Microhardness of the compounds La2CuO4 and La1.85Sr0.15CuO4 at temperatures from 81 to 292 K

The microhardness of La₂CuO₄ and La_1.85Sr_0.15CuO₄ crystals is measured in the temperature range 81–292 K, and the influence of various factors on it is investigated. The thermal activation parameters of the plastic deformation process in the vicinity of the indenter impression are estimated. The change of the phase state of the compound La_1.85Sr_0.15CuO₄ at the temperature T ₀=180 K and the appearance of domain (twin) boundaries formed in the ferroelastic tetraortho transition are not seen in the temperature dependence of the microhardness. The results of the study are compared with previously published results for YBa₂CuO_7−x crystals. Fiz. Tverd. Tela (St. Petersburg) 40, 493–497 (March 1998)     

An Analog of the Sauer Theorem

In this paper, we present an analog of the Sauer theorem for projectively equivalent surfaces in the class of infinitely small equiareal deformations that pointwise preserve the spherical image of the surface.     

Oxidation of 2,4,6-triaryl-4H-thio(seleno)pyrans with selenium dioxide

The oxidation of 2,4,6-triaryl4-H-thio(seleno)pyrans with selenium oxide in pyridine was studied. It is shown that the corresponding 2,4-diaryl-5-aroyl-thiophenes and -selenophenes are formed as a result of the oxidation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 767–769, June, 1989.     

Computer modeling of curves and surfaces

The first part of this work deals with the investigation and modeling of foliations generated by dynamic systems on their phase spaces and configuration spaces. In the second part, we speak in greater detail about curves and surfaces in three-dimensional space and their geometrical characteristics that can be useful for modeling polymer conformation.     

On the distribution of integral points on cones

New results on the distribution of integral points on the cones

Identities Involving Coefficients of Automorphic L-Functions

Let f(z) be a holomorphic Hecke eigenform of weight k with respect to SL(2, ℤ) and let

The plastic deformation of ultrafine grained aluminum at 0.52 K

The plastic deformation of ultra-fine-grained aluminum subjected to equal-channel angular pressing has been studied at a temperature below the superconducting transition point. The stress-strain curves σ(ɛ) for polycrystals and the effect of the superconducting transition on the jump of flow stress Δσ _NS have been investigated. It is shown that the grain refinement, along with the increase in the flow stress, leads to a correlated change in the shapes of the dependences σ(ɛ) and Δσ _NS (σ). The results obtained are explained by the features of dislocation accumulation in ultra-fine-grained polycrystals and by the manifestation of the inertial properties of dislocations under low-temperature plastic deformation.     

Binuclear Oxidovanadium(IV) Complex with the Bridging Chloranilate Ligand: Synthesis and Magnetic Properties

Russian Journal of Coordination Chemistry - The binuclear oxidovanadium(IV) complex [VO(Dbbpy)Cl(Ca)Cl(Dbbpy)VO] (I) is synthesized by the reaction of [VO(Dbbpy)(H2O)Cl2] (Dbbpy is...     

When was ptolemy's star catalogue in ‘Almagest’ compiled in reality? Statistical analysis

This work is devoted to describing new statistical and geometrical procedures for dating ancient star catalogues considering numerical data contained in these catalogues and the known real configurations of stars on the celestial sphere. The method was tested on several star catalogues whose dates are well known (Tycho Brahe, etc.) and on several artificially generated star catalogues. Then the same method was applied to the Almagest. The results obtained do not confirm the traditional dating of the Almagest (2nd century AD or 2nd century BC) but shift its dating to the Arabian epoch: 600–1300 AD.