Areal objects and the problem of the λ term in the theory of gravitation

The following areal objects are considered: an ether thread contracting two material points and a multidimensional ether fibre in the pseudo-Euclidean world of events. An ether space-time model with an arbitrarily determined Riemannian metric is constructed and the problem of the λ term in Einstein equations is discussed in this regard.     

X-ray diffraction study of pore structure of pyrocarbon coatings obtained at various temperatures

X-ray diffraction (large- and small-angle scattering) has been used in an investigation of the pore structure and crystal structure of pyrocarbon coatings obtained by pyrolysis of a number of gaseous hydrocarbons at temperatures of 1300–2000°C. The coatings have a well-developed pore structure. The pore dimensions cover a range from fractions of a nanometer to hundreds of nano-meters. The pore volume and distribution depend primarily on the temperature of deposition. This relationship is extremal in nature. The volume of small pores (R=0.5-3.0 nm) is the greatest when T_d=1500°C; owing to the closed nature of the pores, this leads to an anomalous decrease in pycnometric density, the minimum density being observed at this same temperature. With T_d > 1500°C, growth of the crystals is observed, correlating with the decrease in volume of small pores.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya; No. 5, pp. 982–987, May, 1990.     

Externally definable sets and dependent pairs

We prove that externally definable sets in first order NIP theories have honest definitions, giving a new proof of Shelah’s expansion theorem. Also we discuss a weak notion of stable embeddedness true in this context. Those results are then used to prove a general theorem on dependent pairs, which in particular answers a question of Baldwin and Benedikt on naming an indiscernible sequence.     

Trends in formation of the nanocrystalline structure and cationic ordering in the Dy2O3-HfO2 (1: 1) system

Evolution of the nanocrystalline structure of the complex oxide Dy₂HfO₅ in the course of thermal annealing at temperatures to 1600°C has been studied by a combination of X-ray and synchrotron methods, including traditional and anomalous X-ray diffraction, PDF, EXAFS, and SAXS. The changes in crystallite size upon annealing of the as-synthesized amorphous precursor have been analyzed in detail. The systematic distortions of a fluorite-type perfect crystal structure (space group $Fm\bar 3m$ ) related to the nonequivalence of the local environment of the Dy and Hf cations but not resulting in formation of a pyrochlore-type cationordered structure in this system have been examined.     

Changes in the Structural Dimensionality of Selenidostannates in Ionic Liquids: Formation,Structures, Stability,and Photoconductivity

In situ transformations of selenidostannate frameworks in ionic liquids (ILs) were initiated by treatment of the starting phase K₂[Sn₂Se₅] and the consecutive reaction products by means of temperature increase and/or amine addition. Along the reaction pathway, the framework dimensionalities of the five involved selenidostannate anions develop from 3D to 1D and back, both in top‐down and bottom‐up style. Addition of ethane‐1,2‐diamine (en) led to the reversion of the 2D→1D step from 2D‐{[Sn₂₄Se₅₆]^16?} to 1D‐{[Sn₆Se₁₄]^4?}. As rationalized by DFT investigations, the 2D anion is thermodynamically favored. Photoconductivity measurements reveal that all samples show Schottky contact behavior with absolute thresholds below 10 V. One of the samples exhibits conductive states within the energy range of visible photons.     

A model of melting of rare gases within bubbles of crystalline metal matrix

Abstract

On the basis of experimental results obtained in the present and some other works a model of melting of rare gas solids within bubbles formed in a crystalline metal matrix as a result of ion implantation is proposed. Rare gas solid is supposed to melt on heating at the expense of the bubble volume expansion by emission of a dislocation loop. On this basis the melting temperature can be estimated as one which is enough to provide for a pressure inside a bubble sufficient for the initiation of the dislocation loop punching. Values of melting temperatures obtained in this way are in good agreement with available experimental data.     

On Socle and Semisimple Groups

We prove a theorem that gives a large array of new counterexamples to the known Baer (1949) and S. Chernikov (1959) problems related to socle groups. All these counterexamples are semisimple groups. We also establish many new properties of locally subinvariant semisimple subgroups. In particular, using these properties, we prove that all almost locally solvable M-groups are Chernikov groups.