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The calculation of the three-dimensional structure of crystals of fifteen polymorphic varieties of graphene functionalized with fluorine was carried out by the atom-atom potential method. The energ...

In this paper the results of the studies of reduced activation ferritic-martensitic steel EK-181 (Rusfer-EK-181, Fe–12 Cr–2 W–V–Ta–B) developed in Russia (Bochvar High-Technology Scientific Research Institute of Inorganic Materials—VNIINM) as a structural material for application as the core components of fast neutron, fusion, and hybrid reactors are summarized. Various aspects of hydrogen interaction with Rusfer steel, primarily retention, diffusion, and the effect of various defects on retention, are considered.

We consider a specific version of the authors’ approach to the synthesis of bases of discrete orthogonal transforms (DOTs). The approach takes into account the relation between the structure of basis functions of a transform and the existence of a certain numeral system on the (multidimensional) index set of an input signal. In contrast to Chernov’s prototype paper “Discrete orthogonal transforms with bases generated by self-similar sequences” (2018), which was concerned with DOTs associated with irredundant numeral systems (where each index of the input signal has a unique representation in a chosen numeral system), in the present paper we study the case of the so-called complete numeral systems. In this case, there is no bijection between the set of input indices of DOTs and the set of their digital representations. Potentially, such statements of applied problems naturally appear in image recognition, artificial intelligence, theory of formal languages, mathematical programming, and other areas where the analyzed objects are characterized by many heterogeneous attributes, which can be quantitative, qualitative, and mixed. There may be several copies of each object, and the copies may have inconsistent descriptions, which must be considered and analyzed as a whole. Such objects with many attributes can be represented as multisets (“sets with repetitions”). Since discrete spectral analysis is a basic tool for solving the described problems in the classical “multiple” interpretation of objects, we try to extend some ideas and methods of spectral analysis to the case of multiset objects.

Competitive economic indicators for fast-neuron power reactors can be achieved with high coefficients of fuel burnout, which requires remarkable enhancement of radiation resistance of fuel pin claddings. Nowadays, low-activation vanadium alloys are projected as promising fuel cladding materials in view of their high radiation and thermal resistance in wide temperature and damage dose ranges. Neutron diffraction and small-angle neutron scattering are employed to study the microstructure of the V-4Ti-4Cr alloy subjected to irradiation with fast neutrons in the fluence range up to 1·1020 cm−2. Minor phases precipitated in the system are structurally characterized. The applicability and prospects of neutron diffraction methods in terms of studying the radiation behavior of this kind of alloys are shown.

Ferritic-martensitic steel with rapid decay of activity EK-181 (Rusfer-EK-181, Fe – 12 Cr – 2 W – V – Ta – B) was developed in Russia (A.A. Bochvar Institute) as a structural material for use in the active zones of fast neutron reactors, as well as in thermonuclear and hybrid reactors. The team of authors has been studying various aspects of hydrogen interaction with Rusfer steel for a number of years, primarily retention, diffusion, and the effect of various damages on capture. The paper summarizes the results of the research performed by the authors.

Using the methods of scanning and transmission electron microscopy, a study is performed of the influence of high-temperature annealing on the parameters of structural-phase states of low-activation alloys of the V–Me(Cr, W)–Zr system after different modes of thermomechanical treatments. By the active tensile loading at different temperatures the effect of the treatment regimes and final annealing temperatures on the strength and plasticity characteristics is investigated. The main factors determining the thermal stability of plasticity of the structural-phase state and the mechanical properties of these alloys are discussed.

The elastic (Young’s) modulus and relaxation properties (amplitude-independent internal friction) of bcc metals and alloys (vanadium, V–4Cr–4Ti, V–W–Cr, and V–Ta–Cr—Zr alloys) have been studied in the temperature range of 25–400°С by means of dynamic mechanical spectroscopy within a low-frequency range (0.5–30.0 Hz). No carbon in vanadium and V–W–Cr alloy in solid-solution state is revealed. In the case of vanadium and V–W–Cr alloy, the solid-solution concentrations of oxygen and nitrogen and the diffusion characteristics thereof (diffusion activation energy, characteristic relaxation time, and the preexponential factor in the diffusion equation) have been determined. In the case of V–4Cr–4Ti alloy, carbon, oxygen, and nitrogen solid solutions have not been observed. In V–Ta–Cr–Zr alloy, the solid-solution concentrations of interstitial atoms (C, O, N) are substantially lower than those in vanadium and V–W–Cr alloy. The values of elastic modulus in vanadium alloys can be either higher or lower than the elastic modulus inherent in vanadium depending on type of alloy (alloying) and on temperature. The V–4Ti–4Cr alloy exhibits the smallest value of the elastic modulus among all the materials under study. The temperature curves of the elastic (Young’s) modulus for the studied materials exhibit no features, except for a slight local relaxation of the Young’s modulus in the case of vanadium and V–W–Cr alloy in the temperature range of the relaxation peaks.

The results of an investigation of the influence of microstructure on the oxidation rate of an alloy of the V–Cr–W–Zr system investigated under the conditions of its heat treatment in air are presented. It is shown that the formation of the defect state in the alloy favors an increase in the constant and rate of oxidation. The maximum microstructure effects on the oxidation processes are observed during short treatment durations.

An investigation of the features of structural-phase transformations during heating and cooling of the lowactivation 12%-chromium ferritic-martensitic steel EK-181 (Fe–12Cr–2W–V–Ta–B) is performed in the range of temperatures from 30 to 1100°C by the methods of high-temperature X-ray diffraction analysis (XRD) in situ. The critical points of an (α →γ) - transformation (Ас1 ≈ 850°С, Ас3 ≈ 950°С) in the course of steel heating and the temperature interval (910–890°C) of the diffusion-induced transformation of the austenite →α-ferrite type under cooling are determined. It is shown that the position of these points changes depending on the method (XRD or differential scanning calorimetry) of their identification, which is attributed to the differences in their heating-cooling rates. During heating in the range of temperatures of 830–875°C, a significant increase in the volume fraction of М23С6 carbides is observed. Further temperature increase up to 1000–1100°C leads to their complete dissolution. In the course of cooling of the steel specimens from 1100 to 30°C, there is no carbide particle precipitation.

Железодефицитная анемия — полиэтиологичное заболевание, развитие которого связано с дефицитом железа в организме из-за нарушения поступления, усвоения или повышенных потерь данного микроэлемента, характеризующееся микроцитозом и гипохромной анемией. В практическом руководстве подробно описывается этиология, лабораторная и инструментальная диагностика, тактика ведения пациентов в различных клинических ситуациях. Практическое руководство предназначено для специалистов практического здравоохранения, оказывающих первичную медико-санитарную помощь, в том числе врачей-терапевтов, врачей общей практики (семейной медицины), кардиологов, гастроэнтерологов и других специалистов, оказывающих помощь пациентам с железодефицитной анемией.

The effect of high-temperature thermomechanical treatment (HTMT) with deformation in the austenitic region on the regularities of low-temperature embrittlement of low-activation 12% chromium ferritic-martensitic steel EK-181 is investigated in comparison with traditional heat treatment (THT) during dynamic tests on impact toughness and static tests on uniaxial tension in the range from -196 to 20 degrees C. It is found out that HTMT increases both the tensile strength properties of steel and its impact toughness. At the same time, the temperature of its ductile-brittle transition does not practically change relative to the THT. It is observed that the features of steel microstructure after HTMT, the formation of delaminations (during fracture of Charpy-type specimens) in the planes parallel to the plane of hot rolling, have a positive effect on its impact toughness.

Vanadium alloys are considered as candidate structural materials for thermonuclear fusion reactors (FR) and fast neutron reactors. Some properties of vanadium alloys are especially attractive for FR: fast decay of induced activity, durability in liquid lithium, high temperature strength. At the same time vanadium alloys absorb and dissolve hydrogen isotopes, and hydrogen fluxes through them are quite high. Hydrogen affects on plasticity of vanadium alloys and significantly decreases it at high concentrations. This should be taken into account considering the possibility of vanadium alloys usage as the material of fusion and fission reactors, especially if these materials are assumed to be in contact with radioactive tritium. In this work deuterium permeation through V-4Cr-4Ti alloy with deposited AlN coatings on an adhesion sublayer of Al on it was investigated. Deposition of insulating coatings on blanket structural materials allows to reduce the influence of strong magnetic fields of the tokamak on liquid metal coolant (e.g., lithium flow). It has been demonstrated that the coatings also reduce deuterium permeating fluxes by several times in comparison with V-4Cr-4Ti covered with natural oxide film and about 3–4 orders of magnitude in comparison with literature data for vanadium and its alloys with oxide-free surfaces. Taking into account thermomechanical and insulating properties, moderate swelling under neutron irradiation, thermal conductivity an order of magnitude higher than that of oxide coatings AlN coatings seem to be attractive for application in FR both as insulating and as a coating for hydrogen permeability suppression.

The data on the influence of thermomechanical treatment modes on characteristics of the short-term strength and plasticity of vanadium alloys of different systems (V–Ti–Cr, V–Zr–C, V–Cr–Zr, V–Cr–W–Zr, V–Cr–Ta–Zr) are generalized. It is shown that an application of a modified mode ensures an appreciable increase in the short-term strength at room temperature and elevated temperatures, while maintaining an acceptable plasticity. The principal mechanisms of metastable carbide transformations into oxicarbonitride phase particles with phase-forming elements participation and the conditions of their realization are discussed.

Molecular dynamics simulations have been performed to investigate the defect structure evolution at different development stages of atomic displacement cascades with energies up to 50 keV in iron crystallites in the temperature range from 300 to 900 K. The number of surviving radiation defects in iron crystallites increases according to a power law with increasing energy of the primary knocked-on atom. An increase in the crystallite temperature slightly increases the number of surviving defects. It is found that atomic displacement cascades can lead to radiation-induced grain boundary migration due to the melting and crystallization of the radiation-damaged region. The crystallographic orientation of the irradiated free surface strongly affects the radiation damage behavior. Craters with adatom islands are formed on the (111) free surface, and vacancy loops are nucleated in the (110) near-surface region. Point defects aggregate into clusters of various types during the evolution of atomic displacement cascades. It is shown that the number of surviving point defect clusters can significantly decrease under uniaxial elastic compression.

The influence of thermomechanical treatments, including low-temperature and subsequent warm deformation, on the microstructure and mechanical properties of an austenitic reactor steel (Russian Grade EK-164) is investigated. It is shown that low-temperature plastic deformation (after cooling in liquid nitrogen) gives rise to the formation of a high density of microtwins. In the course of subsequent warm deformation (at T = 600 or 700° C) the localized deformation bands, having an internal fragmented nano-sized structure, propagate in the microtwin structure. It is demonstrated that these microstructure characteristics ensure a multiple (by 3–5 factors) yield strength increase at 20 and 650°C.

The effect of electron and neutron irradiation and post-radiation annealing on the properties of 12% chromium ferritic-martensitic low-activated EK-181 steel treated under various heat conditions has been studied using transmission electron microscopy and resistometry. Both electron and neutron irradiation of EK-181 steel in the 300–340 K temperature range result in radiation-induced solid solution separation during all subsequent heat treatments. Isochronous annealing in the 300–500 K temperature range causes additional solid solution separation. Nanoclusters of point defects with a size from 1.5 to 5 nm and a concentration of 5 × 1016 cm–3 have been observed after neutron irradiation at a fluence of (1–5) × 1019 cm–2. Thermal homogenization of the solid solution occurs above 650 K.

The results of a study of features of the surface scale growth on the V–Cr–Ta–Zr vanadium alloy specimens during short-term oxidation in air are presented. It is shown that in the initial oxidation stages, irrespective of the specimen microstructure, the surface scale growth rate can be an order of magnitude higher than that in the course of long-term treatment. It is found out that the scale is characterized by open porosity formed as a result of sticking of the V2O5 plate-like flakes together. It is suggested that a decrease in the oxidation rate is a consequence of an increase in the surface scale thickness, resulting in a slower supply of oxygen to the specimen surface on which the processes of scale nucleation and growth, as well as diffusion saturation of the subsurface vanadium-alloy layer with oxygen are observed.

For the first time it is shown that the development of resistance to melittin in Acholeplasma laidlawii, a mycoplasma that is widely spread in nature and that is the main contaminant of cell cultures and vaccines, is associated with significant changes in the genomic profile, in cellular and vesicular proteomes, as well as in virulence.

The features of the microstructure, structural-phase transformations, and regularities of the change in the short-term mechanical properties of low-activation 12% chromium ferritic-martensitic steel EK-181 together with the features of its plastic deformation and fracture by the active stretching method in a temperature range from–196 to 720°C are investigated. The high efficiency of dispersive hardening by nanoscale particles V(C, N) provides a weak temperature dependence of the steel strength properties with increasing temperature from 20 to 450°C. A significant increase in the temperature dependence of the steel yield strength is observed in the ductile-to-brittle transition interval (below T ~ 20°C). In a temperature range from–196 to 720°С, the change in the plasticity regularities and the mode of steel fracture are closely related to the features of the temperature dependence of the yield stress and ultimate tensile strength. In the region of temperatures above 0°С (up to ~450°С), these features are determined by the weak temperature dependence of the value of dispersion hardening by nanoscale vanadium carbonitride particles; in the temperature range below 0°С, they are determined by a strong temperature dependence of the thermally activated mobility of dislocations in the crystalline relief (the Peierls barrier, solid solution of impurities).

Thermal stability of the microstructure and high-temperature mechanical properties of the low-activate 12% Cr ferritic-martensitic steel EK-181 are studied at temperatures from 700 to 800°C. It is shown that after traditional heat treatment and annealing at temperatures from 700 to 800°C, the ferritic-martensitic structure of the steel is retained and the density of coarse-dispersed M23C6 particles is increased. After annealing at T = 800°C, the initial recrystallization stages with the formation of new submicrocrystalline ferritic grains are detected. An increase in the annealing temperature from 700 to 800°C leads to a decrease in the strength properties of the steel. Wherein, the character of the temperature dependence of the strength at temperatures from 700 to 800°C is similar to that observed at lower temperatures (from 500 to 700°C).

Based on the 1H relaxation of transverse nuclear magnetization of triblock-copolymer Pluronic F-127 in D2O, we proposed a model of the associated pluronic structure in which the polyethylene oxide ...

Static and fatigue strength at room temperature under conditions of repeated stretching of lowactivated ferrite-martensite 12% chromium steels EK-181 (Fe–12Cr–2W–V–Ta heat treatment + aging in lead at 600°C, 3000 h), EP-823 (Fe–12Cr–W–V–Ni–Mo–Nb, annealed condition), and alloy V–4Ti–4Cr (heat treatment + aging in lead at 600°C, 3000 h) were studied. It was shown that for materials there is straight-line dependence between the level of rupture resistance values and fatigue strength. The maximum fatigue limit of 600 MPa appears in steel EK-181 after a standard heat treatment and aging in lead at 600°C, 3000 h, and the minimal one of 300 MPa is observed in vanadium and V–4Ti–4Cr alloys. The fatigue failure mechanism is predominately of ductile character for all materials studied. The fatigue cracking originates near the surface and in some cases clustering of nonmetallic inclusions is the place of origin. The fatigue crack propagation is related to formation of a typical striation relief. Significant distinctions in the fracture surface relief of specimens after standard heat treatment and aging in liquid lead are not observed.

The paper proposes a new method for calculating Fourier-Galois transforms (number-theoretical transforms), which are a modular analog of the discrete Fourier transform. A number of specific problems related to the calculation of transforms in a finite field can be solved by representing the elements of these fields in “exotic” number systems, which are reductions of the canonical number systems proposed by I. Katai when mapping the corresponding ring of an integer quadratic field into a field of the prime residue classes modulo. The case of binary reduced number systems is studied in detail. It is proved that such number systems exist for any prime number.