37,841 research outputs found

    Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law

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    In the interaction of high-power laser beams with solid density plasma there are a number of mechanisms that generate strong magnetic fields. Such fields subsequently inhibit or redirect electron flows, but can themselves be advected by heat fluxes, resulting in complex interplay between thermal transport and magnetic fields.We show that for heating by multiple laser spots reconnection of magnetic field lines can occur, mediated by these heat fluxes, using a fully implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection rate is dictated by heat flows rather than Alfv\`enic flows. We find that this mechanism is only relevant in a high β\beta plasma. However, the Hall parameter ωcτei\omega_c \tau_{ei} can be large so that thermal transport is strongly modified by these magnetic fields, which can impact longer time scale temperature homogeneity and ion dynamics in the system

    Parenting Among Hispanic and Anglo-American Mothers With Young Children

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    The authors examined parenting practices and developmental expectations among 38 Hispanic and 38 Anglo-American mothers living in the United States. Mothers of children 3 to 5 years of age completed the Parent Behavior Checklist (R. A. Fox, 1994), a 100-item measure of parents\u27 developmental expectations, discipline, and nurturing practices. In addition, the authors appraised the Hispanic mothers\u27 acculturation and selected them for participation if their scores on an acculturation scale indicated (a) that their lifestyle was predominantly Hispanic and (b) that they had not been assimilated into the dominant culture. The 2 ethnic groups were also divided by socioeconomic status (SES). There were significant main effects for ethnicity and SES on the discipline and nurturing scores but not on the expectations scores. The Hispanic and higher SES mothers reported higher discipline and lower nurturing scores than did the Anglo-American and lower SES mothers. An unexpected finding was the tendency for higher SES Hispanic mothers to report more frequent use of discipline than the other 3 groups

    Live User-guided Intrinsic Video For Static Scenes

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    We present a novel real-time approach for user-guided intrinsic decomposition of static scenes captured by an RGB-D sensor. In the first step, we acquire a three-dimensional representation of the scene using a dense volumetric reconstruction framework. The obtained reconstruction serves as a proxy to densely fuse reflectance estimates and to store user-provided constraints in three-dimensional space. User constraints, in the form of constant shading and reflectance strokes, can be placed directly on the real-world geometry using an intuitive touch-based interaction metaphor, or using interactive mouse strokes. Fusing the decomposition results and constraints in three-dimensional space allows for robust propagation of this information to novel views by re-projection.We leverage this information to improve on the decomposition quality of existing intrinsic video decomposition techniques by further constraining the ill-posed decomposition problem. In addition to improved decomposition quality, we show a variety of live augmented reality applications such as recoloring of objects, relighting of scenes and editing of material appearance

    Design and performance evaluation of small, two- and four-stage depressed collectors for a 4.8 to 9.6 GHz high-performance traveling wave tube

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    A program to improve the efficiency of traveling wave tubes (TWT's) for use in electronic countermeasure (ECM) systems by applying multistage depressed collector (MDC) and spent beam refocusing techniques is studied. Three dimensional electron trajectories are computed through-out the slow wave structure of the TWT, the spent beam refocuser, and the depressed collector. Both TWT and MDC performances are analytically evaluated

    RAT0455+1305: another pulsating hybrid sdB star

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    RAT0455+1305 was discovered during the Rapid Temporal Survey which aims in finding any variability on timescales of a few minutes to several hours. The star was found to be another sdBV star with one high amplitude mode and relatively long period. These features along with estimation of T_eff and log g makes this star very similar to Balloon 090100001. Encouraged by prominent results obtained for the latter star we have decided to perform white light photometry on RAT0455+1305. In 2009 we used the 1.5m telescope located in San Pedro Martir Observatory in Mexico. Fourier analysis confirmed the dominant mode found in the discovery data, uncovered another peak close to the dominant one, and three peaks in the low frequency region. This shows that RAT0455+1305 is another hybrid sdBV star pulsating in both p- and g-modes.Comment: Proceedings of The Fourth Meeting on Hot Subdwarf Stars and Related Objects held in China, 20-24 July 2009. Accepted for publication in Astrophysics & Space Scienc

    On small homotopies of loops

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    Two natural questions are answered in the negative: (1) If a space has the property that small nulhomotopic loops bound small nulhomotopies, then are loops which are limits of nulhomotopic loops themselves nulhomotopic? (2) Can adding arcs to a space cause an essential curve to become nulhomotopic? The answer to the first question clarifies the relationship between the notions of a space being homotopically Hausdorff and π1\pi_1-shape injective.Comment: 12 pages, 5 figure

    On the η\eta and η′\eta' Photoproduction Beam Asymmetry at High Energies

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    We show that, in the Regge limit, beam asymmetries in η\eta and η′\eta' photoproduction are sensitive to hidden strangeness components. Under reasonable assumptions about the couplings we estimate the contribution of the ϕ\phi Regge pole, which is expected to be the dominant hidden strangeness contribution. The ratio of the asymmetries in η′\eta' and η\eta production is estimated to be close to unity in the forward region 0<−t/GeV2≤10 < -t/\text{GeV}^2 \leq 1 at the photon energy Elab=9E_\text{lab} = 9~GeV, relevant for the upcoming measurements at Jefferson Lab.Comment: 9 pages, 4 figure

    Machine Assisted Proof of ARMv7 Instruction Level Isolation Properties

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    In this paper, we formally verify security properties of the ARMv7 Instruction Set Architecture (ISA) for user mode executions. To obtain guarantees that arbitrary (and unknown) user processes are able to run isolated from privileged software and other user processes, instruction level noninterference and integrity properties are provided, along with proofs that transitions to privileged modes can only occur in a controlled manner. This work establishes a main requirement for operating system and hypervisor verification, as demonstrated for the PROSPER separation kernel. The proof is performed in the HOL4 theorem prover, taking the Cambridge model of ARM as basis. To this end, a proof tool has been developed, which assists the verification of relational state predicates semi-automatically
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