Solvent Effect on the Spectral Characteristics and Quantum Yields of the Photolysis of Alkylated 1,2-Dihydroquinolines

On the basis of spectral data and the reaction of photolysis and fluorescence quantum yields in different pure solvents and solvent mixtures, it has been concluded that hydrogen bonding between 1,2-dihydroquinolines (DHQs) and a solvent, where the solvent is a proton donor, plays the key role in the reaction of photoinduced solvent addition to the DHQ double bond. The high sensitivity of DHQ photolysis to the solvent composition was shown, allowing us to suggest this reaction as a probe for studying the microenvironment of related compounds in mixtures.     

Molecular Structure of Silatrane Determined by Gas Electron Diffraction and Quantum-Mechanical Calculations

The geometry of silatrane HSi(OCH₂CH₂)₃N has been determined by gas electron diffraction, ab initio calculations, and vibrational spectroscopy of crystal. Using the scaled force field from DFT calculations the amplitudes and perpendicular corrections were calculated. It was assumed that the silatrane molecule has C ₃ symmetry. The following values (r _g bond lengths in Å and _a bond angles in deg. with three standard deviations from the least-squared refinements using a diagonal weight matrix) are: SiN 2.406(27); NC 1.443(7); OC 1.399(11); SiO 1.648(3); CC 1.504(15); NSiO 78.8(21); SiOC 128.1(11); SiNC 105.4(14); CCO 117.0(26); CCN 108.2(30); CNC 113.2(17); OSiO 116.3(13). The 5-membered rings are flattened. The sum of its bond angles is equal to 537.5(42). It is shown that a very large difference is found for Si—N distance from ab initio and DFT calculating.     

Examination of intermediates in globular protein unfolding by the tritium labeling method

Unfolding of polypeptide chain of ribonuclease A in urea and guanidinium chloride (GuCl) solutions under equilibrium conditions involves formation of intermediates whose properties (compactness and preservation of the most of the native hydrophobic core, secondary structures, and native-like folding of the polypeptide chain) correspond to the basic characteristics of the “molten globule” state. Intermediates are “damp” molten globules (with water molecules inside the globule). The examinations performed revealed pronounced distinctions in the properties of the intermediates, above all, in their compactness degrees.     

Molecular Structure of ortho-Fluoronitrobenzene Studied by Gas Electron Diffraction and Ab Initio MO Calculations

The molecular structure of ortho-fluoronitrobenzene (o-FNB) has been investigated by gas-phase electron diffraction and ab initio MO calculations. The geometrical parameters and force fields of o-FNB were calculated by ab initio and DFT methods. The obtained force fields were used to calculate vibrational amplitudes required as input parameters in an electron diffraction analysis. Within the experimental error limits, the geometrical parameters obtained from the gas-phase electron diffraction analysis are mostly in agreement with the results obtained from the ab initio calculations. The main results are: the molecular geometry of o-FNB is nonplanar with a dihedral angle about C–N of 38(3)°. The r _g (C–F) bond is shortened to 1.307(13) Å in comparison with r _g (C–F) = 1.356(4) Å in C₆H₅F.     

Propagation of Perturbations in Quasilinear Multidimensional Parabolic Equations with Convective Term

We establish estimates for the initial evolution of the supports of solutions of a broad class of quasilinear parabolic equations of arbitrary order that have the structure of the equation of strong nonlinear convective diffusion.     

Millimetric electromagnetic radiation of a lightning return stroke

The paper reports results of recording the pulsed microwave radiation of return lightning strokes using a high–time–resolution, 8–mm–wavelength radiometer. The procedure of recording pulsed radiations with millimetric wavelength is briefly described. The complex shape of the recorded pulses is shown to be due to the features of the current system within the antenna spot at the initial stage of a lightning return stroke.     

Singular Cauchy problem for the equation of flow of thin viscous films with nonlinear convection

For multidimensional equations of flow of thin capillary films with nonlinear diffusion and convection, we prove the existence of a strong nonnegative generalized solution of the Cauchy problem with initial function in the form of a nonnegative Radon measure with compact support. We determine the exact upper estimate (global in time) for the rate of propagation of the support of this solution. The cases where the degeneracy of the equation corresponds to the conditions of “strong” and “weak” slip are analyzed separately. In particular, in the case of “ weak” slip, we establish the exact estimate of decrease in the L ²-norm of the gradient of solution. It is well known that this estimate is not true for the initial functions with noncompact supports. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 2, pp. 250–271, February, 2006.     

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