29,798 research outputs found

    Double Beta Decay

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    I review the subject of double beta decay with emphasis upon its implications for the neutrino. It is shown that even if right-handed currents provide the phenomenological mechanism for no-neutrino decay, the fundamental mechanism underlying the process must be neutrino mass. Estimates of the mass required suggest that this mechanism is less likely than the direct mechanism of Majorana mass terms in the mass matrix.Comment: 19 pages (two figures not included) report number UTAPHY-HEP-

    Nonlinear Equations of Equilibrium for Elastic Helicopter or Wind Turbine Blades Undergoing Moderate Deformation

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    A set of nonlinear equations of equilibrium for an elastic wind turbine or helicopter blades are presented. These equations are derived for the case of small strains and moderate rotations (slopes). The derivation includes several assumptions which are carefully stated. For the convenience of potential users the equations are developed with respect to two different systems of coordinates, the undeformed and the deformed coordinates of the blade. Furthermore, the loads acting on the blade are given in a general form so as to make them suitable for a variety of applications. The equations obtained in the study are compared with those obtained in previous studies

    Pension Inequality

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    Pensions may contribute to male/female or black/white inequality to the extent that white males are more likely to receive pensions than are other groups. Conditional on receiving pensions, the value of pension benefits varies because white males have the highest level of expected tenure atretirement. By using a combination of the Current Population Survey and the 1980 Banker's Trust Corpprate Pension Plan Study, we find that the existence of pension plans contributes to black/white inequality but leaves male/female inequality unchanged among whites. Even though females are less likely tor eceive pensions than males, those females who do receive pensions enjoy generous ones. Among blacks, pensions exacerbate sex differences because black women are only about 75% as likely to receive pensions as black males.

    Membrane topology of the ArsB protein, the membrane subunit of an anion-translocating ATPase

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    The ars operon of the conjugative R-factor R773 encodes an oxyanion pump that catalyzes extrusion of arsenicals from cells of Escherichia coli. The oxyanion translocation ATPase is composed of two polypeptides, the catalytic ArsA protein and the intrinsic membrane protein, ArsB. The topology of regions of the ArsB protein in the inner membrane was determined using a variety of gene fusions. Random gene fusions with lacZ and phoA were generated using transposon mutagenesis. A series of gene fusions with blaM were constructed in vitro using a beta-lactamase fusion vector. To localize individual segments of the ArsB protein, a ternary fusion method was developed, where portions of the arsB gene were inserted in-frame between the coding regions for two heterologous proteins, in this case a portion of a newly identified arsD gene and the blaM sequence encoding the mature beta-lactamase. The location of a periplasmic loop was determined from V8 protease digestion of an ArsA-ArsB chimera. From analysis of data from 26 fusions, a topological model of the ArsB protein with 12 membrane-spanning regions is proposed

    A survey of stellar X-ray flares from the XMM-Newton serendipitous source catalogue: Hipparcos-Tycho cool stars

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    The X-ray emission from flares on cool (i.e. spectral-type F-M) stars is indicative of very energetic, transient phenomena, associated with energy release via magnetic reconnection. We present a uniform, large-scale survey of X-ray flare emission. The XMM-Newton Serendipitous Source Catalogue and its associated data products provide an excellent basis for a comprehensive and sensitive survey of stellar flares - both from targeted active stars and from those observed serendipitously in the half-degree diameter field-of-view of each observation. The 2XMM Catalogue and the associated time-series (`light-curve') data products have been used as the basis for a survey of X-ray flares from cool stars in the Hipparcos Tycho-2 catalogue. In addition, we have generated and analysed spectrally-resolved (i.e. hardness-ratio), X-ray light-curves. Where available, we have compared XMM OM UV/optical data with the X-ray light-curves. Our sample contains ~130 flares with well-observed profiles; they originate from ~70 stars. The flares range in duration from ~1e3 to ~1e4 s, have peak X-ray fluxes from ~1e-13 to ~1e-11 erg/cm2/s, peak X-ray luminosities from ~1e29 to ~1e32 erg/s, and X-ray energy output from ~1e32 to ~1e35 erg. Most of the ~30 serendipitously-observed stars have little previously reported information. The hardness-ratio plots clearly illustrate the spectral (and hence inferred temperature) variations characteristic of many flares, and provide an easily accessible overview of the data. We present flare frequency distributions from both target and serendipitous observations. The latter provide an unbiased (with respect to stellar activity) study of flare energetics; in addition, they allow us to predict numbers of stellar flares that may be detected in future X-ray wide-field surveys. The serendipitous sample demonstrates the need for care when calculating flaring rates.Comment: 26 pages, 24 figures. Additional tables and figures available as 4 ancillary files. To be published in Astronomy and Astrophysic

    Imaging ionospheric inhomogeneities using spaceborne synthetic aperture radar

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    We present a technique and results of 2-D imaging of Faraday rotation and total electron content using spaceborne L band polarimetric synthetic aperture radar (PolSAR). The results are obtained by processing PolSAR data collected using the Phased Array type L-band Synthetic Aperture Radar (PALSAR) on board the Advanced Land Observation Satellite. Distinguished ionospheric inhomogeneities are captured in 2-D images from space with relatively high resolutions of hundreds of meters to a couple of kilometers in auroral-, middle-, and low-latitude regions. The observed phenomena include aurora-associated ionospheric enhancement arcs, the middle-latitude trough, traveling ionospheric disturbances, and plasma bubbles, as well as ionospheric irregularities. These demonstrate a new capability of spaceborne synthetic aperture radar that will not only provide measurements to correction of ionospheric effects in Earth science imagery but also significantly benefit ionospheric studies
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