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The biological effects of electromagnetic radiation at ultra high frequency on human keratinocytes were investigated. HaCaT cell system, a spontaneously immortalized human keratinocytes cell line, was chosen as model since skin is usually exposed to electromagnetic radiation at considered frequency more than inner tissues. HaCaT cells were exposed to a pure sinusoidal field at a frequency of 900 MHz (average SAR levels ranging from 0.04 to 0.08 W/kg) in plane wave condition inside a GTEM chamber for time intervals of 18 hours at a controlled temperature of 37 • C. Growth curves were obtained for exposed and control cells, and a reduction in the number of exposed cells in comparison to unexposed ones was found; however the number of dead cells was not significantly different in exposed and unexposed samples. In order to investigate whether the reduction in cell proliferation of exposed cells was due to the activation of a differentiative process, the expression of two hallmarks of differentiation was examined. Both keratin 1 and involucrin expression was increased in exposed in comparison to unexposed cells. These results suggest that this protocol of exposure to 900 MHz electromagnetic field can trigger a differentiation program in HaCaT cells.

In this paper we discuss the advantages of flat coil inductive proximity sensors. The coil copper helix may be realized by application of a photoengraving technique to two side-printed boards by a very cheap process. The low thickness allows one to get the coil closer to the target. This fact allows one to attain a higher sensitivity. The coil's low intrinsic capacitance and inductance allow one to work at high frequencies (up to some megahertz). As a consequence the sensor's time constant may decrease to some microseconds. A discussion of the parameters that influence the sensor's performance is reported. Special attention has been given to the coil's shape, the target and the electronic revealing circuit required for promptly functioning and precise devices. The complete analysis of the influences of these parameters on the sensor's performance gives useful suggestions that allow one to obtain a fast response, high sensitivity and high intrinsic insensitivity versus temperature. This is obtained by adopting flat coils, bimetallic (magnetic-non-magnetic) targets and an electrical bridge or frequency-shifting circuit. This provides a substantial improvement in performance with respect to previous solutions.

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