M. Hietanen, K. Kalliomäki, P-L. Kalliomäki, P. Lindfors
Researchers measured electric and magnetic fields from 35 plastic welding machines operating at 27 MHz with nominal powers of 0.5 to 35 kW. About 70% of the heaters exceeded the common standards of 200 V/m and 0.2 A/m, and 80% exceeded the Finnish proposed standard of 60 V/m and 0.2 A/m. At the worker's position, electric field strength above 190 V/m occurred in 66% of equipment, and leakage above the Finnish proposal of 60 V/m occurred in 94.3% of devices. Magnetic field strength above 0.5 A/m was found in 60% of equipment, and the Finnish proposal of 0.2 A/m was exceeded in 74% of cases.
Wilhelm Kraany-Ergen
H. C. Gloz
Tests on 15 patients using Siemens tube senders showed a lumbar fluid pressure rise from 5 to 52 mm that remained after the current was turned off. The most effective electrode distance was 25 mm with Schliephake electrodes. In two-thirds of cases systolic blood pressure dropped to 20 mm while diastolic pressure stayed constant. Retinal examination revealed venous filling and coiling within 30 seconds, arterial dilation by 1-2 minutes, and these vascular changes persisted for 1-2 hours after exposure.
I.A. Marriott, M.A. Stuchly
Surveys report a high incidence of eye-related complaints among VDU operators, though eyestrain is not recognized as a clinical entity. Reflections from external light sources are the most common and serious factor degrading screen image quality. Adjustable furniture reduces musculoskeletal complaints, but a preferred posture remains undefined. Physical complaints about VDUs are inversely related to job satisfaction.
Unknown authors
Unknown authors
The Department of Health, Education and Welfare reported that implanted pacemaker dysfunction has been observed near electrocautery, radar, communications systems, electric shavers, spark coils, and gasoline ignition systems. The Association for the Advancement of Medical Instrumentation stated that interference signals mimicking a heartbeat can be misinterpreted by pacemakers and change their output. Even microwave ovens complying with leakage limits of 0.0001 mW/cm2 at 5cm may cause electromagnetic interference within a few meters.
Herman Schwan, Kam Li
Leo Birenbaum et al.
Arthur Holly Compton
Russell L. Carpenter
James M. Wyckoff
Good measurements are the key to safe application of both ionizing and nonionizing radiation in industry, medicine, and consumer products. The National Bureau of Standards is expanding its measurement services to radiation users and collaborates with federal agencies to develop realistic measurement requirements for regulations. The report reviews the state of measurement art for X-ray, nuclide, ultraviolet, laser, electromagnetic, and ultrasonic radiation, highlighting the need for stable and accurate transfer standards.
Stephen F. Cleary
Table I summarizes reported in vivo effects in humans including hyperthermia, cataracts, auditory nerve responses, and neurological effects. Reported effects in experimental animals include mutations, hyperthermia, burns, testicular effects, and chromosomal aberrations. In vitro effects listed include mitotic arrest, resonance absorption in methyl palmitate, pearl-chain formation, and enzyme inactivation.
Unknown authors
Female Sprague-Dawley rats were exposed to 2.45 GHz continuous-wave microwaves at 28 mW/cm² for 100 minutes daily from days 6 to 15 of pregnancy. The study included 67 sham-irradiated and 70 irradiated females, resulting in 64 and 66 pregnancies respectively. No significant differences were found in pregnancy rates, litter size, or the incidence of external, visceral, or skeletal anomalies between the groups. In a separate experiment, 35% of adult rats exposed to 40 mW/cm² died from hyperthermia.
Unknown authors
Researchers studied the effect of temperature on isolated rat lenses incubated in tissue culture medium. Lenses maintained clarity in medium 199 with 10% fetal calf serum for up to two weeks, but high glucose caused opacities and globular degeneration within one day. Similar loss of transparency occurred after lenses were warmed to 39°C or 41°C for one hour and then incubated at 37°C for 24 hours. Lenses exposed to 60°C or 65°C for one hour did not become opaque, likely due to fixation.
Unknown authors
Researchers used prolate spheroid and ellipsoidal models to estimate electromagnetic power absorption in adult and infant human heads. A perturbation technique evaluated internal electric fields to estimate time-averaged and space-averaged specific absorbed power. The study compared results with animal experimental data and concluded ellipsoidal models are better than spheroid and sphere types.
Unknown authors
Unknown authors
Five different absorber-lined laboratory test systems were designed and built, and the uncertainty of each test was analyzed. Error values for each parameter were computed for each instrument, and a worst-case composite uncertainty was calculated for each model. Special tests evaluated parasitic interaction of E-field probes with the H-field and impedance loading of meters.
Unknown authors
Research on the biological effects of microwaves is primarily related to the problem of hazard assessment for exposure of man. For the 2-3 GHz range, extrapolation factors for humans are 1:2 for dogs, 1:8 for rhesus monkeys, 2:7 for squirrel monkeys, and 5:2 for rats.
Unknown authors
The study developed a generalized numerical model using the method of moments to compute electromagnetic field distribution and absorbed power in complex-shaped heterogeneous three-dimensional biological bodies. At 2450 MHz, excellent agreement between computed and measured results was obtained for homogeneous and heterogeneous cylinders with various field orientations, and very good agreement was found for rat-shaped models with parallel or orthogonal electric fields.
Unknown authors
The cavity must be mechanically adjustable because its physical dimensions dictate the operating frequency. The prototype cavity cross-section adjusts from 24 by 24 inches down to 6 by 6 inches, and the length adjusts from 4 feet to 1 foot. The cavity is large enough to irradiate mice, cell samples, bacteria, other microorganisms, and phantom scale models. Simultaneous excitation of two cavity modes allows independent control of electric and magnetic field phase and magnitude, enabling selection of virtually any field impedance including plane wave conditions.
Unknown authors
The paper describes a microwave exposure system for three experiments using CW millimeter waves. The system uses a Siemens RWO-60 backward wave oscillator powered by a Micro-Now 702 supply with a 2-hour frequency stability of at least 1 part in 2000 near 50 GHz. A Narda horn with a 1 cm by 1.43 cm aperture is positioned about 2 mm above each biological sample, which is a 1-2.5 mm layer that absorbs nearly all incident power. The instrumentation measures net power leaving the horn and uses a standing wave indicator to keep power constant as samples are changed. The exposure chamber is temperature-stabilized by a water bath, and the horn is heated to match the bath temperature.
Unknown authors
Monolayer cultures of BHK-21/C13 cells were exposed to E-band microwaves at 292 mW/cm2 or U-band at 177 mW/cm2 for 15 minutes, with four cultures per frequency. Protein synthesis was measured by autoradiography of 3H-methionine incorporation across the waveguide axis, providing data at 16 to 25 power densities per band. Results from 100 frequencies between 43–48 GHz and 65–70 GHz showed no significant difference from sham controls and no evidence of a power window.
Unknown authors
After error correction, residual errors were about .1 dB in return loss and 1° in phase. These errors correspond to about 2.5% error in dielectric constant and 12% error in loss tangent for water, and 1.7% and 2.4% for methanol. The probe technique is the only practical approach for in vivo samples but requires multiple measurements for repeatability.
Unknown authors
Unknown authors
Researchers evaluated three BRH applicators and four microwave hyperthermia applicators by thermographically analyzing them using planar phantoms, measuring leakage radiation, net power required to deliver 235 W/kg SAR, and heating patterns. The BRH 2450 MHz applicator had less than 5 mW/cm² leakage for both direct contact and 1 cm spacing, while the 915 MHz applicators exceeded that level when spaced 1 cm from the phantom. The depth of penetration into muscle tissue was nearly identical for both frequencies, at about 2 cm beneath the fat-muscle interface.
