R e v i e w s

Physics of nuclei and elementary particles

Moscow University Physics Bulletin 2015. **70**. N 5. P. 333

Experimental data on inelastic scattering of alpha particles by the $^{11}$B, $^{12}$C, and $^{13}$C nuclei are analyzed using the modified diffraction model and the radii of these nuclei in some <<abnormal>> excited states are found. It is shown that the $0_{2}^{+}$ (7.65 MeV) Hoyle state in the $^{12}$C nucleus is the base state for a new $0_{2}^{+}-2_{2}^{+}-4_{2}^{+}$ rotational band (in addition to the ground-state band), in which the third member is the discovered $4_{2}^{+}$ (13.75 MeV) state. The radii of the $^{12}$C nucleus in the above-mentioned three states are 25–30% larger than its ground state radius. It is found that the radii of the $1/2^{–}$ (8.86 MeV) state in the $^{13}$C nucleus and the $3/2^{–}$ (8.56 MeV) state in the $^{11}$B nucleus are close to the radius of the Hoyle state in $^{12}$C and that a similar rotational band is based on the 8.56 MeV state. The above $^{13}$C and $^{11}$B states can be regarded as analogues of the Hoyle state. The prediction of the alpha-condensation model that a similar analogue in $^{11}$B is the 12.56 MeV state with a radius that is comparable with the nuclear radius of uranium was not confirmed.

Show AbstractR e g u l a r p a p e r s

Condensed matter physics

Moscow University Physics Bulletin 2015. N 5.

W incorporated tin oxide (TO) thin films were grown via spray pyrolysis with various tungsten contents. The films were observed to be polycrystalline tetragonal crystal nature with (301) and (211) preferential planes. From EDX analysis, it was seen the tungsten concentrations in the TO films were slightly higher than ones in the starting solutions. Polyhedron-like and small rod-like grains were observed in the SEM images. 3 at. % W doped tin oxide film has minimum sheet resistance (44.67 Ω) and resistivity (3.685x10-3 Ω.cm) values and maximum figure of merit (75.74x10-5 Ω-1) value. The optical band gap (Eg) of pure film raised from 3.84 eV to 3.91 eV with 3 at. % W contribution level.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 404

This paper describes current transport through а long Josephson junction with an alternating critical–current density. This alternating density can be achieved in experiments bу incorporating a magnetic layer to the weak link in а special manner. The prospects for the practical use of such structures are related to the possibility of obtaining bistable Josephson elements on their basis. Joint analysis of both current–phase relations and dynamic characteristics made it possible to optimize the operation mode for a fast superconducting memory cell based on bistable contact and to assess the energy dissipation for the read and write operations.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 411

Nanocarbon material prepared via dehydrohalogenation of PVC-PVDC copolymer was studied in this work. The results of structural characterization of this material reveal the growth in the chain component fraction with increasing temperature of annealing that increases the specific capacity from 5 to 25 F/g. Chemical activation results in a noticeable growth of the specific capacity to 100 F/g.

Show AbstractTheoretical and mathematical physics

Moscow University Physics Bulletin 2015. **15**. N 5. P. 341

A mathematical model for describing the temperature distribution in the near-surface layer at the water–air interface is proposed. The model is composed based on the theory of contrast structures. Using numerical calculations, the temperature distribution in a 10-cm wide near-boundary layer has been obtained. The calculation results coincide well with the experimental data.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 346

As the scientific community accepts the modern global climate changes, statistical analysis of a time series of hydrometeorological parameters becomes topical. A time series of air temperature was decomposed in this work; the decomposition allows one to distinguish regular, seasonal, and random components and to assess their statistical significance and adequacy to observation results. On the basis of a linear-regression model, a statistically significant increase in the annual average air temperature in the region under study was determined, both for the entire observation period and for separate months of the year.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 353

The problem of estimating the parameters of the model of a measurement experiment using the results of measurements with an error is considered. The mathematical model of the measurement error is formulated in terms of the theory of possibilities; the distribution of the possibilities on the set of error values determines the order that indicates which error values are preferred (that more probably occur during measurement) and which are less preferred. It is assumed that small error values are preferable to large ones. The mathematical model of the experiment depends on unknown parameters. The problem is to specify the values of these parameters by choosing their estimate for which the difference between the results of experiment and the model prediction is the most possible; this estimate is called the estimate of maximum possibility. An example of estimating the parameters of a Mössbauer spectrometric experiment is given.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 362

Water molecules and the hydrogen-bond network are essential structural components of many biological macromolecular systems, such as nucleic acids, as well as fibrillar and globular proteins. The water density in the protein hydration shell is known to differ from that of bulk water. In this paper, spatial density as function of the distance from the protein surface is discussed. The electric potential function is considered in the same way. The resulting profiles of the bound water density are characterized by the presence of several distinct maxima due to the existence of the regular structure of bound water at distances over 7 Å. The minor discrepancies that are observed in both radial functions for different proteins are explained by topological variations that were revealed earlier by studying the valence and dihedral angle-distribution functions for water bound to the same proteins.

Show AbstractRadiophysics, electronics, acoustics

Moscow University Physics Bulletin 2015. **15**. N 5. P. 368

This paper is a continuation of a series of experiments that studied a pulsed discharge that propagates above a liquid surface. A detailed study of the influence of a dielectric barrier on the nature of the propagation of a pulsed discharge above a water surface was conducted. It was shown that the presence of barriers leads to an increase in the initial voltage pulse that is required for discharge propagation. Along with this, a decisive role was played by the barrier that was nearest to the point of the electrode.

Show AbstractOptics and spectroscopy. Laser physics

Moscow University Physics Bulletin 2015. **15**. N 5. P. 374

Abstract—approaches for calculating the amplitudes of nonlinear photoprocesses in the framework of perturbation theory. The convergence of the method is studied based on the example of atomic hydrogen and hydrogenlike ions. The method is used to calculate the angular distributions of photoelectrons for the first time.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 382

We analyze the state of type-I SPDC polarization in nonlinear uniaxial crystals using a coordinate system connected with a pump beam. The entanglement loss due to the Migdall effect is examined. The analytical expressions for polarization components of the signal and idler waves for the frequency-degenerate regime are obtained. The numerical results for BBO crystal are also adduced.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 390

Abstract—We propose a multichannel erbium-doped-fiber ring laser in which the spatial separation of 40 spectral channels is produced by a pair of dispersive elements: a multiplexer and demutliplexer. Both 2- and 3-channel generation modes with the possibility of channel switching and power control were used and studied experimentally. The long-term stability of these generation modes on a several-hour time scale is at least 10%. The generation characteristics are described satisfactorily by a simple phenomenological model. In the framework of this model the interaction between the generation channels, which stems from saturation in the active media, is determined by the cross-saturation coefficients, which depend on the frequency spacing between the channels. Good agreement was found between the experimentally measured spectral dependence of the cross saturation and the spectral shape of the holes in the gain spectrum of the erbium amplifiers. In the three-channel generation mode, suppression of the central channel occurs with an increase in the pumping power. An explanation of this effect is given.

Show AbstractMoscow University Physics Bulletin 2015. **15**. N 5. P. 397

In this paper, a method for distinguishing between liquid samples that are sensitive to the influence of low-intensity physicochemical factors is described. It is based on the calculation of the initial moments of the intensity distribution series in their infrared spectra and comparison of the obtained values with each other. Reliable signs of the coincidence of liquid samples that were obtained in the experiment were used to distinguish distilled water at –0.5 ± 0.5 and –3.0 ± 0.5$^{\circ}$C, and at –3.0 ± 0.5 and –5.0 ± 0.5$^{\circ}$C, and to distinguish between distilled and tap water at 25.0 ± 0.5$^{\circ}$C. For each sample, the moments were calculated for the bending (1640 cm$^{–1}$), combination (2090 cm$^{–1}$), and stretching (3370 cm$^{–1}$) water absorption bands. It was found that when comparing distilled water at –0.5 ± 0.5 and –3.0 ± 0.5$^{\circ}$C the greatest differences are observed for the bending band (50%). When considering distilled water at –3.0 ± 0.5 and –5.0 ± 0.5$^{\circ}$C, the greatest differences occur for the stretching band (54%). When comparing distilled water at 25.0 ± 0.5$^{\circ}$C and tap water at 25.0 ± 0.5$^{\circ}$C, the greatest differences were observed for the bending band (86%).

Show AbstractBiophysics and medical physics

Moscow University Physics Bulletin 2015. **15**. N 5. P. 416

This study is devoted to the investigation of the interaction of photon radiation with an energy of up to 30 MeV with thin layers, which simulates the conditions of radiobiological experiments on determination of the relative biological efficiency (RBE). The values of the absorbed dose of all of the produced particles in irradiated layers were determined via computer simulation using Geant4 and the equivalent dose was calculated. Computer experiments were performed in media of different elemental compositions: water and model biological tissue. We demonstrate that starting from the threshold of photonuclear reactions on light elements the equivalent dose of monochromatic radiation differs from the absorbed dose by a factor of 3‒15 depending on the layer thickness and composition. Similar calculations for bremsstrahlung spectra also demonstrate a noticeable difference between the absorbed and equivalent doses in a layer.

Show AbstractPhysics of Earth, atmosphere, and hydrosphere

Moscow University Physics Bulletin 2015. **15**. N 5. P. 423

A hydrodynamic model for calculating the pressure jump on the leeward slope of a roof during a horizontal air flow that is directed to its slope is proposed for the first time. The model takes the formation of vortices in a viscous layer of an air flow that decelerates in the flow direction into account. When a vortex departs from the viscous layer, flow acceleration occurs at the underlying surface, leading to a considerable pressure drop and to tearing the roof off. It is shown that the negative pressure jump at a site that is adjacent to the roof ridge can be decelerated by several percent with a decreased friction factor and an increased length of the portion of the roof where air flows without separation. A method for considerably reducing the pressure drop is proposed for the first time, viz., the installation of expanding air ducts on the roof, within which a compensatory pressure jump occurs. The results are verified by laboratory studies.

Show Abstract