Experimental Visualization of Dispersion Characteristics of Backward Volume Spin Wave Modes

Basing on the measurement of spatial spectra (spectra of wavenumbers), the dispersion characteristics of the first three modes of backward volume spin wave, propagating along the direction of a constant uniform magnetic field in a tangentially magnetized ferrite film, were visualized firstly. The study was carried out by microwave probing of spin waves with subsequent use of spatial Fourier analysis of the complex wave amplitude for a series of frequencies. It was found that every m-th mode of the backward volume spins wave can be split into n satellite modes due to the existence of layers with similar magnetic parameters in ferrite film. It was found that satellites of the first mode of this wave are excited most effectively, while satellites of the third mode - least effectively, and the effectiveness of satellites excitation decreases as the number n increases. It is found that the theoretical dispersion dependencies of the first three modes of the wave coincide well with the experimental dispersion dependencies of the satellite mode that are excited most effectively.Comment: 14 pages, 5 figure

Imidazole-phosphate polymers : Acid-base properties, association with oligonucleotides and oligosilicates

Water-soluble imidazole-phosphate copolymers were obtained by copolymerization of 1-vinylimidazole with vinyl acetate with subsequent phosphorylation under the action of phosphoric acid. The introduction of phosphate units into the vinylimidazole chain unexpectedly increased the basic properties of the polymer, the buffer capacity at pH 5-7 and activity in coordination with DNA oligonucleotides, which is important in gene therapy and genetic engineering. The condensation of silicic acid in the presence of new polymers leads to the appearance of composite nanoparticles, which are a model of silicon transport vesicles in nature, as well as a new precursor of silicon materials. (C) 2021 Elsevier B.V. All rights reserved.Peer reviewe

Sporadic wind wave horse-shoe patterns

International audienceThe work considers three-dimensional crescent-shaped patterns often seen on water surface in natural basins and observed in wave tank experiments. The most common of these 'horse-shoe-like' patterns appear to be sporadic, i.e., emerging and disappearing spontaneously even under steady wind conditions. The paper suggests a qualitative model of these structures aimed at explaining their sporadic nature, physical mechanisms of their selection and their specific asymmetric form. First, the phenomenon of sporadic horse-shoe patterns is studied numerically using the novel algorithm of water waves simulation recently developed by the authors (Annenkov and Shrira, 1999). The simulations show that a steep gravity wave embedded into widespectrum primordial noise and subjected to small nonconservative effects typically follows the simple evolution scenario: most of the time the system can be considered as consisting of a basic wave and a single pair of oblique satellites, although the choice of this pair tends to be different at different instants. Despite the effective low-dimensionality of the multimodal system dynamics at relatively sho ' rt time spans, the role of small satellites is important: in particular, they enlarge the maxima of the developed satellites. The presence of Benjamin-Feir satellites appears to be of no qualitative importance at the timescales under consideration. The selection mechanism has been linked to the quartic resonant interactions among the oblique satellites lying in the domain of five-wave (McLean's class II) instability of the basic wave: the satellites tend to push each other out of the resonance zone due to the frequency shifts caused by the quartic interactions. Since the instability domain is narrow (of order of cube of the basic wave steepness), eventually in a generic situation only a single pair survives and attains considerable amplitude. The specific front asymmetry is found to result from the interplay of quartic and quintet interactions and non-conservative effects: the growing and grown satellites have a specific value of phase with respect to the basic wave that corresponds to downwind orientation of the convex sides of wave fronts. As soon as the phase relation is violated, the satellite's amplitude quickly decreases down to the noise level