Viktor Anatol’evich Akulichev (On his 70th birthday)

Acoustical Physics -     

Two-gap superconductivity in the Fe-1111 superconductor LaFeAsO1−x F x : A point-contact Andreev-reflection study

Point-contact Andreev-reflection (PCAR) experiments were performed in the Fe-1111 layered superconductor LaFeAsO_0.9F_0.1 with resistive T _c ^on ∼ 27 K. The observation of two pairs of peaks in the low-temperature Andreev-reflection spectra clearly indicates the presence of two order parameters. The behavior of the two gaps as a function of temperature, obtained by fitting the conductance curves by means of the generalized two-band Blonder-Tinkham-Klapwijk model, shows some anomalies. A theoretical analysis performed within the two-band Eliashberg theory with a generic electron-boson coupling can reproduce the low-temperature value of the two gaps but generally fails in giving a satisfactory fit of their overall temperature dependence, indicating the rich and complex physics of these newly discovered superconductors.      

Correction to: Photoluminescence Characteristics of YAG:Ce,Gd Based Phosphors with Different Prehistories

Russian Physics Journal - There was a misprint in the third author’s name. It should read Yangyang Ju instead of Yu Yang yang.     

Cosmic rays as a new instrument of seismological studies

The state of the art of the short-termearthquake prediction problemis considered. A new method for monitoring the 3D stress state in the earthquake-prone zone using high-energy muons in cosmic rays and simultaneous measurements of acoustic and seismic signals in the frequency range from 1 Hz to 1–2 kHz is proposed. To implement this method, muons should be detected simultaneously with extensive air showers in an area of several square kilometers.     

Calculations in exceptional groups over rings

In the present paper, we discuss a major project whose goal is to develop theoretical background and working algorithms for calculations in exceptional Chevalley groups over commutative rings. We recall some basic facts concerning calculations in groups over fields, and indicate complications arising in the ring case. Elementary calculations as such are no longer conclusive. We describe the basics of calculations with elements of exceptional groups in their minimal representations, which allow one to reduce calculations in the group itself to calculations in subgroups of smaller rank. For all practical purposes, such calculations are much more efficient than localization methods. Bibliography: 147 titles.     

Electricoswitchable bonding of metal ions and complexes by calixarenes

The results of authors on designing electroswitchable supramolecular systems based on calix[4]arenes, calix[4]resorcinols, and transition metal ions and complexes are summarized. We consider systems in which the switching is performed owing to electrochemical reactions both of groups grafted to the macrocycle and bound substrates. Examples of electrochemically switchable luminescence are given.     

Structural and magnetic ordering in nanoparticles of complex 3<Emphasis Type="Italic">d</Emphasis>- and 4<Emphasis Type="Italic">f</Emphasis>-element oxides in germanate glass

Germanate glasses doped simultaneously with Fe and rare earth elements Gd, Tb, Dy, and Ho in concentrations of several percent have been investigated. It is shown that the phase state of paramagnetic elements changes from isolated ions and small clusters in the initial glass to crystalline magnetic nanoparticles in the samples subjected to heat treatments. The field dependences of the magnetization of such samples are characterized by magnetic saturation in fields of about 1 kOe and large Faraday rotation in the near-IR region (up to 10 deg/cm in the range from 700 to 800 nm).     

New possibilities of X-ray nanocrystallography of biological macromolecules based on X-ray free-electron lasers

X-ray serial nanocrystallography is a new technique for determining the three-dimensional structure of biological macromolecules from data on the diffraction of ultrashort pulses generated by X-ray free-electron lasers. The maximum achievable resolution for a set of experimental data as a function of the sample sizes and parameters of the equipment is estimated based on simulations of the diffraction process with allowance for changes in the electronic structure of the atoms of the sample under the influence of X-rays. Estimates show that nanocrystallography greatly enhances the possibilities of X-ray analysis, reducing the requirements for the minimum permitted size of the crystals and enabling to explore poorly crystallizable molecular objects, such as many membrane proteins and complexes of macromolecules.     

Suppression of the spectral selectivity of two-layer phase-relief diffraction structures

Optics and Spectroscopy - The method and results of studying the effect of relief depth on the attainable degree of reducing the spectral selectivity of two-layer diffraction structures based on...     

Growth and properties of layered oxycarbonate Bi2Sr4Cu2CO3O8 single crystals

Layered oxycarbonate Bi₂Sr₄Cu₂CO₃O₈ single crystals have been obtained for the first time by free growth in closed vapor-phase cavities. The morphology, structure, composition, and superconducting properties of these crystals have been investigated.