8,348 research outputs found
Proof of Luck: an Efficient Blockchain Consensus Protocol
In the paper, we present designs for multiple blockchain consensus primitives
and a novel blockchain system, all based on the use of trusted execution
environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using
TEEs for existing proof of work schemes can make mining equitably distributed
by preventing the use of ASICs. Next, we extend the design with proof of time
and proof of ownership consensus primitives to make mining energy- and
time-efficient. Further improving on these designs, we present a blockchain
using a proof of luck consensus protocol. Our proof of luck blockchain uses a
TEE platform's random number generation to choose a consensus leader, which
offers low-latency transaction validation, deterministic confirmation time,
negligible energy consumption, and equitably distributed mining. Lastly, we
discuss a potential protection against up to a constant number of compromised
TEEs.Comment: SysTEX '16, December 12-16, 2016, Trento, Ital
Signal transducer and activator of transcription-1 localizes to the mitochondria and modulates mitophagy
The signal transducer and activator of transcription (STAT) proteins are latent transcription factors that have been shown to be involved in cell proliferation, development, apoptosis, and autophagy. STAT proteins undergo activation by phosphorylation at tyrosine 701 and serine 727 where they translocate to the nucleus to regulate gene expression. STAT1 has been shown to be involved in promoting apoptotic cell death in response to cardiac ischemia/reperfusion and has recently been shown by our laboratory to be involved in negatively regulating autophagy. These processes are thought to promote cell death and restrict cell survival leading to the generation of an infarct. Here we present data that shows STAT1 localizes to the mitochondria and co-immunoprecipitates with LC3. Furthermore, electron microscopy studies also reveal mitochondria from ex vivo I/R treated hearts of STAT1KO mice contained within a double membrane autophagosome indicating that STAT1 may be involved in negatively regulating mitophagy. This is the first description of STAT1 being localized to the mitochondria and also having a role in mitophagy
Is the magnetic field in the heliosheath laminar or a turbulent bath of bubbles?
All the current global models of the heliosphere are based on the assumption
that the magnetic field in the heliosheath, in the region close to the
heliopause is laminar. We argue that in that region the heliospheric magnetic
field is not laminar but instead consists of magnetic bubbles. Recently, we
proposed that the annihilation of the "sectored" magnetic field within the
heliosheath as it is compressed on its approach to the heliopause produces the
anomalous cosmic rays and also energetic electrons. As a product of the
annihilation of the sectored magnetic field, densely-packed magnetic
islands/bubbles are produced. These magnetic islands/bubbles will be convected
with the ambient flows as the sector region is carried to higher latitudes
filling the heliosheath. We further argue that the magnetic islands/bubbles
will develop upstream within the heliosheath. As a result, the magnetic field
in the heliosheath sector region will be disordered well upstream of the
heliopause. We present a 3D MHD simulation with very high numerical resolution
that captures the north-south boundaries of the sector region. We show that due
to the high pressure of the interstellar magnetic field a north-south asymmetry
develops such that the disordered sectored region fills a large portion of the
northern part of the heliosphere with a smaller extension in the southern
hemisphere. We suggest that this scenario is supported by the following changes
that occur around 2008 and from 2009.16 onward: a) the sudden decrease in the
intensity of low energy electrons detected by Voyager 2; b) a sharp reduction
in the intensity of fluctuations of the radial flow; and c) the dramatic
differences in intensity trends between GCRs at V1 and 2. We argue that these
observations are a consequence of V2 leaving the sector region of disordered
field during these periods and crossing into a region of unipolar laminar
field.Comment: 36 pages, 15 figures, submitted to Ap
Surgical treatment of a paraspinal abscess with osteomyelitis and spinal cord compression in a rabbit
Penetration And Scattering Of Lower Hybrid Waves By Density Fluctuations
Lower Hybrid [LH] ray propagation in toroidal plasma is controlled by a combination of the azimuthal spectrum launched from the antenna, the poloidal variation of the magnetic field, and the scattering of the waves by the density fluctuations. The width of the poloidal and radial RF wave spectrum increases rapidly as the rays penetrate into higher density and scatter from the turbulence. The electron temperature gradient [ETG] spectrum is particularly effective in scattering the LH waves due to its comparable wavelengths and parallel phase velocities. ETG turbulence is also driven by the radial gradient of the electron current density giving rise to an anomalous viscosity spreading the LH-driven plasma currents. The scattered LH spectrum is derived from a Fokker-Planck equation for the distribution of the ray trajectories with a diffusivity proportional to the fluctuations. The LH ray diffusivity is large giving transport in the poloidal and radial wavenumber spectrum in one -or a few passes - of the rays through the core plasma.Institute for Fusion Studie
Development and evaluation of a Hadamard transform imaging spectrometer and a Hadamard transform thermal imager
A spectrometric imager and a thermal imager, which achieve multiplexing by the use of binary optical encoding masks, were developed. The masks are based on orthogonal, pseudorandom digital codes derived from Hadamard matrices. Spatial and/or spectral data is obtained in the form of a Hadamard transform of the spatial and/or spectral scene; computer algorithms are then used to decode the data and reconstruct images of the original scene. The hardware, algorithms and processing/display facility are described. A number of spatial and spatial/spectral images are presented. The achievement of a signal-to-noise improvement due to the signal multiplexing was also demonstrated. An analysis of the results indicates both the situations for which the multiplex advantage may be gained, and the limitations of the technique. A number of potential applications of the spectrometric imager are discussed
Successful medical management of a domestic longhair cat with subdural intracranial empyema and multifocal pneumonia
Homalg: A meta-package for homological algebra
The central notion of this work is that of a functor between categories of
finitely presented modules over so-called computable rings, i.e. rings R where
one can algorithmically solve inhomogeneous linear equations with coefficients
in R. The paper describes a way allowing one to realize such functors, e.g.
Hom, tensor product, Ext, Tor, as a mathematical object in a computer algebra
system. Once this is achieved, one can compose and derive functors and even
iterate this process without the need of any specific knowledge of these
functors. These ideas are realized in the ring independent package homalg. It
is designed to extend any computer algebra software implementing the
arithmetics of a computable ring R, as soon as the latter contains algorithms
to solve inhomogeneous linear equations with coefficients in R. Beside
explaining how this suffices, the paper describes the nature of the extensions
provided by homalg.Comment: clarified some points, added references and more interesting example
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