Two-dimensional homogeneous cubic systems: Classification and normal forms: IV

This article is the fourth in a series of works devoted to two-dimensional cubic homogeneous systems. It considers a case when a homogeneous polynomial vector in the right-hand part of the system has a quadratic common factor with complex zeros. A set of such systems is divided into classes of linear equivalence, wherein the simplest system is distinguished on the basis of properly introduced structural and normalization principles, being, thus, the third-order normal form. In fact, such a form is defined by a matrix of its right-hand part coefficients, which is called the canonical form (CF). Each CF has its own arrangement of nonzero elements, their specific normalization and canonical set of permissible values for the nonnormalized elements, which relates CF to a selected class of equivalence. In addition, each CF is characterized by: (1) conditions imposed on the coefficients of the initial system, (2) nonsingular linear substitutions that transform the right-hand part of the system under these conditions into a selected CF, and (3) obtained values of CF’s nonnormalized elements. Refs 9.     

Propagation of large-amplitude low-frequency vibrations in polymer melt flows

The propagation of low-frequency periodic pressure pulses along an isothermal stationary flow of various polymer melts in a flat channel of finite length has been experimentally and theoretically investigated. It is shown that as a result of the wave character of the process there is a phase shift between the pressure vibrations at various points along the length of the channel, while the amplitudes of the pressure vibrations decrease along the flow in accordance with a nonlinear law. Analysis of the problem leads to the establishment of a relation between the characteristics of the wave process, the properties of the medium, and the channel geometry.Moscow Institute of Chemical Machine Building. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 493–500, May–June, 1976.     

Reduction of Deuterium Level Supports Resistance of Neurons to Glucose Deprivation and Hypoxia: Study in Cultures of Neurons and on Animals

The effect of a reduced deuterium (D) content in the incubation medium on the survival of cultured neurons in vitro and under glucose deprivation was studied. In addition, we studied the effect of a decrease in the deuterium content in the rat brain on oxidative processes in the nervous tissue, its antioxidant protection, and training of rats in the T-shaped maze test under hypoxic conditions. For experiments with cultures of neurons, 7–8-day cultures of cerebellar neurons were used. Determination of the rate of neuronal death in cultures was carried out using propidium iodide. Acute hypoxia with hypercapnia was simulated in rats by placing them in sealed vessels with a capacity of 1 L. The effect on oxidative processes in brain tissues was assessed by changes in the level of free radical oxidation and malondialdehyde. The effect on the antioxidant system of the brain was assessed by the activity of catalase. The study in the T-maze was carried out in accordance with the generally accepted methodology, the skill of alternating right-sided and left-sided loops on positive reinforcement was developed. This work has shown that a decrease in the deuterium content in the incubation medium to a level of −357‰ has a neuroprotective effect, increasing the survival rate of cultured neurons under glucose deprivation. When exposed to hypoxia, a preliminary decrease in the deuterium content in the rat brain to −261‰ prevents the development of oxidative stress in their nervous tissue and preserves the learning ability of animals in the T-shaped maze test at the level of the control group. A similar protective effect during the modification of the ²H/¹H internal environment of the body by the consumption of DDW can potentially be used for the prevention of pathological conditions associated with the development of oxidative stress with damage to the central nervous system.     

Structural,chemical, and dynamic characteristics of ceramic membranes modified with self-organized supramolecular silicon oxide systems

The changes in structural characteristics, chemical composition, and gas permeability of the modified ceramic asymmetric tubular membranes were studied. The membranes were tested in permeability and selectivity of two gaseous mixtures (H/He and H/Ar). The structure of the modified coating was examined by X-ray powder diffraction and by transmission and scanning electron microscopies.