A method for estimating the local lattice distortions near a magnetic ion from ligand hyperfine parameters: Yb3+trigonal centers in SrF2 and BaF2

An empirical relationship describing the radial dependence of the nondipole part of the anisotropic constant for the ligand hyperfine interaction in alkaline-earth fluorides is proposed. This relationship is used for calculating the distances between the magnetic ion and the fluorine ions involved in its nearest environment. The results of the calculations are in good agreement with the values obtained by other methods for both cubic and tetragonal fluorine centers in these crystals. The distances from the magnetic ion to different groups of nonequivalent fluorine ions of the nearest environment in Yb³⁺ trigonal centers of SrF₂ and BaF₂ are determined. It is found that the Yb³⁺ ion is slightly displaced along the trigonal axis away from the compensating fluorine ion.     

Fundamentals of the nonholonomically covariant formulation of the general theory of relativity

The physical foundations of the nonholonomic formulation of general relativity are determined, and the role of the Fock-Ivanenko coefficients in setting up and developing the tetrad formalism in general relativity is discussed. The physical and geometrical meaning of the nonholonomic transformations used in general relativity is determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 55–60, December, 1974.     

Method for estimating local lattice distortions near a magnetic ion based on the parameters of the ligand hyperfine interaction: Ce3+ in the fluorite homologous series

A method is suggested for estimating local lattice distortions near a paramagnetic center by using the parameters determined from experimental tensors of the ligand hyperfine interaction with surrounding nuclei through the use of a simple mathematical procedure. In general, a tensor with nine independent components can be unambiguously reduced to nine independent parameters characterizing the hyperfine interaction: the isotropic part, deviations from the symmetric and axially symmetric form, the axially symmetric component (containing dipole and pseudodipole contributions), and the angles defining the bond direction. Under certain physical assumptions, these parameters are used to estimate distortions of the first and second coordination shells of Ce³⁺ in the homologous series CaF₂, SrF₂, and BaF₂.     

Enhancements observed in the two-proton invariant mass distribution in the pionless deuteron breakup at 3.3 GeV/c

A sample of “non-spectator” events in the pionless deuteron breakup at a 3.3 GeV/c momentum has been investigated by means of a 1 m HBC at the JINR, Dubna. The two-proton invariant mass spectrum in the charge exchange channel exhibits two enhancements for masses of 2,010 MeV/c² and 2,160 MeV/c². Theoretical calculations taking into account one-pion exchange diagrams and virtual pion absorption by the deuteron have been carried out. It has been shown that the enhancement atM _pp=2,010 MeV/c² can be explained if some kind of singularity near theN-N threshold is required. The observed maximum atM _pp=2,160 MeV/c² is caused mainly by intermediate Δ production and pion absorption on the deuteron.     

On the convergence of difference schemes for generalized Benjamin–Bona–Mahony equation

We consider an initial boundary‐value problem for the generalized Benjamin–Bona–Mahony equation. A three‐level conservative difference schemes are studied. The obtained algebraic equations are linear with respect to the values of unknown function for each new level. It is proved that the scheme is convergent with the convergence rate of order k – 1, when the exact solution belongs to the Sobolev space of order . © 2013 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 301–320, 2014     

Thermostability of rat sarcoma M1 procollagen solutions,procollagen fibers and whole tissues

In close to equilibrium conditions (1° per 400 min), the DSC measurements demonstrated that the melting parameters of white rat sarcoma M1 procollagen equaled to T_m?=?34.4 °C and ΔT_m?=?2.7°, and the same parameters of fibers reconstructed from those solutions of procollagen were T_m?=?38.5 °C and ΔT?=?3.1°. These values were by 1.0° lower and 0.8° wider, and by 1.7° lower and 0.7° wider in comparison with the parameters of procollagen and fibers of healthy rat tissue, accordingly. The simultaneous increase in melting temperature and melting width, and a weak decrease in melting enthalpy demonstrated that sarcoma M1 procollagen had some defects. The considerable decrease by 7° in melting temperature and decrease in thermostability of procollagen fibrils in case of sarcoma M1 in comparison to the healthy norm gives a good prospective potential of using this approach as a quick DSC test to detect various sarcomas, including human sarcomas, by comparing the biopsy material or postsurgical tissues with the normal samples.

     

Pulsed EPR spectroscopy of the V KA center in CaF2:Na

An EPR study of the self-trapped hole center (V _KA center) in Na-doped single-crystal CaF₂ is reported. A five-component hyperfine-interaction tensor was used for the first time to describe EPR spectra adequately. The parameters of the electron spin Hamiltonian of the V _KA center, the tensors of ligand hyperfine interaction with all nearest-neighbor nuclei, and constants of quadrupole interaction with the Na nucleus have been determined. The structure of the center has been unambiguously established from the results obtained, and the mechanisms of its formation are discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 1619–1622 (September 1998)