1,188 research outputs found
Finite size effects in nonequilibrium wetting
Models with a nonequilibrium wetting transition display a transition also in
finite systems. This is different from nonequilibrium phase transitions into an
absorbing state, where the stationary state is the absorbing one for any value
of the control parameter in a finite system. In this paper, we study what kind
of transition takes place in finite systems of nonequilibrium wetting models.
By solving exactly a microscopic model with three and four sites and performing
numerical simulations we show that the phase transition taking place in a
finite system is characterized by the average interface height performing a
random walk at criticality and does not discriminate between the bounded-KPZ
classes and the bounded-EW class. We also study the finite size scaling of the
bKPZ universality classes, showing that it presents peculiar features in
comparison with other universality classes of nonequilibrium phase transitions.Comment: 14 pages, 6figures, major change
TcruziDB: an integrated, post-genomics community resource for Trypanosoma cruzi
TcruziDB () is an integrated post-genomics database for the parasitic organism, Trypanosoma cruzi, the causative agent of Chagas' disease. TcruziDB was established in 2003 as a flat-file database with tools for mining the unannotated sequence reads and preliminary contig assemblies emerging from the Tri-Tryp genome consortium (TIGR/SBRI/Karolinska). Today, TcruziDB houses the recently published assembled genomic contigs and annotation provided by the genome consortium in a relational database supported by the Genomics Unified Schema (GUS) architecture. The combination of an annotated genome and a relational architecture has facilitated the integration of genomic data with expression data (proteomic and EST) and permitted the construction of automated analysis pipelines. TcruziDB has accepted, and will continue to accept the deposition of genomic and functional genomic datasets contributed by the research community
Contact processes with long-range interactions
A class of non-local contact processes is introduced and studied using
mean-field approximation and numerical simulations. In these processes
particles are created at a rate which decays algebraically with the distance
from the nearest particle. It is found that the transition into the absorbing
state is continuous and is characterized by continuously varying critical
exponents. This model differs from the previously studied non-local directed
percolation model, where particles are created by unrestricted Levy flights. It
is motivated by recent studies of non-equilibrium wetting indicating that this
type of non-local processes play a role in the unbinding transition. Other
non-local processes which have been suggested to exist within the context of
wetting are considered as well.Comment: Accepted with minor revisions by Journal of Statistical Mechanics:
Theory and experiment
Non-Classical Response from Quench-Cooled Solid Helium Confined in Porous Gold
We have investigated the non-classical response of solid 4He confined in
porous gold set to torsional oscillation. When solid helium is grown rapidly,
nearly 7% of the solid helium appears to be decoupled from the oscillation
below about 200 mK. Dissipation appears at temperatures where the decoupling
shows maximum variation. In contrast, the decoupling is substantially reduced
in slowly grown solid helium. The dynamic response of solid helium was also
studied by imposing a sudden increase in the amplitude of oscillation. Extended
relaxation in the resonant period shift, suggesting the emergence of the
pinning of low energy excitations, was observed below the onset temperature of
the non-classical response. The motion of a dislocation or a glassy solid is
restricted in the entangled narrow pores and is not likely responsible for the
period shift and long relaxation
Non-equilibrium Phase Transitions with Long-Range Interactions
This review article gives an overview of recent progress in the field of
non-equilibrium phase transitions into absorbing states with long-range
interactions. It focuses on two possible types of long-range interactions. The
first one is to replace nearest-neighbor couplings by unrestricted Levy flights
with a power-law distribution P(r) ~ r^(-d-sigma) controlled by an exponent
sigma. Similarly, the temporal evolution can be modified by introducing waiting
times Dt between subsequent moves which are distributed algebraically as P(Dt)~
(Dt)^(-1-kappa). It turns out that such systems with Levy-distributed
long-range interactions still exhibit a continuous phase transition with
critical exponents varying continuously with sigma and/or kappa in certain
ranges of the parameter space. In a field-theoretical framework such
algebraically distributed long-range interactions can be accounted for by
replacing the differential operators nabla^2 and d/dt with fractional
derivatives nabla^sigma and (d/dt)^kappa. As another possibility, one may
introduce algebraically decaying long-range interactions which cannot exceed
the actual distance to the nearest particle. Such interactions are motivated by
studies of non-equilibrium growth processes and may be interpreted as Levy
flights cut off at the actual distance to the nearest particle. In the
continuum limit such truncated Levy flights can be described to leading order
by terms involving fractional powers of the density field while the
differential operators remain short-ranged.Comment: LaTeX, 39 pages, 13 figures, minor revision
Different facets of the raise and peel model
The raise and peel model is a one-dimensional stochastic model of a
fluctuating interface with nonlocal interactions. This is an interesting
physical model. It's phase diagram has a massive phase and a gapless phase with
varying critical exponents. At the phase transition point, the model exhibits
conformal invariance which is a space-time symmetry. Also at this point the
model has several other facets which are the connections to associative
algebras, two-dimensional fully packed loop models and combinatorics.Comment: 29 pages 17 figure
Implementation of Web-Based Respondent-Driven Sampling among Men who Have Sex with Men in Vietnam
Objective: Lack of representative data about hidden groups, like men who have
sex with men (MSM), hinders an evidence-based response to the HIV epidemics.
Respondent-driven sampling (RDS) was developed to overcome sampling challenges
in studies of populations like MSM for which sampling frames are absent.
Internet-based RDS (webRDS) can potentially circumvent limitations of the
original RDS method. We aimed to implement and evaluate webRDS among a hidden
population.
Methods and Design: This cross-sectional study took place 18 February to 12
April, 2011 among MSM in Vietnam. Inclusion criteria were men, aged 18 and
above, who had ever had sex with another man and were living in Vietnam.
Participants were invited by an MSM friend, logged in, and answered a survey.
Participants could recruit up to four MSM friends. We evaluated the system by
its success in generating sustained recruitment and the degree to which the
sample compositions stabilized with increasing sample size.
Results: Twenty starting participants generated 676 participants over 24
recruitment waves. Analyses did not show evidence of bias due to ineligible
participation. Estimated mean age was 22 year and 82% came from the two large
metropolitan areas. 32 out of 63 provinces were represented. The median number
of sexual partners during the last six months was two. The sample composition
stabilized well for 16 out of 17 variables.
Conclusion: Results indicate that webRDS could be implemented at a low cost
among Internet-using MSM in Vietnam. WebRDS may be a promising method for
sampling of Internet-using MSM and other hidden groups.
Key words: Respondent-driven sampling, Online sampling, Men who have sex with
men, Vietnam, Sexual risk behavio
ToxoDB: an integrated Toxoplasma gondii database resource
ToxoDB (http://ToxoDB.org) is a genome and functional genomic database for the protozoan parasite Toxoplasma gondii. It incorporates the sequence and annotation of the T. gondii ME49 strain, as well as genome sequences for the GT1, VEG and RH (Chr Ia, Chr Ib) strains. Sequence information is integrated with various other genomic-scale data, including community annotation, ESTs, gene expression and proteomics data. ToxoDB has matured significantly since its initial release. Here we outline the numerous updates with respect to the data and increased functionality available on the website
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