Adomian Decomposition Method for the One-dimensional Nonlocal Fisher–Kolmogorov–Petrovsky–Piskunov Equation

Russian Physics Journal - The Adomian decomposition method is applied to construct an approximate solution of the generalized one-dimensional Fisher–Kolmogorov–Petrovsky–Piskunov...     

Photoinduced absorption of THz radiation in semi-insulating GaAs crystal

The influence of optical illumination on transmission of THz radiation through a bulk crystal of semi-insulating GaAs is experimentally studied. It is established that, without additional illumination, absorption of electromagnetic waves with a frequency of about 1 THz in the studied crystal is almost absent. Optical illumination in the spectral range of fundamental absorption of the crystal does not affect the transmission of THz waves. At the same time, if the illumination photon energy is a little below the edge of fundamental absorption, i.e., actually in the transparency region, the transmission of THz radiation drops sharply. At liquid helium temperature, the maximum effect is achieved for the energy of optical photons lower by approximately 30 meV than the crystal band gap. Further shift of the illumination toward lower photon energies is accompanied by almost complete recovery of the transmission. With increasing sample temperature, the spectral range of efficient action of the illumination shifts together with the edge of fundamental absorption toward lower photon energies.     

Kinetics of azidation of isomeric benzenedicarbonitriles

Rate constants and activation parameters of two-step azidation of isomeric dicyanobenzenes with dimethylammonium azide in DMF at 70–100°C were determined. Tetrazole rings are formed from cyano groups in dicyanobenzenes in a stepwise mode following the 1,3-dipolar cycloaddition pattern. The rate of azidation of isomeric dicyanobenzenes is considerably higher than the rate of subsequent azidation of intermediate cyanophenyltetrazolides. The azidation rate constant decrease in going from m-dicyanobenzene to its para and ortho isomers.     

Enantioselective intramolecular hydroamination catalyzed by lanthanide ate complexes coordinated by N-substituted (R)-1,1'-binaphthyl-2,2'-diamido ligands

Ytterbium and lutetium ionic complexes derived from enantiopure substituted (R)-binaphthylamine ligands, of the general formula [Li(THF)n][Ln[(R)-C20H12(NR)2]2], have been investigated for the hydroamination/cyclization of several aminopentenes and an aminohexene. Complexes with isopropyl or cyclohexyl substituents on nitrogen atoms were found to be efficient catalysts under mild conditions for the formation of N-containing heterocycles with enantiomeric excesses up to 78%.     

Enantioselectivity of the reaction of α-amino acids with sodium azide and triethyl orthoformate in the synthesis of tetrazoles

Russian Journal of Organic Chemistry -     

Wavy liquid film in the presence of co- or counter-current turbulent gas flow

The wavy downflow of a viscous liquid film in the presence of the turbulent gas flow was analyzed theoretically. Two-dimensional stationary running waves are calculated in a wide range of Reynolds numbers of liquid and gas. Hydrodynamics of liquid is calculated based on complete Navier-Stokes equations. The wave interface surface is considered as a small perturbation and equations in gas are linearized near the main turbulent flow. Different optimal downflow regimes are determined, and the main wave characteristics are compared in detail with and without the co- and counter-current gas flows. It is shown that at high velocities of the co-current gas flow, the calculated waves correspond to ripples observed in experiments.     

Quantum-mechanical oscillator in a uniform force field

The symmetry group of an isotropic oscillator explaining additional degeneracy of its energy levels was for the first time considered by Demkov [1–3]. He directed attention to the fact that harmonic oscillator Hamiltonian symmetry was beyond the scope of usual geometric concepts and could be expressed using canonical transformations relating coordinates and momenta. We show in this paper how the symmetry properties of the harmonic oscillator Hamiltonian can be used to solve the dynamic problem of an oscillator in a uniform force field.     

Temporal representations of the coefficients of aerodynamic forces and moments experienced by a rectangular wing under conditions of static hysteresis

Results are presented of experimental investigations into the static hysteresis of the aerodynamic characteristics of a rectangular wing with an aspect ratio of λ=5, obtained in static tests of a wing model in a wind tunnel. Variation with time of the aerodynamic forces and moments are analyzed in the range of angles of attack where a transition occurs from one branch of the hysteresis loop to the other.