Short optical solitons in fibers

The dynamics of short (of the order of a few wave periods) intense optical pulses and interaction of short optical solitons in fibers are considered within the framework of the third-order nonlinear Schrodinger equation. It is shown that an initial pulse tends to one or a few short solitons plus a linear quasiperiodic wave when the third-order linear dispersion and nonlinear dispersion have parameters of the same sign. The number and parameters of the solitons depend on the magnitudes of initial pulse parameters. Interaction of short optical solitons having different amplitudes is accompanied by radiation of part of the wave field from the area of interaction, by an increase of the soliton with larger amplitude, and a decrease of the soliton with a smaller one. (c) 2000 American Institute of Physics.     

Radio frequencies in EPR: Conventional and advanced use

This mini-review focuses on various aspects of the application of radio frequency (rf) irradiation in electron paramagnetic resonance (EPR). The development of the electron-nuclear double resonance (ENDOR) technique is briefly described, and we highlight the use of circularly polarized rf fields and pulse ENDOR methodology in one- and two-dimensional experiments. The capability of pulse ENDOR at Q-band is illustrated with interesting experimental examples. Electron spin echo envelope modulation effects induced by an rf field in liquid samples demonstrate another role which rf fields can play. Technical achievements in the design of ENDOR resonators are illustrated by the example of a bridged loop-gap resonator. Finally, the influence of longitudinal rf fields on the dynamics of EPR transitions is explained using a dressed spin resonance treatment.     

The kinetics of self-heating in the reaction between aluminum nanopowder and liquid water

Factors that influenced self-heating in the interaction of aluminum nanopowder produced by electrical explosion with liquid water were studied. The effects of suspension heating, medium pH (over the range 1.0–12.0), admixtures of Cu²⁺, Ni²⁺,and Ag⁺ metal cations (0.0001–0.1 mol/l), and passivating coating (B, F, and Ni) were investigated.     

Molecular design of light-sensitive nanodimensional systems

A universal approach to the molecular design of light-sensitive nanodimensional systems with specific characteristics was developed on the basis of unsaturated and macrocyclic compounds. It was possible to construct various nanodimensional systems within the scope of a single class of compound using a limited number of components. The use of photostructural transformations to control complex formation and mechanical movements in molecular devices and machines is discussed. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 1–7, January-February, 2009.     

Intensification of chemical reactions in aqueous solutions upon irradiation with an accelerated electron beam

The results from investigating the effect of radiation exposure on the rate of chemical reactions in acid aqueous solutions of Fe²⁺, which are widely used in hydrometallurgy of nonferrous metals to extract the target components into solution from ores, are presented. The potential of the applied method is demonstrated.     

Short Envelope Solitons in Nonconservative Media

We consider the dynamics of short envelope solitons within the framework of the third-order nonlinear Schrödinger equation with allowance for both linear losses and pumping by an external wave field. An equation for the soliton amplitude is derived. The stationary value of the soliton amplitude is found.     

Electron microscopy of steel 08G2S wire after electrostimulated drawing

Diffraction electron microscopy has been applied to the microstructure evolution in 08G2S steel after ordinary and electrostimulated drawing; the current pulses affect some fine-structure characteristics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 31–35, December, 1990.We are indebted to V. E. Panin for stimulating interest in this topic.     

Kinetic features of the carbon erosion of a bulk NiCr alloy during the catalytic decomposition of 1,2-dichloroethane

Kinetic features for the carbon erosion (CE) of bulk NiCr alloy (NiCrA, nichrome wire 0.1 mm in diameter) were studied at 450–750°C under conditions of the catalytic decomposition of 1,2-dichloroethane vapor in a reductive atmosphere (H₂). It was found that the CE process takes place more efficiently in the temperature range from 550 to 720°C, leading to the disintegration of the bulk alloy with the formation of a fibrous carbon product. The apparent activation energy of the process was estimated to be 16.8 ± 0.9 kJ/mol. The realization of CE is hampered outside the optimal temperature range because of chlorination (T < 500°C) or blocking of the alloy’s surface by carbonaceous deposits (T > 720°C). The kinetics of the process is characterized by the existence of an induction period, whose duration decreases with an increasing temperature (from 40 min at 550°C to 6 min at 710°C). According to scanning and transmission electron microscopy data, the submicron metallic particles (0.2–0.4 μm) catalyzing the growth of carbon fibers with disordered structure result from the disintegration of the NiCr alloy.     

Surface relief and structure of electroexplosive composite surface layers of the molybdenum-copper system

The surface topography and structure of copper layers exposed to multiphase plasma jets of products of electrical explosion of molybdenum and copper foils are studied using profilometry and scanning electron and light microscopy. Such treatment allows deposition of either layered coatings or alloyed composite layers. It is found that the surface layer roughness parameter is R _a = 3.2−4.0 μm. The thickness of some copper and molybdenum layers of coatings is 15–20 μm. Electroexplosive alloying produces layers 25 μm thick. Sizes of copper inclusions in the molybdenum matrix near the surface of such layers vary from 30 nm to 1–2 μm.