Yahya Akyel

Current state and implications of research on biological effects of millimeter waves: A review of the literature

In recent years, research into biological and medical effects of millimeter waves (MMW) has expanded greatly. This paper analyzes general trends in the area and briefly reviews the most significant publications, proceeding from cell-free systems, dosimetry, and spectroscopy issues through cultured cells and isolated organs to animals and humans. The studies reviewed demonstrate effects of low-intensity MMW (10 mW/cm2 and less) on cell growth and proliferation, activity of enzymes, state of cell genetic apparatus, function of excitable membranes, peripheral receptors, and other biological systems. In animals and humans, local MMW exposure stimulated tissue repair and regeneration, alleviated stress reactions, and facilitated recovery in a wide range of diseases (MMW therapy). Many reported MMW effects could not be readily explained by temperature changes during irradiation. The paper outlines some problems and uncertainties in the MMW research area, identifies tasks for future studies, and discusses possible implications for development of exposure safety criteria and guidelines.

Ultrawide-band electromagnetic pulses induced hypotension in rats

The ultrawide-band (UWB) electromagnetic pulses are used as a new modality in radar technology. Biological effects of extremely high peak E-field, fast rise time, ultrashort pulse width, and ultrawide band have not been investigated heretofore due to the lack of animal exposure facilities. A new biological effects database is needed to establish personnel protection guidelines for these new type of radiofrequency radiation. Functional indices of the cardiovascular system (heart rate, systolic, mean, and diastolic pressures) were selected to represent biological end points that may be susceptible to the UWB radiation. A noninvasive tail-cuff photoelectric sensor sphygmomanometer was used. Male Wistar-Kyoto rats were subjected to sham exposure, 0.5-kHz (93 kV/m, 180 ps rise time, 1.00 ns pulse width, whole-body averaged specific absorption rate, SAR = 70 mW/kg) or a 1-kHz (85 kV/m, 200 ps rise time, 1.03 ns pulse width, SAR = 121 mW/kg) UWB fields in a tapered parallel plate GTEM cell for 6 min. Cardiovascular functions were evaluated from 45 min to 4 weeks after exposures. Significant decrease in arterial blood pressures (hypotension) was found. In contrast, heart rate was not altered by these exposures. The UWB radiation-induced hypotension was a robust, consistent, and persistent effect.

Ultra-wide band electromagnetic radiation does not affect UV-induced recombination and mutagenesis in yeast

Cell samples of the yeast Saccharomyces cerevisiae were exposed to 100 J/m2 of 254 nm ultraviolet (UV) radiation followed by a 30 min treatment with ultra-wide band (UWB) electromagnetic pulses. The UWB pulses (101-104 kV/m, 1.0 ns width, 165 ps rise time) were applied at the repetition rates of 0 Hz (sham), 16 Hz, or 600 Hz. The effect of exposures was evaluated from the colony-forming ability of the cells on complete and selective media and the number of aberrant colonies. The experiments established no effect of UWB exposure on the UV-induced reciprocal and non-reciprocal recombination, mutagenesis, or cell survival.

Lack of Genetic Effects of Ultrawide-Band Electromagnetic Radiation in Yeast

Genetic effects of ultrawide-band (UWB) radiation pulses were studied in the D7 strain of yeast Saccharomyces cerevisiae. Yeast cells were exposed in suspension for 30 min at the UWB pulse repetition rates of 0 Hz (sham treatment), 16 Hz, and 600 Hz. Measured parameters of UWB pulses were as following: 101-104 kV/m peak voltage, 164-166 ps rise time, 1.01-1.02 ns pulse width, and 0 Hz-2 GHz spectral bandwidth. Cells were plated immediately after the exposure and incubated for 7 days at 30°C; then normal and aberrant colonies (mitotic crossovers, segregants, revertants, and convertants) were scored. The experiments established no statistically significant effect of UWB exposure on the colony-forming ability of yeast cells or the occurrence of mutations and chromosome recombinations.

Role of field intensity in the biological effectiveness of millimeter waves at a resonance frequency

Abstract The study replicated the effect of low-intensity millimeter waves (MMW) on isolated nerve function and characterized its dependence on radiation intensity. MMW exposures lasted for 23 min at 0.02, 0.1, 0.5, or 2.6 mW cm−2 (41.34 GHz) and were accompanied by a high-rate electrical stimulation of the nerve (HRS, 20 twin pulses s−1, 9 ms interpulse interval). MMW had no effect on the conditioning compound action potentials (CAPs), but significantly attenuated the HRS-caused decrease of the test CAPs. The magnitude of this effect was virtually the same (20–25%) at field intensities of 0.02, 0.1, and 2.6 mW cm−2. Irradiation at 0.5 mW cm−2m however, did not produce statistically significant changes. The results are consistent with our earlier observations of this MMW effect and provide further evidence for its nonthermal mechanism.

Frequency-Specific Effects of Millimeter-Wavelength Electromagnetic Radiation in Isolated Nerve

Effects of low-intensity millimeter waves (MMW) were studied in isolated frog nerve using a high-rate stimulation (HRS) functional test. Irradiation was performed in 3 frequency bands (41.1441.54, 45.89–45.93, and 50.8-51.0 GHz), at 5 frequencies in each band. The incident power density was 2.5 m W/cm2 for the 45.8945.93 GHz band and 10-fold less for the other two bands. Each nerve underwent a single 38-min MMW or sham exposure accompanied by an HRS train (20 paired stimuli/s for 17 min). The second stimulus in each pair was delivered during the relative refractory period, 9 ms after the first one. HRS caused a temporary and reversible decrease of the amplitude and conduction velocity of compound action potentials. MMW irradiation attenuated these changes; the MMW effect on the conduction velocity could be caused by microwave heating, while the effect on the amplitude apparently was not thermal. The amplitude changed significantly only in the test action potential (the one evoked during the refractory per...

Effect of millimeter waves on UV-induced recombination and mutagenesis in yeast

Effects of millimeter waves (MMW) on cell survival and ultraviolet-induced reciprocal and non-reciprocal recombination and mutagenesis were studied in the diploid D7 strain of the yeast Saccharomyces cerevisiae. MMW exposures lasted for 30 min (0.13 mW cm−2, 61.02–61.42 GHz) and were followed in 60 min by a 100 J m−2 dose of 254 nm ultraviolet (UV) radiation. The effect of the exposures was evaluated from the colony-forming ability of the cells on complete and selective media, and from the number of aberrant colonies formed. The MMW pretreatment did not alter cell survival or the frequency of reverse mutations. The incidence of conversions was higher in most cases in the MMW-treated cells (p < 0.05). MMW also increased the scores of crossover and colored aberrants in isolated experiments, though the average increse for all experiments (performed with different MMW frequencies) was not statistically significant. The results suggested that the MMW irradiation did not alter the UV-induced mutagenesis, but could facilitate recombinagenic processes.

Memory Consolidation In The Rat Following High-peak Power Pulsed Microwave Irradiation

Water-deprived rats were trained in a single trial to find water in one arm of a Y-maze. Immediately following training rats were either exposed to high-peak power microwave pulses (200 pulses, 80 ns width, 700 megawatts or 700 kilowatts) or returned to their cages. Reliable differences were found between groups in errors made on a 24-h retention test in the Y-maze.

Food Demand And Circadian Rhythmicity Following High-peak Power Pulsed Microwave Irradiation

Rats were either exposed to high-peak power microwave (HPPM) pulses (400 pulses, 80 ns width, 700 megawatts or 700 kilowatts) or were placed in the exposure chamber for an equivalent period of time. Immediately thereafter, the rats were placed in home cages equipped with response levers and pellet dispensers. Rats could press the lever to obtain food pellets, which were their only source of food. Each day the number of lever presses required to obtain a single food pellet (the price of food) was increased. The demand for food (consumption as a function of price) was not affected by microwave exposure, but the circadian pattern of food intake was affected.

Behavioral recovery from hyperthermia induced by high peak power microwave pulses

The aftereffects of high-power pulsed microwave radiation were studied on adult Wistar rats trained to perform a lever-pressing task to receive a food pellet. Each trained animal was exposed to a 1-MW peak-power microwave field for 10 min. Whole body dose rate levels were adjusted by using different pulse repetition rates. Only animals exposed at the highest dose level failed to respond immediately after exposure, and this was associated with elevated rectal temperatures. They started responding when their rectal temperatures dropped to pre-exposure levels. It is concluded that these behavioral aftereffects are thermal in nature.<<ETX>>