Volume 64, Nº 1 (2019)

Dispersion properties of eigenwaves of an anisotropic cylindrical solid-state waveguide without frequency dispersion in permittivity tensor components have been analyzed theoretically. The classification of waves has been performed. E type bulk–surface eigenwaves with negative group velocities have been found. The conditions for their existence have been determined. The existence in the waveguide of E-type surface eigenwaves and pseudo-surface eigenwaves of E- and H-types has been shown.

The technique and results of a mass spectrometric study on the yield of positive ions formed upon ionization of xylitol molecules by electron impact are discussed. The mass spectra of xylitol are studied in the range of mass numbers of 10–160 Da and in the range of bombarding electrons energies of 5–80 eV. Based on the analysis of the measured mass spectra, a scheme of xylitol fragmentation is proposed, which contains the most probable channels of formation of ion-fragments upon electron impact, when the energy of the incident electrons significantly exceeds the ionization potential of the molecule. The appearance energies of ionized fragments of xylitol are determined for the first time from the energy dependences of the effective cross-section formation of the ions upon electron impact. The dynamics of ionized fragment formation is studied in the temperature range of the initial substance evaporation of 340–410 K. The behavior of the temperature dependence indicates that the formation processes of water and oxonium cations compete with each other.

The maximum intensity of electromagnetic microwave radiation of ball lightning has been determined in regards to order of magnitude based on the properties of ball lightning taken from the descriptions of its existence in the natural environment. The movement of charged particles along curvilinear paths inside ball lightning can be considered as a physical mechanism of the generation of microwave radiation.

Superintensive bubble boiling (SBB) is implemented in water in the absence of degassing at the end surface of a laser fiber using 100-ns laser pulses. A thulium fiber laser with a radiation wavelength of 1.94 μm and moderate power is used as a radiation source. The generation of bubble microjets in the vicinity of the end surface of the laser fiber is studied with the aid of high-speed photography and acoustic methods. After a threshold transition to the SBB regime, the energy of acoustic emission is predominantly concentrated in an acoustic interval of 10–30 kHz. The acoustic signal is generated due to thermal cavitation. Record-high thermal fluxes of up to 0.16 MW/cm² are reached in the SBB regime. Parameters of the resulting convective fluxes, microbubbles, and broadband acoustic oscillations are determined.

The interaction of a plane shock wave (M = 5) with an ionized plasma region formed before the arrival of a shock wave by a low-current glow gas discharge is considered experimentally and numerically. In the experiment, schlieren images of a moving shock-wave structure resulting from the interaction and consisting of two discontinuities, convex in the direction of motion of the initial wave, are obtained. The propagation of a shock wave over the region of energetic impact is simulated on the basis of the two-dimensional Riemann problem of decay of an arbitrary discontinuity with allowance for the influence of horizontal walls. The systems of Euler and Navier–Stokes equations are solved numerically. The non-equilibrium of the processes in the gas-discharge region was simulated by an effective adiabatic index γ. Based on the calculations performed for equilibrium air (γ = 1.4) and for an ionized nonequilibrium gas medium (γ = 1.2), it is shown that the experimentally observed discontinuities can be interpreted as elements of the solution of the two-dimensional problem of decay of a discontinuity: a shock wave followed by a contact discontinuity. It is shown that a variation in γ affects the shape of the fronts and velocities of the discontinuities obtained. Good agreement is obtained between the experimental and calculated images of density and velocities of the discontinuities at a residual gas temperature in the gas discharge region of 373 K.

Self-rotation (rotation about the center of mass) of dust particles in a magnetic field has been investigated. The angular velocity of self-rotation in a dust trap produced by an rf discharge has been measured for the first time. It has been discovered that the angular velocity is independent of magnetic induction up to 700 G in spite of the action of ion drag. In addition, the dependence of self-rotation velocity on gas pressure in the discharge when the particles are in the dust trap and on power deposited into the discharge has been measured for the first time. Experimental data correlate well with the developed model of dust particle self-rotation, which appears to maintain the stationary charge of the dust particle.

Microwave discharges initiated by an electromagnetic (EM) vibrator and ignited on the inner surface of a dielectric tube in a quasi-optical EM beam are experimentally studied. A threshold level of the microwave field that separates domains of subcritical and deeply subcritical microwave discharges is determined in experiments. Experiments show that streamer channels of the subcritical discharge propagate from the initiator along the propagation direction of the EM wave and in the opposite direction under certain conditions. Variations in the power of the microwave beam can be used to change length of the plasma region of the subcritical discharge along the wave vector of the microwave beam and control the level of the EM energy absorbed in the plasma regions of the deeply subcritical microwave discharge.

Possibilities of magnetic pseudoresonance (a non-resonance peak of magnetic susceptibility) were studied and compared with the ferromagnetic resonance (FMR) in measuring the parameters of thin ferromagnetic films with in-plane uniaxial magnetic anisotropy. The measurements were conducted with two characteristic samples of ferromagnetic films showing this effect. A Q-meter operating at a frequency near 300 MHz (for pseudoresonance) and a standard X-band magnetic resonance spectrometer (for FMR) were used. The Q-meter working at 300 MHz was shown to detect reliably the magnetic pseudoresonance in both epitaxial and polycrystalline films. It was found that the accuracy of determination of the magnetic anisotropy field and orientation of the easy magnetization axis provided by the pseudoresonance method is as good as with FMR, and in some cases the pseudoresonance method gives additional information.

A self-consistent thermodynamic model of thorium dioxide and its dilute alloy Ce_0.05Th_0.95O₂, which are of great importance for atomic power engineering, has been constructed based on generalized Debye and Einstein models. In terms of this model, the temperature dependences of the bulk modulus, density, and heat capacity of the systems have been obtained. The anharmonicity of the acoustical and optical modes of the crystal lattice and its change in passing from ThO₂ to Ce_0.05Th_0.95O₂ has been discussed.

We have studied the effect of the ratio between concentrations of zirconium dioxide (stabilized by CaO) and corundum on phase composition and mechanical properties of nanostructured CaO–ZrO₂–Al₂O₃ ceramic composites. The CaO–ZrO₂–Al₂O₃ composites sintered at temperatures typical of ZrO₂ are found to be characterized by the optimal microhardness/fracture toughness ratio at corundum content \({{C}_{{{\text{A}}{{{\text{l}}}_{2}}{{{\text{O}}}_{3}}}}}\) = 5%. These composites have a high flexural strength; their porosity, coefficient of friction, and wear are typical of those for CaO–ZrO₂ ceramics.

The shock-wave properties of ED-10 epoxy resin have been studied using VISAR and PDV multiple-channel laser interferometers. The Hugoniot of epoxy resin and pressure dependence of sound speed has been obtained and it has been shown that the structure of a shock-wave front corresponds to the model of a Maxwell viscous-elastic body with a typical relaxation time of tangential stresses of 0.3 μs. The spall strength has been measured and its dependence on the strain rate in a sample upon pulse tension has been determined.

The electromagnetic field of a harmonic oscillator moving at a constant velocity has been analyzed. The expression for calculating the Doppler frequency shift at relativistic velocities of its motion is derived using the classical electromagnetic theory. It is shown that the transverse Doppler effect is a special case and also differs from zero in the wave theory. With an increasing velocity of the radiation source, the “red” frequency shift in an electromagnetic wave prevails over the “blue” shift more strongly. The noncontradictory nature of the proposed model relative to the well-known experimental data has been demonstrated.

Novel field emitters made of contacting hafnium and platinum layers have been studied. Calculations aimed at optimizing the characteristics of the multilayer emitters have been conducted. Field emission currents up to 2.0–2.5 mA at a (tentative) current density of up to 200 A/cm² have been achieved. It has been shown that the field emission current can be significantly increased by summing current from several multilayer systems.

The physicochemical properties and structure of the bone matrix are studied in a case of simulated tuberculous osteitis without treatment and after a full course of specific antibacterial therapy. Using X-ray diffraction, infrared spectroscopy, thermal analysis, and scanning electron microscopy, we revealed that tuberculous osteitis causes fine disintegration of the bone matrix due to an increase in nonstoichiometric hydroxyapatite, formation of amorphous calcium phosphates, and a decrease of the organic phase, which is accompanied by embrittlement of the bone matrix. Excessive growth of carbonate-hydroxyapatite crystals of a mixed AB substitution type leads to excessive osteogenesis, accompanied by the uncontrolled growth of bone trabeculae. The presence of “liming” regions in the crystal lattice of hydroxyapatite increases the “binding” properties of the bone matrix in which mycobacteria are immobilized and removed in the composition of detritus.

Application of thin metal absorbers allows one to significantly increase the absorption coefficient and sensitivity of matrix THz microbolometric detectors. It is shown that absorbers characterized by frequency dispersion of conductivity, in contrast to conventional nondispersive absorbers, can provide almost total IR absorption retaining high sensitivity in the THz range.