“Natural” hydrogen and acoustic emission in Kh18N10T steel after barocryodeformation

Hydrogen with different bond energies and indentation-induced acoustic emission in the initial (homogenized) state of Kh18N10T stainless steel and after barocryodeformation by 18 and 31% are studied. A correlation between the acoustic parameters and the hydrogen content in the material is found.     

Polarization singularities in partially coherent combined beams

Vector singularities are predicted and discovered experimentally in partially polarized combined fields formed by incoherent superposition of orthogonally polarized beams. Such singularities are U contours with zero degree of polarization and isolated P points with unit degree of polarization centered at vortices of the orthogonally polarized component of the combined beam. Crossing a U contour switches the polarization state to the orthogonal one. The above-mentioned singularities are adequately described in terms of the complex degree of polarization in the Stokes-space representation. It is shown that the field elements corresponding to the extrema of the complex degree of polarization form the vector skeleton of a partially coherent nonuniformly polarized field.     

Deep deoxygenation of water with a metal-ion exchanger nanocomposite in closed system

Kinetics and dynamics of the reduction of oxygen dissolved in water by metal-ion exchanger nanocomposites differing in the nature (Ag, Cu, Bi, Ni), quantitative content of the introduced metal, and ionic form of the matrix were studied. It is shown that the process of oxygen absorption occurs to the fullest extent with the copper-containing nanocomposite. As the content of the metal increases, the amount of oxygen reduced by a single grain and granular bed grows and reaches the limiting values. It was found on this basis that the material with a copper capacity of 5.0 ± 0.5 mequiv cm^?3 in the H⁺ form is the most efficient for deep removal of molecular oxygen from water. The advisability of using the nanocomposite with the suggested parameters for deep deoxygenation of water in a closed system was confirmed by experiments and calculations.     

Application of New Efficient Hoveyda–Grubbs Catalysts Comprising an N→Ru Coordinate Bond in a Six-Membered Ring for the Synthesis of Natural Product-Like Cyclopenta[b]furo[2,3-c]pyrroles

The ring rearrangement metathesis (RRM) of a trans-cis diastereomer mixture of methyl 3-allyl-3a,6-epoxyisoindole-7-carboxylates derived from cheap, accessible and renewable furan-based precursors in the presence of a new class of Hoveyda–Grubbs-type catalysts, comprising an N→Ru coordinate bond in a six-membered ring, results in the difficult-to-obtain natural product-like cyclopenta[b]furo[2,3-c]pyrroles. In this process, only one diastereomer with a trans-arrangement of the 3-allyl fragment relative to the 3a,6-epoxy bridge enters into the rearrangement, while the cis-isomers polymerize almost completely under the same conditions. The tested catalysts are active in the temperature range from 60 to 120 °C at a concentration of 0.5 mol % and provide better yields of the target tricycles compared to the most popular commercially available second-generation Hoveyda–Grubbs catalyst. The diastereoselectivity of the intramolecular Diels–Alder reaction furan (IMDAF) reaction between starting 1-(furan-2-yl)but-3-en-1-amines and maleic anhydride, leading to 3a,6-epoxyisoindole-7-carboxylates, was studied as well.     

Influence of the choice of a rheological law on computer simulation results of slab subduction

The influence of the choice of the type of yield surface for elastoplastic materials and material constants for the slab and the mantle on the scenario of mathematical modeling of the slab collision is investigated. Computer simulation is performed by the FEM numerical solution of nonlinear equations for deformable solid mechanics, using the MSC.Marc 2005 code. The simulation results essentially depend on the choice of material constants for the slab and the mantle, as well as on the type of the yield surface for the elastoplastic material of the subduction slab. The numerical simulations demonstrate that the primary driving mechanism of subduction can be a geometrical inhomogeneity of the subduction slab near the zone of the slab collision with simultaneous consideration of consolidation of the slabmaterial as the slab descends into the mantle.     

Relationship between Transport Phenomena and Characteristics of the Cluster Structure

Technical Physics - Using a statistical approach, we have estimated the size of water clusters and the number of free molecules participating in transport phenomena. The sizes of clusters and the...     

An experimental study of 19F-19F and 13C-19F spin-spin coupling in molecules of difluoro(fluorosulfonyl)- and difluoro(fluorosulfonyloxy)acetyl fluorides

High-resolution ¹⁹F and ¹³C NMR spectra of difluoro(fluorosulfonyl)- and difluoro(fluorosulfonyloxy) acetyl fluorides were studied, and specific features of complex spin-spin coupling of fluorine and carbon nuclei were characterized. The mechanisms of ¹⁹F and ¹³C coupling were interpreted.