92,978 research outputs found
Neutron halo in deformed nuclei from a relativistic Hartree-Bogoliubov model in a Woods-Saxon basis
Halo phenomenon in deformed nuclei is studied by using a fully
self-consistent deformed relativistic Hartree-Bogoliubov model in a spherical
Woods-Saxon basis with the proper asymptotic behavior at large distance from
the nuclear center. Taking a deformed neutron-rich and weakly bound nucleus
Mg as an example and by examining contributions of the halo, deformation
effects, and large spatial extensions, we show a decoupling of the halo
orbitals from the deformation of the core.Comment: 6 pages, 2 figures, to appear in the proceedings of the International
Nuclear Physics Conference (INPC 2010), July 4-9 2010, Vancouve
Adsorption of Externally Stretched Two-Dimensional Flexible and Semi-flexible Polymers near an Attractive Wall
We study analytically a model of a two dimensional, partially directed,
flexible or semiflexible polymer, attached to an attractive wall which is
perpendicular to the preferred direction. In addition, the polymer is stretched
by an externally applied force. We find that the wall has a dramatic effect on
the polymer. For wall attraction smaller than the non-sequential nearest
neighbor attraction, the fraction of monomers at the wall is zero and the model
is the same as that of a polymer without a wall. However, for greater than, the
fraction of monomers at the wall undergoes a first order transition from unity
at low temperature and small force, to zero at higher temperatures and forces.
We present phase diagram for this transition. Our results are confirmed by
Monte-Carlo simulations.Comment: 15 pages, 6 figure
Community detection in multiplex networks using locally adaptive random walks
Multiplex networks, a special type of multilayer networks, are increasingly
applied in many domains ranging from social media analytics to biology. A
common task in these applications concerns the detection of community
structures. Many existing algorithms for community detection in multiplexes
attempt to detect communities which are shared by all layers. In this article
we propose a community detection algorithm, LART (Locally Adaptive Random
Transitions), for the detection of communities that are shared by either some
or all the layers in the multiplex. The algorithm is based on a random walk on
the multiplex, and the transition probabilities defining the random walk are
allowed to depend on the local topological similarity between layers at any
given node so as to facilitate the exploration of communities across layers.
Based on this random walk, a node dissimilarity measure is derived and nodes
are clustered based on this distance in a hierarchical fashion. We present
experimental results using networks simulated under various scenarios to
showcase the performance of LART in comparison to related community detection
algorithms
Do methanethiol adsorbates on the Au(111) surface dissociate?
The interaction of methanethiol molecules CHSH with the Au(111) surface
is investigated, and it is found for the first time that the S-H bond remains
intact when the methanethiol molecules are adsorbed on the regular Au(111)
surface. However, it breaks if defects are present in the Au(111) surface. At
low coverage, the fcc region is favored for S atom adsorption, but at saturated
coverage the adsorption energies at various sites are almost iso-energetic. The
presented calculations show that a methanethiol layer on the regular Au(111)
surface does not dimerize.Comment: 4 pages, 2 figures, 4 tables, submitted to Phys. Rev. Let
Magnetic Skyrmion Transport in a Nanotrack With Spatially Varying Damping and Non-adiabatic Torque
Reliable transport of magnetic skyrmions is required for any future
skyrmion-based information processing devices. Here we present a micromagnetic
study of the in-plane current-driven motion of a skyrmion in a ferromagnetic
nanotrack with spatially sinusoidally varying Gilbert damping and/or
non-adiabatic spin-transfer torque coefficients. It is found that the skyrmion
moves in a sinusoidal pattern as a result of the spatially varying Gilbert
damping and/or non-adiabatic spin-transfer torque in the nanotrack, which could
prevent the destruction of the skyrmion caused by the skyrmion Hall effect. The
results provide a guide for designing and developing the skyrmion transport
channel in skyrmion-based spintronic applications.Comment: 5 pages, 6 figure
Supernova bound on keV-mass sterile neutrinos reexamined
Active-sterile neutrino mixing is strongly constrained for m_s > 100 keV to
avoid excessive energy losses from supernova cores. For smaller m_s, matter
effects suppress the effective mixing angle except for a resonant range of
energies where it is enhanced. We study the case of \nu_tau-\nu_s-mixing where
a \nu_tau-\bar\nu_tau asymmetry builds up due to the strong excess of \nu_s
over \bar\nu_s emission or vice versa, reducing the overall emission rate. In
the warm dark matter range m_s < 10 keV the mixing angle is essentially
unconstrained.Comment: 6 pages, 4 figures; minor changes, references updated, matches the
published versio
An analysis of dynamical suppression of spontaneous emission
It has been shown recently [see, for example, S.-Y. Zhu and M. O. Scully,
Phys. Rev. Lett. {\bf 76}, 388 (1996)] that a dynamical suppression of
spontaneous emission can occur in a three-level system when an external field
drives transitions between a metastable state and {\em two} decaying states.
What is unusual in the decay scheme is that the decaying states are coupled
directly by the vacuum radiation field. It is shown that decay dynamics
required for total suppression of spontaneous emission necessarily implies that
the level scheme is isomorphic to a three-level lambda system, in which the
lower two levels are {\em both} metastable, and each is coupled to the decaying
state. As such, the total suppression of spontaneous emission can be explained
in terms of conventional dark states and coherent population trapping.Comment: 8 pages, 3 figure
Heavy-tailed statistics in short-message communication
Short-message (SM) is one of the most frequently used communication channels
in the modern society. In this Brief Report, based on the SM communication
records provided by some volunteers, we investigate the statistics of SM
communication pattern, including the interevent time distributions between two
consecutive short messages and two conversations, and the distribution of
message number contained by a complete conversation. In the individual level,
the current empirical data raises a strong evidence that the human activity
pattern, exhibiting a heavy-tailed interevent time distribution, is driven by a
non-Poisson nature.Comment: 4 pages, 4 figures and 1 tabl
Continuum Electromechanical Modeling of Protein-Membrane Interaction
A continuum electromechanical model is proposed to describe the membrane
curvature induced by electrostatic interactions in a solvated protein-membrane
system. The model couples the macroscopic strain energy of membrane and the
electrostatic solvation energy of the system, and equilibrium membrane
deformation is obtained by minimizing the electro-elastic energy functional
with respect to the dielectric interface. The model is illustrated with the
systems with increasing geometry complexity and captures the sensitivity of
membrane curvature to the permanent and mobile charge distributions.Comment: 5 pages, 12 figure
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