Abstract
In this work, we compared the samples obtained by additive technologies. Samples for the study were printed on two different printers using similar DMLS and DMLM technologies. Printing was ...carried out according to the CAD model data. The printing was performed using the manufacturer’s recommended print settings. For printing, we used powders recommended by the manufacturer for these printer models. In the course of the work, the structure and roughness parameters in the initial state were compared. The heat treatment mode was selected. The effect of vacuum annealing on the structure as well as mechanical properties such as uniaxial tension, KCU and fatigue strength was investigated. Based on the results of the work, a conclusion was made about the improvement of 3D printing, as a result of which the products obtained using additive technologies after heat treatment are not inferior in properties to products obtained using industrial technology from a similar alloy.
The biota from the Middle Permian copper-bearing sandstones of the South Urals is comprehensively assessed. Paleofloristic data are recorded from the most important localities. The terrestrial ...tetrapod assemblage from the copper-bearing sandstones of the South Urals (based on the Kargaly Copper Mines, Orenburg Region, Russia) is described. A paleogeographic and paleoenvironmental reconstruction is proposed for the depositional settings of the terrestrial biota localities in the copper-bearing sandstones of the Cis-Urals. It is suggested that these localities were formed in high-energy settings, and result from increased runoff of siliciclastics from the western slope of the Paleourals.
We have studied the interaction of polycrystalline samples of lithium nitride with metallic lithium. We have found that upon contact, metallic lithium spontaneously dissolves into polycrystalline ...lithium nitride samples. Spontaneous penetration of metallic lithium into polycrystalline samples of lithium nitride leads to the appearance of electronic conductivity and the formation of mixed ion-electronic conductors.
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•Interaction of metallic lithium and polycrystalline lithium nitride is studied.•Metallic lithium spontaneously penetrates in a pellet of Li3N.•Penetration of lithium in Li3N leads to short circuit of the cell Li │ Li3N │ Li.•Penetration of Li in Li3N leads to the formation of mixed ion-electronic conductors.
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•Magnetic-field dependent photoluminescence of NV− centers in diamonds is modelled.•A calculation method is proposed to account for coherent polarization transfer.•The method ...reproduces sharp dips from avoided crossings in the field dependence.•Groups of such dips, LAC lines, can be modelled theoretically.
We propose an efficient method for calculating level anti-crossing spectra (LAC spectra) of interacting paramagnetic defect centers in crystals. By LAC spectra we mean the magnetic field dependence of the photoluminescence intensity of paramagnetic color centers: such field dependences often exhibit sharp features, such as peaks or dips, originating from LACs in the spin system. Our approach takes into account the electronic Zeeman interaction with the external magnetic field, dipole-dipole interaction of paramagnetic centers, hyperfine coupling of paramagnetic defects to magnetic nuclei and zero-field splitting. By using this method, not only can we obtain the positions of lines in LAC spectra, but also reproduce their shapes as well as the relative amplitudes of different lines. As a striking example, we present a calculation of LAC spectra in diamond crystals containing negatively charged NV centers.
A determination of the composition of primary cosmic rays in the energy range between 1 and 1000 PeV is an important objective in studies of processes involving the formation and propagation of ...cosmic rays. On the basis of experience gained in exploiting the SPHERE-2 balloon-based facility, a SPHERE-3 facility, which possesses a wider aperture and a better optical resolution, is developed. The current status of work on designing this facility is presented.
The major challenge in optical ceramic technology is the quality of the starting precursor powder for pressing, which is a key element in the optical ceramic industry. One express and helpful ...technique for the estimation of powder quality is the estimation of the quantum yield of up-conversion luminescence; therefore precursor powders must exhibit high values of up-conversion luminescence efficiency. Single-phase solid solutions based on strontium fluoride doped with ytterbium and erbium were synthesised by co-precipitation from aqueous solutions using sodium fluoride, potassium fluoride and ammonium fluoride as fluorinating agents. The asymmetry of X-ray diffraction maxima indicated the presence of two populations of particles with the same chemical composition. The processes of extended flat particles’ growth from smaller particles with a spherical morphology were revealed with transmission electron microscopy and X-ray diffraction. It was shown that when sodium fluoride and potassium fluoride were used they entered the crystal structure in an amount of 3–4 mol% and 1 mol%, respectively. The introduction of sodium and potassium led to an improvement in the sintering ability of particles and a significant increase in the particle size in ceramics by a factor of 5 and 2, respectively, in comparison with the use of ammonium fluoride. The quantum yield values of up-conversion luminescence at the level of tenths of a percent at a low pump power density of 0.1 W cm−2 were very high, which suggests that these synthetic techniques can be considered to be promising for the preparation of precursors of laser ceramics.
The mode of continuous spinning detonation (CSD) combustion of hydrogen in the annular combustor of a model of a hydrogen-fueled detonation ramjet under conditions of approach air stream Mach number ...5.7 and stagnation temperature 1500 K is registered experimentally in a short-duration (pulsed) wind tunnel at the overall air-to-hydrogen equivalence ratio (ER) ranging from 0.7 to 1.4. The maximum values of thrust and specific impulse of the ramjet model are attained at ER = 1.25 and are estimated as 1550 N and 3300 s, respectively. At 1.4 < ER < 1.6, the mode of longitudinally pulsating detonation (LPD) combustion is registered with somewhat lower values of thrust and specific impulse.
•Hydrogen-fueled detonation ramjet is tested in wind tunnel at M5.7 and Tst = 1500 K.•1-m long 0.3-m i.d. ramjet comprises M5 air intake and expanding annular combustor.•Stable spinning detonation mode is obtained at fuel-to-air ratios from 0.7 to 1.4.•Stable pulsed detonation mode is obtained at fuel-to-air ratios from 1.4 to 1.6.•Maximum fuel-based specific impulse above 3000 s and thrust above 1500 N are measured.
Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a ...disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/−OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/−OCl, 10 μM HOCl/−OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BβMet367, γMet264, and γMet94, identified in 10 μM HOCl/–OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress.
•Fibrinogen treated with 10 μM HOCl/−OCl did not lose the functional activity.•Methionines in fibrinogen were the main target for 10 μM HOCl/−OCl.•Some of Met residues in the fibrinogen structure operate as endogenous antioxidants.•The fibrinogen structure is supposed to be adapted to the action of ROS.
Evolution of steam and gas plume generation on the surface of the irradiated metal was investigated experimentally. It is shown that on using GOR-100M operating in free oscillating regime the form of ...a crater developed on being in water the irradiated target surface differs in essence from the topography of the crater developed on processing by laser pulse with the same parameters of the analogical target surrounded by air on normal pressure (105 Pa). It is pointed that the substantial difference of the forms of crater surfaces developed as a result of processing of the identical targets by laser pulses with the identical parameters of the identical targets being in water or air determines by principally different character of plasma and steam and gas mixture flow in the mentioned cases.
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