Specific Features of the Quasilocal State Densities in the Presence of Defects in Media with Spatial Dispersion

The density of stationary quasilocal states of the continuous spectrum arising due to the presence of defects in a medium with spatial dispersion is analyzed. The influence of plane and point defects on the specific features of the spectral quasilocal state density is studied. It is demonstrated that the spectral density has a strict maximum caused by the quasilocal energy level arising in the system. For a plane defect, the energy of the quasilocal level is displaced from the resonance energy of total quasi-particle reflection from the defect. The influence of the quasilocal state on the electronic heat capacity in the presence of the point defect is analyzed.     

Structural studies of Cr-doped mullite derived from single-phase precursors

Cr-doped mullites were prepared from single-phase precursors containing up to 9.60 wt% Cr₂O₃ using a sol-gel technique followed by thermal treatment. Particle induced X-ray emission spectroscopy and X-ray powder diffraction were used to characterize the samples. Mullites were orthorhombic, space group Pbam. Cr doping caused the increase of unit-cell parameters. Strongest expansion was noticed along c-axis followed by a and b (Δc/c=0.089, Δa/a=0.061, Δb/b=0.045% per mole Cr₂O₃). A second phase, namely θ-(Al,Cr)₂O₃, was revealed by XRD in the sample containing 9.60 wt% Cr₂O₃. The structure of mullites was refined by the Rietveld method, location of Cr³⁺ was performed by the EPR spectroscopy. At low chromium doping level (Cr₂O₃ content less than ∼5 wt%) Cr³⁺ ions were substituted for Al³⁺ in the AlO₆ octahedra of the mullite structure (M1 site). For higher doping level, Cr³⁺ ions were additionally substituted for Al³⁺ in the AlO₆ octahedra of the second phase [θ-(Al,Cr)₂O₃ at 1400 °C, or α-(Al,Cr)₂O₃ at 1600 °C] which segregated in the system. Substitution of Cr³⁺ for Al³⁺ on M1 site in the mullite structure resulted in increase of average distances in (M1)O₆ octahedron and decrease of average distances in T*O₄ tetrahedron, while average distances in TO₄ tetrahedron stayed almost constant.     

Interaction of cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin with mono-and polynucleotides: A study by picosecond fluorescence spectroscopy

The interaction of water-soluble cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin (H₂TMPyP4) with some mono-and polynucleotides is studied by time-resolved and steady-state fluorescence spectroscopy, as well as by steady-state absorption spectroscopy. The fluorescence decay kinetics are analyzed by reconstructing the decay time distributions, which made it possible to describe in more detail than previously the complexes formed due to the interaction. The main effect of binding of H₂TMPyP4 adenosine 5′-monophosphate and to poly(dA-dT)₂ is shown to be an increase in the fluorescence lifetime from 4.6 ns in the solution to 8.3 and 12.3 ns, respectively. This effect is explained by a less polar (in comparison with water) environment of porphyrin in complexes, which leads to a decrease in the quenching action of the intramolecular charge transfer state between the porphyrin macrocycle and methyl pyridyl groups. In the case of complex formation with guanine-containing nucleotides (guanosine 5′-monophosphate and poly(dG-dC)₂), the effect of decrease in the quenching action of the intramolecular charge transfer state caused by a decrease in the medium polarity is superimposed by a stronger effect of decrease in the fluorescence lifetime of porphyrin as a result of intermolecular electron transfer from guanine to excited porphyrin. A high sensitivity of this intermolecular quenching to the mutual arrangement of the electron donor and the electron acceptor makes it possible to reveal four types of complexes between H₂TMPyP4 and guanosine 5′-monophosphate, which differ in the positions of four broad peaks in the porphyrin fluorescence decay time distribution (0.1, 0.7, 2.4, and 6.1 ns). For the complex with poly(dG-dC)₂, a narrow peak at 2.8 ns prevails in the fluorescence decay time distribution, with the contributions from two additional narrow peaks at 1.0 and 6.2 ns being small.     

Secondary electron distributions,ionization cross sections and loss functions for O(I)–O(V)

An analytic atomic independent-particle-model is used to generate wave functions for the bound and ionization continuum states of O(I), O(II), O(III), O(IV), and O(V). These wave functions are used in conjunction with the Born approximation to generate continuum generalized oscillator strengths (GOS). From these GOS, we obtain secondary electron distributions, which we represent by smooth analytic functions. From the secondary electron distributions, we obtain electron impact ionization cross sections, which are compared to experiment. Finally, we compute the loss functions.     

Aminomethylation of 1-R-Tetrazoles

The reaction of tetrazole and a series of its 1-substituted derivatives with formaldehyde and alkylamines under mild conditions results in aminomethylation of the heterocyclic ring at the carbon atom with the formation of the corresponding Mannich bases. It was found that strong acids (HCl and CF₃COOH) have an activating action during the process. An ylide mechanism of the reaction was proposed from the data obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 66–71, January, 1991.     

Method of fictitious regions for one class of fourth-order quasilinear elliptical equations

We investigate the application of the fictitious region method to fourth-order quasilinear elliptical equations with Dirichlet and Neumann conditions. Convergence bounds are established for two versions of the fictitious region method.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 56, pp. 21–29, 1985     

Adaptive classification method and measurement of intermittent random process characteristics

Results are presented of an analytic construction and investigation of adaptive data classification algorithms for intermittent turbulence. A decision making rule is presented, relationships are derived to estimate the classification accuracy. A three-level procedure is described for processing the intermittency, including the calculation algorithms for the initial point, self-teaching, and optimal classification. It is shown that the method proposed permits realization of total automation of intermittency data processing.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 119–123, 1987.