11,422 research outputs found
Zero-bias conductance peak and Josephson effect in graphene-NbTiN junctions
We report electronic transport measurements of graphene contacted by NbTiN
electrodes, which at low temperature remain superconducting up to at least 11
Tesla. In devices with a single superconducting contact, we find a more than
twofold enhancement of the conductance at zero bias, which we interpret in
terms of reflectionless tunneling. In devices with two superconducting
contacts, we observe the Josephson effect, bipolar supercurrents and Fraunhofer
patterns.Comment: 6 pages, 5 figure
On the Privacy Practices of Just Plain Sites
In addition to visiting high profile sites such as Facebook and Google, web
users often visit more modest sites, such as those operated by bloggers, or by
local organizations such as schools. Such sites, which we call "Just Plain
Sites" (JPSs) are likely to inadvertently represent greater privacy risks than
high profile sites by virtue of being unable to afford privacy expertise. To
assess the prevalence of the privacy risks to which JPSs may inadvertently be
exposing their visitors, we analyzed a number of easily observed privacy
practices of such sites. We found that many JPSs collect a great deal of
information from their visitors, share a great deal of information about their
visitors with third parties, permit a great deal of tracking of their visitors,
and use deprecated or unsafe security practices. Our goal in this work is not
to scold JPS operators, but to raise awareness of these facts among both JPS
operators and visitors, possibly encouraging the operators of such sites to
take greater care in their implementations, and visitors to take greater care
in how, when, and what they share.Comment: 10 pages, 7 figures, 6 tables, 5 authors, and a partridge in a pear
tre
Ultrafast Molecular Transport on Carbon Surfaces: The Diffusion of Ammonia on Graphite
We present a combined experimental and theoretical study of the
self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight
spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed
ammonia, NH, on graphite. Together with van der Waals corrected density
functional theory calculations we show that the diffusion of NH follows a
hopping motion on a weakly corrugated potential energy surface with an
activation energy of about 4 meV which is particularly low for this type of
diffusive motion. The hopping motion includes further a significant number of
long jumps and the diffusion constant of ammonia adsorbed on graphite is
determined with D=3.9 \cdot 10^{-8}~\mbox{m}^2 /\mbox{s} at 94 K
Homotopy Relations for Topological VOA
We consider a parameter-dependent version of the homotopy associative part of
the Lian-Zuckerman homotopy algebra and provide the interpretation of
multilinear operations of this algebra in terms of integrals over certain
polytopes. We explicitly prove the pentagon relation up to homotopy and propose
a construction of higher operations.Comment: 15 pages, 1 figure, typos correcte
Energy-resolved neutron imaging for reconstruction of strain introduced by cold working
Energy-resolved neutron transmission imaging is used to reconstruct maps of residual strains in drilled and cold-expanded holes in 5-mm and 6.4-mm-thick aluminum plates. The possibility of measuring the positions of Bragg edges in the transmission spectrum in each 55 × 55 µm2 pixel is utilized in the reconstruction of the strain distribution within the entire imaged area of the sample, all from a single measurement. Although the reconstructed strain is averaged through the sample thickness, this technique reveals strain asymmetries within the sample and thus provides information complementary to other well-established non-destructive testing methods
Equivariant differential characters and symplectic reduction
We describe equivariant differential characters (classifying equivariant
circle bundles with connections), their prequantization, and reduction
Violation of Bell's inequality: criterion for quantum communication complexity advantage
We prove that for every Bell's inequality and for a broad class of protocols,
there always exists a multi-party communication complexity problem, for which
the protocol assisted by states which violate the inequality is more efficient
than any classical protocol. Moreover, for that advantage Bell's inequality
violation is a necessary and sufficient criterion. Thus, violation of Bell's
inequalities has a significance beyond that of a non-optimal-witness of
non-separability.Comment: 4 pages, 1 figur
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