23,296 research outputs found

    Circuit breaker utilizing magnetic latching relays Patent

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    Relay circuit breaker with magnetic latching to provide conductive and nonconductive paths for current device

    The helical instability of the positive column in crossed fields and in annular plasma configurations Interim report

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    Helical instability of positive column in crossed fields and in annular plasma configuration

    An x-band waveguide cell for study of microwave propagation through magnetoplasma technical report no. 16

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    Metal X-band waveguide cell for study of microwave propagation through magnetoplasm

    Mixing of a passive scalar in isotropic and sheared homogeneous turbulence

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    In order to calculate the velocity and scalar fields, the three dimensional, time-dependent equations of motion and the diffusion equation were solved numerically. The following cases were treated: isotropic, homogeneous turbulence with decay of a passive scalar; and homogeneous turbulent shear flow with a passive scalar whose mean varies linearly in the spanwise direction. The solutions were obtained at relatively low Reynolds numbers so that all of the turbulent scales could be resolved without modeling. Turbulent statistics such as integral length scales, Taylor microscales, Kolmogorov length scale, one- and two-point correlations of velocity-velocity and velocity-scalar, turbulent Prandtl/Schmidt number, r.m.s. values of velocities, the scalar quantity and pressure, skewness, decay rates, and decay exponents were calculated. The results are compared with the available expermental results, and good agreement is obtained

    The first-mover advantage in scientific publication

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    Mathematical models of the scientific citation process predict a strong "first-mover" effect under which the first papers in a field will, essentially regardless of content, receive citations at a rate enormously higher than papers published later. Moreover papers are expected to retain this advantage in perpetuity -- they should receive more citations indefinitely, no matter how many other papers are published after them. We test this conjecture against data from a selection of fields and in several cases find a first-mover effect of a magnitude similar to that predicted by the theory. Were we wearing our cynical hat today, we might say that the scientist who wants to become famous is better off -- by a wide margin -- writing a modest paper in next year's hottest field than an outstanding paper in this year's. On the other hand, there are some papers, albeit only a small fraction, that buck the trend and attract significantly more citations than theory predicts despite having relatively late publication dates. We suggest that papers of this kind, though they often receive comparatively few citations overall, are probably worthy of our attention.Comment: 7 pages, 3 figure

    Parsec-scale radio morphology and variability of a changing-look AGN: the case of Mrk 590

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    We investigate the origin of the parsec-scale radio emission from the changing-look active galactic nucleus (AGN) of Mrk 590, and examine whether the radio power has faded concurrently with the dramatic decrease in accretion rates observed between the 1990s and the present. We detect a compact core at 1.6 GHz and 8.4 GHz using new Very Long Baseline Array observations, finding no significant extended, jet-like features down to \sim1 pc scales. The flat spectral index (α1.68.4=0.03\alpha_{1.6}^{8.4} = 0.03) and high brightness temperature (Tb108KT_{\rm b} \sim 10^{8}\,\rm K) indicate self-absorbed synchrotron emission from the AGN. The radio to X-ray luminosity ratio of log(LR/LX)5{\rm log}(L_{\rm R}/L_{\rm X}) \sim -5, similar to that in coronally active stars, suggests emission from magnetized coronal winds, although unresolved radio jets are also consistent with the data. Comparing new Karl G. Jansky Very Large Array measurements with archival and published radio flux densities, we find 46%46\%, 34%34\%, and (insignificantly) 13%13\% flux density decreases between the 1990s and the year 2015 at 1.4 GHz, 5 GHz and 8.4 GHz respectively. This trend, possibly due to the expansion and fading of internal shocks within the radio-emitting outflow after a recent outburst, is consistent with the decline of the optical-UV and X-ray luminosities over the same period. Such correlated variability demonstrates the AGN accretion-outflow connection, confirming that the changing-look behaviour in Mrk 590 originates from variable accretion rates rather than dust obscuration. The present radio and X-ray luminosity correlation, consistent with low/hard state accretion, suggests that the black hole may now be accreting in a radiatively inefficient mode.Comment: 14 pages, 5 tables, 5 figures, accepted for publication in MNRA

    Plant Disease Outlook for 1969

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    Knowledge of carryover inoculum is by itself insufficient to predict this year\u27s disease attacks. Two botanists and plant pathologists analyze a number of environmental factors in recommending preventive control measures for 1969
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