358 research outputs found
Scale invariant correlations and the distribution of prime numbers
Negative correlations in the distribution of prime numbers are found to
display a scale invariance. This occurs in conjunction with a nonstationary
behavior. We compare the prime number series to a type of fractional Brownian
motion which incorporates both the scale invariance and the nonstationary
behavior. Interesting discrepancies remain. The scale invariance also appears
to imply the Riemann hypothesis and we study the use of the former as a test of
the latter.Comment: 13 pages, 8 figures, version to appear in J. Phys.
Quantitative study of molecular N_2 trapped in disordered GaN:O films
The structure of disordered GaN:O films grown by ion-assisted deposition is
investigated using x-ray absorption near-edge spectroscopy and Raman
spectroscopy. It is found that between 4 and 21 % of the nitrogen in the films
is in the form of molecular N_2 that interacts only weakly with the surrounding
matrix. The anion to cation ratio in the GaN:O host remains close to unity, and
there is a close correlation between the N_2 fraction, the level of oxygen
impurities, and the absence of short-range order in the GaN:O matrix.Comment: 5 pages, 3 figure
Machine-assisted Cyber Threat Analysis using Conceptual Knowledge Discovery
Over the last years, computer networks have evolved into highly dynamic and interconnected environments, involving multiple heterogeneous devices and providing a myriad of services on top of them. This complex landscape has made it extremely difficult for security administrators to keep accurate and be effective in protecting their systems against cyber threats. In this paper, we describe our vision and scientific posture on how artificial intelligence techniques and a smart use of security knowledge may assist system administrators in better defending their networks. To that end, we put forward a research roadmap involving three complimentary axes, namely, (I) the use of FCA-based mechanisms for managing configuration vulnerabilities, (II) the exploitation of knowledge representation techniques for automated security reasoning, and (III) the design of a cyber threat intelligence mechanism as a CKDD process. Then, we describe a machine-assisted process for cyber threat analysis which provides a holistic perspective of how these three research axes are integrated together
Granzyme K Activates Protease-Activated Receptor-1
Granzyme K (GrK) is a trypsin-like serine protease that is elevated in patients with sepsis and acute lung inflammation. While GrK was originally believed to function exclusively as a pro-apoptotic protease, recent studies now suggest that GrK may possess other non-cytotoxic functions. In the context of acute lung inflammation, we hypothesized that GrK induces pro-inflammatory cytokine release through the activation of protease-activated receptors. The direct effect of extracellular GrK on PAR activation, intracellular signaling and cytokine was assessed using cultured human lung fibroblasts. Extracellular GrK induced secretion of IL-6, IL-8 and MCP-1 in a dose- and time-dependent manner in lung fibroblasts. Heat-inactivated GrK did not induce cytokine release indicating that protease activity is required. Furthermore, GrK induced activation of both the ERK1/2 and p38 MAP kinase signaling pathways, and significantly increased fibroblast proliferation. Inhibition of ERK1/2 abrogated the GrK-mediated cytokine release. Through the use of PAR-1 and PAR-2 neutralizing antibodies, it was determined that PAR-1 is essential for GrK-induced IL-6, IL-8 and MCP-1 release. In summary, extracellular GrK is capable of activating PAR-1 and inducing fibroblast cytokine secretion and proliferation
Non-Fraunhofer Interference Pattern in Inhomogeneous Ferromagnetic Josephson Junctions
Generic conditions are established for producing a non-Fraunhofer response of
the critical supercurrent subject to an external magnetic field in
ferromagnetic Josephson junctions. Employing the quasiclassical Keldysh-Usadel
method, we demonstrate theoretically that an inhomogeneity in the magnitude of
the energy scales in the system, including Thouless energy, exchange field and
temperature gradient normal to the transport direction, influences drastically
the standard Fraunhofer pattern. The exotic non-Fraunhofer response, similar to
that observed in recent experiments, is described in terms of an intricate
interplay between multiple '0-pi'-states and is related to the appearance of
proximity vortices.Comment: 5 pages, 3 figures. To Appear in Physical Review Letter
Computing the endomorphism ring of an ordinary elliptic curve over a finite field
We present two algorithms to compute the endomorphism ring of an ordinary
elliptic curve E defined over a finite field F_q. Under suitable heuristic
assumptions, both have subexponential complexity. We bound the complexity of
the first algorithm in terms of log q, while our bound for the second algorithm
depends primarily on log |D_E|, where D_E is the discriminant of the order
isomorphic to End(E). As a byproduct, our method yields a short certificate
that may be used to verify that the endomorphism ring is as claimed.Comment: 16 pages (minor edits
Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co2MnGa
Spin-orbit torque (SOT) is receiving tremendous attention from both
fundamental and application-oriented aspects. Co2MnGa, a Weyl ferromagnet that
is in a class of topological quantum materials, possesses cubic-based high
structural symmetry, the L21 crystal ordering, which should be incapable of
hosting anisotropic SOT in conventional understanding. Here we show the
discovery of a gigantic anisotropy of self-induced SOT in Co2MnGa. The
magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer
systems despite the high inversion symmetry of the Co2MnGa structure. More
surprisingly, a sign inversion of the self-induced SOT is observed for
different crystal axes. This finding stems from the interplay of the
topological nature of the electronic states and their strong modulation by
external strain. Our research enriches the understanding of the physics of
self-induced SOT and demonstrates a versatile method for tuning SOT
efficiencies in a wide range of materials for topological and spintronic
devices.Comment: 15pages, 4figures (To appear Nano Lett.
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