ELF Coupling to Spherical Models of Man and Animals

Spiegel, R.J.

doi:10.1109/tbme.1976.324649

Cited by 39 publications

(8 citation statements)

References 8 publications

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“…Such studies are desirable for at least two reasons. First, the electric fields and currents induced in human beings by the Bart ULF magnetic field fluctuations (a simple approximate method for calculating the electric fields is discussed by Spiegel [1976] ) could conceivably have nontrivial direct effects. It has been reported, for example, that human reaction times can be altered by artificially produced magnetic field fluctuations at 0.2 Hz [Friedman et al, 1967] or even by naturally occurring and comparatively weak ULF signals [Kb'nig and A nkerrniiller, 1960].…”

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confidence: 99%

Large‐amplitude ULF magnetic fields produced by a rapid transit system: Close‐range measurements

Ho¹,

Fraser–Smith²,

Villard³

1979

Radio Science

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Measurements at a location close to the San Francisco Bay Area Rapid Transit (Bart) systemshow that Bart can produce ultra low frequency (ULF; frequencies less than 5 Hz) magnetic field fluctuations with amplitudes that are 2-3 orders of magnitude greater than the normal background level. The maximum increase in magnetic field fluctuations over the ambient background level occurs in the range 0.01-1 Hz, but significant increases occur at 0.001 and 10 Hz. Although it is generally accepted that moving trains cause magnetic field disturbances, it has not, until recently, been recognized that modern dc-powered rapid transit systems are such powerful sources of ULF electromagnetic fields, and the existence of these sources in densely populated urban areas could have environmental implications. INTRODUCTION Research in 1975 and 1976 on the origin of exceptionally large and continuous ultra low frequency (ULF; frequencies less than 5 Hz) magnetic field fluctuations on the Stanford University campus revealed that the San Francisco Bay Area Rapid Transit (Bart) system was a powerful generator of ULF electromagnetic fields detectable throughout the Bay Area (--• 100 km 2) and probably also over a large surrounding area [Fraser-Smith and Coates, 1978]. Although there have been a number of suggestions for the controlled generation of ULF fields for communication [Lipa et al., 1975; Davis and Willis, 1974], this appears to be the first observation of a large-scale source whose characteristics can be accurately determined. (High-altitude nuclear explosions produce ULF geomagnetic field fluctuations over a large area of the earth, but the fluctuations are largely uncontrolled, and they persist only for a short time [e.g., Green et al., 1962; Kovach and Ben-Menahem, 1966] .) The observation could prove useful in studies of the communication potential of man-made ULF signals, and it is likely to have important implications for studies of the generation and propagation of naturally occurring ULF geomagnetic pulsations [Jacobs, 1970] and for measurements of geomagnetic •Present address: Corkstown Laboratory, Bell-Northern Re-activity at observatories near populated areas.Furthermore, Bart and other modern dc electricpowered rapid transit systems (which are also likely to be powerful sources of ULF fields) are necessarily located in urban areas with high population densities. The finding that these systems are sources of large-amplitude ULF fields may also be important for environmental reasons. Recognizing these possibilities, we undertook a new series of measurements of the Bart magnetic fields at a location much closer to the Bart system than the sites used for the earlier measurements. We also expanded

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confidence: 99%

Large‐amplitude ULF magnetic fields produced by a rapid transit system: Close‐range measurements

Ho¹,

Fraser–Smith²,

Villard³

1979

Radio Science

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“…There have also been theoretical approaches to modeling the coupling of magnetic fields to simple homogeneous geometric models [Spiegel, 1976;Hart and Marino, 19821. Given that the empirical results for electric field induced currents in homogeneous human and animal models emphasize the importance of investigating heterogeneous models and live animals, it seems appropriate to proceed to these systems in the magnetic induction case as well. As indicated in calculations by Polk and Song [ 19901, the deviation from the simple circular induced electric field lines of homogeneous media can be quite striking when inhomogeneities in conductivity are introduced even in simple models.…”

Section: Magnetic Fieldsmentioning

confidence: 99%

Experimental macroscopic dosimetry for extremely-low-frequency electric and magnetic fields

Bracken

1992

Bioelectromagnetics

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Environmental and laboratory exposure to electric and magnetic fields (EMF) in the extremely-low-frequency range (ELF) produces electrical quantities that interact directly with the exposed biological system on a scale small compared to the size of the human body but large with respect to cellular dimensions. The purpose of this paper is to describe these macroscopic electrical quantities and their characterization through measurements on living systems and experimental models. Electric field exposure results in a total induced current, surface electric fields, internal electric fields, and internal currents. Magnetic field exposure results in internal magnetic field, internal electric fields, and internal currents. Basic properties of fields and matter determine the methods by which these quantities can be measured. Quantification or dosimetry for these parameters on a macroscopic basis can be directed to the whole body, a cross section across the body, a local surface area, or a local volume. Models of varying degrees of sophistication have been used to establish spatial distributions of external fields and internal fields and currents.

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“…Hence, the vector electric-field intensity E induced inside a single sphere of a radius, a << h (wavelength, in air), neglecting the influence of adjacent spheres, is given by [Spiegel, 1976;Lin et al, 19731 : The approximately spherical test-tube samples are irradiated by a uniform plane-wave where 9 and i are unit vectors in the y and z directions, respectively, e: = (e/eo) -j (./weo) is the relative complex permittivity, u is sample conductivity, w is radian frequency, and e b t time dependence is assumed for all fields. The first term in (1) is due to the uniform incident electric field (Eo), and the second term is due to the uniform incident magnetic field (Ho = Eo/vo) in the stripline, where vo = 377 ohms, the intrinsic impedance of free space.…”

Section: Equivalent Pi's Calculated At Different Frequenciesmentioning

confidence: 99%

Power density, field intensity, and carrier frequency determinants of RF‐energy‐lnduced calcium‐ion efflux from brain tissue

Joines

Blackman

1980

Bioelectromagnetics

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To explain a carrier frequency dependence reported for radiofrequency (RF)-induced calcium-ion efflux from brain tissue, a chick-brain hemisphere bathed in buffer solution is modeled as a sphere within the uniform field of the incident electromagnetic wave. Calculations on a spherical model show that the average electric-field intensity within the sample remains the same at different carrier frequencies if the incident power density (Pi) is adjusted by an amount that compensates for the change in complex permittivity (epsilon *r) and the change of wavelength, as a function of carrier frequency. The resulting formula for transforming Pi is seen to follow the pattern of both positive and negative demonstrations of calcium-ion efflux that have been observed at carrier frequencies of 50, 147, and 450 MHz. Indeed, all results obtained at these three frequencies, when related by Pi's that produce the same average electric-field intensity within the sample, are seen to be in agreement; no prediction is contradicted by an experiment.

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ELF Coupling to Spherical Models of Man and Animals

Cited by 39 publications

References 8 publications

Large‐amplitude ULF magnetic fields produced by a rapid transit system: Close‐range measurements

Large‐amplitude ULF magnetic fields produced by a rapid transit system: Close‐range measurements

Experimental macroscopic dosimetry for extremely-low-frequency electric and magnetic fields

Power density, field intensity, and carrier frequency determinants of RF‐energy‐lnduced calcium‐ion efflux from brain tissue

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