596 research outputs found
On Byzantine Broadcast in Loosely Connected Networks
We consider the problem of reliably broadcasting information in a multihop
asynchronous network that is subject to Byzantine failures. Most existing
approaches give conditions for perfect reliable broadcast (all correct nodes
deliver the authentic message and nothing else), but they require a highly
connected network. An approach giving only probabilistic guarantees (correct
nodes deliver the authentic message with high probability) was recently
proposed for loosely connected networks, such as grids and tori. Yet, the
proposed solution requires a specific initialization (that includes global
knowledge) of each node, which may be difficult or impossible to guarantee in
self-organizing networks - for instance, a wireless sensor network, especially
if they are prone to Byzantine failures. In this paper, we propose a new
protocol offering guarantees for loosely connected networks that does not
require such global knowledge dependent initialization. In more details, we
give a methodology to determine whether a set of nodes will always deliver the
authentic message, in any execution. Then, we give conditions for perfect
reliable broadcast in a torus network. Finally, we provide experimental
evaluation for our solution, and determine the number of randomly distributed
Byzantine failures than can be tolerated, for a given correct broadcast
probability.Comment: 1
A Scalable Byzantine Grid
Modern networks assemble an ever growing number of nodes. However, it remains
difficult to increase the number of channels per node, thus the maximal degree
of the network may be bounded. This is typically the case in grid topology
networks, where each node has at most four neighbors. In this paper, we address
the following issue: if each node is likely to fail in an unpredictable manner,
how can we preserve some global reliability guarantees when the number of nodes
keeps increasing unboundedly ? To be more specific, we consider the problem or
reliably broadcasting information on an asynchronous grid in the presence of
Byzantine failures -- that is, some nodes may have an arbitrary and potentially
malicious behavior. Our requirement is that a constant fraction of correct
nodes remain able to achieve reliable communication. Existing solutions can
only tolerate a fixed number of Byzantine failures if they adopt a worst-case
placement scheme. Besides, if we assume a constant Byzantine ratio (each node
has the same probability to be Byzantine), the probability to have a fatal
placement approaches 1 when the number of nodes increases, and reliability
guarantees collapse. In this paper, we propose the first broadcast protocol
that overcomes these difficulties. First, the number of Byzantine failures that
can be tolerated (if they adopt the worst-case placement) now increases with
the number of nodes. Second, we are able to tolerate a constant Byzantine
ratio, however large the grid may be. In other words, the grid becomes
scalable. This result has important security applications in ultra-large
networks, where each node has a given probability to misbehave.Comment: 17 page
Laser Machining by short and ultrashort pulses, state of the art and new opportunities in the age of the photons
An overview is given of the applications of short and ultrashort lasers in material processing. Shorter pulses reduce heat-affected damage of the material and opens new ways for nanometer accuracy. Even forty years after the development of the laser there is a lot of effort in developing new and better performing lasers. The driving force is higher accuracy at reasonable cost, which is realised by compact systems delivering short laser pulses of high beam quality. Another trend is the shift towards shorter wavelengths, which are better absorbed by the material and which allows smaller feature sizes to be produced. Examples of new products, which became possible by this technique, are given. The trends in miniaturization as predicted by Moore and Taniguchi are expected to continue over the next decade too thanks to short and ultrashort laser machining techniques. After the age of steam and the age of electricity we have entered the age of photons now
Space-Time Diffusion of Ground and Its Fractal Nature
We present evidences of the diffusive motion of the ground and tunnels and
show that if systematic movements are excluded then the remaining uncorrelated
component of the motion obeys a characteristic fractal law with the
displacement variance dY^2 scaling with time- and spatial intervals T and L as
dY^2 \propto T^(Alpha)L^(Gamma) with both exponents close to 1. We briefly
describe experimental methods of the mesa- and microscopic ground motion
detection used in the measurements at the physics research facilities sensitive
to the motion, particularly, large high energy elementary particle
accelerators. A simple mathematical model of the fractal motion demonstrating
the observed scaling law is also presented and discussed.Comment: 83 pages, 46 fig
Recommended from our members
Preliminary Biomarkers for Identification of Human Ascending Thoracic Aortic Aneurysm
Background: Human ascending thoracic aortic aneurysms (ATAAs) are life threatening and constitute a leading cause of mortality in the United States. Previously, we demonstrated that collagens α2(V) and α1(XI) mRNA and protein expression levels are significantly increased in ATAAs. Methods and Results: In this report, the authors extended these preliminary studies using highâthroughput proteomic analysis to identify additional biomarkers for use in whole blood realâtime RTâPCR analysis to allow for the identification of ATAAs before dissection or rupture. Human ATAA samples were obtained from male and female patients aged 65±14 years. Both bicuspid and tricuspid aortic valve patients were included and compared with nonaneurysmal aortas (mean diameter 2.3 cm). Five biomarkers were identified as being suitable for detection and identification of ATAAs using qRTâPCR analysis of whole blood. Analysis of 41 samples (19 small, 13 mediumâsized, and 9 large ATAAs) demonstrated the overexpression of 3 of these transcript biomarkers correctly identified 79.4% of patients with ATAA of â„4.0 cm (P<0.001, sensitivity 0.79, CI=0.62 to 0.91; specificity 1.00, 95% CI=0.42 to 1.00). Conclusion: A preliminary transcript biomarker panel for the identification of ATAAs using whole blood qRTâPCR analysis in men and women is presented
Self-Stabilizing Byzantine Asynchronous Unison
We explore asynchronous unison in the presence of systemic transient and
permanent Byzantine faults in shared memory. We observe that the problem is not
solvable under less than strongly fair scheduler or for system topologies with
maximum node degree greater than two. We present a self-stabilizing
Byzantine-tolerant solution to asynchronous unison for chain and ring
topologies. Our algorithm has minimum possible containment radius and optimal
stabilization time
COMPARATIVE STUDY OF ANAPLASMA IN JAPAN AND OTHER COUNTRIES
To determine the reservoir animals and vector ticks for Anaplasma phagocytophilum in Far East Asia, which causes human granulocytic anaplasmosis, we analyzed tissue samples from deer and boars in Japan rodents in Taiwan and. Ixodes persulcatus in Russia by PCR-targeted. to 16S rDNA. Anaplasma species including Anaplasma bovis and. Anaplasma centrale-infected wild deer and boars were detected. The detection rates for A. phagocytophilum, A. bovis and. A. centrale in deer were 15,6 %, 21,9 % and. 37,5 %, respectively. These infection rates in wild boar were 3,6 %, 17,9 % and. 3,6 %, respectively. Wild rodents captured in Taiwan were positive for A. phagocytophilum. and. A. bovis. Prevalence rate of A. phagocytophilum. on I. persulcatus ticks in Irkutsk and. in Khabarovsk were 6,3 % and. 11,3 %, respectively. The 16SrDNA sequences detected from Russian ticks were identical to those of A. phagocytophilum. detected, in US and. Europe, and. from tick Ixodes ovatus and. Ixodes persulcatus in Japan. However the sequence detected from deer and boars in Japan were identical to sequences previously detected from deer and cattle in Japan, and. showed. less similarity (98,6 %) with typical A. phagocytophilum.. Sequences detected from wild rodents collected in Taiwan showed higher similarity (99,7 %) with typical A. phagocytophilum but formed the branch from those of A. phagocytophilum. detected in US and Europe. The finding suggests that the A. phagocytophilum-related sequence detected from deer and boars in Japan, and. wild rodents in Taiwan were different from those of typical A. phagocytophilum. found in Ixodid ticks
Measurement of a small atmospheric ratio
From an exposure of 25.5~kiloton-years of the Super-Kamiokande detector, 900
muon-like and 983 electron-like single-ring atmospheric neutrino interactions
were detected with momentum MeV/, MeV/, and
with visible energy less than 1.33 GeV. Using a detailed Monte Carlo
simulation, the ratio was measured to be , consistent with previous results from the
Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from
theoretical models of atmospheric neutrino production.Comment: 14 pages with 5 figure
OspA heterogeneity of Borrelia valaisiana confirmed by phenotypic and genotypic analyses
BACKGROUND: Although European Borrelia burgdorferi sensu lato isolates have been divided into five genospecies, specific tools for the serotype characterization of only three genospecies are available. Monoclonals antibodies (mAbs) H3TS, D6 and I17.3 identify B. burgdorferi sensu stricto (ss.), B. garinii and B. afzelii respectively, but no mAbs are available to identify B. valaisiana. In the same way, specific primers exist to amplify the OspA gene of B. burgdorferi ss., B. garinii and B. afzelii. The aim of the study was to develop species-specific mAb and PCR primers for the phenotypic and genetic identification of B. valaisiana. RESULTS: This study describes a mAb that targets OspA of B. valaisiana and primers targeting the OspA gene of this species. As the monoclonal antibody A116k did not react with strains NE231, M7, M53 and Frank and no amplification was observed with strains NE231, M7 and M53, the existence of two subgroups among European B. valaisiana species was confirmed. CONCLUSIONS: The association of both monoclonal antibody A116k and primers Bval 1F and Bval 1R allows to specific identification of the B. valaisiana isolates belonging to subgroup 1
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