This study deals with phase transitions in magnetic systems when spin fluctuations and electronphonon interaction exchange enhancement occur. It is shown that in this context fluctuations play a substantial role and determine the character of the first-order phase transition that is close to a second-order transition.
Show AbstractA solution of the two-dimensional integro-differential equation describing diffraction of electromagnetic waves on metallic nanovibrators and on nanocrystals coated by a metallic film was obtained. Copper and gold nanoantenna characteristics were studied theoretically in the optical range. It was noted that the dependence of the scattered field on frequency is of a resonant character and the resonant wavelengths of nanovibrators are larger than those of an ideally conducting vibrator of the same size.
Show AbstractThe temporal and spectral characteristics of the terahertz response are measured for crystals of doped lithium niobate with an as-grown domain structure. It is shown that the crystals can be used for narrow-band generation and detection of terahertz waves in the processes of nonlinear-optical conversion of the laser radiation frequency. Frequency tuning in the range from 0.5 to 2.5 THz can be performed, due to both variations in the domain structure period and changes in the nonlinear-optical interaction geometry.
Show AbstractThe generation of the third harmonic of femtosecond laser radiation with a wavelength of 1.24 μm tightly focused into the bulk of fused silica was simulated numerically for the regime with light intensity of $3\cdot10^{13}$ W/cm$^2$, which is extreme for solid bodies. The efficiency of third harmonic generation (THG) was found to be restricted to 0.1% in the regime of plasma formation. This is determined by two competitive processes: a decrease of THG efficiency due to an increase of wave detuning and an increase of THG efficiency due to a growth of focusing asymmetry. In an isotropic medium, determination of the threshold of plasma formation by use of the third harmonic signal is shown to be a more sensitive method as compared with the standard scheme of nonlinear transmittance detection.
Show AbstractThe isotherms of water molecule absorption on hyperfine Langmuir films made based on liquid crystals are investigated. A sharp increase in the adsorption capacity of the films at temperatures of 75°C (for a film with a thickness of ten monolayers) and 102°C (for a film with a thickness of five monolayers) has been revealed. This behavior is explained by structural phase transitions that take place at these temperatures.
Show AbstractThe analytical equations for the current-phase relation (CPR) coefficients for Josephson junctions with a ferromagnetic interlayer in the model where the scattering from $s$ to $d$-band is considered to be the main type scattering of charge carrier in a ferromagnet are obtained. It is shown that the magnitude of the coefficients oscillates and decays with an increase of the interlayer thickness. Both the oscillation period and the decay length for the first and the second harmonics differ by two times. The temperature dependence of the critical current demonstrating 0-$\pi$ temperature transitions is obtained. The possibility of design a flux qubit based on such Josephson junctions is demonstrated.
Show AbstractVariations of the lattice constant and the value of elastic strain in 50 μm foil of Pd-5.3 at %-In-0.5 at %-Ru alloy in the course of its prolonged relaxation under normal conditions after electrolytic hydrogenation were analyzed using the X-ray diffraction technique. Nonmonotonic variations of the concentration of indium atoms were revealed in the subsurface layer of the foil.
Show AbstractIt is demonstrated that the crystalline structure of MgGeN$_2$ can be reduced to the superposition of “approximated” high-symmetry Bravais sublattices by shifting atoms in a unit cell within the range of 5% of the lattice constant. The superimposed Brillouin zones were plotted for crystal lattices and sublattices. The computational results are presented for the electronic structure of MgGeN$_2$ in terms of the theory of the density function. The influence of “hidden” symmetry in this crystal on zone spectra is described.
Show AbstractThe dielectric relaxation and conductivity of polyvinylcaprolactam (PVCL)-water systems of different compositions (with water contents of ∼ 1,5, and 24 wt %) were studied by means of dielectric spectroscopy ($10^{-1}$-$10^7$ Hz) at −100−50°C. It was found that the conductivity of samples with a low content of water upon cooling has an activation character, whereas a cooperative mechanism of conduction holds for the PVCL-water system with 24 wt % water, which switches to an activation character of interactions of water with polymer changes in the course of a glass transition.
Show AbstractIn the present work adsorption isotherms of water molecules, absorption and diffuse reflection spectra and reflected light polarization on hyperfine Langmuir liquid crystal films were investigated. The singularities reflection spectra were discovered by the temperature of the structural phase transition (~70ºC). Some reasonable assumptions about The phase transition nature were made
Show AbstractIn this work, the structure and chemistry of thin nm-thick carbon films deposited on a substrate using strong 13.5 nm EUV irradiation under a strong vacuum were studied. The film structure was studied by Raman spectroscopy in comparison with the Raman spectra of well-known carbon phases: diamond, single-wall nanotubes, nano- and micro-crystalline graphite and amorphous carbon. As well, FTIR spectroscopy was used to study possible IR-active chemical bonds, primarily, hydrogen bonds. It was shown that films deposited on a surface under EUV irradiation consists of amorphous $sp^2$-carbon. The mechanisms of deposition are discussed briefly. Knowledge about the structure and chemistry of such carbon films is very important for EUV lithography.
Show AbstractPolarized tryptophan fluorescence of human serum albumin (HSA) was analyzed to determine the parameters of rotational diffusion (rotational relaxation time, rotational diffusion coefficient, and the effective Einstein radius) of HSA molecules during denaturation under the action of sodium dodecyl sulfate (SDS). Two stages of HSA denaturation under the action of SDS were shown: (1) loosening of protein globules and (2) unfolding of the amino-acid chain of the protein. HSA denaturation under the action of SDS is a two-stage process at pH values lower than the pI of HAS but passes through stage 1 only at pH values higher than the pI.
Show AbstractThis study determined the contribution of Martian topography and the density jump at the Mohorovicic discontinuity ($M$) to the gravity in a quadratic approximation. It also resolved the problem of determining the possible depths of compensation for topography harmonics of various degrees and orders. It shows that all the topography compensation is within the depth range from 0 to 1400 km. Different topographic irregularities are most likely to be compensated at depths that correspond to the upper crust ($\bar d=4.5\pm3.7$ km), crust-mantle transition layer ($\bar d=78\pm24$ km), lithospheric boundary ($\bar d=200\pm34$ km), upper-middle mantle transition layer ($\bar d=400\pm70$ km), or middle-lower mantle transition layer ($\bar d=1120\pm180$ km). This paper presents the lateral distributions of compensation masses for these depths and the respective maps. According to calculations, stresses in the Martian crust and mantle may be as high as $10^8$ Pa. This paper shows that the topographic anomalies of the Tharsis volcanic plateau and the symmetric formation in the eastern hemisphere could have originated and be dynamically maintained by two plumes of melted mantle substance enriched with fluids; these plumes may have their origin at the boundary of the lower mantle.
Show AbstractObservations of a time series of solar activity indices are compared with new simultaneous observations of the flux variations of the photospheric and chromospheric emissions of 33 stars during the HK project that were conducted over the past 20 years. In addition to the known cyclic chromospheric emissions of stars in the 11-year time scale, which was discovered at the Mount Wilson Observatory and Stanford University, we found a recurrence that is similar to the quasi-biennial variations of solar radiation fluxes. The results of calculations of the of radiation flux variation periods of stars at the quasi-biennial scale are given.
Show AbstractThe method for extraction of a slowly varying signal (gravity variations) from an additive mixture of the useful signal and noise, with noise substantially exceeding the measured variations of specific gravity, is discussed. The principal problem is the exclusion of errors related to dynamical characteristics of gravimeters. An alternative to the well-known Kalman filter is proposed.
Show AbstractThis study is devoted to an analysis of the ionization and loss of electrons at early stages of discharge development in air at an altitude of 0–12 km. Ionization in an external electric field and background ionization, electron attachment and detachment from atomic and molecular oxygen, charge exchange, and negative ion conversion are considered. The dependence of the process rate constants on pressure is taken into account. It is demonstrated that the electric field at which effective air ionization begins decreases with increasing altitude.
Show AbstractThe extensive air shower (EAS) muon number spectrum is obtained with increased statistics using the central muon detector of the EAS MSU array, which records muons with energies above 10 GeV. The dependence of the mass composition of primary cosmic rays on the energy is considered. The conclusion is confirmed that for energies from ${3\cdot10^{15}}$ eV (the primary energy spectrum knee) up to $10^{17}$ eV a change in the composition associated with an increase in the proportion of heavy nuclei occurs; however, after the energy of $10^{17}$ eV, the proportion of heavy nuclei begins to decrease and the composition becomes lighter. A comparison with similar data from other experiments is conducted. The existence of an additional component of cosmic rays is confirmed; earlier an indication of its presence was derived from data on the EAS electron number spectrum.
Show AbstractThe statistical problem of the synthesis of a digital processing algorithm for the output signal of the Snail resonant gravitational antenna by analog prototype is considered. The discretization step in the ADC-DAC system is selected on the basis of the Kotelnikov theorem (a sampling theorem) for quasi-harmonic signals.
Show AbstractSpectral analysis is used to investigate periodicities from the data on cosmic rays in the stratosphere, in the neutron component, and in various parameters of solar activity and interplanetary medium for the period from 1965 to 2007 for individual solar cycles.
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