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  • Occupational Health and Environmental Toxicology  (2)
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 13 (1992), S. 237-246 
    ISSN: 0197-8462
    Schlagwort(e): windows ; transient response ; chemical reaction model ; rate constant ; transcription ; teratogenesis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Data in the literature imply that the relationship between exposure and bio-effect involves more than a simple time integral of the field strength to which the living system has been subjected. Windows - ranges in which the system exhibits enhanced sensitivity - have been reported for power (or field strength), frequency, and the duration of the exposure. In this paper we show that such isolated window effects can be accounted for by recognizing the transient character of the response of the biological system. The principal assumption here is that the direct effect of the field is to increase the rates of production and degradation of mRNA or proteins. In this paper we review and extend the mathematical model that quantifies this. The model predicts that, for a given field strength, certain optimum relatively short duration exposures cause significantly larger bio-effects than exposure for much longer or much shorter times. The thinking embodied in the model should provide a framework for obtaining a meaningful working definition of “effective dose” and for predicting the response of subjects to environmental electromagnetic fields. It should help in deciding the relevant variables in the design and analysis of epidemiological studies. 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0197-8462
    Schlagwort(e): dosimetry ; magnetic field exposure ; induced current ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: In-vitro studies of biological effects of electromagnetic fields are often conducted with cultured cells either in suspension or grown in a monolayer. In the former case, the exposed medium can be assumed to be homogeneous; however, eventually the cells settle to the bottom of the container forming a two layer system with different dielectric and conductive properties. In the present work the effect of this separation on the electric field distribution is calculated and experimentally measured at selected positions for a commonly used exposure configuration. The settled cell suspension is modeled by a well-defined two layer system placed in a rectangular container with the base of the container parallel to the direction of the magnetic field. Theoretical calculations based on numerical techniques are done for various two layer systems with different conductivities in each layer. The agreement between the theoretical calculations and the experimental measurements is within ± 1.5 mV/m, or 10% of the maximum induced field when the conductivity of the lower layer is ten times that of the upper layer. This result is well within experimental error. When the thickness of one of the layers is small compared to the thickness of the other layer, it is found that the electric field distribution is essentially that of the homogeneous case. The latter situation corresponds to a typical cell exposure condition. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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