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  • 1985-1989  (1)
  • 1975-1979  (1)
  • 1955-1959
  • 1935-1939
  • 29.15D  (1)
  • Closure  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Measurement of laser light thomson-scattered from a cooling electron beam (1987)
    Springer
    Applied physics 44 (1987), S. 87-92 
    Details
    ISSN: 1432-0649
    Keywords: 41.80E ; 52.25 ; 29.15D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×107 cm−3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10−2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694198
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and closure mechanism of the human umbilical artery (1978)
    Springer
    European journal of pediatrics 128 (1978), S. 247-259 
    Details
    ISSN: 1432-1076
    Keywords: Umbilical artery ; Birth ; Neonatal ; Blood vessel ; Structure ; Closure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The structure of the fully-patent umbilical artery and rearrangement of its structural elements with postnatal closure were examined in 10 centimeter long umbilical cord segments which were double-clamped at different time intervals after delivery. The fully-patent umbilical artery consists of two main layers: an outer layer of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant metachromatic ground substance. No predominantly longitudinal arrangements of cells and fibers reported by earlier investigators could be identified in the inner layer. Closure of the umbilical arteries is initiated by numerous localized contractions which are mainly formed by muscle cells of the outer circular layer. Ultimate closure of larger segments of the umbilical arteries is also mainly produced by contractions of the outer layer. In contrast, the inner layer (which is rich in ground substance) seems to serve mainly as a plastic tissue which can easily be shifted in an axial direction and then folded into the narrowing lumen to complete closure. Electron microscopy reveals that the cells of this layer represent rather poorly differentiated smooth muscle cells which contain only a few tiny myofilaments and can therefore hardly contribute actively to the process of closure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00445610
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    Paper (German National Licenses)
    Fulltext
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