Granulometry of Metal Micropowders Treated in a Planetary-Type Ball Mill

Colloid Journal - Industrial micropowders of metals (aluminum, tungsten, hafnium, nickel, titanium, and zirconium) and a semimetal (amorphous boron) have been mechanically treated in a...     

The discrete Chebyshev algorithm for nonparametric estimation of autocorrelation function of electrochemical random time series

Journal of Solid State Electrochemistry - The discrete Chebyshev algorithm for nonparametric estimation of autocorrelation function of electrochemical random time series is presented. The algorithm...     

Photostimulated luminescence flash: from scientific photography to photonics of nanostructured materials

We have analyzed the possibilities of using the phenomenon of photostimulated luminescence flash for optical diagnosing of energy levels of structural and impurity defects of semiconductor crystals and nanostructures. New data on the spectra of deep localized states associated with adsorbed few-atom clusters Zn _n on the surface of ZnS; clusters Cd _n , Cu _n , and Ag _n on the surface of CdS; and clusters Ag _n on the surface of AgBr(I) have been presented, as well as results of investigation of photostimulated assembling processes of few-atom clusters on the surface of crystals using this phenomenon. We are the first to show the potential of the luminescence flash technique for studying the mutual arrangement of the levels of dye molecules and the bands of the crystal on the surface of which they are adsorbed, as well as of the spectra of localized states in colloidal CdS semiconductor quantum dots.     

Stability of the Coulomb phase in spin ice at finite temperature

The temperature dependence of the concentration of magnetic monopoles in spin ice has been analyzed. It has been shown that magnetic Coulomb interaction between monopoles can lead to a temperature-induced stepwise increase in their concentration by several orders of magnitude. This first-order phase transition is also accompanied by a decrease in the relaxation time by several orders of magnitude and can be considered as the melting of the Coulomb phase of spin ice. The phase diagram, as well as the critical point, has been determined.     

Propanal hydroamination with <Emphasis Type="Italic">p</Emphasis>-aminobenzoic acid

The propanal hydroamination was studied. It was found that the reaction in ethanol proceeded faster than in 2-propanol. By ¹H and ¹³C NMR method the existence was proved of a tautomeric equilibrium in ethanol solution between 4-(propylideneamino)benzoic acid and its enamine form, 4-(prop-1-en-1-ylamino)benzoic acid.     

Dimerization of biradicaloid heterocyclic compounds. Nitro derivatives of pyrrolo[1, 2-a]benzimidazole

A new type of easily dimerized heterocyclic compound, viz., nitro derivatives of 2-phenylpyrrolo[1,2-a]benzimidazole, was discovered. The reaction proceeds by heating the latter in acetic acid. A radical mechanism for the dimerization that takes into account partial protonation of the starting compound is discussed on the basis of electrochemical data, the high -donor capacity of 2-phenyl-4-methylpyrrolo[1,2-a]benzimidazole, the coloration that is characteristic for selfcomplexes, and EPR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 188–196, February, 1984.     

Condensed Imidazo-1,2,4-azines. 31. Synthesis and Chemical Transformations of Substituted 1,2,4-Triazepino[2,3-a]benzimidazoles

By reaction of 1,2-diaminobenzimidazole with 1,3-diketones, acetoacetic ester and its derivatives, we have synthesized substituted 1,2,4-triazepino[2,3-a]benzimidazole and 5H-1,2,4-triazepino[2,3-a]benzimidazol-4-one. By reaction of 5H-2-methyl-1,2,4-triazepino[2,3-a]benzimidazol-4-one with aromatic aldehydes or phenyldiazonium chloride, we have obtained 3-arylidene(phenylazo) derivatives of this compound, and by reaction with P₂S₅ we have obtained 5H-2-methyl-1,2,4-triazepino[2,3-a]benzimidazole-4-thione. We have shown that when reacted with ammonia, primary or secondary amines, the latter forms 4-amino-substituted 2-methyl-1,2,4-triazepino[2,3-a]benzimidazole.     

Electrophilic and nucleophilic substitution reactions in the series of 3-methylxanthine and its derivatives

The reactions of nitration and bromination of 3-methylxanthine were studied. Heating 3-inethyl-8-nitroxanthine with conc. HCl and HBr leads to a replacement of the nitro group by a halogen atom. The alkylation of 8-haloxanthines by alkyl halides were studied. It was shown that boiling 7-substituted 3-methyl-8-bromoxanthine derivatives with POCl₃ and PCl₅ leads to the formation of 2,6,8-trichloro-7-alkyl-purines. The structure of the synthesized compounds was confirmed by counter-synthesis, the data of elementary analysis, and mass spectrometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1129–1132, August, 1984.