Structure and characteristics of chitosan cobalt-containing hybrid systems,the catalysts of olefine oxidation

Cobalt-containing hybrid organo-inorganic materials based on the chitosan-SiO₂, chitosan-Al₂O₃, and chitosan-cellulose systems were obtained. The surface structure and processes that occur during the formation of metal-containing materials, the catalytic properties of which were studied in the oxidation reactions of alkene, were investigated by EPR spectroscopy using a stable pH-sensitive nitroxyl radical, 4-dimethylamino-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazole-1-oxyl, as the adsorbed probe molecules.     

Properties of fluoroantimonates(III) complexes with amino acids

Crystalline complex fluoroantimonates(III) with amino acids (glycine, β-alanine, DL-serine, DL-valine, L-leucine, and L-phenylalanine) have been prepared. The complexes stability in aqueous solutions has been studied with the cementation method. ¹H NMR studies of aqueous solutions of the amino acids complexes with SbF₃ at pH 1–6 and room temperature are reported. Preparation of polycrystalline metal antimony in aqueous solutions of tetrafluoroantimonates(III) complexes with the protonated amino acids has been demonstrated.     

Glass formation along the CsHgBr3-CsPbBr3, Cs2HgBr4-CsPbBr3, and CsHg2Br5-CsPbBr3 sections of the HgBr2-PbBr2-CsBr ternary system

Glass formation is studied along the CsHgBr₃-CsPbBr₃, Cs₂HgBr₄-CsPbBr₃, and CsHg₂Br₅-CsPbBr₃ sections of the HgBr₂-PbBr₂-CsBr ternary system. The glass formation region is demarcated. Characteristic temperatures are determined by differential thermal analysis; the ratio T _g/T _m and the Hruby factor H _R for glassy samples are determined. The data are analyzed, and the most promising glass compositions along the specified sections are determined.     

Copolymers containing functional groups intrinsic to the active centers of serine hydrolases: Synthesis and evaluation of catalytic capability

N-Acryloyl derivatives of histamine, monoethanolamine, and β-alanine, which contain imidazole, hydroxyl, and carboxyl functional groups, respectively, are synthesized and characterized. Copolymers, which are further divided into thermally precipitable and thermally nonprecipitable (soluble) fractions, are obtained via the free-radical copolymerization of N-vinylcaprolactam and the specified comonomers that is initiated by a persulfate–tertiary amine redox system in a medium of 10% aqueous dimethyl sulfoxide (DMSO) at 65°C. It is shown that the soluble fractions of the synthesized copolymers exhibit catalytic activity in the reaction of hydrolysis of 4-nitrophenyl propionate (NPP) at a temperature above the coil-to-globule transition.     

Redox transformations of polynuclear molybdenum alkoxides and their interaction with nitrogenase substrates: experimental and theoretical study

The experimental and theoretical study of the electronic structure and IR spectra of the CO-containing molybdenum(0) alkoxide complexes of different nuclearity was carried out. The binding energy of the dinitrogen ligand was calculated for the tetranuclear K₄[Mo(OR)(CO)₃]₄ complexes catalyzing dinitrogen reduction. The theoretical study of structural changes for the 20-electron reduction of the catalytic cluster of the octanuclear [Mg₂Mo₈O₂₂(MeO)₆(MeOH)₄]^2? complex was performed. The interaction of the reduced cluster with the nitrogenase substrate was considered. Probable coordination modes of N₂, C₂H₂, and CO were analyzed, as well as the protonation reactions of the acetylene complexes, giving rise to two- and four-electron reduction products. The results of quantum chemical calculations are in good agreement with the experimental regularities observed for the catalytic reduction of the substrates in the presence of the Mo-Mg cluster.     

Component interactions in the Cs2CdBr4-Cs2ZnBr4-CsBr ternary system

Component interactions in the Cs₂CdBr₄-Cs₂ZnBr₄-CsBr ternary system have been studied by differential thermal analysis and X-ray powder diffraction. The liquidus surface is comprised of three crystallization fields: CsBr, a solid solution of Cs₂CdBr₄ with Cs₂ZnBr₄ (??), and a Cs₃ZnBr₅-based solid solution (??). The ternary eutectic coordinates are as follows: ??53.5 mol % Cs₂CdBr₄, 1.5 mol % Cs₂ZnBr₄, 45 mol % CsBr, and ??450°C. A Cs₂CdBr₄-Cs₃ZnBr₅ triangulating section, which is characterized by peritectic interaction with peritectic (p) coordinates of 20 mol % Cs₃ZnBr₅ and 480°C, divides the Cs₂CdBr₄-Cs₂ZnBr₄-CsBr ternary system into two ternary systems: Cs₂CdBr₄-CsBr-Cs₃ZnBr₅ and Cs₂CdBr₄-Cs₃ZnBr₅-Cs₂ZnBr₄.     

A reinterpretation of the hydration of micelles of dodecyltrimethylammonium bromide and chloride in aqueous solution

The hydration of dodecyltrimethylammonium (DTAB) micelles is reinterpreted in light of the results of the companion paper (immediately preceding this paper) that showed that the location of the spin probe 16-doxylstearic acid methyl ester (16DSE) changes as a function of the aggregation number, N, of anionic micelles, i.e, that it does not conform to the zero-order model (ZOM). The ZOM requires that the NO(*) moiety diffuse throughout the Stern layer of the micelle and nowhere else. By using the ZOM as a working hypothesis, the previous interpretation (J. Phys. Chem. B 2002, 106, 1926) of 16DSE data proposed that an increasing number of alkyl chain methyl groups occupied the Stern layer as N increased. In this work, the spin probe 5-doxylstearic acid methyl ester that was found to fulfill the ZOM in anionic micelles was measured as a function of N in DTAB and was found to obey the ZOM in this cationic micelle as well. Thus, a simple model of the hydration of micelles that is successful in anionic micelles is also successful in DTAB. The previous results for 16DSE are reinterpreted here as being due to small displacements of the NO(*) moiety as a function of N.     

Stripping voltammetric determination of azide ions

A procedure is proposed for the stripping voltammetric determination of N ₃ ^? ions at a mercury film electrode. It is based on the reduction of the mercury azide formed upon the oxidation of mercury in the presence of N ₃ ^? at ?0.02 to ?0.04V (in reference to an Ag/AgCl electrode) in a 0.1 M Na₂SO₄ supporting electrolyte solution. A linear dependence of the cathodic current peak on the N ₃ ^? concentration is observed in the concentration range from 4 × 10^?9 to 1 × 10^?3 M.     

Estimation of the time a perturbed Lagrangian system stays in an assigned region

The problem of estimating the mean time a weakly perturbed dynamical system stays in a fixed region of the phase variables is investigated. The motion is described by Lagrange's equations with an attractive force potential and in the presence of additive dissipative forces. The corresponding Cauchy problem is obtained in Hamiltonian variables for a non-linear first-order partial differential equation. Its classical positive solution specifies the action functional and the estimate sought for the time interval. The structure of the equations that allows of an explicit solution in terms of expressions for the kinetic and potential energy, as well as dissipative and dispersion matrices for a random Wiener-type perturbation, is established. The phenomenon of the escape of a phase point from different parts of the boundary of the region is investigated. Interesting problems of estimating the time for the inversion of the inner gimbal of a gyroscope, the time taken to reach an assigned level or a potential barrier of a multidimensional oscillatory system that has central symmetry, and the time a non-linear system with two degrees of freedom takes to escape over a potential barrier for a Henon–Heiles potential are investigated as examples.     

Synthesis and Antiviral Properties of Camphor-Derived Iminothiazolidine-4-Ones and 2,3-Dihydrothiazoles

A set of heterocyclic products was synthesized from natural (+)-camphor and semi-synthetic (−)-camphor. Then, 2-Imino-4-thiazolidinones and 2,3-dihydrothiazoles were obtained using a three-step procedure. For the synthesized compounds, their antiviral activity against the vaccinia virus and Marburg virus was studied. New promising agents active against both viruses were found among the tested compounds.