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The article presents calculated and experimental assessments of the possibility of using Ni-rich RPV steels developed by the JSC NPO Central Research Institute of Machine Building Technology (CNIITMASh) as materials for RPVs of next generation reactors taking into account their structural-phase state, mechanical characteristics, and the possibility of manufacturing a shell with an industrially developed wall thickness. In order to improve service characteristics, it is necessary to apply a complex of measures: change the complex alloying of steels, conduct metallurgical purification from impurities (primarily from phosphorus), and optimize the grain size of castings. The calculation took into account the assumed operating temperature, coolant pressure, strength grade of candidate steels, and their thermal and radiation resistance. [ABSTRACT FROM AUTHOR]

The technology has been developed for manufacturing the magnetoresistive tunnel junction based on CoFeB/MgO/CoFeB layers with typical lateral sizes in the range from 200 to 700 nm by means of a set of HSQ/PMMA electronic resistive masks. To study the processes of magnetization reversal in the obtained samples, magnetoresistance curves are plotted. It is shown that elements with both vortex and quasi-uniform distributions of free layer magnetization are revealed, which depends on the structure of the magnetosensitive layer and the geometric parameters of the magnetoresistive tunnel junctions. Moreover, the width of the front of magnetization reversal in the elements with quasi-uniform distributions ranges from 2 to 6 Oe. [ABSTRACT FROM AUTHOR]

Multi-party agreements are used in distributed ledger systems and blockchain networks to reach an agreement on changes in the system. When one of the network participants proposes a transaction to be recorded, it should be first confirmed by certain network participants. A multi-party agreement or consensus determines who exactly these participants are. Based on the historical data set, one can calculate the transaction confirmation probability for each of the participants. In this work, a method of statistical model checking is proposed to determine the probability that the consensus is reached. Sending confirmation requests may require extra costs. In addition to the stated probability, the mathematical expectation of the number of messages received before reaching a consensus is calculated. A consensus model or several consensus models are given in the form of a Markov chain with various message sending strategies. Based on the construction algorithms for the model and specification, a tool that analyzes consensus and sends confirmation messages is developed. [ABSTRACT FROM AUTHOR]

The development of methods for controlling flow and heat transfer in submerged turbulent jets (impact jets) impinging on an obstacle is an important problem, since this configuration is used in various technical applications. Active flow control technology and optimization of the signal that controls the external flow disturbance in impact jets can be applied to use the inherent properties of the flow to further improve heat transfer at the wall. This work used IR thermography and PIV (particle image velocimetry) measurements for optical diagnostics of wall temperature fields and velocity fields under conditions of flow rate disturbance control, including feedback from a local velocity sensor. It was found that low-amplitude sinusoidal disturbances increase the integral temperature on the wall due to the intensification of flow separation on the wall compared to an undisturbed jet. It has also been established that high-amplitude disturbances in the pulsating jet mode make it possible to reduce the integral temperature by increasing the average flow velocity near the wall and compensate for unwanted flow separation. The genetic programming algorithm made it possible to find a self-oscillating mode in jet disturbance with feedback, which improves local heat transfer on the wall no worse than in the case of forced periodic disturbance. [ABSTRACT FROM AUTHOR]

The Zr35Ti25Cu12Be28 rapidly quenched filler metal has been used to obtain a durable and reliable SiC/SiC brazed joint. With the SEM, EDX and XRD methods, the following phases were found and confirmed in the brazed seam: (Zr,Ti)2Cu, ZrBe2, TiBe2. The microstructural studies have revealed the absence of the noticeable reaction layer in the brazed joint. The shear strength tests have shown that the SiC/SiC joint failure occurred by a brittle failure with a formation of a crack and its propagation through the silicon carbide and the brazed joint/SiC interface. But despite this high shear strength of 201 MPa was obtained with 810 °C, 10 min brazing mode. Unbrazing tests with heating to 1450 °C of SiC/SiC joints indicated that the dissolution of the silicon carbide proceeded and a formation of the ZrSi matrix with TiC, ZrC inclusions occurs in the brazed joint, which is the consequence of an increasing filler metal reactivity with temperature. [ABSTRACT FROM AUTHOR]

A Tikhonov-regularized solution of the inverse scattering problem has been physically implemented using a basis of speckles that is adjusted immediately during an experiment and ensures the minimization of regularization-induced diffusion of images. This procedure ensures the stable, minimally diffuse reconstruction of images in the scheme of microscopy of scattering media with a submicron spatial resolution. [ABSTRACT FROM AUTHOR]

The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of "nitrogen-vacancy" (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths. [ABSTRACT FROM AUTHOR]

Monocytes and macrophages play a key role in the development of inflammation induced by lipopolysaccharides (LPS), absorbed from the intestine: these cells form reactive oxygen species (ROS) and cytokines, thus initiating the development of oxidative stress, inflammation and/or apoptosis in all types of tissues. In the cells LPS induce an "internal" TLR4-mediated MAP-kinase inflammatory signaling pathway and cytokines through the superfamily of tumor necrosis factor receptor (TNFR) and the "death domain" (DD) initiate an "external" caspase apoptosis cascade or necrosis activation causing necroptosis. Many of the proteins involved in intracellular signaling cascades (MYD88, ASK1, IKKα/β, NF-κB, AP-1) are redox-sensitive and their activity is regulated by antioxidants thioredoxin, glutaredoxin, nitroredoxin, and glutathione. Oxidation of these signaling proteins induced by ROS promotes development of inflammation and apoptosis, and antioxidants, have an opposite effect: they stabilize the signaling cascades, prevent the vicious circle of oxidative stress, accompanied by inflammation and apoptosis. Reduction of non-enzymatic antioxidants (thioredoxin, glutaredoxin, nitroredoxin, glutathione) requires antioxidant (AO) enzymes thioredoxin reductase (TRXR), glutaredoxin reductase (GLRXR), glutathione reductase (GR), while the AO enzymes SOD, catalase, GPX are needed for ROS degradation. The key AO enzymes (TRXR and GPX) are selenium-dependent and therefore selenium deficiency leads to a decrease in the antioxidant defense, development of oxidative stress, inflammation, and/or apoptosis in various cell types. The Nrf2-Keap1 signaling pathway activated by selenium deficiency and/or oxidative stress is necessary to restore redox homeostasis in the cell. Selenium deficiency also influences expression of some genes. Consequently, growth and proliferation of cells, their movement, development, death, and survival, as well as interaction between cells, redox regulation of intracellular signaling cascades of inflammation and apoptosis, depend on the selenium status of the body. Prophylactic administration of selenium-containing preparations (natural and synthetic (organic and inorganic)) is able to normalize activity of AO enzymes and the general status of the body. Organic selenium compounds have a high bioavailability and, depending on their concentration, can act both as selenium donors preventing selenium deficiency and as antitumor drugs due to their toxicity and involvement in regulation of signaling pathways of apoptosis. Known selenorganic compounds diphenyldiselenide and ethaselen share similarity with the Russian organoselenium compound, diacetophenonylselenide (DAPS-25), which serves as a source of bioavailable selenium, exhibits a wide range of biological activity, including antioxidant activity, that governs cell redox balance and regulates inflammation and apoptosis. [ABSTRACT FROM AUTHOR]

The annealing technique is used to estimate the effect of radiation-induced structural elements on the service properties of the materials used in nuclear power plants: reactor pressure vessel (RPV) and in-vessel internals steels. The WWER-1000 RPV weld seam is affected by a hardening mechanism, the contribution of which is 60–65%, and a nonhardening mechanism resulting in grain-boundary segregation, the contribution of which is 30–35%. Radiation defects 40–45% and G-phase precipitates 35–40% are mainly responsible for the radiation-induced hardening of WWER-1000 internals materials. Radiation-induced structural changes should be eliminated for these materials to be reused. [ABSTRACT FROM AUTHOR]

The radiation-induced structural elements in the materials of water-moderated water-cooled reactor pressure vessels have been studied by TEM and atomic probe tomography at the National Research Center Kurchatov Institute. The effect of Ni concentration in the range from 0.34 to 1.28 wt % on the formation of phases under fast neutron irradiation has been analyzed. The volume density of radiation-induced phases has been shown to depend on the Ni concentration in steel; the phase sizes and compositions remain almost the same. The volume density of these precipitations affects the radiation hardening, one of the radiation embrittlement mechanisms. The quantitative parameters of radiation-induced phases have been shown to control the service life growth, the enhancement of the thermal stability, and the melting technology of reactor vessel steels bearing nickel in the 0.3–0.7 wt % range. [ABSTRACT FROM AUTHOR]

We developed a technology, produced, and tested an ultrasonic installation aimed at treatment of the pipe threads with the help of radial ultrasonic vibrations and studied the microhardness of the outer surface of the thread profile. We also performed metallographic investigations. The pilot field tests of the branch pipes of tubing strings with strengthened threads were carried out and positive results were obtained. [ABSTRACT FROM AUTHOR]

By the analysis of plastic deformation with ultrasound treatment, analytical formulas are obtained for the strain rate and stress rate and the deformation of the thread profile is estimated. The use of ultrasound treatment to correct the geometric parameters of the thread and strengthen its surface is considered. The effectiveness of ultrasound treatment of threads is confirmed. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to the problem of coupled longitudinal and transversal propagations of stress waves in an isotropic thick and elastic rod, based on the Mindlin-Herrmann theory. The novelty is that Hamilton's variational principle is used not only for derivation of the governing equations and set of natural boundary conditions, but also for obtaining the exact solution in terms of Green's functions directly from the Lagrangian. The success of this approach is based on the existence of multiple orthogonalities of the eigenfunctions. The proposed method is much easier than the standard approach of building Green's functions. A numerical example illustrates the method of finding eigenfrequencies and eigenfunctions for isotropic Mindlin-Herrmann rod. [ABSTRACT FROM AUTHOR]

A method is developed for the computer simulation of the disk concentrator in a system for the modification of screw threads by ultrasonic surface plastic deformation. [ABSTRACT FROM AUTHOR]

The inverse problem of identifying the parameters of sets of ordinary differential equations using experimental measurements of three functions that correspond to some components in the vector solution of a set is considered. A private case that is important for applications of chemical and biochemical kinetics when reduced equations linearly depend on the combinations of initial unknown parameters has been studied. An analysis and the numerical results are presented for two types of sets of chemical kinetics equations, such as the Lotka-Volterra model that describes the coexistence of a predator and a prey and the chemical kinetics equations that model enzyme catalysts reactions, including the Michaelis-Menten equations. The search for unknown parameters is confined to the problem of minimizing a quadratic function. In this case, the reduced differential equations of systems are used instead of their vector solutions, which are unknown in most cases. The cases of both stable and unstable search for unknown parameters are analyzed. [ABSTRACT FROM AUTHOR]

A one dimensional model describing the longitudinal vibrations of a cylindrical rod composed of multiple sections with different diameters and made of different materials is derived. The hypothesis that lateral displacements and axial shear stresses in the bar are zero is rejected. The lateral displacements are assumed to be proportional to the axial strain and the Poisson ratio, resulting in the so-called Rayleigh-Bishop equation as opposed to the classical one dimensional wave equation. The Rayleigh-Bishop equation is a fourth order partial differential equation, not resolved with respect to the highest order time derivative. A system of partial differential equations, as well as the corresponding boundary conditions and continuity conditions at the junctions between the sections, are derived using Hamilton's variational principle. An analytical solution is obtained in terms of a Green function. A numerical example is provided for a rod consisting of two cylindrical sections, in which the first five eigenvalues and corresponding eigenfunctions are presented. [ABSTRACT FROM AUTHOR]

The electron spin of nitrogen--vacancy (NV) centers in diamond offers a solid-state quantum bit and enables high-precision magnetic-field sensing on the nanoscale. Implementation of these approaches in a fiber format would offer unique opportunities for a broad range of technologies ranging from quantum information to neuroscience and bioimaging. Here, we demonstrate an ultracompact fiber-optic probe where a diamond microcrystal with a well-defined orientation of spin quantization NV axes is attached to the fiber tip, allowing the electron spins of NV centers to be manipulated, polarized, and read out through a fiber-optic waveguide integrated with a two-wire microwave transmission line. The microwave field transmitted through this line is used to manipulate the orientation of electron spins in NV centers through the electron-spin resonance tuned by an external magnetic field. The electron spin is then optically initialized and read out, with the initializing laser radiation and the photoluminescence spin-readout return from NV centers delivered by the same optical fiber. [ABSTRACT FROM AUTHOR]

The possibility to apply amorphous nickel-based braze alloys for junction of nickel-alloy products used in the control and protection devices of nuclear power plants is demonstrated. Mechanical tests and investigations of the structural phase state of brazed junctions are carried out. [ABSTRACT FROM AUTHOR]

Seeing the big picture of functional responses within large neural networks in a freely functioning brain is crucial for understanding the cellular mechanisms behind the higher nervous activity, including the most complex brain functions, such as cognition and memory. As a breakthrough toward meeting this challenge, implantable fiber-optic interfaces integrating advanced optogenetic technologies and cutting-edge fiber-optic solutions have been demonstrated, enabling a long-term optogenetic manipulation of neural circuits in freely moving mice. Here, we show that a specifically designed implantable fiber-optic interface provides a powerful tool for parallel long-term optical interrogation of distinctly separate, functionally different sites in the brain of freely moving mice. This interface allows the same groups of neurons lying deeply in the brain of a freely behaving mouse to be reproducibly accessed and optically interrogated over many weeks, providing a long-term dynamic detection of genome activity in response to a broad variety of pharmacological and physiological stimuli. [ABSTRACT FROM AUTHOR]

The present paper studies unsteady temperature fields in growing bodies of spherical shape. The growth occurs due to constant accretion of layers of constant thickness on the surface of the main body. In the general case, the temperature of the accreted material is different from that of the main body, which causes a heat flow on the accretion surface. The solution of the initial boundary-value problem of heat conduction is sought as an expansion in the complete system of eigenfunctions of the differential operator generated by the problem. [ABSTRACT FROM AUTHOR]

Broad classes of nonlinear equations of mathematical physics are described that admit order reduction by applying the von Mises transformation (with the unknown function used as a new independent variable and with a suitable partial derivative used as a new dependent variable) and by applying the Crocco transformation (with the first and second partial derivatives used as new independent and dependent variables, respectively). Associated Bäcklund transformations are constructed that connect evolution equations of general form (their special cases include Burgers, Korteweg-de Vries, and Harry Dym type equations and many other nonlinear equations of mathematical physics). Transformations are indicated that reduce the order of hydrodynamic-type equations of higher orders. The generalized Calogero equation and a number of other new integrable nonlinear equations, reducible to linear equations, are considered. [ABSTRACT FROM AUTHOR]

The article presents a study that determines the longitudinal vibrations of a Rayleigh-Bishop rod. The study shows that the error caused by neglecting the effects of the transverse motion of the rod is proportional to the square of the ratio between the characteristic cross-section radius and the length of the rod. It was found that the longitudinal vibrations of the rod described by the second-order wave equation can overestimate the frequencies of the rod free of vibrations.

Highly efficient collection of the fluorescent response of silicon nanoparticles loaded in micro- and nanowaveguide fiber structures is experimentally demonstrated. Micro- and nanowaveguide channels of a fiber structure are used to optically excite nanoparticles, capture their fluorescent response, and deliver the fluorescence signal to the detector. Enhancement of the evanescent field in the modes of nanowaveguide channels improves the efficiency of optical excitation of an analyte. [ABSTRACT FROM AUTHOR]

The problem of construction of an active dynamic damper for a wide frequency band of external perturbations is considered. The problem is formulated as an H ∞ optimal control problem with the use of a degenerate integral functional not containing control explicitly. The problem is solved by applying the approach based on linear matrix inequalities. [ABSTRACT FROM AUTHOR]

We report direct spectral and temporal characterization of ultrashort ultraviolet (UV) pulses resulting from third-harmonic generation by high-intensity Ti: sapphire laser radiation in the atmosphere. The experimental technique implemented in this work enables the measurement of the pulse width and the chirp of the UV field, as well as the electron density of the plasma produced by laser pulses. The bandwidth of the third harmonic generated in our experiments by laser pulses with an initial pulse width of 45 fs supports transform-limited UV pulses as short as 30 fs. [ABSTRACT FROM AUTHOR]

Photonic-crystal fibers are shown to allow efficient spectral transformation of nanosecond laser pulses through parametric four-wave mixing and stimulated Raman scattering. Regimes providing highly efficient transformation of nanosecond laser pulses into white-light broadband radiation (supercontinuum) are identified. A strong parametric coupling between Stokes and anti-Stokes Raman sidebands around the wavelength of zero group-velocity dispersion is shown to increase the bandwidth and to improve the spectral quality of supercontinuum radiation. [ABSTRACT FROM AUTHOR]

The article discusses the study which examines the longitudinal vibrations of a rigid rod with a nonuniform cross-section with the use of the Rayleigh theory. It applies the characteristic equation of motion and the boundary conditions which is derived form Hamilton's variational principle to calculate the eigenvalues for the harmonic vibrations of the rod. Moreover, it employs the method of the separation of variables based on the exact solutions of the equations of the Rayleigh rod's motion.

A one-dimensional model is developed to describe atomic diffusion in a graphite tube atomizer for electrothermal atomic adsorption spectrometry. The underlying idea of the model is the solution of an inhomogeneous one-dimensional diffusion equation, with the diffusion coefficient being a function of temperature over the entire inhomogeneous region. An analytical solution of the problem is obtained in the form of a Green’s function. [ABSTRACT FROM AUTHOR]

The first part of the paper focuses on a detailed description of strictly pseudohyperbolic polynomials. The classes of homogeneous and nonhomogeneous polynomials are considered separately. Based on this description, a priori estimates for pseudohyperbolic PDOs with constant coefficients are obtained and the solvability of the Cauchy problem is developed. [ABSTRACT FROM AUTHOR]

Presents a research on Schwartz alternating method for elliptic boundary-value problems satisfying the maximum principle by A. S. Demidov, J. Mwambakana and A. Fedotov. Support of the Russian Federation for Basic Research on the study; Construction of solutions of the elliptic boundary problems; Application of Schwartz's idea to the problem; Theorems used in the construction of proofs for the solution of the problem.

The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in Pinus sylvestrisforest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses > 1 Gy was shown to induce formation of morphoses and depressed growth; at doses >2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear or close to linear dose-dependence relationship. The acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, moderate, and strong damage of Pinus sylvestrisL. are presented. [ABSTRACT FROM AUTHOR]

Abstract. Time-resolved dependence of the transient current through a ns laser pulse illuminated scanning tunneling microscope (STM) tip/sample gap in tunneling mode and out of tunneling range is presented. A self-designed fast STM-preamplifier (bandwidth 35 MHz) allows one to resolve the fine structure of the transient signal as well as the observation of some effects that are undetectable by using conventional low-band preamplifiers. The dependence of the threshold laser pulse intensity, which corresponds to the beginning of electron emission from tip (in non-tunneling mode), as a function of the tip/sample distance was investigated. At tip/sample distances from tunnel contact up to approximately 1 micro m a linear dependence is found. This behavior is in good agreement with the theory for field enhancement in a STM tip/sample system. In tunneling mode a ns (fast component) as well as a micro s (slow component) current response was found as a result of the laser pulse illumination. These data suggest the tip bending to be an important factor in clarifying the thermal/mechanical mechanism of laser-assisted surface nanomodification. [ABSTRACT FROM AUTHOR]

A resonant method was used to determine the ultrasonic velocity in circular plates of a ferroelectric niobate ceramic having the composition (PbBa)NbO, over the frequency range 3-9 MHz at 19 °C. The average values of the elastic constants are calculated for unpolarized samples. A study is made of the Young's modulus (the ΔE effect) and of the polarization vector P as functions of the polarizing field ℰ and the time for which this field is applied. The ΔE effect and P, which increase monotonically but nonlinearly with increasing ℰ, approach limiting values as functions of the polarization time in different manners. A comparative analysis of the ΔE and polarization curves shows that the domain structure can be thought of as slightly different from that found from a scheme proposed for its behavior during the polarization process. [ABSTRACT FROM AUTHOR]

The cascaded nonlinear-optical transformation of high-power ultrashort light pulses in an ionizing gas medium involving supercontinuum generation, followed by a frequency conversion of this radiation in the field of femtosecond laser pulses with an intensity of 1014–1015 W/cm2 has been demonstrated. Parametric four-wave mixing is shown to allow a highly efficient spectral transformation and shaping of supercontinuum radiation. The maximum efficiency of a parametric frequency conversion of femtosecond laser pulses in an ionizing gas medium achieved under the conditions of our experiments is estimated as 1%. [ABSTRACT FROM AUTHOR]