Unloading of slow-twitch muscles results in increased muscle fatigue and the mechanisms of this effect are poorly studied. We aimed to analyze the role of high-energy phosphates accumulation during ...the first week of rat hindlimb suspension plays in a fiber-type phenotype shift towards fast-type fatigable muscle fibers. Male Wistar rats were divided into 3 groups (n = 8): C - vivarium control; 7HS - 7-day hindlimb suspension; 7HB - 7-day hindlimb suspension with intraperitoneal injection of beta-guanidine propionic acid (β-GPA, 400 mg/kg b w). β‐GPA is a competitive inhibitor of creatine kinase and it reduces concentrations of ATP and phosphocreatine. In the 7HB group, β-GPA treatment protected a slow-type signaling network in an unloaded soleus muscle, including MOTS-C, AMPK, PGC1 α and micro-RNA-499. These signaling effects resulted in a preserved soleus muscle fatigue resistance, slow-type muscle fibers percentage and mitochondrial DNA copy number under muscle unloading.
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•Unloading leads to increased muscleweakness.•Male rats were treated with beta-GPA during 7 -days of unloading.•beta-GPA prevented the unloading-induced muscle fatigue.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The procedure for in situ TEM measurements of bonding strength (adhesion) between diamond and the metal matrix using a Hysitron PI 95 TEM Picoindenter holder for mechanical tests and ...Push-to-Pull devices was proposed. For tensile tests, dog-bone shaped lamellae 280–330 nm thick and ~ 2.5 µm long were used as objects of study. The lamellae were manufactured using the focused ion beam technology from the metal–diamond interface of diamond-containing composite material with a single-phase binder made of Fe–Co–Ni alloy. The experimentally determined bonding strength was 110 MPa.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The present paper gives a detailed description of structural changes in three types of MoCN–Ag coatings (Mo51C15N27Ag7, Mo40C31N23Ag6, and Mo43C14N40Ag3) during dynamic temperature ramp tribological ...tests with particular emphasis on the analysis of wear products to identify adaptive friction mechanisms in the temperature range between 250 and 550°C. Thorough structural characterization using high-temperature XRD, SEM, TEM, GDOES, and Raman spectroscopy provided evidence of various tribo-chemical reactions in the zone of tribological contact affecting lubrication. The coating lubrication in the temperature range between 100 and 400°C was observed to be different. Unlike Mo51C15N27Ag7 coating whose friction coefficient monotonously increased with increasing temperature from 25 to 250°C, the Mo40C31N23Ag6 coating demonstrated low values of friction coefficient up to 250°C due to the tribo-activated formation of carbon-based fibers normal to the sliding direction. The good lubrication of the Mo43C14N40Ag3 coating at elevated temperatures was attributed to almost no wear due to its high hardness and to the formation of a thin tribo-activated MoO3 film at 350°C. However, complete oxidation of the wear track at 400°C resulted in intensive abrasion wear and high friction. Above 400°C, all coatings demonstrated similar values of friction coefficient irrespective of phase composition (melt, Ag6Mo10O33, or MoO3+Ag).
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•Low-friction coatings for broad temperature range•Various tribo-chemical reactions in the tribological contact zones at elevated temperatures•Low friction coefficients due to tribo-activated formation of carbon-based fibers•Good lubrication of MoCN–Ag coatings at elevated temperatures due to almost no wear•Tribo-activated formation of silver molybdate rods with turbostratic structure at 550°C
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hard-yet-tough coatings are required to protect structural materials, cutting, stamping, and forging tools operating under harsh conditions that combine wear, corrosion, and elevated temperatures. To ...reveal the high potential of niobium (Nb) as an additive to binary Ti-based coatings, single-layer and multilayer Nb-doped TiC coatings were obtained by pulsed arc evaporation (PAE), electro-spark deposition (ESD) in vacuum, and combination of these methods. Structure, elemental, and phase compositions were studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, tribological properties, and electrochemical behavior in 3.5% NaCl solution. Tribological tests were carried out under various conditions, such as applied load (5 and 10 N), medium (air and 3.5% NaCl solution), and counterpart material (Al2O3 and 440C steel). Thin PAE coating (1.8 μm thick) consisted of 2–5 × 50–100 nm (Ti,Nb)C crystallites, elongated in direction of the coating growth, embedded in an amorphous matrix (75% sp2 + 25% sp3-hybridized carbon). Thick ESD coating (20 μm) contained TiC grains uniformly distributed in an eutectic Fe(Co)-Fe2(Ti,Nb) matrix with a minor content of Ti-Ni and γ-Fe phases. The single-layer PAE coating demonstrated superior tribological performance both in air and 3.5% NaCl solution, as well as high oxidation resistance during tribocorrosion tests. As a top layer in the PAE/ESD coating, it provided wear protection of less wear-resistant ESD sublayer. It is assumed that the main benefit of the ESD sublayer in the PAE/ESD coating may be that it provides enhanced toughness and high thickness, which prevents a soft substrate from high stress-induced plastic deformation.
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•TiNbC coatings by pulsed arc evaporation (PAE) and electro-spark deposition (ESD)•PAE coatings consist of elongated TiNbC crystallites in a-C matrix (sp2 + 25% sp3)•PAE coatings show superior tribological performance in air and 3.5% NaCl solution•PAE layer provides substantial wear protection of less wear-resistant ESD sublayer
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The problem of motion dynamics of two particles in a supersonic flow behind an incident shock wave was considered numerically and experimentally. The experiments were carried out in a shock tube. ...High-speed shadowgraphy with a laser stroboscope light source was used. The mathematical model was based on the two-dimensional Euler equations. The original, highly scalable, parallel algorithm of the Cartesian grid method for simulation of flows with shock waves in areas with changing geometry was used in the numerical simulations. The main stages of the process were described from the point of view of the realized shock-wave configurations. The effect of changing two modes of supersonic flow around two particles was obtained. The experimental and simulated flow patterns and dynamics of particle motion correlate well.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Mo-Si-B, Mo-Zr-Si-B, and Mo-Hf-Si-B coatings were deposited by magnetron sputtering of the MoSi2-MoB, MoSi2-MoB-ZrB2 and MoSi2-MoB-HfB2 targets. The composition and structure of coatings were ...investigated by glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Mechanical properties were measured by nanoindentation method. The short-time oxidation resistance of coatings was evaluated at temperatures of 1100, 1300, and 1500 °C. The results showed that all coatings deposited onto alumina substrates were characterized by a dense columnar structure. Mo-Si-B coatings contained phases of hexagonal h-MoSi2 and amorphous a-MoB. With the addition of Zr and Hf, an increase in the lattice parameter and a decrease in the grain size of h-MoSi2 by 50 and 25%, respectively, were observed. The base Mo-Si-B coating had a high hardness of 30 GPa. The introduction of Zr and Hf led to a decrease in hardness by 24 and 20%, respectively. The Mo-Si-B coating was characterized by a minimal oxidation depth (<10 nm) at 1100 °C and 1300 °C, but a network of cracks that penetrated to the substrate was formed. Cracks on the surface of the Mo-Zr-Si-B and Mo-Hf-Si-B coatings were not observed; the formation of oxide layers, 0.3–2.0 μm thick, was revealed. The oxidation resistance of coatings at temperature of 1500 °C increased in direction Mo-Si-B → Mo-Hf-Si-B → Mo-Zr-Si-B. The best results for the Mo-Zr-Si-B coating were associated with a smaller grain size, higher thermal stability, and the formation of a protective layer based on SiO2 with the inclusion of ZrO2 crystallites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Protective Zr-Si-B-N coatings were deposited by magnetron sputtering of the 66%ZrB2 + 26%ZrSi2 + 6%Si + 2%ZrO2 composite target at varied partial pressure of nitrogen. The coatings were studied in ...terms of structure, optical characteristics, mechanical and tribological properties, cyclic impact and oxidation resistance. All the coatings were characterized by a dense and defect-free structure, without any well-defined columnar elements. The base of the non-reactive Zr-Si-B coatings was the hexagonal ZrB2 phase with the crystallite size of about 20 nm. Nitrogen doping led to grain size reduction and coating amorphization. An increase in the nitrogen concentration leads to the formation of an amorphous phase а-Si(Zr)BN. The high content of nonmetallic bonds ensured the high transmittance (up to 90 %) in the visible and infrared spectral ranges for the coatings characterized by the maximum nitrogen content. Hardness of the coatings deposited in working gas Ar and Ar + 15%N2 was ~20 GPa. When the coatings were deposited in an atmosphere of pure nitrogen, this value was ≤15 GPa. Due to structure modification as well as increasing elastic recovery and elastic strain to failure, nitrogen doping of the coatings contributed to reduction of the friction coefficient and increased wear resistance under sliding friction conditions and cyclic impact loading. High-temperature oxidation resistance and thermal stability of the coatings decreased after nitrogen doping. The Zr-Si-B coating exhibited the highest oxidation resistance and withstood long-term exposure to 1200 °C and short-term exposure to 1400 °C. The high protective properties were ensured by formation of the silica-based surface protective layer with zirconia crystallites dispersed in it.
•The Zr-Si-B-N coating with the maximum N content had a high transmittance of ~90 %.•The increase in N2 flow rate led to a decrease friction coefficient and wear rate.•The coatings, obtained in Ar and Ar + 15%N2, retain protective properties at 1200 °C.•Zr-Si-B coating had the best oxidation resistance at 1400 °С.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A vascular system in plants is a product of aromorphosis that enabled them to colonize land because it delivers water, mineral and organic compounds to plant organs and provides effective ...communications between organs and mechanical support. Vascular system development is a common object of fundamental research in plant development biology. In the model plant Arabidopsis thaliana, early stages of vascular tissue formation in the root are a bright example of the self-organization of a bisymmetric (having two planes of symmetry) pattern of hormone distribution, which determines vascular cell fates. In the root, vascular tissue development comprises four stages: (1) specification of progenitor cells for the provascular meristem in early embryonic stages, (2) the growth and patterning of the embryo provascular meristem, (3) postembryonic maintenance of the cell identity in the vascular tissue initials within the root apical meristem, and (4) differentiation of their descendants. Although the anatomical details of A. thaliana root vasculature development have long been known and described in detail, our knowledge of the underlying molecular and genetic mechanisms remains limited. In recent years, several important advances have been made, shedding light on the regulation of the earliest events in provascular cells specification. In this review, we summarize the latest data on the molecular and genetic mechanisms of vascular tissue patterning in A. thaliana root. The first part of the review describes the root vasculature ontogeny, and the second reconstructs the sequence of regulatory events that underlie this histogenesis and determine the development of the progenitors of the vascular initials in the embryo and organization of vascular initials in the seedling root.
The effect of added Mo, WC, and ZrO2 nanopowders on the graphitization of diamond grains in metal–matrix composites was studied by Raman spectroscopy. In the presence of Mo and ZrO2 nanoadditives, ...the graphitization process was found to get intensified. But the addition of WC nanopowder was found to suppress the graphitization by 25–30%. This can be expected to improve the adhesion of binder to diamond grains and hence the service life of related cutting tools.
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•Nano alloying of Fe-based binders affects the graphitization of diamond grains.•ZrO2 and Mo nanoparticles promote the graphitization of diamond grains.•WC nanoparticles suppress the graphitization process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The community of cultured pseudomonads isolated from clayey organogenic deposits of the Mramornaya Cave (Primorskii krai) was investigated. The bacterial strains isolated in this work were ...eurythermal and psychrotolerant. Their taxonomic position was determined by high-throughput sequencing of the 16S rRNA gene fragments. Members of the genus
Pseudomonas
are known to inhabit all the ecological niches on Earth and, accordingly, have a wide range of adaptive functions. Microscopic techniques were used to establish the changes in the character of motility and the cell size stability with changes in the cultivation temperature. The studied strains are of scientific and applied interest due to their enzymatic activity against several substrates simultaneously at different temperatures (25 and 4°C), as well as to the ability to secrete cold-active pectinase, protease, and lipase. However, phosphate-solubilizing activity both at 4 and at 25°C became preferable for the strains. The Mramornaya Cave is of karst origin and is characterized by carbonate karst, which explains the preference for calcium phosphate in the studied strains. Analysis of the obtained data showed that the collection of cultivated bacteria obtained in the present work included both typical psychrotolerant ones, which exhibited enzymatic activity at optimal growth temperature, and unique ones, capable of synthesizing a wide range of enzymes under the temperature different from their growth optimum.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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