515 research outputs found
Three-Dimensional Percolation Modeling of Self-Healing Composites
We study the self-healing process of materials with embedded "glue"-carrying
cells, in the regime of the onset of the initial fatigue. Three-dimensional
numerical simulations within the percolation-model approach are reported. The
main numerical challenge taken up in the present work, has been to extend the
calculation of the conductance to three-dimensional lattices. Our results
confirm the general features of the process: The onset of the material fatigue
is delayed, by developing a plateau-like time-dependence of the material
quality. We demonstrate that in this low-damage regime, the changes in the
conductance and thus, in similar transport/response properties of the material
can be used as measures of the material quality degradation. A new feature
found for three dimensions, where it is much more profound than in
earlier-studied two-dimensional systems, is the competition between the healing
cells. Even for low initial densities of the healing cells, they interfere with
each other and reduce each other's effective healing efficiency.Comment: 15 pages in PDF, with 6 figure
Anisotropy and universality: Critical Binder cumulant of the two-dimensional Ising model
We reanalyze transfer matrix and Monte Carlo results for the critical Binder
cumulant U* of an anisotropic two-dimensional Ising model on a square lattice
in a square geometry with periodic boundary conditions. Spins are coupled
between nearest neighboring sites and between next-nearest neighboring sites
along one of the lattice diagonals. We find that U* depends only on the
asymptotic critical long-distance features of the anisotropy, irrespective of
its realization through ferromagnetic or antiferromagnetic next-nearest
neighbor couplings. We modify an earlier renormalization-group calculation to
obtain a quantitative description of the anisotropy dependence of U*. Our
results support our recent claim towards the validity of universality for
critical phenomena in the presence of a weak anisotropy.Comment: 4 pages, 2 figures; one reference and some clarifications adde
Relaxation kinetics of biological dimer adsorption models
We discuss the relaxation kinetics of a one-dimensional dimer adsorption
model as recently proposed for the binding of biological dimers like kinesin on
microtubules. The non-equilibrium dynamics shows several regimes: irreversible
adsorption on short time scales, an intermediate plateau followed by a
power-law regime and finally exponential relaxation towards equilibrium. In all
four regimes we give analytical solutions. The algebraic decay and the scaling
behaviour can be explained by mapping onto a simple reaction-diffusion model.
We show that there are several possibilities to define the autocorrelation
function and that they all asymptotically show exponential decay, however with
different time constants. Our findings remain valid if there is an attractive
interaction between bound dimers.Comment: REVTeX, 6 pages, 5 figures; to appear in Europhys. Letters; a Java
applet showing the simulation is accessible at
http://www.ph.tum.de/~avilfan/rela
Asymmetric Fluid Criticality II: Finite-Size Scaling for Simulations
The vapor-liquid critical behavior of intrinsically asymmetric fluids is
studied in finite systems of linear dimensions, , focusing on periodic
boundary conditions, as appropriate for simulations. The recently propounded
``complete'' thermodynamic scaling theory incorporating pressure
mixing in the scaling fields as well as corrections to scaling
, is extended to finite , initially in a grand
canonical representation. The theory allows for a Yang-Yang anomaly in which,
when , the second temperature derivative,
, of the chemical potential along the phase
boundary, , diverges when T\to\Tc -. The finite-size
behavior of various special {\em critical loci} in the temperature-density or
plane, in particular, the -inflection susceptibility loci and the
-maximal loci -- derived from where -- is carefully elucidated and
shown to be of value in estimating \Tc and \rhoc. Concrete illustrations
are presented for the hard-core square-well fluid and for the restricted
primitive model electrolyte including an estimate of the correlation exponent
that confirms Ising-type character. The treatment is extended to the
canonical representation where further complications appear.Comment: 23 pages in the two-column format (including 13 figures) This is Part
II of the previous paper [arXiv:cond-mat/0212145
Random Sequential Adsorption: From Continuum to Lattice and Pre-Patterned Substrates
The random sequential adsorption (RSA) model has served as a paradigm for
diverse phenomena in physical chemistry, as well as in other areas such as
biology, ecology, and sociology. In the present work, we survey aspects of the
RSA model with emphasis on the approach to and properties of jammed states
obtained for large times in continuum deposition versus that on lattice
substrates, and on pre-patterned surfaces. The latter model has been of recent
interest in the context of efforts to use pre-patterning as a tool to improve
selfassembly in micro- and nanoscale surface structure engineering
Series Analysis of Tricritical Behavior: Mean-Field Model and Slicewise Pade Approximants
A mean-field model is proposed as a test case for tricritical series analyses
methods. Derivation of the 50th order series for the magnetization is reported.
As the first application this series is analyzed by the traditional slicewise
Pade approximant method popular in earlier studies of tricriticality.Comment: 22 pages in plain TeX; 7 PostScript figs available by e-mai
Higher expression of somatic repair genes in long-lived ant queens than workers.
Understanding why organisms senesce is a fundamental question in biology. One common explanation is that senescence results from an increase in macromolecular damage with age. The tremendous variation in lifespan between genetically identical queen and worker ants, ranging over an order of magnitude, provides a unique system to study how investment into processes of somatic maintenance and macromolecular repair influence lifespan. Here we use RNAseq to compare patterns of expression of genes involved in DNA and protein repair of age-matched queens and workers. There was no difference between queens and workers in 1-day-old individuals, but the level of expression of these genes increased with age and this up-regulation was greater in queens than in workers, resulting in significantly queen-biased expression in 2-month-old individuals in both legs and brains. Overall, these differences are consistent with the hypothesis that higher longevity is associated with increased investment into somatic repair
Anderson transition of the plasma oscillations of 1D disordered Wigner lattices
We report the existence of a localization-delocalization transition in the
classical plasma modes of a one dimensional Wigner Crystal with a white noise
potential environment at T=0. Finite size scaling analysis reveals a divergence
of the localization length at a critical eigenfrequency. Further scaling
analysis indicates power law behavior of the critical frequency in terms of the
relative interaction strength of the charges. A heuristic argument for this
scaling behavior is consistent with the numerical results. Additionally, we
explore a particular realization of random-bond disorder in a one dimensional
Wigner lattice in which all of the collective modes are observed to be
localized.Comment: 4 pages, 3 figures, Typo for the localization length corrected.
Should read 1 / \n
Coexistence of excited states in confined Ising systems
Using the density-matrix renormalization-group method we study the
two-dimensional Ising model in strip geometry. This renormalization scheme
enables us to consider the system up to the size 300 x infinity and study the
influence of the bulk magnetic field on the system at full range of
temperature. We have found out the crossover in the behavior of the correlation
length on the line of coexistence of the excited states. A detailed study of
scaling of this line is performed. Our numerical results support and specify
previous conclusions by Abraham, Parry, and Upton based on the related bubble
model.Comment: 4 Pages RevTeX and 4 PostScript figures included; the paper has been
rewritten without including new result
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