Polarization response explored by joint Hamiltonian and stochastic approach

The effect of thermal fluctuations on systems modeled by anharmonic nonconservative Hamiltonians is investigated in the framework of interacting lattice cells each cell obeying to Langevin dynamics. Representative examples addressed to critical phenomena in ferroelectrics include polarization response of a single lattice cell, ergodicity breaking, and birth of a domain, and the effect of nonlocal electroelastic interaction all derived combining the Fokker–Planck, imaginary time Schrödinger, and symplectic integration techniques.     

Nonlinear optical properties of poly(N-vinylcarbazole)-C60 nanocomposites

Physics of the Solid State - The influence of the fullerene content and temperature on the IR absorption and luminescence spectra of poly(N-vinylcarbazole) (PVK)-C60 composites prepared by vacuum...     

Photochemical reactions of triplet benzophenone and anthraquinone molecules with amines in the gas phase

The intermolecular photoinduced reactions between triplet ketone molecules and aliphatic amines and pyridine are studied by the quenching of delayed fluorescence of anthraquinone and benzophenone vapors by diethylamine, dibutylamine, cyclohexylamine, triethylamine, and pyridine. In the temperature range 423–573 K, the delayed fluorescence quenching rate constants k _q are estimated from changes in the decay rate constant and the intensity of delayed fluorescence upon increasing pressure of bath gases. It is ascertained that, in the gas phase, the mixtures under study exhibit both a negative and a positive dependence of k _q on temperature, which indicates that some photoinduced reactions do not have activation barriers. The rate constant k _q is shown to increase with decreasing ionization potential of the electron donors. This points to the importance of interactions with charge transfer in the photoreaction of triplet ketone molecules with aliphatic amines and pyridine in the gas phase. The relationship between k _q and the change in the free energy ΔG upon the photoinduced intermolecular electron transfer, which is the primary stage of the photochemical reaction, is studied. It is shown that the dependence k _q (ΔG) for the donor-acceptor pairs under study is described well by the Marcus equation, in which the average vibrational energies of the donor and acceptor are taken into account for the estimate of ΔG.     

Regularities in the luminescence spectra of solutions with molecular anion impurities

This article deals with the absorption, excitation and luminescence spectra of frozen aqueous solutions of the halide salts and acids with molecular anion impurities CN^-, SCN^-, SeCN^- and CNO^-. It is shown that the spectra at 4.2°K display vibronic structure which is explained by the interaction of electronic transition with intramolecular oscillations of the impurity. Conclusions are also deduced from the results of investigation of temperature dependence of the quantum emission efficiency and the Raman spectra of such systems.     

Effect of metals on melt oxidation of polyethylene

Oxidation of polyethylene (PE) melts in contact with metals (Cu, Pb, Au, Al, Zn, Ag) has been studied by infrared spectroscopy and differential thermal analysis (DTA). These metals may be divided into two groups, depending on their activity for oxidizing PE: namely, high-activity metals (Cu, Pb, Ag, Zn) and low-activity metals (Al, Au). During the oxidation of PE in contact with high-activity metals dissolution of the surface layer of metal is observed with accumulation of metal-containing compounds (salts of carboxylic acids) in the bulk of the polymer. With low-activity metals these phenomena are not observed. The rate of oxidation of PE on low-activity metals approaches the oxidation rate of nonmetals (polytetrafluoroethylene and inorganic glass). With certain high-activity metals (Cu, Pb) the process of oxidation is accelerated only in the early stage of oxidation; then the oxidation rate slows down and the oxidation process ceases. PE films separated from metal after being oxidized on it possess chemical memory, i.e., their oxidation rate depends on the nature of the metal with which they had been in contact, and on the duration of the contact oxidation. The effect of salts of carboxylic acids (metal stearates) on the oxidation of PE melts was also studied. Based on the data obtained, it is concluded that the rate of oxidation of PE melts on high-activity metals is controlled by metal-containing compounds which are the products of contact reactions.     

Photoinduced Gas-Phase Electron Transfer Reactions

The electron transfer quenching process, when a reactive excited state is singlet or triplet, for gas-phase systems (benzophenone and anthraquinone with amines and pyridine as well as carbazole with halomethanes) was systematically investigated using time-resolved fluorescence. Bimolecular rate constants were obtained. Variable-temperature measurements were performed for eight donor-acceptor pairs. It was found that under solvent-free conditions various quenchers differing in photochemical reactivity led to change in quenching rates by almost three orders of magnitude. Positive and negative temperature dependences for the electron transfer rate constants were observed. The data were analyzed in terms of the Marcus-Jortner theory.     

Heat exchange investigation and modernization of furnace of P-67 boiler of 800 MW unit

For the purpose of the development and introduction of the arrangements aimed at increasing the slagless power, economy, and reliability of the P-67 boiler of the 800 MW unit of the Berezovskaya Power Plant No. 1, the variation of heat-engineering characteristics of the coal (lignite) of the open-cast mine “Berezovsky-1” and its slag properties was investigated, the aerodynamics, heat exchange, formation of nitrogen oxides, and the intensity of local slag formation for different operation regimes and variants of the reconstruction of the furnace-burner device were modelled mathematically, the thermal efficiency of furnace walls was studied experimentally during their long-term operation, including the time after their mechanical cleaning, modernization of the system of water sootblowing, under low air excess, coal dust coarsening, loading the lower rows of burners, and lower air blowing.