25,682 research outputs found

    Liquid sloshing in elastic containers

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    Coupled oscillations of elastic container partially filled with incompressible liqui

    Tendency of spherically imploding plasma liners formed by merging plasma jets to evolve toward spherical symmetry

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    Three dimensional hydrodynamic simulations have been performed using smoothed particle hydrodynamics (SPH) in order to study the effects of discrete jets on the processes of plasma liner formation, implosion on vacuum, and expansion. The pressure history of the inner portion of the liner was qualitatively and quantitatively similar from peak compression through the complete stagnation of the liner among simulation results from two one dimensional radiationhydrodynamic codes, 3D SPH with a uniform liner, and 3D SPH with 30 discrete plasma jets. Two dimensional slices of the pressure show that the discrete jet SPH case evolves towards a profile that is almost indistinguishable from the SPH case with a uniform liner, showing that non-uniformities due to discrete jets are smeared out by late stages of the implosion. Liner formation and implosion on vacuum was also shown to be robust to Rayleigh-Taylor instability growth. Interparticle mixing for a liner imploding on vacuum was investigated. The mixing rate was very small until after peak compression for the 30 jet simulation.Comment: 28 pages, 16 figures, submitted to Physics of Plasmas (2012

    Palatable Meal Anticipation in Mice

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    The ability to sense time and anticipate events is a critical skill in nature. Most efforts to understand the neural and molecular mechanisms of anticipatory behavior in rodents rely on daily restricted food access, which induces a robust increase of locomotor activity in anticipation of daily meal time. Interestingly, rats also show increased activity in anticipation of a daily palatable meal even when they have an ample food supply, suggesting a role for brain reward systems in anticipatory behavior, and providing an alternate model by which to study the neurobiology of anticipation in species, such as mice, that are less well adapted to "stuff and starve" feeding schedules. To extend this model to mice, and exploit molecular genetic resources available for that species, we tested the ability of wild-type mice to anticipate a daily palatable meal. We observed that mice with free access to regular chow and limited access to highly palatable snacks of chocolate or “Fruit Crunchies” avidly consumed the snack but did not show anticipatory locomotor activity as measured by running wheels or video-based behavioral analysis. However, male mice receiving a snack of high fat chow did show increased food bin entry prior to access time and a modest increase in activity in the two hours preceding the scheduled meal. Interestingly, female mice did not show anticipation of a daily high fat meal but did show increased activity at scheduled mealtime when that meal was withdrawn. These results indicate that anticipation of a scheduled food reward in mice is behavior, diet, and gender specific

    MAGIC observations of Mkn 421 in 2008, and related optical/X-ray/TeV MWL study

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    The HBL-type blazar Markarian 421 is one of the brightest TeV gamma-ray sources of the Northern sky. From December 2007 until June 2008 it was intensively observed in the VHE (E>100 GeV) band by the MAGIC gamma-ray telescope. The source showed intense and prolonged activity during the whole period. In some nights the integral flux rose up to 3.6 Crab units (E>200 GeV). Intra-night rapid flux variations were observed. We compared the optical (KVA) and X-ray (RXTE-ASM, Swift-XRT) data with the MAGIC VHE data, investigating the correlations between different energy bands.Comment: 4 pages,4figures, Contribution to the 31st ICRC, Lodz, Poland, July 200

    Average-Case Optimal Approximate Circular String Matching

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    Approximate string matching is the problem of finding all factors of a text t of length n that are at a distance at most k from a pattern x of length m. Approximate circular string matching is the problem of finding all factors of t that are at a distance at most k from x or from any of its rotations. In this article, we present a new algorithm for approximate circular string matching under the edit distance model with optimal average-case search time O(n(k + log m)/m). Optimal average-case search time can also be achieved by the algorithms for multiple approximate string matching (Fredriksson and Navarro, 2004) using x and its rotations as the set of multiple patterns. Here we reduce the preprocessing time and space requirements compared to that approach

    STEPS - an approach for human mobility modeling

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    In this paper we introduce Spatio-TEmporal Parametric Stepping (STEPS) - a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS makes abstraction of spatio-temporal preferences in human mobility by using a power law to rule the nodes movement. Nodes in STEPS have preferential attachment to favorite locations where they spend most of their time. Via simulations, we show that STEPS is able, not only to express the peer to peer properties such as inter-ontact/contact time and to reflect accurately realistic routing performance, but also to express the structural properties of the underlying interaction graph such as small-world phenomenon. Moreover, STEPS is easy to implement, exible to configure and also theoretically tractable

    Sharp signature of DDW quantum critical point in the Hall coefficient of the cuprates

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    We study the behavior of the Hall coefficient, RHR_H, in a system exhibiting dx2−y2d_{{x^2}-{y^2}} density-wave (DDW) order in a regime in which the carrier concentration, xx, is tuned to approach a quantum critical point at which the order is destroyed. At the mean-field level, we find that nHall=1/RHn_{\rm Hall}=1/R_H evinces a sharp signature of the transition. There is a kink in nHalln_{\rm Hall} at the critical value of the carrier concentration, xcx_c; as the critical point is approached from the ordered side, the slope of nHalln_{\rm Hall} diverges. Hall transport experiments in the cuprates, at high magnetic fields sufficient to destroy superconductivity, should reveal this effect.Comment: 5 pages, 2 eps figure

    Time evolution of a quantum many-body system: transition from integrability to ergodicity in thermodynamic limit

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    Numerical evidence is given for non-ergodic (non-mixing) behavior, exhibiting ideal transport, of a simple non-integrable many-body quantum system in the thermodynamic limit, namely kicked t−Vt-V model of spinless fermions on a ring. However, for sufficiently large kick parameters tt and VV we recover quantum ergodicity, and normal transport, which can be described by random matrix theory.Comment: 4 pages in RevTex (6 figures in PostScript included
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