Monte Carlo and Perturbation Calculations for a Triangular Well Fluid

1974 ◽  
Vol 52 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Damon N. Card ◽  
John Walkley
Keyword(s):  
Monte Carlo ◽  
Hard Spheres ◽  
Low Density ◽  
Monte Carlo Data ◽  
Density Region ◽  
Wide Range ◽  
Model Fluid ◽  
High Density Region ◽  
Superposition Approximation ◽  
Triangular Well Potential

Monte Carlo data have been generated for a simple model fluid consisting of hard spheres with an attractive triangular well potential. The ranges spanned by the temperature and density are as follows. [Formula: see text] and [Formula: see text]. The machine data have been compared to the modern perturbation theories of (i) Barker, Henderson, and Smith and (ii) Weeks, Chandler, and Andersen. Comparison with the machine data shows that the latter theory is successful in the high density region only, but over a wide range of temperature. The Barker–Henderson approach is best in the low density region but the use of the superposition approximation limits the utility of this theory at high densities.

Density dependence of the Hanle effect of the 4s4p1P1 level of neutral calcium

1980 ◽  
Vol 58 (7) ◽  
pp. 1004-1009 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Density Dependence ◽  
High Density ◽  
Low Density ◽  
Density Region ◽  
Hanle Effect ◽  
Wide Range ◽  
High Density Region

The Hanle effect in the 4s21S0–4s4p1P1 (4226.7 Å) transition in Ca I has been observed over a wide range of densities. The low density observations determine the lifetime of the 1P1 level to be 4.49 ns. Collision parameters are obtained from observations in the high density region.

Structure of chemically reacting particles near a hard wall from integral equations and computer simulations

1996 ◽  
Vol 74 (1-2) ◽  
pp. 65-76 ◽  
Author(s):  
A. Trokhymchuk ◽  
D. Henderson ◽  
S. Sokołowski
Keyword(s):  
Monte Carlo ◽  
Computer Simulations ◽  
Hard Spheres ◽  
Total Density ◽  
Hard Wall ◽  
Monte Carlo Data ◽  
Density Profiles ◽  
Interparticle Potential ◽  
Theoretical Predictions ◽  
Chemically Reacting

We performed Monte-Carlo computer simulations of a fluid of chemically reacting, or overlapping, hard spheres near a hard wall. The model of the interparticle potential is that introduced by Cummings and Stell. This investigation is directed to the determination of the structure of the fluid at the wall, and the orientation of the dimers in particular. In addition, we applied the singlet Percus–Yevick, hypernetted chain and Born–Green–Yvon equations to calculate the total density profiles of the particles. A comparison with the Monte-Carlo data indicates that the singlet Percus–Yevick theory is superior and leads to results that are in reasonable agreement with simulations for all the parameters investigated. We also calculated the average numbers of dimers formed in the bulk part of the system and the results are compared with different theoretical predictions.

TRAFFIC FLOW ON A 3-LANE HIGHWAY

2004 ◽  
Vol 18 (31n32) ◽  
pp. 4161-4171 ◽  
Author(s):  
WEN-YAO CHEN ◽  
DING-WEI HUANG ◽  
WEI-NENG HUANG ◽  
WEN-LIANG HWANG
Keyword(s):  
Cellular Automaton ◽  
Traffic Flow ◽  
Low Density ◽  
Density Region ◽  
Lane Changing ◽  
Driving Behaviors ◽  
Control Scheme ◽  
High Density Region ◽  
Cellular Automaton Method ◽  
Changing Rate

The traffic flow on a 3-lane highway is investigated using a cellular automaton method. Two different kinds of vehicles, cars and trucks, with different driving behaviors are presented on the highway. It is found that in the high density region, a control scheme requiring passing from the inner lane will enhance the traffic flow; while restricting the trucks to the outer lane will enhance the flow in the low density region and also has the benefit of suppressing the unnecessary lane-changing rate.

The density dependence of the Hanle effect in the resonance line of atomic barium

1977 ◽  
Vol 55 (1) ◽  
pp. 83-91 ◽  
Author(s):  
F. M. Kelly ◽  
M. S. Mathur
Keyword(s):  
Cross Sections ◽  
Resonance Line ◽  
Excited Level ◽  
Ground Level ◽  
Multipole Moment ◽  
Low Density ◽  
Density Region ◽  
Hanle Effect ◽  
Wide Range ◽  
Theoretical Predictions

The change in the Hanle effect of the singlet resonance line of neutral barium has been studied over a wide range of density. The low density region has been used to confirm a lifetime of 8.37 ± 0.08 ns for the 6s6p1P1 level. We have determined the cross sections for the relaxation of the multipole moment of order 2 for collisions of the excited level with the ground level and with the metastable 6s5d1D2 level, and comparisons are made with the measured value of [Formula: see text] for the ground level with theoretical predictions.

Ionic recombination in an ambient gas II. Computer experiment with specific allowance for binary recombination

1978 ◽  
Vol 359 (1698) ◽  
pp. 287-301 ◽  
Keyword(s):  
Rate Coefficient ◽  
Laboratory Data ◽  
Computer Experiments ◽  
Computer Experiment ◽  
Recombination Coefficient ◽  
Quasi Equilibrium ◽  
Low Density ◽  
Density Region ◽  
High Density Region ◽  
Ambient Gas

A method of conducting computer experiments on ionic recombination in an ambient gas is described. Account may be taken of binary recombination, and its contribution to the total recombination coefficient may be separated. Recombination in molecular oxygen is treated as an example. It is found that the recombination coefficient for ambient gas (or termolecular) recombination by itself is as predicted by the quasi-equilibrium statistical method in the low density region and as predicted by the Langevin-Harper formula in the high density region. The slightly modified Natanson formula which was introduced to bridge the very wide gap between these two regions is not successful, the pattern of its failure being that it underestimates the influence which the mobilities of the ions have on the recombination coefficient. An unsuspected characteristic of binary recombination revealed by the investigation is that its rate coefficient depends on the density of the ambient gas. Before attempting to extrapolate laboratory data on the total ionic recombination coefficient to zero ambient gas density it is essential to take cognisance of the steep rise of the binary recombination coefficient in the very low density region.

The Pair Correlation Function of the Liquid-Vapour Interface: A Monte Carlo Calculation

1979 ◽  
Vol 34 (10) ◽  
pp. 1236-1238
Author(s):  
B. Borštnik ◽  
A. Ažman
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Correlation Function ◽  
Density Profile ◽  
Pair Correlation Function ◽  
Monte Carlo Calculation ◽  
Pair Correlation ◽  
Low Density ◽  
Density Region ◽  
New Information

Abstract A Monte Carlo simulation of the liquid-vapour interface near the triple point is reported. A monotonic density profile is obtained. In the entire interface the pair correlation function g(r) was found to be very close to the liquid bulk g(r), except for the low density region (ϱ(z)/(ϱliq ≦ 0.25 ) where information was inaccessible. The behaviour of the solution of the BGYB equation for the density profile is explored in the context of the new information concerning the pair correlation function in the interface.

Thermodynamic properties of pure hard sphere, spherocylinder and dumbell fluids

1979 ◽  
Vol 44 (12) ◽  
pp. 3555-3565 ◽  
Author(s):  
Ivo Nezbeda ◽  
Jan Pavlíček ◽  
Stanislav Labík
Keyword(s):  
Monte Carlo ◽  
Equation Of State ◽  
Thermodynamic Properties ◽  
Hard Sphere ◽  
Arbitrary Shape ◽  
Hard Spheres ◽  
Monte Carlo Data ◽  
Universal Equation

A universal equation of state for the fluid of hard bodies of an arbitrary shape is proposed. New Monte Carlo data of the hard sphere system are published and the existing pseudoexperimental data for hard spheres, spherocylindres and dumbells are critically reviewed.

scholarly journals Cooperation mitigates diversity loss in a spatially expanding microbial population

2019 ◽  
Author(s):  
Saurabh Gandhi ◽  
Kirill S. Korolev ◽  
Jeff Gore
Keyword(s):  
Genetic Diversity ◽  
Genetic Drift ◽  
Founder Effect ◽  
Growth Dynamics ◽  
Low Density ◽  
Density Region ◽  
Diversity Loss ◽  
High Density Region ◽  
Expanding Population ◽  
Serial Founder Effect

AbstractThe evolution and potentially even the survival of a spatially expanding population depends on its genetic diversity, which can decrease rapidly due to a serial founder effect. The strength of the founder effect is predicted to depend strongly on the details of the growth dynamics. Here, we probe this dependence experimentally using a single microbial species, Saccharomyces cerevisiae, expanding in multiple environments that induce varying levels of cooperativity during growth. We observe a drastic reduction in diversity during expansions when yeast grows non-cooperatively on simple sugars, but almost no loss of diversity when cooperation is required to digest complex metabolites. These results are consistent with theoretical expectations. When cells grow independently from each other, the expansion proceeds as a pulled wave driven by the growth at the low-density tip of the expansion front. Such populations lose diversity rapidly because of the strong genetic drift at the expansion edge. In contrast, diversity loss is substantially reduced in pushed waves that arise due to cooperative growth. In such expansions, the low-density tip of the front grows much more slowly and is often reseeded from the genetically diverse population core. Additionally, in both pulled and pushed expansions, we observe a few instances of abrupt changes in allele fractions due to rare fluctuations of the expansion front and show how to distinguish such rapid genetic drift from selective sweeps.Significance statementSpatially expanding populations lose genetic diversity rapidly because of the repeated bottlenecks formed at the front as a result of the serial founder effect. However, the rate of diversity loss depends on the specifics of the expanding population, such as its growth and dispersal dynamics. We have previously demonstrated that changing the amount of within-species cooperation leads to a qualitative transition in the nature of expansion from pulled (driven by migration at the low density tip) to pushed (driven by migration from the high density region at the front, but behind the tip). Here we demonstrate experimentally that pushed waves, which emerge in the presence of sufficiently strong cooperation, result in strongly reduced genetic drift during range expansions, thus preserving genetic diversity in the newly colonized region.

Sign in / Sign up

Export Citation Format

Share Document