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According to TF μSR measurements and PM3 M.O.calculations, free radicals formed by muonium addition to styrene, 1 vinylnaphthalene and 2 vinylnaphthalene are of the arylethyl type ( ArCHCH2Mu\mbox$\bullet$) since it is energetically considerably more favourable for Mu\mbox$\bullet$ to add to the vinyl group than to the aromatic rings. In contrast, Mu\mbox$\bullet$ adds to 9 vinylanthracene at the 10 position yielding the 4 vinyldibenzocyclohexadienyl radical, which is more stable by ca 7 kcal/mol than the 9 anthrylethyl radical. For diacetylenes (i.e. MeC4Me) the propensity for muonium addition is to the terminal carbon atoms, but the choice is less clear for Me3SiC4SiMe3. For PhC4Ph, 3 radicals are detected and are assigned to the C1, C2 and ortho ring adducts, with the couplings (and yields): 334 (5.7%), 389 (4.2%), 439 (3.6%). [ABSTRACT FROM AUTHOR]

We have formed adduct radicals (ArCHOMu\bullet) by muonium addition to the carbonyl group of benzaldehyde and its derivatives. The muon coupling is found to be highly sensitive to the nature of substituents in the benzene ring, being increased by electron releasing groups. Similarly, the 14N coupling in a series of nitroxides [ArN(O\bullet)OSiEt3], measured using ESR spectroscopy, is increased by electron releasing substituents and a linear correlation is found between the two; their connected nature is discussed. For the radical derived from benzaldehyde itself, a strong dependence is also found on the solvent in which it is solved. We suggest that this may be used in the study of solvent effects, particularly H bonding, pertinent to organic and bioorganic media. [ABSTRACT FROM AUTHOR]

Examines the epidemiology of measles outbreaks in an island population. Power laws governing epidemics; Description of a model based on the social interaction between individual hosts; Indications of regularities in the system.