R e v i e w s

Optics and spectroscopy. Laser physics

Moscow University Physics Bulletin 2018. **73**. N 5. P. 447

The experiment to verify the adequacy of Heisenberg uncertainty principle, proposed by Karl Popper and implemented in practice, is considered. As in the Einstein-Podolsky-Rosen paradox, the quantum properties of a entangle pair of elementary particles is used. In this case, a ghost image of a narrow gap is formed in fact. The results of the experiment, at first glance, testify in favor of violation of the uncertainty principle. But the analysis of of the gap ghost image spatial resolution shows, that it is not so. A more correct description of diffraction in the case of spatially limited light beams, gives not violations of the uncertainty principle. The results are also can be used to estimate the extreme quality of diffraction limited ghost images.

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Condensed matter physics

Moscow University Physics Bulletin 2018. **73**. N 5. P. 486

We present theoretically the quantum electronic transport through an interferometer asymmetrically coupled with triple quantum dots. Using the Keldysh non-equilibrium Green's function method, the photon-assisted transport properties through the asymmetric quantum system are numerically analyzed. The sidebands of the photon-assisted tunneling process appear when driven by the time-modulated field. The average current spectra are simulated as a function of quantum dot energy to understand the roles of side-coupling strength and time-modulated field in sideband effect and electron tunneling. This is helpful in future design of the basic structures required for quantum computation applications.

Show AbstractMoscow University Physics Bulletin 2018. **73**. N 5. P. 482

Using Density functional theory (DFT) calculations, we study the structural parameters and mechanic properties of Y2Al compound. The independent elastic constants of Y2Al compound were calculated and the results show that Y2Al compound is mechanically stable. Some polycrystalline quantities such as the bulk and shear modulus, Young’s modu-lus, and Poisson’s ratio of Y2Al compound were derived from calculated elastic constants. The obtained results were compared with the existing experimental and other theoretical data.

Show AbstractMoscow University Physics Bulletin 2018. N 5.

Using the method of the molecules electron energy spectra parameterization, we have studied the peculiarities of the energy spectrum of the monometallic molecules of coordination compound of terpyridine with single metal atoms of Rh, Ru, Pt, and electron transport characteristics of this family of molecules single-electron single-atom transistor. For the considered family of molecules the coefficients that specify energy spectrum parametric shell model were determined. It is shown that for considered atoms of the transition metals, the valence electron shell of which contain simmilar number of $d$-electrons, electron transport characteristics of molecular single-atom transistor based on them have similar the form and features.

Show AbstractBiophysics and medical physics

Moscow University Physics Bulletin 2018. N 5.

Material science is very important for developing the linear accelerator. Determination and understanding of material behavior face to X-rays is a basic study for photon beam modifiers improvements. It this study, the 6 MV photon beams produced by Varian Clinac 2100 was modelled by Monte Carlo simulation using BEAMnrc code and thereafter the flattening filter was replaced by a slab of aluminum and copper separately and by slab of both materials combined together with different thickness of 2.5 mm, 5 mm, 7.5 mm and 10 mm. The purpose of this study is to investigate the scattered photons with thickness of combined material slab as a function of off-axis distance. The scattered photons increased with thickness of copper alone slab, combined aluminum-copper slab and copper-aluminum slab, but for aluminum alone slab they decreased with slab thickness. The stacking order of these two materials affects the characterization of scattered photons emergent from material slab with thickness. The combination of materials and the manner that the stacking was done affects the scattered photons production. The material combination could improve the radiotherapy efficiency in beam modifier development using more than two materials.

Show AbstractMoscow University Physics Bulletin 2018. N 5.

Anuclear blood cells, platelets, should have the ability to react to activation in a second. This ability is provided by calcium signaling - the process of signal transduction inside the cell by increasing the cytosolic calcium concentration. Calcium leaks from endoplasmic reticulum into cytosol through the receptor channel to inositol triphosphate (IP3R). As in many other cell types, the increase in cytosolic calcium concentration occurs not monotonously, but in form of oscillations. In this study, mechanisms of these oscillations are explored, both theoretically and experimentally. Total internal reflection microscopy of Fura-2 loaded fibrinogen-bound single platelets was used as means of observation of cytosolic calcium dynamics. To describe the development of oscillations, a mathematical model of the IP3R-ATPase pair was used. This model was derived from the one of Kaiser-De Young (PNAS, 89 (20): 9895-9899, 1992). We have shown that the calcium oscillations in the platelets possess a characteristic peak shape, which can be described theoretically only by introducing corrections into the mathematical model, the physical meaning of which is the cooperative activation of IP3R.

Show AbstractTheoretical and mathematical physics

Moscow University Physics Bulletin 2018. **73**. N 5. P. 457

The nonlinear electrodynamic phase change of the electromagnetic wave after passing through hexapole magnetic field of the pulsar is calculated. It is shown that in virtue of the equations of nonlinear electrodynamics of vacuum any pulse of electromagnetic radiation changes its initial polarization. Front and back of the pulse length $\tau$ are linearly polarized in mutually orthogonal planes, and the part enclosed between them, in general, becomes elliptically polarized wave.

Show AbstractMoscow University Physics Bulletin 2018. **73**. N 5. P. 462

We perform theoretical study and modeling of enhanced high harmonic generation in X-ray band and low harmonics suppression in single pass free electron lasers (FEL) with a two-frequency undulator. For this purpose a phenomenological model of FEL is applied, which accounts for all main losses. The harmonic radiation in a FEL with a two-frequency undulator and in a FEL with a common planar undulator is compared with each other. The harmonic radiation and FEL induced energy spread are studied in a FEL, where lower than n–th harmonics are suppressed, for example, by the 2π/n phase shift of the electrons respectively to photons between the undulator sections. The advantages of the two-frequency undulators in such phase shifted FEL is elucidated. The possibility of intense X-ray radiation of a harmonic in linear regime, exceeding the power of a fundamental harmonic in a FEL, is demonstrated.

Show AbstractRadiophysics, electronics, acoustics

Moscow University Physics Bulletin 2018. **73**. N 5. P. 470

Algorithm of estimating the geometrical and phase corrections for receiving-transmitting transducers of ring antenna array of ultrasound tomograph is proposed. These corrections should be taken into account at the stage of reconstructing the spatial distributions of sound velocity and absorption coefficient of an investigated object (breast). Otherwise, a quantity of obtained tomogram significantly deteriorates.

Show AbstractOptics and spectroscopy. Laser physics

Moscow University Physics Bulletin 2018. **73**. N 5. P. 475

We consider the problem of a plane electromagnetic wave field diffraction on a linear cluster consisting of two plasmonic nanoparticles accounting for the nonlocal effect. The research is based on the mathematical model of the Generalized Non-Local Optical Re-sponse (GNOR). On the basis of the modification of the Discrete Sources Method, a comparative numerical analysis of the scattering characteristics in frequency domain is carried out depending on the geometry of the particles and the distance between them. It has been established that taking account of longitudinal fields has a significant influence both on the extinction cross section and even more on the scattering cross section.

Show AbstractChemical physics, physical kinetics, and plasma physics

Moscow University Physics Bulletin 2018. N 5.

The degree of ionization of the plasma in a nonstationary pulsating discharge created using a stationary power source in subsonic and supersonic air flows is determined. It was experimentally found that the electron density in the plasma near the electrodes varies from 1015 cm-3 to 4·1016 cm-3, and the gas temperature increases from 400 K to 1250 K when the flow velocity varies from 150 m/s to 520 m/s at constant discharge current of 15.5 A. It was shown that the degree of gas ionization in pulsating discharge plasma is of the order of 10-4 at low subsonic airflow velocities, and with an increase in the flow rate it increases sharply and reaches a value of 10-2 at a velocity of 500 m/s.

Show AbstractMoscow University Physics Bulletin 2018. N 5.

Equation of state for gaseous plasma is nicely described by Saha model. In the present paper, we include accounting for finite ion cores volume into this model. This improvement allows to expand Saha model on superhigh densities and moderate temperatures where plasma can be considered liquid. In this domain, thermodynamics of Saha model is essentially close to the one of Tomas-Fermi model which is conventionally used for condensed matter.

Show AbstractMoscow University Physics Bulletin 2018. N 5.

Convective patterns, formed in a plane liquid layer heated from below, are shown to be determined both by conventional dimensionless numbers (Prandtl number, Rayleigh number, Marangoni number) and by the presence or absence of elastic film at the liquid surface, produced by contaminants and stabilizing the surface. The amount of contaminants, contained in distilled water is enough for Marangoni convection to be suppressed. Only additional purification (deionization) of water enables one to observe thermocapillary effect. Mean size of thermal cells, formed at the surface of different liquids, is determined using infrared thermography for various values of layer thickness and bottom temperature. Linear and nonlinear theoretical analysis of convection is performed, taking contamination into account. Good agreement is obtained between theoretical results and experimental data.

Show AbstractAstronomy, astrophysics, and cosmology

Moscow University Physics Bulletin 2018. N 5.

Motion modelling of two low-earth information-related satellites for Earth's gravitational field parameters measurement is presented. The motion model of satellites accounts such affecting the satellites motion factors as nonspherical geopotential,atmospheric resistance, tides, and third-body effects from the Moon, Sun and Solar system's planets. As a result of the modelling search of optimal configuration of satellites for completeness of scientific tasks and possibility of technical realization is performed.

Show AbstractPhysics of Earth, atmosphere, and hydrosphere

Moscow University Physics Bulletin 2018. N 5.

This paper is concerned with the mathematical modeling of multicomponent non-isothermal filtration flow of oil and gas, taking into account the processes of thermal decomposition of kerogen. A system of differential equations describing kerogen’s thermal decomposition is formulated based on field (thermal gas treatment of the Bazhenov formation) and laboratory (pyrolysis studies) data. The one-dimensional initial-boundary value problem obtained is solved numerically. With the implemented software, series of numerical experiments with various values of the model’s parameters were carried out. Two models were investigated: the classical multicomponent non-isothermal filtration flow model and the model supplemented by the equations describing kerogen’s thermal decomposition. The results of these numerical experiments obtained on the basis of two different models were compared. The main physical processes expected – increasing oil saturation, changing porosity, changing the composition of reservoir oil – all of them were reproduced by the model designed. When comparing the results of calculations based on the two models, kerogen’s thermal decomposition was found to affect such parameters as reservoir pressure, phase saturation and accumulated production. Thus, the model proposed in this paper allows us to describe the physical processes taking place in the kerogen-containing formation under thermal treatment more accurately.

Show AbstractMoscow University Physics Bulletin 2018. N 5.

Satellites GRACE have been operating in space for more than 15 years. During this period, not only the unique time series of monthly models were accumulated, but also the methods of data processing and suppression of various errors, primarily related to selective sensitivity along and across the orbit, were substantially improved, which allowed to increase the number of spherical harmonics in GRACE monthly models from 40 up to 80 and even 96. This, in particular, opened new opportunities for investigating post-seismic processes in the areas of major earthquakes. The paper discusses the possible geodynamic processes responsible for growth of a positive gravity anomaly after the Simushir earthquake of November 15, 2006. He anomaly started growing a few months after the earthquake simultaneously with activation of seismicity at the continuation of the zone of the co-seismic rupture in depth. The numerical simulation using data from GPS sites and temporal variations of the gravitational field has shown that viscoelastic relaxation of stresses resulting from an earthquake plays a subordinate role. The main process responsible for post-seismic displacements and the growth of the positive gravity anomaly is post-seismic creep in a vast area around the seismic rupture region, including its extension to a depth of 100 km.

Show AbstractEngineering physics

Moscow University Physics Bulletin 2018. N 5.

The paper presents the results of a numerical modeling on the impact of an electromagnetic field on the strength characteristics of natural and artificial materials and laboratory data on the weakening of materials (Berea sandstones and concrete) under impact of an electric current when the samples are loaded at a constant strain rate

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