1,234 research outputs found
Low temperature expansion for the 3-d Ising Model
We compute the weak coupling expansion for the energy of the three
dimensional Ising model through 48 excited bonds. We also compute the
magnetization through 40 excited bonds. This was achieved via a recursive
enumeration of states of fixed energy on a set of finite lattices. We use a
linear combination of lattices with a generalization of helical boundary
conditions to eliminate finite volume effects.Comment: 10 pages, IASSNS-HEP-92/42, BNL-4767
Helium irradiation effects in polycrystalline Si, silica, and single crystal Si
Transmission electron microscopy (TEM) has been used to investigate the effects of room temperature 6âkeV helium ion irradiation of a thin (â55ânm thick) tri-layer consisting of polycrystalline Si, silica, and single-crystal Si. The ion irradiation was carried out in situ within the TEM under conditions where approximately 24% of the incident ions came to rest in the specimen. This paper reports on the comparative development of irradiation-induced defects (primarily helium bubbles) in the polycrystalline Si and single-crystal Si under ion irradiation and provides direct measurement of a radiation-induced increase in the width of the polycrystalline layer and shrinkage of the silica layer. Analysis using TEM and electron energy-loss spectroscopy has led to the hypothesis that these result from helium-bubble-induced swelling of the silicon and radiation-induced viscoelastic flow processes in the silica under the influence of stresses applied by the swollen Si layers. The silicon and silica layers are sputtered as a result of the helium ion irradiation; however, this is estimated to be a relatively minor effect with swelling and stress-related viscoelastic flow being the dominant mechanisms of dimensional change
The Block Spin Renormalization Group Approach and Two-Dimensional Quantum Gravity
A block spin renormalization group approach is proposed for the dynamical
triangulation formulation of two-dimensional quantum gravity. The idea is to
update link flips on the block lattice in response to link flips on the
original lattice. Just as the connectivity of the original lattice is meant to
be a lattice representation of the metric, the block links are determined in
such a way that the connectivity of the block lattice represents a block
metric. As an illustration, this approach is applied to the Ising model coupled
to two-dimensional quantum gravity. The correct critical coupling is
reproduced, but the critical exponent is obscured by unusually large finite
size effects.Comment: 10 page
A Monte Carlo study of leading order scaling corrections of phi^4 theory on a three dimensional lattice
We present a Monte Carlo study of the one-component model on the
cubic lattice in three dimensions. Leading order scaling corrections are
studied using the finite size scaling method. We compute the corrections to
scaling exponent with high precision. We determine the value of the
coupling at which leading order corrections to scaling vanish. Using
this result we obtain estimates for critical exponents that are more precise
than those obtained with field theoretic methods.Comment: 20 pages, two figures; numbers cited from ref. 23 corrected, few
typos correcte
Ice XII in its second regime of metastability
We present neutron powder diffraction results which give unambiguous evidence
for the formation of the recently identified new crystalline ice phase[Lobban
et al.,Nature, 391, 268, (1998)], labeled ice XII, at completely different
conditions. Ice XII is produced here by compressing hexagonal ice I_h at T =
77, 100, 140 and 160 K up to 1.8 GPa. It can be maintained at ambient pressure
in the temperature range 1.5 < T < 135 K. High resolution diffraction is
carried out at T = 1.5 K and ambient pressure on ice XII and accurate
structural properties are obtained from Rietveld refinement. At T = 140 and 160
K additionally ice III/IX is formed. The increasing amount of ice III/IX with
increasing temperature gives an upper limit of T ~ 150 K for the successful
formation of ice XII with the presented procedure.Comment: 3 Pages of RevTeX, 3 tables, 3 figures (submitted to Physical Review
Letters
Monte Carlo Renormalization of the 3-D Ising model: Analyticity and Convergence
We review the assumptions on which the Monte Carlo renormalization technique
is based, in particular the analyticity of the block spin transformations. On
this basis, we select an optimized Kadanoff blocking rule in combination with
the simulation of a d=3 Ising model with reduced corrections to scaling. This
is achieved by including interactions with second and third neighbors. As a
consequence of the improved analyticity properties, this Monte Carlo
renormalization method yields a fast convergence and a high accuracy. The
results for the critical exponents are y_H=2.481(1) and y_T=1.585(3).Comment: RevTeX, 4 PostScript file
Multi-interaction mean-field renormalization group
We present an extension of the previously proposed mean-field renormalization
method to model Hamiltonians which are characterized by more than just one type
of interaction. The method rests on scaling assumptions about the magnetization
of different sublattices of the given lattice and it generates as many flow
equations as coupling constants without arbitrary truncations on the
renormalized Hamiltonian. We obtain good results for the test case of Ising
systems with an additional second-neighbor coupling in two and three
dimensions. An application of the method is also done to a morphological model
of interacting surfaces introduced recenlty by Likos, Mecke and Wagner [J.
Chem. Phys. {\bf{102}}, 9350 (1995)].
PACS: 64.60.Ak, 64.60.Fr, 05.70.JkComment: Tex file and three macros appended at the end. Five figures available
upon request to: [email protected], Fax: [+]39-40-224-60
Tracking of fluorescently labeled polymer particles reveals surface effects during shear-controlled aggregation
Surface chemistry is believed to be the key parameter affecting the aggregation and breakage of colloidal suspensions when subjected to shear. To date, only a few works dealt with the understanding of the role of the physical and chemical properties of the particlesâ surface upon aggregation under shear. Previous studies suggested that surface modifications strongly affect polymer particlesâ adhesion, but it was very challenging to demonstrate this effect and monitor these alterations upon prolonged exposure to shear forces. More importantly, the mechanisms leading to these changes remain elusive. In this work, shear-induced aggregation experiments of polymer colloidal particles have been devised with the specific objective of highlighting material transfer and clarifying the role of the softness of the particleâs surface. To achieve this goal, polymer particles with a coreâshell structure comprising fluorescent groups have been prepared so that the surfaceâs softness could be tuned by the addition of monomer acting as a plasticizer and the percentage of fluorescent particles could be recorded over time via confocal microscopy to detect eventual material transfer among different particles. For the first time, material exchange occurring on the soft surface of coreâshell polymer microparticles upon aggregation under shear was observed and proved. More aptly, starting from a 50% labeled/nonlabeled mixture, an increase in the percentage of particles showing a fluorescent signature was recorded over time, reaching a fraction of 70% after 5 h
Molecular dynamics study of orientational order and rotational melting in clusters of TeF 6
Molecular dynamics simulations of the behavior of molecules in crystalline clusters of TeF 6 were carried out on systems of 100, 150, 250, and 350 molecules. Several diagnostic functions were applied to investigate whether rotational melting occurred before translational melting. These functions included the coefficient of rotational diffusion D Ξ ( T ), the âorientational Lindemann indexâ ÎŽ Ξ ( T ), the âorientational angular distribution functionâ Q (Ξ, T ), and the âorientational pair-correlation functionâ g Ξ ( r, T ). All indicators implied that rotational melting occurred before translational melting, that it began with the outermost molecules, and that its onset for smaller clusters was at lower temperatures than for larger clusters. Results also showed that the rotational transition coincided with the transition from a lower symmetry phase (monoclinic) to cubic, a phenomenon that had been noted by others to occur with some regularity for systems of globular molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43961/1/10053_2005_Article_BF01426586.pd
Ab-o'th-yate at the Isle of Man
Literatura dialectal. -- Lancashire. -- Pertenece a la colecciĂłn 1800-1950 del Salamanca Corpus. -- Prosa. -- Benjamin Brierley. -- Ab-o'th-yate at the Isle of Man. -- 1869. -- Primera ediciĂłn.[EN] Fiction letters written in the Lancashire dialect.
[ES] Cartas escritas en el dialecto de Lancashire
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