10 research outputs found
Random Field and Random Anisotropy Effects in Defect-Free Three-Dimensional XY Models
Monte Carlo simulations have been used to study a vortex-free XY ferromagnet
with a random field or a random anisotropy on simple cubic lattices. In the
random field case, which can be related to a charge-density wave pinned by
random point defects, it is found that long-range order is destroyed even for
weak randomness. In the random anisotropy case, which can be related to a
randomly pinned spin-density wave, the long-range order is not destroyed and
the correlation length is finite. In both cases there are many local minima of
the free energy separated by high entropy barriers. Our results for the random
field case are consistent with the existence of a Bragg glass phase of the type
discussed by Emig, Bogner and Nattermann.Comment: 10 pages, including 2 figures, extensively revise
A Comparison of Components of Written Expression Abilities in Learning Disabled and Non-Learning Disabled Students at Three Grade Levels
Although written language plays a critical role in academic success, little empirical evidence exists on the normal development of processes involved in producing written products. Even less is known about the writing performance of LD children. This study empirically compared the written products of LD and normal students at three grade levels on The Test of Written Language. Results showed that LD subjects scored significantly lower than normal subjects on most written expression abilities, especially in the mechanical tasks of spelling, punctuation, and word usage.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Flux-lattice melting in two-dimensional disordered superconductors
The flux line lattice melting transition in two-dimensional pure and
disordered superconductors is studied by a Monte Carlo simulation using the
lowest Landau level approximation and quasi-periodic boundary condition on a
plane. The position of the melting line was determined from the diffraction
pattern of the superconducting order parameter. In the clean case we confirmed
the results from earlier studies which show the existence of a quasi-long range
ordered vortex lattice at low temperatures. Adding frozen disorder to the
system the melting transition line is shifted to slightly lower fields. The
correlations of the order parameter for translational long range order of the
vortex positions seem to decay slightly faster than a power law (in agreement
with the theory of Carpentier and Le Doussal) although a simple power law decay
cannot be excluded. The corresponding positional glass correlation function
decays as a power law establishing the existence of a quasi-long range ordered
positional glass formed by the vortices. The correlation function
characterizing a phase coherent vortex glass decays however exponentially
ruling out the possible existence of a phase coherent vortex glass phase.Comment: 12 pages, 21 figures, final version to appear in Phys. Rev.
Commercialism as a Dominant Factor in the American Sports Scene: Sources, Developments, Perspectives
Laser coupling to reduced-scale targets at NIF Early Light
Deposition of maximum laser energy into a small, high-Z enclosure in a short laser pulse creates a hot environment. Such targets
were recently included in an experimental campaign using the first four of
the 192 beams of the National Ignition Facility [J. A. Paisner, E. M.
Campbell, and W. J. Hogan, Fusion Technology 26, 755 (1994)], under
construction at the University of California Lawrence Livermore National
Laboratory. These targets demonstrate good laser coupling, reaching a
radiation temperature of 340 eV. In addition, the Raman backscatter spectrum
contains features consistent with Brillouin backscatter of Raman forward
scatter [A. B. Langdon and D. E. Hinkel, Physical Review Letters 89, 015003 (2002)]. Also,
NIF Early Light diagnostics indicate that 20% of the direct backscatter
from these reduced-scale targets is in the polarization orthogonal to that
of the incident light
X-ray flux and X-ray burnthrough experiments on reduced-scale targets at the NIF and OMEGA lasers
An experimental campaign to maximize radiation drive in small-scale
hohlraums has been carried out at the National Ignition Facility
(NIF) at the Lawerence Livermore National Laboratory (Livermore, CA,
USA) and at the OMEGA laser at the Laboratory for Laser Energetics
(Rochester, NY, USA). The small-scale hohlraums, laser energy, laser
pulse, and diagnostics were similar at both facilities but the
geometries were very different. The NIF experiments used on-axis
laser beams whereas the OMEGA experiments used 19 beams in three
beam cones. In the cases when the lasers coupled well and produced
similar radiation drive, images of x-ray burnthrough and laser
deposition indicate the pattern of plasma filling is very different