Behavior of 3,6-Bis(vinylsulfonyl)-1,2,4,5-tetrafluorobenzene in Homolytic Addition of Dialkyl Phosphites

Reaction of 3,6-bis(vinylsulfonyl)-1,2,4,5-tetrafluorobenzene with dialkyl phosphites at thermal initiation (70°C) gives rise to 3,6-bis(dialkoxyphosphonoethylsulfonyl)-1,2,4,5-tetrafluorobenzenes in up to 45% yield. The formation of diethoxyphosphonyl radicals in the course of the reaction was observed with the use of ESR method applying spin trapping by 2-methyl-2-nitrosopropane. The use as initiator of the azo-bis-isobutyronitrile increased the yield of diadducts to 60%.     

Composite tribological materials based on molybdenum disulfide nanoparticles and polytetrafluoroethylene microgranules

Tribological materials based on molybdenum disulfide nanoparticles localized on the surface of ultradispersed polytetrafluoroethylene were prepared. The composition and properties of the new composite materials were studied. Introduction of ultradispersed additives based on polytetrafluoroethylene with MoS₂ and on polytetrafluoroethylene and nanodiamonds prepared by detonation synthesis (taken as reference samples) decreases the viscosity of MS-20 aviation oil. The dependence of the friction coefficient on the Sommerfeld number for the composites obtained was examined. Introduction of additives leads to a decrease in the friction coefficient with increasing linear sliding velocity, in contrast to the initial oil for which the trend is opposite. The dependence of the friction coefficient on the concentration of additives in the initial oil was demonstrated. Modification of polytetrafluoroethylene microgranules with 3 wt % MoS₂ nanoparticles allows the amount of additive to the oil to be considerably reduced.     

Formation of superacid centers in the structure of zeolite ZSM-5

The structural changes and acid characteristics of the zeolite ZSM-5 modified with titanium and sulfur were studied. The modifier components were chemically bonded to the zeolite structure. The acid characteristics of zeolite changed and superacid centers appeared. A physicochemical study showed that treatment of zeolite with titanium tetrachloride and sulfuryl chloride did not change its structure and molecular-sieve properties.     

Lanthanide Crownphthalocyaninates: Synthesis,Structure, and Peculiarities of Formation

Complexing properties of lanthanide ions with respect to crown-substituted phthalocyanine are analyzed. Complexes of lanthanides (La, Nd, Sm, Eu, Gd, Tb, Yb, Lu, Y) with tetra-15-crown-5-phthalocyanine are synthesized and their structures are studied by photoelectronic, IR, ¹H NMR, and mass spectrometry methods.     

Synthesis of homogeneously mg-doped lithium niobate batch and study of the effect of non-metal impurities on the properties of LiNbO<Subscript>3</Subscript>:Mg crystals

The preparation conditions for the homogeneously doped precursor Nb₂O₅:Mg for the synthesis of granulated lithium niobate batch was studied. The effect of non-metallic impurities in the Nb₂O₅:Mg precursors and the lithium niobate batch on the characteristics of the melt–crystal system and the physicochemical and optical characteristics of the LiNbO₃:Mg crystals was established.     

Effect of free radical oxidation on the structure and function of plasma fibrin-stabilizing factor

Plasma fibrin-stabilizing factor (pFXIII) is a heterosubunit protein, the main function of which is the covalent stabilization of the fibrin matrix. This paper examines the ozone-induced free radical oxidation of plasma fibrin-stabilizing factor at different stages of its enzymatic activation. Electrophoretic data on the accumulation of γ-γ-dimers and α-polymers in the formation of stabilized fibrin suggests that a reduction in the enzymatic activity of FXIIIa is largely dependent on the stage of activation of pFXIII at which the oxidation is carried out. The results of UV, IR, and Raman spectroscopy measurements suggests that the oxidation of the amino acid residues of the polypeptide chains of pFXIII primarily affects cyclic, cysteine, and cystine groups and leads to the formation of oxidation products, being accompanied by the disruption of the protein secondary structure. Dynamic light scattering measurements revealed a loosening of the protein structure in the course of free radical oxidation. Spin label EPR spectroscopy data are suggestive of a change in the pFXIII conformation as a result of oxidative modification. Possible reasons for the different sensitivity of pFXIII to oxidative modification in the process of enzymatic activation are discussed. It is presumed that FXIII-B₂ regulatory subunits function as scavenges of reactive oxygen species, thereby protecting FXIII-A₂ catalytic subunits from oxidation.     

Comparative Study of Real Structure of LiNbO3 : ZnO Crystals Grown by Direct and Homogeneous Doping

Crystallography Reports - A comparative study of the optical and structural homogeneity of a LiNbO3 crystal with a congruent composition and LiNbO3&nbsp;:&nbsp;ZnО ([ZnО]...     

Impact of a Dopant Impurity Electronic Structure on Physical Properties,Defect Structure,and Features of Lithium Niobate Doping Technology

Technical Physics - The macro- and microstructure of doped LiNbO3 crystals is studied, their transmission spectra are investigated, and the effective coefficients characterizing the dopant impurity...     

Study of the kinetics of styrene copolymerization with divinyl sulfide and the structure of macromolecules

The kinetics of the free-radical copolymerization of styrene with divinyl sulfide in the presence of N,N′-bis(vinyloxyethyl)thiuram disulfide as an iniferter has been studied. The rate of polymerization is shown to decrease with increasing iniferter concentration. The structure of the copolymers isolated in the course of copolymerization has been investigated by electron microscopy and compared with that of the copolymers synthesized using AIBN as an initiator. Evolution in the morphology of the polymer phase during the process, which consists in self-organization of the secondary supramolecular structure into spheroids with diameters of 0.1–10 μm, has been revealed. The stages of the formation of polymer particles of various structures are described by the scheme of morphogenesis.