Time spectroscopy in theA 1∑ u + state of Li2

We have determined effective cross-sections for resonant transfer of excitation energy from state-selected Li₂ molecules to ground state Li atoms $$Li_2 A\left( {\upsilon ',J'} \right) + Li2S \to Li_2 X\left( {\upsilon '',J''} \right) + Li2P$$ with two different experimental techniques. Absolute cross-sections were derived from lifetime measurements of 114 rotational levels of theA-state subject to resonant collisions which belong to vibrational statesv′=4, 5, 6, 7 and 11 of⁶Li₂ and⁷Li₂. Cross-sections amount to several thousand Ų dropping off sharply with a resonance half-width of about 16 cm^?1. The resonance behaviour of the collision cross-section inferred from lifetime data could be confirmed by a double resonance technique probing the number of excited atoms with a second laser while the first laser was scanned over the Li₂ X?A absorption band. Due to their high reliability our data prove a good basis for the test of theoretical models. In contrast to earlier investigations significant deviations were found to exist between the measured cross-sections and those predicted by the first-order dipole-dipole scattering theory.     

Synthesis and properties of N-methylmorpholinium 4aryl-6-methyl-5-phenylcarbamoyl-3cyano-1,4dihydropyridine-2-thiolates. Molecular and crystalline structure of 2allylthio-6-methyl-5-phenylcarbamoyl-4-(2chlorophenyl)-3-cyano-1,4-dihydropyridine

By the condensation of an aromatic aldehyde, the anilide of acetoacetic acid, cyanothioacetamide, and Nmethylmorpholine, substituted N-methylmorpholinium 1,4-dihydropyridine-2-thiolates have been synthesized and subsequently used in the synthesis of the corresponding thiones, 2-alkylthiopyridines, thieno[2, 3b]pyridines, and disulfides. X-ray diffraction has been used to establish the structure of 2-allylthio-6-methyl-5phenylcarbamoyl-4-(2-chlorophenyl)-3-cyano-1, 4-dihydropyridine.T. G. Shevchenko Lugansk State Pedagogical Institute, Lugansk 348011. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, Moscow 117813. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1243–1251, September, 1996. Original article submitted May 13, 1996.     

The effect of mechanical activation on the thermal decomposition of chalcopyrite

Experimental results on the influence of preliminary mechanical activation on the thermal decomposition of chalcopyrite are presented and discussed. The following experimental facts were found:

Organophosphorus reagents as extractants-part 3. Synergic effect of triphenyl phosphine oxide and bis(diphenyl phosphinyl) alkanes on extraction of iron(III) from thiocyanate medium with 2,4-pentdione

The extraction of iron(III) from thiocyanate medium was carried out with a synergic combination of 2,4-pentdione (Hacac) and either triphenyl phosphine oxide (Ph(3) PO) or bis (diphenylphosphinyl) alkanes, Ph(2)P(O)(CH(2))(n).P(O)PH(2) [ligand abbreviation, n: dpeO(2), 2; dpbO(2), 4]. Iron(III) was quantitatively separated from its binary mixture with chromium(III), manganese(III), cobalt(II), nickel(II), zinc(II), cadmium(II), mercury(II), lead(II), magnesium(II) and from steel samples. Copper(II) and silver(I) however, interfered. The percentage extraction was 99.0%. The respective extraction constants, K(HA), K(L) or K(syn), for the extracted species, [Fe(NCS)(acac)(2)(H(2)O)] (HA Hacac), Fe(NCS)(3)L(2) [L b Ph(3)PO, dpeO(2) or dpbO(2)], or Fe(NCS)(acac)(2)L were found to be: K(HA), 1.48 x 10(3), K(L), 1.80 x 10(2) (L Ph(3)PO), 2.02 x 10(2) (L dpeO(2) or dpbO(2)) and K(syn), 1.87 x 10(6) (L Ph(3)PO), 2.56 x 10(6) [L dpeO(2) or dpbO(2)].     

Effect of modified fibre glass on the structure and thermophysical properties of pentaplast(pentane)

The results of experimental investigations of the effects of ground fibre glass on the structural parameters and thermophysical characteristics of pentaplast(pentane) were assessed.The degree of crystallinity, thermal conductivity, specific heat and density of pentaplast containing various amounts of modified fibre glass were determined experimentally.The results obtained are discussed in terms of modern theories of the effects of fillers on the properties and structures of polymers.

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Zusammenfassung Es werden die Ergebnisse der experimentellen Untersuchungen des Einfl usses von gemahlenem Fiberglas auf die Strukturparameter und thermophysikalischen Eigenschaften von Pentaplast (Pentan) gewertet.Der Kristallinitätsgrad, das Wärmeleitvermögen, die spezifische Wärme und die Dichte von Pentaplast mit verschiedenem Gehalt an modifiziertem Fiberglas wurde experimentell ermittelt.Die erhaltenen Ergebnisse wurden hinsichtlich moderner Theorien über den Einfluß von Streckmitteln auf die Eigenschaften und die Struktur von Polymeren diskutiert.

     

Chemistry of heteroanalogs of isoflavones. 16. Benzthiazole analogs of isoflavones

The reaction of a-(2-benzthiazolyl)-2, 4-dihydroxy-5-alkylacetophenones with anhydrides and chlorides of carboxylic acids yielded 3-(2-benzthiazolyl)chromones with electron-acceptor and electron-donor substituents, as well as chromones unsubstituted in the 2 -position. Their acylation, alkylation, and aminoacylation reactions and their interaction with electrophilic and nucleophilic reagents were studied.Taras Shevchenko Kiev University, Kiev 252017. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 464–471, April, 1994. Original article submitted March 5, 1994.     

Heteronuclear solid-state correlation spectroscopy

Two-dimensional NMR methods are proposed for correlating the spectra of abundant and dilute spins in solids. The techniques simplify assignment and permit determination of shielding tensors even when extensive overlaps occur. Spin diffusion among abundant spins can be observed indirectly.     

Alpha emitters from uranium mining in the environment

Uranium mining and milling activities usually generate an enhancement of radionuclide concentrations in the environment that may cause increased radiological exposure to mankind. For risk assessment and radiological protection of man and environment in these areas, usually, it is needed to implement radiological surveillance of water, soils, agricultural products, aerosols, and mining waste discharges as well. Radionuclides to be monitored in priority are alpha-emitting nuclides of the uranium natural series. Radioactivity analysis of materials from uranium mining areas of Portugal shows departure from secular radioactive equilibrium amongst uranium series radionuclides, thus rendering invalid the assumption of equilibrium and requiring the actual determination of each radionuclide. Radionuclide measurements performed with high resolution alphaspectrometry, as reported herein, produce accurate results on specific radionuclides that are essential in computing radiation doses to critical groups of the population.     

Modeling and analysis of uranium isotope enrichment by chemical exchange

Starting with an accurate mathematical model a theoretical study for the analysis of the separation of uranium isotopes by chemical exchange has been presented. The experimental data used in this study were obtained by reverse breakthrough technique and the numerical algorithm developed for simulation in previous studies was adapted and found to be suitable for this kind of processes. The model parameters were identified from experimental data and simulations were carried out for different experimental conditions. This revised version was published online in July 2006 with corrections to the Cover Date.