arXiv subjects

I-Ming Tang

Publications and source records attributed to I-Ming Tang.

5 recordsLinked to original sources

arXiv2004

Vacancy-Mediated Disordering Process in Binary Alloys at Finite Temperatures: Monte Carlo Simulations

We have investigated the time evolution of the vacancy-mediated disordering process in binary alloys at finite temperatures. Qualitatively, we monitor the changes in the configurations by taking sequences of snapshots for various temperatures and comparing their morphologies. Quantitatively, we carry out Monte Carlo simulations to determine the time-dependent disorder parameter A(L;T;t) and the time-dependent structure factors Sk(t) for moderately low temperatures. This study differs from previous studies done at infinite temperature in that the vacancy here executes highly active walks, which are subjected to nonlinear feedbacks, instead of the random walks that take place in the limit of T ->infinity. We find that the slope of the log-log plot of A(L; T; t) vs. t for finite temperatures follows the temperature dependence given by the Gompertz function and reaches a limiting value of 1/2 only as the temperature approaches infinity. For the structure factors, namely, Sk(t) vs. t, the overall features are similar to those found at infinite T. The two key differences between our results and those at infinite T are the saturated value and the intermediate region in which the portion of the graph whose slope is equal to one becomes smaller and is gradually replaced by a curve having a slope of 0.5. This last difference is especially evident at very low temperatures.

cond-mat.stat-mech↗

arXiv2004

Modeling of the dynamic pole-to-pole oscillations of the min proteins in bacterial cell division: The effect of an external field

One of the most important steps in the developmental process of the bacteria cell at the cellular level is the determination of the middle of the cell and the proper placement of the septum, these being essential to the division of the cell. In E. coli, this step depends on the proteins MinC, MinD, and MinE. Exposure to a constant electric field may cause the bacteria cell division mechanism to change, resulting in an abnormal cytokinesis. To see the effects of an external field e.g., an electric or magnetic field on this process, we have solved a set of deterministic reaction diffusion equations, which incorporate the influence of an electric field. We have found some changes in the dynamics of the oscillations of the min proteins from pole to pole. The numerical results show some interesting effects, which are qualitatively in good agreement with some experimental results.

physics.bio-ph↗

arXiv2004

Effects of Static Magnetic Field on Growth of Leptospire, Leptospira interrogans serovar canicola: Immunoreactivity and Cell Division

The effects of the exposure of the bacterium, Leptospira interrogans serovar canicola to a constant magnetic field with magnetic flux density from a permanent ferrite magnet = 140 mT were studied. Changes in Leptospira cells after their exposure to the field were determined on the basis of changes in their growth behavior and agglutination immunoreactivity with a homologous antiserum using darkfield microscopy together with visual imaging. The data showed that the exposed Leptospira cells have lower densities and lower agglutination immunoreactivity than the unexposed control group. Interestingly, some of the exposed Leptospira cells showed abnormal morphologies such as large lengths. We discussed some of the possible reasons for these observations.

physics.bio-ph↗

arXiv2004

The dynamics of the min proteins of Escherichia coli under the constant external fields

In E. coli the determination of the middle of the cell and the proper placement of the septum is essential to the division of the cell. This step depends on the proteins MinC, MinD, and MinE. Exposure to a constant external field e.g., an electric field or magnetic field may cause the bacteria cell division mechanism to change resulting in an abnormal cytokinesis. To have insight into the effects of an external field on this process, we model the process using a set of the deterministic reaction diffusion equations, which incorporate the influence of an external field, min protein reactions, and diffusion of all species. Using the numerical method, we have found some changes in the dynamics of the oscillations of the min proteins from pole to pole when compared that of without the external field. The results show some interesting effects, which are qualitatively in good agreement with some experimental results.

q-bio.SC↗

arXiv2004

A one-dimensional Lattice Boltzmann method for modeling the dynamic pole-to-pole oscillations of Min proteins for determining the position of the midcell division plane

Determining the middle of the bacteria cell and the proper placement of the septum is essential to the division of the bacterial cell. In E. coli, this process depends on the proteins MinC, MinD, and MinE. Here, the Lattice Boltzmann method (LBM) is used to study the dynamics of the oscillations of the min proteins from pole to pole. This determines the midcell division plane at the cellular level. The LBM is applied to the set of the deterministic reaction diffusion equations proposed by Howard et. al. [1] to describe the dynamics of the Min proteins. The LBM results are in good agreement with those of Howard et al, and agree qualitatively with the experimental results. Our good results indicate that the LBM can be an alternative computational tool for simulating problems dealing with complex biological system which are described by the reaction-diffusion equations.

q-bio.QM↗