Calculation of the vibronic spectra of adenine

The vibrational structure of the absorption spectra of the first two π-π* singlet transitions of adenine is calculated in the Franck-Condon approximation including Herzberg-Teller interactions. The effect of excitation-induced changes in molecular angles on the intensities of the vibrational components is estimated. Structural models of the adenine molecule in the excited states are constructed. The theoretical and absorption spectra of the first π-π* transition are compared. The results of the electronic structure calculations of adenine by different CNDO/S methods are discussed. Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 2, pp. 334–344, March–April, 1997.     

Dual reactivity of N-heterocyclic carbenes towards copper(II) salts

Complexes of N-heterocyclic carbenes (NHCs) with copper(II) halogenides are unstable. Upon formation, these complexes decompose to give haloamidinium salts. Contrastingly, O-substituted copper(II) NHC complexes are fairly stable. A series of new five-, six- and seven-membered ring NHC complexes of Cu(OAc)(2) have been synthesised and characterised in the solid state.     

Preparation and Properties of Frost-Resistant Room-Temperature-Curable Compounds Based on Oligoethertetraurethane Diepoxides of Various Chemical Structures

New polytetraurethane diepoxides were prepared from oligo(tetramethylene oxide)diols of various molecular masses, various diisocyanates, and glycidol. High-strength frost-resistant cold-curable elastic compounds were prepared on their basis. The use of aminoethylpiperazine as a curing agent allows the cured materials to be prepared in 24 h at room temperature. The elastomers based on isophorone diisocyanate exhibit higher mechanical and thermal characteristics than those based on 2,4-toluene diisocyanate, which is due to higher degree of microphase segregation of soft and hard blocks of elastomers based in isophorone diisocyanate.     

Effect of ultraviolet radiation on polyethylene naphthalate films irradiated with high-energy heavy ions

The effect of UV radiation in the spectral range of 280–400 nm on polyethylene naphthalate (PEN) films has been studied. Changes in the optical absorption spectra of PEN after exposure to accelerated ions and UV radiation have been revealed. Changes in the surface properties have been explored, and the depth of the degraded polymer layer after long-term UV irradiation in air has been measured. Depending on the treatment time, the depth has made 0.1–0.9 μm. The photoablation rate and the quantum yield of monomer unit removal due to UV irradiation of the PEN films have been estimated at ~0.7 × 10^?4 molecule/photon. The possibility of the formation of asymmetric pores in PEN films using controlled photooxidative degradation has been shown.     

On the structure of finite commutative rings with an identity

We describe the structure of the finite primary rings of principal ideals; we prove that every such ring is the factor-ring of the ring of integers of a finite extension of the field of rational p-adic numbers; we touch on the problem of the number of nonisomorphic rings of this type with a fixed number of elements.Translated from Matematicheski Zametki, Vol. 10, No. 6, pp. 679–688, December, 1971.The author wishes to express his deep thanks to A. I. Uzkov and V. P. Elizarov for their regular help and interest in this study.     

Antiturbulent properties of sulfomethylated polyacrylamide under the conditions of thermal,salt, and acid aggressions

Russian Journal of Applied Chemistry - Nonionic polyacrylamide with the weight-average molecular mass of 7 MDa was modified by sulfomethylation. The composition of sulfomethylated polyacrylamides...     

Spin-Dependent Vibrational Spectra of the Gd@C60 Endohedral Metallofullerene

Optics and Spectroscopy - We present an ab initio calculation of the structures and the IR spectra of the endofullerene Gd@C60 in different spin states. The lines in the IR spectra of Gd@C60...     

Deuterium liner and multiparametric studies of the formation of an inverse Z-pinch

A method and results of measurements are presented of the ion energy distribution in a deuterium liner accelerated in the inverse Z-pinch, in which the plasma is accelerated electrodynamically from the liner axis. Knowledge of the deuteron energy distribution is of primary importance for the correct interpretation of the experimental results from the study of the dd-reaction in the range of infralow energies with the use of a liner plasma. Experiments were carried out in a high-current pulsed accelerator (I=950 kA, τ=80 ns) at the Institute of High-Current Electronics of the Siberian Division of the Russian Academy of Sciences (Tomsk, Russia). In the initial state, the liner is a supersonic hollow deuterium jet 32 mm in diameter and 20 mm in length. The liner parameters were measured with the help of optical detectors of H _α and H _β deuterium lines and magnetic probes arranged in a radial direction (along the direction the liner expansion). In addition, scintillation spectrometers and BF₃ counters were used to measure the intensity of the neutron flux produced in the d + d → ³He + n reaction. The results obtained by simultaneously analyzing the data from magnetic probes, optical detectors, and neutron detectors point to the possibility of using a rather simple method for measuring the parameters of the liner accelerated up to energies of 3–6 keV.     

Germanium carboxylates: the first X‐ray diffraction study of germanium(II) dicarboxylate and germanium(IV) tetracarboxylate

Germanium(II) dipropionate (1) has been synthesized and its crystal structure, as well as that of germanium(IV) tetrapropionate (2), has been determined. By contrast to monomeric 2 with monodentate propionate ligands, compound 1 is associated, forming a cyclotetramer [Ge(O₂CEt)₂]₄ (1a) via intermolecular dative C?O → Ge interactions. Copyright © 2005 John Wiley & Sons, Ltd.