63,809 research outputs found

    What We Learn from Quantitative Ultraviolet Spectroscopy of Naked White D warfs in Cataclysmic Variables

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    Using the Hopkins Ultraviolet Telescope and Hubble Space Telescope, observers have now obtained UV spectra with sufficient signal to noise and resolution to allow quantitative spectroscopic analyses of the WDs in several DNe. In the ``cleanest'' DNe, such as U Gem, the observations are allowing the basic physical parameters of the WD -- temperature, radius, gravity, rotation rate, and surface abundances -- to be established. A second component also exists in these systems, which may either be the disk or may be related to the WD itself. Here I summarize the current state of the observations and our understanding of the data, highlighting some of the uncertainties in the analyses as well the prospects for fundamentally advancing our understanding of DNe and WDs with future observations.Comment: 6 pages, 8 figures, to be published in the proc. for Cataclysmic Variables: A 60th Birthday Symposium in Honour of Brian Warne

    Spectroscopic analysis of radiation-generated changes in tensile properties of a polyetherimide film

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    The effects of electron radiation on Ultem, a polyetherimide were studied for doses from 2 x 10 to the 9th power to 6 x 10 to the 9th power rad. Specimens were studied for tensile property testing and for electron paramagnetic resonance and infrared spectroscopic measurements of molecular structure. A Faraday cup design and a method for remote temperature measurement were developed. The spectroscopic data show that radiation caused dehydrogenation of methyl groups, rupture of main-chain ether linkage, and opening of imide rings, all to form radicals and indicate that the so-formed atomic hydrogen attached to phenyl radicals, but not to phenoxyl radicals, which would have formed hydroxyls. The observed decays of the radiation-generated phenoxyl, gem-dimethyl, and carbonyl radicals were interpreted as a combining of the radicals to form crosslinking. This crosslinking is the probable cause of the major reduction in the elongation of the tensile specimens after irradiation. Subsequent classical solubility tests indicate that the irradiation caused massive crosslinking

    Ethnographies of the imagined, the imaginary and the critically real: Blackness, whiteness, the north of England and rugby league

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    Rugby league is part of the white, working-class (male) culture of the north of England, and is a sport that is used by its supporters to (re)produce both an imagined community of nostalgic northernness and an imaginary community of locally situated hegemonically masculine belonging. The invented traditions of its origins link the game to a white, working-class twentieth-century culture of mills, pits, terraced houses and pubs; a culture increasingly marginalised, reshaped and challenged in this century. In this paper we use two medium-term, ethnographic research projects on rugby league (one from Spracklen; the other an on-going project by Timmins) to explore northernness, blackness, whiteness and our own roles in the ethnographies as 'black' and 'white' researchers researching 'race' and identity in a community that remains (but not exclusively) a place for a working-class whiteness to be articulated. We argue that our own histories and identities are pivotal in how we are accepted as legitimate ethnographers and insiders, but those histories and identities also posea critically real challenge to us and to those in the community of rugby league with whom we interact. © 2010 Taylor & Francis

    Derivation of transformation formulas between geocentric and geodetic coordinates for nonzero altitudes

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    Four formulas, for the nonzero altitude transformation from geodetic coordinates (geodetic latitude and altitude) to geocentric coordinates (geocentric latitude and geocentric distance) and vice versa, are derived. The set of four formulas is expressed in each of the three useful forms: series expansion in powers of the earth's flattening; series expansion in powers of the earth's eccentricity; and Fourier series expansion in terms of the geodetic latitude or the geocentric latitude. The error incurred in these series expansions is of the order of one part in 3 x 10 to the 7th power

    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

    Evaluating complementary medicine: methodological challenges of randomised controlled trials

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    Complementary medicine has a different philosophy from conventional medicine, presenting challenges to research methodology. Rigorous evaluation of complementary medicine could provide much needed evidence of its effectiveness. Good design of randomised controlled trials will avoid invalid results and misrepresentation of the holistic essence of complementary medicine. Practitioners need to be recognised as a component in or contributor to complementary treatment. Both specific and non-specific outcome measures with long follow up are needed to adequately encompass the essence of complementary medicine

    Effects of various experimental parameters on errors in triangulation solution of elongated object in space

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    The effects of various experimental parameters on the displacement errors in the triangulation solution of an elongated object in space due to pointing uncertainties in the lines of sight have been determined. These parameters were the number and location of observation stations, the object's location in latitude and longitude, and the spacing of the input data points on the azimuth-elevation image traces. The displacement errors due to uncertainties in the coordinates of a moving station have been determined as functions of the number and location of the stations. The effects of incorporating the input data from additional cameras at one of the stations were also investigated
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