3,867 research outputs found
Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange
We classify and analyze bit errors in the current measurement mode of the
Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability
decays exponentially with increasing bit exchange period and fixed bandwidth,
which is similar to the error probability decay in the voltage measurement
mode. We also analyze the combination of voltage and current modes for error
removal. In this combination method, the error probability is still an
exponential function that decays with the duration of the bit exchange period,
but it has superior fidelity to the former schemes.Comment: 9 pages, accepted for publication in Journal of Computational
Electronic
Generalized gravity and the late-time cosmic acceleration
High-precision observational data have confirmed with startling evidence that
the Universe is currently undergoing a phase of accelerated expansion. This
phase, one of the most important and challenging current problems in cosmology,
represents a new imbalance in the governing gravitational equations.
Historically, physics has addressed such imbalances by either identifying
sources that were previously unaccounted for, or by altering the gravitational
theory. Several candidates, responsible for this expansion, have been proposed
in the literature, in particular, dark energy models and modified gravity
models, amongst others. Outstanding questions are related to the nature of this
so-called "dark energy" that is driving this acceleration, and whether it is
due to the vacuum energy or a dynamical field. On the other hand, the late-time
cosmic acceleration may be due to modifications of General Relativity. In this
work we explore a generalised modified gravity theory, namely
gravity, where is the Ricci scalar, is a scalar field, and is a
kinetic term. This theory contains a wide range of dark energy and modified
gravity models. We considered specific models and applications to the late-time
cosmic acceleration.Comment: 13 pages, 1 figure; slightly revised version, displayed name
corrected. arXiv admin note: text overlap with arXiv:1412.086
Importance of tetrahedral coordination for high-valent transition metal oxides: YCrO as a model system
We have investigated the electronic structure of the high oxidation state
material YCrO within the framework of the Zaanen-Sawatzky-Allen phase
diagram. While Cr-based compounds like SrCrO/CaCrO and CrO
can be classified as small-gap or metallic negative-charge-transfer systems, we
find using photoelectron spectroscopy that YCrO is a robust insulator
despite the fact that its Cr ions have an even higher formal valence state of
5+. We reveal using band structure calculations that the tetrahedral
coordination of the Cr ions in YCrO plays a decisive role, namely to
diminish the bonding of the Cr states with the top of the O valence
band. This finding not only explains why the charge-transfer energy remains
effectively positive and the material stable, but also opens up a new route to
create doped carriers with symmetries different from those of other
transition-metal ions.Comment: 6 pages, 6 figure
Confirmation of and Variable Energy Injection by a Near-Relativistic Outflow in APM 08279+5255
We present results from multi-epoch spectral analysis of XMM-Newton and
Chandra observations of the broad absorption line (BAL) quasar APM 08279+5255.
Our analysis shows significant X-ray BALs in all epochs with rest-frame
energies lying in the range of ~ 6.7-18 keV. The X-ray BALs and 0.2-10 keV
continuum show significant variability on timescales as short as 3.3 days
(proper time) implying a source size-scale of ~ 10 r_g, where r_g is the
gravitational radius. We find a large gradient in the outflow velocity of the
X-ray absorbers with projected outflow velocities of up to 0.76 c. The maximum
outflow velocity constrains the angle between the wind velocity and our line of
sight to be less than ~ 22 degrees. We identify the following components of the
outflow: (a) Highly ionized X-ray absorbing material (2.9 < logxi < 3.9) and a
column density of log N_H ~ 23 outflowing at velocities of up to 0.76 c. (b)
Low-ionization X-ray absorbing gas with log N_H ~ 22.8. We find that flatter
spectra appear to result in lower outflow velocities. Based on our spectral
analysis of observations of APM 08279+5255 over a period of 1.2 years (proper
time) we estimate the mass-outflow rate and efficiency of the outflow to have
varied between 16(-8,+12) M_solar yr^-1 and 64(-40,+66) M_solar yr^-1 and
0.18(-0.11,+0.15) to 1.7(-1.2+1.9), respectively. Assuming that the outflow
properties of APM 08279+5255 are a common property of most quasars at similar
redshifts, our results then imply that quasar winds are massive and energetic
enough to influence significantly the formation of the host galaxy, provide
significant metal enrichment to the interstellar medium and intergalactic
medium, and are a viable mechanism for feedback at redshifts near the peak in
the number density of galaxy mergers.Comment: 27 pages, includes 12 figures, accepted for publication in Ap
On KLJN-based secure key distribution in vehicular communication networks
In a former paper [Fluct. Noise Lett., 13 (2014) 1450020] we introduced a
vehicular communication system with unconditionally secure key exchange based
on the Kirchhoff-Law-Johnson-Noise (KLJN) key distribution scheme. In this
paper, we address the secure KLJN key donation to vehicles. This KLJN key
donation solution is performed lane-by-lane by using roadside key provider
equipment embedded in the pavement. A method to compute the lifetime of the
KLJN key is also given. This key lifetime depends on the car density and gives
an upper limit of the lifetime of the KLJN key for vehicular communication
networks.Comment: Accepted for publicatio
Regularization for effective field theory with two heavy particles
A regularization for effective field theory with two propagating heavy
particles is constructed. This regularization preserves the low-energy analytic
structure, implements a low-energy power counting for the one-loop diagrams,
and preserves symmetries respected by dimensional regularization.Comment: 12 pages, 4 figures. Some typos have been corrected, a sentence has
been moved, and two formulas have been further simplifie
Revisiting the Training of Logic Models of Protein Signaling Networks with a Formal Approach based on Answer Set Programming
A fundamental question in systems biology is the construction and training to
data of mathematical models. Logic formalisms have become very popular to model
signaling networks because their simplicity allows us to model large systems
encompassing hundreds of proteins. An approach to train (Boolean) logic models
to high-throughput phospho-proteomics data was recently introduced and solved
using optimization heuristics based on stochastic methods. Here we demonstrate
how this problem can be solved using Answer Set Programming (ASP), a
declarative problem solving paradigm, in which a problem is encoded as a
logical program such that its answer sets represent solutions to the problem.
ASP has significant improvements over heuristic methods in terms of efficiency
and scalability, it guarantees global optimality of solutions as well as
provides a complete set of solutions. We illustrate the application of ASP with
in silico cases based on realistic networks and data
Bilateral reversed palmaris longus muscle: a rare anatomical variation
We report a case of bilateral reversed palmaris longus muscle (PLM). The muscle
was tendinous in its upper portion and muscular in its lower portion in both
arms. This rare variation has been mentioned only once in the literature as
a surgical finding. According to the literature, a reversed PLM may cause a compartment syndrome in the wrist area, carpal tunnel, and Guyon’s syndrome.
The described variation is also useful to the hand surgeon as a tendon graft,
a tendon for transfer, or as an anatomical landmark for operations at this area
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