The electron acceptor and catalytic properties of zirconium dioxide modified with aluminum and gallium oxides

The electron acceptor properties of the mixed oxide systems 20 mol % M₂O₃-ZrO₂ (M = Al, Ga) and 10 mol % M₂O₃-10 mol % Al₂O₃-ZrO₂ (M = Ga, Y) were studied by recording the EPR spectra of paramagnetic complexes of adsorbed anthraquinone. The EPR data were compared with the catalytic activity of the mixed oxides in the decomposition of propanols and butanols in a pulsed microcatalytic reactor. The Al₂O₃-ZrO₂ and Ga₂O₃-ZrO₂ solid solutions were found to be metastable and decompose as the temperature of calcining increased or a third component was introduced. Correspondence between the EPR data and catalytic experiment results was established. This correspondence substantiates the occurrence of the segregation of the Al₂O₃ and Ga₂O₃ amorphous phases on the surface of zirconia, which accompanies the decay of the M₂O₃-ZrO₂ (M = Al, Ga) metastable solid solutions. The Al₂O₃-ZrO₂ solid solution decomposes more readily than Ga₂O₃-ZrO₂.     

Calculation and analysis of vibrational spectra of adenine–thymine,guanine–cytosine,and adenine–uracil complementary pairs in the condensed state

We have calculated the frequencies of the normal vibrations of the complementary nucleic acid base pairs adenine–thymine, guanine–cytosine, adenine–uracil, corresponding to the Watson–Crick structure, and the adenine–uracil pair, corresponding to the Hoogsteen structure, in condensed states and we interpret the spectra. We determine the contributions of hydrogen bonds to the vibrational modes of the complementary pairs. We have analyzed the nature of the relative displacements of the nucleic acid bases as integral molecular units along the hydrogen bonds. We show the role of hydrogen bonds in tautomeric interconversions of complementary nucleic acid base pairs. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 84–92, January–February, 2009.     

Calculation and interpretation of IR and resonant raman spectra of 5-halosubstituted uracils

We have used valence optical theory to carry out calculation and analysis of in-plane vibrations and intensities of IR spectra for isolated 5-fluorouracil and 5-bromouracil molecules. We give a complete interpretation of the corresponding bands in the absorption spectra. We have carried out a quantum mechanical calculations of the relative intensities in the resonant Raman spectra of 5-fluorouracil and 5-chlorouracil. The calculated spectra for the molecular models obtained agree quantitatively with the experimental spectra, and reproduce the observed characteristic spectral differences in the series of molecules: uracil, 5-fluorouracil, 5-chlorouracil, and 5-bromouracil. The models obtained for the molecules can be used for calculation and analysis of the spectra of other halosubstituted nucleic acid bases. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 437–442, July–August, 2006.     

Investigations of Tautomeric Purine Forms by the Methods of Vibrational Spectroscopy and Resonance Raman Scattering. I. Modeling of the Purine Structure in Different Phase States

In the present work, the methods of vibrational spectroscopy are used to study the occurrence of two tautomeric purine forms in different phase states. It is demonstrated that the N₉H tautomeric purine form is dominant in the isolation matrix, the N₇H tautomer is dominant in the polycrystalline state, and both tautomeric forms coexist in the liquid phase (H₂O solution).     

极限方程有奇性的一类六阶椭圆型方程混合边值问题解的渐近式

该文研究极限方程在部分边界上为退缩椭圆型(椭圆-抛物)的一类六阶椭圆型方程混合边值问题的奇摄动,在适当的假设下,应用改进了的多重尺度法,求得其解包括边界层和套层在内除了半圆域的两个角点外,在整个半圆域中有任意阶的一致有效的渐近展开式.     

Investigation of the stability of Mn<Subscript>12</Subscript> single molecule magnets

The stability of single crystals and monolayers of Mn₁₂ single molecule magnets under the influence of X-ray radiation and other possibly disruptive influences has been investigated by means of synchrotron radiation. Clear evidence for radiation induced sample degradation was found for both single crystals and monolayers. The comparison with spectra obtained after damaging the molecules by Ar⁺ sputtering, metal evaporation or water moistening indicates a possibility to distinguish between radiation damage and other external influences. The results clarify some of the previous conflicting reports on the integrity of Mn₁₂ molecules deposited on surfaces and are linked to the investigations aiming at studies of the electronic and magnetic properties of individual Mn₁₂ clusters.     

Quantum-mechanical calculations of the intensity distribution in spectra of adenine tautomers: I. Spectra of resonant hyper-Raman scattering

The spectra of resonant hyper-Raman scattering of five tautomeric forms of adenine have been theoretically determined for the first time based on quantum-mechanical calculations in the Herzberg-Teller approximation. The occurrence of three structures, Ade-N₉,N₁H⁺, Ade-N₉H(am), and Ade-N₇H(am), in an aqueous solution of adenine has been established.     

Determination of the tautomeric composition of adenine in the gas phase by vibrational spectroscopy methods: II. Analysis of resonance Raman spectra

The resonance Raman spectra of adenine in the gas phase under excitation with laser radiation at wavelengths of 266, 218, and 200 nm have been investigated experimentally. The quantum-mechanical calculations of the intensity distribution in the resonance Raman spectra of three adenine tautomers are performed in the Herzberg-Teller approximation with the inclusion of the Duschinsky and frequency effects. Conclusions regarding the tautomeric composition of adenine in the gas phase are drawn from comparison of the results of quantum-mechanical calculations with experimental data.     

Application of quantum mechanical method to analysis of the intensity distribution in spectra of resonant hyper-Raman scattering of low-symmetry molecules

The quantum-mechanical method of calculating the relative intensities of lines in the spectra of resonant hyper-Raman scattering of polyatomic molecules in the Herzberg-Teller approximation is tested with respect to low-symmetry molecules. The method makes it possible to describe resonant Raman and hyper-Raman scattering spectra, as well as vibronic absorption spectra, from the same viewpoint based on a common set of parameters. The particular features of the implementation of the method are discussed based on the calculation of the spectra of resonant hyper-Raman scattering of chlorobenzene and adenine, and the expedience of the application of the method is illustrated. Satisfactory agreement is obtained between calculation results and available experimental data.