7,032 research outputs found

    Quantum privacy and quantum coherence

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    We derive a simple relation between a quantum channel's capacity to convey coherent (quantum) information and its usefulness for quantum cryptography.Comment: 6 pages RevTex; two short comments added 7 October 199

    Sub-Kolmogorov-Scale Fluctuations in Fluid Turbulence

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    We relate the intermittent fluctuations of velocity gradients in turbulence to a whole range of local dissipation scales generalizing the picture of a single mean dissipation length. The statistical distribution of these local dissipation scales as a function of Reynolds number is determined in numerical simulations of forced homogeneous isotropic turbulence with a spectral resolution never applied before which exceeds the standard one by at least a factor of eight. The core of the scale distribution agrees well with a theoretical prediction. Increasing Reynolds number causes the generation of ever finer local dissipation scales. This is in line with a less steep decay of the large-wavenumber energy spectra in the dissipation range. The energy spectrum for the highest accessible Taylor microscale Reynolds number R_lambda=107 does not show a bottleneck.Comment: 8 pages, 5 figures (Figs. 1 and 3 in reduced quality

    Histological investigations on the thyroid glands of marine mammals (Phoca vitulina, Phocoena phocoena) and the possible implications of marine pollution

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    In 1988 and 1989, thousands of harbor seals (Phoca vitulina) died in the North Sea from phocine distemper infection. The morphology of thyroid glands from 40 harbor seals found dead on the North Sea coastlines of Schleswig-Holstein, Federal Republic of Germany, during an epizootic of phocine distemper, was compared with the morphology of thyroid glands from five healthy harbor seals collected in Iceland. Thyroid glands from seven harbor porpoises (Phocoena phocoena) found dead in 1990 on the North Sea coastlines also were evaluated. Colloid depletion and fibrosis were found in the thyroid glands of harbor seals which died during the epizootic, but not in animals from Iceland. Thyroid glands of the porpoises showed similar lesions, but to a lesser degree, than those observed in the North Sea seals

    Moving to Extremal Graph Parameters

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    Which graphs, in the class of all graphs with given numbers n and m of edges and vertices respectively, minimizes or maximizes the value of some graph parameter? In this paper we develop a technique which provides answers for several different parameters: the numbers of edges in the line graph, acyclic orientations, cliques, and forests. (We minimize the first two and maximize the third and fourth.) Our technique involves two moves on the class of graphs. A compression move converts any graph to a form we call fully compressed: the fully compressed graphs are split graphs in which the neighbourhoods of points in the independent set are nested. A second consolidation move takes each fully compressed graph to one particular graph which we call H(n,m). We show monotonicity of the parameters listed for these moves in many cases, which enables us to obtain our results fairly simply. The paper concludes with some open problems and future directions

    Enhancing Bremsstrahlung Production From Ultraintense Laser-Solid Interactions With Front Surface Structures

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    We report the results of a combined study of particle-in-cell and Monte Carlo modeling that investigates the production of Bremsstrahlung radiation produced when an ultraintense laser interacts with a tower-structured target. These targets are found to significantly narrow the electron angular distribution as well as produce significantly higher energies. These features combine to create a significant enhancement in directionality and energy of the Bremstrahlung radiation produced by a high-Z converter target. These studies employ short-pulse, high intensity laser pulses, and indicate that novel target design has potential to greatly enhance the yield and narrow the directionality of high energy electrons and γ\gamma-rays. We find that the peak γ\gamma-ray brightness for this source is 6.0×\times1019^{19} s−1mm−2mrad−2{\rm s^{-1}mm^{-2}mrad^{-2}} at 10MeV and 1.4×\times1019^{19} s−1mm−2mrad−2{\rm s^{-1}mm^{-2}mrad^{-2}} at 100MeV (0.1%\% bandwidth).Comment: arXiv admin note: text overlap with arXiv:1310.328

    Stellenwert der pelvinen Lymphadenektomie beim klinisch lokalisierten Prostatakarzinom

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    Zusammenfassung: Der Stellenwert und die Ausdehnung der pelvinen Lymphadenektomie beim klinisch lokalisierten Prostatakarzinom werden weiterhin kontrovers diskutiert. Die Lymphadenektomie stellt jedoch bis heute die einzige Methode für ein exaktes Tumorstaging dar. Es gibt zunehmend Hinweise, dass das Entfernen von allen befallenen Lymphknoten einen positiven Einfluss auf das tumorfreie Überleben und evtl. auf das Gesamtüberleben haben könnte. Aus diesem Grund sollte, wenn eine Lymphadenektomie durchgeführt wird, diese Entlang der V.iliaca externa, in der Fossa obturatoria und beidseits Entlang der A.iliaca interna erfolge

    Robust single-parameter quantized charge pumping

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    This paper investigates a scheme for quantized charge pumping based on single-parameter modulation. The device was realized in an AlGaAs-GaAs gated nanowire. We find a remarkable robustness of the quantized regime against variations in the driving signal, which increases with applied rf power. This feature together with its simple configuration makes this device a potential module for a scalable source of quantized current.Comment: Submitted to Appl. Phys. Let
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