La conversion en dose d’une exposition au radon fait l’objet de débats. L’UNSCEAR a défini un coefficient de conversion de la concentration en radon vers la dose efficace à partir de modèles dosimétriques et d’informations épidémiologiques. La CIPR recommande d’évaluer le risque lié au radon à partir des études épidémiologiques. Pour permettre la prise en compte d’une exposition combinée à d’autres sources de rayonnements ionisants, elle a adopté des conventions de conversion en dose efficace inférieures de 10 à 30 % au coefficient de l’UNSCEAR, sur la base du suivi épidémiologique des mineurs d’uranium. Ainsi, des niveaux de référence différents pour la concentration en radon peuvent être déduits d’un même niveau de dose efficace suivant que l’on applique l’un ou l’autre facteur de conversion. Cependant, il convient de rappeler que ces différences sont négligeables par rapport aux incertitudes associées aux études tant dosimétriques qu’épidémiologiques et que les niveaux de référence ne sont que des outils pour aider à réduire aussi bas que raisonnablement possible l’exposition au radon et le risque qui en résulte.

This article presents current R&D activities at Observatoire de Paris – Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique in the fields of low noise mixers and local oscillators for heterodyne instruments dedicated to astrophysics, planetology and the sciences of the atmosphere.

Studies on decision-making processes are generally aimed at identifying farmers' needs and predicting farmers' reactions to technical innovations. In the present paper we study these decision-making processes, with reference to dairy farms, to build a whole-farm computer model (WFM) which simulates farmers' actions. In this study, (i) a multi-tool and multi-step methodology is proposed, which can also be qualified as an iterative and interactive methodology to reveal decision rules and (ii) a generic structure to formalise how action is conducted, termed ‘structure for action modelling’ (SAM). In the case of forage crop-dairy cattle systems, we have tested the current methodology to capture the decision rules and the SAM to represent action concerning farm management. An ‘immersion’ approach, inspired by the ethnographic approach has been adapted to access operational technical decisions (taken on a daily basis). This study helped in understanding how detailed and large approaches can be complementary and can facilitate identification of what can be generalised in a conceptual model. To define the generic structure (SAM), a set of descriptive variables concerning technical operations has been selected. The conceptual model generated is composed of decision rules reconstructed by researchers with farmers' committed participation. The validation method is based on participatory approaches and on comparing of actions simulated by the model with practices on the ground. Not contesting the fact that farmers plan their action, this study also revealed the importance of adjustments in action. For example, 20 to 55% of the time the planned food ration is not distributed to the milking cows because of forage unavailability. We also discuss how this structure can facilitate integration of decision mechanisms in biophysical models and how such an integration of adjustment decision rules can produce more realistic simulations of technical actions. Error of biotechnical evaluations done by the WFM is reduced from about 25% to about 10% with the application of the proposed method.

Depuis sa création en 1928, la Commission internationale de protection radiologique (CIPR) produit régulièrement des recommandations sur la protection contre les rayonnements ionisants ; ces recommandations sont habituellement reprises par les organisations internationales et par les États. Depuis 1990, date des recommandations les plus récentes (Publication 60), la progression des connaissances scientifiques, les développements techniques, le retour d’expérience et le souci d’adhérer à l’évolution de la société, ont incité la CIPR à modifier son système de protection. Le tout dernier projet de recommandations, récemment rendu public pour consultation et appel de propositions, est décrit et discuté.

The potential use of barium zirconate for the manufacture of corrosion-resistant substrates emphasizes the need for a simple, inexpensive, and easily scalable process to produce high-quality powders with well-controlled composition and properties. However, the classical solid-state preparation of barium zirconate leads to an inhomogeneous powder unsuitable for applications in highly corrosive environment. For this paper, the possibility to use the spray-drying technique for the preparation of BaZrO3 powders with a controlled size distribution and morphology was investigated. The influence of the nature and concentration of the precursor solution and the influence of the spray-drying step are discussed on the basis of x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and dilatometric measurements.

Contribution of the French society for radiation protection to the current reflections on the possible improvements of the radiological risk management system. Following the invitation from IRPA to comment on the article written by Professor Roger Clarke entitled "Control of Low Level Radiation Exposure: Time for a Change?", the Board of the French Society for Radiation Protection (SFRP) decided to set up a working group on "controllable dose". The latter, which worked from April 1999 to July 2000, consisted of some twenty members representing the stakeholders involved in radiological protection in France: authorities, experts and professionals from nuclear, medical and research fields as well as associative movement. The present article, which has been approved by the Board of SFRP, summarises the findings of the WG presented during the IRPA-10 Congress in May 2000. The WG first examined the current hypothesis on radiological risk and noted their relevance for a practical management of such a risk. Then, a list of the different exposure situations and their associated characteristic was elaborated in a table form, followed by a discussion on the situations when the system of radiological protection fits well, less well or bad, particularly through the implementation of the general principles of radiological protection. The WG finally made proposals to ICRP for an evolution of the system towards a more operational way.

Apomyoglobin from sperm whale is often used for studies of ligand binding, protein folding, and protein stability. In an effort to describe its conformational properties in solution, homonuclear and heteronuclear (13C and 15N) NMR methods were applied to the protein in its native state. Assignments were confirmed for nuclear Overhauser effects (NOEs) involving side chain and backbone protons in the folded regions of the structure. These NOEs were used to derive distance restraints. The shifts induced by the hydrophobic dye 8-anilino-1-naphthalenesulfonic acid (ANS) were inspected in the regions remote from its binding site and served as an indicator of conformational flexibility. 3JαH-NH values were obtained to assess dihedral angle averaging and to provide additional restraints. A family of structures was calculated with X-PLOR and an ab initio simulated annealing protocol using holomyoglobin as a template. Where the structure appeared well defined by chemical shift, line width, ANS perturbation, and density of NOEs, the low resolution model of apomyoglobin provides a valid approximation for the structure. The new model offers an improved representation of the folded regions of the protein, which encompass the A, B, E, helices as well as parts of the G and H helices. Regions that are less well defined at this stage of calculations include the CD corner and the end of the H-helix. The EF-F-FG segment remains uncharacterized.