Laboratory studies of spectral features of stimulated electromagnetic emission during the ionospheric heating experiments

We present the results of laboratory studies of the formation of a number of spectral components of stimulated electromagnetic emission, which are related to the excitation of small-scale irregularities in the heated ionosphere. In the laboratory experiment, the small-scale irregularity was formed as a result of thermal self-channeling of short-wavelength quasielectrostatic oscillations in a magnetoplasma. Using the method of probing waves, it is experimentally shown that the trapping and waveguide propagation in a small-scale plasma irregularity are exclusively due to Langmuir waves, whereas the upper-hybrid waves with anomalous dispersion are not trapped into the irregularity. It is found that satellites shifted by about 1–2 MHz from the carrier frequency (700 MHz under the experimental conditions) are formed in the Langmuir wave spectrum during the thermal self-channeling. Two mechanisms of generation of spectral satellites have been detected. The first (dynamic) mechanism is observed during the formation of a small-scale irregularity with rapidly increasing longitudinal size. In this case, one low-frequency satellite is excited in the trapped-wave spectrum. The mechanism of the formation of this satellite is apparently related to the Doppler shift of the frequency of the Langmuir waves trapped inside the irregularity. The second (stationary) mechanism is observed in the case of a developed irregularity where its shape is close to cylindrical. In this regime, the trapped-wave spectrum has two symmetric spectral satellites, namely, high- and low-frequency ones. It may be hypothesized that the generation of these satellites is due to scattering of trapped Langmuir waves from drift oscillations of the irregularity.     

Effect of polymer nature on the structure and properties of gel composites with incorporated bentonite particles

Composite gels based on polyacrylamide and poly(N-isopropyl acrylamide) with incorporated sodium bentonite particles are synthesized. It is shown that the presence of hydrophobic isopropyl groups in a polymer molecule promotes the subsequent formation of highly ordered aggregates of clay and cetylpyridinium chloride in a gel composite. An increase in temperature results in the collapse of composite gels based on poly(N-isopropyl acrylamide); however, no marked changes in the structure of lamellar aggregates of clay and surfactant are observed. It is revealed that the gel can stabilize lamellar structures formed in organoclay suspension prior to the incorporation into swollen polymer network.     

Laboratory study of nonlinear trapping of magnetized Langmuir waves inside a density depletion

The formation of a small-scale plasma density depletion region extended along the ambient magnetic field and caused by the nonlinear interaction of the upper-hybrid plasma waves with a magnetoplasma has been observed under laboratory conditions modeling the ionospheric heating experiments. Plasma waves are trapped inside the depletion due to their specific dispersion properties. The threshold of the nonlinear wave trapping significantly increases in the vicinity of the harmonics of the electron gyrofrequency.     

Specific features of the polyelectrolyte behavior of weakly charged cryogels of polyacrylamide and poly(N-isopropylacrylamide)

Specific features of the polyelectrolyte behavior of weakly charged common gels and cryogels of copolymers of polyacrylamide and poly(N-isopropylacrylamide) with sodium acrylamido-2-methyl-1-propyl sulfonate are investigated. The cryogels are synthesized in frozen solutions at ?15°C. It is shown that the polyelectrolyte swelling is significantly weaker in the case of cryogels than that in the case of gels synthesized in solutions. For thermosensitive gels with isopropylacrylamide groups, collapse occurs during heating. Charging of a common gel leads to a noticeable (18°C) increase in the transition temperature. For a cryogel, this growth is 3°C. During the interaction with cetylpyridinium chloride, the gel contraction is much more pronounced for common weakly charged gels. At the same time, walls of pores of a collapsed cryogel contain a smaller amount of the solvent. Isotherms of the adsorption of a cationic surfactant by anionic common gels and cryogels differ insignificantly. Model gels synthesized in concentrated acrylamide solutions exhibit very weak polyelectrolyte swelling, similar to that of cryogels. The behavior of cryogels is explained by a very high local concentration of crosslinks due to a strong entanglement of polymer chains.     

Cardinality of the Set of Delta–Closed Classes of Functions of Multi–Valued Logic

A closure under composition operation and weak version of inversion operation is considered on the set of functions of k–valued logic. The cardinality of the set of all such closed classes is calculated.     

Laboratory modeling of the interaction of electron beams with a magnetoplasma

We present the results of laboratory experiments in which the mechanisms of interaction of electron beams with whistler waves in a magnetoplasma are studied. Different mechanisms of whistler generation during the injection of a modulated electron beam in the plasma are studied, and the mechanism of conversion of the beam kinetic energy to radiation is demonstrated. The processes of whistler wave generation by the modulated beam at the ˇ Cerenkov and Doppler resonances are analyzed in detail. The excitation of whistler waves by means of a nonresonant mechanism of the transition radiation is studied.     

Emission of soft bremsstrahlungγ-rays in p + p → p + p +γ and π−+p → π0+n +γ reactions

Low's theorem [1] on the emission of soft -rays is applied to a study of p + p p+p+ and ^– + p ⁰+ n + reactions. The first two terms in the expansion of the differential cross sections for these processes in powers of the photon energy are obtained (for proton scattering in the ultrarelativistic limit).In conclusion, we wish to express our gratitude to S. M. Bilen'kii and R. M. Ryndin for directing this work.     

Discharges and mechanoelectrical phenomena in charged glasses

Conclusions In high-resistance solid dielectrics (with resistances of 10¹² · cm or higher, when they are irradiated with electron beams, spontaneous electric discharges are observed while the irradiation is occurring. The discharges occur at defects in the surface and develop in the layer within which the charged particles are distributed.When the charged particles are distributed in the surface or near-surface layer of the dielectric, the discharge may be initiated close to the charged surface by a grounded metal needle, even some time after the irradiation. After long storage and self-dis charge of the surface layer of the irradiated dielectric or compensation of the surface charge, discharge of the charge stored in the depth of the dielectric can occur by scratching the surface or pricking it with a needle. When the charge lies deep inside the dielectric, a brush discharge occurs when a strong shock is applied to the surface of the dielectric using a grounded needle.In all the above cases initiation of an electric discharge in the solid dielectric occurred by mechanoelectrical phenomena of direct conversion of mechanical energy into electrical energy with a high field strength. These phenomena occur in solid dielectrics with a defect structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 40–46, February, 1977.     

The Effect of Ion Irradiation on Nanocrystallization and Surface Relief of a Ribbon from Fe72.5Cu1Nb2Mo1.5Si14B9 Alloy

Russian Physics Journal - Using the methods of X-ray diffraction and atomic force microscopy, the process of crystallization of an amorphous Fe72.5Cu1Nb2Mo1.5Si14B9 alloy irradiated with...     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.