Mathematical model of substance active transport via cytoplasmic membrane of microbial cell along concentration gradient

Applied Biochemistry and Biotechnology - Considering the process of methane generation by methanogenic bacteria as an example, the model describes the distribution of methane concentration inside...     

Dynamic interaction of edge dislocations with point defects and prismatic dislocation loops at high-strain-rate deformation of crystals

The motion of an ensemble of edge dislocations at high-strain-rate deformation of a crystal with a high concentration of prismatic dislocation loops and point defects has been analyzed. It has been shown that, under certain conditions, the drag of an edge dislocation by prismatic dislocation loops has the character of dry friction, and the magnitude of the drag force of the dislocation is determined by the relationship between the concentration of prismatic dislocation loops and the density of mobile dislocations. An increase in the density of mobile dislocations leads to an enhancement of their collective interaction, thus facilitating the overcoming of prismatic dislocation loops by edge dislocations. The total drag force of an edge dislocation is a nonmonotonic function of the concentration of point defects, which, under certain conditions, has a minimum.     

Specific features of the dynamic behavior of a screw dislocation under excitation of transverse dislocation vibrations

The dynamic retardation of the motion of screw dislocations at point defects is investigated taking into account the excitation of transverse vibrations of dislocation elements both in the glide plane and in the plane normal to it. It is shown that the inclusion of the vibrations of the dislocation elements in the plane normal to the glide plane does not change the dependence of the retarding force on the glide rate and defect concentration but considerably increases the magnitude of this force (specifically in the case of the isotropic model, the retarding force increases by a factor of 2).     

Influence of hydrostatic compression on the sliding of a pair of edge dislocations in metals with a high impurity concentration

The dynamic drag of dislocations by point defects in hydrostatically compressed metals is theoretically investigated. Account is taken of the influence of a high pressure on dislocation-dislocation and dislocation-point defect interactions. It is shown that the pressure dependence of the force causing dynamic drag of dislocations is determined by competition between these interactions.     

Dynamic drag of dislocations in crystal with structural imperfections

A new mechanism of dynamic drag of dislocations is proposed and analyzed. A pair of dislocations is treated as a linear harmonic oscillator. The dissipation mechanism under investigation involves an irreversible conversion of the kinetic energy of moving dislocations into the vibrational energy of the dislocation oscillator. The proposed mechanism is used for calculating the drag force exerted by stationary trapped dislocations on a moving pair of dislocations and the drag of a solitary dislocation by dislocation dipoles. Radiative drag force acting on a moving pair of dislocations is also calculated.     

Collective overcoming of point defects by dislocations in the dynamic region

A mechanism of collective overcoming of point defects by dislocations during the over-barrier slip has been proposed. It has been shown that the interaction between dislocations promotes the overcoming of point defects at a high dislocation density.     

Molecular dynamics simulation of the aggregation of colloidal particles

The spontaneous time evolution of systems containing N colloidal particles (N = 12, 24, 100) in a spherical cell of volume V at a constant volume fraction φ=0.1 was studied by a molecular dynamics method in the NVT ensemble. The starting velocities of the particles are allocated according to the Maxwell distribution at T=273 K.

Pairwise interaction of the particles was specified by molecular, electrostatic and elastic forces. The changes in the potential energy of the systems were calculated during the establishment of dynamic equilibrium. Coagulation takes place at sufficiently high values of the Hamaker constant. The value of the coefficient of Brownian diffusion, which is calculated from the half-time of coagulation, is found to be close to the known value for aqueous dispersions. The inclusion of electrostatic forces prevents coagulation.

The results obtained are in agreement with those obtained using theories of aggregate formation. Some structural characteristics of aggregates and stable systems are discussed.     

Dynamic slowdown of edge dislocations by point defects in a hydrostatically compressed crystal

The effect a high hydrostatic pressure has on the dislocation vibration dispersion law and point-defect-induced drag force acting on interacting edge dislocations is studied. This effect is shown to be substantially different in different ranges of the dislocation velocity.     

The effect of Guinier–Preston zones on the dynamic yield stress of alloys under the shock-wave load

Technical Physics - The movement of an ensemble of edge dislocations under shock-wave action on an alloy that contains the Guinier–Preston zones has been theoretically studied. The analytical...