Nanostructuring and surface hardening of structural steels by ultrasonic impact-frictional treatment

With two structural steels (the steels 50 and 09G2S) as examples, the paper studies the effectiveness of a new method of ultrasonic impact-frictional treatment (UIFT) for the hardening and nanostructuring of the surface layer with the variation of the tilt angle of the vibrating indenter and the treatment environment. It is demonstrated that treatment with tool tilt angles different from 90° and with the absence of a contact liquid results in the formation of a nanostructured surface layer with increased microhardness. © 2018 Author(s)

BETULIN-3, 28-DIPHOSPHATE SALT COMPLEXES WITH AMINES AND THEIR ANTIOXIDANT ACTIVITY

Objective: Studies of composition, stability and antioxidant properties of the betulin-3, 28-diphosphate complexes with dopamine and trisamine.Methods: The betulin-3, 28-diphosphate (BDP) interaction with amines in a water-alcohol medium was studied by using spectral methods and potentiometric titration. Biochemical indexes such as catalase, superoxide dismutase (SOD), lactate dehydrogenase (LDH) activities and malondialdehyde (MDA) level were estimated in experiments on rats.Results: BDP was synthesized using betulin by POCl3 treatment in the presence of pyridine in dioxane. The complexation of BDP with amines was confirmed by the 31P-NMR and FTIR-spectral data. The stoichiometry of BDP-dopamine complexes was equal to 2:1 and 4:1 and its complexes with trisamine were produced in the ratio 1:1 in a water-alcohol medium. The conditional stability constant К′st of the BDP-trisamine complex is 1130±55 mol∙l-1. BDP-Tris complex improved SOD activity up to 30% and up to 105% in the presence of cytostatic-hydrazine sulfate. The MDA level in erythrocytes decreased up to 57% and in combination with cytostatics (5-fluorouracil and hydrazine sulfate)-up to 11-14%. The catalase activity increased by 44-94% and MDA level in erythrocytes decreased by 22-53% under the action BDP-DA complexes that depends on the dose.Conclusion: The BDP forms stable complexes with trisamine and dopamine that make it possible to use this compound as a component of drug delivery system for high toxicity cytostatics and for readily oxidized catecholamines. It has been shown that both its complexes with amines and the combination with cytostatics enhanced antioxidant activity in an experiment in vitro

The influence of a combined strain-heat treatment on the features of electromagnetic testing of fatigue degradation of quenched constructional steel

The possibilities of the magnetic and eddy-current methods for testing fatigue degradation during low-cycle loading of quenched steel 50 (0.51% C) that was subjected to a combined strain-heat treatment according to an optimal regime that included friction treatment with subsequent tempering at T = 350 C, were investigated. It is shown that for steel that was subjected to a combined nanostructuring treatment, the accumulation of a plastic strain under "hard" cyclic loading can be tested using the coercimetric method and values of the residual magnetic induction on the major and minor magnetic-hysteresis loops, values of the maximum and initial magnetic permeabilities, and readings of an eddy-current instrument at a low excitation frequency of the eddy-current transducer. The appearance of surface fatigue cracks can be tested via eddy-current measurements at high frequencies, when the contribution of the crack formation in the hardened layer to the eddy-current characteristics is considerable. © 2013 Pleiades Publishing, Ltd

Eddy-current testing of fatigue degradation in additionally heat-treated gas powder laser clad NiCrBSi coating under contact fatigue loading

The paper studies the applicability of eddy-current technique to testing fatigue degradation in Ni-18.2Cr-3.3B-4.2Si coating, produced by gas powder laser cladding and subjected to additional high-temperature annealing at 1025 °C, under contact loading. It is demonstrated that eddy-current testing of fatigue degradation in Ni-18.2Cr-3.3B-4.2Si coating under contact loading after high-temperature annealing has certain limitations caused by the high brittleness of this coating. In this case, it is possible to test only a sharp increase in the sizes of contact damages, which occurs at 8×10 5 cycles under these loading conditions and results from the formation of a great number of peripheral ring cracks in the fracture zone; the eddy-current readings α decrease due to the increasing electrical resistivity of the coating. Testing can be performed by eddy-current measurements at high excitation frequencies of an eddy-current transducer (f=72-120 kHz), when the effect of the ferromagnetic steel base on the eddy-current readings α is minimum. © 2018 Author(s)

Eddy-current testing of fatigue degradation upon contact fatigue loading of gas powder laser clad NiCrBSi-Cr 3 C 2 composite coating

The possibilities of the eddy-current method for testing the fatigue degradation under contact loading of gas powder laser clad NiCrBSi-Cr 3 C 2 composite coating with 15 wt.% of Cr 3 C 2 additive have been investigated. It is shown that the eddy-current testing of the fatigue degradation under contact loading of the NiCrBSi-15%Cr 3 C 2 composite coating can be performed at high excitation frequencies 72-120 kHz of the eddy-current transducer. At that, the dependences of the eddy-current instrument readings on the number of loading cycles have both downward and upward branches, with the boundary between the branches being 3×10 5 cycles in the given loading conditions. This is caused, on the one hand, by cracking, and, on the other hand, by cohesive spalling and compaction of the composite coating, which affect oppositely the material resistivity and, correspondingly, the eddy-current instrument readings. The downward branch can be used to monitor the processes of crack formation and growth, the upward branch - to monitor the degree of cohesive spalling, while taking into account in the testing methodology an ambiguous character of the dependences of the eddy-current instrument readings on the number of loading cycles. © 2017 Author(s)

FIRST REPORT ON TRUFFLE-INHABITING FUNGI AND METAGENOMIC COMMUNITIES OF TUBER AESTIVUM COLLECTED IN RUSSIA

Truffles are one of the least studied groups of fungi in terms of their biological and biotechnological aspects. This study aimed to isolate truffle-inhabiting fungi and assess the metagenomic communities of the most common Russian summer truffle, Tuber aestivum. This study is the first to characterize the biodiversity of prokaryotic and eukaryotic organisms living in the truffle T. aestivum using molecular analysis and sequencing. Plant pathogens involved in a symbiotic relationship with truffles were identified by sequencing the hypervariable fragments of the 16S rRNA and 18S rRNA genes. In addition, some strains of fungal symbionts and likely pathogens were isolated and recognized for the first time from the truffles. This study also compared and characterized the general diversity and distribution of microbial taxa of T. aestivum collected in Russia and Europe. The results revealed that the Russian and European truffle study materials demonstrated high similarity. In addition to the truffles, representatives of bacteria, fungi, and protists were found in the fruiting bodies. Many of these prokaryotic and eukaryotic species inhabiting truffles might influence them, help them form mycorrhizae with trees, and regulate biological processes. Thus, truffles are interesting and promising sources for modern biotechnological and agricultural studies

Genome sequences of Acholeplasma laidlawii strains differing in sensitivity to ciprofloxacin

© 2017 Medvedeva et al. Acholeplasma laidlawii is a well-suited model for study of the molecular basis of the adaptation of mollicutes to environmental conditions. Here we present the whole-genome sequences of four strains of A. laidlawii with differential sensitivity to ciprofloxacin

Изотопный состав и регионы-источники зимних осадков в Надымской низменности

According to the forecast of IPCC (Intergovernmental Panel of the Climate Change), an increase in precipitation is expected in this century in the Arctic. The main reason is intensification of evaporation from waters of the Arctic Ocean opening due to the intensive melting of sea ice. It is supposed that these changes will be most severe in winters in the Arctic regions, which are subject to significant anthropogenic load. In this respect, the intensively developed Nadym Lowland may be considered as a promising area for researches. The results of our study showed that the circulation conditions (primarily cyclones coming from the North Atlantic under the Eastern (E) circulation form of the G.Ya. Vangenheim–A.A. Girs classification) significantly influence on the isotopic composition of precipitation in this region. Thus, in the cold period of 2016–2017, the isotopic composition of precipitation changed for δ18О by 21 ‰, and for δD by 167 ‰ (weighted average values δ18О = −22.3 ‰, δD = −172.6 ‰, and dexc = 5.6 ‰). The use of the dew point temperature at the moment of precipitation in the calculations of the isotopic-temperature dependences allows obtaining the following coupling equation: δ18О = 0.67Tdp − 15.2 (R2 = 0.67). On the basis of the joint analysis of synoptic, trajectory and isotopic data, the main regions-sources of atmospheric moisture, precipitated in the Nadym Lowland during the cold period of 2016–2017, were determined. The major contributions were made by the Atlantic Ocean (35.7%), the North Atlantic Ocean and the Arctic Ocean (30.4%), and the Black Sea-Caspian region (20%). The last one is characterized by the most weighted isotopic composition. Inland source regions have contributed the least to precipitation (slightly larger 10%), and their lightweight isotopic composition is related to cryogenic fractionation.В результате совместного анализа синоптических, траекторных и изотопных данных определены основные регионы‑источники поступления атмосферной влаги, выпавшей в виде осадков в Надымской низменности. Наибольший вклад вносит Атлантический океан (35,7%), меньше – северная часть Атлантического океана и Северный Ледовитый океан (30,4%), а также Черноморско‑Каспийский регион (20%) и внутриконтинентальные регионы (немногим более 10%)

Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal