Unknown authors
Researchers measured amplitude-modulated leakage waveforms from 2450 MHz and 915 MHz microwave ovens using a miniature 3-D probe with microwave-diode detector chips. The ovens were made to leak radiation by inserting teflon strips between door seals, and detected envelopes were recorded on analog tape, played back faster, and plotted on an XY recorder. Both ovens' leakage radiation was essentially 100% modulated with large fluctuations. Both modulation spectra contained frequencies within the 3-30 Hz range where biological effects of modulated RF radiation have been reported.
Habib Massoudi, Carl H. Durney, Curtis C. Johnson
Joseph M. Lary, David L. Conover, William E. Murray
The authors reviewed and critically evaluated the radiofrequency biological effects literature through 1982. The review indicated that there appears to be a threshold for adverse biological effects in animals at a specific absorption rate of about 2 W/kg. At SARs between 1.8 and 4.5 W/kg, adverse effects included death, temperature increases exceeding 3%, hemorrhagic lesions, staggering and spasms in chicks, and extreme agitation in dogs. At SARs below 1.8 W/kg no clearly adverse effects were reported, but measurable temperature increases and physiological changes occurred in the 0.17 to 1.8 W/kg range. At SARs below 0.17 W/kg no temperature increases were reported and most effects involved calcium efflux or blood-brain barrier permeability.
Unknown authors
The notice describes a possible radio frequency interference problem where oven leakage fields enter the readout box and may cause erroneous readings. Users should keep the readout box as far from the microwave oven and its leakage fields as possible by keeping the cable extended. Calibration is generally needed only once a year, not every six months, unless probe damage or instrument defect is suspected.
Edward H. Grant, Susan E. Keefe, Shin Takashima
The study investigated the dielectric behavior of bovine serum albumin. Measurements were made from 200 MHz to 10,000 MHz at pH values 3.5, 4.5, 7.0, and 8.5 and concentrations ranging from 0.78 to 21%. A dielectric mixture theory was used to estimate the amount of bound water as a function of concentration and pH.
Unknown authors
Researchers performed transient thermographic measurements on a full-size human head phantom filled with muscle-equivalent material, irradiated by a quarter-wave monopole antenna excited at 100 watts and 456.65 MHz. The maximum specific absorption rate (SAR) occurred when the antenna tip was at the bridge or tip of the nose, while a flat surface like the forehead reduced peak SAR to about one-third of the maximum. Thermal diffusion corrections applied to data at one-inch antenna-to-model spacing yielded a peak SAR of about 200 W/kg in a small superficial region at the bridge of the nose.
Sol M. Michaelson, Herman P. Schwan
A. R. Hart, D. W. McQuitty, N. K. Wagner
Unknown authors
The researchers are developing a magnetic induction system to produce localized hyperthermia in intracranial tumors. Differential heating is achieved using small ferromagnetic seeds that can be stereotactically embedded in residual tumor during craniotomy. In phantom tests, Trial 16 showed a temperature differential greater than 4°C out to 1 cm from the implant site with no significant direct heating of the phantom by the RF field. Heating patterns in single seed phantoms matched the theoretically expected inverse radial distance dependence.
Unknown authors
Unknown authors
Researchers exposed 20 time-bred rats to 100-MHz RF at 500 W forward power (50 mW/cm²) starting on day 6 of pregnancy for 4 hours per day, 7 days per week. The mean specific absorption rate for rats was 2.8 mW/g. No differences were found in growth, neurological development, locomotor activity, hematology, immune function, or mutagenicity between exposed and sham-exposed rats. However, significant changes in regional brain acetylcholinesterase activities were observed in chronically exposed rats.
Unknown authors
Researchers measured whole-body specific absorption rates in single mice and rats exposed to 2450 MHz, 425 MHz, or 100 MHz radiation using twin-well calorimetry. Exposures were performed in three orientations relative to the fields and for three animal weight ranges per species. The 2450 MHz exposures were conducted in an anechoic chamber in the far field, while 425 MHz and 100 MHz exposures used TEM transmission lines (Crawford cells). Measured SAR values were in reasonable agreement with the Radiofrequency Radiation Dosimetry Handbook values but tended to be greater by a factor of 2 and as high as a factor of 4.
R. A. Tell, F. Harlen
The authors used dosimetric and thermoregulatory data to develop a rationale for thermally based RF exposure safety standards limiting both core and local tissue temperature rise to 1°C. They found that if local tissue temperature rise is limited to 1°C, the rectal temperature rise is automatically limited to 0.05°C. The permissible exposure levels are frequency dependent with a minimum of 1.6 mW/cm² in the body resonance region (30-300 MHz) and 10 mW/cm² for frequencies above 2 GHz. Data show these limits need not be modified for most heat stressing environmental conditions.
Unknown authors
Female BALB/c mice were exposed to continuous-wave or pulsed-wave 425-MHz radiation in a TEM transmission line for one hour per day over five consecutive days, with sham-exposed controls. Continuous-wave exposures used power densities of 39, 10, and 2.5 mW/cm², while pulsed-wave exposures used 9, 2.5, and 0.63 mW/cm² with a 1 msec pulse at 250 pulses per second. Mice exposed to pulsed-wave at 9.0 mW/cm² showed increased colonic temperature, but continuous-wave at 39 mW/cm² did not, and peripheral blood cell counts were unchanged. The primary immune response to sheep red blood cells, measured by plaque-forming cell and hemagglutination assays, did not differ between sham and exposed groups or between continuous-wave and pulsed-wave exposures.
Unknown authors
Glenn S. Smith
The paper discusses problems in measuring local electric fields in media with spatially inhomogeneous electrical properties like biological tissue. Simple theoretical analyses describe the operation of electrically short hare and insulated electric field probes in a dissipative medium.
Р. Е. Батковский
They report that advances in radio engineering have uncovered new biological uses for ultra-high frequency electric fields. They also state that the effects of UHF electric fields on living organisms appear very diverse according to recent experiments and clinical data.
William Pearlman, Maitland Baldwin
