107 research outputs found
The Internet AS-Level Topology: Three Data Sources and One Definitive Metric
We calculate an extensive set of characteristics for Internet AS topologies
extracted from the three data sources most frequently used by the research
community: traceroutes, BGP, and WHOIS. We discover that traceroute and BGP
topologies are similar to one another but differ substantially from the WHOIS
topology. Among the widely considered metrics, we find that the joint degree
distribution appears to fundamentally characterize Internet AS topologies as
well as narrowly define values for other important metrics. We discuss the
interplay between the specifics of the three data collection mechanisms and the
resulting topology views. In particular, we show how the data collection
peculiarities explain differences in the resulting joint degree distributions
of the respective topologies. Finally, we release to the community the input
topology datasets, along with the scripts and output of our calculations. This
supplement should enable researchers to validate their models against real data
and to make more informed selection of topology data sources for their specific
needs.Comment: This paper is a revised journal version of cs.NI/050803
Quasiclassical calculation of spontaneous current in restricted geometries
Calculation of current and order parameter distribution in inhomogeneous superconductors is often based on a self-consistent solution of Eilenberger equations for quasiclassical Green's functions. Compared to the original Gorkov equations, the problem is much simplified due to the fact that the values of Green's functions at a given point are connected to the bulk ones at infinity (boundary values) by ``dragging'' along the classical trajectories of quasiparticles. In finite size systems, where classical trajectories undergo multiple reflections from surfaces and interfaces, the usefulness of the approach is no longer obvious, since there is no simple criterion to determine what boundary value a trajectory corresponds to, and whether it reaches infinity at all. Here, we demonstrate the modification of the approach based on the Schophol-Maki transformation, which provides the basis for stable numerical calculations in 2D. We apply it to two examples: generation of spontaneous currents and magnetic moments in isolated islands of d-wave superconductor with subdominant order-parameters s and d_{xy}, and in a grain boundary junction between two arbitrarily oriented d-wave superconductors. Both examples are relevant to the discussion of time-reversal symmetry breaking in unconventional superconductors, as well as for application in quantum computing
Quasiclassical Theory of Spontaneous Currents at Surfaces and Interfaces of d-Wave Superconductors
We investigate the properties of spontaneous currents generated at surfaces
and interfaces of d-wave superconductors using the self-consistent
quasiclassical Eilenberger equations. The influence of the roughness and
reflectivity of the boundaries on the spontaneous current are studied. We show
that these have very different effects at the surfaces compared to the
interfaces, which reflects the different nature of the time reversal symmetry
breaking states in these two systems. We find a signature of the ``anomalous
proximity effect'' at rough d-wave interfaces. We also show that the existence
of a subdominant order parameter, which is necessary for time reversal symmetry
breaking at the surface, suppresses the spontaneous current generation due to
proximity effect at the interface between two superconductors. We associate
orbital moments to the spontaneous currents to explain the ``superscreening''
effect, which seems to be present at all ideal d-wave surfaces and interfaces,
where d_{xy} is the favorite subdominant symmetry.Comment: 13 pages, 17 postscript figure
Landau-Zener-Stuckelberg interferometry
A transition between energy levels at an avoided crossing is known as a
Landau-Zener transition. When a two-level system (TLS) is subject to periodic
driving with sufficiently large amplitude, a sequence of transitions occurs.
The phase accumulated between transitions (commonly known as the Stuckelberg
phase) may result in constructive or destructive interference. Accordingly, the
physical observables of the system exhibit periodic dependence on the various
system parameters. This phenomenon is often referred to as
Landau-Zener-Stuckelberg (LZS) interferometry. Phenomena related to LZS
interferometry occur in a variety of physical systems. In particular, recent
experiments on LZS interferometry in superconducting TLSs (qubits) have
demonstrated the potential for using this kind of interferometry as an
effective tool for obtaining the parameters characterizing the TLS as well as
its interaction with the control fields and with the environment. Furthermore,
strong driving could allow for fast and reliable control of the quantum system.
Here we review recent experimental results on LZS interferometry, and we
present related theory.Comment: 34 single-column pages, 11 figure
Measurements of and production in proton–proton interactions at in the NA61/SHINE experiment
Double-differential yields of and
resonances produced in \pp interactions
were measured at a laboratory beam momentum of 158~\GeVc. This measurement is
the first of its kind in \pp interactions below LHC energies. It was performed
at the CERN SPS by the \NASixtyOne collaboration. Double-differential
distributions in rapidity and transverse momentum were obtained from a sample
of 2610 inelastic events. The spectra are extrapolated to full phase
space resulting in mean multiplicity of (6.73
0.25 0.67) and (2.71
0.18 0.18). The rapidity and transverse momentum
spectra and mean multiplicities were compared to predictions of string-hadronic
and statistical model calculations
Measurements of and production in proton–proton interactions at in the NA61/SHINE experiment
International audienceThe production of and hyperons in inelastic p+p interactions is studied in a fixed target experiment at a beam momentum of 158 . Double differential distributions in rapidity and transverse momentum are obtained from a sample of 33M inelastic events. They allow to extrapolate the spectra to full phase space and to determine the mean multiplicity of both and . The rapidity and transverse momentum spectra are compared to transport model predictions. The mean multiplicity in inelastic p+p interactions at 158 is used to quantify the strangeness enhancement in A+A collisions at the same centre-of-mass energy per nucleon pair
Fine-mapping of prostate cancer susceptibility loci in a large meta-analysis identifies candidate causal variants
Prostate cancer is a polygenic disease with a large heritable component. A number of common, low-penetrance prostate cancer risk loci have been identified through GWAS. Here we apply the Bayesian multivariate variable selection algorithm JAM to fine-map 84 prostate cancer susceptibility loci, using summary data from a large European ancestry meta-analysis. We observe evidence for multiple independent signals at 12 regions and 99 risk signals overall. Only 15 original GWAS tag SNPs remain among the catalogue of candidate variants identified; the remainder are replaced by more likely candidates. Biological annotation of our credible set of variants indicates significant enrichment within promoter and enhancer elements, and transcription factor-binding sites, including AR, ERG and FOXA1. In 40 regions at least one variant is colocalised with an eQTL in prostate cancer tissue. The refined set of candidate variants substantially increase the proportion of familial relative risk explained by these known susceptibility regions, which highlights the importance of fine-mapping studies and has implications for clinical risk profiling. © 2018 The Author(s).Prostate cancer is a polygenic disease with a large heritable component. A number of common, low-penetrance prostate cancer risk loci have been identified through GWAS. Here we apply the Bayesian multivariate variable selection algorithm JAM to fine-map 84 prostate cancer susceptibility loci, using summary data from a large European ancestry meta-analysis. We observe evidence for multiple independent signals at 12 regions and 99 risk signals overall. Only 15 original GWAS tag SNPs remain among the catalogue of candidate variants identified; the remainder are replaced by more likely candidates. Biological annotation of our credible set of variants indicates significant enrichment within promoter and enhancer elements, and transcription factor-binding sites, including AR, ERG and FOXA1. In 40 regions at least one variant is colocalised with an eQTL in prostate cancer tissue. The refined set of candidate variants substantially increase the proportion of familial relative risk explained by these known susceptibility regions, which highlights the importance of fine-mapping studies and has implications for clinical risk profiling. © 2018 The Author(s).Peer reviewe
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