The condensed H$_2$O systems at the pressure above 2 GPa are very different from common water. Since they may exist in the deep of some celestial bodies, the research on these H$_2$O systems are essential to the further discussion of the physical states, elements' distribution, geological evolutions and even the origins of these celestial bodies (including our earth). In addition, as the condensed H$_2$O system is one of the main detonation products, the research on it is also significant to the development of the higher performance explosives. As a result, the condensed H$_2$O systems have been extensively studied by several theoretical and experimental methods in recent decades. Many achievements about the systems have been obtained in the last decades, but there are still some open questions. A brief review of the achievements of the structural and physical properties of the condensed H$_2$O systems up to 2 GPa is included in this paper, as well as some open questions about them are also presented herein.
Show AbstractAbstract—The dependence of the properties of low-lying states of Mo isotopes on the mass number $A = 83-117$ is studied based on the collective and shell models of atomic nuclei. The variation of the nuclear shape with an increasing number of neutrons influences strongly the properties of excited states of Mo isotopes. Decay channels of isovector giant dipole resonance with emission of protons and neutrons are studied in the framework of the combined model. The basic mechanisms of the production of stable Mo isotopes in astrophysical nuclear reactions are described.
Show AbstractIn nano scale, thermodynamic properties of gases show difference from those in macro scales. One of the reasons of this difference is the quantum size effects (QSE), which become significant when compared with the thermal de Broglie wavelength of particles to the characteristic length of the system. In this study, thermodynamic behavior of a photon gas confined in a nanoscale domain is examined in terms of QSE. It is obtained that due to quantum size effects the global thermodynamic properties of a photon gas confined in a nano scale domain are different than those in macro scale. The matter of QSE on thermodynamics of substances at micro/nano scale is relatively a new research area and the new findings might lead to significant new applications.
Show AbstractA self-consistent model for the electronic component of a thin current sheet (TCS) of the Earth’s magnetosphere based on the concept of the tension of lines of force is proposed and studied analytically and numerically. It has been shown that the model has a certain range of applicability, beyond which the results may be incorrect; within the range of correctness the model allows for a quite significant increase in the rate of convergence of the iterative algorithm for solving the total self-consistent model of the TCS, which also includes the Boltzmann equations for the ionic component.
Show AbstractWe developed a simple method for the calculation of the director field distribution in the droplets of nematic liquid crystals (LCs) of any shape, allowing for the interaction of LCs with the droplet surface, as well as the influence of constant electric field. In contrast to different approaches, the approach that is developed in the present paper does not require any simplifying suppositions about the structure of the LC director field. The elastic-continuum theory is used, complemented with the possibility of consideration of point and linear defects. Calculations are performed using the Monte Carlo method on a simple grid. The triangulation technique is used to take the boundary conditions of droplets of a complex shape into account. The developed approach can be used for investigation of the properties of polymer-dispersed liquid crystals (PDLCs). The topological phase transitions in the nematic LC 4-cyano-4′-pentyl-biphenyl (5CB) in spherical and ellipsoidal droplets are investigated in this paper.
Show AbstractThe one loop $SU(2)$ effective potential of a constant chromomagnetic field and thin vortex has been obtained using the background field method in the scope of the Yang–Mills theory. The possible relationship between a Savvidy vacuum and a spaghetti vacuum is discussed.
Show AbstractIn this work the positions of the critical point, the supercritical point, and the maximum fluctuation point in a supercritical isotherm were found for a system with the Lennard–Jones interaction potential. Virial coefficients and methods based on accelerated convergence of the perturbation-theory series, which are well known for such systems, were used. The results were compared with computer-simulation data. As has been established, if one uses the positively defined Weeks–Chandler–Andersen potential as a reference system, the calculated parameters tend monotonically to exact values as a function of the number of virial coefficients. This decomposition is favorably different from the virial one, where the aspiration is not monotonic. These results indicate that this method makes it possible to determine the positions of the three vertices of the supercritical triangle with an accuracy that is comparable to that of a simulated experiment.
Show AbstractThe spectrometer for the GunLab experiment is described. This spectrometer incorporates a dipole magnet, a fluorescent screen, and a CCD camera and is designed to measure the momentum of electron beams in the range of 1–10 MeV/c with a resolution of 0.1%. If a transversely deflecting RF cavity is installed in front of the dipole magnet, one may investigate the ongitudinal phase portrait of a beam. The spectrometer is distinctive in that a Hall sensor is placed in the magnetic field of the dipole magnet. This sensor allows one to accurately measure the magnetic field and, consequently, the momentum of an electron beam.
Show AbstractDefect formation in silicon-on-sapphire films under the action of a gas beam of 30 keV argon cluster ions is studied. Rutherford backscattering in the channeling mode is used to demonstrate the formation of a large number of defects in the volume of a specimen that is irradiated by a cluster ion beam without mass separation. If atomic and light cluster ions are removed from the beam, defect-free etching of the specimen occurs.
Show AbstractA new analytical approximate solution is suggested for the problem of nonlinear parametric generation of light in a cavity. This solution is much more accurate than the known ones. Two- and three-cavity lasing schemes are considered and criteria for their adequacy are ascertained. The accuracy of the results is confirmed by computer simulation
Show AbstractThis work is devoted to the production of cubic boron nitride ($c$-BN) micropowders that are activated by ions of rare-earth elements, such as europium (Eu), terbium (Tb), and thulium (Tm), as well as to the study of the structural properties and photo- and cathodoluminescence of these micropowders. The micropowders have been synthesized from a hexagonal boron nitride powder in the presence of a catalyst under pressures of 4–6 GPa at temperatures of 1800–1900 K. The activation of the micropowders by the rareearth elements (REEs) has been carried out by introducing the corresponding REE compounds into synthesis precursor. The efficiency of the introduction of an impurity into the $c$-BN lattice is ~5%. The composition and structure of the samples have been examined using X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive spectrometry. The results obtained during studying $c$-BN, $c$-BN:Tm, $c$-BN:Tb, and $c$-BN:Eu micropowders using color cathodoluminescence clearly demonstrate their ability to emit light in the wide spectral range, which is of interest for developing new light-emitting devices that are intended for operation in corrosive ambient. An analysis of the photoluminescence spectra of $c$-BN:REE micropowders has made it possible to find that the observed spectral bands belong to the corresponding transitions between the energy levels of the REEs, as well as to determine the probable positions of Tb$^{3+}$ and Eu$^{3+}$ ions in the cubic boron nitride lattice.
Show AbstractSupercomputer modeling of the process of high-energy deposition (ion-beam sputtering) of thin films of silicon dioxide using the molecular dynamics (MD) approach was carried out. The deposition method based on the facilities of the LAMMPS MD program was compared with another method that is known from the literature. An analysis of the structure of the deposited film (density, radial distribution function, concentration of defects) was carried out.
Show AbstractThe thermopower, $S$, magnetothermopower, $\Delta S/S$, resistivity, $\rho$, and magnetoresistivity, $\Delta \rho/\rho$, depending on the temperature $T$ and magnetic field $H$, have been studied in an Nd$_{0.5}$Sr$_{0.5}$MnO$_3$ single crystal consisting of three types of clusters: an antiferromagnetic CE-type with charge-orbital ordering (below the Neel temperature $T_{NCE}\sim 145$ K) and an A-type with $Т_{NA}\sim 220$ K; a ferromagnetic at 234 ≤ $T$ ≤ 252 K, and a ferromagnetic metal phase below the Curie temperature $Т_{С} = 248$ K. The thermopower was found to be negative, indicating the dominance of the electronic type of conductivity. In the $S(Т)$ curves, a sharp minimum is observed in the temperature range of 100 K ≤ $T$ ≤ 133 K, close to $T_{NCE}$, where the absolute $S$ value attains 53 $\mu$V/K. With a further increase in temperature, the absolute $S$ value decreases rapidly; at 200 K it is equal to 7 $\mu$V/K. It then slightly increases, reaching its maximum value of 15 $\mu$V/K at a temperature of 254 K, which is close to $Т_С$. The absolute thermopower decreased under the influence of the magnetic field; i.e., a negative magnetothermopower occurs. In $\{\Delta S/S\}(Т)$ curves, a sharp minimum is observed at $T = 130$ K close to $T_{NCE}$, where the magnetothermopower reaches a huge value of $\sim45\%$ at $H = 13.23$ kOe. A broad minimum in the $\{\Delta S/S\}(Т)$ curves is observed near the Curie temperature and its value is also high, viz., $\sim 15\%$ in the maximum measuring magnetic field of 13.23 kOe. The extremely high magnetothermopower values mean that the charge-orbital ordered nanoclusters or ferron type make the main contribution to the hermopower of the entire sample. The behavior of the $\rho (Т)$ and $\$\{\Delta \rho/\rho\}(Т)$ curves is similar to that of the $S(T)$ and $\{\Delta S/S\}(Т)$ dependencies, which is in agreement with this conclusion.
Show AbstractThe possibility of calculating radial and tangential force constants, as well as elastic constants of face-centered cubic (FCC) metals, has been demonstrated for the case study of nickel on the basis of the experimentally measured phonon spectrum, which is theoretically described by the DeLaunay model in terms of the dynamic matrix $D(q)$. The proposed calculation procedure is an alternative to the Born–von Karman model, which is widely applied for the description of the phonon spectrum in terms of force constants for interatomic interactions and in calculations of elastic constants using the phonon spectrum. The reliability of the obtained force constants for phonon spectrum was verified by comparison between the experimental and calculated data for the phonon spectrum and elastic constants for nickel. The obtained values of force constants for nickel have been compared with the theoretically calculated values using the seudopotential method.
Show AbstractThe regularities in the alterations of chlorophyll a fluorescence induction curves of bean leaves after short (15 min) heating in the range of temperatures from 24 to 45$^\circ$C were determined. A dramatic decrease in the relative f luorescence quenching $(F_{P} –F_{T})/F_{T}$ , as well as the $F_{v} /F_{m}$ ratio, were observed after heating at temperatures above 38$^\circ$C, which indicates a decrease in the photochemical activity of photosystem II. The effect of an increase in the resistance of the photosynthetic apparatus to the temperature of 43$^\circ$C after preheating at 37$^\circ$C was demonstrated.
Show AbstractWe used aptamers, which are functional equivalents of antibodies, in order to develop a nanosensor immunoassay system based on magnetic nanoparticles and a SQUID magnetometer. Selection was used to obtain DNA aptamers to interleukin-6; their affinity to the target protein was characterized by surface plasmon resonance. It was shown that the biotinylated aptamer binds to magnetic nanoparticles that were functionalized with streptavidin.
Show AbstractThe conditions of the resonant excitation of waves on a liquid surface by a horizontal air flow that has a decreasing velocity in the direction of motion were established, such that steady waves occurred when the period of the escape of a chain of eddies that is generated in a viscous layer of an air flow coincided with the period of natural oscillations, which is determined by the dispersion relationship for a group of waves. The dependence of the lengths of steady waves on the air-flow velocity over the surface of clean water and water with a light oil film was obtained. The resulting model was tested experimentally.
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