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  • 1
    Electronic Resource
    Electronic Resource
    White-light and radio sounding observations of coronal transients (1985)
    Springer
    Solar physics 98 (1985), S. 341-368 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A concerted search for coronal transients was conducted with the ‘Solwind’ coronagraph during the solar occultations of the two Helios spacecraft in October/November 1979. The polarization angle and bandwidth of the linearly polarized S-band downlink signal were monitored at the three 64-m tracking stations of the NASA Deep Space Network to determine coronal Faraday rotation and spectral broadening. A one-to-one correspondence could be established between abrupt disturbances in the two signal parameters and the passage of a white-light transient through the signal ray path from spacecraft to Earth. The white-light morphology and the additional information provided by the radio sounding coverage are presented for each of the five distinct events recorded. Although no specific example could be observed in sufficient detail in both white light and Faraday rotation to derive the small-scale magnetic structure, some qualitative descriptions of the orientation and rough estimates of the magnitude of the transient magnetic field could be made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152465
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  • 2
    Electronic Resource
    Electronic Resource
    Inter- and intraspecific variation in gorgonian colony morphology: quantifying branching patterns in arborescent animals (1988)
    Springer
    Coral reefs 7 (1988), S. 139-143 
    Details
    ISSN: 1432-0975
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Geomorphological methods for quantifying branching networks are used to describe inter- and intra-specific differences in branching patterns among two species of arborescent Caribbean gorgonian, Plexaura homomalla, P. flexuosa, and a third, undescribed plexaurid from the San Blas Islands, Panama. There were significant differences among species for first, second and third order branch lengths, and for tributary to source ratios for first and second order branches. Extrapolations from the branching parameters successfully predicted differences in the branch structure of naturally generated colony fragments. Within P. homomalla, significant differences with depth in the lengths and tributary to source ratios of first, second, and third order branches provide a measure of the greater bushiness of shallow water colonies. These measures can be used to quantify morphological differences in both ecological and systematic analyses. Data on the branching characters of these three gorgonian species demonstrate that gross colony form can be studied as a quantifiable component of phenotype and that gorgonians display both species level and ecophenotypic variation in colony form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300973
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  • 3
    Electronic Resource
    Electronic Resource
    Diel variation in the abundance of epifauna associated with seagrasses of the Indian River, Florida, USA (1987)
    Springer
    Marine biology 96 (1987), S. 137-142 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Day-night comparisons of the motile epifauna in the canopy of seagrass beds in the Indian River lagoon, Florida revealed that abundances were not stable over the diel period. Collections were made between February and June, 1982. Higher densities of epifauna occurred on seagrasses at night. For both of the numerically-dominant gastropod and crustacean groups, four of the five top ranked species followed this diel pattern. Crustaceans showed particularly large changes in abundance, averaging a twofold increase in nocturnal samples. Faunal similarity between day and night collections remained high, however, indicating that community structure was preserved during diel abundance changes. Equating epifauna collected from seagrass blades with those associated with the seagrass habitat in general therefore may be erroneous, particularly if collections are made during daylight. Changes in prey availability due to the diel pattern are likely to extend to important community trophic functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394847
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  • 4
    Electronic Resource
    Electronic Resource
    Prostaglandin synthetase inhibitors in insect defensive secretions (1986)
    Springer
    Naturwissenschaften 73 (1986), S. 735-737 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399245
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  • 5
    Electronic Resource
    Electronic Resource
    The frequency of long-duration solar X-ray events (1985)
    Springer
    Solar physics 97 (1985), S. 375-379 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that the long-duration X-ray events tend to ignore the sunspot cycle. This is particularly true for events with durations of 6 hr or more.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165996
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  • 6
    Electronic Resource
    Electronic Resource
    Large-scale structure of the sun's corona from radio observations using the Clark Lake Radioheliograph (1987)
    Springer
    Solar physics 108 (1987), S. 113-129 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present meterwave maps of the solar corona made with the Clark Lake Radioheliograph at 30.9, 50, and 73.8 MHz for one solar rotation. We compare and contrast them with optical data: 10830 Å maps, white-light coronagraph images (SOLWIND and Mauna Loa K coronameter) and forbidden line scans. Most of the sources in the radio maps persist for two days or more, and appear to rotate approximately with the solar rate. A coronal hole seen against the disk at all three frequencies shows interesting similarities and significant differences with the optical signatures of the hole. Elongated features of the 50 MHz corona correspond rather well to the azimuthal position of white light streamers seen in SOLWIND images. Synoptic charts made from the radio maps show overall similarities to synoptic charts constructed from (limb) coronagraph data. Some of the differences may result from the different weightings given by the radio and optical data to density and temperature, or by the different sensitivities to non-radial geometries. We show that the combined use of meter wave and optical images provide considerable new insights into the three-dimensional structure of the low to middle corona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152081
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  • 7
    Electronic Resource
    Electronic Resource
    Properties of metre-wavelength solar bursts associated with coronal mass ejections (1986)
    Springer
    Solar physics 105 (1986), S. 149-171 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An investigation is made to determine the relationship between a coronal mass ejection (CME) and the characteristics of associated metre-wave activity. It is found that (1) the CME width and leading edge velocity can be highly influential in determining the intensity, spectral complexity and frequency coverage of both type II and continuum bursts; (2) the presence of a CME is possibly a necessary condition for the production of a metric continuum event and (3) metric continuum bursts as well as intense, complex type II events are preferentially associated with strong, long lasting soft X-ray events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156384
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  • 8
    Electronic Resource
    Electronic Resource
    Range and accuracy in backscatter measurements (1986)
    Springer
    Optical and quantum electronics 18 (1986), S. 291-308 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The relationship between measurement accuracy and signal-to-noise ratio for attenuation, joint loss, link loss and fault location measurements is established for both coherent and incoherent OTDRs. For each parameter, range is defined as the maximum distance over which a minimum acceptable measurement accuracy, or corresponding minimum acceptable signal-to-noise ratio, is attained. Range, defined in this way, serves as a basis for the comparison of different OTDRs. Results are presented which verify the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02029874
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  • 9
    Electronic Resource
    Electronic Resource
    On the noise of high-transimpedance amplifiers for long-wavelength pulse OTDRs (1987)
    Springer
    Optical and quantum electronics 19 (1987), S. 123-129 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Noise measurements on high-transimpedance amplifiers suitable for long-wavelength OTDRs give results higher than is predicted by normal noise models. Consequently, we have developed two useful techniques to measure independently the noise contribution of the JFET and the feedback resistor to the overall amplifier noise. p ]Our results show that the noise of the JFET is in accordance with an accurate theoretical model for such a device. In contrast, the noise from the feedback resistor is much higher than is predicted from the normal resistance-capacitance model for such a component. This increase results from the distributed nature of high-ohmic resistors. Our results indicate that both choice of resistor manufacturer and individual selection of a resistor from a specific manufacturer are warranted. By selecting a low-noise resistor we demonstrate a 500-MΩ transimpedance amplifier with an input equivalent noise current of 13.8 pA. In comparison, the same amplifier with a noisy resistor had an input equivalent noise current of 23 pA. p ]We use our results to show that a reasonable value of the input equivalent noise current of a low-noise photodiode-amplifier combination is 20 pA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02029880
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  • 10
    Electronic Resource
    Electronic Resource
    Statistics of coherently detected backscatter and range performance of coherent OTDRs (1987)
    Springer
    Optical and quantum electronics 19 (1987), S. 145-168 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We derive the statistics of a coherently detected backscatter waveform taking into account the effects of polarization. For the first time these statistics are related to measurable parameters. We show that for long-range OTDRs the effects of polarization are statistically small. In relation to the demodulation process we used our statistical model to show that for long-range operation and with heterodyne detection all types of demodulation provide similar performance. With homodyne detection half-wave demodulation results in a 7 dB lower signal-to-noise ratio than the other types of demodulation which have similar performance. There is the usual 3 dB advantage of homodyne over heterodyne detection. Our results indicate that with the same launched powers, the signal obtained from a coherent OTDR can have up to a 37 dB better signal-to-noise ratio than one obtained from an incoherent pulse OTDR. This results in a 9 dB range advantage. We verify previously tabulated results which we found apply only for short-range operation. We use our model to predict the limits of long-range performance and to predict the effect of speckle on averaging. Finally, we explain the breakpoint behaviour that can be seen in results already reported and which is characteristic of linear full- or half-wave envelope demodulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02030651
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