Reception of a Signal with Unknown Duration

The maximum likely and optimal (Bayesian) algorithms for detecting an arbitrary-shaped signal observed against the background of Gaussian white noise and for measuring the duration are synthesized. Exact expressions for the characteristics of the maximum likely algorithms are found. The characteristics of the Bayesian algorithms are obtained using computer simulations.     

Decrease in the group velocity of a light pulse in the Bose-Einstein condensate of a dilute gas

A semiclassical theory of electromagnetically induced transparency in a Bose-Einstein condensate is considered. A nonlinear Schrödinger equation that describes the interaction of the Bose-Einstein condensate with an electromagnetic field is derived. An analysis of the obtained solutions to this equation demonstrates a decrease in the group velocity of the light pulse.     

Influence of chemical composition of filler's surface on the burning of foam plastics

The influence of additives such as TiO₂, Al₂O₃ and their mechanical mixture as well as aluminium oxide, the surface of which contains phosphorous and titanium-oxide nanostructures, on the combustibility of foam plast (trade mark PEN-I), produced on the basis of epoxide novolak block-copolymers, was studied. It was stated that the incorporation both phosphorous-containing and titanium-containing oxides in the composition results in significant (in two to five times) decreasing of the samples’ combustibility. The probable mechanism of inhibition of burning process for those combustion retarders was discussed.     

Acrylonitr1le anion-radical detection by infrared internal reflection spectra

The application of internal reflection spectroscopy to the study of interface boundary layers has been extended over cases in which unstable particles appear at the interface as a result of imposing a negative electrical potential on the germanium hemicylinder, used simultaneously as an optical prism in the internal reflection spectroscopic device and as an electrode. The appearance of the particles is detected by their internal reflection spectrum. The method has been applied in the case of the electrochemically induced polymerization of acrylonitrile. Two particles were found to be generated during electrolysis. They are assigned to the anionradical and to the di-anion of acrylonitrile.     

Thermal and Photochemical Reactions of 1,2-Annelated Barrelenes and Hydrobarrelenes in the presence of transition-metal carbonyls

The [Co₂(CO)₈]-mediated retro-Diels-Alder reaction of the annelated barrelenes 1 afforded the 1H-indol-2(3H)-one derivatives 3 (Scheme 1), while the hydrobarrelene 4a , under the same conditions, was converted to the anilide 6 (Scheme 2); 4b remained unaffected. The direct irradiation of 1 led to the annelated cyclooctatetraenes 7 (Scheme 3). On irradiation in the presence of excess of [Fe(CO)₅], 1a , 1b , and 4a gave the tricarbonyliron complexes 8 , 9 , and 11 , respectively (Schemes 3 and 4); under these conditions, 4b was inert.     

Intramolecular Cyclizations of Allenic Acylureas and -Amides

Allenic acids are found to add to dicyclohexylcarbodiimide affording, in the presence of Et₂NH, the 4H-1,3-oxazin-4-ones 5 via 4 . Under neutral conditions, they add to diaryl- or pyridyl(cyclohexyl)carbodiimides and triphenylketene imine to give the corresponding tricyclo[5.2.2.0^1,5]undeca-4,8,10-trien-3-ones 7 , 8 , 9 , and 12 . The allenic phenyl ester 13a dimerises, on heating in a [2+2] head-to-head fashion, to 14 but fails to undergo intramolecular Diels-Alder cyclization, to 15 .     

Acid-Base Properties and Prototropic Tautomerism of Isomeric 1,2,4-Triazin-3- and -5-ones

The acidity and basicity constants of isomeric phenyl(aryl)-1,2,4-triazin-3- and -5-ones in aqueous solution were determined by spectrophotometry: pK _a = 7.3–6.2; pK _BH+= 0.1 to –2.2. 1,2,4-Triazin-3-ones are weaker bases than the corresponding 1,2,4-triazin-5-ones. According to the AM1 calculations, the most thermodynamically favorable tautomer in the gas phase is the oxo form: namely, 2H-tautomers of the neutral bases and 2,4-H,H ⁺-tautomers of the conjugate acids.     

Synthesis of bis(cyclopentadienyl)diazadiene complexes of ytterbium. An X-ray structural study of the Cp2Yb(μ-η2:Ti2-But-N=CH-CH=N-But)Li(DME) complex

Ytterbium complexes, Cp₂Yb(-₂:²-DAB)Li(DME) (1) and CpYb(DAB)K(THF)₂ (2), containing a bridging diazadiene ligand were prepared by the reaction of CpYbCl₂(THF)₃ with (DAB)Li₂ (11) and (DAB)^–K⁺ (12) (DAB = Bu^t-N=CH-CH=N-Bu^t). The structure of complex1 was established by X-ray diffraction analysis. The complex is binuclear: the Yb atom of the Cp₂Yb fragment and the Li atom, which is bonded as well with the chelating DME molecule, are linked by the DAB ligand.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 148–151, January, 1994.     

Influence of chemical modification of the surface of polyethylene with phosphorus, boron, titanium, vanadium, and silicon halides on its vapor permeability

The influence of a gas-phase chemical modification of low-density polyethylene with volatile halides of various elements [PCl₃, TiCl₄, VOCl₃, BBr₃, and Si(CH₃)₂Cl₂] on the surface layer morphology and vapor permeability of polymeric formulations was examined by atomic-force microscopy, chemical analysis, and adsorption method.     

Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles

We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH₂Ph, t-Bu, CH₂Cl, CCl₃, CF₃) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pK_BH ⁺ is −1.8 to −5.2). The values of pK_BH ⁺ determined on the H₀ and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 748–756, May, 2006.