Study on transfers of uranium, thorium and decay products from grain, water and soil to chicken meat and egg contents

International audienceActivity concentrations of the uranium and thorium series radionuclides were determined in chicken meat and eggs as well as in soil, water and other dietary intakes of poultry at five sites of the French territory. These data allow the calculation of transfer coefficients which enrich the database given by the technical report series no. 472 of the IAEA. In egg contents, the highest activity concentrations (in mBq kg-1 fresh weight) are for 226Ra, ranging between 136 and 190 and are much lower for uranium (between 0.51 and 1.30 for 238U). In chicken meat, 238U activity concentration is higher than in egg contents and ranges between 1.7 and 9.7. Concerning 232Th, its activity concentration is lower than uranium and ranges between 0.5 and 4.9. Daily ingested activity concentration by the animals was assessed taking into account the activity concentrations measured in the grains, in the soil and in the drinking water. The activity concentration in grains and the daily intakes allow the calculation of concentration ratios and transfer coefficients for chicken meat and egg contents. In chicken meat the transfer coefficients (d kg-1) range between 0.0018 and 0.0073 for 238U and between 0.0008 and 0.0028 for 232Th. In egg contents they range from 0.00018 to 0.0018 for 238U and are much higher for radium isotopes (0.10-0.23 for 226Ra and 0.07-0.11 for 228Ra). © 2012 The Royal Society of Chemistry

Potential sources affecting the activity concentrations of 238U, 235U, 232Th and some decay products in lettuce and wheat samples

International audienceThe activity concentrations of radionuclides within the uranium and thorium series were determined in wheat and lettuce at five sites in France, and in their respective potential sources crop soils of wheat and crop soils and irrigation waters of lettuce. These data were used to calculate concentration ratios and to enrich the database supported by the technical report series N°472 of the IAEA (2010). For wheat and lettuce, the activity concentrations were in the same range for all radionuclides studied, except for 210Pb, which had higher activity concentrations in wheat, ranging between 1.3 and 11 Bq kg-1 (fresh weight) as compared to 0.4 and 0.7 Bq kg-1 (fresh weight) for lettuce. For wheat, the range of activity concentrations (mBq kg-1; fresh weight) decreased as 210Pb andgt; 226Ra (56-1511) ≈ 228Ra (86-769) andgt; 228Th (19-176) ≈ 238U (11-169) ≈ 234U (12-150) ≈ 230Th (9.08-197.18) ≈ 232Th (8.61-121.45) andgt; 235U (0.53-7.9). For lettuce, it decreased as 228Ra (andlt;320-1221) andgt; 210Pb (409-746) andgt; 226Ra (30-599) ≈ 228Th (andlt;29-347) andgt; 238U (8-120) ≈ 234U (8-121) ≈ 230Th (5.21-134.63) ≈ 232Th (5.25-156.99) andgt; 235U (0.35-5.63). The species differences may reflect different plant physiologies. Through the study of activity ratios of wheat and lettuce in relation with those of the various radionuclide sources it has been possible to highlight the contribution of the main sources of natural radionuclides. Indeed, irrigation water when the uranium concentration is enhanced (andgt;30 mBq L-1) contributed significantly to the activity concentration of uranium in lettuces. Concerning the high activity concentrations of 210Pb, it could be explained by atmospheric particle deposition. The effect of soil particles resuspension and their adhesion to the plant surface seemed to be important in some cases. The soil-to-plant transfer factors were calculated for lettuce and wheat. The values were lower in wheat than in lettuce except for 210Pb which had similar values in the two species (0.11-0.13 respectively). For both species, 210Pb followed by 228Ra (0.015-0.10) and 226Ra (0.010-0.051) displayed the highest transfer factor, whereas 238U had intermediate values (0.0015-0.030) and 232Th exhibited the lowest (0.0014-0.013). © The Royal Society of Chemistry 2012

Bose-Einstein condensation of exciton polaritons

Phase transitions to quantum condensed phases - such as Bose - Einstein condensation (BEC), superfluidity, and superconductivity - have long fascinated scientists, as they bring pure quantum effects to a macroscopic scale. BEC has, for example, famously been demonstrated in dilute atom gas of rubidium atoms at temperatures below 200 nanokelvin. Much effort has been devoted to finding a solid-state system in which BEC can take place. Promising candidate systems are semiconductor microcavities, in which photons are confined and strongly coupled to electronic excitations, leading to the creation of exciton polaritons. These bosonic quasi-particles are 10 9 times lighter than rubidium atoms, thus theoretically permitting BEC to occur at standard cryogenic temperatures. Here we detail a comprehensive set of experiments giving compelling evidence for BEC of polaritons. Above a critical density, we observe massive occupation of the ground state developing from a polariton gas at thermal equilibrium at 19 K, an increase of temporal coherence, and the build-up of long-range spatial coherence and linear polarization, all of which indicate the spontaneous onset of a macroscopic quantum phase

Bose-Einstein condensation of exciton polaritons

Phase transitions to quantum condensed phases - such as Bose - Einstein condensation (BEC), superfluidity, and superconductivity - have long fascinated scientists, as they bring pure quantum effects to a macroscopic scale. BEC has, for example, famously been demonstrated in dilute atom gas of rubidium atoms at temperatures below 200 nanokelvin. Much effort has been devoted to finding a solid-state system in which BEC can take place. Promising candidate systems are semiconductor microcavities, in which photons are confined and strongly coupled to electronic excitations, leading to the creation of exciton polaritons. These bosonic quasi-particles are 10 9 times lighter than rubidium atoms, thus theoretically permitting BEC to occur at standard cryogenic temperatures. Here we detail a comprehensive set of experiments giving compelling evidence for BEC of polaritons. Above a critical density, we observe massive occupation of the ground state developing from a polariton gas at thermal equilibrium at 19 K, an increase of temporal coherence, and the build-up of long-range spatial coherence and linear polarization, all of which indicate the spontaneous onset of a macroscopic quantum phase.</p

Bose-Einstein condensation of exciton polaritons.

Phase transitions to quantum condensed phases--such as Bose-Einstein condensation (BEC), superfluidity, and superconductivity--have long fascinated scientists, as they bring pure quantum effects to a macroscopic scale. BEC has, for example, famously been demonstrated in dilute atom gas of rubidium atoms at temperatures below 200 nanokelvin. Much effort has been devoted to finding a solid-state system in which BEC can take place. Promising candidate systems are semiconductor microcavities, in which photons are confined and strongly coupled to electronic excitations, leading to the creation of exciton polaritons. These bosonic quasi-particles are 10(9) times lighter than rubidium atoms, thus theoretically permitting BEC to occur at standard cryogenic temperatures. Here we detail a comprehensive set of experiments giving compelling evidence for BEC of polaritons. Above a critical density, we observe massive occupation of the ground state developing from a polariton gas at thermal equilibrium at 19 K, an increase of temporal coherence, and the build-up of long-range spatial coherence and linear polarization, all of which indicate the spontaneous onset of a macroscopic quantum phase