Direct 13C-13C spin-spin coupling constants in the vinyl group of N-vinylazoles

The unshared electron pair of the dicoordinated nitrogen atom introduces a stereospecific contribution to the ¹³C-¹³C spin-spin coupling constant (SSCC) in the vinyl group of a series of N-vinylazoles, the value of which depends on the energetics of the unshared pair.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 1989.     

Structure of the internal boundary layer of a gas-discharge plasma in the axisymmetric case

An asymptotic representation for the solution of the problem of the radial structure of the internal boundary (transition) layer and the radial distribution of the basic physical plasma characteristics of the column of a free-burning low-pressure electric are in He is constructed. Sarov. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 185–195, May–June, 1998.     

Phase Behavior of Methane-Pentane Mixture in Bulk and in Porous Media

The adiabatic calorimetry method is used to measure the isochoric heat capacity and the dew-bubble curves for the methane-normal pentane mixtures in bulk for three different mixture compositions of n-pentane. The near-critical behavior of the mixture heat capacity indicates that at low n-pentane concentrations, this system is close to the special point of the critical locus. The effect of porous medium has been investigated for one of the mixtures studied in bulk. It has been shown that in porous medium the essential shift of the dew-bubble curve takes place. In our opinion this shift is caused by the formation of wetting film on the surface of porous medium. The estimation of film thickness resulting from the data obtained yields the value 7–8 nm.     

Lattice dynamics and hydrostatic-pressure-induced phase transitions in ScF3

New phase transitions induced by hydrostatic pressure in a cubic (under standard conditions) ScF₃ crystal are discovered by the methods of polarization microscopy and Raman scattering. The space groups $R\bar 3c$ for Z=2 and Pnma for Z=4 are proposed for the high-pressure phases. A nonempirical computation of the lattice dynamics of the crystal is carried out. It is shown that, under normal pressure, the cubic phase is stable down to T=0 K, while the application of a hydrostatic pressure gives rise to a phonon branch in the vibrational spectrum (between points R and M of the Brillouin zone) with negative values of squares of frequencies. The condensation of soft mode R₅ at the boundary point of the Brillouin zone leads to rhombohedral distortion of the cubic structure with the unit cell volume doubling. The calculated frequencies at q=0 of the ScF₃ lattice in the distorted rhombohedral phase are real-valued; the number and position of frequencies active in Raman scattering are in accord with the experimental values.     

Estimation of the Upper Limit for the Amplitude of the Dipole Anisotropy of the Total Flux of 25-Gev to 1-Tev Cosmic-Ray Electrons and Positrons

Physics of Atomic Nuclei - Searches for the anisotropy of the total electron and positron fluxes in high-energy galactic cosmic rays are performed. Data collected by the PAMELA magnetic...     

Surface‐active metal‐coordinated oligoperoxidic radical initiators. I. The interrelation between the microstructure of ditertiary oligoperoxides and their ability to form stable metal complexes

Carbon‐chain heterofunctional oligoperoxides (HFOs) with ditertiary peroxidic, carboxy, or hydroxy groups formed stable coordinated complexes through their interaction with transition‐metal salts in organic solutions. The oligomeric metal complexes (OMCs) were separated from the reaction mixture and investigated through elemental analysis, voltammetry, and atom‐adsorption, IR, and UV spectroscopy. From these investigations and the calculated values of the mole fraction and formation constants of the stable complexes of the copper cations and HFOs, the probable cooperative mechanism of the complex formation by such oligomers was suggested. The existence of two levels of HFO molecule ordering, namely HFO microstructure and the structure of the hydrogen‐bonded complexes formed by HFOs, explained the cooperative mechanism and some characteristics of the OMC formation. The mole fraction and formation constants of the OMCs were interrelated with the disposition of the complex‐forming groups in the chain of HFOs. From the experimental data, it can be concluded that the complex‐forming groups of the HFOs possessed different reactivities both in the complex formation with metal cations and in the reactions involving the resulting OMCs. The shift in the half‐wave potential of the  O:O bond reduction during the transition from the HFO to a mixture of HFO and Cu²⁺ and to OMC indicated an increase in its reactivity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 516–527, 2000     

Fast etching and metallization of SiC ceramics with copper-vapor-laser radiation

The etching of polycrystalline SiC is studied with the help of radiation of a copper-vapor laser either in air or under the layer of a liquid (H₂O, DMSO). The etching rate in air is as high as 0.24 m/pulse, in DMSO 0.07 gm/pulse at an energy density of 16 J/cm². The etched surface is characterized with Scanning Electron Microscopy (SEM) and X-ray diffractometry. Etching of SiC ceramics in air revealed the partial amorphization of SiC and the formation of microcrystals of elementary Si with an average size of 300 Å. The etched surface of SiC ceramics takes on the ability to reduce Cu from a corresponding electroless plating solution. The adherence of the deposit is as high as 30 N/mm² and is a function of the scanning velocity of the laser beam.     

Manifestation of the bound state \bar NN (1870) in the annihilation process \bar pd \to p_s 5\pi

It is shown that the existence of an N?N bound state with a mass of approximately 1870 MeV and width 10 MeV follows from analysis of the experimental data on the momentum distribution of recoil protons in the annihilation process p?d→p _s5π.     

Anomalies in the variation of elastic properties of cesium during phase transformations under a pressure up to 5 GPa

The pulsed ultrasonic method is used for studying polycrystalline cesium under a pressure up to 5 GPa. Elastic parameters and compression ratio of cesium are determined and anomalies in the elastic properties of cesium during phase transitions CsI-CsII-CsIII-CsIV are revealed. It is found that the CsII-CsIII electron-structure transformation is preceded by anomalous compressibility of the fcc phase of cesium and by softening of longitudinal and transverse acoustic modes of the cesium phonon spectrum.