8,502 research outputs found
Dynamic model for failures in biological systems
A dynamic model for failures in biological organisms is proposed and studied
both analytically and numerically. Each cell in the organism becomes dead under
sufficiently strong stress, and is then allowed to be healed with some
probability. It is found that unlike the case of no healing, the organism in
general does not completely break down even in the presence of noise. Revealed
is the characteristic time evolution that the system tends to resist the stress
longer than the system without healing, followed by sudden breakdown with some
fraction of cells surviving. When the noise is weak, the critical stress beyond
which the system breaks down increases rapidly as the healing parameter is
raised from zero, indicative of the importance of healing in biological
systems.Comment: To appear in Europhys. Let
Herd Behaviors in Financial Markets
We investigate the herd behavior of returns for the yen-dollar exchange rate
in the Japanese financial market. It is obtained that the probability
distribution of returns satisfies the power-law behavior with the exponents (the time interval
one minute) and 3.36( one day). The informational cascade regime appears
in the herding parameter at one minute, while it occurs no
herding at one day. Especially, we find that the distribution of
normalized returns shows a crossover to a Gaussian distribution at one time
step day.Comment: 15 pages, 6 figure
Dynamic model of fiber bundles
A realistic continuous-time dynamics for fiber bundles is introduced and
studied both analytically and numerically. The equation of motion reproduces
known stationary-state results in the deterministic limit while the system
under non-vanishing stress always breaks down in the presence of noise.
Revealed in particular is the characteristic time evolution that the system
tends to resist the stress for considerable time, followed by sudden complete
rupture. The critical stress beyond which the complete rupture emerges is also
obtained
Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris
We obtained, for the first time, astrometrically registered maps of the 22.2
GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular
b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016
January 7 and 26) using the Korean Very-long-baseline Interferometry Network.
The SiO masers show a ring-like spatial structure, while the H2O maser shows a
very asymmetric one-side outflow structure, which is located at the southern
part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO
maser spots are distributed in an inner region, compared to those of the 43.1
GHz SiO maser, which is different from all previously known distributions of
the 86.2 GHz SiO masers in variable stars. The different distribution of the
86.2 GHz SiO maser seems to be related to the complex dynamics caused by the
overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the
position of the central star based on the ring fitting of the SiO masers, which
is essential for interpreting the morphology and kinematics of a circumstellar
envelope. The estimated stellar coordinate corresponds well to the position
measured by Gaia
Putative spin liquid in the triangle-based iridate BaIrTiO
We report on thermodynamic, magnetization, and muon spin relaxation
measurements of the strong spin-orbit coupled iridate BaIrTiO,
which constitutes a new frustration motif made up a mixture of edge- and
corner-sharing triangles. In spite of strong antiferromagnetic exchange
interaction of the order of 100~K, we find no hint for long-range magnetic
order down to 23 mK. The magnetic specific heat data unveil the -linear and
-squared dependences at low temperatures below 1~K. At the respective
temperatures, the zero-field muon spin relaxation features a persistent spin
dynamics, indicative of unconventional low-energy excitations. A comparison to
the isostructural compound BaRuTiO suggests that a concerted
interplay of compass-like magnetic interactions and frustrated geometry
promotes a dynamically fluctuating state in a triangle-based iridate.Comment: Physical Review B accepte
A Novel Cross-Layer Authentication Protocol for the Internet of Things
An innovative cross-layer authentication protocol that integrates cryptography-based authentication and physical layer authentication (PLA) is proposed for massive cellular Internet of things (IoT) systems. Due to dramatic increases in the number of cellular IoT devices, a centralized authentication architecture in which a mobility management entity in core networks administers authentication of massive numbers of IoT devices may cause network congestion with large signaling overhead. Thus, a distributed authentication architecture in which a base station in radio access networks authenticates IoT devices locally is presented. In addition, a cross-layer authentication protocol is designed with a novel integration strategy under the distributed authentication architecture, where PLA, which employs physical features for authentication, is used as preemptive authentication in the proposed protocol. Theoretical analysis and numerical simulations were performed to analyze the trade-off between authentication performance and overhead in the proposed authentication method compared with existing authentication protocols. The results demonstrate that the proposed protocol outperforms conventional authentication and key agreement protocols in terms of overhead and computational complexity while guaranteeing low authentication error probability
The diameter of the world wide web
Despite its increasing role in communication, the world wide web remains the
least controlled medium: any individual or institution can create websites with
unrestricted number of documents and links. While great efforts are made to map
and characterize the Internet's infrastructure, little is known about the
topology of the web. Here we take a first step to fill this gap: we use local
connectivity measurements to construct a topological model of the world wide
web, allowing us to explore and characterize its large scale properties.Comment: 5 pages, 1 figure, updated with most recent results on the size of
the ww
Impurities, Quantum Interference and Quantum Phase Transitions in s-wave superconductors
We study the effects of quantum interference in impurity structures
consisting of two or three magnetic impurities that are located on the surface
of an s-wave superconductor. By using a self-consistent Bogoliubov-de Gennes
formalism, we show that quantum interference leads to characteristic signatures
not only in the local density of states (LDOS), but also in the spatial form of
the superconducting order parameter. We demonstrate that the signatures of
quantum interference in the LDOS are qualitatively, and to a large extent
quantitatively unaffected by the suppression of the superconducting order
parameter near impurities, which illustrates the robustness of quantum
interference phenomena. Moreover, we show that by changing the interimpurity
distance, or the impurities' scattering strength, the s-wave superconductor can
be tuned through a series of first order quantum phase transitions in which the
spin polarization of its ground state changes. In contrast to the single
impurity case, this transition is not necessarily accompanied by a -phase
shift of the order parameter, and can in certain cases even lead to its
enhancement. Our results demonstrate that the superconductor's LDOS, its spin
state, and the spatial form of the superconducting order parameter are
determined by a subtle interplay between the relative positions of the
impurities and their scattering strength
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