4,871 research outputs found
Configuration Space for Random Walk Dynamics
Applied to statistical physics models, the random cost algorithm enforces a
Random Walk (RW) in energy (or possibly other thermodynamic quantities). The
dynamics of this procedure is distinct from fixed weight updates. The
probability for a configuration to be sampled depends on a number of unusual
quantities, which are explained in this paper. This has been overlooked in
recent literature, where the method is advertised for the calculation of
canonical expectation values. We illustrate these points for the Ising
model. In addition, we proof a previously conjectured equation which relates
microcanonical expectation values to the spectral density.Comment: Various minor changes, appendix added, Fig. 2 droppe
Yang-Lee zeros and the helix-coil transition in a continuum model of polyalanine
We calculate the Yang-Lee zeros for characteristic temperatures of the
helix-coil transition in a continuum model of polyalanine. The distribution of
these zeros differs from predictions of the Zimm-Bragg theory and supports
recent claims that polyalanine exhibits a true phase transition. New estimates
for critical exponents are presented and the relation of our results to the
Lee-Yang theorem is discussed.Comment: 15 pages and 5 figure
Recent Results of Multimagnetical Simulations of the Ising Model
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the and Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact results. In
the physically more interesting case we estimate the amplitude of
the critical interfacial tension.Comment: talk presented at the workshop "Dynamics of First Order Phase
Transitions", Juelich June 1-3; FSU-SCRI-92C-87 preprint; 7 pages; sorry no
figures; needs vanilla.st
Structural transitions in biomolecules - a numerical comparison of two approaches for the study of phase transitions in small systems
We compare two recently proposed methods for the characterization of phase
transitions in small systems. The usefulness of these techniques is evaluated
for the case of structural transition in alanine-based peptides.Comment: Accepted for publication in Int. J. Mol. Sci., to appear in a special
issue devoted to R.S. Berr
Helix Formation and Folding in an Artificial Peptide
We study the relation between -helix formation and folding for a
simple artificial peptide, Ala-Gly-Ala. Our data rely on
multicanonical Monte Carlo simulations where the interactions among all atoms
are taken into account. The free-energy landscape of the peptide is evaluated
for various temperatures. Our data indicate that folding of this peptide is a
two-step process: in a first step two -helices are formed which
afterwards re-arrange themselves into a U-like structure.Comment: 15 pages, with 9 eps figure
Helix vs. Sheet Formation in a Small Peptide
Segments with the amino acid sequence EKAYLRT appear in natural occurring
proteins both in -helices and -sheets. For this reason, we have
use this peptide to study how secondary structure formation in proteins depends
on the local environment. Our data rely on multicanonical Monte Carlo
simulations where the interactions among all atoms are taken into account.
Results in gas phase are compared with that in an implicit solvent. We find
that both in gas phase and solvated EKAYLRT forms an -helix when not
interacting with other molecules. However, in the vicinity of a -strand,
the peptide forms a -strand. Because of this change in secondary
structure our peptide may provide a simple model for the
transition that is supposedly related to the outbreak of Prion diseases and
similar illnesses.Comment: to appear in Physical Review
Generalized-ensemble Monte carlo method for systems with rough energy landscape
We present a novel Monte Carlo algorithm which enhances equilibrization of
low-temperature simulations and allows sampling of configurations over a large
range of energies. The method is based on a non-Boltzmann probability weight
factor and is another version of the so-called generalized-ensemble techniques.
The effectiveness of the new approach is demonstrated for the system of a small
peptide, an example of the frustrated system with a rugged energy landscape.Comment: Latex; ps-files include
Partition Function Zeros and Finite Size Scaling of Helix-Coil Transitions in a Polypeptide
We report on multicanonical simulations of the helix-coil transition of a
polypeptide. The nature of this transition was studied by calculating partition
function zeros and the finite-size scaling of various quantities. Estimates for
critical exponents are presented.Comment: RevTex, 4 eps-files; to appear in Phys. Rev. Le
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