The rate constant for electron attachment to SFg, N20, and 02 in liquid argon and xenon was studied as a function of an external electric field up to 5 V cm-1. While Me-" + SF6) and k(e~+ 02) decreased with increasing field strength, Me-+ N20) exhibited a nearly 100 fold increase. The field effect on the rate constant in the liquefied rare gases is related to the increase of the mean electron energy by the external field. By means of the Cohen-Lekner theory electron energy distribution functions were obtained and a rough estimate of the energy dependence of the attachment cross section could be deduced.

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The ability of a number of prediction systems was examined to determine how well they could predict Salmonella mutagenicity. The prediction systems included two computer-based systems (CASE and TOPKAT), the measurement of a physiochemical parameter (ke) and the use of structural alerts by an expert chemist. The computer-based systems operators and the chemist were supplied with the structures of 100 chemicals that had been tested for mutagenicity in the Salmonella test; the actual chemicals were needed for the physiochemical measurement. None of the participants was provided with the chemical names or Salmonella test results prior to submitting their predictions. The three systems that predicted the mutagenicity from the structure of the chemicals produced equivalent results (71-76% concordance with the Salmonella results); the physiochemical system produced a lower (60-61%) concordance.

Small-angle neutron scattering (SANS) has been shown to be an appropriate technique for the structural characterization of fullerenes (1) in solvents with strong SANS contrast (e.g. CSz) and we have extended initial studies of c 6 0 (1) to include C~O and c 8 4 moieties. Deuterated solvents (e.g. toluene-d8) have a high scattering length density (SLD), which is close to that of C~O , so there is virtually no S A N S contrast with the solvent. Hence, these particles are practically "invisible" in such media, though the negative scattering length of hydrogen means that SLD of H' -containing materials is much lower, so they have strong contrast with toluene-dg. Thus, S A N S makes it possible to study the size and shapes of modified buckyballs and this paper describes the first results on cyclohexane-substituted fullerenes.