3,745 research outputs found
Studies of heat source driven natural convection
Natural convection energy transport in a horizontal layer of internally heated fluid with a zero heat flux lower boundary, and an isothermal upper boundary, has been studied. Quantitative information on the time-mean temperature distribution and the fluctuating component of temperature about the mean temperature in steady turbulent convection are obtained from a small thermocouple inserted into the layer through the upper bounding plate. Data are also presented on the development of temperature at several vertical positions when the layer is subject to both a sudden increase and to a sudden decrease in power input. For changes of power input from zero to a value corresponding to a Rayleigh number much greater than the critical linear stability theory value, a slight hysteresis in temperature profiles near the upper boundary is observed between the heat-up and cool-down modes
The Kasteleyn model and a cellular automaton approach to traffic flow
We propose a bridge between the theory of exactly solvable models and the
investigation of traffic flow. By choosing the activities in an apropriate way
the dimer configurations of the Kasteleyn model on a hexagonal lattice can be
interpreted as space-time trajectories of cars. This then allows for a
calculation of the flow-density relationship (fundamental diagram). We further
introduce a closely-related cellular automaton model. This model can be viewed
as a variant of the Nagel-Schreckenberg model in which the cars do not have a
velocity memory. It is also exactly solvable and the fundamental diagram is
calculated.Comment: Latex, 13 pages including 3 ps-figure
Laser-actuated holographic storage device
Device permits automatic selection of one out of thousands of pages in holographic memory system by using laser beam. In typical operation for 2 to 3 C temperature interval, using dc power supply with no power regulation, holograms were successfully written and erased over 2- by 2-cm area, using 80-mW argon laser beam
Theory of tricriticality for miscut surfaces
We propose a theory for the observed tricriticality in the orientational
phase diagram of Si(113) misoriented towards [001]. The systems seems to be at
or close to a very special point for long range interactions.Comment: Revtex, 1 ps figur
Coulomb and Liquid Dimer Models in Three Dimensions
We study classical hard-core dimer models on three-dimensional lattices using
analytical approaches and Monte Carlo simulations. On the bipartite cubic
lattice, a local gauge field generalization of the height representation used
on the square lattice predicts that the dimers are in a critical Coulomb phase
with algebraic, dipolar, correlations, in excellent agreement with our
large-scale Monte Carlo simulations. The non-bipartite FCC and Fisher lattices
lack such a representation, and we find that these models have both confined
and exponentially deconfined but no critical phases. We conjecture that
extended critical phases are realized only on bipartite lattices, even in
higher dimensions.Comment: 4 pages with corrections and update
Critical behavior of a three-dimensional dimer model
The phase transition behavior of a dimer model on a three-dimensional lattice is studied. This model is of biological interest because of its relevance to the lipid bilayer main phase transition. The model has the same kind of inactive low-temperature behavior as the exactly solvable Kasteleyn dimer model on a two-dimensional honeycomb lattice. Because of low-temperature inactivity, determination of the lowest-lying excited states allows one to locate the critical temperature. In this paper the second-lowest-lying excited states are studied and exact asymptotic results are obtained in the limit of large lattices. These results together with a finite-size scaling ansatz suggest a logarithmic divergence of the specific heat aboveT c for the three-dimensional model. Use of the same ansatz recovers the exact divergence (α=½) for the two-dimensional model
Gender-specific Equations for Predicting Maximal Heart Rate in Exercise Stress Testing
Please view abstract in the attached PDF file
Flexible Lipid Bilayers in Implicit Solvent
A minimalist simulation model for lipid bilayers is presented. Each lipid is
represented by a flexible chain of beads in implicit solvent. The hydrophobic
effect is mimicked through an intermolecular pair potential localized at the
``water''/hydrocarbon tail interface. This potential guarantees realistic
interfacial tensions for lipids in a bilayer geometry. Lipids self assemble
into bilayer structures that display fluidity and elastic properties consistent
with experimental model membrane systems. Varying molecular flexibility allows
for tuning of elastic moduli and area/molecule over a range of values seen in
experimental systems.Comment: 5 pages, 5 figure
The Phase Diagram of Random Heteropolymers
We propose a new analytic approach to study the phase diagram of random
heteropolymers, based on the cavity method. For copolymers we analyze the
nature and phenomenology of the glass transition as a function of sequence
correlations. Depending on these correlations, we find that two different
scenarios for the glass transition can occur. We show that, beside the much
studied possibility of an abrupt freezing transition at low temperature, the
system can exhibit, upon cooling, a first transition to a soft glass phase with
fully broken replica symmetry and a continuously growing degree of freezing as
the temperature is lowered.Comment: 4 pages, 3 figures; published versio
Differences in Male and Female Scapular Strength and the Relationship to Sprint Swimming Performance
Please see the pdf version of the abstract
- …