2,230 research outputs found
Propositional Encoding of Constraints over Tree-Shaped Data
We present a functional programming language for specifying constraints over
tree-shaped data. The language allows for Haskell-like algebraic data types and
pattern matching. Our constraint compiler CO4 translates these programs into
satisfiability problems in propositional logic. We present an application from
the area of automated analysis of (non-)termination of rewrite systems
Scaling and energy transfer in rotating turbulence
The inertial-range properties of quasi-stationary hydrodynamic turbulence
under solid-body rotation are studied via high-resolution direct numerical
simulations. For strong rotation the nonlinear energy cascade exhibits
depletion and a pronounced anisotropy with the energy flux proceeding mainly
perpendicularly to the rotation axis. This corresponds to a transition towards
a quasi-two-dimensional flow similar to a linear Taylor-Proudman state. In
contrast to the energy spectrum along the rotation axis which does not scale
self-similarly, the perpendicular spectrum displays an inertial range with
-behavior. A new phenomenology gives a rationale for the
observations. The scaling exponents of structure functions up to
order measured perpendicular to the rotation axis indicate reduced
intermittency with increasing rotation rate. The proposed phenomenology is
consistent with the inferred asymptotic non-intermittent behavior
.Comment: to be published in Europhysics Letters (www.epletters.net), minor
changes to match version in prin
Numerical simulation of 3-D flow around sounding rocket in the lower thermosphere
International audienceNumerical simulations using the Direct Simulation Monte Carlo (DSMC) method are known to be useful for analyses of aerodynamic effects on in-situ rocket measurements in the lower thermosphere, but the DSMC analysis of a spin modulation caused by an asymmetric flow around the rocket spin axis has been restricted to the two-dimensional and axially symmetric simulations in actual sounding rocket experiments. This study provides a quantitative analysis of the spin modulation using a three-dimensional (3-D) simulation of the asymmetric flow with the DSMC method. Clear spin modulations in the lower thermospheric N2 density measurement by a rocket-borne instrument are simulated using the rocket attitude and velocity, the simplified payload structure, and the approximated atmospheric conditions. Comparison between the observed and simulated spin modulations show a very good agreement within 5% at around 100km. The results of the simulation are used to correct the spin modulations and derive the absolute densities in the background atmosphere
Temperature dependence of infrared reflectance spectra of InN
To investigate both the optical and electrical properties of InN, we have measured the infrared reflectance spectra of InN thin
films and performed the fitting analyses of the infrared spectra to obtain not only phonon frequencies and the damping factors
but also the carrier concentration of InN. In this paper, we extend the aim of those analyses to the electron mobility and
demonstrate that the temperature dependence of the electron mobility can be discussed using the infrared reflectance spectra
analyses
The scaling properties of dissipation in incompressible isotropic three-dimensional magnetohydrodynamic turbulence
The statistical properties of the dissipation process constrain the analysis
of large scale numerical simulations of three dimensional incompressible
magnetohydrodynamic (MHD) turbulence, such as those of Biskamp and Muller
[Phys. Plasmas 7, 4889 (2000)]. The structure functions of the turbulent flow
are expected to display statistical self-similarity, but the relatively low
Reynolds numbers attainable by direct numerical simulation, combined with the
finite size of the system, make this difficult to measure directly. However, it
is known that extended self-similarity, which constrains the ratio of scaling
exponents of structure functions of different orders, is well satisfied. This
implies the extension of physical scaling arguments beyond the inertial range
into the dissipation range. The present work focuses on the scaling properties
of the dissipation process itself. This provides an important consistency check
in that we find that the ratio of dissipation structure function exponents is
that predicted by the She and Leveque [Phys. Rev. Lett 72, 336 (1994)] theory
proposed by Biskamp and Muller. This supplies further evidence that the cascade
mechanism in three dimensional MHD turbulence is non-linear random eddy
scrambling, with the level of intermittency determined by dissipation through
the formation of current sheets.Comment: 9 pages, 6 figures. Figures embedded in text. Typos corrected in text
and references. Published in Physics of Plasmas. Abstract can be found
at:http://link.aip.org/link/?php/12/02230
Josephson -state in superconductor-Luttinger liquid hybrid systems
Josephson current through a Luttinger liquid (LL) under a magnetic field is
theoretically studied. We derive an analytical expression of Josephson current
for clean interfaces, by using quasiclassical Green's function and functional
bosonization procedure. We show that critical currents can be renormalized by
electron-electron interactions at perfect transparency when LL is adiabatically
connected with superconductors. We also find that a generation of -state,
due to spin-dependent energy shift in Andreev bound states (ABS), is prohibited
even at zero temperature when the strength of repulsive interactions reaches
some critical value. The suppression of -state is caused by the low energy
fluctuations propagating in LL, and making the Zeeman splitting in ABS blurred.Comment: 5 pages, 4figure
Detection and Localization of Periodontopathic Bacteria in Abdominal Aortic Aneurysms
AbstractObjectivesWe examined a possible link between periodontal disease and abdominal aortic aneurysm (AAA) by studying resected aneurysmal specimens from AAA patients for the presence of periodontitopathic bacteria.DesignProspective case control study.Material and methodsThirty-two AAA patients were enrolled in the study. Periodontitis was classified according to the probing depth of preriodontal pocket. Thirty-two aneurysmal walls, 16 mural thrombi, 5 atherosclerotic occlusive aorta and 5 control arterial tissue, were examined for 7 periodontal bacteria using polymerase chain reaction (PCR) method. The localization of the bacteria in the aneurysmal/atherosclerotic wall was determined by thromboendarterectomy.ResultsAll patients had periodontal disease, and most cases were severe. PCR examination of the aneurysmal specimens showed that 86% were positive for periodontal bacterial DNA. No bacteria were detected in the control specimens. The bacteria were found in both the intimal/medial layer and the adventitial layer of the aneurysmal wall but only in intimal/medial layer of the atherosclerotic occlusive aorta.ConclusionPeriodontopathic bacteria were present in a high percentage of specimens of diseased arteries from AAA patients and were found throughout the whole aneurysmal wall. These bacteria may play a role in the development of AAAs and/or contribute to weakening the aneurysmal wall
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