In most previous 50/60-Hz experiments, subjects were placed in a dielectric cage and the electric field was applied from outside the cage. Although the field outside the cage was kept uniform in space and constant in time, the field inside the cage undergoes undesirable temporal and spatial variations. We have designed an electric-field exposure system that overcomes these problems by having a metal cage constitute a part of the field generating electrodes. The uniformity along the diameter of the cages for mice and cats are more than 84.2% and 74.3%, respectively.
In recent years, an interaction between electromagnetic environment and the living body has attracted researchers' attention. The authors have studied the effect of low‐frequency (50, 60 Hz and dc) electric field on the living body and constructed the electric field exposure system. In the conventional exposure system, animals are exposed to electric field between parallel plate electrodes in an insulated cage. However, the electric field inside the cage has not been investigated in detail. In this paper, the electric field intensity and the field uniformity inside the cage are analyzed. Based on the analysis result, a new exposure system is designed. The electric field distribution inside the cage is analyzed by the finite‐difference method. The field uniformity is more than 84%. The measured value agrees with the calculated value. The new system is simple in structure, can readily be constructed and is reliable for a long time.
The temporal variation of a static electric field inside an animal cage was investigated with a newly developed small, simple field meter. The field inside the cage was found to be highly dependent on the surface conductivity of the dielectric material. As the surface of the cage became dirty because of animal occupancy, the static electric field inside it became considerably smaller from the moment the field was turned on. Clean cages also modified the static electric field inside them, the field decaying from an initial to a much lower value over several hours. The mechanism of field attenuation for both cases is surface leakage. Surface leakage for a clean cage takes place much more slowly than for a dirty cage. This was confirmed by measuring DC insulation resistance. To examine this phenomenon further, the field in a metal cage width high electrical conductivity was measured. The static electric field inside the metal cage was also found to be reduced. An improved cage design that avoids these problems, is suggested for the study of the biologic effects of static electric fields.
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