6,156 research outputs found
Proper motions with Subaru II. A sample in the Subaru/XMM-Newton Deep Survey field
We search for stars with proper motions in a set of deep Subaru images,
covering about 0.48 square degrees to a depth of , taken over a
span of five and a half years. We follow the methods described in
\citet{Richmond2009} to reduce and analyze this dataset. We present a sample of
69 stars with motions of high significance, and discuss briefly the populations
from which they are likely drawn. Based on photometry and motions alone, we
expect that 14 of the candidates may be white dwarfs. Our candidate with the
largest proper motion is surprisingly faint and likely to prove interesting:
its colors and motions suggest that it might be an M dwarf moving at over 500
km/sec or an L dwarf in the halo.Comment: 10 pages, 5 figures. Accepted by Publications of the Astronomical
Society of Japan, to appear in volume 62, February 2010. Revised version:
removed PASJ LaTeX tutorial which was mistakenly appended to pape
Multi-critical point in a diluted bilayer Heisenberg quantum antiferromagnet
The S=1/2 Heisenberg bilayer antiferromagnet with randomly removed
inter-layer dimers is studied using quantum Monte Carlo simulations. A
zero-temperature multi-critical point (p*,g*) at the classical percolation
density p=p* and inter-layer coupling g* approximately 0.16 is demonstrated.
The quantum critical exponents of the percolating cluster are determined using
finite-size scaling. It is argued that the associated finite-temperature
quantum critical regime extends to zero inter-layer coupling and could be
relevant for antiferromagnetic cuprates doped with non-magnetic impurities.Comment: 4 pages, 6 figures. v2: only minor changes; accepted for publication
in Phys. Rev. Let
Proper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
We search for stars with proper motions in a set of twenty deep Subaru
images, covering about 0.28 square degrees to a depth of i ~ 25, taken over a
span of six years. In this paper, we describe in detail our reduction and
techniques to identify moving objects. We present a first sample of 99 stars
with motions of high significance, and discuss briefly the populations from
which they are likely drawn. Based on photometry and motions alone, we expect
that 9 of the candidates may be white dwarfs. We also find a group of stars
which may be extremely metal-poor subdwarfs in the halo.Comment: 12 pages, 8 figures, submitted to PAS
Preparation Of Gas Separation Membranes By Plasma Polymerization With Fluoro Compounds
Plasma polymerization coatings were applied for the preparation of gas separation membranes. Mainly fluoro compounds were used as coating materials. The membranes showed good separation characteristics with high flux for gaseous systems. The plasma polymerization composite parameter given by W/FM plays an important role in obtaining excellent separation characteristics. The correlation between the conversion rate DR/FM, where DR is the deposition rate of plasma polymer, and W/FM is useful to consider the plasma polymer character under the different plasma polymerization conditions (discharge power W and monomer flow rate F). The proper conditions for membrane preparation lie in the intermediate region between the region in which the monomer flow rate is deficient and that in which the discharge power is deficient. Furthermore, the plasma polymerization coatings with the higher molecular weight monomer gave the higher separation characteristics. Plasma polymer composite membranes in this study showed superiority for the molecular sieve type of separation over the solution-diffusion type of separation. © 1984
Spontaneous alloying in binary metal microclusters - A molecular dynamics study -
Microcanonical molecular dynamics study of the spontaneous alloying(SA),
which is a manifestation of fast atomic diffusion in a nano-sized metal
cluster, is done in terms of a simple two dimensional binary Morse model.
Important features observed by Yasuda and Mori are well reproduced in our
simulation. The temperature dependence and size dependence of the SA phenomena
are extensively explored by examining long time dynamics. The dominant role of
negative heat of solution in completing the SA is also discussed. We point out
that a presence of melting surface induces the diffusion of core atoms even if
they are solid-like. In other words, the {\it surface melting} at substantially
low temperature plays a key role in attaining the SA.Comment: 15 pages, 12 fgures, Submitted to Phys.Rev.
Multiscale modeling and simulation for polymer melt flows between parallel plates
The flow behaviors of polymer melt composed of short chains with ten beads
between parallel plates are simulated by using a hybrid method of molecular
dynamics and computational fluid dynamics. Three problems are solved: creep
motion under a constant shear stress and its recovery motion after removing the
stress, pressure-driven flows, and the flows in rapidly oscillating plates. In
the creep/recovery problem, the delayed elastic deformation in the creep motion
and evident elastic behavior in the recovery motion are demonstrated. The
velocity profiles of the melt in pressure-driven flows are quite different from
those of Newtonian fluid due to shear thinning. Velocity gradients of the melt
become steeper near the plates and flatter at the middle between the plates as
the pressure gradient increases and the temperature decreases. In the rapidly
oscillating plates, the viscous boundary layer of the melt is much thinner than
that of Newtonian fluid due to the shear thinning of the melt. Three different
rheological regimes, i.e., the viscous fluid, visco-elastic liquid, and
visco-elastic solid regimes, form over the oscillating plate according to the
local Deborah numbers. The melt behaves as a viscous fluid in a region for
, and the crossover between the liquid-like and
solid-like regime takes place around (where
is the angular frequency of the plate and and
are Rouse and relaxation time, respectively).Comment: 13pages, 12figure
Absence of self-averaging in the complex admittance for transport through random media
A random walk model in a one dimensional disordered medium with an
oscillatory input current is presented as a generic model of boundary
perturbation methods to investigate properties of a transport process in a
disordered medium. It is rigorously shown that an admittance which is equal to
the Fourier-Laplace transform of the first-passage time distribution is
non-self-averaging when the disorder is strong. The low frequency behavior of
the disorder-averaged admittance, where , does not coincide with the low frequency behavior of the admittance for any
sample, . It implies that the Cole-Cole plot of
appears at a different position from the Cole-Cole plots of of any
sample. These results are confirmed by Monte-Carlo simulations.Comment: 7 pages, 2 figures, published in Phys. Rev.
Removal Of Colloidal Silica In Simulated Seawater By A Dynamic Multi-Short-Circuited Galvanic Cell
A dynamic multi-short-circuited galvanic cell (MSCGC) with Pt-AI electrodes has been used to study the removal of colloidal silica from seawater as a pretreatment step for the desalination of seawater by use of reverse osmosis. The rate of silica removal is observed to be affected by the flow rate of the solution through the cell and the dissolved oxygen content of the solution as well as by the nature of the aluminum electrode surface and the number of contact points (short circuits) between the aluminum and platinum. The total silica content is reduced by 95 % by use of this cell configuration. © 1985, American Chemical Society. All rights reserved
Classical Correlation-Length Exponent in Non-Universal Quantum Phase Transition of Diluted Heisenberg Antiferromagnet
Critical behavior of the quantum phase transition of a site-diluted
Heisenberg antiferromagnet on a square lattice is investigated by means of the
quantum Monte Carlo simulation with the continuous-imaginary-time loop
algorithm. Although the staggered spin correlation function decays in a power
law with the exponent definitely depending on the spin size , the
correlation-length exponent is classical, i.e., . This implies that
the length scale characterizing the non-universal quantum phase transition is
nothing but the mean size of connected spin clusters.Comment: 4 pages, 3 figure
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