148,921 research outputs found
Probing edge state conductance in ultra-thin topological insulator films
Quantum spin Hall (QSH) insulators have unique electronic properties,
comprising a band gap in their two-dimensional interior and one-dimensional
spin-polarized edge states in which current flows ballistically. In scanning
tunneling microscopy (STM), the edge states manifest themselves as a localized
density of states. However, there is a significant research gap between the
observation of edge states in nanoscale spectroscopy, and the detection of
ballistic transport in edge channels which typically relies on transport
experiments with microscale lithographic contacts. Here, we study few-layer
films of the three-dimensional topological insulator
(BiSbTe, for which a topological transition to a
two-dimensional topological QSH insulator phase has been proposed. Indeed, an
edge state in the local density of states is observed within the band gap. Yet,
in nanoscale transport experiments with a four-tip STM, 2 and 3 quintuple layer
films do not exhibit a ballistic conductance in the edge channels. This
demonstrates that the detection of edge states in spectroscopy can be
misleading with regard to the identification of a QSH phase. In contrast,
nanoscale multi-tip transport experiments are a robust method for effectively
pinpointing ballistic edge channels, as opposed to trivial edge states, in
quantum materials
A robust high-sensitivity algorithm for automated detection of proteins in two-dimensional electrophoresis gels
The automated interpretation of two-dimensional gel electrophoresis images used in protein separation and analysis presents a formidable problem in the detection and characterization of ill-defined spatial objects. We describe in this paper a hierarchical algorithm that provides a robust, high-sensitivity solution to this problem, which can be easily adapted to a variety of experimental situations. The software implementation of this algorithm functions as part of a complete package designed for general protein gel analysis applications
Geometrical-based algorithm for variational segmentation and smoothing of vector-valued images
An optimisation method based on a nonlinear functional is considered for segmentation and smoothing of vector-valued images. An edge-based approach is proposed to initially segment the image using geometrical properties such as metric tensor of the linearly smoothed image. The nonlinear functional is then minimised for each segmented region to yield the smoothed image. The functional is characterised with a unique solution in contrast with the MumfordâShah functional for vector-valued images. An operator for edge detection is introduced as a result of this unique solution. This operator is analytically calculated and its detection performance and localisation are then compared with those of the DroGoperator. The implementations are applied on colour images as examples of vector-valued images, and the results demonstrate robust performance in noisy environments
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