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Cellular phones are used in the vicinity of the human head, resulting in localized exposure to this part of the body. To simulate exposure during cellular phone use, microwave energy absorption should be focused within the head region of laboratory animals. In this paper, we developed an exposure system using a figure-8 loop antenna to permit localized exposure of a rat head to 1500-MHz microwave fields, simulating human head exposure to cellular phones. We have numerically estimated the specific absorption rate (SAR) in a rat exposed to microwave fields via our new exposure system. The high ratio of SAR averaged over the target tissue (i.e., the brain) to that averaged over the whole body suggests that the figure-8 antenna can realize greater localized exposure than the previously used exposure system. We have also confirmed the effectiveness of our proposed system experimentally. [ABSTRACT FROM AUTHOR]

In this paper, we describe the theory and practical implementation of an electrical impedance probe for making in vivo measurements of the electrical admittance of living tissue. The probe uses concentric annular electrodes and is shown to sample a more localized, yet greater, volume of tissue than the standard four-electrode probe. We have developed a mathematical model for the conduction of current between the probe electrodes assuming that we are investigating a uniform, isotropic, semi-infinite region and taking into account the contact impedance between the electrodes and the organ. The electric fields produced by the probe have been calculated by solving a weakly singular Fredholm integral equation of the second kind. The size and position of the probe electrodes have been optimized to maximize both the accuracy in the admittance measurement and insensitivity to contact impedance. A probe and driving hardware have been constructed and experimental results are provided showing the accuracy of admittance measurements at 50 and 640 KHz. [ABSTRACT FROM AUTHOR]

Attention is drawn to recent paper by Rogers et al. (Aug., 2004) in which ultra-wideband pulses are applied to an isolated muscle as part of deriving a strength-duration curve for threshold stimulation. The paper extends the strength-duration threshold curve for unipolar pulses down to a pulse duration of about 1 ns, on the order of 1000 times shorter than previously studied. Results of the work justify use of traditional mathematical models of the strength-duration curve for nanosecond pulses, as done recently for the electric field resulting from electrostatic discharge through the body (Dawson, et al., 2004). [ABSTRACT FROM AUTHOR]

Erroneous results can be obtained when using the integral formulation suggested in Chiampi’s paper for the computation of the electric field induced in a conductor by certain movements in a static magnetic field. Here, a complete integral formulation to describe the electric field that natural movements in and around high field MRI systems can produce in conducting objects is presented. [ABSTRACT FROM PUBLISHER]