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  • 1
    Electronic Resource
    Electronic Resource
    Ions in holes: An experimental study of ion distributions inside surface features on radio-frequency-biased wafers in plasma etching discharges (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 716-723 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an experimental study of ion fluxes, energy distributions, and angular distributions inside surface features on radio frequency-biased wafers in high-density, inductively driven discharges in argon. Specifically, we present data on ion distributions at the bottom of 100-μm-square, 400-μm-deep "holes" in the wafer. Transmission of ions to the bottom of the holes increases with increasing ion energy and decreases as the sheath size becomes comparable to the hole size. Ion energy distributions at the bottom of the holes are narrower than distributions on the flat wafer surface. The flux of ions remains normal to the wafer surface over most of the hole area but the flux of ions within 6 μm of the wall is angled towards the wall. The observed trends are consistent with effects expected due to bowing of the plasma sheath around the surface features on the wafer. Scattering of ions off sidewalls contributes at most, only a small part of the ion flux reaching the bottom of the hole. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486054
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  • 2
    Electronic Resource
    Electronic Resource
    Characterisation of marine and lacustrine sediments in a drowned thermokarst embayment, Richards Island, Beaufort Sea, Canada (2000)
    Springer
    International journal of earth sciences 89 (2000), S. 503-521 
    Details
    ISSN: 1437-3262
    Keywords: Beaufort Sea Mackenzie Delta Thermokarst lake Embayment Arctic Cesium radiocarbon Geochemistry Permafrost Acoustic stratigraphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. A multidisciplinary study was made of lakes and lagoons in a thermokarst embayment on Richards Island, Canadian Beaufort Sea, in order to investigate the response of the Mackenzie Delta shoreline to changing hydrological influences. Seismo-acoustic profiles made from an amphibious vehicle, combined with sediment core data, show that the deepest lakes contain up to 10 m of transparent or stratified silty mud overlying the Kittigazuit sand basement. Palynological and microfossil data from 21 surface samples allow delineation of freshwater, saltmarsh, tidal flat and subtidal assemblages. These modern reference data allow distinction of freshwater and marine facies in the cores and subsequent interpretation of geochemical content (carbon, ammonia, sulphate). Radiocarbon dates and 137 Cs show that sedimentation rates have increased by an order of magnitude since drowning of the embayment during the past millennium, and that most of this sediment is from the Mackenzie River plume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310000126
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  • 3
    Electronic Resource
    Electronic Resource
    The Effect of Carbonate Soil on Transport and Dose Estimates for Long-Lived Radionuclides at a U.S. Pacific Test Site (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 243 (2000), S. 459-465 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The United States conducted a series of nuclear tests from 1946 to 1958 at Bikini, a coral atoll, in the Marshall Islands (MI). The aquatic and terrestrial environments of the atoll are still contaminated with several long-lived radionuclides that were generated during testing. The four major radionuclides found in terrestrial plants and soils are cesium-137, strontium-90, plutonium-239+240 and americium-241. Cesium-137 in the coral soils is more available for uptake by plants than 137Cs associated with continental soils of North America or Europe. Soil-to-plant 137Cs median concentration ratios (CR) (kBq·kg-1 dry weight plant/kBq·kg-1 dry weight soil) for tropical fruits and vegetables range between 0.8 and 36, much larger than the range of 0.005 to 0.5 reported for vegetation in temperate zones. Conversely, 90Sr median CRs range from 0.006 to 1.0 at the atoll versus a range from 0.02 to 3.0 for continental silica-based soils. Thus, the relative uptake of 137Cs and 90Sr by plants in carbonate soils is reversed from that observed in silica-based soils. The CRs for 239+240Pu and 241Am are very similar to those observed in continental soils. Values range from 10-6 to 10-4 for both 239+240Pu and 241Am. No significant difference is observed between the two in coral soil. The uptake of 137Cs by plants is enhanced because of the absence of mineral binding sites and the low concentration of potassium in the coral soil. Cesium-137 is bound to the organic fraction of the soil, whereas 90Sr, 239+240Pu and 241Am are primarily bound to soil particles. Assessment of plant uptake for 137Cs and 90Sr into locally grown food crops was a major contributing factor in: (1) reliably predicting the radiological dose for returning residents and (2) developing a strategy to limit the availability and uptake of 137Cs into locally grown food crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016090517426
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  • 4
    Electronic Resource
    Electronic Resource
    The Marshall Islands Radioassay Quality Assurance Program: An Overview (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 243 (2000), S. 415-422 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Lawrence Livermore National Laboratory has developed an extensive quality assurance program to provide high quality data and assessments in support of the Marshall Islands Dose Assessment and Radioecology Program. Our quality assurance objectives begin with the premise of providing integrated and cost-effective program support (to meet wide-ranging programmatic needs, scientific peer review, and build public confidence) and continue through from design and implementation of large-scale field programs, sampling and sample preparation, radiometric and chemical analyses, documentation of quality assurance/quality control practices, exposure assessments, and dose/risk assessments until publication. The basic structure of our radioassay quality assurance/quality control program can be divided into four essential elements: (1) sample and data integrity control, (2) instrument validation and calibration, (3) method performance testing, validation, development and documentation, and (4) periodic peer review and on-site assessments. While our quality assurance objectives are tailored towards a single research program and the evaluation of major exposure pathways/critical radionuclides pertinent to the Marshall Islands, we have attempted to develop quality assurance practices that are consistent with proposed criteria designed for laboratory accreditation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016022029721
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    Paper (German National Licenses)
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