A personal, distributed exposimeter: procedure for design, calibration, validation, and application

This paper describes, for the first time, the procedure for the full design, calibration, uncertainty analysis, and practical application of a personal, distributed exposimeter (PDE) for the detection of personal exposure in the Global System for Mobile Communications (GSM) downlink (DL) band around 900 MHz (GSM 900 DL). The PDE is a sensor that consists of several body-worn antennas. The on-body location of these antennas is investigated using numerical simulations and calibration measurements in an anechoic chamber. The calibration measurements and the simulations result in a design (or on-body setup) of the PDE. This is used for validation measurements and indoor radio frequency (RF) exposure measurements in Ghent, Belgium. The main achievements of this paper are: first, the demonstration, using both measurements and simulations, that a PDE consisting of multiple on-body textile antennas will have a lower measurement uncertainty for personal RF exposure than existing on-body sensors; second, a validation of the PDE, which proves that the device correctly estimates the incident power densities; and third, a demonstration of the usability of the PDE for real exposure assessment measurements. To this aim, the validated PDE is used for indoor measurements in a residential building in Ghent, Belgium, which yield an average incident power density of 0.018 mW/m(2)

In vitro effect of fluoride oral hygiene tablets on artificial caries lesion formation and remineralization in human enamel

<p>Abstract</p> <p>Background</p> <p>Aim of this <it>in-vitro</it>-study was to assess the remineralization potential of a tooth cleaning tablet with different fluoride content.</p> <p>Methods</p> <p>Twenty three caries free impacted third molars were examined, enamel surfaces were wax coated leaving two 3 × 4 mm windows for exposure to demineralization/remineralization cycles. The teeth were randomly assigned to 4 groups of 5 control and 6 experimental teeth. Demineralization by standardised HEC-gel, pH 4.7 at 37°C for 72 h, was alternated by rinsing in remineralization solution, pH 7.0 at 37°C for 72 h, total challenge time 432 h. The negative control group N was treated during remineralization cycles with saline; positive control group P was treated with remineralization solution; experimental group D1 was exposed to remineralization solution containing Denttabs^®-tablets with 1450 ppm F; experimental group D2 was exposed to remineralization solution and Denttabs^®-tablets with 4350 ppm F. Each tooth was cut into serial sections and analyzed by polarized light microscopy for assessment of the different zones of white-spot lesions in 3 representative sections. Statistical analysis was based on the <it>Mann-Whitney</it>-Test.</p> <p>Results</p> <p>Both control groups N(-) and P(+) exhibited characteristic white-spot lesions. The remineralization and the demineralization inhibition of the lesions increased considerably from N<P < D1<D2. Denttabs^®-2 administration showed partial/total remineralization including lamination and/or disappearance of the body of the lesion. The different results of all 4 groups were statistically highly significant (p < 0.01) with both tests.</p> <p>Conclusion</p> <p>Based on these results the novel Denttabs^®formulation represents a highly effective oral hygiene product and the remineralization is correlated to the fluoride content.</p