We report on a study of the density response in doped Weyl semimetals or Weyl metals in the presence of an external magnetic field. We show that the applied field leads to a contribution to the density response, which is topological in nature and is closely related to the phenomenon of chiral anomaly. This contribution manifests in a nonanalytic nonclassical correction to the electronic compressibility and the plasmon frequency, proportional to the magnitude of the magnetic field. Such a nonanalytic correction to the electronic compressibility is a smoking-gun feature of Weyl metals, which clearly distinguishes them from ordinary ferromagnetic metals.

The paper is devoted to studying the motion dynamics of stem and ear, as well as particular wheat grains. The purpose of this consideration is to establish parameters of the effect on the plant as a whole, and in particular on the ear, for the efficient extraction of grains from the ear. For this, a mathematical model of the interaction between the elements of the stem-ear-grain system and the conditions for the separation of grain from the ear is built. In a first approximation, a simple stem model consisting of absolutely rigid bodies interconnected by elastic bonds is taken as such a model. Stems with a given moment of inertia act as such bodies, and spiral springs act as elastic bonds.

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The work is devoted to the study of the dynamics of the grain mass in a stripping field installation and a stationary installation for separating grain. At the first stage, a model of the air mass movement in the installation under consideration is constructed and, on the basis of a mathematical model that takes into account the turbulence of the air mass movement, using the finite volume method in the ANSYS package, the velocity and pressure field is calculated. The influence of the technological parameters of the installations on these fields is studied: the diameters and rotation speed of the stripping drum and the additional drum-fan, the shape of the surface of the upper deck of the installation chamber. The calculations performed allow us to choose rational geometric and kinematic parameters at which no stagnant zones arise in the chamber.

This article examines the static and dynamic deformation of the stem of an ear of wheat and of the individual grain. The purpose of the article is to determine the factors of influence on the ear of wheat to isolate the grain. Two stages of grain ripening are considered: in the early stage, the grain is attached to the spike by the stem; in the second, there is no stem, and the grain is attached to the ear by the scales. The ear fluctuations are considered within the Euler–Bernoulli bar theory. The developed model divides the study of the dynamics of the stem of an ear and the dynamics of the grain into two stages. The first stage studies the dynamics of the plant as a whole, while the second stage studies the dynamics of an individual grain in a moving system associated with the ear in bending and vertical fluctuation forms. The model of the ear and the grain fluctuation uses the mechanical characteristics of elastic bonds and elastic bodies, which are determined by spring stiffness, elastic moduli, etc. The results show that in the vertical forms of grain fluctuation, the frequency of fluctuation is much higher than in the bending ones. This article presents the natural fluctuation frequencies of grain at full ripeness and in the early phases of maturation, at which point it is released from the ear.