摘要:

AbstractElectric fields produced by a selection of video display units have been measured over a frequency range from DC to 1 MHz. The magnitude and the time variation of the electric fields were both recorded by means of a single broadband capacitive sensor located on the surface of a simple simulation of the human body. The electric field at a given location was found to be the sum of three discrete components, each having a different spatial and time variation. These components are produced by, respectively, the charged CRT screen, the flyback transformer, and the low‐voltage circuitry. For the units tested, operator exposures are substantially below the limits of existing workplace guideline

ISSN:0197-8462    

DOI:10.1002/bem.2250050102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThis study probed the mechanisms underlying microwave‐induced alterations of thermoregulatory behavior. Adult male squirrel monkeys (Saimiri sciureus), trained to regulate the temperature of their immediate environment (Ta) behaviorally, were chronically implanted with Teflon reentrant tubes in the medical preoptic/anterior hypothalamic area (PO/AH), the brainstem region considered to control normal thermoregulatory processes. A Vitek temperature probe inserted into the tube measured PO/AH temperature continuously while changes in thermoregulatory behavior were induced by either brief (10‐min) or prolonged (2.5‐h) unilateral exposures to planewave 2,450‐MHz continuous wave (CW) microwaves (E polarization). Power densities explored ranged from 4 to 20 mW/cm2(rate of energy absorption [SAR] = 0.05 [W/kg]/[mW/cm2]). Rectal temperature and four representative skin temperatures were also monitored, as was the Taselected by the animal. When the power density was high enough to induce a monkey to select a cooler Ta(8 mW/cm2and above), PO/AH temperature rose ∼ 0.3°C but seldom more. Lower power densities usually produced smaller increases in PO/AH temperature and no reliable change in thermoregulatory behavior. Rectal temperature remained constant while PO/AH temperature rose only 0.2–0.3°C during 2.5‐h exposures at 20 mW/cm2because the Taselected was 2–3°C cooler than normally preferred. Sometimes PO/AH temperature increments greater than 0.3°C were recorded, but they always accompanied inadequate thermoregulatory behavior. Thus, a PO/AH temperature rise of 0.2–0.3°C, accompanying microwave exposure, appears to be necessary and sufficient to alter thermoregulatory behavior, which ensures in turn that no greater temperature excursions occur in this hypothalamic t

ISSN:0197-8462    

DOI:10.1002/bem.2250050103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements were made of the small, transient offsets of vacuolar potential produced in single cells ofNitella flexilisandChara brauniiby isolated bursts of audio frequency electromagnetic radiation. The offsets increased in magnitude with decreasing frequency of the electromagnetic radiation and, below about 6 kHz, seemed to approach a lowfrequency asymptote. This frequency dependence for the offset is shown to be in accordance with a previously developed model in which the incident radiation is weakly rectified by the cell's membrane system.

ISSN:0197-8462    

DOI:10.1002/bem.2250050104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractLiver mitochondria were exposed in vitro at 30°C to microwave radiation (2.45 GHz) during the following states of respiraton: resting, state 1; substrate dependent, state 2; ADP stimulated, state 3; and ADP depleted, state 4. At 10 or 100 mW/g, with succinate as substrate, no effect of exposure was observed on states 1–4 or the respiratory control index (state 3/state 4) of either tightly or loosely coupled mitochondria. When glutamate was used as substrate, no effects were observed at 10 mW/g. However, in the loosely coupled mitochondria the 100 mW/g exposure produced an increase in states 2 and 4 and a decrease in the respiratory control index. The results suggest that the function of loosely coupled mitochondria can be affected at high power levels of microwave radiati

ISSN:0197-8462    

DOI:10.1002/bem.2250050105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractA digital computer simulation has been carried out of the exposure of a cell, modeled as a multilayered spherical structure, to an alternating electrical field. Electrical and electrochemical quantities of possible biological interest can be evaluated everywhere inside the cell. A strong frequency behavior in the range 0–10 MHz has been obtaine

ISSN:0197-8462    

DOI:10.1002/bem.2250050106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe effects of hyperthermia, alone and in conjunction with microwave exposure, on brain energetics were studied in anesthetized male Sprague‐Dawley rats. The effect of temperature on adenosine triphosphate concentration [ATP] and creatine phosphate concentration [CP]was determined in the brains of rats that were maintained at 35.6, 37.0, 39.0, and 41.0°C. At 37, 39, and 41°C brain [ATP] and [CP]were down 6.0, 10.8, and 29.2%, and 19.6, 28.7, and 44%, respectively, from the 35.6°C control concentrations. Exposure of the brain to 591‐MHz radiation at 13.8 mW/cm2for 0.5, 1.0, 3.0, and 5.0 min caused further decreases (below those observed for 30°C hyperthermia only) of 16.0, 29.8, 22.5, and 12.3% in brain [ATP], and of 15.6, 25.1, 21.4, and 25.9% in brain [CP]after 0.5, 1.0, 3.0, and 5.0 min, respectively. Recording of brain reduced nicotinamide adenine dinucleotide (NADH) fluorescence before, during, and after microwave exposure showed an increase in NADH fluorescence during microwave exposure that returned to preexposure levels within 1 min postexposure. Continuous recording of brain temperatures during microwave exposures showed that brain temperature varied between −0.1 and +0.05°C. Since the microwave exposures did not induce tissue hyperthermia, it is concluded that direct microwave interaction at the subcellular level is responsible for the observed decrease in [ATP

ISSN:0197-8462    

DOI:10.1002/bem.2250050107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractMonolayer cultures of human neuroblastoma cells were exposed to 915‐MHz radiation, with or without sinusoidal amplitude modulation (80%) at 16 Hz, at specific absorption rates (SAR) for the culture medium and cells of 0.00, 0.01, 0.05, 0.075, 0.1, 0.5, 0.75, 1.0, 1.5, 2, or 5 mW/g. A significant increase in the efflux of calcium ions (45Ca2+) as compared to unexposed control cultures occurred at two SAR values: 0.05 and 1 mW/g. Increased efflux at 0.05 mW/g was dependent on the presence of amplitude modulation at 16 Hz but at the higher value it was not. These results indicate that human neuroblastoma cells are sensitive to extremely low levels of microwave radiation at certain narrow ranges of SA

ISSN:0197-8462    

DOI:10.1002/bem.2250050108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractA 275‐MHz exposure system, consisting of a circular waveguide irradiator and a transparent plastic animal cage, has been developed to accommodate rhesus monkeys weighing up to 15 kg. The vertically oriented waveguide is composed primarily of stainless steel and is fitted with an inner cage fabricated from a tubular section of acrylic plastic. Circularly polarized electromagnetic energy at 275 MHz, either pulsed or continuous wave (CW), can be propagated from the removable top section of the waveguide. The cage is designed to function as the monkey's permanent home. It is fitted with a lever‐actuated behavioral performance device on which the monkey responds according to a predetermined schedule to obtain a daily food ration. The system can be adapted to provide for the collection of metabolic and physiologic data as well. Dosimetric measurements were conducted with six rhesus monkeys weighing 3.0–7.2 kg and with a 4‐kg model. The dosimetric results show that about one‐third of the net incident energy is absorbed by a subject in this system at a normalized specific absorption rate (SAR) of 0.33 (W/kg)

ISSN:0197-8462    

DOI:10.1002/bem.2250050109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractSpecific absorption rates (SARs) were determined theoretically and experimentally for several spherical models of tissue exposed to electrical fields of TE101mode in a rectangular cavity of 57.3 MHz resonant frequency. The approximate theoretical SAR can be calculated according to the Mie theory by superposition of four plane waves representing the fields excited in the cavity. The theoretical and thermographically determined SAR patterns in spheres with radii of 5, 7.5, and 10 cm and with conductivities of 0.1, 1, and 10 S/m were compared. For a sphere with radius less than 7.5 cm and conductivity less than 1 S/m, the SAR was quite uniform. When conductivity was increased to 10 S/m, the SAR patterns showed higher absorption in the periphery of the largest sphere (10‐cm radius). These characteristics are important in evaluating the scaling technique of exposing a model of a human to very‐high‐frequency fields to obtain power absorption data in humans exposed to high‐frequency or very‐low‐frequ

ISSN:0197-8462    

DOI:10.1002/bem.2250050110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractA series of three experiments was performed to determine the effects of 30‐day exposures to uniform 60‐Hz electric fields (100 kV/m) on reproduction and on growth and development in the fetuses and offspring of rats. In the first experiment, exposure of females for 6 days prior to and during the mating period did not affect their reproductive performance, and continued exposure through 20 days of gestation (dg) did not affect the viability, size, or morphology of their fetuses. In the second experiment, exposure of the pregnant rat was begun on 0 dg and continued until the resulting offspring reached 8 days of age. In the third experiment, exposure began at 17 dg and continued through 25 days of postnatal life. In the second and third experiments, no statistically significant differences suggesting impairment of the growth or survival of exposed offspring were detected. In the second experiment, a significantly greater percentage of the exposed offspring showed movement, standing, and grooming at 14 days of age than among‐sham‐exposed offspring. There was a significant decrease at 14 days in the percentage of exposed offspring displaying the righting reflex in the second experiment and negative geotropism in the third experiment. These differences were all transient and were not found when the animals were tested again at 21 days of age. Evaluation of the reproductive integrity of the offspring of the second experiment did not disclose any d

ISSN:0197-8462    

DOI:10.1002/bem.2250050111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY