Generation and Propagation of Fractional Fluxons in Josephson Media

Journal of Experimental and Theoretical Physics - We consider the problems related to the use of 0–π junctions with a nontrivial current–phase relation in Josephson transmission...     

Catalytic properties of heteropoly compounds in 1,3-butadiene oxidation with hydrogen peroxide

The homogeneous oxidation of 1,3-butadiene (BD) in H₂O₂-HPC-CH₃CN (HPC = heteropoly compound) solutions has been investigated. The route of the reaction depends on the nature of the metal capable of coordinating with active oxygen in the HPC. The products of radical BD oxidation (acrolein, 3-butene-1,2-diol, 2-butene-1,4-diol, furan) form in the presence of H_3+n PMo_{12 ? n} V _n O₄₀ (n = 1, 2) acids. 3,4-Epoxy-1-butene (EB) and acrolein + furan, which form in equal amounts in the presence of the (n-Bu₄N)₅PW₁₁O₃₉Fe(OH) salt, result, respectively, from the electrophilic addition of hydrogen peroxide to BD and from radical BD oxidation on iron-oxygen complexes in the HPC composition. The reaction carried out in the presence of (n-Bu₄N)₃{PO₄[WO(O₂)₂]₄}, (n-Bu₄N)₅Na_0.6H_1.4PW₁₁O₃₉, or (EMIm)₅NaHPW₁₁O₃₉ yields EB with high selectivity on the reacted BD basis (up to 97%) and H₂O₂ (about 100%). The formation and conversion of the phosphotungstate peroxo complexes PW _n O _m ^α? (n = 2, 3, 4) that are active in BD epoxidation have been investigated by ³¹PNMR spectroscopy. The role of the tetrabutylammonium and ethylmethylimidazolium cations in the formation of these complexes has been demonstrated.     

The formation of an active component in V-Mo-Nb-O catalysts of ethane oxidation and ammoxidation

Summary Genesis of an active component in V-Mo-Nb-O catalysts for the oxidation and ammoxidation of ethane was studied. It was shown that the mixing of aqueous solutions of initial reactants leads to the formation of MoV complexes in the solution and to sedimentation of a binary Nb-Mo compound. The latter serves as the basis for the formation of the catalyst active component phase (a triple V-Mo-Nb compound with a variable composition of Mo₅O₁₄-like structure) during the subsequent treatment in air at 400°C.     

The Influence of the Structure of Phosphorus Acids Esters on their Reactivity in Aqueous and Nonaqueous Micellar Solutions

Abstract

The kinetics of the basic hydrolysis of O-alkyl-O-p-nitrophenyl-chloromethylphosphonate in aqueous micellar solutions of cetylpyridinium bromide (CPB) and the aminolysis of these substrates by n-hexylamine in the reverse micelles of polyethylene glycole-600-monolaurate (PM) in toluene has been studied.     

Structure and properties of H<Subscript>8</Subscript>(PW<Subscript>11</Subscript>TiO<Subscript>39</Subscript>)<Subscript>2</Subscript>O heteropoly acid

Heteropoly acid (HPA) H₈(PW₁₁TiO₃₉)₂O·xH₂O (I) is synthesized by three different ways and studied by chemical analysis, potentiometric titration, mass-spectrometry, IR, ³¹P, ¹⁸³W, and ¹⁷O NMR spectroscopy, thermogravimetry, and transmission electron microscopy. Anion I consists of two subparticles of the Keggin structure bridged by Ti-O-Ti. The dimeric anion exists in HPA aqueous solutions at [I] > 0.02 M. At pH > 0.6 it splits to a [PW₁₁TiO₄₀]⁵⁻ monomer stable up to pH ∼ 6. When heated (150–400)°C, I splits into H₃PW₁₂O₄₀ and, apparently, H₃PW₁₀Ti₂O₃₈ without phase separation. Thermolysis products are soluble and when dissolved in water turn again into I. Complete decomposition of I to oxides occurs at ∼450°C.     

Synthesis and properties of phosphorus-tungsten heteropolyacid H6P2W21O71

An electromembrane method has been proposed for the synthesis of H₆P₂W₂₁O₇₁, its resistance to heat in the solid state has been studied, and the Hammett acidity functions of concentrated aqueous solutions measured.Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660049. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 494–497, March, 1992.     

Synthesis of the acyclic precursor of an epothilone D analogue

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