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  • General Chemistry  (38)
  • AEROSPACE MEDICINE  (7)
  • Polymer and Materials Science  (4)
  • 78.70  (2)
  • BIOTECHNOLOGY  (2)
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  • 1
    Publikationsdatum: 2019-05-30
    Beschreibung: Astronauts with thin shielding in radiation exposure from heavy nuclei in solar particle beams
    Schlagwort(e): BIOTECHNOLOGY
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2018-12-01
    Beschreibung: Hazards to man on moon from flare-produced solar particle beams and galactic radiation, noting estimate for life shortening
    Schlagwort(e): BIOTECHNOLOGY
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2019-06-27
    Beschreibung: On the Skylab missions, Ilford G.5 and K.2 emulsions were flown as part of passive dosimeter packs carried by the astronauts on their wrists. Due to the long mission times, latent image fading and track crowing imposed limitations on a quantitative track and grain count analysis. For Skylab 2, the complete proton energy spectrum was determined within reasonable error limits. A combined mission dose equivalent of 2,490 millirems from protons, tissue stars and neutrons was measured on Skylab 2. A stationary emulsion stack, kept in a film vault drawer on the same mission, displayed a highly structured directional distribution of the fluence of low-energy protons (enders) reflecting the local shield distribution. On the 59 and 84-day mission 3 and 4, G.5 emulsions had to be cut on the microtom to 5-7 microns for microscopic examination. Even so, the short track segments in such thin layers precluded a statistically reliable grain count analysis. However, the K.2 emulsions still allowed accurate proton ender counts without special provisions.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-147436 , NAMRL-1220
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2019-06-27
    Beschreibung: Secondaries from nuclear interactions of high energy primaries in the body tissues themselves contribute substantially to the astronaut's radiation exposure in space. The so-called tissue star dose is assessed from the prong number distribution of disintegration stars in emulsion. Prong counts of 1,000 emulsion stars from the Apollo-Soyuz mission reported earlier were re-evaluated. The original scores were divided into sets of 250, 500, 750, and 1,000 emulsion stars and the respective prong number distributions established. The statistical error of the gelatin star number for the four consecutively larger was found to vary, on the 67 percent confidence level, from + or - 25 percent for the count of 250 emulsion stars to + or - 11 percent for 1,000 stars. Seen in the context of the other limitations of the experimental design, the lowest effort of prong-counting 250 stars appears entirely appropriate.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-151724
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-06-27
    Beschreibung: On the Apollo-Soyuz mission each astronaut carried one passive dosimeter containing nuclear photographic emulsions, plastic foils, TLD chips, and neutron-activation foils for recording radiation exposure. This report is limited to the presentation of data retrieved from nuclear emulsions. Protons, most of them trapped particles encountered in numerous passes through the South Atlantic Anomaly, contributed by far the largest share to the mission dose. Their linear energy transfer (LET) spectrum was established from track and grain counts in a G.5 emulsion which is used for medium and high energies, and from ender counts in a K.2 emulsion which is used for low energies. The total mission fluence of protons was found to be equivalent to a unidirectional beam of 448,500 square centimeters. The broad spectrum was broken down into small LET intervals, which allowed for the computation of absorbed doses and dose equivalents. The totals are 51 millirad and 74 millirem. Counts of disintegration stars in K.2 emulsion are incomplete at present. While a total of 467 stars were identified, counting their prong numbers is still in progress. It was concluded that the Apollo-Soyuz astronauts' radiation exposure as such did not contain anything out of the ordinary that would seem to require special attention.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-150916 , NAMRL-1228
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: Heavy nuclei of the primary galactic radiation in space can have the same linear energy transfer yet greatly different lateral distribution patterns of the energy in the microstructure of tissue. Track structure thus presents itself as a new dosimetric parameter for HZE particles which is at present incompletely understood in its radiobiological significance. The theory of track structure distinguishes two regions: core and penumbra. The core is a narrow region with a radius far below 1 micron in tissue where energy deposition occurs mainly through excitations and collective oscillations of electrons. Energy density in the core accounts for slightly more than half the total LET. The penumbra surrounding the core extends laterally several to many microns depending on the energy of the primary. Energy density in the penumbra decreases steeply with the square of increasing radius. The relationships are illustrated with nuclear emulsion micrographs and plots of energy density profiles. The implications of the findings for a dosimetric system for HZE particles are discussed.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-141935 , NAMRL-1214
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: The complexity of direct reading and passive dosimeters for monitoring radiation is studied to strike the right balance of compromise to simplify the monitoring procedure. Trapped protons, tissue disintegration stars, and neutrons are analyzed.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-140365 , NAMRL-1208
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2019-06-27
    Beschreibung: A collection of micrographs is presented taken from nuclear emulsions of personnel dosimeter packs carried by the astronauts on near-earth orbital and lunar missions. It is intended as a pictorial record and illustration of the radiation environment in space and as a supplement to earlier reports and publications of the laboratory in which the emulsion findings have been presented in detail for individual missions. A complete list of those earlier accounts precedes the picture sections.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-149446 , AD-A025970 , NAMRL-MONO-22
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-06-27
    Beschreibung: A brief review is presented of available information on the galactic neutron spectrum. An examination is made of the difficulties encountered in the determination of the dose equivalent of neutron recoil protons in the presence of a substantially larger background of trapped and star-produced protons as well as other ionizing particles in space.
    Schlagwort(e): AEROSPACE MEDICINE
    Materialart: NASA-CR-151865
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 61 (1995), S. 51-53 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 61.80 ; 78.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2–3×1018 cm−3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introducted after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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