Abstract-A Transverse Electromagnetic Mode (TEM) cell is an interesting option for studying the biological effects of radiofrequency radiation at reduced scale (in vitro studies).Controlled and well-characterized exposure conditions are essential for a conclusive investigation: the biological sample is exposed to a uniform incident electromagnetic wave and the dose of absorbed radiation is precisely determined and correlated with the effect. Unfortunately, experimental dosimetry is often unavailable or inapplicable, so that a precharacterized and validated experimental setup is most valuable. As such, the primary objective of the present work is to experimentally validate a computational model of a self-built TEM cell designed for bioelectromagnetic experiments in the 100 MHz-1 GHz frequency range. Validation is achieved by comparing the computed vs. measured values for three significant parameters: scattering parameters, incident electric field distribution, and absorbed power in a set of liquid samples. Successful validation and characterization is achieved by using CST Microwave Studio's finite integration technique (FIT), and respectively a network analyzer for the experimental setup. The secondary objective is a dosimetric study of four different liquid samples loaded in the cell. The absorption coefficient (AC) is used, assimilated to the specific absorption rate (SAR) of energy deposition in the entire sample volume. AC is shown to converge in experiment and simulation up to 800 MHz for all samples. AC doesn't depend directly on the samples' volume (despite greater volumes frequently showing higher absorption) but rather upon the internal field distribution, which in turn mostly depends on the frequency and on the dimensions of the liquid samples.
Abstract-In 2016 a study reported observing a concentration of magnetite nanocrystals in human brains, with four orders of magnitude larger than previously thought. In the context of magnetite's role and function inside the human brain not being properly understood, this development prompts a question concerning the impact that a significant magnetic near-field component, in the hundreds of MHz range, might have on power loss in tissues having ferrimagnetic properties. This article highlights the importance of thorough research on possible thermal and non-thermal effects that could be caused by the magnetic field component to which one could be exposed while using certain communication devices near or in front of the head. Furthermore, this article provides preliminary estimations of magnetic contribution to the specific absorption rate (SAR) of energy deposition in tissues, using two approaches -one based on existing research concerning magnetic hyperthermia, and the other one based on a simulation model that takes into account the magnetic properties of tissues. By simulating the propagation of a 440 MHz wave in a "magnetic" (as opposed to pure dielectric) brain, we observed changes of the SAR values, and, more importantly, superficial hot spots appeared at the surface of small magnetite particles, distributed in the homogenous brain.
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