10 research outputs found
Systematic Study of Electron Localization in an Amorphous Semiconductor
We investigate the electronic structure of gap and band tail states in
amorphous silicon. Starting with two 216-atom models of amorphous silicon with
defect concentration close to the experiments, we systematically study the
dependence of electron localization on basis set, density functional and spin
polarization using the first principles density functional code Siesta. We
briefly compare three different schemes for characterizing localization:
information entropy, inverse participation ratio and spatial variance. Our
results show that to accurately describe defect structures within self
consistent density functional theory, a rich basis set is necessary. Our study
revealed that the localization of the wave function associated with the defect
states decreases with larger basis sets and there is some enhancement of
localization from GGA relative to LDA. Spin localization results obtained via
LSDA calculations, are in reasonable agreement with experiment and with
previous LSDA calculations on a-Si:H models.Comment: 16 pages, 11 Postscript figures, To appear in Phys. Rev.
Assessment of radiolucent lines in cemented shoulder hemi-arthroplasties: study of concordance and reproducibility
We report on the concordance and reproducibility of the evaluation of radiolucent lines in the humeral component of shoulder arthroplasty. Thirty-two shoulder prostheses were assessed independently, on two occasions, by five observers. The level of inter- and intra-observer agreement was calculated using the kappa statistic. Intra-observer agreement: the overall kappa values ranged from 0 to 0.6, meaning poor, fair and moderate agreement levels. Inter-observer agreement: when the anteroposterior (AP) views were analysed, the values obtained for the bone–cement interface ranged from 0.290 to 0.539, meaning a poor-to-moderate agreement. For the cement–implant interface, the values ranged from 0.064 to 0.684, meaning a poor-to-good agreement. When radiolucent lines of the humeral component were analysed, inter-observer agreement proved to be as low as that obtained when total hip or knee components were analysed. Intra-observer agreement showed better results