7,184 research outputs found

    The rotational shear layer inside the early red-giant star KIC 4448777

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    We present the asteroseismic study of the early red-giant star KIC 4448777, complementing and integrating a previous work (Di Mauro et al. 2016), aimed at characterizing the dynamics of its interior by analyzing the overall set of data collected by the {\it Kepler} satellite during the four years of its first nominal mission. We adopted the Bayesian inference code DIAMOND (Corsaro \& De Ridder 2014) for the peak bagging analysis and asteroseismic splitting inversion methods to derive the internal rotational profile of the star. The detection of new splittings of mixed modes, more concentrated in the very inner part of the helium core, allowed us to reconstruct the angular velocity profile deeper into the interior of the star and to disentangle the details better than in Paper I: the helium core rotates almost rigidly about 6 times faster than the convective envelope, while part of the hydrogen shell seems to rotate at a constant velocity about 1.15 times lower than the He core. In particular, we studied the internal shear layer between the fast-rotating radiative interior and the slow convective zone and we found that it lies partially inside the hydrogen shell above r0.05Rr \simeq 0.05R and extends across the core-envelope boundary. Finally, we theoretically explored the possibility for the future to sound the convective envelope in the red-giant stars and we concluded that the inversion of a set of splittings with only low-harmonic degree l3l\leq 3, even supposing a very large number of modes, will not allow to resolve the rotational profile of this region in detail.Comment: accepted for publication on Ap

    On Deciding Local Theory Extensions via E-matching

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    Satisfiability Modulo Theories (SMT) solvers incorporate decision procedures for theories of data types that commonly occur in software. This makes them important tools for automating verification problems. A limitation frequently encountered is that verification problems are often not fully expressible in the theories supported natively by the solvers. Many solvers allow the specification of application-specific theories as quantified axioms, but their handling is incomplete outside of narrow special cases. In this work, we show how SMT solvers can be used to obtain complete decision procedures for local theory extensions, an important class of theories that are decidable using finite instantiation of axioms. We present an algorithm that uses E-matching to generate instances incrementally during the search, significantly reducing the number of generated instances compared to eager instantiation strategies. We have used two SMT solvers to implement this algorithm and conducted an extensive experimental evaluation on benchmarks derived from verification conditions for heap-manipulating programs. We believe that our results are of interest to both the users of SMT solvers as well as their developers

    Genetic Divergence Among Accessions Of Cassava (manihot Esculenta Crantz) Sampled In The Tapajós Region, State Of Pará, Using Agronomic Characters And Microsatellite Markers

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    The aim of this work was to estimate the genetic divergence among accessions of cassava sampled in the Tapajós region in the State of Pará, Brazil, and conserved at the Regional Germplasm Bank of Eastern Amazon, using agronomic descriptors and molecular markers. Twenty-two accessions of cassava were evaluated in the field for two successive years, based on six agronomic descriptors in twelve-months-old plants without a specific experimental design. Accessions were also evaluated with eleven microsatellite loci in an automatic DNA analyser. Descriptive and multivariate statistical analyses were applied. Based on principal components analysis, the character weight of the aerial portion of the plant contributed most to the phenotypical variation. The six traits were used in the analysis of genetic dissimilarity between accessions, and the correlation between matrices generated by morphological and molecular data was estimated. The matrices of genetic dissimilarity were used in the construction of dendrograms using the UPGMA method. We observed a high variation of agronomical descriptors and molecular markers evaluated, which were capable to separate the accessions into distinct groups. A weak positive correlation was detected among the two matrices of genetic distances, which indicates the possibility to explore the genetic diversity using crossings and accessions Amarelinha 36 and Olho roxo 13 are divergent and potentially promising for the generation of heterotic hybrids.3752989300

    Attacks by “Anonymous” WikiLeaks Proponents not Anonymous

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    On November 28, 2010, the world started watching the whistle blower website WikiLeaks to begin publishing part of the 250,000 US Embassy Diplomatic cables. These confidential cables provide an insight on U.S. international affairs from 274 different embassies, covering topics such as analysis of host countries and leaders and even requests for spying out United Nations leaders.\ud The release of these cables has caused reactions not only in the real world, but also on the Internet. In fact, a cyberwar started just before the initial release. Wikileaks has reported that their servers were experiencing distributed denial-of-service attacks (DDoS). A DDoS attack consists of many computers trying to overload a server by firing a high number of requests, leading ultimately to service disruption. In this case, the goal was to avoid the release of the embassy cables.\ud After the initial cable release, several companies started severed ties with WikiLeaks. One of the first was Amazon.com, that removed the WikiLeaks web- site from their servers. Next, EveryDNS, a company in which the domain wikileaks.org was registered, dropped the domain entries from its servers. On December 4th, PayPal cancelled the account that WikiLeaks was using to receive on-line donations. On the 6th, Swiss bank PostFinance froze the WikiLeaks assets and Mastercard stopped receiving payments to the WikiLeaks account. Visa followed Mastercard on December 7th.\ud These reactions caused a group of Internet activists (or “hacktivists”) named Anonymous to start a retaliation against PostFinance, PayPay, MasterCard, Visa, Moneybrookers.com and Amazon.com, named “Operation Payback”. The retaliation was performed as DDoS attacks to the websites of those companies, disrupting their activities (except for the case of Amazon.com) for different periods of time.\ud The Anonymous group consists of volunteers that use a stress testing tool to perform the attacks. This tool, named LOIC (Low Orbit Ion Cannon), can be found both as a desktop application and as a Web page.\ud Even though the group behind the attacks claims to be anonymous, the tools they provide do not offer any security services, such as anonymization. As a consequence, a hacktivist that volunteers to take part in such attacks, can be traced back easily. This is the case for both current versions of the LOIC tool. Therefore, the goal of this report is to present an analysis of privacy issues in the context of these attacks, and raise awareness on the risks of taking part in them
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