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Opal-like structures based on polymethylmethacrylate submicrosphere

Opal-like structures based on polymethylmethacrylate submicrosphere

I. V. Nemtsev$^1$, O. V. Shabanova$^2$, I. A. Tambasov$^3$, A. A. Ivanenko$^3$, V. Y. Zyryanov$^3$

Memoirs of the Faculty of Physics 2020. N 5.

In this work, 2D and 3D metamaterials and colloidal crystals are made from submicron-sized polymethylmethacrylate particles with a polydispersity of less than 5% by self-assembly. Morphological features of the obtained samples were studied using an ultra-high-resolution FE-SEM Hitachi S-5500 scanning electron microscope. Three different surface areas of 3D opal were investigated using the spectroscopy of the reflected light with the angular resolution. The spectra were measured in the range of 400-1250 nm. The above methods revealed a highly ordered structure. A narrow particle size distribution was revealed. The average particle diameter, packing density, q-factor, and reflectivity of the samples were determined. Based on the experimental reflection spectra, the dependence of the maximum reflectivity wavelength on the angle is approximated using the modified Bragg-Snell law. Based on this dependence, the wavelength of the maximum reflection at normal incidence, the particle diameter, and the filling factor were determined. The wavelength of the center of the photonic bandgap is calculated for the highly ordered surface at normal incidence. The experimentally measured the full width of the peak at a half maximum for the best sample was 70 nm, and the q-factor was 12.4. The calculated filling factor for the highly ordered opal was 87%. The average particle diameter obtained by the approximating the reflection spectra is in excellent agreement with the values obtained by electron microscopy. The most interesting result is that the reflectivity of the surface at normal light incidence can reach 98%, and this value depends on the filling factor – the density of the package.

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Detection of ethanol dissolved in water using SPR based sensor

Detection of ethanol dissolved in water using SPR based sensor

R. A. Pavelkin

Memoirs of the Faculty of Physics 2020. N 5.

Planar three–layer sensor structures in the Kretschman configuration supporting the surface plasmon–polariton (SPP) modes are considered in the paper. The structures allow propagation of the SPP modes along the metal–solution interface and are aimed to detect ethanol dissolved in bulk water of various concentrations. Analysis of the resonance characteristics of the SPP mode and sensitivity of the spectral resonance response to changes in the refractive index of the water–ethanol solution is performed using the Fano approximation and effective medium theory in the visible and infrared regions. The spectral regions of maximum sensitivity to changes in the ethanol concentration are discovered. The obtained results open up the possibility of implementation the plasmon structures in sensors outside the water absorption regions and can also be used to design chemical sensors in monitoring of liquids.

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Dissipative solitons in microtubules under action of an alternating electric field

Dissipative solitons in microtubules under action of an alternating electric field

A. S. Batova$^1$, A. N. Bugay$^2$, V. A. Khalyapin$^3$

Memoirs of the Faculty of Physics 2020. N 5.

The paper is devoted to the study of nonlinear excitations in microtubules at the effect of an alternating electric field and the presence of attenuation. Solutions of the type of dissipative solitons are obtained, the parameters of which depend only on the properties of the polymer and external influence. Sustainable excitations are possible when damping is compensated by an external electric field due to parametric resonance with microtubule vibrations.

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Schlieren setup for studying the structure of ultrasound fields in liquids

Schlieren setup for studying the structure of ultrasound fields in liquids

A. I. Tsekhanovich, S. A. Petrosyan, S. A. Tsysar, O. A. Sapozhnikov

Memoirs of the Faculty of Physics 2020. N 5.

The schlieren system developed at the Laboratory for industrial and medical ultrasound of Moscow State University for studying the structure of ultrasound fields is described. The results of computer simulation of the process of passing a light beam through the region of spatio-temporal inhomogeneities of the optical refractive index caused by ultrasound are considered. Experimentally obtained shadow patterns are presented under continuous illumination with white light, which are in good agreement with the simulation results.

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Study of Benard-Rayleigh convection with the particle tracing method

Study of Benard-Rayleigh convection with the particle tracing method

Y. D. Tsitavets$^1$, A. S. Fedotov$^1$, S. A. Movchan$^2$, I. A. Balashov$^2$, A. A. Makarov$^2$, V. V. Chepurnov$^2$

Memoirs of the Faculty of Physics 2020. N 5.

We study phase trajectories in a system with Benard-Rayleigh convection computed by tracing of ideal massless particles in a flow. The velocity of each particle at any moment coincides with the speed of the fluid at the same point. The presented method allows to obtain phase trajectories of the fluid control volumes using the solution of the Navier-Stokes equations. For the Rayleigh number 220 000, the presence of two types of phase trajectories is established, one of which corresponds to the rotation around equilibria centres and is related to the motion inside convective rolls. The second group of particles relates to the chaotic movement of the hottest and coldest fluid at the boundaries. The difference between the phase portraits of a system with Benard-Rayleigh convection when describing the Navier-Stokes equations and the Lorentz system is analyzed.

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Research of the holographic formation of two-dimensional diffractive optical elements by a Bessel-like and Gaussian light field in a photopolymer material

Research of the holographic formation of two-dimensional diffractive optical elements by a Bessel-like and Gaussian light field in a photopolymer material

V. O. Dolgirev, S. N. Sharangovich

Memoirs of the Faculty of Physics 2020. N 5.

This paper presents a research on the holographic formation of two-dimensional diffractive optical elements in photopolymer materials, taking into account two-beam interactions. As a result of the research, it was shown that in the plane perpendicular to the diffraction plane, the diffraction grating is not amplified, and as a consequence, the level of the side maxima in the diffracted beam does not increase either.

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Studying the measurement error in the microseismic sounding method

Studying the measurement error in the microseismic sounding method

A. -. Numalov, D. A. Presnov, R. -. Zhostkov

Memoirs of the Faculty of Physics 2020. N 5.

The results of field experimental work on microseismic sounding of the Bystryanskaya area of ​​the Minusinskaya depression using autonomous receivers are presented. Field materials were processed, a deep section was built using the method of microseismic sounding. The resulting section was interpreted. The dependence of the method error on the record length number was studied. The procedure for calculating the dependence of this statistical error is described. For the first time, a modification of the automatic rejection of microseismic sounding data was tested. An algorithm has been developed and described that improves the quality of the processed data. Comparison of the results obtained by the old and new algorithms is carried out. The differences in the final sections are explained. Comparison and estimation of the distribution of the statistical error on the section by both algorithms is carried out. The prospect of the method for the search for gas deposits is estimated. A technique is proposed that significantly speeds up field work.

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Theoretical Physics at Moscow University: thirties of the twentieth century

Theoretical Physics at Moscow University: thirties of the twentieth century

P. N. Nikolaev

Memoirs of the Faculty of Physics 2020. N 4.

The process of formation of modern teaching methods and scientific research in the field of theoretical physics in the thirties of the twentieth century at Moscow University is investigated. During this period, a whole galaxy of outstanding theoretical physicists was formed here. The activities in this period of I.E. Tamm, the first head of the department of theoretical physics at the Faculty of Physics, and A.A. Vlasov, his postgraduate student, who built the theory of plasma in this period based on the use of an equation called the Vlasov equation, are presented.

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Calibrating the Galactic Classical Cepheid period-luminosity relation based on photometric and spectroscopic data

Calibrating the Galactic Classical Cepheid period-luminosity relation based on photometric and spectroscopic data

Y. A. Lazovik$^{1,2}$, A. S. Rastorguev$^{1,2}$

Memoirs of the Faculty of Physics 2020. N 4.

We present a realization of the maximum-likelihood technique, which is one of the latest modifications of the Baade--Becker--Wesselink method. It allows one to estimate the key Cepheid parameters, the distance modulus, and the interstellar reddening, combining photometric and spectroscopic data (including the effective temperature data). This method is applied to the sample of 44 Galactic Cepheids, for which multiphase temperature measurements are available. The additional data correction is performed to subtract the impact of the component in binary/multiple systems. We also study the effect of shock waves, whose presence in the stellar atmosphere distorts the observational data and leads to systematic errors in the obtained parameters. As a result, we obtain the following period-luminosity relation: $M_v = - (2.67 \pm 0.16) \cdot (log\,P - 1) - (4.14 \pm 0.05)$. Despite the fact that the final calibration is in reasonable agreement with the relations calculated using trigonometric parallaxes, a slight zero-point offset is found, indicating the brighter Cepheids and therefore the longer distance scale. Thus, the Hubble constant estimate based on our period-luminosity relation has to be lower.

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Reference systems in statistical liquid thermodynamics

Reference systems in statistical liquid thermodynamics

P. N. Nikolaev

Memoirs of the Faculty of Physics 2020. N 4.

In the paper there are investigated the basic reference systems in the statistical thermodynamics of liquids from the point of view of the expediency of their use in thermodynamic perturbation theory. A quantum hard-sphere system widely used in this field is considered. As is known, the Wigner-Uhlenbeck-Gropper expansion is not suitable for nonanalytic potentials. Therefore, a special expansion into a series method is used in this work, the efficiency of which has been verified by the example of argon and helium 4.

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