connected patches of the exactly computable ground states of the system we
demonstrate that the growing length scale is the characteristic
size of thermally fluctuating clusters around ``typical'' long-lived
configurations.Comment: RevTex
Tobacco Control Progress in Low and Middle Income Countries in Comparison to High Income Countries
The study aimed to describe worldwide levels and trends of tobacco control
policy by comparing low and middle income countries with other income
categories from 2007 to 2014 and to analyze the corresponding relation to
recent changes in smoking prevalence. Policy measure data representing years
2007 to 2014 were collected from all available World Health Organization (WHO)
reports on the global tobacco epidemic. Corresponding policy percentage scores
(PS) were calculated based on MPOWER measures. Age-standardized smoking
prevalence data for years 2010 and 2015 were collected from the WHO Global
Health Observatory Data Repository. Trends of PS were analysed with respect to
WHO region and OECD country income category. Scatter plots and regression
analysis were used to depict the relationship between tobacco control policy
of 2010 and change in smoking prevalence between 2015 and 2010 by sex and
income category. Combined PS for all countries increased significantly from
47% in 2007 to 61% by 2014 (p < 0.001). When grouped by income category and
region, policies were strengthened in all categories, albeit with varying
progression. By 2014, tobacco control policy legislation had reached 45% in
the Least Developed Countries (LDCs), 59% in Low Middle Income Countries
(LMICs), 66% in Upper Middle Income Countries (UMICs) and 70% in High Income
Countries (HICs). Overall, there was a negative relationship between higher
policy scores and change in smoking prevalence. Although policy strengthening
had been conducted between 2007 and 2014, room for considerable global
improvement remains, particularly in LDCs. View Full-Tex
Non-equilibrium condensation and coarsening of field-driven dipolar colloids
In colloidal suspensions, self-organization processes can be easily fueled by
external fields. One particularly interesting class of phenomena occurs in
monolayers of dipolar particles that are driven by rotating external fields.
Here we report results from a computer simulation study of such systems
focusing on the clustering behavior also observed in recent experiments. The
key result of this paper is a novel interpretation of this pattern formation
phenomenon: We show the clustering to be a by-product of a vapor-liquid first
order phase transition. In fact, the observed dynamic coarsening process
corresponds to the spindodal demixing that occurs during such a transitionComment: 6 pages, 5 figure
Spin dynamics in the Kapitza-Dirac effect
Electron spin dynamics in Kapitza-Dirac scattering from a standing laser wave
of high frequency and high intensity is studied. We develop a fully
relativistic quantum theory of the electron motion based on the time-dependent
Dirac equation. Distinct spin dynamics, with Rabi oscillations and complete
spin-flip transitions, is demonstrated for Kapitza-Dirac scattering involving
three photons in a parameter regime accessible to future high-power X-ray laser
sources. The Rabi frequency and, thus, the diffraction pattern is shown to
depend crucially on the spin degree of freedom
Many-body Green's function theory for electron-phonon interactions: the Kadanoff-Baym approach to spectral properties of the Holstein dimer
We present a Kadanoff-Baym formalism to study time-dependent phenomena for
systems of interacting electrons and phonons in the framework of many-body
perturbation theory. The formalism takes correctly into account effects of the
initial preparation of an equilibrium state, and allows for an explicit
time-dependence of both the electronic and phononic degrees of freedom. The
method is applied to investigate the charge neutral and non-neutral excitation
spectra of a homogeneous, two-site, two-electron Holstein model. This is an
extension of a previous study of the ground state properties in the Hartree
(H), partially self-consistent Born (Gd) and fully self-consistent Born (GD)
approximations published in Ref. [arXiv:1403.2968]. We show that choosing a
homogeneous ground state solution leads to unstable dynamics for a sufficiently
strong interaction, and that allowing a symmetry-broken state prevents this.
The instability is caused by the bifurcation of the ground state and understood
physically to be connected with the bipolaronic crossover of the exact system.
This mean-field instability persists in the partially self-consistent Born
approximation but is not found for the fully self-consistent Born
approximation. By understanding the stability properties, we are able to study
the linear response regime by calculating the density-density response function
by time-propagation. This functions amounts to a solution of the Bethe-Salpeter
equation with a sophisticated kernel. The results indicate that none of the
approximations is able to describe the response function during or beyond the
bipolaronic crossover for the parameters investigated. Overall, we provide an
extensive discussion on when the approximations are valid, and how they fail to
describe the studied exact properties of the chosen model system.Comment: 12 figure
Effects of Exposure to Low Levels of Water-Borne 17b-Estradiol on Nest Holding Ability and Sperm Quality in Fathead Minnows
Long range correlations in the non-equilibrium quantum relaxation of a spin chain
We consider the non-stationary quantum relaxation of the Ising spin chain in
a transverse field of strength h. Starting from a homogeneously magnetized
initial state the system approaches a stationary state by a process possessing
quasi long range correlations in time and space, independent of the value of
. In particular the system exhibits aging (or lack of time translational
invariance on intermediate time scales) although no indications of coarsening
are present.Comment: 4 pages RevTeX, 2 eps-figures include
Performance and scaling of a novel locomotor structure: adhesive capacity of climbing gobiid fishes
Many species of gobiid fishes adhere to surfaces using a sucker formed from fusion of the pelvic fins. Juveniles of many amphidromous species use this pelvic sucker to scale waterfalls during migrations to upstream habitats after an oceanic larval phase. However, adults may still use suckers to re-scale waterfalls if displaced. If attachment force is proportional to sucker area and if growth of the sucker is isometric, then increases in the forces that climbing fish must resist might outpace adhesive capacity, causing climbing performance to decline through ontogeny. To test for such trends, we measured pressure differentials and adhesive suction forces generated by the pelvic sucker across wide size ranges in six goby species, including climbing and non-climbing taxa. Suction was achieved via two distinct growth strategies: (1) small suckers with isometric (or negatively allometric) scaling among climbing gobies and (2) large suckers with positively allometric growth in non-climbing gobies. Species using the first strategy show a high baseline of adhesive capacity that may aid climbing performance throughout ontogeny, with pressure differentials and suction forces much greater than expected if adhesion were a passive function of sucker area. In contrast, large suckers possessed by non-climbing species may help compensate for reduced pressure differentials, thereby producing suction sufficient to support body weight. Climbing Sicyopterus species also use oral suckers during climbing waterfalls, and these exhibited scaling patterns similar to those for pelvic suckers. However, oral suction force was considerably lower than that for pelvic suckers, reducing the ability for these fish to attach to substrates by the oral sucker alone
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