Investigation of the Forest-Fire Model on a Small-World Network

It is shown that the forest-fire model of Bak et al. run on a square lattice network with additional long-range interactions in the spirit of a small-world network results in a scale-free system reminiscent of self-organized criticality without recourse to fine tuning. As the number of these long-range interactions is increased, the cluster size distribution exponent is found to decrease in magnitude as the small-world regime is entered, indicating a change in its universality class. It is suggested that such a model could have applicability in the study of disease spreading in human populations

Simulation Studies of Polymer Translocation through a Channel

Monte Carlo simulation studies of the translocation of homopolymers of length N driven through a channel have been performed. We find that the translocation time τ depends on temperature in a nontrivial way. For temperatures below some critical temperature θc, τ∼T-1.4, whereas for T>θc, τ increases with temperature. The low temperature results are in good agreement with experimental findings as is the dependence of τ on the driving field strength. The velocity of translocation displays the same characteristics as found in experiment but the N dependence of τ shows the linear relationship observed in experiment only for large values of N. A possible reason for this is suggested

Wavelet and receiver operating characteristic analysis of heart rate variability

Multiresolution wavelet analysis has been used to study the heart rate variability in two classes of patients with different pathological conditions. The scale dependent measure of Thurner et al. was found to be statistically significant in discriminating patients suffering from hypercardiomyopathy from a control set of normal subjects. We have performed Receiver Operating Characteristc (ROC) analysis and found the ROC area to be a useful measure by which to label the significance of the discrimination, as well as to describe the severity of heart dysfunction

Molecular dynamics simulation of transition metals as silicon substrates

In recent years the growth of epitaxial layers and strained layer superlattices have been simulated by using the method of molecular dynamics. We have used this method to study the formation of transition metal silicides as the metal is deposited on a silicon substrate. We propose effective empirical potentials to describe the interaction between the metal and silicon and use the Dodson and Stillinger-Weber potentials to model the silicon-silicon interaction. We report on the evolution of nickel layers on the substrate as a function of temperature

The interatomic potential and the long-range S(k) in liquids

It is suggested that information on the hardness of the repulsive potential in metals may be obtained by examining the long-range part of the liquid structure factor. By comparing the measured liquid structure factor of Ni with that of Ar it is shown that Ni has a harder core than Ar

Bonding and dipoles at semiconductor interfaces

We show that the values of the observed barriers to electrical transport across semiconductor interfaces can be explained in terms of a natural line-up corrected by a potential drop determined by the amount of charge transfer across this interface. This electrical dipole, and hence the barrier, can be altered by the judicious use of interlayers at the interface

Calculation of defect migration energies using molecular dynamics

The vacancy migration energy in Fe is calculated by use of the molecular dynamics method and the results are compared with those obtained using static relaxation method

Electronic structure of InGaAs and band offsets in InGaAs/GaAs superlattices

The authors report the results of self-consistent density functional calculations using ab initio pseudo-potentials on InxGa1-xAs/GaAs superlattices for x=0.25, 0.5, 0.75 and 1.0. The calculations were performed for two strained configurations. It was found that for GaAs substrates the valence band offset was almost independent of In content. For the case of InxGa1-xAs substrates, the valence band offset appears to vary non-linearly with the amount of strain in the GaAs layer. As a precursor to obtaining the band offsets, the electronic band structure of InGaAs was calculated for different compositions and strain conditions. These results are analysed and compared with experiment

Calculation of the optical properties of As molecules on Si substrates

We have calculated the imaginary part of the dielectric function for the Si(100)(2 × 1) and As/Si(100 x2 × 1) surfaces. The difference in the intensities as function of energy is found to be in excellent agreement with experiment