Spectral analysis of rare-earth elements in ash of sapropel and its fractions

Quantitative atomic emission spectral analysis was used to study the rare-earth content in sapropel and the rare-earth distribution over the isolated fractions. The conditions for determination of Ce, Y, and La (analytical lines, arc discharge current, exposure time) were selected empirically. We calculated the metrological characteristics of the proposed technique. We have shown that in Tyurin fractionation, the nonhydrolyzable residue fraction has the highest concentrations of these elements. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 273–276, March–April, 2009.     

Femtosecond transient absorption with chirped pump and supercontinuum probe: Perturbative calculation of transient spectra with general lineshape functions, and simplifications

Femtosecond transient UV/vis absorption spectra of molecules in solution show vibronic structure initially while pump and probe pulses overlap, superimposed on bands which broaden and shift on several time scales. Third-order perturbation theory is used simulate and understand such spectra under experimental conditions, i.e., with chirped pump pulses and 40–80 fs pump/probe correlation time. The electronic system is coupled to a solvent bath whose fluctuations enter through a lineshape function g(t). This approach has two advantages. (i) In the general case when g(t) is modelled realistically it provides a distinction of coherent and sequential contributions to early transient spectra. The time-zero stimulated emission band can be extracted, giving access to the relaxation function for the emission frequency. (ii) For limiting forms of g(t) corresponding to the Bloch approximation and to inhomogeneous broadening the threefold time integrals underlying the theory reduce to a single integral. In such cases the lineshape formulation of transient absorption spectra can be used for data fitting.     

Reversible sorption of hydrogen on the novel hybrid material based on mesoporous chromium(<Emphasis Type="SmallCaps">iii</Emphasis>) terephthalate with included rhenium clusters

The interaction of mesoporous chromium(iii) terephthalate [Cr₃O(C₈H₄O₄)₃F(H₂O)₂] (MIL-101) with an aqueous solution of the anionic cluster [Re₄S₄F₁₂]⁴⁻ ({Re₄}) afforded a novel hybrid material {Re₄}@MIL-101. According to the elemental analysis data, one cavity of the nanoporous framework contains up to two-three tetranuclear rhenium clusters. The hybrid sorbent obtained reversibly absorbs up to 3.7 wt.% hydrogen at 77 K and 30 atm.     

Determination of the number of active sites in the metathesis reactions of 1-hexene and cyclopentene on the WC16 -Sn(CH3)4 catalytic system by an isotope method

Conclusion The percentages of primary carbene sites in the metathesis of 1-hexene and polymerization of cyclopentene on the WCl₆-Sn(CH₃)₄ catalytic system, as indicated by a radioisotope method, are 1.3 and 1.4%, respectively, relative to starting WCl₆. The Sn(CH₃)₄ methyl groups which participate in the formation of the starting active complexes enter the reaction products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2805–2807, December, 1986.     

Reliability Analysis for a Two Element System Attended by Two Repairmen

Stationary probabilities for the states of a system, the readiness coefficient, and the average productivity between failures with priority maintenance are obtained.     

Action of Nucleophilic Reagents. 5. Interaction of 2-Iminocoumarin-3-carboxamide with Anthranilic Acid and its Derivatives

N-Substituted 2-iminocoumarins are formed on reacting 2-iminocoumarin-3-carboxamide with anthranilic acid, methyl anthranilate, anthranilamide, and anthranilonotrile. Depending on the reaction conditions these recyclize into the corresponding 3-substituted coumarins or are hydrolyzed to coumarin-3-carboxamide. An alternative synthesis of some of the compounds has been effected.