Early history of bioelectromagnetics.

The early history of bioelectromagnetics is reviewed as I experienced it. The period of time chosen extends from my joining the Institute for Physical Foundations of Medicine in Frankfurt in 1937 to the early 1970s, when I retired from the chair of my department at the University of Pennsylvania. Several themes emerge from these recollections. First, clinical and biological work led almost immediately to a heated controversy about the role of athermal vs. thermal effects; this issue has never been settled to the satisfaction of most. Second, good quantitative work on electrical properties and dosimetry began early, well before World War II; its impact on future developments was significant.     

Numerical dosimetry dedicated to children RF exposure

Children are more and more using wireless communication systems. This growth has strengthened public concern and has highlighted the need to assess the radio frequency (RF) exposure of children. In dosimetry, taking advantage of the improvement of High Performance Calculation systems, great efforts have been carried out to improve the numerical tools and human models used to assess the Specific Absorption Rate (SAR). This paper analyses progress in building child and foetus models for numerical dosimetry purpose. The simulation results, in terms of Specific Absorption Rate over 1 and 10 g of tissues, in specific organs such as brain and averaged over the whole body, are reported and analysed. The results show that compliance methods used nowadays to certify phones are valid for children. The studies also show that specific tissues such as peripheral brain tissues can have higher exposure with children than with adults. Studies performed with plane waves as sources and whole body children models show that the whole body SAR of children can be higher than the WBSAR of adults and that the compliance to ICNIRP reference levels does not guarantee the compliance to ICNIRP basic restrictions. Dealing with the foetus models and dielectric properties great efforts have been made. Preliminary results show that the foetus exposure is often lower than the mother exposure, with an important influencing parameter: the foetus position in the uterus.     

Determination of the induced ELF electric field distribution in a two layer in vitro system simulating biological cells in nutrient solution

In-vitro studies of biological effects of electromagnetic fields are often conducted with cultured cells either in suspension or grown in a monolayer. In the former case, the exposed medium can be assumed to be homogeneous; however, eventually the cells settle to the bottom of the container forming a two layer system with different dielectric and conductive properties. In the present work the effect of this separation on the electric field distribution is calculated and experimentally measured at selected positions for a commonly used exposure configuration. The settled cell suspension is modeled by a well-defined two layer system placed in a rectangular container with the base of the container parallel to the direction of the magnetic field. Theoretical calculations based on numerical techniques are done for various two layer systems with different conductivities in each layer. The agreement between the theoretical calculations and the experimental measurements is within ± 1.5 mV/m, or 10% of the maximum induced field when the conductivity of the lower layer is ten times that of the upper layer. This result is well within experimental error. When the thickness of one of the layers is small compared to the thickness of the other layer, it is found that the electric field distribution is essentially that of the homogeneous case. The latter situation corresponds to a typical cell exposure condition. © 1993 Wiley-Liss, Inc.     

A circular waveguide irradiation system for nonhuman primates: design and dosimetry

A 275-MHz exposure system, consisting of a circular waveguide irradiator and a transparent plastic animal cage, has been developed to accommodate rhesus monkeys weighing up to 15 kg. The vertically oriented waveguide is composed primarily of stainless steel and is fitted with an inner cage fabricated from a tubular section of acrylic plastic. Circularly polarized electromagnetic energy at 275 MHz, either pulsed or continuous wave (CW), can be propagated from the removable top section of the waveguide. The cage is designed to function as the monkey's permanent home. It is fitted with a lever-actuated behavioral performance device on which the monkey responds according to a predetermined schedule to obtain a daily food ration. The system can be adapted to provide for the collection of metabolic and physiologic data as well. Dosimetric measurements were conducted with six rhesus monkeys weighing 3.0-7.2 kg and with a 4-kg model. The dosimetric results show that about one-third of the net incident energy is absorbed by a subject in this system at a normalized specific absorption rate (SAR) of 0.33 (W/kg)/(mW/cm2).     

Energy deposition in a model of man in the near field

The spatial distribution of the specific absorption rate (SAR) was measured in a full-scale model of man using implantable electric field probes. The model was exposed in the near-field of linear and aperture antennas at 350 MHz. Effects of the wave polarization, antenna position and antenna gain on the SAR distribution and the average SAR in the whole-body and body parts are reported.     

Radiation effects on the structure property of CA 80 for measuring personnel radiation doses

The effects of fast and albedo neutrons and alpha particles on the molecular fractions of cellulose nitrate type CA 80, as a tissue equivalent material have been measured through the use of gel permeation chromatography. The samples in the form of thin sheets were exposed to fission neutron fluences in the range 10⁵–10¹⁰ n/cm² and to different energies of alpha particles in the range 1–5 MeV. The effects of irradiation on paraffin phantom, application of lithium borate radiator to the sample and storage of irradiated specimens for different periods were measured. The results indicated that CA80 eluted in one main fraction. Irradiation with neutrons or alpha particles caused fragmentation of this fraction to smaller molecules. Small and acceptable fade of the induced changes by radiation in the polymer due to storage for more than one month were noticed. The possibility of applying this technique in radiation dosimetry was discussed.     

激光与细胞膜相互作用热、电效应的微观机理分析

在细胞膜电偶极矩液晶模型的基础上,用电动力学,量子统计及固体量子理论对激光与细胞膜相互作用的电学及热学效应微观机理进行研究,导出了激光-细胞膜相互作用的极化及其极化驰豫效应和温升效应公式,这些理论研究结果能解释一些相关实验。     

Estimation of Electromagnetic Dosimetric Values from Non-Ionizing Radiofrequency Fields in an Indoor Commercial Airplane Environment

In this article, the impact of topology as well as morphology of a complex indoor environment such as a commercial aircraft in the estimation of dosimetric assessment is presented. By means of an in-house developed deterministic 3D ray-launching code, estimation of electric field amplitude as a function of position for the complete volume of a commercial passenger airplane is obtained. Estimation of electromagnetic field exposure in this environment is challenging, due to the complexity and size of the scenario, as well as to the large metallic content, giving rise to strong multipath components. By performing the calculation with a deterministic technique, the complete scenario can be considered with an optimized balance between accuracy and computational cost. The proposed method can aid in the assessment of electromagnetic dosimetry in the future deployment of embarked wireless systems in commercial aircraft.