The temperature of dielectric transition in a strong magnetic field

The temperature of dielectric transition of electronic system in a strong magnetic field is obtained.     

Density and velocity distribution function for freely expanding matter

For a system of noninteracting particles being initially in a spherical volume of a given radius, the density evolution and the distribution function are considered for various initial conditions. In particular, the conditions under which the density during free expansion of a sphere-shaped cloud of noninteracting particles remains spatially constant, while the boundary remains sharp, are determined. Alternative variants of free spherically symmetric expansion of a particle cloud are considered. The results of this consideration are applicable to various problems of the centrosymmetric explosion, and have astrophysical applications.     

Bond isomerism, formation of heterocyclic cationic complex, and insertion into the tantalum-fluorine bond in the reaction of TaF5 with MeNCO in CH2Cl2

The reaction of tantalum pentafluoride with methyl isocyanate in dichloromethane was studied by ¹⁹F NMR and IR spectroscopy. The reaction was found to give bond isomers TaF₅L, in which methyl isocyanate (L) is coordinated in the monodentate mode via N or O atom, and the heterocyclic cation [(μ-F)(μ-MeNCO)(TaF₄)₂] _n ⁺ (n=1,2). On storage of the reaction mixture, a signal in the C-F bond region appears in the spectrum and other new signals appear, which were assigned to the formation of O- and N- bonded isomers of pentafluoro complex of tantalum with aminocarboxylic acid fluoride anions [FC(O)N(Me)TaF₅]^? and [N{Me)C(F)OTaF₅]^?, which can be considered as insertion of MeNCO into the Ta-F bond. The IR spectroscopy data support these assumptions.     

Eta-meson photoproduction on protons,neutrons, and light nuclei in the nucleon-resonance region

Eta-meson photoproduction on protons, neutrons, and light nuclei is reviewed. New results obtained for photoproduction on protons and neutrons at the GRAAL facility are analyzed in detail. The experiment in question was performed in a gamma-ray beam that was obtained by means of Compton backscattering of laser photons on electrons at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). A comparative analysis of data on the differential cross sections and the asymmetries for eta-meson photoproduction allowed us to reveal some special features and to study the mechanisms of eta-meson photoproduction on nucleons in detail. Data available from the literature on eta-meson photoproduction on light nuclei are discussed in detail. Results that suggest the existence of bound states (etamesic nuclei) are presented. Particular attention is given to the newmethod of “taggedmesons,” which, according to the GRAAL experiment and to simulated results, makes it possible to study thoroughly the interaction of unstable mesons with intranuclear nucleons.     

Response of a Bloch oscillator to a THz-field

In this paper we report on the observation of response of a Bloch oscillator at room temperature to a THz-field of a frequency larger than the Bloch frequency. The oscillator consisted of a semiconductor superlattice structure, with an applied dc voltage giving rise to a dc electron drift current. Submitting the oscillator to a field at a frequency of 3.3 THz caused a sizeable reduction of the current; the THz-field was generated by use of intense THz-radiation pulses focused on an antenna coupled to the superlattice. We attribute the THz-field induced reduction of the current to a frequency modulation of the Bloch oscillations of electrons at the frequency of the THz-field, leading to reduction of the electron drift velocity and, consequently, of the current.     

A new method for the preparation of molybdenum and tungsten oxotetrafluorides

Conclusions A new method has been proposed for the synthesis of molybdenum and tungsten oxotetrafluorides by the reaction of the metal trioxide with the corresponding hexafluoride in a glass reactor.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2643–2644, November, 1985.     

Cell biosensor for detection of phenol in aqueous solutions

A microbial sensor for concentration measurement of phenol in aqueous solutions has been developed. Phenol-utilizing cellsPseudomonas putida GFS-8 immobilized in poly(vinyl)alcohol cryogel were used as a biological transducer. Relationships between phenol concentration in the activating medium and endogenic cell respiration have been established. Cell respiration and phenol concentration in the assay solution positively correlated at a phenol concentration range of 0.1–2.0 mg/L and were linearly dependent in the range of 0.1–1.0 mg/L. A Clark membrane electrode was the physiochemical transducer. The assay may be completed within 5 min. The cells oxidize phenol, pyrocatechol, mesityl oxide, aniline, and do not react with a number of xenobiotics, sugars, and alcohol. With the exception of aniline, most components found in waste waters from phenol production affect neither the assay process nor the ability of these cells to use phenol as exogenic respiratory substrate. The immobilized cells retained their ability to utilize phenol as an exogenic respiratory substrate for up to 1 mo.     

Spectroscopic characterization of mineral crystals produced by the bacterium Azospirillum brasilense

The results of spectroscopic structural and trace elemental analyses of mineral crystals produced by the soil nitrogen-fixing bacterium Azospirillum brasilense cultivated in a synthetic medium are presented and discussed. The mineral formed is shown to have a structure close to struvite (MgNH₄PO₄ × 6H₂O; ASTM file No. 15-762) with some differences which may be attributed to the presence of isomorphic admixtures of other cations (struvite is known to have a variety of forms). AAS/AES and ion chromatography analyses for a number of biologically important microelements and their role in the formation of the crystal structure, as well as some questions related to biomineralization are also discussed.     

Transformed steroids. 113. Cyclobuteno [16α,17α]pregnanes in cycloaddition and oxidation reactions

Conclusions The strained double bond in cyclobuteno[16,17]pregnanes is reactive toward certain dienes and oxidizing agents; here its reactivity toward dienes is increased by high pressure.See [1] for Communication 112.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1902–1904, August, 1980.