The phase-field model of Echebarria, Folch, Karma, and Plapp [Phys. Rev. E 70, 061604 (2004)] is extended to the case of rapid solidification in which local nonequilibrium phenomena occur in the bulk phases and within the diffuse solid-liquid interface. Such an extension leads to the fully hyperbolic system of equations given by the atomic diffusion equation and the phase-field equation of motion. This model is applied to the problem of solute trapping, which is accompanied by the entrapment of solute atoms beyond chemical equilibrium by a rapidly moving interface. The model predicts the beginning of complete solute trapping and diffusionless solidification at a finite solidification velocity equal to the diffusion speed in bulk liquid.

The phase-field model of Wheeler, Boettinger and McFadden is extended to the case of fast solidification in which local non-equilibrium phenomena occur in the bulk phases and within the diffuse solid – liquid interface. Such an extension leads to the characteristic diffusion speeds of atoms (both within the diffuse interface and inside the bulk phases) and to the speed of the interface propagation. As a result, the model is described by a system of hyperbolic equations for the atomic diffusion transport as well as for the phase-field. This model is applied to the problem of solute trapping, which is accompanied by the entrapment of solute atoms beyond chemical equilibrium by a rapidly moving interface. The model predicts the beginning of complete solute trapping and diffusionless solidification at a finite solidification velocity.

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Objective of research: Development of methods for the determination of fenbendazole and its metabolites in milk by liquid chromatography coupled with tandem mass spectrometry. Materials and methods: Fenbendazole was administered orally to five cows. Samples of milk were taken on 1, 3, 5 and 10 days of drug application. The research method includes a description of reagents, plates and equipment; mass-spectrometric conditions for analysis of fenbendazole and its metabolites; preparation of the equipment to operation; preparation of eluent solution; preparation of the chromatograph to analysis; determination of chromatographic parameters of standard drug samples; preparation of milk samples to analysis; establishment of parameters of extracts’ chromatography; procedure of calibration of fenbendazole and its metabolites in eluent. Results and discussion: When studying the pharmacokinetics of fenbendazole and its metabolites (sulfone and sulfoxide) in milk, it was found that the maximal concentrations were determined 24 h after drug administration and were 22,6 ng/ml for fenbendazole sulfone, 34,0 ng/ml for fenbendazole sulfoxide and 19,7 ng/ml for fenbendazole. 10 days after treatment, the concentrations of fenbendazole and its metabolites in milk did not exceed permitted values.

This paper presents the methodology for determination of the parameters of interaction between a rotary-screw vehicle and ice surface. The key parameter is the value of ice cutting force by means of a screw blade. The methodology allowed to obtain results, showing that the value of the cutting force depends on shape of the helical blade. Developed model of the cutting force allowed to conclude that that the width of the cut exerts the greatest influence on the cutting force, but depth and speed of the cutting have the less influence. Analysis of the study results provides the opportunity to find rational geometric parameters of the helical blade. The methodology can be applied for rotary-screw all-terrain vehicles designing.