9,565 research outputs found
Role of the electric field in surface electron dynamics above the vacuum level
Scanning tunneling spectroscopy (STS) is used to study the dynamics of hot
electrons trapped on a Cu(100) surface in field emission resonances (FER) above
the vacuum level. Differential conductance maps show isotropic electron
interference wave patterns around defects whenever their energy lies within a
surface projected band gap. Their Fourier analysis reveals a broad wave vector
distribution, interpreted as due to the lateral acceleration of hot electrons
in the inhomogeneous tip-induced potential. A line-shape analysis of the
characteristic constant-current conductance spectra permits to establish the
relation between apparent width of peaks and intrinsic line-width of FERs, as
well as the identification of the different broadening mechanisms.Comment: 7 pages, 4 figures, to appear in Phys. Rev.
Sex prediction by metric and non-metric analysis of the hard palate and the pyriform aperture
Background: Analysis of the bones and bone fragments of the cranium may be a useful tool for sex diagnosis in the identification of human remains which have been exposed to adverse conditions. The object of the present study was to evaluate sex prediction through metric and non-metric analysis of the hard palate (HP) and the pyriform aperture (PA), using macerated skulls of adult individuals.
Materials and methods: We analysed 312 dry skulls of adult individuals of both sexes, studying the metric and non-metric characteristics of the HP and PA. The accuracy, sensitivity, specificity and positive and negative predictive values were evaluated. A binary logistic regression and a linear regression were performed. The receiver operating characteristic curve was constructed to analyse the perfor- mance of sex diagnosis. Measurements of the HP and the PA were analysed by ANOVA and Tukey’s test. The SPSS v. 20.0 software was used, with a significance threshold of 5%.
Results: The shape of the PA presented 61.9% accuracy, 54.4% sensitivity and 65.7% specificity. The shape of the HP presented 51.5% accuracy, 65.6% sen- sitivity and 44.7% specificity. Only the height of the PA functioned as a good predictor of sex.
Conclusions: The height of the PA produced good diagnostic performance (area under curve = 0.764). The height of the PA was the most reliable indicator for sex prediction, and could be used by forensic scientists to identify sex.
The role of the spin in quasiparticle interference
Quasiparticle interference patterns measured by scanning tunneling microscopy
(STM) can be used to study the local electronic structure of metal surfaces and
high temperature superconductors. Here, we show that even in non-magnetic
systems the spin of the quasiparticles can have a profound effect on the
interference patterns. On Bi(110), where the surface state bands are not
spin-degenerate, the patterns are not related to the dispersion of the
electronic states in a simple way. In fact, the features which are expected for
the spin-independent situation are absent and the observed interference
patterns can only be interpreted by taking spin-conserving scattering events
into account.Comment: 4 pages, 2 figure
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