Culture medium geometry. The dominant factor affecting in vitro RF exposure dosimetry

Biological experiments that expose living cells or tissues to RF energy must have an aqueous medium to provide essential water, ions, nutrients, and growth factors. However, as we show here, the medium inherently functions as a receiving antenna that conveys RF energy to the biological entity in a manner entirely determined by exposure vessel geometry, orientation to the incident RF flux, frequency, and dielectric properties of the medium. We show for two common experimental arrangements that basic antenna theory can predict electromagnetic energy patterns that agree well with those otherwise obtained by computationally intensive methods that require specialized resources

Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult Caenorhabditis elegans.

Reports that low-intensity microwave radiation induces heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9-3 mW kg-1 for 6-well plates) that minimises temperature differentials between sham and exposed conditions (≤0.1 °C). Parallel measurement and simulation studies of SAR distribution within this exposure system are presented. We compared 5 Affymetrix gene-arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against 5 gene-arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). No genes showed consistent expression changes across all 5 comparisons, and all expression changes appeared modest after normalisation (≤ 40% up- or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131). We conclude that the pattern of gene expression in L4/adult C. elegans is substantially unaffected by low-intensity microwave radiation; the minor changes observed in this study could well be false positives. As a positive control, we compared RNA samples from N2 worms subjected to a mild heat-shock treatment (30ºC) against controls at 26 ºC (2 gene arrays per condition). As expected, heat-shock genes are strongly up-regulated at 30ºC, particularly an hsp-70 family member (C12C8.1) and hsp-16.2 . Under these heat-shock conditions, we confirmed that an hsp-16.2::GFP transgene was strongly up-regulated, whereas two non-heat-inducible transgenes (daf-16::GFP; cyp-34A9::GFP) showed little change in expression

Monte-Carlo Based Numerical Dosimetry in Reverberation Chamber Exposure Systems Employed for in-Vivo Rodent Bioassays

A Monte-Carlo based computational approach for the statistical characterization of the whole-body specific absorption rate (wbSAR) variability in large cohorts of rodents exposed to radio-frequency (RF) energy in reverberation chambers (RCs) is applied to adult male rat exposures illustrative of those in a US National Toxicology Program (NTP) cancer bioassay. A large number of 3D electromagnetic field realizations fulfilling Rayleigh fading properties were generated within an electrically-large volume representative of an ideal RC, yielding granular wbSAR distributions for an ensemble of 96 homogeneous rodent models with random mass distribution, postures, positions and orientations. Two case studies were addressed: a “momentary exposure” with each rat fixed in posture, position and orientation, and a “day-long exposure” in which the position, orientation and posture were varied randomly for each subsequent Rayleigh field realization. Over 500 and 2500 field realizations or “snapshots”, respectively, the rats’ instantaneous wbSARs, as well as their individual time-averaged wbSARs, were found to be well fit by lognormal distributions. The large variability in instantaneous wbSARs in the cohort was due in part to the inherent Rayleigh field variability in RCs (70-80%) and in part to weight, posture and position variations (20-30%), while the effect of cage location was found to be small over day-long exposures. Averaging the exposure over field realizations substantially reduces the range of wbSARs in the cohort. Hence, when RF-induced thermal effects are studied, the relevant exposure metric (wbSAR averaged over appropriate times) features a narrower range than instantaneous wbSAR, which is the relevant metric in studies dealing with non-thermal effects. Compared to previous studies, the present approach was found to be computationally more efficient enabling thus a Monte-Carlo analysis by varying concurrently the incident field and the animals posture, position, and orientation. In practice, it can inform the choice of wbSAR targets in rodent bioassay, allowing to identify possible dose-effect trends while avoiding undue thermal stress

Exposure compliance methodologies for multiple input multiple output (mimo) enabled networks and terminals

Multiple input multiple output (MIMO) enabled handsets and base-stations feature antenna systems that generate electromagnetic fields for which relevant exposure standards and guidelines do not explicitly define compliance testing methodologies. Here, through computational modeling, we explore several field summation schemes for evaluating such exposures and propose compliance testing methodologies that limit the degree of exposure under/over-estimation for both base stations and handsets. The methodologies rely on scalar field probe measurements thus avoiding significant equipment upgrades and are applicable to cases where access to signals from eachMIMO antenna element can be arranged

An international inter-laboratory comparison of mobile phone SAR calculation with CAD-based models

International audienc

Investigation of the Transient Fields of Perfectly Conducting Rotational Bodies

A numerical procedure based on the method of moments (MoM) is proposed for studying the transient fields and currents of various objects located near a grounded, perfectly conducting plane. The method takes into account a number of parameters, including the frequency characteristics, radiation patterns and surface current distributions. Results obtained using the proposed approach show good agreement with experimental data

An international interlaboratory comparison of mobile phone SAR calculation with CAD-based models

International audienceAn international interlaboratory comparison for numerical calculations of head phantom SAR involving three mobile phones with computer-aided design-based models has been conducted in order to evaluate the repeatability of such calculations and for providing input in the development of standardized procedures. SAR in the standardized specific anthropomorphic mannequin (SAM) head phantom was calculated by ten laboratories in a blind study manner. The agreement in calculated SAR between the participating laboratories is very similar to the agreement obtained in interlaboratory comparisons involving SAR measurements. The results support the opinion that standardized procedures for numerical calculations of SAR can be developed. The agreement between calculated SAR results and corresponding measurement results ranges from good to poor for the three phone models. Most probably, a significant reason for the observed deviations is the simplifications made to the models, which implies that device modeling specifications are of utmost importance in standards