Vol 50, No 1 (2016)

The aim of this work has been to automate the analysis of kinetic measurements in solving inverse problems in order to recognize the number and form of the independent combinations of reaction rate constants. Software for determining the basis of nonlinear parametric functions of the kinetic parameters of a mathematical model for the mechanism of a complex chemical reaction has been developed and described. The main stages of program construction with the use of a search algorithm for the independent combinations of the rate constants of elementary steps in the mechanism of a complex chemical reaction based on experimental data on the concentrations of reactants are considered.

Electron-beam irradiation in air significantly affects the optical absorption and turbidity of aqueous suspensions and hydrogels of starch due to a change in their aggregative stability. The predominant effect of irradiation consists in an increase in the transparency of solutions and the sedimentation of starch. A maximum susceptibility of the starch dispersions and hydrogels to irradiation has been observed at doses below 3 kGy. The effect weakened with the use of a multienergy electron beam because of the appearance of an excess negative charge in micelles, which prevents their coagulation.

Unlike the case of aqueous solution, two products are formed in the photolysis of 1-bromo-2-hydroxynaphthalene in a cetylpyridinium chloride micellar solution in the presence of sodium sulfite. These products are formed as a result of competitive steps of the primary photochemical process, the C–Br bond photodissociation and the heterolytic dissociation with elimination of the bromide anion. The bond photodissociation results in the product of bromine replacement by the sulfo group. The heterolytic dissociation affords the dimerization product. In the micellar solution, the iodide ions increase the quantum yield of the photosubstitution product due to the heavy atom effect and do not affect the quantum yield of the dimerization product. The halogenated derivatives of hydroxynaphthalene in micelles do not fluoresce in a neutral or alkaline medium.

Photoprocesses in bis(diethylaminobenzylidene)cyclopentanone (D1) and its bis(aza-18-crown-6) derivative (D2) have been studied in acetonitrile. The absorption, fluorescence, and phosphorescence spectra of D1 are similar to those of D2. Laser excitation of oxygen-free solutions of D1 and D2 leads to generation of a triplet state with a lifetime of ∼1 μs and two intermediate species with lifetimes of ∼100 μs and longer than 1 s.

A Hamiltonian has been proposed to study ground and excited states of nano-objects with a periodic structure, which makes it possible to find a general solution as a linear combination of basis functions in the form of normal waves. Terms that allow obtaining easily the solution with varying degrees of accuracy are explicitly defined. The method is suitable for the analysis of both finite and infinitely extended objects, including segments with a periodic structure.

The buildup of–SH groups in methemoglobin by irradiation with emission of spark discharge plasma in air and UV light from a low-pressure mercury lamp (λ = 253.7 nm) has been studied. The concentration of–SH groups increases the during spark discharge treatment, with the methionine amino acid residue in the methemoglobin molecule being reduced by nitrous and peroxynitrous acids; the bonds in the methemoglobin molecule are destroyed within 20 minutes of the spark treatment. By the action of UV radiation, methionine is reduced through chromophores (tryptophan, tyrosine) and methemoglobin is reduced by O₂^.- radical ions to oxy- and deoxyhemoglobin.

Alteration of the surface properties of polytetrafluoroethylene thin films by treatment in atmospheric-pressure surface discharge plasma initiated by dc barrier corona in argon has been studied. It has been shown that the plasma treatment of the polymer film surface leads to a substantial reduction of contact angles and an increase in the total surface energy.

Humic acids (HAs) isolated from high-moor peat have been studied by magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), and Raman spectroscopy. A composite of HAs with graphene oxide (GO) has been prepared for the first time, and the thermal carbonization (900°C) of both HAs and the HA–GO composite has been carried out. With the use of mass spectrometry, it has been found that CO₂ and H₂O molecules are mainly released from HAs into the gas phase at a low temperature (to 150°C). At higher temperatures, carbon monoxide and different low-molecular-weight hydrocarbons also begin to be released. From microscopic examinations, it follows that HA forms small agglomerates with sharply outlined edges as a result of carbonization, whereas the composite forms only large aggregates.