48,107 research outputs found
Perspectives on the revised Ghent criteria for the diagnosis of Marfan syndrome
Three international nosologies have been proposed for the diagnosis of Marfan syndrome (MFS): the Berlin nosology in 1988; the Ghent nosology in 1996 (Ghent-1); and the revised Ghent nosology in 2010 (Ghent-2). We reviewed the literature and discussed the challenges and concepts of diagnosing MFS in adults. Ghent-1 proposed more stringent clinical criteria, which led to the confirmation of MFS in only 32%-53% of patients formerly diagnosed with MFS according to the Berlin nosology. Conversely, both the Ghent-1 and Ghent-2 nosologies diagnosed MFS, and both yielded similar frequencies of MFS in persons with a causative FBN1 mutation (90% for Ghent-1 versus 92% for Ghent-2) and in persons not having a causative FBN1 mutation (15% versus 13%). Quality criteria for diagnostic methods include objectivity, reliability, and validity. However, the nosology-based diagnosis of MFS lacks a diagnostic reference standard and, hence, quality criteria such as sensitivity, specificity, or accuracy cannot be assessed. Medical utility of diagnosis implies congruency with the historical criteria of MFS, as well as with information about the etiology, pathogenesis, diagnostic triggers, prognostic triggers, and potential complications of MFS. In addition, social and psychological utilities of diagnostic criteria include acceptance by patients, patient organizations, clinicians and scientists, practicability, costs, and the reduction of anxiety. Since the utility of a diagnosis or exclusion of MFS is context-dependent, prioritization of utilities is a strategic decision in the process of nosology development. Screening tests for MFS should be used to identify persons with MFS. To confirm the diagnosis of MFS, Ghent-1 and Ghent-2 perform similarly, but Ghent-2 is easier to use. To maximize the utility of the diagnostic criteria of MFS, a fair and transparent process of nosology development is essential
Observation of Majorana fermions with spin selective Andreev reflection in the vortex of topological superconductor
Majorana fermion (MF) whose antiparticle is itself has been predicted in
condensed matter systems. Signatures of the MFs have been reported as zero
energy modes in various systems. More definitive evidences are highly desired
to verify the existence of the MF. Very recently, theory has predicted MFs to
induce spin selective Andreev reflection (SSAR), a novel magnetic property
which can be used to detect the MFs. Here we report the first observation of
the SSAR from MFs inside vortices in Bi2Te3/NbSe2 hetero-structure, in which
topological superconductivity was previously established. By using
spin-polarized scanning tunneling microscopy/spectroscopy (STM/STS), we show
that the zero-bias peak of the tunneling differential conductance at the vortex
center is substantially higher when the tip polarization and the external
magnetic field are parallel than anti-parallel to each other. Such strong spin
dependence of the tunneling is absent away from the vortex center, or in a
conventional superconductor. The observed spin dependent tunneling effect is a
direct evidence for the SSAR from MFs, fully consistent with theoretical
analyses. Our work provides definitive evidences of MFs and will stimulate the
MFs research on their novel physical properties, hence a step towards their
statistics and application in quantum computing.Comment: 4 figures 15 page
Measuring Majorana fermions qubit state and non-Abelian braiding statistics in quenched inhomogeneous spin ladders
We study the Majorana fermions (MFs) in a spin ladder model. We propose and
numerically show that the MFs qubit state can be read out by measuring the
fusion excitation in the quenched inhomogeneous spin ladders. Moreover, we
construct an exactly solvable T-junction spin ladder model, which can be used
to implement braiding operations of MFs. With the braiding processes simulated
numerically as non-equilibrium quench processes, we verify that the MFs in our
spin ladder model obey the non-Abelian braiding statistics. Our scheme not only
provides a promising platform to study the exotic properties of MFs, but also
has broad range of applications in topological quantum computation.Comment: 5+3 pages, 6 figure
Improved mapping functions for atmospheric refraction correction in SLR
[1] We present two new mapping functions (MFs) to model the elevation angle dependence of the atmospheric delay for satellite laser ranging (SLR) data analysis. The new MFs were derived from ray tracing through a set of data from 180 radiosonde stations globally distributed, for the year 1999, and are valid for elevation angles above 3degrees. When compared against ray tracing of two independent years of radiosonde data (1997-1998) for the same set of stations, our MFs reveal submillimetre accuracy for elevation angles above 10degrees, representing a significant improvement over other MFs, and is confirmed in improved solutions of LAGEOS and LAGEOS 2 data analysis.info:eu-repo/semantics/publishedVersio
Charge-impurity-induced Majorana fermions in topological superconductors
We study numerically Majorana fermions (MFs) induced by a charged impurity in
topological superconductors. It is revealed from the relevant Bogoliubov-de
Gennes equations that (i) for quasi-one dimensional systems, a pair of MFs are
bounded at the two sides of one charge impurity and well separated; and (ii)
for a two dimensional square lattice, the charged-impurity-induced MFs are
similar to the known pair of vortex-induced MFs, in which one MF is bounded by
the impurity while the other appears at the boundary. Moreover, the
corresponding local density of states is explored, demonstrating that the
presence of MF states may be tested experimentally.Comment: 5 pages, 5 figure
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