2,410 research outputs found
Using genetic algorithms to generate test sequences for complex timed systems
The generation of test data for state based specifications is a computationally expensive process. This problem is magnified if we consider that time con- straints have to be taken into account to govern the transitions of the studied system. The main goal of this paper is to introduce a complete methodology, sup- ported by tools, that addresses this issue by represent- ing the test data generation problem as an optimisa- tion problem. We use heuristics to generate test cases. In order to assess the suitability of our approach we consider two different case studies: a communication protocol and the scientific application BIPS3D. We give details concerning how the test case generation problem can be presented as a search problem and automated. Genetic algorithms (GAs) and random search are used to generate test data and evaluate the approach. GAs outperform random search and seem to scale well as the problem size increases. It is worth to mention that we use a very simple fitness function that can be eas- ily adapted to be used with other evolutionary search techniques
The Entropy for General Extremal Black Holes
We use the Kerr/CFT correspondence to calculate the entropy for all known
extremal stationary and axisymmetric black holes. This is done with the help of
two ansatzs that are general enough to cover all such known solutions.
Considering only the contribution from the Einstein-Hilbert action to the
central charge(s), we find that the entropy obtained by using Cardy's formula
exactly matches with the Bekenstein-Hawking entropy.Comment: Minor corrections, section 5 refined, references added
Gravitational Chern-Simons Lagrangians and black hole entropy
We analyze the problem of defining the black hole entropy when Chern-Simons
terms are present in the action. Extending previous works, we define a general
procedure, valid in any odd dimensions both for purely gravitational CS terms
and for mixed gauge-gravitational ones. The final formula is very similar to
Wald's original formula valid for covariant actions, with a significant
modification. Notwithstanding an apparent violation of covariance we argue that
the entropy formula is indeed covariant.Comment: 39 page
A Variational Method in Out of Equilibrium Physical Systems
A variational principle is further developed for out of equilibrium dynamical
systems by using the concept of maximum entropy. With this new formulation it
is obtained a set of two first-order differential equations, revealing the same
formal symplectic structure shared by classical mechanics, fluid mechanics and
thermodynamics. In particular, it is obtained an extended equation of motion
for a rotating dynamical system, from where it emerges a kind of topological
torsion current of the form , with and
denoting components of the vector potential (gravitational or/and
electromagnetic) and is the angular velocity of the accelerated frame.
In addition, it is derived a special form of Umov-Poynting's theorem for
rotating gravito-electromagnetic systems, and obtained a general condition of
equilibrium for a rotating plasma. The variational method is then applied to
clarify the working mechanism of some particular devices, such as the Bennett
pinch and vacuum arcs, to calculate the power extraction from an hurricane, and
to discuss the effect of transport angular momentum on the radiactive heating
of planetary atmospheres. This development is seen to be advantageous and opens
options for systematic improvements.Comment: 22 pages, 1 figure, submitted to review, added one referenc
Synchronizing heuristics for weakly connected automata with various topologies
Since the problem of finding a shortest synchronizing sequence for an automaton is known to be NP-hard, heuristics algorithms are used to find synchronizing sequences. There are several heuristic algorithms in the literature for this purpose. However, even the most efficient heuristic algorithm in the literature has a quadratic complexity in terms of the number of states of the automaton, and therefore can only scale up to a couple of thousands of states. It was also shown before that if an automaton is not strongly connected, then these heuristic algorithms can be used on each strongly connected component separately. This approach speeds up these heuristic algorithms and allows them to scale to much larger number of states easily. In this paper, we investigate the effect of the topology of the automaton on the performance increase obtained by these heuristic algorithms. To this end, we consider various topologies and provide an extensive experimental study on the performance increase obtained on the existing heuristic algorithms. Depending on the size and the number of components, we obtain speed-up values as high as 10000x and more
On the General Kerr/CFT Correspondence in Arbitrary Dimensions
We study conformal symmetries on the horizon of a general stationary and
axisymmetric black hole. We find that there exist physically reasonable
boundary conditions that uniquely determine a set of symmetry generators, which
form one copy of the Virasoro algebra. For extremal black holes, Cardy's
formula reproduces exactly the Bekenstein-Hawking entropy.Comment: 17 page
Interleukin-1 polymorphisms associated with increased risk of gastric cancer
Helicobacter pylori infection is associated with a variety of clinical outcomes including gastric cancer and duodenal ulcer disease. The reasons for this variation are not clear, but the gastric physiological response is influenced by the severity and anatomical distribution of gastritis induced by H. pylori. Thus, individuals with gastritis predominantly localized to the antrum retain normal (or even high) acid secretion, whereas individuals with extensive corpus gastritis develop hypochlorhydria and gastric atrophy, which are presumptive precursors of gastric cancer. Here we report that interleukin-1 gene cluster polymorphisms suspected of enhancing production of interleukin-1-beta are associated with an increased risk of both hypochlorhydria induced by H. pylori and gastric cancer. Two of these polymorphism are in near-complete linkage disequilibrium and one is a TATA-box polymorphism that markedly affects DNA-protein interactions in vitro. The association with disease may be explained by the biological properties of interleukin-1-beta, which is an important pro-inflammatory cytokine and a powerful inhibitor of gastric acid secretion. Host genetic factors that affect interleukin-1-beta may determine why some individuals infected with H. pylori develop gastric cancer while others do no
Kerr-CFT From Black-Hole Thermodynamics
We analyze the near-horizon limit of a general black hole with two commuting
killing vector fields in the limit of zero temperature. We use black hole
thermodynamics methods to relate asymptotic charges of the complete spacetime
to those obtained in the near-horizon limit. We then show that some
diffeomorphisms do alter asymptotic charges of the full spacetime, even though
they are defined in the near horizon limit and, therefore, count black hole
states. We show that these conditions are essentially the same as considered in
the Kerr/CFT corresponcence. From the algebra constructed from these
diffeomorphisms, one can extract its central charge and then obtain the black
hole entropy by use of Cardy's formula.Comment: 19 pages, JHEP3, no figures. V2: References added, small typos fixe
The dynamics of apparent horizons in Robinson-Trautman spacetimes
We present an alternative scheme of finding apparent horizons based on
spectral methods applied to Robinson-Trautman spacetimes. We have considered
distinct initial data such as representing the spheroids of matter and the
head-on collision of two non-rotating black holes. The evolution of the
apparent horizon is presented. We have obtained in some cases a mass gap
between the final Bondi and apparent horizon masses, whose implications were
briefly commented in the light of the thermodynamics of black holes.Comment: 9 pages, 7 figure
Longer telomere length in peripheral white blood cells is associated with risk of lung cancer and the rs2736100 (CLPTM1L-TERT) polymorphism in a prospective cohort study among women in China.
A recent genome-wide association study of lung cancer among never-smoking females in Asia demonstrated that the rs2736100 polymorphism in the TERT-CLPTM1L locus on chromosome 5p15.33 was strongly and significantly associated with risk of adenocarcinoma of the lung. The telomerase gene TERT is a reverse transcriptase that is critical for telomere replication and stabilization by controlling telomere length. We previously found that longer telomere length measured in peripheral white blood cell DNA was associated with increased risk of lung cancer in a prospective cohort study of smoking males in Finland. To follow up on this finding, we carried out a nested case-control study of 215 female lung cancer cases and 215 female controls, 94% of whom were never-smokers, in the prospective Shanghai Women's Health Study cohort. There was a dose-response relationship between tertiles of telomere length and risk of lung cancer (odds ratio (OR), 95% confidence interval [CI]: 1.0, 1.4 [0.8-2.5], and 2.2 [1.2-4.0], respectively; P trend = 0.003). Further, the association was unchanged by the length of time from blood collection to case diagnosis. In addition, the rs2736100 G allele, which we previously have shown to be associated with risk of lung cancer in this cohort, was significantly associated with longer telomere length in these same study subjects (P trend = 0.030). Our findings suggest that individuals with longer telomere length in peripheral white blood cells may have an increased risk of lung cancer, but require replication in additional prospective cohorts and populations
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