Spatial mapping of exciton lifetimes in single ZnO nanowires

We investigate the spatial dependence of the exciton lifetimes in single ZnO nanowires. We have found that the free exciton and bound exciton lifetimes exhibit a maximum at the center of nanowires, while they decrease by 30% towards the tips. This dependence is explained by considering the cavity-like properties of the nanowires in combination with the Purcell effect. We show that the lifetime of the bound-excitons scales with the localization energy to the power of 3/2, which validates the model of Rashba and Gurgenishvili at the nanoscale.

Spatial mapping of exciton lifetimes in single ZnO nanowires

We investigate the spatial dependence of the exciton lifetimes in single ZnO nanowires. We have found that the free exciton and bound exciton lifetimes exhibit a maximum at the center of nanowires, while they decrease by 30% towards the tips. This dependence is explained by considering the cavity-like properties of the nanowires in combination with the Purcell effect. We show that the lifetime of the bound-excitons scales with the localization energy to the power of 3/2, which validates the model of Rashba and Gurgenishvili at the nanoscale.

Elastic scattering of fast electrons and positrons by atoms

Elastic scattering of relativistic electrons and positrons by atoms is considered in the framework of the static field approximation. The scattering field is expressed as a sum of Yukawa terms to allow the use of various approximations. Accurate phase shifts have been computed by combining Bühring¿s power-series method with the WKB and Born approximations. This combined procedure allows the evaluation of differential cross sections for kinetic energies up to several tens of MeV. Numerical results are used to analyze the validity of several approximate methods, namely the first- and second-order Born approximations and the screened Mott formula, which are frequently adopted as the basis of multiple scattering theories and Monte Carlo simulations of electron and positron transport.

The present state of aragonese

How much Aragonese is still spoken remains largely an unknown quantity. Naturally, establishing the number of speakers of any variety begs the question of what speaking a language actually means, and the picture is often clouded by the political interests of particular groups, as is the case in Aragon. The strong claim to the continued widespread use of Aragonese made by such associations as the Consello d"a Fabla in Huesca is counterbalanced by that of the more reactionary, sceptical academics at the University of Saragossa, who maintain that Aragonese varieties, ignoring the Catalan of Aragon spoken right down La Franja, the transition area between Aragon and Catalonia, now only survive in certain pockets of resistance across the north of Huesca. This paper will attempt to provide a summary of the available facts and report on some of the author"s own findings during his more recent trips to Aragon. Keywords Spanish dialectology, Aragonese, standardization of Aragonese, vitality of Aragonese