665 research outputs found
Classical ultrarelativistic bremsstrahlung in extra dimensions
The emitted energy and the cross-section of classical scalar bremsstrahlung
in massive particle collisions in D=4+d dimensional Minkowski space M_D as well
as in the brane world M_4 \times T^d is computed to leading ultra-relativistic
order. The particles are taken to interact in the first case via the exchange
of a bulk massless scalar field \Phi and in the second with an additional
massless scalar \phi confined together with the particles on the brane. Energy
is emitted as \Phi radiation in the bulk and/or \phi radiation on the brane. In
contrast to the quantum Born approximation, the classical result is unambiguous
and valid in a kinematical region which is also specified. For D=4 the results
are in agreement with corresponding expressions in classical electrodynamics.Comment: Preprint number adde
Model structure and content of a comprehensive maritime plan: the case of Kaliningrad
The need for maritime spatial planning is articulated in the Strategy for Marine Development of the Russian Federation until 2030. However, Russian legislation contains no provisions regulating this field. This article presents the results of a study aimed to devise a methodology for developing the model structure of a maritime plan for the Baltic Sea. The study methodology is based on current regulations on marine use and na-ture management as well as international maritime planning practices. Since marine planning is closely connected with spatial planning, the study pays special attention to their convergence in developing maritime plans. The authors stress the need for legislative efforts aimed at integrating marine planning in the current legal framework for the regional authorities of different territorial levels. The structure and contents of the maritime plan and the methodological framework for suggested measures are based on relevant regulations, publications, and maps. The main result of the study is the identification of functional offshore areas of federal, regional, and local significance. The research significance of this study is associated with the further development of strategic planning, namely, marine planning. Its practical significance is in devising the legal and methodological framework for marine spatial planning
Majority Rule Dynamics in Finite Dimensions
We investigate the long-time behavior of a majority rule opinion dynamics
model in finite spatial dimensions. Each site of the system is endowed with a
two-state spin variable that evolves by majority rule. In a single update
event, a group of spins with a fixed (odd) size is specified and all members of
the group adopt the local majority state. Repeated application of this update
step leads to a coarsening mosaic of spin domains and ultimate consensus in a
finite system. The approach to consensus is governed by two disparate time
scales, with the longer time scale arising from realizations in which spins
organize into coherent single-opinion bands. The consequences of this
geometrical organization on the long-time kinetics are explored.Comment: 8 pages, 2-column revtex format, 11 figures. Version 2: minor changes
in response to referee comments and typos corrected; final version for PR
Assessing the shape of the viscoplastic iron-ore zone in a blast furnace
A mathematical model permits assessment of the position and shape of the viscoplastic iron-ore zone (cohesion zone) in a blast furnace and identification of a rational configuration for this zone on the basis of readily available information regarding the blast furnace in the baseline period. The model also permits the solution of design problems with variation in the furnace parameters. Modeling results are outlined for the baseline and design periods. © 2013 Allerton Press, Inc
Distribution of dwell times of a ribosome: effects of infidelity, kinetic proofreading and ribosome crowding
Ribosome is a molecular machine that polymerizes a protein where the sequence
of the amino acid residues, the monomers of the protein, is dictated by the
sequence of codons (triplets of nucleotides) on a messenger RNA (mRNA) that
serves as the template. The ribosome is a molecular motor that utilizes the
template mRNA strand also as the track. Thus, in each step the ribosome moves
forward by one codon and, simultaneously, elongates the protein by one amino
acid. We present a theoretical model that captures most of the main steps in
the mechano-chemical cycle of a ribosome. The stochastic movement of the
ribosome consists of an alternating sequence of pause and translocation; the
sum of the durations of a pause and the following translocation is the time of
dwell of the ribosome at the corresponding codon. We derive the analytical
expression for the distribution of the dwell times of a ribosome in our model.
Whereever experimental data are available, our theoretical predictions are
consistent with those results. We suggest appropriate experiments to test the
new predictions of our model, particularly, the effects of the quality control
mechanism of the ribosome and that of their crowding on the mRNA track.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher authenticated version
is available online at DOI:10.1088/1478-3975/8/2/02600
Expression dynamics of a cellular metabolic network
Toward the goal of understanding system properties of biological networks, we investigate the global and local regulation of gene expression in the Saccharomyces cerevisiae metabolic network. Our results demonstrate predominance of local gene regulation in metabolism. Metabolic genes display significant coexpression on distances smaller than the average network distance, a behavior supported by the distribution of transcription factor binding sites in the metabolic network and genome context associations. Positive gene coexpression decreases monotonically with distance in the network, while negative coexpression is strongest at intermediate network distances. We show that basic topological motifs of the metabolic network exhibit statistically significant differences in coexpression behavior
Dynamic Scaling in One-Dimensional Cluster-Cluster Aggregation
We study the dynamic scaling properties of an aggregation model in which
particles obey both diffusive and driven ballistic dynamics. The diffusion
constant and the velocity of a cluster of size follow
and , respectively. We determine the dynamic exponent and
the phase diagram for the asymptotic aggregation behavior in one dimension in
the presence of mixed dynamics. The asymptotic dynamics is dominated by the
process that has the largest dynamic exponent with a crossover that is located
at . The cluster size distributions scale similarly in all
cases but the scaling function depends continuously on and .
For the purely diffusive case the scaling function has a transition from
exponential to algebraic behavior at small argument values as changes
sign whereas in the drift dominated case the scaling function decays always
exponentially.Comment: 6 pages, 6 figures, RevTeX, submitted to Phys. Rev.
Dynamics of Social Balance on Networks
We study the evolution of social networks that contain both friendly and
unfriendly pairwise links between individual nodes. The network is endowed with
dynamics in which the sense of a link in an imbalanced triad--a triangular loop
with 1 or 3 unfriendly links--is reversed to make the triad balanced. With this
dynamics, an infinite network undergoes a dynamic phase transition from a
steady state to "paradise"--all links are friendly--as the propensity p for
friendly links in an update event passes through 1/2. A finite network always
falls into a socially-balanced absorbing state where no imbalanced triads
remain. If the additional constraint that the number of imbalanced triads in
the network does not increase in an update is imposed, then the network quickly
reaches a balanced final state.Comment: 10 pages, 7 figures, 2-column revtex4 forma
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