Potentiometry with Solid Electrodes Based on Oxide Bronzes of Vanadium and Tungsten

A mathematical model is presented and the possibility of analytic application of electrodes of vanadium and tungsten oxide bronzes for the ion-selective determination of concentrations of oxygen-containing vanadium(5+) and tungsten(6+) ions in aqueous solutions 10^–5 to 10^–2 M at controlled pH is established.     

X-ray diffraction analysis of the modulated structure of Bi2Sr2CaFe2O y

The modulated structure of the Bi₂Sr₂CaFe₂O _y compound isomorphous with the Bi₂Sr₂CaCu₂O _y phase was refined by the method of the full profile analysis on the basis of the powder X-ray diffraction data. The analysis was carried out in the superspace group ofN:Abmm: 1 – 11 using the parameters of the unit cell of the basic structurea = 5.466(3),b = 5.446(5) andc = 31.25(9) Å and the modulation vectorq = 0.220(5)b* +c*. The model of excess oxygen interstitials into the BiO plane was used by applying a saw-tooth-type function of the form:U = 2U ₀ [(X ₄ -X ₄ ⁰ /)] [1]. The results point to a strong displacement of the atoms from their positions in the basic structure. An essential improvement of theR factors was obtained by taking into account the modulation waves of the higher harmonics.     

Structure and catalytic activity of metallocomplexes immobilized on carriers

Mono-, bi-, and trinuclear Ru complexes with various ligands immobilized on the surface of silica gels modified with -aminopropyl, formamide, sulfide, cyano, or mercapto groups, catalyze hydrodehalogenation ofp-bromotoluene by the transfer of hydrogen from NaBH4 in 2-propanol both in an Ar atmosphere and in air. The structures of the heterogenized metallocomplex catalysts prepared (the nature of the ligand environment, the oxidation number of the central atom) were studied by IR and XP spectroscopy. The immobilized binuclear Ru^II,III tetraacetate, which retains the structure of the original complex, exhibits higher catalytic activity in the hydrogenolysis ofp-bromotoluene than heterogenized mononuclear systems.For Part 5, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 70–74, January, 1995.     

Catalysis of the transfer of hydrogen from 2-propanol to cyclohexanone by immobilized ruthenium tetrasulfate

Heterogenized metal complex systems prepared by immobilization of ruthenium tetrasulfate on the surface of silica gel containing -aminopropyl groups or on the surface of modified styrene-divinylbenzene copolymer catalyze the transfer of hydrogen from 2-propanol to cyclohexanone in both Ar and air. It has been shown that the activity and stability of the obtained catalysts depend on the concentration of the promoting alkali and on the nature of the support.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1494–1496, August, 1994.     

Heat properties of Bu<Subscript>4</Subscript>NBr solutions in binary mixtures based on formamide

Heat effects of tetrabutylammonium bromide dissolution in mixtures of formamide with methanol and ethylene glycol at 25°C were determined. Partial molar enthalpies of the components of formamide-ethylene glycol mixtures at 25°C were measured by the calorimetric method, and the mixing enthalpies of this system were determined. Within the limits of the second approximation of the Debye-Hueckel theory the standard enthalpies of dissolution Δ_dis H ⁰ were calculated, and the enthalpies of Bu₄NBr transfer from formamide in its mixtures with water methanol and ethylene glycol were found on this basis. The enthalpy parameters of Bu₄NBr pair interactions with the components of the formamide-water, formamide-methanol, and formamide-ethylene glycol mixtures were calculated. The results obtained were compared with the data for the systems containing N-methylformamide and N,N-dimethylformamide.     

Synthesis,structure, and acylation of dihydroquinopimaric acid hydroxy derivatives

Reduction conditions of methyl dihydroquinopimarate with sodium borohydride and lithium aluminum hydride were established. As a result of the reduction 14β-hydroxy, 17α-hydroxy, 14β,17α-dihydroxy, and 14β,17α,21α-trihydroxy derivatives were obtained. The structure of methyl esters of 14β-acetoxy- and 17α-hydroxydihydroquinopimaric acid was established by XRD and NMR methods. Mono-, di-, and triacylates were obtained from the diterpene alcohols.     

Possibility of recording rare muonic decays of <Emphasis Type="Italic">B</Emphasis> mesons at the ATLAS detector in the case of LHC operation in the initial-luminosity mode

The possibility of recording the rare muonic decays B _d,s ⁰ → μ ⁺ μ ^? at the ATLAS detector (LHC, CERN) is studied. The question of what results can be expected within the first three years of LHC operation in the initial-luminosity mode is examined. The most important noncombinatorial background processes are listed for rare muonic decays of B mesons.     

Multiblock (segmented) shape memory copolymers containing Polyurethane and rigid-chain polyimide blocks

Russian Chemical Bulletin - Multiblock (segment) shape memory poly(urethane-imide) copolymers (PUIC) were studied by thermogravimetric analysis, differential scanning calorimetry, and dynamic...     

On the mechanism of intramolecular sensitization of photocleavage of the 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protecting group

A spectroscopic study of a variety of covalently linked thioxanthone(TX)-linker-2-(2-nitrophenyl)propoxycarbonyl(NPPOC)-substrate conjugates is presented. Herein, the TX chromophore functions as an intramolecular sensitizer to the NPPOC moiety, a photolabile protecting group used in photolithographic DNA chip synthesis. The rate of electronic energy transfer between TX and NPPOC was quantified by means of stationary fluorescence as well as nanosecond and femtosecond time-resolved laser spectroscopy. A dual mechanism of triplet-triplet energy transfer has been observed comprising a slower mechanism involving the T1(pipi*) state of TX with linker-length-dependent time constants longer than 20 ns and a fast mechanism with linker-length-dependent time constants shorter than 3 ns. Evidence is provided that the latter mechanism is due to energy transfer from the T2(npi*) state which is in fast equilibrium with the fluorescent S1(pipi*) state. In the case of direct linkage between the aromatic rings of TX and NPPOC, the spectroscopic properties are indicative of one united chromophore which, however, still shows the typical NPPOC cleavage reaction triggered by intramolecular hydrogen atom transfer to the nitro group.     

Coulomb excitation of neutron-rich Zn isotopes: first observation of the 2(1)+ state in 80Zn

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.