Muonium Addition Reactions and Kinetic Isotope Effects in the Gas Phase: k∞ Rate Constants for Mu + C2H2.

The kinetics of the addition reaction of muonium (Mu) to acetylene have been studied in the gas phase at N2 moderator pressures mainly from ∼800 to 1000 Torr and over the temperature range from 168 to 446 K, but also down to 200 Torr at 168 K and over a much higher range of pressures, from 10 to 44 bar at 295 K, demonstrating pressure-independent rate constants, kMu(T). Even at 200 Torr moderator pressure, the kinetics for Mu + C2H2 addition behave as if effectively in the high-pressure limit, giving k∞ = kMu due to depolarization of the muon spin in the MuC2H2 radical formed in the addition step. The rate constants kMu(T) exhibit modest Arrhenius curvature over the range of measured temperatures.

Muon implantation of metallocenes: ferrocene.

Muon Spin Relaxation and Avoided Level Crossing (ALC) measurements of ferrocene are reported. The main features observed are five high field resonances in the ALC spectrum at about 3.26, 2.

[Serotypes and antimicrobial susceptibility of Streptococcus agalactiae].

Background: Streptococcus agalactiae or group B streptococcus, GBS, is the leading cause of neonatal and maternal infections and an opportunistic pathogen in adults with underlying disease. In the last decade, a dramatic increase in the resistance of this microorganism to erythromycin and clindamycin has been observed.

Aim: To determine the serotype distribution and antimicrobial susceptibility of isolates of S.

Muonium addition to DMPO and PBN sorbed in silica-gel.

Nitroxyl radicals were formed by adding the light hydrogen isotope, muonium to the spin traps DMPO (5,5-dimethyl-1-pyrroline-N-oxide) and PBN (N-tert-butyl-alpha-phenylnitrone) sorbed as 30 wt% ethanol solutions in silica-gel; evidence is presented for a specific hydrogen-bonded interaction between the DMPO adduct and the silica surface; longitudinal-field muon spin relaxation measurements (LF-MuSRx) were performed which identified two distinct motional regimes in both samples.

A radiolabelling study of radicals derived from benzene, toluene and benzaldehyde sorbed in model environmental carbon.

Radiolabelled free radicals were formed by the addition of muonium--a radioactive hydrogen atom with a positive muon as its nucleus--to benzene, toluene and benzaldehyde, as sorbed in porous carbon. The activation parameters associated with their reorientational motion were measured using longitudinal-field muon spin relaxation (LF-MuSRx). Two distinct sorbed fractions were detected in each sample, characterised by molecular reorientational activation energies of 5.