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  • 1
    Electronic Resource
    Electronic Resource
    In vivo and in vitro dielectric properties of animal tissues at radio frequencies (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 3 (1982), S. 421-432 
    Details
    ISSN: 0197-8462
    Keywords: dielectric properties ; radio frequencles ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: An open-ended coaxial line and an improved measurement method employing a computer controlled network analyzer were used to measure the permittivity of cat tissues. Muscle, spleen, kidney cortex, liver,and brain cortex were measured in vivo and in vitro at frequencies between 100 MHz and 8 GHz. The differences between the permittivities of these cat tissues, in the aforementioned range of frequencies, when measured in vivo and a few (up to four) hours after death, were found to be within the experimental uncertainty.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250030405
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    Paper (German National Licenses)
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  • 2
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    Far-ultraviolet photometry of the globular cluster omega Cen (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We present far-ultraviolet images of the globular cluster omega Centauri obtained with the Ultraviolet Imaging Telescope (UIT) during the 1990 December Astro-1 mission. A total of 1957 sources are detected at 1620 A to a limiting ultraviolet (UV) magnitude of 16.4 in the central 24 min diameter region of the field and a limit of 15.6 over the remainder of the 40 min diameter field. Over 1400 of these sources are matched with stars on a Stroemgren u band charge coupled devices (CCD) frame obtained with the Cerro Tololo Inter-American Observatory (CTIO) 0.9 m telescope to produce a (far-UV, u) color-magnitude diagram (CMD). Completeness of the sample and error estimates are determined by photometry of artificial stars added to the images. The horizontal branch (HB) of the CMD is heavily populated hotter than 9000 K. A large number of 'extreme HB' stars are found hotter than a conspicuous break in the HB at T(sub e) approximately 16000 K. There is also a significant population of stars above the HB, the brightest of which is 4 mag brighter than the HB. Most of the hotter of these appear to be 'AGB-manque' or 'Post-Early Asymptotic Giant Branch' stars. We compare the observations to recent theoretical evolutionary tracks for the zero-age HB and subsequent phases. The tracks match the data well, with the exception of the hotter HB stars, many of which fall below the zero-age horizontal branch. It is unclear as yet whether these are a special population or an artifact of errors in the models or photometry. We identify 33 stars with T(sub e) greater than or approximately = 50000 K, which are hotter than zero-age HB stars with envelope masses of 0.003 solar mass.
    Keywords: ASTRONOMY
    Type: The Astronomical Journal (ISSN 0004-6256); 108; 4; p. 1350-1363
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  • 3
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    Ultraviolet Imaging Telescope observations of the ScI galaxy NGC 628 (M74) (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Ultraviolet images of NGC 628 at 1520 and 2490 A show that the nucleus has an oblong appearance and that the arms and disk exhibit features not seen in blue or H-alpha images. Aperture photometry of the nucleus gives results that are compatible with observations in other bandpasses and with models. The spiral arms appear more symmetrical in the UV than in other colors; in particular, two gaps are seen on either side of the nucleus. Combined UV and radio data appear to support a large-scale collective phenomenon, perhaps a quasi-static spiral structure mechanism, as being the dominant mode of spiral formation in this galaxy. We report the detection of a low surface brightness object at a distance of 7.6 arcmin southwest of the nucleus.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 395; 1; p. L41-L43.
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  • 4
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    Ultraviolet imaging telescope and optical emission-line observations of H II regions in M81 (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Images of the type Sab spiral galaxy M81 were obtained in far-UV and near-UV bands by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission of 1990 December. Magnitudes in the two UV bands are determined for 52 H II regions from the catalog of Petit, Sivan, & Karachentsev (1988). Fluxes of the H-alpha and H-beta emission lines are determined from CCD images. Extinctions for the brightest H II regions are determined from observed Balmer decrements. Fainter H II regions are assigned the average of published radio-H-alpha extinctions for several bright H II regions. The radiative transfer models of Witt, Thronson, & Capuano (1992) are shown to predict a relationship between Balmer Decrement and H-alpha extinction consistent with observed line and radio fluxes for the brightest 7 H II regions and are used to estimate the UV extinction. Ratios of Lyman continuum with ratios predicted by model spectra computed for initial mass function (IMF) slope equal to -1.0 and stellar masses ranging from 5 to 120 solar mass. Ages and masses are estimated by comparing the H-alpha and far-UV fluxes and their ratio with the models. The total of the estimated stellar masses for the 52 H II regions is 1.4 x 10(exp 5) solar mass. The star-formation rate inferred for M81 from the observed UV and H-alpha fluxes is low for a spiral galaxy at approximately 0.13 solar mass/yr, but consistent with the low star-formation rates obtained by Kennicutt (1983) and Caldwell et al. (1991) for early-type spirals.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 438; 1; p. 181-187
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  • 5
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    Ultraviolet Imaging Telescope photometry of massive stars - The OB association NGC 206 in M31 (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: The Ultraviolet Imaging Telescope (UIT) obtained UV images of the giant M31 OB association NGC 206. Magnitudes in bands at 1520 and 2490 A were obtained for 30 massive stars, which demonstrate the effectiveness of UIT for photometry of moderately crowded hot stars to V about 21. The UV colors and magnitudes observed for stars in NGC 206 place them in the region of the color magnitude diagram occupied by evolutionary models for 30-60 solar mass stars, after correcting for extinction. The brighter stars are systematically redder than the fainter stars, indicating that they are supergiants of age about 4 Myr, while the fainter, bluer stars are nearer age zero. The relative numbers of probable supergiants measured by us and the number of probable main-sequence O stars measured from optical images are in agreement with the relative lifetimes. Calculated UIT colors are presented for a library of standard star spectra constructed from IUE and ground-based observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 395; 1; p. L33-L35.
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  • 6
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    Observations of the light echoes from SN 1987A using the Astro-1 Ultraviolet Imaging Telescope (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: We present the results from images taken from the region of the light echoes around SN 1987A, as acquired on the first flight of the Astro-1 Ultraviolet Imaging Telescope (UIT). They indicate a weighted-average UV echo surface brightness of about 3 x 10 exp -18 ergs/s sq cm A sq arcsec. This is consistent with earlier results obtained by the IUE when scaled by the optical surface brightness of the two different echoes observed. These results indicate that the UV flux emitted by shock from core collapse penetrating the stellar surface cannot be as strong as that predicted by a large class of theoretical models (cited herein), or that previous results on the optical scattering of echoing dust do not apply to these clouds. Prospects for a more accurate measurements once the echoes have propagated to other regions and a background measurements can be obtained with UIT are discussed. They indicate that a more accurate determination of the above results is probable with another epoch of UIT observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 395; 1; p. L25-L27.
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