Abstract Recently, functional and potent RNA interference (RNAi) has been reported in peripheral nerve axons transfected with short-interfering RNA (siRNA). In addition, components of RNA-induced ...silencing complex (RISC) have been identified in axotomized sciatic nerve fibers as well as in regenerating dorsal root ganglia (DRG) neurons in vitro . Based on these observations, and on the fact that siRNA and microRNA (miRNA) share the same effector enzymes, we hypothesized that the endogenous miRNA biosynthetic pathway would respond to peripheral nerve injury. To answer this question, we investigated changes in the expression of miRNA biosynthetic enzymes following peripheral nerve crush injury in mice. Here, we show that several pivotal miRNA biosynthetic enzymes are expressed in an injury-regulated pattern in sciatic nerve in vivo , and in DRG axons in vitro . Moreover, the sciatic nerve lesion induced expression of mRNA-processing bodies (P-bodies), which are the local foci of mRNA degradation in DRG axons. In addition, a group of injury-regulated miRNAs was identified by miRNA microarray and validated by real-time quantitative PCR (qPCR) and in situ hybridization analyses. Taken together, our data support the hypothesis that the peripheral nerve regeneration processes may be regulated by miRNA pathway.
Submicron-grade powders of Na
Zr
(PO
)
(XO
)
compounds (hereafter referred to as NZP) and Ca
Zr
(PO
)
(XO
)
compounds (hereafter, CZP), X = Mo, W (0 ≤ x ≤ 0.5) were obtained by sol-gel synthesis. The ...compounds obtained were studied by X-ray diffraction phase analysis and electron microscopy. An increase in the W or Mo contents was shown to result in an increase in the unit cell volume of the NZP and CZP crystal lattices and in a decrease in the coherent scattering region sizes. Thermal expansion behavior at high temperatures of synthesized NZP and CZP compounds has been investigated. The dependencies of the parameters
and
on the heating temperature, as well as the temperature dependence of the crystal lattice unit cell volume
in the range from the room temperature up to 800 °C, were obtained. The dependencies of the average thermal expansion coefficient (α
) and of the volume coefficient (β) on the W and Mo contents in the compositions of NZP and CZP compounds were studied. Ceramics Na
Zr
(PO
)
(XO
)
with relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS). The increase in the W or Mo contents in the ceramics leads to an increase in the relative density of NZP and to a decrease of the optimum sintering temperature. The mean grain size in the NZP ceramics decreases with increasing W or Mo contents. The study of strength characteristics has revealed that the hardness of the NZP ceramics is greater than 5 GPa, and that the minimum fracture toughness factor was 1 MPa·m
.
This paper introduces the results of hydrolytic stability tests and radiation resistance tests of phosphate molybdates and phosphate tungstates Na
Zr
(PO
)
(XO
)
, X = Mo, W (0 ≤ x ≤ 0.5). The ...ceramics characterized by relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS) of submicron powders obtained by sol-gel synthesis. The study focused on hydrolytic resistance of the ceramics in static mode at room temperature. After 28 days of testing in distilled water, the normalized leaching rate was determined. It was found that the ceramics demonstrated high hydrolytic resistance in static mode: the normalized leaching rates for Mo- and W-containing ceramics were 31·10
and 3.36·10
g·cm
·day
, respectively. The ceramics demonstrated high resistance to irradiation with 167 MeV Xe
multiple-charged ions at fluences ranging from 1·10
to 6·10
cm
. The Mo-containing Na
Zr
(PO
)
(XO
)
ceramics were shown to have higher radiation resistance than phosphate tungstates. Radiation was shown to trigger an increase in leaching rates for W and Mo in the crystal structure of NZP ceramics.
The effect of Sc on plasticity at elevated temperatures(from 300 to 500 °C) and strain rates(from 10−3 to 10−1 s−1)of ultrafine-grained (UFG) Al–0.5%Mg–Sc alloyswas investigated. In the UFG alloys ...with 0.4% and 0.5%Sc at 500 °C and strain rate 1·10−1 s−1, high elongation to failure (~1060%) was achieved. The fractographic analysis of the fracturesin the Al–0.5%Mg alloy demonstrated the crack growth zone to occupy almost whole fracture area.The self-destruction in the crack growth zone has a viscous character.In the UFG alloys with Sc, numerous pits formed as a result of micropore junction were observed. Dependencies of dynamic grain growth (DGG) rate on the temperature and strain rate were determined. The DGG in the Al–0.5%Mg–Sc alloys was found. The kinetics of the DGG in the Al–0.5%Mg–0.2%Sc alloy was shown to be limited by mobility of junction disclinations. In the Al–0.5%Mg–0.5%Sc alloy, it is limited by mobility of oriented misfit dislocations. Al3Sc particles were shown to be possible origin of the micropore formation and of accelerated destruction of the Al–0.5%Mg–Sc alloys at high temperature deformation.
•Al–0.5Mg–Sc UFG alloys have high superplastic characteristics.•A dynamic grain growth (DGG) with the exponent k=∂lg(ḋ)/∂lg(ε̇) = 0.8–1.3.•The DGG rate in the alloys with low Sc content is governed by the mobility of the joint disclinations.•The DGG rate in the alloys with high Sc content is governed by the mobility of the orientation mismatch dislocations.•A formation of pores takes place on the Al3Sc particles in the tensile state.
In this paper we consider a new method for improving the security of fingerprint identification systems. It is based on calculating polarimetric parameters using the Mueller matrix. This method was ...tested on gelatin samples that mimic real tissue with fingerprints. We showed that proposed method can increase the reliability of fingerprint sensors. In conclusion, recommendations on the modification of the laboratory setup and on the improving of the polarimetric technology are given.
Steel degassing in continuous steel melting units Murashov, Viacheslav A.; Strogonov, Konstantin V.; Borisov, Andrey A. ...
Izvestiâ Tomskogo politehničeskogo universiteta. Inžiniring georesursov,
01/2024, Letnik:
335, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The requirements for the quality of steel products dictate the need to increase the share of evacuated steel. In addition, the growing cost of fuel, as well as the desire of society and the state to ...decarbonize various industries, including ferrous metallurgy, requires companies to reduce fuel costs and switch to more modern and cleaner technologies. Reducing the specific fuel consumption, and, accordingly, emissions, is possible due to the transition to continuous production, minimizing the cost of heating the equipment and maintaining the set temperature in the degasser during technological downtime. The article deals with the issues of steel melt degassing in U-type continuous degassers in continuous steel making units. Aim. To consider the influence of rarefaction of a gas bubble on the characteristic size over the melt, speed and time of its surfacing in a U-type degassing unit. Based on the obtained dependences, to determine the characteristic size of a vacuum chamber and energy effect of switching to a continuous vacuumization. Methods.. Results. The authors have determined a bubble characteristic size in a steel melt under vacuum of different degrees. They studied the effect of vacuum on vacuumization speed and the degassing unit dimensions. The energy effect of switching to continuous vacuumization was determined. The proposed methodology is valid for liquid media, the calculations are presented on the example of molten steel. Based on the conducted calculations, the depression influence on molten steel vacuumization was determined. The vacuum chamber dimensions, comparable with RH-vacuum cleaners presented at the market of similar productivity and quality of finished products, as well as reducing energy consumption for steel degassing in a continuous vacuum degasser, compared with the existing circulating installation, were determined.
Context . Observations of meteors in the Earth’s atmosphere offer a unique tool for determining the flux of meteoroids that are too small to be detected by direct telescopic observations. Although ...these objects are routinely observed from ground-based facilities, such as meteor and fireball networks, space-based instruments come with notable advantages and have the potential to achieve a broad and uniform exposure. Aims . In this paper, we describe the first observations of meteor events with Mini-EUSO, a very wide field-of-view telescope launched in August 2019 from the Baikonur cosmodrome and installed on board the Russian Zvezda module of the International Space Station. Mini-EUSO can map the night-time Earth in the near-UV range (290-130 nm) with a field of view equal to 44° × 44° and a spatial resolution of about 4.7 km at an altitude of 100 km from the ground. The detector saves triggered transient phenomena with a sampling frequency of 2.5 µs and 320 µs, as well as a continuous acquisition at 40.96 ms scale that is suitable for meteor observations. Methods . We designed two dedicated and complementary trigger methods, together with an analysis pipeline able to estimate the main physical parameters of the observed population of meteors, such as the duration, horizontal speed, azimuth, and absolute magnitude. To compute the absolute flux of meteors from Mini-EUSO observations, we implemented a simulation framework able to estimate the detection efficiency as a function of the meteor magnitude and the background illumination conditions. Results . The instrument detected 24 thousand meteors within the first 40 data-taking sessions from November 2019 to August 2021, for a total observation time of approximately 6 days with a limiting absolute magnitude of +6. Our estimation of the absolute flux density of meteoroids in the range of mass between 10 −5 kg to 10 −1 kg was found to be comparable to other results available in the literature. Conclusions . The results of this work prove the potential for space-based observations to increase the statistics of meteor observations achievable with instruments operating on the ground. The slope of the mass distribution of meteoroids sampled with Mini-EUSO suggests a mass index of either s = 2.09 ± 0.02 or s = 2.31 ± 0.03, according to two different methodologies for the computation of the pre-atmospheric mass starting from the luminosity of each event.
This article describes the development of a method for improving the security of fingerprint identification systems. It is based on the calculation of the polarimetric parameters of biological tissue ...using Mueller matrices. This method was tested on samples made from gelatin, which have a copy of the papillary pattern and mimic real tissue. It is shown that the proposed method is promising for solving the problem of increasing the security of fingerprint sensors from breaking using finger models. In conclusion, recommendations are given for improving the polarimetric method.
The structure, microstructure, coefficient of thermal expansion (CTE), and mechanical properties of Na1+2xZr2−xCox(PO4)3 ceramics (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were studied. Na1+2xZr2−xCox(PO4)3 ...submicron powders with the NaZr2(PO4)3 structure (NZP, kosnarite type) were obtained by the solid-phase method. The starting reagents (NaNO3, ZrOCl2·8H2O, NH4H2PO4, CoCl2·6H2O, ethanol) were mixed with the addition of ethyl alcohol. The resulting mixtures were annealed at 600 °C (20 h) and 700 °C (20 h). The obtained phosphates crystallized in the expected structure of the NaZr2(PO4)3 type (trigonal system, space group R3¯c). Thermal expansion of the powders was studied with high-temperature X-ray diffraction at temperatures ranging from 25 to 700 °C. CTEs were calculated, and their dependence on the cobalt content was analyzed. Na1+2xZr2−xCox(PO4)3 ceramics with high relative density (93.67–99.70%) were obtained by Spark Plasma Sintering (SPS). Ceramics poor in cobalt (x = 0.1) were found to have a high relative density (98.87%) and a uniform fine-grained microstructure with a grain size of 0.5–1 µm. Bigger cobalt content leads to a smaller relative density of ceramics. During the sintering of ceramics with high cobalt content, anomalous grain growth was observed. The powder compaction rate was shown to be determined by creep and diffusion intensity in the Na1+2xZr2−xCox(PO4)3 crystal lattice. SPS activation energy in ceramics increased as the cobalt content grew. The microhardness and fracture toughness of ceramics did not depend on their cobalt content.
The results of investigations of spark plasma sintering (SPS) kinetics of tungsten carbide nanopowders with different Co content (0.3, 0.6, and 1.0 wt%) and graphite (0.3 and 0.5 wt%) are described. ...The α-WC nanopowders were obtained by direct current (DC) arc plasma synthesis followed by annealing in hydrogen. Ultrathin Co layers were deposited onto the nanoparticles by a chemical-metallurgical method from a salt solution. The excess carbon was introduced by mixing the WC-Co powders with graphite that resulted in the increase of the oxygen concentration. The carbonization of the tungsten carbide hard alloy specimens was demonstrated to take place in SPS. It resulted in different phase compositions, along with hardness within surface and central layers of sintered ceramic specimens. The effects of the initial particle size, of the Co concentration, and of the graphite one on the stages of the SPS of the ultra-low Co hard alloys were studied. The specimens with uniform fine-grained structure, increased density, and improved mechanical characteristics were obtained. The hardness Hv for WC-0.6%Co-0.3%C hard alloy with averaged grain size 1.0–1.5 μm was 20.2–20.5 GPa at the minimum fracture toughness coefficient KIC = 9.2–10.4 MPa m1/2.
•Intense sintering of the WC-Co nanoparticles at Stage II takes place via the creep of cobalt according to Coble.•The sintering of the particles at Stage III-1 goes via the creep, the intensity of which depends on the volume diffusion.•The sintering of the particles at Stage III-2 goes via the diffusion of carbon along the grain boundaries in WC carbide.•The positive effect of graphite is compensated by an increased oxygen concentration at the surfaces of the WC-Co particles.•The specimens have high hardness (20.2–20.5 GPa) and increased fracture toughness (9.2–10.4 MPa m1/2).
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