Chitin-binding antifungal protein from <Emphasis Type="Italic">Ficus carica</Emphasis> latex

A low-molecular-weight protein with antifungal activity was isolated from freshly collected latex of the Inzhir tree (Ficus carica L.) by successive affinity chromatography over chitin, cation-exchange chromatography over SP-Sephadex C-50, and reversed-phase HPLC. The molecular weight of 6481 and the partial N-terminus sequence of the protein were determined (MALDI-TOFMS). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 171–173, March–April, 2008.     

Effect of torsional stresses on the magnetoimpedance of amorphous wires with negative magnetostriction

A model to describe the effect of torsional stresses on the magnetoimpedance of amorphous wires with negative magnetostriction is suggested. An approximate expression for the impedance with regard to the spatial distribution of magnetoelastic anisotropy induced by torsional stresses is derived. It is shown that the relative variation of the impedance is maximal near a critical stress value at which the surface magnetic structure of the wire changes. The calculated dependences of the impedance on the external magnetic field and torsional stress are in good qualitative agreement with experimental data for amorphous wires with negative magnetostriction.     

Temperature behavior of bound magnetic polarons in antiferromagnetic chain

The behavior of a one-dimensional antiferromagnetic (AF) chain doped by non-magnetic donor impurities is analyzed, in the limit of low impurity density n  . The doping leads to the formation of ferromagnetically correlated regions localized near impurities (bound magnetic polarons or ferrons). The temperature evolution of the chain is calculated using an approximate variational method, and a Monte Carlo simulation. Both these methods give the similar results. The analysis of correlation functions for neighboring local spins demonstrates that the ferromagnetic correlations inside a ferron are significant even at high temperatures. The AF correlations in the rest part of the chain decay much faster with temperature. So, the ferron is a stable object that does not disappear even above the Néel temperature _TN$T_{\mathrm{N}}$. At rather small values of the electron–impurity coupling energy V$V$ (for V$V$ lower then the electron hopping integral t  ), the bound ferron depins from impurity retaining its magnetic structure. Such a depinning occurs at T∼V$T\sim V$.     

Frequency spectrum of the nonlinear magnetoimpedance of multilayer film structures

Magnetization reversal by high-frequency current in FeCuNbSiB/Al/FeCuNbSiB three-layer film structures is studied. The frequency spectrum of the voltage arising in a coil wound on the sample as a function of a permanent magnetic field (nonlinear magnetoimpedance) is taken. It is shown that the frequency spectra of the voltage are qualitatively different for the longitudinal and transverse orientations of the field with respect to the direction of the current. Frequency spectrum harmonics are demonstrated to be highly sensitive to a magnetic field. A simple electrodynamic model to describe experimental data is suggested.     

Pinning by twin boundaries and peak effect in YBaCuO high-T c superconductors

Measurements of the imaginary part of the ac magnetic susceptibility of single crystals and melt-textured samples of YBa₂Cu₃O_x (YBCO) at T=77 K in a magnetic field ranging between 1 and 20 kOe are reported. If the dc magnetic field H _dc is rotated in the ab plane of the sample, the magnetic susceptibility and critical current density j _c have peaks corresponding to the magnetic field aligned with twin boundaries. Peaks in the curve of j _c versus magnetic field are observed at angles corresponding to these peaks, where AH _dc in a wide range of magnetic fields. The results have been interpreted in terms of the theory describing twin boundaries as a system of quasi-planar pinning sites. The pinning is strong if the elastic displacements of flux lines are of the order of the vortex lattice constant d _f. These displacements decrease with the magnetic field because of the decrease in d _f, and the contribution of the elastic energy to the Gibbs potential is reduced accordingly, which is the cause of the peak effect. Zh. éksp. Teor. Fiz. 111, 2158–2174 (June 1997)     

A model for torsion-stress effect on nonlinear magnetoimpedance in amorphous wires with negative magnetostriction

A model to describe the influence of torsional stress on nonlinear magnetoimpedance in amorphous wires with negative magnetostriction is proposed. The nonlinear voltage response is found in the framework of the low-frequency approximation taking into account the spatial distribution of the circular magnetic field and the magnetoelastic anisotropy induced by the torsional stress. It is demonstrated that the application of torsional stress results in an increase of the second harmonic amplitude in voltage due to a reinforcement of helical anisotropy in the wire. The second harmonic amplitude is analyzed as a function of external field, torsional stress and current amplitude. The ranges of torsional stress and current amplitude to achieve maximal field sensitivity of the second harmonic are found.     

Charge Distribution and Spin Textures in Magic-Angle Twisted Bilayer Graphene

JETP Letters - The spin density wave existing on the background of the inhomogeneous charge distribution is examined as a possible ground state of the magic-angle twisted bilayer graphene. When...     

Theory of Nematic Superconductivity in Doped Topological Insulators (Brief Review)

JETP Letters - Theoretical studies of the theory of nematic superconductivity in doped insulators of the Bi2Se3 family have been reviewed. It is experimentally shown that their transition to the...     

Stereoselective oxidation of methyl phenyl sulfide in the presence of chiral ionic liquids

Several ionic liquids containing a chiral center either in the cation or in the anion have been prepared. They have been applied as catalysts and solvents for stereoselective oxidation of methyl phenyl sulfide to obtain the respective sulfoxide.     

Complexing ability of the substituted oxathiacrown ethers with vicinal arrangement of the sulfur atoms

Complexing ability of crown ethers opens new ways of designing selective extragents and sensitive receptors to various metal cations. The structure of the oxathiacrown ether complexes with Ag(I), Pb(II), Hg(II), Cd(II), Ni(II), Pd(II) ions was investigated using the methods of mass spectrometry and ¹H NMR spectroscopy. Formation of 1:1 and 2:1 ligand-metal complexes was established.