The fraction of the positively charged unattached radon decay products, 218Po and 214Pb in indoor air was determined by model calculations. The results of the calculations were confirmed by measurements in a test chamber (volume: 8 m3). The fraction of both radionuclides depends on the attachment parameter (S(1)) and the neutralisation rate (nu) in room air.
View Article and Find Full Text PDFLichens were collected in France in the surroundings of a military nuclear facility in Burgundy, near the la Hague reprocessing plant and in an area away from any direct source of contamination. Organically bound tritium (OBT) has been analysed on 18 samples and radiocarbon on 11. It appeared that on the most contaminated spots, the OBT activity in lichens was higher than the background by a factor of 1000 and was still a factor 10-100 at a distance of 20 km from the source.
View Article and Find Full Text PDFRadiat Prot Dosimetry
December 2001
The dose per exposure unit of the short-lived radon and thoron decay products was calculated using a dosimetric approach. The calculations are based on a lung dose model with the structure that is related to the ICRP 66 respiratory tract model. The dose relevant parameters, unattached fraction of the decay product clusters (fp) and size distribution of the unattached and aerosol-attached decay products for different living and working places are reported.
View Article and Find Full Text PDFThe electric charge of the radon decay product, 218Po, has an influence on its mobility characterised by the diffusion coefficient, which chiefly controls the formation of the radioactive aerosol by attachment and the plateout processes on surfaces. These processes strongly affect the dose relevant quantities like concentration and particle size distribution of the short-lived radon decay products. The neutralisation rate of the positive 218Po ions in environmental air was determined quantitatively in chamber experiments.
View Article and Find Full Text PDFWe investigate the vibration dynamics of ellipsoidal silver nanoparticles, using time-resolved optical pump-probe spectroscopy. When excited with femtosecond laser pulses, the particles execute anisotropic shape oscillations. We show that these vibrations are triggered by the thermal expansion of the optically heated particles.
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