Thermoelastic excitation of acoustic waves in biological models exposed to high-peak-power pulsed electromagnetic radiation of extremely high frequency

We experimentally demonstrated for the first time that high-peak-power pulsed electromagnetic radiation of extremely high frequency (35.27 GHz; pulse widths, 100 and 600 ns; peak power, 20 kW) is capable of thermoelastic excitation of acoustic waves in model water-containing objects and muscle tissue of animals. The amplitude and duration of excited acoustic pulses are within the limits of accuracy of theoretical estimates and are a complex nonlinear function of electromagnetic energy input. The propagation velocities of acoustic pulses in water-gelatin models and isolated muscle tissue of animals are close to reference data. The excitation of acoustic waves in biological systems exposed to high-peak-power pulsed microwaves is an important phenomenon that makes an essential contribution to understanding the mechanisms of biological effects in these electromagnetic fields.     

Dependence of anti-inflammatory effects of high peak-power pulsed electromagnetic radiation of extremely high frequency on exposure parameters

A pronounced anti-inflammatory effect of high peak-power pulsed electromagnetic radiation of extremely high frequency was shown for the first time in a model of zymosan-induced footpad edema in mice. Exposure to radiation of specific parameters (35, 27 GHz, peak power 20 kW, pulse widths 400-600 ns, pulse repetition frequency 5-500 Hz) decreased the exudative edema and local hyperthermia by 20% compared to the control. The kinetics and the magnitude of the anti-inflammatory effect were comparable with those induced by sodium diclofenac at a dose of 3 mg/kg. It was found that the anti-inflammatory effect linearly increased with increasing pulse width at a fixed pulse repetition frequency and had threshold dependence on the average incident power density of the radiation at a fixed pulse width. When animals were whole-body exposed in the far-field zone of radiator, the optimal exposure duration was 20 min. Increasing the average incident power density upon local exposure of the inflamed paw accelerated both the development of the anti-inflammatory effect and the reactivation time. The results obtained will undoubtedly be of great importance in the hygienic standardization of pulsed electromagnetic radiation and in further studies of the mechanisms of its biological action.     

The study of the mechanisms of formation of reactive oxygen species in aqueous solutions on exposure to high peak-power pulsed electromagnetic radiation of extremely high frequencies

Using the method of enhanced chemiluminescence in a peroxidase-luminol-p-iodophenol system, we found the formation of reactive oxygen species (in equivalent of hydrogen peroxide concentration) in 1 mM phosphate buffer under the exposure to high peak-power pulsed electromagnetic radiation of extremely high frequencies (37 GHz, peak power 20 kW, pulse width 400 ns, repetition rate 500 Hz). The results obtained show that the formation of hydrogen peroxide in aqueous solutions under the action of electromagnetic radiation is the result of the summary influence of heat and thermoacoustic waves excited in the solutions.     

Lack of behavioral effects in the rhesus monkey: high peak microwave pulses at 1.3 GHz

The current safety standards for radiofrequency and microwave exposure do not limit the peak power of microwave pulses for general or occupational exposures. While some biological effects, primarily the auditory effect, depend on pulsed microwaves, hazards associated with very high peak-power microwave pulses in the absence of whole-body heating are unknown. Five rhesus monkeys, Macaca mulatta, were exposed to peak-power densities of 131.8 W/cm2 (RMS) while performing a time-related behavioral task. The task was composed of a multiple schedule of reinforcement consisting of three distinct behavioral components: inter-response time, time discrimination, and fixed interval. Trained monkeys performed the multiple schedule during exposure to 1.3-GHz pulses at low pulse-repetition rates (2-32 Hz). No significant change was observed in any behavior during irradiation as compared to sham-irradiation sessions. Generalization of these findings to experimental results with higher peak-power densities, other pulse rates, different carrier frequencies, or other behaviors is limited.     

Control of Ehrlich Tumor Growth by Electromagnetic Waves at Resonance Frequency (In Vivo Studies)

In this work, we confirmed our previously published value for the inhibiting resonance frequency (4.5 Hz) of electromagnetic radiation for solid tumor implanted in mice. The inhibiting electromagnetic waves penetrated deeply into the tumor tissue using amplitude modulated waves (AMW). Sixty female Balb/c mice carrying Ehrlich tumor in the thigh were divided into three equal groups. Group A was the control while Groups B and C were both exposed to 4.5 Hz square amplitude modulated waves (QAMW) for 10h (hrs) starting day 10 and day 16 post tumor implantation respectively. Tumor size, telomerase enzyme activity, histopathological examination, and dielectric relaxation of the tumor tissue were used to investigate the tumor activity of the treated and untreated groups of animals. The results indicated that irradiating the tumor tissue with 4.5 Hz QAMW for a period of 10h inhibited tumor growth. Early treatment of the tumor by extremely low frequency electromagnetic field (ELF-EMF) gave better results than delayed treatments.     

The influence of electromagnetic radiation of extremely high frequencies on the pro- and antioxidant status of blood in experiments

The influence of electromagnetic radiation of extremely high frequencies in the noise mode on the level of the activity of proand antioxidant systems in a model of skin-flap ischemia was studied in vivo. Rats of the Wistar line were used in this work. The cutaneous reflex projection field of the animals was exposed once a day for 7 days in the post-operative period to electromagnetic radiation of an extremely high frequency in the range from 53.57 to 78.33 GHz with a dose of 1.2 mJ in the noise mode. The dynamics of proand antioxidant protection were compared to those of intact animals that were not irradiated. Using data on induced biochemiluminescence and estimation of malondialdehyde activity it was shown that irradiation in a course mode contributed to a decrease in the intensity of lipid peroxidation. In parallel we observed an increase in the total antioxidant reserves of blood and the activity of bioradical protection enzymes. Our findings suggest that electromagnetic radiation at extremely high frequencies in a noise mode has a regulatory impact on the state of proand antioxidant systems of the body; this can be used for the correction of postoperative ischemic disorders and the restoration of disturbed homeostasis.     

Effect of pulsed CO2-laser irradiation on bone tissue

Different dynamic effects on biological tissue caused by pulsed laser radiation are described. It is shown that the parameters of these effects which take place on the bone tissue affected by pulsed CO2-laser radiation are directly dependent on the parameters of these pulses and may be predicted for any concrete application.     

Transmission of time varying magnetic field through body tissue

Based on the principles of interaction of electromagnetic waves with semi-infinite media, a simplified model is developed for the study of biological tissue — EM wave interaction problems. The four common types of biological tissues viz, bone, blood, alveolar and muscle tissue, each in turn has been considered. Expression for the transmission loss of the incident EM waves have been derived and numerically evaluated. The results indicate that there is a frequency dependence of the transmission loss and variations with tissue type exist and that losses become significant above 30 MHz. Attenuation for muscular tissue is maximum at frequencies of about 200 MHz whereas the corresponding frequency for lung tissue is nearly the double. Suitable experiments have been designed and performed to verify the salient results of the model and a fair degree of agreement has been found between the experimental results and theoretical predictions. Possibilities for the improvement of the model and future applications of the model have been outlined.     

Design of compact electromagnetic impulse radiating antenna for melanoma treatment

ABSTRACT

Cancer therapy is one of the several new applications which use nanosecond and subnanosecond high voltage pulses. New treatment based on electromagnetic (EM) fields have been developed as non-surgical and minimally invasive treatments of tumors. In particular, subnanosecond pulses can introduce important non-thermal changes in cell biology, especially the permeabilization of the cell membrane. The motivation behind this work is to launch intense subnanosecond pulses to the target (tumors) non-invasively. This works focuses on the design of a compact intense pulsed EM radiating antenna. In tense EM waves radiated at the first focal point of the Prolate Spheroidal Reflector (PSR) are focused at the second focal point where the target (tumor) is present. Two antennas with PSR but fed with different compact wave radiator are designed to focus pulsed field at the second focal point. The PSR with modified bicone antenna feed and PSR with elliptically tapered horn antenna feed are designed. The design parameters and radiation performance are discussed.     

Microwave-induced thermoelastic pressure wave propagation in the cat brain

This paper presents direct measurements of acoustic pressure wave propagation in cat brains irradiated with pulsed 2.45-GHz microwaves. Short rectangular microwave pulses (2 microseconds, 15 kW peak power) were applied singly through a direct-contact applicator located at the occipital pole of a cat's head. Acoustic pressure waves were detected by using a small hydrophone transducer, which was inserted stereotaxically into the brain of an anesthetized animal through a matrix of holes drilled on the skull. The measurements clearly indicate that pulsed microwaves induce acoustic pressure waves which propagate with an acoustic wave velocity of 1523 m/s.     

Indirect and repeated electromagnetic irradiation of extremely high freguency of bacteria Escherichia coli

It has been shown that separate irradiation of distilled water and tris-phosphate buffer containing some inorganic ions, with Escherichia coli K12 grown in anaerobic conditions upon fermentation of sugar (glucose) with "noise" electromagnetic radiation of extremely high frequencies (53.5-68 gHz) or millimeter waves (wavelength of 3 to 8 mm) with low flux capacity (0.01 mW) for 10, 30 and 60 min caused opposite effects, changing the growth of these bacteria. The irradiation of water has a bactericide effect, whereas the irradiation of the buffer stimulates bacterial growth although the buffer itself inhibits the growth. These results point out the role of water in the bactericide action of "noise" electromagnetic radiation of extremely high frequencies, and confirm the significance of membranotropic effects. The bactericide action disappeared after repeated irradiation for 10 and 30 min with 2-h intervals. This indicates the operation of some compensatory mechanisms in bacteria.     

Radiological workers sensitivity to 50 Hz pulsed magnetic fields: preliminary results

In the present study the effect of extremely low frequency pulsed magnetic fields (PMF) was evaluated in lymphocyte cultures from 12 subjects occupationally exposed to low doses of ionising radiations. The PMF signal characteristics were repetition frequency 50 Hz, triangular shape, rise time about 1.2 ms and peak intensity 2.5 mT. The cytokinesis-block technique was employed to evaluate genotoxicity and cytotoxicity in terms of micronucleus frequency and cell proliferation, respectively. When PMF-exposed cultures were compared with their respective controls, a slight but statistically significant increase was detected in both the biological parameters investigated ( p<0.05). The results obtained suggest a possible role of specific employments involving exposure to ionising radiation, in the risk associated with electromagnetic field exposure.     

A study of absorption of energy of the extremely high frequency electromagnetic radiation in the rat skin by various dosimetric methods and approaches

Using experimental and theoretical methods of dosimetry, the energy absorption of extremely high-frequency electromagnetic radiation (EHF EMR) in the skin of laboratory rats was analyzed. Specific absorption rate (SAR) in the skin was determined on the basis of both microthermometric measurements of initial rates of temperature rise in rat skin induced by the exposure and microcalorimetric measurements of specific heat of the skin. Theoretical calculations of SAR in the skin were performed with consideration for dielectric parameters of rat skin obtained from the measurements of the standing wave ratio upon reflection of electromagnetic waves from the skin surface and for the effective area of stationary overheating measured by infrared thermography. A numerical method was developed to determine electromagnetic wave energy reflected, absorbed, and transmitted in the model of flat layers. The algorithm of the method was realized in a computer program and used to calculate SAR in the skin on the basis of the complex dielectric constant of rat skin. The SAR values obtained from experimental measurements, theoretical calculations and numerical analysis are in good mutual correspondence and make about 220-280 W/kg at a frequency of 42.25 GHz and a power of 20 mW at the radiator output. The results obtained can be used for dosimetric supply of biomedical experiments on studying the physicochemical mechanisms of the biological effects of EHF EMR.     

The effect of low-intensity coherent extremely high frequency electromagnetic radiation on growth parameters for <Emphasis Type="Italic">Enterococcus hirae</Emphasis> bacteria

It is found that for Enterococcus hirae ATCC9790 bacteria grown in anaerobic conditions, one-hour exposure to low-intensity (radiant power of 0.06 mW/cm²) coherent extremely high frequency electromagnetic radiation (from 45 to 53 GHz), or millimeter electromagnetic radiation, leads to an appreciable increase in latent growth time and to a decrease in specific growth rate; herein, the effects intensify as the frequency increases from 49 to 53 GHz. The result is enhanced at an increase in the radiation duration from 30 min to 1 h; however, a further increase in the exposure time up to 2 h does not lead to intensification of the effect. It is shown that the effect of extremely high frequency electromagnetic radiation on Enterococcus hirae does not depend on pH of the medium (pH 6.0 or 8.0). It may be expected that these bacteria have protective or reparation mechanisms that compensate long-term action of this radiation; it is not improbable that various mechanisms of pH regulation are present as well.     

Emission of low-frequency electromagnetic waves by a short laser pulse propagating in a plasma with density fluctuations

It is shown that a short laser pulse propagating in a plasma with electron density fluctuations can emit electromagnetic waves with frequencies much lower than the laser carrier frequency. Emissions with frequencies close to the plasma frequency and the doubled plasma frequency in a nonisothermal plasma, as well as emission generated in a turbulent plasma, are examined. The effects in question are related to the transformation of the laser pulse wakefield into electromagnetic radiation by electron density fluctuations. The phenomenon under study opens new possibilities for diagnostics of both plasma fields excited by laser pulses and electron density fluctuations in a plasma.     

Effects of EHF radiation and cytoactive substances on fertilization and early embryonic development of the sea urchin Strongylocentrotus intermedius

This study examines the influence of extremely high frequency (EHF) electromagnetic radiation (42.2 GHz, 100 μW/cm², impulse modulation 1000 Hz) on the gametes and embryos of the sea urchin Strongylocentrotus intermedius. Preliminary radiation treatment reduces the number of fertilized egg cells and the survival rate of embryos at early stages of development up to the pluteus. Methyluracil reduces the degree of expression of biological effects of EHF radiation.     

Possible mechanism of specific action of pulsed UHF-fields

Experimental data were obtained for conditions of stimulation of mechanical vibrations in the liquid models of microwave fields. Possible role of different elastic waves modes in the formation of specific effects in pulsed HF-fields is discussed. Mathematical estimation suggests that excited shearing waves may have biological action. The results obtained suggest an acoustic nature of the action of pulsed HF-fields on biological objects.     

Membranotropic effects of electromagnetic radiation of extremely high frequency on Escherichia coli

It was found that "sound" electromagnetic radiations of extremely high frequencies (53.5-68 GHz) or millimeter waves (wavelength range of 4.2-5.6 mm) of low intensity (power density 0.01 mW) have a bactericidal effect on Escherichia coli bacteria. It was shown that exposure to irradiation of extremely high frequencies increases the electrokinetic potential and surface change density of bacteria and decreases of membrane potential. The total secretion of hydrogen ions was suppressed, the H+ flux from the cytoplasm to medium decreased, and the flux of N,N'-dicyclohexylcarbodiimide-sensitive potassium ions increased, which was accompanied by changes in the stoichiometry of these fluxes and an increase in the sensitivity of H+ ions to N,N'-dicyclohexylcarbodiimide. The effects depended on duration of exposure: as the time of exposure increased, the bactericidal effect increased, whereas the membranotropic effects decreased. The effects also depended on growth phase of bacteria: the irradiation affected the cells in the stationary but not in the logarithmic phase. It is assumed that the H(+)-ATPase complex F0F1 is involved in membranotropic effects of electromagnetic radiation of extremely high frequencies. Presumably, there are some compensatory mechanisms that eliminate the membranotropic effects.     

Resonance Absorption of a Train of Ultrawideband Electromagnetic Pulses in the Ionosphere

The problem of collisionless absorption of ultrawideband electromagnetic pulses in the ionosphere is studied analytically. It is shown that absorption has a resonance character if the repetition rate of a train of pulses is equal to the frequency of the excited plasma waves.