Lattice dynamics of tetracyanoethylene

Lattice dynamics calculations for both crystalline forms of tetracyanoethylene are presented. The comparison of the calculated static and dynamical properties with the experimental data, leads us to suggest an improved parameter set for the “6-exp” potential function for crystals with cyano groups.     

CHEMILUMINESCENCE FROM THE OXIDATION OF AUXIN DERIVATIVES

Abstract— The thiophenyl ester of indole-3-acetic acid and indole-3-acetonitrile produce chemiluminescence in aerated dimethylsulfoxide in the presence of potassium t -butoxide. The emitter is the aromatic aldehyde. In the case of acetonitrile, the other product expected from the cleavage of an intermediate dioxetane, cyanate/isocyanate, has also been identified. Other auxins also chemiluminesce under similar conditions, but the emitters have not been properly identified.
These systems are models for the peroxidase catalyzed oxidation of indole-3-acetic acid to indole-3-carboxaldehyde and as such support the earlier inference (Vidigal et al , 1975) that the excited aldehyde is generated in the enzymic process.
An additional result is the observation of an exciplex between excited indole-3-carboxaldehyde and the thiophenylester of indole-3-acetic acid. This appears to be the first case of chemical generation of an exciplex by a route other than radical ion reaction, presumably by the dioxetane route.     

Energy dependence of the epithermal neutron spectrum shape parameter α with respect to application of comparator-type NAA

The epithermal neutron spectrum shape parameter in nuclear reactors is explained from a theoretical point of view in terms of the neutron slowing down density function. The latter is approximated by Fermi's age theory. Values for are calculated for a simple approximation of a nuclear reactor: a disk shaped fission neutron source in an infinite graphite moderator. The model produces -values with the correct sign and magnitude, compared to experimental values from the literature, determined in a real reactor. It is shown that varies strongly with distance to the neutron source and less strongly with neutron energy. The inappropriateness of average -values, obtained from the slope of quasi-straight lines produced by log-log plots of E^– versus E, for the correction of non-ideal epithermal neutron activation is discussed. Conclusions are formulated concerning the impact of an energy dependent on comparator type NAA.     

Laser photolysis study of the triplet states of nitroaromatic amides

The spectrokinetic indices of the triplet states of nitroaromatic amides were established. The quenching of triplet states by tertiary aromatic amines in apolar solvents leads to the formation of triplet exciplexes. A charge transfer state makes the major contribution to the structure of these exciplexes. Hydrogen atom transfer proceeds efficiently in the case of secondary aromatic amines, leading to the formation of the corresponding neutral radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1912–1915, August, 1989.     

Particle shape in thixotropic aluminium and thorium molybdates gels

Summary Electron microscope examination of thixotropic aluminium and thorium molybdate gels shows that one hour after formation they are constituted by short fibrils of small axial ratio. The fibrils of the aluminium molybdate gels, with ageing at room temperature or with boiling, increase in diameter and length; the fibrous shape of the particles is maintained after two and a half years of ageing; all fibrils are crystalline by electron diffraction. The fibrils of the thorium molybdate gels, except in the gels containing hydrochloric acid, change with ageing at room temperature or with boiling, into plates of hexagonal, elliptical or rectangular profile; the fibrils and plates are crystalline and have the same electron diffraction pattern as the fibrils.This work was aided, in part, by grants from Conselho Nacional de Pesquisas and the Rockefeller Foundation.