Strain wave evolution equation for nonlinear propagation in materials with mesoscopic mechanical elements

Nonlinear wave propagation in materials, where distribution function of mesoscopic mechanical elements has very different scales of variation along and normally to diagonal of Preisach-Mayergoyz space, is analyzed. An evolution equation for strain wave, which takes into account localization of element distribution near the diagonal and its slow variation along the diagonal, is proposed. The evolution equation provides opportunity to model propagation of elastic waves with strain amplitudes comparable to and even higher than characteristic scale of element localization near Preisach-Mayergoyz space diagonal. Analytical solutions of evolution equation predict nonmonotonous dependence of wave absorption on its amplitude in a particular regime. The regime of self-induced absorption for small-amplitude nonlinear waves is followed by the regime of self-induced transparency for high-amplitude waves. The developed theory might be useful in seismology, in high-pressure nonlinear acoustics, and in nonlinear acoustic diagnostics of damaged and fatigued materials.     

Model for the emission of quasi-thermal atoms during sputtering of metals in the nonlinear collision cascade regime

The ion sputtering of metals and frozen inert gases in the nonlinear collision cascade regime, where the density of the energy released in the bulk of the thermal peak exceeds the critical medium temperature, initiates the emission of quasi-thermal atoms. The energy spectrum of such atoms is substantially shifted toward low energies and is not described by a Maxwellian distribution. A simple emission model is proposed on the assumption of collisional motion of sputtered atoms in their flight from a target, and this model is used to derive an analytical formula for the calculation of the energy spectra of quasi-thermal atoms. A comparison of the calculated energy spectra of indium, krypton, and xenon atoms and the spectra measured during ion sputtering of indium and frozen inert gases in the nonlinear collision cascade regime shows their agreement at reasonable values of fitting parameters.     

Photoelectric Properties of Composite Films Based on Organometallic Perovskite CH3NH3PbBr3 Modified with Mixed Cellulose Ester

Physics of the Solid State - It is shown that the introduction of cellulose ester mixed with acetotrimethyl acetate into films of organometallic perovskite CH3NH3PbBr3 significantly increases their...     

Interaction of a shock front with a wavy contact discontinuity

The excitation of Richtmayer-Meshkov instability fora ₀^–1>1 (a ₀ are the amplitude and wavelength of the initial contact discontinuity) is experimentally and numerically investigated. The effect of the curvature of the initial contact discontinuity on the development of the instability is determined.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.5, pp. 168–174, September–October, 1992.     

Memory effects in field-effect transistor structures based on composite films of polyepoxypropylcarbazole with gold nanoparticles

The memory effects in field-effect transistor structures with an active layer based on composite films of a semiconductor polymer, i.e., the carbazole derivative and gold nanoparticles, manifesting themselves in the hysteresis of the transient characteristics of the transistor have been studied. It has been shown that the observed effects are associated with the features of transport in the polymer-gold nanoparticle structure, where the gold particles serve as a medium of charge carrier collection (accumulation). The data writeerase mechanism based on conductivity modulation of the working channel of the field-effect transistor by the gate voltage have been discussed.     

Iron(II) and Cobalt(II) Complexes with 2,6-Bis(1,4-Diphenyl-5-Hydroxy-1H-Pyrazol-3-yl)pyridine: Synthesis,Structures, and Spin States

Russian Journal of Coordination Chemistry - The reactions of 2,6-bis(1,4-diphenyl-5-hydroxy-1H-pyrazol-3-yl)pyridine (L), which is the first representative of a series of...     

Spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene and their resistance to protolytic dissociation and photochemical destruction

The spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene, along with the kinetics of their protolytic dissociation and photochemical degradation in organic solvents of different natures, are studied by means of electronic absorption and fluorescence spectroscopy. It is found that protic solvents have the strongest effect on absorption spectra, while electron donors affect fluorescence spectra due to differences in the mechanisms of solvation for the ground and excited states of molecules. It is shown that the reaction product of the protolytic dissociation of complexes in benzene solutions of acetic acid is a protonated form of ligand. The observable and genuine rate constants of dissociation reactions are determined and activation parameters are calculated. A kinetic model of the process is proposed, and the regularities of the effect the nature of ligand has on the kinetics of dissociation are established. The photochemical degradation of compounds proceeds on monopyrrole products, the photolysis rate falls as the a degree of alkylation increases, and the nature of the substituent in the β-position of the ligand’s pyrrole ring has a greater effect on the stability of a compound.     

Observed evidence of microwave-background formation by thermal radiation of metagalaxy stars

In the opinion of the majority of scientists, to disprove the validity of the Big Bang cosmology, it suffices to demonstrate another convincing mechanism of microwave-background formation, which leads to the conclusion that the background is not a strictly black-body one and/or is not associated with the matter in early epoch [1].Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 7, pp. 817–843, July, 1996.