PubMed · 11117136
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J P McClain. 2000. Making waves.. https://pubmed.ncbi.nlm.nih.gov/11117136/
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Nine small radiation shields made to adhere to the case of mobile phones were tested at 914 and 1880 MHz. Five popular products were tested because advertisements typically claim they are up to 99% effective in blocking radio frequency (RF) radiation emitted from mobile phones. Also, four other conceptually unusual products were tested because advertisements typically claim they emit oscillations that counteract the RF radiation from mobile phones. Each shield was tested on the same mobile phone, and measurements were made to compare the absorption of RF energy in the head with and without each shield attached to the phone. The phone was positioned against a head model, and an automated measurement process was used to determine specific absorption rate (SAR) in the same way it is used at Motorola to test the compliance of mobile phones with respect to human exposure limits. The location of the peak SAR was not observed to change with any of the shields attached to the phone, and the 1 g, peak spatial average SAR did not change by any statistically significant amount. These results indicate the small shields are ineffective in reducing the exposure of the head to RF energy emitted by a mobile phone.
Human exposure by mobile phones in enclosed areas such as train carriages, elevators, and cars is considered. Equivalent power density and whole body specific absorption rate (SAR) are estimated by applying multimode resonant cavity theory and a straight forward worst case approach. The results show that exceeding the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines due to simultaneous use of several mobile phones in enclosed areas is highly improbable.
As the development of quantised storage media progresses, detailed knowledge is required about the magnetisation reversal behaviour of sub-micron sized magnetic structures in external magnetic fields. Using the Lorentz mode of transmission electron microscopy (LTEM) the magnetic microstructure of thin film samples can be imaged with high spatial resolution. A novel approach for in situ magnetising experiments is described which combines the development of a custom-made sample holder which generates two orthogonal in-plane components of magnetic field in the specimen plane with the benefit of computer-controlled variation of the field. We present a specimen stage suitable for a Philips CM30 Twin/LTEM, which allows the generation of well-defined magnetic in-plane fields in the TEM.