RESUMO
We report zero and longitudinal magnetic field muon spin relaxation (µSR) measurements of the spin S = 1/2 antiferromagnetic Heisenberg chain material SrCuO2. We find that in a weak applied magnetic field B0 the spin-lattice relaxation rate λ follows a power law λ is proportional to B(0)(-n) with n = 0.9(3). This result is temperature independent for 5 K ≤ T ≤ 300 K. Within conformal field theory and using the Müller ansatz we conclude ballistic spin transport in SrCuO2.
RESUMO
As compared to other techniques, the mass resolution of the 3D atom probe is rather poor. This low mass resolution derives from the spread in energy of field-evaporated ions. In this work, the single counter-electrode used to remove atoms from the specimen was replaced with a dual counter-electrode. A positive standing voltage V(PA) is applied on the electrode facing the specimen while the second electrode is grounded. As a result, ions experience a post-acceleration between electrodes that lowers energy deficits of ions resulting in an improvement in the mass resolution. This paper reports the study of the resulting improvement in mass resolution as a function of the post-acceleration voltage. It is also shown that, because of the evaporation pulse, ions also undergo a dynamic post-deceleration in the between electrodes. This post-deceleration contributes to the mass resolution increase. Our results show that this very simple device makes it possible to significantly improve the mass resolution of the atom probe. For a low post-acceleration voltage, the mass resolution is 800 FWHM and 200 at full-width tenth-maximum.
Assuntos
Oftalmopatias/etiologia , Olho , Luz , Fenômenos Biofísicos , Biofísica , Olho/efeitos da radiação , Oftalmopatias/diagnóstico , Oftalmopatias/prevenção & controle , Humanos , Luz/efeitos adversos , Iluminação/métodos , Fenômenos Físicos , Física , Radiação , Proteção Radiológica/métodos , Raios Ultravioleta/efeitos adversosRESUMO
The authors report a case of Down's syndrome associated with severe hypoplasia of all four eyelids, which is a new combination. They also discuss the problems of reconstruction in a retarded child.