Showing papers by "Jianqing Wang published in 2004"

Absence of mutagenic effects of 2.45 GHz radiofrequency exposure in spleen, liver, brain, and testis of lacZ-transgenic mouse exposed in utero.

Abstract: A possible mutagenic effect of 2.45 GHz radiofrequency exposure was examined using lacZ-transgenic Muta mice. Pregnant animals were exposed intermittently at a whole-body averaged specific absorption rate of 0.71 W/kg (10 seconds on, 50 seconds off which is 4.3 W/kg during the 10 seconds exposure). Offspring that were exposed in utero for 16 hours a day, from the embryonic age of 0 to 15 days, were examined at 10 weeks of age. To minimize thermal effects, the exposure was given in repeated bursts of 10 seconds of exposure followed by 50 seconds of no exposure. Mutation frequencies at the lacZ gene in spleen, liver, brain, and testis were similar to those observed in non-exposed mice. Quality of mutation assessed by sequencing the nucleotides of mutant DNAs revealed no appreciable difference between exposed and non-exposed samples. The data suggest that the level of radiofrequency exposure studied is not mutagenic when administered in utero in short repeated bursts.

Computation with a parallel FDTD system of human-body effect on electromagnetic absorption for portable telephones

Abstract: Using our recently implemented parallel finite-difference time-domain computation system on Linux-based personal computers, we investigated the human-body effect on the peak specific absorption rate (SAR) in the human head for portable telephones. Taking into account the whole human body, we found that there was a difference within 5.3% for the 1- and 10-g averaged spatial peak SARs and a difference within 19% for the SAR in the brain and eyes compared to the isolated head model. Moreover, in most realistic-use positions, we found that the SAR was slightly decreased due to the body effect. These results further support the rationale of using an isolated human-head model in the SAR evaluation for portable telephones.

Uncertainty evaluation of dosimetry due to plastic holder for restraining small animal in in vivo near field exposure setup

Abstract: In most in vivo exposure setups for testing biological effects of cellular telephones on a small animal, a plastic holder is commonly used for restraining the small animal in order to keep a constant near-field exposure. Although the plastic holder should affect the specific absorption rate (SAR) in the small animal, few researchers have considered its influence in their exposure setup design or dosimetry evaluation. We previously developed an in vivo exposure setup for testing the promoting effect of digital cellular telephones on mouse skin carcinogenesis. In this paper, the influence of a plastic holder for restraining the mouse in the exposure setup was investigated numerically and experimentally. The numerical investigation was conducted by using the finite-difference time-domain (FDTD) method together with a realistically shaped mouse model. The validity of the FDTD modeling was verified by the antenna impedance measurement. As a result, an increase of 18% on the peak SAR was found due to the presence of the mouse holder.

Correspondence between frequency characteristics of radiated emission and input impedance of power-ground planes of PCB

Abstract: The frequency at the peak of electromagnetic radiation from a PCB (Printed Circuit Board) as a result of ground bounce is considered predictable from the frequency characteristics of the input impedance between the power supply and ground layer (below called the PCB impedance). However, the relationship is largely unknown. In this paper, the electromagnetic radiation of the PCB and the frequency spectrum of the PCB impedance are analyzed by the FDTD (Finite-Difference Time-Domain) method and their relational mechanism is studied by comparison with the measured values. It is found that the peak of the electromagnetic radiation appears at the frequency where the PCB is a minimum if the PCB is excited by a voltage source with an internal resistance sufficiently smaller than the PCB impedance, and that this peak is shifted toward the frequency at which the PCB impedance becomes a maximum if the internal resistance is increased. The radiation power ratio derived from the resistive components (called the resonant resistances) at two frequencies where the PCB impedance is maximum and minimum (resonant frequencies) mostly agrees with the ratio of the squares of the radiated electric field. Hence, the radiation peak frequencies of the PCB are determined both by the internal resistance of the excitation source and the resonant resistance of the PCB impedance. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 30–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10209

Time constant of temperature increase in the human head models due to dipole antenna at microwave frequencies

Abstract: The paper investigates the time constant of temperature increase in human head models due to a dipole antenna The frequency band considered is from 900 MHz to 25 GHz In order to discuss this problem thoroughly, hundreds of cases are considered: five frequency bands; two polarizations; two head models, with pressed and impressed ears; ten antenna feeding points The results provide useful information in this field