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The effect of nanosecond repetitive pulsed microwaves on the possibility of triggering a stress response of laboratory mice was investigated. The exposure was carried out every day once per a day during the 5 days' period (4000 pulses per session) with repetition rates of 8, 13, 16 and 22 pulses per second. The source of radiation was a laboratory pulse generator based on a magnetron MI-505 with a carrier frequency of 10 GHz, a pulse duration at half the power level of 100 ns, an output peak power of 180 kW, an electric field strength of 1.5 103 V/cm, a peak power density of 1.5 × 103 kW/cm2). It was found that repeated exposure alters the level of corticosterone in the blood serum. The effect depends on the frequency of repetition of microwave pulses. Possible mechanisms of the effect of radiation on the level of corticosterone are considered.

The effect of X-band HPM pulses from a SINUS-500 relativistic HPM source on Drosophila melanogaster embryos, larvae, and pupae was studied. The test objects were irradiated with 10-ns pulses during 5-min batches at a pulse rate of 3-29 p.p.s. The peak microwave power was 500 MW, the electric field in the irradiation zone was /spl sim/1.5/spl times/10/sup 4/ V/cm and the X-ray dose was 1-3 /spl mu/Rad per pulse. To understand the mechanisms of the effects and to estimate the comparative contribution of microwave and X-ray components of the SINUS-500 radiation, the objects were also exposed to (a) X-ray-free microwave pulses from a magnetron (wavelength 3 cm, pulse width 730 ns, pulse power up to 40 kW, electric field at the object /spl sim/1.5/spl times/10/sup 3/ V/cm), (b) pure X-ray pulses produced in the periodically-pulsed regime by the SINUS-500 facility where the microwave component was cut by a metal screen, and (c) continuous X-rays with nearly the same dose and exposition time (2-30 mRad during 5 min). The irradiation caused notable disturbance in the individual development of Drosophilas in the form of increased PID, teratism of imagoes, delay of imago fly etc. The strength of the effects was dependent upon the stage of development of the organism at the moment of irradiation, and the pulse repetition rate. Repeated extra exposures did not increase the effect. The pulses from the SINUS-500 facility produced a stronger effect than magnetron pulses. The strength of X-ray pulse action depended on the pulse rate while the effect from continuous X-rays was negligibly small. The paper discusses possible mechanisms of action of nanosecond HPM pulses.