Showing papers by "Jianqing Wang published in 2005"

Lack of effects of 1439 MHz electromagnetic near field exposure on the blood-brain barrier in immature and young rats.

Abstract: Possible effects of 1439 MHz electromagnetic near field (EMF) exposure on the blood-brain barrier (BBB) were investigated using immature (4 weeks old) and young (10 weeks old) rats, equivalent in age to the time when the BBB development is completed and the young adult, respectively. Alteration of BBB related genes, such as those encoding p-glycoprotein, aquaporin-4, and claudin-5, was assessed at the protein and mRNA levels in the brain after local exposure of the head to EMF at 0, 2, and 6 W/kg specific energy absorption rates (SARs) for 90 min/day for 1 or 2 weeks. Although expression of the 3 genes was clearly decreased after administration of 1,3-dinitrobenzene (DNB) as a positive control, when compared with the control values, there were no pathologically relevant differences with the EMF at any exposure levels at either age. Vascular permeability, monitored with reference to transfer of FITC-dextran, FD20, was not affected by EMF exposure. Thus, these findings suggest that local exposure of the head to 1439 MHz EMF exerts no adverse effects on the BBB in immature and young rats.

Simulation of exposure and SAR estimation for adult and child heads exposed to radiofrequency energy from portable communication devices.

Abstract: Bit-Babik, G., Guy, A. W., Chou, C-K., Faraone, A., Kanda, M., Gessner, A., Wang, J. and Fujiwara, O. Simulation of Exposure and SAR Estimation for Adult and Child Heads Exposed to Radiofrequency Energy from Portable Communication Devices. Radiat. Res. 163, 580–590 (2005). The level and distribution of radiofrequency energy absorbed in a child's head during the use of a mobile phone compared to those in an adult head has been a controversial issue in recent years. It has been suggested that existing methods that are used to determine specific absorption rate (SAR) and assess compliance with exposure standards using an adult head model may not adequately account for potentially higher levels of exposure in children due to their smaller head size. The present study incorporates FDTD computations of locally averaged SAR in two different anatomically correct adult and child head models using the IEEE standard (Std. C95.3-2002) SAR averaging algorithm. The child head models were obtained by linear sca...

New approach to safety evaluation of human exposure to stochastically-varying electromagnetic fields

Abstract: In this paper, high-frequency (HF) and microwave electromagnetic (EM) fields in experimental fusion facilities were statistically measured, and the exposure levels were compared with safety guidelines to ensure workers' safety. Since leaked EM fields have time-varying characteristics whose amplitudes vary according to a stochastic process, a measurement of their amplitude probability distribution (APD) was conducted. An approach was then presented to derive from the measured APD the specific absorption rate (SAR) in an exposed human body. The statistically-averaged whole-body-averaged SAR showed that the leaked field intensities were low enough to not cause any thermal hazards for the workers in the specific EM environment. The statistically averaged SAR also showed fair agreement with the SAR derived from the time average over 6 min as specified in the safety guidelines. This finding suggests the usefulness of the APD measurement in lieu of a field measurement over a 6-min period because the APD can be obtained in a time period much less than 6 min.

EM Interaction between a 5 GHz Band Antenna Mounted PC and a Realistic Human Body Model

Abstract: A sub-grid finite-difference time-domain (FDTD) method was applied to analyze electromagnetic (EM) interaction between a 5 GH band antenna mounted laptop personal computer (PC) and a human body model in realistic use situations. The investigated situations were a typing and a non-typing PC users, who were simulated with a realistic whole body or half body model. It was found that the body proximity effect was mainly blocking the radiation up to 20 dB towards the body side, and the hands on the keyboard were mainly blocking the radiation up to 10 dB towards the direction at an angle to the head. It was also found that the highest EM absorption in the typing and non-typing situations occurred in the hand and in the chest, respectively, and the hands on the keyboard had a significantly blocking effect for the SAR spread to the head region. The peak SAR levels were low enough compared to the safety guidelines.

FDTD simulation of shielding effectiveness of metal-coated plastics for pulsed electromagnetic fields

Abstract: SUMMARY The use of metal-coated plastics is increasing as shielding materials of electronic and information products due to their lightweight. In this paper, a finite-difference time-domain (FDTD) algorithm, based on the derivation of a time-domain representation of the surface impedance of an equivalent resistive film, was developed to analyze the electromagnetic penetration of pulsed electromagnetic fields through metal-coated plastics. The validity of the proposed algorithm, in both the far-field and near-field cases, was verified by comparing the calculated penetrated electromagnetic fields or shielding effectiveness with theoretical and measured ones. Good agreement between them demonstrated the usefulness of the FDTD algorithm.

Maximum temperature increases in the head and brain for SAR averaging schemes prescribed in safety guidelines

Abstract: This paper presents maximum temperature increase in the head and brain with peak SAR calculated by different averaging schemes. For our computational investigations, it is found that maximum temperature increases in the head are well correlated with peak spatial-average SARs. However, the slope correlating them is largely dependent on the averaging scheme. Additionally, no clear difference is observed in the slope obtained using two head models. Possible maximum temperature increase in the brain for the SAR values is also quantified.

TDR Analysis of Electromagnetic Radiation from a Bend of Micro-Strip Line

Abstract: Discontinuity such as a bend in a micro-strip line is known as one of major radiation sources. The total radiation from the micro-strip line is, however, being generally investigated because of the difficulties in identifying the radiation from some specific location. In this paper, paying attention to the feature of TDR (Time-Domain Reflectometry) measurement, we made an attempt to extract the radiation only from the bend in a micro-strip line. Such an approach is useful in understanding its radiation mechanism. As a result, we found that the larger the bend angle is, the larger the radiation power becomes. The radiation power achieved 3.5% at maximum when the bending angle was 90° at the frequencies below 1 GHz. We also examined the validity of the TDR analysis in comparison with network analyzer measurement. We obtained the radiation power versus frequency from the measured scattering parameters, which exhibited a fair agreement with the TDR result.

Comparison of SAR between adult and children for mobile phones

Abstract: In this article, we introduce some latest research results on the dosimetry of children for mobile phones. The contents include a comparison for the SAR characteristics in anatomical head models of adult and children, and an approach to the age effect of dielectric properties on the peak SAR. An international inter-comparison of SAR calculation is also introduced