44,410 research outputs found

    The Mayflies (Ephemeroptera) of Tennessee, With a Review of the Possibly Threatened Species Occurring Within the State

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    One hundred and forty-three species of mayflies are reported from the state of Tennessee. Sixteen species (Ameletus cryptostimulus, Choroterpes basalis, Baetis virile, Ephemera blanda, E. simulans, Ephemerella berneri, Heterocloeon curiosum, H. petersi, Labiobaetis ephippiatus, Leptophlebia bradleyi, Macdunnoa brunnea, Paraleptophlebia assimilis, P. debilis, P. mollis, Rhithrogenia pellucida and Siphlonurus mirus) are reported for the first time. Rare and vulnerable species occurring in the state are also discussed. This represents the first comprehensive statewide list of mayflies for Tennessee

    A simplified holographic-interferometry technique for real-time flow visualization and analysis

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    A holographic-interferometry technique for flow visualization and analysis that produces real-time moire fringes is described from both experimental and application considerations. It has three chief advantages: real-time data for continuous observation and photography, ease of optical adjustment, and capability of using ordinary-glass test-section windows without affecting the results. A theoretical discussion is presented describing the formation of the fringes in holographic terms and then comparing this result to that which is obtained from a conventional moire approach. A discussion on obtaining density information from the fringe pattern is also included

    Results of magnetospheric barium ion cloud experiment of 1971

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    The barium ion cloud experiment involved the release of about 2 kg of barium at an altitude of 31 482 km, a latitude of 6.926 N., and a longitude of 74.395 W. Significant erosion of plasma from the main ion core occurred during the initial phase of the ion cloud expansion. From the motion of the outermost striational filaments, the electric field components were determined to be 0.19 mV/m in the westerly direction and 0.68 mV/m in the inward direction. The differences between these components and those measured from balloons flown in the proximity of the extremity of the field line through the release point implied the existence of potential gradients along the magnetic field lines. The deceleration of the main core was greater than theoretically predicted. This was attributed to the formation of a polarization wake, resulting in an increase of the area of interaction and resistive dissipation at ionospheric levels. The actual orientation of the magnetic field line through the release point differed by about 10.5 deg from that predicted by magnetic field models that did not include the effect of ring current

    The reverberation signatures of rotating disc winds in active galactic nuclei

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    The broad emission lines (BELs) in active galactic nuclei (AGN) respond to ionizing continuum variations. The time and velocity dependence of their response depends on the structure of the broad-line region: its geometry, kinematics and ionization state. Here, we predict the reverberation signatures of BELs formed in rotating accretion disc winds. We use a Monte Carlo radiative transfer and ionization code to predict velocity-delay maps for representative high- (C IV~IV) and low-ionization (Hα\alpha) emission lines in both high- and moderate-luminosity AGN. Self-shielding, multiple scattering and the ionization structure of the outflows are all self-consistently taken into account, while small-scale structure in the outflow is modelled in the micro-clumping approximation. Our main findings are: (1) The velocity-delay maps of smooth/micro-clumped outflows often contain significant negative responses. (2)~The reverberation signatures of disc wind models tend to be rotation dominated and can even resemble the classic "red-leads-blue" inflow signature. (3) Traditional "blue-leads-red" outflow signatures can usually only be observed in the long-delay limit. (4) Our models predict lag-luminosity relationships similar to those inferred from observations, but systematically underpredict the observed centroid delays. (5) The ratio between "virial product" and black hole mass predicted by our models depends on viewing angle. Our results imply that considerable care needs to be taken in interpreting data obtained by observational reverberation mapping campaigns. In particular, basic signatures such as "red-leads-blue", "blue-leads-red" and "blue and red vary jointly" are not always reliable indicators of inflow, outflow or rotation. This may help to explain the perplexing diversity of such signatures seen in observational campaigns to date.Comment: 15 pages, 17 figures, 2 tables. Accepted by MNRAS 20/7/201
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