38,948 research outputs found
Relative Entropy: Free Energy Associated with Equilibrium Fluctuations and Nonequilibrium Deviations
Using a one-dimensional macromolecule in aqueous solution as an illustration,
we demonstrate that the relative entropy from information theory, , has a natural role in the energetics of equilibrium and
nonequilibrium conformational fluctuations of the single molecule. It is
identified as the free energy difference associated with a fluctuating density
in equilibrium, and is associated with the distribution deviate from the
equilibrium in nonequilibrium relaxation. This result can be generalized to any
other isothermal macromolecular systems using the mathematical theories of
large deviations and Markov processes, and at the same time provides the
well-known mathematical results with an interesting physical interpretations.Comment: 5 page
A lattice Boltzmann model with random dynamical constraints
In this paper we introduce a modified lattice Boltzmann model (LBM) with the
capability of mimicking a fluid system with dynamic heterogeneities. The
physical system is modeled as a one-dimensional fluid, interacting with
finite-lifetime moving obstacles. Fluid motion is described by a lattice
Boltzmann equation and obstacles are randomly distributed semi-permeable
barriers which constrain the motion of the fluid particles. After a lifetime
delay, obstacles move to new random positions. It is found that the
non-linearly coupled dynamics of the fluid and obstacles produces heterogeneous
patterns in fluid density and non-exponential relaxation of two-time
autocorrelation function.Comment: 10 pages, 9 figures, to be published in Eur. Phys. J.
Patterns of variability in early life traits of a Mediterranean coastal fish
Spawning dates and pelagic larval duration (PLD) are early life traits (ELT) crucial for understanding life cycles, properly assessing patterns of connectivity and gathering indications about patchiness or homogeneity of larval pools. Considering that little attention has been paid to spatial variability in these traits, we investigated variability of ELT from the analysis of otolith microstructure in the common two-banded sea bream Diplodus vulgaris. In the southwestern Adriatic Sea, along ~200 km of coast (∼1° in latitude, 41.2° to 40.2°N), variability of ELT was assessed at multiple spatial scales. Overall, PLD (ranging from 25 to 61 d) and spawning dates (October 2009 to February 2010) showed significant variability at small scales (i.e. <6 km), but not at larger scales. These outcomes suggest patchiness of the larval pool at small spatial scales. Multiple causal processes underlying the observed variability are discussed, along with the need to properly consider spatial variability in ELT, for example when delineating patterns of connectivity. Copyright © 2013 Inter-Research
Heralded phase-contrast imaging using an orbital angular momentum phase-filter
We utilise the position and orbital angular momentum (OAM) correlations between the signal and idler photons generated in the down-conversion process to obtain ghost images of a phase object. By using an OAM phase filter, which is non-local with respect to the object, the images exhibit isotropic edge-enhancement. This imaging technique is the first demonstration of a full-field, phase-contrast imaging system with non-local edge enhancement, and enables imaging of phase objects using significantly fewer photons than standard phase-contrast imaging techniques
Spin Polarized and Valley Helical Edge Modes in Graphene Nanoribbons
Inspired by recent progress in fabricating precisely zigzag-edged graphene
nanoribbons and the observation of edge magnetism, we find that spin polarized
edge modes with well-defined valley index can exist in a bulk energy gap opened
by a staggered sublattice potential such as that provided by a hexagonal
Boron-Nitride substrate. Our result is obtained by both tight-binding model and
first principles calculations. These edge modes are helical with respect to the
valley degree of freedom, and are robust against scattering, as long as the
disorder potential is smooth over atomic scale, resulting from the protection
of the large momentum separation of the valleys.Comment: 4 pages, 4 figure
Rates of Neutrino Absorption on Nucleons and the Reverse Processes in Strong Magnetic Fields
The rates of electron neutrino capture on neutron, electron anti-neutrino
capture on proton, and their reverse processes are important for understanding
the production of heavy elements in the supernova environment above the
protoneutron star. Observations and theoretical considerations suggest that
some protoneutron stars may be born with strong magnetic fields. We develop a
numerical method to calculate the above rates in supernova environments with
magnetic fields up to 10^16 G. This method is accurate to the order of one over
nucleon mass. We show that our results have the correct behavior in the limit
of high neutrino energy or small magnetic field. Based on comparison of our
results with various approximations, we recommend efficient estimates of the
above rates for use in models of supernova nucleosynthesis in the presence of
strong magnetic fields.Comment: 21 pages, 4 figures. Some explaination and references are added in
the second versio
Simulation of Coherent Non-Linear Neutrino Flavor Transformation in the Supernova Environment I: Correlated Neutrino Trajectories
We present results of large-scale numerical simulations of the evolution of
neutrino and antineutrino flavors in the region above the late-time
post-supernova-explosion proto-neutron star. Our calculations are the first to
allow explicit flavor evolution histories on different neutrino trajectories
and to self-consistently couple flavor development on these trajectories
through forward scattering-induced quantum entanglement. Employing the
atmospheric-scale neutrino mass-squared difference and values of theta_13
allowed by current bounds, we find transformation of neutrino and antineutrino
flavors over broad ranges of energy and luminosity in roughly the ``bi-polar''
collective mode. We find that this large-scale flavor conversion, largely
driven by the flavor off-diagonal neutrino-neutrino forward scattering
potential, sets in much closer to the proto-neutron star than simple estimates
based on flavor-diagonal potentials and Mikeheyev-Smirnov-Wolfenstein evolution
would indicate. In turn, this suggests that models of r-process nucleosynthesis
sited in the neutrino-driven wind could be affected substantially by
active-active neutrino flavor mixing, even with the small measured neutrino
mass-squared differences.Comment: 23 pages, 12 figures, revtex4 format. Version accepted by PR
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