Oscillations appearing during sorption of amino acids on ion-exchanger grains on the basis of mathematical simulation

Oscillations in concentration and grain size could occur in the process of amino acid sorption on ion-exchanger grains. This phenomenon has been observed in several experimental works. The theoretical explanation of the phenomenon was given earlier by means of an elementary model. In this work the process was studied using a physically more sophisticated model represented by partial differential equations as the result of mathematical simulation. The structure of oscillations inside the grain could not be determined experimentally and also is studied in this work.     

Reaction of 2,4,6-trialkylpyrimidine 1,3-dioxides with electrophilic reagents

The nitrosation of 2,4,6-trimethylpyrimidine 1,3-dioxide and the bromination of 2,4,6-trimethyl- and 2-ethyl-4,6-dimethylpyrimidine 1,3-dioxides take place primarily at the methyl groups in the 4 and 6 positions of the heteroring. In the reaction of 2,4,6-trimethylpyrimidine 1,3-dioxide with phosphorus oxychloride chlorine is incorporated in the methyl group in the 2 position of the heteroring, while in the reaction with acetic anhydride an acetoxy group is incorporated in the methyl group in the 2 position and in the 5 position of the heteroring, whereas in the case of tosyl chloride a tosyloxy group is incorporated in the 5 position of the heteroring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 110–116, January, 1981.     

On the NMR spectrum in antiferromagnetic CsMnI3

An explanation is proposed for the spin-reduction anisotropy observed in an investigation of NMR in the noncollinear six-sublattice antiferromagnet CsMnI₃. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 41–45 (10 January 1999)     

Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.     

On the Diffuse Structure of the Toluene–Water Interface

The electric density profile along the normal to the phase interface between aromatic hydrocarbon toluene and water has been studied by X-ray reflectometry using synchrotron radiation. According to the experimental data, the width of the interface under normal conditions is (3.9 ± 0.1) Å. This value is much larger than a theoretical value of (5.7 ± 0.2) Å predicted by the theory of capillary waves with an interphase tension of (36.0 ± 0.1) mN/m. The observed broadening of the interface is attributed to its own diffuse near-surface structure with a width no less than Å, which is about the value previously discussed for (high-molecular-weight saturated hydrocarbon–water) and (1,2-dichloroethane–water) interfaces.     

Mass spectrometry of molecules and radicals in glow discharge plasma

The article represents a method and equipment developed for mass spectrometric analysis of plasma, that is, for measurement of concentration of atoms and molecules, and their fragments, including free radicals. A compact and inexpensive mass spectrometer is based on a quadrupole residual gas analyzer (RGA-200, Stanford Research Systems). The design of the two-section differential pumping chamber makes it possible to bring the mass-spectrometer analyzer to the entrance diaphragm to a distance of 40 mm in order to measure quick reacting and easily condensed particles. The equipment was used for analyzing the composition of spherical glow discharge plasma in methanol vapor and acetone-nitrogen mixture. A procedure for mass spectrum processing is proposed. Time-varying concentrations of all observed neutral particles are measured. Presently available data on sections of complete and dissociative ionization of molecules and their fragments, which are necessary for reconstructing concentrations of particles in plasma from measured mass spectra, are presented.     

Photoelectron spectra and electronic structure of boron difluoride β-diketonates with aromatic substituents

The electronic structure of boron difluoride chelate complexes of the acetyl acetonate type containing 4-biphenylene, 2-fluorene and 4-trans-stilbene as β-substituents is studied by means of photoelectron spectroscopy and quantum chemistry in the DFT approximation. It is established that the substituents affect the nature and sequence of the spectral bands. It is shown that calculation results corrected to the value of the Koopmans defect reproduce quite well the energy intervals between ionized states of complexes.