Diffusion in a lattice with static disorder

Kharkov Physicotechnical Institute, Ukrainian SSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 89, No. 3, pp. 465–472, December, 1991.     

Selective photochemical isotope “burning” upon the interaction of resonant laser radiation with atoms

The method of laser isotope separation based on selective excited-atom “burning” in a flow with buffer and reagent gases was implemented experimentally for zinc and rubidium. Selective excitation of isotopes was accomplished by the one-photon method using weak absorption lines and at the edge of the Doppler contour of atomic absorption with small isotope shift.     

Use of bulk and surface negative ionization to detect laser-excited molecules

The influence of vibrational excitation of molecules on negative-ion formation in bulk and in surface is analyzed. The magnetron method is used to study the influence of laser emission on the formation of negative ions of the molecules SF 6 and 12. The SF 6 molecules were excited by absorption of C02-1aser emission in the v 3 band. The 12 molecules were excited by Stokes scattering of the second harmonic of a neodymium laser. It is shown that the cross section for dissociative capture in the presence of vibrationally excited 12 molecules is increased by 3-4 orders. With SF~ molecules vibrationally excited in the beam, studies were made of the effects of formation of negative ions from a hot polycrystallinetungsten filament. The physics of the influence of vibrational excitation on negative-ion formation on a surface is analyzed. The maximum sensitivities of methods of vibrationally excited molecules are estimated.Translated from Lazernye Sistemy, pp. 121–142 1982.     

Coherent, polarization and temporal properties of self-frequency shifted solitons generated in polarization-maintaining microstructured fibre

Coherence of both self-frequency shifted solitons and short-wavelength non-soliton radiation generated in a micro-structure fibre was investigated experimentally for the first time. Their spectral, temporal and polarization characteristics were studied as well. We found the solitons generated in 30-cm-long fibre pumped with 50-fs pulses at 795 nm and 835 nm from Ti:Sapphire oscillator to be coherent, whereas degree of coherence of blue-shifted radiation was amounted to 0.25–0.57 depending on wavelength.     

On differential equation on four-point correlation function in the conformal Toda field theory

The properties of completely degenerate fields in the conformal Toda field theory are studied. It is shown that a generic four-point correlation function that contains only one such field does not satisfy an ordinary differential equation, in contrast to the Liouville field theory. Some additional assumptions for other fields are required. Under these assumptions, we write such a differential equation and solve it explicitly. We use the fusion properties of the operator algebra to derive a special set of three-point correlation functions. The result agrees with the semiclassical calculations.     

Conformal algebra and multipoint correlation functions in 2D statistical models

Based on the conformal algebra approach, a general technique is given for the calculation of multipoint correlation functions in 2D statistical models at the critical point. Particular conformal operator algebras are found for operators of the 2D q-component Potts model (1 < q < 4), and the O(N) model (0 < N < 2) at the critical point. A number of four-point correlation functions are calculated for these models.     

Natural fluctuations in a quartz crystal oscillator with automatic gain control

A method is developed for calculation of natural fluctuations in oscillators with automatic gain control (AGC). As an example, a three-terminal capacitive transistor crystal oscillator is considered. It is shown that the AGC system permits stabilization of the amplitude and frequency of the oscillator output signal.     

Theory of hopping transfer in disordered systems

The problem of hopping conduction in a system with randomly distributed impurity centers at low temperatures has been considered in terms of the linearized balance equation. The Gochanour-Andersen-Fayer diagram technique has been used to obtain a self-consistent expression for the configuration-averaged Green’s function, which describes the charge transfer in a disordered system with inclusion of Fermi correlations. In the framework of the developed formalism, a relationship has been derived for hopping conductivity as a function of the temperature with a power law of the density of states. The results obtained agree well with the percolation approach and, in the static limit, lead to the Mott’s law.     

Three-dimensional structure of thymidine phosphorylase from E. coli in complex with 3′-azido-2′-fluoro-2′,3′-dideoxyuridine

The three-dimensional structures of thymidine phosphorylase from E. coli containing the bound sulfate ion in the phosphate-binding site and of the complex of thymidine phosphorylase with sulfate in the phosphate-binding site and the inhibitor 3′-azido-2′-fluoro-2′,3′-dideoxyuridine (N₃F-ddU) in the nucleoside-binding site were determined at 1.55 and 1.50 Å resolution, respectively. The amino-acid residues involved in the ligand binding and the hydrogen-bond network in the active site occupied by a large number of bound water molecules are described. A comparison of the structure of thymidine phosphorylase in complex with N₃F-ddU with the structure of pyrimidine nucleoside phosphorylase from St. Aureus in complex with the natural substrate thymidine (PDB_ID: 3H5Q) shows that the substrate and the inhibitor in the nucleoside-binding pocket have different orientations. It is suggested that the position of N₃F-ddU can be influenced by the presence of the azido group, which prefers a hydrophobic environment. In both structures, the active sites of the subunits are in the open conformation.