Green luminescence in diffusion-doped layers of zinc selenide

Diffusion-doped layers with a green emission band dominating in the room-temperature luminescence spectrum are obtained by annealing single-crystal zinc selenide substrates in tellurium and zinc vapors.     

On an Inverse Problem for a Parabolic Equation

In this paper, we study the inverse problem of the reconstruction of the right-hand side of special form for a parabolic equation in u in which the coefficients of u _t and u depend on u _(x,t) , with overdetermination given by the integral of the solution over time. The Fredholm property for this problem and the existence and uniqueness theorems in Sobolev spaces are established.     

Conductance of a multiterminal ballistic wire

JETP Letters - An experimental study of the two-, three-, and four-terminal resistance of a ballistic wire is carried out. The wire is fabricated on the basis of high-mobility 2D electron gas in an...     

Bounded sets in topological groups and embeddings

We show that the existence of a non-metrizable compact subspace of a topological group G often implies that G contains an uncountable supersequence (a copy of the one-point compactification of an uncountable discrete space). The existence of uncountable supersequences in a topological group has a strong impact on bounded subsets of the group. For example, if a topological group G contains an uncountable supersequence and K is a closed bounded subset of G which does not contain uncountable supersequences, then any subset A of K is bounded in G?(K?A). We also show that every precompact Abelian topological group H can be embedded as a closed subgroup into a precompact Abelian topological group G such that H is bounded in G and all bounded subsets of the quotient group G/H are finite. This complements Ursul's result on closed embeddings of precompact groups to pseudocompact groups.     

The contact problem of electroelasticity for a plane elliptic die

We obtain an exact solution of the problem of the stress-strain state of an elastic piezoelectric half-space acted on by a rigid elliptic die with a flat base. The axis of symmetry of the body coincides with the direction of the field of preliminary polarization of the body. The solution is confined to the case of translational displacement of the die. We determine the quantities that characterize the mechanical and electric fields that arise in the region of contact of the die with the half-space. Bibliography: 7 titles. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 28, 1998, pp. 40–52.     

Benzindoles

A large amount of structural similarity between 4,5-benzindole and naphthalene and between 6,7-benzindole and indole was detected on a basis of a comparison of the absorption, fluorescence, and phosphorescence spectra of isomeric benzindoles with the spectra of indole and naphthalene. A great analogy between indole and 6,7-benzindole as compared with 4,5-benzindole is also observed during the formation of hydrogen bonds, as indicated by the shift in the absorption band of the NH group in the IR spectra of the investigated compounds in the presence of various proton acceptors.     

Infrared absorption spectra of cyanide complexes of group VIII metals with nitrogen- and sulphur-containing ligands

Research into the IR absorption spectra of the products of interaction between nitrosyl pentacyanide complexes of some Group VIII metals and thiourea and thiocyanate has been carried out in the region 400–4000 cm^?1.An assumption has been made concerning the formation of intermediates of the association type. The changes in the spectra during the formation of intermediates indicate a weakening of ligand bonds with a metal-complexing agent.The data obtained for the series of cyanide complexes of Group VIII metals with heterogeneous ligands allow us to suggest a strengthening of the M-S bond between thiourea and metals in the order Os > Ni > Co ? FeThe M-NCS bond between the thiocyanate group and metals of the iron family is practically equivalent.Osmium coordinates the SCN^? group through the sulphur atom.     

Determining the main thermodynamic parameters of caffeine melting by means of DSC

The temperature and enthalpy of the melting of caffeine, which are 235.5 ± 0.1°C and 19.6 ± 0.2 kJ/mol, respectively, are determined by DSC. The melting entropy and the cryoscopic constant of caffeine are calculated.     

Allyl-containing polyaryl ethers with perfluorinated mono- and biphenylene fragments

A method for the synthesis of fluorinated allyl-containing bisphenol based on 4,4′-[(2,3,5,6-tetrafluoro-1,4-phenylene)bis(oxy)]diphenol has been elaborated. Curable aromatic polyethers have been prepared via polycondensation of the synthesized bisphenol with decafluorobiphenyl. The influence of bases, namely K₂CO₃ and NaH, on the molecular weights of polymers has been studied, and the conditions of their curing at allyl moieties have been found. Mechanical, physicochemical, and dielectric properties of allylcontaining polymers are dependent on the method of their preparation and curing.