Determination of Rare-Earth Elements in Sulfide Minerals by Inductively Coupled Plasma Mass Spectrometry with Ion-Exchange Preconcentration

A procedure was developed for determining ultratrace rare-earth elements in sulfide minerals by inductively coupled plasma mass spectrometry with ion-exchange preconcentration. The concentration factor was 200. The found concentrations of rare-earth elements were 6–30 times lower than those in chondrites. For lanthanum and praseodymium, RSD < 10%; for other rare-earth elements, RSD < 6%. The accuracy of the results was verified by the addition of known amounts of Eu, Tb, Tm, and Lu to a chalcopyrite sample at the stage of decomposition with HCl and HNO₃. The calculated yield of rare-earth elements was 94–96%. The detection limit was from 0.06 ng/g (6 × 10^–9%) for lutetium to 5 ng/g (5 × 10^–7%) for cerium. The procedure was used for the determination of rare-earth elements in chalcopyrites, pyrites, and sphalerites.     

Asymptotics of many-electron wavefunctions and calculation of tunnel transitions

A new method for defining the wavefunction asymptotics for many-electron systems in the far-subbarrier region is suggested. The method is based on the Lippman-Schwinger formalism and can provide an accuracy in defining the asymptotics similar to that in the main region of the electron localization (MREL). The wavefunctions in MREL are the basis for obtaining the asymptotics. Molecular, cluster and surface systems are considered. A new approach to the calculation of tunneling transitions is formulated. A general expression for the tunneling current in scanning tunneling microscopy (STM) is obtained which strictly takes into account the penetration factor, the correlation between the tunneling current from individual atoms, and the angular dependence of asymptotics of basic atomic functions. This permits us to state and correctly solve the problem of defining the electron wavefunctions of the surface using the data of the tunneling current measurement at various biases and the positions of the tip.     

Synthesis and properties of pyrimidinylalkylphosphonic acids

Conclusions Some esters of -(oxodihydro-N-pyrimidinyl)butyl- and -(oxodihydro-N-pyrimidinyi)pentylphosphonic acids, and also some diphenyl -(2,4-dioxo-6-methyl-1,2,3,4-tetrahydro-N-pyrimidinyl)alkyl phosphates, were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1397–1401, June, 1975.     

Kinetics of the reaction of triethylphosphite with β-acetoxyethylmethyl ketone

Conclusions The kinetics of the reaction of triethylphosphite with-acetoxyethylmethyl ketone was studied by infrared spectroscopy, and was found to be of the second order.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2614–2616, November, 1968.     

Semiempirical andab initio calculations of the full configuration interaction using iterated Krylov’s spaces

The algorithm proposed previously for calculating the full configuration interaction using the variation matrix of the wave operator involves the numerical solution of the corresponding incomplete eigenvalue problem based on iterated Krylov’s subspaces. In practice, that means using the multistep gradient method as a special version of the Lanczos method. The high efficiency of this algorithm, which can readily be used in personal computer calculations, is proved by particular ab initio calculations of the full configuration interaction for the helium and beryllium atoms as well as by semiempirical calculations of π-shells for naphthalene and diphenylene. The algorithm is of particular assistance in obtaining numerous excited states, which are used for determining various spectral sums (polarizability, van der Waals interaction constants, and photoionization cross sections). Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 1, pp. 14–22, January–February, 1997.     

Optical and chromaticity parameters of transition metal complexes with 1-nitroso-2-naphthol-3,6-disulfonic acid in the presence of surfactants

Optimal conditions for the complexation of transition metal ions [Cu(II), Ni(II), Co(II, III), and Fe(II, III)] with 1-nitroso-2-naphthol-2,6-disulfonic acid have been determined by spectrophotometry in the presence of cationic (cetylpyridinium and cetyltrimethylammonium bromides) and nonionic (OP-10, neonol) surfactants. The introduction of nonionic surfactants does not influence the optical parameters of the system, while the introduction of cationic ones leads to hyperchromic and hypsochromic (for the system Fe(III)-NRS-surfactant) effects. The stoichiometric ratios determined by the method of isomolar series and treatment of the saturation curves of cationic surfactants at pH 4.0 are Me(II): R: surfactant = 1: 2: 4, Me(III): R: surfactant = 1: 3: 6. The molar absorption coefficients and chromaticity parameters of ternary complexes have been determined. A 2–5-fold increase in the molar absorption coefficients and chromaticity functions as compared to binary systems has been revealed.     

Aminomethylation of substituted pyrroles and 4,5,6,7-tetrahydroindoles with biogenic cyclic amines

Aminomethylation of 2-methyl(aryl)-, 2-aryl-3-alkylpyrroles, 4,5,6,7-tetrahydroindole and its 1-vinyl- and 1-benzyl-substituted derivatives with a mixture of 5% water-ethanol solution of formaldehyde and cyclic amine (pyrrolidine, piperazine, and morpholine) without catalyst at room temperature leads to the formation of the corresponding 2-aminomethylpyrroles and 2-aminomethyl-4,5,6,7-tetrahydroindoles in up to 92% yields. In reaction of 1-vinyl-4,5,6,7-tetrahydroindole with formaldehyde water solution and piperazine in a 60% yield 1,4-bis(1-vinyl-4,5,6,7-tetrahydroindol-2-yl)piperazine was obtained, a promising bifunctional monomer and a building block for the synthesis of new indole derivatives, in particular, of biologically active polymers. In the reaction of 2-methylpyrrole and 4,5,6,7-tetrahydroindole with formaldehyde and morpholine along with the С²-aminomethylation the 1-hydroxymethylation of the pyrrole ring was observed.     

Demonstrator of continuous-detonation air-breathing ramjet: Wind tunnel data

First experimental investigations were carried out into the detonation combustion of hydrogen in a demonstrator of an original-design air-breathing ramjet while blowing with an air flow at Mach 4 to 8 in an impulse wind tunnel, and for the first time under these conditions, continuous spin and longitudinal pulsed modes of detonation combustion of hydrogen in an annular combustor were detected.     

Selective precipitation of rare earth orthophosphates with hydrogen peroxide from phosphoric acid solutions

It has been shown for the first time that the use of hydrogen peroxide allows precipitation of rare earth orthophosphates (La–Tb) from phosphoric acid solutions at temperatures below 100°C. Either anhydrous or hydrated orthophosphates with monazite or rhabdophane structure, respectively, can be obtained depending on rare earth element position in lanthanide series and precipitation conditions (orthophosphoric acid and hydrogen peroxide concentration). Hydrated orthophosphates with rhabdophane structure can be prepared by precipitation with hydrogen peroxide for all studied rare earth elements.