The use of industrial oligomers modified by diisocyanates as adhesive and sealing compositions of different purposes

Methods for effective substitution of the traditional polymer-composite materials (PCM) during mounting of an electronic device by new-generation PCMs, including ones based on epoxyurethane oligomers (EPUR oligomers), are suggested. The processes of production of a complex of EPUR oligomer properties and polymers based on them are investigated.     

Degradation of tungsten under the action of a plasma jet

The degradation of the surface and structure of single-crystal tungsten and sintered powder tungsten during the action of a pulsed plasma jet is studied. It is shown that the degradation of a tungsten target during the action of a plasma jet with an energy flux density of 0.25–1 MJ/m² is accompanied by surface evaporation and melting and the fracture of surface layers on scales of 150–250 μm. The results of a numerical simulation of the thermomechanical processes that occur in a tungsten target during the action of a plasma jet are presented. The degradation of tungsten during the action of a plasma jet is shown to proceed almost continuously from the action (evaporation, melting) to the times that are more than three orders of magnitude longer than the action time, which is caused by the thermomechanical processes occurring in the tungsten target. Moreover, the action of thermal stresses leads to structural and morphological changes throughout the sample volume, and these changes are accompanied by recrystallization in adiabatic shear bands.     

Influence of geographic populations on the elemental composition of pine phytomass and soil

In the long-term (30 years) field provenance experiment (Novosibirsk, Russia) with Scotch pine Pinus sylvestris L. from different geographical populations, X-ray fluorescence analysis with synchrotron radiation (XRFSRA) was used to estimate the concentration of 16 chemical elements in different components of the phytomass collected from living trees and the soil under them. The statistically significant influence of the “geographical population” factor on the elemental composition of different components of phytomass and soil was shown. A relationship between chemical properties and morphometric traits was found.     

Luminescence properties of humic substances

A detailed analysis of luminescence properties of humic substances and fulvic acids extracted from peat soil is carried out for the first time. Their fluorescence excitation and emission spectra, fluorescence lifetimes, phosphorescence excitation and emission spectra, and phosphorescence lifetimes at room temperature are investigated. The nature of chromophores of humic substances is discussed. Presented at the International Symposium on Peat Organic Substances, May 15–19, 1995, Minsk, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 489–493, July–August, 1997.     

Ferromagnetic and Spin-Wave Resonance in the [CoFe/Cu]N Superlattice Thin (30-nm) Film

Physics of the Solid State - Angular dependences of the microwave absorption spectra of a (CoFe/Cu)N multilayer film have been studied by the ferromagnetic and spin-wave resonance techniques. The...     

Nonsymmetric values under Hart-Mass-Colell consistency

Let f be a single valued solution for cooperative TU games that satisfies inessential game property, efficiency, Hart Mas-Colell consistency and for two person games is strictly monotonic and individually unbounded. Then there exists a family of strictly increasing functions associated with players that completely determines f. For two person games, both players have equal differences between their functions at the solution point and at the values of characteristic function of their singletons. This solution for two person games is uniquely extended to n person games due to consistency and efficiency. The extension uses the potential with respect to the family of functions and generalizes potentials introduced by Hart and Mas Colell [6]. The weighted Shapley values, the proportional value described by Ortmann [11], and new values generated by power functions are among these solutions. The author is grateful to anonymous referee and Associate Editor for their comments and suggestions.     

Low-frequency relativistic electromagnetic solitons in collisionless plasmas

A relativistic electromagnetic soliton solution in the model of a one-dimensional, unbounded, cold, collisionless plasma is obtained without using the envelope approximation. The breaking of solitons with over-critical amplitudes is observed. The stability of undercritical solitons and the breaking of overcritical solitons are demonstrated by a particle-in-cell computer simulation. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 33–38 (10 July 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Exceptional Substrate Diversity in Oxygenation Reactions Catalyzed by a Bis(μ-oxo) Copper Complex

The enzyme tyrosinase contains a reactive side-on peroxo dicopper(II) center as catalytically active species in C−H oxygenation reactions. The tyrosinase activity of the isomeric bis(μ-oxo) dicopper(III) form has been discussed controversially. The synthesis of bis(μ-oxo) dicopper(III) species [Cu₂(μ-O)₂( L1 )₂](X)₂ ([ O1 ](X)₂, X=PF₆⁻_, BF₄⁻, OTf⁻, ClO₄⁻), stabilized by the new hybrid guanidine ligand 2-{2-((dimethylamino)methyl)phenyl}-1,1,3,3-tetramethylguanidine ( L1 ), and its characterization by UV/Vis, Raman, and XAS spectroscopy, as well as cryo-UHR-ESI mass spectrometry, is described. We highlight selective oxygenation of a plethora of phenolic substrates mediated by [ O1 ](PF₆)₂, which results in mono- and bicyclic quinones and provides an attractive strategy for designing new phenazines. The selectivity is predicted by using the Fukui function, which is hereby introduced into tyrosinase model chemistry. Our bioinspired catalysis harnesses molecular dioxygen for organic transformations and achieves a substrate diversity reaching far beyond the scope of the enzyme.     

The effect of the type of solvent on the structural and dynamic parameters of polyurethane-styrene-co-acrylonitrile blends

The effect of solvents, such as THF, methyl ethyl ketone, ethyl acetate, and acetone, on the structures and molecular dynamics of polyurethane-styrene-co-acrylonitrile blends has been investigated with the use of spin-probe ESR spectroscopy, DSC, IR spectroscopy. There are slight changes in the values of molecular mobility, crystallinity, and elastic modulus of composites containing more than 50% polyurethane, and only at higher contents of the styrene-acrylonitrile copolymer are sharp changes in the structural and dynamic parameters observed in the presence of any solvent. In different solvents, the blend parameters improve in the following series: THF, methyl ethyl ketone, ethyl acetate, acetone. This outcome is determined by the thermodynamic affinities of the dissolved polymers for the solvent. It has been shown that the content of hydrogen bonds between nitrile and urethane groups (a band at 3344 cm^?1) increases with the content of styrene-co-acrylonitrile in a blend. During reversible deformation, the molecular mobility of the radical increases and further tension is accompanied by reduced mobility in the oriented blends, independently of the solvent type.     

Synthesis and crystal structures of new lanthanide isonicotinates: coordination polymers and molecular complexes

New coordination polymers [Ce(C5H4NCOO)3(H2O)2] · 0.5C6H4N2 · 1.5H2O, [Ln(C5H4N-COO)3(H2O)2] (Ln = Ce, Pr) and [Ho(C5H4NCOO)2(H2O)4]NO3, and the tetranuclear complex [Ho4(OH)4(C5H4NCOO)6(H2O)8](NO3)2 · 3.5C6H4N2 · 5H2O were prepared by heating aqueous solutions of lanthanide(III) nitrates with 4-cyanopyridine under conditions of hydro-thermal synthesis. X-ray diffraction study demonstrated that the lanthanide atoms in the coordination polymers are bridged in chains through coordination to the carboxyl group of isonicotinic acid. The metal atoms in the tetranuclear complex are bound in pairs by six bidentate isonicotinate ligands.