Do Dispersing Monkeys Follow Kin? Evidence from Gray-cheeked Mangabeys (Lophocebus albigena)

Among social vertebrates, immigrants may incur a substantial fitness cost when they attempt to join a new group. Dispersers could reduce that cost, or increase their probability of mating via coalition formation, by immigrating into groups containing first- or second-degree relatives. We here examine whether dispersing males tend to move into groups containing fathers or brothers in gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda. We sampled blood from 21 subadult and adult male mangabeys in 7 social groups and genotyped them at 17 microsatellite loci. Twelve genotyped males dispersed to groups containing other genotyped adult males during the study; in only 1 case did the group contain a probable male relative. Contrary to the prediction that dispersing males would follow kin, relatively few adult male dyads were likely first- or second-degree relatives; opportunities for kin-biased dispersal by mangabeys appear to be rare. During 4 yr of observation, adult brothers shared a group only once, and for only 6 wk. Mean relatedness among adult males sharing a group was lower than that among males in different groups. Randomization tests indicate that closely related males share groups no more often than expected by chance, although these tests had limited power. We suggest that the demographic conditions that allow kin-biased dispersal to evolve do not occur in mangabeys, may be unusual among primates, and are worth further attention

Location of the hydrogen donor in InN: Evidence from muonium results

Muon spin depolarization measurements in a zero applied magnetic field confirm the existence of a shallow muonium (Mu) donor in InN, consistent with earlier transverse-field muon spin precession results. The zero-field data imply two Mu(+) centres in InN, similar to those associated with channel and cage sites in GaN. The zero-field results provide strong evidence that the shallow Mu(0) ionizes to Mu(+) at its lowest-energy location. We argue that data on Mu in the III-V nitrides, taken in total, support the assignment of a wurtzite channel location to the shallow hydrogen donor in InN. The present results yield 15.4 +/- 2 meV below the conduction band edge for the donor level depth

The electrical activity of hydrogen and muonium in silicon at high temperatures

Above 500 K in silicon, isolated hydrogen defect centres scatter intrinsic charge carriers strongly by momentary formation of the neutral atomic ground state, located at the tetrahedral cage centre. This is inferred from the analogous behaviour of muonium, via distinctive muon spin rotation and relaxation signals. A consistent interpretation of a surprisingly large shift of the muon Larmor frequency and the strong transverse and longitudinal spin relaxation rates is achieved in terms of charge-state transition rates into and out of the neutral paramagnetic state. The nature of the charge cycle and the interplay with the crystallographic site are discussed and the electrically active level in the energy gap is determined. (C) 2003 Elsevier B.V. All rights reserved

Motion of muonium (hydrogen) in the III-V nitrides

Muon spin relaxation measurements in the III-V nitrides have provided data on the motion of each of the three charge-states of the muonium 'isotope' of hydrogen. Motional parameters are established for Mu(+) in InN, Mu(0) in AlN, and Mu(-) in GaN, with qualitative results in the other materials. Both Mu(+) and Mu(0) show tunneling below 300 K and thermal diffusion at higher temperatures leading to interactions with other impurities or extended defects