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The results of the experimental study of the degradation of steel structures of sewer underground constructions are presented. The distribution of harmful gas elements (sulfur, hydrogen, oxygen) over the wall thickness of sewer pipes along corrosion defects in the form of pits, as well as the character of changes in the microhardness of the metal depending on the hydrogen content and service life, are shown. To confirm the metal softening with increasing hydrogen concentration, the stresses of the crystal lattice (distortion stresses) were measured.

Modeling of the spatial low-cycle crack kinetics for refined service life and survivability of elements of aviation, rocket and space, nuclear, and other critical equipment is studied. The results of experimental studies and numerical calculations of the parameters of shape change are presented, taking into account the characteristics of the microrelief and the complex surface of low-cycle fracture of inclined surface semi-elliptical cracks. A functional relationship is shown between the mesostructural characteristics of low-cycle fragmentation of the surface of the cracks under study with parameters of nonlinear fracture mechanics such as the strain intensity coefficient and the specific elastoplastic work of fracture at a certain point of the defect contour.

The hydrogenation kinetics and the mechanisms of sulfide corrosion cracking of long-term operated pipe shipbuilding 15KhSND and D32 steels were evaluated. With the increase of the service life, these steels were intensively hydrogenated from the inner surface of the pipe, and the concentration of hydrogen exceeded the initial values in 2–2.5 times. The same tendency of microhardness changes in the cross-section of the metal wall of pipes with different service life was observed. Its values in the near-surface layers from the outer side of the pipe increase in 1.5–2 times. With the increase of the stresses during tests under corrosion sulfide cracking in the NACE environment hydrogenation of the samples increases dramatically (approximately 2–3 times), which causes severe embrittlement (an increase of metal microhardness) and the crack growth resistance decrease.

Previous studies have shown that with increasing service life of shipbuilding steels, a strong hydrogen charging of their internal near-surface layers occurs, especially if the service life exceeds 3 years or more. This is known to cause changes in the mechanical properties of steels. Therefore, there is a need to conduct additional experimental studies on the effect of hydrogen in a wide temperature range on the degradation of the structural and phase states of steels, in particular, on changes in the crystal lattice and redistribution of cementite, which directly leads to a decrease in the ductile and deformation properties of the metal, especially at subzero air temperatures. The effect of service life and subzero temperatures on the stress state of the a-matrix lattice and its parameters for the 10KhSND and D32 steels was investigated. A tendency to increase in the value of lattice distortion stresses and decrease in the mass fraction of cementite in specimens of these steels after long-term operation was revealed. Metallographic studies showed that with decrease in the temperature of the cooling medium, the volume fraction of hydrides increases significantly, which leads to embrittlement and softening of steels.

A mechanophysical model for crack growth kinetics computation on stress corrosion fracture of modified 06G2BA and 08KhMCHA pipe steels is adequately expressed through the plane stress-strain state dα / dt and dJ / dt ratios that are dependent on the strain crack tip rate. The crack growth accelerated by an aggressive environment occurs under static and cyclic loading due to transient dissolution and repassivation processes at the crack tip. Such accelerations are divided into three categories, determined by the strain rate: mechanical cracking (fatigue crack and stationary plastic crack), corrosion-accelerated mechanical cracking (corrosion fatigue and corrosion-accelerated plastic crack), and sulfide stress corrosion fracture. Metallographic studies revealed the change in the crack nucleation and propagation mechanisms, from transcrystalline to intercrystalline, related to the viscoplastic and brittle structure of steel specimens cyclically loaded and simultaneously affected by a corrosive environment.

The results of calculated–experimental and numerical studies of the relative strain intensity factors in the case of semi-elliptical inclined surface cracks in the weld joints of 12Kh18N10T austenite stainless steels with the assumption of redistribution of strain and initial residual stresses under nonlinear boundary loading conditions are presented. A parametric equation for the determination of the relative strain intensity factors in the case of semi-elliptical inclined surface cracks is given. This new parametric equation allows one to evaluate the comparative survivability of the local zones of details and construction in the bulk weld joint upon elastoplastic static and low-cycle loading.

New representatives of dioxodihydronaphtho[2,3- b ]furan-, furo[3,2- c ][1]benzopyran-, furo[2,3- d ]pyrano[4,3- b ]pyran-, furo[2',3':4,5]pyrano[3,2- c ]chromene-, and furo[2,3- d ]pyrimidine carboxylates were obtained from the reactions of alkyl 3-bromo-3-nitroacrylates with representatives of carbo- and heterocyclic CH-acids under simple conditions, without the use of organocatalysts. The structures of the synthesized compounds were proven by a set of physicochemical methods, including X-ray diffraction analysis.

The interaction of sodium phytate hydrate C6H18O24P6·xNa·yH2O (phytNa) with Cu(OAc)2·H2O and 1,10-phenanthroline (phen) led to the anionic tetranuclear complex [Cu4(H2O)4(phen)4(phyt)]·2Na+·2NH4+·32H2O (1), the structure of the latter was determined by X-ray diffraction analysis. The phytate 1 is completely deprotonated; six phosphate− fragments (with atoms P1–P6) are characterized by different spatial arrangements relative to the cyclohexane ring (1a5e conformation), which determines two different types of coordination to the complexing agents—P1 and P3, P4, and P6 have monodentate, while P2 and P5 are bidentately bound to Cu2+ cations. The molecular structure of the anion complex is stabilized by a set of strong intramolecular hydrogen bonds involving coordinated water molecules. Aromatic systems of phen ligands chelating copper ions participate in strong intramolecular and intermolecular π-π interactions, further contributing to their association. At the supramolecular level, endless stacks are formed, in the voids of which sodium and ammonium cations and water molecules are present. The stability of 1 in the presence of human serum albumin (HSA) was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. Continuous wave (CW) EPR spectra in water/glycerol frozen solution clearly indicate a presence of an exchange-coupled Cu(II)-Cu(II) dimeric unit, as well as a Cu(II) monomer-like signal arising from spins sufficiently distant from each other, with comparable contributions of two types of signals. In the presence of albumin at a 1:1 ratio (1 to albumin), the EPR spectrum changes significantly, primarily due to the reduced contribution of the S = 1 fraction showing dipole–dipole splitting. The biological activity of 1 in vitro against the non-pathogenic (model for Mycobacterium tuberculosis) strain of Mycolicibacterium smegmatis is comparable to the first-line drug for tuberculosis treatment, rifampicin.

The article presents the results of solving one of the fundamental problems in the field of increasing strength, service life, survivability, reliability and safety of welded joints in critical structures. A model for simulation of elasto-plastic welds failure in steel structures at cryogenic temperatures was developed. It proposed clarifying calculation and experimental methods for analysis and simulation of failure mechanisms taking into account types of forming defects. In addition, effect of heating and cooling cycles, kinetics of elasto-plastic deformation as well as fields of residual stresses and strains were used to predict the results.

Breathing and blood pressure are under constant homeostatic regulation to maintain optimal oxygen delivery to the tissues. Chemosensory reflexes initiated by the carotid body and catecholamine secretion from the adrenal medulla are the principal mechanisms for maintaining respiratory and cardiovascular homeostasis; however, the underlying molecular mechanisms are not known. Here, we report that balanced activity of hypoxia-inducible factor-1 (HIF-1) and HIF-2 is critical for oxygen sensing by the carotid body and adrenal medulla, and for their control of cardio-respiratory function. In Hif2α ⁺/⁻ mice, partial HIF-2α deficiency increased levels of HIF-1α and NADPH oxidase 2, leading to an oxidized intracellular redox state, exaggerated hypoxic sensitivity, and cardio-respiratory abnormalities, which were reversed by treatment with a HIF-1α inhibitor or a superoxide anion scavenger. Conversely, in Hif1α ⁺/⁻ mice, partial HIF-1α deficiency increased levels of HIF-2α and superoxide dismutase 2, leading to a reduced intracellular redox state, blunted oxygen sensing, and impaired carotid body and ventilatory responses to chronic hypoxia, which were corrected by treatment with a HIF-2α inhibitor. None of the abnormalities observed in Hif1α ⁺/⁻ mice or Hif2α ⁺/⁻ mice were observed in Hif1α ⁺/⁻; Hif2α ⁺/⁻ mice. These observations demonstrate that redox balance, which is determined by mutual antagonism between HIF-α isoforms, establishes the set point for hypoxic sensing by the carotid body and adrenal medulla, and is required for maintenance of cardio-respiratory homeostasis.