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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 287-289 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflectance experiments on GaAs/Ga1−xAlxAs single quantum well structures were performed at 4.2 K, with different thicknesses of the front GaAlAs barrier layer (100–1000 A(ring)). The observed exciton reflectance line shapes depend strongly on the thickness of the front barrier layer due to the interferences between the reflected waves from the front surface and the quantum well interfaces. Calculations of the reflectance line shapes show good agreement with the observations. The absorption coefficient for the electron heavy-hole exciton transition in a single quantum well sample is determined. Our study also provides a new understanding of the line shapes measured in photoreflectance experiments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 984-986 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance experiments with magnetic fields up to 14.5 T are performed on epitaxial GaAs and GaAs/Ga1−xAlxAs quantum well samples at room temperature and 2 K. Our experiments show unique and direct evidence that photoreflectance structures are excitonic transitions in all of the above cases.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 9 (1987), S. 169-177 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract More than 2000 blood samples were collected at random from full-time middle school teachers in 9 cities of China and analyzed for lead concentration with strict quality assurance procedures. Questionnaries about the smoking habits, alcohol consumption, residence condition, and fuel used at home were filled out by each person, and information about traffic, and lead concentration in different areas of the environment was also collected as far as possible. The result showed that the geometric mean of blood lead levels of teachers in different cities was ranging between 59–82 μg l−1 among them the lowest levels were found in Nanjing and the highest in Shanghai. The difference between the lowest and the highest value was only 23 μg l−1. Comparing with the results of WHO/UNEP and CEC projects. The overall geometric average blood level in China is lower than in all the other countries except Japan. It indicates that the lead pollution in the general environment of China was not as severe as in the participating countries of WHO/UNEP and CEC projects. This may be attributed by the following factors: The less automobile triffic, the larger proportion of non-leaded gasoline used and the less canned food consumption. Factors influencing the lead levels in blood were also analyzed and the ‘normal value’ (95% upper limit) of blood lead was assessed to be 160 μg l−1.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 22 (1989), S. 131-141 
    ISSN: 0148-7280
    Keywords: acrosome reaction ; lysolecithin ; in vitro fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Four experiments were replicated 1) to establish dose-response relationships between lysophosphatidylcholine (LPC), sperm motility, and the acrosome reaction (AR), 2) to evaluate the influence of rabbit serum (RS) on these endpoints, 3) to compare buck differences in induction of the AR, and 4) to examine fertilizing ability in vitro of sperm tested under the first three objectives. Semen was collected from Dutch-belted rabbits, washed once by centrifugation, resuspended, and preincubated for 2 or 4 hr in a chemically defined medium (DM), DM plus 20% RS, or BSA-free DM plus 20% RS at 37°C. At the end of preincubation LPC was added to the preincubated sperm at concentrations of from 0 to 100 μg/ml. Sperm were examined .5-4 hr later for AR and sperm motility. For in vitro fertilization, sperm and ova were coincubated in DM up to 24 hr after insemination and in a more complex medium for another 24 hr. Addition of LPC to 4-hr-preincubated sperm was more effective for inducing the AR than addition to 2-hr-preincubated sperm. A significant increase (P 〈 .05) in the AR occurred in 15 and 30 min following exposure to 100 and 80 μg of LPC per ml, respectively, but the higher concentration of LPC decreased sperm motility. Addition of 20% RS to DM with or without BSA surprisingly inhibited the AR but maintained sperm motility, as expected. Bucks differed (P 〈 .05) in the initial percentage and the induced percentage of AR sperm. For the AR the optimal concentration of LPC per ml was 80 μg, but for in vitro fertilization 60 μg tended to be superior.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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