30,538 research outputs found
Anomalously Slow Domain Growth in Fluid Membranes with Asymmetric Transbilayer Lipid Distribution
The effect of asymmetry in the transbilayer lipid distribution on the
dynamics of phase separation in fluid vesicles is investigated numerically for
the first time. This asymmetry is shown to set a spontaneous curvature for the
domains that alter the morphology and dynamics considerably. For moderate
tension, the domains are capped and the spontaneous curvature leads to
anomalously slow dynamics, as compared to the case of symmetric bilayers. In
contrast, in the limiting cases of high and low tensions, the dynamics proceeds
towards full phase separation.Comment: 4 pages, 5 figure
Combined effect of frustration and dimerization in ferrimagnetic chains and square lattice
Within the zero-temperature linear spin-wave theory we have investigated the
effect of frustration and dimerization of a Heisenberg system with alternating
spins and on one- and two-dimensional lattices. The combined
effect most visibly appears in the elementary excitation spectra. In contrast
to the ground state energy that decreases with dimerization and increases with
frustration, the excitation energies are shown to be suppressed in energy by
both dimerization and frustration. The threshold value of frustration that
signals a transition from a classical ferrimagnetic state to a spiral state,
decreases with dimerization, showing that dimerization further helps in the
phase transition. The correlation length and sublattice magnetization decrease
with both dimerization and frustration indicating the destruction of the
long-range classical ferrimagnetic. The linear spin wave theory shows that in
the case of a square lattice, dimerization initially opposes the
frustration-led transition to a spiral magnetic state, but then higher
magnitudes of lattice deformation facilitate the transition. It also shows that
the transition to spiral state is inhibited in a square lattice beyond a
certain value of dimerization.Comment: 8 pages, latex, 12 postscript figure
Domain Growth, Budding, and Fission in Phase Separating Self-Assembled Fluid Bilayers
A systematic investigation of the phase separation dynamics in self-assembled
multi-component bilayer fluid vesicles and open membranes is presented. We use
large-scale dissipative particle dynamics to explicitly account for solvent,
thereby allowing for numerical investigation of the effects of hydrodynamics
and area-to-volume constraints. In the case of asymmetric lipid composition, we
observed regimes corresponding to coalescence of flat patches, budding,
vesiculation and coalescence of caps. The area-to-volume constraint and
hydrodynamics have a strong influence on these regimes and the crossovers
between them. In the case of symmetric mixtures, irrespective of the
area-to-volume ratio, we observed a growth regime with an exponent of 1/2. The
same exponent is also found in the case of open membranes with symmetric
composition
Apparent finite-size effects in the dynamics of supercooled liquids
Molecular dynamics simulations are performed for a supercooled simple liquid
with changing the system size from N=108 to to examine possible
finite-size effects. Although almost no systematic deviation is detected in the
static pair correlation functions, it is demonstrated that the structural
relaxation in a small system becomes considerably slower than that in
larger systems for temperatures below at which the size of the
cooperative particle motions becomes comparable to the unit cell length of the
small system. The discrepancy increases with decreasing temperature.Comment: 4 pages 5 figure
Simulation tools for future interferometers
For the design and commissioning of the LIGO interferometer, simulation tools have been used explicitly and implicitly. The requirement of the advanced LIGO interferometer is much more demanding than the first generation interferometer. Development of revised simulation tools for future interferometers are underway in the LIGO Laboratory. The outline of those simulation tools and applications are discussed
On fundamental diffraction limitation of finesse of a Fabry-Perot cavity
We perform a theoretical study of finesse limitations of a Fabry-Perot (FP)
cavity occurring due to finite size, asymmetry, as well as imperfections of the
cavity mirrors. A method of numerical simulations of the eigenvalue problem
applicable for both the fundamental and high order cavity modes is suggested.
Using this technique we find spatial profile of the modes and their round-trip
diffraction loss. The results of the numerical simulations and analytical
calculations are nearly identical when we consider a conventional FP cavity.
The proposed numerical technique has much broader applicability range and is
valid for any FP cavity with arbitrary non-spherical mirrors which have
cylindrical symmetry but disturbed in an asymmetric way, for example, by tilt
or roughness of their mirrors.Comment: 15 pages, 10 figure
Optical Gravitational Wave Antenna with Increased Power Handling Capability
Fundamental sensitivity of an optical interferometric gravitational wave
detector increases with increase of the optical power which, in turn, limited
because of the opto-mechanical parametric instabilities of the interferometer.
We propose to optimize geometrical shape of the mirrors of the detector to
reduce the diffraction-limited finesse of unessential optical modes of the
interferometer resulting in increase of the threshold of the opto-mechanical
instabilities and subsequent increase of the measurement sensitivity. Utilizing
parameters of the LIGO interferometer we found that the proposed technique
allows constructing a Fabry-Perot interferometer with round trip diffraction
loss of the fundamental mode not exceeding ~ppm, whereas the loss of the
first dipole as well as the other high order modes exceed ~ppm and
~ppm, respectively. The optimization comes at the price of tighter
tolerances on the mirror tilt stability, but does not result in a significant
modification of the optical beam profile and does not require changes in the
the gravity detector read-out system. The cavity with proposed mirrors is also
stable with respect to the slight modification of the mirror shape.Comment: 5 pages, 4 figure
Modulation of a Chirp Gravitational Wave from a Compact Binary due to Gravitational Lensing
A possible wave effect in the gravitational lensing phenomenon is discussed.
We consider the interference of two coherent gravitational waves of slightly
different frequencies from a compact binary, due to the gravitational lensing
by a galaxy halo. This system shows the modulation of the wave amplitude. The
lensing probability of such the phenomenon is of order 10^{-5} for a high-z
source, but it may be advantageous to the observation due to the magnification
of the amplitude.Comment: 3 pages, PRD in pres
Direct numerical simulations for non-Newtonian rheology of concentrated particle dispersions
The non-Newtonian behavior of a monodisperse concentrated dispersion of
spherical particles was investigated using a direct numerical simulation
method, that takes into account hydrodynamic interactions and thermal
fluctuations accurately. Simulations were performed under steady shear flow
with periodic boundary conditions in the three directions. The apparent shear
viscosity of the dispersions was calculated at volume fractions ranging from
0.31 to 0.56. Shear-thinning behavior was clearly observed at high volume
fractions. The low- and high-limiting viscosities were then estimated from the
apparent viscosity by fitting these data into a semi-empirical formula.
Furthermore, the short-time motions were examined for Brownian particles
fluctuating in concentrated dispersions, for which the fluid inertia plays an
important role. The mean square displacement was monitored in the vorticity
direction at several different Peclet numbers and volume fractions so that the
particle diffusion coefficient is determined from the long-time behavior of the
mean square displacement. Finally, the relationship between the non-Newtonian
viscosity of the dispersions and the structural relaxation of the dispersed
Brownian particles is examined
- âŠ