摘要:

AbstractA magnetic flux density (MFD) and electric‐field (E‐field) data‐acquisition system was built for characterizing extremely low‐frequency fields in residences. Every 2 min during 24‐h periods, MFD and E‐field measurements were made in 43 homes in King, Pierce, and Snohomish counties of Washington State. The total electrical energy used in each residence during the 24‐h measurement period was also recorded, and maps were drawn to scale of the distribution wiring within 43 m (140 ft) of these homes. Finally, on a separate date, field measurements were made in each home during an epidemiological interview. The results of this study can be summarized as follows: 1) 24‐h‐average MFD measured at two separate points in the family room were correlated, as were a 24‐h‐average bedroom measurement and the mean of the two family‐room measurements. 2) The 24‐h‐average family‐room MFD and E‐field measurements were uncorrelated. 3) The 24‐h‐average total harmonic distortions of family‐room MFD and E‐fields were less than about 24% and 7%, respectively. 4) Residential MFD exhibited a definite 24‐h (diurnal) cycle. 5) The 24‐h‐average and interviewer‐measured MFD were correlated. 6) Residential 24‐h‐average MFD were correlated with the wiring code developed by Wertheimer and Leeper. 7) An improved prediction of 24‐h‐average residential MFD was obtained using the total number of service drops, the distance to neighboring transmi

ISSN:0197-8462    

DOI:10.1002/bem.2250080402

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

年代:1987

数据来源: WILEY

摘要:

AbstractChronic exposure of animals to 60‐Hz electric fields is known to affect the nervous system in a variety of subtle ways. The mechanism whereby these effects are produced remains unknown. One hypothesis is that the effects are a result of direct interaction between neuronal membranes and induced currents. Alternatively, the effects could be produced indirectly, as a result of sensory stimulation and the resulting low‐level stress. To test these hypotheses, a system was developed to expose the surface of an anesthetized cat's paw to surface electric fields up to 600 kV/m while simultaneously measuring, in dorsal root fibers, afferent nerve impulses originating from various receptor types in the exposed paw. Of the 245 receptor units tested, comprising ten cutaneous receptor types, ten responded to the electric field with an increase in firing rate. The most sensitive receptor type was the rapidly adapting field receptor (RAF); eight of 20 (40%) were sensitive to the electric field, with thresholds as low as 160 kV/m. One of 35 rapidly adapting high‐frequency receptors and one of 22 type T hair‐follicle receptors were also sensitive to the electric field. Follow‐up tests on the RAF receptors showed that hair removal reduced but did not eliminate the electric field sensitivity, suggesting that at least one other mechanism was involved in addition to stimulation via hair movement. The most likely mechanism is field‐induced vibrations of the skin, since a further reduction in firing rate occurred following application of mineral oil to the depilated paw. Direct interaction with neuronal membranes is not supported by o

ISSN:0197-8462    

DOI:10.1002/bem.2250080403

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

年代:1987

数据来源: WILEY

摘要:

AbstractRamirez et al (1983) reported reduced egg laying byDrosophila melanogasterand reduced survival of those eggs to adulthood when adult flies were exposed to magnetic fields. In a similar study, no effects from exposures ofDrosophilato 1‐mT, 60‐Hz magnetic fields were fo

ISSN:0197-8462    

DOI:10.1002/bem.2250080404

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper presents three‐dimensional finite difference calculations of induced current densities in a grounded, homogeneous, realistically human‐shaped phantom. Comparison is made with published experimental values of current density at 60 Hz, measured in conducting saline manikins with their arms down by the side. The congruence between calculation and experiment gives confidence in the applicability of the numerical method and phantom shape to other configurations. The effect of raising both arms above the head is to reduce the current densities in the head and neck by ∼50% and to increase those from the thorax downwards by 20–30%. A sensitivity analysis was performed on the shape and dimensions of the phantom, from a 45‐kg, 1.5‐m‐tall person to a 140‐kg, 1.9‐m‐tall person. When the phantom is grounded through both feet the current densities range from 50 to 90 μAm−2in the head (all values for a 60‐Hz, 1‐kVm−1, vertical applied field), 70 to 140 μAm−2in the thorax, 150 to 440 μAm−2at the crotch, and 500 to 2,230 μAm−2in the ankle. When grounded through only one foot the current densities at the crotch range from 400 to 1,000 μAm−2and from 1,000 to 4,400 μAm−2in the ankle of the grounded leg. Scale transformations of the short‐circuit current with phantom h

ISSN:0197-8462    

DOI:10.1002/bem.2250080405

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

年代:1987

数据来源: WILEY

摘要:

AbstractFull‐size models of a man and a rhesus monkey were exposed to radiofrequency (RF) radiation at 225 MHz. The model of man was also exposed to 2,000 MHz. Specific absorption rates (SARs) were measured in partial‐body sections, such as the arms, legs, etc., using gradient‐layer calorimeters. Also, front‐surface thermographic images were obtained to qualitatively show the heating patterns. For all of the configurations used, the SAR in the limbs was much higher than in the torso. Agreement (whole‐body SARs) with spheroidal models was better for both models at 225 MHz than at 2,000 MHz. These results indicate that in the frequency range two orders of magnitude above whole‐body resonance, SAR in the limbs significantly contributes to the whole‐bod

ISSN:0197-8462    

DOI:10.1002/bem.2250080406

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

年代:1987

数据来源: WILEY

摘要:

AbstractAnatomic variability in the deposition of radiofrequency electromagnetic energy in mammals has been well documented. A recent study [D'Andrea et al., 1985] reported specific absorption rate (SAR) hotspots in the brain, rectum and tail of rat carcasses exposed to 360‐ and to 2,450‐MHz microwave radiation. Regions of intense energy absorption are generally thought to be of little consequence when predicting thermal effects of microwave irradiation because it is presumed that heat transfer via the circulatory system promptly redistributes localized heat to equilibrate tissue temperature within the body. Experiments on anesthetized, male Long‐Evans rats (200–260 g) irradiated for 10 or 16 min with 2,450, 700, or 360 MHz radiation at SARs of 2 W/kg, 6 W/kg, or 10 W/ kg indicated that postirradiation localized temperatures in regions previously shown to exhibit high SARs were appreciably above temperatures at body sites with lower SARs. The postirradiation temperatures in the rectum and tail were significantly higher in rats irradiated at 360 MHz and higher in the tail at 2,450 MHz than temperatures resulting from exposure to 700 MHz. This effect was found for whole‐body‐averaged SARs as low as 6 W/kg at 360 MHz and 10 W/kg at 2,450 MHz. In contrast, brain temperatures in the anesthetized rats were not different from those measured in the rest of the body following microwa

ISSN:0197-8462    

DOI:10.1002/bem.2250080407

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

年代:1987

数据来源: WILEY

摘要:

AbstractIntraocularly circulating hot water was used to produce cataracts in nine eyes of seven rabbits by maintaining their retrolental temperatures between 43 °C and 45 °C. A rapid rate of heating (1.3 °C/min) plus a sharp temperature gradient across the eye may have been contributing factors in the consistent production of cataracts at these temperatures. Biomicroscopy and light microscopy showed lens changes similar to those associated with acute exposure to microwave radiation. These findings support the assumption that microwave cataractogenesis is due to the local production of elevated temperatur

ISSN:0197-8462    

DOI:10.1002/bem.2250080408

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

年代:1987

数据来源: WILEY

摘要:

AbstractTransverse electric and magnetic field (TEM) cells are often designed to subject samples to electromagnetic radiation of intrinsic impedance (E/H) that is the same as in free space, 377 ω. Earlier work has shown this value to be correct for the RF region above about 2 kHz. In this study, measurements of magnetic fields in the extremely low frequency regions and at DC indicate the E/H ratio to be around 300 ω for frequencies less than 2 kHz in cells of a particular design. This lower value indicates that care should be taken in estimating AC magnetic field intensities from electric field measurements in TEM cells at frequencies below 2 kH

ISSN:0197-8462    

DOI:10.1002/bem.2250080409

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

年代:1987

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250080410

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

年代:1987

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250080401

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

年代:1987

数据来源: WILEY