Observation of hydrogen induced intermediate borides in PrFeB based alloys by Mössbauer effect spectroscopy

In the present work, a quantitative analysis of the phase compositions by Mössbauer effect spectroscopy of solid and conventional hydrogen disproportionated Pr_13.7Fe_80.3B_6.0 and Pr_13.7Fe_63.5Co_16.7Zr_0.1B_6.0 alloys was carried out. Significant amounts of intermediate borides t-Fe₃B and Pr(Fe, Co)₁₂B₆ were detected after solid hydrogen disproportionation treatment in Pr_13.7Fe_80.3B_6.0 and Pr_13.7Fe_63.5Co_16.7Zr_0.1B_6.0 alloys, respectively. After conventional hydrogenation–disproportionation–desorption–recombination treatment these phases were not detected and in no case residual Pr₂Fe₁₄B-phase was found. It was observed that the amount of intermediate borides after disproportionation can be correlated with the degree of texture after recombination at various temperatures.     

Growth of K(DxH1 − x )2PO4 single crystals from solutions in the K2O-P2O5-(D, H)2O system

Based on the analysis of the K₂O-P₂O₅-D₂O solubility phase diagram, the optimum conditions of KD₂PO₄ crystallization—the compositions of mother solutions and the temperature range of crystallization—in the KH₂PO₄-D₂O system have been determined. The technique of K(D_xH_{1 ? x} )₂PO₄ growth is developed. The DKDP single crystals with deuterium concentration up to 88 wt % are grown on DKDP seeds from KH₂PO₄ solutions in D₂O by the method of temperature decrease.     

Detailed Description of Mixed Symmetry States in 94Mo Using Interacting Boson Model

We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+.     

Relaxation dynamics of a broadband nanosecond acoustic pulse in a bubbly medium

The first experimental observation of the propagation dynamics of a short broadband acoustic pulse in a resonance medium with gas bubbles is carried out. The probing pulse is generated using the optoacoustic effect. It is shown that the theory of short pulse propagation in media with generalized resonance relaxation adequately and accurately describes the dynamics of short pulse dispersion. A possibility to determine the relaxation and resonance parameters of media by the pulsed testing technique is demonstrated.     

Two-stream-like mechanism of zonal-flow generation by Rossby waves in a shallow rotating fluid

It is shown that the small-scale Rossby waves in a shallow rotating fluid placed in a gravitational field can generate large-scale zonal flows by means of a two-stream-like mechanism. This mechanism is revealed under the conditions when the Lighthill instability criterion is not satisfied. The text was submitted by the authors in English.     

Interaction of cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin with mono-and polynucleotides: A study by picosecond fluorescence spectroscopy

The interaction of water-soluble cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin (H₂TMPyP4) with some mono-and polynucleotides is studied by time-resolved and steady-state fluorescence spectroscopy, as well as by steady-state absorption spectroscopy. The fluorescence decay kinetics are analyzed by reconstructing the decay time distributions, which made it possible to describe in more detail than previously the complexes formed due to the interaction. The main effect of binding of H₂TMPyP4 adenosine 5′-monophosphate and to poly(dA-dT)₂ is shown to be an increase in the fluorescence lifetime from 4.6 ns in the solution to 8.3 and 12.3 ns, respectively. This effect is explained by a less polar (in comparison with water) environment of porphyrin in complexes, which leads to a decrease in the quenching action of the intramolecular charge transfer state between the porphyrin macrocycle and methyl pyridyl groups. In the case of complex formation with guanine-containing nucleotides (guanosine 5′-monophosphate and poly(dG-dC)₂), the effect of decrease in the quenching action of the intramolecular charge transfer state caused by a decrease in the medium polarity is superimposed by a stronger effect of decrease in the fluorescence lifetime of porphyrin as a result of intermolecular electron transfer from guanine to excited porphyrin. A high sensitivity of this intermolecular quenching to the mutual arrangement of the electron donor and the electron acceptor makes it possible to reveal four types of complexes between H₂TMPyP4 and guanosine 5′-monophosphate, which differ in the positions of four broad peaks in the porphyrin fluorescence decay time distribution (0.1, 0.7, 2.4, and 6.1 ns). For the complex with poly(dG-dC)₂, a narrow peak at 2.8 ns prevails in the fluorescence decay time distribution, with the contributions from two additional narrow peaks at 1.0 and 6.2 ns being small.     

Aminomethylation of 1-R-Tetrazoles

The reaction of tetrazole and a series of its 1-substituted derivatives with formaldehyde and alkylamines under mild conditions results in aminomethylation of the heterocyclic ring at the carbon atom with the formation of the corresponding Mannich bases. It was found that strong acids (HCl and CF₃COOH) have an activating action during the process. An ylide mechanism of the reaction was proposed from the data obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 66–71, January, 1991.